BACKGROUND OF THE INVENTION Fig. 1 of the drawings illustrates the field of the invention and the problem to be solved representing a schematic sectional view of a log building in which there is no ceiling but slope rafters la and lb forming a roof truss 1 are supported by a ridge beam 6 at the ridge 4 of the roof and by side walls 2 and the uppermost wall beams 2a on the side of eaves 5. The ridge beam 6 is supported by log-built end walls 3 which are higher than the side walls. In the course of time, a log wall is somewhat contracted, and naturally the more the higher it is.

So, the ridge beam 6 is sinking gradually in relation to the uppermost beams 2a of the walls 2 as indicated by arrow A, and at the same time the rafters la and lb of the roof truss 1 are sliding somewhat in relation to the walls as indicated by arrows L the angle of the roof truss becoming larger. The original situation is presented by broken line in Fig. 1. Accordingly, the attachment must allow slow sliding of the rafters and the change of the angle but at the same time be strong and reliable e. g. against forces lifting the roof caused by storm winds.

Moreover, the attachment must be as easy as possible to install and cause the least possible inconvenience during the building and thereafter.

Finnish patent application 865357 presents for the above purpose an attachment solution in which there is a couple of bracket members with hook-shaped cross-sections for coupling the bracket members to each other. A wider bracket member the lower edge of which is formed to make a groove is fastened to the rafter near the wall beam. A narrower bracket member is to be fastened on the wall beam and forms"a hook"adapted to be coupled to the groove. Installation of this kind of bracket members is troublesome because they must be aligned precisely with each other during the installation so that the attachment would work in a desired way and would be reliable. The form of logs is variable, and the upper surface of a wall beam may have such a form that it is impossible to install the bracket members with good alignment without additional operations. The bracket members are straight, and because the pitch of the rafter and at the same time the bracket member fastened thereto is somewat changing the ridge beam gradually sinking, the alignment of the bracket members is worsened. The wider bracket member on the rafter near the wall beam makes the installation of a covering board more troublesome, and the roof being sinking it

may push the covering board off. If the roof is steep, the bracket members must be installed at the outer edge of the wall beam whereby they in every case make the installation of a covering board more troublesome.

Finnish patent application 934921 presents an improved attachment solution. The bracket member functioning as"a hook"either is curved or is attached pivotally to a fastening member. This makes the installation easier and the atttachment function better.

The above problems are alleviated but the installation is still troublesome because the bracket members must be aligned with each other and the problems related to the installation of a covering board are not totally eliminated, either.

SUMMARY OF THE INVENTION An object of the invention is to present an attachment solution by which the above problems are to large extent eliminated.

An attachment of a roof truss of a log building with ridge roof in which a truss rafter supported on a wall beam is attached to the wall beam with an attachment allowing sliding is characterized in that it is essentially consisting of an angle plate in which: one side plate extends longer than the other side plate for fastening the angle plate at the longer extending part thereof to a wall beam; said one side plate includes a bending position in the area between the fastening part and the initial point of the other side plate for bending the angle plate so that said one side plate may be set against the lower face of the rafter and the other side plate against a side face of the rafter; and the other side plate includes a slot extending parallel to the first side plate for fastening screws or like members therethrough to the rafter and for allowing them to slide in the slot.

In an embodiment, said one side plate extends at both ends thereof longer than the other side plate for making fastening parts at both ends and is provided with corresponding bending positions whereby the angle plate may be attached on any side of a rafter.

In another embodiment, the bending position is provided with holes for making bending easier.

The angle plate may be made of bending quality steel plate.

A great advantage of the invention is that only one attachment member is needed which may further be manufactured so that it may be installed on any side of a rafter. For manufacturing attachment members, only cutting of suitable pieces from a plate, e. g. suitable steel plate, perforation and bending are needed. Therefore, this attachment solution is very cheap. The outermost part of the attachment is permanently the bending position of the attachment plate which is very close to the fastening point. The attachment member may be bent to any angle in relation to the rest of the plate. The same attachment member suits

thus for all roof pitches and for all forms of the upper surface of a wall beam, and no harm may be caused for installation and stability of covering boards. Sliding and changing of the pitch of the rafters, which must be allowed for providing a good attachment in this kind of log construction, do not affect the strength and reliability of the attachment against forces litting the roof, for example.

BRIEF DESCRIPTION OF THE DRAWINGS The invention and some embodiments thereof are described in further detail in the following with reference to the accompanying drawings, in which: Fig. 1 presents, for illustrating the field of the invention, a schematic sectional view of an upper part of a log building with ridge roof; Figs. 2 and 3 present an embodiment of the attachment member according to the invention; and Figs. 4 and 5 present the use of the attachment member of Figs. 2 and 3 in attaching a rafter.

DETAILED DESCRIPTION OF THE INVENTION An angle member 8, an angle plate with an L-formed section, includes a first side plate 9 which extends at both ends 1 la and 1 lb thereof longer than a second side plate 10. At the ends 1 la and 1 lb there are corresponding fastening holes 12a and 12b for fastening the member at any end thereof to an upper surface of a wall beam 2a (Fig. 4). As the first side plate is at both ends thereof longer than the second one and provided with fastening holes, it may be fastened on any side of a rafter according to need. (The first side plate could be longer only at one end thereof whereby it could be used for attachment only on one side of a rafter.) Close to the initial point 16 of the second side plate 10 there is a bending position 13a, 13b at which the first side plate is to be bent in a way illustrated by Fig. 4. In the second side plate there is a slot 14 parallel to the first side plate which slot must be wide enough so that thick enough screws or like members (Fig. 4) are able to slide in the slot. The slot must be so long that there is a wide enough range of motion for the screws or like 15 fastened therethrough as the rafters gradually sink with time (Fig. 5).

A suitable material for manufacturing an attachment member is a formable bending quality steel plate the thickness of which is 3 millimeters, for example. The strength and toughness of a material are put to trial mainly at the bending position. A material must have a high enough strength so that the attachment is firm and durable enough, but it must also be bendable to a steep angle and must maintain formability because it must yield somewhat at the bending position as the roof is gradually sinking with time.

Figs. 4 and 5 illustrate accomplishment of the attachment and the operation thereof. In Fig. 4, the first side plate is fastened at the fastening holes 12a of the end l la with screws to the wall beam 2a. The second side plate has a form of a base part of a truncated triangel so that the attachment member could be set against the upper wall beam for fastening without bending it or with bending it only suitably (a little) whereby the fastening is easiest done.

During fastening (before bending) the attachment member is directed to the left in Fig. 4 (not shown). After fastening, the attachment member is bent at point 13a which is provided with a perforation defining the bending position. The bending is advantageously made close to the angle at which the rafter la will be after the attachment. The lower face 17 of the rafter 1 a is set on the first side plate 9 whereby the side 7 of the rafter becomes against the second side plate 10. The fastening is made advantageously with two screws or like members 15 through the slot 14 near the upper end thereof. As the first side plate 9 is against the lower face 17 of the rafter, also fastening with one screw prevents quite well the rafter from rotating around the screw and from rising up, for example a strong wind lifting the roof. Use of two screws makes the attachment more safe. The slot must extend so far down from a lower screw that enough sliding is certainly allowed as the roof is sinking.

Fig. 5 illustrates schematically the operation of the attachment during sinking of the roof. The situation of Fig. 4 is indicated by broken line. The log construction being contracted, the roof is gradually sinking and the rafter la is rotating on the attachment member as shown by arrow A and is sliding downwards as shown by arrow L. During rotation of the rafter, the attachment member is yielding at the bending position 13a and is rotating with the rafter. The rafter coming downwards, the screws 15 fastened thereto are sliding in the slot 14 which continues to be parallel to the lower face 17 of the rafter.

The invention is naturally not restricted to the embodiments described above. The form of the angle member may be any suitable form within the scope of the invention. Instead of perforation, the bending position may be provided with notches extending far enough from the sides, however, in such a way that the remaining neck is durable enough. Also recesses, cutting or other suitable solutions may be contemplated. Bending is also possible without any treatment of the bending position for that, especially if use of thinner or less hard material prove to meet the requirements.

The definition"screw or like members"means here all suitable fastening means which may be fastened through a slot to a rafter so that they are allowed to slide in the slot but keep the rafter otherwise fastened to the attachment member. A preferred alternative for screws are various suitable nails.

The invention may vary within the scope of the accompanying claims.