US2118801A - Process of finishing printing plates - Google Patents

Description

May 31, 1938. w. H. BA NZETT 2,118,301

PROCESS OF FINISHING PRINTING PLATES Filed Aug. 13, 1937 Fla 1 F/4/6 l l INVENTOR.

Mi/l/am l7! Banze/f W I ATTORNEY Patented May 31 1938 I I I 2 11 01- UNITED ,STATES- P TENT err-ice raocsss or rnhzi lis zimmnrorm'rss wuu'm n. migflifhn. N. .r. Application A II III M'IS, 1937, MINI). 158,943

I .1 (cl, Ill-401.3)

The purpose of this invention is to improve of backing metal is shaved oil, and the plate is the method of finishing the printing surface or then trued upto the face again, and shaved irem. face of printing plates to eliminate all irreguthe back. I I larities and unevenness in the printing or con- After all of these manipulations are completed tasting surface of characters or type thereof.. 'at great expenditure of time and labor, the ac-- d The invention is the art or process of planlng, curacy is really dependent on the skill of the grinding or lapping the printing surface or face operator. of electrotype, stereotype, or other typographic It can readily be seen that a short or i or raised character printing plates, which may be displacement of the type face cannot be comflat or curved in order to provide absolutely true pletely corrected from the back of the plate. or even contacting surfaces of the type, charac- In the case of stereotypes the same lockup is ters, or the like, thereof, and, at the same time, pressed against a wet paper mat-', and heat is providing an absolutely true, flat or cylindrical applied to the mat from the opposite side until finished surface. the paper is dry and hard. 'I'hismat then forms W The irregular height of type faces on duplia face mould into which melted stereotype metal ll cated or molded printing plates requires consideris poured to make the complete plate, either flat able make ready work, and padding of both the or curved, the theoretical curves actually provmounting for the plate and also of the impression ing a series of chords approximating a circle, as surface or cylinder, and, although metal has been the face of all characters is originally flat.

planed from the back of the plate, it still leaves Inaccuracies of varying thickness of mat", w irregular type faces or printing faces.- distortion of original lockup and pressure while The individual type characters or linotype being heated, and distortion while the hot metal slugs, rules, borders, etc., are locked in a chase. I is being cast, all contribute toward errors and The chase itself is a surrounding body at right irregularities.

angles to the clamping means. This is then set Various ways of bending the electros to cylinupon a "stone, a smooth level surface,'and all drical form after shaving approximately true are characters or line slugs are beaten or hammered used, and "hot forming fixtures" are applied to from the back so as to try to get the printing try to get true curved plates. Another type of face in a true plane, but this is almost impossible printing plate is made by moulding plastics such ll as, as one section is beaten down, the other secas bakelite into a mould, and as this mould is tion slips a little, etc. made from type,1ocked up in a chase, the irmu- For'an electrotype this locked up original, or larities are also present. master form, is pressed into wax to get an im- All of these irregularities must be corrected in pression in reverse of the type face and the wax a manner knownto the tradeas "make ready" on St impression is black leaded to give it a metallic the press, which is a slow costly operation as an as conducting surface. It is then suspended in an expensive press is idle during this time. It is electrocopper plating solution, and by electrotherefore desirable to eliminate a large portion deposition, a copper shell is deposited on the wax, of this "make ready time that ties up the expenusually from .006" to .010" thick. This shell is sive press, and, at the same time, improve or so stripped from the wax, cleaned in .various ways, perfect the actual contacting printing face of M and the back face is tinned by melting tinfoil Y the type or plates. I over the copper so that the heavy type metal The object of this invention is, therefore, to backing will adhere to the shell when it is poured eliminate all irregularities in the printing face of into it in a molten state. type, and, at the same time, provide plates, the

5 The stripping of the copper shell from the wax, printing surface of which is parallel to the back the "tinning and applying the hot backing metal, so that the distance through the plate is equal all distort the printing face from its original at all points, and, particularly in cylindrical printnearly true plane. It is then placed upon a true ing, the plate may be mounted upon a true cylinsurface and again beaten from the back to try der without underlays, so that the make ready" to bring the printing face to a true plane. time is reduced to a minimum or eliminated. so

There are various ways of doing this, either Another object isto provide a method of commanually or by mechanical means, but they all pensating for unevenness of single characters, have the final objective of trying to get all type such as a bold letter I, by grinding oil the ends, faces to a true plane. I 1 making the'surfaceof the letter in an arc in- After the faceis approximately true, the excess stead of a straight line, thereby making it pos- I8 sible obtain an even impression throughout the length thereof.

A further object is to provide an improved method for finishing the printing surfaces of printing plates, in which the plates may be finished, ready for use, on a separate machine, and then readily mounted upon a printing cylinder, in which the printing cylinder may be perfectly round without the use of underlays or the like.

A still further object is to provide'an improved method for finishing the printing faces of printing plates, in which the contacting surface forms an absolute cylinder, eliminating the necessity of overlays on the impression cylinder to compensate for irregularities as is normally the case.

And a still further object is to provide an improved method of obtaining an absolutely even contacting or printing face of printing plates or type, which is relatively simple and inexpensive.

Other features and advantages of the invention will appear from the following description taken in connection with the drawing, wherein:

Figure 1 is a diagrammatic view showing a printing plate with uneven contacting or printing surfaces of characters or type thereof, greatly exaggerated in order to illustrate an actual condition.

Figure 2 is a similar view with theunevenness also exaggerated showing a curved plate.

Figure 3 is a view showing a printing plate mounted upon a grinding machine, in which the grinding machine is incomplete, and only used for the purpose of illustration. Y

Figure 4 is a. view showing a method of attaching a printing plate to the surface of a cylinder for grinding the face thereof.

The electrotype, stereotype, or plastic printing plate is made in the usual manner of the art as accurate as good trade practice demands, and this plate is mounted with its finished back on a true surface, either a flat or curved plane. In order to true up the printing surface or type face, metal or material is removed from the face in what may be termed a super refining process, preferably on a separate machine, and, although the parts are shown exaggerated in the. drawing, it will be understood that only a few onethousandths of material are removed, however, with the ordinary printing plate this is sufficient to provide an absolutely true surface. On very slender type this requires a very fine grinding process, or a lapping process, and, when'flnished, the thickness of the plate, or the distance frpm the face to the back is absolutely equal at all points.

In the drawing a fiat printing plate is indicated by the numeral I, and this is placed upon a stone 2 having an absolutely true face or exposed surface 3, and it will be noted that the type or characters of the plate I engage the face 3 at a plurality of points, and if these faces were machined off, all of them would rest against and engage the surface 3. These faces are conwould be very difficult, and it would also be very difficult and practically impossible to line up a bevel surface such as that of the type indicated by the numerals I and 8 without damaging the printing face. With any process used up to the present time, which involves forcing the type from the back of the plate, it is substantially impossible to obtain an absolutely true printing face, so that it is necessary to pad the impression plate or cylinder, and also use considerable padding behind the printing plate.

Another plate is shown in Figure 2, in which the plate I has been formed around a curved or cylindrical surface, and it will be appreciated that in bending the plate the hard type surface upon a cylinder I3. and the cylinder is mounted on a shaft H in bearings IS on a base l6, and

a grinding wheel I! is mounted on a traveling carriage l8 and rotated by a motor 19 through a belt 20. It is understood that this is only a typical arrangement, as the grinding wheel may be mounted and operated in any manner or by any means.

In Figure 4 the plate 9 is shown attached to the face of the cylinder I 3 by clamps 2i, however, it will be understood that this plate may be mounted upon the cylinder, or upon a flat plate or any means in any manner or byany means. It will also be understood that any means may be used for surfacing the exposed surface, or turning, grinding, or lapping the surface in order to remove all unevenness or irregularities, and

this may be accomplished by machine or any means.

Thisoperation or process provides a printing plate with a true fiat or curved surface, and that is of equal thickness from the printing face to the back at every point, and, as the final finishing may require the removal of different amounts of metal or material from the face of the plates, each plate will be of an even thickness in itself, however, one plate may vary from another of the same set, and the plates should, therefore, be prepared by refinishing the back or inside to a predetermined thickness, or various uniform thicknesses of sheets of material, such as paper, may be added to the back to compensate for varying finished thickness in order to make the total thickness of all plates equal.

Lapping or finishing the face of the type in this manner also provides sharp edges, so that even worn electrotypes, or any typographic plates, could be relapped or refinished to bring up sharp printing instead of replacing plates with new ones on long runs. a

It will be understood that changes may be made in the process without departing from the spirit of the invention. One of which changes may be in the use of any other type of machine or mechanism for holding the plate while being lapped or finished, another may be in the use of any other process for removing material from the face of the type or plate, and still another may be in the use of this process for obtaining a true printing surface on devices for any other p p The process or operation thereof will be readily understood from the foregoing description, and it will be understood that plates finished in this manner will provide an absolutely true even printing face or surface, and it will be of even thickness throughout, and may be used on true or the like on the printing face, and of the type made from a master mold; which comprises mounting said plate upon a true base and removing material from the printing face thereof to correspond to said base, the distance from the a printing face to the back of the finished plate being equal at all points.

Wm H. BANZE'ITY

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