US 3905731 A
A baffle and casing structure for rotary worm compression-expansion machines of the type having a rotor with oppositely facing working screws and a pair of pinion wheels cooperating with each such screw, the rotor being supported concentrically in a two-part casing having interior baffles to increase the volume of the working chamber defined by the worm threads, pinion wheels and casing interior. The pinion wheels are provided with teeth which engage not less than two nor more than three threads of the respective worms thereby to enable assembly of the pinion wheels through pockets accessible from the casing exterior.
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Description (OCR text may contain errors)
United States Patent Zimmern Sept. 16, 1975 BAFFLE STRUCTURE FOR ROTARY Primary ExaminerC. J. Husar WORM COMPRESSION-EXPANSION Assistant Examin'erbeonard E. Smith MACHINES Attorney, Agent, or Firm-Lane, Aitken, Dunner &
 Inventor: Bernard Zimmern, 27, rue ems Delabordere, Neuilly-sur-Seine (Hauts-de-Seine), France [5 7] ABSTRACT Filed: Oct. 1974 A baffle and casing structure for rotary worm compresslon-expansron machines of the type having a [21 Appl. No.: 512,143 rotor with oppositely facing working screws and a pair of pinion wheels cooperating with each such screw, 52 us. Cl. 418/195 1? suPpmted mmatnmcany a two'part casing having interior baffles to increase the volume of  Int. Cl. F04C 17/04 8 Id f Se h 418 195 the working chamber defined by the worm threads, [5 1 1e 0 arc pinion wheels and casing interior The pinion wheels are provided with teeth which engage not less than  References cued two nor more than three threads of the respective UNITED STATES PATENTS worms thereby to enable assembly of the pinion 1,220,688 3/1917 Sanders 418/195 X wheels through pockets accessible from the casing ex- 3,133,69S 5/1964 Zimmern 418/195 X t i 3,180,565 4/1965 Zimmcm 418/195 X 4 Claims, 5 Drawing Figures PATENTED SEP 1 61975 9 05,731
SHEET U U? 4 BAFFLE STRUCTURE FOR ROTARY WORM COMPRESSION-EXPANSION MACHINES BACKGROUND OF THE INVENTION This invention relates to rotary worm fluid compression-expansion machines and more particularly, it concerns a novel baffle arrangement by which the work output of such machinery is maximized while at the same time providing a structural organization of a casing, rotary worm and cooperating pinion wheels to define the working chambers of such machines and by which assembly of the machine is greatly facilitated.
In US. Pat. No. 3,180,565 issued Apr. 27, 1965 to the present inventor, there is disclosed various embodiments of rotary worm compressors constituted by a casing having a central axis, a disc rotatably and coaxi ally mounted in the casing and having a plurality of spirally extending threads projecting upwardly from a coaxial annular depression of part circular cross-section in the disc and at least one pinion wheel projecting into the casing with teeth meshing with the threads on the disc in a manner such that the pinion teeth mesh with at least two but not more than three threads on the disc at any one time. The inner surface of the casing includes a portion positioned to be swept by the threads on the disc and to, define therewith a plurality of compression-expansion chambers which effect a change in chamber volume during cooperative rotation of the disc and the pinions. As a compressor, for example, fluid introduced into the casing adjacent the periphery of the disc is compressed and discharged through an outlet in the casing near the center of the disc.
In US. Pat. No. 3,632,239 issued .Ian. 4, 1972 to the present inventor, there is disclosed a modified rotary worm fluid compression-expansion machine by which the swept chamber volume and compression ratio is significantly increased by an arrangement in which an increased number of pinion teeth mesh with the rotor or screw. While the modified machine disclosed in this latter patent is thus desirable from the standpoint of increased efficiency and capacity, appropriate engagement of the pinion teeth with the rotary worm teeth requires a measure of twisting movement of the pinion about an axis transverse to its rotational axis during the insertion of the pinion teeth into the threads of the rotor. As a result, assembly of the modified machine requires first an assembly of the pinions with the rotary screw and then an introduction of the screw and meshing pinion or pinions into the casing of the machine.
The problems of assembling the modified machines of the type shown in US. Pat. No. 3,632,239 are exemplified where the modification to enhance the compression ratio is applied to machines of the type shown in the aforementioned US. Pat. No. 3,180,565 or wherein the rotor is in the form of a disc having opposed spiral threads and wherein two pinions are employed on each of the opposed surfaces of the disc. Because of the requirement for preassembling the pinions and rotor, two half casings (i.e., four casing parts) must be used to enclose the rotor. From an assembly standpoint therefore, the increase in operating efficiency resulting from the increase of swept volume and compression ratio attainable only by preassembly of the rotor and pinions, is offset by the expense in assembly of the machine.
SUMMARY OF THE PRESENT INVENTION In accordance with the present invention, the increased efficiency heretofore attainable only by increasing the number of pinion teeth in meshing engagement with the rotary worm or screw of compression expansion machines of the type referred to is achieved by the provision of a baffle on the casing interior contiguous with each of the toothed pinions and extending in contiguous relation about the periphery of the disc throughout an arcuate distance corresponding to the maximum angular width of one groove defined by the spiral threads on the rotor. As a result of the baffle, a significantly increased volume of gas is trapped or swept by the pinion during rotation of the rotary worm while thepinion teeth mesh with only two or three of the rotary worm threads at one time. As a result, the machine may be assembled by first enclosing the rotary worm in a two-part casing and subsequently inserting the toothed pinions radially into appropriately formed casing pockets so that the teeth on the pinions move into meshing engagement with the rotary worm threads without twisting movement of the pinions during the insertion.
Accordingly, among the objects of the present invention are: the provision of a rotary worm compressionexpansion machine of the type referred to by which in creased operational efficiency can be achieved without sacrifice of facility for machine component assembly; the provision of such a machine in which the number of casing parts required for assembly is minimized; the provision of such a machine by which increased efficiency is achieved by a relatively simple baffle arrangement augmenting the volume of the working chambers in such machinery; and the provision of such machinery in which efficiency is optimized, assembly of components greatly simplified and by which compactness of the machine is enhanced in relation to the working capacity of the machine.
Other objects and further scope of applicability will become apparent from the detailed description to follow taken in conjunction with the accompanying drawlngs.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a rotary worm machine incorporating the present invention;
FIG. 2 is an exploded perspective view of the apparatus shown in FIG. 1;
FIG. 3 is an exploded perspective view of the apparatus shown in FIG. 1 illustrating the assembly of pinion wheels;
FIG. 4 is a fragmentary plan view illustrating the working relation of the rotary worm, pinion wheel and bafi'le of the present invention; and
FIG. 5 is a fragmentary cross-section taken on line 55 of FIG. 4.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT As shown in FIGS. 1 and 2 of the drawings, the compression-expansion machine of the present invention includes a casing generally designated by the reference numeral 10 and formed by a pair of axially bolted or otherwise suitably affixed casing halves 12 and 14 which are essentially alike in construction and symmetrica] about a central axis 16 of the machine. A pair of diametrically opposite inlet bosses (partially shown) 18 are provided on the exterior of the casing half 12 and open through arcuate slot-like ports 20 to the outer periphery of the casing interior. Discharge ports (not shown) open from the casing interior near or at the axial center of the casing interior and communicate to the exterior of both casing halves.
A rotor shaft 22 having a drive coupling 24 on one end, is rotatably joumalled at opposite ends in the easing 12 on the axis 16 and supports within the casing a .worm rotor 26 having on oppositely facing surfaces thereof, a pair of screws 28 and 30, each having spirally extending threads 32, the crowns of which make running engagement with a surface formation 34 on the casing half interiors, which surfaces extend over an area delimited by the lines 36. Other portions of the casing interiorare in sealing contact to diminish viscous drag in accordance with the disclosure of French Pat. No. 2,178,346.
.The screws 28 and 30 are formed in accordance with the disclosure of the above-mentioned US. Pat. No. 3,180,565 and as such, the root surfaces 38 between the threads 32 establish in each screw, a coaxial annular depression which is part circular in radial cross section and from which the spirally extending threads 28 project. As a result of this configuration and as shown in FIGS. 4 and of the drawings, each of the screws 28 and 30 may be engaged by two pinion wheels 40 having teeth 42 which mesh with the threads 32 on each of the screws 28 and 30. In accordance with the disclosure of US. Pat. No. 3,180,565, the pinion wheels 40 and screws 28 and 30 are designed such that the teeth 42 on each pinion mesh with at least two but not more than three of the threads 32 on each of the screws 28 and 30 at any one time during concurrent rotation of both the rotor 26 and pinion wheels 40. In accordance with an important feature of the present invention, a pair of baffles 44 extend from each of the casing half interiors out of the surfaces 34 to engage both a peripheral segment of each of the screws 28 and 30 and each of the pinion wheels 40. The arcuate length of each baffle 44 corresponds to the maximum annular width of one of the grooves or roots 38 between the threads 32.
The manner in which the working orientation of the pinion wheels 40 and the rotor screws 28 and 30 is achieved within the casing 12 may be understood by reference to FIGS. 2 and 3 of the drawings. Also in this connection, it is to be noted that to achieve symmetry of both torque and thrust loading in the operation of the machine, tvio pinion wheels 40 are employed with each of the rotor screws 28 and 30 or a total of four pinion wheels in the complete machine. Thus each of the casing halves l2 and 14 is formed with a pair of axially extending diametrically opposed bosses 46 and 48 defining pinion wheel wells or pockets 50 and 52 respectively. The pockets open through radial slots 54 to the interior of the casing and are adapted to be opened exteriorly by removal of cover plates 56 shown in FIG. 1. Each of the bosses 46 and 48 are apertured on the working axis 58 of each pinion wheel 40 to enable axial insertion of a pinion wheel supporting shaft 60 through a central hub 62 in each pinion wheel 40. Thus it will be seen that the machine is easily assembled by mounting the rotor 26 and rotor shaft 22 within the casing by bringing together the casing halves 12 and 14 axially on the shaft 22. Thereafter, the pinion wheels 40 are simply inserted into the pockets 50 and 52 and mounted on the shafts 60 after the latter are inserted through the apertures in the bosses 46 and 48. In this respect, it should be noted that the pockets 50 and 52 into which the pinion wheels 40 are inserted should make a close fit with the pinion wheels to minimize leakage losses during operation of the machine. Although the achievement of such tolerances prevents any twisting movement during insertion of the pinion wheels into engagement with the rotor threads 20 and 30, such twisting movement is not needed because of the limited tooth meshing engagement between the pinion wheels and rotor screws.
In the operation of the machine as a compressor, for example, air drawn into the casing peripherally of the rotor 26 occupies the chambers defined between the threads 32 of the rotor screws 28 and 30 and the interior of the casing halves 12 and 14. As the rotor is rotated in the direction of the helical pitch or clockwise as the rotor screw is illustrated in FIG. 4 of the drawings, for example, the rotor screws are swept by the pinion wheel teeth such that the volume of the screw chambers is reduced to effect compression of the air and an exhaust or discharge thereof through the center of the machine.
With reference again to FIG. 4, the effect of the baffles 44 can be appreciated by noting that the area designated by the reference numeral 62 would ordinarily not be affected by relative rotation of the rotor 26 and pinion wheel 40. Because of the baffle, however, and its sealing relation between the periphery of the rotor and the high pressure radial working face of the pinion wheel 40, the working chamber volume swept by the pinion wheel 40 is increased.
To illustrate the magnitude of increase in swept vol'- ume as a result of the baffles 44, the following example is given. In a machine provided with a rotor having six threads and a cylindrical outside diameter of 404 millimeters, two symmetrical pinion wheels each having eleven teeth, the outside diameter of the pinion being 263 millimeters and the distance between the axis of the rotor and the axis of the pinion being 127 millimeters, the swept volume of a machine without the baffles 44 was approximately 5.3 liters whereas with a baffle positioned contiguous to each of the pinion wheels, the volume per turn of rotor increased to 6.3 liters or 20 percent. This increase in effective working chamber volurn'e coupled with the facility for assembly is believed to constitute a significant advance in rotary worm compression-expansion machines.
Thus it will be appreciated that by the present invention there is provided an improved rotary worm compression-expansion machine by which the abovementioned objectives are completely fulfilled. It will be appreciated further by those skilled in the art that various modifications and/or changes may be made in the disclosed embodiment without departing from the present invention. It is expressly intended therefore that the foregoing description is illustrative of a preferred embodiment only, not limiting, and that the true spirit and scope of the present invention be determined by reference to the appended claims.
1. In a rotary worm compression-expansion machine having a rotor defining oppositely facing concentric spiral screws rotatably supported in a casing on the central axis thereof, each such screws having a plurality of spirally extending threads projecting upwardly from a coaxial annular depression part circular in radial cross-section, the inner surface of the casing having a portion positioned to be swept by the threads and define therewith a plurality of compression-expansion chambers, fluid inlet means in the casing opening adjacent to the periphery of the rotor and fluid outlet means near the center of the rotor, a pair of pinion wheels projecting into said casing and having teeth meshing with each of such screws, the teeth on each pinion meshing with at least two but not more than three threads on each of such screws at any one time, the improvement comprising; a pair of baffles located at and in sealing engagement with the periphery of each -of the concentric screws and in sealing engagement with the pinions.
2. The apparatus recited in claim 1 wherein the easing comprises a pair of axially connected casing halves,
each of said casing halves defining the casing portion to be swept by the threads of respective oppositely facing concentric spiral screws, said baffles projecting from the interior of said casing halves.
3. The apparatus recited in claim 2 wherein each of said casing halves is formed having exterior bosses to establish pinion wheel pockets and including means to support the pinion wheels rotatably in said pockets.
4. The apparatus recited in claim 3 wherein said pinion wheel pockets are of a shape and configuration to receive the pinion wheels with minimal clearances thereby to minimize fluid leakage between the pinions and said pockets,