TECHNICAL FIELD

The embodiments described below relate to, valves in fluid systems, and more particularly, to safety valves.

BACKGROUND

Fluid systems sometimes provide pressurized fluid to an actuator. The actuator may move or convert the pressure in the pressurized fluid into a mechanical force. The pressurized fluid supplied to the actuator may be controlled by a valve. The actuators may be used to apply a force to various parts or components. For example, the actuator may press fit metal items together, keep cable railways in safe positions, compress scrap metal, mold heated components into a shape, etc. These functions may require considerable amount of force.

Operators may be in close proximity with the actuators. For example, an operator may operate an industrial press to press fit a collar onto a shaft. To press fit the collar onto a shaft, the operator may have to reach into the equipment. During this time the operator's hand may be exposed to movement by the actuator. If the valve that provides the pressurized fluid to the actuator, the fluid systems, and the equipment that uses the actuator operate without failure, the operator may reach into the equipment without risk of injury.

However, sometimes the valve, the fluid systems, or the equipment fail. For example, the valve may fail in such a way that pressurized fluid is unexpectedly coupled to the press. In another example, a pneumatically operated brake on the equipment may fail thereby allowing the actuator to move. Unfortunately, these failures may happen when the operator or other people/equipment are exposed to the actuator's movements or pressure. As a result costly injuries or damage to equipment may occur. Safety valves have been developed to detect unsafe conditions and automatically decouple the pressurized fluid supply from the actuator.

For example, DE 31 04 957 C2 discloses a safety valve that monitors conditions to ensure that unsafe conditions do not exist. If the unsafe condition occurs, then the safety valve will automatically decouple the actuator from the pressurized fluid supply. The automatic decoupling may be initiated by pilot valves that are coupled to fluid conduits in the system. Accordingly, the pilot valves will change states if the unsafe condition occurs. The user typically determines what equipment condition is unsafe. However, it is known in the art that when safety valves are in an error state, fluid leaks through the safety valve to the tank and/or the actuator. For example, when the safety valve '957 is in what is called the error state due to the detection of an unsafe condition in the equipment, fluid is still flowing from the pressurized fluid supply to the tank or actuator. More specifically, it is known in the art that pressurized fluid leaks past the lands 104, 106 when the safety valve is in an error state as shown in Figure 3 of the '957 patent. This is due to the lack of positive pressure seals between the lands 104, 106 which must slide along the valve body 12. Therefore, to maintain the pressure to the '957 safety valve, a minimum volumetric fluid flow rate from the pressurized fluid supply may be required. Leaking fluid during when the actuator is fluidly decoupled from the pressurized fluid supply may require additional hardware such as accumulators.

Accordingly, there is a need for a safety valve that fluidly decouples the pressurized fluid supply without leakage. There is also a need for a safety valve that continues to fluidly decouple the pressurized fluid supply when, for example, a pilot valve is actuated.

SUMMARY

A safety valve with a pressure supply port, an actuator port, and a tank port is provided according to an embodiment. According to an embodiment, the safety valve comprises a valve assembly fluidly coupled to the pressure supply port, the actuator port, and the tank port and a first spool half and a second spool half at least partially disposed in the valve assembly. According to an embodiment, the valve assembly is adapted to selectively and fluidly couple the actuator port with the pressure supply port and with the tank port via the first spool half and the second spool half.

A method of forming a safety valve including forming a pressure supply port, an actuator port, and a tank port is provided according to an embodiment. According to an embodiment, the method comprises forming a valve assembly and fluidly coupling the valve assembly to the pressure supply port, the actuator port, and the tank port, forming and at least partially disposing in the valve assembly a first spool half and a second spool half. According to an embodiment, the method further comprises adapting the valve assembly to selectively and fluidly couple the actuator port with the pressure supply port and with the tank port via the first spool half and the second spool half.

A method of operating a valve assembly having a pressure supply port, an actuator port, and a tank port wherein the pressure supply port is fluidly coupled to the actuator port, the operating the valve assembly is provided according to an embodiment. According to an embodiment, the method comprises fluidly coupling the actuator port with the actuator port via a first spool half and a second spool half.

ASPECTS

According to an aspect, a safety valve (100) with a pressure supply port (122), an actuator port (124), and a tank port (126) comprises a valve assembly (110) fluidly coupled to the pressure supply port (122), the actuator port (124), and the tank port (126), and a first spool half (326a) and a second spool half (326b) at least partially disposed in the valve assembly (110), wherein the valve assembly (110) is adapted to selectively and fluidly couple the actuator port (124) with the pressure supply port (122) and with the tank port (126) via the first spool half (326a) and the second spool half (326b).

Preferably, the valve assembly (110) is further adapted to selectively and fluidly decouple the pressure supply port (122) from the actuator port (124) with the first spool half (326a) and the second spool half (326b).

Preferably, the valve assembly (110) is further adapted to selectively and fluidly couple the actuator port (124) with the pressure supply port (122) and with the tank port (126) by selectively coupling the first spool half (326a) with the second spool half (326b).

Preferably, the valve assembly (110) is adapted to selectively couple the first spool half (326a) and the second spool half (326b) by pressing the first spool half (326a) and the second spool half (326b) together.

Preferably, the valve assembly (110) further comprises a first loop chamber (330a) and a second loop chamber (330b).

Preferably, the valve assembly (110) is further adapted to selectively couple the first spool half (326a) and the second spool half (326b) with pressures in the first loop chamber (330a) and the second loop chamber (330b).

Preferably, the first loop chamber (330a) and the second loop chamber (330b) are selectively and fluidly coupled with the pressure supply port (122).

Preferably, the first loop chamber (330a) and the second loop chamber (330b) are part of fluid loops selectively and fluidly coupled to the pressure supply port (122).

Preferably, the valve assembly (110) is further adapted to fluidly de-couple the pressure supply port (122) from the actuator port (124) when a loop supply (306) is fluidly coupled with the second loop chamber (330b).

Preferably, the valve assembly (110) is further adapted to fluidly de-couple a loop supply (306) from the second loop chamber (330b) when the loop supply (306) is fluidly coupled with the second loop chamber (330b) and the loop supply (306) is fiuidly decoupled from the first loop chamber (330a).

Preferably, the valve assembly (110) is further comprises a first spool poppet (322a) and a second spool poppet (322b) wherein the first spool poppet (322a) and the second spool poppet (322b) adapted to selectively and fiuidly couple the actuator port (124) with the tank port (126).

According to an aspect, forming a safety valve (100) including forming a pressure supply port (122), an actuator port (124), and a tank port (126), the forming the safety valve (100) comprises forming a valve assembly (110) and fiuidly coupling the valve assembly (110) to the pressure supply port (122), the actuator port (124), and the tank port (126), forming and at least partially disposing in the valve assembly (1 10) a first spool half (326a) and a second spool half (326b), and adapting the valve assembly (110) to selectively and fiuidly couple the actuator port (124) with the pressure supply port (122) and with the tank port (126) via the first spool half (326a) and the second spool half (326b).

Preferably, the adapting the valve assembly (1 10) further comprises adapting the valve assembly (110) to selectively and fiuidly de-couple the pressure supply port (122) from the actuator port (124) with the first spool half (326a) and the second spool half (326b).

Preferably, the adapting the valve assembly (110) further comprises adapting the valve assembly (110) to selectively and fiuidly couple the actuator port (124) with the pressure supply port (122) and with the tank port (126) by selectively coupling the first spool half (326a) with the second spool half (326b).

Preferably, the adapting the valve assembly (110) further comprises adapting the valve assembly (110) to selectively couple the first spool half (326a) and the second spool half (326b) by pressing the first spool half (326a) and the second spool half (326b) together.

Preferably, the forming the valve assembly (1 10) further comprises forming a first loop chamber (330a) and a second loop chamber (330b).

Preferably, the forming the valve assembly (110) further comprises adapting the valve assembly (110) to selectively couple the first spool half (326a) and the second spool half (326b) with pressures in the first loop chamber (330a) and the second loop chamber (330b).

Preferably, the forming the valve assembly (1 10) further comprises adapting the first loop chamber (330a) and the second loop chamber (330b) to selectively and fiuidly couple with the pressure supply port (122). Preferably, the forming the valve assembly (110) further comprises adapting the first loop chamber (330a) and the second loop chamber (330b) to be part of fluid loops selectively and f uidly coupled to the pressure supply port (122).

Preferably, the forming the valve assembly (110) further comprises adapting the valve assembly to fiuidly de-couple the pressure supply port (122) from the actuator port (124) when a loop supply (306) is fiuidly coupled with the second loop chamber (330b).

Preferably, the forming the valve assembly (110) further comprises adapting the valve assembly to fiuidly de-couple a loop supply (306) from the second loop chamber (330b) when the loop supply (306) is fiuidly coupled with the second loop chamber (330b) and the loop supply (306) is fiuidly de-coupled from the first loop chamber (330a).

Preferably, the forming the valve assembly (110) further comprises forming a first spool poppet (322a) and a second spool poppet (322b) and adapting the first spool poppet (322a) and the second spool poppet (322b) to selectively and fiuidly couple the actuator port (124) with the tank port (126).

According to an aspect, operating a valve assembly (110) having a pressure supply port (122), an actuator port (124), and a tank port (126) wherein the pressure supply port (122) is fiuidly coupled to the actuator port (124), the operating the valve assembly (110) comprises fiuidly coupling the actuator port (124) with the tank port (126) via a first spool half (326a) and a second spool half (326b).

Preferably, the operating the valve assembly (110) further comprises fiuidly decoupling the pressure supply port (122) from the actuator port (124) with the first spool half (326a) and the second spool half (326b).

Preferably, the operating the valve assembly (110) further comprises coupling the first spool half (326a) and the second spool half (326b).

Preferably, the coupling the first spool half (326a) and the second spool half (326b) further comprises coupling the first spool half (326a) and the second spool half (326b) with pressures in a first loop chamber (330a) and a second loop chamber (330b).

Preferably, the coupling the first spool half (326a) and the second spool half (326b) further comprises selectively and fiuidly coupling the first loop chamber (330a) and the second loop chamber (330b) with the pressure supply port (122).

Preferably, the operating the valve assembly (110) further comprises de-coupling the first spool half (326a) and the second spool half (326b) by fiuidly de-coupling the second loop chamber (330b) from the pressure supply port (122). BRIEF DESCRIPTION OF THE DRAWINGS

The same reference number represents the same element on all drawings. It should be understood that the drawings are not necessarily to scale.

FIG. 1 shows a safety valve 100 according to an embodiment.

FIG. 2 shows a cross sectional view of the safety valve 100 taken at section 1-1 shown in FIG. 1.

FIG. 3 shows the cross sectional view of the valve assembly 110.

FIGS. 3a and 3b show enlarged views of the valve assembly 110 shown in FIG.3.

FIG. 3c shows an enlarged view of the cross sectional view of the valve assembly 110 shown in FIG. 3.

FIG. 3d shows an enlarged view of the valve assembly 110 shown in FIG. 3c.

FIG. 4 shows a cross sectional view of the valve assembly 110 in a zero position state.

FIG. 5 shows the valve assembly 110 in a switched position state.

FIGS. 5a - 5c show enlarged views of the valve assembly 110 in the switched position state.

FIG. 6 shows the valve assembly 110 in a safety state.

FIGS. 6a and 6b show enlarged views of the valve assembly 110 in the safety state. FIGS. 7a-7c are schematic representations of the safety valve 100 according to an embodiment.

DETAILED DESCRIPTION

FIGS. 1 - 7c and the following description depict specific examples to teach those skilled in the art how to make and use the best mode of embodiments of a safety valve. For the purpose of teaching inventive principles, some conventional aspects have been simplified or omitted. Those skilled in the art will appreciate variations from these examples that fall within the scope of the present description. Those skilled in the art will appreciate that the features described below can be combined in various ways to form multiple variations of the safety valve. As a result, the embodiments described below are not limited to the specific examples described below, but only by the claims and their equivalents.

To reduce the likelihood of injuries in various industries, governing bodies have implemented regulations and safety standards. Some of these regulations and safety standards place design constraints on systems that are used in the industries. An exemplary safety standard is the European Functional Safety standards is IEC 61508 entitled

"Functional Safety of Electrical/Electronic/Programmable Electronic Safety-related Systems" (E/E/PES). The IEC 61508 is a functional safety standard that is applicable to a variety of industries. In the IEC 61508 standard, the term functional safety may relate to the equipment under control (EUC) and the EUC control systems which depend on the functioning of the E/E/PES systems. The E/E/PES systems may be rated on the basis of their Safety Integrity Levels (SIL). There may be four levels numbering from 1 to 4. SIL-4 may be considered the highest safety integrity level.

Safety valves may be employed in SIL qualified systems. The safety valves may be employed to control a supply of pressurized fluid an actuator that is part of the EUC control system. The safety valves may be monitored by the E/E/PES so that the supply of pressurized fluid is cut off from the EUC when there is an unsafe condition. However, systems designed and implemented to SIL-4 standards may not allow electrical monitoring of the valves. For example, if there is a failure in the EUC, the valve cannot be switched to a 'safe' state by an electrical signal. Prior art safety valves, such as those described in the foregoing, are able to automatically switch to a safe state when abnormal conditions are detected in the system.

However, as discussed in the foregoing, pressurized fluid may leak from the pressure supply to, for example, the actuator port when the prior art safety valve is in an error condition. This may be undesirable because, for example, additional hardware such as accumulators may be required to maintain the fluid pressure. The following describes a safety valve that may not leak from the pressurized fluid supply to, for example, the tank port. The safety valve also self-monitors to ensure that the valve assembly remains in a safety state even if an actuator is energized. Accordingly, a minimal volumetric flow rate or additional hardware, such as accumulators, may not be required.

Safety valve

FIG. 1 shows a safety valve 100 according to an embodiment. The safety valve 100 may include a valve assembly 110 that is coupled to a sub-plate 120. The sub-plate 120 is shown as having a pressure supply port 122, an actuator port 124, and a tank port 126. The valve assembly 110 is also shown as coupled to a first actuator 130 and a second actuator 140. The first actuator 130 and the second actuator 140 may have a first actuator pilot port 132 and a second actuator pilot port 134, respectively, which may be coupled to an EUC and/or E/E/PES or any other appropriate equipment. The valve assembly 110 and the sub-plate 120 may be formed from stainless steel that is machined with fluid conduits. The fluid conduits will be described in more detail in the following with reference to FIGS. 2-6b. The valve assembly 110 and the sub-plate 120 may also include various screw holes (not enumerated) for mounting the valve assembly 110 to the EUC, E/E/PES system, etc.

The pressure supply port 122, the actuator port 124, the tank port 126 may be fluidly coupled to the E/E/PES and/or the EUC. For example, the pressure supply port 122 may be coupled to a pressurized fluid source (not shown), such as a hydraulic pump, that may provide pressurized fluid to the safety valve 100 via the pressure supply port 122.

Accordingly, the safety valve 100 may supply the pressurized fluid from the pressure supply port 122 to the EUC via the actuator port 124. The actuator port 124 may be coupled, for example, to an actuator on the EUC. The tank port 126 may be fluidly coupled to a reservoir, such as a tank, in the E/E/PES. The safety valve 100 may also regulate the flow of the fluid from the actuator port 124 to the tank port 126.

The first actuator 130 and the second actuator 140 may be 3/2 valves although any appropriate valves may be employed. The first actuator pilot port 132 and the second actuator pilot port 142 on the first actuator 130 and the second actuator 140, respectively, may be actuated by the E/E/PES and/or the EUC. Accordingly, the first actuator 130 and the second actuator 140 may be actuated depending on the conditions in the E/E/PES and/or the EUC which will be described in more detail in the following with reference to FIGS. 2-8.

FIG. 2 shows a cross sectional view of the safety valve 100 taken at section 1-1 shown in FIG. 1. The safety valve 100 is depicted without the sub-plate 120 coupled to the valve assembly 110. Although not shown, a pressure opening 240 may be coupled to the pressure supply port 122. Similarly, a tank opening 250 may be fluidly coupled to the tank port 126 and an actuator opening 260 may be fluidly coupled to the actuator port 124. The valve assembly 110 may include a first split spool assembly 210 and a second split spool assembly 220 partially disposed inside and coupled to a valve body 230.

As will be described in the following, the valve assembly 110 may be adapted to selectively and fluidly couple the actuator port 124 with the pressure supply port 122 and with the tank port 126 via the split spool assemblies 210, 220. The split spool assemblies

210, 220 may include spool halves that selectively and fluidly couple the pressure supply port 122 with the actuator port 124 or tank port 126. The split spool assemblies 210, 220 may prevent fluid from leaking from the pressure supply port 122 to actuator port 124 or the tank port 126. The split spool assemblies 210, 220 may also include poppets that provide positive pressure seals. These positive pressure seals may prevent fluid from leaking from the pressure supply port to, for example, the tank port 126. The valve assembly 110 may also include pressure loops with check valves that allow pressurized fluid to leak from the pressure supply port 122 back to the pressure supply port 122 when the valve assembly 110 is in a safe state.

FIG. 3 shows the cross sectional view of the valve assembly 110. The portions of the split spool assemblies 210, 220 described in the following include features that are symmetric. The item reference numbers for pairs of symmetric features include 'a,b' as part of the reference number. With reference to FIG. 3, the valve assembly 110 includes check valves 304a,b that are mechanically coupled to the valve assembly 110 and fluidly coupled to the pressure supply conduit 302 via a pressure supply conduit 302a and a pressure supply conduit 302b, respectively. The check valves 304a,b may be double check valves that prevent fluid flow from the pressure supply conduit 302 to the back loop arms 334a,b but allow reverse fluid flows. If the back loop arms 334a,b pressures are greater than the pressure supply conduit 302 pressure, fluid may flow into the pressure supply conduit 302 via the check valves 304a,b. The pressure supply conduit 302 may also be fluidly coupled to the first split spool assembly 210 and the second split spool assembly 220. The valve assembly 110 also includes a loop supply 306 that is fluidly coupled to the first actuator 130 and the second actuator 140 (not shown) via a first loop supply 306a and a second loop supply 306b. The actuators 130, 140 are also fluidly coupled to loop actuator arms 308a,b, respectively, in the valve assembly 110.

FIGS. 3a and 3b show enlarged views of the valve assembly 110 shown in FIG.3. The first split spool assembly 210 and the second split spool assembly 220 include spool retainers 320a,b coupled to the valve body 230. Spool poppets 322a,b may be slidably coupled to the spool retainers 320a,b. Poppet springs 325a,b may press the spool poppets 322a,b into inner surfaces of the spool retainers 320a,b. The first split spool assembly 210 and the second split spool assembly 220 include spool halves 326a,b that may be pressed towards the middle of the valve assembly 110 by spool springs 327a,b that press against the spool retainers 320a,b.The spool halves 326a,b are also shown as slidably coupled to the valve body 230 via outer spool seals 328a,b. The outer spool seals 328a,b may form a fluid seal between the spool halves 326a,b and the valve body 230.

Loop chambers 330a,b may be a fluid filled space formed by the valve body 230, spool retainers 320a,b, and the spool halves 326a,b. The loop chambers 330a,b may be fluidly coupled to a back loop arms 334a,b. The loop actuator arms 308a,b may be fluidly coupled to the loop chambers 330a,b via a spool channels 332a,b in the spool halves 326a,b. The first split spool assembly 210 and the second split spool assembly 220 may also include a tank conduits 340a,b that are fluidly coupled to poppet conduits 342a,b in the spool poppets 322a,b.

The spool retainers 320a,b, the spool poppets 322a,b, and the spool halves 326a,b may be formed from a stainless steel that has corrosion resistant properties. However, the spool retainers 320a,b, the spool poppets 322a,b, and the spool halves 326a,b may be formed from different materials depending on the application. Similarly, the spool springs 327a,b may be formed from a corrosion resistant spring steel although any appropriate material may be employed. The outer spool seals 328a,b may be a plastic that is selected for abrasion resistance. This may ensure that the seal between the spool halves 326a,b and the valve body 230 is maintained when the spool halves 326a,b slide in the valve body 230. We now turn to the inner portion of the split spool assemblies 210 and 220.

FIG. 3c shows an enlarged view of the cross sectional view of the valve assembly 110 shown in FIG. 3. The spool halves 326a,b may include spool conduits 350a,b and poppet seats 352a,b. The spool poppets 322a,b may include poppet heads 354a,b. The poppet heads 354a,b are shown as proximate to the poppet seats 352a,b. Although not shown in FIG. 3c, the poppet seats 352a,b and the poppet heads 354a,b may be pressed into each other to form a fluid seal. Actuator conduits 360a,b are shown as fluidly coupled to the spool conduits 350a,b. Outer spool seals 362a,b may form seals that fluidly de-couples the actuator conduits 360a,b from the loop actuator arms 308a,b. The poppet fluid seals 364a,b may form seals that fluidly de-couples the spool conduits 350a,b from the loop chambers 330a,b.

The spool conduits 350a,b may be fluidly coupled with the poppet conduits 342a,b due to the poppet seats 352a,b and the poppet heads 354a,b not being pressed into each other. Pressing the poppet seats 352a,b and the poppet heads 354a,b together may fluidly decoupling the spool conduits 350a,b from the poppet conduits 342a,b. As shown, the first spool conduit 350a is fluidly coupled with the second spool conduit 350b. The spool conduits 350a,b are also shown as fluidly de-coupled from the pressure supply conduit 302 and the loop supply 306. The spool conduits 350a,b may be fluidly de-coupled from the pressure supply conduit 302 and the loop supply 306 by pressing the first spool half 326a and the second spool half 326b into each other to form a seal as will be described in more detail in the following with respect to FIG. 3d. FIG. 3d shows an enlarged view of the valve assembly 110 shown in FIG. 3c. The loop supply 306 is shown as a conduit in the valve body 230 that is fluidly coupled to the supply conduit 302. The first spool half 326a may include a spool coupler 329 that extends into the second spool half 326b. The first spool half 326a and the second spool half 326b may press into each other to form a fluid seal at the spool joint 326c. In other words, the spool halves 326a,b may be selectively coupled by the valve assembly 110. Accordingly, the spool conduits 350a,b may be fluidly isolated from the pressure supply conduit 302 and the loop supply 306. Although the spool coupler 329 is shown with a cylindrical shape, any suitable shape may be employed. For example, the spool coupler 329 may have a conical shape. Inner spool seals 366a,b may be circumferentially coupled to the spool halves 326a,b.

The inner spool seals 366a,b are shown as having a square cross sectional area although any suitable cross sectional area may be employed. The inner spool seals 366a,b may comprise a material the same as or different than the material comprising the spool halves 326a,b. The inner spool seals 366a,b may also be formed integral to the spool halves 326a,b. The inner spool seals 366a,b are shown as pressed against an inner surface of the valve body 230 and may form a seal between the loop supply 306 and the actuator conduits 360a,b.

With reference to FIGS. 3-3d, the tank conduits 340a,b may be fluidly coupled to the tank port 126 shown in FIG. 1. In use, the tank conduits 340a,b may be fluidly coupled to, for example, a reservoir (not shown) via the tank port 126. The conduit fluidly coupling the tank conduits 340a,b to the tank port 126 is not shown. Accordingly, the tank conduits 340a,b may fluidly couple the reservoir to the poppet conduits 342a,b in the spool poppets 322a,b. The pressure supply conduit 302 may be fluidly coupled to the pressure supply port 122. In use, the pressure supply conduit 302 may be fluidly coupled to a pressure source (not shown) such as a fluid pump via the pressure supply port 122. Accordingly, the pressure supply conduit 302 may fluidly couple the loop supply 306 to the pressure source.

Also as shown in FIGS. 3-3d, the loop actuator arms 308a,b, the loop chambers 330a,b, the spool channels 332a,b, the back loop arms 334a,b may be selectively and fluidly coupled with each other. Similarly, the tank conduits 340a,b, the poppet conduits 342a,b, and the spool conduits 350a,b may be selectively and fluidly coupled with each other.

Accordingly, the actuator port 124 may be selectively and fluidly coupled to the pressure supply port 122 and the tank port 126. Pressure loops

As shown in the FIGS. 3-3d, the loop actuator arms 308a,b, the loop chambers 330a,b, the spool channels 332a,b, the back loop arms 334a,b may form two fluid pressure loops that apply a pressure to the spool halves 326a,b. That is, the loop actuator arms 308a,b, the loop chambers 330a,b, the spool channels 332a,b, the back loop arms 334a,b may be fluidly coupled to the pressure supply conduit 302 and the loop supply 306. The pressure supply conduit 302 and the loop supply 306 may be at the same pressure.

As described in the foregoing, the fluid pressure loops may automatically sense the pressures in the pressure supply conduit 302 and the loop supply 306 as well as the states of the first actuator 130 and the second actuator 140. The fluid pressure loops may be static fluid pressure loops with a minimal fluid flow through each fluid pressure loops.

Additionally and as will be described in more detail in the following, the fluid pressure loops may allow fluid to leak from the pressure supply port 122 back to the pressure supply port 122 when the valve assembly is in a safety state. Accordingly, fluid may not leak from the pressure supply port 122 to the actuator port 124 or the tank port 126.

The loop chambers 330a,b may be part of the fluid pressure loops between the pressure supply conduit 302 and the loop supply 306. The fluid pressures in the loop chambers 330a,b may apply pressures against the spool halves 326a,b. The pressure in the loop chambers 330a,b may change depending on the pressure in the pressure supply conduit 302, the loop supply 306 and the first actuator 130 and the second actuator 140 states. The pressure changes in the loop chambers 330a,b may move the spool halves 326a,b (e.g., press the spool halves 326a,b together). In other words, the fluid pressures in the loop chambers 330a,b may fluidly couple or decouple the pressure supply port 122 with the actuator port 124 or the tank port 126. The actuators 130, 140 may selectively and fluidly couple the loop chambers 330a,b with the loop supply 306.

As discussed in the foregoing, the safety valve 100 may selectively and fluidly couple an actuator to a pressurized fluid source via the pressure supply port 122 and the actuator port 124. The safety valve 100 may also selectively and fluidly couple the actuator to a reservoir (e.g., tank) via the actuator port 124 and the tank port 126. The safety valve 100 may also selectively and fluidly de-couple the pressure supply port 122 from the actuator port 124. Accordingly, the safety valve 100 may fluidly de-couple the pressurized fluid from the actuator and fluidly couple the actuator to the reservoir to drain the reservoir automatically in response to conditions such as the pressures in the pressure supply conduit 302 and the first actuator 130 and the second actuator 140 states. The valve assembly 1 10 in the safety valve 100 may switch between three states as will be described in the following.

Zero position state

FIG. 4 shows a cross sectional view of the valve assembly 1 10 in a zero position state (which is the same as shown in FIGS. 3 -3d). The zero position state may have pressurized fluid being supplied to the loop supply 306. However, the pressurized fluid may not be coupled to the actuator port 124 or the tank port 126 due to the actuators 130, 140 fluidly coupling the loop supply 306 to the loop chambers 330a,b.

As shown, the actuators 130, 140 may be de-energized. For example, the pilot air may not be supplied to the actuators 130, 140 thereby allowing a spring inside the actuators 130, 140 to fluidly couple the loop supply arms 306a,b to the loop actuator arms 308a,b. However, other states of the first actuator 130 and the second actuator 140 may be employed. For example, it may be desirable to fluidly couple the loop supply 306a and the first loop actuator arm 308a when the first actuator 130 is energized to change the safety valve 100 to another state.

In the zero position state, the spool halves 326a,b are pressed into each other (as shown by the arrows in FIG. 4) by the pressure of the fluid at the loop chambers 330a,b and the spool springs 327a and 327b . Accordingly, the tank conduits 340a,b, the poppet conduits 342a,b, and the spool conduits 350a,b may be fluidly coupled with each other in a depressurized state. The depressurized state is any pressure that is not the same as the pressure in the loop supply 306 which may be pressurized by the pressure supply conduit 302. The safety valve may be changed to a different state by energizing the actuators 130, 140.

Switched position state

FIG. 5 shows the valve assembly 1 10 in a switched position state. The valve assembly 1 10 may be placed in the switched position state by energizing the first actuator 130 and the second actuator 140 when the safety valve 100 is in the zero position state. The time that the valve assembly 1 10 is placed in the switched position is less than 150 milliseconds although other range of time may be suitable. The suitable range of time for switching the valve assembly 1 10 (e.g., moving the positions of the spools 3326a,b) can be achieved by selecting the diameter, for example, of the loop supply 306a,b, loop actuator arms 308a,b, and back loop arms 334a,b by. The diameter may be selected by installing nozzles or flow restrictors in the valve assembly 110 although any suitable means for selecting the diameter may be employed.

As shown, the fluids in the loop chambers 330a,b are not pressurized by the loop supply 306. Accordingly, the force exerted by the pressurized fluid in the loop chamber 306 on the spool halves 326a,b may be greater than the force exerted on the spool halves 326a,b by the loop chambers 330a,b and the spool springs 327a,b. The spool halves 326a,b may therefore pressed apart by the pressure in the loop supply 306. As will be described in more detail in the following, pressing apart the spool halves 326a,b may fluidly couple the pressurize supply port 122 to the actuator port 124. In addition, the tank port 126 may be fluidly decoupled from both the pressure supply port 122 and the actuator port 124.

FIGS. 5a - 5c show enlarged views of the valve assembly 110 in the switched position state. The spool poppets 322a,b are shown as pressed away from the center and against the spool retainers 320a,b. The loop actuator arms 308a,b may be fluidly coupled to the loop chambers 330a,b via the spool channels 332a,b. The loop chambers 330a,b may be fluidly coupled with the back loop arms 334a,b.

In the switched position, the spool poppets 322a,b and the spool halves 326a,b are pressed into each other to form a fluid seal. The spool poppets 322a,b are pressed towards the middle of the safety valve 100 by the spool retainers 320a,b. The spool halves 326a,b are pressed away from the middle of the safety valve 100 by the fluid pressure in the loop supply 306. The spool poppets 322a,b and the spool halves 326a,b being pressed into each other forms a seal between the poppet seats 352a,b and the spool poppets 322a,b.

Accordingly, the spool conduits 350a,b may not be fluidly coupled to the tank conduits 340a,b. Due to the closed states of the first actuator 130 and the second actuator 140, the pressure supply conduit 302, spool conduits 350a,b, and the loop supply 306 are fluidly de- coupled from the loop actuator arms 308a,b. Therefore, the fluid in the back loop arms 334a,b may be depressurized.

With the normal operation of the safety valve 100 described in the foregoing, the following describes how the valve assembly 110 responds to unsafe conditions. Safety state

FIG. 6 shows the valve assembly 110 in a safety state. In the safety state, the pressurize supply port 122 may be fluidly decoupled from the actuator port 124 and the tank port 126 by the spool halves 326a,b being pressed together. In addition, the loop supply 306 may be fluidly decoupled from the first loop chamber 330a. Since the second loop chamber 330b is still pressurized by the fluid in the loop supply 306, the spool halves 326a,b are moved towards the first loop chamber 330a. This movement may cause the second spool half 326b to fluidly decouple the loop supply 306 from the second actuator 140 thereby locking the valve assembly 1 10 in the safety state. In addition, the actuator port 124 is fluidly coupled to the tank port 126 via the second spool assembly 220, as will be described in more detail in the following.

The valve assembly 1 10 may be placed in the safety state due to various reasons (e.g., unsafe conditions, vibration, broken compression spring, etc.). For example, the safety state position shown in FIG. 6 may be reached from the zero or switched position state. The valve assembly 1 10 may reach the safety state from the zero position state when the actuators 130, 140 do not switch simultaneously (e.g., within 150 milliseconds) when the valve assembly 1 10 is switching from the zero to the switched position state. By way of example, the actuators may not be switching simultaneously when the second actuator 140 switches 170 milliseconds after the first actuator switches 130 from the zero position state. For this situation, one can observe by referring to FIG. 3, that the first actuator 130 will depressurize the first loop chamber 330a. Due to the second actuator 140 not actuating as fast at the first actuator 130, the second loop chamber 330b will remain pressurized. As a result, the pressure in the second loop chamber 330b will cause the spool halves 326a,b to move towards the first loop chamber 330a thereby placing the valve assembly 1 10 in the safety state shown in FIG. 6.

The safety state may also be reached when there is a fault in the EUC while the valve assembly 1 10 is in the switched state. For example, when the second actuator 140 is de-energized (e.g., an EUC brake loses pressure while coupled to the second actuator 140) from the position shown in FIG. 5, the loop supply 306b is fluidly coupled to the second loop actuator arm 308b. The second loop chamber 330b is pressurized and therefore exerts an inward force on the second spool half 326b. The inward force on the second spool half 326b is greater than the force exerted outward by the pressurized fluid in the spool supply 306. As a result, the second spool half 326b moves (as shown by the arrows) inward towards the first spool half 326a and presses the spool halves 326a,b to the safety state position shown in FIG. 6. The safety state position will be described in more detail in the following with reference to FIGS. 6a-6b.

FIGS. 6a-6b show enlarged views of the valve assembly 1 10 in the safety state. The second spool half 326b is depicted as pressed towards the middle of the valve assembly 1 10.

When the second spool half 326b moves towards the first split spool assembly 210, the second poppet head 354b may be de-coupled from the second poppet seat 352b (see FIG. 6b). This may fluidly couple the second poppet conduit 342b with the second spool conduit 350b. The spool coupler 329 shown in FIG. 3d may enter the second spool half 326b to form the fluid seal at the spool joint 326c. This may fluidly de-couple the second spool conduit 350b from the loop supply 306 and the pressure supply conduit 302.

As shown in FIG. 6a, the second loop actuator arm 308b may be fluidly de-coupled from the second loop chamber 330b because the second spool channel 332b has moved past the second loop actuator arm 308b. As shown in FIG. 6b, the second spool half 326b forms a fluid seal at a loop inlet 610 on the loop supply 306. The fluid seal at the loop inlet 610 may fluidly de-couple the first loop supply 306a from the pressure supply conduit 302. Accordingly, the pressure supply conduit 302 may be fluidly de-coupled from the first actuator 130. In addition, the second loop chamber 330b, the second back loop arm 334b may be fluidly de-coupled from the second loop actuator arm 308b. However, in the position shown in FIG. 6, pressurized fluid may leak from the second loop actuator arm 308b to the second spool chamber 330b which returns the fluid to the pressure supply conduit 302. The pressurized fluid therefore does not leak from the pressure supply port 122 to the actuator port 124 or the tank port 126 when the valve assembly 110 is in the safety state.

The valve assembly 110 also self-monitors. For example, if the second actuator 140 were to actuate from the safety state position shown in FIG. 6 to fluidly couple the second loop actuator arm 308b to the second tank conduit 340b, the fluid in the second actuator arm

308b flows to the tank port 126. The second loop chamber 330b therefore has a tendency to depressurize due to a small amount of leakage from the second loop chamber 330b to the second actuator arm 308b. However, the first spool spring 327a presses the spool halves 326a,b towards the second spool chamber 330b and maintains the pressure in the second spool chamber 330b. As a result, the second check valve 304b remains open. The second spool chamber 330b therefore remains pressurized by the pressure supply conduit 302b. The leakage from the second spool chamber 330b to the second actuator arm 308b is replaced by a small amount of fluid flow from the pressure supply conduit 302 to the second loop chamber 302b through the second check valve 304b (which remains open due to the equalized pressure). Accordingly, the valve assembly 110 remains in the safety state shown in FIG. 6. As long as fluid pressure is present in the pressure supply conduit 302, the valve assembly 110 will remain in the safety state. To change the valve assembly 110 from the safety state back to the to the zero position state, fluid pressure in the pressure supply conduit 302 must be removed. That is, the pressurized fluid must not be supplied to the pressure supply port 122 to unlock the valve assembly 110.

The foregoing describes the split spool assemblies 210a,b as moving towards the first spool retainer 320a to place the valve assembly 110 in the safety state. However, the valve assembly 110 may also be placed in the safety state when the split spool assemblies 210a,b move towards the second spool retainer 320b in a manner similar to that described with reference to FIGS. 6-6b. From either safety state positions, the valve assembly 110 will not move from the safety state unless pressure is removed from the pressure supply conduit 302. One pressure is removed from the pressure supply conduit 302, the loop supply 306 and the loop chambers 330a,b de-pressurizes which allows the spool springs 327a,b to re- center the spool halves 326a,b in the valve assembly 110.

The zero position, the switched position, and the safety states change how the pressure supply port 122, actuator port 124, and tank port 126 are fluidly coupled. The way the safety valve 100 is switched between these states is described in more detail in the following.

Schematic

FIGS. 7a-7c are schematic representations of the safety valve 100 according to an embodiment. The components shown in the FIGS. 7a-7c represent functions of components in the safety valve 100. As shown in FIGS. 7a-7c, the safety valve 100 includes the pressure opening 240, the tank opening 250, and the actuator opening 260 described with reference to FIG 2. The safety valve 100 also includes the check valves 304a,b described with reference to FIG. 3.

In addition, the safety valve 100 includes a spool valve 710 which is fluidly coupled to the actuator opening 260. The spool valve 710 represents the function of the spool halves 326a,b selectively coupling the pressure opening 240, the tank opening 250, and the actuator opening 260. A balanced valve 720 is adapted to selectively couple the pressure opening 240 to the spool valve 710. The balanced valve 720 is actuated by balanced spool actuators 730a,b. The balance valve 720 and the balanced spool actuators 730a,b represent the loop chambers 330a,b moving the spool halves 326a,b to one side of the safety valve 100. The balanced spool actuators 730a,b are coupled to actuators 740a,b which correspond to the actuators 130, 140. The actuators 740a,b supply the pilot pressures to spool chamber actuators 750a,b. FIG. 7a is a schematic representation of the zero position state described with reference to FIG. 4. As shown in FIG. 7a, the spool valve 710 is being supplied with pilot pressure from the balanced spool actuators 730a,b. Pressurized fluid is being supplied to the spool valve 710 via the balanced valve 720. The actuators 740a,b are not energized and therefore fluidly couple the pressurized fluid to the balanced spool actuators 730a,b. From the zero position state, the safety valve 100 can transition to the switched position described in more detail below with reference to FIG. 7b when the actuators 740a,b actuate simultaneously.

As can be seen in FIG. 7b, the actuators 740a,b are energized and therefore fluidly decouple the pressurized fluid from the balanced spool actuators 730a,b. As a result, the spool valve 710 is actuated to couple the pressure opening 240 and the actuator opening 260 while de-coupling the tank opening 250 and the actuator opening 260. The balanced spool actuators 730a,b receive fluid from actuators 740a,b, respectively. Since the actuators 740a,b actuated simultaneously, the balanced valve 720 's pilot pressures remained balanced. Accordingly, the balanced valve 720 does not actuate and continues to provide pressurized fluid to the spool valve 710.

As can be seen in FIGS. 7a- 7b, the spool valve 710 normally couples the tank opening 250 and the actuator opening 260 when the spool valve 710 has no pilot pressure or the pilot pressures are balanced. The spool valve 710 receives the pressurized fluid from the balanced valve 720 if the balance valve 720 's pilots and the springs are balanced. However, as will be described in more detail in the following, un-balanced pilot pressures in the balanced valve 720 or the spool chamber actuators 750a,b causes the spool valve 710 to return to the normal position that couples the tank opening 250 and the actuator opening 260.

If the balanced valve 720 's pilot or spring pressures are unbalanced, the balanced valve 720 will actuate to decouple the pressurized fluid from the balanced valve 720. For example, if the one of the balanced valve 720 's springs breaks while in the position shown in FIG. 7b, then the balanced valve 720 will actuate to the side of the broken spring. This de-couples the fluid pressure from the spool valve 710 and de-couples pilot pressure from the spool valve 710. As a result, the spool valve 710 to the normal position shown in FIG.

7a from an actuated position. The balanced valve 720 also actuates the balanced spool actuators 730a,b when the balanced valve 720 actuates due to unbalanced pilot pressures.

The pilot pressures supplied by the actuators 740a,b must also remain balanced for the spool chamber actuators 750a,b to remain in the open positions shown in FIGS. 7a and 7b. For example, the first spool chamber actuator 750a has pilot pressures supplied by the first actuator 740a on one side and the second actuator 740b on the other side. The spool chamber actuators 750a,b actuate when the spool chamber actuators 750a,b's pilot and spring pressures are un-balanced. For example, the spool chamber actuators 750a,b will de- couple the pressurized fluid from the spool valve 710's pilots if the actuators 740a,b do not actuate simultaneously.

The safety valve 100 may reach the safety states described with reference to FIG. 6 from either the zero or the switched position state when unsafe conditions occur. The unsafe conditions cause unbalanced pilot or spring pressures. These unbalanced pressures cause the pressurized fluid to be decoupled from the spool valve 710 and cause the spool valve 710 to return to the normally closed position (the position where the tank opening 250 and the actuator opening 260 are fluidly coupled to each other.) The schematic representation of one of the safety state positions is described in the following with reference to FIG. 7c.

As shown in FIG. 7c, the spool chamber actuators 750a,b are actuated to one side. This actuation may be due to various unsafe conditions such as a broken spring in the spool chamber actuators 750a,b or the actuators 740a,b not actuating simultaneously (e.g., within 150 milliseconds). For example, from the switched position state shown in FIG. 7b, the first actuator 740a may not actuate as fast as the second actuator 740b. As a result, the pilot pressures on the spool chamber actuators 750a,b are not balanced. This causes the spool chamber actuators 750a,b to actuate to one side thereby de-coupling the pressurized fluid from the spool valve 710's pilots. As a result, the spool valve 710 returns to the normal position that couples the actuator opening 260 with the tank opening 250. This non- simultaneous actuation of the actuators 740a,b also causes the balanced valve 720 's pilot pressures to become un-balanced thereby causing the balanced valve 720 to actuate to de- couple the fluid pressure from the spool valve 710.

The second safety state is a mirror image of the safety state shown in FIG. 7c. Although the foregoing describes exemplary unsafe conditions to show how the safety valve 100 operates, one of ordinary skill in the art would understand that other unsafe conditions can cause the safety valve 100 to switch to one of the safety states. The unsafe conditions can be inside the safety valve 100, in the EUC that is coupled to the safety valve 100, or any other appropriate equipment. For example, one of ordinary skill in the art would appreciate that the user could configure the EUC to provide pilot pressure to the actuators 740a,b simultaneously only when the EUC is in a safe condition. One of ordinary skill in the art would also recognize, for example, that a broken spring in one of the actuators 740a,b would cause the balanced valve 720 's pilot pressure to become unbalanced, thereby causing the balanced valve 720 to actuate.

The embodiments described above provide a safety valve 100. As explained above, the safety valve 100 may sense unsafe conditions in the safety valve, equipment and systems such as the EUC control system and the E/E/PES. The safety valve 100 may automatically sense (without monitoring by the fluid system 700) the pressures of the fluid that is supplied to, for example, the piston 710 and actuate if an unsafe condition occurs. In the safety state, the valve assembly 110 may not leak fluid from the pressure supply port 122 to the actuator port 124. Instead, fluid may leak from the pressure supply port 122 back to the pressure supply port 122 via pressure loops. Accordingly, the user may not be required to provide the minimal fluid flow rate when the valve assembly 1 10 is in the safety state. The user may therefore not require an accumulator. Additionally, the valve assembly 110 remains in the safety state even if, for example, the second actuator 140 is energized from the safety state. Accordingly, the safety valve 100 also self-monitors.

The detailed descriptions of the above embodiments are not exhaustive descriptions of all embodiments contemplated by the inventors to be within the scope of the present description. Indeed, persons skilled in the art will recognize that certain elements of the above-described embodiments may variously be combined or eliminated to create further embodiments, and such further embodiments fall within the scope and teachings of the present description. It will also be apparent to those of ordinary skill in the art that the above-described embodiments may be combined in whole or in part to create additional embodiments within the scope and teachings of the present description.

Thus, although specific embodiments are described herein for illustrative purposes, various equivalent modifications are possible within the scope of the present description, as those skilled in the relevant art will recognize. For example, the foregoing describes embodiments as being employed with EUC and/or E/E/PES systems. However,

embodiments may be employed in any appropriate fluid supply system. The teachings provided herein can be applied to other fluid systems, and not just to the embodiments described above and shown in the accompanying figures. Accordingly, the scope of the embodiments described above should be determined from the following claims.