Sheet processing machine with radiation dryer

Abstract

Sheet processing machine with a radiation dryer (24) arranged on a sheet transport path (23) and at least one gripper carriage (19) which is guided for transporting a sheet (22) along the sheet transport path (23), wherein the gripper carriage (19) has a reflector (27), wherein the reflector (27) reflects radiation leaving the radiation dryer (24) in the sheet transport direction (29) in the opposite direction to the sheet transport direction (29), wherein the support beam (20) is coated in the area of ​​the reflector (27) or that the reflector (27) is designed as an adhesive tape, wherein the reflector (27) comprises an aluminum layer.

Description

[0001] The invention relates to a sheet processing machine with an integrated radiation dryer according to the features of claim 1.

[0002] A sheet conveyor known from DE 296 16 235 U1 transports the sheets using gripper carriages guided by circulating chains along a sheet transport path. The gripper carriages clamp the leading edges of the sheets and pull them along the sheet transport path, also past the radiation dryer.

[0003] US Patent 4,530,495 A discloses a sheet-processing machine with a radiation dryer, wherein a trailing surface of a gripper carriage with a sheet transport plane has an angle of less than 90° to reduce an unirradiated area of ​​the sheet.

[0004] EP 0 252 602 A1 discloses a sheet processing machine with a radiation dryer, wherein the gripper carriage has a reflector on its upper side to reduce heat.

[0005] DE 33 24 986 A1 discloses a gripper carriage with a traverse that does not hinder uniform drying.

[0006] Because the gripper carriages project from the plane in which they convey the sheets toward the radiation dryer, they shield the leading edge of the sheets from some of the dryer radiation. Areas of the sheets where the shielding is so intense that it does not allow satisfactory drying of the printing ink should not be printed, as the ink may smudge or transfer to other sheets after placement.

[0007] The resulting impaired drying process can manifest itself in reduced abrasion and / or scratch resistance.

[0008] The invention is based on the objective of creating a sheet-processing machine with a radiation dryer.

[0009] The problem is solved according to the invention by the features of claim 1.

[0010] The advantages achievable with the invention consist in particular of the fact that the reflector redirects a portion of the dryer radiation, which would be uselessly absorbed by the gripper carriage in the absence of the reflector, onto the leading edge of a sheet being conveyed by the gripper carriage. While this does not prevent the gripper carriage from shielding the sheet from its radiation before it reaches the radiation dryer, once the gripper carriage has passed the radiation dryer, the reflector redirects radiation that has left the radiation dryer in the direction of sheet transport and would not reach the sheet if propagated unhindered, back onto the sheet. Thus, the leading edge of the sheet is irradiated more intensely after the gripper carriage no longer shields it.

[0011] To be effective across the entire width of the arc, the reflector should preferably extend continuously across the entire width of the arc transport path.

[0012] The reflector should preferably be straight in cross-section at least in one longitudinal direction of the gripper carriage, i.e. in a plane parallel to the leading edge of the sheet conveyed by the gripper carriage, in order to avoid a redistribution of the radiation perpendicular to the sheet transport direction.

[0013] In a section plane orthogonal to the front edge, the reflector can also be straight; however, a convex or, in particular, a concave curved cross-sectional shape can also be useful to optimize the radiation distribution.

[0014] Preferably, the first segment is guided to move in the radial direction, e.g. by means of rails extending in the radial direction.

[0015] A particularly simple solution that achieves a well homogeneous distribution of the radiation dose in the transport direction of the arc is to align the reflector perpendicular to the arc transport direction.

[0016] The reflectivity of the reflector for the radiation of the radiation dryer should preferably be at least 60%, in particular at least 75%.

[0017] Such reflectivity, in particular reflectance, is achievable in the ultraviolet range (especially wavelengths from 200 mm to 380 mm) with an aluminum surface.

[0018] To keep the aluminum surface oxide-free, it should be coated with a protective layer. An oxygen-impermeable protective layer that is permeable to the dryer's UV radiation can contain silicon, and in particular consist of quartz.

[0019] Exemplary embodiments of the invention are shown in the drawings and are described in more detail below.

[0020] They show: Fig. 1 a schematic side view of a bow boom with integrated radiation dryer; Fig. 2 a schematic cross-section of a gripper carriage of the bow boom at the inlet to the radiation dryer; Fig. 3 the grab trolley directly below the radiation dryer; Fig. 4 the grabber carriage when passing the radiation dryer; Fig. 5 a variant of the gripper carriage in a schematic cross-section.

[0021] Fig. Figure 1 shows a side view of a sheet feeder 01 and parts of a final printing unit 02 of a sheet-fed processing machine, e.g., a sheet-fed printing press, here a sheet-fed offset printing press. A printing cylinder 11 of the printing unit 02 transfers a sheet, after a final ink has been applied to the sheet by contact with a rubber cylinder (not shown), to a sheet conveying system 12 of the sheet feeder 01. The sheet conveying system 12 comprises two endless chains 13, which are deflected by sprockets 14 and 15. Further details are shown in the Fig. One sprocket (not shown) guides a lower and an upper run 16; 17 of the chains 13 along a curved path that initially rises obliquely from sprocket 14 to sprocket 15 and then transitions to a horizontal path over a delivery stack 18. Holding tools 19, in particular gripper carriages 19, are mounted on the chains 13 at regular intervals. The gripper carriages 19 each comprise a support beam 20 that extends transversely to the direction of arc transport 29, i.e., the direction of travel of the chains 13, and is attached to both chains 13 (see e.g. Fig. 2) and movable grippers 21 distributed along an edge of the support beam 20, which are designed to clamp the leading edge of a printed sheet 22 on the support beam 20 at the printing cylinder 11 and to pull the sheet 22 along a sheet transport path 23, which here corresponds to the course of the lower run 16, to the delivery stack 18 and release it there.

[0022] When the sheet 22 passes through the sheet transport path 23, its printed side on the printing cylinder 11 is facing upwards. Facing this side, a radiation dryer 24 is arranged between the trusses 16 and 17. The radiation dryer 24 comprises at least one radiation source 25 extending across the entire width of the sheet transport path 23 from one chain 13 to the other. Fig. Figure 1 shows three radiation sources 25; since the number of radiation sources is irrelevant for the effect of the invention, the number of sources is shown in the Fig. For simplicity, only one of each of numbers 2 to 4 is shown.

[0023] As an alternative to arranging the radiation dryer 25 in the sheet feeder for curing printing inks, the radiation dryer 25 can be arranged in a delivery extension. This delivery extension can be used to create a coating flow section after a final unit, such as a coating unit. The reflectors 27 (su) on the gripper carriage 19 can also be used, for example, for coatings, especially UV coatings.

[0024] The radiation source 25 preferably provides UV radiation capable of inducing a chemical drying reaction in the ink printed on the sheet 22; for physical drying, a visible, infrared or microwave radiation source is also suitable.

[0025] The radiation source 25, in particular the UV radiation source 25, can be designed, in particular, as a mercury discharge lamp in the form of an elongated tube extending transversely to the arc transport direction 29 of the chains 13, or as an arrangement of UV LEDs on a support extending transversely to the arc transport direction 29 of the chains 13. The mercury discharge lamp emits essentially all around its axis with approximately the same intensity in all directions and is therefore usually combined with a reflector that restricts its emission in cross-section transverse to the axis to an angular range α; the LEDs, by design, emit only within such a limited angular range α.

[0026] If, as in Fig. As a grabber carriage 19 approaches the radiation source 25, as shown in Figure 2, it simultaneously shadows a leading edge region 26 of the arc 22, which it pulls behind it. This edge region 26 becomes narrower the closer the grabber carriage 19 gets to the radiation source 25, while at the same time the radiation intensity to which the arc 22 is exposed beyond the shadowed edge region 26 increases. The total radiation dose received by the arc 22 until its leading edge reaches the area shown in Figure 2 is... Fig. The position shown in 3, where maximum proximity to the radiation source 25 has been reached, therefore decreases from the rear to the front edge.

[0027] To correct this uneven distribution, a reflector 27 is preferably arranged, and in particular mounted, on a flank of the gripper carriage 19 oriented opposite to the sheet transport direction 29. The reflector 27 can be a flat strip extending along the gripper carriage 19, preferably over the entire length of the radiation source 25. The reflector 27 preferably extends over at least 80% of the length of the support beam 20 of the gripper carriage 19 and / or over a length of the two outer grippers 21 of the support beam 20 and / or the maximum width of a sheet 22 to be processed. It can be formed by a mirror-polished sheet; it comprises a metal layer of aluminum applied, in particular vapor-deposited, to a flat substrate, and a protective layer of quartz covering the metal layer airtight.Such a reflector 27 has a reflectivity for the UV radiation of the radiation source 25 of at least 40%, in particular 60%, preferably at least 75%.

[0028] Another alternative (equivalent to dichroic reflectors) is the application of layer stacks to hafnium oxide and silicon oxide. The thickness of the layers corresponds to a reflection in a specific wavelength range. The more layers of a given thickness are applied, the higher the reflectance.

[0029] The layer system can then be designed so that not only UV radiation and light (for curing) are reflected (like a dichroic reflector in the UV module), but also IR radiation. This prevents the gripper carriage 19 from heating up with IR radiation. However, both variants are possible.

[0030] A part of the gripper carriage 19, in particular part of the support beam 20, can also serve as a reflector 27. For example, a surface of the gripper carriage 19 and / or the support beam 20 is designed with low roughness. This can be achieved, for example, by mechanical processing and / or coating.

[0031] The reflector 27 can also be designed as adhesive tape, in particular as aluminum adhesive tape.

[0032] The reflector 27 can extend along the support beam 20 in one piece or in several parts. Screw holes can be distributed along the reflector 27 for its attachment; further openings, which should, however, only occupy a small part of the reflector surface, can be provided for sensors that serve to check the correct position of the bow 22 on the gripper carriage 19.

[0033] Alternatively, the reflector 27 can also be clamped for attachment.

[0034] In the configuration shown here, the reflector 27 is perpendicular to the arc transport direction 29, i.e., to the running direction of the chains 13. Deviations from this orientation are possible, but should not exceed 30°.

[0035] The moment the reflector 27 is in Fig. Once the reflector 27 has passed the position of maximum proximity to the radiation source 25 shown in Figure 3, its reflective surface is struck by the radiation. The portion of the radiation that strikes the reflector 27 has left the radiation source 25 in the transport direction 29 of the arc 22 and, if it had not been reflected, would have passed along the arc transport path 23 in front of the leading edge of the arc 22, and thus would not have been utilized. Thanks to the reflector 27, this portion is additionally available and is reflected onto those areas of the arc 22 that were previously shaded. The additional dose thus obtained is highest directly at the base of the reflector 27, where the arc 22 was previously shaded for the longest and most intense period.This allows for a uniform distribution of radiation over almost the entire length of the sheet 22, and the sheet 22 can be printed right up to its leading edge without having to fear insufficient drying.

[0036] If the reflectivity of reflector 27 were 100%, it could exactly compensate for the shadowing caused by the gripper carriage 19. To compensate for the reflection losses, it would be conceivable to adjust the reflector 27 as shown in Fig.Figure 5 shows that the reflector 27 is designed to be concave in cross-section, perpendicular to the longitudinal direction of the gripper carriage 19, in order to focus the reflected radiation. Furthermore, by tilting the reflector 27 forward, such that a tangent 28 of the reflector surface forms an obtuse angle β with the sheet 22, the radiation can be predominantly reflected into an area of ​​the sheet 22 not directly adjacent to the reflector 27. While this does not achieve a uniform distribution of the radiation dose across the sheet 22 all the way to the base of the reflector 27, it allows the boundary up to which sufficient drying is achieved to be moved closer to the gripper carriage 19, thus increasing the printable area of ​​the sheet 22.

[0037] The angle β could also be made acute. Then the radiation would be reflected more towards the beginning of the arc. Reference symbol list 01 Bow boom 02 Printing work 03 - 04 - 05 - 06 - 07 - 08 - 09 - 10 - 11 pressure cylinders 12 Bow conveyor system 13 chain 14 sprocket 15 sprocket 16 Trum, lower 17th tower, upper 18 display stacks 19 Holding tool, gripper trolley 20 support beams 21 grippers 22 sheets 23 Bow transport route 24 radiation dryers 25 UV radiation source, radiation source 26 Edge area, front 27 Reflector 28 Tangent 29 Bow transport direction α angle range β angle

Claims

[1] Sheet processing machine with a radiation dryer (24) arranged on a sheet transport path (23) and at least one gripper carriage (19) which is guided for transporting a sheet (22) along the sheet transport path (23), wherein the gripper carriage (19) has a reflector (27), wherein the reflector (27) reflects radiation leaving the radiation dryer (24) in the sheet transport direction (29) in the opposite direction to the sheet transport direction (29), wherein the support beam (20) is coated in the area of ​​the reflector (27) or that the reflector (27) is designed as an adhesive tape, wherein the reflector (27) comprises an aluminum layer. [2] Sheet processing machine according to claim 1, characterized by , that the grab carriage (19) has the reflector (27) on a flank of the grab carriage (19) oriented against the direction of the arc transport (29). [3] Sheet processing machine according to claim 1 or 2, characterized by, that the reflector (27) extends continuously over the entire width of the arc transport path (23). [4] Sheet processing machine according to claim 1, 2 or 3, characterized by that the reflector (27) is straight in section at least in one longitudinal direction of the gripper carriage (19). [5] Sheet processing machine according to claim 1, 2, 3 or 4, characterized by , that an angle β between a tangent (28) of the reflector surface and arc (22) is obtuse. [6] Sheet processing machine according to claim 1, 2, 3, 4 or 5, characterized by , that an angle β between a tangent (28) of the reflector surface and arc (22) is between 60° and 120°. [7] Sheet processing machine according to claim 1, 2, 3, 4, 5 or 6, characterized by , that the reflector (27) is perpendicular to the arc transport direction (29). [8] Sheet processing machine according to claim 1, 2, 3, 4, 5, 6 or 7, characterized by, that the reflector (27) for the radiation of the radiation dryer (24) has a reflectivity of at least 40%. [9] Sheet processing machine according to claim 1, characterized by , that the reflector (27) has a protective layer over the aluminium layer. [10] Sheet processing machine according to claim 9, characterized by that the protective layer contains silicon. [11] Sheet processing machine according to claim 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, characterized by , that the reflector (27) is designed as part of a support beam (20) of the gripper carriage (19).

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