Method for forming double walled integral hinge members in blowmolded

Abstract

A die construction for forming integral hinges (60) for a blow molded carrying case. An edge of the main cavity of a lower die (12) of a blow molding die pair is provided at one peripheral wall portion (40) with sloping channels (38). A core pin (32) extends across and spans the sloping channels. The upper die (10) is provided at one peripheral portion with semi-cylindrical recesses (22) coaxial with the core pin and of the same length as the width of the sloping channel. A heated parison (46, 48) is placed (FIG. 1) between the two dies. With die closing and with the introduction of pressurized air (52) into the parison, the parison is deformed. At the same time, the pressurized air also causes one of the plastic parison sheets (46) of the parison to deform into the semi-cylindrical recess, and the other parison sheet (48) to deform into the sloping channel and also around the core pin. The two parison sheets fuse together around the core pin upon complete closing of the two dies (FIG. 3) to form a hinge boss (60) integral with the remainder of the parison sheets which form a carrying case half. The core pin (32) is then removed, to form a hinge pin recess through the hinge boss. Any number of such hinge bosses may be formed, with a single core pin spanning each sloping channel and each semi cylindrical recess. This construction and method obviates the need to subsequently drill hinge pin receiving holes (61) through the hinge bosses (60).