GB2026723A

GB2026723A - Circuits for Electric Window Winders for Vehicles

Info

Publication number: GB2026723A
Application number: GB7914346A
Authority: GB
Original assignee: Tekron Patents Ltd
Current assignee: Tekron Patents Ltd
Priority date: 1978-01-25
Filing date: 1979-04-25
Publication date: 1980-02-06
Also published as: GB2026723B

Abstract

Various control circuits are described for electric window winders for vehicles. All these circuits allow the window to be fully closed or fully opened by a momentary operation of a control switch. In Figs. 1-3 (not shown), a bistable circuit (30) responds to momentary operation of a control switch (32 or 34). In Fig. 4, a microprocessor 150 responds to momentary operation of control switch 32 or 34. In Figs. 7-11 (not shown), the control switches are provided by a toggle switch having a mechanical retaining latch which operates upon actuation of the toggle switch. Certain of the embodiments also have other features; they limit the current supplied to the motor of the window winder, so that a trapped finger, for example, is unlikely to be broken; and if the window refuses to move when the motor is energised, the motor energisation is reversed at intervals to try to free the window. In a particularly preferred embodiment, Fig. 4. the only operator controls are two push-buttons 32, 34; for opening and closing movement respectively; a momentary operation of the appropriate button will cause the window to close or open fully, while a more prolonged operation of a button will energise the motor for only as long as the button is operated. <IMAGE>

Description

SPECIFICATION Circuits for Electric Window Winders for Vehicles This invention relates to circuits for electric window winders for operating moving windows in vehicles.

Such window winders are normally controlled by a manually-operated switch, and move the window fairly slowly, so that the window can easily be adjusted to the required position. For example, the window might take 5 or 6 seconds to travel between its fully open and fully closed positions. This low speed of travel also helps to reduce the danger of injury to, for example, trapped fingers. However, the need to keep the control switch depressed for several seconds to move the window through its full travel is a nuisance and can be dangerous, especially when the person operating the switch is the driver of the vehicle.

According to one aspect of the present invention, a control circuit for an electric window winder comprises input means which can be manually set in at least two states, and means arranged, when the input means is so set, to supply current to a motor of the window winder to move the window to a position corresponding to the set state of the input means, the said minimum of two states corresponding to the fully open and fully closed positions of the window.

In cases where the input means has only the said minimum of two set states, it may incorporate simple on-off devices for manually setting these states. For example, in one preferred embodiment, two spring-loaded push-buttons are used, each of which sets the corresponding one of a pair of bistable latches, one corresponding to each state. Alternatively, it might be possible to use a manually controlled switch or switches which are latched into an off-normal position to maintain each state for as long as necessary.

Where the input means has only two set states, it is necessary to ensure that the window can be set to a position intermediate between its fully open and fully closed positions. One method of achieving this is to include in the circuit manual control means which are arranged to energise the motor of the window winder in a selected direction for only as long as the manual control means are manually operated to an off-normal state. Such a manual control means might be similar in design to the control switches used with previously proposed window winders, which are usually rocker switches spring-loaded to a central off' position. Where such a rocker switch is provided, it may be possible to arrange that this rocker switch can also be used to set the input means into either of its two states.A preferred way of achieving this result is to arrange that a brief operation of the rocker switch (say, less than 0.3 seconds) is effective to put the circuit into one or other of its latched states, while a more prolonged operation of the rocker switch will result in the circuit going into a state in which the energisation of the motor is maintained for as long as the switch is operated, but ceases immediately the switch is released. An alternative way of achieving this result is to arrange that the motor of the window winder may be kept energised by a sustained pressure of a first, lesser value on the rocker switch, while a second, greater pressure on the rocker switch will set the input means into an appropriate one of its two set states.

A further alternative way of providing the facility for achieving an intermediate position of the window is to provide only control switches which control the setting of the input means, but to arrange that only a relatively prolonged operation of one of these control switches actually sets the input means, while a shorter operation of one of the control switches resets the input means to stop movement of the window. In a variation of this arrangement, a separate control switch might be provided which, when operated, resets the input means to stop movement of the window.

Yet another way of allowing the window to be set in an intermediate position is to provide input means which can be set in a rather larger number of states than two, with each state corresponding to a different position of the window; it might even be possible to provide an input means having a continuum of states, such as a slider potentiometer, so that the window is continuously adjustable. In such a case, some kind of feedback of the position of the window is necessary, in order to establish when the window has reached the required position. Various methods can be used to achieve this feedback.

For example, a photo-sensitive element could be arranged to sense a series of marks provided on the glass of the window, and to feed signals to a counter to increment or decrement the counter as the window is closed or opened. Alternatively, the feedback might be achieved by monitoring electrically the operation of the window winder motor, or, in cases where the manually adjustable input means is mounted close to the window winder, it might be achieved mechanicallv.

The preferred embodiment is so arranged that, if the window should meet an obstruction while it is closing, the motor of the window winder will stall, and the resulting increase in the motor current is sensed, and, as soon as the motor current reaches a certain value, the input means is restored to its normal state, so that the motor is de-energised. By selecting a suitable value for the current at which the motor will be de-energised, the force which can be applied to an obstruction will be limited to a reasonable value, and this may help to prevent injury to people's hands if they should become trapped.This is perhaps more important with circuits using the invention than with previously-proposed circuits, since the operator of a circuit embodying the invention does not have to concentrate his attention on the movement of the window once the circuit is in a latched operating state, and this may result in a greater chance of trapping other people's fingers.

This feature will also ensure that the motor of the window winder is de-energised if it should stall because the window has reached the end of its travel, and therefore a window winder control circuit which incorporates this feature need not include any other means for restoring the circuit to its normal state when the window reaches the end of its travel. However, it may nonetheless be considered desirable to provide other means for detecting when the window reaches either end of its travel, and for de-energising the motor when this occurs.One way of achieving this is to provide limit switches which operate at the ends of the window travel; alternatively, if the circuit includes an arrangement, such as the photosensor and counter arrangement described above, which maintains a continuous record of the position of the window, a signal indicating that the window has reached the end of its travel can easily be obtained from this arrangement. In a simplified version of the photosensor and counter arrangement, only two marks are provided on the glass of the window, to be detected by the photosensor at the fully open and fully closed positions respectively.

In a further variation, the behaviour of the circuit is modified when the window is within, say, 1 to 2 cm of its fully closed position, at least when the window is moving in the closing direction, since this is the part of the window movement in which trapping of a finger is possible. In one possible arrangement, means are provided for sensing an increase in the motor current, and for restoring the input means to normal if the motor current should increase beyond a certain value, but such restoration is inhibited unless the window is within, say, 1 to 2 cm of its fully closed position.With such an arrangement, the motor can exert its full torque to overcome resistance to movement over the major part of its travel; such resistance is most unlikely to be caused by a trapped fingers However, when the window approaches its fully closed position, the torque which the motor can exert is limited to a lesser value, corresponding to the limiting value of motor current. In another possible arrangement, the speed of the window winder motor is reduced during the final stage of its closing movement; this may be advantageous, since even if the control circuit responds rapidly to an increase in motor current, the inertia of the moving parts, if the window is travelling at full speed, may be sufficient to injure a trapped finger.

The reduction of speed may be achieved in various ways; for example, a resistdr may be switched into the motor circuit, or the field strength of the motor may be increased.

It is also possible to arrange that, when the motor current increases beyond a certain value, the input means is not restored to normal; instead, the motor reverses, so that the obstruction (if there is one) is freed. After a short period, the motor would then return to its previous direction of travel, since the obstruction should by now have been removed. If an obstruction is again encountered, this is almost certainly not a human obstruction, and the motor can be allowed to exert its full torque on this attempt to close the window, to clear the obstruction.

If such a system does not reiy on limit switches or other sensors to detect the fully-closed position of the window, the end of the closing travel will be seen as an obstruction, and therefore the window will reverse and then return to its original direction of movement at the end of its travel. The system should therefore be so arranged that on the second (or perhaps third, or even later) occasion on which the window winder motor stalls, the input means is restored to normal, leaving the window fully closed, instead of reversing the motor. This may also be desirable, even where limit switches or the like are used, in case a limit switch should fail.

Since the amount of friction opposing movement of the window may vary considerably, according to the condition of the guides for the window, there may be difficulty in selecting a limiting value for the motor torque, especially during the final part of the window closing movement. A value of torque which is sufficiently low to substantially eliminate the risk of braking a trapped finger may well be so low that it cannot be guarenteed that the window winder will close the window completely; if the window is moving with a considerable amount of friction, the control circuit will not distinguish between this and an obstruction, and will de-energise the motor.

Conversely, a value of torque which is high enough to guarantee that the window can be moved, despite the friction which may be present, will probably be so high that there is an appreciable risk of breaking a trapped finger.

To overcome this difficulty, the control circuit may be arranged to measure continually the torque exerted by the motor of the window winder, and to limit the torque exerted by the motor of the window winder to a value which is a function of the value of torque measured during the preceding part of the closing movement. In this way, the limiting value of torque can be matched to the amount of friction opposing movement of the window, so that, whatever, the amount of friction, only a comparatively small increase in the torque exerted by the motor can occur before the control circuit de-energises the motor. Most of the torque exerted by the motor will be absorbed by friction; if the increase in torque is due to the presence of an obstruction, the force applied to the obstruction will correspond to the amount of the small increase in torque. It should therefore be possible to arrange for the window to close reliably, while keeping the risk of breaking a trapped finger to an absolute minimum.

The arrangement described above depends on being able to use the torque exerted during an earlier part of a closing movement as a reference value. As an alternative, it might be possible to arrange the control circuit to store a reference value derived from torque measurements on previous window-closing movements. For this purpose, it might be desirable to use a nonvolatile store.

Where the window winder control circuit maintains a continuous record of the position of the window, there is no difficulty in determining when the window approaches within, say, 2 cm of its fully closed position. In the simplified photosensor arrangement in which the photosensor co-operates with isolated marks indicating the fully open and fully closed positions of the window, a third mark could be provided to signal that the window is within a certain distance of its fully closed position.

Although it is desirable for the closing force to be limited, as described above, this limited force may not be sufficient to begin movement of the window under all conditions; for example, the window may be iced up. Thus, the control circuit preferably includes means arranged to detect when normal movement of the window has commenced, and means arranged to de-energise the motor of the window winder if, after such normal movement has been detected, the motor draws more than a predetermined current. The normal movement may be detected by any of the methods discussed above, such as by monitoring the motor current, or by means of a photosensor co-operating with marks on the window glass.

If normal movement fails to occur when the motor is energised, this may be due either to the window being at the end of its travel, or to the window being jammed. In order to ascertain which of these conditions exists, the control circuit preferably also includes means arranged, when normal motion of the window is not detected within a predetermined period from setting of the input means, to reverse the energisation of the motor of the window winder. If normal window movement is now detected, the window must have been at the end of its travel; means is preferably provided which is arranged, if normal movement is detected after reversal of the motor energisation, to restore the motor energisation to its original direction, so that the window is returned to its required, end-of-travel position.If normal movement is still not detected, even after motor reversal, this means that the window is jammed. in the preferred embodiment, means is included which is arranged to reverse the energisation of the motor periodically until normal movement is detected. The aiternating force which is thus applied to the window may manage to free the window; as discussed above, this force need not be limited to a value low enough not to damage trapped fingers, since, if the window has not begun to move, there is no danger of fingers becoming trapped.

The invention may be carried into practice in various ways, but five specific embodiments will now be described by way of example, with reference to the accompanying drawings, of which: Figure 1 is a circuit diagram, partly in block form, of an electric window winder control circuit embodying the invention, for use in a motor vehicle; Figures 2a and 2b, taken together, are a flow chart illustrating the operation of part of Figure 1; Figure 3 is a circuit diagram showing one possible way of implementing the flow chart of Figure 2; Figure 4 is a block diagram illustrating a second circuit for controlling an electric window winder, and incorporating a microprocessor; Figure 5 is a flow chart illustrating the programming of the microprocessor of Figure 4;; Figure 6 is a partial flow chart, which can be substituted for part of Figure 5, to produce a version of the second circuit with slightly different behaviour; Figures 7 and 8 are sections taken on spaced, parallel planes, through a control switch embodying the present invention for an electric window winder; Figure 9 is a circuit diagram, showing how the switch of Figures 7 and 8 is used; and Figures 10 and 11 are views, similar to Figure 8, of two modified forms of control switch.

Referring first to Figure 1, the motor of an electric window winder for use in a motor vehicle is shown at 1 0. The motor 10 is energised from the battery of the vehicle (shown at 1 2) through a transistor driver circuit 14, which is controlled logic signals on two lines 16 and 18. A logic '1 signal on the line 1 6 causes the motor 10 to close the window, while a logic '1 ' signal on the line 18 causes the motor to open the window. Such signals can be produced directly by operating a rocker switch 20 which is spring-loaded to a central position, and has two normally-open contacts 22 and 24, which can be closed by operating the rocker switch in its respective directions.For example, by operating the rocker switch to close the contacts 22, the motor 10 will operate to move the window in the closing direction, but will be de-energised as soon as the rocker switch 20 is released. In this way, the rocker switch 20 can be used to move the window to any position within its range of travel.

In addition, signals on the lines 16 and 18 can be produced by signals on two output lines 26 and 28 from an electronic control circuit 30, which is shown in more detail in Figure 3. The circuit 30 is controlled by two push-buttons 32 and 34; by pressing the push-button 32, for example, the circuit 30 is latched into a state in which it provides a signal on the output line 26, to energise the motor in the closing direction. The circuit 30 remains in this state until the motor current exceeds a certain value, which will normally indicate that the window has reached the end of its travel, and the motor 10 has stalled.

The circuit 30 then restores to normal, and the motor 10 is de-energised. A similar sequence of operations will occur, but with the motor 10 energised in the opening direction, if the pushbutton 34 is operated.

The current through the motor 10 is sensed by a low-value series resistor 36; the potential drop across the resistor 36 is monitored by a current sensor circuit 38, which provides an input signal to the circuit 30 on a line 40 if the motor 10 is drawing a normal current, and on a line 42 if the motor is drawing an abnormally high current.

In addition to the input signals from the push buttons 32 and 34 and from the current sensor 38, the logic circuit 30 receives inputs from the contacts 22 and 24 of the rocker switch, over two lines 44 and 46; the purpose of these inputs is to restore the logic circuit to its idle state if the rocker switch 20 should be operated.

The signals on the lines 26 and 28 from the circuit 30 are combined with the signals from the contacts 22 and 24 by two gates 48; the outputs of the gates 48 are connected to the lines 1 6 and 1 8 through a network of inverters 50 and gates 52, which ensure that signals calling for energisation of the motor 1 0 cannot appear on both lines 1 6 and 1 8 simultaneously.

In addition to the basic operations explained above, the logic circuit 30 incorporates a number of other features, and these can best be explained with reference to Figure 2, which is a flow chart illustrating the operation of the circuit 30. In summary, the additional features are as follows.

Although, in general, the motor 10 is stopped when it draws an abnormally high current, the large current pulse which normally occurs when -starting the motor is ignored. If an abnormally high current persists for longer than is normally needed to start the motor 10, it can be conciuded that there is some obstruction to movement of the window. When this occurs, the logic circuit 30 switches its outputs to energise the motor 10 in the opposite direction. If the motor 10 draws an abnormally high current in this direction also, for a period longer than is needed to start the motor under normal conditions, this means that the window is jammed against movement in either direction; for example, it might be frozen up.In this case, the logic circuit 30 keeps the motor 10 energised, reversing the direction of energisation at intervals of about 1 second, in an attempt to free the window. If the window does become free, this is detected by the fact that the motor current falls to a normal value; when this occurs, the energisation of the motor 10 is continued in its original direction, until the motor stalls at the end of its travel, in the usual way.

If the window has still not become free after nine reversals of the motor 10, the circuit 30 reverts to its idle state and de-energises the motor.

If the window is already at the end of its travel, for example, fully closed, but not frozen up, and the push-button 32 is operated, calling for the window to close, the circuit 30 will operate as though the window has been frozen up, but became free immediately after the first reversal.

After the first reversal, the window opens slightly, but the energisation of the motor 10 then returns to its original direction, and the window closes in the normal way.

Although the push-buttons 32 and 34 are described above as separate items from the rocker switch 20, it will be appreciated that these items could all be combined, so that the contacts 22, 24, 32 and 34 are all controlled by a single member such as a rocker. The rocker could then be biased to a central position by means of tworate springs, so that application of a first pressure to the rocker would close only the contacts 22 or 24, while a heavier pressure would also close the contacts 32 or 34.

Referring now in more detail to Figure 2, when either of the push-buttons 32 and 34 is operated, the state of the logic circuit 30 follows the flow chart shown, starting at Box 1,'Start'. Boxes 2 and 3 are self-explanatory. At Box 4, a test is made to see whether the window is moving; the criterion for this is that the motor current must have been within its normal range for at least 0.3 seconds. This period of 0.3 seconds is necessary because of the possibility of mechanical backlash in the window winder drive; such backlash might make it possible for the motor 10 to run normally for a short period after starting, to take up this backlash, but then to stall again if the window itself will not move.

If this test indicates that the window is moving, a 'Normal Motion' latch is set at Box 5. The primary effect of setting this latch is that from now on, the motor 10 is not allowed to draw a prolonged abnormally high current. The motor current is monitored continuously at Box 6; as soon as the current becomes abnormally high, the motor is de-energised at Box 7, and the circuit becomes idle.

If the test at Box 4 indicates that the window is not moving, Box 8 imposes a delay until 0.4 seconds from the start of motor energisation. At Box 9, the value of the motor current is tested to see whether it is abnormally high; if the motor 10 has by now begun to run normally, the test at Box 4 will be repeated, and when the motor current has been normal for 0.3 seconds continuously, the operation of the circuit continues through Boxes 5, 6 and 7, as described above.

If the test at Box 9 indicates that the motor 10 is still stalled, a 'Reversing Cycles' latch is set at Box 10, to initiate the reversing sequence described above. During this sequence, the criterion for determining whether the window is moving or not is again that the motor 10 should have drawn its normal current for 0.3 seconds continuously, and therefore Box 14 carries out the same test as Box 4; however, before Box 14 is reached, the timer which sets the 0.3 second period has been reset, at Box 13. If the window is still stuck, Box 1 5 imposes a delay until 0.4 seconds has elapsed since control passed through Box 13. At the end of this period, the motor current is reversed, at Box 16, and a cycle counter, which counts the number of reversals executed so far, is stepped at Box 1 7. The count of the cycle counter is tested at Box 18, and when the count has reached 9 control is transferred from Box 18 to Box 7 to de-energise the motor 10 and reset the circuit 30. If the count has not yet reached 9, control passes to Box 11, where the same test is carried out as at Boxes 4 and 14, to determine whether the window is yet moving. If the window is still stuck, Box 12 imposes a delay of 0.6 seconds from the last motor reversal, and control is then passed to Box 1 3.

Thus, Boxes 11 to 1 8 form a loop, and this loop repeats until it is broken at Box 11, 14 or 18; on each repeat, the motor is reversed, as described above, and the time taken for each repeat is the sum of the delays at Boxes 12 and 15, which is 1 second.

If the window is freed by the repeated reversals of the motor 10, the loop will be broken either at Box 11 or Box 14, depending on the exact stage at which the window becomes free, and control will pass to Box 19, where the 'Reversing Cycles' latch is reset. At Box 20, the timer used for the test at Box 4 (and 11 and 14) is again reset; at Box 21, the cycle counter is cleared, and at Box 22, the direction of energisation of the motor 10 is restored to its original direction, no matter what its direction immediately before Box 22. Control is then again returned to Box 4, and the state of the circuit 30 runs through Boxes 4 to 7 in the manner previously described.

It will be understood from the foregoing description that, for almost the whole of the time during which the window is actually moving, the test at Box 6 for abnormally high motor current will be carried out continuously. This means that if the window should meet an obstruction such as a hand or a finger, the motor 10 will not exert the maximum torque of which it is capable to try to overcome the obstuction; instead, at some lesser torque, the motor current will have risen sufficiently that control is transferred from Box 6 to Box 7, and the motor is de-energised. This limitation of the torque helps to reduce the danger of injury to trapped fingers, but nonetheless the motor 10 can still exert its full torque when trying to free a jammed window, because control is then vested in another part of the flow chart.

If a hand has become trapped by the window, the normal action to free it would be to press the push-button 34 (or the rocker switch 20) to open the window. However, if the push-button 32 should be pressed in error, the window will first try to close, and then, after the energisation of the motor has been reversed at Box 16, will open slightly before closing again (Box 22). This slight opening provides an opportunity to extricate the trapped hand.

The flow chart of Figure 2 could be implemented in many ways; Figure 3 shows one particular hardware array which can be used. It is believed that the operation of this array should be clear from the foregoing description, taken in conjunction with the following comments. The block 101 represents a clock generator, which runs at 1OHz. Devices 100, 102, 104, 106 and 108 are R-S latches; the R(eset) and S(et) inputs affect the state of the latch only when they are taken to a logic 'O'. The latch 100 is set when the window is to be closed, by operation of the pushbutton 32, and is reset when the time arrives to de-energise the motor. The latch 102 controls the opening movement of the window, in a similar manner.The latch 104 is only set for a very short period after operation of one of the push-buttons 32 and 34, while the logic is reset at Box 2. The latch 106 is the 'Normal Motion' latch, while the latch 108 is the 'Reversing Cycles latch. The devices 110 and 11 2 are D-type flip-flops, which trigger on the leading edge of their clock waveforms, and are reset by a logic '1' applied to their reset inputs. These two flip-flops form the 0.3 second timer. The devices 114 and 11 6 are decade counters, both of which trigger on the leading edge of their clock waveforms, and can be asynchronously cleared by a logic '1' applied to their 'reset' inputs. The counter 114 has ten outputs 0 to 9, of which only one is at any time at a logic '1' level.This counter serves to set the delays occuring at Boxes 8, 12 and 15, and also, in conjunction with the latch 104, resets the logic at Box 2. The counter 116 has a B.C.D. output, of which only the least significant bit is used; it also has a carry output, which is normally at a logic '1', but goes to a logic '0' when the count reaches 9.

This counter serves as the cycle counter; also, its least significant bit controls the reversing of the motor 10. The gate 11 8 combines the various signals calling for resetting of the logic, including the signal which occurs at Box 7. It can be seen from Figure 3 that operation of the rocker switch 20 or either of the push-buttons 32 and 34 will cause such a reset to occur. The Reset input to the latches 100 and 102 overrides their Set inputs; thus, a brief operation of the switch 20 or a push-button 32 or 34 will completely reset the circuit 30, whatever its previous state. A longer operation of the push-button 32 or 34, sufficiently long to allow the reset pusle to terminate and the latch 100 or 102 to become set, is required to cause the circuit 30 to follow the flow chart of Figure 2 beyond Box 2.

Figures 4 and 5 illustrate the hardware and operation of a second form of control circuit.

Referring first to Figure 4, the circuit includes a motor 10, a battery 12, a motor driver circuit 14, a series current sensing resistor 36, and pushbuttons 32 and 34, which all correspond exactly to the same parts of Figure 1. However, instead of the logic circuit 30, a microprocessor 1 50 is used to control the operation of the motor 1 0. The microprocessor is associated with a read-only program memory 152, and a random-access data memory 1 54. In addition to signals from the push-buttons 32 and 34, the microprocessor receives signals from a photo-electric sensor 1 56, which co-operates with marks on the glass of the window to give a digital measure of the position of the window, and also receives signals from the current sensing resistor 36 through an analogueto-digital converter 1 58.

Figure 5 illustrates the operation of the microprocessor in flow chart form; obviously, a corresponding program would be permanently stored in the read-only memory 1 52. The program makes use of a number of memory locations in the random-access memory 1 54; certain of these locations are used as Boolean 'flags', having only two possible values, '0' and '1'; certain of them are used in a similar manner as flags having three states, '0', '1' and '2'; certain of them are used as counters to count the number of times a particular part of the program is executed; and finally, certain of the memory locations are used to record data parameters such as the position of the window, or the current taken by the motor of the window winder.

In Figure 5 and in the following description, each memory location used is identified by a mnemonic such as B, or 1MAx The following memory locations are used as Boolean flags: N-is set to '1' when the window begins to move, and is only reset to '0' when the motor is de-energised.

S-is set to '1' when it is necessary to inhibit the action of the push-buttons 32 and 34, for example because both push-buttons have been operated simultaneously, or because the window strikes an obstruction, or reaches the end of its travel. The flag S cannot be reset to 0 unless both push buttons 32 and 34 are released.

The following memory locations are used as three-state flags: B-when set to '1', indicates that the push button 32 has been operated, calling for the window to close. Similarly, when set to '2', it indicates that the push-button 34 has been operated, calling for the window to open.

E-is set to '1 when the window winder motor is energised in the window-ciosing direction, and to '2' when the motor is energised in the window-opening direction.

The following memory locations are used as counters: T-sets an initial delay of 0.3 seconds from operation of either of the push-buttons 32 and 34. The purpose of this delay will be explained hereinafter.

TR-performs a function similar to that of the counter 114 in Figure 3; that is to say, it determines when reversal of the energisation of the motor is to occur.

CC-performs the same function as the counter 116 of Figure 3; that is to say, it counts the number of motor reversals which have occurred.

The following memory locations store other parameters: W-stores a number indicating the present position of the window, as sensed by the photo-sensor 1 56. When the window is fully closed, W stores a value of zero, and the value increases from zero as the window opens.

W'-stores the value which was previously stored in location W.

L-stores a number corresponding to the fully open position of the window.

G-stores a number corresponding to the position at which the window is, say, 2 cm from its fully closed position.

I-is the measured value of the motor current; however, this location is not updated during the last 2 cm of the closing movement of the window.

IFS used to store the value of motor current measured during the last 2 cm of the closing movement.

IMAXS the absolute maximum permitted value of the motor current.

IFMAX a a value, less than 1MAx' to which the motor current is limited during the last 2 cm of the closing movement.

Referring now to Figure 5 in more detail, program control starts at Box 1 on switching on the electrical system of the vehicle. At Boxes 2 and 3, the position of the window is sensed, and stored in W to provide an initial value for W. At Boxes 4, 5 and 6 the constants IMAM' G and L are set; these constants are not altered during program execution. A base value is also stored in FMAX' although this value will subsequently be modified. At Boxes 8 to 11, the flags B, E, S and N are all set to zero. This completes the initialisation stage of the program.

Program control then passed to Boxes 12, 13 and 14, where the existing value of W is transferred to W', and a new value of W resulting from sensing the position of the window is stored.

The position of the push-buttons 32 and 34 is then sensed at Boxes 1 5 and 16; if neither of the push-buttons is operated, program control passes through Box 17, which has no effect, and is routed by Boxes 18 and 19 to Box 20, since the flags B and E are both at 0. At Box 20, a delay of, in this example, 0.1 second is imposed, and control is then returned to Box 12. The program continues to follow this loop for as long as neither of the push-buttons 32 and 34 is operated.

If now the push-button 32 is operated, calling for the window to close, program control passes from Box 1 5 to Box 21, and from there, since the flag S is 0, to Box 22. Provided that the pushbutton 34 has not also been operated, program control then passes to Box 23, which compares W with zero to check whether the window is already fully closed. If so, program control is passed to Box 24, where the inhibiting flag S is set to 1.

Boxes 25 to 28 have no effect at this stage, and program control then passes again to Box 20, so that a delay occurs and then the program is repeated.

Assuming that the window is not already fully closed, control passes from Box 23 to Box 29, where the flag B is tested to ascertain whether the push-button 32 has only just been operated; if so, B will not yet have been set to 1, and control passes to Box 30, where B is set to 1 to match the state of the push-button. At Box 31, the counter T is zeroed; thus, at this stage, program control will pass through Boxes 32 and 33 to return to the delay at Box 20.

On subsequent executions of the program, control will again arrive at Box 29, assuming that the push-button 32 is still operated, but since the flag B is now set to 1, control passes from Box 29 to Box 34, where the counter T is incremented.

Until 0.3 seconds has elapsed from the operation of the push-button 32, the counter Twill be less than 3, so that program control passed through Boxes 32 and 33 to the delay at Box 20. However, when the push-button 32 has been kept depressed for 0.3 seconds continuously the counter Twill have reached 3, and control will be passed from Box 32 to Box 35. At Box 35, the flag B is tested to ascertain whether the window is to be closed or opened; in the present case, since the window is to be closed, the flag B will by now have been set to 1, so that control passes to Box 36. At Boxes 36 and 37, the flag E is set to 1, and the motor 10 is energised to close the window.

The counter TR is set to an initial value of 6 at Box 38, while the counter CC is zeroed at Box 39. The flag N is still at 0, and therefore control passes through Box 40 to Box 41, where the present index W of the window position is compared with the previous value of W, now stored in W'. If the window has not yet begun to move, control passes to Box 42, where the counter TR is tested.

On the first execution of this part of the program, Tr will have been set to 6, so that program control returns from Box 42 to the delay at Box 20.

On subsequent executions, the program will reach Box 32 again in the manner described above, but the counter T has now reached a value greater than 3, so that control passes through Boxes 32 and 33 to Box 43, where the counter TR is incremented. If the window is still not moving, the program will again follow the route through Boxes 40, 41 and 42 to Box 20. However, if the window begins to move before the counter TR reaches 10, control will be diverted at Box 41 to Box 44. The cycle counter CC is tested at Box 44; since this counter is still at zero, control bypasses Box 45 to reach Box 46, where the flag N is set to 1 to indicate that the window has started to move. At Box 47, the flag E is tested to ascertain whether the motor is energised in the opening or closing direction.At Box 48, the index W of window position is tested; if the window has reached its fully closed positon, W is zero, and control passes from Box 48 to Box 24, where the inhibiting flag S is set to 1, as described above.

Also, at Boxes 25 to 28, the flags B, E and N are cleared, and the motor 10 is de-energised.

Assuming that the window has not yet reached its fully closed position, control is passed from Box 48 to Box 49, where the index W is compared with the constant G to ascertain whether the window is within, say, 2 cm of its fully closed position. If the window is still more fully open than this, the motor current is measured at Box 50, and stored, as I, at Box 51. The parameter FMAX is then updated on the basis of the stored value of I, at Box 52.

The significance of 1FMAX is that, when the window is within 2 cm of its fully closed position, the motor current is not allowed to exceed IFMAX; if it does, the motor is de-energised. The reason for arranging that 1FLAX is continually updated is to take account of variations in the amount of friction in the window guides as their condition changes, with age and wear for example. One possible equation for calculating IFMAX would simply be 1FMAx=1 +constant In other words, the amount by which the motor current is allowed to rise at the end of the window travel is limited to a constant preset value.In a slightly modified form, the I term in the equation above could be replaced by a term which represents an average current based on a plurality of previous values of I. For example, an average value 1M might be updated according to the following equation IM=klM'+(1k)l where k is a constant between 0 and 1, and 1M' is the previous value of 1M After updating 1FLAX at box 52, the value of I is tested against the absolute limiting value 1MAX at Box 53; if 1MAX is exceeded, program control passes to Box 24, so that the inhibiting flag S is set and the motor is de-energised, as described above.Otherwise, operation of the window winder continues normally, with program control passing to the delay at Box 20.

When the window reaches a position within 2 cm of its fully closed position, control is diverted at Box 49 to Box 54, where the motor current is again measured; however, this time the measured value is stored as IFS at Box 55. 1F is compared with 1FLAX at Box 56: as with the test at Box 53, control then passes either to Box 20 or Box 24, depending on whether or not 1F is less than 1FLAX For example, if a finger should be trapped by the closing window, the motor 10 sill stall, and the motor current will therefore rise, but as soon as it reaches 1FMAx' the motor will be de-energised, so that the closing force on the trapped finger will be fairly limited.

If the push-button 32 is released before the window reaches a fully closed position (but after the motor 10 has become energised), program control will pass from Box 1 5 through Boxes 1 6 and 1 7 to Box 18. Since the flag B has not yet been reset to zero, control then passes to Box 57, where the flag E is tested. Since the motor 10 has already been energised, the flag E has been set to 1, and control passes through Boxes 25 to 28, where the flags B, E and N are all cleared, and the motor is de-energised, as described above.

If the window has not begun to move by the time the counter TR reaches 10, the test at Box 42 will divert control to Box 58, where the cycle counter CC is tested; at this stage, CC will still be at zero, so that control passes through Boxes 59, 60 and 61, where the counter TR is zeroed, the cycle counter CC is incremented, and the energisation of the motor 10 is reversed. Control then passes again to the delay at Box 20. Thus, since the counter TR was initially set to 6, the motor 10 will first be energised in the closing direction for 0.4 seconds, then in the opening direction for one second, and further changes in direction of energisation will occur, at Box 61, at one second intervals, until the window becomes free, when Box 41 will pass control to box 44.

Since the cycle counter is now not at zero, control will pass to Box 45, where the direction of the motor energisation is restored to original, and operation then continues as described above from Box 46.

If the window still has not become free after nine reversals, the test of the cycle counter CC at Box 58 will divert control to Box 24, so that the inhibiting flag S is set to 1, and the motor is deenergised, as described above.

If the push-button 34 is pressed, for a period longer than 0.3 seconds, instead of the pushbutton 32, the circuit will operate generally as described above; Box 62 corresponds to Box 21; Box 63 corresponds to Box 23, Box 64 to Box 29; Box 65 to Box 30: Box 66 to Box 36; Box 67 to Box 37; and Box 68 to Box 48. The tests carried out at Boxes 63 and 68 both compare the window position with the predetermined constant L; equality will occur when the window is fully open.

When the window is opening, there is no counterpart to Boxes 49, 54, 55 and 56; the only current limiting is that which occurs at Box 53, because there is no chance of a finger being trapped during an opening movement.

If the push-button 32 (or 34) is released before the counter T has reached 3, the flag E will still be at zero. Program control will reach Box 57 in the manner described above, but will then pass to Box 69, which tests the flag B to find out which of the push-buttons had been operated. After this test, the flag B is reset to zero, at either Box 70 or Box 71, to agree with the state of the push-buttons 32 and 34, and control then passes to either Box 36 or Box 66. From this point, the circuit operates in the manner described above; however, since neither of the push-buttons is now operated, control will pass from Box 1 5 through Box 1 6 to Box 17, rather than being directed to Box 21 or Box 62.From Box 17, control passes to Box 18, and then to Box 19, where the flag E is tested; the fact that the flag E is not at zero indicates that the motor has already been energised, and therefore control is passed to Box 43, so that the circuit continues to operate in the manner described above until the window reaches the end of its travel, or encounters an obstruction, or persistently refuses to move. When one of these things occurs, control will pass through Boxes 24 to 28, so that the flag E, in particular, is zeroed, and the circuit returns to its idle state, in which it remains in the loop of Boxes 12 to 20.

If the motor 10 is de-energised for any of the reasons just mentioned, while one of the pushbuttons 32 and 34 is still operated, the inhibiting flag S is set to 1, so that control is diverted from Box 21 to Box 62 directly to the delay at Box 20.

The flag S cannot become reset, at Box 17, until both the push-buttons have been released. The circuit will become locked in a similar manner if both push-buttons are pressed at once.

Thus, to summarise the operation of the system from the user's point of view, control of the system is provided by the push-buttons 32 and 34 alone there being no counterpart to the rocker switch 20 of Figures 1 to 3. A relatively prolonged operation of one of the push-buttons (longer than 0.3 seconds) will have an effect similar to operation of the rocker switch 20 of Figures 1 to 3; that is, the motor 10 will be energised for only as long as the button is kept depressed. A shorter operation of one of the pushbuttons will cause the circuit to energise the motor 10 until the window reaches the end of its travel. In the former case, the motor will not be energised until the 0.3 second period has elapsed; this ensures that it is possible to move the window through a distance corresponding to energisation of the motor 10 for only, say, 0.2 seconds.In the latter case, the motor 10 is energised as soon as the push-button 32 or 34 is released.

Figure 6, which for convenience consists of two partial figures, Figures 6a and 6b, can be substituted for Figure 5f; that is to say, Figures 5a to 5e, 6a and 6b together make up a complete flow chart.

The flag N, S, B and E operate in exactly the same way as has been previously described. The counters T, TR and CC also operate as previously described, except that the counter TR is used to perform an additional function, very similar to its previous function. The stores W, W, L, G, 1'1MAx' and 1FLAX are used in much the same way as previously described, although now I is used to store the value of the motor current measured at any stage of the movement of the window. In addition, the following memory locations are used: D-a Boolean flag, set to '1' to indicate that the motor energisation has been reversed after the window encounters an obstruction during a closing movement.

R-a counter, counting the number of reversals which occur as the result of the window encountering an obstruction.

I,,,,--a value, dependent on the current drawn by the motor during recent stages of operation, in the closing direction (except for the last 2 cm of the closing movement); ICMAXS the limiting value of motor current during most of the closing movement, and is less than IMAX W5-stores the value stored in W at the moment when the closing window meets an obstruction.

A system prpgrammed according to Figure 6 (together with the relevant parts of Figure 5) operates exactly as previously described, until the window begins to move, as indicated by the flag N being set to '1'. Control then passes to Box 47 If the window is being opened, the flag E is already set to 2, so that control passes to Box 68, which, as before detects whether the window is yet fully open. If not, the motor current is measured and stored at Boxes 50 and 51, and the measured value is checked against the absolute maximum value at Box 53. If the current is excessive, the inhibiting flag S is set to '1', at Box 24; if not, control returns to the 0.1 second delay at Box 20, all as described above.However, it will be noted that neither 1COAX nor 1FLAX is updated duping opening movements of the window.

If the window is being closed, the flag E will be set to '1', the Box 47 will pass control to Box 100, where the flag R is tested. During normal operation, the flag R will be set to '0', and therefore control passes to Box 48, which, as before, checks whether the window is yet fully closed. Assuming that the window is not yet closed, Box 49 then tests whether the window is within, say, 2 cm of its fully closed position. If not, the motor current is measured and stored, at Boxes 101 and 102, and compared with the limiting value ICMAX at Box 103. If the limiting value is exceeded, suggesting that the window has encountered an obstruction, control is passed to Box 110, which is the beginning of a routine for opening the window again, which will be described later.If, on the other hand, the limiting value 1cMAx is not exceeded, the most recent measured current I is used to update the value ICMAX for example using the formulae already discussed for updating 1FLAX Control then returns to the delay at Box 20.

When the window reaches a position within, say 2 cm of its closed position, control passes from box 49 to Box 105 instead of to Box 101.

The motor therefore continues to run in the closing direction, but at reduced speed. At boxes 106 and 107, the motor current is measured and stored, as before, and at Box 108, this current is compared with 1FLAX As at Box 103, control is passed to Box 110 if the current is excessive, or to the delay at Box 20 if the current is not excessive.

Separate limiting values 1COAX and 1FLAX are used during the normal speed and reduced speed parts of the window closing movement, because some change in current can be expected between these two parts of the movement. The reduced speed during the final part of the movement should help to reduce the amount of force applied to a finger trapped in the closing window, as a result of the inertia of the moving parts.

As explained above, if the current at any stage exceeds the relevant limiting value ICMAX or 1FLAX' control is passed to Box 110. At this box, the current value of W is stored in Ws; the use of Ws is that, if the window subsequently manages to reach a more fully closed position, this can be detected by the fact that W is less than Ws, and the circuit returns to normal closing operation when this occurs. At Box 111, the flag D is set to '1' and at Box 112, the motor is reversed, to open the window and allow the obstruction (assuming that there is one) to be removed. At Box 113, the counter R is incremented, and at Box 114, the counter TR is zeroed. Control then passes to the delay at Box 20.

On the next passage through the flow chart, control is diverted by Box 100 to Box 11 5, since the counter R is no longer zero. The flag D is then tested to find out whether the window is being closed or opened; after the first reversal, the window will be opening, so that control passes to Box 11 6. At this box, the counter W is tested to discover whether the window is fully open; if so, control is passed directly to Box 11 8. If the window is not yet fully open, control is passed to Box 11 7, where the counter TR is tested. If the motor has not yet reversed for 0.4 seconds, TR will still be less than 4, and control is therefore passed to Box 50, so that the circuit operates as for a normal window-opening movement until Box 47 is again reached.In the process, a 0.1 second delay occurs at Box 20, and the counter TR is incremented at Box 43.

Thus, when the motor has reversed for 0.4 seconds, or until the window is fully open, control will pass to Box 118, where the flag D is reset to 'O'. Box 11 9 restores the motor energisation to the closing direction, at normal speed; the normal speed is used because it is assumed that, if the obstruction was caused by part of a human body, the obstruction will by now have been removed.

Control now again passes to the delay at Box 20, but since the counter R has not been zeroed, control will again be diverted by Box 100 to Box 11 5, rather than following the path of normal closing operation to Box 48. However, since the flag D has now been reset, Box 11 5 passes control to Box 120, where the counter W is tested to check whether the window is yet fully closed. If it is fully closed, the inhibiting flag S is set at Box 24; if not, control passes to Box 121, where the counter W is compared with its value W5 at the moment when the window encountered an obstruction. IfW is less than Ws, the window has passed the position of the obstruction, and control is passed to Box 126, where the counter R is zeroed. Control then returns to Box 49, so that the circuit is again following the normal closing operation path.

If, on the other hand, the window has not yet passed the position of the obstruction, the motor current is measured and stored at Boxes 122 and 123, and compared with the absolute maximum value 1MAx at Box 124. If the motor current is not excessive, control again passes to the delay at Box 20. If the motor current is excessive, the counter R is tested at Box 125. If this is only the first occasion on which the motor has been reversed as a result of this particular obstruction, R will be equal to 1, and control will be passed to Box 111, so that another reversal of the motor will occur. However, if the motor has twice been reversed and restored to the closing direction of energisation, and the motor still stalls, the inhibiting latch S will be set at Box 24, and the motor will be de-energised.

It will be appreciated that many variations of the flow chart are possible; for example, Box 117 may be eliminated, so that if the window is not fully open, control is always passed to Box 50.

This will result in the window reversing to its fullyopen position on encountering an obstruction, before returning to the closing direction.

As described above, the energisation of the motor is repeatedly reversed when the window seems to be stuck. One of the most likely reasons for the window being stuck is that it is frozen up, and therefore it may be arranged that the motorreversing routine cannot occur unless the ambient temperature, as sensed by a sensor on the vehicle, is close to or below freezing.

The arrangements of Figures 1 to 5 apply the full driving voltage to the motor 10 immediately on starting. However, there may be advantages in applying other voltage waveforms, such as a ramp voltage, on starting of the motor 1 0. In particular, with the circuit of Figures 1 to 3, it may be possible to decide more quickly after the start of energisation of the motor whether the motor is stalled because of a jammed window (or because the window is already at the end of its travel).

It will be appreciated that the circuitry illustrated in Figure 3, together with part of the circuitry shown in Figure 1, could be formed as a single integrated circuit. It will also be appreciated that, instead of using an array of logic devices which is designed specifically for this application, the flow chart of Figure 2, just like the flow chart of Figure 5, could be implemented by using a suitably programmed microprocessor. This is particularly attractive in cases where a microprocessor has already been incorporated in the design of the vehicle, to control other functions, such as those relatihg to engine operation.The amount of computing time required to control a window winder is small in comparison with the computing power of a microprocessor, so that a single microprocessor could control all the electrically controlled windows of the vehicle, in addition to carrying out its other tasks. The tasks other than controlling the window in question could be carried out during the 0.1 second delay occurring at Box 20.

Whether a specially designed integrated circuit or a microprocessor is used, it would be possible to assemble the whole control circuit, including the power transistors in the drive circuit 14, and any other interface devices which are needed, into a single unit having only a few external connections. Such a unit could well comprise a number of semiconductor wafers assembled into a thick-film hybrid circuit.

Where a microprocessor is used, it is particularly easy to incorporate extra features into the operation of the window winder control, although obviously any such features could in principle be implemented by adding extra hardware to the circuit of Figure 3.

Other methods could be used to determine when the window reaches the end of its travel, and whether the window has begun to move. One method of detecting the end of travel of the window is to use limit switches, but limit switches could not tell whether or not the window has begun to move. Another method would be to use a stepping motor of such a type that the difference between its stalled and non-stalled conditions can be detected, for example by monitoring its load current, as with the motor 10.

Thus, the number of stepping pulses fed to the stepping motor (apart from those fed while it is in a stalled condition) would give a measure of the position of the window.

Arrangements such as this might be adversely affected by mechanical wear and backlash in the window winder drive. If this is a problem. it might be possible, especially where a microprocessor is used, to incorporate a learning ability into the control system, so that the system can keep itself matched to the mechanical characteristics of the window winder as mechanical wear takes place.

With any arrangement which provides a continuous record of the present position of the window, it would be possible to use a control circuit in which a continuously adjustable control, such a slider potentiometer, is used in place of the rocker switch 20 and the push-buttons 32 and 34. The control circuit would then continuously compare the position of the window with the position of the control, and energise the window winder motor to correct any disagreement between the control position and the window position.

Although the circuit described above provide a number of desirable features, it may possibly be preferred to use a much simpler arrangement, which nonetheless embodies the invention.

Certain simplified embodiments will therefore now be described.

Figures 7 and 8 show a manually-operable control switch 220, which is intended for use with a reversible electric window winder. The window winder is of the type having an armature and two field windings; energisation of the armature and one field winding causes the winder to open the window, while energisation of the armature and the other field winding causes the winder to close the window. The parts of the switch 220 which are concerned with energising the winder are also largely conventional in construction.Thus, the switch has a manually-rockable control member 227 which is spring-biassed to a central position; when the control member is displaced in either direction from the central position, a cam 228 on the control member 227 closes a pair of contacts 230 to energise the armature, while a further cam 232 on the control member closes one of two pairs of contacts 234 and 236, depending on which way the control member has been displaced from its central position, and therefore energises the appropriate one of the field windings of the window winder. Figure 9 illustrates how the contacts 230, 234 and 236 are connected to the window winder; the armature of the window winder is shown at 224, while the two field windings are shown at 226, and the battery of the vehicle is shown at 225.

The switch 220 also includes a latching arrangement, which engages when the control member 227 has been moved to either limit of its travel, to hold the control member in this position, As can be seen from Figure 7, the spring biasing for the control member 227 is provided by two helical compression springs 229, one to oppose movement of the control member 227 in each direction from its central position. However, as the control member is moved away from its central position towards one of its limit positiohs, it encounters an additional resistance to movement, after the contacts 230 and 234 or 236 have been closed, but before the latching arrangement engages.This additional resistance makes it possible for the driver of the vehicle to avoid inadvertently latching the switch in either of its limit positions; a definite increase in force is needed to overcome this resistance and latch the switch. The additional resistance is provided by two rubber bushes 231, which are fitted around the two biassing springs 229, so that as the control member 227 approaches one of its limit positions, one of the rubber bushes 231 is compressed between the control member 227 and the housing of the control switch.

The latching arrangement comprises a latching pin 238 which can slide, radially to the axis of rocking of the control member 227, in a guide bore in the housing of the switch 220, to penetrate into one of two blind bores 240 in the control member 227. The pin 238 is biassed in the direction to engage in the bores 240 by a bimetallic strip 242 mounted by one end in the housing of the switch, and having its other end connected to the latching pin 238. Thus, the arrangement as so far described will latch the switch in either af its limit positions by engagement of the pin 238 in one of the bores 240. To allow this latching to be released, a heater winding 244 is wound on the bi-metallic strip 242, and is connected in parallel with the armature 224 of the window winder.Thus, when the switch is latched, the bimetallic strip 242 will heat up, and after a short delay, the strip will have curved sufficiently to withdraw the latching pin 238 from the bore 240, so that the switch 220 returns to normal. If, for example, the window winder takes 6 seconds to move the window through its full travel, the latching arrangement may be so arranged that it releases after, say, 8 seconds. Since this means that the window winder 222 will be energised after it has reached the limit of its travel, the winder should either be able to stall without damage, or should include a slipping clutch, or a limit switch which will break the circuit at the end of the travel of the window.

Various such arrangements are already known, and will not be described in detail.

Various modifications of this latching arrangement are possible. For example, the latching pin 238 may be biased into the bores 240 by an ordinary spring arrangement, with an electromagnet being provided to withdraw the pin from the bore after an appropriate delay.

In a further modification, the latching pin 238 is again controlled by an electromagnet, but, as shown in Figure 10, the electromagnet (shown at 260) urges the pin 238 into engagement with the bores 240, against a return spring; a spring 262 may be interposed between the electromagnet 260 and the pin 238, to limit the force which can be applied to the pin 238. The circuitry which is needed to operate the electromagnet 260 could comprise a simple R-C delay circuit This arrangement has the advantage that it is impossible for the switch 220 to remain in a latched position when no power is being applied to the circuit.

In all the arrangements described above, the pin 238 has a square end, and engages in parallel-sided bores 240. In an alternative arrangement, the end-of the pin 238 could be rounded, and engage in part-spherical dimples in the control member 227. This arrangement would allow the switch 220 to be latched, as described above, but it would also allow the switch to be returned manually to its "off" position before the 8 second delay has elapsed.

Figure 11 shows a modification of the lastmentioned arrangement, in which the rounded end of the pin 238, instead of merely dropping into a dimple in the control member at the limit of the travel of the control member, has to ride over a bump 270 as the control member approaches either of its limit positions. With this arrangement, there is no need to use the rubber bushes 231 of Figure 7; the force needed to cause the bumps 270 to push past the pin 238 is sufficient to ensure that inadvertent latching of the switch is avoided.

The arrangements described above operate on the principle of maintaining power to the window winder for a period which is sufficient for a full stroke of the window. As an alternative, limit switches may be incorporated in the window winder itself, and act to release the latching of the control switch. In the case where a latching pin 238 is withdrawn from its latching position by an electromagnet, the electromagnet may simply be energised by operation of a normally-open limit switch when the window reaches either end of its travel. In this case, the power supply to the limit switch should be taken through one of the pairs of contacts 230, 234 or 236, to ensure that the electromagnet does not remain energised when the control switch 220 has restored to normal. In the case where the latching pin 238 is urged towards its latching position by an electromagnet, the power for the electromagnet may again be drawn through the contacts 230, but in this case, a normally-closed limit switch would be required to break the electromagnet circuit and release the latch on the switch 220 when the window reaches the end of its travel.

It should also be understood that the term 'window winders' is to be construed as extending to actuators for closures for other openings; for example, the invention is applicable to motorised sun roofs for motor cars, just as much as to motorised windows.

Normally, each window is controlled by a control device or devices mounted near that window; in most vehicles with electrically operated windows, these windows form part of the doors of the vehicle, and are each controlled by a switch mounted on the associated door, below the window. However, the control circuits may also receive control signals from other sources. For example, controls may be provided at the driver's position, allowing him to control all the windows of the vehicle while driving. These controls would override the other controls. It would also be possible to arrange for the driver to be able to disable completely the controls for the rear windows of the vehicle; this might be desirable for safety reasons when young children are being carried in the rear of the vehicle.

Another possibility would be to arrange for all the windows of the vehicle to close automatically when the doors are locked; this ensures that, provided the driver remembers to lock the vehicle, the windows cannot inadvertently be left open.

Another way of achieving a similar result would be to arrange for the windows to close automatically when the ignition system of the vehicle is switched off. In a preferred version of this arrangement, the ignition switch has an 'Accessories On' position between its 'Off' and 'On' positions, and the windows do not close until the switch is moved from 'Accessories On' to 'Off'. This makes it possible to stop the engine of the vehicle without closing the windows. As an alternative to actually closing the windows, the system could be arranged to give an alarm if the door locks are set or the ignition system is switched off, without all the windows being closed.

Cars with 'central-locking' systems could be conveniently arranged so that the final locking action from outside the vehicle also activates the window-closing routine.

A further facility which might be incorporated is to allow the driver to select a 'ventilation' setting, in which, instead of the windows moving to a fully closed position, they move to a position in which a gap of, say, 2 cm is left open. This facility could be applied to all the windows, or it might be provided only for the window of the driver's door. Where all the windows have this facility, a single switch might be provided to select the 'ventilation' setting for all windows simultaneously, or separate switches might be provided to allow the 'ventilation' setting to be selected for certain windows only. The movement of the windows to their nearly closed position could be triggered by one of the methods discussed above, that is, by locking of the doors of the vehicle, or by switching off the ignition system of the vehicle.

It might be desirable to include a switching device in the automatic window-closing circuit which isolates this function and thereby permits any or all of the windows to be left in pre-set open positions if required.

It may be desirable to arrange that only one of the window winders of the vehicle can be energised at a time, in order to avoid excessive load on the vehicle battery. This can be achieved by arranging for the various window winders to have an order of priority; normally, the driver's window would have the highest priority, so that, when the associated window winder is operating, none of the other window winders of the vehicle can be used. When an arrangement is used which closes all the windows of the vehicle automatically in response to some action such as locking the doors, the windows could be arranged to close sequentially rather than simultaneously, for the same reason.

Claims

1. A control circuit for an electric window winder, comprising input means which can be manually set in at least two states, and means arranged, when the input means is so set, to supply current to a motor of the window winder to move the window to a position corresponding to the set state of the input means, the said minimum of two states corresponding to the fully open and fully closed positions of the window.

2. A circuit as claimed in Claim 1, in which the input means comprises a plurality of manuallyoperable switching devices, each having a normal position which it adopts in the absence of manual forces on the switching devices, and an offnormal position, in which it sets digital memory means, also forming part of the input means, from a normal state to a state corresponding to one of the said set states of the input means, the output of the memory means being connected to control the motor current supplying means.

3. A circuit as claimed in Claim 2, in which the input means comprises two spring-loaded pushbutton switches.

4. A circuit as claimed in Claim 1, in which the input means comprises a plurality of manuallyoperable switching devices, each having a normal position, and an off-normal position in which it may be latched, each of the said set states of the input means being represented by a respective one of the switching devices being latched in its off-normal position, and the switching devices being connected to control the motor current supplying means.

5. A circuit as claimed in any of the preceding claims, which also includes manual control means arranged to energise the motor of the window winder in a selected direction for only as long as the manual control means are manually maintained in an off-normal position.

6. A circuit as claimed in any of Claims 1 to 4 in which the input means comprises a control switch which is so arranged that a steady pressure of a first, lesser, magnitude applied to the control switch will cause the motor of the window winder to be energised in a selected direction for only as long as the said steady pressure is maintained, while a pressure of a second, greater, magnitude applied to the control switch will set the input means into one of its said two set states.

7. A circuit as claimed in Claim 2 or Claim 3, which includes timing means arranged to distinguish between operations of the manuallyoperable switching devices having durations shorter or longer than a predetermined period, and, in response to a shorter operation thereof, to set the input means into one of its two set states, or, in response to a longer operation of one of the manually-operable switching devices, to energise the motor for only as long as the respective manually-operable switching device is kept operated.

8. A circuit as claimed in Claim 7, in which the timing means is also arranged, when a longer operation of one of the switching devices occurs, to delay energisation of the motor until the said predetermined period has elapsed since operation of the switching device.

9. A circuit as claimed in any of the preceding claims, in which the input means is also arranged to allow manual resetting of the input means from a set state to a normal state.

10. A circuit as claimed in any of the preceding claims, which includes means arranged to monitor the torque exerted by the motor of the window winder, and to restore the input means to a normal state and de-energise the motor when the torque exceeds a predetermined value, at least in the window-closing direction.

11. A circuit as claimed in any of Claims 1 to 9, which includes means arranged to monitor the torque exerted by the motor of the window winder, and to reverse the energisation of the motor when the motor torque exceeds a predetermined value in the window-closing direction.

12. A circuit as claimed in Claim 10 or Claim 11, which includes means arranged to disable the torque monitoring means from restoring the input means or reversing the motor energisation during an initial stage of the energisation of the motor.

13. A circuit as claimed in Claim 12, in which the disabling means is arranged to disable the torque monitoring means from restoring the input means or reversing the motor energisation until movement of the window operated by the window winder is detected.

14. A circuit as claimed in Claim 13 in which the disabling means is arranged to disable the torque monitoring means from restoring the input means or reversing the motor energisation until movement of the window has been sensed directly by a position transducer.

1 5. A circuit as claimed in Claim 13, in which the disabling means is arranged to disable the torque monitoring means from restoring the input means or reversing the motor energisation at least until the motor torque falls below a predetermined value.

16. A circuit as claimed in Claim 15, in which the disabling means is so arranged that the torque monitoring means is disabled from restoring the input means or reversing the motor energisation until the motor torque has remained below the predetermined value for a predetermined period.

17. A circuit as claimed in any of Claims 10 to 16, in which the torque monitoring means is arranged to monitor the motor torque by monitoring the current drawn by the motor.

18. A circuit as claimed in any of Claims 10 to 17, which includes means arranged to monitor the torque exerted by the motor over only the final part of the window-closing movement, and to de energise the motor if the torque exceeds a certain value.

19. A circuit as claimed in Claim 18, which includes means arranged to monitor the torque exerted by the motor over at least part of its movement, other than the said final part of the window-closing movement, and to update the magnitude of the said certain value as a function of the torque exerted.

20. A circuit as claimed in Claim 18 or Claim 19, which includes means arranged to monitor the torque exerted by the motor over parts of its movement other than the said final part of its window-closing movement, and to de-energise the motor if the motor torque exceeds a second, predetermined value greater than the first mentioned value.

21. A circuit as claimed in any of the preceding claims, which includes means arranged to reduce the speed of movement of the window over a final part of the window-closing movement.

22. A circuit as claimed in Claim 21, which includes means arranged to interrupt or reverse the energisation of the motor if the motor torque should exceed a certain value during the final part of the window-closing movement, or if the motor torque should exceed a second certain value during another part of the window-closing movement.

23. A circuit as claimed in Claim 22, which includes means arranged to monitor the motor torque, and to update the first certain value as a function of measured torque during the final part of the window-closing movement, and to update the second certain value as a function of measured torque during other parts of the window-closing movement.

24. A circuit as claimed in any of the preceding claims, which includes means arranged, if movement of the window operated by the window winder is not detected within a predetermined period, to reverse the energisation of the motor of the window winder.

25. A circuit as claimed in Claim 24, in which the motor energisation reversing means is arranged to reverse the energisation of the motor at intervals for as long as the input means remains in one of the said set states and movement of the window operated by the window winder has not been detected.

26. A circuit as claimed in Claim 25, which is so arranged that, if movement of the window operated by the window winder has- not been detected after a predetermined number of reversals of the energisation of the motor, the input means is restored from its set state to its normal state.

27. A circuit as claimed in Claim 25 or Claim 26, in which the energisation reversing means is arranged, if movement of the window is detected within a predetermined period after a reversal of the motor energisation by the reversing means, to continue energisation of the motor in the same direction as before the first reversal of the motor energisation.

28. A circuit as claimed in any of Claims 24 to 27, which is arranged to detect movement of the window operated by the window winder by monitoring the torque exerted by the motor of the window winder.

29. A circuit as claimed in any of Claims 1 to 17, which includes means arranged to monitor the torque exerted by the motor of the window winder, and, at least during an initial stage of the energisation of the motor, to reverse the energisation of the motor if the motor torque exceeds a predetermined value.

30. A circuit as claimed in Claim 29, in which, when the motor torque has remained below a predetermined value for a predetermined period, the torque monitoring means is disabled from reversing the energisation of the motor.

31. A circuit as claimed in Claim 28 or Claim 29, or Claim 30, in which the torque monitoring means is arranged to monitor the motor torque by monitoring the current drawn by the motor.

32. A control circuit for an electric window winder, which circuit includes means arranged to monitor the current drawn by the motor of the window winder, and to modify or remove the energisation of the motor if the motor current should exceed a predetermined value, at least in the window-closing direction.

33. A circuit as claimed in Claim 32, which includes means arranged to disable the current monitoring means from reducing or removing the motor energisation during an initial stage of the energisation of the motor.

34. A circuit as claimed in Claim 33, in which the disabling means is arranged to disable the current monitoring means until movement of the window operated by the window winder is detected.

35. A circuit as claimed in Claim 32, or Claim 33, or Claim 34, in which the current monitoring means is arranged to reverse the energisation of the motor if the motor current should exceed the said predetermined value.

36. A circuit as claimed in any of Claims 32 to 35, which is so arranged that the speed of movement of the window is reduced over a final part of the window-closing movement.

37. A control circuit for an electric window winder, the circuit being substantially as herein described, with reference to the accompanying drawings.