FIELD OF THE INVENTION

[0001] The present invention relates to a high pressure solenoid valve, particularly a solenoid valve for controlling the flow of hydrogen fluid.

BACKGROUND OF THE INVENTION

[0002] Valves are required in fluid systems to control the flow of the fluid as desired. Two- way solenoid control valves are electro-mechanical valves designed for use with fluid flows where the valve is controlled between open and closed conditions by energizing and de energizing a solenoid coil. Solenoid valves are used in numerous applications where control of fluid flow and distribution is desired.

[0003] Solenoid valves typically comprise a core assembly including a core (sometimes known as an armature or plunger) and a valve head for seating engagement with a valve seat. In accordance with standard operation of such valve-types, the valve can be operated between closed and open conditions upon energization of a solenoid. Such valves can be normally closed valves, where the valve is closed until the solenoid is energized to open the valve and allow a fluid flow through the valve. Alternatively, such valves can be normally open valves, where the valve is open until the solenoid is energized to close the valve and shut off the fluid flowing through the valve.

[0004] More particularly, in a normally closed valve design, when the solenoid is energized, the core will move to engage and unseat the valve head from the valve seat to open the valve and allow a fluid to flow through the valve from an inlet port to an outlet port. When the solenoid is de-energized, the core and valve head return to the seated position to close the valve and block the fluid from flowing through the valve from the inlet port to the outlet port until the solenoid is energized again.

[0005] Different fluids have different operating requirements. For fluids such as hydrogen, the valves have particular requirements that they must be able to withstand high pressure, high flow applications. Hydrogen also presents particular challenges as its molecules are smaller than air, so sealing the valve is particularly difficult. In addition to this, if hydrogen comes into contact with certain materials, it can compromise the strength of the material. Accordingly, it is important to design the valve to ensure hydrogen passing through the valve is contained within particular areas of the valve, otherwise there would be a significant risk of failure of the valve.

[0006] Previous hydrogen valve designs have functioned well, but it would be desirable to improve the arrangements to further improve their safety and reduce the risk of failure. SUMMARY OF THE INVENTION

[0007] A high-pressure solenoid valve is provided. The high-pressure solenoid valve comprises: a valve body comprising an inlet port, an outlet port and a valve head moveable between a first position and a second position to close or open a connection between the inlet port and the outlet port; and a solenoid assembly fixed to the valve body, the solenoid assembly comprising: a magnetic core fixed to the valve head, the core actuatable to move the valve head between the first and second positions; a core tube surrounding the core; and a solenoid coil surrounding the core tube, wherein the core tube comprises an inner sealing sleeve and an outer reinforcing sleeve, the inner sealing sleeve having a radially outer surface and the outer reinforcing sleeve having a radially inner surface, wherein the radially outer surface of the inner sealing sleeve is in contact with the radially inner surface of the outer reinforcing sleeve along substantially the entire axial length of the inner sealing sleeve.

[0008] This reduces the risk of fluid leaking from the inner sealing sleeve and coming into contact with the outer reinforcing sleeve, which is under significant tensile load in use due to the high pressure within the valve, and so at large risk of failure due to hydrogen embrittlement.

[0009] The outer reinforcing sleeve may comprise three separate parts: a magnetic first part, a magnetic second part and a non-magnetic connecting ring located between and fixed to the first and second parts. The first part, the second part and the connecting ring may together define a blind bore of the outer reinforcing sleeve that locates the inner sealing sleeve.

[0010] It has been found that providing an outer reinforcing sleeve with three separate parts helps to ensure that the core tube can be correctly located, ensuring force is transferred directly to the outer reinforcing sleeve and reducing the risk of tensile failure in the inner sealing sleeve.

[0011] The first part of the outer reinforcing sleeve may have a first end and a second end. The first end may be closed.

[0012] The closed end provides a reaction surface for the inner sealing sleeve to engage. As the inner sealing sleeve and closed end of the outer reinforcing sleeve are in contact, the risk of failure of the inner sealing sleeve due to fatigue stress is reduced, as the tendency of the inner sealing sleeve to impact the outer sealing sleeve in use with a repeating 'pulsing' impact is reduced.

[0013] The blind bore of the outer reinforcing sleeve may have an internal surface. The internal surface may have no gaps in the axial direction.

[0014] As there are no gaps, the force can be transferred easily through the outer reinforcing sleeve.

[0015] The blind bore of the outer reinforcing sleeve may have a diameter and the radially outer surface of the inner sealing sleeve may have a diameter. The diameter of the blind bore of the outer reinforcing sleeve and the diameter of the radially outer surface of the inner sealing sleeve may substantially correspond to one another. The diameter of the blind bore of the outer reinforcing sleeve may be constant and the diameter of the radially outer surface of the inner sealing sleeve may be constant.

[0016] The corresponding diameters help to ensure that the inner sealing sleeve and the outer reinforcing sleeve remain in contact during use.

[0017] The connecting ring may be fixed to the first part and the second part by welding. The connecting ring may be fixed to the first part at a first annular weld seam. The connecting ring may be fixed to the second part at a second annular weld seam.

[0018] Fixing the parts together in this way is particularly reliable and easily repeatable, and helps to reduce the risk of tensile stresses causing failure in the outer reinforcing sleeve.

[0019] The inner sealing sleeve may have a first end and a second end. An axially outer end surface at the first end of the inner sealing sleeve may abut an internal abutment surface of the outer reinforcing sleeve.

[0020] The inner sealing sleeve may have a chamfer between the axially outer end surface at the first end and the radially outer surface of the inner sealing sleeve.

[0021] The chamfer on the inner sealing sleeve helps to ensure that there is no gap between the inner sealing sleeve and the outer reinforcing sleeve. Without the chamfer, any radius on the outer sleeve may cause a gap. The inner sealing sleeve may be closed at the first end and open at the second end to define a blind bore that locates and guides the core.

[0022] An axially inner end surface at the closed first end of the inner sealing sleeve may have a recess that locates a pressure spring that engages the core to bias the core in a direction away from the first end. [0023] The blind bore of the inner sealing sleeve may have a tapered portion at the second end of the inner sealing sleeve. At the tapered portion, the blind bore of the inner sleeve may taper radially outwardly to define an angled surface.

[0024] The inner sealing sleeve may be made of a corrosion resistant material, preferably an austenitic stainless steel, even more preferably 1.4404 grade stainless steel.

[0025] This helps to ensure that the inner sleeve does not suffer from hydrogen embrittlement.

[0026] The closed first end of the first part of the outer reinforcing sleeve may have a through bore in the axial direction.

[0027] The through bore can be used in combination with a sniffer to determine if, for example, hydrogen is escaping from the valve due to a sealing problem. Also, if the connecting ring is welded to the first and second parts of the outer reinforcing sleeve, the through bore allows the air to escape during the welding process.

[0028] The first part of the outer reinforcing sleeve may have a threaded radially outer surface portion. The high-pressure solenoid valve may further comprise a threaded nut that is located on the threaded radially outer surface portion of the first part.

[0029] The second part may have a threaded radially outer surface portion. The second part of the outer reinforcing sleeve may be received in a corresponding threaded bore of the valve body.

[0030] The outer reinforcing sleeve may be made of a high yield strength material, preferably high yield strength stainless steel.

[0031] A core tube is also provided for use in the high-pressure solenoid valve of any statement above.

[0032] The high-pressure solenoid valve of any statement above can be used in a hydrogen-fuelled power station.

BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Embodiments of the invention will now be described with reference to the accompanying drawings, in which:

[0034] Figure 1 is a cross-sectional view of a high-pressure solenoid valve;

[0035] Figure 2 is a cut-away view of a core tube of the high-pressure solenoid valve of Figure 1;

[0036] Figure 3 is a cut-away view of a core, first and second spacers and a valve head of the high-pressure solenoid valve of Figure 1; and [0037] Figure 4 is a cut-away view of a valve body, core tube and core of the high-pressure solenoid valve of Figure 1.

DETAILED DESCRIPTION OF EMBODIMENT(S)

[0038] Figure 1 shows a high-pressure solenoid valve 2. The solenoid valve 2 comprises a valve body 4 and a solenoid assembly 6 that is fixed to the valve body 4. In this description, the terms 'axial' and 'radial' are used in relation to an axis A-A shown in Figure 1 that extends through the centre of the solenoid valve 2. Relative terms such as 'upper', 'lower', 'above', 'below', 'inner', 'outer', etc., which are non-limiting and used for description purposes only, relate to the orientation shown in the figure, e.g. the valve body 4 is below the solenoid assembly 6.

[0039] The valve body 4 has an inlet port 8 and an outlet port 10. In use, the solenoid valve 2 can be located between an inlet pipe and an outlet pipe of a fluid system. Fluid can flow into the solenoid valve 2 through the inlet port 8 and out of the solenoid valve 2 through the outlet port 10. In this embodiment, there is a single inlet port 8 and a single outlet port 10. It will be appreciated, however, that in other embodiments there could be a plurality of inlet ports 8 and/or a plurality of outlet ports 10.

[0040] Between the inlet port 8 and the outlet port 10 is a valve body chamber 12. In the valve body chamber 12 is a valve comprising a valve head 14 and a valve shaft 16 that extends from the valve head 14. Surrounding the valve head 14 and the valve shaft 16 is a generally annular collar 18. The collar 18 locates in the valve body chamber 12. The collar 18 has an axial through bore with an annular stop 20 that extends in a radially inwardly direction from an inner surface of the through bore towards a radially outer surface of the valve shaft 16. Below the stop 20 a valve head cavity 22 is defined by the stop 20 and the collar 18. The valve head 14 moves in the valve head cavity 22 in the axial direction. The valve head 14 is guided by a radially inner surface of the collar 18 and the extent of the movement in the axial direction is limited by engagement of an upper surface of the valve head 14 with the stop 20.

[0041] As can also be seen in Figure 3, the valve head 14 is integral with the valve shaft 16. The valve shaft 16 is generally elongate and extends in the axial direction. The valve shaft 16 has a diameter that is smaller than the diameter of the valve head 14, such that the valve shaft 16 locates in a bore defined by the stop 20 of the collar 18. The valve head 14 has a conical end that corresponds to the shape of a valve seat 24 at a lower end of the valve body chamber 12. As shown in Figure 4, the valve seat 24 comprises the inlet port 8 and the outlet port 10. [0042] The valve head 14 is moveable within the valve head cavity 22 between a first position and a second position. In the first position, the angled surfaces of the conical end of the valve head 14 engage the valve seat 24 and block the inlet port 8 and the outlet port 10 so fluid cannot flow from the inlet port 8 to the outlet port 10. In the second position, the valve head 14 has been moved in an axially upward direction such that the valve head 14 is remote from the valve seat 24 and normally in contact with the stop 20. In this second position, a path is defined from the inlet port 8 to the outlet port 10, so fluid can flow. In other words, in the first position the solenoid valve 2 is closed and in the second position the solenoid valve 2 is open. The radially outer surface of the valve head 14 comprises a plurality of sealing gaskets 26 that engage the radially inner surface of the collar 18 to inhibit the migration of fluid through the collar 18 in an axially upward direction. The collar 18 has an angled surface at its axially lower end that engages a corresponding angled surface of the valve body chamber 12 to inhibit the migration of fluid through the valve body chamber 12 in an axially upward direction. The valve body 4 also comprises an o-ring 28 located between the collar 18 and the valve body chamber 12 to further inhibit the migration of fluid through the valve body chamber 12 in an axially upward direction.

[0043] Above the stop 20 in the collar 18, a core tube cavity 30 is defined. The core tube cavity 30 has a threaded inner surface 32 that locates a core tube 34. In this embodiment, the core tube 34 is threaded into the collar 18, but in other embodiments, the core tube 34 may be fixed to the valve body 4 in an alternative suitable way. It is key that the core tube 34 is securely attached to the valve body 4, as the core tube 34 is intended to support multiple other parts of the solenoid valve 2, as will be explained in more detail.

[0044] The core tube 34 is part of the solenoid assembly 6 and is a located radially outwardly of and surrounds and guides a magnetic core 36 of the solenoid assembly 6. Radially outward of and surrounding the core tube 34 is a solenoid coil 38 in communication with a power source 112. The coil 38 is housed in a solenoid case 40. The solenoid case 40 is retained on the core tube 34 with a nut 42, which is threaded onto the end of the core tube 34. An o-ring 44 is located on the core tube 34 at the upper end of the solenoid case 40, between the nut 42 and the solenoid case 40. A further o-ring 44 is located on the core tube 34 at the lower end of the solenoid case 40, between the collar 18 and the solenoid case 40. As can be seen, the core tube 34 is held securely in the valve body 4 with the threaded connection 32, and the case 40 is held securely on the core tube 34 by the nut 42 that is threaded on the core tube 34. Therefore, any axial stresses that are applied to the core tube 34 when the valve 2 is in use are reacted by the nut 42 and the valve body 4, to reduce the risk of failure of the core tube 34. [0045] As will be described in more detail below, the core 36 is connected to the valve shaft 16 so that when the coil 38 is energised by the power source 112, the core 36 is moved in an axially upward direction, guided by the core tube 34. As the core 36 is connected to the valve shaft 16, the valve head 14 is moved within the valve head cavity 22 to the second position, and fluid can flow from the inlet port 8 to the outlet port 10.

[0046] The core tube 34 will now be described in more detail, as shown most clearly in Figure 2. The core tube 34 is elongate and extends generally along the axis A-A. The core tube 34 comprises an inner sealing sleeve 46 and an outer reinforcing sleeve 48.

[0047] The outer reinforcing sleeve 48 comprises three separate parts: a first part 50, a second part 52 and a connecting ring 54. The connecting ring 54 is located between the first part 50 and the second part 52. The connecting ring 54 is also fixed to the first part 50 and fixed to the second part 52 such that all three parts are fixed to one another. Together, the first part 50, the second part 52 and the connecting ring 54 define a blind bore 56 of the outer reinforcing sleeve 48. The blind bore 56 has an internal surface 62. Importantly, because the first part 50, second part 52 and connecting ring 54 are fixed together in this way, the internal surface 62 of the blind bore 56 has no gaps in the axial direction. In this embodiment, the connecting ring 54 is fixed to the first part 50 and the second part 52 by welding. The connecting ring 54 is fixed to the first part 50 at a first annular weld seam 64. The connecting ring 54 is fixed to the second part 52 at a second annular weld seam 66. It will be appreciated, however, that any suitable method of permanently fixing the components together could be used. In this embodiment, the connecting ring 54 is a single integrally formed component that is, for example, cast or extruded as a single part. It will be appreciated, however, that in alternative embodiments, the connecting ring 54 could comprise a plurality of components fused or fixed together to define a single connecting ring 54.

[0048] The first part 50 and second part 52 are formed of a magnetic material, such as a ferrous metal such as stainless steel. The connecting ring 54, however, does not necessarily need to be magnetic, and so can be formed of any suitable material, for example, a ferrous or non-ferrous metal.

[0049] The radially outer surface of the inner sealing sleeve 46 engages the internal surface 62 of the blind bore 56 along substantially its entire axial length. In this embodiment, the blind bore 56 of the outer reinforcing sleeve 48 has a constant diameter that corresponds to a constant outer diameter of the radially outer surface of the inner sealing sleeve 46. In alternative embodiments, however, the bore 56 may not have a constant diameter and may instead be conical or have a stepped profile, provided the radially outer surface of the inner sealing sleeve 46 engages the internal surface 62 of the blind bore 56 along substantially its entire axial length. [0050] The first part 50 of the outer reinforcing sleeve 48 is located above the second part 52 and the connecting ring 54 and locates on the inner sealing sleeve 46. The first part 50 has a first end 58 and a second end 60. The second end 60 of the first part 50 is open and is fixed to the connecting ring 54. The first end 58 of the first part 50 is closed and acts as a 'cap' for the inner sealing sleeve 46. The underside of the closed first end 58 of the first part 50 defines an abutment surface 76.

[0051] The inner sealing sleeve 46 has a first end 68 and a second end 70. The second end 70 of the inner sealing sleeve 46 is open and terminates at substantially the same axial location as the second part 52 of the outer reinforcing sleeve 48. The first end 68 of the inner sealing sleeve 46 however is closed. The top side of the first end 68 defines an upper end surface 74. The end surface 74 of the inner sealing sleeve 46 opposes and engages the abutment surface 76 of the first end 58 of the first part 50 of the outer reinforcing sleeve 48. The engagement of the end surface 74 of the inner sealing sleeve 46 and the abutment surface 76 of the first end 58 of the first part 50 of the outer reinforcing sleeve 48 is advantageous, because it helps to ensure that expansion forces acting on the inner sealing sleeve 46 in use are reacted by the outer reinforcing sleeve 48, for reasons that will be described in more detail below. The inner sealing sleeve 46 has a chamfer 86 between the end surface 74 at the first end 58 and the radially outer surface of the inner sealing sleeve 46.

[0052] The closed first end 68 of the inner sealing sleeve 46 also defines a blind bore 72 that locates and guides the core 36. An underside of the end surface 74 comprises a recess 78 that locates a first end of a pressure spring 80. The core 36 is elongate and made of suitable magnetic material. A recess 82 in a top surface of the core 36 locates a second end of the pressure spring 80. Therefore, the core 36 is normally biased in an axially downward direction, away from the first end 68 of the inner sealing sleeve 46. When the coil 38 is energised and the core 36 is moved axially upwardly to open the valve, the force of the pressure spring 80 is overcome easily, as the force is configured so that this is the case.

[0053] At the second end 70 of the inner sealing sleeve 46 is a tapered portion 84. At the tapered portion 84, the blind bore 72 tapers radially outwardly to define an angled surface. This angled surface helps to guide any fluid that enters the inner sealing sleeve 46 into the inner sealing sleeve 46 and forces the inner sealing sleeve 46 to engage the outer reinforcing sleeve 48 even more strongly, to further reduce the risk that fluid instead passes into the gap between the inner sealing sleeve 46 and the outer reinforcing sleeve 48, which would be very undesirable. [0054] The inner sealing sleeve 46 is likely to come into contact at some point with a fluid such as hydrogen. Accordingly, the inner sealing sleeve 46 is made of a corrosion resistant material. Preferably, the inner sealing sleeve 46 is made from an austenitic stainless steel. It has been found that a particularly suitable stainless steel is 1.4404 grade stainless steel. In alternative embodiments, however, the inner sealing sleeve 46 may instead only have a coating that is corrosion resistant. For example, zinc-nickel is a particularly suitable coating for this application.

[0055] The outer reinforcing sleeve 48, however, is not intended to come into contact with hydrogen, because of the particular arrangement defined above. Accordingly, the outer reinforcing sleeve 48 can be made of a stronger material than the inner sealing sleeve 46. Any suitable material with a high yield strength can be used, to counteract the high tensile forces that will act on the outer reinforcing sleeve 48 in used. For example, high yield strength stainless steel can be used.

[0056] In this embodiment, the closed first end 58 of the first part 50 of the outer reinforcing sleeve 48 has a through bore 88 extending in the axial direction. The first end 58 of the first part 50 of the outer reinforcing sleeve 48 also has a threaded surface 90. The nut 42 locates on this threaded surface 90 to retain the solenoid case 40 on the core tube 34.

[0057] Between the axially lower end of the core 36 and the axially upper end of the valve shaft 16 is a first spacer 108 and a second spacer 110, located in a spacer cage 114. The first spacer 108 and the second spacer 110 transfer the force from the core 36 as it moves upwardly to the valve shaft 16, to move the valve head 14 upwardly at the same time, to open the solenoid valve 2.

[0058] Passing axially through the valve head 14 and the valve shaft 16 is a valve passage 94 that leads to a release valve 96 located between the first spacer 108 and the second spacer 110. The valve passage 94 is in communication with the outlet port 10. The release valve 96 includes a ball 98 located on a ball seat 100. Connected to the ball 98 is a release shaft 104 that abuts a recess 106 in an underside of the core 36. The ball 98 is biased onto the seat by a spring 102. If the ball 98 is urged away from the ball seat 100 in an axially upward direction with sufficient force to overcome the force of the spring 102, the release shaft 104 engages the core 36, forcing it upwards and dragging the valve head 14 upwards at the same time. As will be understood, this arrangement acts as a safety feature. If the solenoid valve 2 is closed and the pressure of a fluid at the outlet port 10 is too high, the fluid will flow up the valve passage 94 and actuate the release shaft 104, opening the solenoid valve 2 and placing the inlet port 8 in communication with the outlet port 10 so the pressures can equalise, helping to avoid, for example, an explosion. [0059] Where the word 'or' appears this is to be construed to mean 'and/or' such that items referred to are not necessarily mutually exclusive and may be used in any appropriate combination.

[0060] Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.