US2172563A - Printing method - Google Patents

Description

sept.1`2,1939.` Y H' B'BERTQN 2,172,563

l PRINTING uETHob Originalv Filed Dec.` 16, 1932 Fai. v 11 Mz.

Patented Sept. 12, 1939 PATENT OFFICE PRINTING METHOD Herbert Libberton, Chicago, Ill., assigner, by direct and mesne assignments, to Tenak Products Company, Chicago, Ill., a corporation of Illinois Application December 16, 1932, Serial No. 647,504

Renewed December 12, 1936 6 Claims.'

My invention relates in general to printing and has more particular reference to a method of making electrotype printing plates.

At present, electrotype plates are made by electroplating the surface of wax or lead tablets in which the image to be reproduced has previously been moulded.

Among the difficulties and disadvantages encountered in using lead tablets is the enormous pressure required to mould the lead, which prevents set-up type from being directly moulded in the lead tablet. For this reason, asis well known in the art, it is not practical to mould lead tablets directly with a so-called mixed form comprising set-up type and other kinds of form, such as previously prepared electrotype etchings, half-tones, and the like, which can be used for lead moulding. Another distinct disadvantage encountered in moulding lead tablets is the powerful presses required in making the impression. It is also virtually impossible to commercially transport the relatively soft, heavy lead plates after moulding as by mail, freight, or express, in case it may be desired to electroplate the moulded tablet at a place other than where the tablet is impressed. Unless extraordinary care is taken in packing and transporting the tablets, they Will be irreparably damaged in transit and rendered unfit for use. The same disadvantage exists Where the tablets are of Wax, which, being fairly soft, cannot successfully withstand the shocks and jars of transportation after being moulded, but must be handled with care and plated immediately. A

Among the many other difficulties and disadvantagesencountered in using Wax tablets is the expense of making the tablets in the shop where used, involving, as it does, the application of heated wax to a backing plate; the shaving of the wax to proper thickness after application; the labor and expense of maintaining an oven to warm the plate to render the wax soft just before the tablet is placed in the press; the several expert processing steps performed upon the tablet after pressing, including shaving, warming, building up and graphitizing the tablet in order to condition it for the pating bath; the necessary heating of the tablet and plate in order to strip them apart after the tablet has been plated; and the fact that the wax does not receive an absolutely true impression because its' composition and temperature are not and can not be maintained uniform throughout the tablet no matter how carefully controlled; and because the processingsteps of shaving, warming, build- (Cl. l11--25) ing up and graphitizing distort the impressed tablet, however slightly, before it is plated.

An important object of the invention, therefore, is to provide a moulding platel or tablet, more especially adapted for electroplating, which can be moulded cold under relatively low pressures to take a clear, accurate, and undistorted impression from any kind of form, or die which may include set-up type, engravings, etchings, half-tones, or any other form; a tablet which requires no build-up or other processing treatmentafter moulding to condition it for plating; a tablet which is inexpensive to manufacture, light in weight, easily handled and commercially transported either before or after impression, which may be stored Without deterioration and which, for these reasons, can be manufactured at a central factory and shipped to the customer ready for pressing and then may be sent to a remote electroplating plant without danger of damage or deterioration in transit.

Another important object is to eliminate the Various difficulties which arise in electrotyping because of the inherent disadvantages of using -lead or wax as a moulding and plating medium.

Another important object is to provide a exible, substantially inelastic tablet adapted to be moulded in cold condition to receive and hold an impression.

Another object is t6' provide a relatively thin moulding tablet for use in making electrotypes and which can be deformed throughout its entire thickness to take the general outline of a form and which in its surface will take and hold the specific impression of the form.

Another object is to provide a tablet adapted to be deformed throughout its thickness in accordance with the general contour of a form and to receive in its surface a specific, detailed form impression.

Another object resides; in the method of moulding a tablet for electrotyping which consists in moulding a relatively thin plate to the general form shape while simultaneously making a speciiic surface impression.

Another object is to provide a mouldable tablet stiff enough to remain self-supporting, exible enough to absorb minor defiection without distortion, mouldable throughout its entire thickness to take the general contour of a moulding form and having a relatively inelastic surface adapted to receive and hold the specific imprint of the form.

Another important object is to provide a composite moulding tablet for use in electrotyping and including a thin backing plate adapted to be distorted and having a relatively inelastic mouldable surface thereon capable of receiving accurate impressions from a form-of any character.

Another object is to provide a moulding tablet having a moulding surface of relatively soft mouldable material surfaced with a. film or skin of electrical conducting material. Y

Another object is to provide a moulding tablet having a moulding' surface of relatively soft mouldable material surfaced with a thin metallic sheet or skin.

Another important object resides in providing a new and improved material for use, more particularly, in making moulds for electrotyping.

Still another object resides in the reorganizationand simplification of electrotyping methods and technique through the use of my new moulding material.

Numerous other objects and advantages of the inventionv will be apparent from the following de- Figure 3 is a diagrammatic view of a press illustrating a preferred mode of moulding the material;

Figure 4 is a perspective view of a piece of the material as impressed and ready for plating;

Figure 5 is a section taken substantially along line 5-5 in'Figure 4;

Figure 6 is a sectional view 'of a plating bath showing one way of electroplating the moulded tablet;

Figure 7 is a perspective showing how the plated reproduction or electrotype is stripped from the tablet;

Figure 8 illustrates the application of a backing to the electrotype; and

Figure 9 is a section taken through the electrotype as backed with lead and ready forblocking.

To illustrate my invention, I have shown on the drawing, a tablet I I made in accordance with the teachings of my present invention and adapted to accurately receive in its surface impressions especially well suited for electrotyping. The tabletis relatively thin so that it may be deformed throlmhout its entire thickness in order to receive the general impression of the moulding form and to accommodate the material displaced by the form without causing it to bulge upwardly of the surface of the plate and thus leiifect the specific surface conguration impressed by the form. 'I'he tablet is stiff enough to be self-supporting and is flexible enough to absorb minor deflections without becoming distorted. The tablet also in its surface is mouldable to receive the specic imprint of the form and is inelastic enough to retain an imprint pressed therein. The tablet may be made in several ways and of various materials. It may be of monolithic structure in which the material has the requisite characteristics to enable the tablet to Jie formed as heretofore described, or lmay be of laminated structure wherein the surface layer is of material suitable to receive and retain the specic form imprint while the underlying layers support the surface layer and absorb the general displacement of material which occurs when the plate is formed.

One way of making the tablet is to select a suitable, preferably tough, grade of asphalt and to spread the asphalt in a layer of suitable thick- I ness, say .02 of an inch. This mayf be accomplished by heating the asphalt until it becomes uid. An asphalt layer of this character may be cold moulded in the manner hereinafter described to deflect the layer throughout its entire thickness in accordance with the general contour of the form while at the same time'the surface of the layer is receiving the specific imprint of the form. Certain grades of asphalt are somewhat elastic and do not hold the exact impression but tend to rebound slightly after thepressing operation. In order to overcome this, I find it desirable to combine with the asphalt, a non-elastic ller, preferably wax, such as carnauba wax which. because of its unctuous character offsets any adhesive characteristics in the asphalt and facilitates the separation of the form from the tablet after moulding. Other waxes, such as parailin, ozokerite, and the like, and other non-elastic, non-adhesive materials may also be used for the purpose.

In some cases, particularly where the moulding form comprises set-up type, it may be desirable to supply a backing layer to support the mouldable layer and to absorb at least a part of the general impression. Where the tablet is to be shipped after moulding, a backing of relatively strong material is also desirable to prevent damage to the moulded tablet `during transportation. In the illustrated embodiment, the tablet is shown as comprising a backing I3 and a mouldable layer I5. 'I'he backing is preferably of relatively thin, resilient sheet material having an appreciable stiffness in order to form a resilient support for the layer I5. The backing is not so stiff as to be inexible but should permit bending while at the same time be stiff enough to provide substantial support for the relatively flexible and mechanically weak layer I5, and I prefer to utilize hard rolled aluminum sheets approximately .006 of an inch thick. In some cases, depending somewhat upon service requirements, satisfactory results may be had by applying the layer I5 to a backing formed of cardboard paper or sheet copper, and I do not wish to limit the invention to the material forming the backing sheet but any thin sheet of organic or metallic character having the requisite stiffness may be utilized, or, as explained heretofore, eliminated entirely. Where a backing is used however, the layer I5 need not have the mechanical strength provided in the moulding film when used alone" and I have discovered that a moulding composition, including balata gum and certain waxes and resins, has certain desirable characteristics when used with a backing layer. The compound containing balata is comparatively inelastic and tough when cold and can be moulded in substantially cold condition to accurately receive a specific impression of the finest texture used in printing. 'I'he moulding composition, however, when hot, is fluid enough to permit the same to be applied as a relatively thin, uniform layer, appoximately .015 of an inch thick, to the backing sheet I3.

Unmodied wax, of course, is used in makingV mouldable tablets and the various disabilities attending its use have heretofore been mentioned.

The balata ingredient has the characteristic of imparting toughness to waxes with which it is mixed so that by using balata gum as an ingredient, and I prefer to use Surinam sheet balata. for

'arianne geneous. slightly exible yet inelastic ,and ex-J ceedingly tough moulding material. Balata also is exceedingly sticky when hot and will maintain a bond. formed while hot, even after cooling to a non-sticky condition. This characteristic appears to an extent in the resulting composition so that if applied to the plate I3. while hot. the layer I5, after cooling. adheres strongly because of the balata ingredient.

For the wax ingredient, I prefer to use a mixture of beeswax and oarnauba wax'since these are not only mouldable but beeswax has adhesive characteristics which are retained in the composition to assist in holding the layer I5 o'n the plate I3 while the carnauba wax is of unctuous character and makes the matrix easy to pull out of the moulded plate. Any other wax or waxes providingV these characteristics may. of course. be used. Paraifin, preferably the softer grades. and other waxes, such as ozokerite, may be used for the purposes.

The resin ingredient is preferably paraoumar- Parts by weight Balata gum I 6 Paracumarone resin 3 Beeswax 3 Carnauba wax 2. Zinc oxide 'I These ingredients are mixed by heating as in a rubber mill and the composition is immediately ready for use. It may be applied to the backing plate simply by flowing the material onto the backing layer I3 and placing the coated layer hetween squeezing rollers which are adapted to cool and solidify the moulding compound and, at the same time, form the layer I5 to uniform thickness throughout the extent of the tablet. In cooling, the composition adheres to the backing plate even though the same is highly polished. The bond is sufficiently strong to hold the layers together unless forcibly and intentionally stripped apart.

I may, in some cases, use a bonding solution comprising balata gum and a resin such als cumarone. This is applied warm to the plate and adheres more strongly after cooling than- I' tablishment.

.be formed as a layer of powdered graphite which is brushed on to the surface rof the layer I 5. The

graphite may be applied, in the oase of an asphalt layer, almost immediately after the layer cools but where the layei` I5 comprises balata, it is preferable to permit the layer to set for an appreciable period, say twenty-four hours vbefore the graphite is applied.

Alternately, and preferably, however, the layer I6 comprises a relatively thin metallic skin, such as a sheet of lead or similar foil, having a thickness of the order of .001 of an inch.o The tougher the material, the thinner may be the foil and I may use aluminum foil having a thickness of the order of .00025 of an inch. `The foil should be tough enough to take the impression without tearing and as thin as possible so as to take the impression accurately. lIhe use of the lead foil has the advantage that it can be and preferably is a surface skin effect in the tablet whereby, whenset up type is moulded, the build-up, which occurs .in the plate between thetype elements, is kept more uniform throughout the plate. The importance of keeping the build-up as uniform and smooth as possible will become more apparent as the description proceeds.

A still further advantage of utilizing a skin The stacked layers I3, l5 and i6 may y of metalfoil resides in the fact that a tablet employing sheet metal releases more easily from the folding form and when placed inthe plating bath,

the sheet immediately startsto'forin at all points in the moulded foil surface of the tablet and after plating is complete, the tablet strips more easily from the electroplated shell than where the skin It is of graphite. l

The resulting tablet, however formed, isl extremely light and thin and will not ydeteriorate during storage periods. Furthermore, it will not become damaged if handled with ordinary care and may be shipped from the factory to the moulding plant and, after receiving theimpression, be, again shipped to the' electroplating es- In order to use the tablet inthe preparation of electrotypes, a sheet ofthe material is ar-v the layer I6 facing upwardly. A form 2l of any.

suitable character is deposited face downwardly upon the .tablet and the press-actuated to force the matrix into the layer I5. It is not lnecessary to utilize excessive pressures in order to form the tablet but pressures, such as are ordinarily used in the pressing of the ordinary wax tablets may mations conforming substantiallywith the specific impressions received by theflayer I5, and promotes the bonding effect between the layer I5 and the backing plate so that the chances of separation of the layers I3 and I5 after the tablet has been pressed into the desired configuration are substantially lessened.

'I'he material behind the depressions formed in the tablet is thus removed from the zone where the specific impression is received and thus relieves the internal pressure built up in the tablet which, if not relieved, would result either in the rebounding of the impression upon removal of 'the moulding pressure, or in raising the surface of the tablet between the depressions which is known as building up. In either case, the final resulting impression would be untrue. By absorbing the internal pressure by permitting it to deform the entire tablet throughout its thickness so that the reverse side of the tablet also has the general contour of the form, the specific impression on the obverse side of the tablet is preserved exactly as moulded by the form.

It is not, of course, essential to entirely eliminate build-up between the depresisons formed in the tablet. A certain amount of build-up is desirable, especially where the space between depressions is of relatively large area. 'I'he tablet of my invention permits limited uniform building up between depressions. Excessive buildi g up, however, is elimlnated'by keeping the layer thin to thus permit the entire tablet to be deformed and by maintaining the toughness of the material sufficient to prevent the material ilowing freely from under the raised portion of the form and squirting up between the depressions of the tablet. 'Ihe amount of build-up may be regulated by controlling the relative uidity of the material forming the layer I 5. If a greater buildup is desired, a larger proportion of wax, more particularly the unctuous wax ingredient, should be used in preparing the moulding material. Where the surface layer IS is in the form of a thin sheet, the layer acts as a skin and eliminates excessive building up`.and equalizes the builld-un throughout the tablet.

It will be noted that the tablet may receive simultaneously type impressions 23 as Well as the relatively ner impressions 25, such as are made by etchings, engravings, half-tones, and the like. In other words, the tablet of my present invention is adapted to receive impressions from a mixed form,- that is to say, a form including type characters and portions adapted to make relatively ne impressions, and this advantage, as has-heretofore been pointed out, is not present Where the lead tablet is used, and even though a mixed form can be moulded in a wax tablet, the impression in wax is not as accurate nor as fine as may be had if the teachings of my present`invention are followed.

After being impressed, the specifically formed surface' of the layer I5 may be hand-polished with graphite if necessary and then electroplated simply by immersing it in a suitable plating bath 21, which may best be accomplished by fastening the formed tablet on a holding plate 29, preferably of lead, the tablet being attached to the lead plate by means of the tacks 3l, and the plate suspended by means of a holder 33 from the barV 35. Where the layer I6 is in the form of a metallic sheet, it is, of course, unnecessary to polish with graphite since the sheet metal layer I6 affords an ample conducting medium so that the entire impressed surface of the tablet commences`to receive a plated shell as soon as it is deposited in the plating bath.

As is well understood in the electroplating art, an electric potential is applied between the bar 35 and the fluid forming the plating bath, the plate 29 being insulated so that the bath will not deposit metal upon the carrier member 29, but only upon the graphitized surface of the layer I5, the graphitized surface, being electrically connected by means of the tacks 3I through the metallic portions of the carrier member 29 and the hanger 33 to the bar 35, and being exposed to the fluid of the plating bath, will receive a coating of metal.

Where a metallic backing I3 is used, the edges of the backing, being exposed to the plating fluid and electrically connected to the bar 35 because the tacks 3| pass through the backing, provide an excellent contact all around the tablet which facilitates the initial deposit of the plated metal at the edge of the tablet from whence the plated metal spreads inwardly nally covering the entire surface of the tablet.

After the plating process has been carried on suiiiciently to deposit a metallic lm of proper thickness upon the graphitized surface, the tablet may be removed from the plating bath and the deposited lm stripped from the tablet.

The stripping operation is illustrated in Figure '7 of the drawing and after the electroplate 31 has been removed from the tablet, it may be Figures 8 and 9, or finished in any usual manner for use in a printing press.

Among the numerous advantages flowing from my present invention is that the tablet will receive accurately the impression made by a matrix including type as well as the relatively flne impressions made by etchings, engravings, halftones, and similar forms. It is notpossible to accomplish this with either lead or wax tablets of the ordinary sort since wax does not accurately take the relatively ilne impressions made by etchings, half-tones, and the like, while the pressure required to impress etchings, half-tones, and the like, is so great as to break or otherwise damage the relatively large type forms.

Another important advantage resides in eliminating the expense of wax tablets which require space-consuming apparatus in the shop and also consume the operators time.

A further important object is to eliminate the expense of the relatively heavy lead tablets and to provide a lightweight tablet which incorporates the advantages of both wax and lead tablets and which eliminates the disadvantages of both. My tablet also is of lightweight and can be shipped at much less cost than the relatively heavy lead tablets and can be shipped safely to the electroplater after being impressed. My tablet also will take an impression, of a fineness and accuracy equal to that accomplished on a lead tablet, at pressures comparable to those required in moulding wax tablets so that the relatively expensive, hlgh pressure moulding appa-` ratus now required 'in pressing lead tablets may be eliminated.

It is thought that the invention and numerous of its attendant advantages will be understood from the foregoing description and it is obvious that numerous changes may be made in the form, construction, and arrangement of the several parts without departing from the spirit or scope of my invention, or sacricing any of its attendant advantages, the forms herein described being preferred embodiments for` the purpose of illustrating my invention.

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

1. The method of making a molded tablet for use as an electrotype matrix, which consists in applying a layer of plastic material upon an alu- !ninum sheet of predetermined stiiness andthen forming the tablet throughout its entire thickness, including the aluminum sheet, to the general contour or a master pattern while impressing the specific configuration of the pattern upon a surface of the layer of plastic material.

2.. The method of making a molded tablet for 2 use as an electrotype matrix, which consists in assembling a layer of a wax composition containing sufficient balata to permit substantially cold molding of mixed forms upon a malleable, metallic sheet of predetermined stiffness and then in substantially cold condition forming the tablet throughout its thickness;4 including the metal sheet, to the general contour-j of a master pattern y While impressing the specicconguration of the throughout -its thicmcss with the face of a master printing form while impressing the specic conguration of the pattern on the surface.

4. The method of preparing a matrix for electrotyping, comprising providing a tablet having as a surface layer a composition containing an intimate combination of wax and al rubber gum giving toughness and moldability to a degree permitting accurate cold molding of printing forms therein, and impressing said surfacelayer directly in substantially cold condition with the face of a master printing form, less than onehalf of the surface layer composition being rubber gum.

5. The method of preparing an electrotype, comprising cold molding an imprint of a printing form directly in a wax containing sumcient balata to provide the requisite degree of toughness for molding in substantially cold state, and i and suilcient rubber and/or balata to permit sub- 25 stantially cold molding, and impressing said surface layer directly with a printing form in sbstantially cold condition whereby to produce a matrix.

mBERT MBBERTON.

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