GB1070874A - Lightweight constructional elements - Google Patents

Abstract

Lightweight structures are made by binding a plurality of hollow spheres together with an adhesive or binder in a mould, without the application of pressure. The products may be laminated by covering either or both surfaces with panels. The binder may form a foamed matrix filling the interstices between the spheres and may be polyurethane or polystyrene foam. The mould may have vent holes for the escape of excess foam. Various sizes of spheres may be used and they may be, for example, plastic table tennis balls or thin wall metal spheres. Where laminated structures having two surface panels are being made, a plurality of tubular spacers extending from one panel to the other may be incorporated. The binder may be a foamed resin or other adhesive filling the entire space between the spheres or merely an adhesive such as a non-foaming resin, joining the spheres at their points of contact and leaving spaces elsewhere. In Fig. 12 (not shown) to a mould having apertured sidewall (6) and base-board (7) is added a foaming mixture which has not yet begun to foam or is not yet fully foamed. The top board (9) is put on (Fig. 13, not shown) and excess foam is expressed through the apertures (10) in the sidewalls. In Fig. 17 (not shown) the foaming mixture is squeezed through apertures (15) in mould member (13) by ram (14). In Fig. 18 (not shown), a previously prepared mixture of spheres and binder (8) is poured into a concave mould (16) containing a layer of spheres (17). The mould parts may be permanent laminae or else releasable parts previously coated with, for example, a silicone resin. The laminae may be of a light metal, wood or plastic. The products are useful in aircraft construction.