Doctor roll with spiral grooves

Claim 1

IN AN APPARATUS FOR COATING A WEB OF SHEET MATERIAL, A ROTARY DOCTOR ROLLER ADAPTED TO ENGAGE THE COATED WEB AND TO ROTATE IN A DIRECTION WHICH DISPLACES THE SURFACE OF THE ROLLER WHICH ENGAGES SAID WEB IN A DIRECTION OPPOSITE TO THE DIRECTION OF MOVEMENT OF THE WEB SO THAT SAID ROLLER IS ADAPTED TO REMOVE EXCESS COATING MATERIAL AND FOREIGN PARTICLES SUCH AS DIRT FROM THE MOVING WEB, SAID ROLLER BEING FORMED AT ITS EXTERIOR SURFACE WITH A PLURALITY OF PASSAGES DISTRIBUTED ABOUT ITS CIRCUMFERENCE AND EXTENDING FROM ONE END OF THE ROLLER TO THE OTHER END THEREOF FORMING OPENINGS RESPECTIVELY SITUATED AT THE OPPOSITE ENDS OF THE ROLLER, AND AN ELONGATED DOCTOR BLADE EXTENDING LONGITUDINALLY OF AND ENGAGING SAID ROLLER AT A GIVEN LINE ALONG ITS EXTERIOR SURFACE, SAID BLADE HAVING A SURFACE DIRECTED TOWARD SAID ROLLER AND FORMING AN ACUTE ANGLE WITH A PLANE TANGENT TO SAID ROLLER AT THE LINE OF ENGAGEMENT BETWEEN SAID BLADE AND ROLLER, THE DIRECTION OF ROTATION OF SAID ROLLER ADVANCING THE SURFACE THEREOF TOWARD THE LINE OF ENGAGEMENT AT THE SIDE OF SAID BLADE WHICH FORMS AN ACUTE ANGLE BETWEEN SAID PLANE AND THE SURFACE OF SAID BLADE WHICH IS DIRECTED TOWARD SAID ROLLER, SAID PASSAGES BEING FORMED SUCH THAT THE PATH OF ANY GIVEN PASSAGE WHILE BEING TRACED DURING ROTATION OF SAID ROLLER IN THE AREA OF SAID WEB TRAVELS LESS THAN 360* FROM THE POINT OF ENGAGEMENT THEREOF WITH THE BLADE TO THE SUBSEQUENT POINT OF ENGAGEMENT WITH SAID WEB, WHEREBY DURING ROTATION OF SAID ROLLER SAID BLADE WILL PRESS INTO SAID PASSAGES ANY EXCESS COATING ON SAID ROLLER AND THE EXCESS COATING WILL FLOW ALONG SAID PASSAGES OUT OF THE LATTER AT THE SAID OPENINGS SITUATED AT THE ENDS OF SAID ROLLER, SO THAT ANY PARTICLES OF DIRT OR FOREIGN MATTER WILL BE DISPLACED WITH THE EXCESS COATING ALONG SAID PASSAGES AND AWAY FROM SAID ROLLER TO PREVENT STREAKING OF THE WEB.