BACKGROUND OF THE INVENTION Reduced-slack drawbar assemblies or systems typically include a device to cushion and absorb forces placed on the system during car operation. The cushioning and absorption of forces is always done in the buff direction and sometimes in the draft direction as well. While such devices have acceptable absorption capacities, they are often lacking in mechanisms which protect the device against over-solid conditions.

SUMMARY OF THE INVENTION The present invention overcomes the disabilities of the prior art by providing a draft gear having a very high preload, limited axial travel, high energy absorption in both buff and draft directions, and spring package protection in over-solid situations.

In accordance with general draft gear design, the present invention includes a housing with a closed end and an open opposite end which is provided with an internal pocket area wherein are located tapered wear liners. A wedge is mounted for axial movement in the open end of the housing and is situated for direct application of draft or buff forces. Friction devices are positioned within the housing, between the wedge and the wear liners, to absorb through friction some of the energy created by the application of a force to the wedge. A spring seat is positioned between the friction devices and a spring package which can be either an elastomeric pad stack or steel spring group.

The friction devices of this invention include at least two opposed friction shoes, each having a first flat angled inner surface in engagement with a corresponding flat angled inner surface of the wedge. The angled inner surface and the corresponding flat angled inner surface of the wedge form a first selected angle with respect to the major axis of the housing. Each of the two friction shoes also has a second flat outer surface in engagement with one of the two tapered wear liners, located in and at opposite sides of the open end of the housing, forming a second selected angle with respect to the major axis of the housing. Each of the friction shoes also has a third flat, angled face in engagement with a series of two flat angled faces formed in the spring seat. The individual third flat angled face of the shoe and the individual flat face of the spring seat form a third selected angle with respect to the major axis of the housing.

In the preferred embodiment of the invention, the first selected angle of the adjoining surfaces of the friction shoe and the wedge is about 40 degrees, plus or minus about 3 degrees, but as much as 5 degrees. The second selected angle of the adjoining surfaces of the friction shoe and the wear liner surface is about 5 degrees, plus about 3 degrees and minus about 2 degrees. The third selected angle of the adjoining surfaces of the friction shoe and the flat face formed in the spring seat is about 65 degrees, plus or minus about 3 degrees. As is appreciated, all of these angles are measured with respect to the major axis of the housing. An elastomeric pad stack comprises a plurality of concentric elastomeric springs which are made in accordance with U. S. Patent Nos. 4,198, 037; 4,566, 678 and 5,351, 844, which are incorporated by reference herein, may be employed to absorb additional energy. A spring package comprising steel springs can also be employed as an alternative to the elastomeric pad stack.

Thus, an object of this invention is the provision of a draft gear for a reduced- slack drawbar assembly which fits in a standard pocket and has no more than about 25 mm of travel.

Another object of this invention is the provision of a draft gear for a reduced- slack drawbar assembly which absorbs energy in both the buff and draft directions and has a metal shell to protect the spring package, whether an elastomeric package or a steel spring group, in the over-solid condition.

An additional object of this invention is the provision of a draft gear for a reduced-slack drawbar assembly which includes a housing and a spring package that is subjected to a preload of about 30,000 Ibs. to about 50,000 Ibs., depending on whether steel coil springs or elastomeric pads are employed.

DESCRIPTION OF THE DRAWINGS Other features and advantages of the invention will become apparent in the following description of the preferred embodiment taken in conjunction with the drawings, in which: FIG. 1 is a side view of one form of a draft gear embodying features of the present invention and shown in partial cross-section to illustrate various details of construction; FIG 2 is a end view of the draft gear of FIG1 ; FIG. 3 is a side view of another form of draft gear similar to FIG. 1 but having an elastomeric spring package rather than a steel spring package, and illustrating various selected angles for component parts comprising the draft gear; FIG. 4 is a typical force/travel curve of the draft gear which is the subject of this invention ; Fig. 5 is an elevational view of a wedge forming part of the draft gear illustrated in FIG 1, viewed from the left side of the page; FIG. 6 is an end view of the wedge of FIG 5; FIG. 7 is a side view of the wedge of FIG. 5; FIG. 8 is a cross sectional view as seen generally along line 8-8 of FIG. 5; FIG. 9 is an inside elevational view of one of two friction shoes forming part of the draft gear illustrated in FIG. 1 ; FIG 10 is a side elevational view of the friction shoe of FIG. 9; FIG. 11 is a cross sectional view of the friction shoe taken along line 11-11 of FIG. 10 FIG. 12 is an outside elevational view of a spring seat forming part of the draft gear illustrated in FIG. 1; FIG. 13 is a cross sectional view of the spring seat as seen generally along line 13-13 of FIG 12 ; FIG. 14 is a side elevational view of the spring seat of FIG. 12; FIG. 15 is a side elevational view of a wear liner forming part of the draft gear illustrated in FIG. 1; and FIG. 16 is an outside elevational view of the wear liner of FIG. 15.

DESCRIPTION OF THE PREFERRED EMBODIMENT As illustrated in the drawings, a draft gear 10 for a reduced-slack drawbar assembly seen in FIG. 1 includes a housing 12 having an axial bore 14 with one end thereof being closed by a fixed end wall or plate 16. The housing 12 is provided with an opposite open end 18 which includes an internal pocket area 20 wherein are located first and second tapered wear liners 22 and 24. The two wear liners 22 and 24 each have tapered friction surfaces 26 and 28, wherein is carried at least one lubrication insert 30 and 32. Reference to FIGS. 15 and 16 will provide more information about the liners 22 and 24.

The open end 18 carries through the generally box-shaped bore 14 with side pockets 20, all of which terminate with the end surface 34. The open end 18 and the fixed end wall 16 are integrally interconnected by a transition wall section 35 which serves to bind the two together both internally and externally.

Friction devices, such as first and second friction shoes 36 and 38, are placed opposite each other, as shown in FIG. 1, in sliding friction producing engagement with the wear liners 22 and 24. The friction shoes 36 and 38 are assembled as shown in FIG. 1 whereby defining an outwardly opening pocket for receiving the tapered end 40 of the wedge 42.

In addition to the resistance developed in the open end 18 during inward movement of the friction shoes 36 and 38, by the wedge 42 and the spring seat 46, a spring package 44, which in FIG. 1 is a steel spring group while in FIG. 3 it is an elastomeric pad stack, is provided within the transition wall section 36. As shown in FIG. 4 the spring package carries a preload of about 26,000 Ibs. and after about 0.98 inches of compression generates a resistance of about 500 KIPS. Maximum compression is about one inch at which point the outer surface 43 of the wedge 42 is flush with the end surface 34 of the housing 12. Further, it should be noted that at about 0.025 inches of travel, the resistance of the draft gear 10 has increased to about 75 KIPS. As is conventional, a follower plate is normally placed against the wedge and through it the draft gear is compressed. In the event a very large force is exerted against the follower, a force sufficient to compress the spring package beyond its limits, the wedge in FIG. 1 moves to the left for a distance of about one inch, at which point the follower bottoms out on the end surface 34 which exist as positive stops. As a result the spring package is not exposed to the unlimited application of input force. As is conventional, the spring package maintains the wedge 42, the friction shoes 36 and 38, the liners 22 and 24 and the spring seat 46, in operative engagement with each other and with the housing, both during the operation of the draft gear, as well as during periods of non-operation. Additionally, the existence of the preload, once the gag is removed, causes the draft gear to create an effective load on the draft lugs and eliminates the slack in the yoke and gear assembly. Further the spring package, due to its very high preload, resists inward movement of the friction shoes 36 and 38 via a spring seat 46.

The spring seat 46 is disposed between the outward end 48 of the spring package 44 and the third flat angled faces 50 and 52 of the friction shoes 36 and 38 and is adapted for longitudinal movement in the housing 12 to compress the spring package 44, when force is applied to the wedge 42. As shown in FIGS. 12-14, the spring seat 46 includes first, and second flat angled portions 54 and 56, is generally rectangular in shape and has a front 58 and a rear surface 60.

Each of the two friction shoes 36 and 38 are the same in size, shape and function and thus discussion will be limited to friction shoe 38 as shown in FIGS. 9-11 with the understanding that it applies as well to friction shoe 36. The friction shoe 38 has a first, flat angled inner surface 62 in engagement with a corresponding flat angled inner surface 64 of wedge 42. As seen in FIG. 3 these two surfaces form a first selected angle 66 with respect to the major axis 68 of the housing 12. The friction shoe 38 also has a second flat outer surface 70 (FIG. 9) in engagement with one of the tapered friction surfaces 26 or 28 at the two tapered wear liners and forming a second selected angle 72 with respect to the major axis 68 of the housing 12. Further the friction shoe 38 has a third flat angled face 50 in engagement with one of the flat angled faces 54 or 56 of the spring seat 46 whereby forming a third selected angle 74 with respect to the major axis 68 of the housing 12.

The wedge 42 has first and second angled inner surfaces 64 and 65 which are the same in size, shape and function and thus discussion is limited to one thereof. To retain the wedge 42 and the friction shoes 36 and 38 in the open end 18, the wedge is provided with two outwardly projecting flanges 76 and 78 (FIG. 7). During assembly of the draft gear 10, the wedge flanges 76 and 78 are positively retained in assembled relationship in the housing 12 due also in part to the forces generated by the preload to which the spring package 44 is subjected.

As previously discussed, the two tapered wear liners 22 and 24 each have a lubrication insert. It is understood that both tapered wear liners 22 and 24 are the same in size, shape and function and thus discussion will be limited to tapered wear liner 22 as shown in FIGS. 15 and 16 with the understanding that it applies as well to tapered wear liner 24. The wear liner 22 includes an outer section 23 and an inner section 25, which carries the lubrication insert 30. The friction shoe 36 as shown in FIGS. 9 and 11 also includes an outer portion 27 and an inner portion 29, the lubrication insert 31 being carried in the top portion 27. Because the working stroke of the draft gear is limited to 25 mm, material from lubricating insert 31, in shoe 36, does not get distributed over the entire plane of engagement of shoe 36 with liner 22. The addition of lubricating insert 30 in line 22 enables lubricating insert material to be distributed over the plane of engagement of respective inner portions 25 and 29 of the liner 22 and shoe 36, thereby completing the spread of lubricating insert material over the whole liner and shoe engagement plane.

While embodiments of this invention have been shown and described, it should be understood that this invention is not limited hereto except by the scope of the claims.

Various modifications and changes may be made without departing from the scope and spirit of the invention as the same will be understood by those skilled in the art.