WO2005049321A1

WO2005049321A1 - Water pan of an offset press

Info

Publication number: WO2005049321A1
Application number: PCT/IB2004/003750
Authority: WO
Inventors: Xavier Taillefer
Original assignee: Goss International Montataire Sa
Priority date: 2003-11-21
Filing date: 2004-11-16
Publication date: 2005-06-02
Also published as: DE10354430A1

Abstract

A water pan (28) of an offset press (10), having at least one outer wall (44), which has at least one heat pump element (46), in particular a Peltier element. To prevent moisture from condensing from the ambient air onto the outer wall (44) of the water pan (28), the heat pump element (46) is operated in a manner that maintains the temperature of the outer wall (44) of the water pan (28) above the dew point of the ambient air.

Description

WATER PAN OF AN OFFSET PRESS

[0001] The invention is directed to a water pan of an offset press. It is also directed to a method for preventing moisture from condensing from the ambient air onto the outer wall of a water pan of an offset press.

[0002] In conventional offset print units, damping solution is supplied from a water pan, a damping solution vat or a reservoir, to a damping system which transfers and distributes the damping solution to a printing form accommodated on a printing form cylinder. Since the water pan containing the (often cooled or tempered) damping solution constitutes a thermodynamic heat reservoir, moisture from the ambient air is able to condense undesirably onto the outer walls of the water pan or precipitate as dew, thereby enabling drops to form which can interfere with the printing operation by getting onto the printing substrate or electrical components, for example. To overcome this problem, a multiplicity of approaches has already been proposed in the literature, each having a varying degree of success and entailing different constructional outlay.

[0003] From the Geraian Application DE 101 02728 Al, it is known that a water pan of an offset press can be provided on its outer walls with a foamed thermal insulating layer. On the one hand, the insulating layer reduces the transfer of heat from the ambient environment and/or the offset press to the damping solution and, on the other hand, the condensation of water on the outer wall is also reduced.

[0004] The German Utility Model Patent DE 202 19489 Ul describes a damping system of an offset press that includes a heatable structural component, for example a vat or a water pan, having a circulating heat-exchanging medium to enable the temperature of the outer wall of the structural component to be maintained above the dew point of the ambient air.

[0005] The German Application DE 198 52 656 Al discusses a heatable protective element in an offset press for preventing the condensation of water. [0006] The German Application DE 198 56 370 Al describes a device and a method for preventing moisture from condensing from the ambient air in a damping system of an offset press. The temperature of the ambient air is controlled by cooling or heating the ambient air and thereby altering its relative humidity. The temperature difference between the individual components of the damping system and the ambient air should be minimal, in order to reduce or prevent the formation of dew.

[0007] The object of the present invention is to reduce and, in particular, to prevent the condensation of moisture from the ambient air onto a water pan of an offset press.

[0008] This objective is achieved in accordance with the present invention by a water pan having the features as set forth in claim 1. Advantageous further refinements of the present invention are delineated in the dependent claims.

[0009] In accordance with the present invention, a water pan of an offset press is provided on at least one outer wall with at least one heat pump element that permits or effects a heat transfer through the outer wall. The heat pump element is an active element which may produce a temperature difference or a temperature gradient between the inside of the water pan and the outer wall. The heat pump element may be accommodated on or fastened to the outer wall, particularly its exterior side. It may also be accommodated in a side wall or in the bottom of the water pan. The fastening may be accomplished, inter alia, mechanically, for example by a screw connection or a solder connection, or chemically, for example by adhesive bonding.

[0010] By using a heat pump, it is advantageously possible, on the one hand, to increase the temperature of the outer wall, in particular, above the dew point of the ambient air, at least above the temperature of the ambient air, while, on the other hand, the temperature of the damping solution in the water pan is reduced. Condensation or liquefaction of the moisture from the ambient air may be reduced or prevented. In other words, by using a heat pump element to cool the damping solution, it is possible at the same time to increase the surface temperature of the outer wall; namely, the outer wall temperature is not necessarily reduced in response to a cooling of the damping solution, so that moisture condensation need not be feared. In short, as an active element, a heat pump element simultaneously and synergetically makes it possible for the damping solution to be cooled and for the risk of condensation to be reduced.

[0011] One preferred embodiment of the water pan according to the present invention provides for the at least one heat pump element to be a Peltier element. The Peltier element may be operated, in particular, with the cooling side oriented toward the inside and the heating side toward the outside, away from the water pan. The contact surface between the cooling side of the Peltier element and the water pan may be sealed, in particular to prevent undesirable or deleterious condensation on this side. Conventional Peltier elements can generate temperature differences of up to 60 kelvin, temperature differences of as little as 25 kelvin already successfully preventing condensation.

[0012] It is particularly advantageous for the entire outer surface of the outer walls of the water pan to be covered with a number of cooling sides of heat pump elements. In other words, the outer walls of a water pan according to the present invention may be covered with a number of heat pump elements or with an array of heat pump elements.

[0013] In the water pan according to the present invention, a number of heating sides of heat pump elements may be oriented to face away from the water pan. In other words, the heat pump elements may be operated so as to generate a heat flow from the inside to the outside, through the outer wall of the water pan.

[0014] In one advantageous embodiment of the water pan according to the present invention, the heating side of the at least one heat pump element may be connected to a thermally conductive external surface element. The at least one heat pump element may be used to temper a surface element of the outer wall, so that condensation on this element is reduced, preferably completely reduced, or prevented.

[0015] Although a desired functioning of the heat pump element of the water pan according to the present invention is already achieved by a suitable energizing current, it is advantageous for a control unit or control device to be additionally assigned to the at least one heat pump element to enable the generated temperature difference to be varied. In the case that one or more Peltier elements are used, it is possible to influence the temperature difference by controlling the flow of current through the Peltier element or the Peltier elements. In one especially beneficial further refinement, a temperature sensor and a humidity sensor are assigned to the control device or control unit in a way that enables the heat pump element to be controlled as a function of the temperature of the ambient air and of the humidity of the ambient air. Based on the measurement results, the requisite temperature difference of the heat pump element may be set in a way that ensures that the temperature of the outer wall is above the dew point.

[0016] The water pan according to the present invention may be used in a damping system of an offset press. In other words, a damping system in accordance with the present invention of an offset press includes a water pan of this description. An offset press according to the present invention includes at least one damping system having a water pan of this description. The offset press may be a sheet-fed or a web-fed press. A sheet-fed offset press may have a feeder, at least one print unit, typically four, six, eight or ten print units, optionally a surface-finishing unit (varnishing system, punching unit or the like) and a delivery unit. A web-fed offset press, also referred to as rotary press or commercial web press, may have a reel changer, at least one printing unit having two print units, in particular four, six or eight printing units that print on the printing substrate from above and below, a dryer, and a folding apparatus. Typical printing substrates are paper, board, cardboard, organic polymer films and fabric.

[0017] Also included in the context of the inventive idea is a method for preventing moisture from condensing or precipitating from the ambient air (air humidity) onto an outer wall, preferably from preventing the same on all outer walls or on the entire outer surface of a water pan of an offset press. A heat pump element accommodated on the water pan is operated in such a way that the temperature of the outer wall of the water pan is maintained above the dew point of the ambient air. In particular, the temperature and the humidity of the ambient air may be measured, and a requisite outer wall temperature may be determined.

[0018] Other advantages, advantageous embodiments and further refinements of the present invention are explained with reference to the following figures and their descriptions. Specifically, they show:

[0019] Figure 1 a schematic representation of an offset press having a water pan according to the present invention; [0020] Figure 2 a schematic representation of an embodiment of a water pan according to the present invention having a control unit;

[0021] Figure 3 an alternative embodiment of a water pan according to the present invention;

[0022] Figure 4 a cross-sectional representation of a water pan according to the present invention along line IV-IV in Figure 2; and

[0023] Figure 5 a cross-sectional representation of an alternative embodiment of the water pan according to the present invention.

[0024] Figure 1 shows an offset press 10, by way of example a sheet-fed press, without limiting the universality of the use of the water pan of the present invention. Offset press 10 has a feeder 12, four print units 14 and a delivery unit 16. Each print unit 14 includes an impression cylinder 18, a blanket cylinder (also known as transfer cylinder) 20, and a printing form cylinder 24. Print unit 14 also contains a damping system 24 for dampening, and an inking system 26 for inking printing form cylinder 24. Damping system 24 is composed of a vat-shaped water pan 28, a pan roller 30 disposed therein for picking up a damping solution 32 from water pan 28, a metering roller 34 resting against pan roller 30 for producing a damping film, an application roller 36 resting against metering roller 34 and printing form cylinder 24, and a distributor roller 38 resting only against application roller 36 for ensuring smooth and uniform application of the damping film. Water pan 28 according to the present invention will now be explained in detail with reference to the following figures.

[0025] Figure 2 is a schematic representation of one embodiment of a water pan 28 according to the present invention having control unit 48. Water pan 28 is made of a dimensionally stable material, for example of a plastic, stainless steel, or a composite material, such as a fiber-reinforced layered system. Water pan 28 is made up of an open hollow space, for example a vat, having bottom 40 and side walls 42. A heat pump element 46 is accommodated on one outer wall 44 of a side wall 42. Heat pump element 46 is a Peltier element which, as a function of the orientation and intensity of the current flow, produces a temperature difference or a temperature gradient from the inside to the outside, through outer wall 44 and through side wall 42. Heat pump element 46 is at least electrically connected to a control unit 48. Control unit 48 regulates and/or controls heat pump element 46. Control unit 48 receives temperature information about the ambient air surrounding water pan 28 via a temperature sensor 50 or a thermometer, and humidity information (relative humidity) about the ambient air via a humidity sensor 52 or a hygrometer. Depending on the measurements, the heat difference produced by heat pump element 46 may be controlled in such a way that the temperature of outer wall 44 is above the dew point. In other words, for the special embodiment of the Peltier element, the outer surface of outer wall 44 is formed or covered by the heating side of the Peltier element. Alternatively thereto, the heating side of the Peltier element may heat outer wall 44 as such.

[0026] Figure 3 relates schematically to one alternative embodiment of a water pan 28 according to the present invention. In this embodiment, the entire outer surface of water pan 28, of side walls 42 and of bottom 40 is covered by heat pump elements 46, in particular Peltier elements, in the form of an array 54. In such an embodiment, the entire outer surface of the water pan may be brought to a temperature above the dew point. It is clear that the number of required heat pump elements depends on their active surface area in comparison to the total surface area of the outer wall of water pan 28. This number may be a multiplicity of elements or just one single element.

[0027] Figure 4 is a schematic cross-sectional representation of a water pan 28 according to the present invention along line IV-IV in Figure 2. Heat pump element 46 has a heating side 56 and a cooling side 58. Heating side 56 is disposed on the outside and prevents moisture from condensing from the ambient air. Cooling side 58 is disposed on the inside and effects a tempering of the damping solution contained in water pan 28.

[0028] Figure 5 is a cross-sectional representation of an alternative embodiment of water pan 28 according to the present invention. While cooling side 58 of heat pump element 46 is once again disposed on the inside, heating side 56 is in contact with a surface element 60 at least in a way that permits the transfer of thermal energy. In this manner, heat pump element 46 heats external surface element 60, so that its temperature is above the dew point of the ambient air.

[0029] The various, possible accommodations on outer wall 44, as illustrated in Figures 4 and 5, may also be implemented in the alternative embodiment in accordance with Figure 3, by using an array 54 of heat pump elements 46.

REFERENCE NUMERAL LIST

10 offset press 12 feeder 14 print unit 16 delivery unit 18 impression cylinder 20 blanket cylinder 22 printing form cylinder 24 damping system 26 inking system 28 water pan 30 pan roller 32 damping solution 34 metering roller 36 application roller 38 distributor roller 40 bottom 42 side wall 44 outer wall 46 heat pump element 48 control unit 50 temperature sensor 52 humidity sensor 54 array of heat pump elements 56 heating side 58 cooling side 60 surface element

Claims

WHAT IS CLAIMED IS:

1. A water pan (28) of an offset press (10) having at least one outer wall (44), wherein the outer wall (44) is provided with at least one heat pump element (46).

2. The water pan (28) as recited in claim 1 , wherein the at least one heat pump element (46) is a Peltier element.

3. The water pan (28) as recited in claim 1 or 2, wherein the entire outer surface of the outer walls (46) of the water pan (28) is covered with a number of cooling sides (58) of heat pump elements (46).

4. The water pan (28) as recited in one of the preceding claims, wherein a number of heating sides (56) of heat pump elements (46) is oriented to face away from the water pan (28).

5. The water pan (28) as recited in one of the preceding claims, wherein the heating side (56) of the at least one heat pump element (46) is comiected to a thermally conductive external surface element (60).

6. The water pan (28) as recited in one of the preceding claims, wherein the at least one heat pump element (46) is provided with a control unit (48).

7. The water pan (28) as recited in one of the preceding claims, wherein a temperature sensor (50) and a humidity sensor (52) are assigned to the control unit (48) in such a way that the heat pump element (46) is controllable as a function of the temperature of the ambient air and of the humidity of the ambient air.

8. A damping system (26) of an offset press (10), characterized by a water pan (28) as recited in one of the preceding claims.

9. An offset press (10), characterized by a damping system (26) as recited in claim 8.

10. A method for preventing moisture from condensing from the ambient air onto an outer wall (44) of a water pan (28) of an offset press (10), characterized by operation of a heat pump element (46) accommodated on the water pan (28) in a manner that maintains the temperature of the outer wall (44) of the water pan (28) above the dew point of the ambient air.