Patent GB-1449653-A (GB)
Title: Disc brake caliper actuating assemblies incorporating a disc  brake gap adjusting mechanism
IPC: F16D65/56
Filed: 1973-11-08
Abstract: 1449653 Disc brake actuating assemblies; slack adjusters ISHIKAWAJIMA-HARIMA JUKOGYO KK and AKEBONO BRAKE INDUSTRY CO Ltd 8 Nov 1973 [10 Nov 1972] 51820/73 Heading F2E A disc brake caliper actuating assembly incorporates a disc brake gap-adjusting mechanism and comprises a pressing piston, e.g. 4, Fig. 1, frictionally held by a first cylinder of a caliper assembly 1, and adjustment bolt, e.g. 5, which is screwed into an actuating piston, e.g. 8 fitted in a second cylinder, e.g. 7, and which, wherein an operative condition, is frictionally connected at one end with the pressing piston, and an actuating spring, e.g. 20, housed in a third cylinder, e.g. 18, and arranged to act on the actuating piston to apply the brake; the other end of the adjustment bolt 5 is arranged to be acted upon by a spiral spring, e.g. 25, positioned in such a manner that the turning force stored in it is effective to thrust the adjustment bolt 5 rotatably out through the actuating piston 8 whenever there arises a gap between the bolt and the pressing piston 4 so that the gap will be automatically adjusted to restore the adjustment bolt to the operative condition. As shown in Fig. 1, the hollow piston 4 slidable in the first cylinder engages an inner brake pad 28, while the slidable caliper assembly 1 engages an outer brake pad 27; a friction ring 13 is located around piston 4 and is spaced from a snap ring 15 by a wave washer 14. The brake is normally applied by the actuating spring 20 through the actuating piston 8 and the adjustment bolt 5 screwed into it, the head of bolt 5 being in contact with the end of piston 4 and wave washer 14 being thereby stressed. Release is effected by the application of pressure fluid at 10 to a chamber 9 to retract piston 8, whereupon wave washer 14 retracts piston 4, maintaining it in contact with the head of bolt 5. When pads 27, 28 are worn, increased travel of piston 8, bolt 5 and piston 4 occurs on brake application, so piston 4 is pushed slightly relative to friction ring 13 and takes up a new position with respect to it. On brake release, piston 4 is retracted only through the distance governed by wave washer 14, while piston 8 and bolt 5 are fully retracted. The head of bolt 5 is thus separated from piston 4 and is no longer frictionally restrained thereby. In consequence, the spiral spring 25, Fig. 2, having its outer end 32 fixed by a groove in a retaining lid 26, Fig. 1, unwinds slightly, thereby rotating an adjustment spindle 22 which has a tip 23 located in a square section hole 6 in bolt 5. Bolt 5 is thus unscrewed from piston 8 until the bolt head once more contacts the end of piston 4, whereupon the frictional contact between these parts stops further rotation of bolt 5. In another embodiment (Fig. 3, not shown) the compression of the actuating spring may be varied by movement of an adjustable stop behind it, and the retraction stroke of the actuating piston may be varied by adjustment of a similar stop. Also, the caliper may be restored to its original position relative to a fixed support, after progressive movement resulting from lining wear, by rotation of a bolt through a threaded hole in the caliper, the bolt contacting the outer friction pad.