GB1152712A - Improvements in Automatic Adjusters for Vehicle Brakes. - Google Patents

Abstract

1,152,712. Brake wear adjusters. GIRLING Ltd. 15 March, 1967 [15 March, 1966; 5 May, 1966], Nos. 11208/66 and 19819/66. Heading F2E. An automatic wear adjuster for an hydraulic actuator of a vehicle brake, particularly for use in a disc brake, wherein an auxiliary mechanical actuator is fitted in a counter-member of the hydraulic actuator for operation between the latter and the adjuster, comprises a linear ratchet mechanism adapted to be stepped in response to excess travel between a piston of the actuator and the counter-member, which may be either the cylinder or a second piston, and means for positively holding the ratchet mechanism in engagement when under load, i.e. during mechanical operation, to prevent risk of slipping. In the embodiment of Fig. 1, the actuator consists of a fixed cylinder 10 containing a piston 15 which applies a pad 12 directly to one face of a disc (not shown), a second piston 16, constituting the counter-member, acting on a slidable yoke 11 to apply a pad 13 to the opposite disc face. Between the two pistons is disposed a thrust member 23, which is urged by a spring 37 towards a cam 17 journalled in the piston 16, being connected to the cam by a dolly 19, a first ratchet member 21, secured to the piston 15 and having buttress teeth arranged on each of four sections spaced by grooving, and a second ratchet member 22, Fig. 4, consisting of an annular element 27 slotted at 28 to provide spring fingers 29 each having a series of buttress teeth 30 arranged to co-operate with the teeth on the member 21. The member 22 has limited axial movement within a bore in the thrust member, whereby upon movement apart of the pistons during hydraulic operation the member 22 moves into engagement with a flange 36 and then, should adjustment be necessary, is drawn over the member 21 to slip one or more teeth to effect adjustment. During mechanical operation, however, the axial force acting on the thrust member 23 is transmitted via co-operating conical faces 34, 35 on the thrust member and spring fingers 29, respectively, to wedge the two sets of teeth firmly in engagement. The provision of the grooves in member 21 and the slots 28 in member 22 allows the teeth to be brought out of engagement by manual rotation of one of the members, when new linings are fitted. In a modification, Fig. 6, the first ratchet member is the piston 15 itself which is provided with teeth 52 on its inner periphery, the spring fingers 51 having corresponding external teeth and the conical faces 57 on the thrust member and second ratchet member being disposed so as to cause the spring fingers to be pressed outwardly against the piston 15 during mechanical operation. In another embodiment (Fig. 8, not shown) the arrangement is similar to that of Fig. 1 except that the actuator has only a single piston of basically annular form working in an annular chamber in a floating cylinder having a detachable head in which the cam is journalled, the ratchet mechanism being thus located in air instead of being immersed in fluid. A further embodiment (Fig. 9, not shown) is basically the same as that of Fig. 1, but the thrust member is itself formed as a piston and is acted on by the fluid in opposition to the spring (37) so that adjustment is only effected when hydraulic pressure is below a predetermined value above which the spring is overcome.