The invention is applied preferentially, but not exclusively, to make electro-welded metal nets, used as reinforcement for structures made of reinforced concrete.

For this reason, in the description that follows, we shall refer specifically to this application, although the invention can also be used to make nets of other types.

BACKGROUND OF THE INVENTION Various types of machine to make electro-welded metal nets are known, from those which are mainly manual to those characterized by very advanced automation. Automatic machines to make large-size panels of net take up a lot of space and require a high investment; for this reason, in order to be amortized, they have to work substantially in a continuous cycle and guarantee high productivity. These machines are not generally suitable for making panels of net of a special type, for example of small to medium size, that is with sides that can have a length of between about 100 mm up to about 6000 mm, and/or provide apertures of various shape and size, for example so that fixed elements such as manhole covers, pipes or suchlike can be installed on site.

In this case, machines of a known type have to be equipped specifically on each occasion, with considerable stoppages in production, and are greatly over-sized, so that their productivity, in proportion to the investment and functioning costs, considerably decreases.

There is therefore a need in this field to make a machine to produce nets that requires low investment and functioning

costs, and which does not require long set-up times, so that it can be used even only occasionally without entailing an economic damage.

One purpose of the present invention is therefore to achieve a machine to produce metal nets which will be simple and economic to make, which will eliminate waiting and downtimes during the construction step, which is quick to equip with regard to any type of net, even of a special type, to be made, and which is easy to use for the workers and of limited encumbrance so as not to occupy much space when it is not used.

The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.

SUMMARY OF THE INVENTION The present invention is set forth and characterized in the main claims, while the dependent claims describe other characteristics of the present invention or variants to the idea of the main solution.

In accordance with this purpose, a machine to make nets, advantageously metal nets, according to the present invention comprises at least two frames, able to slide along respective parallel planes, each of which includes positioning and support means of the wire elements which will form the metal net.

The frames are able to be moved alternately between a first loading position, wherein the wire elements are positioned and supported on the respective frame, and a second working position wherein attachment means are driven to move into cooperation with the frame and perform the reciprocal attachment of the wire elements, thus making the net.

With this machine, in a cycle to make the metal net, a first step is provided wherein the wire elements are loaded onto a first of the two frames, arranged in the first loading position, and the first frame is subsequently moved to the second working position; a second step wherein, while the wire elements are being attached and the net is being formed in the first frame in the second working position, new wire elements are loaded onto a second frame arranged in the first loading position ; and a third step wherein the metal net produced is discharged, and subsequently the second frame is moved to the second working position and, simultaneously, the first frame is moved to the first loading position, so as to begin a new production cycle.

With the machine according to the present invention it is possible to obtain very limited times for the production of the net, since using two different frames allows to eliminate waiting times and downtimes between the loading step and the attachment step of the wire elements, and also between the discharge step and a new loading step.

According to a first variant, the frames are mounted on bases pivoting on a substantially horizontal axis in order to be able to assume a plurality of positions, inclined in variable manner, which facilitate both the step of loading the wire elements, for example by arranging the relative base in a substantially horizontal position, and also the step of discharging the completed net. Thanks to this variant, the machine according to the present invention allows to make a wide range of sizes, from very small panels, with sides even of 100 mm, to medium size panels with sides in the range of 4000. 6000 mm.

It is also possible to make apertures and/or holes in any position whatsoever of the net, by inclining and/or positioning the relative frame in a suitable manner.

According to another variant, the machine includes first drive means mounted to incline the base which supports the frame in relation to the specific operating steps in progress, and/or second automated means to move the frames linearly from the loading position to the working position and vice versa.

According to another variant, positioning and support means of the wire elements are mounted on the frames; these means being of the interchangeable type, so as to adapt to the various shapes and sizes of the wire elements depending on the net to be made. According to another variant, said positioning and support means are associated with closing means, able to be selectively activated, which prevent the wire elements from accidentally coming out of the relative seatings.

BRIEF DESCRIPTION OF THE DRAWINGS These and other characteristics of the present invention will become apparent from the following description of a preferential form of embodiment, given as a non-restrictive example, with reference to the attached drawings wherein: - fig. 1 is a front view of the machine according to the present invention; - fig. 2 is a transverse section along the line from II to II of fig. 1; - fig. 3 is a transverse section along the line from III to III of fig. 1 ; - fig. 4 is an enlarged view from IV of a detail of the machine in fig. 1.

DETAILED DESCRIPTION OF A PREFERENTIAL FORM OF EMBODIMENT With reference to the attached drawings, a machine 10 according to the present invention is used to make metal nets 11, for example of the electro-welded type with sizes that can vary from about 100 mm to about 6000 mm. In this

case, the metal nets 11 made are of a special type, and have at the center an aperture 12 provided to house a manhole cover, a pipe or otherwise, when installed.

The metal nets 11 are made by means of the reciprocal attachment of a first plurality of metal wires 13 arranged transverse, on a substantially vertical plane, and a second plurality of metal wires 15 arranged longitudinal, on a substantially horizontal plane. In this case, the wires 13 are attached to the wires 15 by means of a welder 16, but it comes within the field of the invention to use a solder pointer, a binder or other suitable attachment means.

The machine 10 comprises a first supporting stand 17 downstream of which, and aligned therewith, a second supporting stand 19 is arranged.

A first panel 20 is hinged to the first stand 17 along a horizontal axis arranged in a substantially median zone thereof, so that the panel 20 can be rotated (fig. 2) from one side of the stand 17 to the other, for reasons that will be explained hereafter.

A second panel 21 is hinged to the second stand 19, in a zone near its lower edge 21a, so that the panel 21 can be turned over (fig. 3) in order to allow the metal net 11 made to be discharged.

On the front face of the first panel 20 and second panel 21 there are two parallel guides 22, arranged advantageously near the respective upper and lower edges (fig. 1). The guides 22 of the panels 20 and 21 are aligned with each other, and the two panels are located very close together, so that the discontinuity of the guides 22 is reduced to a minimum.

According to a variant, not shown in the drawings, in the gap zone between the two panels 20 and 21 there is an

intermediate element which gives continuity to the guides 22 of the panels 20 and 21.

A first 23 and a second 25 supporting frame slide on the guides 22.

In this case, both the first 23 and the second 25 supporting frame comprise wheels 26 (fig. 4) which slide in the guides 22, in order to move the relative supporting frames 23 and 25 with respect to the two panels 20 and 21.

Each frame 23 and 25 comprises a plurality of longitudinal seatings 30 suitable to contain and support relative longitudinal wires or bars 15, and a plurality of transverse seatings, not visible in the drawings, for relative transverse wires or bars 13.

The longitudinal seatings 30 and the transverse seatings can have a shaped conformation, for example V-shaped, widening out at the rear, or with a partly elastic mouth, in order to retain inside them the relative wires or bars 13 and 15. According to a variant not shown, the longitudinal seatings 30 and the transverse seatings are associated with closing means that can be selectively activated.

The two frames 23 and 25 are arranged on two different parallel planes, so that they can slide reciprocally from one panel to the other 20,21. Each frame 23 or 25 can in fact slide between a first loading position, wherein it is in correspondence with the first panel 20, and wherein the loading step is performed with the wires 13 and 15, and a second working position, wherein it is in correspondence with the second panel 21, wherein the wires 13 and 15 are attached, in this case by means of the welder 16.

On the second panel 21 auxiliary guides 27 are also provided, in order to permit the sliding of a supporting trolley 29, on which the welder 16 is linearly mobile.

To be more exact, the welder 16 is mobile between a first inactive position (fig. 4), wherein it is distant from the two frames 23 and 25, and allows the free linear movement thereof, a second operating position, more towards the inside than the first, wherein it moves onto the first frame 23 in order to weld the wires 13 and 15 which are mounted on it, and a third operating position, even further towards the inside, wherein it moves onto the second frame 25, in order to weld the wires 13 and 15 which are mounted on it.

Upstream of the machine 10 according to the invention there is at least a store 31 where the metal wires are deposited; several stores 31 can be provided, for example for differences in length and/or section, to be loaded onto the frames 23 or 25 of the machine 10.

The machine 10 to make metal nets 11 as described heretofore functions as follows.

Firstly, the metal wires 13 and 15 are loaded onto the first frame 23, when the latter is in the first loading position. In this step, the panel 20 can be rotated around its pivoting axis (fig. 2), for example from a first position inclined forwards (shown with a continuous line), in order to facilitate the positioning of the wires 13 in the lower part of the frame 23, to a second position, inclined at the lower part towards the rear (shown with a line of dashes), in order to facilitate the positioning of the wires 13 in the upper part of the frame 23, when nets of a certain size are made. In this case, it is advantageous to arrange the panel 20 in a substantially horizontal position, so as to be able to insert the wires 13 and 15 from the side.

Subsequently, the first frame 23 is made to slide on the panels 20 and 21 into the second working position, while the second frame 25 is in the first position, ready to be loaded

with the relative wires 13 and 15. It is then possible to perform simultaneously both the step of welding the wires 13 and 15 loaded on the first frame 23 by the welder 16, and also the loading of new metal wires 13 and 15 onto the second frame 25.

Once the metal net 11 has been made, the second panel 21 can be made to rotate around its lower edge 21a, so as to facilitate the operations of discharging the net 11 which, in this case, is stacked up on other, previously made nets.

When the metal net 11 has been discharged, the first 23 and the second frame 25 are made to slide along the guides 22, so as to take the first, empty frame 23 to the initial loading position on the first panel 20, and the second frame 25, loaded with the wires 13 and 15, to the second working position on the second panel 21, in order thus to make a second metal net 11. This last operating condition defines the start of a new operating cycle.

It is clear, however, that modifications and/or additions of parts or steps may be made to the machine 10 and the relative method as described heretofore, without departing from the field and scope of the present invention.

For example, according to a variant, the metal wires 13 and 15 can be loaded in a completely automatic manner.

According to another variant, the metal nets 11 made can be turned over by the second panel 21 directly onto a conveyor belt which actuates the discharge towards a storage zone.

It is also clear that, although the present invention has been described with reference to specific examples, a skilled person in the art shall certainly be able to achieve many other equivalent forms of machine to make metal nets and relative method, all of which shall come within the field and scope of the present invention.

It comes within the field of the present invention that several small-size nets can be made simultaneously on the same frame. It is also possible to use three or more frames and three or more supporting panels.