GB2377004A

GB2377004A - Reversing valve

Info

Publication number: GB2377004A
Application number: GB0221587A
Authority: GB
Inventors: William Tsui; Frank Clifford
Original assignee: Falmer Investments Ltd
Current assignee: Falmer Investments Ltd
Priority date: 1998-10-19
Filing date: 1998-10-19
Publication date: 2002-12-31
Also published as: HK1025618A1; GB0221587D0; GB2342979B; CN1251889A; GB2342979A; CN1103417C; GB9822825D0

Abstract

A reversing valve 4 extends through a pillar 2 which supports a vessel 1 used for dyeing yarn 11 or other textile material. Valve 4 is used to divert a primary flow circuit P into a secondary flow circuit through the yarn 11 and has a valve element (16,21 figure 4) which is rotatable to reverse the direction of flow in the secondary circuit. A drive 9 acts on the periphery of the valve element (16, 21) to produce rotation, and thus only a small force is required to rotate and hold the position of the valve element (16, 21). The valve element (16, 21) comprises a tube (16) through the wall of which are provided apertures (19, 20) and an internal divider (21) defining first and second passageways, the first leading from an upstream end of the valve element (16, 21) to apertures (19) and a second leading from apertures (20) to a downstream end of the valve element (16, 21).

Description

REVERSING VALVE The present invention relates to a reversing valve for reversing fluid flow to a device, such as a device used for dyeing yam or other textile material.

In a known arrangement, a reversing valve is incorporated in a primary fluid flow circuit around which fluid is pumped by a pump. The direction of fluid flow around the primary fluid flow circuit is not changed. The reversing valve is used to divert fluid from the primary circuit into one end of a secondary fluid flow circuit that passes through the dyeing equipment. At the end of the secondary fluid flow circuit, the reversing valve collects the fluid and returns it to the primary circuit. By adjusting the reversing valve, the direction of fluid flow around the secondary circuit may be reversed. This reversal of the secondary circuit flow is required for the operation of the dyeing equipment. Sometimes the fluid will be a liquid, and other times it may be air when, for example, it is desired to perform a drying operation in the dyeing equipment.

The known reversing valve is positioned below the vessel of the dyeing equipment. It comprises a vertical tube having an inlet and an outlet which are connectable to the primary flow circuit and which are circumferentially spaced apart around the tube at a separation of, say, 90 degrees. Within the tube is a generally L- shaped valve element having a vertical arm which is aligned with the central vertical axis of the outer tube and a horizontal arm which may be rotated in a generally horizontal plane by rotating the valve element about the central axis passing through the vertical arm. In this way, the horizontal arm may be made to move between the inlet and outlet connected to the primary flow circuit. The top of the vertical arm is connected to one end of the secondary flow circuit, and the annulus formed between the valve element and the tube is connected to the other end of the secondary flow circuit. With this arrangement, whilst the direction of fluid flow around the primary flow circuit remains constant, the direction of fluid flow around the secondary flow circuit may be varied by pivoting the L-shaped valve element around the vertical axis so as to move the horizontal arm between being in fluid communication with the inlet and the outlet in the tube wall.

A disadvantage with this arrangement is that, when moving between the two operational positions of the valve element, the fluid is able to bypass the secondary flow circuit by flowing directly from the inlet to the outlet of the reversing valve. When the valve element is in such an intermediate position, the fact that the fluid flow is bypassing the secondary flow circuit causes the output pressure of the pump in the primary flow circuit to fall and the current of the motor driving the pump to rise to a maximum. The motor current bears an inverse and a non-proportional relationship to the flow rate. Although changes in flow rate take place in response to movement of the valve element, the linear proportionality necessary for accurate control cannot be provided.

A further disadvantage is that it is not possible to use the reversing valve to isolate the secondary flow circuit from the primary flow circuit. Thus, the load of yarn or other textile material in the dyeing vessel cannot be isolated. Thus, it is difficult to change over the yam when treatment has been completed.

It has been a common practice to include a butterfly valve in the primary flow circuit for throttling purposes, and to combine its use for this purpose with the ability to provide isolation of the load in the dyeing vessel.

However, particularly with the larger sizes of butterfly valve, the extremely high fluid velocity as the valve is cracked open tends to hold it closed, and the torque required to open a butterfly valve from the closed position can be very high. Once partly open, however, it tends to snap more fully open as the momentum of the flowing fluid pushes the butterfly valve element out of the way. Conversely, the butterfly valve tends to snap shut when approaching the closed position. Because of the very variable torque required to control the position of the butterfly valve element, it is difficult to achieve a high level of accuracy of flow control.

It is possible that difficulties experienced in attempting to control the flow in prior art arrangements, often blamed on inaccurate flow meters, have in fact been due to the unsuitability of the butterfly valve for use in such an arrangement.

With the known reversing valve positioned at the bottom of the dyeing equipment, a shaft for controlling the reversing valve is positioned below the valve and

extends vertically upwards along the vertical central axis thereof, into the valve and into engagement with the vertical arm of the valve element. Consequently, the shaft and the reversing valve are usually positioned close to floor level. This low level makes access difficult, together with the fact that the components may well be concealed by pipes and valves which an operator would not wish to touch as they would be hot. Furthermore, the shaft and reversing valve may be corroded by spillages from the dyeing equipment The difficulty of access quite often means that the reversing valve is neglected in relation to maintenance.

It is possible to use a horizontal shaft rather than a vertical shaft, to apply torque to the valve element, but this has a complicated construction which increases size and expense. The vessel of the dyeing equipment has traditionally been supported on three or more legs which are welded to the vessel. This spaces the vessel above the level of the floor so that the reversing valve and its drive shaft maybe positioned below the vessel. However, the weight of the vessel when full of liquid and loaded with yarn or other textile material can be considerable, and this can apply considerable stress to the relatively small areas of the welds that connect the vessel to the legs. Chemicals that are spilt can partially evaporate and result in chemical attack on the welds. Vibration that occurs during the operation of the equipment and the repeated fluctuations in temperature can also contribute to stress corrosion cracking of the welds which may be difficult or impossible to repair.

According to a first aspect of the present invention, there is provided a reversing valve for reversing fluid flow to a device, the reversing valve comprising: a valve body having a bore extending from an inlet to an outlet; a plurality of ports in the wall of the bore; a valve element disposed in the bore and rotatable to change the port (s) in fluid communication with the bore inlet and the port (s) in fluid communication with the bore outlet; and drive means arranged to act on the periphery of the valve element to produce circumferential rotation thereof

The bore inlet and bore outlet may be used to connect the reversing valve into a primary flow circuit. The ports may be connected to the ends of a secondary flow circuit, and the valve element is such as to be rotatable to reverse the flow direction around the secondary flow circuit. In a first rotational position, the bore inlet may be in fluid communication with a first end of the secondary circuit via one or more of the ports and the bore outlet may be in fluid communication with a second end of the secondary circuit via one or more of the ports. In a second rotation position, the bore inlet is in fluid communication with the second end of the secondary circuit via one or more of the ports and the bore outlet is in fluid communication with the first end of the secondary circuit via one or more of the ports.

Instead of using a central axial shaft to rotate the valve element, the present invention provides a drive means which is arranged to act on the periphery of the valve element to produce rotation. Because the drive means acts on the periphery, the force required to rotate and position the valve element is reduced. Also, the configuration of the reversing valve is such that fluid flowing through the valve does not tend to apply a troublesomely large circumferential force to the valve element that has to be countered by the drive means. Thus, it is possible to provide accurate positioning of the valve element.

Peripheral rather than central actuation of the valve element gives the designer greater freedom in positioning the drive means relative to the pipework that will, in use, be in the vicinity of the reversing valve.

A wide variety of drive means may be used. For example, in one embodiment, the drive means comprises an actuator which extends tangentially of the bore and carries a drive element which projects inwards into the bore and into a hole in the periphery of the valve element.

In an alternative embodiment, the drive means comprises a rack which extends tangentially of the bore and engages with pinion teeth arranged circumferentially of the valve element.

A first set of ports may be provided for fluid communication with the bore inlet, and rotation of the valve element will switch between these ports so as to place the bore

inlet in fluid communication with the different ends of the secondary flow circuit Similarly, a second set of ports may be provided for fluid communication with the bore outlet, and rotation of the valve element will switch between these ports so as to place the bore outlet in fluid communication with the different ends of the secondary circuit In an alternative arrangement, the valve element is rotatable between (i) a first position in which a first one or plurality of the ports is or are in fluid communication with the bore inlet and a second one or plurality of the ports is or are in fluid communication with the bore outlet and (ii) a second position in which the first port (s) is or are in fluid communication with the bore outlet and the second port (s) is or are in fluid communication with the bore inlet. This is a more economical arrangement as each port functions as an inlet/outlet port and therefore has a dual function, since each port is responsive to circumferential rotation of the valve element to switch between being in fluid communication with the bore inlet and being in fluid communication with the bore outlet.

Preferably, inlet and outlet chambers of the bore separated by the valve element overlap along the bore axis. This overlapping increases the possibilities available for the positioning of the ports. To take advantage of the increased possibilities, it is preferable that the ports are positioned longitudinally of the bore at the overlap, rather than upstream or downstream of the overlap. A particularly favourable arrangement is where the ports lie on a common circumference of the bore.

In the preferred embodiment, the valve element has one or more first passageways leading from the upstream end of the valve element to one or more radially outwardly facing first apertures and one or more second passageways leading from the downstream end of the valve element to one or more outwardly facing second apertures.

Preferably, the first and second apertures lie on a common circumference of the valve element.

In our preferred embodiment, the valve element comprises a tube through the wall of which are provided the first and second apertures, and an internal divider defining the first and second passageways inside the tube.

Depending on the length of the valve element relative to the bore, the first and second passageways may respectively comprise all or some of the inlet and outlet chambers of the bore.

The internal divider may comprise a plurality of plates which extend generally longitudinally of the valve element and separate the first and second passageways.

Preferably, the valve element has an intermediate position at which it closes all of the ports. Such an intermediate position is desirable because it enables the primary flow circuit to be isolated from the secondary flow circuit, so that, for example, yarn or other textile material being treated by the dyeing equipment incorporated in the secondary flow circuit may be replaced after it has been treated.

According to a second aspect of the present invention, there is provided apparatus comprising a device requiring reversal of fluid flow and a reversing valve according to the first aspect of the present invention.

Preferably, the device comprises a vessel supported on a pillar, and the reversing valve extends transversely through the pillar. Because the pillar is provided, there is no need to support the vessel on legs as in the prior art, and this removes the risk of the failure of the welds connecting the legs to the vessel. The pillar may be of sufficient diameter to provide a strong and stable support to the vessel.

Preferably, a part of the valve element is outside the pillar. Consequently, the drive means may also be positioned outside the pillar. This removes the need for seals and the like to enable the drive means to penetrate into the pillar to act on the valve element.

Preferably, the device has a central duct within the pillar, with the duct being at one end of a fluid circuit of the device and being connected to a first one or plurality of the ports of the reversing valve, and with a space between the duct and the pillar being at the other end of the fluid circuit and being connected to a second one or plurality of the ports of the reversing valve. Conveniently, the space in the pillar is annular.

A non-limiting embodiment of the present invention will now be described with reference to the accompanying drawings, in which :-

Fig. 1 is a perspective view of a reversing valve according to the present invention when installed in dyeing equipment, with the dyeing equipment being only partially shown and being shown in cut away ; Fig. 2 is a view generally similar to that of Fig. 1, but showing more of the overall apparatus, when the secondary flow circuit is set up for so-called inside-out flow ; Fig. 3 is similar to Fig. 2, when the secondary flow circuit is set up for so-called outside-in flow; Fig. 4 shows the assembly sequence for the reversing valve of Fig. 1; Fig. 5A and Fig. 5B are sectional and perspective views respectively, showing the operation of the reversing valve during inside-out flow; and Fig. 6A and Fig 6B are sectional and perspective views respectively of the reversing valve, showing its operation during outside-in flow.

Referring firstly to the overall apparatus shown in Fig. 1, dyeing equipment comprises a vertical cylindrical vessel 1 which is supported by a tubular pillar 2 on a solid base plate 3. Because the pillar 2 provides a sturdy support to the vessel 1, there is no need to provide the mounting legs used in the prior art to support the vessel.

A reversing valve 4 in accordance with the present invention pierces through the pillar 2 from side to side thereof along a diameter, such that the two ends of the valve 4 are externally accessible.

The reversing valve 4 has a top port 5 which communicates with a duct 6 of the dyeing equipment. The duct 6 transforms in shape in the upward direction from the rectangular shape of the top port 5 to the circular shape of a seat 7.

The reversing valve 4 also has two side ports 8 (only one of which is visible in Fig. 1).

The reversing valve 4 has two operational positions, and rotation between those positions is achieved by actuating and controlling a drive means 9.

The ends of the reversing valve 4 are connected into a primary flow circuit round which fluid is pumped by a pump driven by a motor. Arrows P indicate the flow direction of the primary flow circuit. This flow direction does not change The

reversing valve 4 is used to divert fluid from the primary flow circuit into a secondary flow circuit, and to receive fluid from the secondary flow circuit and to return it to the primary flow circuit In Fig. 1, the arrows A on the left-hand side show a first mode of flow around the secondary flow circuit when the reversing valve 4 has been rotated to be in a first one of its operational positions. As can been seen, fluid exits the top port 5 and flows out of the top of the duct 6 and would enter the secondary flow circuit Fluid that has passed around the secondary flow circuit then enters the side ports 8 so as to return to the primary flow circuit.

The right-hand side of Fig. 1 has arrows B which show the flow around the secondary flow circuit in a second mode, the reverse of the first mode, when the reversing valve 4 has been rotated to its other operational position. In the second mode, the fluid enters the secondary flow circuit by exiting the side ports 8 It returns to the primary flow circuit by flowing down the duct 6 and into the top port 5 Of course, the first and second flow modes of the secondary flow circuit never exist at the same time as illustrated in Fig. 1. Fig. 1 merely shows both flow modes to try to illustrate what may be achieved by rotating the reversing valve 4 between its two operational positions.

The reversing valve 4 has an intermediate position which is rotationally between its two operational positions. At this intermediate position, the ports 5,8 are closed so as to isolate the secondary flow circuit from the primary flow circuit This enables a load in the vessel 1 to be changed or other operations to be performed on the load Fig. 1 is somewhat diagrammatic, and more detail is shown in Figs 2 and 3 of the apparatus comprising the dyeing equipment and the reversing valve.

In Figs. 2 and 3, there is shown a carrier 10 which sits on the seat 7 and carries a load in the form of bobbins 11 of yarn on perforated tubes.

In the first flow mode of the secondary flow circuit shown in Fig. 2, the fluid passes up the duct 6, into the perforated tubes, radially outwards through the bobbins 11, down past the outer circumference of the carrier 10 adjacent to the side wall of the vessel 1, down the annulus that exists between the pillar 2 and the duct 6 and in through

the two side ports 8 to return to the primary flow circuit. This may be termed inside- out flow.

In Fig. 2, the arrows P of the flow direction in the primary flow circuit are labelled, but all of the other arrows in Fig. 2 are not labelled as there are so many of them All of those other arrows indicate the flow around the secondary flow circuit in the first mode.

In order to reverse the flow direction in the secondary flow circuit, so as to move from the first mode shown in Fig. 2 to the second mode shown in Fig 3, the reversing valve 4 is rotated to its other operational position. For the illustrated embodiment, this involves a rotation through 90 degrees.

For the second flow mode around the secondary flow circuit shown in Fig 3, the fluid leaves the primary flow circuit through the side ports 8, and passes vertically upwards through the annular space 12 between the duct 6 and pillar 2. It then flows up past the outer circumferencial periphery of the carrier 10 and flows radially inwards through the yam of each bobbin 11. The fluid is then collected by the perforated tubes at the centres of the bobbins 11. The fluid flows down the hollow interiors of the perforated tubes and is collected together and flows through the centre of the seat 7 down the duct 6, to return into the primary flow circuit through the top port 5 Again, for the sake of clarity, in Fig. 3 only the arrows P for the primary flow circuit are labelled as such. All of the other, unlabelled arrows show the flow around the secondary flow circuit in the second flow mode.

The flow shown in Fig. 3 is outside-in flow in view of the fact that the flow flows from the outside of each bobbin 11 radially inwards to the core thereof.

Fig. 4 shows the steps (i)- (v) used to make the illustrated embodiment of the reversing valve 4. The completed reversing valve is shown at Fig. 4 (v).

The reversing valve 4 comprises a valve body in the form of a tube 13 having a cylindrical bore 14. Flanges 15 are attached to the ends of the tube 13 to enable the reversing valve 4 to be attached to the pipework of the primary flow circuit so that the reversing valve is integrated in the primary flow circuit.

The port 5 is provided at the top of the tube 13 and the ports 8 are provided at the sides of the tube.

A rotatable valve element comprises a tube 16 having a cylindrical outer surface 17 and a cylindrical inner bore 18. The outer surface 17 slideably rests against the bore 14 of the tube 13 to permit the valve element to rotate in the valve body.

The tube 16 has top and bottom rectangular apertures 19 which are the same size as the top port 5. It also has two rectangular side apertures 20, each of which is also the same size as the top port 5. The apertures 19,20 are equiangularly spaced around the tube 16 and are therefore separated from each other by 90 degrees The rotatable valve element comprises, in addition to the tube 16, an internal divider 21 which separates the bores 14,18 into an upstream chamber 22 which leads from the upstream, inlet end of the reversing valve to the apertures 19, and a downstream chamber 23 which leads from the apertures 20 to the downstream, outlet end of the reversing valve.

The two chambers 22,23 overlap each other along their full lengths and are substantially the same length as the valve element itself The upstream chamber 22 splits into two in the flow direction to provide separate passageways leading to the apertures 19. From the apertures 20, the downstream chamber 23 starts off as two passageways which then join together by the time they reach the downstream, outlet end of the reversing valve.

Because of the overlap of the chambers 22,23, the apertures 19,20 are positioned on a common circumference of the tube 16. Consequently, the ports 5,8 are also positioned on a common circumference of the tube 13. This convenient arrangement means that the reversing valve is longitudinally compact.

The internal divider 21 uses four longitudinal plates 24 to separate the chambers 22,23 in the circumferential direction. End plates 25 are used to complete the isolation of the upstream chamber 22 from the downstream chamber 23.

After the plates 24,25 shown in Fig. 4 (i) have been welded together to produce the internal divider 21 shown in Fig. 4 (ii), the assembled internal divider 21 is longitudinally slid into the bore 18 of the tube 16 and welded thereto to produce the

valve element. The assembled valve element is then slid longitudinally into the bore 14 of the tube 13 so that the cylindrical outer surface 17 of the valve element is rotatably slideably supported by the bore 14. The resulting reversing valve (minus drive means) is shown in Fig. 4 (v).

Rotation of the valve element 16,21 is achieved by applying a circumferential force tangentially to the outer periphery of the valve element rather than using the traditional central shaft of the prior art to apply a rotational torque to the central axis of the valve element.

Drive means to rotate the valve element may be positioned at any longitudinal position of the reversing valve. However, as shown in Figs. 1-3, it is convenient that the drive means 9 should be positioned outside the dyeing equipment, specifically outside the pillar 2 at one end of the reversing valve. An air-operated piston and cylinder device 91 carries a radially-inwardly extending peg 92 (visible in Figs. 1-3) which is carried by the piston or a rod-like extension of the piston of the device 91.

The peg 92 projects into a hole in the tube 16. Thus, when the device 91 reciprocrates through a range of movement, the peg 92 is able to impart a range of rotational movement to the valve element 16, 21. The arrangement is such that the valve element is rotated between its two operational positions shown in Figs. 5 and 6 which are rotationally separated from each other by 90 degrees.

The piston or the rod-like extension of the piston of the device 91 which carries the peg 92 will need to pass through a seal such as an 0 ring or the like, in order to prevent fluid from leaking out of the primary flow circuit. The hole in the tube 16 which receives the peg 92 may be oval, or otherwise specially shaped, in order to accommodate the rotation of the peg 92 relative to the hole as the peg 92 is reciprocated in a linear manner to produce rotation of the valve element. The intention is that, at all rotational positions of the valve element, there should be little or no play between the peg 92 and the hole in the tube 16, so as to enable accurate rotational positioning of the valve element and the accurate holding of any rotational position selected.

Figs. 5A and 5B show the first operational position of the valve element for producing the inside-out flow in the secondary flow circuit, as shown in Fig. 2 In the primary flow circuit, air is pumped around by a blower and is heated prior to reaching the reversing valve. The air is wetted as it passes along the secondary flow circuit and flows in an inside-out manner through the bobbins, prior to returning to the primary flow circuit where it is cooled and dried. The air then circulates around again To move from the first operational position shown in Figs. 5A and 5B, the drive means 9 is operated to extend or contract as appropriate, to move the peg 92 linearly to produce rotation of the valve element 16,21 to rotate through 90 degrees to move from the position shown in Fig. 5A to the position shown in Fig. 6A. In doing so, the circumferential lands between the apertures 19,20 pass through a position at which they close all of the ports 5,8. In this intermediate position of the valve element, flow round the primary and secondary flow circuit is stopped. Because the internal divider 21 blocks direct flow from the inlet to the outlet of the reversing valve, there is never any unwanted bypassing of the secondary flow circuit that would have the undesirable effect, evident in the prior art, in which the output pressure of the pump of the primary flow circuit drops, causing the electrical current of the motor which drives the pump to rise to a maximum value.

Having passed through the intermediate position, the final part of the rotation through 90 degrees takes the valve element to the second operational position shown in Fig. 6A. In this operational position, the reversing valve is configured to produce the outside-in flow in the secondary flow circuit as shown in Fig. 3.

The reversing valve may be returned from the second operational position to the first operational position by activating again the drive means 9. Thus, repeated reciprocation of the drive means can be used to repeatedly move the reversing valve between its two operational positions, each time passing through the intermediate position at which all of the ports 5,8 are closed. There are many possible ways in which the desired rotation of the valve element could be achieved, in which a tangential force is applied to the circumference of the valve element rather than to the central axis thereof. For example, instead of using the peg 92 which projects into a hole of the tube

16, a rack-and-pinion arrangement could be used in which pinion teeth are provided around a circumferential part of the cylindrical outer surface 17 of the tube 16 and these teeth are driven by a rack provided as an extension of the reciprocating piston of the piston and cylinder device 91.

In all of the rotational positions of the valve element, the fluid (whether air or liquid) does not interact with the valve element to produce large or very variable rotational forces acting on the valve element which would have to be resisted by the drive means 9. In fact, comparatively small forces applied by the drive means 9 are able to accurately provide the desired rotational position of the valve element throughout the range of rotational movement of the valve element. A small force provided by the drive means is sufficient because it is acting at a maximum distance from the central axis of the valve element rather than, as in the prior art, directly on the central axis.

In Figs. 1-3, the top of the vessel 1 used to produce a closed vessel is not shown for the sake of clarity. When the valve element is in its intermediate position and the secondary flow circuit is isolated from the primary circuit, the vessel 1 may be opened and the carrier 10 with its bobbin 11 removed. A new carrier 10 with further bobbins 11 may then be inserted into the vessel 1, the vessel closed and the valve element moved to an operational position so that processing may recommence.

Because there is only a single port 5, whereas there are two ports 8, each port 8 is half the size of the top port 5 by virtue of having half the circumferential width even though the longitudinal length is the same. Thus, the cross-sectional area provided by the top port 5 at one end of the secondary flow circuit matches the cross-sectional area provided by the two side ports 8 at the other end of the secondary flow circuit With the valve element in its intermediate position, so that the load of bobbins 11 is isolated from the primary circuit, the main circulating pump of the primary circuit may be used for an auxiliary function such as filling the vessel 1 with liquid at the beginning of an operational process, or emptying the vessel 1 of liquid at the end of an operational process, through auxiliary pipework which is not shown.

By moving gradually from the central, intermediate position towards either of the two operational positions at the extremes of rotational movement of the valve

element, an operator can select a particular rotational position between the intermediate position and one of the maximum operational positions to provide a particular desired flow rate which is less than the full flow rate. This is useful when the material being treated, such as the yarn on the bobbins 11, varies in characteristics such as permeability, and it is desired to chose a particular flow rate to suit the characteristics of the material.

Thus, the operator can freely select any flow rate between a zero flow rate provided by the intermediate position and a maximum flow rate, in either flow direction of the secondary flow circuit, provided by the two fully-rotated operational positions of the valve element. It has been found that the torque required to rotate the valve element is substantially constant throughout the full range of rotational positions of the valve element. This substantially constant torque may therefore be provided by a substantially constant tangential output force produced by activating the drive means 9 To provide smooth and low-friction rotation of the valve element 16,21 in the tube 13 of the valve body, the valve element may be supported around its cylindrical outer surface 17 by sleeves of low-friction material. Alternatively, it could be rotatably supported internally in any suitable way.

The drive means 9 could be positioned above the valve body rather than below, as illustrated. The drive means 9 may be provided with a locking mechanism for holding the intermediate rotational position of the valve element. For example, an actuator could be used to insert a locking pin into the piston of the piston and cylinder device 91 to prevent further movement, until the locking pin is removed.

Quite often, there is not a perfect seal of the cylindrical outer surface 17 of the valve element against the cylindrical bore 14 of the valve body. Thus, there will be a small amount of leakage of fluid directly from the upstream, inlet end of the reversing valve to the downstream, outlet end of the reversing valve. Also, when the valve element is in its intermediate position so as to close the ports 5,8, there may be a small amount of leakage between the primary and secondary flow circuits. It may therefore be necessary to drain or depressurize the vessel 1 before removing and replacing the load that it contains. Under these circumstances, the reversing valve is limited to

providing a reversing function, and does not also provides a sealing or isolating function.

Claims

CLAIMS 1. A reversing valve for reversing fluid flow to a device, the reversing valve comprising: a valve body having a bore extending from an inlet to an outlet; a plurality of ports in the wall of the bore ; a valve element disposed in the bore and rotatable to change the port (s) in fluid communication with the bore inlet and the port (s) in fluid communication with the bore outlet; and drive means arranged to act on the periphery of the valve element to produce circumferential rotation thereof; wherein the valve element has one or more first passageways leading from the upstream end of the valve element to one or more radially outwardly facing first apertures and one or more second passageways leading from the downstream end of the valve element to one or more outwardly facing second apertures.
2. A reversing valve according to claim 1, wherein the drive means comprises an actuator which extends tangentially of the bore and carries a drive element which projects inwards into the bore and into a hole in the periphery of the valve element.
3. A reversing valve according to claim 1, wherein the drive means comprises a rack which extends tangentially of the bore and engages with pinion teeth arranged circumferentially of the valve element.
4. A reversing valve according to any preceding claim, wherein the valve element is rotatable between (i) a first position in which a first one or plurality of the ports is or are in fluid communication with the bore inlet and a second one or plurality of the ports is or are in fluid communication with the bore outlet and (ii) a second position in which the first port (s) is or are in fluid communication with the bore outlet and the second port (s) is or are in fluid communication with the bore inlet.

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5. A reversing valve according to any preceding claim, wherein the ports lie on a common circumference of the bore.
6. A reversing valve according to any preceding claim, wherein the first and second apertures lie on a common circumference of the valve element.
7. A reversing valve according to any preceding claim, wherein the valve element comprises a tube through the wall of which are provided the first and second apertures, and an internal divider defining the first and second passageways inside the tube.
8. A reversing valve according to claim 7, wherein the internal divider comprises a plurality of plates which extend generally longitudinally of the valve element and separate the first and second passageways.
9. A reversing valve according to any preceding claim, wherein the valve element has an intermediate position at which it closes all of the ports.
10. Apparatus comprising a device requiring a reversal of fluid flow and a reversing valve according to any preceding claim.
11. Apparatus according to claim 10, wherein the device comprises a vessel supported on a pillar, and the reversing valve extends transversely through the pillar.
12. Apparatus according to claim 11, wherein a part of the valve element is outside the pillar.
13. Apparatus according to claim 11 or 12, wherein the device has a central duct within the pillar, with the duct being at one end of a fluid circuit of the device and being connected to a first one or plurality of the ports of the reversing valve, and with a space between the duct and the pillar being at the other end of the fluid circuit and being connected to a second one or plurality of the ports of the reversing valve.

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14. Apparatus according to claim 13, wherein the space is annular.