FORCE-RESPONSIVE DETECTORS AND SYSTEMS AND METHODS OF MAKING THEM

Abstract: A force-responsive sensor comprises upper and lower cover layers (10, 12), the upper layer being resilient and flexible and shown as transparent for ease of illustration. An electrically conductive layer (14) carries separate individual electrically insulating spacers (16) which separate it from two electrically conductive members (18, 20). Each of these members (18, 20) has a plurality of spaced resilient fingers (24, 28), the fingers of the two members (18, 20) being inter-digitated. The members are formed as films on the layer (10). Where the members (18, 20) are not supported by the spacers (16), they are normally held apart from the conductive layer (14) by the resilience of the upper layer (10). In response to an applied force (F), one or more of the fingers (24, 28) is pressed into contact with the conductive layer (14) to enable the production of a corresponding electrical signal. The positioning of the spacers (16) ensures that they do not increase the overall width (w) of the sensor. A force applied by a relatively large-area flat object is transmitted by a protruberance (29) to one of the fingers (24, 28). There may be a plurality of protruberances (29) spaced apart along the sensor. The sensor may be used in a safety system for detecting obstructions in a window opening having a motor-slidable window glass.

Description: FORCE-RESPONSTVE DETECTORS AMD SYSTEMS AND METHODS OF A TN^ THEM The invention relates to force-responsive sensors and systems and methods of making them. Sensors and systems embodying the invention, and to be described in more detail below by way of example only, are for use in motor vehicles for detecting the presence of an obstruction in a window opening closable by a motorised window pane. However, such sensors and systems may be used in many other applications. According to the invention, there is provided a force-responsive longitudinally extending sensor, comprising first longitudinally extending electrically conductive means, second electrically conductive means superimposed on the first means, electrically insulating means positioned between and spacing the first means from longitudinally distributed parts of the second means, each remaining part of the second means normally being resiliently held spaced apart from the first means but being able to be flexed against the resilience into contact with the first means in response to a force applied to that remaining part, and means defining at least one protruding means extending transversely to the longitudinal extension of the sensor and outwardly of the second means in a direction away from the first means for receiving a force applied over an area encompassing a plurality 2 of the said remaining parts of the second means and transmitting such force to one said remaining part . According to the invention, there is further provided a force- responsive longitudinally extending sensor, comprising a longitudinal sheet of resilient electrically insulating material first and second parallel -arranged portions of the same surface of which carry respective areas of electrically conductive material, the sheet being folded over on itself to bring the areas of conductive material into superimposition but with longitudinally distributed parts of the second area of conductive material being separated from the first area of conductive material by discrete areas of electrically insulating material between the two areas of electrically conductive material so that the remaining parts of the second area of conductive material are normally resilient held spaced apart from the first area but each remaining part of the second area can be flexed against its resilience into contact with the first area in response to a force applied externally to the sheet . According to the invention, there is also provided a method of making a force-responsive longitudinally extending sensor, comprising the steps of forming a longitudinal resilient sheet of electrically insulating material, forming first and second on respective areas of electrically conductive material, 3 parallel -arranged portions of the same surface of the sheet, folding the sheet over on itself to bring the areas of conductive material into superimposition, forming discrete areas of electrically insulating material between the two areas of electrically conductive material so that longitudinally distributed parts of the second area of conductive material are separated from the first area of conductive material and the remaining parts of the second area of conductive material are normally resilient held spaced apart from each other but each remaining part of second area can be flexed against its resilience into contact with the first area in response to a force applied externally to the sheet. Force-responsive sensors and systems embodying the invention, and window safety systems embodying the invention and for use in motor vehicles, and methods according to the invention of making force-responsive sensors, will now be described, by way of example only, with reference to the accompanying diagrammatic drawings in which: Figure 1 is a perspective view of one of the sensors; Figure 2 is an enlarged end view of the sensor of Figure 1; Figure 3 is a perspective view of an electrically conductive 4 member used in the sensor of Figures 1 and 2 ; Figure 4 is a perspective view of another of the sensors; Figure 5 is an enlarged end view of the sensor of Figure 4 ; Figure 6 is a perspective view of an electrically insulating spacer used in the sensor of Figure 4 ; Figure 7 is a perspective view of a further one of the sensors; Figure 8 is a perspective view of a modified form of the sensor of Figure 7 during a stage in its manufacture; and Figure 9 is a cross-section of a window channel embodying one of the sensors and fitted to the window frame of a motor vehicle. Figures 1,2 and 3 show one of the sensors. It is of indeterminate length 2 and predetermined width w. In response to a force applied to it at individual points along its surface and in a direction perpendicular, or at least transverse, to the plane lw, it produces an electrically detectable signal. As shown in Figures 1 and 2, the sensor has a rectangular cover layer 10 which is made of flexible and resilient electrically 5 insulating material and extends over the entire upper surface (as viewed in Figures 1 and 2) of the sensor. In Figure 1 the cover layer 10 is shown as being transparent in order to reveal the construction of the sensor. Normally, however, it would not be transparent . A similar cover layer 12 is positioned along the under surface of the sensor (as viewed in Figures 1 and 2) ; the layer 12 is also electrically non-conductive. An electrically conductive layer 14 of rectangular form is mounted on the cover layer 12 and covers substantially its whole length and width. The layer 14 is advantageously an electrically conductive film which may be formed by a printed circuit technique on the layer 12. Mounted at intervals on and along the conductive layer 14 are electrically insulating spacers 16 which again may be formed by a printed circuit technique. Two separate inter-digitated electrically conductive members 18 and 20 are formed on the underside of the layer 10. They are advantageously electrically conductive films which may be formed by a printed circuit technique on the layer 10. The shape of the member 18 is shown more clearly in Figure 3. As shown, it comprises an edge portion 22 from which fingers 24 integrally extend. Member 20 is similarly shaped, comprising an edge portion 26 with fingers 28. As shown in Figure 1, members 18 and 6 20 are arranged so that each finger 24 of the member 18 is positioned between two fingers 28 of the member 20. The spacers 16, in combination with the resilience of the cover layer 10 which carries the members 18 and 20, ensure that there is no normal contact between either of the members 18 and 20 and the conductive layer 14. As shown in Figures 1 and 2, a protruberance 29 is mounted on the layer 10 immediately above one of the fingers 24,28. There are advantageously further such protruberances similarly positioned at intervals along the length of the sensor at suitable intervals (for example, at intervals of 5 or 10 cms), each protruberance being positioned over a finger 24 or 28. In operation, a force applied to the sensor in the direction of the arrow F will flex the cover layer 10 and thus press one or more of the fingers 24,28 into electrical contact with the underlying conductive layer 14. An electrical circuit is therefore completed and this can be detected in any conventional way. Clearly, if the force F is applied over a very small area which is positioned between, and less than the area between, two adjacent fingers 24,28, it is possible that no electrical signal 7 will be produced. In practice, therefore, the spacing between the fingers is selected to be sufficiently small to produce the required sensitivity of detection. If the force is applied to the sensor by means of a generally flat object having a width of the same order as or greater than the width w and a length encompassing several fingers 24,28, such a flat object will contact one or more of the protruberances 29 which will therefore ensure that at least one of the fingers 24,28 will flex into contact with the conductive layer 14. In the absence of the protruberances 29, it is possible that a force applied by such a flat object would not cause the production of an electrical signal because no individual finger 24,28 would be caused to flex. When a force is applied over a small area, it may of course be applied directly to the cover layer 10 or may be applied via one of the protruberances 29, depending on the position of the point of application of the force. Although the protruberances 29 have been described as being positioned on the outside surface of the cover layer 10 (or similarly positioned on the layer 14) , they could instead be positioned underneath the cover layer 10 (or layer 14) so as to be covered over by the layer if the layer is sufficiently 8 flexible to make this possible. Each such protruberance would therefore produce an outwardly protruding part of the respective layer for achieving the same aim as each protruberance 29. In Figure 1, the spacers 16 are shown in full line to aid understanding of the drawing. They would of course not in practice be visible. In a modification, the conductive members 18,20 may be replaced by a conductive member or members of any other suitable shape. For example, the conductive members 18,20 could be replaced by a single continuous conductive layer or film extending over the area lw and separated from the layer 14 by separated spacers similar to the spacers 16 and either by its own resilience or by the resilience of the cover layer 12 (in the case where the conductive layer is formed on the layer 12) . Again, protruberances 29 would be positioned at intervals along the cover layer 10 to ensure that a force applied by a relatively large generally flat object causes the production of an electrical signal . Items in Figures 4,5 and 6 which are similar to items in Figures 1,2 and 3 are similarly referenced. In the embodiment of Figures 4 , 5 and 6 , the individual spacers 9 16 of the embodiment of Figures 1,2 and 3 are replaced by a continuous single spacer 32 which is of zig-zag form to define gaps 34 extending widthwise of the sensor and at positions coinciding with the fingers 24 and 28. As before, the fingers 24,28 and the remaining parts of the members 18,20 are formed as films on the underside of the insulating cover layer 10. The portions 36 of the spacer 32 which run in a longitudinal direction of the sensor are positioned between the conductive layer 14 on the one hand and the edge portions 22,26 of the conductive members 18 and 20 on the other hand. The portions 38 of the spacer 32 which run in the transverse direction support the cover layer 10 between the fingers 24,28 and thus indirectly help to support the members 18,20 and maintain their separation from the conductive layer 14. The conductive members 18 and 20 are thus electrically insulated by the spacer 32 from the conductive layer 14. In response to an applied force F, however, and as explained in connection with Figures 1,2 and 3, the cover layer 10 flexes and one or more of the fingers 24,28 is pressed into contact with the conductive layer 14 so as to produce a detectable electrical signal . Again, protruberances 29 are provided on the cover layer 10 and positioned at intervals along the sensor over the fingers 24,28 to ensure that a force applied by a relatively large that object produces the required electrical signal . 10 The spacer 32 can be of any suitable shape so as to provide electrically insulating separation between the members 18 and 20 and the layer 14, the support which it provides extending at least partially across the width of the sensor and being shaped so that the support is sufficient without increasing the overall width of the sensor and without reducing its sensitivity to an applied force F. The spacer 32 can be formed on the conductive layer 14 by a normal printed-circuit technique. Instead, however, it could be a separate sheet. As explained above in connection with Figures 1 to 3 , the conductive layers 18,20 in the embodiment of Figures 4 to 6 could be replaced by one or more conductive members of any suitable shape so as to have conductive portions extending over the gaps in the spacer 32 and supported thereover either by their inherent resilience or by the resilience of the cover layer 12 in the case where the conductive portions are formed as films on the layer 12. Again, though, the protruberances 29 would be provided. Items in Figure 7 which are similar to items in Figures 1 to 6 are similarly referenced. In the embodiment of Figure 7, the individual spacers 16 of Figures 1 to 3 and the spacer 32 of Figures 4 to 6 are replaced 11 by a series of insulating spacers 39 extending widthwise of the sensor at intervals therealong, each spacer being at an angle « to the length of the sensor. In this embodiment, the members 18,20 are replaced by a single continuous flexible conductive layer or film 18A extending over substantially the whole of the area lw. In the same manner as previously described, the spacers 39, in combination with the resilience of the cover layer 10, ensure that there is no normal contact between the conductive layer 18A and the conductive layer 14. In response to an applied force F, however, and as explained in connection with the previous embodiments, the cover layer 10 flexes and the conductive layer 18A over one or more of the gaps between the spacers 39 is pressed into contact with the conductive layer 14 so as to produce a detectable electrical signal. Again, the protruberances 29 ensure that the sensor responds to a force applied by a relatively large generally flat object. The protruberances 29 are preferably positioned over gaps between the spacers 39. Advantageously, the angle <* can be varied to alter the sensitivity of the sensor without increasing the overall width of the sensor. Additionally, the width of the spacers 80 can be varied with the same result. Thus, increasing the angle <* and/or increasing the width of the spacers 39 will decrease the 12 sensitivity of the sensor to the applied force F. Figure 8 shows a stage in manufacture of the sensor of Figure 7. As shown, the cover layers 10,12 are respective parts of a single, electrically insulating base sheet 11 which is initially flat. The electrically conductive layers 18A and 14 are formed as parallel strips on the base sheet 11. The insulating spacers 39 are then formed on one of these parallel strips (or on each of them) . The protruberances 29 are formed on the outside of the base sheet 11 opposite to the conductive strip 18A (or opposite both conductive strips 18A,14). Finally, the base sheet 11 is folded over to produce the finished sensor. Such a method, using a single base sheet 11, can be used to produce a sensor whether or not the protruberances 29 are to be included. The sensors described above can be designed not only to respond to a force applied to the uppermost surface shown in the Figures but also to a force applied to the undersurface . This can be achieved by making the layers 12 and 14 resiliently flexible. In such a case, protruberances similar to the protruberances 29 would be positioned on the undersurface . The sensors shown in Figures 1 to 7 can be used in many applications where it is required to produce an electrical signal in response to an applied force. One particular application 13 relates to the detection of an obstruction in a window opening in a motor vehicle body which is closable by a motorised window glass . Figure 9 shows a section through a window frame 42 of the window opening. A rigid mounting channel 46 is supported by inner and outer frame members 48 and 49. The mounting channel 46 supports a window sealing and guiding channel 50. 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 9 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 14 material . Within the distal edge of each side wall of the channel 50, a force-responsive sensor 70 is embedded so as to run longitudinally along the length of at least part of the channel 50; advantageously, the sensors run 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. Advantageously, each sensor 70 has the form shown in Figures 1 , 2 and 3 , in Figures 4 , 5 and 6 , or in Figure 7. If an obstruction, such as part of the human body, is placed in the window opening when the window glass 44 is wholly or partially open, it will be carried upwardly by the closing window glass and will cause a force F (see Figure 9) to be applied to the distal edges of either or both of the side walls of the channel 50, this force then being transmitted by the material of the channel to the corresponding sensor. As explained in conjunction with the earlier Figures, therefore, one or more of the fingers 24 and/or 28 of the conductive members 18,20 (or the conductive layer 18A in the case of the embodiment of Figure 7) will be moved into electrical contact with the conductive layer 14, thus producing an electrically detectable control signal. This control signal can be used to cause immediate de- energisation of the motor which is raising the window glass, 15 advantageously followed by reversal of the motor to lower it.

Claims: 16 1. A force-responsive longitudinally extending sensor, characterised by first longitudinally extending electrically conductive means (14) , second electrically conductive means (18,20, 18A) superimposed on the first means (14), electrically insulating means (16,32,39) positioned between and spacing the first means (14) from longitudinally distributed parts of the second means (18,20,18A), each remaining part of the second means (18,20,18A) normally being resiliently held spaced apart from the first means (14) but being able to be flexed against the resilience into contact with the first means (14) in response to a force applied to that remaining part, and means (29) defining at least one protruding means extending transversely to the longitudinal extension of the sensor and outwardly of the second means (18,20,18A) in a direction away from the first means (14) for receiving a force applied over an area encompassing a plurality of the said remaining parts of the second means (18,20, 18A) and transmitting such force to one said remaining part . 2. A sensor according to claim 1, characterised in that the electrically insulating means comprises a plurality of discrete insulating means (16,32,39) spaced longitudinally apart. 17 3. A sensor according to claim 1 or 2 , characterised in that the remaining parts of the second means comprise fingers (24) extending generally perpendicular to the longitudinal direction and extending over the first means (14) . 4. A sensor according to claim 1, characterised in that the second electrically conductive means comprises a plurality of electrically conductive strips (24) extending parallel to each other and arranged side by side but with spaces between them along the length of the sensor, the strips (24) being connected to a conductor (22) extending longitudinally of the sensor. 5. A sensor according to claim 4, characterised in that the insulating means comprises a plurality of discrete insulating spacers (29) positioned between respective parts only of at least some of the strips (24) and the first means (14) . 6. A sensor according to claim 5, characterised in that the strips (24) are formed on a flexible resilient layer (10) . 7. A sensor according to claim 4, characterised in that the strips (24) are formed on a flexible resilient layer (10) , and the insulating means comprises insulating means (32) positioned at the spaces between the conductive strips (24) and separating the flexible layer (10) from the first means (14) , the conductive 18 strips (24) being held from the first means (14) by the resilience of the flexible layer (10) until the layer (10) is flexed towards the first means (14) by the applied force. 8. A sensor according to any one of claims 4 to 7, characterised in that the conductive strips (24) are in the form of fingers extending from the conductor (18) . 9. A sensor according to claim 8, characterised in that there are two conductors extending longitudinally of the sensor and parallel to each other and spaced apart, some of the fingers (24) extending from one of the conductors (22) and the other fingers extending from the other conductor, the fingers being interdigitated . 10. A sensor according to claim 4, characterised in that the conductive strips (24) are in the form of fingers extending from the conductor (22) and in that the electrically insulating means comprises discrete insulating means (16) , each positioned adjacent a root of a respective one of the fingers (24) . 11. A sensor according to claim 7, characterised in that the electrically insulating means comprises an electrically insulating layer (32,39) positioned between the first electrically conductive means (18,20, 18A) and the flexible 19 resilient layer (10), the insulating layer (32,39) being provided with gaps (34) corresponding with the positions of the strips (24) to enable the strips (24) to flex therethrough into contact with the first electrically conductive means (14) in response to the force . 12. A sensor according to any preceding claim, characterised in that the first electrically conductive means comprises an electrically conductive layer (14) of generally rectangular configuration with the electrically insulating means (39) placed thereon and overlain by the second electrically conductive means (18A) , the electrically insulating means (39) and the second electrically conductive means (18A) lying within the width of the conductive layer. 13. A sensor according to claim 2, characterised in that the first electrically conductive means comprises an electrically conductive layer (14) of generally rectangular configuration with the electrically insulating means (39) placed thereon and overlain by the second electrically conductive means (18A) , the electrically insulating means (39) and the second electrically conductive means (18A) lying within the width of the conductive layer, the electrically insulating means (39) and the second electrically conductive means (18A) comprising layers substantially co-extensive with the first -mentioned conductive 20 layer ( 14 ) . 14. A sensor according to claim 2 , characterised in that of the discrete insulating means (39) extends across the width of the sensor. 15. A sensor according to claim 14, characterised in that each of the discrete insulating means (39) is positioned at an oblique angle to the longitudinal direction of the sensor. 16. A sensor according to any preceding claim, characterised in that the electrically conductive means (14 ; 18,20, 18A) are applied using a printed-circuit technique. 17. A sensor according to any preceding claim, characterised in that the protruding means (29) is positioned on one of the said remaining parts of the second means (18,20,18A). 18. A sensor according to any preceding claim, characterised by a flexible cover layer (10) superimposed over the second means (18,20, 18A) and for receiving the applied force. 19. A sensor according to any one of claims 1 to 16, characterised by a flexible cover layer (10) superimposed over the second means (18,20,18A), the said area encompassing part of 21 the cover layer (10) , and in that the protruding means (29) is positioned on the cover layer (10) to extend outwardly therefrom. 20. A sensor according to any preceding claim, characterised in that there are a plurality of the protruding means (29) positioned at intervals along the length of the sensor. 21. A sensor according to any preceding claim, characterised in that the or each said protruding means (29) is positioned in alignment with one of the said remaining parts of the second means (18,20, 18A) . 22. A sensor according to claim 18 or 19, characterised by a second cover layer (12) , the second cover layer (12) being positioned on the side of the first electrically conductive means (14) which is opposite to the second electrically conductive means (18,20,18A), whereby the electrically conductive means (14, 18,20, 18A) and the electrically insulating means (16,39) are sandwiched between the two cover layers (10,12). 23. A sensor according to claim 22, characterised in that the two cover layers (10,12) are part of the same folded-over sheet of material (11) . 24. A force-responsive longitudinally extending sensor, 22 comprising a longitudinal sheet of resilient electrically insulating material (11) first and second parallel -arranged portions of the same surface of which carry respective areas of electrically conductive material (14,18A), the sheet (11) being folded over on itself to bring the areas (14,18A) of conductive material into superimposition but with longitudinally distributed parts of the second area (18A) of conductive material being separated from the first area (14) of conductive material by discrete areas (39) of electrically insulating material between the two areas (14,18A) of electrically conductive material so that the remaining parts of the second area (18A) of conductive material are normally resiliently held spaced apart from the first area (14) but each remaining part of the second area (18A) can be flexed against its resilience into contact with the first area (14) in response to a force applied externally to the sheet. 25. A sensor according to claim 24, characterised by at least one protruding means (29) positioned on the outside of the sheet (11) for receiving a force applied over an area of the sheet encompassing a plurality of the remaining parts of the second area (18A) of conductive material and for transmitting that force to a particular one of the remaining parts. 26. A safety system for detecting an obstruction in a framed opening closable by a motor-driven slidable closure member, 23 characterised by a sensor according to any preceding claim mounted on or adjacent the frame of the opening and so positioned that a said force is applied thereto when an obstruction within the opening is carried towards the frame by the sliding closable member, and control means responsive to the said contact between the second electrically conductive means and the first electrically conductive means to arrest motor-driven movement of the closable member. 27. A system according to claim 26, characterised in that the framed opening is a window opening and the closure member is a pane of window glass. 28. A system according to claim 27, characterised in that the window opening is a window opening in a motor vehicle. 29. A method of making a force-responsive longitudinally extending sensor, characterised by the steps of forming a longitudinal resilient sheet (11) of electrically insulating material, forming first and second areas (14,18A) of electrically conductive material on respective areas on respective parallel-arranged portions of the same surface of the sheet (11) , folding the sheet (11) over on itself to bring the areas (14,18A) of conductive material into superimposition, forming discrete areas (39) of electrically insulating material 24 between the two areas (14,18A) of electrically conductive material so that longitudinally distributed parts of the second area (18A) of conductive material are separated from the first area (14) of conductive material and the remaining parts of the second area (18A) of conductive material are normally resilient held spaced apart from the first area (14) but each remaining part of second area (18A) can be flexed against its resilience into contact with the first area (14) in response to a force applied externally to the sheet. 30. A method according to claim 29, characterised by the step of forming at least one protruding means (29) on the outside of the sheet (11) for receiving a force applied over an area of the sheet (11) encompassing a plurality of the remaining parts of the second conductive area (18A) and for transmitting that force to a particular one of the remaining parts.

Inventors: PLOTTNIK REIMUND, PLOTTNIK, REIMUND
Applicants: DRAFTEX IND LTD, PLOTTNIK REIMUND, DRAFTEX INDUSTRIES LIMITED, PLOTTNIK, REIMUND
Application year: 1998
Main classification: E05F15
IPC codes: B60J1, B60J10, E05F15, G01L1, H01H3