US 3216592 A
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Description (OCR text may contain errors)
w. H. Pr-:Tl-:RsoN ETAL 3,216,592
HYDRAULIC DRAFT GEAR e sheets-sheet 1 Nov. 9, 1965 Filed May 25, 1964 MN Nm.
W/LL/AM H. PETERSON CARL ADLER Nov. 9, 1965 w. H. PETERSON ETAL 3,216,592
HYDRAULIC DRAFT GEAR Filed May 25, 1964 6 Sheets-Sheet 2 INVENTORS W/L L/ M H PETERSON CARL A LE? Nov, 9, 1965 w. H. PETERsoN ETAL 3,216,592
HYRAULIC DRAFT GEAR Filed May 25, 1964 6 Sheets-Sheet 3 INVENTORS W/LL/AM H. PETERSON CARL A DI. E l? LLA Nov 9 1965 w. H. PETERSON ETAL 3,216,592
HYDRAULIC DRAFT 4GEAR Filed May 25, 1964 6 Sheets-Sheet 4 INVENTG WILL/AM H. PETERS CARL ADLER law/,7m FEL/ Nov. 9, 1965 w. H. PETERSON ETAL HYDRAULIC DRAFT GEAR G Sheets-Sheet 5 Filed May 25, 1964 NVENTORS W/LL/M H. PETERSON 'RL LE'? Nov 9 1965 w. H. Pla-ransomy ETAL 3,216,592
HYDRAULIC DRAFT GEAR Filed May 25, 1964 6 Sheets-Sheet 6 INVENTORS W/LL/M H. PETERSON CAR/ ADLER @22a/Af *Emi United States Patent O1.
3,216,592 Patented Nov. 9, 1965 3,216,592 HYDRAULIC DRAFT GEAR William H. Peterson, Homewood, and Carl Adler, Chicago, lll., assignors to Pullman Incorporated, Chicago, lll., a corporation of Delaware Filed May 25, 1964, Ser. No. 369,708 Claims. (Cl. 213-43) The present invention relates to draft gear devices and more particularly to a railway draft gear arrangement including a double-acting hydraulic unit which is operative in one direction of travel to resist buff impacts and in the other direction of travel to resist draft impacts encountered during the operation of a railway car in which the draft gear arrangement is employed.
It is `a principal object of the present invention to provide a draft gear arrangement including a double-acting hydraulic unit having a new and improved hydraulic pressure relief valve arrangement which is operative upon buff impact at a pre-selected pressure which is below that tending to damage the hydraulic unit.
It is a further object to provide a draft gear arrangement including a double-acting hydraulic unit having a new and improved hydraulic pressure relief valve arrangement which is operative upon a pre-selected velocity of buff impact which creates pressure forces within the cylinder that are in close proximity to the yield strength of the hydraulic unit.
lt is still a further object to provide a draft gear arrangement including a double-acting hydraulic unit having a yieldable iiexible connection to the coupler yoke so as to preclude damage to the double-acting hydraulic unit.
Generally, the draft arrangement of the present invention includes having a double acting hydraulic unit which is operatively connected with the draft yoke permitting limited relative longitudinal movement between the yoke and the hydraulic unit whereby buff or draft forces applied on the coupler do not result in damage to the unit.
The double acting unit comprises essentially a housing forming a hydraulic fluid-lled reservoir in which there is disposed a cylinder communicating with the interior of the reservoir by way of oriiices formed in the cylinder Wall. Reciprocal within the cylinder is a piston head assembly which is operatively associated with the coupler yoke for responsive movement therewith so that upon buif or draft impact the piston head assembly is movable within the cylinder from a neutral position to a buff impact position. During such movement of the piston head to and from the neutral and buff positions, the latter is operative to displace iiuid from within the cylinder into the reservoir via the orifices at a rate which results in imparting a substantially constant force characteristic to the hydraulic unit. To preclude the formation of a vacuum behind the piston head during movement of the latter to the buff impact position there is provided a surge chamber which is associated with the iiuid receiving reservoir. The surge chamber is constructed in a manner providing an available auxiliary volume in addition to that provided by the interior of the reservoir.
Under some circumstances the velocity of the buff impact is Such that the pressure forces Within the cylinder are of a magnitude causing damage to the cylinder as by failure in yield. In accordance with the present invention, the piston head assembly is provided with a relief valve arrangement which is operative at a pre-selected impact velocity corresponding to a given uid pressure force which is a percentage of the yield strength of the cylinder.
Further objects and features will hereinafter appear.
In the drawings:
FIG. 1 is a fragmentary longitudinal sectional view taken through the draft sill of a railway car and showing the draft gear arrangement embodying the present invention;
FIG. 2 is a fragmentary transverse sectional view of the draft sill and draft gear arrangment shown in FIG. 1;
FIG. 3 is a cross-sectional view taken generally along the lines 3 3 of FIG. 2;
FIG. 4 is a cross-sectional view taken generally along the lines 4 4 of FIG. 2;
FIG. 5 is a cross-sectional view taken generally along the lines 5 5 of FIG. 2;
FIG. 6 is a fragmentary longitudinal cross-sectional view of the piston-piston rod assembly showing the relief valve arrangement embodying the present invention;
FIG. 7 is a cross-sectional view taken generally along the lines 7 7 of FIG. 6 with some of the parts being broken away to show underlying details of structure;
FIG. 8 is a cross-sectional view taken generally along the lines 8 8 of FIG. 2;
FIG. 9 is a fragmentary longitudinal cross-sectional view of the draft gear arrangement of the present invention shown in the neutral position thereof;
FIG. 10 is a view similar to FIG. 9 but showing the components of the draft gear in the position assumed upon draft impact; and
FIG. 11 is similar to FIGS. 9 and l() but showing the components in the position assumed upon buff impact.
Referring now to the drawings, there is shown a draft sill 10 which may be formed integral with or attached as by welding to the respective ends of the center sill (not shown). The draft sill 10 may comprise essentially a pair of vertically disposed and transversely spaced side webs 11 across the upper ends of which there may be fixed as by welding a top cover plate 12. The draft sill structure shown is adapted for use in a railway car having a floor height wherein a portion of the draft sill is elevated above the oor. To this end, the rear end wall 13 of the cover plate depends downwardly to the car floor level as shown in FIG. 2. 'I'he draft sill 10 formed as above described provides a pocket 14 which accommodates the draft gear arrangement 15 of the present in vention.
The draft gear arrangement 15 comprises generally a yoke 16 having pivotally attached between the legs 17 thereof by means of a coupler pin 18 a coupler shank 19. Disposed within a substantially rectilinear opening 20 formed in the bight 52 of the yoke 16 is a resilient cushion device 21 comprising essentially a plurality of rubber pads 22 which are adhered to the opposite sides of metallic separating discs 23. As shown in particular in FIGS. 9, l() and 1l, the inner one of the rubber pads 22 abuts against a follower plate 24 fixed to the end of a piston rod 50 extending from the hydraulic cushion unit 26. The follower plate 24 is formed at its outer face with a hernispherical surface 27 which seats within a complementary concave surface 28 formed on the outer wall of the recilinear opening 20. Along the edges the follower plate 24 is abuttable against stop lugs 25a.
The draft gear arrangement 15 further includes the double acting hydraulic unit 26 of which the latter comprises essentially an outer housing forming a reservoir 31 and having disposed therein a cylinder 30 in which there is reciprocal a piston-piston rod 32. The doubleacting hydraulic cushion unit 26 is disposed between lengthwise spaced front stop lugs 33 and rear stop lugs 34. The front and rear stop lugs 33 and 34 respectively are suitably braced by means of braces 36 and 37 which are fixed along the side webs 11 of the draft sill 10.
The housing or reservoir 31 comprises a tube 38 which is of lesserwall thickness than the cylinder 30 and which is xed at one end to the outer periphery of an annular rib 39 formed on the cylinder head 40. At its other end the tube 38 is xed to a similar annular rib 41projecting from the innerface of a second cylinder head 42. As shown, thesecond cylinder Lhead 42 is yformed with an outer annular disc 43 into the opening of which there is force-fitted an inner disc 44. The outer annular disc 43 projects beyond thel outerface of the inner disc 44 and is internally threaded so asto receive a stop collar 45.
Disposedalong and fixed to the respective inner faces of the annular ribs 39 and 41 of the respective cylinder .heads is thecylinder 30having abore 46 and a wall thickness substantially in excess of the wall thickness of the ,housingltube 38. Suitablefluid seals Asuch as O-rings may be disposed between the ends of the cylinder 31 and the lrespective mating face-.ofgthe cylinder fheads 40 and 42.
Slidably journaled in bearings .47 firmly seated within openings 48 ,andv 49. formed in the respective cylinder heads 40 and.42.is aV piston rod50 of the lpiston-piston rod assembly 32.
The `piston rod50 maybe formed from a tubular rod of `which theY outer diameter is substantially constant for the full length thereof.
As shown, the piston rod 50 `projects ateach of its ends beyondthe cylinder heads 40 and.42. y.Therightend of the piston rod '50, as heretofore cockingmovement between ,the yoke 16 and the piston rod 0 prevents bending of the `piston rod 50.
' Threadably fastened ,to lthe left end of `the piston rod 50 as viewed inFIGS. 9, 10 and 1l is a cap '53 having a rirnj54 to which ythere is` fixed one end of a collapsible belloWsVSS of which the .other-endis xed to a boss 56 formed on the outer face of the second cylinder head 40. A similar vbellows 55 is associated with the opposite end of the piston rod 50 and is xedat one-end to a boss 57 lof the cylinder head 42 and at the other end to the piston rod 50. Communication between the interior of the bellows and the bore 58 of the piston rod 50 is established by way of angularly spaced ports 59 formed on the respective ends of the rod 50.
Fixed to the pistonV rod 50 and 'disposed between the cylinder heads 4 0 and 42for lengthwise movement within the cylinder bore 46 is the piston head 60. The piston head 60 is preferably formed from metal such as cast iron or the like and is xed to the rod .50 by way of two oppositely disposedd-welds. kDisposed within a peripheral groove 61 is a bearing ring 62 which may be formed of a laminated phenolicresin. Advantageously, the bearing ring .62 projects s uciently above the periphery of thepiston head .60 as to prevent metal-to-metal contact between the metal piston head and the inner wall of the cylinder. The bearing ring'62 in this manner proves to be particularly advantageous in overcoming galling at the cylinder wall. y
As shown in particular in FIGS. 9, 10. and 11, the pisyton headr60` is reciprocal withinthe cylinder bore 46 from a neutral position shown in FIG. 9 adjacent to the cylinder head 42 to a contracted position upon buif impact adjacent. to the cylinder head 40. During movement of vthe piston head from the neutral `to buff positions shown Ain FIGS.,9 and 11 respectively, the piston head 60 displaces uids through openings 64 formed in the cylinder 32 and into the fluid reservoir 31. The openings 64 are arranged so that upon movement of the piston head 60 between the neutral and butt' positions there is created a substantially constant resisting force for substantially each increment of travel ofthe piston head v60. To achieve the substantially constant resisting force the openings or orifices 64 may be formed of equal area and having a variable lengthwise spacing so as to closely approximate a substantially constant resisting force, as shown, or may be formed of unequal areas equally spaced to achieve substantially the same eifect. In this connection it should be mentioned that the spacing of the orifices /64 is such that a substantially constant resisting force is obtained both during the travel from the neutral to the bufrr positions and the return travel from the buff to neutral positions.
Upon impact in either direction, that is, from the neutral to .builr positions or vice versathe movement of the piston head 60 may be extremely rapid such that the hydraulic fluid is displaced from the bore 46 tothe reservoir 31 at a correspondingly rapid rate greatly in excess of the rate at which the hydraulic iluid re-enters the cylinder bore 46 on the opposite side of the piston head 60. Under these conditions, a vacuum may be formed behind the rapidly moving piston head 60 so that excessive pressures are created within the housing 4or reservoir 31 which may tend to cause failure of the thin-walled tube 38. To minimize these conditions, there is provideda surge chamber 65 which serves to reduce and minimize the pressure surges within the reservoir 31 during the initial portion of the rapid travel of movement of the piston head 60.
As shown in particular in FIGS. 8 through 1l the surge chamber 65 comprises a housing 66 which may be formed from a single sheet of sheet metal bent to form bottom '67 and side Walls. 'Fixed to the ends of the side walls 68 and bottom-*67 a-s by welding are end walls 69. Across the upper edges of the end andside walls 68 and 69 is a rectangular clamping frame 70 along the outer edge of which there are positioned axially 'threaded clamping collars 71 which receive the threaded end of bolts 72 of which each are supported at their upper end in complementary clamping collars 73 fixed to the outer periphery of the tubular housing 38. Clamped between the rectangular clamping frame 70 .and the outer periphery of vthe tubular housing 38 is a flexible resilient huid-impervious member 74 which may be made from rubber or the like.
In the normal or neutral position of the hydraulic draft unit 26, the flexible member ormembrane 74 snugly overlies a plurality of lengthwise and radially spaced openings 75 formed in the lower portion of the housing 38 so as to retain the hydraulic fluid within the confines of the reservoir or housing 30. Duringthe initial movement of the piston head 60, the hydraulic fluid is discharged through the orifices 64 at at rapid rate which results in an excessive volume of hydraulic fluid entering the reservoir 31 and in a corresponding sudden rapid surge of the pressure forces within the housing 38. This sudden rapid surge in the pressure forces within the chamber or reservoir 31 is effective to displace the exible membrane 74 from overlying position of the openings 75 to the flexed position as shown in phantom in FIG. 8 so that the fluid flow is through the latter openings into the expanded or auxiliary pocket 76.
By providing the additional volumetric extension 76 of the housing or reservoir 31, the uid pressure forces within the housing 38 may be maintained at a value well below that tending to create failure-creating forces. This feature is of significance in that it permits the housing 38 to be formed with a minimum wall thickness.
At the same time, it is to be observed that the formation of the additional volumetric capacity of the surge chamber 65 also facilitates the reiilling of the bore cylinder 46 behind the moving piston head 60 so as to minimize the formation of vacuum therein. Thus, the hydraulic unit 26 is substantially instantly prepared to receive an impact in the opposite direction with the'full quantity of hydraulic fluid available to provide the requisite cushioning force.
The above described operation or movement of the pislton head 60 from the neutral to buff position results in a -resisting force which-is substantially constant-for each increment of travel of the piston head 60 within the cylinder 30. This resisting force within the cylinder 30 will be directly proportional to the speed of impact such that the pressure or resisting forces will increase in accordance with the speed of impact. To maintain the pressure forces corresponding to the resisting force at a level below -that which causes damage to the cylinder 30, there is provided a relief valve arrangement 85.
The relief valve arrangement 85, as shown in FIGS. 6, 7, 9, and 1l, comprises a plurality of angularly spaced openings 86 formed in the piston head 60 which open at one end on the high pressure face 87 of the piston head 60 and at the other end into an inwardly disposed continuous annular groove 88 formed on the low pressure face 89 of the piston head. Partially seated within the annular groove 88 is an annular valve seat 90 having formed on its inner surface a continuous annular passage 91 which communicates at its inner face with a continuous narrow annular orifice 92.
As shown in FIG. 6, the valve seat 90 is formed along its inner periphery with an outwardly proiecting ledge 93 which forms a rib on which there is supported an annular valve member 94. Holding the annular valve 94 in overlying relationship with the annular orifice 92 is a spring arrangement 95. In accordance with the present invention, the spring arrangement 95 is constructed and arranged so as to permit displacement of the annular valve disc 94 away from the opening 92 at a pressure force which closely approximates that of the yield strength of the material from which the cylinder 30 is formed. The spring arrangement 95 is formed from a plurality of Belleville springs 96 which are selected so as to be yieldable under a total pressure force which is a preselected percentage, say for example, approximately 90% of the yield strength of the cylinder and substantially fully deflected to permit substantially free fiow of hydraulic fiuid through the orifice arrangement during a small increase of the .total pressure force.
Assuming that the yield strength of the cylinder is such that an impact velocity of fourteen miles per hour in buff causes failure of the cylinder by yielding, the Belleville spring arrangement 95 is selected such as to open at lower impact forces which correspond to pressure forces approaching 90% of the yield strength of the cylinder material. As shown, the impact speed at which the Belleville springs 96 yield can to some extent be adjusted by selectively turning the threaded support member 97 threadably fastened on the piston rod 50 and supporting the Belleville spring 96.
Assuming now that a buff impact force is applied on the unit 26 causing a fiuid pressure force on the high pressure side or face 87 of the piston 60, this pressure force is transmitted through the angularly spaced openings 86 and through the annular groove 8S, annular passage 91 and annular orifice 92 on to the annular valve member 94. When the pressure forces of the fluid exceed that of the pressure exerted by the Belleville springs 96, the valve member 94 is displaced away from the annular orifice 92 so as to permit iiuid to flow from the high pressure side of the piston head 60 to the low pressure side thereof. Such opening of the valve member 94 is initiated at approximately the preselected pressure force of the yield strength of the cylinder 30. Due to the rapid flexing characteristic of the Belleville springs 96 to a fully defiected position under a small increase of pressure force the hydraulic flow through the openings 86 is maintained substantially uniform. Thus, it should be readily apparent that the relief spring arrangement 95 of the present invention has many advantages over the normal spring relief valve arrangements employed heretofore. In these prior spring arrangements, the spring generally followed Hooks law for spring forces such that the hydraulic iiow occurred through the relief porting at a much lower pressure force value and thereby limiting the maximum resisting or impact absorbing force of the hydraulic unit.
F or returning the hydraulic unit 26 to its neutral position in the absence of a draft impact there is provided a neutral positioning arrangement 77. The neutral positioning arrangement 77 includes a compression spring 78 of which one end is supported in a first open-ended tube 79 fixed to the yoke 16 for movement therewith. The other end of the spring 7g is supported in a second openended tube 80 which is fixed to the underside of a closure Channel 81 attached to the underside of the draft sill 10 between the sidewalls 11. The open-ended tube 79 is fastened to the yoke 16 by means of vertical attachment plates S2 which extend through the closure channel 81 and a slide plate arrangement S3 as shown in FIGS. 3 and 5. Thus, in the absence of draft impact, the spring 78, acting between the open-ended cylinder 80 fixed to the draft sill and the open-ended tube 79 xed to the lengthwise movable coupler yoke 16, is operative to extend the latter outwardly of the draft sill 1t) and thereby to move the piston head 60 fixed to the piston rod 50 to the neutral position shown in FIG. 9.
During normal train action the draft gear components assume the position shown in FIG. 9. In this position the piston head 60 is located within the cylinder 30 adjacent to the cylinder head 42 such that upon buff impact the piston head 60 travels to the left to the position shown in FIG. ll. For the purpose of example only, it may be assumed that the travel of the piston 60 from the neutral position to the buff position is about 10". Assuming now the condition when a buff impact force is applied to the coupler (not shown) the yoke 16 fixed thereto is correspondingly moved to the left as viewed in FIG. l1. This movement of the yoke 16 causes the piston rod S0 to be correspondingly moved whereby the piston head 6) affixed to the piston rod Si) is operative to displace fluid under pressure through the orifice 64 into the reservoir 31 in a manner such that the resisting force of the uid opposing the movement yof the piston head 60 remains approximately constant during each increment of travel toward the cylinder head 40.
As heretofore described during the initial rapid movement of the pinion nead 60 the hydraulic liuid may be displaced through the orifices 64 and into the reservoir 31 at a rate causing high pressure forces therein. During this initial period the surge chamber 65 is operative to reduce and minimize the pressure forces Within the housing or reservoir 31 to tolerable limits by providing the additional volume.
The hydraulic fluid displaced into the reservoir 31 is returned to the cylinder 30 via the orifice 64 behind the moving piston head 60. At the same time the bellows 55 fixed to the left of the piston rod 50 and to the cylinder head 40 expands and received the uid displaced from the bellows 55 associated with the other end of the piston rod 50 by way of the ports 59 and the bore of the tubular rod 50. The bellows 55-55 disposed on the opposite ends of the unit 26 thus provide hydraulic fluid containing chambers about the respective openings in the cylinder heads 40 and 42 and thereby maintain the fluid content within the cylinder 30 substantially constant.
Inward movement of the piston head 60 toward the cylinder head 4i) is limited by engagement of the bight 52 of the yoke 16 with the collar 45. It is to be noted when the bight 52 is engaged with the collar 45 that the rear face of the piston head 60 is spaced from the inner wall of the cylinder 40 to form more or less of a iiuid cushion chamber which prevents shock impact of the piston head 60 and cylinder head 40. As heretofore described, in the event that the impact force approaches the yield strength of the cylinder 30, the Belleville spring arrangement under the influence of the pressure force on the high pressure face 87 of the piston head 60 is operative to yield and permit the hydraulic fluid to flow from the high pressure side of the piston to the low pressure side.
As the piston head 60 moves to the position shown in FIG. 1l the spring 78 is compressed between the supporting tube 79 and tube 80 which are fixed to the draft sill 10 vand yoke 16 respectively. Upon dissipation of the impact venergy the return spring 78 is operative to return the yoke and thereby the piston rod assembly fastened thereto to /the neutral position shown in FIG. 9.
Assuming a condition in which a draft impact is immediately applied to the coupler before the spring action 78 above described takes place, the draft orl pulling movement of the coupler yoke 16 as indicated in FIG. 10 is operative to return the piston head 60 to the neutral position shown. It is to be noted that the pressure relief arlrangement 95 for reducing the pressure forces within the ycylinder 30 is inoperative during the travel from the buff to the neutral positions. The function of the pressure relief arrangement 95 is generally not required in draft because of the lower magnitude of draft impact forces enof the energy of draft impact.
Moreover should the draft impact be applied from the neutral position shown in FIG. 9 it should be readily apparent that the cushioning will be accomplished solely by the resilient cushioning unit 21 with the yoke bight 52 compressing the resilient cushions pads against the follower plate 24.
What is claimed is:
1. A double acting hydraulic cushion device for a draft gear arrangement, said hydraulic device comprising a hy- 'draulic fluid filled housing forming a reservoir, a hydraulic -uid filled cylinder disposed within said reservoir, orifice means formed in said cylinder providing communication between the bore of said cylinder and said reservoir, a
piston head means reciprocable within said cylinder be- -tween a neutral position adjacent one end of said cylinder to a buff position adjacent the other end of said cylinder, pressure relief passage means through said piston head,
'a pressure relief arrangement including valve means mounted on said piston head means on the side facing said one end of said cylinder, Belleville spring means urging said valve means into seating relationship overlying said relief passage means, ysaid Belleville spring means being yieldable at a preselected pressure force of the hydraulic fluid through said pressure relief passage means to unseat said valve -means from overlying relation with said pressure relief passage means and surge chamber means communicating with said'reservoir for providing an auxiliary volume for receiving fiuid displaced from `sa'id cylinder upon movement of said piston head between said buff and neutral positions.
2. A double acting hydraulic cushion device for a draft gear arrangement, said hydraulic device comprising a hydraulic uid filled housing forming a reservoir, a hydraulic iiuid filled cylinder disposed within said reservoir, orifice means formed in said cylinder providing communication between the bore of said cylinder and said reservoir, a piston head means reciprocable within said cylinder between a neutral position adjacent one end of said cylinder to a buff position adjacent the other end of said cylinder, pressure relief passage means through said piston head, said pressure relief passage means including a groove formed on the piston head side facing said one end of said cylinder, valve seat means partially disposed within said groove and including a plurality of conical openings communicating with an annular orifice, valve means seatable over said pressure relief passages, Belleville spring means urging said valve means into seating relationship overlying said pressure relief passage means, said Belleville spring means being yieldable at a preselected pressure force of the hydraulic fluid through said passage means and being fully deflected upon a small increase in the pressure force to unseat said valve means from overlying relation with said pressure relief passage means.
3. In a railway car having a draft sill portion fixed to said car, a draft gear arrangement comprising a yoke member for supporting a coupler thereon, said yoke member being slidably movable relative to said draft sill between a buff limit position upon buff impact and a draft limit position upon draft impact, a double acting hydraulic cushion means including a hydraulic uid containing cylinder, orifice means in said cylinder, a housing coaxially disposed about said cylinder and forming a reservoir for receiving hydraulic fluid displaced through said orifice means, a piston rod slidably supported and extending through the ends of said cylinder, a piston head fixed to said piston rod for movement therewith, said piston head being movable between a neutralwposition adjacent one end of said cylinder to a buff position adjacent the other end of said cylinder, resilient cushion means mounted in said yoke member for movement therewith, one end of said piston rod extending through said resilient cushion means, a follower block fixed to said one end of said piston rod extending through said resilient cushion means, said resilient cushion means being operative to absorb a portion of the kinetic energy of draft impact when said piston head is in said neutral position.
4. The invention as Vdefined in vclaim 3 wherein said yoke is formed with a substantially rectangular cut-out and said resilient cushion means is disposed in said rectangular cut-out.
5. The invention as defined in claim 4 wherein said follower block is formed with a hemispherical surface, and said rectilinear cut-out is formed with a concave surface for receiving said hernispherical surface.
References Cited by the Examiner UNITED STATES PATENTS 2,565,617 8/51 Mercier et al. 267-8 2,917,303 12/59 Vierling 267-8 3,047,162 7/62 Blake 213-8 3,171,546 3/65 Frederick 213-43 ARTHUR L. LA POINT, Primary Examiner.
MILTON BUCHLER, Examiner.