Offset rotary printing press with a device for synchronizing a rotary movement

Abstract

Offset rotary printing press with a device for synchronizing a rotary movement of a printing cylinder (1) driven individually by a single drive (M) with the rotary movement of a blanket cylinder (2) driven centrally by at least one printing press drive (HM) via a drive gear train, wherein the adjacent cylinders (1, 2) are in rolling contact for the transfer of ink or varnish onto a substrate, wherein the individual drive (M) receives position control signals derived from position or motion signals of a rotary angle or rotary motion setpoint encoder (G1) on the drive wheel train, wherein the rotary angle or rotary motion setpoint encoder (G1) is assigned to one leg of the rubber blanket cylinder (2) which can be driven via the drive wheel train, wherein a second rotary angle encoder (G2) is assigned to one leg of the printing cylinder (1), wherein both rotary angle encoders (G1, G2) are connected to a drive controller (R) for the individual drive (M) of the printing cylinder (1) and wherein a secondary gear (7) preventing tooth flank change or backlash is arranged on the rubber sheet cylinder (2) driven via the drive gear train or its leg, wherein - a first gear (5) is arranged non-rotatably on one of the legs of the rubber sheet cylinder (2), which is in tooth mesh with the drive gear train, and - on this first gear (5) the follower gear (7) of the same diameter is arranged, which is rotatably mounted relative to it, which is resiliently supported in the circumferential direction against the first gear (5) and engages together with the first gear (5) in a gear (6) which drives the rubber blanket cylinder (2), so that the first gear (5) and follower gear (7) are in contact with opposite tooth flanks of the gear (6).

Description

[0001] The invention relates to an offset rotary printing press with a device for synchronizing a rotary movement of a printing cylinder driven individually by a single drive with the rotary movement of a blanket cylinder driven centrally by at least one printing press drive via a drive wheel train.

[0002] In rotary printing presses with a central drive gear train, each driven rotating body (cylinder, drum, roller, etc.) or its leg or shaft is assigned at least one drive gear that meshes with one or more gears of adjacent rotating bodies. The drive gear train transmits the drive torques from one or more printing press drives to the rotating bodies. A constant torque flow in the drive gear train ensures reliable tooth engagement of the drive gears and thus a constant circumferential speed, which is a prerequisite for high print quality.

[0003] For ink or varnish transfer to the substrate, adjacent rotating bodies are in rolling contact. Additional torques are transmitted via the frictional surface contact of these adjacent rotating bodies. This occurs even if there is no drive connection between the rolling rotating bodies via the drive gear train. The torques transmitted via surface contact superimpose on the torque flow in the drive gear train and can lead to a reduction in the clamping torques within the drive gear train, potentially even to the point of tooth flank reversal, resulting in duplication and an unclean print image.

[0004] In offset rotary printing presses, printing cylinders or plate cylinders are increasingly being equipped with individual drives to save setup times and perform press-specific register corrections. The printing cylinders transfer the printed image via a blanket cylinder to an impression cylinder that guides the substrate. Due to the frictional surface contact, torque from the individual drive is also transferred from the printing cylinder to the adjacent blanket cylinder and partially introduced into the drive gear train via the drive gear associated with the blanket cylinder. This reduces the load on the drive gear train, particularly the tension between the drive gears of the blanket cylinder and the impression cylinder located upstream of it.A disadvantage of this is that, in the event of torque fluctuations in the drive gear train, the tooth flank contact at the always backlash-prone tooth engagement point is more likely to change, resulting in uncontrolled rotational angular position fluctuations at the blanket cylinder within the backlash. Since the separately driven printing cylinder typically receives its rotational angular position or movement setpoints from a rotary encoder mounted on the blanket cylinder shaft to synchronize its rotation with the centrally driven blanket cylinder, load change reactions of the blanket cylinder are also transmitted to the position control of the individual drive on the printing cylinder, thus superimposing disturbances on its rotational movement as well. Circumferential register deviations and impairments in the quality of the printed image transfer to the substrate are the consequences.

[0005] German patent DE 10 2005 021 334 A1 describes an additional gear drive parallel to the drive gear train of a printing press with individual printing cylinder drives, designed to prevent backlash in the drive gear train. This additional gear drive has two tooth engagement points with the drive gear train and is intended to reduce load change reactions in the drive gear train through axial forces or additional torques. For this purpose, an additional axle for the gear drive is formed between the blanket cylinder and an upstream rotating body. The disadvantages of this design are the complexity of the additional drive axle and the extra installation space required, which is not available at this location.

[0006] DE 199 53 664 A1 discloses a device for ensuring correct tooth engagement when coupling two gears, wherein a projection is arranged eccentrically to one of the two gears and connected to this gear, so that the projection rotates with this gear when this gear is rotated about a central axis of this gear.

[0007] DE 101 15 546 A1 discloses a method and a device for operating a printing press, in particular a sheet-fed offset printing press, wherein the angular position of a wheel train is measured at two different positions, wherein the position of an individual drive is adjusted depending on the difference resulting from these angular positions.

[0008] The invention is therefore based on the objective of creating a space-saving and easily implementable device to avoid tooth flank changes or backlash on rotary angle or rotary motion setpoint generator shafts of the drive gear train in printing presses with position-controlled individual drives.

[0009] According to the invention, the problem is solved by a device having the features of the first claim. Advantageous embodiments are the subject of the dependent claims.

[0010] The device according to the invention for synchronizing the rotary motion of individually driven rotating bodies with the rotary motion of rotating bodies that can be driven centrally by a printing press drive via a drive gear train, wherein the individual drives receive position control signals for synchronization purposes, which are derived from position or motion signals from rotary angle or rotary motion setpoint encoders on the drive gear train, has on those shafts or legs to which the rotary angle or rotary motion setpoint encoders are also assigned, tooth flank changes or backlash that prevent the gear teeth from changing.

[0011] By arranging auxiliary gears on the shafts of the rotary angle or rotary motion setpoint encoders, which are influenced by torques from individual drives, tooth flank changes during torque fluctuations in the drive gear train can be prevented in a simple and space-saving manner, so that the individual drives do not receive rotary angle setpoints from the central printing press drive that are distorted by load change reactions.

[0012] On offset rotary printing presses with individual printing cylinder drives, the setpoint encoders for the printing cylinder drive motors are located on the blanket cylinder legs or their drive shafts. The auxiliary encoders on the blanket cylinder legs prevent tooth flank lifting at the meshing point of the blanket cylinder and impression cylinder drive gears due to torque fluctuations. This ensures that the rotation of the blanket cylinder shaft is free from load change reactions, allowing for the output of undisturbed rotation angle setpoints to the printing cylinder drives. The auxiliary encoder assembly on the blanket cylinder consists of an additional second gear mounted on the existing first gear on the blanket cylinder shaft. This second gear is resiliently supported circumferentially against the first gear and, together with it, engages with the impression cylinder drive gear.

[0013] In principle, follower gears for avoiding backlash are known (for example, DE 1 296 145 A, DE 1 761 228 B, DE 195 40 573 C1, DE 197 24 765 A1, EP 0 849 078 A1). However, their use for influencing rotary encoder signals in printing presses with individual drives is not known from the prior art.

[0014] An additional advantage of a secondary arrangement on the blanket cylinder shaft is that it can also reduce the increased backlash of the blanket cylinder drive gear in a pivoted printing position of the blanket cylinder (in a printing unit not involved in printing).

[0015] The invention will now be explained by way of example using an offset rotary printing press with individual drives for the printing cylinders. The accompanying drawings illustrate: Fig. 1: Schematic representation of a section of an offset printing unit showing the position control of a printing cylinder Fig. 2: Constructive design of a trailer assembly

[0016] As from the Fig. As can be seen in section 1, an offset printing press essentially consists of - a printing cylinder 1, which carries the shape of the printed part image on its surface and is inked by an inking unit (not shown). - a rubber blanket cylinder 2 that transfers the printed part image and - a counter-pressure cylinder 3 which transports the substrate on its surface and forms the printing zone together with the rubber blanket cylinder 2.

[0017] The three cylinders 1, 2, 3 are in direct or indirect rolling contact of their outer surfaces.

[0018] The blanket cylinder 2 and impression cylinder 3 are driven by one or more printing press drives HM via associated drive gears 5, 6, which are part of the central drive gear train. The printing cylinder 1 has its own drive M, which can also be a direct drive.

[0019] To synchronize the rotary motion of the individually driven printing cylinder 1 with the rotary motion of the adjacent blanket cylinder 2, driven by the drive gear train, for slip-free image transfer, a rotary encoder G1 is arranged on the shaft or leg of the blanket cylinder 2, and a second rotary encoder G2 for position control of the printing cylinder 1 is arranged on the leg or shaft of the printing cylinder 1. Both rotary encoders G1 and G2 are connected to a drive controller R for the individual drive M of the printing cylinder 1 and form a drive control system for the individual drive M in a known manner.

[0020] On one of the legs of the rubber blanket cylinder 2, to which the rotary angle setpoint generator G1 is assigned, a first gear 5 is arranged in a rotationally fixed manner and is in tooth mesh with the drive gear train.

[0021] A second gear 7 of the same diameter is arranged on the first gear 5 and is rotatably mounted relative to it. This second gear 7 is resiliently supported in the circumferential direction against the first gear 5 and engages together with the first gear 5 in a gear 6 driving the first gear 5, in particular on the counter-pressure cylinder 3, with the first and second gear 5, 7 bearing against the opposite tooth flanks of the driving gear 6.

[0022] The secondary gear 7 is mounted as a narrow and therefore space-saving gear ring with the outer diameter of the gear 5, concentrically and rotatably on a collar of the first gear 5. The secondary gear 7 can be designed very simply, as no complex axial guidance with its own bearing points is required. The maximum rotation angle of the secondary gear 7 is limited by elongated holes in the circumferential direction or holes with an enlarged diameter and stop pins 8 engaging in the holes on the gear 5.

[0023] The spring elements 9 can, for example, be arranged in a manner known from the prior art (DE 1 296 145 A, DE 1 761 228 B) in corresponding recesses in the circumferential direction between the first and second gear 5, 7 or in the gear 5, wherein one of the spring stop surfaces is extended into the plane of the spring stop surface of the other gear ( Fig. 2).

[0024] The auxiliary gear 7 on the shaft of the rubber blanket cylinder 2 engages with the gear 5 in the gear 6 of the counter-pressure cylinder 3 and, due to its spring load, ensures that the teeth of the drive gear 5 bear against the tooth flanks of the drive gear 6, preferably with aligned teeth, both gears 5, 7 are under spring preload.

[0025] While the auxiliary gear 7 does not engage with any other gear according to its function, it may be provided that the gear 5 transmits parts of the drive torques of the printing press drive HM to other assemblies of the printing press, e.g. via a gear 4 freely rotatable on one of the legs / shaft of the printing cylinder 1 to an inking unit.

[0026] If a printing unit is not involved in printing, the blanket cylinder 2 is pivoted away from the printing cylinder 1 and impression cylinder 3. Gears 5 and 6 remain engaged with significantly increased backlash to maintain the mechanical synchronization of their rotation.

[0027] Since, in the swung-off printing position of the blanket cylinder 2, the profile overlap between the narrow auxiliary gear 7 and the gear 6 of the counter-pressure cylinder 3 is insufficient for smooth running of the auxiliary gear 7 in the meshing of the gear 6 on the counter-pressure cylinder 3, the maximum auxiliary gear travel – i.e., the maximum possible rotation of the gears 5 and 7 relative to each other – is limited to an angle that is smaller than would be required to eliminate the backlash at the meshing between the first gear 5 and the drive gear train in the printing-off position of the blanket cylinder 2. This prevents the auxiliary gear 7 from being pressed against the other drive gear flank in the printing-off position. This measure serves to protect the auxiliary gear 7 from wear and has no effect on the tooth flank contact of the gear 5 on the blanket cylinder 2 in the swung-in printing position.

[0028] Regarding the mode of operation of the device according to the invention: The individual drive M transmits a drive torque to the printing cylinder 1, part of which is transmitted to the adjacent blanket cylinder 2 via frictional surface contact. Due to the shaft connection between the blanket cylinder body and its associated gear 5, the torque transmitted via surface contact at gear 5, because it is in the same direction as the printing press drive torque, leads to a reduction in the tooth contact forces at the tooth engagement points 5, 6. These forces depend on the portion of the drive torque of the printing press drive HM that is transmitted via this point. As long as the drive torque of the printing press drive HM, which is transmitted from gear 6 to gear 5, is greater than the torque introduced via frictional contact 1, 2, this is not critical because it does not cause the teeth of the drive gear 5 to lift off the tooth flanks of gear 6.In certain operating situations (drive torque fluctuations, few active printing units, low ink viscosity), where the central drive torque of the printing press drive HM falls below the torque supplied by the individual drive M, tooth flank lifting or even tooth flank replacement would occur without countermeasures, resulting in abrupt changes in rotational angle position, which are detected by the rotary angle encoder G1 and transmitted as abrupt setpoint changes to the drive controller R, which would then trigger an undesired rotation or an undesired speed jump of the individual drive M with the consequence of the formation of duplication phenomena on the printed sheet.

[0029] The auxiliary gear assembly 5, 7, 8, 9, consisting of two spring-loaded gears 5, 7, which replace the single gear 5 on the rubber blanket cylinder 2, ensures that the tooth flanks of the drive gear 5 remain in tooth flank contact with the gear 6. The auxiliary gear 7 is supported on the opposite tooth flank, and the springs arranged circumferentially between the two gears 5, 7 provide the tooth contact force. The spring force must be dimensioned such that the "tooth lift-off force" resulting from the drive torque of the printing press drive HM and the unloading torque of the individual drive M can at least be compensated.

[0030] For the solution according to the invention, it is irrelevant on which side of the rotating body the rotary encoders G1, G2 or the individual drive M are arranged. It can be provided that the rotary encoders G1, G2 and the individual drive M are arranged on the side of the drive gear train; however, the rotary encoders G1, G2 and / or the individual drive M can also be arranged on the side of the rotating body opposite the drive gear train. List of reference symbols used 1 printing cylinder or plate cylinder 2 rubber blanket cylinders 3 counter-pressure cylinders 4 freely rotating gears 5 first gear (on the rubber blanket cylinder) 6 gear 7 second gear, trailing gear, trailing gear 8 stop pins 9 spring elements G1 Rotary Angle Setpoint Generator G2 rotary encoder on the printing cylinder HM printing press drive M Single drive R drive controller

Claims

Offset rotary printing press with a device for synchronizing the rotary motion of a printing cylinder (1) driven individually by a single drive (M) with the rotary motion of a blanket cylinder (2) driven centrally by at least one printing press drive (HM) via a drive gear train, wherein the adjacent cylinders (1, 2) are in rolling contact for ink or varnish transfer onto a substrate, wherein the single drive (M) receives position control signals derived from position or motion signals of a rotary angle or rotary motion setpoint encoder (G1) on the drive gear train, wherein the rotary angle or rotary motion setpoint encoder (G1) is assigned to one leg of the blanket cylinder (2) driven via the drive gear train, wherein a second rotary angle encoder (G2) is assigned to one leg of the printing cylinder (1), wherein both rotary angle encoders (G1,G2) are connected to a drive controller (R) for the individual drive (M) of the printing cylinder (1), wherein a secondary gear (7) preventing tooth flank change or backlash is arranged on the rubber blanket cylinder (2) driven via the drive gear train or its leg, wherein - a first gear (5) is arranged non-rotatably on one of the legs of the rubber blanket cylinder (2), which is in tooth mesh with the drive gear train, and - the secondary gear (7) of the same diameter, which is rotatably mounted relative to this first gear (5), is arranged on this first gear (5), which is resiliently supported in the circumferential direction against the first gear (5) and engages together with the first gear (5) in a gear (6) driving the rubber blanket cylinder (2), so that the first gear (5) and secondary gear (7) are in contact with opposite tooth flanks of the gear (6). Offset rotary printing press according to claim 1, wherein the first gear (5) and the auxiliary gear (7) engage together with the gear (6) of a counter-pressure cylinder (3). Offset rotary printing press according to claim 1, wherein the rotational mobility of the auxiliary gear (7) is limited to compensating for a maximum backlash which is less than the backlash occurring at the tooth engagement between the first gear (5) and the drive gear train in a printing-off position of the blanket cylinder (2). Offset rotary printing press according to claim 1, wherein the auxiliary gear (7) is only in tooth engagement with the gear (6) of the drive gear train. Offset rotary printing press according to claim 1, wherein the first gear (5) engages in a freely rotatable gear (4) on one of the legs of the printing cylinder (1). Offset rotary printing press according to claim 1, wherein the spring force is dimensioned such that the ‘tooth lifting force’ resulting from the drive torque of the printing press drive (HM) and the relief torque of the individual drive (M) can at least be compensated. Offset rotary printing press according to claim 1, wherein the rotary encoders (G1, G2) and the individual drive (M) are arranged on the side of the drive wheel train.

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