Abstract:
A resistive pinch sensor utilizing electrically conductive wires encapsulated in a resiliently deformable casing. A pinch is detected when one of the wires, which is normally separated by an air gap within the casing, contacts another wire lowering the electrical resistance therebetween. The described pinch sensors have wide activation ranges or angles. Tri-lobed designs provide wide activation range by incorporating at least three electrically-conductive conduits that are substantially equidistantly spaced circumferentially along the inner wall of a tubular casing. One of the conduits, or optionally an axially arranged electrically-conductive core may function as the reference element. Coaxial designs provide wide activation range by incorporating a central electrically-conductive core and a coaxial electrically-conductive tubular outer sheath that are normally spaced apart by at least one non-conductive spacer.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent Application No. 61/267,574, which is incorporated by reference herein in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to pinch sensors, particularly for vehicular closure panels where it is desirable to prevent a closure panel such as a lift gate or side door from closing if a foreign obstacle or object is detected just as the panel closes. 
     BACKGROUND OF THE INVENTION 
     It is known to apply pinch sensors to prevent a closure panel such as a lift gate or side door from closing if a foreign obstacle or object is detected just as the panel closes. The pinch sensors come in different forms, including non-contact sensors such as those based on capacitance changes, and contact sensors which rely on a physical deformation caused by contact with a foreign object. 
     The contact pinch sensors are typically applied in the form of a rubber strip which is routed along and adjacent to the periphery of a vehicle door. The rubber strip embeds two wires which are separated by an air gap. When the two wires contact one another, the electrical resistance therebetween drops, and a controller connected to the two wires monitors the drop in resistance, detecting an object when the drop exceeds a predetermined threshold. The fundamental problem with such conventional pinch sensors, however, is that they have a limited activation angle typically on the order of about thirty five degrees. Thus, in the event the pinch force is applied obliquely rather than head on, the wires may not contact one another. 
     SUMMARY OF THE INVENTION 
     The invention seeks to provide a resistive contact pinch sensor have a considerably wider activation range or angle. It is also desired to provide such a sensor with a low manufacturing cost. 
     According to one aspect of the invention a multi-lobed pinch sensor is provided. The pinch sensor includes a resiliently deformable non-conductive tubular casing having an outer wall and an inner wall that defines an internal hollow region. At least three electrically-conductive conduits are disposed along the inner wall of the casing. In section, the three electrically-conductive conduits are substantially equidistantly spaced circumferentially along the inner wall of the casing, and each electrically-conductive conduit has a periphery that extends into the hollow region. When the casing is suitably deformed, at least one of the electrically-conductive conduits comes into contact with a electrically conductive reference element to thereby lower the resistance therebetween and enable a controller to signal the detection of an obstacle. 
     In the pinch sensor each electrically-conductive conduit preferably comprises an elastomeric electrically-conductive skirt that envelops a low resistance electrical conductor connectable to a controller input. 
     In one embodiment, the casing has a cross-sectional shape of a semi-circular arch, including a base portion and a semi-circular portion. One of the electrically-conductive conduits is disposed along the base portion and functions as the reference element. The other two electrically-conductive conduits are disposed along the semi-circular portion. The internal hollow region includes two rebates that straddle the electrically-conductive reference conduit, where each rebate presents a pivot point enabling the casing to flex such that the corresponding electrically-conductive conduit disposed along the semi-circular portion is directed towards the electrically-conductive reference conduit. 
     In another embodiment, the conductive reference element is provided by an additional electrically-conductive core disposed within the casing inward of the three electrically-conductive conduits. The electrically-conductive core is connected to the casing by one or more non-conductive webs branching from the casing inner wall. The electrically-conductive core preferably has a tri-petal cross-sectional shape so as to trisect the internal hollow region into three air gaps. Each of the electrically-conductive conduits projects partially into one of the three individual air gaps, respectively. Each electrically-conductive conduit is preferably formed from an elastomeric electrically conductive skirt that envelopes a low resistance electrical conductor connectable to one of the controller inputs. These conductive skirts preferably have substantially similar circular cross-sectional profiles and the air gaps have substantially similar sector-shaped cross-sectional profiles of substantially uniform depth, thereby providing a substantially uniform travel for activating the sensor across an activation angle of at least 270 degrees. 
     According to another aspect of the invention a coaxial pinch sensor is provided. The coaxial pinch sensor includes a resiliently deformable non-conductive tubular casing. An electrically-conductive tubular conduit is disposed within the tubular casing, the tubular conduit having an inner wall defining an internal hollow region. An electrically-conductive core is disposed within the electrically-conductive tubular conduit and is normally spaced apart therefrom. When the casing is suitably deformed, the electrically-conductive tubular conduit comes into contact with the electrically-conductive core to thereby lower the resistance therebetween and enable a controller to signal the detection of an obstacle. 
     The coaxial pinch sensor prefereably including at least one non-conductive spacing element disposed between the electrically-conductive core and the electrically-conductive tubular conduit. 
     And the electrically-conductive core is preferably substantively coaxial with the electrically-conductive tubular conduit. 
     According to one embodiment of the coaxial pinch sensor, multiple non-conductive spacing elements are disposed between the electrically-conductive core and the electrically-conductive tubular conduit, these spacing elements being resiliently compressible. In addition, the electrically-conductive core is preferably segmented by a nonconductive divider having an end portion contacting the electrically-conductive tubular conduit. And the electrically-conductive core is preferably formed from an elastomeric electrically conductive skirt that envelops a low resistance electrical conductor. 
     According to another embodiment of the coaxial pinch sensor the electrically-conductive tubular conduit has a cross-sectional shape of a three-quarter cylinder having a base portion and a semi-circular portion. The spacer is connected to the base portion of the electrically-conductive tubular conduit. The electrically-conductive core has a semi-circular cross-sectional shape, and the hollow region includes an air gap that has a substantially sector-shaped cross-sectional profile of substantially uniform depth, thereby providing a substantially uniform travel for activating the sensor across an activation angle of at least 270 degrees. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other aspects of the invention will be more readily appreciated having reference to the drawings, wherein: 
         FIG. 1  is a cross-sectional view of a tri-lobed pinch sensor according to a first embodiment; 
         FIGS. 1A ,  1 B and  1 C are cross-sectional views schematically demonstrating the deformation of the pinch sensor shown in  FIG. 1  under loads directed from top, left and right directions, respectively; 
         FIG. 2  is a cross-sectional view of a variant of the pinch sensor shown in  FIG. 1 ; 
         FIG. 3  is a cross-sectional view of a tri-lobed pinch sensor according to a second embodiment; 
         FIGS. 3A ,  3 B and  3 C are cross-sectional views schematically demonstrating the deformation of the pinch sensor shown in  FIG. 3  under loads directed from top, left and right directions, respectively; 
         FIG. 4  is a cross-sectional view of a variant of the pinch sensor shown in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of a coaxial pinch sensor according to a third embodiment; 
         FIGS. 5A ,  5 B and  5 C are cross-sectional views schematically demonstrating the deformation of the pinch sensor shown in  FIG. 5  under loads directed from top, left and right directions, respectively; 
         FIGS. 6A and 6B  are cross-sectional views of variants of the pinch sensor shown in  FIG. 5 ; 
         FIG. 7  is a cross-sectional view of a coaxial pinch sensor according to a third embodiment; 
         FIGS. 7A ,  7 B and  7 C are cross-sectional views schematically demonstrating the deformation of the pinch sensor shown in  FIG. 7  under loads directed from top, left and right directions, respectively; and 
         FIGS. 8A and 8B  are cross-sectional views of variants of the pinch sensor shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows a tri-lobed pinch sensor  100  in cross-sectional view. The sensor  100  is configured as an elongate bendable strip, but it should be understood that the cross-sectional profile shown in  FIG. 1  is substantially constant along the length of the strip (and do not follow a helical pattern). As such, the pinch sensor  100  may be relatively easily manufactured by extrusion or co-extrusion techniques as known in the art per se. 
     The particular pinch sensor  100  shown in  FIG. 1  achieves a relatively wide activation range or angle by incorporating three electrically-conductive conduits  102  (labeled individually as  102   a ,  102   b ,  102   c ) within a non-conductive tubular casing  110 . In section, the electrically-conductive conduits  102 , which are alternatively referred to as conductive ‘planetary’ lobes, are substantially equidistantly spaced circumferentially along the inner wall of the tubular casing  110  about a central electrically-conductive core  112 . The planetary lobes  102  are insulated from the central conductive core  112  by a hollow region  108  but upon application of a suitable pinch force to deform the tubular casing  110  at least one of the conductive planetary lobes  102  will come into contact with the conductive central core  112 . lowering the resistance therebetween, and enabling a controller (not shown) connected to the conductive planetary lobes  102  and central core  113  to signal the presence of an obstacle. The three conductive planetary lobes  102  can be connected to one voltage polarity, and the conductive central core  112  to an opposite voltage polarity. 
     More particularly, each planetary lobe  102  includes a conductive skirt  104  that is preferably formed from an elastomeric conductive material, e.g., conductive rubber as known in the art per se. The conductive skirt  104  surrounds a low resistance ‘outboard’ electrical conductor  106 , discussed in greater detail below, that is connected to one of the controller inputs (all three electrical conductors being connectable to the same controller input). Each skirt  104  is preferably formed in a closed loop shape such as the illustrated circular shape so as to envelop the corresponding outboard electrical conductor  106 , although it will be understood that a complete encirclement is not essential. 
     The central conductive core  112  includes a conductive tri-petal or trilateral body  113  that is preferably formed from the same material as the conductive skirt  104 . The trilateral body  113  preferably surrounds a low resistance central electrical conductor  114  that is disposed along the longitudinal axis of the pinch sensor  100  and is connected to another input of the controller. 
     The three planetary lobes  102  are partially embedded in a resiliently deformable, non-conductive tubular casing  110 , as may be provided by rubber, that forms the outer periphery of the sensor  100 . The casing  110  encapsulates the conductive portions of the sensor, protecting it from ambient influences. The casing  110  also defines the stiffness of the section and its appearance. The casing  110  has a generally annular shaped peripheral cross-sectional profile (e.g., a three-quarter cylinder as illustrated) with three integrally formed, inwardly leading web portions  111 . The central trilateral body  113  has three corners that are each integrally connected to one of three web portions  111  to thus trisect the casing  100  and define three distinct air gaps labeled individually as  108   a ,  108   b ,  108   c.    
     In the illustrated embodiment about one half  104   j  of the outer periphery of each conductive skirt  104  abuts the casing  110 , and about one half  104   k  of the outer periphery of each conductive skirt  104  projects into one of the air gaps  108   a ,  108   b ,  108   c . Each air gap is preferably crescent or sector shaped in section with uniform depth and sized to permit about one hundred and eighty degrees of the outer periphery of the respective conductive skirt  104  to project into the air gap. The crescent or sector shape of the air gap  108 , coupled with the circular shape of the planetary conductive skirt  104 , also provides a relatively uniform depth d across the air gap  108  between the projecting portion  104   k  of the planetary conductive skirt  104  and the corresponding sidewall  113   a ,  113   b ,  113   c  of the central trilateral body  113 . The distance d is selected to achieve a selected deformation of the casing  110  before one of the planetary lobes  102  contacts the central core  112 , but in any event the preferred design ensures that the sensor  100  has a relatively constant activation travel over a wide range of pinch directions. 
     Each sidewall  112   a ,  112   b ,  112   c  of the central trilateral body  112  faces one of the projecting portions  104   k  of the planetary conductive skirt  104  and subtends it by an angle alpha of about one hundred twenty degrees. As the three planetary lobes  102  are angularly spaced apart from one another by about one hundred and twenty degrees, it will be seen that the pinch sensor  100  has a very wide activation angle. This can be appreciated more fully with additional reference to  FIGS. 1A ,  1 B, and  1 C which demonstrate how the sensor  100  reacts when a pinch force P is applied from top, left and right positions, respectively, and from which it should be appreciated that the sensor  100  has an activation angle of at least about two hundred and seventy degrees. 
     As shown in  FIG. 1  the casing  110  features a flattened end portion  110   b  in order to provide a flat surface to mount an adhesive strip  116  thereto for attaching the sensor to the contours of a support surface. It will be appreciated that in other embodiments such as shown in  FIG. 2  a variant  100 ′ of the pinch sensor can have a completely circular casing  110 ′ which will thus permit an even larger activation angle. 
     In preferred embodiments the electrical conductors  106  and  114  are formed from multiple strands of wire such as copper combined with plastic reinforcing fiber. Such conductors can provide high elasticity in both axial (stretching) and transverse (bending) directions. 
       FIG. 3  shows an alternative embodiment of a tri-lobed pinch sensor  200  in cross-sectional view. The sensor  200  is configured as an elongate bendable strip, but it should be understood that the cross-sectional profile shown in  FIG. 3  is substantially constant along the length of the strip (and does not follow a helical pattern), enabling the pinch sensor  200  to be relatively easily manufactured by extrusion or co-extrusion techniques. 
     The pinch sensor  200  achieves a relatively wide activation range or angle by incorporating three electrically-conductive conduits  202   a ,  202   b , and  203  within a non-conductive tubular casing  210 . In section, the electrically-conductive conduits  102 , which are alternatively referred to as conductive lobes, are substantially equidistantly spaced circumferentially along the inner wall of the tubular casing  210  and/or about a central cylindrical axis  214 . The upper lobes  202   a ,  202   b  are insulated from one another by a central, common, air gap  208 , but upon application of a suitable pinch force to deform the tubular casing  210  one of the conductive upper lobes  202 , which are connected to one input of a controller (not shown), will come into contact with the conductive lower or base lobe  203 , which is connected to another input of the controller, lowering the resistance therebetween, and thus enabling the controller (not shown) to signal the presence of an obstacle. 
     More particularly, each conductive lobe  202 ,  203  includes a conductive skirt  204  that is preferably formed from an elastomeric conductive material, e.g., conductive rubber as known in the art per se. The conductive skirt  204  surrounds a low resistance electrical conductor  206 , such as discussed above, that is connected to a controller input. Each skirt  204  is preferably formed in a closed loop shape such as the illustrated circular shape so as to envelop the corresponding electrical conductor  206 , although it will be understood that a complete encirclement is not essential. The conductive skirts  204  of the upper lobes  202  also include teardrop shaped tail sections  212  that provides a wider face (in comparison with a strict circular profile) relative to the base lobe  203 . 
     Each of the conductive lobes  202  is partially embedded in the resiliently deformable, non-conductive tubular casing  210 , as may be provided by rubber, that forms the outer periphery of the sensor  200 . The casing  210  encapsulates the conductive portions of the sensor, protecting it from ambient influences. The casing  210  also defines the stiffness of the section and its appearance. The particular casing  210  illustrated in  FIG. 3  has a generally inverted U-shaped or semi-circular arch profile in section, including a semicircle portion  210  and a base portion  201   b . The casing  210  also includes a hollow central region that defines the air gap  208 . 
     In the illustrated embodiment about one half of the outer periphery of each conductive skirt  204  abuts the tubular casing  210 , and about one half of the outer periphery of each conductive skirt  204  projects into the air gap  208 . The air gap  208  includes two lower recesses or rebates  208   a ,  208   b  that present pivot points to allow the casing  210  to flex such that the conductive upper lobes  202  are directed towards the conductive base lobe  203  that is situated adjacent the base of inverted U-shaped casing  210 . The tri-lobed pinch sensor  200  also has a wide activation angle as will be appreciated more fully with additional reference to  FIGS. 2A ,  2 B, and  2 C which demonstrate how the sensor  200  reacts when a pinch force P is applied from top, left and right positions, respectively, and from which it should be appreciated that the sensor  200  has an activation angle of at least about two hundred and seventy degrees. 
     As shown in  FIG. 3  the flattened base portion  210   b  of the casing  210  provides a flat surface for mounting an adhesive strip  216  to attach the sensor to an underlying support surface. It will be appreciated that in other embodiments such as shown in  FIG. 4  a variant  200 ′ of the pinch sensor can have a completely circular casing  210 ′ with three equidistantly angularly spaced circumferential conductive lobes  203 , which will thus permit an even larger activation angle. 
       FIG. 5  shows an embodiment of a coaxial pinch sensor  300  in cross-sectional view. The sensor  300  is also configured as an elongate bendable strip, and it will be understood that the cross-sectional profile shown in  FIG. 5  is substantially constant along the length of the strip. 
     The coaxial pinch sensor  300  achieves a wide activation range or angle by incorporating a central electrically-conductive core  302  and a coaxial electrically-conductive tubular outer sheath  304  within a tubular casing  310 . The conductive core  302  and conductive sheath  304  are normally spaced apart by a plurality of spacers/springs  306 , but upon application of a suitable pinch force to deform the tubular casing  310  the conductive sheath  304 , which is connected to one input of a controller (not shown), will come into contact with the conductive core  302 , which is connected to another input of the controller, lowering the resistance therebetween and enabling the controller (not shown) to signal the presence of an obstacle. 
     More particularly, the coaxial sensor  300  includes a resiliently deformable, non-conductive tubular casing  310 , as may be provided by rubber, that forms the outer periphery of the sensor  300 . The particular casing  310  illustrated in  FIG. 5  has a cylindrical inner wall and encapsulates the conductive portions of the sensor, protecting it from ambient influences. The casing  310  also defines the stiffness of the section and its appearance. The particular casing  310  illustrated in  FIG. 5  has a flattened base section  310   b  to which an adhesive foam strip  316  can be applied to mount the sensor to a support surface. 
     The casing  310  has an evacuated central region. The conductive outer sheath  304  is disposed immediately adjacent the inner wall of the casing  310  and is also preferably cylindrical to ensure a mating fit therewith. The central conductive core  302  is disposed within the outer sheath  304 , being substantially coaxial therewith. The conductive core  302  also has a smaller diameter than the outer sheath  304  so as to leave an air gap  308  therebetween. 
     The conductive cylindrical outer sheath  304  is preferably formed from an elastomeric material, such as conductive rubber. 
     The central conductive core  302  is provided as two semi-cylinders  302   a ,  302   b  separated by a divider  314 . Each semi-cylinder is preferably formed from an elastomeric conductive material, e.g., conductive rubber, and envelops a low resistance electrical conductor  318 , such as discussed above, that is connected to a controller input. 
     The divider  314  is formed from a nonconductive material, such as rubber, and has a bulbous end portion  320  that contacts the cylindrical outer sheath  304 . The divider  314  maintains a minimum spacing between the electrical conductors  318  embedded in the two semi-cylinders  302   a  and prevents the collapse of the section in the event the coaxial strip sensor  300  is routed with sharp bends thereto. 
     The spacers/springs  306  are non-conductive resiliently deformable beads that are partially embedded in the semi-cylinders  302   a ,  302   b . About half of the periphery of the spacers/springs  306  project into the air gap  308  so as to contact the conductive outer sheath  304  and prevent self activation of the sensor  300  due to sharp routing bends. The shape, quantity, position and stiffness of the spacers/springs  306  are selected to achieve a desired sensor activation force and travel. 
     The coaxial nature of sensor  300  enables a wide activation angle as will be appreciated more fully with additional reference to  FIGS. 5A ,  5 B, and  5 C which demonstrate how the sensor  300  reacts when a pinch force P is applied from top, left and right positions, respectively, and from which it should be appreciated that the sensor  300  has an activation angle of at least about two hundred and seventy degrees. 
       FIGS. 6A and 6B  shown variants  300 ′ and  300 ″ of the coaxial pinch sensor which employ differently shaped casings  310 ′ and  310 ″. 
       FIG. 7  shows an alternative embodiment of a coaxial pinch sensor  400  in cross-sectional view. The sensor  400  is also configured as an elongate bendable strip, and it will be understood that the cross-sectional profile shown in  FIG. 7  is substantially constant along the length of the strip. 
     The coaxial pinch sensor  400  achieves a wide activation range or angle by incorporating a substantially electrically-conductive central core  402  and a substantially coaxial electrically-conductive tubular outer sheath  404  encapsulated by a nonconductive tubular casing  410 . The conductive core  402  and conductive sheath  404  are normally spaced apart by an uvula-like base structure  406  projecting from the outer sheath  404 , but upon application of a suitable pinch force to deform the casing  410  the conductive outer sheath  404 , which is connected to one input of a controller (not shown), will come into contact with the conductive core  402 , which is connected to another input of the controller, lowering the resistance therebetween and enabling the controller (not shown) to signal the presence of an obstacle. 
     More particularly, the coaxial pinch sensor  400  includes a resiliently deformable, non-conductive tubular casing  410 , as may be provided by rubber, that forms the outer periphery of the sensor  400 . The casing  410  encapsulates the conductive portions of the sensor, protecting it from ambient influences. The casing  410  also defines the stiffness of the section and its appearance. The particular casing  410  illustrated in  FIG. 7  has three-quarter cylindrical shape including a flattened base section  410   b  to which an adhesive foam strip  416  can be applied to mount the sensor to a support surface. 
     The outer sheath  404  is disposed immediately adjacent an inner wall of the casing  410  and is also preferably shaped in the form of a three-quarter cylinder to matingly fit with the casing  410 . The conductive core  402  is disposed within the outer sheath  404 , being substantially coaxial therewith. The conductive core  402  also has a smaller diameter than the outer sheath  404  so as to leave an air gap  408  therebetween. 
     The conductive outer sheath  404  is preferably formed from an elastomeric material, such as conductive rubber. The outer sheath  404  includes a base portion  404   b  that envelops and surrounds a low resistance electrical conductor  418 , such as discussed above, that is connected to a controller input. 
     The uvulate base structure  406  is a nonconductive platform disposed atop the base portion  404   b ). The conductive core  402 , which is preferably formed from an elastomeric conductive material such as conductive rubber is disposed atop the base structure  406  and envelops a low resistance electrical conductor  418 , such as discussed above, that is connected to a controller input. The base structure  406  maintains a minimum spacing between the electrical conductors  418  embedded in the core  402  and sheath  404  and prevents the collapse of the section under sharp bends in the coaxial strip sensor  400 . 
     In the illustrated embodiment the conductive core  402  has a substantially three-quarter circle cross-sectional profile. The air gap  408  is preferably crescent or sector shaped in section over an angular range of about two hundred and seventy degrees. The crescent or sector shape of the air gap  408 , coupled with the three-quarter circular shape of the conductive core, provides a relatively uniform depth d across the air gap  408  and thus a relatively constant activation travel over a wide range of pinch directions. This will be appreciated more fully with additional reference to  FIGS. 7A ,  7 B, and  7 C which demonstrate how the sensor  400  reacts when a pinch force P is applied from top, left and right positions, respectively, and from which it should be appreciated that the sensor  400  has an activation angle of at least about two hundred and seventy degrees. 
       FIG. 8A  shows a variant  400 ′ of the coaxial pinch sensor which employs a more cylindrical casing  410 ′ and outer sheath  404 ′, along with a narrower uvulate base structure  406 ′, thereby enabling an even wider range of activation angles.  FIG. 8B  shows a variant  400 ″ of the coaxial pinch sensor which employs a broader uvulate base structure  406 ″, resulting in a more limited range of activation angles. 
     While the above describes a particular embodiment(s) of the invention, it will be appreciated that modifications and variations may be made to the detailed embodiment(s) described herein without departing from the spirit of the invention.