Patent Publication Number: US-2010122733-A1

Title: Pressure biased micro-fluidic valve

Description:
BACKGROUND 
     These teachings relate generally to pressure biased valves an in particular to pressure biased shutoff valves. 
     In the prior art, sensing the off state of a system when the fluid source reservoir has the ability to be pressurized would require a check valve having a crack pressure higher than the maximum reservoir pressure. The crack pressure is the nominal pressure drop across the valve during operation. This drop in pressure presents difficulties in small micro-fluidic applications. 
     What is needed therefore, is a passive shutoff valve that has no maximum pressure, is self regulating, and has a low nominal operating pressure drop. 
     SUMMARY 
     Embodiments of a valve are disclosed that allow for the control and adjustment of a fluid flow between a valve inlet port and a valve output port as a function of the pressure at the valve inlet port, a pressure at a first pressure input port, and a reference pressure. In one embodiment, the valve that includes two ports—a valve inlet port a valve outlet port, and one or more valve seats circumscribing one or more of the two ports. The valve further includes a diaphragm having first and second major surfaces. The first major surface in a closed position acts as a valve face to cover the one or more valve seats preventing fluid communication therebetween. In an open position, the first major surface unseals the valve inlet port and the valve outlet port and allows for fluid communication therebetween. In addition, the valve includes a first pressure inlet coupled to the second major surface of the flexible diaphragm. The first pressure inlet provides a first pressure to said second major surface to attempt to move the diaphragm into the closed position. The valve also includes a reference pressure providing component operatively coupled to the second major surface of said flexible diaphragm. In one instance, fluid communication between said valve inlet and said valve outlet can be controlled and adjusted utilizing in the first pressure and the reference pressure. 
     Several embodiments of the valve of these teachings are disclosed. Methods for utilizing the valve of these teachings are also disclosed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other features, aspects, and advantages of the present teachings will become better understood with regard to the following description, appended claims, and accompanying drawings. The drawings are not necessarily to scale, emphasis instead being placed on illustration of principles of the teachings. The drawings include the following figures: 
         FIG. 1  is a schematic diagram of one embodiment of the present teachings; 
         FIG. 2  is a schematic diagram of another embodiment of the present teachings; and 
         FIG. 3  is a schematic diagram of yet another embodiment of the present teachings. 
     
    
    
     DETAILED DESCRIPTION 
     The present teachings may be understood by the following detailed description, which should be read in conjunction with the attached drawings. The following detailed description of certain embodiments is by way of example only and is not meant to limit the scope of the present teachings. 
     “Diaphragm” as used herein refers to an element capable of being manipulated such that it can at least partially block the passage of fluid flow between an input port and an output port in a first position and permit the flow of fluid between an input port and an output port in a second position. An “actuating force” is a force that is capable of moving the diaphragm between the first and second positions. A “valve seat” is an element designed to accept a portion of the diaphragm when in the first position, thereby blocking fluid flow from the respective port. 
     The present teachings relate the use of scaled valves to control fluid flow. While the present teachings are not limited to a particular sealing method, in one embodiment, an actuating force pushes a diaphragm against or away from a valve seat to restrict fluid flow and the diaphragm is then sealed to or removed from the valve seat. 
       FIG. 1  depicts one embodiment of a valve of these teachings. In particular, a valve  100  includes a valve outlet seat  106  that extends within the interior  101  of the valve  100 . The valve outlet seat circumscribes a valve outlet port  108  that may be connected to an (or one or more) ancillary apparatus to which flow is to be regulated. Typically, the valve  100  is constructed of molded plastic material, although other materials may be used as well. The valve  100  further includes a valve inlet port  104  that may be connected to a fluid or gas source from which flow is to be regulated. The valve  100  also includes a diaphragm  110  that includes a first major surface  110   a  and a second major surface  110   b . The diaphragm  110  may have a first position  110 ′ and a second position  110 ″. 
     In the first position, the first major surface  110   a  covers the valve outlet seat  106  and the valve outlet port  108 . In this position, the first major surface acts a closed valve face and prevents fluid communication between valve inlet port  104  and the valve outlet port  108 . 
     In the second position, the first major surface  110   a  uncovers the valve outlet seat  106 , valve outlet port  108 ; the valve inlet port  104  is also not covered by the first major surface  110   a . In this position, the first major surface acts an open valve face and allows fluid communication between valve inlet port  104  and the valve outlet port  108 . 
     The valve  100  also includes a first pressure inlet  112 . The first pressure inlet  112  provides for pressure to be exerted against the second major surface  110   b  of the diaphragm  110 . In the embodiment depicted in  FIG. 1 , a reference pressure providing component  114  is also included. 
       FIG. 2  depicts another embodiment of a valve of the pressure biased micro-fluidic valve. In particular, a valve  140  includes a valve inlet seat  102  that extends within the interior  101  of the valve  140 . The valve inlet seat circumscribes the valve inlet port  104  that may be connected to fluid or gas source from which flow is to be regulated. The valve  140  further includes a valve outlet port  108  that may be connected to one or more ancillary apparatus to which flow is to be regulated. The valve  100  also includes a diaphragm  110  that includes a first major surface  110   a  and a second major surface  110   b . The diaphragm  110  may have a first position  110  and a second position  110 ″. 
     In the first position, the first major surface  110   a  covers both the valve inlet seat  102  and valve inlet port  104 . In this position, the first major surface acts a closed valve face and prevents fluid communication between valve inlet port  102  and the valve outlet port  108 . 
     In the second position, the first major surface  110   a  uncovers the valve inlet seat  102 , valve inlet port  104 ; the valve outlet port  108  is also not covered by the first major surface  110   a . In this position, the first major surface acts an open valve face and allows fluid communication between valve inlet port  102  and the valve outlet port  108 . The valve  100  also includes a first pressure inlet  112  and a reference pressure providing component  114 . 
       FIG. 3  depicts yet another embodiment of a valve of the pressure biased micro-fluidic valve. In particular, a valve  200  includes a valve inlet seat  202  that extends within the interior  201  of the valve  200 . The valve inlet seat circumscribes a valve inlet port  204  that may be connected to fluid or gas source from which flow is to be regulated. Typically, the valve  200  is constructed of molded plastic material, although other materials are also within the scope of these teachings. The valve  200  further includes a valve outlet seat  206  that circumscribes a valve outlet port  208  that may be connected to one or more ancillary apparatus to which flow is to be regulated. The valve  200  also includes a diaphragm  210  that includes a first major surface  210   a  and a second major surface  210   b . The diaphragm  210  may have a first position  210 ′ and a second position  210 ″. 
     In the first position, the first major surface  210   a  covers both the valve inlet seat  202 , valve inlet port  204 , valve outlet seat  206 , and valve outlet port  208 . In this position, the first major surface acts a closed valve face and prevents fluid communication between valve inlet port  202  and the valve outlet port  208 . 
     In the second position, the first major surface uncovers both the valve inlet seat  202 , valve inlet port  204 , valve outlet seat  206 , and valve outlet port  208 . In this position, the first major surface acts an open valve face and allows fluid communication between valve inlet port  202  and the valve outlet port  208 . 
     The valve  200  also includes a first pressure inlet  212 . The first pressure inlet  212  provides for pressure to be exerted against the second major surface  210   b  of the diaphragm  210 . In the embodiment depicted in  FIG. 3 , a reference pressure providing component  214  is also provided. In this embodiment, the movement of diaphragm  210  from a closed position  210 ′ to an open position  210 ″ is a function of the various pressures applied to each of the first and second major surfaces of the diaphragm  210 . 
     In the embodiments described hereinabove, the movement of diaphragm  110  (or  210  in  FIG. 3 ) from a closed position  110 ′ to an open position  110 ″ is a function of the various pressures applied to each of the first and second major surfaces of the diaphragm  110 . 
     In one embodiment, each of the first and second surfaces has substantially equal surface areas. As is known, force=pressure*surface area, or F=P*A. In this embodiment, the forces on the first and second major surfaces become: 
         P   out   *A   first ≧( P   in   +P   ref )* A   second    (1) 
     where A first  is the surface area of the first major surface, A second  is the surface area of the second major surface, P out  is the pressure resulting from flow from the valve inlet port  104  (or  204 ,  FIG. 3 ), P in  is the pressure resulting from flow from the first pressure inlet  112  ( 212 ,  FIG. 3 ) and P ref  is the pressure resulting from the reference pressure providing component  114  ( 214 ,  FIG. 3 ). In one embodiment, A first  is substantially equal to A second  (A first =A second ), equation (1) simplifies to: 
         P   out   ≧P   in   +   Pref .   (2) 
     The above conditions is the condition in which the diaphragm moves from position  110 ′ to  110 ″ and moves away from the valve inlet port and valve outlet port and allows fluid communication therebetween. 
     It should be noted that while the reference pressure has been depicted as a pressure, for example provided by a separate pump or other pressure generating element. However, the reference pressure may also be provided by a force, for example provided by a spring, a bimetallic material, or the force may be generated by the elasticity of the diaphragm  110  itself. 
     In another embodiment, the first and second surfaces have unequal surface areas. As is known, force=pressure*surface area, or F=P*A. In this embodiment, the forces on the first and second major surfaces become: 
         P   out   *A   first ≧( P   in   +P   ref )* A   second    (3) 
     where A first  is the surface area of the first major surface, A second  is the surface area of the second major surface. Thus, the control of the fluid flow between the valve inlet port and the valve outlet port may be a function of P in , P out  and the ratio of the first and second surface areas. 
     The condition given by equations (3) hereinabove is the condition in which the diaphragm moves from position  110 ′ to  110 ″ and moves away from the valve inlet port and valve outlet port and allows fluid communication therebetween. In this way, the valve operation may be adjusted to open at pressures that are specific to a particular system by adjusting the first and second surface areas accordingly. 
     As above, it should be noted that while the reference pressure has been depicted as a pressure, for example, as provided by a separate pump or other pressure generating element. However, the reference pressure may also be generated by a force, for example provided by a spring, a bimetallic material, or the force may be generated by the elasticity of the diaphragm  110  itself. 
       FIGS. 1 ,  2 ,  3  also depict the valve  100  ( 140 ,  200 ) for use in a system. In the depicted system, the first pressure inlet  112  is connected to a fluid line  120  that samples the input to the pump  116  via connection  118 . In this embodiment, the pressure at reference port  112  is equivalent to the pump  116  input pressure. Thus when the pump  116  is not operational, the first and second surface areas may be adjusted such that reference pressure and/or the input pressure at inlet  112  will be sufficient to ensure that the diaphragm  110  (or  210 ,  FIG. 3 ) is in the closed position  110 ′ (or  210 ″,  FIG. 3 ) and prevents any fluid communication between the valve inlet port  104  (or  204 ,  FIG. 3 ) and the valve outlet port  108  (or  208 ,  FIG. 3 ). Only after the pump  116  is operational, will the force exerted on the first major surface of the diaphragm  110  (or  210 ,  FIG. 3 ) be sufficient to move the diaphragm  110  (or  210 ,  FIG. 3 ) to the open position  110 ″ (or  210 ″,  FIG. 3 ) and allow fluid communication between valve input port  104  (or  204 ,  FIG. 3 ) and valve output port  108  (or  208 ,  FIG. 3 ). 
     This embodiment is particularly useful in a system in which the valve and pump are located within the fluid supply reservoir or in a fluid supply cartridge. In this instance, the pump will be at rest, i.e., non-operational in the detached state and the valve  100  will prevent fluid from leaving the fluid supply cartridge. However, embodiments of the valve of these teachings can also be used when the valve and pump are separately connected to the fuel reservoir or cartridge. By operation of the embodiments disclosed hereinabove, flow into the valve outlet port is substantially prevented when the pump is inactive. 
     By careful adjustment of the various parameters, for example the size of inlet seat  102 , the size of the valve inlet port  104 , the size of the valve outlet seat  106 , the size of the valve outlet port  108  or the size of the first and second surface areas, the pressure at first pressure inlet may be used to control the fluid flow between the valve input port  104  and valve output port  108 . By using the pressure at the first pressure inlet as the control variable and the fluid volume or flow rate as a controlled variable, a feedback control system may be designed that allows for using the valve  100  as a flow control device. 
     It should be noted that while several embodiments of the reference pressure generating component have been described, these teachings are not limited to only those embodiments. 
     While the present teachings have been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the teachings as defined by the appended claims. All the features disclosed in this specification, including any accompanying claims, abstract, and drawings, may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.