Title:
Quill drive miniature roots blower
Kind Code:
A1


Abstract:
A multi-lobe, or Roots, blower has two multi-lobe rotors connected for rotation to two drive gears one of which drive gears is connected for rotation to a motor by a quill drive spanning one of the rotors. In sequence, the multi-lobe rotors are preferably within a first chamber of a monolithic housing, the drive gears within a second chamber, and the motor outside the housing. In the quill drive a central shaft is affixed at one end to a shaft of the motor, and at its other end to a hollow tubular shaft containing the central shaft. The tubular shaft affixes at its exterior both one of the two drive gears and one of the two multi-lobe rotors. The quill drive thus transmits torque from the shaft of the motor along the central shaft completely through the first chamber and a multi-lobe rotor therein until, ultimately affixing the tubular shaft and the drive gear within the second chamber, the drive gears and the rotors are caused to be rotated. The quill drive Roots blower so constructed is smooth in operation, insensitive to external vibrations and shock, economical and durable.



Inventors:
Adams, Craig (Medford, OR, US)
Application Number:
09/962673
Publication Date:
03/27/2003
Filing Date:
09/26/2001
Assignee:
ADAMS CRAIG
Primary Class:
Other Classes:
418/206.1, 418/200
International Classes:
F04C18/12; F04C23/00; F04C29/00; (IPC1-7): F04C18/18
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Primary Examiner:
TRIEU, THERESA
Attorney, Agent or Firm:
William C. Fuess (San Diego, CA, US)
Claims:

What is claimed is:



1. A multi-lobe blower comprising: a quill drive.

2. The multi-lobe blower according to claim 1 further comprising: a plurality of multi-lobe rotors; connected for rotation to an associated plurality of drive gears; at least one of which drive gears is connected for rotation to a motor; wherein the quill drive spans one of the plurality of multi-lobe rotors.

3. The multi-lobe blower according to claim 2 further comprising: a housing defining two chambers; wherein the plurality of multi-lobe rotors are within one chamber of the housing; wherein the plurality of drive gears are within the other chamber of the housing.

4. The multi-lobe blower according to claim 3 wherein the motor is outside the housing.

5. The multi-lobe blower according to claim 4 further comprising: a shaft connecting a multi-lobe rotor within one chamber of the housing to a drive gear within the other chamber of the housing.

6. The multi-lobe blower according to claim 5 wherein the motor has a shaft and the quill drive comprises: a quill drive central shaft; affixed at its one end to the shaft of the motor and affixed at its other end to a quill drive hollow tubular shaft containing the central shaft and mounting at its exterior both one of the plurality of drive gears and one of the plurality of multi-lobe rotors; wherein the quill drive transmits torque from the shaft of the motor along the quill drive central shaft to the quill drive tubular shaft affixed thereto, and then to that one of the drive gears and to that one of the multi-lobe rotors mounted to this tubular shaft.

7. The multi-lobe blower according to claim 6 wherein the plurality of drive gears are intermeshing; and wherein, by the intermeshing of the plurality of drive gears, that one drive gear driven by the quill drive tubular shaft does drive the other drive gear and then the multi-lobe rotor associated with this other drive gear.

8. A Roots blower comprising: a housing defining at least one chamber: two Roots rotors located within the at least one chamber; mounted on two rotor shafts at least one of which rotor shafts is tubular; a motor, having a motor shaft, located outside the housing's at least one chamber to one side thereof; two intermeshing drive gears, located outside the housing's at least one chamber to the other side thereof, with one drive gear mounted to an exterior of the at least one rotor shaft that is tubular and the other drive gear mounted to the remaining rotor shaft; a quill drive shaft connecting to the motor shaft of the motor at one side of the housing's at least one chamber, and proceeding through the at least one rotor shaft that is tubular, and also through the Roots rotor and the drive gear that are mounted to this at least one rotor shaft that is tubular, and also through the housing's at least one chamber, until, outside the housing's at least one chamber at the opposite side thereof, connecting at its tip to the drive gear mounted upon at least one rotor shaft that is tubular.

9. The Roots blower according to claim 8 wherein the housing defines at least two chambers in one of which chambers are located the two Roots rotors and in another of which chambers are located the two intermeshing drive gears.

10. The Roots blower according to claim 8 further comprising: bearings in the housing at the sides of the at least one chamber supporting both the two rotor shafts at both sides of the Roots blower rotors mounted to the two rotor shafts.

11. The Roots blower according to claim 8 wherein the quill drive shaft is of a quadrilateral cross section.

12. The Roots blower according to claim 11 wherein the quill drive shaft is of square cross section.

13. The Roots blower according to claim 8 wherein the quill drive shaft is tapered from relatively greater thickness at the connected motor shaft to relatively lessor thickness at the connected drive gear.

14. The Roots blower according to claim 6 further comprising: a clamp mounting the motor to the housing.

15. A multi-lobe blower comprising: a motor; a housing affixing at a one side the motor, and defining two chambers; multi-lobe rotors rotationally mounted within a first chamber of the housing that is closest to the affixed motor; intermeshing drive gears, rotationally mounted within the remaining second chamber of the housing, respectively rotationally affixing the multi-lobe rotors; and a quill drive between the motor and a connected one of the intermeshing drive gears; wherein the motor rotates the quill drive to rotate the quill-drive-connected one of the intermeshing drive gears to therein rotate all intermeshing drive gears and those multi-lobe rotors to which the drive gears are rotationally affixed.

16. The multi-lobe blower according to claim 15 comprising: a sheet metal cover plate to the second chamber of the housing in an “L” contour so as to also serve as mounting plate for the entire multi-lobe blower.

17. To a method of rotating multi-lobe rotors in a multi-lobe blower by first-connecting these rotors for rotation to associated drive gears, intermeshing the drive gears for co-rotation, second-connecting for rotation at least one of the intermeshing drive gears to a shaft of a motor, and energizing the motor so as to rotate its shaft, the improvement wherein the second-connecting comprises: spanning with a quill drive one of the multi-lobe rotors.

Description:

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention generally concerns (i) Roots blowers and pumps, especially as may be only some few centimeters or tens of centimeters in size, and (ii) quill drives.

[0003] The present invention particularly concerns a Roots blower, or pump, with a quill drive which quill drive permits (i) rotating Roots blower rotors to be contained within a chamber, to one side of which chamber is (ii) a motor powering the Roots blower, and to the other side of which chamber are (iii) drive gears affixed to shafts, or quills, which are in turn affixed to the rotating Roots blower rotors.

[0004] 2. Description of the Prior Art

[0005] 2.1 Miniature Roots Blower

[0006] The Roots blower, named for its inventor, dates from the 19th century. Roots blowers are most typically constructed at great, multi-meter, size for moving gases, most commonly air, in stationary industrial applications.

[0007] Roots blowers can however be made, and are fully operative, at much smaller—multiple centimeter and tens of centimeter—sizes. An example of such a small Roots blower is shown in U.S. Pat. No. 6,031,610 for a MULTI-LOBE PUMP FOR PARTICLE COUNTERS to the same inventor as is the present invention. The miniature roots blower of that patent, possessed of tolerances particularly suiting its use in moving a gas stream through a particle counter, has a typical construction insofar as the multi-lobe, or Roots blower, rotors within a chamber are next connected via drive shafts to drive gears located outside the chamber, with at least one drive gear being next connected, still on the same side of the chamber, to a drive motor.

[0008] This conventional sequence and layout of (1) rotors (within a chamber), next-connecting via drive shafts to (2) gears, next-connected to (3) a motor, has proven to be susceptible of producing vibration and noise, and of accruing considerable wear upon its bearings.

[0009] Next, a miniature Roots blower is itself susceptible to vibration and shock—should such be encountered—in a manner that large, earth-mounted, Roots blowers are not. The rotors of a Roots blower are most typically of considerable size, weight and mass relative to the blower as a whole. If an entire Roots blower not mounted to the earth—as in the case of a portable instrument such as a particle counter—is externally subjected to vibration or shock then the large (relative to the overall size of the Roots blower) Roots rotors can place considerable stress on their bearings.

[0010] Next, this conventional sequence and layout of parts in a Roots blower is susceptible to misalignment of the motor. Consider that the driven element—the Roots rotors—are separated from the drive motor by the width of the drive gears, making that alignment is difficult, and that wear and vibration result from any misalignment.

[0011] Next, the dis-assembly of the conventional design (miniature) Roots blower of the subject patent in order to lubricate or replace components—such as bearings and/or seals—is difficult.

[0012] Finally, all walls of the housing of the previous (miniature) Roots blower must, and are, constructed at such precision tolerances as are necessary for the precision alignment of rotating components.

[0013] Especially if built with necessary precision and quality for continuous operation at high speed, the MULTI-LOBE PUMP of the previous patent is, despite its modest size, not inexpensive, and typically costs several hundreds of dollars U.S. circa 2001.

[0014] 2.2 A Quill Drive

[0015] The present invention will be seen to employ a quill drive, an existing type of rotary drive the nature of which will become clear. A quill drive is (i) good for transmitting torque over some distance, (ii) tolerant of misalignment, (iii) poorly contributory to vibration, and (iv) tolerant of such vibration and shock as may otherwise exist in the environment of use.

[0016] Quill drives have been used in diverse applications. The only previous application of a quill drive in the area of gas handling known to the inventor is the use of quill drive in the supercharger of an Offenhauser racing engine used in the “Nobi” Indianapolis-type racing car circa 1948. This supercharger was, however, of the centrifugal type, and was accordingly of entirely different construction that are those vane-type superchargers that are most analogous to the Roots blower of the present invention. Additionally, even should a quill drive be found in use to deliver power from (i) a driven drive belt of an internal combustion engine to (ii) the gears of a supercharger, such use would unlikely show such re-arrangement of parts as will later be found to be integral to the use of a quill drive in combination with a roots blower in accordance with the present invention.

[0017] 2.2.1 A Railway Locomotive Quill Drive

[0018] An explanation of a quill drive for railway locomotives is found, circa 2001, on the Internet at <http://www.lightnin-mixers.com/70-80.asp>.

[0019] It there explains that a quill drive uses a mechanical analog of a quill, described in the dictionary as, “the hollow stem of a feather” and “a bobbin or spindle”, as well as a “feather” and, alternatively, what a porcupine has on its back.

[0020] In railway traction terms, a quill drive is where a hollow shaft is placed round the driving axle and the motor drives the quill rather than driving the axle as it does with a nose suspended drive. The quill itself is attached, at one end, to one of the wheels by means of rubber bushed links and, at the other end, to the gearwheel by similar links. The big advantage of such drives is that all the weight of the motor is carried in the bogie frame (so it is a frame mounted motor) instead of it being directly supported by the axle and therefore partially unsprung.

[0021] Various forms of quill drive have been used over the years. Older versions used radially mounted coil steel springs instead of rubber to connect the links to the wheels. Some have the motor mounted parallel with the axle. Others have the motor at a right angle to the axle, as in the UK Class 91 electric locomotives.

[0022] In German the quill is called “Hohlwelle” (hollow shaft).

[0023] Also on the World Wide Web circa 2001, the site <http://www.steamlocomotive.com/GG1/quill.html>describes power transmission in the Pennsylvania Railroad GG1 railroad locomotive by a quill drive.

[0024] The six driving axles of the GG1 were powered by twin traction motors through double-end quill drives. The motors were rated at 385 HP each, thus providing 770 HP per axle or a total of 4620 HP.

[0025] Each driving axle was surrounded by a rotating quill (a hollow tube) that was connected to two large gears, called bull gears, that were almost the same size as the drivers. They were centered on the axle, and connected, one on each end, to the quill. This quill and gear assembly looked like a large cable spool with the drive axle going through the spindle hole and it was almost as wide as the distance between the driving wheels.

[0026] The traction motors were double-ended having a shaft and pinion on each end. Two motors were bolted together and attached to a bearing assembly which allowed the motors to ride on the quill. The motors with their shafts were designed to fit on the quill in such a way as to allow the pinions to mesh with the bull gears.

[0027] 2.2.2 A Quill Drive Bulk Product Mixer

[0028] Another example of a quill drive appears in the LIGHTNIN Series 80 Mixers of LIGHTNIN, 135 Mt. Read Boulevard, Rochester, N.Y. 14611 U.S.A. employ a quill drive. These mixers are used for product mixing in processes with high fluid forces on the impellers, and/or long impeller shaft applications. In the mixers an exclusive hollow quill drive protects the gear train from severe shaft flexure.

[0029] These mixers are described, circa 2001, on the Internet at <http://www.lightnin-mixers.com/70-80.asp>.

[0030] 2.2.3 A Quill Drive Machine Tool

[0031] The use of a variable extension quill drive in a machine tool is described circa 2001 on the World Wide Web site of CNC Automation Inc., 13 Columbia Drive, Amherst, N. H. 03031, at <http://www.cncauto.com/knee1.htm>. The extension of the quill is called “knee travel”, and is extolled as permitting full use of the manual quill at all times. Tools are resettable to Z zero after tool changes by moving the quill to the top of the part and then locking the quill to maintain rigidity. An experienced machine may feel a cut, or dry-run parts before cutting metal, with just a lift of the quill.

[0032] Mounting motors on the quill permits the driving wheels and axle of the machine tool to move in reaction to track conditions without affecting the meshing of the pinions and gears. The traction motors turned the bull gears that reached into and turned the driving wheels. The bull gears and driving wheels were connected by a spider and spring cup arrangement.

SUMMARY OF THE INVENTION

[0033] The present invention contemplates a miniature roots blower having several design features variously directed to (i) reliable low-vibration operation, (ii) economical construction, and (iii) easy assembly, dis-assembly and repair.

[0034] The present invention particularly contemplates a multi-lobe, or Roots, blower, or pump, having a quill drive. The quill drive particularly permits that (i) a motor of the blower can be located be upon one side of a chamber containing rotating Roots blower rotors while (ii) drive gears mounted to shafts of the rotating Roots blower rotors can be located upon the other side of the chamber. This is, to the best knowledge of the inventor, a new construction: all previous Roots blowers have the motor and the drive gears on the same side of the Roots rotors.

[0035] The quill drive so permits this orientation and relationship of parts because a (ii) quill, or drive shaft (actually a drive shaft extension), of the motor passes through a center bore of (ii) one of the Roots blower rotors, this drive shaft then connecting at its tip to (iii) a tubular shaft, this tubular shaft first connecting to one of two intermeshing drive gears and then, as the tubular shaft extends in direction backwards towards the motor, further connecting to (iv) the selfsame Roots blower rotor through which the drive shaft did originally pass. This geometry—which is the essence of the use of quill drive in a multi-lobe, or Roots, blower in accordance with the present invention—will become increasingly clear upon reference to the drawings.

[0036] The orientation and relationship of parts realized by the quill drive particularly permits that (i) the two Roots blower rotors upon their tubular shafts may be well and easily supported upon closely and precisely located bearing surfaces—thereby enhancing operational smoothness of the blower. It permits that (ii) a motor of the Roots blower, located at some distance from the drive gears (namely, across the full width of the rotors) will enjoy superior tolerance to misalignment. It permits that (iii) overall construction of the Roots blower may be simplified by use of a single, dual-chambered, housing, and that his housing need have only simple, inexpensive and readily assembled and disassembled fittings.

[0037] Overall, a quill drive Roots blower in accordance with the present invention realizes superior compactness, smoothness and quietness in operation, durability and longevity, and economies of construction and repair.

[0038] 1. A Quill Drive

[0039] Primary among the design features according reliable operation to a (miniature) Roots blower in accordance with the present invention is that the driven elements—two Roots rotors located within a chamber—are mounted on two shafts—at least one of which shafts is tubular—that are supported (preferably on bearings) close to each side of each rotor. The Roots blower rotors are thus well and fully supported for rotation within their chamber, providing thus a partial basis of both (i) the enhanced operational smoothness, and, as a separate matter, (ii) the enhanced tolerance to external shock and vibration, of a Roots blower in accordance with the present invention. In simplest possible terms, the heavy and large Roots rotors are well supported.

[0040] It is of no advantage that either shaft affixing a Roots rotor should pass through one, first, side wall of the chamber containing the Roots rotors; accordingly, both shafts, preferably as are supported on bearings, preferably terminate in blind bores within this first side wall of the chamber. However, each shaft, preferably as is supported on yet another bearing, does pass through an opposite, second, side wall of the chamber where it then connects to a respective drive gear.

[0041] One of these drive gears is driven by a motor. In accordance with the present invention, this drive is by a quill drive transmitting rotational force from the motor to the driven drive gear. Unlike conventional construction, this drive motor is not immediately adjacent to the gear that is serves to drive, nor is it even located outside of Roots rotors' chamber at the camber's second side. Instead, the motor is located at the outside of the Roots rotors' chamber at the chamber's first side.

[0042] This is highly unusual: the drive motor is outside a first side of the chamber containing the Roots rotors; the drive gears outside the opposite, second, side of the same chamber. It may be wondered how the drive motor connects to the drive gears.

[0043] The mechanism by which the drive motor located outside the chamber at the chamber's second side serves to rotationally connect to drive a gear (the “driven dive gear”) located outside the chamber at the chamber's first side is a drive quill, or shaft. This drive quill, or shaft, passes down the (at least one) hollow tubular shaft, and through the central bore of one Roots rotor, without connecting to either the shaft or the rotor. Then, when the drive quill, or shaft, has exited the chamber at the chamber's second side it connects at its tip (by a drive bushing or the like) to the selfsame hollow shaft through which it has just passed.

[0044] This makes that the drive shaft serves rotate this hollow shaft, and a first drive gear and a first Roots rotor that are fixedly mounted to this hollow shaft. The first drive gear turns a second drive gear that is itself fixed to a second shaft (which shaft is normally also, but need not be, hollow); to which second shaft is also affixed the second Roots rotor.

[0045] Accordingly, a Roots blower in accordance with the present invention having conventional Roots rotors within a conventional chamber has its motor located outside one side of the chamber and its drive gears located outside the other side of the chamber. This ability to put half the drive train (i.e., the motor) outside one side of the chamber, and half the drive train (i.e., the drive gears) outside the opposite side of the chamber, is realized because the motor which is located outside one side of the chamber operates to transmit rotational force through the chamber, and through a bore of one of the roots blower rotors located therein, so as to turn a drive gear at the other side of the chamber by action of a quill drive, as just explained.

[0046] Note that the rotational torque and power of the motor has been transmitted over a distance at least equal to the width of the chamber in which is contained the multi-lobe, or Roots, rotors. In accordance with the principles of a quill drive, this “action at a distance” is actually beneficial.

[0047] Consider that the rotors of a Roots blower are physically extensive, and encounter the force of typically turbulent flowing gas or fluid over a considerable area and moment arm, relative to the overall physical size of the blower. This makes that the bearings of a driving motor of a Roots blower are commonly subject to considerable vibrational and shock forces—magnified by any axial misalignment—no matter how and by what means the motor has heretofore been connected to the Roots blower rotors.

[0048] In the preferred embodiment of a Roots blower in accordance with the present invention where the blower motor must deliver drive force to the drive gears of the Roots blower at, and over, a distance equal to the full width of the blower chamber and blower rotors, these problems of misalignment and vibration/shock would initially seem to be magnified. In other words, the secure, close and strong rotational mounting of the roots blower rotors accorded by the present invention may initially seem to come at the tradeoff expense of increased stresses being placed on the bearings of the motor.

[0049] In accordance with the present invention, such remote projection of rotational force, and such seeming sensitivity to misalignment, as would normally occur over greater dimensions, and such as initially seems to be a disadvantage, is instead turned into an advantage by use of a quill drive. Advantage is realized because a quill drive is known to be effective for (i) transmitting rotational force at a distance, (ii) tolerating misalignment, and (iii) accommodating high levels of shock and/or vibration. Essentially, it is the innate structure of the “quill” that (i) transmits rotational force at a distance, (ii) tolerates misalignment, and (iii) accommodates these high levels of shock and/or vibration.

[0050] Thus, in accordance with the present invention a rotary force of the motor is transmitted to, eventually, the multi-lobe, or Roots, blower rotors with both (i) good tolerance to axial misalignment, and (ii) immunity to shock and vibration, by action of a quill drive operating across a chamber in which the multi-lobe, of Roots, rotors are contained, and even across a Roots rotor itself.

[0051] 2. A Monolithic Dual-Chambered Housing, With One Side Cover Doubling as a Support Bracket

[0052] Not only is the drive, and drive support, structure of a miniature roots blower in accordance with the present invention each of compact, economical and effective, the entire housing of the roots blower uses minimal parts, and is readily assembled and dis-assembled. Both a chamber in which are present the roots blower rotors, and an adjacent chamber in which are present the two gears of the gear drive of the roots blower, are preferably located within a single, monolithic, housing.

[0053] A one side surface to the housing where is attached the motor is substantial and precise, and is most typically cast or machined. Nonetheless to the substantial nature of this side of the housing, the motor is preferably not mounted by to the housing bolts connecting to a mounting flange of the motor—which is common—but rather by an inexpensive clamp, preferably tightened by but a single screw, wrapped a plain cylindrical body of the motor. This type of inexpensive and quick motor mounting is highly subject to misalignment, and is normally poorly tolerated by precision machines. However, in the miniature roots blower of the present invention the quill drive accommodates any reasonable axial misalignment between the motor shaft and the tubular drive, or rotor, shaft, making that an inexpensive motor mount may be used.

[0054] Moreover, the opposite side surface to the housing—which is not required to support bearings—is preferably fabricated as a simple sheet metal cover plate, and is more preferably fabricated as such a cover plate having an “L” contour so as to serve as a ready mounting plate for the entire miniature roots blower.

[0055] These and other aspects and attributes of the present invention will become increasingly clear upon reference to the following drawings and accompanying specification.

BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Referring particularly to the drawings for the purpose of illustration only and not to limit the scope of the invention in any way, these illustrations follow:

[0057] FIG. 1 is a diagrammatic exploded perspective view showing a preferred embodiment of a miniature roots blower in accordance with the present invention.

[0058] FIG. 2 is a cut-away side plan view of the motor and quill drive assembly of the preferred embodiment of the miniature roots blower in accordance with the present invention previously seen in FIG. 1.

[0059] FIG. 3 is an external perspective view of the preferred embodiment of the miniature roots blower in accordance with the present invention previously seen in FIGS. 1 and 2.

[0060] FIG. 4 is an side plan view, showing preferred dimensions, of the preferred embodiment of the miniature roots blower in accordance with the present invention previously seen in FIGS. 1 through 3.

[0061] FIG. 5 is an end plan view, showing preferred dimensions, of the preferred embodiment of the miniature roots blower in accordance with the present invention previously seen in FIGS. 1 through 4.

DESCRIPTION OF THE PREFERRED EMBODIMENT

[0062] The following description is of the best mode presently contemplated for the carrying out of the invention. This description is made for the purpose of illustrating the general principles of the invention, and is not to be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims.

[0063] Although specific embodiments of the invention will now be described with reference to the drawings, it should be understood that such embodiments are by way of example only and are merely illustrative of but a small number of the many possible specific embodiments to which the principles of the invention may be applied. Various changes and modifications obvious to one skilled in the art to which the invention pertains are deemed to be within the spirit, scope and contemplation of the invention as further defined in the appended claims.

[0064] 1. Construction

[0065] A diagrammatic exploded perspective view showing a preferred embodiment of a miniature roots blower, or pump, 1 in accordance with the present invention is shown in FIG. 1. The blower, or pump, 1 is suitable for pumping either gas(es) or fluid(s).

[0066] A motor mount plate 2a secures via a clamp 15 secured by a screw 19 (both best seen in FIG. 3) a motor 10. The motor mount plate 2a itself mounts to a first side of a housing 3 by screws 13, preferably four in number. A first one 18a of two gaskets 18a, 18b seals air and fluid tight the motor mount plate 2a to the housing 3. Any gas or fluid leakage around the motor 10 is normally foreclosed by the motor bushing 16 (hereinafter further discussed) that fits within a complimentary bore (not shown) of the motor mount plate 2a, and/or a pressured abutment of the motor 10 to the motor mount plate 2a, and/or pressure of the clamp 15.

[0067] Within the housing 3 adjacent to motor mount plate 2a is a first chamber 3a in which is contained two roots blower rotors 4. These roots blower rotors 4 are fixedly mounted, in the rotational phase relationship illustrated, to the tubular rotor shafts 5, 6 for rotation therewith. Tubular rotor shaft 6 is primary, and is driven by the motor 10 in a manner to be explained, while tubular rotor shaft 5 is secondary, and driven by gears 8 from the rotor shaft 5, again in a manner to be explained.

[0068] The two tubular rotor shafts 5, 6 are closely supported at either sides of the two roots blower rotors 4 in four bearings 14. Two of the bearings 14 are mounted in complimentary cavities within the motor mount plate 1, in two complimentary cavities (not shown) within a center divider wall to the housing 3 between chambers 3a and 3b of the housing.

[0069] In another, second, chamber 3b of the housing 3 are contained two drive gears 8a, 8b, also fixedly mounted to the tubular rotor shafts 5, 6 for rotation therewith. The rotor shafts 5, 6 are sealed in their passage through the center wall of the housing 3 by shaft seals 12a, 12b.

[0070] In the powered drive of the roots blower rotors 4 of the miniature roots blower 1 of the present invention, the shaft of the motor 10 is coupled through a motor drive bushing 16 to a quill drive shaft 17. This quill drive shaft 17 need not be round, and is preferably of a non-round cross-section, and is more preferably square. It need not be of equal thickness and cross-section along its length in accordance that it may have a controlled pre-set torsional resistance. The quill drive shaft 17 can be made from solid material, typically steel, or from wound wire, so as to form a shaft of any desired torsional resistance. Normally the quill drive shaft 17 is somewhat torsionally elastic.

[0071] The quill drive shaft 17 extends though the bore within one of the Roots blower rotors 4, though the center wall of the housing 3 and any bearing 14 and seal 12, and inside the tubular rotor shaft 6 (as best illustrated in FIG. 2) until terminating in a drive bushing 7 which serves to fixedly rotationally connect the tubular rotor shaft 6. The gear 8a is affixed to the tubular rotor shaft 6, and the other, meshing, gear 8b is affixed to the rotor shaft 5 (which need not be tubular, but which most commonly and preferably is tubular), normally by press fitting. Accordingly, rotation of the quill drive shaft 17 by the motor 10 ultimately results in the rotation of both tubular rotor shafts 5, 6, the gears 8a, 8b, and the Roots blower rotors 4 affixed thereto.

[0072] This quill drive may be observed in the cut-away side plan view of FIG. 2. An external perspective view of the preferred embodiment of the miniature roots blower 1 in accordance with the present invention is shown in FIG. 3, a side plan view in FIG. 4, and end plan view in FIG. 5. The dimension L1 of FIG. 4 is preferably about 3.00 inches, the dimension L2 of FIG. 4 about 4.50 inches, the dimension L3 of FIG. 5 about 1.75 inches, the dimension L4 of FIG. 5 about 3.25 inches for a miniature roots blower in accordance with the present invention. Such a miniature roots blower typically has a gas flow capacity of from one to five cubic feet per minute (1-5 cfm) depending upon pressure (the higher volume occurring at lower pressure) at thirty-three to ten thousand revolutions per minute (33-10,000 rpm).

[0073] 2. Operation

[0074] In the preferred embodiment of a Roots blower, or pump, A in accordance with the present invention, a shaft of the motor 10—or, more preferably, an extension thereof and thereto as is realized by a motor drive bushing 16 rotationally coupling an elongate drive shaft 17 of controlled cross-sectional aspect and torsional rigidity—serves as quill drive shaft. This drive shaft or shaft extension passes first through a first wall of a first chamber 3a of a housing 3, proceeds concentrically down a bore of a first one of the two roots blower rotors 4, then through an opposite second wall of the first chamber 3a of the housing 3, and then through one of the two drive gears 8 until, in the manner of a quill drive, it connects through a drive bushing 7 to a first tubular, or rotor, shaft 6.

[0075] This first tubular, or rotor, shaft 6 proceeds back along the drive shaft (or shaft extension) 17, and, to the limits of any misalignments or shock or vibration, substantially concentrically about this drive shaft (or shaft extension) 17. This first tubular, or rotor, shaft 6 first affixes a first drive gear 8a and then, proceeding upon a bearing surface back through the second wall of the first chamber of the housing 3, affixes the first one of the roots blower rotors 4. Exiting the side of the first roots blower rotor 4, this first tubular, or rotor, shaft 6 preferably terminates in a bearing 14 within the first wall 2b of the first chamber 3a of the housing 13.

[0076] Meanwhile, the first drive gear 8a that is affixed by the first tubular, or rotor, shaft 6 engages a second drive gear 8b that concentrically affixes its own, second, tubular, or rotor, shaft 5. This second tubular, or rotor, shaft 5 first affixing the second drive gear 8b likewise proceeds upon a bearing surface through the second wall of the first chamber 3a of the housing 3, affixes a second one of the roots blower rotors 4, and, exiting the side of this second roots blower rotor 4, preferably terminates in another bearing 14 within the first wall 2b of the first chamber 3a of the housing 3.

[0077] In accordance with the preceding explanation, variations and adaptations of the quill drive roots blower in accordance with the present invention will suggest themselves to a practitioner of the mechanical design arts. For example, the housing could be otherwise constructed, and the quill drive employed from a motor at the same side of the roots blower rotors as are the roots blower gears.

[0078] In accordance with these and other possible variations and adaptations of the present invention, the scope of the invention should be determined in accordance with the following claims, only, and not solely in accordance with that embodiment within which the invention has been taught.