Abstract: The invention relates to an ultrasonic welding apparatus (100) for welding together at least two superposed sheets (1, 2) made of plastics material and traveling continuously along a predetermined path (F), the apparatus (100) being of the type comprising a sonotrode (101) and an anvil (102) disposed facing each other so that their facing surfaces (101′, 102′) define a through gap (102) through which two superposed sheets (1, 2) to be welded together pass, the gap having an inlet section (104) and an outlet section (105), the sonotrode (101) vibrating at high frequencies to emit ultrasound waves. According to the invention, the anvil is fixed and said facing surfaces of the sonotrode and of the anvil are generally plane and converge towards each other such that the section of said through gap decreases continuously between its inlet section and its outlet section.

Abstract: The invention relates to a method for the manufacture of a pack, particularly intended for undergoing preservation treatment, from at least one film (10) comprising two plastic layers, an upper (11) and a lower (12), which form the outer and inner faces of said pack, and a light-metal central layer (13) sandwiched between said upper and lower layers. According to the invention, prior to the operations to make said pack, a laser beam is applied solely to the lower layer of said film, said lower layer forming the inner face of said pack, in order to produce, virtually in the entire thickness of said lower layer, at least one perforation (14) forming at least one precut line.