BACKGROUND ART Until now the most usual way to conceal the attachment of a duct on introduction to a wall, is to start with a long length of profile and cut this to desired lengths and then to glue, screw or nail these parts to the wall as the duct attachment. It also happens that such loose parts, also, or alternatively, are glued on the duct in question.

Cover frames in the form of prefabricated plastic elements also occur and are mounted in parts enclosing the duct. The parts are fastened together when male and female parts are pushed together whereupon the completed cover frame is normally glued onto the wall. Even these cover frames can also be glued to the ducts in question.

The disadvantage with the familiar system of concealing the attachment of ducts to walls lies in the fact that the wall is generally damaged by the dismantling of the cover frame, for example in connection with repairs to the duct. In such cases repairs to the wall are also required. Another disadvantage is that during assembly of this type of cover frame glue or screws or nails must be available to be able to fix the cover frames on the wall/duct.

DESCRIPTION OF THE INVENTION The purpose of the present invention is to achieve a system for concealing an attachment of a duct intended, for example, to enclose electrical and telephone cables to and against a mainly perpendicular wall which does not show any of the above-mentioned disadvantages. The objective has been achieved with the present system which comprises a cover frame arranged to wholly or partly enclose the duct to the wall and which is easily assembled and disassembled. The cover frame according to the invention consists of a C-shaped base part arranged to enclose a duct with a preferably rectangular or square cross-section. The cover frame can also consist of a preferably straight side part to allow complete enclosure of the duct's four sides. The side part comes into use with a detached duct, which is accessible on all sides. If the duct extends along or is immediately attached to a wall, only the base part of the cover frame is used to conceal the duct attachment to the wall.

The cover frame consists of a wall collar, arranged to extend along a wall, and a duct collar, arranged to extend along the duct in fixed state. The wall collar and the duct collar respectively are made of

a spring material and exhibit a cross-section which, during assembly of the cover frame, are deformed elastically when the cover frame is exposed to an external force. During the springing back of the cover frame, after the external force has receded, counter- directional forces arise by which means the friction between the duct collar and the duct increase and retain the cover frame to the wall. The duct collar can produce increased friction on the contact surfaces of the duct or be supplied with a friction element, which can be achieved in many different ways and preferably arranged on two opposite sides of the duct collar. It is preferred that the friction element is in the form of a friction strip which extends along the duct collar and completely encloses the duct.

The mounting of a completely enclosed cover frame on a detached duct is usually done so that the base part is first pushed in perpendicular to the duct until it is in contact with three sides of the duct. After that, side parts are fixed to the base part whereupon the assembled cover frame is pushed by hand with light contact against the wall. Subsequently the cover frame is pressed to the wall with a force, which causes a springing-in of its cross-section against the wall. When the pressure force ceases, the cover frame strives to resume its original shape, whereby the friction element, which is itself between the cover frame and the duct, is exposed to normal forces which increase the friction between the cover frame and the duct and retains the cover frame against the wall.

The concept of a wall collar and duct collar respectively does not mean a limitation to the constructional shape as shown in the description of the

drawings below. These parts of the cover frame can accordingly be presented in many different designs. In an extreme case the cover frame could forego its specific collars and only show a cross-section profile where a single collar extends inclined against both the wall and the duct. The friction elements in this alternative design are located near the part of the cover frame, which is itself in contact with the duct.

Further details and characteristics concerning the present invention are evident in the description to the drawings below and in the claims.

DESCRIPTION TO THE DRAWINGS The invention is described below in the form of a design example in connection with the enclosed drawings.

Figure 1 shows a disassembled, not mounted cover frame seen in a view towards its front.

Figure 2 shows the cover frame according to Figure 1, seen in a view towards its inside.

Figure 3 shows the cover frame according to Figure 1, seen in perspective towards its front.

Figure 4 shows a section through a part of the cover frame provided with a friction strip.

Figure 5 shows the friction strip included in Figure 4 in enlarged cross-section.

Figures 6 and 7 show the cover frame, according to the invention, assembled on a horizontal duct and attached to a wall.

Figures 8 and 9 show the assembly stages for attaching the cover frame to a wall Figure 10 shows the assembled cover frame in a cross-section attached to a wall.

The cover frame 1, which is shown in figures 1 to 3, is intended for assembly on a duct with a rectangular cross-section and comprises a C-shaped base part 1.1 and a straight side part 1.2, which is provided with projecting fixing lugs 1.3 which are shaped to be connected to corresponding cavities 1.4 in the base part 1 and are snap-fixed into these. When the base part 1.1 is united with the side part 1.2, the cover frame is completely closed and can surround the duct on all sides.

In cases where the duct is not detached but having one side located close to or in contact with, for example a wall, the side part 1.2 can be omitted and only the base part 1.1 mounted.

The cover frame 1, that is to say the base part 1.1 as well as the side part 1.2 according to the invention is showing, in a cross-section as seen in Figure 4, partly a wall-contacting wall collar 2.1, partly a duct-contacting wall collar 2.2, which in the cross-section extend to an angle with each other. The wall collar 2.1 shows a surface contact edge 2.3 which extends mainly perpendicular from the outer part of the wall collar 2.1 and is intended to lie against the wall at a distance of, for example, a cavity in the wall, for carrying through or attaching the duct in question. The duct collar 2.2 is, in this example, shown"double- folded"so that an inner section 2.4 extends backwards from the outer edge of the collar and is generally parallel with the side of the duct in towards the interior of the cover frame 1. The inner section 2.4 forms, together with the outer part of the duct collar 2.2, an extended pocket 2.5 which runs round the inside of the cover frame 1 and is used to accommodate a friction strip 3 which, for example, can be made of

rubber material with high friction in surface contact with the outside of the duct. In Figure 4 the wall is represented by the dotted line 4 and the duct by the dotted line 5. The wall collar 2.1 slants somewhat from the duct 5 and against the wall 4, and the duct collar 2.2 slants somewhat from the wall 4 and the duct 5, by means of which a space 6 is created between the wall 4, the duct 5 and the cover frame 1.

The friction strip 3, as seen in Figure 5, shows a generally U-shaped cross-section with a channel 3.1 meant for gripping around the inner edge of the inner section 2.4 on the duct collar 2.2. The two legs which surround the channel 3.1 are made partly by the inner strip 3.2, which is meant to be inserted in the pocket 2.5 which runs around the inside of the cover frame 1, and partly by the outer strip 3.3 which is meant to lie against the duct 5 and by its friction hold the cover frame 1 against duct 5 by the wall 4. The outer strip 3.3 shows, in cross-section, an outward tapering portion 3.4 supporting two oblique, outward-pointing ribs 3.5 which, when the cover frame 1 is brought in towards the wall 4, are folded in towards the tapering portion 3.4 and which, when the cover frame 1 is brought into place, spring out and counteract any sliding of the cover frame 1 from the wall 4.

In assembled condition on a horizontal, detached duct 5, the cover frame 1, as is shown in Figures 6 and 7, is, with the base part 1.1, directed out towards the room and the side part 1.2 located on the back of the duct 5 in that space which is developed between the duct 5 and with the parallel wall 7. Consequently the duct 5 runs along and at a distance from this second wall 7 and is attached to the first wall 4. Usually the duct 5

extends between two parallel walls 4 but which are not shown in the figures.

The assembling of the cover frame 1 on a duct 5 is carried out in the way, which is described in connection with Figures 7 and 8. The base part 1.1 of the cover frame 1 is pushed perpendicularly in towards the front of the duct 5 so that it makes contact with three of the sides of the duct 5. This is done at a distance form the wall 4 in a position, which is shown in Figure 7. Afterwards the side parts 1.2 are fixed to the base part 1.1 with the help of the above-mentioned fixing elements 1.3 and 1.4. Thereafter the cover frame 1 is pushed by hand to make light contact with the wall 4 after which it is pressed against the wall 4 with a force that causes a springing-in against the wall 4 as shown in Figure 8. During the later depression in particular, the cross-section of the cover frame 1 is deformed so that the inner section 2.4 on the duct collar 2.2 is turned out from the duct 5 and reduces the contact force of the friction strip 3 against the duct 5. When the compression forces cease, the collars 2.1 and 2.2 on the cover frame 1 attempt to return to their original position but are prevented from fully doing so by the friction strip 3, through the springing back in the collars 2.1 and 2.2, being compressed against the duct 5. By this there also remains a contact force against the wall 4 next to the contact edge 2.3 on the wall collar 2.1. This position is shown in Figure 9.

It lies within the scope of the invention to allow the cover frame to be divided into more parts than those, which are described above as well as also being suitable for ducts with other than a right-angled cross- section. It also lies within the scope of the invention

to allow the wall collar 2.1 and the duct collar 2.2 to be formed in a single continuous detail which can extend flat or bent between the wall 4 and the duct 5.

Furthermore, the friction strip 3 can also be replaced by other types of friction element such as"pads"or "cushions"and also by one directly on the wall collar 2.2 or an equivalent glued strip. It also lies within the scope of the invention to design the cover frame, or at least the surfaces which come in contact with the ducts, of a material which gives a higher friction between the cover frame and the duct in comparison with a cover frame without a friction element or equivalent and designed in a material with a smooth surface such as hard plastic.