GB2228587A - Controlling drawing of curtains - Google Patents

Abstract

In response to a close (or open) command signal, a motor 52 drives curtains until they reach a first closed (or open) position, whereupon a further signal is generated which causes the motor to drive the curtains to a second closed (or open) position. As described, the command signals are generated manually at 84, 86, or by a light sensor 82 or by a timer 83 and, via a bistable 76 and logic 74, operate energising and direction control circuits 70, 72 for the motor 52. When the first closed (or open) position is reached, a limit switch 58 opens to de-energise the motor, then after a short delay the logic 74 reverses the motor to move the curtains a short distance until the switch 58 closes again and de-energises the motor. This brief reversal relieves mechanical stress on the system. <IMAGE>

Description

DRAWING CURTAINING AND THE LIKE DESCRIPTION The invention concerns the drawing of curtaining and the like between open and closed positions, and more particularly but not exclusively apparatus for automatically effecting such operations.

In this specification the term curtaining is to be taken to mean any arrangement including fabric or other material curtains, blinds, shutters and the like used to cover or partially cover a window, roof light or other opening and the means including tracks, draw cords and the like by which the curtains, blinds, shutters or the like are hung and moved between open and closed positions - that is to say positions in which the curtaining is fully or partially open or closed.

Objects of the invention include the provision of apparatus operable automatically to control both the closing and opening of curtaining.

In one aspect the invention provides apparatus for controlling the drawing of curtaining as hereinbefore defined, which apparatus comprises an electrical motor connectable to the curtaining and operable when so connected to draw the curtaining open and closed, motor drive control means for controlling both the sense and duration of operation of the motor in response to:- a first signal when it is desired to draw the curtaining closed, a second signal when it is desired to draw the curtaining open, and third signal generated whenever the curtaining is drawn to a first open or first closed position, and wherein, the motor drive controller is arranged in response to said third signal indicative that the curtaining has reached said first open (or first closed) position to drive the motor in a direction to close (or open) the curtaining to a second open (or second closed) position.

The light sensitive device may be arranged to monitor a predetermined light level and its output be arranged to provide said first signal in response to the level of light monitored thereby.

The apparatus may further include an interval timer which is reset upon closure of the curtaining and which after a predetermined period provides said second signal to the motor drive control means.

Alternatively the the apparatus may further include a free running timer which provides to the motor drive control means at predetermined time intervals said second signal.

The light sensitive device may be arranged to monitor a predetermined light level and its output be arranged to provide said first and second signals in response to the level of light monitored thereby.

The light sensitive device may be arranged to monitor the level of ambient daylight and to provide said first or said first and second signals to the motor drive control means in response to the monitored level of ambient daylight.

The light sensitive device may be arranged to monitor the level of light emitted by a lamp and to provide said first or said first and said second signals to the motor drive control means in response to the monitored level of light emitted by the lamp.

Desirably, the motor is a reversible motor which may be energised to open and close the curtaining under the control of electronic motor direction control means included in the motor drive control means.

Preferably the third signal is provided by a switch which is operated whenever said curtaining reaches said first open and closed positions.

Draw cords of curtaining coupled to the apparatus are preferably coupled to opposite ends of a flexible cord wound onto and engaged by a pulley wheel fixed to and mounted to rotate with a shaft carried in a support member pivotally mounted on a base plate, the motor being carried by said support member and said shaft being coupled thereto, energisation of the motor to draw the curtaining to said first open and closed positions being arranged to cause the support member to pivot on the base plate to a position at which a first switch supported on the base plate is operated to generate said third signal.

The flexible cord may have fixed thereto a plurality of beads or other members at predetermined spacings and the slot in said pulley wheel have a plurality of enlargements in which said beads are received.

The apparatus may further include a second normally closed switch carried on the motor support member, said second switch being coupled in the power supply to the motor, and having a switch operating arm positioned such that the switch is opened if the motor support member pivots on the base plate further than the position at which a first said switch supported thereon is operated.

The motor drive control means may includes a bistable device driven between first and second stable states by said first and second signals respectively and the outputs of which are used to control both the energisation of the motor and the direction in which it is driven.

The motor drive control means preferably includes interval timer means which is enabled whenever the motor is energised in a sense to open or close the curtaining and means responsive to the output of the interval timer means to prevent further energisation of the motor in a sense to open or close the curtaining after a predetermined period greater than that normally required to draw the curtaining to the first open position from the second closed position or to the first closed position from the second open position.

The motor drive control means may include further interval timer means enabled whenever the motor is energised in a sense to drive the curtaining from said first to the said second open position and from said first to the said second closed position, and means responsive to the output of the further interval timer means to prevent further energisation of the motor in a sense to partially close or open the curtaining after a predetermined period greater than that normally required to draw the curtaining from said first to said second open position and from said first to said second closed position.

The motor drive control means may includes means monitoring the level of current being drawn by the motor whilst the motor is energised and operable to prevent further energisation of the motor if the monitored current exceeds a predetermined level.

The apparatus preferably includes a first manually operable switch operable by a user to halt energisation of the motor whilst the motor is energised in a sense to open or close the curtaining.

The apparatus may also include further manually operable switches operable by a user to provide said first and second signals.

Desirably, the apparatus includes means for providing a visible indication of the sense in which the apparatus will next operate to open or close the curtaining.

The apparatus may include means enabling energisation of other electrical apparatus whilst the curtaining is drawn closed.

The above and other aspects, features and advantages of the invention will become apparent from the following description of an embodiment of the invention made with reference to the accompanying drawings, in which: Figure 1 illustrates schematically curtaining control apparatus embodying the invention, Figures 2, 3 and 4 are side, face and detail side views respectively, illustrating mechanical parts of the apparatus of Figure 1, Figure 5 diagrammatically illustrates electronic control circuitry for the apparatus, and Figure 6 diagrammatically illustrates the control circuitry of Figure 5 in more detail, Referring to Figure 1 the apparatus includes a curtain drawing unit 10 shown mounted on a window sill 12 and coupled to a curtain draw cord 14 which runs upwardly (14A) from unit 10 to a pulley wheel 16 mounted at one end of curtaining track 18 carrying - in the usual way - a pair of curtains 20 and 21. The draw cord runs along (14B) the top of track 18 to a pulley wheel 22 at the other end of the track 18 and then back along (14C) the track, around a pulley wheel 24 mounted adjacent wheel 16 and returns (14D) to the unit 10.

The apparatus further includes a unit 11, linked to unit 10 by a cable 13, which houses electronic control circuitry for unit 10. Cable 13 may be any convenient length enabling unit 11 to be physically mounted adjacent to or spaced from the unit 10.

Run 14B of cord 14 is attached to the top of the innermost edge of curtain 20 and run 14C to the top of the innermost edge of curtain 21 so that if unit 10 is operated to draw run 14A into - and allow run 14D to pass out of unit 10 the curtains will be drawn together. Similarly if the apparatus is operated to draw run 14D into - and allow run 14A to pass out of - unit 10 the curtains will be drawn apart.

Figures 2, 3 and 4 show mechanical parts of the unit 10 connected to the runs 14A and 14D of cord 14 for closing and opening, respectively, the curtaining by two flexible links 30 and 32 as shown. The flexible links 30 and 32 are connected to the runs 14A and 14D by limited extension springs 34 and 36 respectively as shown.

Flexible links 30 and 32 comprise opposite ends of a continuous length of a flexible cord 37 wound onto a pulley wheel 40 having a central slot 42 in which the flexible cord is located. The flexible cord carries fixed thereon a plurality of beads 37 at regular spacing and slot 42 is formed with corresponding enlargements 37' for receiving these beads so that the cord 37 is positively held by and may be driven by rotation of wheel 40. It will be seen that the way in which the cord is wound onto the wheel 40 means that rotation of the wheel counterclockwise (as viewed in Figure 3) will cause link 30 to be more fully wound onto the wheel and link 32 to be drawn from the wheel and that clockwise wheel rotation will cause link 32 to be more fully wound onto the wheel and link 30 to be drawn from the wheel.

Wheel 40 is fixed to and rotates with a shaft 44 journalled at 47 in an arm 50 of an L-shaped member 51.

Shaft 44 is coupled directly to a reversible electrical motor 52 carried on arm 50 of member 51. Wheel 40 may be driven to rotate by motor 52 clockwise or counterclockwise (as viewed in Figure 3).

The lower arm 53 (as viewed in Figures 2 and 3) of member 51 is connected to a base plate 54 by means of a hinge 55.

Lugs 48 and 49 are provided on the sides of first arm 50 of member 51 and support between them a metal shield 56 which extends beneath the pulley wheel 40 as shown and has, at its free, leftmost as viewed in Figure 2, end an upstanding part 57 partially overlying wheel 40 as shown.

Base plate 54 carries beneath shield 56 a magnetic reed switch 58 for which the operating magnet 59 is located on arm 50 beneath the shield 56 as shown. Switch 58 is arranged to be closed by action of magnet 59 when the magnet is adjacent the switch (with arm 53 of member 51 parallel to plate 54) but to open if magnet 59 is carried away from it by rotation of member 51 about the axis of hinge 55.

Arm 53 of member 51 carries a normally closed switch 60 having a switch operating arm 61 engageable, when member 51 pivots around hinge axis 55, with a member 62 carried on the base plate 54.

The spacing of magnet 59 from switch 58 at which switch 58 will open or close and the spacing of switch operating arm 61 from member 62, are such that, if the Lshaped member 51 moves away from the base plate 54 about the pivot axis of hinge 55, magnet 59 will first cease to hold switch 58 closed and thereafter further movement of member 51 about the pivot axis of hinge 55 will cause the switch operating arm 61 to strike member 62 and thereby opening switch 60.

As shown springs 64 are connected between the lugs 48 and 49 and fixings 66 on base plate 54. Springs 64 are under tension and tend to prevent movement of member 51 about the pivot axis of hinge 55 away from the base plate 54.

It will be appreciated that with the arrangement described energisation of motor 52 to drive shaft 44 and wheel 40 counterclockwise (as viewed in Figure 3) causes link 30 to be more fully wound into unit 10 (and link 32 to be drawn from the unit) pulling on run 14A of the draw cord such that the curtains are drawn together until as the curtains are fully closed (with spring 34 fully extended and spring 36 slack). Thereafter no further part of run 14A of the draw cord may be drawn into unit 10 and continued rotation of wheel 40 by motor 52 will increase the tension in link 30 which acts to lift member 51 away from base plate 54, about the axis of hinge 55, against the action of springs 64.

In time magnet 59 moves sufficiently far away from switch 58 allowing this switch to open. As will be described below the opening of switch 58 causes the motor to be deenergised, the direction in which the motor may thereafter be driven to rotate to be reversed (so that the wheel 40 will when next energised rotate clockwise as viewed in Figure 3) and, after a short delay causes motor 52 to be driven in that sense until switch 58 closes once again.

If for any reason switch 58 does not open and motor 52 continues to drive wheel 40 the further movement of the member 51 about the pivot axis of hinge 55 will cause switch operating arm 61 to strike member 62 opening switch 60 and de-energising motor 52.

Subsequent energisation of motor 52 to drive shaft 44 and wheel 40 in a clockwise sense (as viewed in Figure 3) causes link 32 to be more fully wound onto wheel 40 (and link 30 to be drawn from the unit) pulling on run 14D of the draw cord such that the curtains are drawn apart until such time as the curtains are fully drawn open (with spring 36 fully extended and spring 34 slack). Thereafter no further part of the run 14D of the draw cord may be pulled toward unit 10 and continued rotation of wheel 40 by motor 52 will increase the tension in link 32 so that member 51 pivots about hinge 55 against the action of springs 64 until, in time, magnet 59 moves sufficiently far away from switch 58 to allow this switch to open.Once again, the opening of switch 58 causes the motor to be de-energised, the direction in which the motor may thereafter be driven to rotate to be reversed (so that the wheel 40 will when next energised rotate counterclockwise as viewed in Figure 3) and, after a short delay causes motor 52 to be driven in that sense until switch 58 closes once again.

If for any reason switch 58 does not open and motor 52 continues to drive wheel 40 the further movement of the member 51 about the pivot axis of hinge 55 will cause switch operating arm 61 to strike member 62 opening switch 60 and de-energising motor 52.

Unit 11 includes the electronic circuitry controlling operation of unit 10 and includes a light level sensitive device (e.g. a phototransistor or photoresistor) not shown in Figures 2, 3 and 4 - which activates the circuitry controlling operation of the motor to open or close the curtains driven by the unit when a monitored light level (e.g. daylight) falls below a presettable level.

The unit 11 further includes a timer (not shown in Figures 2, 3 and 4) which may be switched into operation to control opening and closing of the curtains in accordance with a preset programme of operations - or simply to ensure the curtains are opened (or closed) a predetermined time after they have been closed (or opened).

The unit 11 includes other switches (not shown in Figures 2, 3 and 4) by means of which a user may cause curtains driven by the unit to open and close as desired independently of a monitored light level (or the timer if that is operational) and which permit movement of the curtains to be stopped when desired partway between fully open and closed positions.

Finally unit 11 includes an LED (not shown in Figures 2, 3 and 4) which is steadily illuminated when the unit is powered but not operating to open or close the curtains and which flashes when operating to open or close the curtains.

These and other details of the this embodiment of the invention will now be described with reference to the following Figures of the drawings.

Figure 5 illustrates schematically the electronic control circuitry for controlling motor 52 of the unit 10 and shows that circuitry to include a motor driver circuit including a motor energiser 70 and a motor director 72 arranged to control energisation and direction of motion respectively of motor 52. The power line from the motor energiser 70 to the motor 52 includes the normally closed switch 60 described above.

The motor energiser and motor director are controlled by drive logic circuitry 74 in turn controlled by the output of a bistable 76. Other inputs to drive logic circuitry 74 are from the limit switch 58 (one of which is via a delay indicated schematically at 78) and from a spring biased normally open switch 80.

The inputs to bistable 76 which cause it to switch between stable states are taken from a light level sensor 82 - connectable to the bistable by closure of a switch 91 spring biased normally open switches 84 and 86, and timer 88 connectable to the bistable by closure of a switch 90.

A LED 92 is coupled to the bistable 76 and is lit steadily whilst bistable 76 is in one state and flashes whilst bistable 76 is in its other state.

The light level sensor 82 may include a photocell or photoresistor the output of which, if switch 91 is closed, is used to trigger bistable 76 between stable states to close curtaining controlled by the unit. Switch 84 may be closed to close the curtaining and switch 86 may be closed to open the curtaining. If timer 88 is linked into the circuit by closure of switch 90 it is effective to control opening of the curtains in accordance with a preset programme of operations - or simply to ensure the curtains are opened a predetermined time after they have been closed.

Operation of the circuitry will be described from a condition in which the curtaining is drawn fully open in daylight and is set, by closure of switch 91, for automatic closing operation when the daylight falls below a preset level. At this time LED 92 is illuminated steadily.

If required, when the apparatus is initially installed, the switch 86 may be closed to drive the curtaining fully open.

When the light falling on light level sensor 82 falls below a preset level bistable latch 76 is tripped into its other state. The output of latch 76 causes LED 92 to flash and the drive logic circuit 74 is triggered to activate motor energiser 70 which in turn energises motor 52. The motor director is set such that the direction in which the motor turns is to close the curtains.

If the user wishes to stop the curtains closing completely he simply closes switch 80 when the curtains are at a position he desires.

Assuming switch 80 is not closed the curtains will continue closing until switch 58 opens. The opening of this switch immediately causes drive logic circuit 74 to deactivate motor energiser 70 cutting off power to the motor and to cause motor director 72 to reverse the direction in which the motor will rotate when next energised. After a short delay - indicated by 78 - the drive logic circuitry 74 will reactive motor energiser 70 to cause motor 52 to rotate in a direction to open the curtains - which rotation will continue until switch 58 closes at which time the motor energiser 70 is de-activated once again.

The LED 92 continues to flash.

The same sequence of operation may be obtained by a user simply closing switch 84.

If switch 90 is closed timer 88 outputs a signal after a predetermined time period which trips bistable 76 into its first state. The output of bistable 76 causes LED 92 to be illuminated steadily and the drive logic circuit 74 is triggered to activate motor energiser 70 which in turn energises motor 52. The motor director has set the direction in which the motor will turn at the end of the closing operation noted above so that the curtaining driven by the unit begins to open.

If the user wishes to stop the curtains opening completely he simply closes switch 80 when the curtains are at a position he desires.

Assuming switch 80 is not closed the curtains will continue opening until switch 58 opens. As before the opening of this switch immediately causes drive logic circuit 74 to de-activate motor energiser 70 cutting off power to the motor and to cause motor director 72 to reverse the direction in which the motor will rotate when next energised. After a short delay - indicated by 78 - the drive logic circuitry 74 will reactive motor energiser 70 to cause motor 52 to rotate in a direction to close the curtains - which rotation will continue until switch 58 closes at which time the motor energiser 70 is de-activated once again.

The LED continues to be steadily illuminated and the unit is in its originally described condition.

The same sequence of operations may be initiated by a user simply closing switch 86.

If switch 58 fails to open - or another fault develops in the circuitry - as the motor support 51 is lifted, switch 60 will as described above shortly thereafter be opened cutting off power to the motor 52. Thus the motor is de-energised until the fault has been repaired and the unit is reset.

Thus it will be seen that unit 10 is controlled to close and open the curtaining with closure initiated by the output of light level sensor 82 indicating a fall in ambient daylight below a preset level (e.g. at dusk) and curtain opening initialed by the output of timer 88 some time later. It will further be seen that closing (or opening) operations continue until the curtaining reaches a first closed and (or open) position at which switch 58 opens and is thereafter driven to a second closed (or open) position with switch 58 closed once again. In this way mechanical stress on the curtaining and the unit 10 is eliminated - after being drawn fully closed (or opened) the curtaining is then partially opened (or closed) again.

Figure 6 illustrates the control circuitry of Figure 5 in more detail and shows it to be powered from a 12VDC supply (battery or mains transformed) and includes power supply lines 100 and 102 across which a 12vide supply is coupled to power the motor 52. The positive supply line 100 includes a 5vdc regulator 104 as shown via which power is supplied to the remainder of the circuitry.

Across lines 100, 102 are coupled the coil of a relay 106 in the emitter-collector path of an NPN transistor 108. Closure of the contacts of relay 106 is arranged as indicated schematically to energise motor 52 and cause it to rotate. The direction of rotation of the motor 52 is controlled by a further double pole relay 110 the coil of which is coupled across supply lines 100 and 102 in the emitter-collector path of a NPN transistor 112.Relay 110 as indicated in the Figure is arranged when in a FIRST, relaxed, state to cause the motor to be energised to rotate in a FIRST direction and when in a SECOND, energised state to cause the motor to be energised to rotate in a SECOND direction The base of transistor 108 is coupled by a resistor 114 and diode 116 to an output terminal 173 of a monostable oscillator 172 which is also coupled - by a capacitor 118 - to a trigger input terminal 120 of a monostable oscillator 122. Oscillators 122 and 172 are standard "555" timers such as made and sold in the United Kingdom under the designation NE555 by the SIGNETICS Company. Oscillator 122 when SET provides an output for a period slightly longer than that normally taken for motor 52 to to be driven to close switch 58. The junction of capacitor 118 and diode 116 is also coupled to a first input of a NAND gate 124 as shown. The of transistor 108 is further coupled via zener diode 126 and diode 128 to output 130 of oscillator 122 which is also coupled down to negative supply line 102 by a resistor 132 and a capacitor 134.

The base of transistor 112 is coupled by a resistor 136 to the output of a NAND gate 138 both inputs of which coupled as shown to the junction of a diode 140 and a diode 142.

The cathode of diode 140 is coupled to the output of a NAND gate 144 and that of diode 142 to the output of NAND gate 124. The junction of these two diodes is coupled up to the supply line 100 by a resistor 145 as shown.

The circuitry further includes a NAND gate 146 and a NAND gate 148 which are coupled to act as a bistable latch driven to one or other stable state in response to inputs thereto from the light level sensing circuitry 82, the manual overriding switches 84 and 86, and the timer 88.

The light level sensing circuitry comprises a voltage divider coupled between the positive supply line 100 and the negative supply line 102 by a diode 150 and including a variable resistor 152 and a light dependent resistor 154. A back up battery or large value capacitor 153 may be coupled by a diode 151 to the junction of diode 150 and resistor 152, diodes 150 and 151 acting to switch power either from the regulator 104 or, if necessary, the back up 153 to the light level sensing circuit 76, bistable 82 and timer 88.

The junction of resistor 152 and light dependant resistor 154 provide both inputs to a NAND gate 156 the output of which is coupled by a switch 91 and a capacitor 160 to a first input of NAND gate 146. The first input of NAND gate 146 also coupled up to the positive supply line 100 by a resistor 162 and down to the negative supply line 102 by a switch 84.

The output of gate 146 is taken to a first input of gate 148 and via a capacitor 166 and a diode 168 to the trigger input 170 of a second monostable oscillator 172 which when SET will provide an output on its terminal 173 to the junction of diode 116 and capacitor 118 - for a presettable period longer than that taken normally for the curtains to be moved from a fully open (or closed) to a fully closed (or open) position. The trigger input 170 of oscillator 172 is also coupled up to positive supply line 100 by a resistor 174.

The second input of gate 148 is coupled by switch 86 to the negative supply line 102, by a resistor 180 to positive supply line 100 and - via capacitor 182 and switch 90 - to the output of timer 88.

The output of gate 148 is coupled to the second input of gate 146 and via a capacitor 188 and a diode 190 to the trigger input 170 of oscillator 172.

The junction of capacitor 166 and diode 168 is coupled down to the negative supply line 102 by a resistor 192 and the junction of capacitor 188 and diode 190 is coupled down to negative supply line 102 by a resistor 194.

The RESET input terminal 196 of oscillator 172 is coupled to the output of a NAND gate 198 by a resistor 200 and by switch 80 to the negative supply line 102. The two inputs to gate 198 are taken from the junction of switch 58 and a resistor 214 coupled across the positive and negative supply lines 100 and 102 as shown. The signal fed to the inputs of gate 198 is also fed as a first input to gate 144 (which receives as its other input the output of gate 148) and to the RESET input terminal 206 of oscillator 122.

The output of gate 148 also coupled to control operation of LED 92 coupled across the positive and negative supply lines 100 and 102.

Each NAND gate provided in the circuitry described is provided with Schmitt trigger inputs so that changes in the input signals thereto will be effective to alter the output of the gate only when that input has steadied preventing possible spurious signals or voltage variations operating the gates.

Operation of the circuit of Figure 6 will now be described, from the condition in which the curtaining is drawn fully open in daylight and is set for automatic closing operation when the daylight falls below a level preset by adjustment of variable resistor 152 and for automatic opening at a time determined by the timer 88. In this condition switches 80, 84 and 86 are open and switches 58, 90 and 91 are closed.

Light falling on light dependent resistor 154 holds both inputs of gate 156 at a logical LOW such that output of gate 156 is at a logical HIGH.

As switch 91 is closed the logical HIGH output of gate 156 is isolated from the first input of NAND gate 146 by capacitor 160. The first input of NAND gate 146 is held HIGH by resistor 162 coupled up to positive supply line 100 and the output of gate 146 is at a logical LOW. The first input of NAND gate 148 is held at a logical LOW from the output of gate 146 whilst the second input of gate 148 is held at a logical HIGH by resistor 180 coupled up to positive supply line 100 and the output of gate 148 is a logical HIGH.

These outputs of the bistable latch are blocked by capacitors 166 and 188 from the input 170 of oscillator 172 which input 172 is held at a logical HIGH by resistor 174 coupled up to positive supply line 100.

Switch 58 is closed holding the inputs to gate 198 at a logical LOW so that the output of gate 198 fed to RESET input 196 of oscillator 172 is a logical HIGH. Output 173 of oscillator 172 is at a logical LOW. As switch 58 is closed a first input of gate 144 is held at logical LOW whilst the second input of gate 144 is a logical HIGH from the output of gate 148. The logical HIGH output of gate 144 is blocked by diode 140. Again, as switch 58 is closed providing a logical LOW to RESET input 206 of oscillator 122 the output 130 of oscillator 122 is at a logical LOW.

A first input to NAND gate 124 is at a logical LOW from the output of gate 146 and the second input to gate 124 is at a logical LOW from the output 173 of oscillator 172. The output of gate 124 is therefore at a logical HIGH but this is blocked by diode 142.

The inputs to gate 138 are both at a logical HIGH from resistor 145 coupled up to the positive supply line 100 and its output is logical LOW holding transistor 112 OFF and keeping relay 110 in the noted FIRST state.

The logical LOW on output 130 of oscillator 122 and on the output of oscillator 172 act through resistor 132, zener diode 126, diode 116 and resistor 114 to hold transistor 108 OFF and relay 106 OPEN.

As daylight falls the resistance of light dependent resistor 154 rises until the output of gate 156 goes to a logical LOW. This change in output is differentiated by capacitor 160 putting a pulse on the first input of gate 146 and the bistable latch formed by gate 146 and gate 148 switches to its other state - the output of gate 146 goes to a logical HIGH and the output of gate 148 to a logical LOW. The change in output of gate 146 is differentiated by capacitor 166 and applied as a trigger pulse to to trigger input 170 of oscillator 172.

The output 173 of oscillator 172 goes logical HIGH which acts through diode 116 to bias transistor 108 ON in turn CLOSING relay 106.

The output of gate 148 has switched to a logical LOW and as a result both inputs to gate 144 are now logical LOW and its logical HIGH output is blocked by diode 140.

At this time the first input to gate 124 is at a logical HIGH (from output of gate 146) and the second input of gate 124 is logical HIGH (from output 173 of oscillator 172) and the output of gate 124 goes to a logical LOW. Diode 142 conducts pulling the inputs to gate 138 to a logical LOW the output of which goes HIGH biasing the base of transistor 112 HIGH. Transistor 112 is turned ON in turn switching relay 110 to its SECOND, energised, state allowing the motor to rotate in a direction to close the curtaining.

The motor 52 is driven to rotate in a sense to close the curtaining until the motor support 51 is lifted and switch 58 OPENS sending the inputs to gate 198 and RESET input 206 of oscillator 122 to a logical HIGH - via resistor 214 from the positive supply line 100. The output of gate 198 goes to a logical LOW and this is applied to RESET input 196 of oscillator 172. As a result output 173 of oscillator 172 goes to a logical LOW putting the base of transistor 108 at a logical LOW turning transistor 108 OFF and allowing relay 106 to relax OPEN.

If the curtains take longer to reach the fully closed position than the preset period of operation of oscillator 172 the oscillator RESETS cutting off power to the motor 52. Thus the action of this oscillator is to monitor operation of the apparatus and provide that the motor is de-energised should a fault develop (e.g. should the draw cord in the curtaining break whilst being opened or closed, or switch 58 fail open).

As output 173 of oscillator 172 goes to a logical LOW a negative pulse is passed by capacitor 118 to trigger input 120 of oscillator 122 triggering operation of this oscillator. The logical LOW from output 173 of oscillator 172 is passed to the first input of gate 124 sending the output of this gate to a logical HIGH which is blocked by diode 142 thus transistor 112 is turned OFF and relay 110 relaxes to its FIRST state.

As switch 58 is still OPEN and the output of gate 148 LOW the logical HIGH output of NAND gate 144 is blocked by diode 140.

Capacitor 134 charges from output 130 of oscillator 122 via resistor 132 until - after a period of time determined by the values of capacitor 134 and resistor 132 - zener diode 126 begins to conduct pulling the base of transistor 108 to a logical HIGH turning transistor 108 ON, CLOSING relay 106 and causing motor 52 to rotate. As transistor 112 at this time is OFF relay 110 is in its FIRST state and motor 52 therefore to rotates in a direction opposite to that to close the curtaining.

This "reverse" driving of motor 52 continues until switch 58 closes RESETTING oscillator 122 and sending output 130 of oscillator 122 to a logical LOW allowing capacitor 134 to discharge quickly via diode 128 and turn transistor 108 OFF and letting relay 106 relax OPEN.

If for any reason switch 58 does not close within the period in which oscillator 122 is SET the "reverse" driving of the curtaining will be stopped as the SET period of oscillator ends and the oscillator RESETS. This acts to monitor the operation of the switch 58 and prevent the curtains being automatically fully opened immediately after being closed - should switch 58 fail in an open condition or the draw cords in the curtaining break.

The apparatus now remains inactive until the output of timer 88 goes to a logical LOW - after a predetermined period - or until switch 86 is closed by a user. This change in output is differentiated by capacitor 182 causing the bistable arrangement of gate 146 and gate 148 to flip to its one state with the output of gate 146 at a logical LOW and output of gate 148 at a logical HIGH and this in turn triggers operation of oscillator 172 - in turn biasing transistor 110 ON and causing energisation of motor 52.

The inputs to gate 124 are at a logical HIGH (from output 173 of oscillator 172) and at a logical LOW (from the output of gate 146) and its output is at a logical HIGH (blocked by diode 142). The inputs to gate 138 are at a logical HIGH - via resistor 204 from supply line 110 and transistor 112 is therefore maintained OFF with relay 110 in its FIRST state.

The motor 52 is therefore driven to open the curtaining until switch 58 OPENS sending the output of gate 198 to a logical LOW terminating operation of oscillator 172, turning transistor 108 OFF and allowing relay 106 to relax OPEN.

As described above oscillator 122 is then triggered. The first input of gate 144 is at a logical HIGH as switch 58 is OPEN and the second input of gate 144 is logical HIGH from the output of gate 148. The output of gate 144 is therefore at a logical LOW allowing diode 140 to conduct, pulling the inputs to gate 138 LOW and thereby turning transistor 112 ON and energising relay 110 to its SECOND state.

Once again, at the end of the delay determined by capacitor 134 and resistor 132 motor 52 is energised to rotate to move the curtaining in a closing sense until switch 58 CLOSES once again. The first input to gate 144 goes to a logical LOW and the logical HIGH output of this gate is blocked by diode 140 with the result that transistor 112 is biased OFF.

Thereafter the bistable acts to ensure the circuitry may only be triggered by closure of switch 84 or by the action of the light level sensing circuit.

The LED 92 is provided to indicate that the circuitry is operational and is arranged to be steadily lit when the bistable (gates 146 and 148) is in its one state and to be flashing when the bistable is in its other state (curtaining being driven to open or close).

The above description assumes fully automatic operation of the circuitry, however, it is possible for the curtaining to be opened or closed by a user independently of the level of daylight by closing switch 84 (to drive the curtaining closed) or switch 86 (to drive the curtaining open).

By closing switch 80 and RESETTING oscillator 172 the movement of the curtaining may be stopped at any desired position between fully open and fully closed.

It will be appreciated that the bistable acts to prevent a user (or indeed the circuit automatically) to energise the motor to open or close the curtaining if the curtaining is already open or closed respectively.

Furthermore it will be appreciated that opening switch 90 uncouples the timer 88 from the bistable and prevents the automatic opening of the curtaining whilst opening switch 91 uncouples the light level sensing circuitry preventing the closing of the curtaining at dusk.

The timer 88 may be implemented as a free running oscillator and counter taking a total of 24 hours before RESETTING to a zero count. The counter may be initialised by momentarily RESETTING it at the appropriate time using a switch associated with it (not shown) or by any suitable connection to the switch 86. If implemented in this way the timer may have a dual count output and be used in place of or to override the light level sensing elements and control both opening and closing of the curtaining.

Alternatively timer 88 may be implemented as an oscillator and counter a taking a shorter period than 24 hours - possibly adjustable between 2 and 12 hours - before RESETTING and which is SET in response to the closure of the curtaining (e.g. by being coupled to receive the signal fed to the first input of gate 146).

In this case the curtains will be drawn closed in response to a fall in in light level below the preset level and will be drawn open again a predetermined time later.

With either implementation of timer the timer and light sensitive element may be linked to ensure that timed opening cannot take place if the light level is still low.

It will be appreciated that should the curtains jam whilst being opened or closed the increasing tension in draw cords will cause the memb'er 51 supporting motor 52 to be lifted - opening switch 58 and thus cutting off power to the motor.

The short "reverse" driving of motor 52 provided by the opening of switch 58 after the curtaining has jammed, or has been fully opened or closed allows the relaxation of the mechanical elements of the apparatus thereby preventing the curtaining being placed under tension by the motor when it is not being energised.

The apparatus described may be provided with a further timer (not shown) which is RESET when the output of oscillator 172 goes HIGH and which in turn may be used to turn on, for example, a lamp for a period whilst the curtains are closed. The output from this timer, if provided, may be used to activate an electronic or electromechanical timing device which is arranged to switch one or more lamps or other devices on and off one or more times.

The embodiments of my invention preferably include further means for preventing motor operation should a fault develop in the apparatus such as the the motor drawing too high a current leading to possible overheating problems.

This may be provided, e.g. as a current sensor (not shown) in the power supply line to the motor which, should the sensed current exceed a predetermined level, outputs a pulse having the same effect as operation of switch 58.

If such means are provided member 51 may be fixedly mounted on plate 54 and springs 64 omitted - as well as switches 58 and 60, however, it is preferred that the arrangement described be implemented - even with current level sensing - to provide for "sticking" of the curtains as they are drawn or possible faulty operation of elements of units 10 or 11.

Thus embodiments of my invention provide that if the curtains controlled by the apparatus do not fully open or close in a period longer than that normally taken (say, twice as long), if the motor draws an unusually high current of it the draw cord tension rises above normally anticipated levels - indicating that curtaining has jammed - further energisation of the motor in the sense in which it was being driven is prevented whilst energisation of the motor in the opposite sense is permitted.

It will be appreciated that various modifications may be made to the arrangements described without departing from the scope of this invention.

In place of, or in addition to, the timer 88; the arrangement may provide that the curtaining are opened if the light level sensor output indicates that it is full daylight.

The particular form and positioning of the various elements (e.g. switches 88 and 60) may be varied as desired.

The LED may be omitted, may be arranged to operate in a manner different to that described (e.g. illuminated only while the curtaining is being drawn) or be supplemented or replaced by a tone sounder which operates as the curtaining is being drawn The motor energisation limitation provided by switch 58 may be supplemented or even provided by other means - e.g. by providing that the actual position of the draw cords are monitored. One way of effecting this would be provide that the beads on the draw cords are passed between a light source and a photoelectric cell - the number of beads passing the cell (and therefore the movement of the draw cord passed the cell) being determined by monitoring the output of the photocell.Again the draw cords could simply be passed around pulley wheels attached to rotation counters to provide an indication of the amount by which the draw cords have moved.

If such other draw cord movement monitoring schemes are provided it is suggested the switch 60 be retained to provide for protection of the apparatus should the draw cords stick or jam whilst the curtains are being opened or closed or a fault develops in the circuitry.

If desired the apparatus may be provided with means enabling it to be controlled by an external timer/programmer to be used to control operation of the apparatus - either completely or simply to control the opening of the curtains after they have been closed.

Embodiments of the invention may be provided to operate vertical slat blinds in which both the horizontal and rotational movement of the slats must be provided.

Essentially such an arrangement would be the same as described above with the two motors being provided - one of controlling the horizontal movement of the slats and the other for controlling the rotational movement of the slats.

Each motor would be separately controlled by a motor control circuit as described above with, if necessary, cross linking between the bistable latches in each circuit to ensure that the correct sequence of blind rotation and horizontal movement is followed in opening or closing the blinds.

Similarly embodiments may be provided to control raising and lowering and rotation of the slats of horizontal slat (Venetian) blinds.

The motor and the means enabling it to be driven as desired may be may be implemented as a reversible motor driven through relays as discussed above or in any other way - for example the reversible motor may be replaced by a unidirectional motor the output of which drives the curtaining via a mechanically reversible clutch mechanism and control of the motors direction of rotation comprise mechanical or electro-mechanical means for operating this clutch. The motor maybe coupled directly to the shaft 44 or be coupled thereto via a gearbox.

The particular form and logical implementation of the other parts of the apparatus may also be varied from that described above.

The light dependent resistor may be replaced by a photocell the output of which is arranged to trip the bistable when the level of daylight falls below a predetermined level. Alternatively the photocell may be arranged to monitor the level of light emitted by a lamp its output be provided as said first signal whenever the level of light emitted by said lamp rises above a predetermined level. Thus the curtaining will be closed whenever the lamp is lit by a person e.g. when entering the room in the dark.

The timer 88 may take a variable time (in dependence upon e.g. temperature, humidity and the like) such that the time of curtaining opening following its closure will vary.

A trigger delay circuit may be provided driven by the resistor 154 or the photocell and its output used to provide control of the bistable - thus providing a time delay before the output of the light level sensing circuitry trips the bistable thus operating, it will be seen, to prevent the curtaining being closed by the passage of a dark cloud.

The delay provided before the motor is reverse driven upon opening switch 58 may be provided - as described - by the characteristics of the elements of the apparatus but may be, if desired, provided by a separate interval timer. This delay prevents the motor being overloaded by being energised to rotate in a "reverse" sense immediately following energisation to rotate in a "forward" sense.

The duration of the short "reverse" driving of the motor may, as described, be provided by the hysterisis inherent in the type of switch used to implement switch 58 or by appropriate adjustment of the timer 122.

Other variations of the apparatus will be apparent to one skilled in the art.

It will be seen that the present invention provides a apparatus for controlling the drawing of curtaining which has the inherent safety features of using a low supply voltage, means for preventing the current drawn by the motor exceeding a predetermined safe level (should the curtaining "stick" when being drawn) and means for limiting the energisation of the motor should an opening or closing operation take longer than a predetermined period (e.g. if the draw cords should break).

Claims (22)

1. Apparatus for controlling the drawing of curtaining as hereinbefore defined, which apparatus comprises an electrical motor connectable to the curtaining and operable when so connected to draw the curtaining open and closed, motor drive control means for controlling both the sense and duration of operation of the motor in response to:- a first signal when it is desired to drawn the curtaining closed, a second signal when it is desired to drawn the curtaining open, and third signal generated whenever the curtaining is drawn to a first open or first closed position, and wherein, the motor drive controller is arranged in response to said third signal indicative that the curtaining has reached said first open (or first closed) position to drive the motor in a direction to close (or open) the curtaining to a second open (or second closed) position.

2. Apparatus as claimed in claim 1, including a light sensitive device arranged to monitor a predetermined light level and the output of which is arranged to provide said first signal in response to the level of light monitored thereby.

3. Apparatus as claimed in claim 1 or claim 2, further including a timer which which is reset upon closure of the curtaining and which after a predetermined period provides said second signal to the motor drive control means.

4. Apparatus as claimed in claim 1 or claim 2, further including a free running timer which provides said second signal to the motor drive control means at predetermined time intervals.

5. Apparatus as claimed in claim 1, including a light sensitive device arranged to monitor a predetermined light level and the output of which is arranged to provide said first and second signals in response to the level of light monitored thereby.

6. Apparatus as claimed in claim 2 or claim 5, wherein the light sensitive device is arranged to monitor the level of ambient daylight and to provide said first or said first and second signals to the motor drive control means in response to the monitored level of ambient daylight.

7. Apparatus as claimed in claim 2 or claim 5, wherein the light sensitive device is arranged to monitor the level of light emitted by a lamp and to provide said first or said first and said second signals to the motor drive control means in response to the monitored level of light emitted by the lamp.

8. Apparatus as claimed in any one of the preceding claims, wherein the motor is a reversible motor which may be energised to open and close the,curtaining under the control of electronic motor direction control means included in the motor drive control means.

9. Apparatus as claimed in any one of the preceding claims, wherein said third signal is provided by a switch which is operated whenever said curtaining reaches said first open and first closed positions.

10. Apparatus as claimed claim 9, wherein draw cords of curtaining coupled the apparatus are coupled to opposite ends of a flexible cord wound onto and engaged by a pulley wheel fixed to and mounted to rotate with a shaft carried in a support member pivotally mounted on a base plate, the motor being carried by said support member and said shaft being coupled thereto, energisation of the motor to draw the curtaining to said first open and closed positions being arranged to cause the support member to pivot on the base plate to a position at which a first switch supported on the base plate is operated to generate said third signal.

11. Apparatus as claimed in claim 10, wherein the flexible cord has fixed thereto a plurality of beads or other members at predetermined spacings and wherein the slot in said pulley wheel has a plurality of enlargements in which said beads are received.

12. Apparatus as claimed in claim 10 or claim 11, further including a second normally closed switch carried on the motor support member, said second switch being coupled in the power supply to the motor, and having a switch operating arm positioned such that the switch is opened if the motor support member pivots on the base plate further than the position at which a first said switch supported thereon is operated.

13. Apparatus as claimed in any one of the preceding claims, wherein the motor drive control means includes a bistable device driven between first and second stable states by said first and second signals respectively and the outputs of which are used to control both the energisation of the motor and the direction in which it is driven.

14. Apparatus as claimed in any one of the preceding claims, wherein the motor drive control means includes interval timer means which is enabled whenever the motor is energised in a sense to open or close the curtaining and means responsive to the output of the interval timer means to prevent further energisation of the motor in a sense to open or close the curtaining after a predetermined period greater than that normally required to draw the curtaining to the first open position from the second closed position or to the first closed position from the second open position.

15. Apparatus as claimed in any one of the preceding claims, wherein the motor drive control means includes further interval timer means enabled whenever the motor is energised in a sense to drive the curtaining from the said first to the said second open position and from the said first to the said second closed position, and means responsive to the output of the further interval timer means to prevent further energisation of the motor in a sense to partially close or open the curtaining after a predetermined period greater than that normally required to draw the curtaining from said first to said second open position and from said first to said second closed position.

16. Apparatus as claimed in any one of the preceding claims, wherein the motor drive control means includes means monitoring the level of current being drawn by the motor whilst the motor is energised and operable to prevent further energisation of the motor if the monitored current exceeds a predetermined level.

17. Apparatus as claimed in any one of the preceding claims, further including a first manually operable switch operable by a user to halt energisation of the motor whilst the motor is energised in a sense to open or close the curtaining.

18. Apparatus as claimed in any one of the preceding claims, further including further manually operable switches operable by a user to provide said first and second signals.

19. Apparatus as claimed in any one of the preceding claims, further including a visible indication of the sense in which the apparatus will next operate to open or close the curtaining.

20. Apparatus as claimed in any one of the preceding claims, further including means enabling energisation of other electrical apparatus whilst the curtaining is drawn closed.

21. Apparatus as claimed in claim 1 and substantially as herein described with reference to Figures 1 to 4 of the accompanying drawings.

22. Apparatus as claimed in claim 1 and including control circuitry substantially as herein described with reference to Figures 5 and 6 of the accompanying drawings.