Patent Publication Number: US-6220295-B1

Title: Three way piezoelectric valve

Description:
This application is a divisional of U.S. patent application Ser. No. 09/350,495, filed Jul. 9, 1999, the contents of which are hereby incorporated herein by reference. 
    
    
     TECHNICAL FIELD 
     The present invention relates to valves employing a piezoelectric actuator. 
     BACKGROUND ART 
     It is well known that certain materials possess piezoelectric properties such that when an electric potential is applied, a mechanical stress is produced within the material causing it to deflect. Such materials include simple naturally occurring and artificial crystals, and more sophisticated artificial ceramic materials. 
     One application of such piezoelectric materials is as valve actuators. In such applications, thin sheets of piezoelectric ceramic material may be laminated to an electrode sheet. A monomorph is an electrode sheet with a piezoelectric layer on one side. A bimorph has piezoelectric layers on both sides. A cantilever-fashion piezoelectric valve has an actuator in which one end of a piezoelectric material beam is securely clamped, and application of electric potential to the clamped end causes the free end to deflect with respect to a valve seat to prevent or enable fluid flow through the valve seat. 
     Generally, prior piezoelectric actuated valves have been designed for very specific applications, and as such, either have incorporated significant application-specific internal structure, e.g., U.S. Pat. No. 4,492,360 to Lee, II et al., or have been part of a significantly more complex larger structure, e.g., U.S. Pat. No. 4,340,083 to Cummins. Besides being suitable for only a narrow range of applications, the structural complexity necessary substantially affects the manufacturing complexity and disadvantageously increases the cost required to produce such valves. 
     Another consideration in the field of piezoelectric valves is the tradeoff which must be made between actuator force and physical displacement—a cantilevered piezoelectric actuator has a decreasing linear relation between the force that the actuator can apply, and the physical displacement of the end of the actuator. For example, maximum force may be produced when the actuator displacement is zero, in which case, force decreases linearly with displacement. Thus, a design tradeoff must be made since a non-zero force must be applied to seat the free end of the actuator on a valve seat without having leakage. Because of the force-displacement relationship, this non-zero force translates into a maximum distance that the free end of the actuator can sit above the valve seat. On the other hand, to open the valve, the free end of the actuator must be some minimum distance above the valve seat to obtain maximum fluid flow through the valve. 
     The difference between the maximum and minimum distances that the free end of the actuator can sit above the valve seat is typically relatively small, e.g., ˜100 microns. This presents a difficult problem for low-cost manufacturing where dimensional tolerances tend to be fairly large. As a result, complicated assembly procedures and/or additional structure have typically been required, which in turn increase the manufacturing cost. 
     SUMMARY OF THE INVENTION 
     A representative embodiment of the present invention includes a simplified three-way piezoelectric valve. Such a valve includes a valve body having an internal valve cavity, a pair of generally opposed positioning members integral to the valve body, and a first port, a second port, and a common port. The first port and the second port each have a valve seat and a passageway in communication with the valve seat, the seat and the passageway being integrally formed in the valve body. The valve also has a piezoelectric actuator having first and second ends. The first end is secured within the valve cavity by the positioning members and has electrical contacts for providing an electric potential to control the position of the second end. The second end is capable of flexing between a first operating position in which the first port is closed and the second port is open, and a second operating position in which the first port is open and the second port is closed. 
     In a further embodiment, the valve body may include a valve housing having one of the positioning members, and a valve cover having the other positioning member. The actuator may further include a valve seat pad of resilient material attached to the second end to sealingly engage the second end against a valve seat that is closed. The valve body may further have a plurality of external surfaces, including one surface having disposed thereon openings for the ports. In such an embodiment, the piezoelectric actuator may lie in a plane that is either substantially parallel to, or substantially perpendicular to the surface having the openings. In addition, or alternatively, the surface having the openings may be part of a manifold mounting flange structure. There may also be an integrated seal associated with the external surface openings for the ports. 
     An embodiment may also include an actuator voltage module integrated into the valve body and electrically connected to the electrical contacts of the piezoelectric actuator, that generates the electric potential to control the second end of the piezoelectric actuator. There may be a control processor which is integrated into the valve body and electrically connected to the electrical contacts of the piezoelectric actuator, and which controls fluid flow through the valve by controlling the position of the second end of the piezoelectric actuator. A pressure transducer in communication with the valve cavity may monitor fluid pressure within the valve cavity for at least one of controlling fluid flow through the valve and detecting faulty valve operation. The valve cavity may include a potting chamber portion that is substantially filled with potting material to enhance the securing of the first end of the piezoelectric actuator by the positioning members. 
     In one embodiment, the valve seat may be either cylindrical-shape or volcano-shape and protrude into the valve cavity. In such an embodiment, the valve seat may further be radially surrounded by a valve seat lip. A volcano-shape valve seat may include an end tip having a relatively small radius of curvature that gradually increases to a relatively larger radius of curvature so as to form a transition to the port passageway. 
     The portion of the valve cavity containing the first end of the actuator may have a volume less than or equal to four times the volume of the first end of the actuator within the portion. Alternatively, the portion of the valve cavity containing the second end of the actuator may have a volume less than or equal to four times the volume of the second end of the actuator within the portion. In another embodiment, the portion of the valve cavity containing the second end of the actuator may be configured so that the second end of the actuator deflects through more than one quarter the volume of the portion when flexing between the closed position and the open position. 
     Another embodiment includes a method of manufacturing a three-way piezoelectric valve. The method includes providing a valve body having an internal valve cavity, a pair of generally opposed positioning members integral to the valve body, and first, second, and common ports. The first port and the second port each have a valve seat and passageway in communication with the valve seat, the seat and the passageway being integrally formed in the valve body. The method also includes suspending a piezoelectric actuator having first and second ends. The first end has electrical contacts for providing an electric potential to control the position of the second end. The first end contacts one of the positioning members and the second end contacts one of the protruding valve seats without bending or flexing the actuator. The method also includes securing the first end of the piezoelectric actuator to the positioning members. 
     In a further embodiment of the method of manufacturing, before the suspending, the method may further include attaching a valve seat pad of resilient material to the second end of the piezoelectric actuator. The suspending may also include supplying a vacuum pressure to a port with a valve seat so that the second end of the piezoelectric actuator is held against that valve seat. The suspending may utilize a special positioning fixture to hold and position the piezoelectric actuator. The suspending may utilize shimming tapes to position the piezoelectric actuator. The securing may utilize ultraviolet-curable adhesive. The securing may substantially fill the potting chamber with adhesive material. The method may further include attaching a top cover over the valve body to enclose the valve cavity such that the valve cavity is accessible to fluid only via the valve ports. The suspending may also include electrically connecting the first end of the actuator to is an electric power supply and applying a voltage to the actuator such that the second end of the actuator flexes away from contacted valve seat, and the attaching includes measuring a force required to position the top cover pressing against the flexed second end of the actuator. In such a method, the attaching may further include pressing the top cover against the flexed second end of the actuator until the force measured equals a minimum value of force. 
     A preferred embodiment includes a valve having a valve body and a piezoelectric actuator. The valve body has an internal valve cavity, a pair of generally opposed positioning members integral to the valve body, which divide the cavity into an operating chamber and a potting chamber, wherein the operating chamber is defined in part by first and second chamber walls, and first, second, and common ports, at least one of the ports including a valve seat and a passageway in communication with the valve seat, wherein the valve seat is located in a recess in the first wall. The piezoelectric actuator has first and second ends. The first end is secured within the valve cavity between the positioning members and has electrical contacts for providing an electric potential to control the position of the second end. The second end is capable of flexing between a first operating position in which the first port is closed and the second port is open, and a second operating position in which the first port is open and the second port is closed. A valve seat pad is mounted on the second end of the piezoelectric actuator for sealing a valve seat when the piezoelectric actuator is in a closed position, such that the valve seat pad extends into the recess, past a plane defined by the wall of the recess, when the piezoelectric actuator is in the closed position. 
     In a further related embodiment, the valve seat extends into the recess. Such a valve may further include a valve housing having one of the positioning members, and a valve cover having the other positioning member. The valve seat may have a top that is radially surrounded by a valve seat lip. A valve seat may have a cylindrical shape, or a volcano shape which may include an end tip having a relatively small radius of curvature that gradually increases to a relatively larger radius of curvature so as to form a transition to the port passageway. In addition, or alternatively, either the potting chamber or the operating chamber, or both may have a volume less than or equal to four times the volume of the actuator within the potting chamber. The operating chamber may be configured so that the second end of the actuator deflects through more than one quarter the volume of the operating chamber when flexing between the closed position and the open position. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be more readily understood by reference to the following detailed description taken with the accompanying drawings, in which: 
     FIG. 1A is a top view of a two-way valve embodiment of the present invention. 
     FIG. 1B is a cross-sectional view of the valve shown in FIG.  1 A. 
     FIG. 2A is a top view of a three-way valve embodiment of the present invention. 
     FIG. 2B is a cross-sectional view of the valve shown in FIG.  2 A. 
     FIG. 3 illustrates the end tip of a protruding valve seat volcano. 
    
    
     DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS 
     A preferred embodiment of the present invention is a simple, low-cost, piezoelectric-actuated valve suitable for a wide range of applications. FIGS. 1A and 1B illustrate a two-way valve embodiment of the present invention showing respectively a top view and a cross-sectional view of such an embodiment. Valve  101  has a valve body which includes a valve base  102  and a top cover  130  that together define a cavity  103 , within which is positioned a piezoelectric actuator  105  having a rigidly fixed end  121  and a free end  123 . The cavity  103  has connected thereto, a first port  107  in fluid communication via the cavity  103  with a second port  109 . As shown in FIG. 1B, the first port  107  and the second port  109  are preferably adjacent to each other in the same plane and have external openings in a common external surface  106 . Alternatively, the valve  101  may be configured and operated using the port  109  as the first port, and the port  107  as the second port. 
     An embodiment may also include an o-ring seal  104  around each of the openings in the common external surface  106  for ports  107  and  109  to prevent leaks when the valve  101  is mounted to a valve manifold. When the external openings for ports  107  and  109  are adjacent to each other in the same plane, the o-ring seal  104  may be a single integrated piece, or separate seals for each port. Similarly, an embodiment also may include having the common external surface  106  as part of a valve mounting flange  110  having a mounting hole  111  to aid in the mounting of the valve  101  to a valve manifold. 
     In a preferred embodiment, generally opposed actuator mounts  119 , which are non-adjustable and integral to the valve body, divide the cavity  103  into an operating chamber  125  and a potting chamber  127 . Preferably, the volumes of the operating chamber  125  and the potting chamber  127  are minimized. Minimizing the volume of the operating chamber results in reduced “dead volume” of fluid trapped within the valve  101 . Minimizing the volume of the potting chamber  127  reduces problems with shrinkage of the potting material filling the volume as described below. For example, the volume of the operating chamber  125  and/or the potting chamber  127  may be less than or equal to four times the volume of the portion of the actuator  105  within the chamber. Alternatively, the operating chamber  125  may be configured so that the free end  123  of the actuator  105  deflects through more than one quarter the volume of the operating chamber when flexing between operating positions. The volume of the operating chamber  125  may also be minimized, as shown in FIG. 1B by locating the valve seat  115  in a recess in one of the enclosing walls of the operating chamber  125 . A valve seat pad  117  is attached to the free end  123  of the actuator  105  so that when the valve  101  is in a closed position, the pad extends into the recess past a plane defined by the wall of the operating chamber  125 . The valve seat pad  117  should be composed of an elastomeric material that can easily deform, in response to a small force, around the valve seat  115  to form a fluid seal. In a preferred embodiment, the valve seat pad  117  is made of silicone rubber. 
     The valve  101  may be structured so that one of the actuator mounts is integral with the top cover portion  130  of the valve body, while the other actuator mount is integral with the valve base  102  portion of the valve body. The fixed end  121  of the actuator  105  is rigidly positioned cantilever-style between the opposing actuator mounts  119 . The fixed end  121  of the actuator  105  has electric contacts  129  to control the actuator  105 , and the potting chamber  127  is partially or entirely filled with potting material, typically epoxy, which rigidly holds in place the fixed end  121  of the actuator  105 . 
     A preferred embodiment also includes an actuator controller  131  which includes one or more of an actuator voltage module, a status transducer, and a local processor controller. In order to activate the actuator  105 , a relatively high potential must be applied, typically, about 200 volts. If the high voltage control components are separate from the valve  101 , electrical code requirements place a substantial burden on the allowable wiring and on the separation spaces required for the circuit layout. This adds a significant cost and size penalty to the system unit. By integrating the high voltage electronics into actuator controller  131  in the valve base  102 , the valve itself may be controlled by relatively low voltage signals, e.g., 3 to 24 volts using standard low-cost wiring and design layouts. The incorporation of the status transducer into the actuator controller  131  allows for communication with the control processor through the same low voltage wiring. This allows feedback from the transducer to the control processor, and enables intelligent control of the valve. For example, a pressure transducer may be mounted on the valve base  102  to measure the cavity pressure. The signal from the pressure transducer may then be used to confirm the operation of the valve  101  and thus provide for a measure of fault protection. Alternatively, the signal from the pressure transducer may be used to calculate the fluid flow rate when the valve  101  is used as a proportional valve. 
     The first port  107  may be configured to introduce fluid into the valve  101 . In a preferred embodiment, the first port  107  is connected to the operating chamber  125  of the cavity  103  via a first port passage  113  through a protruding valve seat, also called a volcano  115 , which is non-adjustable and integral to the valve body, and which extends into the operating chamber  125 . The free end  123  of the actuator  105  may be fully or partially encased in, or have attached thereto, resilient material that, in a preferred embodiment, is in the form of a valve seat pad  117  adhesively attached to the free end  123  of the actuator  105 . The valve seat pad  117  rests sealingly on the volcano  115  to prevent fluid flow through the valve  101 , and lifts off the volcano  115  to allow fluid flow through the valve  101 . The second port  109 , being in fluid communication with the operating chamber  125 , may allow fluid in the operating chamber  125  to flow out of the valve  101 . 
     In a preferred embodiment, the first port  107  and the second port  109  are disposed to emerge from a single common external surface  106  of the valve  101 . This arrangement facilitates the use of multiple such valves positioned on a single-flow system manifold. In such a multiple-valve system, use of a single valve manifold reduces assembly cost and overall system size. Proper selection of the common external port surface permits either a small individual valve footprint on the valve manifold, or a low valve profile. 
     To operate the actuator  105 , an electric potential is applied via the electric contacts  129  attached to the fixed end  121 . In a preferred embodiment, when no potential is applied to the actuator  105 , the valve seat pad  117  on the free end  123  of the actuator  105  rests on the valve seat volcano  115 . Although the valve seat pad  117  covers the volcano  115 , there is no fluid seal because the valve seat pad  117  has not deformed over the volcano  115 . The deformation of the valve seat pad  117  over the volcano  115  creates the fluid seal isolating the first port passage  113  from the cavity  103 . This is the preferred neutral position of the actuator  105  because it allows maximum force to be available, since only displacement sufficient to cause the deformation of the valve seat pad  117  is required of the free end  123  of the actuator  105 . When a first polarity electric potential is applied to the actuator  105 , the piezoelectric effect causes the free end  123  of the actuator  105  to flex towards the volcano  115  with maximum force so that the valve seat pad  117  rests sealingly thereon, preventing fluid flow through the valve  101 . This arrangement also allows for a relatively large displacement of the free end  123  of the actuator  105  away from the volcano  115  when a second opposite polarity electric potential is applied to the actuator  105 , permitting maximum fluid flow through the valve  101 . 
     When the free end  123  of the actuator  105  presses the valve seat pad  117  against the volcano  115 , the resulting interaction forms a leakproof seal. The valve seat pad  117  deforming around the raised lip at the end of the volcano  115  results in such a leakproof seal. In one representative embodiment, the valve seat could extend into the operating chamber  125  in a cylindrical shape, rather than the sloping sides of the volcano shape. In another embodiment, the raised lip of the valve seat need not be at the very end of the valve port, as in the volcano design, but may be some radial distance from the port proper so long as it completely surrounds the port and so long as the valve seat pad is large enough to completely engage the lip. 
     The volcano shape does offer operational advantages not realized in other styles and shapes of valve seat, specifically, with respect to entrance and exit flow losses, since the valve seat is an entrance/exit orifice that contributes to the overall fluid flow resistance. The volcano shape minimizes this flow resistance. As a result, the free end  123  of the actuator  105  needs to travel a relatively shorter distance above the end of the valve seat to permit maximum fluid flow through the valve. 
     For example, in one typical prior art design, the free end of the piezoelectric actuator must be displaced approximately one half valve port diameter above the valve seat before maximum fluid flow through the valve is achieved. The volcano-shaped valve seat of a preferred embodiment, on the other hand, requires only that the actuator be moved one quarter of the port diameter above the valve seat. Since, as previously discussed, a trade-off must be made between actuator displacement and actuator force, reducing the required displacement increases ability to form a positive seal between the actuator and the valve seat. 
     The end tip  301  of the valve seat volcano  115  is shown in FIG.  3 . The end tip  301  has a small radius of curvature that transitions to a larger radius of curvature as the flow channel  303  enters the valve port volcano  115 . The slope of the volcano  115  is roughly 45 degrees in a preferred embodiment, but that particular angle is not required. The small radius of curvature at the end tip  301  of the volcano  115  provides the valve seat pad  117  of the actuator  105  with a structure around which to deform and thereby create a leakproof seal. The gradual widening of the flow channel  303  and the external slope of the volcano  115  reduce the orifice losses and increase the maximum flow rate through the valve  101 . 
     FIGS. 2A and 2B illustrate a three-way valve embodiment of the present invention showing respectively a top view and a cross-sectional view of such an embodiment. The valve body respectively has a valve base  202  and a top cover  230  that together define a cavity  203 , within which is positioned a piezoelectric actuator  205  having a rigidly fixed end  221  and a free end  223 . The cavity  203  has connected thereto, a first port  207 , a second port  208 , and a common port  209 . As shown in FIG. 2B, the first port  207 , the second port  208 , and the common port  209  are preferably mutually adjacent to each other in the same plane. As in the two-way valve, an embodiment of a three-way valve may also include arranging the positioning of the first port  207 , second port  208 , and common port  209  so that all three emerge from a common external surface  206  of the valve  201  which is substantially planar. In one embodiment, one or more of the ports, e.g., the second port  208 , may be integral with the top cover  230  portion of the valve body, while the remaining ports are integral with the valve base  202  portion of the valve body. 
     An embodiment may also include an o-ring seal  204  around each of the ports  207 ,  208 , and  209  to prevent leaks when the valve  201  is mounted to a valve manifold. When the external openings for ports  207 ,  208  and  209  are adjacent to each other in the same plane, the o-ring seal  204  may be a single integrated piece, or separate seals for each port opening. A related embodiment also may include having the common external surface  206  as part of a valve mounting flange  210  having a mounting hole  211  to aid in the mounting of the valve  201  to a valve manifold. 
     In a preferred embodiment, generally opposed actuator mounts  219 , which are non-adjustable and integral to the valve body, divide the cavity  203  into an operating chamber  225  and a potting chamber  227 . Preferably, the volumes of the operating chamber  225  and the potting chamber  227  are minimized as discussed with respect to the two-way valve. For example, the volume of the operating chamber  225  and/or the potting chamber  227  may be less than or equal to four times the volume of the portion of the actuator  205  within the chamber. Alternatively, the operating chamber  225  may be configured so that the free end  225  of the actuator  205  deflects through more than one quarter the volume of the operating chamber when flexing between operating positions. As in the two-way valve, the volume of the operating chamber  225  may also be minimized, as shown in FIG. 2B, by locating either or both of the valve seats  215  and  216  in a corresponding recess in one of the enclosing walls of the operating chamber  225  and encasing the free end  223  of the actuator  205  in a resilient valve seat pad  217  which, when one of the ports  207  or  208  is closed, extends into the corresponding recess past a plane defined by the wall of the operating chamber  225 . 
     As in the two-way valve, a preferred embodiment of the three-way valve  201  may be structured so that one of the actuator mounts is integral with the top cover  230  portion of the valve body, while the other actuator mount is integral with the valve base  202  portion of the valve body. The fixed end  221  of the actuator  205  is rigidly positioned cantilever-style between the opposing actuator mounts  219 . The fixed end  221  of the actuator  205  has electric contacts  229  attached to control the actuator  205 , and the potting chamber  227  is partially or entirely filled with potting material, typically epoxy, which rigidly holds in place the fixed end  221  of the actuator  205 . As in the two-way valve, an embodiment of a three-way valve may also include incorporating into the valve  201  an actuator controller (not shown) having one or more of an actuator voltage module, a status transducer, and a local controller processor. 
     In a preferred embodiment, the first port  207  is connected to the operating chamber  225  of the cavity  203  via an inlet passage  213  within a first port volcano  215 , which protrudes into the operating chamber  225 . The second port  208  is connected to the operating chamber  225  via an inlet passage  214  through a second port volcano  216 , which protrudes into the operating chamber  225 . The first port volcano  215  and the second port volcano  216  are both non-adjustable and integral to the body of the valve  201 . The free end  223  of the actuator  205  may be fully or partially encased in, or have attached thereto, resilient material that, in a preferred embodiment, is in the form of a valve seat pad  217 , which comprises two sections adhesively attached to opposite sides of the free end  223  of the actuator  205 . In operation, the valve seat pad  217  presses sealingly against one of the volcanos so as to prevent fluid flow through that port, and away from the other volcano so as to allow fluid flow between the port associated with the other volcano and the common port  209 . 
     In a preferred embodiment, when no potential is applied to the actuator  205 , the valve seat pad  217  on the free end  223  rests against the first port volcano  215 , but does not seal it because the valve seat pad  217  has not deformed over the volcano  215 . To operate the actuator  205  so as to prevent fluid flow between the first port  207  and the common port  209 , while allowing fluid flow between the second port  208  and the common port  209 , a first polarity electric potential is applied via the electric contacts  229  attached to the fixed end  221 . This flexes the free end  223  of the actuator  205  against the first port volcano  215  with maximum force so that the valve seat pad  217  deforms over the first port volcano  215  to form a seal that prevents fluid flow between the first port  207  and the common port  209 , while allowing maximum fluid flow between the second port  208  and the common port  209 . 
     When an opposite second polarity electric potential is applied via the electric contacts  229  attached to the fixed end  221  of the actuator  205 , the piezoelectric effect causes the free end  223  of the actuator  205  to flex away from the first port volcano  215  and the valve seat pad  217  to sealingly engage the second port volcano  216 . This prevents fluid flow between the second port  208  and the common port  209 , while allowing maximum fluid flow between the first port  207  and the common port  209 . 
     In an alternate embodiment, when no potential is applied to the actuator  205 , the valve seat pad  217  on the free end  223  rests against the second port volcano  216 , but does not seal it because the valve seat pad  217  has not deformed over the volcano  216 . To operate the actuator  205  so as to prevent fluid flow between the second port  208  and the common port  209 , while allowing fluid flow between the first port  207  and the common port  209 , a first polarity electric potential is applied via the electric contacts  229  attached to the fixed end  221 . The piezoelectric effect causes the free end  223  of the actuator  205  to flex against the second port volcano  216  with maximum force so that the valve seat pad  217  deforms over the second port volcano  216  to form a seal that prevents fluid flow between the second port  208  and the common port  209 , while allowing maximum fluid flow between the first port  207  and the common port  209 . 
     When an opposite second polarity electric potential is applied via the electric contacts  229  attached to the fixed end  221  of the actuator  205 , the piezoelectric effect causes the free end  223  of the actuator  205  to flex away from the second port volcano  215  and the valve seat pad  217  to sealingly engage the first port volcano  215 . This prevents fluid flow between the first port  207  and the common port  209 , while allowing maximum fluid flow between the second port  208  and the common port  209 . 
     An embodiment of the present invention is also directed to a method of manufacturing a valve with a piezoelectric actuator, such as shown in FIGS. 1A and 1B. The procedure to attach the piezoelectric actuator  105  to the valve base  102  begins with the actuator  105  receiving a series of electrical checks for proper operation, after which three electric contacts  129  are attached to the actuator  105 . 
     The valve seat pad  117  is attached to the end of the actuator  105 . Then, the actuator  105  is placed in the valve base  102  so that the fixed end  121  rests on one actuator mount  119  with the volcano  115  centered on the valve seat pad  117 . Significantly, the actuator  105  is placed in position without deformation or stress to ensure proper neutral position (zero applied potential). Positioning of the actuator  105  may utilize a special positioning fixture that includes two spring-loaded supports that provide structural support at the points on the actuator  105  where the fixed end  121  rests on the actuator mount  119  and where the free end  123  seals the volcano  115 . The fixture also supplies a vacuum pressure to the volcano  115  via the first port  107 , thereby ensuring that the valve seat pad  117  is in proper contact with the end of the volcano  115 . 
     The thickness of the actuator  105  and the valve seat pad  117  is tightly controlled, as is the relative relationship of the end of the volcano  115  and the actuator mounts  119 . If necessary, different thickness adhesive tapes may be used either as a shim to aid in achieving the proper geometry of the actuator  105  and the valve seat pad  117 , or to attach the valve seat pad  117  to the actuator  105 . Selection of proper thickness tape may in part be determined by inspecting the pieces of the body of the valve  101  and measuring the distance from the top of the volcano  115  to the top of the valve base  102 . 
     To complete assembly of the valve, adhesive is applied into the potting chamber  127  in the rear of the valve base  102  to the intersection of the actuator mount  119  and the actuator  105 , allowing the adhesive to wick underneath the actuator  105 , and the adhesive joint is cured. A preferred embodiment uses ultraviolet-curable glue and ultraviolet-transparent housing materials which allow the adhesive joint to set up very rapidly under ultraviolet light without requiring excessive temperatures or time. Use of a transparent housing also has the advantage of allowing for visual inspection of the placement of the actuator  105  during assembly of the valve. The assembly is inspected to verify that the ultraviolet curable glue wicked across the entire contact line between the actuator  105  and the actuator mount  119 , so that the actuator  105  is secure. At this point, the actuator may be removed from the mounting fixture. Then, the top cover  130  is attached to the valve base  102 . Finally, the potting chamber  127  of the valve  101  is filled with adhesive until the fixed end  121  of the actuator  105  is completely covered, and the exposed edge is cured. 
     In manufacturing a three-way valve  201  in FIGS. 2A and 2B, the actuator  205  is placed within the valve base  202  without flexing or deformation so that the fixed end  221  rests on one actuator mount  219 , while the valve seat pad  217  rests on one of the volcanoes  215  or  216 . This will allow for maximum sealing force between the valve seat pad and the selected volcano  215  or  216  when that volcano&#39;s associated port is desired to be shut, with flow allowed through the other, unsealed volcano and port. 
     In a further and related embodiment, the actuator  205  is placed on the valve base  202  such that the valve seat pad  217  covers the volcano seat  215  in the base. The actuator  205  is tacked into place by injecting UV curable glue into the potting chamber  227  between the valve base  202  and the actuator  205 . The actuator  205  is connected to a power supply and the appropriate voltage is applied to the actuator such that the actuator bends away from the volcano seat  215  in the base  202  to the maximum extent possible. 
     The top cover  230  is attached to a means for measuring the force on the top cover, such as a force gauge or balance, and is lowered onto the base  230 . The lip on the base  202  that seats the top cover  230  is dimensioned so that the cover can be positioned on the lip without force. The depth of the lip is dimensioned to accommodate the expected manufacturing variations in the dimensions of the base  202  and top cover  230 . Selection of the lip clearance dimension and depth is well known to one of ordinary skill in the mechanical arts. As the top cover  230  is lowered onto the base  202 , the top cover will contact the fully extended actuator  205  which will produce an upward force on the top cover as the cover is lowered further. The top cover  230  is lowered until the upward force produced by the actuator  205  on the top cover matches the minimum closing force. The minimum closing force is determined by balancing several factors such as the deformation characteristics of the valve seat  216  and the force-displacement characteristics of the actuator  205 , and is chosen to provide an adequate sealing force to seal the volcano valve seat  216  in the top cover  230 . The selection of the minimum closing force is well known to one of ordinary skill in the mechanical arts. In a preferred embodiment of the invention, the specific value of the minimum closing force is 25 gram-force. 
     The top cover  230  is held in this position while UV curable glue is applied to the lip on the base  202 . The UV curable glue is sufficiently fluid so that the glue is wicked completely into the space between the lip of the base  202  and the top cover  230 . A UV source is applied to the valve  201  to cure the glue, making a rigid and leakproof seal between the top cover  230  and the base  202 . The remaining portion of the potting chamber  227  between the actuator  205  and the top cover  230  is filled with the UV curable glue and cured with the UV source.