Pumps – Motor driven – Electric or magnetic motor
Patent
1992-04-21
1993-12-21
Bertsch, Richard A.
Pumps
Motor driven
Electric or magnetic motor
417413B, F04B 1700
Patent
active
052717240
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a valve equipped with a position detector of the type in which the body of the valve is formed by machining a silicon plate by such micromachining techniques as photolithographic technology or similar technologies and a micropump incorporating such a valve.
BACKGROUND OF THE INVENTION
These micropumps may be used notably for the in situ administration of medicaments, the miniaturization of the micropump optionally permitting the permanent implantation thereof into the body. These pumps enable a precise dosage of small quantities of fluids to be injected.
These micropumps are in particular described in the article "A piezoelectric micropump base on micromachining of silicon" by H. van Lintel et al. which appeared in "Sensors and Actuators", No 15, 1988, pages 153-167. These pumps essentially comprise a stack of three wafers, i.e. is a silicon wafer disposed between two glass wafers.
The silicon wafer is etched in order to form a cavity which together with one of the glass wafers defines a pump chamber, an inlet valve and an outlet valve, communicating the pump chamber respectively with an inlet channel and an outlet channel, and a regulating valve. A control element, e.g. a piezoelectric disc, is provided on one wall of the chamber. This piezoelectric disc may by deformed when it is subjected to an electrical voltage which causes deformation of the wall of the pump chamber and hence variation in the volume thereof.
The micropump functions as follows. At rest the inlet and outlet valves are in the closed position. When an electrical voltage is applied the wall of the pump chamber deforms and the pressure increases therein until the outlet valve opens. The fluid contained in the pump chamber is then driven towards the outlet channel. During this phase the inlet valve is held closed by the pressure prevailing in the pump chamber. When, however, the electrical potential is removed or reversed, the pressure therein diminishes. This causes closure of the outlet valve and opening of the entry valve. Fluid is thereby drawn into the pump chamber.
As already indicated above, these micropumps are useful especially for the administration of medicaments. It is therefore important to be able to monitor the correct functioning of these micropumps. Moreover in some cases the pump flow rate may drop considerably, e.g. when bubbles of air are present in the pump chamber, or when the pressure in the exit channel becomes too high.
SUMMARY OF THE INVENTION
Obviously, such malfunctioning should be detected. It has been noted that the movement of a valve might be used for such a purpose. Therefore, an object of the present invention is to provide a valve having a position detector which is, in addition, simple, viable and inexpensive.
More specifically, it is an object of the invention to provide a valve comprising a first wafer and a second wafer bonded to the first wafer to define the valve seat, which is characterized in that it comprises a position detector having a first electrical contact facing the back face of the valve body at such a distance that there is a mechanical contact between the valve body and the first electrical contact when the valve is in the open position, a second electrical contact so that is forms an electrical impedance with said first electrical contact, influenced by said mechanical contact, and a detection circuit sensitive to the electrical impedance between said electrical contacts.
The mechanical contact between the valve body and the first electrical contact thus ensures the largest possible electrical impedance difference between the open and closed positions of the valve.
It is also an object of the invention to provide a micropump equipped with such a position detector.
The characteristic features and advantages of the invention are better illustrated by the following description give for purpose of example, but which is not limiting and with reference to the accompanying drawings in which
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 show
REFERENCES:
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patent: 4965415 (1990-10-01), Young et al.
patent: 5029805 (1991-07-01), Albarda et al.
patent: 5085562 (1992-02-01), van Lintel
Article entitled "A piezoelectric micropump based on micromachining of silicon" Sensors and Actuators, No. 15, pp. 153-167, 1988, by Harald T. G. van Lintel.
Basichas Alfred
Bertsch Richard A.
Westonbridge International Limited
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