Measuring and testing – Volume or rate of flow – Proportional
Reexamination Certificate
1999-10-22
2001-07-03
Oen, William (Department: 2855)
Measuring and testing
Volume or rate of flow
Proportional
C073S861470, C073S861580
Reexamination Certificate
active
06253605
ABSTRACT:
DESCRIPTION
The present invention relates to a proportioning element for proportioning a fluid flow from an input side to an output side of the proportioning element, the proportioning element being suitable to be used e.g. in a proportioner for dosing medicaments in the field of medical engineering.
In the field of medical engineering, proportioners are known, which comprise flow resistors whose flow rate depends on the pressure with which the medium to be proportioned is acted upon before the flow resistor, when seen in the direction of flow. For detecting the pressure difference, two different pressure sensors are normally used, the pressure sensors being arranged before and after the flow resistor, when seen in the direction of flow.
Known flow resistors consist e.g. of glass capillaries or microchannels in a capillary form. A disadvantage of such known proportioners is that they have a complicated structural design due to the fact that a flow resistor and two different pressure sensors, which arranged before and after the flow resistor when seen in the direction of flow, are required.
In the Patent Abstracts of Japan, P 1828, Nov. 18, 1994, Vol. 18, No. 609, a means for measuring a flow rate is described, in the case of which an elastic plate with an opening is arranged in a passage or in a tube through which fluid flows. Furthermore, means for detecting the deflection of the elastic plate are provided in the elastic plate.
DE 195 29 396 A1 discloses a measuring device for measuring the flow rate of a medium flowing in a flow cross-section, in the case of which a plate acted upon by the medium is flexible due to cuts formed therein, the plate having provided thereon strain gauges for detecting a deflection of the plate.
DE 42 23 067 C2 describes a micromechanical flow restrictor which is implemented in a multilayer structure. This flow restrictor is adapted to be used in combination with a micromechanical valve for micromechanical proportioners.
DE-AS-19 43 021 teaches that a means is used for measuring the flow through a tube according to the differential pressure flow metering method in the case of which an elastic deformation of a component depending on the pressure to be measured is converted into an electric signal. The strain gauges used for detecting the elastic deformation are directly attached to an elastic orifice plate which is arranged in the tube through which the fluid flows.
Starting from the above-mentioned prior art, it is the object of the present invention to provide a proportioning element which has a simple structural design and which permits exact proportioning of media, even if they are chemically aggressive.
This object is achieved by a proportioning element according to claim
1
.
The present invention provides a proportioning element for proportioning a fluid flow from an input side to an output side of the proportioning element, which comprises a membrane provided with at least one opening acting as a flow resistor for a medium to be proportioned. The membrane has integrated therein pressure sensors used for detecting a pressure difference between the input side and the output side of the proportioning element. The proportioning element is implemented as a semiconductor chip, the membrane being a semiconductor membrane. Areas of the semiconductor chip which are exposed to the medium to be proportioned are covered with a passivation layer.
Preferably, the pressure sensor is defined by piezoresistive resistors arranged on or in the membrane. The semiconductor chip, which may consist e.g. of silicon, has in addition preferably integrated therein a temperature sensor.
A proportioner including a proportioning element according to the present invention can e.g. comprise a controllable pressure transducer and a control device for controlling the controllable pressure transducer in dependence upon the pressure difference detected by means of the pressure sensor and/or the temperature detected by means of the temperature sensor.
An alarm signalling device can be provided for outputting an alarm if flow passages arranged before and/or after the membrane have a leak or are clogged or if the at least one opening of the membrane is clogged; such malfunctions can be recognized on the basis of the pressure difference detected by the pressure sensor.
By means of the proportioning element according to the present invention chemically aggressive flow media can easily be proportioned. In comparison with known proportioners, the proportioning element according to the present invention is also advantageous insofar as the pressure difference is determined directly by means of a sensor instead of being determined by two pressure measurements relative to the atmosphere, the results of the two measurements being then subtracted from one another. Furthermore, the flow resistor, i.e. the restriction, according to the present invention is integrated directly in the pressure sensor. Hence, only a single chip is required, the chip fulfilling both the function of differential pressure measurement and the function of the flow resistor, i.e. the flow restricting function.
Further developments of the present invention are disclosed in the dependent claims.
In the following, a preferred embodiment of the present invention will be explained in detail, part of the explanation referring to the single figure enclosed.
REFERENCES:
patent: 4330003 (1982-05-01), D'Alonzo
patent: 4986127 (1991-01-01), Shimada et al.
patent: 5463904 (1995-11-01), Kalinoski
patent: 5469749 (1995-11-01), Shimada et al.
patent: 5804701 (1998-09-01), Berger
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patent: 4143343C2 (1994-09-01), None
patent: 195 29396 (1995-08-01), None
patent: 0239331 A2 (1987-09-01), None
patent: 0239331B1 (1992-05-01), None
patent: 2064826A (1981-06-01), None
patent: 60127814 (1986-12-01), None
patent: 02114279 (1992-01-01), None
patent: 02286168 (1992-06-01), None
patent: 6-229793 (1994-09-01), None
Fraunhofer-Gesellschaft zur Forderung der Angewandten Forschung
Glenn Michael A.
Oen William
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