The present invention relates to railway car coupling arrangements and, more particularly, to drawbar connections with slack adjusting wedges.
With the higher loads carried by modern railway trains, it is important to maintain close butted relationships between coupler draft components to lessen impact forces under buff conditions. Since most drawbar connection parts are cast with little or no finish machining to provide dimensional control, it is desirable to provide a coupling device which is self adjusting under various wear conditions to lessen the slack in such connections. One type of self adjusting articulated connection is shown in U.S. Pat. No. 3,716,146.
In slackless drawbar coupling arrangements, the drawbar extends between the sides of the car sill. The butt end of the drawbar is arcuate convex and abuts a complementary front concave surface of a follower block. The back surface of the follower abuts the front surface of a wedge shim which has a rear surface that abuts the rear wall of the pocket casting within the car sill. Either or both of the front and rear surfaces of the shim member diverge upwardly to provide the gravity assisted wedging force which makes the coupling arrangement slackless. When the butting surfaces become worn, the shim member drops slightly to maintain the essentially slackless connection.
In the pocket casting of the drawbar coupling arrangement, top, bottom and vertically disposed side walls provide a cavity for the follower and the shim. The side walls limit the lateral translation and therefore rotation of the follower about the vertical axis of arcuate butt end of the drawbar upon the horizontal angling of the drawbar. Such rotation of the follower may cause the wedge shim to rotate about the car longitudinal axis and possibly hang up between the vertical walls, especially when the shim is small in height relative to its width. The known method of controlling such rotation of the follower and the relative orientation between the shim and the follower is to provide for a very close tolerance between the vertical side walls of the cavity and the shim and the follower side edges. Due to the cast nature of such components the procedure requires an uneconomical amount of tolerance design and machining of finished parts.
Accordingly, it is an object of the present invention to provide an improved slackless drawbar coupling arrangement.