Method for forming a seal ring and an intermetallic seal

Abstract

The present invention is a seal ring for forming a metal-to-metal seal between two opposing metal surfaces. The seal ring comprises an expandable body and a metal jacket mounted around the expandable body. The metal jacket has a discontinuity that extends around the inner or outer circumference of the expandable body. The expandable body is adapted to expand toward or into the discontinuity when inflated, pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface to form a seal.

Description

Technical Field

[0001] The present invention relates to a sealing ring or gasket and a method of forming a metal-to-metal seal. In particular, but not limited thereto, the present invention relates to a sealing ring for use in simultaneously sealing two portions of a vacuum chamber.

Background Art

[0002] Metal sealing rings are often used to provide an airtight or liquidtight seal between two metal surfaces, such as between the flanged joints of two vacuum chambers joined to each other. In some applications, the metal sealing ring is a flat circular metal gasket made of a relatively soft metal such as copper or aluminum, and is generally compressed between metal surfaces or flanges such as "CF" flanges made of a harder metal such as stainless steel. Each of the CF flanges is provided with a circular ridge or "knife edge" that bites into each face of the gasket, causing the metal of the gasket to be extruded around the knife edge, thereby forming a seal between the two metal surfaces. The flanges and the metal gasket can be used, for example, to form a very effective seal in an ultra-high vacuum system, but have several drawbacks, including the need for careful alignment ("fitting") of the flange and the metal gasket and a high clamping force. If the compression load on the gasket is non-uniform or too high, the quality of the seal can also be significantly reduced.

[0003] Generally, metal surfaces include fine irregularities, i.e., irregularities in the height of the surface. When two hard metal surfaces are in contact, the irregularities do not easily deform with respect to each other, and as a result, passages through which a fluid (e.g., a gas or a liquid) can be transferred remain between the irregularities.

[0004] Metal seals work by utilizing the principle of plastic deformation of a soft metal layer into irregularities on a hard metal surface. This process is sometimes called "keying in," where the passages between the irregularities are closed or significantly reduced in size, thereby forming an effective seal. This process is interrupted when the soft metal surface moves laterally over the hard metal surface. The sealing element (e.g., a sealing ring) can also be damaged by such lateral movement, potentially preventing the formation of an effective seal. Therefore, to enable precise engagement of the sealing surfaces and prevent damage to the sealing element, the sealing surfaces are usually in contact and compressed along the normal direction, i.e., perpendicular to the surface. In particular, ultra-high vacuum (UHV) sealing technology typically requires that the metal surfaces engage with each other in a direction perpendicular to their surfaces.

[0005] Figure 1A shows a schematic cross-sectional view of a metal seal ring 101 deformed against an uneven metal surface 103 by a compressive force directed perpendicular to the surface 103, resulting in the seal ring "keying in" to the irregularities of the metal surface 103. Figure 1B shows how the failure of the metal seal ring to conform to the irregularities of the metal surface 103 when the compressive force includes a component 107 directed laterally to the metal surface results in multiple potential leak paths 109 that can allow fluid to be transferred through the seal, i.e., between the seal ring 101 and the metal surface 103.

[0006] In some applications, geometric constraints may prevent surfaces from being aligned along a direction perpendicular to the surface. For example, some vacuum chambers may be manufactured with angled segments (sectors) that need to be joined together, such as in the case of annular or ellipsoidal (e.g., spherical) vacuum chambers where the segments are arranged like an orange bag. In such cases, it may be impossible to assemble the vacuum chamber without the segments having to move laterally relative to each other to some extent. Even when surfaces can be aligned along a perpendicular direction, lateral movement of surfaces relative to each other can still occur due to unbalanced forces applied to the surfaces, such as those resulting from tightening bolts one at a time around the circumference of a flange.

[0007] Figure 2 shows a segmented annular vacuum chamber 201 formed from six equiangular segments, of which only three segments 203, 205, and 207 are shown in the figure. A seal ring 209 is provided between the sealing surfaces 211 of the segments. During the assembly of the vacuum chamber 201, the final segment 205 is positioned along the radial installation direction, i.e., along the direction toward the central axis of the vacuum chamber 201. Thus, the relative motion of the final segment 205 with respect to each of the other two segments 203, 207 includes both a tangential component (i.e., a component perpendicular to the adjacent surface 209) and a radial component (i.e., a component parallel to the surface 209). The tangential component of the motion generates a compressive force that deforms the seal ring 209 to form a (key-in) seal, while the radial component of the motion may reduce the extent to which the seal ring 209 can deform into irregularities on the metal surface (as described above, see, for example, Figure 1B), thereby reducing the effectiveness of the seal. The thickness of the metal seal ring 209 is also limited by the gaps between segments 203, 205, and 207 during the assembly of the vacuum chamber.

[0008] International Publication No. 2020254543 describes an inflatable metal seal ring for forming a metal-to-metal seal between two opposing metal surfaces. The metal seal ring comprises a tubular metal body and an inlet tube extending from the body for introducing internal pressure into the body. The body is adapted to deform under internal pressure on each of the opposing metal surfaces to form a seal. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] International Publication No. 2020254543 [Overview of the project] [Problems that the invention aims to solve]

[0010] This disclosure seeks to overcome or at least mitigate the problems described above in existing methods for forming intermetallic seals. [Means for solving the problem]

[0011] According to a first aspect of the present invention, a seal ring or gasket is provided for forming a metal-to-metal seal between two opposing metal surfaces, the gasket comprising an expandable body in the form of a closed loop and a metal jacket having a discontinuity that extends at least partially around the closed loop and around the outer surface of the expandable body and extends around the closed loop, the expandable body being configured to push open the opposing portion of the metal jacket adjacent to the discontinuity when expanded to form a seal when in use.

[0012] According to a second aspect of the present invention, a gasket or seal ring is provided for forming a metal-to-metal seal between two opposing metal surfaces. The seal ring comprises an expandable or inflatable ring-shaped body (e.g., an expandable ring-shaped body) and a metal jacket (e.g., a substantially tubular metal jacket) disposed around, wrapped around, or attached to the ring-shaped body. The metal jacket has a discontinuity (e.g., a break or opening). In other words, the metal jacket may have, for example, a divided tube around the ring of the ring-shaped body. The discontinuity extends around the inner or outer circumference of the ring-shaped body (i.e., the inner or outer boundary of the ring-shaped body). The ring-shaped body is adapted to expand toward or into the discontinuity when expanded, pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface (e.g., from outside the plane of the ring-shaped body in opposite directions) to form a seal.

[0013] Embodiments of the present invention provide a gasket having a body that expands or inflates under internal pressure to press a surrounding metal jacket against first and second metal surfaces, thereby creating a seal between the surfaces. Because the body expands during use, the body and metal jacket can be fully housed within a groove in the first surface so that the second surface can be brought to a position relative to the first surface from any direction without contacting the gasket or damaging the gasket. The expansion of the body then forces the metal jacket open around the entire closed loop, creating a seal. In some implementations, the body may be fitted to expand (substantially) elastically, while the metal jacket is fitted to deform plastically in response to the expansion of the body. For example, the body may be fitted to be more elastic than the metal jacket, which allows greater force to be applied to the metal jacket and thus a more effective seal can be achieved.

[0014] Discontinuities in the metal jacket may allow a larger proportion of force to be used to expand the expandable body and deform the metal jacket relative to the metal surface (compared to a metal jacket without such discontinuities). In some cases, less metal may be required to fabricate the metal jacket. The contact area between the metal jacket and the metal surface may increase by expanding the expandable body toward or into the discontinuity. For example, a portion of the cross-section of the metal jacket adjacent to the discontinuity that initially curves away from the metal surface may be flattened or straightened relative to the metal surface as the expandable body expands and increases the contact area between the metal jacket and each metal surface. Increasing the contact area may result in a more effective (e.g., lower leakage rate) and / or more robust seal.

[0015] After the metal-to-metal seal is formed, the metal jacket provides an impermeable barrier that prevents fluids (e.g., gases or liquids) from entering or leaving the central region enclosed by the expandable body. The metal jacket extends continuously around the expandable body; that is, the metal jacket has no discontinuities (e.g., breaks or openings) other than discontinuities that extend around the loops of the expandable body.

[0016] Generally, the discontinuity of the metal jacket extends around the outer circumference (i.e., the radial outermost boundary) of the expandable body so that the metal jacket extends between the expandable body and the central region surrounded or enclosed by the expandable body. Alternatively, in some embodiments, the discontinuity extends around the inner circumference of the expandable body so that the metal jacket extends between the expandable body and the radially outer region of the expandable body.

[0017] The expandable body may be adapted to expand axially when expanding toward an opposing metal surface, before or during expansion toward or into a discontinuity in the metal jacket. For example, the expandable body may be adapted to expand along an axial direction defined with respect to the central axis of the seal ring (accompanied by expansion of the seal ring toward or into a discontinuity, radially along the central axis). The expandable body may be adapted so that the amount of axial expansion exceeds the amount of radial expansion, at least before the metal jacket contacts an opposing metal surface.

[0018] At least before expansion, the outer surface of the expandable body may have a radial cross-section (defined with respect to the central axis of the seal ring) with recesses facing the discontinuities in the metal jacket. In some implementations, the radial cross-section of the outer surface of the expandable body may be C-shaped.

[0019] Preferably, the metal jacket contacts the expandable body around the outer or inner circumference of the expandable body on the opposite side of the discontinuity. For example, the discontinuity may extend around the outer circumference of the expandable body, integrated with the metal jacket that contacts the inner circumference of the expandable body. That is, the discontinuity may be positioned radially outward with respect to the position where the metal jacket contacts the expandable body before expansion.

[0020] In some implementations, the metal jacket includes one or more outward-facing ridges (i.e., projections formed on the outer surface of the metal jacket) that deform against opposing metal surfaces when the expandable body is expanded to form a seal. Each ridge is preferably located on one of each opposing portion of the metal jacket. Expanding the expandable body may bring one or more ridges located on the outside of the metal jacket into contact with a second metal surface and / or seal groove. The edges may increase the contact pressure between the metal jacket and the second metal surface and / or seal groove. In some implementations, the ridges may be plastically deformable.

[0021] The metal jacket and the expandable body may be formed from different materials, with the metal jacket material being softer (and / or more ductile) than the expandable body material. Therefore, the expandable body may be able to exert greater force on the metal jacket, causing it to deform relative to the metal surface.

[0022] In some implementations, the expandable body can be bistable (for example, when it is positioned between (e.g., limited to) two opposing metal surfaces to form at least a metal-to-metal seal). That is, the expandable body may have an alternative equilibrium configuration, i.e., a stable configuration in which the expandable body can transition (in at least one direction) between these configurations in response to, for example, a change in the temperature of the expandable body or a change in the internal pressure within the expandable body.

[0023] For example, an expandable body may have alternative equilibrium configurations in which the curvature of an internal or external component or part of the expandable body is reversed or flattened relative to the initial equilibrium configuration. As used herein, a bistable expandable body encompasses a polystable, i.e., expandable body having more than two equilibrium configurations, and for example, an expandable body may have multiple parts whose curvature can be reversed or flattened.

[0024] The expandable body can be adapted to push open opposing portions of the metal jacket to form a seal during a transition period in which the expandable body moves towards or reaches an alternative equilibrium configuration from a starting equilibrium configuration of the expandable body. In this context, an “equilibrium” configuration refers to the shape, arrangement or alignment of the expandable body that is locally or globally at minimum potential energy, i.e., stable with respect to (small) perturbations or deformations of the expandable body. In some implementations, the expandable body is adapted to elastically deform during the transition (e.g., from start to reach) such that multiple transitions of the expandable body from the starting equilibrium configuration to the alternative equilibrium configuration are possible, for example without a (significant) decrease in elasticity. For example, the transition to reach or towards the alternative equilibrium configuration can be reversible such that a gasket or at least the expandable body can be reused, for example to reform a seal or create a new seal. The metal jacket can be configured to plastically deform during the transition, for example to form a more effective seal.

[0025] For example, an expandable body may be adapted to push open opposing portions of the metal jacket to form a seal during a transition period from the initial equilibrium configuration to an alternative equilibrium configuration of the expandable body. During use, the expandable body may not reach the alternative equilibrium configuration due to geometric constraints from opposing metal surfaces, such as the sidewalls of a seal groove where a gasket is positioned or provided. The expandable body may then only reach an intermediate configuration between the initial equilibrium configuration and the alternative equilibrium configuration. However, in the intermediate configuration, the expandable body can be adapted to exert a biasing force on opposing portions of the metal jacket. For example, when in the intermediate configuration, the expandable body may have a larger range along the direction toward the opposing surfaces (e.g., dimensions perpendicular to one or more of the opposing surfaces) than when in either the initial or alternative equilibrium configuration. The intermediate configuration can be elastically biased toward the alternative equilibrium configuration so as to prevent the expandable body from transitioning back to the initial equilibrium configuration. For example, an expandable body may be adapted to have a transition state or configuration in which the expandable body can relax toward the alternative equilibrium configuration preferentially over the initial equilibrium configuration.

[0026] An expandable body may have an inlet into an internal volume enclosed by the walls of the expandable body, through which the expandable body is expanded or inflated. For example, the inlet may have a tube extending from the expandable body to connect to a pressure source. This tube may, in some cases, pass through the side wall of a metal jacket. The expandable body may be inflated by introducing fluid into the internal volume through the inlet. In some examples, the tube may include a valve that may allow the internal pressure to be maintained within the expandable body after the pressure source has been removed. The valve may also be used to allow the pressure source to be reconnected so that the internal pressure within the expandable body can be further increased, restored to a previous level, or otherwise changed.

[0027] Alternatively, the expandable body may be expanded by a physical or chemical change of a substance contained within the internal volume. In such cases, the internal volume of the expandable body may remain sealed (without an inlet) to prevent pressure loss, at least during expansion of the expandable body. In some examples, the manufacture and use of gaskets can be simplified.

[0028] In such cases, the expansion of the expandable body may be initiated in several different ways. For example, the expandable body may initially comprise a substance cooled below its boiling or sublimation point such that subsequent active or passive heating of the expandable body increases the vapor pressure of the substance, thereby driving the expansion of the expandable body. For example, the expandable body may initially comprise liquid nitrogen (or another liquefied gas) or solid carbon dioxide such that expansion is driven by the boiling of the liquid nitrogen or the sublimation of the carbon dioxide. More generally, the expansion of the expandable body may be driven by causing a phase transition (e.g., by heating or cooling) of a substance or material within the expandable body. As an example, the expandable body may comprise a material that expands upon solidification (e.g., germanium, silicon, gallium, bismuth, or antimony), such that a phase transition can be caused by cooling the molten material below its melting point.

[0029] As another example, expansion may be driven by the decomposition of a substance or material within the expandable body. For example, the expandable body may comprise a substance or material that can decompose by deflagration or detonation, such that the decomposition can be initiated by a sound wave such as ignition or a shock wave. For example, expansion can be driven by the decomposition or detonation of a primary or secondary explosive such as sodium azide. In some implementations, expansion may be driven by heat generated by the decomposition or chemical reaction of one or more substances (e.g., substances within the internal volume of the expandable body). For example, the heat may cause expansion of a gas within the expandable body.

[0030] Therefore, expandable bodies may be adapted to expand. For example, an expandable body may have an internal volume enclosed by the walls of the expandable body, the internal volume comprising (i) an inlet for introducing a fluid into the internal volume to expand the body, or (ii) a substance for introducing a fluid into the internal volume to expand the body by a physical or chemical change of the substance, or both. The expandable body may be equipped with an initiation mechanism that can be used to initiate a chemical or physical change, such as a heater, an electrical stimulator or spark generator, an electromagnetic coupling mechanism (for example, for inducing an electric current for heating the expandable body or surrounding equipment), a shock wave generator such as a detonator, and the like.

[0031] In some implementations, the expandable body may comprise a shape memory alloy (sometimes also called a heat-recoverable alloy or shape memory effect alloy). A shape memory alloy can deform at temperatures below its transition temperature (e.g., phase transition temperature) but is induced to return to (e.g., be biased towards) a specific configuration at temperatures above its transition temperature. That is, a shape memory alloy can be adapted to return to a preset configuration when heated. In one example, the expandable body is introduced into a metal jacket at a temperature below its transition temperature (e.g., cryogenic temperatures) and then actively or passively heated by allowing it to reach thermal equilibrium with the environment (e.g., room temperature), expanding as the expandable body attempts to return to a preset "expanded" configuration (i.e., a configuration with dimensions larger than the corresponding dimensions of the metal jacket). Thus, opposing portions of the metal jacket can be pushed open as the expandable body returns to or attempts to return to its expanded configuration. Shape memory effect alloys may include, for example, copper-aluminum-nickel or nickel-titanium (NiTi) alloys.

[0032] A third aspect of the present invention provides a method for forming an intermetallic seal between opposing first and second metal surfaces. This method is

[0033] A step of providing the above-described gasket or sealing ring between the first and second metal surfaces,

[0034] The process includes the step of expanding or extending the expandable body toward or into a discontinuity within the metal jacket, thereby pressing the opposing portion of the metal jacket adjacent to the discontinuity against a metal surface to form a seal.

[0035] Preferably, at least during the initial stage of expansion, the curvature of the recess in the radial cross-section of the outer surface of the expandable body decreases, thereby pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface. In some implementations of this method, the first metal surface is provided with a seal groove, and the step of providing a seal ring between the first and second metal surfaces includes the step of positioning the seal ring within the seal groove. Reversal or flattening of the curvature of the recess in the radial cross-section of the outer surface of the expandable body may be limited by contact between the metal jacket and the sidewall of the seal groove. Thus, the recess in the radial cross-section of the expandable body may be straightened relative to the sidewall of the seal groove after expansion of the expandable body. In some implementations, the recess becomes convex (at least to some extent) before contacting the sidewall. Thus, the expandable body can be bistable, as it can transition from an initial equilibrium configuration with a recess to another equilibrium configuration in which the recess becomes convex or flat. In some examples, the transition is reversible so that the gasket or at least the expandable body can be reused. The inversion or flattening of the recess (i.e., the transition between equilibrium configurations) can generate a force to push open the opposing portions of the metal jacket to form a seal. The internal pressure within the expandable body then decreases, which may cause the expandable body to relax (i.e., partially contract), providing an additional biasing force to support the seal.

[0036] Generally, a seal groove may have any cross-section that can accommodate a metal seal ring, such as a square or rectangular cross-section, or a curved cross-section such as a semicircle.

[0037] The seal ring may be housed within the seal groove without protruding from the first metal surface in a direction perpendicular to it. Since the seal ring does not protrude from the seal groove (at least along the direction perpendicular to the first metal surface), the first and second metal surfaces are not forced to approach each other along the direction perpendicular to the first metal surface. For example, the first and second metal surfaces may approach each other or even touch each other when they are positioned in place, and the second metal surface may be able to slide on the first metal surface (or vice versa). This method thus allows the integration of the first and second metal surfaces to be separated from deformation of the metal jacket. Scratches or abrasions on the metal jacket surface are also avoided, which is particularly important for ultra-high vacuum (UHV) seals, which are known to be sensitive to this type of damage.

[0038] Therefore, a more effective seal may be produced when there are geometric constraints on how the first and second metal surfaces can be joined (i.e., integrated), particularly meaning that at least some lateral movement of the surfaces is required when the seal ring is engaged. The method may further include positioning the second metal surface over the first metal surface to cover the seal groove, for example by moving the first and / or second metal surface into a predetermined position. The first and / or second metal surfaces may be positioned by sliding, and such metal surfaces are (substantially) parallel and in contact with each other during positioning. The seal ring may deform relative to the bottom surface of the seal groove, such that the seal ring is positioned between the second metal surface and the bottom surface of the seal groove.

[0039] To manufacture seal rings of different heights, metal jackets of various respective thicknesses (i.e., jackets with walls of different thicknesses) may be used with an expandable body of a general (e.g., identical) design. Therefore, by selecting the appropriate metal jacket, it may be possible to fit the metal seal ring to a seal groove of different depths. For example, the metal jacket may be selected to provide a predetermined gap or clearance between the metal jacket and the second metal surface before the expandable body expands. Thus, the thickness of the metal seal ring can precisely match the depth of the seal groove while still allowing the first and second metal surfaces to slide against each other. Some gap or clearance between the metal jacket and the second metal surface before the expandable body expands may be preferable to take into account (e.g.) manufacturing tolerances. Therefore, in some implementations, the thickness of the metal seal ring may be selected to provide a predetermined gap that is the same as, or greater than, the expected manufacturing tolerances of the metal seal ring, the first and second metal surfaces, and / or the seal groove.

[0040] This method may further include connecting components (e.g., vacuum chamber components) on which the first and second metal surfaces are provided, in order to prevent relative movement between the first and second surfaces during the expansion of the expandable body. These components may be bolted together, for example.

[0041] The first and second metal surfaces may be located on each of the angled segments of the vacuum chamber. For example, the vacuum chamber may be an annular vacuum chamber having multiple angled segments that need to be sealed together from end to end in order to provide an annular internal volume in which a vacuum can be maintained. The angled segments are aligned before forming a seal between them, which may involve moving the second metal surface and / or the first metal surface to bring the surfaces into contact with each other, with at least one component (or all) of that movement being parallel to the first and / or second metal surfaces.

[0042] The first and second metal surfaces may be located on the respective angled segments of a vacuum chamber, such as an annular or ellipsoidal vacuum chamber. The vacuum chamber may be assembled, including the angled segments, before the seal ring is expanded.

[0043] According to a fourth aspect of the present invention, an intermetallic seal is provided which is formed between two opposing metal surfaces using the method described above.

[0044] A fifth aspect of the present invention provides a vacuum chamber comprising one or more metal seals or seal rings as described above. The first and second metal surfaces are provided on different segments or components of the vacuum chamber. Each seal ring may be positioned in a corresponding seal groove provided on one of the metal surfaces of the vacuum chamber components (in some cases, the metal surface of the other vacuum chamber component may also have a complementary seal groove). In some implementations, the vacuum chamber may comprise a plurality of angled segments arranged to surround an internal volume (e.g., an annular internal volume), and one or more metal seal rings form each seal between pairs of angled segments. In some examples, the vacuum chamber may be a plasma chamber, e.g., a tokamak plasma chamber or a stellarator plasma chamber.

[0045] Herein, embodiments of the present invention will be described simply by reference to the accompanying schematic diagrams in which corresponding reference numerals indicate corresponding parts. [Brief explanation of the drawing]

[0046] [Figure 1A] This is a schematic cross-sectional view of a metal seal in which a compressive force is applied to the seal ring along the direction normal to the surface. [Figure 1B] This is a schematic cross-sectional view of a metal seal in which a compressive force is applied to the seal ring along a direction having a component parallel to the surface. [Figure 2] This is a schematic top view of half of a segmented annular vacuum chamber. [Figure 3]Figure 3A is a schematic vertical cross-sectional view of a metal seal ring according to one embodiment of the present invention. Figure 3B is an enlarged view of Figure 3A. [Figure 4] These are schematic vertical cross-sectional views of the metal seal ring in Figures 3A and 3B at various expansion stages. [Figure 5] These are schematic vertical cross-sectional views of the metal seal ring shown in Figures 3A and 3B, which indicate the inlet tube. [Figure 6] This is a schematic vertical cross-section of another metal sealing ring where the inlet tube is used as a connection inlet. [Figure 7] Figure 5 is a schematic vertical cross-sectional view of an alternative configuration for the metal seal ring. [Modes for carrying out the invention]

[0047] Figure 3A shows a cross-sectional view of a metal gasket or seal ring 301 for forming a metal-to-metal seal between two opposing metal surfaces 303 and 305. The metal seal ring 301 is provided in a seal groove (or channel) 307 formed on the first surface of one of the metal surfaces 303. The cross-section shown in Figure 3A is a radial cross-section with respect to an axis Z perpendicular to the plane of the seal ring 301. The metal surfaces 303 and 305 are provided on different parts of a vacuum chamber, each having a radially inner region (left side where the Z axis is shown in Figure 3A) corresponding to the internal volume of the vacuum chamber. When in use, the seal ring 301 provides a seal that prevents a gas (e.g., air) from being transferred between the metal surfaces 303 and 305 from the high-pressure radially outer region (right side in Figure 3A) to the low-pressure radially inner region (left side in Figure 3A).

[0048] The metal seal ring 301 should generally be understood to have an annular structure, for example, a structure formed by rotating the cross-section of the metal seal ring 301 around the Z-axis. Generally, the metal seal ring 301 may have a different shape depending on the application, rather than being a circle around the Z-axis. For example, the metal seal ring 301 may be elliptical, or it may follow a closing path of any shape surrounding the Z-axis. The metal seal ring 301 is preferably substantially planar, i.e., has a uniform range along the Z-axis, but may be non-planar in some cases. The seal ring 301 can be used in any orientation such that the Z-axis is perpendicular as shown in Figure 3A, or it may be positioned along any other direction, such as horizontally, depending on the orientation of the surfaces 303, 305 to be sealed.

[0049] The metal seal ring 301 comprises an expandable or expandable ring-shaped body 311 and a metal jacket 315 around the expandable body 311.

[0050] The expandable body 311 comprises a ring-shaped conduit or tube that traces a closed path. The expandable body 311 is hollow and has an internal volume 313. The internal volume 313 preferably has no walls so as not to interrupt the path of the conduit around the expandable body 311. The expandable body 311 is configured to expand or inflate when pressure is generated inside the internal volume 313. For example, the expandable body 311 may have one or more inlets for introducing fluid into the internal volume 313 and / or for compressing the fluid contained in the internal volume 313 to generate internal pressure. The fluid may be a liquid, such as hydraulic fluid, or a gas. The inlets (or each inlet) may be a tube connected to the internal volume 313 and connectable to an external pressure source, such as a pump or compressor. In some embodiments, internal pressure may instead be generated by heating a substance (solid, liquid, or gas) confined within the internal volume, or by a pressure-generating chemical reaction, such as vaporizing or decomposing a solid or liquid substance into a gas. The substance may be introduced into the internal volume 313 through the inlet before the inlet is closed to seal the internal volume 313.

[0051] The metal jacket 315 is at least partially wrapped around or fitted around the outer surface of the expandable body 311. The expansion of the expandable body 311 deforms the metal jacket 315, causing it to deform relative to the opposing metal surfaces 303, 305 during use, forming a seal between them. The expandable body 311 may plastically deform so that the internal pressure can be reduced without the expandable body 311 returning to its initial form in order to maintain the seal. Alternatively, the internal pressure may be continuously maintained by an external pressure source, and the internal pressure may be maintained by sealing the expandable body 311, such as by closing the inlet. Alternatively, as will be described in more detail below with respect to Figures 4A to 4F, the expandable body 311 may be configured to provide a biasing force that maintains the seal when the internal pressure is reduced.

[0052] The expandable body 311 is preferably made of a high-strength and relatively ductile material, such as a metal, for example, an austenitic nickel-chromium alloy such as Inconel 718. Depending on the application, other (non-metallic) materials may be used additionally or as substitutes. The metal jacket 315 is preferably made of a soft or ductile material so as to deform easily (e.g., more easily than the expandable body 311) to form an effective seal. For example, non-ferrous metals such as aluminum or copper (preferably substantially pure non-ferrous materials) may be used.

[0053] The metal jacket 315 comprises a segmented tube and extends in a closed loop around the entire length of the expandable body 311. The metal jacket 315 has only a discontinuity, preferably a single discontinuity, that extends around its length so that the jacket 315 does not form a continuous closed loop around the expandable body 311 in radial cross-section. In the example shown in Figure 3A, the discontinuity is an opening 317 formed between the spaced ends 318A, 318B of the metal jacket 315, such that the metal jacket 315 has a C-shaped or U-shaped cross-section. Alternatively, the ends 318A, 318B may extend beyond each other, touching or overlapping, so that the jacket 315 completely surrounds or encloses the expandable body 311 in radial cross-section. Nevertheless, the ends 318A, 318B can move relative to each other when the metal jacket 315 is deformed by the expansion of the expandable body 311.

[0054] The opening 317 or other discontinuity preferably extends around the metal jacket 315 at substantially the same relative position to the expandable body 311 to ensure uniform deformation of the metal jacket 315. More preferably, the discontinuity is located either substantially on the inner or outer circumference of the expandable body 311 so that the metal jacket 315 deforms substantially equally in both directions along the Z axis. More preferably, the discontinuity extends substantially around the outer circumference of the metal jacket 315, i.e., oriented away from the Z axis and away from the space enclosed by the metal seal ring 301, as shown in Figure 3A. Thus, the opening 317 is oriented away from the high vacuum (i.e., low pressure) side of the seal so that the metal jacket 315 forms a barrier between the high vacuum side and the expandable body 311.

[0055] The metal jacket 315 has ridges 319 on its outer surface, i.e., outwardly oriented projections for which it is preferably plastically deformable relative to the second metal surface 303 and the seal groove 307. Each ridge may extend around the entire circumference of the metal jacket (i.e., around the Z-axis). In this example, opposing ridges 319 are formed on both sides of the opening 317. However, ridges may also be formed in other locations, for example, closer to the Z-axis or on the opposite side of the metal jacket 315 from the opening 317. However, the ridges 319 are generally optional, and the metal jacket 315 may have no ridges, or one or more. In some implementations, the ridges may be “knife edges” that can cut into the metal surfaces 303, 305, and for example, the ridges 319 may be coated with aluminum (or another relatively hard metal) to form the knife edges.

[0056] The expandable body 311 has a radial cross-section with a recess 321 facing the opening 317 or other discontinuities within the metal jacket 315. Thus, the expandable body 311 has notches or grooves that extend circumferentially around the expandable body (i.e., around the Z-axis) and are directed toward the opening 317 in the metal jacket 315. In this example, the radial cross-section of the expandable body 311 is somewhat convex, i.e., there is a single concave region 321. As will be described below in relation to Figures 4A to 4F, the concave region 321 preferentially expands the expandable body 311 toward the opposing metal surfaces 303, 305 as the concave region straightens, thereby improving the performance of the seal by increasing the pressure acting on the metal jacket 315 when the seal is formed.

[0057] Before expansion, the metal seal ring 301 is configured to fit into a seal groove 307 formed in the first metal surface 303. In this example, the seal groove 307 has a square cross-section, but other cross-sectional shapes such as rectangular, elliptical, or semicircular shapes can also be used.

[0058] Before the seal is formed, the metal seal ring 301 does not protrude from the seal groove 307, i.e., it does not extend beyond the first metal surface 303 in a direction perpendicular to the first metal surface 303 (this corresponds to the Z-axis direction in the figure). Therefore, the second metal surface 305 may move over the first metal surface 303 without contacting the metal seal ring 301 to cover the seal groove 307, i.e., the second metal surface 305 may approach the first metal surface 303 from any direction (limited only by the contacting surfaces 303, 305) while the two surfaces remain in contact, or it may slide to a predetermined position on the first metal surface 301. As can be seen from the enlarged view shown in Figure 3B, a small gap 309 (measured perpendicular to the first metal surface 303) may be provided between the metal seal ring 301 and the second metal surface 305. The gap 309 may be selected taking manufacturing tolerances into account to further ensure, for example, that the metal seal ring 301 does not protrude from the seal groove 307. In some cases, the gap 309 may be 0.1 mm to 0.5 mm. In some cases, the seal ring may have a thickness of about 5 mm (thickness is the size of the seal ring in the direction parallel to the Z axis).

[0059] Figure 4 shows the metal seal ring 301 (excluding the raised portion 319) at different stages A to F during seal formation. In this example, the seal is formed by gradually increasing the pressure within the internal volume of the expandable body 311.

[0060] In step A, the metal seal ring 301 is housed in the seal groove 307 within the first metal surface 303, with a gap 309 between the metal seal ring 301 and the second metal surface 305 and the bottom of the seal groove 307.

[0061] In step B, the vacuum chamber components, which are provided with the first and second metal surfaces 303 and 305, are joined to each other using fasteners 401 (e.g., bolts) to prevent relative movement between the metal surfaces 303 and 305 when the expandable body 311 is expanded.

[0062] In step C, the metal jacket 315 expands until there is no gap 309 between the metal jacket 315 and the bottom of the second metal surface 305 and the seal groove 307. Thus, the metal jacket 315 begins to deform relative to the bottom of the second metal surface 305 and the seal groove 307. The configuration of the expandable body 311 (i.e., including the concave region 321) means that the initial expansion of the expandable body 311 acts to straighten the concave region 321, thereby pushing the metal jacket 315 toward the bottom of the second metal surface 305 and the seal groove 307. Following contact between the metal jacket 315 and the opposing metal surfaces 303, 305, the expandable body 311 begins to expand or continues to expand radially (i.e., parallel to the first metal surface 303 and away from the Z-axis in the embodiment shown in the figure).

[0063] In step D, the contact areas 403, 405 between the metal jacket 315 and the bottom of the second metal surface 305 and the seal groove 307 increase as the expandable body 311 expands radially. The radial expansion of the expandable body 311 reduces the curvature of the ends 318A, B of the metal jacket 315 adjacent to the opening 317 of the metal jacket 315, causing these portions to unfold along the bottom of the second metal surface 305 and the seal groove 307. The curvature of the concave region 321 also decreases, i.e., the concave region 321 becomes straighter, and the force that deforms the metal jacket 315 relative to the bottom of the second metal surface 305 and the seal groove 307 increases.

[0064] In step E, the radial expansion of the expandable body 311 continues until the body contacts the side wall 405 of the seal groove 307 and the concave region 321 becomes substantially straight. The side wall 405 acts as a stopper to prevent the expandable body 311 from expanding excessively, which may result in a decrease in contact pressure between the seal and the sealing surface, thereby weakening the seal, and eventually the metal jacket 315 may no longer be in contact with the second metal surface 305 and the bottom of the seal groove 307.

[0065] In step F, once the pressure inside the expandable body 311 reaches its maximum, it may decrease to, for example, atmospheric pressure, and in some cases, the elastic strain inside the expandable body 311 may be reduced, as a result of the expandable body 311 ceasing to contact the side wall 405. Such contraction may increase the contact pressure between the metal jacket 315 and the second metal surface 305 and the bottom of the seal groove 307. Thus, the elastic strain accumulated in the expandable body 311 may act as a biasing force that helps prevent loss of sealing ability during small relative movements of the first and second metal surfaces 303, 305 (e.g., fretting, impact loading). In some examples, the expandable body 311 is configured and positioned together with the seal groove 307 such that the concave region 321 becomes convex during expansion of the expandable body 311 and becomes substantially linear when the internal pressure inside the expandable body 311 is reduced.

[0066] Alternatively, in some implementations, the pressure may be maintained so that, for example, the expandable body 311 does not contract.

[0067] It has been found that even when a seal is formed, the components may be heated (up to, for example, 300°C), which may reduce the contact pressure to some extent, but the seal remains effective. Therefore, even at the "burnout" temperatures used in high-vacuum applications, the integrity of the seal may be maintained.

[0068] One or more seals formed using the metal seal ring 301 described above in relation to Figures 3A, 3B, and 4 may be used, for example, in the annular vacuum chamber 201 described above in relation to Figure 2.

[0069] The metal seal ring 301 may be formed entirely of metal, which is particularly suitable for harsh chemical and physical environments that could degrade seal rings made of other materials.

[0070] Figure 5 is a schematic vertical cross-sectional view of the seal ring 301, relative to a different position than the cross-sections in Figures 3A, 3B, and 4. The expandable body 311 is provided with an inlet 502 on the side opposite the discontinuity of the metal jacket 315. The inlet 502 is connected to an inlet pipe 504 that extends through the side walls of the metal jacket 315 and the seal groove 307. A fluid source or pressure source (not shown) can be connected to the inlet pipe 504 to introduce fluid into the internal volume 313 of the expandable body 311 via the inlet 502.

[0071] Figure 6 is a schematic vertical cross-sectional view of another seal ring 601, similar to the seal ring 301 in Figure 5, except that there is no inlet to the expandable body 611 and the inlet tube 604 terminates after the metal jacket 315, i.e., in front of or after the expandable body 611. The inlet tube 604 comprises one or more wires 606 used to initiate the expansion of the expandable body 611. For example, one or more wires 606 can be used to supply current to a heater 608 (in this case extending around the outer circumference of the expandable body 611) or to another initiation mechanism that initiates a chemical or physical reaction (e.g., phase change) of substance or material (not shown) within the internal volume 313 of the expandable body 611. In another implementation, the expandable body may comprise (e.g., formed by) a shape memory effect alloy (such as NiTi) and a heater 608 used to raise the temperature of the shape memory effect alloy above its transition temperature, thereby driving the expansion of the expandable body 611. In this case, the expandable body 611 may or may not have an internal volume. As another example, one or more wires 606 can be used to ignite or detonate a flammable or explosive substance (e.g., sodium azide) in the internal volume 313 of the expandable body 611.

[0072] In another implementation of the seal ring 601 shown in Figure 6, the inlet tube 606 is omitted, but there is still a through-hole penetrating the side wall of the metal jacket 315 and the seal groove 307, which allows one or more wires 606 to reach the heater 608 or other starting mechanism.

[0073] Figure 6 is a schematic vertical cross-sectional view of yet another seal ring 701, similar to the seal ring 301 in Figure 5, except that the recess 721 of the expandable body 715 faces outward from the opening 317 of the metal jacket 315. Thus, the expandable body 715 can be expanded radially within the metal jacket 315. In this case, the inlet pipe 704 does not extend through the metal jacket 315, which may simplify the structure.

[0074] While specific embodiments of the present invention have been described above, it should be recognized that the invention may also be carried out in ways other than those described. The above description is intended to be illustrative, not limiting. Accordingly, it will be apparent to those skilled in the art that modifications to the invention described below can be made without departing from the claims set forth below.

Claims

1. A gasket for forming an intermetallic seal between two opposing metal surfaces, A closed-loop expandable body, A metal jacket having discontinuous portions that extend at least partially around the closed loop and around the outer surface of the expandable body, and extending around the closed loop. Equipped with, The expandable body is configured to expand during use to push open the opposing portion of the metal jacket adjacent to the discontinuous portion, thereby forming a seal, and is a gasket.

2. The gasket according to claim 1, wherein the expandable body is bistable when positioned between two opposing metal surfaces to form at least a metal-to-metal seal.

3. The gasket according to claim 1 or 2, wherein the expandable body is adapted to push open the opposing portions of the metal jacket to form the seal during a transition period from the initial equilibrium configuration of the expandable body to or to an alternative equilibrium configuration of the expandable body.

4. The gasket according to claim 3, wherein the expandable body is adapted to apply a biasing force to the opposing portion of the metal jacket when the expandable body is in a configuration intermediate between the initial equilibrium configuration and the alternative equilibrium configuration.

5. The gasket according to claim 4, wherein the intermediate configuration of the expandable body between the initial equilibrium configuration and the alternative equilibrium configuration is elastically biased toward the alternative equilibrium configuration.

6. The gasket according to any one of claims 3 to 5, wherein the expandable body is adapted to be elastically deformable during or over the entire period of the transition.

7. The gasket according to any one of claims 3 to 6, wherein the metal jacket is adapted to undergo plastic deformation during the transition.

8. The gasket according to any one of claims 3 to 7, wherein the expandable body is adapted to transition from the initial equilibrium configuration of the expandable body toward or toward the alternative equilibrium configuration of the expandable body in response to a change in the temperature of the expandable body or a change in the internal pressure within the expandable body.

9. The gasket according to any one of claims 1 to 8, wherein the expandable body comprises a shape memory alloy.

10. The gasket according to claim 9, wherein the shape memory alloy is adapted to transition to an expanded state when heated above the transition temperature of the shape memory alloy.

11. The gasket according to any one of claims 1 to 10, wherein the expandable body comprises a tube configured to expand under internal pressure.

12. The gasket according to any one of claims 1 to 11, wherein the expandable body is adapted to expand, and the expandable body is configured to push open the opposing portion of the metal jacket adjacent to the discontinuity when expanded, thereby forming the seal when in use.

13. The gasket according to any one of claims 1 to 12, wherein the discontinuity extends around either the inner or outer circumference of the closed loop.

14. The gasket according to any one of claims 1 to 13, wherein the expandable body is configured to expand toward or into the discontinuity.

15. The gasket according to claim 13 or 14, wherein the expandable body is configured to expand along an axis substantially perpendicular to the plane of the expandable body.

16. The gasket according to any one of claims 1 to 15, wherein the expandable body is configured to press the metal jacket against an adjacent metal surface when expanded, thereby forming a seal when in use.

17. The gasket according to any one of claims 1 to 16, wherein the expandable body is configured to push open opposing portions of the metal jacket adjacent to the discontinuity in opposite directions along an axis substantially perpendicular to the plane of the closed loop.

18. The gasket according to any one of claims 1 to 17, wherein the outer surface of the expandable body has a radial cross-section having a recess facing the discontinuity in the metal jacket, at least before expansion.

19. The gasket according to claim 18, wherein the radial cross-section of the outer surface of the expandable body is hollow C-shaped.

20. The gasket according to any one of claims 1 to 19, wherein the metal jacket contacts the expandable body around the outer or inner circumference of the expandable body opposite to the discontinuity.

21. The gasket according to any one of claims 1 to 20, wherein the metal jacket comprises one or more outward-facing protrusions.

22. The gasket according to any one of claims 1 to 21, wherein the metal jacket and the expandable body are formed of different materials, and the material of the metal jacket is softer than the material of the expandable body.

23. The gasket according to any one of claims 1 to 22, wherein the expandable body is provided with an inlet for inlet into an internal volume surrounded by the wall of the expandable body.

24. The gasket according to claim 23, wherein the inlet comprises a pipe extending from the expandable body for connection to a pressure source.

25. The gasket according to any one of claims 1 to 24, wherein the expandable body is configured to expand under internal pressure, and following the expansion of the expandable body and the reduction of the internal pressure, the expandable body is configured to maintain a biasing force against the opposing portion of the metal jacket.

26. A gasket for forming an intermetallic seal between two opposing metal surfaces, A ring-shaped body adapted to expansion, A metal jacket is arranged around the ring-shaped body and has discontinuous portions that extend around the inner or outer circumference of the ring-shaped body. Equipped with, A gasket, wherein the ring-shaped body is adapted to expand toward or into the discontinuity when expanded, pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface to form the seal.

27. A method for forming an intermetallic seal between opposing first and second metal surfaces, A step of providing a gasket according to any one of claims 1 to 26 between the first and second metal surfaces, The steps include: extending the expandable body toward or into the discontinuity within the metal jacket, pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface, and forming the seal; Methods that include...

28. The method according to claim 27, wherein the expandable body pushes open the opposing portions of the metal jacket to form the seal during a transition period from the initial equilibrium configuration of the expandable body to or reaching an alternative equilibrium configuration of the expandable body.

29. The method according to claim 28, wherein the expandable body is prevented from reaching the alternative equilibrium configuration by a sealing groove in or on one or both of the opposing first and second surfaces, thereby allowing the expandable body to reach a configuration intermediate between the initial equilibrium configuration and the alternative equilibrium configuration in which the expandable body applies a biasing force to the opposing portions of the metal jacket.

30. The method according to claim 29, wherein the configuration of the expandable body, which is located between the initial equilibrium configuration and the alternative equilibrium configuration, is elastically biased toward the alternative equilibrium configuration.

31. The method according to any one of claims 27 to 30, wherein, at least before expansion, the outer surface of the ring-shaped body has a radial cross-section having a recess facing the discontinuity in the metal jacket, and at least during the initial stage of expansion, the curvature of the recess in the radial cross-section of the outer surface of the expandable body decreases, thereby pressing the opposing portion of the metal jacket adjacent to the discontinuity against the metal surface.

32. The method according to any one of claims 27 to 31, wherein the first metal surface includes a seal groove, and the step of providing the gasket between the first and second metal surfaces includes the step of placing the gasket in the seal groove.

33. The method according to claim 32, wherein the inversion or flattening of the curvature of the recess in the radial cross-section of the outer surface of the expandable body is limited by contact between the expandable body and the side wall of the seal groove.

34. The method according to claim 33, wherein the recess in the radial cross-section of the expandable body is straightened with respect to the side wall of the seal groove during expansion of the expandable body.

35. The method according to any one of claims 32 to 34, wherein the seal ring is housed in the seal groove without protruding from there toward the first metal surface in a direction perpendicular to the first metal surface, and the method further comprises the step of positioning the second metal surface on the first metal surface so as to cover the seal groove.

36. The method according to any one of claims 27 to 35, further comprising a connecting component on which the first and second metal surfaces are provided in order to prevent relative movement between the first and second metal surfaces of the expandable body during expansion.

37. The method according to any one of claims 27 to 36, wherein the first and second metal surfaces are provided on each of the angled segments of the vacuum chamber.

38. The method according to any one of claims 27 to 37, wherein the expandable body is bistable, and the method further comprises the step of moving the expandable body between alternative stable configurations, thereby causing the expandable body to push open the opposing portions of the metal jacket during the transition to form the seal.

39. An intermetallic seal formed between two opposing metal surfaces using the method according to any one of claims 27 to 38.

40. A vacuum chamber comprising one or more intermetallic seals as described in claim 39.

41. The vacuum chamber according to claim 40, comprising a plurality of angled segments arranged to surround an internal volume, wherein one or more intermetallic seals are formed between pairs of the angled segments.

Images