Pilot operated fluid valve

Abstract: A gas purge valve comprising a housing (2) provided with an inlet (22) for connecting to a liquid system to be purged. A flexible diaphragm (14) formed with an aperture (16) of restricted dimension is maintained in the housing dividing it into first (18) and second (20) chambers, the first chamber communicating with the inlet. A pilot valve (30) controlled first outlet (26) is formed in the second chamber and a second outlet (42) is formed in the first chamber. There is also provided a diaphragm seating (46) formed in the first chamber, being engageable by said diaphragm so as to seal said second outlet; the arrangement being such that the pilot valve is displaceable between a first position in which gas is discharged from the second chamber so as to vent the second chamber and a second position in response to liquid presence, so as to seal the first outlet. The diaphragm is displaceable in response to differential pressure created by the venting into unsealing the second outlet for full venting of the first chamber.

Description: FIELD OF THE INVENTION The present invention is in the field of fluid flow valves and is particularly, but not exclusively, concerned with such valves which are designed to serve as gas discharge valves or gas purge valves. BACKGROUND OF THE INVENTION Such air purge valves are installed in liquid systems such as, for example, water mains distribution lines or sewage collection systems, or liquid tanks, and are designed to discharge air (typically in water supply systems) or other gasses (e.g. in sewage systems), thus avoiding the formation of gas pockets and gas bubbles which interfere with the liquid flow and also have bad influence on accessories fitted to the liquid system. Several types of air purge valves are known. According to one type, disclosed for example in US Patent No. 4,770,201, there is a housing having a fluid through-flow aperture with a valve seating formed in the housing and bounding said aperture. A flexible closure membrane is secured at one end to the housing and is adapted to be biased, under fluid pressure in the housing, against the valve seating so as to seal the aperture. Membrane displacing means are secured to an opposite end of the membrane so that displacement of the displacing means in a first sense progressively detaches successive transverse portions of the membrane from the seating so as to open the aperture while displacement of the displacing means in an opposite sense allows for the membrane to become sealingly biased against the seating. This type of air purge valve is known as the "automatic kind" in which in view of the relatively small dimensions of the aperture, the valve cannot cope with the situation when large quantities of air have to be discharged, wherein not all the air is released and some of it passes into the line, causing build-up of air pressure and ultimately the creation of an air lock. A second type of air purge valves typically comprises a spherical float located in a housing which is coupled at a lower end thereof to the system to be vented and is provided at its upper end with a venting aperture. When fluid is introduced into a liquid system comprising such a valve, large amounts of air may be discharged via the venting aperture, while in the course of normal operation with the flow of liquid through the system, the housing fills with liquid and the spherical float is forced upwardly against the outlet aperture, sealing the same. When the liquid system is being drained, the float is displaced downwardly under its own weight thereby opening the outlet aperture with consequent venting of the system. In this type of air purge valve, so-called "kinetic valve", the valve has a relatively large aperture through which large quantities of air can be rapidly and effectively vented. However, with such a kinetic valve, once the housing thereof has filled with liquid and the float has been pressed against the large aperture so as to seal it, the valve will only reopen once the pressure in the housing has dropped to atmospheric pressure and, in consequence the kinetic valve cannot be used for the continuous relief of small amounts of air. Moreover, such air purge valves have the drawback of being substantially sensitive, where dirt, tolerances of manufacture dimensions or due to erosion of various components, etc., have great influence on the behavior of the float and its response to changes of the fluid flowing therethrough (liquid or gas), thus performances of such air purge valves are somewhat inaccurate and may malfunction. Another drawback of such air purge valves is that they tend to cause so-called "hammering" in the liquid system wherein the system undergoes pressure shocks. Even more so, such air purge valves are substantially bulky, heavy and expensive. US-A-5449018, which forms a basis for the preamble of claim 1, discloses a flow control valve having a housing, an inlet to the housing for connecting to a liquid system to be purged, a flexible diaphragm maintained in the housing serving to divide the housing into first and second chambers, the first chamber communicating with the inlet. An aperture of restricted dimensions is formed in the diaphragm and a diaphragm seating is formed in the first chamber which is engagable by the diaphragm. It is therefore an object of the present invention to provide a new and improved gas purge valve, substantially overcoming the above drawbacks. SUMMARY OF THE INVENTION According to the present invention, there is provided a gas purge valve comprising a housing; an inlet to said housing for connecting to a liquid system to be purged; a flexible diaphragm maintained in said housing and serving to divide it into first and second chambers; said first chamber communicating with said inlet; an aperture of restricted dimensions formed in said diaphragm; a diaphragm seating formed in said first chamber and engageable by said diaphragm; characterised by a pilot valve controlled first outlet formed in said second chamber; a second outlet formed in said first chamber, said second outlet being sealed when said diaphragm engages said diaphragm seating; the arrangement being such that said pilot valve is displaceable between a first position in which gas is discharged from said second chamber so as to vent the second chamber and a second position in response to liquid presence, so as to seal said first outlet; whilst said diaphragm is displaceable in response to differential pressure created by said venting into unsealing said second outlet for full venting of said first chamber. Preferably, said diaphragm seating is annular and said diaphragm is essentially circular with its perimeter flanged between the first and second chambers being clamped to one another and said diaphragm is normally biassed against said diaphragm seating. In still a preferred embodiment, the pilot valve comprises an inlet and an outlet which are substantially circular openings and a spherical float member floatingly displaceable between said inlet and outlet openings; said openings having a diameter smaller than the diameter of said spherical float member, wherein said float member sealingly engages at least said outlet opening. In order to obtain best results, the aperture of said diaphragm is smaller than said first outlet of said second chamber and said second outlet is essentially bigger than said first outlet. In accordance with another embodiment of the present invention, the valve may be used for preventing collapse of the liquid system when it is being drained. For this purpose said float member sealingly engages also the inlet opening of said pilot valve so as to prevent gas flow into the housing during draining said liquid system, thus resulting in pressure decrease in both said first and second chambers, entailing disposition of the diaphragm from its normally sealing position to an unsealing position, allowing venting of the liquid system. According to still another embodiment of the present invention, the size of said aperture's section area at the diaphragm's sealing position is smaller than at an unsealing position, thereby changing the flow behavior so that on the one hand, displacement motion of the diaphragm from the unsealing position slows down towards the sealing position. The size of said aperture's section area is variable by an interposing member comprising a stem projecting towards said aperture and coaxial with said aperture; at least at the sealing position of the diaphragm a portion of the stem is encircled by the aperture; said stem having different cross sections along its longitudinal axis. In a preferred embodiment, said stem projects from a top surface of the second chamber and has a wider cross-section at a bottom end thereof extending adjacent said aperture at the sealing position of said diaphragm. The stem may be displaceable along its longitudinal axis by a manually operated handle. For specific applications, a stem having a conical or exponential or stepped profile is suitable. In accordance with further embodiments of the present invention, the gas purge valve may further comprise additional accessories such as a liquid relief valve for discharging liquid at high pressure above a predetermined pressure threshold, an automatic gas purge valve for discharging substantially small amounts of gas, a liquid indicator for indicating the presence of liquid in the liquid system, etc. Either of these accessories may be positioned in either the first or second chamber. In a specific embodiment, said pilot valve may be an automatic gas purge valve. The gas purge valve may further comprise a fluid flow control assembly comprising a sealing valve mounted on a stem movable with respect to a fixed sealing valve seat within the first chamber of the housing, between an open position and a closed position. BRIEF DESCRIPTION OF THE DRAWINGS For better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which: Fig. 1 is a longitudinal sectioned elevation of a gas purge valve in accordance with the present invention, the diaphragm shown in its sealing position; Fig. 2 is a longitudinal sectioned elevation of a gas purge valve in accordance with the present invention, the diaphragm shown in an unsealing position; Fig. 3 is a longitudinal cross-section of the gas purge valve according to the present invention, shown in a position full with liquid; Fig. 4 is a longitudinal sectioned elevation of a further embodiment of a gas purge valve according to the present invention shown in a venting position; Fig. 5 is the gas purge valve as in Fig. 1 further comprising an automatic gas purge valve and a liquid relief valve; Fig. 6 is a longitudinal cross-sectioned elevation of a gas purge valve according to the present invention comprising a flow behavior controller; Fig. 7 is a longitudinal cross-sectioned elevation of a gas purge valve according to the present invention illustrating a further embodiment of the flow behavior controller; Fig. 8 is a longitudinal cross-sectioned elevation of a gas purge valve according to the present invention illustrating diaphragm biasing means; Fig. 9 is a longitudinal cross-sectional elevation of another embodiment of a gas purge valve according to the present invention, comprising a liquid flow control faucet. Fig. 10 is a longitudinal cross-sectioned elevation of a gas purge valve according to the present invention showing a first embodiment of a liquid indication means; and Fig. 11 is a longitudinal cross-sectioned elevation of a gas purge valve according to the present invention illustrating a further embodiment of a liquid indication means. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS Referring first to Fig. 1 of the drawings, there is seen a gas purge valve comprising a two-piece housing 2 consisting of a lower portion 4 and an upper portion 6 , which are screw-clamped together by bolts 8 and nuts 10 at their joining peripheral flanges 12 and 13. A diaphragm 14 made of a flexible material such as, for example, rubber or silicone, is clamped between the adjoining flanges 12. The diaphragm 14 has a substantially circular central aperture 16 and it divides the housing 2 into a first chamber 18 and a second chamber 20 at the bottom and top portions, respectively. The first chamber 18 has at its lower end an inlet opening 22 with a flanged end 24 for connecting to a liquid system such as a mains water distribution line or a sewage system (not shown). The second chamber 20 has a first outlet 26 with an internally screw-tapped boss 27 to which is screw-fitted a pilot valve assembly generally designated 30 and comprising an inlet 32 communicating with said outlet 26 , and an outlet 34 of essentially similar dimensions as of inlet 32. A sphere-like float member 36 is displaceable between a lower position in which it rests on support ribs 38 at the inlet 32 , allowing fluid flow between the ribs 38 , and between an upper position in which it sealingly bears against an " O "-ring 40 accommodated at the circular outlet 34. A second outlet 42 is formed near a top end of the lower portion 4 , reinforced by ribs 44 and bound by an annular diaphragm seating 46, providing a seat for the diaphragm 14 and ensuring sealing of the outlet 42 by said diaphragm. It should be noted, that the cross-section area of the aperture 16 is substantially smaller than that of the inlet 32 and outlet 34 of the pilot valve 30 . At the position shown in Fig. 1, the gas purge valve is in its so-called "rest" position in which no fluid flows in the liquid system. Attention is now directed to Fig. 2 of the drawings illustrating the gas purge valve according to the present invention in its so-called "open" or "un-sealed" position. This position occurs, for example, when the mains liquid supply line is being filled with liquid, wherein air (or other gasses in case of a sewage collection system) enters the valve via inlet 22 of the housing. In this position, air is pressurized at the top chamber 20 to above external atmospheric pressure and thus exits through the pilot valve 30 via gaps between the ribs 38, resulting in pressure decrease in chamber 20 with respect to chamber 18 , in consequence of which the flexible diaphragm 14 raises and thus disengages the diaphragm seating 46 , unsealing the outlet 42 and enabling massive air discharge therethrough. However, as soon as forces acting on both faces of the diaphragm 14 come to equilibrium, the diaphragm returns to its original position in which it rests over the diaphragm seating 46 sealing the second outlet 42, (as seen in Fig. 1). When, however, liquid fills the system, as can be seen in Fig. 3, it enters the gas purge valve through inlet 22 , fills the first chamber 18 and gradually also the second chamber 20 while expelling small amounts of air (or gas) which is discharged via the pilot valve 30 as hereinabove explained. When the liquid reaches the outlet 32, the buoyancy forces acting on the float member 36 overcome the gravity force, entailing displacement of the float member 36 to its sealing position, in which it sealingly bears against the " O "-ring 40, thus preventing liquid discharge via the outlet 34. In this position, the force acting on the top surface 50 of diaphragm 14 is substantially bigger than that acting on its lower surface 52 , thus ensuring that the diaphragm maintains its sealing position, preventing liquid discharge through the outlet 42. It should be realized that the diaphragm 14 may be normally biassed against said diaphragm seating 46 or may be in slack contact with the seating, whereby higher liquid pressure shall be required to cause sealing of the outlet 42. The valve according to the present invention is suitable also for venting a liquid system being drained, so as to prevent collapsing of its walls and accessory members under vacuum. For explaining how the present invention may be used for this purpose, further attention is directed to Fig. 4 of the drawings. The inlet opening 32 of the pilot valve 30 is a continues circular opening and comprises an " O "-ring for sealing engagement with the float member 36 when the latter is in its lowermost position, wherein air is prevented from entering the gas purge valve. According to the arrangement of this embodiment, when the liquid system is drained, liquid evacuates the housing 2 causing pressure decrease within the housing 2 . Since the pressure within the housing is substantially lower than the external, atmospheric pressure, and since air cannot enter the top chamber 20 via the pilot valve 30, the external air at atmospheric pressure pushes the diaphragm 14 to its unsealing position and enters via opening 42, thus venting the liquid system, preventing it from collapsing. According to a specific embodiment, rather than using " O "-rings 40 and 58 , the float member 36 may be itself coated with a resilient material so as to sealingly engage the circular inlet 32' or outlet 34 as may be the case. In Fig. 5 of the drawings, there is illustrated a gas purge valve according to the present invention on which an automatic air purge valve 60 (schematically illustrated) is mounted on the upper portion 6 of the housing 2 . Such an automatic air purge valve is in particular suitable for discharging substantially small amounts of gas (regardless of its pressure) and is disclosed, for example, in U.S. Patent No. 4,770,201, incorporated herein by reference. It should be understood that such an automatic gas purge valve may be installed in addition to the pilot valve 30 or instead, as it is also suitable as a pilot valve. Furthermore, the automatic gas purge valve may be positioned so as to discharge gas either from the top chamber 20 as seen in Fig. 5 or, from the bottom chamber 18 (not illustrated). Further seen in Fig. 5, the gas purge valve may incorporate an integral liquid relief valve 62 (schematically illustrated), the purpose of which is to discharge liquid from the housing at a pressure above a predetermined threshold, as known per se. In an ideal gas purge valve, the diaphragm slowly ends its displacement towards the sealing position, so as to prevent shock waves known as "hammering" in the liquid system. Obtaining such characters may be by a flow behavior regulator 66 as seen in Fig. 6 of the drawings, in which such a regulator comprises a stem 68 projecting downwardly from the upper portion 6 and penetrating into the opening 16 of the diaphragm 14 . In the application seen in Fig. 6, the stem 68 has at its lower portion a tapering cross-section which ensures that the cross-section area of aperture 16 is minimal at the sealing position and it increases towards the unsealing position, as can readily be understood. It should be obvious to a person versed in the art that the longitudinal cross-section of the stem may alternatively be exponential or stepped, etc. in accordance with specific flow behavior requirements. Fig. 7 of the drawings illustrates a screw-threaded shaft 70 rotatably mounted within an internally threaded boss 72 at the top portion of the housing 2 , with a handle 74 for rotating the shaft 70 so as to axially displace it with respect to the aperture 16 of diaphragm 14, thus elevating or lowering the tapering end portion 76 of the shaft 70 as can be appreciated, for obtaining different flow characters of fluid flow through the aperture 16. Also seen in Fig. 6, there is shown a conical compression spring 75 having one end thereof bearing against a top wall of the housing and an opposed end bearing against the top surface 50 of the diaphragm 14 , whereby said diaphragm is biased against the diaphragm seating 46 into the sealing position. In Fig. 8 of the drawings the diaphragm 77 is pre-stressed over the diaphragm seating 46, with its peripheral portion clamped between adjacent flange portions 78 and 79 of the lower portion 4' and the upper portion 6' of the housing 2 , whereby the diaphragm 77 is biased into the sealing position and where a higher preliminary force is required to shift the diaphragm into the unsealing position. Fig. 9 of the drawings is another embodiment of the present invention in which the gas purge valve is integrally provided with a fluid flow control assembly, namely a faucet, generally designated 80 comprising a valve member 82 linked to a screw-threaded stem 84 adapted for axial displacement within a corresponding screw-threaded bushing 86 fixed to the bottom portion 4 of the housing 2 by radial ribs 88 . The stem 84 is rotatably supported by a boss 90 at the top portion 6 of the housing 2 and is rotatable by a handle (not shown) so as to axially displace the valve member 82 with respect to an annular valve seat 94 . The valve 82 comprises adjacent its perimeter a seal 96 adapted for engaging with the valve seat 94 . In Fig. 9 the fluid faucet 80 is seen in a closed position in which the valve 82 sealingly engages the valve seat 94 , whereby liquid passage between the bottom chamber 18 and the top chamber 20 is prevented. This situation is useful for servicing the gas purge valve, e.g. cleaning, repairing, etc. As can be appreciated, rotating the stem (by a handle - not shown) entails disengagement of the valve 82 from the valve seat 94 , whereby the gas purge valve may return to normal operation. In Fig. 10 of the drawings a flag member 100 is attached to the float member 36' and is adapted to project from the outlet opening 34 of the pilot valve 30 . the arrangement is such that at the presence of liquid within the upper chamber 20, the float member 34' moves upward with the flag member 100 projecting from the housing 2 , indicating the presence of liquid. Fig. 11 illustrates another embodiment of a liquid indicator where a flag member 102 is attached to the top surface 50' of the diaphragm 14'. The flag member 102 is adapted for projecting through an aperture 104 at the upper portion 6 ', whereby at the absence of liquid within the valve said flag member projects from the housing , while at the presence of liquid within the valve, the flag member is retracted as shown in Fig. 11. It should be obvious to a person versed in the art that the gas purge valve according to the present invention may comprise any of the above-mentioned accessories, e.g. automatic gas purge valve, liquid relief valve, liquid flow regulator, fluid indicator, liquid flow control assembly, etc. at any required combination.

Claims: A gas purge valve comprising a housing (2); an inlet (22) to said housing (2) for connecting to a liquid system to be purged; a flexible diaphragm (14) maintained in said housing (2) and serving to divide it into first (18) and second (20) chambers; said first chamber (18) communicating with said inlet (22); an aperture (16) of restricted dimensions formed in said diaphragm (14); a diaphragm seating (46) formed in said first chamber (18) and engageable by said diaphragm (14); characterised by a pilot valve (30) controlled first outlet (26) formed in said second chamber (20); a second outlet (42) formed in said first chamber (18), said second outlet being sealed when said diaphragm (14) engages said diaphragm seating (46); the arrangement being such that said pilot valve (30) is displaceable between a first position in which gas is discharged from said second chamber (20) so as to vent the second chamber and a second position in response to liquid presence, so as to seal said first outlet (26); whilst said diaphragm (14) is displaceable in response to differential pressure created by said venting into unsealing said second outlet (42) for full venting of said first chamber. A gas purge valve according to claim 1, wherein said diaphragm (14) is normally biassed against said diaphragm seating (46). A gas purge valve according to claim 1, wherein said diaphragm seating (46) is annular and said diaphragm (14) is essentially circular with its perimeter flanged between the first and second chambers being clamped to one another. A gas purge valve according to claim 1, wherein the pilot valve 30 comprises an inlet (32) and an outlet (34) which are substantially circular openings and a spherical float member (36) floatingly displaceable between said inlet and outlet openings; said openings having a diameter smaller than the diameter of said spherical float member (36), wherein said float member is adapted for sealing engagement of at least said outlet opening (34). A gas purge valve according to claim 4, wherein said float member (36)is coated with an elastic material. A gas purge valve according to claim 1, wherein the aperture (16) of said diaphragm (14) is smaller than said the first outlet (26) of said second chamber (20), and said second outlet (44) is essentially bigger than said first outlet (26). A gas purge valve according to claim 4, wherein said float member (36) sealingly engages also the inlet opening (32) of said pilot valve (30) so as to prevent gas flow into the housing (2), wherein draining said liquid system results in pressure decrease in both said first and second chambers (18, 20), entailing disposition of the diaphragm (14) from the normally sealing position to an unsealing position, allowing venting of the liquid system. A gas purge valve according to claim 1, wherein the size of said aperture's section area at the diaphragm's sealing position is smaller than at an unsealing position, thereby changing the flow behavior so that on the one hand displacement motion of the diaphragm (14) from the unsealing position slows down towards the sealing position. A gas purge valve according to claim 8, wherein the size of said aperture's section area is variable by an interposing member comprising a stem (68) projecting towards said aperture (16) and coaxial with said aperture; at least in the sealing position of the diaphragm (14) a portion of the stem (68) is encircled by the aperture (16); said stem having different cross sections along its longitudinal axis. A gas purge valve according to claim 9, wherein said stem (68) projects from a top surface of the second chamber (20) and has a wider cross-section at a bottom end thereof extending adjacent said aperture (16) at the sealing position of said diaphragm (14). A gas purge valve according to claim 10, wherein the cross-section of said stem (68) is conical or exponential or has a stepped configuration. A gas purge valve according to claim 10, wherein the stem (68) is externally displaceable along its longitudinal axis by a manually operated handle (74). A gas purge valve according to claim 1, wherein said housing (2) further comprises a liquid relief valve (62) for discharging liquid at high pressure above a predetermined pressure threshold; said liquid relief valve (62) positioned in either the first or second chamber (18, 20). A gas purge valve according to claim 1, wherein the housing (2) further comprises an automatic gas purge valve (60) for discharging substantially small amounts of gas; said gas purge valve (60) connected to either the first chamber (18) or the second chamber (20). A gas purge valve according to claim 1 or 14, wherein said pilot valve (30) is a gas purge valve. A gas purge valve according to claim 1, wherein said valve further comprises a liquid indicator (102) for indicating the presence of liquid in the liquid system. A gas purge valve according to claim 16, wherein said liquid indicator consists of a retractable flag member (100) associated with a float member (36') of said pilot valve, which flag member projects from the housing in response to liquid presence within said second chamber. A gas purge valve according to claim 16, wherein said liquid indicator consists of a retractable flag member associated with the diaphragm (14'), whereby at the absence of liquid within the housing said flag member (102) projects from said housing. A gas purge valve according to claim 1, wherein said valve further comprises a fluid flow control assembly (80) comprising a sealing valve (82) mounted on a stem (84) movable with respect to a fixed sealing valve seat (94) within the first chamber (18) of the housing (2), between an open position and a closed position. A gas purge valve according to claim 9 or 19, wherein said interposing member (76) and said fluid flow control assembly (80) have a common stem (84). A gas purge valve according to claim 2, comprising a spring member for biasing said diaphragm. A gas purge valve according to claim 2, wherein said diaphragm (14) is pre-stressed over said diaphragm seating (46).

Inventors: KATZMAN YUVAL, KATZMAN, YUVAL
Applicants: A R I KFAR CHARUV, A.R.I. KFAR CHARUV
Application year: 1996
Main classification: F16K24
IPC codes: F16K7, F16K24