Patent ID: 7942176

Claim:
In the method of forming a drum shell that consists of sheet plywood, the steps that include: a) trapping and forming the shell under pressure and heat into generally cylindrical configuration, b) providing separate sets of inner and outer cooling platens adapted to respectively engage the interior and exterior surfaces of the heated shell, c) trapping the heated shell between such cooling platens, at elevated pressure, d) allowing the shell to cool while trapped between said cooling platens, at elevated pressure, e) and removing the cooled shell from between the cooling platens, f) said trapping and forming including relatively displacing a primary set of inner and outer semi-circular platens toward one another to trap and progressively deform the sheet plywood into U-shape having leg portions projecting in generally parallel relation from a bend formed between the primary platens, and thereafter relatively displacing a secondary set of inner and outer semi-circular platens toward one another, then toward the primary platens to trap and progressively deform the sheet plywood leg portions into semi-circular shape, there being a gap maintained between the primary and secondary set platens.