Title of Invention

A PROCESS FOR MAKING A COMPOSITE VESSEL

Abstract

A process for fabricating a composite vessel includes: A) preforming a composite shell (63) for the vessel (by, for example, winding fiberglass and a thermoplastic material onto a thermoplastic mandrel), the shell having at least one opening for access to the interior; B) introducing an inflatable liner (66) fabricated from a thermoplastic film (67) into the composite shell through the opening; C) surrounding the composite shell with an outer thermoplastic film; D) in a mold (60) (which may optionally itself be heated), heating the thermoplastic film liner, the composite shell and the outer thermoplastic film while applying at least one force (e.g., by evacuating the mold, pressurizing the interior of the thermoplastic film liner or both) which tends to urge the thermoplastic film liner, the composite shell and the outer thermoplastic film outwardly; E) continuing step D) until the thermoplastic film liner, the composite shell and the outer thermoplastic film consolidate and the resulting composite structure becomes fluid and flows to conform to the interior surface of the mold, thereby forming the composite vessel; F) allowing the formed composite vessel to cool; and G) removing the formed composite vessel from the mold. The resulting composite vessel exhibits superior mechanical and aesthetic properties.

Full Text

FORM 2 THE PATENTS ACT 1970 [39 OF 1970] & THE PATENTS RULES, 2003 COMPLETE SPECIFICATION [See Section 10; rule 13] "A PROCESS FOR MAKING A COMPOSITE VESSEL" ESSEF CORPORATION, of Executive Center East, Suite 314, 4020 Mt. Carmel-Tabasco Road, Cincinnati, Ohio 45255, United States of America, The following specification particularly describes the invention and the manner in which it is to be performed: 05-067-2005 METHOD FOR FABRICATING COMPOSITE PRESSURE VESSELS AND PRODUCTS FABRICATED BY THE METHOD Field of the Invention This invention relates to the art of fabricating pressure vessels and, more particularly, to improved methods for fabricating composite pressure vessels and to composite pressure vessels made in accordance with the improved methods. Background of the Invention Pressure vessels, such as hot water heaters, boilers, pressurized gas tanks and the like, have traditionally been fabricated from metal such as steel. However, in recent years, the use of composite pressure vessels has become more prevalent. These composite pressure vessels have typically been fabricated by a filament winding process which utilizes thermoset plastic resins such as epoxies, polyesters and vinylesters. Briefly, this technology is the process of impregnating dry fibers, such as fiberglass strands, with catalyzed resin prior to application to a mandrel. Preimpregnated fibers ("prepreg") may also be used. The mandrel and applied composite are then cured, at ambient temperature or with heat, to set-up the laminate and obtain a hard resin and fiber laminate shell. This shell is either removed from the mandrel or the mandrel itself becomes part of the finished product. Although the specific product application determines the exact function of the resin, in all c-ases, in all cases it serves as the support structure for keeping the continuous fiber strands in position. The thermoset resins used in these processes can be categorized as of the low temperature commodity type which are characterized by their relative ease of use, low cost and availability. These resins have long served to meet the performance requirements of a wide range of pressure vessel products. However, these resin systems have well known drawbacks which may include their limited temperature capabilities, unsatisfactory finished product aesthetics, lack of extended durability, lack of appropriateness for recycling and manufacturing related issues such as downtime due to clean-up and material handling costs. Further, there are environmental concerns arising from worker exposure to vapor, overspray, emissions, etc. encountered during the fabrication processes. Some engineered thermoset resins improve performance through higher temperature capability, but unacceptable material costs are associated with them. In addition, because of the materials and processes employed, composite pressure vessels prepared according to the prior art processes inherently have residual and significant internal stresses which, along with certain temperature sensitive incompatibilities of the materials, limit the pressure and temperature ranges in which the pressure vessels find use. Thus, increasing performance demands, environmental issues, manufacturing issues and new market opportunities have emphasized the limitations of the use of thermoset resins in the 2 manufacture of composite pressure vessels. Composite pressure vessels with higher temperature and pressure capabilities, improved appearance and greater durability and impact resistant characteristics and which, as to fabrication, are more environmentally-friendly, more cost effective and present fewer manufacturing issues, are accordingly highly desirable. Therefore, it will be recognized by those skilled in the art that a process for fabricating composite pressufe vessels which achieves improvement in all these areas requires a fundamentally different philosophy. It is to the provision of such a fundamentally improved process, and to pressure vessels made by such process that the present invention is directed and by which the following characteristics are obtained: improved contact at higher temperatures between the fiber and resin, better control over reinforcement/matrix ratio, scrap materials which can be effectively recycled, diminished regulation issues caused by emissions, higher processing speeds for the winding (or other overlaying mode) and curing steps, potential labor savings due to less material handling, floor space reduction, adaptability to automation, a safer environment for employees, simplification of processing lines and of material storage and handling, faster changeover times, faster startups, lower training costs, lower energy costs, etc. Therefore, pressure vessels fabricated according to the process are substantially stress relieved and exhibit improved performance over the prior art pressure vessels in that, inter alia, they can withstand higher pressures and temperatures, are more impact resistant and also have a significantly better finish. Objects of the Invention It is therefore a broad object of this invention to provide an improved process for fabricating a composite pressure vessel. It is more particular an object of this invention to provide such an improved process which enjoys advantages including, as opposed to prior art processes of fabricating composite pressure vessels: better control over reinforcement/matrix ratio, scrap materials which can be effectively recycled, diminished regulation issues caused by emissions, higher processing speeds for the winding (or alternatives to winding) and curing steps, substantial labor savings due to less material handling, floor space reduction, susceptibility to automation, a safer environment for employees, simplification of processing lines and of material storage and handling, faster changeover times, faster startups, lower training costs, lower energy costs, etc. In another aspect, it is an object of this invention to provide a process for fabricating composite pressure vessels which, in use, enjoys long term performance at least as good as that of traditional pressure vessels. In yet another aspect, it is an object of this invention to provide high quality composite pressure vessels fabricated according to new processes. -3 WE CLAIM: 1. A process for making a composite vessel, having at least one closed end, comprising the steps of: A) fabricating a thermoplastic liner for the vessel; B) overlaying onto the thermoplastic liner a layer comprising commingled fiber and thermoplastic material to obtain a composite intermediate structure; C) pressing and heating the composite intermediate structure to effect at least partial consolidation of the components thereof in pressing and heating apparatus comprising: 1) an upper bag; and 2) a lower bag; 3) the upper and lower bags being of such dimensions that, when in operative pressing and heating mutual positions, their facing peripheral regions abut to substantially encompass the composite intermediate structure; D) placing the at least partially consolidated composite intermediate structure in a mold; B) heating the composite intermediate structure in a mold while applying at least one force thereto tending to urge the composite intermediate structure against and into the shape of the interior walls of the mold; F) continuing step E) until the thermoplastic liner and the overlaid layer fully consolidate to form a composite vessel; G) cooling the mold and composite vessel until the composite vessel is solidified; and H) removing the formed composite vessel from the mold. 2. The process as claimed in claim 1 wherein the upper and lower bags of the pressing and heating apparatus are fabricated from silicone rubber and in which each of the upper and lower bags contain heaters. 3. The process as claimed in claim 2 wherein, during step B), the fiber and thermoplastic material are wound onto the thermoplastic liner to obtain the composite intermediate structure. 4. The process as claimed in claim 3 wherein at least one force applied during step B) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 5. The process as claimed in claim 2 wherein the fiber and thermo¬plastic material constitute are commingled in a fabric prior to being overlaid onto the thermoplastic liner. 6. The process as claimed in claim 5 wherein at least one force applied during step B) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 7. The process as claimed in claim 2 wherein at least one force applied during step B) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 8. The process as claimed in claim 1 wherein the pressing and heating apparatus comprises the upper and lower bags respectively carried in facing relationship by upper and lower press components. 9. The process as claimed in claim 8 wherein the upper and lower bags of the pressing and heating apparatus are fabricated from silicone rubber and wherein each of the upper and lower bags contain heaters. 10. The process as claimed in claim 9 wherein, during step B), the fiber and thermoplastic material are wound onto the thermoplastic liner to obtain the composite intermediate structure. 11. The process as claimed in claim 10 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 12. The process as claimed in claim 9 wherein the fiber and thermoplastic material constitute are commingled in a fabric prior to being overlaid onto the thermoplastic liner. 13. The process as claimed in claim 12 wherein at least one force applied during step B) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 14. The process as claimed in claim 9 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 15. The process as claimed in claim 8 wherein, during step B), the fiber and thermoplastic material are wound onto the thermoplastic liner to obtain the composite intermediate structure. 16. The process as claimed in claim 15 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 17. The process as claimed in claim 2 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 18. The process as claimed in claim 17 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 19. The process as claimed in claim 8 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 20. The process as claimed in claim 1 wherein, during step B) the fiber and thermoplastic? material are wound onto the thermoplastic liner to obtain the composite intermediate structure. 21. The process as claimed in claim 20 wherein least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 22. The process as claimed in claim 1 wherein the fiber and thermoplastic material constitute arc commingled in a fabric prior to being overlaid onto the thermoplastic liner. 23. The process as claimed in claim 22 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. 24. The process as claimed in claim 1 wherein at least one force applied during step E) is obtained by introducing gas pressure into the interior of the composite intermediate structure. Dated this 9th day of March, 2001 (RANJNA MEHTA DUTT) OF REMFRY & SAGAR ATTORNEY FOR THE APPLICANTS 16

Documents:

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in-pct-2001-266-mum-cancelled pages(5-7-2005).pdf

in-pct-2001-266-mum-claims(granted)-(5-7-2005).doc

in-pct-2001-266-mum-claims(granted)-(5-7-2005).pdf

in-pct-2001-266-mum-correspondence(22-3-2006).pdf

in-pct-2001-266-mum-correspondence(ipo)-(19-2-2007).pdf

in-pct-2001-266-mum-drawing(5-7-2005).pdf

in-pct-2001-266-mum-form 19(27-4-2004).pdf

in-pct-2001-266-mum-form 1a(5-7-2005).pdf

in-pct-2001-266-mum-form 2(granted)-(5-7-2005).doc

in-pct-2001-266-mum-form 2(granted)-(5-7-2005).pdf

in-pct-2001-266-mum-form 3(30-1-2006).pdf

in-pct-2001-266-mum-form 3(5-7-2005).pdf

in-pct-2001-266-mum-form 3(9-3-2001).pdf

in-pct-2001-266-mum-form 5(9-3-2001).pdf

in-pct-2001-266-mum-form-pct-ipea-409(9-3-2001).pdf

in-pct-2001-266-mum-form-pct-isa-210(9-3-2001).pdf

in-pct-2001-266-mum-petition under rule137(5-7-2005).pdf

in-pct-2001-266-mum-petition under rule138(5-7-2005).pdf

in-pct-2001-266-mum-power of authority(5-7-2005).pdf

in-pct-2001-266-mum-power of authority(9-12-2005).pdf

in-pct-2001-266-mum-power of authority(9-3-2001).pdf