Technological background A support with these features is known from EP 553666.

This support, like other similar devices formed in accordance with the prior art, is subject to combined bending and compressive stress of the elements of which it is composed. Of these, the inner element, which is necessarily of smaller dimensions so that it can be fitted inside the outer element, is the element which is subject to the most critical stress.

Various arrangements have been developed to ensure the strength of the inner element.

The first and most widespread arrangement is that of making the inner element of a different and stronger, although heavier, material than that used for the construction of the outer element. Typically, the outer element is made of aluminium alloy and the inner element is made of steel. Moreover, it is usual to make the inner element considerably shorter than the outer element.

Although, on the one hand, all of these arrangements favour the strength of the support, even though it is subjected to large loads, on the other hand, they compromise its weight, manoeuvrability, and suitability for large longitudinal adjustments, as well as its ability, as a whole, to withstand combined bending and compressive stress.

Description of the invention The main task of the invention is to provide a support, particularly for building works, which is designed structurally and functionally to overcome the disadvantages discussed with reference to the prior art mentioned.

An important object of the present invention is to provide a telescopic support in which the problems of wear connected with adjustment with ring nuts are prevented.

Yet another object is to provide a support with a structure such that problems of slipping-out are prevented.

Yet another object is that of providing a support having a simple structure.

One of the main objects is to provide an inexpensive telescopic support structure.

The main task, the objects set out, and others which will become clearer from the following, are achieved by a telescopic support, particularly for building use, formed in accordance with the appended claims.

Brief description of the drawings Further characteristics and advantages of the invention will become clearer from the description of a preferred but not exclusive embodiment thereof, indicated by way of non-limiting example with reference to the drawings, in which: Figure 1 shows, in a perspective view, a telescopic support, particularly for building use, with a structure according to the invention, Figure 2 shows a portion of a support according to the invention in longitudinal section, and Figure 3 shows the support of the previous drawings in cross-section.

Preferred embodiment of the invention With particular reference to the drawings described above, a telescopic support, particularly for building works, with a structure according to the invention, is generally indicated 10.

The support 10 comprises an inner tubular element 11, slidable telescopically in an outer tubular element 12. The elements 11 and 12 are provided with shaped support plates 13 at their ends.

As can be seen in Figure 3, the inner element 11 is made of extruded aluminium alloy and has, in cross-section, a series of recurring corrugations extending substantially continuously longitudinally and distributed at regular intervals around both its inner periphery and its outer periphery. The resisting cross-section which is subject to compression stress is thus increased and a stiffening of the inner element of the support, which increases its strength, is also achieved.

The corrugations have an approximately sinusoidal shape with respect to a median circle of the element 11 and portions of screw thread are formed on at least some of the outer ridges, so as to form a plurality of thread sectors 17.

The corrugations define a plurality of first re-entrant portions 14 arranged circumferentially at intervals of 45° and an outer profile having longitudinal recesses 15 which define ridges or first projections 16, also spaced apart circumferentially by 45°.

Alternatively, the outer corrugations may be formed by milling and, in this case, the inner tubular element is initially provided with a continuous external screw thread which is subsequently milled to produce longitudinal recesses 15 as indicated above.

The outer tubular element 12 also has a shaped cross-section with an inner profile defining second projections and second re-entrant portions, 18 and 19, respectively.

There is thus a series of recurring corrugations extending substantially continuously longitudinally and spaced apart at regular intervals around the circumference of the element with an approximately sinusoidal shape with respect to the median circle of the element and with a profile complementary with the corrugations of the inner element 11.

As can be seen in Figure 3, when the inner element 11 is fitted in the outer element 12, the first projections 16 of the inner element 11 fit in the second re-entrant portions 19 of the outer element 12 so that the support 10 has a plurality of points of contact between the two tubular elements 11 and 12 even in the presence of minimal oscillations, ensuring a considerable increase in the stability of the structure in comparison with conventional systems.

A thread sector of one first projection 16 is removed, for example, by a mechanical flattening process, so as to produce a flat and slightly recessed surface 16a.

The extension of the inner element 11 from the outer element 12 is adjusted by clamping means which can lock the relative sliding of the elements in at least one of the two directions of sliding. A ring nut 20 engaged by male/female screw coupling on the interrupted thread portions of the inner element 11, is used for this purpose and, in conditions of use, comes into stop abutment bearing on a shaped plate 21 fixed firmly to the top of the outer element 12.

The shaped plate 21 is made of tough metal to prevent problems of wear of the bearing surface between the plate 21 and the ring nut 20 owing mutual friction during extension-adjustment operations.

Upon completion of the adjustment, the assembly constituted by the inner element 11 and by the ring nut 20 is clamped in the desired position by a spring hook 22 which is articulated to the top of the element 12 and engages on a lower flange 23 of the ring nut 20.

A safety pawl 25, fixed in a corresponding threaded hole 24 in the flat surface 16a of the inner element 11, extends in the corresponding second re-entrant portion 19a of the outer element 12.

A plate 27 suitable for forming a catch for the pawl 25 is fixed in the second re-entrant portion 19a, in the vicinity of the upper end of the outer element 12, by means of screws 26.

The pawl 25 and the plate 27 ensure both that it is completely impossible for the inner element 11 to slip out of the outer element, and that a portion 28 of the inner element 11 is inserted in the outer element 12, thus ensuring the stability of the assembly in use.

Advantageously, the inner and outer elements 11 and 12 may be made of aluminium alloy or of another light alloy.

The present invention has been found in practice to have led to the achievement of the objects proposed.

Moreover, a support structure is provided which prevents problems of wear connected with the operation to adjust the relative extension of the inner and outer elements.

Furthermore, the support 10 solves the problem of slipping of the inner element 11 out of the outer element 12 as well as setting-up problems with regard to reduced stability should the support 10 be used with the element 11 extending too far from the outer element 12; the portions of the two tubular elements which interact are thus sufficient to ensure the equilibrium and stability of the assembly with respect to the vertical axis.

The structure is simple and inexpensive.