This invention relates to arrangement and method in sound damping o-f ventilating conduits in frame- work elements.

Parallel conduits in the direction of the span of pre¬ fabricated framework' elements are often used for bran¬ ching off the ventilation system in a building. Hereby sons of the conduits in the framework elements are con- πeced in one end to a feeding conduit, and the air is thereafter passed on through the conduits to exhaus¬ ting means connected to a conduit somewhere along its length, or at its end. In order to achieve a better sound d-anping of sound from fans , which occurs in ven- tiiating systems it has been shown that a good damping can be achieved if the ventilating air is circulated in two ormore conduits before being let out in the room. For that purpose, a transverse connection is established between two separate parallel conduits so that these conduits are connected in series for the ventilating air, which hereby is passed in zigzag through the conduits in the frame-work elements.

Thus, the invention relates to a construction, which is so formed, that the framework acts as sound damping means for noice from fans and sound, which is trans¬ mitted from one room to another via the ventilating piping and the invention also relates to a method for producing said transverse connections between the conduits in the framework. Thus, the invention con- sists of an arrangement where the parallel conduits in the framework are closed in their ends by means of concrete plugs, which normally are casted on the buil¬ ding place after the erection of the framework elements

and which conduits have at le s one connection which is placed transversely between two conduits ^' : and which is placed at that end of the framework elements, which is opposite to the inlet end of the conduits for the ven- tiiating air. Hereby two or more conduits may be connec¬ ted in series b means of the transverse connection.

The object of the invention is to describe a solution of the above stated problem and the characterizing .fea¬ tures of the invention are started in the following claims.

The invention will now be described in connection with the accompanying drawings.

Fig, 1 shows two embodiments of the invention, where a concrete slab is cut and taken apart in its two parts.

Fig. 2 is a perspective view of a concrete slab in a third embodiment of the invention.

Fig. 3 is a side view of a concrete slab according to Fig. 2.

Fig. 4 is a cross section in the plane of the slab where three of the mentioned embodiments are shown in the form of a complete product.

Fig. 1 is thus a perspective view showing a concrete slab 1, an the slab is cut transversely so that a small piece 2 has been parted, whereby the openings of five conduits 3, 4, 5, 6 and 7 are shown, A transverse con¬ nection 8 has been opened between the conduits 3 and 4 by that a cavity has been cut down in both conduit 3 and the conduit 4 from the upper side 9 of the slab before the concrete has been set. After that cavity has been cut and after that the concrete has set, the

vity is covered in the ^' upper side 9 by means of plastic, a rubber plug or other suitable material. The plug is shown by phantom lines and is denoted by 10. The plug only reaches the upper edge of the conduits 3 and 4 and 5 it is thus seen, that a connection 8 is established between the two conduits 3 and 4 under the plug 10. See also Fig. 3 and the following.

A second embodiment of the transverse connection is al¬ so shown in Fig. 1 from which the connection between

10 conduits 5, 6 and 7 can be seen. This connection has been established by that a boring has been drilled transversely to the conduits 5, 6 and 7 and ending in the conduit 5. The boring is parallel to the upper side 9. In order to establish a connection only between the

1.5 conduits 5, 6 and 7 the boring is plugged between the edge 11 of the slab and the conduit 7 by a plug 10 and this can be done after that- the slab has been set by inserting an expander plug or the like in the boring. Concrete or plastic can also be used for this purpose.

20 This embodiment is also shown in Fig. 4 according to what will be described below. It is obvious that according to the two embodiments described any number of conduits can be connected though in the first case it has been described a connection between the two conduits and

25 the second embodiment includes a connection between three conduits.

In Fig. 2 a third embodiment is shown for establishing the connection between the conduits. This is shown by a connection being established between the conduits 3, 30 4 and 5. In this case the conduits are opening in the the front side 13 of the slab. The connection is formed by that a notch 14 has been made between the conduits 3 and 4 nd; between the conduits 4 and 5 in the front side 3. The notch is so deep that its cross section area

is that of theconduits. After that the notch has been made and the slab has set, the notch ^' 14 is covered by a plate 15 or by other suitable means, see Fig. 3. It can be seen that hereby the notch 14 is closed at the front edge 13 and that thus the connection is made between all the three conduits 3/ 4 and 5, see also Fig. 4.

Fig. 4 is a cross section along the upper side 9 of the concrete slab 1. In order to show the invention Fig. -4 shows how* the conduits 3, 4, 5 and 6 are connected so a medium can pass in series through all four conduits. Initially all conduits are opened in the front side 16 of the slab 1 while the oppsite front side 17 has no openings to the conduits. Between the conduits 3 and 4, there is a transverse connection 8, which has been formed according to the first described embodiments and thus the cavity 8 is covered in the upper side by a plug or a cover, which can not be seen from Fig. 4. The connection between the conduits 4 and 5 has been estab- lished according to the third described embodiment and thus the embodiment, which can be seen from Figs. 2 and 3. Thus, a notch has been made in the front side 16 between the conduits 4 and 5 where¬ by the interconnection 14 is made and the notch has been covered by the plate 15 against the front side

16. Finally, a transverse connection has been established between the conduits 5 and 6 by drilling a bore from side 18 of the slab, which correspond to the boring from side 11 in Fig. 1. The plug 12 has been inserted in the boring from the long side 18 and thus the left end of the conduits 5 and 6 has been interconnected and the medium is prevented from passing out of the side 18. -It is only by way of an. example that all three embodi¬ ments ε-,re shown in Fig. 4.

The inventive idea can be. varied in many ways and re¬ ferring to Fig. ^' 4 it can be seen that the transverse connection between two conduits could be established by drilling a bore from the side 18 all the way through 5 the slab whereafter this boring could be plugged between conduits 4 and 5 in the left end of the slab, whereby the medium is passed in series through all four conduits according to the arrows in Fig. 4. The passage for the medium through the conduits can of course follow another

10. path than the one shown in Fig. 4. It is also possible to establish transverse connections between two conduits by that a hole is drilled from a mouth of anyone of the conduits 3-7 and that the drilling is carried out in inclined direction to the longitudinal axis of the

15 conduits and thus into an adjacent conduit. It is also possible to ^' use other methods for closing the recess forming the transverse connection so that the connec¬ tion passes through a conduit but is closed to the conduit in question, by that a piece of a pipe having

20 the same diameter as the conduits is inserted in the transverse connection.