Web coating method and apparatus

A rotary web coater for depositing a thin film of a liquified coating material onto a flexible moving web of base material, comprising a rigid supporting frame structure including a pair of laterally spaced side frames of a plate-like construction, an impression cylinder having opposite end shafts rotatably mounted at the opposite ends in said side frames and rigidly supporting said cylinder for rotation on a fixed axis in said side frames, a pivot arm member having a precision bearing mounted on said end shafts of said impression cylinder adjacent said frame, a nip adjustment means mounted to said frame and including a pre-loaded ball bearing lead screw rotatably mounted to said frame and having a follower, a slide housing substantially enclosing said lead screw and including a slide means slidably affixed to said side frames to slidably support the housing on the frame, means interconnecting said slide housing to said lead screw for movement in accordance with the rotation of the lead screw, a pivot link pivotally connected to the lower end of said slide housing and pivotally connected to the outer end of said pivot arm member, a power cylinder unit having a cylinder end pivotally affixed to the frame and having a sliding piston rod aligned with said pivot arm member, a clevis connection connecting the pivot arm member to said piston rod, a stepping motor means coupled to said pre-loaded ball bearing lead screw for accurately positioning said pivot arm member against the position of said cylinder unit, a set of pivot arm member extensions extending upwardly from said pivot arm member and including an upper portion extending outwardly over the impression cylinder, said set of arm member extensions including aligned pivot openings, a pivot shaft extended to said openings and having pivot bearings between the shaft and the arm member extensions to rotatably support the shaft in said arms, a depending pivot arm interposed between said extension arms on said shaft and depending downwardly in front of said impression cylinder and having bearing openings;

• an offset cylinder having end bearings, means securing said bearings within said bearing opening in said depending arms and rotatably supporting said offset cylinder with its axis of rotation parallel to the axis of rotation of said impression cylinder, a preloaded rotary bearing lead screw mechanism, a slide housing slidably secured to the underside of said pivot arm member, a pre-loaded ball bearing lead screw rotatably journaled in said housing and projecting outwardly beneath the pivot arm member, said lead screw mechanism having a follower on said lead screw coupled to said slide housing as a stop, a pivot leg having one end connected to said housing and the opposite end connected to said depending pivot arm, a power cylinder unit secured to said depending pivot arm and to the pivot arm member extensions defining a high force motor means holding the depending pivot arm against said stop, stepping motor means coupled to said lead screw and operable to rotate said lead screw and move said slide housing in increments of a few millionth's of an inch for each step of the stepping motor means, a gravure cylinder mounted within said frame beneath and in alignment with said offset cylinder, a fountain beneath said gravure cylinder and located for immersing the gravure cylinder in a coating material contained within the fountain, said first lead screw operating to pivot said pivot arm member and thereby adjust the nip between said offset cylinder and said gravure cylinder, said second lead screw being operable to move said depending pivot arm to thereby adjust said offset cylinder with respect to said impression cylinder.

The process of applying a coating by passing of a web through a coating applicator having an impression roll rotatably mounted in a fixed bearing structure and a gravure cylinder rotatably mounted in fixed bearing structure and within a fountain having a coating liquid in combination with an offset cylinder rotatably mounted in a support means mounted in a pivotal support having a pivot axis for pivotal movement of said offset cylinder toward and away from the impression cylinder and having a pivotal mounting means connected to said support means for vertical displacement of said support means with respect to said gravure cylinder, said web being adapted to be passed directly in an offset mode of applying the coating to the web and alternatively passed directly between said offset cylinder and said gravure cylinder in a direct mode of applying the coating to the web, said gravure cylinder transferring said coating from said fountain in both said offset mode and said direct mode, comprising the steps of selectively presetting said support means in a first position locating said offset cylinder with respect to the impression cylinder to establish a selected nip pressure with said web passing between said impression cylinder and offset cylinder and operating in said offset mode, or in a second position spacing said offset cylinder with respect to said impression cylinder by a distance to prevent any interaction therebetween with the web passing between the offset cylinder and gravure cylinder and operating in said direct mode, presetting said pivotal mounting means in a first position to adjust the nip between said offset cylinder and said gravure cylinder to transfer the coating to the offset cylinder in said offset mode and in a second position to adjust said nip to permit passage of the web over the offset cylinder with transfer of the coating from the gravure cylinder to the web in said direct mode, after the selectively presetting of the support means and pivotal mounting means, passing said web through said apparatus in said direct mode or in said offset mode to receive said coating material, removing a quantity of coating applied to said web from a selected portion of the coated web, weighing the removed web coating to thereby determine a preselected thickness of the coating, manually readjusting the settings of said support means and said pivotal mounting means for any variation in the determined thickness from said preselected thickness and thereby establish a manually set nip setting of the offset cylinder, and thereafter operating said apparatus in an automatic mode with said manually set nip settings to deposit a uniform thickness of said coating material on said web.