GB2024105A - Multicolour lithographic printing - Google Patents

Abstract

A multicolor lithographic cylinder proof press is characterized in that inking means 39, 40 and blanket cylinders 36, 37 are provided as arranged alternately in the carriage 35, and in that the interval between blanket cylinders is equal to the interval between printing plate beds 32, 33 which correspond thereto, and to the interval between inking means which correspond thereto, so that the blanket cylinders are all lowered together onto their printing plates, and so that blurring of the printed picture due to shocks caused by the raising and lowering of the blanket cylinders and/or inking means is effectively avoided. <IMAGE>

Description

SPECIFICATION A multicolor lithographic proof press This invention relates to a lithographic proof press, and more particularly relates to a multicolor lithographic proof press which performs at least two-color proof printing in one printing process.

Lithogaphic proof presses are known of the monochromatic type, in which printing of one color is performed in one printing process. In Fig. 1 is schematically shown such a monochromatic proof press. A printing plate bed 2 for mounting a printing plate, and a printing paper bed 3 for mounting a printing paper which is to be printed on, are mounted on a frame 1, and a carriage 4 is movably mounted to the frame in a manner to slide reciprocatingly to and fro in a horizontal direction over the printing paper bed and the printing plate bed, to the right and the left directions in Fig. 1. In the carriage 4 are mounted a blanket cylinder 5, water rollers 6, and inking rollers 7. On the frame 1 are mounted a damper 8 and a water distributing plate 9, on its one end, and an inking device 10 on its other end.

The water rollers 6 and the inking rollers 7 are mounted in the carriage 4 so as to be movable up and down, so that they are not brought into contact with the paper on the printing paper bed 3, when they are passed over it, by being lifted up at that time.

In order to perform proof printing by the proof press in Fig. 1, a lithographic printing plate is mounted on the printing plate bed 2, and a piece of printing paper is mounted on the printing paper bed 3. The carriage 4 is then reciprocated to and fro. Water and printing ink are applied from the damper 8 and the inking device 10 to the water rollers 6 and the inking rollers 10, respectively. The ink is applied from the inking rollers 7 to the printing plate on the printing plate bed 2, is transferred to the surface of the blanket cylinder 5, and is then printed onto the paper on the printing paper bed 3.

During this process, the up and down motions of the various rollers in the carriage 4 are controlled by well known systems of limit switches and the like, so as to produce the desired sequence of operations.

Such a proof press is very suitable for monochromatic printing. However, for multicolor printing, it is not convenient. As is well known, in multicolor printing, an original picture is separated to a plurality of color separation pictures; for example, into magenta, cyan, yellow, and black pictures. Color separation plates are prepared for each of these colors. Then a color reproduction plate is printed by printing from all of these color separation plates, with ink of the appropriate color, in superimposition. If this is done with a monochromatic press, such as the one illustrated in Fig. 1, this means several changes of color, which involves washings of the blanket cylinder, the inking rollers, and so forth. Alternatively, it has been practiced to provide a plurality of monochromatic proof presses, one for each color separation. This requires high cost and a lot of space.

Therefore, in order to avoid these disadvantages, a multicolor lithographic proof press has been already proposed, as shown in Fig.

2 in a rather diagrammatical form for the case of a two-color printing process. In this figure, first and second color printing plate beds 1 2 and 13, for mounting first and second color printing plates, are mounted on a frame 11, and a printing paper bed 1 4 is mounted on the frame 11 at the end of the row of printing plate beds. The carriage 1 5 is movably mounted to the frame 11 in a manner to slide reciprocatingly to and fro in a horizontal direction over the printing paper bed and the printing plate beds. In the carriage 1 5 are mounted a first and a second color blanket cylinder 1 6 and 1 7, a first and second set of water rollers 1 8 and 19, and a first and second set of color inking rollers 20 and 21.

All of these are mounted rotatably to the carriage 15 such a way that they may be raised and lowered therein to and away from the frame 11.

On the frame 11, at the printing paper end thereof, are disposed first and second color inking devices 22 and 23. Also, not shown in the figure, are provided first and second water providing means for damping the water rollers 18 and 19.

The arrangement of these cylinders is as shown in Fig. 2. It is readily appreciated that the overall length of this proof press is about twice as long as that of the monochromatic press of Fig. 1. Thus, the overall efficiency of utilization of space is about the same as if two individual monochromatic proof presses for the two colors were provided.

The operation of the press of Fig. 2 can be easily conceived. As the carriage 1 5 is reciprocated to and fro over the printing plate beds 1 2 and 1 3 and the printing paper bed 14, the rollers and blanket cylinders are moved up and down in the carriage so that the inking rollers are lowered towards one and only one of the printing plate beds each, but not towards the printing paper bed, and the blanket rollers are lowered each towards one and only one of the printing plate beds, and also towards the printing paper bed. Thus the printing plates are inked by the inking rollers with the individual correct colors of ink, and the blanket rollers each picks up an image from one of the printing plates in its correct color ink and transfers it to the printing paper.

Raising and lowering means mounted in the carriage raise and lower the inking rollers and blanket cylinders at the appropriate times.

With the arrangement of cylinders as shown in Fig. 2, which can of course be extended to the case of more than two colors, there is, as mentioned above, no advantage in space utilization over the use of several monochromatic presses. There is also another severe disadvantage. Because the blanket cylinders 1 6 and 1 7 are mounted rather close together, while one of them is rolling on its printing plate and picking up the image therefrom, the other is moved up or down in the carriage.

This causes a shock, which has a tendency to disturb the image which is being picked up.

This has been heretofore combatted by either making the entire frame 11 and carriage 1 5 of a very sturdy and heavy construction, or by moving the carriage 1 5 slowly; in either case, the problem has not been fully overcome, and this vibration shock has had the effect of reducing printing quality.

It is an object of the present invention to provide a multicolor lithographic proof press free from the abovementioned defects, which is compact, lightweight, and reliable.

According to the present invention there is provided a multicolor lithographic proof press, comprising a frame, a printing paper bed and a plurality of printing plate beds all mounted to the frame in a row, the printing paper bed being at one end of the row, a carriage which is movably mounted to the frame in a manner to slide reciprocatingly to and fro in a horizontal direction over the printing paper bed and the printing paper beds, the same number of blanket cylinders as printing plate beds, which are mounted in the carriage and are adapted to move up and down therein in such a way that, as the carriage is moved along the row of beds in the direction of the printing paper bed, each of them is lowered towards one and only one of the printing plate beds, and towards the printing paper bed, and the same number of means for inking the printing plate beds as printing plate beds, which are mounted in the carriage and are adapted to move up and down therein in such a way that, as the carriage is moved along the row of beds in the direction of the printing paper bed, each of them is lowered towards one and only one of the printing plate beds, but not towards the printing paper bed; characterized in that: in their order of mounting in the carriage, the blanket cylin- ders and the means for inking are arranged alternately, the blanket cylinder which is low ered towards each printing plate bed coming just after the means for inking which is low ered towards that printing plate bed, in the direction along the carriage from the printing paper bed along the row of printing plate beds; and that: the distances between the blanket cylinders are substantially the same as the distances between their respectively corre sponding printing plate beds towards which they are lowered, and the distances between the means for inking are substantially same as the distances between their respectively corresponding printing plate beds towards which they are lowered; and that: the blanket cylinders are all lowered towards their respectively corresponding printing plate beds at substantially the same time, as the carriage is moved along the row of beds towards the printing paper bed; and that: the means for inking are all lowered towards their respectively corresponding printing paper beds at substantially the same time, as the carriage is moved along the row of beds towards the printing paper bed.

In order that the present invention may be better understood, a preferred embodiment will now be described in detail, in connection with the appended drawings. It should be clearly understood, however, that the description of the embodiment, and the drawings, are given for the purposes of explanation and illustration only, and are not intended to be limitative of the scope of the present inven tion, which is to be defined solely by the appended claim.In the drawings: Figure 1 is a schematic view of a conven tional monochromatic lithographic proof press; Figure 2 is a similar view of a conventional two-color lithographic proof press; Figure 3 is a similar view of a two-color lithographic proof press according to the pre sent invention; Figure 4 is a diagram illustrating the up and down movements of the various rollers in the press of Fig. 3; and Figure 5 is a fragmentary longitudinal cross section of a lifting means for a blanket cylin der in the press of Fig. 3.

Referring to Fig. 3, there is shown a two color lithographic proof press according to the present invention, in which the arrangement of the blanket cylinders, and of the inking systems, is different from the conventional arrangement. On a frame 31 are provided a first color printing plate bed 32 and a second color printing plate bed 33. At the end of the row of these printing plate beds is provided a printing paper bed 34. The carriage 35 is movably mounted to the frame 31 and can reciprocate to and fro, sliding over the beds, in the same way as in the presses already described. First and second color blanket cyl inders 36 and 37 are mounted in the carriage 35, and also water rollers 38 and first and second sets of first and second color inking rollers 39 and 40 are mounted in the car riage, as shown in the figure. All of these are arranged to be movable up and down in the carriage 35, as hereinafter explained, so that the printing is performed properly, by the inking rollers being each set lowered towards one and only one of the printing plate beds, but not towards the printing paper bed, while the blanket cylinders are each lowered to wards one and only one of the printing plate beds, and also towards the printing paper bed, and the water rollers are lowered towards both of the printing plate beds, but not towards the printing paper bed.

On the left hand end of the frame 31 as seen in the figure are arranged a damper 41 for supplying water to the water rollers 38, and a water distributing plate 42. On the right hand end as seen in the figure are provided first and second color inking devices 43 and 44 for supplying ink to the inking roller sets 39 and 40, respectively.

Fig. 4 shows the raising and lowering sequences for the blanket cylinders and the inking and water rollers. Herein the areas designated as A, B, C, D, E, and F correspond to the areas designated similarly in Fig. 3.

This diagram corresponds to the raising and lowering sequence used during rightwards travel of the carriage 1 5. During leftwards travel of the carriage, the blanket cylinders are not lowered, but the inking and water rollers are controlled as per Fig. 4, also.

In Fig. 5 is shown a lifting means for the first color blanket cylinder 36, which is also applicable to the other blanket cylinder, and the rollers. The carriage 35 is provided with a pair of vertical slots in both its sides, in which a pair of bearings 45 are fitted, which are movable up and down, and which support the axial shaft of the first color blanket cylinder 36. A pair of air cylinders 46, each having a rod 47, are mounted to the carriage 35, and the rods 47 are coupled to the bearings 45.

By supply of air from an air compressor 47, via a solenoid distributing valve 48, the bearings 45 may be moved up and down. An on/off switch for moving the first color blanket sylinder 36 up and down is attached to the lower side end of the carriage 35, and contact members 51 of the desired number are mounted to the frame 31 so as to contact the switch 50. The solenoid distributing valve 48 is controlled by the output signals from the switch 50 via a relay circuit 52. By properly positioning the contact members 51, the blanket cylinder 36 may be adapted to move according to Fig. 4. Similarly, by provision of other contact members 51 in other lines, as shown by the two-dotted lines in Fig.

5, the other blanket cylinder, and the rollers, may also be controlled in their up and down motion, as per Fig. 4.

The blanket cylinders 36 and 37 are held in the up position on the return or leftwards stroke of the carriage 35 by their backlash, since they are driven by a wheel and a rack, not shown, mounted on the frame 31. They are raised at the instant when the carriage ceases to move rightwards and starts to move leftwards by inputting to the relay circuit 52 an ON signal which is output from a control circuit for the carriage drive motors (not shown) when the motor is reversely driven.

The distinguishing feature of this design of press is that the distance P1 between the blanket cylinders is the same, or substantially so, as the distance P2 between the corresponding printing plate beds towards which they are lowered, and, indeed, is also substantially the same as the distance between the last printing plate bed and the printing paper bed, as may be seen from Fig. 3. Further, the inking roller sets are each located just before its respective blanket cylinder, in the carriage, as opposed to the press of Fig. 2, in which they are all grouped together. Thus, in this design, the blanket cylinders and inking means are arranged alternately in the carriage.

Further, the blanket cylinders are all lowered towards their respective printing plate beds at substantially the same time, and hence the aforementioned problems with regard to shock are effectively avoided. Further, the inking means are also all substantially simultaneously lowered towards their respective printing plate beds. By this overall configuration, it is arranged that raising and lowering of none of the rollers or cylinders occurs when any image is being taken from a printing plate, or is being transferred to the printing paper, and hence smudging caused by shock cannot occur. Therefore, the present press can be constructed in a lighter fashion than can a press as in Fig. 2, and also it can be operated more quickly. Further, as will be seen, the press of Fig. 3 is shorter than the conventional one of Fig. 2. The press of Fig. 3 could be even further shortened, but it has been made as long as it is in the figure in order to facilitate setting and removal of the printing paper sheets.

Although the present invention has been shown and described with reference to a particular embodiment thereof, it should be understood that various changes to the form of any particular embodiment may be made by one skilled in the art, without departing from the scope of the invention. For instance, the invention is not restricted to a two-color press, but, according to the principles of the appended claim, could be applied to a press which printed three or more colors. Therefore, it is to be understood that the scope of the present invention is to be defined solely by the claim, which follows.

Claims (2)

1. A multicolor lithographic proof press, comprising: a frame; a printing paper bed and a plurality of printing plate beds all mounted to the frame in a row, the printing paper bed being at one end of the row; a carriage which is movably mounted to the frame in manner to slide reciprocatingly to and fro in a horizontal direction over the printing paper bed and the printing plate beds; the same number of blanket cylinders as printing plate beds, which are mounted in the carriage and are adapted to move up and down therein in such a way that, as the carriage is moved along the row of beds in the direction of the printing paper bed, each of them is lowered towards one and only one of the printing plate beds, and towards the printing paper bed;; and the same number of means for inking the printing plate beds as printing plate beds, which are mounted in the carriage and are adapted to move up and down therein in such a way that, as the carriage is moved along the row of beds in the direction of printing paper bed, each of them is lowered towards one and only one of the printing plate beds, but not towards the printing paper bed; characterized in that: in their order of mounting in the carriage, the blanket cylinders and the means for inking are arranged alternately, the blanket cylinder which is lowered towards each printing plate bed coming just after the means for inking which is lowered towards that printing plate bed, in the direction along the carriage from the printing paper bed along the row of printing plate beds; and that:: the distances between the blanket cylinders are substantially the same as the distances between their respectively corresponding printing plate beds towards which they are lowered, and the distances between the means for inking are substantially the same as the distances between their respectively corresponding printing plate beds towards which they are lowered; and that: the blanket cylinders are all lowered towards their respectively corresponding printing plate beds at substantially the same time, as the carriage is moved along the row of beds towards the printing paper bed; and that: the means for inking are all lowered towards their respectively corresponding printing plate beds at substantially the same time, as the carriage is moved along the row of beds towards the printing paper bed.

2. A multicolor lithographic proof press constructed, arranged and adapted to operate substantially as hereinbefore described with reference to Figs. 3-5 of the accompanying drawings.