WO1996008402A1

WO1996008402A1 - Railroad truck

Info

Publication number: WO1996008402A1
Application number: PCT/US1995/011593
Authority: WO
Inventors: Richard Gassler; Alan Tom Lim; Patrick George Mcauliffe
Original assignee: Northrop Grumman Corporation
Priority date: 1994-09-13
Filing date: 1995-09-13
Publication date: 1996-03-21
Also published as: AU3511295A

Abstract

A railroad truck is described which provides optimum steering. It is a forced steering truck having leaf springs as the sole primary elements in its suspension system. It further includes a stabilizer arrangement for inhibiting hunting.

Description

RAILROAD TRUCK

DISCLOSURE Background of the Invention The present invention relates to railroad cars, and, more particularly, to a forced steering truck arrangement for a railroad car. This invention is an improvement to the invention of U.S. Patent No. 5,249,530 entitled "FORCED STEERING RAILROAD TRUCK SYSTEM WITH CENTRAL TRANSVERSE PIVOTED SHAFT".

A standard railroad car traditionally is supported for rolling on a track by trucks (referred to sometimes as a "bogey") at its ends. Each truck has set(s) of wheels connected to the car body via a laterally extending bolster. That is, the car body has a protuberance at each of its ends which is mounted within a center bowl on a truck bolster positioned at such end. The wheel sets (typically in the U.S. a pair of sets, each of which has a wheel for each track) are suspended from the bolster by a suspension system. In a conventional arrangement the suspension system includes side frames and a plurality of springs. Railroad car trucks generally are designed with the type of load in mind. That is, passenger railroad car trucks are specialized for passenger cars, whereas trucks for freight cars are specialized for the type of freight. Even so, most conventional railroad car trucks are of a ^•■three-piece" design. (Three-piece truck designs have five or more major parts - a lateral bolster, two side frames and two or more wheel sets. A wheel set is a rigid assembly of an axle, two wheels and bearings - each wheel is fixed to the axle and does not rotate independently of it.)

Each wheel itself has a generally conical cylindrical surface for riding on a track rail - the cylindrical surface is conical in shape to center the truck between the tracks on straight rail and to facilitate operation in curves. That is, it provides steering capability. However, it also causes the wheels to "hunt", i.e., describe a sinusoidal path, on straight track. That is, the difference in wheel radii cause the axle to adjust to the unequal radii by yawing away from the wheel rolling on the largest radius. This causes the conventional three-piece truck to parallelogram, creating rolling resistance and wheel and track wear.

The axle yaw angle and acceleration increases with speed, creating a large lateral wheel force that can cause the wheel to climb or overturn the rail. Axle yaw also creates lateral acceleration at frequencies that can be damaging to lading and the railroad car structure.

If a designer of a railroad truck was only interested in minimizing the unfavorable effects of steering on straight track, the axle of each of the wheel sets will be maintained rigid and perpendicular to the track. However, while the increase in stiffness will reduce the unfavorable effects of straight track axle yaw, it will also prevent the axle from steering or yawing in curves.

The two competing design criteria is at least partially responsible for the many different truck designs which have been provided. One class of these truck arrangement is known as "forced steering" arrangements. These are arrangements in which the movement of the car body is fed back to the truck to control the angular positioning of the truck's wheels/wheel sets with respect to such body. The fundamental principles that separate the forced steering truck from a typical truck is a forced steering mechanism and extremely high side frame yaw stiffness. Since an arrangement which is based on forced steering is typically an expensive one, use of the same is reserved for cars designed to freight more expensive loads, e.g., automobiles. Summary of the Invention The present invention is a forced steering truck arrangement which is relatively simple in construction - yet it has features which make the same very attractive. It includes a stabilizer which cooperates with a steering link connected to the car body to resist car movement. Although this seems to be just the opposite of what is desired, it has been found that the use of such a stabilizer can inhibit hunting and yet allow movement of the wheels/wheel sets as is desired in curves. The truck of the invention also includes a suspension systemwhich adds to its efficacy. Such suspension system is made up primarily of leaf springs. Although leaf springs are in-of-themselves more expensive than the traditional coil springs which are part of the suspension system of most trucks, the use of the same in this invention eliminates the need to have side frames or other structure as part of such suspension. The forced steering design incorporated into the truck of the invention provides optimum steering without preventing use of a conventional brake arrangement.

The invention combines into one truck, the ability to prescribe a smooth sinusoidal path on a straight track and precise steering in curves to lower the wheel-to-rail angle of attack. This lowers wheel and rail wear, fuel consumption and critical lateral loads onthe rail mounting and supporting structure. Other features and advantages of the invention either will become apparent or will be described in connection with the following, more detailed description of a preferred embodiment of the invention.

Brief Description of the Drawing

With reference to the accompanying drawing: FIG. 1 is an elevational view of a preferred embodiment of a truck incorporating the invention, showing its relationship to a railroad car body; FIG. 2 is an isometric view of the preferred embodiment of FIG. 1; FIG. 3 is a sectional view illustrating certain components of the preferred embodiment;

FIG. 4 is a partial isometric view illustrating the steering mechanism of the preferred embodiment of FIG. 1; FIG. 5 is a reduced plan view showing the relationship of a standard brake arrangement to the steering mechanism of the preferred embodiment;

FIG. 6 is a plan view of the steering mechanism of the preferred embodiment of the invention; FIG. 7 is a schematic top view illustrating a relationship between trucks of the preferred embodiment of the invention, railroad cars, and railroad tracks;

FIG. 8 is a schematic isometric view showing various aspects of the steering mechanism incorporated into the preferred embodiment;

FIG. 9 is an end sectional view of the preferred embodiment, showing some detail; and

FIG. 10 is an enlarged sectional view showing a stabilizer arrangement incorporated into the preferred embodiment.

Detailed Description of the Preferred Embodiment The following relatively detailed description is provided to satisfy the patent statutes. It will be appreciated by those skilled in the art, though, that various changes and modifications can be made without departing from the invention.

A preferred embodiment of the forced steering truck arrangement of the invention is generally referred to in the drawings by the reference numeral 11. Such truck is designed to engage one end of a rail car, referred to in phantom at 12, and support it on railroad track indicated at 13. In this connection, the truck of the invention includes a bolster 14 (FIG. 2) which extends laterally between the longitudinal sides of the truck. Bolster 14 is spaced centrally between a pair of wheel sets respectively made up with parallel axles 15 and 16 to the ends of which are rigidly secured spaced wheels 17, 18 and 19,20. (It will be seen that for convenience the sides of the truck which are meant to be along the sides of a car body when the truck is assembled with a railroad car are referred to as the longitudinal sides, whereas the direction orthogonal thereto is referred to as "laterally" of the truck.)

Bolster 14 is hollow and box-shaped in section. It includes a conventional center bowl 21 and a standard axial kingpin 22 for securing the truck to the bottom of a railroad car. Standard railroad cars have a protuberance to fit into the center bowl 21 and a cavity which will receive the kingpin 22.

The bolster 14 supports at its opposite ends, upside down U-shaped spring mounts 23, each of which captures a pair of leaf spring sets 24 and 26, respectively. As is best illustrated in FIG. 3, the leaf springs of each set are generally conventional in design and, in this connection, each is made up of a plurality of leaves 27 which are secured together by bands 28. Each of the leaf springs is mounted at its center within the spring mount associated therewith, via a resilient elastomeric liner pad 29. (See FIG. 3) Such springs are held in position by retainer pins which extend through slots 31 in the mounts as shown in FIG. 2.

In keeping with the invention, the opposite ends of each of the leaf springs of sets 24 and 26 extend away from the leaf spring center at the bolster to the wheels of the truck on the same longitudinal side. For example, the opposite ends of the springs 26 of set shown in FIG. 3 extend to the wheels 18 and 20. Such spring ends 32 and 33 terminate just over the standard wheel bearings 34 and 36 for the wheel sets. As best illustrated in FIG. 3, the respective spring ends bear against interface wear liners supported by pedestal links 37 and 38 (which will be described in more detail hereinafter) that, in turn, include structure for interfacing with the wheel bearings. In this connection the interface wear liners on the pedestal links are simply hard rubber or plastic selected to provide contact without entirely preventing movement between the spring ends and the pedestal links. The spring ends 32 and 33 are directly over the axles and the full suspension system is made up, in essence, of the leaf springs. In this connection, the pedestal portions and bearings between the spring ends and the wheel sets act at the point of engagement only as load transmitters between such spring ends and the wheel axles. While the pedestals are part of the steering system as will be discussed below rather than of the suspension, each includes an upwardly projecting stop 39 for limiting total suspension motion during unusually large vertical suspension demands, and supports the leaf spring in the rare occurrence of spring component failure.

An important component of the forced steering truck arrangement of the invention is the steering mechanism. It is actually divided into two separate parts generally referred to in the drawings by the references numerals 42 and 43 (see FIG. 4) . Both of these parts are essentially the same and only one will be described in detail. Each includes a car body link 44 for connection to the car body via a downwardly extending flange 46 (FIG. 1) . The link is connected to a Pitman lever follower 47 which, in turn, extends through a slot 48 (FIG. 10) in the box bolster 14 wherein it is rigidly connected to a torque tube 49. Such torque tube extends centrally between the wheels on one of the sides of the truck to a position at which it is connected to a steering link pin 51. The pedestal links 37 and 38 on each side of the truck are pivotally connected via pins 52 (FIG. 9) to such steering link pin. It will be seen that although the steering link pin is axially connected to the torque tube, the pedestal links are eccentrically connected to the steering link pin (and, hence, indirectly to the torque tube) at positions which are on opposite sides of the torque tube axis.

While operation of the steering mechanism is relatively easy to understand, schematic FIG. 8 has been included to facilitate a description. In such figure, the various components are represented simply as linear links connecting the various pivot points together. These links are given the same reference numeral primed as the components to which each corresponds. Thus, the car body flange 46 is represented at 46', the car body link 44 is represented at 44', the Pitman lever at 47' and the torque tubes at 49'. The torque tubes 49' are on a common axis represented at 53 and it will be seen that rotary motion of each about its axis as represented by the arrow 54, will result in retraction or extension of both of the pedestal links 37' and 38'. These links are connected in turn to the wheels on the respective sides of the truck. The axes of rotation of the wheel sets and, hence, of the wheels are represented in FIG. 8 at 56. The manner in which the steering mechanism of the invention converts motion of the car body at its point of connection to the wheel spacing on each side of the truck is relatively straightforward. Assuming for explanation's sake that the car body flange 46 of steering part 42 moves away from the torque tube of such part, the car body link 44 will follow the same. The result will be that the Pitman lever link 47 will also follow the same, placing torque on tube 49 to rotate it about its axis. The steering link which is rigidly connected to the torque tube will in turn rotate the pedestal links 37 and 38 to separate the wheels on the side of the truck of which the steering part is associated.

As mentioned previously, each of the two parts of the steering mechanism are the same. Each should be the reverse image of the other, and the distances of the two flanges 46 from the center axis of the car should be the same. As illustrated by FIG. 5, the provision of the steering mechanism as two parts enables use of a conventional truck braking system of the type which extends through the center of the bolster. The steering reaction which is a consequence of the invention is illustrated in FIG. 7. The car bodies of railroad cars 12' and 12'' are represented respectively on straight (often referred to in the art as "tangent") track at 13' and curved track at 13". The lengths of the various links and tubes are selected to maintain the wheel sets of each truck generally parallel to one another in straight track. However, because of the steering mechanism the distance between the wheels on opposite sides of the truck in curves will vary, i.e., the distance between the trucks will be reduced on the inside of a curve whereas it will be increased on the outside of the curve. There are certain dimensional relationships which preferably are selected to provide optimum steering, i.e., so that the truck axles will remain congruent with a radius of the curve. The dimensions which are important in the relationship are shown in FIGS. 7 and 8. One is the separation distance S between the two wheel sets of each truck when the sets are on straight track, and another is the separation distance W between the wheels of each set. The center distance L between the two trucks on a rail body is also part of the relationship.

The important dimensional relationships in the steering mechanism itself are illustrated for part 42'. The distance denoted by e of the eccentric connection of one of the pedestal links 37'-38' from the axis 53 of the torque tube of which it is a part is one of such important distances. Another is the height or distance h of the Pitman lever between the connection between the car body link 44 and the torque tube axis for optimum steering, the connection of the Pitman lever to the torque tube also should be a distance d from the center of rotation of the car body when the truck travels straight down a tangent track.

The distances which have been identified should be related as follows for optimum steering: e/h ≥ WS/2Ld (While in an exact and optimum arrangement there will be an exact equality between the two parts of the equation, as a practical matter there will be tolerances which will have to be accommodated so that the relationship which is obtained will only be approximately equal.) When such relationship is achieved, the axles will always be congruent with the radii of the curves in the track. Moreover, the wheel sets will in general be maintained parallel to one another in straight track.

As an important aspect of the forced steering truck arrangement of the invention, a stabilizer is provided for resisting the reaction of the steering mechanism to movement of the car body. It tends to resiliently urge the steering link toward a selected, neutral position. As illustrated in FIG. 10, such stabilizer is mechanically implemented in a simple manner by the preferred embodiment of the invention. The car body link 44 (partial) is shown pivotally connected to the Pitman lever follower 47. Although not illustrated in such view, the Pitman lever is rigidly secured to the torque tube 49 of its associated steering part for rotation about the intersection point 57. Such Pitman lever also is divided into two opposed tits 58 and 59 that engage a rocker beam 61. (It is to be noted that the tits 58 and 59 engage the surface of the rocker 61 through inserts 62 provided when the stabilizer is manufactured to take up any space between the tits and the rocker beam.) Rocker beam 61 normally is held by a loading pin 66 with its edge flanges 63 in engagement with nubs 64 which project inwardly from the interior wall of the bolster. In this connection, the head of such loading pin is resiliently urged to maintain the rocker beam in the position illustrated by a spring 67, which spring is in compression between such head and the bolster.

It will be seen that with the above arrangement movement of the link 44 in either of the directions indicated by arrow

68 will result in a corresponding rocking of the Pitman lever

47 and, hence, of the rocker beam 61. That is, while the beam 61 will be normally urged into the neutral position illustrated in FIG. 10, upon car body movement the beam 61 will be rocked against the compressive force of spring 67 to disengage one of its end tits from the bolster flange. The force of resistance can be selected as desired by properly selecting the compression and response curve of the spring 67.

It will be seen from the above that the stabilizer tends to inhibit "hunting" on straight track by resisting the tendency of the truck and, hence, the wheels to rotate relative to the railroad car body. Although such resistance will also be present when steering is desired, i.e., in curves, it can be overcome. It will be noted, though, that the compressive force provided by the stabilizer will tend to "straighten out" the wheels and, hence, the truck as it leaves a curve.

It is desirable for design and control purposes that only the stabilizer be provided to resist the turning motion of the railroad car body relative to the truck. In this connection, it is common to provide constant contact side bearings on a truck, which side bearings engage the car body to resist turning movement. With the present invention, such side bearings are designed to offer little or no resistance to turning movement, although they can provide the support needed for the car body to prevent rocking as is conventional. With reference to FIGS. 2 and 9, for example, the side bearings are simply roller bearings 69 in channel sections 71. As is known, roller bearings provide little or no resistance to rotation.

As mentioned at the beginning of the detailed description, Applicant is not limited to the specific embodiment described above. Various changes and modifications can be made. For example, although the invention is described in detail in connection with a truck having two wheel sets, from the broad standpoint the same principle insofar as forced steering is concerned is applicable to trucks having only one or more than two wheel sets. The principle is that the steering linkage to the car should be designed to provide radial alignment of the wheel set(s) in curves.

The description is exemplary, rather than exhaustive. The claims, their equivalents and their equivalent language define the scope of protection.

Claims

CLAIMSWhat is claimed is:

1. In a forced steering truck arrangement for a railroad car, which arrangement has a steering link adapted to be connected to a railroad car body; a stabilizer connected to said steering link to resist movement thereof by said car body.

2. The forced steering truck arrangement of claim 1 having in combination with said stabilizer, a side bearing for engagement by said car body selected to offer little or no resistance to movement of said car body.

3. The forced steering truck arrangement of claim 1 wherein said stabilizer is connected to said steering link to resiliently urge said steering link toward a selected, neutral position.

4. The forced steering truck arrangement of claim 3 wherein said stabilizer comprises the combination of:

(A) a follower connected to said steering link to be moved thereby when the latter moves; and (B) a spring connected to said follower to resist movement thereof and resiliently urge the same and, hence, said steering link to a selected, neutral position.

5. The forced steering truck arrangement of claim 4 wherein said follower is a Pitman lever and said spring is positioned to be compressed whenever said Pitman lever moves.

6. The forced steering truck arrangement of claim 1 for supporting a railroad car longitudinally on a track by at least two trucks separated by a center distance L, each of which trucks has at least two, generally parallel wheel sets with a separation distance between the same of S in the direction to be longitudinal of said car and the wheels of each set having a separation distance between the same of W in the direction to be lateral of said car, the combination with said stabilizer of a steering mechanism for the wheels on at least one longitudinal side of said truck, said steering mechanism including:

(A) a torque tube which extends generally parallel to the axles of said wheel sets to between said wheels on at least one longitudinal side of said truck; (B) a steering pin connected to said torque tube respectively at a location between the wheels of said truck at said side;

(C) a pair of pedestal links eccentrically connected to said steering pin at respective positions which are on opposite sides of the torque axis of said torque tube at said location;

(D) a Pitman lever connected to said torque tube to apply torque to the latter and rotate it about its axis; and (E) a car body link for securing said car body to said lever and moving said lever proportional to rotation of said car body; said steering mechanism satisfying the relationship: e/h _= WS/2Ld where: e = the distance between the axis of said torque tube and a position at which either of said pedestal links is eccentrically connected to said steering pin; h = the distance between said torque tube axis and the location at which said Pitman lever is connected to said car body link; d = the distance between the axis of said torque tube at said Pitman lever and the center of rotation of said car body.

7. The forced steering truck arrangement of claim 6 wherein there are two parts to said steering mechanism, each of which includes the recited elements respectively for the wheels of said truck on an associated longitudinal side thereof.

8. The forced steering truck arrangement of claim 7 further comprising a conventional brake mechanism for the wheels of said truck located between said two steering mechanisms.

9. In a forced steering truck arrangement for a railroad car, which arrangement includes a bolster to be connected centrally thereof to the railroad car body and at least two wheels sets respectively positioned on opposite sides of said bolster providing wheels to be at longitudinal sides of said car body, a suspension for said wheel sets made up solely of a plurality of springs extending respectively from said bolster to said wheel sets on opposite longitudinal sides of the truck arrangement.

10. The forced steering truck arrangement of claim 9 wherein each of said springs is a leaf spring which is connected at its center to said bolster and has two opposite ends extending on opposite sides of said bolster away therefrom to wheels at the side of said truck having said spring.

11. In a forced steering truck arrangement for a railroad car, a steering mechanism for a single truck comprising a pair of body steering links adapted to be connected directly at spaced apart locations to a railroad car body.

12. The forced steering truck arrangement of claim 11 wherein each of said body steering links is connected to control the longitudinal spacing between two or more truck wheels on an associated longitudinal side of said truck.

13. The forced steering truck arrangement of claim 12 wherein each of said truck wheels is part of a rigid wheel set which extends laterally of said railroad car.

14. The forced steering truck arrangement of claim 11 wherein said steering mechanism is divided into two parts, one of said body steering links being associated with each of said parts and wherein each of said parts includes:

(A) a torque tube which extends generally parallel to the axles of said wheel sets to between wheels on at least one longitudinal side of said truck;

(B) a steering pin connected to said torque tube at a location between the wheels of said truck at said side;

(D) a Pitman lever connected to said torque tube to apply torque to the latter and rotate it about its axis; and

(E) a car body link for securing said car body to said lever and moving said lever proportional to rotation of said car body.

15. The forced steering arrangement of claim 14 for supporting a railroad car longitudinally on a track by at least two trucks separated by a center distance L, each of which trucks has at least two, generally parallel wheel sets with a separation distance between the same of S in the direction to be longitudinal of said car and the wheels of each set having a separation distance between the same of W in the direction to be lateral of said car, the combination with said stabilizer of a steering mechanism for the wheels on at least one longitudinal side of said truck, wherein said steering mechanism part satisfies the relationship: e/h ≥ WS/2Ld where: e = the distance between the axis of said torque tube and a position at which either of said pedestal links is eccentrically connected to said steering pin; h = the distance between said torque tube axis and the location at which said Pitman lever is connected to said car body link; d = the distance between the axis of said torque tube at said Pitman lever and the center of rotation of said car body.

16. A forced steering truck arrangement for a railroad car, which arrangement includes:

(A) a bolster to be connected to a car body and extend laterally thereof; (B) a pair of wheel sets on opposite sides of said bolster providing wheels on the longitudinal sides of said truck;

(C) a pair of steering links adapted to be connected to a railroad car body; (D) a stabilizer connected to said steering link to resist movement thereof by said car, said stabilizer including:

(a) a follower connected to said steering link to be moved thereby when the latter moves; and (b) a spring connected to said follower to resist movement thereof and resiliently urge the same and, hence, said steering link to a selected, neutral position;

(E) a suspension for said wheel sets made up solely of a plurality of leaf springs extending from said bolster to said wheel sets on said opposite longitudinal sides of said truck, each of which leaf springs is connected at its center to said bolster and has two opposite ends extending on opposite sides of said bolster away therefrom to wheels at the side of said truck having said spring; and (F) each of said steering links being connected to control the longitudinal spacing between a pair of associated wheels on an associated longitudinal side of said truck.

17. The forced steering truck arrangement of claim 16 for supporting a railroad car longitudinally on a track by at least two trucks separated by a center distance L, each of which trucks has at least two, generally parallel wheel sets with a separation distance between the same of S in the direction to be longitudinal of said car and the wheels of each set having a separation distance between the same of W in the direction to be lateral of said car, the combination with said stabilizer of a steering mechanism for the wheels on at least one longitudinal side of said truck, said steering mechanism including:

(A) a torque tube which extends generally parallel to the axles of said wheel sets to between said wheels on at least one longitudinal side of said truck;

(C) a pair of pedestal links eccentrically connected to said steering pin at respective positions which are on opposite sides of the torque axis of said torque tube of said location;

(E) a car body link for securing said car body to said lever and moving said lever proportional to rotation of said car body; said steering mechanism satisfying the relationship: e/h a- WS/2Ld where: e = the distance between the axis of said torque tube and a position at which either of said pedestal links is eccentrically connected to said steering pin; h = the distance between said torque tube axis and the location at which said Pitman lever is connected to said car body link; d - the distance between the axis of said torque tube at said Pitman lever and the center of rotation of said car body.