GB2104842A - Converting printing presses - Google Patents

Abstract

An offset newspaper printing press as shown is produced by conversion of a direct letterpress machine cylinders 20 and 30 are the original impression and plate cylinders, the plate(s) being replaced by an offset blanket. The original inking system is removed and replaced by a module which is pivotally mounted and includes new plate cylinder 40 and an associated inker, which, as shown, also may incorporate a damper pivotting of the module trips the plate cylinder 40, and the inker/damper may also be pivotable with respect to the module to trip the ink/damping application to the plate. The original drive to the cylinders 20 and 30 is retained, and the new module is driven from the existing inker drive. <IMAGE>

Description

SPECIFICATION Offset conversion module for newspaper printing press The offset conversion module for newspaper printing press disclosed and claimed in this application relates to improvements in newspaper printing press of the type disclosed in Dahlgren Patent No. 4,208,963, dated June 24, 1980 and Dahlgren Patent No. 4,233,898 dated November 1 8, 1980, the disclosures of which are incorporated herein by reference in their entirety for all purposes.

Newspaper presses heretofore devised have utilized a variety of printing processes including letter press, relief printing, and lithographic printing processes. A majority of the printing presses presently in use in the United States are letter presses with plate cylinders having saddles which carry type fonts. After being inked, the type fonts apply an image directly to a web of paper.

The opposite side of the web of paper is generally engaged by an impression cylinder to provide a desired paper pressure at the printing nip.

A number of letter presses have been converted to direct lithographic printing presses by installing a dampening system in combination with the existing inker to permit replacement of the molded type fonts with lithographic printing plates. The lithographic printing plates generally engage the web which is backed by an impression cylinder. Conversion of letter presses to direct lithographic printing processes has offered numerous commercial advantages to newspaper publishers.

In an effort to achieve quality approximating that achieved by commercial processes for printing magazines and similar publications on quality paper, printing presses have been made available to the newspaper publishing industry which utilize offset lithographic printing processes wherein an image is transferred from an inked lithographic printing plate to a resilient blanket and then printed onto a web of paper. Such offset newspaper printing presses offer improved printing quality and a number of newspaper publishers have purchased new offset printing presses for publishing newspapers.

Since newspaper publishing companies generally employ a iarge number of printing couples for simultaneously printing a large number of pages for a newspaper, the investment in newspaper presses is substantial. In addition, changing from letter press to an offset lithographic process may require acquisition of a new building in which the new printing press is erected while the existing letter press is used for publishing the newspaper. After the new printing press has been installed, it can be used for publishing the newspaper. However, the existing letter press and all of the associated equipment including unwind reel stands, pipe rolls, folders, superstructure and the like, as well as the building in which the existing printing press is housed, must be sold or be used for producing only subquality work.

Efforts have been made heretofore for converting letter press or direct lithographic newspaper printing presses to offset lithographic printing to eliminate the necessity of obtaining a complete new printing press. The conversion of such presses has generally comprised the addition of new impression cylinders adjacent existing impression cylinders to permit attachment of offset blankets about the periphery of the existing impression cylinder for converting the cylinder to a blanket cylinder for transferring an image from a printing plate to the web. Such systems use the original printing cylinders which are modified to accommodate lithographic printing plates. Such attempts to convert letter presses have not enjoyed wide spread commercial success because space is not available on many presses for accommodating the additional impression cylinders.Further, movement of wet ink on a web into engagement with impression cylinders which are not precisely the same diameter as the blanket cylinder in an associated printing couple can result in set-off of ink from the web to the impression cylinder and then back to the web.

The invention described herein addresses the problem of converting an existing newspaper direct printing press to offset lithographic printing while utilizing as many parts as possible of the existing direct printing press to minimize the expense of the conversion. In addition, the web routing is not changed which minimizes disruption of production while a printing couple is being converted.

An improved method is disclosed of converting an existing newspaper printing press, which prints directly from a printing cylinder to a web, to an offset printing press, which prints from a printing cylinder onto a blanket cylinder which offsets the printed image to a web. The method comprises removing the existing ink train; drilling and tapping bolt holes for module side frames; installation of the module, including a new plate cylinder; modifying the existing plate cylinder to accommodate a blanket.

Inkers and dampeners of the type disclosed in U.S. Patent No. 4,208,963 and U.S. Patent No.

4,233,898 employ a single form roller and are used for replacing existing multi-form roller inkers which are employed in existing letter press and direct lithography newspaper printing presses.

The single inker form roller is located on the new side frames to permit movement of the plate cylinder upon actuation of a throw-off cylinder to move the printing plate out of engagement with the blanket cylinder while maintaining contact with the form roller. This permits rotation of the new blanket cylinder and the existing impression cylinder to pull a web through the printing press before moving the printing plates into engagement with the blanket cylinders without the additional movement of form rollers.

A primary object of the invention is to provide a new and improved method of converting a standard newspaper printing press which prints directly from a printing cylinder to a web to an offset printing press without alteration of the standard web routing through the printing press.

Another object of the invention is to provide an offset newspaper printing press in which a blanket cylinder and an ink coated form roller engage the printing plate to permit movement of the plate cylinder relative to the form roller for separating surfaces of the plate cylinder and the blanket cylinder while the blanket cylinders are maintained in driving relation with opposite sides of a web extending between the blanket cylinders.

A further object of the invention is to provide an offset conversion module for a newspaper printing press which can be constructed at a site away from the press room and installed on an existing printing press for conversion of the press to an offset printing press while eliminating the necessity of removing existing printing cylinders from the printing press.

A still further object of the invention is to provide an offset conversion module for newspaper printing presses having an improved inking and dampening system associated with a newly provided plate cylinder, the module being adapted for mounting between existing sideframes of a newspaper printing press after the existing ink train has been removed.

Other and further objects will become apparent upon referring to the detailed description hereinafter following and the drawings annexed hereto.

Description of drawing Drawings of a preferred embodiment of the invention are annexed hereto so that the invention may be better and more fully understood, in which: Fig. 1 is a side elevational view of the operator side of the printing press; Fig. 2 is a cross-sectional view taken along line 2-2 of Fig. 3; Fig. 3 is a cross-sectional view taken along line 3-3 of Fig. 1; Fig. 4 is a cross-sectional view taken along line 4-4 of Fig. 2; and Fig. 5 is a cross-sectional view taken along line 5-5 of Fig. 3.

Numeral references are employed to designate like parts throughout the various figures of the drawing.

Description of a preferred embodiment As best illustrated in Figs. 1 and 5 of the drawing, the numeral 10 generally designates a printing press converted to form a pair of offset lithographic newspaper printing couples, the operator side of printing unit being illustrated in Fig. 1. The inside of the side frame on the operator's side of the printing press is illustrated in Fig. 2.

The illustrated printing press is constructive from components of an existing direct printing press for printing newspapers. Impression cylinder 20 is an existing impression cylinder about which a web of paper extends and modification thereof is not necessary. The printing cylinder 30 is the existing printing cylinder in the letterpress which has been modified to form a blanket cylinder by equipping the cylinder with saddles of the type disclosed in U.S. Pat. No.

3,874,292 which issued April 1, 1975 to Robert L. Parsley, entitled "Plate Clamp", the disclosure of which is incorporated herein by reference in its entirety for all purposes. Such saddles are used in converting letterpresses for direct lithographic printing processes. However, in this case, a blanket is secured to cylinder 30.

Plate cylinder 40 is a portion of the offset conversion module which will be hereinafter more fully described, which is installed in lieu of the existing ink train which has been removed from the letterpress.

Gears 1 7 and 18 on impression cylinder 20 are of conventional design and components of the existing letterpress.

Compound gear 31, having an outer segment 32 and an inner segment 34, mounted on blanket cylinder 30 is of conventional design and is a portion of the existing press drive frame. Idler gear 35 and drive gear 36 are also portions of the existing press drive. Gear 36 is in a position and was mounted on a shaft for driving the existing train of rollers forming the inker which was removed from the standard unit to permit installation of the offset conversion module.

Shaft 37 extends through the operator's side sideframes 1 6 of the printing press and has gear 36 mounted on the outer rim thereof. A gear 38 is mounted on the inner end of shaft 37 which extends through sideframe 52 of offset conversion module 50, as will be hereinafter more fully explained. Sideframe 53 of conversion module 50 is pivotally secured by a pivot pin 55 extending into the gear side sideframe 15 of the printing press. As will be hereinafter more explained, pin 55 and shaft 37 are axially aligned and sideframes 52 and 53 of offset conversion module 50 pivot relative to press sideframes 1 5 and 16 about the axes of shaft 37 and pin 55.

Plate cylinder 40 is a new component which was not part of the existing letter press. However, plate cylinder 40 is of conventional design and further description thereof is not deemed necessary. Opposite ends of plate cylinder 40 are rotatably secured in sideframes 52 and 53 of the conversion module and a plate cylinder drive gear 39 is drivingly secured to plate cylinder 40 and disposed in meshing relation with gear 38.

From the foregoing, it should be readily apparent that rotation of the existing gears 1 7, 1 8, 31, 35 and 36 of the printing press will impart rotation to shaft 37 which will drive plate cylinder 40 through gears 38 and 39. Thus, plate cylinder 40 is driven by the existing printing press drive and is driven at press speed.

The bearings supporting impression cylinder 20 and blanket cylinder 30 are existing components of the letter press and are not modified for installation of the conversion module 50 in the printing press. However, it should be noted that blanket cylinder 30, which is a modified printing cylinder, is generally mounted in eccentric bearings for adjustment of paper pressure.

In Figs.1,2 and 5 of the drawing, the illustrated printing unit 10 comprises two printing couples which are substantially identical, one couple being a mirror image of the other couple. Components of the second couple are designated by prime numerals corresponding to numerals designating like parts in the first printing couple.

Plate cylinders 40 and 40' have journals extending outwardly from opposite ends thereof which are rotatably secured by bearings 42 and 43 to module sideframes members 52 and 53, which support the plate cylinders 40 and 40' and the inker and dampener.

As best illustrated in Figs. 2 and 3 of the drawing, support member 52 is vividly secured to the press sideframe 16 by shaft 37 which has gears 36 and 38 mounted on opposite ends thereof. Modules support member 53 on the gear side of the printing press is pivotally secured by a pin 55 to the press sideframe 15. Shaft 37 and pin 55 are axially aligned to permit simultaneous rotation of support members 52 and 53 about axes of shaft 37 and pin 55. As best illustrated in Fig. 2, a plate throw-off cylinder 54 is pivotally connected to the press sideframe and the rod end of the cylinder is pivotally connected to module sideframe 52 such that actuation of plate throw-off cylinder 54 moves printing plate 40 into or out of engagement with blanket cylinder 30.A pressure adjustment screw 56 extends through a lug 57 secured to press sideframes 15 and 16 and engage module sideframe members 52 for controlling pressure between plate cylinder 40 and blanket cylinder 30.

Plate cylinder throw-off cylinder 54 is preferably actuated by a source of compressed air (not shown) through a suitable valving.

The inking and dampening system employed for applying ink and dampening fluid to printing plates 40 and 40' is similar to that disclosed in the common owned Patent No. 4,233,898, dated November 18, 1980, entitled "Reversible Newspaper Press", and incorporates features disclosed in commonly owned Patent No.

4,208,963, dated June 24, 1980, the disclosure of which is incorporated herein by reference.

As will be hereinafter more fully explained, both ink and dampening fluid are applied by a single form roller 70 to the printing plate on plate cylinder 40. Ink is applied to form roller 70 by an inker generally designated by the numeral 80 and dampening fluid is applied to form roller 70 by a dampener generally designated by the numeral 90. It will be appreciated that form roller 70 and rollers 72, 74 and 76 are elements common to the dampener 80 and the inker 90.

Form roller 70 preferably has a resilient surface adapted to be urged into pressure indented relation with the printing plate on the surface of plate cylinder 40. Rollers 72, 74 and 76 are preferably vibrator rollers which are urged into pressure indented relation with the surface of form roller 70 and oscillate longitudinally in a direction parallel to the axis of form roller 70.

Inker 80 comprises a metering roller 82 having a resilient surface urged into pressure indented relation with a harder surface on inker transfer roller 84.

The surface of ink metering roller 82 dips into ink on an ink pan 85 to carry ink to the ink metering nip 86 between metering roller 82 and transfer roller 84. As the surface of ink metering roller 82 rotates toward the ink metering nip 86 between metering roller 82 and transfer roller 84, a relatively heavy layer of ink is picked up and lifted on the surface of metering roller 82. At the point of tangency, or cusp area at the ink metering nip 86, a bead of ink is piled up forming an excess of ink. The greatness of the excess of ink forming the bead at the metering nip is regulated by virtue of the fact that excessive ink will fall back into the pan 85 by gravity. Further, the surface speed of metering roller 82 controls the rate at which ink is delivered to ink metering nip 86.

The bead of ink at the ink metering nip 86 becomes a reservoir for ink which is drawn to the surface of ink transfer roller 84. As rollers 82 and 84 rotate in pressure indented relation, a layer of ink is sheared and metered between adjacent surfaces of the rollers which move in the same direction at different surface speeds. Ink in the ink metering nip 86 forms a thin lubricating layer to prevent frictional deterioration of the surfaces of the rollers. The metered film on the surface of transfer roller 84 is transferred to the surface of form roller 70 at an ink transfer nip 88. The surface of transfer roller 84 is preferably hard and is urged into pressure indented relation with the resilient surface on form roller 70, adjacent surfaces moving in the same direction at different surface speeds.

Form roller 70 will normally be rotated at a surface speed which is substantially equal to the surface speed of the printing plate carried by plate cylinder 40. The form roller 70 will normally rotate at a surface speed which is significantly greater than the surface speed of transfer roller 84 for forming a film of ink on form roller 70 which is significantly thinner than the film of ink which is carried by transfer roller 84 from the metering nip 86 to the transfer nip 88. By regulating the differential surface speeds between transfer roller 84 and form roller 70, the amount of ink applied to the printing plate on plate cylinder 40 can be regulated.

Within limits, if the surface speed of transfer roller 84 is increased, the ink film on the surface of the transfer roller 84 is presented to the form roller 70 at a faster rate and more ink is transferred to the surface of form roller 70 and consequently to the lithographic printing plate.

The ink metering roller 82 is preferably driven at a surface speed significantly slower than the surface speed of the form roller 70 and at a speed equal to or less than the surface speed of the transfer roller. It is only necessary that ink metering roller 82 rotate at a speed which is sufficient to maintain a desired quantity of ink in the ink metering nip 86. When using a water-like ink having very low viscosity, ink metering roller 82 might be driven at substantially the same surface speed as ink transfer roller 84.

Ink applied by ink transfer roller 84 to the surface of form roller 70 is smoothed and conditioned by vibrator roller 72 urged into pressure indented relation with the surface of form roller 70.

After ink has been applied by form roller 70 to the printing plate on plate cylinder 40 at nip 89, an irregular film of ink remains on the surface of form roller 70 bearing a "ghosted image" corresponding to the image on the printing plate.

This irregular film of ink is moved through a nip between ink storage roller 74 and form roller 70 for removing excess ink from the surface of form roller 70 and reapplying the excess ink to depleted portions on the surface of form roller 70 for redistributing ink which remains on the surface of form roller 70 after applying ink to the printing plate at the nip 89.

Dampener 90 comprises a dampening fluid metering roller 92 having a resilient surface urged into pressure indented relation with a dampening fluid transfer roller 94 having a hydrophilic surface which is dampening fluid receptive and ink rejecting. The dampening system may be of the type disclosed in Patent No. 3,986,452 dated October 1 9, 1 976, entitled "Liquid Applicator for Lithographic Systems".

Dampening fluid metering roller 94 dips into dampening fluid in dampening fluid pan 95 and carries dampening fluid to the dampening fluid metering nip 96 where a film of dampening fluid is formed onto the surface of hydrophilic transfer roller 94. The metered film of dampening fluid on hydrophilic roller 94 is transferred at dampening fluid transfer nip 98 to the ink coated surface of resilient transfer roller 70. The rate at which dampening fluid is applied to the surface of form roller 70 is controlled by the surface speed of transfer roller 94.

A third material conditioning roller 76 is positioned after the inker 80 and the dampener 90 and is urged into pressure indented relation with the surface of form roller 70. Roller 76 rotates at substantially the same surface speed as form roller 70 and conditions the layer of ink and dampening fluid on form roller 70 to make it receptive to plate on cylinder 40 at nip 89.

Ink and dampening fluid are applied to form roller 70' for application to the printing plate on plate cylinder 40' in the same manner. Like parts of the inker 80' aiid the dampener 90' are designated by primed reference numerals.

Referring to Fig. 4 of the drawing, it will be noted that form roller 70 and form roller 70' have journals extending outwardly from opposite ends thereof which are rotatably secured in bearing 100 and 102, respectively. Bearing 100 and 102 are mounted in inker sideframes 108 and 110 which are pivotally mounted to the conversion module sideframes 52 and 53 by pins 111.

Surfaces of form roller 70 and plate cylinder 40 can be separated by actuation of a throw-off cylinder 1 54 connected between frame member 52 and 108 and between members 53 and 110, respectively.

On the operator side of the printing press, a stub shaft 11 2 is secured to the inker sideframe 108 and supports an idler gear 114 in meshing relation with gear 38 and gear 11 5 on form roller 70.

From the foregoing, it should be readily apparent that impression cylinder 20, blanket cylinder 30, plate cylinder 40 and form roller 70 are driven by power delivered from the press drive shaft drivingly connected to gears 18 as illustrated in Figs. 1, 3 and 4 of the drawings.

It should be appreciated that the inking and dampening systems which apply ink and dampening fluid to form roller 70 mounted on frame members 108 and 110 for applying ink and dampening fluid at nip 89 to plate cylinder 40 permits movement of form roller 70 relative to plate cylinder 40 for throwing the printing press on-impression and off-impression without disturbing the position of plate cylinders 40 and 40'. Further, plate cylinder 40 can be thrown-off of blanket cylinder 30 without disturbing nip 89 between the form roller 70 and plate cylinder 40.

The method of converting an existing newspaper printing press which prints directly from a plate cylinder to a web to form an offset printing press which prints from a plate cylinder onto a blanket cylinder which offsets the printed image to a web accomplishes the objects of the invention hereinbefore discussed.

It should be understood that other and further embodiments of the invention may be devised without departing from the basic concept thereof.

Claims (9)

Claims

1. A method of converting an existing newspaper printing press, which prints directly from a plate cylinder to a web of paper to form an offset printing press which prints from a plate cylinder onto a blanket cylinder which offsets the printed image to a web of paper, the improvement comprising the steps of: attaching offset blankets to the existing printing cylinders to convert the printing cylinders to blanket cylinders; removing the existing inker; pivotally securing a module to existing press sideframes, the module including a plate cylinder and an inker; and drivingly connecting the existing press drive to the plate cylinder.

2. The method of Claim 1 wherein the step of drivingly connecting the existing press drive to the plate cylinder comprises: securing a module drive gear to an existing inker drive shaft; and drivingly connecting the plate cylinder and the inker to the module drive gear.

3. An offset newspaper printing press having a web of paper routed between an impression cylinder and a blanket cylinder supported between press sideframes; a plate cylinder engaging the blanket cylinder such that an inked image from a printing plate is offset by the blanket cylinder to the web of paper, the improvement comprising: a pair of support members; means pivotally securing one of said support members to each press sideframe; means rotatably securing opposite ends of the plate cylinder to said support members; means to move said support members between a first position wherein the surface of the printing plate engages the blanket cylinder and a second position wherein surface of the printing plate and the blanket cylinder are separated; a pair of inker sideframes; means rotatably securing said inker sideframes to said support members; a form roller rotatably supported by said inker sideframes; means to move said inker sideframes between a first position wherein said form roller engages the surface of the printing plate and a second position wherein surfaces of the form roller and the printing plate are separated; an ink transfer roller; means supporting said ink transfer roller in pressure indented relation with said form roller; and means forming a film of ink on said ink transfer roller.

4. The offset newspaper printing press of Claim 3 said support members comprising: a pair of frame members, said plate cylinder having opposite ends rotatably supported by said frame members.

5. A printing press according to claim 3 or claim 4, said inker comprising: an ink metering means; an inker transfer roller having an ink receptive surface; a form roller engaging the printing plate, said form roller having an ink receptive surface urged into pressure relation with said ink transfer roller to form an ink transfer nip; means supporting said ink metering means and said ink transfer roller in pressure relationship to form an ink metering nip between adjacent surfaces of the ink metering means and the ink transfer roller; speed control means secured to control the surface speed of said ink transfer roller relative to the surface speed of said form roller to maintain the surface speed of the transfer roller less than the surface speed of said form roller; means to supply an excess of ink to said ink metering nip to replenish ink on the surface of the ink transfer roller which is moving from the ink transfer nip to said ink metering nip.

6. A printing press according to claim 5, with the addition of: an ink storage oscillator roller supported in rotative contact with the surface of a film of ink on the form roller surface which has just moved from the printing plate to remove excess ink from portions of the surface of the form roller and to add the ink to depleted areas on the surface of the form roller which is moving toward said ink transfer nip.

7. A printing press according to claim 5 or claim 6, said speed control means comprising: brake means associated with said transfer roller to maintain the surface speed of the transfer roller less than 50% of the surface speed of the form roller.

8. A printing press according to any one of claims 5 to 7, said means to supply ink to said metering nip comprising: a reservoir of low viscosity letterpress, newsprint type ink.

9. A method of converting an existing newspaper printing press to form an offset printing press substantially as hereinbefore described with reference to and as shown in the accompanying drawings.

1 0. A printing press substantially as hereinbefore described with reference to and as shown in the accompanying drawings.