US3400833A - Railway car cushioning device - Google Patents

Description

3 Sheets-Sheet 1 Sept. 10, 1968 R. G. POWELL RAILWAY CAR CUSHIONING DEVICE Filed April 22, 1966 INVENTOR ,Qc/Meo G powa/ Sept. 10, 1968 R. G. POWELL 2 M .Ohm l L r w//// fw/v/ 4 l @m *SAM* me B w l, N w n mv/ N/////M u.

VZW/ZV 7^/ Q Sept. 10, 1968 R. G. POWELL RAILWAY CAR CUSHIONING DEVICE 3 Sheets-Sheet 3 Filed April 22, 1966 INVENTOR. Q/c/Ae G Po WEL L BY United States Patent liice 3,400,833 Patented Sept. 10, 1968 3,400,833 RAILWAY CAR CUSHIONING DEVICE Richard G. Powell, Houston, Tex., assigner to ACF Industries, Incorporated, New York, N.Y., a corporation of New Jersey Filed Apr. 22, 1966, Ser. No. 544,548

10 Claims. (Cl. Z13- 8) ABSTRACT OF THE DISCLOSURE An oleo-pneumatic cushioning device for railway cars which collapses and achieves internal metered transfer of hydraulic fluid between a pair of hydraulic chambers in addition to achieving compression of a compressible fluid within the unit to dissipate energy applied thereto. The lunit includes a lockup device which is operative to prevent the` interchange of hydraulic fluid between the hydraulic chambers upon the application to the unit of forces of low magnitude, but which is responsive to a predetermined increase in fiuid pressure within one of the hydraulic chambers developed by the application of forces in excess of a predetermined magnitude to unlock and allow the interchange of hydraulic fluid between the hydraulic chambers thereby allowing the unit to collapse and dissipate energy.

This invention relates to cushioning devices for railway cars and more particularly to cushioning devices adapted to be operatively connected to a coupler adjacent the end of a railway car for absorbing impact forces exerted against the coupler.

The present invention is especially directed to a cushioning system or shock absorbing system in which the metering of a fluid is employed as an energy dissipative device. The majority of cushioning systems used for end-of-car cushioning employ the principal of hydraulic fluid metering to dissipate the energy. This method of energy dissipation is velocity sensitive in that the amount of energy dissipation is directly proportional to the velocity of fluid fiowing through the metering orifice of the cushioning device. On downgrade run-ins of the cushioning devices, the velocity of fluid flowing through the metering orifice will be low and the energy dissipated will also be low allowing low loads to collapse the cushioning device.

Because of the velocity sensitive nature of this method of energy dissipation, the cushioning device will be permitted to go solid or completely contract under the application of extremely low velocity impacts such as slack run-in during a downgrade locomotive braking condition. When a sizable number of railway cars are included in a single train, the length of the train may shorten considerably by the sum of the travel of the cushioning units on all of the railway cars equipped with such units. Additionally, slack run-outs of the coupled railway cars without a sufficient energy dissipation in each of the cushioning units create an acceleration which increases with each successive car. Other objections which result from present end-of-car hydraulic fluid metering systems include the gradual lengthening of a train when the brakes are released after a stop, the creeping of cars at loading docks and the inability of some cushioning units to return to neutral or centered position sufficiently rapid after an impact to be ready for a second impact.

Another problem in present end-of-car cushioning units employing iiuid metering systems results from the wear of the piston seals caused by the continuous back and forth movement or hunting of the piston which is induced by normal train operation. With the present systems, the train action induces continuous reciprocation or hunting of the piston with many reversals of the piston seals. As a buff load is gradually applied, the train action caused by the velocity sensitive nature of the cushioning device produces a relatively large drift of the hydraulic cushioning device causing increased wear on the piston seals and the cylinder seals of the cushioning device.

Thus, the two main undesirable features in present endof-car cushioning units are: l) The uncontrolled hunting or longitudinal reciprocation induced by train action on the piston or the movable portions of the device, and (2) the slack run-in of the cushioning device upon the application of continuous low velocity impact load with the cushioning device going solid and thereby having insufficient energy dissipating capability when the cushioning unit is subject to a draft force when in the full buff position.

It is therefore a primary object of the present invention to provide a novel cushioning device of the fluid metering type for an end-of-car cushioning system which eliminates the uncontrolled hunting or longitudinal back and forth movement of the piston which is induced by normal train action.

A further object of this invention is the provision of a novel fluid metering type of cushion device which retains its full energy dissipating capability under train operating conditions involving draft and buff forces which are below a predetermined minimum.

A further object of this invention includes the provision of a resilient draft gear in combination. with such a fluid metering type of hydraulic cushioning device to supplement and complement the cushioning action of the hydraulic cushioning device.

The present invention comprises a hydraulic-pneumatic cushioning device of the fluid metering type for dissipating energy applied to the coupler of the railway cars. In operation, the invention is effective to maintain in positive resistance to impact forces until a predetermined uid pressure is reached within specific areas of the cushioning device. Basically, the cushioning device comprises inner and outer cylinders which cooperate in. telescoping relationship to define an inner variable volume hydraulic fluid chamber and an outer variable volume hydraulic chamber separated by an orifice plate. An elongated metering member is fixed to one of the cylinders and is received within a metering orifice formed in the orifice plate. The metering member cooperates with the orifice to vary the effective size thereof in response to the relative positioning of the inner and outer cylinders. A free fioating piston disposed within the inner cylinder in sealed relation with the inner cylindrical wall thereof forms a movable partition separating the inner hydraulic chamber from a variable volume pneumatic chamber. The pneumatic chamber is filled with a compressible fiuid such as compressed air or nitrogen and is maintained under a predetermined pressure. The fluid pressure within the pneumatic chamber is operative under conditions of no load to maintain the cushioning device in its extended or neutral position. This is accomplished by causing the floating piston to force a majority of the hydraulic fluid from the inner hydraulic chamber to the outer hydraulic chamber. Upon receiving a buff force or impact load, the cushioning device will contract causing the hydraulic fluid within the high pressure outer hydraulic chamber to be forced through the metering orifice into the low pressure inner hydraulic chamber causing movement of the free floating piston and increasing the pressure within the pneumatic chamber. As this occurs, a large amount of the energy applied to the cushioning device is dissipated.

The cushioning device includes means which prevent contracting thereof under low impact loads until such time as a predetermined fluid pressure is reached within the high pressure outer hydraulic uid chamber, thereby allowing the low force impacts to be absorbed by a resilient cushioning mechanism which is provided for simultaneous cooperation with the hydraulic-pneumatic cushionin g device both in draft and buff.

As the predetermined unlocking pressure is reached within the outer or high pressure hydraulic chamber, the hydraulic cushioning device will unlock and contract absorbing a substantial amount of the energy applied thereto. As the hydraulic-pneumatic cushioning device is contracted, it cooperates with the resilient cushioning mechanism to achieve a relatively smooth transition of forces, thereby precluding any transmission of jarring from the coupler of the railway car to the underframe thereof.

The cushioning device is provided with a variable auxiliary draft cushioning chamber defined between the inner and outer cylinders which is in fluid communication with the inner hydraulic chamber. Means is provided for control of the ingress and egress of hydraulic fluid between the inner hydraulic chamber and the lauxiliary draft cushioning chamber to provide cushioning in draft as well as in buff.

While this application is primarily directed toward the cushioning of railway cars, it is not intended that the scope of the application be limited thereto. It is deemed apparent that the invention Will have application in dock facilities for ocean going vessels. The dock facility may have movable bumper portions which are hydraulically cushioned to prevent damage from impacts. The invention may also be employed in the landing gear systems of aircraft to protect the aircraft against damage which might occur as a result of severe landing impacts.

Other and further objects of this invention will be obvious upon understanding of the illustrated embodiment about to be described or will be indicated in the appended claims, and various advantages not referred to herein will occur to one skilled in the art upon ernployment of the invention in practice. A preferred embodiment of the invention has been chosen for the purpose of illustration and description and is shown in the accompanying drawings forming a part of the specification wherein:

FIGURE 1 is a side elevational view of a plurality of railway cars coupled to each other;

FIGURE 2 is a plan view having portions thereof broken away showing the hydraulic cushioning device comprising this invention mounted within a thick sill adjacent the rea-r end of a `draft gear and coupler structure, the cushioning device being illustrated in a neutral position;

FIGURE 3 is a fragmentary sectional view of the cushioning device of FIGURE 2 illustrating the cushioning unit in the neutral position thereof;

FIGURE 4 is a fragmentary sectional view of the cushioning device of FIGURE 3 illustrating the lockup mechanism of the cushioning unit in the neutral position thereof.

Refer-ring now to the drawings for a better understanding of this invention, railway cars 10 illustrated in FIG- URE 1 are interconnected by means of couplers 12. With reference to FIGURE 2, assuming that the railway cars 10 are of the cushioned underframe type, an end-of-car cushioning system will be arranged inwardly of each of the couplers 12. A fixed center sill generally designated 14 within which the cushioning system is arranged is a hat-shaped sill having side webs 16 with bottom legs 18. The center sill construction is provided with an open outer end 19 which is flared to receive the coupler member 12 and to allow swinging of the coupler member relative to the center sill construction. Connection between the coupler member 12 and the center sill 14 of the railway car is achieved by means of a yoke member 22 `disposed within the center sill and transmitting forces from the coupler to the draft gear 4and hydraulic cushioning unit structure as described in detail hereinbelow. A shank portion 24 of the coupler 12 is connected to the yoke 22 by means of a pivot pin 26. A coupler carrier 29 is located at the flared portion of the center sill structure and supports the shank portion 24 of the coupler 12. While the coupler 12 has been shown as a type F coupler (Association of American Railroads designation) mounted about a vertical pin, it is to be understood that the present invention may, if desired, be employed with a type E couplerl connected to a horizontal key. Mounted within the yoke 22 is `a resilient draft gear generally designated 28 and comprising a plurality of resilient pads 30 separated by metal plates 32. A front follower block 34 in engagement with the draft gear 28 is adapted to engage front stops 36 secured to the inner surface of the fixed sill structure 14 to define an outward limit and to transmit draft forces to the center sill structure.

AS illustrated in FIGURES 2 and 3 forming an important part of this invention, a hydraulic-pneumatic cushioning unit generally designated 38 is positioned rearwardly of the draft gear 28. The hydraulic cushioning unit 38 (which is frequently referred to in the trade as an ole-pneumatic cushioning unit) comprises an outer cylinder 40 and an inner cylinder 42 movably cooperating in telescoping relationship. Disposed within the inner cylinder 42 is a floating piston 44 dividing the inner cylinder into a pneumatic chamber 46 and an inner hydraulic chamber 48. An outer hydraulic fluid chamber 50 formed within the outer cylinder 40 contains a relatively incompressible liquid such as hydraulic fluid. The pneumatic fluid chamber 46 formed within the inner cylinder 42 contains a compressible fluid such as air or dry nitrogen gas which is maintained under a static pressure. A metering pin 52 is secured to the closed end or base of the outer cylinder 40 and has a free end thereof received within a metering orifice 54 in an orifice plate 56 forming a closure for the inner end of the inner cylinder 42. The orifice 54 provides fluid communication between the inner hydraulic chamber 48 and the outer hydraulic chamber 50, thereby providing for the interchange 0f hydraulic fluid between the outer and inner hydraulic chambers upon relative movement of the inner and outer hydraulic cylinders. The metering pin 52 is tapered as illustrated in FIGURE 3 and cooperates with the metering orifice 54 to define a velocity sensitive control for controlling the interchange of hydraulic fluid between the inner and outer hydraulic chambers. The metering pin 52 varies the effective size of the metering orifice 54 in response to relative positioning of the inner and outer hydraulic cylinders 40 and 42.

Referring now to FIGURE 2 the inner cylinder 42 has an end cap 58 thereon which serves the double function of a rear follower block. The end cap 58 has an externally threaded inner extension 60 engaging internal threads within the inner cylinder 42 as illustrated in FIGURE 3. The inner cylinder 42 extends through an opening 62 in the yoke 22 and the end cap 58 engages a peripheral shoulder or rim 64 defined inwardly of the yoke 22. Thus, upon forward movement of the yoke 22 which would occur upon the application of a draft force, the shoulder 64 in engagement with the end cap 58 causes extending movement of the inner cylinder 42. The end cap 58 in addition to further extending the inner cylinder 42 of the cushioning unit 38 will cause compression of the resilient draft gear 28 and through the follower plate 34 will transmit the energy applied to the draft gear to the center sill structure 14. The outer cylinder 40 abuts a rear support 66 secured to the fixed sill structure 14. An end cap stop 68 is provided with a lug 70 which engages a portion of the front face of the outer cylinder 40 as illustrated in FIGURE 2 to maintain the outer cylinder in its proper position. The rear abutment surfaces 72 on the end cap stop 68 engage the end cap 58 to limit the rearward travel of the inner cylinder 42 upon exertion of impact forces against the'coupler 12 as shown in FIGURE 2.

With reference now to FIGURE 3 illustrating an important part of this invention, a packing gland adapter 84 is retained at one extremity of the outer cylinder 40 and carries a packing member 86 therein for the establishment of a fluid tight seal between the outer cylinder 40 and the inner cylinder 42. A retainer 85 is threadedly engaged within the gland adapter 84 and retains the packing 86 and an -outer bearing 87 in assembly between the inner and outer cylinders 42 and 40. An inner annular bearing member 88 is retained at one extremity of the inner cylinder 42 for the establishment of bearing engagement between the inner cylinder and the inner wall 89 of the outercylinder 40.

The packing lassembly 86 and the bearing member 88 cooperate to define a variable volume annular `draft cushioning chamber 94 between the inner and outer cylinders. An annular pressure responsive fluid flow control mechanism 96 is disposed about the outer circumference of the inner cylinder 42 and is axially movable relative tothe inner cylinder 42 and a stop `surface 100 formed on a spacer member 102. i i

With reference now particularly to FIGURE 3, the iiow control mechanism 96 includes a generally ring-like body member having at least one and preferably a series of poppet valve constructions which prevent the `flow of hydraulic fluid in one direction and allow the flow of hydraulic fiuid in the opposite direction in response to predetermined fiuid pressure differential across the poppet valve structure. Each of the pressure responsive flow control or poppet structures comprises a steppedvalve housing bore 97 which is internally threaded lat its outer extremity to receive a valve seat structure 99. The valve seat`99 is provided with an axial bore and a frusto-conical seat surface. A poppet 101 is disposed within the bore and is maintained in engagement with the valve seat under a predetermined mechanical bias by a spring 103.l

The `poppet 101 is a generally rectangular member and when disposed within the cylindrical valve housing bore denes'a plurality of ow passages between the poppet edges and the bore. An annular groove 105 interconnects theinner periphery of the ow control mechanismiwith each of the bores 97 and a recess 107 formed at the inner periphery of the flow control mechanism provides a How passage from the groove 105 'to the ports 104 in the inner cylinder 42. The annular recess 107 obviates the need for precise radial alignment of the flow control mechanism' relative to Ithe ports 104.`Anannular. recess 109 is formed at the inner periphery 'of `the flow control mechanism 96 defining 'an annular shoulder for engagement with the stop 98 on the inner cylinder 42. The draft cushioning mechanism being loosely received by the inner cylinder 42 is movable axially of theinner cylinder within limits`defined by the shoulder 100 and the stop 98. As illustrated in FIGURE 3, a clearance exists between the outer circumference of the flow control mechanism 96 and the inner cylindrical wall 89 of the outer cylinder 40.

Hydraulic fluid flowing from the inner` `hydraulic chamber V48 into the draft cushioning chamber 94 passes through the ports 104 and around the flow control mechanism 96 by means of the clearance between the flow control mechanism 96 and the inner cylindrical wall 89 of the outer cylinder. During flow of hydraulic fluid into the draft cushioning chamber 94, the ow control mechanism 96 is maintained in engagement with the stop 98 by the hydraulic fluid allowing the iow of hydraulic fluid between -the surface 100 and the flow control mechanism `96 and around the exterior periphery of the flow control mechanism into the draft cushioning chamber 94. Upon reversal of the flow of hydraulic fluid from the draft cushioning chamber 94 to the low pressure inner hydraulic chasmber 48, which occurs during extension of the cushioning device to its normally extended or static position, the flow control mechanism 96 is forced by the flowing uid to move into intimate engagement with annular stop surface 100 of the spacer member 102 to prevent the flow of hydiraulic uid around the outer periphery of the ow control mechanism 96 in the return direction. The flow control mechanism 96 in its relation with the inner cylinder 42 defines a calibrated fixed flow control orifice or uid flow passage which restricts the ow of hydraulic fiuid being exhausted from the draft cushioning chamber 94, thereby causing substantial energy dissipation as the cushioning unit is extended by its internal pressure after being collapsed by an impact or buff force. The uid How control mechanism therefore provides a snubbing action preventing excessively rapid extension of the cushioning unit thereby controlling slamming or rebounding of the same. The draft cushioning mechanism will also dissipate energy applied to the inner cylinder in draft when the inner cylinder is in its collapsed position or neutral position as will be explained in detail hereinbelow. Y

Referring now to FIGURES 3 and 4 forming an important part of this invention, the hydraulic cushioning unit is particularly adapted to permit contraction of the outer and inner cylinders 40 and 42 thereof only when a predetermined fluid pressure is reached within the high pressure hydraulic chamber 50 of the outer cylinder 42A. The hydraulic cushioning unit will therefore remain in its neutral position until a buff force is applied thereto of suiicient magnitude to raise the uid pressure within the outer hydraulic chamber to a predetermined level. As pointed out above, the outer hydraulic chamber 50 contains a relatively incompressible iiuid, such as hydraulic fiuid, which is metered through an orifice 54 in an orifice plate 56 fixed at the inner end of the inner cylinder 42 under control of a metering pin 52 secured to the closed end of the outer cylinder 40. The metering pin 52 cooperates with the metering orifice 54 to define a velocity sensitive control for the cushioning unit responsive to relative positioning of the inner and outer cylinders 40 and 42. The free floating piston 44 is disposed for movement within the inner cylinder 42 and separates the compressible fluid such as air, nitrogen, Ior other suitable gasiform fiuid from the hydraulic fluid within the inner hydraulic chamber 48. In order for the cushioning device 36 to be collapsed under buff forces, hydraulic uid must flow from the outer hydraulic chamber 50 through the metering orifice 54 and into the inner hydraulic chamber 48. In conventional oleopneumatic type cushioning units, employing the orice plate-metering pin arrangement of velocity sensitive control, the interchange of hydraulic fiuid between the inner and outer hydraulic chambers is accomplished merely by applying a force on the cushioning unit of sufficient magnitude to cause the pressure in the outer chamber to exceed the inner chamber uid pressure. The instant invention, however, contemplates the prevention of fluid interchange between the inner and outer hydraulic chambers until a predetermined hydraulic fluid pressure differential is established therebetween. This allows the cushioning unit 38 to remain in a neutral position during conditions of low impact and to allow contraction of the unit only under large magnitude force application.

To prevent the ow of hydraulic fluid from the outer chamber 50 to the inner hydraulic chamber 48 under condition of low impact force applied to the hydraulic cushioning device 38, a lockup member generally designated is disposed within the inner hydraulic chamber 48 and is adapted to establish a fluid tight seal with the orifice plate 56 about the metering orifice 54. The lockup member 120` comprises a generally cylindrical body portion 122 formed with a bearing aperture 124 receiving a generally cylindrical enlarged outer extremity of the metering pin 52 in bearing engagement therewith. The body portion 122 is provided with a generally cylindrical bore 128 of larger diameter than the bearing aperture 124. A piston 130 is provided with an externally threaded extension 132 which is received within an internally threaded bore 134 formed within lthe metering pin 52. The piston 130 is provided with an annular sealing element 136 for the establishment of a fluid tight seal with the cylindrical bore 128. A closure member 138 is received within an enlargement formed at the outer extremity of the bore 128 and cooperates with an annular seal member 140 to form a sealed closure for one extremity of the lookup member 120. The closure member 138 bears against an annular shoulder 139 defined by the enlargement to prevent movement of the closure in one direction. A snap ring 142, retained within a groove 143 formed at one extremity of the lookup member 120, retains the closure member 138 against excessive movement in the opposite direction.

The body portion 122 of the lookup member 120 is provided with an annular shoulder 144 and an axial extension defining an annular seal retaining7 lip 146. An annular retainer member 148 is threadedly received by the body portion 122 and cooperates with the annular shoulder 144 and annular lip 146 to define a groove 150 for containing a sealing member 152. The sealing member 152 is preferably formed of an elastomeric material which is impervious to the fiuid contained within the hydraulic cushioning unit. The retainer member 148 is provided with an annular lip 154v which cooperates with the lip 146 to define an outer restriction for the annular groove 150. The lips 146 and 154 bear against the sealing member 152 maintaining the sealing member within the groove 150, thereby positively preventing the seal 152 from being displaced from the groove by hydraulic fiuid fiowing under high pressure.

Inadvertent separation of the lookup member 120 from the metering pin 52 is prevented by cooperation of the piston 130 with a shoulder 156 dened by the intersection of the bore 128 and the bearing aperture 124. Engagement between the piston 130 and the shoulder 15'6, however, will occur infrequently due to the pressure depression or partial vacuum developed in the area 158 of the bore 128 defined between the piston 130 and the closure 138 upon movement of the piston within the bore 128. The seal 136 of the piston 130 maintains a positive fluid tight seal between the piston and the bore 128, thereby maintaining the area 158 in a sealed condition.

Fluid pressure from the outer hydraulic chamber is communicated to the bore 128 of the lookup member 120 by a series of fiuid passages 160 and bears on the piston 130, thereby maintaining the lookup member 120 in the condition illustrated in FIGURE 4.

The operational concept of the invention depends upon the difference in the effective area of the lookup member 120 which is exposed to the hydraulic fiuid pressure within the inner hydraulic chamber 48 as compared to the effective area of the lookup member exposed to uid pressure within the outer hydraulic chamber 50 and, also, the Huid pressures within the inner and outer hydraulic charnbers. For example, the compressible fluid chamber 46 of the inner cylinder may be charged with a gasiform fluid under a static Apressure in the range of 260 p.s.i., which acting through the floating piston 44 exerts the same pressure on the hydraulic fluid within the inner hydraulic chamber 48, The hydraulic uid within the inner hydraulic chamber therefore acts upon an effective area represented by the diameter D1 of the sealing member 152 when the sealing member is in sealing engagement with a sealing surface 153 formed on the orifice plate 56. The hydraulic fluid within the outer hydraulic chamber 50 acts through a smaller effective area A defined by the difference in area defined by diameters D1 representing the area of sealing contact between the sealing member 152 and the sealing surface of the orifice plate and D2, representing the diameter of the cylindrical bore 128. Fluid pressure within the bore 128 acting on the interior shoulder 156 of the lookup member will balance a portion of the force applied by the hydraulic fluid against the exterior surface area of the lookup member defined by the sealing member 152 thereby defining the resultant effective annular area A. It is therefore apparent that due to the construction of the lookup member 120, the differential or effective areas in communication with the inner and outer fluid chambers effectively provide for automatic pressure responsive control of the lookup member 120. Since the small effective area A of the lookup member is in communication with fluid within the outer hydraulic chamber 50, it is apparent that, in order to break the seal between the sealing member 152 and the surface 153 of the orifice plate 56 thereby unlocking the lookup member 120, the pressure of the hydraulic fiuid within the chamber 50 must rise to a level considerably above the pressure of the inner hydraulic chamber 48. Assuming, for example, that the inner hydraulic chamber 48 is maintained under a static pressure of 260 p.s.i. by the compressible fiuid in the chamber 46 and that the effective area A, represented by ythe difference in diameters D1 and D2, is 1.5 square inches, a fiuid pressure of 1810 1p.s.i. is required in the outer hydraulic chamber to effect unlocking of the lookup member. A hyckaulic cushioning unit embodying the invention may be so designed that a buff force in the order of 100,000 lbs. is required to effect a fluid pressure of 1810 p.s.i. in the outer hydraulic chamber. It is apparent therefore that in accordance with such an embodiment of the invention a buff force below 100,000 lbs. will not unlock member 120 and the cushioning unit 38 will remain in its neutral and locked position.

With the hydraulic unit 38 in its neutral locked condition, the lookup member 120 will effectively prevent the flow of hydraulic fiuid between the inner and outer hydraulic chambers when the unit is subjected to a low level buff force or a draft force. The cushioning unit 38 when subjected to a draft force in its neutral locked position will extend to its fully extended position without any transfer of hydraulic fiuid between the inner and outer hydraulic chambers. This extension will be small, for example less than two inches in a unit having a 30 inch stroke, and will cause a vacuum to be formed within the outer hydraulic fluid chamber 50` developing a void or vapor lbubble therein. Hydraulic fiuid within the draft cushioning chamber 94 will be metered into the inner hydraulic chamber 48 by the fiow control mechanism 96 in the manner described above. The additional volume of hydraulic fiuid forced into the inner hydraulic chamber 48 will force the piston 44 toward the outer extremity of the inner cylinder thereby further compressing the compressible fiuid within the chamber 46.

Upon dissipation of the draft force the cushioning unit 38 will be forced to return to its neutral position by the compressed gas within the chamber 46 which acts on the piston and forces a volume of hydraulic fluid to flow from the inner hydraulic chamber 48 into the draft cushioning chamber 94. At the same time the void or vapor bubble will dissipate and the cushioning unit 38 will have returned to its neutral position.

The resilient draft gear 28 will act simultaneously with the hydraulic cushioning unit 38 in draft between the neutral and fully extended positions to effect a smooth force transition in the same manner discussed above.

Operation When the coupler structures 12 of the railway cars are impacted with a force which is less than that required for unlocking the lookup member 120 with the cushioning unit in its neutral locked condition, the cushioning unit Ibecause of the lookup member will remain in its neutral position as illustrated in FIGURE 3 and will transmit the force directly from the resilient draft gear to the underframe of the railway car. The resilient draft gear under low impact loads (buff loads under 100,000 lbs., for example) will therefore be effective acting alone to dissipate sufficient energy to afford ample protection to the railway car lading under such low impact conditions. Assuming that the coupler structure 12 of the railway oar has received a buff impact which is above the force required to unlock the cushioning unit 38, the pressure of the hydraulic fluid within the outer hydraulic chamber 50 will rise to a sufficient magnitude that acting through the small effective annular area A represented by the difference in the areas defined by diameters D1 and D2', the force produced on the lookup member will be greater than the force on the lockup member developed by the fluid pressure within the inner hydraulic chamber 48 acting through the area defined by the diameter D1. Under this condition the lockup member 120 will break the sealing engagement between the sealing member 152 and the sealing surface 153 of the orifice plate 56, thereby allowing the ow of hydraulic Huid from the outer hydraulic chamber 50 to the inner hydraulic chamber 48 causing contraction of the hydraulic cushioning unit 38. Contraction of the cushioning unit 38, after the unlocking operation has taken place, is therefore controlled solely by the cooperative relationship between the metering pin 52 and the orifice 54 thereby causing the cushioning unit to be velocity sensitive in its contraction. Fluid flowing from the outer hydraulic chamber 50 to the inner hydraulic chamber 48 subsequent to the unlocking operation is under control of the metering pin 52 causes energy dissipation controlled by the effective size of the metering orifice. Hydraulic fiuid flowing into the inner hydraulic chamber 48 causes the free floating piston 44 to move toward the outer extremity of the inner cylinder 42, thereby compressing the compressible fiuid within the pneumatic chamber 46. During a maximum 4buff impact the fluid pressure of the compressible gasiform fluid Within the chamber 46 maybe raised from its precharged pressure of 260 psi. to a pressure range of 1500 p.s.i., for example.

After the hydraulic cushioning unit 38 has been fully compressed by the buff force and the buff force has been dissipated, the fluid pressure within the pneumatic chamber 46 will force hydraulic fluid disposed'within the chamber 48 through the metering orifice 54 into the outer hydraulic chamber 50. This will allow the hydraulic' cushioning unit 38 to expand toward its neutral or FIGURE 3 position.

As was explained hereinabove, upon contraction of the cushioning unit 38 hydraulic fluid will be forced through the ports 104 and into the draft cushioning cham-ber 94. Return of the hydraulic unit to its neutral position therefore will be determined by the calibrated flow passage structure defined by the clearance between the inner cylinder 42 and the inner periphery of the flow control mechanism 96. Extension of the cushioning unit 38 therefore will be retarded by the flow control mechanism 96 thereby preventing excessively rapid extension of the cushioning unit which could produce undesirable results such as slamming the cushioning unit to its fully extended position or rebounding of the unit. Rebounding of the cushioning unit is undesirable oscillation produced by excessively ra'pid over extension of the cushioning unit,

Assuming that the hydraulic cushioning unit 38 is subjected to a draft force while the unit is in a contracted condition, the fluid flow control mechanism 96 will be moved by the hydraulic fluid axially into engagement with the annular surface 100 of the spacer member 102, thereby preventing the flow of hydraulic fluid around the exterior periphery of the ow control mechanism in thereturn direction. Since under this condition fluid may not flow around the exterior periphery of `the flow control mechanism and since the calibrated orifice or flow passage structure is too small to afford sufficient fluid flow from the draft cushioning chamber 94 to the inner hydraulic chamber 48 to dissipate draft forces, it is obvious that uidpressure within the draft cushioning chamber 94 will build rapidly to a high level. The fluid under pressure will therefore act upon the poppet structures-1411 in the fiow control mechanism 96 and when reaching a predetermined pressure differential relative to the pressure within the inner hydraulic chamber will cause actuation of the poppet structures, allowing a sufficient flow of uid through the -flow control mechanism to the inner hydraulic chamber 48 from the draft cushioning chamber 94 and resulting in substantial dissipation of energy. The flow control mechanism 96 is therefore responsive to the fluid pressure differential between the draft cushioning chamber 94 and the inner hydraulic chamber 48 to control extension of the cushioning unit and to cause dissipation of energy in draft. The draft cushioning cham-ber 94 and the flow control mechanism 96 are so designed that anticipated draft forces are readily dissipated. It is pointed out also that the4 draft cushioning mechanism cooperates with the resilient draft gear 28 allowing a smooth dissipation of draft forces thereby protecting the lading within the railway car. For example, the hydraulic cushioning unit will allow draft extension thereof a predetermined distance beyond the neutral position thereof. As pointed out above, with the cushioning unit 38 in its locked condition, full extension of the cushioning unit will occur without interchange of fiuid between the inner and outer hydraulic chambers. When the hydraulic cushioning unit has been fully extended, further dissipation of draft energy occurs only in the resilient draft gear 28. The resilient draft gear effectively prevents subjection of the cushioning unit to excessive draft forces `and effects a smooth transition of forces between t-he coupler and underframe structures of the railway car.

As the hydraulic cushioning unit 38 moves from a contracted condition to its neutral position. as illustrated in FIGURE 3, the sealing member 152 will again engage the sealing surface 153 of the orifice plate 56 thereby effecting a seal and again defining the area differential defined by the difference in areas represented by the diameters D1 and D2 as indicated hereinabove. The hydraulic cushioning unit upon reaching its neutral position therefore will again become locked and subsequent contraction of the cushioning unit will occur only upon reaching sufficient fluid pressure within the fluid chamber 50 to unlock the cushioning unit in the manner described above.

It will be evident from the foregoing that I have provided a unique oleopneumatic cushioning unit which effectively prevents downgrade run-ins of the hydraulic cushioning unit due to train operation. Due to the unique construction of the instant invention, the cushioning device will not be permitted to go solid or to be completely contracted under the application of low velocity impacts such as slack run-in during a downgrade locomotive braking condition, for example. The hydraulic cushioning unit incorporating the instant invention will be maintained locked in a neutral position until such time as buff forces developed by impact become sufficiently high to cause an increase in hydraulic pressure within the: outer hydraulic chamber of the cushioning unit to cause unlocking of the lockup member ofthe respective cushioning units. Since the hydraulic cushioning unit incorporating the invention will normally be retained in its neutral position, continuous back and forth movement of the free piston due to train action is effectively prevented and piston seals therefore experience little wear thereby prolonging the life of the cushioning unit. Subsequent to impact forces and unlocking of the lockup member and dissipation of the impact forces, slack run-outs of the coupled railway cars will be effectively prevented by the draft cushioning mechanism set forth hereinabove. Excessively rapid extension of the cushioning unit as well as rebounding of the same is effectively prevented by the draft cushioning mechanism, thereby reducing any tendency of damage to the railway car lading by slamming or rebounding of the cushioning unit. The hydraulic cushioning unit of the invention cooperates with the resilient draft gear structure both in buff and draft, thereby producing a cushioning effect thereby producing smooth force transition thereby giving maximum protection to the railway car lading. Therefore it is seen that this invention is one well adapted to obtain all of the objects hereinabove set forth together with other advantages which become obvious and inherent from thc description of the apparatus itself.

It will be understood that certain combinations and subcombinations are of utility and may be employed without reference to other features and subcombinations.

What is claimed is:

1. A railway car having an underframe structure, a coupler device movably carried by said underframe structure, an oleopneumatic cushioning unit interposed between said underframe structure and said coupler device and adapted to dissipate buff forces applied to the coupler device to protect the lading within the railway car from excessive shock, said cushioning unit comprising inner and outer tubular members disposed in telescoping relation and being movable one relative to the other between collapsed, neutral and fully extended positions, means closing the outer extremities of said tubular members, an orifice plate closing the inner extremity of the inner tubular member and defining an inner'variable volume low pressure hydraulic chamber within said inner tubular member and an outer variable volume high pressure hydraulic chamber within said outer cylinder, hydraulic fluid filling said inner and outer hydraulic chambers, means maintaining the hydraulic fluid within said inner hydraulic chamber under a static pressure, a metering orifice formed in said orifice plate allowing the interchange of hydraulic fluid between said inner and outer hydraulic chambers, a metering pin cooperating with said metering orifice to define a velocity sensitive control for the interchange of hydraulic fluid between the inner and outer hydraulic chambers, said orifice plate defining a substantially planar sealing surface, a lockup member disposed Within said low pressure hydraulic chamber of said cushioning unit and adapted in the neutral to fully extended positions of the cushioning unit to form a seal with said sealing surface to prevent the interchange of hydraulic fluid between said hydraulic chambers, said lockup member when in sealing engagement with said sealing Surface defining a first effective surface area of said lockup member through which said static pressure within said inner low pressure hydraulic chamber acts to maintain said sealing engagement, said seal defining a second surface area of said lockup member through which fluid in said outer hydraulic chamber acts, said lockup member providing an inner surface area through which said fluid pressure in said outer hydraulic chamber acts to balance a portion of the force acting on said second surface area thereby defining an effective third surface area which is less than said first surface area.

2. A railway car as set forth in claim 1, said lockup I member comprising a body portion having a bearing aperture formed therein, said metering pin having a generally cylindrical end portion received within said bearing aperture, said body portion having a bore formed therein of larger size than said bearing aperture and defining a pressure balancing chamber, at least one fluid passage communicating fluid pressure exteriorly of said lockup member to said pressure balancing chamber, whereby in the locked position of said lockup member uid pressure within said pressure balancing chamber develops a force balancing a portion of the force applied to said lockup member by the fluid within said outer hydraulic chamber.

3. A cushioning unit comprising an outer tubular member, an inner tubular member slidably disposed in radial spaced relation within said outer tubular member, base means closing the outer ends of said members, sealing means secured to one of said members and closing said radial space between the members to form a main variable volume chamber enclosed by said members, an orifice plate secured to the inner open end of said inner tubular member and dividing said main chamber into an inner low pressure hydraulic fluid chamber and an outer high pressure hydraulic fluid chamber, a fixed area opening in said orifice plate, a metering pin carried by the base of said outer tubular member and movable through the opening in said orifice plate to vary the effective area thereof, hydraulic fluid in said inner and outer chambers, a movable piston disposed within said inner tubular member and defining a compressible fluid chamber, gas under pressure disposed within said compressible fluid chamber and acting on said piston to pressurize said hydraulic fluid within said inner hydraulic fluid chamber, and lockup valve means carried by said metering pin within said inner chamber, said lockup valve means having an annular sealing element establishing an annular seal with said orifice plate about said orifice plate opening thereby isolating said outer chamber from the effect of said gas pressure, said hydraulic fluid in said inner low pressure hydraulic chamber acting against said lockup valve under the influence of said gas pressure and causing said lockup valve to maintain said annular seal with said orifice plate thereby preventing the interchange of hydraulic fluid between said hydraulic chambers, the seal between said lockup valve and said orifice plate being broken by a force differential developed by a predetermined increase in hydraulic fluid pressure within said high pressure outer hydraulic chamber which acting through a small area of said lockup valve in communication with the hydraulic fluid in said high pressure outer hydraulic chamber is effective to overcome the force created by the hydraulic fluid within said inner hydraulic chamber acting under pressure influence of said gas pressure against a large area of said lockup Valve encompassed by said annular seal, thereby allowing the occurrence of metered interchange of hydraulic fluid between the inner and outer hydraulic chambers to achieve dissipation of energy only when hydraulic fluid pressure in said high pressure hydraulic chamber reaches a predetermined level.

4. The structure of claim 3 characterized in that said valve means is mounted on said metering pin in interengagement therewith and for axial movement relative thereto, vacuum means normally maintaining said valve means in full interengagement with said metering pin and permitting movement of said valve means relative to said metering pin upon the application of external force to said tubular members.

5. The structure of claim 4 characterized in that said lockup valve means is formed with a generally cylindrical bore having a closed end, the free end of said metering pin extending into said bore in sealing engagement therewith, upon movement of said lockup valve means relative to said metering pin a vacuum developing within said bore and biasing said lockup valve means toward full interengagement with the free end of said metering pin.

6. The structure of claim 4, characterized in that said lockup valve means is formed with a generally cylindrical bearing aperture adapted for a sliding fit with the free extremity of said metering pin, a generally cylindrical bore formed in said lockup valve means of larger diameter than said bearing aperture and coaxial therewith, a piston fixed to the free extremity of said metering pin and having a fluid tight fit with said bore, upon movement of said lockup valve means relative to said metering pin, a vacuum developing within said bore and biasing said lockup valve means toward full interengagement with said metering pin.

7. A hydraulic cushioning unit for use in railway cars comprising inner and outer tubular members disposed in telescoping relation and being relatively movable between collapsed neutral and fully extended positions, means closing the outer ends of said tubular members, said inner member having an orifice plate fixed at its inner extremity defining a barrier separating the inner and outer variable volume hydraulic chambers, hydraulic fluid disposed within said hydraulic chambers, said orifice plate having a metering orifice formed therein for allowing the interchange of hydraulic fluid between the inner and outer hydraulic chambers, means defining a variable volume gas chamber within said inner tubular member,

pressurized gas disposed within said gas chamber and maintaining the hydraulic uid within the inner hydraulic chamber under pressure, a metering pin connected to one of said tubular members and cooperating with said metering orice to control the interchange of hydraulic fluid between said inner and outer hydraulic chambers upon relative movement of said tubular members, a lockup member disposed Within said inner hydraulic chamber and supported by said metering pin, said lockup member in the neutral position of said cushioning unit establishing a single annular seal with said orifice plate about said metering orifice thereby preventing the interchange of hydraulic fluid between said inner and outer hydraulic chambers, said lockup member when in sealing engagement with said oriiice plate presenting a large effective area thereof to the pressurized hydraulic uid in said inner hydraulic chamber and a small effective area thereof to hydraulic fluid within said outer hydraulic chamber, whereby a substantially greater pressure is required within said outer hydraulic chamber than in said inner hydraulic chamber to break said sealing engagement.

8. A hydraulic cushioning unit as set forth in claim 7, said lockup member having an axial bore extending partially therethrough, cylindrical means on said metering pin in fluid tight sealing engagement within said bore, said cylindrical means and bore cooperating to develop a vacuum within said bore upon relative movement of said lockup member and said metering pin whereby said lockup member is biased toward its fully interengaged relation with said metering pin.

9. A hydraulic cushioning unit as set forth in claim 8, said cylindrical means comprising a piston iixed to the free extremity of said metering pin, a sealing member carried by said piston and establishing sealing engagement between said piston and the wall defining said bore.

10. A hydraulic cushioning unit as set forth in claim 8, a retainer member received by said lockup member and cooperating with said lockup member to define an annular groove having an outer restriction, an annular sealing member of larger dimension than said restriction received and retained in said groove, a sealing portion of said sealing member extending beyond said lockup member and adapted for sealing engagement with said orice plate.

References Cited UNITED STATES PATENTS 2,737,301 3/1956 Thornhill 213-43 2,994,442 8/ 1961 Frederick 213-43 3,257,000 6/1966 Cope 213-43 DRAYTON E. HOFFMAN, Prima/jy Examiner.

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