GB1354631A - Disc brakes - Google Patents

Abstract

1354631 Spot-type disc brakes; fluid-pressure release; slack adjusting AUTOMOTIVE PRODUCTS Ltd 14 Dec 1972 [24 Jan 1972] 3275/72 Heading F2E In a spot-type disc brake which may be applied by a fluid-pressure-operated piston or by spring means acting on the same piston, and released by separate fluid pressure acting on at least one brake-release piston, the brake release piston or one of them is also arranged to be acted on by the first-mentioned fluid pressure to oppose partially the action of the spring means. As shown, brake pad 19 may be applied to disc 10 by pressure fluid supplied at 29 to the inside of brake-applying piston 18, pad 21 being applied by reaction through axially-movable disc 10 and fixed caliper 11 or fixed disc 10 and movable caliper 11. Alternatively, in the absence of fluid pressure at 30 and 31 acting on release pistons 27 and 26 respectively, Belleville washers 23 apply the brake through piston 26, integral sleeve 33, stem 32 threaded within it, these last two members constituting a push rod 22, frusto-conical surfaces 36 on stem-head 35 and 37 in piston 18, and piston 18. If, in the absence of fluid pressure at 30 and 31, fluid pressure is supplied at 29 to actuate piston 18, then the brake will tend to be applied both by fluid pressure and spring action: but the spring force is partially overcome by pressure at 29 communicating also with the left-hand end of a reduced portion 28 of brake-release piston 27. Thus the risk of excessive load is reduced. With fluid pressure supplied at either 30 or 31, the spring force is overcome and the brake may be applied and released by admission of fluid pressure to, and release from, piston 18. Slack adjustment.-Piston 18 is prevented from rotating by peg 45, sleeve 33 is normally prevented from rotating by engagement of non- circular extension 47 in plate 48, and stem 32 is normally prevented from rotating by engagement of surfaces 36, 37. During normal fluidapplication of the brake with piston 26 held by fluid pressure at 30 or 31, a spring 39 urges stem 32 to follow piston 18 until the clearance between screw-threads 34 is taken up. If piston 18 continues to move, surfaces 36, 37 separate, so spring 39, now under compression, is able to rotate stem 32 through thrust bearing 42, thus lengthening push rod 22 until surfaces 36, 37 again meet. Manual release.-When the brake is being applied by Belleville washers 23, inward movement of piston 26 &c. is limited by abutment against piston 27. If no fluid pressure is available at 30 or 31 and if push rod 22 is not at its minimum length, the brake may be released by removing plate 48 and rotating sleeve 33, to shorten push rod 22 and consequentially retract piston 18. Re-setting.-Before replacing worn brake pads, piston 18 may be retracted by rotating sleeve 33 as above. Brake-release piston 26 may be omitted, the other brake-release piston 27 being either fixed to sleeve 33 or co-operating with an abutment thereon. In Fig. 2 (not shown) two axiallyslidable brake discs are provided.