CA1065802A - End of car cushioning unit - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

A hydraulic end of car cushioning device for use in railway freight cars. The device is intended for use between the coupler shank and car under-frame of a fixed sill type car and is designed so as to provide a long cushioning stroke under high impact loads. A load responsive check valve is interposed in the metering system of the cushioning device for preventing changes in length of the unit under lower buff and draft forces as occur in train action. More specifically there is provided a cylinder with a piston received in the cylinder and the piston and cylinder defining a chamber adapted to receive fluid. A
primary metering device includes an orifice and a cooperating metering rod, the device being in communication with the chamber for passing fluid therethrough at a restricted rate upon relative movement of the piston and the cylinder.
A pressure responsive valve is provided in series flow arrangement with the primary metering device for precluding the flow of fluid through the primary metering device until a predetermined force is applied to the cushioning device.

Description

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, This invention relates to a cushioning unit and more particularly to a cushioning unit adpated for use at the ends of railway cars.
This is a division of copending Canadian Patent Application Serial Number 206,788, filed August 12, 1974.
It has been the practice to upgrade existing, -fixed sill railway cars by providing them with end of car cushioning devices. Hydraulic cushioning units have been proposed for this purpose. The cushioning unit, however, ;
experiences widely different types of loadings. When making up a train in a switching or classi~ication yard, the car .
receives extreme shock loadings due to high velocity impacts~ .
J:
Under such conditions, it is desirable to provide an extremely ..
long cushioning stroke to effectively absorb these impacts.
Long stroke end of car cushioning units, however, are not desirable when the train has been made up and is in transit. ~
The units have a tendency to extend the length of the train considerably during these conditions and cause considerable problems when -the slack is taken up. : .
An object of the invention is to provide an end `
of car cushioning unit that provides a long stroke under high impacts but which resists changes in length under lower ~
loading. ~: :
~t is a further object of `the invention to provide an end o~ car cushioning unit that requires a predetermined force to be applied to it before its cushioning operation becomes ef~ective. :
According to the present invention there is provided a cushioning unit including a cylinder and a p.iston received within the cylinder, the piston and -the .~ .
cylinder defining a chamber adapted to receive a fluid. ..

Primary metering means is provided in communication with '' ' ''"~ '..

.

~6~;i8C1 2 , the chamber for passing fluid therethrough at a restricted rate upon relative movement of the piston and the cylinder.
The primary metering means includes an orifice and a cooperating me-tering rod. Means are provided for precluding the flow of fluid through the primary metering means until a predetermined force is applied to the cushioning unit.
The cushioning unit of the present invention is particularly adapted to be interposed between a coupler and a car ~rame of a railway car for damping shock ~orces.
In a specific embodiment, a bleed passage may be provided which bypasses the means for precluding flow through the primary metering means for permitting a restricted rate of flow of the fluid.
Figure 1 i5 a longitudinal cross-sectional view taken through the end of a railway car having a cushioning unit embodying this invention with the car structure being shown in phantom.
~igure 2 is an enlarged view showing the metering device of the cushioning unit as it appears under buff forces.
Figure 3 is an enlarged view, in part similar to Figure 2, showing the device as it appears when it 5~(~Z

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e~periences draft ~orces.
Figure 1 illustrates an end of car cushioning unit embodying this invention, identified generally by the reference numeral 11. The end of car cushioning unit 11 is adapted to be interposed between a coupler shank 12 and the car under~rame 13. The installation may be accomplished in any of a variety ~f manners and, for this reason, the car structure has been sho~n only ; in phantom. Certain details of the illustrated installation will be described, but should only be considered as exemylary in nature.
The cushioning unit 11 includes a cylinde~
assembly 14 comprised o~ a cylinder head 15, a tubular cylin~er 1~ and a closure plug 11. The cylinder 16 defines a cylindrical bore 18 closed at one end by the . ,: . . .
cylinder head 15 and at the other end by the plug 17 to ! deine a fluid receiving chamber 19.
- The chamber 19 is divided into two sections by ~eans of a piston assembly 21 that is slidably supported within the bore 18. ~he piston assembly 21 includes an ori~ice plate 22 that is af~ixed to a ~ain piston 23 hy m~ans o~ bolts 24, only one oE which appears in the drawings. An anti~riction bushincJ 25 en~ages the bore 18 and is trapped between outstanding flanges of the orifice plate 22 and the main piston 23. The pi.ston 23 `-ig als~ Eormed with an annular groove 26 in whi~h a piston ring 27 is positioned to sealingly engage the bore 1~. -- ., ~ .
A piston rod 28 is af~i~ed in any known manner to the piston assembly 21 and extends through an opening 29 formed in the closure plug 17. A bushing 31 and seal assembly 32 ~arried by the closure plug 17 supports and sealingly ', .~

~)6S~02 e~gagas the pis ton rod 28.
The piston rod 28 has af~ixed to its outer end a draft collar 33 that is trapped in a draft lug assembly, indica-ted by the re~erence numeral 34 that is fi~ed in any suitable manner to the under~rame oE the associated railway car. The cooperation of the draEt lug asse~bly 34 with the draft collar 33 couples the piston rod 28 and piston a~sembly 21 to the car underframe 13. That is, the piston assembly 21 is held against any su~stantial movement relative to the underframe structu~e 13.
~he cylinder head 15 is formed at i-ts outer end ~. .
with a socket 3S that r~ceives the coupler shank 12 Alligned openings 36 and 37 are ~ormed on opposite sides of the socket 35 to receive a draft key (not shown) for fi~ing the coupler shank to the cylinder head 15. Thus, the cylinder assembly 14 is af~ixed ~or movement with the coupler shank 12. A stop block 3a is i~ed to the under~rame 13 and is abuttingly engaged by the cylinder head 15 when the cushioning unit 11 is in lts fully extenaed draft position (Figure 1).
. 20 A metering rod 39 af predetermined conEiguration i~ afixed to the cylinder head 15 and extends concent~ically into the cavity 19. An appropriatel.y sizea orifice opening 41 is ormed in the ori~ice plate 22 ~or coope.ration with the ~.
metering rod 39. The piston rod 2a ls Eormed with an elongated cylindrical opening 42 that is aligned with the ori~ice ~pening 41 and which is adapted to receive, without restriction, the metering rod 39 at the extreme position oE the piston assembly 21 relative -t.o the cylinder assembly 14 in the buf~ :
conditio~
In orde-r to preclude relative movement of the piston assembly 21 and cylinder assembly 14 until large impact farces axe received, there is provided a pressure presponsive valve assembly, indicated generally by the reference numberal 43 and :
shown in most detail in Figures 2 and 3. The pressure responsive valve assembly 43 includes one or more passages 44 that extend axially through the piston 23 between a cavity 45 formed betwecn the main piston 23 and orifice plate 22 and an annular relief 46 formed in the main piston 23. The flow ~ -through the passage 44 is controlled by a valve member 47 ~ ~ :
which is a conical-shaped annular spring disk member of the ~:
general form of a Belleville springO In the nonflow condition the outer peripheral edge 48 of the valve member 47 sealingly engages the main piston 23. An opposite `
peripheral edge 49 sealingly engages a collar 51 that is ~ ~
received around a recess 52 at the outer end of the piston .
rod 28 and which is axially held in position by the main piston 23. As will become apparent, the valve member 47 acts as a two-way, pressure responsive valve. :
The chamber 19 is partially filled with hydraulic fluid ~:
. to a level indicated by the phantom line 53. Gas, such as Nitrogen~ at a high pressure is charged into the cavity 19 above the oil level 53. The gas pressure acts as a return spring to hold the cushioning unit 11 in the position shown in Figure 1. For a reascn which will become more apparent, one or more passages 54 extend through the collar 51 at a ~:
point radiall~ inwardly of the valve member 47.
~s has been noted, Figure 1 illustrates the cushioning .
unit 11 in its normal installed position. Impact forces applied to the cushioning unit from the coupler shank 12 or .. .. ..
from the car Erame structure 13 via the draft lug assembly 34 tend to cause relative movement between the piston assembly :

21 and the cylinder assembly 14. This relative movement can ::

only be accomplished by forcing the oil through the oriice opening 41. If the valve assembly 43 were not provided, any ~ ,~ ' ', .

~5~35)Z :

force greater than the force required to overcome the g~s pressure in the chamber 19 would result in such relative movement. Under low impact forces, such relative movement is undersirable since it will result in considerable changes - 5a -~ 6S802 - -~ in train length and attendant problems~
The valve 43, howqver, preculdes any Elow through the orifice opening 41 by blocking the passa~e 44 until a prede-termined force i5 applied. When this predetermined ~;
Eorce is reached, the pressure acting through the passage 44 on the valve member 47 will cause its peripheral edge 48 to deflect away from the main piston 23 as shown in Fi~ure 2 and permit flow. The metering rod 39 and orifice opening 41 will provide ~luid resistance to continuea movement, as is well known.
When the force is relieved, the valve member 47 will again move to its closed position. The gas pressure acting on the oil 53 will, however, cause the unit to return to its normal position (Figure 1) since the oil can be forced through the restricted passage 54 past the closed valve .
assembly 43. This return will occur at an extremely slow rate.
In the event a draEt force is exerted on tha cushioning unit 11 before return to -the normal position is ... . . .
reached, the cushioning unit 11 will als~ be operative to resist such forces. Rapid runout will be pre-cluded by the `
closure of the valve 43. If the drat force is sufficiently large, howe~er, the valve member 47 will deflect so that its peripheral portion 49 moves away rom -the collar 51 ~Figure 3) ~ ~`
and permit~ Elow back khrough the opening 41. Thus, lt should be readily apparent that the valve assembly 43 acts ag a pressure responsive valve for controllin~ flow in either direction through the orifice opening 41.
It is to be understood that -the foregoing des~ription is that of a preferred e~bodiment of the invention. Various changes and modifications may be made without departing from the spirit and scope o~ the invention as deEined by the appended clai~s.

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Claims (6)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An end of car cushioning unit adapted to be interposed between a coupler and a car frame of a railway car for damping shock forces, said cushioning unit comprising a cylinder, a piston received within said cylinder, said piston and said cylinder defining a chamber adapted to receive a fluid, primary metering means in communication with said chamber, said primary metering means passing fluid therethrough at a restricted rate upon relative movement of said piston and said cylinder, said primary metering means comprising an orifice and a cooperating metering rod, and means for precluding the flow of fluid through said primary metering means until a predetermined force is applied to said cushioning unit.

2. An end of car cushioning unit as set forth in claim 1 wherein the means for precluding flow through the primary metering means comprises pressure responsive valve means.

3. A cushioning unit comprising a cylinder assembly defining a cavity adapted to receive a fluid, a piston supported for reciprocation within said cavity, an orifice opening extending through said piston for communicating flow between opposite sides of said piston, a fixed metering rod extending into said cavity and adapted to cooperate with said orifice, a passage extending through said piston in series with said orifice, pressure responsive valve means for controlling the flow through said passage for precluding flow through said orifice until a predetermined force is applied to said cushioning unit.

4. A cushioning unit as set forth in claim 3 wherein the pressure responsive valve means comprises a conical-shaped annular spring disk having inner and outer peripheral edges, its outer peripheral edge being adapted to sealingly engage a first portion of said piston on one side of said passage and its inner peripheral edge being adapted to engage a second portion of said piston on the other side of said passage.

5. A cushioning unit as set forth in claim 4 wherein the outer peripheral edge of the spring disk is adapted to be deflected away from the first portion of the piston under the influence of sufficient force in one direction for permitting flow past said outer peripheral edge, the inner peripheral edge of said valve element being adapted to deflect away from sealing engagement with the second portion of the piston upon the application of sufficient force in the opposite direction to permit flow past said inner peripheral edge.

6. A cushioning unit as set forth in claim 5 further including a bleed passage extending through said piston for permitting return flow of fluid through the orifice at a restricted rate independently of the pressure responsive valve.