GB688247A - Improvements in and relating to clutch-brake mechanism - Google Patents

Abstract

688,247. Magnetic fluid clutch-brake combinations. BRITISH THOMSON-HOUSTON CO., Ltd. May 22, 1951 [June 2, 1950], No. 11934/51. Class 80 (ii). [Also in Group XXXIV] A combined clutch and brake employing a magnetically susceptible fluid, preferably a mixture of powdered iron and oil, comprises a; driven rotor 9 of magnetic material, a fixed: permanent-magnet brake 13, a driving rotor 20, 21, 22, and a fixed coil 23. Energisation of coil 23 overrides the field of magnet 13 so that iron powder which was concentrated in the gap between the rotor 9 and magnet 13, thereby braking the rotor, is drawn around the periphery of, and through holes 27 in, the rotor 9 to couple the driving and driven rotors. The annular magnet 13 (which may be replaced by an electromagnet) is surrounded by a non-magnetic ring 14 and a magnetic ring 15 secured to a non- magnetic housing 1. The housing has a magnetic cover 3 carrying the coil 23 which is arranged between inner and outer magnetic rings 20, 22 of the driving rotor, the spacer ring 21 being non-magnetic. The time delay between clutch and brake operation is predetermined by the clearance around the rotor 9 and by the size and number of the holes 27. Preferably excitation is by direct current, but alternating current, particularly of the higher frequencies, may be employed provided the magnetic parts are laminated. In a modification a magnetic rotor is keyed for limited axial movement on a driven shaft and is moved to clutching or braking position by the corresponding field, the gaps being filled with a magnetic fluid. Reference has been directed by the Comptroller to Specifications 649,553 and 686,141.