GB2143474A - Printing machine - Google Patents

Abstract

A printing machine (50) having a plate cylinder (52), a contact cylinder (54) e.g. of metal and an inking drum (72) in rotating engagement is disclosed. Circumferential bearer surfaces (120, 124, 126) may be provided respectively on each end of the plate cylinder (52), the contact cylinder (54) and the drum (72) to reduce the load on the drive for the printing machine and the transmission system utilised for rotation of the plate cylinder (52), contact cylinder (54) and anilox drum (72). A gear motor (100) may be provided to continue rotation of the drum (72) when disengaged from the transmission system (74) for maintenance purposes. The machine may utilise the framework of a known rotary letterpress machine. <IMAGE>

Description

SPECIFICATION Printing machine The present invention relates generally to a web-ffed rotary letterpress machine and more particularly to a rotary letterpress machine which has been structurally modified so as to be able to produce high quality printing by various processes such as flexography, off set, rotogravure, etc.

The printing of newspapers is usually performed on web-fed rotary letterpress machines since such machines can print at very high speeds, are generally relatively easy to operate, and require minimal maintenance in comparison with other types of printing machines.

However, these machines are typically noisy, primarily due to the large number of gears required to drive the many rollers needed in these machines. In addition, these machines are dirty and create an unhealthy working environment due to the dissemination of ink from the surface of the rapidly rotating rollers.

Also, these machines cannot be used for the production of high quality printed material such as "glossy" magazines which require offset lithographic printing machines.

Because of the foregoing, it has become desirable to develop a relatively quiet and "clean" rotary letterpress machine which can produce high quality printing by various printing processes.

It is an object of the present invention to provide a high speed web-fed rotary letterpress machine which avoids or reduces to a substantial extent the disadvantages of such machines as used heretofore. It is also an object of the present invention to provide such a machine which will produce a printed product having the quality associated with offset lithographic machines but without the inherent cost penalties.

The invention provides a printing machine comprising a plate cylinder, a contact cylinder in operating engagement with said plate cylinder, a drum for the application of ink to said plate cylinder, said ink application drum being in operating engagement with said plate cylinder and being substantially oppositely disposed from said contact cylinder, and means for simultaneously rotating said plate cylinder, said contact cylinder and said ink application drum.

In this case the impression cylinder of the prior art rotary letterpress printing machine is replaced by a common contact cylinder which does not require the use of a blanket as does the prior art machine. The impression cylinder may be reused by substituting it for the plate cylinder so as to form a nip between itself and the common contact cylinder for the passage of the paper web therethrough. An anilox drum is provided adjacent to the plate cylinder and substantially oppositely disposed from the common contact cylinder so as to provide an even distribution of ink on the plate cylinder from an ink supply system.The anilox drum is driven by a toothed belt transmission system, however, inasmuch as bearer contact surfaces are provided on the ends of the plate cylinder, the common contact cylinder and the anilox drum, the load on the printing machine drive and transmission system is greatly reduced. Means are provided permitting the lowering of the anilox drum to allow for the clearing of a paper jam or the performance of maintenance. Drive means are also provided to ensure that the anilox drum continues to rotate, but at a slower rate, when in the lowered position so that inking of the anilox drum is maintained.

The invention will now be described with reference to the accompanying drawings in which: Figure 1 is a schematic drawing of a prior art rotary letterpress printing machine as viewed from the operating side of the machine, Figure 2 is a schematic drawing of a rotary letterpress printing machine incorporating the present invention and as viewed from the operating side of the machine.

Figure 3 is a schematic diagram of a rotary letterpress printing machine incorporating the present invention and as viewed from the press drive side of the machine, Figure 4 is a partial front view of a rotary letterpress printing machine incorporating the present invention and illustrating the machine drive mechanism located on the operating side of the machine, Figure 5 is a partial front view of a rotary letterpress printing machine incorporating the present invention and illustrating the machine drive mechanism located on the press drive side of the machine.

Referring now to the drawings, Figure 1 is a schematic drawing of a prior art rotary letterpress printing machine 10 suitable for the printing of newspapers at a rate of up to 60,000 newspapers per hour from rolls of newsprint paper delivered at up to 2000 ft./min. (610 metres/min.). The printing machine 10 is a double sided and each side has a plate cylinder 1 2 and an impression cylinder 14 mounted thereon. At the drive side of the machine 10, a motor (not shown) drives, through drive shafts 16,18 and bevel gears 20,22, 24 and 26 (all shown in dotted lines), the left hand plate cylinder 1 2 and the right hand impression cylinder 14.At the operating side of the machine 10, i.e. at the other end of the plate cylinders 1 2 and the impression cylinders 14, the left hand plate cylinder 1 2 and left hand impression cylinder 14 are connected together through gearing (not shown) so that the rotation of the driven left hand plate cylinder 1 2 in one direction causes the left hand impression cylinder 14 to rotate in the opposite direction. Similarly, the right hand impression cylinder 14 and the right hand plate cylinder 1 2 are connected together through gearing (not shown) so that the rotation of the driven right hand impression cylinder 14 causes the right hand plate cylinder 1 2 to rotate in the opposite direction.

An ink reservoir 28 having a fountain roller 30 immersed therein is provided at the base of each side of the machine 10. A blade 32 is positioned adjacent each fountain roller 30 to control the quantity of ink entrained in the roller 30. Ink is transferred by each fountain roller 30 from each reservoir 28 to an ink feed roller 34, a first transfer roller 36, an auxiliary drum 38, second transfer rollers 40, a main drum 42, and form rollers 44 to the respective plate cylinder 12. Distributor rollers 46 may be provided adjacent each auxiliary drum 38 and each main drum 42, if desired.

All of the foregoing rollers and drums associated with the ink supply system are driven from shafts 1 6 and 1 8 by appropriate gearing (not shown), and the purpose of these rollers and drums is to ensure that an even coating of ink, in terms of thickness and distribution, is transferred to each plate cylinder 1 2. For this purpose, the auxiliary drum 38 and the main drum 42 are reciprocated axially which requires additional drive means (not shown) to accomplish same.

The need to drive all of the foregoing rollers and drums contributes greatly to the power consumed by the machine 10 and to its noisy operation. Furthermore, the rotation of these rollers and drums causes the ink to enter the machine itself and into the surrounding atmosphere creating a dirty and unhealthy work environment. In addition, because of the inherent complexity of this machine 10, the replacement of any worn or damaged rollers or drums is a time consuming operation involving costly machine downtime.

Referring now to Figure 2, a schematic drawing of a rotary letterpress printing machine 50 embodying the present invention is illustrated. This machine 50 is similar to the previously discussed prior art printing machine 10 in that it can print newspapers at a rate in excess of 60,000 newspapers per hour and can be readily produced by converting such a prior art machine 10. If, however, the motor and/or the drive gearing of the machine 10 are changed, or an entirely new machine is built, faster operating speeds can be obtained.

Printing machine 50 is similar to the prior art rotary letterpress printing machine 10 in that it is double sided. Mounted on each side of the machine 50 is a plate cylinder 52 and a common contact cylinder 54, the latter cylinder replacing the impression cylinder 14 of machine 10. The drive of the foregoing cylinders is accomplished by means of a motor (not shown) which drives, through drive shafts 56, 58 and bevel gears 60, 62, 64 and 66 (all shown in dotted lines), the left hand plate cylinder 52 and the right common contact cylinder 54.At the opposite end of the left hand plate cylinder 52 and the left hand common contact cylinder 54, intermeshing drive gears 68, as shown in Fig. 4, are provided to operatively connect these cylinders so that the rotation of the driven left hand plate cylinder 52 in one direction causes rotation of the left hand common contact cylinder 54 in the opposite direction. Similarly, at the opposite end of the right hand common contact cylinder 54 and the right hand plate cylinder 52, intermeshing drive gears 68 are provided to operatively connect these cylinders so that the rotation of the driven right hand common contact cylinder 54 in one direction causes rotation of the right hand plate cylinder 52 in the opposite direction.

The common contact cylinders 54 are ground steel rollers having a chromium coating thereon, such a coating attracting the paper which is passed through the nip 70 between each contact cylinder 54 and its adjacent plate cylinder 52 during printing, but repelling the printing ink. Since the contact cylinders 54 have a rigid surface rather than the resilient surface of a blanket as on the impression cylinders 14 utilised for the prior art rotary letterpress printing machine 10, the machine 50 provides less resistance to the paper passing through the nip 70 than does the machine 10 which results in less linting of the paper in the region of the nip 70. Because of this, there is less damage to the paper and a cleaner and healthier working environment results.In addition, inasmuch as blankets are not required for the operation of the machine 50, blanket slots are not required in the contact cylinders 54, whereas such slots are required in the impression cylinders 14 of the prior art printing machine 10. The absence of such slots in the contact cylinders 54 also results in less resistance to the paper passing through the nip 70. And lastly, inasmuch as the machine 50 does not utilise blankets for the printing process, the problems of blanket wear and bedding-in do not exist with this machine.

The plate cylinders 52 are standard forgings and may be designed to suite the particular application. As such, these cylinders 52 may be produced by modifying the impression cylinders 14 of the prior art printing machine 10. In any event, the plate cylinders 52 are adapted to receive printing plates of polymeric material, the plates being secured to the cylinders 52 by any known means, but preferably by the magnetic snap-on and lock up method.

The central portion of each plate cylinder 52 is undercut to a depth of between 0.063 inch to 0.145 inch (1.6 to 3. 68mm) to provide for a cushion between the printing plate and the surface of the plate cylinder 52. By using the plate cylinders 52 and the contact cylinders 54 of the present invention, a high quality print can be achieved due to the smoother ink application from type to paper and the absence of resistance between the type and the blanket.

An engraved screen inking or anilox drum 72 is provided adjacent each plate cylinder 52 and is positioned so as to be substantially oppositely disposed from the contact cylinder 54 that is in driving engagement with the plate cylinder 52. The anilox drum 72 may be split axially into a plurality of sections to accommodate different newspaper widths and/or the production of newsprint in different colour. In the latter case, each axial section would be used for the production of a specific newsprint colour, however, the colour could be changed, if desired. Each anilox drum 72 is driven by a transmission system, shown generally by the numeral 74 in Fig. 4, which connects the anilox drum 72 with the drive gears 68 mounted on the ends of the plate cylinder 52 and the common contact cylinder 54.The transmission system 74 includes a gear 76 which is mounted adjacent to and inwardly of the drive gear 68 on the end of the plate cylinder 52. The gear 76 engages a mating gear 78 mounted on a shaft 80 attached to an upright frame member 82. A toothed sprocket 84 is mounted inwardly of the mating gear 78 on the shaft 80. A toothed belt 86 connects the toothed sprocket 84 with a similar toothed sprocket 88 mounted on a shaft 90 which passes through the upright frame member 82. Another toothed sprocket 92 is mounted on the opposite end of the shaft 90 and inwardly of the upright frame member 82. A toothed belt 94 connects the toothed sprocket 92 with a similar toothed sprocket 96 mounted on the end of the anilox drum 72.An air clutch 98 is mounted on the end of the shaft 90 outwardly of the toothed sprocket 88 and controls the operation of the transmission system 74 as will be hereinafter described.

At the opposite end of the anilox drum 72, i.e. at the press drive side of the machine 50, a gear motor 100 is provided with a toothed sprocket 102 on the output thereof. A toothed belt 104 connects the toothed sprocket 102 with a similar toothed sprocket 106 mounted on a shaft 108 which passes through an upright frame member 110. Another toothed sprocket 11 2 is mounted on the opposite end of the shaft 108 and inwardly of the upright frame member 11 0. A toothed belt 114 connects the toothed sprocket 11 2 with a similar toothed sprocket 11 6 mounted on the other end of the anilox drum 72. An air clutch 11 8 is mounted on the shaft 108 inwardly of the toothed sprocket 106 and controis the rotation of the anilox drum 72 as will now be described.It should be noted that although a toothed belt drive system has been illustrated for both the press drive side and the operating side of the machine, a gear drive system could also be utilised.

During normal operation, air clutch 98 is actuated whereas air clutch 11 8 is not actuated causing the anilox drum 72 to be driven by the transmission system 74 via gear 76, mating gear 78, sprocket 84, belt 86, sprocket 88, sprocket 92, belt 94, and sprocket 96. When it is desired to disengage the anilox drum 72 from the transmission system 74 so as to clear a paper jam, etc, air clutch 98 is deactuated which disconnects the transmission system 74 from the drum 72.

Deactuation of air clutch 98 causes the actuation of air clutch 118 and the slight lowering of the anilox drum 72 by hydraulic or pneumatic means (not shown). The lowering of the anilox drum 72 permits the removal of the paper jam or the performance of maintenance which may be required. By actuating the air clutch 118, the gear motor 100 can drive the anilox drum 72 via sprocket 102, belt 104, sprocket 106, sprocket 112, belt 114 and sprocket 11 6. In this manner, the gear motor 100 continues to drive the anilox drum 72, but at a slower rotational speed than the transmission system 74, so that correct inking of the anilox roller 72 is maintained and a line on the printed paper which would otherwise be produced if the anilox roller 72 stops rotating is avoided.With this approach and apparatus, changes of inks, papers printing material and the like can be made, as well as removal of paper jams, without impairing print quality.

To accurately position the printing plates on each plate cylinder 52 relative to its adjacent contact cylinder 54, each plate cylinder 52 has a raised circumferential section 1 20 (a bearer) at the end thereof. These raised circumferential sections 1 20 comprise relatively short end sections of the plate cylinder 52 and have a slightly larger diameter than the central region 1 22 of the plate cylinder to which the printing plates are attached. The radial height of these raised circumferential sections 120 is approximately 0.015 inch (380,u) resulting in an approximately 0.010 inch (254,u) impression in the paper passing through the nip 70.These raised circumferential sections 1 20 (bearers) contact complementary circumferential bearer surfaces 124,126 provided on the ends of the contact cylinder 54 and the anilox drum 72, respectively. In this manner, the bearers provide a constant true contact surface between the plate cylinder 52 and the contact cylinder 54 and between the plate cylinder 52 and the anilox drum 72. Because of this, the bearers assist in the driving of the plate cylinders 52, contact cylinders 54, and anilox drums 72, and greatly decrease the load on the main drive system and the transmission system 74.

In addition, the use of these bearers accurately defines and maintains the width of the nip 70 and the impression of the paper web, and accurately positions the engraved screen surface of the anilox drum 72 relative to the printing plates so as to provide the controlled transfer of ink from the anilox drum 72 to the printing plates. And lastly, inasmuch as the diameters of the plate cylinders 52, contact cylinders 54 and anilox drums 72 are equal, the bearers ensure the correct registration of the print image for each revolution of these components. Thus, print quality is greatly improved by this machine 50.

Referring again to Figures 2 and 3, an ink supply system shown generally by the numeral 128, is provided for each side of the machine 50. The ink supply system 1 28 is comprised of an ink reservoir 130, a variable flow pump 132 mounted adjacent the ink reservoir 130, an ink application bridge 1 34 mounted adjacent the anilox drum 72, and a recovery tank 1 36. An ink supply line 1 38 is provided between the output of the variable flow pump 1 32 and the ink application bridge 1 34 and an ink return line 140 connects the recovery tank 1 36 to the ink reservoir 1 30.

The foregoing ink supply system 1 28 provides a controlled continuous supply of ink from the reservoir 1 30 to the anilox drum 72. Either oil-based or water-based inks can be used by the machine 50.

It should be noted that the paper web could also be inserted between the plate cylinder 52 and the anilox drum 72 rather than between the plate cylinder 52 and the contact cylinder 54. In addition, facilities may be provided on the machine 50 to reverse the direction of rotation of the plate cylinders 52, the contact cylinders 54, and the anilox drums 72 for add-on colour humps, double humps, halfdecks or back-up half-decks.

The printing machine of the present invention provides many advantages over the prior art printing machines. In addition to the advantages previously referred to, the weight of the resulting machine is considerably less, by up to 5000 Ib. (2268 Kg) than the weight of the prior art printing machine 10. In addition, there are no set-off printing problems and colour pagination is simplified, i.e., any page or pages of the newspaper can be readily produced in colour. Waste of paper and ink is reduced to less than 1%. Also, the power consumption of the machine 50 is reduced by up to 10% due to the absence of gear drives to the ink system and the elimination of an oscillating drive to the auxiliary drum 38 and the main drum 42 of the prior art machine 10. For the same reason, the noise level of the machine 50 is significantly less than that of the prior art printing machine 10, and oil leaks and mist are greatly reduced. Furthermore, due to the absence of blanket slots in the contact cylinders 52, an extra two lines of printing per page of newspaper can be obtained. And lastly, existing web-fed rotary letterpress machines can be readily converted to the printing machine of the present invention and, after conversion, the components thereof, e.g. plate cylinder 52, contact cylinder 54 and/or anilox drum 72 can be easily replaced, if required.

Claims (14)

1. A printing machine comprising a plate cylinder, a contact cylinder in operating engagement with said plate cylinder, a drum for the application of ink to said plate cylinder, said ink application drum being in operating engagement with said plate cylinder and being substantially oppositely disposed from said contact cylinder, and means for simultaneously rotating said plate cylinder, said contact cylinder and said ink application drum.

2. The printing machine as defined in claim 1 further including one or more circumferential surfaces on said plate cylinder, said one or more circumferential plate cylinder surfaces contacting said contact cylinder and said ink application drum to assist said rotating means in the rotation of said contact cylinder and said ink application drum.

3. The printing machine as defined in claim 2 wherein said one or more circumferential plate cylinder surfaces comprises two circumferential plate cylinder surfaces, one of said two circumferential plate cylinder surfaces being located adjacent one end of said plate cylinder and the other of said two circumferential plate cylinder surfaces being located adjacent the other end of said plate cylinder.

4. The printing machine as defined in claim 3 wherein said two circumferential plate cylinder surfaces are raised with respect to the central portion of said plate cylinder.

5. The printing machine as defined in any one of claims 2 to 4 further including one or more circumferential surfaces on said contact cylinder and on said ink application drum, said one or more circumferential contact cylinder surfaces and said one or more circumferential ink application drum surfaces contacting said one or more circumferential plate cylinder surfaces.

6. The printing machine as defined in claim 5 wherein said one or more circumferential contact cylinder surfaces comprises two circumferential contact cylinder surfaces, one of said two circumferential contact cylinder surfaces being located adjacent one end of said contact cylinder and the other of said two circumferential contact cylinder surfaces being located adjacent the other end of said contact cylinder.

7. The printing machine as defined in claim 6 wherein said one or more circumferential ink application drum surfaces comprises two circumferential ink application drum surfaces, one of said two circumferential ink application drum surfaces being located adjacent one end of said ink application drum and the other of said two circumferential ink application drum surfaces being located adjacent the other end of said ink application drum.

8. The printing machine as defined in any one of claims 1 to 7 wherein said rotating means comprises a plurality of gears operatively connected to said plate cylinder, said contact cylinder and said ink application drum, said plurality of gears being in intermeshing engagement.

9. The printing machine as defined in any one of claims 1 to 7 wherein said rotating means comprises one or more toothed belts operatively connected to said plate cylinder, said contact cylinder and said ink application drum.

10. The printing machine as defined in any one of claims 1 to 7 wherein said rotating means comprises a plurality of gears and one or more toothed belts operatively connected to said plate cylinder, said contact cylinder and said ink application drum, said plurality of gears being in intermeshing engagement.

11. The printing machine as defined in any one of claims 1 to 10 further including means for disengaging said ink application drum from operating engagement with said plate cylinder.

1 2. The printing machine as defined in claim 11 further including means for continuing rotation of said ink application drum when it is disengaged from operating engagement with said plate cylinder.

1 3. The printing machine as defined in any one of claims 1 to 1 2 wherein said ink application drum is comprised of one or more sections in axial alignment.

14. The printing machine as defined in any one of claims 1 to 1 3 further including an ink reservoir and means for supplying ink from said reservoir to said ink application drum.

1 5. A printing machine substantially as hereinbefore described with reference to and as illustrated in Figs. 2 to 5 of the accompanying drawings.