US1947986A - Formation of printing dies - Google Patents

Description

` Feb. 20, 19345 M HARLEY 1,947,986

` FORMATIQN 0F PRINTING DIES Filed yNov.1 11, 1932 2 sneetssheet 1 Feb. 20, 1934. L M"HAR| EY 1,947,986

FORMATION OF PRINTING DIES Filed Nov. l1, 1932 2 Sheets-Sheet 2 q \1\ v X Y if L Patented Feb. 20, 1934 PATENT oFFicE v 1,947,986 FORMATION OF PRINTING DIES Lee M. Harley, Brooklyn, N. Y.. assigner to 'James .H. Matthews & Company, a corporation of Pennsylvania Application November 11, 1932 Serial No. 642,213

4 claims. (c1. 10i-sis) This invention relates to improvements in rubber printing dies or blocks and to improvements in their formation.

The rubber printing dies ,or blocks to which the improvements apply are dies or blocks shaped in the form of flexiblesheets, and which, after shaping, are mounted on rigid carriers, perhaps plane-surfaced but ordinarily cylindrical. Thus a rocking or rotary printing block is formed, useful for example, for printing legends upon paper cartons. I cite this particular instance of the use of printing dies or blocks by way of example, but do not exclude from the eld of utility many other and varying particular uses.

This invention deals particularly with the solution of problems arising in the use of the printing dies or blocks and particularly in the use of printing dies or blocks having thereon lines of type, and sometimes devices, which present unequal suriace areas to the article to be printed. When pressure is applied up'on the printing die or block in the operation oi printing there is present a tendency for the lettering or devices of larger body to print less clearly than the smaller type of lesser surface area, unless the pressure be made adequate to produce perfect contact between the larger type, and devices, and the article or material to which the legend is applied. If the pressure be made adequate to secure a perfect printing from the larger type and devices,

. such pressure results in the distortion of the lines ci smaller type, causing a blurred printing by them.

It is-usual practice to compensate for this difiiculty by means of a make-ready on the printing cylinder or head by which the` printing die or block is carried. The make-ready" consists in applying a mat of some nature to the printing cylinder or head in position to lie behind type of4 larger size and body or a device having a relatively great surface area and body. Whether or no the make-ready be used there is a tendency for the pressure necessary to print the type or devices of large body to crush frail material such as the corrugated board used in the manufacture of cartons.

I have discovered that I may obviate these difculties by variation in the hardness of the rubber used for type or devices of relatively extended printing area and type of relatively"constricted printing area. By roughly proportioning the relative hardness ofv the rubber composing the printing surfaces of the die or block, so that the type having greater area and volume is `of lesser hardness than the type oi lesser size. the make-ready on printing cylinders or heads is made unnecessary and the crushing of frail material to which the printed matter is applied is eliminated.

A rubber printing d e or block so made may have a fabric and rubber backing such as that disclosed in the patent of Harold R. Wade and Lee M. Harley No. 1,742,885, dated January 7, 1930, or may be applied to a backing consisting of a solid sheet of rubber. It has been found fur- 'ther that, if a sheet of solid rubber be used, advantages in printing, and advantages in manufacture, are obtained by using a rubber of a hardness greater than that heretofore employed.

In the accompanying drawings Figure I is an illustrative plan View of a rubber printing die or block comprising type lines in which the type are of varied size together with a design or device of relatively great surface area, this figure of the drawings being illustrative of the improvements of the invention; Figure II is a cross-sectional view through a vulcanizing mold as prepared for the initial shaping and vulcanization of a rubber printing die or block made in accordance with this invention; and-Figure III is asimilar view illustrating the process of vulcanization-succeeding a partial vulcanization of the type rubber and the application of a sheet f of backing rubber thereto for the nal and complete vulcanization of the printing die or block; Figure IV is a cross-sectional View taken on the line IV-IV of Figure I; Figure V is a fragmentary longitudinal section through a mold showing the use of an all-rubber specially prepared backing member; and Figure VI is a similar view showing the use of a rubber and fabric backing member.

With reference to Figure I of the drawings the several lines of type shown and the relatively large device are mounted on a backing 1 which may be either the fabric backing of Patent No, 1,742,885, noted above,'a solid rubber backing or any other form of backing found suitable in use. As a specific example of the variation in .the hardness of the different type lines and the device shown, it may be stated that the relatively extended device 2 has a durometer hardness oi 50 on the instrument scale; that the larger lines of type have a durometer hardness of -.65; and

rubber, and which is designed for measuring the hardness of the elastic and semi-elastic grades of rubber.

It should be understood that the above-noted hardness values are illustrative only. The important fact is that the device 2, having the corrugated board used in making up a carton. In so doing, the pressure employed may be such as is sufcient to obtain complete printing contact vof the device 2 which is ofy the softest rubber. That pressure does not causedistortion of the type lines 3 and 4, or distortion of the type line 5, because the greater rigidity of the material constituting these type lines compensates for their lesser body.

The preferred method of manufacturingthis type of printing die or block is in substantial. accordance with the disclosure cf the above-noted Patent No. 1,742,885. In accordance with that method. as shown in Figure II strips of rubber 6, '7, and 8 .are applied to the face of a mold 9. These strips 6, 7, and 8 are of green rubber which when vulcanized produces type corresponding in hardness to the elements 2, 3 and 4l, and 5 shown in Figurel. The strips cover the incut areas producing the design and type lines of Figure I. Having so covered the inout design, the rubber is desirably shaped by closing the press, and subjected to partial vulcanization.

After a short initial vulcanization, the backing, which may be the backing member 1l, of canvas lightly coated with green rubber, as shown in Figure VI, or which may be an all--rubberl sheet 10, as shown in Figures III and V, is laid dlrectly upon the rubber lying on the mold. Before applying the backing additional rubber, vof similar grade, may be added to that in each of the inout areas of the mold, to insure complete lling of those areas. vThe vulcanizing press is then againpbrought to bear upon the backing sheet and vulcanization is continued to completion.

If a solid rubber sheet be used as a backing,

lthe hardness of this sheet is of advantage inpressing the materialof the strips into the incut areas of the mold to form the type, since it is of sufficient hardness to resist a tendency-to flow under the pressure applied bythe vulcanizing press. By utilizing for the backing member rubber of an adequate hardness, I avoid the tendency, previously present, for the inout areas to remain unlled, because the owing of the backing rubber has permitted the rubber intended for the characters to spread away from the incut areas which it should wholly fill.

It will be noted that only the smallest characters shown are of rubber having a hardness equal to the hardness of the rubber constituting the body of the backing member. If a single line die, or a plural line die, which comprises fairly large `Character members of substantially the same size, be made up, all the character members are of rubber having a hardness less than that of the rubber in the body of the back` memes ing member. In any case, character members, save those of very small size. are of rubber having a hardness less than that of the body rubber of the backing member.

It is desirable that, if a hard-rubber backing sheet be used, this sheet be composite, as shown in Figure V, comprising a body l0 which will vul- Acanize to a durometer hardness no less than lon the durometer scale and a light contact coating 12 of green rubber which will vulcanize to a 8f much softer rubber, such, for example, as rubber of a hardness of 50 on the durometer scale.v This is for the reason that the softer rubber has greater adhesive properties. It thus vulcanizes more completely to the rubber constituting the type, when presented to and vulcanized to 4'the type rubber.

The lower durometer scale limit of 80 is given forv the rubber backing for the reason that a backing sheet possessing a hardness above this lower limit has to a superior degree themanufacturing advantage noted above, and also possesses sufficient stiffness to prevent stretching or distortion of the backing when it is applied to a printing cylinder. I have not yet determined the upper llimit of hardness which may be satisfaccharacter members, save those of smallest size,

renders possible the general use of a backing rubber harder than that heretofore used. The diversity in hardness between large character members and backing members has, however, an adlltl ' vantageous effect even though the backing hardness be less than 80 durometer.

While the procedure given above is preferred as being the most economical and eicient method of making the rubber printing die or block, it is possible to produce the dies or bloclrs by a single step vulcanization process otherwise similarly conducted. If a single step vulcanization process is l2@ used, it is of course necessary that suicient `rubber be initially applied over the lncut areas in the mold to assure a complete i'llling of these areas.

'l2-claim as my invention:

1. In a printing die or block the combination of a backing member with rubber character members of at least two different sizes;permanently mounted thereon, the relative hardness of the rubber in the character members being greater for the character members of lesser size than for the character members of greater size.

2. In a printing die or block the combination of a backing member with rubber character members of diverse size permanently mounted thereon, the relative hardness of the rubber in the various size classes of character member being roughly proportioned inversely to the size of the several classes of character member present.

3. The combination of claim 1 in which the backing member comprises a rubber body havingv a -hardness of atleast eighty on the rubber durometerscale. 1

The combination of claim 2 in which the backing member comprises a rubber body having a hardness of at least eighty on the rubber dur- 145 ometer scale.`

LEE M. HARLEY.

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