Stabilizing High Speed Railway Trucks

Abstract

In a railway truck a pivot between the truck frame and the cooperating bolster is permitted to have lateral displacement to improve the riding qualities of the truck. The pivot is maintained automatically centered by motor means which oppose centrifugal forces that would displace the pivot, e.g., while the truck traverses a curve, thereby ensuring that lateral displacement is still possible under such conditions. A special design of such a truck is provided with a bolster comprising two parts, designated upper and lower parts, the lower bolster part being pivotally mounted on the truck transom, while the upper bolster part mounts the vehicle body for vertical springing movement; the two bolster parts are connected together by an articulated linkage for lateral arcuate movement about a longitudinal tilting axis under the action of motor means.

Description

FIELD OF THE INVENTION

This invention is concerned with improvements in or relating to railway trucks, and especially but not exclusively to such trucks intended for use in high speed passenger cars.

REVIEW OF THE PRIOR ART

It is a continuing requirement for railway vehicles, particularly passenger cars, to achieve higher speeds combined with a safe, comfortable ride, and it is now considered a normal requirement for such cars to travel at speeds as high as 120 m.p.h., speeds in excess of this figure usually requiring a specially built track structure. It is of course apparent that faster scheduled train times can be achieved if the average speed can be maintained as near as possible to the maximum, even around curves, but attempts to take present normal passenger cars around curves at these speeds, even when the track is given the maximum possible banking elevation, results in uncomfortably high lateral forces (i.e., greater than 0.05 g.) being applied to the passengers. Accordingly, a number of proposals have been made hitherto to tilt the cars about a longitudinal axis, and thereby reduce the lateral force applied to passengers.

It is found that careful location of the tilting or roll axis is required relative to the center of gravity if the maximum effective banking angles are to be compatible with passenger safety. From considerations of speed, comfort and safety the center of gravity is designed to be as low as possible, and desirably the roll axis should be just below the center of gravity, so that relatively high tilt angles can be employed in curves, while the resultant of the centrifugal and gravity forces is still within the middle one third of the track gauge, which is the generally accepted safety limit.

It is desirable also to provide as far as possible that the structure and components used in the trucks are, as much as possible, the same or very closely similar to those of existing vehicles, so that the servicing and maintenance thereof can readily be accomplished with existing railway equipment, shop skills and personnel.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a new railway truck having a laterally displaceable pivot between the truck and a cooperating bolster, and wherein means are provided for maintaining the pivot centered against the action of centrifugal forces tending to displace it laterally, for example as the truck traverses a curve.

In accordance with the invention there is provided a railway truck comprising a truck frame constituted by transversely spaced side frames and transom means extending between the said frames; at least two wheel and axle assemblies mounted by the frame and on which the truck runs; a bolster frame; a truck frame pivot member mounted by the truck frame and engageable with a cooperating bolster frame pivot member mounted by the bolster frame, the pivot members cooperating with one another to constrain the bolster frame for pivoting movement about a generally vertical axis, one of the said pivot members being mounted by its mounting for lateral movement relative to its frame, motor means operatively connected between one of the pivot members and its respective frame and operative to move the pivot member laterally, detector means operative with the truck upon the presence of a condition applying a force on the said pivot members urging lateral movement of the pivot axis from a center position, and means operative in response to said detector means for actuating the motor means to at least oppose the said force and urge the said pivot axis toward the said center position.

DESCRIPTION OF THE DRAWINGS

A particular preferred embodiment will now be described, by way of example, with reference to the accompanying diagrammatic drawings, wherein

FIG. 1 is a perspective view with the bolster displaced vertically from the truck frame for clarity of illustration,

FIG. 2 is a similar view of the bolster with parts thereof broken away for greater clarity of illustration,

FIG. 3 is a section taken on the line 3--3 of FIG. 1,

FIG. 4 is a view similar to that of FIG. 3, but showing the car body supported by the truck frame in an inclined attitude, as when traversing a curve, and

FIG. 5 is a schematic diagram of the control circuit for the automatically operated bolster centering devices of the embodiment.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The particular preferred embodiment illustrated herein and modifications thereto are also described and claimed in our copending application Ser. No. 2796, filed Jan. 14, 1970. The embodiment comprises a four-wheel, high-speed passenger truck, having a frame which is a unitary steel casting to provide maximum rigidity. The frame comprises two parallel side frame members 10 and 11, which have their center portions (10a and 11a respectively) depressed to the greatest possible extent, these members being connected to one another intermediate their ends by two longitudinally spaced transoms 12 and 13. The truck runs on two similar wheel and axle assemblies, each constituted by a respective axle 14 and pair of wheels 15. The truck is of course provided with conventional brakes, but the specific details of the construction and arrangement thereof will be apparent to those skilled in the art, and are not further described herein since they form no part of the present invention. A truck in accordance with the present invention may also be a motorized unit, in which case each axle will, for example, be driven by a respective electric motor and gear unit (not illustrated) mounted on the frame and operatively connected to the respective axle.

Each axle 14 is rotatably mounted in the frame by a respective pair of journals 18, each of which in this particular embodiment is mounted and guided for the necessary generally vertical movement by two resilient suspension units 19. These suspension units are of the kind comprising a plurality of flat layers of a suitable rubber, or a suitable rubber like material, interleaved with flat metal plates, and provided with metal end plates by which the unit is connected respectively to the journal and the adjacent side frames. Such units operate in compression and have a longitudinal compression axis generally perpendicular to the plane of the said flat plates; they inherently have the characteristic of a highly damped spring and are able to accommodate a substantial amount of movement along their longitudinal axis, while permitting relatively high shear displacement of their end plates, the shear characteristic being controllable by control of the compression along the said axis. The compression axes of the two units 19 supporting each journal 18 are inclined towards each other to intersect at or close to the normal loaded position of the rolling axis of the axle.

The car body that is to be mounted on the truck is indicated diagrammatically herein in FIGS. 3 and 4 as a flat floor member 20, having two downwardly extending bracket members 21 fastened to the underside thereof on either side adjacent each truck. Bolster frame means for mounting the body on the truck frame comprise lower and upper bolster members 22 and 23 respectively, the lower bolster member 22 being supported by the side frames and pivotally connected to the frame between the transoms 12 and 13, while the upper bolster member 23 is supported by the lower bolster member and in turn supports the vehicle body 20.

The means supporting the lower bolster member 22 on the truck frame comprise four resilient suspension units 24, disposed at the four corners of a rectangle with their longitudinal compression axes generally vertical, spigots such as 25 on the lower bolster fitting into the top plate of the respective unit 24. Each suspension unit 24 is mounted between the depressed portion of the respective side frame and an upwardly curved portion of the bolster member, the arrangement permitting the use of relatively long units, while maintaining the lower bolster as low as possible in the truck in order to maintain the center of gravity of the whole truck as low as possible. The center portion of the lower bolster is depressed as much as possible, and is provided with a downwardly extending spigot 26 that is freely rotatable without play in an aperture 27 in a pivot member 28.

The pivot member 28 is mounted between the two transoms 12 and 13 by two opposed longitudinally spaced resilient suspension units 29, and also by motor means constituted by two opposed motor units to be described in detail below, the motor units being connected to the member 28 via respective suspension members 30. Each unit 29 is disposed between a flat surface of the respective transom and a corresponding flat surface of the pivot member 28, with the longitudinal compression axes thereof coincident and extending longitudinally of the truck, while each unit 30 extends between a flat surface of the pivot member and the adjacent end of a piston 31 of a respective motor unit 32 mounted inside the respective depressed central frame portion.

The upper bolster member 23 has the general form of an open frame, and in this embodiment comprises two parallel transverse members 33 connected rigidly together by two end members 34 and a central member 35. The two end members 34 carry respective massive laterally spaced air springs 36, mounted with their compression axes vertical, by which the car body 20 is mounted on the bolster, the springs being supplied in conventional manner with operating air under pressure from the train air pressure line. The end portions of the lower bolster member 22 extend upwards into the respective openings in the upper bolster member, so as to reduce the overall height of the composite bolster as much as possible.

Each end of the upper member 23 is connected to the respective end member 34 of the lower member 22 by an articulated linkage comprising a generally Y-shaped link member 37, which is operative as a bellcrank lever and is pivoted to the member 22 about its crank pivot axis by a pivot rod 38. The end of one crank arm of the link member 37 is connected by a pivot rod 39 to the adjacent ends of two spaced parallel links 40, the other ends of the links 40 being connected by a pivot rod 41 to the member 34. The ends of the other crank arms of the Y link members 37 are connected by pivot rods 42 to the respective ends of a connecting link 43, which extends through apertures 44 provided in the member 22, the link 43 being bowed upwards to clear the depressed central portion of the member 22 over its full range of movement.

The articulated linkage is completed by means of a depending link 45 fixed rigidly at its upper end to the central member 35 and pivoted at its lower end by a rod 46 to one end of a short transverse link 47 that is disposed generally parallel to the connecting link 43 and is accommodated in a recess therein. The other end of the transverse link 47 is connected to the link 43 by a pivot rod 48.

The required rolling or tilting motion of the two bolster parts relative to one another is produced under the control of mechanism to be described in detail below, this mechanism controlling the operation of motor means comprising two double-acting hydraulic units 50, which are disposed one on each side of the bolster. Each unit 50 comprises a cylinder member 51 pivotally connected at 52 to the lower bolster member 22 and a piston member 53 pivotally connected at 54 to the upper member 23. It will be apparent that of course the connection of the units 50 can be reversed. Diagonally extending links 55 (FIG. 1) are connected by spherical rubber bushings to the lower bolster 22 and to brackets 56 fastened to the car floor approximately in the center thereof, so that they will not foul the truck side frames as the car body tilts relative thereto. Laterally extending links 57 (FIGS. 3 and 4) are connected by similar bushings to the upper bolster member and the brackets 21 of the car floor. These links 55 and 57 ensure that there can be no substantial transverse and/or longitudinal motion between the bolster and the car body, and the springs 36 are required to accommodate only vertical displacement and to provide only vertical springing.

The action of the connecting linkage can be seen by a comparison of FIGS. 3 and 4, which show the upper bolster member respectively in its horizontal position and in one of its extreme tilted positions. It is important to note that one action of the linkage is to keep the roll center 58 approximately stationary in the position illustrated during the bolster tilting, avoiding the large lateral motions that would be encountered for example with a suspension comprising two spaced single links. The tilting action illustrated in FIG. 4 is produced by an increase in length of the motor units 50, forcing the upper bolster member 23 to the left (as seen in the Figure) relative to the lower member 22. This movement of the upper member 23 causes a corresponding clockwise movement of the links 37 about the rods 38 via the connection constituted by the end members 34 and the links 40. This lateral movement of bolster member 23 causes a corresponding lateral movement of connecting link 43, via the links 45 and 47, that applies an additional clockwise rotation to the bellcrank links 37. In the absence of the links 43, 45 and 47, and their described action on the links 37, the lateral displacement of the upper bolster member would cause it to tilt about a laterally moving effective axis disposed approximately midway between the rods 38, and at the same level as the axes of these rods (i.e., below the level of the floor 20). The effect of these additional links is therefore to raise the height of the tilt axis 58, and by careful choice of the lengths of the individual links of the articulated linkage it can be located in the desired position.

In this particular embodiment the immediately adjacent ends of the two bolster members have the lower bolster member end above the respective upper bolster member end, so that the upper bolster member is suspended by the articulated linkage from the lower bolster member. It is also contemplated that the two bolster members may be suspended from one another by some other means, the connecting linkage ensuring that the required relative movement takes place between them upon operation of the motor units 50.

In a passenger vehicle the preferred height of the axis 58 above the car floor is such that it is located approximately at the level of an elbow of the average seated passenger. The actual determination of the lengths of the links to achieve this result for a particular truck construction can be effected by one of the methods known to those skilled in the art, such as a graphical method.

Referring especially to FIG. 5, each of the motor units 32 is supplied with an operating liquid under pressure, usually a suitable oil. This liquid is drawn from a reservoir 60 by a pump 61 and supplied thereby to a pressure reservoir 62, the pump being controlled in a known manner by means which are now shown to maintain the liquid in the reservoir 62 between predetermined pressure limits. Liquid from the reservoir is fed via pipes 63 to two servo valves 64, which are controlled via pipes 65 from a hydraulic slave pilot transducer 66. The transducer 66 is in turn controlled electrically by a master transducer device, indicated herein as box 67, and to be described in more detail below. The servo valves 64 feed liquid via respective pipes 68 and air-containing reservoirs 69 to their respective motor units 32. While the truck is running straight the servovalves 64 maintain substantially equal high pressures in their motor units 32, centering the member 27, the excess oil returning to the reservoir 60 via pipes 70. The usual random track forces applied to the member 27 are absorbed by the reservoirs 69, the air in these reservoirs causing them to act as air springs.

As the vehicle traverses a curve corresponding large lateral centrifugal forces are applied to the lower bolster member, and thence to the pivot pin 26 and pivot member 27, so that the latter is urged to move off center. The device 67 feeds a corresponding control signal to the slave transducer 66 that in turn operates one or both of the servovalves 64 to effectively increase the pressure applied to one motor unit and decrease the pressure applied to the other motor unit, so that a corresponding force is applied to the member 27 by the units opposing the said centrifugal forces and urging the member 27 to return to its central position.

Such a control can be arranged to maintain the member 27 substantially central at all times, with the result that the shear forces applied to the suspension units 24 and 29 are very considerably reduced, so that more resilient units can be used than if these units sustained the effect of these lateral forces. Such more resilient units of course result in a softer and quieter suspension. In an alternative arrangement the centering of the member 27 is controlled by a movement detector member 74 mounted on the pivot member 27 and connected by a link 75 to one of the side frames. The detector member can operate as described above for the transducer 67, or may be mechanically connected to a servovalve such as the valve 64, that is operative under control of the detector member to supply additional oil under pressure to the appropriate motor unit cylinder 32 until the pivot block has been moved back to its center position. Such a centering system operates completely automatically under control of the detector member and independently of the tilting control system. In this embodiment the oil supplied from the pump 61 and reservoir 62 is also fed to the tilting motor means 50 via connecting pipes 71 and a servovalve 72.

Since the links 55 and 57 between the upper bolster member 23 and the car body 20 prevent relative lateral and rotational motions thereof only relative vertical motion need be accommodated by the main secondary suspension air springs 36. Such springs do not therefore have to resist and/or accommodate the relatively large lateral translation motions that would otherwise be applied to them by a fast moving train. The connection between the upper and lower bolster members, namely the articulated linkage and the operator units 50, only permit relative lateral motion thereof under the control of the units 50, which is in effect a rotational motion about the center 58. The weight of the car body and of the bolster is supported from the truck frame by the units 24 which are designed principally to accommodate the pivoting of the vehicle body on the truck as it traverses a curve. The wheel primary suspension units 19 permit vertical translation of the axle 15 and a limited lateral translation of the wheels relative to the frame, such as to accommodate the usual irregularities in the track.

It will be seen therefore that the various required springing and mounting functions are separated out into three distinct groups, thereby assisting in permitting conventional components to be used. The first group comprises the upper bolster member 23 and the associated air springs 36 which provide vertical secondary springing with no lateral motion. The second group comprises the mounting of the upper bolster member to the lower bolster member, whereby the two members function as a single unit between the frame and the car body for mounting the latter, but are moved relative to one another to provide the lateral tilting of the car body. The third group comprises the special pivot suspension which freely permits the pivoting motion of the bolster relative to the truck frame, accommodates lateral displacements of the bolster relative to the truck frame and permits the bolster structure to remain centered despite high lateral centrifugal forces generated by deficiencies in the track superelevation.

It will therefore be apparent to those skilled in the art that all of the parts of the suspension are of relatively conventional construction and can readily be manufactured and services using conventional existing equipment, shop skills and personnel.

Claims

What we claim is:

1. A railway truck comprising a truck frame constituted by transversely spaced side frames and transom means extending between the said side frames; at least two wheel and axle assemblies mounted by the frame and on which the truck runs; a bolster frame supported on the truck frame; a truck frame pivot member mounted by the truck frame and engageable with a cooperating bolster frame pivot member mounted by the bolster frame, the pivot members cooperating with one another to constrain the bolster frame for pivoting movement about a generally vertical axis, one of the said pivot members being mounted by its mounting for lateral movement relative to its frame; motor means operatively connected between one of the pivot members and its respective frame and operative to move the pivot member laterally with respect to its respective member, detector means operative with the truck upon the presence of a centrifugal force on the pivot members urging lateral movement of the pivot axis from a center position, and means operative in response to said detector means for actuating the motor means to at least oppose the said force and urge the said pivot axis toward the said center position.

2. A truck as claimed in claim 1, wherein the said motor means comprise oppositely operating hydraulic units in operative engagement between the truck frame and the truck frame pivot member, means for supplying operating liquid under pressure to the said hydraulic units, and a reservoir containing operating liquid and gas connected between each hydraulic unit and the said liquid supplying means, whereby the gas in the said reservoirs provides the effect of springs accommodating minor movements of the truck frame pivot member.

3. A truck as claimed in claim 1, wherein the said motor means comprise opposed hydraulic units comprising respective cylinder members each mounted in a respective truck side frame and having their respective piston members in operative engagement with the truck frame pivot member.

4. A truck as claimed in claim 3, wherein the said detector means comprises a movement detector member mounted on the truck frame operatively connected between the truck frame pivot member and a truck side frame and providing a corresponding signal upon movement of the truck frame pivot member from the center position, and the means responsive to the detector means comprise servo means receiving the said signal and feeding operating liquid to the said hydraulic units in response thereto.

5. A truck as claimed in claim 3, wherein the truck frame pivot member is mounted on the transom means for lateral movement relative to the truck frame by opposed longitudinally extending resilient suspension units having their compression axes coincident and disposed longitudinally of the truck.