Note: Descriptions are shown in the official language in which they were submitted.
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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~ .
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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
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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
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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
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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~. -
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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
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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
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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
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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
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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
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- -~ 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
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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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