GB607080A - Improvements in control gear for electric cranes and the like - Google Patents

Abstract

607,080. Transmitting mechanical power. VAUGHAN CRANE CO., Ltd., and SADLER, G. V. Jan. 25, 1946, Nos. 2472 and 7429. [Class 38 (iv)] An electric motor 1 drives the hoisting drum of a crane or the like through an eddy current coupling 2, 3, the excitation of which is controlled, to vary the lifting speed, by a rheostat or other " stepless " regulator 11a operated by a hand wheel 12 in which is' incorporated a switch 11 having contacts which are maintained closed, in any position of the regulator, only by the application of pressure by the operator. Release of pressure de-energizes a contactor 9, thereby also de-energizing both the coupling and a release coil 13 for a brake on the drum. As shown, the coupling is energized from a potentiometer 14 connected across the brake release coil. A switch 10 controls the motor contactor 8. In the case of an A.C. motor, direct current for energizing the coupling may be obtained by rectifiers of which may be constituted by the coil 13. Other arrangements are described wherein two further stepless regulators and eddy current couplings are associated with the motor to operate cross-traversing mechanism, and wherein a second motor and two more couplings and regulators provide for longitudinal travelling of the crane. Another coupling and regulator may be associated with the first motor to provide a positive lowering torque for a light load, or this coupling may be energized simultaneously with the hoisting coupling to permit the hoisting or lowering of light loads at creeping speeds. Electrical interlocks may be provided to prevent energization of the couplings prior to starting of the motors. Overwinding and over-speed protection may also be provided. Specification 540,346, [Group XXXVII], is referred'to.