Spring-loaded brake cylinder for a railway vehicle brake

Claim 1

A spring-loaded brake cylinder for an air-brake system of a railway vehicle and having an auxiliary release device, comprising a cylinder having a piston therein and a first spring acting on one side of the piston to load the same in one direction and the other side of the piston being subjected to a pressure medium introduced into the cylinder, a first screw coupling comprising first and second coupling members, said first coupling member comprising a threaded shaft having a reversible thread thereon rotatably mounted within said cylinder and supported against axial displacement, said shaft having a first end, said second coupling member including a nut threaded upon said shaft, a compression spring acting upon said second coupling member, second coupling means for coupling said second coupling member to said spring loaded piston for retaining said second coupling member against rotation when the pressure acting against said piston is below a predetermined level, said second coupling means comprising an axially displaceable non-rotatable annular coupling element surrounding one of said first and second coupling members and having a coupling surface engageable with a corresponding coupling surface on the other of said first and second coupling members, a tubular member attached to said spring loaded piston, means for guiding non-rotatably said annular coupling element for axial displacement within said tubular member, an annular shoulder on said tubular member, said annular coupling element being disposed between said annular shoulder and one of said first and second coupling members, abutment means for limiting the axial displacement of said nut relative to said first end of said shaft in a direction opposite to said one direction of loading of said first spring, upon abutting engagement of said second coupling member with said abutment means said piston can be displaced by the pressure medium a distance greater than the distance required for disengagement of said second coupling member from said spring-loaded piston, and spring biased means for locking said annular coupling element with respect to said piston upon abutting engagement of said second coupling member with said abutment means, and a third spring acting against said annular coupling element with a force less than the locking force of said spring biased locking means.