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US 5,685,452 AGranted
Container bottom with elevations made of a polymeric material and a process for production thereof
AssigneePerstorp AB
InventorKarl-Gustaf Kristoffersson
Life of this patent
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AssigneePerstorp AB
InventorKarl-Gustaf Kristoffersson
Estimating the term…
Bottom (1) to a container, box, basket, barrel, cask or the like (8) made of a polymeric material and preferably produced by injection moulding. Material thickening and essentially scalloped, jagged and/or wave-like elevations (5) constitute an integrated part of the upper (3) and/or lower (4) surface of the bottom (1). The height (FIG. 12, A-B) of the elevations (5) is 0.5-20 mm representing at least 20% of the maximum thickness of the bottom (1). Intervening spaces (6) are formed between the material thickening elevations (5). A container (8) including a bottom (1) is produced by injection moulding and is cooled in the mould in such a way that the elevations (5) hold a core temperature exceeding the surface temperature to such an extent that the core shrinkage is larger than the surface shrinkage. A strong inner tensile stress is obtained, whereby the elevations (5) work as pretensioned reinforcing bars.
A bottom comprising an integrated part of a container which is constituted of a polymeric material, wavylinear beveled material thickening elevations and widths constituting an integrated part of the upper surface of the bottom, each said material thickening elevation including a core constituting a pretensioned reinforcing bar responsive to an internal stress generated through a differential between a core shrinkage and a surface shrinkage derived during cooling of the polymeric material during molding thereof in which a core temperature exceeds a surface temperature, a lower surface of said bottom being planar and the core shrinkage being greater than that the corresponding surface of the material of the thickening elevations, whereby the shrinkage differential results in generating high internal tensile stresses such that the material thickening elevations resultingly produce said pretensioned reinforcing bars.
Dependencies are inferred from the claim text.