GB2045467A - Control system for a reversible electric motor - Google Patents

Abstract

A control system for a reversible electric motor 10 which drives a roller shutter door 13 between upper and lower limiting positions, has a reversing switch 11 and limit switches 25, 26 respectively operable by a part 27 on the door 13 in its upper and lower positions to cause the switch 11 to arrest door movement. A timer switch 28, 31, is operated by the switch 25 and causes the door 13 to be lowered after a predetermined interval in its upper position. Raising of the door may be caused by a sensing device 20 responsive to the presence of a vehicle. If an obstruction is detected by detector 30 while the door is being lowered, the door moves upwards and remains in its upper position. <IMAGE>

Description

SPECIFICATION Control system for a reversible electric motor This invention relates to a control system for a reversible electric motor which is intended to be used for driving a device in respective opposite directions between two limiting positions.

In particular the invention relates to a control system for an electric motor which is intended for driving a door between open and shut positions. In a specific embodiment the invention is applicable to an electric motor for a vertically movable shutter door.

According to the invention a control system for an electric motor which is intended to be used for driving a device in respective first and second directions between two limiting positions comprises a reversing switch for said motor, said reversing switch being selectively operable from a first state in which current flow to the motor is interrupted, to second or third states in which said motor will run in respective opposite directions, first and second limit arrangements operable by said device at respective ones of said limiting positions, for setting said reversing switch to its first state, and a timing means initially settable by operation of said first limit arrangement for permitting operation of said reversing switch to its third state at a predetermined interval after operation of said first limit arrangement.

An embodiment of the invention will now be described by way of example only and with reference to the accompanying drawing which shows, diagrammatically a reversible electric motor and its associated control system.

As shown a three-phase electric motor 10 is provided with a reversing switch arrangement, indicated generally at 11 and is connected to drive a hoist 1 2 for a roller shutter door 13, whereby the door 1 3 may be moved from a lower limiting position in which it is shut, to an upper limiting position in which it is open.

The switch arrangement 11 includes contacts 14, 1 5 which are operable by respective electrical actuators 16, 1 7. In the de-energised condition of the actuators 16, 1 7 the contacts 14, 1 5 occupy a first position in which supply to the motor 10 is cut off.

Energisation of the actuator 1 6 moves the contacts 1 4 to a position in which the motor 10 is driven in a direction to raise the door 13, and energisation of actuator 1 7 moves the contact 1 5 to a position in which the motor 10 lowers the door 1 3. Contacts 14, 15 have associated contacts 14a, 15a, such that when the actuator 1 6 is energised, the actuator 1 7 cannot be energised, and vice versa.

The actuators 16, 1 7 are energisable from line and neutral supply rails 18, 1 9 which also provide the supply for the remainder of the control system.

A detector device 20 includes an inductive loop 21 which is adapted to detect the presence of a vehicle adjacent the door 1 3 and to close a switch 22 in response to such detection. A selector switch 23 is operable to connect the switch 22 to a realy R1, whereby the relay R1 is energised in response to the aforesaid vehicle detection. In an alternative position of the selector switch 23 the relay R1 may be energised by a manual switch 24. The relay R1 has contacts R1A and R 1 B which are shut when the relay R1 is energised.

Limit switches 25, 26 are operable by an abutment 27 on the door 13, such that switch 25 is shut when the door 1 3 is in an upper limiting position, and switch 26 is open when the door 1 3 is in a lower limiting position. A relay R3 is energisable by the switch 25 and has a contact R3A in series between contact R1A and relay R1; a contact R3B in series between contact R1B and contact 15a and a contact R3C in series with a timing device 28. The contacts R3A, R3B and R3C are shut when relay R3 is energised.

Relay R1 is thus self-latching when relay R3 is energised. The timing device 28 includes a switch 29 which shuts when a predetermined time has elapsed after the device 28 is first energised through contacts R3C. A selector switch 30 is ganged with the switch 23 and in one position permits the actuator 1 7 to be energised through the switch 29. In its other position the selector switch 30 permits the acturator 1 7 to be energised through a manual switch 31. Manual operation, either by switch 24, or switch 31 is possible in one of the positions of switches 23, 30.

Operation of the limit switch 26 permits energisation of a relay R4, this relay having a contact R4A between the switch 30 and actuator 17.

A photo-electric detector 32 includes a switch 33 which is closed in response to detection of any object in the path of movement of the door 1 3. A relay R2 is energisable through the switch 33 and has a contact R2A which is shut when the relay R2 is energised, and a contact R2B which is open when relay R2 is energised.

The contacts 1 5 of switch arrangement 11 include a further contact 15b series with an alarm device 34, whereby the device 34 is operative as the door 1 3 is being lowered. An emergency stop switch 35 in the line 1 8 is operable to de-energise all of the aforesaid relays and detectors to arrest movement of the door 13.

In use, with the door 1 3 in its lowered position, limit switches 25, 26 are open and relays R3 and R4 are de-energised, so that contacts R3A, R3B are shut and contacts R3C R4A are open. With contact R3C open, the timer 28 is not energised and contact 29 is alsa open. Su-bsequent energisation of relay R I, either through detector device 20 or switch 24, mairttains relay R1 energised, through contacts R1 A, R3A, whereupon contact R113 siluts and actuator 16 is energised to operate contracts 14. The motor 10 is thus driven in a direction to raise the door l 3.

Upward snoverrient of door 13 shuts, limit switch 26, energising relay R4 and shutting contact R4A. At the upper limit of travel of the door 13 the abutment 27 shuts limit switch 25, energising- relay R3 and opening contacts R3A and R3B.Relay RI and actuator 16 are therefore de-energised and contacts 14 are opened to arrest the motor 1;0. At the same tme contact R3C is shut, starting the timer 28 After a predetermined interval the switch 29 of the timer 28 shuts and, provided the switches 23, 30 are in the appropriate positions, the actuator 17 is energised to operate the contacts 15 and drive the motor 10 in a direction to lower the door 13.It will be noted that contacts R2B are shut since relay R2 was energised when the door 1 3 ceased to obscure the photo-electric detector 32. Downward movement of the door 13 ceases when limit switch 26 is re-opened by the abutment 27, de-energising R4 and opening contact R4A, whereby actuator 17 is deenergised and the motor 10 is stopped.

If an obstruction is detected by the detector 32 while the door 13 is being lowered, relay R2 is energised. Contact R2B opens to stop downward door movement and contact R2A shuts. Since contact R3B is already shut the actuator 16 is energised and the door 13 moves up. Upward movement continues, while the obstruction is present, until the limit switch 25 energises the relay R3 and opens contact R3A. Though the timer 28 will then start and the contact 29 will shut after a predetermined interval, the door 13 will not be lowered while the obstruction remains present and contact R2B remains open.

Claims (7)

1. t. A control system for an electric motor which is intended to be used in driving a device in respective first and second directions between two limiting positions, comprising a reversing switch for said motor, said reversing switch being selectively operable from a first state in which current flow to the motor is interrupted, to second or third states in which said motor will run in respective opposite directions, first and second limit arrangements operable by said device at respective ones of said limiting positions, for setting said reversing switch to its first state, and a timing means initially settable by operation of said first limit arrangement for permitting operation of said reversing switch to its third state at a predetermined interval after operation of said first limit arrangement.
2. 2. A control system as claimed in claim 1 in which said first limit arrangement includes a first switch device having a first contact operable to cause said reversing switch to be set to its first state, and a second contact operable to energise said timing means.
3. 3. A control system as claimed in claim 1 or c[aim 2 in which said second limit arrange merit includes a relay having a contact opera ble to cause said reversing switch to be set to said first state.
4. 4. A control system as claimed in claim 3 in which said reversing switch includes first and second actuators which are respectively operable to set said switch to said second and third states, said actuators being de-energised by operation of said first switch device and said relay respectively.
5. 5. A control system as claimed in any preceding claim which includes detector means, responsive to the proximity of a body, for setting said reversing switch to said sec ond state.
6. 6. A control system as claimed in elairn 5 in which said detector means comprises an inductive loop, switch means operable in re sponse to detection of a body by said loop, and a latching relay operable by said switch means, said latching relay including a contact for causing said reversing switch to be set to its second state when said second limit means is not operated by said device.
7. 7. A control system for an electric motor, substantially as hereinbefore described with reference to and as shown in the accompany ing drawing.