Rotary lithographic printing press with ink and dampening fluid separator

Abstract

The rotary printing device for relief or offset printing a moving web comprises cylinders free of rotational imbalance, thin printing form means directly carried by the smooth, uninterrupted surface of the printing form cylinder, an inking roller in engagement with the printing form cylinder, supply means to meter an ink film of uniform thickness to the inking roller, and scrapping off means to remove the ink not taken away from the inking roller by the image areas of the printing form means. The cylinders are interchangeable for changing the format of the matter to be printed.

Parent Case Text

This application is a continuation-in-part of application Ser. No. 739,843, filed June 25, 1968, now abandoned.

Description

BACKGROUND OF THE INVENTION

The invention relates to a rotary printing devices for printing a moving paper web, comprising printing forms, the image areas of which lie in a plane above the plane of the non-image areas or in the same plane as the non-image areas. It is understood that ink is applied to the outer peripheral surface of the printing forms of both types of printing devices, one type designed for relief printing the other for lithographic offset printing.

The rotary relief printing devices nowadays in use commonly include printing form cylinders provided with grooves, in which other complicated printing plate holding means engage. The printing stereo plates have a considerable weight in the range of 12 - 17 kg while being 11 to 13 mm thick. When the printing form cylinder is rotated up to speeds of 667 rpm, considerable imbalances caused by the non-uniform distribution of the cylinder and plate masses with respect to the cylinder axis will lead to vibration of the cylinder and faulty printing therewith. Faulty printing may also occur when the stereo plates used are lifted from the cylinder surface as considerable centrifugal forces are acting on them. Some relief printing devices have pressure cylinders coated with a separate rubber blanket fastened in an axial groove in the surface, resulting in further imbalances and the necessity of the provision of equal diameters. The same hazards occur with rotary lithographic offset printing devices in which the offset printing form plates are fastened by clamping means to the printing form cylinder. As the rotary lithographic offset printing devices include transfer cylinders commonly covered with separate rubber blankets held in place by fastening means engaging in cylinder grooves, further running instabilities may be caused by the vibrations of the transfer cylinder caused by the imbalances during rotation. As the rubber blanket is fixed to the transfer cylinder in a tensioned state the Shore hardness of the blanket surface is not uniform along the entire periphery leading to different printing characteristics therealong. Similar difficulties arise from the pressure roller carrying a separate rubber blanket, too.

In the inking mechanism of the rotary relief and lithographic offset printing devices, the quantity of ink supplied to the printing form cylinder is metered by the changing of the width of the gap between a dipping roller dipping into the ink fountain and a flexible doctor, the inking roller being in contact with a dipping roller. The width of the gap is adjusted zonewise in an axial direction along the periphery of the co-operating roller by a plurality of adjustment screws as it is disclosed in the U.S. Pat. No. 3,037,451 to Davis. This is held to be necessary as the distribution of image and non image areas on the printing forms carried by the printing form cylinder is not uniform in axial direction along the cylindrical peripheral surface printing surface, because without adjustment considerable accumulation of ink would occur in the inking mechanism. By zonewise regulation the negative ink relief left on the surface of the inking cylinder after the contact of the image areas with the inking cylinder surface, is thus reduced in its mean thickness; the accumulation, however, is not avoided. Further the zonewise regulation leads to complicated inking devices and hinders automatic control of the printing process as a plurality of set screws have to be actuated to get a faultless printing. The distributing of ink will be more complicated, if for lithographic offset printing the inks of a high viscosity are used. Therefore in each inking mechanism a plurality of inking rollers and rubbing rollers leading to multiple ink splitting are included to provide an uniform ink film for the inking roller. Often the rubbing rollers are subjected to shifting movement along the direction of their axes additionally to their rotation to enhance the rubbing and the distributing of the pasty ink.

Other inking devices include dipping rollers in contact with wiper blades and being screened so that only the ink remaining in the screen portions is transferred to the next roller of the device, zonewise regulation is thus not avoided.

As the rotary lithographic offset printing devices include wetting or dampening devices known per se comprising a dampening roller co-operating with the surface of the printing form means carried by the printing form cylinder to cover the non-image areas with the liquid, the rotary offset printing devices show the very grieve disadvantage that part of the dampening fluid applied to the printing form to repel the ink is transferred from the printing form cylinder to the one or more inking rollers in the contact with the printing form cylinder and back to the ink fountain.

During the run of the printing device the dampening fluid, for example water, leads to a "turning gray" of the ink, because the dampening fluid taken from the printing form non-image areas is rubbed and emulsified in the ink. Another expression to describe this phenomenon is to say "that the ink goes into water". Because of this emulsification it is impossible to run lithographic offset printing devices over along period of time without replacing the emulsified ink or refresh it by exchanging part of the ink and adding fresh ink.

Another disadvantage of the known rotary relief and offset printing devices resides in the fact that they are not designed for simply changing the format of the matter to be printed.

To change the printing format with rotary relief printing devices of the prior art both the printing form and the pressure cylinders have to be supported interchangeable because the diameters have to be of equal length to avoid that the fastening groove for fastening the rubber blanket might be opposed to the printing form.

According to the specified disadvantages of the commonly used rotary relief and lithographic offset printing devices the general aim of the present invention is to provide a printing device of the above identified type which is simple in construction and therefore easily and safely operable, for example in under developed countries.

Important objects of the invention are bringing about printing devices, in which less vibrations occur during the operation thereof; having simple inking mechanisms comprising only a few members, and interchangeable printing form cylinders and interchangeable transfer cylinders in the case of the rotary lithographic offset devices.

Still another important object is to provide printing devices, which allow the change of format and are nevertheless simple in construction. A further object is to prevent the ink from "turning gray", which is used in a rotary lithographic offset printing device.

A further object is to simplify preparation, application and removement of printing form means to the printing form cylinder.

SUMMARY OF THE INVENTION

In accordance with the invention, a rotary relief printing device for printing a moving web comprises, in combination, a frame, a printing form cylinder rotatably mounted upon said frame, said printing form cylinder having a smooth, uninterrupted peripheral cylindrical surface, thin relief printing form means directly carried by said printing form cylinder surface, said web engaging said printing form means, a pressure cylinder rotably mounted upon said frame adjacent said printing form cylinder and parallel thereto engaging said web in opposed relation with respect to engagement of said web and said printing form means, an inking roller rotably mounted upon said frame and engaging said printing form means, supply means for supplying an ink film of uniform thickness to said inking roller said ink having a low viscosity, and scrapping-off means engaging said inking roller and removing the ink not taken away from said inking roller by said printing form means.

A rotary lithographic offset printing device according to the invention comprises, in combination, a frame, a printing form cylinder rotably mounted upon said frame, said printing form cylinder having a smooth, uninterrupted peripheral cylindrical surface, thin offset printing means carried directly by said printing from cylinder surface, a transfer cylinder rotably mounted upon said adjacent frame said printing from cylinder and parallel thereto and having a closed rubber periphery engaging said printing form means, said web engaging said transfer cylinder periphery, a pressure cylinder rotably mounted upon said frame adjacent said transfer cylinder and parallel thereto engaging said web in opposed relation with respect to engagement of said web and said transfer cylinder, a dampening roller rotably mounted upon said frame dampening said printing form means with a dampening fluid, an inking roller rotably mounted upon said frame engaging said printing form means, supply means for supplying an ink film of uniform thickness to said inking roller, said ink having a low viscosity, and scrapping-off means engaging said inking roller and removing the ink not taken from said inking roller by the printing form means and the dampening liquid transferred from said printing form cylinder to said inking roller.

As with both printing devices according to the invention the causes of vibration are avoided by the use of smooth surfaced printing from cylinders and of thin printing form means, no faulty printing will occur in any of the devices as in the case of the rotary lithographic offset printing device the transfer cylinder is provided with a closed rubber cylindrical periphery, too. The printing speed may be increased.

For the printing form means light weight sensitized plates sensitive to actinic rays, i.e. to light or corpuscles as electrons, may be used. Such plates made of plastic material having 2 to 4 mm thickness are marketed under the protected trademarks DYCRIL, NYLONPRINT or KODAK-Relief. Other sensitized plates and materials therefor, which may be used with the invention, are disclosed in the U.S. Pat. Nos. 2,980,535 to Schroeter and 3,102,030 to H. Hoerner. The plates either comprise a support element and a layer of sensitized material or are entirely made of the sensitized material. Except the plastic plates thin sensitized metal plates made of copper, zinc, or other metals may be used. In the above mentioned patents several reproduction methods are disclosed to which the plates have to be subjected to achieve a hard printing surface layer either on the substrate or the sensitized material itself; after the printing image has been copied onto the sensitized surface layer by means of the actinic rays, and one of the photosetting devices known per se or a positive transparency. The photosetting devices allow the setting of 100 to 2,000 letters per second in comparison to a setting rate of 20 letters per second with the help of normal letter setting devices employing lead letters. The preparation time for ready to print printing form means is considerable reduced. Commonly the material is photo sensitive and exposed to light. Materials are known which need only to be exposed to provide offset printing forms as the wettability of the exposed areas differs from the non exposed areas. The non-image areas of relief printing plates of the above kind are much more shallower with respect to the image area level as it is to be observed with the normal stereo plates (0.25 mm in comparison to 0.9 to 1 mm). It is therefore of advantage that the printing device runs without heavy vibrations as otherwise the non-image areas would be moved too near towards the ink film offered on the surface of the inking roller. As the printing plates having hard surfaces are simply pasted on to the surface of the printing form cylinder without any particular fastening means, no imbalance leading to vibrations of considerable amplitude are generated. This bonding is not to be compared with the pasting of rubber printing plates onto the printing form cylinders of Anilin or Flexo printing devices, which are not subjected to any considerable pressure.

According to the invention the printing form cylinder bearing means and the frame are designed to allow for an easy removement of the printing form cylinders from the frame for pasting said plates onto said surface by means of an adhesive and for removing them by for example solving the bonding means used by hot water.

For the provision of the printing form means in another embodiment of the invention a layer of the sensitized material as classified above and eventually a supporting layer may be applied to the smooth uninterrupted surface of the printing form cylinder. The image to be printed is then copied from an image transparancy positive and the layer then subjected to a reproduction or preparation treatment similar to the operation from intaglio printing. With this invention a device is disclosed for spraying such a layer onto the smooth surface of the printing from cylinder. According to the invention an ink film of uniform thickness is metered to the inking roller for application of ink to the image areas of the printing form means used. If the sensitized layer is only used for the delimiting and covering of the particular areas of the printing form cylinder surface, the metallic surface of the cylinder will be envolved in forming the ready to print printing form. A rotogravure cylinder with a photosensitive layer is described in the U.S. Pat. No. 3,294,889 to Downie.

The ink to be used in the devices of the invention is of a low viscosity in comparison to the inks used up-to-know in relief and lithographic offset printing. The plurality of rubbing rollers and inking rollers is avoided. Proceeding from the point of view that every unit of image area only needs a certain quantity of ink regardless whether it is part of a larger image area or part of a raster point, according to the invention an ink film is metered to the printing form cylinder, the thickness of which is uniform along the entire length of the inking roller. The different embodiments of the supply means are designed to vary the thickness of that uniformly thick ink film supplied to the inking roller. The ink film is metered for example between a rigid doctor knife and a roller in contact with the inking roller or between a movable roller and the inking roller, the width of the gap respectively the nip being variable simultaneously along the entire length thereof.

To avoid accumulation of ink which is not taken from the inking roller surface by the image areas of the printing form means and which forms a negative ink relief on the inking roller surface, according to the invention scrapping-off means are provided which remove this negative ink relief from the ink roller thus avoiding the accumulation of ink in the ink supply mechanism. The scrapping-off means may comprise a wiper blade being movable towards or away from the surface of the inking roller on a squeezing roller co-operating with said inking roller to remove the ink relief therefrom. Although it is known to remove the ink from a rubbing roller in contact with the inking roller by a doctor, this is only done to prevent an accumulation of ink in case of rapture of paper and it does not avoid the zonewise regulation. As the run of the printing device is substantially free of vibrations, a wavy distribution of ink of the low viscosity on larger image areas to form ink films of non-uniform thickness is avoided. In the case of the rotary relief printing device the removed ink is directly transferred back to the ink fountain being part of the ink supply means, whereas the removed ink with the lithographic offset printing device according to the invention is let into a dampening liquid-ink separator, within which the dampening liquid admixed and emulsified in the scrapped-off ink is separated from the ink. The purified ink is let back into the ink fountain; thus, the characteristics of the ink are not any more altered by the admixture of water. For the separator several techniques may be employed.

One embodiment of the invention uses a vacuum separator, within which the ink and the fluid are separated because of their different evaporation characteristics, with another embodiment it is proposed to let the components separate by deposition. The separator is of considerable importance because the dampening fluid will easily emulsify with the ink of low viscosity. The ink allows the provision of a very simple inking mechanism without a plurality of rubbing and inking rollers; moreover such an ink will more easily dry after it has been applied to the web to be printed.

The rotary printing devices according to the invention are designed to allow for an easy removement of the printing form cylinder to remove the plates or the printing form layer and for a change of format of the matter to be printed. As the printing plates are pasted directly on to the surface of the printing form cylinder and as no conventional register sheets have to be used, the printing device may be operated with very short stopping times. With relief printing devices according to the invention only the printing form cylinder is interchangeable by a printing cylinder of a different diameter and the pressure cylinder is provided with a rubber coating and is movably arranged within the frame to get into operational contact with printing form cylinders of different diameters employed in the printing device.

With the rotary lithographic offset printing device the printing form cylinder and the transfer cylinder may be according to the invention interchangeable by another set of said cylinders, the diameters of the two cylinders being part of one set being equal. It may be of advantage to support the pressure roller for interchanging, too, as a constant contact line pressure between the transfer cylinder and the pressure cylinder is either achieved by providing a pressure cylinder having the same diameter as the transfer cylinder or by altering the forces acting on the pressure cylinder, the diameter of which is different from that the transfer cylinder. The interchangeability may be reached by slots provided in the frame and by spindle means connected to the bearing means of the pressure cylinder in case of the relief printing press.

In the case the rotary lithographic offset printing device or press, the interchangeability may be reached by slots and two spindle means connected to the bearing means of the transfer cylinder and to the bearing means of the pressure cylinder, respectively.

According to the invention the pressure applied to the pressure cylinder of the rotary relief printing device is applied by a steel roller in contact with said pressure roller, the diameter of which is smaller than that of the steel roller and which is covered with a closed rubber layer extending over its entire cylindrical periphery. Other objects and advantages will become apparent as the following description proceeds, taken with the accompanied drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross section of a printing form cylinder with a smooth uninterrupted surface,

FIG. 2 is a part cross section of a printing form cylinder according to FIG. 1 having a relief printing form plate pasted onto its surface,

FIG. 3 is a part cross section of a printing form cylinder according to FIG. 1 having a lithographic offset printing form layer applied to its surface,

FIG. 4 is a part cross section of an offset transfer cylinder with a smooth uninterrupted surface having a closed rubber layer applied thereto,

FIG. 5 is a side view of a device for applying layers of a material sensitive to actinic rays to the surface of a printing form cylinder according to FIG. 1,

FIG. 6 is a cross section along line VI--VI of FIG. 5,

FIG. 7 is a side elevation view of a rotary relief printing device according to the invention for the printing of a moving web,

FIG. 8 is a side elevational view of a first embodiment of the inking device according to the invention,

FIG. 9 is a side elevational view of a part of another embodiment of a rotary relief printing device with a second embodiment of the inking device according to the invention,

FIG. 10 is a cross section of an embodiment of an rotary relief printing device according to the invention like that of FIG. 9, the cross section plane being that plane defined by the line X--X in FIG. 9,

FIG. 11 is a schematic representation of an rotary lithographic offset printing device according to the invention for printing a moving web,

FIG. 12 is a side elevational view of a first embodiment of a rotary lithographic offset printing device according to the invention and similar to FIG. 11 with removable cylinders and with a third embodiment of the inking device,

FIG. 13 is a cross section of a third embodiment of the inking device along the line XIII--XIII of FIG. 12 with a partly schematic diagram of a first embodiment of a separator for the separation of ink and dampening fluid used in the lithographic offset printing process,

FIG. 14 is a schematic diagram of a second embodiment of the separator and

FIG. 15 is a side elevational view of a second embodiment of a rotary lithographic offset printing device according to the invention and similar to FIG. 11 with removable and interchangeable cylinders and with the third embodiment of the inking device.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The printing form cylinders 1 of both the rotary relief printing press and the lithographic offset printing press comprise each a cylindrical sleeve 2 having a smooth uninterrupted surface and shaft members 3a and 3b at the ends, respectively, to provide cylinders with uniform mass distribution with respect to the axis of rotation. It is understood that the important feature is the smooth surface of the cylinders and that the construction of the shaft members is no part of the invention.

Referring now to FIG. 2, a thin flexible printing form plate 4 for relief printing is directly pasted onto the surface of cylinder 1 by means of a layer 5 of an adhesive, which may be soluble in hot water for quick removement of the plate 4 after finishing the run of the printing press. The fresh printing plate includes a layer of a material sensitive to actinic rays, particularly to light rays and a support for the layer or is entirely made up of such a material. Such materials and the reproduction techniques to develop printing plates therefrom are well known in the art, for example as disclosed in the U.S. Pat. No. 2,980,535 to G. A. Schroeter and No. 3,102,030 to Hoerner.

Whereas in FIG. 2 a printing form plate for the relief printing process is shown, FIG. 3 refers to a printing form for the lithographic offset printing process in form of a layer 6 of a material sensitive to actinic rays, which has been applied in its unexposed state to the smooth surface of the cylinder 1. After the application the printing images are directly copied onto the layer surface. The layer is then treated as are described in the above mentioned U.S. Patents or in accordance with other known methods, if the exposure to said rays does not alter the dampening characteristics of the exposed layer areas itself to an extent being sufficient for lithographic offset printing. The portions 6a of the layer 6 are the ink accepting image areas and the portions 6b the dampening fluid accepting areas. It is understood that such layers directly applied may be used for the preparation of relief printing forms and that such plates may be used for the preparation of lithographic offset printing forms, if the proper materials for the sensitive layers and the eventual supports and reproduction technics are used. The main advantage is that the printing form cylinders have not to be provided with grooves for the engagement of plate fastening means for relative heavy plates as it is done commonly in prior art presses.

With a rotary offset printing press according to the invention the transfer cylinder 7 which is constructed like the printing form cylinder 1 is not provided with a separate rubber blanket, but has a rubber layer 8 of a uniform thickness vulcanized to its smooth surface thus avoiding imbalances caused by a non-uniform mass distribution and eliminating the fixing of the rubber blanket in a tensioned state, which leads to a non-uniform Shore hardness and non-uniform printing characteristics along the surface of the transfer cylinder.

By means of the device of FIG. 5 a layer 6 of sensitive material possibly underlaid by a supporting layer, (not shown) can be applied as disclosed in the above mentioned U.S. patent to Schroeder or in accordance with any other known equivalent method to the smooth surface of the printing form cylinder 1. The shaft members 3a and 3b are rotably supported in rests 9a and 9b of a frame 9. A pulley 10 is keyed to the shaft member 3b and driven by an electric motor 11 via a V-belt 12. In a spaced relation to the cylinder 1 a spindle 13 is rotably supported. The threaded spindle is turned by a reversible second electric motor 14 or may be rotated by means of a hand wheel (not shown). A spray gun 15 is carried by a supporting member 16 extending between brackets 17 and 18 and is movably connected to the spindle 13 for moving up and down in direction of the axis of the cylinder 1 depending on the direction of rotation of the second electric motor 14 as it is indicated by the arrows in FIG. 5. The spray gun is provided with a container 19 into which the material 20 to be sprayed onto the surface of the cylinder is filled. Via the combination of rotation of the cylinder 1 by the first electric motor 11 and of the linear movement of the spray gun 15 a layer of uniform thickness may be applied to the surface of the sleeve 2 (compare FIG. 6). If a support layer is to be sprayed first, the container 19 may be filled with the support layer material.

Referring to FIG. 7 a rotary relief printing device constructed according to the invention includes a supporting frame 21 in which with the shown embodiment two printing units 22 and 23 are arranged. The moving paper web 24 to be printed on both sides is drawn from a paper roll 25a supported together with second roll 25b in a paper roll carrier 25.

Each of the printing units 22 and 23 includes a printing form cylinder 26 having a smooth uninterrupted surface onto which a plurality of printing plates 27 is pasted after the plates have been prepared for the printing run. The printing form cylinders 26 and the plates 27 are similar to the printing cylinder 1 of FIG. 1 and the relief plates 4 of FIG. 2, respectively. The printing form cylinder of each printing unit cooperates with a pressure cylinder which comprises a smooth rubber surface layer 28 and the diameter of which is smaller than that of the printing form cylinder 26 to achieve a high contact pressure. By means of the pressure cylinder different printing pressures may be exerted on the paper web let through the nip between the printing form and pressure cylinders. As it is shown in phantom lines with unit 23 of FIG. 7 the pressure cylinder may be backed by a steel roller 30. The rubber surface layer of the pressure roller being movable supported in said frame is ground to a substantially cylindrical surface and has an uniform Shore hardness. The inking device of each printing unit includes an ink fountain 31 filled with an ink of a low viscosity. The viscosity of ink is rather low in comprison to the inks used up-to-now in rotary relief and lithographic offset printing devices. The viscosity is determined by the binding agents, the coloring agents and the substrates mixed to get the desired ink. The ink to be used with the invention may have a viscosity like or may be a usual newspaper printing ink or Anilin ink. Into the ink fountain 31 of the left inking device of FIG. 7 a dipping roller 32 dips. If the dipping roller is rotated the surface area leaving the ink draw ink out of the fountain. The quantity of ink drawn from the fountain is metered to a desired quantity by means of a rigid doctor-knife 33 which is described in more detail in FIG. 8.

The inking device further comprises an inking roller 34 which cooperates with the dipping roller 32 as well as with the printing form cylinder 26. A portion of the metered ink film on the surface of the dipping roller is transferred to the inking roller 34. As the inking roller cooperates with the printing form cylinder 26 the image areas of the printing plates 27 will take part of the ink from the inking roller 34 leaving a negative ink relief on the surface of the roller 34. This negative relief is taken from the roller by means of a scrapping-off device 36 including a wiper 35, whereby later on the inking rollers 34 contacts the dipping roller 32 with a surface area free of printing ink. The scrapped-off ink is let back to the ink fountain 31 by means of a pipe 37. The ink may be removed with an other embodiment by means of a squeezing roller in contact with the inking roller, and/or pour directly back into the ink fountain. After printing both sides of the paper web the latter is guided in a manner known per se to folders to be folded.

FIG. 8 shows the arrangement of the rigid doctorknife 33 and of the wiper 35 in more detail. The rigid knife 33 is carried by a supporting member 38, which is slidably arranged on a bracket 39 extending between the side stands on the frame and being fastened thereto. In the bracket 39 an adjustment screw 40 is provided the free end of which engages the supporting member 39 to move it towards the surface of the dipping roller 32 or away from it. The supporting member 38 is guided for movement exactly in parallel to the axis of the roller by means of guiding plates 41 which are stationarily arranged in the machine frame. By turning the adjustment screw the width of the gap between the free edge of the knife 33 and the surface of the dipping roller 32 is varied along the entire length of the gap simultaneously to the same extent, i.e. the width may be adjusted in its entirety.

The wiper 35 of the scrapping-off device 36 comprises the wiper blade 35a which contacts the surface of the inking roller 34 and a trough 35b, wherein the scrapped-off ink is gathered. The ends of the trough 35b are closed by plates 35c and 35d, which are for example welded to the wiper blade and to the trough. It may be possible that the wiper blade is made of a more resilient material like a hard rubber so that such welding is impossible. The wiper 35 is carried by a shaft 42 by means of two or more carrying arms 43 and 44, the shaft being rotably supported in a sub-assembly (not shown) of the frame of the device. A worm gear 45 is used to move the wiper 35. The worm gear 45 consists of a worm gear sector 45a keyed to the shaft 42 and a worm 45b keyed to a second shaft 46 rotably supported in two bearing blocks 47 and 48 fastened to the frame of the press by bolts 47a and 48a. After loosening the bolts 47a and 48a the wiper 35 may be pivoted away from the roller 34. A hand wheel 49 is fastened to the end of the shaft 46 extending in a direction substantially perpendicular to the axis of the shaft 42 for rotating the worm 45b. As the worm 45b rotates and is not axially displaced with respect to shaft 46 the shaft 42 is rotated and the wiper blade 35 is moved towards the surface of the inking roller 34 or away from it.

Whereas this arrangement is used in the printing mechanism 23 shown at the left of FIG. 7, the inking device of the printing mechanism 22 shown at the right uses a known screened dipping roller 32s for the transportion of the ink. As the ink from the screen pits of the screened roller is delivered to the inking roller 34 in droplet like quantities distributed along the periphery of the inking roller, a smoothening roller 50 has to be provided, which cooperates with the inking roller and smoothens the ink on the surface thereof to form an ink film of uniform thickness.

As with both printing mechanisms the trough 35b is connected to the pipe 37 and as the wiper is rotated with respect to the axis of shaft 42 the pipe 17 is made of a rigid portion 37a leading the ink back into the fountain and of a flexible portion 37b being connected to the trough 35b and the rigid portion 37a. Thus the wiper 35 may be pivoted out of engagement with the surface of the inking roller without moving the entire length of pipe 37.

The printing mechanism shown in FIG. 9 differs from the printing mechanisms of FIG. 7 in that the axes of the cylinders and rollers lie in a substantially horizontal plane, whereas the cylinders and rollers of the rotary relief printing press of FIG. 7 are arranged vertically one above the other. Further the inking roller 34 does not cooperate with a dipping roller, but with an auxiliary roller 51, and a scrapping-off device is not needed as will become clear from the following part of the description.

As the axes of the inking roller 34 and of the auxiliary roller 51 lie in a substantially horizontal plane a trough like space 52 having an approximately triangular cross section is defined between them, when they contact each other or are arranged slightly apart to form a nip or gap 53 therebetween below the space 52. The ink of low viscosity is filled into the trough 52 which is closed at its ends with plates not shown. To vary the width of the gap 53 between the rotably, but not movable supported inking roller 34 and the auxiliary roller 51, the shaft members 54a and 54b of the latter are in a manner known per se rotably supported in eccentric bearings 55 and 56, which themselves are rotably supported in the frame 1 of the printing press. The bearing members 55 and 56 are provided with worm gear sectors which engage worms 57 and 58. These worms are drivingly connected via bevel gears 59, 60, 61, and 62. Referring to FIG. 10, the bevel gears 59 and 60 are keyed to one of the shafts 63 and 64, respectively, which are rotably supported in the frame. To the other end of each of the shafts 63 and 64 the worms 57 respectively 58 are fastened. The bevel gears 61 and 62 are keyed to the ends of a third shaft 65 extending in parallel to the axis of the auxiliary roller 51 from one side stand of the frame to the other, and engage the bevel gears 59 and 60, respectively. With the embodiment shown in FIG. 10 an reversible electric motor 66 is drivingly connected to shaft 63 of worm 57. Depending on the direction of rotation of the electric motor 66 the width of the nip between the inking roller 34 and the auxiliary roller 51 is narrowed or broadened in its entirety thus adjusting the quantity of ink being drawn through the nip by the inking roller, because of the eccentricity of the bearing members with respect to the shaft members of the auxiliary roller being altered. The rotation of the shaft 63 may be achieved by a hand wheel, too. The ink of low viscosity is supplied to the trough 52 via a pipe 67 by means of a pump 68. The suction opening of the pump is arranged below the level of ink in the ink fountain 31. The pump 68 is driven by an electric motor 69 which is electrically connected by conductors 70 and 71 with a power supply 72 and by electric lines with end switches 73 and 74 of a level meter 75. The level meter 75 further includes an actuation 77 arm provided at its one end with a float 76 floating on the surface of the ink within the trough 51. The other end of the actuation arm 77 is rotably supported in a fixed bearing 78 and provided with an T-like actuation lug 77a. The ends of the T-beam may contact the switching elements 73a and 74a of the switches, respectively, depending on the quantity of ink in the trough. The end switches are electrically connected by electric lines 79 and 80 with the electric motor 69. The circuity is such that the motor will drive the pump, if the level is lowered below a given value and will stop driving, if the level reaches a given maximum value.

As part of the surface of the printing form cylinder 26 respectively the image areas thereof is in direct contact with the ink in the trough 52 and as because of this the negative relief is immediately filled by the ink in the fountain a scrapping-off device is not necessary; one may say that the auxiliary roller 51 fulfills the tasks of metering of an ink film of uniform thickness to the inking roller as well as scrapping-off the negative relief from the inking roller after the image areas of the printing plates 27 have taken ink from the surface of the roller.

With the embodiment shown in FIG. 9 the printing form cylinder 26 and the inking roller 34 have substantially the same diameters. The shaft members 81a and 81b of the printing form cylinder 26 are rotably supported in eccentric bearings 82 and 83 in the same manner like the auxiliary roller 51, only one shaft member 81a, one bearing 82, and one of the worms 84 and 85 being shown in FIG. 9. With this arrangement the nip between the inking roller 34 and the printing form cylinder 26 may be varied. The pressure cylinder 29 and the steel roller 30 co-operating therewith are supported in bearing plates 86 and 87 (only 86 shown) and are movable in the frame 21 in direction of the arrows shown in FIG. 9 and may be removed through the slot 88 in frame 21.

FIG. 11 is a schematic representation of a rotary lithographic offset printing press according to the invention. The printing press comprising a printing form cylinder 89, a transfer cylinder 90, and a pressure cylinder 91. Onto the smooth uninterrupted surface printing plates 4 are pasted or a printing form layer 6 is applied as is described in connection with FIGS. 1 to 3. As both means may be used with the invention in the following text the printing form will be generally referenced by the number 92. The transfer cylinder 90 has a smooth uninterrupted surface and has a rubber layer 93 vulcanized to that surface in the form of a closed cylindrical coating which may be ground after the vulcanizing to an exact cylindrical form and be provided with uniform Shore-hardness, while the pressure cylinder is of steel, has a smooth, uninterrupted cylindrical surface.

The printing form cylinder 89 co-operates in a manner known per se with an inking roller 34 and two dampening rollers 95 and 96 to apply dampening fluid to the non-image areas of the printing means 92 first and to apply then ink to the image areas. According to the invention, an ink of low viscosity is used here, too, and is applied to the inking roller respectively the printing form cylinder in form of a layer of uniform thickness. Exactly as it was described with the rotary relief printing press of FIG. 7 the uniform thickness may be reached by use of a rigid-doctor knife 33, when a dipping roller with a smooth surface is used, or by means of a doctor-knife and a smoothening roller 50, when a screened dipping roller is used. In FIG. 11, the latter embodiment is shown in dashed line. Further the uniform thickness of the ink film may be reached by varying the width of the nip between the inking roller 34 and the dipping roller 32, or the ink supply arrangement of FIG. 9 may be used with the offset device.

In the FIGS. 11 to 15 the same reference numbers are used for those parts which have already been described in connection with the rotary relief printing press, for the inking devices as well as for the scrapping-off devices. With respect to the scrapping-off devices the main difference is that the liquid scrapped off from the surface of the inking roller 34 is not let back directly into the ink fountain 31, but into a separator device 97 in which the ink is separated from the dampening fluid, the ink being let back into the ink fountain via a pipe 98 and the dampening liquid removed from the inking and scrapping-off system via a pipe 100.

FIG. 12 shows a side elevational view of a first embodiment according to FIG. 11. The three cylinders 89, 90 and 91 are removable from the side stands of the frame 1 of the press, when stopping members 101, 102 and 103 bolted to the frame are removed from the frame. One stopping member is shown lying on the shop floor. The printing form cylinder 89 may then be simply rolled out of the frame into the position given by the dotted lines in FIG. 12. While the cylinder 89 is lying on the supporting structure 104 the printing form 92 may be removed. For example the plates 4 may be removed by solving the bonding by use of hot water and replaced by new ones pasted to the desired areas of the cylinder surface, or the cylinder is lifted by overhead carrying means and transported to a device as described in FIGS. 5 and 6 for removing the old printing form layer, applying a new layer, exposing it to copy the new printing image and subjecting it to the appropriate reproduction technic. For the removement of the old layer grinding and honing apparatuses may be used or etching may be employed.

Whereas the inking roller 34 is rotably, but fixedly supported in the frame the dipping roller 32 is rotably supported in excentric bearings 105 and 106. As it is shown with bearing 105 each bearing is provided with a worm gear sector, which engages a worm 107 respectively 108. The worms 107 and 108 are drivingly connected as in the system of eccentric bearing shown in FIG. 10, the only difference being the movement by a hand wheel 109 for the sake of simplicity there are no reference numbers given for the driving members.

The dampening liquid is lifted from the dampening liquid fountain 110 and applied to the surface of the printing form cylinder 89 and by means of a train of three rollers 111, 112, and 113. The mixture of dampening liquid and ink which is scrapped-off from the surface of the inking roller 34 is let into a container 114 of a separating device 115.

Two embodiments of the separator are diagrammatically shown in the FIGS. 13 and 14.

With the embodiment of FIG. 13 a valve 116 is provided in the pipe 37 leading the liquid scrapped off the inking roller 34 into the container 114. The container is carried by a frame work 117, which is rotably supported by a post 118. At least one other container 114a is carried by the frame work. A piston-cylinder drive 119 is fastened to the free end of the post to carry a cover 120 adapted to close one of the containers 114 and 114a having the same opening size. The piston of the drive carries the cover by means of a bracket 121, one end of which slidably surrounds the post. Any other lifting and lowering construction or hand operation may be employed. The cover is provided with an opening 122 which is connected by means of a conduit to the entrance of a vacuum pump 123. The separator 115 may further include a pump 124 to pump the separated ink from one of the containers back to the ink fountain 31.

The separator works as follows: The ink-dampening liquid I and DF mixture is scrapped-off by the wiper blade 35a and let into the container 114 by the pipe 37. When the container is filled up to a given level the valve 116 is closed and the frame work rotated 180 degrees so that the containers 114 and 114a change places. Then the valve 116 is opened again. The amount of fluid gathered in the trough will be reduced to normal level and start filling up the container 114a. Then the piston-cylinder drive 119 is actuated to lower the cover 120 onto container 114. When the container is closed by the cover the pump 123 starts to work and produces a vacuum above the liquid mixture in the container which enhances the evaporation of the dampening fluid DF in the mixture. The separating time needed depends on the components of the mixture to be treated. Means for stirring the mixture may be provided on the inner side of cover 120 and the operation may be automatically controlled by level meters metering the level a scrapped-off mixture in the container and electric circuitry.

When the separation time has elapsed the cover is raised and the container 114 may be emptied into the ink fountain by hand or by means of the pump 124. In the pump circuit a known filter may be arranged to remove paper particles and other defilement from the ink let back to the fountain. As no dampening fluid reaches the ink fountain the prior art "turning gray" is avoided so that very long printing runs may be planned. When the container 114 is empty, the frame work is rotated moving container 114 back into its first position and 114a in the position beneath the cover.

If the arrangement is such that there is a plurality of containers 114 there may be no need of a vacuum pump, because the sedimentation of the heavier component of both the ink I and the dampening fluid will enable a sufficient separation of the mixture. In FIG. 14 the dampening fluid DF is the lighter component.

The second embodiment of a rotary lithographic offset printing device according to the invention and similar to the schematic diagram of FIG. 11 is a printing device for printed matters of different formats. In FIG. 15 the printing form cylinder 89 is removable and interchangeable through the slots 125 provided in the side stands of the frame 21 of the press. The transfer cylinder 90 is held in its position by bearing elements 126 which engage in slots 127 extending from the inner ends of the horizontal slots 125 and extending in a vertical direction. By means of couplings 128 the bearing elements are each connected to a threaded spindle 129. The spindle 129 passes through the threaded bore of a worm gear 130 which is rotably, but fixed supported on a bearing plate 131. The worm gear 130 meshes with a worm 132, which is keyed to a shaft 133 extending from side stand to side stand and drivingly connects the worms 132 of each lifting and lowering mechanism, when driven by an electric motor 134. These means are arranged on the outsides of the two side stands of the frame 21, respectively. It is understood that other driving connections may be provided. Like lifting and lowering mechanism are connected to the pressure cylinder bearings. The members of the pressure cylinder moving mechanism are arranged on the inside of the respective side stand of the frame 21 and their reference numbers are provided with an apostroph. No coupling has been provided between the spindles 129' of the mechanism and the bearing elements 126' as the pressure cylinder is a steel cylinder, which has not to be frequently removed out of the frame 21.

The change format the stopping members 135 in the slots 125 are removed and the printing form cylinder 89 is rolled out onto the frame work 104. Then a reversible electric motor 134 driving the shaft 133 is appropriately energized until the transfer cylinder 90 is lowered to the slots 125. Then the bearing members 126 and the spindles 129 are decoupled by for example removing bolts 136 connecting the halfes of the couplings. Then the transfer cylinder is rolled out of the frame onto the frame work 104. The rolled out cylinders are lifted and replaced by a set of cylinders of different diameter. Then first the new transfer cylinder is rolled into the slots 126 and coupled to the spindles 126 and lifted up in the vertical slots. Then the new printing form cylinder is rolled into the slots 125 and the stopping members 135 are placed into the frame. Then the new transfer cylinder is lowered into contact with the new printing form cylinder. To exert the proper pressure on paper web 24 passed between the transfer cylinder and the pressure cylinder 91, the latter is lowered into contact with the new transfer cylinder after having been lifted from the old transfer cylinder in the beginning of the interchange operation. The spindles 129' and the bearing members 126' may be, however, also connected by means of a quick to loose coupling, when the pressure cylinder is to be interchanged, too. Normally the different contact pressure between the interchanged transfer cylinder and the not interchanged pressure cylinder may be set to the desired value by means of the spindles 129'.

Although only interchangeability of the printing form and the transfer cylinder has been shown in FIG. 15, the invention also includes the interchangeability of the pressure cylinder.

When the diameter of the cylinders 89 and 90 have to be changed the dampening device 137 and the inking and the dipping roller with the respective fountains have to be arranged movably with respect to the frame to be lifted or lowered in contact with the printing form cylinders of different diameters. Since this can be readily accomplished by people having ordinary mechanical skill, a more detailed description is not considered necessary.

Although the interchangeability is only shown for a rotary lithographic offset printing device the same idea may be employed according with the cylinders of rotary relief printing devices constructed according to the invention.

The invention discloses a printing press which is very simple in its design and in which the features of smooth surfaced cylinders, thin and easy to prepare printing means, and the inking devices for the use of an ink of low viscosity and the interchangeability of the cylinders allow especially the use of such printing devices in under-developed countries with a low technical standard.

It will be apparent that other and further forms of the invention may be devised without department from the spirit and the scope of the appended claims.

Claims

What is claimed is:

1. A rotary lithographic offset printing device for printing a moving web, comprising, in combination, a frame, a printing form cylinder rotatably mounted upon said frame, said printing form cylinder having a smooth, uninterrupted peripheral cylindrical surface, thin offset printing form means carried directly by said printing form cylinder surface, a transfer cylinder rotatably mounted upon said frame adjacent said printing form cylinder and parallel thereto and having a closed cylindrical peripheral rubber surface engaging said printing form means, said web engaging said transfer cylinder periphery, a pressure cylinder rotatably mounted upon said frame adjacent said transfer cylinder and parallel thereto and engaging said web in opposed relation with respect to engagement of said web and transfer cylinder, a dampening roller rotatably mounted upon said frame for dampening said printing form means with a dampening fluid, an inking roller rotatably mounted upon said frame engaging said printing form means, an ink fountain, ink supply means for supplying an ink film of uniform thickness to said inking roller, scraping-off means engaging said inking roller and removing the ink not taken from said inking roller by the printing form means and the dampening liquid transferred from said printing form cylinder to said inking roller, an ink and dampening fluid separator communicating with said scraping-off means, and separated ink transfer means interconnecting said ink supply means and said separator, said ink supply means including an ink layer thickness adjusting member defining a border extending parallel to the axis of said inking roller, said border being adjustably displaceable as a whole parallel to itself.