The device for welding thermoplastic parts includes a matrix for positioning the parts to be assembled, the matrix including an amagnetic insulating insert that defines joining zones in which the welds must be produced, a bladder defining a sealed volume and means for producing a partial vacuum in the sealed volume, and means for moving a magnetic induction head to near the joining zones and without making contact with the bladder. The welding process includes positioning at least one first part, then of placing metal inserts on areas of the first part corresponding to the joining zones that must be welded, and then positioning at least one second part. A bladder is put in place covering the parts and a partial vacuum is created in the volume defined by the bladder. The magnetic induction head is moved to produce the weld bead without contact while the partial vacuum is maintained.

A magnetic insert for enhancing the magnetic field of an induction heating device is provided. The magnetic insert is manufactured by use of a composition comprising a mouldable polymer matrix and a soft magnetic material.

A thermoplastic welding apparatus includes a thermoplastic welding tool, at least one tooling surface in the thermoplastic welding tool, a magnetic induction coil in the thermoplastic welding tool and generally encircling the at least one tooling surface and at least one smart susceptor in the thermoplastic welding tool at the at least one tooling surface. The magnetic induction coil is adapted to generate a magnetic flux field oriented generally parallel to a plane of the at least one smart susceptor.

The present invention relates to an induction sealing device for heat sealing of packaging material. The sealing device comprises a conductor partly encapsulated in a supporting body for cooperation with the packaging material during sealing. The coil conductor has a reduced cross sectional area at at least one position along the coil conductor so as to concentrate the magnetic flux induced by the coil conductor at the at least one position. The invention also relates to a method of heat sealing a packaging material using the induction sealing device.