MANUFACTURE OF ENVELOPE FOR AIRSHIP OR BALLOON BY MULTI-DIVISION GORE

PURPOSE:To improve productivity and prevent wrinkles at connection by forming a bellows-like folded piece out of a belt-like film material, only one side of which can be welded, folding and welding this bellows-like piece to form it into the gose shape, cutting and removing the film material on the outside of a weld line, and then turning the gore inside out. CONSTITUTION:On the rectangular part in the middle of a belt-like film material 1, the surface of which can be welded, trough lines 3 are formed at equal intervals as the base of a basic form 2, and the film material is folded into the shape of bellows along the trough lines 3. The basic form 2 of either of the ends of the belt-like body 1 is superimposed on the other folded piece, and welded by high frequency welding, etc., at the inner side of the film material 1 to form a gore 5. In this case a weld line 4 is formed in order for the shape of the gore 5 to be formed symmetrically with respect to a center trough line 3. The film material is then cut off along the weld line 4 to form an envelope 6 consisting of plural gores 5. After that, the envelope is turned inside out.