Production method and apparatus for double curve formed products

A production apparatus for double curve formed products in which an internal curved portion thereof and an external curved portion thereof are connected with each other integrally at one end and have a separating distance therebetween, said production apparatus comprising:

• an inner die having an engaging portion for engaging an end portion of a sheet shaped treatment product, and an external processing curved surface provided on an external circumferential surface portion continuous from said engaging portion;
• an outer die having an engaging portion for engaging the other end portion of said treatment product, and an internal processing curved surface provided on an internal circumferential surface portion continuous from said engaging portion, said outer die being coaxially and rotatably mounted outside of said inner die;
• and
• a rotation driving means for rotating said outer die in which said one end of said treatment product is engaged and said outer die in which said other end portion of said treatment product is engaged, relative to each other in such a direction that a middle portion of said treatment product is folded back, to plastically deform said middle portion of said treatment product so as to be along the processing curved surface of said inner die.

A production apparatus for double curve formed products in which an internal curved portion thereof and an external curved portion thereof are connected with each other integrally at one end and have a separating distance therebetween, said production apparatus comprising:

• an inner die in which an engaging portion for engaging an end portion of a treatment product formed in a circular sheet shape is provided in a part of an external circumferential surface which serves for a processing curved surface for said treatment product;
• an outer die in which an engaging portion for engaging the other end portion of said treatment product is provided in a part of an internal circumferential surface which serves for a processing curved surface for said treatment product, said outer die being mounted out of said inner die rotatably therearound coaxially with said inner die;
• and
• a rotation driving means for rotating said outer die in which said other end portion of said treatment product is engaged, with respect to said inner die in which said one end of said treatment product is engaged, in such a direction that a middle portion of said treatment product is folded back, to plastically deform said treatment product so as to be along the processing curved surface of said inner die.

A production method for double curve formed products, comprising:

• a first step in which a front end of a sheet material is inserted into an engaging groove in a shaft inserted so as to form an annular cavity portion in a cylindrical body in which an opening is formed on a side face thereof, said sheet being inserted through said opening to engage said front end of said sheet material into said engaging groove;
• a second step in which said cylindrical body and said shaft are rotated relative to each other in a single direction until a rear end of said sheet material is engaged with an engaging portion formed in an internal circumferential surface of said cylindrical body;
• and
• a third step in which said cylindrical body and said shaft are rotated relative to each other in a direction different from said single direction.