JP2005519794A - Method for expressing characteristics, method and apparatus for determining characteristic amount, and method for selecting appropriate cylinder tension in printing press roller - Google Patents

Abstract

Disclosed are a method for characterizing a layer (06), a method and a device for detecting a reference number, and a method for selecting a suitable layer to be applied to rollers (01, 02, 11, 12 16) or for selecting suitable roller geometries of a printing press, according to which a reference number characterizing the layer is formed or used. Said reference number characterizes the unwinding behavior independently of a measuring device or an application in a special printing unit.

Description

  The present invention provides a method for expressing characteristics according to claim 1, 4, 6, 8 or 26, a method and apparatus for determining a characteristic quantity, and a method for selecting an appropriate cylinder in a roller or a press roller with an appropriate geometry. Relates to the method of selection.

  In the case of a printing press, for example a rotary printing press, between one or more rollers in an inking device, between an inking device and a printing device cylinder, in some cases between several printing device cylinders, and even from the printing device cylinder Ink is applied to a web, for example a paper web, toward an impression cylinder (hereinafter all referred to as a roller). For this purpose, in some cases, the transfer of ink between two adjacent rollers cooperating via a web is preferably carried out in each case between a roller with a “hard” surface and a roller with a “soft” surface. .

  Since some surface pressure is required for ink transfer, at least a roller with a soft surface will be deformed in its surface area. This deformation of a soft surface, e.g. made as an elastomer cover (barrel, rubber blanket, metal blanket, sleeve, coating), can result from material properties and (for example, the distance between the rollers, the various strengths of the web, etc.) ) According to the size of the push, the effective diameter of these rollers will change when rolling on the cooperating rollers, that is, the surface pressure and the effective outer peripheral surface will change. In the case of mechanically or electronically driven rollers, different surface speeds can occur depending on the material used and the amount of indentation, i.e. slips can be caused at the nip. There is. The slip generated in this way creates a tangential force due to friction, thereby degrading the print quality (blur, double) and causing the transmission of disturbing forces, and also the service life of the plate or cylinder Will decrease.

  According to DE 43 15 456 A1, a blanket with an uncompressed layer and a compressed elastomer layer is known, with the compressed elastomer layer increasing the tolerance for the effective printing outer peripheral surface. If the layer structure is optimized, there will be almost no change in surface length if the cooperating cylinders are within the predetermined cylinder loading or range of cylinder alignment positions, ie two cylinders rolling on each other. The rotation angle difference is not affected by the amount of push-in within that range. An experimental model for various torso and various torso conditions in which the first torso to be driven and a torso or a second torso that is rolled together freely support each other. The rotation angle difference can be obtained based on

  In TAGA Proceedings 2001, from page 211 of the article disclosed by this application under the title "The effect of printing blankets on the rolling conditions of printing cylinders", a characteristic quantity representing the rolling characteristics of the elastic bracket is known. This allows the designer to calculate the transmission ratio between the transfer cylinder and the plate cylinder. The apparatus for determining the rolling characteristics has a roller driven from the outside and a roller driven by friction, and the angular velocity of these rollers can be measured by a photoelectric angle decoder.

  It is an object of the present invention to provide a method for representing a characteristic, a method and apparatus for determining a characteristic quantity, and a method for selecting an appropriate blanket in a roller or a method for selecting an appropriate roller geometry of a printing press.

  According to the invention, this problem is solved by the features of claims 1, 4, 6, 8, 24 or 26.

  An advantage that can be achieved with the present invention is that it allows a quantitative description of the waistline in terms of conveying or rolling properties, and the properties so produced depend on the geometry of the measuring device and the geometry of the printing unit. Is not to. The characteristic quantity used to represent the characteristic of the lining is removed from the part related to the specific geometry, and can be applied to the measuring apparatus or the printing unit. This description becomes available quantitatively, not simply qualitatively (eg convenient transport, inconvenient transport).

  The method of expressing the characteristics of the tension based on the characteristic quantities creates a uniquely defined expression between the manufacturer of the tension and the designer of the printing press. While pre-determined, the press can be configured as ordered, while if the press configuration is pre-determined, the waistline can be selected as desired. Both the upholstery and the press configuration can already be revealed at the front end, or a laborious trial that must be carried out at the press for a specific configuration and each type of strap The program can be omitted.

  Therefore, according to an advantageous solution, the lining for a given pair of cylinders can be selected as follows. That is, it can be selected that when the indentation occurs, the mass of the trunk is stretched due to the incompressible component of the trunk and that the narrowing of the spacing with respect to the turning point is compensated at that time. According to the method of the present invention, such a requirement can be obtained, and an appropriate waistline can be selected.

  Furthermore, it is advantageous to have the printing device geometry for a given appropriate tension so that in at least one region of the variable indentation the rolling characteristics are independent or only slightly dependent on the indentation. Is to select.

  The measurement value required for forming the characteristic quantity is obtained by a measuring device having two rollers, for example. According to an advantageous embodiment, the measuring device has a lever for converting the displacement motion in order to capture the interval or the interval change (push-in amount). An even greater conversion can be effected via an eccentric that moves the barrel, in which case the lever is fixedly connected to the bearing ring to be displaced.

  The characteristic quantities obtained for a single lining can be applied to various printing device configurations, which does not depend on the geometry of the measuring device used. In this case, an algebraic rule between the geometry and the characteristic quantity may be defined and known.

  It is further advantageous that a printing device can be configured that is optimized with respect to rolling characteristics. That is, for example, when the transfer cylinders co-operate with the counter pressure cylinders having substantially the same circumference, a double transfer cylinder with a cylinder having a characteristic amount α of 0.989 to 0.999, 0 An equal-size circumferential transfer cylinder having a cylinder with a characteristic amount α of .980 to 0.995 is constructed. The characteristic amount α shown here must be protected within at least one relative indentation range that is actually important.

  The above-described configuration of the printing device is particularly advantageous in the case where the transfer cylinder and the counter impression cylinder are driven independently of each other. This minimizes motor addition, motor design and control costs.

  Next, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a view showing a path of a compression type rubber blanket passing through a roller gap.

  FIG. 2 is a view showing a path of an uncompressed rubber blanket passing through the roller gap.

  FIG. 3 is a diagram showing a transmission ratio measured with respect to a change in the pushing amount.

  FIG. 4 shows the transmission ratio qualitatively.

  FIG. 5 is a diagram illustrating an embodiment of a printing apparatus.

  FIG. 6 is a diagram illustrating an embodiment of a printing apparatus.

  FIG. 7 is a diagram illustrating an embodiment of a printing apparatus.

  FIG. 8 is a diagram illustrating an embodiment of a printing apparatus.

  FIG. 9 is a diagram showing an embodiment of the measuring apparatus.

  10 is a detailed side view of the apparatus according to FIG.

A work machine, for example a printing press, has rollers 01; 02 that roll on each other, which form a roller gap 03 in the contact area. In the case of a printing machine, this is a roller 01; 02 of an inking device or a lacquer device, or a cylinder 01; 02 of a printing device. In the embodiment shown in FIGS. 1 and 2, the cylinder 01; 02 comprises a _plate cylinder 01 having an effective diameter _DwPZ and a transfer cylinder 02 of the offset printing apparatus. One of the cylinders 01; 02, for example the transfer cylinder 02, has a soft elastomer layer 06 having a strength t on the outer cover of a sufficiently incompressible and inelastic core 04 having a diameter _DwGZK . The core 04 and the layer 06 together form the effective diameter _DwGZ of the transfer cylinder 02. The effective diameter _DwPZ is determined at the outer casing of the plate cylinder 01 effective for rolling, and in some cases includes an unillustrated _{printing plate attached to the} base casing. The cylinder 01 having a hard surface may be configured as the impression cylinder 01 that cooperates with the transfer cylinder 02.

  Depending on the entrainment state of both cylinders 01; 02 or the position of their alignment, ie the distance between their axes, a sufficiently incompressible and inelastic plate cylinder jacket 01 sinks into the soft layer 06 and in the layer 06 A push-in amount S is caused for the course without interference. In accordance with the jacket characteristics (compressibility and / or elasticity characteristics) of the layer 06, this pushing amount S causes the above-mentioned problems on the effective outer peripheral surfaces of both cylinders 01; 02.

  Therefore, according to the approach of the present invention, the description of the rolling characteristics of this type of layer 06 does not depend on a specific application example or measurement apparatus, and an appropriate layer 06 is selected based on this description. The dimensions of the rollers 01; 02 can be selected. If an ideal compressed layer 06 (for example, cork) and an ideal non-compressed layer 06 (for example, solid rubber) are used, the limit for effective outer peripheral surface characteristics can be determined. The actual layer 06 consists of a heterogeneous composite material, for example consisting of a fabric, an air cushion layer, an adhesive layer and a rubber cover, ie it is composed of both compressed and non-compressed components, which is the above-mentioned limit. Exist between cases. Here, as a solution, the relative position with respect to the measured or desired characteristic and the two extreme characteristics theoretically required, that is, complete compressibility and complete incompressibility, is determined or determined.

  The following is an example of an analytical calculation of an idealized limit case. In this case, the transport speed of the layer 06 in the roller gap 03 is considered for both ideal limit cases.

In the ideal compressible case, the compression of the layer 06 occurs due to the indentation of the layer 06 in the roller gap 03. The velocity v ₀ of the layer 06 when not disturbed decreases to the velocity v ₁ due to the reduction of the effective diameter D _wGZ in the narrow region (FIG. 1). The effective diameter _DwGZ is reduced by a value twice the amount S in the region of the line connecting the center points of both cylinders:

進みおよび／または遅れを表す回転数比または伝達比Ｉに関して胴０１；０２の回転数ｎ_ＧＺ；ｎ_ＰＺもしくは周波数ｗ_ＧＺから、

From a rotational speed ratio or transmission ratio I representing a lead and / or delay, from the rotational speed n _GZ of the cylinder 01; 02; n _PZ or the frequency w _GZ

となり、圧縮性の事例では版胴０１の表面速度ｖ_ｐであれば、

In the case of compressibility, if the surface speed v _p of the plate cylinder 01 is

となる。

It becomes.

In the case of “True Rolling”, ie when the cylinder rolls freely, the surface speeds v _p : v ₁ of both cylinders 01; 02 are equal. Minor slips due to friction of the cylinder bearings driven via frictional forces are ignored. Therefore, if the transmission ratio is an ideal compressible case,

と表すことができる。

It can be expressed as.

  When the incompressible medium passes through a narrowed section, the continuity equation is established, which indicates that the mass flow rate is always kept constant. When applied to the pushing amount S of the layer 06 in the roller gap 03, this means that the conveyance speed is increased in the narrow area or the contact area of the rolling cylinder 01; 02 (FIG. 2).

(Through the cross-section A ₀₎ before the roller gap 03 (through a cross-section A ₁₎ mass flow and mass flow rate in the roller gap narrow portion is constant.

The cross-section A ₀ ; A ₁ can be obtained by the length t and the strength t or the strength t or the strength t or the push amount S.

層６における内側速度ｖ_Ｇｉと外側速度ｖ_Ｇａとの間の速度プロファイルが狭幅領域において直線的であるとし、さらに周縁速度が胴０１；０２の表面速度により求められるすれば、搬送速度の積分により平均速度が得られる。したがって連続方程式［６］を以下のように記述することができる：

If the velocity profile between the inner velocity v _Gi and the outer velocity v _Ga in the layer 6 is linear in the narrow region, and the peripheral velocity is determined by the surface velocity of the cylinder 01; Gives the average speed. Thus, the continuous equation [6] can be written as follows:

角周波数ωと複数の変形に対する式［３］を用いると、非圧縮性の限界事例に対する回転数比もしくは伝達比は次式のようになる：

Using the angular frequency ω and equation [3] for multiple deformations, the rotational speed ratio or transmission ratio for the incompressible limit case is:

In FIG. 3, the transmission ratio I is shown for several measurements. In this case, for each layer 06, that is, for each different rubber blanket 06, the rotational speed ratio n _GZ / n _PZ for four different pushing amounts S is recorded, and the transmission ratio I is calculated therefrom.

  Connecting each measurement point results in a good approximation of straight lines, all of which start at the intersection of the limit cases that are also written here. The offset that can be identified with respect to the intersection point is due to the different strengths t of the rubber blankets 06 used.

  FIG. 4 shows the rotation speed ratio or transmission ratio in an ideal compressive case, an ideal incompressible case, and an actual case.

In order to represent the characteristics of the layer 06, for example, the rubber blanket 06, first, at least one measurement point (push-in amount S) is measured by an appropriate measuring device (described later) to determine the actual transmission ratio _Ireal . Since the geometry of the measuring device is known, the theoretical transmission ratio I for the ideal compressible case and the ideal incompressible case already exists if the strength t is known. Or it can be formed. Here, the characteristic amount α is formed on the basis of the ratio between the transmission ratio I actually generated when measured by, for example, an appropriate measuring device with respect to the same pushing amount S, and the ideal limit case. Based on the at least partially idealized and linearized equation, the characteristic quantity α thus defined is the rolling characteristic (elongation) of the layer 06 for all indentations S, or at least for the region considered. (Or compression). The characteristic value α can now be defined as follows:

ここでＡは実際の非圧縮性伝達比Ｉと理論上の非圧縮性伝達比Ｉとの差を、Ｂは理論上の圧縮性伝達比Ｉと理論上の非圧縮性伝達比Ｉとの差を、それぞれ同じ押し込み量Ｓについて表す。式［９］による特性量αの定義において、実際の層０６が理想的に非圧縮性の特性であればα＝０であり、実際の層０６が理想的に圧縮性の特性であればα＝１である。

Where A is the difference between the actual incompressible transmission ratio I and the theoretical incompressible transmission ratio I, and B is the difference between the theoretical incompressible transmission ratio I and the theoretical incompressible transmission ratio I. For the same push amount S. In the definition of the characteristic amount α by the equation [9], α = 0 if the actual layer 06 is ideally incompressible, and α if the actual layer 06 is ideally compressible. = 1.

  The characteristic quantity α can also be formed by different types of algebraic rules, which describe the relative position of the actual transmission ratio I to the position of the extreme transmission ratio I that can be theoretically determined. . That is, another normalization can be selected, for example, a range of values can be selected by a multiplier or a shift by addition / subtraction can be selected. In addition, the difference may be reversed in the division, or the numerator and denominator may be exchanged. Nonetheless, in order to obtain the proper configuration of the cylinder 01; 02 from the appropriately represented rubber blanket 08, or to obtain the appropriate rubber blanket 06 from the configuration of the cylinder 01; 02. In order to do this, it is important to know the algebraic rule [9] that forms the basis of the characteristic quantity α. Instead of the speed ratio I, a lead or lag, a ratio of angular velocities, or other equivalent quantities representing the lead or lag can also be used with the rules matched accordingly.

In a method for determining an at least partly constant characteristic quantity α which represents the characteristics of the layer 06 and which has been removed of the part relating to the geometry of the measuring device, ie its influence has been removed, first of all (for example the resulting transmission ratio I (based on the _real ) the transport properties are measured depending on the indentation S, and the position of the measurement point (or multiple measurement points) is relative to the corresponding extreme point that can theoretically be determined for the measuring device. It is relatively required. For this purpose, the measured transmission ratio and the theoretically determined transmission ratio I _real ; I _komp ; I _inkmp are at least partly related to each other, for example according to the algebraic rule [9]. In the simplest case, the characteristic value α can be determined on the basis of a single measured value for the push-in amount S.

On the other hand, for a rubber blanket 06 having a characteristic quantity α known to be measured by the manufacturer, for example, an algebraic rule belonging to it, and a known cylinder geometry (diameters D _GZK , D _wPZ ), the cylinder 01; The expected slip can be calculated at the front end for the expected transmission ratio I or the individual push amount S. According to the rule according to equation [9]:

が成り立つ。

Holds.

Therefore, the characteristic amount α can quantitatively represent the change in the effective diameter _DwGZ of the transfer cylinder 02 when the specific push-in amount S is _satisfied , and furthermore, when the cylinder 01; 02 rotates synchronously with respect to the angle. It is also possible to calculate the slip generated.

In the method for designing the cylinder 01; 02, for example, for the purpose of avoiding unnecessary forces in the slip or the drive, the strength t and the predetermined shape (diameter D _GZK ; D _{wPZ) in} one cylinder of the cylinder 01; 02 ) based on the known least partially constant characteristic amount α for a given layer 06 with the other cylinder 02; it is possible to obtain the _{D GKZ;} diameter _D WPZ 01. Thus, for example, the desired characteristic amount α, the desired course characteristic in the relationship between the transmission ratio I and the push-in amount S (vertical height and gradient in the diagram), and for example a rubber blanket 06 with a known diameter _DwPZ of the plate cylinder 01 On the other hand, the required diameter D _{GZK of the} core 03 or the total diameter D _wGZK + 2t of the transfer cylinder 02 can be obtained.

In this way, the effective outer peripheral surface characteristic or deformation characteristic of the layer 06 (rubber blanket 06, sleeve, metal blanket, ink roller coating / barrel / cover) represented by the characteristic amount α is determined as an ideal effective outer peripheral surface. Can be involved together in the selection of diameters D _GZK ; D _wGZ ; D _wPZ . By using the characteristic amount α for the predetermined rubber blanket 06, the diameters D _GZK ; D _wGZ ; D _wPZ can be determined so that an optimum effective outer peripheral surface is achieved. According to one embodiment, the diameters D _GZK ; D _wGZ ; D _wPZ can also be optimized to minimize the deviation from the effective effective outer surface optimal for the various rubber blanket 06 spectra. In order to use various rubber blankets 06 or to use special rubber blankets 06 in existing printing apparatuses, the number or strength of the underlay between the jacket and the rubber blanket 06 is set to the diameter _DGZK . Already required at the printing front end to align and can be considered in the equipment.

In contrast, in one method, an appropriate layer 06, such as a rubber blanket 06, can be selected based on the printing device geometry given previously (diameter D _GZK ; D _wPZ ). In this case, firstly, an algebraically extreme case for the transport characteristics is determined depending on the indentation amount S, and then the desired characteristics (gradient, vertical height in the diagram) for the actual layer 06 transport characteristics. Is determined at least in part, and then a characteristic quantity α is formed which is free of special geometric influences on the required layer 06, for example a rubber blanket 06. At this time, the relative position of the desired progress characteristic or the desired value with respect to the algebraically determined progress characteristic or value is determined for at least one value of the push-in amount S.

  If the characteristic quantity α is formed based on the same algebraic rule with respect to the description of the relative position, the rubber blanket 06 with the corresponding characteristic quantity α can be selected. If different algebraic rules are used to measure and determine the characteristic quantity α in the rubber blanket 06 and to obtain the desired characteristic quantity α based on the geometry of the cylinder 01; Can be moved to each other.

When the cylinder geometry changes, the theoretically determined transmission ratio I _komp ; I _inkmp straight line is tilted and the intersection with the I axis is shifted, so that the characteristic amount α is constant (rubber blanket 06 If the same remains), the absolute position of the straight line changes for the actual transmission ratio _Ireal , while the relative position is maintained.

However, even if the characteristic amount α changes (even if a rubber blanket 06 having another characteristic is selected), if the cylinder geometry of the printing apparatus remains the same, the theoretically determined transmission ratio I _komp : I _inkomp The straight line relative to the actual transmission ratio _Ireal is tilted and takes another gradient.

Accordingly, a tying 06 with a characteristic quantity α tailored to a particular printing device geometry will generally not match different geometries, and in particular will not match for different diameters D _GZK ; D _wPZ .

According to one advantageous embodiment in which an effective outer peripheral surface is obtained which is independent of the encasement state or the alignment position, the waistline 06 and the printing device geometry are aligned with each other as follows. That is, at least in a region actually related to the push amount S or the relative push amount S *, at least the gradient between the transmission ratio I _real and the push amount S in FIG. 4 is substantially zero, that is, dI _real / dS. Aligned to be ≈0. The relative indentation amount S * is defined here as the ratio S / t, ie by the indentation amount S with respect to the original strength t of the unindented layer 06. A suitable range for the relative push-in amount S * can be, for example, 6% to 10% in general considerations, but in particular may be 6.5% to 9%. However, it may be advantageous to distinguish between the “types” of nips for those areas. If the nip between the transfer cylinder 02; 01 and the plate cylinder 01; 02 is actually in the range of 6% to 7%, for example, the nip between the plate cylinder 02 and the satellite cylinder 16 is important. If so, it is 9% to 10%. The absolute value of the gradient dI _real / dS should be at least 0.01 1 / mm or less within these ranges, in particular 0.005 1 / mm. The considered strength t is, for example, between 1.6 and 2.5 mm for one advantageous type of waistline 06, while having a lower elasticity or surface pressure and / or an elastic characteristic curve ( For the second advantageous type with a small (surface pressure / push-in amount), the strength is, for example, between 3.5 and 5 mm.

  The printing devices or printing units depicted in FIGS. 5 to 8 are all drawn in a straight line for simplicity, i.e. the rotation axes of the cylinders involved are all located in one plane in the drawings. Yes. However, the cylinders of the printing device may be arranged at an angle to each other, and the following embodiments are equally applicable to a linear cylinder arrangement or an angled arrangement of cylinders or groups of cylinders.

  FIGS. 5 and 6 show a printing unit 07 which is advantageously arranged and arranged as a so-called double printing device 07. The transfer cylinder 02 associated with the plate cylinder 01 of the first cylinder pair 01; 02 cooperates with the counter impression cylinder 11 which is also configured as the transfer cylinder 11 via the printing object 08, for example, the web 08, A plate cylinder 12 is similarly associated with the impression cylinder 11. All four cylinders 01; 02; 11; 12 are mechanically driven independently from each other by different drive motors 13 (FIG. 5). According to one embodiment, the plate cylinder and the transfer cylinder 01; 02; 11; 12 are respectively coupled in pairs, and a set of drive motors (in the plate cylinder 01; 12, transfer cylinder 02; 11 or in parallel). 13 (FIG. 6).

The plate cylinder 01; 12 and the transfer cylinder 02; 11 are configured in the first embodiment as a double circumferential cylinder 01; 02; 11; 12, that is to say substantially two longitudinal printing surfaces, for example It is constructed as a cylinder with a circumference consisting of two newspaper pages. These cylinders are constructed to have an effective diameter _DwGZ ; _DwPZ of _260-400 mm, in particular 280-350 mm. On the outer cover of the core 04, the transfer cylinder 02; 11 has at least one cylinder 06 having a characteristic quantity α of 0.989 to 1.000, for example 0.989 to 0.999, in particular 0.993 to 0.997. Respectively. With such a configuration, the rolling or driving of the cylinder 01; 02; 11; 12 without sufficient slip is ensured over a wide range without torque transmission. The speed ratio _Ireal is advantageously selected as follows. That is, when the push-in amount S or the relative push-in amount S * changes, at least within the above-mentioned range with respect to the relative push-in amount S * of the corresponding pair of cylinders from 1.000 / n to 0.002 at the maximum. The deviation is selected to be 001. Here, the variable n represents the ratio between the number of printing surfaces in the circumferential direction on the transfer cylinder 02; 11 and the number of printing surfaces of the same size in the circumferential direction of the plate cylinder 01; 12. In this embodiment, the cylinders 01; 02; 11; 12 are both double circumferences, so n = 1 applies and the deviation is from 1.000 to a maximum of 0.002, for example 0.001.

In the case of the second embodiment, the plate cylinder 01; 12 and the transfer cylinder 02; 11 are configured as a circumferential cylinder 01; 02; 11; 12 of equal magnification, that is, substantially one longitudinal printing. It is configured as a cylinder 01; 02; 11; 12 having a circumference consisting of a plane, for example a newspaper page. These cylinders are configured to have an effective diameter _DwGZ ; _DwPZ of ₁₅₀ to ₁₉₀ mm. On the jacket of the core 04, the transfer cylinder 02; 11 has at least one cylinder 06 having a characteristic quantity α of 0.980 to 1.000, for example 0.980 to 0.995, in particular 0.983 to 0.993. Respectively. The speed ratio I _real is again advantageously selected as follows. That is, when the push-in amount S or the relative push-in amount S * changes, at least within the above-mentioned range with respect to the relative push-in amount S * of the corresponding cylinder pair, from 1.000 / n to a maximum of 0.002, especially 0.00. The deviation is selected to be 001 or 1.000 to 0.002, in particular 0.001.

According to a third embodiment, not shown, the plate cylinder 01; 12 is configured as an _equal circumferential cylinder 01; 12 having an effective diameter _DwPZ of ₁₅₀ to ₁₉₀ mm, and the transfer cylinder 02; the circumference of the body 02 of the double having an effective diameter _{D WGZ} of 260~400mm particular 280～350Mm; is configured as 11. On the outer cover of the core 04, the transfer cylinder 02; 11 has at least one cylinder 06 having a characteristic amount α of 0.987 to 1.000, for example, 0.997 to 1.000. The speed ratio I _real is again advantageously selected as follows. That is, when the push-in amount S or the relative push-in amount S * changes, at least within the above-mentioned range with respect to the relative push-in amount S * of the corresponding cylinder pair, from 1.000 / n to a maximum of 0.002, especially 0.00. The deviation is selected to be 001, and here n = 2, so that the deviation is selected from 0.500 to 0.002, especially 0.001.

The printing unit 14 shown in FIGS. 7 and 8 is part of a larger printing unit, for example a 5 cylinder type, 9 cylinder type or 10 cylinder type printing unit, or as a 3 cylinder type printing unit 14. It can be driven. In this case, the transfer cylinder 02 cooperates with a cylinder 16 that does not guide ink, for example, an impression cylinder 16 such as a satellite cylinder 16. In this case, the “soft” jacket of the transfer cylinder 02 cooperates with the “hard” jacket of the plate cylinder 01 on one side and the “hard” jacket of the satellite cylinder 16 on the other side. In this case, the effective diameter _DwPZ applied in the above-described consideration for the plate cylinder 01 can be appropriately substituted as the diameter _DwSZ of the satellite cylinder 16 into the equation relating to the cooperation between the transfer cylinder 02 and the satellite cylinder 16. In the case of the embodiment (FIG. 7) with at least the transfer cylinder 02 and the satellite cylinder 16 driven independently of each other, the one or more satellite cylinders 16 have one inherent drive motor 13 whereas the plate cylinder. And the transfer cylinders 01; 02 are mechanically coupled and driven by one common drive motor 13 (FIG. 7) or mechanically independent of each other by one unique drive motor 13 Driven (FIG. 8).

The plate cylinder 01, transfer cylinder 02 and satellite cylinder 16 in the first embodiment for FIG. 6 are of double circumference with an effective diameter _DwGZ ; _DwPZ ; _DwSZ of _260-400 mm, for example 280-350 mm. It is comprised as the trunk | drum 01; 02; 16. On the outer cover of the core 04, the transfer cylinder 02; 11 has at least one cylinder 06 having a characteristic amount α of 0.990 to 0.999, for example 0.993 to 0.997. With such a configuration, the rolling or driving of the sufficiently slip-free cylinder 01; 02; 16 is ensured over a wide range without torque transmission.

In the second embodiment for FIG. 7 or FIG. 8, the plate cylinder 01, the transfer cylinder 02 and the satellite cylinder 16 are of the same circumference, i.e. a circumference consisting essentially of one longitudinal printing surface, for example a newspaper surface. It is comprised as cylinder 01; 02; 16 which has. These cylinders are configured to have an effective diameter _DwGZ ; _DwPZ ; _DwSZ of _120-180 mm, for example 130-170 mm. On the outer cover of the core 04, the transfer cylinder 02 has at least one trunk 06 having a characteristic amount of 0.980 to 0.995, for example, 0.983 to 0.993.

In the case of a third embodiment not shown for FIG. 7 or FIG. 8, the plate cylinder 01 is configured as a circumferential cylinder 01 of _{equal magnification} with an effective diameter DwPZ of 120-180 mm, for example 130-170 mm. The transfer cylinder 02 and the satellite cylinder 16 are constructed as a double circumferential cylinder 02; 16 with an effective diameter _DwGZ ; _DwSZ of _260-350 mm, for example 280-320 mm. On the outer cover of the core 04, the transfer cylinders 02; 11 respectively have at least one trunk 06 having a characteristic quantity α of 0.985 to 0.995, for example 0.990 to 0.995.

In a fourth embodiment not shown for FIG. 7 or FIG. 8, the plate cylinder 01 and the transfer cylinder 02 are of equal circumference with an effective diameter _DwPZ ; _DwGZ of _120-180 mm, for example 130-170 mm. cylinders 01; 02 are constructed as satellite cylinder 16, cylinder 02 of twice the circumference with 260~350mm example effective diameter _{D WSZ} of 280～320Mm; is configured as 16. On the outer cover of the core 04, the transfer cylinder 02; 11 has at least one cylinder 06 having a characteristic quantity α of 0.985 to 0.995, for example 0.990 to 0.995. If the plate cylinder 01 and the satellite cylinder 16 have different dimensions, an ideal compromise may be found in that case on demand at both nips.

  As described above, the characteristic amount α of the waistline 06 is obtained by measuring the waistline 06 with an appropriate apparatus and subsequently performing processing based on an algorithm. An embodiment of a measuring device that is particularly suitable for determining the characteristic quantity α is depicted in FIG. 9 as viewed from above and in FIG. 10 as an enlarged side view.

  The measuring device has at least two cylinders 17; 18 or rollers 17; 18, which are mounted in a frame 19 so as to be rotatable, for example on both sides. At least one of these two cylinders 17; 18 here has a hard jacket surface which is sufficiently incompressible and inelastic. At least one of the two cylinders 17; 18 is supported so that the axial distance a between the rotation axes of both cylinders 17; 18 can be changed. In the case of this embodiment, the cylinders 17 constituted by “hard” jacket surfaces and corresponding to the plate cylinders or satellite cylinders 01; 12; In this embodiment, the other cylinder 18 is fixed in position and supported by the frame 19 in the conventional manner. The support portions of the trunks 17; 18 are rigid and are constructed without play. As for the former, the bearing section is correspondingly solid. A play-free construction is achieved by providing a conical seat on the bearing or by shrink fitting. However, the other cylinder 18 may be movable and the rigid cylinder 17 may be fixedly supported, or both cylinders 17; 18 may be movably supported together. In some cases, the mobility can be realized by turning the cylinder 17; 18 supported by a lever or a linear guide.

  In the preferred embodiment, the eccentric bushing 21 has an eccentricity e (n 2 * t to 4 * t) which is generally 2 to 4 times the strength t of the layer 06 to be measured by the device. For some layers 06, for example, between 3 and 8 mm, especially 4-6 mm, and for stronger types, 8-16 mm, especially 10-14 mm. The position of the eccentricity e makes an angle γ of 75 ° to 120 °, in particular 85 ° to 110 °, with the plane E at the basic position. Here, the basic position is regarded as the following position between the cylinders 17 and 18. That is, at that position, both jackets come into linear contact with substantially no push-in S.

  In an advantageous embodiment, the displacement of the eccentric bush 21 is effected via a lever 22 connected to the eccentric bush 21, which lever 22 can be displaced about the pivot axis of the eccentric bush 21 by an actuator 23. The actuator 23 can be basically configured in various forms, for example, a motor-driven screw spindle. In this embodiment, the actuator 23 is configured as a cylinder 23 to which a pressure medium can be applied, which is pivotally mounted on the frame 19, and the piston rod 24 of this cylinder is pivotally mounted with the lever 22. Connected (or vice versa).

  The actuator 23 displaces the lever 22 toward the stopper 26, and this stopper limits the displacement movement of the eccentric bush 21 so that the axial distance between the cylinders 17; The stopper 26 is configured to be positionally adjustable with respect to the displacement limit direction with respect to the lever 22, but can be fixed to the frame 19 at a desired position. In this embodiment, a screw bolt 27 that can be turned in a screw fixed to the frame has, for example, a screw spindle or a fine screw, and a stopper 26 is provided on the end face thereof. By rotating the screw spindle 27 manually or by a motor, the stopper can be further moved in the direction of the lever 22 or moved away from the lever 22.

  The movement or position of the eccentric bush 21 or lever 22 is determined by the displacement measuring part 28 according to an advantageous embodiment. According to this embodiment, this measurement is obtained by a micrometer or dial gauge 28 fixedly arranged on the frame, and a movable and free tappet of this measuring part cooperates with the lever 22. According to an advantageous arrangement of the dial gauge 28, the rotation of the indicator corresponds to a linear movement of the tappet smaller than 0.05 mm, in particular 0.02 mm or less. Nevertheless, the displacement measuring part 28 may be realized in another way instead of a mechanical configuration, for example it can be realized electrically and / or magnetically. In this case, the measurement value can be converted from a mechanical signal to an electrical signal, or the directly obtained electrical signal can be supplied to a data processing device (not shown).

  According to an advantageous arrangement for obtaining a high measurement accuracy, the distance b between the rotation axis A measured at the lever 22 and the measurement point of the displacement measuring part is made larger than the eccentricity e. The ratio between the distance b and the eccentricity e is advantageously 20 or more, for example 50 or more. From the eccentricity e, the distance b, the resolution of the displacement measuring unit, and the known straight line with respect to the displacement of the rotating shaft, the movement of the cylinder 17 in the outer jacket is defined. The measurement accuracy of the measuring apparatus configured as described above has reproducibility at a pushing amount S of 0.005 mm or less.

  According to one embodiment, the stopper is variably configured by a motor. At this time, the position of the stopper 26 can be obtained as an electric signal or set as an electric signal. At the same time, the measurement value of the displacement measuring unit 28 is also obtained as an electric signal. In the case of this embodiment, one or a plurality of positions or one or a plurality of axial distances a with respect to the cylinder 17 can be taken automatically via a data processing device or a control device.

  In the case of another embodiment that is not shown, the adjustment of the stopper 26 and the displacement measuring unit 28 is performed by means such as a screw spindle with fine threads driven by an electric motor capable of controlling the angle. Via the angular position, the data processing device obtains information about the position or vice versa.

  In order to determine the zero point of indentation, i.e. the position in which there is no indentation S between both cylinders 17; 18 and only linear contact has occurred, the measuring device is for example one on one side of the gap between cylinders 17; 18. Or it has the some light source which is not illustrated. In this case, it is possible to detect the indentation zero point through the gap of light when the two cylinders 17; 18 are brought close to each other, at which time light no longer shines through the gap. This light can be manually captured by the human eye on the opposite side of the gap, or it can be detected, for example, by one or more detectors for automatic operation. In the case of an automatic method, a signal is transferred to a data processing device not shown. By using light in this way, the accuracy of indentation zero point adjustment can be made 0.005 mm or less, for example, an accuracy of 0.002 mm or less can be achieved.

  In order to capture the rolling characteristics of both cylinders 17; 18, one of both cylinders 17; 18 can be rotationally driven by an external drive 29, for example an electric motor 29. In the case of FIG. 9, the electric motor 29 drives, for example, a drive wheel 36, such as a belt wheel 36, a belt wheel 36, a transmission device 37, for example, a belt 37, in particular a toothed belt 37, to drive a drive wheel 38, for example a belt wheel 38, in the hard body 17. The barrel 18 is only driven via friction. However, the electric motor 29 may drive the soft cylinder 18 via the belt 37, for example, while the hard cylinder 17 may be driven by friction. According to one advantageous embodiment, the electric motor can be switchably connected to a hard or soft cylinder 18; 17. According to one embodiment, one or even both of the cylinders 17; 18 have an electric motor 29 that is position controlled or at least rotationally controlled to drive it axially. The adverse effect exerted on the rolling characteristics via friction by the drive of one cylinder 17; 18 is avoided by using a bearing part with extremely low friction. In this way, a maximum deviation between the measured transmission ratio I of up to 0.01% and the “actual” transmission ratio I can be achieved.

  The angular velocities or individual rotation angles in both cylinders 17; 18 can be measured by a rotation generator 31; 32 arranged on the cylinders 17; 18 or individual pivots, for example by a photoelectric angle decoder.

  In order to avoid breaking the contact between the two cylinders 17; 18 that roll on each other, the hard cylinder 17 preferably has an uninterrupted continuous jacket in the area where it rolls with the soft cylinder 18. doing. However, this can be achieved in such a way that a plurality of “alternative plate types” or “equivalent plate types” provided on the outer cover are arranged in a circumferentially displaced manner (for example 180 °). Alternatively, if the rigid cylinder 17 has only one finite alternative version, the resulting seam or duct is sealed by the cover 33 (see, for example, FIG. 9). The same applies to the soft body 18, and in this case, as an example, in FIG. 9, two covers 06 that are shifted from each other by 180 ° in the circumferential direction are provided with a cover 34 that is at most half the length of the body. The state is drawn. Such an arrangement of the jacket 06 ensures a steady contact between one of the jackets 06 and the rigid body 17.

  By means of the rotation generators 31; 32 and the subsequent stages for various pushing amounts S, the angular velocities and possibly advance or delay of both cylinders 17; 18 are captured with high accuracy. Driving is carried out alternately via a hard or soft cylinder 17; 18. In this case, the movable body 17; 18 is moved by the displacement of the eccentric bush 17 in order to adjust the axial distance a. The adjustments described above are configured in a particularly comfortable manner, for example, in a printing press. In this case, the indentation zero point is obtained based on a light gap between the jackets (for example, a fluorescent tube under the roller gap). Further, in this case, it is possible to accurately set and measure the push-in amount S (by the displacement measuring unit 28) by fine adjustment (stopper 26). By using one or more measuring points for the known geometry of the cylinders 17; 18 and the indentation S (where S> 0), the characteristic quantity α according to the algebraic rules, eg equations [5], [8], [9] Is determined as described above.

FIG. 1 is a view showing a path of a compression type rubber blanket passing through a roller gap. It is a figure which shows the path | route of the non-compression type | mold rubber blanket which passes along a roller gap. It is a figure which shows the transmission ratio measured about the change of pushing amount. It is the figure which expressed the transmission ratio qualitatively. It is a figure which shows the Example of a printing apparatus. It is a figure which shows the Example of a printing apparatus. It is a figure which shows the Example of a printing apparatus. It is a figure which shows the Example of a printing apparatus. It is a figure which shows the Example of a measuring apparatus. FIG. 10 is a detailed side view of the device according to FIG. 9;

Explanation of symbols

01 Roller, Cylinder, Plate Cylinder, Counter Pressure Cylinder 02 Roller, Cylinder, Transfer Cylinder 03 Roller Gap 04 Core 06 Layer, Rubber Blanket, Cylinder 07 Printing Unit, Double Printing Machine 08 Printed Material, Web 11 Roller, Cylinder, Transfer Cylinder , Counter pressure cylinder 12 roller, cylinder, plate cylinder 13 drive motor 14 printing unit, 3 cylinder type printing unit 16 roller, cylinder, counter pressure cylinder, satellite cylinder 17 roller, cylinder 18 roller, cylinder 19 frame 21 eccentric bush 22 lever 23 Actuator, cylinder 24 Piston rod 26 Stopper 27 Screw bolt 28 Displacement measuring unit, dial gauge 29 Drive unit, electric motor 31, 32 Rotation generator 33, 34 Cover 36 Drive wheel, belt wheel 37 Transmission device, belt, toothed belt 38 Driving wheel Belt wheel _{D wGZ, D wPz, D wWGZ} , D wSZ diameter ω the angular frequency W _{GZ, W PZ} frequency a distance A difference A _{0, A 1} section b spacing B difference e eccentricity E plane α characteristic amount γ angles (e, E )
I Speed ratio, transmission ratio,
I _real Measured actual rotational speed ratio, transmission ratio I _komp compression ratio rotational speed ratio, transmission ratio I _inkamp non-compressible rotational speed ratio, transmission ratio L length n variable n _GZ rotational speed n _PZ rotation speed S Indentation S * Relative indentation t Intensity v ₀ , v ₁ , v _Gi , v _Ga velocity v _p surface velocity

Claims (37)

In the method of selecting the layer (06) on the rollers (01; 02; 11; 12; 16),
First, an extreme value (I _komp ; I _inkomp ) relating to the rotational speed ratio that theoretically occurs between the completely compressible case and the completely incompressible case is determined from the predetermined printer geometry. Partially depending on the amount of push-in (S),
Extrema of the rotational speed _ratio; calculated rotational speed ratio of the actual layer for _{(I komp I inkomp) (06} ) the desired relative position of _{(I real)} at least in part,
At least in part, for a desired layer (06), a specific geometry of the particular layer (06) is obtained by associating the desired characteristic with the algebraic rule to the characteristic for the theoretically determined extrema (I _komp ; I _inkomp ). Forming a characteristic quantity (α) with the influence removed;
How to select the layer on the roller.   Method according to claim 1, characterized in that the characteristic quantity (α) of the represented layer (06) is formed by first measuring in a measuring device and then removing the influence of the measuring device geometry by the same algebraic rule. The algebraic rule represents a relative position of a measured rotational speed ratio (I _real ) relative to two extreme values (I _komp ; I _inkomp ) with respect to the rotational speed ratio for the indentation amount (S). The method described. Comprising at least two cooperating rollers (01; 02; 11; 12; 16), at least one of the rollers (02; 11) having an elastic layer (06) on its jacket; In the printing unit of the type in which the other rollers (01; 12; 16) have a sufficiently undeformable jacket,
The layer (06) has at least a characteristic amount (α) of 0.980 to 0.999 representing the elastic properties of the layer in the relative indentation (S *) region, where the characteristic amount is an algebraic rule.

I _komp ; I _inkomp is the rotational speed ratio for the extreme case of a completely compressible or completely incompressible layer (06) and I _real represents the desired rotational speed ratio Printing unit. The rotation speed ratio _Ireal is 0.001 or less, for example, 0.001 from 1.000 / n when a change occurs in at least one region of the relative pushing amount (S *) of the layer (06). Where n is the ratio of the number of prints in the circumferential direction on the roller (02; 11) with the layer (06) to the number of prints on another roller (01; 12; 16). The printing unit according to claim 4, wherein At least two cooperating rollers (01; 02; 11; 12; 16), at least one of the rollers (02; 11) having an elastic layer (06) on its jacket The other rollers (01; 12; 16) in a printing unit of the type having a sufficiently undeformable jacket,
The geometry of the layer (06) and both rollers (01; 02; 11; 12; 16) are alternately coordinated with each other;
The rotation speed ratio ( _Ireal ) of each roller (01; 02; 11; 12; 16) is maximum when a change occurs in at least one region of the relative push-in amount (S *) of the layer (06). There is a deviation from 1.000 / n by 0.002, where n is the number of printing faces in the circumferential direction on the roller (02; 11) having the layer (06) and another roller (01; 12; 16). The printing unit is characterized in that it represents a ratio to the number of printed surfaces in (1). The rotation speed ratio (I _real ) of the rollers (01; 02; 11; 12; 16) is 1. Deviation from 000 / n, where n is the number of printed surfaces in the circumferential direction on the roller (02; 11) with the layer (06) and the number of printed surfaces in another roller (01; 12; 16). The printing unit according to claim 6, which represents a ratio of Comprising at least two cooperating rollers (01; 02; 11; 12; 16), at least one of the rollers (02; 11) having an elastic layer (06) on its jacket; In a printing unit of the type in which the other roller (01; 12; 16) has a sufficiently undeformable jacket,
The geometry of the layer (06) and both rollers (01; 02; 11; 12; 16) are alternately adjusted to each other, and the rotation speed ratio for at least one region of relative indentation (S *) _{(I real)} and indentation amount (S) and difference quotient _(dI real / dS) is a printing unit, characterized by having a deviation from zero only 0.001 1 / mm at the maximum. For the region of relative indentation (S *), the layer (06) has a characteristic quantity (α) of 0.980 to 1.000 representing the elastic characteristic of the layer, and the characteristic quantity is an algebraic rule.

I _komp ; I _inkomp is the rotational speed ratio for the extreme case of a completely compressible or completely incompressible layer (06), and I _real represents the desired rotational speed ratio. Or the printing unit of 8. The relative amount of push for at least the region of the (S *), rotational speed ratio _{(I real)} and indentation amount (S) and difference quotient _(dI real / dS) is the deviation from zero only up to 0.001 1 / mm The printing unit according to claim 4, wherein The printing unit according to claim 10, wherein the difference quotient (dI _real / dS) is substantially zero.   The range of relative indentation (S *) to the nip between the roller configured as the transfer cylinder (02; 11) and the roller configured as the plate cylinder (01; 12) is between 6% and 7%. The printing unit according to any one of claims 4 to 10.   The range of relative indentation (S *) to the nip between the roller configured as the transfer cylinder (02; 11) and the roller configured as the satellite cylinder (16) is between 9% and 10%. The printing unit according to claim 4. Both rollers (01; 02; 11; 12; 16) each have an effective diameter ( _DwGZ ; _DwPZ ) of ₂₆₀ to ₃₅₀ mm, the layer (06) having a characteristic of 0.989 to 1.000 Printing unit according to claim 4 or 9, wherein the printing unit has a quantity (α). Both rollers (01; 02; 11; 12; 16) each have an effective diameter ( _DwGZ ; _DwPZ ) of _120-180 mm, and the layer (06) is 0.980-0.990 The printing unit according to claim 4 or 9, wherein the printing unit has a characteristic quantity (α). The roller (02; 11) having the elastic layer (06) has an effective diameter ( _DwGZ ; _DwPZ ) of ₂₆₀ to ₄₀₀ mm, and another roller (01; 16) has an effective diameter (150 to 190 mm). The printing unit according to claim 4 or 9, wherein _DwGZ ; _DwPZ ) and the layer (06) has a characteristic quantity (α) of 0.987 to 1.000.   The roller (02; 11) having the elastic layer (06) is configured as a transfer cylinder (02; 11), and the roller (01; 12) having the sufficiently undeformable covering is a plate cylinder (01 A printing unit according to claim 4, 6 or 8, configured as 12).   The roller (02; 11) having the elastic layer (06) is configured as a transfer cylinder (02; 11), and the roller (16) having the sufficiently undeformable jacket is used as a satellite cylinder (16). 9. A printing unit according to claim 4, 6 or 8, which is configured.   Printing according to claim 4, 6 or 8, wherein both rollers (01; 02; 11; 12; 16) are configured as cooperating rollers (01; 02; 11; 12; 16) in an inking device. unit.   One of the rollers (01; 02; 11; 12; 16) is driven by a motor, and the other of the rollers (01; 02; 11; 12; 16) is simply driven by friction. The printing unit according to claim 19.   The transfer cylinder (02; 11) cooperates with a third roller (16) configured as a satellite cylinder (16), which third roller (01; 02; 11; 12) 18. A printing unit according to claim 17, wherein the printing unit is driven mechanically independent of the drive motor (13).   Printing unit according to claim 4, 6, 8, 17, 18 or 19, wherein both rollers (01; 02; 11; 12) are driven in pairs by a common drive motor (13).   20. Both said rollers (01; 02; 11; 12; 16) are driven mechanically independently of each other by two drive motors (13), according to claim 4,6,8,17,18 or 19 Printing unit. In the device for determining the rolling characteristics of the elastic layer (06),
The axial spacing (a) between the roller (18) carrying the layer (06) and the roller (17) having a substantially non-deformable jacket can be varied, both of these rollers (17; 18) the rotational speed ratio (I _real ) of
At least one of the two rollers (17; 18) is supported by an eccentric bush (21) in the frame (19).
A device that determines the rolling characteristics of an elastic layer.   25. A lever (22) for converting the movement of a roller (17) is fixedly connected to the eccentric bush (21), and the movement of the lever (22) is determined by a displacement measuring part (28). The device described. In the device for determining the rolling characteristics of the elastic layer (06),
The axial spacing (a) between the roller (18) carrying the layer (06) and the roller (17) having a substantially non-deformable jacket can be varied, both of these rollers (17; 18) the rotational speed ratio (I _real ) of
The change of the shaft spacing (a) is determined by the displacement measuring part (28) at the lever (22) for converting the movement of the roller (17),
A device that determines the rolling characteristics of an elastic layer.   26. The device according to claim 25, wherein at least one of the two rollers (17; 18) is supported by an eccentric bush (21), the eccentric bush and the lever (22) being fixedly connected to each other.   28. The device according to claim 24 or 27, wherein the ratio of the distance (b) from the measurement point of the displacement measuring part (28) to the rotation axis (A) and the eccentricity (e) in the lever (22) is 20 or more.   The eccentricity (e) corresponds to a plane (E) and 75 to 75 which are defined by the rotation axis of the roller (17; 18) at the position of the roller (17; 18) in which both outer covers are in linear contact with each other. 28. Apparatus according to claim 24 or 27, wherein the apparatus forms an angle of 120 [deg.].   27. Apparatus according to claim 24 or 26, wherein the individual angular velocity and / or rotational angular position is determined by a rotation generator (31; 32) provided for each roller (17; 18).   One of the rollers (17; 18) is driven by an external drive unit (29), and the other roller (18; 17) is simply driven by friction with the one roller (29). 27. The device according to 24 or 26.   32. Device according to claim 31, wherein said drive (29) is interchangeably associated with said one roller or the other roller (17; 18).   27. The device according to claim 25 or 26, wherein the displacement measuring part (28) is configured as a dial gauge having a resolution of 0.05 mm / 360 ° or less.   27. Device according to claim 25 or 26, wherein a repositionable stopper (26) is provided for the lever (22).   27. Apparatus according to claim 25 or 26, wherein the lever (22) is displaceable by an actuator (23).   36. A device according to claim 34 or 35, wherein the lever (22) can abut against the stopper (26) by means of an actuator (23) configured as a cylinder (23) to which a pressure medium is applied.   27. An apparatus according to claim 24 or 26, wherein a light source is provided on one side of the gap between each roller (17; 18) for determining the indentation zero point.

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