GB1400415A - Means for adjusting the separation between two relatively movable members - Google Patents

Abstract

1400415 Internal shoe drum brakes; slack adjusters GIRLING Ltd 7 July 1972 [9 July 1971 11 Sept 1971] 32301/71 and 42462/71 Heading F2E Means for automatically adjusting the separatoin between two relatively-movable members, e.g. a strut 6 and a brake shoe 2 of an internal shoe drum brake, comprises a lever 19, 20, Figs. 5, 8, mounted on one of the members, e.g. shoe 2, a cam 13 rotatably mounted on the lever and adapted to bear on the second member, e.g. strut 6 to define the spacing between the members, a ratchet element 14 associated with the cam, and a pawl 23 co-operating with the ratchet element for rotating the cam 13 relative to the lever 19 when pivotal movement of the lever in one direction exceeds a predetermined amount. The strut 6 indirectly bears on the opposite shoe 1, Fig. 8, so the latter shoe may be regarded as the above-mentioned second member, and it is the separation between the shoes which is automatically adjusted, to take up lining wear. Lever 19 is connected to shoe 1 by a tension spring (not shown); the ratchet element 14 is in the form of a disc integral with cam 13, and a second cam 12 is provided, both cams being keyed on a spindle 11. The spindle 11 engages in a notch 10 provided in the web of shoe 2. Pawl 23 having locating notches 25, 26 is retained in an opening 24 in the web of shoe 2 by a spring 18 which also urges it into contact with the ratchet disc 14, Fig. 6. The shoes are applied by a double-ended hydraulic cylinder (not shown) located between their upper ends and released by a tension spring (not shown). In operation, when the shoes are separated on brake application, lever 19 is pivoted clockwise about end 20 by the spring (above referred to) which connects it to shoe 1, so spindle 11 is moved slightly out of notch 10, and ratchet disc 14 is drawn away from pawl 23. If lining wear results in pawl 23 jumping a tooth, disc 14 is rotated clockwise on brake release, so a portion of each of cams 12, 13 of greater radius now contacts the end of strut 6. Preferably strut 6 forms part of a mechanical applying means for parking as shown in Fig. 8: such application does not result in slackadjustment. In Figs. 1 to 4 (not shown) the pawl is of a different shape, and is accommodated in an edge notch of the web; spring 18 is located above the web.