GB642320A - Improvements in or relating to magnetically operated, speed responsive control apparatus - Google Patents

Abstract

642,320. Dynamo - - electric machines. INDIANA STEEL PRODUCTS CO. June 26, 1947, No. 16874. Convention date, Jan. 2. [Class 35] [Also in Groups XIX and XXXVII] A magnetically-operated, speed-responsive control apparatus comprises a rotating primary control member, a movable secondary control member, means for producing a magnetic field between these two members to urge the secondary control member in one direction and an eddy current member disposed in the magnetic field between the two control members so that when either the magnetic field or the eddy current member is rotated by the primary control member, the magnetic field is modified by eddy currents as a function of the speed to permit movement of the secondary control member in the opposite direction. In the arrangement shown for actuating switch contacts 44 included in the circuit of the starting winding 8 of an induction motor 1 which is enclosed in a sealed housing 6, the primary control member comprises the rotor shaft 14 on which is secured a bar magnet 34, and the housing has an end wall 32a of conducting material. The secondary control member 36 comprises a contact actuating, pivoted magnetic member 38 attracted towards the magnet 34 against the action of a spring 42 so as to close the contacts 44. When the rotor speed attains a predetermined value the spring overcomes the reduced magnetic pull and the contacts open. In an alternative arrangement, Fig. 3 (not shown), the eddy current member is secured to the rotor shaft and disposed between a non-magnetic and non-conducting end wall of the cup-shaped member and a magnetic member which may also be secured to the rotor shaft extension. The secondary control member comprises a U-shaped magnet pivoted at the end of one leg.