GB2116791A

GB2116791A - Device for starting a winding drum type elevator

Info

Publication number: GB2116791A
Application number: GB08300380A
Authority: GB
Inventors: Masumi Kanbe
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 1982-01-12
Filing date: 1983-01-07
Publication date: 1983-09-28
Also published as: HK94086A; GB8300380D0; GB2116791B

Abstract

A device for starting a winding drum type elevator, which employs an induction motor, includes a starting circuit for starting the motor at full torque in upward operation, but at reduced torque in downward operation. Where a three-phase motor (1) is used, starting in upward operation is controlled by three contacts (11a, 11b, 11c) which connect the motor for three-phase operation, whereas starting in downward operation is controlled by two contacts (12a, 12b) which connect the motor for single-phase operation. The device may include an additional contact (17) which is closed in downward operation after a predetermined time interval or when a predetermined speed is reached to commence three-phase operation. Torque reduction may alternatively be achieved by reducing the voltage supplied to a single-phase motor. <IMAGE>

Description

SPECIFICATION Device for starting a winding drum type elevator This invention relates to a device for starting a winding drum type elevator.

A winding drum type elevator has been proposed as an elevator small in size, low in speed and short in lifting distance. Such an elevator is as shown diagrammatically in Fig.

1.

In Fig. 1, reference numeral 1 designates a three-phase induction motor; 2, a worm driven by the motor 1; 3, a worm gear engaged with the worm; 4, a winding drum coupled to the worm gear; 5, a main cable which is wound on the winding drum 4 or unwound from the same; 6, a block which is rotatably mounted on the ceiling 7 of a shaft and around which the main cable 5 extends; and 8, a cage to which one end of the main cable 5 is fastened.

In moving the cage upwardly, a brake (not shown) is released to start the motor 1, so that the winding drum 4 is turned through the worm 2 and the worm gear 3, i.e., the main cable 5 is wound on to the winding drum 4, whereby the cage 8 is moved upwardly. In order to move the cage 8 downwardly, the motor 1 is turned in the opposite direction to turn the winding drum 4 in the opposite direction, so that the main cable 5 is unwound from the winding drum 4 and the cage 8 is moved downwardly by its own weight.

When the speed of the motor 1 reaches the synchronous speed, a dynamic braking force acts on the motor 1, and when the speed is decreased to the extent that the dynamic braking torque is in balance with the load torque, the cage 8 is run at a constant speed.

Since the elevator is designed as described above, if starting torque is produced so as to provide suitable acceleration for the upward movement operation, in the downward movement operation the starting shock is large and persons are not comfortable in the cage 8.

This difficulty may be overcome by increasing the inertial moment; however, in this case, a large amount of heat is generated by the motor 1, and accordingly it is necessary to increase the size of the motor 1. The torque generated by the motor 1 may be suppressed by inserting start resistance; however, in this case, the starting circuit is unavoidably intricate.

An object of this invention is to eliminate the above described difficulties accompanying a conventional winding drum type elevator.

According to the present invention there is provided a device for starting a winding drum type elevator in which a winding drum driven by an induction motor is provided, and in the upward movement operation a cage thereof is run by winding a main cable thereof on said winding drum, while in the downward movement operation said cage is run by unwinding said main cable from said winding drum, said device comprising an operation circuit which operates to cause said motor to operate in an ordinary state in upward movement operation and to start with low torque in downward movement operation.

In the accompanying drawings; Figure 1 is an explanatory diagram outlining a winding drum type elevator; Figure 2 is a circuit diagram showing a first example of a winding drum type elevator starting device according to this invention; Figure 3 is a characteristic diagram indicating torque with slip for a description of the operation of the device in Fig. 2; Figure 4 is a circuit diagram showing a second example of the device according to the invention; Figure 5 is a circuit diagram showing a third example of the device according to the invention; Figure 6 is a characteristic diagram indicating torque with slip for a description of the operation of the device in Fig. 5; Figure 7 is a circuit diagram showing a fourth example of the device according to the invention.

Referring firstly to Fig. 2, reference characters R, S and T designates the phases of a three-phase AC power source; U, V and W, the terminals of an electric motor 1; 11 a, 11 b and 11 c, upward movement electromagnetic contactor contact means which are connected between the phases R, S and T and the terminals U, V and W and are closed in the upward movement operation; 1 2a, a downward movement electromagnetic contactor contact means which is connected between the phase R and the terminal V and is closed in the downward movement operation; and 1 2b, a downward movement electromagnetic contactor contact means which is connected between the phase S and the terminal U.

In Fig. 3, reference numeral 1 3 designates the torque of the motor 1 when the latter is energized by three-phase alternating current; 14, the torque of the motor 1 when the latter is energized by single-phase alternating current; 15, load torque in upward movement operation; and 16, load torque downward movement operation.

In upward movement operation, when the contact means 1 la through 1 Ic are closed, three-phase alternating current is supplied to the motor 1, as a result of which the cage 8 is run at the speed which is determined by the point A where the motor torque 1 3 is in balanced with the load torque 1 5.

In downward movement operation, when the contact means 1 2a and 1 2b are closed, single-phase alternating current is supplied to the motor 1. The motor 1 is started moderately by being pulled by the load torque 1 6 attributed to the weight of the cage 8, so, that the cage is accelerated smoothly. Thus, the speed of the motor 1 exceeds the synchronous speed, and the cage runs at the speed which is determined by the point B where the dynamic braking torque 14 is in balance with the load torque 1 6.

Fig. 4 shows a second example of a device according to the invention. Fig. 4 is similar to Fig. 2 except that a downward movement electromagnetic contactor contact means 1 7 is provided which is connected in parallel with the contact means 11 c and which is closed a predetermined period of time after the downward movement operation is started (or immediately after the speed of the cage 8 reaches a predetermined value substantially).

Similarly as in the case of Fig. 2, in starting downward movement operation, single-phase alternating current is supplied to the motor 1.

When the speed of the cage 8 has substantially reached the predetermined value, the contact means 1 7 is closed, so that threephase alternating current is appplied to the motor. As a result, the cage 8 is run at the speed which is determined by the point C where the dynamic braking torque 1 3 is in balance with the load torque 1 6. Thus, the heat generation of the motor 1 due to the single-phase operation is suppressed, while the increase of the speed of the cage 8 is limited.

A third example of the device according to the invention is shown in Figs 5 and 6.

In Fig. 5, reference characters R and S designate a single-phase AC source; 21A, the starting winding of an electric motor 21; 21 B, the main winding of the same 21; 21C, a starting capacitor connected in series to the starting winding 21A; 211, a transformer having terminals 211a and 21 1b of a rated voltage (100V or 200V for instance) and a terminal 21 1c of a voltage lower than the rated voltage on the secondary side; 212a, an upward movement electromagnetic contactor contact means which is connected between the terminal 211 a and one end of the main winding 218 and which is closed in the upward movement operation; 212b, an upward movement electromagnetic contactor contact means which is conneted between the terminal 211 b and the other end of the main winding 218 and which is closed in the upward movement operation; 212c, an upward movement electromagnetic contactor contact means which is connected between the starting winding 21A and the main winding 21B; 212d, an upward movement electromagnetic contactor contact means which is connected between the main winding 21 B and the starting capacitor 21C; 213a, a downward movement electromagnetic contactor contact means which is connected between the terminal 211a and the one end of the main winding 218 and which is closed in the downward movement operation; 213b, a downward movement electromagnetic contactor contact means which is connected between the terminal 21 1c and the other end of the main cable 21 B; 213c, a downward movement electromagnetic contactor contact means which is connected between the main winding 21 B and the starting capacitor 21 C; and 213d, a downward movement electromagnetic contactor contact means which is connected between the main winding 21 B and the starting winding 21A.

In Fig. 6, reference numeral 214 designates the torque of the motor 21 which is provided when a rated voltage is applied thereto; 215, the torque of the motor 21 which is provided when a voltage lower than the rated voltage is applied; 216, the load torque in upward movement operation, and 217, the load torque in downward movement operation.

In upward movement operation, when the contact means 21 2a through 21 2d are closed, the rated voltage of single phase is supplied to the starting winding 21A and the main winding 21 B, to start the motor. As a result, the cage is run at the speed which is determined by the point A' where the motor torque 214 is in balanced with the load torque 216.

In downward movement operation, when the contact means 21 3a through 21 3d are closed, a voltage lower than the rated voltage is applied to the starting winding 21A and the main winding 218. In this case, the motor torque 21 5 is decreased in proportion to the square of voltage; however, the motor is sufficiently started by the low torque, being pulled by the load. Thus, the motor 21 is started moderately, and the cage is accelerated smoothly. Thus, the speed of the motor 21 exceeds the synchronous speed, and the cage is run at the speed which is determined by the poiont B' where the dynamic braking torque is in balance with the load torque 217.

The fourth example, shown in Fig. 7, is similar to the third example shown in Fig. 5 except that a downward movement electromagnetic contactor contact means 21 8a is provided which is connected in parallel with the contact means 21 2b and which is closed a predetermined period of time after downward movement operation starts (or immediately after the speed of the cage reaches a predetermined value) and a downward movement electro-magnetic contactor contact means 218b is provided which is connected between the terminal 21 1c and the contact means 213b, the contact means 21 8b being operated as opposed to the contact means 218a.

As in the third embodiment in Fig. 5, in starting downward movement operation a voltage lower than the rated voltage is applied to the motor 21. When the speed of the cage substantially reaches the predetermined value, the contact means 21 8a is closed, while the contact means 21 8b is opened, so that the rated voltage is applied to the motor 21. As a result, the cage is run at the speed which is determined by the point c' where the dynamic braking torque 214 is in balance with the load torque 217. Thus, the increase of speed of the motor 21 due to the low voltage operation is suppressed, and the rated speed is maintained.

In the above-described embodiments, the motors are of the capacitor start system; however, it goes without saying that the technical concept of the invention is applicable to other type motors.

As is apparent from the above description, in the devices for starting a winding drum type elevator described, the motor is operated with a torque lower than its rated one in starting downward movement of the cage of the elevator. Therefore, in starting downward movement of the cage, persons therein are comfortable, and yet the device can be manufactured at relatively low cost.

Claims

1. A device for starting a winding drum type elevator in which a winding drum driven by an induction motor is provided, and in the upward movement operation a cage thereof is run by winding a main cable thereof on said winding drum, while in the downward movement operation said cage is run by unwinding said main cable from said winding drum, said device comprising an operation circuit which operates to cause said motor to operate in an ordinary state in upward movement operation and to start with low torque in downward movement operation.

2. A device as claimed in claim 1, in which said operation circuit comprises; first switching means which, in the upward movement operation, are closed to apply electric power to said motor to allow the latter to operate in ordinary state; and second switching means, which, in the downward movement operation, are closed to apply electric power to said motor to allow the latter to start with low torque.

3. A device as claimed in claim 1, in which said operation circuit operates to change the low torque operation in the downward movement operation over to the ordinary operation when the speed of said cage reaches a predetermined value.

4. A device as claimed in claim 3, in which said operation circuit comprises; first switching means which, in the upward movement operation, are closed to apply electric power to said motor to allow the latter to operate in ordinary state; second switching means which, in the downward movement operation, are closed to apply electric power to said motor to allow the latter to start with low torque and third switching means for applying electric power to said motor to allow the latter to operate in ordinary state when the speed of said cage reaches said predetermined value after said elevator has been started.

5. A device as claimed in claim 1, in which three-phase alternating current is supplied to said motor, and said operation circuit operates to supply, in the upward movement operation, three-phase alternating current to said motor to allow the latter to operate in ordinary state, and to supply single-phase alternating current to said motor in starting the downward movement operation.

6. A device as claimed in claim 5, in which first switching means are provided between said motor and the phases of threephase AC source, said first switching means being closed to supply three-phase alternating current to said motor in the upward movement operation, and second switching means are provided between said motor and two predetermined phases of said three-phase AC source, said second switching means being closed to supply single-phase alternating current to said motor in the downward movement operation, said first and second switching means forming said operation circuit.

7. A device as claimed in claim 6, in which said operation circuit comprises; third switching means provided between said motor and the remaining phase of said three-phase AC source, said third switching means being closed when said cage has a predetermined speed after the downward movement operation has been started, to apply three-phase alternating current to said motor to allow the latter to operate in ordinary state.

8. A device as claimed in claim 1, in which single-phase alternating current is applied to said motor, and said upward operation circuit operates to apply, in the upward movement operation, a predetermined voltage to said motor to allow the latter to operate in ordinary state, and to apply, in the downward movement operation, a voltage lower than said predetermined voltage to said motor to allow the latter to start with low torque.

9. A device as claimed in claim 8, in which single-phase alternating current is applied to said motor through a transformer having an output terminal for providing a predetermined voltage and an output terminal for providing a voltage lower than said predetermined voltage, and said operation circuit comprises; first switching means which is connected between said output terminal providing said predetermined voltage and said motor and which is closed in the upward movement operation to allow said motor to operate in ordinary state; and second switching means which is connected between said motor and said output terminal for providing said voltage lower than said predetermined voltage, said second switching means being closed in start ing the downward movement operation to allow said motor to start with low torque.

10. A device as claimed in claim 9, in which said operation circuit further comprises; third switching means provided between said motor and said output terminal for providing said predetermined voltage and said output terminal for providing said voltage lower than said predetermined voltage, said third switching means operating to supply said predetermined voltage to said motor when said cage has a predetermined speed after the downward movement operation has been started to allow said motor to operate in ordinary state.

11. A device for starting a drum winding type elevator in which a winding drum is driven by an induction motor, substantially as herein before described with reference to Figs.

2 and 3 of the accompanying drawings.

1 2. A device for starting a drum winding type elevator in which a winding drum is driven by an induction motor, substantially as herein before described with reference to Figs.

4 and 3 of the accompanying drawings.

1 3. A device for starting a drum winding type elevator in which a winding drum is driven by an induction motor, substantially as hereinbefore described with reference to Figs.

5 and 6 of the accompanying drawings.

14. A device for starting a drum winding type elevator in which a winding drum is driven by an induction motor, substantially as hereinbefore described with reference to Figs.

7 and 6 of the accompanying drawings.