Patent GB-962158-A (GB)
Title: Control of elevator motors
IPC: B66B1/52
Filed: 1960-06-30
Abstract: 962,158. Automatic speed control. MACHINEFABRIEK DER FIRMA P.M.DUYVIS & CO. N.V., and COLNER ELEKTROMOTOREN FABRIK JOHANNES BRUNCKEN. June 30, 1960 [June 30, 1959; Nov. 4, 1959], No. 22984/60. Heading G3R. Two-stage braking of an elevator motor down to inching speed is controlled by comparing the speed of the elevator motor with a falling reference speed derived from a pilot motor, the reference speed being greater than that of the elevator motor at the commencement of braking but during the first braking stage, braking is made so weak that the elevator motor speed falls at a lower rate than the reference speed, while during the second braking stage braking is made so strong that the elevator motor speed falls at a greater rate than the reference speed, the change from the first to the second braking stage occurring consequent upon the elevator-motor speed overtaking the reference speed during the first stage. In Fig. 2, between a two-speed pole-changing elevator motor 12 and a pilot motor 13 is coupled a contact operating device 16 which, upon reversal of the relative speed between the motors, initiates the second braking stage. Fig. 5, represents the speed-time sequence of operations during braking. Prior to an instant O, the speed M of the pilot motor 13 and the speed of the elevator motor 12 are shown to be constant. P indicates the speed of the elevator motor under maximum positive load, and N its speed at maximum negative load i.e. load assisting the drive. S represents the higher synchronous speed of the motor. At the instant O, a lift shaft switch 59 is actuated and a brake which produces uniform retardation R of the pilot motor comes into operation. Simultaneously a low-speed winding 50<SP>1</SP> of the elevator motor is switched on to the supply and, since a contactor 52 is unenergized an impedance 51 is in circuit and the elevator motor has a weak braking action. At a point X, the speed of the elevator motor overtakes the speed of the pilot motor and by the time a point Y is reached, the contactor 52 is operated by the contact device 16. The impedance 51 is thus short circuited and strong regenerative braking of the elevator motor is produced. The contactor 52 is maintained in this position by a hold-contact even though the elevator motor again reaches the speed of the pilot motor at a point Z. The two-stage braking is still effective when the impedance S 1  is not used. In this case, when a high-speed winding 50<SP>11</SP> of the elevator motor is switched off, the elevator slows by inertia until the low-speed winding 50<SP>1</SP> is connected to give the second stage braking. When, as in the case of a high speed elevator travelling short distances between successive stops, braking is required at a speed substantially less than fall speed, speed-responsive switches 62, 63 are provided. In Fig. 9, I, II, III represent speedtime conditions of the elevator with three different cage loads. At a speed B, the switch 62 opens and switches off a contactor 61 which connects the high-speed winding 50<SP>11</SP> of the elevator motor to the supply. Simultaneously braking of the pilot motor commences. For conditions I, II, the second-stage braking takes place as before when the low-speed winding 50<SP>1</SP> is switched in. In condition III, the switch 63 switches on the low-speed motor winding when inching speed is reached. Figs. 3, 4 show the construction of the contact device 16. A slip-ring member 26 is secured to the shaft 21 of the pilot motor and the member 26 carries an insulating disc 22 having a contact 42 for co-operation with contacts 40, 41 mounted on the housing of the motor. A pulley 33 belt-driven from the elevator motor is rotatably mounted on the shaft 21 and carries a disc 35 on which a contact 45 movable between contacts 43, 44 is secured. The disc 22 is driven by the motor shaft 21, and the disc 35 by the pulley 33, through slipping clutch means.