US2810485A - Shock absorbing device - Google Patents

Description

Oct. 22, 1957 R. J. HOUSMAN SHOCK ABSORBING DEVICE Filed Aug. 51, 1954 5 Sheets-Sheet 1 JTI{J F. :{L 3

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R. J. HOUSMAN Oct. 22, 1957 SHOCK ABSORBING DEVICE Filed Aug. 31, 1954 Oct. 22, 1957 Filed Aug. 31, 1954 5 Sheets-Sheet 4 INVENTOR. I

Oct. 22, 1957 R. J. HOUSMAN 2,810,485

SHOCK ABSORBING DEVICE Filed Aug. 31, 1954 5 Sheets-Sheet 5 6'0 INVENTOR.

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SHOCK ABSORBING DEVICE Richard J. Housman, Dolton, BL, assignor to Cardwell Westinghouse Company, a corporation of Delaware Application August 31, 1954, Serial No. 453,342

15 Claims. (Cl. 213-221) This invention relates to shock absorbing devices and more particularly to buffers such as are used between railway cars. i

The general type of buffer with which the present invention is concerned comprises two slidingly telescoped followers and is commonly employed between the ends of coupled railway cars to absorb car-to-car forces in buti. U. 5. Patent No. 2,515,188, issued on July 18, 1950, is illustrative of this type of buffer.

In that patent, the desirability of employing a plurality of rubber-like cushioning bodies, arranged to act in series, rather than a single rubber-like body of the same overall length, was recognized and an arrangement embodying this idea is shown therein.

A series of cushioning bodies not only provides a freer cushioning action but is additionally important because of the greater ease of manufacture, assembly, inspection, and replacement that it permits. In incorporating this type of cushioning means in a buffer, certain practical problems are presented.

The first of these problems is twofold. On the one hand, it is necessary to provide for adequately confining and guiding a series of cushioning elements to maintain the elements in proper alignment during contraction and expansion of the buffer. The individual elements of the series must be confined in a floating manner with respect to longitudinal movement, but must be restricted in freedom for lateral movement in order not to interfere with the essential relative movement of the surrounding fol lowers.

On the other hand, the ultimate contraction of the butter under load must be limited to prevent excessive compression of the cushioning elements and this is preferably accomplished by metal-to-metal abutment of the two followers.

Another and equally important problem is to provide adequate locking means to maintain the two followers in assembled relationship and to prevent separation of the followers during operation of the buffer.

It is the principal object of the present invention to provide a buffer of novel design that will adequately and positively overcome these problems; that requires a minimum of parts; and that is economical to manufacture.

Other objects and advantages of the invention will be apparent during the course of the following description.

In the accompanying drawings forming a part of this specification, and in which like numerals are employed to designate like parts throughout the same,

Fig. 1 is a plan view of two butters abutting each other between the adjacent ends of two railway cars;

Fig. 2 is an exploded perspective view of the parts of the buffer of the present invention;

Fig. 3 illustrates the relative position of the buffer parts during assembly;

Fig. 4 illustrates the relative position of the buffer part after assembly is completed;

nite States Patent a 2,810,485 Patented Oct. 22, 1957 Figs. 5 and 6 are views taken along the lines 55 and 6-6 respectively of Fig. 3; and

Figs. 7 and 8 are views taken along the lines 77 and 8-8 of Fig. 4.

It should be understood that the description of the preferred form of the invention is for the purpose of complying with section 112, title 35 of the United States Code, and that the appended claims should be construed as broadly as the prior art will permit.

Fig. 1 illustrates a typical application wherein two butters, each designated generally at 10, are mounted for cooperation on the adjacent ends of two railway cars, generally indicated at 11. Each buffer is mounted on a wooden base block 12 and secured to its associated railway car by suitable bolts 13.

Briefly, the present invention comprises a pair of slidingly telescoped followers, hereafter referred to as a casing and a plunger, which house a series of cushioning elements and a guiding and locking member, hereafter referred to as a key. The cushioning elements are telescoped over the key and are freely movable longitudinally of the key but their lateral movement is constrained and guided by the cooperation between the key and the inner peripheral surfaces of the cushioning elements. The casing is formed with a stepped-diameter to provide an internal shoulder that cooperates with one end of the plunger to provide metal-to-metal contact and limit the inward advance of the plunger. This internal shoulder extends around the entire inner periphery of the casing and presents a relatively large, evenly distributed, total area that is readily capable of withstanding peak shock forces.

The key is also effective to lock the buffer in assembled relationship. The casing and plunger are each provided with a series of circumferentially spaced projections that are adapted to engage and prevent separation of the two parts during operation of the buffer. The key engages both the casing and the plunger and prevents relative rotation and thus the locking lugs cannot be disengaged as it is impossible to rotate the casing relative to the plunger. Unlocking is accomplished by displacing the key longitudinally a distance suflicient to disengage the casing. The casing may then be rotated out of engagement with the plunger and removed.

Referring now to the drawings and particularly to Fig. 2, reference character 15 designates a generally cylindrical hollow casing with parts broken away for purposes of illustration. The casing is of stepped-diameter construction forming an internal circumferential shoulder 16 that divides the casing into an inner longitudinal base portion 18 and an outer longitudinal portion 20. The outer portion 20 is larger than the inner portion 18 and is adapted to slidingly receive a plunger 22.

The inner portion is provided with a rectangular mounting flange 24 formed with an upraised boss 26 through which a pair of mounting holes 28 are drilled. The flange 24 is centrally apertured, as at 30, to provide access to the casing. Medially thereof, the inner portion 18 is formed with an inwardly directed circumferential shoulder 32 that defines a-hexagonally shaped central opening 33. The hexagonal shape is preferred though any non-circular shape would suflice, as is explained hereinafter. A plurality of radially disposed longitudinal ribs 34 surround the opening 33 and extend from the flanged base 24 to the shoulder 32 to reinforce and strengthen this portion of the casing.

The casing 15 of the buffer is also provided with a step 35 that may be integral therewith or welded thereto.

The outer portion 20, at its free end, is provided with a plurality of circumferentially spaced inwardly projecting lugs 36, two opposing lugs of which are formed with 3 a substantially flat face and the remainder are tapered inwardly.

The plunger 22 is also a generally cylindrical hollow barrel having a conventional flanged outer Wall 38 at one end. The other end 39 is adapted to abut against the internal 'shoulder 16 of the casing. The arrangement provides a substantial evenly distributed metal-to-metal contact surface that limits the inward movement of the plunger 22 relative tothe casing 15 and is adequate to withstand the peak shoeks occasioned thereby.

Medially of its length the plunger barrel is also provided with an inwardly directed circumferential shoulder 40 that defines a hexagonally shaped central opening 11. As in the case of the opening 33, the hexagonal shape is preferred though any non-circular shape would suffice.

A plurality of radially disposed longitudinal ribs 42 surround the opening 41 and extend from the flanged wall 38 to the shoulder 40 to reinforce and strengthen the plunger 22. Between the ribs 42, the outer wall of the plunger is provided with a series of openings44.

The plunger is also divided into an inner longitudinal portion 46 and an outer longitudinal portion '48. The inner longitudinal portion has a generally hexagonal external surface providing a plurality of flat faces 50. The vertices have been flattened to provide a plurality of fiat faces 52 narrower than the faces 50 and alternating therewith about the cireumference of the plunger. The outer portion has a smooth cylindrical external surface of a diameter such that it is flush with the mid points of the fiat faces 50 of the inner portion. With this arrangement, the plunger is provided with a plurality of spaced circumferential portions which project outwardly of the cylindrical surface defined by the outer portion 48. The plurality of transverse faces 54 so formed acts as lugs and cooperate with the lugs 36 of the casing.

Mounted between the casing and the plunger and completely enclosed thereby is a key 56, preferably in the form of a hexagonal tube, having a shoulder flange 58 at one end. The flange 58 may be integral or may be a separate plate telescoped over the tube and secured thereto, as by welding.

A hexagonal shape is preferred for the tube 56 though any non-circular shape is permissible. The shoulder end of the tube is adapted to be inserted in the opening 33 and the important feature is that they be identically shaped and of substantially the same size. The exact non-circular shape selected is unimportant since any non-circular shape will prevent relative turning movement between the tube 56 and the casing 15. The other end of the tube is adapted to be inserted in the opening 41 and here again the parts maybe of any desired non-circular shape to prevent relative turning of the tube 56 and the plunger 22.

A series of cushioning elements 69 are telescoped over the tube and are guided thereby. The elements 65), as best seen in Figs. 3, 4, and '8, comprise a centrally apertured metal disc '62 having a series of spaced holes 64, arranged in an annular pattern, punched therein, and a pair of rubber rings 66 and 68 mounted on the opposite surfaces of the disc and integrally interconnected through the holes 64.

The rubber ring 66 is formed with a projecting annular head 78 and the other ring of the pair is formed with a matinggroove 72. When a series of elements are brought together, the annular bead of one element cooperates with the annular groove of theadjacent producing a tongue and groove effect which assists in maintaining the rubber rings in'aligriment. V V

The shoulder 58 of the tube is formed with a bead of metal 74 and the shoulder 40 of theplunger 22 is formed with a groove 76 to cooperate Withthe tongue and groove of the'end elements of the'series of cushioning elements. This effect supplements the guidinga'ctio'n which the tube exerts onthe inner periphery of th'ernetal discs.

In this 'corinection," V hould'be stated that'the shap eof theaper t-ii'fs of "the discs is' iiniri'iporttiiit' as it is nothecessary to prevent relative turning movement between the discs and the tube. The important feature here is to limit the lateral movement of the discs and to permit free longitudinal movement.

The various parts of the buffer have now been described in detail and in order to better understand their functioning and operation, the assembly procedure will be explained. I v

Referring principally toFigs. 3, 5, and 6, it may be seen that the buffer is preferably vertically disposed during assembly. The plunger 22 is vertically arranged on the outer flange 38 and with its open end facing upwardly. The cushioning units 60 are then placed in the barrel of the plunger in aligned relationship, they rest on the shoulder 40 and extend above the open end. The cushioning units are arranged so that a beaded rubber ring 66 is lowermost and its tongue 70 engages the groove 76 formed in the shoulder '40. The remainder of "the units are also interconnected by the tongue and groove action previously described. g V v The hexagonal key tube 56 is tele'scoped within the series of cushioning units and extends into the hexagonal opening 41 of the shoulder '40. The beaded shoulder 58 of the key tube rests on the uppermost rubber ring 68 and the metal tongue 74 engages in the groove to complete the cushioning 'unit assembly.

The final operation involves the mounting of the casing l5 and it is telescoped over the plunger 22. In doing this, it is necessary to position the casing relative to the plunger such that the lugs 36 of the casing are aligned with the flat faces 50 of the plunger; the flat faces 52 and associated lugs 54 of the'plunge'r will then be aligned with the smooth portions of the casing 15. This position of the parts is illustrated in Figs. 3 and 6. In this position the ca'singlS and plunger 22. may be moved longitudinally relative to each other as the cooperating lugs are free of engagement.

As the parts are brought together and the various lugs pass between one another, the relative longitudinal motion will be blocked by the-engagement of the shoulder 32 withthe end of the tube 56. Simultaneously, relative rotar'y moveme'nt'is blocked by the lugs 36 and 54. Thisis clearly shown in Figs. 3 and 5. The casing and plunger are 'so designed that when their respective lugs are' 'outof, alignment and permit longitudinal movement,

thehexagonal openings 33 and 41 of the casing and plunger respectively are also out of alignment. Since the hexagonal tube 56 is engaged in the opening 41, its position is controlled thereby and it is necessarily out of alignment with the opening 33.

To, completethe assembly, an air piston, generally indicated at 80 in Fig. 3 is inserted at one end of the casing through the openings 30 and 33 and engages the shoulder 58 ofthetube. The piston 80 exerts a suitable force on the tube to compress the cushioning units. This causes the tube and easing tomo've downwardly until the casing lugs ;-36 -are disposed adjacent the smooth outer portion 48 of the plunger. In this region the casing may be rotated -relative to the plunger until the hexagonal opening 33 and hexagonal tube-56 become aligned and permit the shoulder 32 to seat on the shoulder 58. The hexagonal tubethen blocks any rotary movement and as the air piston 80 is Withdrawn, the cushioning units expand causing the casing and plunger to move apart.

Figs. 4, 7, 'andfS illustrate theposition of the parts after-the assembly is completed. In the preferred embodimerit, the casing is turned 30 in order to move the lugs fio'rn the spaces position to the overlapped or aligned position, this point the lugs 36 and 54 are aligned and "after adimit'ed expansion, they engage each other to block further expansion. g

In o'rder todis'assemble the buffer of Fig. 4 for maintenance and repair purposes, an air piston forces the key til'be -56 21ew11warmynmi1 the end of the tube is entirely beneath the shoulder 32 of the casing. "With the casing 15 and tube thus disengaged, the casing may be rotated 30 relative to the plunger to move the lugs from the overlapping position of Fig. 8 to the spaced position of Fig. 6. The casing may then be removed.

In applying the buffer to a railway car, the rectangular flange 24 is bolted to the end of the car and the outer flange 38 receives the bufiing loads. Such a load forces the plunger 22 inwardly against the cushioning action of the cushioning elements and the inward travel is limited by the abutment of the plunger end 39 and internal shoulder 16 of the casing. When the load is removed, the resilient cushioning elements force the plunger outwardly until the lugs 36 and 54 abut each other and limit further movement.

Since the tube 56 prevents relative rotary movement of the casing 15 and plunger 22, the locking lugs remain aligned through all conditions of operation and the buffer is automatically and positively locked together. In addition the tube 56 prevents transverse movement of the cushioning elements and avoids the possibility of one of these units interfering with the path of movement of the plunger end.

I claim:

1. A buffer comprising an inner hollow member having non-circular exterior and interior portions; annular resilient means mounted in said inner hollow member and projecting outwardly thereof; an elongated key telescoped within said resilient means and projecting into said hollow member, said key having a non-circular exterior cooperating with the non-circular interior of said inner hollow member to prevent relative rotation; and an outer hollow member telescoped over said inner hollow member to house said resilient means and said key, said outer hollow member having non-circular interior portions at each end, the non-circular portion at one end cooperating with a non-circular exterior portion of said key to prevent relative rotation, and the non-circular portion at the other end cooperating with the non-circular exterior portion of said inner hollow member to prevent outward movement between said hollow members; whereby said resilient means yieldingly urge said hollow members outwardly.

2. A butler comprising an inner hollow member having non-circular exterior and interior portions; an annular resilient means mounted in said inner hollow member and projecting outwardly thereof; an elongated key telescoped within said resilient means and projecting into said hollow member, said key having a shoulder engaging the free end of said resilient means, said key having a noncircular exterior cooperating with the non-circular interior of said inner hollow member to prevent relative rotation; and an outer hollow member telescoped over said inner hollow member to house said resilient means and said key, said shoulder of said key having abutting engagement with said outer hollow member to compress said resilient means between said members, said outer hollow member having non-circular interior portions at each end, the non-circular portion atone end cooperating with a non-circular exterior portion of said key to pre vent relative rotation, and the non-circular portion at the other end cooperating with the non-circular exterior portion of said inner hollow member to limit axial expansion when the two members are in normal operative position, said members being relatively rotatable to disengage said lastentioned non-circular portions and permit unlimited axial expansion; said resilient means being compressible to permit said key to be shifted axially out of engagement with said outer hollow member to permit said outer hollow member to be rotated relativexto said key and said inner hollow member.

3. A butter comprising an inner hollow member having non-circular exterior and interior portions; locking means projecting into said inner hollow member, said locking means having a non-circular exterior cooperating with the non-circular interior of said inner hollow member to prevent relative rotation; an outer hollow member telescoped over said inner hollow member to house said locking means, said outer hollow member having non-circular interior portions at'each end, the non-circular portion at one end cooperating with a non-circular exterior portion of said locking means to prevent relative rotation, and the non-circular portion at the other end cooperating with the non-circular exterior portion of said inner hollow member to limit axial expansion when the two members are in normal operative position, said members being relatively rotatable to disengage said last-mentioned noncircular portions and permit unlimited axial expansion; and resilient means telescoped over said locking means and yieldingly urging said locking means and outer hollow member away from said inner hollow member, said resilient means being compressible to permit said looking means to be shifted axially out of engagement with said outer hollow member to permit said outer hollow member to be rotated relative to said locking means and said inner hollow member.

4. A buffer comprising an inner hollow member having polygonal exterior and interior portions; annular resilient means mounted in said inner hollow member and projecting outwardly thereof; an elongated key telescoped within said resilient means and projecting into said hollow member, said key having a shoulder engaging the free end of said resilient means, said key having a polygonal exterior cooperating with the polygonal interior of said inner hollow member to prevent relative rotation; and an outer hollow member telescoped over said inner hollow member to house said resilient means and said key, said shoulder of said key having abutting engagerent with said outer hollow member to compress said resilient means between said members, said outer hol- 7 low member having polygonal interior portions at each end, the polygonal portion at one end cooperating with a polygonal exterior portion of said key to prevent relative rota-tion, and the polygonal portion at the other end cooperating with the polygonal exterior portion of said inner hollow member to limit axial expansion when the two members are in normal operative position, said members being rotatable to disengage said last-mentioned polygonal portions and permit unlimited axial expansion; said resilient means being compressible to permit said key to be shifted axially out of engagement with said outer hollow member to permit said outer hollow member to be rotated relative to said key and said inner hollow member.

5. A buffer comprising an inner hollow member having polygonal exterior and interior portions; locking means projecting into said inner hollow member, said locking means having a polygonal exterior cooperating with the polygonal interior of said inner hollow member to prevent relative rotation; an outer hollow member telescoped over said inner hollow member to house said locking means, said outer hollow member having polygonal interior portions at each end, the polygonal portion at one end cooperating with a polygonal exterior portion of said locking means to prevent relative rotation, and the polygonal portion at the other end cooperating with the polygonal exterior portion of said inner hollow member to limit axial expansion when the two members are in normal operative position, said members being rotatable to disengage said last-mentioned polygonal portions and permit unlimited axial expansion; and resilient means yieldingly urging said locking means and outer hollow member away from said inner hollow member, said resilient means being compressible to permit said locking means to be shifted axially out of engagement with said outer hollow member to permit said outer hollow member to be rotated relative to said locking means and said inner hollow member.

6. A shock absorbing device comprising a casing; a key mounted therein and projecting therefrom, said casing and key having cooperating surfaces preventing relative rotation; a plunger mounted in said casing and projecting therefrom, said plunger being capable of longitudinal inward and outward movement relative to the casing, said plunger and said key having cooperating surfaces preventing relative rotation, said casing and plunger being relatively rotatable into and out of interlocking positions for limiting longitudinal outward movement of the plunger relative to the casing; and resilient means within said plunger and resisting said inward longitudinal movement, said resilient means being compressible whereby said key may be shifted longitudinally out of engagement with said casing whereby said casing and plunger are relatively rotatable.

7. For use in a shock absorbing device including a casing; a plunger mounted in casing and projecting therefrom, said plunger being capable of longitudinal inward and outward movement relative to the casing; first means limiting said relative inward movement; and second means limiting said relative outward movement; a plurality of cushioning units aligned in series between said casing and plunger, each unit comprising a spacer disc having a series of holes and a rubber pad mounted on opposite faces of said disc, said pads being integrally interconnected through said holes, one of the pads on'the spacer disc being provided with an annular tongue portion and the other pad being provided with a complementary annular groove whereby adjacent units of the series are interengaged.

8. For use in a shock absorbing device including a casing; a member mounted therein and projecting therefrom, said member having a flanged shoulder adapted to abut a portion of said casing and prevent relative inward movement of said member to said casing; a plunger mounted in said casing and projecting therefrom, said plunger being capable of longitudinal inward and outward movement relative to said casing, said plunger having an inwardly flanged shoulder; first means limiting said relative inward movement of said plunger and said casing; and second means limiting said relative outward movement of said plunger and said casing; a plurality of cushioning units aligned in series and telescoped over said member in sliding relation, each unit comprising a spacer disc having a series of holes and a rubber ring mounted on opposite faces of said disc, said rings being integrally interconnected through said holes, one of the rings on the spacer disc being provided with a tongue portion and the other ring being provided with a complementary groove whereby adjacent units of the series are interengaged, one of said shoulder flanges being provided with a tongue and the other with a complementary groove whereby said cushioning units are interengaged with said shoulders.

9. A shock absorbing device comprising an'inner hollow member having a surface forming a spring seat, an elongated key mounted in said inner hollow member and projecting from one end thereof, said key having a transversely extending surface forming a second spring seat,-

resilient means between said spring seats, an outer hollow member telescoped over said inner hollow member for longitudinal inward and outward movement relative thereto and having a surface adapted for abutting engagement with said key, whereby said resilient means urges said members apart, said inner hollow member and said key having cooperating surfaces adjacent the other end of said inner hollow member for preventing relative rotation, said outer hollow member and said key having cooperating surfaces preventing relative rotation, said members being relatively rotatable into and out of interlocking positions for limiting longitudinal outward movement therebetween, said resilient means being compressi-bie to permit said key to be shifted longitudinally out of engagement with said outer hollow member whereby said members are relatively rotatable.

10. A shock absorbing device comprising an inner hollow member having'a surface forming a spring seat, an elongated key mounted in said inner hollow member and projecting from one end thereof, said key having a transversely extending surface forming a second spring seat, resilient means between said spring seats,'said key and resilient means being in telescoping relationship, an outer hollow member telescopedpover, said inner hollow member for longitudinal inward and outward movement relative thereto and having a surface adapted for'a'butting engagement with said key, whereby said resilient means urges said members apart, said inner :hollow member-and said key having cooperating surfaces preventing relative rotation, said outer hollow member and said key having cooperating surfaces preventing relative rotation, said members being relatively rotatable into and out of interlocking positions for'limiting longitudinal outward movement therebetween, said resilient means being compressible to permit said key to be shifted longitudinally out of engagement with said outer hollow member whereby said members are relatively rotatable.

11. A shock absorbing device comprising an inner hollow memb'er'having'an annular internal shoulder forming a spring seat, an elongated key having one end telescoped within said annular 'shoulderandhaving a sutface coo perating therewith to prevent relative rotation, said key having an intermediate annular shoulder forminga second spring seat, resilient means telescoped over said key and acting between said spring seats, and an outer hollow member telescoped over said inner hollow member for longitudinalinward-and outward movement relative thereto and havingan annular internal shoulder adapted for abutting engagement with said annular shoulder of said key whereby said resilient meansu'rges said members apart,'the other end of said elongated key telescoping'w'ithin said annular shoulder of said-outer hollow member and havingasurface cooperating therewith to prevent'relative rotation, said members being relatively rotatable into and out 'of interlocking positions for limiting longitudinal outward movement therebetween, said. outer member having'an opening affording access to'said other end of said key for compressing said resilient means whereby 'sai'dkey may be'shifted longitudinally out of engagement with said outer hollow 'rne'mbento permit relative rotation between said members.

12. A butter comprising an inner hollow member, annular resilientmeans mounted in said inner hollow member andprojecting outwardly thereof, an elongated key telescoped within said 'resilient'means and projecting into said hollow member, said hollow member and key having cooperating surfaces preventing relative rotation, and an outer hollow member telescoped over said inner hollow member to house said resilient means and said key, said resilient means being compressed between said members, said outer hollow member and key having cooperating surfaces preventing relative rotation and said members being relatively rotatable into and out of interlocking positions for limiting longitudinal outward movement between said members.

13. A buffer comprising an inner hollow member having non-circular exterior and interior portions, said interior portion being continuous; a one-piece elongated key projecting into said inner hollow member, said key having a pair of spaced apart, continuous, non-circular exterior wall portions, one of the 'said wall portions of said key being of substantially the same size and shape as, and cooperating with'the non-circular interior of said inner hollow member to prevent relative rotation; an

outer hollow member telescoped over said inner hollow member to house said key, said outer hollow member having non-circular interior portions at each end, the noncircular portion at one end being continuous and'being of substantially the same size and shape as, and cooperating with the other continuous non-circular exterior wall portion of said key to prevent relative rotation, and the noncircular portion at the other end cooperating .with the non-circular exterior portion of said inner hollowmember to prevent-outward movement between said hollow members; and resilient means in telescoping relation with said key and reacting between said hollow members to urge them outwardly.

14. A buffer comprising an inner hollow member having polygonal exterior and interior portions; a one-piece elongated key projecting into said inner hollow member, said key having a pair of spaced apart polygonal exterior wall portions, one of said wall portions of said key being of substantially the same size and shape as, and cooperating with the polygonal interior of said inner hollow member to prevent relative rotation; an outer hollow member telescoped over said inner hollow member to house said key, said outer hollow member having polygonal interior portions at each end, the polygonal portion at one end being of substantially the same size and shape as, and cooperating with the other polygonal exterior wall portion of said key to prevent relative rotation, and the polygonal portion at the other end cooperating with the polygonal exterior portion of said inner hollow member to prevent outward movement between said hollow members; and resilient means in telescoping relation with said key and reacting between said hollow members to urge them outwardly.

15. For use in a shock absorbing device including a casing; a plunger mounted in said casing and projecting therefrom, said plunger being capable of longitudinal inward and outward movement relative to the casing; first means limiting said relative inward movement; and second means limiting said relative outward movement; a plurality of cushioning units aligned in series between said casing and plunger, each unit comprising a spacer disc carrying rubber pads on its opposite faces, one of the pads on the spacer disc being provided with an annular tongue portion and the other pad being provided with a complementary annular groove whereby adjacent units of the series are interengaged.

References Cited in the file of this patent UNITED STATES PATENTS 2,340,335 Marsh Feb. 1, 1944 2,420,701 Dath May 20, 1947 2,434,944 Marsh Jan. 27, 1948 2,445,723 Brown July 20, 1948 2,486,741 Gabriel Nov. 1, 1949 2,491,158 I Brennan Dec, 13, 1949

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