EP0615843A1 - Printing unit with a mechanism for ink distributing cylinders - Google Patents

Abstract

A printing unit (10) comprises a number of inking rollers (20) rotatably mounted about their axes (48, 50, 52), a rotatable shaft (90) and a mechanism (32) for axially reciprocating the rollers (20) in response on the rotation of the shaft (90). The mechanism (32) comprises a number of eccentrics (116) fixed on the shaft (90) which rotate with the shaft (90). Each of the eccentrics (116), as it rotates with the shaft (90), transfers a single torque to the shaft (90) in response to the axial movement of a respective one of the rollers (20). The fixed positions of the eccentrics (116) relative to one another on the shaft (90) minimizes the sum of the individual torques and the fluctuations in the sum of the individual torques during the rotation of the eccentrics (116). The harmful effect of the torques on the printed image is thus minimized.

Description

The present invention relates to a printing unit of a printing press, and in particular to a printing unit with a mechanism for inking rollers.

The U.S. Patent No. 3,994,222 discloses a printing unit with rotating inking rollers and a mechanism for axially reciprocating the friction rollers. The reciprocating movements of the rubbing rollers promote the even application of the ink film to the rollers. The mechanism producing the reciprocating movement of the friction rollers comprises a rotatable shaft with several eccentrics mounted thereon and rotating therewith. The rotating eccentric actuate a lever mechanism which axially moves the friction rollers back and forth. The axial movement of the friction rollers is resisted by the inertia effect of the friction rollers and by the friction between them and the other rollers with which they come into contact during the axial movement. This resistance is transmitted to the shaft by the rotating eccentrics in the form of torques which oppose the rotation of the shaft. Since the shaft is rotated by the same gear train as the printing cylinder in the printing press, the torques transmitted from the eccentrics to the shaft can be transmitted to the rotating printing cylinders by the gear train. Such transmitted torques can significantly affect the printed image.

According to the present invention, a printing unit comprises a number of inking rollers which are rotatably mounted about their axes, a rotatable shaft and a mechanism for generating the axial reciprocation of the friction rollers due to the rotation of the shaft. The mechanism includes one Number of eccentrics that are attached to the shaft and rotate with it. Each of the eccentrics produces an axial movement of a respective one of the friction rollers when it rotates with the shaft. Each of the eccentrics transmits a single torque to the shaft when it moves the respective friction roller axially. The sum of the individual torques changes when the circumferential positions of the eccentrics and the axial positions of the friction rollers change. The eccentrics are fixed on the shaft in positions which are offset with respect to one another about the axis of the shaft. The offset positions of the eccentrics minimize both the sum of the individual torques and the magnitudes of the changes in the sum of the individual torques during the rotation of the eccentrics.

In a printing unit constructed according to the present invention, the inking rollers are moved back and forth practically without impairing the printed image. Each of the eccentrics rotating with the shaft moves its respective friction roller axially back and forth. The axial position of the friction roller changes as the circumferential position of the rotating eccentric changes. Since the rotating eccentric is connected to the friction roller, this transmits a torque to the shaft while it is moving the friction roller back and forth. The magnitude of the torque changes as the circumferential position of the rotating eccentric changes. Each of the rotating eccentrics transmits a single torque that contributes to an overall torque. Likewise, the total torque changes in size when the individual torques change in size. This total torque can be transmitted through the gear train to the rotating printing cylinders and can significantly affect the print image. However, the present invention minimizes the total torque and the magnitude changes in the total torque. The total torque thus remains at a relatively low value and is not subject to large fluctuations. The low, even torque affects the smooth running of the printing unit cylinders less than a larger, strongly fluctuating torque, which has an impact effect on the printing unit cylinders.

Fig. 1

ist eine schematische Ansicht eines Druckwerks mit einer ersten Ausführung der vorliegenden Erfindung;

Fig. 2

ist eine Draufsicht auf einen Teil des in Fig. 1 gezeigten Druckwerks;

Fig. 3

ist eine Ansicht entlang der Linie 3-3 der Fig. 2;

Fig. 4

ist eine Draufsicht auf einen Teil des in Fig. 1 gezeigten Druckwerks;

Fig. 5A, 5B und 5C

sind jeweils eine Ansicht entlang der Linien 5A-5A, 5B-5B und 5C-C der Fig. 4;

Fig. 6 und 7

sind graphische Darstellungen der Drehmomentcharakteristik des in Fig. 1 gezeigten Druckwerks;

Fig. 8

ist eine graphische Darstellung der Drehmomentcharakteristik eines hypothetischen Druckwerks zum Vergleich mit der Fig. 7;

Fig. 9

ist eine schematische Ansicht eines Druckwerks mit einer zweiten Ausführung der vorliegenden Erfindung;

Fig. 10

ist eine Ansicht von Teilen des in Fig. 9 gezeigten Druckwerks.

These and other features of the present invention are further illustrated by the following description of preferred exemplary embodiments in conjunction with the accompanying drawings, which are explained below.

Fig. 1

is a schematic view of a printing unit with a first embodiment of the present invention;

Fig. 2

is a plan view of part of the printing unit shown in Fig. 1;

Fig. 3

Figure 3 is a view taken along line 3-3 of Figure 2;

Fig. 4

is a plan view of part of the printing unit shown in Fig. 1;

5A, 5B and 5C

Figure 4 is a view along lines 5A-5A, 5B-5B and 5C-C of Figure 4, respectively;

6 and 7

are graphical representations of the torque characteristic of the printing unit shown in Fig. 1;

Fig. 8

is a graphical representation of the torque characteristic of a hypothetical printing unit for comparison with FIG. 7;

Fig. 9

is a schematic view of a printing unit with a second embodiment of the present invention;

Fig. 10

is a view of parts of the printing unit shown in Fig. 9.

As shown schematically in FIG. 1, a printing unit 10 comprises a plurality of rollers and cylinders in order to print on a running web 12. An ink fountain roller 14 receives ink from an ink fountain 16. A siphon roller 18 reciprocates between the ink fountain roller 14 and a first ink rub roller 20 to transfer ink from the ink fountain roller 14 to the first ink rub roller 20. Additional rubbing rollers 20 transfer the ink to a plurality of inking rollers 22, which apply the ink to a printing plate on a plate cylinder 24. A blanket cylinder 26 transfers the inked print image from the printing plate on the plate cylinder 24 to the web 12 as it moves through the nip between the blanket cylinder 26 and a printing cylinder 28. The impression cylinder 28 can be another blanket cylinder for printing on the other side of the web.

The printing unit 10 further comprises a drive and a mechanism 32 for generating the back and forth movement of inking rollers. The drive 30 drives a gear train 34, which is shown schematically in FIG. 1 in broken lines. The gear train 34 rotates the plate cylinder 24, the blanket cylinder 26, the impression cylinder 28 and a plurality of inking rollers 20. The mechanism 32 moves these friction rollers axially back and forth. The axial movements of these rubbing rollers contribute to the uniform distribution of the ink film transferred to the inking rollers 22.

As shown in detail in FIG. 2, there are three pins 42, 44 and 46 with respective axes 48, 50 and 52 in the printing unit 10. The pins 48, 44 and 46 are rotatable about their axes in a side frame 54 of the printing unit 10 stored and are connected to respective of the friction rollers 20 (as shown schematically) which rotate with the pins 42, 44 and 46 in the printing unit 10. Mechanism 32 reciprocates these friction rollers 20 by axially reciprocating pins 42, 44 and 46 as the pins rotate about their axis.

The pins 42, 44 and 46 extend in sleeves 60 through the side frame 54 and are axially movable and rotatably mounted in the sleeves 60 on roller bearings 62. Sealing sleeves 64 and further seals 66 seal the sleeves 60, so that no color can flow in from the friction rollers 20.

Three drive wheels 70 are received on the three journals 42, 44 and 46 to rotate them. A first intermediate gear 72 engages the first drive gear 70 on the first pin 42 and also engages the second drive gear 70 on the second pin 44. The first idler gear 72 is supported in a roller bearing 74 and rotates freely about a shaft 76 which is attached to the side frame 54. The first idler gear 72 thus enables the first drive gear 70 on the first pin 42 to be driven by the second drive gear 70 on the second pin 44.

A second intermediate gear 78 engages in the second drive gear 70 on the second pto shaft 44 and in the third drive gear 70 on the third pintle shaft 46. The second idler gear 78 is also connected to a rotatable shaft 80. Thus, the idler gear 78 drives the second and third drive gears 70 and also rotates the rotatable shaft 80.

As shown in FIG. 3, the drive 30 rotates the second idler gear 78 via a pair of drive wheels 84. Also shown in FIG. 3 is a pair of drive wheels 88 that has a dampening roller drives with a pin 89. The drive wheels 88 rotate the dampening roller in response to the rotation of the second drive wheel 70 on the second pin 44.

Reference is again made to FIG. 2, in which the mechanism 32 has a shaft 90 with an axis 92 extending perpendicular to the axes 48, 50 and 52 of the pins 42, 44 and 46. The shaft 90 is rotatably supported about its axis 92 in bearings 94 which are located at the shaft ends. One of the bearings 94 is located in an arm 96 that is bolted to the side frame 54, as shown in FIG. 3. The other bearing 94 is located in a housing 98, which is also screwed into the side frame 54. In the housing 98 there is also a worm wheel 100 which is connected to the shaft 90 and engages in a worm thread on the shaft 80. The shaft 90 is thus connected to the second intermediate gear 78 and is rotated by the latter through the shaft 80 and the worm gear 100. In addition, the shaft 90 and the three pins 42, 44 and 46 are connected to the drive 30 by the second intermediate wheel 78 and are all rotated by this at the same time.

The mechanism for reciprocating the friction rollers also comprises three eccentrics 110, 112 and 114 mounted on the shaft 90. Each of the three eccentrics 110, 112 and 114 consists of an eccentric part 116, a housing 118 and a cover plate 120. The eccentric part 116 of the first and second eccentrics 110, 112 are arranged axially on the shaft 90 between an enlarged part 121 of the shaft 90 and the ends of the sleeves 122 fitted over the shaft 90. The eccentric part 116 of the third eccentric 114 is placed axially between two of the sleeves 122 on the shaft 90. The three eccentric parts 116 are all fixed on the shaft 90 and rotate when the shaft 90 rotates in the housing 118 in sliding contact with the housing.

As shown in FIGS. 4 and 5A to 5C, the three eccentric parts 116 are fixed on the shaft 90 in positions which are circumferentially offset from one another. This means that the center 123 of each eccentric part 116 is offset by 120 ° with respect to the center 123 of each other eccentric part 116 about the axis 92 of the shaft 90.

Mechanism 32 for reciprocating the friction rollers further includes three connectors 124, 126 and 128, as shown in FIG. 2. The first connector 124 connects the first cam 110 to the first pin 42. The second connector 126 connects the second cam 112 to the second pin 44, and the third connector 128 connects the third cam 114 to the third pin 46. Each of the three connectors 124, 126 and 128 has a bracket 130 which is rotatably connected to the associated eccentric housing 118 by means of a bolt 132. Each bracket 130 is axially attached to the associated pin 42, 44 or 46 with an axial fastener 134 and has a roller bearing 136 for rotation of the associated pin shaft 42, 44 or 46 in the bracket 130.

During operation of the printing unit 10, the pins 42, 44 and 46 are rotated by the drive 30 via the gear train, which consists of the various gears described above. The rotation of the pins 42, 44 and 46 causes the rotation of the associated friction rollers 20, which lead ink through the printing unit.

The shaft 90 in the mechanism 32 is rotated together with the rotating pins 42, 44 and 46, as also described above. When the shaft 90 rotates, the eccentric parts 116 rotate in sliding contact with the eccentric housings 118 and thereby cause the eccentric housings 118 to move back and forth parallel to the Axes 48, 50 and 52 of the pins 42, 44 and 46. Since the pins 42, 44 and 46 are axially connected to the eccentric housing 118 by the connecting bracket 130, the reciprocating movements of the eccentric housing 118 on the bracket 130 and the pin 42, 44 and 46 exercised. As shown in FIG. 1, the teeth of the first and second idler gears 72 and 78 are wide enough to remain engaged with the teeth of the associated drive gears 70 as they move axially with the pins 42, 44 and 46. Thus, the mechanism 32 causes the pins 42, 44 and 46 to move axially back and forth as they are rotated by the drive 30. The back and forth movements of the pins 42, 44 and 46 are oscillation-like movements which promote the distribution of the paint by the rotating rubbing rollers 20.

While the rotating eccentric parts 116 axially reciprocate the pins 42, 44 and 46 and the friction rollers 20, the rotating eccentric parts 116 and the shaft 90 exert alternating forces on the side frame 54 through the arm 96 and the housing 98. Such forces can shake the side frame 54. The rotating eccentric parts 116 also transmit torques to the rotating shaft 90. Such torques arise from the inertia effect of the reciprocating friction rollers 20 and from the friction between the latter and other rollers in the printing unit 10, with which the friction rollers 20 move axially come into sliding contact. These torques in the rotating shaft 90 can be transmitted via the various gears to the drive 30 and to the printing cylinders 24, 26 driven thereby, and thus adversely affect their rotation and the image printed on the web 12.

Mechanism 32 for reciprocating the friction rollers according to the present invention minimizes that disadvantageous effect of the rotating eccentric parts 116. A single torque transmitted to the shaft 90 by a single rotating eccentric part 116 changes when the rotating eccentric part 116 changes the axial position of the associated friction roller 20. The individual torque is thus at all times related to the currently assumed circumferential position of the individual eccentric part 116. Therefore, the individual torque can be represented with a rectified sine wave. The single torque reaches a maximum value when the rotating eccentric part 116 has moved its associated friction roller 20 in the one axial direction and in the reverse axial direction at the end of its movement distance. The rectified sine wave representing the individual torques will thus reach a maximum value when the rotating eccentric part 116 is in the position in which it reverses the axial direction of movement of the associated friction roller 20.

The total torque in the shaft 90 resulting from the rotation of the three eccentric parts 116 is equal to the sum of the three individual torques transmitted from the three eccentric parts 116 to the shaft 90. The total torque is therefore at all times related to the currently assumed circumferential positions of the three rotating eccentric parts 116 ° are offset about the axis 92. Since the three individual torques are related to the circumferential positions of the three individual rotating eccentric parts 116, the individual rectified sine waves representing the three individual torques are phase-shifted by 120 °. The axial movements of the three reciprocating friction rollers 20 are equally out of phase by 120 °. The individual torques therefore reach the maximum at different times, but at equal time intervals during a rotation of the shaft 90 by 360 °. It follows from this that the sum of the individual torques at any point in time does not differ significantly from the sum at any other point in time. Changes in the sum of the individual torques can thus be minimized in size. The total torque of the rotating shaft 90 is therefore not subject to large fluctuations during the operation of the printing unit 10 and retains an essentially constant value. Likewise, the forces transmitted from the rotating shaft 90 to the printing cylinders 24 and 26 in the printing unit 10 remain at an essentially constant level. Such constant forces damage the printed image much less than changing forces which act on the cylinders 24 and 26 and can cause them to vibrate.

   t = 0, 1, . . . 360.The principles outlined above regarding torque in shaft 90 are graphically illustrated in FIGS. 6 and 7. FIG. 6 shows the three individual torques transmitted from the three individual eccentric parts 116 shown in FIGS. 5A to 5C to the shaft 90. The value of the torque transmitted from each eccentric part 116 to the shaft 90 is shown on the vertical coordinate axis in FIG 6 measured. The angular movement of each eccentric part 116 about the axis 92 of the shaft 90 is measured on the horizontal coordinate axis in FIG. 6 as a time value. Curve a (t) represents the torque attributable to the eccentric portion 116 of FIG. 5A and takes the form of a rectified sine wave as described above. In particular, the torque presented with curve a (t) is a function of an angular movement as follows:

t = 0, 1,. . . 360.

Da die drei Exzenterteile 116 der Fig. 5A, 5B und 5C um die Achse 92 der Welle 90 um 120° versetzt sind, sind auch die drei Kurven a(t), b(t) und c (t) entlang der horizontalen Koordinatenachse der Fig. 6 um 120° versetzt. Somit erreichen die drei Kurven a(t), b(t) und c(t) (mit je einem Einheitswert von 1) Höchstwerte in gleichmäßigen Zeitabständen während einer vollständigen Umdrehung der Welle 90. Dadurch ergibt sich eine Minimierung der Änderungen in der Summe der mit den Kurven a(t), b(t) und c(t) dargestellten einzelnen Drehmomente, wie oben beschrieben. Dies ist in Fig. 7 graphisch dargestellt, worin $\text{d(t) = a(t) + b(t) + c(t)}$

. Der Wert der Kurve d(t) schwankt in einem kleinen Bereich ΔT. Somit zeigt die Kurve d(t) den relativ konstanten Wert des Gesamtdrehmoments, der gemäß der vorliegenden Erfindung in der Welle 90 während ihrer Rotation aufrechterhalten wird.The curves b (t) and c (t) similarly represent the torques attributable to the eccentric parts 116 of FIGS. 5B and 5 (c) as follows:

Since the three eccentric parts 116 of FIGS. 5A, 5B and 5C are offset by 120 ° about the axis 92 of the shaft 90, the three curves a (t), b (t) and c (t) are also along the horizontal coordinate axis of FIG Fig. 6 offset by 120 °. Thus, the three curves a (t), b (t) and c (t) (each with a unit value of 1) reach maximum values at equal time intervals during a complete rotation of the shaft 90. This results in a minimization of the changes in the sum of the with the curves a (t), b (t) and c (t) individual torques as described above. This is shown graphically in Figure 7, in which $\text{d (t) = a (t) + b (t) + c (t)}$

. The value of the curve d (t) fluctuates in a small range ΔT. Thus curve d (t) shows the relatively constant value of the total torque that is maintained in shaft 90 during its rotation in accordance with the present invention.

In addition to minimizing the fluctuations in the total torque in the shaft 90, the present invention also minimizes the maximum value achieved by the total torque.

For example, curve d (t) shown in FIG. 8 represents the total torque that would form in shaft 90 if the three eccentrics 116 were not offset about axis 92. In this case, each of the three individual torques with a unit value of 1 would reach a maximum value. Then the total torque would peak at a unit value of 3, as opposed to the unit value of only 2 for maximum values of the total torque shown in FIG. 7. The present invention thus minimizes the maximum values of the total torque reached in the shaft 90 and also the range ΔT in which the value of the total torque fluctuates, since the three eccentrics 116 are optimally offset about the axis 92.

   n = Gesamtanzahl der Exzenter (vorzugsweise mindestens drei)
Die vorliegende Erfindung kann ferner auf Druckwerke angewandt werden, in welchen Exzenter auf einem oder mehreren Wellen, die durch einen gemeinsamen Getriebezug rotiert werden, angebracht sind. Solch ein Druckwerk ist in Fig. 9 schematisch dargestellt.A first preferred embodiment of the present invention has been described so far, in which the mechanism 32 for reciprocating the friction rollers 20 comprises three eccentrics 116 mounted on the shaft 90. However, the present invention can also be applied to mechanisms in which different numbers of eccentrics are mounted on a shaft. In such a case, two of the eccentrics would be offset around the axis of the shaft, at least by the following angle A:

n = total number of eccentrics (preferably at least three)
The present invention can also be applied to printing units in which eccentrics are mounted on one or more shafts which are rotated by a common gear train. Such a printing unit is shown schematically in FIG. 9.

As shown in Fig. 9, a printing unit 200 has an upper plate cylinder 202 and an upper blanket cylinder 204 for transferring a print image to the top of a web 206 and a lower plate cylinder 208 and a lower blanket cylinder 210 for transferring a print image to the bottom of the web Track 206. Drive 212 and gear train 214 rotate cylinders 202, 204, 208 and 210. Printing unit 200 also has an upper mechanism 220 and a lower mechanism 222 for reciprocating the friction rollers.

The upper mechanism 220 includes a pair of eccentrics 224 and 226 mounted on a rotatable shaft 228 with an axis 229. The eccentrics 224 and 226 are connected to a respective pair of inking rollers 230 and 232 and move them axially back and forth as the shaft 228 rotates. The eccentrics 224 and 226 can be connected to the friction rollers 230 and 232 in the manner described in FIG. 2.

The lower mechanism 222 also includes a pair of eccentrics 236 and 238 which are mounted on a rotatable shaft 240 with an axis 241. The eccentrics 236 and 238 are likewise connected to a respective pair of inking rollers 242 and 244 and move them axially back and forth as the shaft 240 rotates. The friction rollers 230, 232, 242 and 244 are rotated together with the shafts 228 and 240 by the drive 212 via the gear train 214.

The eccentrics 224, 226, 236 and 238 on the two shafts 228 and 240 are arranged with respect to each other according to the present invention. This means that the two eccentrics 224 and 226 are offset by an angle of 180 ° about the axis 229 of the shaft 228, in accordance with the formula A = 360 / n, where n = 2. That of the two eccentrics 224 and 226 on the neighboring side frames exercised back and forth Floating forces therefore tend to cancel each other out and are thus stabilized to minimize the shock of the side frame resulting from the upper mechanism 220. The other two eccentrics 236 and 238 are similarly offset by an angle of 180 ° about the axis 241 of the shaft 240 and have the same minimal tendency to shake the adjacent side frame. In addition, each of the eccentrics 224, 226, 236 and 238 is offset with respect to each other of these eccentrics 224, 226, 236 and 238 by an angle of at least 90 °, according to the formula A = 360 / n, where n = 4. Da If the two pairs of eccentrics are on separate shafts 228 and 240, the latter angle A is measured between positions which are superimposed on the horizontal and vertical coordinate axes X and Y, as shown in FIG. 10. With the four eccentrics 224, 226, 236 and 238 so arranged with respect to one another, as shown in FIG. 10, the sum of the respective torques transmitted in the gear train 214 and the range in which the sum fluctuates are minimized.

Claims (11)

A printing unit (10) which comprises the following features:
a number of inking rollers (20) which are rotatably mounted about their axes (48, 50, 52);
a rotatable shaft (90) with an axis (92);
a gear (34) for rotating said rollers (20) and said shaft (90);
a mechanism (32) for axially reciprocating said rollers (20) in response to rotation of said shaft (90), said mechanism (32) comprising a number of eccentrics (116) mounted on said shaft ( 90) are fixed and rotate therewith and each of the eccentrics (116) axially moves a respective one of the said rollers (20) during the rotation of the said shaft (90);
each of said eccentrics (116) transmits a single torque to said shaft (90) while the eccentric (116) rotates with the shaft (90) and axially moves a respective one of said rollers (20), the sum of said individual torques changes when the circumferential positions of said eccentrics (116) and the axial positions of said rollers (20) change during rotation of said eccentrics (116); and
a compensation arrangement in said mechanism (32) whereby the sum of said individual torques and the magnitude of the changes in the sum of individual torques resulting from the rotation of said eccentric (116) are minimized. A printing unit (10) according to claim 1,
characterized by
that the compensating arrangement consists in that said eccentrics (116) are offset with respect to one another about said axis (92) of said shaft (90). A printing unit (10) according to claim 1,
characterized by
that during a complete rotation of said shaft (90) about said axis (92), said individual torques reach maximum values at uniform time intervals. A printing unit (10) according to claim 1,
characterized by
that each of the eccentrics (116) is offset with respect to each of the other eccentrics (116) about the axis (92) of the shaft (90), namely by an angle of at least A, where A = 360 ° / n, and n is the total number of the mentioned eccentrics. A printing unit (10) according to claim 1,
characterized by
that the number of eccentrics (116) consists of three eccentrics (116) which are fixed on the shaft (90) in positions which are offset by 120 ° with respect to one another about the axis (92) of said shaft (92). A printing unit (10) according to claim 1,
characterized by
that the mechanism (32) moves the rollers (20) axially out of phase with respect to one another by 120 °. A printing unit (200) which comprises the following features:
a number of inking rollers (230, 232, 242, 244) which are rotatably mounted about their axes;
a number of rotatable shafts (228, 240) with respective axes (229, 241);
a gear (214) for rotating said rollers (230, 232, 242, 244) and said shafts (228, 240) simultaneously;
a mechanism (220, 222) for axially reciprocating said rollers (230, 232, 242, 244) in response to simultaneous rotation of said shafts (228, 240), said mechanism (220, 222) being one Number of eccentrics (224, 226, 236, 238) mounted on said shafts (228, 240) rotating with the shafts (228, 240) and each of said eccentrics (224, 226, 236, 238) during the rotation of the respective shaft (228, 240) axially moves a respective one of said rollers (230, 232, 242, 244);
each of said cams (224, 226, 236, 238) transmits a single torque to the respective said shaft (228, 240), while the eccentric (224, 226, 236, 238) with said respective shaft (228, 240) rotates and moves a respective one of said rollers (230, 232, 242, 244) axially, the sum of said individual torques changing when the circumferential positions of said eccentrics (224, 226, 236, 238) and the axial positions of the change said rollers (23, 232, 242, 244) while rotating said eccentrics (224, 226, 236, 238); and
a balancing arrangement in said mechanism (220, 222) whereby the sum of said individual torques and the magnitude of the changes in the sum of individual torques are minimized. A printing unit (200) according to claim 7,
characterized by
that the compensating arrangement consists in that the named eccentrics (224, 226, 236 and 238) assume positions on the said shafts (228, 240) which are circumferentially offset with respect to one another. A printing unit (200) according to claim 7,
characterized by
that during a complete revolution of said shafts (228, 240), said individual torques reach maximum values at regular time intervals. A printing unit (200) according to claim 7,
characterized by
that each of the eccentrics (224, 226, 236, 238) is offset by an angle of at least A with respect to each of the other eccentrics (224, 226, 236, 238), where A = 360 ° / n, and n is the total number the mentioned eccentric (224, 226, 236, 238) and is three or larger. A printing unit (200) according to claim 7,
characterized by
that the number of rotatable shafts are two rotatable shafts (228, 240) and that the number of eccentrics are four eccentrics (224, 226, 236, 238), ie two eccentrics on each of said shafts (228, 240), whereby each of the four eccentrics (224, 226, 236, 238) is circumferentially offset by at least 90 ° with respect to each other of the four eccentrics (224, 226, 236, 238).

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