US2751829A - Machine for developing photo-printed coatings on metal webs - Google Patents

Description

N. B. MEARS MACHINE FOR DEVELOPING PHOTO-PRINTED COATINGS ON METAL WEBS Filed June 25. 1951 3 Sheets-Sheet l June 26, 1956 N. B. MEARS 2,751,829

MACHINE FOR DEVELOPING PHOTO-PRINTED COATINGS 0N METAL WEBS Filed June 25. 1951 3 Sheets-Sheet 2 I N V EN TOR. M

June 26, 1956 NB. MEARS 2,751,829

MACHINE FOR DEVELOPING iHOTOJRINTED COATINGS ON METAL WEBS Filed June 25. 1951 3 Sheets-Sheet 3 IN VEN TOR.

%& Z @4/ from 5r MACHINE FOR DEVELOPING PHOTO-PRlNTED COATINGS N METAL WEBS Norman E. Meats, West St. Paul, Minn, assignor to Buckbee-M-ears Company, St. Paul, Minn, a corporation of Minnesota Application June 25, 1951, Serial No. 233,323

2 Claims. (Cl. 95-94) This invention relates to the manufacture of articles of precision from thin metal webs by a succession of operations which may comprise coating one or both sides of the web with a light-sensitive material, photo-printing a pattern or design on the light-sensitive coating, developing the printed coating to expose the areas of the metal covered by the soluble portions of the coating, heating the web to carbonize or otherwise harden the insoluble coating defining the pattern or design, and thereafter etching through the exposed areas of the web to form apertures therein of the precise sizes and shapes and in the precise locations required. The present invention relates particularly to a machine for developing and heat treating the photoprinted coating on webs of the class described.

It is an object of my invention to provide a machine for automatically, rapidly, thoroughly and uniformly developing the photo-printed surfaces of thin metal Webs.

A particular object is to provide a machine of the class described which is adapted to continuously move an elongated photo-printed web through one or more baths and sprays of suitable developing liquid and then through a heating chamber wherein the insoluble coating defining the design or pattern is rendered sufliciently durable to resist the action of the etching agent subsequently applied to form apertures in the metal of the web.

A further and particular object is to provide an improved machine of the class described comprising a plurality of tanks containing a developing liquid or liquids in combination with means for guiding and actuating the web through the liquid in the tanks, the guiding means comprising a plurality of pairs of wheels arranged to support the web along its margins only during its passage through and to and from the tanks whereby the thin metal web and essential coating thereon are protected against damage caused by contact with any of the machine parts.

Among the articles of manufacture which may be improved and reduced in cost by the use of the present invention are apertured masks for television tubes, control grids for electric discharge devices, fine screens for mechanical separation of solid particles, reticles for fire control and sighting instruments and other articles requiring precise location of minute perforations or apertures in thin metal blanks.

If the apertures in such articles are to be formed by etching, the metal web or blank sheet must be less than .02 inch thick and is usually within the range .001 to .006 inch thick. Pure metals, e. g., copper, silver, nickel or tin are best suited for accurately controlled etching treatment and the Web should be of uniform thickness. Thin webs of this character are difficult to handle because of their malleability, flexibility, and general tendency to become locally deformed as by wrinkles, creases and other indentations, and the photo-printed coating, prior to the heat treatment, is fragile and subject to damage or destruction by frictional contact with parts of the machine. By the present invention such detrimental de- "nited States Patent Ofiice 2,751,829 Patented June 26, 1956 formation of the metal web and damage to the coating is avoided and important economies in the quantity production of photo-printed webs are obtained.

Referring to the accompanying drawings which illustrate an embodiment of my invention, by way of example and not for the purpose of limitation:

Figure 1 is a side elevational view showing the develop ing machine, with a portion of one of the tank walls broken away to show parts otherwise concealed;

Fig. 2 is a vertical section taken approximately on the line 2--2 of Fig. 1;

Fig. 3 is a fragmentary horizontal section taken on the line 33 of Fig. 1;

Fig. 4 is a fragmentary section taken on the line 44 of Fig. 2;

Fig. 5 is a fragmentary sectional view of the coupling for the receiving reel shaft;

Fig. 6 is a side elevational view of the oven for heat treating the developed coating, together with the associated power-actuated reel;

Fig. 7 is a top plan view of the oven and associated mechanism with a portion of the top wall broken away;

Fig. 8 is a central vertical longitudinal section through the oven;

Fig. 9 is a fragmentary section taken on the line 9-9 of Fig. 8, and

Fig. 10 is a fragmentary section taken on the line 10-40 of Fig. 9.

As shown in Figs. 1, 2 and 3, I provide a plurality of tanks, indicated respectively by the numerals 11, 12 and 13, adapted to contain developing liquid or solution. These tanks are supported on a suitable frame which projects upward from the top of the tanks to support revoluble guide members for the coated web to be treated. An elongated web 15 carrying the photo-printed coating to be treated may be withdrawn from a roll 14 and is trained successively on pairs of guide wheels 16, 17, 18, 19, 20, 21, 22, 23 and 24 arranged to guide it to and from baths of liquid contained in tanks 11, 12 and 13. These guide wheels convey the web along a sinuous path beneath the surface of the liquid in the several tanks.

A water supply pipe 25 has valve controlled branch pipes 26, 27, and 28 adapted to supply Water to the several tanks. As best shown in Fig. 3, the pipe 27 has a pair of horizontally extending branches 27a and 27b provided with spray nozzles 27c arranged to direct liquid sprays against opposite coated surfaces of the web 15 as the latter emerges from the tank 12. The branch 27b has a swivel connection with the pipe 27 which permits this branch to be swung to an inoperative position, indicated in broken lines in Fig. 2, when the web 15 is to be threaded between the spray pipes in preparation for the operation of the machine. By a similar arrangement of branch pipes 26a and 26b, each carrying spray nozzles, the surfaces of the web 15 as it leaves the tank 11 may be sprayed. Liquid in the tanks 11, 12 and 13 is maintained at a predetermined elevation by means of overflow pipes 29 having their open upper ends located at the elevation required. These overflow pipes may be connected to drain or waste conduits 30 at their lower ends.

The several pairs of guide wheels 16-24 are free to revolve on axially disposed supporting shafts, and, as best shown in Figs. 2 and 3, each of these wheels has an annular flange 31 and a narrow cylindrical periphery 32 adapted to support the Web 15 by engagement with a narrow longitudinally extending margin thereof only. As shown, the flanges 31 of each pair are disposed closely adjacent to the opposite side edges respectively of the web. By this arrangement of rotary guide members I avoid all frictional contact with the photo-printed coating on the web and thereby guard against damage to the coating defining the design on the web. Each of the pairs of guide wheels 16, 18, 2t), 22 and 24 are supported on fixed frame members provided with bearings for the axial shafts for these wheels and each of the pairs of wheels 17, i9, 21 and 23 are movable substantially vertically from their normal submerged positions near the bottom of the tanks to positions near the tops of the tanks. When in the latter positions the web may be passed or threaded readily from one pair of guide wheels to another and beneath the lower peripheries of the wheels 17, 19, 21 and 23.

To facilitate the raising and lowering of the normally submerged guide wheels, an axial shaft 33 supporting each pair of them is slidable vertically under the guidance of a pair of channel shaped guides 34 and each end of the shaft 33 is connected to a vertically extending bar 35 which is slidable in one of the guides 34. At their upper ends the bars 35 of each pair are connected together by a cross bar 36 and a pulley 37 is mounted centrally on the bar 36 for engagement with a cord 38. One end of this cord is anchored on a cross bar 39 extending across the top of the overhead frame and the opposite end is provided with a handle 41 adapted to be manipulated to raise and lower the normally submerged guide wheels, the cord being trained on suitably located pulleys 41 and 42 and being provided with a fastening cleat 43 secured to one of the side frame members of the machine. By suitable manipulation of the cord 38, the elevation of the connected wheels 21 may be adjusted and these wheels may be supported in the upper part of the tank 12 during the threading of the web preparatory to operation of the machine. Similar mechanism is provided for raising and lowering the normally submerged pairs of guide wheels 17, 19 and 23.

To protect the coated surfaces of the web against damage in the handling of the roll 14, a web or continuous strip 44 of paper or other suitable material is usually wound between the several convolutions of the metal web 15 on the roll 14. As the web 15 is withdrawn from this roll the protecting strip 44 is also withdrawn and wound on a roll 45 supported in suitable bearings carried by the frame of the machine.

In operation, the web 15 is withdrawn continuously from the roll 14 by means of the reel hereinbefore described whereby tension is applied to the developed web 15a as it leaves the periphery of the guide wheels 24. Thus the web is moved from the guide wheels 16 along the circuitous path beneath the surface of the liquid in the tank 11 determined by the pairs of guide wheels 17, 18 and 191, and is then passed over the guide wheels 26 to and beneath the surface of the liquid in the tank 12 under guidance of the wheels 21, thence over the peripheries of the wheels 22 to the tank 13 and, after passing through the liquid in the latter, under the guidance of the wheels 23, is carried over the Wheels 24 to the heat treating mechanism.

When certain of the common types of cold top or hot top enamels are used as the light sensitive coating on the metal web, the photo-printed coating may be developed by the use of ordinary tap Water in the tanks 11 and 12 and it is preferable to use a suitable wetting agent in an aqueous solution in the tank 13. Such wetting agent may be added from time to time as required in suitable proportion to the water fed to the tank 13 through the pipe 36.

As shown in Figs. 6l0, the thoroughly washed and developed web 15a passes, while in continuous motion, to and through a heating chamber, indicated generally by the numeral 46, in which the web is heated to a temperature sufficient to harden, bake on, or carbonize the remaining coating defining the design or pattern on the web. A pair of guide wheels 47 are supported on a bracket projecting from an end of the chamber 46 to guide the developed web 15a to a narrow, elongated opening 48 in an end wall of the chamber and pairs of guide wheels 49 and 50 are mounted within the chamber 46 to carry the web along a sinuous path to an exit opening 51 in the cham- 4 her. Each of the guide wheels 47, 49 and 50 is, like those of the developing mechanism, formed and arranged to make contact with the coated web only along a margin thereof.

Air within the chamber is heated to the desired elevated temperature by groups of heating elements 52 arranged to heat opposite sides of the web and having bafiie plates 53 disposed to diffuse the heat. A fan 54 is operatively connected to an electric motor 55 and arranged to circulate the heated air in the chamber 46. It will be evident that all of the heating elements in the chamber 46 are spaced from the web undergoing heat treatment and that photo-printed areas of the Web are heated by radiation from the bathe plates 53 and chamber walls and by convection from the heated air currents. Heat is not conducted to the coated areas of the web directly from any heating element. Access to the web within the chamber 46 is provided through a top opening which is normally closed by a door 56.

Upon emerging from the chamber 46, the heat treated web indicated at 15b is wound on a reel 57 which is rotated at a suitable speed through connections with an electric motor 58, speed reducing gearing in a casing 5 and chain drive connections with an axial shaft 6% carrying the reel 57. To facilitate the removal and replacement of the reel 57, the shaft 66 is made removable longitudinally from the reel and through a supporting bearing 61 and is provided with a coupling sleeve 62 operatively connecting the shaft 60 with a coaxial driven shaft 63. As best shown in Fig. 5, the sleeve 62 has a fixed connection with the shaft 66 and is provided with a pin 64 engaging the shaft 63 in a transversely extending slot 65 in the end thereof.

As indicated in Figs. 6 and 8, a continuous strip 66 of paper or other protective material may be fed from a roll 67 to the reel 57 so that the successive convolutions of the web 15b on the reel are separated one from another by the protective strip 66. To guard against damage to the web 15b as it passes out through the opening 51 in the chamber 46 adjustable guides 68 are provided for engagement with the margins only of the web. As best shown in Figs. 9 and 10, each of the guides 68 has a notch disposed to slidably receive a margin of the web and is mounted on a plate 69 by means of screws 7% fitting in elongated slots in the guides to permit adjustment of one guide relative to the other, laterally of the web. The supporting plates 69 are also made adjustable in a similar manner to accommodate webs of various widths.

In operation, it will be evident that the heat treating mechanism, like the developing mechanism, operates continuously as the web is drawn through the machine by the power-driven reel 57. Where the coating on the web is a hot top enamel composed, for example, of a bichromate and glue, it should be carbonized preparatory to etching treatment and may require heating to a temperature on the order of 550 to 600 degrees F. for a period of about five and one-half minutes. To aiford such heat treatment the web may be caused to travel at a rate of approximately 16" per minute along a path of about ten feet in length within the heating chamber 46. Otherwise, if the web has been coated with a cold top enamel, it may be hardened sufficiently to resist the etching agent by heating to a temperature of from 300 to 400 degrees F. for a shorter period of time. The reel 57 is rotated at a speed which will cause the developing and heating treatment to be continued for the period of time required. The use of this machine results in the elimination of much of the hand work ordinarily required and more rapid, thorough and uniform treatment of the web, with resultant economies in the cost of preparing the web for the etching treatment.

My invention makes the mass production of thin metal articles of precision of a wide range of sizes and shapes feasible because the outlines and designs of a multiplicity of individual articles may be reproduced photo-mechanically on metal webs of many feet in length, of self-sustaining thickness and widths best suited to the particular article to be formed. Where articles of large size, e. g., of several square feet in area, such as the larger aperture masks for color television tubes are to be formed, a single row of the photo-printed coatings defining the individuai masks may be disposed along a web such as the web 25 and the individual photo-printed designs may extend entirely across the web between the narrow margins thereof engaged by the guide wheels, as hereinbefore described in detail.

In other cases, the coatings defining the individual articles may be arranged in a plurality of rows extending longitudinally and spaced laterally of the web. For such arrangement, additional guide wheels may be provided to support the Web intermediate its margins and arranged to make rolling contact with the longitudinal areas of the web between rows of the coatings defining such laterally spaced designs. Thus narrow wheels, without flanges, may be provided on each of the shafts supporting the flanged guide wheels at suitably spaced intervals on the several axial shafts supporting each pair of flanged guide wheels.

Either before or after the etching treatment, the individual articles may be separated one from another by die cutting the web along the outline of each article, or the separation of the individual articles may be performed by etching procedure simultaneously with or subsequent to the formation of the apertures in the thin metal blank or web by etching.

Having described my invention, what I claim as new and desire to protect by Letters Patent is:

1. A machine for developing and baking photoprinted coatings of fragile character on both sides of an elongated metal Web simultaneously comprising, means for guiding said web for longitudinal movement along a determined path with both of the photo-printed coatings exposed for treatment, said guiding means engaging the web along its longitudinal margins only, means spaced along said path for successively applying developing fluid to both of the coated sides of the web and then heating both to a temperature sufficiently high to bake on the coatings, said heating means comprising, a heating chamber containing radiant heating elements which are spaced from the path of said web at opposite sides and longitudinally thereof whereby said coatings are heated equally at opposite sides of the web solely by radiation and con vection, and power-actuated means for continuously mor ing the web along said path and through said heating chamber under sumcient tension to support the web in spaced relation to said heating elements.

2. A machine for developing and baking photo-printed coatings on both sides of a metal web in accordance with claim 1 wherein said power-actuated means for continuously moving the web comprises a reel disposed to receive the web from said heating chamber.

References Cited in the file of this patent UNITED STATES PATENTS 891,289 Pease June 23, 1908 1,156,922 Nasief Oct. 19, 1915 1,579,399 Salins Apr. 6, 1926 1,924,758 Sullivan Aug. 29, 1933 2,169,758 Capstatf Aug. 15, 1939 2,385,681 Brick Sept. 25, 1945 2,541,353 Goetz et a1. Feb. 13, 1951

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