Title of Invention

A METHOD FOR MAKING A CHEMICAL DEVICE ELEMENT HAVING COATED ASSEMBLY PARTS

Abstract

The invention concerns a method for making assembly parts (101, 192, 111, 112) for manufacturing a chemical device element (100) comprising fixing an anticorrosive coating (31, 32) on an untreated assembly part (21, 22), by an operation including a brazing process under controlled atmosphere and, optionally forming the coated part (101, 102) by plastic deformation. The brazing temperature is preferably lower than about 750 °C, and more preferably ranging between 600 °C and 720 °C. The inventive method enables an anticorrosive coating having a thickness less than 1 mm to be firmly fixed on a steel plate.

Full Text

METHOD FOR MAKING A CHEMICAL DEVICE ELEMENT COMPRISING A METAL SUPPORTING PART AND AN ANTI-CORROSIVE METAL COATING Domain of the invention The invention relates tc devices for manipulation, storage and treatment of chemicals intended for use in the chemical industries. In particular, it relates to mixers, treatment devices and conveyance devices capable of manipulating highly corrosive products such as concentrated acids or bases. In this application, the expression "chemical device element" collectively denotes in particular storage containments, tanks, heat exchangers, reactors, mixers, treatment devices and conveyance devices. More specifically, the invention relates to a method for making clad metal products such as chemical device elements or assembly parts designed for making chemical device elements, comprising at least one metal supporting part and an anti-corrosive metal coating. State of the art Chemical industries use many chemical device elements for manipulation, storage and / or treatment of highly corrosive chemicals and that consequently have to be resistant to attack by these components. In order to guarantee good resistance to corrosion, the chemical device elements usually comprise steel supporting parts and an anti-corrosive metal coating based on so-called "noble" metals such as titanium, tantalum, zirconium, a nickel-based alloy or stainless steel. Chemical device elements may be made by assembly of assembly parts, such as plates, previously coated with an anti-corrosive metal coating. The anti-corrosive coating may be fixed to the supporting part by different means such as knurling, explosion cladding, hot rolling or simple cladding with no junction between the plate and the anti-corrosive coating. Some applications, such as devices with low internal pressure, require a strong bond between the metal supporting part and the anti-corrosive coating/ in other words a bond that has good resistance to tear off, to prevent separation between them that could for example cause collapse of the anti-corrosive coating. Knurling, explosion cladding and rolling can give very strong support / coating bonds, but these techniques cannot be used for an anti-corrosive coating thinner than 0.7 mm. Brazing can give very strong bonds between support and coating and can reduce the thickness of the coating. However, brazing introduces additional difficulties. In particular, the difference in the coefficient of thermal expansion between the substrate and the coating material (for example the coefficient of expansion of steel is about twice as high as the coefficient of tantalum) generates mechanical stresses. These stresses weaken and deform the coating. Moreover, the brazing operation may cause the formation of interrr.etallic compounds that could weaken the bond between the support and the coating. These difficulties are exacerbated by operations to form the coated supporting part, if necessary, particularly by plastic deformation. US patent 4 291 104 by Fansteel provides information about the use of coatings subjected to prior deformations, the deformed parts being called "convolutions", in order to solve random distortion problems that arise due to differential expansion between the support and the coating. This solution does not prevent the formation of intermetallic compounds and reduces the area of the interface between the coating and the support, which causes weakening of the support / coating bond. Furthermore, this solution introduces serious difficulties during subsequent forming of the coated part. In particular, it is difficult to contemplate the possibility of calendering large-si zed coated parts between rollers when the coating is deformed. These deformations are also generally weakened by compression during forming operations. Therefore the Applicant searched for a method of solidly fixing a thin anti-corrosive coating onto a metal supporting part that could be used for an industrial implantation, which enables subsequent deformation of the coated part and that could be applied to large parts (typically plates with a surface area of more than about 1 m2) . Description of the invention The purpose of the invention is a method for making a clad metal product comprising a metal supporting part (preferably steel) and an an~i-corrosive metal coating, characterized in that the anti-corrosive coating is fixed onto the supporting part by brazing under a controlled atmosphere, so as to create a mechanical junction between at least one determined portion of the supporting part and at least one determined portion of the coating. The Applicant has observed that the inventive method can be used to firmly fix an anti-corrosive coating less than 1 mm thick, or even less than 0.5 mm, and possibly less than or equal to 0.3 mir. thick, onto a metal part, particularly a steel part. According to a first side of the invention, the clad metal product is an assembly part to be used for making a chemical device element. Seen from this side, the manufacturing method comprises: fixing of an anti-corrosive coating onto a supporting part (or "untreated assembly part") by brazing, under a controlled atmosphere; forming of the coated part, if necessary, by plastic deformation, so as to produce a coated assembly part (or "shape part") . According to a second side of the invention, the clad metal product is a chemical device element. Seen from this side, the manufacturing method comprises: fixing of an anti-ccrrosive coating on at least a first and a second untreated assembly part, by brazing uflder. a controlled atmosphere; forming of the said coated parts by plastic deformation; assembly of the said parts (typically by operations including welding so as to form the said chemical device element. The invention is particularly advantageous when assembly parts are formed after the anti-corrosive coating has been applied, in other words after the anti-corrosive coating has been fixed onto the supporting parts (or "untreated assembly parts"). In particularly, this variant of the invention simplifies handling, transport, storage and treatment of coated parts. According to this advantageous embodiment of the invention, the surface of uncreated assembly parts to be coated is typically essentially plane. The said parts may include parts that have previously been formed by machining, drilling, reaming, plastic deformation or any other means. In one preferred embodiment of the invention, the anti-corrosive coating is fixed by brazing at a temperature of less than about 750°C, and preferably between 600°C and 720°C, in a controlled atmosphere, which preferably contains an inert gas so as to prevent oxidation of the coating during brazing. The applicant has noted that the use cf sufficiently low brazing temperatures considerably reduces deformation of coatings caused by the brazing operation and that are caused by differential expansion between the untreated part and the coating. In this case it is not necessary to predeform the coating to compensate for the differential expansion effect. Figure 1 diagrammatically illustrates a portion of a clad metal product according to the invention. Figure 2 diagrammatically illustrates one embodiment of the inventive method. Figure 3 shows a sectional view diagrammatically illustrating the method for making an assembly part, according to one embodiment of the invention. Figure 4 diagrammatically illustrates the method for making a chemical device element, seen in sectional view, according to one embodiment of the invention. Figure 5 diagrammatically illustrates the method for making a chemical device element, seen in sectional view, according to one embodiment of the invention. Detailed description of the invention According to the invention, the method for making an assembly part (111, 112) to be used for making a chemical device element (100), said assembly part comprising a metal supporting part (2, 21, 22) and at least one anti-corrosive metal coating (3, 31, 32), comprises: fixing of an anti-corrosive coating (3, 31, 32) onto a supporting part (2, 21, 22) by an operation including a brazing operation in a controlled atmosphere; possibly forming of the coated part (101, 102) by plastic deformation, so as to produce a coated assembly part (or "shape part1') (111, 112). According to one preferred embodiment of the invention, the method for making a chemical device element (100) comprises: the production cf at least one first intermediate coated assembly part (101) and a second intermediate coated assembly part (102) using the method according to the invention; forming of intermediate coated parts (101, 102) by plastic deformation, so as to produce coated assembly parts (111, 112) with a determined shape; production of a chemical device element (100) by assembly of coated assembly parts (111, 112). More precisely, in this embodiment, the method for making a chemical device element (100) comprising at least one first and one second coated assembly part (111, 112), each of the said coated assembly parts comprising a metal supporting part (21, 22) and at least one anti-corrosive metal coating (31, 32), comprises: the supply of at least one first (21) and one second (22) supporting part; the fixing of an anti-corrosive coating (31, 32) on each of the said supporting parts (21, 22) by a method including a brazing operation under a controlled atmosphere and using at least one brazing material (41, 42), so as to produce intermediate coated parts (101, 102) ; forming of intermediate coated parts (101, 102) by plastic deformation, so as to produce coated assembly parts (111, 112) with a determined shape; assembly of coated assembly parts (111, 112), typically by operations including welding, so as to obtain the said chemical device element (100) . The controlled atmosphere in the said chamber (10) is preferably composed essentially of inert gas. The inert gas atmosphere is preferably at a determined pressure P. This atmosphere is typically . formed by evacuation of the initial atmosphere from the chamber (typically down to a residual pressure of between about 0.1 and 1 Pa) and introduction of the said inert gas until a given pressure P is reached. This purge operation may be repeated more than once. The inert gas may be a rare gas (typically argon or helium) or nitrogen or a mix of these gases. The inert gas pressure in the chamber (10) is typically between approximately 102 and 105 Pa (in other words between 1 mbar and 1 bar). A low pressure P limits the unfavourable impact of reagents (such as water or oxygen) that may be present in the industrial inert gases. The coated parts (101, 102) are typically deformed plastically by rolling or calendering. In one preferred embodiment of the invention, the said brazing operation typically comprises: insertion of at least one brazing material (4, 41, 42) between a metal supporting part (2, 21, 22) and an anti-corrosive coating (3, 31, 32) so as to form an initial assembly (5, 51, 52); possibly, application of a cladding pressure on the said initial assembly (5, 51, 52); introduction of the initial assembly (5, 51, 52) into a chamber (10) wi~h a controlled atmosphere provided with at least one heating means (11), such as a resistance; formation of an inert gas atmosphere in the said chamber (10) (and more particularly in the vicinity of the said assembly); heating of the said assembly (5, 51, 52) to a temperature equal to at leasr the brazing temperature of the said brazing material (4, 41, 42). The brazing material (4, 41, 42) may be inserted between the supporting part (2, 21, 22) and the anti-corrosive coating (3, 31, 32) in two steps. In particular, insertion may include: deposition of the brazing material (4, 41, 42) on the supporting part (2, 21, 22), adjacent to the so-called "bond" surface; positioning of the anti-corrosive coating (3, 31, 32) on the supporting part (2, 21, 22) so as to form the said initial assembly (5, 51, 52). In this preferred embodiment of the invention, the method for making a chemical device element (100) is characterised in that it comprises: manufacturing of intermediate coated assembly parts (101, 102) according to a method comprising a brazing operation including: formation of an initial assembly (51, 52) comprising a supporting part (21, 22), an anti-corrosive coating (31, 32) and at least one brazing material (41, 42) between the supporting part and the coating; introduction of the initial assembly (51, 52) into a brazing chamber with controlled atmosphere (10); formation of a controlled atmosphere in the said chamber (10); heating of the said assembly (51, 52) to a temperature equal to at least the brazing temperature of the said brazing material (41, 42) so as to fix the anti-corrosive coating (31, 32) on the supporting part (21, 22) by brazing; • forming of the said intermediate coated parts (101, 102) by plastic deformation, so as to obtain the said coated assembly parts (111, 112); • assembly of the coated assembly parts (or "shape parts") (111, 112), so as to obtain the said chemical device element (100). In some cases, it may be advantageous to firstly deposit the brazing material (4, 41, 42) on the anti-corrosive coating (3, 31, 32) adjacent to the "bond" surface, and then to position the supporting part (2, 21, 22) on the anti-corrosive coating, so as to form the said initial assembly (5, 51, 52). The brazing temperature, that is typically equal to the melting temperature of the, brazing material, is such that the material melts and produces an intimate bond with the element with which it is in contact (metal supporting part and / or anti-corrosive coating). The brazing temperature is preferably less than approximately 7 50°C, and even better between 600°C and 72 0°C. These temperatures can shorten the duration of the brazing operation. Normally, the brazing operation includes bringing the said determined parts towards each other so as to obtain a spacing D that is preferably chosen so as to prevent the formation of gas bubbles or bond defects between bond surfaces during the brazing operation. The spacing D is typically less than 0.1 mm. The method advantageously includes the application of a cladding pressure on the said initial assembly (5, 51, 52) during all or part of the brazing operation. More precisely, it is advantageous to apply a mechanical cladding pressure on the said assembly before and / or during the said heating. This cladding pressure is exerted such that the supporting part and the anti-corrosive coating are clamped in contact with each other so as to compress the brazing material, which in particular results in the required value for the spacing D between the supporting part and the cladding. The cladding pressure may be applied by a mechanical clamping system (12), such as a system of spring rods and clamping plates or a pneumatic system (such as an inflatable cushion). The low temperature brazing operation according to one preferred embodiment of the invention limits degradation of the mechanical clamping system (12) . The cladding pressure is typically more than 0.1 MPa, preferably more than 0.3 MPa, and even better more than 0.5 MPa. The said determined parrs are called bond surfaces. The junction between the supporting part and the coating may be created by several bond surfaces. The surface (and more precisely the bond surface(s)) of the supporting parts (21, 22) and / or the coatings (31, 32) is advantageously treated in advance before the brazing operation, particularly so as to eliminate surface oxides. For example, at least one treatment can be applied chosen from among chemical, electrochemical, physicochemical and mechanical treatments (such as chemical or electrochemical stripping, in machining or rubbing down). These treatments may be combined. For supporting parts, the treatment applies to at least the surface to be coated. In order to increase the solidity of the junction, the inventive method may also comprise the deposition of at least one coat that could improve the bond of the brazing material and limit the formation of weakening compounds. The deposition may be made chemically, electrolytically or by vapour phase (physical vapour phase or chemical vapour phase deposition) . The said coat is typically metallic, for example made of titanium or copper. The deposit may be made on the supporting part (2, 21, 22), on the metal coating (3, 31, 32) or on both. The deposit is made before the brazing operation. The brazing material is preferably distributed uniformly between the supporting part and the anti-corrosive coating so as to obtain a uniform bond coat and to increase the contact surface area between these two elements. The supporting part (2, 21, 22) is preferably made of steel. The steel used is usually a carbon steel or a stainless steel. The metallic anti-corrosive coating (3, 31, 32) is typically made of titanium, a titanium alloy, tantalum, a tantalum alloy, zirconium, a zirconium alloy, nickel-based alloy or stainless steel. The brazing material (4, 41, 42) may be a meltable alloy (typically a eutectic alloy) or a fusible metal. The said material (4, 41, 42) may contain a flux. It is advantageous if the brazing material can diffuse in the element with which it is in contact, which provides a very strong bond between the said elements. The brazing material is typically in the form of a powder, a sheet or a lattice. In his tests, the applicant has observed that the lattice has the advantage that it efficiently compensates for any variations in the spacing D between bond surfaces. The brazing material (4, 41, 42) is typically made of a material containing silver, copper, zinc, cadmium or tin, or a mix of these elements, that have a brazing temperature of less than about 750°C, and preferably between 600°C and 720°C. The supporting parts 2, 21, 22) and the anti-corrosive coating (3, 31, 52) may typically be in the form of a plate or a sheet metal. These elements may be cut in advance, particularly to form openings and access paths. The supporting parts or the untreated assembly parts (21, 22) may also comprise integrated assembly means such as protuberances (211, 212, 221, 222). Coated shape parts (111, 112) are typically made with semi-cylindrical, convex or other shapes. The operation for the assembly of coated assembly parts (111, 112) designed to produce a chemical device element (100), comprises the formation of joints (60, 60a, 60b, 70, 70a, 70b) between the said parts, typically by welding operations using any known means. Joints between the supporting parts (21, 22) are normally made separately from the joints between coating parts (31, 32) . In order to make these joints, the applicant has developed a particularly advantageous variant of the inventive method in which the ends (61, 61a, 61b, 62, 62a, 62b) of the metal parts (21, 22) are previously hollowed out, typically by machining, before the coating is fixed, as illustrated in Figure 5. This variant considerably facilitates the formation of joints between assembly parts. In particular, it eliminates the need for machining of the supporting part after brazing, which would otherwise be necessary to make junctions between supporting parts. According to one preferred embodiment of this advantageous variant of the invention, the process for manufacturing a chemical device element comprises: the formation of recesses (81, 82) at the ends (61, 62) of the said supporting parts (21, 22) that will be joined together before the brazing operation, so as to prevent brazing between each coating (31, 32) and each supporting part (21, 22) adjacent to the said recesses; moving the ends (71, 72) of each coating (31, 32) clear, typically by lifting these ends (71, 7 2), after the brazing operation; the formation of a joint (60) between the ends (61, 62) of the said supporting parts (21, 22), typically by welding; the formation of a joint (70) between the ends (71, 72) of the said coatings (31, 32), typically by welding. The coatings are fixed on supporting parts using the processes described above. The purposes of the recesses (81, 82) are to prevent brazing between supporting parts (21, 22) and coatings (31, 32) where they are formed, called the separation area (91, 92) in the remainder of this description. In order to achieve this, the depth P of the recesses (81, 82) may be relatively shallow, typically between 1 and 5 mm, wl|ich avoids reducing the mechanical characteristics of the supporting part (21, 22). The width L of the said recesses (81, 82) is fixed so as to make it easy to move the junction area between the supporting parts clear. The length L is typically between 10 and 50 mm. The recess (81, 82) is typically in the form of a plane area parallel to the plane of the ends (61, 62) of the supporting parts (21, 22). More precisely, the process for manufacturing a chemical device element (100) according to this advantageous variant of the invention includes: the supply of at least one first supporting part (21) and one second supporting part (22); the formation of recesses (81, 82) at the ends (61, 62) of the said supporting parts (21, 22) that are to be joined; fixing of the coating (31, 32) onto each supporting part (21, 22) by brazing in a controlled atmosphere (preferably at a temperature below 750°C, and even better between 600 and 720°C), thus producing intermediate coated assembly parts (101, 102); forming (typically by rolling or calendering) of intermediate coated parts (101, 102), thus producing coated assembly parts (111, 112); moving the ends (71, 72) of each coating (31, 32) clear, typically by lifting these ends (71, 72); the formation of joints (60) between the ends (61, 62) of the said supporting parts (21, 22), typically by welding operations; the formation of joints (70) between the ends (71, 72) of the said coatings (31, 32) , typically by welding operations. The said chemical device element (100) is typically included in the group including storage containments, tanks, heat exchangers, reactors, mixers, treatment devices and conveyance devices. Example Manufacturing tests en assembly parts coated according to the inventive method have been made using carbon steel plates and anti-corrosive coatings made of tantalum. The brazing material was a silver-based alloy containing copper, zinc and tin. Mechanical pressure was applied continuously during the brazing operation. The brazing temperature was less than 7 00 °C. The junction between the steel plate and the tantalum sheet metal had very few defects after brazing and its hardness did not exceed 150 Hv. Forming tests with a low radius of curvature showed that there was no breakage in the junction. Advantages of the invention Clad metal products obtained using the method according to the invention have the advantage of a high transverse thermal conductivity due to a close bond between the supporting part and the anti-corrosive coating over most of the bond surface, which is not the case for a bond obtained, for example, by knurling which only produces bonding series. A transverse thermal conductivity is particularly advantageous in chemical devices comprising heat transfer means such as a heat exchanger or a double cooling or heating skin. Clad metal products according to the invention also have a high formability and are consequently easy to use in making chemical device elements. The manufacturing method eliminates the need for the machining step for the supporting part during subsequent welding operations to make chemical device elements. List of numeric references 1 Clad metal product 100 Chemical device element 101, 102 Intermediate coated assembly part 111, 112 Coated assembly part 2 Metal supporting part 21,22 Untreated supporting part or assembly part 211, 212, 221, 222 Integrated assembly means 3,31,32 Coating 4,41,42 Brazing material 5,51,52 Initial assembly 60 Joint between supporting plates 61, 61a, 61b, 62, 62a, 62b End of an assembly part 7 0 Joint between coatings 71, 71a, 71b, 72, 72a, 72b End of a coating 81,82 Recesses 91,92 Separation area 10 Chamber with controlled atmosphere 5 11 Heating means 12 Clamping system CLAIMS 1. Method for making a chemical device element (100) comprising at least one first and or.e second coated assembly part (111, 112), each said coaced assembly part comprising a metal supporting part (21, 22) and at least one metallic anti-corrosive coating (31,32), the said method being characterised ir. that it comprises: • manufacturing of intermediate coated assembly parts (101, 102) according to a method comprising a brazing operation including: formation of an initial assembly (51, 52) comprising a supporting part (21, 22), an anti-corrosive coating (31, 32) and at least one brazing material (41, 42) between the supporting part and the coating; introduction of the initial assembly (51, 52) into a brazing chamber with controlled atmosphere (10); formation of a controlled atmosphere in the said chamber (10); heating of the said assembly (51, 52) to a temperature equal to at least the brazing temperature of the said brazing material (41, 42) so as to fix the anti-corrosive coating (31, 32) on the supporting part (21, 22) by brazing; • forming of the said intermediate coated parts (101, 102), so as to obtain the said coated assembly pares (111, 112); • assembly of the crated assembly parts (111, 112), so as to obtain the s aid chemical device element (100) . 2. Manufacturing methrd according to claim 1, characterised in that the crazing temperature is less than approximately 7 50°C. 3. Manufacturing methrd according to claim 2, characterised in that the brazing temperature is between 600°C and 720°C. 4. Manufacturing methci according to any one of claims 1 to 3, characterised in that the controlled atmosphere is composed essentially of inert gas. 5. Manufacturing method according to claim 4, characterised in that the inert gas is chosen from the group comprising rare gasses, nitrogen and mixes of them. 6. Manufacturing methcd according to any one of claims 1 to 5, characterised in that the controlled atmosphere in the chamber (10) is a pressure P between approximately 102 and 105 Pa during brazing. 7. Manufacturing method according to any one of claims 1 to 6, characterised in that it also comprises application of a cladding pressure on the said initial assembly (51, 52) during all or part of the brazing operation. 8. Manufacturing method according to claim 7, characterised in that the cladding pressure is more than 0.1 MPa, preferably more than 0.3 MPa, and even better more than 0.5 MPa. 9. Manufacturing methoc according to any one of claims 1 to 8, characterised in that it also comprises at least one prior surface treatment of the said supporting parts (21, 22) to be coated, and in that this treatment is chosen from the group comprising chemical, electrochemical, physicochemical and mechanical treatments and combinations cf them. 10. Manufacturing methed according to any one of claims 1 to 9, characterised in that it also comprises deposition of at least one coat that could improve the bond of the brazing material and limit the formation of weakening compounds. 11. Manufacturing method according to claim 10, characterised in that the said coat is metallic. 12. Manufacturing method according to claim 10 or 11, characterised in that the deposition is made chemically, electrolytically or by vapour phase. 13. Manufacturing method according to any one of claims 1 to 12, characterised in that the said coating (31, 32) is less than 1 mm thick. 14. Manufacturing method according to any one of claims 1 to 12, characterised in that the said coating (31, 32) is less than 0.5 mm thick. 15. Manufacturing method according to any one of claims 1 to 14, characterised in that the said coating (31, 32) is a metal chosen from the group comprising tantalum, tantalum alloys, titanium, titanium alloys, zirconium, zirconium alloys, nickel-based alloys or stainless steels. 16. Manufacturing method according to any one of claims 1 to 15, characterised in that the brazing material (41, 42) contains sliver, copper, zinc, cadmium or tin, or a mix of these elements. 17. Manufacturing method according to any one of claims 1 to 16, characterised in that the brazing material is in the form of a powder, a sheet or a lattice, 18. Manufacturing method according to any one of claims 1 to 17, characterised in that the said supporting part (21, 22) is a steel part. 19. Manufacturing method according to claim 18, characterised in that the said steel is a carbon steel or a stainless steel. 20. Manufacturing method according to any one of claims 1 to 19, characterised in that the said supporting part (21, 22) is in the form of a plate or a sheet metal. 21. Manufacturing method according to any one of claims 1 to 20, characterised in that the said coating (31, 32) is in the form of a plate or a sheet metal. 22. Manufacturing method according to any one of claims 1 to 21, characterised in that it also comprises: the formation of recesses (81, 82) at the ends (61, 62) of each supporting part (21, 22) that will be joined together before the brazing operation, so as to prevent brazing between each coating (31, 32) and each supporting part (21, 22) adj acent to the said recesses; moving the ends (71, 72) of each coating (31, 32) clear, after the brazing operation; the formation of a joint (60) between the ends (61, 62) of the said supporting parts (21, 22); the formation of a joint (70) between the ends (71, 72) of the said coatings (31, 32) . 23. Manufacturing method according to claim 22, characterised in that the joints (60) between the ends (61, 62) of the said supporting parts (21, 22) and the joints (70) between the ends (71, 72) of the said coatings (31, 32) are made by welding. 24. Manufacturing method according to any one of claims 1 to 23, characterised in that the said chemical device element (100) is chosen from the group comprising storage containments, tanks, heat exchangers, reactors, mixers, treatment devices and conveyance devices. 25. A method for making a chemical device element substantially as herein described with reference to the accompanying drawings.

Documents:

2655-chenp-2004 abstract granted.pdf

2655-chenp-2004 claims granted.pdf

2655-chenp-2004 description(complete) gratned.pdf

2655-chenp-2004 drawings granted.pdf

2655-chenp-2004-claims.pdf

2655-chenp-2004-correspondnece-others.pdf

2655-chenp-2004-correspondnece-po.pdf

2655-chenp-2004-description(complete).pdf

2655-chenp-2004-drawings.pdf

2655-chenp-2004-form 1.pdf

2655-chenp-2004-form 3.pdf

2655-chenp-2004-form 5.pdf

2655-chenp-2004-pct.pdf