BACKGROUND AND SUMMARY OF THE INVENTION
The invention relates generally to railway car truck friction damping arrangements, and more particularly to a railway car truck friction shoe spring group.
The present invention is directed to a friction shoe suspension control spring group for a railroad car truck and in particular to a suspension control spring group having three concentrically nested coil springs and to a friction shoe including a body having a sloped face and a vertical face. The suspension control spring group applies force to the friction shoe which dissipates energy throughout the range of suspension travel thereby controlling the relative motion between the side frames and bolster as the railway car travels down the track.
Railroad car trucks of a design known as a three piece railway car truck include a pair of spaced apart side frames and a bolster that extends transversely between the side frames. The bolster is resiliently supported at each end on a respective side frame by a plurality of suspension springs. Wedge shaped friction shoes are used in such railroad car trucks to dampen movement of the bolster with respect to the side frame of the railroad car truck. Friction shoes are usually generally triangular wedge shaped such that two laterally spaced sloped faces are each in contact with one of two laterally spaced sloped faces of the bolster. The friction shoe is also comprised of a vertical face that is in contact with a corresponding wear plate mounted on a vertical face of a side frame column. The wear plate on the vertical column of the side frame is usually comprised of steel. Accordingly, the friction shoe acts as a motion damping wedge between the bolster and the wear plate on a vertical column of the side frame.
The friction shoe also is comprised of a bottom section that joins the vertical face and the two laterally sloped face. The bottom section includes a spring lug in the form of a hollow protrusion extending form the bottom section. Such design spring lug saves weight as it has a hollow core. Further, the bottom of the spring lug is open which allows water or other debris to pass out of the friction shoe.
The friction shoe is wedged into engagement between the sloped faces of the bolster and the vertical column of the side frame by a suspension control spring group. Such spring group typically comprises one or two concentrically grouped coil springs, or an elastomeric solid or hollow spring may comprise one or more of the springs in the spring group. Resistance to sliding movement of the friction shoe with respect to the side frame, which in turn provides dampening of vertical bolster movement, is provided by the frictional forces generated between the friction shoe vertical face and a wear plate on the side frame vertical column. This also provides improved truck squaring capability and warp stiffness.
It is an object of the present invention to provide an improved railway car truck suspension control spring group and friction shoe that is comprised of three concentrically nested springs wherein the damping frictional force on the vertical movement of the bolster is better controlled with greater energy dissipation.
BRIEF DESCRIPTION OF THE DRAWING FIGURES
FIG. 1 is an exploded isometric view of a railway car truck in accordance with an embodiment of the present invention;
FIG. 2 is a detailed partial isometric view of a portion of a railway car truck in accordance with an embodiment of the present invention;
FIG. 3 is a isometric view of a friction shoe in accordance with an embodiment of the present invention;
FIG. 4 is a bottom view of a friction shoe in accordance with an embodiment of the present invention;
FIG. 5 is a side view of a friction shoe in accordance with an embodiment of the present invention;
FIG. 6 is an exploded isometric view of a friction shoe and spring group in accordance with an embodiment of the present invention, and
FIG. 7 is a partial cross sectional view of an assembled spring group in accordance with an embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to FIG. 1, a friction wedge 8 of the present invention is shown in a railroad car truck. The railway car truck includes two side frames 2 which are spaced apart and generally parallel to one another. Each side frame 2 includes a bolster opening 13 formed by a pair of spaced apart vertical columns 14. A planar wear plate 15 is connected to the interior surface of each column 14. The railway car truck also includes a bolster 1 which extends generally transversely between the side frames 2. Each end 12 of the bolster 1 is located within a respective bolster opening 13 and is vertically supported on a side frame 2 by a plurality of helical coil suspension springs 10. The bolster end 12 is also supported by the friction shoes 8 which themselves are supported by suspension control springs 9. The suspension control springs 9 and suspension springs 10 are themselves supported on a spring support section 16 of each side frame 2. Suspension control springs 9 and suspension springs 10 are resiliently compressible to thereby allow the ends of the bolster 1 to move vertically upwardly and downwardly within the bolster openings 13 and with respect to the side frames 2. Each bolster end 12 includes a plurality of sloped walls 22. Each sloped wall 22 is adapted to engage a sloped surface 20 of a respective friction shoe 8. Friction shoe 8 is seen to provide a damping force to the vertical motion of bolster 1 while supported on suspension control springs 9 and suspension springs 10 as the railway car travels on the rails.
Railway wheels 4 are mounted on axles 3. Axle bearings 5 are mounted on the ends of axles 3. Bearing adaptor 6 and pad 7 are provided to receive axle bearings in side frame pedestal openings 2A. Center bowl 11 on the top surface of bolster 1 is provided to help support the railway freight car on the truck.
As best shown in FIG. 2, friction shoe 8 includes a body 17. Body 17 is generally triangular or wedge-shaped. The body 17 includes a base having a generally horizontal bottom wall 34. The bottom base surface 34 is adapted to engage the top end of a set of concentrically nested suspension control springs 9. The body 17 also includes a generally vertical front wall includes a front face 19. The body 17 also includes a sloped surface 29 which may be comprised of laterally spaced sloped walls 20 and 20A that extend at an inclined angle of thirty-five to forty-five degrees between the base 34 and vertical front face 19 and approximately 150 to 178 degrees relative to each other. Sloped surface 29 is adapted to engage inclined walls 22 of the bolster 1. The proportion of combined spring rates of the suspension control spring group engaging with the friction shoes to the combined spring rates of the suspension springs engaging with the bolster is between 12 and 18 percent in the empty railway car truck condition and between 20 and 27 percent in the loaded railway car truck condition. A single friction shoe inner, middle and outer coil spring provide a normal force on the column wear plate of between 3000 and 5000 pounds in the static empty railway car truck condition and between 7,500 and 12,000 pounds force under the static loaded railway car truck condition.
As best shown in FIGS. 3, 4, and 5, the front face 19 of friction shoe body 17 is in direct contact with and extends from an intersection 31 with bottom base surface 34. Front face 19 of friction shoe body 17 is in direct contact with and extends from an intersection with top edge 25 of center spacing section 21 of sloped surface 29. Bottom base surface 34 may include a spring lug 37 extending therefrom. Spring lug 37 is usually cylindrical in shape, with a bottom surface 41 of spring lug 37 is flat when it engages with the inner suspension control spring 44. The friction shoe 8 may be made from metals such as steel or iron.
Referring now to FIGS. 6 and 7, suspension control spring group 9 is shown to comprise an outer coil spring 42, a middle coil spring 43 located concentrically inside outer coil spring 42, and an inner coil spring 44 located concentrically inside middle coil spring 43.
Outer coil spring 42, middle coil spring 43, and inner coil spring 44 may be comprised of steel coil springs or solid or hollow elastomeric springs. Middle coil spring 43 is seen to surround the outer cylindrical surface of spring lug 37. Inner coil spring 44 is seen to contact bottom surface 41 of spring lug 37 upon sufficient compressive force downward onto spring group 9. Under empty or lightly loaded railcar conditions, spring group 9 may be uncompressed 110 and not in contact the friction shoe bottom surface 34 or spring lug bottom surface 41.
The damping force by the friction shoe 8 can vary as may be selected from the various materials for friction shoe body 17 and the force with which the front face 19 is impinged against side frame column wear plate 15 which is directly related to the vertical force applied to the bottom of the friction shoe 8 by the suspension control spring group 9.
Patent Application
20180257677
