US3108023A

US3108023A - Apparatus for painting tubular surfaces

Info

Publication number: US3108023A
Application number: US92559A
Authority: US
Inventors: Douglas E Griesemer; Morris R Weingarten
Original assignee: RCA Corp
Current assignee: RCA Corp
Priority date: 1961-03-01
Filing date: 1961-03-01
Publication date: 1963-10-22
Anticipated expiration: 1980-10-22

Description

Oct. 22, 1963 n. E. GRlEsEMER ETAL 3,108,023

APPARATUS FOR PAINTING TUBULAR SURFACES Filed March 1. 1961 United States Patent O 3,108,023 APPARATUS EUR PAENTHNG TUBULAR SURFACES Douglas E. Griesemer and Morris R. Weingarten, L ancaster, Fa., assignors to Radio Corporation 'of America,

a corporation of Delaware Filed Mar. 1, 1961, Ser. No. 92,559 8 Claims. (Cl. 118-215) 'Ihis invention relates to apparatus for painting or coating cylindrical surfaces and particularly to apparatus for painting a spiral stripecoating or coatings on 1an internal conically-shaped surface of the tubular wall of a cathode ray tube bulb. l

One type of cathode ray oscillograph tube, which has a bulb including a faceplate, a neck, and an interconnecting conical funnel section, is provided with a spiral strlpe of conductive paint (coating material) on the internal surface of the funnel. ln operation of the tube, an electrical potential is applied to the ends of the spiral 'str1pe to produce a gradient .electrostatic field longitudmally along the funnel section of the tube. Accordingly, the spiral stripe must be electrically continuous, and none of the turns of the spiral should be shorted out. Discontinuities, if present, prevent current flow along the spiral stripe and thus prevent generation o-f the desired gradient electrostatic field. Electrical shorts between turns o-f the spiral, if present, result in nonuni-formities of the desired gradient electrostatic field.

A device for painting the spiral stripe on the internal surface of the tunnel may include a paint applicator which is inserted into the funnel in contact with the internal surface thereof. The funnel and the coating device may then be rotated and moved longitudinally relative to each other so that the paint applicator traverses the desired spiral path on the bulb. However, some difficulties are encountered in painting the spiral since the surface to be painted varies in circumference along the longitudinal axis thereof. If uniformity oi the stripe is to be achieved, theV amount of paint applied per lineal unit length of the stripe must be maintained constant. This may be done either by continuously varying the rate of feeding of the conductive paint to the applicator, or continuously varying both the rotational and axial advance speeds or the apparatus. Prior ant apparatuses for achieving either of these two alternatives for maintaining uniformity of the spiral stripe have, at the best, been complex and costly.

It is'therefore an object of my invention to provide a new and improved apparatus ifor painting cylindrical surfaces and particularly a new and improved apparatus for painting spiral stripe conductive coatings on the internal surface of funnel-shaped cathode ray tube bulbs.

lt is a further object of my invention to provide a simple and inexpensive apparatus which will apply spiral stripe coatings on internal conical surfaces and which in so doing will automatically maintain constant the amount of coating material applied per lineal unit length of the stripe.

Briefly, apparatus accordi-ng to my invention comprises a pair of rollers rotationally coupled to each other, as for example by being fixed to a common shaft. The rollers are supported at the end of an arm which is extendable into a cathode ray tube bulb to position the peripheries of the two rollers in contact with the internal surface to be painted. Upon rotation and longitudinal advance of the bulb relative to the rollers, one roller is rotatably driven by its frictional contact with the surface and thus acts as a drive for the other roller which continuously dips into a paint-filled well and applies the paint -to the bulb surface in a spiral stripe.

ice

ln the drawings:

FIG. 1 is lan elevation View of apparatus according to the invention showing its application to a work piece in the form of a cathode ray tube envelope; and

FIG. 2 is an enlarged perspective view of a portion of the apparatus of FIG. 1.

Painting apparatus according to the invention may be attached to a conventional machine lathe -for the purpose of painting spiral str-ipe coatings on an internal surface of a cathode ray tube bulb. Thus, in FIG. 1 only those portions of the lathe which are necessary to an understanding of the invention :are shown. These lathe portions include a chuck 12 adapted to be rotatably mounted on the head stock of the lathe and a carriage 14 adapted to be moved toward and away from the chuck 12 by the lead screw of the lathe.

In operation, a cathode ray tube bulb 16 to be painted is mounted in the chuck 1 2 Afor rotation about its longitudinal axis 18, and the painting apparatus 10 according to the invention is mounted on the carriage 14 lfor extension into the bulb 16. The painting apparatus x10 may for example be mounted as shown on a lathe tool post 20 xed to the carriage '14.

The painting apparatus 10 comprises a bracket 22 which vis fixed, as by bolts to the lathe tool post 20. An arm 24 is pivotalfly mounted between its ends on the bracket 22 near the Ifree end thereof by a horizontal pin 26. The arm 24 4is oriented to extend `generally parallel to the bracket 22 so that it may be extended along withl the bracket into the bulb 16 through a neck section 30 thereof. A paint applicator 312 is` pivotally mounted on a yoke 34, which is in turn mounted on the support arm 24 near one end thereof. Bias means is provided for rotatably urging the arm 24 about its pivot 26 to press applicator l32 upward and against the internal conical surface `35 of the bulb lo. One simple fform of this means may comprise a Weight 36 hung from the other end of the support arm 24. Other alternative means, such as a spring loading of the support arml 24, for urging the applicator 32 into contact with the bulb surface 3S can be used.

FIG. 2 illustrates the details of the paint applicator 32 and its yoke support 34. The applicator 32 comprises a support member or block 37 through which a shaft 38 is rotatably mounted. A tracking or drive rolier 40 is fixed 'to the shaft 38 on one side of the support block 37 and a paint, i.e. applicator, roller` 42 is fixed to the shaft 38 on the opposite side of the support block 37. The two

rollers

40 and 42 are thus rotatably coupled together and are preferably closely spaced to each other. Collars 44 (only one of which is shown) are fixed to the ends of the shaft 38 to retain the rollers 40 4and 42 thereon. The shaft 38 is so disposed relative to the support block 37, and the rollers 401 and 42 are of such size, that both rollers extend slightly above one surface 46 'of the support block 37 so that they may peripherally contactthe surface 35 to be painted.

A housing member 48 having three sides and a bottom is secured to the support block 37 to partially enclose the paint roller 42. The housing `48 in combination with the end wall `S0 of the support block A37 thus provides a paint tank .52. When the paint tank 52 is lled or partially illed with a suitable paint, the painting roller 42 will extend or continuously dip into the paint. Y

In la preferred embodiment of the applicator 32, both the drive roller 40' and paint roller 42 are provided with peripheral bands or Itires 53 and 54, respectively, of a desired material. For example, since the drive wheel 40 should make good frictional gripping contact with the internal bulb surface 35, its band 53 is preferably of a material such as rubber. The band 54 on the paint roller is of a material most suitable for picking up and apply- 3 ing paint to the surface 35. The paint roller band 54 may be of a material such as felt, nylon, or leather. Alternatively, the paint roller band 54 may be omitted and the peripheral surface of the paint roller -42 knurled.

The yoke 34, which supports the applicator 32 on the arm 24, comprises a pair of generally L-shaped members 60. The two L-shaped members 60` are secured to the end of the support arm 24 by a bolt 62. The support block 37 is pivotally supported between the L-arms 60 at their ends by screws 66 (only one of Iwhich is shown) fastened to the support block 37. The support block 37 is preferably provided with slot-like recesses 68 at the sides thereof into which the L-arms 6) are disposed. The recesses 68 are of a sufficient depth and width to receive the L-arms 6G so that they do not extend beyond the ends of the support block 36. This minimizes the overall size of the applicator 32 and its mounting means 34, thus permitting it to be inserted into a smaller bulb neck than would otherwise be possible.

In the operation of the painting apparatus 10, the tank 52 is filled with a paint suitable for application to the bulb surface 35. Such a paint may, for example, comprise the ordinary conductive coating paint known in the industry as aquadag. With the 'bulb 16 mounted in the chuck 12, and the painting apparatus mounted on the carriage 14, the applicator 32 is then inserted into the bulb as shown in FIG. 1. The drive roller 4Q is thus pressed into frictional rolling contact with the bulb surface 35 by the force of the weight 36. The drive of the lathe is rthen engaged so as to rotate the bul-b 16 and axially advance the carriage 14 to move the applicator 32 in a direction toward the bulb neck 30. The drive roller is frictionally rotatably driven by virtue of its trolling contact with the rotating bulb surface 35. The painting roller 42, being coupled to the drive roller 49 is thus also rotatably driven. Rotation of the paint roller 42 causes it to pick up paint from the tank 52, and apply it to the bulb surface 35.

The amount of paint per unit stripe length applied to the surface 35 is automatically maintained constant since the amount of paint picked up is dependent on the rotary speed of the paint roller 42 which is in turn dependent upon the lineal length of the rolling contact of the drive roller 40. By properly adjusting the rotary speed of the bulb 16 and the axial movement of the carriage 14, a spiral stripe 69 of desired pitch is automatically applied to the bulb surface 35. The pivotal mounting of the applicator 32 on the ends of the yoke arms 64 permits the two

rollers

40 and 42 to maintain peripheral contact with the bulb surface 35 even though :the slope of the surface 35 relative to the axis 18 varies, and even though the diameters of the two rollers are different as hereinafter more fully described.

The amount of paint necessary to paint the desired stripe in some bulbs may be suitably contained in the tank 52. On the other hand, it may be desirable to feed additional paint to the tank 52 during the painting of the spiral. Furthermore, it may be desirable to maintain a uniform level of paint in the well 52. In order to continuously feed paint to the tank 52, an optional feature of the invention may be provided. This optional feature as shown in FIG. 2 comprises a small flexible tube 7) cornmunicating with the tank 52 and extending out of the bulb 16 along .the arm 24 and bracket 22. If desired, a pair of tubes 70 may be provided so that paint may be continuously circulated into and out of the tank 48 during the painting of the bulb surface 35.

The invention has been described in terms of painting a spiral stripe with spaced turns. However, a continuous complete coverage of the surface 35 may be obtained by adjusting the pitch of the spiral traversed by the applicator 32 so that one turn of the spiral is contiguous with or overlaps the adjacent turns. The width of the painting roller 42 may be increased so as to facilitate this mode of operation.

The diameters of the drive roller 4t) and the paint roller 42 need not be equal. In some cases it may be desirable to make the drive roller 40, for example, smaller than the paint roller 42 so that the paint roller will have a greater peripheral speed than that which would provide rolling contact between the paint roller 42 and bulb surface 35. The paint roller 42 will thus have a sliding relationship, faster or slower as desired, with the bulb surface 35 and will pick up and apply a greater or less amount of paint than would be the case if exact rolling contact existed. Such an embodiment of the apparatus 1? might be particularly desirable if the bulb surface 35 is soiled with foreign materials, such as the organic lacquer normally used as a preparatory surface for aluminization of the phosphor screens of cathode ray tube bulbs. A skidding application of paint by the paint roller 42 might tend to abrade soiled areas and thus force an adherence of the paint thereto where it would otherwise not adhere.

Since, according to the invention, a separate drive roller 40 is used to provide the rotation for the paint roller 42, and since the drive roller 40 can be positioned to precede the paint roller 42 along the spiral path, the drive roller never becomes wet with paint. By thus remaining dry, good frictional nonsiip contact of the drive roller with the bulb surface, and thus uniform driving of the paint roller, is assured. This would not be the case if a single roller were used for both providing drive and applying paint. Furthermore, the use of separate drive and paint rollers makes it possible to drive the paint roller at a peripheral speed other than that of rolling contact. The modification providing this feature and the advantages thereof are described in the preceding paragraph.

What is claimed is:

1. Apparatus for coating a cylindrical surface of a work piece comprising rotatable means on which said work piece can be mounted for rotation about the axis of said cylindrical surface, means movable rectilinearly parallel to said axis, an elongated support pivotally mounted on said movable means with one end thereof extendable axially along said cylindrical surface when said work piece is mounted on said rotatable means, a paint applicator pivotally mounted on said elongated support adjacent said one end thereof, said paint applicator comprising a drive roller and a paint roller rotatably coupled together and disposed to make peripheral contact with said tubular surface, and means for supplying paint to said paint roller.

2. Apparatus for painting a spiral stripe on the internal tubular surface of a cathode ray tube bulb, said apparatus comprising: rotatable means for supporting a cathode ray tube bulb for rotation about its longitudinal axis; advance means movable in a direction generally parallel to said longitudinal axis; a paint roller supported from said advance means and extendable into said bulb into peripheral contacting relationship with said internal tubular surface, means urging said roller against said internal surface into said contacting relationship, means for supplying paint to said roller, means for rotating said rotatable means and longitudinally advancing said advance means to cause said roller means to traverse a spiral path on said internal tubular surface, and drive means other than said roller coupled between said roller and said internal surface for controllably rotating said roller at speeds such that the peripheral speeds of said roller and the rates of traversal of said spiral path by said roller are maintained at a substantially constant ratio.

3. Apparatus adaptable for mounting on the carriage of a lathe for painting spiral stripe coatings on the internal conical surfaces of cathode ray tube bulbs, said apparatus comprising a bracket adapted to be mounted on said carriage, an arm pivotally mounted on said bracket about a given axis, a support member pivotally mounted on said arm adjacent an end thereof about an axis parallel to said given axis, a drive roller and a paint roller rotatably coupled to each other and rotatably mounted on said support member fwith their axes parallel and so disposed that both of said rollers can simultaneously make peripheral contact with said internal conical surface to be painted, and a paint tank mounted on said support member and so disposed that said paint roller extends thereinto.

4. Apparatus for painting a spiral stripe coating on the surface of a tubular member, said apparatus, when oriented in :operating disposition, comprising a bracket, a support arm pivotally mounted on said bracket about a rst horizontal axis, a paint applicator mounted on said arm adjacent one end thereof, and means pivotally urging said arm about said rst horizontal axis in a direction to move said pain-t applicator upwardly, said paint applicator comprising a support block pivotally mounted on said arm about a second horizontal axis, a shaft rotatably mounted in said support block on a third axis movable in a plane perpendicular to said second axis when said support block is rotated about said second axis, a drive roller and a paint roller fixed to said shaft, and an open top paint tank mounted on said support member with said paint roller disposed partly therein and extending out through the top opening thereof.

5. Apparatus according to claim 4 and wherein said paint roller is of larger diameter than said drive roller.

6. Apparatus according to claim 4 and including a paint feed tube connected' to said paint tank and extending therefrom back along said arm whereby said tube can be connected to a reservoir of paint to continuously feed paint to said tank during a painting operation of said apparatus.

7. Apparatus for applying a coating to a surface of a work piece while said work piece is being rotated, comprising a means for supporting and rotating said work piece, a movable supporting member movable parallel to the axis of rotation of said work piece, an elongated support member pivotally mounted on said movable means, an applicator pivotally mounted on said elongated support at one end thereof, said applicator comprising a drive roller and an applicator roller rotatably coupled together and adapted to make peripheral contact with the surface of said work piece, and means for supplying a coating material to said applicator roller.

8. Apparatus for applying a coating -to a surface of a work piece While said work piece is being rotated, comprising a movable supporting member movable parallel to the axis of rotation of said Work piece, an elongated support member pivotally mounted on said movable means, an applicator pivotally mounted on said elongated support at one end thereof, said applicator comprsing a drive roller and an applicator roller rotatably coupled together and adapted to make peripheral contact with the surface of said work piece, means for supplying a coating material to said applicator roller, and biasing means connected to the elongated support member for urging s-aid rollers against the surface of said work piece.

References Cited in the le of this patent UNITED STATES PATENTS 2,284,491 Mandell May 26, 1942 2,709,414 Powell et al May 3l, 1955 2,876,733 Bauman Mar. l0, 1959

Claims

1. APPARATUS FOR COATING A CYLINDRICAL SURFACE OF A WORK PIECE COMPRISING ROTATABLE MEANS ON WHICH SAID WORK PIECE CAN BE MOUNTED FOR ROTATION ABOUT THE AXIAL OF SAID CYLINDRICAL SURFACE, MEANS MOVABLE RECTILINEARLY PARALLEL TO SAID AXIS, AN ELONGATED SUPPORT PIVOTALLY MOUNTED ON SAID MOVABLE MEANS WITH ONE END THEREOF EXTENDABLE AXIALLY ALONG SAID CYLINDRICAL SURFACE WHEN SAID WORK PIECE IS MOUNTED ON SAID ROTATABLE MEANS, A PAINT APPLICATOR PIVOTALLY MOUNTED ON SAID ELONGATED SUPPORT ADJACENT SAID ONE END THEREOF, SAID PAINT APPLICATOR COMPRISING A SRIVE ROLLER AND A PAINT ROLLER ROTATABLY COUPLED TOGETHER AND DISPOSED TO MAKE PERIPHERAL CONTACT WITH SAID TUBULAR SURFACE, AND MEANS FOR SUPPLYING PAINT TO SAID PAINT ROLLER.