Offset printing machine

Abstract

 Offset printing machine comprising a plate cylinder (2) for receiving the block (5), an inking apparatus (6) mounted at the plate cylinder, a blanket cylinder (3) and an impression cylinder (4) serving to press the material to be printed (9) against the blanket cylinder. The blanket cylinder (3) is supported by bearings (11) mounted fixedly in the frame (1) of the printing machine and the plate cylinder (2) and the impression cylinder (4) are adjustable in relation to the blanket cylinder (3), such as through eccentric bushes mounted in the machine frame (1).

Description

[0001] The invention relates to an offset printing machine comprising a plate cylinder for receiving the block, an inking apparatus mounted at the plate cylinder, a blanket cylinder and an impression cylinder serving to press the material to be printed against the blanket cylinder, with at least one of the cylinders being supported by the frame of the machine in such a way that it is adjustable in relation to the other cylinder or cylinders.

[0002] Such a machine is known from EP-A-0 453 850. With this machine, at both its ends, the blanket cylinder is supported by bearings mounted in eccentric bushes incorporated in knee levers. By means of the eccentric bushes the blanket cylinder can be adjusted in relation to the other cylinders, and through the knee levers the cylinder is adjustable for switching the machine on and off.

[0003] At high printing speeds, transitions between the plate cylinder and the block and at the ends of the blanket mounted on the blanket cylinder can cause vibrations. This phenomenon has been described in EP-A-0 131 813, for example, though with this known machine two plate cylinders and two blanket cylinders cooperating therewith are applied for printing material two-sidedly.

[0004] In this case, occurence of vibrations is counteracted by positioning the one blanket cylinder somewhat obliquely. Obviously, this results in the fact that the distance between the cylinders is not equal across the total length.

[0005] According to the invention, it has turned out that the occurence of vibrations can be counteracted in particular by providing for the fact that the blanket cylinder is supported by bearings fixedly mounted in the frame of the printing machine, and that the plate cylinder and the impression cylinder are supported by the frame in such a way, that they are adjustable in relation to the blanket cylinder.

[0006] Surprisingly, the occurence of vibrations can thus be counteracted by supporting the blanket cylinder extremely stable in the machine frame, while the other cylinders can be adjustable .

[0007] Since the distance across which the plate cylinder is to be adjustable is only small, its adjustability will cause no problems as far as the arrangement of the inking apparatus is concerned.

[0008] Preferably, it will be provided for, that the axes of the three cylinders will be almost in one plane. Due to the fact that the plate cylinder and the impression cylinder are adjustable in relation to the blanket cylinder, a deviation from this plane can occur, but this deviation will only be very small, since the cylinders also need only be slightly adjusted for obtaining an optimum result.

[0009] The occurence of vibrations can be counteracted further by fixedly mounting the blanket substantially seamless to a clamping bush, which can be slid onto the blanket cylinder owing to a slight expansion, and after that fixedly clamps itself on the cylinder.

[0010] It is known per se to apply such clamping bushes in printing machines for fastening blocks onto the plate cylinder.

[0011] For mounting and dismounting such thin-walled clamping bushes, the cylinder jacket can be provided with openings through which compressed air can be supplied. Owing to this, the diameter of the clamping bush can be enlarged to a very small degree so that movement of the clamping bush on the cylinder is possible.

[0012] In order to enable easy mounting and dismounting of such a clamping bush on the blanket cylinder, it can be provided for, that the bearing through which at least the one end of the blanket cylinder is supported in the frame of the machine, is received within a part to be mounted to the machine frame and bridging an opening in the frame, said opening being so large that after removing the part, the bush can be moved through the opening on removing it from the blanket cylinder or mounting it on the cylinder.

[0013] Then, the blanket cylinder need not be removed from the machine in mounting or dismounting a clamping bush.

[0014] The invention is further explained by means of an embodiment, illustrated in the drawing, in which:

Fig. 1 shows diagrammatically a cross-sectional view across an offset printing machine according to the invention; and

Fig. 2 shows diagrammatically a view of a part of the machine according to Fig. 1.

[0015] The printing machine shown in the drawing comprises the frame 1, in which the plate cylinder 2, the blanket cylinder 3 and the impression cylinder 4 are supported.

[0016] The block 5, on which ink can be applied by means of the inking apparatus 6, is fastened to the plate cylinder 2. The ink is transferred onto the blanket 7 of the blanket cylinder 3. As mentioned earlier, the blanket 7 can be situated on a somewhat flexible bush 8 which can be clamped on the cylinder 3 in the way described above.

[0017] On using the machine, the ink is transferred from the blanket 7 onto the material to be printed 9 at the other side contacting the impression cylinder 4. For guiding the material 9 further means known per se will be present.

[0018] The shaft 10 of the blanket cylinder 3 is supported by the bearing 11, which is incorporated in a ring 12 which is fixedly connected to the frame 1, such as by means of bolts 13, only the axis thereof being indicated. The ring 12 bridges an opening 14 in the frame 1, said opening 14 being so large, that after removing the ring 12, the bush 8 can be moved through the opening 14 on removing it from the blanket cylinder 3 or mounting it on the cylinder.

[0019] The shafts 15 and 16 of the plate cylinder 2 and the impression cylinder 4, respectively, are supported in eccentric bushes 17 and 18, respectively, as described in earlier mentioned EP-A-0 453 850. Therefore, a further description of this construction will not be given.

[0020] As appears from the way of supporting the cylinders 2, 3 and 4 as described, the blanket cylinder is fixedly supported in the frame 1 and the plate cylinder and the impression cylinder are adjustable for determining the proper distance between these cylinders and the blanket cylinder. Here, the axes 19, 20 and 21 of the plate cylinder 2, the blanket cylinder 3 and the impression cylinder 4, respectively, will be substantially in one plane 22.

[0021] Further, at the other ends of the plate cylinder 2 and of the impression cylinder 4, the shafts will be supported in the same way as indicated in Fig. 2. The shaft of the other end of the blanket cylinder can be executed in a simpler way, since on this side there need not be an opening in the frame 1 for passing the clamping bush 8.

[0022] It will be obvious, that only one possible embodiment of an offset printing machine according to the invention has been illustrated in the drawing and described above and that many changes can be made without being beyond the inventive idea.

Claims

1. Offset printing machine comprising a plate cylinder (2) for receiving the block (5), an inking apparatus (6) mounted at the plate cylinder, a blanket cylinder (3) and an impression cylinder (4) serving to press the material to be printed (9) against the blanket cylinder (3), with at least one of the cylinders (2, 3, 4) being supported by the frame (1) of the machine in such a way that it is adjustable in relation to the other cylinder or cylinders, characterized in that the blanket cylinder (3) is supported by bearings (11) fixedly mounted in the frame (1) of the printing machine, and that the plate cylinder (2) and the impression cylinder (4) are supported by the frame in such a way, that they are adjustable in relation to the blanket cylinder (3).

2. Offset printing machine according to claim 1, characterized in that the axes (19, 20, 21) of the plate cylinder (2), the blanket cylinder (3) and the impression cylinder (4), respectively, are substantially in one plane (22).

3. Offset printing machine according to claim 1 or 2, characterized in that the blanket (7) is fixedly mounted to a clamping bush (8), substantially seamless, said bush being slidable onto the blanket cylinder (3) owing to a slight expansion, and after that fixedly clamps itself on the cylinder.

4. Offset printing machine according to claim 3, characterized in that the bearing (11), through which at least the one end of the blanket cylinder (3) is supported in the frame (1) of the machine, is received within a part (12) to be mounted to the machine frame (1) and bridging an opening (14) in the frame, said opening being so large that after removing the part (12), the clamping bush (8) can be moved through the opening on removing it from the blanket cylinder (3) or mounting it on the cylinder.

Drawing