US3467059A - Method and apparatus for applying a fluid coating - Google Patents

Description

Sept. 16, 1969 R. KORNER ET AL METHOD AND APPARATUS FOR APPLYING A FLUID COATING Filed July 11. 1966 M R R w x O T- 2 TO PER secowo SPEED UP 40 TO 200 REM.

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PAUSE IN TILT PHOSPHOR [SLURRY l0 T0 60 secouos FIG.4.

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IITO 15 PER sscouo RESUMED TILT T! LT STOPPED WITNESSES United States Patent 3,467,059 METHOD AND APPARATUS FOR APPLYING A FLUID COATING Renzo L. Korner, Horseheads, and Himanshu M. Patel,

Cayuta, N.Y., assignors to Westinghouse Electric Corporation, Pittsburgh, Pa., a corporation of Pennsylvania Filed July 11, 1966, Ser. No. 564,203 Int. Cl. Bc 11/14 US. Cl. 118-53 4 Claims ABSTRACT OF THE DISCLOSURE This invention relates to a method and apparatus for rotating and tilting a panel of a color television tube to apply a liquid coating thereto and removing the excess coating material therefrom by spinning off of the panel and collecting the excess on a rotating collector member. A second stationary collector member is associated with the rotating collector and the excess liquid drains into the stationary collector from the rotating collector.

This invention relates to a method and apparatus for applying a fluid coating to a foundation member and recovering the excess fluid.

One specific embodiment of the invention is that in which a phosphor slurry is applied to the face plate panel of a cathode ray tube in the manufacture of color television tubes.

In one method of manufacturing color cathode ray tubes, the phosphor screen is disposed on the surface of the face plate portion of the tube by depositing the phosphor slurry on the panel and then swirling the phosphor slurry over the face plate. The face plate panel consists of the viewing or face plate portion of the cathode ray tube and a rim or flange extends substantially perpendicular to the face plate portion. The rim and the face plate portion are normally referred to as the face plate panel. This face plate panel is sealed to the funnel portion of the tube after certain manufacturing steps.

In the method mentioned above in which the phosphor slurry is swirled over the surface of the face plate, the normal process is to first mount the face plate panel such that the viewing portion is substantially horizontal with the rim extending upwardly. The phosphor slurry which normally includes a phosphor of one color as well as a water soluble photoresist or light sensitive material is then dispensed on the upper or inner surface of the face plate panel. The phosphor slurry may be poured onto the central portion of the face plate and the slurry is then swirled over the surface by rotating and tilting the face plate panel. The excess slurry is removed by gravitational and centrifugal forces and normally washed away and lost. The slurry coating is then normally dried by suitable techniques such as infrared heat and then exposed to ultraviolet light. The areas of the phosphor and photoresist coating where the light strikes become hard due to the presence of photoresist and adhere to the face plate. The ultraviolet light renders the photoresist material in the exposed areas insoluble in water, whereas in the unexposed areas the photoresist retains its solubility in water. The panel is then Washed in water to remove the undesired phosphor-photoresist covered areas which are the unexposed areas and then the desired pattern of phosphor remains as is well known in the art. This phosphor screen is then dried and the above method is repeated for the other color phosphors to produce a multi-color phosphor screen.

In this prior art technique, the process is wasteful insofar as allowing the expensive excess phosphor slurry to be lost. This is particularly true in view of some of the recent developments in phosphors in which certain of the phosphors are more expensive. Another problem is that certain of the materials in the phosphor slurry create a problem as far as the affluent water treatment.

Accordingly, it is the general object of this invention to provide a new and improved method of coating a foun dation member with a fluid and recovering the excess fluid.

It is another object to provide a new and improved apparatus for coating a foundation member with a liquid and recovering the excess liquid.

It is a more particular object of this invention to provide an improved method and apparatus for coating a color television viewing screen with a phosphor slurry and recovering substantially all of the excess phosphur slurry for reuse.

Briefly, the present invention accomplishes the above cited objects by providing apparatus for rotating and tilting a foundation member onto which a liquid coating is to be applied and in which a first collector is mounted about the foundation and rotates and tilts with said foundation for collecting the excess liquid after coating the foundation member. The excess liquid is removed by gravitational and centrifugal forces. A second collector member mounted about said first collector member tilts with the apparatus but does not rotate and collects the excess liquid collected by the first collector. The excess liquid is removed from said first collector by centrifugal and gravitational forces. The excess liquid is removed from said second collector by gravity flow.

These and other objects and advantages of the present invention will become more apparent when considered in view of the following detailed description and drawings, in which:

FIGURE 1 is an elevational view of a filming machine, partly diagrammatic, embodying this invention;

FIG. 2 is an enlarged sectional view of a portion of FIG. 1;

FIG. 3 is a diagrammatic view illustrating a face plate panel in the initial load or phosphor slurry dispensing position;

FIG. 4 is a diagrammatic view illustrating the face plate panel in a second position after the coating is applied and just prior to removal of excess slurry;

FIG. 5 is a diagrammatic view illustrating the face plate panel in a third position after substantial removal of excess phosphor slurry to rotating collector; and

FIG. 6 is a diagrammatic view illustrating the face plate panel in a fourth position after and final phase of operation.

Referring to FIGS. 1 and 2, the filming and drying machine has a base 10 which is normally secured to the floor and is provided with two upright members 11 between which is rotatably supported a horizontal shaft 12. The shaft 12 has a spur gear 14 attached to one end thereof and is meshed with a worm gear 15 driven by an electric motor 16 which rotates the shaft 12 about its horizontal axis. The electric motor 16 is controlled by a suitable timing means illustrated by the block 18. Mounted to the shaft 12 is a tubular support member 20 which is in turn secured to a non-rotating cylindrical collector member 22. The members 20 and 22 are rigidly secured to the shaft 12 and rotate therewith.

A rotary shaft 24 is also secured to the shaft 12 and rotates therewith and the shaft 24 also rotates about its own axis. The shaft 24 is driven by a motor 26 which is controlled by suitable timing means 28. The end of the shaft 24 extends through the support member 20 and the shield 22 and is secured to a turntable 30. The turntable 30 consists of a disk-like base 32. Mounting lugs 34 are provided on the base 32 for attaching and securing a rectangular or cylindrical tube face panel 36 to the base 32. In the specific device shown, mechanical means are shown for securing and holding the tube panel 36 but it is, of course, obvious that a vacuum chuck or any suitable means may be used holding the tube face panel 36. The base member 32 is a circular disk and mounted 'at the periphery of the base 32 is a rotating collector member 40 which is rigidly secured to the base 32 and rotates therewith. The collector 40 is tubular in shape and of greater diameter than base 32 and tapers inwardly to form a frustoconical configuration. The larger diameter ends of the collector 40 surrounds the base 32 with an annular space 42 provided therebetween. The larger diameter end of the collector 40 extends below the upper surface of the base 32. The smaller diameter end of the collector 40 extends above the upper surface of the panel 36. Mounting members 44 are secured to the base 32 and the inner surface of the collector 40 for securing the member 40 to the base 32. The annular space 42 which is provided at the lower portion of the turntable surrounding the outer periphery of the base 32 permits any liquid that is thrown from the tube panel 36 onto the collector 40 to leave the collector 40 through this annular space 42.

The liquid leaving the turntable 30 will be collected by the non-rotating collector 22. The collector 22 is cylindrical in shape and provided with an aperture 46 in one section thereof to permit liquid collected therein to be drained from the non-rotating collector 22. The collector 22 which is substantially L-shaped in cross section is provided with an annular base portion 50 below the base 32 and substantially parallel to the base 32 and extending from its inner diameter adjacent the outer periphery of the base 32 to beyond the collector 40. An upwardly extending flange 52 is provided on the inner periphery of the base portion 50 and an upwardly extending flange 54 is provided on the outer periphery of the annular base member 50.

The operation of the machine is best illustrated by FIGS. 3, 4, and 6. The tube panel 36 is mounted as illustrated in FIGS. 1, 2 and 3 wherein the table 30 is in a horizontal position. The phosphor slurry consisting of suitable materials such as phosphor (zinc sulfide), polyvinyl alcohol, ammonium dichromate and water is introduced into the center portion of the tube panel 36. The amount of the liquid may be about 150 cc. and about 20 percent of this slurry will be required to coat the tube panel 36. The tube panel 36 is then rotated at a speed of about 2 to 20 rpm. by motor 26 and simultaneously the tube is tilted forward from its horizontal position at a rate of A to 1 per sec. by motor 16. This is illustrated in FIG. 3. The face panel 36 continues this movement until it rotates to an angular position 20 to 30 from where it started. This is illustrated in FIG. 4. A pause in tilting of from to 60 sec. duration now takes place during which rotation is increased to 40 to 200 r.p.m. Tilting then resumes at a rate of 1 to per sec. as shown in FIG. 5 until a total angular displacement of from 80 to 120 is reached as shown in FIG. 6. Rotation and forced drying is continued for another 2 to 4 minutes.

The phosphor slurry flows from the inner portion of the panel 36 and coats the inner surface during the operation between FIG. 3 and FIG. 4. During the opera- 4 tion as represented between FIG. 4 and FIG. 5, the excess phosphor slurry is thrown over the upper edge of the panel 36 and is collected on the inner surface of the rotating collector 40. In that the rotating collector 40 is a portion of a cone instead of a cylinder, centrifugal force is added to the gravitational force to drive the spun excess phosphor slurry downward toward the opening 42. The opening 42 permits the slurry to spin and drain off onto the non-rotating collector 22 and is collected therein. The phosphor slurry will flow within the fixed shield 22 by gravitational forces to the aperture 46 provided in the lower portion of the shield 22 when tilted. This liquid may then be collected in a container provided below and the material thus collected may be reused.

It should be noted that when the slurry arrives at the rotating collector 40, it is subjected to centrifugal force. Under this condition, the droplets of slurry can not exist as individual droplets. The centrifugal force will flatten the droplets immediately so that no buildup can take place. This is an important feature because the thicker the slurry accumulation on the rotating shield 40, the more likely flaking will result. Flaking is undesirable because the particles could ruin the screen if they were to land on the screen surface.

We claim as our invention:

1. A filming apparatus for coating a liquid on a tube panel comprising a tube panel holder for holding said tube panel, means for rotating and tilting said tube panel holder, a rotatable collector member provided about said tube panel and secured to said tube panel holder for collecting excess liquid from said tube panel when said tube panel and said rotatable collector are rotated by said means at a speed to throw said excess liquid from said tube panel, an opening in the lower portion of said rotatable collector member for draining said excess liquid from said rotatable collector, and a non-rotatable collector surrounding said rotatable collector for collecting said excess liquid drained from said rotatable collector and permitting gravity flow of said excess liquid from said non-rotatable collector.

2. The filming apparatus as described in claim 1 in which the inner surface of said rotatable collector is frusto-conical surface with the enlarged end facing inwardly.

3. The filming apparatus as described in claim 1 in which said opening is annular.

4. The filming apparatus as described in claim 3 in which said non-rotatable collector is provided with an aperture through which said excess liquid flows from said filming apparatus.

References Cited UNITED STATES PATENTS 2,054,155 9/1936 Dulken 118-55 X 3,364,054 1/ 1968 Weingarten. 3,376,153 4/1968 Fiore.

DAVID KLEIN, Primary Examiner US. Cl. X.R.

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