WO2020250169A1

WO2020250169A1 - Air-release valve and corresponding system

Info

Publication number: WO2020250169A1
Application number: PCT/IB2020/055484
Authority: WO
Inventors: Hagay Weisbrod
Original assignee: Noyad Biomed Ltd.
Priority date: 2019-06-11
Filing date: 2020-06-11
Publication date: 2020-12-17

Abstract

An air-release valve (100, 200, 300) for releasing air from a pipeline to a surrounding atmosphere includes a float (108, 208, 308) within a float chamber (104, 204, 304) and a venting aperture (106, 206, 306). A plug (110, 210, 310) is displaceable relative to the venting aperture to selectively allow release of air from the valve casing. A pneumatic actuator, linked to the plug, has a first surface (114, 214, 314) exposed to a pressure within the float chamber and a second surface (116, 216, 316) in opposed relation to the first surface, to provide a pressure-balanced plug. A first linkage (120, 220, 320) mechanically interconnects the plug and the pneumatic actuator. A linkage (118, 218, 318) mechanically links displacement of the float to motion of the plug from an open position to a sealing position.

Description

Air-Release Valve and Corresponding System

FIELD AND BACKGROUND OF THE INVENTION

The present invention relates to an air-release valve for pipelines and, in particular, it concerns a balanced air-release valve.

It is known to provide air-release valves for discharging air or other gases from a pipeline conveying liquid. The functions of such valves may be one or more of the following: discharging air during filling or charging of the system; admitting air into the system during drainage of the system; and releasing accumulated air or other gases from the system while it is operating under pressure.

These different functions have greatly differing requirements in terms of operating pressures and desired flow rates, and therefore pose considerable challenges for implementation in a single device. A further consideration, particularly during filling of a system, is the risk of damage to the valve and/or pipeline due to a“slam” effect, where a rapidly advancing column of water is abruptly stopped by sudden closure of a valve, delivering a large impulse due to the momentum of the advancing water column within the pipeline. A further consideration is the desire to reduce air release valve size and reduce size of inner components, in order to reduce overall costs of the air release valve.

SUMMARY OF THE INVENTION

The present invention is an air-release valve.

According to the teachings of an embodiment of the present invention there is provided, an air-release valve for releasing air from a pipeline to a surrounding atmosphere, the air-release valve comprising: (a) a valve casing for connection to the pipeline, the valve casing defining a float chamber and a venting aperture; (b) a float deployed within the float chamber so as to be raised according to a level of liquid within the float chamber from a fully lowered position to a fully raised position; (c) a plug displaceable relative to the venting aperture between an open position in which the venting aperture allows gas flow between the valve casing and the surrounding atmosphere and a sealing position in which the plug seals the venting aperture; (d) a pneumatic actuator in fluid interconnection with the float chamber, the pneumatic actuator having a first surface exposed to a pressure within the float chamber and a second surface in opposed relation to the first surface; (e) a first linkage mechanically interconnecting the plug and the pneumatic actuator, the plug, the pneumatic actuator and the first linkage being configured such that, when the second surface of the pneumatic actuator is exposed to a pressure of the surrounding atmosphere, the plug is insensitive to variations in the pressure within the float chamber; and (f) a second linkage mechanically interconnecting the float and the plug such that displacement of the float from the fully lowered position to the fully raised position displaces the plug from the open position to the sealing position, wherein the second linkage defines, for at least a portion of the displacement of the float from a fully lowered position to the fully raised position, a regulated air-release region, and wherein displacement of the plug within the regulated air release region occurs as a function of displacement of the float such that the displacement of the plug is less than the displacement of the float. The air regulated region thus achieves a float force amplification in a way that the floating force and gravity force that acts on the float is transformed by the second linkage to a greater force that acts on the plug.

According to a further feature of an embodiment of the present invention, the second linkage is a one-sided linkage such that lowering of the float does not positively displace the plug away from the sealing position, and wherein the plug is resiliently biased away from the sealing position.

According to a further feature of an embodiment of the present invention, the second linkage is configured to provide a non-linear relationship between displacement of the float and displacement of the plug, the non-linear relationship including a rapid closure region during a first portion of displacement of the float from the fully lowered position and a regulated air-release region during a second portion of displacement of the float towards the fully raised position, the regulated air release region having a rate of change of plug position with float displacement at least one order of magnitude smaller than the rapid closure region.

According to a further feature of an embodiment of the present invention, the second linkage is configured such that progressive rising of the float generates a decrease in a venting area between the plug and the venting aperture to a first minimum venting area, followed by an increase in the venting area, followed by a further decrease in the venting area.

According to a further feature of an embodiment of the present invention, the second linkage comprises a rotary linkage mechanically linked to the float so as to be rotated by displacement of the float, the rotary linkage having an axis of rotation and an actuation surface deployed for displacing the plug.

According to a further feature of an embodiment of the present invention, the second linkage comprises an abutment block having an actuation surface deployed for displacing the plug, the abutment block being mechanically linked to the float so as to be displaced linearly by displacement of the float.

According to a further feature of an embodiment of the present invention, the valve casing further comprises a pneumatic chamber in fluid interconnection with the float chamber, and wherein the pneumatic actuator comprises a displaceable partition deployed within and subdividing the pneumatic chamber, the displaceable partition providing the first surface and the second surface, the second surface being exposed to a control volume of the pneumatic chamber.

According to a further feature of an embodiment of the present invention, the first linkage comprises an axially displaceable stem interconnecting the plug and the displaceable partition.

According to a further feature of an embodiment of the present invention, the displaceable partition is a piston deployed in sliding contact with an inner surface of the pneumatic chamber.

According to a further feature of an embodiment of the present invention, the displaceable partition is a flexible diaphragm.

According to a further feature of an embodiment of the present invention, there is also provided a pneumatic pilot valve switchable between a first state in which the control volume is maintained at a pressure of the surrounding atmosphere and a second state in which the control volume is connected to a source of pressure above the pressure of the surrounding atmosphere, forcing the plug towards the sealing position.

According to a further feature of an embodiment of the present invention, the pilot valve has a feed line in fluid communication with the float chamber so as to receive an internal pipeline pressure that is supplied to the control volume in the second state. According to a further feature of an embodiment of the present invention, the pilot valve has a feed line in fluid communication with a pressure accumulation volume, the pressure accumulation volume being connected to the float chamber via a check valve so as to store a quantity of pressurized air for supply to the control volume in the second state.

According to a further feature of an embodiment of the present invention, the control volume is connected to the surrounding atmosphere via a bleed orifice, the air- release valve further comprising a control valve switchable between a first state in which a feed line provides fluid communication between the float chamber and the control volume, and a second state in which the feed line is closed.

According to a further feature of an embodiment of the present invention, the control valve is mechanically linked to the float or to the second linkage such that raising of the float switches the control valve from the first state to the second state.

According to a further feature of an embodiment of the present invention, the control valve is mechanically linked to the float or to the second linkage such that lowering of the float switches the control valve from the second state to the first state, the switching from the first state to the second state occurring at a first level of the float and the switching from the second state to the first state occurring at a second level of the float, the second level being lower than the first level.

According to a further feature of an embodiment of the present invention, the plug is biased to an intermediate position between the open position and the sealing position, and wherein the control volume is connected to the surrounding atmosphere via a bleed orifice, the air-release valve further comprising a feed line providing fluid communication between the float chamber and the control volume, the feed line including a check valve deployed so as to prevent air flow from the float chamber to the control chamber, but to allow suction of air from the control chamber when a pressure within the control chamber drops below atmospheric pressure.

There is also provided according to the teachings of an embodiment of the present invention, an air-release valve for releasing air from a pipeline to a surrounding atmosphere, the air-release valve comprising: (a) a valve casing for connection to the pipeline, the valve casing defining a float chamber and a venting aperture; (b) a float deployed within the float chamber so as to be raised according to a level of liquid within the float chamber from a fully lowered position to a fully raised position; (c) a plug displaceable relative to the venting aperture between an open position in which the venting aperture allows gas flow between the valve casing and the surrounding atmosphere and a sealing position in which the plug seals the venting aperture; (d) a pneumatic actuator in fluid interconnection with the float chamber, the pneumatic actuator having a first surface exposed to a pressure within the float chamber and a second surface in opposed relation to the first surface; (e) a first linkage mechanically interconnecting the plug and the pneumatic actuator, the plug, the pneumatic actuator and the first linkage being configured such that, when the second surface of the pneumatic actuator is exposed to a pressure of the surrounding atmosphere, the plug is insensitive to variations in the pressure within the float chamber; and (f) a second linkage mechanically interconnecting the float and the plug such that displacement of the float from the fully lowered position to the fully raised position displaces the plug from the open position to the sealing position, wherein the second linkage is configured to provide a non-linear relationship between displacement of the float and displacement of the plug, the non linear relationship including a rapid closure region during a first portion of displacement of the float from the fully lowered position and a regulated air-release region during a second portion of displacement of the float towards the fully raised position, the regulated air release region having a rate of change of plug position with float displacement at least one order of magnitude smaller than the rapid closure region.

There is also provided according to the teachings of an embodiment of the present invention, an air release system for a pipeline, the air release system comprising: (a) an air-release valve switchable between a first mode of operation in which a venting area of a venting aperture varies as a function of a level of a float and a second mode of operation in which a rate of venting of air is limited, at least while the pipeline is at a raised pressure; (b) an electrical actuator deployed for switching the air-release valve between the first mode and the second mode; and (c) a controller comprising at least one processor, the controller being in electrical connection with the electrical actuator, the controller being responsive to a signal indicative of a predicted arrival of liquid at the air- release valve during filling of the pipeline to actuate the electrical actuator to switch the air-release valve from the first mode of operation to the second mode of operation. According to a further feature of an embodiment of the present invention, the signal is selected from the group consisting of: a liquid level sensor; a pipeline pressure sensor; and an actuation signal for a liquid pump.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein:

FIG. 1A is a schematic vertical cross-sectional view taken through an air-release valve, constructed and operative according to an embodiment of the present invention;

FIG. IB is an enlarged view of a plug and diaphragm assembly from the air- release valve of FIG. 1A;

FIGS. 2A-2C are partial cross-sectional views of the air-release valve of FIG. 1A showing the valve in a fully open state, a flow regulating state, and a fully closed state, respectively;

FIGS. 3A-3C are graphs illustrating a variation of air flow area at the venting aperture as a function of float displacement for the air-release valve of FIG. 1A, with a circle denoting the location on the graph corresponding to the states of FIGS. 2A-2C, respectively;

FIG. 4A is a schematic vertical cross-sectional view taken through an air-release valve, constructed and operative according to a further embodiment of the present invention;

FIG. 4B is an enlarged view of a plug and diaphragm assembly from the air- release valve of FIG. 4 A;

FIG. 4C is a graph illustrating a variation of air flow area at the venting aperture as a function of float displacement for the air-release valve of FIG. 4A;

FIG. 5A is a schematic vertical cross-sectional view taken through an air-release valve, constructed and operative according to a further embodiment of the present invention;

FIG. 5B is an enlarged view of a plug and diaphragm assembly from the air- release valve of FIG. 4 A; FIG. 5C is a graph illustrating a variation of air flow area at the venting aperture as a function of float displacement for the air-release valve of FIG. 4A;

FIG. 6A is a schematic vertical cross-sectional view taken through an air-release valve, constructed and operative according to a further embodiment of the present invention implemented as a modification to the valve of FIG. 5A to provide externally controllable switching of the valve state;

FIGS. 6B and 6C are enlarged views of the region of FIG. 6 A marked by a dashed rectangle, showing the air-release valve in a first state and a second state, respectively;

FIG. 7 is a view similar to FIG. 6B illustrating a variant implementation of this embodiment;

FIG. 8A is a schematic vertical cross-sectional view taken through an air-release valve, constructed and operative according to a further embodiment of the present invention implemented as a modification to the valve of FIG. 4A to provide rapid ingress of air during draining of the pipeline, while providing a limited flow cross-section during filling of the pipe;

FIGS. 8B-8D are enlarged views of the region of FIG. 8A marked by a dashed rectangle, showing the air-release valve during regulated air release, during filling of the pipeline and during draining of the pipeline, respectively;

FIG. 8E is a view similar to FIG. 8B illustrating a combination of this embodiment with the externally controllable switching of FIG. 6A;

FIG. 9A is an enlarged partial vertical cross-sectional view taken through an air- release valve, constructed and operative according to a further embodiment of the present invention implemented as a modification to the valve of FIG. 5A, providing switching between an anti- slam mode of operation and a normal air-release regulating mode of operation;

FIG. 9B is a view similar to FIG. 9 A illustrating the anti- slam mode of operation;

FIGS. 9C and 9D are views similar to FIG. 9 A illustrating successive positions during rising of a float of the air-release valve and switching to the normal air-release regulating mode of operation;

FIGS. 9E and 9F are views similar to FIG. 9 A illustrating a range of positions during subsequent air-release regulating operation; FIGS. 9G and 9H are views similar to FIG. 9 A illustrating a combination of this embodiment with the externally controllable switching of FIG. 6A, shown in a regulating state and a closed state, respectively; and

FIG. 10 is a schematic block diagram illustrating a system employing the air- release valve of FIG. 4 A or FIG. 5 A.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention is an air-release valve for use with a liquid-conveying pipeline.

The principles and operation of air-release valves according to the present invention may be better understood with reference to the drawings and the accompanying description.

By way of introduction, the present invention is exemplified herein with reference to a number of non-limiting embodiments, which share various features and have various components that are analogous. Thus, FIGS. 1A-3C illustrate a first embodiment of an air-release valve, generally designated 100, FIGS. 4A-4C illustrate a second embodiment of an air-release valve, generally designated 200, and FIGS. 5A-5C illustrate a third embodiment of an air-release valve, generally designated 300. For conciseness of explanation, the following general description will be presented in a manner that is generic to these three exemplary embodiments, where analogous features are referred to by similar reference numerals with the first digit changed to correspond to the embodiment. Thus, the description of elements referred to below by reference numerals 102, 104, 106 etc. should be understood to refer equally to analogous elements 202, 204, 206 etc., respectively, of air-release valve 200 and 302, 304, 306 etc., respectively, of air- release valve 300.

Similarly, FIGS. 6A-10H describe a range of additional features which, unless stated otherwise, can be used interchangeably with the air-release valves 200 and 300. For conciseness of presentation, these features are illustrated arbitrarily with one or the other of these embodiments, but may be implemented interchangeably with these and other embodiments. Turning now generically to FIGS. 1A-5C, there are shown an air-release valve 100, 200 or 300, constructed and operative according to non-limiting embodiments of the present invention, for releasing air from a pipeline (not shown) to a surrounding atmosphere. In general terms, the air-release valve is formed with a valve casing 102 (and 202, 302, and likewise throughout) for connection to the pipeline. Valve casing 102 defines a float chamber 104 and a venting aperture 106. A float 108 is deployed within float chamber 104 so as to be raised according to a level of liquid within float chamber 104 from a fully lowered position to a fully raised position. A plug 110 is displaceable relative to venting aperture 106 between an open position, in which the venting aperture allows gas flow between the interior of valve casing 102 and the surrounding atmosphere (FIG. 2A), and a sealing position, in which plug 110 seals venting aperture 106 (FIG. 2C).

The air-release valve also includes a pneumatic actuator, typically implemented as a diaphragm 112 or a piston (not shown), in fluid interconnection with float chamber 104. A first surface 114 of the pneumatic actuator is exposed (directly or indirectly) to a pressure within float chamber 104. A second surface 116 of the pneumatic actuator is in opposed relation to first surface 114. A first linkage mechanically interconnects plug 110 and the pneumatic actuator. This first linkage, the pneumatic actuator and the plug are configured such that, when the second surface 116 of the pneumatic actuator is exposed to a pressure of the surrounding atmosphere, plug 110 is insensitive to variations in the pressure within the float chamber 104.

“Insensitive” to variations in pressure in this context refers to an arrangement which is fully or partially pressure compensated, such that variations in pressure within the pipeline act both on the plug 110 and on first surface 114 to at least partially cancel a tendency for variations in pipeline pressure to force the plug closed or open. In certain particularly preferred implementations as illustrated throughout this document, a particularly simple implementation of the first linkage is as an axially displaceable stem

120 interconnecting plug 110 and a displaceable partition of the pneumatic actuator. As mentioned, the displaceable portion may be a piston deployed in sliding contact with an inner surface of the pneumatic chamber (not shown), in which case the piston typically has a diameter the same as that of plug 110 in order to achieve balanced operation. In the case of a flexible diaphragm 112, the diameter of the diaphragm is chosen to provide a suitable balanced effect, according to the structure and deployment of the diaphragm. As a rough rule of thumb, an“effective diameter” of a diaphragm can be assumed to be roughly the average of two diameters: (1) the linkage/actuator diameter supporting diaphragm from the second surface 116 side, and (2) inner diameter of casing supporting the diaphragm in the area of diaphragm outer diameter. An "effective diameter" of diaphragm that is similar to the plug diameter 110 may provide balanced operation.

Although the axially displaceable stem 120 is a particularly simple and elegant implementation of the first linkage, it should be noted that the invention is not limited to such an implementation, and various other mechanical linkages may be used. For example, if the pneumatic actuator and the plug are deployed side-by-side, a rocker linkage (not shown) can be used. If the linkage provides a displacement ratio other than 1: 1, the size of the displaceable partition of the pneumatic actuator is preferably adjusted in order to maintain overall balanced operation.

A second linkage 118 mechanically interconnects float 108 and plug 110 such that displacement of float 108 from the fully lowered position (FIG. 2A) to the fully raised position (FIG. 2C) displaces plug 110 from the open position to the sealing position.

According to one particularly preferred but non-limiting aspect of the present invention, second linkage 118 is configured to provide a non-linear relationship between displacement of float 108 and displacement of plug 110. As illustrated in the non-limiting example of FIGS. 3A-3C, the non-linear relationship preferably includes a rapid closure region during which a first portion of displacement of the float from the fully lowered position to an intermediate position (FIGS. 2B and 3B) causes a rapid displacement of the plug and corresponding rapid reduction in the air flow area between plug 110 and venting aperture 106. The non-linear relationship also preferably includes a regulated air-release region during a second portion of displacement of the float towards the fully raised position, from FIG. 2B to FIG. 2C. The regulated air release region preferably has a rate of change of plug position with float displacement at least one order of magnitude smaller than in the rapid closure region, as reflected by the different gradients of the regions to the left and right of the dashed line in FIGS. 3A-3B. (The gradients are shown here as negative, to convey the decrease in air flow area (proportional to plug displacement) with float displacement, but the aforementioned rates of change refer to the magnitudes only.) Second linkage 118 may be implemented in any suitable form which provides the required nonlinear relationship between float displacement and plug displacement. In the non-limiting examples of air-release valves 100 and 300, second linkage 118 includes a rotary linkage 122 mechanically linked to float 108 so as to be rotated by displacement of the float. Rotary linkage 122 has an axis of rotation 124 and an actuation surface 126 deployed for displacing plug 110. Actuation surface 126 may essentially have an arbitrary external shape defined so that the rate of change of plug displacement with rotation of rotary linkage 122 varies as a desired function, and that the overall function of float displacement (rising) generates the corresponding desired displacement profile for plug 110. In one non-limiting example illustrated in air-release valve 100, a first part of actuation surface 126 is flat, thereby defining a clear point of transition between the rapid air-release region of operation and a more gentle spiral curvature corresponding to the regulated air-release region. However, use of a flat region is not necessary, and a similar result can be achieved by changing the gradient of the spiral curvature, as will be clear to a person of ordinary skill in the art.

In an alternative set of embodiments exemplified with reference to air-release valve 200, second linkage 218 includes an abutment block 228 having an actuation surface 230 deployed for displacing plug 210. Abutment block 228 is mechanically linked to float 208 so as to be displaced linearly by displacement of the float. Here too, a desired relationship between rising of float 208 and displacement of plug 210 is defined by suitable shaping of actuation surface 230, which preferably has a significant change in gradient to define a transition between the rapid air-release region of operation and the regulated air-release region.

Referring again generically to all embodiments, valve casing 102 may be assembled from a number of separate components to define the various recited features. The valve casing 102 is preferably connected to the pipeline at a local high-point via a connecting tube 132 which typically opens into float chamber 104 near the bottom of the chamber.

It is a particular feature of air-release valves according to one non-limiting aspect of the present invention that second linkage 118 is a one-sided linkage, otherwise stated as a“one-way linkage,” such that lowering of the float does not positively displace the plug away from the sealing position. In other words, the various actuation surfaces of the second linkage press against the plug on one side so as to selectively displace it towards its closed state, but do not pull it back away from the venting aperture 106. In such embodiments, plug 110 is preferably resiliently biased away from the sealing position, such as by a spring 134, so as to tend to return to an at least partially open state when float 108 drops. This feature has various mechanical advantages, particularly in the context of implementations which provide parallel pneumatic actuation, as will be exemplified further below.

Turning now to a feature specific to the embodiment of FIGS. 1 A-2C, in this case, the pipeline internal balancing pressure applied to first surface 114 acts inwardly, towards stem 120. In order to deliver the internal pipeline pressure to the volume above the diaphragm 112 (or piston), a connecting passageway 136 is provided through stem 120, serving to equalize pressure between the internal volume of float chamber 104 and the volume above the diaphragm. Clearly, although not visible in the views illustrated, connecting passageway 136 is somewhat offset relative to actuating surface 126, or the actuating surface 126 may feature a slot aligned with the passageway, to ensure that actuating surface 126 does not obstruct the passageway during operation.

In the embodiment of FIGS. 1 A-2C, the volume surrounding stem 120 appears to be internal to the valve casing 102, but has a relatively large venting area to the surrounding atmosphere and is functionally considered to be like an external volume. Thus, both the upper surface of plug 110 and the second surface 116 of diaphragm 112 are effectively exposed to atmospheric pressure while first surface 114 of diaphragm and the lower surface of plug are effectively exposed to the float chamber pressure, and balancing of forces is maintained.

Turning now to air-release valves 200 and 300 of FIGS. 4A-4B and 5A-5B, most of the features of these embodiments have already been described above in the generic description. These exemplary embodiments implement the valve casing 202 or 302 with a pneumatic chamber in fluid interconnection with the float chamber, for example, via a pressure-equalization channel around or next to stem 220 or 320. In these cases, the pneumatic actuator is preferably implemented using a displaceable partition (e.g., diaphragm 212 or 312) deployed within and subdividing the pneumatic chamber. The surface 214, 314 is exposed to the interior pressure of the float chamber and hence of the pipeline, thereby balancing our pressure acting on the interior of plug 210, 310. The part of the pneumatic chamber delimited by diaphragm 212, 312 is referred to herein as a “control volume” 238, 338 of the pneumatic chamber, which provides various additional functionality as described below. In the basic implementation of FIGS. 4A and 5A, the control volume is open to the surrounding air, thereby balancing external air pressure acting on the outside of plug 210, 310, thereby providing balanced operation of the valve, as described previously.

FIGS. 4C and 5C illustrate the variation of air flow area with float displacement for air-release valves 200 and 300, respectively, illustrating a non-linear relationship including a rapid closure region and a regulated air-release region, analogous to FIGS. 3A-3C described above. Both here and in air-release valve 100, the form of the non-linear relationship is not limited to the form illustrated, and may vary considerably according to the desired characteristics, and need not be monotonic in its variation. By way of a further non-limiting example, a dashed line shows an alternative implementation in which the air flow area drops at the end of the rapid closure region to a low minimum value and then, on further rising of the float, initially increases before reaching the gentle slope of the regulation region.

Turning now to FIGS. 6A-10H, these illustrate various additional functionality which is achieved by adding various pneumatic control architectures in connection with control volume 238 or 338. Air-release valves 200 and 300 are generally interchangeable for the purpose of these architectures, and all features described should be understood to apply interchangeable to both of these implementations.

FIGS. 6A-6C illustrate an air-release valve according to a further aspect of the present invention in which air-release valve 300 is supplemented by a pneumatic pilot valve 400, switchable between a first state (FIGS. 6 A and 6B) in which control volume 338 is maintained at a pressure of the surrounding atmosphere and a second state (FIG. 6C) in which control volume 338 is connected to a source of pressure above the pressure of the surrounding atmosphere, thereby forcing the plug towards the sealing position. Although an external source of pressure could be used for this purpose, the particularly preferred implementation illustrated here provides actuating pressure to pilot valve 400 from a feed line 402 in fluid communication with float chamber 304 so as to provide an internal pipeline pressure to control volume 338 in the second state. The fluid connection paths for the first and second states are illustrated by arrows in the enlarged views of FIGS. 6B and 6C, respectively. In FIG. 6B, valve 400 connects a passageway from control volume 338 to a vent passageway 404, allowing equalization of a pressure within control volume 338 with that of the surrounding atmosphere. In this state, operation of air-release valve 300 is identical to the balanced, float-operated function described above, where the valve operation is insensitive to variations in pressure within or outside the pipeline, and motion of the float caused by variations in water level provides rapid air release during filling of the pipeline and rapid air intake during draining of the pipeline, and performs gradual regulated release of air when the pipeline is full and in operation, releasing accumulated gas in a controlled manner to maintain the liquid level at a predefined level within the float chamber 304.

When valve 400 is switched to its second state, as illustrated in FIG. 6C, the valve connects feed line 402 to control volume 338, thereby exposing the control volume to the internal pressure of the float chamber and hence of the pipeline. This cancels out the pressure-balancing effect of the pneumatic actuator and shifts the balance of forces towards closure of plug 310, even when float 308 has not been raised to achieve float- actuated closure.

Control of valve 400 may be manual control through a manually- operated handle, or may be operation via a solenoid or other powered actuator, allowing remote control of the system, for example, as will be described below with reference to FIG. 10.

In addition to the elegance of this solution in that no external pressure source is required to close off the air-release valve, the use of pipeline pressure as the pressure source has an additional advantage in that the closure effect is inherently canceled or even reversed, so that the pressure actively opens the plug, in case of negative pressure (partial vacuum) during draining of the system, allowing rapid ingress of air during draining of the pipeline and minimizing risks of pipe implosion due to vacuum.

In certain cases, it may be desirable to enable active closure of the air-release valve even under conditions in which the internal pipeline pressure has dropped to a level that is not sufficient to close the pneumatic actuator in the scheme of FIG. 6C. For such cases, a modification of this structure is illustrated in FIG. 7. In this case, pilot valve 400 has a feed line 402 in fluid communication with a pressure accumulation volume 406, which is connected to float chamber 304 via a check valve 408. Check valve 408 serves to store a quantity of pressurized air within pressure accumulation volume 406 corresponding to the maximum pressure reached by the pipeline since the last operation of valve 400. This accumulated pressure is then channeled via feed line 402 when valve 400 is switched to its second state so as to apply pressure to control volume 338, thereby actuating plug 310 to its closed position.

Turning now to FIGS. 8A-8D, in certain cases, it may be preferably to define a relatively restricted default opening area for venting gas during filing of the pipeline, while at the same time ensuring a large opening area during drainage of the pipeline, thereby minimizing risks of pipe implosion due to vacuum. FIGS. 8A-8D illustrate an air- release valve according to a further aspect of the present invention which offers a solution for these requirements. This solution is illustrated arbitrarily as a modification of air- release valve 200 illustrated above, but could equally be implemented as a modification of air-release valve 300.

As shown in FIGS. 8A-8C, plug 210 is in this case biased to an intermediate position between the open position and the sealing position. This can be achieved, for example, by supplementing spring 234 with an opposing spring 410, where the balance between the springs defines the intermediate position. Control volume 238 is here shown connected to the surrounding atmosphere via a bleed orifice (i.e., flow constriction) 412. A feed line 414, providing fluid communication between float chamber 204 and control volume 238, includes a normally-closed check valve 416 deployed to prevent air flow from float chamber 204 to control chamber 238, while allowing suction of air from control chamber 238 when a pressure within the float chamber drops below atmospheric pressure.

Under normal operating conditions, when pressure within the pipeline is above atmospheric pressure, as occurs during filling and during normal pipeline operation, check valve 416 remains closed, and bleed orifice 412 allows equalization of pressure between the surrounding atmosphere and control chamber 238. This results in the normal balanced air-release valve functionality described above with reference to air-release valve 200, modified by the fact that the default“open” position of plug 210 is here the intermediate position of FIGS. 8A-8C, thereby limiting the rate of air release during filling of the pipeline so as to reduce the risk of a“slam” effect. During draining of the pipeline, as soon as the pressure within float chamber 204 falls below atmospheric pressure, check valve 416 opens and air is drawn from control chamber 238. Due to the high flow impedance of bleed orifice 412, almost the entirety of the pressure drop between the surrounding atmosphere and the low pressure interior of the pipeline occurs across the bleed orifice, resulting in a pressure within control chamber 238 which is essentially the same as the float chamber pressure. This results in cancelling out of the pressure balancing effect, and leaves the full atmospheric pressure acting on the outside of plug 210. The resulting force compresses spring 410 and displaces plug 210 away from its intermediate position towards the fully open position, as illustrated in FIG. 8D, to allow rapid ingress of air during draining.

Although FIGS. 8A-8D have been illustrated without an externally controlled pilot valve, the assembly is modular and allows addition of pilot valve 400 as illustrated in FIG. 8E. The structure and function of the pilot valve is identical to that described above with reference to FIGS. 6A-6C.

Turning now to FIGS. 9A-9F, there is illustrated a further non-limiting aspect of the present invention according to which motion of float 308 is used, in addition to mechanically driving motion of plug 310, to additionally switch a control valve, thereby changing the mode of operation of the pneumatic control. In the particular example illustrated here, this switching is employed to switch between an anti- slam protection mode when the float is fully lowered and the normal air-release regulation mode when the float is raised. However, the principle of performing switching of pneumatic control mode according to motion of the float may be applied to other situations, and to other solutions for the same issue. For example, switching could be actuated by an additional float dedicated for this purpose, or performed by an electric actuator triggered by a reed switch and a magnet with suitable circuitry. The exemplary embodiment shown here is presented in the context of an adaptation of air-release valve 300, but could equally be implemented using air-release valve 200 with corresponding changes that will be readily understood by a person of ordinary skill in the art.

As in the previous implementation, control volume 338 is connected to the surrounding atmosphere via a bleed orifice 412. A control valve 418 is switchable between a first state (FIGS. 9 A and 9B) in which a feed line 420 provides fluid communication between float chamber 304 and control volume 338, and a second state (FIGS. 9C-9F) in which feed line 420 is closed. Control valve 418 is preferably mechanically linked to float 308, directly or via second linkage 318, such that raising of the float switches control valve 418 from the first state to the second state.

In the non-limiting example illustrated here, control valve 418 is implemented as an actuator rod 422 which carries two seals 424a and 424 b which slide along a cylindrical bore 426 which intersects feed line 420. In the first state of FIGS. 9 A and 9B, seal 424a reaches a broadened passageway in which there is a fluid flow path around the seal, allowing flow from float chamber 304 to control volume 338 and bleed orifice 412. When actuator rod 422 is displaced leftwards as shown, seal 424a engages cylindrical bore 426 such that the two seals together isolate the intersection with feed line 420, cutting off fluid connection between float chamber 304 and control volume 338. Displacement of actuator rod 422 is here achieved by engagement of a pin 428 in a shaped slot 430 formed in rotary linkage 322, although other forms of mechanical linkage, or electrical actuation such as by a reed switch, cooperating with a magnet and actuating a solenoid valve, can also be used.

FIG. 9A illustrates this implementation in a fully-lowered state of float 308. In this position, the engagement of pin 428 in slot 430 defines a position of actuator rod 422 in which seal 424a is in non- sealing relation to cylindrical bore 426, and a fluid flow can pass from float chamber 304 along feel line 420. This first state of control valve 418 defines a slam-protecting mode in which a build-up of internal pipeline pressure known to occur as a precursor to arrival of a rapidly advancing column of water acts to apply pressure in control volume 338 which, together with the pressure on the rear surface of plug 310, overcomes spring 334 and the pressure on the first surface 314 to force closure of plug 310 against aperture 306. The pressure at which this closure takes place can be defined by suitable choice of the properties of spring 334. This state, shown in FIG. 9B, reduces the rate of air release from via the assembly to slow venting at whatever rate is allowed by bleed orifice 412, thereby generating a significant trapped-air cushion which slows the advancing column of water and minimizes the risk of a slam effect.

When the liquid level rises sufficiently to start raising float 308, the engagement of pin 428 in slot 430 is such that, as the device reaches its regulation region of operation, actuator rod 422 is displaced sufficiently for seal 424a to engage cylindrical bore 426 and cut off fluid connection between float chamber 304 and control volume 338 (FIGS. 9C and 9D). Pressure within control volume 338 then equalizes with the surrounding atmosphere via bleed orifice 412, and the air-release valve functions as a balanced, float- actuated air-release valve entirely as described above with reference to FIGS. 1 A-5C.

The risk of a slam effect addressed by the first state of control valve 418 only typically occurs during filling of the pipeline. Accordingly, it may be advantageous for switching back to the first state to occur only at or near the fully lowered state of the float, outside the normal operating range of the air-release valve while the pipeline is in use. Thus, the mechanically linkage to the float or to the second linkage is preferably implemented such that lowering of the float switches the control valve from the second state to the first state at a level that is lower than the level at which switching from the first state to the second state occurs. This is achieved in the exemplary implementation illustrated here by appropriate shaping of slot 430, rendering it sufficiently wide or otherwise enlarged so that, in the second state of the control valve 418, a wide range of motion of float 308 and corresponding displacement of plug 310 occurs without contact of pin 428 against the sides of slot 430, as seen in FIGS. 9E and 9F. If the pipeline is subsequently drained, lowering of float 308 to its fully lowered position will return control valve 418 to its first state, as illustrated in FIG. 9A, thereby reactivating the slam- protection state.

Although illustrated thus far without an externally controlled pilot valve, this implementation may optionally additionally receive a block with pilot valve 400 to add the option of externally-controlled switching, as illustrated in FIGS. 9G and 9H. This added functionality is relevant when control valve 418 is in its second state, i.e., during normal air-release functionality of the system, and is fully analogous in structure and function to the operation described above with reference to FIGS. 6A-6C.

Turning finally to FIG. 10, in all implementations in which an externally actuated pilot valve 400 is provided, this may advantageously be integrated into an overall control system, such as is represented schematically in FIG. 10. The system shown here includes a reservoir 500, preferably provided with a level sensor 502, a pipeline 504, and a pump

506 for delivering liquid from reservoir 500 along pipeline 504. An air-release valve 200 or 300, modified according to any of the above variants which includes externally- actuated pilot valve 400, is interconnected with pipeline 504 at a local high-point. A controller 508 is connected to level sensor 502, pump 506 and an electric actuator (not shown separately) of pilot valve 400, for controlling operation of the system. During filling of the pipeline, controller 506 is preferably configured to preempt arrival of a column of liquid to the air-release valve, either based on elapsed time of operation of pump 506 or on measurements of level sensor 502 indicating the quantity of liquid that has been introduced, and to actuate pilot valve 400 to close the air-release valve, thereby trapping a sufficient air cushion to mitigate any slam effect. Subsequent brief opening and closing of the valve can then be used to complete venting of air from the line without allowing sufficient build-up of momentum in the liquid column to pose a risk of slam damage. Once liquid levels reach their normal working level, the normal regulation functionality of the air-release valve takes over, and the remotely controlled pilot valve 400 is left open.

The various system components mentioned herein may be implemented using standard off-the-shelf components which are not in themselves new, and which will therefore not be described here in detail. A wide range of suitable pumps, liquid level sensors, electric actuators and controllers are commercially available and are well known in the art. The controller typically includes at least one processor or other logic circuitry, which may be custom hardware or a general purpose processor operating under a suitable operating system and software, or any other hardware/software combination, as is known in the art.

The present invention may be employed to advantage in a wide range of contexts in which pipelines carrying liquids employ gas-release valves, including but not limited to, potable water supplies, agricultural applications, waste water applications, sewage applications, and various industrial processing applications.

It will be appreciated that the above descriptions are intended only to serve as examples, and that many other embodiments are possible within the scope of the present invention as defined in the appended claims.

Claims

WHAT IS CLAIMED IS:

1. An air-release valve for releasing air from a pipeline to a surrounding atmosphere, the air-release valve comprising:

(a) a valve casing for connection to the pipeline, said valve casing defining a float chamber and a venting aperture;

(b) a float deployed within said float chamber so as to be raised according to a level of liquid within said float chamber from a fully lowered position to a fully raised position;

(c) a plug displaceable relative to said venting aperture between an open position in which said venting aperture allows gas flow between said valve casing and the surrounding atmosphere and a sealing position in which said plug seals said venting aperture;

(d) a pneumatic actuator in fluid interconnection with said float chamber, said pneumatic actuator having a first surface exposed to a pressure within said float chamber and a second surface in opposed relation to said first surface;

(e) a first linkage mechanically interconnecting said plug and said pneumatic actuator, said plug, said pneumatic actuator and said first linkage being configured such that, when said second surface of said pneumatic actuator is exposed to a pressure of the surrounding atmosphere, said plug is insensitive to variations in the pressure within said float chamber; and

(f) a second linkage mechanically interconnecting said float and said plug such that displacement of said float from said fully lowered position to said fully raised position displaces said plug from said open position to said sealing position,

wherein at least a portion of the displacement of said float from a fully lowered position to the fully raised position provides a regulated air-release region, and wherein displacement of said plug within the regulated air release region occurs as a function of displacement of said float such that the displacement of said plug is less than the displacement of said float.

2. The air-release valve of claim 1, wherein said second linkage is a one-sided linkage such that lowering of said float does not positively displace said plug away from said sealing position, and wherein said plug is resiliently biased away from said sealing position.

3. The air-release valve of claim 1 or 2, wherein said second linkage is configured to provide a non-linear relationship between displacement of said float and displacement of said plug, said non-linear relationship including a rapid closure region during a first portion of displacement of said float from said fully lowered position and said regulated air-release region during a second portion of displacement of said float towards said fully raised position, said regulated air release region having a rate of change of plug position with float displacement at least one order of magnitude smaller than said rapid closure region.

4. The air-release valve of claim 3, wherein said second linkage is configured such that progressive rising of said float generates a decrease in a venting area between said plug and said venting aperture to a first minimum venting area, followed by an increase in said venting area, followed by a further decrease in said venting area.

5. The air-release valve of claim 3, wherein said second linkage comprises a rotary linkage mechanically linked to said float so as to be rotated by displacement of said float, said rotary linkage having an axis of rotation and an actuation surface deployed for displacing said plug.

6. The air-release valve of claim 3, wherein said second linkage comprises an abutment block having an actuation surface deployed for displacing said plug, said abutment block being mechanically linked to said float so as to be displaced linearly by displacement of said float.

7. The air-release valve of claim 1 or 2, wherein said valve casing further comprises a pneumatic chamber in fluid interconnection with said float chamber, and wherein said pneumatic actuator comprises a displaceable partition deployed within and subdividing said pneumatic chamber, said displaceable partition providing said first surface and said second surface, said second surface being exposed to a control volume of said pneumatic chamber.

8. The air-release valve of claim 7, wherein said first linkage comprises an axially displaceable stem interconnecting said plug and said displaceable partition.

9. The air-release valve of claim 7 or claim 8, wherein said displaceable partition is a piston deployed in sliding contact with an inner surface of said pneumatic chamber.

10. The air-release valve of claim 7 or claim 8, wherein said displaceable partition is a flexible diaphragm.

11. The air-release valve of any one of claims 7 to 10, further comprising a pneumatic pilot valve switchable between a first state in which said control volume is maintained at a pressure of the surrounding atmosphere and a second state in which said control volume is connected to a source of pressure above the pressure of the surrounding atmosphere, forcing said plug towards said sealing position.

12. The air-release valve of claim 11, wherein said pilot valve has a feed line in fluid communication with said float chamber so as to receive an internal pipeline pressure that is supplied to said control volume in said second state.

13. The air-release valve of claim 11, wherein said pilot valve has a feed line in fluid communication with a pressure accumulation volume, said pressure accumulation volume being connected to said float chamber via a check valve so as to store a quantity of pressurized air for supply to said control volume in said second state.

14. The air-release valve of any one of claims 7 to 10, wherein said control volume is connected to the surrounding atmosphere via a bleed orifice, the air-release valve further comprising a control valve switchable between a first state in which a feed line provides fluid communication between said float chamber and said control volume, and a second state in which said feed line is closed.

15. The air-release valve of claim 14, wherein said control valve is mechanically linked to said float or to said second linkage such that raising of said float switches said control valve from said first state to said second state.

16. The air-release valve of claim 15, wherein said control valve is mechanically linked to said float or to said second linkage such that lowering of said float switches said control valve from said second state to said first state, said switching from said first state to said second state occurring at a first level of said float and said switching from said second state to said first state occurring at a second level of said float, said second level being lower than said first level.

17. The air-release valve of any one of claims 7 to 10, wherein said plug is biased to an intermediate position between said open position and said sealing position, and wherein said control volume is connected to the surrounding atmosphere via a bleed orifice, the air-release valve further comprising a feed line providing fluid communication between said float chamber and said control volume, said feed line including a check valve deployed so as to prevent air flow from said float chamber to said control chamber, but to allow suction of air from said control chamber when a pressure within said control chamber drops below atmospheric pressure.

18. An air-release valve for releasing air from a pipeline to a surrounding atmosphere, the air-release valve comprising:

(e) a first linkage mechanically interconnecting said plug and said pneumatic actuator, said plug, said pneumatic actuator and said first linkage being configured such that, when said second surface of said pneumatic actuator is exposed to a pressure of the surrounding atmosphere, said plug is insensitive to variations in the pressure within said float chamber; and (f) a second linkage mechanically interconnecting said float and said plug such that displacement of said float from said fully lowered position to said fully raised position displaces said plug from said open position to said sealing position,

wherein said second linkage is configured to provide a non-linear relationship between displacement of said float and displacement of said plug, said non-linear relationship including a rapid closure region during a first portion of displacement of said float from said fully lowered position and a regulated air-release region during a second portion of displacement of said float towards said fully raised position, said regulated air release region having a rate of change of plug position with float displacement at least one order of magnitude smaller than said rapid closure region.

19. An air release system for a pipeline, the air release system comprising:

(a) an air-release valve switchable between a first mode of operation in which a venting area of a venting aperture varies as a function of a level of a float and a second mode of operation in which a rate of venting of air is limited, at least while the pipeline is at a raised pressure;

(b) an electrical actuator deployed for switching said air-release valve between said first mode and said second mode; and

(c) a controller comprising at least one processor, said controller being in electrical connection with said electrical actuator, said controller being responsive to a signal indicative of a predicted arrival of liquid at said air- release valve during filling of the pipeline to actuate said electrical actuator to switch said air-release valve from said first mode of operation to said second mode of operation.

20. The system of claim 19, wherein said signal is selected from the group consisting of: a liquid level sensor; a pipeline pressure sensor; and an actuation signal for a liquid pump.