GB1462180A - Actuating device - Google Patents

Abstract

1462180 Slack-adjusting brake transmitting mechanism TWIFLEX COUPLINGS Ltd 15 Aug 1974 [28 Aug 1973] 40444/73 Heading F2E A brake actuator includes a diaphragm acting on a slide rod to which a push rod is screwed, the two rods being relatively rotated during the return stroke when the actuating stroke length exceeds a predetermined value and being coaxial with the line of action of the diaphragm. As shown a brake is applied by downward movement of a push rod 22, non-rotatable relative to a casing 1, on pressurization of a diaphragm chamber 6. On excessive movement due, e.g. to brake-pad wear, a pivoted and spring-loaded pawl 31 rides over the next tooth on a ratchet ring 30 secured to a cylinder 18, secured in turn to a slide rod 14 acted upon by the diaphragm 5. On brake release, and consequent return of slide rod 14 by a spring 20, ring 30, and consequently slide rod 14, is forced to rotate, so push rod 22 is screwed out slightly by threaded connection 25 with slide rod 14. The effective length of the combination 14, 22 thereby increased. A resilient, rather than a pivoted pawl may be used. Instead of fluid pressure, brake application may be by a spring located above diaphragm 5, in which case release may be by fluid pressure under diaphragm 5 (Fig. 4, not shown) or by electromagnetic attraction, spring 20 being dispensed with in these cases. In Fig. 6 (not shown) the ratchet ring secured to the slide rod is acted upon by a further ratchet ring rotatable on the slide rod, spring urged towards the further ratchet ring and rotated in opposite directions on actuation and release by engagement of projections on it with a helical groove in a fixed part.