A SPRAY VALVE

TECHNICAL FIELD

The present invention relates to a dampening device or spray beam in a printing press.

BACKGROUND OF THE INVENTION

A dampening device, which is arranged in the proximity of a printing press roller in a printing press, is used to apply fountain solution on a printing press roller for transfer to a plate cylinder and further to a blanket cylinder and finally to a paper web to form the final printing product.

The fountain solution is needed for obtaining the intended printing function and quality in the printing press, such as an offset printing press, as is well known in the art. A spray dampening device is normally in the form of a spray ramp with spray nozzles provided with electrically controlled spray valves, the spray valves being opened and closed responsive to control signals from a control system controlling the need of fountain solution. Such spray valves are normally electromagnetic valves.

Electromagnetic valves are, however, not perfect; they have long opening and closing times and also a long reaction time, i.e. the time from control signal commence- ment to actual valve reaction, due to magnetic reluctance. The slow reaction and the long opening and closing times make it hard to run electromagnetic valves at over 100 Hz, although there are electromagnetic valves capable of higher frequencies. The long opening and closing times also reduce the dynamic range, i.e. the range from the lowest possible fountain solution supply rate to the highest possible fountain solution supply rate (which, of course, corresponds to a valve having a full duty cycle, i.e. is open all the time ) .

The long opening and closing times also pose another problem, namely that there is a risk that fountain solution is gathered locally m too large amounts on the printing press rollers. Even though several rollers are used to even out the fountain solution before it is transferred to the plate cylinder, so called water spots may occur on the printed product, due to the inaccurate control of the magnetic valves and the too long spray pulses.

There are solutions available m the art, such as film dampening apparatuses, where a dampening roller is in direct contact with the fountain solution, where the roller applies an even film of fountain solution on the printing press rollers; these solutions are usually used for high- quality products. However, film dampening apparatuses have other disadvantages; for example, the fountain solution in the container of fountain solution could be contaminated by ink, since the printing press rollers gather up ink from che plate cylinders and transfer it back to the container of fountain solution. This makes the film dampening appa- ratuses less practical. Since spray dampening systems are contact free, they are preferable, but needs to be im ^¬ proved .

The present invention solves the above problems by providing a spray valve having short opening and closing times. A closing and opening actuator is made of a shape memory material or a magnetostrictive material.

In order to facilitate production of the actuator, the actuator may be m form of a pair of bars actuating an anchor/plunger, wherein the bars the bars are made of a magnetic shape memory material or a magnetostπctive material .

In another embodxment of the invention, a plunger made of a magnetic shape memory material or a magneto- stπctive material could be used, wherein the plunger is provided for opening and closing the spray valve. In order to ensure a proper sealing, the plunger could be spring-biased against a valve seat of the spray valve .

BRIEF DESCRIPTION OF THE DRAWINGS Further objects, advantages and features of the invention will appear from the description of several embodiments of the invention with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic perspective view of the essential parts in a printing press according to the present invention,

Figs. 2 and 3 are perspective views showing a spray bar provided with spray valves and nozzles, wherein Fig. 3 is shown m a larger scale, Fig. 4 is a section view showing a prior art magnetic valve for spray nozzles,

Fig. 5 is a section views showing a valve for spray nozzles according to the invention, and

Figs. 6 and 7 are exploded perspective views showing a preferred embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Fig. 1 is a schematic side view of a printing unit i comprising an ink tray 2, an ink train 3, ink rollers 4, a dampening device or spray bar 5 with spray valves having spray nozzles 6 (shown m Figs. 2a-b and 3a-b) , a fountain solution train 7, a plate cylinder 8, a blanket cylinder 9, a blanket 10 and a paper web 11.

The ink contained in the ink tray 2 is transferred by the ink train 3 to the plate cylinder 8 and to the print areas thereof by the ink rollers 4.

The fountain solution contained in the dampening de- vice 5 is sprayed to a first roller of the fountain solution train 7 and further transferreα by other rollers 7b in the fountain solution train 7 to the plate cylinder 8. The print of the plate cylinder 8 is transferred to the paper web 11 via the blanket cylinder 9. Fig. 2 shows a spray bar provided with spray valves having spray nozzles 6. An enlargement A of a portion of the spray bar 5 of Fig. Ia is shown in Fig. 3.

Fig. 4 shows the essential parts of a prior art valve 20 provided with a spray nozzle 6 to control the amount of fountain solution supplied to the spray nozzle 6 and applied onto the first roller of the fountain solution train 7. The spray valve 20 comprises a spring 21, a valve seat 22, an output opening 23 connecting the interior of the valve 20 with the nozzle 6, a valve plunger or plunger 24 and a housing 37. The plunger 24, which is arranged inside the housing 37, is biased against the valve seat 22 by the spring 21. The housing 37 being a solenoid is connected to an electrical means 25. By activating the solenoid 25 the plunger 24 is retracted, thereby unblocking the valve seat 22. Thereby, pressurized fountain solution, which is feed to the spray valve by a conduit 27 connected to the spray valve and through a wall of the solenoid 37 to the interior of the solenoid, is immediately feeded through the opening 23 of the valve seat 22 to the nozzle 6. The nozzle 6 ejects the fountain solution onto a first roller of the fountain solution train 7. A tip of the plunger 24 positioned closest to the valve seat 22 is normally provided with a rubber sealing to guarantee a tight seal between the plunger 24 and the valve seat 21 m the closed position. The valve 20 is closed when the solenoid 25 is inactivated,

since the spring 21 wiJ 1 bias the plunge 24 against the valve seat 22.

Fig, 5 shows the essential parts of a valve 30 according to the invention provided with the spray nozzle 6 to control the amount of fountain solution supplied to the spray nozzle 6 and applied onto the printing press roller or the first roller of the fountain solution train 7, where the standard solenoid-operated spring-biased plunger 24 has been replaced by a spring-biased valve plunger or plunger 31 having actuating bars 39 made of a magnetic shape memory material or magnetostπctive material. Each bar 39 has a length L. The va±ve 30 is also provided with a valve seat 32. The plunger 31 is m one end connected to a mid-portion of a beam 40. The beam 40 is connected m each end to a bar 39. A base 38 m the other end supports each bar 39. Similar to the prior art spray valve 20, the spray valve 30 is open if the solenoid 35 is activated.

The bars 39 can also be made of a shape memory material being a temperature sensitive material, or an electro- stπctive material.

In Figs. 6 and 7, a prererred embodiment of a valve according to the present invention is shown m exploded views. The reference numerals used for the embodiment shown m Figs. 6 and 7 differ from the reference numerals used related to the earlier figures.

The embodiment shown in Figs. 6 and 7 comprises a combined plunger/anchor 100, which includes a valve head 110 adapted to engage and seal against a spray nozzle (nob shown) . The valve head 110 and a T-shaped portion 120 are joined by a stem 130. A cover 140 is adapted to close a front portion 150 of an actuator housing 160, e.g. by providing both the front portion 150 and the actuator housing 160 with cooperating threads.

Moreover, the embodiment of Figs. 6 and 7 comprises two transfer bodies 170 and 180, manufactured from a ferro-

magnetic material and having a size adapted to fit in openings 190 and 200 (not visible on drawing) arranged on opposite sides of the actuator housing 160. The embodiment of Figs 6 and 7 also includes two coils 210 and 220, which comprise a number of turns, e.g. 100, of electrically conductive wire provided with a sheet of insulation covering the surface of wire, a design well known by persons skilled in the art of coils for electromagnetic equipment.

The magnetic field produced by the coils is amplified and concentrated by a core 230 made from a ferromagnetic material. The core 230 comprises an outer ring 240, from which extends two inwardly facing protrusions 250 and 260, on which rings the coils 210, 220 are mounted in an assembled state. The embodiment of Figs. 6 and 7 also includes two identical bars 270, 280 made from a magnetostπctive material, i.e. a material whose characteristics will be described m more detail below. A coil spring 290 is arranged to engage the T-shaped portion 120, and hence press the valve head 110 towards the spray nozzle (not shown) . A closure 300, optionally provide with a seal 310, arranged for sealing between the closure and the housing 160, is adapted to enclose the bars 270, 280 and the coil spring 290 m the housing 160. Below, the assembly and the function of the embodiment according to Figs. 6 and 7 λ?I11 be described:

In a first assembly step, the plunger/anchor 100 inserted into the housing 160, such that the T-shaped portion 120 is visible through the openings 190, 200; after the insertion of the plunger/anchor 100, it might be possible to mount either, but not both, of the transfer bodies 170, 180 into ]ts corresponding opening 190 or 200. The mounted transfer body will support one side of the stem 130 and the T-shaped portion 120 of the plunger/anchoi 100. The mounted transfer body will also serve as support for the bars 270,

280 made from MSM or magnetostπctive material, which are mounted thereafter such that one end of the bars rests against the T-shaped portion 120 and one end against a surface being fixed to the housing 160. After the mounting of the bars 270, 280, the remaining transfer body 170 or

180 is mounted m its corresponding opening 190 or 200. The mounting of the remaining body will ensure the positioning of the bars 270, 280 between the T-shaped portions and the surface being fixed to the housing 160. In another assembly step, the coils 210, 220 are mounted onto the protrusions 250, 260 of the core 230, after which the core is mounted over the housing such that the protrusions will squeeze the transfer bodies 170, 180 into engagement with the housing 160.In a preferred embodi- ment, there are provided compressible seals 175, 185 extending around a periphery of the transfer bodies 1/0, 180 and being in contact with shoulders 177, 187 arranged to squeeze the seals 175, 185 towards surfaces of the hosing 160. In a final assembly step, the coil spring 290 is inserted into the housing 160 such that one end of the spring engages the T-shaped portion 120 and urges it towards the bars 270, 280. The other end of the coil spring will come into engagement with the closure 300. By varying the amount of insertion of the closure 300, a pretension, i.e. the force of the spring urging on the T-shaped portion, of the coil spring 290 could be varied.

In a preferred embodiment of the invention, the housing 160, the plunger/anchor 100, the bars 270, 280, the coil spring 290 and the closure 300 are all made from corrosion resistant material, e.g. stainless steel, brass, bronzw or the like. The housing, the plunger/anchor and the closure could also be made from plastic.

In case all the above components are manufactured from corrosion resistant material, it is possible to run

the valve with the house being filled with fountain solution. In such a case, the fountain solution could be supplied to the housing in virtually any position, although a preferred position very close to the valve head 110; the supply of fountain solution could also e.g. be arranged by the provision of a hole drilled from an exterior of the housing 160 to the interior of the housing 160.

By filling the housing with fountain solution, overheating and wear (by friction between the bars and the supporting surfaces of the transfer bodies) of the bars and the transfer bodies could be avoided.

Typical materials of the MSM material Ni-Mn-Ga alloys. A very suitable MSM material has been disclosed in EP-Bl-O 838 095, EP-Bl-O 997 953, WO-Al-03/078922 and WO-Al- 2004/078367; the description parts of these documents are herewith incorporated by reference.

The MSM material described m EP-Bl-O 838 095, EP-Bl- 0 997 953, WO-Al-03/078922 and WO-A1-2004/078367 is in one way a fairly typica] MSM, m that it undergoes a dimension increase if subjected to a magnetic field. However, by using new and surprising effects, the MSM material according to these documents get a uniquely high dimension increase, which makes the material extremely suitable for the valves according to the present invention. The term valve plunger covers all different plungers, valve bodies or valve actuating members that serves to be an actuating part that is activated to open and close the valve .

The plunger 31 can also made of the shape memory material, whereby the bars 39 are not needed. The magnetic field will m that case act directly on the plunger 31. Compared with the spray valve 30 having bars 39 of the shape memory material a spray valve 30 having a plunger 31 of the shape memory material is closed if the solenoid 35 is activated.

To further reduce internal friction and wear, the surfaces of the plunger/anchor 130 and the transfer bodies 170 and 180 that are m engagement with one another may be coated with a friction reducing coating, e.g. of the type sold under the trademark Teflon.

The invention is not limited to the above- described examples or to the drawings showing examples of embodiments, but can be varied within the scope of the appended claims .