The invention relates to a coupling piece for frame-works, panels or the like, adapted to be connected, in a corner of a frame-work, panel or the like, with border channels or edge portions thereof, said coupling piece comprising two, in particular mutually perpendicular, legs, at least one thereof being provided with a recess having a coupling pin directed parallel to a border edge of said leg for coupling, by means of a coupling element, said coupling piece with another coupling piece having a leg positioned against the corresponding leg of said first coupling piece, a rotational movement around said pin being possible, a border portion of said legs being rounded around the pin in question in such a manner that the roundings of both mutually coupled legs are allowed to roll around each other. Such a coupling piece is known from EP-A 0 068 583.

Therein a fixed pin is provided in a recess of a leg, said pin being situated in the longitudinal median plane, the coupling element being formed by a resilient U-shaped clip being adapted to be clamped around two pins of coupling pieces arranged adjacent to each other; the roundings are substantial¬ ly cylindrical around the pin axis.

Panels or the like interconnected by means of such coupling pieces can be rotated around the pins in question, and also superposed panels can be interconnected in this manner.. Since the roundings are, in particular, polygonally shaped, a more or less fixed adjustment in given angular positions can be obtained under spring action of the coupling clips.

Such a construction of the coupling pieces has some draw-backs. The hinge connection obtained by coupling cannot be unambiguously secured, which, in particular in the case of superposed panels or the like, will lead to instability when exerting transverse forces on the assembly. Applying and re¬ moving said clips requires a rather substantial force, and detached clips can get lost.

It is an object of the invention to provide a coupling

piece of the above-mentioned kind which does not have said draw-backs.

To that end the coupling piece is characterised in that the coupling element consists of two pins interconnected by a bridge, in that the leg in question is provided with two parallel bores which are symmetrical in respect of the longi¬ tudinal median plane and open into the recess in question, in which bores a pin of a coupling element fits in a slidable way, the interaxial distance of the pins of a coupling element being substantially equal to the interaxial distance of said bores, and in that the rounding consists of two parts having an axis coinciding with the axis of the adjacent bore, and having a radius which is substantially equal to half the interaxial distance of said bores, all this in such a manner that, when interconnecting two coupling pieces by means of such a coupling element, a rotation around the axes of both pins with a rolling movement of the roundings in question on each other is allowed.

In each recess such a coupling element can be provided, and, in the case of aligned panels, a double coupling and, thus, an unambiguous locking can be obtained by means of the mutually off-set coupling elements of adjacent coupling pieces.

In particular one pin of a coupling element can have such a length in respect of the length of the recess that said pin, when longitudinally shifted in a bore, cannot be pulled out of said bore, the other pin being so much shorter that, when shifting said coupling element, the latter pin can be swung out of said recess and can be shifted into another bore and vice versa. In each recess a coupling element can already be provided beforehand, said element then remaining unlosable with the coupling piece, and by shifting said coupling element the shorter pin can be engaged with an adjacent bore of another coupling piece. Moreover said bores can be open at least at the end opposite to said recess at the inner side of the leg, in order to allow tilting the longer pin present therein in such a manner that it can be pulled from the bore or can be inserted therein,' and the terminal portion of the leg in question can

also be profiled in such a manner that, when applying the coupling piece on a frame-work channel or panel, an inserted longer pin will be secured against tilting. This allows to insert a coupling element into the recess, said element then remaining locked after providing the coupling piece on a frame-work portion or panel , without impeding the shifting of said coupling piece in the bore in question.

In order to facilitate shifting said coupling piece into the desired position, the longer pin can be provided with a terminal bulge, and stops can be provided in said bores which, together with said bulge, will limit the shifting of said pin in said bore.

Moreover the roundingscan be knurled, the knurlings of two roundings belonging to two parallel bores will be off-set by half a knurl distance, so that the knurlings of two coupled coupling pieces will mesh; in this manner a gear-wheel effect will be obtained insuring a uniform hinge effect.

In particular said legs are provided with a snap lock for fixing a frame-work channel or the like thereon. The invention will be elucidated below in more detail by reference to a drawing, showing in:

Fig. 1 a lateral view, partially in section, of a coupling piece of the invention;

Fig. 2 a top view of the coupling element of Fig. 1; Fig. 3 a section along the line III - III of Fig. 2;

Fig. 4 a lateral view of a coupling element for such a coupling piece;

Fig. 5 a lateral view of two intercoupled coupling pieces of Fig. 1; Figs. 6A and B top views of coupled coupling pieces of Fig. 5 in two different positions; and

Fig. 7A and B lateral views corresponding with Fig. 6 of other coupling possibilities.

The coupling piece 1 shown in Figs. 1..3 comprises two mutually perpendicular legs 2 forming each others mirror image, said legs being substantially U-shaped in section, and having a terminal portion 3 which is adapted to be inserted into a hollow frame-work channel 4 or the like, a resilient locking tongue 5 serving for locking such a channel. Said

locking tongue 5 can be pushed away through a hole 6 for releasing the locking. Near the corner portion of the coupling piece 1, each leg is provided with a recess 7. As appears from Fig. 3, in the border wall 8 of said recess 7 two apertures 9 are formed symmetrically in respect of the longitudinal median plane of the leg 2, said apertures opening into the cavity 10 of the leg 2.

The wall portion 11 of the leg 2 joining the recess 7 is, as will appear in particular from Fig. 3, rounded near the outer edges 11* , and is, there, provided with a knurling or toothing 12. The teeth of both are mutually off-set by a half tooth distance. The radius of the roundings 11 ^l is equal to half the interaxial distance of the apertures 9.

Fig. 4 shows a coupling element 13 consisting of a bridge piece 14 provided with two parallel pins, viz. a longer pin 15 and a shorter pin 16. The interaxial distance between said pins corresponds to the interaxial distance of the apertures 9, and the thickness of said pins substantially corresponds to the width of said apertures. The longer pin 15 has a thinner terminal portion 15' terminating in a thicker head 15" having a thickness which, again, is equal to that of the initial portion of the pin 15.

Such a coupling element 13 can be inserted with the longer pin 15 obliquely into the recess 7 and through an aperture 9, since the adjoining cavity 10 is open at its lower side. As soon as the bridge piece 14 has been brought above the recess, the pin 15 can be turned upright, and can be shifted further in the axial direction of the aperture 9. Stops 17 can cooperate with the head 15", and determine an inserted and retracted position of the coupling piece. The shorter pin 16 can then be inserted into the adjacent aperture 9. When arranging a frame-work channel 4, a bottom portion 18 thereof will be situated below the cavity 10, thereby pre¬ venting that the longer pin will be tilted and will be removed from the coupling piece, but said pin remains shiftable.

Figs. 5 and 6 show two coupling pieces 1 interconnected by means of a coupling element 13, the longer pin 15 thereof being inserted in one coupling piece, and the shorter pin 16 in the other one. Since the interaxial distance between the

pins 15 and 16 is equal to the interaxial distance between the apertures 9, and the radius of the roundings 11' is half said interaxial distance, the coupling pieces can be rotated around the axes of said pins 15 and 16, the teeth 12 of said roundings which are off-set by half a tooth distance will intermesh. If, as shown in Fig. 6B, the coupling pieces are rotated flatly against one another, the teeth 12 on the lateral walls provide a correct alignment. This is the position in which inserting the shorter pin 16 into an aper- ture 9 of the adjoining coupling piece can be done in the easiest way.

In the straight position shown in Fig. 5, a second coupling element 13 can be inserted if desired for unambiguous¬ ly locking said position as shown in Fig. 6A at 13'. It will be clear that, in the same manner, also at the other side of the coupling pieces of Fig. 5 additional coupling pieces 1 can be provided.

Fig. 7A shows the connection according to Figs. 5 and 6B after rotation by 90°, and Fig. 7B shows how in the position of Fig. 7A a third coupling piece can be added. In the same manner a fourth coupling piece can be provided.

In this manner many forms of spatial assemblies can be constructed. If only one coupling element 13 is present in a coupling piece 1, a hinge movement by 90° is possible, which may be desired for instance if adjoining frame-work portions should be adapted to be folded. If a rigid interconnection between two frame-work portions is desired, this can be ob¬ tained by means of two coupling elements 13 as shown in Fig. 6. In practice a coupling element 13 is provided in each recess 7, the shorter pin 16 thereof being inserted into the other aperture 9, so that said coupling elements will be connected with the coupling piece 1 in a virtually unlosable way. Removing a longer pin 15 from the coupling piece requires some effort, since a certain clamping in the cavity 10 and of the head 15" behind a stop 17 will be present, so that also without a frame-work channel 4 being present the coupling elements 13 cannot get lost.

Although, in the drawing, the legs 2 are mutually per-

pendicular, it is also possible to provide said legs at a different angle, and even to interconnect both legs of a coupling piece by means of a hinge allowing to direct them at arbitrary angles. Furthermore it will be clear that in Fig. 7 the interconnected coupling pieces 1 can be mutually rotated for obtaining corresponding orientations of the respective frame-works, and that, then, also more than four coupling pieces can be interconnected.