Methods for coating a foil using a coating system with an adjustable gap between two rollers
In a coating system, two rollers are arranged adjacent to one another. A donor foil with rheological material dispensed thereon is advanced through a gap between the two rollers. Such gap spreads the dispensed material over the donor foil, coating the donor foil with a layer of the material with a uniform thickness associated with the gap width. Each roller is supported on a holder. Adjustment of the gap width may be effected by keeping the position of one of the holders fixed, while horizontally translating the position of the other holder. The position of the translatable holder may be adjusted by pistons and linear actuators. The pistons may bias the moveable holder towards the stationary holder. The linear actuators mounted on the moveable holder may extend respective arms against the stationary holder, thereby countering the biasing of the pistons and pushing the moveable holder away from the stationary holder.
1 . A method for coating a foil with a coating system, the coating system comprising:
a dispensing unit arranged to apply a material on a first foil advanced through a first gap between a first roller supported by a first holder and a second roller supported by a second holder; a first linear actuator mounted on the second holder for adjusting a position of a first arm; a second linear actuator mounted on the second holder for adjusting a position of a second arm; a first piezoelectric sensor mounted on the first holder for detecting a contact of the first arm on the first piezoelectric sensor; a second piezoelectric sensor mounted on the first holder for detecting a contact of the second arm on the second piezoelectric sensor; a piston configured to bias the second holder towards the first holder, wherein the first arm and the second arm are configured to counter the piston's biasing of the second holder towards the first holder when the first arm and second arm are extended; and a controller configured to control the first linear actuator and the second linear actuator so as to adjust a position of the second roller relative to a position of the first roller, thereby adjusting a width of the first gap between the first roller and the second roller;
the method comprising:
applying the material by the dispensing unit on the first foil located within the first gap between the first roller supported by the first holder and the second roller supported by the second holder;
advancing the first foil through the first gap between the first roller supported by the first holder and the second roller supported by the second holder, the first gap being associated with a thickness of a layer of the material applied on the first foil;
biasing the second roller by the piston towards the first roller;
adjusting the position of the first arm by the first linear actuator mounted on the second holder, wherein extension of the first arm by the first linear actuator counters the biasing of the second roller towards the first roller; adjusting the position of the second arm by the second linear actuator mounted on the second holder, wherein extension of the second arm by the second linear actuator counters the biasing of the second roller towards the first roller;
detecting, by the first piezoelectric sensor mounted on the first holder, the contact of the first arm on the first piezoelectric sensor;
detecting, by the second piezoelectric sensor mounted on the first holder, the contact of the second arm on the second piezoelectric sensor; and
controlling with the controller the first linear actuator and second linear actuator so as to adjust the position of the second roller relative to the position of the first roller, thereby adjusting the width of the first gap between the first roller and the second roller.
2 . The method of claim 1 , further comprising advancing a second foil through the first gap with the second roller so as to remove a residue on the second foil from a previous coating or to recover an unused material on the second foil.
3 . The method of claim 1 , further comprising:
maintaining the first holder in a stationary position; and
moving the second holder with respect to the first holder.
4 . The method of claim 1 , further comprising:
measuring, by a first displacement sensor mounted on the second holder, a first distance between the first displacement sensor and the first holder; and
measuring, by a second displacement sensor mounted on the second holder, a second distance between the second displacement sensor and the first holder.
5 . The method of claim 1 , wherein the material is a liquid, a paste, an adhesive or a polymeric solution.
6 . The method of claim 1 , further comprising:
rotating the first roller by a first motor about an axis of the first roller; and
rotating the second roller by a second motor about an axis of the second roller.
7 . The method of claim 1 , further comprising removing a residual material from the first roller and the second roller with cleaning systems, wherein each of the cleaning systems comprises a knife, a scraper, or a sponge with a solvent.
8 . The method of claim 1 , further comprising vibrating the first roller or the second roller with an ultrasound transducer.
9 . The method of claim 1 , further comprising:
prior to advancing the first foil through the first gap, positioning the second roller to contact the first roller; and
measuring, by a displacement sensor mounted on the second holder, a distance between the displacement sensor and the first holder.
10 . The method of claim 1 , further comprising:
prior to advancing the first foil through the first gap, positioning the second roller to contact the first roller;
extending the first arm until the contact of the first arm on the first piezoelectric sensor is detected; and
at a moment the contact of the first arm on the first piezoelectric sensor is detected, recording a position of the first arm.