Motion Dampening Means Between The Chassis And Trucks Of A Railroad Car

Abstract

A railroad car is provided with motion dampening fluid units capable of automatically shifting back and forth between operation in accordance with one set of operating characteristics when the car is not loaded and a different set of operating characteristics when the car is loaded.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The body of a railroad car normally is seated upon the wheeled trucks which support it without being rigidly affixed thereto. As the car moves over a track, the dynamic forces to which the trucks are subjected cause the body of the car to sway, rock or roll from side to side. The amplitude of the body roll tends to increase as the speed of the car approaches a critical speed, and tends to decrease as the speed of the car recedes from or surpasses these critical speeds. When the car speed approximates a critical speed, the forces which are at resonance cause excessive sway, rock or roll, as a consequence of which wheel lift-off, lading damage and damage to the car may ensue. Accordingly, the invention relates generally to devices for reducing car body roll to a tolerable level at all speeds, the purpose being to eliminate wheel lift-off and to reduce pitch and vertical motion.

2. Description of the Prior Art

It is now conventional to interpose hydraulic dampers between the body of a car and the trucks upon which the car is supported, for the purpose of reducing the roll, pitch and vertical motion of the car body as the car moves over a track. Reference may be had to U.S. Pat. No. 3,415,203, issued to Frank W Hughes and Stuart A. Schwam, Dec. 10, 1968, for such an arrangement. This arrangement calls for the use of dampers that are double acting under all conditions of loading, and for this reason has not proved to be entirely satisfactory.

SUMMARY

When the car is under load, the level of motion as the car moves over a track is such as to require double-acting dampers, but when the car is not under load, the level of motion as the car moves over a track is reduced to such an extent that single-acting dampers may be used. Accordingly, dampers that are double acting under all conditions of loading provide unnecessary damping when the car is not under load. This is harmful and to be avoided. Therefore, the principal object of this invention is to provide dampers that have characteristics which change to accommodate car loading, i.e., that are double acting when the car is under load and single acting when the car is not under load.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a fragmentary side elevation of a railroad car constructed in accordance with the invention;

FIG. 2 is a fragmentary end elevation of the railroad car shown in FIG. 1;

FIG. 3 is an enlarged section on line III--III in FIG. 1;

FIG. 4 is a section on line IV--IV in FIG. 3;

FIG. 5 is a view of the chassis and the damper connection indicated by lines V--V in FIG. 3;

FIG. 6 is a view of truck side frame and damper connection indicated by lines VI--VI in FIG. 3;

FIG. 7 is an enlarged section on line VII-VII in FIG. 5;

FIG. 8 is an enlarged section on line VIII--VIII in FIG. 6;

FIG. 9 is an elevation of the hydraulic damper, part being shown in section; and

FIG. 10 is a reduced section on line X--X in FIG. 9.

The following description is directed to the specific form of the invention shown in the drawings. It is not addressed to the scope of the invention, which may be practiced in various forms.

Referring to the drawings, a body 10 of a railroad car is supported upon a pair of trucks 12 which travel over rails 14 carried by ties 16 nested in a bed 18.

The body 10 of the car is typical. It includes a chassis having a horizontally extending floor 20, a center sill 22 extending longitudinally of the car and underlying the floor 20 and body bolsters 24 extending transversely of the car, as shown.

The trucks 12 are typical. Each includes a truck bolster 26 with opposite end portions 28 respectively extending into central bolster openings or windows 29 formed in a pair of laterally spaced side frames 30. Each side frame 30 comprises an upper member 32 over the opening 29, a lower member 34 under the opening 29 and bolster guide columns 31 respectively on opposite sides of the opening 29. Each end portion 28 of the bolster 26 extending into an opening 29 is seated upon a group of compression springs 36. Each end portion of each side frame 30 mounts a journal 38. Each pair of corresponding journals 38 respectively receive opposite end portions of an axle 40 carrying wheels 42, which engage the heads of the rails 14.

Associated with each truck are a pair of hydraulic motion dampening mechanisms 44, one on each side of the truck. Each of the mechanisms 44 includes an upper section 46 and a lower section 48. The upper section 46 includes a piston rod 50 having in the lower extremity thereof a central bore 54 and a counterbore 56. Fitted into the bores 54 and 56 is a valve seat 58, and threaded into the bore 54 is a sleeve 60 which serves to secure the valve seat in position. Slidably fitted into the sleeve 60 is a valve 62 including a hollow cylindrical part 64 closed at its upper end by a wall 66. Extending upwardly from the wall 66 is a reduced diameter portion 68, slightly tapered axially, and extending about the base of the portion 68 in an annular groove 70 and a series of circumferentially spaced holes 72. The valve 62 is biased upwardly against the seat 58 by a compression spring 74 suitably housed within the valve part 64 and the sleeve 60. Extending about the axially tapered reduced diameter portion 68 of the valve, within the valve seat 58, is an annular orifice 75, which orifice communicates with the groove 70 and the series of holes 72. The lower extremity of the piston rod 50 is reduced in diameter to form a circumferentially extending shoulder 77. Threaded onto the lower extremity of the piston rod 50 is a piston head 76. Extending about the upper surface of the piston head 76 is a groove 78 and a series of circumferentially spaced holes 79. Overlying the groove 78 is a flapper valve 80, the inner marginal area of which underlies the shoulder 77.

The lower section 48 of the hydraulic damper 44 includes a base 84 having in the upper surface thereof a bore 88, a first counterbore 90 and a second counterbore 92. Received by the bore 88 is a valve seat 94 secured in position by an annulus 96 threaded into the bore 88. Underlying the valve seat 94 and slidably fitted into the counterbore 90 is a valve 98 including a hollow cylindrical part 100 closed at its upper end by a wall 102. Extending upwardly from the wall 102 is a reduced diameter portion 104 slightly tapered axially, and extending about the base of the portion 104 is an annular groove 106 and a series of circumferentially spaced holes 108. The valve 98 is biased upwardly against the seat 94 by a compression spring 110 suitably housed within the valve part 100 and the counterbore 90. Extending about the axially tapered reduced diameter portion 104 of the valve, within the valve seat 94, is an orifice 111, which orifice communicates with the groove 106 and the series of holes 108.

The upper end of the base 84 is reduced in diameter, as at 112 and 114, these reduced diameter portions forming annular shoulders 116 and 118. Formed in the annular shoulder 116 is an annular groove 120 and a series of circumferentially spaced holes 122. Overlying the groove 120 is a flapper valve 124 fitted within an annular member 125 having at the top thereof a radially inwardly extending flange 126, and having at the base thereof a radially outwardly extending flange 128 seated upon the shoulder 118. Interposed between the flange 128 and the lower extremity of a cylindrical member 130 fitted over the annular member 125 is a packing 132. Fitted over the base 84 is a cylindrical member 134. The space between the lower extremity of the piston rod 50 and the base 84 within the cylindrical member 130 affords a compression chamber 139.

Fitted into the upper end portion of the cylindrical member 134 is a gland member 140 having a reduced diameter lower end portion 142 extending downwardly into the upper end portion of the cylindrical member 130. Interposed between the gland 140 and the upper extremity of the cylindrical member 130 is packing 144. The gland 140 is fitted over the piston rod 50 and is provided with O-rings 146 and 148. Threaded into the upper end portion of the cylindrical member 134 is a gland nut 150 which serves to secure the gland 140 in position. The annular space between the gland 140 and the piston head 76 and between the piston rod 50 and the cylindrical member 130 affords an extension chamber 151 which is in communication with the counterbore 56 via a series of radially extending passages 82. The annular space between the gland 140 and the base 84 and between the cylindrical members 130 and 134 affords a reservoir or auxiliary chamber 153 which is in communication with the counterbore 92 and holes 122 via a series of radially extending passages 136 and with an annular oil groove 155 extending about the inner surface of the gland 140 via a radially extending passage 157. Mounted on the piston rod 50 and extending downwardly over the cylindrical member 134 is a shroud 152, as shown.

The inside diameter of the cylindrical member 130 is uniform throughout the length of the member traversed by the piston head 76, which is provided with a pair of axially spaced piston rings 138 engaging the inner surface of the member. The internal surface of the lower or compression chamber section of the member is uniform and uninterrupted by recesses and the like throughout every area thereof. However, the uniformity of the internal surface of the upper or extension chamber section of the member is interrupted by a groove 159 extending longitudinally of the member throughout the length of the upper or extension chamber section of the member, which is approximately equal to that of the lower or compression chamber section of the member.

The upper end portion of the piston rod 50 is provided with a tongue 154 extending upwardly between the arms of a clevis 156, which clevis is affixed to the body bolster 24. The tongue 154 is fitted with a bushing 158 which receives a spherical element 160. A bolt 162 extends through the arms of the clevis and the spherical element 160, and a nut 164 is threaded on the end of the bolt.

The lower end of the base 84 is provided with a tongue 166 which tongue extends downwardly alongside the upper end portion of a bracket 168 from which there extends a pintle 170. The tongue is fitted with a bushing 172 which receives a spherical element 174. The pintle 170 extends through the spherical element 174, and a nut 176 is threaded on the end of the pintle.

It will be noted that when the car body 10 is not under load, the springs 36 support the same at an elevation comparatively high above the underlying trucks 12, as a consequence of which the sections 46 and 48 of each damper 44 are disposed for operation of the piston head 76 in the upper section of the cylindrical member 130, in the area of the groove 159. In addition, when the car body 10 is under load, the springs 36 are compressed and support the same at a lower elevation above the underlying trucks 12, as a consequence of which the sections 46 and 48 of each damper 44 are disposed for operation of the piston head 76 in the lower section of the cylindrical member 130, below the groove 159.

In the use of the hydraulic dampers 44, normally extension chamber 151 and compression chamber 139 are filled with oil, and reservoir 153 is partially filled with oil. When the body of the car rolls to one side, the damper 44 on that side contracts, and when the body rolls to the other side, said damper is extended. When the damper 44 contracts, the compressive forces cause the piston rod 50 to move farther into the cylindrical member 130, reducing the size of the compression chamber 139 and increasing the size of the extension chamber 151. Thereupon, the flapper valve 80 opens, and an unrestricted flow of oil passes from the compression chamber 139, through the series of holes 79 into the extension chamber 151. This is true whether the piston is working in the extension chamber section of the cylindrical member 130, as when the car is not under load, or working in the compression chamber section of the cylindrical member 130, as when the car is under load. However, when the piston is working in the extension chamber section of the member, there is an unrestricted flow of oil from the compression chamber 139 to the extension chamber 151 via the groove 159 as well as via the series of holes 79. A restricted flow of oil passes from the compression chamber 139, through the series of holes 72, annular orifice 75 and the several passages 82 into the extension chamber 151. The flapper valve 124 remains closed. Furthermore, since all the oil displaced from the compression chamber 139 cannot be accommodated by the extension chamber 151, fluid pressure forces the valve 98 downwardly against the influence of spring 110. Initially a restricted flow of the excess oil occurs from the compression chamber 139, through the annular orifice 111, the series of holes 108 and the several passages 136 into the reservoir 153. When the fluid pressure becomes great enough to force the whole of the valve 98 below the valve seat 94 against the influence of spring 110, a free flow of the excess oil occurs from the compression chamber 139, through the valve seat 94, the series of holes 108 and the several passages 136 into the reservoir 153.

When the piston is working in the compression chamber section of the cylindrical member 130 and the damper 44 is extended, the tension forces cause the piston rod 50 to move outwardly in cylindrical member 130 increasing the size of the compression chamber 139 and decreasing the size of the extension chamber 151. The flapper valve 80 remains closed. Oil is forced out of the extension chamber 151 through the several passages 82. Fluid pressure forces the valve 62 downwardly against the influence of spring 74. Initially a restricted flow of oil passes from the extension chamber 151, through the several passages 82, the annular orifice 75 and the series of holes 72 into the compression chamber 139. When the fluid pressure becomes great enough to force the whole of the valve 62 below the valve seat 58, a free flow of the oil passes from the extension chamber 151, through the several passages 82, the valve seat 58 and the series of holes 72 into the compression chamber 139. Furthermore, since the volume of oil displaced from the extension chamber is less than that which can be accommodated by compression chamber 139, the flapper valve 124 opens and an unrestricted flow of oil passes from the reservoir 153 through the several passages 136 and the series of holes 122 into the compression chamber 139.

The passage through which the oil flows from the compression chamber 139 to the reservoir 153 when the damper 44 contracts, and through which the oil flows from the extension chamber 151 to the compression chamber 139 when the damper 44 is extended, are of a size to restrict the flow so that considerable force is required at low velocity to contract or extend the damper 44. Thus some of the energy tending to cause the body 10 to roll relative to the rail head is dissipated, resulting in a dampening action which affords a stable car at all speeds.

When the piston is working in the extension chamber section of the cylindrical member 130 and the damper 44 is extended, the tension forces cause the piston rod 50 to move outwardly in cylindrical member 130 increasing the size of the compression chamber 139 and decreasing the size of the extension chamber 151. The valves 62 and 80 associated with the piston head remain closed, but nevertheless oil is forced out of the extension chamber 151 into the compression chamber 139. A restricted flow passes from the extension chamber 151, through the several passages 82, the annular orifice 75 and the series of holes 72 into the compression chamber 139. A free flow passes from the extension chamber 151 into the compression chamber 139 via the groove 159, by means of which the oil by-passes the piston head 76 and the valves 62 and 80 associated therewith. Since the volume of oil displaced from the extension chamber is less than that which can be accommodated by compression chamber 139, the flapper valve 124 opens and an unrestricted flow of oil passes from the reservoir 153 through the several passages 136 and the series of holes 122 into the compression chamber 139.

In view of the foregoing, it will be appreciated that dampers are provided that are double acting when the car is under load and single acting when the car is not under load. When the car is under load and the dampers are double acting, the dampers act to yieldably resist both contraction and extension thereof. When the car is not under load and the dampers are single acting, the dampers act to yieldably resist contraction, but not extension.

The dampers are not only effective to resist body roll, but also pitch and vertical movement. When the body of a car which is under load pitches, the dampers at one end of the car tend to contract and those at the opposite end of the car tend to be extended. All the dampers yieldably resist the pitching of the car body. When the car body is not under load, the dampers at the end thereof that tend to lift off the associated truck do not resist pitching of the body. Nevertheless, pitching is reduced because the dampers at the other end of the body yieldably resist the tendency of that end of the body to settle down farther onto the associated truck. While the amplitude of the pitching may be greater than it would be if vertical movement was yieldably resisted at both ends of the car, the body is not under load and therefore there is no danger of lading damage. Consequently, a greater degree of pitching may be tolerated.

When the body of a car which is under load moves vertically (translatory movement) relative to the underlying trucks, all the dampers, front and rear, yieldably resist the movement. When the car body is not under load, the dampers do not resist upward movement of the body. Nevertheless, vertical movement is reduced because all the dampers yieldably resist downward movement of the body. While the vertical movement may be greater than it would be if upward movement was yieldably resisted by all dampers, the body is not under load. Therefore, as noted hereinabove, there is no danger of lading damage, and consequently a greater degree of vertical movement may be tolerated.

It will be understood that the truck 12 is not shown and described herein by way of limitation. To the contrary, the truck may take various forms. For example, the side frame 30 may be replaced with one which does not have a member 32 extending over the end of the truck bolster, but otherwise similar to the side frame 30. In addition, the compression springs 36 may be replaced by one or more cushions made of a suitable rubber composition.

Claims

What is claimed is:

1. In a railroad car, the combination comprising:

A. a pair of trucks each including wheeled frames respectively disposed on opposite sides thereof,

B. a car body including a chassis pivotally mounted upon said trucks and resiliently supported thereon at a predetermined upper level when said car body is not under load and at a lower level when said car body is under load, and

C. at least one motion dampening unit on each side of said car, each of said units being connected between said chassis and a side frame of one of said trucks, and each including

1. a piston and cylinder assembly, the head of said piston being disposed in the extension end of said cylinder and being characterized by a one-way acting mode of operation when said car body is supported as aforesaid at said predetermined upper level, and being disposed in the compression end of said cylinder and being characterized by a two-way mode of operation when said car body is supported as aforesaid at said lower level, and

2. means confined to the extension end of said cylinder and operative for automatically switching said piston and cylinder assembly from said two-way acting mode of operation to said one-way acting mode of operation in response to movement of said car body from said lower support level to said predetermined upper support level and the consequent shift of said piston head from working in the compression end of said cylinder to working in the extension end of said cylinder.

2. The combination according to claim 1 wherein the interface between the extension end of the cylinder and the compression end of the cylinder is approximately midway between the opposite ends of said cylinder, and the means for automatically changing the mode of operation of the piston and cylinder assembly in response to movement of the car body from the lower to the upper support level includes fluid passage means operative for providing unrestricted flow of fluid between said extension end of the cylinder and said compression end of the cylinder when the piston head works in said extension end of the cylinder.

3. The combination according to claim 2 wherein the fluid passage means providing unrestricted flow of fluid between the extension and compression ends of the cylinder when the piston head works in said extension end of the cylinder affords an effective by-pass around said piston head.

4. The combination according to claim 3 wherein the inside diameter of the cylinder is uniform throughout the full length thereof, and the means for by-passing the piston head comprises a groove extending the full length of the extension end of the cylinder.