Printing press for printing on a sheet

Abstract

The invention relates to a printing press for printing on a printing form (6), comprising two cylinders (1, 2) in the form of a blanket cylinder (1) and a blanket cylinder (2), which together form a printing nip (3), in front of which a blowing device (11) is arranged. The blanket cylinder (1) has a cylinder channel (4) and the blanket cylinder (2) has a tension channel (7). On one of the cylinders (1, 2) a sealing device (16) or a sealing device half is fixed, which seals the printing nip (3) when the tension channel (7) is opposite the cylinder channel (4) and prevents the blowing device (11) from blowing gas through the printing nip (3).

Description

Technical Field

[0001] The present invention relates to a printing press for printing on sheets, comprising two rollers in the form of a pressure roller and a blanket roller, which together form a printing gap, and a blower is provided in front of the printing gap. Background Technology

[0002] DE 10 2019 127 868 A1 describes a printing press having a blower device located in front of the printing gap. This blower device ejects a first blower air jet and a second blower air jet. The second blower air jet is inclined against the sheet transport direction to prevent air from blowing under the sheet.

[0003] By tilting the second air jet, airflow is prevented from blowing under the page only before the printing gap. It has not been recognized that if both rollers have channels and are positioned opposite each other each time the rollers rotate, the first air jet will be blown under the page after the printing gap. Summary of the Invention

[0004] The objective of this invention is to provide a printing press in which air is prevented from blowing under the pages after the printing gap.

[0005] The task is solved by a printing press for printing on sheets, comprising two rollers in the form of a pressure roller and a blanket roller, which together form a printing gap. A blower is provided in front of the printing gap. The press roller has a roller channel and the blanket roller has a tension channel. A sealing device or a half of a sealing device is fixed on one of the rollers. The sealing device or the half of the sealing device seals the printing gap when the tension channel is opposite to the roller channel and prevents the blower from blowing gas through the printing gap.

[0006] Various extensions of this invention are possible:

[0007] The sealing device can be submerged into the tensioning channel or the roller channel during sealing.

[0008] The sealing device can be fixed on the pressure roller.

[0009] The sealing device can be submerged into the tensioning channel during sealing.

[0010] The sealing device can be arranged on a protective cover that covers a portion of the roller channel.

[0011] The sealing device or half of the sealing device may extend over the maximum page width. Attached Figure Description

[0012] The extended scheme is derived from the following description of the embodiments and figures.

[0013] Figure 1 This shows the printing gap environment of the offset printing mechanism or varnishing mechanism of a sheet printing press. Detailed Implementation

[0014] The accompanying drawing shows a portion of the printing press. This portion shows a pressure cylinder 1 and a blanket cylinder 2, which together form a printing gap 3. The pressure cylinder 1 has a cylinder channel 4, in which a gripping system 5 for holding the printed sheet 6 is provided. The blanket cylinder 2 has a tensioning channel 7, in which a tensioning device 8 for holding and tensioning the blanket 9 is provided. The blanket 9 can be an offset printing cloth or a varnishing cloth.

[0015] A blower device 11 is provided in front of the printing gap 3 along the conveying direction 10. The blower device sprays a jet of air 12 toward the feed wedge 13 between the pressure roller 1 and the blanket roller 2 to press the printed sheet 6 against the pressure roller 1. As indicated by the arrow in the attached figure, the sprayed air flows toward the printing gap 3.

[0016] The diagram shows a stage in which the roller channel 4 and the tension channel 7 face each other, and in the discharge wedge 14 behind the printing gap 3, the rear edge 15 of the printed sheet conveyed on the pressure roller 1 still sticks to the blanket roller 2 due to slippage or inertia.

[0017] Without the sealing device 16 of the present invention, the following danger would occur at this stage: the blowing air ejected by the blowing device 11 toward the printing gap 3 would flow through the printing gap 3 into the discharge wedge 14 and blow onto the rear edge 15. As a result, the rear edge 15 would be further lifted from the pressure roller 1 and, in the worst case, would collide with the device 17 behind the printing gap 3 and smear or soil the device.

[0018] The sealing device 16 of the present invention prevents the blown air ejected by the blown device 11 from flowing through the printing gap 3 in the above-mentioned stage by sealing the gap that temporarily appears through the opposition of the roller channel 4 and the tension channel 7.

[0019] The sealing device 16 is fixed to the pressure roller 1 and sinks into the tensioning channel 7 during sealing. A protective cover 18 is provided in the roller channel 4, covering the portion of the roller channel 4 between the gripping system 5 and the preceding channel wall 19, and extending sealingly below the peripheral line 20 of the pressure roller 1. The sealing device 16 is arranged on this protective cover 18. The sealing device 16 protrudes from the peripheral line 20. The sealing device is positioned immediately in front of the channel wall 19 and, when sinking into the tensioning channel 7, almost touches the section of the rubber blanket 9 extending within the tensioning channel 7.

[0020] The sealing device 16 is preferably made of a rubber-elastic material and extends substantially along the axial length of the cylinder or the maximum width of the sheet 6 that can be processed in the printing press. The sealing device 16 is a strip with, for example, a quadrangular profile.

[0021] In addition to the variations shown in the attached drawings of the sealing device arrangement, other variations are also possible:

[0022] The sealing device 16 can be fixed to the rubber blanket roller 2 and sink into the roller channel 4 during sealing.

[0023] Similarly, the sealing device 16 may consist of a first sealing device half arranged in the roller channel 4 of the pressure roller 1 and a second sealing device half arranged in the tension channel 7 of the rubber blanket roller 2, wherein the two sealing device halves are in contact with each other or almost in contact with each other when sealing the printing gap 3.

[0024] The sealing device 16 can also be configured as a labyrinth sealing device, wherein the first sealing device half arranged on the pressure roller 1 sinks into the tension channel 7 during sealing, and at the same time the second sealing device half arranged on the rubber cloth roller 2 sinks into the roller channel 4 during sealing.

[0025] Appendix Label Table

[0026] 1. Pressure roller

[0027] 2. Rubber Blanket Roller

[0028] 3 Printing gap

[0029] 4. Roller Channel

[0030] 5. Capture System

[0031] 6 printing sheets

[0032] 7 tensioning channels

[0033] 8 tensioning devices

[0034] 9. Rubber cloth

[0035] 10 Conveying direction

[0036] 11. Pulse jetting device

[0037] 12. Air jet

[0038] 13 Feed wedge

[0039] 14 Discharge wedge

[0040] 15 Rear Edge

[0041] 16 Sealing device

[0042] 17 devices

[0043] 18 Protective Cover

[0044] 19. Passage Wall

[0045] 20. Surrounding Lines.

Claims

1. A printing press for printing on a sheet (6), comprising two rollers in the form of a pressure roller (1) and a blanket roller (2), the pressure roller and the blanket roller together forming a printing gap (3), and a blower (11) provided in front of the printing gap, characterized in that, The counter-pressure roller (1) has a roller channel (4) and the rubber cloth roller (2) has a tensioning channel (7). A sealing device (16) or a half of a sealing device is fixed on the pressure roller (1) or the rubber blanket roller (2). The sealing device or the half of the sealing device seals the printing gap (3) when the tensioning channel (7) is opposite to the roller channel (4) and prevents the blowing device (11) from blowing air through the printing gap (3). The sealing device (16) sinks into the tension channel (7) or the roller channel (4) during sealing.

2. The printing press according to claim 1, characterized in that, The sealing device (16) is fixed on the pressure roller (1).

3. The printing press according to claim 2, characterized in that, The sealing device (16) sinks into the tensioning channel (7) during sealing.

4. The printing press according to claim 2, characterized in that, The sealing device (16) is arranged on the protective cover (18), which covers a portion of the roller channel (4).

5. The printing press according to claim 3, characterized in that, The sealing device (16) is arranged on the protective cover (18), which covers a portion of the roller channel (4).

6. The printing press according to any one of claims 1 to 5, characterized in that, The sealing device (16) or half of the sealing device extends over the maximum page width.

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