Fluid ejection or control device
United States Patent 3924974
A tube-like chamber for ejection of fluid is formed of magnetostrictive material. In a preferred form, the chamber contains a nozzle through which fluid contained in the chamber may be ejected as the volume of the chamber is decreased through magnetostrictive action. In cross-section, the chamber is preferably formed of two arcs of respective circles. The chamber is formed of a first type of magnetostrictive material such that the arcs contract circumferentially in response to a circumferential magnetic field induced in tube in the direction of the length of the arcs. A flat member is disposed along the axis of the chamber and spans between opposite portions of the wall of the chamber. In cross-section, the flat member forms a chord of the two arcs. The flat member is formed of a second magnetostrictive material such that the chord expands in the direction of span in response to a lateral magnetic field induced in the flat member in the direction of span of the flat member. The flat member is in contact with the arcs, and thereby, an efficient closed loop magnetic field path comprising the two arcs and the chord is formed. When a circumferential magnetic field is induced in the chamber and a lateral magnetic field is induced in the flat member, the arcs contract circumferentially and the chord expands in the direction of span thereby causing the shape of the cross-section of the tube to distort. As a result of this distortion, the volume of the chamber is substantially decreased and fluid is ejected from the nozzle.
US Patent References:
Pumping device
Abrams - April 1943 - 2317166
Supersonic lubricant homogenizer
Hall - May 1957 - 2791403
Magnetostrictive ink jet
Adams - August 1967 - 3334350
LOW FREQUENCY MAGNETOSTRICTIVE FLEXURAL TRANSDUCER
Semmelink - June 1970 - 3515965
Pumping device
Abrams - April 1943 - 2317166
Supersonic lubricant homogenizer
Hall - May 1957 - 2791403
Magnetostrictive ink jet
Adams - August 1967 - 3334350
LOW FREQUENCY MAGNETOSTRICTIVE FLEXURAL TRANSDUCER
Semmelink - June 1970 - 3515965
Inventors:
Fischbeck, Kenneth Henry (Princeton, NJ)
Leyton Deceased., Eric Mcphail (LATE OF Princeton, NJ)
Leyton Deceased., Eric Mcphail (LATE OF Princeton, NJ)
Application Number:
05/456162
Publication Date:
12/09/1975
Filing Date:
03/29/1974
View Patent Images:
Export Citation:
Assignee:
RCA Corporation (New York, NY)
Primary Class:
Other Classes:
239/101, 239/4, 347/1, 347/68
International Classes:
B41J2/045; F04B43/09; F04B43/00; B05B1/08; G01D15/18; B05B17/04; F04B17/00
Field of Search:
239/4,101,102 340/11 310/26 417/322 346/75
Primary Examiner:
Husar C. J.
Assistant Examiner:
Smith, Leonard
Attorney, Agent or Firm:
Norton, Smiley E. J. R. E.
Claims:
What we claim is
1. The Combination comprising:
2. The combination recited in claim 1 wherein said first material is a first magnetostrictive material selected so that the length of said bow-like shape contracts in response to a magnetic field directed along the length of said bow-like shape; and second material is a second magnetostrictive material selected so that the length of said chord expands in response to a magnetic field directed along the length of said chord; and means for coupling said control signal to said tube-like chamber includes means for including a magnetic field directed along the length of said bow-like shape and a magnetic field directed along the length of said chord.
3. A device for controlling fluid in a tube-like chamber comprising:
4. The device of claim 3 wherein the length of one of said first and second members dimensionally contracts in response to said signal, and the length of the other of the first and second members expands in response to the signal.
5. The combination comprising:
6. The combination recited in claim 5 wherein said first material is a first magnetostrictive material selected so that the length of said bow-like members contracts in response to a magnetic field directed along the length of said bow-like shape; said second material is a second magnetostrictive material selected so that the length of said chord expands in response to a magnetic field directed along the length of said chord; and means for coupling said control signal to said tube and said flat member includes means for inducing magnetic fields directed along the lengths of said bow-like shapes and a magnetic field directed along the length of said chord.
7. The combination recited in claim 5 wherein said output port is a nozzle.
8. The combination recited in claim 7 wherein said nozzle is located within a fluidic rectifier including a chamber, having an orifice opposite the orifice of said nozzle, and arranged to surround said nozzle with fluid to inhibit the formation of air bubbles within said nozzle.
9. The combination recited in claim 7 wherein a second flat member is located within said tube, disposed along the axis of said tube transverse to said first mentioned flat member, and spanning said tube; the portion of said bow-like shaped subtended by said first mentioned flat member and said second flat member being arcuate sections.
10. The combination recited in claim 9 wherein said second flat member is formed of a magnetostrictive material selected so that said second flat member expands in a direction transverse to said chord in response to said control signal.
11. The combination recited in claim 10 wherein said arcuate sections are arcs of circles.
12. The combination recited in claim 7 wherein said bow-like shapes are arcuate.
13. The combination recited in claim 12 wherein said bow-like shapes are arcs of circles.
14. The combination recited in claim 13 wherein said magnetic field includes a pair of magnetic pole pieces adjacent opposite ends of said chord.
15. The combination recited in claim 13 wherein said means for inducing the magnetic fields includes a coil wound around said flat member in the direction of the axis of said tube.
16. The combination recited in claim 15 wherein said coil is formed by a printed circuit affixed to said flat member.
1. The Combination comprising:
2. The combination recited in claim 1 wherein said first material is a first magnetostrictive material selected so that the length of said bow-like shape contracts in response to a magnetic field directed along the length of said bow-like shape; and second material is a second magnetostrictive material selected so that the length of said chord expands in response to a magnetic field directed along the length of said chord; and means for coupling said control signal to said tube-like chamber includes means for including a magnetic field directed along the length of said bow-like shape and a magnetic field directed along the length of said chord.
3. A device for controlling fluid in a tube-like chamber comprising:
4. The device of claim 3 wherein the length of one of said first and second members dimensionally contracts in response to said signal, and the length of the other of the first and second members expands in response to the signal.
5. The combination comprising:
6. The combination recited in claim 5 wherein said first material is a first magnetostrictive material selected so that the length of said bow-like members contracts in response to a magnetic field directed along the length of said bow-like shape; said second material is a second magnetostrictive material selected so that the length of said chord expands in response to a magnetic field directed along the length of said chord; and means for coupling said control signal to said tube and said flat member includes means for inducing magnetic fields directed along the lengths of said bow-like shapes and a magnetic field directed along the length of said chord.
7. The combination recited in claim 5 wherein said output port is a nozzle.
8. The combination recited in claim 7 wherein said nozzle is located within a fluidic rectifier including a chamber, having an orifice opposite the orifice of said nozzle, and arranged to surround said nozzle with fluid to inhibit the formation of air bubbles within said nozzle.
9. The combination recited in claim 7 wherein a second flat member is located within said tube, disposed along the axis of said tube transverse to said first mentioned flat member, and spanning said tube; the portion of said bow-like shaped subtended by said first mentioned flat member and said second flat member being arcuate sections.
10. The combination recited in claim 9 wherein said second flat member is formed of a magnetostrictive material selected so that said second flat member expands in a direction transverse to said chord in response to said control signal.
11. The combination recited in claim 10 wherein said arcuate sections are arcs of circles.
12. The combination recited in claim 7 wherein said bow-like shapes are arcuate.
13. The combination recited in claim 12 wherein said bow-like shapes are arcs of circles.
14. The combination recited in claim 13 wherein said magnetic field includes a pair of magnetic pole pieces adjacent opposite ends of said chord.
15. The combination recited in claim 13 wherein said means for inducing the magnetic fields includes a coil wound around said flat member in the direction of the axis of said tube.
16. The combination recited in claim 15 wherein said coil is formed by a printed circuit affixed to said flat member.
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention pertains to the field of fluid flow control devices and particularly pertains to fluid ejection devices. One embodiment of the invention is particularly useful in the field of ink jet printing apparatus.
2. Description of the Prior Art
Fluid flow control devices are known in the prior art having the form of a tubular member through which fluid flows. The amount of fluid flowing through the tubular member is controlled by providing means to alter the cross-sectional area of the tube. Some of such fluid flow control devices are adapted to eject jets of fluid or fluid drops by placing a nozzle having a relatively small orifice at one end of the tube, closing off the other end of the tube to the flow of fluid and subjecting the tube to sharp volumetric changes in response to a control signal.
These prior art devices have taken a variety of forms. One such form includes a tube surrounded by a piezoelectric material adapted to contract the tube radially inwardly, in response to an electrical control signal, and thereby decrease the volume of the tube. Another form includes a tube formed from a magnetostrictive material and adapted to contract axially, in response to an axial magnetic field, and thereby decrease the volume of the tube.
The properties of magnetostrictive materials and the operation of magnetostrictive structures are well known in the art. For instance, it is well known that certain ferromagnetic metals and alloys, such as nickel and nickel-iron alloys, contract in the direction of a magnetic field induced in the metal regardless of the polarity of the magnetic field; whereas, certain other ferromagnetic metals and alloys, such as iron and iron-nickel alloys, expand in the direction of a magnetic field induced in the metal regardless of the polarity of the magnetic field. For a more detailed description of the magnetostrictive properties of metals see, for example, "Magnetostriction Transducers," a handbook published by the International Nickel Company in July, 1968.
Typical examples of prior art magnetostrictive fluid control devices may be found in U.S. Pat. No. 2,317,166, issued to R. Abrams on Apr. 20, 1943, and U.S. Pat. No. 3,334,350 issued to R. A. Adams on Aug. 1, 1967. In each of the Abrams and Adams patents there is shown a magnetostrictive fluid control device including a magnetostrictive cylindrical member about which is wound an electrical coil. The ends of the cylindrical member are adapted to prevent substantial amounts of fluid from flowing through the cylindrical member. An orifice is provided in one end of the cyclindrical member to allow fluid under pressure to be ejected from the cylindrical member. The cylindrical member is adapted to contract axially in response to an axial magnetic field. When a control current manifesting control information is applied to the coil an axial magnetic field is induced in the cylindrical member. In response to this induced magnetic field the cylindrical member axially contracts resulting in a decrease of volume within the cylindrical member and a corresponding increase in the pressure acting on the fluid and causing thereby the ejection of fluid. The Abrams patent also discloses placing another magnetostrictive structure, having a similar shape to the above described cylindrical member and adapted to expand axially, concentrically within the cylindrical member and channeling the fluid between these cylindrical members to form a fluid flow control device.
In fluid control applications generally large volume displacements are desired. The type of magnetostrictive structures adapted to contract axially produce high pressure but low volume displacements. In addition, magnetostrictive structures of the type described above have inefficient magnetic field paths requiring undesirably large amounts of drive signal power. Further, the magnetostrictive structures adapted to respond to axial magnetic fields have relatively short eddy current paths which result in undesirable long time responses to the drive signal. Accordingly, there is a need for a magnetostrictive fluid control device which makes efficient usage of the magnetostrictive effect to produce significant volumetric displacements while requiring only relatively low drive signal power and responding to such a drive signal in relatively short response times.
There are known magnetostrictive devices useful in producing vibrations in various fluid mediums for applications such as sonar and the like. Of particular interest are magnetostrictive structures having tubular shaped adapted to produce radially directed waves in response to oscillatory radial contractions and expansions of the tubular structure established by oscillatory circumferential (azimuthal) magnetic fields induced in the tubular structure. One such structure is shown in FIG. 7 of "Magnetostriction Transducers" referred to above. Heretofore the principles of this magnetostrictive art have not been utilized in the fluid control art.
SUMMARY OF THE INVENTION
In accordance with the invention, a tube-like chamber for fluid, including an output port, is provided, which is operable in response to a control signal to control the flow of fluid out of the chamber through the output port. The chamber is formed of two members of dissimilar materials. In cross-section, the first member, has a bow-like shape which is preferably arcuate. The second member spans the first member so that, in cross-section, the second member spans a chord of the first member. In response to the control signal, the bow-like shape is contracted in length, while the chord is expanded in length thereby producing a geometric distortion of the cross-section of the chamber resulting in a significant reduction in area defined by the bow-like shape and the chord.
As a result of this geometric distortion, the volume enclosed by the chamber is substantially reduced. The flow of fluid through the output port is thereby controlled.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an isometric view of a prior art magnetostrictive fluid control device.
FIG. 2 is an isometric view of a prior art magnetostrictive vibration device useful in sonar applications and the like.
FIG. 3 is an isometric view in partial cross-section, of the preferred embodiment of the invention useful as a fluid jet device.
FIG. 4 is a cross-sectional view taken in the direction of the cross-section of FIG. 3 showing another embodiment of the invention.
FIG. 5 is a cross-sectional view taken in the direction of the cross-section of FIG. 3 showing still another embodiment of the invention.
FIG. 6 is a cross-sectional view taken in a direction transverse to the direction of the cutaway cross-sectional view of FIG. 3 showing another embodiment of the invention providing a fluidic rectifier useful in an ink jet printing apparatus.
In the following description, the same reference numbers in different figures refer to the same or similar elements.
DESCRIPTION OF THE PRIOR ART (FIGS. 1 and 2)
Preliminary to a detailed description of the preferred embodiment of the invention, the prior art briefly described in the Prior Art portion of the present specification will be described in detail.
FIG. 1 is an isometric view of a magnetostrictive prior art device used to control the flow of fluids being typical of the devices disclosed in the Abrams and Adams patents cited above. The prior art structure of FIG. 1 is formed of a cylindrical tube 10 about which is wound electrical helical coil 12. Cylindrical tube 10 is formed from a magnetostrictive material such as nickel, a nickel-iron alloy, cobalt or a cobalt-iron alloy which contracts axially when subjected to the axial magnetic field created by coil 12. Thus, when current flows through coil 12, an axial magnetic field is generated which acting on cylindrical tube 10 contracts it axially. It is to be noted, as previously stated, that the magnetostrictive effect when a magnetostrive material is subjected to a magnetic field is independent of the polarity or sense of the magnetic field. For example, cylindrical tube 10 will contract axially in response to an axial magnetic field whether the magnetic field is directed in the direction of arrow 17 or arrow 19. Therefore, when current is made to flow through coil 12, in either a positive or negative sense, cylindrical tube 10 contracts axially, that is, in height L. As cylindrical tube 10 contracts axially, its volume is reduced since its height is reduced.
The structure of FIG. 1 may be modified to form a fluid jet device if one end of cylindrical tube 10 is effectively closed to the flow of fluid and nozzle 13 or like structure is placed at the other end of cylindrical tube 10. In this modified structure forming a fluid jet, a rejection in the volume of the tube 10 causes the pressure within tube 10 to increase. The increased pressure within tube 10 results in the ejection of a jet fluid from nozzle 13.
The expression for the volumetric change within cylindrical tube 10 when subjected to an axial magnetic field may be shown to be: ##EQU1## where V is the original volume within cylindrical tube 10, ΔV is the change in volume within cylindrical tube 10 when cylindrical tube 10 is subjected to an axial magnetic field, L is equal to the original length of cylindrical tube 10, ΔL is equal to the change in length of cylindrical tube 10 when circular tube 10 is subjected to a magnetic field and σ p is Poisson's ratio for the magnetostrictive material which forms cylindrical tube 10 and is assumed to be approximately equal to 0.3. Thus, according to expression (1), if the length of cylindrical tube 10 is decreased by 30 ppm (parts per million) the volume of cylindrical tube 10 is decreased 12 ppm. This rather small volumetric change may be better appreciated by realizing that a 30 ppm decrease in length, is accompanied by a 9 ppm increase in the perimeter of cylindrical tube 10 which is counter-productive to the volumetric decrease. That is, while the height of the cylinder decreases, resulting in a decreased volume, the cross-sectional area of the tube increases, tending to oppose the decreased volume.
The performance of the prior art structure of FIG. 1 (typically Abram U.S. Pat. No. 2,317,166) may be enhanced by inserting a smaller diameter and shorter magnetostrictive cylindrical tube 16, closed at both ends which expands axially when subjected to an axial magnetic field, coaxially within magnetostrictive cylindrical tube 10 as is shown in phantom in FIG. 1. When this modified structure of FIG. 1 including cylindrical tube 16 is subjected to an axial magnetic field, the volume between cylindrical tubes 10 and 16 is decreased as cylindrical tube 16 expands lengthwise and cylindrical tube 10 constricts thereby subjecting fluid 14 to a relatively high pressure increase.
FIG. 2 is an isometric view of a magnetostrictive prior art device useful in sonar applications and the like. The prior art device of FIG. 2 is similar to the device shown in FIG. 7 of the "Magnetostrictive Transducers" handbook cited above. The prior art device of FIG. 2 is formed of cylindrical tube 20 and planar magnetic core 22. Cylindrical tube 20 is formed of a suitable magnetostrictive material, such as nickel or a nickel-iron alloy, so that the curcumference of tube 20 decreases to contract radially in response to an azimuthal, or circumferential magnetic field, i.e., a magnetic field (indicated by arrows 24a and 24b) directed circumferentially through the cylindrical wall of tube 20. Thus, circular tube 20 is formed of a magnetostrictive material such that when circular tube 20 is subjected to a circumferential magnetic field the circumference of circular tube 20 contracts and thereby each point along the circumference is moved radially inwardly, that is, in effect, circular tube 20 contracts radially inwardly. Core 22 is formed of a suitable material, laminated or unlaminated, in which a magnetic field may be readily induced and is wound with electrical coil 26 whose axis is transverse to the longitudinal axis of cylindrical tube 20. When current flows through coil 26, a magnetic field (indicated by arrows 24a) is induced in core 22 which is magnetically coupled through air gap 23 to the cylindrical wall of tube 20 to induce an azimuthal magnetic filed indicated by arrows 24b in the cylindrical wall of tube 20. The azimuthal magnetic field induced in the cylindrical wall of tube 20 cause cylindrical tube 20 to vibrate radially.
In sonar applications circular tube 20 is immersed in water (preferably with the inner portion of the cylinder sealed off from the water). Coil 26 is periodically energized to cause cylindrical tube 20 to vibrate radially thereby generating radially directed sonar waves.
The expression: ##EQU2## can be shown to represent the volumetric change within circular tube 20 when circular tube 20 is subjected to an azimuthal magnetic field, where V is the original volume within cylindrical tube 20, ΔV is the volumetric change within cylindrical tube 20 when cylindrical tube 20 is subjected to an azimuthal magnetic field, P is the original periphery of cylindrical tube 20, ΔP is the change in periphery of cylindrical tube 20 when cylindrical tube 20 is subjected to an azimuthal magnetic field and σ p is Poisson's ratio for the magnetostrictive material forming cylindrical tube 20 and is assumed to be equal approximately to 0.3. According to expression (2), if the periphery of cylindrical tube 20 is caused to decrease 30 ppm the resultant volumetric decrease, ΔV, is equal to 51 ppm. This relatively significant volumetric decrease in comparison to the 12 ppm volumetric decrease of the prior art structure of FIG. 1 may be appreciated by noting that the change in the cross-sectional area of cylindrical tube 20 varies as the periphery squared. Thus, an azimuthal magnetic field acting on a cylindrical magnetostrictive tube produces approximately a 4 1/4 times greater volumetric change than does an axial magnetic field acting on a cylindrical tube of the same dimension.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (FIG. 3)
FIG. 3 is an isometric view of the preferred embodiment of the present invention being a fluid jet device useful in generating jets of fluid. FIG. 3 includes a cross-sectional view taken in the direction of the longitudinal axis of the fluid jet structure to show the cross-section of the fluid jet structure. The fluid jet structure of FIG. 3 is particularly useful in applications such as ink jet printing, fuel injection or the like. The fluid jet device of FIG. 3 is formed of a tube 30 having curvilinear cross-section 34 formed by two bow-like shaped sections 34a and 34b, a flat or planar member 32, disposed along the axis of tube 30 and spanning opposite wall portions of tube 30 along the major diameter of the curvilinear cross-section 34 thereby forming a chord of the two bow-like shaped sections (34a and 34b) and nozzle 36, joined to tube 30 at intersection 37 between tube 30 and nozzle 36. Flat member 32 divides tube 30 into two chambers or passageways 35a and 35b for fluid each having a cross-sectional area enclosed by a bow-like shaped section and the chord spanning the bow-like shaped section. The bow-like shaped sections are preferably arcuate in shape.
Tube 30 is formed from any suitable magnetostrictive material, such as nickel or a nickel-iron alloy, selected so that the arcuate section contracts circumferentially in length in response to an azimuthal magnetic field passing circumferentially through curvilinear cross-section 34. Thus, tube 30 is formed of a magnetostrictive material such that when tube 30 is subjected to a circumferential magnetic field the circumference of tube 30 contracts and thereby points along the circumference are moved radially inwardly that is, in effect, tube 30 contracts radially inwardly. The arcuate sections may be of any suitable curvilinear shape, such as circular, elliptical, parabolic, hyperbolic or the like. In a preferred form of the invention the arcuate sections are arcs of circles whose diameters are greater than the major diameter of cross-section 34.
Flat member 32, spanning the major diameter of cross-section 34 is formed from any suitable magnetostrictive material, such as iron or an iron-nickel alloy selected so that the straight line section expands laterally in length in the direction of the span of chord-like member 32 in response to a lateral magnetic field directed along the major diameter of cross-section 34.
Coil 38, wound around flat member 32 in the direction of the axis of tube 30, is provided to generate the magnetic field indicated by arrows 33. Although only one winding of coil 38 is shown for simplicity, it will be appreciated that coil 38 may include any suitable number of windings. In one form of the preferred embodiment, coil 38 is a printed circuit attached to lateral member 32.
Flat member 32 is suitably connected to opposite wall portions of cross-section 34 to create a highly efficient magnetic path for a magnetic field generated in response to a current flowing through coil 38. When a current flows through coil 38, a magnetic field, indicated by arrows 33, is generated. The magnetic field comprises a lateral magnetic field flowing in the direction of span within flat member 32, and an azimuthal magnetic field flowing circumferentially within curvilinear tube 34.
The control signal current may be of any suitable type, such as a D.C. level, a single pulse or a pulse train, depending on the particular application. For instance, if it were desired to use tube 30 (without nozzle 36) as a fluid control device to control the amount of fluid flowing therethrough, the current supplied to coil 38 should be a D.C. control signal; the required current determining the cross-sectional area of tube 30, and thus, the amount of fluid flowing therethrough. If it is desired to use tube 30 (with nozzle 36) as a fluid ejection device, the current supplied to coil 38 should be a pulse train or the like.
In response to the magnetic field flat member 32 expands laterally in the direction of span as curvilinear tube 30 contracts circumferentially thereby producing a geometric distortion in the cross-sectional area of curvilinear tube 30 and a corresponding reduction of the volume within curvilinear tube 30. As was noted above, the magnetostrictive effect is independent of the sense in which the magnetic field flows, and therefore, although the magnetic field is assumed to flow in the direction as indicated by arrows 33, the magnetostrictive effect would be the same if the sense of the magnetic field were reversed.
Nozzle 36, having orifice 39, is connected to end 31a of tube 30. End 31b of tube 30 is coupled to any suitable source of fluid, which may be under sufficient pressure, to supply fluid to tube 30 and to prevent fluid from flowing out of end 31b. Orifice 39 is relatively small compared with cross-sectional area 34 of tube 30. As cross-section area 34 is geometrically distorted in response to the magnetic field, thus reducing the volume of tube 30, a jet of fluid from tube 30 is ejected through orifice 39.
It will be appreciated that a nozzle (36) is not required to practice the invention and that the structure 29 of FIG. 3 without nozzle 36 has general application wherever it is desired to control the flow of fluid. Thus, by the application of a suitable control current to coil 38, the cross-sectional area of tube 30 and, thus, the volume thereof may be used to control the amount of fluid flowing through tube 30. As described above, the current applied to coil 38 may be either an A.C. type (a pulse or pulse train) or a D.C. type (a level) of signal depending on the application.
FIGURES OF MERIT OF THE PREFERRED EMBODIMENT
The fluid control device of FIG. 3, embodying the invention, has several significant advantages over prior art fluid control devices. As an example of the significant volumetric change produced within curvilinear tube 30 as cross-section 34 undergoes the geometric distortion according to the invention, consider the curvilinear tube 30 as having the following initial dimensions:
where c is the length of the major diameter of cross-section 34 or the width of lateral member 32, R is the radius of the circle of which each half of curvilinear cross-section 34 is an arcuate section, θ is the central angle of the circle of radius R defining the arcuate sections which form cross-section 34 and l is the length of the arcuate sections which form cross-section 34 subtended by central angle θ. Assuming that c increases by 30 ppm as l decreases by 30 ppm in response to the magnetic field indicated by arrows 33, the ratio of the change in the cross-sectional area to the original cross-sectional area, ΔA/A, can be shown to be 28.53 × 10 - 4 . The expression: ##EQU3## relates the change in the volume to the change in cross-sectional area of a magnetostrictive device of the type shown in FIG. 3 when subjected to a magnetic field comprising a lateral magnetic field and an azimuthal magnetic field. Utilizing expression (3), the ratio of the change in volume to the original volume of the magnetostrictive fluid control device of FIG. 3 having the initial dimensions and dimensional changes as given above is 28.44 × 10 - 4 (2844 ppm). The ratio of the change in volume to the original volume for the prior art magnetostrive structure of FIG. 1 is 12 × 10 - 6 (12 ppm). Thus, the magnetostrictive fluid control device of FIG. 3, embodying the invention, is capable it is believed, of developing a volumetric change as much as 237 times greater than the volumetric change produced by the prior art structure of FIG. 1.
It will be appreciated that, according to the invention, a curvilinear magnetostrictive tube with a flat magnetostrictive member spanning across and along the major axis of the tube will, when subjected to a magnetic field which increases the width of the flat member while simultaneously decreasing the length of arc spanned by the flat member, undergoes distortion resulting in a volumetric change which may be hundreds of times greater than that achievable in prior art structures.
As will now be described, the invention provides for a low reluctance magnetic path permitting the use of relatively low power energizing signals as compared to the relatively higher power energizing signals required by prior art structures. Further the invention provides for an eddy current path which results in a shorter response time than that of the prior art structures.
Thus, in order to appreciate the advantages of the present invention over the prior art, the following discussion of figures of merit for evaluating power requirements and response times of magnetostrictive fluid control devices will be helpful.
It can be shown that the inductance per unit turn of the energizing coil 12 of the prior art structure of FIG. 1, subjected to an axial magnetic field developed by the coil is given by the expression: ##EQU4## where P is the perimeter of tube 10, L is the length of tube 10, δ is the thickness of tube 10 and μ is the magnetic permeability of the material which forms tube 10. Similarly, it can be shown that the inductance per unit turn of energizing coil 26 of the structure of FIG. 3, subjected to an aximuthal magnetic field developed by the coil, is given by the expression: ##EQU5## where P is the perimeter of tube 30, L is the length of tube 30, δ is the thickness of tube 30 and μ is the magnetic permeability of the material which forms tube 30. If p, L, μ, and δ are the same for both tube 10 and tube 30, the ratio of the inductance of the structure of FIG. 3 to the prior art structure of FIG. 1 is given by the expression: ##EQU6## Therefore, according to expression (6), since L may be typically 5 to 10 times P, the inductance per unit turn of the structure of FIG. 3, embodying the invention may be a 100 times greater than the inductance per unit turn of the prior art structure of FIG. 1. Thus, because of this significant increase in the inductance per unit turn of the structure of FIG. 3 over the inductance per unit turn of the prior art structure of FIG. 1, the current requirements of the structure of FIG. 3 is significantly lower than that of the prior art structure of FIG. 1.
The response time of magnetostrictive structures is dependent, in part, as known, on the response time constants of the conduction paths through which eddy currents may flow. The time constant associated with eddy current paths may be determined by the equation: ##EQU7## where r e is the electrical resistance of the eddy current path and r m is the magnetic reluctance of the eddy current path. The electrical resistance, r e , and the magnetic reluctance, r m , of the prior art structure of FIG. 1 subjected to an axial magnetic field can be shown to be given respectively by the equations: ##EQU8## and ##EQU9## where σ is the electrical conductivity of tube 10 and all other symbols have the same meaning as in expression (4). Accordingly, the time constant for the structure of prior art FIG. 1 is given by the equation:
Similarly, the electrical resistance, r e , the magnetic reluctance, r m , and the time constant of the structure of FIG. 3 subjected to an azimuthal magnetic field can be respectively shown to be given the equations: ##EQU10## By comparing equation (12) to equation (9) it can be seen that the structure of FIG. 3, according to the invention, provides for a 4 to 1 reduction of the time constant over the prior art of FIG. 1.
STRUCTURAL CONSIDERATIONS OF THE PREFERRED EMBODIMENT From an examination of expression (5) it will be appreciated that the current required by the fluid control structure of FIG. 3 varies as the periphery P of cross-section 34 (since its inductance varies inversely as P). From an examination of expression 12 it will be further appreciated that the speed of response of the structure of FIG. 3 varies inversely as the square of the thickness of tube 30 (δ 2 ). Accordingly, it is preferable, wherever possible, to make the periphery of tube 30 as small and thin as possible.
Nevertheless, consideration should be given to insure that tube 30 is thick enough to withstand the strain developed when it is subjected to the pressure resulting from the fluid being compressed. For example, assuming that tube 30 is formed from nickel, which has a Youngs' modulus of ##EQU11## that the fluid contained within tube 30 is water, which has a bulk modulus of ##EQU12## and that the strain in the wall of tube 30 when constricted due to fluid pressure is selected to be equal to one-half the magnetostrictive strain and the remaining strain is used to create a fluid pressure of ##EQU13## the thickness of tube 30 can be shown to be related to the perimeter P of tube 30 by the ratio of the bulk modulus of water to Young's modulus according to the equation: ##EQU14## An examination of equation (13) demonstrates that the thickness of tube 30, under these conditions, should be greater or equal to ##EQU15## Consideration should also be given to assuring that flat member 32 is thick enough to withstand, without buckling, the forces exerted on it by the arcuate sections of tube 30.
Further consideration should be given to arranging the thickness and magnetic reluctance of flat member 32 in relation to the thickness and magnetic reluctance of the wall of tube 30 to assure that the lateral magnetic field induced in flat member 32 is readily coupled and circumferentially flows in the wall of tube 30.
USE OF THE PREFERRED EMBODIMENT IN VARIOUS FLUID INJECTION APPLICATIONS
Fluid jets of the type shown in FIG. 3 have a variety of uses. For instance, the fluid jet structure of FIG. 3 is particularly useful in an ink jet printing apparatus. In an ink jet printing apparatus, for example, the fluid jet of FIG. 3 may be readily supplied with ink from an ink reservoir and operated to impinge ink on a recording medium. In addition, fluid jets of the type shown in FIG. 3 are useful for applications such as fuel injection for internal combustion engines used in automobiles and the like. For example, an eight cylinder automobile requires 12,000 jets of 0.02 cc (cubic centimeters) per minute assuming that the automobile engine turns at 3,000 revolutions per minute while traveling at 60 miles per hour (1 mile per minute) and averages 15 miles per gallon. Therefore, the required volumetric change, ΔV, of the fluid jet structure of FIG. 3 would be 2 × 10 - 8 m 3 . This is achievable by providing the fluid jet of FIG. 3 to be approximately 4 inches long with a major diameter of approximately 1/2 inch. With these dimensions, a jet of fluid would be ejected approximately at a pressure of 953 psi (pounds per square inch).
OTHER EMBODIMENTS OF THE PRESENT INVENTION
FIG. 4 is a cross-sectional view taken in the same direction as the cutaway cross-sectional view of FIG. 3 illustrating another embodiment of the present invention. The fluid control device of FIG. 4 is formed of curvilinear magnetostrictive tube 40 similar to curvilinear tube 30 of FIG. 3 having a generally oval cross-section 42 and a cruciform member 44, comprising flat members 44a and 44b, which span both the minor (44b) and major (44a) diameters of generally oval cross-section 42. Magnetostrictive tube 40 is formed of a suitable magnetostrictive material such as nickel or a nickel-iron alloy and is adapted to contract circumferentially in response to an azimuthal magnetic field. Cruciform member 44 is formed from a suitable magnetostrictive material such as an iron-nickel alloy and is arranged to expand radially outwardly when subjected to a magnetic field directed along both the minor and major diameters of cross-section 42 in a manner as previously described. Cruciform member 44 provides rigidity to tube 40 and therefore tends to maintain the geometric integrity of cross-section 42. In an alternate embodiment only one of the lateral members (44a or 44b) may be formed of a magnetostrictive material while the other is formed of any suitable structural material such as metal or plastic.
Generally, elliptical cross-sectional 42 is divided into quadrants (48a through 48d) by cruciform member 44. Each quadrant subtends an arcuate section of cross-section 42. Each of these arcuate sections is an arcuate section of a suitable curvilinear shape such as a circle, ellipse, parabola or the like. Preferably the arcuate sections are of circular shape. In another embodiment, tube 40 may have a generally circular cross-section and cruciform member 44 may be formed of flat members of equal length.
Coil 46 is wound in the axial direction of tube 44 as is shown in FIG. 4. When current passes through coil 46, a magnetic field, indicated by arrows 43, comprising an azimuthal magnetic field, flowing circumferentially within tube 40, and lateral magnetic fields, flowing respectively along the major and minor axes of cross-section 42 within cruciform member 44, is generated. When the fluid control device of FIG. 4 is subjected to these magnetic fields, tube 40 contracts circumferentially, while the lateral members 44a and 44b forming cruciform member 42 expand radially outwardly producing a geometric distortion of the cross-sectional area of tube 40 in a manner similar to that as previously described.
The fluid control device of FIG. 4 may be adapted to form a fluid jet similar to the fluid jet of FIG. 3 by attaching a nozzle similar to nozzle 36 of FIG. 3 at one end of tube 40 and coupling the other end of tube 40 to a source of fluid under pressure adapted to supply fluid to tube 40.
In operation, fluid flows through or is contained within each quadrant of cross-section 42 depending on whether tube 40 is adapted to be used respectively as a fluid flow control device or a fluid jet. In either case, as cross-section 42 undergoes a geometric distortion in response to a suitable magnetic field, the volume within tube 40 is reduced. However, if tube 40 is adapted to be used as a fluid flow control device the reduced volume impedes the flow of fluid and the flow of fluid is thereby controlled. If, however, tube 40 is adapted to be used as a fluid jet the reduced volume causes a relatively high pressure to be developed in the fluid and a jet of fluid is thereby ejected from the orifice of the nozzle. If tube 40 is adapted to be used as a fluid flow control device, a D.C. type of signal is preferably applied to coil 46. If tube 40 is adapted to be used as a fluid jet an A.C. type of signal is preferably applied to coil 46.
It should be understood and appreciated that the volumetric changes achievable from the structure of FIG. 4 are not as large as those obtainable from the structure of FIG. 3. However, the structural strength of the structure of FIG. 4 provided by cruciform member 44 may be advantageous over the structure of FIG. 3 in applications requiring structural strength.
FIG. 5 is a cross-sectional view taken in the same direction as the cutaway cross-sectional view of FIG. 3 showing another embodiment of the present invention. The fluid control structure of FIG. 5, except for the absence of coil 38, is identical to the fluid control structure of FIG. 3. Tp provide the magnetic field which causes tube 30 to contract circumferentially while flat member 32 expands laterally, magnet 50 comprising a so-called north (N) pole 50b and a south (S) pole 50a are substituted for coil 38 of FIG. 3. North (50b) and south (50a) pole magnets may be formed using magnetic structure of any suitable form known in the art. The magnetic pole structure is preferably of the electromagnetic type, so that the fluid control structure of FIG. 5 may be selectively operated in accordance with an electrical control signal which is provided to operate a magnetic field, as indicated by arrows 52a and 52b, between pole pieces 50b and 50a.
The direction of the magnetic field is indicated by the arrows. It should again be noted that although the sense of the azimuthal magnetic field in tube 30 of FIG. 5 is opposite to that of the direction of the azimuthal magnetic field in tube 30 of FIG. 3, the magnetostrictive effect producing a geometric distortion of the cross-sectional area of tube 30 in FIG. 5 will be similar to the magnetostrictive effect producing a geometrical distortion of the cross-sectional area of tube 30 in FIG. 3. Thus, the operation of the structure of FIG. 5 to control fluid flow is similar to the operation of the structure of FIG. 3 as previously explained.
FIG. 6 is a cross-sectional view taken in a direction transverse to the direction of the cutaway cross-sectional view of FIG. 3 and shows an embodiment of the present invention useful as an ink jet device with a fluidic rectifier. Fluid jet 60 may comprise structures similar to the ones shown in FIGS. 3, 4, or 5 or modification of these structures according to the invention. The end 61 of fluid jet 60 opposite nozzle 36 communicates with reservoir 68 which serves to supply ink to tube 30 of fluid jet 60. Plate 62 is a part of chamber 69 which is provided to contain fluid around nozzle 36. Plate 62 is provided with orifice 64 through which fluid jets generated by jet 60 may be ejected out of chamber 69.
It should be appreciated by those skilled in the fluid jet art that fluid jets of the type that produce jets fluid or fluid drops by reciprocable pumping action are susceptable to the formation of air bubbles. Such air bubbles cause the jets to malfunction and limit the frequency at which these jets can be operated. That is, as fluid is ejected from the nozzle of the fluid jet, air tends to be drawn in through the nozzle of the jet due to the reciprocating action of the jet and is formed into air bubbles which tend to conjest the orifice and cause the jet to malfunction.
In FIG. 6, as ink is ejected from nozzle 36 and passes through orifice 64, the fluid surrounding nozzle 36 replaces the fluid evacuated by the fluid jet and prevents air from being drawn into orifice 39, thereby substantially preventing malfunction due to air bubbles. The fluid in outer chamber 69 maybe filtered and circulated to enhance the operation of the fluidic rectifier to remove particles and air bubbles, which may clog orifice 39. Although fluid jet 60 is shown in FIG. 6 as being connected to ink reservoir 68 so that ink ejected through orifice 64 from nozzle 36 may be replenished from reservoir 68, it should be appreciated that reservoir 68 may be eliminated since fluid jet may be suitably operated so that ink ejected from nozzle 36 may be replenished by aspiration through orifice 39 of nozzle 36 as tube 30 regains its original volume through relaxation of the magnetostrictive effects.
Although the above embodiments of the invention have been described having the form of magnetostrictive devices, it will be appreciated by those skilled in the art that other materials, such as piezoelectric materials, which can be adapted to expand and contract in response to electric fields may be used instead of or in conjunction with the magnetostrictive materials to form the fluid control and fluid jet devices according to the present invention.
As earlier mentioned, the signal applied to the bow-like and other members may be of other than electrical or magnetic nature. For example, the signal could be mechanical and effective to alter the lengths of the both members as those members are observed at cross-sections taken through the previously described chamber and bow-like members along the length of the chambers.
Further, in the embodiments of the invention shown in FIGS. 3-6, there has been shown a second member (32 in FIG. 3, 44a in FIG. 4, etc.) which is formed of flat material and which extends directly and coextensively with the chord delineated by spaced-apart points on the bow-like member, as such chords are viewed in cross-sections taken along the lengths of the chambers within the respective devices of the figures. It is to be realized that this second member need not be flat and need not coincide with the above-mentioned chords. Instead, the second member might, for example, have average radius of curvature smaller than the average radius of curvature of the bow-like member. Under such conditions, the second member could be disposed (a) with the ends of a cross-section taken therethrough in coincidence with the above-mentioned spaced points on the bow-like member cross-section and (b) with respect to the bow-like member so that the inward-facing surfaces of the members (which form a fluid containing chamber) define, in cross-section, a crescent shape.
1. Field of the Invention
This invention pertains to the field of fluid flow control devices and particularly pertains to fluid ejection devices. One embodiment of the invention is particularly useful in the field of ink jet printing apparatus.
2. Description of the Prior Art
Fluid flow control devices are known in the prior art having the form of a tubular member through which fluid flows. The amount of fluid flowing through the tubular member is controlled by providing means to alter the cross-sectional area of the tube. Some of such fluid flow control devices are adapted to eject jets of fluid or fluid drops by placing a nozzle having a relatively small orifice at one end of the tube, closing off the other end of the tube to the flow of fluid and subjecting the tube to sharp volumetric changes in response to a control signal.
These prior art devices have taken a variety of forms. One such form includes a tube surrounded by a piezoelectric material adapted to contract the tube radially inwardly, in response to an electrical control signal, and thereby decrease the volume of the tube. Another form includes a tube formed from a magnetostrictive material and adapted to contract axially, in response to an axial magnetic field, and thereby decrease the volume of the tube.
The properties of magnetostrictive materials and the operation of magnetostrictive structures are well known in the art. For instance, it is well known that certain ferromagnetic metals and alloys, such as nickel and nickel-iron alloys, contract in the direction of a magnetic field induced in the metal regardless of the polarity of the magnetic field; whereas, certain other ferromagnetic metals and alloys, such as iron and iron-nickel alloys, expand in the direction of a magnetic field induced in the metal regardless of the polarity of the magnetic field. For a more detailed description of the magnetostrictive properties of metals see, for example, "Magnetostriction Transducers," a handbook published by the International Nickel Company in July, 1968.
Typical examples of prior art magnetostrictive fluid control devices may be found in U.S. Pat. No. 2,317,166, issued to R. Abrams on Apr. 20, 1943, and U.S. Pat. No. 3,334,350 issued to R. A. Adams on Aug. 1, 1967. In each of the Abrams and Adams patents there is shown a magnetostrictive fluid control device including a magnetostrictive cylindrical member about which is wound an electrical coil. The ends of the cylindrical member are adapted to prevent substantial amounts of fluid from flowing through the cylindrical member. An orifice is provided in one end of the cyclindrical member to allow fluid under pressure to be ejected from the cylindrical member. The cylindrical member is adapted to contract axially in response to an axial magnetic field. When a control current manifesting control information is applied to the coil an axial magnetic field is induced in the cylindrical member. In response to this induced magnetic field the cylindrical member axially contracts resulting in a decrease of volume within the cylindrical member and a corresponding increase in the pressure acting on the fluid and causing thereby the ejection of fluid. The Abrams patent also discloses placing another magnetostrictive structure, having a similar shape to the above described cylindrical member and adapted to expand axially, concentrically within the cylindrical member and channeling the fluid between these cylindrical members to form a fluid flow control device.
In fluid control applications generally large volume displacements are desired. The type of magnetostrictive structures adapted to contract axially produce high pressure but low volume displacements. In addition, magnetostrictive structures of the type described above have inefficient magnetic field paths requiring undesirably large amounts of drive signal power. Further, the magnetostrictive structures adapted to respond to axial magnetic fields have relatively short eddy current paths which result in undesirable long time responses to the drive signal. Accordingly, there is a need for a magnetostrictive fluid control device which makes efficient usage of the magnetostrictive effect to produce significant volumetric displacements while requiring only relatively low drive signal power and responding to such a drive signal in relatively short response times.
There are known magnetostrictive devices useful in producing vibrations in various fluid mediums for applications such as sonar and the like. Of particular interest are magnetostrictive structures having tubular shaped adapted to produce radially directed waves in response to oscillatory radial contractions and expansions of the tubular structure established by oscillatory circumferential (azimuthal) magnetic fields induced in the tubular structure. One such structure is shown in FIG. 7 of "Magnetostriction Transducers" referred to above. Heretofore the principles of this magnetostrictive art have not been utilized in the fluid control art.
SUMMARY OF THE INVENTION
In accordance with the invention, a tube-like chamber for fluid, including an output port, is provided, which is operable in response to a control signal to control the flow of fluid out of the chamber through the output port. The chamber is formed of two members of dissimilar materials. In cross-section, the first member, has a bow-like shape which is preferably arcuate. The second member spans the first member so that, in cross-section, the second member spans a chord of the first member. In response to the control signal, the bow-like shape is contracted in length, while the chord is expanded in length thereby producing a geometric distortion of the cross-section of the chamber resulting in a significant reduction in area defined by the bow-like shape and the chord.
As a result of this geometric distortion, the volume enclosed by the chamber is substantially reduced. The flow of fluid through the output port is thereby controlled.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is an isometric view of a prior art magnetostrictive fluid control device.
FIG. 2 is an isometric view of a prior art magnetostrictive vibration device useful in sonar applications and the like.
FIG. 3 is an isometric view in partial cross-section, of the preferred embodiment of the invention useful as a fluid jet device.
FIG. 4 is a cross-sectional view taken in the direction of the cross-section of FIG. 3 showing another embodiment of the invention.
FIG. 5 is a cross-sectional view taken in the direction of the cross-section of FIG. 3 showing still another embodiment of the invention.
FIG. 6 is a cross-sectional view taken in a direction transverse to the direction of the cutaway cross-sectional view of FIG. 3 showing another embodiment of the invention providing a fluidic rectifier useful in an ink jet printing apparatus.
In the following description, the same reference numbers in different figures refer to the same or similar elements.
DESCRIPTION OF THE PRIOR ART (FIGS. 1 and 2)
Preliminary to a detailed description of the preferred embodiment of the invention, the prior art briefly described in the Prior Art portion of the present specification will be described in detail.
FIG. 1 is an isometric view of a magnetostrictive prior art device used to control the flow of fluids being typical of the devices disclosed in the Abrams and Adams patents cited above. The prior art structure of FIG. 1 is formed of a cylindrical tube 10 about which is wound electrical helical coil 12. Cylindrical tube 10 is formed from a magnetostrictive material such as nickel, a nickel-iron alloy, cobalt or a cobalt-iron alloy which contracts axially when subjected to the axial magnetic field created by coil 12. Thus, when current flows through coil 12, an axial magnetic field is generated which acting on cylindrical tube 10 contracts it axially. It is to be noted, as previously stated, that the magnetostrictive effect when a magnetostrive material is subjected to a magnetic field is independent of the polarity or sense of the magnetic field. For example, cylindrical tube 10 will contract axially in response to an axial magnetic field whether the magnetic field is directed in the direction of arrow 17 or arrow 19. Therefore, when current is made to flow through coil 12, in either a positive or negative sense, cylindrical tube 10 contracts axially, that is, in height L. As cylindrical tube 10 contracts axially, its volume is reduced since its height is reduced.
The structure of FIG. 1 may be modified to form a fluid jet device if one end of cylindrical tube 10 is effectively closed to the flow of fluid and nozzle 13 or like structure is placed at the other end of cylindrical tube 10. In this modified structure forming a fluid jet, a rejection in the volume of the tube 10 causes the pressure within tube 10 to increase. The increased pressure within tube 10 results in the ejection of a jet fluid from nozzle 13.
The expression for the volumetric change within cylindrical tube 10 when subjected to an axial magnetic field may be shown to be: ##EQU1## where V is the original volume within cylindrical tube 10, ΔV is the change in volume within cylindrical tube 10 when cylindrical tube 10 is subjected to an axial magnetic field, L is equal to the original length of cylindrical tube 10, ΔL is equal to the change in length of cylindrical tube 10 when circular tube 10 is subjected to a magnetic field and σ p is Poisson's ratio for the magnetostrictive material which forms cylindrical tube 10 and is assumed to be approximately equal to 0.3. Thus, according to expression (1), if the length of cylindrical tube 10 is decreased by 30 ppm (parts per million) the volume of cylindrical tube 10 is decreased 12 ppm. This rather small volumetric change may be better appreciated by realizing that a 30 ppm decrease in length, is accompanied by a 9 ppm increase in the perimeter of cylindrical tube 10 which is counter-productive to the volumetric decrease. That is, while the height of the cylinder decreases, resulting in a decreased volume, the cross-sectional area of the tube increases, tending to oppose the decreased volume.
The performance of the prior art structure of FIG. 1 (typically Abram U.S. Pat. No. 2,317,166) may be enhanced by inserting a smaller diameter and shorter magnetostrictive cylindrical tube 16, closed at both ends which expands axially when subjected to an axial magnetic field, coaxially within magnetostrictive cylindrical tube 10 as is shown in phantom in FIG. 1. When this modified structure of FIG. 1 including cylindrical tube 16 is subjected to an axial magnetic field, the volume between cylindrical tubes 10 and 16 is decreased as cylindrical tube 16 expands lengthwise and cylindrical tube 10 constricts thereby subjecting fluid 14 to a relatively high pressure increase.
FIG. 2 is an isometric view of a magnetostrictive prior art device useful in sonar applications and the like. The prior art device of FIG. 2 is similar to the device shown in FIG. 7 of the "Magnetostrictive Transducers" handbook cited above. The prior art device of FIG. 2 is formed of cylindrical tube 20 and planar magnetic core 22. Cylindrical tube 20 is formed of a suitable magnetostrictive material, such as nickel or a nickel-iron alloy, so that the curcumference of tube 20 decreases to contract radially in response to an azimuthal, or circumferential magnetic field, i.e., a magnetic field (indicated by arrows 24a and 24b) directed circumferentially through the cylindrical wall of tube 20. Thus, circular tube 20 is formed of a magnetostrictive material such that when circular tube 20 is subjected to a circumferential magnetic field the circumference of circular tube 20 contracts and thereby each point along the circumference is moved radially inwardly, that is, in effect, circular tube 20 contracts radially inwardly. Core 22 is formed of a suitable material, laminated or unlaminated, in which a magnetic field may be readily induced and is wound with electrical coil 26 whose axis is transverse to the longitudinal axis of cylindrical tube 20. When current flows through coil 26, a magnetic field (indicated by arrows 24a) is induced in core 22 which is magnetically coupled through air gap 23 to the cylindrical wall of tube 20 to induce an azimuthal magnetic filed indicated by arrows 24b in the cylindrical wall of tube 20. The azimuthal magnetic field induced in the cylindrical wall of tube 20 cause cylindrical tube 20 to vibrate radially.
In sonar applications circular tube 20 is immersed in water (preferably with the inner portion of the cylinder sealed off from the water). Coil 26 is periodically energized to cause cylindrical tube 20 to vibrate radially thereby generating radially directed sonar waves.
The expression: ##EQU2## can be shown to represent the volumetric change within circular tube 20 when circular tube 20 is subjected to an azimuthal magnetic field, where V is the original volume within cylindrical tube 20, ΔV is the volumetric change within cylindrical tube 20 when cylindrical tube 20 is subjected to an azimuthal magnetic field, P is the original periphery of cylindrical tube 20, ΔP is the change in periphery of cylindrical tube 20 when cylindrical tube 20 is subjected to an azimuthal magnetic field and σ p is Poisson's ratio for the magnetostrictive material forming cylindrical tube 20 and is assumed to be equal approximately to 0.3. According to expression (2), if the periphery of cylindrical tube 20 is caused to decrease 30 ppm the resultant volumetric decrease, ΔV, is equal to 51 ppm. This relatively significant volumetric decrease in comparison to the 12 ppm volumetric decrease of the prior art structure of FIG. 1 may be appreciated by noting that the change in the cross-sectional area of cylindrical tube 20 varies as the periphery squared. Thus, an azimuthal magnetic field acting on a cylindrical magnetostrictive tube produces approximately a 4 1/4 times greater volumetric change than does an axial magnetic field acting on a cylindrical tube of the same dimension.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT (FIG. 3)
FIG. 3 is an isometric view of the preferred embodiment of the present invention being a fluid jet device useful in generating jets of fluid. FIG. 3 includes a cross-sectional view taken in the direction of the longitudinal axis of the fluid jet structure to show the cross-section of the fluid jet structure. The fluid jet structure of FIG. 3 is particularly useful in applications such as ink jet printing, fuel injection or the like. The fluid jet device of FIG. 3 is formed of a tube 30 having curvilinear cross-section 34 formed by two bow-like shaped sections 34a and 34b, a flat or planar member 32, disposed along the axis of tube 30 and spanning opposite wall portions of tube 30 along the major diameter of the curvilinear cross-section 34 thereby forming a chord of the two bow-like shaped sections (34a and 34b) and nozzle 36, joined to tube 30 at intersection 37 between tube 30 and nozzle 36. Flat member 32 divides tube 30 into two chambers or passageways 35a and 35b for fluid each having a cross-sectional area enclosed by a bow-like shaped section and the chord spanning the bow-like shaped section. The bow-like shaped sections are preferably arcuate in shape.
Tube 30 is formed from any suitable magnetostrictive material, such as nickel or a nickel-iron alloy, selected so that the arcuate section contracts circumferentially in length in response to an azimuthal magnetic field passing circumferentially through curvilinear cross-section 34. Thus, tube 30 is formed of a magnetostrictive material such that when tube 30 is subjected to a circumferential magnetic field the circumference of tube 30 contracts and thereby points along the circumference are moved radially inwardly that is, in effect, tube 30 contracts radially inwardly. The arcuate sections may be of any suitable curvilinear shape, such as circular, elliptical, parabolic, hyperbolic or the like. In a preferred form of the invention the arcuate sections are arcs of circles whose diameters are greater than the major diameter of cross-section 34.
Flat member 32, spanning the major diameter of cross-section 34 is formed from any suitable magnetostrictive material, such as iron or an iron-nickel alloy selected so that the straight line section expands laterally in length in the direction of the span of chord-like member 32 in response to a lateral magnetic field directed along the major diameter of cross-section 34.
Coil 38, wound around flat member 32 in the direction of the axis of tube 30, is provided to generate the magnetic field indicated by arrows 33. Although only one winding of coil 38 is shown for simplicity, it will be appreciated that coil 38 may include any suitable number of windings. In one form of the preferred embodiment, coil 38 is a printed circuit attached to lateral member 32.
Flat member 32 is suitably connected to opposite wall portions of cross-section 34 to create a highly efficient magnetic path for a magnetic field generated in response to a current flowing through coil 38. When a current flows through coil 38, a magnetic field, indicated by arrows 33, is generated. The magnetic field comprises a lateral magnetic field flowing in the direction of span within flat member 32, and an azimuthal magnetic field flowing circumferentially within curvilinear tube 34.
The control signal current may be of any suitable type, such as a D.C. level, a single pulse or a pulse train, depending on the particular application. For instance, if it were desired to use tube 30 (without nozzle 36) as a fluid control device to control the amount of fluid flowing therethrough, the current supplied to coil 38 should be a D.C. control signal; the required current determining the cross-sectional area of tube 30, and thus, the amount of fluid flowing therethrough. If it is desired to use tube 30 (with nozzle 36) as a fluid ejection device, the current supplied to coil 38 should be a pulse train or the like.
In response to the magnetic field flat member 32 expands laterally in the direction of span as curvilinear tube 30 contracts circumferentially thereby producing a geometric distortion in the cross-sectional area of curvilinear tube 30 and a corresponding reduction of the volume within curvilinear tube 30. As was noted above, the magnetostrictive effect is independent of the sense in which the magnetic field flows, and therefore, although the magnetic field is assumed to flow in the direction as indicated by arrows 33, the magnetostrictive effect would be the same if the sense of the magnetic field were reversed.
Nozzle 36, having orifice 39, is connected to end 31a of tube 30. End 31b of tube 30 is coupled to any suitable source of fluid, which may be under sufficient pressure, to supply fluid to tube 30 and to prevent fluid from flowing out of end 31b. Orifice 39 is relatively small compared with cross-sectional area 34 of tube 30. As cross-section area 34 is geometrically distorted in response to the magnetic field, thus reducing the volume of tube 30, a jet of fluid from tube 30 is ejected through orifice 39.
It will be appreciated that a nozzle (36) is not required to practice the invention and that the structure 29 of FIG. 3 without nozzle 36 has general application wherever it is desired to control the flow of fluid. Thus, by the application of a suitable control current to coil 38, the cross-sectional area of tube 30 and, thus, the volume thereof may be used to control the amount of fluid flowing through tube 30. As described above, the current applied to coil 38 may be either an A.C. type (a pulse or pulse train) or a D.C. type (a level) of signal depending on the application.
FIGURES OF MERIT OF THE PREFERRED EMBODIMENT
The fluid control device of FIG. 3, embodying the invention, has several significant advantages over prior art fluid control devices. As an example of the significant volumetric change produced within curvilinear tube 30 as cross-section 34 undergoes the geometric distortion according to the invention, consider the curvilinear tube 30 as having the following initial dimensions:
where c is the length of the major diameter of cross-section 34 or the width of lateral member 32, R is the radius of the circle of which each half of curvilinear cross-section 34 is an arcuate section, θ is the central angle of the circle of radius R defining the arcuate sections which form cross-section 34 and l is the length of the arcuate sections which form cross-section 34 subtended by central angle θ. Assuming that c increases by 30 ppm as l decreases by 30 ppm in response to the magnetic field indicated by arrows 33, the ratio of the change in the cross-sectional area to the original cross-sectional area, ΔA/A, can be shown to be 28.53 × 10 - 4 . The expression: ##EQU3## relates the change in the volume to the change in cross-sectional area of a magnetostrictive device of the type shown in FIG. 3 when subjected to a magnetic field comprising a lateral magnetic field and an azimuthal magnetic field. Utilizing expression (3), the ratio of the change in volume to the original volume of the magnetostrictive fluid control device of FIG. 3 having the initial dimensions and dimensional changes as given above is 28.44 × 10 - 4 (2844 ppm). The ratio of the change in volume to the original volume for the prior art magnetostrive structure of FIG. 1 is 12 × 10 - 6 (12 ppm). Thus, the magnetostrictive fluid control device of FIG. 3, embodying the invention, is capable it is believed, of developing a volumetric change as much as 237 times greater than the volumetric change produced by the prior art structure of FIG. 1.
It will be appreciated that, according to the invention, a curvilinear magnetostrictive tube with a flat magnetostrictive member spanning across and along the major axis of the tube will, when subjected to a magnetic field which increases the width of the flat member while simultaneously decreasing the length of arc spanned by the flat member, undergoes distortion resulting in a volumetric change which may be hundreds of times greater than that achievable in prior art structures.
As will now be described, the invention provides for a low reluctance magnetic path permitting the use of relatively low power energizing signals as compared to the relatively higher power energizing signals required by prior art structures. Further the invention provides for an eddy current path which results in a shorter response time than that of the prior art structures.
Thus, in order to appreciate the advantages of the present invention over the prior art, the following discussion of figures of merit for evaluating power requirements and response times of magnetostrictive fluid control devices will be helpful.
It can be shown that the inductance per unit turn of the energizing coil 12 of the prior art structure of FIG. 1, subjected to an axial magnetic field developed by the coil is given by the expression: ##EQU4## where P is the perimeter of tube 10, L is the length of tube 10, δ is the thickness of tube 10 and μ is the magnetic permeability of the material which forms tube 10. Similarly, it can be shown that the inductance per unit turn of energizing coil 26 of the structure of FIG. 3, subjected to an aximuthal magnetic field developed by the coil, is given by the expression: ##EQU5## where P is the perimeter of tube 30, L is the length of tube 30, δ is the thickness of tube 30 and μ is the magnetic permeability of the material which forms tube 30. If p, L, μ, and δ are the same for both tube 10 and tube 30, the ratio of the inductance of the structure of FIG. 3 to the prior art structure of FIG. 1 is given by the expression: ##EQU6## Therefore, according to expression (6), since L may be typically 5 to 10 times P, the inductance per unit turn of the structure of FIG. 3, embodying the invention may be a 100 times greater than the inductance per unit turn of the prior art structure of FIG. 1. Thus, because of this significant increase in the inductance per unit turn of the structure of FIG. 3 over the inductance per unit turn of the prior art structure of FIG. 1, the current requirements of the structure of FIG. 3 is significantly lower than that of the prior art structure of FIG. 1.
The response time of magnetostrictive structures is dependent, in part, as known, on the response time constants of the conduction paths through which eddy currents may flow. The time constant associated with eddy current paths may be determined by the equation: ##EQU7## where r e is the electrical resistance of the eddy current path and r m is the magnetic reluctance of the eddy current path. The electrical resistance, r e , and the magnetic reluctance, r m , of the prior art structure of FIG. 1 subjected to an axial magnetic field can be shown to be given respectively by the equations: ##EQU8## and ##EQU9## where σ is the electrical conductivity of tube 10 and all other symbols have the same meaning as in expression (4). Accordingly, the time constant for the structure of prior art FIG. 1 is given by the equation:
Similarly, the electrical resistance, r e , the magnetic reluctance, r m , and the time constant of the structure of FIG. 3 subjected to an azimuthal magnetic field can be respectively shown to be given the equations: ##EQU10## By comparing equation (12) to equation (9) it can be seen that the structure of FIG. 3, according to the invention, provides for a 4 to 1 reduction of the time constant over the prior art of FIG. 1.
STRUCTURAL CONSIDERATIONS OF THE PREFERRED EMBODIMENT From an examination of expression (5) it will be appreciated that the current required by the fluid control structure of FIG. 3 varies as the periphery P of cross-section 34 (since its inductance varies inversely as P). From an examination of expression 12 it will be further appreciated that the speed of response of the structure of FIG. 3 varies inversely as the square of the thickness of tube 30 (δ 2 ). Accordingly, it is preferable, wherever possible, to make the periphery of tube 30 as small and thin as possible.
Nevertheless, consideration should be given to insure that tube 30 is thick enough to withstand the strain developed when it is subjected to the pressure resulting from the fluid being compressed. For example, assuming that tube 30 is formed from nickel, which has a Youngs' modulus of ##EQU11## that the fluid contained within tube 30 is water, which has a bulk modulus of ##EQU12## and that the strain in the wall of tube 30 when constricted due to fluid pressure is selected to be equal to one-half the magnetostrictive strain and the remaining strain is used to create a fluid pressure of ##EQU13## the thickness of tube 30 can be shown to be related to the perimeter P of tube 30 by the ratio of the bulk modulus of water to Young's modulus according to the equation: ##EQU14## An examination of equation (13) demonstrates that the thickness of tube 30, under these conditions, should be greater or equal to ##EQU15## Consideration should also be given to assuring that flat member 32 is thick enough to withstand, without buckling, the forces exerted on it by the arcuate sections of tube 30.
Further consideration should be given to arranging the thickness and magnetic reluctance of flat member 32 in relation to the thickness and magnetic reluctance of the wall of tube 30 to assure that the lateral magnetic field induced in flat member 32 is readily coupled and circumferentially flows in the wall of tube 30.
USE OF THE PREFERRED EMBODIMENT IN VARIOUS FLUID INJECTION APPLICATIONS
Fluid jets of the type shown in FIG. 3 have a variety of uses. For instance, the fluid jet structure of FIG. 3 is particularly useful in an ink jet printing apparatus. In an ink jet printing apparatus, for example, the fluid jet of FIG. 3 may be readily supplied with ink from an ink reservoir and operated to impinge ink on a recording medium. In addition, fluid jets of the type shown in FIG. 3 are useful for applications such as fuel injection for internal combustion engines used in automobiles and the like. For example, an eight cylinder automobile requires 12,000 jets of 0.02 cc (cubic centimeters) per minute assuming that the automobile engine turns at 3,000 revolutions per minute while traveling at 60 miles per hour (1 mile per minute) and averages 15 miles per gallon. Therefore, the required volumetric change, ΔV, of the fluid jet structure of FIG. 3 would be 2 × 10 - 8 m 3 . This is achievable by providing the fluid jet of FIG. 3 to be approximately 4 inches long with a major diameter of approximately 1/2 inch. With these dimensions, a jet of fluid would be ejected approximately at a pressure of 953 psi (pounds per square inch).
OTHER EMBODIMENTS OF THE PRESENT INVENTION
FIG. 4 is a cross-sectional view taken in the same direction as the cutaway cross-sectional view of FIG. 3 illustrating another embodiment of the present invention. The fluid control device of FIG. 4 is formed of curvilinear magnetostrictive tube 40 similar to curvilinear tube 30 of FIG. 3 having a generally oval cross-section 42 and a cruciform member 44, comprising flat members 44a and 44b, which span both the minor (44b) and major (44a) diameters of generally oval cross-section 42. Magnetostrictive tube 40 is formed of a suitable magnetostrictive material such as nickel or a nickel-iron alloy and is adapted to contract circumferentially in response to an azimuthal magnetic field. Cruciform member 44 is formed from a suitable magnetostrictive material such as an iron-nickel alloy and is arranged to expand radially outwardly when subjected to a magnetic field directed along both the minor and major diameters of cross-section 42 in a manner as previously described. Cruciform member 44 provides rigidity to tube 40 and therefore tends to maintain the geometric integrity of cross-section 42. In an alternate embodiment only one of the lateral members (44a or 44b) may be formed of a magnetostrictive material while the other is formed of any suitable structural material such as metal or plastic.
Generally, elliptical cross-sectional 42 is divided into quadrants (48a through 48d) by cruciform member 44. Each quadrant subtends an arcuate section of cross-section 42. Each of these arcuate sections is an arcuate section of a suitable curvilinear shape such as a circle, ellipse, parabola or the like. Preferably the arcuate sections are of circular shape. In another embodiment, tube 40 may have a generally circular cross-section and cruciform member 44 may be formed of flat members of equal length.
Coil 46 is wound in the axial direction of tube 44 as is shown in FIG. 4. When current passes through coil 46, a magnetic field, indicated by arrows 43, comprising an azimuthal magnetic field, flowing circumferentially within tube 40, and lateral magnetic fields, flowing respectively along the major and minor axes of cross-section 42 within cruciform member 44, is generated. When the fluid control device of FIG. 4 is subjected to these magnetic fields, tube 40 contracts circumferentially, while the lateral members 44a and 44b forming cruciform member 42 expand radially outwardly producing a geometric distortion of the cross-sectional area of tube 40 in a manner similar to that as previously described.
The fluid control device of FIG. 4 may be adapted to form a fluid jet similar to the fluid jet of FIG. 3 by attaching a nozzle similar to nozzle 36 of FIG. 3 at one end of tube 40 and coupling the other end of tube 40 to a source of fluid under pressure adapted to supply fluid to tube 40.
In operation, fluid flows through or is contained within each quadrant of cross-section 42 depending on whether tube 40 is adapted to be used respectively as a fluid flow control device or a fluid jet. In either case, as cross-section 42 undergoes a geometric distortion in response to a suitable magnetic field, the volume within tube 40 is reduced. However, if tube 40 is adapted to be used as a fluid flow control device the reduced volume impedes the flow of fluid and the flow of fluid is thereby controlled. If, however, tube 40 is adapted to be used as a fluid jet the reduced volume causes a relatively high pressure to be developed in the fluid and a jet of fluid is thereby ejected from the orifice of the nozzle. If tube 40 is adapted to be used as a fluid flow control device, a D.C. type of signal is preferably applied to coil 46. If tube 40 is adapted to be used as a fluid jet an A.C. type of signal is preferably applied to coil 46.
It should be understood and appreciated that the volumetric changes achievable from the structure of FIG. 4 are not as large as those obtainable from the structure of FIG. 3. However, the structural strength of the structure of FIG. 4 provided by cruciform member 44 may be advantageous over the structure of FIG. 3 in applications requiring structural strength.
FIG. 5 is a cross-sectional view taken in the same direction as the cutaway cross-sectional view of FIG. 3 showing another embodiment of the present invention. The fluid control structure of FIG. 5, except for the absence of coil 38, is identical to the fluid control structure of FIG. 3. Tp provide the magnetic field which causes tube 30 to contract circumferentially while flat member 32 expands laterally, magnet 50 comprising a so-called north (N) pole 50b and a south (S) pole 50a are substituted for coil 38 of FIG. 3. North (50b) and south (50a) pole magnets may be formed using magnetic structure of any suitable form known in the art. The magnetic pole structure is preferably of the electromagnetic type, so that the fluid control structure of FIG. 5 may be selectively operated in accordance with an electrical control signal which is provided to operate a magnetic field, as indicated by arrows 52a and 52b, between pole pieces 50b and 50a.
The direction of the magnetic field is indicated by the arrows. It should again be noted that although the sense of the azimuthal magnetic field in tube 30 of FIG. 5 is opposite to that of the direction of the azimuthal magnetic field in tube 30 of FIG. 3, the magnetostrictive effect producing a geometric distortion of the cross-sectional area of tube 30 in FIG. 5 will be similar to the magnetostrictive effect producing a geometrical distortion of the cross-sectional area of tube 30 in FIG. 3. Thus, the operation of the structure of FIG. 5 to control fluid flow is similar to the operation of the structure of FIG. 3 as previously explained.
FIG. 6 is a cross-sectional view taken in a direction transverse to the direction of the cutaway cross-sectional view of FIG. 3 and shows an embodiment of the present invention useful as an ink jet device with a fluidic rectifier. Fluid jet 60 may comprise structures similar to the ones shown in FIGS. 3, 4, or 5 or modification of these structures according to the invention. The end 61 of fluid jet 60 opposite nozzle 36 communicates with reservoir 68 which serves to supply ink to tube 30 of fluid jet 60. Plate 62 is a part of chamber 69 which is provided to contain fluid around nozzle 36. Plate 62 is provided with orifice 64 through which fluid jets generated by jet 60 may be ejected out of chamber 69.
It should be appreciated by those skilled in the fluid jet art that fluid jets of the type that produce jets fluid or fluid drops by reciprocable pumping action are susceptable to the formation of air bubbles. Such air bubbles cause the jets to malfunction and limit the frequency at which these jets can be operated. That is, as fluid is ejected from the nozzle of the fluid jet, air tends to be drawn in through the nozzle of the jet due to the reciprocating action of the jet and is formed into air bubbles which tend to conjest the orifice and cause the jet to malfunction.
In FIG. 6, as ink is ejected from nozzle 36 and passes through orifice 64, the fluid surrounding nozzle 36 replaces the fluid evacuated by the fluid jet and prevents air from being drawn into orifice 39, thereby substantially preventing malfunction due to air bubbles. The fluid in outer chamber 69 maybe filtered and circulated to enhance the operation of the fluidic rectifier to remove particles and air bubbles, which may clog orifice 39. Although fluid jet 60 is shown in FIG. 6 as being connected to ink reservoir 68 so that ink ejected through orifice 64 from nozzle 36 may be replenished from reservoir 68, it should be appreciated that reservoir 68 may be eliminated since fluid jet may be suitably operated so that ink ejected from nozzle 36 may be replenished by aspiration through orifice 39 of nozzle 36 as tube 30 regains its original volume through relaxation of the magnetostrictive effects.
Although the above embodiments of the invention have been described having the form of magnetostrictive devices, it will be appreciated by those skilled in the art that other materials, such as piezoelectric materials, which can be adapted to expand and contract in response to electric fields may be used instead of or in conjunction with the magnetostrictive materials to form the fluid control and fluid jet devices according to the present invention.
As earlier mentioned, the signal applied to the bow-like and other members may be of other than electrical or magnetic nature. For example, the signal could be mechanical and effective to alter the lengths of the both members as those members are observed at cross-sections taken through the previously described chamber and bow-like members along the length of the chambers.
Further, in the embodiments of the invention shown in FIGS. 3-6, there has been shown a second member (32 in FIG. 3, 44a in FIG. 4, etc.) which is formed of flat material and which extends directly and coextensively with the chord delineated by spaced-apart points on the bow-like member, as such chords are viewed in cross-sections taken along the lengths of the chambers within the respective devices of the figures. It is to be realized that this second member need not be flat and need not coincide with the above-mentioned chords. Instead, the second member might, for example, have average radius of curvature smaller than the average radius of curvature of the bow-like member. Under such conditions, the second member could be disposed (a) with the ends of a cross-section taken therethrough in coincidence with the above-mentioned spaced points on the bow-like member cross-section and (b) with respect to the bow-like member so that the inward-facing surfaces of the members (which form a fluid containing chamber) define, in cross-section, a crescent shape.