GB1178932A - A Hoist Brake Application Retarding Device - Google Patents

Abstract

1,178,932. Winching apparatus; brakes; builders' hoists. MARTIN HOIST & ENG. CO. Ltd. 3 July, 1968 [21 July, 1967], No. 33783/67. Headings B8B and B8H. A device for retarding the speed of application of a winding drum brake in the event of overspeed of the drum or at the end of a wind, comprises a shock-absorbing unit 25 which is effective to slow down the movement of a linkage system 11, 14 controlling a combined brake and clutch arrangement for the drum 10. once the said linkage 11,14 has been unlatched from a further linkage system 16, 17 which normally controls the brake and clutch arrangemeat. The unit 25 mounted on the link 11 includes a plunger 26 on a rod 27 which is biased by a spring 28 outwardly of the unit cylinder, the latter having a small diameter orifice 30 and a large diameter pipe 24 for the exhausting of air from the cylinder during normal operation of the brake, whereupon the only retarding of the brake action is due to compression of the spring 28 as the rod 27 moves down to engage an abutment 29. Due to overspeed or at the end of a wind, a latch element 19 is pivoted on the link 17 out of engagement with the link 11 and an abutment 21 on the element 19 then releases a spring- loaded tap 22 on the link 11 into a position in which it closes the air pipe 24. Upward movement of the plunger 26 within the unit 25 and corresponding downward movement of the link 11, is therefore restricted by the airflow through the aperture 30, as the rod 27 engages the abutment 29. The latched linkage system 11, 14, 17 is normally lifted at one end by a control rope attached to an eye 18, to release the brake and engage the clutch, and is lowered by a weight 15 to apply the brake and disengage the clutch. During over-speed of the drum 10, a centrifugal device 31 engages a lever 35 to unlatch the element 19 via a rope 36. At the end of a wind, the element 19 is engaged by a load carrier, to unlatch the links 11 and 17.'