CONTROL VALVE UNIT

Abstract: A control valve unit (10) has a central axis and comprises a plurality of modules (24, 25, 26, 27, 28, 29) each provided with coupling means (47, 48) for coupling one module to another in a leak-tight fashion, the modules (24, 25, 26, 27, 28, 29) being detachably coupled together in a linear arrangement along the central axis and each being independently rotatable about the central axis. The modules (24, 25, 26, 27, 28, 29) are formed of a plastics material, and comprise valves and other fluid control devices (36, 38, 44, 46, 84) for the control of fluid flow from a fluid circuit (12) through the control valve unit (10) to a terminal load (14), such as a fan coil unit. The coupling means (47, 48) comprise interengaging annular flanges (50, 52, 56, 58, 60, 112) and annular recesses (64, 114) which are locked together by means of a clip (70) to form leak-tight joints between the modules (24, 25, 26, 27, 28, 29).

Description: Control valve unit The present invention relates to a control, or combination, valve unit, specifically but not exclusively for use with heating and cooling systems, including air- conditioning units. Heating and cooling systems in buildings are typically arranged in the form of a circuit having various terminal loads, such as fan coil units, radiators and cooling coils. Each such terminal load must be controlled by several control devices, so that the performance of the load can be adjusted and optimised as necessary. The control devices needed typically include valves, strainers and means for balancing flow through the load, and a large number of control devices can e required for a single terminal load. At present, the majority of control devices are manufactured and supplied separately, and are connected together only at the point of installation in the circuit. Thus there is a requirement to achieve a large number of leak tight joints during installation, making the process difficult and time-consuming. Furthermore, the joining of a large quantity of separate standard components generally leads to the control device as a whole occupying a significant amount of potentially valuable space. Also, as the various control devices are not connected prior to installation, it is not possible to run any tests to ensure that the devices operate properly until time and expense has been expended on the installation process. The use of standard components can additionally mean that the control of a terminal load is not sufficiently tailored to meet the requirements of that particular load. It is an aim of the present invention to address one or more of the aforementioned disadvantages. Accordingly, a first aspect of the present invention is directed to a control valve unit having a central axis and comprising a plurality of modules each provided with coupling means for coupling one module to another in a leak-tight fashion, the modules being detachably coupled together in a linear arrangement along the central axis and each being independently rotatable about the central axis. This offers the advantage that all the control needed for a terminal load may be provided in a single modular unit . The control valve unit is assembled as a whole before installation, thus avoiding the necessity and difficulty of achieving a number of leak-tight joints ,in situ, such as is required by the use of many separate valve components. The chance of joint leakage is thereby much reduced. Furthermore, the modular configuration occupies far less space than separate components each requiring their own connections, so that much less installation space is required. Each of the modules can be rotated until the overall shape of the unit is that which best fits the available space, so that any unit can be modified as circumstances demand. The modular nature of the unit also means that a range of modules having different features can be provided, and a customised unit assembled from the modules to include each of the particular features which a user requires. Advantageously, the modules are formed substantially of a plastics material. According to the prior art, valve fittings are made of metals such as iron or brass, and plastic offers a less costly alternative. Conventional metal working facilities such as foundries are becoming less prevalent as technology advances, so that working with plastics is becoming more convenient. Also, a control valve unit made of plastics is less heavy than a metal unit, and components performing equivalent functions can be also be made on a more compact scale. These are important advantages for units which are to be fitted into potentially constrained surroundings in limited space . In a preferred embodiment, the modules include an input module positioned at one end of the control valve unit and provided with an input port and an output port for connection to a fluid circuit, and a load module positioned at the other end of the control valve unit and provided with a supply port and a return port for connection to a terminal load, the input port being in fluid connection with the supply port by means of a fluid passage and the return port being in fluid connection with the output port by means of a fluid passage, and the modules comprising valves for the control of fluid flow through the terminal load. Hence, the unit only requires connection to a fluid circuit at four points, so that installation is simple and straightforward. As all the required control valves are assembled within the unit before installation, by coupling the required modules together, the unit can be rigorously tested prior to installation to ensure that its performance is optimised. Hence post-installation adjustment and maintenance is much reduced and simplified. Preferably, the control valve unit further comprises one or more intermediate modules positioned between the input module and the load module, the fluid connections between the input port and the supply port and between the return port and the output port passing through each of the intermediate modules. These intermediate modules can incorporate a range of different valves and components to perform different fluid control functions. Advantageously, the fluid connection between the return port and the output port follows a path which substantially encompasses the path followed by the fluid connection between the input port and the supply port. This configuration allows for the fluid connections between the ports to be maintained when the modules are rotated relative to one another. Advantageously, the coupling means is an outer coupling comprising a male coupler comprising at least one annular flange situated towards one end of a first module and protruding outwardly from the outer surface of the module and a further annular flange protruding from the same end of the module in the axial direction, and a female coupler comprising at least one annular flange situated towards one end of second module to be jointed to the first module and protruding outwardly from the outer surface of the module and an annular recess running around the same end of the module, such that when a male coupler and a female coupler are coupled together the said further annular flange and the annular recess co- operate to form an annular aperture to receive sealing means. Preferably a coupler has a pair of outwardly protruding annular flanges. Thus, leak-tight seals are readily and simply created. The annular configuration of the coupling means allows for the modules to be rotated with respect to one another whilst they are coupled together. Preferably, the coupling means further comprises an inner coupling in which the male coupler further comprises a central annular flange protruding from the same end of the module as the outer annular flanges and in the axial direction, having a smaller diameter than the outer axially protruding annular flange and being located between the input port fluid connection and the output port fluid connection, and the female coupler further comprises a central annular recess running around the same end of the module as the outer annular recess, having a smaller diameter than the outer annular recess and being located between the input port fluid connection and the output port fluid connection, such that when a male coupler and a female coupler are coupled together the central annular flange and the central annular recess cooperate to form a central annular aperture to receive sealing means. This inner coupling creates a leak-tight seal between the two fluid connections which is maintained during and after rotation of the modules. Advantageously, the sealing mean ' s are O-ring seals. In a preferred embodiment, a clip is used to lock a male coupler to a female coupler. Preferably, a module is provided with a male coupler at one of its ends, and a female coupler at its opposite end. Any module can therefore be coupled to any other module. In an advantageous embodiment, one of the intermediate modules is a flow measurement module comprising an orifice device situated on the fluid connection between the input port and the supply port. This allows for measurement of a pressure differential which can be used to balance the fluid flow in the circuit. Preferably, one of the intermediate modules is a strainer module comprising a fluid strainer situated on the fluid connection between the input port and the supply port. The fluid strainer may be provided with a drain cock. The strainer filters foreign matter from the fluid to prevent clogging of and damage to the terminal load and fluid circuit . Advantageously, one of the intermediate modules is a balancing module comprising a balancing valve situated on the fluid connection between the return port and the output port. The balancing valve may be an automatic balancing valve or alternatively it may be a static balancing valve. The balancing valve is used to achieve appropriate setting of the load circuit within the total system circuit. Preferably, one of the modules comprises a flow control device comprising a proportioning valve. Advantageously, the proportioning valve is a four-port proportioning valve, but alternatively it may be a two-port proportioning valve. Preferably, the proportioning valve is provided with a test point. In an advantageous embodiment, the flow control device is incorporated into the load module. The proportioning valve is used to control performance of the terminal load. Thus the relative fluid flow through the terminal load is regulated by the control valve unit. Advantageously, one of the intermediate modules is a bypass module which provides a passage for fluid connection between the input port and the output port and comprises a bypass valve situated on the passage, an isolating valve situated on the fluid connection between the input port and the supply port and a further isolating valve situated on the fluid connection between the return port and the output port. Preferably the bypass valve is an isolating valve. Alternatively, the bypass valve and the isolating valve situated on the fluid connection between the return port and the output port are combined as a three-way valve 1 This means that fluid flow within the circuit can bypass the terminal load if required. Advantageously, one or more of the modules further comprises one or more test points. Hence, pre-installation testing of the unit may be readily carried out, and the test points can be further used to analyse the performance of the unit after installation, so that performance may be optimised. Preferably, one of the modules further comprises air bleeding means. All air can thereby be excluded from the fluid circuit . Preferably, one of the modules further comprises draining means. This allows fluid to be drained from the control valve unit and/or the terminal load if required for the purposes of maintenance and servicing. Advantageously, one of the modules comprises pressure measurement means for measuring the pressure between the input fluid connection and the output fluid connection. This measurement can be made at any of the joints between the modules, so that the module with the pressure measurement means can be located at any position within the control valve unit. A 'second aspect of the present invention is directed to an air-conditioning device comprising a control valve unit and a fan coil unit, the fan coil unit being connected to the supply and return ports of the control valve unit . The modular control valve unit mentioned above is especially advantageous for use with fan coil units in the installation of air- conditioning systems. Such units are often positioned behind false ceilings in, for example, hotel rooms. The fitting of air-conditioning in existing buildings must be done in whatever space is available, and modern building methods frequently attempt to minimise the space allocated for such facilities, so that units generally have to be fitted into small and cramped locations. Hence, devices which are relatively small, and which can further be altered to fit the available space, are advantageous. A third aspect of the present invention is directed to a module for use in a modular control valve unit having a central axis, the module having an input fluid passage and an output fluid passage passing through it, and coupling means for detachably coupling the module to one or more similar modules in a leak-tight fashion, and in use, the module being independently rotatable about the central axis of the control valve unit . Preferably, the coupling means are provided at one or both ends of the module. Advantageously, the module further comprises one or more fluid control devices, especially valves, positioned on one or both of the fluid passages. Preferably, the module is made of plastics material. A fourth aspect of the present invention is directed to a clip for coupling a joint between two coupled components each having a flange arrangement on their outer surfaces near the joint, the clip comprising two or more parts each having two ends such that when the parts are positioned end to end so that adjacent ends abut one another, the parts form a continuous encompassing whole to encompass the joint, the clip being U-shaped in cross-section, the U-shape having a base, and two side walls protruding from the base towards the centre of the encompassing whole which in use cooperate with the flange arrangements, and the clip further comprising locking means to lock the parts of the clip in an encompassing position around the joint. The clip can be quickly and easily fitted, and also quickly and easily removed if the components need to be decoupled. With suitable flange arrangements, for example, including an O-ring seal, the clip can be used to create non-permanent leak-tight joints without the need for sealants and the like. Preferably, the clip comprises two parts. Advantageously, the parts are arc-shaped, so that the encompassing whole of the clip has the shape of a ring. Thus the clip can be used with components such as the modules of the first and second aspects of the present invention, or other cylindrical components such as pipes. Preferably the locking means comprise grooves in the outer surface of the base of the U-shape of the clip located near each end of each part of the clip, and U-shaped locking tags, such that in use the side walls of the U-shape of each tag engage with the grooves so that the base of the U-shape of a tag extends over the abutment between the adjacent ends of the parts of the clip, one tag being required for each abutment of the ends of the parts. The locking tags act to pull the parts of the clip together and hence make the joint more secure . Alternatively, the locking means comprises hooks provided one at each end of each part of the clip such that in use a hook on one end of one part interengages with the hook on the abutting end of the adjacent part. This embodiment of the locking means is especially simple to use, as the parts of the clip can be fitted around the joint by means of a "push-fit" action. Alternatively, the locking means comprise protrusions on the surface of the side walls of the clip which engage with recesses provided in the side of the flanges of the flange arrangements. Alternatively, the locking means comprise recesses in the surface of the side walls of the clip which engage with protrusions provided on the side of the flanges of the flange arrangements. These embodiments of the locking means also allow the parts of the clip to be fitted around the joint by means of a "push-fit" action. In a preferred embodiment, the clip further comprises spaced-apart indentations in the inner surface of the base of the U-shape, which cooperate with spaced-apart extensions on the flanges of the flange arrangements, so that the coupled components can be coupled together in a limited number of pre- determined orientations. Alternatively, the extensions are provided on the inner surface of the base of the U-shape of the clip, and the indentations are provided on the flanges. This feature is advantageous for use with components that need to be coupled together in specific relative orientations, as the extensions and indentations can be arranged so that the components and the clip will only fit together in the specific orientations. This can reduce the amount of specialist knowledge needed to install the components. A fifth aspect of the present invention is directed to a bypass valve device comprising an input fluid passage, an output fluid passage and a connecting fluid passage connecting the input fluid passage and the output fluid passage, and further comprising a valve which acts at a position downstream of the connecting passage to block or allow fluid flow through the input fluid passage, a valve which acts at a position upstream of the connecting passage to block or allow fluid flow through the output fluid passage upstream of the connecting passage, and a valve which acts to block or allow fluid flow through the connecting fluid passage. A number of valve position permutations are possible which create different fluid flow paths, to permit bypassing of parts of a fluid circuit, or reversal of the fluid flow direction. Advantageously, three valves are provided in the bypass valve device, one in each of the fluid passages. Preferably, the three valves are spool valves. Alternatively, the three valves are ball valves. Three valves provide a wide range of permutations of valve positions, and hence a wide range of fluid flow permutations. Alternatively, two valves are provided in the bypass valve device, the first being an isolating valve which acts to block or allow fluid flow through the input fluid passage, and the second being a three-way valve which in a first position acts to block fluid flow through the output fluid passage and allow fluid flow through the connecting passage, and in a second position acts to block fluid flow through the connecting passage and allow fluid flow through the output fluid passage. Two valves reduces the number of valve position permutations available, but also decreases the complexity of the device, leading to reduced costs. A reduction in the number of moving parts is also advantageous as the maintenance requirement of the bypass valve device is reduced. Advantageously, the first valve is a spool valve, and the second valve is a wedge gate valve. Preferably, the bypass valve device is for use in a fluid circuit containing a fluid strainer provided with a drain cock. Simple cleaning of the fluid strainer is thereby made possible, by using the valves to reverse the fluid flow direction to clean debris from the strainer. The debris can then be removed from the system via the drain cock. Advantageously, the bypass valve device has a modular structure for use in a modular control valve unit . An example of a control valve unit made in accordance with the present invention, and examples of some of its constituent parts, will now be described with reference to the accompanying drawings, in which: Figure 1 shows a block diagram of a control valve unit connected to a terminal load and a fluid circuit; Figure 2 shows a cross-section of a control valve unit according to a first aspect of the present invention; Figure 3 shows a perspective view of the exterior of a module of the control valve unit of Figure 2 ; Figures 4, 5 and 6 show fluid circuit diagrams of various embodiments of the control valve unit; Figure 7 shows a perspective view of the exterior of the control valve unit of Figure 2; Figures 8 and 9 show cross-sectional and plan views of a clip according to a further aspect of the present invention; Figure 10 shows plan views of an alternative embodiment of the clip; Figures 11 and 12 show cross-sectional and plan views of a further alternative embodiment of the clip; Figure 13 shows cross-sectional views of a bypass module according to a further aspect of the present invention; Figure 14 shows cross-sectional views of an alternative embodiment of the bypass module; Figure 15 shows a fluid circuit diagram of a control valve unit incorporating the bypass module of Figure 13; and Figure 16 shows a fluid circuit diagram of a control valve unit incorporating the bypass module of Figure 14. Figure 1 shows a control valve unit 10 connected between a fluid circuit generally indicated at 12 and a terminal load 14. The arrows A and B indicate the direction of fluid flow. The terminal load 14 may be a fan coil unit, a calorifier coil, a heating coil, a cooling coil, a radiator, an air handling unit coil, a heat exchanger coil, or a similar device. For the purpose of example in the following discussion, the terminal load is assumed to be a fan coil unit for use in air-conditioning, but the invention is by no means limited to this application. Figure 2 shows the control valve unit 10 in more detail. The unit 10 has an elongate structure, with a central axis indicated by dotted line 15. Six modules are coupled together in a linear arrangement along the axis 15, and together comprise the control valve unit 10. The modules are coupled via coupling means in the form of male and female couplers 47, 48. An input module 24 is situated at one end of the unit 10, and is provided with an input port 16 and an output port 18 for connection to the fluid circuit 12. A load module 28 is situated at the opposite end of control valve unit 10, and is provided with a supply port 20 and a return port 22 for connection to the terminal load 14. Four further, intermediate, modules are disposed between the input module 24 and the load module 28. In order, beginning adjacent to the input module 24 these are a bypass module 25, a flow measurement module 26, a strainer module 27, and a balancing module 29. All of the modules have a circular cross-section at their ends. The input port 16 is connected to the supply port 20 by means of a fluid passage to form a continuous fluid connection 17 between the two, which passes through all of the modules. Similarly, the return port 19 is connected to the output port 18 by means of a further fluid passage to form a continuous fluid connection 19 between the two, which also passes through all of the modules. The two fluid connections are not straight, and each follows a somewhat serpentine path, as they pass around and through various components of the control valve unit 10, which will be discussed shortly. The fluid connection 19 connecting the return port 19 to the output port 18 deviates around the fluid connection 17 between the input port 16 and the supply port 20 and encompasses it, although the two are not coaxial throughout the length of the control valve unit 10. They are, however, coaxial at the end of each module where that module is coupled to an adjacent module. This is illustrated in Figure 3, which shows a perspective view of the exterior of the bypass module 25. The circular cross section at the end of the module 25 is readily apparent. The input port fluid connection 17 passes near the centre of the module at this end point, and the output port fluid connection 19, after passing through the lower part of the module (as viewed in the Figure) diverges to form an annular aperture which encompasses the input port fluid connection 17. The serpentine nature of the fluid connections 17, 19 is further readily apparent from Figure 2, in which the fluid connections 17, 19 are shown as shaded areas, which are clearly not continuous along the section shown in the Figure. Each of the intermediate modules is provided with a male coupler 47 at one end, and a female coupler 48 at the other end. The input module 24 and the load module 28 are each only coupled to one other module, so are provided respectively with a male coupler and a female coupler, at their respective ends adjacent to the intermediate modules. The male coupler 47 comprises a pair of annular flanges 50, 52 protruding outwardly from the outer surface of a module in the radial direction, and located towards one end of the module. The flanges 50, 52 having a gap 54 between them. The flange 52 closest to the end of the module protrudes less far than the flange 50 further from the end of the module. An additional annular flange 56 is provided around the end rim of the module, which extends beyond the end of the module in the axial direction. A further, central, annular flange 112 also extends beyond the end of the module in the axial direction, but is located around a wall separating the input port fluid connection 17 and the output port fluid connection 19, and thus is of a smaller diameter than the annular flange 56. The female coupler 48 comprises a pair of annular flanges 58, 60 similar to the pair of flanges 50, 52 of the male coupler 47, being of a similar size to those flanges 50, 52, and also protruding outwardly from the outer surface of a module in the radial direction and located towards the end of the module. The flanges 58, 60 have a gap 62 between them. The flange 60 closest to the end of the module protrudes less far than the flange 58 further from the end of the module. An annular recess 64 runs around the end rim of the module, and has a greater diameter than the diameter of the axially extending flange 56 of the male coupler 47. An outer O-ring seal 68 is disposed within the recess 64. A further, central, annular recess 114 runs around a wall separating the input port fluid connection 17 and the output port fluid connection 19, and thus is of a smaller diameter than the annular recess 6 . The central annular recess 114 has a greater diameter than the central axially extending flange 112 of the male coupler. A second, central, 0-ring seal 116 is disposed within the recess 114. When a male coupler 47 and a female coupler 48 are pushed together, the radially extending flanges 52, 60 closest to their ends abut one another, and also the axially extending flange 56 closes over the recess 64 to form an annular aperture, which is filled by the outer O-ring seal 68. The central axially extending flange 112 closes over the recess 114 to form a central annular aperture which is filled by the central O-ring seal 116. Thus a seal is provided between the input port fluid connection 17 and the output port fluid connection 19 by the central O-ring seal 116, and a seal is provided between the output port fluid connection 19 and the exterior of the control valve unit 10 by the outer O-ring seal 116. Sealing means other than O-ring seals could be used. To maintain the couplers in this configuration, and thus to couple two modules together with a leak tight joint, a clip 70 which engages with the radially extending flanges 50, 52, 58, 60, is detachably locked around the outside of the couplers 47,48. This forms a leak-tight seal between the modules, which can, nonetheless, be loosened or unfastened if movement or decoupling of the modules is required. The clip 70 will be discussed in greater detail later. The bypass module 25 contains a flushing bypass valve arrangement 44, comprising two spool valves 32, 33, and a further spool valve not shown. One of the valves is situated on the input port fluid connection 17, one of the valves is situated on the output port fluid connection 19, and the remaining valve is situated in a connecting fluid passage 34 connecting the input port fluid connection 17 to the output port fluid connection 19 at a point before the first above- mentioned spool valve, and after the second above-mentioned spool valve. The construction and operation of the bypass module 25 will be discussed in more detail later. The flow measurement module 26 contains an orifice device having the form of an orifice plate and two measurement points 84. These do not appear in Figure 2, as they lie in a different plane, but can be seen in Figure 7. The orifice device is positioned on the input port fluid connection 17. The strainer module 27 incorporates a fluid strainer 36 which is also positioned on the input port fluid connection 17. The fluid strainer 36 may be provided with a drain cock (not shown) through which its contents can be drained. The balancing module 29 comprises a balancing valve 38, located on the output port fluid connection 19. The load module 17, in addition to carrying the supply and return ports 20, 22, also houses a flow control device 31. This comprises a four-port proportioning valve 46, which is connected across the two fluid connections 17, 19. Alternatively, a two-port proportioning valve may be used, located on the output port fluid connection 19. A number of test points (not shown) are also provided in various modules, which connect the exterior of the control valve unit 10 with the interior of the modules to allow testing of the performance of the control valve unit 10. An air bleed valve (not shown) may also be provided, to allow air to be eliminated from the fluid circuit 12. The modular and compact nature of the control valve unit 10 allows for rigorous testing of the unit before it is installed, so that its performance can be optimised. Installation itself is relatively straightforward, as only four connections need to be made, at the input port 16, the output port 18, the supply port 20 and the return port 22. Also, the circular configuration of the coupling means between each module means that the modules can be independently rotated about the central axis 15 of the control valve unit whilst they are coupled together. By loosening or removing the clip around a particular coupling means, the joint between two modules is loosened so that one or other module can be rotated with respect to the other module. The external shape of the control valve unit 10 can thereby be altered to better fit into the space available. The clip is then replaced or tightened to reform the leak-tight joint between the modules. Following installation, fluid from the fluid circuit 12 enters the control valve unit 10 through the input port 16. The fluid flows along the fluid connection 17 and passes through the flushing bypass valve arrangement 44, the orifice device and the strainer 36. The orifice device permits measurement to be made, via the two measurement points, of the pressure differential within the orifice plate, which can then be correlated to fluid flow rate so that the flow rate to the terminal load 14 can be regulated by setting of the balancing valve 38. The strainer 36 acts to remove any foreign bodies from the fluid. The fluid then leaves the control valve unit 10 through the supply port 20 whence it enters the fan coil unit 14, and after circulating therethrough, it re-enters the control valve unit 10 through the return port 22. It then flows along the output port fluid connection 19, and through the proportioning valve 46 of the flow control device 31 to the balancing valve 38. This valve acts to balance the flow in such a way that each fan coil unit connected to the fluid circuit receives fluid of an equivalent temperature regardless of the distance of that fan coil unit from any boiler in the circuit. After leaving the balancing valve 38, the fluid flows through the flushing bypass valve arrangement 44 before leaving the control valve unit 10 through the output port 18, where it returns to the fluid circuit 12. Fluid may also be made to flow between the fluid connections 17, 19 in the load module 28, depending on the setting of the four-port proportioning valve 46, which controls what proportion of the fluid passing along the input port fluid connection 17 enters the fan coil unit 14 and what proportion bypasses the fan coil unit 14 by being diverted into the output port fluid connection 19. Furthermore, the fan coil unit 14 and part of the control valve unit 10 may be bypassed entirely, by appropriate use of the flushing bypass valve arrangement 44. The spool valve 32 and the further valve not shown in Figure 2 act as isolating valves. If the spool valves situated on the input port and output port fluid connections 17, 19 are closed so as to prevent fluid flow, and the spool valve situated in the fluid passage 34 connected between the two fluid connections 17, 19 is opened so as to allow fluid flow, all the fluid entering the control valve unit 10 will be diverted through the fluid passage 34 and out of the output port 18 without entering the remainder of the control valve unit 10. This allows the fan coil unit 14 and the control valve unit 10 to be isolated from the rest of the fluid circuit 12 for cleaning and maintenance, or if operation of the fan coil unit 14 is not desired. Once the control valve unit 10 is installed, the test points can be used to test and monitor operation of the control valve unit 10, and to determine whether this is optimised for operation of the fan coil unit 14. Adjustments to the control valve unit components can then be made as necessary. The configuration of the control valve unit 10 is not limited to that shown in Figure 2. The various modules can be substituted, included or excluded as necessary to provide the control required for a particular fan coil unit 14, or an alternative terminal load, and to meet the requirements of the user. The nature of the modules themselves does not affect the overall purpose and advantages of the control valve unit 10. For example, the balancing valve 38 contained within the balancing module 29, which is used to balance the fluid flow through the terminal load, may be an automatic balancing valve or a manually-set, static, balancing valve, depending on which is most appropriate for a particular load and desired operating method. Also, the four-port proportioning valve 46 may be replaced by a two-port proportioning valve, if that is more suitable for a given control function. The flow control device 31 may incorporated into a module separate from the load module 28, so that control valve units could be configured without a flow control device. Additionally, a module comprising pressure measurement means for measuring the pressure between the input fluid connection and the output fluid connection may be included. This measurement can be made at any of the joints between the modules, so that the module with the pressure measurement means can be located at any position within the control valve unit . Other configurations within the scope of the present invention will be readily apparent to the man skilled in the art; the precise nature of the components included within the control valve unit will depend on the terminal load and the control thereof which is desired. Figures 4, 5 and 6 show a range of possible configurations (although the scope of the present invention is not limited to those configurations shown), depicted as fluid circuits, which includes the use of a four-port proportioning valve 46 instead of a two-port proportioning valve 72, the use of an automatic balancing valve 74 and the use of a static balancing valve 76. Other components shown are isolating valves 78, which may be, for example, ball valves, spool valves or gate valves, a flushing bypass valve arrangement 44, an orifice device 80, a strainer 38 and test points 82. The arrows indicate the direction of flow of fluid entering and leaving the control valve unit . The various configurations illustrated are summarised in Table I below. Embodiment Static Automatic Flushing Four port Two port No Balancing balancing bypass proportioning proportioning proportioning 3(a) no yes yes yes no no 3(b) no yes no yes no no 3 3((cc)) nnoo yyeess nnoo nnoo no yes 3(d) no yes no no yes no 4(a) yes no no yes no no 4(b) yes no no no yes no 4(c) yes no yes no no yes 5 5((aa)) yyeess nnoo yyeess nnoo yes no 5(b) no yes yes no yes no 5(c) yes yes yes no no yes Table 1 In addition, a single control valve unit may be conf igured and installed to control an array of terminal loads , rather than providing control of a single load as disclosed hereabove . Figure 7 shows the external appearance of the control valve unit 10 , from which the circular shape of the module ends and their couplers can be seen, as indicated, for example, at 86, the joint between the strainer module 27 and the balancing module 29. This illustrates how each module can be rotated with respect to the module (s) adjacent to it and how this action will alter the external shape of the control valve unit because of the way in which the various components protrude from the central circular portion. The fluid connections 17, 19 between the ports are maintained during and after rotation of the modules because of the fact that at each joint the input port fluid connection 17 and the output port fluid connection 19 are coaxial, as shown in Figure 3, and hence have rotational symmetry. Figure 8 shows cross-sections of a male coupler 47 (Figure 8(b)), a female coupler 48 (Figure 8(a)) and a clip 70 (Figure 8(c)) in a non-coupled position. Figure 9 shows the clip 70, which is made of a plastics material, in more detail. Figure 9(a) shows an end view, and Figure 9(c) shows a side view. The clip comprises two semicircular parts or halves 86, which form a ring when their respective ends are abutted together. In use, this ring completely encircles the joint between two modules coupled together, and is put into place by pushing one half 86 around one side of the joint, and the other half 86 around the other side of the joint, to form a ring. Figure 9(b) shows a cross- section through the clip, along line A-A in Figure 9(a) . The clip is U-shaped in cross section, the U having a base 88 and two side walls 90, the side walls extending from the base towards the centre of the ring. When positioned around a joint, the side walls 90 protrude into the gaps 54, 62 in the male and female couplers and substantially fill them, with the base extending over the abutting flanges 52, 60. The outer flanges 47, 48 encase the clip 70 and retain it in place over the joint . Each end of each of the halves 86 of the clip 70 has a groove 92 in the outside surface of the base 70, running in the axial direction across the width of the clip, and positioned slightly away from the end. Locking tags 94 cooperate with these grooves 92 to lock the halves 86 of the clip 70 together when the clip is positioned around a joint. The locking tags are also substantially U-shaped. Each of the two side walls of the U-shape protrude into a groove 92 on each of the halves 86, and the base of the U-shape extends over the abutting ends of the halves 86. The clip thus acts to pull the two halves 86 of the clip together so that a leak- tight joint is formed between the male and female couplers 47, 48. Figure 10 shows an alternative embodiment of the clip 70, which differs from that shown in Figures 8 and 9 in that different means are employed to lock the two halves 86 of the clip together. Each end of each half 86 is formed into a hook 118. One end of one half 86 has a hook 118 facing inwardly towards the centre of the encompassing whole of the clip 70, and the end of the other half 86 which abuts the first mentioned end has a similar hook facing outwardly away from the centre. Thus, when the two ends abut, the hooks 118 interengage and lock the two halves together 118. The hooks 118 are shaped such that when they are interengaged the surface of one hook 118 is in contact with the surface of the abutting hook 118, so that the clip 70 is substantially a continuous ring. The shape of the hooks 118 also allows the two halves 86 to be joined together by a "push-fit" method, which provides for the clip 70 to be fitted around a joint simply and quickly, and without the need for any tools. As shown in Figure 10, each half 86 of the clip 70 has an inwardly facing hook and an outwardly facing hook, so that each half of 86 is the same shape as the other half 86. This reduces manufacturing costs. However, an equivalent result can be achieved by providing one half 86 with two inwardly facing hooks 118, and providing the other half 86 with two outwardly facing hooks 118. Figures 11 and 12 show an alternative embodiment of the clip 70. Figure 11 shows a female coupler 48, and male couple 47 and a clip 70 in an uncoupled configuration. The outer flanges 50, 58 of the coupler 47, 48 each have recesses 96 on the side of the flanges facing towards the abutting flanges 52, 60. The clip 70 has protrusions 98 on the outer surface of each of its side walls 90. When the clip is positioned around the couplers to form a joint, the protrusions 98 engage in the recesses 96 to hold the clip in place, via a "push-fit" mechanism. The flanges 50, 58 are made of plastic, so that they will yield slightly outwards to permit ingress of the clip 70 until the protrusions 98 engage with the recesses 96. In the embodiment shown, the protrusions and recesses are intermittently spaced around the circumferences of the flanges 50, 58 and the clip 70, but could extend continuously around the circumferences. The abutting flanges 52, 60 of the couplers 47, 48 have extensions 100 extending from their ends which are spaced apart regularly and intermittently around the circumference of the flanges 52, 60 (and thus locally increasing the length of the flange) . Figure 12 shows a cross-sectional end view of one half 101 of the clip 70. Three cross-sections through the clip 70 are shown as Figures 11 (a) , (b) and (c) . The inner surface of the base 88 of the clip 70 has indentations 102 regularly spaced apart around the circumference of the clip, so that the base 88 varies in thickness, the base at cross-section Figure 12 (a) being much thicker than the base at cross-section Figure 12 (c) . These indentations 102 engage with the extensions 100 on the couplers 47, 48, so that the clip can only be positioned around the couplers at positions in which the extensions 100 align with the indentation 102. This feature permits regulation of the relative positions of the modules being coupled, in that a module can only be placed in a position in which the extensions 100 in its coupler 47, 48 line up with the extensions on the adjacent module, to enable the clip 70 to be fitted. The number of extensions 100 and indentations 102 provided give the number of orientations which the modules can take. This is important in that certain components of the modules may be required to have a certain orientation to function properly. None of the embodiments of the clip is limited to use with modules of a control valve unit. They may be used in other applications such a joining pipes or modular components of alternative systems, assuming that the parts to be joined are shaped to cooperate with the shape of the clip. The configuration of flanges used on the control valve unit modules of the present invention is advantageous in giving a secure leak-tight joint, but the clip can be used with other and/or simpler flange configurations. For example, a single annular radially protruding flange on each part to be coupled together is sufficient, provided that the ends of the parts abut one another and the flanges rest against the inner surfaces of the side walls of the clip. The protrusions and recesses of the second embodiment may be located such that the protrusions are on the flanges and the recesses are on the clip. This also applies to the extensions and indentations, as the extensions may be provided on the clip, and the indentations on the flanges. Additionally, the clip need not be circular, as it may readily be made in alternative shapes to be used for coupling non-circular parts. Furthermore, the clip need not be plastic. The clip may also be made in more than two parts, provided that together the parts form a continuous ring (or non-circular shape) to completely encompass a joint. Figure 13 shows the bypass module 25 in more detail, incorporating the flushing bypass valve arrangement 44. The bypass module 25 comprises three spool valves 32, 33, 104. These are positioned in a triangular arrangement, as evident from the small circular drawings in Figure 13, which show the positions of the valves from below the module 25. In all cases, the arrows in the Figures indicate the direction of fluid flow. Figure 13 (a) shows a cross-section though the module 25 at the level of the hindmost spool valve 104. This valve is positioned on the fluid connection 19 between the return port 22 and the output port 18. When the valve 104 is in the closed position (pushed in) as shown on the left hand side of Figure 13 (a) , the flow of fluid along the connection 19, indicated by the shaded area in the Figure, is blocked. The right hand side of Figure 13 (a) shows the valve 104 in the open (pulled out) position, which allows fluid to pass along the connection 19. Figure 13 (b) shows a cross-section though the module 25 at the level of remaining spool valves 32, 33. The valve 32 is positioned on the fluid connection 17 between the input port 16 and the supply port 20. When the valve 32 is in the closed position (pushed in) as shown on the left hand side of Figure 13(b), the flow of fluid along the connection 17, indicated by the shaded area in the Figure, is blocked. The right hand side of Figure 13 (b) shows the valve 32 in the open (pulled out) position, which allows fluid to pass along the connection 17. Figure 13 (c) shows the same cross-section though the module 25 as Figure 13 (b) , but illustrates the operation of the remaining spool valve 33, the bypass valve. This valve 33 is located on the fluid passage 34 which connects the input port fluid connection 16 to the output port fluid connection 19, at a positioned upstream (with regard to normal flow) of the spool valve 32 on the connection 17 and downstream of the spool valve 104 on the connection 19. When the valve 33 is in the closed position (pushed in) as shown on the left hand side of Figure 13 (c) , the flow of fluid along the passage 34 is blocked, as indicated by the shaded area in the Figure. The right hand side of Figure 13 (c) shows the valve in the open (pulled out) position, which allows fluid to pass along the passage 34. The bypass function is thus achieved by closing the valves 32 and 104 to block the fluid connections 17, 19 and opening the remaining valve 33 to opened the fluid passage 34. Fluid entering the control valve unit at the input port 16 is thus prevented from flowing through the unit and is instead diverted along the passage 34, after which it must flow back out of the unit via the output port 18, owing to the blockage of the output port fluid connection 19. The flow thus bypasses the terminal load, and the majority of the modules of the control valve unit . Other fluid flow patterns can be achieved if desired by setting the three spool valves in alternative permutations of open and closed. Any or all of the spool valves can be replaced by other valve types, such as ball valves. Figure 14 shows an alternative embodiment of the bypass module 25, which performs the same function as that described above, but uses only two valves. Figure 14 (a) shows a cross-section through the bypass module 25 at a level with a spool valve 106 located on the output port fluid connection 19, and also on the fluid passage 34 between the input port fluid connection 17 and the output port fluid connection 19. When the spool valve 106 is in a first position, shown on the left hand side of Figure 14 (a) , the output port fluid connection 19 is blocked. The fluid connection 19 is opened by moving the spool valve 106 to a second position as shown on the right hand side of Figure 14(a), allowing fluid to flow along the connection 19, illustrated by the shaded area in the Figure. Figure 14 (b) shows a cross-section through the bypass module 25 at a level with a wedge gate valve 108 located on the input port fluid connection 17. When the wedge gate valve 108 is in a closed position, shown on the left hand side of Figure 14(b), the input port fluid connection 17 is blocked. The fluid connection 17 is opened by moving the wedge gate valve 108 to an open position as shown on the right hand side of Figure 14 (b) , allowing fluid to flow along the connection 19, indicated by the shaded area in the Figure. Figure 14 (c) shows a further depiction of the spool valve 106, when bypass operation is being used. When the spool valve 106 is in the first position, which, as mentioned above, blocks the output port fluid connection 19, the fluid passage 34 is opened. Conversely, in the second position, the spool valve 106 opens the fluid connection 19 but closes the fluid passage 34. The spool valve therefore works as a three-way valve. Bypass is achieved by setting the wedge gate valve 108 to the closed position and setting the spool valve 106 to the first position. This blocks both the input port fluid connection 17 and the output port fluid connection 19, but opens the fluid passage 34 so that fluid entering the bypass module is immediately diverted back out again, thus bypassing the terminal load and the remainder of the control valve unit. The flow in this case is shown by the shaded area in Figure 14(c) . Once again, other fluid flow patterns can be achieved if desired by setting the two valves in alternative permutations of open and closed. An example of an application for an alternative flow pattern will now be given, with reference to Figures 14 and 15. As mentioned above, it can be desirable to include a fluid strainer in the control valve unit, the fluid strainer being located in a strainer module. The strainer is a fine mesh device which filters foreign bodies such as grit and other debris out of the fluid circulating through the fluid circuit. This is particularly important during installation and commissioning of the control valve unit and terminal load, as a lot of debris can be filtered out during initial flushing of the circuit . The debris is retained in the strainer, and will accumulate over time to a point where it is desirable to remove it to return the strainer to peak efficiency. This can be effected by removal of the strainer, cleaning it and subsequently replacing it, but this method requires that the unit be drained, and that leak tight joints be unmade and remade to dismantle the equipment, which can be time- consuming, awkward, and lead to increased risk of leaks in the circuit. These problems can be addressed by use of either of the flushing bypass valve arrangements described above. Debris can be cleaned from the strainer by reversing the fluid flow through the strainer to wash the accumulated debris away from the mesh. If the strainer has a drain cock fitted, washing fluid containing the debris can be drained from the strainer, so that the strainer is cleaned. The necessary reversal of fluid flow can be achieved by using particular settings of the flushing bypass valves. Figure 15 shows a fluid circuit depiction of a control valve unit 10 and fan coil unit 14, the control valve unit 10 having a strainer 36 and a flushing bypass means of the three spool valve embodiment shown in Figure 13. To obtain reverse flow, the valves are set as follows: the spool valve 32 on the input port fluid connection 17 is closed to block fluid flow from the input port 16 to the rest of the control valve unit 10 and fan coil unit 14; the bypass spool valve 33 on the fluid passage 34 is also closed to block fluid flow along the passage 34; the spool valve 103 on the output port fluid connection 19 is open to that fluid can flow along the connection 19; and the strainer drain cock 110 is open. The fluid pressure within the fluid circuit is such that with the valves set like this, the direction of fluid flow reverses itself, indicated by the arrows in Figure 15, so that fluid is drawn into the control valve unit 10 through the output port 18, and flows through the control valve unit 10 along the output port fluid connection 19 contrary to the usual direction for normal operation of the system. The fluid passes through the fan coil unit 14, back into the control valve unit 10 through the supply port 20 and reaches the strainer 36, where the debris is picked up and washed out of the strainer 36 by the fluid flowing out of the control valve unit 10 through the strainer drain cock 110, where it can be collected in a bucket or the like. After cleaning, closure of the drain cock 110 and opening of the spool valve 32 to the input port fluid connection 17 will return the system to normal operation. The same procedure can be readily performed in the control valve unit is fitted with a flushing bypass means of the spool valve/wedge gate valve embodiment shown in Figure 14. In this case, as shown in Figure 16, in which the arrows indicate direction of flow, the wedge gate valve 108 on the input port fluid connection 17 is closed to block fluid flow from the input port 16 to the rest of the control valve unit 10 and fan coil unit 14; the three-way spool valve 106 is set to its second position, so that flow along the flow passage 34 is blocked, and flow along the output port fluid connection 19 is permitted; and the drain cock 110 is opened. As before, this arrangement of the valves causes the fluid flow to be reversed under its own pressure, and cleaning of the strainer occurs as described in the preceding paragraph. Once again, after cleaning, closure of the drain cock 110 and opening of the wedge gate valve 108 to open input port fluid connection 17 will return the system to normal operation. Thus either of the flushing bypass means embodiments permits simple and effective cleaning of a strainer fitted with a drain cock without the need for any dismantling of the control valve unit. This aspect of the present invention is not limited to use with a modular control valve unit according to another aspect of the present invention, but is equally suitable for use in any fluid circuit which incorporates a strainer with a drain cock.

Claims: Claims 1. A control valve unit having a central axis and comprising a plurality of modules each provided with coupling means for coupling one module to another in a leak-tight fashion, the modules being detachably coupled together in a linear arrangement along the central axis and each being independently rotatable about the central axis. 2. A control valve unit according to claim 1, in which the modules are formed substantially of a plastics material. 3. A control valve unit according to claim 1 or claim 2, in which the modules include an input module positioned at one end of the control valve unit and provided with an input port and an output port for connection to a fluid circuit, and a load module positioned at the other end of the control valve unit and provided with a supply port and a return port for connection to a terminal load, the input port being in fluid connection with the supply port by means of a fluid passage and the return port being in fluid connection with the output port by means of a fluid passage, and the modules comprising valves for the control of fluid flow through the terminal load. 4. A control valve unit according to claim 3, in which the control valve unit further comprises one or more intermediate modules positioned between the input module and the load module, the fluid connections between the input port and the supply port and between the return port and the output port passing through each of the intermediate modules. 5. A control valve unit according to claim 3 or claim 4, in which the fluid connection between the return port and the output port follows a path which substantially encompasses the path followed by the fluid connection between the input port and the supply port . 6. A control valve unit according to any preceding claim, in which the coupling means is an outer coupling comprising a male coupler comprising at least one annular flange situated towards one end of a first module and protruding outwardly from the outer surface of the module and a further annular flange protruding from the same end of the module in the axial direction, and a female coupler comprising at least one annular flange situated towards one end of second module to be jointed to the first module and protruding outwardly from the outer surface of the module and an annular recess running around the same end of the module, such that when a male coupler and a female coupler are coupled together the said further annular flange and the annular recess co-operate to form an annular aperture to receive sealing means. 7. A control valve unit according to claim 6, in which a coupler has a pair of outwardly protruding annular flanges. 8. A control valve unit according to claim 6 read appendent to claim 5, in which the coupling means further comprises an inner coupling in which the male coupler further comprises a central annular flange protruding from the same end of the module as the outer annular flanges and in the axial direction, having a smaller diameter than the outer axially protruding annular flange and being located between the input port fluid connection and the output port fluid connection, and the female coupler further comprises a central annular recess running around the same end of the module as the outer annular recess, having a smaller diameter than the outer annular recess and being located between the input port fluid connection and the output port fluid connection, such that when a male coupler and a female coupler are coupled together the central annular flange and the central annular recess cooperate to form a central annular aperture to receive sealing means. 9. A control valve unit according to any one of claims 6 to 8, in which the sealing means are O-ring seals. 10. A control valve unit according to any one of claims 6 to 9, in which a clip is used to lock a male coupler to a female coupler. 11. A control valve unit according to any one of claims 6 to 10, in which a module is provided with a male coupler at one of its ends, and a female coupler at its opposite end. 12. A control valve unit according to any one of claims 4 to 11, in which one of the intermediate modules is a flow measurement module comprising an orifice device situated on the fluid connection between the input port and the supply port . 13. A control valve unit according to any one of claims 4 to 12, in which one of the intermediate modules is a strainer module comprising a fluid strainer situated on the fluid connection between the input port and the supply port. 14. A control valve unit according to claim 13, in which the fluid strainer is provided with a drain cock. 15. A control valve unit according to any one of claims 4 to 14, in which one of the intermediate modules is a balancing module comprising a balancing valve situated on the fluid connection between the return port and the output port. 16. A control valve unit according to claim 15, in which the balancing valve is an automatic balancing valve. 17. A control valve unit according to claim 15, in which the balancing valve is a static balancing valve. 18. A control valve unit according to any preceding claim, in which one of the modules comprises a flow control device comprising a proportioning valve. 19. A control valve unit according to claim 18, in which the proportioning valve is a four-port proportioning valve. 20. A control valve unit according to claim 18, in which the proportioning valve is a two-port proportioning valve. 21. A control valve unit according to any one of claims 18 to 20, in which the proportioning valve is provided with a test point . 22. A control valve unit according to any one of claims 18 to 21 read appendent to claim 3, in which the flow control device is incorporated into the load module. 23. A control valve unit according to any one of claims 4 to 22, in which one of the intermediate modules is a bypass module which provides a passage for fluid connection between the input port and the output port and comprises a bypass valve situated on the passage, an isolating valve situated on the fluid connection between the input port and the supply port and a further isolating valve situated on the fluid connection between the return port and the output port. 24. A control valve unit according to claim 23, in which the bypass valve is an isolating valve. 25. A control valve unit according to claim 23 or 24, in which the bypass valve and the isolating valve situated on the fluid connection between the return port and the output port are combined as a three-way valve. 26. A control valve unit according to any preceding claim, in which one or more of the modules further comprises one or more test points. 27. A control valve unit according to any preceding claim, in which one of the modules further comprises air bleeding means. 28. A control valve unit according to any preceding claim, in which one of the modules further comprises draining means. 29. A control valve unit according to claim 3 or any one of claims 4 to 28 read appendent to claim 3, in which one of the modules further comprises pressure measurement means for measuring the pressure between the input fluid connection and the output fluid connection. 30. An air-conditioning device comprising a control valve unit according to any preceding claim and a fan coil unit, the fan coil unit being connected to the supply and return ports of the control valve unit. 31. A module for use in a modular control valve unit having a central axis, the module having an input fluid passage and an output fluid passage passing through it, and coupling means for detachably coupling the module to one or more similar modules in a leak-tight fashion, and in use, the module being independently rotatable about the central axis of the control valve unit. 32. A module according to claim 31, in which the coupling means are provided at one or both ends of the module. 33. A module according to claim 31 or 32, in which the module further comprises one or more fluid control devices, especially valves, positioned on one or both of the fluid passages . 34. A module according to any one of claims 31 to 33, in which the module is made of plastics material. 35. A clip for coupling a joint between two coupled components each having a flange arrangement on their outer surfaces near the joint, the clip comprising two or more parts each having two ends such that when the parts are positioned end to end so that adjacent ends abut one another, the parts form a continuous encompassing whole to encompass the joint, the clip being U-shaped in cross-section, the U-shape having a base, and two side walls protruding from the base towards the centre of the encompassing whole which in use cooperate with the flange arrangements, and the clip further comprising locking means to lock the parts of the clip in an encompassing position around the joint. 36. A clip according to claim 35, which comprises two parts. 37. A clip according to claim 35 or 36, in which the parts are arc-shaped, so that the encompassing whole of the clip has the shape of a ring. 38. A clip according to any one of claims 35 to 37, in which the locking means comprise grooves in the outer surface of the base of the U-shape of the clip located near each end of each part of the clip, and U-shaped locking tags, such that in use the side walls of the U-shape of each tag engage with the grooves so that the base of the U-shape of a tag extends over the abutment between the adjacent ends of the parts of the clip, one tag being required for each abutment of the ends of the parts . 39. A clip according to any one of claims 35 to 37, in which the locking means comprises hooks provided one at each end of each part of the clip such that in use a hook on one end of one part interengages with the hook on the abutting end of the adjacent part. 40. A clip according to any one of claims 35 to 37, in which the locking means comprise protrusions on the surface of the side walls of the clip which engage with recesses provided in the side of the flanges of the flange arrangements. 41. A clip according to any one of claims 35 to 37, in which the locking means comprise recesses in the surface of the side walls of the clip which engage with protrusions provided on the side of the flanges of the flange arrangements. 42. A clip according to any one of claims 35 to 41, in which the clip further comprises spaced-apart indentations in the inner surface of the base of the U-shape, which cooperate with spaced-apart extensions on the flanges of the flange arrangements, so that the coupled components can be coupled together in a limited number of pre-determined orientations. 43. A clip according to any one of claims 35 to 41, in which the clip further comprises spaced apart extensions on the inner surface of the base of the U-shape, which cooperate with spaced-apart indentations in the flanges of the flange arrangement, so that the coupled components can be coupled together in a limited number of pre-determined orientations. 44. A bypass valve device comprising an input fluid passage, an output fluid passage and a connecting fluid passage connecting the input fluid passage and the output fluid passage, and further comprising a valve which acts at a position downstream of the connecting passage to block or allow fluid flow through the input fluid passage, a valve which acts at a position upstream of the connecting passage to block or allow fluid flow through the output fluid passage upstream of the connecting passage, and a valve which acts to block or allow fluid flow through the connecting fluid passage . 45. A bypass valve device according to claim 44, in which three valves are provided in the bypass valve device, one in each of the fluid passages. 46. A bypass valve device according to claim 45, in which the three valves are spool valves . 47. A bypass valve device according to claim 45, in which the three valve are ball valves. 48. A bypass valve device according to claim 44, in which two valves are provided, the first being an isolating valve which acts to block or allow fluid flow through the input fluid passage, and the second being a three-way valve which in a first position acts to block fluid flow through the output fluid passage and allow fluid flow through the connecting passage, and in a second position acts to block fluid flow through the connecting passage and allow fluid flow through the output fluid passage. 49. A bypass valve device according to claim 48, in which the first valve is a spool valve, and the second valve is a wedge gate valve. 50. A bypass valve device according to any one of claims 44 to 49, in which the bypass valve device is for use in a fluid circuit containing a fluid strainer provided with a drain cock. 51. A bypass valve device according to any one of claims 44 to 50, which has a modular structure for use in a modular control valve unit.

Inventors: CLARKE NEIL, SELBY DUNCAN, STOKES JONATHAN, WEST JOHN, CLARKE, NEIL, SELBY, DUNCAN, STOKES, JONATHAN, WEST, JOHN
Applicants: CLARKE NEIL, CRANE LTD, SELBY DUNCAN, STOKES JONATHAN, WEST JOHN, CLARKE, NEIL, CRANE LIMITED, SELBY, DUNCAN, STOKES, JONATHAN, WEST, JOHN
Application year: 2000
Main classification: F16K
IPC codes: A61M39, F16K27, F25B41