Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
2000-08-18
2001-04-24
Buiz, Michael (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625400, C137S625650, C251S129060
Reexamination Certificate
active
06220295
ABSTRACT:
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
Bouchard Clement D.
Grant Kevin Lee
Hillis John William
Hurley Patrick J. F.
Ormerod, III William W.
Bromberg & Sunstein LLP
Buiz Michael
DEKA Products Limited Partnership
Krishnamurthy Ramesh
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