US2227882A - Method of printing and apparatus therefor - Google Patents

Description

Jan. 7,' 1941. AF R 2,227,882

METHOD OF PRINTING AND APPARATUS THEREFOR Filed March 5, 1957 3 Sheets-Sheet fi ZL'O Jffrz/an- 5 MM, 5 012 M242 1,

Jan. 7, 1941. P. FRAZIER METHOD OF PRINTING AND APPARATUS THEREFOR 3 Sheets-Shet 2 Filed March 5, 1937 P. A, FRAZIIER Jan. 7, 1941 I METHOD OF PRINTING AND APPARATUS THEREFOR Filed March 5. 19s? 3 Sheets-Sheet 3 Patented Jan. 7, 1941 UNITED STATES METHOD OF PRINTING AND APPARATUS THEREFOR Philip A. Frazier, Oak Park, Ill.- ApplicationMarch 5, 1937, SerialNo; 129,211

5 Claims.

This invention relates in general to the art of letterpress, direct or relief printing, and more particularly to improvements in the method and apparatus of providing resiliency in printing, to the end that the irregularities under the printing surface are compensated for during the printing operation. The invention further relates to method and apparatus for obtaining a so-called squeeze impression.

It is well known to those skilled in the art that the finest commercial printing is accomplished when two relatively hard printing surfaces are employed. This method requires such precision and skill that for ordinary purposes its use is practically prohibitive. In. ordinary practice it is necessary to build up both printing. surfaces by means of various paoltings'v in the. form of underlays and overlays. The present invention contemplates obtaining a squeeze impression by methods and apparatus unknown to the art. The invention relates to letterpress printin employing wood mounts or metal bases in fiat bed or platen presses or curved-plates carried on cylinders in rotary presses and may be employed with any type of printing plate, for example, electrotypes, streotypes, zinc, or copper plates.

tary presses.

By direct relief or letterpress printing is meant that class of printing which is carried out on standard presses in which the surface supporting the material to be printed upon, which is of a relatively soft or embossable nature, is maintained during printing at a fixed distance from the surface supporting the plate by which the printing is done. The plates are of the type known as letterpress in which the printing surfaces are raised above thegeneral level of' the plate. In letterpress: printing; the printing pressures are developed by compression of the, material to be printed upon, held between rigid surfaces which are maintained apart at predetermined. distances.

In letterpress printing, more or less pressure is required to satisfactorily transfer ink from the printing surface to thematerial to be printed. All the mechanical inaccuracies in the printing surface, the support for the printing surface and the support for the material to be printed become apparent in the printed impression becauseof the application of pressure. Letterpressmen have attempted for years to compensate for these minuteinaccuracies. Obviously, a non-yielding support for the printed material would gave a sharp definition to the printed subject, but a non-yielding support cannot be used because of the mechanical difficulties involved in presenting an absolutely accurate printing surface and support for the printing surface,

The invention finds a widefield of utility for the purposes indicat'edLin flat bed and ro- In order: to absorb the. variations in pressure arising from inaccuracies in the printing, surface and printing support, a relatively soft or yielding support for the printed material was employed; The employment of a relatively soft or yieldingsupportingmember for the material to, be printed. permitted thehigh characters in the printing element to push into the supporting member, which resulted in embossing the printed material, known as impression. It was, therefore, necessary to alter the surface. of the supporting member to compensate for inequalities of pressure by cutting away where impression showedi and building up the supporting surface where more pressure was needed. Altering the surface of the support for the material to be printed is called make-ready. The term make-ready has also been used to denote various other steps such as leveling up the form, but for the present purposes limited sense. Make-ready is exceedingly costly, in that it is laborious, requires several proof printings and necessitates the services of skilled and experienced printers. The costs of printing are greatly increased by the fact that the presses are idle during make-ready.

In a platen press, make-ready does no harm other than toadd to ind'er press the distorted circumference of the impression cylinder, due to make-ready, tends to become in untimed relation to the speed of the printing element supported on the reciprocating bed, resulting in producing sheets out of register, stretched sheets, slurs and worn plates. In rotary presses, particularly web presses, the same difficulties are presented, but in the case of stretched sheets and register the difficulties are cumulative and may also result in breaking the Web.

It is, therefore, an object of the present invention to eliminate the necessity for makeready as well as the time consuming make-ready itself, and the above mentioned difficulties arising from the use of make-ready. Only a small proportion of the mechanical inaccuracies in printing arise from inaccuracies in the printing surface, and it has been found that these inaccuracies may be compensated for by employing a slightly yielding support for the material to be printed. B yieldingly supporting the printing element, all other mechanical inaccuracies may be absorbed, and a printing structure is obtained adapted to produce a perfect printing impression if the surface of the printing element is relatively uniform, for example, as in a page of type matter. However, to obtain an even impression from a printing element having a halftone and blank portions on its printing surface, additional or less pressure, respectively, is required. If the same pressure is applied to the the term is used in its I the cost. In a fiat bed cyl-.

type on the printing surface as is applied to the half tones thereon, there is serious danger of punching through or securing too heavy or an uneven impression. Accordingly, means is provided beneath the printing surface to supply pressure appropriate to the various portions of the printing surface.

A further object of the invention is to secure a finer grade printing than has been formerly possible in ordinary commercial printing. In addition thereto a further object of the-present invention is to provide a method and apparatus to obtain a squeeze impression by employing a relatively harder impression surface than printing surface and at the same time to secure sufficient printing pressure to form a clear, distinct impression without punching through or slurring.

A further important object of the invention is to provide methods and means of yieldingly supporting a printing element, such as a plate, in printing position, the plate being yieldingly supported throughout its entire area, whereby printing pressure between the plate and the surface being printed may be substantially uniform throughout the area of the plate, to the end that the resulting printing is of uniform texture.

A further object of the invention is to provide a printing structure whereby the printing mount or plate may be employed in subsequent printing operations without the necessity of providing new or additional make-ready.

A further object of the invention is to provide a method and apparatus for regulating the varying amounts of pressure required to print different portions of a printing plate embodying half tones and ordinary type without overlay.

A further object of the invention is to provide a method and apparatus for printing, in which a uniform printing impression may be obtained in reciprocating presses in which the bearer rails have become worn, thereby changing the adjustment between the impression cylinder and the travel of the bed. In accordance with the present invention provision is made for compensating any wear on the bearer rails, and the adjustment between the cylinder and bed is not altered when the rails become worn.

A feature of the invention is the provision of mean-s of absorbing pressure variation arising from irregularities in the printing and impression surfaces, plates, beds and cylinders without resort to make-ready. An additional feature of the invention is the provision of means of regulating the varying amounts of pressure required to print different portions of a printing plate or plates by means of a patterned resilient material wherein the pattern of the underlay is changed to conform with the requirements of the printing surface.

It has been found that the foregoing desirable results may be obtained by employing resilient material between the curved printing plate and printing cylinder in rotary presses and between the printing plate and base in flat bed presses, by means of which the printed impression is of uniform texture, due to the fact that its resilient material will absorb inaccuracies in the bed and printing element. Any slight inaccuracies in the printing surface may be absorbed by employing a slightly yielding support for the material to be printed.

An additional feature resides in the provision of resilient material which may be conveniently manufactured in sheet form in large quantities and stored with a view towards commercial practicability and convenience to the electrotyper or printer.

An additional feature resides in the provision of a printing structure adapted to print evenly upon material of different thicknesses without adjusting the printing members. For example, paper cloth and cardboard of 'diiferent thicknesses may be printed upon by the improved structure without adjusting the printing members.

The printing surface may be yieldingly supported by interposing resilient material having a pattern temporarily displaceable between the plate and base. Satisfactory results have been obtained by employing a strip of rubber matting or any resilient composition having compressible projections, thereby increasing the displacement space when pressure is applied. Where additional or less pressure is required as in the case of halftones and blank portions, respectively, additional or less pressure may be provided by varying the thickness or resiliency of the yielding material or by varying the displacement space of the yielding material or its supporting area.

The invention will be readily understood from the following description in conjunction with the accompanying drawings in which preferred embodiments of the invention are shown.

In the drawings:

Fig. 1 is a perspective view of a printing block embodying the invention;

Fig. 2, a side elevational view of a printing block embodying the invention;

Fig. 3, a side view, partly in elevation and partly in section, taken along lines 3-3 of Fig. 4 of a plate mounted upon a honeycomb base embodying the invention;

Fig. 4, a plan view of bodying the invention;

' Fig. 5, a side elevation of the impression cyl inder and plate cylinder of a rotary press embodying the invention;

Fig. 6, a side elevation of a plate cylinder, un'derlay, and curved printing plate, the parts being shown in disassembled relationship;

Fig. 7, a sectional view of a plug adapted to be inserted in a printing base;

Fig. 8, an end view of an impression cylinder embodying a feature of the invention;

Fig. 9, an enlarged plan View of one form of resilient matting upon which a printing plate may be mounted; and

Fig. 10, an enlarged, vertical sectional view of the resilient matting shown in Fig. 9.

Referring to the embodiment shown in Figs. 1 and 2, the reference character 8 indicates a printing mount of wood which, when assembled and locked with other similar mounts, forms a printing foundation. A strip 9 of resilient material lies between the upper surface 0 of the b k a and a printing plate I I. The resilient strip 9 preferably comprises a rubber matting l2 having a fabric backing I3 and projecting disks M of compressible rubber.

Satisfactory results have been obtained by employing a resilient material or matting of .046 inch thickness under acker gauge reading, but it is to be understood that the invention is not limited thereto and that the resilient matting or material may be varied either way. As shown in Fig. 10, which is enlarged approximately six times, the resilient projecting portions M are approximately .028 inch thick under Hacker gauge reading. The

a honeycomb base emthickness of the resilient portions 14, as shown in Fig. 9, are spaced apart from one another to afford a displacement area, and it is to be understood that the shape, height and spacing of the resilient portions I l may be varied considerably to afford displacement areas or pattern-s when pressure is applied to the printing plate mounted thereon. As .shown, the projecting portions cover approximately 25-40% of the surface area of the resilient material, but this area may be varied within wide limits within the scope of the invention.

The printing plate H is of conventional form, and for convenience has on its printing surface a halftone indicated at I5, type It and bare portions ll. As shown in Figs. 1 and 2 a piece of sheet material I9, for example, paper .004 inch in thickness, underlies the entire printing surface. This releases pressure from non-printing areas. An addition piece of sheet material It, such as paper preferably about .006 inch in thickness, underlies the halftone area for additional pressure. The base portions indicated at H on the printing surface are not backed up with sheet material. Thus the portions 15 and It of the plate, where increased impression is desired, are relatively more firmly backed than are the remaining portions of the plate. When a printing impression is made, the more firmly backed portions of the plate provide increased printing pressure on the corresponding areas of the printing surface.

The printing block comprising the wooden mount 8, resilient underlay 9, sheeted backing and plate H, may be assembled and retained in assembled relationship in any satisfactory manner, for example, by cement, or the components may be held together by nails or screws 20. The retaining agent 20 should provide for limited vertical movement of the plate ll upon the resilient backing 9, the plate should not be secured to the block in such constricted fashion that the resiliency of the underlay is lost. As shown in Fig. 2, a bore 2| may be provided in the printing plate which is slightly greater than the diameter of the nail extending through the plate, the strip of sheet material, the resilient underlay into the wooden base. Thus limited vertical movement of the plate upon the resilient blanket is provided for.

It will thus be understood that a resilient printing element is provided, adapted to absorb any inequalities in pressure derived from an inaccurate bed or inaccuracies in the wooden base. In connection with the improved printing element, an impression cylinder having a hard, cylindrical periphery without overlay or packing may be employed. The invention includes the employment of a slightly yielding support for the material to be printed. Thus in flat bed presses an impression cylinder having a surface adapted to yield from .001 to .003 inchhas been found to be very satisfactory. A hard rubber cylinder may be employed or, as shown in Fig. 8, a cylinder 5 having a cylindrical layer 6 of cork and a surface shell i of Formica, aphenol-formaldehyde condensation product, provides a surface adapted to absorb any slight inaccuracies in the printing surface.

Other forms of resilient material may be employed within the scope of the invention, for

example, the rubber projections on the matting.

may be conical or irregular in shape, and the position of the matting 9 may be reversed so as to have the projections l4 bearing against the wood mounting I0. In like fashion a resilient mat-ting having a plurality of adjacent cut-out portions providing a displ-aceable pattern is within the scope of the invention.

The invention may also be utilized with various types of metal bases well known to the art. In Figs. 3 and 4 the invention is illustrated in connection with plates secured by hooks upon a metal base of the honeycomb type. Obviously, the invention may also be employed upon metal bases (not shown) having grooves in which clamping devices are inserted to hold the plates in register upon the base. In Figs. 3 and 4 the metal base 22 is shown provided with a plurality of cylindrical holes or bores 23 diagonally arranged. A strip 2 of resilient material, similar to that shown and described in connection. with Figs. 1 and 2, and comprising a rubber matting 2'5 having fabric backing 2E and disc-like projections 21 of compressible rubber, lies between the metal base .22 and the printing plate 28. For convenience, the printing plate is shown similar to that illustrated; in Figs. 1 and 2 and has on its printing surface a halftone 29, type 38 and low spots 3|. In a manner similar to that described in connection with Figs. 1 and 2, the sections under the portions of the plate carrying the halftone 29 and type 30 may be built up by inserting paper strips (not shown) OfitlliCkIlGSSGS of .006 inch and .004 inch, respectively, therebyincreasing the printing pressure upon the half tones and type. The sections under the low left bare.

It is preferred, however, to increase the pressure under the halftones and type, by inserting metal plugs 32 in the bores 23 of the honeycomb base underlying the halftone'and type portions, as clearly shown in Figs. 3 and 4. The plugs 32 are. preferably provided with slots 32a and an adiacent yielding portion 32b to obtain a frictional engagement in the bores 23. The top surface of the plugs may be flush with the surface of the base 22 thereby filling up the displacement space provided by bores 23 or the tops of the plugs may protrude slightly above the base increasing the pressure upon the printing surface above the plugs. The plugs may also be provided with small bores 32c adaptedto be engaged by gripping members (not shown) to facilitate their removal. As clearly shown in Fig. 3, when the plugs 32 are employed, the resilient projecting members -21 are somewhat compressed before being subjected to printing pressure and, obviously, cannot extend into the bores 23 as when the plugs are removed. The resilient matting 2A is preferably cemented to the bottom of plate 2123. Highly satisfactory results have been obtained by employing "plates carrying the resilient matting which are .006 inch above normal type high, and accordingly, in utilining the invention, the standard metal base of .759 inch thicknessis preferably out down to .715 inch to compensate for the insertion of the rubber matting of .046 inch in order that the improved printing assembly may conform and be utiiized with standard beds. The invention may likewise be practiced by utilizing bases of standard thickness by reducing the thickness of the plates. For example, the standard thickness of electrotypes for flat bed presses is .152 inch, and the metal on the back of the electrotype may be shaveddown until it is .112 inch thick.

In this manner a highly satisfactory metal printing base is provided, adapted to print evenly and to absorb any inaccuracies in the bed or base. It will be understood that an impression cylinder spots 3! are preferably having a smooth, peripheral surface may be employed without packing or overlay. A cylinder having a slightly yielding surface as shown in Fig. 8 may be utilized.

The invention may likewise be utilized in rotary presses having an impression cylinder 38 and plate cylinder 39 rotatably carried on shafts 40 and 4|, respectively, of the press. The impression cylinder 38 has a smooth, peripheral surface 42 and preferably does not carry any overlay or packing. The impression cylinder may have a slightly yielding surface adapted to absorb any inaccuracies in the surface of the curved plate 43 and for this purpose may be equipped with a cylindrical cork shell 53 and a smooth surface shell 54 of Formica. The curved printing plate 43 illustrated has a printing surface similar to that of the plate shown in Figs. 1 and 2 comprising a half tone 44, type 45 and low spots 46 and is secured to the plate cylinder 39 by hooks or clamping devices well known to the art. A resilient strip 41 comprising a rubber matting 48, fabric backing 49 and rubber disc-like projections 50, is suitably secured to the bottom of the plate 43, for example, by adhesives or cement. The curved plates 43 are preferably cast or cut down until they are .04 inch thinner than the standard plates of 0.187 inch thickness usually employed in rotary presses. In manner similar to' that shown in Figs. 1 and 2, paper strips of a thickness of .006 and .004, respectively, may be secured to the fabric backing 49 of the matting, by adhesives, or they may be suitably secured to the bottom of plate 43. It will also be understood that the resilient matting 41 may be reversed so that the projections 50 gear against the surface of the plate cylinder 39 and that various shapes of projecting portions 50 may be employed within the scope of the invention in order to obtain a yieldably supported printing surface adapted to equalize any variations arising from irregularities in the surface of the impression cylinder, the surface of the plate cylinder, and the printing plates 43.

Compressible material which is not permanently displaceable may be substituted for rubber in the resilient matting. For example, the use of any resilient spongy material is contemplated, such as may be made by mixing flour of lead, or of a selected alloy of lead, with tin and/or zinc and/ or antimony with a substantial quantity of latex so that the metallic flour is uniformly distributed throughout the latex. During the vulcanizing process the metallic flour is fused so that, after cooling, a sponge-like metallic skeleton frame is formed.

It will also be understood that other methods and means of varying the amount of pressure in localized areas, for example, under half tones, other than thin strips of sheet material or protruding plugs in honeycomb bases, may be employed within the scope of the invention. For example, the thickness or degree of hardness of the rubber matting may be increased in areas where it is desired to apply additional pressure or the displacement space may be increased or constricted to secure the desired pressure.

It will be understood from the foregoing that the invention broadly comprises the provision of a resilient support for printing elements of the character mentioned, and the invention is not restricted to the particular character or mode of applying such a resilient support. On the contrary, the invention consists broadly in the provision of any resilient material beneath a printing element during the printing operation in order that the printing element may be yieldably supported, and preferably includes a relatively less yielding support for the material to be printed, to the end that the printing impression may be uniform throughout its entire area.

It is believed that the invention will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the various components, Without departing from the spirit or scope of the invention, the forms herein described being simply selected embodiments for the purpose of illustrating the invention.

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

1. In a structure for relief or letterpress printing, a printing base having a plurality of adjacent cut-out portions along its upper surface to provide a displacement space, a member, having a printing pattern, mounted upon the upper surface of said base, said pattern having portions requiring different printing pressures to form an even impression, resilient material interposed between said member and said base, and means for varying the area of said displacement space to conform with the printing pressure requirements of said printing pattern.

2. In a structure for relief or letterpress printing, a printing plate secured to a base, said printing plate having a letterpress printing surface requiring different printing pressures to form an even impression, resilient material interposed between said printing plate and said base, and means in the base supporting said resilient material permitting variation in the area of support of said printing plate, whereby the variations in the printing pressure requirements of the printing surface of said plate may be obtained.

3. The structure specified in claim 2 in which the members disposed in said bores have portions extending slightly above the upper surface of said base.

4. The method of relief or letterpress printing with a letterpress printing plate having a printing surface requiring different printing pressures to form an even impression, which comprises mounting said printing plate upon resilient ma- .terial interposed between said plate and a base to which the plate is secured, and inserting means in the base supporting the resilient material permitting variation in the area of support of said printing plate, whereby the variations in the printing pressure requirements of the printing surface of said plate may be obtained.

5. In a structure for relief or letterpress printing, a printing element comprising a base having a plurality of vertical bores, a metallic printing plate secured thereon in a manner to permit limited vertical movement, a sheet of resilient material underlying said plate, said plate having a letterpress printing surface, portions of which require different printing pressures to form an even printing impression, and members inserted in said bores beneath the plate portions requiring increased pressure.

PHILIP A. FRAZIER.

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