AU2008201992B2 - A fluid flow control valve - Google Patents

Abstract

A Fluid Flow Control Valve Abstract There is disclosed herein a fluid flow control valve member (10) for a valve (100). The valve member (10) comprises a piston (12) having a first side (14) and an opposite second s side (16). A stem (18) extends generally perpendicularly from the first side (14) of the piston (12) for engagement with a tap spindle (not shown). An o-ring (20), extends circumferentially around the stem (18) and is located in a substantially circular groove (22) on the first side (14) of the piston (12). A surface of the o-ring (20) projects from the groove (22). A disc (26) is slidably mounted on the stem (18). When the valve (100) is 10 open, mains water pressure on the second side (16) of the valve member (10) urges the valve member (10) toward the tap spindle, such that the disc (26) engages the spindle and compresses the resilient o-ring (20) against the piston (12). The resilience of the o-ring (20) biases the piston (12) away from the spindle and the disc (26). As a result of the compression of the o-ring (20), the spacing between the piston (12) and the disc (26) is 15 reduced, which thereby reduces a flow rate through passageways (24) in the piston (12).

Description

S&F Ref: 845705 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Combobulator Pty Ltd, of Applicant: an Australian company, ACN 119 196 806, of A3/1 Campbell Parade, Manly Vale, New South Wales, 2093, Australia Actual Inventor(s): Cameron Bartholomew Smart Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: A fluid flow control valve Associated Provisional Application Details: [33] Country: [31] Appl'n No(s): [32] Application Date: AU 2007902405 07 May 2007 The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(1 226880_1) - 1 A Fluid Flow Control Valve Technical Field The present invention relates to a fluid flow control valve. 5 The present invention has been developed for use as a mains water tap valve and will be described hereinafter with reference to this application. However, it will be appreciated that the invention may also be used in non-mains pressure systems, such as gravity systems. Background of the Invention 10 Known mains water taps typically include a tap body having a passage extending therethrough defining an inlet port at one end and an outlet port at an opposite end. An annular valve seat is provided in the passage between the inlet port and the outlet port. A valve member is axially movable within the passage into and out of sealing engagement with the valve seat to respectively close and open the tap. The valve member typically is includes a rubber washer carried on a circular head and a stem extending from the head. The stem is engageable within a spindle in the tap body, and the spindle is axially movable within the tap body between a closed position and an open position. In the closed position, the spindle urges the valve member into sealing engagement with the valve seat. In the open position, the valve member is free floating between the valve seat 20 and the spindle so as to move out of engagement with the valve seat in response to water pressure and thereby to allow water to pass through the tap. A disadvantage of known tap valves is that they are not well suited to handle a large range of water pressures. Accordingly, the flow rate through known valves varies as a result of 25 fluctuations in mains water pressure. Moreover, even small movements of the spindle can result in coarse adjustments of water flow. A further disadvantage of known tap valves is that when the spindle is in the open position, the valve member is free floating between the valve seat and the spindle, and 30 accordingly, changes in water pressure can cause the valve member to slam closed against the valve seat, causing a noise referred to as water hammer.

-2 Another disadvantage of known tap valves is that the tap washer is prone to high wear, which leads to leaks. Another disadvantage of known tap valves is that the washer has a short service life and 5 becomes less efficient as it ages and wears. Yet a further disadvantage of known tap valves is that they often vary in efficiency and performance depending on the temperature of water being used. io Another disadvantage of known tap valves is that the rotational friction generated when the tap is turned on and off wears the valve seat as well as the washer. Another disadvantage of known tap valves, which are located in a pipe network, is that backfeeding and/or backsyphonage can occur. 15 Another disadvantage of known tap valves is that the washer deteriorates if the tap is left open for a long period, such as is often the case in water meter taps. To overcome most of the above disadvantages, the fluid flow control valve disclosed in 20 International Patent Publication No. WO 89/12192, the disclosure of which is incorporated herein in its entirety by reference, was developed. However, this valve does not overcome the problem of fluctuations in mains water pressure causing significant variance in the fluid flow rate through the valve. Object of the Invention 25 It is the object of the present invention to substantially overcome or at least ameliorate one or more of the above disadvantages. Summary of the Invention Accordingly, in a first aspect, the present invention provides a fluid flow control valve member for a tap having a tap spindle, said valve member comprising: 30 a piston having a first side and an opposite second side; a stem extending generally perpendicularly from the first side of said piston for engagement with said tap spindle; -3 at least one passageway extending through the piston to provide for fluid flow between the first side and the second side of said piston; a resilient member associated with said piston and adapted to resiliently bias the piston away from the tap spindle to control a spacing between the piston and the spindle 5 and thereby to control a flow rate through said at least one passageway. The resilient member is preferably adapted to automatically deform in response to changes in fluid pressure on the second side of the piston when the tap is open, so as to control the spacing between the piston and the spindle and thereby maintain a substantially constant fluid flow rate through the tap. Preferably, the fluid flow rate 10 through the tap changes by less than about 5L/min if the fluid pressure varies between about 150kPa and about 500kPa. More preferably, the fluid flow rate through the tap changes by less than about 2L/min if the fluid pressure varies between about 150kPa and about 350kPa. The resilient member is preferably located on the first side of said piston. The resilient is member is preferably adapted to be compressed between the piston and the tap spindle in response to an increase of fluid pressure on the second side of said piston. The resilient member preferably has a linear spring rate of between around 5N/mm and around ION/mm, and more preferably between around 6N/mm and around 8N/mm. In some embodiments, the resilient member is an o-ring. The o-ring is preferably located 20 in a substantially circular groove on the first side of the piston. In addition to controlling the spacing between the piston and the spindle, the o-ring is preferably also adapted to at least partially deform in response to an increase of fluid pressure on said second side of said piston to reduce a cross-sectional area of said passageway. Even more preferably, the o-ring is adapted to expand in a direction substantially perpendicular to the stem, in 25 response to the resilient member being compressed between the piston and the tap spindle, and thereby to reduce the cross-sectional area of the passageway. The o-ring preferably extends circumferentially around the stem. The o-ring preferably expands radially outwardly from the stem in response to being compressed between the piston and the tap spindle. 30 In other embodiments, the resilient member is a compression spring. One end of the compression spring is preferably located in a substantially circular groove on the first side of the piston.

-4 One end of the passageway preferably extends into a substantially circular groove on the first side of the piston. A plurality of said passageways are preferably provided between the first and the second side of the piston. Four of the passageways are preferably provided. The passageways are preferably substantially equally spaced apart around the 5 piston, substantially at a fixed distance from the stem. A disc is preferably slidably mounted on the stem. The resilient member is preferably located between the piston and the disc, such that the resilient member resiliently biases the disc away from the piston to control a spacing between the disc and the piston and thereby to control the flow rate through the at least one passageway. The disc is 1o preferably adapted to sealingly engage the first side of the piston upon closing the tap to seal said at least one passageway. The disc is preferably also adapted to sealingly engage the first side of the piston, when fluid pressure on the second side of the tap exceeds a predetermined level, to close said at least one passageway. The disc preferably has a diameter greater than an outer diameter of the groove. More preferably, the disc diameter is is less than or equal to a diameter of the piston. The disc is preferably formed from an engineered resin. The engineered resin is preferably a glass filled nylon. Alternatively, the disc can be formed from brass, stainless steel, ceramics or plastics. The disc preferably includes a non-circular aperture for engaging a non-circular key portion of the stem to prevent relative rotation between the disc and the stem. 20 A blind opening is preferably provided generally centrally on the second side of the piston. In a second aspect, the present invention provides a fluid flow control valve comprising: a generally cylindrical valve chamber defining a longitudinal axis and having an inlet port and an outlet port; 25 a valve seat adjacent said inlet port; a valve member axially reciprocably movable within said valve chamber, along said longitudinal axis, between a closed position in which said valve member sealingly engages said valve seat and an open position in which said valve member is disengaged from said valve seat, said valve member comprising: 30 a piston having a first side and an opposite second side; a stem extending generally perpendicularly from the first side of said piston for engagement with said tap spindle; -5 at least one passageway extending through the piston to provide for fluid flow between the first side and the second side of said piston; a resilient member associated with said piston and adapted to resiliently bias the piston away from the tap spindle to control a spacing between the piston and the spindle 5 and thereby to control a flow rate through said at least one passageway. The resilient member is preferably adapted to automatically deform in response to changes in fluid pressure on the second side of the piston when the tap is open, so as to control the spacing between the piston and the spindle and thereby maintain a substantially constant fluid flow rate through the tap. Preferably, the fluid flow rate io through the tap changes by less than about 5L/min if the fluid pressure varies between about 150kPa and about 500kPa. More preferably, the fluid flow rate through the tap changes by less than about 2L/min if the fluid pressure varies between about 150kPa and about 350kPa. The resilient member is preferably located on the first side of said piston. The resilient is member is preferably adapted to be compressed between the piston and the tap spindle in response to an increase of fluid pressure on the second side of said piston. The resilient member preferably has a linear spring rate of between around SN/mm and around ION/mm, and more preferably between around 6N/mm and around 8N/mm. In some embodiments, the resilient member is an o-ring. The o-ring is preferably located 20 in a substantially circular groove on the first side of the piston. In addition to controlling the spacing between the piston and the spindle, the o-ring is preferably also adapted to at least partially deform in response to an increase of fluid pressure on said second side of said piston to reduce a cross-sectional area of said passageway. Even more preferably, the o-ring is adapted to expand in a direction substantially perpendicular to the stem, in 25 response to the resilient member being compressed between the piston and the tap spindle, and thereby to reduce the cross-sectional area of the passageway. The o-ring preferably extends circumferentially around the stem. The o-ring preferably expands radially outwardly from the stem in response to being compressed between the piston and the tap spindle. 30 In other embodiments, the resilient member is a compression spring. One end of the compression spring is preferably located in a substantially circular groove on the first side of the piston.

-6 One end of the passageway preferably extends into a substantially circular groove on the first side of the piston. A plurality of said passageways are preferably provided between the first and the second side of the piston. Four of the passageways are preferably provided. The passageways are preferably substantially equally spaced apart around the 5 piston, substantially at a fixed distance from the stem. A disc is preferably slidably mounted on the stem. The resilient member is preferably located between the piston and the disc, such that the resilient member resiliently biases the disc away from the piston to control a spacing between the disc and the piston and thereby to control the flow rate through the at least one passageway. The disc is to preferably adapted to sealingly engage the first side of the piston upon closing the tap to seal said at least one passageway. The disc is preferably also adapted to sealingly engage the first side of the piston, when fluid pressure on the second side of the tap exceeds a predetermined level, to close said at least one passageway. The disc preferably has a diameter greater than an outer diameter of the groove. More preferably, the disc diameter is is less than or equal to a diameter of the piston. The disc is preferably formed from an engineered resin. The engineered resin is preferably a glass filled nylon. Alternatively, the disc can be formed from brass, stainless steel, ceramics or plastics. The disc preferably includes a non-circular aperture for engaging a non-circular key portion of the stem to prevent relative rotation between the disc and the stem. 20 A blind opening is preferably provided generally centrally on the second side of the piston. An outer diameter of the piston is preferably only marginally smaller than an inner diameter of the valve chamber so as to define a restricted annular passageway therebetween. The ratio of the outer diameter of the piston to the inner diameter of the 25 valve chamber is preferably between around 0.95 and around 0.997. The ratio of the outer diameter of the piston to the inner diameter of the valve chamber can be selected to control a flow rate of fluid through the valve. Brief Description of the Drawings Preferred embodiments will now be described, by way of examples only, with reference 30 to the accompanying drawings, in which: Fig I is a side elevational view of a preferred embodiment of a fluid flow control valve member; -7 Fig 2 is a cross-sectional view taken along line 2-2 of Fig 1; Fig 3 is a top plan view of the valve member of Fig 1, shown with the disc removed; Fig 4A is a top plan view of the disc of the valve member of Fig. 1; Fig 4B is a side elevation of the disc of Fig 4A; 5 Fig 5 is a cross-sectional view of a first embodiment of a fluid flow control valve incorporating the valve member of Fig 1, with the valve member shown in a closed position; Fig 6 is a cross-sectional view of the fluid flow control valve of Fig 5, with the valve member shown in an open position; 10 Fig 7 is a chart of the results exhibited by the valve of Figs 5 and 6 when subjected to the test procedure defined in Australian Standard: ATS 5200.037.2; Fig 8 is a cross-sectional view of a second embodiment of a fluid flow control valve incorporating a second embodiment of a fluid flow control valve member, with the valve member shown in a closed position; is Fig 9 is a cross-sectional view of the fluid flow control valve of Fig 8, with the valve member shown in an open position; Fig 10 is a cross-sectional view of a third embodiment of a fluid flow control valve incorporating the valve member of Figs 8 and 9, with the valve member shown in an open position; and 20 Fig 11 is a cross-sectional view of a third embodiment of a fluid flow control valve member. Detailed Description of the Preferred Embodiments Referring in particular to Figs 1-3 of the drawings, there is provided a fluid flow control valve member 10. The valve member 10 comprises a piston 12 having a first side 14 and 25 an opposite second side 16. A stem 18 extends generally perpendicularly from the first side 14 of the piston 12 for engagement with a tap spindle (not shown). As shown in Fig 2, a blind opening 19 is provided generally centrally on the second side 16 of the piston 12. The blind opening 19 increases the surface area of the second side 16 of the piston 12 and increases a lifting force applied to the piston 12 caused by an increase in fluid 30 pressure on the second side 16 of the piston 12. A resilient member, in the form of an o-ring 20, extends circumferentially around the stem 18 and is located in a substantially circular groove 22 on the first side 14 of the piston 12. A surface of the o-ring 20 projects from the groove 22. The o-ring 20 has a -8 linear spring rate, measured in an axial direction, of between around 6N/mm and around 8N/mm. Four passageways 24 extend through the piston 12 to provide for fluid flow between the first side 14 of the piston 12 and the second side 16 of the piston 12. One end of each 5 passageway 24 extends into the groove 22. The passageways 24 are substantially equally spaced apart around the piston 12 at a fixed distance from the stem 18. A disc 26 formed from an engineered resin, in the form of glass filled nylon, is slidably mounted on the stem 18, such that the o-ring 20 is located between the piston 12 and the disc 26. The combined thickness of the piston 12 and disc 26 is around 6mm. As best io seen in Fig 1 and 2, the disc 26 has a diameter greater than an outer diameter of the groove 22 and less than a diameter of the piston 12. As best seen in Figs 3 and 4, the stem 18 has a non-circular key portion 28 engageable with a non-circular aperture 30 in the disc 26 to prevent relative rotation between the disc 26 and the stem 18. This prevention of relative rotation reduces friction between the disc 26 and the o-ring 20 and 15 thereby advantageously substantially increases the service life of the o-ring 20. The prevention of relative rotation also reduces friction between the disc 26 and the stem 18 and thereby also advantageously increases the service life of the disc 26. In use, as shown in Figs 5 and 6, the valve member 10 is located in a valve chamber 32, and the valve member 10 and valve chamber 32 together define a fluid flow control valve 20 100. The valve chamber 32 is generally cylindrical, with an outer diameter of the piston 12 of the valve member 10 being only marginally smaller than an inner diameter of the valve chamber 32 so as to define a restricted annular passageway 34 therebetween. The specific ratio of the outer diameter of the piston relative to the inner diameter of the valve chamber is selected to provide for a specific flow rate through the valve 100. In the 25 illustrated embodiment, the outer diameter of the piston 12 is 18.07mm and the inner diameter of the valve chamber 32 is 18.25mm, which provides for a controlled fluid flow rate through the valve 100 of approximately 9L/min. The valve chamber 32 has an inlet port 36 at one end and an outlet port 38 at an opposite end. An axis 40 extends between the inlet port 36 and the outlet port 38. A valve seat 42 30 is located adjacent the inlet port 34. The valve member 10 is axially reciprocably movable within the valve chamber 32, along the axis 40, between a closed position, as shown in Fig 5, in which the valve member 10 -9 sealingly engages the valve seat 42 and an open position, as shown in Fig 6, in which the valve member 10 is disengaged from the valve seat 42. The valve seat 42 includes a sealing member, in the form of an o-ring 44, that is engageable by a circumferential circular flange 46 extending axially from the valve s member 10. The o-ring 44 is retained in a groove 48, as disclosed in earlier International Patent Publication No. WO 89/12192, the disclosure of which is incorporated herein in its entirety by reference. The o-ring 44 includes a first upper sealing surface 50 engageable by the circular flange 46 on the valve member 10 and a second lower sealing surface 52 engageable with the valve seat of the tap (not shown). 10 A spigot 54 extends axially from the valve seat 42 for engagement with the valve port of the tap (not shown). The spigot 54 includes a sealing member, in the form of an o-ring 56, extending around the periphery thereof for sealingly engaging an inner surface of the tap's valve port. In use, the valve 100 is inserted in a mains water tap (not shown) such that the spigot 54 is engages with the tap's valve port (not shown). The stem 18 of the valve member 10 is then engaged with the tap's spindle (not shown) in the conventional manner. When the tap has been assembled, screwing the tap handle in one direction causes the spindle to move axially toward the valve seat 42 to urge the valve member 10 toward the closed position, as shown in Fig 5. In the closed position, the disc 26 is sealingly engaged with 20 the first side 14 of the piston 12 to close the passageways 24. Screwing the tap handle in the opposite direction moves the spindle away from the valve seat 42 and disengages the valve member 10 from the valve seat 42, as shown in Fig 6. When the valve 100 is open, as shown in Fig 6, mains water pressure on the second side 16 of the valve member 10 urges the valve member 10 toward the tap spindle, such that 25 the disc 26 engages the spindle and compresses the resilient o-ring 20 against the piston 12. The resilience of the o-ring 20 biases the piston 12 away from the spindle and the disc 26. As a result of the compression of the o-ring 20, the spacing between the piston 12 and the disc 26 (as well as between the piston 12 and the spindle) is reduced, which thereby reduces a flow rate through the passageways 24. If the mains water pressure 30 becomes sufficiently high, the o-ring 20 compresses sufficiently to allow the disc 26 to sealingly engage the first side 14 of the piston 12 to close the passageways 24, thereby forcing all water to flow through the restricted annular passageway 34 between the piston 12 and the valve chamber 32. Accordingly, it will be appreciated that the resilience of the -10 o-ring 20 controls the spacing between the piston 12 and the tap spindle and thereby controls the flow rate through the passageways 24 and indeed through the tap. A second order of flow control is provided by the o-ring 20 being adapted automatically to at least partially deform and expand radially outwardly in a direction substantially 5 perpendicular to the stem 18 in response to an increase of fluid pressure on the second side 16 of the piston 12. This deformation and expansion of the o-ring 20 partially covers the passageways 24 and thereby reduces their cross-sectional areas to control the fluid flow rate through the outlet port 38. Conversely, when the mains water pressure on the second side 16 of the piston 12 reduces, the compression of the o-ring 20 between the to piston 12 and the tap spindle is reduced, allowing the o-ring 20 to elastically return to its original size and thereby expose the passageways 24 and increase their cross-sectional areas to control the fluid flow rate through the outlet port 38. Fig. 7 shows a graph of the results exhibited by the valve 100 of Figs 5 and 6 when subjected to the test procedure defined in Australian Standard: ATS 5200.037.2, the is contents of which are incorporated herein by reference. The graph shows that the flow rate through the valve 100 remains substantially constant (i.e. varies by less than 2.0 L/min) despite the mains water pressure changing between 150 and 500kPa. Figs 8 and 9 illustrate a second embodiment of a valve 200 and valve member 10A, wherein the valve chamber 32 and spigot 54 are of unitary construction and the valve seat 20 42 is defined by an annular flange extending radially outwardly from the inlet port 36. To facilitate sealing engagement between the valve member 10 and valve seat 42, an o-ring 60 is captively retained in a groove 62 on the second side 16 of the piston 12. A washer 64 is also provided to effect sealing engagement between an underside of the annular flange 42 and a tap seat (not shown). The valve 200 has other components in common 25 with valve 100 described in the first embodiment above, where like reference numerals indicate equivalent components. Fig 10 illustrates a third embodiment of a valve 300 similar to those of Figs 5 and 6 and Figs 8 and 9, where like reference numerals indicate equivalent components. However, the valve chamber 32 of the valve 300 is integrated into the body of a tap 400, similarly to 30 the valve disclosed in the Applicant's co-pending Australian Provisional Patent Application No. 2007901237, the disclosure of which is incorporated herein in its entirety by reference.

- 11 Fig 11 illustrates a third embodiment of a fluid flow control valve member I OB, which functions identically to the valve 10 of Figs 1-10, where like reference numerals indicate equivalent components. However, in valve member lOB, the o-ring 20 is replaced with a compression spring 20A for biasing the piston 12 away from the disc 26 (and away from 5 the tap spindle). It will be appreciated that the illustrated valve members 10, 1 0A, 1 OB and valves 100, 200, 300 advantageously provide for substantially constant fluid flow by virtue of o-ring 20 or compression spring 20A controlling the spacing between the piston 12 and the disc 26, during fluctuating mains pressure, to thereby control the flow rate through the 10 passageways 24 and maintain a substantially constant flow rate through the valve. Moreover, due to the o-ring 20 or compression spring 20A being located in the groove 22 and being covered by the disc 26, the o-ring 20 or compression spring 20A is protected from overcompression and from excessive frictional forces. Accordingly, the service life of the o-ring 20 or compression spring 20A is advantageously increased. Also, due to the 15 piston 12 and disc 26 having a combined thickness of approximately 6mm, the valve member 10, 1 OA, I OB is advantageously suitable for use in most conventional tap valve chambers. If the piston 12 and disc 26 are too thick, insufficient clearance is provided between the piston 12 and the valve seat 42, which results in the valve 100, 200, 300 not being able to be adequately opened. 20 Whilst the invention has been described with reference to a specific embodiment, it will be appreciated that it may also be embodied in many other forms. For example: * more or less than four fluid passageways 24 can be provided; e the disc 26 can be omitted such that the o-ring 20 is deformed by direct contact with the tap spindle; 25 e other changes to the structure of the valve chamber and valve member can also be made, such as those disclosed in the Applicant's co-pending Australian Provisional Patent Application No. 2006905596, the disclosure of which is incorporated herein in its entirety by reference; * the disc 26 can be formed from other materials, such as brass, stainless steel, 30 ceramics or plastics; * the outer diameter of the piston can be set at 17.5mm, 17.93mm, 18.11mm or 18.2mm to provide, respectively, for controlled fluid flow rates of 15L/min, - 12 12L/min, 6L/min or 2L/min when used in conjunction with a valve chamber having an inner diameter of 18.25mm; e the piston 12 and stem 18 can be formed from other materials, such as brass, stainless steel, plastics or ceramics; and/or s e a cylindrical spring can be used instead of the helical spring 20A of Fig 11.

Claims (44)

1. A fluid flow control valve member for a tap having a tap spindle, said valve member comprising: a piston having a first side and an opposite second side; 5 a stem extending generally perpendicularly from the first side of said piston for engagement with said tap spindle; at least one passageway extending through the piston to provide for fluid flow between the first side and the second side of said piston; a resilient member associated with said piston and adapted to resiliently bias the io piston away from the tap spindle to control a spacing between the piston and the spindle and thereby to control a flow rate through said at least one passageway.

2. A fluid flow control valve member according to claim 1, wherein the resilient member is adapted to automatically deform in response to changes in fluid pressure on the second side of the piston when the tap is open, so as to control the spacing between is the piston and the spindle and thereby maintain a substantially constant fluid flow rate through the tap.

3. A fluid flow control valve member according to claim 2, wherein the fluid flow rate through the tap changes by less than about 5L/min if the fluid pressure varies between about 150kPa and about 500kPa. 20

4. A fluid flow control valve member according to claim 2, wherein the fluid flow rate through the tap changes by less than about 2L/min if the fluid pressure varies between about l50kPa and about 350kPa.

5. A fluid flow control valve member according to any one of the preceding claims, wherein the resilient member is located on the first side of said piston. 25

6. A fluid flow control valve member according to claim 5, wherein the resilient member is adapted to be compressed between the piston and the tap spindle in response to an increase of fluid pressure on the second side of said piston.

7. A fluid flow control valve member according to any one of the preceding claims, wherein the resilient member has a linear spring rate of between approximately 5N/mm 30 and approximately 1 ON/mm.

8. A fluid flow control valve member according to claim 7, wherein the resilient member has a linear spring rate of between approximately 6N/mm and approximately 8N/mm. -14

9. A fluid flow control valve member according to any one of the preceding claims, wherein the resilient member is an o-ring.

10. A fluid flow control valve member according to claim 9, wherein the o-ring is located in a substantially circular groove on the first side of the piston. 5

11. A fluid flow control valve member according to claim 9 or claim 10, wherein in addition to controlling the spacing between the piston and the spindle, the o-ring is also adapted to at least partially deform, in response to an increase of fluid pressure on said second side of said piston, to reduce a cross-sectional area of said passageway.

12. A fluid flow control valve member according to claim 11, wherein the o-ring is 10 adapted to expand in a direction substantially perpendicular to the stem, in response to the resilient member being compressed between the piston and the tap spindle, and thereby to reduce the cross-sectional area of the passageway.

13. A fluid flow control valve member according to any one of claims I to 8, wherein the resilient member is a compression spring. is

14. A fluid flow control valve member according to claim 13, wherein one end of the compression spring is located in a substantially circular groove on the first side of the piston.

15. A fluid flow control valve member according to any one of the preceding claims, wherein one end of the passageway extends into a substantially circular groove on the 20 first side of the piston.

16. A fluid flow control valve member according to any one of the preceding claims, wherein a plurality of said passageways are provided between the first and the second side of the piston.

17. A fluid flow control valve member according to any one of the preceding claims, 25 wherein a disc is slidably mounted on the stem.

18. A fluid flow control valve member according to claim 17, wherein the resilient member is located between the piston and the disc, such that the resilient member resiliently biases the disc away from the piston to control a spacing between the disc and the piston and thereby to control the flow rate through the at least one passageway. 30

19. A fluid flow control valve member according to claim 17 or claim 18, wherein the disc is adapted to sealingly engage the first side of the piston upon closing the tap to seal said at least one passageway.

20. A fluid flow control valve member according to any one of claims 17 to 19, wherein the disc is adapted to sealingly engage the first side of the piston, when fluid pressure on 15 the second side of the tap exceeds a predetermined level, to close said at least one passageway.

21. A fluid flow control valve comprising: a generally cylindrical valve chamber defining a longitudinal axis and having an inlet port and an outlet port; a valve seat adjacent said inlet port; a valve member axially reciprocably movable within said valve chamber, along said longitudinal axis, between a closed position in which said valve member sealingly engages said valve seat and an open position in which said valve member is disengaged from said valve seat, said valve member comprising: a piston having a first side and an opposite second side; a stem extending generally perpendicularly from the first side of said piston for engagement with a tap spindle; at least one passageway extending through the piston to provide for fluid flow between the first side and the second side of said piston; a resilient member associated with said piston and adapted to resiliently bias the piston away from the tap spindle to control a spacing between the piston and the spindle and thereby to control a flow rate through said at least one passageway.

22. A fluid flow control valve according to claim 21, wherein the resilient member is adapted to automatically deform in response to changes in fluid pressure on the second side of the piston when the tap is open, so as to control the spacing between the piston and the spindle and thereby maintain a substantially constant fluid flow rate through the tap.

23. A fluid flow control valve according to claim 22, wherein the fluid flow rate through the tap changes by less than about 5L/min if the fluid pressure varies between about l50kPa and 500kPa.

24. A fluid flow control valve according to claim 22, wherein the fluid flow rate through the tap changes by less than about 2L/min if the fluid pressure varies between about l50kPa and 350kPa.

25. A fluid flow control valve according to any one of claims 21 to 24, wherein the resilient member is located on the first side of said piston.

26. A fluid flow control valve according to claim 25, wherein the resilient member is adapted to be compressed between the piston and the tap spindle in response to an increase of fluid pressure on the second side of said piston. - 16

27. A fluid flow control valve according to any one of claims 21 to 26, wherein the resilient member has a linear spring rate of between approximately 5N/mm and approximately ION/mm.

28. A fluid flow control valve according to claim 27, wherein the resilient member has 5 a linear spring rate of between approximately 6N/mm and approximately 8N/mm.

29. A fluid flow control valve according to any one of claims 21 to 28, wherein the resilient member is an o-ring.

30. A fluid flow control valve according to claim 29, wherein the o-ring is located in a substantially circular groove on the first side of the piston. 10

31. A fluid flow control valve according to claim 29 or claim 30, wherein, in addition to controlling the spacing between the piston and the spindle, the o-ring is also adapted to at least partially deform in response to an increase of fluid pressure on said second side of said piston to reduce a cross-sectional area of said passageway.

32. A fluid flow control valve according to claim 31, wherein the o-ring is adapted to is expand in a direction substantially perpendicular to the stem, in response to the resilient member being compressed between the piston and the tap spindle, and thereby to reduce the cross-sectional area of the passageway.

33. A fluid flow control valve according to any one of claims 21 to 28, wherein the resilient member is a compression spring. 20

34. A fluid flow control valve according to claim 33, wherein one end of the compression spring is located in a substantially circular groove on the first side of the piston.

35. A fluid flow control valve according to any one of claims 21 to 34, wherein one end of the passageway extends into a substantially circular groove on the first side of the 25 piston.

36. A fluid flow control valve according to claim 35, wherein a plurality of said passageways are provided between the first and the second side of the piston.

37. A fluid flow control valve according to any one of claims 21 to 36, wherein a disc is slidably mounted on the stem. 30

38. A fluid flow control valve according to claim 37, wherein the resilient member is located between the piston and the disc, such that the resilient member resiliently biases the disc away from the piston to control a spacing between the disc and the piston and thereby to control the flow rate through the at least one passageway. -17

39. A fluid flow control valve according to claim 37 or claim 38, wherein the disc is adapted to sealingly engage the first side of the piston, upon closing the tap, to seal said at least one passageway.

40. A fluid flow control valve according to any one of claims 37 to 39, wherein the disc 5 is adapted to sealingly engage the first side of the piston, when fluid pressure on the second side of the tap exceeds a predetermined level, to close said at least one passageway.

41. A fluid flow control valve according to any one of claims 21 to 40, wherein an outer diameter of the piston is only marginally smaller than an inner diameter of the valve io chamber, so as to define a restricted annular passageway therebetween.

42. A fluid flow control valve according to claim 41, wherein the ratio of the outer diameter of the piston to the inner diameter of the valve chamber is between approximately 0.95 and approximately 0.997.

43. A fluid flow control valve member for a tap having a tap spindle, said valve 15 member substantially as hereinbefore described with reference to Figs 1-7, Figs 8-10 or Fig 11 of the accompanying drawings.

44. A fluid flow control valve substantially as hereinbefore described with reference to Figs 1-7, Figs 8-9, Fig 10 or Fig 11 of the accompanying drawings. Dated 6 May, 2008 20 Combobulator Pty Ltd Patent Attorneys for the Applicant/Nominated Person SPRUSON & FERGUSON