Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/002—Resistance welding; Severing by resistance heating specially adapted for particular articles or work
  • B23K11/008—Manufacturing of metallic grids or mats by spot welding
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
  • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
  • B23K11/00—Resistance welding; Severing by resistance heating
  • B23K11/10—Spot welding; Stitch welding
  • B23K11/11—Spot welding
  • B23K11/115—Spot welding by means of two electrodes placed opposite one another on both sides of the welded parts

Definitions

• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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:
• 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.
• 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.
• 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.
• 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.
• a slider 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• 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.
• the safety of said device is improved by avoiding movements of the electric welding assemblies, particularly the lower one.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
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• Butt Welding And Welding Of Specific Article (AREA)

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• 2011
  • 2011-01-18 EP EP11705254.8A patent/EP2665577A1/de not_active Withdrawn
  • 2011-01-18 WO PCT/IB2011/050213 patent/WO2012098426A1/en not_active Ceased

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