Control method and system in a printing press

FIELD OF THE INVENTION

[0001] The present invention relates to printing equipment. More specifically, the present invention relates to a system and a method for controlling the temperature of ink and/or coatings in printing presses.

BACKGROUND OF THE INVENTION

[0002] Printing stations typically use cooling systems in order to control the temperature of the ink. Plate heat exchangers may be used for example, in which two separate circuits are made to exchange heat, i.e. a circuit of cooling water and a circuit of ink (see Figures 1 and 2). Alternatively, the ink reservoir itself may be provided with a cooling jacket where cooling water circulates, and may be a double walls container with cooling water circulating in between two exterior walls.

[0003] There is a need in the art for a control method and system in a printing press.

BRIEF DESCRIPTION OF THE DRAWINGS [0004] In the appended drawings:

[0005] Figure 1 is a schematic view of a system with a heat exchanger on the ink feed line, as known in the art;

[0006] Figure 2 is a schematic view of a system with a heat exchanger on the ink return line, as known in the art; [0007] Figure 3 is a schematic view of a system according to an embodiment of an aspect of the present invention;

[0008] Figure 4 is a schematic view of a system according to an embodiment of an aspect of the present invention;

[0009] Figure 5 is a section of a tube for a line according to an embodiment of an aspect of the present invention;

[0010] Figure 6 is a section of a tube for a line according to an embodiment of an aspect of the present invention; and

[0011] Figure 7 is a perspective view of a segment of a tube according to an embodiment of an aspect of the present invention.

SUMMARY OF THE INVENTION

[0012] More specifically, in accordance with the present invention, there is provided a printing station comprising a reservoir, a printing unit connected to the reservoir by a feeding line and a return line; and a temperature controlling unit; at least one of: i) the feeding line and ii) the return line comprising an inner tube and an outer tube, liquid from the reservoir circulating in the inner tube and liquid from the temperature controlling unit circulating in the outer tube.

[0013] There is further provided a method for controlling temperature of ink or coating in a printing station, comprising providing a reservoir, providing a printing unit, providing a temperature controlling unit, directing ink or coating from the reservoir to the printing unit in a first tube, and from the printing unit back to the reservoir in a second tube; and circulating a temperature controlling liquid from the temperature controlling unit in a third tube housing one the first and second tubes. [0014] Other objects, advantages and features of the present invention will become more apparent upon reading of the following non-restrictive description of specific embodiments thereof, given by way of example only with reference to the accompanying drawings.

DESCRIPTION OF EMBODIMENTS OF THE INVENTION

[0015] As illustrated in Figure 3 of the appended drawings, an exemplary printing station 10 comprises a reservoir 12 connected to a printing unit 14.

[0016] The reservoir 12 is typically an ink or coating reservoir, and is actuated by a pump.

[0017] The printing unit 14 generally comprises a printing chamber such as an anilox roll or cylinder, in the case of a central impression unit for example. It may be other industrial presses, such as stack presses or gravure presses for example.

[0018] Ink or coating from the reservoir 12 is directed to the printing unit 14 via a feeding line 16 and then returns to the ink reservoir 12 via a return line 18.

[0019] Correcting fluids, such as solvents for example, may be fed to the printing station 10 through feeding lines controlled by valves (not shown).

[0020] A sensor unit 20 may be connected between the pump of the reservoir 12 and the printing chamber of the printing unit 14, to collect parameters transmitted in real time to a remote network for example (not shown).

[0021] According to an embodiment of the present invention as illustrated for example in Figures 3 and 5, the feeding line 16 comprises an inner tube 22 and an outer tube 24 housing the inner tube 22. The ink flows in the inner tube 22, while a liquid, here cooling water, flows in the outer tube 24. The cooling water comes from a temperature controlling unit, here a chilling unit 30, via a pump 31. [0022] The inner tube 22 is a thin-walled tube to increase heat transfer between the ink and the cooling water therethrough.

[0023] Both inner and outer tubes 22, 24 are made in a heat conductive material so that the fluid, i.e. cooling water in this example, circulating in between the wall of the outer tube 24 and the wall of the inner tube 22 can remove heat from the ink flowing in the inner tube 22. Moreover the material needs to be compatible with the fluid circulating in the inner tube 22, i.e. typically ink, which may based on water or on solvents for example. Stainless steel or Inconel™ for example are found to be adapted materials. Thermally conductive polymers and plastics may also be used,

[0024] The length of the feeding line 16 may be increased by increasing the length of both inner and outer tubes 22 and 24 of course. For compactness purposes, the feeding line 16 may also be folded on itself so as to provide a longer length of tube while reducing the space occupancy. As long lengths of heat transfer are thus possible without undue space occupancy, the heat transfer capacity per unit of length may be reduced. The material of the tubes 22, 24 is then selected to be flexible, and/or the tubes 22, 24 are thin walled tubes.

[0025] According to an embodiment of the present invention as illustrated for example in Figure 4, the return line 18 comprises an inner tube 26, and an outer tube 28 housing the inner tube 26, the ink flowing back from the printing unit 14 to the reservoir 12 in the inner tube 26, while cooling water, coming from the chilling unit 30, flows in the outer tube 28.

[0026] Again, both inner and outer tubes 26, 28 are made in a heat conductive material so as to allow heat transfer between the two tubes 26 and 28, while being compatible with the ink flowing in the inner tube 26.

[0027] It could be contemplated circulating the ink or coating within the outer tubes and the temperature controlling liquid in the inner tube. However, such configuration may be less efficient and controllable due to the effect of the outside environment on the outer tube. [0028] By providing tubes, either the inner tube 22, 26 or both the inner and outer tubes 24, 28, that are corrugated, i.e. which surfaces are provided with ribs 25 , as illustrated for example in Figures 6 and 7, as opposed to tubes having linear surfaces, an increased heat transfer surface may be obtained. Moreover, a corrugated inner tube 22 is found to cause agitation of the ink flowing thereinside, resulting in an improved temperature uniformity of the ink across the inner tube 22,

[0029] It has been found that circulating the cooling liquid and the ink in opposite directions may increase efficiency of the heat transfer through the wall of the inner tube.

[0030] As the tubes of the present invention are typically thin-walled, and may be corrugated as described hereinabove, they may be mechanically reinforced to sustain operating pressures in the system 10, by providing a braid band 29 wrapped about the outer tube 24, 28 (see Figures 5 and 6).

[0031] Although the above examples are concerned with cooling the ink where the feed line 16 and/or the return line 18 are used as cooling lines, it may be contemplated using the feed line and/or the return line as heating lines. Water, alcohol, glycol or ionized water may be used for example. The present invention provides a system and a method for cooling or heating the temperature of ink and/or coatings on printing presses,

[0032] As people in the art will appreciate, the present system avoids complex geometries and cavities inherent to plate heat exchangers or shell and tubes heat exchanger, and is thus easier to maintain and clean up.

[0033] Although the present invention has been described hereinabove by way of embodiments thereof, it may be modified, without departing from the nature and teachings of the subject invention as recited herein.