GB525340A - Improvements in and relating to electric hoists - Google Patents

Abstract

525,340. Electric hoists. YALE & TOWNE MANUFACTURING CO. Feb. 17, 1939, No. 5406. Convention date, Oct. 20, 1938. [Class 78 (v)] An electric hoist comprises a winding drum 25 keyed to a sleeve 22 carrying a pinion 28 which is driven through gearing 30, 34, 36 from a co-axial shaft 21 coupled to a motor shaft 19. The pinion 34 is internally threaded to ride on its shaft 35 against a friction disc 33 which carries a pinion of the gear train, gripping in this action a ratchet wheel 31 held by a spring- pressed pawl 32, which normally sustains the load when the motor stops. On reversing the motor the pinion 34 retracts from the disc 33, thus freeing the wheel 31 and allowing the load to fall. A rate of fall greater than that determined by the motor speed will, however, result in the disc 33 and pinion 34 being brought toward one another again, with binding of, and effective pawl action on, the wheel 31. The outer end of the shaft 21 carries the drum 37 of a band brake, the bands being normally spring- pressed on to the drum exterior, but having their ends forceable apart. by a cam 40 on a shaft 45 rockable by the core 43 of a solenoid in the motor circuit. The inside of the brake drum 37 is furnished with vanes which draw air in through louvres 47 to cool the drum and adjacent parts, an exhaust vent 47a being provided below the casing. The hoist has bolt-eyes 11 for suspension from a trolley, and the cable 48 passes round a sheave 49 for attachment to the drum casing. Hand-operated switches control the motor and brake solenoid, and a pivoted lever 55 extends across the path of the rising sheave to shut off the power automatically at the end of the wind.