Patent Publication Number: US-11389857-B2

Title: Apparatus and method to make a wire mesh

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a Section 371 of International Application No. PCT/IT2018/050101, filed Jun. 5, 2018, which was published in the English language on Dec. 13, 2018, under International Publication No. WO 2018/225108 A1, which claims priority under 35 U.S.C. § 119(b) to Italian Application No. 102017000061837, filed Jun. 6, 2017, the disclosures of each of which is incorporated herein by reference in their entireties. 
     FIELD OF THE INVENTION 
     Embodiments of the present invention concern an apparatus to make a wire mesh usable, for example, as, or in association with reinforcements for reinforced concrete structures, or a containing and/or separation mesh. 
     The present invention allows to obtain wire meshes having links of desired sizes, homogeneous or differentiated. Furthermore, the present invention also concerns a method to make a wire mesh. 
     The present invention is applicable to wire meshes whose components are all or partly welded together. 
     Embodiments of the present invention also concern a unit for positioning longitudinal wires to make the wire mesh, as well as a unit to remove and supply the longitudinal wires to a coupling and possible welding unit. 
     BACKGROUND OF THE INVENTION 
     Apparatuses are known for making wire meshes defined by a plurality of longitudinal wires located distanced from each other and by a plurality of transverse wires distanced from each other and welded to the longitudinal wires transversely to the development of the latter. 
     Known apparatuses usually comprise a first unit to feed the longitudinal wires, configured to supply, substantially simultaneously in the connection zone between longitudinal wires and transverse wires, a plurality of longitudinal wires distanced from each other. 
     Known apparatuses comprise a unit to feed the transverse wires to supply, on each occasion, and in the desired position, a transverse wire to the plurality of longitudinal wires. 
     These apparatuses comprise, where welding is provided, at least one welding unit to weld, on each occasion, the transverse wire to one or more longitudinal wires in the zones of reciprocal overlap. 
     In the state of the art, the reciprocal distance between the longitudinal wires is determined, on each occasion, by the reciprocal positioning of the individual feed units of the feeding group of the longitudinal wires, which positioning is defined in an initial setting step of the apparatus. 
     However, this known solution has numerous disadvantages, especially if it is necessary to make, with a single apparatus, wire meshes having links defined by wires having different sections and/or sizes, or even meshes whose longitudinal and/or transverse pitch is differentiated on each occasion by reason of specific production batches. 
     An apparatus is also known from DE-A-44.23.737 for making meshes comprising a first unit to feed longitudinal wires, a second unit to feed, on each occasion, at least one transverse wire, and a welding unit provided to weld each transverse wire to the longitudinal wires. 
     This apparatus, described in DE-A-44.23.737, also comprises a positioning unit configured to receive one longitudinal wire from the first feed unit at a time. 
     The longitudinal wires are located parallel to a first direction and are released toward the positioning unit, by the first feed unit, so as to distance them from each other according to a predetermined pattern. Specifically, the positioning unit comprises a positioning device provided to move the longitudinal wires in a direction orthogonal to their oblong development, that is, in a direction orthogonal to the first direction. Therefore, in the positioning unit a loading plane, or loading zone, is provided, in which the longitudinal wires are disposed approximately at the desired distance dictated by the particular configuration of the wire mesh to be obtained. Directly in the loading zone a plurality of gripping members are disposed, each of which is provided to remove one of the longitudinal wires and transfer it in a direction parallel to the longitudinal development of the longitudinal wires and toward the welding unit in which they are welded with the transverse wires. 
     The welding unit is directly aligned with the loading plane, or loading zone of the longitudinal wires, in a direction parallel to the longitudinal development of the latter. 
     The gripping members, moving in the direction parallel to the longitudinal development of the longitudinal wires, supply the latter at entrance to the welding unit which then, by successive steps, causes the longitudinal wires to advance, in order to weld the transverse wires on the latter. 
     Given the great length that the longitudinal wires can have, usually from a minimum of 5 m to even 12-15 m or more, the loading plane, or loading zone, remains occupied by the longitudinal wires for a good part of the welding operations as well, that is, the operations to transport the longitudinal wires toward the welding unit. 
     This implies rather long downtimes as regards the feeding of the longitudinal wires, with consequent losses in productivity and efficiency of the plant. The feed of the longitudinal wires toward the loading plane, in fact, usually requires significant working times, since all the longitudinal wires defining a wire mesh must be provided to the loading plane and reciprocally distanced at least in an approximate way. 
     During the transfer steps of the longitudinal wires toward the welding unit, and at least until the longitudinal wires have been introduced into the welding unit, it is not possible to start the positioning of a new group of longitudinal wires in the loading plane, since the latter is occupied by the previous group of longitudinal wires formed. 
     There is therefore a need to perfect and make available an apparatus and a method to make a wire mesh which overcome at least one of the disadvantages of the state of the art. 
     One purpose of the present invention is to provide an apparatus to make wire meshes which allows to reduce the working times of wire meshes by avoiding downtimes. 
     The present invention also sets out to provide an apparatus to make wire meshes which is extremely versatile and does not limit the production of wire meshes having pitches of sizes limited to a few ranges. 
     Another purpose is to provide an apparatus that occupies limited spaces or, in any case, less than the bulk of known apparatuses. 
     Another purpose of the present invention is to provide an apparatus able to produce wire meshes whose distances, at least between the longitudinal wires, have equal values, different values, or mixed values. 
     The invention can also be applied to apparatuses suitable to obtain wire meshes with longitudinal and transverse wires located orthogonal or with a desired angle. 
     The present invention is particularly suitable to obtain meshes in which the longitudinal wires are at predetermined distances and can be defined on each occasion in relation to the purposes of the mesh. 
     It is also a purpose of the present invention to provide an efficient apparatus which allows to reduce, and even to cancel, the setting times and stop times of the apparatus, even when there is a change in format of the wire mesh. 
     The present invention also sets out to provide a method for making wire meshes rapidly and with a pitch between the metal wires that is defined on each occasion. 
     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 independent claims, while the dependent claims describe other characteristics of the invention or variants to the main inventive idea. 
     Embodiments described here concern an apparatus to make a wire mesh with longitudinal wires and transverse wires connected to each other and defining links of the desired size and/or disposition. 
     In the present invention, by connection between longitudinal wires and transverse ones, we mainly mean by welding, but the invention is applicable to any type of connection. Hereafter in the description by the term welding we therefore mean any type of connection. 
     The apparatus to make a wire mesh comprises a welding unit, a first feeder configured to feed longitudinal wires, and a second feeder configured to feed, on each occasion, at least one transverse wire into the welding unit. 
     In accordance with one aspect of the present invention, the apparatus comprises a positioning unit configured to receive from the first feeder a plurality of longitudinal wires disposed parallel to a first direction and distanced according to a pre-set pattern. 
     The positioning unit comprises at least one positioning device configured to move the longitudinal wires keeping them parallel and distanced from each other in a direction of movement orthogonal to the first direction. 
     The apparatus comprises a plurality of gripping members each configured to remove one of the longitudinal wires from the positioning unit and to transfer them in respective directions of feed and toward the welding unit. 
     The directions of feed are located reciprocally distanced from each other according to a pattern coordinated with that which the longitudinal wires will assume when welded to the transverse wires. 
     In accordance with one aspect of the present invention, the positioning unit comprises a preparation zone and a delivery zone adjacent to each other in a direction parallel to the direction of movement. 
     The gripping members are located in the delivery zone in order to remove the longitudinal wires that are found in that zone. 
     The preparation zone has a width, in a direction parallel to the direction of movement, at least equal to or greater than the width of the delivery zone. 
     In this way, while in the preparation zone the first feeder delivers a first group of longitudinal wires, disposing the latter already distanced by a predefined distance, in the delivery zone a second group of longitudinal wires already previously positioned and received from the preparation zone, can be fed to the welding unit. This avoids having to stop the preparation of the longitudinal wires while waiting for the loading plane to be free. 
     Thanks to the present invention it is possible to make wire meshes with longitudinal wires and transverse wires welded and reciprocally distanced according to a pattern defined according to the batches to be produced. 
     The present invention also allows to rapidly and correctly position the longitudinal wires in relation to the distance that they will assume when the transverse wires are welded. 
     This considerably reduces the production times of the wire meshes and does not require long times for the format change of the wire mesh to be made. 
     Embodiments of the present invention also concern a method to make a wire mesh that provides to feed longitudinal wires with a first feeder and to feed with a second feeder, on each occasion, at least one transverse wire to the welding unit. 
     According to the present invention the method provides to:
         receive from the first feeder a plurality of longitudinal wires which are disposed in a positioning unit parallel to a first direction and distanced according to a pre-set pattern,   move the longitudinal wires with a positioning device, keeping them parallel and distanced from each other in a direction of movement orthogonal to the first direction,   remove each of the longitudinal wires from the positioning unit with a respective gripping member, and   transfer the longitudinal wires with the gripping members in respective directions of feed and toward the welding unit, said directions of feed being located reciprocally distanced from each other according to a pattern coordinated to that which the longitudinal wires will assume when welded to the transverse wires.       

     The method in accordance with the present invention also provides that the positioning unit comprises a preparation zone and a delivery zone adjacent to each other in a direction parallel to the direction of movement, and in that whereas in the preparation zone the first feeder delivers a first group of longitudinal wires, distanced from each other according to a pre-set pattern, in the delivery zone the gripping members remove a second group of longitudinal wires previously prepared in the preparation zone. 
     In accordance with a possible implementation of the method, it can be provided to position a plurality of welding heads of the welding unit each aligned with a respective direction of feed and based on the interaxis between the longitudinal wires of the wire mesh to be made. 
     In accordance with another possible implementation of the method, it is provided to position each of the gripping members aligned with a respective direction of feed. 
     In accordance with another possible implementation of the method, it is provided to supply, to the positioning unit with said first feeder, the longitudinal wires reciprocally distanced according to a pattern similar to that of the subsequent removal, to perform a first removal of some of the longitudinal wires with the respective gripping members, to translate in the direction of movement the longitudinal wires remaining on the positioning unit so as to perform at least a second removal of at least some of the remaining longitudinal wires with respective gripping members. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other characteristics of the present invention will become apparent from the following description of some embodiments, given as a non-restrictive example with reference to the attached drawings wherein: 
         FIG. 1  is a schematic representation of an apparatus to make a wire mesh, in which possible positions of the longitudinal wires are shown; 
         FIGS. 2-5  schematically show a positioning unit and a removal and supply unit in subsequent steps of positioning and removal of longitudinal wires; 
         FIG. 6  is a perspective view of a possible embodiment of a gripping member of a removal and supply unit; 
         FIG. 7  is a schematic view that shows a gripping unit of the removal and supply unit; 
         FIG. 8  is a schematic view of a welding unit according to a possible embodiment of the present invention. 
     
    
    
     To facilitate comprehension, the same reference numbers have been used, where possible, to identify identical common elements in the drawings. It is understood that elements and characteristics of one embodiment can conveniently be incorporated into other embodiments without further clarifications. 
     DETAILED DESCRIPTION OF SOME EMBODIMENTS 
     Embodiments described here, with reference to the attached drawings, concern an apparatus  10  to make a wire mesh  11 . In particular, with the present invention it is possible to make wire meshes  11  having the size of the links and disposition of the wires that make up the wire mesh  11  predefined on each occasion. 
     The wire meshes  11  are defined by longitudinal wires  13  and by transverse wires  14 . The longitudinal wires  13  and the transverse wires  14  can have the same diameter or different diameter. 
     The pitch between longitudinal wires  13  and/or the pitch between transverse wires  14  can be, on each occasion, defined according to the operating requirements that the wire mesh  11  will have during use. 
     The wires, whether they are longitudinal  13  or transverse  14 , can have a cross-section shape that is round, oval, square, rectangular or polygonal. 
     The longitudinal wires  13  and the transverse wires  14  can be smooth, ribbed or corrugated to obtain, during use, a better grip in the concrete. The longitudinal wires  13  and the transverse wires  14  can be rolled and/or drawn. 
     The transverse wires  14  are welded to the longitudinal wires  13 , for example electro-welded in correspondence with the zones of reciprocal overlap. 
     According to one aspect of the present invention, the apparatus  10  comprises a first feeder  15  configured to feed one longitudinal wire  13  on each occasion, disposing it in a first direction D 1 . In particular, the longitudinal wire  13  is positioned with its oblong development parallel to the first direction D 1 . 
     According to a possible variant embodiment, not shown, the first feeder  15  is configured to feed, on each occasion, more than one longitudinal wire  13 , for example to feed two, three or more longitudinal wires  13 . 
     In particular, it can be provided that the first feeder  15  is configured to feed the longitudinal wire  13  moving it in a direction aligned with the first direction D 1 , or in a direction parallel to the first direction D 1 , for example by supplying it from above or laterally. 
     According to a possible solution ( FIG. 1 ), the first feeder  15  can comprise a store  25  in which the longitudinal wires  13  already pre-cut to a predetermined length are positioned. 
     According to a possible variant embodiment, not shown, the first feeder  15  can comprise one or more wire unwinding reels and cutting and straightening means provided to define the length of the first longitudinal wires  13 . 
     According to a possible solution, the first feeder  15  can comprise a drawing member  22  provided to feed the longitudinal wires  13  in a direction aligned to the first direction D 1 . 
     The store  25  can be provided with respective positioning devices, not shown, provided to position the longitudinal wires  13  in correspondence with the drawing members  22 . 
     The first feeder  15  can also comprise measuring means  24 , for example a counter roller, provided to detect the length of the longitudinal wire which is fed, on each occasion, by the drawing member  22 . 
     Downstream of the first feeder  15  a positioning unit  31  is provided, configured to receive a plurality of the longitudinal wires  13  from the first feeder  15  and to position them parallel to each other and reciprocally distanced according to a predetermined pattern. 
     In accordance with a possible solution, the positioning unit  31  is located adjacent, with respect to the first direction D 1 , to the first feeder  15 . 
     In accordance with possible solutions, the positioning unit  31  comprises at least one positioning device  45  configured to receive the longitudinal wires  13  and to move them keeping them parallel and distanced from each other in a direction of movement D 2  orthogonal to the first direction D 1 . 
     According to an advantageous solution, the positioning unit  31  comprises a plurality of positioning devices  45  located parallel to each other, in a direction orthogonal to the first direction D 1 , and each configured to move the longitudinal wires  13  in a direction orthogonal to the first direction D 1 . 
     The at least one positioning device  45 , in this case the positioning devices  45 , define a support plane  46  on which to dispose the longitudinal wires  13 , all lying on a common lying plane. 
     The at least one positioning device  45 , in this case each positioning device  45 , can comprise a plurality of housing seatings  34  associated with a support element  33  and reciprocally distanced from each other by a predetermined pitch. 
     In particular, it can be provided that the housing seatings  34  are provided on at least one portion of the support element  33  one adjacent to the other. Each housing seating  34  is configured to receive at least one of the longitudinal wires  13 . 
     The support element  33  is configured to support the housing seatings  34  aligned with each other in a direction orthogonal to the first direction D 1 . 
     According to a possible solution, the positioning unit  31  can comprise a preparation zone  50  and a delivery zone  51  located adjacent in a direction parallel to the direction of movement D 2 . In other words, the preparation zone  50  and the delivery zone  51  are adjacent in the direction of movement D 2 . 
     The preparation zone  50  has a first width L 1 , measured in a direction parallel to the direction of movement D 2 , at least equal to or greater than a second width L 2 , also measured in a direction parallel to the direction of movement D 2 , at least equal to or greater than the width L 2  of the delivery zone  51 . 
     In this way, while in the delivery zone  51  there is a first group of longitudinal wires  13  ready, or possibly transferring to the welding unit  17 , the preparation zone  50  can be used to load and position correctly on the positioning unit  31  a new group of longitudinal wires  13  already reciprocally distanced from each other. 
     This solution allows to drastically reduce the downtimes of feeding the longitudinal wires to the welding unit, considerably increasing productivity and plant efficiency. 
     The first width L 1  and the second width L 2  can be at least equal to, or greater than, the width of the wire mesh  11  to be obtained, or at least equal to the reciprocal distance between the two longitudinal wires located on the external perimeter of the wire mesh  11 . 
     In the preparation zone  50  the first feeder  15  supplies, on each occasion, one of the longitudinal wires  13  until a positioning pattern is defined for the longitudinal wires  13  defining a wire mesh  11 . Once the loading of the group of longitudinal wires  13  defining a wire mesh  11  has been completed in the preparation zone  50 , the same are moved and taken into correspondence with the delivery zone  51  so that they can be removed. 
     The support element  33  is configured to take the housing seatings  34  from the preparation zone  50  to the delivery zone  51 . 
     According to possible solutions, the support element  33  can comprise at least one of either a chain, a belt, a conveyor belt, a cable. 
     In accordance with a possible solution, shown in  FIGS. 2-5  for example, the support element  33  integrates the housing seatings  34 . 
     By way of example only ( FIGS. 2-5 ), it can be provided that the support element  33  comprises a chain and the links of the latter, due to how they are conformed, define the housing seatings  34 . 
     In accordance with possible variant embodiments, not shown, the housing seatings  34  can be made in shaped bodies, which are attached to the support element  33  according to a predetermined pitch. 
     The support element  33  can develop in a closed ring and wind around return rollers  47 . 
     In this way, the support element  33  defines a first return segment  33   a , facing upward during use, and configured to define, on each occasion, the support plane  46 , and a second return segment  33   b  opposite the first return segment  33   a , and facing downward during use. 
     In accordance with this embodiment, it can be provided that a part of the first return segment  33   a  is positioned in the preparation zone  50  while a second part of the first return segment  33   a , consecutive to the first return segment  33   a , is positioned in the delivery zone  51 . 
     By way of example only, it can be provided that the housing seatings  34  are reciprocally distanced from each other by a pitch comprised between 15 mm and 100 mm, preferably between 30 mm and 70 mm. 
     According to possible solutions, an actuation device  48  can be associated with the support element  33  and is configured to move the support element  33  and the housing seatings  34  in a direction of movement D 2  orthogonal to the first direction D 1 . 
     The actuation device  48  can be associated with at least one of the two return rollers  47 . 
     The housing seatings  34  in this way can be taken into the preparation zone  50  where each longitudinal wire  13  supplied by the first feeder  15  is positioned in the housing seatings  34 . The housing seatings  34  are then translated toward the delivery zone  51  to allow the longitudinal wires  13  to be removed as described below. 
     By suitably coordinating the discharge action of the longitudinal wire  13  in the housing seatings  34 , with the movement of the positioning devices  45  it is possible to obtain a control of the positioning of the longitudinal wires  13  in the housing seatings  34 , and therefore to obtain a precise control of the reciprocal position of the longitudinal wires  13  themselves. 
     In particular, by suitably coordinating the positioning, or the discharge, of the longitudinal wires  13  in the housing seatings  34 , it is possible to dispose the longitudinal wires according to an already predefined pattern close to that of the subsequent remove, as described below. 
     According to a possible solution, if there are several positioning devices  45 , it can be provided that each of them is provided with at least two support elements  33  located parallel to each other and each of which is provided with respective housing seatings  34 . 
     In particular, it can be provided that a first of the two support elements  33  can be positioned in the preparation zone  50  to receive the longitudinal wires  13  from the first feeder  15  and can be moved toward the delivery zone  51  to allow the subsequent removal of the longitudinal wires  13 . While a second of the two support elements  33  can be positioned in the delivery zone  51  to allow the subsequent removal and delivery of other longitudinal wires, and is movable toward the preparation zone  50  and vice versa. The first and second support elements  33  can be moved alternately between the preparation zone  50  and the delivery zone  51  and vice versa, alternately exchanging their position, that is, when one is located in the preparation zone  50  the other is located in the delivery zone  51 , and vice versa. 
     This solution allows to drastically reduce the downtimes between the positioning steps of the longitudinal wires  13  in the positioning unit  31  and the subsequent removal steps. 
     The support element  33  can be provided with the housing seatings  34  for only a portion of its overall length, or for a longitudinal extension substantially mating with the length of the delivery zone  51 . 
     In accordance with a possible solution, the first feeder  15  can comprise a supply unit  30  able to provide, in sequence, a single longitudinal wire  13  to the positioning unit  31 . 
     In particular, once it has received a longitudinal wire  13 , for example from the drawing member  22 , the supply unit  30  delivers it to the specific housing seating  34  of the positioning device  45 . 
     The supply unit  30  can be configured to supply the single longitudinal wire  13  by translating it in a direction parallel to the direction of movement D 2 . 
     According to possible solutions, the supply unit  30  can comprise a plurality of screws  43  distanced from each other in a direction parallel to the first direction D 1 . The screws  43  each allow to support the respective longitudinal wire  13  in correspondence with different zones of the longitudinal extension of the latter. 
     In particular, the first feeder  15  feeds one of the longitudinal wires  13  in correspondence with respective cavities each of which is defined between a respective spiral of the respective screw  43 . 
     By making the screws  43  rotate in a synchronized manner, it is possible to make the longitudinal wire  13  advance in a direction parallel to the axes of the screws  43  and to discharge it into one of the housing seatings  34  of the positioning device  45 . 
     To this purpose, the screws  43  can be disposed with their axes of rotation substantially orthogonal to the first direction D 1  and parallel to the direction of movement D 2 . 
     The use of the screws  43 , moreover, allows to butt the longitudinal wires  13 , for example in correspondence with an abutment body  49 , possibly present at the side of the supply unit  30  and the positioning unit  31 . 
     According to one aspect of the present invention, the apparatus comprises a removal and supply unit  32  configured to remove the longitudinal wires  13  from the positioning unit  31  and supply them to a welding unit  17 . 
     The removal and supply unit  32  comprises a plurality of gripping members  36  disposed adjacent to each other along a positioning axis substantially parallel to the movement axis D 2 . 
     The gripping members  36  are configured to remove individual longitudinal wires  13  from the housing seatings  34  and to move them each in respective directions of feed, in the case shown in  FIGS. 1-5  the directions of feed A 1 , A 2 , A 3 , A 4 , A 5  and A 6 . The directions of feed A 1 -A 6  are located reciprocally distanced from each other according to a pattern coordinated with that which the longitudinal wires  13  will assume once they have been welded to the transverse wires  14 . 
     The reciprocal distances between the directions of feed A 1 -A 6  can therefore correspond with the reciprocal distances between the gripping members  36 . 
     With the solution of the present invention, it is possible to provide that the reciprocal distances between the longitudinal wires  13  do not necessarily correspond to a pitch or a multiple of the pitch between the housing seatings  34 . The reciprocal distances are completely independent from the housing seatings  34  and are determined on each occasion according to the structural resistance parameters required of the mesh. 
     The gripping members  36  can be located in correspondence with one side of the support plane  46  of the positioning unit  31  which is located parallel to the direction of movement D 2 . In this way, each of the gripping members  36  can take and feed one of the terminal ends of the longitudinal wires  13 . 
     The gripping members  36  can be positioned, at least in the condition where they remove the longitudinal wires  13 , above or below the support plane  46  so as to be able to take the longitudinal wires  13  with the simple activation of the gripping members  36 . 
     The removal and supply unit  32  can comprise a positioning guide  37 , located parallel to the direction of movement D 2  and on which the gripping members  36  are positioned. 
     The removal and supply unit  32  can comprise positioning means, not shown, provided to position each gripping member in a predefined position along the positioning guide  37  and corresponding to the reciprocal distance between the movement distances A 1 -A 6 . The positioning means can be driven in the initial setting step of the apparatus according to the construction parameters required for the construction of the mesh. 
     Each gripping member  36  can comprise at least one removal gripper  38  configured to take a longitudinal wire  13  from a respective housing seating  34 . 
     In accordance with a possible solution, the removal gripper  38  can have a gripping amplitude that is greater than or equal to the pitch between contiguous housing seatings  34 . 
     In this way the removal gripper  38  with a gripping action can remove a longitudinal wire  13  even if not perfectly aligned with the corresponding direction of feed A 1 -A 6 . 
     Closing the removal gripper  38  causes the alignment of the end of the longitudinal wire  13  to the corresponding direction of feed A 1 -A 6 . 
     In other embodiments, the gripping member  36  can comprise, or also comprise, a holding gripper  39  able to retain the longitudinal wire  13  removed, to also allow it to be subsequently drawn in the corresponding direction of feed A 1 -A 6 . 
     According to possible embodiments, the gripping members  36  can each comprise an actuation device  53  configured to move the gripping members  36  between a gripping position, in which they remove the corresponding longitudinal wires  13  from the housing seatings  34 , and a holding and supply position in which the gripping members  36  retain and supply the longitudinal wires  13  in the corresponding welding heads  26 . 
     In particular, it can be provided that the actuation devices  53  are mobile in a direction orthogonal to the support plane  46 , or to take the gripping members into a gripping condition or of non-interference with the movement of the longitudinal wires  13 . 
     Each gripping member  36  can comprise a detection device  40  able to detect the presence of the longitudinal wire  13  when it is located in the removal gripper  38  and/or in the holding gripper  39 . 
     According to possible embodiments, the detection device  40  is configured to detect the presence of the longitudinal wire  13  by contact, for example it can be provided with a mobile portion  41  located in the alignment direction A 1 -A 6  where the longitudinal wire  13  will be positioned. When the longitudinal wire  13  comes into contact with the mobile portion  41 , the latter rises up without obstructing the longitudinal wire  13  and provides a signal confirming the grip of the longitudinal wire  13 . The confirmation signal can comprise a signal of consent to the start of subsequent operating steps, a luminous signal, an acoustic signal. 
     The gripping members  36  can be installed on a common support structure  52  mobile between the positioning unit  31  and the welding unit  17  in a direction parallel to the directions of feed A 1 -A 6 . 
     The movement of the support structure  52  allows to simultaneously translate all the longitudinal wires  13  in the directions of feed A 1 -A 6 . 
     In accordance with possible solutions, the support structure  52  can be installed on guides  35  located parallel to the directions of feed A 1 -A 6 . The guides  35  can have a longitudinal extension greater than or equal to the length of the longitudinal wires  13 . In this way, when the support structure  52  is moved, the longitudinal wires  13  are extracted completely from the support plane  46 , leaving the latter free. 
     In accordance with possible solutions, the positioning unit  31  can comprise lifting members  42  able to lift the longitudinal wires  13  above the support plane  46 , and remove them from the housing seatings  34 . In this way, when the longitudinal wires  13  are moved in the directions of feed A 1 -A 6 , they do not slide in the housing seatings  34 , causing possible wear. 
     The lifting members  42  can be positioned between at least one pair of positioning devices  45  and can be mobile vertically with respect to the support plane  46 . 
     The lifting members  42  can each comprise a support plane, with a substantially flat shape and provided to completely lift the longitudinal wires  13  from the positioning devices  45 . 
     The lifting members  42  can be disposed in the delivery zone  41 . When the longitudinal wires  13  are lifted by the lifting members  42 , the positioning devices  45  can be moved again to position themselves in the preparation zone  50 , or in proximity to it. This further increases the efficiency of the apparatus and reduces downtimes. 
     The apparatus  10  in accordance with the present invention also comprises a welding unit  17  configured to weld the longitudinal wires  13  with at least one transverse wire  14 . 
     In particular, it can be provided that the welding unit  17  comprises a plurality of welding heads  26  each of which is configured to weld a respective longitudinal wire  13  with the at least one transverse wire  14 . 
     The welding heads  26  can be installed aligned with each other along a common positioning axis which is orthogonal to the directions of feed A 1 -A 6 . 
     In particular, it can be provided that each welding head  26  is aligned with a respective axis of feed A 1 -A 6 . 
     In this way, once the longitudinal wires  13  have been removed from the positioning unit  31 , the removal and supply unit  32  transfers them in correspondence with the welding heads  26  for translation along the axes of feed A 1 -A 6 . 
     Each welding head  26  can be positioned in correspondence with one of the reciprocal overlap zones of the respective wires. For example, the welding heads  26  can be positioned, for example during the initial setting steps, by suitable actuators along a positioning guide  27 . 
     In accordance with possible embodiments, each welding head  26  can comprise a first electrode  28  and a second electrode  29  opposite each other with respect to the reciprocal overlap zones of the longitudinal wire  13  and the transverse wire  14 . 
     The first and second electrodes  28  and  29  can be electrically powered by an electric energy generator, not shown, to apply the energy necessary for welding to the longitudinal wires  13  and the transverse wires  14 . 
     At least one of either the first electrode  28  or the second electrode  29  can be selectively movable between a first position, in which the two electrodes  28  and  29  are distanced from each other, defining a gap, where the wires to be welded can be located, and a second welding position, in which the two electrodes  28  and  29  clamp and weld the wires. 
     The welding heads  26  can each be provided with feed means, not shown, and configured to make the longitudinal wires  13 , received from the removal and supply unit  32 , advance through the welding unit  17  itself. 
     Depending on the advance pitch of the longitudinal wires  13  and the frequency with which the transverse wires  14  are supplied, the interaxis between the transverse wires  14  is defined on each occasion. 
     The apparatus  10  also comprises a second feeder  16  provided to feed, on each occasion, at least one transverse wire  14  located transversely to the axes of feed A 1 -A 6 . The second feeder  16  can be substantially analogous to the first feeder  15  described above. 
     According to a possible solution ( FIG. 1 ), the second feeder  16  can comprise one or more reels  20  to supply a longitudinal wire  13 , a possible straightening member  21 , a drawing member  22  and a cutting member  23  configured to cut the metal wire to a predefined length and to define the transverse wires  14 . The second feeder  16  can also comprise measuring means  24  substantially analogous to what was described above for the first feeder  15 . 
     With reference to  FIGS. 2-5 , a sequence of the positioning and removal steps of the longitudinal wires  13  is shown. 
     In particular, the gripping members  36  are located at a distance from each other according to predetermined distances and established by specifications, which substantially correspond with the reciprocal distances that the longitudinal wires  13  will assume when welded to the transverse wires  14 . 
     The first feeder  15  delivers a longitudinal wire  13  on each occasion to the positioning unit  31 , disposing it in a corresponding housing seating  34 . The delivery of the longitudinal wires  13  is such that once all of these are positioned in correspondence with the delivery zone  51 , they assume a position, that is, a reciprocal positioning of the wires, which is close to that of the directions of feed. 
       FIGS. 2-6  show the feed of four longitudinal wires  13  by means of four gripping members  36  disposed in respective directions of feed A 1 -A 4 . 
     With reference to  FIG. 2 , the longitudinal wires  13  located in correspondence with the directions of feed A 1 , A 3  and A 4  can be removed from the respective gripping members  36 . 
     Subsequently, in order to remove the longitudinal wire  13  that has not been removed, a movement of the positioning device  45  is provided, according to the direction indicated by the arrow F ( FIG. 3 ), to dispose the longitudinal wire  13  in a position suitable for removal by the free gripping member  36  ( FIGS. 4 and 5 ). 
     With reference to  FIG. 1 , three possible positioning configurations S 1 , S 2 , S 3  of the longitudinal wires  13  are shown. 
     In the first configuration S 1 , the first feeder  15  delivers the longitudinal wires  13  to the positioning unit  31 , disposing them reciprocally distanced from each other so that when located in the delivery zone  51  each is aligned to one of the directions of feed A 1 -A 6 . 
     In the second configuration S 2 , when the longitudinal wires  13  are taken to the delivery zone  51 , only some of them are aligned to the respective directions of feed A 1 -A 6 , in this case to the directions of feed A 2  and A 3 . The longitudinal wires  13  located in these positions can be removed directly by the respective gripping members  36 . Subsequently, a translation is provided, with the positioning devices  45 , of the remaining longitudinal wires  13  not removed, in order to dispose them in correspondence with the other gripping members  36  and carry out the subsequent removal of the longitudinal wires  13 . 
     In the third configuration S 3 , only the longitudinal wire  13  located in correspondence with the direction of feed A 4  can be removed by the respective gripping member  36 . Subsequently, with the positioning devices  45 , it is possible to translate the longitudinal wires  13  laterally to dispose them in correspondence with the respective gripping members  36  provided for their removal. 
     In accordance with this solution, even if the first feeder  15  does not deliver the longitudinal wires  13  to the positioning unit  31  in positions close to those of the subsequent removal by the removal and supply unit  32 , by suitably coordinating the actuation of the positioning devices  45 , it is possible to dispose the longitudinal wires  13  in the positions suitable for removal by the removal and supply unit  32 . 
     According to possible embodiments, the apparatus  10  comprises a control and command unit  12  configured to manage and coordinate the functioning of the units of the apparatus  10  to make wire meshes  11  which have the desired links on each occasion. 
     In particular, the control and command unit  12  can be connected at least to the first feeder  15 , to the positioning unit  31  and to the removal and supply unit  32  in order to coordinate their drive and allow the correct removal of the longitudinal wires  13  by the removal and supply unit  32 . 
     Embodiments of the present invention also concern a machine to supply longitudinal wires  13  which comprises the first feeder  15 , the positioning unit  31  and the removal and supply unit  32  as described above. 
     It is clear that modifications and/or additions of parts and/or steps can be made to the apparatus  10  and to the method to make wire meshes  11  as described heretofore, without departing from the field and scope of the present invention. 
     According to a possible variant embodiment ( FIG. 7 ), each gripping member  36  of the removal and supply unit  32  can be moved along three orthogonal axes X, Y, and Z (shown in  FIG. 7 ) by means of suitable movement members  44 . The movement members  44  can comprise actuators, motor members, guides, mobile sliders, or other devices able to move in a direction defined by at least one orthogonal axis X, Y, Z. The axis X can be perpendicular to the directions of feed A 1 -A 6 . The axis Y can be parallel to the corresponding directions of feed A 1 -A 6 . The axis Z is orthogonal to the axis X and to the axis Y. 
     It is also clear that, although the present invention has been described with reference to some specific examples, a person of skill in the art shall certainly be able to achieve many other equivalent forms of the apparatus  10  and the method, having the characteristics as set forth in the claims and hence all coming within the field of protection defined thereby.