GB2378998A - Valve assembly for controlling flow from a storage tank, eg in a central heating system - Google Patents

Abstract

A valve assembly suitable for controlling the flow of fluid from a fluid storage means, for example an expansion tank in a central heating system, consists of a bore having a closure member 38 movable between an open and closed position. Under normal operating conditions, the closure member 38 floats on or in fluid in the valve assembly. In the event of a sudden reduction in pressure, e.g. due to a leak in the system downstream, the closure member 38 switches to the closed position and is held in place by a non-return means, e.g. a magnet (32, Figure 2). The bore may include primary apertures 60 and auxiliary apertures 62, wherein, as the closure member 38 switches to the closed position, it moves to prevent flow through the primary apertures 60, thereby restricting the flow of fluid to the auxiliary apertures 62 (Figure 7), which causes the closure member 38 to be brought swiftly to the closed position (Figure 8).

Description

Valve assembly The present invention relates to a valve assembly, more

particularly, but not exclusively, to a valve assembly which is suitable for use to control the flow of fluid from a fluid storage means, for example a tank in a central heating system.

5 A conventional central heating system comprises anumber of radiators, connectedtogether in a series, in a closed loop system.

Water, which is heated indirectly by means of a boiler, circulates through the system of radiators.

The system is not totally sealed, in order to allow for expansion and contraction of the water circulating, and therefore some losses in the water volume occur. The system is thus provided with 10 an expansion tank which serves to maintain the water volume. The expansion tank is fed from the mains water supply and the water that it feeds to the central heating system is controlled by a conventional ball valve.

While central heating systems are generally very convenient and reliable and provide a safe and effective way of heating a building, they do have the disadvantage that if there is catastrophic 1 S damage to the system, for example a radiator or connecting pipe develops a leak, either through corrosion or frost damage, then the water will escape from the system into the location where the leak is present. Not only will the water in the system flood out, but the expansion tank will continue to supplywatertothesystem end will itselfbereplenishedbythemains supply. If the premises where the leak occurs are left empty for even a relatively short time, and the leak is 20 therefore undetected, a substantial volume of watermay flow into the building, causing significant darnage to the building and to fixtures and fittings.

It is an obj ect of the invention to provide a valve assembly for controlling the flow of fluid from a fluid storage means for at least temporary storage of fluid, the fluid storage means having an outlet means for releasing fluid from the fluid storage means.

It is another object ofthe present invention to provide a valve assembly for controlling the flow of water from the expansion tank of central heating system, as referred to above.

It is a further object ofthepresent invention to provide a valve assemblywhich canberetrofitted to an existing fluid storage means, for example in a central heating system.

5 According to a first aspect ofthe invention there is provided a valve assembly which is suitable for controlling the flow of fluid from a fluid storage means, which valve assembly switches between an open position in which fluid can flow through the valve assembly and a closed position in which fluid is prevented from flowing through the valve assembly, in which the valve assembly switches from the open position to the closed position in response to an increase in the rate of flow of fluid through 10 the valve assembly above a predetermined value.

The valve assemblypreferably switches when the flow rate of fluid out ofthe valve assembly is greater than the flow rate of fluid in to the valve assembly.

The valve assemblymay switch from the open position to the closed position in response to both a fall in the level of fluid flowing through the valve assembly and the increase in the rate of flow o f 1 S fluid.

In a preferred embodiment ofthe invention the valve assembly comprises a housing having a bore and a closure member which is reciprocable in the bore between the open position and the closed position. Preferably, the housing includes aplurality of apertures through which fluid from the fluid storage 20 means enters the valve assembly, in use, whereby, in the open position, the closure member is buoyant on or in the fluid in the housing.

The plurality of apertures may consist of a plurality of primary apertures and a plurality of auxiliary : it.

apertures, wherein, in use, as the valve switches from the open position to the closed position, the closure member moves to cover the primary apertures, thereby restricting the flow of fluid into the housing to the auxiliary apertures.

Preferably, the housing consists of a sleevememberand abaseportion, the sleevememberbeing 5 adjustably mounted on the base portion.

The valve assemblypreferablyincludes anon-retu nmeans provided to releasablymaintain the closure member in the closed position after the valve assembly has switched from the open position.

In a preferred embodiment, the non-return means consists of a ceramic magnet or a ferrite magnet.

Alternatively, the non-return means may consist of an electromagnetic arrangement.

10 Further, the non-return means may consist of aplurality of downwardlydepending fingers on the internal surface ofthe bore, which prevent upward movement ofthe closure member from the closed position.

The valve assembly may include an automatic re-set means, for automatically resetting the valve to the open position after the valve assembly has switched to the closed position, for example a 15 solenoid arrangement.

According to the second aspect ofthe invention there is provided a valve assemblywhich is suitable for use to control the flow of fluid from a tank, which valve assembly switches between an open position in which fluid can flow through the valve assembly and a closed position in which fluid cannot flow through the valve assembly, in which the valve assembly is switched in response to a 20 predetermined relatively high increase in the rate of flow of fluid through the valve assembly.

Other preferred features of the invention are set out in the dependent claims.

The invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure I is a longitudinal section through a first embodiment of a valve assembly in accordance with the invention, in the open position; 5 Figure 2 is a similar view to Figure 2, in the closed position; Figure 3 is an exploded view of a second embodiment of a valve assembly in accordance with the invention; Figure 4 is a view from the front ofthe sleeve member ofthe embodiment illustrated in Figure 3; 10 Figure 5 is a cross sectional view through the sleeve member of Figure 4; Figure 6 is a diagrammatic view ofthe valve assembly of Figure 3, in use, showing the float in a first open position; Figure 7 is a view similar to Figure 6, showing the float in an intermediate open position; Figure 8 is a view similar to Figure 7, showing the float in a closed position; 15 Figure 9 is a diagrammatic view of a third embodiment of a valve assembly in accordance with the invention; and Figure 10 is a diagrammatic view of a sleeve member for use in the second embodiment of the invention, having a modified float.

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Referring to Figure 1, a valve assembly shown generally at 10 consists of a sleeve member 12 slidably received on a tube 14. The sleeve member 12 has a cap 16 at its upper end, and a plurality of apertures 18 which are provided in the side walls of sleeve member 12. The inner diameter ofthe sleeve member 12 is greater then the outer diameter ofthe tube 14. The sleeve 5 member 12 is sealingly engaged with the tube 14 byrneans oftwo rubber O-rings 20 disposed on the tube 14. The sleeve member 12 is disposed on the tube 14 so that a first end ofthe tube 14 extends into the area bounded by the apertures 18. The tube 14 defines a central passage 22. An annular stainless steel seating face 24 is provided around the bore on the first end ofthe tube 14.

An elbow (not shown) is provided at the other end ofthe tube 14 and terminates at an outlet in a 10 connecting portion (not shown).

A plunger 26 is slidably and reciprocablyreceived in the sleeve member 12 above the first end of the tube 14. The plunger 26 has a guide extension 28 arranged centrally on its outer end face, which guide extension 28 extends through a central aperture in the closed end 16. The plunger 26 is retained in the sleeve 12 bythe cap 16. An annular rubber seal 30 is provided on the inner end 15 face ofthe plunger 26. An annular ceramic magnet 32 is provided, concentric with the seal 30, on the inner end face of the plunger 26.

In use, the valve assembly 10 is located with the tube 14 substantiallyvertical in the expansion tank of a central heating system, and is in communication with the system bymeans ofthe connecting portion. 20 Under normal operating conditions, the valve assembly 10 is in an open condition, in which water flows through the apertures 18 from the tank and through the tube 14 into the central heating system underpressure. The plunger 26 floats on the water flowing through the apertures 18 at a distance d' above the tube 14.

If a leak occurs in the central heating system fed by the expansion tank in which the valve assembly 25 10 is installed, a sudden reduction in pressure occurs downstream in the central heating system.

This pressure reduction causes an increase in flow rate through the valve assembly 10 which causes

the level of water flowing through the valve assembly 10 to drop. Since the plunger 26 floats on the water flowing through the valve assembly 10, the drop in the level of water flowing through the valve assembly 10 causes the plunger 26 to move in a direction towards the tube 14. The plunger 26 continues to move towards the tube 14, until the magnetic attraction between the magnet 32 and 5 the seating 24 brings the end face ofthe plunger 26 into contact with the seating face 24, as shown in Figure 2.

The contact between the annular seal 30 on the plunger 26 and the seating face 24 forms an effective seal against the flow of wafer through the apertures 18, until the leak can be repaired, for example. Magnetic contact between the magnet 3 2 and the steel seating face maintains the plunger 10 26 in the closed position shown in Figure 2.

Once the plunger 26 is in sealing contact with the seating face 24, the water in the expansion tam; will rise to its normal operating level. Once the water level reaches the normal operating level, the incoming mains water supply will shut off via the ball cock valve in the expansion tank.

The volume of water released through the valve assembly 10, and hence the damage to the building 1 5 in which the central heating system protecting by the valve assembly 10 is installed, is thus greatly reduced. After the leak has been repaired, for example, the plunger 26 can be returned to the open position by pulling the guide extension 28 upwardly.

Since the sleeve 12 is slidably received on the tube 14, the distance 'd' at which the plunger 26 is 20 maintained in the open position is selectively adjustable. In this respect, byincreasing the distance d', a delay canbe introduced in the time inwhichtheplunger26 falls to the closedposition. In use, this is particularly advantageous in preventing the valve assembly 10 from switching to a closed position in a period of a small drop in flow pressure, for example, when fillinglbleeding radiators in the central heating system. Hence, the flow rate at which the valve assembly 10 is switched to 25 the closed position can be predetermined.

If a small drop in pressure does occur, the flow rate through the valve assembly 10 will increase and the level of level ofthewaterI1owing through the valve assemblywill drop. Provided that the distance 'd' has been suitably adjusted, the drop in the level of water flowing through the valve assembly 10 will not tee sufficient to cause theplunger26 to tee moved to the closed position, i.e. 5 the plunger 26 will not fall to a distance at which the magnetic attraction between the magnet 32 and the seating 24 will be sufficient to move the plunger 26 to the closed position. Instead, as the flow of water through the central heating system returns to a steady state, the plunger 26 will return to its predetermined 'floating'position, as the level ofthe water flowing through the valve assembly 10 rises. l O Itwill be appreciated that the magnet 32 maybeprovided on eitherofthe tube 14 orplunger 26, to provide a magnetic contact therebetween in the closed position.

Referring to Figure 3, a second embodiment of a valve assembly is shown generally at 34, which includes a tubular sleeve member 36 having abore extending therethrough, vertically as viewed in Figure 3, a float 38 forreciprocablemovement within apart ofthe bore ofthe sleeve member 36 15 and a cap 40 for providing a closure member at the upper end ofthe sleeve member 36, as viewed.

The valve assembly34 furtherincludes abodyportion42 having a first connectionportion 44, projecting verticallyas viewed inFigure 3, on which the lower end ofthe sleeve member36 is adjustably receivable, and a second connection portion 46, at the right hand end of the body portion 42 as viewed in Figure 3, extending in a direction orthogonal to the first connection portion 20 44. Thebodyportion42 has abore, the axis of which extends through the first connection portion 44, vertically as viewed in Figure 3, and turns at an elbow through 90 degrees, to the right as viewed in Figure 3, to extend through the second connection portion 46.

An adapter 48 is provided having a bore extending right to left as viewed in Figure 3, for removable connection with the second connection portion 46 of the body portion 42. A threaded connecting 25 portion 50 is provided at the right hand end of the adapter 48, for connection to a fluid outlet means, not shown, aboutwhich apair of washers 52 and a flange nut 54 maybe secured, in use,

as will be described later.

The bore extending through the adapter 48 has an internal diameter greater than the external diameter ofthe second connection portion 46. Hence, apair of O-rings 56 are mounted about the secondconnectionportion46 in locating grooves (notvisible in Figure 3), to provide a push fit 5 sealing connection between the adapter 48 and the body portion 42, in use.

The external diameter ofthe first connection portion44 is less than the internal diameter ofthe bore ofthe sleeve member 36. Three O-rings 58 are mounted about the first connection portion 44 in locating grooves (not visible in Figure 3), to provide apush fit sealing connection between the body portion 42 and the sleeve member 36, in use.

10 The sleeve member 36 includes two sets of apertures, primary apertures 60 and auxiliary apertures 62. Four elongate primary apertures 60 are provided at a uniform radial spacing from one another in the upperpart ofthe sleevemember36, onlytwo of which are clearlyvisible in Figure 3. As can be seen clearly in Figure 4, the primary apertures 60 have a principal axis which extends vertically, in the direction ofthe longitudinal axis ofthe sleeve member 36. Four elongate auxiliary apertures 15 62, having a principal axis extending orthogonally to the principal axis of the primary apertures 60, are provided equidistantly about the sleeve member 36, below the primary apertures 60.

As can be seen in Figure 5, the internal surface of the sleeve member 3 6 is formed with a radial projection or shoulder 64 on which an annular stainless steel float seat 66 is secured, by means of adhesive for example. The upper surface ofthe float seat 66 is coated with tenon to provide a 20 smooth surface upon which debris will not readily adhere and/or accumulate, in use. Altematively, xylan or other similar materials can be used.

An indicator, in the fomm of a circumferentialblackline 68, is provided on the sleeve member 36 justbelow the upper end oftheprirnary apertures 60, as viewed in Figures 3 and 4, for accurately setting the height ofthe sleeve member 3 6 on the bodyportion 42, in use, as will be described in 25 further detail below.

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As can be seen in Figure 3, the float 3 8 includes a stem 70. The cap 40 has a central aperture, not visible in Figure 3, through which the stem 70 extends, in use. A ferrite magnet, strontium ferrite Y30H-2 (not visible in the Figures) is provided cenkallyin the bottom ofthe float 38. The magnet is set flush with the bottom ofthe float 38, and an O-ring(not visible in the Figures) is provided in 5 arecess about the magnet, which protrudes slightly from the bottom ofthe float 38. In use, the magnet and O-ringprovide magnetic and sealing engagement with the float seat 66 on the sleeve member 36.

The process of installation ofthe valve assembly34 in a fluid supply system (notillustrated)will now be described.

1 0 The fluid supply system includes a fluid storage means, in the form of a tank, for at least temporary storage of fluid to be supplied to the system, the tarn having an inlet means for providing fluid to the system from a fluid supply and an outlet aperture for releasing fluid from the tank, an outlet pipe for discharging fluid from the tank in to the system downstream, and a tank adapter for sealing communication between the tank and the outlet pipe.

1 5 Under normal working conditions, the tank stores fluid from the fluid supply to a normal working level in the tank. As fluid is drawn in to the fluid supply system from the tank through the tank adapter and outlet pipe, as required, the nonnal working level is maintained by a flow of fluid from the fluid supply through the inlet means.

To install the valve assembly 34, the flow of fluid from the fluid supply is prevented and the level 20 of fluid in the tankis reduced from the nonnal working level to a level below the level ofthe outlet pipe. The outlet pipe is then disconnected, along with the tank adapter. One ofthe washers 52 is placed about the threaded connectingportion 500fthe adapter48 ofthe valve assembly 34, which is then positioned in the tank outlet aperture, with the threaded connecting portion SO extending outwardly through the wall of the tank. Another washer 52 is placed about the Treaded 25 connecting portion 50 on the outside of the tank and the flange nut 54 is threaded onto the connecting portion 50 and screwed firmly into place. The outlet pipe is then connected to the

threaded connecting portion SO of the adapter 48.

With the sleeve member 36 removed from the body portion 42, as shown in Figure 3, the second connectionportion 46 ofthe bodyportion36 is pushed into the bore ofthe adapter48, from the inside ofthe tank, ensuring that the first correction portion 44 is in a vertically extending position.

5 A keymaybe provided on the bodyportion42 for alignment with agroove on the adapter48, for correctly aligning the adapter 48 and bodyportion 42 with respect to one another, with the first connection portion 44 extending vertically.

The tank is then refilled to the nonnal working level by restarting Me fluid supp ly to the system, and the system is then allowed to run for 5 minutes to enable the system. to stabilise. The sleeve 10 member36 is assembledwith the cap 40 secured inplace on the upper end ofthe sleevemembef 36, end with the float 38 located for reciprocable movement in theupperpart ofthe bore ofthe sleeve member 36. The sleeve member 36 is then pushed fully onto the first connection portion 44 ofthebodyportion42, with the float 38 in magnetic and sealing engagement with the float seat 66.

With the system still running, the level ofthe fluid in the tank is adjustedto aleveljust abovethe 15 level ofthe black line 68 on the sleeve member36, for example 5 mm above the black line 68. To fine adjust the setting ofthe sleeve member 36 on the bodyportion 42, relative to the level of fluid in the tank, the sleeve member 36 can bemoved upwards on the first connectionportion 44 until the level of the fluid in the tank matches the level of the black line 68.

If the inlet means for the tank includes aballvalve assemblyforcontrollingthe flow of fluid from 20 the fluid supply, as in a typical cistern for example, and hence the level of fluid in the tank, the level ofthe water in the tank can be adjusted by adjusting the ball valve float aim setting to the required limiting position.

To set the valve assembly 34 to an open position, the float 38 is raised within the upperpart ofthe sleeve member 36, with the stem 46 positioned to extend through the aperture in the cap 40. With 25 the system still running, the float 38 is then allowed to find an equilibrium floating position.

Operation of the valve assembly 34 installed in the above system will now be described with reference to Figures 6 to 8, inwhich only the upper part ofthe valve assembly 34 and the fluid level in the tank is illustrated.

The valve assembly 34 is shown in Figure 6, in use, set with the float 3 8 occupying an equilibrium 5 buoyant position in the sleeve member 36, with the level ofthe fluid in the tank set to the black line, 68, as described above. The external diameter ofthe float 38 is less than the internal diameter of the sleeve member 36, so that, when the tank is filled with fluid to the level ofthe black line 68, for example, the float 3 8 is buoyant in the fluid, with fluid being present at least partially between the walls of the float 38 and the internal surface of the sleeve member 36.

1 0 In the equilibrium position shown in Figure 6, the valve assembly 34 is in a first open position under normal operating conditions, in which any flow from the tank through the valve assembly 34 into the system is equivalent to, or immediately replenished by, the flow of fluid from the fluid supply through the inlet means. In this respect, the level ofthe water in the tank, and thereby the level of the float 38 in the sleeve member 36 remains substantiallyconstant. Any flow of fluid through the 1 5 valve assembly 34 into the system downstream of the tank may pass through both the primary and auxiliary apertures 60, 62, as indicated.

If an undesired amount of fluid is released by the system downstream from the tank, e.g. if a leak occurs in the system downstream from the tank, a sudden reduction in pressure occurs in the system. 20 As described above with reference to the first embodiment of Figures 1 and 2, the reduction i pressure causes an increase in the flow rate of fluid through the valve assembly 34, above the rate of flow through the inlet means from the fluid supplyundernorrnal working conditions. Hence, there is a drop in the level of fluid in the tank. Since the float 3 8 is buoyant in the fluid in the tar k, under normal working conditions, the drop in the level of fluid in the tank causes the float 3 8 to 25 dropprogressivelywithin the sleevemember 36, from the first openposition in Figure 6 to the intermediate position in Figure 7.

In the intermediate open position shown in Figure 7, the level ofthe fluid is below the bottom of the primary apertures 60, leaving only the auxiliary apertures 62 open, thus restricting the flow path for the fluid passing through the valve assembly 34. The restriction ofthe flow path causes a substantial increase in the rate of flow of fluid through the auxiliary apertures 62. The increased rate of flow 5 of fluid through the valve assembly 34 has a scouring and cleansing effect of the fluid on the seating face ofthe float seat 66, which assists in removing debris which has accumulated on the float seat 66 during the period of normal working conditions. Further, the increase in flow rate through the valve assembly 34 in the intermediate open position, draws the float 3 8 rapidly towards the float seat 66.

10 The float 38 is drawn downwardsbytheincreased flow of fluidthroughthe auxiliary apertures 62.

At some point, the float 3 8 comes under the magnetic attraction between the magnet in the bottom of the float 3 8 and the float seat 66. At this point, the magnetic attraction between the float 3 8 and the float seat 66 combines with the effect ofthe falling fluid level on the float 3 8, to snatch the float 38 downwards and to bring the bottom ofthe float 38 swiftly into contact with the float seat 66, 15 to the closed position shown in Figure 8.

In the closedposition shownin Figure 8, the magnetic attractionbetweenthe float 38 and the float seat 66, in combination with the contact between the O-ring on the bottom of the float 3 8 with the float seat 66, seals the valve assembly 34 to prevent further flow of fluid through the valve assembly 34. 2 0 Once the valve assembly 34 is in the closed position, the flow of fluid Trough the inlet means from the fluid supply begins to refill the tank to the normal working level.

The volume of fluid released through the valve assembly 34, as a result ofthe undesired loss of fluid downstream from the tank is thus minimised. Afterthe source ofthe undesired loss is dealt with satisfactorily, the valve assembly 34 is re-set to the equilibrium position shown in Figure 6, by 25 raising the float 38 from contact with the float seat 66.

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Figure 9, which shows the third embodiment ofthe valve assembly, indicated generally at 70, includes an auto-reset means for automaticallyresetting the valve to the first open position after the valve assemblyhas switched to the closedposition. Only the upper part ofthe valve assembly 70 is illustrated, the other components of the valve assembly 70 being in accordance with tile 5 embodiment of Figures 3-8.

The valve assembly 70 includes a sleeve member 72 having an upper adapter 74 and a cap 76.

The sleeve member 72 has afloat78 reciprocablymountedtherein above a float seat 80. Apush-

pull solenoid arrangement 82 is located onthe cap 76 which is connected to a 48V power supply by cable 84, for operation of the solenoid arrangement 82.

10 A shaft orpin 86 extends downwardly from the solenoid arrangement 82 into the upper adapter 74. A lifting cage 8 8 of substantially inverted Ushaped cross-section is connected to the lower end of the shaft 86.

The float 78 includes a stem 90 which extends through an aperture in bottom wall ofthe upper adapter 74, and a clip 92 is connected adjacent the free end of the stem 90.

15 The valve assembly 70 is shown in a first open position in which the float 78 is in an equilibrium buoyant state, mounted in a tank in a fluid supply system substantially as described above.

When the valve assembly70 is switchedtotheclosedposition,withthebottom ofthe float78 in contact with the float seat 80, the stem 90 extends through the aperture in the bottom ofthe upper adapter 74 by a short distance.

20 The free ends ofthe cage 88 each have aflange 94 defining en opening between which the stem 90 extends, as can be seen in Figure 9. The diameter ofthe clip 92 on the stem 90 is greater than the diameter ofthe opening definedbythe flanges 94. When the float 78 is in the closedposition, the clip 90 remains above the flanges 94. When it is desired to re-set the valve assembly 70 to the open position, the solenoid arrangement 82 is activated, bymeans of a button (not illustrated),

whereby the solenoid raises the shaft 86 and hence the cage 88. As the cage 88 is lifted, the flanges 94 engage the clip 92 on the stem 90. The upwards action ofthe solenoid arrangement is sufficient to lift the float 78 from the closed position in to the open position. The button is then re pressed for the solenoid arrangement 82 to release the shaft 86, to return the cage 88 to the 5 position illustrated.

Figure 10 shows a sleeve member 96 for use in a valve assembly in accordance with the second embodiment oftheinvention, in which amodified float 98 isreciprocablymounted. As canb seen, the float 98 includes a stem 100 having a loop or ring 102 formed at its free end.

One end of a length of cord or other flexible member may be attached to the loop 102, by tying 10 for example, and a free end of the cord maintained at a distance away from the valve assembly on which the sleeve member 96 is assembled, in use. If the float 98 is required to be moved from the closed position, the free end ofthe cord can be pulled, to move the float 98 upwardly in the sleeve member 96, to unseat the float 98 to an open position.

This is of advantage in that the float 98 can be set to an openposition on the valve assembly, in use, 15 without the need forthe userto puttheirhands into the fluidin which the valve assemblyis installed.

Although not illustrated, the first embodiment ofthe invention may alsotee provided with a ring or loop, as described with reference to Figure 10.

In the embodiments describedherein, the sleeve member, cap, float/plunger, body portion and adapter are produced from glass bead filled acetal polymer, although any suitable material could 20 be used.

Although the described embodiments use a ceramic or strontium-ferrite magnet in the plunger/float, any suitable magnetic means may be used, for example an electro-magnetic arrangement.

Mechanical non-return means maybe provided on the valve assembly, as an alternative to the a,...

magnet, to maintain the float/plunger in the closed position. For example, a plurality of fingers may be provided on the inner surface ofthe sleeve member, which fingers restrict the upward movement of the float/plunger, once the float/plunger has moved downwardly past the fingers.

In a preferred embodiment (not illustrated), a sensor is incorporated in the valve assembly to 5 activate an audible and/or visual alarm if the valve assembly is detected in the closed position, or if a rise in the water level in the valve assembly is detected. For example, a photo interrupter proximity switch maybe positioned adj acent the float/plunger stem, to detect movement of the stem, and to trigger an audio/visual alann in the event of movement ofthe stem above a pre-set value. 10 The inventionhas application in any fluid supplysystem which includes a fluid storage means, for at least temporary storage of fluid to be supplied to the system, having an inlet means forproviding fluid to the system from a fluid supply and an outlet for releasing fluid from the fluid storage means into the system.

In particular, the invention has application in a central heating system, wherein the valve assembly 15 is installed in the expansion tank, as described above. If a leak occurs in the central heating system, fedbythe expansion tank in which the valve assemblyis installed, a sudden reduction inpressure occurs downstream in the central heating system. This pressure reduction causes an increase in flow rate through the valve assembly, to switch the valve assembly to the fully closed position, as described above.

2 0 The invention also has application in a fluid cooling system for machinery, for example in inj ection moulding machinery or CHIC machinery. For example, such a system includes a fluid circuit, in which a plurality of cooling fluid pipes are provided, in parallel and/or in series, for supplying cooling fluid to specific components ofthe machinery, under a normal working flow rate/fluid pressure. In this application, the valve assembly is installed in a tank fitted in the fluid circuit of the 2 5 fluid cooling system at a position before Me first pipes in the system, with cooling fluid flowing through the valve assembly under the normal working conditions. If a leak occurs in the system, , \.,

for example due to a burst pipe, the subsequent reduction in pressure downstream switches the valve from an open position to the fillly closed position, preventing unnecessary loss of cooling fluid' substantially as described above.

It will be appreciated that the invention has application in other such cooling systems. In one 5 example of a valve assembly in accordance with the invention being used in an alternative application, the valve assembly is installed in spot welding machinery, as part of a closed circuit cooling system. The cooling system includes a header tank in which the valve assembly is mounted, substantially as described above, through which fluid is circulated for cooling the machinery. If a burst pipe, damaged joint or leak, for example, occurs downstream ofthe valve 1 0 assembly, a sudden reduction in pressure occurs, which causes an increase in flow rate through the valve assembly, to switch the valve assembly to the fully closed position, as described above, to prevent damage to the machinery.

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Claims (1)

1. Claims

   1. A valve assembly which is suitable for controlling the flow of fluid from a fluid storage means, which valve assembly switches between an open position in which fluid can flow through the valve assembly and a closed position in which fluid is prevented Tom flowing 5 through the valve assembly, in which the valve assembly switches from the open position to the closed position in response to an increase in the rate of flow of fluid through the valve assembly above a predetermined value.

   2. A valve assembly as claimed in claim 1, in which the valve assembly is switched when the flow rate of fluid out of the valve assembly is greater than the flow rate of fluid in to the 10 valve assembly.

   3. A valve assembly as claimed in claim 1 or claim 2, in which the valve assembly switches from the open position to the closed position in response to both a fall in the level of fluid flowing through the valve assembly and the increase in the rate of flow of fluid.

   4. A valve assembly as claimed in any one of claims 1 to 3, in which the valve assembly 1 5 comprises a housing having a bore and a closure member which is reciprocable in the bore between the open position and the closed position.

   S. A valve assembly as claimed in claim 4, in which the housing includes a plurality of apertures through which fluid from the fluid storage means enters the valve assembly, in use, whereby, in the open position, the closure member is buoyant on or in the fluid in the 90 housing.

   6. A valve assembly as claimed in claim 5, in which the plurality of apertures consist of a pluralityofprimaryapertures and apluralityofauxiliary apertures, wherein, inuse, as the valve assembly switches from the open position to the closed position, the closure member moves to cover the primary apertures, therebyrestricting the flow of fluid into the housing . .. ,# c, '

   to the auxiliary apertures.

   7. A valve assemblyas claimed in anyone of claims 4to 6, in which the housing consists of a sleeve and a base portion, the sleeve being adjustably mounted on the base portion.

   S 8. A valve assembly as claimed in any one of claims 4 to 7, in which the valve assembly includes a non-return means provided to releasably maintain the closure member in the closed position after the valve assembly has switched from the open position.

   9. A valve assembly as claimed in claim 7, in which the non-retum means consists of a ceramic magnet or a ferrite magnet.

   l O 10. A valve assembly as claimed in claim 7, in which the non-return means consists of an electromagnetic arrangement.

   A valve assembly as claimed in claim 7, in which the non-return means consists of a pluralityofdownwardlydepending fingers ontheinternal surface ofthe bore, which prevent upward movement of the closure member from the closed position.

   15 12. A valve assemblyas claimed in anypreceding claim, in which the valve assemblyincludes an automatic re-set means, for automatically resetting the valve to the open position after the valve assembly has switched to the closed position.

   13. A valve assembly as claimed in claim 1 1, in which the automatic reset means comprises a solenoid arrangement.

   2 0 14. A valve assembly as claimed in any preceding claim, in which the valve assembly includes an audible andlor visual alann, which is activated when the valve assembly is switched to the closed position.

   .... As, c

   1 5. A valve assembly as claimed in any preceding claim, in which the valve assembly includes a sensor for detecting the reciprocable movement of the closure member.

   16. A valve assemblywhich is suitable foruse to control the flow offluid from a sank, which valve assembly switches betvveen an open position in which fluid can flow through the valve 5 assembly and a closed position in which fluid cannot flow through the valve assembly, in which the valve assembly is switched in response to a predetermined relatively high increase in the rate of flow of fluid through the valve assembly.

   17. A valve assembly substantially as hereinbefore described, with reference to and as illustrated in Figures 1 to 2, or Figures 3 to 8, or Figure 9 or [Figure 10.