Pumps – Motor driven – Electric or magnetic motor
Patent
1998-07-29
1999-12-07
Thorpe, Timothy S.
Pumps
Motor driven
Electric or magnetic motor
4174133, F04B 1700
Patent
active
059972637
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a micro-machined filter for a micropump having at least two first plate-forming means which define a pumping chamber.
More precisely, the present invention relates to a filter which makes it possible within a liquid to retain particles of excess size (e.g. impurities) that are moving towards and through one or more valves of a micropump, so as to avoid impeding operation thereof. This problem arises particularly, but not exclusively, with micropumps of the piezoelectrically controlled type or with a sensor, such as a pressure sensor, said components receiving a liquid between an element made of silicon and an element made of glass that faces the silicon element.
With micropumps, there also arises the problem of leakage rate when the pump is not in operation. Another object of the present invention is to limit leakage rate of a micropump which is not in operation. Too great a leakage rate through a micropump can be harmful to proper operation, to reliability, and to the precision of such a micropump. For micropumps that are to be implanted in the human body to deliver liquid at a well-controlled rate, it is important for the reliability of such a pump to be long-lasting.
An object of the present invention is to provide a micro-machined filter for a micropump so that the liquid leaving the filter does not contain particles of excessive size capable of impeding proper operation of any of the elements and members of the micropump.
To achieve this object, the filter is characterized in that said filter comprises liquid feed means, liquid collection means, second plate-forming means and silicon plate-forming means, said second plate-forming means and said silicon plate-forming means facing each other and forming, between them, a cavity designed to receive a liquid, said cavity being partially closed by at least one transverse partition of height that is smaller than the depth of the cavity and which separates the cavity into an upstream portion and a downstream portion relative to said partition, said silicon plate-forming means being fixed at least in part in leakproof manner on said second plate-forming means; in that said downstream portion of the cavity communicates with said pump chamber; and in that the assembly comprising both first plate-forming means, the silicon plate-forming means, and the second plate-forming means, constitutes a sandwich structure.
By means of the invention, the problem of particles whose excessive size is harmful to the operation of a component such as a micropump is solved by interposing a partition shutting off partially and almost entirely a longitudinal cavity along which the fluid flows.
Two functions of the filter of the invention can thus be distinguished: reducing leakage rate through the valves; and improving the reliability of the micropump. The flow of liquid through the inlet and/or outlet valves when the micropump is at rest is small, providing the size of the admitted particles is small. In addition, because of the filter, when the micropump is active, there is no risk of a particle of excessive size preventing a valve from closing and disturbing priming of the micropump.
With such a filter, resistance to liquid flow is very small, while maintaining a high level of filtering. The partition preferably crosses the cavity in a folded hairpin-bend configuration. This makes it possible to keep the dimensions of the filter small for given total length of partition.
In the embodiments described below, the cavity is a groove etched in the surface of a silicon plate. In the preferred embodiment of the filter for a micropump, one of the first plate-forming means and the silicon plate-forming means constitute a single plate and the other of the first plate-forming means and the second plate-forming means constitute a single glass plate.
Other characteristics and advantages of the present invention appear better on reading the following description of embodiments of the invention given as non-limiting examples. The description refers to the accomp
REFERENCES:
patent: 4797211 (1989-01-01), Ehrfeld et al.
patent: 4895562 (1990-01-01), Hok
patent: 5085562 (1992-02-01), van Lintel
Leungki Yit Shun
van Lintel Harald
Gartenberg Ehud
Thorpe Timothy S.
Westonbridge International Limited
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