Fluid handling – With indicator – register – recorder – alarm or inspection means – Position or extent of motion indicator
Reexamination Certificate
1999-05-26
2001-02-20
Lee, Kevin (Department: 3753)
Fluid handling
With indicator, register, recorder, alarm or inspection means
Position or extent of motion indicator
C137S552000
Reexamination Certificate
active
06189565
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a valve arrangement and in particular to a valve arrangement in which the operation of the valve can be automatically monitored.
2. Description of the Prior Art
Automatic monitoring of the operation of a valve, i.e., its opening and closing, is particularly useful when the valve is used in conditions wherein safety is critical or in precise control conditions. Such conditions as may exist, for example, in patient ventilator systems where the operation of valves must be precisely controlled in order to ensure that a correct dose of anaesthetic is delivered to a patient.
A valve arrangement, useable in patient ventilators, is described in U.S. Pat. No. 5,265,594 and includes a variable aperture through which fluid may flow. A resilient diaphragm closure elements is also provided which is adjustable to vary the size of the aperture in response to the action of a co-operating valve stem, part of which forms a moveable solenoid core. A sensor unit is also provided which senses the aperture size by monitoring the electrical properties of an electrical circuit that includes the solenoid and valve stem. In this way the position of the valve stem within the solenoid can be determined and hence an indication of the degree of opening of the aperture is obtained. A signal is emitted from the sensor unit indicating the aperture size or changes therein, which is used to control the current supplied to the solenoid.
A further valve arrangement, useable in fire protection sprinkler systems, is described in U.S. Pat. No. 5,584,319 and includes an optical sensor unit from which a signal is emitted indicating whether the valve is open. Light from the sensor unit is reflected from a valve stem and detected by a photodetector only when the valve stem is moved to unblock an aperture and open the valve.
Both valve arrangements operate by monitoring the position of the valve stem from which the position of a closure element, and hence the size of the aperture is inferred. In certain circumstances, for example as the valve arrangement becomes worn, the valve stem may move before any changes in the size of the valve aperture occurs and so may cause erroneous signals to be emitted from the sensor unit. Moreover, sticking of the closure element, may again cause measurements made based on the valve stem to provide erroneous signals output from the sensor unit.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a valve arrangement which alleviates at least one of the aforementioned problems associated with prior art arrangements.
The above object is achieved in accordance with the principles of the present invention in a valve arrangement having a variable aperture through which fluid flows, a closure element which is adjustable to vary the size of the aperture, and a sensor unit which generates an output signal dependent on the aperture size, the sensor unit including a light detector positioned to detect light which has passed through the aperture. The detector unit generates the aforementioned output signal dependent on the detection of light passed through the aperture.
Thus, by sensing light, which may be ambient light or light from a dedicated source, which passes through the aperture of the valve its opening and closing can be monitored directly. The sensed light is used to produce an output signal from the sensor unit indicative of the actual size of the aperture, or simply indicative of whether the valve is open or closed.
Preferably, the sensor unit includes a radiation detector and a complementary radiation source, the detector and source respectively being positionable upstream and downstream of the fluid flow on opposite sides of the aperture. This enables the valve arrangement to be used in the absence of ambient light.
The detector can provide an output proportional to the level of incident radiation, and this output can then be used in the calculation of the size of the aperture open to fluid flow.
The sensor unit also may be capable of monitoring the rate of change of the aperture size which may, for example, be used to determine the presence of unwanted oscillations in the valve opening.
The detector can be configured to provide a number of outputs, each indicative of light having passed through an associated region of the aperture. The respective outputs can be used to monitor the operation of the associated regions of the aperture and may, for example, provide a more accurate calculation of the size, or identify uneven opening, of the aperture.
In an embodiment of the arrangement according to the invention the fluid flow rate is automatically controlled in order to achieve a desired flow. This is accomplished by causing the sensor unit to emit a signal indicative of the actual size of the aperture and by providing a controller which measures the pressure difference upstream and downstream of the aperture, receives the output signal emitted from the sensor unit, and determines a flow rate from the measured pressure difference and the aperture size.
REFERENCES:
patent: 5202673 (1993-04-01), Conrad
patent: 5265594 (1993-11-01), Olsson et al.
patent: 5584319 (1996-12-01), Cholin
patent: 5764053 (1998-06-01), Chang
patent: 0 063 010 (1982-10-01), None
patent: 0 603 592 (1994-06-01), None
patent: 149 286 (1981-05-01), None
Lee Kevin
Schiff & Hardin & Waite
Siemens-Elema AB
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