GB1429629A - Vehicle brake operating devices and to brake assemblies - Google Patents

Abstract

1429629 Disc brakes; wear adjustment; preventing rattle AUTOMOTIVE PRODUCTS Ltd 7 Nov 1973 [14 Nov 1972] 52544/72 Heading F2E A disc brake with brake pads 16, 17 includes a cylinder 12 containing a piston 24 movable to apply the pad 16 to a disc 10, the retracted position of the piston 24 being adjustable to compensate for pad wear by adjusting the length of an abutment member comprising a screw-threaded stem 27 and an internally screwthreaded sleeve 38 mounted on the stem 27; the piston 24 is movable by fluid pressure within the cylinder 12 or mechanically by rotation of the stem 27 by pivoting of a lever 31 the lever 31 being coupled to the stem 27 via a pawl 35 urged resiliently into engagement with teeth 32 formed on the stem 27 outside the cylinder 12, and the pawl 35 being disengageable from the teeth 32 to allow rotation of the stem 27 to reduce the length of the abutment member 27, 38 when the wear on pads 16, 17 requires their renewal. As shown, the pawl 35 is defined by a catch member 33 pinned at 34 to the lever 31, a coil spring 36 urging the pawl 36 into engagement with the teeth and acting through the catch member 33 upon the lever 31. The cylinder 12 forms part of a fixed support 11 surrounded by a movable member 22 and lugs 13 secure the support 11 to a flange of a stub axle or an axle casing. The support 11 also has projections 14 between which the pads 16, 17 are mounted on pins 51, the pins 51 are held within holes in a bent-up portion 47 of a member 45 by retaining clips, and the member 45 also has portions 49 extending normal to the disc 10 and having secured thereto a wire clip 50 for locating the member 22 in a chordal plane on the respective side of the brake disc 10. An antirattle plate spring 53 supported by the pins 51 bears on the outer edges of backing plates 20, 21 of the brake pads 16, 17. When fluid pressure is admitted to the cylinder 12 the piston 24 is moved to apply the pad 16 and a piston 25 is moved to act upon member 22 to apply the pad 17. During pressure actuation the stem 27 is carried by the piston 25 and the sleeve 38 moves with piston 24 until a clearance between the co-operating threads is taken up. If further separation of the pistons 24, 25 occurs the sleeve 38 tends to be left behind the piston 24, separating respective frusto-conical clutching surfaces 39, 40 on the sleeve 38 and the piston 24 but the action of a spring 41 causes sleeve 38 to rotate to increase the length of abutment member 21, 38 thereby compensating for brake pad wear. The brake is applied mechanically by rotation of stem 27 by movement of lever 31 against the action of spring 36, e.g. by means of a Bowden cable. The sleeve 38 is held against rotation by clutch surfaces 39, 40 and the stem 27 rotates to axially separate parts 38, 27 to apply the brakes. By pivoting the catch member 33 relative to lever 31 against spring 36 the pawl 35 is disengaged from teeth 32, and the stem 27 may then be rotated to reduce the length of abutment member 27, 38 to allow renewal of pads 16,17.