US4549578A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Coded fluid control system
Assignee: ExxonMobil Upstream Research Co
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Filing: 1984-03-21
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Granted: 1985-10-29
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Expires: 2004-03-21
Abstract
Abstract A fluid control system 10 and selector valve 24 for use therein, for controlling a plurality of fluid actuated elements 12, such as valve operators. The fluid actuated elements are controlled from an operating station 52, which is located remotely from the fluid actuated elements 12. Instructions regarding which of the fluid actuated elements 12 it is desired to operate are transmitted by coded signal from the operating station 52 to the selector valve 24, which is positioned proximate the fluid actuated elements 12. The coded signal is transmitted in binary form through a plurality of code input lines 30, each code input line carrying one binary digit of the code. Each of the fluid actuated elements 12 is represented by a corresponding binary code. In response to receiving the binary code corresponding to a given one of the fluid actuated elements 12, the selector valve 24 establishes a fluid circuit serving to introduce fluid pressure to or release pressure from that one of the fluid actuated elements 12, causing it to alter its condition. The present invention is especially well suited for use in the hydraulic control of a satellite well subsea production system.
Inventors
- 👤 David A. Hibbs
- 👤 Wynn P. Rickey
- 👤 Paul N. Stanton
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-30 17:50
CPC Classifications
F; F15; F15B; F15B13/00; F15B13/02; F15B13/06; F15B13/07; E; E21; E21B; E21B33/00; E21B33/02; E21B33/03; E21B33/035; E21B33/0355; Y; Y10; Y10T; Y10T137/00; Y10T137/8158; Y10T137/8175; Y10T137/8192; Y10T137/8593; Y10T137/86389
Claims Analysis
Total Claims: 35
Claim 1
Independent Claim
253 words
A valve for routing fluid from at least one fluid supply conduit to a selected one of a plurality of fluid receiving conduits, said valve comprising: an input pressure port adapted to be placed in fluid communication with said fluid supply conduit; a plurality of outlet pressure ports, each being adapted to be placed in fluid communication with a corresponding one of said fluid receiving conduits; a fluid passageway element moveable through a number of positions relative to said outlet pressure ports, in at least some of said positions said fluid passageway element establishing fluid communication from said input pressure port to at least one of said outlet pressure ports; an actuator having a plurality of code input ports and an output member moveable to a number of distinct positions, each of said code input ports being adapted to receive a pressure signal, there being two possible pressure signals associated with each code input port, a relatively high pressure signal and a relatively low pressure signal, the signal existing at a given time at each code input port defining one bit of a multi-bit select code, the actuator being adapted to adjust the output member to a position corresponding to the applied select code; and, means for interfacing the actuator output member and the fluid passageway element such that the application of a select code to the code input ports causes the routing valve to establish fluid communication from the inlet pressure port to an outlet port corresponding to said applied select code.
Claim 2
Dependent Claim
253 words
A valve for routing fluid from at least one fluid supply conduit to a selected one of a plurality of fluid receiving conduits, said valve comprising: an input pressure port adapted to be placed in fluid communication with said fluid supply conduit; a plurality of outlet pressure ports, each being adapted to be placed in fluid communication with a corresponding one of said fluid receiving conduits; a fluid passageway element moveable through a number of positions relative to said outlet pressure ports, in at least some of said positions said fluid passageway element establishing fluid communication from said input pressure port to at least one of said outlet pressure ports; an actuator having a plurality of code input ports and an output member moveable to a number of distinct positions, each of said code input ports being adapted to receive a pressure signal, there being two possible pressure signals associated with each code input port, a relatively high pressure signal and a relatively low pressure signal, the signal existing at a given time at each code input port defining one bit of a multi-bit select code, the actuator being adapted to adjust the output member to a position corresponding to the applied select code; and, means for interfacing the actuator output member and the fluid passageway element such that the application of a select code to the code input ports causes the routing valve to establish fluid communication from the inlet pressure port to an outlet port corresponding to said applied select code.
Claim 3
Dependent Claim
83 words
The valve as set forth in claim 1, wherein: said input pressure port, said outlet pressure ports and said fluid passageway element are components of a rotary valve, said fluid passageway element defining a rotor of said rotory valve; said actuator is a linear actuator, said output member extending from a fully retracted position a set amount for each select code; and, said interfacing means includes means for causing rotation of said rotor in response to linear movement of said actuator output member.
Claim 4
Dependent Claim
131 words
The valve as set forth in claim 1 wherein: said actuator has: a housing defining a cylinder, said code input ports establishing fluid communication with said cylinder and being axially spaced one from the other along said housing; a plurality of axially moveable pistons within said cylinder, each of said pistons being moveably connected to each adjacent piston, each of said pistons being associated with a corresponding one of said code input ports, said pistons each being adapted for axial extension of a predetermined amount in said cylinder in response to the application of a high pressure signal at the corresponding code input port; and, means for causing each piston to assume an unextended position in response to the absence of a high pressure signal at the corresponding code input port.
Claim 5
Independent Claim
335 words
A system for controlling a plurality of subsea hydraulic valves from a surface control station, comprising: a control conduit associated with each of said subsea valves, said subsea valves each being adapted to operate in response to the application of hydraulic pressure to the corresponding control conduit; a hydraulic pressure supply; a selector valve situated proximate the seafloor, said selector valve being adapted to establish fluid communication between said pressure supply and a selected one of said control conduits, said selector valve having: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a pressure signal controllably variable between two pressure levels, the pressure level at each code input port representing one bit of a multi-bit binary select code, each select code corresponding to a position of said output member, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing select code; a multiple position valve having an inlet pressure port adapted for receiving pressurized fluid from said hydraulic pressure supply, a plurality of outlet pressure ports each in fluid communication with a corresponding control conduit, and a fluid passageway element adapted to be moved to a number of positions, each such position establishing fluid communication between said inlet pressure port and at least one of said outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member so that movement of said output member causes movement of said fluid passageway element, each position of said output member causing said passageway element to assume a corresponding position establishing fluid communication between said inlet pressure port and a corresponding outlet pressure port; a plurality of code input conduits, each being in fluid communication with a corresponding one of the code input ports; and, means for applying to the code input conduits a select code corresponding to that one of the subsea hydraulic valves which it is desired to address.
Claim 6
Independent Claim
335 words
A system for controlling a plurality of subsea hydraulic valves from a surface control station, comprising: a control conduit associated with each of said subsea valves, said subsea valves each being adapted to operate in response to the application of hydraulic pressure to the corresponding control conduit; a hydraulic pressure supply; a selector valve situated proximate the seafloor, said selector valve being adapted to establish fluid communication between said pressure supply and a selected one of said control conduits, said selector valve having: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a pressure signal controllably variable between two pressure levels, the pressure level at each code input port representing one bit of a multi-bit binary select code, each select code corresponding to a position of said output member, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing select code; a multiple position valve having an inlet pressure port adapted for receiving pressurized fluid from said hydraulic pressure supply, a plurality of outlet pressure ports each in fluid communication with a corresponding control conduit, and a fluid passageway element adapted to be moved to a number of positions, each such position establishing fluid communication between said inlet pressure port and at least one of said outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member so that movement of said output member causes movement of said fluid passageway element, each position of said output member causing said passageway element to assume a corresponding position establishing fluid communication between said inlet pressure port and a corresponding outlet pressure port; a plurality of code input conduits, each being in fluid communication with a corresponding one of the code input ports; and, means for applying to the code input conduits a select code corresponding to that one of the subsea hydraulic valves which it is desired to address.
Claim 7
Dependent Claim
19 words
The control system of claim 4, wherein said select code applying means is situated at said surface control station.
Claim 8
Dependent Claim
40 words
The control system of claim 4, wherein the control system is adapted to control a plurality of groups of subsea hydraulic valves, there being a plurality of selector valves, one selector for each of said groups of subsea hydraulic valves.
Claim 9
Dependent Claim
96 words
The control system of claim 6, wherein the selector valves each have at least a first and a second code input port, said first code input port of each selector valve being in parallel fluid communication with a single first code input conduit, and said second code input port of each selector valve being in fluid communication with a single second code input conduit, whereby the first code input port of each selector valve is supplied with a common signal and the second code input port of each selector valve is supplied with a common signal.
Claim 10
Dependent Claim
36 words
The control system of claim 6, wherein the flowpaths intermediate the select code applying means and the code input ports of the selector valves are arranged such that each selector valve receives a common select code.
Claim 11
Dependent Claim
23 words
The control system of claim 4, further including means for selectively connecting and disconnecting said input pressure port to said hydraulic pressure supply.
Claim 12
Dependent Claim
31 words
The control system of claim 6, further including means for selectively applying pressure from said hydraulic pressure supply to the input pressure port of a selected one of said selector valves.
Claim 13
Dependent Claim
163 words
The control system of claim 6, further including an additional selector valve for controlling the application of hydraulic pressure from said hydraulic pressure supply to said plurality of selector valves, said additional selector valve being adapted to receive a select code from a second means for applying a desired select code; each of the input pressure ports of said plurality of selector valves being in fluid communication with a corresponding one of the outlet pressure ports of said additional selector valve, the input pressure port of said additional selector valve being adapted to be placed in fluid communication with said pressurized hydraulic fluid supply; each select code applied to said additional selector valve by said second select code applying means causing said additional selector valve to establish a fluid communication path intermediate said additional selector valve input pressure port and that one of the additional selector valve outlet pressure ports corresponding to the select code applied by said second select code applying means.
Claim 14
Dependent Claim
204 words
A hydraulic selector valve for use in controlling a plurality of hydraulically actuated elements, comprising: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a pressure signal, there being two possible pressure signals associated with each code input port, one of said pressure signals being of a higher pressure level than the other, the signal existing at the code input ports at a given time defining the bits of a multi-bit binary select code, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing multi-bit select code, each select code representing a certain position of said output member; and, a multiple position valve having: a valve body defining at least one input pressure port and a plurality of outlet pressure ports; a fluid passageway element adapted to be moved to a number of positions, each such position establishing fluid communication between said input pressure port and at least one of said outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member such that movement of said output member causes movement of said fluid passageway element.
Claim 15
Dependent Claim
204 words
A hydraulic selector valve for use in controlling a plurality of hydraulically actuated elements, comprising: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a pressure signal, there being two possible pressure signals associated with each code input port, one of said pressure signals being of a higher pressure level than the other, the signal existing at the code input ports at a given time defining the bits of a multi-bit binary select code, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing multi-bit select code, each select code representing a certain position of said output member; and, a multiple position valve having: a valve body defining at least one input pressure port and a plurality of outlet pressure ports; a fluid passageway element adapted to be moved to a number of positions, each such position establishing fluid communication between said input pressure port and at least one of said outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member such that movement of said output member causes movement of said fluid passageway element.
Claim 16
Dependent Claim
68 words
The hydraulic selector valve of claim 12, wherein: said binary actuator is a linear binary actuator having an output member being extendable and retractable through a range of positions, each position corresponding to at least one select code; said multiple position valve is a rotary valve; said fluid passageway element is a rotor of said multiple position valve; and, said coupling means is a rack and gear assembly.
Claim 17
Dependent Claim
74 words
The hydraulic selector valve of claim 13 wherein said multiple position valve has first and second input ports and first and second sets of outlet pressure ports, said fluid passageway element being adapted to establish fluid communication between said first input pressure port and a selected one of said first set of outlet pressure ports, and between said second input pressure port and a selected one of said second set of outlet pressure ports.
Claim 18
Independent Claim
384 words
A system for controlling a plurality of groups of fluid-actuated valves from a central control station, comprising: a control conduit associated with each of said valves, each of said valves being adapted to operate in response to the application of fluid pressure to the corresponding control conduit; a fluid pressure supply; a plurality of first selector valves and a second selector valve, each selector valve having: an input pressure port; a plurality of outlet pressure ports; a plurality of code input ports, each adapted to receive a pressure signal which can be altered between a first pressure level and a second pressure level higher than said first pressure level, the pressure level at each code input port representing one bit of a binary select code, each output pressure port being represented by a corresponding binary select code; and, means for adjusting the selector valve upon receipt of a binary select code to establish fluid communication between the input pressure port and that one of the output pressure ports corresponding to the then-existing binary select code; each one of said first selector valves being associated with one fluid-actuated valve group, each valve control conduit of said valve group being in fluid communication with a corresponding outlet pressure port of said first selector valve; a plurality of first selector valve code input conduits, each being in fluid communications with a corresponding one of said first selector valve code input ports; means for applying to said first selector valve code input conduits a select code corresponding to that one of the valves within each group which is to be operated; said input pressure port of each first selector valve being in fluid communication with a corresponding one of the outlet pressure ports of said second selector valve, said second selector valve inlet pressure port being adapted to receive pressurized fluid from said fluid pressure supply; a plurality of second selector valve code input conduits, each being in fluid communication with a corresponding one of said second selector valve code input ports; and, means for applying to said second selector valve code input conduits a select code corresponding to that one of the second selector valve outlet pressure ports which is in fluid communication with that one of the first selector valves which it is desired to operate.
Claim 19
Independent Claim
384 words
A system for controlling a plurality of groups of fluid-actuated valves from a central control station, comprising: a control conduit associated with each of said valves, each of said valves being adapted to operate in response to the application of fluid pressure to the corresponding control conduit; a fluid pressure supply; a plurality of first selector valves and a second selector valve, each selector valve having: an input pressure port; a plurality of outlet pressure ports; a plurality of code input ports, each adapted to receive a pressure signal which can be altered between a first pressure level and a second pressure level higher than said first pressure level, the pressure level at each code input port representing one bit of a binary select code, each output pressure port being represented by a corresponding binary select code; and, means for adjusting the selector valve upon receipt of a binary select code to establish fluid communication between the input pressure port and that one of the output pressure ports corresponding to the then-existing binary select code; each one of said first selector valves being associated with one fluid-actuated valve group, each valve control conduit of said valve group being in fluid communication with a corresponding outlet pressure port of said first selector valve; a plurality of first selector valve code input conduits, each being in fluid communications with a corresponding one of said first selector valve code input ports; means for applying to said first selector valve code input conduits a select code corresponding to that one of the valves within each group which is to be operated; said input pressure port of each first selector valve being in fluid communication with a corresponding one of the outlet pressure ports of said second selector valve, said second selector valve inlet pressure port being adapted to receive pressurized fluid from said fluid pressure supply; a plurality of second selector valve code input conduits, each being in fluid communication with a corresponding one of said second selector valve code input ports; and, means for applying to said second selector valve code input conduits a select code corresponding to that one of the second selector valve outlet pressure ports which is in fluid communication with that one of the first selector valves which it is desired to operate.
Claim 20
Dependent Claim
35 words
The valve control system as set forth in claim 15, wherein the code input ports of said first selector valves are connected in parallel to a common set of first selector valve code input conduits.
Claim 21
Dependent Claim
32 words
The valve control system as set forth in claim 16, wherein said fluid-actuated valves are subsea hydraulic well control valves, each group of hydraulic well control valves corresponding to a single well.
Claim 22
Dependent Claim
38 words
The valve control system as set forth in claim 17, wherein the control station is located above the surface of the water, said first and second selector valve select code applying means being located at the control station.
Claim 23
Dependent Claim
162 words
The valve control system as set forth in claim 15, wherein the first and second selector valves include: a binary actuator containing said code input ports and a moveable output member, each select code corresponding to a position of said output member, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing select code; a multiple position valve containing said input and outlet pressure ports and a fluid passageway element adapted to be moved through a number of positions, each such position establishing fluid communication between said inlet pressure port and at least one of said outlet pressure ports; and means for coupling said fluid passageway element to said actuator output member so that movement of said output member causes movement of said fluid passageway element, each position of said output member causing said passageway element to assume a corresponding position establishing fluid communication between said inlet pressure port and a corresponding outlet pressure port.
Claim 24
Dependent Claim
50 words
The system as set forth in claim 15, wherein said fluid-actuated valves are double acting valves and wherein there are two control conduits associated with each of said valves, each of said control conduits being in fluid communication with a unique one of said first selector valve outlet pressure ports.
Claim 25
Dependent Claim
288 words
A control valve adapted for applying fluid pressure from a fluid pressure source to a selected one of a group of fluid conduits, said control valve comprising: a valve body defining an input pressure port and a plurality of outlet pressure ports, said outlet pressure ports each being adapted to be placed in fluid communication with a corresponding one of said fluid conduits, said input pressure port being adapted to receive pressurized fluid from a source external to said control valve; a fluid passageway element within said valve body, said fluid passageway element being moveable within said valve body through a series of positions, each outlet pressure port corresponding to one position of said fluid passageway element, said fluid passageway element being configured to establish fluid communication between said inlet pressure port and a selected one of said outlet pressure ports in response to said fluid passageway element being placed in the position corresponding to said selected outlet pressure port; an actuator having a plurality of code input ports and an output member moveable through a number of positions, each of said code input ports being adapted to receive a pressure signal, each combination of pressure signals applied to said code input ports at a given time defining a select code, each select code corresponding to a position of said output member, said actuator being adapted to adjust said moveable output member to the position corresponding to the then-existing select code; and means for coupling said fluid passageway element to said actuator output member so that the application of a select code to said code input ports causes said fluid passageway element to be driven by said actuator output member to a position corresponding to such select code.
Claim 26
Dependent Claim
288 words
A control valve adapted for applying fluid pressure from a fluid pressure source to a selected one of a group of fluid conduits, said control valve comprising: a valve body defining an input pressure port and a plurality of outlet pressure ports, said outlet pressure ports each being adapted to be placed in fluid communication with a corresponding one of said fluid conduits, said input pressure port being adapted to receive pressurized fluid from a source external to said control valve; a fluid passageway element within said valve body, said fluid passageway element being moveable within said valve body through a series of positions, each outlet pressure port corresponding to one position of said fluid passageway element, said fluid passageway element being configured to establish fluid communication between said inlet pressure port and a selected one of said outlet pressure ports in response to said fluid passageway element being placed in the position corresponding to said selected outlet pressure port; an actuator having a plurality of code input ports and an output member moveable through a number of positions, each of said code input ports being adapted to receive a pressure signal, each combination of pressure signals applied to said code input ports at a given time defining a select code, each select code corresponding to a position of said output member, said actuator being adapted to adjust said moveable output member to the position corresponding to the then-existing select code; and means for coupling said fluid passageway element to said actuator output member so that the application of a select code to said code input ports causes said fluid passageway element to be driven by said actuator output member to a position corresponding to such select code.
Claim 27
Dependent Claim
66 words
The control valve as set forth in claim 21, wherein the valve body defines at least two inlet pressure ports, each of said inlet pressure ports having a corresponding set of outlet pressure ports, and wherein for each position of the fluid passageway element fluid communication is established between each inlet pressure port and a corresponding outlet pressure port in the corresponding outlet pressure port set.
Claim 28
Dependent Claim
34 words
The control valve as set forth in claim 21, wherein said valve body and fluid passageway element are elements of a rotary valve, said fluid passageway element being the rotor of said rotary valve.
Claim 29
Dependent Claim
17 words
The control valve as set forth in claim 21, wherein said actuator is a linear binary actuator.
Claim 30
Independent Claim
466 words
A system for operating a plurality of control valves in a subsea well control system, each of said valves having first and second control ports, said system comprising: a surface control station; a selector valve situated proximate the seafloor, said selector valve having: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a hydraulic signal controllably variable between two pressure levels, the pressure level at each code input port representing one bit of a multi-bit binary select code, each select code corresponding to a position of said output member, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing select code; a multiple position valve having first and second inlet pressure ports, first and second sets of outlet pressure ports, and a fluid passageway element adapted to be moved through a number of positions, each such position establishing hydraulic communication between said first inlet pressure port and one of said first outlet pressure ports and between said second inlet pressure port and one of said second outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member so that movement of said output member causes movement of said fluid passageway element, each position of said output member causing said passageway element to assume a corresponding position establishing hydraulic communication between said first inlet pressure port and one of said first outlet pressure ports and between said second inlet pressure port and one of said second outlet pressure ports; a first and a second control conduit associated with each of said control valves, said first control conduit establishing hydraulic communication between said first control port and a corresponding one of said first outlet pressure ports and said second control conduit establishing hydraulic communication between said second control port and a corresponding one of said second outlet pressure ports, the first and second outlet pressure port pair associated with each control conduit pair corresponding to a single position of said fluid passageway element, whereby each position of said fluid passageway element establishes fluid communication between said first selector valve inlet pressure port and the first control port of the control valve corresponding to that position and between said second selector valve inlet pressure port and the second control port of said control valve corresponding to that position; a plurality of code input conduits, each being in fluid communication with a corresponding one of said code input ports; means for applying to said code input conduits a select code corresponding to that one of the control valves which it is desired to address; and, means for applying hydraulic pressure to a selected one of said first and second inlet pressure ports.
Claim 31
Independent Claim
466 words
A system for operating a plurality of control valves in a subsea well control system, each of said valves having first and second control ports, said system comprising: a surface control station; a selector valve situated proximate the seafloor, said selector valve having: a binary actuator having a plurality of code input ports and a moveable output member, each of said code input ports being adapted to receive a hydraulic signal controllably variable between two pressure levels, the pressure level at each code input port representing one bit of a multi-bit binary select code, each select code corresponding to a position of said output member, said binary actuator being adapted to adjust said output member to a position corresponding to the then-existing select code; a multiple position valve having first and second inlet pressure ports, first and second sets of outlet pressure ports, and a fluid passageway element adapted to be moved through a number of positions, each such position establishing hydraulic communication between said first inlet pressure port and one of said first outlet pressure ports and between said second inlet pressure port and one of said second outlet pressure ports; and, means for coupling said fluid passageway element to said actuator output member so that movement of said output member causes movement of said fluid passageway element, each position of said output member causing said passageway element to assume a corresponding position establishing hydraulic communication between said first inlet pressure port and one of said first outlet pressure ports and between said second inlet pressure port and one of said second outlet pressure ports; a first and a second control conduit associated with each of said control valves, said first control conduit establishing hydraulic communication between said first control port and a corresponding one of said first outlet pressure ports and said second control conduit establishing hydraulic communication between said second control port and a corresponding one of said second outlet pressure ports, the first and second outlet pressure port pair associated with each control conduit pair corresponding to a single position of said fluid passageway element, whereby each position of said fluid passageway element establishes fluid communication between said first selector valve inlet pressure port and the first control port of the control valve corresponding to that position and between said second selector valve inlet pressure port and the second control port of said control valve corresponding to that position; a plurality of code input conduits, each being in fluid communication with a corresponding one of said code input ports; means for applying to said code input conduits a select code corresponding to that one of the control valves which it is desired to address; and, means for applying hydraulic pressure to a selected one of said first and second inlet pressure ports.
Claim 32
Dependent Claim
33 words
The control system of claim 25, wherein said control valves are latching piloted control valves, each of said piloted control valves controlling the operation of a hydraulically actuated component of a subsea well.
Claim 33
Dependent Claim
42 words
The control system of claim 25, wherein the system is adapted to control a plurality of groups of subsea hydraulic control valves, there being a plurality of selector valves, one selector valve for each of said groups of subsea hydraulic control valves.
Claim 34
Dependent Claim
86 words
The control system of claim 27, wherein said means for applying hydraulic pressure to a selected one of said first and second inlet pressure ports of said plurality of selected valves includes a master selector valve, said master selector valve being adapted to receive a select code from a second means for applying a select code; each of the two inlet pressure ports of said first selector valves being in hydraulic communication with a corresponding pair of the outlet pressure ports of said master selector valve.
Claim 35
Dependent Claim
86 words
The control system of claim 28, wherein the two master selector valve outlet pressure ports corresponding to each first selector valve correspond to a single position of the master selector valve fluid passageway element, whereby once a selected control valve is addressed by application of the appropriate select codes to said master selector valve and said plurality of selector valves, hydraulic pressure may be applied to the first and second control ports of said selected control valve in any sequence with the select codes remaining unchanged.
References Cited (Backward Citations)
US3253678A
Cited
US3702909A
Cited
US3882759A
Cited
US3993100A
Cited
US4185541A
Cited
US4280531A
Cited
US4407183A
Cited
US4356841A
Cited
US4378848A
Cited
US4250929A
Cited
US4397334A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1988-10-28 | 1989-04-29 | 1989-10-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1992-10-28 | 1993-04-29 | 1993-10-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1996-10-28 | 1997-04-29 | 1997-10-29 | $7700.00 | Window Closed / Lapsed |