The present invention relates to a panel of composite structure. Primarily it is intended to provide by the in¬ vention a panel of composite structure which is well suited to form a platform in scaffolds, i. e. the element of a scaffold, which forms the floor of the several floor plans of the scaffold. The mounting and demounting of scaffolds is a heavy and laborious work since the elements of scaf¬ folds of conventional type are heavy and hard to handle. Those people who are engaged in this type of work therefore often suffer of difficult industrial injuries. However, scaffolds have been proposed re¬ cently which are composed of light elements which do not weigh over 10 kg except the platforms which in these scaffolds are made of wood and are relatively heavy. Accordingly, there is a clear need of a lig- hter and more easily handled scaffold platform.

Also in another sector of the building indus¬ try, viz. in case of mold panels it is desired to reduce the weight without reducing the stiffness of the mold panels as a consequence thereof, so that the mold panels can be more easily handled than the mold panels available today, which are made of iron and/or wood.

The object of the invention is to provide a panel of composite structure which can be used as a scaffold panel or a mold panel and in all prob¬ ability can be used also in other connections and which is of such structure that it can be classified as a light element.

According to the invention this object is achieved by the panel having obtained the charac¬ teristics of claim 1.

The invention also provides a method for manu¬ facturing the panel having the characteristics of claim 8.

In order to explain the invention in more de- tail reference is made to the accompanying drawing in which

FIG. 1 is a side view of a scaffold panel ac¬ cording to the invention,

FIG. 2° is a plan view of the scaffold panel, FIG. 3 is a cross sectional view of the scaf¬ fold panel in the left half of the metal structure only, forming part of the scaffold panel, and in the right half of the complete scaffold panel, and

FIG. 4 is a fragmentary perspective view of the end portion of the scaffold panel.

The scaffold panel shown in the drawing is of a composite structure and comprises two longitudinal edge girders 10 of box-shaped profile and two sheets 11 located between the girders and mutually spaced. In the preferred embodiment the edge girders consist- of a material having a coefficient of elasticity which is larger than the coefficient of the material of the sheets to impart to the scaffold panel the necessary stiffness. Preferably the edge girders consist of steel, and in that case they should be surfaced e. g. zinkified or aluminized, to prevent ' corrosion, the sheets preferably consisting of alu¬ minium sheets which have a coefficient of elasticity which is about 1/3 of the coefficient of elasticity

2 of steel (about 7000 and about 21000 kg/m ) . The sheets form hook-shaped edge portions 12, and at these edge portions the sheets engage hook-shaped - edge portions 13 of the edge girders. The edge girders and the sheets define a cavity 14 which ex- tends continuously between the sheets into the box-

shaped girders ^' as will be seen from the left half of

FIG. 3, and this cavity isfilled with a core material 15 as will be seen from the right half of

FIG. 3. The core material can con- sist of a rigid foam material, preferably a foamed plastics material such as foamed polyurethane free of freon and having

2 a density of 55 kg/m . As com- pared with freon foam the foam which is free from freon has a lower K value but this factor is of no importance in connection with a scaffold platform and, therefore, the environmental considerations outweigh when choosing foamed plastics material. The foamed plastics material not only stiffens the box structure formed by the edge girders and the sheets but also binds the engagement between the hook- shaped portions 12 and 13 the binding being par¬ ticularly effective if the hook-shaped portions are arranged in an oblique angle, substantially 45°, to the plane of the sheets as in the embodiment dis- closed. The stiffness of the scaffold platform made as a composite structure will be further increased by providing as the upper sheet a grooved sheet - preferably having wide shallow grooves as shown in the drawing - the lower sheet preferably being of the same type although the grooves of this sheet do not affect the stiffness; however, it is advan¬ tageous to build the scaffold of identical elements as far as it is possible.

Each edge girder forms on the upper side there- of an edge border 16, and between the edge borders the scaffold platform is provided on the upper side thereof with a surface covering 18 the thickness of which corresponds to the height of the edge borders. The edge borders thus prevent the surface covering from being kicked loose. Preferably the surface

covering consists of a rubber sheeting which has been attached to the surface of the edge girders and. the upper sheet by vulcanization after said surface having been primed. The vulcanization requires a temperature of about 160°C, and heating of the scaffold platform to this temperature has no adverse effects because the polyurethane foam will be af¬ fected at about 200°C only. The surface covering forms an aήti-skid and wear layer on the scaffold panel and also protects the upper sheet against pen¬ etration e. g. if a heavy and sharp object were dropped onto the scaffold panel. Moreover, the sur¬ face covering can easily be cleaned and is nice to walk on and, additionally, it protects the hook- shaped engaging portions 12, 13 on the upper side of the scaffold platform against penetration of water thereinto and following corrosion.

The scaffold platform is terminated at the ends thereof by means of end caps 18 of plastics which close the cavity of the scaffold platform, filled with foamed plastics material, at the ends of the platform. On the lower side the scaffold platform forms two recesses 19, preferably rubber faced, in each edge girder to receive therein the bars or beams of the scaffold, in which the scaffold plat¬ form is to be supported. Several scaffold platforms are arranged in a row one beside the other on said ^* bars or beams to form a floor plane in the scaffold. Finally, it should be mentioned that each edge girder on the inner side thereof forms a longitudi¬ nal channeled depression 20. By this arrangement the" edge girder can be used as a handle in order that the scaffold platform can be easily carried and handled. When the scaffold platform described is manu-

factured by the method of the invention the follow¬ ing procedure is applied. When the edge girders 10 and the two sheets 11 have been engaged with each other at the hook-shaped portions 12, 13 in a fix- ture which secures the position and interengagement of the elements, the two end caps 18 are mounted to close the cavity 14 defined by the edge girders, the sheets, and the end caps. In one end cap there is provided an aperture and through this aperture a nozzle is inserted for injecting the components of the rigid foam plastics material 15 which shall form part of the scaffold platform structure. These com¬ ponents are foamed in the cavity 14 and fills this cavity to set in situ therein. During this setting the engagement at the hook-shaped portions 12, 13 will be bound. The aperture in said one end cap then is closed preferably by means of a plastics plug. When the scaffold platform has been removed from the fixture the surface covering 17 is attached to the upper side of the scaffold platform.

The metal sheets 11 can be replaced by sheets of another material than metal e. g plastics or wood. It is not necessary that the core material iε a foamed material since other materials which adhere to the sheets and the edge girders and can be in¬ jected into the cavity defined by the sheets and girders to fill said cavity, can also be used in connection with the invention.