EP2620285B1

EP2620285B1 - Cleaning system for an ink chamber

Info

Publication number: EP2620285B1
Application number: EP12152401.1A
Authority: EP
Inventors: Wolfgang Brusdeilins; Gordon Whitelaw
Original assignee: Bobst Bielefeld GmbH
Current assignee: Bobst Bielefeld GmbH
Priority date: 2012-01-25
Filing date: 2012-01-25
Publication date: 2019-11-13
Anticipated expiration: 2032-01-25
Also published as: EP2620285A1; ES2761329T3

Description

The invention relates to a system for cleaning an ink chamber with a cleaning liquid.
In the printing industry there is frequently a need to clean an ink chamber with water or with an organic solvent, depending upon the type of ink being used. For example, in a flexographic printing press, an ink chamber is formed between two doctor blades which engage a segment of a peripheral surface of a rotating anilox roller or engraved roller, so that minute pits formed in the surface of the engraved roller may take up ink from the ink chamber when the surface of the engraved roller passes through the ink chamber. From time to time, and in any case when the ink in the ink chamber has to be replaced with ink of a different colour, it is necessary to clean the ink chamber by scavenging it with the cleaning liquid. In case of solvent-based inks, it is necessary to use organic solvents as cleaning liquid. Because such solvents are easily inflammable, the equipment for supplying the cleaning liquid, such as pumps and the like, must be explosion-proof.
In a known cleaning system ( EP 0 958 920 A1 ), the cleaning liquid is pumped into or out of the ink chamber by means of membrane pumps or peristaltic pumps that are driven by explosion-proof motors.
In another known cleaning system ( US 5,674,571 ), to empty the ink chamber, a liquid is pumped into the reservoir with a first pump while being drained with a vacuum jet-pump placed downstream from a collection reservoir. The system, however, cannot be activated by the sole action of a pressurised air source.
It is an object of the invention to provide a cleaning system that can be installed at low costs and is easy to operate.
To that end, the cleaning system according to the invention is defined by claim 1 and comprises a source of compressed gas and a jet pump driven by said compressed gas and connected to said ink chamber.
This cleaning system has the advantage that the pump has practically no movable mechanical parts and can be driven only by the compressed gas, e.g. compressed air, which is generally available, anyway, in a printing press environment. Consequently, the cleaning system is inherently explosion-proof, so that no specific anti-explosion measures are required.
The system according to the invention requires only comparatively low installation and maintenance costs.
More specific optional features of the invention are indicated in the dependent claims.
In a preferred embodiment, the jet pump is arranged for draining the cleaning liquid from the ink chamber. The same jet pump or a separate jet pump may be used for supplying the cleaning liquid into the ink chamber. In the former case, a suction port of the drain pump is connected to the ink chamber via one or more drain passages. As long as cleaning liquid is contained in the ink chamber, it will be drained through the drain passage. If the ink chamber is not vented, an underpressure will be created in the ink chamber and this underpressure may be used for sucking new cleaning liquid into the ink chamber. Preferably, a switching valve is provided for connecting an inlet port of the ink chamber either to a reservoir for the cleaning liquid or to the open air. At the end of the cleaning process, the ink chamber will be vented via the switching valve, so that the jet pump draws an air current through the ink chamber for drying the same.
In a particularly preferred embodiment, the jet pump is incorporated in a valve body that is arranged to open and close the drain passage and is operated by the compressed air. The valve body may be biased into a closed position and arranged such that, when compressed air is passed through the jet pump for driving the same, the valve body is shifted into an open position in which the suction port of the jet pump is connected to the drain passage. Then, as soon as the supply of compressed air is interrupted, the valve body will automatically return into the closed position, thus assuring that, when the ink chamber is filled with ink, the ink may not leak-out through the drain passage.
Thanks to its low costs, the cleaning system according to the invention is suitable not only for printing presses but also for a so-called proofer apparatus, e.g. an apparatus as described in applicant's co-pending European patent application 11 155 963.9 filed on February 25, 2011 .
An embodiment example of the invention will now be described in conjunction with the drawings, wherein:

Fig. 1: is a schematic cross-sectional view of an ink fountain with a cleaning system according to the invention;
Fig. 2: shows a jet pump in a sectional view taken along the line II-II in Fig. 1;
Fig 3: is a sectional view of the jet pump in an inoperative condition;
Fig. 4: shows a switching valve in a sectional view taken along the line IV-IV in Fig. 1; and
Fig. 5: shows the switching valve in a condition for supplying cleaning liquid into the ink fountain.

As is shown in the drawing, an ink fountain 10 is set against a segment of a peripheral surface of an engraved roller 12, so that the latter may be inked with liquid ink contained in an ink chamber 14 of the ink fountain.
Doctor blades 16, 18 extend in axial direction of the engraved roller 12 and are mounted to top and bottom parts, respectively, of a body 20 of the ink fountain by means of clamping plates 22. The doctor blades 16, 18 are arranged such that they engage the peripheral surface of the engraved roller 12 with a respective edge, so that the surface segment between the edges of the doctor blades is exposed to the inside of the ink chamber 14 while the ink is contained therein. On both axial ends, the ink fountain is provided with seals (not shown) which engage the surface of the engraved roller so as to prevent the leakage of ink.
A cleaning system comprises a jet pump 24 that is connected to a source 26 of compressed air via a control valve 28 and an air supply line 30 and has a suction port connected to the interior of the ink chamber 14 through a number of drain passages 32.
A discharge port of the jet pump 24 is connected to a discharge line 34 through which the compressed air and the liquid sucked in via the drain passages 32 may be discharged. While the air is discharged into the atmosphere, optionally via a filter, the liquid discharged via the discharge line 34 may be collected in a container 36.
A cleaning liquid reservoir 38 is connected to the top end of the ink chamber 14 via a liquid supply line 40, a switching valve 42 and the number of supply passages 44. The switching valve 42 may be shifted into a position in which it disconnects the supply passages 44 from the liquid supply line 40 and connects them to a vent port 46 for venting the ink chamber 14.
The switching valve 42 is a pneumatically actuated valve actuated by compressed air that is supplied from the compressed air source 26 via another control valve 47.
When a cleaning cycle is to be performed for cleaning the ink chamber 14, the control valve 28 is opened, so that the jet pump 24 is driven and creates an underpressure in the ink chamber 14. The switching valve 42 is held in the position in which it connects the ink chamber to the liquid supply line 40, so that cleaning liquid is sucked into the ink chamber 14 from the reservoir 38. The cleaning liquid flows through the ink chamber 14 and is drained via the drain passages 32 at the bottom end by means of the jet pump 24 and is then discharged into the container 36, while new cleaning liquid is sucked-in from the reservoir 38. When the cleaning cycle is to be terminated, the control valve 47 is operated for bringing the switching valve 42 into a state in which it connects the supply passages 44 to the vent port 46, so that the ink chamber 14 is vented with air while cleaning liquid that is still contained in the ink chamber is drained via the drain passages 32. Finally, when all cleaning liquid has been removed from the ink chamber, the jet pump 24 may be operated for some time for creating an air current through the ink chamber 14 for accelerating the process of drying the walls of the ink chamber. It will be understood that during the entire process the engraved roller 12 may be kept rotating so that the surface of the engraved roller will be cleaned as well.
Optionally, the jet pump 24 may also be used for draining ink from the ink chamber 14 at the start of the cleaning cycle.
Fig. 2 shows only the ink fountain 10 but not the engraved roller 12 that delimits the ink chamber 14 together with a wall of the body 20 of the ink fountain.
The jet pump 24 comprises a nozzle 48 and a discharge tube 50 that is coaxial with the nozzle 48 and is connected therewith through a cage 52 that is open at its outer peripheral surface. The jet pump 24 is fixedly mounted in a tubular valve body 54 that is slidable in a bore 56 of the body 20 of the ink fountain. The bore 56 extends in a direction in parallel with the axis of the engraved roller 12 and is closed at both ends by bushings 58, 60. The bore of the nozzle 48 is connected to the air supply line 30 via the bushing 58, and the discharge tube 50 projects into the bushing 60 and is connected to the discharge line 34 via this bushing 60.
The tubular valve body 54 has a number of bores 62 in its peripheral surface. In the condition shown in Fig. 2, these bores 62 communicate with the drain passages 32, so that the ink chamber 14 is connected to the suction port (formed by the cage 52) of the jet pump 24. A number of guide pins 64 prevent the valve body 54 from rotating relative to the bushing 58 and relative to the drain passages 32.
A helical compression spring 66 is provided between the bushing 60 and the valve body 54 for biasing the valve body and the jet pump 24 downwards in Fig. 2. However, in the condition shown in Fig. 2, the force of the spring 66 is overcome by the pressure of the compressed air acting upon the bottom face of the nozzle 48 and driving the jet pump. Thus, as long as the supply of compressed air continues, the ink chamber 14 communicates with the jet pump 24 and liquid is sucked-in via the drain passages 32.
When the control valve 28 is closed and the supply of compressed air is cut off, the spring 66 expands and shifts the valve body 54 into the position shown in Fig. 3. In this position, the radial bores 62 of the valve body 54 are offset relative to the drain passages 32, so that no liquid can leak out from the ink chamber 14 via the drain passages 32. As long as the ink chamber 14 is filled with ink, the valve body 54 will be held in the position shown in Fig. 3.
As is shown in Fig. 4, the switching valve 42 is accommodated in a bore of the body 20 that also extends in parallel with the axis of the engraved roller 12. A double-cone valve body 68 of the switching valve 42 cooperates with two oppositely oriented conical valve seats 70, 72 that are located on opposite sides of a valve chamber 74. The supply passages 44 extend radially from the valve chamber 74 to the ink chamber 14.
In the condition shown in Fig. 4, the valve body 68 is biased upwards by a spring 76 and engages the valve seat 72, so that the valve chamber 74 is separated from the liquid supply line 40. The second cone of the valve body 68 is separated from the valve seat 70, so that the valve chamber 74 communicates with the vent port 46 via a connection passage 78. Thus, when the switching valve 42 is in this condition and the jet pump 24 creates an underpressure in the ink chamber 14, air will be drawn-in through the vent port 46.
The bottom end of the valve body 68 in Fig. 4 is connected to a piston 80 that is slidable in a cylindrical bore 82 of the body 20. The compressed air supply line from the control valve 47 is connected to the bore 82 above the piston 80. Thus, when the control valve 47 is opened, the air pressure will force the piston 80 and the valve body 68 downward against the force of the spring 76, so that the switching valve 42 switches to the state that has been shown in Fig. 5.
In this state, the lower cone of the valve body 68 is disengaged from the valve seat 72, so that the liquid supply line 40 is connected to a passage 84 that opens into the valve chamber 74. On the other hand, the upper cone of the valve body engages the valve seat 70 and blocks the connection between the valve chamber 74 and the vent port 46. Consequently, when the switching valve is in this condition and an underpressure is created in the valve chamber 14, cleaning liquid will be sucked-in from the liquid supply line 40.

Claims

A system for cleaning an ink chamber (14) with a cleaning liquid, comprising a source (26) of compressed gas, and a jet pump (24) driven by said compressed gas and connected to the ink chamber (14), wherein the jet pump (24) is arranged to drain the cleaning liquid from the ink chamber (14), characterized in that the system comprises a valve body (54) arranged to open and close said drain passage and operated by said compressed gas and wherein the jet pump (24) is incorporated in the valve body (54) and wherein the jet pump or a separate jet pump supplies the cleaning liquid to the ink chamber.
The system according to claim 2, wherein the valve body (54) is slidable in a bore (56) in a body (20) of the ink fountain (10) between a position in which at least one radial bore (62) of the valve body (54) connects a suction port of the jet pump (24) to at least one drain passage (32) that communicates with the ink chamber (14), and a position, in which the valve body (54) blocks the communication between the jet pump (24) and the ink chamber (14), the movement of the valve body (54) in the bore (56) being controlled by pressure of said compressed gas acting upon an end face of the valve body and driving the jet pump (24).
The system according to claim 1, 2 or 3, comprising a switching valve (42) which connects a supply passage (44) that communicates with the ink chamber (14) either to a vent port (46) or a supply line (40) for said cleaning liquid.
The system according to claim 4, wherein said switching valve (42) is connected to a piston (80) and is operated by compressed gas supplied by said source (26) and acting upon said piston (80).