Device for sterilizing a thermoplastic strip used for the hot-forming of sterile containers and sterile packaging installation using the device

An installation for the sterile packaging of a sterile product in sealed packages, said installation comprising a reel of thermoplastic strip material, means to unwind said thermoplastic strip from said reel in a stepwise manner so as to extend along a feed path, a heating chamber positioned adjacent said feed path and including a plurality of heating elements for heating said thermoplastic strip to its softening temperature through the entire thickness of said strip, a hot-forming device including a movable mold and a punch engageable with said thermoplastic strip for producing container portions therein, a filling station for depositing a sterile product in said container portions, means for sterilizing a cover strip and means for guiding the sterilized cover strip onto said thermoplastic strip so that it overlies container portions in which sterile product has been deposited, sealing means for sealing said sterilized cover strip over said container portions, cutting means for severing said sealed container portions from said thermoplastic strip to provide discrete filled and sealed containers, discharge means for removing said discrete filled and sealed containers, enclosure means defining a first sterile, enclosure on both sides of said thermoplastic strip extending from said heating chamber to a location immediately upstream of the sealing means, a means for sterilizing the thermoplastic strip comprising a sterilizing heating device situated upstream of the heating chamber and further comprising a second sterile enclosure communicating with the first sterile enclosure of the heating chamber via a passage through which the thermoplastic strip extends, wherein the second sterile enclosure of said sterilizing means encloses said sterilizing heating device;

• said sterilizing heating device comprising a plurality of sterilizing heating resistors of the type having essentially instant thermal response for generating an instantaneous thermoplastic strip surface temperature which exceeds the softening temperature of said strip, an adjustable power source, a control circuit connecting said adjustable power source to said sterilizing heating resistors and switching means mounted in said control circuit for intermittently, operatively connecting said heat resistors to said power source for automatically, repetitively energizing said sterilizing heating resistors, with each said energization time period not exceeding five seconds.