GB2297713A

GB2297713A - Washing device for a printing unit of a printing machine

Info

Publication number: GB2297713A
Application number: GB9602336A
Authority: GB
Inventors: Gerhard Loos
Original assignee: Heidelberger Druckmaschinen AG
Current assignee: Heidelberger Druckmaschinen AG
Priority date: 1995-02-07
Filing date: 1996-02-06
Publication date: 1996-08-14
Anticipated expiration: 2016-02-06
Also published as: JP3027706U; GB2297713B; DE19503950A1; DE19503950B4; GB9602336D0

Description

1 WABRING DEVIC9 POR A PRINTING UNIT OP A PRINTING XACKINZ 2297713 The

invention relates to a washing device for a 5 printing unit of a printing machine, said device comprising a feed pipe having outlet nozzles for applying wash-up fluid onto a roller of the printing unit under pressure and a control unit supplying metered amounts of the wash- up fluid to the feed pipe.

Such a washing device is known from the publication DE 25 04 572 C2 in which, through a control unit, wash-up fluid being under overpressure is led from a reservoir to a chamber causing a piston to be moved back against the force of a compression spring. Due to the piston motion, a second piston is displaced and presses the wash-up f luid, available in a second chamber, through nozzles onto a roller. In order to prevent the nozzles from continuing to drip, the control unit is switched so that the supply of fresh washup fluid is interrupted, via the compression spring, the first piston is moved so that the available wash-up fluid is pressed through ducts into the chamber followed by the second piston. At the same time, the wash-up f luid is sucked back from the outlet nozzles and the feed pipe and is also led into the second chamber. Until the subsequent wash-up process which, for example, may take place after a weekend or an interruption of several days, the wash-up fluid remains in said second chamber. Since the second chamber is connected to the outside and only partly filled, part of the wash-up fluid evaporates. Furthermore, the structural efforts of the known solution are enormous and do not permit a precisely metered supply of fresh wash-up fluid.

Proceeding f rom this state of the art, it is the object of the invention to provide a washing device permitting a precisely metered washing programme and requiring only minor technical efforts, by using fresh washup f luid and nevertheless reliably preventing the nozzles from continuing to drip after completion of a wash- up 2 process.

According to the present invention, we provide a washing device for a printing unit of a printing machine, said device comprising a feed pipe having outlet nozzles for applying wash-up fluid onto a roller of the unit, a control unit for supplying metered amounts of pressurised wash-up fluid to said feed pipe, and, independently of the supply of wash-up fluid, a cylinder in which a piston is movable by drive means connected to the feed pipe, and wherein, via said control unit, said piston is retracted into said cylinder by means of said drive means, after the supply of wash-up fluid has been switched off, thus sucking back the wash-up fluid from nozzles.

This low-cost solution requires little structural effort and prevents the nozzles from continuing to drip, with the wash-up fluid having to be sucked back only from the front area of a respective nozzle until the wash-up fluid is prevented from automatically overflowing the highest point of the nozzle. Wash-up devices already in use may be retro-fitted with this device.

In advantageous embodiments of the invention, a pneumatic cylinder or an electromagnet is provided as a drive means for the movable piston. Said drive means may be connected, for example, electrically to a control unit so that, when switching off the supply of wash-up fluid, the drive means is automatically switched on and the piston sucks the wash-up fluid back from the nozzles. When again switching on the wash-up device, the piston pushes the washup fluid back into the feed pipe, thus enabling a wash-up programme to be effected as intended.

A further advantageous embodiment of the invention is characterised in that the cylinder is provided at the downstream end of the feed pipe, and that the stroke volume of the cylinder extends as an extension of the interior space of the feed pipe. Instead of providing a locking cap at the end of the feed pipe, it is thus possible simply to screw a cylinder onto said end, and as soon as a connection to the control unit has been provided, the cylinder is ready 3 to be operated.

Several embodiments of the invention are now described by way of example with reference to the accompanying drawings, in which:L- FIGURE 1 shows a feed pipe featuring outlet nozzles; FIGURE 2 is a fragmentary longitudinal sectional view of the feed pipe, a cylinder and piston with the supply of wash-up fluid being switched off; FIGURE 3 is a fragmentary view, similar to Figure 2, showing the position of the piston during the wash-up process; FIGURE 4 shows a modified embodiment; and FIGURE 5 shows an embodiment having a dual feed duct.

As can be seen from the drawings, through a plurality of outlet nozzles 2, distributed over the length of a respective roller 1, wash-up f luid 3 is applied onto the outer cylindrical surface of the roller 1 of an inking unit (not illustrated) of a printing machine. Said outlet nozzles are attached to a feed pipe 4 to which fresh wash- up f luid is supplied, f or example through a f eed duct 5. Said f eed duct 5 is connected to a control unit (not illustrated) controlling the supply of wash-up fluid, for example by means of an electrically actuated valve.

Independently of the supply of wash-up fluid, a cylinder 6 is screwed onto a thread 7 provided at the end of the f eed pipe 4, to provide an extension of the f eed pipe 4. A piston 8 connected to a drive means 10 via a piston rod 9 is provided inside the cylinder 6. The drive means 10 may be a pneumatic cylinder, an electromagnet or an electromotor, for example. Via a fastening bracket 11, the drive means 10 is connected to the cylinder 6.

Figure 2 shows the position of piston 8 when said piston is moved back as soon as the supply of wash-up fluid is switched off. In this case, the stroke volume 12 is filled with wash-up fluid which is sucked back from the front area of a respective nozzle 2. As soon as the level 13 of the wash-up fluid lies below the highest point of the nozzle 2, any unintended dripping of the wash-up fluid is 4 prevented. For this purpose, the stroke volume 12 is designed corresponding to the number of nozzles 2 and the volume of wash-up fluid to be sucked back.

In Figure 3, the piston 8 has been moved to the left and the wash-up fluid available in the stroke volume 12 has been forced into the feed pipe 4, thus enabling a wash-up process to be undertaken in the inking unit.

The modified embodiment according to Figure 4 shows an arrangement of cylinder 6 provided in the feed duct 5 between control unit and feed pipe 4, i.e. upstream of nozzles 2, also producing the aboye-mentioned effect.

Figure 5 shows an embodiment using wash-up fluid based on vegetable oil. Here, two feed ducts 5 are provided, one for the wash-up fluid and one for the purpose of rinsing afterwards. A bridge 14 connects the two piston rods 9 to each other, the drive means 10 acting on said bridge 14.

It will of course be understood that the present invention has been described above purely by way of example, and modifications of detail can be made within the scope of the invention.

Claims

CLAIMS:

1. A washing device for a printing unit of a printing machine, said device comprising a feed pipe having outlet nozzles for applying wash-up fluid onto a roller of the unit, a control unit for supplying metered amounts of pressurised wash-up fluid to said feed pipe, and, independently of the supply of wash-up fluid, a cylinder in which a piston is movable by drive means connected to the feed pipe, and wherein, via said control unit, said piston is retracted into said cylinder by means of said drive means, after the supply of wash- up fluid has been switched off, thus sucking back the wash-up fluid from nozzles.

2. washing device according to claim 1, wherein the drive means for the movable piston is an electromagnet.

3. washing device according to claim 1, wherein the drive means for the movable piston is pneumatically operated.

4. Washing device according to claim 1, 2 or 3, wherein the cylinder is provided at a downstream end of the feed pipe and the stroke volume of said cylinder is an extension of the interior space of said feed pipe.

5. Washing device according to claim 1, 2 or 3, wherein the cylinder is provided in a feed duct disposed between control unit and feed pipe, upstream of the nozzles.

6. Washing device according to claim 1, 2 or 3, wherein the cylinder has two pistons therein, one for wash-up fluid and one for water, said pistons being connected to the drive means via a bridge.

7. Washing device, substantially as hereinbefore described with reference to the accompanying drawings.

8. A printing unit of a printing press having a washing 6 device as claimed in any one of claims 1-7.