GB2055230A

GB2055230A - Reversing mechanism for an automatic door opener

Info

Publication number: GB2055230A
Application number: GB8020886A
Authority: GB
Original assignee: Firmaframe Nominees Pty Ltd
Current assignee: Firmaframe Nominees Pty Ltd
Priority date: 1979-06-29
Filing date: 1980-06-26
Publication date: 1981-02-25
Also published as: CA1148634A; NZ194125A

Abstract

A reversing mechanism for a door which has an electrical drive means 1 for opening and closing the door comprises an electrical sensing circuit 27k, 100k, 24k and 0.22 OMEGA connected with the electrical drive means 1 to sense any change from normal electrical drive conditions in the drive means 1, caused as a result of the door striking an object during closing, and circuit means BC337 connected to the sensing circuit arranged to reverse the drive of the electrical drive means 1 in response to detecting such change causing the door to open. <IMAGE>

Description

SPECIFICATION Reversing mechanism for an automatic door opener This invention relates to a reversing mechanism for an automatic door opener and relates particularly but not exclusively to such for use on garage doors of the roller shutter type or the tilt type.

In the art of shutting doors such as garage doors, there is a provision provided that if the door should strike an- object under the door during moving to the closed position, then the door should automatically reverse to move to the open position so as to prevent damage to the object under the door. Previous to the present invention such reversing has been triggered by sensing pressure exerted between drive gears of a motor drive mechanism used to open the door. For example, under normal closing operation there is a certain force between the gears in the drive train from the motor to the drum onto which the curtain is wound and unwound. If an object is placed under the door such that the door strikes the object when closing then an increased force will be transmitted through the gears.This increased force has, in one instance, been arranged to cause the meshing gears to move apart and such movement has been arranged to trigger an electrical switch which reverses the current supplied to the motor to, in turn, reverse the direction of drive of the motor which in turn opens the door. The mechanics of this known type of mechanism are very complicated and add greatly to the cost of a door fitted with this sensing system.

Accordingly, it is an object of the present invention to provide an automatic reversing mechanism for a door, which is superior to the prior art type referred to above by nature of its cost.

Accordingly, the present invention provides, an improved reversing mechanism for, a door with an electrical drive means for opening and closing the door, the mechanism comprising: an electrical sensing circuit connected with the electrical drive means to sense an electrical change in any normal electrical drive conditions in the drive means, caused as a result of the drive means exerting greater pressure to close the door than under normal drive conditions, such change being representative of the door striking an object during closing, circuit means connected to the sensing circuit arranged to reverse the drive of the electric driving means in response to detecting such change whereby to cause the door to open.

Most preferably the electrical change sensed is a change in the current flowing to the electrical drive means.

In order that the present invention can be more clearly ascertained a preferred construction will now be described with reference to the accompanying drawings wherein Figure 1 is an electrical circuit diagram of one preferred circuit for use with a roller shutter door.

In the diagram there is shown an electrical motor 1 which is drive connected with a mechanism (not shown) to open and close a garage door. The mechanism may conveniently comprise a gear train which drives a drum onto which the curtain of the door is wound.

Alternatively, if the door is a tilt lift door then the mechanism may conveniently comprise a gear train which is arranged to extend or retract a lever which, in turn, is fitted to the door and opens the door when retracted and closes the door when extended. The motor 1 may be of any suitable type having either rotor windings and field windings which can be connected in any known manner such as for a compound motor, a series motor and the iike, or it can be a motor with a permanent magnet stator and rotor windings as shown in the preferred embodiment. The motor 1 is, in turn, supplied from a D.C. voltage source of 24 V.D.C.

obtained from a mains A.C. supply after being suitably transformed and then rectified.

In the circuit there is shown a series of relays, starting at the top, R.L.L., R.L.R., R.L.U.P., R.L.D.N.

Reiay R.L.L. is a relay used for switching on a light not shown in the circuit diagram, for approximately a two minute period when the door is opened. This is used for illuminating the area behind the door such as a garage or the like. The light may be a 24V lamp which is connected across the 24V line when relay R.L.L. closes or alternatively may be a mains operated lamp which operates when relay R.L.L. closes.

R.L.R. is a reversing relay which reverses the drive to the motor if there is an object under the door when it is being closed.

R.L.U.P. is the relay used to open the door from the closed position.

R.L.D.N. is the relay used to close the door from the open position.

A start button START is shown in the circuit and is used for manually operating the electronic circuit to cause the door to be raised and lowered.

A series connection of resistors 24K and 27K, a variable potentiometer 100K are connected in parallel with a 0.22 ohm 5 watt resistor and all are arranged such that a portion of the current fed to the motor during the door closing sequence can appear across the base emitter terminals of transistor BC337 to sense any change in the motor operating current, such as an increase. This causes the motor to reverse its direction of rotation when it is moving to close the door if an object is under the door. Thus an increase of current is delivered to the motor when the door strikes the object. This is sensed and the door reopened. A remote radio control unit of known construction is provided which when operated gives output signals which simulate any signals delivered by the 'start' button switch.

Upper and lower stops are provided in the door frame for the door's travel which represent the fully open and fully closed positions. Limit switches Top L/S and Bottom L/S are positioned to be respectively activated when the door reaches the open and the closed positions.

The operation of the circuit will now be described. If the door is closed and the start button is operated or alternatively the remote control unit is operated, then R.L.U.P. and R.L.L.

close and cause the door to drive up until the top limit switch Top L/S opens. R.L.L. activates the lamp for the period determined by the timer NE 555. The time is set by the 1.8m resistance and the 33fly capacitor. When the door is open and the start button is pressed, or alternatively the remote control unit is operated and signals a change required, then R.L.D.N. closes and causes the door to drive down until the bottom limit switch opens.

If prior to the bottom switch being reached, the start is pressed or alternatively the remote control is operated, then R.L.R. will close causing R.L.D.N.

to drop out and R.L.U.P. to close. These actions reverse the direction of rotation of the motor and change the direction of movement of the door. The door will then subsequently switch off when it reaches the top limit switch.

If the door is moving to the closed position and is stopped by an obstruction then the overload current to the motor as sensed by resistors 27K, 100K,24K and 0.22 ohms and provide a voltage across the transistor BC337 to cause it to switch "on" and then transistor BC557 to switch "on" resulting in RLR closing and the motor operating in the reverse direction to open the door. Desirably the top limit switch is adjusted to provide an over travel so that it will not close when the door is moving from the door open to the closed position until a minimum of 1 second after the start of closing the door. This is to provide an interlock in the necessary circuitry. If power should fail during operation of the door then the door will cease movement. On resumption of power to the apparatus and on reclosing the start button or resignalling the radio transmitter of the remote control unit then the door will move up until it opens the top limit switch.

The potentiometer 100k is used to adjust the value of voltage across the series connection of resistances 24k, 1 00k, and 27k so that the transistor BC337 can be adjusted to switch when there is an increase in current to the motor above a selected amount caused by the door striking an object when it is being moved to the closed position.

A code combination feature can be incorporated in the remote control device so that the door can be operated only when a selected code is signalled.

Claims

1. A reversing mechanism for a door which has an eiectrica! drive means for opening and closing the door, the mechanism comprising: an electrical sensing circuit connected with the electrical drive means to sense an electrical change in any normal electrical drive conditions in the drive means, caused as a result of the drive means exerting greater pressure to close the door than under normal driving conditions, such change being representative of the door striking an object during closing, circuit means connected to the sensing circuit arranged to reverse the drive of the electric driving means in response to detecting such change whereby to cause the door to open.

2. A reversing mechanism for a door as claimed in claim 1 wherein the electrical change sensed is a change in the current flowing to said drive means.

3. A reversing mechanism for a door as claimed in claim 2 wherein said change in the current flowing is sensed by a resistance circuit connected with said drive means so that if the current increases to said drive means as a result of an increased load placed on said drive means then an increased current will flow in said resistance circuit.

4. A reversing mechanism as claimed in claim 3 wherein said drive means is a D.C. electric motor whose direction of rotation can be altered by altering the polarity of the supply and wherein said switch circuit includes a transistor switch connected to, in turn, operate a relay switch which will reverse the polarity of the D.C. supply to said D.C. motor.

5. A reversing mechanism as claimed in claim 4 wherein said resistance circuit is adjustable so that only changes in current above a selected amount will cause said D.C. motor to reverse.

6. A reversing mechanism for a door which has an electrical drive means for opening and closing the door substantially as herein described with reference to the accompanying drawings.