Abstract:
A variable analog output pressure switch having a diaphragm attached to a plunger, the plunger controlling the amount of light detected by a photocell or photodetector, the photocell or photodetector outputting voltage roughly proportional to an applied pressure on the diaphragm.

Description:
TECHNICAL FIELD 
   This invention relates generally to a pressure switch and, more particularly, to a pressure switch which outputs a variable analog signal. 
   BACKGROUND 
   A pressure switch is a type of switch in which the switching action is triggered by pressure in the surrounding environment. Pressure switches have been proposed for use in various kinds of electro-mechanical devices. A typical pressure switch has a diaphragm that is impinged upon by media, such as air under pressure, and upon reaching a particular pressure the diaphragm causes the switch contacts of the pressure switch to be actuated from the off-to-on or on-to-off position by snap action, creating a binary type output. 
   However, in many instances, such as in modern control systems, it is desirable to utilize a switch that provides an analog output such that the output varies according to applied pressure or vacuum. Conventional pressure switches do not meet this need because snap action actuation of the conventional switches causes a binary signal to be output instead of an analog signal. For example, snap action actuation from the off-to-on or on-to-off position does not allow for an output that is approximately proportional to applied pressure or vacuum. 
   SUMMARY 
   The present disclosure provides examples of pressure switches which output a variable analog signal instead of a binary signal, such that the output varies according to applied pressure or vacuum. Such pressure switch devices can be integrated with an additional mechanism within the switch which actuates a discrete switch that provides a binary output, in addition to the variable analog output provided by the switch. 
   In accordance with one aspect of the present disclosure, a variable analog pressure switch is provided in which an optical mechanism is actuated in response to pressure, instead of a snap action mechanism. 
   In one example, the analog output provided by the switch varies according to light detected by a photodetector in the optical mechanism. The optical mechanism in the example includes a shutter-like device which gradually cuts off light supplied in the direction of the detector, in response to pressure in the surrounding environment. The photodetector provides an output (for example, a voltage) which varies according to an amount of light detected by the photodetector (for example, linearly or otherwise monotonically) 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The features of the present disclosure can be more readily understood from the detailed description below with reference to the accompanying drawings wherein: 
       FIG. 1  is a cross-sectional view of a variable analog output pressure switch according to an example of the present disclosure; 
       FIG. 2  is a cross-sectional view of a variable analog output pressure switch according to another example of the present disclosure; and 
       FIG. 3  is a cross-sectional view of a variable analog output pressure switch according to yet another example of the present disclosure. 
   

   DETAILED DESCRIPTION 
   In describing examples and preferred embodiments in connection with the drawings, specific terminology is employed for the sake of clarity. However, the disclosure of this patent specification is not intended to be limited to the specific terminology so selected, and it is to be understood that each specific element includes all technical equivalents that operate in a similar manner. 
   Referring now to  FIG. 1 , an example of a pressure switch  100  with an optical mechanism will be discussed. Electrical switching of the pressure switch  100  occurs when a fluid (such as air) enters a pressure port  2  and exerts pressure or force on a diaphragm  4 . The diaphragm  4  is coupled to a plunger  8 . The plunger  8  is abutted on an inner surface thereof by a spring  6 . The spring  6  creates a spring force against the plunger  8  that is controlled by a threaded screw  14 . The threaded screw  14  may be adjusted such that the spring force is increased or decreased depending on the desired pressure at which the pressure switch  100  is to respond. Thus, generally the plunger will move in a direction from the diaphragm towards the spring (that is, depressed) when the force translated through the diaphragm exceeds the spring force. 
   A light emitting diode (LED)  10  and a photodetector  12  are positioned relative to each other on opposite sides of the plunger  8  such that the photodetector  12  detects an amount of light from the LED  10 . The photodetector  12  supplies an output according to an amount of light the photodetector  12  detects. The pressure switch  100  is in a non-activated state when the plunger  8  is not depressed, allowing the light from the LED  10  to be completely transmitted to the photodetector  12 . When force is exerted on the diaphragm  4 , the plunger  8  acts as a shutter and gradually moves to block the light generated by the LED  10  from reaching the photodetector  12  as it is depressed. Thus, the pressure switch  100  can output a variable voltage based on an amount of light detected by the photodetector  12 . 
   Another example ( FIG. 2 ) of a pressure switch with optical mechanism will now be discussed. Electrical switching of pressure switch  200  occurs from pressure created from a fluid (such as air) entering pressure port  22  which channels the fluid to exert a force on a diaphragm  24 . The diaphragm  24  is coupled to a plunger  28 . The plunger  28  is abutted on an inner surface thereof by a spring  26 . The spring  26  creates a spring force against the plunger  28  that is controlled by a threaded screw  34 . The threaded screw  34  may be adjusted such that the spring force is increased or decreased depending on the desired pressure at which the pressure switch  200  is to respond. 
   A photocell  30  is placed in close proximity to the plunger  28  such that a shutter  32 , attached to the plunger  28 , is capable of gradually blocking light from a light source (not shown) to the photocell  30  as the plunger  28  is depressed. The pressure switch  200  is in a non-activated state when the plunger  28  is not depressed, allowing light to be completely transmitted to the photocell  30 . When force is exerted on the diaphragm  24 , the plunger  28  is depressed causing the spring  26  to compress and the shutter  32  to gradually block light transmission to the photocell  30 . The pressure switch  200  supplies a variable output based on an amount of light detected by the photocell  30 . 
   The plunger  28  is abutted on an outer surface thereof by a spring  36 . The spring  36  creates a spring force against the plunger  28  on the outer surface thereof. As pressure is decreased on the diaphragm  24 , the spring  36  acts as deactuation means by exerting its spring force on the outer surface of the plunger  28 . As the plunger  28  is forced against the spring  36 , the shutter  32  allows more light to reach the photocell  30 , and thus, the pressure switch  200  returns to a deactuated state. 
   Referring now to  FIG. 3 , another example of a pressure switch with optical mechanism will be discussed. Electrical switching of a pressure switch  300  occurs when pressure created from a fluid entering a pressure port  42  exceeds a certain level and exerts a corresponding force on a diaphragm  44 . The diaphragm  44  is affixed to a plunger  52 . The plunger  52  is abutted on an inner surface thereof by a spring  46 . The spring  46  creates a spring force against the plunger  52  which is controlled by a threaded screw  58 . The threaded screw  58  may be adjusted such that the spring force is increased or decreased depending on the desired pressure at which the pressure switch  300  is to respond. 
   A photocell  48  is placed in close proximity to the plunger  52  such that a shutter  50 , attached to the plunger  52 , is capable of blocking light to the photocell  48  as the plunger  52  is depressed. The pressure switch  300  is in a non-activated state when the plunger  52  is not depressed, allowing light to be completely transmitted to the photocell  48 . When force is exerted on the diaphragm  44 , the plunger  52  is depressed causing the shutter  50  to gradually block light transmission from the photocell  48 . The pressure switch  300  supplies a variable analog output based on an amount of light detected by the photocell  48 . 
   The plunger  52  is abutted on an outer surface thereof by an actuator  54  for a discrete switch  56 . When the plunger  52  is not fully depressed, the actuator  54  is not activated and the discrete switch  56  is in an off position (or, alternatively, an on position). When the plunger  52  is fully depressed, the actuator  54  activates the discrete switch  56  to an on position (or, alternatively, an off position). When activated, the discrete switch  56  outputs a binary signal. By integrating the discrete switch  56  into the pressure switch  300 , a user has the dual functionality of supplying analog and binary outputs. 
   It should be understood that the discussion above is merely illustrative for the purpose of demonstrating exemplary embodiments of a pressure switch with optical mechanism. 
   For example, while an LED is used in one exemplary embodiment, other well-known light sources (for example, laser diodes, photodiodes, etc.) can alternatively be used. Similarly, while a photocell may be used as a proposed photodetector, other light detection devices, such as phototransistors, etc., can be used instead. Further, it should be apparent that a pressure responsive actuation mechanism other than those shown in  FIGS. 1-3  can be used alternatively. 
     FIGS. 1-3  show some preferred embodiments. However, it should be apparent that the present disclosure as directed to a pressure switch with optical mechanism, can include the following components. The optical mechanism includes a light source and light detector which are relatively positioned such that the light detector detects an amount of light from the light source. The switch also includes a pressure-responsive actuation device which causes a shutter device to translate (or rotate or otherwise move) gradually to a position in a light path between the light source and the light detector. As the shutter gradually enters the light path, the amount of light detected by the detector decreases. The detector provides an analog output varying according to the amount of light detected by the detector. 
   The above specific examples and embodiments are illustrative, and many variations can be introduced on these embodiments without departing from the spirit of the disclosure or from the scope of the appended claims. For example, elements and/or features of different illustrative embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims.