GB2159942A - Fluid valve position sensor - Google Patents

Abstract

A fluid valve comprising a valve member 20 movable relatively to a valve seat 10 through a range of positions between a valve fully open position and a valve closed position by pressure of the fluid applied to the valve. A light conducting path is defined through the valve from a light input end 52 to an output end 60. Light is transmitted along the light conducting path and a non-electrically operable device 42,66 is provided to vary the proportion of the light delivered to the input end which is transmitted to the output end. The amount of light transmitted is varied in accordance with the position of the valve member so that the amount of light delivered to the output end is a function of the position of the valve member relative to the seat. In other embodiments, light transmission is varied by varying the length of an optical path separating the ends of two fibre-optic cables. <IMAGE>

Description

SPECIFICATION Valve This invention concerns a fluid valve of the type (hereinafter called the type referred to) comprising a valve member movable relatively to a valve seat through a range of positions between a valve fully open position and a valve closed position by pressure of the fluid applied to the valve.

The fluid pressure can be hydraulic or pneumatic pressure.

Valves of the type referred to can include relief valves and instrument protector valves. A relief valve is connected to a conduit carrying fluid under pressure and is automatically closed whilst the pressure is below a predetermined value but opens automatically when the pressure rises above that value allowing fluid to bleed off through the valve to relieve the excess pressure in the conduit. On the other hand a protector valve is normally open allowing the fluid pressure in the conduit to be applied beyond the valve to some sensitive apparatus, for example a pressure gauge, whilst the fluid pressure is below a pre-determined value. But on the pressure rising beyond that pre-determined value the protector valve automatically closes to prevent the excess fluid pressure from being applied to the sensitive apparatus so the chance of the latter being damaged is reduced.

In some instances it is desirable to know if valves of the type referred to are functioning or in what position the valve member is. But mere external visual inspection of known valves may not provide this information or visual inspection may not be convenient because the valves are at remote locations. Therefore providing the valve with an incorporated valve monitoring transducer to give an output signal representative of the valve condition would be desirable. But the fluid controlled by the valve may be inflammable or explosive or the valve may be used in an inflammable or explosive environment. In either case the spark hazard inherent in the use of an electrically operating transducer and electrical cable connected to the valve to carry therefrom information signals in the form of one or more electrical parameters renders such electrical monitoring dangerous.Also, electrical information signals can be subject to interference at radio frequency from other electrical equipment making the information signals useless.

An object of the invention is to provide a valve of the type referred to adapted to be capable of providing a non-electrical signal indicative of the valve condition, in which the signal is of a form capable of being transmitted over some distance from the valve.

According to the invention a fluid vaive of the type referred to comprises a light conducting path having an input end into which light can be input for transmission along the path to an output end of said path, said path comprising varying means non-electrically operable to vary the amount of light transmitted beyond the varying means to the output end, and the arrangement being such that the varying means is caused to operate in accordance with the position of the valve member so that the amount of light transmitted to the output end is a function of the position of the valve member relative to the seat.

Preferably, the light conducting path comprises optical fibres.

The light conducting path may comprise fibreoptic cable and the varying means may comprise a portion of the cable and a device to variably deform said portion by increasing and decreasing amounts whereby transmission of light through said portion is variable between substantially total or a predetermined maximum at low or substantially no deformation and a pre-determined minimum at a predetermined maximum amount of deformation. The variation in light transmission may be due to creation of diffusion of the light in said portion in proportion to the deformation which may be a function of pressure applied to the portion by the device.

Alternatively the light conducting path may comprise first and second fibre-optic cables with an optical path between the two, and the varying means acting on the optical path to vary the amount of light reaching the second cable from the first. The varying means may be obstructing means operable to vary the extent it obstructs passage of light along the optical path to the second cable. For example, the obstructing means may be a shutter device.

Alternatively, the varying means may comprise optical filter means movable in the optical path to a varying extent depending on the attitude of the valve member. For example, the filter means may be a key-hole filter or a filter (for example a film filter) with varying degrees of opaqueness or translucence along its length of travel across the optical path.

Alternatively, the varying means may comprise an arrangement to vary the length of the optical path between a light emitting end of the first fibre optic cable and the light receiving end of the second fibre optic cable in accordance with the attitude of the valve member, whereby the intensity of the light received by the second cable varies. For example such an arrangement may make use of the fact that the beam emergent from the light emitting end diverges outwardly relative to the beam axis, so that the longer the optical path the lesser the amount of light at the sides of the beam is incident on the receiving end.The variation of the length of the optical path may be achieved by moving the light emitting end relatively to the light receiving end or by moving relatively to either or both said ends reflecting means arranged to direct the beam from the emitting end onto the receiving end. The range of variation of the length of the optical path is preferably smaller than the range of movement of the valve member and conversion means may be provided to reduce the variation in optical path length to a pre-determined fraction of the movement of the valve member.

At some distance light transmitter means may be provided (away from any explosive environment) to provide a light output conveyed to the input end of the conducting path by a preliminary fibre optic cable. The transmitter means may convert electrical energy to light energy and may be an electronic device actuated as desired by an electrical input. The transmitter means may comprise a lightemitting diode.

Also at some distance from the valve light receiver means may be provided to electronically convert a received light input signal to an electrical output signal. An input to the receiver means is connected to the output end of the conducting path by a return fibre-optic cable. The electrical output signal may be of a form simply indicating whether or not the valve is open or closed, or be utilized by instrumentation simply to show that situation. Or the electrical output may be in the form of an analogue signal used by instrumentation to indicate not only if the valve is closed or open but to what extent the valve is open.

If desired, the receiver means may be arranged to provide an alarm output signal to indicate for example, a break in either fibre-optic cable, means being provided to make a comparison between the optical input signal to the first fibre-optic cable and the optical output signal from the second fibre-optic cable or observe the optical output signal so that when the latter is absent the alarm signal is produced.

The invention will now be further described, by way of example, with reference to the accompanying drawings, in which Figure 1 is a diagrammatic view partly in section of a pressure relief valve formed in accordance with the invention; Figure 2 is a fragmentary section on lines ll-ll of Figure 1; Figure 3 is a fragmentary and diagrammatic view of an instrument protector valve formed in accordance with the invention; Figure 4A is a diagrammatic cross-sectional view of modification of the valve of Figure 1 when the valve is closed; Figure 4B is similar to Figure 4A but when the valve is open, and Figure 5 is a diagrammatic cross-sectional view of a further modification of the valve in Figure 1.

In the drawings like references refer to corresponding parts.

With reference to Figures 1 and 2, the pressure relief valve shown in closed position has a body 2 formed with an internally threaded inlet bore 4 leading to a passage 6 to a chamber 8 containing a resilient valve seat 10 with a through side aperture 12 opening into passage 14 leading to an internally threaded outlet bore 16. Co-operating with the valve seat is a valve member constituted by a shaft tip 18 and a collar 20 on a shaft 22 sliding through a seal 24 and a bore 26 at the lower end of a housing 28 screwed to the body 2. In the housing, the shaft has another collar 30 which slides in housing bore 32 through which the upper part of 22A of the shaft ascends to be guided by a bore in plug 34 screwed into the threaded upper end of the bore 32 and abutting a helical biasing spring 36 pressing on the collar 30.

Fluid under pressure is supplied to inlet 4 and if that pressure is in excess of a predetermined value the force exerted on the spindle tip 18 overcomes the force of the spring 36 so the whole of spindle 18, 22, 22A lifts to bring the chamferred lower end of valve member 18 clear of the seat 10 whereby fluid from inlet 4 can enter the chamber 8 and bleed off through the outlet 16. Alternatively, in a modified design (not shown) the spindle 22 may be assisted in rising using pilot operated means.

When the fluid pressure at inlet 4 drops below the pre-determined value, the valve closes automatically by action of the spring. The pressure value at which the valve operates is selectively variable according to the initial compression of the spring 36 as determined by the position of the plug 34.

Also screwed into the upper end of bore 32 is a block 38 having a bore 40 in which the upper part 22A of the spindle slides, this upper part being formed with a reduced diameter or waisted shank portion 42 thus leaving a cavity 44 between the shank and the wall of bore 40. Extending through the block into the bore 40 are two passages containing respective fibre-optic cables 46 and 48 having facing ends 46A, 48A at opposite ends of an optical path P across the bore in the manner of a chord to the cross section of the bore 40, so offset from the bore axis that the shank 42 does not obstruct the optical path. Cable 46 is connected at 50 to a fibre-optic cable 52 transmitting light generated in a transmitter 54 in response to an electrical input 56.Cable 48 is connected at 58 to a fibre optic cable 60 connected to an input to a receiver 62 converting received light from cable 60 to an electrical output 64.

When the valve is fully closed the distance d between the optical path P and the base of a conical face 66 at the bottom end of the shank portion 42 is substantially equal to the distance the spindle 22, and 22A lifts for the valve member to just cease contact with the valve seat 10 so that the valve becomes open. Therefore as the valve opens, the face 66 moves across the optical path as a shutter resulting in the optical path becoming partially blocked by the bulk of the spindle part 22A.

Thus reduced light from cable 46 can reach cable 48 and so the electrical output 64 changes in correspondence with the reduction of light. The output 64 is supplied to indicator means (not shown) which responds thereto so that when the valve is closed and light reaches the receiver 62 from cable 60 the output 64 causes the indicator means to give an indication that the valve is closed whereas when reduced light reaches the receiver because the valve is open the indicator means responds to indicate the valve is open. Should either of the fibre optic cables be broken a no light condition at the receiver will initiate operation of alarm means.

The transmitter and receiver may be combined in a transceiver, 68.

With reference to Figure 3, the instrument protector valve indicated generally at 102 is shown closed and comprises a body 104 formed at each end with internally threaded bores 106 and 108.

Bore 106 is for connection to a source of pressure fluid, for example, a pressure fluid supply line, and bore 108 is for connection to a pressure sensitive device, for example, a pressure gauge.

The body is also formed with an internally threaded cavity 110 into which is removably screwed an end 112a of an element or cartridge 112 bearing on a sealing ring 114 on a shoulder of the cavity wall.

The bores 106 and 108 lead into cavity 110 through further bores 116 and 118.

Cartridge end 1 12a is formed with a bore 120 opening at one end into a conical recess forming a valve seat 122. Sliding in bore 120 is a rod 124 formed with an annular groove containing an 0ring seal 126. Rod 124 is waisted at 128, has a frust-conical part 130 (which may have a cone angle similar to that of valve seat 122), and an extension 132 integral with a piston 134 from which a projection or pip 136 extends. Between the part 130 and piston 134 is a resilient, sealing O-ring 138 surrounding the extension 132.

Bore 118 opens to an annular groove 140 in the end part 112a. Also formed in that end part is a bore 142 extending from the groove 140 to the bore 120 and valve seat 122 at its other end.

Above end part 112a, the cartridge 112 is formed with a compartment 144 into which bore 120 opens. This compartment is closed by a screw-in cover 146 bracing one end of a helical compression spring 148 pressing at its other end on a loose two- tier plate 150 applied to an end of the rod 124 to urge a valve member comprised of part 130 and ring 138 away from the valve seat 122.

The insertion of end part 112a in the cavity 110 forms a chamber 110a in the end of that cavity.

The piston 134 is located in the chamber 110a.

Bore 116 opens in to the chamber 110a adjacent the chamber's end wall 152 acting as a stop for the pip 136 which not only limits the extent to which the valve member 130, 138 can be moved clear of the valve seat 122 by the pressure of spring 148 but also ensures face 134a of the piston is exposed to the fluid pressure in bores 106, 116.

The effective surface area of face 134b of the piston is reduced by the extension 132 and is thus less than that of the face 134a. Because of this the fluid pressure delivered by bores 106, 116 to chamber 110a produces a resultant force acting to urge the piston 134 in opposition to the spring 148. The aforesaid resultant force is a function of the fluid pressure in the bores 106, 116. When the pressure in bores 106, 116 is below a pre-determined value, the aforesaid resultant force on the piston 134 does not exceed the force of the spring 148 and thus the valve member 130, 138 is pushed off the seat 122 to leave a gap or route between the valve member and seat so that bore 106 and bore 108 are in communication through the open route.But when the pressure in bores 106, 116 attains at least the pre-determined value, the aforesaid resultant force on piston 134 overcomes the force of spring 148 and presses the valve member onto the seat 122 to close the route. Thus bore 108 is isolated from bore 106 so that further pressure variation in bore 106 is not communicated to bore 108 until the pressure in bore 106 falls below the pre-determined value which enables the route to be opened again.

The pre-determined fluid pressure value at which the valve closes can be varied by altering the force exerted by spring 148 by varying the screwed-in position of the cover 146.

The optical fibre system is similar to that described with reference to Figures 1 and 2, except that the block 38 is screwed into the cartridge 112 and the waisted shank 42 with the conical end face 66 is provided on spindle 154.

When the valve 102 is fully open pip 136 contacts end wall 152 thus determining the lowest position of the spindle 154 which is the distance D lower than in Figure 3 so there is a maximum passage of light from cable 46 to cable 48. When the valve member 130, 138 rises to close the valve the conical face 66 rises to partially block the optical path as in Figure 3, just as the valve closes completely. Therefore the reduced light signal indicates, in this case, valve closure.

In the embodiments in Figures 1 to 3 the conical face 66 partially obstructs the optical path just about as the spindle portion 22A or spindle 154 rises to its maximum height position. But if desired the conical face 66 can be extended along the shank portion 42 so that obstruction of the light progressively increases as the spindle rises and vice-versa as the spindle falls. Thus, the amount of light received at any instant by receiver 62 is an analogue of the position of either valve at that instant such that output 64 can be used to operate indicator means giving an indication of the extent to which the valve is open or closed.

In a variation, either spindle 22A or 154 can be modified by mounting thereon, in place of the waisted shank 42, optical filter means, for example a key-hole filter or other filter having varying degrees of opaqueness or translucence along its length of travel across the optical path. Thus as the spindle moves so does the filter means whereby the intensity of the transmitted light is a function of the position of the valve member. Guide means can be provided to prevent rotation of the spindle about its axis.

If desired, the two fibre optic cables associated with block 38 or 158 could be replaced by a single cable arranged to be deformed to an extent which is a function of the position of spindle portion 22A or spindle 154.

In the modification in Figures 4A and 4B the fibre-optic cable 48 is mounted in a cover 200 screwed into the end of the housing 28. The light receiving end of cable 48 substantially directly facing the light emitting end of the cable 46 mounted in a spool 202 which is constrained to slide vertically within the cover 200 without rotation about the axis of the spool, the cable passing through a relatively large opening 204 in the cover to allow movement of the cable. The upper end of the spindle 22A is formed with a shoulder 206 and a spigot 208 engaging a spring 210 braced against the underside of the spool. A spring 212 interposed be tween the top 214 of the cover and the spool acts to hold the cables apart.

In Figure 4A the valve is closed and the optical path P is a maximum whereby the light received by cable 48 is a minimum. The spring 210 is primarily intended to absorb a substantial part of the vertical movement of the spindle in either direction but acts in combination with the spring 212 such that the spool 202 moves with the spindle in the same direction but through a distance which is a lesser amount than that used by the spindle. The combined effect of springs 210 and 212 can be to cause the spool 202 to move through a distance which is a pre-determined fraction of the spindle movement. In Figure 4B the valve is fully open showing the optical path has decreased to its minimum length so that the light received by cable 48 is a maximum for the optical system the Figures 4A and 4B.Therefore the receiver means 62 (Figure 1) is arranged to provide an output to indicate the valve is open when the receiver light signal increases above a pre-determined level or the ratio of the amount of light received by cable 48 to that as cable 46 decreases to pre-determined amount.

The arrangement in Figure 5 acts rather similarly to that in Figures 4A and 4B except that the optical path P is derived by reflecting the emergent beam from a cable 46 (mounted in the cover 200A) onto the end of the cable 48 using a dish reflector 220 in the upper surface of spool 202A. Vertical movement of the spool causing the optical path to vary in length being the shortest when the valve is fully open so that the light receives a cable 48 is a maximum.

The receiver 62 can be arranged to give an output signal which at any instant corresponds to the attitude of the valve member.

If the optical systems in Figures 4A to 5 are applied to the valve in Figure 3 the receiver 62 is arranged to respond to a light signal on cable 48 of a certain minimum intensity as indicating the valve is open and to certain maximum intensity as indicating the valve is closed.

Claims (14)

1. A fluid valve of the type referred to comprising a light conducting path having an input end into which light can be input for transmission along the path to an output end of said path, said path comprising varying means non-electrically operable to vary the amount of light transmitted beyond the varying means to the output end, and the arrangement being such that the varying means is caused to operate in accordance with the position of the valve member so that the amount of light transmitted to the output end is a function of the position of the valve member relative to the seat.

2. A fluid valve according to claim 1, wherein the light conducting path comprises an optical fibre.

3. A fluid valve according to claim 2, wherein the varying means comprises a portion of the optical fibre and a device for variably deforming said portion whereby transmission of light through said portion is variable between substantially total or a predetermined maximum at iow or substantially no deformation and a predetermined minimum at a predetermined maximum amount of deformation.

4. A fluid valve according to claim 2, wherein the light conducting path comprises first and second fibre-optic cables with an optical path between the two, and the varying means acts on the optical path to vary the amount of light reaching the second cable from the first.

5. A fluid valve according to claim 4, wherein the varying means comprises obstructing means operable to vary the extent it obstructs passage of light along the optical path to the second cable.

6. A fluid valve according to claim 5, wherein the obstructing means is a shutter device.

7. A fluid valve according to claim 4, wherein the varying means comprises optical filter means movable in the optical path to a varying extent depending on the attitude of the valve member.

8. A fluid valve according to claim 7, wherein the filter means comprises a key-hole filter.

9. A fluid valve according to claim 7, wherein the filter means has varying degrees of opaqueness or translucence along its length of travel across the optical path.

10. A fluid valve according to claim 4, wherein the varying means comprises an arrangement to vary the length of the optical path between a light emitting end of the first fibre optic cable and the light receiving end of the second fibre optic cable in accordance with the attitude of the valve member, whereby the intensity of the light received by the second cable varies.

11. A fluid valve according to claim 10, wherein the beam emergent from the light emitting end diverges outwardly relative to the beam axis, so that the longer the optical path the lesser the amount of light is incident on the receiving end.

12. A fluid valve according to claim 10 or 11, wherein the variation of the length of the optical path is achieved by moving the light emitting end relatively to the light receiving end or by moving relatively to either or both said ends reflecting means arranged to direct the beam from the emitting end onto the receiving end.

13. A fluid valve according to claim 12, therein the range of variation of the length of the optical path is smaller than the range of movement of the valve member and conversion means are provided to reduce the variation in optical path length to a predetermined fraction of the movement of the valve member.

14. A fluid valve substantially as hereinbefore described with reference to the accompanying drawings.