Fluid handling – Systems – Multi-way valve unit
Reexamination Certificate
1999-03-18
2001-01-16
Michalsky, Gerald A. (Department: 3753)
Fluid handling
Systems
Multi-way valve unit
C137S625440, C251S129060
Reexamination Certificate
active
06173744
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a piezoelectric valve with a one piece housing and a controllable sealing seat arranged within an elongated cavity in the housing. In particular, the valve employs an elongated piezoelectric bending element sealed off from and pushed into and held within the housing. The free end of the bending element closes or opens a sealing seat in accordance with an applied control current.
A piezo-ceramic bending converter is shown in EP-A1 0 191 011, in which the bending element is built into the housing in such a way that, at one end, it is supported at three points, of which one is adjustable and serves, at the same time, for contacting the middle electrode. The bending element is tightly connected and uses a separate guide spring which is connected to the housing and presses the bending element against the points of support. Using the free end of the bending element, an exhaust or intake air nozzle can be alternately closed or opened. The electric contacts for the piezoelectric bending element are brought out of the housing and sealed off.
The electrodes of the bending element and the contact pieces in the interior of the housing are not protected or insulated but are directly exposed to the streaming medium. As a result operation of the known arrangement with electrically conducting liquids is not possible. When a condensate forms, there is the danger of an electric short in the interior of the housing, and danger of corrosion at the points of contact. Since the points of contact are located in the interior of the housing, and are not separated from the work area, the electric contact points must be lead out of the housing in a gas-tight manner. The sealing-off between the bending element and the openings or nozzles to be controlled requires high-quality surfaces and exact inter-positioning, in order to achieve the lowest possible leakage values. The described conditions result in a relatively elaborate and costly manufacturing process as well as the additional disadvantage that the housing assembly is glued together and can only open by damaging it. Accordingly, the relatively expensive bending elements cannot be removed and reused after installation and adjustment.
A bending converter constructed as described above is shown in DE 44 10 153 C1, which suggests attaching an insulating cover layer onto the bending element. While this allows for the control of aggressive or electrically conducting liquids, the other described disadvantages remain.
Finally, WO 97/09555 shows a piezoelectric valve with a one piece housing having an lateral opening for receiving the bending element, which is cast permanently together with a casting material. Although the interior of the housing is sealed off, the device may not be dismantled without damaging or destroying the bending element. Furthermore, it is not insulated and thus has limited applications.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve on a piezoelectric valve for control of various media, such that, the described disadvantages can be avoided in a simple and inexpensive manner. It is also an object to provide a peizoelectric valve which, in the case of installation or adjustment errors, the entire valve can be taken apart without damaging the bending element and in which single parts thereof can be used again.
The problem is solved by a piezoelectric valve in which the piezoelectric bending element employs a partially elastic insulating cover for sealing off the interior of the housing. The insulation covering need not be glued or permanently sealed so that the bending element can be withdrawn from the housing without damage after installation and adjustment, and be easily used again.
In an exemplary embodiment, the housing has an elongated opening and the bending element is slidably locatable therein. The bending element has a covering formed of a one piece element sleeved over the bending element, and has a sealing bulge or flange extending transverse with respect to the longitudinal direction of the bending element. A terminal shoe is secured on the proximal end of the bending element which, when installed in the housing, clamps the flange between an application surface of the housing and an abutting surface of the terminal shoe. In this way, the covering is a simple construction and is effectively sealed by means of the sealing bulge, which provides the necessary outward sealing of the interior of the housing between the housing and the terminal shoe, while allowing non-destructive disassembly.
The terminal shoe, can also incorporate a portion of the electrical contacts of the bending element which, thus, upon insertion into the elongated opening in the housing is positioned properly for electrical connection.
According to another embodiment, a flexible latch is provided for the terminal shoe which snaps into a latch opening in the housing. The latch can be disengaged if necessary. Alternatively, the flexible latch can also be provided in the housing with a corresponding latch opening in the terminal shoe. The arrangement greatly facilitates the assembly, installation and dismantling of the valve, in particular, the relative position of the various installed elements with respect to one another.
The covering, according to an exemplary embodiment of the invention, comprises a thinly walled elastomer which is reinforced in the area of the sealing bulge and/or the sealing seat. By means, of the thinness of the walls, the effects from the longitudinal thermal expansion and swelling can be minimized. This is particularly useful in the area of the nozzles where it is advantageous that mechanical freedom of movement of the bending element is only nominally impaired.
According to a further advantageous embodiment of the invention, the length of the covering prior to installation is slightly smaller than the length of bending element in the non-installed state. Upon installation, the covering stretches to better position and secure the covering onto the bending element.
According to another embodiment of the invention, the interior of the covering, is de-aerated or vented into the environment via surface roughness of the bending element and/or via additional grooves, notches, canals or the like formed in the bending element and the terminal shoe. As a result, the covering is pressed against the surface of the bending element depending on the operational pressure, and lifting off or separation of the covering from the bending element, especially in the area of the nozzles, can be prevented.
REFERENCES:
patent: 4340083 (1982-07-01), Cummins
patent: 4492360 (1985-01-01), Lee, II et al.
patent: 4765370 (1988-08-01), Ariizumi et al.
patent: 2134223 (1984-08-01), None
Frisch Herbert
Strasser G{umlaut over (u)}nther
Wirtl Hannes
Dykema Gossett PLLC
Hygrama AG
Michalsky Gerald A.
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