Control mechanism for electric motors

摘要

475,963. Automatic control systems. CHICAGO FLEXIBLE SHAFT CO. April 27, 1936, No. 11944. Convention date, June 3, 1935. [Class 38 (iv)] [Also in Group XXXVII] Speed.-A control switch for an electric motor driving, for example, a household mixer, includes a rotatable member 46, Figs. 2 and 3, driven by the motor and carrying co-operating contacts 57, 58, the contact 57 being mounted on a leaf spring 56 carried by a weighted arm 53 pivoted at 52, and tending to leave the contact 58 as the spring 56 flexes with increasing motor speed, and the arm 53 rotating under the influence of centrifugal force to keep the contacts closed at predetermined motor speeds. The switch controls a resistance 42 and condenser 40, Fig. 13, in the motor circuit to maintain the motor speed constant at a value determined by the extent to which the arm 53 is permitted to rotate by a cam 68 which engages a button 55 on a projection 54 of the arm 53. The cam 68 is adjusted by a knob 26 which has a cammed groove 93 engaging a pin 94 which rotates a spring-biassed bifurcated lever 79 engaging rings 73 of a sleeve 67 sliding on the extension of the motor shaft and having projecting fingers forming the cams 68, 69. The elements on the member 46 forming the switch mechanism are duplicated on the opposite side of the motor shaft 29 for balancing only, the duplicate mechanism having no contact. The knob 26 on its inner face 96 has a detent 98, Fig. 12, which, in the position of the knob, permits a spring switch blade 43 to open contacts 45, 46, in the motor circuit. The switch contacts 57, 58 are connected to conducting rings 49, 51 on the member 46 which contact with spring-pressed contact brushes 35, 36, carried on a partition 27 of the motor casing. Upon rotation of the knob 26 from its off position, the contacts 44, 45 in the motor circuit are closed to start the motor and, depending upon the position to which the knob is moved, the cam 68 limits the extent of rotary movement of the arm 53 about its pivot 52. This determines the constant speed at which the motor is maintained.