Patent GB-1118833-A (GB)
Title: Self-adjusting brake actuating mechanism
IPC: F16D65/14
Filed: 1966-06-15
Abstract: 1,118,833. Brakes. H. S. HOLLNAGEL and H. E. HOLLNAGEL. 15 June, 1966 [16 June, 1965; 3 June, 1966], No. 26636/66. Heading F2E. Brake operating mechanism, which includes a cylinder housing 11, a piston 26 connected to a brake element (e.g. pad 27) and working in a recess or bore 19 of the housing, and a sealing ring 40 disposed in an annular recess defined between the wall of the cylinder bore and a reduced rear portion of the piston, is provided with automatic wear adjustment means comprising a friction ring 41 which is an interference fit in the bore 19 immediately rearwards of the sealing ring, a washer 43 which has a flange 44 seated against the base of an annular groove 42 in said piston and a flange 45 engaging the friction ring, and a ferrule 47 retained in said groove by spring clip 49, the forward end of the ferrule being spaced away from the flange 44 by spring 46 in the brake released position a distance equivalent to the normal brake clearance. The housing forms a fixed caliper straddling a brake disc 29 which has axial play so that when piston 26 is moved to the left on brake application, the disc is first engaged by the pad 24 and then moved into contact with another pad 20, carried by the housing, said pads being preferably circular in shape and secured to the caliper and piston by offset screws to prevent pad rotation. On leftward movement of the piston, ferrule 47 is carried with the piston and compresses spring 46. Should excessive brake pad wear or clearance exist, the ferrule engages the flange 44 and carries the washer 43 with it. This washer in turn overcomes the frictional resistance of the friction ring with the wall of the cylinder bore and moves it a distance equivalent to the excess brake pad clearance. On brake release, the friction ring remains at its repositioned station, and spring 46 returns the piston and spaces the flange 44 of the washer from the ferrule by a distance equal to the desired pad clearance. The friction ring is provided with peripheral slots, Fig. 2 (not shown). In a modification, Figs. 4 and 5 (not shown), friction ring and washer 41 and 43 are replaced by a single double flanged friction ring washer (51) having frictional engagement with the bore 19. In a further embodiment, Fig. 7, the adjustment means comprises a friction ring 59 which is notched at its inner and outer peripheries to give it a degree of flexibility and which is frictionally fitted into the caliper bore 19, a plate 63 secured to the piston and having peripheral portion spaced from the piston by a distance 65 corresponding to the desired pad clearance, and a sinuous wave shaped spring ring 54 disposed between the outermost portion of the plate 63 and the friction ring. On brake application, piston and plate 63 move to the left compressing spring ring 54. If pad clearance or wear is excessive, the plate engages the friction ring and repositions leftwards a distance equivalent to the excess wear. On brake release, spring ring returns the piston and re-establishes the distance between the plate and the friction ring. The brake operating mechanism may be incorporated in an internal expanding brake.