Fluid handling – Processes
Reexamination Certificate
1999-07-22
2001-10-30
Lee, Kevin (Department: 3753)
Fluid handling
Processes
C137S554000
Reexamination Certificate
active
06308723
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to position sensing systems and in particular to a system for and method of detecting valve position.
BACKGROUND OF THE INVENTION
Fluid transfer systems, such as aircraft environmental control systems, extensively employ valves for delivery and regulation of engine bleed air for such purposes as passenger cabin pressurization and temperature control. Any failure of a valve to open or close will negatively affect environmental control system performance and, in some instances, affect aircraft dispatchability.
Although valve failures can sometimes be calculated via measurements of the temperature and pressure of the bleed air, such failure detection schemes tend to be elaborate and require significant testing and analysis to ensure adequate function. Further, implementation of algorithms needed for such calculations increase development costs, airplane down time and retrofit cost.
It is desirable to detect valve failure when the airplane is grounded and the systems are off. The preferred approach to valve failure detection is deterministic position indication through the use of valve position sensing instruments. With respect to such instruments, the position indicator, wiring, and interface circuit associated therewith, ideally, are cost effective, lightweight, interchangeable and able to operate in engine environments of severe vibration and temperature. Moreover, it is preferable to use a standardized design for all valve applications to achieve commonality and mass economy. Traditional position indicators such as limit switches and potentiometers are of low reliability due in large part to their incorporation of opening and closing electrical contacts. More reliable aerospace quality devices such as rotary variable transformers, rotary variable differential transformers and linear variable differential transformers are undesirably expensive. Eddy current sensors, Hall effect sensors, proximity sensors and other alternatives, such as optical switches, can operate only within a relatively small temperature range.
Accordingly, a need exists for an improved position indicator, the implementation and operation of which is simple, and the components of which are cost effective, lightweight, interchangeable and able to operate in extreme engine environments.
SUMMARY OF THE INVENTION
According to principles of the present invention, a sensor beam provides a linear or non-linear continuous signal to a computer that translates the signal into a valve position reading.
In one embodiment of the invention, a sensor beam incorporating piezo-resistive components forming a Wheatstone bridge abuts a cam mounted on a butterfly valve spindle. Valve movement causes rotation of the cam that, in turn, bends a beam causing strains in the piezo-resistive components, thereby altering the resistance of the Wheatstone bridge. The computer or the other electronic device measures the resistance change by means of an output signal transmitted by the sensor beam and calculates valve position based thereon.
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patent: 5048343 (1991-09-01), Oboodi et al.
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patent: 5609183 (1997-03-01), Parker
patent: 5736635 (1998-04-01), Onodera
patent: 42 28 307 A1 (1994-03-01), None
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PCT/US99/27412 International Search Report.
Louis Ronald J.
Oboodi Reza
Allied-Signal Inc.
Lee Kevin
Newburry, Esq. Keith
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