EP4429834A1

EP4429834A1 - Plant and process for uncoiling wire-rod coils

Info

Publication number: EP4429834A1
Application number: EP22769772.9A
Authority: EP
Inventors: Stefano COVAZZI
Original assignee: Promostar Srl
Current assignee: Promostar Srl
Priority date: 2021-11-11
Filing date: 2022-08-19
Publication date: 2024-09-18
Anticipated expiration: 2042-08-19
Also published as: IT202100028730A1; WO2023084324A1; US20240416404A1; EP4429834B1

Abstract

The present invention refers to a plant and a process for uncoiling wire rod from wire-rod coils produced in rolling mills. In particular, the invention refers to an apparatus provided with a control system that makes it possible to considerably reduce, if not completely eliminate, the risk of accidents for the operators, thus achieving a degree of safety that meets the most demanding standards. The plant comprises the differential activation of devices that break down a safe area in order to guarantee a completely safe process of continuous uncoiling and manual operation.

Description

“PLANT AND PROCESS FOR UNCOILING WIRE-ROD COILS”

TECHNICAL FIELD OF INVENTION

[0001] The present invention refers to a plant and a process for uncoiling wire-rod coils coming from rolling plants. In particular, the invention refers to an apparatus provided with a control system that makes it possible to considerably reduce, if not completely eliminate the risk of accidents for the operators, thus achieving a degree of safety that meets the most demanding standards. The plant also makes it possible to standardize the processes and times of a particular step for uncoiling said wire-rod coils.

PRIOR ART

[0002] Plants for uncoiling wire-rod coils have been known for some time. Such wire-rod coils generally belong to two types: for the vertical uncoiling and the horizontal uncoiling of the wire-rod coils. The former requires a certain height because they include vertical towers along which the wire rods uncoil, while the latter requires a certain length because the support for the wire-rod coils extends horizontally.

[0003] With reference to the vertical systems, a set of equipment extends along a deployment line comprising an uncoiling tower, a pair of vertical supports for the wire-rod coils to be uncoiled and a welding machine to weld the tail end of a first coil to the head of a second wire rod coil. Some more complex systems include at least a pair of trolleys on which are loaded coils of wire rods with a horizontal axis by means of a bridge crane with a hoisting hook or by means of lift trucks. The trolleys are then moved parallel to each other near a pair of uncoiling supports or fingers, each provided with a reclinable support base and a trestle fastened to the same.

[0004] The loading of wire-rod coils on the supports requires the horizontal positioning of the same supports by reclining their base so as to allow the carriage to run under the trestle and make it possible to fit the coil on the trestle. At this point, once the fastening bands of a first coil have been removed manually by an operator, one or more turns of the coils are unwound from the head and from the tail. Subsequently, the support base of the first coil is lifted vertically to allow the head of the wire rod of the first coil to pass through an uncoiling tower, positioned in line between the two bases of said supports, to then be connected to a pulling unit, while the tail is prepared to be welded to the head of a second coil. It should be noted that all these operations also require the manual intervention of an operator.

[0005] The pulling unit is then connected in turn to a straightening or stretching unit, for example to obtain straight bars to cut to length as demanded by specific requirements or preferences or for other processes on the wire rods that then can also be reassembled in coils.

[0006] In this configuration can start the unrolling of the first coil.

[0007] Further, a welding machine alongside the uncoiling line is activated by an operator to weld the tail end of the first coil to the head of the second coil. Afterward, the welded portion is left free on the ground. Sometimes, for more complex and costly systems, said welded portion is manually inserted into gripping pliers positioned between said two supports and in front in the direction of their loading with the coils.

[0008] At this point, the second coil can also be lifted vertically in the uncoiling position.

[0009] When the first coil is completely unwound, the operator generally follows manually the welded portion, which is dragged by the drag unit to allow the change of coil so as to obtain a continuous unwinding of the wire rods from a plurality of coils. Alternatively, this portion is released by the gripping pliers as a result of the dragging force of said pulling unit.

[0010] In particular, the operations of loading the coils on the respective supports, the vertical movement of the support bases and the passage from the uncoiling of an unwound coil to the next one occur in a single area.

[0011] This area is usually bordered by a protection grid open on the coil reception side. Thus, the operator has free access to the inside of this area to carry out all the required operations so that there can be a change of the coils in a continuous mode. However, in this manner the operator is xposed to the so-called “residual” risks of accidents that can also be serious, considering the material being handled and by the forces of the relative equipment involved.

[0012] Optical systems have also been proposed to verify the presence of persons near said equipment, but they have only partially solved the risks of accidents and, in any case, have the purpose of stopping production, with the necessity of restarting the machines and consequently slowing down production.

[0013] Consequently, at present there is no system for controlling the processing steps that make it possible for to operator to work in complete safety while avoiding the necessity of stopping production.

SUMMARY OF THE INVENTION [0014] The purpose of the present invention is therefore the design of an uncoiling and welding of wire rods continuous mode from coils that guarantees the highest possible level of safety.

[0015] Thus, a first objective of the invention is a system for uncoiling and welding wire rods from coils in continuously mode comprising a set of safety devices activated so as to guarantee maximum safety during all the steps of operation.

[0016] A second objective is a system for continuously uncoiling and welding wire rods from coils comprising a set of safety devices that guarantee an automatic change of wirerod coils to allow an uncoiling of the same in a continuous mode.

[0017] A third objective is a process for uncoiling and welding wire-rod coils in a continuous mode comprising command and control steps that guarantee the greatest possible safety for the operator.

[0018] A further objective is a process for securing the change of wire-rod coils in an apparatus for the uncoiling and welding of wire rods in a continuous mode.

BRIEF DESCRIPTION OF THE FIGURES

[0019] Advantages, characteristics and other objectives of the invention will become evident from the description which follows, given by way of non-limitative example, with reference to the enclosed figures, wherein:

- figure 1 is a schematic overhead view of a system according to the present invention;

- figure 2 is a schematic overhead view of the plant of figure 1 in a first operating condition of loading a first wire-rod coil on a first support;

- figure 3 is a schematic overhead view of the plant of figure 1 in a second operating condition for the preparation of the first wire-rod coil for uncoiling;

- figure 4 is a schematic overhead view of figure 1 in a third operating condition for the preparation of the second wire-rod coil for uncoiling;

- figure 5 is a schematic overhead view of the plant of figure 1 in a fourth operating condition for welding the tail end of the first wire-rod coil to the head of the second wire rod coil;

- figure 6 is a schematic overhead view of the plant of figure 1 in a fifth operating condition for blocking the welding in holding pliers;

- figure 7 is a schematic overhead view of the plant of figure 1 in a sixth operating condition for changing the coil being uncoiled;

- figure 8 is a schematic overhead view of the plant of figure 1 in a seventh operating condition for loading a new coil. DETAILED DESCRIPTION OF THE INVENTION

[0020] With reference to figure 1 , the plant according to the invention is indicated in general with reference numeral 1 . The plant includes at least one first support 2 for a first coil W1 of a wire-rod and a second support 3 for a second wire-rod coil W2, a vertical uncoiling tower 4 in line between said first and second supports, a welding machine 5 to weld the tail end of the first wire-rod coil in the uncoiling position with the head of the second wire-rod oil in the uncoiling waiting position, a holding gripper 6 of the welded portion of said coils positioned between said two supports and upstream with respect to the direction of their loading with the coils, a drag unit 7 downstream of the uncoiling tower for the first dragging of the wire rod. Afterward, the next dragging takes place in the dragging block (not shown but completely conventional) provided with a drum (capstan) on which the wire rod is wound to allow the speedy advancement through the various subsequent processing machines (rolling stands, stretching panels, etc.).

[0021] An enclosure 8 encloses on three sides the first and second supports, 2 and 3, respectively, the uncoiling tower, the drag unit 7 and the holding gripper 6, leaving one side open for loading the wire-rod coils on the respective supports.

[0022] It should be noted that the enclosure is effectively the only safety system presently put into effect to avoid the risk of accidents to the operators during the unwinding operations from the wire-rod coils. In fact, the access to the uncoiling area which includes the above-mentioned devices is possible only from the front, that is, from the loading position of the wire-rod coils, W1 and W2, respectively, on the respective first and second supports 2 and 3, respectively or, in other words, upstream of the operations for preparing the coils to be uncoiled.

[0023] In particular, the enclosure 8 comprises four upright elements 80, 81 , 82, 83 between which are fastened protection metal grids (not shown in the figures) so as to surround a C-shaped space. Two front upright elements 80, 81 form the free ends of the C-shaped space and identify the entrance side for the wire-rod coils to be loaded on the respective supports.

[0024] The supports 2 and 3 are conventional structures adapted to be loaded with a corresponding coil W1 , W2 of wire rod to be uncoiled and include a trestle 20, 30 that supports the coil during the uncoiling and a base 21 , 31 for supporting said coil. The base 21 , 31 of each support is provided with a lifting mechanism on the opposite side with respect to the side of reception of the coil in the enclosure 8 so as to bend the trestle horizontally in the position of reception of the coil itself (see figure 2). [0025] The uncoiling tower 4 is a prior art structure that rises vertically between said two supports 2, 3 and includes a trestle 40 on top of which is installed a wire coil guide bell 41 followed by a return roller 42 for the downward movement of the wire coil toward the drag unit 7.

[0026] The drag unit 7 is also entirely conventional and includes a set of rolls, one of which is powered so as to operate on the wire rod to drag it to the pulling monobloc.

[0027] The holding gripper 6 is positioned at the limit of the area defined by the enclosure 8 and is preferably installed on a wall 60 that extends longitudinally to the loading direction of the wire-rod coils W1 , W2. The wall thus has a first end 61 bearing the gripping jaws of said gripper, which is turned toward the outside of the enclosure 8, and an opposite second end 62, which is thus turned toward the inside of the enclosure.

[0028] Advantageously, adjacent to the gripper 6 are positioned means 9 to delimit alternately the passage between the first support 2 of the first wire-rod coil W1 and the holding gripper 6, and between the second support 3 of the second coil W2 and said gripper. Preferably, said means are door hinged close to the holding gripper 6. According to a first variant embodiment, the door is hinged to said second end 62 so as to rotate alternately toward the first support 2 or the second support 3. This movement will be provided for example by an electric motor controlled by a relative command and control unit, or more preferably by a pneumatic cylinder, solenoid valve and position sensors, as will be explained later in detail. Alternatively, the means can be an optical photocell or laser system.

[0029] Moreover, advantageously, the plant 1 includes perimetric sensors adapted to identify a first safety zone A barred during the uncoiling of the first coil W1 from the first support 2, a second safety zone B barred during the uncoiling of the second coil W2 from the second support 3. Preferably, the perimetric sensors are optical sensors, such as for example photocells or lasers. In particular, two first perimetric sensors include two units 10A, 10B, one of which 10A is installed near the end of the enclosure 8, near a front upright element 80 and the other 10B on the wall 60 supporting the holding gripper 6. Similarly, two second perimetric sensors comprise two units 1 1 A, 1 1 B, one of which 1 1 A is installed near the end of the enclosure 8 in proximity of the other upright 81 and the other 1 1 B on the wall 60 on the opposite side with respect to the other unit of the first sensors.

[0030] Advantageously, then, the space between the enclosure 8 and each of the two supports first 2 and second 3 is barred to the passage of persons or things. This passage is controlled by passage boundary means 12, 13 that can be simply an enclosing section or additional perimetric sensors like those previously described. Therefore, they can be mechanical or optical means that delimit the passage.

[0031] A third perimetric sensor finally includes two optical units 14A, 14b, similar to the ones previously described, positioned in opposition to each other at a preset distance from the open side of the enclosure 8 so as to delimit a very large area that practically includes all the equipment and areas of movement of the wire rods, except for the welding machine 5, as indicated by the strip S consisting of white and black bands in figure 1 .

[0032] In fact, the welding machine 5 is positioned not only outside the enclosure 8 but also externally to the wire-rod coils loading path. Alternatively, it could also be fixed centrally, with variations in the spaces available and in the presence if any of the loading trolleys, but still outside the area defined by the enclosure 8 and by the strip S.

[0033] According to a preferred variant embodiment, the equipment 1 also includes a pair of grippers 15, 16 fixed to the ground. Preferably, these grippers are each fixed outside the enclosure 8, to the side of the path for loading the wire-rod coils and generally in line with a front upright 80, 81 . Said grippers have the purpose of temporarily locking the head end or tail end of coils before they are welded, in order to avoid accidental end sudden shifts or slips that could cause injuries to the operators.

[0034] In the case in which a system is provided for loading the wire-rod coils on the respective support by means of trolleys, two parallel loading paths 22, 23 are provided in front of the open side of the enclosure 8. Each path includes a track (not shown) for a trolley 24, 25 carrying a wire-rod coil having a horizontal axis. Once a coil is loaded on a respective trolley, for example by means of a bridge crane provided with a pick-up hook from a storage area for wire-rod coils, the trolley is moved in front of the respective uncoiling support 2, 3. Once the coil has been unloaded from the trolley and loaded on the support, as explained below, the trolley is removed from the enclosure 8 to be loaded with a new wire-rod coil.

[0035] According to the present invention, the procedure for uncoiling and welding wirerod coils in continuous mode is carried out by means of operating steps controlled in a safe manner to guarantee the safety of the operators. In fact, the process includes the steps of: a) delimiting a safe area for the operator, wherein b) at least two wire-rod coils are loaded on respective support; c) connecting the tail end of the first wire-rod coil with the head of a second wire- rod coil; d) uncoiling in sequence said coils by passing in a vertical uncoiling tower; wherein are advantageously performed the steps of: e) activating in devices for subdividing in a differential mode the safe area to define different areas, in which a first area A delimits the uncoiling area of the first coil, a second area B delimits the uncoiling change area between the first and the second coil, a third area C delimits the uncoiling area of the second coil; f) stopping the uncoiling process in all the steps of moving the wire rods when said devices detect a trespassing in one of said safe areas.

[0036] The step a) delimiting the operator safety area inside of which are carried out the automatic movements of wire-rod coils is achieved for example by building an enclosure as previously described. In place of the nets, it is possible to install panels of impactresistant material, such as reinforced metal or plastic, possibly transparent so that all the components of the devices at work can be seen at all times.

[0037] Step b), in which the coils are loaded onto the supports is generally carried out by means of lifting hook of a bridge crane that brings the coils directly to the supports placed horizontally in the receiving position. Alternatively, a trolley like the one previously described runs up to the supports so as to fit the coil directly on the support trellis (figure 2).

[0038] Normally, the coils reach the supports while still tied by metal or plastic bands. Thus, once they are fit onto the supports the operator can break these bands. In this manner, it is possible to unwind about two turns of the coil at the tail end to position it in the welding machine. At this point, the first support 2 of the first coil W1 is lifted in the vertical position and the head of the first coil W1 is fixed to the drag unit 7 after being passed through the uncoiling tower 4 in a completely conventional manner (figure 3). Preferably, the tail end of the first wire-rod coil is engaged in the corresponding holding gripper 15 to be blocked for the greater safety of the operator.

[0039] At this point, the first safety zone A, where the first coil is unwound, is activated. Thus, the means that delimit the passage 10A, 10B and 9 will be activated. Preferably, the above first perimetric sensors 10A, 10B are activated to detect any wire rod going past the passage before the first support 2 between a front upright 80 and the wall 60 of the gripper 6, and the door 9 closing the passage between the wall 69 and the gripper and the same second support 3 (figure 3).

[0040] In this condition, the uncoiling of the first wire-rod coil W1 can begin in complete safety. In addition, advantageously, the detection of the preset end quantity of wire rod is activated. This detection can be either mechanical or electronic, and this can be based on an optical reading of the quantity of remaining turns.

[0041] Subsequently, the second wire-rod coil W2 can also be loaded on the corresponding second support 3 and its tail end can be unwound for about two turns and left on the ground. The head, instead, is brought to the welding machine 5 (figure 4). In this manner, the operator is free to carry out the welding between the head of the second coil W2 and the tail end W1 of the first coil W1 (figure 5).

[0042] It should said that, preferably, the tail end of the second coil W2 can be reversibly blocked on the corresponding gripper 16 for greater safety of the operator during the handling involved for welding (figures 4 and 5).

[0043] Once welding is completed, the operator brings the welded portion to the holding gripper 6 (figure 6). It should be said that such movement take place in complete safety because the operator remains outside said first safety zone A.

[0044] Now, the operator gets out not only of the area bordered by the enclosure 8 but also of the area in front of it and moves again to the welding machine 5, thus also outside the coil loading path (figure 7).

[0045] In this condition, can also be activated the second safety zone B, which consists in marking out all the area that is also in front of the holding gripper 6 and preferably is marked on the ground with the above-mentioned band S with white and black strips of figure 7. Preferably, said zone is marked by the above third perimetric sensor 14A, 14B. [0046] With the activation of said zone, the coil change can be carried out safely. The change, in particular, can take place only after the system has verified the conditions of:

- welded wire rod blocked in the holding gripper;

- first and second support in the uncoiling position;

- confirmation by the operator that welding has been performed;

- attainment of an end quantity of wire rod in the firs coil W1 .

[0047] Once these conditions have been verified, the holding gripper 6 is automatically unlocked to release the welded portion and thus allow the completion of uncoiling the first coil and the start of the second coil. In particular, before the unlocking, when the end quantity of wire rod from the first coil is detected, the system slows down the uncoiling speed by acting on the rotation speed of the capstan or of the pull rollers of the corresponding unit. After the unlocking of the holding gripper, the uncoiling speed is again returned to the standard value. In addition, a system of verification of the end quantity of wire rod, also from the second coil W2, identical to the one of the above first coil W1 , is activated.

[0048] When the first coil W1 is completely unwound, it is possible to move on with loading on the first support 2 a new wire-rod coil to begin a new continuous uncoiling cycle. For this purpose, the third safety zone C is activated to prevent access to the area before the second support 3 of the second wire-rod coil W2 through the activation of the second perimetric sensor 1 1 A, 1 1 B that marks the space immediately in front of the upright 81 of the enclosure proximal to said second support and to the wall 60 that supports the holding gripper 6. The boundary between said wall 60 and the first support 2 of the first wire-rod coil W1 is also activated, preferably by moving the door 9 to block said passage. Finally, the prearrangement of the means that delimit the passage also prevents the passage between the first support 2 and the enclosure 8.

[0049] In this condition, the first support 2 can be inclined by positioning the trestle 20 horizontally and allow the new loading cycle to begin in absolute safety. Obviously, in this case, the new coil on the first support 2 will have to weld its head to the tail end of the second coil W2.

[0050] From the description just given it is evident that the uncoiling and wire-rod welding process in the continuous mode and the relative plant are capable of guaranteeing a safety system that is highly effective in preventing accidents to the operators.

[0051] Thus, a further objective of the present invention is a process for securing the safety of the change of wire-rod coils in a plant for uncoiling and welding wire rods in a continuous mode, comprising the steps of: a) identifying a safety area comprising a first support for a first wire-rod coil, a second support for a second wire-rod coil, an uncoiling tower interposed in line between said first and second support holding, a gripper of the welding portion between the tail end of the first coil and the head of the second coil, identifying devices for dividing said area into safety zones based on the steps of movement of the wire rods; b) activating in a differential mode said devices for dividing the safety area to define different zones, wherein a first zone delimits the uncoiling zone of the first coil, a second zone delimits the uncoiling change zone between the first and the second coil, a third zone delimits the uncoiling zone of the second coil; c) stopping the uncoiling process of all the steps of moving the wire rods should at least one of said devices detect a trespassing into one of said zones.

[0052] Preferably, the securing process is achieved in accordance with the steps previously described with reference to the continuous mode of uncoiling and welding the wire rods from wire-rod coils.

[0053] From what has been described to this point, it is evident that all the problems connected with the prior art uncoiling plants in terms of control and safety for the operators have been resolved. In fact, the division into differentiated safety zones controlled by delimitation devices have the great advantage of allowing the operator to access only non-dangerous zones in order to actuate all the operations necessary to allow the uncoiling in the continuous mode, that is, without interruptions of any kind.

[0054] Moreover, the systems of detecting trespasses in the safety areas are connected to each other and to a computer so as to verify at every instant every point of possible access to said areas. The activation of the systems, and therefore of the relative areas, takes place only after the verification of specific conditions that in turn if they are met allow the control of the devices.

[0055] It is thus evident that the plant and the relative process according to the present invention make it possible to achieve the highest standards demanded by the provisions in terms of safety.

[0056] Modifications to the plant and to the process of the invention can however be adopted by the technician skilled in the field, without however departing from the scope of patent protection of the following claims.

Claims

1. Plant (1 ) for continuously uncoiling and welding wire rods, comprising at least a first support (2) for a first wire-rod coil (W1 ) and a second support (3) for a second wirerod coil (W2), an uncoiling vertical tower (4) in line between said first and second supports, a welding machine (5) for welding the tail of the first wire-rod coil in the uncoiling position with the head of the second wire-rod coil in a position for waiting for the uncoiling, a holding pliers (6) for the welding portion of said coils positioned between said supports and before their loading side of the coils, a drag unit (7) downstream the uncoiling tower, a fencing (8) enclosing on three sides the first (2) and second (3) supports, the tower (4) and the holding pliers (6), characterized by further comprising means (9) for alternately delimiting the passage between the first support (2) and the pliers (6) and between the second support (3) and the pliers (6), means (12;13) for delimiting the passage between the fencing (8) and the first support (2) and between the fencing and the second support (3), perimeter sensors (10A,10B;1 1 A,1 1 B; 14A,14B) adapted to, also cooperating with said means (9), delimit a first safety zone (A) baring the passage during the uncoiling of the first coil (W1 ), a second safety zone (B) baring the passage during the change from the first (W1 ) to the second (W2) coils and a third safety zone (C) baring the passage during the uncoiling of the second coil (W2).

2. Plant according to claim 1 , further comprising two blocking pliers (15,16), one close to each of the first (2) and second (3) support of the wire-rod coils.

3. Plant according to claim 1 or 2, wherein said means (9) delimiting the passage are a door hinged close to said holding pliers (6).

4. Plant according to any one of claims 1 to 3, wherein said perimeter sensors comprise first (10A,10B) and second (1 1 A,11 B) optical sensors in turn each comprising two units (10A,10B;1 1 A,11 B) one (10A;1 1 A) mounted close to the end of the fencing (8) and close to a front upright (80 ;81 ), and the other (10B ; 11 B) mounted onto the wall (60) carrying the holding pliers (6), a third optical sensor (14A,14B) comprising two units a first unit (14A) and a second unit (14B) positioned opposite each another and at a preselected distance to the open side of the fencing (8).

5. Process for continuously uncoiling and welding wire-rods from coils, comprising the steps of: a) delimiting a safety area for the operator, wherein b) loading at least two wire-rod coils onto respective supports; c) welding the tail of the first wire-rod coil with the head of the second wire-rod coil; d) uncoiling one after the other said coils through an uncoiling vertical tower; characterized in that e) activating differentially devices for dividing the safety area into different zones, a first zone (A) delimiting an uncoiling zone of the first coil, a second zone (B) delimiting the zone for changing the uncoiling from the first to the second coil, a third zone (C) delimiting the zone for uncoiling the second coil; f) stopping all the steps of moving the wire-rods of the uncoiling process if said devices would detect a violation of one of said zones. Process according to claim 5, further comprising the steps of: activating first means for delimiting a first safety zone (A) for uncoiling the wirerod from the first coil; activating a drag unit to start the uncoiling of the first coil; activating a system for detecting a preselected amount of terminal wire-rod of the first coil; activating a welding machine to weld said tail with said head. Process according to claim 6, further comprising the steps of: blocking the tail of a first coil in a safety position after the loading of said coil onto a first support; blocking the head of a second coil in a safety position after the loading of said coil onto a secondo support; unblocking the tail of the first coil and the head of the second coil and positioning both in a welding machine. Process according to claim 7, further comprising the subsequent steps of: blocking the welded potion in a holding pliers; detecting the condition of: welded rod-wire hold on the holding pliers, first and second supports in uncoiling position, confirmation of welding and reaching of a terminal amount of wire-rod of the first coil; activating second means for delimiting a second safety zone (B) for uncoiling wire-rods from first and second coils; automatically unblocking the holding pliers at the end of the uncoiling of the first coil to allow the beginning of the uncoiling of the second coil from the second support. Process according to claim 8, further comprising the subsequent steps of: - activating delimiting means of a third safety zone (C) for uncoiling wire-rod from the second coil and disenabling the means for delimiting said second safety zone;

- activating a system for detecting a preselected amount of terminal wire-rod of the second coil;

- loading the first support with a new coil and repeating the steps according to claim 5-8, welding the head of the new coil with the tail of the second coil. Process for safety changing the wire-rod coil in a continuous uncoiling and welding plant for coil, comprising the steps of: a) identifying a safety area comprising a first support for a first wire-rod coil, a second support for a second wire-rod coil, an uncoiling tower positioned in line between said first and second support, a holding pliers for the welding portion of the tail of the first coil and of the head of the second coil, devices for dividing said area into safety zones depending on the moving steps of the wire-rods; b) differentially activating said devices for dividing said safety area for defining different zones, wherein a first zone delimits the uncoiling zone of the first coil, a second zone delimits the changing zone from the first and the second coils, a third zone delimits the uncoiling zone of the second coil; c) stopping all the moving steps of the uncoiling process of the coils if at least one of said devices would detect a violation of one of said zone.