WO2012098426A1

WO2012098426A1 - Automatic device for the continuous production of metal, reticular, tridimensional, electrowelded lattice girders

Info

Publication number: WO2012098426A1
Application number: PCT/IB2011/050213
Authority: WO
Inventors: Claudio Bernardinis
Original assignee: A.W.M. S.P.A.
Priority date: 2011-01-18
Filing date: 2011-01-18
Publication date: 2012-07-26
Also published as: EP2665577A1

Abstract

Improvements to the automatic device for the continuous production of electrically welded tridimensional metallic lattice girders, particularly those having an isosceles triangle cross-section. These improvements affect: the bending assembly and the underlying electric welding assembly (16), which is fixed with a distance of the electrodes (6, 7) that is adjustable in relation to the spacing of said lattice girder, for the simultaneous electric welding of the two bent lateral segments (1) to the two lower longitudinal members (5) of the lattice girder being formed; a lower movable slider (11) with automatic stroke for the forward advancement, with programmed spacings (P), of the two lower longitudinal members (5) together with the welded lateral bent segments (1); and finally the use of two cutting assemblies, one for each lower longitudinal member, capable of trimming the downward protrusions of the ends (1.1) of the welded segments (1). The movable slider (11), in addition to causing the advancement of the lower longitudinal members by the chosen spacing, positions them in the upper electric welding region (9), where simultaneous welding (10) of the central upper longitudinal member (15) to the bending points of the two lateral bent segments (1) occurs, again automatically, thus providing the permanent connection between the two lower longitudinal members (5) and the upper one (15). These improvements provide considerable advantages: by reducing production times, they also allow the height variation of the lattice girder being manufactured, they reduce maintenance in general and in particular electrode maintenance, improve the quality of the finished product, and finally ensure greater safety of the automatic device.

Description

AUTOMATIC DEVICE FOR THE CONTINUOUS PRODUCTION OF METAL, RETICULAR, TRIDIMENSIONAL, ELECTROWELDED LATTICE GIRDERS

Field of application

The present invention relates to several improvements to an automatic device for the continuous production of tridimensional electrically welded metallic lattice girders having a triangular cross-section, which has the following advantages: increasing the height of the lattice girders; increasing the production rate; reducing maintenance interventions; improving the quality of the product and its handling; improving the safety of the device, avoiding possible uncontrollable stray currents, using fixed electric welding assemblies at adjustable distances.

As is known, this device is fed continuously by coils of rods which are straightened and directed, in a rectilinear and mutually parallel manner, in three advancement lines, an upper one and two lower ones, which are symmetrical and equidistant from the upper rod, forming in cross-section the three vertices of an isosceles triangle. Two segments of steel rods bent in the shape of an inverted letter V, one for each side, are welded electrically, instantly and automatically to said rods, which act as longitudinal members, and are made to adhere to the longitudinal members on the two oblique sides of the cross-sectional triangle to then be welded electrically in an upward region to the upper longitudinal member and in a downward region to the two respective base longitudinal members. Said device for forming electrically welded lattice girders is already known and patented in Italy (patent no. 1381868 dated July 25, 2007) by the same company which owns the present patent application. The disclosures of Italian patent no. 1381868, to the extent it is described above and hereinafter, are understood to be incorporated integrally herein by reference.

The present invention, in order to obtain the above cited competitive improvements, focuses in particular on the electric welding assembly, which welds simultaneously the two base longitudinal members to the two lateral bent rod segments; this assembly is of the static type, i.e., it does not move but operates automatically in the presence of the segments, while the programmed advancement of the lattice girder being constructed is performed by another automatic carriage or slider located downstream, which performs the simultaneous positioning for electric welding to the upper longitudinal member, while downstream the ends that protrude downward of the lateral rods for connection between the longitudinal members are trimmed.

Ultimately, these solutions make the device more productive and safer and the resulting product is better finished and has a higher quality.

Background art

In the current background art, automatic devices are known in the field for the continuous production of electrically welded metallic lattice girders, particularly for lattice girders having a triangular transverse cross- section, in which the upper longitudinal member at the centerline is constituted by a large steel rod and by two lower base longitudinal members, which are symmetrical and mutually parallel with respect to the upper longitudinal member, have a narrower diameter and constitute the vertices of an isosceles triangle. The three longitudinal members are mutually connected by means of the electric welding of the two continuous rods in the form of a "continuous Z" or with portions of rods shaped like an inverted letter V on the two oblique sides so as to form a lattice girder that has a triangular cross-section.

An automatic device is also known, as already mentioned earlier, which has been patented in Italy by the same company that is the proprietor of the present improvement and is intended to produce continuously tridimensional metallic lattice girders that have a triangular transverse cross- section. Said device uses, for the lateral connections, rod segments which are bent in the shape of an inverted letter V. Various disadvantages have been observed in the first prototypes built, such as for example difficulties in controlling stray currents in the movable electric welding assembly, which is mounted on an automatic movable carriage or slider with controlled advancement and is meant to electrically weld the lower ends of the lateral rods shaped like an inverted letter V to the two base longitudinal members. Moreover, a particularly low productivity has been observed even if the production occurred continuously and without the aid of magazines for feeding bent segments or magazines of pre-worked parts. The segments were in fact cut and bent at the time of their direct use on the line. However, the market for these devices is becoming increasingly demanding, requiring ever greater productivity in the unit time and a higher quality of the finished product: i.e., for example, downward trimming of the ends that protrude from the electric welding of the lateral elements for connection to the lower longitudinal members has been requested with great interest.

Furthermore, known devices do not allow varying the height of the lattice girder until its advancement has been completed, since the step of bending the two lateral segments to be welded electrically in a downward region to the base longitudinal members occurs only after said advancement.

Therefore, in order to overcome these drawbacks and at the same time respond positively to the further requirements of the market of the field, the present improvements have been made, providing new devices that are adapted to solve especially the problems of stray currents and improving the safety of the automatic device while providing a higher production with a product having improved quality and characteristics.

Summary of the invention

The aim of the present invention is therefore to provide improvements to automatic devices for the continuous production of tridimensional metallic lattice girders, particularly those having a transverse cross-section shaped like an isosceles triangle, having the following main characteristics:

- providing an automatic electric welding assembly which is fixed, not movable, but with electrodes that can be adjusted according to the distance of the double welding spacing on the two lateral sides, so as to weld the lower ends of the two inverted V-shaped lateral segments onto the respective two base longitudinal members. In this manner, greater certainties as to the safety of the device are achieved, ensuring perfect containment of stray currents in a fixed, circumscribed and limited region;

said electric welding assembly is also provided with automatic lower locators, one for each end of said two lateral segments, in order to delimit precisely the angle of their bending and their correct positioning so as to ensure perfect execution of the electric welding between the ends and the lower longitudinal members; said electric welding assembly operates on the two bent segments that are lateral to the respective base longitudinal members, said segments being arranged at the time of electric welding so that their axis is offset with respect to the axis of advancement of the rods to be bent, in order to gain time by bringing forward their advancement during the movement of the lattice girder that has just been welded. These vertical planes where the axes of the bent rods lie during welding are different and parallel to the vertical planes of advancement of said straight rods to be cut and bent, and therefore it is also possible to vary the height of the lattice girder continuously by cutting the rods to the desired size and by beginning to bend them even before the advancement of the lattice girder occurs once the welding of the previous segments has occurred;

providing an automatic slider or carriage, downstream of the lower welding assembly, which is capable of gripping the lattice girder being built and of moving it forward by the desired spacing, in order to position it correctly with respect to the second upper fixed electric welding assembly, in order to weld the two bent segments in the vicinity of each bend to the upper longitudinal member; - providing an additional assembly, downstream with respect to the second upper electric welding assembly and again arranged below the lattice girder, which is provided with two shears, one for each side, capable of trimming, with respect to the base longitudinal members, the ends of the two bent rod segments that protrude downward, which are lateral and permanently welded.

Essence of the invention

The aim and objects of the invention are achieved according to the characteristics of the main claim and/or of any other claim cited in this patent text by providing some improvements to the automatic device for the continuous production of electrically welded tridimensional metallic lattice girders, particularly those having a transverse cross-section shaped like an isosceles triangle, by using segments of rods which are bent in the shape of an inverted letter V for lateral connection.

A first improvement consists in providing electric welding assemblies of the fixed type, a lower one and an upper one, which are not movable, i.e., not mounted on carriages or sliders as currently occurs. In particular, the lower one, located below and at the two base longitudinal members, is provided with electrodes or electric welding points whose distance is adjustable in relation to the spacing at which the lower ends of the rod segments bent like an inverted letter V are located on the two base longitudinal members. This electric welding assembly performs simultaneously two welds per side and is assisted in this by particular automatic abutment locators, which have the purpose of stopping the bending stroke of the lateral segment and at the same time ensuring the exact positioning of the bent end on the corresponding longitudinal member, thus performing a perfect electric welding of the respective parts.

The choice to use a static and clearly delimited lower electric welding assembly is advantageous for the safety of the device as a whole; this makes it possible to isolate, circumscribe and control stray currents in a limited region of operation.

A second improvement of the automatic device for the continuous forming of metallic lattice girders relates to the different axis and plane of vertical arrangement for positioning the segments, during their electric welding on the lower longitudinal members, with respect to the actual axis and vertical plane of advancement and bending of the two successive upper straight rods that must be bent by the known bending device. This solution allows a gain in execution time for the two bending and electric welding steps. During the electric welding step it is in fact possible to perform the advancement of the rod and during the forward movement of the freshly welded lattice girder it is possible to start bending the two upper rods, which are subsequently positioned and welded electrically; this reduces the production time between one bending and electric welding step and the next. Furthermore, the fact of occupying different vertical working planes, for the advancement of the straight rod subjected to cutting to size with subsequent bending and for electric welding, provides a further advantage, making it possible to vary the height and sometimes even the spacing of the lattice girder being formed.

Further advantages are highlighted by the use of the fixed electric welding assembly for the segments on the longitudinal members, such as the reduction of the wear of the electrodes and of the corresponding maintenance, greatly reducing the economic operating costs of said automatic device.

According to another improvement to the device, a slider is used which can move automatically, operates below the two longitudinal base members and is provided with at least one automatic clamp for each longitudinal member, which is capable of gripping it and moving it forward by the preset programmed spacing and at the same time of positioning the upper vertices of the two lateral segments in the upper electric welding region in order to join them to the upper central longitudinal member, thus forming the rigid structure of the lattice girder.

According to another characteristic of the invention, an automatic trimming station is used downstream of the upper electric welding and advancement assembly and upstream of the final unit for cutting the lattice girder to size. It comprises automatic cutters that cut the lower ends, which protrude downward, of the lateral segments welded previously to the two base longitudinal members: this is done to improve the quality of the finished product and facilitate its handling and storage.

Description of the drawings

A solution according to the present invention is shown by way of preferential but non-limiting example in the four accompanying drawings, wherein:

Figure 1 is a front view of the region of the automatic device for forming metallic lattice girders having an isosceles triangular cross-section for the intervention of the improvements related to the lower static electric welding assembly, the slider for the advancement of the product and its positioning at the upper static electric welding assembly, and the assembly for trimming the four ends of the two lateral bent segments;

Figure 2 is an enlarged-scale front view of the bending region of the lateral connecting segments shaped like an inverted letter V, highlighting the lower abutment locators for the end of the bending that precedes the electric welding of said ends to the two lower longitudinal members;

Figure 3 is a transverse sectional side view of the same region of Figure 2, highlighting the lower electric welding elements and the abutments pins that can move so as to retract for the abutment or halting of the bending of the two lateral connecting segments between the three longitudinal members. It furthermore illustrates the different position of their axes on parallel vertical planes of the two rods bent during electric welding with respect to the axes and the corresponding vertical planes of the two straight rods in upward advancement;

Figure 4 is a front view of the region downstream of the upper electric welding assembly and of the lattice girder advancement slider where the assembly for trimming the lower ends of the lateral bent segments works.

As can be seen from the various figures, the improvements to the automatic device for the continuous production of electrically welded metallic lattice girders having a triangular cross-section with three continuous longitudinal members at the vertices, an upper central one 15 and two lower symmetrical ones 5, relate in particular to three regions of said device: the lower electric welding region 16, the lattice girder advancement and upper electric welding region 17, and the region 18 for trimming the lower protrusions of the bent segments for lateral connection.

The region 16 is characterized by the lower electric welding assembly, which is fixed, i.e., not movable, and has the electrodes 6, 7 at mutually adjustable distances in relation to the spacing of the lateral rods 1 which are bent like an inverted letter V. Since the two parallel vertical electric welding planes 20 are different from the advancement planes 19 of the upper straight rods 1 , it is possible to perform the advancement of said rods, their cutting to size and their bending simultaneously with the lower electric welding of the two preceding lateral segments. Said rods 1 advance automatically symmetrically with respect to the upper central longitudinal member 15, are cut to size and then bent with the known bending assembly 3 on the movable bending pins 2. This "duality" of working surfaces allows bringing forward the advancement of the rod to be cut and bent while the previous bent one is being welded and/or is in the advancement phase after welding, gaining production time.

Furthermore, said segments 1 have the angular bending stroke delimited by two movable locators 4 for each segment. The locators 4 are actuated automatically, protrude if necessary to delimit the bending stroke during the bending step: in this manner they ensure the exact positioning of the ends in order to perform perfect electric welding between them and the respective longitudinal member 5. Said locators retract automatically flush to allow the advancement of the lattice girder being built.

Said lower automatic electric welding assembly is also provided with electrodes, a positive one 6 and a negative one 7, or vice versa, which are adapted to press the longitudinal member 5 with the end of the respective segment 1 and thus perform welding between them 8.

The forward motion of the product being formed, region 17, occurs by means of a lower slider 11, which can move on guides that have an adjustable advancement in order to be able to perform any spacing P required in the construction of the lattice girder. Said automatically movable slider is provided with a clamp for a longitudinal member 5 of the type with automatic grip 12, whose distance is adjustable, since the distances can vary according to the design requirements. The slider 1 1 simultaneously draws forward, by the preset spacing, the two lower longitudinal members 5 together with the two lateral bent portions 1 joined to them, and the latter are arranged at the upper electric welding assembly 9, where their symmetrical joining 10 occurs also with the upper central longitudinal member 15.

Further downstream, in the region 18, the downward protrusions 1.1 of the segments 1 welded to the lower longitudinal members 5 are trimmed; this occurs by means of two adapted automatic cutting devices which are composed of an adapted locator 14 and a lower cutter 13, said pair being mutually opposite for each longitudinal member 5.

Therefore, the indicated improvements reduce the production times of lattice girders, improving the geometric configuration of the finished product, faithfully complying with the design parameters and without useless protrusions of the lateral segments, which might cause difficulties in handling and in their stacking. Moreover, the safety of said device is improved by avoiding movements of the electric welding assemblies, particularly the lower one.

Of course, the invention is not limited to the described example of embodiment, starting from which it is possible to provide other shapes and embodiments, and the details of execution may in any case vary without thereby abandoning the essence of the invention as stated and claimed hereinafter.

Claims

1. An improvement to an automatic device for the continuous production of electrically welded tridimensional metallic lattice girders, particularly in the construction of lattice girders having an isosceles triangle cross-section, in which the three vertices are constituted by three longitudinal members, a central upper one (15) and two lower ones (5), which are mutually parallel and symmetrical with respect to the upper longitudinal member, on which the lateral connections with the lower ones are performed, leaving free the base side between the two lower longitudinal members (5), by electric welding of a succession of segments of steel rods (1), bent in the shape of an inverted V shortly before their electric welding to the base longitudinal members, characterized in that it provides for the use of the following apparatuses:

- a first fixed automatic electric welding assembly in the lower region (16), with electrodes at distances which are mutually adjustable in a longitudinal direction, adapted for electric welding between the two base longitudinal members (5) and the two bent ends of the rod segment (1) shaped like an inverted V, with two pairs of electrodes (6, 7) for each side, and with automatic and simultaneous operation. Said first electric welding assembly is arranged below the device for forming the segments (1) cut to size and bent instantly;

- for each electric welding position, i.e., of the pair of electrodes (6, 7) of said first automatic electric welding assembly, an arrangement with automatically movable locator (4) is used which is activated, protruding and acting as a locator when the segment (1) is bent, thus determining the end of the stroke of the angular bending of said segment, thereby maintaining said end protruding downward in position for the subsequent step of automatic electric welding (8) between the segments (1) and the respective base longitudinal member (5);

- a second assembly constituted by a movable slider (1 1), which is located below the lattice girder being formed, whose stroke is automated and adjustable in steps (P) which are programmed in order to determine the advancement of the lattice girder with the desired spacing by means of automatic clamps;

- a trimming assembly, which is arranged downstream with respect to the movable slider (11) and/or upper electric welding assembly (9) and below the lattice girder being formed, and before the final unit for cutting the lattice girder, capable of cutting the lower protruding ends (1.1) of the bent segments (1) welded electrically laterally (8) to the two base longitudinal members (5).

2. The improvement according to the first claim, characterized in that the two proper axes that lie on parallel vertical planes (19) for the advancement and bending of the straight rods (1), to be cut to size and bent in the shape of an inverted letter V, lie on parallel and distant planes with respect to the advancement axes (20) of the bent rods in the position for electric welding with the lower longitudinal members (5). This is done to reduce the advancement times of the rods (1) to be cut to size and to be bent during the step of advancement of the lower longitudinal members after electric welding to the previous electrically welded segments.

3. The improvement according to the preceding claims, characterized in that the different vertical parallel planes of advancement, bending and electric welding of the segments (1) that define the lateral connections between the longitudinal members, the upper one (15) and the lower ones (5), make it possible to adjust simultaneously and automatically the height variation of the lattice girder being formed.

4. The improvement according to the preceding claims, characterized in that the device, downstream of the upper electric welding unit (9) in the region (18), is provided with lower cutting devices (13, 14), which operate in both sides of the lattice girder being formed and perform the lower trimming of the protrusions (1.1) in a downward direction of the bent lateral segments (1).

5. The improvement according to the preceding claims, characterized in that the movable slider (11) is provided with at least two automatic grip clamps (12), one for each lateral side of the lattice girder being formed, at a mutual adjustable distance, in order to grip the lower longitudinal members (5) and/or the lateral bent segments (1) welded electrically in (8) in order to cause the forward advancement of the lattice girder being constructed by the desired spacing (P).

6. The improvement according to the preceding claims, characterized in that said first electric welding assembly is arranged exactly below the device for forming the segments (1) cut to size and bent instantly.