Coating apparatus

[57] ABSTRACT

Coating apparatus for the application of fluid media to a traveling web wherein a unique fountain arrangement is provided for a reverse angle doctor blade to minimize foaming.

Claims, 2 Drawing Figures

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PATENTED0CT3 1972 3,695,221

SHEET 1 OF 2

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PATENTED oct 3 1972

3.695,221

SHEET 2 OF 2

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3,695,221

COATING APPARATUS

BACKGROUND AND SUMMARY OF THE INVENTION

The species of coater with which the instant invention is concerned has a reverse angle doctor blade which refers to the fact that the blade develops a scraping as contrasted to a wiping action on the applicating roll. Further, the blade itself, according to the prior art, constitutes a portion of the fluid reservoir which, in effect, renders the arrangement “fountainless.” In this connection, I use the term “fountainless” to refer to the fact that there is no separate trough carrying the coating fluid and which is transferred therefrom by a conventional fountain roll.

Although reverse angle doctor blades have been installed in fountainless fashion in the past, a number of drawbacks have attended their operation. One significant disadvantage has been the tendency of the ink or other fluid to foam. By a unique structural arrangement, I have achieved the rapid passage of the fluid past the applicating roll, thereby reducing the shearing action of the roll on the same fluid.

Rapid throughflow of the fluid is achieved through the use of a casing having ends spaced from the roll ends. Additionally, the amount of fluid subject to shearing action is reduced through a unique baffling arrangement.

DETAILED DESCRIPTION

The invention is described in conjunction with an illustrative embodiment in the accompanying drawing, in which:

FIG. 1 is a fragmentary side elevational view of the portion of the coating apparatus equipped with the fountainless reverse angle doctor blade; and

FIG. 2 is a fragmentary top plan view of the apparatus of FIG. 1.

Although the invention is seen in fragmentary form, it will be appreciated that the fountainless reverse angle doctor blade dealt with in detail herein is part of an overall larger machine (not shown) which provides means for unreeling a web, conducting the same through various stations, and presenting the same in condition for ultimate dispensing, as by rewinding, severing, folding, etc. Thus, the numeral 10 (see FIG. 2) designates generally a portion of a machine frame which is integrated with other web processing devices. Shown journaled in the frame 10 is a roll 11 supported within a suitable bearing 12. It will be appreciated that only one half of the roll 11 is shown, the other half of the machine being essentially symmetrical to that shown in FIG. 2. The instant invention has application to both offset gravure and gravure rolls. In the latter case, the fluid applied to the gravure roll is conducted to a different position from where the doctoring occurs, and thereafter applied to a web W backed by a suitable rubber covered impression cylinder 13 also carried by the frame 10.

The roll 11 is equipped with a shaft extension as at 1 la which extends through an outer housing generally designated 14 and suitably interconnected with the frame 10 as at 15 in FIG. 2. The housing 14 is equipped with a screen 14α through which excess fluid (viz., ink, glue, clay coating, etc.) passes for collection and recirculation through a fluid inlet 16 (see the left hand side of FIG. 1). The housing is suitably slotted in its top to provide access for the cylinder 13.

Fluid entering at inlet 16 is delivered to a casing generally designated 17 defined by a back wall 18, a bottom wall 19, and end walls 20. It will be noted (see the central portion of FIG. 2) that the end wall 20 is located a spaced distance from the end face 21 of the roll 11. Thus ink or other coating fluid can escape through this narrow controlled gap and is removed from the end face 21 by means of a wiper 22. The wiper consists of a flexible blade constructed of mylar or the like which is in wiping engagement with end face 21 of the roll 11. This cleans the roll face 21 and minimizes fluid splatter or slinging.

Fluid entering the inlet conduit 16 passes over a baffle 23 and thence into the reservoir section 24 where it is in contact with the periphery of the roll 11. Excess fluid is removed by the coaction of the periphery of the roll 11 and the reverse angle doctor blade generally designated 25. The direction of rotation of the roll 11 is indicated by the arrow shown adjacent the doctor blade 25 and designated by the numeral 26. As indicated previously, there is not a tight or close seal at 27; rather, a small gap is defined by the juxtaposition of the end wall 20 and the end face 21 of the roll 11. The width of the gap 27 is sized to permit fluid to escape from the fountain or reservoir portion 24 and be recirculated back into the casing 17 along with added fluid to maintain a desired fluid level as at 28 in the fountain casing 17. The tendency of the fluid to foam, particularly where the fluid is of relatively low viscosity, as is the case with inks and certain adhesives and emulsions applied during packaging operations, is materially reduced through the spacing 27 and interposition of the baffle 23 which also improves fluid distribution within the casing 17. The ink or other fluid enters the casing below the top of the baffle and has to flow thereover to reach the doctor blade.

I also provide certain advantageous adjustments relative to the doctor blade 25. For example, I provide a hand wheel 29 (shown only in outline on FIG. 1, but clearly designated in the lower central portion of FIG. 2) which operates to move the casing 17, and hence the doctor blade 25, horizontally toward and away from the roll 11. This movement establishes the level of doctor blade pressure against the roll 11. For this purpose, I equip the shaft 30 (which carries the handwheel 29) with a worm 31 (FIG. 2). The worm 31 is engaged with a worm gear 32 (see FIG. 1) affixed to a threaded rod 33. The rod 33 is coupled to a block 34 which rides in ways 35 mounted on a cross part 10α of the frame 10. Four blocks 34 are provided across the width of the machine and support a pivot shaft 36. The pivot shaft 36 has a pair of angle blocks 37 and 38 for each sliding block 34. The angle blocks 37 and 38 are fixed to the shaft 36 and also to a cross bar 39, the latter by bolts 40. The casing 17, in turn, is secured to the cross bar 39.

Turning the handwheel 29 thus moves the casing 17 in an in or out movement. This necessarily results in equivalent movement of the doctor blade 25 inasmuch as the latter is secured to the bottom wall 19 of the casing 17 by means of a clamp block 41. The extent of inward movement is limited by a stop nut 42 (see FIG. 1) positionably mounted on a rod 43 fixed to block 34. As

3,695,221 the block 34 moves inward, the nut 42 engages frame part 10b.

Because the casing 17 and doctor blade 25, including clamp block 41, are clamped to a support and pivot shaft 36, the entire assembly can be pivoted around the axis of shaft 36 by means of turning the shaft 36 as indicated by the arrow 44 (see FIG. 2). The purpose of this construction is to permit rotating the fountain casing upward, when the fountain and blade are first sufficiently retracted to clear the roll, so that the blade can be readily serviced, inspected, and replaced. This also allows varying the wiping angle.