US3045595A

US3045595A - Printing machine and printing blanket therefor

Info

Publication number: US3045595A
Application number: US20629A
Authority: US
Inventors: Gurin Emanuel
Original assignee: Individual
Current assignee: Individual
Priority date: 1960-04-07
Filing date: 1960-04-07
Publication date: 1962-07-24
Anticipated expiration: 1979-07-24

Description

July 24, 1962 E. GURIN 3,045,595

PRINTING MACHINE AND PRINTING BLANKET THEREFOR Filed April 7, 1960 i a mmmmfim V up 0' INVENTOR Z'mrzzzeZ 624777;,

ATTORNEY 3,045,595 PRINTING MACHINE AND PRINTING BLANKET THEREFOR Emanuel Gurin, P.0. Box 10142, Caparra Heights, San Juan, Puerto Rico Filed Apr. 7, 1960, Ser. No. 20,629 2 Claims. (Cl. 101415.1)

The present invention relates to printing machines, and especially printing machines of the offset type. More particularly, the present invention relates to a printing cylinder for such machines and in combination therewith a novel printing blanket formed of elastomer coated dimensionally stable smoother paper.

In offset printing, the ink for printing comes from the impression receiving contact on to an impression receiving and yielding printing blanket surface and then into contact with the surface to be printed so as to make an imprint thereon.

Printing cylinders of offset printing machines are ordinarily provided with a printers blanket composed of a plurality of layers of fabric conventionally bonded and surface-coated with a composition layer having as a major constituent natural rubber, synthetic resins, and synthetic rubber.

Heretofore, it has been accepted that these offset printing blankets had to be composed of a plurality of layers so as to insure the proper strength and thickness to the blanket. The multi-ply printing blankets currently used are difficult and expensive to manufacture and have to be discarded in toto upon surface wear, and for other reasons such as surface damage, etc.

These difficulties and expense have been obviated in accordance with the invention disclosed in my copending application, Serial No. 603,600, filed August 13, 1956, now U.S. Patent No. 3,012,498, wherein a novel single ply printers blanket for an offset printing press cylinder was formed of high tenacity cellulose acetate woven smooth rayon material, said single ply having a thickness of about .005 to 015 inch and a strength of between 150 and 500 pounds per lineal inch With an ink receiving rubber or synthetic elastomer coating on said single ply of a thickness of from .015 to .025 inch, said single ply being superimposed over a packing blanket which covers said offset printing press cylinder, the total thickness of said single ply and packing blanket being that of a conventional multi-ply blanket. With lesser amounts of ink receiving coating, the normal wear of the blanket caused the underlying weave to strike through at which point an impression of the weave was picked up in offset printing use and the blanket had to be discarded in toto.

The freedom from surface irregularity, which is found I by use of a smooth surfaced dimensionally stable paper and which is difficult to achieve with a woven backing eliminates this disadvantage at a substantial saving in cost of materials. The inherent irregularity in the fabric blanket of my copending application Serial No. 603,600, filed August 13, 1956, may be partially smoothed out by stretching and tightening the fabric blanket on the cylinder. These irregularities are not present in the dimensionally stable smooth surfaced paper backed blanket of the invention. In the light of the excellent printing achieved by the present construction without the requirement for excessive stretching of the blanket substantial ice advantages are found over the embodiment of my copending application. A minute movement of the stretched woven base due to tension is avoided in fitting the blanket to the cylinder and improved features of the printing surface results.

Heretofore there have been used hard paper covered tympan rollers to protect the paper which is printed by a printing cylinder; examples of such paper covered tympan rollers being shown in Page, U.S. Patent No. 2,544,- 279 and Woodell, U.S. Patent No. 2,232,989. These hard paper covered tympan rollers are obviously different in their use in printing, since they serve as a backing for the reverse side of the paper which is printed by the printing cylinder whereas the offset printers blanket construction of elastomer coated thin paper of the present invention per se constitutes the printing surface in offset printing.

There has also been used heretofore soft press blankets in high speed newspaper printing, a soft paper or felt covered press blanket to cushion the cylinders which are opposed to the impression cylinder, these termed press blankets and also serving to protect the reverse side of the paper being printed. Examples of these heavy paper or felt press blankets are shown in Fennone, U.S. Patent No. 1,891,150 and Schacht, U.S. Patent No. 1,897,864. These thick felt structures also do not function as an ink transferring structure as does the elastomer coated dimensionally stable paper printers blanket of the present invention.

In the press blankets and tympan blankets of these cited prior art structures, the common requirement which is to be met is to prevent the reverse side of the paper being printed from becoming deformed, indented, or cut by the action of the hard metal type surface and printing is not by the blanket covering but by the type face itself.

In offset printing, the expectation heretofore has been that a strong, thick multi-ply laminated structure was essential in order to provide strength and an adhesively secured built-up structure which is necessary as the dimensionally stable backing for the clearance between the offset roller and the paper sheet feeding roller operating at high speed. The multi-ply laminate was also deemed essential in providing an unyielding smoothness of the printing surface. The dimensional stability of the offset roller blanket was achieved by a single composite blanket structure. It was particularly unexpected that the laminated printing blankets heretofore employed for offset printing could be eliminated in favor of a single ply of elastomer coated smooth and dimensionally stable paper which is backed by a separate non-adhered backing member to absorb shock during printing will achieve highly eificient continuous offset printing, and to attain long wear of the blanket with surprising freedom from registration difficulties even after it has been subjected to long printing usage.

It has been discovered that the single backing layer'consisting of smooth dimensionally stable paper coated with elastomer when backed with another independent shockabsorbing backing sheet, which preferably may also be smooth surfaced multiple ply paper, or paper board of subtracted thickness provides superior smoothness and dimensional stability for printing blanket, the smoothness and stability being superior to that which results when an adhesive is interposed between the elastomer coated paper and a separate backing sheet and also being better than that which utilizes a soft separate packing material in direct supporting relation to the single ply coated paper blanket.

It has been further observed that the use of the single ply coated blanket of the invention with a paper backing having a hard surface, separate and non-adherent paper surface permits much sharper impression during offset imprinting depending upon the surface hardness of the stock being printed. This sharper impression is aided by using even thinner coatings of elastomer for the offset blanket. For example, a rubber coating on the high tensile strength paper backing which is as thin as .003 to .005 inch provides very sharp impressions for offset printing on hard metal surfaces such as metal can bodies. In instances where a relatively rough and imperfect softer surface is to be printed a somewhat thicker coated layer would be employed.

It is not only the dimensionally stable and smoothness characteristics of the good strength paper base which afford superior printing characteristics since the paper backing must also be sufficiently flexible to overcome wrinkling of the blanket. The flexibility must not be had at a surface of sufficient smoothness to provide uniformity in printing. In the laminated printers blankets, a multiply paper backing would tend to make the blanket too stiff and unyielding, wrinkles developing before mounting the blanket or appearing during usage due to improper mounting could not be easily smoothed and this would result in discarding the blanket when this condition occurred. Similarly the use of thin hard metal backings although capable of providing excellent smoothness, suffers the same defect as the multi-ply laminated blankets, e.g., wrinkles cannot be ironed out by tensioning during mounting of the blanket on the offset roller.

It is one of the objects of the present invention, therefore, to provide for an offset printing press having a printing cylinder, novel blanket means including a single ply covering blanket of high tensile strength paper and completely independent of a packing blanket, which is preferably a dense hard packing for placing the printing blanket in proper relation to the rollers used for bringing the paper into contact therewith.

Another object of the invention is to provide a novel high tensile strength single ply printers blanket for offset printing formed of flexible smooth surfaced, dimensionally stable, paper having a thickness of between about .003 to about .025 inch and coated with an ink impression receiving elastomeric coating varying in thickness from about .003 to about .025 inch, said blanket being adapted for use with an independent shock absorbing inner packing blanket and holding said inner blanket in place on an offset printing cylinder.

Another object of the present invention is to provide in combination with a printing cylinder a plurality of elastomer coated single ply paper printing blankets and an inner packing blanket, the outer single ply paper printing blanket covering and holding the inner blankets in place on a printing cylinder of an offset press.

Other objects and advantages of the present invention will become apparent from the subsequent description and figures of the drawing wherein:

FIG. 1 is a diagrammatic section of a portion of the blankets, and

FIG. 2 is a diagrammatic end elevation of a printing cylinder having mounted thereon a pair of blankets of varied lengths.

Referring to the figures of the drawing, FIG. 1 represents diagrammatically an independent top or covering blanket indicated in general at 10, comprising a high tensile strength paper 11 and an ink-receiving coating 12. At 13 there is indicated diagrammatically a lower or packing blanket which is preferably of a single ply as shown.

Referring to FIGURE 2, there is shown at 14 a conventional printing cylinder of an offset printing press. As shown, the printing cylinder has mounted thereon the covering blanket 10 and the packing blanket 13. As indicated at 15, the packing blanket 1-3 is of a lesser length than the covering blanket 10. The ends 16 and 17 of the

blankets

10 and 13, respectively, are held between a bar 18 and a holding bar 19, and means are provided to hold the bars together and to the cylinder as indicated by the screw or bolt 20. Rotatable with the cylinder is a conventional tightening roll 21 having a ratchet wheel 22 rotatable therewith. The end 23 of the blanket 10 is wound about the tightening roll and the roll is held in position by the pawl 24 cooperating with the ratchet wheel 22. By this means different stretch of the two

blankets

10 and 13 is avoided.

The backing layer 11 of the offset blanket 10 is formed of a single sheet of high tensile strength paper of uniform thickness of about .003 to about .025 inch, preferably high tensile strength kraft paper, calendercd or supercalendered to a hard surface finish and having a Mullen bursting strength of between 50-200 pounds for a base weight of 20 to pounds a tensile strength of between 20 and pounds between 20 and 90 pounds base weight. The high bursting kraft paper is preferred because it is readily available commercially in the uniform thickness between .008.025 inch and in this form possess superior qualities for the blanket of the present invention. These properties of kraft paper are shared by other strong fiber papers made as smooth dimensionally stable sheets such as paper made from jute fibers, from sisal fibers, from hemp fibers and from long wood pulp fibers by the sulfite process. It will be understood that these papers are like the kraft paper of the above description and exhibit approximately equal tensile or tearing strength in both the long and cross directions so that when sharply creased the wrinkles which form may be smoothed by tensioning the paper. The paper should be dimensionally stable i.e., substantially incapable of stretch or distortion under the tension which is necessary for mounting the blanket.

The ink receiving layer 12 has a uniform thickness of from about .003 inch to about .025 inch preferably in the range of .003-.008 inch when printing is to be done on hard surfaces such as metal and preferably between .015- .022 inch when printing is to be done on soft surfaces such as cardboard.

Elastomer film thickness between .005 and .020 inch are suitable for ofiset printing of letter writing stock, the heavier thicknesses providing longer blanket life.

The synthetic elastomer material is composed of natural or synthetic rubber of the types known in the art. These are, for example, polymerized butadiene, acrylonitrile copolymers, olefin polysulfides, polymerized chloroprene, etc. The rubber may compose 50% or more of the finished composition and may contain the usual accelerators antioxidants, reinforcing pigments, fillers, softeners, plasticizers, activators, and of course a vulcanizing agent such as sulfur. The total thickness, therefore, of the covering blanket will be between .020 and .040 inch and preferably approximately .030.

As antioxidants there may be utilized such materials as Neozone A (Dupont), i.e., phenyl-alpha-napthalamine, as well as others well known in the rubber compounding art. As softeners there may be such materials as tricresyl phosphate, paraffin, dibutyl phthalate, etc. As accelerators there may be used such materials as Santocure (Monsanto) or N-cyclohexyl-Z-benzothiazyl-sufonamide, mercaptobenzothiazol, tetramethylthiuramdisulfide, etc.

The reinforcing pigments or fillers may include any of the various grades of carbon black, whiting, clays or the like. The composition should also preferably contain zinc oxide as an activator for the accelerator and stearic acid as plasticizer and aid in vulcanizing. Preferably in order to render the composition spreadable, there is incorporated with the solid materials a suitable solvent, preferably a hydrocarbon such as toluol, in the proportion of one part of the solid ingredients to one part of toluol or in somewhat greater proportions.

Since the conventional printers blanket in the case of a three-ply blanket has a thickness of from .062 to .066 inch, and from .072 to .076 in the case of a four-ply blanket, the packing blanket 13 should preferably be of a thickness so that the composite dimension of both the covering blanket .10 and the blanket 13 is equal to these figures.

It is preferred that the packing blanket 13 consists of a hard base material and the utilization of one or more of the high tensile strength paper printing blankets of the present invention to make up the necessary thickness represents a novel, advantageous and convenient assembly which has not been heretofore employed.

As mentioned above the provision of a hard independcut and separate backing surface improves the printing characteristics of the present blanket, this hard surface providing a relatively unyielding backing against which the outer blanket is tensioned and unwrinkled and imparting dimensional stability which cannot be achieved if a soft packing material is employed.

As may be understood, depending on the particular undercut of the printing cylinder, there may also be used with the blanket and the underlying paper blanket the conventional paper underpacking and make-ready.

The following specific example serves to illustrate a suitable covering blanket 10:

Example High tensile strength kraft paper having a hard surface finish and having a Mullen bursting strength of 90 pounds tensile strength between 38 and 70 pounds in a thickness R of .010 inch is conventionally coated with a composition of the following constitution:

Bnna N, 100 parts by weight; Santocure 1, one part by weight; Neoxone A, one part by Weight; carbon black, 50 parts by weight; dibutyl phthalate, ten parts by weight; zinc oxide, five parts by weight; sulfur, two parts by weight; and stearic acid, one part by weight. To the foregoing solid constituents for each part of solid there was added one part of toluol. Thte mixture was suitably milled and then coated on the fabric in a conventional manner to form a smooth coating of .020 inch in thickness. It was then vulcanized at 290 F. for approximately two hours. The resultant single ply printers blanket was mounted upon a cylinder of an oifset printing press in the manner indicated in FIGURE 2 over a packing blanket and was capable of receiving sufiicient tension to maintain both the cover blanket and the packing blanket on the printing cylinder.

The characteristics of other suitable kraft paper which is similarly coated is shown below:

1. In an offset printing press having an offset cylinder for receiving an inked impression, blanket means for covering said cylinder including a packing blanket, an independent covering blanket consisting of a single ply of dimensionally stable flexible, hard surfaced paper having a thickness of .003 to .025 inch whereby the covering blanket has a relatively smooth surface and a Mullen bursting strength of between 50 and 200 pounds, and an ink-receiving coating consisting of vulcanized elastomer on said single ply of from .003 to .025 inch, the total thickness of said blanket means being that of a conventional mnlti-ply blanket and means to retain said blankets on said offset cylinder.

2. In an offset printing press having an offset cylinder for receiving an inked impression, blanket means for covering said cylinder including a packing blanket, an independent covering blanket consisting of a single ply of dimensionally stable, hard surfaced paper having a thickness of .003 to .025 inch whereby the covering blanket has a relatively smooth surface and a Mullen bursting strength of between 50 and 200 pounds, and an ink-receiving coating consisting of vulcanized elastomer on said single ply of from .003 to .025 inch, the total thickness of said blanket means being that of a conventional multiply blanket means for securing one end of both blankets to said cylinder and means to secure the other end of said covering blanket to said cylinder whereby said covering blanket retains said packing blanket on said cylinder.

References Cited in the file of this patent UNITED STATES PATENTS 364,287 Pfeil June 7, 1887 1,211,706 Hoerbelt Jan. 9, 1917 1,892,623 McElroy Dec. 27, 1932. 2,020,479 Sites Nov. 12, 1935 2,027,322 Rice Jan. 7, 1936 2,793,588 Stempel May 28, 1957