FLOW REGULATING DEVICE
United States Patent 3722858
A flow regulating valve for hydraulic systems including a housing having inlet and outlet ports and a port crossing bore, a sleeve mounted in the bore of the housing and provided with a first opening communicating with the inlet port and a second opening on the opposite side communicating with the outlet port, the walls of the second opening forming knife edges at the inner surface of the sleeve and sloping outwardly to the outer surface of the sleeve, a throttle spool mounted in the sleeve and provided with a cavity of decreasing size communicating at its larger end with the first opening of the sleeve and at its smaller end with the second opening of the sleeve, and means for relatively moving said sleeve and throttle spool to adjust the size of a sharp-edged orifice defined by overlap of the smaller end of the cavity with the second opening of the sleeve.
US Patent References:
Flow regulator
Tremmel - April 1938 - 2115675
Regulating valve for liquids and gases
Gabriel - August 1927 - 1638152
/1141276.html
Smith - June 1915 - 1141276
Backwash and regeneration valve for water conditioning system
Gressman et al. - January 1967 - 3298396
Valve
Long - August 1951 - 2564223
Flow regulator
Tremmel - April 1938 - 2115675
Regulating valve for liquids and gases
Gabriel - August 1927 - 1638152
/1141276.html
Smith - June 1915 - 1141276
Backwash and regeneration valve for water conditioning system
Gressman et al. - January 1967 - 3298396
Valve
Long - August 1951 - 2564223
Inventors:
Sugimoto, Masashi (Nagoya, JA)
Moriyama, Yoshiki (Okazaki, JA)
Moriyama, Yoshiki (Okazaki, JA)
Application Number:
05/098311
Publication Date:
03/27/1973
Filing Date:
12/15/1970
View Patent Images:
Export Citation:
Assignee:
Norio, Nomura (Anjo-shi, JA)
Primary Class:
Other Classes:
251/212, 251/175
International Classes:
F15B21/04; F16K5/04; F16K5/10; F15B21/00; F16K5/00; F16K5/10; F16K5/18
Field of Search:
251/209,208,175,212 137/625.3
Primary Examiner:
Rosenthal, Arnold
Claims:
What is claimed is
1. A flow regulating valve for pressure fluid systems, comprising a housing having inlet and outlet ports and a bore crossing said ports, a sleeve mounted in said bore and provided with a first opening in one side communicating with said inlet port and a triangular opening in the opposite side communicating with said outlet port, said triangular opening having tapered walls sloping outwardly toward the outlet port and terminating in knife edges at the inner surface of the sleeve, a throttle spool mounted movably in the bore of said sleeve and having a cavity of decreasing size passing through the spool for communicating at its larger end with said inlet port and said first opening of the sleeve, and at its reduced end with said outlet port and said triangular opening of the sleeve, said cavity terminating in its reduced end in a hole of circular shape, and means for relatively moving said throttle spool and sleeve with respect to one another to form a sharp-edged orifice of adjustable size defined by the overlap of said circular hole at the reduced end of said cavity with said triangular opening of the sleeve, said throttle spool being urged toward the outlet port side of the sleeve by fluid pressure acting essentially on said cavity of the throttle spool.
2. A flow regulating valve according to claim 1, wherein said bore of said housing is cylindrical, said sleeve being also cylindrical with a cylindrical bore therein, said throttle spool being a cylinder, and said means for relatively moving said sleeve and throttle spool comprises means for rotating one with respect to the other.
3. A flow regulating valve as set forth in claim 1, wherein said sleeve is fixed unmovably within said housing and said throttle spool is movable within said bore of said sleeve.
4. A flow regulating valve according to claim 1, wherein said circular hole at the reduced end of the throttle cavity is defined by a knife edge.
5. A flow regulating valve according to claim 4, wherein said cavity of said throttle spool is cylindrical for a major portion of its volume and decreases in size for a minor portion of its volume terminating in said circular hole, the knife edge of said circular hole being formed by an annular slope tapering inwardly toward said outlet port of the housing.
1. A flow regulating valve for pressure fluid systems, comprising a housing having inlet and outlet ports and a bore crossing said ports, a sleeve mounted in said bore and provided with a first opening in one side communicating with said inlet port and a triangular opening in the opposite side communicating with said outlet port, said triangular opening having tapered walls sloping outwardly toward the outlet port and terminating in knife edges at the inner surface of the sleeve, a throttle spool mounted movably in the bore of said sleeve and having a cavity of decreasing size passing through the spool for communicating at its larger end with said inlet port and said first opening of the sleeve, and at its reduced end with said outlet port and said triangular opening of the sleeve, said cavity terminating in its reduced end in a hole of circular shape, and means for relatively moving said throttle spool and sleeve with respect to one another to form a sharp-edged orifice of adjustable size defined by the overlap of said circular hole at the reduced end of said cavity with said triangular opening of the sleeve, said throttle spool being urged toward the outlet port side of the sleeve by fluid pressure acting essentially on said cavity of the throttle spool.
2. A flow regulating valve according to claim 1, wherein said bore of said housing is cylindrical, said sleeve being also cylindrical with a cylindrical bore therein, said throttle spool being a cylinder, and said means for relatively moving said sleeve and throttle spool comprises means for rotating one with respect to the other.
3. A flow regulating valve as set forth in claim 1, wherein said sleeve is fixed unmovably within said housing and said throttle spool is movable within said bore of said sleeve.
4. A flow regulating valve according to claim 1, wherein said circular hole at the reduced end of the throttle cavity is defined by a knife edge.
5. A flow regulating valve according to claim 4, wherein said cavity of said throttle spool is cylindrical for a major portion of its volume and decreases in size for a minor portion of its volume terminating in said circular hole, the knife edge of said circular hole being formed by an annular slope tapering inwardly toward said outlet port of the housing.
Description:
BACKGROUND OF THE INVENTION
1. FIELD OF THE INVENTION
The present invention relates to a flow regulating valve for use in pressure fluid, or hydraulic systems, such as hydraulically operated apparatus, machine tools, and the like, and more particularly to a flow regulating valve which is capable of maintaining a constant flow at a uniform rate regardless of changes of viscosity of the operating fluid by changes of ambient temperature.
2. DESCRIPTION OF THE PRIOR ART
Hydraulic systems for apparatus and machine tools of recent design have been reduced in dimension, and these require small diameter, high pressure, hydraulic actuators and flow regulating valves capable of controlling precisely very small flow rates of operating fluid, regardless of changes in ambient temperature.
In the prior art, a flow regulating valve has been introduced which tries to meet the above requirements, and which comprises two hollow cylinders coaxially coupled to each other tightly, but slidably, or rotatably. One of the cylinders is provided with an opening in the circumference, the opening being a curved triangle forming an isoceles triangle when the cylinder surface is developed into a plane. Each side of the triangular opening terminates as a knife edge. The other cylinder has an oblong opening on the circumference and each side of the oblong is also knife edged. When the two hollow cylinders are rotated with respect to each other, the triangular and oblong openings overlap to form an orifice having its complete outline bounded by a sharp edge, the rate of flow of the pressure fluid being controlled by changes in the size of this sharp-edged orifice.
The conventional flow regulating valve briefly described above, however, has a drawback in that there is considerable leakage of operating fluid from portions of the device other than the sharp-edged orifice, said other portions including the circumferential space extending from the sharp-edged orifice between the two hollow cylinders. Moreover, the amount of leakage is greatly affected by changes in the rate of flow of the operating fluid through the sharp-edged orifice. It is very difficult to precisely control flow rates of the operating fluid because of the leakage, particularly when a very low flow rate of the fluid to be passed is determined by a small opening of the sharp-edged orifice.
A FURTHER DISADVANTAGE OF THE ABOVE-DESCRIBED CONVENTIONAL FLOW REGULATING VALVE IS THAT THE OPENING IN ONE CYLINDER IS FORMED WITH KNIFE EDGES AT THE BASES OF SLOPING WALLS WHICH ARE TAPERED WIDER TOWARD THE INLET PORT SIDE. Consequently, the slopes of the knife edge walls become the main wetted perimeters in controlling low flow rates of the operating fluid. This increases the undesirable effect of changing the flow due to the viscosity of the operating fluid moving along the knife edge slops, and prevents precise control of low rates of flow of pressure fluid through the valve.
SUMMARY OF THE INVENTION
The present invention provides a flow regulating valve which is capable of maintaining a substantially precisely regulated flow rate regardless of changes in viscosity of the pressure fluid caused by changes of ambient temperature, and regardless of high, or low, rates of flow of the pressure fluid. The valve embodies a housing having inlet and outlet ports, a hollow sleeve within the housing and having openings in communication with said ports, and a throttle spool mounted within the sleeve and provided with a cavity of decreasing size communicating at its larger end with the inlet opening of the sleeve, and at its smaller end with the outlet opening of the sleeve, so that relative movement of the sleeve and throttle spool serves to adjust the size of a sharp-edged orifice defined by the overlap of the reduced end of the cavity of the spool with the outlet opening of the sleeve. With this construction, the defects and disadvantages of the above described conventional valve are overcome, and precise regulation of the flow of the pressure fluid is attained.
A first important object of the invention is, therefore, to provide a flow regulating valve which is capable of minimizing the leakage of operating fluid from portions of the valve other than its sharp-edged orifice, so that a substantially constant and precisely regulated pressure fluid flow is obtained with good temperature compensating effect, and regardless of changes of ambient temperature, and even at very low rate of flow of the pressure fluid through the device.
It is a second important object of the invention to provide a flow regulating valve, having the above mentioned characteristics, wherein the effect of the viscosity of the operating fluid, flowing along the wetted perimeters of the sharp-edge orifice, or changes of such viscosity, is much lessened, or minimized, in controlling the rate of flow of the pressure fluid through the valve.
Another important object of the invention is to provide a flow regulating valve, having the above mentioned characteristics, wherein adjustment of the flow of the operating fluid can easily be accomplished and wherein no re-adjustment is required due to changes in viscosity of the pressure fluid.
A still further object of the invention is to provide a flow regulating valve, having the above described characteristics, whose construction is much simplified and thereby the cost of fabrication is greatly lowered, while the efficiency of operation is considerably increased.
BRIEF DESCRIPTION OF THE DRAWING
The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, wherein like reference characters indicate like parts throughout the several Figures, and in which:
FIG. 1 is a central vertical section of a preferred embodiment of the present invention;
FIG. 2 is a fragmentary, enlarged, sectional view of the embodiment shown in FIG. 1;
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1, and looking in the direction of the arrows;
FIG. 4 is a perspective view of the throttle spool forming the core of the regulator shown in FIG. 1;
FIG. 5 is a perspective view of the sleeve which surrounds the throttle spool of FIG. 4;
FIG. 6 depicts a cross-sectional view corresponding to FIG. 3, but with the throttle spool turned so that the sharp-edged orifice defined by the throttle spool and sleeve has the smallest opening thereof;
FIG. 7 is a fragmentary perspective view to an enlarged scale of the sharp-edged orifice corresponding with the condition shown in FIG. 6; and
FIG. 8 is a cross-sectional view corresponding to FIG. 3, but with the throttle spool turned so that the sharp-edged orifice defined by the spool and sleeve has the largest opening thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, and more Particularly to FIGS. 1 - 3, the regulating valve, according to the present invention, comprises a housing 1 provided with an inlet port A at the upper side, an outlet port B at the lower side, and a stepped cylindrical bore 2 communicating with the inlet and outlet ports. A sleeve 3, of pipe-shape, is mounted within the bore 2 of the housing and fixedly secured by a key 5. The sleeve has an axial bore 4, and as best shown in FIG. 5, a collar 3a at one end, a round hole 6 which opens to inlet port A of the housing through one side, and a triangular opening 7 cut through the wall of the sleeve, at the side opposite the round hole 6, so as to communicate with the outlet port B of the housing. All three sides 8 of the triangular opening 7 taper inwardly from the outer surface to the inner surface of the sleeve 3 to form knife edges at the inner surface of the sleeve, as best shown in FIG. 7.
A solid, cylindrical throttle spool 9, which is best shown in FIG. 4, is rotatably engaged within the axial bore 4 of the sleeve 3. The throttle spool is provided with a small diameter portion 10 at one end, a cylindrical cavity 11 with a spherical end portion passing from one side toward the other, and a circular hole 12 tapering inwardly from the spherical end portion of cavity 11 to form a knife edge opening 13 at said other side of the spool. The pressure plate 14, having a hole 15 concentric with the axis of the throttle spool, is secured on the housing 1 to fix the axial positions of the sleeve 3 and the throttle spool 9. An adjusting dial 17 is secured by a pin 16 to the small diameter portion 10 of the throttle spool 9, said Small diameter portion 10 jutting out of the housing 1 through the hole 15 of the pressure plate 14.
The tapered hole 12, of the spool 9, and the triangular opening 7, of the sleeve 3, overlap, as seen in FIG. 7, to form a sharp-edged orifice R, whose size is adjustable by turning the throttle spool by means of the dial 17. Unnumbered O-rings are provided, as shown in FIG. 1, to seal the throttle spool to the sleeve and the sleeve to the housing so as to prevent leakage of pressure fluid therefrom and restrict the flow of pressure fluid to the ports, openings and orifices mentioned above. The ports and orifices in the housing, sleeve and throttle spool are so designed as to have the sleeve 3 and the throttle spool 9 urged toward the outlet port B of the housing 1 by pressure fluid delivered into the cavity 11 from the Inlet port A.
The above described regulator operates in the following manner. Pressure fluid delivered to the inlet port A, of the housing, flows into the round hole 6 of the sleeve 3, and into the cavity 11, of the throttle spool 9. The pressure fluid is finally discharged through the outlet port B of the housing after the quantity per unit time, or rate of flow, is reduced by the hole 12 tapering inwardly from the spherical cavity at the bottom end of cavity 11 into the knife edge opening 13, and the sharp-edged orifice R, defined by overlap of opening 13 with the triangular knife-edged hole 7 in the sleeve 3. The quantity of pressure fluid discharged from the outlet port B in a given unit of time is controlled by rotation of the adjusting dial 17 to change the size of the orifice R. The pressure fluid urges the sleeve 3 and the throttle spool 9 toward the outlet port B, and at the outlet port B side, the spaces between the cylindrical bore 2 of the housing and the outer surface of the sleeve 3, and between the bore 4 of the sleeve 3 and the throttle spool 9 become very small to minimize possible leakage from places other than the sharp-edged orifice R.
The sloping sides 8, of the triangular opening 7, which terminate in knife edges, form the major wetted perimetrical edges along whose lengths the pressure fluid contacts the orifice R. Since these walls 8 taper, or widen toward the outlet port B, the effect of the viscosity of the pressure fluid on the rate of flOw through the device is minimized. Similarly, the effect of the viscosity of the pressure fluid in controlling the rate of flOw while the pressure fluid moves along the tapered sidewall of the hole 22 in the throttle spool, is also very small since the wetted perimeter of this tapered hole and its knife edge 13 is very small in area. Consequently, very precise adjustment can be made to the rate of flow of the pressure fluid even when such rate is extremely small, as for example, between 30cc. and 100cc. per minute.
FIG. 7 depicts the position of the various parts and the size of the sharp-edged orifice R when a very small rate of flow of the pressure fluid, as from 30cc. - 100cc. per minute, passes out through outlet port B.
FIG. 8 depicts the size of the sharp-edged orifice R when it is largest and the flow rate Of the pressure fluid is greatest. It is obvious that in discharging pressure fluid at a maximum rate, the same precise adjustment as for low flow rate is obtainable since the effects of viscosity and of leakage, from places other than through the sharp-edged orifice R, are smaller, the sleeve 3 and the throttle spool 9 being urged with greater force toward the outlet port B, as shown in FIG. 8
Although a certain specific embodiment of the invention has been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not intended to be restricted to the exact showing of the drawing and description thereof, but is considered to include reasonable and obvious equivalents.
1. FIELD OF THE INVENTION
The present invention relates to a flow regulating valve for use in pressure fluid, or hydraulic systems, such as hydraulically operated apparatus, machine tools, and the like, and more particularly to a flow regulating valve which is capable of maintaining a constant flow at a uniform rate regardless of changes of viscosity of the operating fluid by changes of ambient temperature.
2. DESCRIPTION OF THE PRIOR ART
Hydraulic systems for apparatus and machine tools of recent design have been reduced in dimension, and these require small diameter, high pressure, hydraulic actuators and flow regulating valves capable of controlling precisely very small flow rates of operating fluid, regardless of changes in ambient temperature.
In the prior art, a flow regulating valve has been introduced which tries to meet the above requirements, and which comprises two hollow cylinders coaxially coupled to each other tightly, but slidably, or rotatably. One of the cylinders is provided with an opening in the circumference, the opening being a curved triangle forming an isoceles triangle when the cylinder surface is developed into a plane. Each side of the triangular opening terminates as a knife edge. The other cylinder has an oblong opening on the circumference and each side of the oblong is also knife edged. When the two hollow cylinders are rotated with respect to each other, the triangular and oblong openings overlap to form an orifice having its complete outline bounded by a sharp edge, the rate of flow of the pressure fluid being controlled by changes in the size of this sharp-edged orifice.
The conventional flow regulating valve briefly described above, however, has a drawback in that there is considerable leakage of operating fluid from portions of the device other than the sharp-edged orifice, said other portions including the circumferential space extending from the sharp-edged orifice between the two hollow cylinders. Moreover, the amount of leakage is greatly affected by changes in the rate of flow of the operating fluid through the sharp-edged orifice. It is very difficult to precisely control flow rates of the operating fluid because of the leakage, particularly when a very low flow rate of the fluid to be passed is determined by a small opening of the sharp-edged orifice.
A FURTHER DISADVANTAGE OF THE ABOVE-DESCRIBED CONVENTIONAL FLOW REGULATING VALVE IS THAT THE OPENING IN ONE CYLINDER IS FORMED WITH KNIFE EDGES AT THE BASES OF SLOPING WALLS WHICH ARE TAPERED WIDER TOWARD THE INLET PORT SIDE. Consequently, the slopes of the knife edge walls become the main wetted perimeters in controlling low flow rates of the operating fluid. This increases the undesirable effect of changing the flow due to the viscosity of the operating fluid moving along the knife edge slops, and prevents precise control of low rates of flow of pressure fluid through the valve.
SUMMARY OF THE INVENTION
The present invention provides a flow regulating valve which is capable of maintaining a substantially precisely regulated flow rate regardless of changes in viscosity of the pressure fluid caused by changes of ambient temperature, and regardless of high, or low, rates of flow of the pressure fluid. The valve embodies a housing having inlet and outlet ports, a hollow sleeve within the housing and having openings in communication with said ports, and a throttle spool mounted within the sleeve and provided with a cavity of decreasing size communicating at its larger end with the inlet opening of the sleeve, and at its smaller end with the outlet opening of the sleeve, so that relative movement of the sleeve and throttle spool serves to adjust the size of a sharp-edged orifice defined by the overlap of the reduced end of the cavity of the spool with the outlet opening of the sleeve. With this construction, the defects and disadvantages of the above described conventional valve are overcome, and precise regulation of the flow of the pressure fluid is attained.
A first important object of the invention is, therefore, to provide a flow regulating valve which is capable of minimizing the leakage of operating fluid from portions of the valve other than its sharp-edged orifice, so that a substantially constant and precisely regulated pressure fluid flow is obtained with good temperature compensating effect, and regardless of changes of ambient temperature, and even at very low rate of flow of the pressure fluid through the device.
It is a second important object of the invention to provide a flow regulating valve, having the above mentioned characteristics, wherein the effect of the viscosity of the operating fluid, flowing along the wetted perimeters of the sharp-edge orifice, or changes of such viscosity, is much lessened, or minimized, in controlling the rate of flow of the pressure fluid through the valve.
Another important object of the invention is to provide a flow regulating valve, having the above mentioned characteristics, wherein adjustment of the flow of the operating fluid can easily be accomplished and wherein no re-adjustment is required due to changes in viscosity of the pressure fluid.
A still further object of the invention is to provide a flow regulating valve, having the above described characteristics, whose construction is much simplified and thereby the cost of fabrication is greatly lowered, while the efficiency of operation is considerably increased.
BRIEF DESCRIPTION OF THE DRAWING
The novel features that are considered characteristic of the invention are set forth with particularity in the appended claims. The invention, itself, however, both as to its organization and its method of operation, together with additional objects and advantages thereof, will best be understood from the following description of a specific embodiment when read in connection with the accompanying drawing, wherein like reference characters indicate like parts throughout the several Figures, and in which:
FIG. 1 is a central vertical section of a preferred embodiment of the present invention;
FIG. 2 is a fragmentary, enlarged, sectional view of the embodiment shown in FIG. 1;
FIG. 3 is a cross-sectional view taken along line 3--3 of FIG. 1, and looking in the direction of the arrows;
FIG. 4 is a perspective view of the throttle spool forming the core of the regulator shown in FIG. 1;
FIG. 5 is a perspective view of the sleeve which surrounds the throttle spool of FIG. 4;
FIG. 6 depicts a cross-sectional view corresponding to FIG. 3, but with the throttle spool turned so that the sharp-edged orifice defined by the throttle spool and sleeve has the smallest opening thereof;
FIG. 7 is a fragmentary perspective view to an enlarged scale of the sharp-edged orifice corresponding with the condition shown in FIG. 6; and
FIG. 8 is a cross-sectional view corresponding to FIG. 3, but with the throttle spool turned so that the sharp-edged orifice defined by the spool and sleeve has the largest opening thereof.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawing, and more Particularly to FIGS. 1 - 3, the regulating valve, according to the present invention, comprises a housing 1 provided with an inlet port A at the upper side, an outlet port B at the lower side, and a stepped cylindrical bore 2 communicating with the inlet and outlet ports. A sleeve 3, of pipe-shape, is mounted within the bore 2 of the housing and fixedly secured by a key 5. The sleeve has an axial bore 4, and as best shown in FIG. 5, a collar 3a at one end, a round hole 6 which opens to inlet port A of the housing through one side, and a triangular opening 7 cut through the wall of the sleeve, at the side opposite the round hole 6, so as to communicate with the outlet port B of the housing. All three sides 8 of the triangular opening 7 taper inwardly from the outer surface to the inner surface of the sleeve 3 to form knife edges at the inner surface of the sleeve, as best shown in FIG. 7.
A solid, cylindrical throttle spool 9, which is best shown in FIG. 4, is rotatably engaged within the axial bore 4 of the sleeve 3. The throttle spool is provided with a small diameter portion 10 at one end, a cylindrical cavity 11 with a spherical end portion passing from one side toward the other, and a circular hole 12 tapering inwardly from the spherical end portion of cavity 11 to form a knife edge opening 13 at said other side of the spool. The pressure plate 14, having a hole 15 concentric with the axis of the throttle spool, is secured on the housing 1 to fix the axial positions of the sleeve 3 and the throttle spool 9. An adjusting dial 17 is secured by a pin 16 to the small diameter portion 10 of the throttle spool 9, said Small diameter portion 10 jutting out of the housing 1 through the hole 15 of the pressure plate 14.
The tapered hole 12, of the spool 9, and the triangular opening 7, of the sleeve 3, overlap, as seen in FIG. 7, to form a sharp-edged orifice R, whose size is adjustable by turning the throttle spool by means of the dial 17. Unnumbered O-rings are provided, as shown in FIG. 1, to seal the throttle spool to the sleeve and the sleeve to the housing so as to prevent leakage of pressure fluid therefrom and restrict the flow of pressure fluid to the ports, openings and orifices mentioned above. The ports and orifices in the housing, sleeve and throttle spool are so designed as to have the sleeve 3 and the throttle spool 9 urged toward the outlet port B of the housing 1 by pressure fluid delivered into the cavity 11 from the Inlet port A.
The above described regulator operates in the following manner. Pressure fluid delivered to the inlet port A, of the housing, flows into the round hole 6 of the sleeve 3, and into the cavity 11, of the throttle spool 9. The pressure fluid is finally discharged through the outlet port B of the housing after the quantity per unit time, or rate of flow, is reduced by the hole 12 tapering inwardly from the spherical cavity at the bottom end of cavity 11 into the knife edge opening 13, and the sharp-edged orifice R, defined by overlap of opening 13 with the triangular knife-edged hole 7 in the sleeve 3. The quantity of pressure fluid discharged from the outlet port B in a given unit of time is controlled by rotation of the adjusting dial 17 to change the size of the orifice R. The pressure fluid urges the sleeve 3 and the throttle spool 9 toward the outlet port B, and at the outlet port B side, the spaces between the cylindrical bore 2 of the housing and the outer surface of the sleeve 3, and between the bore 4 of the sleeve 3 and the throttle spool 9 become very small to minimize possible leakage from places other than the sharp-edged orifice R.
The sloping sides 8, of the triangular opening 7, which terminate in knife edges, form the major wetted perimetrical edges along whose lengths the pressure fluid contacts the orifice R. Since these walls 8 taper, or widen toward the outlet port B, the effect of the viscosity of the pressure fluid on the rate of flOw through the device is minimized. Similarly, the effect of the viscosity of the pressure fluid in controlling the rate of flOw while the pressure fluid moves along the tapered sidewall of the hole 22 in the throttle spool, is also very small since the wetted perimeter of this tapered hole and its knife edge 13 is very small in area. Consequently, very precise adjustment can be made to the rate of flow of the pressure fluid even when such rate is extremely small, as for example, between 30cc. and 100cc. per minute.
FIG. 7 depicts the position of the various parts and the size of the sharp-edged orifice R when a very small rate of flow of the pressure fluid, as from 30cc. - 100cc. per minute, passes out through outlet port B.
FIG. 8 depicts the size of the sharp-edged orifice R when it is largest and the flow rate Of the pressure fluid is greatest. It is obvious that in discharging pressure fluid at a maximum rate, the same precise adjustment as for low flow rate is obtainable since the effects of viscosity and of leakage, from places other than through the sharp-edged orifice R, are smaller, the sleeve 3 and the throttle spool 9 being urged with greater force toward the outlet port B, as shown in FIG. 8
Although a certain specific embodiment of the invention has been shown and described, it is obvious that many modifications thereof are possible. The invention, therefore, is not intended to be restricted to the exact showing of the drawing and description thereof, but is considered to include reasonable and obvious equivalents.