Abstract:
A shielded pressure-actuated circuit in which two parts of a circuit may be selectively brought into contact. In one embodiment, the circuit is formed as a touch-controlled potentiometer. A shielding layer permits operation in environments of greater than 50 degrees Celsius above ambient temperatures. The shielding layer also extends the useful life of the device by increasing its durability. In one embodiment, the shielding layer comprises borosilicate or fiberglass affixed to the apparatus at the place where a force is applied to actuate the device.

Description:
RELATED APPLICATION  
       [0001]     This Application claims priority to U.S. provisional patent application Ser. No. 60/702,866 filed on Jul. 27, 2005. 
     
    
     BACKGROUND  
       [0002]     The present invention relates to pressure-actuated electronic components. More particularly, the invention may relate to pressure-actuated electronic components configured as potentiometers, which in some embodiments are actuated by touch control.  
         [0003]     Potentiometers for controlling voltage selection are used in numerous types of applications in both home and industry. For example, these devices may be used in the control panels of such things as aircraft and aerospace applications, large construction equipment, computers, lighting systems, arcade games, or kitchen appliances, to name just a few.  
         [0004]     The functionality and dependability of pressure-actuated devices, including pressure-actuated potentiometers, are subject to degradation in high-temperature environments. The functionality and dependability of such a device may also degrade over time as components of the device become worn under the pressure used to actuate the device.  
       SUMMARY  
       [0005]     In one embodiment of the present invention, a pressure-actuated circuit apparatus is configured as a linear potentiometer. A shielding material is affixed to the area to which pressure may be applied to actuate the device. This shielding material may provide for increased durability and for operation in high-temperature environments.  
     
    
     BRIEF DESCRIPTION OF THE FIGURES  
       [0006]     The objects and features of the present invention will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. Understanding that these drawings depict only typical embodiments of the invention and are, therefore, not to be considered limiting of its scope, the invention will be described and explained with additional specificity and detail through the use of the accompanying drawings in which:  
         [0007]      FIG. 1  is a cross-sectional view of a prior art device.  
         [0008]      FIG. 2  is a cross-sectional view of a prior art device as in  FIG. 1 , with a contact wiper showing the device in use.  
         [0009]      FIG. 3  is a cross-sectional view of one embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0010]     Referring now to the figures, a description of some embodiments of the present invention will be given. It is expected that the present invention may take many other forms and shapes, hence the following disclosure is intended to be illustrative and not limiting, and the scope of the invention should be determined by reference to the appended claims.  
         [0011]     Referring now to  FIG. 1 , an exemplary touch-controlled apparatus in the prior art is shown with a top layer  10  having a shunt  40  adjacent to a bottom layer  30  having a conductive surface  50 . Top layer  10  and shunt  40  may be affixed to one another using any method known to those skilled in the art. Similarly, bottom layer  30  and conductive surface  50  may be affixed to one another using any method known to those skilled in the art. In some embodiments, shunt  40  comprises a collector which may comprise silver or other conductive materials as is known in the art. Conductive surface  50  may comprise carbon or other materials as is known in the prior art. Top layer  10  and bottom layer  30  may be held apart by separator  20 . Because shunt  40  is affixed to top layer  10  and conductive surface  50  is affixed to bottom layer  30 , the placement of separator  20  between top layer  10  and bottom layer  30  also creates a space between shunt  40  and conductive surface  50 . In  FIGS. 1-3 , the size of separator  20  and of the space between shunt  40  and conductive surface  50  is not to scale.  
         [0012]     Referring now to  FIG. 2 , when a prior art device is in use, contact wiper  60  may depress top layer  10  such that shunt  40  contacts conductive layer  50 . The area of top layer  10  on which contact wiper  60  may operate to activate the apparatus may be called the actuation area. When the embodiment comprises a potentiometer, the electrical resistance provided by the apparatus varies depending on the position of contact wiper  60  within the actuation area. Contact wiper  60  may comprise a user&#39;s finger, a mechanical implement, or any number of other means capable of exerting a force on top layer  10  sufficient to cause flexure in which shunt  40  comes into contact with conductive surface  50 .  
         [0013]     In prior art devices as shown in  FIG. 1  and  FIG. 2 , the repeated contact of contact wiper  60  with top layer  10  creates wear on top layer  10  or other portions of the apparatus such that the apparatus will eventually cease to function correctly. This is especially true when contact wiper  60  takes a constant position set in a thermal environment on top layer  10  after a prolonged period of time, depressing top layer  10  to form a pre-actuated contact between shunt  40  and conductive surface  50 .  
         [0014]      FIG. 3  shows an embodiment of the present invention comprising a pressure-actuated circuit comprising a linear potentiometer having a shielding layer  90  affixed to top layer  10 . Shielding layer  90  comprises, in this embodiment, a durable and heat resistant material  92  such as borosilicate or fiberglass, which exhibits the flexibility needed to permit contact wiper  60  (not shown in  FIG. 3 ) to cause shunt  40  to come into contact with conductive surface  50  when supplied with a force consistent with the application for which the apparatus is intended. In one embodiment, the flexibility needed for the combination of top layer  10  and shielding layer  90  is appropriately 10 mils downward across the entire actuation area. In one embodiment, shielding layer  90  further comprises a heat-resistant adhesive  94 .  
         [0015]     In one embodiment, the flexibility of shielding layer  90  and top layer  10  in combination is such that they may be flexed to permit contact between shunt  40  and conductive surface  50  using an operator&#39;s fingertip or a mechanical actuation device. In some embodiments, less flexibility in shielding layer  90  will be required because contact wiper  60  will be engaged with more force than would be exerted by an operator&#39;s fingertip.  
         [0016]     In one embodiment, shielding layer  90  comprises a layer of a fiberglass material  92  bonded to top layer  10  by an adhesive  94  comprising an epoxy or any similar heat-resistant adhesive. In one embodiment, shielding layer  90  comprises a piece of fiberglass material  92  having a thickness of 5 mils and a heat-resistant adhesive  94  having a thickness of approximately 2 mils.  
         [0017]     In some embodiments, shielding layer  90  comprises a thickness of between approximately 1 mil and 10 mils.  
         [0018]     Depending upon manufacturing needs and the intended operating environment, top layer  10  may—but need not—be thinner than in prior art devices because of the addition of shielding layer  90 .  
         [0019]     Shielding layer  90  may increase heat resistance of the apparatus, permitting operation in environments in which prior art devices would likely fail. Experiments have shown that one embodiment of the present invention is able to withstand long-term operating temperatures of 50 degrees Celsius above ambient temperatures.  
         [0020]     Further, because shielding layer  90  is a material of generally greater durability compared to top layer  10 , contact between contact wiper  60  and shielding layer  90  creates less wear on the device for each use than in prior art devices. Experiments have demonstrated that one embodiment of the present invention is able to withstand more than one million additional use cycles compared to a prior art apparatus. The durability of an apparatus formed according to this embodiment will obviously vary according to the specific materials used to construct the device-including the top layer  10 , shunt  40 , conductive surface  50 , and shielding layer  90  as well as the environment to which the device is subject during operation, including, without limitation, the force with which contact wiper  60  is applied, and the temperature and humidity in which the device operates.  
         [0021]     The present invention may be embodied in other specific forms without departing from its spirit or essential characteristics. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The scope of the invention is, therefore, indicated by the appended claims rather than by the foregoing description. All changes which come within the meaning and range of equivalency of the claims are to be embraced within their scope.