Patent GB-308184-A (GB)
Title: Means for controlling electric hoists and elevators
IPC: B66B1/08
Filed: 1927-12-19
Abstract: 308,184. McDermid, P., and MacDermid, P. S. Dec. 10, 1927. Electric plant; electric push-button systems. -The hoisting motor 16 is supplied with current by a generator 5 having a split field winding 6, 7 which is so connected in the main supply 3, 4 and to controlling resistances 10, 11 that when the cage switch 42, or other controlling device, is on the stop position, the currents passing through the split field windings will be equal and opposite so that no current will be generated and the motor will be stationary, but when the cage switch, &c. is operated to raise or lower the cage a greater current will be caused to flow in one part of the split field winding than in the other and the resulting field will generate a current to start and actuate the hoisting motor. The motor 1 which drives the generator 5 receives current from the mains 3, 4 through the starter 2. The outer ends of the oppositely wound wind ings 6, 7 are connected by leads 8, 9 containing resistances 10, 11 to the main 3, and the junction of the windings is connected by the lead 12 to the main 4. Each lead 9 contains an over-run and field and brake switch 14 and a creep switch 15. The field winding 17 of the motor 16 is connected by leads 18, 19 to the mains 3, 4, and the field winding 20 is connected by the lead 21 to one brush of the motor 1 and by the lead 22 to the mains 3. A brake and field control switch 23 is inserted in the lead 19, and an electromagnetic brake 24 is connected as a shunt across the leads 18, 19. An auto-dynamic brake coil 25 is controlled by the switches 27, 28. Contactor switches 10<1>, 11<1> controlled by solenoids 30, 31, 33, 34 cut out the resistances 10, 11 when closed. The solenoids 30, 31, 33, 34 and the solenoids 32, 35 controlling the switches 23, 27, 28, are connected by leads 39, 38, 37, 36, 40 and 41 to the car switch 42, and to the supply mains by leads 43 - - 48. The leads 36 - - 39 may be controlled by a master switch 69. When the switch 42 is central, the windings 6, 7 neutralize each other and no current is generated. When the switch is moved to either side, one of the solenoids 30, 31, 33, 34 is energized to cut out resistances from one of the circuits 8, 9 so that the winding in this circuit creates a predominant field, and therefore a current is produced by the generator 5. The resistances 10, 11 may be of different values so that by cutting them out in turn, the motor is accelerated. The switches 15 are controlled by solenoids 40<1> connected by leads 41<1> with the lead 48, and by leads 45, 46 to the switch 47. Each solenoid 40' controls also a switch 49 in leads 50 providing a shunt path to the solenoid 32, and thereby causes the energizing of the field winding 17 and brake 24 when one of the switches 15 is closed. The switch 47 is mounted on the top of the cage and is actuated by a cam provided at each floor, the parts being so arranged that when the cage is level with the floor, the arm of the switch occupies the zero position, but when the cage is above or below the floor, the arm is moved to energize one of the solenoids 40' and thereby cause the opening of the switch 15. A weak field is thus established in the generator which generates a small current supply to the motor and causes creeping. The over-run switches 14 act in a similar way. A slack cable switch 60 and a gate lock switch 61 are provided in the lead 43. The apparatus can be used with push-button control. With alternating current supply the arrangement is similar except that an exciter is provided for the generator. An oversized exciter is fitted so that it can supply direct current for the brake and controller.