Force-responsive detectors and systems

A safety system, such as for detecting obstructions in a window opening having a motor-slidable window glass (32) and for arresting the window glass in the presence of such an obstruction, comprises a glass-receiving channel (34). The base (48) defines a hollow chamber (60) incorporating a sensor (62). The sensor supports two substantially parallel longitudinally extending force-responsive sensing units (12, 14) each positioned immediately adjacent to a respective one of the side walls (44, 46) of the channel (34). If an obstruction in the window opening is carried upward by the slidable window pane (32), it will apply a force to the distal edge of one or both of the side walls (44, 46) and this force will be transmitted to the respective sensing unit (12, 14). Electrically conductive strips of the relevant sensing unit (12, 14) move into contact to produce an electrical signal which arrests the window glass. A third, similar, sensing unit (13) of the sensor (62) is positioned to produce a corresponding electrical signal when a force is applied to it by the distal edge of the closing window glass. This is used to indicate completion of travel of the window glass.

BACKGROUND OF THE INVENTION
 The invention relates to a force-responsive longitudinally extending
 sensor, comprising a flexible longitudinally extending support having a
 predetermined width, first and second sensing means mounted on the support
 and spaced apart across the width of the support and extending therealong
 in substantially parallel configuration so as each to produce a respective
 signal in response to a respectively applied force.
 Such sensors may be used, for example, in motor vehicles for detecting the
 presence of an obstruction in a window opening closable by a motorised
 window pane. However, such sensors may be used in many other applications.
 DESCRIPTION OF THE PRIOR ART
 One form of such a sensor is shown in DE-A-21 57 597. Here, the support
 comprises a channel-shaped window-glass receiving and sealing channel, the
 first and second sensing means being respectively positioned on and
 running along the two distal edges forming the longitudinal mouth of the
 channel. With such an arrangement, the two sensors must be separately
 mounted on the channel edges. If this is done after insertion of the
 channel into its rigid mount, two separate operations are necessary. If
 the sensors are mounted on the channel before the channel is mounted in
 its rigid frame, the sensors may be liable to damage during handling.
 The invention aims to deal with these problems.
 BRIEF SUMMARY OF THE INVENTION
 According to the invention, therefore, the sensor as first set forth above
 is characterised in that the support is a substantially planar base.

DESCRIPTION OF PREFERRED EMBODIMENTS
 The sensor shown in FIG. 1 is of indeterminate length l and predetermined
 width w. In a manner to be explained and in response to a force applied to
 the sensor at individual predetermined points along its surface, and in a
 direction perpendicular, or at least transverse, to the plane lw, it
 produces an electrically detectable signal.
 The sensor has a 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.
 A base layer 11 is positioned along the undersurface of the sensor; the
 layer 11 is made of similar material to that of the cover layer 10.
 Between the layers 10,11 three separate strip-like sensing units 12,13 and
 14 are mounted. Units 12 and 14 are mounted along opposite longitudinal
 edges of the sensor and unit 13 is mounted between them. FIG. 1 shows
 these units only diagrammatically. One such unit is shown to an enlarged
 scale in FIG. 2; the others are the same.
 As shown in FIG. 2, the unit comprises an electrically conductive layer 15
 mounted on the cover layer 11. Layer 15 extends along the length l but
 only for a small part of the width w. The layer 15 is advantageously in
 the form of an electrically conductive film which may be formed by a
 printed circuit technique on the layer 11. A series of electrically
 insulating spacers 16 each of narrow strip form is mounted on the
 conductive layer 15. The spacers 16 extend generally widthwise but slanted
 across the layer 15 and are positioned at regular intervals along the
 layer, each spacer 16 being at an angle a to the length of the strip. The
 spacers 16 can be applied by a printed circuit technique.
 A further electrically conductive layer 18 lies over the conductive layer
 15, so as to be placed on top of the insulating spacers 16. The cover
 layer 10 overlays the conductive layer 18.
 The conductive layers 18 can be in the form of electrically conductive
 films applied by a printed circuit technique.
 The layers 10,11, and the electrically conductive layers 15 and 18 are
 flexible. However, the resilience of the conductive layers is such that
 the layers 15 and 18 of each sensing unit 12,13,14 are normally held apart
 by (that is, electrically insulated by) the insulating spacers 16.
 In operation, a force applied in the direction of the arrow F1,F2 or F3
 (FIG. 1) will flex the cover layer 10, and this in turn will flex the
 electrically conductive layer 18 of the appropriate one of the sensing
 unit 12,13,14, so as to bend it into electrical contact with the
 respective one of the layers 15. This electrical contact can be
 electrically detected to produce an output signal.
 Clearly, if the force F1,F2 or F3 is applied immediately over one of the
 insulating spacers 16, it is possible that no electrical signal will be
 produced. In practice, therefore, the spacing between the insulators 16 is
 selected to be sufficiently large in relation to the size of the spacers
 16 as to produce the required sensitivity of force detection.
 A force applied to the cover layer 10 within one of the regions 20,22 (FIG.
 1) between the sensing units 12,13,14 will not normally produce an
 electrical signal--unless it is sufficiently close to one of the layers 18
 to press such layer into electrical contact with the corresponding layer
 15.
 Normally, the construction of the sensor is such that forces
 correspondingly positioned to the forces F1,F2 and F3 but applied to the
 base sheet 11 from the opposite direction will also produce electrical
 signals.
 FIG. 3 shows a modification to the sensor of FIG. 1. For ease of
 illustration, FIG. 3 omits the over layer 10. As shown, the sensor of FIG.
 3 differs from that of FIG. 1 in that, at one end of the sensor, the
 sensing unit 12 has an integral portion 12A extending widthwise across the
 sensor towards and into integral connection with the sensing unit 14, so
 that the conductive layers 15 of these two sensing units are connected as
 are their conductive layers 18.
 The sensor illustrated in FIG. 4 is substantially the same as the sensor
 illustrated in FIG. 3. The only difference is that the strip-like spacers
 16 of FIGS. 1,2 and 3 are replaced by multiple small cylindrical or
 disc-shaped insulators 24, only some of which are shown in the Figure.
 Otherwise, the construction is as described with reference to FIGS. 1,2
 and 3. The spacers 24 can be applied by a printed circuit technique.
 The sensor illustrated in FIG. 4 operates in generally the same manner as
 for FIGS. 1,2 and 3. When a force (similar to the force F1,F2 or F3 in
 FIG. 1) is applied to the sensor of FIG. 4, the cover sheet 10 flexes and
 correspondingly flexes the appropriate one of the conductive layers 18 so
 that it is pressed into contact, between adjacent insulating discs 24,
 with the appropriate conductive layer 14 to produce an electrical signal.
 FIG. 5 shows a perspective view of a motor vehicle having a door 30 with a
 window pane 32 which is motor-driven by a motor 33. The window pane 32
 slides up and down within a sealing and guiding channel indicated
 generally at 34. FIG. 6 illustrates in enlarged form how a sensor of the
 form shown in FIGS. 1, 3 and 4 may be incorporated into such a window
 channel in order to detect the presence of an obstruction in the window
 opening when the window pane is raised into the closed position.
 FIG. 6 shows the inner and outer body panels 36 and 38 adjacent the door
 opening in the vehicle body. These body panels are bent over to support a
 stiff channel 40 (normally made of steel or similar material) forming the
 door frame. The channel 40 supports the window sealing and guiding channel
 34 which is advantageously made from extruded rubber or plastics material
 defining side walls 44 and 46 integral with a base 48 and having a mouth
 50 for receiving the window pane 32. The distal edges of the side walls
 44,46 are bent over to provide lips 52 which extend over the bent-over
 edges of the body panels 36,38 to hide them and to seal against them. In
 addition, the side walls 44,46 provide integral lips 54 which resiliently
 make contact with the opposite sides of the window pane 32 as it enters
 the window channel and seal against the window pane. Side wall 44 is
 additionally provided with a lip 56 near the base 48 of the channel. The
 faces of the lips 54 and 56 which are contacted by the window pane 32 may
 be covered with flock or other low friction material.
 The side walls 44,46 carry shoulders 58,59 which engage the distal edges of
 the bent-over body panels 36,38 to hold the window channel 42 in position
 in the door frame channel 40.
 The base 48 of the window channel 34 is formed with a longitudinally
 extending hollow chamber 60 in which one of the sensors (indicated
 generally at 62 in FIG. 6) is positioned. The sensor 62 is illustrated
 only diagrammatically. The three sensing units 12,13 and 14 are indicated
 but their details are not visible in FIG. 6. The sensor 62 in FIG. 6 may
 be of the form shown in FIGS. 1 to 4.
 As the window pane 32 rises, any obstruction in the window opening (e.g. a
 finger or other part of the human body) will be carried upwardly with the
 rising window pane and eventually be forced by the window pane into
 contact with the distal edge of one (or perhaps both) of the walls 44, 46.
 This is shown by the arrows F4. The resultant force will be transmitted by
 the appropriate side wall and applied to the appropriate sensing unit 12
 or 14 of the sensor 62, causing an electrical signal to be produced in the
 manner explained in connection with FIGS. 1, 2, 3 and 4. This signal is
 applied through a connection 63 or 64 to appropriate detecting and control
 circuitry 65 to stop the motor 33 and thus to stop the movement of the
 window pane. This signal is used, through appropriate detecting and
 control circuitry, to stop the movement of the window pane immediately.
 Advantageously, the window pane is then caused to move in the downward
 direction.
 When the window pane 32 enters the channel 34 through the mouth 50, it
 makes contact with the base 48 of the window channel and applies a force
 to the sensing unit 13 of the sensor 62, causing this unit to produce an
 electrical signal on a line 66 which is applied to the detecting and
 control circuitry 65. This signal is used to indicate that the window pane
 has completed its closing travel, and de-energises the motor.
 The integral connecting portion 12A shown in the sensors of
 FIGS. 3 and 4 enables the electrical continuity of the sensing units 12 and
 14 to be continuously monitored from one end of the sensor 62. Thus, a
 small electrical current can be continuously passed from the end A of
 sensing unit 12 (see FIG. 3) to the end B of sensing unit 14. If any
 damage occur s to any part of sensing unit 12 or 14, this will result in
 interruption of this current and consequent detection of the failure. If
 the connecting portion 12A is omitted (as in the case of the sensor shown
 in FIG. 1), electrical continuity of each sensing unit 12, 14 is more
 difficult to monitor. It would be necessary to feed the current into one
 end of each such unit and to monitor it from the other end which would
 require electrical connections to each end of the window channel.
 Alternatively, a separate conductive connection could be added at the
 distal end of the sensor, corresponding to the connecting portion 12A.
 However, this would require an additional manufacturing step. The
 formation of the integral connecting portion 12A is very much simpler.
 The incorporation of the sensing unit 13 in the sensor, for detecting the
 fully closed position of the window pane, is advantageous because it
 provides a simple and inexpensive means for detecting this state. It
 requires only a minor modification to the construction of the sensor. It
 is thus advantageous compared with known means for detecting the fully
 closed position of the window glass which may rely on detecting the
 increase in motor current when its rotation is stalled at the end of the
 travel of the window glass. However, the sensing unit 13 may be omitted if
 some other means of sensing the fully closed position of the window glass
 is provided.
 Because the sensor 62 is embedded in the chamber 60, it is protected from
 damage. Because it is positioned below the base of the channel 34, any
 distortion of the material of the channel which its presence causes will
 not be externally visible. Its incorporation in a hollow chamber keeps the
 overall weight of the channel to a minimum.