US3473942A

US3473942A - Aluminizing process

Info

Publication number: US3473942A
Application number: US491273A
Authority: US
Inventors: Malcolm E Magill; Walter Wentworth Slobbe
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1965-09-29
Filing date: 1965-09-29
Publication date: 1969-10-21
Anticipated expiration: 1986-10-21
Also published as: US3326224A; GB1158487A; DE1564724A1

Description

Oct. 21, 1969 E. MAGILL. ETAL. 3,473,942

ALUMINIZING PROCESS Filed Sept. 29, 1965 4 Sheets-Sheet l q INVENTORS lg MALCOLM E. MAG/LL 1 hg lTER. WENTWORTH 540555 ATTGRNEY Oct. 21, 1969 M. E. MAGILL ETAL 7 ALUMINIZING PROCESS Filed Sept. 29, 1965 4 Sheets-Sheet 2 INVENTORS g 5 W's/7E2 Mal-cowl E. MAG/LL Wmrwomk/ 540555 BY ATTORNEY M. E. MAGILL ETAL ALUMINIZING PROCESS Get. 21, 1969 4 Sheets-Sheet 4 Filed Sept. 29, 1965 INVENTORS MALCOLM E. MAG/LL .8 WRITER wz/vrwoxm $4055: BY

ATTOR/Vf) 3,473,942 ALUMiNlZING PROCESS Malcolm E. Magill and Wfiter Wentworth Slohhe, Seneca Falls, NIL, assignors to Sylvania Electric Products line, a corporation of Delaware Filed Sept. 29, 1965, Ser. No. 491,273 Int. Cl. 1805c 1.7/02; (109k 1/00; B44c 1/22 US. Cl. 117-8 2 Claims ABSTRACT F THE DISCLOSURE A process for aluminizing the inner surface of cathode ray tube face panels of different perimetric shapes wherein the lacquer material is discretely removed from the panel sidewall portion by orienting a liquid-issuing nozzle in a manner to contact and follow the inner perimetric contour of the moving sidewall portion of the panel. By positioning the nozzle tracking means to contact and equidistantly follow the panel sidewall, there is provided a constant and substantially bulbous terminal formation of flushing liquid which peripherally follows the border of the lacquer coated screen and flushes the superfluous lacquer from the panel sidewall portion.

This invention relates to the manufacturing of cathode ray tubes and more particularly to a method for achieving improved lacquering and aluminizing of the screened face panel thereof.

It is conventional practice in the art of manufacturing color television cathode ray tubes, to apply a thin film or coating of aluminum to the back of the cathodoluminescent phosphor screen, that being the screen surface normally oriented toward the electron gun in the tube and away from the viewer. This aluminum coating provides a mirror-like finish which reflects, toward the viewer, a portion of the light from the screen which would otherwise be lost within the tube. It has been found that tubes so treated exhibit improved brightness and contrast in display presentation that is not evidenced in non-aluminized tubes.

In color cathode ray tube fabrication, a multi-phosphor patterned screen is usually applied on the inner surface of the substantially cup-shaped tube face panel in a manner to be suitably viewed therethrough. The formed screen is thence processed before the face panel is hermetically joined to the funnel or envelope portion of the tube. The plural cathodoluminescent phosphors, per se, are suitably disposed as multitudinous dots or discrete stripes in accordance with the several established procedures well known to the art. Prior to the application of the aluminized mirror coating, the multi-phosphor screen is precoated or overlaid with a thin film of lacquer to provide a suitable surface upon which to form the mirror. In addition, the lacquer serves as a temporary barrier to prevent the aluminum from penetrating and poisoning the phosphor crystals, thereby reducing or destroying the luminescent qualities thereof, during the aluminizing procedure. This lacquer film is subsequently removed by baking whereupon the reflective aluminum remains supported directly by the phosphor screen.

The deposition of the lacquer film, whether it be by the spray or slurry techniques, usually covers the whole of the interior of the face panel, coating not only the screen portion but also the peripheral panel skirt or sidewall area as well.

The aluminum coating is conventionally applied by a vaporization technique and usually covers the whole of the interior of the screen panel including the sidewall area. Since the lacquer is removed from the screen area by baking subsequent to aluminizing, it is important to renitcd States Patent 0 move all traces of lacquer from the sidewall area, peripheral to the screen, prior to aluminizing as any residual lacquer underlaying the aluminum on the substantially smooth sidewall area prevents adherence of the aluminum to the glass, and results in localized blistering of the aluminum coating when said residual lacquer is volatilized from therebetween during the aforementioned subsequent panel bake-out. It is important to have tight adherence of the aluminum coating to the panel sidewall not only to prevent blisters but also to insure electrical continuity of the anode coating covering the interior surface of the tube envelope, of which, the aluminum on the panel sidewall is an integral part.

Upon drying of the disposed lacquer film, prior to deposition of the aluminum film thereover, removal of the extraneous lacquer from the inner surface of the panel sidewall is a substantially manual operation. A lint-free cloth, moistened with a suitable solvent, is utilized to expedite softening and removal of the lacquer film from the panel skirt. This operation requires manual dexterity, especially in the area surrounding the several metallic buttons that are embedded in the sidewall of the panel, as it is desired to remove all of the extraneous lacquer up to substantially the edge of the screen. It has been found that the undesired lacquer can be removed with the exercising of proper care and diligence when the film is substantially dry as disturbing the wet lacquer adjacent the screen, with a solvent moistened cloth, is a delicate time consuming operation. Removal of the dried film is not entirely without complications as the wiping action tends to produce a somewhat roughened edge, and, in addition, there is the aforementioned difficulty of entirely removing all of the dried lacquer from the skirt area. Unfortunately, inadequate removal of the extraneous lacquer from the skirt area is not evidenced until after consummation of the subsequent aluminizing and lacquer bake-out processing steps. It is then that the tell-tale blisters make their appearance to indicate aluminizing of inferior quality along with a resultant increase in the scrap level of the manufacturing process. Even though the blisters may be small and not ruptured, they still are undesirable as they provide a possible source of loose metallic particles within the tube. Therefore, it is highly desirable to prevent blistering and at the same time insure electrical continuity by removing all traces of the lacquer film from that portion of the face panel where it is not desired.

Accordingly, an object of the invention is to reduce the aforementioned disadvantages and to provide an improved aluminizing process for color cathode ray tube fabrication.

Another object is to provide a method for discretely removing the extraneous portion of the lacquer film beyond the screen area to promote the formation of an unblemished film of aluminum over the whole of the interior of the screened panel.

An additional object is to provide a lacquer removal process to improve the quality of the aluminized color cathode ray tube product and additionally effect improved etficiency in tube manufacturing.

The foregoing objects are achieved in one aspect of the invention by the provision of an improved screened panel aluminizing process, wherein the applied lacquer, which forms an underlay over the screen for the subsequent aluminum coating, is removed while still in the liquid stage, from the skirt or sidewall portion of the panel adjacent the screen area. This is accomplished by positioning and thence rotating, a freshly lacquered panel on a horizontal plane with the inner surface oriented in an exposed downward position. A liquid issuing nozzle is oriented to perimetrically track the inner surface of the panel sidewall in substantially equidistant relationship.

The stream of liquid activated to issue from the nozzle impinges upon the moving sidewall in a circumferential sweeping manner to effect a constant substantially bulbous terminal formation of liquid which discretely flushes the lacquer material from the sidewall before film formation thereof materializes.

For a better understanding of the present invention, together with other and further objects, advantages, and capabilities thereof, reference is made to the following specification and appended claims in connection with the accompanying drawings in which:

FIGURE 1 is a partial cross-sectional view of an inverted color cathode ray tube face panel showing the cathodoluminescent screen with the lacquer coating covering the whole of the interior surface of the panel;

FIGURE 2 is another partial cross-sectional view of the same panel illustrating the flushing procedure for discretely removing the lacquer coating from the sidewall portion of the panel;

FIGURE 3 is still another partial cross-sectional View showing the panel with the lacquer removed from the sidewall portion of the panel;

FIGURE 4 is a top plan view showing the positioning of the face panel for removing the lacquer coating from the sidewall portion thereof;

FIGURE 5 is a partially detailed elevational view taken along the line 55 of FIGURE 4, with portions omitted to provide clarity, illustrating the horizontal inverted positioning of the panel;

FIGURE 6 is a partially sectioned elevational enlargement taken along the line 6-6 of FIGURE 4 detailing panel positioning prior to initiating lacquer coating removal;

FIGURE 7 is a plan view showing horizontal orientation of the liquid flushing nozzle and means for maintaining equidistant relationship with the panel sidewall;

FIGURE 8 is an enlarged exploded perspective showing features of the lacquer coating removal means; and

FIGURE 9 is a top plan view showing adaptations for accommodating a rectangular cathode ray tube face panel for lacquer coating removal.

In referring to the drawing, FIGURES 1, 2, and 3 show cross-sectional elevations of a cathode ray tube face panel 11 before attachment to the envelope funnel portion. Suitably embedded within the wall of skirt portion 15, and spaced therearound, are a plurality of metallic buttons 17, one of which is shown. The function of these buttons is to properly orient and support a foraminous shadow mask or grid, not shown, which is utilized for both screen formation and subsequent tube operation. The panel which may be round, elliptical, or rectangular in shape, has a substantially transparent viewing portion 13 and a sidewall or skirt portion 15 perimetrical thereto. On the inner surface of the panel a patterned cathodoluminescent screen 19, comprising a repetitive plurality of color-emitting phosphors, is suitably disposed in accordance with one of the known techniques of the art.

After the forming of the screen, the whole of the interior of the face panel 11 is rinsed with an aqueous wetting solution, not shown, containing a quantity of a selected Water soluble organic solvent which lowers the surface tension of the water. This provides uniform wetting of the panel and enables the aqueous solution to more closely follow the horizontal contour of the phosphor screen. When the lacquer coating is applied to the interior of the panel, the aqueous wetting film, being contiguous upon the topography of the screen, forms a thin continuous barrier to prevent lacquer penetration of the phosphor materials comprising the screen and thereby facilitates the deposition of a uniform lacquer coating 21 thereover.

A lacquer material formulation suitable for this usage has been found to comprise a solution of acrylic resin solids dissolved in at least one organic solvent selected from the group consisting essentially of toluene and xylene with the resin solids therein ranging substantially from 4.6 to 5.0 percent by weight. A suitable plasticizer, such as dibutyl phthalate, is added thereto in an amount less than one percent based on the weight of the resin solids. The resultant lacquer solution has a viscosity substantially within the range of 3.8 to 4.4 centistokes at 25 degrees centigrade. When toluene alone is used as the solvent, lacquer set up progresses in approximately 45 seconds (at approximately 25 degrees centigrade) to a film formation state. Thus, if the extraneous lacquer coating, disposed on the panel sidewall, is'to be removed by water flushing, such operation must be initiated within approximately 35 seconds of lacquer application.

It has been found that, if desired, the time of lacquer film formation can be retarded by adding xylene to the lacquer formulation with the toluene content being decreased accordingly.

The lacquer material is applied as a coating over the whole of the interior of the panel in accordance with one of the procedures known to the art such as by slurrying or spraying. From a manufacturing consideration, it is desired that the extraneous lacquer coating be removed from the panel sidewall immediately following lacquer coating application.

With reference to FIGURE 2, there is shown the method for expeditiously removing the lacquer coating from the panel sidewall in accordance with the invention. The freshly lacquered panel 11 to be subjected to the discrete lacquer removal operation, is horizontally oriented in an inverted manner and supported with the open face thereof in a downward position by suitable means not shown in FIGURE 2 but subsequently illustrated in FIG- URES 4 and 6 and fully described later in this specification. A plurality of liquid-issuing nozzles 23, one of which is shown, are oriented in a manner to maintain a substantially equidistant relationship with the skirt or sidewall portion 15 of the panel 11. Thus, when relative rotation 25 is provided between the panel sidewall 15 and the nozzle 23, the stream of liquid 27 issuing from the nozzle impinges upon the sidewall with desired constancy in a circumferential or perimetrical sweeping motion. In this instance, the stream of liquid 27 is water free from contaminating inclusions, although the invention is not intended to 'be limited to such as other compatible solvents may also be utilized.

With further reference to FIGURES 2 and 7, the nozzle 23 has a longitudinal axis 29 extended therethrough and sequentially maintained in a pivoted manner to effect substantially right angle ((15) relationship with a progressive line 33 tangential to the inner perimeter of the sidewall 15. Thus, during the relative rotational movement of the panel sidewall and the nozzle, there is maintained therebetween both a substantially constant distance and a substantially consistent angular orientation. These factors coupled with a water supply of constant pressure that is free of cavitations and gaseous inclusions provide a stream of water 27 that is discretely nozzle formed and directed toward the inner portion of the panel sidewall 15. The pressure of the stream of water is predetermined to effect a constant substantially bulbous terminal formation of water 37 upon impingement with the sidewall. This terminal formation of water has a substantially constant area configuration in keeping with the inner contour of the panel perimeter whether it be substantially straight or arcuate, to provide a substantially consistent pattern of impingement thereon and effect a discretely formed peripheral trimming edge of water having a vertical apex 39 oriented to substantially follow the border 41 of said lacquer coated screen.

When the perimetric contour of the panel is other than arcuate, as for example, a panel of substantially rectangular shape 4.3 with substantially arcuately formed corners 45 as illustrated in FIGURE 9, it is important that the pattern of water impingement and the trimming edge thereof exhibit uniformity regardless of the differential perimetric contour to prevent the trimming water from climbing the corners of the panel. This uniformity of the liquid trimming pattern is achieved by predetermining the area of Water impingement according to the most acute curvature of the perimeter in conjunction with the panel tracking means 49 fully described later in this specification. Whatever the size of the water trimming configuration, the volume of the stream of water is sufiicient to completely flush the extraneous lacquer coating from the panel sidewall before the inception of lacquer film formation. Thus, as shown in FIGURE 3, the cathode ray tube face panel 11 is ready for luminizing, wherein the cathodoluminescent screen portion is covered with a film of lacquer 21' from which the extra lacquer beyond the screen perimeter thereof has been water trimmed and flush removed to provide a lacquerfree sidewall surface.

In FIGURES 4, 5, and 6 lacquer removal means, in the form of a mechanical apparatus 48, is shown whereby the aforedescribed method of discrete lacquer removal from the panel sidewall is expeditiously accomplished.

In part, this lacquer removal apparatus 48 comprises a panel accommodation stage 51, which is circular in shape with a large central opening 53 therein. This stage is horizontally positioned and adequately supported around its peripheral region between vertically oriented pairs of stage rollers 55 contacting the upper and lower surfaces thereof. At least three pairs of these rollers are utilized in substantially equispatial relationship therearound, each pair being located on a suitable bracket 57 and afiixed to the top portion 59 of a horizontal base platform 61. The lateral placement of the stage is achieved and maintained by employing at least three spaced apart confining rollers 63 positioned to make circumferential contact with the circular stage. These confining rollers are mounted in a horizontal rotatable manner atop vertical holders 65 also oriented on the top of the base platform 61.

The periphery 50 of the circular stage 51 is formed to cooperate with associated drive means 67. As shown, the periphery is substantially channel-shaped to be congruent with a belt or chain-type linkage 69 which is utilized to impart desired rotation to the stage, from a powered drive gear or pulley 71, for a predetermined period of time to be later explained.

The aforementioned central opening 53 in the panel accommodation stage 51 is diametrically larger than the largest dimension of the cathode ray tube face panel 11 to be positioned therein. With particular reference to FIGURES 4 and 6, the lacquer coated face panel 11 is oriented open face down within the above-mentioned central opening 53. It is temporarily held therein by the panel edge 18 resting on the forward portions 77 of at least three spaced-apart panel rests 79. These, being pivoted means formed for vertical movement, are aflixed to the top of the base platform 59 and extended in a plane substantially parallel therewith toward the panel accommodation stage 51 thereabove.

The fulcrum or pivot 81 permits the forward portion 77 of the panel rest 79 to subsequently drop at a predetermined time to a slightly lower position in accordance with programmed actuation accorded to the rear portion 83 of the panel rest. An adjustable stop 85 in conjunction with a vertical resilient means 87, such as a helical spring, and a vertical pressure means 89, having a plunger 91 of restricted stroke, imparts predetermined vertical movement to the forward portion 77, the sequence of which will be later explained.

With the panel vertically preoriented on the panel rests 79, the retention of its horizontal position is facilitated by at least three panel retainers of two

types

93 and 95, spaced apart to make external tri-point peripheral contact with the external sidewall portion of the panel. Each of the two retainers 93, with the respective body portions 97 aifixed to the panel accommodation stage 51, has a panel contact pad 99 of substantially non-resilient plastic material formed and placed to fit the panel external periphery. The third panel retainer 95, which completes the triangulated retention arrangement, is likewise ailixed to the accommodation stage. This retainer is manually operated by lever 101 and has a resilient contact pad 103. When predetermined pressure is applied by mechanical linkage from lever 101, the panel 11 is securely positioned in an undistorted manner by the three retainers. Thus, the panel and the accommodation stage are oriented with a vertical axis 104 common to both.

With the panel properly positioned and retained relative to the accommodation stage by the

panel retainers

93 and 95, the panel rests 79 are dropped free from the edge of the panel to positions in a common plane therebeneath, and rotary movement is imparted to the stage by drive means 67. Lacquer coating removal means 105, quiescently positioned to be within the confines of the inverted panel on a plane substantially parallel with the top of the base platform 61, is actuated to bring the tracking portion thereof in contact with the inner sidewall surface of the revolving panel. This contact relationship with the moving sidewall is made by at least one panel tracking means 49 terminally afiixed to the inner end of a hollow tube 107 which is arcuately movable in a horizontal plane about pivot means 109 located on base platform 61; the pivot means having height adjustment provisions 110 to effect adaptability to the apparatus. Horizontal pressure means 111, located on base platform 61, has a horizontal plunger 113 oriented to make contact with an impact pad 115 integral to the exterior of tube 107. The plunger thrust imparts, to the lacquer removal apparatus, horizontal movement in the direction of the axis 104 and removes the panel tracking means 49 from the panel sidewall 15, this being the position of the coating removal means 105 during the aforementioned quiescent state wherein panel loading and unloading is accomplished. Reciprocal movement to bring the tracking means in contact with the inner surface of the panel sidewall is imparted by horizontal resilient means 117, in the form of a tensioned spring, which has one end attached to tube 107 at connection 119 in opposition to a point of aflixture 121 on base platform 61.

With reference to FIGURES 2, 4, 5, 7, and 8, the flushing liquid 27 is supplied to the nozzle 23, from a source not shown, through a flexible conduit 123, thence through the hollow tube 107 and its connecting hose 125. The inner extremity of tube 107, distal to pivot means 109, is closed by the jointure 127 with the vertical support post 129.

Tracking means frame 131 has a slotted opening 133 to receive support post 129 which is secured therein by set screw 135. A vertical swivel pin 137, on frame 131, mates with tracking head aperture 141 to provide pivoted movement to the head 139. A limit pin 175, adjacent to the swivel pin, slidably mates with an arcuate slot 173 in the base of the tracking head 139 to limit the arcuate movement thereof; the arcuate slot 173 being in spaced circumferential relationship with aperture 141. The upstanding portion 143 of the tracking head has a slotted bore 143 to accommodate placement of nozzle 23. Clamping screw 147, inserted through vertical bore 149, mates with a tapped hole, not shown, in upstanding portion 143 to secure the nozzle 23. A pair of rollers 151 and 151', having respective aXes 152 and 152', are movably mounted on the tracking head on vertical pins 153 and 153' in a manner for the peripheries thereof to extend beyond the forward edge 155 of the head. Thus, the rollers make two-point mobile contact with a portion of the inner surface 16 of panel sidewall adjacent the open edge 18 thereof.

The stance of this two-point roller contact with the panel sidewall is directly related to the center distance B of the axes 152 and 152'. As previously mentioned, it is important for the distance between the nozzle 23 and the inner surface of sidewall 15 to remain substantially constant during panel rotation in order to provide a consistent terminal formation of flushing water upon impingement with the sidewall. To maintain this desired distance relationship, the axes spread or center distance B is determined by the diameter of the rollers and the inner curvature of the panel sidewall. For a round panel, as shown in FIGURE 4, the stance of the two-point roller contact is not critical as the uniform curvature of the panel 11 facilitates a constant nozzle-sidewall distance relationship to effect a consistent water impingement pattern on the panel sidewall during the circumferential progression thereof. However, with a rectangular shaped panel 43, as illustrated in FIGURE 9, the stance of the two-point contact of the tracking rollers must be such as to maintain substantially the same nozzle-sidewall distance relationship at the arcuate corners 45 as on the straightaway portions 47 and 47'. Such is accomplished by selecting a roller center distance that will correctly track the corners; the tracking rollers having diameters in accordance therewith. Thus, an accurate cam follower relationship is provided wherein the inner surface of the panel sidewall, adjacent the open edge thereof, forms a continuous enclosed cam surface which is followed by the rollers of the tracking means, the rollers being held in contact therewith by the horizontal resilient means 117.

The rectangular panel 45, as shown in FIGURE 9, is held substantially at two corners by panel retainers 93' having contact pads 99 oriented to effect seated contact with the panel sidewall portions adjacent the corners of one side 44 thereof. The compression panel retainer 95 is positioned at substantially the mid-section of the opposite side 44 of the panel with the resilient contact pad 103' making contact therewith. Predetermined pressure is exerted by lever 101' to securely orient and retain the rectangular panel 45 in an undistorted manner within the accommodation stage 51 on an axis 104 common to both the panel and the stage.

With reference to FIGURES and 6, the top of the base platform 61 has an opening 159 therein at least as large as the central opening 53 in the panel accommodation stage 51. Suitably fitted into and positioned therein is an open drainage well 161, as of stainless steel, having a drainage port 163 to facilitate disposal of the liquid flushing effluent.

As described, placement of the lacquered panel 11 on the panel rests 79 is followed by the compressional orientation and retention of the panel by the

respective panel retainers

93 and 95. The operational sequence of the mechanical combination 48 is automatically governed by control center 167, designated in FIGURE 4. Details of this center are not shown or described as various known systems of control means can be utilized to initiate a desired sequence of operations. A multiple sequence timing device having provisions for automatic reset is preferred for this operation. Functioning of the mechanical combination is actuated by control switch 169 which initiates an automated program of related operations. The several vertical pressure means 89 are simultaneously activated to retract their respective plungers 91, which action permits the expansion of the vertically positioned springs 87 to simultaneously lower the forward portions 77 of the panel rests 79, thus freeing the open edge 13 of the panel from any obstructions. Activation of drive means 67 provides rotation to the circular panel accommodation stage 51 whereupon the several horizontal pressure means 111 are simultaneously activated to retract their respective plungers 113 thus permitting the horizontally oriented tension springs 117 to pull the panel tracking means 49 toward the moving panel sidewall; the tracking rollers 151 and 151' making contact with the inner surface 16 of the sidewall 15 in the region adjacent the open edge 18 of the panel. A stream of water 27 is thence initiated to issue from each nozzle 23 and impinge upon the moving lacquer-covered panel sidewall. The pattern of water impingement thus formed provides .1 consistent terminal formation of water 37 having a trimming edge 39 that efiiciently flushes away the extraneous lacquer coating from the panel sidewall, and from around the metallic buttons 17 embedded therein, before the inception of lacquer film formation thereon. The relative rotation between the panel sidewall and the stream of flushing water, should have uniformity and a constant rate of speed to provide the desired pattern of water impingement on the panel sidewall. The speed of rotation is related to the size of the panel and the perimetric length of the sidewall portion thereof, and should be of a rate to provide an initial flush of water to the whole of the perimetric length of the sidewall before lacquer film formation materializes. Additionally, it is important that splashing impingement and uncontrolled deformation of the peripheral trimming edge of water be strictly avoided. Upon completion of the flushing operation, there follows in sequence: cessation of the liquid flow, stoppage of the stage rotation, activation of the horizontal pressure means 111 whereupon the plunger 113 extends to move the tracking means 49 away from contact with the inner surface 16 of the panel sidewall. Subsequent activation of the vertical pressure means 89 extends the plungers 91 thereof to reposition the several respective panel rests 79 against the open edge 18 of the panel. Thus, the automatic cycle of the mechanical lacquer trimming apparatus is completed. Release of the horizontal panel retainers frees the panel to facilitate removal thereof from the trimming device.

The lacquer material remaining in the panel is retained in the form of a film covering the cathodoluminescent screen area where it adheres in conformance to the topography thereof. Upon drying of the lacquer film, a thin layer of aluminum is applied over the whole of the interior of the panel, preferably by a vacuum vaporization technique well known to the art.

The aluminizing procdeure is completed by a baking operation wherein the panel is subjected to a baking heat of approximately 450 degrees centigrade to decompose and volatilize the lacquer film from the screen area and remove other volatile materials that may be present.

Thus, there is provided an improved aluminizing proc ess for color cathode ray tubes wherein the discrete removal of the extraneous lacquer material from the panel sidewall promotes the formation of an unblemished film of aluminum over the whole of the interior of the screened panel. This process of coating removal advantageously utilizes the inner perimeter of the panel sidewall as a cam surface intimately contacted by at least one follower tracking means accommodating a liquid issuing nozzle to maintain substantially equidistant relationship therebetween and facilitate the formation of a uniform pattern of liquid flushing impingement perimetrically therearound. In addition to the superior quality of the resultant aluminized tube product, the discrete lacquer removal process provides improved efiiciency in color cathode ray tube manufacturing heretofore unachieved.

While there has been shown and described what is at present considered the preferred embodiment of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention as defined by the appended claims.

What is claimed is:

1. A process for aluminizing the inner surface of a cathode ray tube face panel of substantially rectangular shape having a sidewall portion with defined arcuate corners perimetrical to a viewing surface with a cathodolumi nescent screen disposed thereon, said process comprising the steps of:

applying an aqueous Wetting film to the interior of said screened panel to form a thin continuous barrier over said screen;

coating the interior of said panel and said wetted screen with a lacquer material;

positioning said freshly lacquer coated panel in an inverted manner with said inner surface oriented in an exposed downward position;

rotating said panel about an axis to effect horizontal movement to said sidewall portion;

positioning holding means accommodating at least one liquid-issuing nozzle to substantially contact said sidewall portion;

tracking said nozzle holding means in a manner to equidistantly follow the inner perimetric contour of said moving sidewall portion;

activating liquid issuance from said nozzle to provide a constant pressured stream of flushing liquid to impinge upon the inner surface of said moving sidewall in a circumferential motion to provide a constant and substantially bulbous terminal formation of liquid upon impingement therewith, said terminal formation being of a substantially constant area configuration predetermined according to the arcuate corners of the contour of said moving perimeter to provide a substantially consistent pattern of impingement on said sidewall and elfect a discretely formed peripheral trimming edge of liquid having a controlled vertical apex oriented to substantially follow the border of said lacquer coated screen, the volume of said stream of liquid being sufiicient to completely flush said lacquer coating from said sidewall before the inception of lacquer film formation to provide a lacquer-free sidewall surface; applying a thin layer of aluminum over the whole of the interior of said panel; and baking said panel to decompose and volatilize said lacquer material from said screen area and remove other volatile materials that may be present. 2. The process for aluminizing the inner surface of a cathode ray tube face panel according to claim 1 wherein said flushing liquid is water.

References Cited UNITED STATES PATENTS 2,987,415 6/1961 Taggett 117-102 ALFRED L. LEAVITI, Primary Examiner I. A. BELL, Assistant Examiner US. Cl. X.R.