Patent GB-1057100-A (GB)
Title: Improvements in disc brakes
IPC: F16D55/226
Filed: 1964-12-03
Abstract: 1,057,100. Disc brakes. SOC. ANON. D.B.A. Dec. 3, 1964 [Dec. 4, 1963], No. 49257/64. Heading F2E. In a disc brake comprising a floating stirrup and friction pad assembly 12 located in a recess formed in a U-shaped fixed support member 15 having limbs 16 and 18 either side of a disc 10, a pair of levers 34, 36, pivoted by removable pins 38 at their outer ends to the support member, are biased by springs 54, connected between each lever and projections 56, against bearing surfaces 45 or 46 on opposite sides of the stirrup to urge friction pads 64, 66, Fig. 2 (not shown), into contact with the bottom 32 of the recess, thereby permitting axial movement of the stirrup but damping radial movement thereof to minimize noise. Lever extensions 44 carry blocks of plastics material having a low coefficient of friction to guide the stirrup axially and further reduce noise. In order to prevent inadvertent release of the stirrup from the recess in the event of spring failure, safety pins 40 secured to the levers, each of which levers comprise two arms located on either side of the limbs 16 and 18, pass through holes 42 of larger diameter in the fixed support 15. The clearances between pins 40 and holes 42 are such as to permit the springs to retain the stirrup against the base of the recess unhindered but prevent pivotal movement of the levers out of engagement with the stirrup. To facilitate replacement of the pads, the assembly 12 may be removed radially outwards on removal of the pins 38 and retraction of the levers, the line of action of the springs passing to the other side of the pins 40 to hold the levers in the reacted position. The relative dispositions of the pins 40 and the springs and the hole/pin clearances are such that, on the said retraction, the springs are not extended beyond any extension they may undergo during normal use as retention means of the stirrup. The friction pads, bevelled at 14, comprise linings bonded to sheet iron backing plates 67 which may be ribbed and which extend to the straight edges 30, 30<SP>1</SP> and 32 of the linings, but fall short of the arcuate edge thereof. The thus-reinforced edges 30, 30<SP>1</SP> transmit the braking torque to edges of the support member recess which are accordingly reinforced by plate members 22 and 24. The backing plates are each provided with a tapered hole 75, the hole of one plate being engaged by a split ring carried by a flanged projection 74 integral with a brake actuating piston 62 working in a cylinder formed in the cast stirrup and the hole of the other plate being similarly retained by a flanged bolt secured to the leg of the stirrup disposed on the other side of the disc as illustrated in Fig. 4 (not shown). Automatic wear adjustment means, Fig. 2, comprises a friction ring 102, located between a washer 96 and a dished plate 100 secured to the piston, which ring frictionally engages a pin 104 secured in the end of the cylinder. The distance j between the dished plate and the ring when the piston is in the retracted inoperative position defines the normal brake clearance. If on actuation of the piston 62, the piston stroke exceeds said distance j, cup 98 displaces the ring 102 on the pin. On brake release, an 0-ring seal in the cylinder bore, which has been distorted by movement of the piston, recovers its normal shape and, in doing so, retracts the piston until the piston abuts the washer 96 against the friction ring to restore the clearance distance j.