Stretch rod for the form-and-fill head of a machine for forming and filling containers produced from preforms
The invention relates to a stretch rod for the form-and-fill head of a machine for forming and filling of containers produced from preforms. The object of the invention is to devise a stretch rod of this type which can be cleaned and/or disinfected without being disassembled and without any other intervention. According to the invention, the object is achieved by a stretch rod ( 5 ) for the form-and-fill head ( 3 ) of a machine for forming and filling (molding and filling) of containers produced from preforms ( 2 ), which rod comprises a drive unit for axially moving said stretch rod ( 5 ). At least the part ( 6 ) of the drive unit which is connected to the stretch rod ( 5 ) is arranged in a drive chamber ( 11 ) which is sealed off from the regions of the form-and-fill head ( 3 ) which come into contact with the filling material (the material with which the container is being filled). The inventive stretch rod is characterized in that the sealing action is achieved by a seal ( 12 ) which surrounds the stretch rod ( 5 ).
1. A form-and-fill head of a machine for simultaneously reshaping and filling a heated preform to produce a container filled with a liquid filling material, said form-and-fill head comprising:
a stretch rod; and
a drive unit connected to the stretch rod, said drive unit being configured to move the stretch rod such that the stretch rod stretches the heated preform axially during a forming and filling phase;
wherein at least a part of the drive unit is arranged in a drive chamber, and
wherein the drive chamber is sealed off from regions of the form-and-fill head that come into contact the liquid filling material during the forming and filling phase by a seal which surrounds and circumferentially contacts the stretch rod.
2. The form-and-fill head according to claim 1 , wherein a sealing surface of the seal is in a fixed position relative to the drive chamber.
3. The form-and-fill head according to claim 2 , wherein the seal is a cylindrical bellows, roll bellows, or expandable sleeve.
4. The form-and-fill head according to claim 1 , wherein the stretch rod is axially movable relative to the seal, and for a cleaning process the stretch rod is movable into a position in which the stretch rod is not in contact with the seal.
5. The form-and-fill head according to claim 4 , wherein the stretch rod has an encircling groove in a region which does not come into contact with the seal during the forming and filling phase.
6. The form-and-fill head according to claim 1 , wherein the seal which surrounds and circumferentially contacts the stretch rod is pressure resistant on one side.
7. The form-and-fill head according to claim 6 , wherein the seal is a lip seal.
8. The form-and-fill head according to claim 1 , wherein the drive unit comprises a magnetic coupling comprising:
a first magnet unit that disposed in the drive chamber and is connected to the stretch rod; and
a second magnet unit that is disposed outside the drive chamber.
9. The form-and-fill head according to claim 8 , wherein the second magnet unit is axially displaceable.
10. The form-and-fill head according to claim 8 , wherein the second magnet unit is in a fixed position and a magnetic field of the second magnet is dynamically controllable.
11. The form-and-fill head according to claim 8 , wherein the first magnet unit is supported at a distance from walls of the drive chamber.
12. The form-and-fill head according to claim 11 , wherein the first magnet unit is supported at the distance from walls of the drive chamber by spacer means.