The invention is concerned, however, with the requirement that not only should the arrangement be able to detect a force applied over a small area but also a force applied over a relatively large area.

According to the invention, therefore, the sensor arrangement as first set forth above is characterised by force-applying means arranged to apply the predetermined force at positions clear of the spacer means.

Force-responsive sensors and systems embodying the invention, for use in window safety systems in motor vehicles, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a cross-section through one of the sensors; Figure 2 is an underneath view of a first part of the sensor of Figure 1; Figure 3 is a plan view of a second part of the sensor of Figure 1; Figure 4 is a perspective view of a motor vehicle showing where one of the sensors can be mounted in a window channel; Figure 5 is a section on the line V-V of Figure 4; Figure 6 is an enlarged view of part of Figure 5 showing the sensor of Figures 1 to 3 mounted, in the window channel; Figure 7 is a plan view showing a stage in the construction of a modified form of the sensor of the preceding Figures; Figure 8 corresponds to Figure 7 but is an end view showing a later stage in the manufacture of the sensor of Figure 7; Figure 9 is an end view of a further modified form of the sensor ; Figure 10 is an underneath view of part of the sensor of Figure 9; Figure 11 is a plan view of another part of the sensor of Figure 9; and Figure 12 corresponds to Figure 6 but shows the sensor of Figures 9-11 mounted in the window channel.

Figures 1,2 and 3 show one of the sensors 5. It is of indeterminate length and predetermined width. In response to a force applied to it at individual points along either of its large surfaces and in a direction perpendicular, or at least transverse, to such surface, it produces an electrically detectable signal in a manner to be described.

As shown in Figure 1, the sensor has an upper rectangular cover layer 10 which is made of flexible and resilient electrically insulating material and extends over the entire upper surface (as viewed in Figure 1) of the sensor. The cover layer 10 carries spacers 12A and 12B made of electrically insulating material which are positioned at intervals along the length of the cover layer, as will be described in more detail below with reference to Figure 2. In addition, the underside of the cover layer 10 carries an electrically conductive strip 14 extending along the full length of the sensor.

The sensor 5 also has a lower or base layer 16 which is again made of electrically insulating and flexible and resilient material. It extends over the entire lower surface (as viewed in Figure 1) of the sensor. The layer 16 carries a longitudinally extending strip 18 of electrically conductive material on its upper surface which, like the conductive layer 14, extends along the full length of the sensor.

Figure 2 is an underside view of the cover layer 10, removed from the sensor. Figure 2 shows how the spacers 12A, 12B are positioned at intervals along the length of the sensor and staggered in relation to each other across the width of the cover layer 10.

Figure 3 is a plan view of the base layer 16 when removed from the sensor.

When a force is applied to the cover layer 10 in the direction of the arrow A (Figure 1), the layer 10 flexes and the conductive strip 14 will be pressed into contact with the conductive strip 18. This assumes, of course, that the base layer 16 is suitably supported. Similarly, if a force is applied in the direction of the arrow B, the layer 16 flexes and again contact between the conductive strips 14 and 18 will take place (assuming that the cover layer 10 is properly supported). If the conductive strips 14 and 18 are connected to a suitable electrical supply, an electrical signal will thus be produced when contact between the conductive strips 14 and 18 occurs.

In this way, an electrical signal can be produced by the sensor 5 in response to a force applied at substantially any point along its length.

The spacers 12A, 12B, in combination with the resilience of the cover layer 10, ensure that there is no normal contact between the strips 14 and 18.

The spacers 12A, 12B and the conductive strips 14,18, are advantageously formed on the layers 10 and 16 by means of a printed circuit technique.

The spacers 12 are shown in Figures 1 and 2 as being of rectangular form in plan and cross-section. However, they can be of any suitable shape.

As shown in Figure 4, a motor vehicle has a door 40 supporting a window frame 42 in which a window glass 44 is upwardly and downardly slidable. The window glass 44 is raised and lowered by means of an electric motor operable under control of an occupant of the vehicle. Figure 5 shows a section through the window frame 42, comprising a rigid mounting channel 46 supported by inner and outer frame members 48 and 49. The mounting channel 46 supports a window sealing and guiding channel 50 having side walls having side walls 50A and 50B. The window channel 50 may be made of extruded or moulded flexible material such as rubber or plastics material. The distal edges of the side walls of the channel have outwardly directed lips 52 and 54 which extend over the corresponding edges of the mounting channel 46. Near the base of the channel 50, it has further outwardly directed lips 56 and 58 which engage the curved-over edge regions of the frame members 48 and 49 and resiliently hold the channel 50 within the mounting channel 46.

The channel 50 also has lips 60 and 62 which extend across the mouth of the channel and a further inner lip 64 near the base of the channel. Figure 5 shows the window glass 44 which, as it rises to the closed position, enters the channel 50 with the outer surfaces of the lips 60 and 62 bearing against its opposite faces and the lip 64 bearing against the edge of the glass. The surfaces of the lips 60,62, 64 which make contact with the glass 44 may be covered with a layer of flock 66 or other similar material.

Within the distal edge of each side wall of the channel 50, one of the sensors 5 (as shown in Figures 1 to 3) is embedded as a unit so as to run longitudinally along the length of at least part of the channel 50; advantageously, each sensor 5 runs along that part of the channel 50 which extends along the top of the window opening and down the"A"pillar of the vehicle to the region of the rear view mirror. Figure 5 shows the sensors 5 merely diagrammatically.

Figure 6 shows an enlarged view of the region"X"of Figure 5, and shows how the sensor 5 is mounted within a hollow chamber 70 in the material of the side wall 50A of the channel 50. The chamber 70 has a generally planar upper internal wall which abuts against the outer surface of the cover layer 10 of the sensor 5.

Along its lower surface, however, the hollow chamber 70 has a longitudinally extending ridge 71 which is in contact with the undersurface of the base layer 16, and which thus produces longitudinally extending hollow grooves 74,76. If an obstruction, such as part of the human body, is placed in the window opening when the window glass 44 (Figure 5) is in the open or partly open position, and the window is then caused to rise by energisation of the driving motor, the obstruction will be carried upwardly by the closing window glass and will cause a force F to be applied to the outwardly facing surface 78 of the material of the side wall 50A of the channel 50. This force will be transmitted by the material of the channel to the ridge 71, causing the base layer 16 to flex so that the conductive strip 18 moves into electrical contact with the conductive strip 14.

An electrically detectable control signal will therefore be produced which can be used to cause immediate de-energisation of the window glass driving motor, advantageously followed by reversal of the motor to lower the window glass away from the obstruction.

The constructior. of the sensor 5 in the opposite side wall 50B of the channel 50 is the same.

As shown in Figure 5, the base of the channel 50 is provided with two longitudinally extending chambers 72 to increase the resilience of the side walls of the channel. This additional resilience ensures that only a low reactive force is applied to the obstruction by the window glass during the very short period of time in which it may continue tc rise after the sensor 5 has produced the control signal. Clearly, the resilience of the side wall must not be so great as to reduce the sensitivity of the sensor. The hollow chambers 72 may be omitted.

The arrangement shown in Figure 6 is advantageous in that it will not only detect a force F applied to a small part of the total area of the surface 78 (e. g. insertion of a human finger into the window opening) but it will also detect a force applied over an extended area of the surface 78 (e. g. by a human arm or head).

This is because the sensor 5 has no electrically insulating spacers extending across its full width (for example, at intervals along the length of the sensor), so that there is nothing to prevent such a large-area force from causing the ridge 71 to move the conductive strip 18 into contact with the conductive strip 14.

Figures 7 and 8 show how a sensor of the general form shown in Figures 1 to 3 may conveniently be produced. In the sensor of Figures 7 and 8, the separate electrically insulating layers 10 and 16 are replace by a single resilient and flexible electrically insulating layer 80. By means of a printed circuit technique preferably (or other suitable technique), electrically <BR> <BR> <BR> <BR> <BR> insulating spacers 12A, 12B are formed on the upper surface of the layer 80 along two lines, one line being immediately adjacent an edge 82 of the layer 80 and the other line being between the edge 82 and the centre line 84 of the layer 80. Again, the spacers 12A, 12B are staggered in relation to each other along the length of the sensor.

An electrically conductive strip 18, corresponding to the strip 18 of the sensor 5 of Figures 1 to 3, is formed onto the upper surface of the layer 80, between the spacers 12A and 12B. A narrower electrically conductive strip 14, corresponding to the strip 14 of the sensor 5 of Figures 1 to 3, is formed on the upper surface of the layer 80, mid-way between the centre line 84 of the layer 80 and the edge 86.

A bending operation is then carried out, bending one half of the layer 80 onto the other half, along a bend line coinciding with the centre line g4. The result of this is to produce the sensor 88 shown in Figure 8. Such a sensor may be used in the same way as described above with reference co Figures 1 to 3 and 4 to 6.

Figures 9-11 show another modified sensor.

In the sensor 89 of Figures 9 - 11, there is an upper layer 90 which is made of resilient and flexible electrically conductive material having narrow longitudinally extending electrically insulating edge regions 92 and 94 and carrying an electrically insulating spacer 96. In addition, the sensor has a lower or base layer 98, again made of flexible and resilient electrically conductive material and with narrow longitudinally extending electrically insulating edge regions 100 and 102. Figure 10 shows an underside plan view of the layer 90, and Figure 11 shows a plan view of the layer 98.

Figure 12 corresponds to Figure 6 and shows how the sensor 89 of Figures 9 to 11 can be incorporated as a unit within a hollow chamber in the material of the wall of the channel 50 (Figure 5) of the window glass of a motor vehicle door.

As shown in Figure 12, the hollow chamber 104 of Figure 11 differs from the hollow chamber 70 of Figure 6 in that the hollow chamber 104 has longitudinally extending grooves or recesses 106,108 instead of the longitudinally extending ridge 71 of Figure 6. The internal surface of the chamber 70 is thus in contact with the sensor 89 over longitudinally extending regions 109,110, 111 and 112. Within the chamber 104, the resilience of the layers 90,98, together with the electrically insulating spacer 96, ensure that the conductive areas of the layers 90 and 98 are normally held spaced apart. However, in response to a force F applied to the surface 78 of the flexible material, by an obstruction present in the window opening while the window glass is rising (in the manner explained in conjunction with Figure 6), the material of the window channel in the regions 111 and 112, on each side of the groove 108, causes the conductive area of the lower layer 98 of the sensor to move into contact with part of the conductive area of the upper layer 90, thereby producing an electrical signal. Again, the sensor will respond not only to a force F applied to a small part of the area of the surface 78 but also to a force applied over a large part of this area.

The narrow insulating regions 92,94, 100,102 ensure that inadvertent contact does not occur between the two layers 90,98.