IL183641A - Pilot valve - Google Patents

Description

PILOT VALVE Field of the Invention The present invention relates to piloted hydraulic operated control valves, and more particularly to a pilot valve for hydraulic operated control valves, capable of functioning alternately as a two-way or three-way pilot valve, in response to varying line conditions, for full and efficient utilization of hydraulic operated control valves over the entire service condition range.

Background of the Invention Piloted hydraulic operated control valves, responsive to line flow rate, upstream or downstream line pressure, are known, normally utilized in large valves wherein high actuation forces are involved. Typical constructions of hydraulic control valves may include direct, reverse or dual acting, piston or diaphragm actuators, associated with trim portion seated between flow communicated inlet port and outlet port. The trim portion may include a basic stem, disk and seat configuration, or more sophisticated balanced valves, such as double seat valves, balanced cage guided plugs, balanced pistons, and single seat valves with balancing diaphragms.

In modern, more simply constructed (direct acting) diaphragm control valves, a reinforced diaphragm serves as both the actuator and trim. When the control chamber is pressurized, the flow passage is restricted by the reinforced diaphragm distorted against a seat surrounding the inlet passage. The control chamber, sealed by the diaphragm circumference, having a surface area greater than that of the inlet passage, allows certain pressure to overcome the upstream pressure and cut the flow. When the valve is to be opened, pressure in the control chamber is reduced and the upstream pressure reverts the diaphragm. A steel compression spring is often introduced to the upper chamber to assist closure of the valve.

The diaphragm valve has the advantage of leak free operation due to the absence of a stem and seal, is mainly used in irrigation or domestic water supply systems, and, in conjunction with a pilot valve, may perform as flow rate control valve, an upstream relief valve, downstream pressure reducing valve (PRV), backpressure sustaining valve, altitude control valve, or some combination of the above.

Pilot valves for such applications have many variants according to their use. Taking for example pilot valves for use in pressure reducing applications, these are known in two main arrangements, two-way pilot valves and three-way pilot valves. Both types utilize an adjustable spring loading a diaphragm, with the downstream pressure fed into the pilot valve's control chamber, acting upon the diaphragm against the spring force, to actuates a trim portion.

Traditional two-way pilot valves for pressure reducing applications are essentially small pressure reducers, wherein the main valve's upstream pressure is in flow communication with the inlet port of the pilot valve through an external flow restrictor and the outlet port of the pilot valve is in flow communication with the main valve's downstream pressure. The control chamber of the main diaphragm valve is in flow communication with between the external flow restrictor and the trim portion of the pilot valve. An example of such arrangement can be found for instance in U.S. Patent No. 3,592,223 to James R. Reese.

In modern two-way pilot valves, a dual opposing disk spool, balanced to the upstream pressure, is actuated by the diaphragm, the control pressure is drawn from between the opposing disks, thus eliminating the need of the external restrictor. An example of such arrangement can be found, for instance, in U.S. Patent No. 6,263,905 to Hiroshi Yokota, et al.

Three-way pilot valves are commonly constructed with a plunger spool having reduced diameter portion, wherein both inlet and outlet ports are normally closed when downstream pressure is within the set point limit. Only when downstream pressure rises above or drops below the set point, the spool slides to open the control port to the upstream or to the downstream pressures, respectively. Since there is no continuous flow in three-way pilot valves, the outlet port is sometimes vented to atmosphere instead of connecting to the downstream, having a better opening of the main control valve during high demand conditions. When using that option, however, a small amount of water is wasted each time the control valve is actuated for larger opening. An example of such arrangement is schematically shown for instance in U.S. Patent No. 5,383,646 to Zvi Weingarten.

Clearly, vented three-way pilot valves can deliver control pressure in the full spectrum between upstream pressure down to atmospheric pressure, allowing wider service condition range, in the cost of wasted water. However, two-way pilot valves as described above, having continuous flow while maintaining the required downstream pressure, act faster and have better dynamic response effectively eliminating hunting or oscillation.

Consequently, a need exists for a pilot valve employing the two-way functionality when possible, and the vented three-way functionality during high demand conditions.

Summary of the Invention It is thus one of the objects of the present invention to provide a pilot valve for full and efficient utilization of hydraulic operated control valves over the entire service condition range.

According to the present invention there is provided a dual function pilot valve, comprising, an adjustable spring loading a diaphragm, with the controlled pressure fed into the pilot valve's control chamber, acting upon the diaphragm against the spring force, to actuate a plunger spool having first and second reduced diameter portions, the plunger spool is axially movable in a bored at least five port housing, assembled with at least six radial seals, separating and sealing the five ports, wherein the first and second ports, in conjunction with the plunger spool's first reduced diameter portion, acts as a flow control valve, the third, fourth and fifth ports, in conjunction with the plunger spool's second reduced diameter portion, acts as a diverting valve, allowing controlled flow between said fourth port to said third or fifth ports.

In a preferred embodiment of the present invention, a dual function pilot valve is provided, wherein a specific geometric relation between the simultaneously actuated flow control valve and diverting valve, related to predefined gap between said plunger spool's, first and second reduced diameter portions, permits utilization of the dual function pilot valve in four operative modes associated to four different service conditions. During the first operative mode, there is flow communication between the first and second ports, while during the second operative mode there is flow communication between the first and second port, as well as between the third and fourth port. During the third operative mode there is flow communication between the fourth and third or fifth ports alternately, and during the fourth operative mode there is flow communication between said fourth and fifth ports.

Brief Description of the Drawings The invention will now be described in connection with certain preferred embodiments with reference to the following illustrative figures so that it may be more fully understood.

With specific reference now to the figures in detail, it is stressed that the particulars shown are by way of example and for purpose of illustrative discussion of the preferred embodiments of the present invention only and are presented in the cause of providing what is believed to be the most useful and readily understood description of the principles and conceptual aspects of the invention. In this regard, no attempt is made to show structural details of the invention in more detail than is necessary for a fundamental understanding of the invention, the description taken with the drawings making apparent to those skilled in the art how the several forms of the invention may be embodied in practice.

In the drawings: Fig. 1 is a schematic sectional view of a dual function pilot valve, according to the present invention; Fig. 2 is a schematic sectional view of the pilot valve of Fig. 1, shown connected to symbolically represented main hydraulic control valve, in a pressure reducing application, with the pilot valve in the first of four operative modes; Fig. 3 is essentially same as Fig. 2, with the pilot valve shown in the second of four operative modes; Fig. 4 is essentially same as Fig. 2, with the pilot valve shown in the third of four operative modes; Fig. 5 is essentially same as Fig. 2, with the pilot valve shown in the fourth of four operative modes; Figs. 6 and 6a are schematic sectional and top views of the adjustment portion of the pilot valve according to a preferred embodiment of the present invention, illustrating dual stage spring, and Fig. 7 is a schematic sectional view of the pilot valve of Fig. 1, shown connected to a symbolically represented main hydraulic control valve, in a backpressure sustaining/relief valve application, with the pilot valve in the second of four operative modes.

Detailed Description of the Preferred Embodiments Referring to Fig. 1, there is shown a sectional schematic view of a dual function pilot valve according to the present invention, generally referenced 10. A spring 12, adjustable by set screw 14, and washer 16, loads a diaphragm 18, which seals a control chamber 20. External pressure, admitted through control chamber port 22, acts upon the diaphragm 18 against the spring force, to actuate a stem and trim portion associated with the diaphragm. According to a preferred embodiment of the present invention, the trim portion is composed of a plunger spool 24 directly connected to the center of diaphragm 18. The spool 24, having first and second reduced diameter portions 26, 28, is axially movable in a bore 29 of at least five-port (30, 32, 34, 36, 38) housing 40. The bore 29 of housing 40, is assembled with at least six identical radial seals generally referenced 42, separating and sealing the five port chambers, yet permitting axial displacement of the plunger spool 24.

In one preferred embodiment the radial seal 42 is composed of a typical socket 44 internally and externally stepped to accept internal 46, and external 48, O-ring seals, respectively. The radial seals 42 are fitted into the housing's 40 bore, with flow admitting spacers 50 as required, separating between the radial seals 42, a bonnet 52 is securing the assembly.

Yet with reference to Fig. 1, the first port 30 and second port 32, in conjunction with the first reduced diameter portion 26 of the plunger spool 24, acts as a simple flow control valve generally referenced 54. The third port 34, fourth port 36 and fifth port 38, in conjunction with the plunger spool 24 second reduced diameter portion 28, acts as a diverting valve generally referenced 56, allowing controlled flow between fourth port 36 to fifth port 38 or to third port 34. In another preferred embodiment, related to utilization of the same dual function pilot valve in different applications, as will be hereinbelow explained, an additional sixth port 58 (shown by a broken line), and an extra radial seal 42 are provided between the second port 32 and third port 34.

With reference to Figs. 2 to 5, the dual function pilot valve 10 is shown connected to a symbolically represented main hydraulic control valve generally referenced 60. The main valve 60 includes an inlet port 62, outlet port 64, diaphragm 66 and control chamber 68. In the described preferred embodiment, wherein the dual function pilot valve 10 is fitted to a main control valve 60 in a pressure reducing application, the first port 30 is in flow communication with the upstream pressure 62, the second port 32 and fourth port 36 are in flow communication with the main valve's control chamber 68, the third port 34 and the pilot valve's control chamber port 22 are in flow communication with the downstream pressure 64, the fifth port 38 is vented and the sixth port 58, if applied, is plugged.

In operation, a specific geometric relation between the simultaneously actuated flow control valve 54 and the diverting valve 56 related to predefined gap between the plunger spool's 24, first 26 and second 28 reduced diameter portions, permits utilization of the dual function pilot valve 10 in four operative modes associated to four different service line conditions, during first operative mode, there is flow communication between the first port 30 and second port 32 (Fig. 2), during second operative mode there is flow communication between the first port 30 and second port 32 as well as between the third port 34 and fourth port 36 (Fig. 3), during third operative mode there is flow communication between the fourth port 36 and third port 34, or fifth port 38 alternately (Figs. 4, 5), and during the fourth operative mode there is flow communication between the fourth port 36 and fifth port 38 (Fig. 5).

With respect to the above-described four operative modes, it can be seen that while serving in the first operative mode (Fig. 2), defined by high downstream pressure and no demand, the dual function pilot valve 10, delivers full upstream pressure to the control chamber 68 of the main valve 60, effectively cutting the flow. During service in the second operative mode (Fig. 3), defined by normal downstream pressure and low to medium demand, the dual function pilot valve 10 acts as a modern two way opposing disk pilot valve using the first port 30 as inlet, third port 34 as outlet, while the second and fourth ports, 32, 36, are in flow communication through the control chamber 68. While serving in this second operative mode, the pilot valve 10 is able to deliver the control chamber 68 of the main valve, with pressure in the entire range between the upstream pressure and the downstream pressure, constantly keeping flow through the pilot valve 10. During service in the third operative mode (Figs. 4, 5), defined by normal downstream pressure and medium to high demand the dual function pilot valve 10 acts as a vented three way pilot valve, using the third port 34 as inlet, the fifth port 38 as outlet and the fourth port 36 delivers pressure to the control chamber 68 in the full range between the downstream pressure and atmospheric pressure. During service in the fourth operative mode (Fig. 5), defined by high demand dropping the downstream pressure below any controllable mode, the dual function pilot valve entirely vents the main valve's 60 control chamber 68 through the venting fifth port 38, admitting maximum flow through the main valve 60. The dual function pilot valve automatically and continuously shifts between the above described four operative modes as downstream line pressure fed to the pilot valve's control chamber is changing due to flow fluctuations in the main line.

In some installations depending on the specific system requirements, it is preferred to activate the two functions of the dual function pilot valve at different downstream pressure ranges or service conditions, accordingly, with reference to Fig. 6, in a another preferred embodiment of the present invention, there is provided a single wire spring, generally referenced 70, having external coil 72 and internal coil 74, wherein the internal coil 74 is shorter that the external coil 72, coming into effective operation against the trust washer 16 while in the first and second operative modes only.

The dual function pilot valve was described herein above, by a way of an example operative in pressure reducing application, however its use is not limited to that application only. Such pilot valves may be used in other hydraulic control valve applications as well, including, flow rate control valve, an upstream relief valve, back-pressure sustaining valve, altitude control valve, or some combination of the above.

For an example, and with reference to Fig. 7, the dual function pilot valve 10 is fitted to a main control valve 60 in a back-pressure sustaining/relief valve application. The first port 30 is vented, the second port 32 and fourth port 36 are in flow communication with the main valve's control chamber 68, the third port 34, if applied, is plugged, the fifth port and the pilot valve's control chamber port 22 are in flow communication with the upstream pressure 62 and the sixth port 58 is in flow communication with the downstream pressure 64. Here, the first port 30, second port 32 and sixth port 58, in conjunction with the first reduced diameter portion 26 of the plunger spool 24, act as a diverting valve generally referenced 80, allowing controlled flow between second port 32 to sixth port 58, or to first port 30. The fourth port 36 and fifth port 38, in conjunction with the second reduced diameter portion 28 of the plunger spool 24, act as a simple flow control valve generally referenced 82.

In operation, the above-described specific geometric relation between the simultaneously actuated flow control valve 82 and the diverting valve 80 related to a predefined gap between the first and second reduced diameter portions 26, 28 of the plunger spool 24, permit utilization of the dual function pilot valve 10 in four operative modes associated with four different service line conditions. During first operative mode, there is flow communication between said fourth and fifth ports, 36, 38. During second operative mode, there is flow communication between the fourth and fifth ports, 36, 38, as well as between the second and sixth ports 32, 58. During third operative mode, there is flow communication between the second and sixth ports 34, 58, or first port 30, alternately, and during the fourth operative mode, there is flow communication between the second and first ports, 32, 30.

With respect to the above-described four operative modes, and in relation to the back-pressure sustaining/relief valve application of Fig. 7, while serving in the first operative mode (not shown), characterized by too low upstream pressure, the dual function pilot valve 10, delivers full upstream pressure to the control chamber 68 of the main valve 60, effectively cutting the flow. During service in the second operative mode (Fig. 7), characterized by normal to low upstream pressure, the dual function pilot valve 10 acts as a modern two-way opposing disk pilot valve using the fifth port 38 as inlet, sixth port 58 as outlet, while the second and fourth ports 32, 36 are in flow communication through the control chamber 68. While acting in this second operative mode, the pilot valve 10 is able to deliver the control chamber 68 of the main valve, with pressure in the entire range between the upstream pressure and the downstream pressure, constantly keeping flow through the pilot valve 10. During service in the third operative mode (not shown), characterized by normal to high upstream pressure, the dual function pilot valve 10 acts as a vented three-way pilot valve, using the sixth port 58 as inlet, the first port 30 as outlet, and the second port 32 delivers pressure to the control chamber 68 in the full range between the downstream pressure and atmospheric pressure. During operation in the fourth operative mode, characterized by too high upstream pressure beyond any controllable mode, the dual function pilot valve entirely vents the control chamber 68 of the main valve 60 through the first port 30, admitting maximum flow through the main valve 60. The dual function pilot valve automatically and continuously shifts between the above-described four operative modes as upstream line pressure fed to the pilot valve's control chamber changes, due to flow fluctuations of the supply line.

It will be evident to those skilled in the art that the invention is not limited to the details of the foregoing illustrated embodiments and that the present invention may be embodied in other specific forms without departing from the spirit or essential attributes thereof. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims rather than by the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.

Claims (15)

WHAT IS CLAIMED IS:

1. A dual function pilot valve, comprising, an adjustable spring loading a diaphragm, with the controlled pressure fed into the pilot valve's control chamber, acting upon the diaphragm against the spring force, to actuate a plunger spool having first and second reduced diameter portions, said plunger spool is axially movable in a bored at least five port housing, assembled with at least six radial seals, separating and sealing the at least five ports, wherein the first and second ports, in conjunction with the plunger spool's first reduced diameter portion, acts as a flow control valve, the third, fourth and fifth ports, in conjunction with the plunger spool's second reduced diameter portion, acts as a diverting valve, allowing controlled flow between said fourth port to said third or fifth ports.

2. A dual function pilot valve as claimed in claim 1, wherein a specific geometric relation between the simultaneously actuated said flow control valve and said diverting valve, related to predefined gap between said plunger spool's, first and second reduced diameter portions, permits utilization of the dual function pilot valve in four operative modes associated to four different service conditions, during first operative mode, there is flow communication between said first and second ports, during second operative mode there is flow communication between said first and second port, as well as between said third and fourth port, during third operative mode there is flow communication between said fourth and third or fifth ports alternately, and during the fourth operative mode there is flow communication between said fourth and fifth ports.

3. A dual function pilot valve as claimed in claim 2, wherein said pilot valve is fitted to a main control valve in a pressure reducing application, by said first port being in flow communication with the upstream pressure, said second and fourth ports being in flow communication with the main valve's control chamber, said third port and the pilot valve's control chamber being in flow communication with the downstream pressure, and said fifth port being vented.

4. A dual function pilot valve as claimed in claim 3, wherein while serving in said first operative mode, the dual function pilot valve, delivers full upstream pressure to said main valve's control chamber, during service in said second operative mode, the dual function pilot valve acts as a modern two way opposing disk pilot valve using said first port as inlet, third port as outlet, while the second and fourth ports are in flow communication through said main valve's control chamber, during service in the third operative mode, said dual function pilot valve acts as a vented three way pilot valve, using said third port as inlet, fifth port as outlet and said fourth port delivers pressure to the main valve's control chamber, during service in the fourth operative mode, said dual function pilot valve entirely vents the main valve's control chamber through said fifth port.

5. A dual function pilot valve as claimed in claim 4, wherein said downstream pressure acting upon said diaphragm against said spring force to actuate said plunger spool, automatically shifts said dual function pilot valve to the first operative mode during high downstream pressure and no demand, to the second operative mode during normal downstream pressure and low to medium demand, to the third operative mode during normal downstream pressure and medium to high demand, and to the fourth operative mode during high demand and low downstream pressure.

6. A dual function pilot valve as claimed in claim 1, wherein said radial seals are composed of a socket internally and externally stepped to accept internal and external O-ring seals respectively, said radial seals are fitted into said housing's bore with flow admitting spacers as required, separating between the radial seals, with a bonnet-securing the assembly.

7. A dual function pilot valve as claimed in claim 1, wherein a sixth port, and an extra radial seal are provided between said second port and said third port, for utilization of the dual function pilot valve in different applications.

8. A dual function pilot valve as claimed in claim 7, wherein said sixth port is plugged, while said pilot valve is fitted to a main control valve in a pressure-reducing application.

9. A dual function pilot valve as claimed in claim 7, wherein said first port, second port and sixth port, in conjunction with said first reduced diameter portion of said plunger spool, allow controlled flow between second port to sixth port, or to the first port, said fourth port and fifth port, in conjunction with the second reduced diameter portion of the plunger spool, act as a simple flow control valve.

10. A dual function pilot valve as claimed in claim 9, wherein same geometric relation between the simultaneously actuated said flow control valve and said diverting valve, related to said predefined gap between said first and second reduced diameter portions of the plunger spool, permit utilization of the dual function pilot valve in four operative modes associated with four different operation conditions; during first operative mode, there is flow communication between said fourth and fifth ports, during second operative mode there is flow communication between said fourth and fifth port, as well as between said second and sixth ports, during third operative mode there is flow communication between said second and sixth or first ports alternately, and during the fourth operative mode, there is flow communication between said second and first ports.

11. A dual function pilot valve as claimed in claim 7, wherein said pilot valve is fitted to a main control valve in a back-pressure sustaining/relief valve application, by said first port being vented, said second and fourth ports being in flow communication with the main valve's control chamber, said third port being plugged, said sixth port being in flow communication with the downstream pressure, said fifth port and the pilot valve's control chamber, being in flow communication with the upstream pressure.

12. A dual function pilot valve as claimed in claim 10, wherein while operating in said first operative mode, said dual function pilot valve, delivers full upstream pressure to the control chamber of said main valve, during operation in said second operative mode, said dual function pilot valve acts as a modern two-way opposing disk pilot valve using the fifth port as inlet, sixth port as outlet, while the second and fourth ports are in flow communication through the control chamber, during operation in said third operative mode, said dual function pilot valve acts as a vented three-way pilot valve, using the sixth port as inlet, the first port as outlet and the second port delivers pressure to the control chamber and during operation in said fourth operative mode, the dual function pilot valve entirely vents the main valve's control chamber through the first port.

13. A dual function pilot valve as claimed in claim 10, wherein said upstream pressure acting upon said diaphragm against said spring force to actuate said plunger spool, automatically shifts said dual function pilot valve between said four operative modes as upstream line pressure fed to the pilot valve's control chamber is changing, due to flow fluctuations of the supply line.

14. A dual function pilot valve as claimed in claim 1, wherein said spring is a single wire spring having external coil and internal coil, the internal coil is shorter that the external coil, coming into effective operation against said trust washer while in the first and second operative modes only.

15. A dual function pilot valve according to claim 1, substantially as hereinbefore described and with reference to the accompanying drawings. For the Applicant WOLFF, BREGMAN AND GOLLER