SELF-STEERING RAILWAY TRUCK

Abstract: A self-steering railway truck, especially a powered locomotive type, provides limited freedom for axle steering motion in the truck frame (12), with a separate linkage of parallel rods (42) and a steering beam (40) for transmitting traction and braking forces to the truck frame. The linkages of two end axles (24) are interconnected for equal and opposite motion in a manner effective to maintain stability, and to leave room for maintaining traction motors and brake equipment, and also to separate the effects resulting from yaw and lateral axle motions.

Description: This invention relates to steerable railway trucks (that is, steerable bogeys of the kind used to support the ends of rail vehicle carbodies) as specified in the preamble of claim 1, for example as disclosed in US-A-727 919. The invention is particularly concerned with self-steering railway trucks of a type wherein the axles are allowed limited freedom to seek substantially radial positions in a curve. In preferred embodiments the invention relates to powered railway trucks for locomotives and the like, especially of the type wherein individual traction motors are supported between the frame and individual axles driven thereby. Various types of steerable railway trucks, (exemplified by the disclosures made in US-A-727 919; DE-A-837 711; US-A-956 900; US-A-727 918; US-A-2 296 106 and FR-A-2 513 583), have been proposed wherein the angular positions of the axles and their associated wheels are allowed or forced to adjust during curve negotiation to maintain more or less radial positions with respect to the curve. The purpose of such arrangements is, generally, to reduce friction and wear of wheels and rails by minimising lateral creep forces. Although most applications have been proposed for non-powered railway car trucks, some locomotive applications have also been proposed. Prior steering railway trucks have included some having soft primary suspensions which allow relatively free longitudinal and/or lateral motion of the wheel and axle assemblies within established limits. Some arrangements include inter-axle connections that require related motions among axles of the same truck. Some of the arrangements are such that lateral wheel and axle motion gives rise to forced yaw or steering, whereas other arrangements substantially isolate these functions. Both powered and unpowered axles have been arranged for steering. However, forced steering of powered axle vehicles relative to truck turning motion in relation to the carbody is common. The present invention is concerned with an improved arrangement for self-steering railway trucks, and particularly for powered railway trucks such as in locomotives, in which equalised self-steering of the axles is provided. To this end, the present invention provides a self-steering railway truck characterised by the features specified in the characterising portion of claim 1. The invention thereby makes available an improved arrangement of a self-steering railway truck, which is particularly applicable to powered railway trucks such as in locomotives, in which equalised self-steering of the axles is provided by means of a linkage including interconnected steering beams and traction rods. The mechanism provided is so arranged as to separate the effects of steering and lateral motions of the axles and is particularly adapted for powered truck applications, in which it extends around the sides and one end of the axle and frame-supported traction motors. Although particularly adapted to the requirements of two-axle motor-powered road-locomotive type railway trucks, the invention is also capable of use in unpowered trucks, and in railway trucks having three or more axles wherein the extreme end axles are interconnected by linkage in conformity with the invention. In a preferred arrangement of a self-steering railway truck in accordance with the invention, traction or connecting rods extend longitudinally from journal boxes at the ends of each axle to a steering beam that extends transversely and is pivotally mounted at its centre to the truck frame. The steering beams of the opposite end axles are preferably interconnected by means of a link or linkage to require equal and opposite oscillating motions of the steering beams during like steering motions of the axles. The steering beams and traction rods are preferably mounted at substantially the same height as the axle to minimise the effect of traction forces on weight distribution. The invention is applicable to various forms of railway trucks, including powered and unpowered trucks, trucks having dual or other multiple axles, and trucks with or without bolsters. However, in the following description specific reference will be made for explanatory purposes to application of the invention to a two-axle bolster-type powered railway locomotive truck. In the drawings: Figure 1 is a fragmentary side view of a two-axle railway locomotive truck in accordance with the invention as installed under a locomotive carbody; Figure 2 is a corresponding top view of the truck from the line 2--2 of Figure 1, in the direction of the arrows; Figure 3 is an enlarged longitudinal sectional view, with parts in elevation, through a central frame, linkage and bolster portions from the line 3--3 of Figure 2, in the direction of the arrows; Figure 4 is a transverse sectional view from the line 4--4 of Figure 2, in the direction of the arrows; Figure 5 is a diagrammatic plan view showing interconnected axles and steering linkage as positioned for operation on tangent track; and Figure 6 is a diagrammatic view of the interconnected axles and steering linkage but showing their operating positions on curved track. With reference now to the drawings, reference numeral 10 generally indicates a powered self-steering railway truck of the road locomotive type supporting one end of a locomotive carbody 11 shown in Figures 1, 3 and 4 by phantom lines. The railway truck 10 includes a unitary frame 12, which may be fabricated, cast or manufactured in some other manner. The frame 12 includes a pair of generally parallel, laterally spaced, longitudinally extending side frames 14 and 15 interconnected by a pair of transoms 16 and 17 that are longitudinally spaced equidistant from a central transverse vertical plane 18. A central longitudinal vertical plane 19, located equidistant from the side frames 14 and 15, intersects the transverse plane 18 in a central vertical axis 20. Adjacent their ends, the truck side frames 14 and 15 include downwardly extending pedestals 22 for receiving journal boxes 23 that are rotatably supported on the ends of axles 24 carried by rail-engaging wheels 26. The wheels 26 are arranged in laterally spaced pairs each interconected by a single axle 24, to form longitudinally spaced wheel and axle assemblies. The journal boxes 23 are disposed in the pedestals between bearing surfaces formed by pedestal liners 27 or other suitable pedestal bearing surfaces. A small amount of longitudinal clearance is provided to allow for limited longitudinal motion of the journal boxes 23 relative to the truck frame 12 for self-steering of the wheel and axle assemblies in a manner to be subsequently described. Lateral stops, not shown, are provided between the journal boxes and the truck frame to limit lateral motion of the wheel and axle assemblies to a predetermined amount. The truck frame is supported on the journal boxes by a relatively soft primary suspension comprising coil springs 28, which could if desired be replaced by rubber or other suitable alternative resilient suspension means or devices. Centrally of the truck, a transverse bolster 30 is carried within a space bounded by the side frames 14 and 15 and the transoms 16 and 17. The bolster is supported upon the truck frame by means of a relatively stiff secondary suspension which may comprise, but is not limited to, rubber sandwich elements 31. Front and rear bearing plates 32 are provided between the bolster 30 and the transoms 16 and 17, and in operation substantially limit movement of the bolster to lateral and vertical motions relative to the truck frame, and transfer longitudinal traction and braking forces between the bolster and the truck frame. A centre bearing 34 is provided at the centre of the bolster for pivotally connecting the truck to a downward projection 35 of the carbody 11. For powering the wheel and axle assemblies to drive the locomotive, the railway truck is provided with a pair of traction motors 36. Each motor has an outer end 37 supported by conventional bearing means on one of the axles 24, and an inner end 38 carried from the adjacent transoms 16 and 17 by means of a depending link 39. The link is flexibly or swivelly connected at its ends to allow a limited amount of both longitudinal and lateral motion between the inner end of the traction motor and the adjacent transom member from which it is supported. To provide for limited self-steering action of the wheel and axle assemblies in conformity with the invention, while still transmitting traction and braking forces between the wheel and axle assemblies and the truck frame, the railway truck is provided with suitable traction linkage. This linkage includes a pair of lateral steering beams 40 pivotally connected at their centres to the truck frame and each connected at their ends to the journal boxes of one of the wheel and axle assemblies by means of connecting rods (traction rods) 42. The traction rod connections are preferably by means of rubber bushings, spherical connections or other movable joints to permit relative vertical motion between the steering beams and the journal boxes connected thereto. The central pivotal mounting of the steering beams 40 is provided by upper and lower supporting plates 43 and 44 of a support structure carried below the transoms 16 and 17 of the truck frame and carrying pivot pins 46 and 47 on which the front and rear steering beams 40 are respectively pivotally carried. The pivot pins 46 and 47 are vertically disposed along the central longitudinal plane 19 of the railway truck and are spaced equidistant from the vertical central axis 20, just inwardly of the transoms 16 and 17. The steering beams 40 are, in turn, interconnected for substantially equal and opposite pivotal motions. For this purpose, a link 48 interconnects laterally offset forward and rearward extensions 50 and 51 of the rear and front steering beams 40 respectively by means of pin and bushing connections 52 and 53. Braking action for the railway truck may be provided for in any suitable manner. The illustrated embodiment includes more or less conventional brake rigging, including wheel-engaging brake shoes 55 carried by conventional frame-supported brake rigging 56 actuated by truck frame-supported air brake cylinders 58. If desired, vertical motions of the truck frame with respect to the wheel and axle assemblies may be damped in a conventional manner by means of friction or hydraulic damping devices 59 connected between the truck frame 12 and one or more of the axle-carried journal boxes 23. For the purposes of carrying out the invention, the traction linkage comprising the steering beams and connecting rods is preferably disposed at substantially the same height as the axle. The traction rods extend forwardly in a parallel and generally horizontal orientation from the journal boxes 23 at the ends of the axles 24 towards the central plane 18 of the railway truck. At this location the traction rods are connected to the steering beams to define a linkage passing essentially around three sides of the traction motors, so as to avoid extending through or otherwise impinging upon the space provided for the traction motors and the brake linkage adjacent the truck wheels. If desired, the wheel treads may be formed with a larger than normal taper to encourage self-steering action, although this is not necessarily a requirement of the present design, since the design permits self-steering action to occur even with the normal wheel tread taper conventionally provided for locomotive trucks. In operation, normal pivotal action of the truck with respect to the railway carbody is provided by the centre bearing connection between the truck and the carbody. Such action could alternatively be provided by bolsterless suspension means or other support means known in the art. In known manner, the clearance provided between the pedestals 22 and their associated journal boxes 23 permits relative longitudinal motion of the axles within the truck frame so as to allow self-steering of the wheel and axle assemblies within the truck frame. Such action is known in the art to allow the axle members of conventionally or more highly tapered wheel and axle assemblies, of the flanged rail-engaging type herein considered, to seek more or less radial positions during curving action of a railway vehicle. Such self-steering action of the wheel and axle assemblies is known to reduce friction and wear between the wheels and rails, and in powered trucks has been found to provide more efficient application of tractive effort and to reduce traction-limiting wheel slip during curving action. However, unrestrained self-steering action of the axles may have the effect of reducing the stability of a railway truck to an unacceptable degree. This is avoided in the present instance by the interconnection of the steering beams 40 by way of the nearly transverse link 48, which limits the pivotal motion of the steering beams to substantially equal and opposite oscillating motion. This, in turn, limits the turning motions of the connected wheel and axle assemblies to like equal and opposite oscillating motions so that self-steering action is allowed, but only to the extent that the turning motions of the axles are in equal and opposite amounts, all within the limits provided by clearances between the truck pedestals and journal boxes. Traction and braking forces are also carried from the wheel and axle assemblies to the truck frame by way of the traction linkage consisting of the traction links 42 and the steering beams 40. Thus all traction and braking loads are carried by way of the pivot pins 46, 47 to the truck frame and from the truck frame by way of the bearing plates 32 to the bolster 30, where they pass through the centre bearing 34 to the carbody 11. Because of the parallel and longitudinal orientation of the traction rods, the application of traction and braking forces does not create any side thrust forces on the wheel and axle assemblies. Also, lateral motions of the axles relative to the truck frame, allowed within desired limits to accommodate track variations and other side thrust loads, do not introduce any yaw, or steering, component of force into the system, as is the case with diagonally interconnected axles commonly provided (see, for example, the disclosures made in US-A-4 428 301; DE-A-3 232 289 and DE-A-3 221 755). Thus the present invention allows complete separation of yaw and lateral motions of the truck axles to be maintained. The present invention accordingly makes available a self-steering railway truck which permits self-steering of the axles using a low-mounted steering beam and longitudinal connecting rods to carry tractive forces between the axles and the truck frame. The wheels and axles steer within the frame and are not guided or forced to steer or connected to the carbody. The steering beams are interconnected by means of the extensions 50 and 51 and the link 48 to control self-steering to be equal and opposite in direction. Also, because non-diagonal linkage is used, lateral axle motion does not cause undesired steering action. In the context of the described embodiment, the steering beams 40 and the rods 42 pivot at the centres 46 and 47 to the truck frame 12. These parts are not connected to the carbody supported by the truck frame (in contrast to what is the case with the link 48 disclosed in US-A-727 919), and so they do not cause forced steering of the wheels but only allow self-steering through equal and opposite angles controlled by the link 48. The coil springs 28 are yieldable for steering and lateral motions of the axles, but provide a centring, or restoring, force that urges the axles into their straight-ahead positions (there being no such restoring force available with the suspension springs 14 disclosed in the said US-A-727 919). In the present arrangement as described, also, the traction linkages 40 and 42 extend around the traction motors for a locomotive, thereby allowing self-steering action of the axles in a powered railway truck.

Claims: A steerable railway truck (10), in which the truck comprises a pair of longitudinally-spaced rail-engaging wheel and axle assemblies (24,26), each including a pair of wheels (26) laterally interconnected by an axle (24); a frame (12) supported near opposite ends thereof by said axles (24), and having a central longitudinal and vertical plane (19); yieldable retaining and suspension members (23,27,28) supporting the frame (12) on the axles (24); and a plurality of force-transmitting linkages (40,42,43,44,46,47), each of which connects a respective one of the wheel and axle assemblies (24,26) to the frame (12), each of the linkages (40,42,43,44,46,47) including a lateral steering beam (40) and a pair of parallel connecting rods (42), characterised in that the steerable railway truck is a self-steering truck (10) in which each lateral steering beam (40) is free from any connection to an associated carbody (11) except by way of the frame (12); the yieldable retaining and suspension members (23,27,28) provide a centring, restoring force to resiliently urge the wheel and axle assemblies (24,26) towards centred positions whilst permitting limited self-induced yawing of the assemblies (24,26) to occur during movement of the assemblies (24,26) along curved railway tracks; the steering beams (40) are interconnected with each other; each steering beam (40) has a centre (46,47) pivotally connected to the frame (12) in said central plane (19) thereof, and the connecting rods (42) nominally extend in planes parallel to said central plane (19) and pivotally connecting points on the steering beams (40) laterally opposite to and equidistant from the centres (46,47) thereof to points of the wheel and axle assemblies (24,26) longitudinally aligned with their interconnected steering beam points. A steerable railway truck (10) according to claim 1, characterised in that the wheels (26) are fixed to and are rotatable only with their respective axles (24), and the force-transmitting linkages (40,42,43,44,46,47) are interconnected to require self-steering yaw motions of the wheel and axle assemblies (24,26) to be of opposite sense and of equal extent. A steerable railway truck (10) according to claim 2, characterised in that the steering beams (40) are located at substantially the same height as the axles (24), and the connecting rods (42) occupy positions which are at least substantially horizontal. A steerable railway truck (10) according to claim 2, characterised in that the truck frame (12) is carried primarily above the axles (24), the steering beams (40) are located below a central portion of the frame (12) near the level of the axles (24), and the connecting rods (42) occupy positions which are at least substantially horizontal. A steerable railway truck (10) according to claim 2, characterised in that the steering beams (40) are connected to the truck frame (12) at adjacent locations near a point between and equidistant from the axles (24). A steerable railway truck (10) according to claim 5, characterised in that the truck (10) has only two of the wheel and axle assemblies (24,26). A steerable railway truck (10) according to claim 1, characterised in that the truck (10) includes a traction motor (36) drivingly connected to each axle (24), and the connecting rods (42) are operative to carry traction forces from the wheels (26) to the truck frame (12) without transmitting significant traction-related yaw forces to the wheel and axle assemblies (24,26). A steerable railway truck (10) according to claim 7, characterised in that each force-transmitting linkage (40,42,43,44,46,47) extends partially around the traction motor (36) for its respective axle (24). A steerable railway truck (10) according to claim 7, characterised in that a linkage mechanism (48,50,51) interconnects the force-transmitting linkages (40,42,43,44,46,47) to obtain self-steering yaw motions of the wheel and axle assemblies (24,26) that are of opposite sense and equal extent. A steerable railway truck (10) according to claim 9, characterised in that the linkage mechanism (48,50,51) is connected between the steering beams (40). A steerable railway truck (10) according to claim 10, characterised in that the steering beams (40) are connected to the truck frame (12) at adjacent locations near a point between and equidistant from the axles (24), and the linkage mechanism (48,50,51) includes a link (48) connected to both of the steering beams (40).

Inventors: GODING, DAVID JASON, RASSAIAN, MOSTAFA
Applicants: GENERAL MOTORS CORPORATION
Application year: 1986
Main classification: B61F5
IPC codes: B61F5