Spreader device for maintaining the shape of the plastic liner in non-circular cross section cylinders during winding with composite material and method of using such device

Spreader device specifically designed for manufacturing cylinders having a polygonal cross-section through filament winding technology, wherein a reinforcing fiber of composite material is wound around the outer peripheral surface of a plastic liner having a polygonal cross section, said liner having vertical sides joined by rounded vertices, a bottom wall, and an upper wall provided with an opening, said spreader device comprising a bar axially arranged in said liner, connected to a plurality of members which can be brought into contact with the inner surface of the liner to support it and maintain the shape thereof during the filament winding, characterized in that wherein said members are vertically extending wings, parallel to the axis of the bar and having a length substantially equal to the length of said vertical sides of the liner, in a number corresponding to said vertices, actuated by articulated connecting rods movable in opposite directions along said bar and rotatable in opposite directions, for bringing said wings from a position of closure adjacent to said bar to a position of opening in contact with said vertices of said liner.