US3330212A - Etching machine paddle - Google Patents

Description

y 11, 1967 M. H. FISHABER ETAL 3,330,212

BTCHING MACHINE PADDLE Filed Oct. 24, 1965 INVENTORS. Marv/n H, F/lshaber John 0. H/ckenson 97' TORNE Y United States Patent 3,330,212 ETCHING MACHINE PADDLE Marvin H. Fishaber, Saginaw, and John D. Hickerson,

Midland, Mich., assignors to The Dow Chemical Company, Midland, Mich, a corporation of Delaware Filed Oct. 24, 1965, Ser. No. 504,965 Claims. (Cl. 10384) This invention relates to etching machines and more particularly concerns a novel paddle device, especially useful in curved plate powderless etching, and adapted to be used in curved plate etching machines.

Present commercially available curved plate paddle type etching machines splash the etchant substantially perpendicular to the plate or cylinder axis, while said cylinder rotates with periodic reversals. As the cylinder rotates in this manner and etching of the metal occurs, the etchant is naturally caused to flow in currents over the plate in the direction of curvature. This commonly results in severe tailing or in other words, the formation of excessively elongated image side walls in the direction of curvature. Transversely, the image shoulders are essentially perpendicular to the face of the plate and in many cases severe undercutting or undermining of the image may result.

It has been found beneficial in the powderless etching of curved plates or cylinders to impinge or splash the etchant solution in other than a perpendicular direction onto the plate during rotation relative to the cylinder axis.

The primary object of the present invention is to provide an improved paddle device for use in a curved plate powderless etching machine.

Another object of the invention is to provide a novel paddle for impinging etchant in a powderless etching machine onto a curved segment or cylinder at an angle of less than 90 degress to the axis of said cylinder.

Another object of the invention is to provide such a paddle which will impinge etchant onto a rotating plate in a sequential cycle of alternately opposing angles of less than 90 degrees to the plate or cylinder axis.

The invention will be more readily understood from the following detailed description and the accompanying drawing wherein:

FIG. 1 is an isometric view, partially cut away of an etching machine utilizing the novel paddle of the present invention wherein two paddles of one embodiment of the novel paddle device are disposed within the machine in a spaced relationship to each other on opposite longitudinal sides of a rotating curved plate held by a cylindrical plate holder or mandrel.

FIG. 2 is a side view of one of a novel paddle device similar to that shown in FIG. 1 except that the arrays of vanes on the fins thereof are oppositely directed.

FIG. 3 is an end view of the novel paddle device shown in FIG. 1.

With reference to the drawing and specifically to FIG. 1 the novel paddle 8 of the present invention comprises in general a plurality of longitudinally disposed outwardly extended fin members 10 around or forming an axle 12 on which to rotate. Each such fin 10 is provided along its lip or outer longitudinal portion 14 a longitudinal array 16 of parallel spaced directional vanes 18, with each set of vanes being preferably alternately directionally opposed. Preferably, the lip or outer longitudinal portion 14 of each fin 10 wil be angled in a common direction (toward the plate) so as to scoop-11p or skim etchant from the supply thereof at the bottom of the machine and impinge same against the rotating plate. These angles should not preferably exceed about 60.

FIG. 2 in side elevation shows in a more clear manner the alternating directional attitude of the vanes 18 on the various fins 10, and FIG. 3 shows an end view of the 3,330,212 Patented July 11, 1967 paddle and the common angulus disposition of the lip of each fin.

While there is no actual limitation as to the number of fins comprising the present novel paddle, a preferred and convenient number has been found to be four (4). In any event, the fins should be reasonably and equally spaced apart. It is preferred to have the direction of the vanes on the lip of alternate fins as opposing so as to impinge etchant first in one direction and then in another. The direction of the vanes, however, may be cycled in most any manner to obtain the desired etching effect as heretofore described.

In order that the present device be resistant to attack itself by the various etching solutions, most of which contain appreciable amounts of mineral acids such as nitric and hydrochloric acids, the device should be fabricated, for example, of stainless steel or other acid etch-resistant material.

When employing the present novel invention in an etching machine it is manifest that support and drive means (not shown in drawing) must be provided for operation thereof. In practice it is hereby intended that the present novel device be constructed as to render it adaptable to a simple substitution for conventional paddles in present conventional machines.

With this novel paddle when the paddle 8 is caused to rotate in an etching machine 20 and contact a level 22 of etching liquid 24- in the machine in conjunction with vanes or alternate fins it will operate to cyclically impinge (not shown) etchant at an angle of less than onto a rotating plate 26 to be etched, first in one direction then in another opposing direction. Splashing or impinging etchant in this directional manner produces a more uniform fiow of said etchant around the side walls of an image on the plate as it rotates, thus greatly reducing elongated image shoulders in the direction of curvature and undercutting in the transverse direction.

Among the advantages of the invention are that a significant improvement in shoulder uniformity of an etched image is obtained which allows deeper etching without undercutting of the image in the transverse direction of the curvature. Cleaner edges of the highlight dot areas in the direction of curvature are also obtained. Moreover, the paddles of the present invention can also be used for high quality etching of flat plates. Thus, if a machine has two plate movement mechanisms (i.e., one detachable means for movement of a fiat plate and a separate means for movement of a cylindrical or curved plate) the same machine can be conveniently used for etching either kind of printing plate. Overall, a general improvement in the appearance and quality of the etched curved plate is obtained by means of the present invention.

The terms curved plate or curved segment as used herein refers broadly to curved surfaces in general use for engraving and printing and include, for example, magnesium or zinc plate, sheet, thin wrap-around sheet, extruded tubing, extruded cylinders, impact extruded cans, thin wrap-around foil, and the like.

The following example serves to further illustrate the present invention but is not to be construed as limiting the invention thereto.

Example of invention A standard model M-32 Master brand powderless etching machine adapted for curved plates was modified by removing the conventional paddles (2 in number) and replacing these with one embodiment of present novel paddles substantially as shown in the appended drawing. The machine so-modified was then charged with 77 liters of a powderless etc-hing bath comprising 10 volume percent of 42 B. nitric acid, 0.685 percent by volume of monochlorododecyl diphenyloxide sodium sulfonate; 0.15

percent by weight of a monocarboxylic acid; 2.5 volume percent of a mixture of aromatic solvents of Panasol AN-1, Solvesso 150, and dodecyl benzene; the balance of the bath being essentially water.

a The bath was adjusted to a temperature within the range of fromabont 70 to 73 F. An etchable combinationcurvedplate or segment 8 inches in diameter exhibiting line and halftone image areas was clamped to the mandrel in the machine and rotated at about 30 to 60 'r.p.m., the direction of rotation being reversed about every seconds. Vanes on the fins of the paddles were longitudinal axis of the paddle. The paddles in the machine were also rotated at from about 300 to about 380 r.p.m. so as to splash etchant bath against the plate. The 1 machine was operated in this manner 'for about 8-10 minutes, whereupon, the machine was stopped and the etched plate removed and rinsed. The depth of etch varied from 18 to 21 thousandths of an inch. Because of the angle of the vanes on the paddle fins the angle at which the etchant impinged the plate during the etching 'operation was substantially non-perpendicular to the longitudinal axis of the plate.

As a quantitative measurement and indication of the quality of etching, an average angle of difference was obtained by computing the image shoulder angle in the direction of curvature and also in the transverse direction and determining the average difference over a number of measurements on the plate. The angle of difference so-determined was about 18, which is very acalternately set at opposing angles of about 30 to the a ceptable and quite desirable. This showed that an image a .dot, for example, had a substantially uniform shoulder.

Comparative example The procedure of the above example was repeated under the same conditions except that the conventional standard paddles were employed in the M-32 machine. The etchant impinged the plate perpendicularly. Again the angle of difference of the image shoulder was measured and computed, but was found to be about 34. This indicates that the image shoulder "in the direction of curvature was undesirable in that it was excessively elongated compared to the image shoulder in the trans- V verse direction and therefore the plate was of only limited 7 or marginal use for printing.

when, for example,

used therein provides an outstanding increase in quality of the etched plate by substantially reducing the elonga tion of the image shoulder" in the direction of curvature.

The present invention can be modified or changed without departing from the spirit or scope thereof, and it is understood that the present invention is only limited as defined in the appended claims.

We claim: 7 a 4 1. A rotatable paddle for use in curved plate etching machines comprising: a plurality of fin members each coupled along one longitudinal edge to form aycommon axle, the outer longitudinal portion' of each fin carrying an array of parallel, spaced, directional vanes, said vanes being disposed at an angle of less than to the longitudinal axis of the paddle and at least two of said arrays of vanes being directionally opposed. i

2. The paddle of claim 1 wherein uniformly circumferentially spaced apart.

3. The paddle of claim 1 wherein there are jacent fins.-

4. The paddleof claim portion of each fin is angled at less than 90"to the trans:

verse axis of said fin in the direction in which said paddle would be rotated.

5. The paddle of claim 1 wherein the vanes are angled with respect to the longitudinal axis of the paddle approximately 30.

7 References Cited UNITED STATES PATENTS 7 DONLEY I. STOCKING, Primary Examiner.

Clearly, the novel paddles of the present invention 7 H. F. RADUAZO, Assistant Examiner.

substituted in a conventional curved plate etching machines for thestandard paddles normally he fin members are four formly spaced fin members, the array of vanes on each fin being directionally opposed to the vanesof the ad- 1 wherein the outer longitudinal i

Claims (1)

1. A ROTATABLE PADDLE FOR USE IN CURVED PLATE ETCHING MACHINES COMRPISING: A PLURALITY OF FIN MEMBERS EACH COUPLED ALONG ONE LONGITUDINAL EDGE TO FORM A COMMON AXLE, THE OUTER LONGITUDINAL PORTION OF EACH FIN CARRYING AN ARRAY OF PARALLEL, SPACED, DIRECTIONAL VANES, SAID VANES BEING DISPOSED AT AN ANGLE OF LESS THAN 90* TO THE LONGITUDINAL AXIS OF THE PADDLE AND AT LEAST TWO OF SAID ARRAYS OF VANES BEING DIRECTIONALLY OPPOSED.

Images