Anti-Rotation Coupling for a Scroll Machine

This invention generally pertains to anti-rotation couplings used in scroll machines, and specifically to "Oldham couplings."

Fluid displacement apparatus of the scroll type typically include two parallel plates, eachhaving an involute wrap element disposed on one side. These involute elements, having offset and parallel axes, intermesh with each other such that the sides of the involutes and the parallel plates define sealed fluid pockets.

As one involute orbits the other, the fluid pockets move from an inlet port, along the flank surfaces of the involute wrap elements, and through an outlet port. Depending on the configuration of the involutes and their direction of orbital rotation, the volume of these moving pockets will either increase, decrease, or remain relatively constant. Thus, a scroll machine may function as an expander (vacuum pump), a compressor, or a liquid pump, respectively.

If one involute element were free to rotate with respect to the other, some of the fluid pocket seals would leak and the intermeshed involutes would bind together.Therefore, to prevent this it is necessary to have an anti-rotation coupling that maintains a fixed angular relationship between the involutes yet still allows one to orbit the other.

Designs for such couplings are well known in the prior art. For example, U.S. Pat. No. 3,924,977 discloses a conventional "Oldham coupling" comprising an annular ring with four sliding keys disposed at 90.degree. intervals around its perimeter. Two of the keys, at opposite sides of the ring engae slots in the orbiting element while the other two engage slots in the stationary portion of the machine. Although this coupling is effective, its bulk requires substantial space within the scroll machine and it is somewhat costly to manufacture.

Therefore, it is an object of this invention to provide a simple anti-rotation coupling that requires minimal space in a scroll machine.

It is a further object to provide an anti-rotation coupling that is less expensive to manufacture than conventional coupling designs.

It is yet a further object of this invention to produce an anti-rotaton coupling from an integral sheet metal stamping.

These and other objects will be apparent from the attached drawngs and the description of the preferred embodiments that follow below.

The subject invention is an improved coupling for maintaining a fixed angular relationship betwen two parallel scroll plates within a scroll machine. Both scroll plates include an involute wrap element that intermeshes with the other wrap element.

The coupling, comprising a generally annular ring blanked as a unitary piece from sheet metal, includes a plurality of tabs disposed around its periphery. These tabs extend in a radial direction at spaced apart intervals around the ring with at least one tab slidingly engaging at least one slot disposed in the orbiting scroll plate, and with at least one other tab generally perpendicular to the first slidingly engaging at least one slot in a stationary portion of the scroll machine.

The tabs, being free to slide within the slots, allow one scroll plae to be driven in an orbital path relative to the other while constraining it in a fixed rotational relationship. This coupling means requires minimal space within the scroll machine because the coupling is a relatively thin item that can be easily blanked from sheet metal in a single operation.

FIG. 1 shows a cutaway view of the scroll machine with the improved "Oldham coupling" having two tabs above and two tabs below the thrust bearing.

FIG. 2 shows a cross-sectional view of the improved coupling lying below the scroll plates.

FIG. 3 shows an isometric view of the improved coupling.

FIG. 4 shows a cutaway view of the scroll machien with the improved coupling disposed between the scroll plates as described in the second embodiment.

FIG. 5 shows a top cutaway view of the scroll machine with the coupling disposed around the scroll elements as described in the second embodiment.

Illustrated in FIG. 1 is a scroll compressor incorporating the subject invention, generally denoted by numeral 4. As in many other scroll compressors, two parallel, intermeshed scroll elements 6 and 8 are driven to orbit relative to each other in a fixed angular relationship. In compressor 4, this fixed angular relationship is maintained by the subject invention which is a novel variation of an "Oldham coupling." This anti-rotation coupling 10 is shown in FIG. 3.

Coupling 10 includes an oblong ring 12 having substantially flat faces joined by inner and outer circumferential edges with four spaced apart tabs 14, 16, 18, and 20 extending outwardly from its perimeter (outer circumferential edge) at 90.degree. intervals. This simple design facilitates manufacture of the coupling as a unitary piece, not requiring assembly or fabrication of component parts. For example, it can be blanked and formed from sheet metal in a single progressive die operation. In addition, since coupling 10 is relatively thin, the material cost and space required within compressor 4 is minimal.

In the first embodiment shown in FIG. 2, coupling 10 isdisposed aroudn drive pin 22 which extends from the bottom faceof orbiting scroll element 8. Coupling 10 is disposed directly below and generally parallel to orbiting scroll element 8. Referring to FIGS. 1 and 2, two parallel tabs 14 and 16, extending from opposite sides of ring 12 and adjacent thrust bearing 24 are bent upwardly to slidingly engage slots 26 and 28 which are dispsoed in the bottom face of orbiting scroll element 8. This sliding engagement allows orbiting scroll element 8 to move in one direction relative to coupling 10 and prevents it form rotating with respect to the coupling. Two other tabs 18 and 20 are perpendicular to the first two tabs and are bent downwardly to extend underneath thrust bearing 24, slidingly engaging slots 30 and 32. Alternatively, tabs 18 and 20 may be co-planar with ring 12, i.e., not downwardly offset, if ring 12 clears thrust bearing 24. These slots are disposed in a stationary portion of compressor 4 such as frame 34. As illustrated in FIG. 1, tabs 30 and 32 are longer than the first two tabs because, they are dispsoed on the shorter axis of oblong ring 12 and msut extend further to remain slidingly engaged in their respective slots 30 and 32. The sliding engagement of tabs 18 and 20 with slots 30 and 32 in frame 34 prevents coupling 10 from rotating but allows coupling 10 to move along the Y-axis. Therefore, drive pin 22 orbits in a circulr path within ring 12, as coupling 10 moves along the X-axis sliding within slots 26 and 28, and forcing scroll element 8 along with it as it moves along the X-axis. Coupling 10 thus insures that scroll element 8 moves in fixed angular relationship relative to fixed scroll element 6.

Coupling 10 is lubricated with oil from reservoir 36. Centrifugal pump 38 moutned on the lwoer end of hollow drive shaft 40 delivers oil from reservoir 36, up through hollow drive shaft 40 and into cavity 42 which is disposed in the lower side of swing link 44. Oil received in cavity 42 is centrifugally slung outward to the perimeter of the cavity where the inlet of riser 46 is located. Riser 46, vertically disposed in swing link 44, provides a path for the oil and directs the flow towards thrust bearing 24 and coupling 10.

In the second embodiment, coupling 10' is disposed between and extends around scroll elements 6' and 8' as shown in FIGS. 4 and 5. Anti-rotation coupling 10' is similar to coupling 10 in FIG. 3 as it includes ring 12' with four tabs 14', 16', 18' and 20' disposed around its perimeter (circumferential edges) at 90.degree. intervals and can be blanked as a unitary piece from sheet metal. But referring to FIGS. 4 and 5, it is shown that tabs 18' and 20' extend inward form ring 12' and slidingly engage slots 30' and 32' which are dispsoed on the top faceof orbiting scroll element 8'. Theother two tabs 14' and 16', extending outward from and perpendicular to the first two, slidingly engage slots 26' and 28' which are disposed in the outer perimeter of stationary scroll element 6'. The sliding engagement of tabs 14', 16', 18' and 20' in their respective slots 26', 28', 30' and 32' serves the same purpose as the similar arrangement described in the first embodiment.

Although the invention is described with respect to two preferred embodiments, modifications thereto will become apparent to those skilled in the art. Therefore, the scope of the invention is to be determined by reference to the claims which follow.