WO2005014950A1

WO2005014950A1 - Lattice girder with bent ends

Info

Publication number: WO2005014950A1
Application number: PCT/EP2004/007534
Authority: WO
Inventors: Claudio Bernardinis
Original assignee: A.W.M. S.R.L.
Priority date: 2003-07-22
Filing date: 2004-07-08
Publication date: 2005-02-17
Also published as: ITUD20030159A1

Abstract

The present invention relates to an improvement to the ends of three-dimensional electrowelded metallic lattice girders suitable for manufacturing floors in the building sector and in the industrial prefabrication sector. The rods (4) for connection among the longitudinal members are arranged vertical at the end of the lattice girder (1.1), then the upper longitudinal member (2) is shortened, and finally the ends of the lower longitudinal members (3.1, 3.2) are bent downward (12) so as to form a tooth or supporting surface for the end of the lattice girder (for example on a beam 9).

Description

L_ATTIC_E GIRDER WITH BENT ENDS

Field of application

The present invention relates to the improvement to the ends of three-dimensional electro welded metallic lattice girders, suitable for manufacturing floors in the building sector or in the industrial prefabrication sector, particularly by utilizing waste protrusions to provide new points for supporting or anchoring the entire structure during installation. One or more supporting or anchoring points are provided by using the ends of the profiled elements having an improved cross-section that constitute the longitudinal members, by simply bending them downward or shaping them appropriately according to the requirements of the application. Said improvement improves the mechanical characteristics of the ends of lattice girders, thus ensuring its structural support also to simple resting contact of the ends alone.

These improvements are performed automatically during the automated manufacturing of said lattice girders, and therefore do not require manual interventions.

Background art

Various systems for manufacturing electrowelded metallic lattice girders, in order to manufacture floors or building prefabrication elements, are known in the background art. Metallic lattice girders are usually composed of two or three longitudinal members formed by profiled elements having an improved cross-section, which are arranged so as to be mutually parallel on a vertical plane or in space (in an isosceles triangle-like configuration), which are mutually connected by a continuous electrowelded element that also constitutes the supporting feet on the lower side. Said lattice girders have technical drawbacks in certain applications requiring a brief supporting area for their ends during installation or also an anchoring of said lattice girder in order to avoid displacement along the longitudinal axis.

Currently, the protruding end elements of lattice girders lie at different levels with respect to the supporting surface, and therefore particular end supports are manufactured which are welded manually to the installed longitudinal members. These particular supports are of two kinds: a level-setting support or an anchoring support. The level-setting support consists of a cross (two mutually welded pieces of metal profiled element), with a downward support at the same level as the supporting feet of the lattice girder; the lateral arms support the lower longitudinal members of the lattice girder and are welded to them, while the upper arm of the cross is welded to the end of the upper longitudinal member. This is done to keep at the same level and in alignment all the longitudinal members during installation, otherwise end support would occur on the lower longitudinal members, since the base feet seldom coincide with this point. The anchoring support instead has a further shaped portion, which ends with a vertical tooth having an end that is at a lower level than the base feet of the lattice girder. In this manner, the end of the lattice girder rests on the supporting point (e.g. a vertical panel) and at the same time the contoured tooth reaches beyond the supporting panel, preventing accidental longitudinal movement of the lattice girder.

Said supporting elements are built separately, one by one, in order to adapt to the geometric characteristics of the lattice girder, and are welded manually during installation: this causes several drawbacks, which lead to higher building costs. The time required to install the lattice girders in fact increases, because it is necessary to weld the supports of the ends manually and individually, thus also increasing the costs of the respective supports and the costs for the action of the operator.

Summary of the invention

The aim of the invention is to provide automatically, during its manufacture, an electrowelded metallic lattice girder suitable for floors or other prefabricated structures whose ends are equipped to support the entire structure so that it is perfectly aligned and/or has an end anchoring tooth, avoiding longitudinal movements of said lattice girder.

In this manner, the installation times of the lattice girder are reduced and at the same time the longitudinal movement thereof during installation is prevented.

Essence of the invention

The aim of the invention is achieved according to the characteristics of the main claim and/or of any other claim cited in this patent text by virtue of the automatic provision, during its manufacture, of a three-dimensional electrowelded metallic lattice girder that is suitable for manufacturing floors or other structural components of buildings, having the particularity that its ends are structurally suitable to support the entire load, while maintaining the level and its position during concrete injection or reinforcement operations.

The invention consists in providing, during the step for the automated construction to size of the three-dimensional electrowelded metallic lattice girders, an end supporting structure, maintaining the sectional geometric characteristics of the entire lattice girder and using for this purpose the same profiled elements that constitute the longitudinal members and the continuous rods for mutually connecting them.

Generally, the lattice girder is composed of three longitudinal members, constituted by profiled elements having an improved surface, which are parallel and are arranged so as to have a transverse cross-section that is shaped like an isosceles triangle, two of said profiled elements forming the lower vertices and one of said profiled elements foπning the upper vertex, and by two narrower continuous zigzag rods, each of which connecting laterally the respective lower longitudinal member to the upper one by electrowelding, reproducing at a lower level the supporting feet of said structure: in this case, the present invention preferably acts at the ends of the lower longitudinal members, by bending them through 90° downward (vertically) so that the head surface reaches the same level as the supporting feet arranged with a constant pitch along said lattice girder. In this case, the bending performed at the ends of the lower profiled elements produces end resting points that are capable of supporting the entire load of the structure and of the concrete (or other material) without flexing excessively proximate to the end (currently this occurs unless particular end supports are used).

Another variation of the present invention consists in automatically bending the two ends of the two lower longitudinal members of the lattice girder, providing two vertical teeth that are bent downward at 90° and whose lower end is at a lower level than the plane of the supporting feet of said lattice girder. Said teeth are meant to avoid the longitudinal movement of the lattice girder during reinforcement operations: since it is lower than the supporting feet of the lattice girder, it interferes with the frame for containing the concrete casting and thus does not allow its accidental movement.

Another variation of the present invention consists in bending at 90° downward and then in an L- shape, again downward, one or two of the two ends of the lower longitudinal members of the lattice girder, simultaneously providing the lattice girder supporting level and the anchoring tooth at a lower level, avoiding the movement of the lattice girder along the longitudinal axis.

Said bends of the ends of the longitudinal members, depending on the requirements, are provided automatically by machine during the manufacture of said lattice girders or in separate operations; accordingly, any subsequent manual intervention to weld the end tabs is avoided completely. In summary, the lattice girders are provided with the end structural reinforcement provisions, ready for use.

Accordingly, the present invention achieves the intended aim and overcomes the observed drawbacks of conventional lattice girders, by using for reinforcement purposes the very ends of the longitudinal members (bending), which in many cases are considered waste (because they are usually cropped), and at the same time providing said supporting end automatically and directly on the machines that manufacture said lattice girder or on automatic apparatuses provided specifically for this purpose. This provides an optimum lattice girder of the set size, with the mechanical characteristics required according to the applicable statutory provisions in the field of the manufacture of floors or building elements in general.

Brief description of the drawings These and other characteristics of the present invention will become better apparent, by way of preferred but non-limiting example, in the three accompanying drawings, wherein: Figure 1 is a partial perspective view of the end of a conventional electrowelded metallic lattice girder suitable to manufacture floors or other building structures; Figure 2 is a perspective view of the reinforcement cross to be welded to the end of the lattice girder (current method); Figure 3 is a perspective view of a reinforcement cross provided with a lower anchoring tooth (current method); Figure 4 is a partial perspective view of the end of a lattice girder with the manually welded simple cross-like reinforcement tip (current method); Figure 5 is a partial perspective view of the end of a lattice girder with the cross-like reinforcement tip with a manually welded lower tooth (current method); Figure 6 is a side view of the application of the lattice girder, provided with a cross-like reinforcement tab, welded at the supporting level on a metallic supporting beam; Figure 7 is a side view of the application of the lattice girder, provided with a reinforcement tab welded at the supporting level and with an anchoring tooth, on formwork or on a panel for containing the concrete; Figure 8 is a partial perspective view of the end of an improved lattice girder according to the invention, i.e., with a 90° downward bend of the two ends of the lower longitudinal members; Figure 9 is a side view of the modification to be performed automatically at the ends of a conventional lattice girder, i.e., the rotation of the lateral connecting rods, positioning and fixing them by electrowelding on the upper longitudinal member; Figure 10 is a side view of the second step of preparation of the tip of the lattice girder, i.e., the downward bending of the lower longitudinal members at 90°, with or without shortening the bent tooth, and shortening the upper longitudinal member; Figure 11 is a side view of a first version of the bending of the two tips of the lower longitudinal elements, forming a broad downward tooth, the lower end of which lies below the level of the feet; the lattice girder rests on the upper surface of the formwork, while the large anchoring tooth grips the vertical surface, avoiding the longitudinal movement of said lattice girder; Figure 12 is a side view of a second version of the bending of the tips of the lower longitudinal members, forming a tooth that is bent downward at 90°, its end being at the same level as the feet, the lattice girder resting on a metallic supporting beam; Figure 13 is a side view of a third version of the bending of the tips of the lower longitudinal members, similar to Figure 12, but with the addition, by welding, of an element shaped like an inverted letter L, which acts as an engagement tooth; if the ends of the longitudinal members are extensive and allow downward bending in the foπn of an inverted double L, the welding step is avoided; Figure 14 is a partial perspective view of a modular application on underlying corrugated sheet metal, composed of multiple lattice girders arranged side by side, each with improved ends suitable to support the axial stress.

As shown in the accompanying drawings, the structural improvement providable automatically, in line or with separate operations, at the ends of three-dimensional electrowelded metallic lattice girders suitable to manufacture floors consists in modifying the structure of the tips of the lattice girders by using the same materials that constitute the lattice girder. The improvement operation occurs automatically with the machines that manufacture the lattice girder, in line or by means of separate machines. This step is performed during construction and therefore subsequently does not require further interventions by operators (for example welding of preassembled tabs or additional supports). Usually, three-dimensional electrowelded metallic lattice girders 1 are composed of three parallel longitudinal members, an upper one 2 and two symmetrical lower ones 3J and 3.2, which are mutually connected by continuous electrowelded rods 4, one for each side (or other equivalent solutions), which also form the lower supporting feet 5. Said lattice girders end with cropped longitudinal members and so do the lateral connecting rods. The supporting feet usually do not correspond to the ends, and therefore additional end reinforcements, of the simple cross-like type 6 or of the type formed by a cross with an engagement tooth 8, are currently welded manually and separately. In this manner, if end support is required, for example on a beam 9 at the same level as the feet 5, the crosspieces 6 are welded, whereas if anchoring to prevent movement of the lattice girder is also required, the tabs such as 7, with a lower anchoring tooth 8 that is ideal on supporting panels or formwork 10 for containing the concrete, are welded.

As already noted earlier, subsequent interventions on the lattice girders are uneconomical, and therefore it has been thought to provide a lattice girder with an end structure that is improved during the automatic construction of said lattice girder.

The invention therefore consists in arranging vertically, at the end of the lattice girder, the continuous rods 4 that connect the profiled elements that act as longitudinal members, and in electrowelding them to the upper profiled element 2. The upper profiled element is then cropped proximate to the rod 4, the ends of the two lower longitudinal member profiled elements 3J and 3.2 are bent downward at 90° in order to provide a large tooth 11, whose end is at a lower level than the feet 5 of the lattice girder, or a short tooth such as 12, the lower end of which is at the same level as the feet 5.

In summary, the improvements according to the present invention performed automatically during the steps for the construction of the lattice girder are equivalent to the more expensive ones currently performed manually.

In another version, the ends of the lower longitudinal members 3J and 3.2 of the lattice girders 1J are bent by means of a first 90° downward bend 12, to the end of which a tooth shaped like an inverted letter L 13 is welded in order to obtain the anchoring tooth. This operation becomes unnecessary if the length of the lower longitudinal members allows two bends, the first bend acting as a support at the same level as the feet and the second bend forming the anchoring tooth.

Said lattice girders with improved ends are suitable to act individually or in a modular manner by using them side by side and parallel to each other on an underlying corrugated metal sheet 14.

Furthermore, if the three-dimensional lattice girder has two or more lower longitudinal members, the 90° downward end bend is provided on at least one profiled element.

Finally, since each lattice girder has two ends, said ends are improved in the same manner or in a different manner, depending on the requirements for support or use of said lattice girder.

The invention is of course not limited to the examples of embodiment described above, from which it is possible to provide other embodiments and other methods of embodiment, and the details of execution may in any case vary without thereby abandoning the essence of the invention as stated and claimed below.

Claims

1. A structural improvement providable automatically at the ends of three-dimensional electrowelded metallic lattice girders suitable for manufacturing floors in the building sector or in the prefabrication sector, characterized in that it is performed automatically during the manufacture of said lattice girder and/or in subsequent separate operations, and in that additional profiled elements or appendages pre-built for this purposes are not used, but rather the same materials used to manufacture the lattice girder are used; in particular, the ends of the lower longitudinal member or members (3J, 3.2) of the lattice girder (1J) are bent downward (12), the bent lower or end surface being at the same height as the feet (5) of the lattice girders (1J) or forming an anchoring tooth (11), whose lower surface is at a lower level than said feet; the upper longitudinal member (2) of the lattice girder (1J) is shortened by an extent that is useful for comiecting it to the lateral rod (4). Furthermore, preferably, the continuous lateral rod or rods (4) for the mutual comiection of the longitudinal members (2, 3J, 3.2) are arranged vertically proximate to the end of the lattice girder and their ends are shortened and electrowelded to said upper longitudinal member (2).

2. The structural improvement to the ends of lattice girders according to claim 1, characterized in that the lower longitudinal member or members is or are bent downward at their end in a double-L shape; a first downward bend at 90° (12), until it reaches the level of the plane of the lateral supporting feet (5) of the lattice girder (1J), a second forward bend at 90° (horizontally), maintaining the same level that has been reached, and a last downward bend at 90° (8), reaching a level that is lower than the level of the supporting surface, thus forming an anchoring tooth for preventing the longitudinal movement of said lattice girder.

3. The structural improvement of the ends of lattice girders according to claims 1 and 2, characterized in that the types of improvement of the ends are three: simple level-setting improvements (12), improvements with an anchoring tooth (11), and combined level-setting and anchoring improvements (8); said improvements being performed automatically during the manufacture of the lattice girder and/or in subsequent steps outside the system, whose ends are equipped equally in the described types depending on the application requirements of the design.

4. A lattice girder (1J) suitable for manufacturing floors comprising at least two lower longitudinal members (3J, 3.2) and an upper member (2) extending in a substantially parallel manner to the lower longitudinal members (3J, 3.2), the members (2, 3J, 3.2) being mutually connected by rods means (4), one for each side, so as to form a lower supporting feet (5) of the lattice girder (1J), wherein the respective ends of the lower longitudinal members (3J, 3.2) are bent to form a respective anchoring tooth (11, 12), wherein the lower surface of the anchoring tooth (11) is at a lower level than the lateral supporting feet (5) of the lattice girder (1J) or wherein the lower surface of the anchoring tooth (12) is at the same level as the lateral supporting feet (5) of the lattice girder (1J).

5. The lattice girder (1J) of claim 4, wherein the lower longitudinal members (3J, 3.2) are bent downward at 90°.

6. The lattice girder (1J) of claims 4 or 5, wherein the lower surface of the anchoring tooth (12) is at the same level as the lateral supporting feet (5) of the lattice girder (1J), the anchoring tooths (12) further including a respective L-shaped extension (13) extending at a lower level than the lateral supporting feet (5) of the lattice girder (1J).

7. The lattice girder (1J) of one or more of claims 5-7, wherein the rods means (4) are continuous rods (4) electrowelded to the upper member (2).

8. The lattice girder (1J) of claims 6 or 7, wherein the L-shaped extension (12) is welded to its respective anchoring tooth (12).

9. A method for manufacturing a lattice girder (1J) suitable for manufacturing floors comprising at least two lower longitudinal members (3J, 3.2) and an upper member (2) extending in a substantially parallel manner to the lower longitudinal members (3J, 3.2), comprising the steps of: mutually connected the members (2, 3J, 3.2) by rods means (4), one for each side, so as to form a lower supporting feet (5) of the lattice girder (1J), and bending the respective ends of the lower longitudinal members (3J, 3.2) to form a respective anchoring tooth (11, 12), wherein the lower surface of the anchoring tooth (11) is at a lower level than the lateral supporting feet (5) of the lattice girder (1J) or wherein the lower surface of the anchoring tooth (12) is at the same level as the lateral supporting feet (5) of the lattice girder (1J).

10. The method of claim 9, wherein the lower longitudinal members (3J, 3.2) are bent downward at 90°.

11. The method of claims 9 or 10, wherein the lower surface of the anchoring tooth (12) is at the same level as the lateral supporting feet (5) of the lattice girder (1J), and further comprising the step of providing a respective L-shaped extension (13) of the anchoring tooth (12) extending at a lower level than the lateral supporting feet (5) of the lattice girder (1J).

12. Method of one or more of claims 9-11, wherein the rods means (4) are formed by continuous rods (4) electrowelded to the upper member (2).

13. Method of claims 11 or 12, wherein the L-shaped extension (12) is welded to its respective anchoring tooth (12).

14. The structural improvement to the ends of lattice girders according to claim 2, characterized in that the lattice girder with terminal (8) may be obtained by means of a technical solution by welding of an extension with an L-shaped metal bar (13) on the tooth of the lattice girder (12), wherein the solution can be performed automatically during the manufacturing of the lattice girder and/or successive phases outside of the automatic device per se.