Abstract:
A linear pressure switch is described that has two conductors separated by strips of insulation. The conductors are resilient members that can vary in thickness and material along with the insulation to provide a range of switch sensitivities. The switch can include connectors and an attachment mechanism that facilitates the installation and removal the switch from a given application. In addition, the switch can ergonomically enhanced actuation. The switches can be stacked in layers and selectively have different sensitivities to provide a desired signal output for each switch in a given application. The switch can also include external coatings on the jacket which enhance the feel and resistance of the jacket to wear and misuse.

Description:
FIELD OF THE INVENTION 
   The present invention relates to pressure activated linear switches and more specifically to improved pressure activated linear switch apparatuses that can be directly connected to an external surface, have ergonomic structures to facilitate activation and a range of external connector configurations. 
   BACKGROUND OF THE INVENTION 
   Linear switches have a broad range of applications that include mats that activate doors, electrical safety interrupts and automobile sensors. The problems associated with linear switches are well known and include those associated with coiling for transportation and storage as well as the ability to mass produce switches tailored for individual applications. 
   In particular, the tailoring of linear switches to individual applications can be a time consuming problem in which a section of linear switch is cut, spliced and hard wired into a circuit. This connection between the conductors of the switch and circuit can become an additional reliability problem beyond that of the switch itself. Further, the failure of the switch requires the removal and replacement of a hard wired portion of the circuit that is often further complicated by the use of a specialized channel or adhesive that attaches and fixes the switch to an external surface. 
   Linear switches are typically fixed in position against a substantially rigid surface in order to assure reliable activation. Specialized channels can fix linear switches in position and facilitate the activation of the switch, but these channels require additional fasteners to be installed and then a cumbersome and time consuming sliding integration of the linear switch and channel. 
   Another problem with linear switches is their lack of sufficient tactile sensation. Many common linear switches employed in channels, for example, have a raised backbone or ridge along the top longitudinal centerline of the switch that is made of the same dense polymer or rubber materials as the jacket. This raised backbone can facilitate switch actuation in many automated or industrial applications by providing a limited tactile sensation of the switch and direction for activating the switch, but locating and compressing the dense polymer or rubber materials along the narrow ridge can be difficult for many applications. 
   A linear pressure switch apparatus is needed that has an attachment mechanism for readily fixing into position, connectors for ease of placement and removal from a circuit and that can be actuated with a softer tactile sensation with improved ergonomic qualities. Further, a linear pressure switch apparatus is needed that can discriminate between a range of actuation forces. 
   SUMMARY OF THE INVENTION 
   A linear pressure switch apparatus is described that comprises a first elongate conductor plate that has a pair of opposed faces, a second elongate conductor plate that has a pair of opposed faces and at least one insulative strip that separates and electrically isolates the first conductor plate and the second conductor plate. A jacket encases the structure of the conductors and the at least one insulative strip. The jacketed structure provides an at least water resistant barrier. An attachment mechanism is adapted to fix the jacketed structure in position on an external structure. 
   A linear pressure switch apparatus is described that comprises a first elongate conductor plate that has opposed terminal end portions, a second elongate conductor plate that has opposed terminal end portions, an insulative strip that separates and electrically isolates the first conductor plate and the second conductor plate. A jacket encases the conductors and the at least one insulative strip and provides a jacketed structure that is at least water resistant barrier. A set of connectors are coupled to the terminal end portions of the conductors that extend through the jacket and are adapted to interface with a mating set of conductors. 
   A linear pressure switch apparatus is described that comprises a first elongate conductor plate that has opposed terminal end portions, a second elongate conductor plate that has opposed terminal end portions, an insulative strip that separates and electrically isolates the first conductor plate and the second conductor plate. A jacket encases the conductors and the at least one insulative strip and provides a jacketed structure that is at least water resistant barrier. A bias member is positioned between the jacket and the first elongate conductor plate that is a resilient foam. The bias member provides a tactile sensation to the activating of the conductors. 
   A linear pressure switch array is described that comprises a first elongate conductor plate that has a pair of opposed faces, a second elongate conductor plate that has a pair of opposed faces, a first insulative strip that separates and electrically isolates the first conductor plate and the second conductor plate, a third elongate conductor plate that has a pair of opposed faces, a fourth elongate conductor plate that has a pair of opposed faces, a second insulative strip that separates and electrically isolates the third conductor plate and the fourth conductor plate, a fifth elongate conductor plate that has a pair of opposed faces, a sixth elongate conductor plate that has a pair of opposed faces and a third insulative strip that separates and electrically isolates the fifth conductor plate and the sixth conductor plate. The sensitivity of each pair of conductive plates varies to provide a range of activation signals. A jacket encloses the conductor plates and insulative strips to form a jacketed structure. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Preferred embodiments of the invention are described below with reference to the drawings, wherein like numerals are used to refer to the same or similar elements. 
       FIG. 1  is a front and side perspective view of a linear pressure switch apparatus constructed in accordance with the present disclosure showing one preferred attachment mechanism; 
       FIG. 2  is an exploded front and side perspective view of the linear switch of  FIG. 1  that shows one preferred positioning of the insulation; 
       FIG. 3  is frontal view of the linear switch of  FIG. 1  with an attachment mechanism that includes a base plate and fasteners; 
       FIG. 4  is frontal view of the linear switch of  FIG. 1  with an attachment mechanism that includes a base plate that is adapted to interface with a standard channel; 
       FIG. 5  is front and side perspective view of a second embodiment of the linear switch of  FIG. 1  that includes a bias member; 
       FIG. 6  is a front and side perspective view of a third embodiment of the linear switch of  FIG. 1  with a molded end cap; 
       FIG. 7  is a front and side perspective view of a fourth embodiment of the linear switch of  FIG. 1  showing a two pin connector on the bottom surface of the switch; 
       FIG. 8  is a is a front and side perspective view of a sixth embodiment of the linear switch of  FIG. 1  showing jumper cables and connectors for the connecting of the switch from a single terminal end portion; 
       FIG. 9  is a front and side perspective view of the bottom of the linear switch of  FIG. 8  showing a four pin connector system; 
       FIG. 10  is a front view of a seventh embodiment of the linear switch of  FIG. 1  showing a stacked array of linear switches of varying sensitivities that provide multiple levels of signal actuation; 
       FIG. 11  is a front and side perspective view of the linear switch of  FIG. 1  showing external markings to delineate caution and the function of the switch; and 
       FIG. 12  is a front view of the switch of  FIG. 4  in an activated position. 
   

   DETAILED DESCRIPTION 
   Referring initially to  FIG. 1 , linear pressure switch  10  is a parallel conductor continuous length switch that includes a first conductor  12  and a second conductor  14  positioned in spaced relation by insulation  16 . Conductors  12  and  14  are conductive plates that preferably have an elongate shape with opposed longitudinal edges  18 , opposed terminal end portions with lateral edges  20 , an outward directed face  22  and an inward directed face  24 . Conductors  12  and  14  can be made of any electrically conductive material, but are preferably made of spring steel. Linear switch  10  is a normally open momentary pressure sensitive switch. 
   Switch  10  is shown as an in-line switch with a first set of connectors  13  and a second set of connectors  15  that are adapted to interface with mating connectors. Connectors  13  and  15  are shown as standard spade connectors, but it is understood that connectors  13  and  15  can have any structure, angular orientation, positioning or configuration. Connectors  13  and  15  advantageously facilitate the field installation and removal of switch  10  in a circuit. 
   Insulation  16  has a predetermined thickness that provides an air gap that separates and electrically isolates conductors  12  and  14  in a first position of switch  10 . Insulation  16  is preferably a pair of strips of insulation  16  with each strip positioned in proximity to one of longitudinal edges  18 . Insulation  16  extends approximately the length of switch  10 . Insulation  16  can vary in both lateral width, height and in material to provide a desired degree of switch sensitivity. Insulation  16  is preferably a resilient foam material that separates conductors  12  and  14  in the first position and can be compressed by a force approximately perpendicular to face  22  to make electrical contact between conductors  12  and  14  in a second position. In one preferred embodiment, insulation  16  is 3M—No. 4016 double coated urethane foam tape. The approximate height of the air gap provided by insulation  16  can vary depending upon the desired application, but typically ranges between 0.003 and 0.1875 inches. 
   Linear switch  10  preferably includes an attachment mechanism  26  that fixes switch  10  in position against an external surface. Attachment mechanism  26  as defined herein is a mechanical device for securely fixing switch  10  to an external structure without the use of adhesives. In this preferred embodiment, attachment mechanism  26  is a set of at least one aperture that is adapted to receive one or more fasteners  28  that extend through switch  10  and into the external structure. Fasteners  28  are preferably threaded screws that can be fabricated from any suitable material such as for example metals, polymers and/or composites that securely attach switch  10  to the external structure. 
   As shown in  FIG. 2 , linear switch  10  defines a set of one of more apertures  30  that receive fasteners  28 . Apertures  30  preferably have a non-conductive layer  32  positioned between conductors  12  and  14 . Layer  32  preferably functions to provide an at least water resistant seal for switch  10  and can also be selectively employed to provide an electrically insulation barrier between conductors  12  and  14 . Layer  32  can include devices such as an O-ring, sleeve or grommet, for example. 
   In addition, one or more additional insulation members  34  are preferably added in proximity to aperture  30  to provide an insulation barrier between conductors  12  and  14 . Insulation members  34  are preferably the same material as insulation strips  16 . Insulation members  34  are shown as strips approximately perpendicular to the longitudinally aligned insulation strips  16 , but it is understood that insulation  34  can have any shape, material or angular orientation to include a planar circular disc or angular shape that provides the required electrical isolation of conductors  12  and  14  when switch  10  is fixed in position by fastener  28 . 
   It is also understood that apertures  30  can be positioned at any location on switch  10 , to include through insulation strips  16 , depending upon the intended application. Apertures  30  are preferably positioned approximately along the longitudinal centerline of switch  10  to minimize the number of apertures  30  and fasteners  28  to advantageously reduce the time required for installation and removal of a given switch  10 . Alternatively, apertures  30  in proximity to longitudinal edges  18  preserve the continuous activation capability of switch  10 . Apertures  30  in proximity to longitudinal edges  18  that extend through insulation strips  16  can selectively include a washer, grommet or sleeve to improve the resistance to water intrusion. Fasteners  28  in applications with apertures  30  in proximity to longitudinal edges  18  can also have heads with reduced dimensions in one or more dimensions so that the heads of fasteners do not extend beyond longitudinal edges  18 . 
   Referring now to  FIG. 3 , attachment mechanism  26  can also include a base plate  36 . In this preferred embodiment of attachment mechanism  26 , base plate  36  has a set of one or more fasteners  28  that can be a monolithically formed or an integrally connected assembly with base plate  36 . Fasteners  28  are preferably snap-fit type devices that readily push into and attach with a previously prepared hole in an external surface. As described previously, fasteners  28  can be approximately aligned with the longitudinal centerline or any other position on switch  10 . Base plate  36  is attached to outward face  22  of second conductor  14  using known methods such as for example adhesives, heat bonding or fasteners. Switch  10  is encapsulated in an outer covering or jacket  38  to form an at least water resistant jacketed structure. Jacket  38  is preferably a shrink tube, molded, extruded or other type of protective barrier that covers the length of conductors  12  and  14 . 
   As shown in  FIG. 4 , a second embodiment of base plate  36  includes a flange  40  that interfaces with an external structure that is an exemplary standard channel  42 . Flange  40  in this preferred embodiment has an inverted “T” shape that extends downward from switch  10  that is configured to correspondingly mate and slidingly engage with a mounting track  43  of channel  42 . Different channels  42  vary the vertical position of the mounting track  43  and thereby vary the amount that a given linear switch is recessed into or extends above the outer walls of channel  42 . Base plate  36  can be advantageously connected to linear switch apparatus  10  to position the linear switch at the desired elevation relative to channel  42 . Channel  42  fixedly connects to another external structure such as a wall or floor and provides structural support for the deflection of first conductor  12  relative to conductor  14  for the activation of switch  10 . 
   Referring now to  FIGS. 4 and 5 , switch  10  includes a bias member  44  that is positioned between jacket  38  and face  22  of conductor  12  and preferably extends the full lateral width between longitudinal edges  18 . Bias member  44  is preferably a resilient material that is readily compressed with a relatively softer touch than the semi-rigid raised ridge material commonly employed in many applications. Bias member  44  provides an improved sensitivity and ergonomic feel to switch  10  that can be advantageously employed in applications directed towards public use which necessitate the ability of switch  10  to be activated by a broad range of people to include those that are infirm and/or handicapped. Switch  10  can also include an additional lower strip  46  that is attached to face  22  of conductor  14  that can further aid in achieving contact between conductors  12  and  14 . 
   As shown in  FIG. 6 , the terminal end portions of switch  10  can also include a cap  48  through which connectors  13  and  15  (not shown) extend. Cap  48  can provide additional structural support to cantilevered connectors  13  and  15  and resistance to water intrusion. Cap  48  is preferably molded, shrunk or an extruded layer that can interface with a mating connector to provide an encapsulated at least water resistant interface. 
   Referring now to  FIG. 7 , the bottom of switch  10  is shown with fastener  28  extending outwardly. Fastener  28  in this preferred embodiment does not extend through switch  10 , but the head of fastener  28  is connected to the bottom of switch  10  using a bonding mechanism such as an adhesive or heat. Cover  38  can also provide a mechanical bonding layer to secure fastener  28  to switch  10 . In this preferred embodiment, separate pinned connectors are provided for connectors  13  and  15  (not shown). Pinned connectors provide reliable secure coupling as well as ease of field connection and disconnecting. 
   As shown in  FIG. 8 , switch  10  in this preferred embodiment includes jumpers  50  that are coupled to second set of connectors  15  to provide the connecting of switch  10  from a single terminal end portion of switch  10 . This embodiment provides a switch  10  that loops into an external circuit vice as an in-line portion of the external circuit. This provides an advantageous concentration of connectors  13  and  15  on one terminal end portion of switch  10 . The four pin switch configuration eases design, installation and repair processes by enabling the coupling to be done at a single point. In this embodiment, second set of connectors  15  are electrically isolated from the adjacent conductor  12  or  14  by a pad or layer  52 . 
   Referring now to  FIG. 9 , switch  10  in another preferred embodiment has a single four pin connector  54  that provides for a simple coupling to an external circuit. Connector  54  is coupled with conductors  12  and  14  to provide a single point ease of connection and disconnection with the external circuit. 
   As shown in  FIG. 10 , switch  10  in this preferred embodiment is an array of switches  10   a ,  10   b  and  10   c  stacked in parallel with conductors  56 ,  58 ,  60  and  62  separated by insulative strips  16 . Conductors  56 ,  58 ,  60  and  62  can be shared common conductors or alternatively conductors for separate circuits. In this embodiment, strips of insulation  16  reduce the dimensions of the air gap between conductors and thereby increase the sensitivity of each switch from  10   a  to  10   c . The application of a force in a direction approximately perpendicular to face  22  of conductor  56  displaces each conductor  56 ,  58 ,  60  and  62 , but that displacement will bring conductors  60  and  62  into contact first due to their reduced air gap. The application of additional force will activate switches  10   b  and  10   a  in sequence. The differing signals from switches  10   a ,  10   b  and  10   c  can be employed to operationally distinguish, for example, contact made by a movable device with a lightly displaceable object such as a chair and a rigid structure such as a wall. 
   Referring now to  FIG. 11 , switch  10  can include spray on coatings to jacket  38  such as those applied to truck beds to form liners or non-skid, for example. In addition, jacket  38  can have markings that denote warning or hazard through the use of colors, symbols and terms. 
   As shown in  FIGS. 1 ,  4  and  12 , bias member  44  is positioned between jacket  38  and conductor  12 . Bias member  44  is preferably a resilient relatively soft foam that compresses under a force F. Conductors  12  and/or  14  bend under the application of force F that is approximately perpendicular to face  22  of conductor  12  through bias member  44 . In response to force F, conductor  12  in this example deflects across the air gap provided by strip insulation  16  into contact with conductor  14 . This momentarily activates switch  10  until force F is removed and the resilience of insulation  16  separates conductors  12  and  14 . Bias member  44  provides an additional sense of tactile feel during compression and provides an additional bias to the displacement force. Varying the thickness of conductors  12  and  14  as well as the thickness, material and width of strips of insulation  16  and bias member  44  can vary the sensitivity of switch  10  for a given application. 
   In the preceding specification, the present disclosure has been described with reference to specific exemplary embodiments thereof. It will be evident, however, that various modifications, combinations and changes may be made thereto without departing from the broader spirit and scope of the invention as set forth in the claims that follow. While the present invention is described in terms of the varying embodiments of attachment mechanisms, connector configurations, soft actuation, and multiple circuit sensitivity for example can be combined with one or more novel features of the other embodiments. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense.