The present disclosure generally concerns the field of methods and arrangements that are used to print to a substrate.
Printing to a substrate—for example a paper or cardboard or the like—may in general take place by means of the most varied printing methods, for example by means of offset printing methods or digital printing methods. It is hereby known that different printing methods react with different sensitivity to changes, for example of the ambient temperatures and/or the ambient moisture. Changes in ambient temperature and/or ambient moisture may lead to altered print results, altered print quality and/or to altered capability for further processing, for example via folding, bending, binding, cutting etc.
This circumstance is presently often confronted in that the substrate to be printed to is either stored directly in the immediate environment of a printing machine or printing line with which the substrate should be processed, or in that the storage of the substrate takes place in a special heated storage space in which the climatic conditions (primarily temperature and moisture) are as similar as possible to those in the printing room. In this way it should be achieved that the substrate may adapt (with regard to temperature and moisture) to the conditions in the printing room. In addition to this, the substrate may be exposed with radiant heaters, for example, and thus may be warmed. A warming of the substrate may also take place with the aid of saddle heaters.
If the substrate must be stored for a non-negligible time—for example one day or longer—under the corresponding conditions for the adaptation to (for example) the temperature, this conventional procedure leads to a significant space requirement in the printing room, and resulting from this to significant costs, since the modern printing lines can process large quantities of substrate in this time. In addition to this, the print result and/or the result of further processing may furthermore fluctuate due to—for example—seasonally changing ambient temperature and ambient moisture under which printing and storage take place.
This is a state which may be improved.
It is an object to specify a method and a printing system that enable it to be possible to execute the printing process and/or the further processing cost-effectively and with little effort (in particular with low space requirement), under conditions that are as advantageous as possible for the printing and/or the further processing of the printed materials and that are largely independent of the temperature ratios in the environment of a printing machine.
In a method or system to control a temperature of a substrate to be printed to and which exhibits said temperature during a traversal of a printing system, specifically selecting or controlling a fluid temperature of a liquid fluid to be applied onto the substrate to specifically influence the substrate temperature, the fluid being applied onto the substrate before the substrate is printed to. At least one of the fluid temperature and a quantity of the fluid applied onto the substrate per time unit at least depending on at least one of a first measurement value for a temperature of the substrate before the application of the fluid and a second measurement value for a surface temperature of the substrate after the application of the fluid.
For the purposes of promoting an understanding of the principles of the disclosure, reference will now be made to the preferred exemplary embodiments/best mode illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the of the disclosure is thereby intended, and such alterations and further modifications in the illustrated embodiments and such further applications of the principles of the disclosure as illustrated as would normally occur to one skilled in the art to which the disclosure relates are included herein.
Accordingly, a method is disclosed for controlling a substrate temperature (in particular a substrate surface temperature) which substrate to be printed to exhibit during a traverse of a printing system, wherein a fluid temperature of a fluid to be applied onto the substrate is specifically selected or controlled, and the fluid brought to the fluid temperature is applied onto the substrate, and the substrate temperature is hereby specifically effected.
According to an exemplary embodiment, a printing system is also disclosed for printing to a substrate, in particular by means of a digital printing method, wherein the printing system has at least one applicator to apply a fluid to the substrate and at least one temperature adjuster. The temperature adjuster is provided in order to bring the fluid to a specifically selected or controlled fluid temperature. The printing system according to the exemplary embodiment is designed for the implementation of a method to control a substrate temperature according to the exemplary embodiment.
The idea forming the basis of the present exemplary embodiment is to select or control, in a targeted manner, the temperature of a fluid that should be applied onto the substrate. In that this fluid is applied onto the substrate, the temperature of the substrate may be specifically affected (and thus controlled) while this travels through the printing system. A parameter of the substrate that is relevant to the printing method and/or the further processing—namely the temperature of the substrate itself—may thus be specifically adjusted independently of the conditions in the environment of the printing machine and, for example, may advantageously be kept constant at an optimal value. Given the exemplary embodiment, a direct effect on the substrate temperature thus takes place without a detour via the ambient temperature. A storage of the substrate—for example in the form of voluminous paper rolls—in the direct environment of the printing machine may be avoided, whereby a significant savings in space and costs may advantageously be achieved given precisely the printing lines that, presently, are often long in any event. The control of the substrate temperature may additionally be realized with little effort given the present exemplary embodiment.
The temperature of the substrate that is affected by means of the fluid may presently be in particular a surface temperature of the substrate, thus the temperature in a surface region of said substrate. Alternatively, however, if needed the affected substrate temperature may also be a temperature inside the substrate or across its entire cross section. The temperature of the substrate may vary along the path of the substrate upon traversing the printing system. Presently, a targeted influencing of the substrate temperature that the substrate exhibits during the traversal of the printing system may also in particular be understood as a targeted influencing of a substrate temperature at one point or in a region of the run path of the substrate.
The present exemplary embodiments are explained in detail in the following drawing figures.
These drawing figures impart a further understanding of the embodiments of the disclosure. They illustrate embodiments and—in connection with the Specification—serve for the explanation of principles and concepts of the exemplary embodiments. The elements of the drawings are not necessarily shown true to scale relative to one another.
Identical, functionally identical and equivalent elements, features and components are—insofar as not stated otherwise—are respectively provided with the same reference characters in the drawing figures.
A cross section through a substrate 19 in an initial state is shown in
Only an upper half of the cross section of the substrate 19 is depicted in
In the presently described exemplary embodiments, the substrate 19 is preferably processed via printing in digital printing methods, for example a liquid toner-based or dry toner-based electrographic printing method. However, a printing to the substrate 19 could also be provided in an inkjet process. Alternatively, instead of being printed to in a digital printing method, the substrate 19 could be printed to in an offset process.
In the initial state, the substrate 19 is not a homogeneous substance, as is clear from
Some components of a printing system (which is not entirely visible in
As is clear from
An example of a design of the fluid applicator 6 is schematically drawn in
In the example of
The fluid applicator 6 of
In
Moreover, a distance A between the location of the application of the fluid 38 to the substrate 19 and the location at which the printing takes place (i.e. any location at which the ink or toner transfer to the substrate 19 takes place in the print group 10) is drawn in
Further additional print groups and/or a coating group and/or a further processor with devices to bind, stack, fold, bend or cut the substrate 19 (which are not shown in
In the first exemplary embodiment, the fluid 38 may also be designated as a primer. The fluid 38 is in particular present as a liquid and thus may also be designated as a primer liquid. One or more properties of the substrate 19 may be adapted by means of the fluid 38 to the respective particular requirements of the printing method that is to be used, i.e. for example the requirements of a liquid toner process, a dry toner process or, instead of these, an inkjet process. In this way, by means of the application of the fluid 38 to the substrate 19 (which takes place at a location in the substrate path 22 upstream of the print group 10, and thus before the printing), the substrate 19 is prepared for the subsequent printing in the print group 10.
In the event that the print group 10 is designed for offset printing, the fluid 38 could be what is known as a dampening solution which may likewise be present in liquid form.
For the preparation of the substrate 19 by means of the fluid 38, a substrate property of the substrate 19 is selected, or multiple substrate properties of the substrate 19 are selected, under consideration of the printing method by means of which the substrate 19 should be printed to in the print group 10. By means of the application of the fluid 38 in the fluid applicator 6, before the printing a targeted homogenization (and thus targeted adjustment) of the selected substrate property or substrate properties takes place in the directions of the planar extent of the substrate 19.
In particular, one or more of the following properties are considered as specific substrate properties or substrate parameters that are to be homogenized, and thus in particular are to be adjusted:
The homogenized substrate properties may be different depending on the selected printing method. For example, a homogenization of the absorption capability may be useful for a printing in the inkjet process or in the liquid toner process and be advantageous for the print result. For example, in this way a non-uniform deposition of toner particles from the carrier fluid of a liquid toner may be reduced. A homogenization of electrical properties (such as resistance, conductivity or static charging capability) may in particular take place given electrographic processes such as liquid toner or dry toner processes, and be advantageous for a uniform migration of toner particles to the points of the substrate surface 20 that are to be inked. A homogenization (and thereby an adjustment) of a chemical property of the substrate 19 may also be considered as needed. For example, in the event of an inhomogeneous distribution of a substance/material (for example of a binder or a salt) in a substrate, a chemical property that is ascribed to this substance/material could be made uniform via the homogenization by means of the fluid 38.
As shown in
In particular, for example, an electrical conductivity or an electrical resistance or an absorption capability within the entirety of the strokes 31, 32, 33 may be homogenized over the area and therefore may be adjusted.
The fluid 38 may include water, for example an aqueous solution or aqueous dispersion solution. The fluid 38 may include water as well as an additive substance or multiple additive substances that are added to the water. The additive substances and the water thus represent respective fluid components of the fluid 38. The fluid 38—as primer liquid, for example—may be a mixture of different components, wherein each of the ingredients or fluid components that are included therein may serve to optimize individual properties of the substrate 19. In the interaction of the individual ingredients, the desired homogenization of the substrate properties may be achieved with the aid of an optimized mixture. Instead of a liquid, however, a gas may also be used as a fluid 38 for optimization of the substrate properties via homogenization.
For example, the fluid 38 (which, according to the first exemplary embodiment of
The water proportion of the fluid 38 may be used for areal homogenization of the electrical resistance of the substrate 19. In one variant, a suitable salt may additionally be added to the fluid 38 to assist in the homogenization of the electrical resistance or of the electrical conductivity.
In the field of digital printing, a homogenization of the electrical resistance of the substrate 19 has advantages given liquid toner and dry toner processes. The homogenization of the absorption capability may in particular have an advantageous effect given liquid toner processes.
In order to implement the homogenization, the amounts of fluid 38 that are to be applied onto the substrate per area unit of said substrate, and the temperature of the fluid 38, as well as its composition, are to be suitably selected and adjusted to one another, as well as to the substrate 19 and the printing method. In the event that one or more additive substances in water are used for the fluid 38, the composition may be understood as concentrations of the additive substances in the fluid 38. In the selection for the fluid quantity that is applied to the running substrate 19 per time unit, and thus for a given travel or transport velocity of the substrate 19 per area unit, it is to be heeded that the mechanical structure of the substrate 19 is not destroyed by too great an amount of water, for example.
In an advantageous additional variant, the fluid 38 may also be designed to affect the behavior of the carrier fluid for the toner (carrier) in the event of a subsequent printing in an electrographic (for example electrophotographic) liquid toner process. The toner particles are suspended in the carrier. In this variant, the fluid 38 as primer liquid should ensure that the toner particles in the nip are transferred onto the substrate at their provided position, and optimally do not deviate from their nominal position due to the behavior of the carrier at this point, meaning that the position deviation upon transfer of the toner particles should be reduced or avoided. A manner of “short-term retention” of the carrier fluid is thus also sought via the primer liquid as fluid 38.
In order to achieve optimal print results and/or optimal results in the further processing (for example given folding, bending or binding) after printing, optimally independently of the prevailing environment conditions (in particular ambient temperatures and ambient moisture) that affect the climate in the printing room, in the first exemplary embodiment of the disclosure according to
The substrate temperature to be controlled may hereby be a surface temperature of the substrate 19 if the influencing of the substrate surface temperature (i.e. of a temperature in a surface layer of the substrate 19, for example on the order of the thickness of the strokes 31-33) is already sufficient to achieve the desired printing properties or further processing properties. Alternatively, the temperature may be influenced over the entire thickness of the substrate 19, thus also inside it.
In the first exemplary embodiment of the disclosure (see
For combinations of printing methods and/or further processing processes and substrate 19, for example in which an increase of the substrate temperature yields a better result in printing or in further processing, the substrate temperature may thus be specifically adjusted for an optimized result.
In a preferred variant of the first exemplary embodiment of the disclosure, the fluid 38 comprises water. By means of the application of the fluid 38 to the substrate 19, it is thus achieved that a moisture content of the substrate (substrate moisture) is also to be specifically influenced in addition to a targeted control of the substrate temperature. With consideration of the moisture content of the substrate 19, a dependency of the printing result and further processing result on the environmental conditions may thus also be avoided, or at least result. For example, the moisture content at location 11 or in the region 23 (see above) may hereby be controlled.
The moisture content in the substrate 19 may thus be adjusted for optimized print quality and/or optimized capability for further processing of the printed substrate 19. By means of a specifically influenced moisture content, it is achieved that moisture-dependent properties (for instance the wetting capability) of the substrate 19, its electrical properties (such as resistance, conductivity and capacitance), but also mechanical properties (for instance the fragility upon bending or binding) are specifically influenced.
Given suitable adjustment of the substrate moisture, for example, what is known as the problem of “fracture in folding” in the post-processing of the printed substrate 19 may be avoided. The moisture content of the substrate 19 may also influence its running properties and be selected accordingly such that advantageous running properties are achieved.
It may be useful to control the substrate temperature and the moisture content in the substrate 19 in such a manner that these respectively assume a constant value selected under consideration of in particular the printing method and the substrate type, whereby these parameters no longer vary in a manner that is advantageous to the printing method.
A controller (not shown in
In other words: the substrate temperature that should be specifically influenced may thus be a substrate temperature which the substrate 19 has upon coating (i.e. at the point in time of the transfer of a coating agent), wherein the coating agent may, for example, be a printing ink or a coating or a lamination, and may be drawn into the substrate 19 or remain as a layer on its surface.
In variants of the first exemplary embodiment, the substrate temperature and/or substrate moisture that should be specifically influenced may be a temperature of the substrate 19 and/or a moisture that the substrate 19 exhibits upon further processing or post-processing after printing, i.e. downstream of the print group 10 along the path 22 of the running substrate 19. The substrate temperature and/or the substrate moisture that the substrate 19 exhibits in a lamination process or the like could also be specifically influenced.
It may also be provided—for example in one variant of the first exemplary embodiment—that the substrate temperature downstream of the fluid applicator 6 (i.e. after this) does not fall below a predefined temperature value over a defined sub-region 23 of the path 22 of the substrate 19 through the printing system, or over the entire path of said substrate 19 downstream of the fluid applicator 6.
In this way, the substrate temperature may be optimally controlled for the actual printing or coating process, in particular the ink transfer or toner transfer or coating agent transfer onto the substrate, and/or for the post-processing/further processing.
The fluid temperature of the fluid 38 is advantageously specifically selected or controlled in such a way that the substrate temperature assumes a value above the ambient temperature or room temperature in the printing room, thus in the environment of the printing system and preferably above all ambient temperatures or room temperatures that may occur under the typical operating circumstances and environmental conditions. Similarly, the moisture content of the substrate 19 may also be increased beyond a moisture content that the substrate 19 would assume given storage under the climatic environment conditions in the environment of the printing system. In such variants, substrate temperature and substrate moisture are thus increased by means of the fluid 38 beyond their normal measurement present under ambient conditions. In this way, the working window within which the printing (and if applicable the further processing) of the substrate 19 takes place may be selected so as to be reproducible. Overall, the use of the fluid 38 to adjust the substrate temperature and substrate moisture thus enables not only an optimized result of printing (and if applicable further processing) in a printing line, but rather may also contribute to a constant good result over time. Such a procedure is advantageous in cases in which an increase of the substrate temperature beyond the ambient temperature results in a better printing result or further processing result.
The viscosity, surface tension and tack of liquids (such as a primer liquid, but also a printing ink) normally follow a temperature dependency of type X=X=X0·exp(Ea/(k·T)), meaning that they decline for constant X0, Ea, k with increasing temperature T. In such an Arrhenius equation, X for example designates the viscosity, thus X0 designates a reference viscosity, Ea an activation energy and k the Boltzmann constant. If a glass transition occurs in the temperature range of interest, however, the aforementioned properties often no longer change according to the aforementioned equation. Diffusion processes are also temperature-dependent.
The heating of the fluid 38—and the increase of the substrate temperature that is thereby controlled, for example to values above the room or ambient temperature—thus have an additional advantageous effect because liquids such as primer liquids (as well as dampening agents, inks and general coating agents) may have improved penetration into the surface of the substrate due to the decreasing viscosities, surface tensions and/or tacks, which may likewise contribute to an additional improvement in the achievable print quality and reduce fluctuations of the print quality or coating quality.
After the application of a fluid 38 in liquid form to the running substrate 19 (in-line application), before the following printing by means of the print group 10 a sufficient time should be available in which the fluid 38 (applied as a liquid) may penetrate sufficiently. The substrate 19 travels in the direction 21 through the printing system. The distance A along the path 22 (see
A warming of the fluid 38 thus enables an accelerated, faster penetration of the fluid 38, thus a shorter penetration time, and therefore enables a shorter distance A for a given printing speed, which has an advantageous effect on the total length L of the printing line (which is often quite long anyway, considering the devices—such as paper take-off and devices for further processing via cutting, folding, bending, binding, take-up, sorting etc.—situated before and after the print group 10). For a half-life of the penetrating amount of approximately 200 milliseconds, and given negligibility of a reverse lamination if only a small portion of the applied quantity of liquid still remains on the substrate surface 20, a distance A of approximately 0.6 meters (for example) results for a print speed of 1 meter/second.
In the first exemplary embodiment, as described in the preceding the substrate 19 exhibits, at the location of the printing 11 by means of the print group 10, a specifically controlled substrate temperature that is advantageous for the printing leads and that to print results that are as optimal as possible. In addition to this, as in the conventional procedure the substrate 19 does not need to be stored in the immediate proximity of the printing system for a longer time in order to assume the ambient temperature. The substrate moisture may likewise advantageously be controlled at a predefined location 11 or a predefined region 23.
A substance or primer in the form of a fluid 38 (in particular a liquid) is hereby used to adjust substrate temperature and substrate moisture, which fluid 38 may also be used for other purposes—for example, as already cited in the preceding, in order to achieve a large areal homogenization or averaging of selected substrate properties such as electrical resistance, electrical conductivity, electrostatic charging capability, absorption capability and/or wetting capability, or in order to influence additional properties (for example a running capability of the substrate 19).
In one variant, the fluid 38 could be cooled before the application on the substrate 19 in order to specifically select or control the fluid temperature of said fluid 38, for example such that the substrate temperature assumes a value below the ambient temperature or the room temperature in the printing room. This may be advantageous if it turns out that a selected printing method achieves particularly good results for a given substrate type precisely at substrate temperatures that are below the temperatures in the environment of the printing system. In particular, this could occur in environments with very high ambient temperatures.
The advantages of the apparatus of the fluid 38 by means of the fluid applicator 6 are also clear from
The printing system 1 may be a digital printing machine or digital printing line. Digital printing methods are particularly well suited for frequently changing print jobs, which also may involve frequent changing of the substrate 19 to be printed to. The space savings due to the omission of a storage of a number of different substrates 19 in large quantities in the immediate proximity of a printing machine or printing line is therefore particularly advantageous in the case of digital printing methods.
In all exemplary embodiments of the disclosure, the supply feed of the substrate 19 may take place continuously from a roll 4 as described in the preceding and in the following, as schematically drawn in
On the one hand, as described above the distance (designated with A in
As shown in the preceding, in the first exemplary embodiment of the disclosure a temperature adjustment or a tempering of a fluid 38 (for instance a coating agent, a primer, a dampening agent, an additive or in general a substance to be applied on the substrate 19 before the actual printing method)—preferably a liquid—thus takes place in order to hereby control the substrate temperature. The substance to be applied may, for example, also be a printing ink or a coating. The substrate temperature is thus controlled by means of a targeted selection or adjustment of the temperature of the applied substance. A regulation of the substrate temperature is likewise possible.
Substrate properties that are more homogeneous over an area are set by means of a homogenizing application of a fluid 38, in particular of a suitable liquid such as water with additive substances. In addition to this, the moisture content of the substrate is controlled or regulated.
The targeted influencing of substrate temperature and substrate moisture after the fluid applicator 6 (for example at a location 11 or in a region 23 of the substrate path 22) not only enables advantageous effects on the print quality and the further processing capability of the printed substrate 19, but can also enable a monitoring of the shrinkage of the substrate 19 during the traversal of the printing system. This may reduce the dimensions of the substrate 19 that are to be compensated, for example upon cutting of the printed substrate 19. An optimal tempering and liquid utilization of the substrate 19 may also make its shrinkage during the traversal of the printing system easier to reproduce. A regulation of the shrinkage is possible.
As already explained, the distance A along the travel path 22 of the substrate 19—for which distance A a minimum value may be determined from the travel velocity of the substrate on the one hand and, on the other hand, the time that the fluid 38 requires for a sufficient penetration—lies between the location of the application of the fluid 38 (in liquid form, for instance) and the subsequent first print group 10. For example, the travel velocity of the substrate 19 may be between approximately 1.0 meters/second and approximately 2.0 meters/second. An increase of the fluid temperature of the fluid 38 has an advantageous effect with regard to the possible printing speeds (and thus the travel velocities of the substrate) because higher printing speeds are possible for a given distance A due to the penetration speeds that are higher with increasing temperature.
Similarly, a targeted heating of the substrate 19 by means of the tempered fluid 38 has the further advantage that the carrier fluid used in liquid toner methods likewise penetrates faster, which in turn has an advantageous effect with regard to a possible limitation of the possible printing speeds due to the penetration speed of the carrier.
Multiple advantageous effects may thus be achieved simultaneously with only comparably small cost via the use of the fluid 38 both for the purposes of homogenization of the substrate properties and for the control of the substrate temperature and substrate moisture. Moreover, the tempering of the fluid 38 (for example by heating it) not only has a use in controlling the substrate temperature; rather, by using a heated fluid 38, this penetrates faster, meaning that the sought homogenization and (if applicable) adjustment of the selected substrate properties is achieved in a shorter amount of time. In some cases, a reduced amount of fluid may additionally be required for the homogenization, in particular in comparison with unheated fluid 38. On the other hand, with the aid of the heating of the fluid 38 it may be possible to place a sufficient amount of fluid 38 for the desired homogenization or adjustment of the substrate parameter(s) into the substrate 19 in the available time.
Given heating of the fluid 38, a deeper penetration into the substrate 19 of fluid components or additives included in the fluid 38 may also be achieved. The tempering of the fluid 38—in particular increasing or decreasing temperature—may thus be advantageously used for a targeted control of the penetration depth of one or more of the additive substances included in the fluid 38.
In the second exemplary embodiment of
In detail, in the second exemplary embodiment of
The electrical resistance of the substrate 19 in its transversal or thickness direction Q (thus transversal to the substrate surface 20 through the substrate 19)—thus the volume resistance—is also measured at a measurement point 55 that is situated adjacent to the measurement point 53 and likewise before the fluid applicator 6, wherein for this a second measurer 56 is provided that delivers a second measurement value 56a.
Furthermore, in the second exemplary embodiment the substrate surface temperature is measured by means of a third measurer 64 at a measurement point 63 after the exit of the substrate 19 from the fluid applicator 6. The substrate surface temperature is also measured at a further measurement point 65 by means of a fourth measurer 66, wherein the measurement takes place by means of the fourth measurer 66 shortly before the substrate 19 travels into the print group 10. In this example, the print group 10 may represent a first print group (which may be followed by additional print groups that are not drawn in
Similar to as at the measurement point 55, the electrical resistance in the transversal direction Q of the substrate 19 is measured by means of a fifth measurer 68 at an additional measurement point 67 in the print group 10, and a measurement value 68a is hereby obtained.
For example, the measurement of the substrate surface temperatures by means of the measurers 54, 64, 66 may respectively take place via the measurement of infrared emission (IR emission).
For example, as depicted in
The rollers 57, 58 or the drums 45, 46 hereby contact the substrate 19 on its surface on both sides. For example, the electrical resistance may be measured as a kind of “line resistance” between the contact lines of the two rollers 57, 58 or of the two drums 45, 46 with the substrate 19. Given this measurement method, a resistance is obtained as a measured electrical resistance that is averaged over the entire width of the substrate web, transverse to its transport direction 21. The peripheral surfaces of both rollers 57, 58 are entirely conductive, for example. For a given timing frequency of the measurement or sampling frequency, averaged or integrated resistance values for a respective stripe of the moving substrate are thus obtained, wherein the stripe extends over the entire width of the substrate web.
For a homogenization of the electrical resistance of the substrate 19 over the area, the measurement of the electrical resistance may advantageously alternatively take place by means of the system schematically drawn in
In yet another variant of an arrangement for resistance measurement that is schematically illustrated in a partial view in
In one variant (not graphically depicted) of the arrangement of
Downstream of the applicator 6, an additional measurement may also take place by means of rollers 57, 58′ or 57, 58″ (designed corresponding to
It is thus clear that, in the systems of
In combination with any of the resistance measurement methods of
However, suitable application nozzles (which, for example, could be executed similar to inkjet nozzles) could also apply the fluid 38 to the substrate 19 across its width.
In variants of the exemplary embodiments, such application nozzles could additionally be useful in order to apply the fluid 38 not uniformly in the width direction B of the substrate 19 but rather depending on the resistance measurement for various positions along the width direction B of the substrate web (see
The measurement of electrical resistances is generally known per se to the person skilled in the art, which is why additional devices and circuits that are used for resistance measurement (in
As explained with regard to the first exemplary embodiment (see
According to the second exemplary embodiment, upon operation of the printing system a data set (see reference character 85a) that (for example) includes a nominal substrate temperature and a nominal moisture content of the substrate may initially be provided from the database 85 for a selected substrate 19 which should be printed to in the print group 10, as well as for a given printing method. The database 85 may thus include at least one substrate database that associates substrates of defined types and defined thickness with nominal substrate temperature and nominal moisture contents with which optimized print results may be achieved, and which may be accessed during the printing process. The nominal substrate temperature and nominal moisture contents may also additionally be dependent on the composition of the fluid 38 and be stored in corresponding data sets of the database 85. The preferred operating points to be incorporated into the substrate database may be determined for different substrate types, substrate thicknesses etc., for example via tests.
For example, it may be established that these nominal values (for example the nominal temperature, for instance as a surface temperature of the substrate 19) should optimally be achieved at least at a predefined point or in a predefined segment of the path 22 of the substrate 19 through the printing system, in particular at the location 11 of the printing by means of the print group 10 or multiple such print groups, in order to achieve an optimal print result. Nominal substrate temperature (for instance nominal substrate surface temperature) and nominal moisture content may in many cases be constant over time for a selected substrate 19 and a selected printing method, but in principle could instead also vary over time in a predefined manner. The nominal substrate temperature and the nominal moisture content of the substrate may define a nominal operating point of the printing system, wherein the nominal operating point may be associated with a defined fluid. The printing system may also comprise devices for further processing (see reference characters 15 in
The achieved substrate temperature will normally not correspond at the sought point or in the sought region to the fluid temperature of the fluid 38. The applied quantity of fluid 38 and its fluid temperature are to be selected, depending in particular on printing speed and/or substrate type and/or substrate thickness (thermal capacity) and/or fluid composition (as well as depending on the prior temperature of the substrate 19 measured by means of the measurer 54), in such a manner that the nominal temperature at the sought point or in the sought region is achieved with defined tolerance. This is produced by means of the regulator 78 in the example of
Dependencies of the fluid quantity and fluid temperature that are required to achieve the nominal substrate temperature on the printing speed, the substrate thickness and/or the substrate type may likewise be stored in the database 85.
In a preferred variant, the database data which is included in the database 85 may, however, alternatively be designed such that optimal operating points are stored for defined substrates, substrate thicknesses and fluid compositions, wherein these optimal operating points are characterized by the fluid temperature, the fluid quantity to be applied and the resulting achieved substrate temperature. To fill the database, an optimal combination of fluid temperature, applied fluid quantity and achieved substrate temperature is hereby preferably determined via tests and stored for different printing speeds. These stored combinations may be accessed during the printing.
For example, for a defined combination of printing methods and substrate type, a preferred fluid composition could additionally be determined (for instance with a view towards a homogenization of a substrate parameter that is to be achieved), likewise with the aid of experiments and tests.
The velocity with which the substrate 19 is transported through the printing system in the direction 21 may be provided by the regulator 78, for example via a controller for the entire printing system.
In the exemplary embodiment of
Given the determination of the quantity of fluid 38 to be applied and its fluid temperature by means of the regulator 78, it may also in particular be taken into account by this that—as indicated above—the selection of the fluid temperature may influence the penetration into the substrate 19 of additive substances that are included in the fluid 38. The composition may thus be taken into account in the selection of fluid temperature and quantity of fluid 38 to be applied, for example in order to achieve a desired penetration depth of an additive substance into the substrate 19. In other words: for a defined fluid 38, fluid temperature and fluid quantity may be matched to one another in order to achieve the desired penetration.
In the exemplary embodiment of
As drawn in
According to the alternative design of the database as described above, the operating points with the stored combination of fluid temperature and fluid quantity may be taken from this, and the fluid 38 may be applied accordingly to the substrate 19.
In a preferred variant according to the exemplary embodiment of
It is noted that the regulator 78 and the database 85 may form separate components, may be merged together into one component, or may be integrated into a control device (not shown in Figures) for the entire printing line or printing machine. Significant functions of the regulator 78 and the database 85 may also be realized as software components and be executed with the aid of a data processing device or a computer.
In
As depicted in
For example, water with at least one first additive substance included therein—for instance a first aqueous solution or aqueous dispersion solution—as a first fluid 38′, and water with at least one second additive substance included therein—for instance a second aqueous solution or aqueous dispersion solution—as a second fluid 38″, could be applied in succession onto the substrate 19. The application may hereby in principle take place as explained in detail above with regard to the first exemplary embodiment. It may hereby be achieved that the first and second additive substances are conveyed into the inside of the substrate 19 via the penetration of the fluids 38′ and 38″, such that a sought distribution of the first and second additive substances in the cross section of the substrate 19 or in one or more of the strokes 31, 32, 33, or in the entirety of the strokes 31, 32, 33, is achieved in the transversal direction Q (see for instance
In addition to this, a deep penetration of the additive substances may also be assisted via tempering (in particular heating) of one or both fluids 38′, 38″. The penetration is also accelerated via heating of one or both fluids 38′, 38″.
In one variant, it is also conceivable to provide only the first fluid 38′ as water with an additive substance included therein, whereas the second fluid 38″ may essentially be water. In this variant, one or both of the fluids 38′, 38″ may also respectively be tempered—in particular heated—before the application.
By means of the water application in the second step via the fluid applicator 6″, the additive substance that was already introduced in the first step may be conveyed or “pushed in” deeper into the substrate. The distance A′ between the application locations of the two fluid applicators 6′ and 6″ and the distance A″ between the application location of the second fluid applicator 6″ and the location 11 of the printing by means of the first print group 10 may be selected such that, for a given travel velocity of the substrate 19 in direction 21, the sought distribution of the additive substance or of the multiple additive substances on the substrate surface 20 and in the thickness direction Q and depth of said substrate 19—and in this way the sought homogenization of the selected substrate propert(y/ies)—may be achieved, for example at the location 11 of the printing, in particular under consideration as well of the possibly implemented tempering of one or both of the fluids 38′, 38″. In addition to this, the distance A′, A″—in particular A″—should be selected such that the substrate 19 may be printed to by means of the print group 10, wherein in particular a liquid applied onto the substrate 19 as a fluid 38′, 38″ should penetrate so far that essentially no reverse lamination may occur in the nip of the print group 10.
In summary, in the example of
In the third exemplary embodiment illustrated in
Given suitable selection of the respective fluid (for instance as water or water with additive substances), the moisture content of the substrate 19 may additionally be specifically influenced or controlled by means of both the application of the first fluid 38′ and the second fluid 38″.
A targeted influencing of one or more selected substrate properties with the goal of their homogenization (and thus their adjustment), and hereby a preparation of the substrate 19, may advantageously take place with the aid of multiple fluids 38′, 38″. For example, multiple additive components (for instance binder-like additive substances, salts etc.) that influence one or more substrate properties could be included in one fluid, or the additive components may be distributed among multiple fluids 38′, 38″. A control or regulation of the one or more selected substrate propert(y/ies) or their homogeneity may be implemented. One or more substrate propert(y/ies) may hereby respectively be measured at one or more selected locations along the travel path 22, in particular before and/or after the application of one or more of the fluids. The amount of the respective fluid 38′, 38″ that is applied per time unit onto the substrate 19, and the fluid temperature of the respective fluid 38′, 38″, may respectively be adjusted at least depending on the measurement value or measurement values obtained in this manner. As described above, the respective composition of the fluid 38′, 38″ may hereby be taken into account as well.
In contrast to this, in a fourth exemplary embodiment of the disclosure that is illustrated in
A substrate 19′ prepared via application of the first fluid 38′ is present at the point U, for example on the paper roll 8. The fluid 38′ may hereby be water with an additive substance, and in particular may be applied onto the substrate 19 for targeted homogenization of one or more selected substrate properties, whereby then a substrate 19′ is present on the paper roll 8, in which substrate 19′ a homogenization of one or more selected substrate properties—for example the absorption capability and/or the electrical resistance or other properties—has already been implemented, or has been prepared via the application of the first fluid 38′, for a defined printing method in which the substrate 19′ should be printed to later. The substrate 19′ may be placed in interim storage and be printed to later. The substrate 19 could also be prepared for printing in a defined printing method and be delivered as a prepared substrate 19′ to a customer for their use especially in such a printing method. For example, in the initial state the substrate 19 may be a conventional offset paper. Via application of the first fluid 38′, a prepared substrate 19′ is generated which, for example, is prepared paper optimized for a printing in a digital printing method (for example a liquid toner method).
The prepared substrate 19′ may be processed at a later desired point in time in a printing line or printing machine. In the exemplary embodiment of
In the fourth exemplary embodiment of
It is noted that an “offline priming” does not necessarily need to take place in two stages with one fluid application implemented “offline” and one implemented “inline”; rather, a substrate 19 may also be prepared via just one fluid application by means of a fluid applicator. In such a substrate, the substrate properties of interest would then already be homogenized after the one fluid application. Such a substrate could likewise be placed in interim storage for further use, or be delivered to a customer for their use. Multiple fluids could also be applied in succession “offline”, as needed.
With regard to a possible cooling of one or both of the fluids 38′, 38″, the statements already made above with regard to fluid 38 may be referenced. In the preceding examples of
In variants (which are not graphically depicted) in which more than two fluids are applied before the printing to the substrate 29, in variants of the examples of
In developments, the exemplary embodiment may be used given printing to substrates 19 within the scope of the most varied applications, for example given book printing or packaging printing.
The exemplary embodiments described in the preceding enable a substrate (for example paper or cardboard) to be obtained that is prepared for a subsequent printing by means of the fluid 38 or the fluids 38′, 38″. Physical/chemical framework conditions for the printing and/or further processing may be adjusted by means of the fluids 38, 38′, 38″, wherein in particular substrate temperature substrate surface temperature and substrate moisture may be specifically influenced and selected substrate parameters may be homogenized.
In the preceding exemplary embodiments, the fluids 38, 38′, 38″ are preferably liquids. In particular, the fluid 38, 38′, 38″ may respectively be an aqueous solution, an aqueous dispersion solution or aqueous dispersions, or instead may be water. Emulsions would also be conceivable. In additional variants of the preceding exemplary embodiments, the fluid 38, 38′, 38″ may be present in a different form, for example in liquid form as an oil or a wax or in gaseous form, for instance as water vapor with or without additive substances.
Possibly necessary measurements of the absorption capability or the wetting capability of the substrate 19 for the homogenization (possibly to be conducted) of these substrate properties may be conducted (for example as prior tests) with the aid of methods that are known as such to the person skilled in the art.
The absorption capability of the substrate may be measured with different methods, for instance via the penetration behavior of a liquid applied onto the substrate surface, wherein the selection of the liquid due to the different molecular properties and their interaction with the substrate components has an influence on the measured penetration time. For example, the methods according to Cobb or Cobb-Unger—known as such to the person skilled in the art—may be used.
If the conditions for a printing process should be characterized, the penetration times for various layer thicknesses should be determined. For example, this may take place with a test design for penetration tests, which test design includes a coating device, an illumination device and a high-speed camera. A doctoring rod may be mounted in the coating device. With the doctoring rod, a defined layer thickness of a liquid is applied onto the substrate to be tested and the intensity of the light reflected on the surface coated with the liquid is measured. The duration of the entire penetration phenomenon is characteristic of substrate, liquid and layer thickness.
Considering the wetting capability of the substrate, with regard to what is known as the contact angle measurement methods may be applied that are likewise known as such to the person skilled in the art and therefore are not explained in detail here.
If an electrostatic charging capability of the substrate 19 should presently be homogenized, a measurement of the electrostatic charging capability may be realized by means of no-contact potential measurement probes. The probe is hereby arranged opposite a conductive counter-electrode that is at ground potential, wherein the substrate 19 is arranged between the potential measurement probe and the counter-electrode.
Moreover, in the exemplary embodiments described in the preceding it is possible to supplement the respective printing system with a system by means of which, during the printing process, it may be established whether the fluid 38, 38′, 38″ respectively applied in the fluid applicator 6, 6′, 6″ has sufficiently penetrated so that a subsequent printing in the print group 10 may take place. For example, this may take place in such a manner that the substrate 19 is illuminated upstream of the print group 10 and the intensity of the reflected light is measured. To what extent fluid is still present on the substrate surface 20 may be concluded from the reflection during the printing process. In variants of the exemplary embodiments described in the preceding, the information obtained in this way may enter into the determination of the amount of fluid to be applied, for example diaphragm the regulator 78, such that a problem-free printing may take place.
Given the preceding exemplary embodiments, it may also be provided in variants that one or more component(s) included in the fluid 38 or the fluids 38′ and/or 38″ exhibit(s) a glass transition in the temperature range in which the application and the printing take place, and if applicable in the further processing. The glass transition temperature of the respective additive or of the respective component may likewise advantageously be used with the assistance of a tempering of substrate and/or fluid(s). For example, this may take place in such a manner that an additive or a fluid component of one of the fluids 38, 38′, 38″ remains on the surface 20 of the substrate and there undergoes a glass transition while the other components of the fluid 38, 38′ or 38″ penetrate into the substrate.
If (as a subsequent fluid) an additional liquid that is formed as a mixture strikes such a prepared surface, the glass formed in the region of the surface—like any other liquid given a suitably selected layer thickness—can let penetrate (“transmit”) into the substrate a component or multiple components of the subsequent mixture while other components remain “stuck”, i.e. are held back. One example for such a behavior could be non-polar substances which are “transmitted” while polar substances or particles remain “stuck”.
Although preferred exemplary embodiments are shown and described in detail in the drawings and in the preceding specification, they should be viewed as purely exemplary and not as limiting the disclosure. It is noted that only preferred exemplary embodiments are shown and described, and all variations and modifications that presently or in the future lie within the protective scope of the disclosure should be protected.
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20160229203 A1 | Aug 2016 | US |