GB1480741A - Automatic adjusters for brake systems - Google Patents

Abstract

1480741 Automatic slack adjusters; spot-type disc brakes GIRLING Ltd 20 Sept 1974 [21 Sept 1973] 44402/73 Addition to 1190841 Heading F2E The present automatic adjuster makes use of a phenomenon described in the main Specification, namely that when a screw thread connection between two members is under a given load a larger torque is required to turn the members relatively to one another in a direction against the load than in a direction with the load, it dispenses with the thrust bearing formerly found necessary as an abutment for the adjuster return spring, and it incorporates an anti-knockback device to prevent reverse rotation of one of the rotatable members. Construction.-A strut 18, non-rotatable, has a non-reversible screw thread connection 27 with a nut 24, rotation of the latter in one direction effecting adjusting extension of the device. Rotation of nut 24 in the opposite direction is prevented by a one-way clutch mechanism shown as an annular ratchet member 40 splined to nut 24 and having teeth facing teeth on an end closure 41 of a fixed "container" 32, and held against it by a wavy washer spring 42. The nut 24 is in turn surrounded by an annulus 28 with which it has a reversible screw thread connection 31 of greater pitch than that of connection 27. A friction surface 35 on annulus 28 engages a friction surface 36 on an inturned flange 37 of container 32. A coil compression spring 33 is located between a shoulder 38, extending from nut 24, and annulus 28. One end of strut 18 is a sliding fit in a reduced bore 22 of a cylinder body 15 and is engaged by a dolly 20 in turn engaged by a cam 19. In operation, when no appreciable wear takes place, hydraulic pressure applied at a space 23 urges a piston 12 to the left and urges the strut 18, nut 24 and cylinder body 15 to the right. There is no appreciable clearance at connection 27, but axial clearance is provided at connection 31 to determine normal brake slack (container 32 being force-fitted in piston 12). Spring 33 is compressed. If friction-lining wear takes place during brake application, the clearance at reversible screw thread connection 31 is first taken up, after which this connection causes a relative rotation between nut 24 and annulus 28 (to lengthen the assembly); it is the nut which rotates, around strut 18. When the brake is released, the clearance at the reversible screw thread connection 31 is transferred to the opposite flanks of the threads, and because of the excess travel which previously took place due to lining wear, the connection 31 causes a relative rotation between nut 24 and annulus 28 but this time in the opposite direction. Also, this time, the pressure at friction faces 35, 36 is relieved and the frictional torque is greater at connection 27. Therefore annulus 28 rotates on nut 24 to re-set the adjuster. The adjuster may be incorporated in a spottype disc brake.