Patent ID: 7308780

Claim:
An apparatus for continuous tight heat-sealing of the longitudinal overlapping edges of tubular pieces of thermoplastic film, the thickness of which may be limited, produced by unwinding the film from a reel and advancing the film longitudinally through a tubularizing mandrel, said apparatus comprising: guide means for guiding and for holding the longitudinal edges of the tubularized film so that the longitudinal edges overlap with an intimate and sufficiently distributed contact; a sealing head, disposed in an opposing position relative to, and a short distance from, the guide means, the sealing head made of a material with good mechanical strength and with a low coefficient of friction in relation to the film to be sealed and with a high degree of thermal insulation, the sealing head adapted to direct at least one continuous jet of air or other gas onto the edges of the film to be sealed, wherein the jet of air or other gas being heated to an appropriate temperature and at an appropriate pressure; and a fixed generator of hot compressed air controlled by a suitable supply and control means, the generator connected to the sealing head via a flexible or jointed means, the sealing head being mounted on means of approach and withdrawal, such that, when the film advances, the sealing head is placed a short distance from the film, in an operation position to seal the film, whereas when the film stops, the sealing head is withdrawn from the film, wherein the sealing head, viewed end-on in the direction of advance of the film to be sealed, is of an essentially rectangular shape, the sealing head has beveled upper long sides, and an upper face of the sealing head has a footprint essentially the same as an effective footprint of the guide means over which the edges of the film to be sealed slide.