A valve

Abstract

A valve 10 includes a housing 12 with a central bore 42, a lead screw 50, a fluid inlet 20 and outlet 22, and a barrier 24 inside the housing that partially obstructs fluid flow. A flexible diaphragm 28 with inlet bleed holes 30 is movable towards a closed position where it contacts a valve sealing face on the barrier, preventing fluid from flowing from the inlet to the outlet. A fluid outlet bleed port 36 controls fluid flow from an outlet cavity 34 to the fluid outlet. A valve stem 46 and a connected outlet bleed port seal 40 move within the bore towards and away from a valve sealing face. A motor 14 moves these towards the valve sealing face, causing fluid pressure to build up in the outlet cavity which moves the flexible diaphragm to its closed position. The valve stem holds the flexible diaphragm in the closed position when it is closed. The valve may be used in a domestic or bulk potable water metering system and may help mitigate the effects off suspended solid particles in the water, low flow pressure, excessively high flow pressure, and high back pressure.

Description

BACKGROUND OF THE INVENTION This patent application relates to a valve for fluids, particularly for use in a water system. Valves of various designs are commonly used in the remote and manual flow control of potable water in domestic and bulk water reticulation networks. Common knowledge is that valves, of any design may fail to function properly for the following reasons. When suspended solid particles in the transporting medium are trapped between the shut-off seal and the shut-off valve seat. The dripping domestic faucet is a typical example of such a failure. No matter how forcibly the faucet is turned shut, it will not completely stop the water flow. When water delivery pressure reduces to below 2 bar a pressure assisted, or pilot operated diaphragm valve may not shut fully. Similarly, when a high back pressure condition is induced from the down-stream reticulation branch, the diaphragm valve may open under the low flow pressure condition. When remotely controlled, battery operated valves of various designs are subjected to high delivery pressure, example greater than 8 bar, they may have difficulty in shutting, or even beginning to shut, through inadequate strength of the installed electric motor or solenoid. With battery powered valves, the prime mover device, be it motor or solenoid, is commonly sized minimally by the manufacturer, to avoid the use of high voltage batteries. There are systems that deploy more powerful prime movers, to avoid this failure mode, but they tend to be excessively bulky, and deploy batteries that require frequent replacement because high electric current draw is necessary to drive the valve open / shut mechanism. In the domestic and bulk potable water conveying field, the need exists for an automatic valve that is designed to mitigate the effects of the following conditions. • Suspended solid particles in the water • Low flow pressure • Excessively high flow pressure • High back pressure to the valve Generally this requires a high electrical current draw prime mover system, necessitating bulky motors and batteries, with the added necessity for frequent battery replacement. The present invention provides an alternate valve design which address the above problems. SUMMARY OF THE INVENTION According to one example embodiment, a valve includes: a housing having a central bore therein; a lead screw located in the central bore, the lead screw including a screw thread formation formed thereon; a fluid inlet into the housing; a fluid outlet from the housing, the fluid outlet in fluid communication with the inlet; a barrier located inside the housing between the fluid inlet and fluid outlet, the barrier partially obstructing flow of fluid from the fluid inlet to the fluid outlet, the barrier having a valve sealing face located on top of the barrier; a flexible diaphragm with a plurality of fluid inlet bleed holes to allow fluid to move from an inlet cavity on one side of the flexible diaphragm to an outlet cavity on another side of the flexible diaphragm, the flexible diaphragm movable towards and away from a closed position wherein when the flexible diaphragm is in the closed position it is seated on the valve sealing face thereby preventing fluid from flowing from the fluid inlet, over the barrier and to the fluid outlet; a fluid outlet bleed port to allow fluid to move from the outlet cavity to the fluid outlet; a fluid outlet bleed port seal movable between an open position in which fluid can flow from the outlet cavity, via the outlet bleed port to the fluid outlet, and a closed position in which fluid cannot flow from the outlet cavity, via the outlet bleed port to the fluid outlet; a valve stem located in the central bore and connected to the outlet bleed port seal, the valve stem having a screw thread formation thereon sized to engage with the screw thread formation on the lead screw so that the valve stem is thereby movable within the central bore towards and away from a closed position in contact with the valve sealing face; and a motor connected to the lead screw and thereby to the valve stem to move the valve stem within the central bore so that when the valve stem and the outlet bleed port seal are moved into the closed position, fluid cannot flow from the outlet cavity, via the outlet bleed port to the fluid outlet, thereby causing a fluid pressure build up in the outlet cavity which in turn moves the flexible diaphragm to its closed position thereby preventing fluid from flowing from the fluid inlet to the fluid outlet, further wherein when the valve stem and the flexible diaphragm are in the closed position the valve stem holds the flexible diaphragm in the closed position, and further wherein when the motor moves the valve stem and the outlet bleed port seal away from the closed position, fluid is able to flow from the outlet cavity, via the outlet bleed port to the fluid outlet which releases fluid pressure in the outlet cavity and thereby allows the flexible diaphragm to move away from the closed position which in turn allows fluid to flow from the fluid inlet to the fluid outlet. The valve may further include a shut-off disc attached to the flexible diaphragm wherein when the valve stem is in its closed position it contacts the shut-off disc to hold the flexible diaphragm in its closed position. The motor may be attached to a small gear which is connected to a larger gear which is connected to the lead screw, whereby the motor rotates the small gear which rotates the larger gear which rotates the leads screw. In one example the flexible diaphragm includes at least four holes. The holes in the flexible diaphragm may be between 1.8mm and 2.5mm in diameter. The lead screw is typically restrained in the axial direction by entrapment between a top flat face of the valve housing and a thrust bearing. The thrust bearing may be restrained axially by a flat face of a gear holder which forms part of the housing. The valve stem is preferably prevented from rotating via two guide pegs attached to an end face of the valve stem which are in cooperation with corresponding guide pockets located in the housing. The motor may be a 3 volt motor with a current draw of 0.1 amps. The valve housing may have a lower valve housing portion and an upper valve housing portion which attaches to the lower valve housing portion via fasteners. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a perspective view of a valve housing; Figure 2 is a side cross sectional view of the housing of Figure 1 showing the valve located inside; Figure 3 is a side cross sectional view of a portion of the valve shown in Figure 2 in an open position; and Figure 4 is a side cross sectional view of a portion of the valve shown in Figure 2 in a closed position. DESCRIPTION OF PREFERRED EMBODIMENTS In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of an embodiment of the present disclosure. It will be evident, however, to one skilled in the art that the present disclosure may be practiced without these specific details. Referring to the accompanying figures, the present invention relates to a valve 10 for fluids. One application of the valve 10 is for deployment in the domestic and bulk potable water-metering and water-flow control field. It will be appreciated that it is not necessarily restricted to this specific field and that the valve 10 may be deployed in any number of fields, where the flow of liquids or gasses may be controlled remotely. Referring to the accompanying Figures, a valve 10 includes a valve housing 12 which has a lower valve housing portion 12a and an upper valve housing portion 12b which attaches to the lower valve housing portion 12a via fasteners. The valve 10 includes a motor 14 attached to a small gear 16. The small gear 16 is connected to a larger gear 18 and the function of this will be described in more detail below. The valve has a fluid inlet 20 into the housing 12 and a fluid outlet 22 from the housing. The fluid inlet 20 and the fluid outlet 22 are in fluid communication as can best be seen in Figure 2. Referring to Figure 2, the horizontal stippled lines show fluid located in various parts of the open valve which will be described below in more detail. A barrier 24 is located inside the housing 12 between the fluid inlet 20 and fluid outlet 22. The barrier 24 partially obstructs flow of fluid from the fluid inlet 20 to the fluid outlet 22. When the valve is in the open position illustrated in Figures 2 and 3, fluid is able to flow from the inlet 20, over the top of the barrier 24, and to the outlet 22. The barrier 24 has a valve sealing face 26 located on top of the barrier. A flexible diaphragm 28 is located inside the housing. The edges of the flexible diaphragm 28 are trapped between two parts of the housing 12a and 12b as can be seen in Figure 2, thereby causing a pressure seal. The flexible diaphragm 28 includes a plurality of fluid inlet bleed holes 30 to allow fluid to move from an annular inlet cavity 32 on one side of the flexible diaphragm 28 to an annular outlet cavity 34 on another side of the flexible diaphragm 28. The flexible diaphragm 28 includes at least four holes. The holes are between 1.8mm and 2.5mm in diameter. From the outlet cavity 34, when the valve is in the open position illustrated, the fluid is able to flow to a fluid outlet bleed port 36 to a central cavity 38 and then onto the fluid outlet 22. The flexible diaphragm 28 is movable towards and away from a closed position in which it is seated on the valve sealing face 26 thereby preventing fluid from flowing from the fluid inlet 20, over the barrier 24 and onto the fluid outlet 22. This is illustrated in Figure 4. The valve also includes a fluid outlet bleed port seal 40. The fluid outlet bleed port seal 40 is movable between an open position and a closed position. When the fluid outlet bleed port seal 40 is in the open position illustrated in Figures 2 and 3. Fluid can flow from the outlet cavity 34, via the fluid outlet bleed port 36 and central cavity 38 to the fluid outlet 22. When the fluid outlet bleed port seal 40 is the closed position illustrated in Figure 4, fluid cannot flow from the outlet cavity 34 to the bleed port 36. This causes a buildup of pressure in the outlet cavity 34 as fluid moves from the inlet 20 through the fluid inlet bleed holes 30 into the outlet cavity 34 but cannot escape from the outlet cavity 34. Thus, it will be appreciated that when the flexible diaphragm 28 and fluid outlet bleed port seal 40 are both in the open position, fluid flowing through the valve has two paths through which it can flow. The first fluid path is from the fluid inlet 20, over the barrier 24 and through the central cavity 38 to the fluid outlet. 22 The second fluid path is from the fluid inlet 20 to the inlet cavity 32, then through the fluid inlet bleed holes 30 in the flexible diaphragm 28 to the outlet cavity 34 and from there down through the fluid outlet bleed port 36 and central cavity 38 to the fluid outlet 22. When the valve moves into the closed position as will be described below, both of these fluid paths are closed. The housing 12 includes a central bore 42. A valve stem 46 is located in the central bore and connected to the outlet bleed port seal 40. The valve stem 46 has an internal screw thread which is in cooperation with a corresponding external screw thread 44 on a lead screw 50. The lead screw 50 is integral with the gear 18 and is thereby rotated by the small motor 14 via the small gear 16 attached. The lead screw 50 and gear 18 are restrained in the axial direction by entrapment between a top flat face 52 of the valve housing 12 and a thrust bearing 54. Furthermore, the thrust bearing 54 is restrained axially by a flat face 56 of a gear holder 58 which forms part of the housing 12. Furthermore, the valve stem 46 is prevented from rotating via two guide pegs 60, attached to an end face of the valve stem 46, which are in cooperation with corresponding guide pockets located in the housing. A shut-off disc 48 and a diaphragm backing washer 62 are attached to the flexible diaphragm 28 to form an assembled unit. When the valve stem 46 is in its closed position it comes into contact with the shut-off disc 48 to hold the flexible diaphragm 28 in its closed position. When the valve is in the open condition illustrated in Figure 3, the flexible diaphragm 28, valve stem 46 and connected fluid outlet bleed port seal 40 are retracted away from their respective closed positions. As the valve is connected in line with a flowing fluid supply, the fluid is permitted to flow through the valve from the inlet 20 to the port 22, as has been described above. In detail, fluid enters the inlet 20 and fills the annular cavity 32 and flows into the central cavity 38 and exits the valve. Simultaneously, a small volume of fluid flows through the fluid inlet bleed holes 30 and into the cavity 34 above the flexible diaphragm 28, and from there out through the outlet bleed port 36 into the valve outlet flow stream. In this case, the hydrostatic pressure on both sides of the flexible diaphragm 28 is equal, and the diaphragm remains in the open, or fully retracted position, thus maintaining the valve in the open condition, regardless of the magnitude of the fluid pressure or volumetric flow rate of the liquid. When a “close-valve” signal is transmitted to the motor control system, the motor begins to rotate the gear 18 and thereby the lead screw 50 is rotated, thus causing the valve stem 46 to move from a fully retracted position downwards toward the flexible diaphragm 28. As the valve stem 46 moves towards the closed position, the attached outlet bleed port seal 40 also begins to move to its closed position and begins to shut the outlet bleed port 36. The out flow of liquid through the outlet bleed port 36 begins to be constricted. The hydrostatic pressure in the outlet cavity 34 above the flexible diaphragm 28 thus begins to increase beyond the pressure on the inlet cavity 32 side of the flexible diaphragm 28. Since the projected area of the flexible diaphragm 28 is greater on the outlet cavity 34 side of the flexible diaphragm 28 than on the area bounded by the inlet cavity 32, the flexible diaphragm 28 moves down towards the valve sealing face 26, due to the force exerted on the flexible diaphragm 28 by the fluid pressure. The advancing valve stem 46 with its outlet bleed port seal 40 continues to restrict the outflow of liquid, thus ensuring that the flexible diaphragm 28 continues to advance towards the valve sealing face 26. The valve stem 46 continues to advance until it fully contacts with the outlet bleed port 36 walls. At this time, the flexible diaphragm 28 has sealed fully against the valve sealing face 26 thus shutting the valve fully. This is illustrated in Figure 4. In this position, the valve stem 46 is in its fully closed position and is in physical contact with the shut-off disc 48 thereby physically holding the flexible diaphragm 28 and its closed position. It will be understood and appreciated from the above explanation that the lead screw 50 with outlet bleed port seal 40 and associated rotary and axial motion mechanism does not provide the force necessary for closing and sealing the flexible diaphragm 28 against the valve sealing face 26. This mechanism, which may be termed the servo mechanism, does not have to over-power the force generated by the fluid flow pressure over the diaphragm area, to shut the valve. Furthermore, with the valve stem 46 in the fully valve closed position, it is locked in position by the interconnecting screw threads thus providing a mechanical means of maintaining the diaphragm in the valve shut position, in the possible event of a transient zero inlet pressure condition, or a high transient back pressure from the outlet reticulation and associated system. This valve closed lock feature does not rely on a continuous hold-back force exerted by the prime mover, because the fine-pitch cooperating screw threads of the valve stem and of the lead screw prevents reversibility of the servo mechanism. From the above explanation, it should be evident that a low power rated motor may be employed for moving the lead screw down and up, for the valve shutting and opening sequence. Typically, when testing of a prototype of the valve, a 3 volt motor with a current draw of 0.1 amps was found sufficient for shutting and opening a 17 mm nominal bore valve on a potable water line, at 2.5 cubic meter per hour, at 16 bar line pressure. Such low power consumption requirements are most desirable for battery powered automatic valves employed in the potable water metering and control field, where battery longevity is essential. Automatic valves employed in the potable water metering and control environment are periodically required to shut and open in conditions of dirty water, or water with suspended solids, of irregular sizes, in the order of 1-2 mm. Generally, pilot operated, or servo assisted valves do not operate well under such dirty water conditions, because suspended solids restrict or totally block the inlet and outlet bleed orifices, because these orifices are small, by intentional design. Solid particles may also become embedded in the valve shut-off element, be it a diaphragm, or valve seat. The invention makes use of larger, multiple inlet bleed holes and a larger outlet bleed port hole, than is common in the known art, to overcome the threat of bleed hole blockage. Typically, in the known art, servo assisted diaphragm valves employ a single small inlet bleed hole and a single small outlet bleed hole. Any increase in quantity and size of bleed holes causes adverse flow dynamics of the water through the diaphragm cavity, and out into the exit flow stream, thus causing the valve to shut prematurely, or inadvertently, or to not re-open once the valve open signal is given. In the case of the invention, the quantity and size of the inlet bleed holes is balanced with the size of the outlet bleed hole, to ensure proper opening and closing of the valve. Additionally, in the potable water metering and control environment it is desirable that an automatic valve can be throttled, or partially shut, to limit flow to the end user. The valve 10 described and illustrated above allows for the stopping of the lead screw 50 travel at a position between fully open and fully closed which thereby alters the volumetric flow rate. It will be appreciated from the above explanation that the lead screw 50 with outlet bleed port seal 40 and associated rotary and axial motion mechanism do not provide the force necessary for closing and sealing the diaphragm 28 against the valve sealing face 26. This mechanism, which may be termed the servo mechanism, thus does not have to over-power the resultant force generated by the fluid flow pressure over the diaphragm 28 area, to shut the valve. Furthermore, with the lead screw in the fully “valve-shut” position, it provides the means of maintaining the diaphragm in the valve shut position, in the possible event of a transient zero inlet pressure condition, or a high transient back pressure from the outlet reticulation and associated system. This valve closed lock feature does not rely on a continuous hold-back force exerted by the prime mover, because the fine-pitch cooperating screw threads of the valve stem and of the lead screw prevents reversibility of the servo mechanism.

Claims

1. A valve including:a housing having a central bore therein;a lead screw located in the central bore, the lead screw including a screw thread formation formed thereon;a fluid inlet into the housing;a fluid outlet from the housing, the fluid outlet in fluid communication with the inlet;a barrier located inside the housing between the fluid inlet and fluid outlet, the barrier partially obstructing flow of fluid from the fluid inlet to the fluid outlet, the barrier having a valve sealing face located on top of the barrier;a flexible diaphragm with a plurality of fluid inlet bleed holes to allow fluid to move from an inlet cavity on one side of the flexible diaphragm to an outlet cavity on another side of the flexible diaphragm, the flexible diaphragm movable towards and away from a closed position wherein when the flexible diaphragm is in the closed position it is seated on the valve sealing face thereby preventing fluid from flowing from the fluid inlet, over the barrier and to the fluid outlet;a fluid outlet bleed port to allow fluid to move from the outlet cavity to the fluid outlet;a fluid outlet bleed port seal movable between an open position in which fluid can flow from the outlet cavity, via the outlet bleed port to the fluid outlet, and a closed position in which fluid cannot flow from the outlet cavity, via the outlet bleed port to the fluid outlet;a valve stem located in the central bore and connected to the outlet bleed port seal, the valve stem having a screw thread formation thereon sized to engage with the screw thread formation on the lead screw so that the valve stem is thereby movable within the central bore towards and away from a closed position in contact with the valve sealing face; anda motor connected to the lead screw and thereby to the valve stem to move the valve stem within the central bore so that when the valve stem and the outlet bleed port seal are moved into the closed position, fluid cannot flow from the outlet cavity, via the outlet bleed port to the fluid outlet, thereby causing a fluid pressure build up in the outlet cavity which in turn moves the flexible diaphragm to its closed position thereby preventing fluid from flowing from the fluid inlet to the fluid outlet, further wherein when the valve stem and the flexible diaphragm are in the closed position the valve stem holds the flexible diaphragm in the closed position, and further wherein when the motor moves the valve stem and the outlet bleed port seal away from the closed position, fluid is able to flow from the outlet cavity, via the outlet bleed port to the fluid outlet which releases fluid pressure in the outlet cavity and thereby allows the flexible diaphragm to move away from the closed position which in turn allows fluid to flow from the fluid inlet to the fluid outlet.

2. A valve according to claim 1 further including a shut-off disc attached to the flexible diaphragm wherein when the valve stem is in its closed position it contacts the shut-off disc to hold the flexible diaphragm in its closed position.

3. A valve according to claim 1 or claim 2 wherein the motor is attached to a small gear which is connected to a larger gear which is connected to the lead screw, whereby the motor rotates the small gear which rotates the larger gear which rotates the leads screw.

4. A valve according to any preceding claim wherein the flexible diaphragm includes at least four holes.

5. A valve according to any preceding claim wherein the holes in the flexible diaphragm are between 1.8mm and 2.5mm in diameter.

6. A valve according to any preceding claim wherein the lead screw is restrained in the axial direction by entrapment between a top flat face of the valve housing and a thrust bearing.

7. A valve according to claim 6 wherein the thrust bearing is restrained axially by a flat face of a gear holder which forms part of the housing.

8. A valve according to any preceding claim wherein the valve stem is prevented from rotating via two guide pegs attached to an end face of the valve stem which are in cooperation with corresponding guide pockets located in the housing.

9. A valve according to any preceding claim wherein the motor is a 3 volt motor with a current draw of 0.1 amps.

10. A valve according to any preceding claim wherein the valve housing has a lower valve housing portion and an upper valve housing portion which attaches to the lower valve housing portion via fasteners.

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