DEVICE FOR JOINING TWO UPRIGHTS

TECHNICAL FIELD

^■ The present invention relates to a device for joining two uprights. BACKGROUND ART

As is known some metal support structures such as for example the structures used for stages comprise a series of uprights and cross-members that must be joined coaxially to one another to define the desired height and the length of the span. The current method for joining two coaxial uprights envisages the use of sleeves that are fixed to the corresponding upright by means of welding. It is apparent that the use of welded joints results in a number of evident drawbacks such as the weakening of the upright in the welding zone which is thermally altered and due to which the capacity of the structure is reduced. Moreover production times are long especially when plates are used as the interconnecting members in that their geometric shape prevents the use of automated production processes. Lastly the use of welding means the structure has an extremely poor appearance.

DISCLOSURE OF INVENTION The object of the present invention is to produce a device for joining two uprights which overcomes the drawbacks described above in that no special machining processes are required and in that it enables the

structures to be assembled and dismantled simply and quickly.

The object of the present invention is a device for joining two coaxial uprights characterized in that ^' it comprises: a first sleeve fixed by means of a screw to the axial end of a first of said uprights; a second sleeve fixed by means of a screw to the axial end of a second of said uprights; and a metal member (13) having a first head inside said first sleeve and a second head inside said second sleeve .

BRIEF DESCRIPTION OF THE DRAWINGS

In order to better understand the present invention, a non-limiting preferred embodiment thereof will now be described by way of example with the help of the figures in the accompanying drawing, in which: figure 1 is a perspective view of a trellis structure ; figure 2 is a plan view of a part of the structure of figure 1; and figure 3 is a cross-sectional view of a part of the structure of figure 1.

BEST MODE FOR CARRYING OUT THE INVENTION With reference to figure 1, designated as a whole by number 1 is a part of a structure defined by two metal trellises 2 arranged coaxially with respect to one another and joined to one another by means of a device

3. In this embodiment the trellises 2 comprise four vertical uprights 4 arranged at the vertices of an imaginary rectangle and a plurality of tie rods (not illustrated) arranged between contiguous pairs of uprights 4; the tie rods being welded at the ends thereof to the corresponding uprights 4.

With reference to figure 3, the uprights 4 are internally hollow and have an internally threaded axial end section 6 inside which there is screwed an externally threaded cylindrical metal block 7 having a threaded central hole 8. Inside the upright 4 there is an annular shoulder 9 against which the block 7 rests . Moreover the length of the block 7 is such that the outwardly facing axial end of said block 7 is at a given distance from the end edge of the upright 4 once screwed to the end of the threaded section 6 of the upright 4.

With reference to figures 1, 2 and 3, the device 3 for each pair of uprights 4 of the two trellises 2 to be joined comprises: a first sleeve 11 fixed by means of a screw 12 to the axial end of a first upright 4 of the first trellis 2 by means of screwing the screw 12 into the hole 8 of the block 7 ; a second sleeve 11 fixed by means of a screw 12 to the axial end of a first upright 4 of the second trellis 2 by means of screwing the screw 12 into the hole 8 of the block 7 ; and a metal member 13 having a first head 14 inside the

first sleeve 11 and a second head 15 inside the second sleeve 11.

Each sleeve 11 is defined by a cylindrical metal member 16 internally cup-shaped and coaxial to the respective upright. Preferably the outside diameter of the member 16 is the same as the outside diameter of the upright 4. The member 16 has a base wall 17 that rests against the axial end of the respective upright 4 and a cylindrical lateral wall 18 that has a diametral through hole 21 coaxial to a through hole 22 in the housed head 14 or 15. A taper pin 23 is inserted into the holes 21 and 22 in order to fix the member 13 to the sleeve 11. Preferably the length of the pin 23 is greater than the outside diameter of the member 16 so that the ends of the pin 23 remain outside the member 16. The base wall 17 has a through hole 24 through which the threaded shank of the screw 12 can be screwed into the hole 8 of the block 7 ; the head of the screw 12 coming to rest against the inside surface of the base wall 17. The heads 14 and 15 of the member 13 are shaped and in particular are substantially cone-shaped. Preferably the development of the inside face of the wall 18 is complementary to the development of said heads 14 and 15. Moreover the outside surface of the base wall 17 of each sleeve 11 has a plurality of projections 25 defined along a circumference the diameter of which is smaller than the inside diameter of the upright 4. Once

assembled, the projections 25 remain inside the space defined between the outwardly facing axial end of the block 7 and the end edge of the upright 4 ; said projections 25' being useful for centering the sleeve 11 with respect to the relative upright 4. The device 3 also comprises bars 26 that connect the sleeves 11 fitted to the uprights 4 of a same trellis 2 and which substantially form a rectangularly-shaped perimeter that is the same as the imaginary perimeter defined by the uprights 4 of a same trellis 2. Said bars 26 are preferably a one-piece construction with said sleeves 11 and can be used to support and fasten any cross-members

(not illustrated) which may be part of the structure 1.

In use, first of all the blocks 7 are screwed inside the uprights 4 up to the end of the threaded section 6 and then the sleeves 11 are placed on the uprights 4 of both trellises 2 by inserting the projections 25 into the end of the upright 4. Next, the screw 12 is tightened for each sleeve 11, and lastly the head 14 is inserted into the first sleeve 11 and fixed with the pin 23. The head 15 is then inserted into the second sleeve 11 and is fixed with the pin 23 thus joining the uprights 4 of two trellises 2.

The advantages of the present invention are apparent from the above description.

In particular with the device according to the invention uprights can be joined simply and quickly and without welding. Moreover laboratory tests have found

that the mechanical properties of the joining device in terms of its shearing, torsional and flexural strength are the same as or better than those of the joining systems currently in use. Lastly it is to be noted that the uprights can also be disconnected quickly and easily, making the device according to the present invention useful for itinerant structures, i.e. structures which it must be possible to assemble and dismantle fairly frequently and in a short time. Lastly, it is clear that modifications and variations may be made to the device 3 described and illustrated herein without departing from the scope of the present invention.