Balancing film shrinkage during thermoplastic container mfr. - using heating strips which are positioned under longitudinal and lateral film edges between preformed containers between deep-drawing and punching stations

摘要

To prevent lateral shrinkage after heat forming of thermoplastic film containers, a film strip is drawn forward at regular intervals through preheating, forming filling, covering and stamping stations. During strip progress through the machine a sensor controls the operation of the final processing stations in relation to the position of the deep-drawn containers. Prevention of shrinkage laterally across the film when the machine stops is achieved by maintaining the film temp. at the deep drawing temp. as it passes between the deep-drawing and punching stations. The film temp. is maintained between containers by heating strips positioned under the longitudinal and lateral edges between containers. USE/ADVANTAGE - The process and device are used during mfr. of containers, esp. in polypropylene film on a forming, filling and stamping machine and prevent lateral film shrinkage during machine stops giving a uniform edge around each container.