DE19934658A1 - Printing device - Google Patents

Abstract

Radius (rPC) of image cylinder (2), radius (rIT) of transfer cylinder (5), material and form of elastic coating (7) and positioning of the cylinders are selected so the overdrive, resulting from changes in engagement due to non-circular shape of image cylinder, is expressed as: VIT at nip/VIToutside of nip. Hence possible errors due to non-circular shape of image cylinder are prevented.

Description

The invention relates to a printing device with an image cylinder, a Bilderzeu supply device for imaging the lateral surface of the image cylinder and an over transfer cylinder, which transfers the image from the image cylinder to a printing material, wherein the transfer cylinder has an elastic jacket that is on the image transfer The area of the image cylinder has a deformation and one of the cylinders drives the other over friction.

Such printing devices are mainly found in color copiers with electrostatic Imaging application. Such a printing device is used, for example, in the EP 0 791 860 A2. To achieve high print quality, the Prints have high register accuracy. One tries this requirement with Measurements and controls of the image generation of the image cylinders, by aligning the pictures to each other so that the different colors printed exactly on top of each other. However, it has been found to be a source of error is present that does not refer to the mutual assignment, but to the Quality of the printing process for each individual color: due to an out-of-roundness of the image fluctuations in the angular velocity of the driven cylinder Cylinder, i.e. the image cylinder or the transfer cylinder. It also occurs when imaging an out-of-round image cylinder, the image is already distorted generation on. These errors within the printing of each color affect the Image quality in that even if the leading edges of each color print the following areas are no longer set up are in register since they are pulled apart by the sources of error described or be upset. The result is a mismatch in image areas that perceived as color deviations and blurred boundaries.

The invention is therefore based on the object of a printing device at the outset  mentioned type in such a way that register errors within the individual, pressure generated by a printing device can be avoided.

The object is achieved in that the radius of the image cylinder, the radius of the transfer cylinder, the material and the design of the elasti the jacket and the storage of the cylinders are selected and designed in such a way that for the cylinder driven by the friction one of changes in the Engagements - as a result of image cylinder out-of-round - dependent overdrive results in the possible image due to the out-of-roundness of the image cylinder mistakes are avoided.

The invention is based on the observation that the ovality of the image cylinder leads to another "source of error". One of them is that an area of the Image cylinder, which has a larger radius due to its out-of-roundness, not only is driven more slowly in terms of angular velocity, as is the case with rigid ones Surfaces is the case, but at the same time an acceleration through behavior of the elastic jacket. This is explained using a figure. Kick it So two image distorting effects that overlap and their tendency are opposed. The latter, however, does not in itself lead to the effects cancel each other out.

With regard to the effect described above, the invention is based on the knowledge that that it is possible to change a behavior by setting different boundary conditions to achieve ten of the elastic jacket, which leads to the abolition of the effects mentioned leads. This behavior of the elastic jacket is that it is larger Radii of the image cylinder is compressed more than smaller ones and therefore must "flow" faster through the smaller gap. This makes it possible for a the occurrence of fluctuations against the angular velocity, as is the case with a drive with a rigid cylinder would prevent. An angular velocity error can occur in this way thus be eliminated at its source of origin in the area of friction, by the selection and configurations mentioned such that the angles speed of the cylinder driven by the friction despite an out-of-roundness of the image cylinder is constant. It does not matter whether the image cylinder is included  is equipped with a drive and drives the transfer cylinder or vice versa. However, the transfer cylinder is preferably equipped with the drive and drives the image cylinder. This is a convenient flow of power because of the transmission cylinder then has a load on both sides.

Furthermore, it has been shown that imaging caused by out of roundness Error that already manifests itself on the image cylinder with the illustration occurs: The out-of-roundness of the image cylinder affects the image generation at first to the extent that lines that are transverse to the direction of movement of the image cylinder are further apart in the area of larger radii than in areas of smaller radii. The reason is that the imaged area with the same angular velocity and larger Radii is larger than for smaller radii. Without a countermeasure, too this causes an error of the type mentioned at the beginning. However, this too Fall is countered by the behavior of the elastic jacket in their tendency directed effect achieved. This behavior of the elastic jacket is that when interacting with a larger radius, the elastic material more is pressed together and therefore its surface in the image transmission area more is pulled apart. This is the surface that is pulled apart stretched areas of an image from the image cylinder to the transfer cylinder upset. The surface then stretches in the contact area after the deformation rich again between the image and transfer cylinders, which makes the further apart lines with large radii are merged more than that Lines with smaller radii because the deformation was less there. This effect ent speaks of the change in overdrive due to the out-of-round condition Radius changes. So here, too, there are two opposite tendencies that are however, also do not cancel automatically. Through an appropriate selection and However, the above-mentioned circumstances can be designed such that image errors, which due to the out-of-roundness of the image cylinder during the imaging of the same arise from the change in the overdrive as a result of the runout of the Image cylinder-related changes in engagement are corrected as soon as the Surface of the elastic jacket after passing through the deformation on the Image transfer point relaxed and error compensation occurs.  

Both error compensations can be achieved through a number of configurations of the Affect printing device. The radius has an immediate effect on this of the image cylinder and the material and design of the elastic jacket as well the storage of the cylinders. The radius of the transfer cylinder, however, has only little influence if extreme values are chosen. The selection of designs conditions and material properties can partly be determined mathematically, whereby they however, because of the large number of influencing factors, ultimately verified by tests and need to be corrected. Partly the values, properties and dimensions nations can also be determined through series of tests. In practice are part of these configurations and selection options within certain areas give, so that the freely selectable factors must be changed so that the mentioned goals can be achieved. For example, there are certain sizes of the radii of Image cylinder and transfer cylinder due to the space required for image generation direction and other necessary or desirable devices. The choice of materials for the elastic sheath is also limited, especially as far as possible Materials still have other requirements, such as the behavior of the waiters surface for image transmission, durability and low wear as well as good power transmission wearing. With regard to the mounting of the cylinders, a fixed mounting is possible it is possible that at least one of the cylinders has a spring-loaded bearing, such that that depending on the out-of-roundness of the image cylinder, a change in the center distance is effected. Then the selected spring constant is one of those to achieve the desired success factors to be selected.

When determining these influencing variables, it has been shown that the achievement of a constant angular velocity of the driven cylinder can be achieved simultaneously with the compensation of the image errors caused by the out-of-roundness of the image cylinder. The conditions for such a constant angular velocity can be determined computationally, the decisive variables being the radius of the image cylinder (r _PC ) and the sensitivity (Sens). The sensitivity indicates the strength of the change in the ratio of the surface speed (V _PC ) of the image cylinder to the surface speed (V _IT ) of the transfer cylinder as a function of the engagement (Eng), the latter being the measure of the infeed and thus the deformation.

For permanently mounted cylinders, the condition for a constant angular velocity of the cylinder driven by friction is:

Sens _{M is} the Sensitivity Magic, that is the sensitivity at which the angular velocity (ω _PC or ω _IT ) of the driven cylinder no longer changes due to radius deviations (Δr _PC ) of the image cylinder. Eng gives the average engagement between the cylinders. Sens _T is the amount of change in the ratio of the surface speeds of the image cylinder to the transfer cylinder, that is

due to the change in torque, and T is the mean torque.

This means that you can specify a radius of the image cylinder and by off choice of material and design of the elastic jacket adjust a sensitivity bar, by which the above condition is met. Or it would be possible to define a sensitivity and the matching radius of the image cylinder determine. Since the latter by the space requirements of the aggregates to be attached It is advisable to choose the first solution. At a spring-loaded storage, the spring constant also affects the size of the Sensi tivity. On the effects of material selection and designs detailed below.

In practice it has been shown that the condition mentioned can be simplified in many cases. So it is possible that for cases in which the change in sensitivity due to torque changes is small, this torque-dependent part can be neglected for the fulfillment of the condition. It is therefore usually sufficient that the following condition is met:

Furthermore, it has been shown that in the event that the radius (r _PC ) of the image cylinder is very large in relation to the engagement (Eng), the latter is negligible. The condition to be met, which is sufficient for most applications, is then:

These aforementioned relationships between the sizes make it easier to find the circumstances with which the object of the invention can be achieved. This consists in that the Sensitivity Magic (Sens _M ) is achieved through a selection of the material as well as the design of the elastic jacket and the design of the cylinder bearings. These circumstances can be influenced by a variety of measures, although calculations are often possible, but it is essential to carry out a series of tests for each individual machine configuration and to change individual values until the Sensitivity Magic (Sens _M ) is found .

For example, the material for the elastic sheath can be selected according to the Poisson number () of the material. The Poisson number results from the behavior of a material that is subjected to tensile forces. The Poisson number () is the ratio of the transverse strain (ε _c ) to the longitudinal strain (ε _n )

The negative sign arises from the fact that the transverse expansion is a shrinkage is. The relationship between Poisson's number and sensitivity is that the latter increases as the Poisson number increases.

Furthermore, the selection of the material for the elastic jacket can be made according to the compressibility of the material. The compressibility refers to the change in volume under pressure, whereby

the change in volume (ΔV) to the initial volume (V) is proportional to the Ratio of the applied pressure to the compression module (K) with reverse Sign behaves. The compression module is a material constant. Here applies that the sensitivity decreases as the compression modulus is reduced  device. The compression module is especially for porous material for the size of the Sensitivity crucial material constant. The more air or gas inclusions in material, the lower the compression modulus and thus the sen sitivity. Through such a porous configuration, material such as rubber, the as a solid material has a high compression modulus, change such that the desired sensitivity, i.e. the sensitivity magic is achieved.

The Sensitivity Magic can also be achieved by a corresponding Thickness of the elastic jacket is chosen. The relationship applies: the thicker the elastic jacket, the lower the sensitivity.

Another way to achieve Sensitivity Magic while doing so To guarantee other properties is that the elastic jacket different layers. For example, one embodiment provides that the elastic jacket consists essentially of a highly elastic material and a in relation to it has a relatively hard, but still elastic cover layer. To this This way a low sensitivity and at the same time a hard surface for the Achieve image transfer. An elastic is expediently used as the cover layer cal material such as rubber, preferably selected polyurethane. Another execution tion form provides that the elastic jacket consists essentially of a highly elastic material exists, in which at least a relatively hard intermediate layer is embedded is. This achieves a wide range for the adjustability of the sensitivity. This setting is made by the position and the modulus of elasticity of the inserted Intermediate layers.

If a spring-loaded bearing is selected for at least one of the cylinders, a corresponding spring constant can also be selected to achieve a sensitivity magic (this is a sensitivity magic with regard to the overall system, i.e. including the elastic jacket and the spring-loaded bearing) . In such an embodiment, the spring action determines how much the change in radius (Δr _PC ) acts as a change in engagement. This creates a virtual sensitivity, whereby the sensitivity decreases with increasing suspension. Such a suspension makes it possible to achieve the conditions for Sensitivity Magic even with an elastic jacket made of relatively strong material. The spring-loaded bearings are expediently designed in such a way that the spring action acts only in the direction of the axis spacing change. This can prevent shifts in the image transmission area. For example, it can be provided that leaf springs are arranged which extend with their broad side transversely to the direction of the axis spacing change. An expedient embodiment provides that at least one of the cylinders is mounted on journals which are spring-mounted on the housing and have pivot bearings in the interior of the cylinder. This largely prevents interference from vibrations or bends. To prevent vibrations it can also be provided that the spring-loaded bearings are provided with damping.

The foregoing is an enumeration of the main ways in which the Sensi to achieve tivity magic. This list is not exhaustive, it is possible, further influence through determination and testing of all boundary conditions to determine sizes. However, the number of influencing variables is not important bend. The decisive factor is that one or more influencing variables are available stand that can be changed without being given for design reasons Geometries or properties necessary due to other functions change too have to.

The printing device according to the invention is particularly suitable for use with color copiers electrostatic imaging, where the image on the image cylinder for everyone The print was rebuilt and then transferred to the substrate using a transfer cylinder is transmitted. However, the printing device according to the invention is also for others Printing machines with one image cylinder and one transfer cylinder can be used, if an out-of-roundness of the image cylinder is to be corrected.

The principle of the invention is illustrated with the aid of sketches and graphics explained. In addition, implementation options are shown in the figures. It demonstrate

Fig. 1 shows the basic structure of the printing apparatus according to the invention,

FIG. 2a is a drawing for explaining the principle of the invention,

Fig. 2b is a diagram showing for explaining the principle of the present invention an analogous effect,

Fig. 3a is a diagram showing the overdrive function of the engagement,

FIG. 3b is a diagram showing the overdrive function of the torque,

Fig. 4 is a diagram for explaining the discovery of the present invention to be achieved Sensitivity Magic,

Fig. 5 is a schematic diagram for explaining the effects that are caused by a non-circular image cylinder,

Fig. 6a u. 6b embodiments for the design of the elastic jacket of the transfer cylinder and

Fig. 7 shows an embodiment for a sprung cylinder bearing.

Fig. 1 shows the basic structure of the printing apparatus 1 of the invention. This consists of an image cylinder 2 , on the lateral surface 4 of which an image is applied by means of an image generating device 3 . This image is transmitted in an image transfer area 8 from the image cylinder 2 to a transfer cylinder 5 . The transfer cylinder 5 transmits the image to a printing material 6 , which is guided on a belt 22 past the transfer cylinder 5 in the direction of the arrow 23 . An impression cylinder 21 ensures the necessary counter pressure when the image is transferred to the printing material 6 . It is also possible to provide a cylinder instead of the belt 22 which guides the printing material 6 .

The transfer cylinder 5 has an elastic jacket 7 , which has a thickness 12 . This elastic jacket 7 is located on the core 20 of the transfer cylinder 5th The transfer cylinder 5 is driven by the belt 22 in the direction of arrow 25 and in turn drives the image cylinder 2 in the direction of arrow 24 via friction. However, an embodiment is also possible in which the image cylinder 2 drives the transfer cylinder 5 in a corresponding manner or in which a drive is arranged on the transfer cylinder 5 . In the contact area 8 of the image cylinder 2 and the transfer cylinder 5 , the elastic jacket 7 is deformed 9 . The image transfer from the image cylinder 2 to the transfer cylinder 5 takes place in this deformation region.

The problem to be solved by the invention is that the radius r _{PC of} the image cylinder 2 deviations and these radius changes Δr _{PC can be} the cause of image errors. A source of image errors - when looking at rigid cylinders - is that a friction-driven cylinder with different radii is driven more slowly at larger radii than at smaller radii and the resulting differences in angular velocity ω _PC would have the effect that the Beginnings of pictures (and thus the rest of the pictures) would be postponed. Another source of error is also related to changes in radius Δr _PC . This error occurs directly at the imaging device 3 , since the lateral surface 4 moves past the imaging device 3 faster at the same angular velocity in an area of larger radii than in the area of smaller radii. However, both errors can be eliminated by the behavior of the elastic jacket 7 in the deformation area 9 . The extent of this deformation 9 is the Engage ment Eng, which is determined to what extent the center distance between the Bildzylin 2 and transfer cylinder 5 is smaller than the sum of the radii of the Bildzylin ders r _pc and the transfer cylinder r _IT .

Fig. 2a shows a drawing for explaining the principle of the invention. This is illustrated by FIG. 2b, which explains the principle according to the invention with an analog effect. Due to the deformation 9 of the elastic jacket 7 , its highly elastic material 13 has to overcome a narrow point caused by the tight engagement. This can only be overcome if the highly elastic material 13 is accelerated in the region of the deformation 9 . This highly elastic material 13 behaves similarly to a liquid 27 which - as shown in FIG. 2b - has to pass through a tube 26 which has a wide tube area 28 , a constriction 29 and then again the wide tube area 28 . The liquid flows in the wide tube region 28 at a speed V _X , then must be accelerated in the constriction 29 to a higher speed V _{Nip in} order to resume the original speed V _X when it exits the constriction 29 in the wide tube region 28 . The elastic jacket 7 behaves in an analogous manner in the device according to the invention, as shown in FIG. 2a. In the deformation area 9 , the "flow speed" of the elastic material 13 in the area of greatest engagement Eng is accelerated to a maximum speed V _{IT in the nip} , which is greater than the speed V _X , which is in the area of a radius r _X due to the angular speed ω _{IT of} the Transfer cylinder, 5 would occur under normal circumstances. This V _{IT in the nip} is the surface speed in the area of the deformation 9 . However, since the surface speed V _{IT in the nip has a} driving effect on the image cylinder 2 , the surface speed V _{IT in the nip is} identical to the surface speed V _{PC of} the driven image cylinder 2 . However, the above-mentioned effect would also occur if the image cylinder 2 were to drive the transfer cylinder 5 . In the manner described, the driven cylinder, for. B. the image cylinder 2 , driven faster than would be the case with rigid cylinders 2 and 5 . The surface speed V _{PC is} greater than an imaginary surface speed V _{X of} the transfer cylinder 5 at a radius r _x and also greater than the surface speed V _{IT of} the transfer cylinder 5 outside the nip, since it corresponds to the surface speed of the transfer cylinder in the nip V _{IT in the nip} . The ratio of the surface speed in the nip V _{IT in the nip} to the surface speed of the transfer cylinder 5 outside the nips V _IT is the overdrive. It is a measure of how much the image cylinder 2 is driven faster due to the effect described.

Is the image cylinder 2 out of round, so occur radius changes Δr _{PC of} the radius r _PC , this has a direct effect on the effect just described in that an acceleration of the angular velocity ω _{PC of} the Bildzylin 2 occurs at larger radii and one at smaller radii Slowing down the angular velocity of the image cylinder 2 . This effect is opposite to a fluctuation in an angular velocity ω _PC , which would occur in rigid cylinders 2 and 5 as a result of Radiusän changes Δ _PC . In order to prevent a fluctuating angular velocity ω _{PC of} the image cylinder 2 , it is therefore only necessary that the overdrive is set in such a way that it compensates for the change in the angular velocity ω _PC by changes in the radius Δr _PC . This is the idea on which the invention is based.

Another idea on which the invention is based is that another source of error can also be eliminated in this way. This source of error is that the lateral surface 4 of the image cylinder 2 even at constant angular velocity ω _PC with larger radii passes the imaging device 3 faster than with smaller radii. The compensation of this error is described further below in relation to FIG. 5.

Fig. 3a shows a diagram illustrating the overdrive by representation of the relationship of V _PC V _IT in response to the commitment Eng. If the commitment is 0, the effect described for FIGS . 2a and 2b does not occur and the surface speed V _{pc of} the image cylinder 2 corresponds to the surface speed V _{IT of} the transfer cylinder 5 . This means

With increasing engagement, this ratio changes, since the surface speed V _{PC of} the image cylinder 2 becomes increasingly faster than the surface speed V _{IT of} the transfer cylinder 5 . This results from the fact that the V _Nip , which is identical to the surface speed V _PC, increases with increasing engagement Eng. This increase is shown in Fig. 3a. The slope of this curve, that is to say the change in the ratio V _PC to V _IT, is the sensitivity, which represents a property of the material and structure of the elastic jacket 7 . Another circumstance that influences the sensitivity is the already mentioned elastic mounting of one of the cylinders 2 or 5 or both cylinders 2 and 5 .

However, there is also another effect shown in Fig. 3b, which must be considered as soon as it occurs to a greater extent, which in turn depends on the nature and structure of the elastic jacket 7 . The overdrive is dependent on the torque in such a way that the overdrive decreases with increasing torque

can be determined. The negative slope of the curve shown in the diagram in FIG. 3b is the sensitivity, which is dependent on the torque, this is Sens _T. This counteracting effect was taken into account by Sens _T .T in the formula already described above.

FIG. 4 shows a diagram for explaining the discovery of the present invention to be achieved Sensitivity Magic, SENSM. In the diagram, the radius r _{PC of} the image cylinder 2 is plotted on the abscissa and the angular velocity ω _{PC of} the image cylinder 2 on the ordinate. This shows the influence of the selected sensitivity on the effects of out-of-roundness - that is, changes in radius Δr _PC - on the angular velocity ω _PC . These changes in radius Δr _PC were plotted as deviations from an average radius. Depending on the sensitivity that results from the configuration of the elastic jacket 7 or the configuration of the spring-loaded bearing 11 , one or the other of the effects described above predominates. If the sensitivity is 0 or low, the ratio of the change in radius Δr _PC to a change in the angular velocity ω _{PC of} the image cylinder 2 is determined by line 31 . This means that the larger the radius r _PC , the lower the angular velocity ω _PC . For example, this is the normal effect on rigid surfaces of a driving and a driven cylinder when the radius changes. If the sensitivity is very high, i.e. there is a very high overdrive, the ratio of the change in radius Δr _PC to the change in angular velocity ω _{PC is} characterized by the course of line 32 . This means that the angular velocity ω _PC , becomes larger with a larger radius r _PC . The sensitivity can be adjusted in such a way that it runs parallel to the abscissa by means of an appropriate nature of the elastic jacket 7 , optionally with a spring-loaded bearing 11 . Then, the angular velocity ω of the _PC-driven friction cylinder is image 2 r changes of the radius of the image cylinder _PC 2 independently. In this way it is ensured that not only the angular velocity ω _{IT of} the driving transfer cylinder 5 but also the angular velocity ω _{PC of} the driven image cylinder 2 is constant despite the out-of-roundness of the image cylinder 2 . If this condition is met, an angular velocity error due to an out-of-roundness is eliminated at its point of origin, the friction between the two cylinders 2 and 5 . This works regardless of whether the image cylinder 2 drives the transfer cylinder 5 or vice versa.

Fig. 5 shows a schematic diagram to explain the effects caused by an unrun the image cylinder 2 . A constant drive of the transfer cylinder 5 , which gives it a constant angular velocity ω _PC , is transmitted by the effects just described such that the angular velocity ω _{PC of} the image cylinder 2 is constant, regardless of whether the radius r _{PC has} differences Δr _PC or Not. However, this does not prevent the occurrence of a further error source, which consists in the fact that, at a constant angular velocity ω _PC, the lateral surface 4 passes at a larger radius r _PC + Δr _PC faster at the image generation device 3 than at a smaller radius r _PC . As a result, an image area on the part of the lateral surface 4 with a larger radius r _PC + Δr _PC in relation to the lateral surface 4 with a smaller radius r _{PC is shown} in a stretched manner, already during imaging by the image forming device 3 . However, this effect can also be compensated for by setting the sensitivity as Sensitivity Magic. It is thereby achieved that in the area of the deformation 9 , i.e. also in the area of the image transmission 8, the surface of the elastic jacket 7 is stretched more with larger radii than in the area of smaller radii, and this expansion of the surface of the elastic jacket 7 changes after passing through the deformation 9 pulls together again in such a way that the image area stretched by the large radius r _PC + Δr _PC on the lateral surface 4 is returned to its desired length. By setting the sensitivity as Sensitivity Magic, it is thus possible to prevent two error occurrences with one measure, in that the overdrive prevents angular velocity errors from occurring and eliminates the image errors just described during transmission to the transfer cylinder 5 .

Fig. 6a and 6b show exemplary embodiments for the configuration of the elastic jacket 7 of the transfer cylinder 5.

FIG. 6a shows how the core 20 of the transfer cylinder 5 a highly elastic material 13 is applied, which is covered with a relatively hard cover layer 14. In this way, a surface that is optimal for image transmission can be combined with a highly elastic or compressible layer 13 in order to achieve the desired sensitivity.

Fig. 6b shows an embodiment of the elastic coat 7 with an intermediate layer 15. This intermediate layer 15 can, for example, consist of harder material. Such an intermediate layer 15 enables a targeted adjustability of the sensitivity. Of course, an elastic jacket 7 with an intermediate layer 15 can also be provided with a cover layer 14 .

Fig. 7 shows another embodiment of a spring-loaded cylinder bearing 11. An axle 17 is slidably mounted in the housing 19 of the machine in the direction of the double arrow 30 . In this case, the axle journal 17 can only deflect in one direction by arranging a leaf spring 16 ; this is the direction of the axle spacing change between two cylinders 2 and 5 . The pivot bearing 18 , for example a ball bearing, is located inside the cylinder 2 or 5 , which interacts with the other cylinder 5 or 2 . Such spring-loaded bearings 11 are in addition to the selection of the material and the design of the elastic jacket 7 a further possibility to influence the sensitivity, which is then a virtual sensitivity, that is, a sensitivity of the overall system. This sensitivity arises from a change in engagement due to the elastic change in distance. The spring-loaded cylinder mounting represents, for example, one possibility of nevertheless achieving the Sensitivity Magic despite a relatively hard material of the elastic jacket 13 , for example when using a solid material.

Reference symbol list

1

Printing device

2nd

Image cylinder

3rd

Imaging device

4th

Lateral surface

5

Transfer cylinder

6

Substrate

7

elastic coat

8th

Image transmission area

9

deformation

10th

storage

11

spring loaded storage

12

Elastic jacket thickness (= d)

13

strong elastic material

14

Top layer (relatively hard)

15

Intermediate layer

16

Leaf springs

17th

Axle journal

18th

Pivot bearing (e.g. ball bearing)

19th

casing

20th

Core of the transfer cylinder

21st

Impression cylinder

22

Belt for printing material transport

23

Arrow: Direction of movement of the belt

24th

Arrow: Direction of rotation of the image cylinder

25th

Arrow: Direction of rotation of the transfer cylinder

26

tube

27th

liquid

28

Wide tube range

29

Narrowing of the tube

30th

Double arrow: possibility of movement of the journal

31

Sensitivity - effect of radius change predominates

32

Sensitivity - effect of the overdrive predominates
r _PC

Radius of the image cylinder (PC: photo conductivity cylinder)
Δr _PC

Change in radius of the image cylinder due to out-of-roundness
average diameter of the image cylinder for out-of-roundness
r _IT

Radius of the transfer cylinder (IT: Intermediate transfer cylinder)
ω _PC

Angular velocity of the image cylinder
ω _IT

Angular velocity of the transfer cylinder
V _PC

Surface speed of the image cylinder
V _IT

Surface speed of the transfer cylinder outside the nip
V _{IT in the nip}

Surface speed at the point of maximum deformation
V _X

Velocity at a radius r _X

(= r _IT

- narrow)
Close engagement = measure of maximum deformation
Closely

average maximum deformation if the image cylinder is out of round
Sens Sensitivity is the ratio of the surface speed of the image cylinder (V _PC

) to the surface speed of the transfer cylinder (V _IT

) depending on the commitment
Sens _M

Sensitivity Magic is the sensitivity at which the angular velocity (ω _PC

or ω _IT

) of the driven cylinder (

2nd

or

5

) no longer due to radius deviations (Δr _PC

) of the image cylinder (

2nd

) changed
Sens _T

the change in the ratio of the surface speeds of the Image cylinder (

2nd

) to the transfer cylinder (

5

), so

  due to the change in torque
T is the mean torque

Poisson number
ε _c transverse elongation
ε _n longitudinal expansion

Claims (22)

1. Printing device ( 1 ) with an image cylinder ( 2 ), a device Bilderzeugungseinrich ( 3 ) for imaging the lateral surface ( 4 ) of the image cylinder ( 2 ) and a transfer cylinder ( 5 ), the image of the image cylinder ( 2 ) on a printing material ( 6 ) transmits, the transfer cylinder ( 5 ) having an elastic jacket ( 7 ) which has a deformation ( 9 ) on the image transfer region ( 8 ) from the image cylinder ( 2 ) and wherein one of the cylinders ( 2 or 5 ) over the other Friction drives, characterized in that the radius (r _PC ) of the image cylinder ( 2 ), the radius (r _IT ) of the transfer cylinder ( 5 ), the material and the design of the elastic jacket ( 7 ) and the bearing ( 10 , 11th ) the cylinder ( 2 , 5 ) are selected and designed such that there is an overdrive dependent on changes in engagement (Eng) - as a result of an out-of-roundness of the image cylinder ( 2 ) - for the cylinder ( 2 or 5 ) driven by the friction
results in which the possible image errors caused by the out-of-roundness of the image cylinder ( 2 ) are avoided. 2. Printing device according to claim 1, characterized in that the selection and refinements take place such that the Winkelgeschwin speed (ω _PC or ω _IT ) of the cylinder driven by the friction ( 2 or 5 ) is constant despite a runout of the image cylinder ( 2 ) . 3. Printing device according to claim 1 or 2, characterized in that the selection and refinements take place in such a way that image errors which arise from the out-of-roundness of the image cylinder ( 2 ) when imaging the same, by changing the overdrive
as a result of the changes in engagement (Eng) caused by the out-of-roundness of the image cylinder ( 2 ) are corrected as soon as the surface of the elastic jacket ( 7 ) relaxes at the image transfer point ( 8 ) after passing through the deformation ( 9 ). 4. Printing device according to claim 1, 2 or 3, characterized in that the cylinders ( 2 , 5 ) are fixed. 5. Printing device according to claim 1, 2 or 3, characterized in that at least one of the cylinders ( 2 , 5 ) has a spring-loaded bearing ( 11 ), such that an axis distance change is effected as a function of the out-of-roundness of the image cylinder ( 2 ) . 6. Printing device according to one or more of claims 1 to 5, characterized in that the image cylinder ( 2 ) is driven by the transfer cylinder ( 5 ). 7. Printing device according to one or more of claims 2 to 4 or 6, characterized in that the selection is made such that for the sensitivity (Sens) - this is the change of the ratio of the surface speed (V _PC ) of the image cylinder ( 2 ) to the surface speed (V _IT ) of the transfer cylinder ( 5 ) depending on the engagement (Eng), the latter being the degree of deformation ( 9 )

• - the following condition is met:
  

where the sizes are defined as follows:

• - Sens _M = Sensitivity Magic, that is the sensitivity at which the angular velocity (ω _PC or ω _IT ) of the driven cylinder ( 2 or 5 ) no longer changes due to radius deviations (Δr _PC ) of the image cylinder ( 2 )
• - r _PC = radius of the image cylinder ( 2 ),
• - Eng = average engagement between cylinders ( 2 and 5 ),
• - Sens _M = the change in the ratio of the surface speeds of the image cylinder ( 2 ) to the transfer cylinder ( 5 ), that is to say as a result of the change in torque, V _PC / V _IT
• - T = the mean torque.

8. Printing device according to claim 7, characterized in that for cases in which the change in sensitivity due to torque changes is small and therefore can be neglected for the fulfillment of the condition, the following condition is met:
9. Printing device according to claim 8, characterized in that in the event that the radius (r _PC ) of the image cylinder ( 2 ) is very large in relation to the engagement (Eng), the latter is neglected and the condition to be fulfilled is thus as follows:
10. Printing device according to one of claims 1 to 9, characterized in that the Sensitivity Magic (Sens _M ) is achieved by a selection of the material and the design of the elastic jacket ( 7 ) and the design of the storage of the cylinders ( 2 , 5 ) . 11. Printing device according to one of claims 1 to 10, characterized in that the selection of the material for the elastic jacket ( 7 ) is made according to the Poisson number of the material. 12. Printing device according to one of claims 1 to 11, characterized in that the selection of the material for the elastic jacket ( 7 ) is carried out according to the compressibility of the material. 13. Printing device according to claim 12, characterized, that a porous material is selected. 14. Printing device according to one of claims 1 to 13, characterized in that a corresponding thickness ( 12 ) of the elastic jacket ( 7 ) is selected. 15. Printing device according to one of claims 1 to 14, characterized in that the elastic jacket ( 7 ) consists of different layers ( 13 , 14 , 15 ). 16. Printing device according to claim 15, characterized in that the elastic jacket ( 7 ) consists essentially of a highly elastic mate rial ( 13 ) and has a relatively hard, but still elastic cover layer ( 14 ). 17. Printing device according to claim 15 or 16, characterized in that the elastic jacket ( 7 ) consists essentially of a highly elastic material ( 13 ), in which at least one relatively hard intermediate layer ( 15 ) is embedded. 18. Printing device according to one of claims 5 to 17, characterized in that a constant spring constant for the spring-loaded bearing ( 11 ) is chosen to achieve the Sensitivity Magic (Sens _M ). 19. Printing device according to one of claims 5 to 18, characterized in that the spring-loaded bearings ( 11 ) are designed such that the spring action acts only in the direction of the center distance change. 20. Printing device according to claim 19, characterized in that leaf springs ( 16 ) are arranged which extend with their broad side transversely to the direction of the center distance change. 21. Printing device according to one of claims 5 to 20, characterized in that the spring-loaded bearings ( 11 ) are provided with a damping. 22. Printing device according to one of claims 5 to 21, characterized in that at least one of the cylinders ( 2 or 5 ) on the housing ( 19 ) spring-mounted pin ( 17 ) with pivot bearings ( 18 ) is mounted inside the cylinder.