WO1994025277A1

WO1994025277A1 - Apparatus for transferring a printing fluid to a printing roller

Info

Publication number: WO1994025277A1
Application number: PCT/NL1994/000099
Authority: WO
Inventors: Pieter Gilles Uithoven
Original assignee: Machinefabriek 'csw' B.V.
Priority date: 1993-05-05
Filing date: 1994-05-04
Publication date: 1994-11-10
Also published as: AU6857594A

Abstract

The invention relates to an apparatus for transferring a printing fluid such as an ink or lacquer from supply means to the outer surface of a printing roller, which apparatus comprises: a feed roller (16) receiving the fluid from the supply means (15); and a number of transfer rollers (17, 20, 21, 25, 26) co-acting with their surfaces such that the fluid can be transferred to the printing roller (27); wherein to at least one transfer roller is added a satellite system comprising at least one satellite roller (22, 23); such that all transfer rollers (17, 20, 21, 25, 26) and satellite rollers (22, 23) forming part of the apparatus are driven at equal peripheral speeds and in corresponding directions.

Description

APPARATUS FOR TRANSFERRING A PRINTING FLUID TO A PRINTING ROLLER

The invention relates to an apparatus for transfer¬ ring a printing fluid, such as an ink or lacquer, from a supply container to the outer surface of a printing roller, in particular a so-called plate cylinder. An object of the invention is to embody such an apparatus such that spraying and misting of printing fluid during transfer from the one roller to the other is reduced to a minimum. It will of course be apparent that the spraying or misting of the fluid as always occurs in known apparatus of this type is unfavourable. Loss of valuable printing fluid occurs, while said wasted print¬ ing fluid causes fouling, which in turn results in a longer average standstill time in respect of necessary servicing. A related objective of the invention is to reduce as much as possible the use of the fluid itself.

Another object of the invention is to embody such an apparatus such that the print quality achieved meets very high standards, wherein so-called ghost images in partic- ular are avoided.

In order to realize the stated objects the invention provides an apparatus for transferring a printing fluid such as an ink or lacquer from supply means to the outer surface of a printing roller, which apparatus comprises: a feed roller receiving the fluid from the supply means; and a number of transfer rollers co-acting with their surfaces such that the fluid can be transferred to the printing roller; wherein to at least one transfer roller is added a satellite system comprising at least one satellite roll¬ er; such that all transfer rollers and satellite rollers forming part of the apparatus are driven at equal periph- eral speeds and in corresponding directions. The use of a satellite system is essential to the invention. Such a satellite system, which is not arranged directly in the path along which the ink transport takes place directly, has the object of enhancing the homogene- ity of the layer thickness of the printing fluid. Use can hereby be made at the feed of a reduced fluid layer thickness, while the homogeneity is greatly improved on the discharge side. In addition no detectable colour differences occur at the edges of relatively large sur- faces of one colour.

In a simple embodiment the apparatus has the special feature that at least one individual satellite roller is added to at least one transfer roller.

A more refined version is that in which at least two satellite rollers are added to at least one transfer roller. This latter embodiment is preferably embodied such that a third satellite roller co-acts with the said two satellite rollers.

Even better results are obtained with a version in which between the first and the third of a first, second and third transfer roller is arranged an additional transferring system acting in parallel with the second transfer roller and comprising at least one transfer roller. A further improvement of the printing quality is obtained with an embodiment in which the number of trans¬ fer rollers co-acting with the printing roller amounts to at least two.

In order to ensure that the co-acting surfaces of the pairs of rollers mutually co-act in slip-free manner while the generation of heat nevertheless remains limit¬ ed, the surfaces of all pairs of two co-acting rollers can in preference be respectively comparatively hard, for instance of steel, and comparatively soft, for instance of rubber. It will be apparent in this respect that co- acting hard surfaces share an insufficient coefficient of friction to ensure an effective mutual driving. The use of two relatively soft rollers has the drawback of a needlessly high generation of heat. The latter described embodiment in particular can have the special feature that a comparatively soft satel¬ lite roller co-acts with at least one comparatively hard transfer roller. In order to bring about the best possible homogene¬ ity of the transfer the embodiment is recommended in which the satellite roller has a diameter differing from the transfer roller. Particularly favourable is the embodiment in which the satellite roller has a smaller diameter than the transfer roller. Such an embodiment in particular ensures a very good transfer quality, while the space occupied remains limited.

It is recommended to be able to adjust the co-action between pairs of rollers for purposes of optimalization. In this context the apparatus can be provided with first adjusting means for adjusting the relative positions and therewith the mutual pressure of two co-acting rollers.

Use can also be made of second adjusting means for adjusting the relative longitudinal directions of two co- acting rollers. This latter embodiment in particular can guarantee a homogeneous layer thickness over the whole lengthwise direction of the printing roller.

The invention will now be elucidated with reference to the annexed drawings. Herei : figure 1 shows two co-acting rollers to illustrate spraying or misting of printing fluid; figure 2 shows four mutually co-acting rollers to elucidate the layer thickness distribution; figure 3 is a schematic view of a first embodiment of the invention; figure 4 shows a view corresponding with figure 3 of a further embodiment corresponding with figure 6; figure 5 shows a printing machine which includes a number of apparatus according to the invention; figure 6 is a partial side view of an apparatus as according to figure 4; figure 7 is a schematic view of the drive unit of the apparatus of figure 6; figure 8 shows partially in side view and partially in broken away view the apparatus according to figure 6; figure 9 shows partially in top view and partially in broken away view the apparatus according to figure 6; figure 10 shows a cross section of the detail X of figure 9; and figure 11 is a perspective view of that part of the apparatus of figure 6 corresponding with figures 8 and 9.

Figure 1 shows the manner in which the spraying of printing fluid occurs due to the co-action between two rollers 1, 2. The rollers 1, 2 are driven at equal pe- ripheral speeds and in corresponding directions 3, 4. A layer of printing fluid 5, 6 is applied to both rollers by way of non-drawn means. It should be noted that the layer in question is very thin and that figure 1 is not drawn to scale. The thickness of the layer can amount for instance to several micrometres. The quite tough fluid is subjected to forces, including inertia forces, as it leaves the pinch 7 such that a part of the fluid will further move as a cloud of mist 8 moving tangentially in space, where it can result in fouling of the machine. By way of introducing the invention, figure 2 shows schematically the manner in which the printing fluid can be distributed over a number of co-acting rollers and the manner in which the transfer from feed 9 to discharge 10 can take place. Four rollers 11, 12, 13, 14 are drawn in figure 2. In this illustrative example these are drawn with the same diameters and are driven at equal speeds and in corresponding directions. It is noted aside that the driving of the rollers can take place through mutual frictional contact but that external drive means are also applied for this purpose.

The relevant layer thicknesses are shown in figure 2 with numbers in brackets. On the feed side the roller 11 has for instance a layer thickness (2) . At the point of its contact with roller 12 the roller 11 transfers a part of the relevant fluid mass to this roller 12. The layer arriving there with thickness (1) obtains a thickness (1.5), while the layer of fluid on roller 11 likewise acquires a thickness of (1.5). A transfer thus takes place at the position of all pinches between the rollers such that the sum of the layer thicknesses at the feed equals the sum of the layer thicknesses at the discharge of the relevant pinch.

Figure 3 shows a first embodiment of the invention. A supply container 15 contains a supply of printing fluid. By means of a metering device, which is drawn in somewhat more detail in figure 6, a precisely determined amount of fluid is transferred from the supply container to a feed roller 16. From this roller 16 transfer of fluid takes place to a roller 17 with steel outer surface by means of an intermediate roller 18 which, via means which are not drawn, can perform a reciprocating movement as according to arrow 19. Roller 16 thus only comes into contact with the feed roller for a predetermined part of the time, there takes up fluid and transfers this to the steel roller 17 for a predetermined time.

A number of soft rollers, that is, rollers having for instance a rubber outer surface, 20, 21, 22, 23 co- act with the steel roller 17. Rollers 22 and 23 have mutually differing diameters and are both smaller than roller 17. Rollers 22 and 23 are satellite rollers and serve to improve the transfer quality of the fluid by the roller 17. Rollers 20 and 21 likewise have a smaller diameter than the steel roller 17 and transfer fluid to a steel roller 24. This latter co-acts in analogous manner with rubber rollers 25, 26 which together transfer fluid to a printing roller 27, typically designated as "plate cylinder" . This finally transfers the fluid to the pass¬ ing surface 28 for printing. Attention is drawn to the fact that the apparatus according to the invention relates to the rollers 17, 20, 21, 22, 23, 24, 25, 26 and 27. The supply container 15, feed roller 16 and intermediate roller 18 are the usual supply means for feeding printing fluid to the actual feed roller in the system according to the invention, namely roller 17. The roller 16 can for instance also have a speed differing from the other rollers. The said rollers in the system according to the invention do however rotate at equal speeds. Figure 6 shows a configuration containing the same rollers as the system according to figure 3. A further number of satellite systems are however added to this configuration. A hard roller 29 thus co-acts with the soft rollers 22, 23. In addition the soft roller 26, which operates as it were in parallel with the soft roller 25, is replaced by a system of rollers 30, 31, 32, 33. As everywhere, they are successively hard and soft. The rollers 30, 32, 33 are therefore soft and roller 31 is hard. The system 30, 33 provides a transfer path for printing fluid acting in parallel with roller 25. Figure 5 shows a printing apparatus 34 which can print fed-in cans 35. For this purpose the latter are guided along the transfer surface 28 (see also figures 3 and 4) . At the position of the printing station 35 a rotation is per¬ formed of the cans being carried along and supported by a wheel 36 so that they can be printed by the respective printing plates forming part of the surface 28. This surface 28 is printed by the respective apparatus accord- ing to the invention which are disposed along the periph¬ ery of the surface 28. These apparatus are designated with 37, 38, 39, 40, 41, 42.

Figure 6 shows by way of example the apparatus 37. The apparatus 38-41 can be embodied identically. The organization of the apparatus 37 corresponds with the disposition drawn in figure 4. Corresponding elements are therefore designated, as everywhere in these drawings, with the same reference numerals as in figure 4. The only difference from figure 4 is that the roller 28, which co- acts with rollers 22 and 23, is omitted in figure 6.

Clearly shown is that the surface 28 of the plate cylinder carries a number of printing plates 43.

The supply container 25 has on its outlet a metering knife 44 which can be placed relative to the feed roller 26 such that a precise dosing of the fluid 45 is ensured. Attention is drawn to the fact that the '«'ord "fluid" is used for all suitable printing masses, including relatively viscous fluids which should rather be deemed pastes. Figure 7 shows schematically the manner in which driving of the diverse rollers can take place. This will be apparent with reference to the diagram shown. It can also be seen from this diagram that a number of rollers are driven via the shown transmission, while others are driven as free-turning rollers at the same peripheral speed by friction contact.

It is noted for the sake of completeness that roll¬ ers 17 and 24 can be driven such that, in addition to a rotational movement, they also make an axial oscillating movement. This enhances a homogeneous fluid layer thick¬ ness.

Figures 8-11 show provisions with which the rollers 25 and 26 according to figure 3 can be adjusted in rela- tion to rollers 24, 27.

Rollers 25 and 26 are mounted with their respective ends in associated frames 46, 47 and 48, 49 respectively. Both frames are rotatable round the centre line of roller 24 in the manner designated in figures 8 and 11. Figure 8 in particular clearly shows this method of rotatable suspension. It will be apparent that when frames 48, 49 rotate round the centre line of roller 24 only the rela¬ tive angular position of rollers 24, 26 changes. The mutual angular position of the centre lines of the roll- ers and the mutual distance of the centre lines do not hereby change.

The frames 46, 47, 48, 49 are displaceable through a limited distance relative to the support frame 50 forming part of the apparatus 37 (see also figures 6 and 7) . Use is made for this purpose of sliding blocks 51, 52, 53 and 54 which are shown in particular in figures 9 and 10 and which are slidable in oblique position. These blocks are all provided with a continuous threaded hole, with which corresponding screw threads, all designated with 55, co- act. The screw threads are arranged on respective shafts which can be rotated individually by control means. When a relevant shaft is rotated an axial displacement of the associated sliding block 51-54 takes place, whereby a sideways displacement also takes place as the shafts to be described hereinbelow are mounted fixedly relative to the support frame 50.

Figure 10 shows the manner in which the shaft 56 which co-acts with the sliding block 54 can be rotated individually and, if desired, coupled to the shaft 57 which co-acts with sliding block 53. The shaft 57 is hollow. Extending through this shaft 57 is a fitting part of shaft 56. A control knob 58 has a slotted hole 59 in which fits a locking pin 60 which is fixedly attached to shaft 57. As shown in figure 10, each shaft 56, 57 can in this manner be individually controlled, but, through co¬ operation of pin 60 and slotted hole 59, both shafts can also be rotated simultaneously by means of knob 58. In the case of simultaneous rotation a parallel displacement of roller 26 takes place since the angle, shown particu¬ larly clearly in figure 10, at which the sliding blocks co-act with the support frame 50 is the same for all blocks. When only one of the two shafts 55 or 56 is rotated, the one end of the roller remains in place while the other undergoes a certain rotation. The precise parallel position of the centre lines of roller 26 and roller 24 can herewith be adjusted. The parallel dis¬ placement can be used to adjust the pressure force be¬ tween roller 26 and roller 27. It will be apparent that for the other rollers the same applies mutatis mutandis as stated for the rollers described with reference to figures 9-11.

Figure 8 shows with an arrow 81 the oscillating movement of the roller 24 already described briefly above.

The number of apparatus according to the invention, which amounts to six in the configuration of figure 5, can in principle be left to free choice, in accordance with the desired number of colours.

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Claims

1. Apparatus for transferring a printing fluid such as an ink or lacquer from supply means to the outer surface of a printing roller, which apparatus comprises: a feed roller receiving the fluid from the supply means; and a number of transfer rollers co-acting with their surfaces such that the fluid can be transferred to the printing roller; wherein to at least one transfer roller is added a satellite system comprising at least one satellite roll¬ er; such that all transfer rollers and satellite rollers forming part of the apparatus are driven at equal periph¬ eral speeds and in corresponding directions.

2. Apparatus as claimed in claim 1, wherein at least one individual satellite roller is added to at least one transfer roller.

3. Apparatus as claimed in claim 1, wherein at least two satellite rollers are added to at least one transfer roller.

4. Apparatus as claimed in claim 3, wherein a third satellite roller co-acts with the said two satellite rollers.

5. Apparatus as claimed in any of the foregoing claims, wherein between the first and the third of a first, second and third transfer roller is arranged an additional transferring system acting in parallel with the second transfer roller and comprising at least one transfer roller.

6. Apparatus as claimed in any of the foregoing claims, wherein the number of transfer rollers co-acting with the printing roller amounts to at least two.

7. Apparatus as claimed in any of the foregoing claims, wherein the surfaces of all pairs of two co- acting rollers are respectively comparatively hard, for instance of steel, and comparatively soft, for instance of rubber.

8. Apparatus as claimed in claim 7, wherein a com¬ paratively soft satellite roller co-acts with at least one comparatively hard transfer roller.

9. Apparatus as claimed in claim 8, wherein the satellite roller has a diameter differing from the trans¬ fer roller.

10. Apparatus as claimed in claim 9, wherein the satellite roller has a smaller diameter than the transfer roller.

11. Apparatus as claimed in claim 1, comprising first adjusting means for adjusting the relative posi¬ tions and therewith the mutual pressure of two co-acting rollers.

12. Apparatus as claimed in claim 1, comprising second adjusting means for adjusting the relative longi¬ tudinal directions of two co-acting rollers.

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