DESCRIPTION

In systems for assembling metal scaffolding formed of tubes and couplings or clamps which connect the tubes at the intersections, clamps are currently provided, which are fastened by friction to the outer surface of the tubes, with the use of bolts and "hammer-headed pins"; the bolts must be tightened to extremely high stresses, which at times cause breakages. On the other hand, loosening of a clamp and breakage of a bolt or of a hammer-headed pin can cause extremely serious damages.

The finding in question relates to an improvement in systems for the assembly of scaffolding, to prevent the dangers inherent to current systems.

These and other objects and advantages will be apparent from the text hereunder.

In substance, according to the present invention, the tubes have annular depressions in the outer surface, and corresponding bosses are correspondingly formed on the partial concave cylindrical surface of the intermediate cores and of the caps of the clamps, suitable - in coupling on the tubes - to be housed in said annular depressions. Interferences are thereby created to prevent slipping of the clamps along the tubes, irrespective of the degree of pressure obtained by tightening the clamp on the tube.

The bosses can advantageously be developed as portions of annular bosses in said partial concave cylindrical surfaces of the clamps.

The annular depressions in the tubes are advantageously positioned at constant modular distances along the tubes, repeatable also at connections between axially contiguous tubes with the presence of joining elements composed of guide rods inside the tubes. Correspondingly, two bosses can be provided in the partial concave cylindrical surfaces of the clamps, at the same distance from each other as the modular distance between the contiguous annular depressions found in the tubes. Said bosses in the partial concave cylindrical surfaces of the clamps can be formed directly during casting with the components of the clamps.

The annular depressions in the tubes can be formed by generating deformation of the walls of the tubes by cold or hot rolling or the like. Said annular depressions in the tubes can be obtained - alternatively - by mechanical

machining with removal of material.

The invention will be better understood by following the description and accompanying drawing, which shows non-limiting practical embodiments. In the drawing: Figures 1 and 2 show a clamp mounted on tubes orthogonal to each other, produced according to the invention, in a view with parts removed and in the view according to IMI in Figure 1 ;

Figure 3 shows the connection between coaxial and contiguous tubes, with two caps, in a partly sectional view; and Figure 4 shows an isolated view of an end portion of a tube.

In the drawing the numeral 1 indicates the conventional component used to form metal tubes of the structure made of structural metal known as "Innocenti" tubes or the like, whilst the numeral 3 generically indicates a conventional clamp for connecting vertical metal tubes and horizontal metal tubes. The metal tubes are composed of sections of one or more standard lengths; these sections are coupled to one another using joining and aligning elements or rods 5, having a disc-shaped core 5A which is interposed between the edges of the coupled sections 1 , and two section bars 5B (usually with a section in the shape of a cross), which are inserted in the cavities of contiguous sections to facilitate assembly of the various vertical components of a tubular structure. Conventionally, the clamps 3 have tightening assemblies to connect two tubes positioned orthogonal to each other and placed beside each other until they are almost in contact. These clamps generally comprise an intermediate core 3A which forms two partial seats 4A - with partial concave cylindrical surfaces - orthogonal to each other and facing in opposite directions to support the tubes positioned orthogonally, and at the level of each of the seats 4A formed by the central core 3A, two cap elements 3D, generally indicated as caps, with seats 4B similar to the seats 4A. Bolts 3C with respective nuts which can be four in number, or two in number and with the presence of two elements 3E, known as hammer- headed pins, allow tightening of the surfaces 4A, 4B on the tubes. By means of nuts 3C and the optional hammer-headed pins 3E, the tubes are tightened orthogonal to each other in conditions which allow stable reciprocal positioning simply through compression and consequently friction between the concave surfaces 4A and 4B of the core 3A and of the caps 3 B with the _. inner cylindrical

surfaces of the tubes 1. This embodiment - which is moreover used universally - is not devoid of dangers, as the bolts can become loose, thereby endangering the effect of connection of these clamps or couplings, with possible serious consequences on the stability of the platform of metal scaffoldings and naturally also dangers for workers.

The object of the finding is to prevent these risks and these dangers with simple arrangements which are described hereunder.

In the first place the tubes 1 are provided on the outer surface thereof with annular depressions 12, formed at modular distances M from one another for the purpose of placing clamps or couplings 3 in various positions differentiated by multiples of the module M. At the level of the end E (see Figure 4) of the various sections of tube 1 , the annular depressions 12E are produced at a distance Mo from the ends E of the sections of tube, so that the modular distance between the two depressions 12E of two contiguous sections is complied with (see in particular Figure 4) to take account of the thickness of the disc-shaped core 5A of the joining and aligning element 5.

These annular depressions 12 can be produced by removing material from the tubes or respectively also with deformations produced by rolling so that the thicknesses of the tubes remain practically the same, also at the depressions, or in any other suitable way, obviously in compliance with the strength to be guaranteed by said tubular components. The depressions 12 can have any profile optionally with rounded edges and flattened areas and also with a depth that is relatively very limited.

At the level of the annular grooves 12 and 12E, in the concave seats 4A of the central core 3A and respectively 4B of the caps 3B, bosses 14 (in the core 3A) and 16 (in the caps 3B) are formed, which in the drawing have a partial curved development.

These bosses 14 and 16 can be obtained directly during casting of the cores 3A and of the caps 3B, or also, in the pre-existing material, with facing material. Obviously, the sectional profiles of the bosses 14 and 16 must correspond with the depressions 12, although they could also be single or multiple projections rather than having a curved development.

With this simple arrangement, when coming to assemble the tubular elements of two orthogonal directions - i.e. vertical and horizontal - connections

- A -

with the clamp or coupling take place not by simple friction and compression, but also and above all through interference between the grooves 12 and the bosses 14 and 16. This connection prevents the risk of slipping between tubular elements and clamps even when the nuts have not been tightened or do not remain tightened, as is essential for conventional clamps. For safe assembly it is unnecessary to subject the bolts 3C to excessive overstress (with the danger of these bolts breaking due to the stresses to which they are subjected), it being suffice to prevent excessive loosening, which can be obtained with relatively limited tightening and/or with the presence of lock nuts or other solutions of evident conception to prevent rotation of the nuts.

An increase in assembly speed and compliance with the integrity of some of the components, in particular the bolts, which no longer have to be subjected to overstressing, are obtained with this arrangement. The various components, especially those of the clamps, are not stressed by extremely high continuous strains as is the case of conventional clamps, but with relatively limited stresses for reasons already expounded and evident.

The strength that must be complied with for the tubular elements can be obtained with a limited increase in thickness or with adequate solutions in forming the annular grooves 12. Two bosses 14 and respectively 16, spaced apart by the same modular distance M, are provided in the concave surfaces 4A, 4B of the core 3A and of the caps 3B, in order to obtain two bosses cooperating with the two grooves 12 of the tubular elements, and also safe connection between contiguous tubular components, as the annular grooves 12E of the ends of contiguous tubular thicknesses are spaced apart so that they receive the bosses 14 and 16 of the partial concave cylindrical surfaces of the clamps or couplings, formed by the core 3A and respectively by the caps 3B of the clamp.

Figure 3 shows the use of two caps 3B to connect two contiguous and aligned tubular sections 1X, 1Y using the conventional component 5, 5A, 5B described above, and without a clamp. The two caps 3B, with their bosses 16, engage the annular depressions 12E of the ends of the two tubes, so that connection between contiguous and abutting tubes 1X, 1Y is obtained through interference (and not through friction).

At the level of the annular depressions 12E and those 12 contiguous

thereto, the projections 12E inside the tubes 1 can cooperate with the section bars 5A to limit or actually more or less take up all the slack which otherwise occurs between the two inner surfaces of the tubes 1 and the section bars 5A; this is an advantage which has no drawbacks, as the section bars 5A are in any case easy to insert even when they are required to go beyond the inner projections 12E in proximity to the ends of the sections of tube 1.

The presence of annular depressions 12, 12E also facilitates placement of the structure made of structural metal which is not always - or rather almost never - able to be positioned on a flat and horizontal surface, that is, which currently requires the use of supporting elements or leveling "feet" which are difficult to select. According to the invention, it is instead sufficient to use "feet" which allow coincidence, in the same horizontal plane, of any one of the annular depressions to be obtained, to immediately allow correct placement of the clamps or couplings for connecting vertical tubes and horizontal tubes. The "feet" must allow only for compensations within an extent of the modular distance M between contiguous annular depressions 12.

It is understood that the drawing only shows an exemplification provided purely as a practical embodiment of the finding, which may vary in forms and arrangements without however departing from the scope of the concept on which the finding is based. Any reference numerals in the appended claims are provided to facilitate reading of the claims with reference to the description and to the drawing, and do not limit the scope of protection represented by the claims.