GB2212420A

GB2212420A - Manufacturing a junction of a tubular reticular structure

Info

Publication number: GB2212420A
Application number: GB8827019A
Authority: GB
Inventors: Riccardo Belleli
Original assignee: Agenzia Nazionale per le Nuove Tecnologie lEnergia e lo Sviluppo Economico Sostenibile ENEA; Belleli SpA
Current assignee: Agenzia Nazionale per le Nuove Tecnologie lEnergia e lo Sviluppo Economico Sostenibile ENEA; Belleli SpA
Priority date: 1987-11-18
Filing date: 1988-11-18
Publication date: 1989-07-26
Also published as: GB8827019D0; IT8722672A0; NO885146D0; NO885146L; IT1232960B

Abstract

A process for manufacturing a junction of a tubular reticular structure comprising a spine with branches comprises a first step in which cylindrical bushes 1 adapted to form the spine are subject to hot pre-deformation by axial compression inside a die 4 adapted to form protrusions 5a in the regions where a branch 5 is to be provided; a second step of extracting each bush from the die; a third step of extruding the branches at the protrusions; and a fourth step of connecting the bushes by means of circumferential welds, to form the structure (Fig 6, not shown). <IMAGE>

Description

PROCESS FOR MANUFACTURING A JUNCTION OF A TUBULAR RETICULAR STRUCTURE AND JUNCTION OBTAINED WITH THE PROCESS The invention relates to a process for manufacturing a junction of a tubular reticular structure and to the junction obtained with the process.

The great diffusion of lattice girders, in which the members are constituted by tubular elements converging into junctions, is known; these junctions are technically and economically very important in the structure since heavy loads concentrate on them.

These Junctions are structured so as to comprise a rectilinear element, or spine, which becomes part of the main structure; branch elements extend therefrom and are adapted to couple the tubes which converge into the junction.

According to a known method, said junctions are produced by welding the branches to the spine, but junctions thus obtained are intrinsically weak due to the presence of the weldings between the spine and the branches, particularly in case of fatigue stress, as occurs for example for the supporting structures of off-shore platforms due to the waves to which they are subject; sophisticated weld checking and the addition of reinforcements do not solve the problem completely, and entail considerable cost increases.

In order to reduce the disadvantages of welded Junctions, various solutions have been proposed: the most interesting consists in obtaining the branches by extruding curved elements which are then welded to one another longitudinally so as to form the spine, since with known processes it is not possible to directly extrude a cylindrical spine since this would produce branches which are either too short or too small in diameter and are therefore unusable. Junctions with a spine obtained by welding curved elements, however, are not free from disadvantageous characteristics, since they seldom provide a circular spine; circularity is important to resist combined bending and compressive stresses; they also ,have longitudinal welds proximate to the branches in structurally critical regions.

The aim of the present invention is to provide a process for manufacturing a junction of a tubular reticular structure which can use extrusion to obtain the branches without having to divide the spine into curved elements.

Within the scope of the above described aim, an obJect of the invention is to provide a junction of a tubular reticular structure which has excellent structural and resistance characteristics.

The proposed aim is achieved by a process for manufacturing a Junction of a tubular reticular structure, said junction comprising a spine from which branches derive, said process being characterized in that it comprises a first step in which a monolithic cylindrical bush adapted to form the spine undergoes hot pre-deformation by axial compress ion inside a die adapted to form protrusions at the regions where a branch is to be provided: a second step of extracting the bush from the die; a third step of extruding the branches at the protrusions provided on the bush. If the Junction comprises a plurality of bushes, these steps are followed by a fourth step of connection of said bushes by means of circumferential welds.

A junction for tubular reticular structure according to the invention is characterized in that its spine comprises at least one monolithic cylindrical bush provided with extruded branches.

Further characteristics and advantages of the invention will become apparent from the description of a preferred but not exclusive embodiment of the invention, illustrated only by way of non-limitative example In the accompanying drawings, wherein: figure 1 is a longitudinal sectional view of a bush contained in the die for carrying out the first step of the process1 at the end of said first step; figure 2 is a reduced-scale side view of the outer jacket of the die illustrated in figure 1; figure 3 is a sectional view according to the line III III of figure 2; figure 4 is a reduced-scale side view of the inner core of the die illustrated in figure 1; figure 5 is a sectional view according to the line V-V of figure 4;; figure 6 is a view of a junction according to the invention, comprising the bush obtained with the die illustrated in the preceding figures.

With reference to the above described figures, the process according to the invention consists in inserting a monolithic cylindrical bush 1 inside a die which rests on the base 2 of a press and comprises an inner core 3 and an outer jacket 4; the bush is heated beforehand, and the preheating can be uniform in the entire body of the bush or, as in the case of the bush 1, its end regions la, ib may be kept cold or be cooled after heating, as their rigidity may facilitate the operation.

While the inner core 3 is cylindrical, the outer jacket 4 has expansion channels 5 and 6 in the regions where a branch is to be provided, and so when the bush 1 is axially compressed by the action of the press on the basement whereof it rests, material is displaced inside the channels 5 and 6, forming protrusions 5a in the channel 5, and an increase in thickness where branches are not to be provided.

When the action of the press is complete and the predeformed bush has cooled, the resulting condition is the one shown in figure 1.

At this point the bush must be extracted from the die, and for this purpose the outer jacket 4 is first of all disassembled into the three curved elements 4a, 4b and 4c of which it is composed by. slackening the locking bolts arranged between the flanges 7a, 7b which said curved 4 elements have at their longitudinal edges.

Once the bush is released from the outer jacket 4, it is lifted and its inner core 3, which during the preceding operation rested on a support 8, is extracted by disassembling said support into its three components 3a, 3b and 3c in the shape of complementary wedges by initially downwardly extracting the inner wedge 3a. Now the predeformed bush 1 is ready for the subsequent step, which consists in extruding the branches at the pre-deformed protrusions.

This step requires steps which are common practice in workshops; a ball or ogive is forced to exit from each appropriately heated protrusion to obtain the required branches1 achieving the final configuration of the bush, which is indicated by the reference numeral 9 in figure 6; in this figure 9a indicates the branch formed at the protrusion 5a, and 9b indicates the branch formed at the protrusion formed in the expansion channel 6.

In this extrusion step the female die can be constituted by the same outer jacket used in the first step.

It should be noted that the process according to the invention is particularly advantageous with respect to the known art since the availability of displaced material in the protrusions allows to produce, at said protrusions, extruded branches of adequate length and considerable diameter with respect to the spine's diameter without having to form said spine by means of curved elements, but by using monolithic cylindrical bushes, and it should be furthermore noted that a plurality of branches, possibly with different inclinations, can be obtained at each bush.

The bushes 10 and 11, respectively having the branches lOa, 10b and 1lea, lib, are also obtained with a process of the above described type, and in a subsequent step of the process they are assembled aligned by means of circumferential welds to form the junction shown in figure 6; this junction, which can be further stiffened by means of rings inserted in the spine or by inserting crosslike elements, has excellent resistance characteristics due to the rigorous circularity of the spine and to the presence of exclusively circumferential welds.

The described invention is susceptible to numerous modifications and variations, all of which are within the scope of the inventive concept: with regard to the inner core of the die, for example. it should be noted that the possibility of extracting said core from the pre-deformed bush can be provided in any manner, and it should be furthermore noted that said core can comprise means adapted to facilitate the displacement of bush material to form the protrusions, said means comprising for example a pusher adapted to be actuated simultaneously with the axial compression action of the bush, or a circuit for conveying pressurized fluid in the region where the protrusion is to form.

With regard to the outer jacket of the die, it should be noted that the removable assembly of the curved elements which constitute it can be obtained by whatever means, and it should be furthermore noted that during compression it can rest on the base of the press, with the interposition of yielding supports adapted to appropriately lower for example if contact with the jacket of the press actuation beam is intended.

With regard to the junction, it should be stressed that it can be provided, in particularly simple cases, by using a single bush.

In the practical embodiment of the invention, all the details may be replaced with other technically equivalent elements; furthermore, the materials employed and the shapes and dimensions may be any.

Claims

1. Process for manufacturing a junction of a tubular reticular structure, said junction comprising a spine from which branches derive, said process being characterized in that it comprises a first step in which a monolithic cylindrical bush adapted to form the spine undergoes hot pre-deformation by axial compression inside a die adapted to form protrusions at the regions where a branch is to be provided; a second step of extracting the bush from the die; a third step of extruding the branches at the protrusions provided on the bush.

2. Process for manufacturing the junction of a tubular reticular structure, said junction comprising a spine from which branches extend, characterized in that it comprises a first step in which monolithic cylindrical bushes adapted to form the spine are subject to hot pre-deformation by axial compression inside a die adapted to form protrusions at the regions where a branch is to be provided: a second step of extracting each bush from its die: a third step of extruding the branches at the protrusions provided on the bushes; a fourth step of connecting the bushes in alignment to form the spine by means of circular welds.

3. Process according to claims 1 and 2, characterized in that said at least one bush is uniformly heated during the first pre-deformation step.

4. Process according to claims 1 and 2, characterized in that during the first pre-deformation step said at least one bush is heated and a region at at least one end is kept cold.

5. Process according to one or more of the preceding claims1 characterized in that the die used in the first step comprises an inner core and an outer jacket configured and arranged so as to determine a portion of annular space adapted to contain a monolithic cylindrical bush, the inner core being configured so as to be extractable from the bush after pre-deforming and cooling it, the outer jacket being obtained by means of removably assembled curved elements having channels for the expansion of the material of the bush in the regions where a protrusion is to be formed.

6. Process according to one or more of the preceding claims, characterized in that the inner core of the die can be disassembled into a plurality of removably assembled elements.

7. Process according to one or more of the preceding claims, characterized in that the elements which are removably assembled to constitute the inner core of the die are in the shape of complementary wedges.

8. Process according to one or more of the preceding claims1 characterized in that the inner core of the die comprises means adapted to facilitate the displacement of bush material to form the protrusions.

9. Process according to one or more of the preceding claims, characterized in that the inner core of the die comprises means adapted to facilitate the displacement of bush material to form the protrusions, said means comprising a pusher adapted to be actuated simultaneously with the axial compression of the bush.

10. Process according to one or more of the preceding claims, characterized in that the inner core of the die comprises means adapted to facilitate the displacement of bush material to form the protrusions, said means comprising a circuit for conveying pressurized fluid in the portion of space where the protrusion forms.

11. Process according to one or more of the preceding claims, characterized in that the curved elements which form the outer jacket of the die are removably assembled by means of the contact of flanges provided at their longitudinal edges and by locking with bolts associated with said flanges.

12. Process according to one or more of the preceding claims, characterized in that the outer jacket of the die adopted in the first pre-deformation step constitutes the female die in the third extrusion step.

13. Process according to one or more of the preceding claims, characterized in that yielding supports constitute the rest for the outer jacket of the die used in the first deformation step.

14. Junction of tubular reticular structure, characterized in that its spine comprises a monolithic cylindrical bush with extruded branches.

15. Junction of tubular reticular structure, characterized in that its spine comprises a plurality of monolithic cylindrical bushes with extruded branches, said bushes being superimposed and connected by circumferential welds.

16. Junction according to claims 14 and 15, characterized in that it comprises stiffening elements obtained with rings inside the spine and possible cross-like elements.

17. Process for manufacturing a junction of a tubular reticular structure substantially as herein described with reference to the accompanying drawings.

18. A junction of tubular reticular structure substantially as herein described with reference to the accompanying drawings.