GB2149241A - Control apparatus for hoisting drum elevator - Google Patents

Abstract

A hoisting drum elevator having a cage 13 driven by an induction motor 1 which is energized by 3-phase power when ascending and by single-phase when descending. Comparator means detects whether the rotational speed of the motor rotated by the cage's own weight in the down-movement exceeds a predetermined value, and if so change-over control means (4a, 4b) connects single-phase electric power to the motor so that the motor is allowed to continuously rotate even if holding torque is generated by the single-phase excitation to ensure a positive downward running of the elevator. <IMAGE>

Description

SPECIFICATION Control apparatus for hoisting drum elevator The present invention relates to a control apparatus for a hoisting drum elevator, and more particularly to such an apparatus which is adapted for preventing a three-phase motor from coming a standstill against torque acting between a rotor and a stator of the motor to hold the latter at a stationary position when the elevator is driven for downward movement using single-phase excitation of the motor.

Such torque will be referred to as "holding torque" hereinafter.

Proposals have been heretofore made to single-phase excite the three-phase motor of an elevator system, whereby the cage of a hoisting drum elevator is operated when the latter is downwardly driven.

A torque characteristic of the three-phase motor when it is single-phase excited is shown in Fig. 1. That is, torque in either forward or reverse direction is generated dependently upon a rotational direction of the motor. However, holding torque is generated due to the interaction of an alternating magnetic field of the stator and a current of the rotor produced thereby at a starting of the motor in either direction with a single phase excitation thereof.

On the other hand, in a hoisting drum elevator, the motor is forced to rotate in one direction due to gravity acting on the cage after release of the brake. However, when the weight of the cage as a whole is small, there is a tendency that it is relatively difficult to rotate the motor in a desired direction even with a combination of the gravitational torque and a torque due to the single-phase excitation, because of frictions of bearing portions of the motor and associated gears and those between the cage and guide rails which are specifically large in the starting period of the motor.

The hoisting drum elevator is occasionally used as a hoist for lifting and lowering constructive components of a building before mounting the cage thereon. In such case, it is usual that a hook is attached to an end of a main wire and a rope is hooked thereby and that, when the hook is to be lowered, an operator pulls the rope down. However, for the reasons set forth above, extremely great force is required to pull the rope down if the motor is single-phase excited to lower the wire. This will render the elevator impossible for use in raising and lowering such weighty components. An approach has been made to single-phase excite the motor after pulling the hook by a rope. But it is not desirable since the operation becomes complicated.

An object of the present invention is to provide a control-apparatus for a hoisting drum elevator, in which, when the hoisting drum elevator is downwardly driven, a singlephase power is supplied to the motor after a brake is released and after the rotation speed of the motor becomes higher than a predetermined value so that the motor can start to rotate against the holding torque.

Embodiments of the invention will be now described with reference to the accompanying drawings.

Fig. 1 is a diagram showing a torque characteristic of a motor under single-phase excitation, Fig. 2 is a circuit diagram showing one example of a control apparatus for a hoisting drum elevator according to the invention, Fig. 3 is a circuit diagram showing one example of a running command control circuit in the invention, and Fig. 4 is a circuit diagram showing an example of application of the hoisting drum elevator according to the invention for raising and lowering of the baggage or luggage.

Fig. 2 shows an embodiment of control device of a hoisting drum elevator according to the invention, wherein numeral 1 denotes a three-phase induction motor (hereinafter referred to as "motor"). The motor 1 is connected through control device to a three-phase power source 2. The control device includes a contactor 3 whose contacts 3a, 3b, and 3c are connected in series with lines of R, S, and T phases which connect the motor 1 with the three-phase power source 2, respectively. Bilateral thyristors 4a, 4b are connected in series with the respective lines of the R, S phases. The gate of the thyristor 4a and the R phase line are connected with each other through a normally open contact Aa of a relay A as will be described later.Numeral 5 denotes a full wave rectifier input terminals of which are connected through contacts 6a and 6b of a contactor 6 to the S phase line at a junction between the thyristor 4b and the contact 3b and a point on the T phase line in the side of the power source, respectively. DC output terminals of the rectifier 5 are connected through contacts 7a and 7b of a contactor 7 to the contacts 3b and 3c in the side of the motor 1, respectively.

Numeral 8 denotes a wire drum coupled to the motor 1. Numeral 9 denotes a brake means which is disposed between the motor 1 and the wire drum 8 and which includes a solenoid 9a adapted to apply a brake force when actuated. The solenoid 9a is connected through a contact 10a of a switch 10 to a DC power source 11. A wire 1 2 is wound on the drum 8, whose free end is connected to a cage 1 3. Numeral 14 denotes a speed detector for detecting the rotational speed of the motor 1.

Fig. 3 shows an embodiment of a control circuit of the control device for commanding upward and downward running of the hoisting drum elevator. The control circuit incorporates therein an OR gate 20 having inputs to receive an upward running command signal UP and a downward running command signal DN, respectively. An output of the OR gate 20 is connected to a base of a transistor 21.

A parallel circuit of the contactor 3 and switch 10 is connected in series between a collector of the transistor 21 and a power source V.

Numeral 22 denotes a comparator for comparing a downward speed setting signal VT from a speed pattern generator (not shown) with a speed signal V5 from the speed detector 14.

The output signal from the comparator 22 and the downward running command signal DN are applied to an AND gate 23 whereas an output signal of the AND gate 23 and the upward running command signal UP are applied to an OR gate 24. An output of the OR gate 24 is connected to a base of a transistor 25. The relay A is connected between a collector of the transistor 25 and the power source V.

Operation of the instant embodiment will be explained hereinafter.

When the hoisting drum elevator is required to be upwardly operated at a given speed, the OR gates 20, 24 are supplied with the upward running command signal UP, thereby conducting the transistors 21 and 25. The contactor 3, the switch 10 and the relay A are thus activated to close the contact Aa of the relay A to thereby fully ignite the thyrister 4a to activate the solenoid 9a to thereby release the brake means 9 and to close the contact 1 ova, respectively.Then, by increasing a firing angle of the thyristor 4b gradually to ultimately ignite the same, the rotational speed of the motor 1 increases to allow it to operate with three-phase power to thereby raise the cage 1 3. In decelaration control of the cage when it is upwardly operated, the contactor 3 is dropped out to open its contacts 3a, 3b and 3c whereas the contactor contacts 6a, 6b and 7a, 7b are closed to supply a DC electric power to the motor 1 from the rectifier 5, and a turn-on angle of the thyristor 4b is controlled to generate variably controlled brake torque, whereby the motor 1 is decelerated and the cage 1 3 is arrived at a desired story.

When the hoisting drum elevator is required to be downwardly operated at a given speed, the thyristor 4b is interrupted whereas only the thyristor 4a is allowed to conduct. In this case, the brake is initially opened and after the motor 1 attains a predetermined rotational speed by the cage's own weight, the thyristor 4a is ignited.

More specifically, in downward operation, when the downward running command signal DN is generated, the OR gate 20 provides an output by which the transistor 21 is made conductive. This will actuate the contactor 3 and the switch 10 to close the respective contacts 3a, 3b, 3c and 1 Oa. With the closure of the contact 1 Oa, the solenoid 9a is excited to release the brake means 9. At this moment, since the thyristor 4a is non-conductive, and yet the other thyristor 4b is maintained as interrupted when the elevator is operated downward in an acceleration or constant running mode, an electric power is not supplied to the motor. For this reason, when the brake is released, the motor 1 initiates its rotation under the cage's own weight.When the rotational speed of the motor 1, that is, the speed signal V5 detected by the speed detector 14 becomes more than the set value VT, the comparator 22 provides an output signal [H].

The AND gate 23 is actuated with the [H] output and the downward running command signal DN, and the [H] signal generated therefrom is supplied to the OR gate 24 and then to the transistor 25, conducting the same.

The relay A is therefore actuated to close its contact Aa, thus conducting the thyristor 4a.

When the thyristor 4a is turned on, the motor 1 is single-phase excited to generate singlephase torque. In this case, since the single phase excitation of the motor 1 is performed after it starts to rotate under the cage's own weight, its rotation can continue even if the holding torque is generated and thus the cage is allowed to go down.

Fig. 4 shows an example of application of the hoisting drum elevator to raising and lowering of the constructive components, wherein the hook 1 5 is attached to the suspended end of the wire 1 2 and includes another rope 1 6 engaged in the hook 1 5. In Fig. 4, like numerals are used to designate like or corresponding parts in Fig. 2.

In this embodiment, when the downward command signal is generated by a remote switch, the contactor 3 and the switch 10 are actuated in the same manner as in Fig. 2, and with the closures of the switch contact 1 0a the solenoid 9a is excited to release the brake means 9. Under such condition, the wire 1 2 can be pulled down by the rope 1 6 to rotate the motor 1. When the rotational speed of the motor 1 becomes higher than the set value VT, the relay A is actuated. This will make the thyristor 4a conductive to thereby singlephase operate the motor 1 so that the wire 1 2 can be easily discharged from the drum 8.

It is noted that the speed detector and change-over control means for changing an operation mode of the motor to a single-phase mode in a down-movement operation are not limited to those described in the embodiment.

According to the invention as above set forth, the hoisting drum elevator is designed so that, in its down-movement operation, a single-phase electric power is supplied to the motor after the brake is released and the rotational speed of the motor becomes higher than a predetermined value. Accordingly, the motor is not held in a shutdown condition even if the holding torque is generated by single-phase excitation, so that a down-movement running of the elevator is ensured.

Claims (7)

1. A control apparatus for a hoisting drum elevator in which a three-phase motor coupled to a drum on which a wire rope is wound, is driven by single-phase excitation thereof when a cage connected to a free end of the wire rope is downwardly operated, comprising; a comparator for comparing a rotational speed of said motor rotating in a direction corresponding to the downward movement of the cage with a predetermined setting value to generate a signal when the rotational speed is more than the predetermined value; signal generating means responsive to the output signal of said comparator for generating a signal, and change-over means responsive to said signal from said signal generating means for initiating supply of a single-phase electric power to said motor.

2. A control apparatus for a hoisting drum elevator as claimed in Claim 1, further comprising means responsive to a running command for releasing the brake and for actuating a switch to connect said motor with an electric power source.

3. A control apparatus for a hoisting drum elevator as claimed in Claim 1, wherein said change-over means is so actuated as to supply a three-phase electric power to said motor when the upward running is commanded.

4. A control apparatus for a hoisting drum elevator as claimed in Claim 3, further comprising controlled rectifier elements connected to two-phases of a three-phase electric power source, respectively, and wherein said changeover means is adapted to supply a full ignition command to one of said control rectifier elements.

5. A control apparatus for a hoisting drum elevator as claimed in Claim 4, wherein said change-over means is adapted to supply said full ignition command to one of said control rectifier elements when an upward running command signal is generated and when said signal generating means generates a signal.

6. A control apparatus for a hoisting drum elevator as claimed in Claim 4, wherein the cage initiates its running by its own weight at the commencement of the downward running while none of said control rectifier elements are ignited.

7. A control apparatus for a hoisting drum elevator as claimed in Claim 6, wherein said control rectifier elements, which have no full ignition signal supplied in the downward operation, is constantly held in an interrupted condition.