VEHICLE DRUM BRAKES

摘要

Adjuster means include a plurality of adjustment members 78 operated in unison to move (a) friction member(s), and an operating member 91 having thereon respective pawls 110 for engagement respectively with sets of ratchet teeth on the adjustment member. In the drum brake of Figures 8-13 screw-threaded said adjustment members 78 are rotated with respect to a non-rotatable nut 79 each time the amount of camshaft rotation required to apply the brake exceeds a predetermined value. A sensor bar 90 which rotates with camshaft 76 moves from beneath an operating bar 91 allowing an edge 114 of the latter to snap into the path of return movement of the bar 90. Upon release of the brake, the bar 90 engages the edge 114 and moves bar 91 against the action of a spring (107) until a ramp surface 115 on bar 91 engages a fixed pin 101 and causes edge 114 to spring clear of the bar 90, whereupon the bar 91 returns to its starting position under the action of the spring (107). During this angular reciprocation of the bar 91, pawls 110 thereon engage respective ratchet wheels 111 on the adjustment members 78 and rotate the latter by the same amount. In arrangement of Figures 1-7 a block (18) of friction material is carried by a tray (19) which is moved bodily upon application of the brake, the block being moved along the tray by means of two adjustment member screws (46) to compensate for wear. A bar (54) with pawls (55) acts on ratchet wheels (53) and both screws are rotated by the same amount when adjustment is required.