In the production, storage and handling of standardized building components, including door frames, it is important that these be easy to assemble, that they be as stable as possible, and that at the same time the number of essential variants can be kept as low as possible and can be utilized for several alternative use

This is particularly important with door frames, since in the door industry today there is to a large extent a desire to make use of symmetrical components. In the use of symmetrical mounting a door leaf and door frame today can be stored separately, and the direction of door opening need not be decided until the frame members are mounted together with the door leaf. If one can also utilize several types of thresholds, e.g., flat threshold, split threshold, etc., in conjunction with standard vertical frame members (posts) and top pieces (heads) , one can thereby also reduce the dealers' and users' stock to a minimum at the same time as the producer can increase his series sizes and reduce necessary stock, something which improves the economy of the whole chain ^' from producer to consumer.

The traditionally constructed door frame has a mortise and tenon joint. In order for such a frame to be symmetrical, the rabbet (gr of the head and that of the threshold must be the same, and this means that the threshold (which is made of expensive, hard materials) must be made of thicker materials than necessary, something which increases the cost of the product and makes the threshold higher, which is not desirable. And if such a frame is to utilize a flat threshold, one no longer may use the same post but must now make a special post having a different groove form for this purpose. This is also the case if one does not intend to use a threshold at all.

Various methods have been developed to avoid these problems, e.g., using joints with center pins and connecting blocks. Another

Another method is described in Norwegian patent no. 136 218. Here the tenon is removed from the post. The head is offset and contains a cut-away groove which is to receive the rabbeting projection on the post. The threshold is counter-wedged and lies between the posts without any corresponding offsetting as in the head.

What characterizes the properties of the various methods is that the mortise and tenon joint i -far more stable and can therefore be more easily handled and transported without damage, while, for example, the method last described requires fewer variants. It is not as easy to assemble, however, and comes apart more easily during transport and mounting prior to being nailed securely into the wall. Since the door leaves often are transporte with an assembled frame lying horizontally in high pallets, damages related to transport are relatively frequent.

The present invention retains all of the advantages through the fact that the same component covers several areas of usage at the same time as it ensures a significantly improved stability both in assembly and in handling. The invention involves a special "locking arrangement" of the corner joints which prevents the component parts from being pressed apart during transport and storage.

The invention thus relates to the features which are disclosed in the characterizing parts of the patent claim.

In addition to the above advantages, a door frame according to the patent claim is less expensive to produce than other symmetrical frames. This is due to the fact that in the process of production one can utilize a standard double tenoning apparatus in series with the profile plane, and can carry out formation of all corner connections automatically in the same production stage without interruption, a feature which is otherwise not possible. The frame's "locking joint" moreover requires less expenditure of time for nailing the pieces together, since not as many nails are needed to ensure the stability in transport and handling.

The profile of the door frame can easily be dimensioned in such a way that with an ordinary building saw it is easy to alter a frame of a width of, e.g., 92 mm to one of, e.g., 68 or 72 mm or other desired widths. This entails a significant simplifica¬ tion in stock and series sizes.

Reference is made to the drawings which show a preferred embodiment of the invention, wherein Fig. 1 shows preferably a side frame member (post) having a raised profile .projection 3, and where Fig. 2 preferably shows a top piece (head) for the frame. Fig. 3 shows a connected corner joint.

The side post with the raised profile projection 3 is cut off at a right angle, with a groove 4 which is made along the entire width of the post, preferably having a width of 4 - 10 mm and a depth of 2 - 5 mm, so that the post is terminated with two end surfaces.

The corresponding top piece (head) for the frame is similarly provided with a profile projection 3 like that of the side post and is provided with a cut-out slot 5 extending preferably through the entire depth of said post. The width of the slot corresponds approximately to the width of the profile projection 3 and the distance from the frame member's or the head's end surface 9 to the end surface 6 of the slot 5 preferably corre¬ sponds to the thickness of the corresponding frame member having the profile projection 3. The frame member as shown in Fig. 2 is further provided with a projection 7 on each side of the slot 5. These projections are in addition provided with an elevated part 8 having a height of preferably 2 - 5 mm and a width of preferably 4 - 10 mm, said elevated part fitting into the groove 4 of the corresponding frame member.

It will be understood that the head can be formed like the side element (post) described herein, and that the post can be formed like the head or top piece herein described.

With the interconnection of the frame members described herein, one obtains a stable corner joint which is locked in all direction and which is easy to, for example, nail together in mounting.