GB209595A - Improvements relating to safety devices for winding or hoisting apparatus - Google Patents

Abstract

209,595. Raeburn, C. E., and Metropolitan-Vickers Electrical Co., Ltd. Dec. 29, 1922. Overwinding, preventing; emergency power cut-off gear; speed controlling.-In winding and hoisting apparatus provided with means for causing the rapid retardation of the load in the event of overwinding or emergency occurring when winding in either direction, and with means for causing gradual retardation of the load at any point within the limits of the safe run, further means are provided for preventing the rapid retardation in the event of the failure of the power supply or under any conditions save that of an actual overwind, this means also in some cases preventing the retardation in the event of an overwind, provided the cage is travelling slowly, and also being adapted to be cut out readily in case of emergency, leaving the mechanism for rapid retardation fully operative. Fig. 1 shows one application of the invention to pit-winding gear furnished with ordinary brake engines. The apparatus includes a 3-phase induction motor 1 driving the winding drum (not shown), a selfexciting series-wound direct-current generator 4 mechanically connected to the winding drum, and a rheostat 9, the rotating arm of which is connected with the depth indicator or with the winding drum, thus making the speeds of both the motor 1 and rheostat proportional to the speed of the cage. The operation of the rheostat 9 is governed in accordance with the position of the cage so as to vary the resistance in series with the field winding 5 of the generator 4, and thus maintain the voltage of the latter substantially constant and below that necessary to open the relay 11. Excessive speed raises the voltage and opens the relay, thus de-energizing a coil 24 and opening a main switch 25 to cut off the power to the motor 1 and brake solenoid 46. The brake solenoid then operates fluid-pressure controlling means whereby a weighted piston in the cylinder 14 falls to apply the brake. A bye-pass in a cataract cylinder 15 prevents the rapid application of the brake until the controlling arm 44 is released by energization of the solenoid 17, the coil of which is in circuit with the generator 4 through the limit switches 13, 19. Thus the opening of the main switch 25 during the normal run only allows the gradual application of the brake, the circuit of the solenoid 17 remaining broken at the limit switches, but a speed at or beyond the limits of run sufficient to cause the opening of the main switch will also energize the solenoid 17 and will result in the withdrawal of the catch 16 and a rapid braking action. Should the cage overwind and trip the limit switches when travelling slowly, the voltage of the generator 4 will be insufficient to cause the solenoid 17 to withdraw the catch 16. If the power supply fails while the cage is travelling, a potential transformer 22 and the coil 24 are de-energized and the main switch 25 opened. By manipulation of the switches 30, 31 by hand, the brakes may be applied rapidly irrespective of the position of the cage. A modified system is described in which the system will operate in the event of failure of the generator 4. The application of the invention to a winding motor fed from a direct-current generator on the Ward-Leonard principle also is described. Specification 196,411 is referred to.