EP0718100A1 - Method for applying a spacing-substance on a printing sheet and sheet printing press provided for carrying out such a method - Google Patents

Abstract

The deposition system allows a spacer material to be applied to the surface of the printed sheet (1) in the form of discrete spacer particles (2) which are fixed after their application. Pref. the spacer particles have a dia. of between 5 and 30 micrometres and are regularly spaced across the surface of the sheet at a relative spacing of between 50 and 400 micrometres to provide a uniform surface coating.

Description

The invention relates to a method for applying a spacer material to printed sheets and a sheet-fed printing press equipped to carry out the method.

The application of a spacer material to a printed sheet pursues the goal of protecting the printed image from damage which can occur in particular in a delivery of a sheet-fed printing press when a delivery stack is formed.

For this purpose, it is proposed in the prior art, among other things, to dust the surface of printed printed sheets with a powder. A suitable pollination device is known for example from the document DE 38 19 203 A1. However, the use of powder materials also leads to disadvantageous consequences. For example, the sheet printing machine is contaminated by the powder used, since it does not only get onto the surface of the printing sheet, but in particular also settles on sheet transport means which convey a respective sheet from a printing unit to a stacking device. The dusted-on powder can moreover detach itself from the printed sheet in the case of a repeated printing operation and thus lead to contamination of the printing units of a sheet-fed printing machine and, as a result, to an increased proportion of waste.

From JP Hei 5-85074 A it is known to coat a printed sheet with an aqueous emulsion of wax and an alcohol-fatty acid ester. This emulsion becomes even and flat on the whole Surface of the previously printed sheet applied. The disadvantage here is that considerable amounts of the emulsion mentioned are required, in particular in the case of large-format printed sheets, and that no air cushions can form between the individual bases when stacking such flat coated sheets. This complicates in particular an edge-accurate stack formation.

Accordingly, the object of the present invention is to provide a method or a printing machine equipped for carrying it out, which eliminates the aforementioned disadvantages and, in particular, achieves good and damage-free alignment of a stack of printed printed sheets.

This object is achieved by the method according to claim 1 and a printing press equipped according to claims 13, 14, 22 and 25, respectively.

The advantage of the solution according to the invention is that the spacer material is not applied over the entire surface of the sheet, but rather only selectively. On the one hand, this saves spacer material, and on the other hand, the punctiform spacer particles applied when the sheets are stacked ensure that air cushions form between the individual sheets, which enable the stack to be easily aligned without damaging the printed image on a particular sheet and are easy to process ensure the same.

The spacer particles preferably have a size of approximately 5 to 30 micrometers and are randomly applied to the sheet at a mutual mean spacing of 50 to 400 micrometers in such a way that an at least almost equal number of spacer particles is present on mutually identical partial surfaces of the surface of the sheet. Here The average distance selected from the range of 50 to 400 micrometers specified depends on the desired coverage density of the spacer particles, depending on the print image present, the consistency of the colors used for its creation and the nature of the print medium used.

In a preferred embodiment, the spacer particles are mixed with the printing ink or the dispersion varnishes used to refine the printed surface of the sheet and then applied together on the sheet. Additional devices for applying the spacer particles can thus be dispensed with. The spacer particles are fixed on the sheet by automatically gluing them using the printing ink or the lacquer in the course of drying them. The refining properties, in particular of the lacquer, in particular its contribution to increasing the gloss, are not impaired if the size of the particles of the spacer does not exceed a certain level. An upper limit for this dimension can be set at around 10 micrometers.

The spacer particles of the paint or lacquer are preferably mixed in a ratio of 1:10 to 1: 100.

A further advantageous embodiment of the method is characterized in that water and a water-soluble adhesive are added to the spacer and that this mixture is applied to the sheet (1) in the form of individual spacer particles (2) with a coating of water and adhesive.

Further variants of the method according to the invention consist in that the spacer particles (2) indirectly via at least one printing unit cylinder or be applied directly to the sheet.

A further preferred embodiment is characterized in that the spacer material is provided in the form of spacer particles (2) with a coating of water-soluble adhesive, and that when the spacer particles (2) are applied, the adhesive is activated by moistening to remove the spacer particles on the sheet (1) to fix.

Furthermore, wax is preferably used as the spacer, which is applied to the sheet in the form of wax particles.

A process variant based on this is characterized in that the wax particles (2) are obtained from a melt, drops being separated from them for application, and that the wax particles (2) are fixed by partial penetration of the drop into the arch (1 ) or sticking to the surface of the sheet (1) and then cooling and solidifying.

In this variant of the method, which is advantageous with regard to the fixation of the wax particles, partially not yet fully solidified wax particles penetrate into the arch and fix themselves automatically with increasing solidification. It is also advantageous here that an easy-to-use and easily controllable single-substance system can be used.

Another variant of the method is characterized by the formation of a respective one of the wax particles in the form of a core from a first wax and one of the core surrounding sheathing from a second wax with a lower melting point than the first wax.

To fix the wax particles, the coating is first melted on, while the strength of the core is maintained. Compared to the variant described above, it is advantageous here that the process can run with similar other advantages at lower values of the necessary temperatures.

In a further variant of the method, it is preferably provided that the wax particles are provided in the form of powder and that the fixing is carried out by brief thermal treatment.

Another process variant is finally characterized in that an aqueous suspension containing the wax particles is provided and the wax particles are fixed on the sheet by brief thermal treatment.

A printing press for printing sheets, in particular with an inking unit and with printing unit cylinders in the form of a plate cylinder, a blanket cylinder and a printing cylinder, is equipped with an application device for carrying out the method for punctually applying spacer particles formed from a spacer material to the sheet with a container for storage of the spacer material and with rollers in the form of a take-up roller for receiving the spacer material from the container and an applicator roller associated therewith, the printing cylinder or the applicator roller having an outer surface with a surface structure suitable for punctual application of the spacer material particles and formed by means of depressions.

An alternative to this equipment of the printing press mentioned is to equip it with an application device for the selective application of spacer particles formed from a spacer to the sheet with a container for storing the spacer and with rollers in the form of a pick-up roller for receiving the spacer from the container, one Applicator roller for punctual application of the spacer particles on the blanket cylinder or the printing cylinder and an intermediate roller arranged between the take-up roller and the applicator roller, at least one of the lateral surfaces of the impression cylinder, applicator roller and intermediate roller having a surface structure which is suitable for punctual application of the spacer particles and is formed by depressions.

In both cases, it is provided in a preferred embodiment that the applicator roller is assigned to the printing cylinder and that the printing cylinder has the surface structure.

When the depressions are formed in the lateral surface of the impression cylinder, it is preferably provided that the surface structure of the impression cylinder has spherical-spherical elevations and valleys between them, representing the depressions, are dimensioned such that at least one spacer particle can be accommodated therein, while another preferred embodiment provides is that the applicator roller is assigned to the impression cylinder or the blanket cylinder, and that the depressions are provided in the outer surface of the applicator roller and are formed by means of cups adapted to the size of the spacer particles or at least substantially grooves running in the circumferential direction of the outer surface.

In a preferred embodiment of the printing press, which is equipped with the application device having the intermediate roller mentioned, the application roller is the printing cylinder or assigned to the blanket cylinder and the depressions are formed in the lateral surfaces of the application roller or the intermediate roller by means of cups adapted to the size of the spacer particles or at least essentially grooves running in the circumferential direction of the lateral surface.

The above-mentioned adaptation of the cells to the size of the spacer particles is carried out in a particularly advantageous manner in such a way that a respective cell is dimensioned such that it can accommodate a spacer particle. In this way, the desired distribution of the spacer particles transferred to the sheet can be brought about directly by the distribution of the cells.

Regardless of which of the application devices mentioned the printing press is equipped with, it is further preferably provided that the depressions have a hydrophilic surface and are surrounded by hydrophobic surface areas.

In a further embodiment of the application devices mentioned, they are characterized in that the pick-up roller has an elastic jacket surface, while a further embodiment, which is advantageous in particular with regard to regulating the mean mutual spacing of the spacer particles, is distinguished by a difference in the peripheral speeds of the rollers of the application device.

A further development of the invention is characterized in particular by a printing machine having an inking unit and printing unit cylinder in the form of a plate cylinder, a blanket cylinder and a printing cylinder for printing sheets by a spray device which sprays a spray liquid formed by the spacer onto one of the printing unit cylinders or the sheet one Storage container for the spray liquid, a nozzle, a pump which supplies the spray liquid from the storage container to the nozzle, two mutually parallel, gap-forming rollers which limit a spray cone emerging from the nozzle, and with a cleaning device assigned to the two rollers, the Remnants of the spray liquid adhering to the rollers are removed from the rollers and returned to the storage container.

It is further preferably provided that the nozzle can be pivoted, the application of the spray liquid being interrupted by pivoting the nozzle.

In a further embodiment it is provided that the rollers of the spray device are arranged so as to be displaceable parallel to one another in order to be able to close the gap between them and thus to interrupt the application of the spray liquid.

In another development of the invention, a printing machine which has in particular an inking unit and printing unit cylinder in the form of a plate cylinder, a blanket cylinder and a printing cylinder for printing sheets is characterized by a spray device with a nozzle directed towards a printing unit cylinder, in particular the printing cylinder, and a container for storage a possibly a mixture with an adhesive-forming spacer and with a conductive plate, which is arranged such that the opening of the nozzle is in the space between the plate and the printing unit cylinder, an electrical field can be formed between the printing unit cylinder and the plate and at Activating this electrical field, particles of the spacer or the mixture are drawn from the nozzle to the printing unit cylinder.

The invention is described in more detail below with the aid of the detailed description of several exemplary embodiments (with reference to the attached figures).

Fig. 1

eine Lackschicht mit Wachspartikeln auf einem bedruckten Bogen zur Erläuterung eines ersten Ausführungsbeispiels des erfindungsgemäßen Verfahrens,

Fig. 2a

einen mit einer Mischung aus Wasser und Klebstoff umhüllten Wachspartikel bzw. einen Wachspartikel in Form eines Kerns aus einem ersten Waschs mit einer Umhüllung aus einem zweiten Wachs mit niedrigerem Schmelzpunkt,

Fig. 2b

den Wachspartikel gemäß Fig. 2a nach dessen Fixierung auf dem Bogen,

Fig. 3

aus einer Wachsschmelze stammende, auf einen Bogen aufgetragene Wachspartikel entsprechend einem weiteren Ausführungsbeispiel des erfindungsgemäßen Verfahrens,

Fig. 4

ein Schema eines Teils einer Druckmaschine zum Bedrucken von Bogen mit einer einem Druckwerkszylinder zugeordneten Auftragvorrichtung für Wachspartikel,

Fig. 5a

ein eine Oberflächenstruktur aufweisendes, stark vergrößert dargestelltes Teilstück eines Druckzylinders im Längsschnitt,

Fig. 5b

ein Fig. 5a entsprechendes Teilstück im Querschnitt,

Fig. 6a u. 6b

schematische Darstellungen eines Teils der Druckmaschine, wobei jeweils eine Auftragvorrichtung unterschiedlich angeordnet ist,

Fig. 7a u. 7b

schematisch das Zusammenwirken einer Aufnahmewalze und einer Auftragwalze,

Fig. 8a

einen stark vegrößerten Längsschnitt eines Teilstücks einer mit Vertiefungen versehenen Walze einer Auftragvorrichtung für den Abstandstoff,

Fig. 8b

ein Schema eines Teils der Druckmaschine zur Verdeutlichung der Anordnung einer Auftragvorrichtung für den Abstandstoff,

Fig. 9

schematisch eine Sprühvorrichtung zum Auftragen des Abstandstoffs,

Fig. 10a u. 10b

schematisch die Sprühvorrichtung gemäß Figur 9 zur Veranschaulichung der Unterbrechung eines von der Sprühvorrichtung abgegebenen Sprühkegels,

Fig. 11a u. 11b

jeweils ein Schema eines Teils der Druckmaschine mit jeweils unterschiedlich angeordneten Sprühvorrichtungen gemäß Figur 9,

Fig. 12

schematisch eine weitere Auftragvorrichtung für den Abstandstoff.

Show:

Fig. 1

a lacquer layer with wax particles on a printed sheet to explain a first exemplary embodiment of the method according to the invention,

Fig. 2a

a wax particle coated with a mixture of water and adhesive or a wax particle in the form of a core from a first wash with a coating made from a second wax with a lower melting point,

Fig. 2b

2a after its fixing on the arch,

Fig. 3

wax particles originating from a wax melt and applied to an arch in accordance with a further exemplary embodiment of the method according to the invention,

Fig. 4

1 shows a diagram of part of a printing press for printing sheets with an application device for wax particles assigned to a printing unit cylinder,

Fig. 5a

FIG. 2 shows a section of a printing cylinder with a surface structure, shown in greatly enlarged form, in longitudinal section,

Fig. 5b

5a corresponding section in cross section,

Fig. 6a u. 6b

schematic representations of a part of the printing press, wherein an application device is arranged differently,

Fig. 7a u. 7b

schematically the interaction of a take-up roller and an applicator roller,

Fig. 8a

a greatly enlarged longitudinal section of a portion of a roller provided with recesses of an applicator for the spacer,

Fig. 8b

1 shows a diagram of a part of the printing press to illustrate the arrangement of an application device for the spacer material,

Fig. 9

schematically a spray device for applying the spacer,

10a u. 10b

schematically the spraying device according to FIG. 9 to illustrate the interruption of a spray cone emitted by the spraying device,

11a u. 11b

each a schematic of a part of the printing press, each with differently arranged spraying devices according to FIG. 9,

Fig. 12

schematically another applicator for the spacer.

First, with reference to FIGS. 1 to 3, various options are presented for how the spacer material can be applied to the sheet and fixed there. Spherical or teardrop-shaped wax particles with a size of 5 to 30 micrometers are preferably used as the spacer. This choice of size ensures that the wax particles are not visible to the naked human eye, that is to say that no changes in color, loss of gloss or other changes in the optical properties of a printed product are recognizable. The waxes which are preferably used are, in particular, polyethylene waxes which, compared with today's powder materials, have good sliding properties which result from the fact that the wax liquefies at the surface pressure of the wax particles and forms a lubricating film.

In the example of FIG. 1, the wax particles 2 are mixed with a dispersion lacquer 3, which is used to refine the surface of the sheet 1. This is preferably done in a ratio of 1:10 to 1: 100 (parts by weight). The wax particles 2 are then applied accordingly to the sheet 1 previously printed with ink 5 using a coating unit. In this case, the lacquer layer 3 applied to the paper for finishing acts like an adhesive for the wax particles 2, which holds them to the paper surface and fixes them on the sheet 1 during the drying of the lacquer layer.

A further possibility of fixing a wax particle 2 on a sheet 1 is explained below with reference to FIG. 2. As shown schematically in FIG. 2a, the wax particles 2 are coated with an aqueous solution 4 of adhesive. The dissolved adhesive has the task of fixing the wax particle 2 on the paper after it has been applied to the sheet 1. This happens because that after the application of the wax particle 2, the aqueous solution 4 runs and partially penetrates into the paper, as is shown schematically in FIG. 2b. The wax particle 2 is thus fixed in a punctiform manner on the paper without the adhesive having an optically disadvantageous effect.

If the wax particles 2 are used in the form of a powder or as part of an aqueous suspension without an adhesive component, there is a possibility within the scope of the invention for fixing the wax particles 2 on the sheet 1 following application to the latter by briefly heating the sheet 1. The result of this is that a liquid film, possibly surrounding the wax particles 2, formed by the suspension, evaporates, and that the wax particles 2 are melted on the surface, so that part of a respective wax particle 2 strikes into the paper and the wax particles 2 after cooling are fixed to the sheet 1.

The aqueous suspension mentioned can either be provided for application to the sheet 1 or can also be formed by mixing the wax particles 2 provided in powder form with the liquid portion of the suspension during the application of the wax particles 2. In any case, dust formation is avoided.

Instead of directly applying the wax particles 2 to the paper, an indirect application can also be carried out by first applying the wax particles 2 to a roller and only then transferring them to the paper.

Possibilities within the scope of the invention for enveloping a wax particle 2 with a shell, such as, for example, one from solution 4 mentioned, will be discussed in more detail later in the description.

With reference to FIG. 3, a further possibility is shown of how the wax particles 2 can be applied to the paper and fixed there. In this figure, wax particles 2 are shown schematically, which are applied to the paper. A certain part of the wax of the wax particles 2, as indicated, has penetrated into the paper, with which the necessary fixation is achieved. After the wax particles 2 have a solid physical state at ambient temperature and thus cannot penetrate the paper, at least a part of the wax particle must be brought into a viscous state so that this part can penetrate the paper. This can be done on the one hand by a thermal treatment after the wax particles 2 have been applied. On the other hand, however, it is also possible to store the wax particles 2 as a melt before application. This requires a temperature of around 100 to 300 ° C. From this melt, drops of wax are formed, for example by means of a spraying device according to FIG. 9 or 12, and sprayed onto the sheet 1. An initially melted wax drop cools during this time and increasingly solidifies. When the wax drop comes into contact with the sheet 1, part of the not yet fully solidified wax penetrates the paper and, after a further certain cooling time and associated solidification, causes the wax particles 2 to form from the wax drops and fix them on the sheet 1.

When setting the distance covered by the wax droplet between the spray device and the sheet 1, care must be taken that this is not too long. Then the wax drop cools down too much and therefore no longer has sufficient fluid melt that would be necessary for fixation. On the other hand, if the distance covered is too short, the wax drop does not cool down sufficiently, which leads to the fact that it drops onto the paper Impacting wax drops melt away too much and are therefore too low in relation to the paper surface.

A modification of the previously described method is that a wax melt is again used for fixing on the paper, but in which wax particles are in at least almost solid aggregate state. This can be achieved by using two waxes with different melting points, the fixing wax having a lower melting point. The wax particles separated from the melt and then encased with a coating made of the wax with a lower melting point are fixed in place, as in the example described above, by penetrating the melted wax into the paper and then solidifying it.

This has the advantage that it is possible to work at lower temperatures than would be the case when the wax particle serving as a spacer is melted, which has to be mechanically much more stable and therefore also has a higher melting point.

Another possibility of a thermal fixation is to coat the wax particles 2 with a hot melt adhesive and to heat the wax particles 2 applied and thus coated. The temperature provided for this must correspond exactly to the melting point of the hot melt adhesive, which is then used for fixing. However, the melting point of the wax particle 2 should not be reached in order to prevent it from melting.

Instead of enveloping the wax particles 2 with a hot melt adhesive, a water-soluble adhesive can be used for this. This adhesive can then be activated by targeted moistening on the surface of the sheet. Due to the water absorption capacity of the paper forming the sheet the water is removed from the adhesive and the wax particles are then fixed on the surface of the sheet.

Various devices for carrying out the method according to the invention and its embodiments are described below with reference to FIGS. 4 to 12.

FIG. 4 is a diagram of a part of a printing press for printing on the sheets 1. In particular, a printing unit 25 and an adjoining delivery arm 21 are shown. The printing unit 25 comprises a printing cylinder 12, a blanket cylinder 15 and a plate cylinder 16, around which an inking unit 18 and, in the case of operation of the printing machine in the wet offset process, a dampening unit 17 are grouped. A respective sheet 1 is fed to the impression cylinder 12 by means of a sheet guide cylinder 19. The printing cylinder 12 is assigned an application device 11 with an application roller 13 and a take-up roller 14, which picks up a suspension of water, adhesive and spacer particles 2 provided therein from a storage container 24.

In order to selectively apply the spacer particles 2 according to the invention on the sheet 1, in a first variant of the application device 11 with an application roller 13 with a smooth outer surface, the pressure cylinder 12 according to FIG Spacer particles 2 contained in the suspension are forced to have their desired distribution. When the printing cylinder comes into contact with the paper, the layer thickness of water and adhesive in the non-recessed areas of the outer surface of the printing cylinder 12 is too small to allow any appreciable transfer of adhesive by liquid splitting onto the paper effect. The spacer particles 2 in the depressions 31 adhere to the paper due to the water-soluble adhesive. When the spacer particles 2 are detached from the depressions 31 as a result of the sheet 1 being peeled off from the pressure cylinder 12, in general only a portion of a liquid 6 formed from water and adhesive is carried along by the respective spacer particle 2 in the form of an envelope, as is shown schematically in FIG. 5b is shown. However, there are no procedural disadvantages from the part of the liquid 6 remaining in the depression 31.

The application roller 13 can either have the diameter of the printing cylinder 12 and a corresponding cutout for the grippers of the printing cylinder 12. However, it can also be designed with a smaller diameter and can be turned on and off, for example by means of a cam control, in order to avoid the grippers of the pressure cylinder 12 in the parked state.

The assignment of the application device 11 to the printing cylinder 12 explained so far has the effect that the spacer particles 2 are not applied to the printed side of the sheet 1 but to the back of the sheet. However, this has no influence on the function of the spacer particles 2 as spacers.

FIGS. 6a and 6b each show a diagram of a part of a printing press which essentially corresponds to that shown in FIG. 4. In contrast to the exemplary embodiment shown in FIG. 4, the application device 11 is, however, not assigned to the printing cylinder 12 but to the blanket cylinder 15, whereby according to FIG. 6a it is placed with respect to this in such a way that first color and then the spacer particles 2 on the Blanket cylinder 15 are transferred. This sequence is reversed in the arrangement according to FIG. 6b.

After the blanket cylinder 15 has a substantially smooth surface, the outer surface of the application roller 13 of the application device 11 is provided with a certain surface structure in the exemplary embodiments according to FIGS. 6a and 6b in order to punctually remove the spacer particles 2 and with the desired distribution already explained by means of a to apply the blanket cylinder 15 stretched blanket on the paper.

In an advantageous embodiment, the lateral surface of the application roller 13 is provided with cups 27. These cups 27 are dimensioned such that a spacer particle 2 can be picked up with a little water-soluble adhesive. The surfaces of the wells 27 are preferably hydrophilic, while the remaining surface portions of the outer surface of the application roller 13, which come into contact with the rubber blanket of the blanket cylinder 15, preferably have a hydrophobic property, for example due to a special coating. As already described in connection with FIG. 4, the spacer particles 2 or the suspension are removed from the storage container 24 by means of the pick-up roller 14 and fed to the applicator roller 13. Supported by the described acceptance behavior of the outer surface areas of the application roller 13, the wells 27 fill with the spacer particles 2 or with the suspension, while the non-recessed outer surface regions of the application roller 13 remain uninvolved in the transfer of the spacer particles 2. The desired distribution of the spacer particles 2 is determined here by a corresponding distribution of the cups 27 in the lateral surface of the application roller 13.

The pickup roller 14 is preferably provided with an elastic jacket surface. The contact pressure between the applicator roller 13 and the take-up roller 14 is set such that most of the liquid is squeezed out of the well again when a well is filled without spacer particles 2. This process is illustrated schematically in FIGS. 7a and 7b. FIG. 7a shows the case of a cup filling without spacer particles 2. By choosing an elastic outer surface of the pick-up roller 14, the area of the outer surface of the pick-up roller 14 lying above the cup 27 of the applicator roller 13 bulges into the cup 27. The degree of curvature depends, on the one hand, on the elasticity of the lateral surface and, on the other hand, on the contact pressure between the application roller 13 and the receiving roller 14. This curvature has the effect that any liquid, in particular water-soluble adhesive, which may be in the well 27 is squeezed out when there is no spacer particle 2 in the well 27. This prevents adhesive dissolved in water from being transferred without spacer particles 2 and the printed product thereby being impaired optically.

FIG. 7b, on the other hand, shows the case in which a spacer particle 2 is located in one of the cups 27 of the application roller 13. The spacer particle 2 ensures that the elastic outer surface of the take-up roller 14 bulges toward its axis, as is indicated schematically in the figure. When choosing the contact pressure or the material for forming the elastic outer surface of the take-up roller 14, care must be taken that, in the preferred use of spacer particles 2 in the form of wax particles, a respective wax particle 2 does not deform excessively when it comes into contact with the application roller 13.

In order to facilitate the operational filling of the cups 27 with a respective wax particle 2, the drive of the two rollers 13, 14 can be designed so that there is preferably a low relative speed between these two rollers, the relative speed being variable. The advantage here is that the wax particles 2 more easily get into the wells 27 due to the friction between the two roll surface areas.

The application device 11 'shown in FIG. 8b is slightly modified compared to the application device described above. The suspension taken up by the take-up roller 14 is not transferred directly to the application roller 13, but first to an intermediate roller 30, from which the transfer to the application roller 13 then takes place.

Instead of a surface structure formed by means of the cups 27, the intermediate roller 30 - like the rest of the applicator roller 13 - can have grooves or grooves 32 running in the circumferential direction of the lateral surface or in a direction inclined to the circumferential direction,
as shown schematically in Figure 8a. The way in which the wax particles 2 are received and passed on to the applicator roller 13 or to the blanket cylinder 15 essentially corresponds to that of the lateral surface provided with cups 27.
The desired distribution of the wax particles 2 is in this case achieved by a suitable choice of the distances between the grooves 32 and a peripheral speed of the intermediate roller 30 which then deviates from that of the applicator roller 13. For example, has
the applicator roller 13 the peripheral speed of the blanket cylinder 15 and the intermediate roller 30 a lower peripheral speed, so that in the individual Grooves 32 of the intermediate roller 30 lying wax particles 2 transferred to the applicator roller 13 at a distance which is increased compared to a distance between the wax particles 2 located in the grooves 32.

As already mentioned above, the application device 11 can, for example, also lie in front of the plate cylinder 16 or can be assigned to the printing cylinder 12.

In order to achieve the desired distribution of the wax particles 2, a surface structure formed by means of depressions 31 in the form of valleys between spherical dome-shaped elevations, cups 27 or grooves 32 is basically only required on one of the lateral surfaces involved in the transfer of the wax particles 2. However, it can be quite advantageous if two wax surfaces provided with a respective surface structure follow one another on the way of the wax particles 2 from the storage container 24 to the outer surface of the printing cylinder 12 or the rubber blanket cylinder 15, for example one with the grooves 32 on the way to the rubber blanket cylinder 15 provided surface of the intermediate roller 30 and a surface of the application roller 13 provided with the cups 27 or also a surface 32 of the application roller 13 provided with grooves 32, the grooves of the intermediate roller 30 and application roller 13 having different inclinations with respect to the respective longitudinal axis of the roller, or as for example on the Towards the printing cylinder 12, a lateral surface of the application roller 13 provided with the grooves 32 and a lateral surface of the printing cylinder 12 provided with the depressions 31 in the form of the valleys between the spherical spherical elevations.

As already mentioned, instead of using the application roller 13 of the application device 11 or 11 ′, the wax particles 2 can also be applied using a spray device 40, by means of which a spray liquid formed by means of the spacer substance is sprayed and which can be arranged in the printing press in such a way that the sheet 1 itself or a printing cylinder contacting it is sprayed. The spray liquid can be in the form of the above-mentioned melt of the wax used as a spacer or in the form of the above-mentioned aqueous suspension containing the wax particles 2 and an adhesive dissolved in water.

In general, such a spray device 40 comprises nozzles 41, to which compressed air is supplied on the one hand via a corresponding compressed air line 48 and on the other hand the spray liquid via a spray line 49. The spray liquid supplied via the spray line 49 is sucked out of a reservoir 46 by means of a pump 47. To limit a spray cone formed on a respective nozzle 41, a limiting device is preferably provided, which is formed from two rollers 42, 43, as shown in FIG. 9. The arrangement of the two rollers 42, 43 is such that a gap is formed between them through which a part of the spray cone can pass. In order to prevent residues of the spray liquid deposited on the lateral surfaces of the rollers 42 and 43 from clogging the gap, the two rollers 42, 43 are rotated and doctored off. The direction of rotation is selected so that the two lateral surfaces in the area of the gap rotate opposite to the spray direction.

A cleaning device for the rollers 42, 43, which consists of doctor blades 44 and 45 in the arrangement shown in FIG. 9, cleans the rollers 42, 43 of adhering residues of the spray liquid and returns them to the reservoir 46.

The amount of the spray liquid passing through the gap between the rollers 42 and 43 can be controlled in addition to the setting of spray parameters, such as the amount of compressed air or the amount of the spray liquid fed to the nozzle, by the width of the said gap. For this purpose, the rollers 42, 43 are arranged so as to be adjustable relative to one another. In addition to a parallel displacement of the two rollers 42 and 43 to each other, which results in a constant width of the gap over the entire length of the rollers 42 and 43, it is also conceivable, by a corresponding displacement of one of the rollers 42 and 43, a different width of the gap over the Adjust press width. To switch off or interrupt the spray cone, in addition to switching off the pump 47 or the compressed air 48, there is the possibility shown in FIG. 10a of pivoting the nozzle 41 in such a way that the spray cone emitted by it does not hit the gap. Here, however, it is expediently ensured that the spray liquid gets into the reservoir 46. In the example shown in FIG. 9, this is achieved in that the nozzle 41 is located inside the storage container 46 and, after pivoting, is directed, for example, onto a side wall of the same. Another possibility is to close the gap formed by the two rollers 42, 43 by moving them towards one another, as is shown schematically in FIG. 10b. In addition to a parallel displacement of one of the rollers 42, 43, a displacement into an obliquely upward or obliquely downward position is also possible.

By correspondingly interrupting the spray cone, it can be achieved in particular that, for example, spraying of gripper devices by means of which the sheets 1 are transported is prevented.

Just as in the case of the use of the application device 11 described, there are 40 different arrangement options for these in the printing machine if spray devices are used. Two possibilities of this are shown in FIGS. 11 a and 11 b. In FIG. 11 a, the spray device 40 is arranged in such a way that the spray liquid hits the printed side of the sheet 1. In FIG. 11b, however, a spray device 40 'is directed according to the functional principle of the spray device 40 to an area of the printing cylinder 12 on which the sheet 1 is placed as the rotation thereof continues. The spray liquid is thus applied indirectly via the pressure cylinder 12 to the back of the sheet 1. Of course, other conceivable arrangements are also possible.

Figure 12 shows schematically a further embodiment of a spray device. In contrast to the spray device 40 described above, it is not compressed air but an electric field that is used to apply the spray liquid.

The spray device 60 shown in FIG. 12 comprises a nozzle 51 which is supplied with the spray liquid from a reservoir 55. In the example shown, the nozzle 51 is aligned radially with the pressure cylinder 12. An electrical voltage is applied to a plate 53, which is substantially perpendicular to the intended orientation of the nozzle 51, and to the pressure cylinder 12, which builds up an electric field.

The spray liquid contained in the reservoir 55 is preferably a mixture 56 of wax particles 2 in an adhesive solution. The wax particles 2 and adhesive 58 adhering to them become by the electric field accelerated, which ultimately ensures the necessary fixation of the wax particles 2 on the paper of the sheet 1.

This device 60 can preferably be arranged at the same locations in the printing press as the aforementioned application devices 11, 11 ', 40, 40'. A nozzle array is arranged across the entire width of the sheet 1 transversely to the sheet running direction. The selective application of the wax particles 2 and a control of the application amount is carried out by switching the applied voltage on and off.

Claims (25)

Process for applying a spacer material to sheets which are printed on and then stacked by means of a printing machine using printing unit cylinders,
marked by
the steps:
Providing a spacer that is solid at least at ambient temperature,
selective application of individual spacer particles (2) formed from the spacer to a surface of the sheet (1) and fixing the applied spacer particles (2) on the sheet (1). Method according to claim 1,
characterized by
that the spacer particles (2) have a size of 5 to 30 micrometers and are randomly applied at a mutual mean distance of 50 to 400 micrometers to the sheet (1) in such a way that at least one of the same partial areas of the surface of the sheet (1) almost the same number of spacer particles is present. Method according to claim 1,
characterized by
that the spacer particles (2) are applied together with a paint or varnish to the sheet (1) and then fixed while drying on the sheet (1). Method according to claim 3,
characterized by
that the spacer particles (2) are mixed in a ratio of 1:10 to 1: 100 (parts by weight) of the paint or lacquer. Method according to claim 1,
characterized by
that water and a water-soluble adhesive are added to the spacer, and that this mixture is applied to the sheet (1) in the form of individual spacer particles (2) with a coating of water and adhesive. Method according to claim 1,
characterized by
that the spacer particles (2) are applied indirectly via at least one printing unit cylinder (12, 15) or directly to the sheet (1). Method according to claim 1,
characterized by
that the spacer in the form of spacer particles (2) is provided with a coating of water-soluble adhesive, and that when the spacer particles (2) are applied, the adhesive is activated by moistening in order to fix the spacer particles on the sheet (1). Method according to claim 1,
characterized by
that wax is used as a spacer, which is applied in the form of wax particles (2) to the sheet (1). A method according to claim 8,
characterized by
that the wax particles (2) are obtained from a melt, drops from which are separated for application, and that the wax particles (2) are fixed by partial penetration of the drop into the sheet (1) or sticking to the surface of the sheet (1) and is achieved by subsequent cooling and solidification. A method according to claim 8,
characterized by it
a formation of a respective one of the wax particles (2) in the form of a core (2 ') from a first wax and a covering (4') surrounding the core (2 ') from a second wax with a melting point lower than that of the first wax. A method according to claim 8,
characterized by
that the wax particles (2) are provided in the form of powder, and that the fixation is carried out by brief thermal treatment. A method according to claim 8,
characterized by
that an aqueous suspension containing the wax particles (2) is provided and the wax particles (2) are fixed on the sheet (1) by brief thermal treatment. Printing machine for printing sheets (1), in particular with an inking unit (18), and with printing unit cylinders in the form of a plate cylinder (16), a blanket cylinder (15) and a printing cylinder (12),
characterized by it
an application device (11) for the selective application of spacer particles (2) formed from a spacer onto the sheet (1) with a container (24) for storing the spacer and with rollers in the form of a pick-up roller (14) for receiving the spacer from the container (24) and an applicator roller (13) assigned to them, the pressure cylinder (12) or the applicator roller (13) having an outer surface with a surface structure which is suitable for punctual application of the spacer particles (2) and is formed by means of depressions (31, 27, 32) . Printing machine for printing sheets (1), in particular with an inking unit (18), as well as with printing unit cylinders in the form of a plate cylinder (16), a blanket cylinder (15) and a printing cylinder (12)
characterized by it
an application device (11 ') for the selective application of spacer particles (2) formed from a spacer onto the sheet (1) with a container (24) for storing the spacer and with rollers in the form of a pick-up roller (14) for receiving the spacer from the Container (24), an application roller (13) for the selective application of the spacer particles (2) to the blanket cylinder (15) or the impression cylinder (12) and an intermediate roller (30) arranged between the pick-up roller (14) and the application roller (13) wherein at least one of the lateral surfaces of the pressure cylinder (12), applicator roller (13) and intermediate roller (30) has a surface structure which is suitable for the punctual application of the spacer particles (2) and is formed by means of depressions (31, 27, 32). Printing machine according to claim 13 or 14,
characterized by
that the applicator roller (13) is assigned to the impression cylinder (12) and that the impression cylinder (12) has the surface structure. Printing machine according to claim 13 or 14,
characterized by
that the surface structure of the pressure cylinder (12) has spherical dome-shaped elevations and valleys between them which represent the depressions (31) are dimensioned such that at least one spacer particle (2) can be accommodated therein. Printing machine according to claim 13 or 14,
characterized by
that the application roller (13) is assigned to the impression cylinder (12) or the blanket cylinder (15), and that the depressions are provided in the lateral surface of the application roller (13) and are adapted to the size of the spacer particles (2) or at least grooves (32) extending essentially in the circumferential direction of the lateral surface are formed. Printing machine according to claim 14,
characterized by
that the applicator roller (13) is assigned to the impression cylinder (12) or the blanket cylinder (15) and the depressions in the lateral surfaces of the applicator roller (13) or the intermediate roller (30) by means of cups (27) adapted to the size of the spacer particles (2) ) or at least substantially grooves (32) extending in the circumferential direction of the lateral surfaces. Printing machine according to claim 13 or 14,
characterized,
that the depressions (27, 32) have a hydrophilic surface and are surrounded by hydrophobic surface areas. Printing machine according to claim 13 or 14,
characterized by
that the pickup roller (14) has an elastic jacket surface. Printing machine according to claim 13 or 14,
characterized by it
a difference in the peripheral speeds of the rollers of the application device (11 or 11 ') Printing machine for printing sheets (1), in particular with an inking unit (18), and with printing unit cylinders in the form of a plate cylinder (16), a blanket cylinder (15) and a printing cylinder (12),
characterized by it
a spray device (40) which sprays a spray liquid formed by means of the spacer onto one of the printing unit cylinders (12, 15) or the sheet (1), with a reservoir (46) for the spray liquid, a nozzle (41), a pump (47 ), which supplies the spray liquid from the reservoir (46) to the nozzle (41), two mutually parallel, gap-forming rollers (42, 43) which delimit a spray cone emerging from the nozzle (41), and one of the two Cleaning device (44, 45) associated with rollers (42, 43), which removes residues of the spray liquid adhering to the rollers (42, 43) from the rollers (42, 43) and returns them to the storage container (46). Printing machine according to claim 22,
characterized by
that the nozzle (41) is pivotable, the application of the spray liquid can be interrupted by pivoting the nozzle (41). Printing machine according to claim 2,
characterized by
that the rollers (42, 43) of the spray device (40) are arranged so as to be displaceable parallel to one another in order to be able to close the gap between them and thus to interrupt the application of the spray liquid. Printing machine for printing sheets (1), in particular with an inking unit (18), and with printing unit cylinders in the form of a plate cylinder (16), a blanket cylinder (15) and a printing cylinder (12),
characterized by it
a spraying device with a nozzle (51) directed towards a printing unit cylinder, in particular the printing cylinder (12), a container (55) for storing a spacer material which may form a mixture with an adhesive, and a conductive plate (53) which is arranged such that the opening of the nozzle (51) is located in the space between the plate (53) and the printing group cylinder (12), an electrical field being able to be formed between the printing group cylinder (12) and the plate (53) and particles of the spacer material when this electrical field is activated or the mixture can be drawn from the nozzle to the printing unit cylinder (12).

Images