Many worktables used in offices and technical studios and many types of desk include two legs joined together by a crosspiece that creates the supporting base of the tabletop.

In other types of production, the crosspiece is substituted by a pair of ledges, each being coupled and/or fixed to the top end of a corresponding leg and its top face being level with the face on the other ledge, this surface creating the supporting base of the table top.

In any case the coupling and/or locking devices used in known systems provide a relatively stable joint between the legs and the supporting elements of the table top, however only in the initial period of the table's use.

In fact extensive use of the table, often worsened by loading it with heavy weights and through time pushed sideways more or less accidentally, causes a progressive reduction in the stability of the worktop's supporting frame, that thereby begins to show signs of annoying wobbling, due to the growing play that is produced between the parts joined by means of known locking devices.

This invention intends to overcome this inconvenience.

In particular one of the scopes of this invention is to produce a locking device that can be easily applied to both tables with a crosspiece supporting the worktop connecting the two legs together transversally, and to tables that instead have at least one pair of ledges, each coupled to the top end of a corresponding leg.

In both applications, the main scope is to produce a locking device that will entirely eliminate the initial play in the joint between said elements, and to prevent that said play is produced through time after the usual stresses a table's loadbearing frame inevitably undergoes.

Said scopes are achieved by the production of a locking device between leg and supporting elements of a table's worktop, said table including: -one or more legs; -at least one ledge attached to the end of each leg, creating the supporting base of the table's worktop;

-a profile sheet metal supporting the tabletop and set crossways to the main symmetrical axis of the ledge, joined to at least one of said ledges and creating the same supporting base as the ledge, said ledge having at least one hook fastened in a corresponding slot of at least one of said legs, and at least one tongue with a hole for fixing it to the table leg, said device being characterised in that it has at least one screw engaging into the table leg and passing through coaxial holes in the sheet metal and the tongue, said screw having a shank with a threaded tip connected by a countersunk section to second shank with a larger diameter than the threaded section and the same diameter as the hole in said tongue, this same screw making a solid, play-free coupling of the ledge to the leg when it is fully screwed into the threaded hole on the leg.

According to a preferred form of execution of the invention the locking device is applied with one ledge for each leg, coupled to the inside face of the table leg and overlapped by a straight rim of said profile sheet metal.

According to a variant in execution, at least one table leg has two opposite faces with coupling locations for a corresponding ledge, thereby being able to receive two examples of the same ledge mounted on opposite sides of the leg.

The above scopes shall be better illustrated later during the description of a preferred form of execution of the invention, given as a guideline but not a limitation and illustrated in the attached diagrams, where-.

-fig. 1 illustrates, side by side, a prospective view of the top end of a leg and the ledge ready to be coupled to it; -fig. 2 illustrates a front view of said top end of a leg seen from the contact and coupling face of the ledge ; -fig. 3 shows a side view of the ledge seen from a normal line of its plane of mirror symmetry; -fig. 4 shows a second side view of the same ledge seen from a line belonging to its plane of mirror symmetry ; -fig. 5 shows a prospective view of the ledge coupled to the leg ready to be overlapped by the profile sheet metal and receive the locking screw; -fig. 6 shows an enlarged cross-section of the part related to the initial joining of leg, ledge and sheet metal crosspiece, with the locking screw only just engaged in the thread of the hole on the leg's body ; -fig. 7 shows the same elements as in fig. 6, but with the screw fully tightened in its final position locking the actual elements together;

-fig. 8 shows a similar cross-section to fig.'s 6 and 7, the locking device used to join a leg to two opposite ledges partly overlapped by the straight rims of the profile sheet metal.

As seen in fig. 1, the parts of a table, before they are joined together by means of the locking device invention, are each of the legs indicated by 1 with a ledge indicated by 2.

For this purpose, at the same height of the inside face 11 of the leg, two slots 111 and 112 (fig.'s 1,2) have been cut out, designed to receive two respective hooks 21 and 22 (fig.'s 1,4) protruding from the upright face 23 of the ledge 2.

Along the top edge of the same side 11 of the leg two grooves 113 and 114 (fig.'s 1 and 2) of different depths have been cut out, designed to receive the two tongues 24 and 25 (fig.'s 1,4) belonging to the ledge.

Said tongues have respective holes 240 and 250 of the same diameter, having parallel axes and being equal in distance from the upright face 23 of the ledge (fig. 3).

These tongues are fitted onto the same upright face of the ledge at different heights, so that they line up with said grooves of different depths belonging to the leg.

The scope of this constructive detail will be explained later.

A horizontal plate 12 has been attached to the inside of the leg's hollow body, with two symmetrical threaded holes 121 and 122 that are each aligned with holes 240 and 250 respectively on the ledge's tongues when the leg and ledge are coupled together (fig. 5).

As seen again in fig. 5, the front 13 and back 14 edges of the top of the leg act as a support for the channel base 31 of the profile sheet metal 3 that has two straight, parallel rims 32 and 33 raised above said channel base, so that the central part of one of them rests on the top flat face 26 of the ledge 2.

When positioning said profile sheet metal on the leg with the ledge already hooked into place, care has to be taken in aligning the two holes 311 and 312, belonging to the channel base 31 of the actual profile sheet metal, with their respective holes 240 and 250, belonging to the two tongues on the ledge. In this way the profile sheet metal is set with its length perpendicular to the main symmetry x-x of the ledge and with the top faces of the two straight rims 32 and 33 set horizontal and level.

Said faces, together with the top of the flat spline 27 applied to the face 26 of

the ledge and having the same thickness as said rims (fig.'s 7 and 8), create the supporting base of the table's worktop (not illustrated).

The leg, ledge and profile sheet metal assembly is locked together by means of a pair of especially shaped screws. As in fact seen in figures 5 to 7, each screw 4 has a shank with a threaded tip 41 connected by a countersunk section 42 to second shank 43 with a larger diameter than the threaded section and the same diameter as the hole in each of the ledge's tongues, said shank coming immediately under the screw's head 44.

As seen in detail in fig. 6 the screw 4, inserted into hole 312 and then hole 240 in the sheet metal and tongue respectively, has the beginning of its thread only just engaged in the hole 121 of the plate 12 belonging to the leg and its countersunk section 42 begins to tighten against the inside surface of the hole 240 in the tongue, gradually pulling all the aforesaid holes into alignment.

The status on completing the locking of the screw has been illustrated in fig. 7, where it can be seen that the thread 41 of the screw fully engaged in the threaded hole of the plate 12 and the head 44 of the same screw tightened against the channel base 31 of the profile sheet metal 3.

In this position the countersunk section 43 of the screw is precisely engaged in the hole 240 of the tongue 24, thereby making the ledge's upright face 23 press firmly against its counterpart 11 on the leg and firmly locking together the profile sheet metal 3, ledge 2 and table leg 1.

As can again be seen in fig. 7, the firmness of the coupling is also assisted by the solid pressure between the flat channel base 31 of the profile sheet metal and the top edges 13 and 14 of the leg (fig. 5), basically level with the top face of the tongue 24 set higher than the second tongue 25.

The reason why said two tongues are not set at the same height on the front face of the ledge is explained by figure 8, which shows how the table can be extended by adding a second segment to the former.

In this case the table's structure requires three legs, and precisely the cross- section of a central leg is shown in said figure, where it can be seen that said central leg has two ledges 2 and 2'hooked to it, being identical but mounted on opposite sides of the leg 1.

In this application the tongue 24, belonging to the right-hand ledge 2, and its counterpart 25'belonging to the left-hand ledge 2', are overlapping without impediment, setting their respective holes 240 and 250'in line with the

threaded hole 121 in the plate 12 and thereby allowing to use a single screw 4 to lock all the supporting elements of the table top to the central leg 1'.

It is quite clear that the two end legs of a work table, including any number of level segments, will each require a single ledge to be hooked onto them, turned towards the inside of the table. It is equally clear that all the intermediary legs will instead require two opposing ledges to be hooked onto them, as described and illustrated above.

It is also evident that the application of the invention's concepts set forth herein can be extended to tables that have at least two legs, joined together by a continuous crosspiece mounted beneath the worktop. The locking device invention can in fact be applied by the same method to each of the two ends of the crosspiece itself, these ends being produced with the same construction criteria as the ledges described above.

Yet again said concepts can be applied to a single legged table, provided the leg has a sufficiently wide floor standing base to make the worktop stable and fixed to at least one ledge hooked up to at least one flat side of the leg, each ledge being locked to the leg by means of the same invention device.

The above descriptions and illustrations clearly explain how the locking device invention achieves all the set scopes, in particular the aspects regarding the elimination of play in the joint between the elements that make up the supporting frame of the worktop of a table, even when this includes more than one segment.

In the production of the invention modifications may be made in the execution of parts of the leg, ledge and the profile sheet metal. Each variant in execution shall fall under the protection of this invention.