Abstract: A box-shaped plastic housing of integrally molded resin comprises a flat-shaped bottom wall having a peripheral edge and an upright wall extending upwardly from the peripheral edge of the bottom wall. The bottom wall and the upright wall cooperatively define an integral box-shaped molded product. The thickness of the bottom wall is in the range of two-thirds to one-third with respect to the thickness of the upright wall. The bottom wall is provided with at least one rib on its inner surface. The housing is produced by an injection molding process using a mold having a mold cavity which is provided with a groove on the inner surface of the cavity corresponding to each rib.

Abstract: An injection molding process for producing an integrally molded box-shaped plastic housing of a resin material. The housing includes integral portions of a bottom wall of a first thickness and an upright wall of a second thickness, the first thickness being in the range of from one-third to two-thirds of the second thickness and the bottom wall portion including at least one integral rib structure. A cavity is formed in a mold having cavity portions, respectively corresponding to the bottom and upright wall portions and the rib structure, in fluid communication. Fluid resin is injected through respective injection gates directly communicating with the rib structure cavity portion and the upright wall cavity portion, which provide passageways for flow of the liquid resin therethrough, thereby completely filling all cavity portions.