Patent GB-297562-A (GB)
Title: Improvements in and relating to electric lifts
IPC: B66B1/36
Filed: 1927-09-02
Abstract: 297,562. Fothergill, J. Sept. 2, 1927. Electric plant; electric push-button systems. - In an electric lift when the cage comes to rest above a floor level, a striker on the cage closes a switch D.S.S. which is connected in parallel with the switch operating mechanism of the " down " solenoid D of the motor reversing control and the motor moves the cage downwards until the striker opens the switch and the cage stops level with the floor. Similarly if the cage stops below a floor it closes a switch U.S.S. in parallel with the switchoperating mechanism of the " up " solenoid U of the motor reversing control and the cage is moved up to the floor level. The striker is held out pf operating position whenever the normal controlling devices are in operation by a solenoid F in circuit with the solenoids of the motor reversing switches. The operation of the normal control circuit is prevented when the slowing-down device is brought into action and vice versa by a circuit breaker which is actuated by a solenoid in series with the floor switches and operates (1) a switch which cuts out all push-button or other handoperated devices for starting or stopping the lift, (2) a switch which places all armature resistances in circuit, and (3) another switch which brings into operation means for obtaining a creeping speed on the motor. The Figure shows a five floor push-button controlled lift system provided with the floor-levelling device. If the cage is at a lower floor and the third floor call button CB<3> is pressed, a circuit is completed from the negative main to the positive main through the lead 10, fuse 11, contacts 12, 13, lead 14, interlock switch 15, lead 16, push CB<3>, lead 17, floor relay FR<3>, lead 18, direction switch DS<3>, lead 19, " up " contactor coil U, lead 20, brake coil 21, gate locks GS, and control fuse 22. Owing to the excitation of the coil U a circuit is completed from the positive main through switches 23, blow-out 24, contacts 25, 26, lead 27, armature 28, lead 29, contacts 30, 31, lead 32, armature resistance 33, lead 34 and series starting coils 35 to the negative main. At the same time a parallel circuit is completed from the fuse 11 in the negative main, by lead 36, relay 37, and lead 38 to floor relay switch FR<3>. The relay 37 moves the bridge piece 39 to complete at once a circuit from the positive main thereby causing the withdrawal of the striker E. The cage moves until the switch DS<3> is moved to mid-position when the circuit first described above is broken and the motor controller is moved to the " off " position. When the circuit closed through the push CB<3> is interrupted through the corresponding direction switch DS<3> and the cage is stopped, or nearly so, the circuit through the relay 37 is broken, and as this relay acts against a dash-pot 43, it is ensured that the cage is at rest, or almost at rest, before the solenoid F operating the striker E is de-energized. After the cage has actually, or virtually, stopped, if there is any variation from the floor level, the striker E will engage one of the switches USS, DSS. The switch engaged causes the energizing of a relay 44, the circuit being completed from the fuse 11 in the negative main through contacts 12, 45, lead 46, contact 47, bridge 39, contact and lead 48, one of the switches DSS, USS, and either by lead 49 to solenoid D, or by lead 50 to solenoid C, proceeding thereafter by lead 20, brake coil 21, gate locks GS and control fuse 22 to the positive main. The energizing of the relay 44 opens the normally closed interlock switch 15 to ensure that the landing and cage push-button circuit is inoperative during floor-levelling operations, and also opens a normally closed interlock switch 51 through which a winding 52 at other times is energized to cut out armature resistances 33, thereby ensuring that all armature starting resistance remains in circuit while levelling is effected. Relay 44 is provided with a contactor 53 by means of which a creeping speed is obtained by the usual methods, such as by connecting a resistance 54 in parallel with the motor armature.