US3429454A - Railway car draft gfar with automatic cushioning control - Google Patents

Description

L 0 R T N O C G N I N 0 I H s w N m T m m 5T U A. A LH G H .W HR A E WG T F A R D R m 7 6 9 W1 n, 6 M2 8 l u J d e l i F Feb 25, 1969 Sheet I 2 3M mm 9 om m3 h 5 RIDIGUM INVENTOR. WILLIAM H GLASS BYROBERTJB a ATTORNEY N Ki \w Feb. 25, 1969 w, L S ET AL 3,42%,454

RAILWAY CAR DRAFT GEAR WITH AUTOMATIC CUSHIONING CONTROL Filed July 26, 1967 Sheet 2 of 2 INVENTOR. WILLIAM HGLASS BY ROBETJ. BRIDIGUM ATTORNEY United States Patent O 3,429,454 RAILWAY CAR DRAFT GEAR WITH AUTOMATIC CUSHIONING CONTROL William H. Glass and Robert J. Bridigum, Pittsburgh, Pa., assignors to Westinghouse Air Brake Company, Wilmerding, Pa., a corporation of Pennsylvania Filed July 26, 1967, Ser. No. 656,187 US. Cl. 213-8 14 Claims Int. Cl. B61g 9/12, 11/00, 9/02 ABSTRACT OF THE DISCLOSURE A don-bled piston hydraulic draft gear device for a cashioned nnderframe type of railway car having a body supporting sliding or floating center still straddling a fixed center sill and movable relative thereto in response to inettia forces effective on the car body to cause one piston to act jointly with car coupler bufiing forces effective on the other piston to provide for energy absorption proportional to the load on the car and effective to act in opposition to the downward pitching of the front end of the car resulting from the impacting of the car with another upon coupling of the couplers of the respective cars.

Conventional cushioned underframe type of railway cars comprise a single piston and cylinder device subject to both the inertia forces resulting from the movement of the body-supporting sliding sill relative to the fixed center sill occurring upon impacting of a moving car with a stationary car and the bufling force imparted to the car couplers upon the moving car striking the stationary car. Since this single cylinder device must be capable of providing for the absorption of both inertia and buff forces, the length of stroke of this device and the corresponding amount of movement of the sliding sill with respect to the center sill is unduly long thereby resulting in a reduction in the length of the car body relative to the distance between coupler faces at the respective opposite ends of the car.

Accordingly, it is the general purpose of this invention to provide an automatic load-controlled hydraulic draft gear embodying two parallel-related integral hydraulic cylinder devices, subject respectively to inertia forces resulting from movement of a body-supporting sliding sill and bufiing forces active on a car coupler, thereby enabling an increase in the length of the car body relative to the distance between coupler faces without a reduction in energy absorption by the draft gear which is adapted to fit within the yoke pocket of a draft gear yoke.

More specifically, according to the invention, two parallel integral hydraulic cylinder devices each having a piston subject respectively to inertia forces and butting forces, in response to which said pistons cause a fluid displacement from the corresponding cylinder to a load sensing and weighing cylinder device interposed bebween a car bolster and a car body to cause a correspondingly upward displacement of a piston within the cylinder device whereby the weight of the car body and load carried thereon is used to resist the upward movement of this piston. Furthermore, this upward movement imparted to the car body by this piston is effective to counteract the rocking of the car body about its center of gravity as a result of the decelerated forces acting on the car. Accordingly, this multipiston and cylinder arrangement provides automatic car cushioning control in accordance with the load carried by the car.

In the accompanying drawings:

FIG. 1 is an elevational cross-sectional view of a novel hydraulic draft gear device for a railway freight car.

Patented Feb. 25, 1969 FIG. 2 is an elevational cross-section view, taken along the line 22 of FIG. 1 and looking in the direction of the arrows, showing the construction and arrangement of a car bolster on which is mounted a load-weighing cylinder device that respectively supports a fixed center s'ill and a body-supporting sliding center sill.

FIG. 3 is an elevational cross-sectional view, taken along the line 33 of FIG. 1 and looking in the direction of the arrows, showing how the draft gear device is disposed between the opposite sides of a horizontal type of draft gear yoke and within the fixed center sill.

In FIGS. 1, 2 and 3 of the drawings is shown a cushioned draft gear device constructed in accordance with the invention. This draft gear device is carried in an elongated yoke pocket or slot 1 formed between parallel and spacedapart left and right-hand vertical walls 2 (FIGS. 2 and 3) and 3 of a draft gear yoke 4. The left-hand end of the draft gear yoke 4 is provided, as shown in FIG. 1, with a substantially rectangular shaped opening 5 in which is received a shank 6 of a railway freight car coupler, the head of which has been omitted from the drawings since it forms no part of the invention. The right-hand end of the shank 6 abuts the left-hand vertical face of a follower 7 that is disposed within the yoke pocket 1, it being understood that the width of this follower is the same as the width of the yoke pocket 1 and that this follower is placed in this yoke pocket subsequent to placing the draft gear device therein.

The shank 6 is provided with an elongated slot 8 for receiving a shank pin 9 that extends through corresponding coaxial elongated slots (not shown) in the opposite vertical side walls 2 and 3 of the draft gear yoke 4 and also through a pair of aligned substantially rectangular holes or slots 10 formed respectively in a pair of spaced-apart vertical parallel walls adjacent the left-hand end of a fixed center sill 11, it being apparent from FIG. 1 that the length of these slots 10 is substantially greater than the length of the slot 8 in the shank 6. The shank pin 9 is retained in place by a cotter pin (not shown). The shank pin 9 thus provides an operative connection between shank 6 of the car coupler and the draft gear yoke 4 through which draft forces are transmitted to the draft gear device. Buff forces are transmitted directly from the shank 6 of the car coupler to the draft gear device in a manner hereinafter made apparent.

After the shank 6 of the car coupler has been secured to the draft gear yoke 4 by the shank pin 9, a hollow boxlike striker 12, having extending therethrough a rectangular-shaped opening that is somewhat larger in cross-section than the cross-section of the draft gear yoke 4, is slipped over the right-hand end of the draft gear yoke 4 and moved in the direction of the left-hand, as viewed in FIG. 1, until the left-hand end of the striker 12 is substantially in alignment with the left-hand end of the draft gear yoke 4. The striker 12 is allowed to rest in this position on the draft gear yoke 4 until a draft gear device 13 hereinafter described is assembled and then placed in the yoke pocket 1.

As can be seen from FIGS. 2 and 3 of the drawings, the hereinbefore-mentioned fixed center sill 11 may be fabricated as by welding 21 top plate 14 to two oppositely arranged American Association of Railroads Z- sections 15 and 16 so as to form a fixed center sill pocket 17. Thereafter, an elongated slot 18 (FIG. 1) is formed, as by, for example, the use of an acetylene torch, in the top plate 14 and the upper flanges of the Z-sections, 15 and 16 (FIG. 2), the purpose of this slot 18 being to accommodate the upper portion of the draft gear device 13 which extends therethrough and also through an elongated slot 19 (FIG. 1) formed in a floor 20 of the railway car adjacent the left-hand end thereof, this end of the fioor being supported by an end sill (not shown) as is conventional in railway freight car construction.

The floor 20 to the right of the draft gear device 13, as shown in FIG. 1, is supported by a sliding or floating center sill 21, it being understood that the entire car body is supported by and movable with this center sill in response to draft and buff forces imparted to the car coupler.

As shown in FIG. 2, the sliding sill 21 may be fabricated as by Welding a top plate 22 to two oppositely arranged American Association of Railroads Z- sections 23 and 24 which are arranged in straddling relation to the fixed center sill 11 so as to form between the fixed center sill 11 and the sliding sill 21 a sliding sill pocket 25. Subsequent to this welding operation, the main underframe is secured to the sliding sill upon which underframe, it will be understood, the car body including the hereinbefore-mentioned floor 20 is constructed according to conventional practice of railway car builders.

The draft gear device 13 comprises a single casing 26 (FIG. 1) in which is embodied two parallel hydraulic cylinder devices or fluid motors 27 and 27a. The single casing 26 is provided with two spaced-apart parallel and oppositely extending bottom bores 28 and 29, the bottom bore 28 being arranged vertically above the bottom bore 29 and opening in the opposite direction. As shown in FIG. 1, the left-hand end of the upper bottom bore 28 is connected to the right-hand end of the lower bottom bore 29 by a passageway 30 formed in the casing 26.

As can be seen from FIG. 1, the casing 26 has formed therein a chamber 31 which is in communication with the passageway 30 via a tapered bore 32 provided in the casing 26.

As shown in FIG. 1 of the drawings, a piston 33 is provided with a peripheral annular groove in which is inserted an O-ring 34 prior to placing the piston 33 in the bottom bore 28. Also, prior to placing the piston 33 in the bottom bore 28, the left-hand end of a piston rod 35 is press-fitted into a bottom bore 36 provided in the righthand face of this piston.

Subsequent to securing the piston rod 35 to the piston 33 and inserting the O-ring 34 in the groove in this piston in the manner just explained, the piston 33 is introduced into the right-hand end of the bottom bore 28 in the easing 26.

Next, a nonpressure head 37 having a central bore 38 is slipped over the right-hand end of the piston rod 35 and then pushed in the direction of the left-hand, as viewed in FIG. 1, until it is in abutting relationship with the right-hand end of the cylinder device 27. The pressure head 37 is then secured to the right-hand end of this cylinder device 27 by any suitable means (not shown).

As can be seen from FIG. 1, the pressure head 37 is provided with a counterbore 39 coaxial with the bore 38. A packing 40 is first placed in this counterbore 39 after which an annular packing nut 41 is slipped over the righthand end of the piston rod 35 and then screw threaded into a screw-threaded counterbore 42 that is coaxial with the counterbore 39. The packing nut 41 thus serves to retain the packing 40 in the counterbore 39 and in sealing relationship with the periphery of the piston rod 35.

The hydraulic cylinder device 27a of the draft gear device 13 comprises a piston 43 that is provided with a peripheral annular groove, a central bore 44 and a coaxial screw-threaded counterbore 45.

Prior to placing the piston 43 in the bottom bore 29, an O-ring 46 is inserted in the peripheral annular groove in this piston. Also, a piston rod 47 having external screw threads corresponding to the internal screw threads of counterbore 45 is screw threaded into this counterbore thereby securing this piston rod 47 to the piston 43.

Formed integral with the threaded end of the piston rod 47 is a tapered metering pin or plunger 48 that extends through the bore 44 in the piston 43. The taper per inch of the metering pin 48 is the Same as that of the tapered bore 32. However, it should be noted that the diameter of the metering pin 48 at its larger or left-hand end is somewhat less than the diameter of the tapered bore 32 at its left-hand end.

Subsequent to inserting the O-ring 46 in the groove in the piston 43 and securing the piston rod 47 thereto, this piston is positioned so that the metering pin 48 extends in the direction of the bottom bore 29 in the casing 26 and is coaxial with this bottom bore. With the piston 43 and metering pin 48 thus positioned, they are moved toward the casing 26 and the piston 43 introduced into the left-hand end of the bottom bore 29 in this casing 26.

Next, a nonpressure head 49 having a central bore 50 is slipped over the left-hand end of the piston rod 47 and then pushed in the direction of the right-hand, as viewed in FIG. 1, until it abuts the left-hand end of the cylinder device 27a. This pressure head 49 is then secured to the left-hand end of the cylinder device 27a by any suitable means (not shown).

As shown in FIG. 1, the pressure head 49 is provided with a counterbore 51 that is coaxial with the bore 50 and has internal screw threads formed adjacent its outer end. A packing 52 is now placed in the counterbore 51 after which an annular packing nut 53 is slipped over the left-hand end of the piston rod 47 and thereafter screw threaded into the screw-threaded end of the counterbore 51 to retain the packing 52 therein.

Subsequent to assembling the draft gear device 13 in the manner just explained, the pistons 33 and 43 are respectively moved from the position in which they are shown in FIG. 1 to a position at the opposite end of the corresponding bottom bores 28 and 29 by manually exerting a push on the outer end of the respective piston rods 35 and 47.

Assuming that the fixed center sill 11 is positioned within the sliding sill pocket 25 of the Sliding Sill 21 in the position indicated in FIG. 2, and further assuming that the car body-supporting sliding sill 21 and the fixed center sill 11 are supported by any suitable means, such as, for example, the usual overhead crane found in railway car builders assembly plants, the hereinbefore-mentioned assembly including the draft gear yoke 4, to which is secured the car coupler by having its shank 6 secured thereto by the shank pin 9, and the striker 12, which is resting on the left-hand end of the draft gear yoke 4, is positioned below the fixed center sill pocket 17 so that the center line of this assembly is parallel with the center line of the center sill pocket 17 and the fixed center sill 11.

The above-described assembly may now be raised vertically by any suitable means (not shown) until it is positioned within the fixed center sill pocket 17 as shown in the drawings. This assembly is now retained temporarily in this position by any suitable means (not shown).

The horizontal type of draft gear yoke 4 is permanently supported by two parallel spaced-apart longitudinally extending angle brackets 54 and 55 (FIGS. 2 and 3) which are now secured by any suitable means, such as for example, welding or a plurality of rivets, respectively to the inside vertical faces of the hereinbefore-mentioned Z- sections 15 and 16. It will be understood that subsequent to securing these angle brackets 54 and 55 to the respective Z-seotions 15 and 16, the hereinbefore-mentioned means for temporarily retaining the assembly including the draft gear yoke 4 in the position shown in the drawings is now removed.

Next, the assembled draft gear device 13 is positioned below the draft gear yoke 4 so that the center lines of the piston rods 35 and 47 are parallel :to the horizontal center line of the yoke 4. The draft gear device 13 may now be moved upward by any suitable means (not shown), so that the upper portion of the casing 26 of this draft gear device passes through the yoke pocket 1 in the draft gear yoke 4, the elongated slot 18 in the fixed center sill 11, and the elongated slot 19 in the Car floor 20, until this draft gear device 13 occupies the position shown in the drawings.

At this time a draft gear carrier plate 56 is secured by any suitable means, such as, for example spot welding, to feet 57 and 58 (FIGS. 2 and 3) that are integral with the respective Z- sections 15 and 16 of the fixed center sill 11. The width of this draft gear carrier plate 56, as shown in FIG. 2, is substantially greater than the width of the fixed center sill 11 or the distance between the opposite ends of the feet 57 and 58 in order to support thereon adjacent each of these feet a plurality of rollers 59 which are disposed between this carrier plate 56 and feet 60 and 61 that are integral with the respective Z- sections 23 and 24 of the sliding sill 21. These rollers 59 are retained on the top surface of the carrier plate 56 between the feet 57 and 58 of the respective Z- sections 15 and 16 and a pair of vertically disposed skirts 62 and 63 which are secured respectively to the feet 60 and 61 by any suitable means, such as, for example, spot welding along their upper edge. It will be apparent from FIG. 2 that the skirts 62 and 63 and the feet 57 and 58 provided a track for the plurality of rollers 59 which roll therealong and support the car body-carrying sliding sill 21 upon movement thereof in response to draft and buff forces in a manner hereinafter described in detail.

Furthermore, it will be apparent from the drawings that, subsequent to securing the draft gear carrier plate 56 to the feet 57 and 58 of the respective Z- sections 15 and 16 of the fixed center sill 11, this carrier plate supports thereon the casing 26 of the draft gear device 13. Therefore, the means used to move this draft gear device 13 upward to the position shown in the drawings and maintain it in this position until the carrier plate 56 is secured to the feet 57 and 58, may now be removed.

Subsequent to positioning the draft gear device 13 in the position in which it is shown in FIG. 1, the pistons 33 and 43 are moved to the position shown in FIG. 1 by manually exerting a pull on the respective piston rod 35 and 47. With the pistons 33 and 43 and the piston rods 35 and 47 in this position, the right-hand end of the piston rod 35 abuts a bumper block 64 which is disposed in an opening 65 formed in the car floor 20 and secured, as for example by welding, to the top plate 22 of the sliding sill 21 so as to be movable therewith.

It will be noted from FIG. 1 that, while the piston 43 and piston rod 47 occupy the position shown, the left-hand end of the piston rod 47 abuts the right-hand vertical face of the hereinbefore-mentioned follower 7.

The left-hand vertical face of the follower 7, in addition to abutting the right-hand end of the shank 6 of the car coupler, as hereinbefore-stated, also abuts a pair of front draft gear lugs 66 and 67 which are secured respectively, as for example, by welding, to the top flanges of the two Z- sections 15 and 16 constituting the fixed center sill 11, and to the draft gear carrier plate 56, it being understood this welding operation is performed prior to welding the plate 56 to the feet 57 and 58 of the Z- sections 15 and 16. These front draft gear lugs 66 and 67 serve to transmit draft forces to the fixed center sill 11, it being understood that these forces are transmitted through the draft gear device 13.

In order that buff forces imparted to the draft gear device 13 via the car coupler during humping operations may be transmitted to the fixed center sill 11, a pair of rear draft gear lugs 68 and 69 are secured respectively, as for example by welding, to the top flanges of the two Z- sections 15 and 16, and to the carrier plate 56 as shown in FIG. 1, it being understood that this welding operation is also performed prior to welding the draft gear carrier plate 56 to the feet 57 and 58.

In place of a conventional truck bolster, each car truck of a freight car equipped with two draft gear devices 13 constituting the present invention, one located adjacent each end of the car, is provided with a specially designed car bolster 70 (FIGS. 1 and 2). Substantially midway its ends, the car bolster is provided with a vertically disposed bottom bore 71 in which is carried a load sensing or weighing cylinder device 72.

The load sensing or weighing cylinder device 72, as shown in FIG. 1, comprises a cup-shaped cylinder body 73 having therein a bottom bore 74. Slidably mounted in the bottom bore 74 is a piston 75 which cooperates with the wall surface and end of the bottom bore 74 to form on the lower side of this piston 75 a chamber 76.

Extending through the wall of the bottom bore 74 in the cylinder body 73 and the wall of the bottom bore 71 in the car bolster 70 is a screw-threaded bore 77 in which is received a screw-threaded end of a short nipple 78. The opposite end of this nipple 78 extends into one end of a piece of flexible hose 79 the opposite end of which extends through an opening 80 suitably formed in the draft gear carrier plate 56 and receives therein one end of a second short nipple 81. The opposite end of this nipple 81 is provided with external screw threads which have screw-threaded engagement with corresponding internal screw threads formed in a bore 82 extending through the casing 26 of the draft gear device 13 and opening into the chamber 31 in this casing 26. Thus the chambers 76 and 31 are constantly in communication one with the other.

It will be noted from FIG. 1 of the drawings that the upper face of the piston 75 is provided with a bottom bore 83 into which is press-fitted one end of a hollow piston rod 84. The opposite end of the piston rod 84 extends through a bore 85 formed in a non-pressure head 86 that is secured to the upper end of the cylinder body 73 by any suitable means (not shown).

The non-pressure head 86 is provided with a counterbore 87 that is coaxial with the bore 85. Disposed in this counterbore 87 is a swab or packing 88 that is saturated with any suitable lubricant for lubricating the periphery of the piston rod 84 upon upward movement of the piston 75 in the bottom bore 74. The outer end of the counterbore 87 is provided with internal screw threads for receiving therein corresponding external screw threads formed on an annular nut 89 which serves to retain the swab 88 in this counterbore 87.

The upper end of the hollow piston rod 84 is provided with a counterbore 90 for receiving therein with a turning fit an annular member 91 that is secured to the bottom of the draft gear carrier 56 by any suitable means such as, for example, welding.

Disposed within the annular member 91 and secured thereto and to the bottom of the draft gear carrier plate 56 by any suitable means (not shown) is a king pin 92 the lower end of which extends with a turning fit through a bore 93 formed in a second annular member 94 that is disposed in the upper end of the hollow piston rod 84 and secured thereto by any suitable means such as, for example welding. The above-described construction provides for turning of the car truck with respect to the car body which turning is necessary when a railway car travels on a curved track.

In order to prevent leakage of fluid under pressure from the chamber 76 to an annular chamber 95 above the piston 75, this piston is provided with a peripheral annular groove in which is inserted an O-ring 96 that forms a seal with the wall surface of the bottom bore 74.

The annular chamber 95 is constantly open to atmosphere via a passageway 97 that extends through the cylinder body 73 'and the bolster 70 to prevent dash pot action within the annular chamber 95.

After the draft gear device 13 and the load sensing or weighing cylinder device 72 have been assembled and connected by the flexible hose 79 as shown in FIG. 1 of the drawings, and while the car is empty, a screw-threaded filler plug (not shown) is removed from a corresponding screw-threaded bore (not shown) in the casing 26. Subsequent to removal of this filler plug, a hydraulic fluid, such as a suitable oil, is poured into the interior of the casing 26 until the chamber 76, hose 79, chamber 31,

7 tapered bore 32, bottom bore 29 on the right-hand side of piston 43, passageway 30 and the bottom bore 28 on the left-hand side of piston 33 are completely filled, after which the filler plug is replaced.

The hereinbefore-mentioned striker 12 may now be moved from the position in which it was placed, adjacent the left-hand end of the yoke 4, in the direction of the right-hand, as viewed in FIG. 1, along the yoke 4 until the right-hand end thereof can be inserted into the lefthand end of the fixed center sill pocket 17 (FIG. 1), after which the striker 12 is pushed in the direction of the right-hand until it occupies the position shown in FIG. 1. With the striker 12 in this position, it is welded to the left-hand end of the fixed center sill 11, as indicated by the reference numeral 98 in FIG. 1.

OPERATION It should be noted that the kinetic energy absorbed by the draft gear device 13 of the present invention in buff is twice that in draft for the reason that in buff the piston 43 of the hydraulic cylinder device 27a is subjected to the buffing force and the piston 33 of the hydraulic cylinder device 27 is subject to the inertia force of the car body and the load carried thereby as the result of the movement of the body-supporting sliding sill 21 relative to the fixed center sill 11 occurring upon the application of a buffing force to the car coupler whereas, upon the application of a force of draft to the car coupler, only the piston 43 is subject to this force.

However, it should be noted that upon the application of 4 a force of draft to the car coupler at one end of the car, the piston 33 of the draft gear device 13 at the opposite end of the car is subject to the inertia force of the car body and its load as the result of the movement of the sliding sill 21 relative to the fixed center sill 11 it being understood that the direction of movement of the sliding sill 21 at this time is opposite the direction of movement of the sliding sill in response to the application of a buffing force to the car coupler at the one end of the car.

It will be further noted that the draft gear device 13 at the above-mentioned opposite end of the car, in addition to being subject to the inerita force of the car body and its load as the result of the movement of the sliding sill 21 relative to the fixed center sill 11, is also subject to a draft force resulting from this car being coupled to the adjacent car. Accordingly, it will be understood that the capacity of each draft gear device 13 is the same in draft as in buff. Therefore, when a car coupled in a train is started from rest by the tractive effort of the locomotive, the cylinder device 27a of the draft gear device 13 on that end of the car nearest the locomotive is subject to a draft force whereas the cylinder device 27 of this draft gear device 13 is subjected to no force, and simultaneously the cylinder devices 27a and 27 of the draft gear device 13 on the opposite end of this car are subject respectively to a draft force and an inertia force.

So long as the kinetic energy developed as the result of a buff or a draft impact imparted by each to the other of two adjacent railway car couplers upon the colliding of the two cars carrying these couplers does not exceed the capacity or amount of kinetic energy for which the draft gear was designed to absorb by more than a certain amount, the stress induced in the couplers and the various parts constituting the bodies of the cars will be limited to a value below or not in excess of the elastic limit of the materials of which the car couplers and car bodies are constructed.

It should be understood that, in draft, kinetic energy is transmitted from the car coupler through the shank pin, the draft gear yoke, the draft gear device, the follower and the front draft gear lugs to the fixed center sill, and in buff, kinetic energy is transmitted from the car coupler through the coupler shank, the follower, the draft gear device and the rear draft gear lugs to the fixed center sill.

(a) Bufj impact-car detached for humping Let it be supposed that a detached freight car, while traveling along a track in a classification yard at some slow speed such as, for example, fourteen miles per hour, collides with a standing car or string of cars on this track. This moving car has a certain amount of kinetic energy. As the couplers on the adjacent ends of the moving car and the standing car come into contact, each coupler imparts an impact to the other, the impact imparted to each coupler by the other being the same. These couplers operate automatically at this time to couple the two cars together.

Let it be assumed that the shank 6 shown in FIG. 1 of the drawings is the shank of the car coupler on a standing car that is struck by the moving car. Therefore, upon collision of the moving car with the standing car, some of the kinetic energy of the moving car is transmitted from the coupler on the moving car through the shank 6 of the coupler on the struck car and the follower 7 on this car to the corresponding piston rod 47, it being understood that the direction of the blow imparted as the result of this impact acts in the direction of the right-hand, as viewed in FIG. 1.

Since the piston rod 47 having metering rod 48 integral therewith has screw-threaded engagement with the screwthreaded counterbore 45 in the piston 43, it is apparent that the piston rod 47 transmits the bufiing force of impact of the two colliding cars to the piston 43 of the draft gear device 13 on that end of the struck car adjacent the moving car to cause movement of this piston 43 and metering rod 48 in the direction of the right-hand relative to the casing 26, the right-hand end of which abuts the rear draft gear lugs 68 and 69.

This movement of the piston 43 in the direction of the right-hand within the bottom bore 29 in casing 26 is in the direction to cause this piston 43 to decrease the volume of the bottom bore 29. As the piston 43 and metering rod 48 are thus moved in the direction of the right hand, the piston 43 is effective to force the oil in the bottom bore- 29 to flow therefrom, and the metering rod 48 is moved into the tapered bore 32.

As hereinbefore explained, the bottom bore 28, passageway 30, tapered bore or orifice 32, chamber 31, hose 79 and chamber 76 are all full of oil. Since the piston 33 is at the righthand end of its stroke, there can be no flow of oil to the bottom bore 28. Therefore, in order for oil to be forced from the bottom bore 29 by the piston 43, there must be an increase in the volume of the chamber 76 which can only result from upward movement of the piston 75 in the bottom bore 74 of the load weighing cylinder device 72.

As hereinbefore explained, the piston rod 84 of the piston 75 supports in the counterbore the annular member 91 which is secured to the draft gear carrier plate 56 that in turn supports the rollers 59 on which, as shown in FIG. 2, rest the feet 60 and 61 of the Z- sections 23 and 24 of the car-body-supporting sliding center sill 21. Consequently, it is apparent that upward movement of the piston 75 is resisted by one half the weight of the car body and the load carried thereon, it being understood that the other half of the weight of the car body and its load is supported by the identical load weighing cylinder device located adjacent the other end of the car.

From the foregoing, it is apparent that the work done by the piston 43 in displacing oil from the bottom bore 29 and forcing it into the chamber 76 is equal to the work done by the piston 75 as it lifts the weight of the left-hand end of the car vertically upward a distance that provides for an increase in the volume of the chamber 76 that is equal to the volume of the oil forced from the bottom bore 29 by the piston 43.

It is well known that the work done in lifting a Weight vertically is equal to the product of the weight and the distance that the weight is lifted. Therefore, it is apparent that the greater the load carried on the car body the 9 greater the weight to be lifted by fluid forced into the chamber 76 and, therefore, the greater the amount of work done upon upward movement of the piston 75 a chosen distance.

It is apparent that the kinetic energy that is not absorbed in lifting the weight of the car body and the load carried thereon, or by other means hereinafter discussed, is transferred as kinetic energy from the piston 43- via the oil in the casing 26 to this casing and thence via the rear draft gear lugs 68 and 69 to the fixed center sill 11 of the respective car with its load .carried in the body thereof which is supported by the sliding sill 21 that in turn is supported on the rollors 59 which rest on the draft gear carrier plate 56 that is welded to the fixed center sill 11. This remaining kinetic energy that is thus transmitted to the standing car is effective to move the standing car, or string of standing cars if one or more cars are coupled to the struck car, provided this remaining kinetic energy is great enough to overcome the inertia of the standing car or cars.

Let it be assumed that this remaining kinetic energy is great enough to move the standing car or string of cars from a standing position. It is well known that a body or weight possesses that characteristic called inertia which is defined by Chambers Technical Dictionary, edited by C. F. Tweney and L. E. C. Hughes, revised edition with supplement, published 1961, as follows:

Inertia (Mech., Phys). Reluctance of a body to change its state of rest or of uniform velocity in a straight line. Inertia is measured by mass when linear velocities and accelerations are considered; and by moment of inertia (q.v.) for angular motions (i.e. rotations about an axis).

Accordingly, the car body and the load carried thereon, both of which are supported on the rollers 59', by reason of their inertia will, therefore, be reluctant to change their state of rest or, in other words, resist movement from their state of rest as the result of the kinetic energy transmitted to the corresponding coupler of a standing car and thence to the fixed center sill 11 of this car. Consequently, this kinetic energy transmitted to the fixed center sill 11 will cause movement of this fixed center sill and the car trucks relative to the sliding center sill 21 upon which is supported the car body and the load carried thereon.

Upon this movement of the fixed center sill 11 and casing 26 of the draft gear device 13 relative to the sliding center sill 21 and the car body supported thereon, the sliding sill 21 is effective via the bumper block 64 and piston rod 35 to maintain the piston 33 of the cylinder device 27 against movement. Consequently, the casing 26 of the draft gear device 13 now moves in the direction of the right-hand, as viewed in FIG. 1.

It is apparent that, in order for the casing 26 to move in the direction of the right-hand, as viewed in FIG. 1, relative to the stationary piston 33, the piston 33 forces oil from the bottom bore 28. Since the piston 43' is subject to the force of the impact of the two colliding cars, as hereinbefore explained, there can be no flow of oil to the bottom bore 29. Accordingly, in order for oil to be forced from the bottom bore 28 by the piston 33 as the casing 26 is moved in the direction of the right-hand, as viewed in FIG. 1, there must be an increase in the volume of the chamber 76 and an upward movement of the piston 75 in the bottom bore 74 against the resistance offered by one half the weight of the car body and the load carrier thereon. Therefore, it is apparent that as the load carried by the car is increased, this resistance is correspondingly increased thus providing for control of the resistance to the bufiing forces automatically.

As hereinbefore explained in connection with the displacement of oil from the bottom bore 29 to the chamber 76 by the piston 43, it will be apparent that the work done by the piston 33 in displacing oil from the bottom bore 28 and forcing it into the chamber 76 is equal to the 10 Work done by the piston 75 as it lifts the weight of the left-hand end of the car upward a distance that provides for an increase in the volume of the chamber 76 that is equal to the volume of the oil forced from the bottom bore 28 by this piston 33.

It is apparent from FIG. 1 that the oil flow initiated by movement of both the piston 33 and the piston 43' from the respective bottom bores 28 and 29 to the chamber 31 in the draft gear device 13 and the chamber 76 in the load weighing cylinder device 72 is through an orifice formed between the periphery of the tapered metering pin 48 and the inside Wall surface of the tapered bore 32. It is also apparent from FIG. 1 that as the piston 43 and tapered metering pin 48 move in the direction of the right-hand so that the metering pin 48 travels further into the tapered bore 32, the cross-sectional area of this orifice is decreased.

The oil flow through the orifice provided between the periphery of the metering pin 48 and the Wall surface of the tapered bore 32 is at a relatively high velocity and creates great turbulence in the chamber 31. This great turbulence is caused, at least in part, by the high velocity oil impinging directly against the right-hand vertical wall surface of the chamber 31, and is responsible for dissipation of much of the kinetic energy of the oil in the form of heat.

Furthermore, the friction of the draft gear yoke 4 and other moving parts is effective to dissipate or absorb some of this kinetic energy. Therefore, all the kinetic energy transmitted to the car couplers and shank 6 on each of the two colliding cars is dissipated (1) in the form of the work done by the pistons 33 and 43 in forcing oil from the respective bottom bores 28 and 29 to the chamber 76, which is equal to the work done by the piston 75 in lifting one half the Weight of the car body and the load carried thereon as this piston 75 is moved upward to increase the volume of the chamber 76 an amount equal to the volume of the oil forced out of the bottom bores 28 and 29 by the respective pistons 33 and 43, (2) in the form of heat by the passing of the oil through the orifice, (3) the turbulence in the chamber 31, and (4) the friction of the various parts of the draft gear devices, or is transferred via the rear draft gear lugs 68 and 69 to the fixed center sill 11 of the respective car.

The standard coupler used on freight cars is designed to withstand a predetermined buff or compression impact blow Without inducing a stress therein that exceeds the elastic limit of the steel, of which the coupler is constructed. In order that the buff stress established by the impact of the two colliding cars is maintained constant during the time required for the pistons 43 and 33 to successively travel their maximum length of stroke in the respective bottom bores 29 and 28 in the casing 26 of the draft gear device 13, the area of the orifice provided by the tapered bore 32 and the metering rod 48 must be varied so as to provide or maintain a constant oil pressure in the bottom bores 29 and 28, which constant pressure establishes a corresponding constant force that must not exceed the allowable force that can be transmitted through the casing 26 of the hydraulic gear device 13 to the rear draft gear lugs 68 and 69 and thence to the fixed center sill 11 and the car body slidably supported thereon 'by the sliding sill 21 without inflicting damage to the lading carried by the car.

As the piston 43 moves in the direction of the righthand in the bottom bore 29 of the casing 13 of the hydraulic draft gear device 13 from the position in which it is shown in FIG. 1 at an initial velocity corresponding to the degree of the impact blow on the car coupler as the result of the collison of the moving car with the standing car or cars, the pressure of the oil in the bottom bore 29 is increased at a rapid rate due to the combined effect of the inertia of the oil in this chamber and the limited area of the orifice provided by the tapered bore 32 and metering rod 48, through which orifice the oil flows from the bot- 1 1 tom bore 29 to the chamber 31 and thence to the chamber 76 via the hose 79.

In order that the force developed by the increase of the pressure of the oil in the bottom bore 29 'be limited to and thereafter maintained at a value which will not induce a stress in either the coupler or the structure of the car in excess of the elastic limit as the piston 43 and metering rod 48 move in the direction of the right hand, subsequent to the right-hand end of the metering rod 48 entering the left-hand end of the tapered bore 32, a distance equal to the length of the metering pin 48 from its righthand end to the right-hand face of the piston 43, this metering pin 48 must be tapered this distance, it being understood that the taper of the metering pin 48 is the same as that of the tapered bore 32, as hereinbefore stated. It will be apparent that as the tapered metering pin 48 passes through the tapered bore 32, the area of the orifice is decreased at a rate corresponding to the angle of the taper of the metering rod 48. Furthermore, it will be understood that the initial velocity of the piston 43 has been reduced as it moves in the direction of the right hand, as viewed in FIG. 1, as part of the kinetic energy of the striking car is absorbed by doing work as each respective load weighing cylinder device 72 lifts the corresponding end of the respective car in the manner hereinbefore described. Therefore, in order to maintain a constant pressure in the bottom bore 29 as the piston 43 and meteing pin 48 move in the direction of the right hand with a constantly decreasing velocity, the area of the orifice provided by the tapered bore 32 and the metering rod 48 must be decreased at a certain corresponding rate. Consequently, by providing that the metering rod 48 is tapered in the direction shown in FIG. 1, this requirement that the orifice area be constantly decreased at this certain constant rate is insured.

The center of gravity of a railway freight car, whether empty or loaded, is above the horizontal center line of the car couplers. Therefore, normally when a moving car of conventional design strikes a like standing car or string of cars, a moment is produced on the struck car which is the product of the force of impact imparted to this car by the moving car and the vertical distance between the horizontal center line of the car couplers and the center of gravity of this car. The effect of this moment on the struck car is to rotate the body of this struck car about th center of gravity of the car in the direction to cause that end of the struck car that is adjacent the moving car to clip or move downward toward the rails, it being understood the car truck springs 'at this end of the car, which springs resiliently support one half of the weight of the car body and its load it it is loaded, deflect or are compressed to allow this end of the car to dip downward.

It should be noted, however, that the hereinbeforementioned upward movement of the piston 75 in the bottom bore 74 of the load weighing cylinder device 72 acts in the direction to balance or counteract the above-mentioned moment acting on the car body. Consequently, the dipping that occurs on cars of conventional design when a moving car strikes a standing car or string of cars is greatly reduced or entirely eliminated when the cars are provided at each end with a draft gear device 13 and a load weighing cylinder device 72 connected by a hose 79 or, in other words, when the cars are provided with the apparatus constituting the present invention.

Since, as hereinbefore stated, the impact imparted to each coupler by the other is the same, what has been stated above in regard to the struck car equally applies to the draft gear apparatus provided on the moving car.

The pressures established in the bottom bores 28 and 29 in response to the corresponding pistons 33 and 43 traveling respectively in the direction of the left and right hand through their full length of stroke constitutes a hydraulic head of oil for forcing the oil from the respective bottom bores 28 and 29 through the orifice formed between the metering rod 48 and the tapered bore 32 to the chambers 31 and 76.

The general equation for the velocity of spouting liquid is V= /2gH, where V=theoretical velocity in feet per second, g=acceleration of gravity in feet per second per second, and H=head of liquid in feet. The discharge from an orifice in cubic feet per second is equal to the product of the actual velocity and the area of the jet. (The above equations are from section 5, page 09 of Power Volume, twelfth edition, Kents Mechanical Engineers Handbook.)

The total quantity of oil discharged from the orifice may be expressed by the equation Q 712, where n represents the discharge in cubic feet per second and t the time in seconds that the discharge through the orifice continues.

From the above equations, it is apparent that the total quantity of oil discharged from the bottom bores 28 and 29 through the orifice to the chambers 31 and 76 is dependent on the sum of the pressures in the bottom bores 28 and 29 and the sum of the length of time required for the two pistons 33 and 43 to travel the respective full length of their strokes. The length of travel of a standard sliding sill used on freight cars today is approximately thirty inches. Also, it will be understood that the kinetic energy absorbed by a single piston draft gear device used with this standard sliding sill is a function of this length of stroke. In the draft gear device 13 constituting the present invention it is apparent that the time required for the discharge of oil through the orifice is dependent on the sum of the time required for the piston 33 to complete the full length of its stroke, which length of stroke it will be understood is the same as the length of travel of the sliding sill 21, and the time required for the piston 43 to complete the length of its stroke. Since the full length of stroke of the two pistons 33 and 43 may be approximately the same, it is apparent that the kinetic energy absorbing capacity of the draft gear device 13 for a chosen travel of the sliding sill 21 is approximately twice the kinetic energy absorbing capacity of a single piston conventional draft gear device used with a sliding sill having the same length of stroke as the sliding sill 21. From the above it may be seen that by the use of the draft gear device 13 the length of stroke or travel of the sliding sill can be reduced one half and yet obtain the same cushioning protection for the lading or load carried by the freight car.

Freight cars using conventional sliding sill construction require, in addition to the draft gear device operatively connected to the sliding sill and located approximately midway the length of the car, two other draft gear devices, one associated with each of the two car couplers. It may be noted, however, that by using a draft gear device 13 at each end of a freight car only two draft gear devices per car are required thereby reducing substantially the cost of providing adequate cushioning for the lading carried in the body of the car.

The amount of kinetic energy absorbed may be expressed mathematically in manner well known to those skilled in the art by use of the general equation for kinetic energy:

nw m(at) E 2 T 2 Where m=mass=weight+g; v=velocity in feet per second; a=acceleration in feet per second per second; t: time in seconds.

Reference may be had to the American Society of Mechanical Engineers Paper No. 61WA256 covering The Design of Cushioning Gears for Rail-Car Applications by Robert L. Hassenauer and George E. Novak presented at the Winter Annual Meeting in New York, N.Y., Nov. 26-Dec. 1, 1961, for a fuller explanation of a method of calculating the relative acceleration between a rail car and its lading occurring as the result of a moving car striking a stationary car or string of cars.

13 From the above-mentioned equation for kinetic energy lem it will be appreciated that where the sum of the length of stroke of the two pistons 33 and 43 is equal to the length of stroke of the piston of a standard draft gear device operatively connected to a sliding sill having twice the length of travel as the sliding sill 21, the time required for the oil to be forced from the bottom bores 28 and 29 through the orifice provided between the periphery of the metering rod 48 and the wall of the tapered bore 32 to the chambers 31 and 76 is the same as the time required for the piston of the standard draft gear device to force the oil through the orifice of this standard draft gear device. Accordingly, it will be apparent that the kinetic energy dissipated by flow of the oil through the orifice of the draft gear device 13 associated with the sliding sill 21 is the same as the kinetic energy dissipated by a standard draft gear device associated with a sliding sill having a length of travel twice the length of travel of the sliding sill 21. In other words, for the same cushioning effect, the draft gear device 13 provides for reducing the travel of the sliding sill fifty percent.

When the velocity of the moving car and the velocity of the struck car or string of cars become the same, there is no further deceleration of the moving car, and, likewise, no further acceleration of the struck car or string of cars. Accordingly, in view of the above-mentioned general equation for kinetic energy of mV T and the general equation for force of F =ma, where F: force in pounds, mt=mass=weight divided by 32.174 feet per second per second (acceleration due to gravity), and a=acceleration in feet per second per second, it is apparent that and that if F/a be substituted for m in the above-mentioned general equation for kinetic energy, it will be seen that From this equation for force, it will be seen that when a, the acceleration, becomes zero, the force F likewise becomes Zero. Therefore, it is apparent that when the velocity of the moving car and the velocity of the struck car or cars become the same, at which time there is no acceleration or deceleration of any of these cars, the impacting force acting on the piston rods 35 and 47 and the corresponding pistons 33 and 43 is likewise zero, for if zero be substituted for a in the equation the force F becomes zero.

One-half the weight of the car and its load is now acting in a downward direction on the piston 75 via the piston rod 84 and, therefore, is effective to move the piston 75 downward to cause it to force oil to flow from the chamber 76 to the bottom bores 28 and 29 via nipple 78, hose 79, nipple 81, chamber 31, tapered bore 32 and passageway 30. The oil thus supplied to the bottom bores 28 and 29 will cause the respective pistons 33 and 43 and their corresponding piston rods 35 and 47 to be moved to the position in which they are shown in FIG. 1 or in other words to the original position these pistons and piston rods occupied prior to the moving car striking the standing car or string of cars.

14 (b) Draft impact-car coupled in a train Let it be assumed that a freight car provided with a draft gear device 13 at each end is coupled in a train.

Now let it be supported that the train is standing and the engineer desires to start the train. To do so, he moves the controller handle from idle position to a power position. This effects the supply of power to the driving wheels of the locomotive to start the locomotive from a stopped position. The initial movement of the locomotive is transmitted from the coupler at the train end of the locomotive to the coupler at the locomotive end of the first car in the train. Accordingly, let it be supposed that the shank 6 shown in FIG. 1 of the drawings is the shank of the coupler at the locomotive end of the first car in the train. Therefore, the initial movement of the locomotive is effective to exert a pull or jerk and thereby establish a force that acts in the direction of the left hand on the shank 6 shown in FIG. 1. This force acting on the shank 6 is transmitted through this shank to the shank pin 9. Since the shank pin 9 extends through the hereinbeforementioned elongated slots in the opposite vertical side walls 2 and 3 (FIGS. 2 and 3) of the draft gear yoke 4, the shank pin 9 is effective to transmit the force exerted by the locomotive to the draft gear yoke 4. As shown in FIG. 1, the right-hand end wall of the draft gear yoke pocket 1 abuts the right-hand end of the casing 26 of the draft gear device 13. Therefore, the pull on the draft gear yoke 4 in the direction of the left hand, as viewed in FIG. 1, will be transmitted to the casing 26. Accordingly, upon movement of the draft gear yoke 4, the casing 26 is moved in the direction of the left hand in response to the pull exerted in this direction by the locomotive on the shank 6 of the car coupler.

It will be noted that the upper and lower ends of the left-hand side of the follower 7 normally abut, respectively, the front draft gear lugs 66 and 67 which, as hereinbefore stated, are secured to the fixed center sill 11 of the car. Likewise, it will be noted that the right-hand side of the follower 7 abuts the left-hand end of the piston rod 47. Accordingly, it will be apparent that as the draft gear yoke 4 and the casing 26 are moved in the direction of the left hand, the casing 26 is moved with respect to the piston 43, piston rod 45 and metering rod 48 to decrease the volume of the bottom bore 29 on the right-hand side of the; piston 43. As this movement of the yoke 4 and casing 26 continues in the direction of the left hand, the piston 43 is effective to force the oil in the bottom bore 29 to flow at a relatively high velocity through the orifice formed between the periphery of the metering rod 48 and the wall surface of the tapered bore 32, as this metering rod enters this bore, to chambers 31 and 76 to respectively dissipate kinetic energy as heat and do work in moving the piston upward in the manner hereinbefore explained.

Furthermore, the friction of the draft gear yoke 4 and other moving parts of the mechanism are effective to dissipate or absorb some of this kinetic energy transmitted by the pull or jerk of the locomotive to the shank 6 of the car coupler. Therefore, all of the kinetic energy resulting from the jerk exerted on the shank 6 of the coupler on that end of the first car adjacent the train end of the locomotive is dissipated (1) in the form of the work done by the piston 43 in forcing oil from the bottom bore 29 to the chamber 76 to lift one half the weight of the car body and the load carrier thereon, (2) in the form of heat by the passing of the oil through the orifice, (3) the turbulence in the chamber 31, and (4) the friction of the various parts of the draft gear mechanism, or is transferred via the oil in the casing 26 to the piston 43 and thence to the fixed center sill 11 via the piston rod 47, follower 7 and the front draft gear lugs 66 and 67. This remaining kinetic energy that is not absorbed by the hydraulic draft gear mechanism and friction but is transmitted to the fixed center sill 11 of the first car in the train is effective to move this center sill 11 and the two trucks 0f the car to which it is connected from their standing position in the same direction as the initial movement of the locomotive.

The inertia of the car body and the load carried thereon resist movement from their state of rest. Since the car body and the load carried thereon are supported on the sliding sill 21 which rests on the rollers 59 which in turn are supported on the draft gear carrier 56 that is secured to the Z-sections 15 and 16 (FIG. 2) that constitute the fixed center sill 11, it will be apparent that as the fixed center sill 11 and the two car trucks are moved in the direction of the left hand, as viewed in FIG. 1, by the tractive effort of the locomotive, the inertia resistance of the car body and its load causes the car body, the load therein and the sliding sill 21, all of which are supported on the plurality of rollers 59, to move, as viewed in FIG. 1, in the direction of the right hand relative to the fixed center sill 11 which, it will be understood, is being pulled by the tractive effort of the locomotive in the direction of the left hand. Stated in other Words, the inertia resistance of the car body and the load carried thereon tends to prevent movement of the car body and sliding sill 21 simultaneously with movement of the fixed center sill 11 and the two car trucks operatively connected thereto.

This inertia resistance of the car body and its load to movement in the direction of the left hand simultaneously as the fixed center sill 11 and the two car trucks are moved in the direction of the left hand by the tractive effort of the locomotive, is effective to cause the sliding sill 21 to move in the direction of the right hand relative to the fixed center sill 11 and transmit a force to the piston 33 of the draft gear device 13 at the right-hand end of the car via the corresponding bumper block 64 and piston rod 35. The right-hand end of the casing 26 of the draft gear device -13 at the right-hand end of the car rests against the front draft gear lugs 66 and 67 at this end of the car so that this casing 26 is moved in the direction of the left hand as the fixed center sill 11 is moved in the direction of the left hand by the tractive effort of the locomotive. Since the sliding sill 21 with the car body and its load supported thereon, the piston rod and piston 33 are now being moved in the direction of the right hand, as viewed in FIG. 1, and the casing 26 of the draft gear device 13 at the right-hand end of the car is now being moved in the direction of the left hand, it is apparent that this piston 33 will force oil from the corresponding bottom bore 28 to the chamber 76 of the load Weighing cylinder 72 carried by the bolster of the car truck at the right-hand end of the car in the manner hereinbefore explained. This supply of oil to the chamber 76 is effective on the lower face of the piston 75 to lift the right-hand end of the car against one half the weight of the car body and the load thereon in the manner hereinbefore explained. Accordingly, it is apparent that the draft gear apparatus at the right-hand end of the car absorbs kinetic energy by doing work in lifting the right-hand end of the car. Therefore, the total kinetic energy absorbed in draft is equal to the sum of the kinetic energy absorbed by the two draft gear devices located at the respective opposite ends of the car. From the foregoing, it is apparent that for a given force applied to the shank 6 of the car coupler, either in buff or in draft, the draft gear device or devices 13 absorb the same amount of kinetic energy.

The operation of the draft gear devices associated with the car couples at the adjacent ends of any two coupled cars in a train is the same as the operation of the draft gear device associated with the coupler at the train end of the locomotive and the draft gear device associated with the coupler at the locomotive end of the first car in the train. Therefore, a detailed description of the operation of the draft gear devices associated with the car couplers at the respective adjacent ends of two coupled cars is not deemed necessary.

Having now described the invention, what we claim as new and desire to secure by Letters Patent is:

1. In a railway car having at least one truck bolster, a fixed center sill supported at one end on said bolster and provided with a fixed center sill pocket, and a carbody-carrying sliding sill movably supported in straddling relation to the fixed center sill for longitudinal movement with respect thereto, a hydraulic draft gear assembly comprising:

(a) a draft gear yoke movable in the fixed center sill pocket relative to the fixedcenter sill responsively to draft and buff forces exerted thereon, said yoke having an elongated slot,

(b) a draft gear device disposed in said elongated slot and pocket and having two fluid motors, each of said fluid motors comprising a hollow cylinder and a piston slidably mounted therein for cooperation therewith to form a chamber containing hydraulic fluid, one of said fluid motors being interposed between said yoke and the fixed center sill in such a manner that relative movement between the corresponding cylinder and piston, caused by movement of said yoke relative to the fixed center sill in either direction, effects the displacement of hydraulic fluid from the corresponding chamber of said one fluid motor to cause the absorption of an amount of energy corresponding to the amount of movement of the yoke relative to the fixed center sill and the other of said fluid motors being interposed between said yoke and the sliding sill in such a manner that movement of the piston of said other fluid motor relative to its corresponding cylinder, in response to movement of the sliding sill in one direction relative to the fixed center sill, effects the displacement of hydraulic fluid from the corresponding chamber of said other fluid motor to cause the absorption of another amount of energy corresponding to the amount of movement of the sliding sill in response to inertia forces acting thereon, and

(c) a third fluid motor comprising a hollow cylinder and a piston slidably mounted therein for cooperation therewith to form a displacement chamber containing hydraulic fluid and connected to the chambers of said two fluid motors, said third fluid motor being carried by the truck bolster and supporting one end of the fixed center sill whereby, upon displacement of hydraulic fluid from the chamber of either or both of said fluid motors to said displacement chamber, said third fluid motor is effective to absorb energy in lifting a portion of the load supported on the fixed center sill in response to the increase in pressure of hydraulic fluid effected in said displacement chamher.

2. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that said two fluid motors of said draft gear device are arranged one above the other with their longitudinal center lines lying in the same vertical plane, the longitudinal center line of the lower fluid motor coinciding substantially with the longitudinal center line of the fixed center sill and the longitudinal center line of the upper fluid motor being disposed above the sliding sill and parallel to the longitudinal center line thereof.

3. A hydraulic draft gear assembly, as claimed in claim 1, further characterized by a flow-restricting orifice through which hydraulic fluid is supplied from said two fluid motors to said displacement chamber.

4. A hydraulic draft gear assembly, as claimed in claim 3, further characterized in that one of said two fluid motors is provided with a tapered metering pin which, upon operation of said one fluid motor in response to buff or draft forces is moved into said orifice to effect a decrease in the effective area of said orifice, thereby to regulate the force on said draft gear yoke.

5 In a railway car having a pair of truck bolsters one at each end thereof, a fixed center sill supported at its respective opposite ends on said truck bolsters and provided with a center sill pocket, and a car-body-carrying sliding sill movably supported in straddling relation to the fixed center sill for longitudinal movement with respect thereto, the combination of a pair of hydraulic draft gear assemblies, one at one end of the car and the other at the opposite end of the car, each draft gear assembly comprising:

(a) a draft gear yoke movable in the fixed center sill pocket relative to the fixed center sill responsively to draft and buff forces exerted thereon, said yoke having an elongated slot,

(b) a draft gear device disposed in said elongated slot and pocket and having two fluid motors, each of said fluid motors comprising a hollow cylinder and a piston slidably mounted therein for cooperation therewith to form a chamber containing hydraulic fluid, one of said fluid motors being interposed between said yoke and the fixed center sill in such a manner that relative movement between the corresponding cylinder and piston by movement of said yoke relative to the fixed center sill in either direction, effects the displacement of hydraulic fluid from the corresponding chamber of said one fluid motor in response to the application of a draft or buff force to said yoke to cause the absorption of an amount of energy corresponding to the amount of movement of the yoke relative to the fixed center sill and the other of said fluid motors being interposed between said yoke and the sliding sill in such a manner that movement of the piston of said other fluid motor relative to its corresponding cylinder in response to movement of the sliding sill in one direction relative to the fixed center sill by inertia forces acting on the sliding sill resulting from only the application of a buff force to said yoke causes the absorption of another amount of energy corre sponding to the amount of movement of the sliding center sill, and

(c) a third fluid motor comprising a hollow cylinder and a piston slidably mounted therein for cooperation therewith to form a displacement chamber connected to the chambers of said two fluid motors of the draft gear device at the corresponding end of the car, said third fluid motor being carried by the truck bolster at said corresponding end and supporting the corresponding end of the fixed center sill whereby, upon displacement of hydraulic fluid from the chamber of either or both of said two fluid motors at said corresponding end to said displacement chamber, said third fluid motor is effective to absorb energy in lifting a portion of the load supported on the fixed center sill in response to the increase in pressure of hydraulic fluid efiected in said corresponding displacement chamber,

(d) the other of said fluid motors of the draft gear device at the opposite end of the car cooperating with the fixed center sill on movement of the sliding sill in the direction opposite said one direction relative to the fixed center sill resulting from the application of a draft force to the yoke at the one end of the car to cause the absorption of said another amount of energy concurrently with absorption of energy by said one fluid motor of the draft gear device at said one end of the car.

6. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that said draft gear device is slidably supported on the fixed center sill for limited longitudinal movement within said fixed center sill pocket.

7. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that said third fluid motor comprises a piston rod, and in that the fixed center sill is provided with a king pin that is received in said piston rod of said third fluid motor to thereby provide for 18 angular movement between the fixed center sill and the truck bolster.

8. A hydraulic draft gear assembly as claimed in claim 1, further characterized by a flexible conduit via which hydraulic fluid is supplied from said two fluid motors of said draft gear device to said bolster-supported third fluid motor to maintain fluid communication between said two fluid motors and said third fluid motor notwithstanding relative angular movement between the fixed center sill and the bolster.

9. A hydraulic draft gear assembly, as claimed in claim 7, further characterized in that the connection between the chambers of said two fluid motors of said draft gear device and said displacement chamber of said third fluid motor constitutes a hydraulic link and in that upon flow of hydraulic fluid from one or both of the chambers of said two fluid motors to said displacement chamber of said third fluid motor, in response to actuation of said one or both of said two fluid motors in response to a force acting thereon, said piston and piston rod transmit a lifting force to the fixed center sill whereby it is moved vertically upward until the work done in lifting the said fixed center sill is equal to the work done by said one or both of said two fluid motors in forcing fluid therefrom through said hydraulic link to said third fluid motor.

10. A hydraulic draft gear assembly, as claimed in claim 7, further characterized in that the force transmitted to the fixed center sill by the piston and piston rod of said third fluid motor is resisted by a gravitational force that acts in the opposite direction and is of a magnitude proportional to the load carried on the fixed center sill.

11. A hydraulic draft gear assembly, as claimed in claim 2, further characterized in that upon application of a buff force to one fluid motor of the draft gear device, the other fluid motor of the draft gear device is subject to an inertia force proportional to the weight of the load carried on the sliding sill.

12. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that for each increment of increase of travel of said pistons of said two fluid motors, the energy absorbing capacity of said draft gear device is increased proportionally to the summation of the increment of increase of travel of said pistons.

13. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that both of said fluid motors of said draft gear device are operative to cause the absorption of the kinetic energy of impact of two colliding railway cars in response to the application of a buff force to the corresponding draft gear yoke, and in that only one of said fluid motors of said draft gear device is operative to cause the absorption of kinetic energy resulting from the application of a draft force to the corresponding draft gear yoke.

14. A hydraulic draft gear assembly, as claimed in claim 1, further characterized in that the pressure chamber of said one fluid motor and that of said other fluid motor are connected 'without restriction, and in that the pressure chamber of said one fluid motor communicates with the pressure chamber of said third fluid motor via a flow-restricting orifice, the piston of said one fluid motor having thereon a metering rod in coaxial alignment with said orifice and which is moved into said orifice upon relative movement between the piston of said one fluid motor and its corresponding cylinder in response to buff or draft forces to reduce flow from the pressure chambers of said one and said other fluid motors to the displacement chamber of said third fluid motor.

References Cited UNITED STATES PATENTS 3,259,252 7/1966 Peterson 21343 DRAYTON E. HOFFMAN, Primary Examiner.

U.S. Cl. XJR. -454; 213-43

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