The invention relates to a lattice truss of the type defined in the introductory portion of the patent claim.

The object of the invention is to provide a lattice truss of the stated type in which only normal forces occur, i.e. either tension or pressure in the lattice bars.

This object is achieved according to the invention in that the lattice truss stated in the opening paragraph is characterized by the features defined in the characterizing portion of the patent claim.

Thus, the centre-of-gravity lines of each individual one of the bar elements extending to a joint extends through the axis of the pivot. Owing to the symmetry about the longitudinal centre plane the truss does not contain any bending excentricities either with respect to this plane. Thus, each of the joints will be a hinge where the calculation of the forces of load including the dead load does not have to allow for addition of moment loads. The lattice truss of the invention has the additional advantage that the lattice bars can be transported connected with the head of the rafter or the foot of the rafter in a state folded together with the member in question so that the truss can be pre-assembled and rapidly be erected on the building site.

The invention will be explained more fully below with reference to the drawing in which

fig. 1 shows a lattice truss of a generally known type,

figs. 2-5 show a joint connection according to the in¬ vention used in all the joints in whcih the head or the foot of the rafter is connected with two lattice bars,

where

fig. 2 shows the ends of two lattice bars and a pipe section according to the invention, in perspective with the members drawn apart,

fig. 3 shows the same elements as fig. 2 in perspective, but with the pipe section in position in the lattice bar called the second type lattice bar,

fig. 4 shows the same elements as fig. 3 in perspective, but with the lattice bar, called the first type, in po- sition with respect to the second type lattice bar and the pipe section, and

fig. 5 shows the finished joint connection at the rafter head in perspective, but before the bolt shown in the drawing has been screwed in.

The general lattice truss of fig. 1, which is supported at the ends, consists of a rafter head 1 and a rafter foot 2 and lattice bars 3 interconnecting these. In all the joints in which the rafter head or the rafter foot is connected with two lattice bars, the joint is assembled as shown successively in figs. 2 to 5.

Fig. 2 shows the upper end of a first type lattice bar 10 made of a thin sheet to form a hollow profile,

C-profile or U-profile. The lattice bar 10 has rec¬ tangular recesses 11,12 in one set of opposite sides 13,14. The recesses 11, 12 can receive and snugly surround a second type lattice bar 20 likewise manu¬ factured of a thin sheet to form a hollow profile, C- profile or U-profile. In one set of opposite walls 21, 22 the lattice bar 20 has mating holes 23, 24 for a pipe section 30, which has internal threads 31, 32 at each end and the same length as the internal spacing between the second set opposite walls 15, 16 of the first type lattice bar 10; the second set opposite walls 15, 16 have mating holes 17, IB for bolts which are shown and described in connection with fig. 5.

Fig. 3 shows how the pipe section 30 has to be disposed when positioned in the mating holes 23, 24 in the lattice bar 20, and fig. 4 shows how the first type lattice bar 10 is positioned so as to surround and sup¬ port the second type lattice bar 20 in a position in which the mating holes 17, 18 are in register with the threaded holes 31, 32 in the pipe section 30.

Fig. 5 shows a rafter head 40 whose profile, which is essentially a U-profile, has been manufactured by cold deformation. For reasons of strength the profile has additional bends along the edges so that in the embodi- ment shown the profile resembles that of a hat.

As shown in fig. 5, the undamped connection of fig. 4 is introduced between the branches 41, 42 in the U- profile of the rafter head 40. These branches 41, 42 have mating holes of the same diameter as the mating holes in the lattice bar 10. The Allen screw 50 shown in fig. 5 is inserted through the mating hole 43 in

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the side of the rafter head 40 shown in fig. 5 and through the mating hole 18 in the web member 10 and is then screwed into the threads 32; and a corresponding Allen screw 50 is inserted through the mating hole (not shown) in the opposite branch 42 of the U-profile and through the mating hole 17 in the lattice bar 10 and is then screwed into the threads 31 in the other end of the pipe section 30.

The joint connection shown in fig. 5 at the rafter head 40 is identical with a joint connection at the rafter foot when fig. 5 is turned upside down, the same U-shaped profile being used for the rafter foot as for the rafter head.

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