Measuring and testing – Fluid pressure gauge – Diaphragm
Reexamination Certificate
1997-02-12
2001-06-26
Felber, Joseph L. (Department: 2732)
Measuring and testing
Fluid pressure gauge
Diaphragm
C604S153000
Reexamination Certificate
active
06250164
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to sensing fluid pressure.
BACKGROUND
Pressure measurements of fluid flowing within a tube can be made in a variety of ways. For example, a strain gage, may be placed on the outside of the tube. However, as internal pressure of a tube changes, the tube “balloons,” i.e., the tube wall stretches, varying the tube wall thickness, in the area where the strain gage is located. Forces due to the internal pressure of the tube, and forces due to variations in thickness along the tube wall, hinder accurate measurement of the internal pressure alone.
Another method uses a “T” fitting to divert a portion of the fluid to a pressure transducer. This method adds cost, complexity, and increases the probability of leakage, and may produce trauma to the fluid (if the fluid is blood, trauma can result in hemolysis).
SUMMARY OF THE INVENTION
The invention is a method of sensing fluid pressure in which a deformable tube provides an accessible and substantially flat section. Deflection of the flat section reflects line pressure. In one embodiment, the invention is a fluid pressure sensing apparatus, comprising a deformable tube for carrying fluid and at least one constraint member comprising an inner surface and a pressure sensing opening. The inner surface comprises a substantially flat portion and a constraint portion. The tube is positioned against the inner surface and constrained by the constraint portion such that a portion of the tube is deformed against the substantially flat portion of the inner surface. This produces a substantially flat section of the tube adjacent to, and accessible through, the pressure sensing opening. Similarly, in another embodiment, a method of manufacturing a fluid pressure sensing apparatus comprises the steps of: providing a deformable tube, and constraining the tube to provide an accessible and substantially flat section of the tube.
REFERENCES:
patent: 4483196 (1984-11-01), Kurtz et al.
patent: 4758228 (1988-07-01), Williams
patent: 4825876 (1989-05-01), Beard
patent: 5044203 (1991-09-01), Wiest et al.
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patent: 25 33 078 A1 (1977-02-01), None
patent: 38 38 689 C1 (1990-06-01), None
patent: 0 471 492 A2 (1992-02-01), None
patent: WO 97/34523 (1997-09-01), None
O'Brien Richard J.
Sorich Richard A.
Wirbisky Alan
Felber Joseph L.
Medtronic Inc.
Patton Harold R.
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