Draft Gear

Abstract

A draft gear adapted to be operatively connected to a coupler of a railway vehicle is provided with a novel and improved cushioning member comprising spaced face to face elements having a rigid sheet carrying frusto-shaped substantially nonporous elastomeric protuberances on each face thereof and a flexible plastic foam filling the interstices between the elements.

Description

This invention relates generally to a draft gear adapted to be operatively connected to a coupler of a railway vehicle and more particularly to such a draft gear provided with a novel and improved buff and draw cushion to absorb coupler forces.

It has been proposed before to provide draft gears containing rubber cushioning members. One draft gear of this type is disclosed, for example, in U.S. Pat. Nos. 2,640,603 and 2,686,667. The cushioning device used in the draft gear is composed of a plurality of elements having a sheet metal core between rubber surfaces vulcanized to each side thereof. The rubber has an undulated surface of alternate hills and valleys which extend in one direction across the element. The rubber of the hills displaces into the adjacent valleys under compression until the valleys are filled at which point the rubber surface acts substantially as a solid rubber block. Further compression often results in rupture of the rubber.

Another draft gear is disclosed in U.S. Pat. No. 2,720,319. Cushioning elements having a sheet metal core carrying rubber bars on the faces thereof are disposed in the gear box. The bars are frusto-pyramidal shaped in cross-section and extend discretely across the face of the plate in the opposite direction. The rubber bars compress under load in one direction into the valley therebetween and will often burst or rupture under heavy loads.

It is an object of this invention to provide an improved draft gear for railway vehicles. Another object of the invention is to provide a draft gear having an elastomeric cushioning member adapted to absorb greater coupler forces without rupture of the elastomeric element. A more specific object of the invention is to provide a draft gear for railway vehicles having a cushion adapted to absorb coupler forces which comprises longitudinally spaced rigid plates carrying flexible elastomeric layers therebetween adapted to compress under such forces with reduced tendency to rupture and to compression set.

Other objects will become apparent from the following description with reference to the accompanying drawing in which

FIG. 1 is a longitudinal sectional side elevation of an embodiment of the draft gear provided by the invention;

FIG. 2 is a plan section taken along the line 2--2 of FIG. 1;

FIG. 3 is a cross-section taken along the line 3--3 of FIG. 1; partially broken away to illustrate the structure of the cushioning pad disposed in the draft gear pocket;

FIG. 4 is a longitudinal section through a cushion provided by the invention;

FIG. 5 is a side elevation partially in section, illustrating the embodiment of FIG. 1 compressed under buff; and

FIG. 6 is a plan view, partially in section, illustrating the embodiment of FIG. 1 compressed under draft.

Referring now to the drawing, as illustrared in FIGS. 1 and 2, a draft gear 10 has a yoke 11 with pocket 15. A front follower 12 just behind the butt 13 of a coupler shank 14 is disposed in pocket 15. The draft gear 10 and the coupler are mounted in a center sill 16-16 of a railway vehicle. The yoke 11 may be of conventional construction, the one illustrated in the drawing having rear end wall 17, top wall 18 and bottom wall 19 terminating in wings 20 and 21, respectively. Key 22 secures shank 14 of the coupler to wings 20 and 21. The forward end of the coupler may be of any conventional construction such as that of a standard "E" or "F" type coupler so it is not illustrated.

A cushioning device is disposed in pocket 15. As illustrated in FIGS. 1 and 2, the cushioning device may be divided into a forward draft cushion and a buff cushion separated by an intermediate follower block 27. A rear plate 28 rests against rear end wall 17 and may have a U-shape with the legs of the U being parallel to top wall 18 and bottom wall 19. A metal plate 29 is disposed against follower 12. A pair of compressible cushions 30 and 31 separated by a metal disc 32 are disposed between plate 29 and intermediate plate 27. A similar pair of compressible cushions 33 and 34 are disposed between intermediate plate 27 and rear plate 28 and are separated by disc 35. An axial bore 36 extends longitudinally through plates 27, 28 and 29, discs 32 and 35 and cushions 30, 31, 33 and 34. Rod 37 has a head 38 in counter-sink pocket 39 of plate 29. The shaft of rod 37 extends longitudinally through bore 36 and terminates in a threaded end having a nut 40 which secures the assembly of plates 27, 28, 29, discs 32 and 35 and cushions 30, 31, 33 and 34 against relative longitudinal separation but the units of the assembly can slide over the rod 37. Liners 42 and 43 are secured to the inner sides of top and bottom walls 18 and 19 to reduce the cross-section of pocket 15 about the buff cushions 33 and 34.

Referring now to FIGS. 3 and 4, each cushion 30, 31, 33 and 34 is composed of spaced metal sheets 44 carrying symmetrically oriented frusto-pyramidally shaped protuberances 45 on each face thereof. An opening 46 is provided through sheet 44 at the base of each protuberance 45 so a protuberance 45 on one face of the sheet is integral with a protuberance 45 on the opposite face of the sheet 44. The apices of opposing protuberances 45 of adjacent sheets abut each other. Interstices 47 surround the protuberances 45. Interstices 47 are filled with an elastomeric polyurethane foam 48. As shown in the drawing protuberances 45 are discrete with respect to each other in both directions.

As indicated in FIGS. 3 and 4 a unitary pad or block may be formed by stacking sheets 44 carrying protuberances 45 in a suitable mold 49 and pouring or injecting a foamable polyurethane mixture into the mold about the stacked elements. The liquid mixture will react and expand into the interstices. Axial bore 36 may have been drilled through the elements prior to stacking to provide an opening for introduction of foamable reaction mixture. Bore 36 will become filled with foam during molding and may be removed by drilling to provide bore 36 for assembly of the cushioning device. A covering layer 50 of foam may be left about the assembly to provide a smooth surfaced block.

The rubber coated elements of the cushions may be fabricated by molding rubber on the sheets 44 and vulcanizing by conventional processes. Spaced perforations are provided in the sheet equal in number to the number of protuberances to be carried on each side of the sheet. The sheet is preferably metal, such as molybdenum steel or the like but it may also be a rigid plastic. The elastomer may be natural rubber, synthetic rubber or an elastomeric synthetic resin such as a non-porous polyurethane but butyl rubber is preferred. It is preferred that the edge between the sides of the frusto-pyramidal protuberances be slightly curved or rounded so that sharp edges are avoided. In this way the apex and base of each protuberance has curved or rounded corners. The elastomer molded on the surface of the supporting sheet may have a density of from about 18 to about 125 pounds per cubic foot. It is preferred that the frusto-shaped protuberance join the rigid plate at an included angle of 5.degree. to 45.degree..

The polyurethane foam used to fill the interstices between protuberances may be any suitable flexible, microporous polyurethane and may be prepared by the process disclosed in "Polyurethanes: Chemistry and Technology" by Saunders and Frisch, published by Interscience Publishers (1964), particularly Chapters V, VI and VII or by any other suitable known process. Preferably, the density of the polyurethane foam should be from about 18 to about 50 pounds per cubic foot. One foam of the type contemplated by the invention is disclosed in U.S. Pat. No. 2,850,464.

The draft gear provided by the invention is illustrated in buff in FIG. 5 and in draft in FIG. 6. As shown in FIG. 5, coupler forces applied against front plae 29 by follower 12 compress all four cushions 30, 31, 33 and 34 and rod 37 moves towards the rear of the gear box. Hence, the large shock forces associated with the humping of cars is absorbed by all four pads. In draft, however, only the cushions 30 and 31 exert a back-pressure against the coupler butt because cushions 33 and 34 are enclosed by liners 42 and 43 and exert a back-pressure only against intermediate plate 27.

The number of layers of sheets carrying frusto-shaped protuberances may be varied depending upon the coupler forces anticipated but it has been found so far that the four cushions 30, 31, 33 and 34 each containing four sheets with butyl-rubber protuberances on each face and the interstices filled with polyurethane foam within the above density range provide the best results for the draft gear of railway vehicles commonly used by European railways. The flexible foam between the protuberances not only tends to resist displacement of the rubber and rupture thereof but also because it has less tendency to compression set, the foam tends to restore the protuberances to their normal dimensions and shape after compressive forces are released. Data obtained by compressing a pad like 30, 31, 33 and 34 is given in my copending application filed on the same date of this application and entitled "Shock Absorber" Ser. No. 295,539, filed Oct. 6, 1972, the disclosure of which is incorporated herein by reference thereto.

Although the invention has been described in detail for the purpose of illustration, it is to be understood that such detail is solely for that purpose and that variations can be made therein by those skilled in the art except as it may be limited by the claims.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A draft gear adapted to be operatively connected to a coupler and to be disposed in a center sill of a railway vehicle, said draft gear comprising a pocket and a cushioning means therein, means comprising a front follower for transmitting coupler forces to the cushioning means for absorption thereby, said cushioning means comprising a pair of compressible cushions disposed in end to end relationship in said pocket with a first cushion abutting the front follower and the second cushion adjacent to the rear end of the draft gear, a rigid plate between the two cushions, the cross-section of said pocket adjacent to the second cushion being less than the cross-section of the pocket adjacent to the first cushion and less than the cross-section of the rigid plate thereby providing a stop for the plate, each of said cushions comprising a plurality of face to face elements having a rigid sheet carrying on each face thereof symmetrically disposed frusto-shaped substantially non-porous elastomeric protuberances having their bases secured to the sheet and the apices of the protuberances carried by one sheet abutting the apices of the protuberances of the facing sheet, and a flexible elastomeric homogeneous foam filling the interstices between the protuberances and joining the elements together.

2. The draft gear of claim 1 wherein the protuberances are frusto-pyramidal shaped.

3. The draft gear of claim 2 wherein each of said cushions is separated into two end to end parts by a metal disc spacer.

4. The draft gear of claim 3 wherein the said rigid sheets are metal, the protuberances are rubber and the foam is a polyurethane foam having a density of from about 18 to about 50 pounds per cubic foot.

5. The draft gear of claim 4 wherein the rigid plate is metal, a metal plate is disposed beween each cushion and the adjacent follower, an axial bore extends through the plates and the cushions and a rod extends through the bore, said rod being adapted to slide in the bore upon compression and release of the cushioning means.

6. The draft gear of claim 1 wherein the protuberances are rubber, the rigid sheets are metal and the foam is an elastomeric polyurethane foam.

7. The draft gear of claim 6 wherein said cushioning means comprises four pads of face to face metal sheets carrying on each face thereof frusto-pyramidal shaped rubber protuberances, an intermediate meal plate separates the pads into buff and draft pairs, and a liner in the pocket about the buff pads reduces the cross-section to less than the cross-section of the intermediate plate whereby expansion of compressed buff pads exerts a back pressure only against the intermediate plate and back pressure against the coupler shaft is only exerted by the draft pads.

8. The draft gear of claim 7 wherein the cushioning means has an axial bore and a rod is disposed in the bore and secures the elements of the cushioning means from separating.

9. The draft gear of claim 8 wherein a U-shaped metal member encloses the end of the rod and permits longitudinal movement of the rod between the legs thereof.