The present invention relates to a. so-called engage¬ ment profile or a beam of the type defined in more de¬ tail in the preamble of the claim.

A beam according to the invention is preferably made of thin steel plate by bending in a manner that the beam comprises one or several web plates extending lengthwise of the beam substantially at a constant dis¬ tance from each other and are perpendicular or inclined relative to the fastening plane of the beam. These web members are interconnected by members of the same sheet material. Thus, the beam is preferably made of a single sheet blank. For fastening it to its under¬ laying bed, the beam further comprises one or several fastening strips, which are preferably integral parts of the web members and and whereby the beam is fasten¬ ed to a level supported by said beam. Such a support¬ ed level can be made e.g. of wood, such as boards, woodboard, plywood, blockboard, chipboard, fiberboard, gypsum board or the like, into which the engagement profiles formed in a per se known manner on fastening strips sink and engage as the strips are clamped against the level e.g. by means of a suitable press. The beam can also be used for supporting and re- inforσing a concrete slab, whereby it is placed on top of a concrete slabe during its casting prior to the setting of concrete, the studs engaging in ^" concrete. Thus, in a particularly preferred case, the studs are designed so that the blade side of said studs is pro- vided with a transverse toothing or roughening, as dis¬ closed in the Applicants' earlier Patent No. 65643.

A drawback with, the above type of beam is, however, a relatively- weak strength under major stresses as t sheet material of such beam is thin, the sheet thick nesses being e.g. 1 - 1,5 mm. Such a thin sheet mat ial begins to fracture quite easily because of buck¬ ling. In order to provide a beam with greater stren it can of course be made of a thicker sheet material However, manufacturing will be more difficult and co will be higher because the raw material is more expe sive and working- is more difficult. Especially, the preparation of engagement studs will be more difficu with thicker sheet material.

When studying tensions in the above type of beam it can be noted, especially as far as bending is concer that the greatest stresses occur in the upper and lo portions of the beam cross-section while in the mid- portion, in a so-called neutral plane, the stress i zero. In the upper edge of the cross-section, i.e. fastening strips, there prevails a compression stres while in the lower edge there is accordingly a tensi stress. Some of the stresses in the fastening strip is naturally taken up by the plate or board which is supported by the beam, but if this plate is weak, th stress on the strips may become too great, especiall since such strips are weakened by the reduction in t amount of basic material as a result of stamping of studs.

The basic idea and object of the invention is thus t provide a solution to the above problems and to impr the strength of an engagement beam without substanti ly increasing the actual material thickness of a bea so as not to unduly increase the weight and anufact ing costs of a beam.

The invention is mainly characterized, by what is set forth in the. characterizing clause of the claim.

The invention will now be described in more detail with reference made to the accompanying drawings which illustrate a few preferred embodiments of the invention and their details and advantages. In the drawings

fig. 1 is a perspective view of one preferred embodi- ment of a beam of the invention as. seen oblique¬ ly from the front,

figs. 2-5 are perspective partial views showing mainly diagrammatically different embodiments of the fastening strips for a beam of the invention,

fig. 6 is another perspective view showing an embodi¬ ment of the invention in which the main re¬ inforcement, strip comprises a flat steel strip,

fig. 7 is a partial view of the reinforcement strip of the preceding embodiment,

fig. 8 is a partial view of one modification of the embodiment shown in fig. 6,

fig. 9 shows an embodiment in which the reinforcement strips include studs the same way as fastening strips.

fig. 10 shows one modification of the embodiment shown in fig. 9 ,

fig. 11 shows an ambodiment in which the reinforcement strip comprises a steel bar and

fig. 12 shows yet another embodiment of the beam.

A beam shown in the embodiment of _. fig. 1 comprises a sheet blank, e.g. a blank of 1-2 mm thick, galvanized or black steel sheet, which is bent either by means of a bending press or by rolling into a shaped list having the shape of a flat-bottomed V, wherein sides 1 serve as web portions interconnected by an inter¬ mediate strip 2. Joined to the ends of sides 1 are fastening strips 3, formed in a per se known manner with fastening studs or teeth 4 for fastening the beam to a sheet blank or a boarding to be supported or reinforced e.g. by compressing with an appropriate press so that studs 4 are tightened in a sheet blank. studs 4 are preferably fitted with a transverse rough¬ ening or teeth for securing them more firmly than smooth studs. The ^' beam can also be used for reinfor¬ cing concrete slabs, especially rather thin slabs, the beams being placed on top of a concrete slab in- side a casting mould during the casting of concrete so as to set the studs completely inside the concrete. After the concrete is set, the result is a firm and relatively rigid, but still rather light concrete slab element, which is suitable for a wall or floor element. of course, the concrete can be further reinforced e.g. with a steel-wire mesh. According to the invention, the beam is reinforced, by fitting the most stress-laden parts thereof with reinforcement strips 5, 6, 1 , extend¬ ing lengthwise of the beam and preferably made of the same material as. the beam itself. The first reinforce¬ ment strip 5 is. thus placed at intermediate strip 2 outside and/or inside extending crosswise slightly on top of the web portions. In addition, further re¬ inforcement, strips 6, 7 are placed upon fastening strips 3, i.e. on the opposite, side of studs 4, and

those too extend, slightly on top of the web portions. The reinforcement, strips of this- embodiment are pre¬ ferably secured by means of e.g. resistance welding, such as disc welding, the jointing proceeding length- wise of the beam.

The reinforcement of fastening strips 3 can also be achieved preferably by making the fastening strips originally somewhat wider and then, after punching out the studs, by bending the extra width e.g.. into a round hem (fig. 2), a single hem (fig. 3), a double hem (fig. 4) or an open fold (fig. 5) . The reinforce¬ ment of fastening strips prevents them from buckling under major stresses, especially if the basic material, i.e. the building slab to be supported, has a poor bearing strength or if the question is about a board¬ ing structure with a gap between individual boards.

Fig. 6 illustrates another embodiment of the invent- ion, wherein the cross-section of a beam is substant¬ ially in the shape of a flat-bottomed V, the same way as in the preceding embodiment shown in fig. 1. In this embodiment, the main reinforcement is provided by a flat reinforcement strip 5 which is preferably fastened in contact with the inner beam surface upon the intermediate strip 2. The fastening can be made even more effective in one of the following manners. The connection between sides 1 and intermediate strip 2 of a profiled beam can be rounded so as partially surround the edge of reinforcement strip 5. The width of reinforcement, strip 5 is selected to slightly ex¬ ceed the internal width of'rwhere it is mounted on a profiled beam. Furthermore, the. side edges of a re¬ inforcement strip can be provided with roughenings or ribs 8 (fig. 7) , which secure firmly to the walls of

its mounting, spot as- said reinforcement, strip 5 is forced in position e.g. in a press by means of a suit¬ able tool and back, stop or by rolling.

Fig. 8 discloses a modification, of the embodiment shown in fig. 6, wherein the fastening of a reinforce¬ ment strip 5 is secured with a profiled, strip, design¬ ed so that its bent side portions clamp the side edges of intermediate strip 2 of the beam for locking re- inforcement strip 5 in position. Profiled strip 9 is dimensioned so that the distance of its side portions from each other is slightly less than the width of intermediate strip 2 of the beam so, when clamping it in position, there will be a stress caused by deflect- ion which clamps said reinforcement strip 5 firmly in position. Profiled strip 9 can also be provided with studs for fastening two board with a beam.

According to one embodiment of the invention (fig. 8) ,. the reinforcement of a beam can also be provided in a manner that said fastening strips 3 comprise base strips 3', which are smooth, i.e. without studs 4, and join with sides 1 , as well as reinforcement strips 6, 7 formed with studs 4. Reinforcement strips 6 and 7 are secured to base strips 3' e.g. by means of integrally formed welts 6 ¹ , 7' by compressing or rolling the welts closed after pushing reinforcement strips 6, 7 into position on top of base strips 3'. For this engagement, the upper edge of sides 1 of the beam and the junction of base strips 3' are appropri¬ ately shaped so as to produce a bead 1 ' for securing the edge of the welt of a reinforcement, strip there- below.

in the embodiment, shown in fig. 9, said fastening

strips 3 are provided with studs 4. In addition to that, said reinforcement strips 6, 7 are also provided with studs 4 * , whose spacing is at least roughly the same as that of the former studs. Such reinforcement strips are intended to be fastened in position after securing a beam firmly to a slab to be strengthened, whereby the reinforcement strips are compressed into position so that their studs 4 ' pass through the stud holes in fastening strip 3.

In the embodiment of fig. 9, the reinforcement strip is made of round,, so-called ribbed steel bar. There¬ fore, the lowest part of a beam cross-section is de¬ signed as a tube 10 for inserting a round ribbed steel bar 11 therein. After this, said ribbed bar 11 is secured even more firmly by shaping a tube 10 e.g. by lateral pressing to make it conform to the shape of a ribbed steel bar.

it is also possible to have several tubular members 10 as well as ribbed steel bars 11 serving as a re¬ inforcement strip. Tube 10 can be made of sides 1 or it can be made separately and attached to a web plate.

The embodiment shown in fig. 10 is in a way a combinat¬ ion of the embodiments shown in figs. 8 and 9. In this embodiment, a fastening strip 3 consists of smooth cover strips 3", joining with sides 1 and provided with holes 13, as well as of reinforcement strips or lists 6, 7 fitted with studs 4' the same way as in the embodiment of fig. 9. These studs have the same spacing as holes 13 in cover strips 3". When it is secured, the beam is first pressed against, an engagement level so that cover strips 3" come against the engagement level, whereafter the actual fastening is effected by

pressing reinforcement lists 6, 7 in, so that their studs 4' penetrate into the engagement level through holes 13 in cover strips 3".

In a very simple embodiment shown in fig. 11, a beam of the invention only comprises a single side 1 and a single studded fastening strip 3, bent to an angle of circa 90 ° relative to a web plate. The lower edge of a web plate is provided with a tubular member 10, into which is fitted and secured a ribbed steel bar 11 serving as a reinforcement list the same way as above. Side 1 can be corrugated in longitudinal di¬ rection to provide a required rigidity.

in the above embodiments, a beam of the invention has been considered -to have an equal height over its en¬ tire length. It is within the invention, however, to make a beam converging at both ends, thus reducing the height of a profile towards the ends. Fig. 12 shows such a beam diagrammatically in side view. The ends of side 1 can be further provided with means 12 for locking the ends of ribbed steel bars 11. Thus, it is also possible to give the reinforcing steels a per se known prestress to increase the bearing capacity of a beam. The beam shown in fig. 12 may have e.g. a V-shaped cross-section.

A beam as shown in fig. 12 can be preferably manufac¬ tured, by deep drawing technique, whereby the cross- section of a beam is substantially in the shape of a flat-bottomed V the same way as in fig. 7. The re¬ inforcement list can thus be a flat steel strip 5, fixed in position in a conventional manner. The de¬ sign, shown in fig. 12 offers the advantage that even the gable edges of a beam will be provided with fast-

ening studs, whereby the beam does not easily dis engage from its position under varying loads ove a longer period of time.

5 The above describes but a few examples of beam em bodiments within the scope of the invention. It obvious that the. structures of these embodiments still be arbitrarily combined with each other to ate further embodiments which can thus be conside

10 as part of the invention. It should also be note that in certain cases a beam may have, several sid and fastening strips 3 as well as intermediate st 2, whereby the cross-section of a beam can be e.g. the shape of W. The beam can be manufactured by

15 either galvanized or black steel sheet. In the l case, a finished, reinforced beam can be subjecte hot-dip galvanizing in a conventional manner. In tain cases, this might even improve the fastening a reinforcement list, the galvanizing having the

20 effect as soldering. The cross-sectional shape of beam may have a variety of alternatives in differ embodiments. One and the same beam can be provid with one or a plurality of reinforcement lists 5 o