High-Pressure Filter Apparatus and Related Methods

Abstract

High-pressure filter housings and devices useful for containing fluids under high pressure, where an exemplary housing includes first and second pieces having complementary tapered mating surfaces capable of forming a fluid-tight seal without a gasket located between the surfaces, and methods of making and using the high-pressure filter devices are described.

Description

[Technical Field]

[0001] SUMMARY OF THE INVENTION The present disclosure relates to housings and devices useful for containing fluids under high pressure. [Background technology]

[0002] Across a wide range of industries and applications, various types of fluid containers and fluid processing vessels are designed to contain liquid or gaseous fluids at high pressures. Examples include isotactic press devices (see, e.g., U.S. Patent Application Publication No. 2007 / 0218160), pressurized flow control structures (see, e.g., U.S. Patent Application Publication No. 2013 / 0240062), and high-pressure filter devices (see, e.g., U.S. Patent Application Publication No. 2018 / 0193785).

[0003] A fluid container or vessel must be capable of containing a fluid at high pressure and for a sustained period, either in a static or flowing state. The container or vessel must be stable to the pressure and temperature conditions of the fluid, be chemically stable, and not be degraded by the contained fluid. The container or vessel is constructed from components that fit together to form a fluid-tight seal that prevents fluid from escaping from the interior of the container or vessel.

[0004] The need for high-pressure fluids spans many industries, including, as more specific examples, the chemical processing industry, the automotive and aerospace industries, and the semiconductor manufacturing industry. Depending on their applications, the processes using the fluids may often require the fluids to be largely free of impurities. As a result, many systems using high-pressure fluids include filter devices that remove impurities from the fluid while it is under pressure.

[0005] Semiconductor manufacturing operations require high-purity fluids for various processing steps. As an example, liquid tin is a type of molten metal used to expose the extreme ultraviolet (EUV) light used in the photolithography process. For use in the photolithography process, liquid tin must be free of impurities, contaminants, and particles that could disrupt the process. Filtering the molten metal to remove impurities requires that the molten metal be passed through a filter at high pressure and temperature.

[0006] The filter and liquid metal stream must be contained in a filtering device that is leak-proof at temperatures that may exceed 200 degrees Celsius and pressures that may exceed 5,000 pounds per square inch (psig) or even exceed 8,000 psig or more. Certain filtering device designs currently available may be useful at temperatures and pressures that approach or meet these ranges for filtering fluids under pressure. However, as with many commercial endeavors, the need for improved performance is constant. Current or previous designs of high-pressure filtering equipment must continually be improved to meet ever-higher performance requirements.

[0007] There is a continuing need for filtering equipment that provides leak-tight performance at high temperatures and pressures for filtering a variety of fluids, including molten metals, other types of liquids, and gases. Summary of the Invention

[0008] A high-pressure filter apparatus is described that can withstand very high internal pressures without leaking or otherwise failing. Examples include a housing piece and an end piece, with a tapered joint between the housing piece and the end piece having complementary tapered surfaces. A mechanical fitting releasably secures the end piece to the housing piece to form a seal between the tapered joint surfaces. The tapered joint is formed between a surface of the housing piece and a surface of the end piece, and no gasket is present between the surfaces. Methods of making and using the high-pressure filter apparatus are also described.

[0009] There are various known filtering systems useful for filtering fluids at high pressures and temperatures. Some of these include filter housing structures made from metals formed by welding or brazing. While welded and brazed structures are useful and can handle high internal pressures, welded or brazed seams within pressure vessels can create areas of reduced strength. For example, welding high-melting-point metals or alloys can cause a reduction in material strength by as much as 50% due to recrystallization.

[0010] U.S. Patent Application Publication No. 2018 / 0193785 describes a high-pressure filter device that can avoid the need for a welded seam and uses a tapered (e.g., conical) engagement between two housing sections, with a gasket positioned between the surfaces of the tapered engagement to form a seal. The gasket used to create the high-pressure seal can pose manufacturing and operational challenges. The gasket can slip, deteriorate, or otherwise fail, potentially resulting in seal failure and leaks, especially if the seal and gasket are subjected to significant pressures. Furthermore, as an additional structural element of the filter device, the gasket can act as a source of contaminants. Furthermore, gasket materials exhibit physical properties that differ from those of the other components of the filter device, including different thermal expansion coefficients.

[0011] In one aspect, the present disclosure relates to a high-pressure filter apparatus having a sealing surface between a housing piece and an end piece. The apparatus includes: a housing piece including a first tapered mating surface, a filter chamber, and a fluid flow opening connected to the filter chamber; a filter located within the filter chamber; an end piece including a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces and a fluid flow opening connected to the filter chamber; and a mechanical fitting that releasably secures the end piece to the housing piece under pressure to form a seal between the first and second tapered mating surfaces.

[0012] In another aspect, the disclosure relates to a method for filtering a fluid, the method including providing a high-pressure filter apparatus including: a housing piece including a first tapered mating surface, a filter chamber, and a fluid flow opening connected to the filter chamber; a filter located within the filter chamber; an end piece including a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces and a fluid flow opening connected to the filter chamber; and a mechanical fitting that releasably secures the end piece to the housing piece under pressure to form a seal between the first and second tapered mating surfaces; and passing an impurity-containing fluid through the filter to remove the impurities from the fluid.

[0013] In another aspect, the present disclosure relates to a method of forming a high-pressure filter apparatus. The method includes providing a filter; a housing piece including a first tapered mating surface, a filter chamber, and a fluid flow opening connected to the filter chamber; and an end piece with a second tapered mating surface adapted to contact the first tapered mating surface under pressure. The method further includes fixing the filter in position within the filter chamber; and connecting the end piece to the housing piece using a mechanical fitting under pressure to form a seal between the first and second tapered mating surfaces without disposing a gasket material between the first and second tapered mating surfaces.

[0014] In yet another aspect, the present disclosure relates to a high-pressure filter apparatus. The apparatus includes a fluid inlet at an inlet end, a fluid outlet at an outlet end, a metal sidewall between the fluid inlet and the fluid outlet, a filter chamber defined by the metal sidewall, and a filter positioned within the filter chamber. The apparatus is capable of containing a fluid within the filter chamber at a fluid pressure of at least 40,000 psig at 20 degrees Celsius without leaking. [Brief explanation of the drawings]

[0015] [Figure 1A] 1 shows an exploded view of an exemplary filtering device as described. [Figure 1B] 1 shows an assembly diagram of an exemplary filtering device as described. [Figure 1C] 1 shows an exploded view of an exemplary filtering device as described. [Figure 1D] 1 shows an assembly diagram of an exemplary filtering device as described. [Figure 2A] 1 shows an exploded view of an exemplary filtering device as described. [Figure 2B] 1 shows an assembly diagram of an exemplary filtering device as described. DETAILED DESCRIPTION OF THE INVENTION

[0016] The drawings are intended as non-limiting examples and are schematic and not necessarily to scale.

[0017] A high-pressure filter device is described that includes a housing piece and an end piece, having a tapered joint between opposing complementary tapered surfaces of the housing piece and the end piece, and not having a gasket between the two tapered mating surfaces. A mechanical fitting is used to releasably secure the end piece to the housing piece, and pressure is applied between the two opposing mating surfaces to create a seal between the tapered mating surfaces. Methods of making and using the high-pressure filter device are also described.

[0018] As used herein, "mechanical fitting" refers to a mechanical engagement useful for joining pieces of a described device into an assembled, functional device and capable of being selectively assembled and disassembled to assemble and disassemble the device. The mechanical fitting preferably allows for the application of varying amounts of pressure between two pieces of the device, particularly at the two tapered mating surfaces described. Examples of useful mechanical fittings include opposing threaded surfaces. A portion of the fitting, such as a threaded surface, may be included on a surface of a housing piece, a surface of an end piece, or may be present on a piece other than the end piece or housing piece.

[0019] Previous filter device designs have proposed using complementary tapered surfaces to form a seal, but the design involves using a gasket between the two surfaces. See U.S. Patent Application Publication No. 2018 / 0193785.

[0020] In contrast, the seal described between two opposing tapered surfaces does not require the placement of a gasket material or device between the two surfaces. Eliminating gaskets from high-pressure seals offers certain advantages. Gaskets can fail or deteriorate during use, especially under significantly higher pressures. Gaskets also add process and material requirements when designing and assembling filtering devices and can be a source of contaminants for fluids passing through the filtering device. Furthermore, gasket materials exhibit different physical properties than the other components of the filtering device, including different thermal expansion coefficients, which result in different expansion and contraction characteristics of the filtering device components during temperature changes.

[0021] As used herein, the term "gasket" refers to a material that can exist physically separate from both surfaces of a tapered junction, can be placed between the surfaces when assembling a filter device, and can preferably be removed or repositioned as needed during assembly without damaging either surface. When contained between mating surfaces and placed under pressure, the gasket creates a seal between the two opposing mating surfaces that prevents fluid from flowing through the surfaces and leaking out of the junction.

[0022] Examples of known gasket materials include thin layers of solid or flowable materials that have a thickness, compressibility, and conformability that allows them to be placed in contact with each of two opposing surfaces of a joint and prevent fluids from flowing between them when placed under pressure between the two opposing surfaces of the joint. These include, among others, metal gaskets in the form of thin metal sheets placed between two opposing mating surfaces; polymer adhesives, optionally with a solvent, placed between two opposing mating surfaces; cork, fabric, cardboard, or other similar compressible materials; "form-in-place" gasket materials, including curable polymers such as silicone and optionally with a solvent; and Teflon (e.g., as a paste or tape).

[0023] In accordance with this specification, the two opposing tapered surfaces of a tapered junction of a high-pressure filter apparatus do not require, and can specifically eliminate, the presence of either these or another type of gasket material, and the two opposing tapered surfaces of the tapered junction are in direct contact to form a seal effective to prevent fluid flow therethrough.

[0024] The term "gasket" does not include materials applied or formed in such small amounts as a thin layer of material on the surface of a tapered joint that they cannot be separated from the underlying surface without damaging it. Examples of materials that are not considered "gaskets" include materials deposited on one or both of two opposing tapered surfaces by deposition methods such as electroplating (anodization), atomic layer deposition (ALD), chemical vapor deposition (CVD), physical vapor deposition (PVD), or their derivatives. Typically, materials applied by such methods cannot be removed from the surfaces without damaging them. Also, typically, the materials may have a thickness of less than 10 microns, or less than 5 microns, or less than 1 micron before being assembled under pressure as the surfaces of a tapered joint.

[0025] The term "gasket" also does not refer to tapered mating surfaces that have been treated to irreversibly affect the mechanical properties of the surface, for example, by heat treatment to improve hardness properties, passivation methods, etc. See below.

[0026] A tapered joint is a joint that includes two opposing tapered surfaces, each having a three-dimensional shape centered on the longitudinal axis of the housing, extending longitudinally along the length of the housing, and having two ends and an opening at each of the two ends. The opening at one end of the tapered joint is larger than the opening at the other end of the joint. Between the larger-diameter open end and the smaller-diameter open end, the opposing joint surfaces extend in a direction along the length of the housing, and the diameter of the opposing joint surfaces gradually decreases along the length of the joint surfaces.

[0027] According to certain examples of tapered joints, the opposing tapered mating surfaces are conical, meaning that the surfaces taper gradually along a straight line, i.e., linearly tapered. Other examples of tapered joints include two opposing tapered mating surfaces that are not linear, but taper along a curved or rounded line along the length of the surfaces between the two open ends.

[0028] To form a high-pressure seal between two tapered surfaces without adding a gasket between them, specific characteristics of the tapered mating surfaces that form the seal can be controlled or selected. Some characteristics of the opposing tapered surfaces that can be selected to create a tapered joint with an effective seal at high pressure include the angle of the two tapered surfaces, which can be the same or slightly different; the size (area) of the two tapered surfaces; the finish (smoothness or roughness) of one or both of the two tapered surfaces; and the physical and mechanical properties of the two tapered surfaces, such as hardness and flexibility, resulting from the makeup (composition) of the two surfaces.

[0029] Additional factors that can be controlled or selected to cause opposing tapered mating surfaces to maintain a leak-tight seal can include one or both of the operating (fluid) pressure within the filter device during operation and the pressure placed longitudinally between the two opposing tapered surfaces of the junction during operation. Regarding the former, the higher the fluid pressure inside the filter device during use, the stronger the seal formed at the tapered junction can be. Regarding the latter, the amount of longitudinal pressure applied between the opposing tapered surfaces can affect the seal's ability to function without leakage; this pressure between the surfaces can be influenced or controlled using the described mechanical fittings, for example, by selecting the amount of torque applied to the threaded fitting.

[0030] An exemplary tapered junction is conically tapered, i.e., linearly tapered. A conical junction is conical, i.e., has two opposing surfaces that are in the form of portions of linearly tapered surfaces of a cone sidewall. The "angle" of the conical surface refers to the angle of the imaginary apex of the cone, which is coincident with the longitudinal axis of the housing piece or end piece that contains the conical junction.

[0031] For taper junctions that are not linearly tapered, i.e., tapered but not conically tapered, the angle of the junction refers to the angle formed at the imaginary apex of the structure by two lines connecting the apex to the largest diameter of the tapered junction surface at opposite ends of the junction surface.

[0032] The angle of the opposing tapered mating surfaces may be any angle (measured at the imaginary apex of the cone containing the conical surfaces) that together are useful for forming an effective seal when the two surfaces engage with pressure applied from one surface to the other. In some exemplary tapered junctions, the angle of the female surface and the angle of the male surface may be equal or substantially equal (within 0.1 or 0.2 degrees), with each angle ranging from 30 to 90 degrees. In these or other exemplary tapered junctions, the male surface may have an angle slightly less than the angle of the female surface; for example, the angle of the male surface may be at least 0.5 degrees or at least 1 degree less than the angle of the female surface.

[0033] Optionally, one or both of the opposing surfaces of the tapered joint may be prepared or treated to have a surface texture (roughness) that improves the seal between the surfaces. Specific examples of useful surface treatments include electrolytic polishing or mechanical polishing processes. Electrolytic polishing processes, also known as "reverse plating" processes, use an electrochemical solution to remove very small amounts of the exterior surface of a metal part.

[0034] One or both surfaces of a tapered joint can be selected or treated to have mechanical properties, such as hardness, strength, or yield strength, to create a seal between the surfaces that functions without leaking at high pressures and temperatures. The mechanical properties of the tapered sealing surface can have different requirements than those of the gasket material used between the two surfaces, allowing the mechanical properties of the opposing surfaces to be selected or modified to improve the performance of the seal between the surfaces. For example, heat treating one or both tapered surfaces can reduce or increase the surface hardness. Reducing the surface hardness can increase ductility, allowing for a greater ability to eliminate leak paths between the surfaces. Increasing the surface hardness can increase resistance to yielding. One or both surfaces can be treated, and each surface can be treated differently; for example, the male surface can be treated to be harder than the female surface, allowing the male surface to be pressed into the female surface without yielding.

[0035] The amount of pressure applied between two surfaces can also affect the performance of the seal. The pressure applied longitudinally along the length of the device from one tapered surface to the other can be controlled by the amount of torque applied to a threaded mechanical fitting, for example, in a threaded end piece on a two-piece device or a threaded compression collar (see below) on a three- or four-piece device. If the amount of pressure applied between the surfaces is too low, the seal may fail more easily. If the amount of pressure applied between the surfaces is too high, the sealing surfaces may be damaged if the ultimate strength of the sealing surface material is reached during assembly or operation.

[0036] The described filter devices, including the housing pieces, end pieces, and mechanical fittings (as part of the end pieces, housing pieces, or separate pieces), can be prepared from a wide range of metallic materials, including, inter alia, refractory metals (including alloys), alloys such as stainless steel, nickel and nickel alloys, aluminum and aluminum alloys, and other metals. Refractory metals include niobium, molybdenum, tantalum, tungsten, rhenium, and alloys containing one or more of these, such as: an alloy containing molybdenum and rhenium (MoRe), an alloy containing tungsten and rhenium (WRe), an alloy containing molybdenum, hafnium, and carbon (MoHfC, or "MHC"), or an alloy containing titanium, zirconium, and molybdenum (TiZrMo).

[0037] A particular material may be selected based on factors such as mechanical properties such as strength and ductility, ease of processing, and compatibility with the fluid contained by the filter device during operation. For filter devices designed to process liquid metals at high pressures and temperatures, the housing piece, the end pieces, or both may preferably be prepared from a high-melting-point metal.

[0038] Refractory metals such as molybdenum may be preferred materials for use with filter devices that process liquid metals such as tin because they can be thermally stable and chemically resistant. Molybdenum can withstand high temperatures (e.g., above the freezing point of tin) without significant expansion or softening. However, a challenge with using molybdenum is that its strength is significantly reduced by welding; for example, welded molybdenum may exhibit less than 50% of the strength of unwelded molybdenum.

[0039] To avoid the loss of strength due to welding, the described filter apparatus uses mechanical fittings to connect the housing pieces with the device's end pieces, eliminating the need for welded or brazed seams. By avoiding welded or brazed seams, the filter apparatus can be formed from materials selected based on compatibility with the fluid contained by the device during operation, and need not be selected to provide a specific level of mechanical strength. The described high-pressure filter apparatus can be prepared from a high-melting-point metal, such as molybdenum, while avoiding welding or bonding processes that create weak seams in the filter apparatus. In an exemplary device, both the end pieces and the housing pieces may be made from a high-melting-point metal. If desired, the end pieces and the housing pieces may be made from two different materials, for example, two different high-melting-point metals.

[0040] Example filter devices constructed and assembled according to the present disclosure can perform at very high pressures and temperatures, while the tapered junctions function as fluid-tight seals without allowing fluid to escape from the pressurized interior of the device. Examples of useful or preferred high-pressure filter devices can provide leak-proof filtering of fluids such as molten metals at pressures reaching or exceeding 5,000 pounds per square inch gauge (psig), or reaching or exceeding 10,000, 20,000 psig, 30,000 psig, or even 35,000, 40,000, 45,000, 50,000, 55,000, or 60,000 psig, at different temperature conditions, optionally at ambient temperature (20 degrees Celsius) or at temperatures reaching or exceeding 230 degrees Celsius, e.g., 250 or 300 degrees Celsius.

[0041] Filter devices can be measured for performance at high pressure and ambient (room) temperature, or at high pressure and operating temperature, to assess the maximum internal pressure the device can withstand without failure, where failure refers to the onset of any amount of leakage from a device such as a seal. These tests are sometimes called "burst tests" and can be performed using water as the test fluid.

[0042] According to certain useful or preferred filter devices described, the devices may include an internal pressure of at least 40,000 psig, or at least 45,000 psig, at least 50,000 psig, at least 55,000 psig, or at least 60,000 sig tested at 20 degrees C. Also, according to certain useful or preferred filter devices described, the devices may be capable of accommodating internal pressures of at least 40,000 psig, or at least 45,000 psig, at least 50,000 psig, at least 55,000 psig, or at least 60,000 psig tested at elevated (operating) temperatures, for example, temperatures of 200 degrees Celsius or greater, or 250 degrees Celsius or greater, or 300 degrees Celsius or greater.

[0043] An exemplary high-pressure filter device may be constructed with a first piece, referred to as a "housing piece," mechanically secured to a second piece, referred to as an "end piece." The housing piece is configured to include two opposing ends, each having a fluid opening with a length between the ends and an open interior, referred to as a "filter chamber," adapted to accommodate at least a portion of a filter. The surfaces of the housing pieces include tapered mating surfaces.

[0044] The end piece also includes two opposing ends, each having a fluid opening. The end piece also includes a tapered mating surface complementary to the tapered mating surface of the housing piece. When the housing piece and the end piece are assembled to form the filter device, the filter can be positioned within a filter chamber. The filter chamber may be substantially or entirely defined by the housing piece, or may be defined partially by the housing piece and partially by the end piece.

[0045] The device includes a mechanical fitting that releasably secures the housing piece to the end piece. The mechanical fitting can be any type of fitting or fastener that can be used to assemble the housing piece and end piece together so as to contact the tapered mating surface of the end piece with the tapered mating surface of the housing piece and maintain a longitudinal amount of pressure between the two tapered mating surfaces to create a fluid-tight seal at the contacting tapered surfaces. In an exemplary device, the mechanical fitting is of a type that allows the fitting to be used to apply a controlled amount of longitudinal pressure between two opposing surfaces of the tapered mating surface; for example, the mechanical fitting may include a threaded surface that can be rotated to increase or decrease the amount of longitudinal pressure applied between the two opposing tapered surfaces.

[0046] According to one exemplary device, referred to as a "three-piece device," the mechanical fitting includes a threaded surface on a collar (e.g., a "compression collar") that is separate from the end piece and separate from the housing piece. The threaded collar has a threaded surface that engages a complementary threaded surface on the housing piece while the end piece is positioned between the threaded collar and the housing piece. The end piece does not require a threaded surface on the housing piece or a threaded surface adapted to engage with the threaded surface on the end piece. The threaded collar also has a shoulder surface that contacts a complementary surface on the end piece, such as a flange, to apply pressure to the end piece longitudinally toward the housing piece. The flange may be a permanent (integral) structure of the end piece or may be adjustably attached to the end piece, such as by a threaded fitting that allows the adjustable flange to be adjustably positioned along the length of the end piece (see the "four-piece" example in Figures 1C and 1D).

[0047] With a first end of the end piece engaged with the housing piece and a threaded collar positioned over the second end of the end piece with the threaded surface of the collar engaging the threaded surface of the housing piece, the threaded collar can be rotated about the threaded surface of the housing piece to apply pressure to the surface of the end piece and advance the end piece toward the housing piece. The tapered surface of the end piece contacts the tapered surface of the housing piece, and the collar can be rotated an amount to create a controlled amount of pressure between the opposing surfaces of the tapered interface to create a leak-tight seal between the two opposing surfaces.

[0048] According to a different exemplary device, referred to as a "two-piece device," the mechanical fitting includes a threaded surface on the end piece that directly engages a complementary threaded surface on the housing piece while the end piece is engaged with the housing piece. With the threaded surface of the end piece engaged with the threaded surface of the housing piece, the end piece can be rotated relative to the threaded surface of the housing piece to advance the tapered surface of the end piece toward the tapered surface of the housing piece. The tapered surface of the end piece contacts the tapered surface of the housing piece, and the end piece can be rotated a desired amount to create a controlled amount of pressure between the opposing surfaces of the tapered interface, creating a leak-tight seal between the two opposing surfaces.

[0049] Referring to FIG. 1A, an exploded side view of the described exemplary high-pressure filter apparatus 100 is shown. The apparatus 100 includes a housing piece 102, an end piece 104, a filter 106, and a collar 108. The apparatus 100 is referred to as a "three-piece" apparatus because it includes a housing piece, a separate end piece, and a separate collar piece that includes a portion of a mechanical fitting (threaded surfaces) that is not integrated into the end piece. As shown, the apparatus 100 may be referred to as having a "forward" end toward the fitting 108 and a "rearward" end toward the housing piece 102. The terms "forward" and "rearward" are used for convenience when referring to features of the apparatus 100 and do not refer to any structural requirements or method of use of the apparatus 100, such as the direction of fluid flow through the apparatus 100, which may be in any direction between the front and rear of the apparatus 100.

[0050] The housing piece 102 includes a filter chamber 120 extending longitudinally within the housing piece 102, defined by the inner surface of the housing piece's cylindrical sidewall. One end of the housing piece 102 (the "rear" end) has a first fluid flow opening 130, and a second end of the housing piece 102 (the "front" end) has a second fluid flow opening 132. Between opening 132 and filter chamber 120, the housing piece 102 includes a conical (or other tapered) surface 110, which is shown as a female surface but may be a male surface. The filter 106 is adapted to fit within the filter chamber 120 such that fluid flowing in either direction between the fluid flow openings 130 and 132 must pass through the filter 106. The end of the housing piece 102 has a threaded outer surface 134 adapted to engage with a threaded inner surface 162 of the mechanical fitting 108.

[0051] The end piece 104 includes a flow channel 144 defined by the inner surface of the cylindrical sidewall of the end piece 104. One end of the end piece 104 (the "rear" end) has a first fluid flow opening 140, and a second end of the end piece 104 (the "forward" end) has a second fluid flow opening 142. The end of the end piece 104 also has a conical (or other tapered) surface 150 adapted to engage with the conical surface 110 of the housing piece 102 to form a tapered, e.g., conical, joint. While the conical surface 150 is shown as a male surface, it could also be a female surface. Located along the length of the end piece 104 between the forward and rearward ends is a flange 146 including a front surface 148 adapted to contact a shoulder surface 174 of the mechanical fitting 108.

[0052] The device 100 includes a mechanical fitting in the form of opposing threaded surfaces that can be reversibly assembled and disassembled to assemble and disassemble the device 100. One threaded surface of the mechanical fitting is the threaded surface 134 of the housing piece 102, and the other threaded surface of the mechanical fitting is the threaded surface 162 of the collar 108. The collar 108 further includes a channel 160 that extends along the length of the collar 108 between a first end (the "rear" end) and an opening 170, and to a second end (the "front" end) having a second opening 172. The collar 108 is shown as a compression collar, which includes a threaded inner surface 162 that engages the threaded surface of the housing piece 102 and a shoulder surface 174 adapted to contact and apply pressure against the front surface 148 of the end piece 104. When assembled, the opposing conical surfaces 110 and 150 function as sealing surfaces that can be brought together in direct contact with one another under pressure without a gasket between the two opposing surfaces to create a liquid-tight seal.

[0053] 1B shows the device 100 in an assembled form. To assemble the device 100, the collar 108 is placed over the forward end of the end piece 104, and the rearward end of the end piece 104 is placed through the opening 132 in the housing piece 102. The threaded surface 162 of the collar 108 engages the threaded surface 134 of the housing piece 102, forming a mechanical fit between the two opposing threaded surfaces. The shoulder surface 174 of the mechanical fit 108 engages the forward surface 148 of the end piece 104. As the collar 108 rotates about the outer threaded surface 134, it applies pressure to the flange 146, advancing the conical surface 150 of the end piece 104 toward and contacting the conical surface 110 of the housing piece 102. Under sufficient pressure between conical surfaces 110 and 150, the two surfaces form a fluid-tight seal as described herein, which can accommodate fluid flow within device 100 at significantly elevated pressures and temperatures.

[0054] The filter 106 is disposed within the filter chamber 120 of the housing piece 102 and is held between a rear opening 130 of the housing piece 102 and a front opening 142 of the end piece 104 connected to the housing piece 102. One side of the filter 106 is in fluid communication with the opening 142, and a second side of the filter 106 is in fluid communication with the opening 130. The openings 142 and 130 provide an inlet ("housing inlet") and an outlet ("housing outlet") for the high-pressure filter apparatus 100. In use, either opening may be an inlet, and either opening may be an outlet. The inlet and outlet allow the apparatus 100 to be connected to a high-pressure filter fluid flow circuit.

[0055] Figures 1C and 1D show a variation of the device 100 of Figures 1A and 1B. According to the device 100 of Figures 1C and 1D, a movable flange 146 engages the end piece 104 with a threaded engagement that allows the flange 146 to be adjustably positioned along the length of the end piece 104.

[0056] The device 100 of Figures 1C and 1D is sometimes referred to as a "four-piece" device because the device includes a housing piece, a separate end piece, a separate collar piece that includes a portion of the mechanical fitting (the threaded surface) that is not incorporated into the end piece, and an adjustable flange piece.

[0057] 1A and 1B , in addition to the adjustable flange piece 148, which can move along the length of the end piece 104, a further difference is the arrangement of opposing threaded surfaces of the mechanical fitting formed between the collar 108 and the housing piece 102. Specifically, as included in the device 100 of FIGS. 1A and 1B , the housing piece 102 includes a threaded surface 132 on an outer surface of the housing piece 102, and the collar 108 includes a threaded surface 162 on an inner surface. In contrast, as included in the device 100 of FIGS. 1C and 1D , the housing piece 102 includes a threaded surface 132 on an inner surface of the housing piece 102, and the collar 108 includes a threaded surface 162 on an outer surface. The arrangement of FIGS. 1C and 1D may advantageously allow for the use of a collar 108 having a smaller diameter than the diameter of the collar 108 shown in FIGS. 1A and 1B .

[0058] End piece 104 includes a movable flange 146 that includes a threaded inner surface that engages the threaded outer surface of end piece 104. Collar 108 fits over the front end of end piece 104 and includes a shoulder surface 174 adapted to contact and apply pressure to a front surface 148 of movable flange 146. By rotating collar 108 to advance collar 108 toward front surface 148, shoulder surface 174 presses against front surface 148, moving end piece 104 toward housing piece 102. If desired, movable flange 148 can be positioned to provide a desired positioning of end piece 104 relative to housing piece 102 during assembly. Preferably, to prevent uncontrolled rotation of the movable flange 148 around the threaded portion of the end piece 104 during use, the thread between the movable flange 148 and the outer surface of the end piece 104 may have a thread direction opposite to that of the inner threaded surface 134 and the outer threaded surface 162 (e.g., having right-hand threads), e.g., a "reverse thread" (e.g., left-hand thread).

[0059] 1D shows the device 100 in an assembled form. The movable flange 146 is placed on the threaded exterior of the end piece 104 and moved along the length of the end piece 104 to a desired position. A collar 108 is placed over the forward end of the end piece 104, and the rearward end of the end piece 104 is placed within the opening 132 of the housing piece 102. The threaded surface 162 of the collar 108 engages the threaded surface 134 of the housing piece 102, forming a mechanical fit between the two surfaces. A shoulder surface 174 of the collar 108 engages the front surface 148 of the movable flange 146, which is mounted on the outer threaded surface of the end piece 104. As the collar 108 rotates about the inner threaded surface 134, it exerts pressure on the flange 146, advancing the conical surface 150 of the end piece 104 toward and contacting the conical surface 110 of the housing piece 102. Under sufficient pressure between conical surface 110 and conical surface 150, the two surfaces form a liquid-tight seal capable of containing fluid flow within device 100 at significantly elevated pressures and temperatures.

[0060] 2A, an exploded side view of a different exemplary high-pressure filter apparatus is shown. Apparatus 200 includes a housing piece 202, an end piece 204, and a filter 206. Apparatus 200 is referred to as a "two-piece" apparatus because it includes a housing piece and an end piece, with a portion of the mechanical fitting incorporated into the housing piece in the form of an internal threaded surface 234 and a portion of the mechanical fitting incorporated into the end piece in the form of an external threaded surface 246.

[0061] Housing piece 202 has a filter chamber 220 extending lengthwise within housing piece 202. One end of housing piece 202 (the "rear" end) has a first fluid flow opening 230, and the other end of housing piece 202 (the "front" end) has a second fluid flow opening 232. Between opening 232 and filter chamber 220, housing piece 202 includes a conical (or other tapered) surface 210, which is shown as a female surface but may be a male surface. Filter 206 is adapted to fit within filter chamber 220 such that fluid flowing between fluid flow opening 230 and fluid flow opening 232 must pass through filter 206. The end of housing piece 202 has a threaded surface 234 adapted to engage with a threaded surface 246 on end piece 204. Together, threaded surface 234 on housing piece 202 and threaded surface 246 on end piece 204 are the described "mechanical fit."

[0062] End piece 204 includes a flow channel 244 therein. One end of end piece 204 has a first fluid flow opening 240 and the other end of end piece 204 has a second fluid flow opening 242. Also, the end of end piece 204 has a conical surface (or other tapered surface) 250 adapted to engage with conical surface 210 of housing piece 202 to form a tapered (e.g., conical) joint. Along the length of end piece 204 is a threaded surface 246 adapted to engage with threaded surface 234 of housing piece 202.

[0063] When housing piece 202 and end piece 204 are assembled to form device 200 (see FIG. 2B), opposing conical surfaces 210 and 250 function as sealing surfaces that can come into direct contact with each other under pressure to create a fluid-tight seal, with no gasket material disposed between the two opposing surfaces.

[0064] To assemble device 200, threaded surface 246 of end piece 204 engages threaded surface 234 of housing piece 202 to form a mechanical fit that can be selectively and reversibly assembled and disassembled. See FIG. 2B. The rearward end of end piece 204, having opening 240, extends through the forward end of housing 202 and orients conical surface 250 of end piece 204 in facing contact with conical surface 210 of housing piece 202.

[0065] As end piece 204 rotates relative to threaded surface 234, conical surface 250 of end piece 204 advances toward and contacts conical surface 210 of housing piece 202. Under sufficient pressure between conical surfaces 210 and 250, the two surfaces form a fluid-tight seal as described herein that can accommodate fluid flow within device 200 at significantly elevated pressures and temperatures.

[0066] Filter 206 is disposed within filter chamber 220 of housing piece 202 and is held between a rear opening 230 of housing piece 202 and a front opening 242 of end piece 204 connected to housing piece 202. One side of filter 206 is in fluid communication with opening 242, and a second side of filter 206 is in fluid communication with opening 230. Openings 242 and 230 provide an inlet ("housing inlet") and an outlet ("housing outlet") for high-pressure filter apparatus 200. In use, either opening may be a housing inlet, and either opening may be a housing outlet. The inlet and outlet allow apparatus 200 to be connected to a high-pressure filter fluid flow circuit.

[0067] The "filter membrane" or (also known as "filter element") that may be retained within the described filter device to remove contaminants from the fluid stream passing therethrough may be any useful filter membrane, including filter membranes of the type known to process fluids at high temperatures, pressures, or both.

[0068] The filter membrane may be, for example, a sintered porous filter element known to be useful for filtering liquid metals and gases at high pressures or temperatures.

[0069] Useful filter membranes may have pore sizes ranging from about 0.1 to about 5 microns, e.g., from about 0.5 to about 1.5 microns, as measured by bubble point according to ASTM E 128. Exemplary filter membranes may be made from materials including titanium, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, titanium nitride, and silicon carbide.

[0070] The filter elements of the present disclosure can be used to filter a variety of liquid metals and gases. For example, the filter elements of the present disclosure can be used to filter gases ranging from inert gases such as argon to corrosive gases such as hydrogen bromide. Gases that can be filtered include, for example, argon, nitrogen, carbon dioxide, hydrogen bromide and hydrogen chloride, and hydrides. The filter elements of the present disclosure can also be used to filter supercritical fluids, such as carbon dioxide in its supercritical state.

[0071] The described filter device can be used to filter gases and liquids, including molten metals ("liquid metals"). Metals that can be filtered include tin, lead, sodium, cadmium, selenium, mercury, and materials that generally melt below about 400 degrees Celsius. Gases that can be processed at high temperatures and pressures include, by way of non-limiting example, argon, nitrogen (N), hydrogen bromide (HBr), hydrogen chloride (HCl), and carbon dioxide (CO).

[0072] The following are exemplary apparatus and methods herein.

[0073] Aspect 1. A high pressure filter device having a sealing surface between a housing piece and an end piece, A housing piece, a first tapered interface; a filter chamber, and Fluid flow opening connected to the filter chamber Including, housing pieces; a filter located within the filter chamber; An end piece, a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces; and Fluid flow opening connected to the filter chamber an end piece including: a mechanical fitting that releasably secures the end piece to the housing piece by pressure to form a seal between the first and second tapered mating surfaces; A high-pressure filter device comprising:

[0074] Aspect 2. The end piece comprises a threaded surface; the housing piece has a threaded surface complementary to the threaded surface of the end piece; the mechanical fitting comprises a threaded surface on the housing piece that engages with a threaded surface on the end piece; 2. The filter device of embodiment 1.

[0075] Aspect 3. The housing piece has a threaded surface; the device further comprising a collar including a threaded surface complementary to the threaded surface of the housing piece; an end piece including an end that engages with the housing piece and an end that engages with the collar; the mechanical fitting comprises a threaded surface on the housing piece that engages with a threaded surface on the collar; 2. The filter device of embodiment 1.

[0076] Embodiment 4. The filter device of any of embodiments 1 to 3, wherein the housing piece and the end piece each comprise a high melting point metal.

[0077] Embodiment 5. The filter device of any of embodiments 1 to 4, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

[0078] Embodiment 6. The filter device of any one of embodiments 1 to 5, wherein the filter has an average pore size in the range of 0.1 to 5 microns.

[0079] Embodiment 7. The filter apparatus of any of embodiments 1 to 6, wherein the filter apparatus is capable of containing fluid within the filter chamber at a fluid pressure of at least 40,000 psig at 20 degrees Celsius without leaking.

[0080] Embodiment 8. The filter apparatus of embodiment 7, wherein the filter apparatus is capable of containing fluid within the filter chamber at a fluid pressure of at least 45,000 psig at 20 degrees Celsius without leakage.

[0081] Embodiment 9. The filter device of embodiment 7 or 8, wherein the filter device is capable of containing a fluid within the filter chamber at a fluid temperature of at least 230 degrees Celsius without leakage.

[0082] Embodiment 10. The filter device of embodiment 7 or 8, wherein the filter chamber is capable of containing a fluid at a fluid temperature of at least 300 degrees Celsius without leakage.

[0083] Embodiment 11. The filter device of any of embodiments 1 to 10, wherein one of the first and second tapered mating surfaces is a female surface and the other of the first and second tapered mating surfaces is a male surface, and wherein the angle of the female tapered mating surface is at least 0.5 degrees greater than the angle of the male tapered mating surface.

[0084] Embodiment 12. The filter device of any of embodiments 1 to 11, wherein one or both of the first and second tapered interface surfaces comprises a polished surface.

[0085] Embodiment 13. The filter device of any of embodiments 1 to 12, wherein one or both of the first and second tapered mating surfaces comprises a heat-treated surface.

[0086] Embodiment 14. The filter device of any of embodiments 1 to 13, wherein the housing piece comprises a refractory metal or refractory metal alloy and the end piece comprises a different refractory metal or refractory metal alloy.

[0087] Embodiment 15. The filter device of any of embodiments 1 to 14, wherein the housing piece has a higher hardness than the end piece.

[0088] Embodiment 16. A method of filtering a fluid, comprising: A housing piece, a first tapered interface; a filter chamber, and Fluid flow opening connected to the filter chamber Including, housing pieces; a filter located in the filter chamber; An end piece, a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces; and Fluid flow opening connected to the filter chamber an end piece including: a mechanical fitting that releasably secures the end piece to the housing piece by pressure to form a seal between the first and second tapered mating surfaces; providing a high-pressure filter device comprising: Passing the impurity-containing fluid through a filter to remove the impurities from the fluid; A method comprising:

[0089] Embodiment 17. The method of embodiment 16, comprising passing the fluid through the filter chamber at a fluid pressure of at least 40,000 psig.

[0090] Embodiment 18. The method of embodiment 16 or 17, comprising passing the fluid through the filter chamber at a fluid temperature of at least 230 degrees Celsius.

[0091] Embodiment 19. The method of any one of embodiments 16 to 18, wherein the housing piece and the end piece each comprise a high melting point metal.

[0092] Embodiment 20. The method of any one of embodiments 16 to 19, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

[0093] Embodiment 21. The method of any one of embodiments 16 to 20, wherein the fluid is a liquid metal.

[0094] Embodiment 22. A method of forming a high-pressure filter device, comprising: filter, A housing piece, a first tapered interface; a filter chamber, and Fluid flow opening connected to the filter chamber Including, housing pieces; an end piece including a second tapered mating surface adapted to contact the first tapered mating surface under pressure; and securing the filter in position within the filter chamber; connecting the end piece to the housing piece using a mechanical fitting under pressure to form a seal between the first tapered mating surface and the second tapered mating surface without disposing a gasket material between the first tapered mating surface and the second tapered mating surface; A method comprising:

[0095] Embodiment 23. The method of embodiment 22, wherein the housing piece and the end piece each comprise a high melting point metal.

[0096] Embodiment 24. The method of embodiment 22 of embodiment 23, wherein one of the first and second tapered mating surfaces is a female surface and the other of the first and second tapered mating surfaces is a male surface, and the angle of the female tapered mating surface is at least 0.5 degrees greater than the angle of the male tapered mating surface.

[0097] Embodiment 25. The method of any of embodiments 22 to 24, wherein one or both of the first and second tapered mating surfaces comprises an abrasive surface.

[0098] Embodiment 26. The method of any of embodiments 22 to 25, wherein one or both of the first and second tapered mating surfaces comprises a heat-treated surface.

[0099] Embodiment 27. The method of any one of embodiments 22 to 26, wherein the housing piece comprises a refractory metal or refractory metal alloy and the end piece comprises a different refractory metal or refractory metal alloy.

[0100] Embodiment 28. The method of any one of embodiments 22 to 27, wherein the housing piece has a higher hardness than the end piece.

[0101] Aspect 29. A high-pressure filter device, comprising: a fluid inlet at the inlet end; a fluid outlet at the outlet end; a metal sidewall between the fluid inlet and the fluid outlet; a filter chamber defined by a metal sidewall; and A filter located within the filter chamber Including, A high-pressure filter apparatus capable of containing fluid within a filter chamber at a fluid pressure of at least 40,000 psig at 20 degrees Celsius without leakage.

[0102] Aspect 30. The filter device of claim 29, wherein the filter chamber can accommodate a fluid pressure of at least 45,000 psig at 20 degrees Celsius without leakage.

[0103] Embodiment 31. The filter device of embodiment 29 or 30, which is capable of containing fluid within the filter chamber at a fluid temperature of at least 230 degrees Celsius without leakage.

[0104] Embodiment 32. The filter device of any of embodiments 29 to 31, wherein the metal sidewall comprises a high melting point metal.

[0105] Embodiment 33. The filter device of any of embodiments 29 to 32, wherein the metal sidewall does not include a weld seam.

[0106] Embodiment 34. The filter device of any of embodiments 29 to 33, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

[0107] Embodiment 35: The filter device of any of embodiments 29 to 34, wherein the filter has an average pore size in the range of 0.1 to 5 microns.

Claims

1. 1. A high-pressure filter apparatus having a sealing surface between a housing piece and an end piece, comprising: A housing piece, a first tapered interface surface; a filter chamber, and Fluid flow opening connected to the filter chamber a housing piece including: a filter located within the filter chamber; An end piece, a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces; and Fluid flow opening connected to the filter chamber an end piece including: a mechanical fitting that releasably secures the end piece to the housing piece under pressure to form a seal between the first tapered mating surface and the second tapered mating surface; A high-pressure filter device comprising:

2. the end piece has a threaded surface; the housing piece has a threaded surface complementary to the threaded surface of the end piece; the mechanical fitting comprises a threaded surface on the housing piece that engages with a threaded surface on the end piece; The filter device according to claim 1 .

3. The housing piece has a threaded surface, the device further comprising a collar including a threaded surface complementary to the threaded surface of the housing piece; an end piece including an end that engages with the housing piece and an end that engages with the collar; the mechanical fitting comprises a threaded surface on the housing piece that engages with a threaded surface on the collar; The filter device according to claim 1 .

4. 4. The filter arrangement of claim 1, wherein the housing piece and the end piece each comprise a high melting point metal.

5. 5. The filtering device of claim 1, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

6. 6. The filter device of any one of claims 1 to 5, wherein the filter has an average pore size in the range of 0.1 to 5 microns.

7. 7. The filter apparatus of any one of claims 1 to 6, wherein the filter chamber can accommodate a fluid pressure of at least 40,000 psig at 20 degrees Celsius without leaking.

8. 8. The filter device of claim 7, wherein the filter chamber can accommodate a fluid pressure of at least 45,000 psig at 20 degrees Celsius without leaking.

9. 9. A filter device according to claim 7 or 8, capable of containing fluid within the filter chamber without leakage at a fluid temperature of at least 230 degrees Celsius.

10. 9. A filter device according to claim 7 or 8, capable of containing fluid within the filter chamber at a fluid temperature of at least 300 degrees Celsius without leakage.

11. 11. The filter device of claim 1, wherein one of the first and second tapered mating surfaces is a female surface and the other of the first and second tapered mating surfaces is a male surface, and the angle of the female tapered mating surface is at least 0.5 degrees greater than the angle of the male tapered mating surface.

12. 12. The filter apparatus of claim 1, wherein one or both of the first and second tapered interface surfaces comprises a polished surface.

13. 13. The filter apparatus of claim 1, wherein one or both of the first and second tapered mating surfaces comprises a heat-treated surface.

14. 14. A filter arrangement according to any preceding claim, wherein the housing pieces comprise a refractory metal or refractory metal alloy and the end pieces comprise a different refractory metal or refractory metal alloy.

15. 15. A filter device according to any one of claims 1 to 14, wherein the housing pieces have a higher hardness than the end pieces.

16. 1. A method of filtering a fluid, comprising: A housing piece, a first tapered interface surface; a filter chamber, and Fluid flow opening connected to the filter chamber a housing piece including: a filter located in a filter chamber; An end piece, a second tapered mating surface that contacts the first tapered mating surface under pressure without a gasket material disposed between the first and second tapered mating surfaces; and Fluid flow opening connected to the filter chamber an end piece including a mechanical fitting that releasably secures the end piece to the housing piece under pressure to form a seal between the first tapered mating surface and the second tapered mating surface; providing a high-pressure filter device comprising: Passing the impurity-containing fluid through a filter to remove the impurities from the fluid; A method comprising:

17. 17. The method of claim 16, comprising passing the fluid through the filter chamber at a fluid pressure of at least 40,000 psig.

18. 18. The method of claim 16 or 17, comprising passing the fluid through the filter chamber at a fluid temperature of at least 230 degrees Celsius.

19. 19. The method of any one of claims 16 to 18, wherein the housing piece and the end piece each comprise a refractory metal.

20. 20. The method of any one of claims 16 to 19, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

21. 21. The method of any one of claims 16 to 20, wherein the fluid is a liquid metal.

22. 1. A method of forming a high pressure filter apparatus, comprising: A filter, A housing piece, a first tapered interface surface; a filter chamber, and Fluid flow opening connected to the filter chamber a housing piece including: an end piece including a second tapered mating surface adapted to contact the first tapered mating surface under pressure; and securing the filter in position within the filter chamber; connecting the end piece to the housing piece using a mechanical fitting under pressure to form a seal between the first and second tapered mating surfaces without disposing a gasket material between the first and second tapered mating surfaces; A method comprising:

23. 23. The method of claim 22, wherein the housing piece and the end piece each comprise a refractory metal.

24. 24. The method of claim 22 or 23, wherein one of the first and second tapered mating surfaces is a female surface and the other of the first and second tapered mating surfaces is a male surface, and the angle of the female tapered mating surface is at least 0.5 degrees greater than the angle of the male tapered mating surface.

25. 25. The method of any one of claims 22 to 24, wherein one or both of the first and second tapered mating surfaces comprises an abrasive surface.

26. 26. The method of any one of claims 22 to 25, wherein one or both of the first and second tapered mating surfaces comprises a heat treated surface.

27. 27. The method of any one of claims 22 to 26, wherein the housing pieces comprise a refractory metal or refractory metal alloy and the end pieces comprise a different refractory metal or refractory metal alloy.

28. 28. A method according to any one of claims 22 to 27, wherein the housing pieces have a higher hardness than the end pieces.

29. A high-pressure filter device, comprising: a fluid inlet at the inlet end; a fluid outlet at the outlet end; a metal sidewall between the fluid inlet and the fluid outlet; a filter chamber defined by a metal sidewall; and A filter located within the filter chamber Including, capable of containing fluid within the filter chamber at a fluid pressure of at least 40,000 psig at 20 degrees Celsius without leakage; High pressure filter device.

30. 30. The filter apparatus of claim 29, wherein the filter chamber can accommodate a fluid pressure of at least 45,000 psig at 20 degrees Celsius without leaking.

31. 31. A filter apparatus according to claim 29 or 30, capable of containing fluid within the filter chamber without leakage at a fluid temperature of at least 230 degrees Celsius.

32. 32. The filter apparatus of any one of claims 29 to 31, wherein the metal sidewall comprises a refractory metal.

33. 33. The filtering apparatus of any one of claims 29 to 32, wherein the metal sidewall does not include a weld seam.

34. 34. The filtering apparatus of any one of claims 29 to 33, wherein the filter comprises titanium, silicon carbide, tungsten, tantalum, molybdenum, niobium, alumina, titanium oxide, or titanium nitride.

35. 35. The filter device of any one of claims 29 to 34, wherein the filter has an average pore size in the range of 0.1 to 5 microns.

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