Method for forming articles from plastic sheet material

Abstract

Abstract A vacuum-forming operation in which a pair of adjacent compartment liners are formed from a single sheet of thermoplastic material. A sheet of thermoplastic material is disposed to extend over the molds, and is heated, causing it to soften while the molds are held in pivoted position in which the confronting surfaces are substantially spaced from one another. Mold assist-plugs and the molds are then moved. relative to one another, to urge the sheet into general close conformity with the molds. While the sheet of material is still soft, the assist-plugs further are caused to engage the mod frame structure, through the intermediacy of the sheet, pivoting the frame structure and causing adjacent wall portions of the molds to move toward one another and assume their closely spaced position. Air entrapped between the heated sheet and the walls of the mold not provided with the auxiliary section is then evacuated through a number of small ports or vents in the walls, thereby forming on of the desired liners, whereupon the auxiliary section of the other mold is projected and air entrapped between the heated sheet and the mold is evacuated, forming the other of the desired liners with an undercut region. The liners are then cooled, the extended auxiliary mold section is retracted from the undercut region, and the liners are stripped as a unit from the undercut region, and the liners are stripped as a unit from the molds.

Inventors

• 👤 N Houghton

Bibliographic Details