Method of molding a re-enforced article

#The invention relates to method and apparatus for re-enforcing rotationally molded elements, particularly useful for thickwall products made of foamed plastics materials.

#In the design of rotationally molded products it occasionally happens that certain parts are subjected to stresses higher than others; or that certain parts are inherently of less rigidity and/or strength due to their design, e.g. large-span planar portions.

#One way of overcoming this difficulty is to increase the wall thickness of the product. This however, is a costly solution since, as known in the art of rotational molding it is very difficult to form products of varying wall thickness, and normally all the walls would have to be of excessive thickness without serving any useful purpose.

#These and other features of the invention will become apparent from the ensuing description of two preferred embodiments thereof, given by way of example only, with reference to the attached drawings, wherein

#FIG. 1 illustrates a known re-enforcing method;

#FIG. 2 is a cross-sectional view of a re-enforcing arrangement according to the invention, substituting that of FIG. 1; and

#In FIG. 1 there is shown a product portion having a first planar wall 1 of foamed plastics, and a second wall 2 extending parallel to the wall 1. By forming oppositely located depressions 3 and 4 in mold walls 5, the walls 1 and 2 become engaged with each other and fused together at the region 6. This contact between the walls acts as a rigid distance-piece, for re-enforcing the respective area of the product.

#Instead of the special mold design, the same result could have been achieved by completely filling the inner space between the mold walls 5, however, at the expense of extra materials.

#In the arrangement of FIG. 2 the same walls 1 and 2 are spacedly interconnected during the rotational forming thereof by a pair of embedded inserts 7 and 8, which may be temporarily supported at their appropriate places by small studs 9 and 10 projecting from the inner surfaces of the mold walls 5, and fitting into suitable holes formed in inserts 7 and 8, respectively.