A printing unit for a rotary printing press

Abstract: The different cylinders (1,3,6,7) of a printing unit in a rotary printing press are arranged in a vertical row under the impression cylinder (8) of the press and are rotatable in a frame (13) of the printing unit. Each cylinder is at each end rotatably journalled in a bearing housing (30,31), which is displaceable on a vertical bearing rail (39). A hydraulic cylinder (43) is arranged in the frame under the lowermost bearing housing in a stack thereof for lifting the bearing housings into engagement with each other or for lowering them.

Description: Technical Field The present invention relates to a rotary printing press, in which a web to be printed is arranged to be conducted via an impression cylinder, wherein cylinders, such as a screen cylinder, a form cylinder, a plate cylinder, and a rubber blanket cylinder, of a printing unit in the press being arranged in a vertical row under the impression cylinder. Background of the Invention In conventional rotary printing presses of the above kind, a typical example being shown in GB-A-1 212 801, the printing units are normally arranged in the same framework arrangement as the other parts of the printing press, and the framework is placed on the floor. The construction can hereby be compact but is at the same time difficult to work with. The Invention A considerably more elegant construction with great advantages in terms of both design and handling is according to the invention attained in that the cylinders of the printing unit are rotatably arranged in a separate frame for the printing unit, which hereby forms a casette. A printing unit built in this way as a casette can be suspended from a beam structure, which contains the other means of the printing press, including the impression cylinder. Special advantages are attained in that each end of each cylinder is rotatably journalled in a bearing housing, which is displaceable along a vertical bearing rail because in this way the cylinders can easily be brought apart from each other for service and maintenance. A hydraulic cylinder may preferably be arranged in the frame under the lowermost bearing housing in a stack of bearing housings for lifting the housings into contact with each other or to lower them. As neighbouring bearing housings are in contact with each other in their working position, the same mutual position for the cylinders are obtained when the cylinders have been brought apart and are again brought together. In order to attain a so called "kiss" or "touch" between neighbouring cylinders a wedge arrangement can be provided between two neighbouring bearing housings, the wedge arrangement consisting of two opposite wedges, of which one is fixed and the other is displaceable in its longitudinal direction, so that the distance between the bearing housings and thus the cylinders can be finaly adjusted. If the cylinders are lowered with no other arrangements being made, they will still be in contact with each other but further down. It is advantageous if the cylinders instead are brought apart, so that a distance is obtained between all the cylinders. This may according to the invention be attained in that all the bearing housings in a stack are displaceable along a spacing rod, which is provided with cams and is rotatable by means of a rotating mechanism between a position in which the bearing housings are freely movable along the spacing rod in relation to the cams and a position in which the cams constitute stop means for the bearing housings in their movements downwards along the spacing rod. In this way service can be made on each individual cylinder. If cylinders moreover shall be removed from the printing unit, each bearing housing may be provided with a clamp, which may be pivoted down from a vertical closed position to a horizontal open position, in which the cylinder is free to be removed from the bearing housing. In order to prevent the cylinder from unintentionally rolling off from the clamp in its horizontal position the clamp may be provided with an oblique edge at its outer end. When the cylinders again shall be brought together, it is of outmost importance that they resume their proper positions in relation to each other and that the gears are in proper position for engagement. Such an alignment and proper gear engagement can be obtained by means of a vertical ruler, which is parallely displaceably arranged in the frame and is intended for aligning cooperation with bevelled surfaces on the stub axles of the cylinders. Brief Description of the Drawings The invention will be further described below under reference to the attached drawings, in which FIG 1 is a diagrammatic side view of a printing unit according to the invention, FIG 2 is a side view of a printing press, of which the printing unit according to the invention is a part, FIG 3 is a view seen obliquely from above of the printing press according to FIG 2 with certain parts at the top side left out for the sake of clarity, FIG 4 is a side view of the printing unit according to the invention, FIG 5 is a front view of the printing unit (to a smaller scale than FIG 4), FIG 6 is a perspective view of two printing units under use in a printing press, FIG 7 is a perspective view illustrating how a cylinder is removed from the printing unit according to the invention, FIG 8 and 9 are a side view and a top view, respectively, of a bearing housing with neighbouring means for the printing unit according to the invention to a larger scale, and FIGS 10 and 11 in a perspective view and a diagrammatic side view, respectively, of the printing unit are intended to illustrate an aligning ruler. Detailed Description of Preferred Embodiments A printing unit for a rotary printing press diagrammatically shown in FIG 1 has a number of cylinders described below, which are driven synchronously by means not shown in FIG 1, for example gearwheels (illustrated in FIG 3). In the configuration illustrated in FIG 1 the printing unit in a lowermost position has a screen cylinder 1 (often called an anilox cylinder), which at rotation picks up printing ink from a doctor chamber 2. The printing ink, which preferably has a very high viscosity, is deposited on the screen cylinder 1, which in a known manner is provided with a very large number of small depressions for pickup of the printing ink on its entire peripheral surface. From the screen cylinder 1 the ink is transferred to a form cylinder 3, which bears against the screen cylinder and rotates with the same speed and whose surface is some-what elastical by being made of ground rubber material. In order to accomplish a distribution of the ink on the form cylinder 3 which is as even as possible, an oscillating cylinder 4 (a polished steel cylinder) is in rotational engagement with the form cylinder 3, while a rubber cylinder 5 in turn is in rotational engagement with the oscillating cylinder 4. In the preferred embodiment a fully sactisfactory distribution of the ink on the form cylinder 3 is obtained by means of the two cylinders 4 and 5, but a greater number of ink distributing cylinders may of course be arranged in the vicinity of the form cylinder 3. The next cylinder in the printing unit is a plate cylinder 6, on the periphery of which a printing plate is arranged. At least a part of the periphery of the plate cylinder 6 is made of a magnetic metal material, while the thin and pliable printing plate has a metal base adhering to the periphery of the plate cylinder. Over the metal base the printing plate is provided with a plastic layer, in which the desired printing pattern is worked out. Other ways of attaching the printing plate on the plate cylinder 6 are possible, such as by mechanical or vacuum based means. The plate cylinder 6 bears against the form cylinder 3 and has the same peripheral speed. The screen cylinder 1, the form cylinder 3 and the plate cylinder 6 preferably have the same diameter. From the plate cylinder 6 the print is transferred to a rubber blanket cylinder 7 (i.e. a rubber blanket covered steel cylinder), which is in contact therewith and has the same peripheral speed. By the fact that the rubber blanket cylinder 7 preferably has twice as big diameter as the plate cylinder 6 and thus twice as big periphery, the rubber blanket cylinder obtains two full impressions from the plate cylinder at each revolution. The rubber blanket cylinder 7 can alternatively have three or more times as big diameter as the plate cylinder. Engaging the rubber blanket cylinder 7 is finally an impression cylinder 8, preferably with the same diameter as the former one. A web 9 to be printed is conducted between these two cylinders; this web can be made of a paper material or any other suitable material. FIG 1 is a very schematic illustration of a printing unit. No journallings, drives or the like are shown. Further guiding in these respects can be obtained from FIGS 2 and 3 together with the description thereof. By means of a printing unit as described above it is possible to obtain a printing process which can be said to be an intermediary between flexographic printing and offset printing. At flexographic printing, which is most suitable for the printing of single coloured, large areas and not for four colour-printing, use is made - apart from the impression cylinder - of a block cylinder engaging the web and a screen cylinder cooperating with the block cylinder for receiving the ink. At offset printing on the other hand the process is more complicated with a greater number of cylinders and with printing ink and fountain solution (on the non-printing portions of the plate). With the new printing process it is posible to obtain a printing quality which is very close to that otherwise only obtained by offset printing. FIG 2 is a side view of a rotary printing press. This printing press is provided with four printing units of the kind illustrated in FIG 1 (or alternatively of some other kind). Each such printing unit, the impression cylinder 8 over which the web is conducted not being regarded as included in the printing unit, has been given the collective reference numeral 10. The reason why the number four has been chosen is of course the traditional one, namely that all printing colours can be obtained by means of the four colours yellow, bluish red (magenta), greenish blue (cyan) and black. In special cases, when a special colour ("house colour") is used to a large extent for printing, a fifth printing unit can be provided for this colour. A distinctive feature with the printing press according to FIG 2 is that it is formed around a strong beam structure 11, from which the printing units 10 are suspended and on which in principle all other equipment, described in short below, is arranged. This beam structure 11 is in the shown case supported by means of pillars 12 from the floor but could in principle quite as well be suspended from the ceiling of a printers building. The advantage with this construction is that the floor under the printing press is free for the operators and that the printing units and other equipment are extremely accessible. Each printing unit 10 is arranged in a frame 13, which thus is suspended from the beam structure 11. Each printing unit 10 with its frame 13, which together can be called a cassette, can accordingly easily be dismounted and exchanged to a new one and/or be serviced. The web 9 enters the printing press to the right in FIG 2, where it is first exposed to surface treatment at 14 and thereafter for cleaning at 15. A lateral guiding arrangement 16 is arranged at the end of the beam structure 11 and accomplishes a lateral guiding of the web by turning around an axis parallel with the longitudinal axis of the beam structure 11. The web tension, which is essential for the function of the printing press and the quality of the print, is controlled by means of entrance nip cylinders 17 and exit nip cylinders 17' and also - if needed - a web tension arrangement 17'', which consists of a tilting lever, which is controlled by means of a pneumatic cylinder and has a roller, over which the web 9 is conducted. After having passed over the impression cylinder 8 in a printing unit, where the web 9 has been provided with print in the form of an array of high viscosity printing ink, the web 9 passes a drying device 18. In the actual case this drying device 18 consists of UV-lamps, as the used printing ink is of the type hardened by means of UV-radiation. Alternatively, hot air drying or other drying can be used. When the web 9 has passed all printing units 10 in the printing press and accordingly been provided with the desired four colour-print, it can pass through an inspection system, for example past a stroboscope lamp 19, so that an operator can check the printing quality, before the printed web 9 leaves the printing press to the left in FIG 2. The impression cylinders 8, over which the web 9 is conducted, are rotatably journalled in the beam structure 11, whereas the cylinders 1, 3-7 of each printing unit 10 are rotatably journalled in the frame 13. At the exchange of printing format, i.e. a change of cylinder diameters, or possibly a change of printing ink the printing unit cassettes 10, 13 can easily be removed from the printing press and be replaced by new casettes. These new casettes can be prepared during the previous run. Altogether this means that the time lost at casette exchange becomes extremely short. At a casette exchange the web 9 is further not affected, which minimizes the waste at changes. It appears from FIG 2 that the printing unit casettes 10, 13 can be suspended from brackets 20 at the underside of the beam structure 11 and accordingly can be pulled out laterally and handled for example with trolleys or a traverse. The construction is very operator friendly and leaves the floor in principle free. The suspended printing units with the ink storage (the doctor chambers 2) furthest down has the effect that ink cannot pour over the equipment. The web path between the printing units can be very short and stable. In FIG 3, where the printing press is shown in an oblique top view, devices on the top side of the beam structure 11 are omitted in order that certain aspects of the design shall appear more clearly and not be blocked by these devices. It appears in FIG 3 that the beam structure 11 in the shown case consists of longitudinal beams 11' and cross beams 11''. The beam structure 11 is supported by the pillars 12. The impression cylinders 8, the entrance nip cylinders 17 and the exit nip cylinders 17' are rotatably journalled in the longitudinal beams 11' of the beam structure. The impression cylinders 8 and the entrance nip cylinders 17 in the beam structure 11 are arranged to be driven by means of an electric primary motor 21 via longitudinal drive shafts 22 and angle joints 23. The exit nip cylinders 17' are arranged to be driven by means of an electric motor 21'. A jib arrangement 24 is provided on either side of the beam structure 11 and consists for example of cross bars 24', attached to the longitudinal beam 11', and a longitudinal bar 24''. The jib arrangement 24 at one side of the beam structure 11 is also visible in FIG 2. The jib arrangement 24 can, if required, be supported by pillars 12. The brackets 20 mentioned above or roller conveyors for the printing unit casettes 10, 13 are arranged at the lower side of the jib arrangement 24. As shown in FIG 3, this means that printing unit casettes 10, 13 in one set can be pulled out to the right under the jib arrangement 24 for after treatment after a previous print run and preparations for a coming print run, at the same time as a second set of printing unit casettes 10, 13 are in the position for printing under the impression cylinders 8. (Only one printing unit casette 10, 13 in printing position is for the sake of clarity provided with a reference numeral in FIG 3). When the printing is completed, the second set of printing unit casettes 10, 13 can easily be brought out under the jib arrangement 24 to the left in FIG 3, while the printing unit casettes 10, 13 under the jib arrangement 24 to the right in FIG 3, prepared for the coming printing, are brought into position for printing under the impression cylinders 8. An extremely short replacement time between different print runs is hereby obtained and accordingly a very high efficiency. The system can be completed with an external handling system in the form of trolleys or a traverse for handling the printing unit casettes 10, 13, possibly more than two sets. It appears clearly in FIG 3 that the different cylinders in each printing unit casette 10, 13 are connected to each other by means of a set of gearwheels. When the casette is brought into its printing position under its impression cylinder 8, the uppermost gearwheel in this gearwheel set will be brought into engagement with a corresponding gearwheel of an output gearbox 25 on the outgoing shaft of the impression cylinder 8. It should be observed that the beam structure 11 with the printing units 10, 13 arranged thereunder is the core of the construction and that the jib arrangements 24 can be present or not. The present invention relates to the printing unit per se in the printing press, and this printing unit will now be described under reference to FIGS 4-11. As earlier mentioned, the printing press is provided with four or more suspended printing units, which all in principle have the same design, and accordingly only one printing unit will be described. FIGS 4 and 5 show the printing unit in a side view and a front view, respectively. In the frame 13 of the printing unit the screen cylinder 1, the form cylinder 3, the plate cylinder 6 and the rubber blanket cylinder 7 are journalled by means of bearing housings, which for the three first mentioned cylinders are of equal size and have been given the numeral 30 but for the rubber blanket cylinder 7 is larger and has been given the numeral 31. The design for the bearing housings 30 and 31 are in principle the same, and the description of the bearing housing 30 is also appicable to the bearing housing 31 in relevant parts. It appears especially clearly from FIG 7, that the stub axle for the cylinder, in this case the form cylinder 3, is provided with a permanently mounted roller bearing 32, which is arranged in the bearing housing 30. The bearing housing 30 is provided with a pivotable clamp 33, which can be fixed to the bearing housing 30 by means of bolts 34. In order to prevent the cylinder 3 from unintentionally rolling off the clamp 33 in the horizontal lowered position, the clamp has an oblique edge 33'. It also appears from FIG 7 that a gearwheel 35 at the end of each cylinder stub axle is a gearwheel with oblique teeth (even if straight-toothed gearwheels are shown in other figures for the sake of simplicity). The larger gearwheel for the rubber blanket cylinder 7 has the numeral 36. All gear-wheels are arranged outside the frame 13. In order to obtain an operation which is as silent as possible, every second wheel may be made of a harder material and the remaining wheels of a softer material. As most clearly appears from FIGS 8 and 9, each bearing housing 30 (and 31) is provided with a spacing unit 37 and an axial bearing unit 38 for the mounting and guiding of the bearing housing in the frame 13 in a way to be described below. A vertical bearing rail 39 is fixedly arranged at either side of the frame 13 and forms an axial bearing together with the bearing unit 38, which is provided with balls, so that the bearing housings 30 and 31 accordingly become vertically displaceable in an easy manner. The spacing unit 37 is provided with a vertical bore 40 for a spacing rod 41, which in FIG 4 only is indicated by means of its center line. The two spacing rods 40, which are rotatably journalled in the frame 13, can be rotated synchronously for example 90° by means of a rotating mechanism 42 at the under side of the printing unit (FIGS 4 and 5). Each spacing rod 41 is provided with a number of cams 41' and the bore 40 in each spacing unit 37 has a corresponding channel 40'. In the position shown in FIG 9 the bearing housing 30 can accordingly move freely in relation to the spacing rod 40, whereas the mutual distance of the cams 41' along the rod 40 in relation to the height of the bearing housings leads to the situation, especially well illustrated in FIG 4 but also shown in FIGS 6, 10 and 11, where the bearing housings "hang" on the cams 41', when the rod has been rotated for example 90° by means of the rotating mechanism 42 and the bearing housings 30 (and 31) have been allowed to descend from their positions against each other. Under each stack of bearing houses 30 and 31 a hydraulic cylinder 43 for lifting and lowering the bearing housings is arranged in the frame 13. At lifting the bearing housings will come into engagement with each other via wedge means described below, and at lowering the above described, hanging position is obtained, in which the cylinders 1, 3, 6 and 7 can be released from their bearing housings 30 and 31 and possibly be exchanged and serviced. Wedge means, consisting of a fixed wedge 44 on the upper side of the bearing housing 30 and an adjustable wedge 45 at the under side of the bearing housing situated there-above, are arranged between two neighbouring bearing housings 30 in the stack. Due to the greater diameter of the rubber blanket cylinder 7 a distance element 46 (FIG 4) is arranged between the bearing housing just below the bearing housing 31 and its fixed wedge 44. The adjustable wedge 45 can be displaced in the longitudinal direction of the bearing housing by means of an adjustment screw 47. The bearing housing 30 for the lowermost cylinder 1 has no adjustable wedge 45, and the uppermost bearing housing 31 has no fixed wedge 44. The wedge angle of the wedge pair 44, 45 is small, for example 1°, for obtaining high accuracy in the adjustment of the contact or distance between neighbouring cylinders, so called "kiss" or "touch". The once adjusted position between neighbouring cylinders is regained, when the cylinders 1, 3, 6 and 7 are brought together by means of the hydraulic cylinders 43 after earlier having been brought apart, but a manual adjustment at each end of each cylinder can of course always be performed. A corresponding adjustment between the rubber blanket cylinder 7 and the impression cylinder 8 taking account of the thickness of the used web can be performed by means of a motor-driven wedge. For the purpose of obtaining correct mutual positions at the bringing together of the cylinders 1, 3, 6 and 7, so that the print will obtain a correct position and engagement of the gears can occur, the following arrangement is used. One of the stub axles of each cylinder 1, 3, 6 and 7 has a bevel in vicinity of the gearwheel 35 or 36, and a vertical ruler 48 (FIGS 10 and 11) can be brought in engagement will all these bevels in connection in the bringing together of the cylinders 1, 3, 6 and 7. The ruler 48 is connected with the frame 13 by means of two links 49 for obtaining a parallel displacement. Indicating means 50 for indicating a correct gear engagement for the impression cylinder 8 are provided on the rubber blanket cylinder 7, which in the shown case has two bevels on the stub axle, as two diametrically opposed positions are correct for this cylinder. The operation at the preparation of the printing unit for printing is as follows: The cylinders 1, 3, 6 and 7 are manually rotated to a roughly correct position, whereupon final alignment occurs by means of the ruler 48. The drive wheel of the impression cylinder is brought to a correct position by means of a servo motor, and the engagement of the gearwheels occurs by means of the lifting cylinders 43.

Claims: A rotary printing press, in which a web (9) to be printed is arranged to be conducted via an impression cylinder (8), wherein cylinders (1, 3, 6, 7), such as a screen cylinder (1), a form cylinder (3), a plate cylinder (6), and a rubber blanket cylinder (7), of a printing unit in the press are arranged in a vertical row under the impression cylinder (8), characterized in that the cylinders (1, 3, 6, 7) of the printing unit are rotatably arranged in a separate frame (13) for the printing unit, which hereby forms a casette. A press according to claim 1, characterized in that each end of each cylinder (1, 3, 6, 7) is rotatably journalled in a bearing housing (30, 31), which is displaceable along a vertical bearing rail (39). A press according to claim 2, characterized in that a hydraulic cylinder (43) is arranged in the frame (13) under the lowermost bearing housing (30) in a stack of bearing housings for lifting the housings into contact with each other or to lower them. A press according to claim 3, characterized in that all the bearing housings (30, 31) in a stack are displaceable along a spacing rod (41), which is provided with cams (41') and is rotatable by means of a rotating mechanism (42) between a position in which the bearing housings are freely movable along the spacing rod in relation to the cams and a position in which the cams constitute stop means for the bearing housings in their movements downwards along the spacing rod. A press according to claim 4, characterized in that each bearing housing (30, 31) is provided with a clamp (33), which may be pivoted down from a vertical closed position to a horizontal open position, in which the cylinder (1, 3, 6, 7) is free to be removed from the bearing housing. A press according to claim 5, characterized in that the clamp (33) at its outer end is provided with an oblique edge (33') for preventing the cylinder (1, 3, 6, 7) from unintentionally rolling off from the clamp in its horizontal position. A press according to claim 3, characterized in that a vertical ruler (42) is parallelly displaceably arranged in the frame (13) and is intended for aligning cooperation with bevelled surfaces on the stub axles of the cylinders (1, 3, 6, 7).

Inventors: ANDERSSON INGVAR, HERSENIUS BENGT, ANDERSSON, INGVAR, HERSENIUS, BENGT
Applicants: TETRA LAVAL HOLDINGS & FINANCE, TETRA LAVAL HOLDINGS & FINANCE SA
Application year: 1995
Main classification: B41F5
IPC codes: B41F13, B41F27