Field of the invention

This invention relates generally to reinforcement bar (rebar) mesh, and especially, but not exclusively, to rebar mesh of a kind that can be folded up into rolls that are subsequently rolled out in the formation of reinforcement mesh for concrete slab, e.g. a concrete slab or roadbed.

Background of the invention

One type of reinforcement bar mesh has multiple spaced reinforcement bars (rebars), linked by substantially parallel steel straps that extend generally normal to the bars. The straps are sufficiently flexible or bendable for the mesh to be rolled up into rolls for storage and transport. These rolls are particularly effective for assembling and delivering reinforcement mesh into concrete roadbeds, for example by mobile workstations such as that described in the present applicant's international patent publication WO 2005/042849. The mobile workstation described therein includes a rear sloping apron along which reinforcing mesh is delivered to a roadbed as the workstation moves or is drawn slowly forward. A roll of transverse reinforcing rods is unrolled to form a series of spaced apart reinforcement rods in contact with longitudinally extending rods that are either delivered by guides onto the apron or themselves rolled out from rolls positioned along an edge of the apron. The respective rods are tack welded at selected intersections to form an orthogonal reinforcement mesh that is delivered in turn to the roadbed. It is more common in practice to tie the rods together at selected intersections rather than to use tack welding.

In rolled up rebar mesh, and as described in WO 2005/042849, the steel straps are typically welded to the rebars where the straps intersect the rebars in the mesh. International patent publication WO 2009/124520 describes a machine suitable for connecting reinforcing steel rods or bars to at least one support strip. The described technique for assembling what the publication describes as 'uniaxial reinforcing steel mats' is cold welding. European patent 862958 also discloses a machine for assembling 'welded wire mesh' in which the automatic fastening machine is described as an electrode welding device.

International patent publication WO 2011/042240 describes the formation of reinforcing steel rod mat, including welding reinforcing steel rods and stay braces. An arrangement for rolling up reinforcement rod mesh during its manufacture is described in European patent 1515811. US patent 7909067 describes reinforcement bar mesh comprising reinforcement bars tied by twisted wires.

An issue for rolls of reinforcing bars linked by steel straps welded to the rebars is that many countries do not allow reinforcement steel to be welded, because of concerns about the consistency and integrity of behaviour of the steel in a reinforced product. This somewhat limits the market available for the rebar rolls and meshes disclosed in the aforementioned publications.

It is an object of the present invention to address this limitation of current commercially available products and provide a reinforcement bar mesh with bendable steel straps, but without any welding to the rebars.

Reference to any prior art in the specification is not, and should not be taken as, an acknowledgment or any form of suggestion that this prior art forms part of the common general knowledge in Australia or any other jurisdiction or that this prior art could reasonably be expected to be ascertained, understood and regarded as relevant by a person skilled in the art.

Summary of the invention

In a first aspect, the invention provides a reinforcement bar mesh comprising multiple spaced reinforcement bars linked by one or more substantially parallel metal, preferably steel, straps that extend generally normal to the bars, wherein each bar is secured to the or each strap without welds to the bar by being firmly held between the respective strap and an overlying metal, preferably steel, strap portion that is fixed to the strap on opposite sides of the bar. In a second aspect, the invention provides a method of producing a reinforcement bar mesh comprising multiple spaced reinforcement bars linked by substantially parallel metal, preferably steel, straps that extend generally normal to the bars, comprising: relatively laying each reinforcement bar in turn across one or more steel straps at a fixing station; where each bar intersects a strap, placing a metal strap portion substantially parallel to the or each strap and over the reinforcing bar and the strap to either side of the reinforcing bar; and fixing the strap portion and strap together on both sides of the bar whereby the bar is firmly held between the respective strap and the strap portion.

In a third aspect, the invention provides a reinforcement bar mesh comprising multiple spaced reinforcement bars linked by one or more substantially parallel metal straps that extend generally normal to the bars, wherein each bar is secured to the or each strap without welds to the bar by a swage and rivet arrangement. Preferably, the strap and the strap portion are both deformed, e.g. substantially relatively symmetrically, to curve around the bar. The interface plane of the strap and strap portion may contain the axis of the bar.

In an advantageous embodiment, said deformation is effected by swaging the strap and strap portion about the reinforcement bar, while simultaneously effecting said fixing by forming indentations that rivet the strap and strap portion together.

In a convenient arrangement, the strap portion is a second strap, and both straps are delivered, from one or more stored sources, about the reinforcement bar at the fixing station. There are preferably two or more straps linking the reinforcement bars at spaced locations along the bars: in the just described embodiment, each strap is a pair of juxtaposed straps.

In one embodiment, the mesh is delivered in a direction parallel to the axis of the straps and folded into a roll for storage and transport. The straps are sufficiently flexible, or at least bendable, to permit such rolling up.

As used herein, except where the context requires otherwise, the term "comprise" and variations of the term, such as "comprising", "comprises" and "comprised", are not intended to exclude further additives, components, integers or steps. Brief description of the drawings

The invention will now be further described by way of example only, with reference to the accompanying drawings, in which:

Figure 1 depicts a segment of partly rolled up reinforcement bar mesh according to an embodiment of the invention, suitable for unrolling onto an apron for assembly of orthogonal rebar mesh;

Figure 2 is a fragmentary perspective view of a representative intersection between reinforcement bar and straps;

Figure 3 is a fragmentary cross-section on the line A-A in Figure 2; and

Figure 4 shows the two halves of a suitable tool for swaging the straps onto a reinforcement bar and riveting straps together on either side of the bar.

Detailed description of the embodiments

The reinforcement bar mesh 10 shown in Figure 1 includes a series of spaced parallel lengths 12 of standard reinforcement bar (e.g. 16mm diameter) linked by respective pairs 20 of juxtaposed metal, preferably steel, straps 22, 23. Each reinforcement bar 12 has a non-smooth surface profile with spiral rib elements 13 typical of such bars and in this case is cylindrical. Each of straps 22, 23 is a 19 x 0.5mm band of high tensile steel. The bars are typically at 120mm centre-to-centre spacing, though this will of course vary according to the specifications for their use, along with the dimensional and material parameters of both the straps and the bars. As illustrated, there are two pairs of straps 22, 23, but in other embodiments there may be only one, or three or more pairs of straps.

The steel straps are correspondingly and relatively symmetrically deformed, around and to opposites sides of the bar at each intersection, so that the interface plane between the straps contains the axis of the bar. Moreover, the straps are riveted together at opposite side of the bar so as to lock in the deformation of each strap and so that the bar is firmly held between the straps. This form of fixture between the straps and bars is achieved by swaging with a hydraulic press tool that simultaneously forms the rivet indentations. A suitable two part tool 40 for this purpose is depicted in Figure 4. The bottom part 48 of the tool receives the lower strap from a supply reel, along a guideway defined by four posts 42. An elongate depression or channel 44 of symmetrical arcuate cross section is formed in the tool face and extends transversely to the strap axis, midway between posts 42. Each reinforcing bar is successively laid in turn centrally of this depression, e.g. by being delivered from above or directed in along its axis. The second strap 23 is then laid between the posts and the other matching part 50 of the tool (with a corresponding channel 45 and blind holes 43 to receive posts 42) closed down in a manner such that the tool swages the straps on to the tool by deforming them into the respective channels or depressions 44, 45. As the tool parts almost close, respective protrusions 46 on the upper tool part 50 cooperate in recesses 47 on lower tool part 48 to punch into the juxtaposed straps to either side of the bar so as to form complementary cold worked indentations 60, 61 by which the two straps 22, 23 are riveted together. In an alternative arrangement, only one of the straps is continuous bar-to-bar, while in place of the other strap there is a discrete strap portion at each bar. In the illustrated embodiment, multiple strap portions are provided by a single continuous strap 22 or 23.

It will be appreciated that no welding is employed in this procedure, and so there can be no question of compromising the integrity or predictable properties of the reinforcing bars.

Typically, the illustrated mesh is delivered continuously in the direction aligned with straps 22, 23. The thus formed mesh may then be rolled up to form substantial rolls (as depicted in Figure 1 at 100) for storage and transport. At a worksite, sets of the rolls may be unrolled in two orthogonal directions, directly onto a concrete pour site or onto an intermediate assembly apron, to form an orthogonal assembly of rebars that are tied together at a selected proportion of the bar intersections. The apron may be on a mobile workstation such as that described in the aforementioned international patent publication WO 2005/042849, in which case the formed reinforcing bar mesh, or matt, is continuously laid rearwardly onto a roadbed as the mobile workstation moves or is drawn slowly forward.

In another embodiment, the reinforcement bar mesh is formed on site in a construction zone in a process in which straps and bars are continuously delivered to a fixing station and the formed mesh is continuously relatively fed out onto a bed on which wet concrete is subsequently poured. The bed may be a roadbed, and the fixing station may be mobile and moved steadily forward at a rate to match the rate of formation of the mesh.

The illustrated embodiment of mesh construction and construction method provides, in a straightforward manner, a Tollable reinforcement bar mesh or mat that is free of welds and is therefore acceptable in markets where welded roll-up mats are not welcome.