US2872954A

US2872954A - Automatic cathode-ray tube manufacturing apparatus

Info

Publication number: US2872954A
Application number: US610102A
Authority: US
Inventors: James S Bailey
Original assignee: Rauland Borg Corp
Current assignee: Rauland Borg Corp
Priority date: 1956-09-17
Filing date: 1956-09-17
Publication date: 1959-02-10
Anticipated expiration: 1976-02-10

Description

Feb. 10, 1959 J. s. BAILEY 2,872,954

AUTOMATIC CATHODE-RAY TUBE MANUFACTURING APPARATUS Filed Sept. 17. 1956 2 Sheets-Sheet 1 Rack United States PatentfO AUTOMATIC CATHODE-RAY TUBE MANUFACTURING APPARATUS James S. Bailey, Chicago, Ill., assignor to The Rauland Corporation, a corporation of Illinois Application September 17, 1956, Serial No. 610,102

1 Claim. (Cl. 141-263) production has resulted in the expenditure of largesums of money and man-power to the end of providing a machine which will carry out the process of applying a luminescent screen in a completely automatic manner and which will accomplish this result etficiently and dependably.

With the advent of aluminized television screens, it became desirable to apply a film of organic material over the back surface of the luminescent screen; it likewise is highly desirable that the film applying process be completely mechanized. It has been appreciated that this filming process should preferably be carried out on the same apparatus that is utilized to apply the luminescent screens, since more efficient and economical operation would result from the attendant reduction of-bulb handling.

Various approaches at mechanization have been tried, usually involving the use of a continuously moving conveyor onto which the bulbs are loaded at one end, are carried slowly along beneath associated screening and filming apparatus, and finally are carried around and under the other end of the conveyor to decant excess settling solution out of the screen and filmed bulb. However, it has been found that the shrinkage rates tend to run excessively high; a shrinkage rate is a' measure of the percentage of unsatisfactory tubes produced by the screening and filming apparatus. Rejection of the bulbs may be the result of any of various reasons, including uneven distribution of the film or the application of either too heavy or too light a layer of the film.

Apparatus capable of overcoming the aforementioned difiiculties and which permits the automatic continuous production of cathode-ray tubes of very good quality at lower shrinkage rates than possible with prior art techniques is claimed and described in the co-pending application of Jerome J. OCallaghan, Serial No. 600,851, filed July 30, 1956, now Patent No, 2,845,043, dated July 29, 1958, and assigned to the same assignee as the present invention. In that application, there is included a description of apparatus for dispensing film solution onto the surface of settling solution previously utilized in the settling of luminescent particles onto the faceplate of the bulbs. The film dispenser must be capable of depositing the film solution onto the settling solution surface in accurately predetermined quantities and in a manner which minimizes any sort of disturbance to the settling solution to provide an improved dispenser for use with cathode-ray tube screening apparatus.

Another object of the present invention is to provide an improved film solution dispenser for dispensing accurately predetermined quantities of the solution and which is capable of dispensing the film solution onto the settling solution surface with a minimum of disturbance.

A further object is to provide an improved dispenser in which film solution contained therein under a substantially constant pressure is dispensed at a reduced pressure and thus at a correspondingly reduced velocity.

Still another object of the present invention is to provide a film' dispenser which contains film solution under a pressure higher than desirable for satisfactory film dispensing and yet which is capable of dispensing the film solution at a very low velocity.

Apparatus for dispensing film solution onto settling solution contained within a cathode-ray tube bulb, in accordance with the present invention, includes a conduit for conveying the film solution. Control means, including a first tube having a predetermined internal crosssectional area, is disposed in fluid coupling relation with the conduit for establishing the volume flow rate of the film solution at a predetermined velocity. Dispensing means, including a second tube of pipette character having an internal cross-sectional area greater than that of the firsttube, receives-the film solution from the control means and dispenses the film solution at a velocity less than that established by the control means.

The features of the present invention which are believed to be novel are set forth with particularity in the appended claim. The organization and manner of operation of the invention, together with further objects and advantages thereof, may best be understood by reference to the following description taken in connection with the accompanying drawings, in the several figures of which like reference numerals identify like elements and in which:

Figure l is a general'view, partially broken away, of cathode-ray tube manufacturing apparatus embodying the present invention;

Figure 2 is a fragmentary view, partly in cross section, of a film dispenser embodying the present invention; and

Figure 3 is a cross sectional view taken along line.3-3 of Figure 2. g

In the overall view of the apparatus shown in Figure l for purposes of illustration, a series of cathode-ray tube bulbs 20, supported with their neck portions 20a uppermost and their faceplates 20b horizontal, are carried horizontally from left to right by a conveyor 21 moved at a uniformspeed by means of a drive motor 22 coupled to. conveyor 21 through a gear-unit 23 and a sprocket 24. Sprocket 24, at the right end of the apparatus, and a similar sprocket 25, at the other end of the apparatus, are journaled in bearings 26 mounted upon a stationary horizontal beam 27. Suitable conventional mechanism may be employed to maintain a constant tension in conveyor 21. Bulbs'20 are secured to conveyor 21 by means of hinged clamps 29.

Carried above conveyor 21 on a stationary track-way 30 supported by uprights 28 is a screening carriage 31 movably supported on track-way 30 by rollers 32; trackway 30 is supported separately from conveyor 21 to minimize the transfer of vibration from one carriage to the conveyor. A piston cylinder 33 is mounted on carriage Slandencloses a piston having a piston rod 34 afiixed at its outer end to a block 35 secured to track-way 30, extension of piston rod 34 being effective to move carriage 31 in the direction of movement of conveyor 21.

Carriage 31 includes equipment for first dispensing a measured quantity of a settling solution into one of the bulbs 20 and then for dispensing a measured quantity of a slurry including a luminescent phosphor into the previously settling solution. For injecting thesettling solution, a conduit 38 is supported for vertical movement by a flexible linkage 3? guided over an idler gear 40 and aflixed to the piston rod 41 of a hydraulic actuator 42. Hydraulic actuator 42 is operated only in response to engagement of a conventional cam follower 43, moving from left to right, with a cam 44 supported by track-way 30. On the upper end of conduit 38 is a conventional dispenser 16 for delivering a measured quantity of settling solution from a reservoir indicated at 47 and operated in response to suitable micro-switches (not shown) during the time that conduit 38 is lowered to a preset position within one of bulbs 20. Mounted to telescope over conduit 38 is a neck-finder and guiding means 50 for accurately directing conduit 38 through neck portions 20a upon the down-stroke of conduit 38.

For dispensing the slurry of luminescent powder into .the settling solution previously dispensed through conduit 38, there is a conduit 55 suspended from a flexible linkage 56 for vertical movement by means of a hydraulic actuator 57 keyed to operate by action of a cam follower 58 engageable with cams 44 in the same manner as actuator 42. A guiding means is mounted on conduit 55 and is identical with guiding means 50. At the upper end of conduit 55 is a mixing hopper 60 into which a measured quantity of powder is injected from adispenser 61 together with solution from a reservoir indicated at 62, the solution and powder being thoroughly stirred by a mixer 63 and then, upon operation of a magnetic .valve 64 keyed by micro-switches or other suitable means to open when conduit 55 is projected within a bulb 20, the mixture or slurry is allowed to flow downwardly -through conduit 55 into the body of settling solution 65 previously dispensed into bulbs 20.

A second carriage 70 is carried on track-way 30 by means of wheels 71 and supports siphoning and film dispensing equipment. Carriage 70 is similarly driven by means of a hydraulic actuator including a piston cylinder 72 enclosing a piston from which a piston rod 73 extends; .piston rod 73 is aflixed at its outer end to a block 74 supported by track-way 30.

Carriages

31 and 70 are controlled in their movement along track-way 30 by means of a synchronizing system which includes a valve 76 (shown only in connection with carriage 70 for sake of clarityof the drawing, identical valves being employed for controlling the operation of actuators 33and 72) having an operating member 77 engageable with one of a series of cams 78 alfixed on conveyor 21, one cam 78 being provided for each of the bulbs 20; a detailed description of this synchronizing system is included in the above-mentioned co-pending OCallaghan application. Also cooperating with the synchronizing system is a stationary cam 79 carried on a frame-member 79a and which cooperates with valve 76 to limit movement of carriage 70 and cause reversal in its movement after a complete cycle of operation. A similar cam (not shown) is provided in connection with carriage 31.

In the instant embodiment, carriage 70 supports equipment utilized in the filming portion of the overall process; included on carriage 70 are rough and fine siphon systems for removing a portion of settling solution 65 from bulbs 20, the rough siphon being capable of removing the settling solution at a high-volume flow rate and being operated to lower the solution level only approximately to a particular level desired in connection with the below-described operation of the film dispensing equipment. This rough siphon system comprises a conduit 80'supported from a flexible linkage 81 afiixed to a hydraulic actuator 82 and controlled to effect reciprocation of conduit 80, in the same manner as for actuators 42- and 57,

by means of a cam follower 83 engageable with earns 44. A guiding means 85 telescopes over conduit 80 in a manner identical with that of guiding

means

50 and 59. Conduit 80 is-coupled by a flexible hose 86 to a suction systern indicated at 87 and described in more detail in the co-pending OCallaghan application. Spaced in the direction of conveyor movement beyond conduit is a fine siphon conduit 88 provided with a guiding means 89 and suspended by a flexible element 90 from a hydraulic actuator 91 responsive to a cam follower 92, reciprocation of conduit 88 being initiated in the same manner as that above described with respect to conduit 38. If desired, reciprocation of both conduits 30 and 88 may be controlled by a single common actuator. Conduit 88 is coupled to suction system 87 by a hose 93 and is utilized for drawing oft settling solution 65 down to a very accurately preselected level.

Carriage 70 also supports a film dispenser for applying precisely measured amounts of film solution onto the surface of the settling solution remaining in the bulbs 20 after the siphoning steps and arranged to insure the formation of an even film over the settling solution surface. The illustrated embodiment of the film dispenser includes a'conduit depending downwardly from a reservoir 101 supported by a flexible element 102 attached to a hydraulic actuator 103 controlled by a cam follower-104 to operate in the same manner as that above described with respect to conduit 38, so as to lower conduit 100 successively into each of bulbs 20 during their movement by conveyor 21. Conduit 100 also includes a guiding means 106 which operates in a manner similar to that of guidingmeans 50 and the others and which,

again, is described in detail in the aforementioned co pending OCallaghan application. The film dispenser includes a valve for controlling the fiow of film solution into bulbs 20, which valve is operated by an air cylinder 107 powered by an air source indicated at 108 upon the actuation .of suitable micro-switches which function in response to the lowering of conduit 100 to project its lower -end into one of the bulbs 20.

Power for all of the hydraulic actuating devices is provided by a single hydraulic power pack indicated at 110, which may be of conventional construction including a reservoir of hydraulic fluid and a pump for maintaining hydraulic pressure in the system. Hydraulic power pack 110 is coupled to each of

hydraulic actuators

42, 57, 82,

'91, and 102; in addition, hydraulic power pack 110 is utilized together with valve 76 and the corresponding valve associated with carriage 31 to control the extension of piston rods 73 and 34 for moving

carriages

70 and 31, respectively.

Before proceeding further, it is desirable to understand the general operation of the apparatus shown in Figure 1. In operation, bulbs 20 are secured by clamps 29 onto conveyor 21 at the lefthand end of the apparatus. The bulbs are then carried smoothly and evenly from left to right while they undergo the several above mentioned operations. Initially, a measured amount of settling solution 65 is introduced into each of the bulbs 20 through conduit 38. During the initial filling period, conduit 38 is lowered to project its lower end within the bulb while the bulb continues its uniform movement, the

synchronizing system being effective to move conduit 38 from left to'right in precise step with the bulb movement. Subsequently, after conduit 38 has been withdrawn, earriage 31 is moved to the left to bring conduit 55 into a position where it is lowered into the bulb 20 previously filled with settling solution 65. Again, carriage 31, and hence conduit 55 is moved along precisely in step with the bulb movement during a period of time when the powder slurry from hopper 60 is flowing through conduit 55 into settling solution 65.

After the powder slurry has been introduced into the bulbs 20, the powder settles through settling solution 65 during the time interval elapsing as conveyor 21 moves 'the bulbs progressively along toward a position beneath conduit 80 of the rough siphon. By the time conduit 80 is lowered to immerse its lower end into solution 65,

a desired amount of phosphor has settled into adhering relation with faceplate 20b. After the rough and fine siphoning steps, respectively by means of

conduits

80 and 88, film dispenser conduit 100 is lowered to a position at which its lower end is slightly above the surface of the remaining amount of solution 65, and film solu tion from reservoir 101 is dispensed onto the settling solution surface. After withdrawal of conduit 100, the remaining settling solution is decanted from bulbs 20 out from under the solidified or partially solidified film layer during travel of the bulb around sprocket 24 at the righthand end of Figure 1. During the decanting, the film layer first aflixes itself to the upper inside portions of the bulb near faceplate 20b and then, as the bulb is tipped outwardly, the film layer falls smoothly over the faceplate as the settling solution is poured off out from under the film layer. After decanting of the excess solution, the bulbs are returned along the underside of the conveyor to the loading station, at the left end of Figure 1, from where they are removed.

The general advantages resulting from the moving of the bulbs 20 slowly and evenly along their path of travel are old and well known in the art; more accurate and even settling of the luminescent powder is obtained by preventing agitation or sloshing of solution 65. Hence, frame 28 is of rugged construction and the entire assemblage is constructed of heavy, strong materials and preferably is firmly secured to a suitable foundation. It is also preferred to employ suitable conventional apparatus to prevent operation either of the raising and lowering mechanisms or of the dispensers 61 and 62 in the absence of a bulb in a particular set of the clamps 29.

Figure 2 shows in detail the film dispenser mentioned above with respect to Figure l and comprising a conduit 100 suspended from a flexible linkage 102. Figure 2 also illustrates guiding means 106. In this instance, guiding means 106 comprises a sleeve 164 secured to an inverted funnel-shaped member 165 slidable within a box 166 afiixed to floor 70a and having a hole 167 in its top surface 167a. Sleeve 164 has a collar 170 adapted to land on surface 167a and which, in cooperation with the upper end of sleeve 164 and the different vertical dimensions of the apparatus, limits downward movement of first the guiding means and then conduit 100 to predetermined positions. Conduit 100 is carried at its upper end portion 210 by means including a housing 211 hooked onto flexible chain 102. The bottom surface 212 of housing 211 abuts against the upper end of sleeve 164 to limit downward movement of conduit 100 and thereby to determine the lowermost position of the conduit lower end 214. Flexible means such as chains 215 are connected between bottom surface 212 and collar 170; as shown in Figure 2 wherein conduit 100 is in its lower position, chain 215 is slack, the excess links piling on top of collar 170. However, as flexible linkage 102 pulls the conduit upwardly, chain 215 becomes taut after conduit lower end 214 is raised to a position above neck 20a and, as conduit 100 continues to move upwardly, guiding means 106 also is raised free of neck portion 20a so that, after the withdrawal of conduit 100, carriage 70 may be moved back to its initial position ready for the next cycle. For guiding conduit 100 within sleeve 164, a pair of

bearings

217 and 218 are secured respectively within the upper and lower parts of sleeve 164.

More particularly with respect to the film dispenser itself, reservoir 101 is relatively wide as compared with its height, the upper end of conduit 100 being coupled into the bottom of reservoir 101 so that film solution 220 stored therein flows downwardly from reservoir 101 through conduit 100. For controlling the flow of film solution 220 through conduit 100, a valve is disposed in conduit lower end portion 214. As shown in detail in Figure 3, the preferred valve comprises a valve stem 222 which is journaled in the bore of and cooperates with a hollow valve cylinder 223 pressed within lower conduit end 214. Valve stem 222 is an elongated rod extending through reservoir 101 and coupled at its top end by a lever 224 to air-cylinder 107 which, when actuated by compressed air from source 108, causes valve stem 222 to rotate. Near the lower end of valve stem 222 is a longitudinal groove 225. Another groove 226 is cut longitudinally partially along the bore of valve cylinder 223; groove 225 is positioned on valve stem 222 to span the remaining, ungrooved portion of valve cylinder 223 when valve stem 222 is turned to vertically align

grooves

225 and 226. Valve stem 222 is of a diameter less than the internal diameter of conduit so as to provide a space 227 which is filled with solution from reservoir 101. With valve stem 222 turned as shown in Figure 3, the flow of solution in conduit 100 is prevented; however, when valve stern 222 is turned to align

grooves

225 and 226, solution flows from space 227 through

grooves

225 and 226 from where it is conducted downwardly through a tube 230 about which more will be said below.

As so far discussed, the film dispenser, including guiding means 106, is described in detail and claimed in the aforesaid co-pending OCallaghan application. The problem is to very evenly and smoothly apply the film solution onto the surface of settling solution 65. To this end, solution 65 is accurately siphoned down to a precisely controlled level'which is controlled through the cooperation of accurate vertical dimensioning of conduit 88 and guiding means 89 and the similar accurate positioning of film dispenser conduit 100 by accurately dimensioning the latter with respect to the vertical dimensioning of guiding means 106 together with correlating the levels of top surfaces 167a associated respectively with each of the guiding means 85, 89 and 106. As a result of this cooperation between the siphoning and the positioning of lower conduit end 214, the latter is spaced above the surface of solution 65 by a minimum distance so as to reduce splashing of the film solution into the settling solution surface. As the preferred valve comprising stem 222 and cylinder 223 is operated, that is, as stem 222 is rotated to move

grooves

225 and 226 out of alignment and thereby terminate film solution flow, the column of film solution is sliced laterally. The result of cleanly severing the column of film solution is to terminate its flow without imparting increased velocity to the film solution remaining just below the valve, which increased velocity, if permitted, would tend to propel the last drop or two of film solution into the settling solution whereupon uneven distribution of the film solution occurs. It should be noted that a substantially constant head of pressure is maintained on film solution 220. In use, reservoir 101 is of a capacity to store solution for a long period of time, preferably for at least a regular work-shift of the attending personnel. The pool of film solution 220 contained in reservoir 101 is substantially greater in width than in height, while conduit 100 preferably is many times as long as the height of film solution in reservoir 101; the length of conduit 100 preferably is well over an order of magnitude greater than the height of stored solution. As a result, the variation in the height of the film solution stored in reservoir 101 is but a very small percentage of the total length of the film dispensing apparatus and, hence, the pressure imparting downward movement to the film solution remains substantially constant during long periods of operation. Therefore, by controlling the action of air-cylinder 107 to hold the film solution valve in its open position for a constant time interval, a very closely controlled amount of film solution is always dispensed onto the settling solution surface. The control of the air-cylinder may be accomplished by any of numerous well known timing devices which may be either electrically or mechanically operated.

The present invention contemplates improving film dispenser performance by providing means for effectively minimizing the pressure at which the film solution is dispensed; the invention permits dispensing the film solution 7 onto the settling solution surface at a very low velocity even when a disproportionately large pressure head exists on the film solution contained in portions of the conduit above its lower end. Thus, it has particular utility in a film dispenser of the above described character wherein, for purposes of maintaining a substantially constant pressure head over a long period of time, film solution is stored in a wide, shallow reservoir from where it flows through a conduit having a length preferably well over an order of magnitude greater than the height of the stored solution. Such a dispenser maintains a substantially constant pressure head for the reason that the amount of change in solution level in the reservoir is but a small percentage of the totalheight of the system and hence of the total pressure head as viewed at the bottom of the dispenser conduit. Thus, while a comparatively long conduit is preferred, the resultant pressure head tends to impart a correspondingly high velocity to the dispensed solution. However, by reducing the pressure on the solution before it is dispensed from conduit lower end 214, its velocity is lowered to a point at which the film solution flows lightly onto the surface of settling solution 65 without imparting turbulence thereto. To this end, a portion of conduit 100 is of a predetermined internal cross-sectional area; a tube 230 of small diameter fits snugly within the bore of conduit 100 preferably near the lower end thereof below valve cylinder 223 and thus in fluid coupling relation with the conduit. Immediately below tube 230 is a second tube 232 of a larger diameter and in fiuid coupling relation with tube 230. In the present instance,

tubes

230 and 232 are of one-piece construction, both being drilled longitudinally through a plug 234 pressed within the lower end of conduit 100 up against valve cylinder 223. The upper end is counterbored as indicated at 236 to receive film solution from groove 226 and to provide space for the lower end of valve stem 222.

When groove 225 is moved into alignment with groove 226, film solution 220 flows by gravity downward through space 227 and the aligned grooves into tube 234%. The internal diameter of the latter is of a size such that its cross-sectional area preferably is smaller than the crosssectional area of all portions of the fluid path above tube 230; however, the total cross-sectional area of

grooves

225 and 226 may be of a similar magnitude. The result is that tube 230 controls the volume rate of flow in the dispenser; the resultant pressure on the film solution flowing through tube 230 together with the cross-sectional area of the latter determines the amount of film solution which is dispensed for a given time interval of valve opening.

Upon emerging from tube 230, the film solution enters tube 232 of larger internal diameter than that of tube 230. While in actual use with conventional film solutions dispensed in comparatively small quantities tube 232 may be considerably larger in internal diameter than tube 230. its maximum cross-sectional area must be sufficiently small that it retains what may be termed a pipette char-- actor; in other words, when closed at its upper end, the tube or pipe retains a column of liquid within its bore against the force of gravity. By way of analogy, it is common knowledge that when the upper end of a typical drinking straw is sealed after the lower end of the straw has been immersed into a pool of water, the water will be retained within the lower portion of. the straw even though the latter is withdrawn from the pool. This effect is the result of a combination of several factors; in gencral, it can be said that the cross-sectional area of such a pipette tube as related to its length, and thus its internal volume, must be less than that value at which the weight of the liquid held within the tube exceeds the surface tension forces which tend to retain the undersurface of the liquid intact and to seal the liquid to the inner walls of the tu e. As long as the weight of the liquid remains below the critical pipette amount, the liquid does notrun out of the bottom of the tube when its top is closed; any tendency of the liquid to move downwardly relative to the tube is resisted bya resultant vacuum within the other end of the tube. In the present instance, the film solution in tube 230 acts as a seal for the upper end of tube 232 and therefore prevents the solution within the latter from running away from the solution in the former.

'Thus, as solution emerges from tube 230 into tube 232 it acquires an increased cross-sectional area; with a given velocity of the solution established in tube 230, the velocity of solution flow within tube 232 is reduced in proportion to the difference in the cross-sectional areas of the two tubes. For practical purposes, the usual film solutions can be treated as incompressible whereupon the volume rate of flow equals the cross-sectional area multiplied by the velocity. In the present apparatus, the volume rate of How is maintained substantially constant by the action of tube 230 in response to the substantially constant pressure head above tube 230. Thus, as the area increases the velocity decreases. Therefore, in accordance with the present invention, the pressure and hence the velocity at which the film solution is dispensed from conduit 160 is reduced below that pressure and velocity which would otherwise occur.

Such a velocity reduction as is attained by the present invention is enhanced by minor head losses or reductions in pressure head resulting from changes in the crosssectional area of the fluid column. It may be shown that a pressure head reduction h exists which corresponds approximately to the following equation:

where D is the internal diameter of tube 230, D is the internal diameter of tube 232, V is the velocity of the film solution in tube 239 and g is the constant representing the force of gravity. Such a reduction is the equivalent of shortening the length of conduit while yet the latter in actuality remains of a comparatively long physical length.

As mentioned above, tube 230 preferably is of a crosssectional area smaller than that of any portion of thc flow path above tube 239. The result of this is to permit accurate ..iow control of the dispensed film solution while requiri 1g that only

tubes

230 and 232 need be machined to accurate tolerances, since the internal crosssectional areas above plug 234 may be of substantially larger cross-sectional area than that of tube 230. In addition, the reduction in cross-sectional area as the fluid enters tube 230 contributes an additional head loss or reduction in pressure head. it may be shown that this reduction of pressure head 11 is given approximately by the following equation:

7 Z 2 aggi Where V is the velocity of the solution above tube 230, g is the gravitational constant and K is a constant which becomes larger as the amount of cross-sectional area reduction increases. The value of K is subject to empirical determination; by way of example, for at 2:1 reduction the constant is usually between A and /2 depending to some extent upon the characteristic of the particular solution employed.

The present invention contributes to improved film dispensing by enhancing laminar flow in the dispensed solution. As the valve comprising cylinder 223 and stem 222 is closed, small rotational forces may be introduced into the film solution in the upper portion of tube 230. The narrow, elongated character of this tube together with the yet longer tube 232 contributes to smoothing out any turbulence existing in the solution present in these tubes.

In a commercial embodiment of the invention which has been operated steadily for several months while producing screened and filmed cathode-ray tubes at a commercially profitable and competitive shrinkage rate, the

following typical parameters are employed. Bulbs 20 are spaced approximately 20 inches apart on conveyor 21 which is moving uniformly at a speed of approximately 1%, feet per minute. In the first step of the process, a conventional 21 inch cathode-ray tube bulb is filled with about 22.5 liters of a deionized water-electrolyte settling solution dispensed through conduit 38. In the next step of the process, the powder slurry dispensed through conduit 55 is a mixture of 7.7 grams of commercial grade fluorescent powder and 215 milliliters of potassium silicate in 500 milliliters of deionized water. Rough siphon conduit 80 is spaced from powder disensing conduit 55 by a distance such that the powder is permitted to settle for approximately 14 minutes. The rough siphon then takes the settling solution level down to about 2% inches above conveyor 21 after which fine siphon conduit 88 removes the settling solution down to a precise level above conveyor 21 whereupon the depth of the remaining solution is about two inches. Film dispensing conduit 100 is subsequently lowered to dispose its extreme lower end just above the settling solution surface whereupon 0.5 to 1 cubic centimeter, depending on tube screen size, of floating-type nitrocellulose lacquer, the film solution, is applied onto the settling solution surface; the lacquer has a viscosity of 1220 cps. at 80 F. Reservoir 101 is approximately one inch in height and six inches in diameter, while conduit 100 is approximately 60 inches long. Tube 230 has an internal diameter of .046 inch and is approximately 1" long. Tube 232 has an internal diameter of .063" and is approximately 4 /z inches long. It must be emphasized that close attention to detail is required to produce satisfactory screening and filming.

It will thus be seen that the dispenser of the present invention is capable of dispensing the film solution in accurately predetermined amounts onto the settling solution surface with a minimum of disturbance to the latter. Even though the film solution contained within the film dispenser conduit is under a pressure head normally in excess of that permissible for proper dispensing, the pressure on the film solution actually dispensed is reduced to a value aifording correspondingly reduced velocities to the film solution as it is deposited onto the settling solution.

While a particular embodiment of the present invention has been shown and described, it will be obvious to those skilled in the art that changes and modifications may be made without departing from the invention in its broader aspects. Accordingly, the aim in the appended claim is to cover all such changes and modifications as fall within the true spirit and scope of the invention.

I claim:

An apparatus for dispensing a liquid film solution, under conditions which inhibit turbulence, onto a settling solution contained within a cathode-ray tube bulb supported with its neck portion uppermost comprising: a constant pressure reservoir for storing a body of film solution; a first conduit having a passageway of predetermined cross-sectional area coupled to and depending downwardly :from said reservoir; 21 second conduit having a passageway smaller in cross-sectional area than that of said first conduit and depending in coaxial alignment therefrom; valve means interposed between said first and second conduits for discharging said film solution from said reservoir to said second conduit; a third conduit constituting the discharge outlet of said apparatus, depending in coaxial alignment from said second conduit and having a passageway with a cross-sectional area large with respect to that of said second conduit and said passageway having a length such that a column of said liquid supported therein by the surface tension of the liquid at the lower extremity of the passageway will not break the surface at said extremity; and means for projecting and withdrawing the lower end of said third conduit into and out of said bulb neck portion.

References Cited in the file of this patent UNITED STATES PATENTS 1,477,485 Haskell Dec. 11, 1923 2,030,084 Winton Feb. 11, 1936 2,282,576 Hamilton et al. May 12, 1942 2,823,500 Brown Feb. 18, 1958 FOREIGN PATENTS 112,738 Austria Aug. 10, 1929