US3596773A

US3596773A - Hydraulic draft gear and cushioning unit

Info

Publication number: US3596773A
Application number: US799175A
Authority: US
Inventors: William H Peterson
Original assignee: Pullman Inc
Current assignee: Pullman Standard Inc; Pullman Inc
Priority date: 1969-02-14
Filing date: 1969-02-14
Publication date: 1971-08-03
Anticipated expiration: 1988-08-03

Abstract

A double-acting hydraulic cushion unit for a railway car which is formed with a hydraulic-fluid-filled cylinder having a closed end and an open end afforded by an apertured cylinder head. A piston assembly is disposed for relative reciprocating movement within the cylinder and includes a piston rod which slidingly moves through the cylinder head. The unit is provided with a flexible accumulator boot connected to the cylinder head and to the piston rod to close the open end of the cylinder. A metering means comprises a metering pin on the cylinder which cooperates with a slidable orifice plate in the piston, the orifice plate having one position in buff impact and another position on the return stroke of the piston assembly to facilitate the transfer of fluid from one side of the piston head to the other. A fluidpressure-responsive valve means is movably disposed in a chamber contiguous with the accumulator to a position overlying passages communicating with the accumulator and to a position clear of said passages. The fluid-pressure-responsive valve is designed to also restrict the flow of fluid from one side of the piston during the return stroke of the piston and upon a draft impact stroke to cushion said impact. The piston rod also includes metering openings also serving on the return stroke to meter the fluid to the accumulator boot. In one embodiment relief valves are provided in the piston to open upon predetermined fluid pressures on opposite sides of said piston.

Description

United States Patent [72] Inventor William H. Peterson llomewoodJll. [21] AppLNo. 799,175 [22] Filed Feb. 14,1969 [45] Patented Ang.3, 1971 [73] A'ssignee Pullman-Incorporated ChicagoJll.

[54] HYDRAULIC DRAFT GEAR AND CUSHIONING UNIT 14 Claims, 12 Drawing Figs.

[52] US. 213/8, 213/43. 188/88, 267/115 [51] Int. B6lg9/04, B6lg9/12 [50] FleldolSeareh 213/8,43, 223; 267/115; 188/88.509, 88.510, 96,100

56 immense UNITED STATES PATENTS 3,070,363 12/1962 Ellis,.lr 213/43 3,190,458 6/1965 Zanow... 213/43 3,232,443 2/1966 Smith 213/8 $275,164 911966 Peterson 213/43 3,412,870 11/1968 Rollins..... 213/8 3,458,054 7/1969 Thompson 213/43 Primary ExaminerDrayton E. Hoffman Attorneys-Hilmond O. Vogel and Wayne Morris Russell ABSTRACT: A double-acting hydraulic cushion unit for a railway car which is formed with a hydraulic-fluid-filled cylinder having a closed end and an open end afforded by an apertured cylinder head. A piston assembly is disposed for relative reciprocating movement within the cylinder and includes a piston rod which slidingly moves through the cylinder head. The unit is provided with a flexible accumulator boot connected to the cylinder head and to the piston rod to close the open end of the cylinder. A metering means comprises a metering pin on the cylinder which cooperates with a slidable orifice plate in the piston, the orifice plate having one position in buff impact and another position on the return stroke of the piston assembly to facilitate the transfer of-fluid from one side of the piston head to the other. A fluid-pressure-responsive valve means is movably disposed in a chamber contiguous with the accumulator to a position overlying passages communicating with the accumulator and to a position clear of said passages.- The fluid-pressure-responsive valve is designed to also restrict the flow of fluid from one side of the piston during the return stroke of the piston and upon a draft impact stroke to cushion said impact. The piston rod also includes metering openings also serving on the return stroke to meter the fluid to the accumulator boot. In one embodiment relief valves are provided in the piston to open upon predetermined fluid pressures on opposite sides of said piston.

PATENTEDAUS 3911 3596173

sum

1 or 5 IN VE N TOR L WILLIAM H. PETERSON 8% ATT'Y.

PATENTEDAUB 3197a v SHEET 2 or 5 W W: a z

. I u i .1 Lg] INVENTOR WILLIAM H. PETERSON Mai/723 PATENTEDAUB 3m:

sum 3 or s INVENTOR WILLIAM H. PETER N BY Wa KTT'Y.

PATENTEU Aus 3:911

SHEET Q [If 5 INVENTOR WILLIAM H. PE ERSON PATENTEUAUB 3m 3596.773

' sum 5 [IF 5 INVENTOR p I l lll WILLIAM H. PETERSON WfiM AT'T'Y.

nvmuuuc mum'r GEAR AND cusmoumc uurr SUMMARY unit particularly adapted for railroad cars which during operation provides cushioning for both buff and'draft impacts to which a railroad car is subjected. The cushioning unit of the present invention may readily be incorporated in the underframe' at opposite ends of the car to provide end-of-car cushioning for the impacts which are applied to the coupler of the car. A primary object of the present invention is to provide a cushioning unit having a metering pin arrangement which cooperates with a metering orifice provided in the piston head of the unit. The metering arrangement provides for a substantially constant force travel of the piston relative to the cushioning cylinder in a buff impact condition. Further, the metering arrangement includes a sliding orifice plate which during return of the piston to a neutral position is movable to DETAILED DESCRIPTION Referring now particularly to FIGS. 1 through 4 and 7, a hydraulic cushion unit is designated by the reference character 10. The hydraulic cushion unit 10, as shown in FIG. The invention relates to a hydraulic draft gear or cushioning provide an increased flow of fluid to a chamber containing the metering Jpin thus assuring the quick return of the unit to its neutral position. Further, the piston assembly is disposed in the neutral position in lengthwise spaced relation from a cylinder head forming one end of the cylinder thus permitting a limited travel of the piston towards said cylinder head in the event of the application of a draft'impact. The cylinder head is provided with a cavity and a slidable valve assembly which in a buff position permits fluid flow from a flexible accumulator to a chamber disposed between the cylinder head and one side of the piston. The valve assembly is so disposed relative to the cylinder rod of the piston assembly as topermit a restricted flow of the fluid to said accumulator from said last-mentioned chamber during the return stroke and during a draft impact thereby providing cushioning or snubbing to absorb the forces of the said-draft impact. In amodified embodiment thepiston rodis further provided with metering openings which also during the-return stroke of the piston head provide'for a smooth retumof the unit to a neutral position. The piston'assembly has a piston rod which is connected to a-yolte arrangement asv sociated with a standard coupler. The yoke arrangement provides' with a center still a pair of pockets disposed on opposite sides of the yoke which contain leaf springs adapted to return the piston assembly to its neutral position aftera draft impact.

BRIEF DESCRIPTION OF THE DRAWINGS FIGQI is a schematic plan view of one end of a railroad car showing an underframe having at one end thereof a hydraulic draft gear and cushion unit;

FIG. 2 isa plan view partially in section of -an end-of-car cushion unit in one end of a car underframe;

FIG. 3 is a side elevational view of the arrangement shown in FIG. 2;

FIG. 4 is a cross-sectional'view through a hydraulic cushion unit disposed in the center sill of a railroad car underframe;

FIG. 5 is a cross-sectional view showing the connection of a coupler to a yoke, connected to the piston rod of a piston assembly;

FIG. 6 is a cross sectional view similar to FIG. 4 disclosing a modified hydraulic cushion unit;

FIG. 7 is a perspective view of a modification of the cushioning unit disclosed in FIG. 4;

FIG. 8 is a frontal elevational view of a piston assembly;

FIG. 9 is a cross-sectional view taken substantially along the line 9-8 of FIG. 8;

FIG. 10 is a cross-sectional view taken substantially along the line 10-10 of FIG. 9;

FIG. 11 is a cross-sectional view taken substantially along the line 11-11 of FIG. 9; and

FIG. 12 is a detail cross-sectional view of a relief valve.

1, is positioned at the ends of a railroad car 11 having a conventional underframe 12 including a center sill 13. The hydraulic unit 10 includes a cylinder 14 having a closed end formed by an end plate 15. The end plate 15 has connected thereto a metering pin 16 disposed in a chamber A. The metering pin 16 includes tapering metering slots 17. A cylinder head 18 is disposed intermediate the ends of the cylinder 14 and is disposed therein within an annular undercut 19. An annular valve plate 20 is also disposed in the undercut 19 and includes ports 21 which communicate with a chamber B as best shown in FIG. 7. A suitable locking arrangement 22 locks the valve plate 20 and cylinder head 18 in the undercut 19. A valve element or ring 23 is longitudinally movable within an annular recess or chamber 24 provided in the cylinder head 18. A similar valving arrangement is shown in applicant's US. Pat. No. Re. 26,472, issued Oct. 1, I968.

A piston assembly is generally designated at 25 and includes a rod 26 having an elongated bore 27. A piston 28 connected to the rod 26 has a frontal side which with the end plate 15 forms the chamber A and with its rear side, the annular valve plate 20' and cylinder head 18 forms the chamber B. The piston 28 is provided with a laminated plastic slide ring 29 suitably described in the aforementioned patent. The piston 28 as indicated at 30 is threaded to the end of the rod 26 and in its frontal face is provided with an enlarged annular bore 31 in which a snap ring 32 is secured. A metering plate 33 is longitudinally slidably contained within the bore 31 and includes an arcuate peripherally extending edge 34. A plurality of circumferentially extending bores 35 are provided in the metering plate 33 about a longitudinally extending metering orifice 36.

The piston 28 is provided with a pair of vertically spaced longitudinally extending bores 37 and a pair of transversely spaced longitudinally extending bores 28.'

Relief valves

39 and 40, as best shownin FIGS. 8 and 9, are respectively provided in the

bores

37 and 38.

Relief valves

39 and 40 have certain common parts each including tubular spool-shaped body 41 having an end 42 and an annular undercut passage v43. The end 42 includes bleed openings 44 and a substantially small tubular piston element 45, which is adapted to be slidingly engaged within a bore 46 provided in the piston 28. 1

As best shown in FIGS. 4 and 9, the relief valves 39hav theirpiston elements facing the chamber B and these are effective to operate during certain excessive draft impacts. The relief valves 40 have their piston elements 45 facing the chamber A and are effective during certain excessive buff impacts. The relief valves 39 include retainer elements 47 having projections 48 provided with open end bores 49. The retainer elements 47 are retained within the bores 37 by means of snap rings 50. Springs 51 within the bodies 41 bias the piston elements 45 in the position indicated in FIG. 9. As best shown in FIG. 12, one of the relief valves 40 is disclosed and the spring 51 is wrapped about a retainer element 47' having an open end bore 48 and being suitably threaded into the piston 28. The piston element 45 of each relief valve 40 is movable within a bore 53 provided in an annular retaining plate 52 suitably secured relative to the bore 37 by means of a snap ring As best shown in FIGS. 7, 9 and 12, the piston 28 is provided with

annular passages

54 and 55 encircling the

relief valves

39 and 40. An annular passage 56 is also provided in one end of the piston rod 26 which communicates with openings 57 opening inwardly with respect to the elongated bore 27 The annular passage 56 communicates with the annular passages 54. As best shown in FIGS. 7 and 8 the frontal face of the piston 28 is provided with a plurality of passages 58 which open into the chamber A. The passages 58 are in direct communication with the annular passages 55 of the piston 28. The rear face of the piston 28 as shown in FIG. 11 is also provided with similar-passages 59 opening into the chamber B and being in communication with the annular passages 54.

The cylinder 14 is closed by a flexible accumulator boot 60 having one end sealingly connected to the piston rod 26 by means of a connecting arrangement 61 more specifically described in the aforementioned patent. The accumulator boot 60 includes an open end portion 62 which is also sealingly connected to the intermediate cylinder head 18 by means of a securing ring 63. The bore 27 by means of a plurality of openings 64 is in communication with the interior of the accumulator boot 60. Theintermediate cylinder head 18 includes a bore 65 which encircles the piston rod 26 and is circumferentially spaced with respect thereto. The bore 65 communicates with an enlarged annular bore 66 provided in the valve plate 20 and which also is circumferentially spaced relative to the piston rod 26.

The ports 21, the annular chamber or recess 24, and bores 65 and 66, provide a passageway means from the chamber B to the accumulator boot 60. The bore 27 with the

openings

64 and 100 leading to the accumulator boot 60 provide a passageway system in the piston rod 26, communicating the chamber A with the accumulator boot 60.

Referring now particularly to FIGS. 2and 3, the center sill 13.0fthe underframe 12 includesa pair of upright walls 70 having at their lower ends outwardly projecting flanges 71 and having a top wall 72. A transversely extending stop 73 is supported on the walls 70 within the'center sill-13, and provides a pocket 74 in which the cushion unit '10 is disposed. The end plate 15 of the cylinder 14 is provided with, forwardly projecting stop elements 75 which are longitudinally slightly spaced from from stop lugs 76 extending through openings 77 in the vertical walls 70. The lugs 76 are retained in position by means of brackets 78 suitably connected to the upright walls 70. Thus the cylinder 14 is restrained against limited longitudinal movement within the center sill by the stop 73 and the top ele- -rnents 75'and 76.

As best shown in FIGS. 4 and 6, a spring retainer plate 79 is fixed on the cylinder 14 and supports one end of a spring 80 encircling a portion of the cylinder 14 and the piston assembly, said spring 80 being in engagement with the rear wall portion 81 of a yoke 82. The yoke 82 is provided with laterally projecting vertical lug elements 83 which with the vertical walls 70 and inwardly projecting stop lugs 84 provide a leaf spring pocket 85 on each side of the yoke 82. Lugs project through openings 86 in the walls 70 and are secured by means of brackets 87-to the upright walls 70: A' pair of leaf spring assemblies 88 are disposed in each of the pockets 85 in the manner indicated in FIG. 2..The ends of the center sill 13 are also provided with a bottom cover plate 89.

As best shown in FIG. the yoke 82 is provided with a spherical socket 91 and a bore 92 into which the piston rod 26 projects. A threaded connecting member 93 conforming to the spherical socket 91 is suitably threaded on the end of the rod 26. The connector 93 has an arcuate coupler-engaging surface 94 which is adapted to receive the arcuate end of a coupler stem 95. The stem 95 is provided at its forward end with a conventional coupler head 96. The yoke 82 is also provided at its forward end with a suitable bell-mouth structure 97- of conventional design. The stem 95 is mounted for relative pivotal and sliding movement by means of a key 98 which is carried on the coupler stem 95 and slides within elongated slots 99 of the yoke 82.

THE OPERATION The chambers A and B, passageway means, and passageway I system are completely charged with a suitable hydraulic fluid.

passes through the metering orifice 36 providing a constant force travel of the piston 25. The fluid passing from the chamber A through the bore 27 passes into the accumulator 60. The pressure differential between the accumulator 60 and the chamber B provides for movement of the valve element 23 into engagement with the valve plate 20 uncovering the bore 65 thereby freely permitting fluid from the accumulator 60 to fill up the chamber B. During the buff impact, the orifice plate 33 is an engagement with the end of the piston rod 26 whereupon the bores 35 are covered. 7

Upon cessation of the buff force the spring'80 returns the piston assembly 25 to the neutral position shown in FIG. 4. Upon such return movement the orifice plate 33 moves into engagement with the snap ring 32 and the bores 35 are now incommunication with the bore 27 permitting a volume flow into thechamber A, thus, assuring the quick return of the piston 28 to its neutral position. During this return movement of the piston 28 the valve element 23 is disposed over the bore 65 so a limited or restricted flow of fluid is possible since, as best shown in FIG. 7, The inner peripheral surface of the valve element 23 is of arcuate construction providing with the piston rod 26 a small annular passage 23 through which a restricted flow of fluid can pass from the chamber B onto the accumulator 60 'as best shown in FIG. 7. The restrictedpassage 23 provides for the smooth andeven return of the piston'head 28 to the neutral position. The valve'element 23 thus moves to its open position on the buff or closing stroke'of the piston 28. On the return stroke of the piston 28 toits neutral position the valve element 23 is in a partially closed position over the bore 65 through permitting by virtue of the opening 23' a restricted flow of fluid to the accumulator 60.

In the embodiment shown in FIG. 7, the piston rod 26 is also provided with metering openings 100 communicating with the bore 27 and the accumulator boot- 60. During the return stroke these openings also function as metering openings to return fluid from the chamber B to the accumulator boot 60 in a smooth and efficient manner. If desired, the opening 23' may be substantially eliminated by providing a tighter sliding fit with the piston rod 26 in which'case the metering on the return stroke is provided solelyby the metering openings 100.

In the event of a draft impact on the coupler head 96, the yoke 82 moves in a direction away from the cylinder 14 compressing the leaf spring assemblies 88 until they are in flat contiguous relation which then prevents further outward movement of the yoke 82. Simultaneously, the piston28 is moved toward the valve plate 20 and fluid from the chamber 8- flows through the ports 21, bore 66, through the restricted opening 23' into the accumulator boot 60. The restriction provided by the opening 23' results in a cushioning or snubbing actionfor cushioning the draft impact during its application. During such draft impact fluid from the bore 27 is free to pass through the'metering orifice 36 and through the bores 35. Upon the cessation of the draft impact the leaf spring assemblies 88 return the piston 28 to the neutral position shown in FIG. 4. Thus it can be seen that the metering pin 16 with the metering orifice 36 provides a constant force travel of the piston 28 during the buff stroke. On the draft impact stroke the valve element 23 provides a sufficient restriction of fluid flow from the chamber B into the accumulator 60 to afford the cushioning or snubbing action during said impact.

In FIG. 6 a further modified cushion unit 10 is disclosed. The primary difference between the cushion unit of FIG. 6 and that shown in the other FIGURE is that the

relief valves

39 and 40 are absent from the piston head 28. Otherwise all of the parts are the same and are so designated. In certain applications and constructions it may be desirable to eliminate-the relief valves. In operation the relief valves function as follows: during a buff stroke of the piston 28, provided the pressure within chamber A exceeds a predetermined amount, the piston elements 45 of the relief valves 40 will move causing the annular undercut passage 43 of each relief valve body 41 to provide for communication between the

annular passages

54 and 55. Fluid thus can now flow through the openings 58 through the

annular passages

54 and 55 to the annular passage 56 and through openings 57 into the interior of the bore 27 which fluid ,is then directed through the openings 64 to the accumulator boot 60. I

In the'event that the fluid pressure within the chamber B exceeds a predetermined amount the piston elements 45 facing the chamber 8 are moved to open the valves 39 wherein the undercut passage 43 provides for communication between the

annular passages

54 and 55. Fluid may now flow through the openings 59, as best shown in H6. 11, through the passages 54 and into passages 55 which permit fluid to flow through the openings 58 into the chamber A, thus relieving the excessive pressures of chamber 8. The

bleed openings

44 and 49 of the relief valves 40 are provided to permit free operating movement of therelief valves since the unit is completely filled with hydraulic fluid.

As previously described, a limiting tilting movement of the cylinder from the horizontal is permitted by the loose clearance provided by the stop elements 75 relative to the lugs 76. The yoke 82 is not confined for guiding movement within the sill l3 and thus during buff impact all forces to be dissipated are absorbed first in the hydraulic cushioning device. Precise guiding of the yoke 82 is not required since the flexible boot does not require the precision of guiding movement required in cushioning devices having sliding SCQISpThUS the total forces are first absorbed in the cushioning device.

What 1 claim is:

l. A double-acting hydraulic cushion unit for relieving the buff and draft impacts imposed on the couplers of a railway car, said cushion unit comprising:

a cylinder having a closed end and an open end,

a piston assembly including a piston head and a piston rod disposed in said cylinder having lengthwise travel relative to said closed end,

a cylinder head mounted in said cylinder adjacent said open end and having passageway means, said piston rod being movable through said cylinder head during said travel,

a flexible accumulator connected between said cylinder and said piston rod for closing the open end of said cylinder, said passageway means providing communication between a first chamber defined by said piston head and said cylinder head,

valve means disposed in said passageway means and operable upon a predetermined pressure differential between said first chamber and a second chamber defined by said piston head and said closed end to provide fluid flow from said accumulator through said passageway means to said first chamber,

said valve means having restrictive flow means being operable during the movement of said piston assembly in a draft direction toward said cylinder head for permitting a restricted flow of fluid from said first chamber to said accumulator;

a passageway system formed in said piston rod providing communication between said second chamber and said accumulator,

hydraulic fluid filling said chambers and means metering the flow of said fluid between the second and first chambers during travel of said piston head,

said metering means including a metering pin having a me tering surface and being supported by said cylinder within said second chamber,

said piston having a bore facing said second chamber and communicating with said passageway system,

a metering element disposed in said bore and having limited axial movement relative to said piston, said metering element including a metering orifice cooperating with said metering orifice cooperating with said metering surface during lengthwise travel of said piston assembly toward said closed end to meter the flow of fluid from said second chamber to said passageway system,

said metering element having at least one opening radially spaced relative to said orifice which during the aforesaid travel of said piston assembly is in a position closed by said piston'assembly and which during movement of said piston assembly in an opposite direction is axially moved within said bore, and said opening of said metering element communicates with said passageway system and said second chamber.

2. The invention in accordance with claim 1,

wherein said metering element includes aplurality of said radially disposed and circumferentially disposed openings which during travel toward said closed end are closed by an adjacent wall portion of said piston assembly and which during travel in an opposite direction are moved from said wall portion permitting fluid flow therethrough.

3. The invention in accordance with claim 1 said valve means comprising a port in said passageway means providing communication between said first chamber and said accumulator, and

a valve element shiftable during a pressure differential between said first chamber and said accumulator to positions opening said port and partially blocking said port.

4. The invention in accordance with claim 3,

said valve element comprising a ring-shaped valve plate encircling said piston rod and slidably supported thereon,

and

said valve plate in the partially blocking position of said port providing for a restricted flow through said passageway means to said accumulator.

5. The invention in accordance with claim 1, including:

' relief valve means in said piston head including relief ports opening outwardly into said first and second chambers,

valve elements in said head adapted to open said ports in response to a predetermined pressure differential between said chambers whereby fluid from one chamber is delivered to the other.

6. The invention in accordance with claim 5,

said piston head having a passage providing communication between said ports and said passageway system.

7. In a railway car having an underframe, a double-acting hydraulic cushion unit for relieving the buff and draft impacts imposed on the couplers of said car, said cushion unit comprising:

a cylinder having a closed end and an open end,

a cylinder head mounted in said cylinder adjacent said open end and having passageway means including at least one opening providing for movement of said piston rod during said travel,

a second chamber defined by said piston head and said closed end,

a passageway system formed in said piston rod providing communication between said first chamber and said accumulator,

hydraulic fluid filling said chambers and means metering the flow of said fluid between the first and second chambers during travel of said piston head; the improvement comprising means connecting said cylinder to said underframe,

a coupler-carrying member connected to said piston rod for travel therewith,

biasing means between said cylinder and said coupler-carrying member urging said piston assembly in a direction toward said open end,

first stop means on said underframe,

second stop means on said coupler-carrying member,

said stop means being longitudinally spaced and providing on opposite sides of said coupler-carrying member with said underframe a plurality of pockets,

spring means disposed in said pockets between said stop means, and in a nonoperating position of said piston assembly positioning said piston head in relatively spaced relation between said closed end and said cylinder head, and

valve means on said cylinder head providing with said passageway means a restricted flow of fluid from said first chamber to said accumulator during movement of said piston assembly toward said open end during a draft impact whereby said spring means is compressed.

8.. The invention in accordance with claim 7,

said valve means comprising a ring-shaped valve element encircling said piston rod and during said movement on a draft impact being adapted to partially block the flow of fluid to said passageway means and to said accumulator.

9. The invention in accordance with claim 8,

said spring means comprising a plurality of nested springs.

10. In a railroad car having a center sill structure, a hydraulic cushioning unit for relieving the buff and draft impacts imposed upon the couplers of said car, said cushioning unit being positioned adjacent and within one end of said center sill structure, and comprising:

a cylinder member having an inner end part and an outer end part facing outwardly of the car and a piston member including a piston head and a piston rod disposed in said cylinder member and having lengthwise travel relative to said end parts,

said piston rod extending longitudinally of said sill structure and outwardly of said outer end part,

metering means for metering hydraulic fluid flow within said cylinder member on buff and draft impacts being applied to said cushioning unit to cushion the application of such impacts to said sill structure,

a coupler-carrying element mounted in said sill structure,

a coupler-carrying element mounted in said sill structure outwardly of said cushioning unit for movement longitudinally of said sill structure and being connected with said piston rod for travel therewith,

means for operatively connecting the car coupler to said coupler-carrying element, v

biasing means between said cylinder member and said coupler-carrying element urging said piston member in a direction toward said outer end part,

attachment means for securing said cushioning unit to said sill structure against buff and draft impacts applied to said cushioning unit including a resilient cushioning means being disposed within the center sill structure and in general longitudinal alignment with said'biasing means interposed between one of said cushioning unit members and said sill structure for absorbing draft impacts when said piston head is adjacent said outer end part, and stop means being carried within said sill structure and said 7 coupler-carrying element for limiting movement of one of said cushioning unit members in draft,

said stop means including a first stop on said center sill structure and a second stop cooperative with one of said cushioning unit members, said second stop being longitudinally spaced from said first stop and said resilient cushioning means being disposed between said stops.

11. The invention according to claim 10, and

said second stop being carried by said coupler carrying element.

12. The invention according to claim 10, and

said resilient cushioning means including spring means disposed between said first and second stops.

13. The invention according to claim 10, and

said resilient cushioning means including a plurality of nested springs.

14. The invention according to claim 10, and

a flexible expansible boot being connected between said cylinder member and said piston rod to provide a seal between said cylinder member and said piston rod.

Claims

1. A double-acting hydraulic cushion unit for relieving the buff and draft impacts imposed on the couplers of a railway car, said cushion unit comprising: a cylinder having a closed end and an open end, a piston assembly including a piston head and a piston rod disposed in said cylinder having lengthwise travel relative to said closed end, a cylinder head mounted in said cylinder adjacent said open end and having passageway means, said piston rod being movable through said cylinder head during said travel, a flexible accumulator connected between said cylinder and said piston rod for closing the open end of said cylinder, said passageway means providing communication between a first chamber defined by said piston head and said cylinder head, valve means disposed in said passageway means and operable upon a predetermined pressure differential between said first chamber and a second chamber defined by said piston head and said closed end to provide fluid flow from said accumulator through said passageway means to said first chamber, said valve means having restrictive flow means being operable during the movement of said piston assembly in a draft direction toward said cylinder head for permitting a restricted flow of fluid from said first chamber to said accumulator; a passageway system formed in said piston rod providing communication between said second chamber and said accumulator, hydraulic fluid filling said chambers and means metering the flow of said fluid between the second and first chambers during travel of said piston head, said metering means including a metering pin having a metering surface and being supported by said cylinder within said second chamber, said piston having a bore facing said second chamber and communicating with said passageway system, a metering element disposed in said bore and having limited axial movement relative to said piston, said metering element including a metering orifice cooperating with said metering orifice cooperating with said metering surface during lengthwise travel of said piston assembly toward said closed end to meter the flow of fluid from said second chamber to said passageway system, said metering element having at least one opening radially spaced relative to said orifice which during the aforesaid travel of said piston assembly is in a position closed by said piston assembly and which during movement of said piston assembly in an opposite direction is axially moved within said bore, and said opening of said metering element communicates with said passageway system and said second chamber.

2. The invention in accordance with claim 1, wherein said metering element includes a plurality of said radially disposed and circumferentially disposed openings which during travel toward said closed end are closed by an adjacent wall portion of said piston assembly and which during travel in an opposite direction are moved from said wall portion permitting fluid flow therethrough.

3. The invention in accordance with claim 1, said valve means comprising a port in said passageway means providing communication between said first chamber and said accumulator, and a valve element shiftable during a pressure differential between said first chamber and said accumulator to positions opening said port and partially blocking said port.

4. The invention in accordance with claim 3, said valve element comprising a ring-shaped valve plate encircling said piston rod and slidably supported thereon, and said valve plate in the partially blocking position of said port providing for a restricted flow through said passageway means to said accumulator.

5. The invention in accordanCe with claim 1, including: relief valve means in said piston head including relief ports opening outwardly into said first and second chambers, valve elements in said head adapted to open said ports in response to a predetermined pressure differential between said chambers whereby fluid from one chamber is delivered to the other.

6. The invention in accordance with claim 5, said piston head having a passage providing communication between said ports and said passageway system.

7. In a railway car having an underframe, a double-acting hydraulic cushion unit for relieving the buff and draft impacts imposed on the couplers of said car, said cushion unit comprising: a cylinder having a closed end and an open end, a piston assembly including a piston head and a piston rod disposed in said cylinder having lengthwise travel relative to said closed end, a cylinder head mounted in said cylinder adjacent said open end and having passageway means including at least one opening providing for movement of said piston rod during said travel, a flexible accumulator connected between said cylinder and said piston rod for closing the open end of said cylinder, said passageway means providing communication between a first chamber defined by said piston head and said cylinder head, a second chamber defined by said piston head and said closed end, a passageway system formed in said piston rod providing communication between said first chamber and said accumulator, hydraulic fluid filling said chambers and means metering the flow of said fluid between the first and second chambers during travel of said piston head; the improvement comprising means connecting said cylinder to said underframe, a coupler-carrying member connected to said piston rod for travel therewith, biasing means between said cylinder and said coupler-carrying member urging said piston assembly in a direction toward said open end, first stop means on said underframe, second stop means on said coupler-carrying member, said stop means being longitudinally spaced and providing on opposite sides of said coupler-carrying member with said underframe a plurality of pockets, spring means disposed in said pockets between said stop means, and in a nonoperating position of said piston assembly positioning said piston head in relatively spaced relation between said closed end and said cylinder head, and valve means on said cylinder head providing with said passageway means a restricted flow of fluid from said first chamber to said accumulator during movement of said piston assembly toward said open end during a draft impact whereby said spring means is compressed.

8. The invention in accordance with claim 7, said valve means comprising a ring-shaped valve element encircling said piston rod and during said movement on a draft impact being adapted to partially block the flow of fluid to said passageway means and to said accumulator.

9. The invention in accordance with claim 8, said spring means comprising a plurality of nested springs.

10. In a railroad car having a center sill structure, a hydraulic cushioning unit for relieving the buff and draft impacts imposed upon the couplers of said car, said cushioning unit being positioned adjacent and within one end of said center sill structure, and comprising: a cylinder member having an inner end part and an outer end part facing outwardly of the car and a piston member including a piston head and a piston rod disposed in said cylinder member and having lengthwise travel relative to said end parts, said piston rod extending longitudinally of said sill structure and outwardly of said outer end part, metering means for metering hydraulic fluid flow within said cylinder member on buff and draft impacts being applied to said cushioning unit to cushion the application of such impacts to said sill structure, a coupler-carrying element mounted in said sill sTructure, a coupler-carrying element mounted in said sill structure outwardly of said cushioning unit for movement longitudinally of said sill structure and being connected with said piston rod for travel therewith, means for operatively connecting the car coupler to said coupler-carrying element, biasing means between said cylinder member and said coupler-carrying element urging said piston member in a direction toward said outer end part, attachment means for securing said cushioning unit to said sill structure against buff and draft impacts applied to said cushioning unit including a resilient cushioning means being disposed within the center sill structure and in general longitudinal alignment with said biasing means interposed between one of said cushioning unit members and said sill structure for absorbing draft impacts when said piston head is adjacent said outer end part, and stop means being carried within said sill structure and said coupler-carrying element for limiting movement of one of said cushioning unit members in draft, said stop means including a first stop on said center sill structure and a second stop cooperative with one of said cushioning unit members, said second stop being longitudinally spaced from said first stop and said resilient cushioning means being disposed between said stops.

11. The invention according to claim 10, and said second stop being carried by said coupler carrying element.

12. The invention according to claim 10, and said resilient cushioning means including spring means disposed between said first and second stops.

13. The invention according to claim 10, and said resilient cushioning means including a plurality of nested springs.

14. The invention according to claim 10, and a flexible expansible boot being connected between said cylinder member and said piston rod to provide a seal between said cylinder member and said piston rod.