Abstract: In producing a twin sheet thermoformed structure, a mold is provided with major rib producing structures segregrated into discrete tabs with gaps between tabs. A first sheet of material is fused upon itself by drawing the material into the gaps between tabs from both sides of the gap. The material drawn into the gaps fuses upon contact with material being drawn into the gap from the other side forming a cross rib which tends to stabilize the side walls of the major rib. The first sheet is then fused to a second sheet of material to create a twin sheet structure.

Abstract: A cover of generally rectangular shape having a deformation reinforced central section comprises thermoforming top and bottom sheets of thermoplastic to form a specially configured arrangement of strengthening ribs which extend in longitudinal and oblique directions and of a post and receptacle centrally of the sheets, and pressing the sheets together to form a closed interior. The longitudinal ribs on the bottom sheet intersect and are welded to the oblique ribs or the top sheet respective and the post is welded into the receptacle to reinforce the center of the cover. The sheet edges are welded together to reinforce the cover shape and form a reinforced hinge support.

Abstract: A simulated fabric is produced by heating a substrate having a layer of flocked material so that both the substrate and the flocked material are softened, and applying the surface of a mold, having a finely detailed simulated fabric pattern on it, to the flocked material to plastically deform the flock to a thickness less than the original thickness such that it acquires substantially the same pattern as on the mold surface.