Unit for sterilizing web-fed material on a machine for packaging pourable food products
A unit for sterilizing a web ( 2 ) of packaging material on a machine ( 1 ) for packaging pourable food products, the unit having a bath ( 7 ) containing a sterilizing agent, in which the web ( 2 ) is fed continuously; a process chamber ( 8 ) connected to an outlet ( 12 ) of the bath ( 7 ), and which houses wringing rollers ( 18 ) interacting with the web ( 2 ), and a nozzle ( 22 ) for directing a stream of air on to the web ( 2 ) and removing residual sterilizing agent from the web; an aseptic chamber ( 25 ) communicating with the process chamber ( 8 ) via an opening ( 27 ) for passage of the web ( 2 ), and in which the web ( 2 ) is folded and sealed longitudinally to form a tube ( 29 ) which is filled continuously with the product for packaging; and an air processing circuit ( 24 ) for controlling process conditions, and having a conduit ( 56 ) for feeding a first stream of sterile air into the aseptic chamber ( 25 ), a conduit ( 54 ) for feeding a second stream of sterile air to the nozzle ( 22 ) and housing a heater ( 69 ) for controlling the temperature of the air supplied to the nozzle ( 22 ), and a distributor for regulating the two streams of air.
1. A sterilizing unit for sterilizing a web of packaging material on a machine for packaging pourable food products, the sterilizing unit comprising:
a bath containing a sterilizing agent, in which said web is fed continuously;
an aseptic environment comprising a process chamber connected to an outlet of said bath and housing drying means for removing residual sterilizing agent from said web; and an aseptic chamber communicating with said process chamber via an opening for the passage of said web, and in which said web is folded and sealed longitudinally to form a tube which is filled continuously with the product for packaging;
said drying means comprising at least one nozzle for directing a stream of sterile air on to said web; and
an air processing circuit for controlling the process conditions in said aseptic environment, and comprising suction means for drawing air from said process chamber; and air processing means comprising first heating means, and first supply means for feeding sterile air into said aseptic chamber;
comprising second supply means for supplying sterile air from said air processing means to said nozzle; and second heating means associated with said second supply means and for controlling the temperature of the air supplied to said nozzle.
2. A unit as claimed in claim 1 , comprising first valve means for adjustably connecting said first supply means and said second supply means to said air processing means.
3. A unit as claimed in claim 2 , wherein said first valve means comprise a distributor having an inlet connected to said air processing means, first and second outlets connected to said first supply means and said second supply means respectively, and a first and a second shutter for regulating flow from said inlet to each of said outlets.
4. A unit as claimed in claim 3 , wherein said distributor comprises a casing having a cylindrical cavity in turn having an axis; said inlet and said outlets being defined by respective holes formed in said casing, having axes perpendicular to said axis of said cavity, and communicating with said cavity.
5. A unit as claimed in claim 4 , wherein said shutters have respective cylindrical sealing surfaces coaxial with said cavity, and which slide hermetically with respect to an inner surface of said cavity.
6. A unit as claimed in claim 5 , wherein said shutters rotate about said axis of said cavity.
7. A unit as claimed in claim 6 , wherein said shutters are controlled by respective actuators.
8. A unit as claimed in claim 3 , wherein one of said shutters comprises a hole permitting residual flow to said second supply means, even when said second outlet is closed.
9. A unit as claimed in claim 2 , comprising a transition chamber communicating with an inlet of the bath and with said suction means; and second valve means interposed between said process chamber and said transition chamber, and movable between an open position in which said process chamber communicates directly with said transition chamber, and a closed position in which said process chamber communicates with said transition chamber via said bath.
10. A unit as claimed in claim 9 , wherein said transition chamber communicates with the outside environment through a normally-closed orifice which opens under low pressure.
11. A unit as claimed in claim 1 , comprising a barrier for producing a localized pressure drop between said aseptic chamber and said process chamber; said barrier defining said opening, through which said web is fed, between said process chamber and said aseptic chamber.
12. A unit as claimed in claim 1 , for processing a web of packaging material fitted with opening devices projecting from one face of said web; wherein said opening is asymmetrical with respect to the traveling plane of said web, and is higher on the side facing the face of said web from which said opening devices project.
13. A unit as claimed in claim 12 , comprising a roller for guiding said web and housed in said aseptic chamber, immediately downstream from said opening; said barrier comprising a partition defining said opening and shaped to get close to said roller.