Valve arrangement

Abstract: A valve arrangement includes a variable aperture (2) through which fluid may flow, a closure means (4) adjustable to vary the size of the aperture (2) and a sensor unit (9) adapted to generate an output signal dependent on the aperture size. The sensor unit (9) comprises a light source (13,14) and a detector (15,16) disposed one upstream and one down stream of the aperture (2) to detect light passed through the aperture (2) and to generate the output signal dependent on the detection of the light, for example to a visual display unit (10) having indicators (11,12) that may be selectively activated to show if the valve is open or closed .

Description: 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. The automatic monitoring of the operation of a valve, that is the opening and closing, is particularly useful when the valve is used in safety critical or precise control conditions. Such conditions 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. One valve arrangement, useable in patient ventilators, is described in US 5 265 594 (Olsson et al) and includes a variable aperture through which fluid may flow. A resilient diaphragm closure means 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 may be determined and hence an indication of the degree of opening of the aperture may be obtained. A signal may be output 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 US 5 584 319 (Cholin) and includes an optical sensor unit from which may be output a signal indicating whether or not the valve is open. Light from the sensor unit is arranged to be reflected from a valve stem and be 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 may be inferred the position of a closure element and hence the size of the aperture. 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 output from the sensor unit. Moreover, sticking of the closure means, may again mean that measurements made on the valve stem lead to erroneous signals output from the sensor unit. It is further known from EP 0063010 (Hurst et al), which document discloses an arrangement as defined in the preamble of claim 1, to provide a valve arrangement including an ionising radiation source and complementary detector adapted to cooperate with a closure means to monitor its position directly and thus gain an indirect indication of the aperture size. It is an aim of the present invention to alleviate at least one of the problems associated with the prior art arrangements. Accordingly there is provided a valve arrangement described in and characterised by claim 1. Thus, by sensing the light, which may be ambient light or light from a dedicated source, which passes through the aperture of the valve its opening and closing, i.e. aperture size, may be monitored directly. The sensed light may then be used to provide an output signal from the sensor unit indicative of the actual size of the aperture or simply of whether the valve is open or closed. Usefully, the detector may be adapted to provide an output proportional to the level of incident radiation which output may then be used in the calculation of the size of the aperture open to fluid flow. The sensor unit may also be adapted to monitor 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 may be configured to provide a plurality of outputs, each indicative of light having passed through an associated region of the aperture. The plurality of outputs may be advantageously 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. An advantageous embodiment of the arrangement according to the present invention provides for the automatic control of the fluid flow rate in order to achieve a desired flow. This is achieved by arranging for the sensor unit to output a signal indicative of the actual size of the aperture and by providing a controller comprising means adapted to measure the pressure difference upstream and downstream of the aperture, to receive the signal output from the sensor unit and to determine a flow valve from the measured pressure difference and the input aperture size. Embodiments of the valve arrangement according to the present invention will now be described by way of example only and with reference to the drawings of the accompanying figures of which: Figure 1 shows a schematic representation of a valve arrangement according to the present invention with automatic on/off detection. Figure 2 shows a schematic representation of an alternative valve arrangement according to the present invention including automatic opening control. Figures 3 show a valve arrangement of the present invention having a light tight housing with reflective surfaces disposed to provide multiple light reflections therein (Figure 3b). Considering Figure 1, a portion of a valve 1 is shown having an aperture 2 through which fluid may flow connected to a conduit 3. A closure means 4 comprising a fluid tight housing 5 through which passes a fluid channel 6 is provided in fluid tight connection with the aperture 2. The closure means 4 is mounted so as to be rotatable within the aperture 2 between a closed position in which the channel 6 is substantially perpendicular to the direction of fluid flow through the aperture 2 and an open position in which the channel 6 is substantially parallel to the flow direction and thereby vary the size of the aperture 2 through which fluid may flow. A projection 7 is provided on the closure means 4 which travels in a groove 8 within the wall of the valve 1 as the closure means 4 rotates. The projection 7 and groove 8 are cooperatively arranged to stop the rotation of the closure means 4 at the fully open and the fully closed positions. A sensor unit 9 is provided and configured to sense changes in the size of the aperture 2 corresponding to the valve 1 being fully open and the valve being fully closed and to output a signal to a display unit 10 which displays the operational status (open or closed) of the valve 1. The display unit 10 may simply comprise two visual indicators 11,12 which are actuated in a mutually exclusive manner when the valve 1 is respectively open and closed. The sensor unit 9 comprises a light emitting diode (LED) light source 13 which is operated to provide a pulsed output at a known frequency. A first optical fibre 14 is arranged to lead light from the LED 13 and into the valve 1 so that light from the LED 13 may pass through the channel 6 of the closure means 4 when in either the fully opened or the fully closed position. A second optical fibre 15 is arranged within the conduit 3 to capture light passing from the first optical fibre through the conduit 6, along the direction of fluid flow, when the closure means 4 is rotated to open the valve 1. The second optical fibre 15 conveys the captured light to an associated photodetector 16 where it produces an electrical signal proportional to its intensity. The electrical signal from the photodetector 16 is passed to a phase sensitive detector and amplifier unit 17 which is operated at the pulse frequency of the LED 13. Any amplified electrical signal of the correct frequency and phase is then passed to a comparitor 18 where its amplitude is compared with a reference amplitude and from where a signal is output to activate one or other of the visual indicators 11,12 only when the amplitude of signal from the unit 17 matches or exceeds the reference amplitude. In this way problems with false signals, for example caused by only a partially open valve 1, may be reduced. A third optical fibre 19 is also included within the sensor unit 9 and is arranged within the wall of the valve 1 to capture light passing from the first optical fibre through the conduit 6, perpendicular to the direction of fluid flow, when the closure means 4 is rotated to close the valve 1. The third optical fibre 19 conveys the captured light to an associated photodetector 20 where it produces an electrical signal proportional to its intensity. The electrical signal from the photodetector 20 is passed to the unit 17 and onward to the comparator 18 and processed in a manner similar to that described above for the situation in which the valve 1 is open. Considering now the solenoid type valve arrangement of Figure 2, the general operating principles of which are well known in the art and so will be provided only in sufficient detail to facilitate the understanding of the novel aspects of the embodiment. A valve 21 is provided with an open end 22 around the open periphery of which is a resilient sealing member 23 against which a sealing head 24 of a closure member 25 may be urged to close the valve 21. A valve stem 26 of the closure member 25 is operatively connected to the sealing head 24 and forms a moveable core of a solenoid 27. Thus by varying the current through the solenoid 27 the valve stem 26 is caused to move to vary the relative position of the sealing head 24 with respect to the sealing member 23. This movement thereby produces a consequent variation in the size of the aperture 28 through which fluid may flow. The valve arrangement also comprises a sensor unit 29 which is adapted to monitor light passing through the aperture 28, to calculate the area A ap of the aperture 28 therefrom and to output the calculated area to flow control unit 30. The sensor unit 29 comprises a light source 31, detection means 32a..n,33 and a microprocessor 34. The light source 31 is located within the open end 22 of the valve 21 and arranged to provide an even illumination across the entire aperture 28. A plurality of optical fibres 32a..n are provided to collect light from the source 31 after it has passed through the aperture 28. The fibres 32a..n are disposed so as to each collect light passing through a different associated region of the aperture 28 and to deliver the collected light to a detector unit 33 (for example a single photodetector) which provides an electrical output proportional to the integrated intensity of the light from all of the fibres 32a..n. The detector unit 33 may also be adapted to discriminate between the light from each of the fibres 32a..n (for example by replacing the single detector with a detector for each fibre 32a..n) then variations in the intensity of the light collected by each fibre 32a..n may be used to determine if the valve is opening correctly, for example whether or not any part of the sealing head 24 is sticking to the resilient sealing member 23. The output from the detector unit 33 representing the integrated light intensity is provided to the microprocessor 34 which is configured to use this output together with a value of the intensity of the light output from the light source 31 (which value may be predetermined, calculated within the microprocessor 34 from a knowledge of the operating characteristics of the light source 31 and the power supplied to it, or directly measured using a further detector unit) in the calculation of the area of the aperture 28. A flow control unit 30 comprises pressure sensors 35,36 located to measure fluid pressure respectively upstream P up and downstream P down of the fluid flow, on opposite sides of the aperture 28. A microprocessor 37 is configured to determine the ratio, P r = P up /P down , between the two pressures measured by the sensors 35,36. Obviously, a single microprocessor may be used to replace the microprocessors 34,37 of the sensor unit 29 and the control unit 30 respectively. The output from the sensor unit 29 representing the calculated size of the aperture 28 is also input into the microprocessor 37 of the control unit 30 and the microprocessor 37 is programmed to calculate the volume flow Q vol using the known relationship: Q vol = K.P r .A ap where K is a constant dependent on the gas used and the temperature. The microprocessor 37 is also programmed to compare the calculated flow value with a desired flow value and to output a control signal to the solenoid power source 38 to vary the current through the solenoid so to vary the area of the aperture 28 to bring the calculated and desired flow values to congruence. The entire valve arrangement may be enclosed in a light tight housing 39 to exclude unwanted ambient light. In certain situations, particularly where there is only a small pressure difference between the fluid inside and that outside of the valve 21 oscillations in the position of the closure member may occur which can lead to undesirable oscillations in the flow of fluid from the valve 21. For example, the solenoid power source 38 may be operated so that fluid at a particular pressure inside the valve 21 forces the closure member 25 open to produce a predetermined size of the aperture 28 and hence a predetermined flow. However, as the closure member 25 moves to open then the pressure of the fluid within the valve 21 drops. This may cause the closure member 25 to move to close the aperture 28, so increasing the pressure of the fluid within the valve 21. The increased pressure then acts to move the closure member 25 to open again and thus oscillitary movements in the closure member 25 may be generated. Therefore, advantageously, the sensor unit 29 may be additionally, or alternatively adapted to detect oscillations in the movement of the closure member 25, for example by arranging for the microprocessor 34 to determine the rate of change of the area of the aperture 28. Upon detection of oscillitory movements the flow control unit 30 may be operated to control the solenoid power source 38 to eliminate the oscillations. Turning now to Figures 3 in which a portion of a valve arrangement is shown and in which features common with previously described arrangements are given identical reference numerals. A light tight housing 40, similar to the housing 39 of Figure 2, is provided in order to exclude ambient light from a detector 41. This detector 41 is arranged within the housing 40 to collect light passing from a source 42 located within an open end 43 of a valve 44. A reflective coating 45 is applied to the internal surfaces of the housing 40 so that light passing from the source 42, through an aperture 28 formed between a sealing member 23 and a closure element 25, undergoes multiple reflections within the housing (as illustrated in Figure 3b by the broken lines which represent light paths). In this way the detector 41 senses an integrated or average light intensity of all light passing through the aperture 28. Thus the detected light intensity is substantially independent of the location of the detector 41 within the housing 40 and an integrated intensity measurement is provided without the need of the multiple detector optical fibre elements 32a..n, such as are shown in the arrangement Figure 2. The external walls of the valve 44 that lie within the housing 40 may also be provided with a reflective coating 45 to enhance the multiple reflections and so the averaging effect of the light intensity. The detector 41 provides an output proportional to the detected light intensity which is passed to a microprocessor 34. This microprocessor 34, together with the detector 41 and source 42 form a sensor unit 46 which operates substantially as previously described in respect of Figure 2 to determine the area of the aperture 28. It will be appreciated by those skilled in the art that variations may be made to the above described embodiments while still remaining within the scope of the invention as claimed. For example and without limitation, one or other of the detectors 16,20 and respective optical fibres 15,19 may be removed so that the sensor unit 9 will actively detect only the open or the closed position of the valve 1; a continuous output light source may replace the pulsed source 13 with consequent changes needed to be made to the detection circuitry of the sensor unit 9; the detector 16,20 and/or light source 13 may be placed to collect and/or deliver light without the need for optical fibres 14 and/or 15,19; the fibre optic bundle 32a..n may be replaced with a plurality of suitably positioned photodetectors; the valve arrangement may be configured so that light entering the valves 1, 21 may be detected instead of that exiting; and ambient light may replace light from dedicated sources 13,31.

Claims: A valve arrangement including a variable aperture (2,28) through which fluid may flow, a closure means (4,25) adjustable to vary the size of the aperture (2,28) and a sensor unit (9,29,46) comprising a radiation source (13,14,31,42) and complementary detector (16,20,32a..n,33,41) adapted to cooperate with the closure means (4,25) to generate an output signal indicative of the aperture (2,28) size characterised in that the detector (16,20,32a..n,33,41) and the radiation source (13,14,31,42) are positioned one upstream and one downstream of the fluid flow on opposite sides of the aperture (2,28), the source (13,14,31,42) being adapted to illuminate the aperture (2,28) with light and the detector (16,20,32a..n,33,41) being adapted to detect light from the source (13,14,31,42) passed through the aperture (2,28) and to generate the output signal dependent on the detection. An arrangement as claimed in claim 1 characterised in that the detector (32a..n,33,41) is adapted to provide an output proportional to the level of incident radiation useable within the sensor unit (29,46) to determine the aperture size and in that the output signal of the sensor unit comprises at least a component indicative of the determined size. An arrangement as claimed in claim 2 characterised in that there is further provided means (30) adapted to measure the pressure upstream and downstream of the aperture (28), to receive an input indicative of the aperture size as determined by the sensor unit (29), to calculate therefrom a flow value of fluid through the aperture (28) and to output a signal indicative of the calculated flow value. An arrangement as claimed in any of the claims 1 to 3 characterised in that the detector comprises a plurality of elements (32a..n) spaced apart to each provide a discrete output dependent on light having passed through an associated region of the aperture (28). An arrangement as claimed in any of the claims 1 to 4 characterised in that there is further provided means to inhibit effects of ambient light comprising a light-tight housing (39,40) disposed to exclude ambient radiation from detection by the detector (32a..n,41). An arrangement as claimed in claim 5 characterised in that the detector (41) is situated downstream the aperture (28) within the light-tight housing (40) and in that the light-tight housing (40) is provided with reflective internal surfaces (45) arranged to multiply reflect incident light therefrom to provide an average light intensity within the housing (40) for detection by the detector (41).

Inventors: SKOG GOERAN, SKOG, GOERAN, Skog, Göran
Applicants: MAQUET CRITICAL CARE AB
Application year: 1999
Main classification: F16K37
IPC codes: F16K37, G01B11