Abstract:
A mesovalve having a diaphragm situated between a first chamber and a second chamber. There may be an inlet and an outlet in the first chamber. The diaphragm may provide an orifice between the first and second chambers. There may be a first electrode on the diaphragm and a second electrode on an inside surface of the second chamber. The diaphragm may have first and second positions, or numerous variable positions. Applying a voltage across the electrodes may electrostatically move the diaphragm to the second position during which the outlet is at least partially opened for fluid communication with the inlet, the orifice is closed and the diaphragm is stopped in the second position by a cushioning fluid pressure in the second cavity to prevent pull-in. Removing the voltage from the electrodes may let the diaphragm return to the first position, open the orifice and close the outlet.

Description:
BACKGROUND  
       [0001]     The present invention pertains to valves and particularly to electrostatically actuated valves. More particularly, the invention pertains to electrostatically actuated valves for modulation.  
         [0002]     A patent application that may relate to the present invention is U.S. patent application Ser. No. 10/174,851, filed Jun. 19, 2002, which is herein incorporated by reference. Patents that may relate to the present invention include U.S. Pat. No. 6,288,472; U.S. Pat. No. 6,179,586; U.S. Pat. No. 6,106,245; U.S. Pat. No. 5,901,939; U.S. Pat. No. 5,836,750; and U.S. Pat. No. 5,822,170; all of which are herein incorporated by reference. This application may be related to a patent application having attorney docket no. H0003388-0765 (1161.1167101), entitled “Electrostatically Actuated Gas Valve” by Bonne et al., and being filed approximately concurrently, and a patent application having attorney docket no. H0007507 (1100.1283101), entitled “Media Isolated Electrostatically Actuated Valve” by Cabuz et al., all of which are incorporated herein by reference.  
         [0003]     Electrostatic actuators which are voltage driven may be controlled relative to only one-third of the total displacement when a pull-in (viz., snapping) effect occurs. The voltage span for this control may have many times a small value making the valve control a difficult task. In other words, electrostatic actuators may be voltage driven for a limited displacement; however, a pull-in effect may occur after that displacement. There may be many techniques to delay or avoid this phenomenon that makes many electrostatic actuators inappropriate for many applications.  
       SUMMARY  
       [0004]     The invention is a device that may increase the stability for an electrostatically actuated mesovalve structure for use in modulating a flow and/or pressure of a fluid. It may have an air spring that controls the displacement of an electrostatic actuator thereby making it effective for modulator applications. The device may be designed to meet specific application needs by the size of a buffer volume, the diameter of a valve seat and diaphragm pre-stress as design control parameters. The present mesovalve may be a low cost, low power plastic valve made with mesopump technology. The device may use less than one micro joule of power needed for one actuation. The present structure may offer a solution for delaying or avoiding the pull-in effect thereby making the device appropriate for stable applications flow and pressure control and modulation. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0005]      FIGS. 1 and 2  show a mesovalve structure for flow modulation;  
         [0006]      FIGS. 3 and 4  show a mesovalve structure for pressure modulation; and  
         [0007]      FIG. 5  shows a controller connected to the mesovalve structure. 
     
    
     DESCRIPTION  
       [0008]     In an electrostatic modulator, the electrostatic force may work against a force that keeps two electrodes of the actuator apart. This force may be generated by an elastic, force, a pneumatic force, or the like. By applying a driving voltage, the actuator position may be controlled one third of the initial distance between the electrodes, and the then pull-in (snapping) effect occurs. This control may be done for a certain span of the driving voltage until the pull-in threshold. This threshold value may be small, thus not offering a good resolution for the control driving voltage and making control difficult. If the force that keeps the electrodes apart increases with the displacement of the electrodes, the pull-in effect may occur at one-third of the displacement also but at a higher threshold value. The higher voltage control range may offer a higher resolution for the control of the electrostatic actuator. The present invention may be a mesovalve which avoids the pull-in for a very high control voltage range. The invention may have several applications such as for example a pilot valve for a gas valve for modulation applications. The Figures are not necessarily to scale.  
         [0009]      FIGS. 1 and 2  show an illustrative example of a mesovalve  10  that may be applicable for flow modulation control. Mesovalves may be micro-structures. A top part  11  and a bottom part  12  may be plastic molded parts. The parts may also be made from other material with other kinds of fabrication techniques. The top part  11  may have an aluminum (Al) deposition applied to the angled bottom side of the top part to form an electrode  13  with a dielectric  14  formed on the electrode  13 . Magnifications  32  and  33  illustrate the layer arrangement incorporating layers  13  and  14  on upper part  11 . These magnifications are not necessarily drawn to scale. At the top of a chamber  15  at least partially enclosed by the surface of electrode  13  and dielectric  14  may be an orifice  16  that connected the chamber  15  with a closed buffer volume  17 . Volume  17  may be contained by an enclosure  18  which is attached to the upper part  11 . Volume  17  may be adjustable.  
         [0010]     The top part  11  and the bottom part  12  may be made from any suitable semi-rigid or rigid material, such as plastic, ceramic, silicon, and the like. In one illustrative example, the parts  11  and  12  may be constructed by molding a high temperature plastic such as ULTEM™ (available from the General Electric Company, Pittsfield, Mass.), CELAZOLE™ (available from the Hoechst-Celanese Corporation, Summit, N.J.), KETRON™ (available from the Polymer Corporation, Reading, Pa.), or some other suitable material. In some examples, the material used for a diaphragm  19  may have elastic, resilient, flexible or other elastomeric properties. In other examples, the diaphragm  19  may be made from a generally compliant material which may be elastically deformed and yet return to its original shape or form when the deforming force or forces are removed. In one example, the diaphragm  19  may be made from a polymer such as KAPTON™ (available from E.I. du Pont de Nemours &amp; Co., Wilmington, Del.), KALADEX™ (available from ICI Films, Wilmington, Del.), MYLAR™ (available from E. I. du Pont de Nemours &amp; Co., Wilmington, Del.), or any other suitable material. An advantage of using a polymer based substrate for a port and/or diaphragm is that the resulting valve may be cheaper and lighter, and/or more suitable for small handheld, or even disposable or reusable applications.  
         [0011]     The one or more electrodes  22  of the diaphragm  19  may be provided by patterning a conductive coating on the diaphragm  19 . For instance, the one or more electrodes may be formed by printing, plating or an EB deposition of metal. In some cases, the electrode layer may be patterned using a dry film resist. The same or similar techniques may be used to provide the electrode  13  on the inner surface of the upper part  11 . Rather than providing a separate electrode layer, it is contemplated that the diaphragm  19  and/or inner surface of the upper part  11  may be made conductive so as to operate as an electrode, if desired. A dielectric, such as a low temperature organic and inorganic dielectric, may be used as an insulator between the actuating electrodes  13  and  22 . The dielectric may be coated as a layer  23  over the electrode  22  on the diaphragm  19  and as a layer  14  on the electrode  13  on the inner surface of upper part  11 .  
         [0012]     The outer circumference of diaphragm  19  may be secured by the connection area  21  of upper part  11  and lower part  12 . The diaphragm  19  may span the breadth of the upper  11  and lower  12  parts. Diaphragm  19  may have an aluminum deposition on the top side of the diaphragm which operates as an electrode  22 . A deposition of a dielectric  23  may be applied on the electrode  22 . Magnification  31  illustrates the layer arrangement relative to diaphragm  19 . This magnification is not necessarily drawn to scale. There may be an orifice  24  in the diaphragm  19  close to the edge of the valve chamber  15 . The lower side of diaphragm  19  and a seat  25  at the top of port  26  may form a normally closed valve. The valve may be closed in  FIG. 1  since the valve is not energized with an electric potential connected to electrodes  13  and  22 . When not energized, the diaphragm  19  may be pushing down against the seat  25  and the way from port  27  to port  26  may be closed. The central seat  25  may be slightly higher than the clamping edge of the diaphragm  19 . Because of the pre-induced stress, the diaphragm  19  may seal the valve seat  25 . The valve may also be regarded as a normally closed valve due to the restoring force of the diaphragm. Further, the diaphragm may be pushed down on the valve seat with an electrostatic repelling force of the electrodes. Also, there may be a tension mechanism, such as a spring, connected to the diaphragm to apply a downward force or an upward force on the diaphragm, as a design may indicate.  
         [0013]     By an application of a voltage to the electrode  13  of the top part  11  and the electrode  22  of the diaphragm  19 , the diaphragm may move up and the connection between port  27  and port  26  may be at least partially opened, as shown in  FIG. 2 , permitting a fluid communication between the ports. This movement may be regarded as being caused by an electrostatic attraction or force. The fluid may be a gas or liquid. The diaphragm may be regarded as having a closed position and an open position, or many various open and closed positions.  
         [0014]     Magnification  34  illustrates the layer arrangement where a portion of diaphragm  19  is up against upper part  11 . Magnification  34  is not necessarily drawn to scale. When the diaphragm moves up, the orifice  24  may come in contact with the chamber  15  wall of the upper part  11 . The orifice  24  may become closed as it comes in contact with the dielectric layer  14  on the electrode that is on the inside surface of chamber  15 , thereby sealing off the chamber  17  from any volume or ports below the diaphragm  19 . The contact of orifice  24  at its edge is shown by a magnification  42  in  FIG. 2 . This magnification is not necessarily drawn to scale. Under increasing voltage applied to the electrodes  13  and  22 , the diaphragm may move up a certain distance but will stop because of the pressure of air or gas that builds up in the closed volumes  15  and  17  above the diaphragm  19 . The value of the buffer volume  17  may determine the displacement of the diaphragm before stopping for a certain maximum voltage. The value of the buffer volume  17  may be changed to adjust the displacement of diaphragm  19 . The pressure of the volume should stop the diaphragm before the pull-in occurs and the resulting displacement of the diaphragm may be smooth and stable. The fluid (e.g., gas or air) in the volumes  15  and  17  in the top of the diaphragm may work like a variable “air spring”. The variation of the pneumatic impedance made by a variable restrictor between the diaphragm  19  and the valve seat  25  may be smooth and stable. For certain in and out pressures P 1  and P 2  at ports  27  and  26 , respectively, where P 1 &gt;P 2 , there may be a well-controlled modulation of a flow  29  from port  27  to port  26  via enlarged volume  28 . The maximum flow  29  may be adjusted by the size (e.g., diameter) of the valve seat  25 .  
         [0015]     There may be a flow sensor  39  situated in port  27  and connected to a controller  40 . The controller may also be connected to the electrodes  13  and  22 . The controller  40  may modulate the flow  29  per a prescribed rate with voltages to the electrodes based on inputs from the sensor  39 .  FIG. 5  shows controller  41  connected to the mesovalve arrangement  10 .  
         [0016]      FIGS. 3 and 4  show an illustrative example of a mesovalve  10  that may be applicable for pressure modulation control. The structure of device  10  in these Figures is the same as the device  10  in  FIGS. 1 and 2 , except for restrictors  35  and  36 , and chamber  37  which may be added. The modulated pressure Ps provided the device may be that in the chamber  37 . Chamber  37  may be connected to port  27  with the pressure P 1  that is to be modulated. At the entrance of port  27  is an input pressure P 1  and within that port may be a restrictor  36 . The other port  26  may have a restrictor  35  and an output pressure P 2  at the exit of the port. The central pole or seat  25  may be slightly higher than the clamping edge of the diaphragm  19  and because the pre-induced stress of the diaphragm may seal the seat  25  of the valve. Application of a voltage across the electrodes  13  and  22  (described above) of the upper part  11 and diaphragm  19 , respectively, the diaphragm  19  may move up and the connection between port  27  and  26  is opened, permitting fluid communication between the ports. A portion of the diaphragm  19 , including the lateral orifice  24 , may come in contact with upper part  11 . The orifice  24  may be closed and seal off the volume  28  below the diaphragm from the chamber  15  above the diaphragm  19 .  
         [0017]     Under increasing voltage applied to electrodes  13  and  22 , the diaphragm  19  may go a certain distance but will stop because of the pressure that builds up in the diaphragm closed chamber volume  15  and buffer volume  17  which is coupled to volume  15  via the orifice or channel  16 . The value or size of the buffer volume  17  may determine the upward movement and displacement of the diaphragm  19  before it stops at a certain place for a certain magnitude of a driving voltage applied to the electrodes  13  and  22 . The magnitude of the driving voltage may be set a certain maximum. The buffer volume  17  may be adjustable. The diaphragm  19 , along with the pneumatic resistance of the gas being compressed in volumes  15  and  17  and the set voltage, diaphragm  19  may stop before the pull-in occurs. The movement or the dynamic displacement of diaphragm  19  may be smooth and stable. The gas being compressed in volumes  15  and  17  by the upward moving diaphragm may provide some resistance against the top of the diaphragm  19 . This resistance against the diaphragm works like a variable “air spring.” There may be a variable pneumatic impedance made a variable restrictor which is constituted by the adjustably moving diaphragm and the valve seat  25  situated on the output port  26 . This variable pneumatic impedance, together with the restrictors  36  and  35  of ports  27  and  26 , respectively, may form a pneumatic pressure divider. For a certain input pressure P 1  at the entrance of port  27  and output pressure P 2  at the exit of port  26 , where P 1 &gt;P 2 , one may have a well controlled modulation of the pressure Ps.  
         [0018]     There may be a pressure sensor  41 situated in port  27  and connected to a controller  40 . The controller may also be connected to the electrodes  13  and  22 . The controller  40  may modulate the pressure of the flow  29  per a prescribed pressure with voltages to the electrodes based on inputs from the sensor  41 . Programming and/or software may be implemented for control of arrangement or structure  10  by controller  40 .  FIG. 5  shows controller  40  connected to the mesovalve arrangement  10 .  
         [0019]     The structure  10  may be easily designed to meet various applications such as, for example, use in a disposable cartridge for a micro-cytometer or other devices. Structure  10  may also be incorporated in MEMS structures, devices and the like.  
         [0020]     In the present specification, some of the material may be of a hypothetical nature even though not necessarily indicated as such.  
         [0021]     Although the invention is described with respect to at least one illustrative embodiment, many variations and modifications will become apparent to those skilled in the art upon reading the present specification. It is therefore the intention that the appended claims be interpreted as broadly as possible in view of the prior art to include all such variations and modifications.