US3412870A

US3412870A - End-of-car hydraulic buff and draft cushioning

Info

Publication number: US3412870A
Application number: US611456A
Authority: US
Inventors: Dallas W Rollins
Original assignee: ACF Industries Inc
Current assignee: Joy Manufacturing Co
Priority date: 1967-01-24
Filing date: 1967-01-24
Publication date: 1968-11-26
Anticipated expiration: 1985-11-26

Description

FiG.

Nov. 26, 1968 D. w. RoLLINs 3,412,870

ENDOF-CAR HYDRAULIC BUFF AND DRAFT CUSHIONING Filed Jan. 24, 1967 4 Sheets-Sheet l D. W. ROLLINS END-OF-CAR HYDRAULIC BUFF AND DRAFT CUSHIQNING 4 Sheets-Sheet 2 I Nov. 26, 1968 Filed Jan. 24, 1967 v f77/@MY Nov. 26, 1968 D. w. RoLLlNs 3,412,870

CAR HYDRAULIC BUFF AND DRAFT CUSHIONING END-OF- 4 Sheets-Sheet 5 Filed Jan. 24, 1967 Nov. 26, 1968 D. w. RoLLlNs 3,412,870

END-OF-CAR HYDRAULIC BUFF AND DRAFT CUSHIONING Filed Jan. 24, 1967 4 Sheets-Sheet 4 INVEN TOR. Az/.As M Poza/v5 MMM/L MMV@ United States Patent ce 3,412,870 Patented Nov. 26, 1968 3,412,870 END-OF-CAR HYDRAULIC BUFF AND DRAFT CUSHIONING Dallas W. Rollins, St. Charles, Mo., assignor to ACF Industries, Incorporated, New York, NX., a corporation of New Jersey Filed Jan. 24, 1967, Ser. No. 611,456 Claims. (Cl. 213-8) ABSTRACT OF THE DISCLOSURE A hydropneurnatic shock absorber connected to each coupler of a railroad car has a piston positioned by a spring to an intermediate point of its travel to provide buff and draft cushioning. The shock absorber has an axial hollow perforated metering tube and check valves in a partition between two liquid chambers providing a very low speed of return after a compression or extension of the shock absorber. The metering tube includes pressure relief and check valves at both its ends which permit additional cushion travel and prevent overloading which might result from impacts occurring before the cushion has returned sufficiently.

Background of the invention The invention relates to hydraulic cushioning assemblies for railroad cars and particularly end-of-car hydropneumatic cushioning devices for absorbing both buff and draft impacts.

It is the usual practice to provide a draft gear between each coupler and an end-of-car hydraulic cushion to cushion draft forces, although hydraulic cushions acting upon draft and buff forces have also been proposed. In the latter type of cushions the piston must normally be held in an intermediate position, from which it is capable of moving in either direction with a high .absorption of energy under high impact forces. After a cushioning stroke the piston should return to its normal position without a violent recoil, but quickly enough to be in a position to cushion a succeeding shock.

A problem found in the use of end of car cushioning -units is the creation of free slack in the tr-ain by the inability of the cushioning units to dissipate enough energy during draft travel or cushion return after a compression thereof. The cushion may be fully compressed by relatively low magnitude buff forces applied slowly over a sufii-cient period. On the other hand, the return `rate` from a full buff to a neutral position of the cushion may be -about inches per second, or 0.9 mile per hour, and therefore, the cushion will not absorb an appreciable amount of energy during tir-ain run-out unless the velocity of the coupler relative to the car exceeds this speed, or la relative velocity between adjacent cars of about 1.8 m.p.h. Thus, for cushions having an 11 inch stroke, the result during run-out from full run-in will be 22 inches of slack per car with no energy dissipation as the length of the car increases. This, then creates a sudden jerk when the slack is used up, and the rubber draft gears usually provided must absorb this sudden jerk or shock.

Summary of the invention The present invention mitigates the run-out shock problem by reducing the shock absorber return speed threshold at which appreciable energy dissipation occurs to a value of 2 or 3 inches per second. This is done by using one-way valves which reduce the return speed without making the buff forces excessive. Since the return of the shock absorber unit, which is preferably of the hydropneumatic type, is considerably retarded, the unit may be subjected to a succeeding impact before it has returned. For such eventualities the shock .absorber is enabled to provide a small additional reserve cushioning stroke in buff and draft. Valves, serving as secondary metering means, are used for making the reserve cushioning effective under severe conditions. The outer cylinder of the shock absorber is integral with a yoke connected to the coupler and is formed so as to be confined by four corner rails or guides, while the inner cylinder and the piston at its inner end are stationary and attached to the center filler of the center sill.

Brief description of the drawing The invention will be fully understood from the following description and the accompanying drawing, where- FIGS. 1 to 3 are sectional views of a shock absorber in Ia normal position, an extended position, and a compressed position, respectively.

FIG. 4 is an enlarged sectional view of a portion of the shock absorber.

FIG. 5 is a top view of a shock absorber and its associated underframe structure.

FIG. 6 is a partly sectional View taken along the centerline of FIG. 5.

FIG. 7 is .a partial side elevational View of the draft key area of FIG. 5.

FIG. 8 is a sectional View taken on line 8 8 of FIG. 6.

FIG. 9 is a sectional view taken along line 9 9 of FIG. 6.

Description of the preferred embodiment Referring particularly to FIGS. 1 to 4, cushioning unit 10 comprises an outer cylinder 12 and an inner -cylinder 14. Cylinder 12 is integral with yoke 16 and has an .axial perforated metering tube 18. The inner end of cylinder 14 carries a piston 20 which has a close sliding t on metering tube 18. On the inner end of tube 18 is fixed piston 22, and a floating piston 24 is positioned in cylinder 14. The pistons define

chambers

26, 28, and 30 adapted to be filled with oil and chamber 32, which is maintained under a high gas pressure, to form a hydropneumatic shock absorber. The outer end of cylinder 14 is formed by cap 34, which is adapted to be coupled to center filler 35 in the center sill of the car, and is equipped with an air valve 36 through which chamber 32 is charged to a high pressure. The space between the inner and outer cylinders forms an oil filled snubbing chamber 38 having openings 39 through which oil is forced into and out of chamber 38 to reduce the rate at which the cushion returns to its normal extended condition.

Tube 18 includes a number of orifices 40 dimensioned and spaced to meter the flow of fluid so as to provide -a desirable force-travel characteristic of high efiiciency. After piston 20 passes the last orifice 40, in either direction, it would not normally be able to travel any further because the oil would then be trapped in

chamber

26 or 28 and could not escape. Accordingly, pressure responsive check Valves 42 and 44 and preset pressure relief valves 46 and 48 are provided at the ends of tube 18 for allowing liquid to fiow into and out of tube 18 at both ends thereof, .and thus allow piston 20 to travel the additional distance between the last orifice 40 and valves 42-48. In a shock absorber having a normal buff stroke of 11 inches and a draft stroke of 21/2 inches, for eX- ample, the 'additional travel may be one inch and a half inch respectively. Piston 22 has one or more check valves 50 which open only during compression of the shock absorber for a purpose which will be explained below.

Referring now to FIGS. 5-8, the center sill 52 of the car terminates in a iiared end 54 for accommodating coupler shank 56, which is pivotally connected to vertical pin 58. Coupler shank 56 is supported by an upwardly biased spring coupler carrier 60. Pin 58 extends through the forward end of yoke 62 which is integral with cylinder 12 of the shock absorber. A pair of

keys

63, 64 extending through yoke 62 are held by

retainers

65 and 66, which slide on

rods

67, 68 and form abutments for draft spring 76 for centering cushion 10 in its normal position, from which it is capable of draft and buff travel. Retainers and

draft spring abutments

65, 66 are guided by channels 71, 72 welded to the center sill along and between slots 73 and 74 in which

keys

63 and 64 slide.

Cylinder 12 has cruciform similar ends or

flanges

75 and 76, as indicated in FIG. 9. Substantially rectangular bar guides 77-80 are positioned in the corners of the cruciforms of ends 7S, 76 and extend beyond their range of travel both forwardly and rearwardly.

Guides

77 and 78 are welded in the upper corners of center sill 52, and

guides

79 and 80 are welded to cover plate assembly 82 so that they constitute supports for cushion 10 when cover plate assembly 82 is fastened to center sill flanges 83, 84. Rear stops 85, 86 and forward stops 87, 88 are adapted to be encountered by

key retainers

65 and 66 to limit buff and draft strokes of the cushion, so as to prevent bottoming of piston and resulting damage thereof.

The construction shown and described herein permits straight-forward assembly and disassembly and easy inspection of the cushion, as will be evident to those skilled in the art. During assembly, for example, the gas pressure in the cushion is removed, and the cushion is inserted through the bottom opening of the center sill, which is uncovered by removing plate 82. The cushion is then extended to about its normal size and

keys

63 and 64 are inserted. Each

retainer

65, 66 is put in place and each

rod

67, 68 is passed through its respective spring 70 and the retainer and pinned in place, Coupler pin 58 is inserted through coupler shank S6 and yoke 62 and held in place by any suitable means, such as a welded plate at the bottom of the center sill. The cushion 10 may then be charged to its proper gas pressure through valve 36. Cover plate 82, with guides and

supports

79, 80, is then fastened in place.

The operation of the cushioning arrangement will now be described. The pressure in chamber 32 tends to expand cushion 10, while springs 70 act to compress the cushion. The gas pressure in chamber 32 and the springs 70 are proportioned so that piston 22 will .occupy an intermediate position, about as shown in FIG. l, so as to permit, say, about 11 inches of buff stroke and 21/2 inches of draft strokes normally. During a buff stroke cylinder 12 moves rearwardly toward fixed piston 20, and therefore, liquid is forced out of chamber 26 through openings 40 into metering tube 18 and into

chambers

28 and 30 and expanding chamber 38, effecting hydraulic cushioning and simultaneously compressing the air in chamber 32 to afford the necessary return force for extending the cushion after the end of the buff impact. At the beginning of the buff stroke there are few .openings 40 communicating with chamber 28, and the effect of this would be a tendency to cause cavitation in chamber 28. To prevent such cavitation without increasing the speed of return, spring pressed check valves 5t) are provided to permit free tiow from chamber to chamber 28 and to prevent ow through these valves out of chamber 28. Similar check valves may be placed in some of the metering tube holes to permit ow into the tube but prevent flow out out of the tube to reduce the return velocity of the cushion. Since the return of the cushion is considerably retarded by snubbing chamber 38, the metering means and valves S0 to a value, say, of about two inches per second, the cushion may possibly be subjected to a second impact before it has adequately returned. Valves 42 and 46, therefore, permit about one additional inch of buff stroke beyond the normal buff stroke, that is, beyond the last opening 40 in the metering tube 18. Pressure relief valve 46 near the end of the last inch of chamber 26 prevents overload, as in the event of an excessive impact or a second impact before adequate return of the cushion following a first buff impact, by permitting ow out of chamber 26. Valve 42 permits flow into chamber 26 to enable the piston to return after such additional travel beyond the last hole 48 in the metering tube;

Valves 44 and 48 at the other end of metering tube 18 act similarly to valves 42 and 46 to permit an additional draft travel of, say, one half inch to prevent overload due to an excessive impact or a quick second impact before the cushion has adequately returned from a first impact. Since valve 48, like valve 46, is a preset pressure relief valve, it permits flow from chamber 28 only when a severe draft impact condition occurs.

For simplicity the shock absorber structure has been shown at one end of the car only, since the structure connected to the coupler at the other end is exactly the same.

I claim:

1. A railroad car having a coupler and end-of-car cushioning means comprising a hydraulic shock absorber including an outer cylinder and an inner cylinder in said outer cylinder for telescoping relative movement, each cylinder having a chamber filled with a liquid, means for fixing one of said cylinders to the car, means for connecting the other cylinder to said coupler, said inner cylinder having a piston on its inner end in sealing engagement with the outer cylinder, a floating piston in the inner cylinder forming at the outer end of the inner cylinder a chamber adapted to be filled with a gas under high pressure to provide an air spring tending to hold the shock absorber in an extended condition, first metering means interconnecting the liquid lled chambers for providing a metered flow of liquid therebetween over a normal predetermined cushioning stroke of said shock absorber, wherein the improvement includes secondary metering means for enabling said cylinders to travel relative to each other a relatively small additional distance beyond said normal stroke when a severe impact on the coupler occurs, said secondary metering means communicating with said outer cylinder at a point thereof beyond said normal cushioning stroke for metering the tiow of liquid over said additional travel distance, said first metering lmeans including an axial perforated tube extending from the outer end of said outer cylinder through said piston into the inner cylinder, said secondary metering means including a preset pressure relief valve in said tube located adjacent the outer end of said outer cylinder for admitting liquid from said outer cylinder to said tube.

2. The combination defined in claim 1, wherein said relief valve is located between the last perforation in said tube and the outer end of the outer cylinder.

3. The combination defined in claim 2, including a pressure responsive check valve in said tube adjacent the outer end of said outer cylinder for admitting liquid from said tube to said outer cylinder.

4. The combination defined in claim 3, including a pressure responsive relief valve in the wall of said tube at its inner end for admitting liquid from the chamber of the inner cylinder to said tube when said piston is positioned beyond the last perforation at the inner end of said tube during a draft stroke of said shock absorber.

5. The combination defined in claim 4, including a pressure responsive check valve in the wall of said tube at the inner end of said tube for admitting liquid from said tube to said chamber of the inner cylinder.

6. The combination defined in claim 2, including a piston tixed to the inner end of said tube and in sliding sealing engagement with said inner cylinder, and a pressure responsive check valve in said last mentioned piston for passing liquid during compression of said shock absorber.

7. In a railroad car having a coupler, a center sill having a center filler and an end of car hydraulic shock absorber mounted for buff and draft cushioning and located in one end of the center sill between the coupler and the center filler, said shock absorber including an outer cylinder, a piston in said cylinder, and rigid cylindrical means connected to said piston, said cylindrical means including an inner cylinder extending rearwardly from said piston for telescopic movement in said outer cylinder, each cylinder having a chamber lled with liquid, and metering means interconnecting the liquid filled chambers for providing a metered flow of liquid therebetween, and spring means for holding said shock absorber in an extended condition normally, the improvement comprising: said cylindrical means extending rearwardly from said piston and having means at its rear end for xedly connecting said cylindrical means center filler against axial movement in either direction, said outer cylinder constituting the forward portion of said shock absorber and yoke means integral with said outer cylinder and extending forwardly therefrom and pivotally connecting said shock absorber to said coupler.

8. Apparatus according to claim 7, wherein said outer cylinder has a pair of cruciform anges near its front and rear ends and a plurality of longitudinal bars extending through said cruciform anges in close registry therewith for guiding the longitudinal movement of said outer cylinder.

9. Apparatus according to claim 8, including a removable cover plate connected to the bottom .of said center sill below said shock absorber, a pair of said longitudinal bars being xed to said cover plate and another pair of said longitudinal bars being fixed to said center sill.

10. Apparatus according to claim 7, including a key extending laterally through the yoke means and the center sill, a pair of retainers on the ends of said key, spring means acting on said retainers in a direction to compress said shock absorber, means for mounting said retainers and said key for longitudinal movement, and forward and rear stops fixed to the center sill for engaging said retainers to limit their movement and thereby limit the buff and draft travel of the shock absorber.

References Cited UNITED STATES PATENTS 3,164,264 1/1965 Price et al 213-43 3,207,324 9/1965 Blake 213-8 3,216,592 11/1965 Peterson et al. 213-43 DRAYTON E. HOFFMAN, Primary Examiner.