A doctor method and apparatus is disclosed and includes a doctor roll ( 12 ) supported in a coater ( 1 ) suitable for applying coating to a paper web surface or a roll surface ( 4 ) for subsequent transfer to the paper web. The doctor includes a doctor roll ( 12 ), a support ( 11 ) for the doctor roll ( 12 ), a front support ( 3 ) for holding the roll support ( 11 ) and a rear support or retainer ( 18 ) cooperates with and helps stabilize the support ( 11 ) and doctor roll ( 12 ). The present invention minimizes the variation moving of the doctor roll ( 12 ) has on the coating on the moving surface ( 4 ), be it web or roll, and thus can improve coating quality.
1. A method for doctoring a coating excess applied by a coater to a moving surface with a doctor roll, comprising the steps of:
(1) applying excess coating to the moving surface,
(2) rotating a doctor roll in a doctor roll support having upstream and downstream ends adjacent the moving surface and the excess coating thereon,
(3) moving the doctor roll support and doctor roll toward or away from the moving surface for controlling the amount of excess coating removed from the moving surface by the doctor roll,
(4) limiting the movement of the doctor roll and the doctor roll support in the direction the moving surface is moving, the step of limiting movement of the doctor roll support comprising generally pivoting the upstream end of the doctor roll support about an axis upstream of the doctor roll,
(5) retaining the downstream end of the doctor roll support against a downstream retaining member,
(6) sliding the downstream end of the doctor roll support against the retaining member,
(7) loading the doctor roll against the moving surface for establishing the force of the doctor roll toward the moving surface, and
(8) doctoring the excess coating off the moving surface with the doctor roll,
whereby the coating on the moving surface is consistently doctored by said doctor roll.
2. A method for doctoring as in claim 1 , further comprising the step of supplying coating to and removing the excess coating from a paper or board web, whereby the coating on the paper or board web is consistently doctored by said doctor roll.
3. A method for doctoring as in claim 1 , further comprising the steps of
applying a coating excess by a coater to a moving roll surface of a roll, removing excess coating from the roll surface with the doctor roll, then transferring coating from the roll surface to a paper/board web, whereby the coating on the moving roll surface is consistently doctored by said doctor roll and then transferred to the paper/board web.
4. A method as in claim 1 , further including the step of pivoting the doctor roll and doctor roll support about the pivoting axis in the coater integral with the doctor roll.
5. A method as in claim 1 , further including the step of pivoting the doctor roll and doctor roll support about the pivoting axis downstream of the coater, which may be separate from the doctor roll.
6. A method as in claim 1 , further including the step of pivoting the doctor roll support on a curved bar upstream of the doctor roll.
7. A method as in claim 6 , further including the steps of pivoting the doctor roll support off the curved bar upstream of the doctor roll and in the coater which is integral with the doctor roll, and at least particularly sealing the excess coating in the integral coater with the curved bar.
8. A method as in claim 6 , further comprising the step of pivoting the doctor roll off of the downstream end of the curved bar.
9. A method as in claim 6 , further including the step of applying the excess coating to the moving surface upstream of the doctor roll and doctor roll support and closely adjacent the curved bar.
10. A method as in claim 1 , further including the further step of cooling the doctor roll support.
11. A method as in claim 1 , further including the steps of curving the downstream end of the doctor roll support and pivoting and sliding the curved downstream end of the doctor roll support against the retaining member.
12. A method as in claim 1 , further including the step of rotating the doctor roll in a direction so that at the point of contact with coating on the moving surface the doctor roll moves in the opposite direction of the moving surface.
13. A method as in claim 1 , further including the step of preventing lifting of the doctor roll support.
14. A method as in claim 4 , further including the steps of
pivoting the doctor roll support on a curved bar upstream of the doctor roll,
pivoting the doctor roll support off a downstream portion of the curved bar upstream of the doctor roll at least particularly sealing the excess coating in the coater with the curved bar,
applying the excess coating to the moving surface upstream of the doctor roll and doctor roll support and closely adjacent the curved bar, including the further steps of
cooling the doctor roll support,
curving the downstream end of the doctor roll support,
pivoting and sliding the curved downstream end of the doctor roll support against the retaining member,
rotating the doctor roll in a direction so that at the point of contact with coating on the moving surface the doctor roll moves in the opposite direction of the moving surface, and
preventing lifting of the doctor roll support.
15. A method as in claim 5 , further including the steps of:
pivoting the doctor roll support on a downstream end of a curved bar upstream of the doctor roll,
cooling the doctor roll support,
curving the downstream end of the doctor roll support,
pivoting and sliding the curved downstream end of the doctor roll support against the retaining member,
rotating the doctor roll in a direction so that at the point of contact with coating on the moving surface the doctor roll moves in the opposite direction of the moving surface, and
preventing lifting of the doctor roll support.