GB816969A - - Google Patents

Abstract

816,969. Topping winches. SCHARFFE & CO. April 18, 1957 [April 21, 1956], No. 12782/57. Class 78 (5). Winch drum 6 is driven from reversible motor 12 through gearing 14, 15, 17, 18, 20, 11 and is furnished with brake 500 and ratchet-and-pawl 47, 21, the two being interlocked so as to be operated by a single lever 26. The brake 500 comprises disc 50 which is frictionally engaged by plate 54 biased by springs 55, the disc being connected to and driven by the motor shaft 13 through shaft 48 and gears 63, 64, there being additionally included a centrifugal brake 62. To raise the derrick the starting-handle 34 is swung clockwise by the operators to rotate controlshaft 32 so that cam 41 operates a switch to start motor 12 whilst cam 42 acts against springs 55 to release brake 500. To lower the derrick, handle 34 is swung firstly clockwise, then anti-clockwise, the first movement causing the motor to rotate clockwise to free the pawl- and-ratchet and the second movement causing the motor to lower the derrick whilst releasing the brake. To avoid clattering by the pawl- and-ratchet the pawl may be swung aside from the ratchet by means of the lever 26. The strength of motor is sufficient only to raise the derrick when the latter is unloaded. The strength of the pawl-and-ratchet, however, is sufficient to support the derrick even when fully loaded.