US3593659A

US3593659A - Offset printing apparatus having disposable dampening and inking means

Info

Publication number: US3593659A
Authority: US
Inventors: Robert D Brackett
Original assignee: Polaroid Corp
Current assignee: Polaroid Corp
Priority date: 1968-06-26
Filing date: 1968-06-26
Publication date: 1971-07-20
Anticipated expiration: 1988-07-20

Abstract

In an offset printing press, disposable dampening and inking materials, supplied in premoistened and preinked form, are supported in an unrestrained manner by dampening and inking cylinders, respectively, and disposed between them and the plate cylinder to provide controlled dampening and inking of the pressplate.

Description

United States Patent [72] Inventor Robert D. Bracket! 1,954,550 4/1934 Weide 101/142 X Wakefield, Mass. 2,006,364 7/1935 Morse 101/348 X |21] Appl. No. 740,212 2,181,935 12/1939 Carroll 101/227 [221 Filed June 26,1968 2547,47] 4/1951 Janke 101/218 X [45] Patented July 20,1971 2,713,304 7/1955 Thomas 101/117 [73] Assignee PolaroidCorporation 2,782,712 2/1957 Claff et a1. 101/227 X Cambridge, Mass. 2,800,855 7/1957 Claffet al. 101/148 2,913,980 11/1959 Lindemann 101/148 3,220,837 11/1965 Land et al.... 101/455 X [54] OFFSET PRINTING APPARATUS HAVING 3,242,554 6 Raym nd l /l4 X DISPOSABLE DAMPENING AND INKING MEANS 3,273,224 /1966 Spicer 101/148 X 18 Claims, Drawing Figs. 1,687,016 10/1928 Green 101/336 52 vs. C: 101/142, FOREIGN PATENTS 101/147, 101/348, 101/227, lOI/367, 83/663, 993,084 5/1965 Great Britain 248/206 mtg 1435 2, 11g 240,101 247 1,147,300 6/1957 France 83/9262 [51] lnt.CI B4lf7/04, B4l f7/24,B41f3l/34 Field ofSearch 101/142, 227, 226, 224,147,148, 348, 349, 415.1,141,

[56] References Cited UNITED STATES PATENTS 1,383,531 7/1921 Craig 101/227 UX 1,580,917 4/1926 Putt 83/342X I 54 ea a,

Primary Examiner-Robert E. Pulfrey Assistant Examiner-Clifiord D. Crowder Attorney-Brown and Mikulka ABSTRACT: In an offset printing press, disposable dampening and inking materials, supplied in premoistened and preinked form, are supported in an unrestrained manner by dampening and inking cylinders, respectively, and disposed between them and the plate cylindler to provide controlled dampening and inking of the pressplate.

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@MQMJM ATTORNEYS PATENTED JUL 20 l97l SHEET 2 OF 4 FEE-3.5

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PATENTEDJUL20I97| 3.593659 sum 3 0F 4 A 'ENTOR.

51:01am, and M ATTORNEYS OFFSET PRINTING APPARATUS HAVING DISPOSABLE DAMPENING AND INKING MEANS The invention concerns an offset printing press of simplified construction, adapted especially to the extremely rapid provision of smallto-medium-quantity production runs" and to the employment, as a printing or pressplate of a photographic paper" print. This type of pressplate, in the interest of maximum rapidity from camera exposure to duplicate prints and from the aspect of superior tonal values, is advantageously produced from rapid-processing or so-called self-developing film materials of the type manufactured by Polaroid Corporation, Cambridge, Massachusetts, U.S.A., having a very fast film speed and involving a diffusion transfer method if image formation. The print or pressplate is preferably mounted on a plate cylinder by a simple mounting clip or clamp. An inking cylinder releasably mounting a disposable sleeve coated with a premilled ink is employed. The inking sleeves, each capable of producing as many as I or more prints, are supplied in hermetically sealed capsules. The apparatus also embodies a supply means for a paper stock in roll form in conjunction with an automatic sheet cutter.

An inking sleeve can be installed on the inking cylinder and an exhausted sleeve removed therefrom and replaced by another in a few seconds. The apparatus is adapted to produce either black-and-white or full-color prints, rendered in line or in halftone using one or more pressplates and precoated inking sleeves depending upon the subject matter.

Use of a print of the character above described as a printing plate will be noted as providing several distinct advantages among which, importantly, are:

Utmost speed from picture-taking to duplication in quantity, that is, an ability to run off duplicate copies of the print immediately following the photographic exposure using the aforesaid self-developing type of film.

An avoidance of the many steps involved in having to make conventional, e.g., metallic, printing plates with marked savings in time, attendant equipment and expense.

The saving in time and equipment provided by incorporation in the apparatus of the preinked disposable inking sleeve components where, usually, a plurality of milling rolls, ink solutions or mixtures and a considerable period for rendering inks in a usable state are necessary.

The simplification and reduction in printing costs made possible by using a paper stock in roll form in conjunction with a relatively simple, automatic sheet cutter.

In accordance with the aforesaid considerations, objects of the invention are to provide printing apparatus especially adapted to relatively small, rapid and economical production runs" of high quality in line or half-tone to provide printing apparatus of the character described utilizing paper prints as printing plates, the prints being produced by materials and methods identified with Polaroid Corporation; to provide apparatus of the type stated wherein printing plates are produced by self-developing film materials and are available for use immediately following a photographic exposure; to provide apparatus as characterized embodying a preinked disposable inking sheath or sleeve supplied in a hermetic capsule; to provide apparatus as set forth wherein a removable and disposable dampening sleeve is included; to provide inking and dampening sleeves as described which are adapted to movement longitudinally of their mounting cylinders for providing fresh functional surfaces; to provide apparatus of the structure defined adapted to utilize as a printing sheet material a paper stock in roll form, thereby simplifying the paper feeding system; to provide apparatus of the category stated which includes a novel automatic sheet cutter; and to provide apparatus of the character describedwhich is adapted to produce both black-and-white and full-color prints.

Other objects of the invention will in part be obvious and will in part appear hereinafter.

The invention accordingly comprises the apparatus possessing the construction, combination of elements and arrangement of parts which are exemplified in the following detailed disclosure, and the scope of the application of which will be indicated in the claims.

For a fuller understanding of the nature and objects of the invention, reference should be had to the following detailed description taken in connection with the accompanying drawings wherein:

FIG. I is a diagrammatic perspective view of the printing press apparatus from the left side;

FIG. 2 is a diagrammatic perspective view of the printing press apparatus from the right side;

FIG. 3 is a diagrammatic perspective view of the paper cutter;

FIG. 4 is a diagrammatic perspective view of a shaft for releasably mounting a cylinder of the printing press;

FIG. 5 is a fragmentary detail of the shaft of FIG. 4;

FIG. 6 is a diagrammatic side view of the principal elements of the printing press apparatus;

FIG. 7 is a diagrammatic perspective view of the plate cylinder;

FIGS. 8 and 9 are diagrammatic perspective views of the inking and dampening cylinders and cooperating sleeves; and

FIG. I0 is a diagrammatic view, in cross section, of several printing plate structures especially adapted to incorporatio with the apparatus.

In FIG. I the offset printing apparatus 10 is shown from the left side. It includes a rigid U-shaped frame 12, composed of a metal such as aluminum or steel, between the upwardly extending arms or sides 12a of which are mounted the several rotatable elements of the apparatus. As more fully shown in conjunction with FIG. 6, these rotatable elements include the following: a dampening cylinder 14 resiliently surfaced at 16 and having a removable dampening sleeve 18 composed of a water-absorbent material such as a blotting paper; a plate cylinder 20 including a printing plate retaining clip 22 releasably clamping a paper press plate 24; an inking cylinder 26 resiliently surfaced at 28 and having a removable inking sleeve 30 composed of a resilient material such as rubber, neoprene or the like; a blanket or offset cylinder 32 including a rubber cover or so-called blanket 34; an impression cylinder 36; the relatively vertically disposed paper-advancing

means

38 and 40, each including a pair of rubber-faced, frictionally engaging driving or propelling wheels 42; a pair of vertically disposed paper-shearing elements in the form of

rolls

44 and 46 having hardened

metallic inserts

48 and 50 with a tautened steel cutting wire 52 extending longitudinally of the face of the lower insert; and a paper-supply roll 54 carrying a continuous length of printing paper 56.

As shown more clearly in FIG. 2, the apparatus is driven by clockwise rotation of the counterweighted hand crank 58. A manual drive is preferred because it is: suited to the relatively small printing runs intended and to minimum bulk, weight and cost factors. On the other hand, an electric motor can be employed for the purpose. In response to turning of the handcrank 58, the several cylinders and rollers are rotated in directions indicated by the arrows, as provided by a plurality of intermeshing gears of by frictional contact of their surfacing components with one another or with the paper 56.

The gears, mounted at the tips of their respective shafts, are preferably composed of a plastic material such as nylon and have pitch diameters enabling a 1:1 ratio of functional diameters of the rotatable elements. The gears comprise a primary driving and paper-advancing or propelling gear 62 located at the extremity of the handcrank shaft, a first idler gear 66 en gaging gear 62, the blanket gear 68 engaged by gear 66, the pressplate gear 70 driven by gear 68, a second idler gear 72 driven by gear 62 and driving the upper cutter-roll gear 74, and the lower cutter-roll gear 76 driven by gear 74. It will be noted that the axes of the

paper cutting rolls

44 and 46, while parallel to one another, are not parallel to those of the other principal rotatable elements but are disposed at an angle of 5 relative thereto for a reason to be described below. Accordingly, the idler gear 72 is a bevel gear tapering slightly outwardly and having an axis which extends in a direction intermediate of the angularly different axes, above mentioned, namely, at an angle of 2.5 with respect thereto.

Completing the structure shown in FIGS. I and 2, a manually actuatable rod-shaped cam element 78, overturned at its extremity in the form of a lever 78a, underlies and is adapted to raise or lower the clip or clamp 22 for, respectively, releasing or clamping the paper pressplate 24. An inclined tray 80 is provided to collect and stack the individual printed sheets severed by the cutter rolls and ejected from the apparatus. The tray includes an overturned base portion 80a at one extremity releasably engaging the transverse rod 82. It is pivotally mounted on a support component 84 at its other extremity.

The dampening cylinder I4, inking cylinder 26 and blanket cylinder 32 are mounted for rotation on the cam-type shafts 86, 88 and 90, respectively. These shafts, one of which is shown in detail in FIGS. 4 and 5, extend transversely between the U-shaped frame members 12a, being removably mounted in apertures formed therein. An inner sleeve 92 of the cylinder is mounted on portions 864 of the shaft which are eccentrically disposed relative to the

portions

86b and 860 thereof. The shaft portions 861) and 860 are adapted to be releasably mounted in the apertures 94 of the upstanding main frame portions 12a. A circular groove 86d is adapted to receive a retaining pin 96 fastened to the frame. A section 86c of the shaft is provided with a longitudinal slot 862,. The shaft also includes an enlarged end portion 86g terminating in a handle 86h. ,The portion 863 is positioned within a ring 96 integral with the frame portion 12a. A spring-biased hardened-steel ball 100 is mounted within the end portion 86g and provides a frictional contact with the inner surface of ring 98 sufficient to hold the shaft at any position to which it has been rotated.

When the shaft 86 has been turned by manual actuation of the handle 86h so as to align the slot 86c, with the pin 96, the shaft can be inserted in or removed from its mounting apertures. The shaft is shown at locked position in FIG. by reason of the positioning of pin 96 in groove 86d. The eccentricity of shaft portions 86a upon which each cylinder sleeve 92 is mounted permits a translational movement of the cylinder toward or away from the plate cylinder responsive to turning of the handle 86h. The cylinders rotate about the stationary sleeves 92 on suitable bearings. The shafts of other of the rotatable elements may be assumed to be mounted in bearing inserts of the frame, e.g., inserts of phosphor bronze impregnated with a lubricant. A pair of yokelike limit stops I02 and 104, pivotally attached to the frame members 120 at 106 and 108 and slightly spaced from the ends of the

cylinders

14 and 26 determine the degree to which the dampening and inking sleeves l8 and 30 can move longitudinally of the cylinders during operation.

The cutter rolls 44 and 46 are shown in greater detail in FIG. 3. As previously intimated, the axes of these rolls are not parallel to the axes of other rotatable elements nor at 90 to the direction of movement of the paper 56 but are angularly disposed at 5 to the other axes. The cutting wire 52 is so angularly disposed across the face of the metal insert 50 that when the

inserts

48 and 50 are brought together in facing relation the wire extends at 5 to a plane which would include the axes of both cutter rolls 44 and 46 and parallel to the axes of the other rotatable elements. This relative disposition of axes provides an effective cutting structure in which the wire is forced into, compresses and severs the paper while involving a miminum of resistance to rotation of the cutter rolls. This is believed to be due to a distribution of the cutting force throughout a rotation of the cutter rolls which is greater than would be the case where the axes of both of the cutter rolls and the cutting wire at 90 to the direction of movement of the paper 56.

The inking sleeve 30, illustrated in FIG. 8, is formed of a rubber, neoprene or other elastic material of a given resiliency. It is supplied precoated with a layer of a suitable lithographic ink Il0 composed, for example, of chosen proportions of pigment, vehicle, drier and compounds for adjusting its working qualities. It is to be assumed that the ink has previously undergone milling, kneading or other treatment ofa nature comparable to that provided by the multiroll inking system ofa conventional printing press. Accordingly, the ink is to be regarded as of a correct consistency when coated on the sleeve 30. The thus-coated sleeve 30 is provided in a hermetically sealed capsule I I I formed, for example, of a plastic such as a polystyrene. When inserted in the capsule, a cover element I12 is fitted thereto and a pressure-sensitive tape 114, having a noncoated tab 114:: for removal purposes, is bound around the edge of the cover and contiguous portions of th capsule to provide an airtight seal.

To install the inking sleeve, the guide 104 is pivoted upwardly to open position, the shaft 88 is released and pulled outwardly, and the inking cylinder 26 is lifted from the printing press. An inking sleeve 30 is removed from its sealed capsule ii I and slipped over the inking cylinder, after which the cylinder is remounted. Both the inking sleeve and capsule may be regarded as of a disposable category or the sleeve may again be inked and stored in the capsule for future use.

The moistening sleeve 18, shown in FIG. 9, is composed ofa paperlike material of a fibrous, porous and hygroscopic type such as a form of blotting paper, surface-treated in an appropriate manner as for instance by a resinous plastic substance, to a degree insufficient to offset its absorptive properties but to anchor its fibers against displacement. The sleeve is preimpregnated with a suitable moistening solution, e.g., a solution of seven parts water to one part glycerin, and supplied in a hermetically sealed capsule of the type used for the inking sleeve and described relative to FIG. 8. Opening of guide 102 and removal of the moistening cylinder 14 to install or remove the sleeve I8 are accomplished in the manner previously explained. Both sleeves I8 and 20 are adapted to a slight longitudinal movement on their respective cylinders during a given printing run. This movement, to the extent permitted by the guides I02 and I04, provides a varied source of moistening liquid and ink and is made possible by the somewhat loose fit of the sleeves, enhanced by a slight taper of their inner diameters.

Means for releasably and easily mounting the printing press on a flat surface such as that of a table top are indicated in FIG. 2. A rectangular aperture 116 is formed in the base of the supporting frame 12. The entire base, including the aperture H6, is covered on its lower surface by a sheet I18 of a resilient material such as a rubber or neoprene which is bonded thereto. A rectangular metal plate 120, of appreciably smaller dimensions than the aperture 6, is fastened to the inner (upper) surface of the sheet 118, as by the rivets 122. A yokelike cam-follower 124 is fixedly attached to the central portion of the upper surface of plate 120. A rodlike cam element 126 is mounted in bearing means 128 of the base 12b of the supporting frame so as to extend transversely thereacross, its camming portion 126a being adapted to bear against and force upwardly the cam-follower portion 124a in response to manual rotation of the lever 130 which is fastened to an end of cam element 126. Upward movement of the cam follower also lifts the attached plate and that portion of the resilient sheet I I8 fastened thereto within the area of aperture 116, the sheet 118 stretching as required to provide a concavity at the area I16 with respect to the remaining planar sheet portions. A vacuum is thus provided within the concavity which serves to hold the printing press firmly against displacement on the table top.

It will be noted that the paper pressplate 24 is attached by the clip 22 to the plate cylinder 20 at one end only, namely, at that leading end which is drawn or pulled due to rotation of the cylinder in a given direction. The trailing portions and opposite end of the pressplate are not fastened to the cylinder and thus are allowed to assume an unhampered, natural and firm seating against the cylinder surface. The plate cylinder, as well as the impression cylinder, are preferably composed of a metal such as aluminum.

The relative disposition and movement of the cylinders and other rotatable elements is shown graphically in FIG. 6. It will be understood that the moistening sleeve 18 applies the moistening solution to the paper pressplate 24 prior to application thereto of the printing ink 110 by the inking sleeve 30. The frictionally surfaced propulsive wheels 42 are of slightly larger diameter than that of the periphery of the blanket 34 and that of the impression cylinder 36 to insure a positive forward movement of the sheet 56 in a flat slightly tautened condition.

Conventional printing inks and papers may be employed in conjunction with the pressplates, the preinked and premoistened sleeves, and other elements of the apparatus, as described. An example of a suitable printing paper is a socalled 70-pound offset enamel."

The printing apparatus, as above described, is adapted to the production of either black-and-white or color prints rendered in line or in halftone the latter in terms ofa screen of up to 150 lines or greater to the inch. Where, for example, a full-color rendition is the objective, the cutter rolls would not initially be employed, roll 44 being pivotally mounted by means, not shown, for bodily movement away from roll 46, as indicated by the broken line 132. A first continuous length of the paper would be impressed from the blanket in the form of an image by, for example, a red ink supplied by a red-ink precoated inking sleeve 18 with. a color-separation paper pressplate representing the warm color of the photographic subject. The continuous length of paper would be run successively through the apparatus for providing correctly registered green and blue color-separation images and possibly a light black image. With impression of the last image, the cutter would again be functionally positioned. While the blanket is shown as permanently installed and subject to cleansing, it would be possible to utilize separate blanket sleeve for each color, of a cleansable or disposable type.

Examples of paper pressplates of types contemplated in apparatus of the present invention are illustrated in FIG. 10. The lithographic type of pressplate 134 of example a" includes a paper support 136 with printing-ink-repellent and moisteningsolution-receptive areas 138, and printing-ink-receptive areas 140 rendered in terms of an imagewise deposition of silver. Example b" represents a functionally similar structure 1340 wherein the imagewise silver deposition is slightly raised with respect to the plane of the nonimage-carrying areas which are approximately identified with the support to produce, in effect, a relief form of printing plate. As an example of a system for preparing paper pressplates, mention may be made of that described and claimed in U.S. Pat. No. 3,220,837. In the ex ample c a somewhat different structure produced by a diffusion transfer method followed by a subsequent surface treatment is illustrated. The etched" form thereby provided includes the hydrophilic or moistening-solution-receptive area 142 and the indented oleophilic or printing-ink-receptive areas 144.

As previously intimated, the incorporation with the apparatus of paper pressplates of the type derived from a highspeed self-developing film enables the production of a succession of duplicate prints of the highest quality and capable of the widest possible range of content immediately following a photographic exposure. When a pressplate of this type is combined with the minimum makeready characteristics of the preinked inking sleeve and the premoistened moistening sleeve, the overall production cycle is desirably simplified, extremely rapid and economical.

Since certain changes may be made in the above apparatus without departing from the scope of the invention herein involved, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. An offset printing apparatus adapted to effect the inking of a pressplate and transfer of anink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame; a plate cylinder rotatably mounted on said frame, said plate cylinder adapted to have a pressplate mounted thereon; means for dampening such pressplate after it is mounted on said plate cylinder; an inking cylinder rotatably mounted on said frame adjacent said plate cylinder; means for rotating at least said plate cylinder; means for inking such pressplate after it is mounted on said plate cylinder including resilient sheet material supplied in precoated form with ink of correct printing consistency supported by said inking cylinder in an unrestrained manner so as to permit oscillatory motion of said precoated sheet material with respect to the longitudinal axis of said inking cylinder, said precoated sheet material being disposed between said inking cylinder and said plate cylinder in pressure contact therebetween such that said precoated sheet material is repeatedly pressed against such pressplate for repeated inking thereof and is driven longitudinally of said inking cylinder for providing fresh functional surfaces to such pressplate responsive to rotation of said plate cylinder; means for limiting said movement of said precoated sheet material across said inking cylinder; a blanket cylinder rotatably mounted on said frame adjoining said plate cylinder for removal of an ink impression of such pressplate during each rotation of said plate cylinder; means for receiving a supply of printing material; means for feeding such printing material from such supply means past said blanket cylinder; and means for pressing such printing material against said blanket cylinder for transferring an ink impression of such pressplate to such printing material.

2. An offset printing apparatus, as defined in claim I, wherein said pressplate is a paper print of a type formed by a diffusion transfer process.

3. An offset printing apparatus, as defined in claim 2, wherein said paper print is ofa type formed from a high speed self-developing film material involving a deposition of silver on areas utilized for image formation.

4. The offset printing apparatus of claim 1 wherein said limiting means comprise a pair of members disposed adjacent the edges of said sheet material and spaced apart a distance slightly exceeding the lateral dimension thereof whereby a slight movement of said material with. respect to the longitudinal axis of said inking cylinder is permitted during rotation of said plate cylinder 5. The offset printing apparatus ofclaim l wherein said link ing cylinder is demountable and said precoated sheet material comprises a sleeve loosely fitted to said inking cylinder and adapted to he slipped thereon.

6. The offset printing apparatus of claim 5 wherein said limiting means comprise a pair of members spaced apart a distance slightly exceeding the longitudinal dimension of said sleeve which, in cooperation with the loose fit thereof, permit a slight longitudinal movement of said sleeve on its cylinder during operation rotation of the latter.

7. The offset printing apparatus of claim 5 wherein said limiting means comprise a yokelike member having an open end portion for providing a pair of opposed members spaced apart a distance exceeding the longitudinal dimension of said sleeve, and said yokelike member is displaceably mounted on said frame with its open end portion adjacent the ends of said sleeve.

8. The offset printing apparatus of claim 5 including a pair of rolls, and a severing element in the form of a tautened wire extending lengthwise across one of said rolls, said rolls rotatably mounted in said frame at a small angle to said blanket cylinder, and said wire disposed on said one roll at the same angle but opposite direction to the mounting angle of said rolls such that said wire is substantially parallel to the axis of said blanket cylinder, and means for feeding said paper from said blanket cylinder between said severing rolls.

9. An offset printing apparatus, as defined in claim 5, wherein said preinked sleeve is composed of a resilient material and a layer of printing ink formed on its surface has been treated prior to its application to said sleeve to assume a form completely adapted to transfer to said pressplate for printing purposes.

10. An offset printing apparatus adapted to effect the inking of a pressplate and transfer of an ink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame having spaced apart upright members; a plurality of shafts supported in apertures of said upright members and extended thereacross; a plate cylinder rotatably mounted on a first of said shafts, said plate cylinder adapted to have a pressplate mounted thereon; an inking cylinder rotatably mounted on a second of said shafts adjacent said plate cylinder; means for rotating said plate cylinder; means for inking such pressplate after it is mounted on said plate cylinder including sheet material supplied in precoated form with ink of correct printing consistency disposed between said inking cylinder and said plate cylinder in pressure contact therebetween and supported by said inking cylinder in an unrestrained manner so as to permit movement of said sheet material with respect to the longitudinal axis of said inking cylinder; said second shaft having a centrally located cylinder-support portion eccentrically disposed relative to its end portions for providing a translational motion of said inking cylinder toward or away from said plate cylinder upon rotation of said second shaft, a spring biased member mounted in said second shaft at one end thereof and adapted to provide frictional contact between said second shaft and one of said upright members so as to hold said shaft at any position to which it is rotated; a retaining member displaceably mounted on one of said upright members; and a circular groove disposed on said second shaft and adapted to releasably receive said retaining member, thereby providing for withdrawal of said inking cylinder shaft and removal of said inking cylinder for replacement of said precoated sheet material.

ll. An offset printing apparatus adapted to effect the inking of a pressplate and transfer of an ink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame; a plate cylinder rotatably mounted on said frame, said plate cylinder adapted to have a pressplate mounted thereon; means for inking such pressplate after it is mounted on said plate cylinder; a dampening cylinder rotatably mounted on said frame adjacent said plate cylinder; means for rotating at least said plate cylinder; means for dampening such pressplate after it is mounted on said plate cylinder including sheet material supplied in premoistened form with moistening solution of correct printing consistency supported by said dampening cylinder in an unrestrained manner so as to permit oscillatory motion of said premoistened sheet material with respect to the longitudinal axis of said dampening cylinder, said premoistened sheet material being disposed between said dampening cylinder and said plate cylinder in pressure contact therebetween such that said premoistened sheet material is repeatedly pressed against such pressplate for repeated dampening thereof and is driven longitudinally of said dampening cylinder for providing fresh functional surfaces to such pressplate responsive to rotation of said plate cylinder; means for limiting said movement of said premoistened sheet material across said dampening cylinder; a blanket cylinder rotatably mounted on said frame adjoining said plate cylinder for removal of an ink impression of such pressplate during each rotation of said plate cylinder; means for receiving a supply of printing material; means for feeding such printing material from such supply means past said blanket cylinder; and means for pressing such printing material against said blanket cylinder for transferring an ink impression of such pressplate to such printing material.

12. The offset printing apparatus of claim ll wherein said limiting means comprise a pair of members disposed adjacent the edges of said sheet material and spaced apart a distance slightly exceeding the lateral dimension thereof whereby a slight movement of said material with respect to the longitudinal axis of said dampening cylinder is permitted during rotation of said plate cylinder.

13. The offset printing apparatus of claim 11 wherein said dampening cylinder is demountable and said premoistened sheet material comprises a sleeve loosely fitted to said dampening cylinder and adapted to be slipped thereon.

14. The offset printing apparatus of claim 13 wherein said limiting means comprise a pair of members spaced apart a distance slightly exceeding the longitudinal dimension of said sleeve which, in cooperation with the loose fit thereof, permit a slight longitudinal movement of said sleeve on its cylinder during operational rotation of the latter.

15. The offset printing apparatus of claim 13 wherein said limiting means comprise a yokelike member having an open end portion for providing a pair of opposed members spaced apart a distance exceeding the longitudinal dimension of said sleeve and said yokelike member is displaceably mounted on said frame with its open end portion adjacent the ends of said sleeve.

16. An offset printing apparatus, as defined in claim 13, wherein said premoistened sleeve is composed of a fibrous, porous, hygroscopic, paperlike material pretreated to prevent displacement of its fibers.

17. An offset printing apparatus adapted to effect the the inking of a pressplate and transfer of an ink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame; a plate cylinder rotatably mounted on said frame, said plate cylinder adapted to have a pressplate mounted thereon; a dampening cylinder rotatably mounted on said frame adjacent said plate cylinder; means for dampening such pressplate after it is mounted on said plate cylinder including sheet material supplied in premoistened form with moistening solution of correct printing consistency supported by said dampening cylinder in an unrestrained manner so as to permit oscillatory motion of said premoistened sheet material with respect to the longitudinal axis of said dampening cylinder; an inking cylinder rotatably mounted on said frame adjacent said plate cylinder; means for inking such pressplate after it is mounted on said plate cylinder including resilient sheet material supplied in preinked form with ink of correct printing consistency supported by said inking cylinder in an unrestrained manner so as to permit oscillatory motion of said precoated sheet material with respect to the longitudinal axis of said inking cylinder; said cylinders rotatably mounted in said frame with said premoistened and said precoated sheet material disposed between said plate cylinder and said dampening and inking cylinders, respectively, in pressure contact therebetween such that said premoistened and said precoated sheet material are sequentially and repeatedly pressed against such pressplate for repeated dampening and inking thereof and are driven longitudinally of their supporting cylinders for providing fresh functional surfaces to such pressplate responsive to rotation of said plate cylinder; means for limiting premoistened and said precoated sheet material across their respective cylinders; a blanket cylinder rotatably mounted on said frame adjoining said plate cylinder for removal of an ink impression of such pressplate during each rotation of said plate cylinder; means for receiving a supply of printing material; means for feeding such printing material from such supply means past said blanket cylinder; and means for pressing such printing material against said blanket cylinder for transferring an ink impression of such pressplate to such printing material.

18. The offset printing apparatus of claim 33 wherein said dampening and inking cylinders are demountable and said sheet materials comprise sleeves loosely fitted to their respective cylinders and adapted to be slipped thereon, and said limiting means comprise a pair of members disposed adjacent the ends of each sleeve and spaced apart a distance slightly exceeding the longitudinal dimension of each sleeve which, in cooperation with the loose fit thereof, permit a slight longitudinal movement of said sleeves on their cylinders during operational rotation of the latter.

Claims

1. An offset printing apparatus adapted to effect the inking of a pressplate and transfer of an ink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame; a plate cylinder rotatably mounted on said frame, said plate cylinder adapted to have a pressplate mounted thereon; means for dampening such pressplate after it is mounted on said plate cylinder; an inking cylinder rotatably mounted on said frame adjacent said plate cylinder; means for rotating at least said plate cylinder; means for inking such pressplate after it is mounted on said plate cylinder including resilient sheet material supplied in precoated form with ink of correct printing consistency supported by said inking cylinder in an unrestrained manner so as to permit oscillatory motion of said precoated sheet material with respect to the longitudinal axis of said inking cylinder, said precoated sheet material being disposed between said inking cylinder and said plate cylinder in pressure contact therebetween such that said precoated sheet material is repeatedly pressed against such pressplate for repeated inking thereof and is driven longitudinally of said inking cylinder for providing fresh functional sUrfaces to such pressplate responsive to rotation of said plate cylinder; means for limiting said movement of said precoated sheet material across said inking cylinder; a blanket cylinder rotatably mounted on said frame adjoining said plate cylinder for removal of an ink impression of such pressplate during each rotation of said plate cylinder; means for receiving a supply of printing material; means for feeding such printing material from such supply means past said blanket cylinder; and means for pressing such printing material against said blanket cylinder for transferring an ink impression of such pressplate to such printing material.

2. An offset printing apparatus, as defined in claim 1, wherein said pressplate is a paper print of a type formed by a diffusion transfer process.

3. An offset printing apparatus, as defined in claim 2, wherein said paper print is of a type formed from a high speed self-developing film material involving a deposition of silver on areas utilized for image formation.

4. The offset printing apparatus of claim 1 wherein said limiting means comprise a pair of members disposed adjacent the edges of said sheet material and spaced apart a distance slightly exceeding the lateral dimension thereof whereby a slight movement of said material with respect to the longitudinal axis of said inking cylinder is permitted during rotation of said plate cylinder

5. The offset printing apparatus of claim 1 wherein said linking cylinder is demountable and said precoated sheet material comprises a sleeve loosely fitted to said inking cylinder and adapted to be slipped thereon.

11. An offset printing apparatus adapted to effect the inking of a pressplate and transfer of an ink impression therefrom to printing material for economically producing relatively small printing quantities with a minimum of makeready, said apparatus comprising: a supporting frame; a plate cylinder rotatably mounted on said frame, said plate cylinder adapted to have a pressplate mounted thereon; means for inking such pressplate after it is mounted on said plate cylinder; a dampening cylinder rotatably mounted on said frame adjacent said plate cylinder; means for rotating at least said plate cylinder; means for dampening such pressplate after it is mounted on said plate cylinder including sheet material supplied in premoistened form with moistening solution of correct printing consistency supported by said dampening cylinder in an unrestrained manner so as to permit oscillatory motion of said premoistened sheet material with respect to the longitudinal axis of said dampening cylinder, said premoistened sheet material being disposed between said dampening cylinder and said plate cylinder in pressure contact therebetween such that said premoistened sheet material is repeatedly pressed against such pressplate for repeated dampening thereof and is driven longitudinally of said dampening cylinder for providing fresh functional surfaces to such pressplate responsive to rotation of said plate cylinder; means for limiting said movement of said premoistened sheet material across said dampening cylinder; a blanket cylinder rotatably mounted on said frame adjoining said plate cylinder for removal of an ink impression of such pressplate during each rotation of said plate cylinder; means for receiving a supply of printing material; means for feeding such printing material from such supply means past said blanket cylinder; and means for pressing such printing material against said blanket cylinder for transferring an ink impression of such pressplate to such printing material.

12. The offset printing apparatus of claim 11 wherein said limiting means comprise a pair of members disposed adjacent the edges of said sheet material and spaced apart a distance slightly exceeding the lateral dimension thereof whereby a slight movement of said material with respect to the longitudinal axis of said dampening cylinder is permitted during rotation of said plate cylinder.