TRUSSED GIRDER FOR THE CONSTRUCTION INDUSTRY AND METHOD FOR PRODUCING A TRUSSED GIRDER OF THIS KIND

Abstract

The invention relates to a trussed girder (10) for the construction industry, having an upper flange (14) and having a lower flange (16) made of square timber, which extend along the longitudinal axis (12) of the trussed girder (10) and which are connected to one another by a plurality of struts (24), which are each arranged so as to extend obliquely to the flanges (14, 16). The struts are formed by at least one strut run (18), the upper side and underside (26, 28) of which are formed in an undulating manner in the axial direction and are arranged so as to extend parallel to one another with radii corresponding to one another. The strut run (18) is mortised or dovetailed in the axial direction alternately by means of the upper flange and the lower flange (14, 16) and is formed as a single-piece wood material part. The invention additionally relates to a method for producing trussed girders of this kind, in particular on a mass scale.

Claims

1. Trussed girder (10) for the construction industry, having an upper flange (14) and having a lower flange (16) made of square timber, which flanges extend along the longitudinal axis (12) of the trussed girder (10) and which are connected to one another by a plurality of struts (24) which are each arranged so as to extend obliquely to the flanges (14,16), the struts being formed by at least one strut run (18), the upper side and underside (26, 28) of which are formed in an undulating manner in the axial direction and are arranged so as to extend parallel to one another having radii R1, R2 corresponding to one another, the strut run (18) being mortised or dovetailed in the axial direction with the upper flange and the lower flange (14, 16) and being formed as a single-piece wood-based material part.

2. Trussed girder according to claim 1, characterized in that the strut run (18) consists of a high-density wood fiber material.

3. Trussed girder according to either claim 1 or claim 2, characterized in that the strut run has lateral faces (24) which are arranged so as to extend plane-parallel to one another.

4. Trussed girder according to any of the preceding claims, characterized in that the strut run (18) engages in grooves (40) of the two flanges (14, 16), each groove base (46) of which forms a semi-circular profile in the longitudinal direction of the flanges (14,16), the lateral walls (42) of the groove (40) that extend in the longitudinal direction each including an acute angle , and the strut run (18), together with the mortises or dovetails (36) thereof which are glued to each of said lateral walls (42), including a corresponding acute angle .

5. Trussed girder according to claim 3, characterized in that the two flanges (14, 16) are connected to one another by two or more strut runs (18) which are arranged behind one another in the axial direction.

6. Method for producing a plurality of trussed girders (10) according to any of the preceding claims, comprising the following steps: a) providing (102) upper and lower flanges (14, 16) made of square timber; b) providing (104) wood-based material boards, in particular high-density wood fiber boards (48);

Description

[0014] In the drawings:

[0015] FIG. 1 shows an exploded perspective view of the components of a trussed girder having an upper flange and having a lower flange made of squared timber, and having a strut run which is formed as a single piece or part;

[0016] FIG. 2 shows a cross section of the trussed girder according to FIG. 1;

[0017] FIG. 3 shows a partial longitudinal section of the trussed girder according to FIG. 1;

[0018] FIG. 4 shows a wood fiber board having individual cutting lines, along which the strut runs for a plurality of trussed girders according to FIG. 1 are cut out or cut free.

[0019] FIG. 1 shows an exploded perspective view of the components of a portion of a trussed girder 10 for the construction industry. The trussed girder 10 extends a few meters in the direction of the longitudinal axis 12 thereof and has dimensions which are common for a trussed girder of this kind in the construction industry. It is self-evident that the trussed girder 10 can be provided in special lengths, in particular for special constructions, as can be required in formwork for concrete ceilings or concrete walls.

[0020] The trussed girder 10 has an upper flange 14 made from square timber and a lower flange 16 made from square timber. A strut run 18 which is formed as a single piece is used to connect the two flanges 14, 16. The strut run 18 is formed as a single-piece wood-base material board blank, in this case as a high-density fiber board blank. The strut run 18 therefore consists of a high-density wood fiber material.

[0021] The strut run has struts 20, 22, which are each arranged extending obliquely relative to the flanges 14, 16. Lateral faces 24 of the struts 20, 22 that face away from one another are designed to be plane parallel or substantially plane parallel to one another in this case.

[0022] According to FIG. 1, the strut run 18 has an undulating basic shape. The strut run 18 therefore has an upper and an underside 26, 28, each of which undulate in the axial direction. The strut run 18 thus forms wave crests or protrusions 30 and wave troughs or indentations 32 on the upper and lower sides, respectively. In the direction of the vertical axis 34 of the strut run 18 and of the trussed girder 10, which axis runs orthogonally relative to the longitudinal axis, each indentation 32 of the upper side 26 is arranged relative to a protrusion 30 of the underside 28 of the strut run 18. In a corresponding manner, a protrusion 30 of the upper side 26 of the strut run 18 is arranged in alignment with an indentation 32 of the underside.

[0023] When the trussed girder 10 is in the assembled state, the strut run 18 can be mortised or, according to the embodiment shown in FIG. 1, dovetailed with the two flanges 14, 16. For this purpose, in the region of the wave crests of the upper and underside 26, 28 of the strut run 18, each strut run has a plurality, in this case two, dovetails 36. The width of the dovetails 36 tapers, preferably along the vertical axis 34 of the strut run 18 in the direction of the apex or the free end 38 thereof. The dovetails 36 therefore have a triangular or substantially triangular cross section. When the trussed girder 10 is in the joined state, the dovetails 36 engage in grooves 40 of the flanges 14, 16, which grooves extend in the axial direction of the trussed girder 10. One dovetail 36 of the strut run 18 is associated with each groove 40.

[0024] The dovetails 36 of the strut run 18 are glued to lateral walls 42 of the grooves 40, according to FIG. 2. The dovetails 36 of the strut run 18 that are arranged on the upper side are therefore glued into the grooves 40 of the upper flange 14, and the dovetails 36 of the strut run 36 that are arranged on the underside are each glued into grooves 40 of the lower flange 16. The lateral walls 42 of the grooves 40 that extend in the axial direction can each include an acute angle , according to FIG. 2. In a corresponding manner, the lateral surfaces 44 (cf. FIG. 1) of the dovetail 36 of the strut run 18 that is glued in the respective groove 40, which lateral surfaces are glued to said lateral walls 42, can include a corresponding acute angle . The respective lateral surfaces 44 of the dovetails 36 and of the grooves 40 are therefore not parallel to one another in this case. The dovetails 36 therefore taper in the direction of the free end 38 thereof. The width b of the grooves 40 correspondingly decreases along the vertical axis 34 in the direction of the groove base 46 as a result of the inclusion of the acute angle . As a result, glue applied to the lateral surfaces 44 is not or is only slightly moved in the direction of the groove base 46 when the dovetails 36 are inserted into the grooves 40. The glue therefore remains on the surfaces of the grooves 40 and the dovetails 36, which surfaces are to be glued to one another, as a result of which enough glue remains for firm and durable gluing of the lateral surfaces 44 in place.

[0025] FIG. 3 shows a longitudinal section of a portion of the joined trussed girder 10. Together with the flanges 14, 16, each of the struts 20, 22 includes an acute angle of approximately 45 that is not described in greater detail. The dovetails 36 of the strut run 18 extend into the grooves 40 of the flanges 14, 16 and are glued to the lateral walls 42 (FIG. 2) thereof in a precisely fitting manner. The groove bases 46 of the grooves 40 each have a semi-circular profile in the axial direction. The dovetails 36 or the protrusions 30 of the strut run 18 form a corresponding semi-circular profile. A gap 48 can be provided between the groove-base-side free end 38 of the dovetails 36/protrusions 30 and the groove base 46 of the groove 40, in which the relevant dovetail 36 is glued, as shown in the groove 40 in the upper left of FIG. 3. This gap 48 can receive the amounts of glue which are displaced when joining the strut run 18 to the flanges 14, 16 by means of pressing the lateral surfaces 44 of the dovetails 36 against the lateral walls 42 of the grooves 40, and it is therefore possible to insert the dovetails 36 into the grooves 40 of the flanges 14, 16 without said amounts of glue causing displacement resistance.

[0026] The upper and the underside 26, 28 of the strut run 18 are arranged so as to extend parallel to one another. It should be noted that the protrusions 30 and indentations 32 of the strut run 18 that are arranged in alignment with one another in the direction of the vertical axis 34 each have radii R.sub.1, R.sub.2 which correspond to one another. All protrusions 30 and indentations 32 of the strut run 18 have radii R.sub.1, R.sub.2 which correspond to one another. The identical radii R1, R2, as opposed to the usual concentric radii, allow the strut run 18 to have a larger glued surface in the region of the flange 14, 16 for an improved transmission of force, while the free struts 24 between the flanges 14, 16 are narrower and therefore lighter than in conventional struts of the same width. This results in two advantages; less waste in the production of the strut run 18, and a lower consumption of materials, and also that improved load-bearing properties can be achieved in the finished trussed girder 10 of same weight, and a lower weight can be achieved in the trussed girder which has the same load-bearing properties.

[0027] By means of the undulating shape and contouring of the strut run 18, the trussed girder 10 can be produced more easily and inexpensively, as is described below with additional reference to FIGS. 4 and 5. The method of production 100 according to the invention, according to the block diagram shown in FIG. 5, comprises the following steps:

[0028] In a first step 102, upper and lower flanges 14, 16 are provided which are provided with the grooves. In a further step 104, a plurality of wood-based material boards 48, in particular high-density (wood) fiber boards are provided, of which a side view of one wood-based material board 48 is shown in FIG. 4 as an example.

[0029] In a further step 106, the strut runs 18 are produced by means of respectively cutting or sawing the wood-based material boards 48 along a plurality of undulating cutting lines 50. The cutting lines 50 are arranged offset and parallel to one another in an extension direction 52 of the relevant wood-based material board and each have the mutually corresponding (i.e. identical) radii R.sub.1, R.sub.2 (FIG. 3). As a result, waste 54 of the wood-based material board only arises substantially at edges 56 of the wood-based material board 48 which are arranged opposite one another in the extension direction 52 of the wood-based material board 48. If necessary, the strut runs 18 also have to be shortened to a length suitable for the trussed girder 10 (FIG. 3).

[0030] If the strut run is dovetailed with the flanges 14, 16 (FIGS. 1 to 3), the dovetails 36 of the strut run 18 are produced in step 108 by a machining production method, preferably by means of milling.

[0031] In a subsequent step 110, in each case an upper and a lower flange 14, 16 is dovetailed or mortised with at least one of the strut runs 18 to form a trussed girder 10. In this case the dovetails 36 of the strut run 18 are glued to the respective lateral walls 42 of the grooves 40 (FIG. 2) of the two flanges 14, 16. Step 110 is repeated to produce each further (structurally identical) trussed girder 10.

[0032] By means of the production method 100 according to the invention, the trussed girders 10 can be produced in large quantities, in a manner which substantially completely utilises the material of the wood-based material boards or high-density (wood) fiber boards 48 used in production, i.e. in a manner which has low material input, is inexpensive and requires low effort.