Fluid flow control assembly

• US 8,540,207 B2
• Filed: 12/04/2009
• Issued: 09/24/2013
• Est. Priority Date: 12/06/2008
• Status: Active Grant

• Current Assignee: Dunan Microstaq, Inc. (Zhejiang Dun'an Artificial Environment Co., Ltd.)
• Original Assignee: Dunan Microstaq, Inc. (Zhejiang Dun'an Artificial Environment Co., Ltd.)
• Inventors: Hunnicutt, Harry A., Best, Christiaan S.
• Primary Examiner(s): Fristoe, Jr., John K
• Assistant Examiner(s): Venkatesan, Umashankar
• Application Number:
  US13/132,908
• Publication Number:
  US 20120000550A1
• Time in Patent Office: 1,390 Days
• Field of Search: 251/28, 251/30.01, 251/30.02, 251/48, 251/50, 137/625.35, 137/270
• US Class Current: 251/30.02
• CPC Class Codes: F15B 13/0402 for linearly sliding valves, e.g. spool valves
• CPC Class Codes: Y10T 137/7761 Electrically actuated valve

Abstract

A device has been disclosed that may include a spool valve including a body having a first connector and a second connector and a spool movable relative to the body for controlling flow between the first connector and the second connector. The reversible flow control assembly further may include a pilot valve device developing a single pressure command in the form of a fluid at a command pressure. The spool valve may be responsive to the single pressure command developed in said pilot valve device to control flow between the first connector and the second connector without regard to the direction of flow. The majority of axial forces acting on the spool to position the spool relative to the body when fluid is flowing through the valve may be fluid forces.

Claims

1. A device, comprising:

a pilot valve responsive to a command signal for supplying a fluid at a command pressure to a pilot valve control port; and

a pilot operated spool valve having;

a body having a first connector and a second connector, each of said first connector and second connector being adapted for fluid communication with an external circuit; and

a spool disposed for sliding movement in said body, said spool having a first end portion and a second end portion opposite said first end portion, said first end portion of said spool being in fluid communication with said pilot valve control port such that said spool is urged to move in a first direction by said fluid at said command pressure, said spool being movable to control a fluid flow between said first connector and said second connector through said body proportionally to said command pressure when said fluid flow is a forward flow from said first connector to said second connector and when said fluid flow is a reverse flow from said second connector to said first connector;

said spool valve using negative feedback in the form of fluid at a feedback pressure acting on said spool in a second direction, opposite said first direction, to position said spool in conjunction with said fluid at said command pressure;

said spool valve utilizing unstable equilibrium of fluid forces to switch between controlling said forward flow and said reverse flow.

2. A device, comprising:

a pilot valve device responsive to a command signal for supplying a fluid at a command pressure to a pilot valve control port; and

a pilot operated spool valve having;

a body having a first connector and a second connector, each of said first connector and second connector being adapted for fluid communication with an external circuit; and

a spool disposed for sliding movement in said body, said spool having a first end portion and a second end portion opposite said first end portion, said first end portion of said spool being in fluid communication with said pilot valve control port such that said spool is urged to move in a first direction by said fluid at said command pressure, said spool being movable through a first range of positions to control, proportionally to said command pressure, the flow of a fluid when the fluid is flowing through said body in a forward direction from said first connector to said second connector, said spool being movable through a second range of positions, offset from said first range of positions, to control, proportionally to said command pressure, the flow of the fluid when the fluid is flowing through said body in a reverse direction from said second connector to said first connector, a portion of said fluid flowing through said body having a feedback pressure and acting on said spool in a second direction, opposite said first direction, to position said spool in conjunction with said fluid at said command pressure, the magnitude of said feedback pressure being generated at least in part as a function of the position of said spool.

3. The device of claim 2, said body further defining:

a command chamber in fluid communication with said pilot valve control port to receive said fluid at said command pressure;

a feedback chamber receiving said fluid having said feedback pressure; and

a bore communicating at a first end portion with said command chamber and at a second end portion with said feedback chamber, said spool being disposed for sliding movement in said bore.

4. The device of claim 3, said spool further defining:

an exterior surface;

a central portion between said first end portion and said second end portion;

a first axial end face on said first end portion which is in fluid communication with said command chamber;

a second axial end face on said second end portion which is in fluid communication with said feedback chamber and having an opening defined therein;

an axial passageway communicating with said opening in said second axial end face, said axial passageway extending into said central portion of said spool;

a first port at a first axial location in said central portion of said spool providing communication between said exterior surface and said axial passageway; and

a second port in said central portion of said spool at a second axial location between said first axial location and said second end portion of said spool providing communication between said exterior surface and said axial passageway.

5. The device of claim 4, said body further defining:

a first cavity communicating with said bore in said body at a first axial location along said bore;

a second cavity communicating with said bore in said body at a second axial location along said bore which is closer to said feedback chamber than said first axial location;

a third cavity communicating with said bore in said body at a third axial location along said bore, said third location being between said first axial location and said second axial location;

said first connector being in fluid communication with said first cavity and with said second cavity; and

said second connector being in fluid communication with said third cavity, such that when said spool is in said first range of positions, a flow path for forward flow of fluid through said spool valve is established from said first connector, to said second cavity, through said spool via, sequentially, said second port, said axial passageway, said first port, to said third cavity, and thence to said second connector, and such that when said spool is in said second range of positions, a flow path for reverse flow of fluid through said spool valve is established from said second connector, to said third cavity, through said spool via, sequentially, said second port, said axial passageway, and said first port, to said first cavity, and thence to said first connector.

6. The device of claim 5 wherein said spool is movable to a shutoff position between said first range of positions and said second range of positions, where substantially no fluid communication exists between said axial passageway in said spool and either said first cavity or said second cavity.

7. The device of claim 6, said spool valve further comprising:

a first spring urging said spool to move from said second range of positions toward said shutoff position; and

a second spring urging said spool to move from said first range of positions toward said shutoff position.

8. The device of claim 4, said spool further defining:

a circumferential groove formed in said exterior surface of said spool at a third axial location between said first axial location and said first end portion of said spool; and

an aperture providing fluid communication between said circumferential groove in said exterior surface of said spool and said axial passageway formed in said spool.

9. The device of claim 4, wherein said first port is one of a plurality of ports spaced apart circumferentially about said spool at said first axial location, and said second port is one of a plurality of ports spaced apart circumferentially about said spool at said second axial location.

10. The device of claim 4, wherein:

said spool further defines;

a third port in said central portion of said spool at a third axial location spaced a first axial distance from said first axial location toward said first end portion of said spool, said third port providing communication between said exterior surface and said axial passageway; and

a fourth port in said central portion of said spool at a fourth axial location spaced said first axial distance from said second axial location toward said first axial location and, said fourth port providing communication between said exterior surface and said axial passageway; and

said body further defines;

a first cavity communicating with said bore in said body at a first axial location along said bore;

a second cavity communicating with said bore in said body at a second axial location along said bore which is closer to said feedback chamber than said first axial location;

a third cavity communicating with said bore in said body at a third axial location along said bore, said third location being between said first axial location and said second axial location;

said first connector being in fluid communication with said first cavity and with said second cavity; and

said second connector being in fluid communication with said third cavity, such that, when said spool is in said first range of positions, a flow path for forward flow of fluid through said spool valve is established from said first connector, to said second cavity, through said spool via, sequentially said second port, said axial passageway, and said first port, to said third cavity, and thence to said second connector, and such that when said spool is in said second range of positions, a flow path for reverse flow of fluid through said spool valve is established from said second connector, to said third cavity, through said spool via, sequentially said fourth port, said axial passageway, and said third port, to said first cavity, and thence to said second connector.

11. The device of claim 10, wherein said first and said second ports each have a first cross-sectional flow area, and wherein said third and said fourth ports each have a second cross-sectional flow area different than said first cross-sectional flow area.

12. The device of claim 10, wherein said spool is movable to a shutoff position, between said first range of positions and said second range of positions, where substantially no fluid communication exists between said axial passageway in said spool and either said first cavity or said second cavity.

13. The device of claim 12, said spool valve further comprising:

a first spring urging said spool to move from said second range of positions toward said shutoff position; and

a second spring urging said spool to move from said first range of positions toward said shutoff position.

14. The device of claim 13, said spool further defining:

a circumferential groove formed in said exterior surface of said spool at a third axial location which is a second axial distance toward said first end portion of said spool from said first axial location, said second distance being greater than said first axial distance; and

an aperture providing fluid communication between said circumferential groove in said exterior surface of said spool and said axial passageway formed in said spool.

15. The device of claim 14, wherein said first port is one of a plurality of ports spaced apart circumferentially about said spool at said first axial location, said second port is one of a plurality of ports spaced apart circumferentially about said spool at said second axial location, said third port is one of a plurality of ports spaced apart circumferentially about said spool at said third axial location, and said fourth port is one of a plurality of ports spaced apart circumferentially about said spool at said fourth axial location.

16. The device of claim 10, wherein, when said spool is in said first range of positions, and fluid communication is established between said first connector and said second connector, through said second cavity, through said spool via said second port, said axial passageway, and said first port, and through said third cavity, the presence of fluid in said second connector at a pressure higher than that existing in said first connector results in an instability in flow such that any decrease in command pressure would cause said spool to move in said second direction toward said command chamber, resulting in decreased communication between said second cavity and said second port, resulting in an increase in pressure in said axial passageway and thus pressure in said feedback chamber, further urging said spool to move in said second direction toward said command chamber, resulting in said spool moving disproportionately to said change in command pressure, said spool moving out of said first range of positions toward said second range of positions.

17. The device of claim 5, wherein, when said spool is in said first range of positions, and fluid communication is established between said first connector and said second connector, through said second cavity, through said spool via said second port, said axial passageway, and said first port, and through said third cavity, the presence of fluid in said second connector at a pressure higher than that existing in said first connector results in an instability in flow such that any decrease in command pressure would cause said spool to move in said second direction toward said command chamber, resulting in decreased communication between said second cavity and said second port, resulting in an increase in pressure in said axial passageway and thus pressure in said feedback pressure, further urging said spool toward said command chamber, resulting in said spool moving in said second direction disproportionately to said change in command pressure, said spool moving out of said first range of positions toward said second range of positions.

18. The device of claim 2, further including a first stop structure limiting movement of said spool in said first direction at a position providing substantially the least resistance to flow through said body of any of said first range of positions, and a second stop structure limiting movement of said spool in said second direction at a position providing substantially the least resistance to flow through said body of any of said second range of positions.

19. The device of claim 2, wherein said pilot valve device is a microvalve.

20. The device of claim 2, wherein said pilot valve device comprises a fluid conduit extending between a first pilot connection port and a second pilot connection port, the flow through which fluid conduit is regulated by two variable orifices in series, one of which is normally open and one of which is normally closed, said pilot valve control port being connected in fluid communication with said fluid conduit between said variable orifices.

21. The device of claim 20 wherein said normally closed orifice is connected in fluid communication with said first connector via said first pilot connection port and said normally open orifice is in fluid communication with said second connector via said second pilot connection port.

22. The device of claim 2, wherein said spool valve is responsive to a single pressure command developed in said pilot valve device.

23. The device of claim 15, wherein said first, second, third, and fourth ports each has the same cross-sectional flow area, and wherein there are more of one of said first, second, third, and fourth ports at the associated one of said first, second, third, and fourth axial locations than at another of said first, second, third, and fourth axial locations, whereby the device forms an asymmetric valve.

24. The device of claim 15, wherein at least one said first, second, third, and fourth ports has a different cross-sectional flow area from another of said first, second, third, and fourth ports at a different one of said first, second, third, and fourth axial locations, whereby the device forms an asymmetric valve.

25. The device of claim 4,

said spool further defining:

a third port in said central portion of said spool at a third axial location spaced a first axial distance from said first axial location toward said first end portion of said spool, said third port providing communication between said exterior surface and said axial passageway; and

a fourth port in said central portion of said spool at a fourth axial location spaced said first axial distance from said second axial location toward said first axial location and, said fourth port providing communication between said exterior surface and said axial passageway;

said body further defining;

a first cavity communicating with said bore in said body at a first axial location along said bore, said first connector being in fluid communication with said first cavity; and

a second cavity communicating with said bore in said body at a second axial location along said bore which is closer to said feedback chamber than said first axial location said second connector being in fluid communication with said second cavity,

such that when said spool is in said first range of positions, a flow path for forward flow of fluid through said spool valve is established from said first connector, to said first cavity, through said spool via, sequentially said first port, said axial passageway, and said third port, to said second cavity, and thence to said second connector, and such that when said spool is in said second range of positions, a flow path for reverse flow of fluid through said spool valve is established from said second connector, to said second cavity, through said spool via, sequentially said fourth port, said axial passageway, and said second port, to said first cavity, and thence to said first connector.

26. The device of claim 25, wherein said valve has a greater maximum cross-sectional flow area when controlling one of forward flow and reverse flow, than when controlling the other one of forward flow and reverse flow.

27. The device of claim 25, wherein said first, second, third, and fourth ports each has the same cross-sectional flow area, and wherein there more of one of said first, second, third, and fourth ports at the associated one of said first, second, third, and fourth axial locations than at another of said first, second, third, and fourth axial locations, whereby the device forms an asymmetric valve.

28. The device of claim 25, wherein at least one said first, second, third, and fourth ports has a different cross-sectional flow area from another of said first, second, third, and fourth ports at a different one of said first, second, third, and fourth axial locations, whereby the device forms an asymmetric valve.