brake cylinder for disc brakes with nachstellvorrichtung

摘要

1434369 Wear adjustment; spot-type disc brakes AUTOMOTIVE PRODUCTS Ltd 19 June 1973 [19 June 1972] 28530/72 Heading F2E The brake operating motor cylinder 13 of a spot type disc brake comprises a piston 14 co-operable with a thrust member of adjustable length and constituted by a stem 20 and a sleeve 25 in screw threaded interengagement: to adjust for wear during a fluid pressure brake application the stem 20 is rotatable on the sleeve 25 but should excessive pressure be applied an arrangement comprising a piston 32 and a peg 37 acts to prevent adjustment. As shown, the sleeve 25 and piston 14 have respective frusto-conical surfaces 26, 27 which form a core clutch and the sleeve 25 is urged towards the piston 14 by a spring 28. A screw thread 24 on stem 20 co-operates with a thread on sleeve 25 but there is a clearance between the threads to allow of relative axial movement without rotation-the screw thread 24 is preferably of square cross-section. The piston 32 is received in a bore through sleeve 31 and is biased by a spring 33. The piston 32 has an annular recess 35 and the peg 37 is received in recess 35 and also projects through a radial bore 36 in stem 20 to co-operate with the remainder of thread 24 on stem 20 to form a continuous thread. During normal brake actuation piston 14 will be moved rightwardly and as sleeve 25 follows this movement the clearance between the threads is first taken up and thereafter the sleeve 25 rotates on stem 20 to adjust for wear. In the event of excess pressure being supplied to motor cylinder 13 (e.g. during a panic stop) piston 32 is moved against the bias of spring 33 and coaction between a ramp surface 39 on peg 37 and recess 35 forces the peg 37 radially outwardly and locks sleeve 25 against rotation. The brake may be applied mechanically by rotation of stem 20 about its axis by means of an arm connected to a Bowden cable. The cylinder 13 is formed integrally with a slidable body 10 having a bridge member 12.