Measuring and testing – Fluid pressure gauge – Bourdon
Patent
1996-12-09
1998-04-28
Oem, William L.
Measuring and testing
Fluid pressure gauge
Bourdon
73700, 73718, G01L 702
Patent
active
057447276
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a pressure gauge for very high pressures and based upon a principle similar to the bourdon tube, comprising a substantially straight, beam-shaped measuring element having one or more elongate cavities lying eccentrically in the cross-section of the measuring element, and possibly being supported by a holder member at one end.
When very high pressures are referred to here, these can typically be of the order of magnitude 1000 bar. Moreover for interesting uses of such a pressure gauge it is of significance that the ambient temperatures can be rather high, typically 200.degree. C, while at the same time the pressure gauge should have small geometrical dimensions.
A pressure gauge in the principle consists of a spring element and a measuring or sensor device. Common pressure gauges or transducers being commercially available and based upon silicium technology can employ silicium membranes as spring element, provided with diffused piezo-resistors as sensor devices. Such resistors however, are not suitable for high ambient temperatures. Capacitive sensor devices on silicium membranes will not have a sufficiently large deflection if they shall be dimensioned for high pressures. In summary the known spring elements being used for measuring moderate pressures, such as membranes and bourdon tubes are poorly suited for high pressures, if they shall be employed together with a measuring or sensor device based upon the detection of movement, because the absolute movement is small when the spring element shall be small.
The present invention takes advantage of the long well known bourdon tube principle, which previously has been utilized in various configurations for pressure measurement. A specific example in the form of a bourdon barometer or microbarometer is described on page 459 in "Handbok i finmekanik" , K G Bertmarks Forlag Aktiebolag, Sweden. The measuring element in this known, somewhat special barometer consists of a bent spiral shaped and evacuated metal tube, one end of which is attached to a holder member or frame.
In practical applications contemplated in connection with the present invention, in particular the very high pressures and the small dimensions desired, quite different solutions are required however, than in the microbarometer just mentioned.
Within classical pressure measurements it has long since been known that an eccentrically bored bourdon tube is a well suited spring element for measurement of high pressures. Such pressure gauges are described by: J. Wuest: Theorie des Hochdruckmessrohres mit ausmittiger Bohrung; Ingenieurarchiv XIX Band 1951 and J. Gielessen: Elastisches Stabmanometer mit exzentrischer Bohrung fur Druche bis 9500 kp/cm2; Zeitschrift fur angewandte Physik BAnd 8 Heft 4, 1956.
These known forms of pressure transducers intended for high pressures, all have the pressure medium concerned, introduced interiorly. The essentially straight, beam-shaped measuring or spring element with an elongate eccentric cavity, under pressure influence will assume a curvature or deflection being proportional to the pressure applied. These known forms of pressure gauge or transducers can be regarded as representing the closest technical background for the present invention.
In view of the above discussed, known techniques, a pressure gauge as referred to in the introduction to this description, has novel and specific features consisting primarily therein that the measuring element is composed of two substantially plate shaped parts manufactured in planar technology, preferably of silicium or quartz, that one plate part is provided with an elongate recess in that surface which faces against a cooperating surface on the other plate part, so as to form the eccentric cavity (cavities), that both plate parts are jointed at said surfaces in such a manner that said cavity (cavities) is (are) sealingly closed, and that the measuring element is adapted to be subjected exteriorly to the very high pressures to be measured.
Thus the invention has taken advantage of the known meas
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Hanneborg Anders
Ohlckers Per
Serck-Hanssen Fin
Amrozowicz Paul D.
Oem William L.
Sinvent A/S
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