The present invention concerns a longitudinal friction welding (FSW) machine, and a related longitudinal friction welding procedure.

The invention falls within the technical field of machines and technologies for welding welded joints of hollow metal profiles, in particular within the technical field of longitudinal welding technologies for pipes and other shaped profiles.

Friction welding is a welding procedure that makes it possible to obtain the union between two metal elements, by exploiting the heat generated by the friction of a tool placed in contact with the elements themselves.

The heat generated by the tool is sufficient to plasticise the quantity of metal elements located in close proximity of their interface.

This type of welding is particularly suitable forthose materials that suffer from the high thermal shocks resulting from traditional fusion welding techniques, such as alloys of aluminium, copper, and magnesium, as well as polymeric materials.

Currently, known friction longitudinal welding machines include a welding head, on which a tool equipped with a conical tip and a shoulder is mounted.

The tool is positioned at the interface between the two materials to be welded so that the tip penetrates the space that separates them, while the shoulder is positioned in contact with the surfaces of the two materials adjacent to the interface itself.

The tool moves along the interface mechanically mixing the two materials while they are in the plastic state, and in addition gives a shape to the weld bead by applying pressure during its movement.

Before starting its movement, the tool is kept in contact with the interface in the initial position for a certain time, in order to transfer sufficient heat to soften the adjacent region of material, and then it moves at a constant and well-defined speed, depending on the nature and size of the material to be welded.

The welding of metal pipes, and more generally of profiles having a radial or axial symmetry, presents intrinsic issues due to the geometry of the pieces and to the movements that the welding head must perform to obtain a proper result.

Usually, machines for friction welding of pipes or hollow elements require that the pipe itself and the piece to be connected are fastened to an element, for example by means of bolted flanges, jaws or other known systems. In some cases, this system hinders the welding area and slows down the operations for inserting and removing the elements to be welded.

In particular, further issues are encountered as the use of flanges or other known fastening systems is not immediate, given the lengthy duration required for assembling and dismantling the flanges and the respective counter-flanges and their bolts.

Another drawback of the known technique is that, generally, welding machines of this type include a single welding tool which, in the case of elements of considerable size, would take a long time to complete the entire welding.

Currently known welding processes (such as MIG/WIG/TIG) have some drawbacks compared to longitudinal friction welding (FSW).

In particular, these drawbacks are:

- higher risk of having welding defects or irregularities;

- lower welding speed;

- greater energy consumption for the same length of the weld bead;

- need to use filler materials and process gases;

- welding a higher "wall thickness" requires more than one weld bead.

Furthermore, it is possible that, due to the stresses to which the pipe is subjected during the welding process, it remains stuck due to interference on the supports, causing further delays due to interventions by technical personnel to remove the pipe from its seat.

To date, according to the prior art, friction welding machines do not tolerate the presence of a GAP at the ends of the pipe or profile to be welded. Furthermore, the FSW process may require a support from the opposite side of the tool.

In particular, the size of the support or welding bar are in some cases very limited due to the products to be obtained.

For this reason, if the pipe to be welded is small, the support will be equally small and if the support has a certain length it could have deflection problems caused by the force of the welding tool and the clamping system.

High deflection negatively affects the reliability of the longitudinal welding process.

In particular, an objective of the invention is to provide a machine and procedure for friction welding which solve the above mentioned drawbacks. In particular, an objective of the invention is to provide a machine and procedure for friction welding that make it possible to adjust the welding progress.

Furthermore, it is the aim of the present invention to provide a friction welding machine, and a related procedure, which are more versatile and flexible than the prior art.

Another aim of the invention is to provide a friction welding machine and a related procedure that allow welding to be carried out on hollow metal profiles with different diameters and sizes.

Another aim of the invention is to provide a friction welding machine and a related procedure which do not present limitations due to the support size.

Finally, a final aim of the present invention is to provide a friction welding machine and a related procedure which allow welding operations even with two or more welding tools.

These and other aims are achieved by a friction welding machine and a related procedure according to the attached independent claims.

Further detailed technical characteristics are specified in the attached dependent claims.

The present invention will now be described, by way of non-limiting example, according to some of its preferred embodiments, and using the attached figures, wherein:

- Figure 1 is a perspective view of the friction welding machine in its closed configuration, according to the invention;

- Figure 2 is a further perspective view of the machine in Figure 1 in its open configuration;

- Figure 3 is a further perspective view of the machine in Figure 1 in its open configuration and with the insertion of an element to be welded;

- Figures 4A-4C illustrate the locking device and the clamping elements for the element to be welded, according to the invention;

- Figure 5 illustrates a detail of the element to be welded 8 kept open, according to its elastic limit, to allow the insertion of the welding tip, according to the invention;

- Figures 6A-6B illustrate the connection between the interlock and the welding bar via the pneumatically operated connector of the longitudinal friction welding machine, according to the invention; - Figures 7A-7B illustrate the removable and adjustable abutment of the longitudinal friction welding machine, according to the invention;

- Figures 8A-8C illustrate the welding tool and its position relative to the element to be welded of the longitudinal friction welding machine, according to the invention;

- Figure 9 is a further illustration of the welding tool, according to the invention;

- Figures 10A-10C are schematic representations of the devices and additional support elements of the longitudinal friction welding machine, according to the invention;

- Figure 11 shows the welding tip connected to the welding tool of the longitudinal friction welding machine, according to the invention.

Referring to Figure 1 , a preferred embodiment of the friction welding machine according to the invention is represented.

In particular, this machine carries out longitudinal friction welding operations on curved or bent metal sheets of various types of elements and profiles to be welded.

Referring to the above figures, the friction welding machine is indicated with the numerical reference 100 and, in its first embodiment, according to the present invention, includes a frame or mount 5, a plurality of locking or clamping devices 3, an interlock 1 , a welding bar 6 and at least one welding unit 2.

Advantageously, in preferred but non-limiting embodiments, such locking or clamping devices 3 are two.

In particular, the frame 5 serves to sustain and support the entire machine 100 and its components and is fastened to the ground with fastening elements that vary depending on use.

Advantageously, the frame 5 is configured to raise and/or lower to modify its height and the welding working height.

In particular, although the frame 5 can rise and lower, the welding bar 6 always remains connected to the frame 5 itself and is unable to perform any movement.

The interlock 1 is connected to the frame 5 and varies from a working or closed configuration (Figure 1 ) to a rest or open configuration (Figure 2).

This interlock serves to support the welding bar 6 when the machine 100 is in the working configuration and furthermore, the interlock 1 , opening and moving to the rest configuration, allows the insertion or removal of the element to be welded 8, still to be welded or already welded.

Advantageously, the interlock 1 is connected to the frame 5 by means of an actuator or a cylinder which, by modifying its extension, allows the movement of interlock 1 from the closed configuration to the open configuration and vice versa.

In detail, the interlock 1 is connected to the frame 5 by means of hinges which allow the rotation of the interlock 1 itself on the frame 5.

The locking devices 3 comprise a pair of bars arranged on opposite sides and fastened to the frame 5 with fastening elements at a defined height.

Advantageously, the bars of the locking devices 3 include a plurality of clamping elements 10 which can be adjusted horizontally and vertically to allow welding operations on different types of elements.

In particular, these clamping elements 10 serve to maintain the element to be welded 8 in position during the welding operations of the machine 100.

Furthermore, the clamping elements 10 serve to minimise the deflection of the welding bar 6, by reducing the force applied thereon.

In more detail, each clamping element 10 is operated by an element inside it which allows the application of a certain clamping force.

In particular, advantageously, this element can be an electric motor, an electromechanical system, a pneumatic cylinder, a hydraulic cylinder, etc. , depending on conditions.

The clamping elements 10 can act in two different modes:

- they can all together exert a clamping force, or

- they can individually exert a greater clamping force, so as to exert a high force only in the welding area, limiting the deflection of the welding bar 6 as much as possible.

Advantageously, thanks to the independence of each individual clamping element 10, it is possible to obtain a greater clamping force in the area where welding is being carried out and a lesser force in the other areas. The independence of the clamping elements 10 allows the clamping force to be locally increased.

This advantage makes it possible to minimise the deflection and deformation of the bar 6, allowing its size to be reduced or increased to obtain a wider range of sizes and variations. Placed between the locking devices 3 there is the welding bar 6 adapted to support the elements to be welded 8.

This welding bar 6 is connected at a first end to the frame 5 and, at a second end, it is designed to house and connect with the interlock 1 when the machine 100 is in a closed configuration.

The interlock 1 and the frame 5 act as support elements of the welding bar 6 to reduce its deflection and to support the welding bar 6 itself during welding operations.

The welding bar 6 is able to accommodate different types and shapes of elements to be welded 8 made up of curved or bent metal sheets with a hollow profile.

Advantageously, to assist the interlock 1 and the frame 5, the machine 100 can include one or more pairs of mobile support elements 12, one connected to the frame 5 (external element) and the other to the welding bar 6 (internal element), longitudinally movable on the side opposite the welding area and the welding unit 2.

In particular, the elements 12 are vertically adjustable, linearly movable and are arranged, the first one inside the element to be welded 8 and the second one externally to it.

In detail, the elements 12 are separated only by the wall of the element to be welded 8.

These support devices 12 are adjustable and orientable in the vertical direction and are made up of an internal part and an external part.

This adjustment makes it possible to modify the distance of the support elements 12 from the welding unit 2 and from the welding area itself.

The support devices 12 serve to support the welding bar 6 during the welding operations.

Advantageously, the support elements 12 can also be used to support the element to be welded during the steps of insertion and removal from the welding bar.

Optionally, the aforementioned support elements 12 can include wheels or rollers to facilitate their movement.

In detail, the element to be welded 8 moves in the same longitudinal direction as the welding, allowing its removal when the elements 12 reach the end of their stroke in the linear guide. Advantageously, the support provided by the interlock 1 , the frame 5 and the elements 12 makes it possible to reduce the deflection of the welding bar 6 caused by the welding force, the clamping force and the weight of the bar 6 itself, also allowing the welding bar 6 to not be bent during the opening of the interlock 1 and allowing the frame 5 to not be overloaded.

The welding direction and the movement of the element to be welded 8 are always preferably parallel to the welding bar 6 and the ground.

The welding unit 2 is connected to the frame 5, above the welding bar 6 and the locking device 3.

Advantageously, the welding unit 2 is connected to a device which allows its longitudinal translation along the direction of the bar 6 itself.

Advantageously, the welding unit 2 is adjustable in height and its inclination is also adjustable.

Furthermore, in more detail, the welding unit 2 includes a rotating welding tool 20 which carries out the friction welding, externally to the element 8, and a lever 21 which presses the element to be welded 8 onto the bar 6.

More specifically, the welding is carried out by a welding tip 23 protruding from the welding tool 20 and which penetrates the element to be welded 8 to create the welding bead.

Advantageously, one or more sensors can be connected to the welding unit 2 to control and adjust the entire welding process, for example to control the position of the welding tool 20 relative to the element to be welded 8.

By way of example, a distance sensor connected to the welding unit 2 would guarantee, through the action on the lever 21 , to maintain the correct contact between the welding tool 20 and the element 8 and the correct penetration of the welding tip 23.

Furthermore, it would also be possible to control and adjust the penetration of the tip 23 of the welding tool 20 into the element to be welded 8 in such a way as to obtain a correct penetration while avoiding a potential negative impact caused by the deflection of the welding bar 6.

Optionally, this device can comprise a carriage sliding along a guide fastened to the frame 5 of the machine 100.

In this case, the welding units 2 can be moved along the welding direction by means of a motor or another movement device. To carry out a more effective welding, it is preferable that the area to be welded is straight and that the element 8 has a flat area near the area to be welded or is bent with flat and/or straight edges or ends.

For example, a round tube can be made with a curved metal sheet, in this case the metal sheet can have an "apple" shape containing a flat area near the welding area.

Advantageously, this solution allows the ends to be welded to be in a position preferably parallel to each other, decreasing the probability of having welding irregularities or defects.

In further embodiments, these ends to be welded can be in further positions such as, by way of example only, inclined or "V"-like.

After the longitudinal welding process, the welded tube can be deformed in a further calibration step to reach the desired final shape.

By way of example, if it would be desirable to obtain a round tube, the newly welded element can be rounded or calibrated to obtain the final round shape.

Furthermore, the machine 100 according to the invention also makes it possible to carry out welding on curved elements which do not require a subsequent calibration step.

Advantageously, in a preferred embodiment, the machine 100 includes two or more welding units 2 capable of carrying out simultaneous welding operations and positioned at a certain distance from each other.

This distance can be variable depending on needs, usage requirements and the length of the element to be welded 8.

In particular, the presence of multiple welding units, due to simultaneous welding in multiple areas, makes it possible to reduce the time of the entire process.

Advantageously, the welding units 2 can be controlled and planned with a tolerance, by way of example, less than 0.2 mm.

Even more advantageously, the welding units 2 can comprise interchangeable welding tools according to needs or in case of wear thereof.

Even more advantageously, the machine 100 comprises a drive system or control unit 4, fastened to the frame 5, comprising a display and selection keys or elements to allow the command and control of the operation of the machine 100.

In particular, the drive system or control unit 4 is connected to all the mobile components of the machine 100 itself and configured to control its movements. Even more particularly, this drive system 4 can protrude from the frame 5 so as to allow use at a safe distance from the welding area and therefore at a distance from areas at high temperatures or subject to sparks and other potential dangers for the operators.

Advantageously, a positioning plate 18 is connected to the welding bar 6, as visible in Figure 6B, for stopping and positioning a welding entry/exit plate 17 wherein the welding of the element to be welded 8 can be started and stopped.

In particular, the welding entry/exit plate 17 allows the entry and exit of the rotating welding tool 20 in contact with the element to be welded 8.

Advantageously, the welding entry/exit plate 17 makes it possible to obtain defect-free welds in the initial or starting and final or stopping welding zones.

In particular, the plate 17 is kept in contact with the element 8 by the positioning plate 18. During the welding process, the plate 17 will be welded together with the element 8. At the end of the welding process, the plate 17 will be removed through a cutting operation.

Advantageously, this plate 17 makes it possible to obtain a complete welding along the entire length of the element to be welded 8.

In this way, some areas wherein the welding bead is not complete (for example holes or areas of incomplete penetration) will no longer be in the element to be welded 8, but will be in the plates 17 which will be cut at the end of the welding.

Above the plate 17 there is a removable and adjustable stopper or abutment 14 for aligning the element to be welded 8 to the welding bar 6.

Advantageously, to facilitate alignment operations, the removable and adjustable stopper or abutment 14 also includes an eccentrically adjustable bolt 15.

Operationally, at the beginning of the processing the interlock 1 is raised, the clamping elements 10 are retracted and the element to be welded 8 is inserted in the area enclosed by the bars of the locking devices 3, outside the welding bar 6 (Figures 2 and 3). In particular, it is inserted after the opening of the interlock 1 from the area wherein the interlock 1 itself was fastened towards the inside of the machine 100, as visible in Figures 2 and 3.

In some cases, it is possible to widen the device to be welded 8 with a manual device to obtain a larger opening which can be, for example, 10 mm (Figure 5).

The widening must take place in the elastic range of the element to be welded 8, so that it can close again when the manual device is removed. Subsequently, the interlock 1 is lowered and connected to the welding bar 6, providing the correct support to the welding bar 6 during welding operations.

The connection is made via a pneumatically operated connector 22 and ensures a precise positioning of the welding bar 6 (Figures 6A and 6B).

At this point the abutments or stoppers 14 are positioned correctly, all the welding parameters are adjusted and the welding units 2 are positioned with all those elements that guarantee the correct maintenance in position of the welding bar 6 and of the element to be welded 8.

To align the element to be welded 8 to the welding bar 6, the element 8 is pulled towards the eccentrically adjustable bolt 15, which is held by the removable stopper or abutment 14 (Figure 7A).

Advantageously, this removable and adjustable stopper or abutment 14 is present on both sides of the element to be welded 8.

At this point it is possible to lock a first side, aligned with the stopper or abutment 14, by moving the clamping elements 10 into contact with the welding bar 6 and by locking the tube on the welding bar 6 itself.

To complete the preliminary operations, it is necessary to remove the abutment 14, add the welding entry/exit plate 17 and the positioning plate 18, and finally push the positioning plate 18 against the element to be welded 8 and fasten it with a screw (Figure 6B).

The welding entry/exit plate 17 is necessary to avoid defects on the starting and finishing areas of the welding. In the absence of the same, the start and stop would take place inside the element to be welded 8, with the consequence that a part of the element 8 itself could present defects that need to be repaired.

To carry out the locking operations on the second side, the clamping elements 10 are moved onto the welding bar 6, locking the element to be welded 8 onto the welding bar 6.

At this point you can begin the longitudinal friction welding (FSW) process.

The welding unit or head 2, after being started by an operator, then proceeds with the welding operations.

The rotary welding tool 20 can now move downwards into the welding entry/exit plate 17, remaining in position until the set welding process temperature is reached (Figure 8C). Once the process temperature has been reached, the rotating welding tool 20 moves longitudinally along the section to be welded of the element 8 (Figure 8B).

In particular, during this phase the following situations occur:

- a lever 21 presses the element to be welded 8 onto the welding bar 6;

- each clamping element 10 presses, with pressure, the element to be welded 8 onto the welding bar 6;

- the clamping element 10, which is in line with the welding tool, presses the element to be welded 8 with a greater pressure onto the welding bar 6.

When the welding unit 2 has welded the set length and has entered the welding entry/exit plate 17, the process stops and the tool 20 is withdrawn from the welding entry/exit plate 17.

Finally, the clamping elements 10 are retracted and subsequently the interlock 1 is opened for the removal of the welded element 8.

At the end of the welding operations, you can proceed either with the insertion of a further element to be welded 8 or with the closing of the machine by operating the interlock 1 and connecting it with the welding bar 6 (Figure 1 ).

All welding start/end, positioning, adjusting and managing operations of the welding unit 2 are controlled by the drive system or control unit 4.

Advantageously, the machine 100 is designed to weld profiles made with curved or bent metal sheets or with pre-assembled profiles and the thickness of the walls is variable as is the material which can be for example an alloy of aluminium or magnesium, steel, stainless steel, copper, brass, etc.

Even more advantageously, the machine 100 is designed to allow a continuous or intermittent longitudinal friction welding (FSW) on an element to be welded 8 curved or bent in the longitudinal direction. Furthermore, this welding will not present any defects or irregularities of the surface on the internal side of the element to be welded 8.

The invention thus conceived and illustrated here is susceptible to numerous modifications and variations, all falling within the scope of the inventive concept.

Furthermore, all details may be replaced by other technically equivalent elements.

Finally, the components used, as long as they are compatible with the specific use, as well as the size, may be any according to the needs and the state of the art. Where the features and techniques mentioned in any claims are followed by reference signs, such reference signs have been included for the sole purpose of increasing the intelligibility of the claims and, accordingly, such reference signs have non-limiting effect on the interpretation of each element identified by way of example by these reference signs.