Welding apparatus

Abstract

A welding apparatus includes a movable assembly (2) for at least one electrode through which current can flow to perform a welding process. The assembly (2) includes at least one cylinder (3) and at least one rod (4) rigidly supporting the electrode; the rod (4) is at least partially housed in the cylinder (3) and is coaxially movable along the longitudinal axis (A) of the cylinder (3) in alternating linear motion to press the electrode onto the portion to be welded with a corresponding welding force. The apparatus includes a device (6) for measuring the welding force, comprising: a plate (7) stably situated between the rod (4) and the electrode, having corresponding surfaces (7a, 7b) arranged perpendicular to the longitudinal axis (A); and a plurality of deformation sensors (8) housed in through slots (9) disposed in the plate (7) and distributed along an imaginary circumference (B) centered on the longitudinal axis (A).

Description

[0001] This invention relates to welding equipment.

[0002] As is well known, the term "resistance welding" identifies a large class of methods in which the materials to be welded are heated by resistance.

[0003] More precisely, the technique requires pressing at least one electrode onto the part to be welded, and then allowing current to flow through the electrode and these parts; due to the Joule effect, the current causes localized heating at the contact points between these parts and the electrode until the material involved liquefies and the subsequent welding occurs.

[0004] Similarly, it is known that in order to ensure a good weld, three parameters must be properly adjusted and kept under control: current intensity, welding time, and the force applied to each part during the welding process.

[0005] Although effective instruments are now known to be able to control and adjust the desired values ​​with sufficient reliability for the first two parameters mentioned above, none of the various solutions for controlling welding force to date are entirely satisfactory.

[0006] In fact, in some cases, pressure gauges and pressure regulating valves are used, employing "indirect" control because they can read and control a preset pressure loop value, which, multiplied by the cross-section of the cylinder pushing the electrode, should yield the desired force. However, the pressure gauge reads the pressure level at a point in the loop more or less away from the pusher cylinder, and therefore does not account for the cylinder's sliding friction and its negative weight, or the forces generated during welding that may counteract the pusher cylinder's action when operating "off-axis" (when the welding electrode is not coaxial with the cylinder).

[0007] Therefore, in practice, resistance welding machines using pressure gauges and regulating valves cannot produce force values ​​corresponding to the expected values: the factors listed above, which can vary unpredictably with each welding cycle, determine generally unacceptable oscillations and deviations, especially when the repeatability of the welding process is a critical factor.

[0008] Other resistance welding machines attempt to control welding forces using sensors capable of measuring deformation of the machine's own structure, which occurs during the welding phase due to the forces generated. Because of the disturbances and interference caused by the large currents involved, these sensors are placed quite far from the welding point. This results in such machines suffering from the same drawbacks described in the previous type of machine: the inability to properly account for force components dissipated by friction between the various parts of the cylinder's movable rod. Consequently, it is impossible to know the exact value of the force applied by the welding electrode to the layer of material to be welded.

[0009] The two methods described above are also subject to further inaccuracies, such as due to related temperature (which alters the system’s output by causing further changes in the force at the electrodes) and hysteresis. The measuring component is affected by hysteresis, which occurs when moving from a higher adjustment value to a lower value and vice versa.

[0010] For these reasons, and given the impossibility of obtaining precise information about the forces generated during welding, operators are occasionally forced to halt production in order to check the actual forces applied to the electrodes by inserting force measuring instruments (such as sample weighing sensors) between the electrodes and then make the necessary adjustments.

[0011] However, it should be considered that this check is usually performed when there is no current flowing at the electrodes, so the force value read and the subsequent new adjustment will not correspond to the working conditions that occur during welding. In addition, during welding, the current flow between the electrodes generates an electromagnetic force in the opposite direction to the applied force, and thus the force can be subtracted from the contact of the electrodes.

[0012] The objective of this invention is to solve the above-mentioned problems by providing a welding device that can perform optimal measurement of welding force (i.e., the force applied by the electrode to the part to be welded).

[0013] In this regard, the object of the present invention is to provide a welding apparatus capable of reading and correctly adjusting the welding force, regardless of the position of the electrode relative to the axis of the push rod cylinder.

[0014] Another object of the present invention is to provide a welding apparatus capable of performing optimal measurement of welding force without being affected by distortions caused by electromagnetic forces and other disturbances generated during the welding process.

[0015] Another object of the present invention is to provide a welding device that ensures high operational reliability.

[0016] Another object of the present invention is to provide a welding apparatus that employs a technology and structural architecture that is an alternative to conventional equipment.

[0017] Another object of the present invention is to provide a welding apparatus that can be easily implemented using readily available components and materials.

[0018] Another object of the present invention is to provide a welding device that is low in cost and safe in application.

[0019] As will become more apparent below, this objective, along with these and other objectives, is achieved by the welding apparatus according to claim 1.

[0020] Further features and advantages of the invention will become more apparent from the following detailed description of preferred, but not exclusive, embodiments of the welding apparatus according to the invention, which are illustrated by way of non-limiting example in the accompanying drawings, in which:

[0021] Figure 1 This is a right-side front perspective view of the welding equipment according to the present invention;

[0022] Figure 2 yes Figure 1 Left front perspective view of a sub-assembly of a welding equipment, which includes a cylinder and a measuring device;

[0023] Figure 3 yes Figure 2 The front view of the child component;

[0024] Figure 4 It is intercepted along line IV-IV. Figure 3 Cross-sectional view.

[0025] Figure 5 yes Figure 2 The right-side exploded front perspective of the child components;

[0026] Figures 6 to 12 A measuring device according to a first embodiment of the invention is shown, more specifically, without a deformation sensor:

[0027] Figure 6 This is an exploded perspective view taken from above the measuring device;

[0028] Figure 7 From Figure 6 A perspective view taken from above the measuring device;

[0029] Figure 8 From Figure 6 A perspective view of the measuring device from below the plate;

[0030] Figure 9 From Figure 6 A view from below the measuring device's panel;

[0031] Figure 10 It was intercepted along line XX. Figure 9 Cross-sectional view;

[0032] Figure 11 It is intercepted along line XI-XI. Figure 9 Cross-sectional view;

[0033] Figure 12 yes Figure 11 Significantly magnified details;

[0034] Figures 13 to 17 A measuring device according to a second embodiment of the present invention is shown, more specifically:

[0035] Figure 13 This is an exploded perspective view taken from above the measuring device;

[0036] Figure 14 From Figure 13 A perspective view of the measuring device from below the plate;

[0037] Figure 15 From Figure 14 The view from below the panel;

[0038] Figure 16 It is intercepted along line XVI-XVI. Figure 15 Cross-sectional view;

[0039] Figure 17 It is a cut along a plane perpendicular to the longitudinal axis. Figure 14 A cross-sectional view of the plate.

[0040] Referring specifically to the accompanying drawings, reference numeral 1 generally indicates a welding apparatus according to the invention, comprising a moving assembly 2 for at least one electrode (not shown in the drawings, but known in any case). Current can flow through the electrode to perform welding on two or more portions to be welded together, the portions being arranged along the moving trajectory (alternating translation) of the electrode.

[0041] More specifically, component 2 includes at least one cylinder 3 (typically pneumatic, hydraulic, or hydrohydraulic) and at least one rod 4 that rigidly supports the electrode (indirectly, as will be seen): more specifically, rod 4 is at least partially housed in cylinder 3 and moves coaxially along the longitudinal axis A of cylinder 3 in alternating linear movements to press the electrode onto the portion to be welded with a corresponding welding force. Welding force is generated during the stroke of rod 4 being withdrawn (partially or entirely) from cylinder 3, according to methods known per se, when the electrode supported by rod 4 comes into contact with the portions. When welding is complete, rod 4 can then be re-entered into cylinder 3 (as part of its alternating linear movements) to facilitate removal of the weld and preparation of device 1 for another processing step.

[0042] More precisely, according to methods known per se, the apparatus 1 typically defines a support surface 5 on which the parts to be welded (e.g., a pair of metal plates) can be placed, and the support surface is effectively arranged along the travel of the electrode (or at the end of the travel) such that the electrode can press the parts onto the surface 5 and weld them by the flow of current.

[0043] At surface 5, the second electrode can function (from the opposite side), or in any case, the portion that allows current flow can itself be the second electrode.

[0044] In any case, the technology and methods themselves are known to date, so there is no need to discuss them further.

[0045] It should also be noted that, in a preferred application, the device 1 is configured to perform resistance welding (in various known types), wherein the part to be welded is resistively heated while the electrodes press it onto the surface 5 (or more generally, the part to be welded is clamped between the corresponding electrodes).

[0046] In any case, the device 1 according to the invention provides the possibility of being used to perform another type of welding process.

[0047] According to the invention, the device 1 includes a measuring device 6 for welding force: more specifically, as will be better explained below, the device 6 measures the value of the force exerted by the rod 4 and the corresponding electrode on the part to be welded during the welding process.

[0048] Device 6 includes a plate 7 stably positioned between rod 4 and electrode, having corresponding surfaces 7a and 7b arranged perpendicular to longitudinal axis A. It can be visually seen, even from the accompanying drawings, that surfaces 7a and 7b of plate 7 are identified by two larger dimensions of plate 7 (a third dimension, thickness or height, thus aligned / parallel to longitudinal axis A).

[0049] Plate 7 is preferably, but not exclusively, made of a non-magnetic metallic material, and its shape is substantially rectangular (as shown in the attached figure), square, circular, or similar.

[0050] In addition, device 6 includes multiple deformation sensors 8 (for simplicity, only in...) Figure 13 (As shown in the figure), it is housed in a through groove 9, which is in turn disposed in a plate 7 and distributed along an imaginary circumference B (when viewed from above or below the plate 7), the imaginary circumference B being centered on the longitudinal axis A (its outline is as shown in the figure). Figure 9 , Figure 15 and Figure 17 (As shown).

[0051] Sensor 8 measures the deformation of plate 7, which is positioned in direct contact with the electrode or the element supporting the electrode (as will become clearer below) and / or, in any case, in the immediate vicinity of the weld point, deforming (only) through the generated welding force. Therefore, the readings obtained by sensor 8 make it possible to obtain optimal measurements of the welding force without any interference or distortion affecting or altering the read values. Thus, from this point onward, the predetermined objective is achieved.

[0052] Specifically, according to two particular practical embodiments, plate 7 has four (as in...) Figures 6-12 In the solution) or eight ( Figures 13-17 The plate 7 has multiple slots 9, which in both cases have the same dimensions and are regularly distributed along an imaginary circumference B. The circumferential range of the slots 9 (i.e., measured along the imaginary circumference B) leaves a small space (e.g., between five and ten millimeters) between the end of one slot 9 and the beginning of the next. In any case, the remaining sections of the plate 7 between the end of one slot 9 and the beginning of the next slot 9 can be conveniently calculated with respect to the type of material used, the maximum load on the cylinder 3, and more generally, the minimum and maximum expected deformations.

[0053] In any case, it should be noted that the scope of protection claimed herein includes plates 7 with any number of slots 9, which do not need to be identical to each other and / or need not be distributed in a regular manner around an imaginary circumference B.

[0054] In the preferred embodiment, for the purpose of providing a non-limiting example of the application of the invention, it is also Figure 13 As shown, each sensor 8 is a resistance strain gauge, which includes a rigidly deformable element applied to a layered support 8a. The support 8a is then rigidly applied to one of the two end walls 9a of the corresponding groove 9, which are positioned relative to each other along an imaginary circumference B.

[0055] It is known that, as the object (plate 7) subjected to the support 8a deforms due to the stress, the deformable element also deforms, thereby changing the resistance that impedes the flow of current: this change is properly measured, making it possible to find the value of the deformation and thus the value of the force applied to the plate 7.

[0056] In a preferred embodiment where more accurate welding force measurement is possible, and further reference to the appendix... Figure 13Each slot 9 (regardless of their number) accommodates a pair of strain gauges (or even a pair of other sensors 8), which apply strain to the corresponding end wall 9a (or are arranged at another point in the slot 9). Depending on the specific requirements, it is conceivable to have two sensors 8 in the same slot 9 adhered at the same axial height (i.e., measured along the longitudinal axis A) or at different heights.

[0057] The presence of two or more sensors 8 (whether strain gauges or other types of sensors, housed in the same or even different slots 9) makes it possible to automatically compensate for the final result and make it an absolute value independent of the location where the welding force is applied.

[0058] Usefully, each surface 7a, 7b of plate 7 has a receiving groove 10 for electrical connection (wire, etc.) of sensor 8 between each pair of adjacent slots 9, and each groove 10 is effectively arranged along an imaginary circumference B.

[0059] For simplicity, electrical connections are not shown in the accompanying drawings (except for schematically illustrating connections to...). Figure 13 The recesses (outside the terminals of the sensors 8) are known in themselves and are therefore readily intuitive to those skilled in the art. The recesses 10 (preferably, but not exclusively, having a semi-circular bottom or otherwise a circular bottom) effectively define a recess in which the electrical connections between the sensors 8 are arranged without the risk that these electrical connections might be crushed or damaged when the surfaces 7a, 7b adhere to surrounding components of the device 1 (as will be better explained below or as...). Figure 1 or Figure 4 (Can be clearly seen).

[0060] To be precise, in order to ensure optimal protection of the sensor 8 (and corresponding electrical connection) used to measure deformation and thus force, the groove 9 and the recess 10 are advantageously closed by corresponding annular protective plugs 11, which are applied to the corresponding surfaces 7a, 7b of the plate 7 and are arranged along the imaginary circumference B.

[0061] The annular blockage 11 prevents dust, debris and other kinds of impurities from entering the plate 7, thereby maintaining the integrity and functionality of the components housed in the slots 9 and recesses 10.

[0062] Conveniently, the welding equipment 1 includes an electronic control and management unit configured to actuate the moving component 2 and adjust the intensity of the welding force. This unit includes instructions for adjusting the intensity of the welding force based on data collected by a sensor 8, which is controlled by the unit itself for this purpose.

[0063] The electronic unit can be of any type, and for example, it can be an electronic controller mounted on device 1; however, the possibility of using different types of electronic units (mounted or not mounted on device 1) is not excluded, and thus the electronic unit can be any hardware platform, reprogrammable or otherwise, which in any case can act on the strength of the welding force and / or the stroke of rod 4.

[0064] More specifically, the electronic unit is configured to compare the actual welding force generated during a defined welding cycle (process) (typically lasting a few tenths of a second) with a preset force value. In the event of a deviation, intervention can initially be made immediately during that cycle, but more commonly (given the very short duration of a single cycle), the detection of the deviation ensures that the unit automatically corrects itself in the next cycle to compensate for the deviation. From a practical standpoint, to set, control, and modify the welding force, the electronic unit can, for example, act on the loop pressure (via a proportional servo valve) of the circuit responsible for the movement of lever 4, modifying the loop pressure to achieve and maintain the desired load.

[0065] Advantageously, the measuring device 6 includes a connection cable 12 for connecting the sensors 8 to a signal converter so as to transmit the data collected by these sensors 8 to an electronic control and management unit. Thus, in other words, during the application of the load generated by component 2, the deformation of the sensors 8 is converted into an electrical signal, which is then processed by the electronic unit, for example, capable of returning the applied load, denoted as daN.

[0066] The connecting cable 12 is at least partially housed in the track 13, which is arranged along one side of the plate 7 and positioned to communicate directly or indirectly with the slot 9 (where the sensor 8 is housed).

[0067] Similar to the groove 10, the track 13 makes it possible to have an actual receiving portion in the plate 7 for connecting the cable 12 without it protruding from the body of the plate 7 itself, and thus keeping it protected.

[0068] Specifically, to ensure better protection, track 13 is preferably closed by insert 14 (metal or made of another material), which is applied to the corresponding side of plate 7 and perforated to allow connecting cable 12 to exit (e.g. from) Figure 7 (It can be clearly seen in the middle).

[0069] Usefully, plate 7 has a lateral recess 15, which is configured to communicate directly or indirectly with slot 9 and to house electronic components associated with sensors 8 and their external electrical connection terminals.

[0070] For example, such as Figure 17As shown, there is a possibility that the recess 15 is connected to one of the grooves 9 through the first cylindrical hole 16 (therefore, due to the groove 10, the recess 15 is also connected to the other grooves 9).

[0071] In this way, all the sensors 8 can be interconnected with what is housed in the recess 15. Furthermore, the second cylindrical hole 17 connects the recess 15 and the track 13 to complete the connection between various components, all of which are effectively held within the body of the plate 7.

[0072] It should be noted that the recess 15 can also be closed by a contoured plug 15a for the same protective purpose as the previously described annular plug 11 and insert 14.

[0073] In a preferred embodiment that does not limit the application of the invention under any circumstances, the first surface 7a of the plate 7 is stably anchored to the free end of the rod 4, while the second surface 7b of the plate 7, opposite to the first surface 7a, is stably anchored to the support block 18 of the electrode.

[0074] More specifically, plate 7 is integrally formed with rod 4 by a series of first screws 19, which are inserted into corresponding first holes 20 provided along plate 7 (uniformly distributed around longitudinal axis A). The contact area between rod 4 and plate 7 effectively corresponds to the outer diameter of rod 4 (except for the additional center hole 21 for the cable outlet): in this way, the connection between rod 4 and plate 7 created by tightening the first screws 19 does not produce any deformation on plate 7.

[0075] Similarly, and further referring to a preferred but not exclusive embodiment, on the opposite side in contact with the rod 4, thus along the second surface 7b, there exists a shallow circular recess 22, coaxial with the longitudinal axis A, and its dimensions are wider than the diameter of the rod 4. In this way, the mounting surface of the plate 7 on the support block 18 can correspond to the entire second surface 7b of the plate 7 minus the surface of the shallow recess 22, in the region outside the diameter of the rod 4.

[0076] It should also be noted that in the portion of plate 7 between the end of one slot 9 and the beginning of the next slot 9 (along the imaginary circumference B), there is an axial “continuity” (no gaps or cavities) between rod 4 and block 18: these portions are preferably arranged along the primary working direction and the secondary working direction.

[0077] The welding equipment according to the present invention is operated as follows.

[0078] As can be seen, the electrode support block 18 (or the electrode in any case) is anchored to the rod 4, which in turn can make alternating linear movements along the longitudinal axis A. In this way, the device 1 acts as a press, and when the electrode reaches or moves toward the limit position of maximum withdrawal from the cylinder 3, the electrode is under pressure, pressing against the two portions previously arranged on the surface 5, so that welding of these portions can be performed (preferably, but not exclusively, resistance welding, depending on various techniques).

[0079] The methods and components involved in the welding are of conventional type; the special feature of the present invention is the use and structure / configuration of the measuring device 6, which, as can be seen, is located between the free end of the rod 4 and the electrode (between the rod 4 and the block 18).

[0080] The device 6 includes a plate 7, which together with the groove 9 internally defines a receiving portion for a sensor 8, which is used to measure the deformation that will occur on the plate 7 when the rod 4 pushes the electrode onto the part to be welded and applies the necessary welding force.

[0081] Since plate 7 is placed in direct contact with or in the immediate vicinity of the welding point (electrode or electrode support block 18), the deformation of plate 7 read by sensor 8 is due to the deformation caused by the welding force applied to each part, and this reading is unaffected by disturbances that would affect readings taken by sensors that are more or less away from the welding point according to conventional methods. The sliding friction of rod 4, the negative effects of this sliding friction, dissipation and other reactions that may occur during welding, and the effects of dissipation and other reactions that may occur during welding at a distance from the welding point do not affect the reading of sensor 8 in any way; sensor 8 remains absolutely accurate and precise.

[0082] The slot 9 provides shielding and protection for the sensor 8 against any disturbances, forces, or interference caused by the high-intensity current flowing through the electrodes during welding, and makes the sensor 8 insensitive to these disturbances. For this reason, the present invention allows the sensor 8 to be positioned in the immediate vicinity of the weld point and to read the force in real time during the processing.

[0083] Therefore, it has been seen that the device 1 according to the invention fully achieves the set objectives because the invention is able to perform optimal measurement of welding force (i.e., the force applied to the part to be welded) during actual welding, thereby eliminating any process uncertainty.

[0084] Because plate 7 is in contact with the electrode and / or the corresponding block 18, and sensors 8 are arranged along the longitudinal axis A, the readings taken by these sensors are absolutely accurate and correct even when the electrode is not aligned with the longitudinal axis A (as occurs in some applications). Therefore, device 1 is able to perform welding force readings and correct adjustments regardless of the position of the electrode relative to the longitudinal axis A of cylinder 3. This represents an undeniable and further very practical advantage achieved by the invention, as it is well known that one of the main problems associated with the use of pressure-sensing elements (which are sometimes used in conventional equipment to detect welding force) is actually related to the fact that such systems are sensitive to the position of the electrode closure point relative to the position of the force sensor employed, due to their design.

[0085] Furthermore, it can be seen that the plate 7 with groove 10, track 13 and recess 15 (as well as cylindrical holes 16, 17) allows all the components required for the operation and functional connection of the sensor 8 to be accommodated, shielded and protected (also by means of plugs 11, 15a and insert 14), which again makes the measurement performed by the device 6 reliable and accurate (because each part of it is insensitive to distortion and interference).

[0086] For example, through an interface associated with the electronic unit, the operator can program various parameters associated with performing the welding cycle, such as: the direct force applied to the electrode during the welding phase (in daN), the time in seconds or milliseconds for performing the approach to the upper electrode (the electrode supported by rod 4), the current value required for the welding effect (in amperes), and the time in seconds or milliseconds for performing the welding.

[0087] To reiterate, the device 1 according to the invention does not require information about the position of the electrodes relative to the longitudinal axis A, as it has been seen that this does not affect the readings of the device 6.

[0088] For purely illustrative purposes (and certainly not to limit the application of the invention), possible welding cycles may include the following values: welding force equal to 500 daN, approach time equal to 0.2 seconds, current equal to 40,000 A, and welding time equal to 0.3 seconds.

[0089] At this point, when starting the cycle in sequence, the following steps are performed: the rod 4 supporting the upper electrode is lowered within a set proximity time; the pressure required for the cylinder 3 to apply the set welding force is determined by the electronic unit through feedback to the servo valve; and welding is started by sending current to the electrode within the programmed time length and intensity when the device 6 detects that the force applied to the electrode corresponds to the desired value.

[0090] Therefore, the present invention enables direct and independent control and management of each individual step of each individual welding cycle.

[0091] This represents another advantage of the invention, where, in known solutions, the operator typically has to set time values ​​that include all cyclic steps, resulting in different welding effects between cycles (e.g., less time used in the electrode approach step leads to a longer time in the next step of the cycle, etc.), thus creating considerable production variability.

[0092] Finally, it should be noted that any deviation between the obtained reading and the preset force (e.g., due to misalignment between the longitudinal axis A and the electrode and / or due to electromagnetic effects generated during welding) will be automatically compensated and corrected by the electronic unit in the next cycle.

[0093] This invention is thus conceived to accommodate many modifications and variations, all of which are within the scope of the appended claims. Furthermore, all details can be replaced by other technically equivalent elements.

[0094] In the illustrated embodiments, the various features shown in relation to the specific examples may be interchanged with other different features present in other embodiments in reality.

[0095] In practice, the materials and dimensions used can be arbitrary, depending on the requirements and existing technology.

[0096] This application claims priority to Italian Patent Application No. 102020000018202, the disclosure of which is incorporated herein by reference.

[0097] Where a technical feature mentioned in any claim is followed by a reference numeral, the sole purpose of including such reference numerals is to increase the comprehensibility of the claim, and therefore, such reference numerals do not have any limiting effect on the interpretation of each element identified by way of example by such reference numerals.

Claims

1. A welding apparatus comprising a moving assembly (2) for at least one electrode through which an electric current can flow for a welding process, said assembly (2) comprising at least one cylinder (3) and at least one stem (4) rigidly supporting said electrode, said stem (4) being at least partially housed in said cylinder (3) and being coaxially movable with an alternating rectilinear motion along a longitudinal axis (A) of said cylinder (3) so as to press said at least one electrode against a portion to be welded with a corresponding welding force, characterized in that, The welding apparatus comprises a device (6) for measuring the welding force, said device comprising a plate (7) stably interposed between the rod (4) and the at least one electrode, having respective faces (7a, 7b) arranged at right angles to the longitudinal axis (A), and a plurality of deformation sensors (8) housed in through slots (9) provided in the plate (7) and distributed along an imaginary circumference (B) centred on the longitudinal axis (A), and each of the sensors (8) is a resistance strain gauge, said strain gauge comprising a deformable element rigidly applied to a laminar support (8a) in turn rigidly applied to one of the two end walls (9a) of the respective slot (9) opposite each other along the imaginary circumference (B).

2. The welding apparatus of claim 1, wherein, The plate (7) has a number of slots (9) equal to four or eight, having mutually identical dimensions and regularly distributed along the imaginary circumference (B).

3. The welding apparatus of claim 1, wherein, Each of the slots (9) houses a pair of the strain gauges applied to the respective end wall (9a).

4. The welding apparatus of any one of claims 1-3, wherein, Each face (7a, 7b) of the plate (7) has, between each pair of adjacent slots (9), a housing recess (10) for the electrical connection of the sensors (8), arranged along the imaginary circumference (B).

5. The welding apparatus of claim 4, wherein, The slots (9) and the recesses (10) are closed by respective annular protective plugs (11) applied on the corresponding faces (7a, 7b) of the plate (7) and arranged along the imaginary circumference (B).

6. The welding apparatus of any one of claims 1-5, wherein, The welding apparatus comprises an electronic control and management unit configured for actuating the movement assembly (2) and adjusting the intensity of the welding force, said unit comprising instructions for adjusting the intensity of the welding force as a function of the data collected by the sensors (8), controlled by the unit.

7. The welding apparatus of claim 6, wherein, The device (6) comprises connection cables (12) for connecting the sensors (8) to signal converters for transmitting the data collected by the sensors (8) to the electronic control and management unit, said connection cables (12) being at least partially housed in a track (13) provided along one side of the plate (7) and arranged in direct or indirect communication with the slots (9).

8. The welding apparatus of any one of claims 1-7, wherein, The plate (7) has lateral pockets (15) arranged in direct or indirect communication with the slots (9) and housing electronic components associated with the sensors (8) and the external electrical connection terminals of the sensors (8).

9. The welding apparatus of any one of claims 1-8, wherein, A first face (7a) of the plate (7) is stably anchored to the free end of the rod (4), and a second face (7b) of the plate (7), opposite the first face (7a), is stably anchored to a support block (18) of the at least one electrode.

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