The previously known sets of rails of the kind referred to above consist of two guiding rails consisiting of profiles having C-shaped cross sections. The rail means which connect the guiding rails with each other are also shaped as rails having C-shaped cross sections and are guided with respect to the guiding rails by means of balls arranged between the guiding rails and the connecting rail means.

The known sets of rails referred to suffer from the drawback of having a very small degree of stability because the guiding rails and the connecting rail means may wobble with respect to each other which is particularly unlucky because two such sets of rails serve to connect two halves of a table and in the extended position of the table in question it is of great importance that the sets of rails connect the halves of the table with each other in a stable way so that accidental pushes applied to the table do not result in a shaking and e.g. splashing over of wine glasses.

It is the object of the present invention to provide a set of rails as stated above which both in the extended position and in the pushed together position may be readjusted in such a way that the set of rails constitutes a very stable structure, and this object is according to the present invention obtained by the two guiding rails being shaped as tubes having an interior cross section shape differing from circular cylindrical shape and by the ends of the connecting rail means being accomodated in a respective one of the guiding rails in the pushed together condition of the set of rails, the connecting rail means, moreover, having an exterior cross section shape differing from circular cylindrical shape in such a way that the connecting rail means are clampable in the guiding rails by rotation of the connecting rail means with respect to the guiding rails. Due to this structure it is achieved that the ends of the connecting rail means which are accomodated in the guiding rails

in the extended position of the table will be clamped with respect to the guiding rails along the full length of the portions which are accomodated in the guiding rails, whereby the stability of the set of rails aimed at is achieved and, accordingly, also of a table provided with two sets of rails according to the invention.

It should be noticed that an adjustable support for a window which is pivotable about a horizontal axis is known from published German patent specification No. 2313411. Such support consists of a fork to be secured to a stationary window frame. A stud is pivotably supported by the fork, and one end of a tube is secured to the stud. The tube extends into another tube and the upper end of the other tube is rigidly secured to another stud which is pivotably connected with a pivotable intermediate part which is pivotably connected with a stud for being secured to the movable window frame. The two tubes have non-circular cross section and the rotatably supported outer tube is provided with a handle, by means of which the outer tube may be rotated whereby the length of the window support may be adjusted. However, such structure cannot be used as a set of rails for an extension table because such set of rails needs two guiding rails, one to be secured to each of the corresponding table parts which makes a rotation of the outermost parts of such set of rails impossible. Furthermore, the object of the present invention is to achieve stability of an extendable set of rails for achieving a corresponding stability of a table in the extended position, whereas a window support serves solely to support the corresponding window in different open positions.

The invention will hereinafter be further explained with reference to the drawing, on which

Fig. 1 schematically and seen from below shows an embodiment of the set of rails according to the present invention in a partly extended condition and connected with the lower surface of two table top parts,

Fig. 2 shows the set of rails shown on Fig. 1 in the pushed together position of the table,

Fig. 3 shows a section through the set of rails shown on Fig. 1 in the non-locked condition of the set of rails,

Fig. 4 shows a picture corresponding to Fig. 3, but through the set of rails in locked condition, and

Fig. 5 shows a longitudinal section through a further embodiment of the set of rails according to the invention.

The set of rails shown on Figs. 1 and 2 constitutes one of two sets with which an extension table B is provided. On Fig. 1 the table B is seen from below in partly extended condition, and in Fig. 2 the table is also seen from below, but in the pushed together condition.

The set of rails consists of two guiding rails 21 and 31, which are shaped as tubes and have the cross section shape which is shown outermost on Figs. 3 and 4. The two tubes 21 and 31 are identical and are provided with lugs for being secured to the corresponding part of the table.

The two guiding rails 21 and 31 are mutually connected by means of connecting rail means 11 which according to the embodiment shown on Figs. 1 and 2 are constituted by a tube 11 having the cross section shape shown innermost on Figs. 3 and 4. At each of its ends the connecting tube 11 is provided with a washer 10 which is secured in the corresponding tube end, and wherein a hole is provided. Each hole serves for accomodating one of the ends of a connecting rod 20, which end is bent in such a way as to catch behind the edge of the hole. Each connecting rod 20 is connected with an end cover 23, and the end covers are arranged on the ends of the outer tubes 21 and 31 facing away from each other, and in such a way that the inner tube 11, cf. Fig. 1, cannot be drawn further out of the guiding tubes 21 and 31 than indicated as far as the left hand part of the set of rails in Fig. 1 is concerned.

The inner tube 11 is as it appears from Figs. 1 and 2 provided with a handle 12 at the centre and by means of the handle the inner tube 11 may be rotated from the position showr on Fig. 3 and to the position shown on Fig. 4, whereby the ends of the inner tube 11 are

clamped within the outer tubes 21 and 31.

From Fig. 3 and 4 it will be seen that the guiding rails 21,31 have an interior cross section shape which differs from circular cylindrical shape, and that the connecting rail means 11 have an outer cross section shape which also differs from cylindrical shape, viz. in such a way that a clamping of the ends of the connecting rail means 11 with respect to the guiding rails 21, 31 is achieved by rotating the connecting rail means 11 as indicated above, no matter whether the set of rails is pushed completely together or is extended more or less for supporting one or more loose table top plates. It will be understood that several other cross section shapes than the generally elliptical shapes shown on Fig. 3 may be used in order to achieve the object referred to above.

Fig. 5 shows a longitudinal section through a little more than one half of an amended embodiment of the set of rails according to the present invention. The other half is constructed symmetrically, and, accordingly, only one half is shown and explained. This set of rails also comprises two guiding rails of which, however, only the right 31 is shown. This guiding rail is provided with two brackets 22,22 for securing to the corresponding half of the table and is shaped as a tube. The connecting rail means consist according to the embodiment shown on Fig. 5 of a central inner tube 35 provided with a handle 12 corresponding to Figs. 1 and 2. Each of the two ends of the tube 35 is slidably accomodated in an end of a corresponding intermediate tube 36, the other end of which is accomodated in the corresponding outer tube 31. The central tube 35 has an outer cross section shape which differs from circular cylindrical shape, and the intermediate tubes 36 have an inner cross section shape which also differs from circular cylindrical shape and in such a way that the central tube 35 will be clamped within the intermediate tubes 36 by being rotated in the same way as illustrated on Figs. 3 and 4 as far as the outer tubes 21 and the inner tube 31 are concerned. Moreover, each intermediate tube 36 has an outer cross section shape which differs from cylindrical cross section shape as explained in connection with the inner tube 11 on Figs. 1 and 2. Moreover, the outer tubes 31 are shaped with an inner cross section shape which is clampable with respect to the intermediate tubes 36 in the same way

as explained in connection with Figs. 3 and 4.

It will be understood that also the set of rails according to Fig. 5 may be transferred to a stable rigid structure by rotating the central tube 35, because such rotation will clamp the ends of the central tube 35 with respect to the adjacent ends of the intermediate tubes 36 and thereby the rotation will be transferred to the intermediate tubes 36, whereby the latter will be brought into a clamping position with respect to the outer tubes 31.

Also the embodiment according to Fig. 5 is provided with connecting rods in order to prevent the set of rails to be drawn apart. The connecting rods are constituted by a first connecting rod 37, one end of which is bent as shown at 38, whereby an end cover 39 may be arranged upon the bent end. The end cover 39 comprises a bottom wall 40 for closing the open end of the tube 31 and a stopper part 41 offset inwardly with respect to the wall 40 for being inserted into the end of the tube 31. The stopper part 41 is provided with a hole for accomodating the bent end 38. The rod 37 extends through a washer 42 secured in the accomodated end of the corresponding intermediate tube 36 and the rod 37 extends further on, however, only so far that the end of the rod 37 does not strike against a washer corresponding to the washer 43 and positioned at the other end of the tube 35. Between the two washers 42 and 43 the rod 47 is provided with laterally extending lugs 45 produced by compressing a part of the rod material in such a way that two opposite projections in the form of "nails" are produced.

It will be understood that the projections 45 by full extension of the set of rails will cooperate with the washer 42 so as to prevent the intermediate tube 36 from being drawn too far out of the outer tube 31, and in this condition the bent end 38 forms a stop.

A withdrawal of the central tube 35 with respect to each of the intermediate tubes 36 is prevented by means of a further rod 46, one end of which is provided with a bend 47 which is passed through a hole in the adjacent washer 43. The other end of the rod 46 is passed through another hole in the washer 42 and is bent so as to form an eye 48 which surrounds the rod 37 so that interference with

the latter is avoided.

Due to the outer cross section shape of the intermediate tubes 36 and the interior cross section shape of the guiding tubes, the guiding tubes 21 and 31 of this embodiment can also be clamped with respect to the connecting rail means 35,36 in any position of the halves of the table with respect to each other.