Brake shoe adjusting mechanism for a railway vehicle braking unit

Claim 1

A braking unit for mounting on a spring supported frame of a railway vehicle, and comprising a housing adapted to be attached to the spring supported frame, actuator means on said housing, a brake shoe carried by said housing and engageable with the peripheral braking surface of a railway vehicle wheel, means within said housing for translating movement of said actuator means into a force to move said brake shoe into braking position against said wheel, and means within said housing and responsive to variation from a predetermined distance between the disengaged brake shoe and wheel for adjusting automatically from either direction the play between the disengaged brake shoe and the wheel, said adjusting means being moveable radially with respect to the vehicle wheel and comprising a casing slideably mounted within said housing for movement toward said vehicle wheel in response to said translating means, a helically splined spindle slideably mounted within said casing for axial movement therein, first spring means urging said spindle toward said wheel, a coupling nut threaded on said spindle splines and having oppositely disposed coupling surfaces thereon, a pair of oppositely disposed coupling surfaces on said casing and straddling said nut coupling surfaces, the distance between said casing coupling surfaces being greater than the distance between said nut coupling surfaces, second spring means urging said coupling nut toward the wheel, and abutment means resiliently mounted within said housing at a distance from said coupling nut when the brake is disengaged equal to the play between the disengaged brake shoe and the wheel braking surface and yieldable under the force exerted by said coupling nut and said second spring means, said casing and spindle both being hollow cylinders with their opposite ends being closed, and a spring within said spindle acting against said closed ends to urge said closed ends apart.