GB2448418A

GB2448418A - A filter unit

Info

Publication number: GB2448418A
Application number: GB0806598A
Authority: GB
Inventors: John Joseph Power; Fergal Joseph Power
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-04-12
Filing date: 2008-04-10
Publication date: 2008-10-15
Anticipated expiration: 2028-04-10
Also published as: IE20080275A1; IES20080274A2; GB0806598D0; GB2448418B

Abstract

A filter unit comprises a filter housing defining a filter accommodating chamber 10 for accommodating a filter element, a fluid inlet 15 and a fluid outlet 13 formed in the filter housing communicating with the filter accommodating chamber 10. An access opening 16 formed in the filter housing to the filter accommodating chamber 10 for accommodating a filter element 11 therethrough to the filter accommodating chamber. A primary closure element 17 is releasably and sealably engageable in the access opening for sealably closing the access opening and for retaining the filter element in the filter accommodating chamber. A vent opening is provided in the primary closure element for venting the filter accommodating chamber and a secondary closure element 30 releasably and sealably engageable in the vent opening for sealably closing the vent opening. Advantageously the filter unit may be used when supplying compressed air to pneumatically operated apparatus.

Description

"A filter unit and a valve comprising the filter unit" The present

invention relates to a filter unit, and to a valve comprising the filter unit, and in particular, the invention relates to such a filter unit and a valve for controlling a compressed air supply, although, needless to say, the valve and the filter unit may be used for controlling the supply of other fluids, both in liquid and gaseous.

In the supply of compressed air to pneumatically operated apparatus, particularly such pneumatically operated apparatus which is controlled by pneumatic valves and o the like, it is essential that a clean supply of compressed air is provided. This, thus, requires filtering of the compressed air in a compressed air line prior to the compressed air being delivered to the pneumatic apparatus. However, the provision of a filter in a compressed air line can be problematical. In particular, due to the fact that filters require regular cleaning and/or replacement, it is essential that such filters is be easily accessible for replacement and cleaning. In general, in known filtering systems for filtering compressed air, the filter is not always easily accessible.

Furthermore, in general, it is necessary to withdraw the filter from a chamber in which the filter is located for the purpose of cleaning or replacing the filter. This is time consuming, and in certain cases can be hazardous due to the fact that the chamber may be pressurised as access is being gained to the filter.

There is therefore a need for a filter unit, and a valve comprising the filter unit, which addresses these problems.

The present invention is directed towards providing a filter unit, and a valve comprising the filter unit which is suitable for controlling and filtering a fluid supply which addresses at least some of the problems of prior art valves and filter units.

s According to the invention there is provided a filter unit comprising a filter housing defining a filter accommodating chamber for accommodating a filter element therein, a fluid inlet formed in the filter housing communicating with the filter accommodating chamber, and a fluid outlet formed in the filter housing communicating with the filter accommodating chamber, an access opening formed in the filter housing to the filter accommodating chamber for accommodating a filter element therethrough to the filter accommodating chamber, a primary closure element releasably and sealably engageable in the access opening for sealably closing the access opening and for retaining the filter element in the filter accommodating chamber, a vent opening in the primary closure element for venting the filter accommodating chamber, and a secondary closure element releasably and sealably engageable in the vent opening for sealably closing the vent opening.

In one embodiment of the invention the secondary closure element is operable in three states, namely, a closed state engaged in the vent opening sealably closing the vent opening, a purging state disengaged from the vent opening for facilitating purging of the filter accommodating chamber through the vent opening, and an intermediate state engaged in the vent opening permitting restricted communication through the vent opening with the filter accommodating chamber for venting thereof.

Preferably, the vent opening is provided by an elongated primary bore extending through the primary closure element.

Advantageously, the primary bore is internally threaded, and the secondary closure element is externally threaded for engaging the internal threads in the primary bore for securing the secondary closure element in sealable engagement in the closed state in the primary closure element.

In one embodiment of the invention a secondary sealing means is provided for i o sealing the secondary closure element in the closed state in the primary closure element.

Preferably, the primary bore extending through the primary closure element defines a secondary valve seat for sealably engaging the secondary sealing means with the secondary closure element in the closed state Advantageously, the secondary sealing means comprises a secondary 0-ring seal located on the secondary closure element.

Preferably, the secondary closure element is operable in the intermediate state in the primary bore with the secondary sealing means disengaged from the valve seat defined by the primary bore.

In one embodiment of the invention an elongated secondary bore extends into the secondary closure element from a downstream end to an upstream end, and the upstream end of the secondary bore is closed by an upstream end cap adjacent the upstream end thereof, and at least one venting bore extending through the secondary closure element communicates the secondary bore with the filter accommodating chamber through the primary bore when the secondary closure element is in the intermediate state for facilitating venting of the filter accommodating chamber.

Preferably, each venting bore extends from the secondary closure element Jo downstream of the secondary sealing means.

In one embodiment of the invention the secondary closure element comprises a secondary plug member.

s Preferably, the access opening is formed by an elongated internally threaded access bore for engaging a correspondingly externally threaded portion of the primary closure element.

In one embodiment of the invention a primary sealing means is provided for sealing the primary closure element in the access bore.

Preferably, a primary valve seat is formed in the access bore, and the primary sealing means is located on the primary closure element and is engageable with the primary valve seat.

In one embodiment of the invention the primary sealing means comprises a primary 0-ring seal.

In another embodiment of the invention the primary closure element comprises a primary plug member.

In another embodiment of the invention the filter housing is formed by a portion of a main housing, another portion of the main housing forming a valve housing having a to valve chamber therein, a main inlet port and a main outlet port being provided in the main housing, one of the main inlet port and the main outlet port being formed in the valve housing for providing one of an inlet to and an outlet from the valve chamber, and the other of the main inlet and the main outlet being formed by one of the fluid inlet and the fluid outlet of the filter housing.

Preferably, the valve chamber communicates with the filter accommodating chamber through one of the fluid inlet and the fluid outlet.

Advantageously, the valve chamber communicates with the filter accommodating chamber through the fluid inlet.

Preferably, the main outlet port is formed by the fluid outlet of the filter housing.

Advantageously, a valving element is located in the valve chamber.

Preferably, the valving element is provided by a valving member of ball shape construction.

Ideally, the valve chamber is located upstream of the filter accommodating chamber.

Preferably, the fluid inlet and the fluid outlet of the filter housing are arranged for accommodating flow of fluid in a generally axial direction and a generally radial direction sequentially through a filter element located in the filter accommodating chamber Advantageously, the fluid inlet and the fluid outlet of the fitter housing are arranged to accommodate fluid through a filter element located in the filter accommodating chamber initially in the generally axial direction and subsequently in the generally radial direction.

In one embodiment of the invention the fluid inlet defines a centrally located inlet axis, and the fluid outlet defines a centrally located outlet axis, the fluid inlet and the fluid outlet being disposed relative to each other so that a plane containing the inlet axis and a plane containtng the outlet axis are disposed at approximately 900 to each other The invention also provides a valve comprising the filter unit according to the invention Further the invention provides a valve comprising a main housing forming a filter housing defining a filter accommodating chamber for accommodating a filter element therein, and a valve housing defining a valve chamber communicating with the filter accommodating chamber through one of a fluid inlet to the filter accommodating chamber and a fluid outlet from the filter accommodating chamber, and a valving element being located in the valve chamber for controlling the flow of fluid through the valve chamber and the filter accommodating chamber, an access opening formed in the filter housing to the filter accommodating chamber for accommodating a filter element therethrough to the filter accommodating chamber, a primary closure element releasably and sealably engageable in the access opening for sealably closing the access opening and for retaining the filter element in the filter accommodating chamber, a vent opening in the primary closure element for venting the filter accommodating chamber, and a secondary closure element releasably and sealably engageable in the vent opening for sealably closing the vent opening.

In one embodiment of the invention a main inlet port and a main outlet port are provided in the main housing, one of the main inlet port and the main outlet port being formed in the valve housing for providing one of an inlet to and an outlet from the valve chamber, and the other of the main inlet and the main outlet being formed by one of the fluid inlet and the fluid outlet of me filter accommodating chamber.

Preferably, the valve chamber communicates with the filter accommodating chamber through the fluid inlet Advantageously, the main outlet port is formed by the fluid outlet of the filter accommodating chamber.

Preferably, the fluid inlet and the fluid outlet of the filter accommodating chamber are arranged for accommodating flow of fluid in a generally axial direction and a generally radial direction sequentially through a filter element located in the filter accommodating chamber.

Advantageously, the fluid inlet and the fluid outlet of the filter accommodating chamber are arranged to accommodate fluid through a filter element located in the filter accommodating chamber initially in the generally axial direction and subsequently in the generally radial direction.

is Ideally, the fluid inlet defines a centrally located inlet axis, and the fluid outlet defines a centrally located outlet axis, the fluid inlet and the fluid outlet being disposed relative to each other so that a plane containing the inlet axis and a plane containing the outlet axis are disposed at approximately 900 to each other.

Preferably, the valve chamber is located upstream of the filter accommodating chamber.

Advantageously, the valving element is provided by a valving member of ball shape construction.

The invention will be more clearly understood from the following description of a preferred embodiment thereof, which is given by way of example only, with reference to the accompanying drawings, in which: Fig 1 is a partly sectional front elevational view of a valve according to the invention incorporating a filter unit also according to the invention, Fig. 2 is a view substantially similar to Fig. I of the valve of Fig. 1 in a different state, Fig. 3 is a view substantially similar to Fig. 1 of the valve of Fig. 1 in another different state, Fig. 4 is a view substantially similar to Fig. 1 of the valve of Fig. I in a further different state, Fig 5 is an enlarged transverse cross-sectional front elevational view of a detail of the valve of Fig. 1 illustrating the valve of Fig 1 in the state of Fig. 1, and Fig. 6 is an enlarged transverse cross-sectional front elevational view of a portion of the valve of Fig. I illustrating the valve in the state of Fig. 2. I0

Referring to the drawings, there is illustrated a valve according to the invention, indicated generally by the reference numeral 1, for controlling the supply of a fluid, which in this embodiment of the invention is compressed air. In this embodiment of the invention the valve is manually operable, although it may be solenoid operated or operated by any other means. The valve 1 incorporates a filter unit, also according to the invention and indicated generally by the reference numeral 2 for filtering the compressed air as it passes through the valve 1. The valve 1 is a ball valve and comprises a main housing 3 which forms a valve housing 4 and a filter housing 5 which is integral with the valve housing 4, and forms the filter unit 2. A valve chamber 6 is formed within the valve housing 4, and a valving element, namely, a valving member 7 of ball shape construction is located in the valve chamber 6 for controlling fluid flow through the valve chamber 6. A hand knob 8 carried on a shaft 9 extending from the valving member 7 is provided for operating the valving member 7 between an open state and a closed state. The operation of such ball valves and valving members of ball shape construction will be well known to those skilled in the art.

The filter housing 5 defines a filter accommodating chamber 10 which communicates with the valve chamber 6, and within which a filter element 11 is located for filtering the fluid through the valve 1. A main inlet port 12 in the main housing 3 is provided for coupling to a fluid source and for delivering the fluid into the valve chamber 6 in the valve housing 4. A main outlet port 13 in the main housing 3 forms a fluid outlet 14 from the filter accommodating chamber 10 through which fluid is delivered from the filter accommodating chamber 10, and in turn from the valve 1. A fluid inlet 15 to

II

the filter accommodating chamber 10 communicates the filter accommodating chamber 10 with the valve chamber 6 for facilitating fluid flow from the valve chamber 6 to the filter accommodating chamber 10.

The valve chamber 6 and the filter accommodating chamber 10 are located relative to each other, and the fluid inlet 15 and the fluid outlet 14 are also located relative to each other, so that fluid passing through the valve 1 passes from the valve chamber 6 into the filter accommodating chamber 10 through the fluid inlet 15, and passes initially in a generally axial direction into the filter element 11 and subsequently in a io generally radial direction from the filter element 11 through the fluid outlet 14. This is achieved by virtue of the fact that the fluid inlet 15 defines a central inlet axis, and the fluid outlet 14 defines a central outlet axis, which is perpendicular to the central inlet axis.

is An access opening formed by an internally threaded access bore 16 accommodates the filter element 11 into and out of the filter accommodating chamber 10. A primary closure element comprising an externally threaded primary plug member 17 is engageable with the internally threaded access bore 16 for retaining the filter element 11 in the filter accommodating chamber 10, and for releasably and sealably closing the filter accommodating chamber 10. A primary sealing means, namely, a primary 0-ring seal 18 located in a primary groove 19 extending externally circumferentially around the primary plug member 17 sealably engages a primary valve seat 20 formed in the access bore 16 for sealably closing the access bore 16.

A vent opening provided by an elongated primary bore 21 extends axially through the primary plug member 17 and communicates through the primary plug member 17 with the filter accommodating chamber 10 for facilitating venting and purging the valve 1. A secondary closure element, namely, a secondary plug member 22 is S engageable in the primary bore 21 and is operable in three states, namely, a closed state illustrated in Figs. 1 and 5 sealably closing the primary bore 21, a purging state illustrated in Fig. 3 with the secondary plug member 22 disengaged and removed from the primary bore 21 for facilitating purging of the filter accommodating chamber 10, and an intermediate state illustrated in Figs. 2 and 6 for facilitating venting of the filter accommodating chamber 10, prior to purging of the filter accommodating chamber 10 or prior to removal of the filter element 11. The secondary plug member 22 is externally threaded at 23 for engaging corresponding internal threads 24 of the primary bore 21.

A secondary sealing means comprising a secondary 0-ring seal 25 is located in a secondary groove 26 extending externally circumferentially around the secondary plug member 22 adjacent an upstream end 27 thereof for engaging a secondary valve seat 28 formed in the primary bore 21 for sealing the secondary plug member 22 in the primary plug member 17 when the secondary plug member 22 is in the closed state, for in turn sealably closing the filter accommodating chamber 10.

An elongated secondary bore 30 extends axially into the secondary plug member 22 from a downstream end 31 to the upstream end 27, and is closed at the upstream end 27 by an end cap 32. A pair of radial venting bores 34 extend radially through the secondary plug member 22 downstream of the secondary 0-ring seal 25 for communicating the secondary bore 30 with the filter accommodating chamber 10 through the primary bore 21 when the secondary plug member 22 is engaged in the primary bore 22, and is in the intermediate state illustrated in Figs. 2 and 6 with the secondary 0-ring seal 25 disengaged from the secondary valve seat 28 for facilitating venting of the filter accommodating chamber 10 through the secondary bore 30.

A counter-bore 35 is formed in the primary bore 21 upstream of the valve seat 28 for accommodating a downstream end 36 of the filter 11 in the primary plug member 17.

The main inlet port 12 is extemaUy threaded at 35 for coupling the valve 1 to a compressed air supply, and the main outlet port 13 is externally threaded at 36 for facilitating connection of the valve 1 to a suitable coupling of pneumatically operated apparatus. The main outlet port 13 may be coupled to the pneumatically operated apparatus through, for example, a solenoid controlled valve (now shown).

The main housing 3 and the components of the valve 1, induding the valving member 7, the shaft 9 and the primary and secondary plug members 17 and 22 may be of any suitable material, and typically will be of metal, such as stee', brass or stainless steel. The filter element 11 may be of any suitable material, and typically, will be a porous sintered filter element.

In use, the valve 1 is coupled into a pipe-work system in which the flow of fluid is to be controlled. As mentioned above, the valve 1 is particularly suitable for use in a compressed air system for providing a compressed air supply to pneumatically operated apparatus through, for example, a solenoid operated valve (not shown).

The main inlet port 12 is coupled to the compressed air supply, and the main outlet port 13 is coupled to the solenoid operated valve (not shown). With the filter element 11 located in the filter accommodating chamber 10, and the primary plug member 17 sealably secured in the access bore 16, and the secondary plug member 22 sealably secured in the primary bore 21 of the primary plug member 17 in the closed state, the valve 1 is ready for use. When it is desired to deliver compressed air through the valve 1 to the solenoid valve (not shown), the hand knob 8 is operated for operating the valving member 7 into the open state and the hand knob 8 is operated for operating the valving member 7 into the closed state when the solenoid valve (not shown) is to be isolated from the compressed air supply.

When it is desired to purge the filter accommodating chamber 10 and the filter element 11, the hand knob 8 is operated for closing the valve 1. The secondary plug member 22 is then loosened in the primary bore 21 into the intermediate state so that the secondary 0-ring seal 25 disengages the secondary valve seat 28 for venting the filter accommodating chamber 10 and the system downstream of the valve 1. The secondary plug member 22 is then removed from the primary bore 21 so that the valve 1 is in the purging state. The hand knob 8 is operated for opening the valve 1 for purging the filter accommodating chamber 10 and the filter element 11 through the primary bore 21. On completion of purging, the valve 1 is operated into the closed state, the secondary plug member 22 is returned to and secured in the closed state in the primary bore 21.

Should it be desired to replace the filter element 11, the hand knob 8 is operated for closing the valve 1, and the secondary plug member 22 is loosened in the primary bore 21 into the intermediate state for venting the filter accommodating chamber 10 and the system downstream of the valve 1. On completion of venting, the primary plug member 17 is disengaged from the access bore 16, and as the primary plug member 17 is being disengaged from the access bore 16, the filter element 11 is withdrawn from the filter accommodating chamber 10. The filter element 11 is then io replaced in the counter-bore 35 in the primary plug member 17 with a new filter element 11, and with the primary plug member 17 is entered into the access bore 16, and urged into the filter accommodating chamber 10. The primary plug member 17 is then sealably secured in the access bore 16. Once the primary plug member 17 has been tightly and sealably secured in the access bore 16, the secondary plug is member 22 is then secured in the closed state in the primary bore 21, thus re-sealing the filter accommodating chamber 10.

The advantages of the invention are many. A particularly important advantage of the invention is that it provides a valve which in turn provides a filtered supply of fluid, for example, compressed air to a system to which the fluid supply is to be controlled by the valve. This is a particular advantage where the va've is used to provide a supply of compressed air to pneumatically operated apparatus via a solenoid operated valve. Since the compressed air supply is filtered by the valve according to the invention prior to being delivered to the solenoid valve, the integrity of the solenoid valve is maintained. A particularly important advantage of the valve according to the invention is achieved when used for supplying a compressed air supply to pneumatically operated valves. Additionally, a particularly important advantage of the valve and the filter unit according to the invention is that the valve, the filter accommodating chamber and the filter can be readily easily purged while the filter is still in position in the filter accommodating chamber. This is achieved by initially venting the filter accommodating chamber and the pneumatic system downstream of the valve according to the invention, and then withdrawing the secondary plug member from the primary bore so that the valve according to the invention is in the purging state. Once the secondary plug member has been removed from the primary bore, the valve 1 is operated into the open state for purging the valve, the filter and the filter accommodating chamber.

Additionally, the filter unit according to the invention provides for ready and easy removal and replacement of the filter. All that is required is to operate the secondary plug member into the intermediate state for venting the filter accommodating chamber, and then withdrawing the primary plug member with the secondary plug member in the intermediate state from the access bore. As the primary plug member is being withdrawn from the access bore, the filter element is withdrawn along with the primary plug member.

A further particularly important advantage of the invention is that it provides for safe venting of the filter accommodating chamber after the valve has been operated into the closed state. Once the filter accommodating chamber has been safely vented, the filter element may be safely removed or may be safely purged by removing the secondary plug member.

While the valve I and the filter unit 2 have been described as being of a particular configuration, the filter unit and the valve may be of any other suitable configuration, and while it is desirable, it is not essential that the main outlet port 13 and the fluid inlet 15 to the filter accommodating chamber 10 be disposed relative to each other so that respective central axes defined by the main outlet port 13 and the fluid inlet are disposed at right ang'es to each other. l0

While the valve 1 and the filter unit 2 have been described for use in a compressed air system, the valve I and the filter unit 2 may be used in any other fluid supply system AdditonaIly, it is envisaged in certain cases that the filter unit may be provided without the valve.

IS

It will also be appreciated that while the valve and the filter unit according to the invention have been described for supplying compressed air to pneumatically operated apparatus through a solenoid operated valve, the valve I and the filter unit 2 may be used for supplying any type of fluid to any type of system, whether the system incorporates a solenoid operated valve, pneumatically operated valves or otherwise.

Claims

Claims 1. A filter unit comprising a filter housing defining a filter

accommodating chamber for accommodating a filter element therein, a fluid inlet formed in the filter housing communicating with the filter accommodating chamber, and a fluid outlet formed in the filter housing communicating with the filter accommodating chamber, an access opening formed in the filter housing to the filter accommodating chamber for accommodating a filter element therethrough to the filter accommodating chamber, a primary closure element releasably and sealably engageable in the access opening for sealably closing the access opening and for retaining the filter element in the filter accommodating chamber, a vent opening in the primary closure element for venting the filter accommodating chamber, and a secondary closure element releasably and sealably engageable in the vent opening for sealably closing the vent opening.

2. A filter unit as claimed in Claim 1 in which the secondary closure element is operable in three states, namely, a closed state engaged in the vent opening sealably closing the vent opening, a purging state disengaged from the vent opening for facilitating purging of the filter accommodating chamber through the vent opening, and an intermediate state engaged in the vent opening permitting restricted communication through the vent opening with the filter accommodating chamber for venting thereof.

3. A filter unit as claimed in Claim 2 in which the vent opening is provided by an elongated primary bore extending through the primary closure element.

4. A filter unit as claimed in Claim 3 in which the primary bore is internally threaded, and the secondary closure element is externally threaded for engaging the internal threads in the primary bore for securing the secondary closure element in sealable engagement in the closed state in the primary closure element.

5. A filter unit as claimed in Claim 3 or 4 in which a secondary seating means is provided for sealing the secondary closure element in the closed state in the primary closure element.

6. A filter unit as claimed in Claim 5 in which the primary bore extending through the primary closure element defines a secondary valve seat for sealably engaging the secondary sealing means with the secondary closure element in the closed state.

7. A filter unit as claimed in Claim 6 in which the secondary sealing means comprises a secondary 0-ring seal located on the secondary closure element.

8. A filter unit as claimed in Claim 7 in which the secondary closure element is operable in the intermediate state in the primary bore with the secondary sealing means disengaged from the valve seat defined by the primary bore.

9. A filter unit as claimed in any of Claims 5 to 8 in which an elongated secondary bore extends into the secondary closure element from a downstream end to an upstream end, and the upstream end of the secondary bore is closed by an upstream end cap adjacent the upstream end thereof, and at least one venting bore extending through the secondary closure element communicates the secondary bore with the filter accommodating chamber through the primary bore when the secondary closure element is in the intermediate state for facilitating venting of the filter accommodating chamber.

10. A filter unit as claimed in Claim 9 in which each venting bore extends from the secondary closure element downstream of the secondary sealing means.

11. A filter unit as claimed in any preceding claim in which the secondary closure element comprises a secondary plug member.

12. A filter unit as claimed in any preceding claim in which the access opening is formed by an elongated internally threaded access bore for engaging a correspondingly externally threaded portion of the primary closure element.

13. A filter unit as claimed in Claim 12 in which a primary sealing means is provided for sealing the primary closure element in the access bore.

14. A filter unit as claimed in Claim 13 in which a primary valve seat is formed in the access bore, and the primary sealing means is located on the primary closure element and is engageable with the primary valve seat.

15. A filter unit as claimed in Claim 13 or 14 in which the primary sealing means comprises a primary 0-ring seal.

16. A filter unit as claimed in any preceding claim in which the primary closure element comprises a primary plug member.

17. A filter unit as claimed in any preceding claim in which the filter housing is formed by a portion of a main housing, another portion of the main housing forming a valve housing having a valve chamber therein, a main inlet port and a main outlet port being provided in the main housing, one of the main inlet port and the main outlet port being formed in the valve housing for providing one of an inlet to and an outlet from the valve chamber, and the other of the main inlet and the main outlet being formed by one of the fluid inlet and the fluid outlet of the filter housing.

15. A filter unit as claimed in Claim 17 in which the valve chamber communicates with the filter accommodating chamber through one of the fluid inlet and the fluid outlet.

19. A filter unit as claimed in Claim 17 or 18 in which the valve chamber communicates with the filter accommodating chamber through the fluid inlet.

20. A filter unit as claimed in any of Claims 17 to 19 in which the main outlet port is formed by the fluid outlet of the fitter housing.

21. A filter unit as claimed in any of Claims 17 to 20 in which a valving element is located in the valve chamber.

22. A filter unit as claimed in Claim 21 in which the valving element is provided by a valving member of ball shape construction.

23. A filter unit as claimed in any of Claims 17 to 22 in which the valve chamber is located upstream of the filter accommodating chamber 24. A filter unit as claimed in any preceding claim in which the fluid inlet and the fluid outlet of the filter housing are arranged for accommodating flow of fluid in a generally axial direction and a generally radial direction sequentially through a filter element located in the filter accommodating chamber.

25. A filter unit as claimed in Claim 24 in which the fluid inlet and the fluid outlet of the filter housing are arranged to accommodate fluid through a fitter element located in the filter accommodating chamber initially in the generally axial direction and subsequently in the generally radial direction 26. A filter unit as claimed in Claim 24 or 25 in which the fluid inlet defines a centrally located inlet axis, and the fluid outlet defines a centrally located outlet axis, the fluid inlet and the fluid outlet being disposed relative to each other so that a plane containing the inlet axis and a plane containing the outlet axis are disposed at approximately 90 to each other.

27. A filter unit substantially as described herein with reference to and as illustrated in the accompanying drawings.

s 28. A valve comprising the filter unit as claimed in any preceding claim.

29 A valve comprising a main housing forming a filter housing defining a filter accommodating chamber for accommodating a filter element therein, and a valve housing defining a valve chamber communicating with the filter accommodating chamber through one of a fluid inlet to the filter accommodating chamber and a fluid outlet from the filter accommodating chamber, and a valving element being located in the valve chamber for controlling the flow of fluid through the valve chamber and the filter accommodating chamber, an access opening formed in the filter housing to the filter accommodating chamber for accommodating a filter element therethrough to the filter accommodating chamber, a primary closure element releasably and sealably engageable in the access opening for sealably closing the access opening and for retaining the filter element in the filter accommodating chamber, a vent opening in the primary closure element for venting the filter accommodating chamber, and a secondary closure element releasably and sealably engageable in the vent opening for sealably closing the vent opening.

30. A valve as claimed in Claim 29 in which the secondary closure element is operable in three states, namely, a closed state engaged in the vent opening sealably closing the vent opening, a purging state disengaged from the vent opening for facilitating purging of the filter accommodating chamber through the vent opening, and an intermediate state engaged in the vent opening permitting restricted communication through the vent opening with the filter accommodating chamber for venting thereof.

31. A valve as claimed in Claim 30 in which the vent opening is provided by an elongated primary bore extending through the primary closure element.

32. A valve as claimed in Claim 31 in which the primary bore is internally threaded, and the secondary closure element is externally threaded for engaging the internal threads in the primary bore for securing the secondary closure element in sealable engagement in the closed state in the primary closure element.

33. A valve as claimed in Claim 31 or 32 in which a secondary sealing means is provided for sealing the secondary closure element in the closed state in the primary closure element.

34. A valve as claimed in Claim 33 in which the primary bore extending through the primary closure element defines a secondary valve seat for sealably engaging the secondary sealing means with the secondary closure element in the closed state.

A valve as claimed in Claim 34 in which the secondary sealing means comprises a secondary 0-ring seal located on the secondary closure element 36. A valve as claimed in Claim 35 in which the secondary closure element is operable in the intermediate state in the primary bore with the secondary sealing means disengaged from the valve seat defined by the primary bore.

37. A valve as claimed in any of Claims 33 to 36 in which an elongated secondary bore extends into the secondary closure element from a downstream end to an upstream end, and the upstream end of the secondary bore is closed by an upstream end cap adjacent the upstream end thereof, and at least one venting bore Jo extending through the secondary closure element communicates the secondary bore with the filter accommodating chamber through the primary bore when the secondary closure element is in the intermediate state for facilitating venting of the filter accommodating chamber.

38. A valve as claimed in Claim 37 in which each venting bore extends from the secondary closure element downstream of the secondary sealing means.

39. A valve as claimed in any of Claims 29 to 38 in which the secondary closure element comprises a secondary plug member.

40. A valve as claimed in any of Claims 29 to 39 in which the access opening is formed by an elongated internally threaded access bore for engaging a correspondingly externally threaded portion of the primary plug member.

41. A valve as claimed in Claim 40 in which a primary sealing means is provided for sealing the primary closure element in the access bore.

42. A valve as claimed in Claim 41 in which a primary valve seat is formed in the access bore, and the primary sealing means is located on the primary closure element and is engageable with the primary-valve seat.

43. A valve as claimed in Claim 41 or 42 in which the primary sealing means comprises a primary 0-ring seal.

44. A valve as claimed in any of Claims 29 to 43 in which the primary closure element comprises a primary plug member.

45. A valve as claimed in any of Claims 29 to 44 in which a main inlet port and a main outlet port are provided in the main housing, one of the main inlet port and the main outlet port being formed in the valve housing for providing one of an inlet to and an outlet from the valve chamber, and the other of the main inlet and the main outlet being formed by one of the fluid inlet and the fluid outlet of the filter accommodating chamber.

46 A valve as claimed in any of Claims 29 to 45 in which the valve chamber communicates with the filter accommodating chamber through the fluid inlet.

47. A valve as claimed in Claim 45 or 46 in which the main outlet port is formed by the fluid outlet of the filter accommodating chamber.

48. A valve as claimed in any of Claims 29 to 47 in which the fluid inlet and the fluid outlet of the filter accommodating chamber are arranged for accommodating flow of fluid in a generally axial direction and a generally radial direction sequentially through a filter element located in the filter accommodating chamber.

49 A valve as claimed in Claim 48 in which the fluid inlet and the fluid outlet of the filter accommodating chamber are arranged to accommodate fluid through a filter element located in the filter accommodating chamber initially in the generally axial direction and subsequently in the generally radial direction.

50. A valve as claimed in Claim 48 or 49 in which the fluid inlet defines a centrally located inlet axis, and the fluid outlet defines a centrally located outlet axis, the fluid is inlet and the fluid outlet being disposed relative to each other so that a plane containing the inlet axis and a plane containing the outlet axis are disposed at approximately 900 to each other.

51 A valve as claimed in any of Claims 29 to 50 in which the valve chamber is located upstream of the filter accommodating chamber 52. A valve as claimed in any of Claims 29 to 51 in which the valving element is provided by a valving member of ball shape construction.

53. A valve substantially as described herein with reference to and as illustrated in the accompanying drawings.