초록 ▼

A strong foam core structural member having an integral skin and a method of forming the foam core structure using conventional tooling, such as a clamshell mold. The method includes injecting a fluid foamable resin reaction mixture under pressure in a mold between a pair of pervious, absorbant, fle

A strong foam core structural member having an integral skin and a method of forming the foam core structure using conventional tooling, such as a clamshell mold. The method includes injecting a fluid foamable resin reaction mixture under pressure in a mold between a pair of pervious, absorbant, flexible sheets, preferably each including a nonresilient open mesh skrim. The sheets are thus expanded against the mold faces by the foaming reaction mixture, which saturates the sheets and forms a smooth skin integral with the foam core. The pervious sheets permit entrapped gasses to escape, forming a smooth integral skin on the foam core, which substantially improves the strength of the structure. The structure may also be strengthened by adding perforated reinforcement plates and injecting the fluid resin reaction mixture through and around the plates. The reinforcement plates thus become integral with the foam core.

대표청구항 ▼

1. The method of forming a foam resin core structure having a smooth composite reinforced integral skin, comprising the following steps: (a) inserting two pervious, absorbant, low density, flexible sheets in an enclosed die assembly having opposed spaced apart die surfaces and side surfaces, said

1. The method of forming a foam resin core structure having a smooth composite reinforced integral skin, comprising the following steps: (a) inserting two pervious, absorbant, low density, flexible sheets in an enclosed die assembly having opposed spaced apart die surfaces and side surfaces, said die surfaces forming an enclosed die cavity, said sheets positioned within said die cavity in spaced apart relationship to one another and generally parallel to said opposed spaced die surfaces, and said opposed die surfaces having pressure relief openings, (b) injecting a fluid foamable thermosetting resin reaction mixture under pressure into said enclosed die cavity and into the space between said sheets, said reaction mixture foaming and expanding or forcing said sheets against said opposed spaced die surfaces, said sheets absorbing said fluid thermosetting resin while permitting gas to escape therethrough into said pressure relief openings, and said resin saturating said sheets and forming a thin resin film on the exterior surfaces of said sheets adjacet said opposed spaced die surfaces, and (c) curing said foamed thermosetting resin in said enclosed die cavity, forming a thermoset resin foam core between said sheets and a relatively smooth composite reinforced integral skin on opposed sides of said core, said composite reinforced integral skin comprising said absorbant sheets soaked with thermosetting resin and a smooth external film of resin. 2. The method of forming a foam resin core structure as defined in claim 1, securing an open mesh, relatively nonresilient flexible skrim sheet in face to face contact to each of said absorbant sheets, then inserting said sheets in said die cavity with said absorbant sheets positioned closest to said opposed spaced die surfaces for forming the outer skin of said foam resin core structure. 3. The method of forming a foam resin core structure defined in claim 1, characterized in that said reaction mixture is a liquid foamable rigid polyurethane having a density sufficient to expand said sheets against said opposed die surfaces, but wet enough to saturate said sheets, forming a thin film of polyurethane on the exterior surface of said sheets. 4. The method of forming a foam resin core structure defined in claim 3, characterized in that said sheets each comprise a pair of pervious, absorbant, low density paper sheets having a loosely woven, relatively nonresilient flexible skrim sheet located between said absorbant sheets. 5. The method of forming a foam core structure defined in claim 1, including locating a perforated metal place in said die cavity and between said sheets and injecting said fluid foamable resin reaction mixture through the perforations in said plate, such that said foam core is integral through the perforations in said plate. 6. The method of forming a foam resin core structure having a smooth composite reinforced integral skin, comprising the following steps: (a) inserting two pervious, composite absorbant skin sheets in an enclosed mold cavity having opposed spaced apart contoured mold surfaces facing and generally parallel to said skin sheets, said skin sheets positioned within said mold cavity in spaced apart relationship to one another, said skin sheets each comprising outer and inner pervious, low density, absorbant, flexible paper sheets and a relatively nonresilient, flexible, open mesh skrim sheet located between said paper sheets, (b) injecting a fluid foamable thermosetting resin reaction mixture under pressure into said mold cavity and into the space between said skin sheets, said reaction mixture foaming and expanding or forcing said skin sheets against said opposed spaced mold surfaces, said skin sheets absorbing said fluid thermosetting resin while permitting gas to escape therethrough, said resin saturating said absorbant paper sheets and forming a thin resin film on the exterior surfaces of said outer paper sheets, adjacent said opposed contoured mold surfaces, and (c) curing said foamed thermosetting resin in said die cavity, forming a thermosetting resin foam core between said skin sheets and a relatively smooth composite reinforced integral skin on opposed sides of said core, said composite reinforced integral skin comprising said skin sheets soaked with thermosetting resin and a relatively thin exterior film of resin. 7. The method of forming a foam resin core structure as defined in claim 6, wherein said reaction mixture is a liquid foamable rigid polyurethane having a density great enough to expand said skin sheets against said opposed mold surfaces, but low enough to saturate said skin sheets, forming a thin film of polyurethane on the exterior surfaces of the outer absorbant sheets. 8. The method of forming a foam resin core structure defined in claim 6, including placing an elongated metal reinforcing plate in said mold at a position between said absorbant skin sheets such that said fluid foamable resin reaction mixture flows around said reinforcing plate and said plate becomes an integral part of said resin foam core structure.