US3217897A

US3217897A - Hydraulic draft gear arrangement

Info

Publication number: US3217897A
Application number: US310661A
Authority: US
Inventors: Peterson William Hartin
Original assignee: Pullman Inc
Current assignee: Pullman Standard Inc; Pullman Inc
Priority date: 1963-09-23
Filing date: 1963-09-23
Publication date: 1965-11-16
Anticipated expiration: 1982-11-16

Description

Nov. 16, 1965 w. H. PETERSON HYDRAULIC DRAFT GEAR ARRANGEMENT '7 Sheets-Sheet 1 Filed Sept. 23. 1963 wl'lv INVENTOR. WILLJAM H. PETERsoN Nov. 16, 1965 W. H. PETERSON 3,217,897

HYDRAULIC DRAFT GEAR ARRANGEMENT Filed Sept. 23, 1963 7 Sheets-Sheet 2 mmvron. W|| \Am H. PETERSON Nov. 16, 1965 w. H. PETERSON HYDRAULIC DRAFT GEAR ARRANGEMENT 7 Sheets-Sheet 3 Filed Sept. 25, 1963 LK F7 //A INVENTOR. W\L\ \AM H. PETERsoN FE-H r RRRRRRRRRRRRRRRRRRRRRRRRRRR NT IN WlLUAM H. PETERSON Y M U M F R-F5- I Nov. 16, 1965 w. H. PETERSON 3,

HYDRAULIC DRAFT GEAR ARRANGEMENT Filed Sept. 25, 1963 '7 Sheets-Sheet 5 INVENIORQ! W\L.\.\AM H. PETERSON Nov. 16, 1965 W. H. PETEMSQN 3,217,897

HYDRAULIC DRAFT GEAR ARRANGEMENT Filed Sept. 25, 1965 '7 Sheets-Sheet 6 INVENTOR. \N\\ \AM H- PETERSON Now. m Wfifi W. M. wfin'fimmm HYDRAULIC DRAFT GEAR ARRANGEMENT 7 Sheets-Sheet '7 Filed Sept. 23, 1963 INVENTOR. WmLtAM H, PETERSON United States Patent 3,217,897 HYDRAULIC DRAFT GEAR ARRANGEMENT William Hartin Peterson, Homewood, lll., assignor to Pullman Incorporated, Chicago, 121., a corporation of Delaware Filed Sept. 23, 1963, Ser. No. 310,661 '7 (Ilaims. (Cl. 213-43) The present invention relates to railway draft device and more particularly to a railway draft gear arrangement including a double acting hydraulic device operative to resist the buff and draft impact encountered during operation of the railway cars in which the draft gear arrangement is employed.

It is a principal object of the present invention to provide a draft gear device incorporating a double acting hydraulic unit which is of simple construction and economical to manufacture.

It is a further object to provide a double acting hydraulic device for use in a draft gear wherein the hydraulic device is devoid of movable relief valving components for controlling the pressures resulting from the displacement of the hydraulic fluid upon impact to the cushion unit.

It is a further object to provide a double acting hydraulic device for use in a draft gear wherein the hydraulic device is constructed and arranged to be accommodated in a limited space While at the same time providing a maximum force resisting buff or draft impact.

Generally the draft device of the present invention includes hydraulic draft gear having a double acting hydraulic unit operatively connected with the draft yoke so as to be responsive to impact in buff or draft on the coupler carried by the yoke. The double acting hydraulic unit comprises essentially a housing providing a fiuid filled reservoir in which there is disposed a cylinder communicating therewith by way of orifices formed in the cylinder. Reciprocable within the cylinder is a piston-piston head assembly which is operatively associated for movement With the yoke so that upon buff or draft impact the piston-piston head assembly is movable from a neutral position to displace fluid within the cylinder into the reservoir via the orifices at a rate which results in imparting substantially constant force travel closure characteristics to the hydraulic unit. To minimize pressure forces within the reservoir during the displacement of the fluid by the piston-piston head assembly, a surge chamber means is associated with the reservoir. The surge chamber is constructed in a manner providing an available auxiliary volume to the reservoir such that the additional volume in the latter does not create pressure forces tending to rupture the reservoir structure.

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 arrangement 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 44 of FIG. 2;

FIG. 5 is a cross sectional view taken generally along the lines 55 of FIG. 2;

FIG. 6 is a cross sectional view taken generally along the lines of 66 of FIG. 2 and showing in particular the rub plate arrangement interposed between the underside of the draft gear yoke and the draft gear retaining plate;

FIG. 7 is a greatly enlarged view taken generally along the lines 7-7 of FIG. 2;

3,Zl7,87 Patented Nov. 16, 1965 FIG. 8 is a fragmentary longitudinal cross sectional view of the draft gear arrangement showing the components thereof disposed in the neutral position;

FIG. 9 is a fragmentary longitudinal cross sectional view of the draft gear arrangement shown. in FIG. 8, but showing the position of the components upon buff impact at the coupler;

FIG. 10 is a fragmentary longitudinal cross sectional view of the draft gear arrangement shown in FIG. 8, but showing the position of the components upon draft impact at the coupler;

FIG. 11 is a fragmentary longitudinal cross sectional view of the draft gear arrangement, showing a one piece piston rod construction and an integrated piston head application;

FIG. 12 is a cross-sectional view taken generally along the lines 1212 of FIG. 11; and

FIG. 13 is a cross section view taken generally along the lines 13-13 of FIG. 12 and showing in particular the details of the over speed accommodating means provided in the piston head.

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 comprises essentially a pair of shown. The draft sill It comprises essentially a pair of vertically disposed and transversely spaced side webs 11 across the upper ends of which there is fixed as by welding a top cover plate 12. The draft sill structure as shown is adapted for use in a railway car having a fioor height wherein a portion of the draft sill is raised above the deck. To this end the rear end wall of the cover plate 12 depends downwardly to the car floor level. The draft sill as formed above provides a pocket 14 which accommodates the draft gear arrangement 16 embodying the present invention.

The draft gear arrangement 16 comprises generally a yoke 17 having pivotally attached thereto by means of a coupler pin 18 the shank 19 of a coupler. A resilient cushion means 21 is associated with the yoke 17 for absorbing a portion of the draft impact applied on the coupler and a double acting hydraulic unit 22 is operatively connected to the yoke 17 for absorbing a portion of the buff impact and also for absorbing a portion of the draft impact along the resilient cushioning means 21.

The yoke 17 as shown includes a pair of vertically spaced arms 23 supporting the coupler pin 18 about which the coupler shank 19 is turnable in the conventional manner. The bight 24 of the yoke 17 is formed of a substantially rectangular section having an opening 26 provided therein.

Disposed within the bight pocket 2a is the resilient cushion means including a plurality of rubber pads 27 adhered along the opposing faces thereof to metallic separating discs 2?. Fixed to one end of the cushion means 21 is a follower plate 29 which is engageable with stop lugs Sit-31 suitably braced by means of reinforcing braces 32 fiXed to the respective side Web 11 and to the respective stop lugs on the opposite side from the cushion means follower plate 29. I

Spaced lengthwise of the draft sill and fixed along the opposing sides are front stop lugs 33 and rear stop lugs 34 each of which are suitably braced by means of

braces

36 and 37 respectively which are also fixed along the side webs 11 of the draft sill 10. Disposed between the stop lugs 33-33 and stop lugs 34-37 and held fixed against lengthwise movement thereby is double acting hydraulic cushion unit 22.

The double acting hydraulic unit 22 includes generally a housing or reservoir 38 which serves as a fluid reservoir, a cylinder 39, a piston rod, piston assembly 41 reciprocable Within the cylinder 39 from a neutral position N to a position adjacent one end thereof upon impact in one direction and to a position at the opposite direction whereby fluid is displaced via openings 42 in the cylinder 39 into the reservoir 38. As more fully to be explained hereinafter the flow of the displaced fluid is regulated by the arrangement of openings 42 in the cylinder 39 communicating with the reservoir 38 so as to achieve a substantially constant force which resists the movement of the piston in a manner providing a maximum energy absorption capacity for the length of the piston stroke employed. During the initial movement of the piston in a piston rod assembly 41, the pressure of the fluid within the reservoir 38 may suddenly surge such that failure causing forces are present therein. In order to minimize the pressure surges there is provided a surge chamber means 81 which serves to maintain the pressure within the reservoir substantially constant.

As shown in particular in FIGS. 7-9, 12 the housing or reservoir 38 comprises a tube 40 which is of a lesser wall thickness than the wall of the cylinder 39. The tube 46 is fixed at one end to the outer periphery of an annular rib 44 formed on a first cylinder head 46 and at its other end the tube 44 is fixed to the outer periphery of an annular rib 47 formed on an outer annular section 48 of the second cylinder head 49. Suitably fastened within the opening of the annular section 48 as by a force fit is a circular plug section 51 having an opening 52 formed therein. Threaded into the forward end of the annular section 48 is an annular ring 53 of which one end abuts the outer wall of the annular section and the outer edge the plug 51. The other end projects outwardly of the annular section 48 and forms a stop 54 as more fully to be explained hereinafter.

Coaxially disposed within the housing 38 is the cylinder 3% which has a wall thickness substantially in excess of the wall thickness of the housing tube 40. The cylinder 39 is fixed as by welding at its respective ends to the inner of the

annular ribs

44 and 47 of the cylinder heads 46 and 49. Suitable fluid seals such as O-rings 57 may be disposed between the mating faces of the cylinder heads 46 and 49 and the ends of the cylinder 39.

Slidably journaled in bearings seated within the

openings

52 and 58 of the cylinder heads 49 and 44 respectively is a piston rod 59 of the piston-piston rod assembly 41. As shown, the piston rod 59 is formed from a tubular rod of which the outer diameter of one end 61 is reduced to provide a shoulder against which the piston head 62 is fixedly held by means of an outer sleeve 63.

Threadably fastened to the reduced end of the tubular rod 59 is a cap 64 having a rim 66 which is recessed along its inner diameter and receives one end of the sleeve 63. In this manner the sleeve 63 is held fixed against lengthwise movement on the tubular rod 61. Axially threaded into the cap is a plug 67 sealing fluid filling opening 68 which is employed to charge the device with fluid as more fully to be explained hereinafter.

At its other end the tubular rod 66 has threaded thereto a connecting cap 69 which is threadably fastened to the bight 24 of the yoke 17. The connecting cap 69 is formed with a rearwardly projecting boss 71 to which there is fixed by means of a hose clamp 72 or the like at one end of an expansible bellows 73 of which the other end is fixed to a boss 74 formed on the insert plug 51 of the cylinder head 49 by a hose clamp 72. A similar ex pansible bellows '76 is associated with the opposite end of the piston rod 59, and is fixed at one end by a clamp 72 to the cap 64. The other end is fixed by a clamp 72 to a boss 77 formed on the cylinder head 46. The piston rod 59 is formed at each end with a plurality of radially spaced openings 78 providing communication with the respective expansible bellows 73 and 76 associated therewith for receiving fluid displaced therebetween as more fully to be explained hereinafter.

The piston head 62 is provided with a piston ring 79 bearing preferably formed of a laminated resin such, as

4 for example, a type designated by the NEMA (National Electrical Manufacturers Association) as 9 Coarse, Grade C. A piston ring formed of the aforementioned material has been found to be particularly advantageous in overcoming galling between the mating metallic surfaces of the cylinder 39 and the piston head 62.

As shown, the piston head 62 is reciprocable within the cylinder 39 and upon reciprocation between the cylinder heads 44 and 49 displaces fluid through the openings 42 formed in the cylinder 39 and into the fluid reservoir 38. The piston head 62 normally assumes a neutral position (FIG. 8) and is movable to position adjacent the cylinder head 48 upon buff impact (FIG. 9) and to a position adjacent the cylinder head 49 upon draft impact (FIG. 10). The travel of the piston head upon buff impact is greater than the travel in draft impact and thereby provides a correspondingly greater energy absorbing capacity for the buff impacts which, as is well known, are greater than those encountered in draft and tend to cause more damage to the car structure and the lading supported thereon.

For the purpose of imparting a substantially constant force resisting the impact in buff and draft imposed on the device the ports or orifices 42 may be either variable spaced or made of variable size so that the fluid pressure opposing the movement of the piston remains about the same for each movement of travel thereof from the neutral position shown in FIG. 8 towards the buff or draft positions shown respectively in FIGS. 9 and 10. In the preferred form the orifices 42 are of equal area and are spaced lengthwise of the cylinder in radially staggered relationship along the length of the cylinder 39, as shown for example in FIG. 7, to achieve the desired substantially constant force closure characteristics during travel toward the buff and draft positions.

Upon impact in either direction particularly toward the buff position, the movement of the piston 62 is extremely rapid such that the displaced fluid is discharged into the reservoir 38 occurs at a rapid rate greatly in excess of the rate at which the fluid re-enters the cylinder 39 on the opposite side of the piston head. At the same time a vacuum may be formed behind the moving piston head 42. This rapid rate of flow of the hydraulic fiuid into the housing 38 creates excessive pressures therein creating forces on housing and the portion of the cylinder 39 containing the vacuum which may cause failure thereof.

In accordance with the present invention there is associated with the reservoir 38 a surge chamber 81 which serves to reduce and minimize the pressure surges within the reservoir 38 during the initial portion of rapid movement of the piston. The surge chamber 81 comprises a housing 82 which may be formed of a sheet bent to form a bottom 83 and side walls 84. Fixed to the ends of the side walls and bottom as by welding are end walls 86. Secured along the upper edge of the side walls 84 and the end walls 86 is a rectangular clamping frame 87. Spaced lengthwise along the outer edge of the clamping frame 87 are axially threaded clamping collars 88 which threadably receive the threaded ends of bolts 89 supported adjacent the upper ends thereof by complementary clamping collars 91 fixed to the outer periphery of the housing 38. A locking nut 92 is threaded onto the lower projecting ends of the bolts 89 to firmly hold the surge chamber 31 fixed to the housing 38.

Clamped between the clamping frame 87 and the periphery of the housing 33 is a resilient fluid impervious member $3 which may be formed from rubber or the like. In the normal position of the hydraulic unit 22 the flexible member or membrane 93 snugly overlies a plurality of the lengthwise and radially spaced openings 94 and retains the hydraulic fiuid within the confines of the reservoir 38. However, during the initial movement of the piston 62 within the cylinder 39 causing the hydraulic fluid to be discharged through the orifices 42 at a rapid rate there results an excessive volume of fluid in the housing 30 and a corresponding sudden rapid surge in the pressure. At the same time the force of the fluid pressure within the reservoir 33 is applied onto the flexible membrane 93 via the openings 94 such that membrane 93 is extended into the surge chamber 01 as shown in phantom lines in FIG. 7 until the pressure forces on both sides thereof are substantially equal. The excessive hydraulic fluid is thus retained within the volume defined between the outer surface of the housing 38 and the inner wall of the expanded flexible membrane 93. In this manner the fluid pressure within the housing 33 may be maintained at value well below that tending to create failure creating forces.

In this connection it should be noted that the initial air pressure within the surge chamber 81 is such as to apply a force on the flexible membrane 93 to withstand pressures which may normally be assumed by the housing and is yieldable upon excessive pressure of the magnitude encountered during the initial rapid movement. However, upon further movement of the piston head 62, the hydraulic fiuid flows through the orifices 42 behind the moving piston may be adequate to accommodate the fluid flow therethrough at a rate compatible to the rate of discharge through the orifices 42 in front of the moving piston head 62. During this period the pressure forces within the housing 38 may be such that the flexible membrane 93 is not expanded and assumes its normal position contacting the outer periphery of the overlying openings 94.

For returning the hydraulic unit 22 to its neutral position shown in FIG. 8 from the bud. or draft positions shown in FIGS. 9 and respectively, there is provided a neutral positioning arrangement 96. The neutral positioning arrangement includes a compression spring 97 one end of which is supported in a first open ended tube 98, and engages the enclosed end 99 thereof. The other end of the spring 97 is supported in a second open ended tube 101 and engages the closed end wall 102 thereof. As shown, in FIGS. 4 and S the first open-ended tube 98 is fixed by means of vertical attachment plates 103 to the underside of the lower channel member 104 fastened along its downwardly depending flanges 106 to the side webs 11 of the draft sill 10.

As shown in particular in FIGS. 3, 4, 5 and 6, supported on the upper side of the horizontal web 107 of the channel 103 is a rectangular wear plate 108 having laterally spaced elongate slots 109 opening at the forward edge. Abutting the forward edge of the wear plate 108 between the inner sides of the slots 109 is a stem 111 of a T-shaped plate 112 arranged to provide a pair of shoulders 113 forming stops. The elongate slots 109 and sides of the stem 111 are aligned with slots formed in the horizontal web 107 of the channel 104.

Extending through the

respective slots

109 and 114 are vertical attachment plates 116 fixed at one end to the second spring support tube 101 and at the other end to the underside of the coupler yoke 17. In this manner the second spring support tube 101 is mounted for movement with the coupler yoke 17 and the first spring support tube 98 is fixed to the draft sill 10. Thus, upon impact to the coupler in buff whereupon the coupler yoke 17 is moved inwardly the second spring support tube 101 fixed thereto is correspondingly moved thereby to compress the spring 97 against the end wall 99 of the first support tube 93 fixed to the channel 104 of the draft sill 10. When the force of the buff impact has been dissipated the spring 97 is operative to return the yoke 17 to the neutral position as shown in FIG. 8 so that the piston head 62 on the piston rod 61 which is fixed at one end to the yoke 17 is also returned to the neutral position.

'Upon impact in draft the resilient cushion unit 21 is compressed against the stops 31 so that upon dissipation of the impact the resiliency of the cushion unit 21 serves to return the yoke 17 and the piston head 62 to the neutral position. In this connection it should be mentioned that the spring 97 is partially compressed in the neutral position of the components of the draft gear, to the extent that it elongates when the yoke 17 moves outwardly relative to the draft sill 11 and thereby remains supported between the fixed spring housing 98 and the movable spring housing 99. The precompressed spring 97 exerts a force of a magnitude just sufiicient to maintain the yoke 17 in the neutral position such that a minimum compressive force is exerted on the resilient cushion unit 21.

In operation during normal train action the draft gear components assume the neutral position shown in FIG. 8. In this position the piston head 62 is located within the cylinder such that butf impact causes a travel of the piston head 62 to the left greater than that the travel to the right as caused by the draft impact. For purpose of example only, it may be assumed that the travel upon buff impact from the neutral position is about 10" while the travel in draft impact from the neutral position is about 1%". Such difference in travel between buff and draft is dictated by the greater compression loading imposed on the railway car in buff than in draft.

Assuming now the condition when a buff impact force is applied to the coupler, the yoke 17 fixed thereto is correspondingly moved. The movement of the piston rod is to the left as viewed in FIGS. 8 and 9 and causes the piston rod fixed thereto to displace fluid under pressure through the orifices 42 in a manner such that the resisting force of the fluid opposing the movement of the piston head 62 remains approximately constant for each increment of travel of the piston head 62 toward the cylinder head 46. As heretofore described during the initial rapid movement of the piston head 62, the fluid may be displaced through the orifices 42 and into the reservoir 38 in a manner causing high pressure forces therein. During this initial period the surge chamber 81 as previously described is operative to reduce and minimize these pressure forces to Within tolerable limits.

The displaced fluid within the reservoir 38 is returned to the cylinder 39 via the orifices 42 behind the moving plston head 62. At the same time the bellows '76 fixed to the left end of the piston rod 61 and to the cylinder head 46 expands and receives the fluid displaced from the bellows 73 associated with the opposite end of the piston rod 61 via the ports 78 and the bore of the tubular rod. The bellows 73 and 76 thus provide a fluid containing chamber about the

respective openings

52 and 58 in the cylinder heads 42 and thereby maintains the fluid content within the cylinder 39 constant.

Inward movement of the piston head 62 toward the cylinder head 46 is limited upon engagement of the bight 24 of the yoke 14 with the end 45 of the collar 45. It is to be noted that when the bight 24 is engaged with the end 45 the rear face of the piston head 62 is spaced from the inner wall to form more or less of a fluid cushion chamber which prevents sharp impact of the piston head 62 and cylinder head 46.

As the piston head 62 moves to the position shown in FIG. 9, the spring 97 is compressed between supporting tube 98 which is fixed to the draft sill 10 and the supporting tube 101 which is fixed for movement with the yoke 17. Upon dissipation of the impact energy return spring 97 1s operative to return the yoke 17 and the piston-piston rod assembly fastened thereto to the neutral position shown in FIG. 8.

Assuming now an impact in draft, the coupler yoke 17 1s pulled or moved outwardly of the draft sill 10. During outward movement the resilient cushion unit 21 is compressed between bight 24 of the yoke 17 and the follower plate 29 which abuts the stops 31. At the same time the piston head 62 moves toward the cylinder head 49 to the position shown in FIG. 10. During the movement to the right the piston head 62 displaces fluid through the openings 42 similarly as described above in connection with the buff impact such that a force resisting the movement of the coupler is provided by the hydraulic unit 22. Thus, the resilient cushioning unit 21 and the hydraulic unit 22 are operative to absorb a portion of the energy of draft impact. It is of course, readily apparent that the hydraulic or cushion unit 22 is also operative upon draft impact to provide approximately constant force travel closure characteristics during its length of travel while the resilient cushion means functions in its usual manner providing a gradual increasing force travel closure characteristic. Upon dissipation of the draft impact the resilient cushion device 21 is operative to return the device to its original neutral position shown in FIG. 8.

Referring now to FIGS. 11-13 there is shown a cushion unit 220 which is substantially identical to that disclosed in FIGS. 110 and similarly associated within the draft gear arrangement 16. The cushion unit 220 differs primarily in respect to the piston rod and piston head structure of which the latter may be provided with an arrangement for accommodating over speed and high mass impacts. The components common to the structures illustrated in FIGS. 1-10 and FIGS. 11-13 are similarly designated.

As shown in FIG. 11, the piston rod is formed of a tubular section 221. The outer diameter of the rod 221 is of substantially constant diameter along the length.

The piston head 222 is formed with an axial opening 223 having a diameter substantially equal to that of the outer diameter of the rod 221 whereby the piston head 222 is slidably assembled thereon and selectively positioned intermediate the ends thereof.

For fixing the piston head 222 on the rod 221, each of the opposing side walls 222:: and 222b are formed with cutouts 224 about the axial opening 223. The cutouts 224 are in the form of I-grooves to provide joints which may accommodate slag welds 226 deposited therein at each side of the piston head and which serve to fix the piston head on the rod. A single J-groove may be provided at only one side wall of the piston head and the slag weld deposited entirely from that side with the weld metal extending substantially the full depth through the piston head around the piston rod to an axial bore at the other side of the head. Either welding arrangement affords a solid connection between the piston rod and head.

The cushion unit 220 illustrated in FIGS. 11-13 is constructed to withstand impact speeds normally encountered in train operation. Through inadvertence or the like the conditions of impact at the couplers of a car may involve excessive masses and at high impact speeds which are higher than those normally prescribed for safe train action.

To accommodate the cushion unit 220 to these conditions there is formed in the piston head 222 a plurality of pair of orifices 227227 and 228228 providing fluid passageways. As shown there are two pairs of orifices 2Z8228; the respective pairs being disposed in diametrically spaced relation to each other.

The pairs of orifices 227227 are formed with valve seats 229 formed on the wall 222a of the piston head while the orifices 228228 are formed with valve seats 229 formed on opposite wall 222b. Seated in the valve seats 229 of each of the pairs of orifices 227227 and 228228 are ball valve members 232. Holding the ball valves 232 in seated engagement with the respective valve seats of the pairs of orifices is an associated leaf spring 233.

As shown in particular in FIG. 13, typically each of the leaf springs 233 is fastened intermediate its ends by means of screw 234 which is fastened to the piston wall associated with the valve seats 231 in which the balls are seated. Adjacent each of the ends of the leaf spring 233 there is formed a dimple like portion 236 which nestingly engages respective ones of the ball valve members 232. Tightening or loosening of the screw 234 is operative to control the pressure exerted on the ball valve and thereby determines the force of hydraulic fluid pressure required to unseat the same. In accordance with the present invention the springs 233 are each adjusted to yield and release the ball valves 232 from seating engagement within the valve seats at fluid pressures corresponding to the high mass and overspeed impacts of the magnitude described above.

Thus under impact masses and speeds normally encountered in train operation the springs 233 are operative to maintain the ball valves 232 seated within the respective valve seats and such that hydraulic fluid flow does not occur through the orifice 227227 or 228228. However, should a high mass end overspeed impact occur in buif the ball checks overlying the orifices 227227 are unseated and the hydraulic fluid flows through the orifices while the orifices 228228 remain closed. Upon impact in draft the orifices 22$228 are open to permit the hydraulic fluid to flow therethrough and the orifices 227227 remain closed.

What is claimed is:

1. A double acting hydraulic cushion device for a draft gear arrangement said hydraulic device comprising a hydraulic fluid filled housing forming a reservoir, a hydraulic fluid filled cylinder disposed within said reservoir, orifice means formed in said cylinder providing communication between the bore of said cylinder and said reservoir, a fluid displacement means reciprocable within said cylinder from a neutral position intermediate the ends of said cylinder for displacing fluid through said orifices from one side of said fluid displacement means to the other side thereof via said reservoir, and surge chamber means in operative association with said reservoir for providing an auxiliary volume accommodating the excessive displaced fluid which is not displaced to said other side of said fluid displacement means during movement thereof from said neutral position.

2. The invention as defined in claim 1 wherein said fluid displacement means comprises a piston head mounted intermediate the ends of a piston rod and said piston rod is joined in cylinder heads at each end of said cylinder.

3. The invention as defined in claim 2 wherein said piston rod is a hydraulic fluid containing hollow tubular member and the journaled ends thereof, projects outwardly of the respective cylinder heads, and wherein expansible hydraulic fluid receiving bellows are fixed to each of the projecting ends and to respective ones of the cylinder heads.

4. The invention as defined in claim 1 wherein said orlfices in said cylinder wall are each of substantially equal area and are variably spaced lengthwise of said cylinder so as to impact substantially constant force travel closure characteristics to said hydraulic cushion device upon movement of said fluid displacement means in either direction from said neutral position.

5. The inventions as defined in claim 1 wherein said reservoir housing includes openings, and wherein said surge chamber comprises a hermetically sealed chamber disposed over said openings, and a flexible member is superposed over said openings, said flexible member normally closing off said openings to maintain the fluid within said reservoir, and being flexed outwardly away from said housing upon pressure forces of said hydraulic fluid within said reservoir during movement of said fluid displacement to provide an auxiliary volume for said hydraulic fluid within said reservoir and thereby maintain said pressure forces within limits tolerable to said reservoir housing.

6. The invention as defined in claim 5 wherein said hermetically sealed chamber comprises a bottom wall, side walls, end walls, a substantially rectangular frame fixed to the upper edges of said side and end walls, said frame being contoured complementary to said reservoir housing, and wherein said flexible member is disposed between said rectangular frame and said reservoir housing so as to be superposed over said openings in said housing, to said housing to clamp said flexible member between said frame and said housing.

7. A double acting hydraulic cushion device for a draft gear arrangement, sai-d hydraulic device comprising a hydraulic fluid filled housing forming a reservoir, a hydraulic fluid filled cylinder disposed within said reservoir, orifice means formed in said cylinder providing communication between the bore of said cylinder and said reservoir, a fluid displacement means reciprocal within said cylinder for displacing fluid through said reservoir from one side of said fluid displacement means to the other side thereof via said orifices, and a flexible fluid pressure responsive chamber means in operative association with said reservoir for providing an auxiliary volume accommodating the excessive displaced fluid which is not displaced to said other side of said fluid displacement means during movement of said fluid displacement means causing fluid pressure surges in said reservoir.

References Cited by the Examiner ARTHUR L. LA POINT, Primary Examiner.

LEO QUACKENBUSH, Examiner.

Claims

1. A DOUBLE ACTING HYDRAULIC CUSHION DEVICE FOR A DRAFT GEAR ARRANGEMENT SAID HYDRAULIC DEVICE COMPRISING A HYDRAULIC FLUID FILLED HOUSING FORMING A RESERVOIR, A HYDRAULIC FLUID FILLED CYLINDER DISPOSED WITHIN SAID RESERVOIR, ORIFICE MEANS FORMED IN SAID CYLINDER PROVIDING COMMUNICATION BETWEEN THE BORE OF SAID CYLINDER AND SAID RESERVOIR, A FLUID DISPLACEMENT MEANS RECIPROCABLE WITHIN SAID CYLINDER FROM A NEUTRAL POSITION INTERMEDIATE THE ENDS OF SAID CYLINDER FOR DISPLACING FLUID THROUGH SAID ORIFICES FROM ONE SIDE OF SAID FLUID DISPLACEMENT MEANS TO THE OTHER SIDE THEREOF VIA SAID RESERVIOR, AND SURGE CHAMBER MEANS IN OPERATIVE ASSOCIATION WITH SAID RESERVOIR FOR PROVIDING AN AUXILIARY VOLUME ACCOMMODATING THE EXCESSIVE DISPLACED FLUID WHICH IS NOT DISPLACED TO SAID OTHER SIDE OF SAID FLUID DISPLACEMENT MEANS DURING MOVEMENT THEREOF FROM SAID NEUTRAL POSITION.