Abstract:
A structure embodying a switch and method of operating thereof for creating a latching switch is disclosed. The latching switch utilizes an electrorheologic fluid and the electronic latch function thereof is actuated by a pressure signal and deactivated by the removal of both the pressure signal and a holding voltage.

Description:
CROSS REFERENCE TO RELATED APPLICATION  
       [0001]     This application is related to U.S. patent application Ser. No. ______ having Attorney Docket No. SP05 and filed herewith. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to a switch and a method of operation thereof, and, more particularly, to a switch and a method of operating thereof that provide electronic latching of the switch and that utilizes an electrorheologic fluid, wherein the electronic latching is actuated by a pressure signal and deactivated by the removal of both a pressure signal and a latching voltage.  
       BACKGROUND OF THE INVENTION  
       [0003]     The electronic and electromagnetic latching relays are well-known and fine wide applications in the field of controlling electrical signals. These electronic and electromagnetic latching relays find limited use in the field of controlling the flow of fluids. More particularly, the flow of fluid is typically controlled by a pressure signal applied to a fluid control valve that responds thereto by either being activated or deactivated. It is desired that a switch be provided for that is used in conjunction with the control of the pressure signal so as to control the flow of fluid and which switch provides a latching function that locks into whatever mode is energized for on or off condition of the related fluid control switch.  
       OBJECTS OF THE INVENTION  
       [0004]     Accordingly, it is an object of the present invention to provide a switch and a method of operation thereof that provides a latching function for the flow of liquid controlled by a pressurized signal.  
         [0005]     It is a further desire of the present invention to provide a switch and a method of operation thereof that is activated by a pressure signal and deactivated by both the pressure signal and a latching voltage.  
         [0006]     It is another object of the present invention to provide a switch, and a method of operation thereof, that provides control over the flow of fluid even in the unattended loss of a pressure signal that initiated the activation of the switch itself.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention is directed to a switch, and a method of operation thereof, that is activated by a pressure signal and deactivated by the removal of both the pressure signal and a holding voltage.  
         [0008]     The latching switch comprises a chamber containing an electrorheologic fluid. The chamber has first, second, third and fourth terminals and has an opening serving as an input portion capable of receiving a pressurized fluid. The latching relay further comprises at least a pair of spaced apart electrodes located within the chamber and with one of the electrodes connected to the first terminal. The latching relay further comprises at least a pair of switches each having first and second fixed contacts and each contact thereof being operatively interconnectable therebetween by a movable contact. Each of the switches being responsive to the received pressure so as to be rendered operable. One of the pair of switches has its first and second fixed contacts respectively connected to the second and third terminals. Further, the other of the pair of switches has its first contact connected to the fourth terminal and its second contact connected to the other electrode. The latching switch further has first and second diaphragms respectively and completely covering each of the pair of switches. Each of the first and second diaphragms being flexibly responsive to the pressurized fluid.  
         [0009]     The method of latching a switch comprises the steps of: a) providing a chamber containing an electrorheologic fluid and having first, second, third and fourth terminals and having an opening capable of receiving a pressurized fluid; b) providing at least a pair of spaced apart electrodes being located with the chamber. The method further comprises: c) connecting one of said electrodes to the first terminal; and d) providing at least a pair of switches each having first and second fixed contacts operatively interconnectable therebetween by a movable contact, each switch thereof being located within the chamber and being responsive to the received pressurized fluid. The method further comprises the steps of: e) connecting the first and second fixed contacts of one of the pair of switches to the second and third terminals respectively; f) connecting the other of the pair of switches so that its first contact is connected to the fourth terminal and its second contact is connected to the other electrode of the pair of spaced apart electrodes; g) providing first and second diaphragms respectively and completely covering each of the pair switches, each of the first and second diaphragms being flexibly responsive to the pressurized fluid; h) connecting the first, second, third and fourth terminals respectively to a ground potential, an input signal, an output signal, and a latching voltage; and finally, i) applying the pressurized fluid. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a schematic of the latching switch according to the present invention;  
         [0011]      FIG. 2  is an illustration of the chamber of the latching switch of  FIG. 1 ; and  
         [0012]      FIG. 3  illustrates the dipole interaction induced by an E-field associated with the operation of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]     With reference to the drawings, wherein the same reference number indicates the same element throughout,  FIG. 1  is a schematic of a latching switch  10  in accordance with the present invention which, as will be described hereinafter, is activated by a pressure signal and deactivated by the removal of both the pressure signal and a latching voltage.  
         [0014]     The latching switch  10  comprises a chamber  12  having first, second, third and fourth terminals respectively identified by reference number  14 ,  16 ,  18 , and  20 . The chamber  12  has an opening  12 A, which serves an input port for receiving pressurized fluid, shown by directional arrow  22 , and which serves as a pressure signal for operating switch  10 .  
         [0015]     A pair of spaced apart electrodes  24  and  26  are located within the chamber  12  and one of the electrodes, such as  24 , is connected to the first terminal  14 .  
         [0016]     The latching switch  10  further comprises at least a pair of switches  28  and  30  located within the chamber  12  and responsive, as will be further described to the received pressure fluid  22 . As seen in  FIG. 1 , each of the switches have first and second fixed contacts that are operatively interconnected therebetween by a movable contact. One of the pair of switches, indicated in  FIG. 1  as switch  28 , has its first and second fixed contacts respectively connected to terminal  16  and  18 . The other switch  30  has its first fixed contact connected to terminal  20  and its second fixed contact connected to the second electrode  26 . The chamber contains an electrorheologic fluid  32 .  
         [0017]     The switches  28  and  30  within the chamber  12  are respectively separated from the electrorheologic fluid  32  by means of the flexible diaphragms  28 A and  30 A. The materials selected for the flexible diaphragms  28 A and  30 A include those from the plastics family including polyethylene, polycarbonate and vinyl, as well as those from the rubber family including latex or silicone, in addition to those from the metal family including copper or aluminum.  
         [0018]      FIG. 1  shows switches  28  and  30  as being normally open switches and arranged in parallel within the chamber  12 . In general, the first switch  28  having it first fixed contact connected so the second terminal  16  is used to latch a desired input signal present on the second terminal  16 . The second fixed contact of switch  28  is connected to third terminal  18  and provides the output signal from the latching switch  10  when switch  28  is rendered operative, as will be further described herein. The second switch  30  is connected in series with two parallel electrodes  24  and  26  at the entrance to the chamber  12 , that is in correspondence with the opening  12 A. This second switch  30  is used to apply a voltage across the electrodes. More particularly, the second switch  30  applies the positive potential of the voltage, connected to the fourth terminal  20 , to the second electrode  26 , whereas the negative potential of the applied voltage is present at the electrode  24  by way of the first terminal  14  that is connected to the ground. The voltage applied across the electrodes  24  and  26  serves as a latching voltage, as will be further described.  
         [0019]     As shown in  FIG. 2 , the electrodes  24  and  26  are respectively located on the roof and floor of the chamber  12 . As further seen in  FIG. 2 , the chamber  12  itself is filled with an electrorheologic fluid  32 , known in the art and may be of the type more fully described in U.S. Pat. No. 6,186,176, herein incorporated by reference. Further, the electrorheologic fluid  32  is composed of nanoparticles  34 , shown in  FIG. 2 .  
         [0020]     As is known in the art, electrorheologic fluids  32  represent a class of smart materials, consisting of nanometers to micrometer sized solid particles  34  suspended in a liquid, whose Theological properties are controllable by an external electric field applied across the electrodes  24  and  26 . The electric field may be further described with reference to  FIG. 3 .  
         [0021]      FIG. 3  illustrates a dipole interaction of the dispersed particles  34  in the electrorheologic fluid  32  induced by an E-field. More particularly,  FIG. 3  illustrates an E-field  38  creating three phases  40 ,  42  and  44  of dipole interactions.  
         [0022]     In general, the operation of the electrorheologic fluid  32  can be reversibly transformed from a liquid to a solid within a short period of time, such as one-hundredth of a second. While in a solid state (with the electric field  38  applied), the strength of that solid formed by the electrorheologic fluid  32  provides a relatively high yield stress which is a critical parameter of the electrorheologic fluid  32 .  
         [0023]     In the absence of an electric field, dispersed particles  34  in the electrorheologic fluid  32  shown in  FIG. 2 , move freely and are randomly distributing as shown by directional arrow  46 . More particularly, with reference to  FIG. 3 , in the presence of a low electric field, such as, and as shown by phase  40 , the dispersed particles  34  are polarized and aligned by electrostatic attraction forces from changes shown by directional arrow  46 . As seen in phase  42 , in presence of a medium electric field the particles  34  contact each other to form a chain. In the presence of a high electric field, as seen in phase  46 , individual chains combined with nearby chains perform thick columns. The viscosity of the electrorheologic fluid  32  is thus increased with corresponding increases in electric field, resulting in directional solidification when the influence of the applied field is sufficient.  
         [0024]     The electric field that is desired to be applied across the electrodes  24  and  26 , that is, the latching voltage across electrodes  24  and  26 , is in the order of 2 KV/mm as is known in the art. More particularly, it is desired that the latching voltage will provide a yield stress in the electrorheologic fluid in the order of 1-40 KPa. For such a yield stress factor, the electrode spacing needs to be in the order of about 0.1 mm to obtain these fields with a reasonable voltage. Under these desired conditions, the pressure activating the latching switch  10  is selected to respond to a pressure signal  22 , shown in  FIG. 1 , in the range of a few pounds per square inch.  
         [0000]     In Operation  
         [0025]     The switch  10  of  FIG. 1  is actuated by applying pressure, indicated by directional arrow  22 , at the pressure inlet port  12 A. This pressure causes both normally opened switches  28  and  30  to close. This closing action causes both the latching voltage at terminal  20  to appear across the electrodes  24  and  26  and the signal applied to input terminal  16  to appear at the output terminal  18 .  
         [0026]     The signal at terminal  18  is latched by the latching voltage that is now applied across the electrodes  24  and  26 . This latching voltage serves to stiffen the electrorheologic fluid  32  to the point that the electrorheologic fluid  32  does not flow under applied pressure. This non-flow means that even if the inlet pressure, indicated by directional arrow  22 , applied at the pressure input port  12 A were to be removed, the pressure within the chamber  12  will not be relieved until the latching voltage is removed. This non-flow also means the signal at terminal  16  will continue to appear at the terminal  18  until the latching voltage is removed.  
         [0027]     It should now be appreciated that the practice of the present invention provides for a switch and a method of operation thereof that provides for latching and that utilizes an electrorheologic fluid. The switch of the present invention is activated by a pressure signal and deactivated by the removal of both the pressure signal and a latching voltage. Further, the switch of the present invention maintains its selected mode until the removal of the latching voltage.  
         [0028]     While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in the form of details maybe made therein without departing from the spirit and scope of the invention.