US2137075A - Controlling system for lifts - Google Patents

Description

Nov. 15,1938. A, A, CHUBB 2,137,075

CONTROLLING SYSTEM FOR LIFTS Filed Sept. 17, 1936 4 Sheets-Sheet l ATTOE/VEV Nov. 1 5, 1938. A CHUBB 2,137,075

CONTROLLING SYSTEM FOR LIFTS Filed Sept. 17/1936 4 Sheets-Sheet 2 X r m a O QJA. U K

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Nov. 15, 1938.

A. A. CHUBB CONTROLLING SYSTEM FOR LIFTS nnl Filed Sept. 17, 1936 ECQGLI 'INRITIPS? 4 Sheets-Sheet 4 5 Y VA D D V5 (U 1) Patented Nov. 15, 1938 UNETED STATES @ATENT OFFER signor to The General Electric Company Limited, London, England Application September 17, 1936, Serial No. 101,221 In Great Britain September 18, 1935 11 Claims.

This invention relates to electro-magnetic systems of lift control, and has for its object the provision of means whereby the levelling of the lift at a floor is rendered substantially independent of the load carried in the lift car.

As is well known, lift driving motors operated from alternating current supplies do not easily afford a wide range of speed control. Thus, for

example, the pole changing type of machine, w though it enables a certain set of speeds to be obtained, does not easily permit a smooth change from one speed to another. This smooth change is essential in the case of a motor operating a u lift, preferably during acceleration as well as during deceleration.

According, therefore, to the present invention, a lift driving motor operated by alternating current functions in conjunction with an eddy current brake, the extent of energization of the brake being dependent on the load. in the lift, this load being measured by the time taken for the lift to pass between certain predetermined points during the decelerational period.

H In one embodiment of the present invention, an alternating current induction motor driving a lift is started in either direction by means of the normal slip-ring method. When deceleration on approaching a floor is required, the maximum value of eddy current braking is applied, and soon afterwards resistance is inserted in the rotor circuit of the motor, this causing the car to decelerate. It should here be noted that the value of the resistance in the rotor circuit is con- V stant for all loads.

After a short period of deceleration the lift is timed in its passage between two fixed points in the lift shaft. If the load in the lift is one helping the motor to drive, the passage of the car between the points is rapid.

Conversely, if the load is a hindering one, the lifts passage is relatively slow. According to the time taken by the lift in this passage between the said two points, resistance is inserted in the M field circuit of the brake, so that in the case of c a helping load, nearly full energizaticn is main.- tained, whereas for a hindering load the braking is reduced. By this means, the lift reaches the required floor level at approximately the same 50 creeping speed whatever the load, and can therefore be stopped at the floor with great accuracy by a further friction brake employed for the purpose. If necessary, a slight over-compounding may be effected by .55 values so that the lift arrives at a floor with suitable choice of resistance (or. rite- 152) slightly greater creeping speed with a hindering load than with a helping one.

The sequence of operations is governed by means of one or more inductor relays situated on the lift car, co-o-perating with a sequence switch of the step-by-step variety, the contact banks of which are interconnected with various controlling relays. The timing of the lift is performed by a further step-by-step switch which during the timing period rotates at a fixed rate.v The points between which the lift is timed are marked by inductor plates situated in the lift shaft at places reached and. passed by the lift prior to its arrival at any required floor. Connections between the inductor relay and the sec-- 0nd or timing switch are such that passage of one plate initiates switch stepping and passage of another plate arrests switch motion. The switch contact banks are connected to resistances which are inserted between a transformer and a rectifier supplying the eddy current brake magnet field coils, variations in the switch position causing variations in the current flowing through the braking field.

One arrangement in accordance with the invention will now be described by way of example with reference to the accompanying diagram-- matic drawings, of which Figures 1 and 1A com bined show a circuit diagram of the electrical connections of the gear and Figures 2 and 2A show a code diagram for the readier understanding of Figures 1 and 1A.

In the drawings, the lift motor comprises a, stator ST connected through contactor contacts to the three-phase supply mains, and a rotor R0 connected through slip rings to starting resistances. An eddy-current brake EB and a friction brake BK operate on the motor shaft, and this shaft is arranged to drive the lift carriage LC through any suitable form of gearing. The eddy-current brake EB is energized through the rectifier RA from the transform-er TR, and the friction brake is removed from the driving shaft when its coil is energized through the rectifier RC.

Two step-by-step switches of a known type and as used in telephone systems are used in the controlling circuit. These switches comprise magnets A and B and contact banks A1, A2, A3 and B1, B2, B; respectively. The switch A used as a sequence controller, and the switch B acts as a timing device to measure time taken by the lift to pass between fixed points in the shaft.

It is proposed to describe the operation of the system by means of a typical traverse of the lift. The control mechanism is shown as being hand-operated, the switches CSU and CSD being operable by hand from the lift car. Closure of switch CSU causes the lift to travel up, and CSD causes the lift to travel down. Whenever the starting handle is moved away from the normal ofi position, contact CS is broken, no matter what direction of travel is required. All apparatus is shown in a normal position, i. 0. one in which the apparatus rests when the lift is at a floor and all the gates are closed. Under these conditions the relay GL is operated, since its circuit includes the emergency stop button ES and the gate locks GA GB and (30. Its contacts are shown in operated positions.

Assuming that the lift operator closes contact CSU (and consequently opens contact CS), a circuit is completed from the positive of contact 9 1, via contacts rm, v3, n1, CSU, UL the upper limit switch, which is normally closed and ddi to relay UD which operates.

udl prevents false operation of the relay DD which drives the lift in the opposite direction.

udz locks UD operated, so that it is not released when contact us opens later.

udg prepares to operate relay C.

U6 4 opens a self-interrupting circuit of the switch magnet A.

uds operates the gate lock catch RCR and prepares a locking and operating potential for other relays later. Relay SC is also operated through bank A2.

ude breaks a self-interrupting circuit for the switch magnet B.

14617 and lLds apply current to the stator windings ST and to the brake magnet BK.

801 and so: short-circuit resistances in the rotor circuit used for deceleration.

8C3 prepares to operate relays V and VA.

On removal of the friction brake BK from the driving shaft, the lift commences to move, a large starting current being induced in the windings of the rotor R0. A potential derived from a rotor winding is applied via transformer and the rectifier RB to the relay VS, which operates immediately its contact cs1 operating relay VA from positive on contact 303. Contact var locks VA operated, contact 'UCLz prepares to operate relay V later, and contact Dds reduces the current through relay VS. As the rotor speed increases, the rotor currents decrease, so that after a short interval the potential applied to VS is reduced to such an extent that this relay releases. Contact 2731 now operates relay V, the contacts 121 and of which short circuit resistances in the rotor circuit and the machine runs up to full speed.

The lift continues to travel in the shaft until some distance ahead of the floor at which it is required to stop. At this point, the switch CSU is opened, and the contact CS closes. Nothing happens until an inductor plate in the shaft is passed, which operates relay Z momentarily, relay UD being held operated by its contact mix. This inductor relay Z, in closing contact Z1 momentarily operates relay PS.

ps1 locks relay PS operated to Ztds.

ps2 prepares an operating path for relay C.

A series of plates is now passed by the inductor relay Y, each plate operating the relay momentarily. Each of these operations pulls up and releases relay C. When the first of this series of plates is encountered, relay C operates.

01 energizes the switch magnet A but the switch, being of the reverse drive type, does not yet take a step.

c2 operates relay EC from uds via bank A3.

801 locks relay EC operated to M15.

(202 applies full potential to the eddy-current brake EB via the rectifier RA from the first contact of the switch bank B3 and the transformer TR.

Release of relay C on passage of the first plate de-energizes the driving magnet A, and the switch takes a step forward. The current in the. eddy-current brake begins to rise, causing a progressive deceleration against the drive of the motor. This must not, however, be continued for long, as the motor would proceed to draw a large over-load current from the supply. Another plate is now passed by the relay Y, and on operation and release of relay C for the second time, the switch reaches the third contact in its banks. Wiper A2 breaks the connection to relay SC and this relay releases.

s01 and $02 open short circuits across resistances in the rotor circuit.

so; releases relays V and VA.

in and 122 open short circuits on further resistance in the rotor circuit, and both stator and rotor currents are reduced to a value appreciably below that of starting, so that the motor drives the lift against the eddy-'cmrent brake with only a very reduced effort.

The lift is now allowed to decelerate for a short space until the effect of the load in the lift is appreciable. Another plate is now passed by relay Y, and C operates for a third time. Closure of contact 02 operates relay M through wiper A3.

m1 locks relay M operated.

m2 applies positive from udt via bank B1 to the switch magnet B and the relay N, operating both.

The contact 111 of relay N performs a. function which will be described later. Operation of the magnet B opens the interrupter contacts db and relay S operates in series with the resistance X. Contact .91 now releases magnet B and the switch takes a step, closing the contacts db and short circuiting relay S which also releases. This cycle of mutual interruption between S and B continues, the switch (wipers of B1, B2, B3) being driven at a uniform and predetermined rate over its contacts. The wiper of B3 in moving over its bank inserts resistance in the circuit of the eddycurrent brake, reducing its effectiveness progressively.

This condition continues until a further plate is pased by relay Y. The time of transit between the plates is naturally dependent on the load in the lift, since if this load is a helping one, the passage of the lift between the plates is fairly rapid. If on the other hand, the load is a hindering one, the passage between the plates is longer than normal, and this passage time determines the extent of travel of the switch B. If the load is a helping one the brake energization must be large in order to cause adequate speed reduction, and conversely if the load is a hindering one, considerably less braking is required. Assuming that the load is a helping one, then the switch B takes a few steps only, inserting a small amount of resistnace in the circuit of the brake EB. The second timing plate is then passed by the inductor Y, and operation of relay C causes the application of potential from contact 02 via bank A3 and contact on to the second coil of relay M, short-circuiting it. Release of the relay cuts the circuit of the self-interrupting cycle of S and B at contact 1212, and the switch B remains positioned for the remainder of the lifts travel. Release of relay C allows the magnet A to de-energize and step the switch to the fifth contact.

The lift now decelerates under the influence of a braking force which is proportional to the load in the lift. If necessary, the effect of overcompounding can be obtained so that the lift when it reaches a distance of a few inches from the floor at which it is required to stop, has a slower creeping speed with a helping load than with a hindering load. This enables more accurate levelling to be made with the friction brake BK than if exactly the same speed is reached during deceleration independently of the load.

When a point a few inches ahead of the required floor is reached, the last plate is encountered by the inductor Y, and C is energized for the last time. Contact 01 energizes the magnet A and 02 operates the relay NR.

n11 releases relay UD.

udq and uds tie-energizes the stator and both brakes, causing the friction brake BR to be applied to its sheave and stop the lift at the floor.

11 114 completes a self-interrupting circuit for the magnet A through its interrupter contact dot.

uds releases the gate latch relay RCR, and also relays EC, NR and PS.

uds completes a self-interrupting circuit for the relay S and magnet B, and holds relay N operated.

udz breaks the holding circuit of relay UD.

uds opens the circuit of C, previously broken by ps2.

01 de-energizes the magnet A, and enables the switch to step to its first contact by self-interruption, when the stepping circuit is broken by wiper A1 and the switch stops.

The relay S and magnet B from positive through bank B2 interrupt each others circuits as previously described, stepping the switch B until its wiper B2 rests on the first contact, when the stepping circuit is broken. During this time, relay N is held operated, and its contact in prevents operation of either of the driving relays UD or DD, so that the lift cannot be started until this timing switch B has reached a zero position, when the relay N releases.

In the meantime, the gate is opened, and one of the gate contacts GA-GC releases relay GL the contacts 911 and 912 of. this relay preventing operation of either of the driving relays or of relay C until reclosure of the gates.

From the foregoing it will be seen that a measurement of the load in the lift has been effected by measuring the time taken by it to pass between two fixed points or plates in the shaft. During normal travel from one floor to a distant one, both inductor relays Y and Z are operated by the passage of plates in the shaft, but their contacts are prevented from causing any action by the open condition of contacts ps2 and CS, until the handle of the driving switch has been returned to normal by the lift attendant, so that the deceleration process can only be commenced after this action has been performed by the operator.

Although my invention has been described in connection with a manually operated lift, it should be understood that it is easily applicable to one in which automatic operation combined with call storage is effected. The only adaptation necessary to fulfil these conditions is that of putting the relays UD and DD under the control of devices which register calls in combination with a furtherdevice which follows the movement of the lift, these causing suitable operation or closure of the contacts CSU, CSD and CS. These call storage and car following devices are well-known in the art, and are not described in further detail as they form no part of the present invention, though it is to be understood that the scope of the said invention is intended to cover all obvious modifications of control of the lift such as that described.

Finally, although in the drawings the bank B3 is shown connected directly to the controlling resistances, it might be necessary to arrange that the switch operated a number of contactors which in turn switch the resistances in or out of circuit.

I claim:

1. In a lift control system for serving a plurality of floors, a motor for driving the lift, control means, relays operated by the control means for effecting operation of the motor for up and down travel of the lift, an eddy-current brake arranged to control deceleration of the motor for stopping the lift at a floor, and means including variable resistance controlled by the speed of the lift when approaching the floor at which the lift is to stop for varying the effect of said eddy-current brake during deceleration, the arrangement being such that with a helping load in the lift the speed is greater and the amount of resistance inserted is less than with a hindering load when the speed is less and more resistance is inserted.

2. In a lift control system for serving a plurality of floors, a motor for driving the lift, control means, relays operated by the control means for effecting operation of the motor for up and down travel of the lift, an eddy-current brake arranged to control deceleration of the motor for stopping the lift at a floor, resistance for controlling the current to the eddy-current brake while the motor is decelerating, the speed of the motor during deceleration being controlled by the load in the lift, and means controlled by the lift for varying said resistance according to the speed of the lift during deceleration.

3. In a lift control system for serving a plurality of floors, a motor for driving the lift, control means, relays operated by the control means for effecting operation of the motor for up and down travel of the lift, an eddy-current brake arranged to control deceleration of the motor for stopping the lift at a floor, a circuit including a tapped resistance for controlling current to the eddy-current brake, switching means cooperating with said tapped resistance for varying the resistance in said eddy-current circuit according to the speed of the lift during deceleration, said deceleration speed being determined by the load in the lift, and a relay operated by the lift for controlling operation of said switching means.

4. A lift control system as in claim 3 wherein said relay operated by the lift is arranged to be operated by an inductor relay during deceleration of the motor, said inductor relay being operated by inductor plates which are passed by the lift.

5. In a lift control system for serving a plurality of floors, a motor for driving the lift, control means, relays operated by the control means for effecting operation of the motor for up and down travel of the lift, an eddy-current brake arranged to control deceleration of the motor for stopping the lift at a floor, a circuit including a tapped resistance for controlling current to the eddy-current brake, a step-by-step switch cooperating with the tappings of said resistance for varying the resistance in said eddy-current circuit, automatic impulsing means for stepping said switch at a fixed rate during deceleration and relay means controlled by the lift for starting and stopping the stepping of said automatic impulsing means when the lift reaches prearranged distances from the floor at which it is to stop.

6. A lift control system as in claim 5 wherein an inductor plate relay arranged to be operated during deceleration by a plurality of inductor plates controls the starting and stopping of said automatic impulsing means.

7. A lift control system as in claim 5 wherein a ,step-by-step sequence switch is arranged to start and stop operation of said automatic impulsing means, and a relay arranged to be actuated by the lift controls the stepping of said sequence switch.

8. In a lift control system for serving a plurality of floors, an alternating current motor for driving the lift, resistance coils in the rotor circuits of the motor, control means having an off position, relays arranged to be energized by operation of the control means for effecting operation of the motor for up and down travel of the lift, an eddy-current brake for controlling the motor during deceleration, a sequence relay arranged to be operated by the lift while travelling to a stop at a floor, and only when said control means is in its off position, for controlling operation of said brake, sequence step-by-step switching means controlled by said last named relay,

relays controlled by said sequence switching means and operating contacts for short circuiting and inserting said rotor resistances, the arrangement being such that said resistances are short-circuited at normal speed of the motor and inserted during deceleration when said eddy-current brake is operated and an inductor plate relay arranged to cooperate with a plurality of inductor plates in sequence for operating said sequence relay.

9. A lift control system as in claim 8 wherein additional lift inductor plate operated relay means controlled by said control means and operable only when the latter is in its oil position is provided for preparing an operating circuit for said sequence relay.

10. A lift control system as in claim 8 wherein a tapped resistance is provided for controlling current to said eddy-current brake and an automatically stepping switch for controlling insertion of said resistance is provided, the starting and stopping of which is arranged to be controlled by said sequence relay.

11. A lift control system as in claim 8 wherein there is provided an electromagnetically operated holding brake cooperating with the motor shaft, said brake being arranged to be released upon efiecting operation of the motor by energization of said up and down relays and to become effective to stop and hold the motor when said relays are deenergized.

ALEXANDER ALBERT CHUBB.

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