Metal-reinforced sealing plate for pilot-operated gate valve

Abstract

Seal (500, 501; 600; 900; 1000; 1100) for a pilot-operated slide valve, comprising: a metal disc (520, 521; 630, 632; 930, 932; 1032, 1030, 1036; 1130, 1132, 1136) having a generally planar first surface, a generally planar second surface, a generally cylindrical outer surface, and a central axial opening (508, 509; 608; 808; 908; 1008; 1108) extending from the first surface to the second surface; an annular groove (522, 523; 626; 922; 1022; 1122) in the second surface having a first, smaller width in a first portion adjacent to the second surface and a second, larger width in a portion remote from the second surface; and a thermoplastic insert (518, 519; 618; 918; 1018; 1118) in the annular groove (522, 523; 626; 922; 1022; 1122) having at least one generally planar surface substantially flush with the second surface of the metal disc (520, 521; 630, 632; 930, 932; 1032, 1030, 1036; 1130, 1132, 1136).

Description

CROSS-REFERENCE TO RELATED APPLICATIONS: BACKGROUND OF THE INVENTION 1. Field of the invention.

[0001] This invention relates to valves. In particular, it relates to subplate-mounted pilot-operated spool valves. 2. Description of the state of the art

[0002] US Patent No. 5,771,931 to Watson discloses a reciprocating sleeve-type valve mechanism having a valve housing in which a cage member is disposed. A piston movably disposed within the valve housing provides linear opening movement of a cylindrical sealing sleeve relative to spaced-apart polymer seals within the housing. Closing movement of the sealing sleeve is provided by a return spring. Sealing between the cage member and a wear-resistant ceramic outer lining of the sealing sleeve is provided by a seal assembly comprising a centrally disposed elastomeric sealing ring with auxiliary polymer wiper rings disposed on opposite sides thereof.The seal assembly provides a bearing and guiding function to stabilize the seal sleeve during its opening and closing movement and to wipe particles from the sealing surface of the seal sleeve and to maintain efficient sealing with the seal sleeve while the valve is opened and closed.

[0003] US Patent No. 4,887,643 to Tomlin et al. describes a housing having a cage with fluid supply ports, vent ports, and an outlet port. A pilot-operated hollow spool valve element is telescopically movable within the cage and engages conical seats at opposite ends of the cage. Elongated supply and vent slots, oriented transversely to the axis of the cage and valve element, provide passageways for maximum flow. The ends of the spool are in contact with the cage at all times, and the axial extent of contact between the spool and the cage is greater than fifty percent. The spool engages the interior of the cage at the supply and vent ports to reduce flow restrictions. A recess, coaxially disposed at each end of the cage, receives one of the valve seats.The housing rests against the cage to appropriately load the valve seats. A damper cup dampens the valve element. A pilot spindle is connected to the valve element externally. A seal carrier ensures a seal between contact surfaces of an underwater control device. Valves of the above-mentioned type are also known from documents US 5 771 931 A and US 4 011 892 A. DE 17 75 606 A discloses a seat ring for a ball valve. The seat ring comprises an elastic core, an inner and an outer ring part made of sealing material, wherein the inner ring part has a seating surface that bears against the ball, wherein the core has profile branches that enclose the inner ring part and approach the ends of the seating surface, and wherein one of the profile branches of the core forms, together with the inner ring part, an axially yielding lip.Document CH 388710 discloses an annular seal that is clamped against a first workpiece by a clamping piece and has an inclined surface with which it seals against another workpiece. A reinforcement is embedded in the annular seal. Document US 2005 / 0224119 A1 discloses a control valve for changing the flow direction of a fluid. The control valve comprises a sealing element in which a support ring is embedded.

[0004] US Patent US 4 457 489 A to Gilmore describes underwater fluid line connections for remotely controlled valves.

[0005] It has been found that the polymer sealing plates in valves of this type tend to deform due to deflection when subjected to higher pressures. The present invention provides a remedy for this problem. SUMMARY OF THE INVENTION

[0006] The upper and / or lower sealing plates of a subplate-mounted, pilot-operated spool valve are reinforced with a metal ring. In a number of preferred embodiments, the metal ring is made of steel. The sealing plates may comprise an engineering thermoplastic such as polyoxymethylene (POM), marketed by EI DuPont de Nemours under the trademark DELRIN®. The plastic may be molded to the metal ring. In other embodiments, the molded plastic and metal ring(s) are mechanically bonded together. BRIEF DESCRIPTION OF THE MULTIPLE VIEWS OF THE DRAWING(S) Fig. 1 is a cross-sectional view of a prior art subplate-mounted normally closed spool valve. Fig. 2 is a cross-sectional view of a subplate-mounted, normally closed spool valve having upper and lower sealing plates not in accordance with the invention. Fig. 3 is a cross-sectional view of a subplate-mounted, normally open spool valve having upper and lower sealing plates not in accordance with the invention. Fig. 4A is a cross-sectional view of an upper sealing plate for a gate valve according to a first embodiment not in accordance with the present invention. Fig. 4B is a cross-sectional view of a lower seal plate for a gate valve according to the first embodiment. Fig. 5A is a cross-sectional view of an upper sealing plate according to a second embodiment of the invention. Fig. 5B shows the sealing plate made of Fig. 5A before fitting the annular thermoplastic seal. Fig. 5C is a cross-sectional view of a lower sealing plate according to a second embodiment of the invention. Fig. 5D shows the sealing plate made of Fig. 5C before fitting the annular thermoplastic seal. Fig. 6A is a cross-sectional view of an upper sealing plate according to a third embodiment of the invention. Fig. 6B shows the sealing plate from Fig. 6A before fitting the annular thermoplastic seal. Fig. 7A is a cross-sectional view of an upper sealing plate according to a fourth embodiment of the invention. Fig. 7B shows the sealing plate from Fig. 7A before fitting the annular thermoplastic seal. Fig. 8A is a cross-sectional view of an upper sealing plate according to a fifth embodiment of the invention. Fig. 8B shows the sealing plate from Fig. 8A before fitting the annular thermoplastic seal. Fig. 8C is an exploded view of the sealing plate of Fig. 8A. Fig. 9A is a cross-sectional view of an upper sealing plate according to a sixth embodiment of the invention. Fig. 9B shows the sealing plate from Fig. 9A before fitting the annular thermoplastic seal. Fig. 9C is an exploded view of the sealing plate of Fig. 9A. Fig. 10A is a cross-sectional view of an upper sealing plate according to a seventh embodiment of the invention. Fig. 10B shows the sealing plate from Fig. 10A before fitting the annular thermoplastic seal. Fig. 10C is an exploded view of the sealing plate of Fig. 10A. Fig. 11A is a cross-sectional view of an upper sealing plate according to an eighth embodiment of the invention. Fig. 11B shows the sealing plate from Fig. 11A before fitting the annular thermoplastic seal. Fig. 11C is an exploded view of the sealing plate of Fig. 11A. DETAILED DESCRIPTION OF THE INVENTION

[0007] The invention is best understood by reference to the exemplary embodiment(s) illustrated in the figures of the drawing and described below.

[0008] Fig. Figure 1 shows a prior art reciprocating sleeve-type (or "spool" type) valve mechanism 100. An upper portion 101 threads into a valve body 102. In the case of subplate-mounted ("SPM" valves), 102 may be a subplate.

[0009] The valve is actuated by a piston 104 which responds to hydraulic pressure supplied via a pilot pressure port 114. An outer spring 108 and a concentric inner spring 110 acting on the end plate 112 position the piston 104 in the Fig. 1 when the hydraulic pilot pressure decreases to a certain level. Valve 100 is a normally closed valve ("NC valve") - that is, in the absence of hydraulic pressure at port 114, the valve, under the influence of springs 108 and 110, operatively closes the supply port to the functional port (and opens the functional port to the exhaust port).

[0010] The lower portion of valve 100 includes an upper polymer seal 130, a valve cage 116, a lower polymer seal 140, and a valve spool or sealing sleeve 118. The spool 118 slides within the inner bore of the cage 116 in response to the action of a valve stem 106 connected to the piston 104. A T-seal 120 and wiper / auxiliary seals 122 provide a seal between the inner bore of the valve cage 116 and the outer cylindrical surface of the spool 118. The outer surface of the valve cage 116 includes a circumferential groove for retaining an O-ring seal 124 for sealing against the walls of the bore in the valve body 102.

[0011] The valve spool 118 has an upper annular sealing surface 126 which abuts a surface 136 of a seal 130 when the valve is in the closed position and a lower annular sealing surface 128 which abuts a surface 146 of a seal 140 when the valve is in the open position.

[0012] The upper disc seal 130 includes a circumferential groove for an O-ring seal 132 and a groove in the wall of its central axial opening for a stem seal 134. Similarly, the lower seal 140 includes a circumferential groove for retaining the O-ring seal 142. In the illustrated valve, the central axial opening 144 of the sealing disc 140 is internally threaded for engagement with an insertion / removal tool (not shown).

[0013] The illustrated sealing plates can be used as an upper sealing plate and, in certain embodiments, as a lower sealing plate. Those skilled in the art will recognize that embodiments intended for use as a lower sealing plate need not include a groove on the inner diameter of the central axial opening for receiving a seal. Instead, the central axial opening in the lower sealing plate can be internally threaded to facilitate insertion and removal of the sealing plate into and from the bore by attachment to a corresponding externally threaded tool.

[0014] In operation, the functional port is in fluid communication with the vent port via vent port openings 152 in the valve cage 116 when the valve 100 is in the closed position. In the closed state, the supply port fluid communication with the central channel 154 via supply flow port openings 150 in the valve cage 116 (and thus the functional port) is blocked by the sealing engagement of the sealing surface 125 with the seal 130. When the valve 100 is in the open position, the spool 118 moves (as aligned in Fig. 1) downward until the sealing surface 128 engages the seal 140. This action closes fluid communication between the vent port and the functional port, and since the sealing surface 126 has consequently moved away from the surface 136 of the seal 130, fluid can flow from the supply port via openings 150 into the central channel 154 of the spool 118, through the central opening 144 in the seal 140, and out of the functional port.

[0015] It has been found that, in practice, the pressure of the sealing surface 126 on the polymer seal 130 and the pressure of the sealing surface 128 on the polymer seal 140 can, over time, cause these seals to deform. Most often, the deformation takes the form of coning of the sealing plate—that is, the central portion of the sealing plate deflects axially toward the spool. Such deformation can impair the sealing effectiveness of the valve.

[0016] Fig. Figure 2 shows a subplate-mounted valve 200 equipped with improved sealing washers. In particular, the upper seal 230 is different from the one shown in Fig. 4A and discussed below, and the lower seal 240 is of the type shown in Fig. 4B. In all other aspects, the valve 200 is identical to the valve 100 (in Fig. 1). The upper and lower ends of the spool 218 engage the upper seal 230 and the lower seal 240, respectively, when the spool moves in response to hydraulic pilot pressure. As will be appreciated by those skilled in the art, this means that many prior art SPM valves can be readily retrofitted with improved upper and lower sealing discs in accordance with the present invention.

[0017] Fig. Figure 3 shows a normally open, subplate-mounted valve 300 equipped with improved sealing washers. In particular, the upper seal 330 is different from the one shown in Fig. 4A and discussed below, and the lower seal 340 is of the type shown in Fig. 4B. The upper and lower ends of spool 318 engage upper seal 330 and lower seal 340, respectively, when the spool moves in response to hydraulic pilot pressure. Except for sealing discs 330 and 340, valve 300 is a conventional, normally open spool valve. As will be appreciated by those skilled in the art, this means that many prior art SPM valves can be readily retrofitted with improved upper and lower sealing discs.

[0018] As indicated by the cross-hatch patterns in the drawing figures, the sealing plates comprise at least two materials with different properties. The portion of the sealing plate that contacts the sealing surface of the gate valve comprises a thermoplastic material. Other portions of the sealing plate are made of a harder and / or stiffer material, such as a metal. A specific preferred metal is steel. This combination of materials results in a sealing plate with improved dimensional stability and deformation resistance, while also maintaining the sealing effectiveness of prior art single-material sealing plates.

[0019] Sections of the gasket sheet may contain DELRIN® polyoxymethylene or similar polymers. Polyoxymethylene (POM), also known as acetal, polyacetal, and polyformaldehyde, is an engineering thermoplastic used in precision parts requiring high stiffness, low friction, and excellent dimensional stability. Like many other synthetic polymers, it is manufactured by various chemical companies with slightly different formulas and is therefore sold under several trade names, such as Delrin, Celcon, Hostaform, etc.

[0020] POM is characterized by its high strength, hardness, and stiffness up to ~40 °C. POM has a density of ρ = 1,410-1,420 g / cm 3and is inherently opaque white due to its highly crystalline composition. POM is a tough material with an extremely low coefficient of friction, high abrasion resistance, high heat resistance, and low water absorption. It is dimensionally stable in contact with moisture and heat; resistant to chemicals, solvents, bending, and creep; and exhibits a high-gloss, low-friction surface.

[0021] A polyoxymethylene thermoplastic polymer can be prepared by the ionically initiated polymerization of formaldehyde + CH2 to obtain a linear molecule of the type -CH -CH = CH2 -. Individual molecules can contain over 1500 -CH2- units. Since the molecule has no side chains, dense crystals are formed.

[0022] POM is commercially available in granular form and can be molded into the desired shape by applying heat and pressure. The two most commonly used molding processes are injection molding and extrusion. Rotational molding and blow molding are also possible.

[0023] When delivered as extruded rod or extruded sheet, POM can be machined using conventional processes such as turning, milling, drilling, etc.

[0024] Other engineering plastics and thermoplastics may also be used to make the sealing sheets of the present invention.

[0025] Now on Fig. Referring to Figure 4A, there is shown an upper sealing plate 400 according to a first embodiment of the present description. The sealing plate 400 includes a thermoplastic body 412 in a generally annular configuration, having an upper, generally planar surface 402, an opposite lower, generally planar surface 404, and a central axial opening 408 providing a passage from the upper surface 402 to the lower surface 404. The peripheral surface 416 is generally cylindrical and may include a circumferential groove 406 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 400 and the bore of the mounting plate into which the valve is inserted.

[0026] The central axial bore 408 may have in its inner wall an undercut groove 410 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 400 and an actuator shaft xyz.

[0027] A metal reinforcement ring 414 is molded into the thermoplastic body 412 to provide additional strength to the seal plate 400. In a specific preferred embodiment, the metal reinforcement ring 414 is made of steel, and the thermoplastic body 412 comprises Delrin® polyoxymethylene. The seal plate 400 may be formed by injection molding or other molding techniques known in the art. The mold cavity may be provided with means for appropriately positioning the reinforcement ring 414 within the cavity before and during injection of the thermoplastic material. After the body 412 has cooled, the surfaces 402, 404, and / or 416 may be smoothed and polished, as desired, by machining and / or grinding, as is well known in the art. The sealing grooves 406 and 410 can be formed into the body 412 or subsequently machined into the body 412.The metal reinforcement ring 414 may be machined, stamped from semi-finished sheet metal, cut from semi-finished rods, formed from molten material, or manufactured by any other method known in the art.

[0028] Now on Fig. Referring to Figure 4B, a corresponding lower sealing plate 401 according to a first embodiment is shown. The sealing plate 401 includes a thermoplastic body 413 in a generally annular configuration, having an upper, generally planar surface 403, an opposite lower, generally planar surface 405, and a central axial opening 409 providing a passage from the upper surface 403 to the lower surface 405. The peripheral surface 417 is generally cylindrical and may include a circumferential groove 407 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 401 and the bore of the mounting plate into which the valve is inserted.

[0029] The central axial bore 409 may have an internal thread 411 for engagement with an insertion and removal tool (not shown) having a corresponding externally threaded shank.

[0030] A metal reinforcement ring 415 is molded into the thermoplastic body 413 to provide additional strength to the seal plate 401. In a specific preferred embodiment, the metal reinforcement ring 415 is made of steel, and the thermoplastic body 413 comprises Delrin® polyoxymethylene. The seal plate 401 may be formed by injection molding or other molding techniques known in the art. The mold cavity may be provided with means for appropriately locating the reinforcement ring 415 within the cavity before and during injection of the thermoplastic material. After the body 413 has cooled, the surfaces 403, 405, and / or 417 may be smoothed and polished, as desired, by machining and / or grinding, as is well known in the art.The sealing grooves 407 and 411 may be formed into the body 413 or subsequently machined or cut into the body 413. The metal reinforcement ring 415 may be machined, stamped from stock sheet, cut from stock rods, formed from molten material, or manufactured by any other method known in the art.

[0031] Now on Fig. 5 Referring to Fig. 1, there are shown an upper and a lower sealing plate according to a second embodiment of the invention. Fig. Figure 5A shows an upper metal sealing plate with a thermoplastic insert. The sealing plate without the thermoplastic insert is shown in Fig. 5B. The sealing plate 500 includes a metal body 520 in a generally annular configuration, having an upper, generally planar surface 502, an opposite lower, generally planar surface 504, and a central axial opening 508 providing a passage from the upper surface 502 to the lower surface 504. The peripheral surface 516 is generally cylindrical and may include a circumferential groove 506 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 500 and the bore of the mounting plate into which the valve is inserted.

[0032] The central axial bore 508 may have in its inner wall an undercut groove 510 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 500 and an actuator shaft xyz.

[0033] The metal sealing plate 500 has an annular cavity 522 with a generally T-shaped cross-section (see Fig. 5B) having an outwardly undercut groove 524 and an inwardly undercut groove 526. In a specific preferred embodiment, the metal body 520 is made of steel, and the thermoplastic insert 518 comprises Delrin® polyoxymethylene. The metal body 520 may be formed by machining a metal blank or by other methods known in the art. The annular cavity 522 may serve as a mold cavity for injection molding the thermoplastic insert 518. Alternatively, a generally annular blank of thermoplastic material having inner and outer diameters approximately equal to those of the annular cavity 522 may be heated to a temperature below the melting point of the material and then forced into the cavity 522.Those skilled in the art will appreciate that the thermoplastic material will at least partially flow into the undercut grooves 524 and 526, thereby anchoring the insert 518 in the cavity 522. After the insert 518 cools, the exposed surface of the insert 518 (at the bottom surface 504) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art.

[0034] As in Fig. 5A, the annular cavity 522 is disposed within the metal body 520 such that the thermoplastic insert 518 is located within the gate seal contact surface. Seal contact surfaces for both normally closed (NC) and normally open (NO) gate valves are shown. Fig. 6A, Fig. 7A, Fig. 8A, Fig. 9A, Fig. 10A and Fig. 11A show similar see-through views of slider contact surfaces.

[0035] Now on Fig. 5C and Fig. Referring to Figure 5D, a corresponding lower sealing plate 501 according to a second embodiment of the invention is shown. A lower metal sealing plate with a thermoplastic insert is shown in Fig. 5C. The sealing plate without the thermoplastic insert is shown in Fig. 5D. The sealing plate 501 includes a metal body 521 in a generally annular configuration, having an upper, generally planar surface 503, an opposite lower, generally planar surface 505, and a central axial opening 509 providing a passage from the upper surface 503 to the lower surface 505. The peripheral surface 517 is generally cylindrical and may include a circumferential groove 507 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 501 and the bore of the mounting plate into which the valve is inserted.

[0036] The central axial bore 509 may have an internal thread 511 for engagement with an insertion and removal tool (not shown) having a corresponding externally threaded shank.

[0037] The metal sealing plate 501 has an annular cavity 523 with a generally L-shaped cross section (see Fig. 5D) having an outwardly undercut groove 525 and an inwardly undercut groove 527. In a specific preferred embodiment, the metal body 521 is made of steel, and the thermoplastic insert 519 comprises Delrin® polyoxymethylene. The metal body 521 may be formed by machining a metal blank or by other methods known in the art. The annular cavity 523 may serve as a mold cavity for injection molding the thermoplastic insert 519. Alternatively, a generally annular blank of thermoplastic material having inner and outer diameters approximately equal to those of the annular cavity 523 may be heated to a temperature below the melting point of the material and then forced into the cavity 523.Those skilled in the art will appreciate that the thermoplastic material will at least partially flow into the undercut grooves 525 and 527, thereby anchoring the insert 519 in the cavity 523. After the insert 519 has cooled, the exposed surface of the insert 519 (at the bottom surface 505) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art.

[0038] As in Fig. 5C, the annular cavity 523 is disposed within the metal body 521 such that the thermoplastic insert 519 is located within the gate seal contact surface. Seal contact surfaces for both normally closed (NC) and normally open (NO) gate valves are shown.

[0039] Now on Fig. 6A and Fig. Referring to Figure 6B, there is shown an upper sealing plate according to a third embodiment of the invention. Fig. Figure 6A shows an upper metal sealing plate with a thermoplastic insert. The sealing plate without the thermoplastic insert is shown in Fig. 6B. The sealing plate 600 includes metal body portions 630 and 632 press-fitted together in a generally annular configuration, having an upper, generally planar surface 602, an opposite lower, generally planar surface 604, and a central axial opening 608 providing a passage from the upper surface 602 to the lower surface 604. The peripheral surface 616 is generally cylindrical and may include a circumferential groove 606 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 600 and the bore of the mounting plate into which the valve is inserted.

[0040] The central axial bore 608 may have in its inner wall an undercut groove 610 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 600 and the actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0041] When assembled (as shown in Fig. 6B), the metal sealing plate 600 includes an annular cavity 622 having a generally L-shaped cross-section and having a groove 626 extending inwardly therefrom. In a particular preferred embodiment, the metal body portions 630 and 632 are steel, and the thermoplastic insert 618 comprises Delrin® polyoxymethylene. The metal body portions 630 and 632 may be formed by machining a metal blank or by other methods known in the art. An interference fit is provided at the joint 634. Those skilled in the art will appreciate that the portion of the thermoplastic insert 618 that extends into the groove 626 serves to anchor the insert 618 within the cavity 622.The exposed surface of the insert 618 (at the lower surface 604) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art, to make its surface flush with the lower surface 604 of the metal body portions 630 and 632.

[0042] The thermoplastic insert 618 may be manufactured by machining, molding, or other methods known in the art. The upper surface of the insert 618 may be provided with an annular groove for retaining the seal 628, which may be an O-ring seal.

[0043] As in Fig. 6A, the annular cavity 622 is disposed between the metal body portions 630 and 632 such that the thermoplastic insert 618 is disposed within the contact surface of the slide seal.

[0044] Now on Fig. 7A and Fig. Referring to Figure 7B, there is shown an upper sealing plate according to a fourth embodiment of the invention. Fig. Figure 7A shows an upper metal sealing plate with a thermoplastic insert. The sealing plate without the thermoplastic insert is shown in Fig. 7B. The sealing plate 700 includes a metal body 720 having a generally annular configuration, with an upper, generally planar surface 702, an opposite lower, generally planar surface 704, and a central axial opening 708 providing a passage from the upper surface 702 to the lower surface 704. The peripheral surface 716 is generally cylindrical and may include a circumferential groove 706 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 700 and the bore of the mounting plate into which the valve is inserted.

[0045] The central axial bore 708 may have in its inner wall an undercut groove 710 for holding a seal, which may be a T-seal (as shown in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 700 and the actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0046] As in Fig. 7B, the metal sealing plate 700 includes an annular cavity 722 open to the surface 704. The outer and inner walls of the annular cavity 722 include grooves 724 and 726, respectively, adapted to receive retaining clips 740 and 742. When installed, the retaining clips 740 and 742 provide shoulders in the annular cavity 722 that retain the thermoplastic insert within the cavity 722. In the illustrated embodiment, the retaining clip 740 is an inner Circlip™ retaining ring and the retaining clip 742 is an outer Circlip™ retaining ring.

[0047] In a specific preferred embodiment, the metal body 720 is made of steel, and the thermoplastic insert 718 comprises Delrin® polyoxymethylene. The metal body 720 may be formed by machining a metal blank or by other methods known in the art. The exposed surface of the insert 718 (at the bottom surface 704) may be smoothed and / or polished, as desired, by machining and / or grinding, as is well known in the art, to make its surface flush with the bottom surface 704 of the metal body 720.

[0048] The thermoplastic insert 718 may be manufactured by machining, molding, or other methods known in the art. The upper surface of the insert 718 may be provided with an annular groove for retaining the seal 728, which may be an O-ring seal.

[0049] As in Fig. 7A, the annular cavity 722 is disposed in the metal body 720 such that the thermoplastic insert 718 is disposed within the contact surface of the slide seal.

[0050] Now on Fig. 8A, Fig. 8B and Fig. Referring to Figure 8C, there is shown an upper sealing plate according to a fifth embodiment of the invention. Fig. Figure 8A shows an upper metal sealing plate with a thermoplastic insert. Fig. Figure 8B shows the sealing plate without the thermoplastic insert. Fig. 8C shows an exploded view of the sealing plate 800. The sealing plate 800 includes a metal body 820 in a generally annular configuration, having an upper, generally planar surface 802, an opposite lower, generally planar surface 804, and a central axial opening 808 providing a passage from the upper surface 802 to the lower surface 804. The peripheral surface 816 is generally cylindrical and may include a circumferential groove 806 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 800 and the bore of the mounting plate into which the valve is inserted.

[0051] The central axial bore 808 may have in its inner wall an undercut groove 810 for holding a seal, which may be a T-seal (as shown in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 800 and the actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0052] As in Fig. 8B, the metal sealing plate 800 includes an annular cavity 822 open to the surface 804. The outer and inner walls of the annular cavity 822 are threaded in the portion nearest the surface 804. The thermoplastic insert 818 is retained within the annular cavity 822 by an outer retaining ring 840 and an inner retaining ring 842. The retaining ring 840 is externally threaded to engage the threads on the outer wall of the cavity 822, and the retaining ring 842 is internally threaded to engage the threads on the inner wall of the cavity 822. Wrench holes 844 in the upper surface 802 of the metal body 820 and wrench holes 846 and 848 in the retaining rings 840 and 842, respectively, may be provided to facilitate assembly of the sealing plate 800.

[0053] In a specific preferred embodiment, the metal body 820 is made of steel, and the thermoplastic insert 818 comprises Delrin® polyoxymethylene. The metal body 820 may be formed by machining a metal blank or by other methods known in the art. The exposed surface of the insert 818 (at the bottom surface 804) may be smoothed and / or polished, as desired, by machining and / or grinding, as is well known in the art, to make its surface flush with the bottom surface 804 of the metal body 820.

[0054] The thermoplastic insert 818 may be manufactured by machining, molding, or other methods known in the art. The upper surface of the insert 818 may be provided with an annular groove 850 for retaining the seal 828, which may be an O-ring seal.

[0055] As in Fig. 8A, the annular cavity 822 is disposed in the metal body 820 such that the thermoplastic insert 818 is disposed within the contact surface of the slide seal.

[0056] Now on Fig. 9A, Fig. 9B and Fig. Referring to Figure 9C, there is shown an upper sealing plate according to a sixth embodiment of the invention. Fig. 9A shows an upper metal sealing plate with a thermoplastic insert. In Fig. Figure 9B shows the sealing plate without the thermoplastic insert. Fig. Figure 9C shows an exploded view of the sealing plate 900.

[0057] The sealing plate 900 includes metal body portions 930 and 932 that thread together to form a generally annular sealing plate having an upper, generally planar surface 902, an opposite lower, generally planar surface 904, and a central axial opening 908 providing a passage from the upper surface 902 to the lower surface 904. The peripheral surface 916 is generally cylindrical and may include a circumferential groove 906 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 900 and the bore of the mounting plate into which the valve is inserted.

[0058] The central axial bore 908 may have in its inner wall an undercut groove 910 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 900 and an actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0059] Body portion 932 is generally disc-shaped and externally threaded. Body portion 930 is generally annular and internally threaded. Wrench holes 944 in body portion 932 and wrench holes 946 in body portion 930 may be provided to receive a tool (not shown) for assembling and disassembling upper seal plate 900.

[0060] When assembled (as shown in Fig. 9B), the metal body portions 930 and 932 form an annular cavity 922 having a generally L-shaped cross-section and outwardly defining a groove 926. In a specific preferred embodiment, the metal body portions 930 and 932 are steel, and the thermoplastic insert 918 comprises Delrin® polyoxymethylene. The metal body portions 930 and 932 may be formed by machining from metal blanks or by other methods known in the art. A threaded connection is provided at the junction 934. Those skilled in the art will appreciate that the portion of the thermoplastic insert 918 that extends into the groove 926 serves to anchor the insert 918 within the cavity 922.The exposed surface of the insert 918 (at the lower surface 904) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art, to make its surface flush with the lower surface 904 of the metal body portions 930 and 932.

[0061] The thermoplastic insert 918 may be manufactured by machining, molding, or other methods known in the art. The inner surface of the insert 918 may be provided with an annular groove 952 for retaining a seal 954, which may be an O-ring seal. An inner circumferential groove 956 may be provided below the threaded portion of the body portion 930 for retaining a seal 958, which may be an O-ring seal. The seals 954 and 958 may provide a fluid-tight seal between the thermoplastic insert 918 and metal body portions 930 and 932, respectively.

[0062] As in Fig. 9A, the annular cavity 922 is disposed between the metal body portions 930 and 932 such that the thermoplastic insert 918 is disposed within the contact surface of the slide seal.

[0063] Now on Fig. 10A, Fig. 10B and Fig. Referring to Figure 10C, there is shown an upper sealing plate according to a seventh embodiment of the invention. Fig. 10A shows an upper metal sealing plate with a thermoplastic insert. In Fig. Figure 10B shows the assembled sealing plate without the thermoplastic insert. Fig. Figure 10C shows an exploded view of the upper sealing plate 1000.

[0064] The sealing plate 1000 includes metal body portions 1030, 1032, and 1036 held together by machine screws 1060 to form a generally annular sealing plate having an upper, generally planar surface 1002, an opposite lower, generally planar surface 1004, and a central axial opening 1008 providing passage from the upper surface 1002 to the lower surface 1004. The peripheral surface 1016 is generally cylindrical and may include a circumferential groove 1006 for retaining a seal, which may be an O-ring seal, for sealing between the sealing plate 1000 and the bore of the mounting plate into which the valve is inserted.

[0065] The central axial bore 1008 may have in its inner wall an undercut groove 1010 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 1000 and an actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0066] The body portion 1036 is generally disc-shaped and includes an annular projection 1072 on its lower surface. Countersunk holes 1062 are sized and spaced apart to receive screws 1060 and extend from the upper surface of the disc 1036 to its underside. The body portions 1030 and 1032 are generally annular and include a plurality of threaded bores 1064 sized and spaced apart to receive and engage machine screws 1060.

[0067] Body portion 1030 has an inner shoulder 1070, and body portion 1032 has an outer shoulder 1070'. When assembled, shoulders 1070 and 1070' together form a rabbet into which annular projection 1072 on the underside of disc 1036 can fit. This rabbeted connection can provide more precise alignment of body portions 1030, 1032, and 1036 than that provided solely by screws 1060.

[0068] When assembled (as shown in Fig. 10B), the metal body portions 1030, 1032, and 1036 form an annular cavity 1022 having a generally T-shaped cross-section. In a specific preferred embodiment, the metal body portions 1030, 1032, and 1036 are made of steel, and the thermoplastic insert 1018 comprises Delrin® polyoxymethylene. The metal body portions 1030, 1032, and 1036 may be formed by machining from metal blanks or by other methods known in the art. The exposed surface of the insert 1018 (at the lower surface 1004) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art, to make its surface flush with the lower surface 1004 of the metal body portions 1030, 1032 and 1036.

[0069] The thermoplastic insert 1018 may be manufactured by machining, molding, or other methods known in the art. The outer peripheral surface of the insert 1018 may be provided with a shoulder 1066 for retaining a seal 1074, which may be an O-ring seal. The inner surface of the generally annular thermoplastic insert 1018 may have a shoulder 1068 for retaining a seal 1076, which may be an O-ring seal. The seals 1074 and 1076 may provide a fluid-tight seal between the thermoplastic insert 1018 and the metal body portions 1030, 1032, and 1036.

[0070] As in Fig. 10A in phantom, the annular cavity 1022 is disposed between the metal body portions 1030, 1032, and 1036 such that the thermoplastic insert 1018 is disposed within the contact surface of the slide seal.

[0071] Now on Fig. 11A, Fig. 11B and Fig. Referring to Fig. 11C, there is shown an upper sealing plate according to an eighth embodiment of the invention. Fig. 11A shows an upper metal sealing plate with a thermoplastic insert. In Fig. Figure 11B shows the assembled sealing plate without the thermoplastic insert. Fig. Figure 11C shows an exploded view of the upper sealing plate 1100.

[0072] The sealing plate 1100 is the Fig. 10, but does not have the crimped joint between the metal body portions. The seal plate 1100 includes metal body portions 1130, 1132, and 1136 held together by machine screws 1160 to form a generally annular seal plate having an upper, generally planar surface 1102, an opposite lower, generally planar surface 1104, and a central axial opening 1108 providing a passage from the upper surface 1102 to the lower surface 1104. The circumferential surface 1116 is generally cylindrical and may include a circumferential groove 1106 for retaining a gasket, which may be an O-ring seal, for sealing between the seal plate 1100 and the bore of the mounting plate into which the valve is inserted.

[0073] The central axial bore 1108 may have in its inner wall a groove 1110 for holding a seal, which may be a T-seal (as in Fig. 1, Fig. 2 and Fig. 3) for sealing between the upper sealing plate 1100 and an actuator shaft xyz (as shown in Fig. 1, Fig. 2 and Fig. 3).

[0074] The body portion 1136 is generally disc-shaped. Countersunk holes 1162 are sized and spaced to receive screws 1160 and extend from the top surface of the disc 1136 to the bottom thereof. The body portions 1130 and 1132 are generally annular and include a plurality of threaded bores 1164 sized and spaced to receive and engage machine screws 1160.

[0075] When assembled (as shown in Fig. 11B), the metal body portions 1130, 1132, and 1136 form an annular cavity 1122 having a generally T-shaped cross-section. In a specific preferred embodiment, the metal body portions 1130, 1132, and 1136 are made of steel, and the thermoplastic insert 1118 comprises Delrin® polyoxymethylene. The metal body portions 1130, 1132, and 1136 may be formed by machining metal blanks or by other methods known in the art. The exposed surface of the insert 1118 (at the lower surface 1104) may be smoothed and / or polished as desired by machining and / or grinding, as is well known in the art, to make its surface flush with the lower surface 1104 of the metal body portions 1130, 1132 and 1136.

[0076] The metal body portion 1130 may have a circumferential shoulder 1180. In the assembled state (as in Fig. 11B), the shoulder 1180 and the underside of the metal body portion 1136 form a groove 1106. The metal body portion 1132 may have an inner shoulder 1182. In the assembled state (as shown in Fig. 11B), the shoulder 1182 and the underside of the metal body portion 1136 form a groove 1110.

[0077] The thermoplastic insert 1118 may be manufactured by machining, molding, or other methods known in the art. The outer peripheral surface of the insert 1118 may be provided with a shoulder 1166 for retaining a seal 1174, which may be an O-ring seal. The inner surface of the thermoplastic insert 1118 may have a shoulder 1168 for retaining a seal 1176, which may be an O-ring seal. The seals 1174 and 1176 may provide a fluid-tight seal between the thermoplastic insert 1118 and the metal body portions 1130, 1132, and 1136.

[0078] As in Fig. 11A in phantom, the annular cavity 1122 is disposed between the metal body portions 1130, 1132, and 1136 such that the thermoplastic insert 1118 is disposed within the contact surface of the slide seal.

[0079] While specific embodiments of the present invention have been illustrated and described, they are not intended to limit the scope of this patent. Those skilled in the art will recognize that various changes and modifications may be made without departing from the spirit and scope of the present invention as encompassed by the following claims.

Claims

[1] Seal (500, 501; 600; 900; 1000; 1100) for a pilot-operated slide valve, comprising: a metal disc (520, 521; 630, 632; 930, 932; 1032, 1030, 1036; 1130, 1132, 1136) having a generally planar first surface, a generally planar second surface, a generally cylindrical outer surface, and a central axial opening (508, 509; 608; 808; 908; 1008; 1108) extending from the first surface to the second surface; an annular groove (522, 523; 626; 922; 1022; 1122) in the second surface having a first, smaller width in a first portion adjacent to the second surface and a second, larger width in a portion remote from the second surface; and a thermoplastic insert (518, 519; 618; 918; 1018; 1118) in the annular groove (522, 523; 626; 922; 1022; 1122) having at least one generally planar surface substantially flush with the second surface of the metal disc (520, 521; 630, 632; 930, 932; 1032, 1030, 1036; 1130, 1132, 1136). [2] The seal of claim 1, wherein the first surface is a top surface (502, 602, 902, 1002, 1102) and the second surface is a bottom surface (504, 604, 904, 1004, 1104). [3] A seal for a pilot-operated spool valve according to claim 2, wherein the central axial opening (508) in the metal disc (520) has a first portion adjacent the upper surface (502) having a first inner diameter, a second portion adjacent the lower surface (504) having a second inner diameter equal to the first inner diameter, and a third portion (510) between the first portion and the second portion having a third inner diameter greater than the first and second inner diameters. [4] The seal of claim 1, wherein the first surface is a lower surface (505) and the second surface is an upper surface (503). [5] Seal according to claim 4, wherein the central axial opening (509) in the metal disc (501) is provided with an internal thread (511). [6] Seal (600) according to claim 2, wherein the metal disc (630, 632) comprises: a metal body portion (632) having a generally planar upper surface, a generally planar lower surface, a central axial opening extending from the upper surface to the lower surface, and a stepped outer surface (634) having a first portion having a first outer diameter and a second portion having a second outer diameter greater than the first outer diameter; a metal ring (630) having a generally planar upper surface, a generally planar lower surface, a central axial opening extending from the upper surface to the lower surface, and having a first portion with a first inner diameter substantially equal to the first outer diameter of the metal body portion (632) and a second portion with a second inner diameter greater than the first inner diameter, the metal ring (630) having a first outer portion with a first thickness, a second inner portion with a second thickness less than the first thickness, and a third portion between the first portion and the second portion with a third thickness less than the second thickness, such that,when the metal body portion (632) and the metal ring (630) are pressed together with an interference fit between the first portion of the metal body portion (632) and the first portion of the metal ring (630), an annular cavity is formed between the metal body portion (632) and the metal ring (630), the annular cavity forming the annular groove (626) and being open to the lower surface (604); and, wherein the thermoplastic insert (618) is inserted into the cavity and has a surface that is substantially flush with the lower surface of the metal body portion (632) and the metal ring (630). [7] The seal of claim 6, wherein the thermoplastic insert (618) comprises polyoxymethylene. [8] The seal of claim 6, further comprising a groove in the upper surface of the thermoplastic insert (618) and a seal (628) in the groove. [9] Seal (700) for a pilot-operated slide valve, comprising: a metal disc (720) having a generally planar upper surface (702), a generally planar lower surface (704), a central axial opening (708) extending from the upper surface (702) to the lower surface (704), and an annular groove (722) in the lower surface (704) having a generally rectangular cross-section such that the groove has an inner wall and an outer wall; a first groove (726) in the inner wall of the annular groove (722), a second groove (724) in the outer wall of the annular groove (722); an annular thermoplastic insert (718) in the annular groove (722) having a generally T-shaped cross-section with an inner shoulder and an outer shoulder, the thermoplastic insert (718) having at least one generally planar surface substantially flush with the lower surface (704) of the metal disc (720); a first retainer (742) in the first groove (726) in the inner wall of the annular groove (722) which bears against the inner shoulder of the thermoplastic insert (742); and, a second holder (740) in the second groove (724) in the outer wall of the annular groove (722) which bears against the outer shoulder of the thermoplastic insert (718). [10] The seal of claim 9, wherein the thermoplastic insert (718) is molded from polyoxymethylene. [11] The seal of claim 9, wherein the first retainer (742) is an outer spring clip. [12] The seal of claim 9, wherein the second retainer (740) is an inner spring clip. [13] The seal of claim 9, further comprising an annular groove in the thermoplastic insert (718) and a seal (728) in the groove. [14] A seal according to claim 13, wherein the seal (728) located in the groove is an O-ring seal. [15] Seal (800) for a pilot-operated slide valve, comprising: a metal disc (820) having a generally planar upper surface (802), a generally planar lower surface (804), a central axial opening (808) extending from the upper surface (802) to the lower surface (804), and an annular groove (822) in the lower surface (804) having a generally rectangular cross-section, such that the groove (822) has an inner wall and an outer wall, an external thread in a portion of the inner wall adjacent the lower surface (804) of the metal disc (820), and an internal thread in a portion of the outer wall adjacent the lower surface (804) of the metal disc (820); an annular thermoplastic insert (818) in the annular groove (822) having a generally T-shaped cross-section with an inner shoulder and an outer shoulder, the thermoplastic insert (818) having at least one generally planar surface substantially flush with the lower surface of the metal disc (820); a first internally threaded metal ring (848) configured and spaced to engage the external thread in the portion of the inner wall adjacent the lower surface of the metal disc (820) and to bear against the inner shoulder of the thermoplastic insert (818); and a second externally threaded metal ring (846) configured and spaced to engage the internal thread in the portion of the outer wall adjacent the lower surface of the metal disk (820) and to bear against the outer shoulder of the thermoplastic insert (818). [16] The seal of claim 15, wherein the thermoplastic insert (818) is molded from polyoxymethylene. [17] The seal of claim 15, further comprising an annular groove in the thermoplastic insert (818) and a seal (828) in the groove. [18] The seal of claim 15, further comprising wrench holes (844, 846, 848) in the metal disc (820), the first metal ring (848), and the second metal ring (846). [19] Seal (900) according to claim 2, wherein the metal disc (930, 932) comprises: a metal body portion (932) having a generally flat upper surface, a generally flat lower surface, a central axial opening extending from the upper surface to the lower surface, a stepped outer periphery consisting of a first externally threaded portion adjacent the upper surface having a first, larger outer diameter and a second, non-threaded portion adjacent the lower surface having a second, smaller outer diameter; a metal ring (930) having an upper surface and a lower surface and a stepped inner surface with a first internally threaded portion adjacent to the upper surface having a first, larger inner diameter and a non-threaded portion adjacent to the lower surface having a second, smaller inner diameter, such that when the metal body portion (932) is screwed into the metal ring (930), an annular cavity is created, the cavity forming the annular groove (922); wherein the thermoplastic insert (918) is annular and has a shoulder on its outer periphery which is held in the annular cavity on the stepped inner surface of the metal ring (930). [20] The seal of claim 19, wherein the thermoplastic insert (918) is molded from polyoxymethylene. [21] The seal of claim 19, further comprising an annular groove in the thermoplastic insert (918) and a seal (954) in the groove. [22] The seal of claim 19, further comprising wrench holes (944, 946) in the metal body portion (932) and the metal ring (930). [23] The seal of claim 19, further comprising an O-ring seal (958) between the thermoplastic insert (918) and the metal ring (930). [24] Seal (1000) according to claim 2, wherein the metal disc (1030, 1032, 1036) comprises: a metal body portion (1036) having a generally planar upper surface, a generally planar lower surface, a central axial opening extending from the upper surface to the lower surface, and a plurality of through countersunk holes (1062) extending from the upper surface (1002) to the lower surface (1004); an annular projection on the lower surface of the metal body portion (1036) having an outer diameter and an inner diameter; a first metal ring (1030) having a stepped upper surface and a flat lower surface, an outer diameter equal to the outer diameter of the metal body portion (1036), a stepped inner surface having a first portion adjacent the upper surface with a first, larger inner diameter and a second portion adjacent the lower surface with a second, smaller inner diameter and a plurality of threaded bores (1062) open to the upper surface; a second metal ring (1032) having a stepped upper surface and a flat lower surface, an inner diameter equal to the inner diameter of the metal body portion (1036), a stepped outer surface with a first portion adjacent to the upper surface having a first, smaller outer diameter and a second portion adjacent to the lower surface having a second, larger outer diameter and a plurality of threaded bores (1064) open to the upper surface; wherein the seal (1000) further comprises a plurality of machine screws (1060) extending through the through holes (1062) in the metal body portion (1036) and engaging the threaded bores (1064) in the first metal ring (1030) and the second metal ring (1032) such that the metal body portion (1036), the first metal ring (1030) and the second metal ring (1032) form an annular cavity having a generally T-shaped cross-section and open to the lower surface, the annular cavity forming the annular groove (1022); wherein the thermoplastic insert (1018) is inserted into the annular cavity and has an exposed lower surface that is flush with the lower surfaces of the first metal ring (1030) and the second metal ring (1032), wherein the thermoplastic insert is annular and has a shoulder on its outer periphery and a shoulder on its inner periphery that are held in the annular cavity by the stepped inner surface of the outer metal ring (1030) and by the stepped outer surface of the inner metal ring (1032). [25] Seal according to claim 24, wherein the thermoplastic insert (1018) consists of polyoxymethylene. [26] A gasket according to claim 24, wherein the annular projection on the metal body portion (1036) forms a hemmed joint with the stepped upper surface of the first metal ring (1030) and the stepped upper surface of the second metal ring (1032). [27] The seal of claim 24, further comprising a first O-ring seal between the thermoplastic insert (1018) and the inner metal ring (1032) and a second O-ring seal between the thermoplastic insert (1018) and the outer metal ring (1030). [28] Seal (1100) according to claim 2, wherein the metal disc (1130, 1132, 1136) comprises: a metal body portion (1136) having a generally planar upper surface, a generally planar lower surface, a central axial opening extending from the upper surface to the lower surface, and a plurality of through countersunk holes (1164) extending from the upper surface to the lower surface; a first metal ring (1130) having a flat upper surface and a flat lower surface, an outer diameter equal to the outer diameter of the metal disc, a stepped inner surface having a first portion adjacent the upper surface with a first, larger inner diameter and a second portion adjacent the lower surface with a second, smaller inner diameter and a plurality of threaded bores (1164) open to the upper surface; a second metal ring (1132) having a flat upper surface and a flat lower surface, an inner diameter equal to the inner diameter of the metal disc, a stepped outer surface having a first portion adjacent the upper surface with a first, smaller outer diameter and a second portion adjacent the lower surface with a second, larger outer diameter and a plurality of threaded bores (1164) open to the upper surface; wherein the seal further comprises a plurality of machine screws (1160) extending through the through holes (1164) in the metal body portion (1136) and engaging the threaded bores (1164) in the first metal ring (1130) and the second metal ring (1132) such that the metal body portion (1136), the first metal ring (1130), and the second metal ring (1132) form an annular cavity of generally T-shaped cross-section open to the lower surface, the annular cavity forming the annular groove (1122); and wherein the thermoplastic insert (1118) in the annular cavity has an exposed lower surface that is flush with the lower surfaces of the first metal ring (1130) and the second metal ring (1132), the thermoplastic insert being annular and having a shoulder on its outer periphery and a shoulder on its inner periphery that are held in the annular cavity by the stepped inner surface of the outer metal ring (1130) and by the stepped outer surface of the inner metal ring (1132). [29] Seal according to claim 28, wherein the thermoplastic insert (1118) consists of polyoxymethylene. [30] The seal of claim 28, further comprising a first O-ring seal between the thermoplastic insert (1118) and the inner metal ring (1132) and a second O-ring seal between the thermoplastic insert (1118) and the outer metal ring (1130). [31] Pilot-operated slide valve comprising: a generally cylindrical cage having a central axial cavity open at both ends and a plurality of generally radial openings connecting the central axial cavity to the outer cylindrical surface of the cage; a slider configured to be slidable within the central axial cavity of the cage and having a first sealing surface at a first end and a second sealing surface at an opposite second end; a seal according to any one of claims 1 to 30, configured to engage the first sealing surface of the slider when the slider is at a first position within the central axial cavity of the cage.

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