GB2254591A

GB2254591A - Guidance assembly for the wheelsets of a railroad car.

Info

Publication number: GB2254591A
Application number: GB9207296A
Authority: GB
Inventors: Eero Jaakola
Original assignee: VALTIONRAUTATIET
Current assignee: VALTIONRAUTATIET
Priority date: 1991-04-12
Filing date: 1992-04-01
Publication date: 1992-10-14
Anticipated expiration: 2012-04-01
Also published as: DE4212198A1; GB9207296D0; FI87333B; GB2254591B; FI87333C; FI911777A; PL168780B1; PL294181A1; FI911777A0

Description

-1 25 45 'M C- 1 GUIDANCE ASSEMBLY FOR THE WHEELSETS OF A RAILROAD CAR The

present invention relates to an assembly in accordance with the preamble of claim 1 for the guidance of wheelsets of railroad cars, in particular freight cars.

The purpose of wheelset guidance in railroad cars is to facilitate sufficient motion of the wheelset in curving and to control the motion and limit excessive amplitudes of motion. A wheelset is comprised of two flanged wheels connected with a stiff axle. Because of the stiff axle connecting the wheels, the rotation speed of the wheels naturally becomes equal. The load-bearing surface of the wheels is machined conical so that the wheel diameter increases toward the center line of the track. When the car traverses a curve, the outer wheel of a wheelset must travel a longer distance than the inner wheel, which is, however, contradictory to the fact that a rigid axle does not permit different rotational velocities for the wheels. The necessary difference of wheel travel is equalized by employing coning of the rotating wheel treads. When the wheelset meets the curve, the tangential direction of the wheels coincides with the tangent of the curve, thereby forcing the wheels radially outward from the curve. This forces the wheelset to be laterally displaced from the track center line and transversely outward from the curve tangent, thus causing the contacting tread diameter of the outside wheel to increase while the contacting tread diameter of the inner wheel correspondingly decreases, in this way accounting for the difference of distances travelled by the wheels and allowing the wheels to roll without longitudinal creepage on the rails. A further requirement is that the wheelset axle must stay aligned radial to the curve.

In two-axle cars the wheelsets guidance is conventionally accomplished by fork-shaped hornguides, which are rigidly fixed to the beams of the car underframe and act with 0 play on the bearing housings of the wheelsets. The guides are stiffly mounted on said beams, and a suitable play for longitudinal and lateral motion is provided between the bearing housings and the guides to permit necessary wheelset shift while traversing a curve. The bearing housings are typically sprung under the car using leaf springs 2 is placed above the bearing housing, whereby the leaf springs are tied to the car underframe with the help of tie clamps. At low speeds, say, under 130 km/h the centering action of the tie clamps and the friction of the clamp element surfaces steer the wheelset and the guidance means act only as amplitude limiters of large motions of the wheels. The motion of the wheelsets can be damped with the help of hydraulic or friction dampers.

In four-axle or multiple-axle cars the wheelsets are conventionally combined into bogies in which at least two wheelsets are mounted in a common bogie frame which is pivotally mounted beneath the car underframe. In curving the bogie can align tangential to the curve, thus permitting the action of the radial steering forces. The wheels are suspended either by suspending them from the side beams of the bogie, or alternatively, the suspension is adapted between side beams of the bogie and the transverse structures of the bogie. A part of the suspension structures can be placed between the bogie frame and the car underframe structures.

The above described suspension methods are, however, limited by several disadvantages. The above-described guidance arrangement for a two-axle car is spade consuming and the damping and stiffness adjustment of the guide elements is awkward.

Similarly, a pivoted bogie construction requires a large space, and moreover, the bogie is rather heavy thus contributing to car weight and thereby reducing the loading capability. If the wheelsets are suspended from the bogie, the bogie must be designed extremely stiff, which particularly in leaf-spring-suspended bogies again leads to large C1 structures and heavy weight. The bogie dimensions can be reduced by suspending the b bogie frame to the car underframe, but this alternative adds bogie weight to the dead weight.

It is an object of the present invention to achieve a guidance assembly of the wheelsets that facilitates suspending the wheelsets directly to the car underframe and makes it possible to control transversely acting foCes imposed on the wheelset.

3 The invention is based on the concept of connecting the sliding guides of the bearing housing with a rod aligned longitudinal to the car, whereby said rod is connected to the car underframe via torsion bars whose torsional stiffness about an a-xis parallel with the car's vertical axis is appropriately adjusted for each guidance assembly.

More specifically, the assembly according to the invention is characterized by what is stated in the characterizing part of claim 1.

The invention offers significant benefits.

A four-axle railroad car constructed in accordance with the present invention eliminates a separate bogie structure, allowing the wheelsets to be directly suspended from the car underframe. In this fashion the dead weight can be minimized, because structures moving vertically along with the wheelsets are obviated entirely. The axles of wheelsets at one end of the four-axle car can be made to steer the car at approximately equal transverse forces. The guidance and support structures of the wheelset can have a fairly shallow construction, as structures above the mounting points of the spring are not needed. The guidance of the bearing housings and the support of the spring can be implemented in the space below the spring. This approach permits, if desired, a lower floor level of the car interior and, correspondingly, a greater effective loading height of the car. The area between the wheels remains free. because all support and guidance elements are situated vertically essentially at the bearing housings.

A number of embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings in which:

Figures 1 to 3 show diagrammatically the behaviour of different steering arrangements of wheelsets in a curve.

Figure 4 shows a diagrammatic side view of an embodiment of the present invention.

4 Figure 5 shows a diagrammatic top view of the assembly illustrated in Fig. 4 Figure 6 shows an enlarged detail of the diagram of Fig. 5.

C1 Figure 7 shows a diagrammatic view of another embodiment of the present invention.

Figure I shows the behavior of a conventional two-axle railroad car in a curve. The dashed line K designates the center axis of the car. The wheelset tends to slip out from the curve as is exaggeratedly illustrated in the diagram. To permit creepage- and slip- free travel of the wheelset in a curve, the wheelset must be guided so as to allow its alignment radial to the curve. This requirement can be satisfied by, for instance, suspending the wheelset using springs mounted on tie clamps which permit a sufficient motion of the wheelset. The excursion of the wheelset is limited by a sliding guide acting on the bearing housing with suitable play.

The behavior of a typical four-axle railroad car bogie is shown in Figure 2. According to the diagram the center axis of the bogie aligns tangential to the curve and each of the wheelsets separately tends to align radial to the curve within the confines of their guidance elements. Thus, the axes of the wheelsets do not stay parallel, but rather, subtend an angle.

The assembly according to the present invention guides the wheelsets in a curve so that the wheelset can shift in the direction of its axle. According to Figure 4 the wheelsets are suspended from frame beams 9 of the car underframe using conventional standardized tie clamps 8. The bearing housings 6 of each wheelset are adapted to the center of a spring 7 and the ends of axles 12. Thus, the wheels 11 are located between the bearing housings 6. The rotation of the bearing housings 6 is prevented by slide blocks 5 whose guideways permit the vertical motion of the bearing housings 6. The slide blocks 5 are interconnected above the bearing housings 6 by a rod 10 and below the housings by a longitudinally aligned rod 2. The ends of the longitudinal rods 2 are ID interconnected by transverse rods 3 with swivel joints 14 at their ends. The rods 2 and 3 form a rectangular link mechanism, which interconnects the slide blocks 5 that confine the motions of the wheelsets.

The guidance assembly is connected to the car underframe via torsion bars 1 passing through the transverse beam 9 interconnecting the wheelsets. The torsion bars 1 join the upper rod 10 and the longitudinal bar 2 at their midpoints and the torsion bars are connected to the transverse beam 9 by means of an articulated element 4. One of the longitudinal rods has a damper 13 connected to it for damping the motion of the guidance assembly. Figure 6 shows enlarged the mating area of the slide block 5 and p the bearing housing 6. As can be seen from the diagram of Fig. 6, appropriate transverse and longitudinal plays a and b are provided between the slide block 5 and the bearing housing 6. By virtue of the plays, the wheelsets can perform in straight running and in large-radius curves similarly to the wheelsets of a two- axle railroad car with a conventionally sprung guidance of the wheelsets, and the guidance assembly reacts to movements only when the transverse forces grow larger.

1 30 The assembly functions under a larger transverse force, e.g., in a small- radius curve as follows. When the car enters the curve, the leading wheelset is shifted relative to the center axis K of the car radially toward the center of the curve by the rails in the manner illustrated in Fig. 3. Then, the bearing housings 6 of the leading wheelset are pressed against their sliding guides 5 and the guides 5 resultingly rotate the longitudinal rods 2. The rods 2 are rotated about the center of rotation formed by the torsion bar 1, whereby the longitudinal rods 2 force the sliding guides 5 of the trailing wheelset toward the outside of the curve, thus obviously shifting the entire wheelset under the thrust of the sliding guide. Since the ends of the longitudinal rods 2 are interconnected by the transverse rods 3, the rods 2 and 3 together form a symmetrical rectangular link mechanism in which the shifts at all bearing housings 6 are equal.

In normal running the wheelsets are initially steered by springs 7 in the same manner as the wheelsets of a two-axle car. Wheq the car enters a curve, both wheelsets align tangential to the curve (Fig. 1) and steer the car via the tie links along the curve. The 6 inertial force generated by the rotation of the car compels the car toward the outside of the curve. When the transverse force grows over a predetermined limit, play a between the bearing housing 6 and the sliding guide 5 goes to zero first at the leading wheelset. Then, the sliding guide 5 begins to rotate the bars 2 and 10 about the pivot point formed by torsion rod 1. As the transverse play a in the guidance elements of both wheelsets goes to zero, the sliding guides 5 gain steering force. Simultaneously, the bars 2 and 10 are rotated approximately tangential to the curve underlying the torsion bar 1. Then, the sliding guides 5 of the bearing housings 6 exert essentially equal steering forces. The steering forces imposed on the wheelsets differ only by the forces inflicted on tie clamps so that the force components related to the curve geometry have different lines of action, while thecomponents, which are caused by the shifting of the car within the guidance play a, act in the same direction.

When the car again enters a straight section of track, the guidance assembly returns to its centered state under the guidance of the bearing housings 6 as the wheelsets center themselves with the center line of the track due to the coning of the wheel treads. The centering effect can be accentuated with the help of a spring. The spring can be integral with the entity formed by the torsion bar 1 and the articulated element 4, or alternatively, a separate spring can be used.

The centering force can be appropriately adjusted by the design of, e.g., the articulated element 4 functioning between the torsion bar I and the underframe beam 9. Said element 4 can be a bearing or a conventional damper of torsional motion. The centering force is also affected by the bending stiffnesses of the transverse 3 and, in particular, the longitudinal rods 2. if the element 4 is extremely stiff.

The assembly according to the present invention transversely force-steers the wheelsets in curving but does not align them radial to the curve. In order to permit radial alignment of the wheels 11 in curving, plays a and b must be provided between the sliding guides 5 and the bearing housing 6. Each of the wheelsets is independently steered tangential to the curve within the confines set by plays a, b. The longitudinal CP 7 motion is determined by play b within a maximum shift of 2b. The clearances standardized by the international organizations of railroads for railroad vehicle components permit a satisfactory function of the assembly according to the invention for curves of conventionally used radii if the length of the wheelbase remains shorter than 10 m. Concisely, this embodiment performs the steering of the wheelsets by the springs 7 and the tie clamps 8, while the sliding guides backed by the guidance assembly act solely as limiters of large-amplitude motions and backing members for imposed forces.

The guidance assembly of a two-axle railroad car can be implemented in a vastly simpler manner than that necessary for a four-axle car. Here is needed only a longitudinal rod 2 for each bearing housing 6. The rod 2 is connected at its one end to the sliding guide 5, while the other end of the rod 2 is connected via the torsion bar 1 to the car underframe, e.g., to a transverse beam 9. The ends of the longitudinal rods 2 need not necessarily be interconnected by a transverse rod 3, while such an arrangement is possible for strengthening the structure and equalizing the transverse forces. The torsion bars 1 can be fixed to the car underframe by, e.g., a weld joint, whereby the steering forces are determined by the stiffness of the assembly. Thus, the discussed guidance assembly of the two-axle railroad car can be considered as a half of the four-axle car guidance assembly diagrammatically illustrated in Figs. 4 and 5. The guidance assembly for a two-axle car can also be designed symmetrical with respect to the wheelset in the longitudinal direction of the car. Such an assembly has two adjacent longitudinal rods and two torsion bars per each bearing housing.

In addition to those described above, the present invention can have alternative embodiments. Thus, plays illustrated in Fig. 6 can be replaced by resilient constructions which permit equivalent motions. The guidance assembly can also be equipped with hydraulic or friction dampers. The suspension and guidance of the wheelsets can be implemented in alternative ways different from those described above 30 using, e.g., coil springs or rubber, hydr4Ulic or gas springs. The bearing housings 6 can also be placed between the wheels I I on the axles 12. The sliding guide 5 permitting the vertical motion can be omitted if the longitudinal rods 2 are designed vertically resilient or they are vertically articulated with the torsion bar 1.

9

Claims

CLAIMS linked to 1. An assembly for the guidance of at least one railroad

car wheelset comprising an axle, two wheels mounted on the axle and at least two bearing housings with bearings adapted on the axle, said wheelset being a railroad car underframe by means of resilient elements, characterized in that said assembly incorporates, located to both sides of the railroad car as viewed along its longitudinal axis, a structure in which connected to each being housing, is a rod which is aligned essentially longitudinal to the railroad car, each longitudinal rod is connected to the railroad car underframe by means of a single element having a predetermined torsional stiffness about an axis parallel with the railroad car's vertical axis.
2. An assembly as def ined in claim 1, in which the longitudinal rods are connected to the bearing housings of consecutive wheelsets so that each rod is connected to two bearing housings located on the same side of the railroad car.
3. An assembly as defined in claim 1, in which the longitudinal rods are interconnected by at least one of their respective ends using a transverse rod.
4. An assembly as defined in claims 2 and 3, in which the longitudinal rods are interconnectedat both of their respective ends using a transverse rod.
5. An assembly as defined in c aims 2 or 4, in which - the longitudinal and transverse rods are interconnected using swivel elements whereby the rods form an articulated rectangle.
6. An assembly as defined in claim 1, in which the resilient element is comprised of a torsion bar and a resilient link element with which the torsion bar is connected to the railroad car underframe.
7. An assembly as defined in claim 1, in which the resilient element is a torsion bar which is fixed stationary to the railroad car underframe and the longitudinal rod, whereby the stiffness of the torsion bar determines its resilience.
8. An assembly as def ined in claim 1, in which the resilient element is comprised of a torsion bar which is fixed to the railroad car underframe via a bearing.
9. An assembly as defined in claim 1, in which a damper is adapted between at least one longitudinal or a transverse rod and the railroad car underframe.
10. An assembly as def ined in claim 1, in which the longitudinal rods are adapted below the centres of the bearing housings.
11. An assembly for the guidance of at least one railroad car wheelset substantially as herein described with reference to Figures 4 to 7 of the accompanying drawings.

0377b