Patent Description:
Irrigation Low Pressure Systems (LPS) tubes are delicate and subject to rupture on overpressure and pressure surges. To protect them from damage, such systems are typically provided with pressure reducing valves (PRV) which throttle a variable inlet pressure to produce a relatively constant outlet pressure at a desired value.

Patent publications <CIT> and <CIT> both relate to pressure control valves which include a pressure release function for excess downstream pressure.

One aspect is a pressure regulating and pressure releasing valve, as set out in the appended claims.

Various embodiments are herein described, by way of example only, with reference to the accompanying drawings, wherein:.

The following detailed description is of the best currently contemplated modes of carrying out the invention. The description is not to be taken in a limiting sense, but is made merely for the purpose of illustrating the general principles of the invention, since the scope of the invention is best defined by the appended claims.

As an additional precaution, low pressure irrigation systems may be provided with a pressure relief valve which opens in the case of excess pressure in the line to vent the excess pressure to the atmosphere. Instead of the pressure relief valve being an additional system component which would add cost and involve additional installation and maintenance overheads to the system, in certain embodiments a single valve functions as a pressure regulation valve and a pressure relief valve, in one valve body.

Additionally, instead of starting to operate the pressure relief function only when the pressure peaks above a preset level, and suffering from a relatively slow response time, the valve, in certain embodiments, prevents a pressure surge and buildup prior to development of the pressure surge and buildup on the downstream system. The valve ties the relief opening move to the pressure reducing move, anticipating and eliminating the potential downstream pressure rise. The relief port is configured to open on the same pressure regulation/reduction move. In contrast, existing pressure reduction valves react to remedy the downstream pressure only after the valve senses the pressure rise over the set points.

The principles and operation of a Pressure Reducing and Relief Valve according to the invention may be better understood with reference to the drawings and the accompanying description.

As shown in <FIG>, a pressure reducing and pressure releasing valve <NUM> comprises a valve body <NUM> defining an inlet port A and an outlet port C, a valve seat <NUM> and a pressure release opening D also called the pressure relief port D.

Valve <NUM> also comprises a pressure regulating plug <NUM> configured to be displaced during a first portion of a motion from an open position, which provides a continuous flow path from the inlet port A to the outlet port C (by for example passing between the valve seat <NUM> and plug <NUM>), to a closed position in which the plug <NUM> is closed against the valve seat <NUM> to obstruct the continuous flow path. During the first portion of the motion the closed position is reached when plug <NUM> is displaced enough to contact valve seat <NUM>, thereby cutting off the continuous flow path (of fluid such as water). The displacement of plug <NUM> may be linear relative to valve seat <NUM> during the first part (and second part) of the motion.

Valve <NUM> further comprises a spring <NUM> configured to bias the plug <NUM> from the closed position to the open position. Plug <NUM> typically has an actuation surface <NUM> exposed to a pressure at the outlet port C such that the pressure at the outlet port C displaces the plug <NUM> against the bias of the spring <NUM> toward the closed position. Actuation surface <NUM> may be a flange at a rear of plug <NUM>.

As seen for example in <FIG>, valve seat <NUM> has a cylindrical portion and sleeve <NUM> of plug <NUM> also has a cylindrical portion. The cylindrical portion of plug <NUM> moves telescopically in overlap with the cylindrical portion of valve seat <NUM> during a second portion of the motion.

As shown in <FIG> (and <FIG> and <FIG>), further displacement of plug <NUM> beyond the closed position during a second portion of the motion that is beyond a range of the first portion of the motion, opens a relief flow path from the outlet port C through the pressure release opening D to an area external to the valve body <NUM>.

<FIG> depicts one particular configuration of valve body <NUM>. In this configuration, valve body <NUM> has a central part <NUM> and a peripheral part <NUM>. Valve seat <NUM> and plug <NUM> are structured such that the fluid flow path travels through the central part <NUM> of valve body <NUM> and the relief flow path is in the peripheral part <NUM> of the valve body <NUM>. An outer wall of plug <NUM> may be radially inward from an inner wall (throat) of the valve seat <NUM> (relative to a longitudinal axis running through the central part of the valve body from the inlet port to the outlet port).

<FIG> depicts another configuration of valve body <NUM> in which the valve seat <NUM> and the plug <NUM> are structured such that the continuous flow path (of fluid such as water) travels through the peripheral part <NUM> and at least a portion of the relief flow path travels through the central part <NUM>. An outer wall <NUM>, for example an outer side wall <NUM>, of plug <NUM> may be radially outward from valve seat <NUM>. Valve body <NUM> further comprises a central relief conduit <NUM> situated such that the relief flow path passes between a rear wall of the plug and the central relief conduit <NUM>.

<FIG> depicts another configuration of valve body <NUM> in which the valve seat <NUM> and the plug <NUM> are structured such that the continuous flow path travels through the peripheral part <NUM> and at least a portion of the relief flow path travels through the central part <NUM> (as in <FIG>). An outer wall of the plug <NUM> may be radially outward from the valve seat <NUM>. In this version shown in <FIG>, however, the relief flow path runs through an opening in a side wall <NUM> of plug <NUM> rather than alongside the rear wall <NUM> of plug <NUM>. In one implementation, the relief flow path travels through relief windows <NUM> in the central part <NUM> of valve body <NUM> to reach the relief port D at which pressure is P3 (atmospheric pressure) (<FIG>).

In general, valve body <NUM> has a central part <NUM> and a peripheral part <NUM> and the valve seat <NUM> and plug <NUM> are structured such that one of the following is true: (i) the fluid flow path travels through the peripheral part <NUM> of valve body <NUM> and at least a portion of the relief flow path travels through central part <NUM> of valve body <NUM> or (ii) the fluid flow path travels through central part <NUM> of valve body <NUM> and the relief flow path is in the peripheral part <NUM> of valve body <NUM>.

In accordance with certain embodiments, for example those shown in <FIG>, <FIG> and <FIG>, displacement of plug <NUM> is not affected by the pressure at the inlet port A. This may be accomplished by configuring the placement of the edge 143A of the sleeve <NUM> of plug <NUM> (i.e. the most forward and inward edge of plug <NUM> or of sleeve <NUM>) relative to throat <NUM> of valve seat <NUM> as shown in <FIG> (which removes the effect of pressure from inlet port A against plug <NUM>) or as shown in <FIG> or as shown in <FIG>. The forward edge of sleeve <NUM> is situated relative to valve seat <NUM> such that the continuous flow fluid (from inlet port A) does not affect displacement of the plug <NUM> (or does affect it significantly).

Plug <NUM> may have a flange <NUM> at the rear of plug <NUM> that functions as an actuation surface <NUM>. This actuation surface/flange <NUM> also functions as the Relief closure. Plug <NUM> and piston <NUM> move past the closed position into the throat <NUM> and open the relief port D as the seal <NUM> move away from the seat line <NUM>.

Plug <NUM> is not affected by the upstream pressure P1 and is driven by the piston <NUM> pushed by the downstream pressure P2 and plug <NUM> stays in equilibrium with the preset spring <NUM> force.

The plug <NUM> closing position starts at the point at which the edge 143A of plug <NUM> engages the seat lip <NUM>.

The opening of the relief port D starts as the piston seal <NUM> move away from the relief seat line <NUM>.

To avoid plug <NUM> getting stuck when it meets valve seat <NUM>, the fit between them cannot be too tight. One option is leaving a minimal clearance. A further option is to have, besides plug seal <NUM>, an additional seal (not shown) similar to the O-ring plug seal <NUM>. This additional seal may be situated between plug <NUM> and throat <NUM> of valve seat <NUM> in order to seal the space between plug <NUM> and throat <NUM> of valve seat <NUM>. This is relevant beginning in the closed position of <FIG> and continuing after plug <NUM> is displaced further as shown in <FIG>. Such an additional seal would be as an alternative to relying on leaving the minimal clearance between plug <NUM> and throat <NUM> to minimize leakage of fluid. Use of the additional seal would be a design consideration that depends on whether one considers the minimal leakage (resulting from leaving the minimal clearance without the additional seal) to be acceptable.

As the downstream pressure P2 rises, piston's <NUM> force prevails over the force of the spring <NUM> and plug <NUM> moves to close, thereby reducing the downstream pressure P2.

If the downstream pressure P2 drops beyond the set point, the spring <NUM> prevails and the valve plug <NUM> opens thereby recovering the downstream pressure P2. Spring <NUM> and plug <NUM> are configured such that when pressure at the outlet port C drops below a set point, plug <NUM> is opened by spring <NUM> and the continuous flow path is restored so as to recover pressure P2 at the outlet port C.

The following parts of valve body <NUM> are labeled in <FIG>:.

Plug <NUM> may have a rear wall <NUM> at the rear of plug <NUM> that functions as an actuation surface <NUM>. This actuation surface <NUM> also functions as the Relief closure. Plug <NUM> including its rear wall <NUM> move past the closed position so as to enclose seat <NUM> and open the relief port D as the seal <NUM> move away from the seat line <NUM>.

Plug <NUM> is not affected by the upstream pressure P1 and is driven by the actuation surface/rear wall <NUM> pushed by the downstream pressure P2 and plug <NUM> stays in equilibrium with the preset spring <NUM> force.

The plug <NUM> closing position starts at the point at which the lip <NUM> of plug <NUM> engages the seat lip <NUM>.

If the downstream pressure P2 drops beyond the set point, the spring <NUM> prevails and the valve plug <NUM> opens thereby recovering the downstream pressure P2. Spring <NUM> and plug <NUM> are configured such that when pressure at the outlet port C drops below a set point, plug <NUM> is opened by spring <NUM> and the continuous flow path (of fluid such as water) is restored so as to recover pressure P2 at the outlet port C.

As the lip <NUM> of plug <NUM> of the valve moves past the main valve flow closing position, it opens the relief flow windows <NUM> to the collection channel <NUM> and to the drain port D to P3 (atmosphere).

The plug <NUM> is unaffected by upstream pressure P1 and is driven by the cross-section of rear flange <NUM> of plug <NUM> affected by the downstream pressure P2 and plug <NUM> stays in equilibrium with the preset spring <NUM> force.

The closing position of pressure reducing plug <NUM> starts as the plug lip <NUM> engages the seat lip <NUM>. At the same instance the relief flow starts as the relief window tip <NUM> move away from the seal <NUM>.

As the downstream pressure P2 rises, the force of plug <NUM> (which is equal to the cross section of piston <NUM> times P2) prevails over the force of the spring <NUM> and the plug <NUM> moves to close, thereby reducing the downstream pressure P2.

If the downstream pressure P2 drops beyond the set point, the force of spring <NUM> prevails over the force of plug <NUM> and plug <NUM> is reopened by the force of the spring <NUM>, thereby recovering the downstream P2.

The following parts of valve body <NUM> ae labeled in <FIG>.

In <FIG>, the length of sleeve <NUM>, i.e. side wall <NUM> of plug <NUM>, is such that in some embodiments plug <NUM> closes at or around the same time that the relief flow along relief flow path to relief port D opens. The further displacement of the plug <NUM> during the second portion of the motion begins to open the relief flow path just when plug <NUM> is closed against valve seat <NUM>.

In other versions of valve body <NUM>, sleeve <NUM> of plug <NUM> may be lengthened or shortened (in proportion to the other parts of valve body <NUM>) compared to <FIG>. For example, if sleeve <NUM> is lengthened relative to <FIG>, for example as shown in <FIG>, the flow along relief flow path to relief port D opens only after the closing of plug <NUM>. For example, in the context of the embodiment shown in <FIG> this is only after plug <NUM> enters the throat (i.e. inner wall) of valve seat <NUM> (in one non-limiting example after plug <NUM> enters valve seat <NUM> and has traveled <NUM>% of its expected travel inside valve seat <NUM>). Accordingly, in that case, plug <NUM> is long enough that the further displacement of plug <NUM> beyond the closed position during the second portion of the motion begins to open the relief flow path only after plug <NUM> is closed against valve seat <NUM>. In some embodiments, a length of the sleeve <NUM> of plug <NUM> beyond a threshold length of sleeve <NUM> (wherein the threshold length of sleeve <NUM> is the length of sleeve <NUM> such that the relief flow path opening would occur simultaneously with the closing of plug <NUM> against valve seat <NUM>) corresponds to a range of positions in which plug <NUM> has closed against valve seat <NUM> and the opening of the relief flow path has not yet occurred.

On the other hand, as shown in <FIG>, if sleeve <NUM> of plug <NUM> is shortened relative to <FIG>, the flow along relief flow path to relief port D opens prior to the closing of plug <NUM> (as a non-limiting example, prior to the last <NUM>% of the traveling of plug <NUM> before its closing). In that case, the first portion of the motion or displacement of plug <NUM> and the second portion of the motion of plug <NUM> overlap. Plug <NUM> is short enough that its further displacement during the second portion of the motion opens the relief flow path prior to the closing of plug <NUM> against valve seat <NUM>.

In some embodiments, the magnitude that the length of the sleeve <NUM> is shorter than a threshold length of the sleeve <NUM> (wherein the threshold length of sleeve <NUM> is the length of sleeve <NUM> such that the relief flow path opening would occur simultaneously with the closing of plug <NUM> against valve seat <NUM>) corresponds to a range of positions in which the relief flow path is open without plug <NUM> having closed against valve seat <NUM>.

Claim 1:
A pressure regulating and pressure releasing valve (<NUM>), comprising:
(a) a valve body (<NUM>) defining an inlet port (A), an outlet port (C), a valve seat (<NUM>) and a pressure release opening (D);
(b) a pressure regulating plug (<NUM>) displaceable from an open position, which provides a continuous flow path from the inlet port (A) to the outlet port (C), to a flow-throttling position in which the plug (<NUM>) is at least partially closed against the valve seat (<NUM>) to obstruct the continuous flow path, the plug being further displaceable beyond said flow-throttling position to a pressure-release position in which a pressure relief flow path is opened from the outlet port (C) through the pressure release opening (D) to an area external to the valve body; and
(c) a spring (<NUM>) configured to bias the plug (<NUM>) from the pressure-release position to the open position,
the plug having an actuation surface (<NUM>) exposed to a pressure at the outlet port (C) such that the pressure at the outlet port displaces the plug against the bias of the spring toward the closed position, thereby variably throttling the continuous flow path to achieve outlet pressure regulation,
and wherein increased pressure at the outlet port causes further displacement of the plug beyond the flow-throttling position towards the pressure-release position, thereby opening the pressure relief flow path from the outlet port through the pressure release opening,
characterized in that the valve seat (<NUM>) comprises a first cylindrical wall and the plug (<NUM>) comprises a second cylindrical wall, displacement of the plug from the open position to the flow-throttling position being an axial motion of the second cylindrical wall towards, and coaxially aligned with, the first cylindrical wall, and wherein displacement of the plug to the pressure-release position brings the first and second cylindrical walls into overlapping relation.