GB1559998A - Letterpress and direct lithographic printing apparatus utilizing letterpress printing press - Google Patents

Description

(54) LETTERPRESS AND DIRECT LITHOGRAPHIC PRINTING APPARATUS UTILIZING LETTERPRESS PRINTING PRESS (71) We, TOKYO KIKAI SEISAKUSEIO, LID.. a Japanese Company, of 26-24 Shiba 5 chome, Minato-ku, Tokyo, Japan, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to improvements in and concerning the letterpress printing press.

More particularly, the present invention relates to a letterpress printing apparatus improved so that it functions alternatively as a letterpress printing press and direct lithographic printing press.

In letterpress printing the printing ink is caused to adhere to the raised surface of a printing plate whereas in planographic printing which uses a printing plate of even surface the printing ink is caused to adhere to grease-retaining areas and water to adhere to water-retaining areas respectively of the surface of the printing plate. Because of this great difference, it has heretofore been customary to carry out letterpress printing with a letter press printing press and planographic printing with a planographic printing press. The actual operation of letterpress printing on the letterpress printing press is preceded by a preparatory operation which comprises the steps of setting the type in accordance with a given manuscript for thereby producing a negative plate, pressing a paper mold against said negative plate, then making a stereotype by pressing a lead plate against said paper mold and mounting the stereotype as the printing plate in those tion on the plate cylinder in the press. Since letterpress printing calls for such complicated preparatory operations and consequently entails much time and labor before actual printing can be started, it inevitably suffers from a disadvantage that it cannot be used for the quick printing of news and other matter of similar nature. In contrast, planographic printing can be startedas soon as the printing plate is obtained simply by having a given manuscript printed in a negative pattern on the surface of a metal plate which is then set in position on the plate cylinder in the press. For the reasons given above, planographic printing proves lo be particularly desirable for the kind of printing which requires quickness of operation such as in news printing. Actually; however, newspapers are often printed by letterpress printing presses. For economic reasons, however, it is hardly practical to convert these letterpress printing presses into planographic printing presses.

An attempt has been made to accomplish planographic printing on a letterpress printing press which is modified by incorporation of a damping unit adapted so as to apply the water to the printing plate through the medium of an ink roller or ink cylinder. This attempt has failed to produce prints of sufficient clarity, because the water during the transfer mingles with and emulsifies the ink from said roller or cylinder and the resultant ink emulsion disadvantageously adheres to the surface of said plate cylinder. A measure for precluding said emulsification of the ink with the water by addition of an alcohol has been tried.

This method necessitates consumption of large volumes of alcohol and, therefore, proves to be uneconomical.

An object of the present invention is to provide a printing apparatus which permits direct lithographic printing to be carried out easily by use of a conventional letterpress printing press.

According to the present invention, there is provided a letterpress printing apparatus adaptable for direct lithographic printing; said apparatus comprising printing plates mounted in position on said press, said plate mounts serving either lithographic or letterpress plates, ink application means for applying the printing ink to the surfaces of said printing plates and damping units for use in lithographic printing disposed independently of said ink application means and adapted to apply water to said surfaces of the printing plafes, whereby the printing ink and water are separately transferred onto the surfaces of said printing plates and are thereafter transferred onto a web or a sheet.

Thus, the printing apparatus readily permits direct lithographic printing to be carried out by simply providing the conventional letterpress printing press with said damping unit. Further, with this apparatus letterpress printing can naturally be effected by stopp;ng the delivery of water and mounting letterpress printing plates on the plate cylinders. The sole requirement for the rollers serving to deliver water to the printing plates is that they be independent from the ink cylinders. These damping rollers are not limited with respect to their relative position in the press. Change of printing plates, therefore, is not inconvenienced on account of the provision of said damping rollers.

The other obiects and characteristics of the present invention will become apparent from the descriotion to be given in detail hereinbelow with reference to the accompanving drawings, in which: Figure I is a schematic side view illustrating one embodiment of the present invention wherein a roll paper tvpe letterpress printing press is provided with a damning unit.

Figure 2 is a partial sectional view illustrating one embodiment of the damning unit to be incorporated in a letterpress printing press for the purpose of the present invention.

Filre 3 is a partiallv sectional view illustrating another embodiment of the damping unit to be incorporated in a letternress printing press for the purpose of the present invention Figure 4 is a schematic side view illu strains one embodiment of the present invention wherein a sheet paper type letterpress printing press incorporating a damping unit.

Thiires 5 and 6 are each a schematic side view illustrating an embodiment of the damning unit incorporated in a flat base type letterpress printing press for the purpose of the nresent invention.

With reference to the accompanving drawings, Figure 1 shows a rotary printing press for newspapers as one preferred embodiment of the letterpress rotary printing press.

The operating principle of this press also applies to other letterpress rotary printing presses which are need for printing maa- zines and other similar forms of printed matter.

Two opposed impression cvlinders I are kent in rolling contact, as illustrated, with respective plate cylinders 2 each covered with a printing plate 3. The ink which has been kneaded between ink cylinders 5 and distributing cylinders 6 is transferred from a forme roller 4 onto the plate surface of the printing plate 3. Impressions are produced on both faces of a web 11 by causing said web 11 to pass successively through the rolling contact lines formed in the two pairs each of the impression cylinder 1 and the printing plate 3 of plate cylinder 2.

The present invention enables planographic printing to be obtained on a letterpress printing press by having damping units 9 disposed, one each, outside the plate cylinder 2 in the letterpress printing press as illustrated so as to provide water supply for the printing plate 3.

The damping unit 9 is only required to be of a type capable of delivering a controlled amount of water continuously to the printing plate 3. One example of a damping unit which satisfies the requirement is a roller type damping unit 9 which, as illustrated in Figure 2, has a plurality of water retaining blocks 13 of a flexible material arranged in the shape of spaced flaps around and fastened at 'the opposite end portions thereof onto a rotary shaft 12 so as to permit the medial portions of said blocks 13 to swell outwardly, with the lower part of the rotary shaft thereof immersed in a water trough 10. In this embodiment, said damping unit 9 is kept in rolling contact with a damping roller 8 via a metal roller 7. Since the swelled parts of said blocks readily deform when brought into contact with the metal roller 7, no excessive pressure is exerted on the metal roller or on the shaft 12 of the damping unit. Even if the roller portion of said damping unit and the metal roller 7 rotate at different peripheral speeds, there ensues no evolution of heat due to friction therebetween. The delivery of water, therefore, can be smoothly and safely effected by said metal roller 7 and damping roller 8.

Furthermore, the water-retaining blocks 13 extend in the axial direction and are usually divided lengthwise into four sections.

If a given web 11 for printing has a smaller width, then the blocks in those of said four sections which are not used may be constricted such as with a belt (not illustrated).

Consequently, the swelled portions of the blocks in the unused sections are drawn together and prevented from delivering water from the water trough, with the result that the feeding of water will be effected only in the remaining sections so as to cover only the width of the web in use.

The damping unit 9 may be of a construction which has, as illustrated in Figure 3, a layer of sponge 131 covering the surface of a rotary shaft 12 connected to a driving mechanism (not illustrated), with the lower portion of the rotary shaft 12 and the sponge layer 131 immersed in a water trough 10.

Similarly to the construction of Figure 2, the embodiment shown in Figure 3 is illustrated as having a freely detachable metal roller 7 interposed between the damping unit 9 and the damping roller 8. Besides the examples cited above, there may be incorporated a damping unit adapted so that water may be delivered in a controlled amount by means of brush roller or spray directly to the printing plate 3 or indirectly through ilie medium of a damping roller 8 or metal roller 7.

When planographic printing is started on a letterpress printing press incorporating a damping unit as described above, planographic printing plates 3 are set in position on the plate cylinders 2 in the press and water is applied by the damping roller 8 to the printing plate 3. Thereafter, the ink which has been kneaded between the ink cylinders 5 and the distributing cylinders 6 is further applied by the forme roller 4 to the printing nlate 3. On the printing plate 3, the ink is allowed to adhere to the areas having affinity for grease and the water to adhere to the areas having affinity for water and the ink deposited on the printed plate 3 is then transferred onto the web 11. Thus, direct lithographic printing proceeds smoothly. In this case, since the ink and water do not remain on the printing plates long enough to mingle with each other before they are transferred onto the surfaces of the web, planographic printing can be carried out as effectively on the letternress printing press as is possible on a planographic printing press. Ordinary letterpress printing can readily be carried out by first deactivating the damping rollers 8 bv some suitable means such as, for example, removal of the roller 7 or the roller 8 and mounting letterpress printing plates on the plate cylinders.

In conventional planographic printing, water is first applied to the printing plates and ink subsequently applied thereto. The embodiment just described also involves the same procedure of first applying water and subsequently applying the ink to the printing plates.

As the result of a further study, the inventor has made a discovery that planographic printing can be obtained as effectively by a procedure of applying water to the printing plate subsequent to the ink as by said procedure of applying water prior to the ink. (Refer to the damping units indicated in chain lines in Figure 1.) Generally the printing plate is coated in advance with a sllbstance comDosed mainly of gum arabic. When the printing is to be performed. the substance is removed from the printing plate for example by washing with water before the actual printing operation is started. When printing is effected by the procedure of applying water subsequent to the ink, however, this substance is left intact on the printing plate and the plate is mounted in position on the plate cylinder.

As printing is started, the ink first adheres to this substance on the printing plate. When the web comes into contact with the printing plate for the first impression, said substance is transferred in conjunction with the ink onto the web. After that, water is applied to the printing plate. From this point onward, therefore, the order of application of water and the ink is similar to that involved in the procedure of applying water prior to the ink.

Since the damping unit 9 is not limited with respect to its location in the press as described above, it can be disposed at any position insofar as it does not interfere with the attachment and detachment of printing plates to and from the plate cylinders. Use of the printing apparatus of this invention, therefore, serves the purpose of enhancing the efficiency of operation in the art of printing where rapidity of operation constitutes an indispensable requirement.

The preceding embodiment has been described as using a roll paper type letterpress printing press incorporating a damping unit.

Now, another embodiment using a sheet paper type letterpress printing press will be described with reference to Figure 4.

With reference to Figure 4, 1, 1 denote impression cylinders, 2, 2 plate cylinders for mounting printing plates 3, 3 thereon, 4, 4 forme rollers serving to transfer the printing ink from the ink cylinders 5, 5 to the printing plates 3, 3, and 6, 6 distributing rollers adapted to cooperate with the ink cylinders 5, 5 to impart a kneading motion to the ink.

These cylinders and rollers are held in rolling contact as illustrated to produce prints on both surfaces of the sheet 11. By 14 is denoted a device for preventing reverse transfer.

In the sheet paper type letterpress printing press having the construction as described above is comprised of two symmetrically arranged halves and for the sake of convenience in explanation, only one half will be described. A damping roller 8 associated with a damping unit 9 is located to contact the printing plate 3 of the plate cylinder at a point before the form rollers 4 relative to the direction of rotation of the plate cylinder 2. Said damping unit is similar to that used in the first embodiment.

A damping unit having a construction similar to that illustrated in Figure 2 or Figure 3 may be used.

In the letterpress printing press of the construction described above, desired planographic printing can be effected similarly to the first embodiment, by mounting planographic printing plates 3 on the plate cylinder 2, causing the ink kneaded by a plur ality of ink cylinders 5 and distributing cylinders 6, transferring kneaded ink to the printing plate 3 through a plurality of forme rollers 4 and thereafter delivering water by means of damping rollers 8, whereby prints will be obtained on both surfaces of a sheet 11 cut to prescribed dimensions.

In this embodiment, the damping unit and associated rollers 7 and 8 can, as shown in chain line in Figure 4, also be provided at a point following the forme rollers 4 to apply water to printing plate 3 after ink has been applied thereto.

Figures 5 and 6 represent embodiments in which planographic printing is effected by use of a flat base type letterpress printing press incorporating therein a damping unit.

In Figure 5, 1 denotes an impression cylinder and 21 a plate base for mounting a printing plate 31 thereon. Of the group of rollers disposed on the impression cylinder I side, those denoted by 4 are forme rollers adapted to transfer the ink from the ink cylinders 5 onto the printing plate 31 and that denoted by 6 is a distributing roller adopted to cooperate with the ink cylinders 5 to impart a kneading motion to the ink.

They are held in rolling contact as illustrated. 17 denotes an ink kneading base of which the surface is held in contact with a group of ink distributing rollers 6 in contact with an ink cylinder 5 to impart a kneading motion to the ink as illustrated.

15 and 16 are an ink delivery roller and an ink transfer roller respectively.

In the flat base type letterpress printing press having the construction as described above, the damping unit 9 is disposed above, and damping roller 8 is held in contact with, the printing plate 31.

Figure 6 represents another embodiment involving use of a flat base type letterpress printing press. In this press, 1 denotes an impressing cylinder, 21 a plate base for mounting a printing plate 31 thereon, 4 a forme roller adapted to transfer the ink from the ink cylinder 5 to the printing plate 31, 6 a distributing roller adapted to knead the ink in cooperation with the ink cylinder 5, 15 an ink delivery roller serving to extract the ink from the ink pan associated therewith and 16 an ink transfer roller. All these rollers are held in rolling contact as illustrated. In the one-face letterpress printing press having the construction as described above. a damping unit 9 is disposed at one end of the press and a damping roller 8 is held in contact with the printing plate 31.

The only requirement which the damping units 9 must fulfil is that it be capable of delivering a controlled amount of water to the printing plates 31. Typical examples of the damping unit 9 are found in Figure 2 and Figure 3.

The flat base type letterpress printing press illustrated in Figure 5 and Figure 6 are referred to as two-revolution presses.

One cycle of printing is effected when the impression cylinders 1 complete two revolutions. To be specific, the forme rollers 4 apply the ink to the printing plate 3 on the plate base 21 while said plate base moves in the direction of the arrow "A" during its reciprocating 'motion, prints are subsequently made on the web or sheet 11 when the impression cylinder 1 descends and comes into contact with the printing plate 31, and thereafter said impression cylinder 1 ascends and the printing is suspended while the plate base 21 returns in the direction of the arrow "B". The transfer of the ink is made from the forme rollers 4 to the printing plate 31 by the reciprocating motion of the plate base 21. In the case of the flat base type letterpress printing press illustrated in Figure 5, the ink transfer is effected from the ink kneading base 17 connected with said plate base 21 to the forme rollers 4 and no ink application to the plate base 21 is effected while the plate base 21 is in motion in the direction of the arrow "A".

In these embodiments, the ink is transferred in one direction from the ink cylinders 5 via the forme rollers 4 to the printing plate 31. In the other direction, water of a suitable volume is transferred from the damping unit 9 via the metal roller 7 and the damping roller 8 to the printing plate 31.

Consequently on the printing plate 31, water is uniformly dispersed on the ink and, in that state, used in the printing. The volume of water thus supplied to the printing plate 31 must be controlled within the range in which the water will not cause emulsion of the ink. For this reason, the water supply in damping unit must be suitably adjusted.

The damping unit 9 illustrated in Figure 2 is so adapted that the volume of water transferred to the metal roller 7 is regulated by changing the speed of rotation of the driving motor (not illustrated}.

Desired planographic printing is effected as described above. When letterpress printing is desired to be made with this apparatus, it can be obtained simply by stopping the delivery of water from the damping unit. The ceasation of the water delivery can be accomplished by discontinuing the water delivering action of a brush roller or spray. If the damping unit 9 includes a freely detachable metal roller 7, then the delivery of water can be stopped by removing said metal roller 7 and thereby releasing the damping roller 8 from rolling contact. With the delivery of water thus suspended completely, desired letterpress printing can be performed with the printing apparatus. In this case, letterpress print ing plates must be mounted on the plate cylinders as a matter of course.

In the flat base type letterpress printing press as described hereinbefore, the damping unit 9 is disposed so that the forme rollers 4 are positioned between the damping unit 9 and the impression cylinder 1.

However, it may be disposed between the impression cylinder 1 and the forme rollers 4.

As is plain from the foregoing description, the present invention enables direct lithographic printing to be carried out easily on a letterpress printing press by having said letterpress printing press provided additionally with a damping unit so adapted as to provide delivery of a suitable amount of water to the plane surfaces of offset printing plates mounted in position on the plate cylinders in said press. When necessary, the planographic printing can immediately be switched to letterpress printing by stopping the delivery of water and mounting letterpress printing plates on the plate cylinders instead of said planographic printing plates.

Thus, the present invention has made it possible to convert a conventional letterpress printing press into a combination letterpress and direct lithographic printing apparatus.

Any letterpress printing press can be converted into such a combination printing apparatus merely by replacing letterpress printing plates with planographic printing plates and incorporating into the press a damping unit. The present apparatus, therefore, proves to be extremely advantageous from the economic point of view, for it obviates the necessity for purchasing a separate planographic printing press.

Furthermore, the present invention is not affected in practice by the sequence in which the application of water and that of the ink to the printing plates take place. Thus, the damping unit can be disposed at a desired position in the letterpress printing press where it does not interfere with changing the plates.

WHAT WE CLAIM IS:- 1. A letterpress printing apparatus adaptable for direct lithographic printing said apparatus comprising printing plates mounted in position on said press, said plate mounts serving either lithographic or letterpress plates, ink application means for applying the printing ink to the surfaces of said printing plates and damping units for use in lithographic printing disposed independently of said ink application means and adapted to apply water to said surfaces of the printing plates, whereby the printing ink and water are separately transferred onto the surfaces of said printing plates and are thereafter transferred onto a web or a sheet.

2. A printing apparatus as claimed in claim 1, wherein the damping units apply water to the surfaces of printing plates after the ink application means has applied the printing ink to said surfaces of the printing plates, and the printing ink and water are thereafter transferred onto the web or the sheet.

3. A printing apparatus as claimed in claim 1, wherein the ink application means applies the printing ink to the surfaces of printing plates after the damping unit has applied water to said surfaces of the printing plates, and the printing ink and water are thereafter transferred onto the web or the sheet.

4. A printing apparatus as claimed in any one of claims 1 to 3, wherein the damping unit comprises a water pan and a roller formed by attaching a water-retaining material attached to a rotary shaft and disposed so that the lower portion thereof is immersed in the water held in said water pan, whereby the water in the water pan is delivered to the printing plates via said roller and a damping roller.

5. A printing apparatus as claimed in any one of claims 1 to 3, wherein the damping units comprises a water pan and a flapped roller formed by having a plurality of water-retaining bars of a flexible material arranged in the shape of spaced flaps and fastened at opposite ends thereof to a rotary shaft so as to permit the medial portions of said bars to swell outward, with said roller disposed so that the lower portion thereof is immersed in the water held in said water pan, whereby the water in the water pan is delivered to the printing plates via said flapped roller and a damping roller.

6. A printing apparatus as claimed in any of the preceding claims, wherein said damping roller is freely detachably supported in position.

7. A printing apparatus substantially as herein described with reference to the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (7)

**WARNING** start of CLMS field may overlap end of DESC **. ing plates must be mounted on the plate cylinders as a matter of course. In the flat base type letterpress printing press as described hereinbefore, the damping unit 9 is disposed so that the forme rollers 4 are positioned between the damping unit 9 and the impression cylinder 1. However, it may be disposed between the impression cylinder 1 and the forme rollers 4. As is plain from the foregoing description, the present invention enables direct lithographic printing to be carried out easily on a letterpress printing press by having said letterpress printing press provided additionally with a damping unit so adapted as to provide delivery of a suitable amount of water to the plane surfaces of offset printing plates mounted in position on the plate cylinders in said press. When necessary, the planographic printing can immediately be switched to letterpress printing by stopping the delivery of water and mounting letterpress printing plates on the plate cylinders instead of said planographic printing plates. Thus, the present invention has made it possible to convert a conventional letterpress printing press into a combination letterpress and direct lithographic printing apparatus. Any letterpress printing press can be converted into such a combination printing apparatus merely by replacing letterpress printing plates with planographic printing plates and incorporating into the press a damping unit. The present apparatus, therefore, proves to be extremely advantageous from the economic point of view, for it obviates the necessity for purchasing a separate planographic printing press. Furthermore, the present invention is not affected in practice by the sequence in which the application of water and that of the ink to the printing plates take place. Thus, the damping unit can be disposed at a desired position in the letterpress printing press where it does not interfere with changing the plates. WHAT WE CLAIM IS:-

1. A letterpress printing apparatus adaptable for direct lithographic printing said apparatus comprising printing plates mounted in position on said press, said plate mounts serving either lithographic or letterpress plates, ink application means for applying the printing ink to the surfaces of said printing plates and damping units for use in lithographic printing disposed independently of said ink application means and adapted to apply water to said surfaces of the printing plates, whereby the printing ink and water are separately transferred onto the surfaces of said printing plates and are thereafter transferred onto a web or a sheet.

2. A printing apparatus as claimed in claim 1, wherein the damping units apply water to the surfaces of printing plates after the ink application means has applied the printing ink to said surfaces of the printing plates, and the printing ink and water are thereafter transferred onto the web or the sheet.

3. A printing apparatus as claimed in claim 1, wherein the ink application means applies the printing ink to the surfaces of printing plates after the damping unit has applied water to said surfaces of the printing plates, and the printing ink and water are thereafter transferred onto the web or the sheet.

4. A printing apparatus as claimed in any one of claims 1 to 3, wherein the damping unit comprises a water pan and a roller formed by attaching a water-retaining material attached to a rotary shaft and disposed so that the lower portion thereof is immersed in the water held in said water pan, whereby the water in the water pan is delivered to the printing plates via said roller and a damping roller.

5. A printing apparatus as claimed in any one of claims 1 to 3, wherein the damping units comprises a water pan and a flapped roller formed by having a plurality of water-retaining bars of a flexible material arranged in the shape of spaced flaps and fastened at opposite ends thereof to a rotary shaft so as to permit the medial portions of said bars to swell outward, with said roller disposed so that the lower portion thereof is immersed in the water held in said water pan, whereby the water in the water pan is delivered to the printing plates via said flapped roller and a damping roller.

6. A printing apparatus as claimed in any of the preceding claims, wherein said damping roller is freely detachably supported in position.

7. A printing apparatus substantially as herein described with reference to the accompanying drawings.