WO1997045680A1

WO1997045680A1 - Improvements in and relating to a valve

Info

Publication number: WO1997045680A1
Application number: PCT/GB1997/001394
Authority: WO
Inventors: Graham Downey; Alan Green
Original assignee: Euro Innovations Limited
Priority date: 1996-05-25
Filing date: 1997-05-21
Publication date: 1997-12-04
Also published as: AU2967397A; EP0901599A1

Abstract

A valve (2) comprising a valve body (4), and a plunger (6) capable of movement relative to the valve body, the valve body comprising an inlet (8) and an outlet (10) whereby movement of the plunger (6) is for selectively establishing a path of fluid communication between the inlet (8) and the outlet (10), in which the valve body (4) includes an air gap between the inlet (8) and the outlet (10), and the plunger (6) is at least partly removable from the air gap whereby a substantial region about the air gap is free from valve components.

Description

IMPROVEMENTS IN AND RELATING TO A VALVE

Field of the Invention

The present invention relates to valves, and more particularly, though not exclusively, to valves for use in domestic boiler water circuits. The invention also relates to methods of operating a valve.

Background to the Invention

International patent application no. WO96/06308 discloses a valve comprising an inlet, an outlet and a path of fluid communication between the inlet and outlet, means for selectively allowing fluid to flow along the path of fluid communication and an opening from the valve to atmosphere from the fluid flow path, whereby when fluid is prevented from flowing along the path of fluid communication, an atmosphere gap is created between the inlet and outlet. The atmosphere gap is formed by a vent to atmosphere at which time water is prevented from flowing out through the atmosphere gap by the operation of the valve. The atmosphere gap ensures that the inlet is properly separated from the outlet, the latter of which typically is connected to a water heating system.

Although the valve of WO96/06308 has been found to be advantageous, it is desirable to include a larger atmosphere gap between the inlet and outlet for, inter alia, regulatory approval.

The spring return action of the valve of WO96/06308 is advantageous in that at about full filling pressure it returns the valve actuator to the closed position. However, the sensitivity and reliability of this effect depends very much on the friction between the '0' -rings around the actuator and the valve body. Since the resistance tends to vary over time as the '0' -rings wear, it will be appreciated that the pressure at which the return action occurs varies over time and under differing conditions.

There is also a more complex valve construction providing an air gap in EP-A-0, 182, 058. The construction disclosed includes components close to the air gap and makes no provision for preventing back syphonage in the closed configuration (ie, in which the inlet and outlet are separated by the air gap) .

It is an aim of preferred embodiments of the present invention to obviate or overcome disadvantages of the prior art, whether referred to herein or otherwise.

Summary of the Invention

According to the present invention in a first aspect, there is provided a valve comprising a valve body, and a plunger capable of movement relative to the valve body, the valve body comprising an inlet and an outlet whereby movement of the plunger is for selectively establishing a path of fluid communication between the inlet and the outlet, in which the valve body includes an air gap between the inlet and the outlet, and the plunger is at least partly removable from the air gap whereby a substantial region about the air gap is free from valve components.

By providing a configuration in which the atmosphere gap is provided by a substantial spacing between the inlet valve body and the outlet valve body, preferred embodiments of the present invention provide a construction in which the risk of syphonage is minimised.

Suitably, the path of fluid communication comprises a bore having a diameter and the free region about the air gap is at least twice and preferably three times the bore diameter. Typically, the bore is of substantially constant cross-section, but if it varies, the diameter at the inlet of the outlet portion of the valve adjacent the air gap is determinative of the diameter of the bore for this purpose.

Suitably, the valve comprises an actuator button for moving the plunger. Advantageously, in at least one configuration of the valve, at least part of the valve body is at least partly contained within the actuator button. Suitably, the actuator button is generally hollow.

Suitably, the plunger is removable from the valve body, and includes means to prevent water flowing from the inlet through the valve when the plunger is removed.

Suitably, the valve comprises means biassing the valve towards its closed configuration. Suitably, the biassing means comprises a spring. Suitably, the spring is between the actuator button and the valve body. In this way, a reverse pressure can move the valve to its closed configuration, ie, it can act as an independent non-return valve.

Suitably, there is provided a fitment to prevent access to said inlet or said outlet.

Suitably, the fitment comprises a plug. Suitably, the valve body comprises means for interengaging with the plug. Suitably, the interengagement means comprises a screw thread.

Suitably, the valve body comprises at least one cylindrical hole blocked by the fitment. More suitably, there are two such cylindrical holes. Suitably, the fitment is generally T-shaped in cross-section. More suitably, the head of the T-shaped fitment plugs a hole in the valve body. Alternatively or in addition, the leg of the T-shaped fitment plugs a hole in the valve body.

Suitably, the fitment comprises means to prevent water flowing from the inlet past the fitment. More suitably, the water flow prevention means comprises at least one '0' -ring about the fitment.

According to the present invention in a second aspect, there is provided a valve comprising an inlet, an outlet, an actuator means for selectively establishing a path of fluid communication between the inlet and the outlet, and a latch mechanism which in a first position secures the actuator means in a position to establish the path of fluid communication between the inlet and the outlet, and in a second position does not so secure the actuator means.

Suitably, means are provided whereby the latch mechanism transfers between its first and second positions dependent on the pressure of fluid acting upon the latch mechanism.

Suitably, the latch mechanism transfer means comprises means biassing the latch mechanism towards the first position. Preferably, means are provided whereby the pressure at which the latch mechanism transfers between its first and second positions can be varied. Suitably, the variation means adjust the bias of the latch mechanism.

Suitably, in the first position the latch mechanism interengages with the actuator means.

Suitably, the latch mechanism comprises a latch finger which interengages with a recess in the actuator means. Suitably, the biassing means biasses the finger towards the actuator.

Suitably, the latch mechanism comprises a deformable finger for interengaging with another part of the valve.

Suitably, the actuator means comprises a plunger which moves between an open position and a closed position.

Suitably, the valve of the second aspect of the present invention is further modified according to the first aspect of the present invention, or vice versa.

According to the present invention in a third aspect, there is provided a method of operating a valve according to the second aspect of the present invention, which method comprises the steps of:

a) establishing a path of fluid communication between the inlet and the outlet;

b) operating the plunger whether manually or automatically to prevent the flow of fluid from said inlet to said outlet; and c) removing the plunger from the air gap.

Suitably, the plunger is removed from the valve body.

Suitably, access to the inlet or outlet is or are subsequently prevented. The inlet or outlet is or are therefore plugged to prevent access and tampering.

Brief Description of the Drawings

The present invention will now be described, by way of example only, with reference to the drawings that follow; in which:

Figure 1 is an end elevation of a valve according to the present invention.

Figure 2 is a cross-sectional front elevation on the line X-X in Figure 1 with the valve in an open configuration.

Figure 3 is a cross-sectional front elevation on the line X-X in Figure 1, with the valve in a closed configuration.

Figure 4 is a cross-sectional schematic front elevation of a second embodiment of a valve according to the present invention similar to that shown in Figures 1- 3.

Figure 5 is a schematic cross-sectional elevation similar to Figure 4, but with the plunger removed.

Figure 6 is a schematic cross-sectional elevation of the valve shown in Figure 5, with a plug in place. Figure 7 is a schematic side elevation of the plug shown in Figure 6.

Figure 8 is a schematic plan view of the plug shown in Figure 7.

Figure 9 is a schematic perspective illustration of the plug shown in Figures 7 and 8, with the plunger shown in Figure 4.

Figure 10 is a schematic cross-sectional front elevation of a third embodiment of the present invention.

Figure 11 is a schematic cross sectional illustration of a fourth embodiment of the present invention.

Figure 12 is a plan view of the valve shown in Figure 11.

Figure 13 is an enlarged partly sectional view of the latching mechanism of the valve shown in Figures 11 and 12.

Description of the Preferred Embodiments

Referring to Figures 1-3 of the drawings that follow, there is shown a valve 2 comprising a generally cylindrical hollow valve body 4 within which slidingly engages a plunger 6. The valve body 4 includes an inlet 8 and an outlet 10 both of which include standard BSP fittings for connection to, in the case of inlet 8 a water supply under pressure (not shown) inlet, and in the case of outlet 10 the inlet of a domestic boiler water heating system (not shown) . The inlet 8 and outlet 10 include non-return valves 9 and 11 respectively (not shown in these Figures) for preventing the back-flow of water.

Between the inlet 8 and outlet 10 there is disposed a 20mm air gap, indicated generally at 12 which, as shown in Figure 2 , is breached by the plunger 6 in the open configuration of the valve 2. Beneath the air gap 12 is a hole 14 leading to a drain 16.

Adjacent the outlet 10 is provided a latch mechanism indicated generally at 18. The latch mechanism 18 is located in a cylindrical bore 20 in the valve body 4. The cylindrical bore 20 includes a shoulder 22 leading to a reduced diameter cylindrical bore portion 24.

The latch mechanism 18 itself comprises a latch finger 26 including a hemispherical head 28. The latch finger 26 is mounted on a generally n-shaped body 30 which slidingly engages in cylindrical bore 20. Latch finger 26 maintains a clearance fit through the reduced diameter cylindrical bore portion 24. In an exterior annular portion of latch body 30 is located a rubber 'O'-ring 32 which engages the interior of bore 20. The latch finger 26 is biased upwardly towards the plunger 6 by a helical spring 34 fixed against a screw fitted latch plug 36. The latch plug 36 includes a slotted head 38 enabling it to be tightened and undone by a screwdriver, and a stud flange 40 to engage the helical spring 34.

The plunger 6 forms part of an actuator mechanism indicated generally at 42. The plunger 6 is generally cylindrical and includes a longitudinal blind bore 44. Additionally, the plunger 6 includes an annular slot 46 shown in Figure 2 aligned with the inlet 8, and a bore 48 between the blind bore 44 and annular slot 46 thereby, in the configuration shown in Figure 2 enabling the bore 44 to be in communication with the inlet 8. The bore 44 extends from the slot 46 to the other end 49 of the plunger 6.

In external annular slots longitudinally spaced along the plunger 6 are rubber 'O' -rings 50, 52 and 54. '0'- rings 50 and 52 lie on either side of the annular slot 46. 'O'-ring 54 lies adjacent the end 49 of the plunger 6 which in Figure 2 is in the vicinity of outlet 10. Between 'O'-ring 54 and the end of plunger 6 is an exterior annular curved recess 56.

In screw-fitting engagement with the end of plunger 6 distant from curved recess 56 is an extension piece 58 the exterior diameter of which is less than the exterior diameter of plunger 6. The end of extension piece 58 distant from plunger 6 is secured by screw-fitting engagement with a button 60 which includes an internal cylindrical cavity 62. A helical spring 64 lies within the cavity 62 and abuts against a shoulder 66 (part of which is formed by the valve body about inlet 8) on the exterior of the valve body 4. A screw threaded cap piece

68 fits over the end of valve body 4 and includes a cylindrical hole therethrough through which extension piece 58 can slide, but plunger 6 cannot.

Referring now specifically to Figure 2 the valve 2 is shown in its open configuration in which water under pressure is permitted to flow from the inlet 8 to the outlet 10. In this configuration the button 60 has been depressed as far as it will go to abut against the cap piece 68. It will be noted that a considerable volume of the valve body 4 is partly encased by the hollow button 60. As the plunger 6 moves towards the outlet 10 the end 49 of the plunger 6 abuts against the hemispherical head 28 of latch finger 26. The curved head 28 of latch finger 26 means that the finger 26 is forced away from the plunger 6 against the bias of spring 34 until the end of

5 plunger 6 passes latch finger 26. When the curved recess 56 becomes aligned with latch finger 26, the hemispherical head 28 rises into interengagement with the curved recess 56. This serves to secure the plunger 6 in place.

10 In this configuration, water flows in through the inlet 8, through the annular slot 46, bore 48 and bore 44 to the outlet 10. By passing through the internal bore 44 of plunger 6, the water is able to bridge the air gap 12.

15 It is noted that in this open configuration '0' -rings

50 and 52 ensure water cannot pass from the inlet 8 to the outside of the valve 2, and 'O'-ring 54 ensures that water passing to the outlet 10 cannot pass back to the air gap 12. It is noted that the outlet 10 is in fluid

20 communication with the latch mechanism 18 in which the 'O'-ring 32 ensures that water does not pass out through the cylindrical bore 20.

The operation of the valve 2 is substantially -25 similar, to the extent that it includes like parts, to the valves shown in Figures 9-12 and 13-14 of International patent application no. PCT/GB95/01993 (published as WO96/06308) the entire content of which is incorporated herein by reference. 30

In use, as the water pressure in the heating system

(not shown) in fluid communication with the outlet 10 builds up, a back pressure is exerted on the plunger 6 and, more particularly, on the latch mechanism 18:

35 specifically the latch finger 26 and latch body 30. The W

- 11 - back pressure, when sufficient, acts against the bias of helical spring 34 to force the latch finger 26 downwards in the cylindrical bore 20 away from the plunger 6. When the hemispherical head 28 of latch finger 26 clears the curved recess 56 of plunger 6, the plunger 6 becomes released and the helical spring 64 can act against button 60 to force the plunger towards its closed configuration shown in Figure 3.

It is noted that as the plunger 6 moves towards it closed configuration (Figure 3) , the flow of water from the inlet 8 to the bore 44 is cut off before 'O'-ring 54 reaches the air gap 12. At this point the non-return valve (not shown) in outlet 10 closes off. Subsequently, the 'O'-ring 54 clears the air gap 12, but because the non-return valve in outlet 10 is closed, water does not escape from the heating system.

It is noted that in the closed configuration neither the inlet nor the outlet is in fluid communication with the air gap 12.

In its closed configuration, the plunger 6 is entirely clear of the air gap 12, thereby to ensure the 20mm gap of air between inlet 8 and outlet 16 is maintained. The 'O' -rings 52 and 54 ensure water does not escape the inlet 8 from the valve 2.

It will be appreciated, therefore, that in use the valve 2 can be used in an automatic manner in the filling of heating systems etc with water. With the valve 2 located between a pressurised water supply and a system to be filled, when the button 60 is depressed to the "open" configuration shown in Figure 2, water passes through the valve to the system and when the system is full, the back pressure operating on the latch mechanism 18 acts, against spring 64, to transfer the valve to its closed configuration as shown in Figure 3. The pressure at which the latch mechanism 18 releases the plunger 6 is determined substantially by the force exerted against movement of the latch body 30 by the helical spring 34. The force exerted by the helical spring 34 can be adjusted by varying the position of the latch plug 36 in the bore 20. The spring 34 is not overworked and therefore the pressure of automatic release from the open to the closed configuration for the valve 2 is substantially constant over time and can readily be adjusted by movement of the latch plug 36. If for any reason the latch mechanism 18 needs to be replaced, because it consists of so few parts it can readily be manufactured, it is cheap to replace and can easily be exchanged simply by removal of the latch plug 36. It can also be replaced at any time without having to drain the outlet or turn off the water pressure to the inlet.

Referring to Figures 4-9 of the drawings that follow, there is shown a second embodiment of the present invention. In Figures 4-6 similar parts are identified by like reference numerals where applicable.

Figure 4 shows the valve in an open configuration. It differs from the valve shown in Figures 1-3 primarily in the detail of the end of the plunger 6 distant from the end 49, in the construction of the inlet 8.

The plunger 6 at its end distant from end 49 includes a frusto-conical portion 70 extending to an increased diameter portion 72. The valve body 4 around the vicinity of inlet 8 includes an open end 74 of sufficient size to enable the plunger 6 to pass therethrough. The inlet 8 additionally comprises an entry valve 76 of similar construction to the latch mechanism 18 in that it comprises a finger 78 with a hemicylindrical head 80. The finger 78 is integral with a 'n' -shaped body 82 supported by a spring 84 which rests on a support plate 86. The body 82 includes slots 83 in its side to allow water to pass. The support plate 86 includes a central hole 88 through which water can flow. On the shoulder 90 of body 82, and about finger 78 is a rubber 'O'-ring 92 enabling the entry valve 76 to seal against the valve body 4.

In operation, when the plunger 6 is inserted in to the valve body 4, its frusto-conical portion 70 depresses the finger 78 of the entry valve 76 to allow water to flow through inlet 8. When the system is filled and the back pressure on latch mechanism 18 disengages from the plunger, a spring (not shown) biasses the plunger 6 towards its closed configuration, closing the entry valve 76 in the process as the frusto-conical portion 70 clears finger 78. Similarly, if back pressure arises from a fault, the bias transfers the valve to its closed configuration.

In the case of this second embodiment, the plunger 6 can then be removed from the valve body 4 as shown in Figure 5. The then empty open end 74 is filled by a plug fitment 94 as shown in Figure 6 to prevent unauthorised interference with the valve.

Referring now additionally to Figures 7-9 of the drawings that follow, the plug fitment 94 is shown in more detail. The plug fitment 94 is generally 'T' -shaped in cross section comprising a head 96 that fits in the end 74 by a screw fitting and a leg 98 the end of which fills hole 100 through which, as shown in Figure 4 the plunger 6 passes when the valve 2 is in its open configuration. The head 96 comprises two blank bores 97 which enable corresponding pins 99 in the end 49 of plunger 6 to engage and screw the fitment 94. The pins 99 are shown most clearly in Figure 9 of the drawings that follow. The head 96 and leg 98 carry annular '0' -rings 102, 104 respectively to prevent leakage from the vicinity of inlet 8. Thus both exits from the vicinity of inlet 8 through valve body 4 are closed against fluid flow by fitment 94.

The second embodiment of the present invention provides a valve which can conveniently and reliably be used to fill a water system, and then disabled so as to be tamper proof by removing the plunger 6 and inserting the fitment 94. Access to the inlet 8 by unauthorised personnel can usually be prevented unless they have the required key which, conveniently, is provided at one end of the plunger in the form of the pins 99.

In a further embodiment, the boiler and valve may be adapted so that the boiler is rendered inoperable until the plug fitment is correctly inserted in the valve. Additionally or alternatively, the boiler may be rendered inoperable unless the valve is fully in its closed configuration.

The boiler can be rendered inoperable by interrupting the water flow, by deactivating its electrical controls or in any other way apparent to a person skilled in the art.

This ensures the plunger is fully removed from the air gap before the boiler is operated.

Referring to Figure 10 of the drawings that follow, there is shown a third embodiment of the present invention in which similar parts are identified by like reference numerals where applicable.

The embodiment of Figure 11 is similar to that of Figures 1-3 except that no air gap 12 is provided. Reference numerals have been omitted as they are not required for an understanding of this embodiment. It provides an automatic filling valve which will cut itself off from its inlet supply when a suitable back pressure is reached.

Referring to the Figures 1-13 of the drawings that follow, there is shown a fourth embodiment of the present invention. The fourth embodiment is similar to the first embodiment shown in Figures 1-3 and similar reference numerals are used for like parts. Some reference numerals have been omitted for clarity. The difference between the first and fourth embodiments lies in the latching means.

In the fourth embodiment of Figures 1-13, the button 60 is formed from a deformable plastics material such as polypropylene. The open end (indicated generally at 100) of the button 60 includes a plurality of longitudinal slots 102 defining fingers 104 between them. The fingers 104 include inwardly directed tips 106. The fingers 104 are deformable radially.

The shoulder 66 includes a collar 108 screw fitted or otherwise secured thereto. The collar 108 defines an annular channel 110 between itself and shoulder 66 into which tips 106 project when the valve is in the open position shown in Figures 11 and 12. The resilience of the fingers 104 holds the button 60 in place during the filling operation. When the back pressure on the button 60 is sufficient, the tips 106 of fingers 104 are forced over collar 108 and the valve transfers to its closed configuration by the bias of spring 64.

This is a simpler latch construction that can be used to make the valve shorter as well.

In the most preferred embodiments of the present invention, there is a region around the air gap that is free from valve components of at least three times the diameter of the bore of the valve. The free region ensures a minimal risk of syphonage from outlet to inlet in order to comply with Water Research Council (WRC) requirements. A free region of twice the bore diameter provides considerable safety, but three times ensures compliance with WRC regulations.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification

(including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A valve comprising a valve body, and a plunger capable of movement relative to the valve body, the valve body comprising an inlet and an outlet whereby movement of the plunger is for selectively establishing a path of fluid communication between the inlet and the outlet, in which the valve body includes an air gap between the inlet and the outlet, and the plunger is at least partly removable from the air gap whereby a substantial region about the air gap is free from valve components.

2. A valve according to Claim 1, in which the path of fluid communication comprises a bore having a diameter and the free region about the air gap is at least twice and preferably three times the bore diameter.

3. A valve according to Claim 2, in which the bore is of substantially constant cross-section.

4. A valve according to any preceding Claim, in which the valve comprises an actuator button for moving the plunger.

5. A valve according to Claim 4, in at least one configuration of the valve, at least part of the valve body is at least partly contained within the actuator button.

6. A valve according to Claim 4 or 5, in which the actuator button is generally hollow.

7. A valve according to any preceding Claim, in which the plunger is removable from the valve body, and includes means to prevent water flowing from the inlet through the valve when the plunger is removed.

8. A valve according to any preceding Claim, in which the valve comprises means biassing the valve towards its closed configuration.

9. A valve according to Claim 8, in which the biassing means comprises a spring.

10. A valve according to Claim 9, in which the spring is between the actuator button and the valve body.

11. A valve according to any preceding Claim, in which there is provided a fitment to prevent access to said inlet or said outlet.

12. A valve according to Claim 11, in which the fitment comprises a plug.

13. A valve according to Claim 12, in which the valve body comprises means for interengaging with the plug.

14. A valve according to Claim 13, in which the interengagement means comprises a screw thread.

15. A valve according to any one of Claims 11-14, in which the valve body comprises at least one cylindrical hole blocked by the fitment.

16. A valve according to Claim 15, in which there are two such cylindrical holes.

17. A valve according to Claims 15 or 17, in which the fitment is generally T-shaped in cross-section.

18. A valve according to Claim 17, in which the head of the T-shaped fitment plugs a hole in the valve body.

19. A valve according to Claims 17 or 18, in which the leg of the T-shaped fitment plugs a hole in the valve body.

20. A valve according to any one of Claims 11-19, in which the fitment comprises means to prevent water flowing from the inlet past the fitment.

21. A valve according to Claim 20, in which the water flow prevention means comprises at least one 'O'-ring about the fitment.

22. A valve comprising an inlet, an outlet, an actuator means for selectively establishing a path of fluid communication between the inlet and the outlet, and a latch mechanism which in a first position secures the actuator means in a position to establish the path of fluid communication between the inlet and the outlet, and in a second position does not so secure the actuator means.

23. A valve according to Claim 22, in which means are provided whereby the latch mechanism transfers between its first and second positions dependent on the pressure of fluid acting upon the latch mechanism.

24. A valve according to Claim 23, in which the latch mechanism transfer means comprises means biassing the latch mechanism towards the first position.

25. A valve according to Claim 24, in which means are provided whereby the pressure at which the latch mechanism transfers between its first and second positions can be varied.

26. A valve according to Claim 25, in which the variation means adjust the bias of the latch mechanism.

27. A valve according to any one of Claims 22-26, in which in the first position the latch mechanism interengages with the actuator means.

28. A valve according to Claim 27, in which the latch mechanism comprises a latch finger which interengages with a recess in the actuator means.

29. A valve according to Claim 28 when dependent on any one of Claims 24-16, in which the biassing means biasses the finger towards the actuator.

30. A valve according to any one of Claims 22-29, in which the latch mechanism comprises a deformable finger for interengaging with another part of the valve.

31. A valve according to any one of Claims 22-29, in which the actuator means comprises a plunger which moves between an open position and a closed position. W 7 680 CT/GB97 01394

- 22 -

32. A valve according to any one of Claims 22-31 further comprising the additional features of any one of Claims 1-21.

33. A method of operating a valve according to the second aspect of the present invention, which method comprises the steps of:

a) establishing a path of fluid communication between the inlet and the outlet;

b) operating the plunger whether manually or automatically to prevent the flow of fluid from said inlet to said outlet; and

c) removing the plunger from the air gap.

34. A method of operating a valve according to Claim 33, in which the plunger is removed from the valve body.

35. A method of operating a valve according to Claim 34, in which access to the inlet or outlet is or are subsequently prevented.