IL37864A - Inner seal assembly for rotary piston machines - Google Patents

Description

Inner seal assembly for rotary piston machines AUDI HSU fTO UNION AKTIBfJGBSBLISCHAPT and WANEEL GMBH C;-35968 INNER SEAL ASSEMBLY FOR ROTARY PISTON ITIACHINES i f .

The rotary piaton machines of the type to which the present invention is applicable normally comprise an outer body or housing and an inner body or rotor eccentrically mounted on a crankshaft for rotation in the housing. The outer peripheral surface of the rotor and the adjacent housing malls define a plurality of working chambers which, during relative rotation of the rotor, vary in volume. In order to promote efficient operation of the mechanism, particularly when functioning as an internal combustion engine, the chambers are preferably sealed from one another by seal means disposed between the rotor and housing It has been common practice to provide radially movable inner seal-rings in a peripheral groove in a disk connected to the eccentric of the crankshaft to abut a radially dis-posed annular wall formed in the rotor end wall or face, which seal-rings function to prevent liquid coolant and/or lubricant, flowing through the rotor, from passing into the working chambers. Other outer seal means are located radially outwardly of the inner seal-rings to prevent leakage of gaseous fluid out of the working chambers between the rotor end face and the\end wall of the housing. The aforementioned inner seal-rings are effective only when a predetermined pressure in the liquid in the rotor is maintained to bias the rings axially into abutment ?> against the groove walls. Obviously, when the mechanism is not operating, the predetermined differential fluid pressure across the rings does not exist and, therefore, a positive seal is not achieved. In other known seal assemblies a seal-ring is provided which surrounds the inner seal assembly to provide a seal when the engine is at a standstill. This- supplemental seal, houiever, becomes ineffective uihen the engine is operating because the seal is forced out of contact with the sealing surface by the liquid pressure generated when the engine is running. It has 'also been proposed in an inner seal assembly to provide a wavy spring tuasher to bias the seal-ring against the groove mall so that this mechanical means provides a biasing force independent of the differential fluid pressure across the seal ring. This inner seal assembly is relatively complex and difficult to assemble into the mechanism. Also, at certain engine speeds it has been found that the split seal-rings lift from the axially extending sealing surface on the rotor. This unseating of the seal rings is caused by the negative acceleration forces directed radially inwardly which act on the seal-ring at certain points during its rotation. These negative acceleration forces acting on the rotor and the components carried by the rotor are fully described and explained in the United States Patents to Bentele et al, No. 3,176,915; Jones, No. 3,496,916; and Jones et al, No. 3,456,625.

Accordingly, it is an object of this invention to provide an inner seal assembly that is capable of providing an effective seal during high speed operation of the mechanism as ujell as uihen the mechanism is at a standstill.

It is another object of the present invention to provide an inner seal assembly uihich can be preassemtfled and installed in the mechanism and removed therefrom as a unitary member.

A further object of this invention is to provide an inner seal assembly having a seal-ring and ancoacting 0-ring in iiihich uiear of the O-ring is obviated.

A feature of the present invention is the capability of pre-assembling the inner seal assembly and thereby being able to quickly and easily position it in an annular space defined by a peripheral groove formed in a disk secured to the crankshaft and an adjacent, axially extending annular mall of the rotor. Thus, to achieve a unitary inner seal assembly the assembly is constructed of a seal-ring, a support ring interlocking uiith the seal-ring in such a manner as to allow limited relative axial movement between the tuio rings, and a biasing means disposed between the seal-ring and support ring to urge the two rings apart in an axial direction. The assembly also includes a resilient annular seal means carried by the seal-ring. Uihen the inner seal assembly is positioned in the rotor mechanism as aforesaid, the seal-ring sealing abuts a radially extending tuall of the disk under the urging of the biasing means uihile the resilient, annular, seal means seals the interstices between the seal-ring and the axially extending, annular wall of the rotor.

Another feature of this invention is the means for connecting the inner seal assembly with the member against which the resilient annular seal means abuts so that the assembly rotates uiith such member to obviate frictional wear of the seal means.

Summary of the Invention The invention, therefore, contemplates a ^novel inner seal assembly comprising a seal-ring, a support ring interconnected uiith the seal-ring so as to provide for their conjoined rotation and permit limited relative axial movement between the two rings. A biasing means, which may be in the form of a u/avy washer, is disposed in an annular pocket defined between' the seal-ring and the support ring to urge the two rings apart to the limit of relative axial movement in that direction. A resilient seal means carried by the seal-ring completes the unitary inner seal assembly. The components of the inner seal assembly are dimensioned so that in an axial direction it is slightly larger that the space defined by the peripheral step in the disk and the surface of the housing end wall of the mechanism so that the support ring and the seal-ring are resiliently urged in abutment by the biasing means against the said surface of the housing end wall and the radially extending step of the disk, the resilient annular seal means being in abutment against an axially extending surface formed on the rotor of the rotary mechanism.

In another aspect of this invention, the inner seal assembly is connected to the rotor for conjoined rotation therewith so that there is no frictional wear on the resilient seal means bearing against the axially extending surface of the rotor.

In another embodiment of the invention it is contemplated that a bearing surface of a material having a low coefficient of friction, be provided between the abutting surfaces of the seal-ring and the radial surface of the disk. The low friction material may be in the form of a ring of carbon or other non-metallic material having self-lubricating characteristics, such as poly-tetrafluoroethylene, inserted in the seal-ring or in the disk.

In a further embodiment of the present invention it is contemplated that a low friction material be interposed between the abutting surfaces of the resilient seal means and the axially extending, annular surface of the rotor. This material of a low coefficient of friction may be coated on the resilient seal means or thB aforementioned annular, axially extending surface of the rotor. This minimizes the distortion" or stress which tends to be imposed on the resilient seal means whin the inner seal assembly mov/es slightly axially as the rotor and the disk, carried by the eccentric crankshaft, move axially relative to each other. ' * In a still further embodiment of this invention the inner seal assembly may comprise an annular membrane which, along its inner peripheral portion, is clamped in the seal-ring, while its outer peripheral edge portion is secured in the rotor. This construction insures the relatively long operative life of the inner seal assembly in spite of the relative axial movement between the rotor and the eccentric shaft.

In an additional alternative embodiment the inner seal assembly may comprise, in place of the resilient seal means of the 0-ring type, an annularly split, tubular, metal ring.

Brief Description of the Drawings The invention will be more fully understood from the following detailed description thereof when condidered in connection with the accompanying drawing wherein several embodiments of the invention are illustrated by way of example and in which: Fig. 1 is a fragmentary view in cross-section through a rotary mechanism having an inner seal assembly according to a first embodiment of the invention; Fig. 2 is an enlarged, fragmentary view in cross-section of the inner seal assembly shown in Fig. 1; Fig. 3 is a fragmentary, cross-sectional view taken substantially along line 3--3 of Fig. 2, on a slightly smaller scale and mith parts broken away for ' illustration purposes; Fig. 4 is a fragmentary, cross-sectional view, similar to Fig. 2, showing another embodiment of the invention; Fig. 5 is a view similar to Figs. 2 and 4 showing a third embodiment of this invention; Fig. 6 is a vietu similar to Figs. 2,4 and 5 illustrating a fourth embodiment of the present invention; and Fig. 7 is a view in cross-section of a fifth embodiment of the invention.

Description of Preferred Embodiments of the Invention Now referring to the drawings and, more particularly, Figs. 1, 2 and 3, the reference number 10 generally designates an inner seal assembly according to one embodiment of this invention, uhich assembly is disposed in a rotary mechanism 12 of the type such as disclosed in the United States Patent No. 2,988,065.

The rotary mechanism 12, which may be an internal combustion engine, comprises a rotor 14 which is mounted on the eccentric portion 16 of a crankshaft 18 for rotation within a housing consisting of a peripheral wall 20 and two opposite end walls 22 (only one of which is shown). The surface 24 of peripheral wall 20 may have, in cross-section, a double epitrochoidal shape so that, with rotor 1 of three-sided configuration, a plurality of working or, combustion chambers (not shown) are formed which successively expand and contract in volumetric size as the rotor rotates. To render the working chambers fluid tight as possible, apex seals 26 are carried by the rotor at the juncture of the side walls thereof to abut the peripheral wall surface 24. To seal the interstices or space 30 between the face 32 of rotor 14 and the surface 34 of end wall 22, enseal means 36 is mounted on the face 32 of rotor 1 to impinge surface 34 and thereby minimize gaseous fluid leakage from the combustion chambers (not shown) in space 30. To prevent liquid leakage, such as lubricating and/or cooling oil, from flowing from the interior 38 of rotor 14 and from bhe area 40 adjacent crankshaft 18, through space 30 into the combustion chambers (not ahown), inner seal assembly 10, according to this invention, is dispo-sediinnan annular groove difined by a peripheral step 42 in a disk 44, an axially extending annular inner wall 46 in face 32 of rotor 14, and the' surface 34 of end wall 22. The disk 44 is connected to eccentric 16 of crankshaft 18 by suitable means, such as a plurality of bolts 48 (only one of which is shown). A seal-ring 50 is carried by disk 44 to prevent liquid in the area 40 from bypassing inner seal assembly 10.

A best shown in Figs. 2 and 3, inner seal assembly 10 comprises a seal-ring 52, a support ring 54 interconnected with seal-ring 52 for conjoined rotation and limited axial movement relative to each other, and a biasing means 56, such as a wavy spring washer or the like, disposed between the support and seal-ring to urge the rings axially away from each other. An annular seal means 58, such as an 0-ring or the like, carried by seal-ring 52 completes the inner seal assembly.

The seal-ring 52 has a radially extending sealing face 60 which abuts the radially extending aall 62 of disk 44. The inner peripheral surface 64 of seal-ring 52 is in contact with and is supported on the axially extending surface 66 of step 42 of disk 44. An annular stepped portion 68 is provided in the outer peripheral surface of seal-ring 52 on which is seated an 0-ring 58 and, hen assembled in mechanism 12, contacts annular wall 46.

The support ring 54 consists of a radially extending body portion 70 which impinges the surface 34 of the adjacent end wall 22 of the housing of mechanism 12., The- support ring 54 has a plurality of circumfsrantially spaced, axially exten-r ding, legs 72 each of which extend through arcuate shaped notches or cut-outs 74 formed in inner peripheral surface 64 of seal-ring 52. Each of the legs 72 has- a radially, outwardly extending, end portion 76 which is receivable in a radially extending groove 78 which communicates with each of the cutouts 74 in the seal ring. Each groove 78 and its associated cut-out 74 form a shoulder 80 which serves to engange and limit relative axial movement between seal-ring 52 and support ring 54 in ar.direction urging the rings to separate.

The seal-ring 52 has an annular recess 82 formed in the surface adjacent to support ring 64, which forms a pocket for wavy washer 56 and permits opposite sides of washer 56 to simultaneously engage seal-ring 52 and support ring 54.

To connect seal assembly 10 to rotor 14 so that the assembly will rotate together with rotor 14 and thereby substantially reduce frictional wear on 0-ring 58 which would otherwise occur, support ring 54 is provided with a plurality of circum-ferentially spaced, radially extending fingers 84 each of which is receivable in one of a plurality of radial grooves 86 formed in rotor face 32 (see Fig. 3).

The overall dimensions of the seal ring assembly 10 is such that it is receivable within the annular groove defined by step 42 in disk 44, annular wall 46, and end wall surface 34 so that wavy spring washer 56 is slightly compressed and, thereby, resiliently biases seal-ring 52 and support ring 54 into abutment against surfaces 62 and 34, respectively. To permit this resilient, axial movement between the seal and support rings, end portions 76 of legs 72 are smaller in dimension in an axial direction that grooves 78.

In the assembly of the components comprising seal ring assembly 10, uavy spring masher 56 is positioned in annular recess 82 in seal-ring 52 and support ring 54 is interconnected tuith the seal-ring by insertion of legs 72 in cut-outs 74 of the seal-ring 52. Thereafter, the end portions 76 of legs 72 are bent to extend into the grooves 78 in seal-ring 52 so that, under the urging of u/avy spring washer 56, end portions 76 abut shoulder 80. The 0-ring 58 is then inserted in stepped portion 68 of the seal-ring to thus provide an inner seal assembly of unitary construction uihich can be readily and quickly inserted or removed form the annular step 42 of sisk 44.

In operation of rotary mechanism 12 uiith inner seal assembly 10 assembled in the mechanism as shown and described herein, the inner seal assembly functions to effect a fluid seal when the mechanism is in operation and when at a standstill. The 0-ring 58 effects a seal along annular mall 46, while sealing face 60 of seal-ring 52 effects a seal by abutment against wall 62 of disk 44 under the urging of wavy spring washer 56. Since inner seal assembly 10 is keyed for conjoined rotation with rotor 14, 0-ring 58 is only subject to the slight wear resulting from deformation caused by the small relative axial movement between rotor 14 and disk 44. The cooperative function of support ring 54, seal-ring 52 and wavy spring washer 56. in biasing sealing face 60 against surface 62, provides a fluid seal which is independent of liquid and gaseous fluid pressures and is maintained when the mechanism is operating or at rest.

In Fig. 4 is shoum an inner seal assembly 10A according to another embodimen of this invention. The inner seal assembly 10A differs from inner seal assembly 10 shouin in Fig. 1,2 and 3, essentially only in that the spring biasing means for axially urging the support ring and seal-ring apart acts, throughLthe O-ring rather than directly against the seal ring. The parts in inner' seal assembly 10A corresponding to like parts of inner seal assembly 10, shall be designated by the same number but ■ with the suffix A added thereto.

In inner seal assembly 10Af seal-ring 52A does not have an annular recess for reveiving mavy spring uiasher 56A and, instead, has a pressure ring 90 disposed adjacent O-ring 58A in stepped portion 68A of seal-ring 52A . The side of pressure ring' 90 is provided luith a concave surface 92 to receive O-ring 58A, while the opposite side is flat to reveive abutment of tuavy spring masher 56A . The advantage of this construction is that simultaneously, uiith achieving an axial force urging support ring 54A and seal-ring 52.A to separate, there is provided a force pressing O-ring 58A against inner mall 46A of rotor 1 A .

In Fig. 5 is shouin an inner seal assembly 10 B according to a third embodiment of the present invention wherein parts corresponding to like parts of the embodiment shown in Fig. 1 to 3 are designated by the same reference number mith the suffix B a d ded thereto. The inner seal assembly 10B essentially differs from the inner seal assemblies 10 and 10A in that 0-ring 58B is positioned in a peripheral groove 94 formed in the sea l-ring. In addition, a band 96 of material having a louj coefficient of friction, such as polytetrafluo-roe th yl enB , is placed in the bottom of groove 94 so that O-ring 58B rests thereon. The band 96 serves to minimize friction at O-ring 58B when axial relative movement between seal assembly 10B and rotor 14B occur-s so that the consequent deformation of the O-ring which might occur through such frictional engagement is substantially minimized. The support ring 54B has axially extending, circumferentia lly spaced, tongue portions 98 engagijng arcuate slots 100 in rotor 14 instead of the keying interconnection (fingers 84 and grooves 86) disclosed in inner seal assemblies 10 and 10A.

Obviously, band 96 may be employed in inner 1 seal assemblies and 10A , as uiell as in seal assembly 1 OB without departure from the scope and spirit of this invention.

Alternatively, in place of band 96, the outer surface of O-ring 58B or inner uiall 46B of rotor 14B may be provided with a coating of suitable material having a law coefficient of friction.

In Fig. 6 is illustrated an inner seal assembly 10C according to a still further embodiment of this invention wherein parts corresponding to like parts of the inner seal assembly shouin in Figs. 1 to 3 and 5 are identified by the same number but with the suffi C added thereto.

The basic difference in seal assembly 0C from inner seal assemblies 10, 10A and 10B shouin in Figs. 1 to 5 is that, in place of the 0-ring type annular seal means, a hollow metal ring 102 is provided. To provide ring 102 uiith radial resiliency, it is formed with an annular slit 104. A coating 106 of low coefficient material may be applied to the outer surface of ring 102 thereby diminishing the amount of frictional contact between the ring and inner wall 46C of rotor 14C and the surfaces of stepped portion 68C of seal-ring 52C. The coating 106 may be composed of polytetrafluoroethylene or other material hawing self-lubricating characteristics.

In this assembly it is also contemplated to minimize the amoun of frictional engagement between sealing face 60C of seal-ring 52C and the adjacent radia mall 62 of -disk 44. This may be accomplished by the mounting on sealing face 60C an insert 108 of material having allow coefficient of friction, such as a carbon ring or ring of polytetrafluoroethylene. manifestly, insert 108 may be employed in inner seal assemblies 10, 10A and 10B 'without deviation from the scope and spirit of the present invention.

Similar to the embodiment of Fig. 5, support ring 54C, has axially extending, circumferentially spaced, tongue portions 98C which engage arcuate slots in rotor 14C to thereby key inner seal assembly 10C to the rotor for conjoined rotation therewith.

In Fig. 7 is illustrated an inner seal' assembly 10D according to embodiment of this invention, wherein parts corresponding to like parts of inner seal assembly 10 are designated by the 8ame number but with the suffix D added thereto.

In inner seal assembly 10D the 0-ring type seal has been replaced by an annular membrane 09 of resilient material, such as rubber or resilient plastic, the inner peripheral portion 110 thereof being clamped by a ring 112 in a groove 113 in seal-ring 52D while the outer peripheral portion 11¾ is secured in rotor 14D. The clamping ring 112 may be made of material having self-lubricating characteristics so as to minimize the friction between the face 115 of ring 112 and surface 62D of disk 44D. The outer peripheral portion 114 of membrane 109 is formed with a U-shape in cross-section so as to embrace an annular flange 116 which is attached to support ring 54D. The portion 114 is dimensioned so that uihen the axially extending annular flange portion 118 of inner seal assembly 10D is inserted in an annular groove 120 in rotor 14D, the portion 114 is compressed and sealingly engages the wall 122 of groove 120. This clamping of support ring 54D in groove 120 of rotor 14D secures support ring 54D against axial movement relative to rotor 14D. The axial movement of seal-ring 52D relative to disk 44D is limited in a direction auiay from support ring 54D by a flanged end portion 126 of an annular ring 124 which radially extends into the line of axial movement of a plurality of lugs 128 extending radially from the inner periphery of seal-ring 52D. The annular ring 124 may be constructed of sheetmetal and suitably fastened, as by melding or the like, to leg 72D of support ring 54D. The lugs 12Θ are located to extend into the space between three or more circumferentially spaced, axially extending ribs 130 formed on legs 72D of support ring 54D. The biasing means 560, comprises in this inner seal assembly a plurality of separate segments with each segment disposed in the space between the adjacent ribs 130. The lugs 128 and ribs 130 coact to spline connect the support ring 54D and seal-ring 52D for conjoined rotation. Thus, inner seal assembly 100, similar to the previously described inner seal assemblies, is ariunitary assembly and is connected to rotor 14D to rotate with the latter and be rotatively carried relative to disk 44D.

In fabricating inner seal assembly 10D, membrane 109 may be molded at its peripheral portion 114 to annular flanges 116 and 118 of support ring 54D, or, if a separate element forced into engagement with the support ring and/or bonded to!the latter.

The annular ring 124 may be secured to leg 72D, after the segmental biasing means 56D and seal-ring 52D are positioned relative to support ring 54D, to thereby lock seal-ring 52D to support ring 540. Thereafter, the inner peripheral portion 110 of membrane 109 is inserted in groove 113 and clamped in place by securing ring 112 to seal-ring 52D. This completed unitary inner seal assembly is then capable of being secured in rotor 1 14D and in the stepped portion 62D of disk 44D.

It is believed nou readily apparent that the present invention provides a novel inner seal assembly for a rotary mechanism which is relatively simple in construction and capable of maintaining a fluid seal uihen the mechanism is operating or at a standstill. It is an inner seal assembly which can be preassem-bled as a unitary member u/hich is capable of insertion in and removal from the rotary mechanism quickly and easily. It is an inner seal assembly which has a relatively long operative life by minimizing frictional and distortional uiear on a resilient seal means forming part of the assembly.

Although several embodiments of the invention have been illustrated and described in detail, it is to be expressly understood that the invention is not limited thereto. Various changes can be made in the arrangement of parts uiithout departingPfrom the spirit and scope of the invention as the same mill notu be understood by those skilled in the art.

What is claimed is:

Claims (20)

1. CLAimS In a rotary piston machine having a rotor- supported for rotative movement on a crankshaft and in which the rotor has an annularly, axially extending mall and the crankshaft has attached thereto a disk having a peripheral ste forming a radially extending annular mall disposed adjacent to said axially extending mall, the combination of an inner seal assembly disposed on said peripheral step and comprising: a) a seal-ring disposed adjacent said radially extending wall of said disk and the axially extending u/all of the rotor; b) a support ring; c) said support ring and seal-ring being interconnected for conjoined rotation and limited axial movement relative to each other; d) a biasing means carried by said support ring and seal-ring to urge the said support ring and seal- ring in a direction tending to separate the rings and thereby resiliently urge said seal-ring into s sealing engagement inith said radially extending mall; e) a resilient seal means connected to said seal-ring to thereby effect a fluid seal adjacent said axially extending mall; and f) said seal-ring, support ring, biasing means and resilient seal means being constructed and arranged for preassembly as a unitary structure for insertion and removal from said peripheral step as a unit.

2. The apparatus of Claim 1 wherein said support ring has means for connection with the rotor to thereby rotate with the latter .

3. The apparatus of Claim 2 Wherein said support ring connecting means comprises a plurality of circum erentially spaced, projecting portions each of.which is receivable in a recess in the rotor.

4. The apparatus of Claim 3 wherein said projecting portions extend radially from the peripheral portion of the support ring.

5. The apparatus of Claim 1 wherein said support ring includes a plurality of circumferentially spaced, axially extending legs and wherein the seal-ring includes a plurality of circumferentially spaced notches for receiving said legs to thereby interconnect the support and seal-rings for rotation together.

6. The apparatus of Claim 5 wherein each of said legs have a distal end portion extending radially outwardly and said notches each have a radially extending recess portion to form a shoulder, said recess being dimensioned to receive said radially, outwardly extending leg portions whereby limited axial movement of said seal and support rings in a direction away from each other is achieved.

7. The apparatus of Claim 1 wherein said resilient seal means is an O-ring carried by the seal-ring to abut said axially extending wall.

8. The apparatus o Claim 1 ujherein said resilient seal means , is an annularly split, tubular rings

9. The apparatus of Claim 8 wherein said ring has an outer layer of material having a loin coefficient of friction.

10. The apparatus of Claim 7 wherein thB 0-ring abuts a layer of material of low coefficient of friction carried by said seal-ring. I

11. The apparatus of Claim 1 wherein said resilient seal means is an annular ring-shaped membrane connected at one peripheral portion to the support ring and at the other peripheral portion connected to the seal-ring.

12. The apparatus of Claim 1 wherein said biasing means is a wavy spring washer.

13. The apparatus of Claim 1 wherBin said seal-ring has an annular face which abuts said radially extending surface of the disk and wherein a layer of material of low coefficient of friction is interposed between the annular face and extending surface.

14. In a rotary mechanism hawing a rotor supported for rotative movement on a crankshaft and in which the rotor has an annular, axially extending wall and the crankshaft has attached thereto a disk having a peripheral step forming a radially extending, annular wall disposed adjacent to said axially extending wall, the combination of an inner seal assembly disposed on said peripheral step and comprising: - 1Θ a) a seal-ring disposed adjacent said radially extending mall of said disk and the axially extending mall of the rotor; b) a support ring; c) said support ring and the seal-ring being interconnected for conjoined rotation and limited axial movement relative to each other; d) a biasing means carried by said support ring and seal- ring to resiliently urge the support ring and seal- ring in a direction to separate the rings and thereby urge eaid seal-ring into sealing engagement ujith said radially extending ujall; e) a resilient seal means connected to said seal-ring to thereby effect a fluid seal adjacent said axially extending mall; and f) said support ring having means for connection with said rotor so that the inner seal assembly rotates with said rotor.

15. The apparatus of Claim 14 uiherein said seal-ring, support ring, biasing means and resilient sealing means are constructed and arranged for interconnection into a unitary structure capable of placement on and removal from said peripheral step.

16. The apparatus of Claim 14 therein said resilient seal means is an 0-ring carried by the peripheral portion of the seal- ring so as to sealing engage said axially extending wall.

17. The apparatus of Claim 16 wherein a band of material having a loiu coefficient of friction is carried by said seal-ring so that the 0-ring abuts the band.

18. The apparatus of Claim 1 wherein the biasing means is a wavy spring masher.

19. The apparatus of Claim 14 uiherein said means for connecting the support ring to said rotor is spline means disposed around the periphery o the support ring and engaging corresponding spline means on said rotor.

20. The apparatus of Claim 19 uiherein the support ring spline means comprises a plurality of circum erentially spaced projecting portions and the rotor spline means comprises a plurality of circum erentially spaced recesses into which said projecting portions are receivable. ' the, Applicants \ A