DE-A-33 43 651 discloses an electrical installation sys- tem which serves to facilitate the mounting of the elec- trical components in the building. It is well-known that some time is wasted in that the individual trades have to wait for each other on a building site, since it iS dif- ficult to coordinate the processes, and this problem has not been solved by the prior art, far front it.

The object of the invention is to make the installation work more effective and flexible so that e. g. carpenters, painters and electricians can work more independently of each other, and also so that the ever increasing interna- tional trade in building elements is not impeded by na- tional standards for the electrical components.

This object is achieved in that the concealed installa- tion system is drilled through a covering for the build- ing part to provide a hole in which a coupling frame is arranged, said coupling frame being fixed mechanically relative to the concealed installation system so that the coupling frame and the concealed installation system to- gether form a cavity to receive current-carrying wires and respective electrical components.

What previously constituted the base of a known mounting frame, e. g. in the form of an installation box, is now constituted by the cavity which is provided in the first instance within the building part by means of the con- cealed electrical installation system. Later on when the cavities are drilled, the coupling frame of the invention is mounted, which coupling frame, in one embodiment, pre- dominantly has the shape of a pipe section with a cross- section contour that corresponds to the electrical com- ponent which is to be mounted in the building part.

The centering of the drilling may be facilitated by using magnets, and once a hole has been made, other holes may advantageously be made by means of a drill jig.

The coupling frame comprises coupling means which are adapted to be inserted through the hole and are adapted to be fixed so that the coupling frame is secured.

The coupling frame may be adapted to receive a partition wall to separate a power current installation from a weak current installation. The installation as a whole is routed through the concealed installation system, but can in this manner be terminated in respective cavities for associated electrical components.

The invention also relates to a coupling frame for per- forming the method according to claim 1. The coupling frame is characterized in that it is adapted to be in- serted into a hole which extends through a building cov- ering, which covers the concealed installation system, and into the installation cavity, and that the coupling frame has coupling means which are adapted to fix the

coupling frame mechanically relative to said installation cavity.

Preferably, the external wall of the coupling frame ad- joins the edge of the hole in the building part, and the internal wall of the coupling frame is shaped to cooper- ate with securing means on a current-carrying component.

As mentioned, the coupling frame may be a pipe section with a predetermined cross-sectional contour so as to provide full access to the installation cavity in the concealed installation system. In some cases it is expe- dient to arrange a loose bottom in the coupling frame.

The invention moreover relates to an electrical installa- tion system for a building, said system comprising a dis- tributed network of possible junctions for electrical components. According to the invention, the junctions comprise a plurality of mutually electrically connected, essentially closed cavities which are concealed behind a building covering.

These closed cavities may be formed as a closed box which, arranged behind a building covering, is particu- larly expedient for cooperation with a coupling frame ac- cording to the invention when the box is drilled via the building covering. The boxes may be interconnected by means of cables or pipes for receiving wires, but the boxes may also be interconnected by means of closed ducts. Hereby, a distributed network of ducts and boxes may be achieved, said ducts and boxes optionally having the same cross-sectional dimensions.

It is a very great advantage of the invention that it al- lows the boxes or ducts to have an extent which is con-

siderably greater than what is necessary for a single electrical component. In case of a distributed network of ducts there is thus very great freedom in arranging elec- trical components when carpenters and painters have fin- ished their work, but also in the event that separate boxes are used in the concealed installation systems, the boxes may have such an extent that-once carpenters and painters have finished their work-there is great free- dom in carrying out drilling and mounting of more con- tacts, switches, etc. side by side, vertically or hori- zontally.

The installation system according to the invention also involves great advantages in the export of building ele- ments with a pre-fabricated installation system to coun- tries which may have different standards for the electri- cal components which are to be placed in the building parts. The dimensions of the electrical components used in various countries may vary greatly, but owing to the extent of the closed installation boxes both large and small mounting frames can be made according to the inven- tion, and it is therefore just necessary to manufacture special coupling frames which fit the electrical compo- nents in size but also with respect to the coupling means for securing the electrical components in the coupling frames.

The securing means of the coupling frame may be adapted to engage an internal wall of the concealed duct or the concealed boxes, and when the external rim of the coup- ling frame extends completely or partly inwardly over the hole in the building covering, the ducts or the boxes may be clamped to engage the internal side of the building covering.

The coupling frame may be inserted into the hole in dif- ferent ways, so that, during the insertion, the securing means are retracted and are caused to assume their ac- tive, engaging position only when the coupling frame is in position in the hole.

The invention will be explained more fully by means of some embodiments with reference to the drawing, in which figs. 1 and 2 schematically show the principe according to the invention, figs. 3 and 4 show an embodiment of a coupling frame for use in connection with the invention, fig. 5 shows another example of a coupling frame, figs. 6 and 7 show a building part in which the mounting frame is to be established, fig. 8 shows a drill jig for use in connection with the mounting, fig. 9 schematically shows an embodiment of an installa- tion system according to the invention, while fig. 10 schematically shows another embodiment of an in- stallation system according to the invention, Fig. 1 shows a concealed installation box 1, a front plate 2 and a rear plate 3 of a building part, such as a plaster wall, as well as a coupling frame 4 or 5.

As will be described later in connection with figs. 9 and 10, the invention may be used in connection with a dis- tributed network of concealed installation boxes which are interconnected by means of cablesorwires6,7, and/or a distributed duct system which contains cables or wires.

The unique aspect of the invention is that, in the first instance, the installation just comprises the closed con- cealed installation, e. g. as shown in fig. 2, but where no drilling of the concealed installation boxes has been carried out as yet. The drilling will depend partly on the type of coupling frame to be mounted, which in turn also depends on which types of contacts or switches, etc. are to be arranged later in the coupling frame. This makes it easier to export building elements which also contain the concealed installation to various countries having different standards for electrical equipment, since the drilling necessary to allow mounting of the correct coupling frame corresponding to the relevant in- stallation equi. pment s carried out after the building parts have been erected.

Even if the concealed installation is not to be exported, the method of the invention provides the advantage that the carpenter and the painter can finish their work be- fore the electrician starts the mounting. The trades are thus more independent of each other.

The two shown types of coupling frames 4 and 5 will be explained more fully later with reference to figs. 3-5.

But it will be appreciated on the basis of figs. 1 and 2 how the concealed installation box 1 is mounted in a par- tition wall, preferably so that the installation box en-

gages the rear s : Lde of a plaster board, following which a hole is drilled, as appears from fig. 2, in which the coupling frame 4 or 5 may be arranged. The coupling frame 4 may be intended for a socket outlet, while the coupling frame 5 may be intended for a switch (see fig. 10). The coupling frame 5 of fig. 2 is also shown in figs. 3 and 4, where fig. 4 moreover shows an electrical component which is arranged in the coupling frame. The coupling frame comprises a substantially cylindrical wall consist- ing of wall parts Ba-8d (the other wall parts are not designated since they basically function in the same man- ner as 8a-8d). Film hinges 9,10 are present between the wall parts Ba, d and 8c, b, respectively, so that the wall parts 8a and 8b can move toward each other, thereby al- lowing the flanges 11, 12, which are integral with the wall parts 8a and 8b, respectively, to get within the substantially circular contour which the coupling frame 5 has, which in turn corresponds to the contour of the hole which is drilled through the wall 2 and the concealed in- stallation box 1. The coupling frame 5 may hereby be ar- ranged in the hole, and then the walls Bc and 8d are straightened out to the position shown in fig. 4, whereby the projections 11, 12 engage the inner side of the wall of the concealed installation box 1 which faces the plas- ter board 2. An electrical component is indicated at 13, having an engagement area 14,15 for engagement with the bosses 16, 1'7 and 18,19, respectively. This prevents collapse of the wall parts Ba-8d of the coupling frame 5.

The described example of a coupling frame can be manufac- tured at very low costs.

Another example of a coupling frame is shown in greater detail in fig. 5, where the wall 20 of the coupling frame is formed to receive another type of electrical component

than the one shown at 13 in fig. 4. The mounting means for the embodiment shown in fig. 5 are made in a manner known per se by means of three strips 21-23, which each are provided with a toothing 24 and are placed in a groove with an elastic ratchet pawl 25. Each of the strips 21-23 ends in a claw, e. g. 27 or 28, which, in the position shown in fig. 5, is dispose within the contour of the hole drilled in the wall (see fig. 1) so that the coupling frame can be mounted in the hole. When the strips are then pulled, the claws will be caused to en- gage the internal wall of the concealed installation box, whereby the coupling frame is mounted.

In comparison with known installation boxes, e. g. a box for recessed mounting, the invention may be regarde as a "two-part"box, there being provided a concealed instal- lation system in the first instance, and only after drilling and mounting of coupling frames will the instal- lation resemble what is known from prior art boxes for recessed mounting. As already mentioned, the advantage of the invention is that the working operations for the various trades are more flexible, and that different types of coupling frames and associated electrical compo- nents may be arranged freely to a much higher degree than before. The partition wall 29 shown in fig. 5 is just an accessory which may optionally be mounted in the coupling frame if it is desired e. g. to separate a power current installation from a weak current installation.

A description will be given below of some working opera- tions which serve to demonstrate how easy it is to use the installation system according to the invention. Figs.

6 and 7 show how the drilling may be carried out through the plate wall 2 by means of e. g. a spoon bit 30. The

concealed installation box 1 may be provided with a strong circular magnet 31, and it may be detected by means of a search magnet 32 in a manner known per se where the first hole may advantageously be drilled in the plate wall 2.

When/if more holes are to be drilled in the same instal- lation box 1 (or duct), the drill jig 33 shown in fig. 8 may advantageously be used, said drill jig containing a pair of mutually perpendicular levels 34, 35. When the hole has been centered, as explained in connection with fig. 6, it may be marked, before using the spoon drill 30, where a further hole must be, and the hole, as ex- plained in connection with fig. 6, is caused to be flush with a hole 36 in the drill jig so that the hole 37 de- fines the next hole which is to be drilled after the levels have been set correctly. Drilling may be continued in this manner to provide a desired number of holes ver- tically above each other or horizontally side by side, depending on how large installation boxes are used for the concealed installation.

As shown in fig. 9, the concealed installation may basi- cally consist of a plurality of concealed installation boxes 38,39 which are interconnected by means of cables or pipes for wires 40-42. By means of the described mag- net centering system it is easy for the electrician to hit the mark in the finished wall plate.

The concealed installation system may also comprise a distributed network of closed ducts 43 which are posi- tioned behind a plate wall 44. This embodiment has the advantage that later there is great freedom in drilling additional coupling frames vertically or horizontally

side by side. Fig. 10 also shows an electrical component 45, which may be a switch, a socket outlet, a telephone jack, a data terminal, control lamps, etc. According to the invention the installation does not have to comprise a specific type or a specific make of coupling frames and associated electrical components. The invention also al- lows mixing of different types, when only the drilling is carried out in accordance with the dimension or contour of the coupling frame used.