The function of an arch enclosure is, like a mould, to define a surface incorporated in a house wall when casting an arch. Conventionally, arch enclosures are produced on-site, which is time-consuming and laborious, personnel producing the arch enclosure furthermore being exposed to the elements and often also under pressure from other trades wanting to get on with their tasks whilst construction work is in progress.

The object of the present invention is to produce an arch enclosure of the generic type, which can be prefabricated and preferably delivered to the construction site fitted to a prefabricated wall element.

This object is achieved by an arch enclosure which has the features specified in the characterizing part of claim 1.

The invention moreover affords the following advantages: The arch enclosure and its outside and inside flanges prevent moisture getting into the underlying wall structure during casting of the arch and whilst the building is under construction.

The arch enclosure according to the invention provides a straight, external arch surface incorporated in underlying wall elements.

During the construction period, the risk of industrial injuries is reduced by an externally fitted guard rail, which can be fitted at an earlier stage than is the case with conventionally produced arch enclosures and which through its external fitting impedes the construction work only to a very slight extent and can easily be removed after construction work has been carried out.

The invention will be explained in more detail below with reference to the drawing attached, in which figure 1 shows a diagrammatic perspective view of a part of a first preferred embodiment of an arch enclosure according to the invention. Figure 2, in a view similar to that in figure 1, shows an alternative embodiment of an arch enclosure according to the invention. Figure 3 shows a cross-section through an arch cast using the arch enclosure in figure 1.

In the drawing 1 generally denotes an arch enclosure. This generally comprises a sheet metal profile with a horizontal U-shape, one leg 2 of which has a width defined by the thickness of a wall element 3. The length of the arch enclosure 1 is determined by the width of the wall element 3. The leg 2 is therefore fabricated to cover the upper surface 3 a of the wall element 3 and has a flange 2a, designed to cover an upper section of the inside of the lower wall element 3. The wall element has beams 4 of timber or sheet metal and an outer panel 5 of plaster, plywood, masonite, bitumen-impregnated fibreboard or the like fixed to the beams, and there is insulation 6 between the beams.

A sheet metal section 7 aligned essentially at right angles to the leg 2 joins the leg 2 to the other leg 8 of the U-profile, which along its remote edge has a flange 8a essentially parallel with the section 2. The intermediate section 7 has a flange 7a at the bottom, which covers a piece of the upper part of the outer panel 5. The flange 7a may naturally also be seen as a flange belonging to the leg 2.

9 denotes an upright reinforcement bar, which is preferably fixed to the leg 2 and to the flange 8a by welding. In order to produce a good fixing between the leg 2 and the reinforcement bars 9, the latter are formed with an angled section 9a. Horizontal reinforcement bars l Oa, l Ob are arranged at intervals from one another and in proximity to the legs 2 and 8.

For fitting a guard rail 11, as will be explained in more detail in connection with figure 3, pairs of fixing members 12 are arranged at suitable intervals from one another on the sheet metal section 7.

In the embodiment of an arch enclosure according to the invention shown in figure 2, the reinforcement bars 9 are replaced by sheet metal triangles 13, whilst the reinforcement bars 10,1 Ob remain. The sheet metal triangles 13 are located at intervals from one another and are fixed to the leg 2, to the sheet metal section 7 and to the reinforcement bars 10, lOb. The object of these sheet metal triangles 13 is the same as that of the reinforcement bars 9, that is to give the arch enclosure the requisite rigidity and stability and a certain fixing in a concrete arch, for which the arch enclosure constitutes an outer boundary.

The application and function of the arch enclosure will now be explained in more detail with reference to figure 3. As stated, the figure shows the function of the arch enclosure 1 according to the invention in connection with the casting of a concrete beam 14 on a sheet metal support layer 15. It will be appreciated that with the arch enclosure 1 according to the invention it is in no way decisive for the final outcome whether the plates of the sheet metal supporting layer 15 project by different lengths over the wall element 3; should there be differences, these are bridged by the concrete mass in the concrete beam 14.

The arch enclosure 1 is firmly anchored in the concrete beam 14 by the reinforcement bars 10a, l Ob or the sheet metal triangles 13 and by its construction prevents water from the still green concrete mass running down into the wall element 3. The flange 7a likewise prevents rain from getting into wall element 3. Preventing water from getting into the wall element 3 in this way, where it can give rise to mould and associated health risks, is crucial to the quality of the building.

The guard rail 11 is of conventional type mounted in the fixing members 12 arranged on the sheet metal section 7 of the arch enclosure. It will be noted that the invention makes it possible, before casting the arch 14, to fit the guard rail 11 to the outside of the arch enclosure, where it constitutes the least possible obstruction.