Abstract:
A force-responsive sensor is disclosed, such as for incorporation in a safety system for detecting an obstruction in a window opening closable by a motorized slidable window pane. The sensor is mounted within a hollow volume in flexible material running alongside the top frame member of the window opening. The sensor comprises an upper flexible and resilient layer supporting a continuous longitudinally extending conductive strip. This upper layer is spaced from a similar layer supporting a continuous longitudinally extending conductive strip, the two layers being separated from each other by insulating spacers spaced at intervals along the length of the sensor. Any obstruction in the window opening is carried upwardly by the rising window glass and applies a force to the flexible material. A ridge in the lower wall of the hollow chamber responds by causing contact between the two conductive strips to produce a warning signal. The construction is such that the sensor responds not only to a point force but also to a force applied over a substantial length of the window frame.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a force-responsive longitudinally extending sensor arrangement, comprising first longitudinally extending electrically conductive strip means defining a first longitudinally extending continuous electrically conductive region, second longitudinally extending electrically conductive strip means defining a second longitudinally extending continuous electrically conductive region, the strip means being mounted so that the two regions are superimposed and are normally resiliently separated from each other by electrically insulating spacer means which are situated between the two strip means, the two regions being able to be flexed against the resilience relatively towards each other in response to a predetermined force so that contact occurs between at least a portion of one of the regions and a corresponding portion of the other region. 
     SUMMARY OF THE INVENTION 
     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. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     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: 
     FIG. 1 is a cross-section through one of the sensors; 
     FIG. 2 is an underneath view of a first part of the sensor of FIG. 1; 
     FIG. 3 is a plan view of a second part of the sensor of FIG. 1; 
     FIG. 4 is a perspective view of a motor vehicle showing where one of the sensors can be mounted in a window channel; 
     FIG. 5 is a section on the line V—V of FIG. 4; 
     FIG. 6 is an enlarged view of part of FIG. 5 showing the sensor of FIGS. 1 to  3  mounted in the window channel; 
     FIG. 7 is a plan view showing a stage in the construction of a modified form of the sensor of the preceding Figures; 
     FIG. 8 corresponds to FIG. 7 but is an end view showing a later stage in the manufacture of the sensor of FIG. 7; 
     FIG. 9 is an end view of a further modified form of the sensor; 
     FIG. 10 is an underneath view of part of the sensor of FIG. 9; 
     FIG. 11 is a plan view of another part of the sensor of FIG. 9; and 
     FIG. 12 corresponds to FIG. 6 but shows the sensor of FIGS. 9-11 mounted in the window channel. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIGS. 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 FIG. 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 FIG. 1) of the sensor. The cover layer  10  carries spacers  12 A and  12 B 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 FIG.  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 FIG. 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. 
     FIG. 2 is an underside view of the cover layer  10 , removed from the sensor. FIG. 2 shows how the spacers  12 A,  12 B 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 . 
     FIG. 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 (FIG.  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  12 A,  12 B, 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  12 A,  12 B 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 FIGS. 1 and 2 as being of rectangular form in plan and cross-section. However, they can be of any suitable shape. 
     As shown in FIG. 4, a motor vehicle has a door  40  supporting a window frame  42  in which a window glass  44  is upwardly and downwardly slidable. The window glass  44  is raised and lowered by means of an electric motor operable under control of an occupant of the vehicle. FIG. 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  50 A and  50 B. 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  43  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. FIG. 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 FIGS. 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. FIG. 5 shows the sensors  5  merely diagrammatically. 
     FIG. 6 shows an enlarged view of the region “X” of FIG. 5, and shows how the sensor  5  is mounted within a hollow chamber  70  in the material of the side wall  50 A 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  (FIG. 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  50 A 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 construction of the sensor  5  in the opposite side wall  50 B of the channel  50  is the same. 
     As shown in FIG. 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 to 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 FIG. 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 S 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 . 
     FIGS. 7 and 8 show how a sensor of the general form shown in FIGS. 1 to  3  may conveniently be produced. In the sensor of FIGS. 7 and 8, the separate electrically insulating layers  10  and  16  are replaced by a single resilient and flexible electrically insulating layer  80 . By means of a printed circuit technique preferably (or other suitable technique), electrically insulating spacers  12 A,  12 B are formed on the upper surface of the layer  80  along two lines, one line being immediately adjacent an edge  82  to the layer  80  and the other line being between the edge  82  and the centre line  84  of the layer  80 . Again, the spacers  12 A,  12 B 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 FIGS. 1 to  3 , is formed onto the upper surface of the layer  80 , between the spacers  12 A and  12 B. A narrower electrically conductive strip  14 , corresponding to the strip  14  of the sensor  5  of FIGS. 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  94 . The result of this is to produce the sensor  88  shown in FIG.  8 . Such a sensor may be used in the same way as described above with reference to FIGS. 1 to  3  and  4  to  6 . 
     FIGS. 9-11 show another modified sensor. 
     In the sensor  89  of FIGS. 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 . FIG. 10 shows an underside plan view of the layer  90 , and FIG. 11 shows a plan view of the layer  98 . 
     FIG. 12 corresponds to FIG.  6  and shows how the sensor  89  of FIGS. 9 to  11  can be incorporated as a unit within a hollow chamber in the material of the wall of the channel  50  (FIG. 5) of the window glass of a motor vehicle door. 
     As shown in FIG. 12, the hollow chamber  104  of FIG. 11 differs from the hollow chamber  70  of FIG. 6 in that the hollow chamber  104  has longitudinally extending grooves or recesses  106 ,  108  instead of the longitudinally extending ridge  71  of FIG.  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 FIG.  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 .