Rotary welding device and related method

A rotary device for welding a continuous web, comprising

• a rotary drum rotating about a respective axis of rotation,
• a plurality of welding units for welding the continuous web and mounted on the rotary drum in such a way as to be angularly spaced from each other, each welding unit being configured to pass from a non-operating position to an operating position, and vice versa, during the rotation of the rotary drum;
• a movement mechanism configured to simultaneously vary radial positions of the welding units by simultaneously radially moving the welding units towards or away from the axis of rotation of the rotary drum;
• for each of the welding units, a first supporting element and a second supporting element connected thereto for supporting the continuous web and disposed, respectively, upstream and downstream of the each of the welding units with reference to a rotation direction of the rotary drum, to keep the continuous web tensioned when the each of the welding units is at the operating position;
• the first supporting elements and the second supporting elements connected with the welding units being supported by a load-bearing structure connected to the welding units in such a way that the simultaneously radially moving the welding units also causes simultaneously radially moving the first supporting elements and the second supporting elements towards and away from the axis of rotation of the rotary drum;
• the load-bearing structure comprising mounting bodies, each for a respective pair of the first supporting elements and the second supporting elements, and connecting bodies, each of which connects the load-bearing structure to one of the welding units;
• and
• wherein the mounting bodies are movably coupled to respective connecting bodies which are distinct from each other;
• each of the mounting bodies being movable towards and away from a respective one of the connecting bodies.

A rotary method for welding a continuous web, comprising:

• providing a plurality of welding units for welding the continuous web disposed around a common axis of rotation in such a way as to be angularly spaced from each other;
• conveying the continuous web around the axis of rotation and a step of welding the continuous web during the step of conveying the continuous web;
• depending on a weld spacing to be obtained, varying the weld spacing by simultaneously varying radial positions of the welding units and the continuous web by simultaneously radially moving the welding units and the continuous web towards or away from the axis of rotation;
• the step of varying the radial positions of the welding units being carried out at a same time as the step of varying the radial position of the continuous web;
• and
• the step of varying the radial position of the continuous web comprising disposing the continuous web around the axis of rotation in such a way as to define a polygonal perimeter having a length that is variable as a function of the radial position of the continuous web relative to the axis of rotation to adapt to the radial position variation of the welding units.