DE20001524U1 - Device for rinsing a gumming station in a system for washing, gumming and drying printing plates - Google Patents

Description

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Dipl. Phys. Ulrich Twelmeier Dr. techn. Waldemar Leitner Dr. phiI. not. Rudolf Bauer-J Dipl. /ng. Helmut Hubbuch-J 99 J European Patent Attorneys

HA02E003DEU/MSOOS016/TW/ms/01/28/2000

Peter Hanosek, Staig 10 ₁ 75236 Kämpfelbach-Ersingen

Device for rinsing a gumming station in a system for washing, gumming and drying printing plates

The invention is based on a device for rinsing a rubberizing station with the features specified in the preamble of claim 1. Some of the features of the preamble are known from EP 0 703 861 B1.

Figure 1 shows the essential elements of a system for washing, gumming and drying printing plates in an oblique view without frame and casing, as shown in EP 0 703 861 B1,

Figure 2 shows a detail of a longitudinal section through a pair of rollers in the rubberizing station with subsequent drying device,

Figure 3 shows the view of the roller pair from Figure 2 with a printing plate clamped in the roller gap, and

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Figure 4 is a schematic representation of a known device for

Flushing such a rubberizing station.

The device has, in succession, an infeed table 1, a washing station 2, a rinsing station 3, a rubberizing station 4, a drying device 5 and an outfeed table 6. In the washing station 2 there is a tub 7 for collecting the washing liquid, in the rinsing station 3 there is a tub 8 for collecting the rinsing water, in the rubberizing station 4 there is a tub 9 for collecting the rubberizing liquid. If necessary, further washing and rinsing stations can be provided.

In each station there are at least two pairs of rollers consisting of an upper roller 10 and a lower roller 11, namely one pair of rollers on the input side of the station and another pair of rollers on the output side of the station. The roller pairs 10, 11 have the task of conveying the printing plates 13, which is why at least one roller in each pair of rollers can be driven. They also have the task of guiding the printing plates 13, which is why the sequence of roller gaps is in a common alignment and the lower roller 11 has a recess 12 near one end to accommodate a folded edge 14 of the printing plates 13. The recesses 12 of the lower rollers are also in a common alignment. For the purposes of the present invention, however, the guidance of the printing plates 13 by the interaction of a folded edge 14 with the recesses 12 is not important. The pair of rollers on the output side of each station also has the task of squeezing the liquid from the printing plate. The rollers 10, 11 therefore have a rubber casing, for example, which simultaneously creates the frictional connection with the printing plates 13 required for conveying them. To do this, the upper rollers 10 are pressed against the lower rollers 11. For this purpose, the upper rollers 10 can be spring-mounted in such a way that they can be raised against spring force.

As Figure 2 shows, the last pair of rollers 10, 11 in the gumming station 4 is used to apply a gumming liquid to the top of the printing plate 13. For this purpose, the top roller 10 on the inlet side of the roller gap is assigned a spray pipe 18 which extends parallel to the top roller 10 and sprays gumming liquid from a series of nozzles 19 onto a distributor plate 20 which rests resiliently against the top roller 10 and distributes the gumming liquid as a film 21 on the top roller 10, which applies it to the top of the printing plate 13 in the roller gap. On the outlet side of the roller gap, above the roller gap, there is a blow pipe 22 which runs parallel to the top roller 10 and which has nozzle openings 23 distributed along its length directed towards the roller gap, from which air is blown into the outlet side of the roller gap in order to prevent gumming liquid from running through the roller gap. At some distance from the blowpipe 22, two further blowpipes 24 and 25 are provided, one above and one below the pressure plate 13, which, through nozzle openings, apply cold air or warm air to both sides of the pressure plate 13 in order to dry it.

The dried printing plates 13 run onto the discharge table 6, from which they can be removed.

In the rubberizing station, the spray pipe and the rollers 10 and 11 must be rinsed before the system is switched off, otherwise the rubber coating will dry, the nozzles 19 of the spray pipe will become clogged and the two rollers 10 and 11 will stick together, which would lead to damage to the roller coating when the system is started up again.

In order to be able to rinse the spray pipe 18 and the rollers 10 and 11, it is known to feed fresh water from the water network into the supply line 28 to the spray pipe 18 after switching off the supply of rubber liquid. The spray pipe 18 and its nozzles 19 are rinsed with the fresh water and

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freed from the gumming liquid. The water also reaches the upper roller 10 through the nozzles 19 of the spray pipe 18 and is distributed over both rollers 10 and 11 as they rotate, so that the gumming liquid is also rinsed off the two rollers 10 and 11.

Figure 4 shows the known device for applying the rubberizing liquid and for subsequently rinsing off the rubberizing liquid. The spray pipe 18 is connected via a supply line to an OR valve 29, which is connected on the one hand to the fresh water supply line 27 and on the other hand to a feed line 30 for rubberizing liquid. In the switching position shown in Figure 4, the OR valve 29 connects the fresh water supply line 27 to the spray pipe 18. In the fresh water supply line 27 there is a shut-off valve 31 designed as a solenoid valve. In the other switching position, the OR valve 29 connects the spray pipe 18 to a source for the rubberizing liquid, consisting of a tank 32 and a pump 33, which is located in the feed line 30 leading from the tank 32 to the OR valve 29.

The tub 9 has an outlet at its bottom to which a drain line 34 is connected, which leads to a 2/3-way valve 35, which in one of its switching positions connects the drain line 34 with a line 36 leading back to the tank 32 and in its other switching position, which is shown in Figure 4, connects the drain line 34 with a waste water line 37. During rubberizing, the solenoid valve 31 in the fresh water supply line 27 is closed and the OR valve 29 to the pump 33 is open; the pump 33 pumps rubberizing liquid from the tank 32 into the spray pipe 18. The excess rubberizing liquid is collected by the tub 9 and returned to the tank 32 via the drain line 34, the 2/3-way valve 35 and the line 36. For flushing, first the pump 33 is switched off and the 2/3-way valve 35 is switched so that it connects the drain line 34 with the waste water line 37, as shown in Figure 4. Then the solenoid valve 31 in the fresh water supply line 27 is opened and the spray pipe 18 and the pair of rollers 10 and 11

rinsed until the gum liquid is washed off the rollers 10, 11. The mixture of gum liquid and water flows into the waste water line 37.

The state of the art has the disadvantage that if suction occurs in the water pipe network, rubber fluid can be sucked into the fresh water supply line 27. This must be prevented at all costs. The installation of a backflow preventer is considered to be an inadequate safeguard.

The present invention is based on the object of showing a way how the suction back of rubber fluid into the fresh water supply line can be prevented without great effort.

This object is achieved by a device having the features specified in claim 1. Advantageous developments of the invention are the subject of the dependent claims.

As a result of the design of the flushing device according to the invention, the fresh water supply line no longer has a direct connection with the supply line to the nozzles through which gumming liquid and the flushing liquid, which essentially consists of fresh water, flow alternately. If suction occurs in the fresh water supply line, only the fresh water and air still contained in the fresh water supply line can be sucked back, but no gumming liquid.

The rinsing liquid can consist of pure fresh water. However, it is also possible to add additives to the fresh water that promote the rinsing process.

The object of the invention is achieved in a simple and inexpensive manner. All that is required is to interrupt the fresh water supply and to fill a storage tank

for temporarily storing fresh water. The capacity of the storage tank can be relatively small since the storage tank can be continuously refilled from the fresh water supply line. For this purpose, a level sensor can be provided to monitor the highest level and a level sensor to monitor a lower level in the storage tank, and these two level sensors can control a solenoid valve in the fresh water supply line in such a way that the solenoid valve opens when the specified lower level is undershot and closes when the specified maximum level is reached. Another possibility is to provide a shut-off valve in the fresh water supply line which is controlled by a float switch which closes the shut-off valve when the highest specified level is reached and increasingly opens the shut-off valve in the fresh water supply line when the level drops below the maximum level.

Another possibility is to provide only a shut-off valve, e.g. a solenoid valve, in the fresh water supply line and to provide the reservoir with an overflow to limit the water level. In this case, it is sufficient to open the solenoid valve in the fresh water supply line for a predetermined period of time, selected based on experience or adjustable, before switching off the system, so that fresh water flows into the reservoir, which is fed to the nozzles by a pump in order to rinse these and the rollers for the selected period of time and to remove the rubber fluid. Excess water can flow off via the overflow. The water level never reaches the mouth of the fresh water supply line.

The rinsing liquid can be fed from the reservoir to the nozzles using a pump. The reservoir for the rinsing liquid could also be arranged so high that the rinsing liquid can be fed to the nozzles by gravity alone. It is particularly preferred to provide a common pump for feeding the rubberizing liquid and the rinsing liquid, which

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can be connected either to the tank for the rubberizing liquid or to the reservoir for the rinsing liquid. This ensures effective forced rinsing with minimal effort and safe separation of the fresh water network from the rubberizing liquid.

Figure 5 shows, in a schematic representation similar to Figure 4, an embodiment of a device according to the invention in a system for which the representations in Figures 1 to 3 apply in the same way as examples. The device according to the invention differs from the known device in that the fresh water from the fresh water supply line 27 is not fed directly into the supply line 28 to the spray pipe 18, but into a storage container 38 which has an outlet 39 in the bottom, an overflow pipe 40 at some height above the bottom and a lid with a ventilation opening 41. The fresh water supply line leads from above into the storage container 38 and opens at a distance d above the overflow pipe 40. The distance d is selected so that water cannot be sucked back into the fresh water supply line 27 under any circumstances. A suitable distance is d = 50mm.

A line 42, in which a solenoid valve 43 is located, leads from the outlet opening 39 into the feed line 30 leading from the tank 32 to the pump 33, with another solenoid valve 45 located between the junction 44 of the line 42 into the feed line 30 and the tank 32. These two solenoid valves 43 and 45 replace the OR valve 29 of the known device from Figure 4.

Otherwise, the device according to the invention corresponds to the device in Figure 4. Corresponding parts are therefore designated with corresponding reference numbers. Instead of the two solenoid valves 43 and 45, a 2/3-way valve could also be used.

The device according to the invention works as follows:

During gumming, the solenoid valves 31 and 43 are closed and the solenoid valve 45 is open. The pump 33 sucks gumming liquid from the tank 32 and feeds it into the spray pipe 18, from which it exits through the nozzles 19 and hits the upper roller 10. The excess gumming liquid is collected in the tub 9 and leaves it through the drain line 34, which is connected to the return line 36 by the 2/3-way valve 35, so that the excess gumming liquid is returned to the tank 32. For rinsing, the 2/3-way valve 35 is switched so that the drain line 34 is connected to the waste water line 37. The solenoid valve 45 is closed and the solenoid valves 31 and 43 are opened. The pump 33 sucks rinsing liquid, which is essentially fresh water, from the storage tank 38 and feeds it into the spray pipe 18, from which it reaches the rollers 10 and 11 so that they are rinsed. The mixture of rinsing water and rubber liquid reaches the waste water pipe 37 via the drain pipe 34. At the same time, fresh water is refilled into the storage tank 38 from the fresh water supply pipe 27, but no later than until the water level reaches the overflow pipe 40.

-11 -Reference number list:

1 Infeed table 2 Washing station 3 Rinsing station 4 Rubberizing station 5 Drying device 6 Discharge table 7 Tub 8th Tub 9 Tub 10 Top roller 11 Lower roller 12 Puncture 13 Printing plates 14 edge 15 16 17 18 Spray tube 19 Nozzles 20 Distribution plate 21 Movie 22 Blowpipe 23 Nozzle openings 24 Blowpipe 25 Blowpipe 26 Conveying direction 27 Fresh water supply 28 Supply line to the spray pipe 29 OR - Valve 30 Feed line 31 Shut-off valve (solenoid valve) 32 tank 33 pump 34 Drain line 35 2/3 - way - valve 36 return line 37 sewer line 38 Storage container

Claims (8)

1. Device for rinsing a gumming station in a system for washing, gumming and drying printing plates, having the following features: a) In the rubberizing station ( 4 ) at least one pair of rollers ( 10 , 11 ) is provided, which are arranged one above the other with a horizontal axis of rotation; b) there is a gap between the rollers ( 10 , 11 ) through which the printing plates ( 13 ) can be moved, the two rollers ( 10 , 11 ) touching the printing plates ( 13 ) on their upper and lower sides; c) nozzles ( 19 ) are arranged along the upper roller ( 10 ), through which a liquid can be applied to the upper roller ( 11 ); d) the nozzles ( 19 ) are selectively connectable to a source ( 32 , 33 ) for a rubberizing liquid and to a source ( 38 , 33 , 27 ) for a rinsing liquid consisting essentially of water; e) a trough ( 9 ) is arranged under the pair of rollers ( 10 , 11 ) which collects the gum liquid and rinsing liquid running off the rollers ( 10 , 11 ) and printing plates ( 13 ); f) means ( 34 , 35 , 36 , 37 ) for draining the rubber liquid and the rinsing liquid are connected to the tub ( 9 ) g) the source ( 38 , 33 , 27 ) for the rinsing liquid comprises a reservoir ( 38 ) which is provided with means ( 40 ) for limiting the level of the rinsing liquid; h) the storage tank ( 38 ) has a connection ( 27 ) for fresh water, the mouth of which is located above the highest level of the rinsing liquid in the storage tank ( 38 ). 2. Device according to claim 1, characterized in that the connection ( 27 ) for the fresh water can be shut off by the means for limiting the level. 3. Device according to claim 1 or 2, characterized in that a level sensor is provided as the means for limiting the level. 4. Device according to claim 1, 2 or 3, characterized in that the connection ( 27 ) for the fresh water can be opened by means which respond to a level below the highest level of the rinsing liquid. 5. Device according to claim 1, 2 or 3, characterized in that a float switch is provided in the storage container ( 38 ), which controls a valve located in the fresh water supply line ( 27 ). 6. Device according to claim 1 or 2, characterized in that an overflow ( 40 ) is provided as a means for limiting the level. 7. Device according to one of the preceding claims, characterized in that a solenoid valve ( 31 ) is provided in the fresh water supply line ( 27 ). 8. Device according to one of the preceding claims, characterized in that a pump ( 33 ) is provided, which can be connected with its suction side selectively to a tank ( 32 ) for the rubberizing liquid and to the storage container ( 38 ) for the rinsing liquid and is connected with its pressure side to the nozzles ( 19 ).