The present invention relates to valves for a fluid transport system. In particular the invention relates to a ball valve for use with liquids at low temperature, particularly in aircraft fuel systems.
In liquid transfer systems, the use of ball valves is well known. Ball valves generally have a spherical shroud, housing a spherical ‘ball’ acting as a closure member of the ball valve, which comprises an opening through its middle, to allow the passage of fluid through the valve along a flow path when the opening is aligned to direct flow through the shroud, and to prevent the passage of fluid when the spherical closure member is aligned substantially perpendicular to the direction of fluid flow in the flow path.
In many applications, the valve will be oriented to have a horizontal direction of flow through the shroud. This means that fluid can collect in the bottom of the spherical shroud. If the fluid which collects in the bottom of the shroud can solidify, for example if it is water and the water can freeze, then there is a risk that it could jam the valve in an open or closed position. In particular, in aircraft fuels systems, water can potentially find its way into the fuel, for example, by ingress of non-zero humidity air entering the tanks via the wing vents as they are emptied of fuel during engine operation, or by ingress of humid air when the tanks are opened to atmospheric levels of humidity during maintenance or dissolved water in the uplifted fuel during refuelling on the ground. It is therefore near impossible to prevent any water from being present in an aircraft fuel system. Where a sump exists in the fuel system, such as in the bottom of a spherical ball valve, water, being of greater density than fuel, will tend to collect in the sump. At normal operational altitudes, fuel temperatures can often be at below 0 degrees Centigrade and so water in the system may be prone to freezing. Water freezing in the sump of the ball valve can potentially therefore solidify and could prevent the valve from moving from a closed position to an open position, or vice versa.
The present invention therefore seeks to address these issues and to provide an improved valve for a fluid transport system.
A first aspect of the invention provides a fluid control valve comprising a valve body, having a valve chamber disposed between an inlet and an outlet of the valve, the valve chamber providing a fluid flow path between an inlet opening and an outlet opening of the valve chamber, a closure member configured to be rotated between a closed position, in which the flow path through the valve chamber is closed by the closure member closing one of the inlet and outlet openings, and an open position, in which the closure member is moved away from the flow path and the flow path through the valve chamber is open; wherein the valve chamber comprises an inner side wall which provides a substantially straight or substantially convex path through the valve chamber, so as to prevent fluid from gathering in the valve chamber when the valve is oriented with the side wall toward the bottom of the valve.
Accordingly, the present invention provides what can be termed a ‘sumpless’ valve, which operates in a similar manner to a conventional ball valve, but which, when appropriately oriented, avoids having any significant ‘sump’ in the valve, in which fluids may gather due to gravitational influence and subsequently solidify, which can in certain situations prevent actuation of the valve between open and closed positions.
The substantially straight or convex side wall extends through a major portion of the valve chamber, for example more than half of the extent of the valve chamber in a flow direction through the valve, so that a majority of the valve chamber has no sump in it. A small sump may be necessary near to the outlet or inlet which is sealed by the closure member, to enable proper sealing of the outlet or inlet, but the valve chamber is substantially sumpless, since the substantially straight or convex wall extends through more than a third of the length of the chamber, preferably through more than a half the length of the chamber, more preferably through more than two-thirds of the length of the chamber and more preferably through more than three quarters of the length of the valve chamber without descending below the level of a straight flow path between the inlet and the outlet.
The inner side wall may be planar, or it may have a concave shape when viewed in a direction of flow through the valve chamber. In either case the inner side wall is typically straight or convex when viewed in cross-section transverse to a direction of flow through the valve chamber—thereby providing a substantially straight or substantially convex path through the valve chamber.
The valve chamber may be at least part spherical. This allows the closure member to rotate out of a linear flow path through the valve chamber, into a part of the valve chamber which is out of the direct flow path, leaving a flow path through the valve which a substantially open bore and which is not obstructed by the closure member. Alternatively the part of the valve chamber which is out of the direct flow path may be non-spherical, for instance cylindrical.
The closure member may be at least part spherical. This allows the closure member to locate in a part spherical part of the valve chamber, out of the way of a principal, substantially straight, fluid flow path through the valve chamber. Alternatively the closure member may be at least part cylindrical, allowing it to locate in a part cylindrical part of the valve chamber.
The closure member may be arranged to rotate toward a side of the valve chamber substantially opposite the substantially straight or substantially convex inner side wall. This can further assist with removing the closure member from the principal flow path through the valve chamber when the valve is open.
The closure member may comprise a seal located in a substantially circumferential groove on a part-spherical surface of the closure member. This can assist with sealing the valve shut when the closure member is in its closed position.
The substantially straight or substantially convex inner side wall may comprise a recess for receiving a portion of the closure member. This can assist with permitting full engagement around the full circumference of the closure member to close the opening, and if any seal is present, helps engage the seal with the inlet or outlet opening which is closed by the closure member.
The recess may have a depth of around 10% of the width of the flow path through the inlet or outlet opening, which is engaged by the closure member to close the flow path.
The recess is sized to just retain the lower portion of the rotatable closure member and is shaped to provide a laminar flow when the valve is open. In the prior art designs shown in
The recess may have a first inclined surface arranged toward the inlet and a second inclined surface arranged towards the outlet. The first inclined surface may be arranged at a first angle relative to the substantially straight or substantially convex inner side wall. The first angle is preferably greater than a second angle, at which the second inclined surface is arranged relative to the substantially straight or convex inner side wall.
A rotation axis, around which the closure member rotates between its closed and open positions may be offset from a centre, or a centre of curvature, of the valve chamber. The offset may be configured such that on rotating the closure member toward its closed position, a substantially radial gap between an outer surface of the closure member and an inner surface of the valve chamber is reduced. This can allow a gap to be provided between the closure member and the inner surface of the valve chamber when the valve is open, which can help with flushing of the valve and also avoid wear on seals provided on the closure member, but can also allow positive engagement of the closure member with the inlet or outlet opening to close the flow path. Where a seal is present, this can further enable the seal to be compressed against the inlet or outlet to prevent flow through the valve.
The closure member may comprise a seal and the reduction in the substantially radial gap may therefore compress the seal.
The closure member may be radially displaceable relative to a rotation axis, about which the closure member is arranged to rotate between its open and closed positions. This can enable the closure member to be advanced toward and away from the inlet or outlet which it is arranged to close, to open or close the flow path through the valve. This can further enable establishment of a positive seal between the valve body and the closure member. Retraction of the seal from the surfaces which it engages to seal the valve, can allow movement of the closure member between its open position its closed position without creating friction or wear between the seal and the walls of the valve or valve chamber.
A retraction mechanism may be provided and may be arranged to retract the closure member toward the rotation axis. This can facilitate retraction of the closure member to enable it to rotate away from the inlet or outlet with which may be arranged to engage to close the flow path through the valve.
The retraction mechanism may comprise a cam mechanism arranged to draw the closure member toward the rotation axis on rotation of a rotatable member of the cam mechanism. This allows retraction of the closure member from the inlet or outlet to be carried out via a rotational input.
The valve may further comprise a fixed guide and a follower member connected to the closure member. The follower member may be arranged to follow a profile of the fixed guide as the closure member is rotated between its closed and open positions. This allows the radial position of the closure member relative to its rotation axis to be controlled during rotation of the closure member between its open and closed positions.
The fixed guide may comprise a substantially arcuate portion. This can help to maintain the closure member at a substantially fixed radial position relative to its rotation axis during at least a part of its movement between its open and closed positions.
The profile of the fixed guide may comprise a notch, arranged to permit the closure member to move away from the rotation axis to close the flow path. The notch may be a radially extending portion of the fixed guide, extending radially relative to the rotation axis of the closure member. This can allow radial displacement of the follower member relative to the rotation axis.
A biasing element may be provided and may be arranged to bias the closure member away from the rotation axis. This can help to bias the closure member into a closed position, where it engages the inlet or outlet opening of the valve chamber.
The retraction mechanism may comprise a rotatable cam member, arranged to engage a follower member connected to the closure member, to retract the closure member on rotation of the rotatable cam member.
The follower member may be arranged to engage both of the rotatable cam member and the fixed guide. This enables a single follower member to be used to take a retraction input from the rotatable cam member and also to align the closure member relative to the fixed guide during rotation of the closure member between its open and closed positions.
The closure member may be rotatable about, and axially displaceable relative to, a rotation axis about which the closure member rotates between its open and closed positions.
Typically the valve is oriented with the inner side wall toward the bottom of the valve.
Typically the closure member is configured so that the one of the inlet and outlet openings which is closed by the closure member in its closed position is clear of obstruction by the closure member when the closure member is in its open position.
Typically the closure member is arranged to rotate into a side of the valve chamber outside the flow path when it is rotated to its open position.
Typically the fluid flow path between the inlet opening and the outlet opening of the valve chamber is substantially cylindrical or frustoconical.
Typically the fluid flow path between the inlet opening and the outlet opening of the valve chamber is not obstructed by the closure member when the closure member is in its open position. In one embodiment the fluid flow path between the inlet opening and the outlet opening of the valve chamber is obstructed by a drive shaft of the closure member when the closure member is in its open position, but in another embodiment it is not obstructed by the closure member, or any other part, when the closure member is in its open position.
The configuration of the rotatable closure member and/or the retraction mechanism may be advantageously implemented in combination with any form of valve chamber, although their use in combination with the substantially straight or convex lower side wall is preferred.
The valve may find utility in any road, rail, marine, space or airborne vehicle, in particular an aircraft, or in any fluid control system, particularly for use with water contaminated liquids where low temperatures may occur.
Embodiments of the invention will now be described with reference to the accompanying drawings, in which:
Typical aircraft fuel valve requirements are as follows and can be relevant to the requirements of the valve of the present invention:
To allow or terminate the flow of fuel on command from the Fuel Controller.
To minimise fuel flow resistance when open.
To be safe from rupture or collapse due to either high positive or negative internal pipe pressure.
To typically have a horizontal axis to enable the valve to be located externally to the fuel tank adjacent the (typically spar mounted) valve actuating motors in the wing.
To work over a large temperature range −55° C. to +85° C.
The present invention proposes an alternative structure for a ball valve, which is based upon a structure for a general ball valve illustrated in
A closure member 207 is provided for closing the outlet opening 206. It will be appreciated that the inlet opening 205 and the outlet opening 206 can be reversed by connecting the valve such that the fluid flow flows in an opposite direction to that indicated by arrow 208. The inlet and outlet of the valve are therefore substantially interchangeable although in view of the configuration of the valve, it can be preferable to have the normal direction of fluid flow through the valve in the inlet to outlet direction indicated by arrow 208 in the figure. This is because pressure from the inlet side when the valve is closed will tend to bias the closure member 207 toward the outlet opening 206 which it closes, which increases the sealing force of the closure member 207 at the outlet opening 206. It can therefore be preferable to have the closure member arranged to close the outlet opening 206. Conversely, if the closure member is arranged to close the inlet opening, the force required to open the valve may be reduced, which may be beneficial in certain circumstances. The closure member 207 is arranged so as to be rotatable about a rotation axis 209. The rotation axis may preferably be located at or near to a substantial centre of the valve chamber. By rotation of the closure member 207 in a direction of arrow 210, the closure member 207 can be rotated upwardly in the Figure and substantially out of the flow path from inlet to outlet through the valve, indicated by arrow 208. A connecting member 211 can be provided to connect the closure member 207 to its point of rotation 209. An O-ring seal 212 may be located on the outer part-spherical surface 213 of the closure member, to improve its sealing engagement with the inner walls of the valve chamber 204, or with the outlet opening 206.
As can be seen in the Figure, the valve chamber 204 includes a substantially straight inner side wall 214, which provides a substantially straight path through the valve 2. The wall 214 is substantially straight in the direction of flow through the valve, so it appears straight when viewed in cross-section from the side as in
When the valve is appropriately oriented with the substantially straight inner side wall toward the bottom of the valve with gravity acting in a direction of arrow 20, then the build-up of fluid in the bottom part of the valve can be avoided. The valve is therefore sumpless, since the volume of the valve chamber below a lowest straight line drawn between the inlet to the outlet (in other words, below the cylindrical volume 330) is minimised or reduced to zero. Such minimisation or reduction to zero of this sump volume may also be achieved by a substantially convex inner side wall 214 being oriented toward the bottom of the valve. That is, rather than providing a substantially straight path through the valve as shown in
The closure member 307 is mounted on a shaft 309a running along the axis of rotation 309 which is driven by a motor (now shown) on the right-hand side of the valve (in the viewing direction of
The lower part of the chamber may be circular in cross-section as shown in
When the closure member 307 is moved to its open position as in
As shown in
Moving the valve back to the closed position is essentially a reversal of the process of opening the valve. From the position illustrated in
It can be preferable to a have a small recess 70 in the lower part of the valve in order to allow the closure member 207 and the preferable seal 212 to properly close the outlet opening. Any such recess can represent a potential “sump”, where fluids may gather and potentially solidify if left in that location. However, appropriate dimensioning of the recess 70 can ensure that any fluids at risk of solidification are flushed from the recess 70 during operation of the valve, such as when it is in its open state.
As can be seen in
It is also possible to provide a profile in fixed guide 403 which has a profile toward its closed end, the closed end designating the end at which the follower member 406 is located when the valve is in its closed configuration, the profile being configured to guide the follower member to extend the closure member 307 away from the rotation axis 209 in order to force the closure member to a sealed position against the inlet or outlet opening which it closes, and to lock it in place by nature of the rotational force holding the valve in its closed position.
All embodiments on the invention can be used in conjunction with a rotational input, such as from an electric or hydraulic drive motor, or any form of rotational input means. The input means is preferably reversible to provide reversible rotation between the open and closed configurations of the valve.
It will be apparent from the above description that the invention can optionally provide a valve comprising a ball valve rotor, in which the ball has been deleted and replaced by a partial-arc-shaped, or at least partially spherical seal.
The valve chamber can be formed with a partially spherical shroud, provided with a flattened wall at the bottom, such that the partial-arc-shaped or part-spherical valve rotor or closure member can rotate by around 90 degrees from an open position to a closed position. A spherical valve can be provided without a lower sump recess. A small recess in the lower shroud or valve chamber may be provided to accommodate the end of travel of the closure element to its closed position, and to accommodate the o-ring seals. The optional retraction mechanism withdrawal mechanism can improve seal life.
A sumpless ball valve of the invention can therefore preventing water (from the fuel) collecting and freezing, and consequentially jamming the mechanism.
A single o-ring or equivalent seal can be provided, while ensuring all parts of the mechanism are flushed by fuel when in the open configuration. The small lower recess void can be shaped to ensure turbulence flushes any moisture through when open.
The valve may comprise no sealed voids, when open, where water or other relatively dense materials can collect, freeze and jam the mechanism.
For 2-way flows where water is not an issue, closure members of the present invention may be duplicated, facing in opposite flow directions, with optional duplicated retraction mechanisms as described above, but facing in opposite direction to one another. This would enable high pressure bi-directional flows to be effectively sealed, which flows could otherwise have the potential to overcome the spring loading force encouraging the closure member to its closed position due to pressure on the closure member.
Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.
Number | Date | Country | Kind |
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1422323.4 | Dec 2014 | GB | national |