This application is a U.S. National Phase application of PCT/EP2018/053719, filed on Feb. 14, 2018, claiming the benefit of Swedish Patent Application No. 1750145-3, filed on Feb. 17, 2017, both of which are incorporated herein by reference in their entireties.
The present invention concerns fabrics for cleaning printing cylinders as well as related cleaning apparatus and methods.
To be able to have a functional printing process with printing cylinders fulfilling a desired printing result, these printing cylinders must more or less often be cleaned. Many different cleaning methods have been used in the past, for example spraying a cleaning liquid on the cylinders or cleaning the cylinders one by one by means of a type of cleaning cloth. This disclosure focus on a cleaning method using a type of cleaning fabric.
One type of cleaning fabric and cleaning method is known from U.S. Pat. No. 5,974,976 which discloses a cleaning system using a pre-soaked cleaning fabric for cleaning a printing press. The pre-soaked cleaning fabric is kept wrapped up around a core and is sealed by means of a sleeve such that the cleaning fabric may be transported and stored away without compromising its cleaning abilities until the seal is broken and the cleaning fabric shall clean the printing press. The cleaning fabric is soaked with an organic compound solvent.
Different types of solvents have been tried in order to get the desired cleaning effect, but there are problems with the compounds used today. For example, so called toning is caused when the printing cylinders, after being cleaned, start rolling and printing again. Toning is when the colour distribution on the printed surface is uneven, creating an undesired printing result. The toning will eventually even out after the printers have been in operation for a while, but the already printed material goes to waste.
WO2005/113243A1 discloses a certain type of cleaning fabric. It describes the use of a non-woven material as a cleaning fabric in combination with organic solvents as the cleaning liquid. This WO publication illustrates the need for a low-volatility cleaning liquid and the importance of the strength and abrasion resistance of the cleaning fabric. Hence, the known cleaning fabric presented therein gives no solution to the problems of toning, which can be very costly, for instance when the printers need to be cleaned more often and large amount of material has to be thrown away.
Further background art is reflected for instance in the documents CA2039898A, DE102006039736A1, EP0348609A2, EP2735446A1, U.S. Pat. Nos. 5,030,292A, 6,284,720B1 and WO2008/035168A1.
However, none of these publications presents a reliable solution to the issues with toning. Thus, there is room for improvement.
An object of the present invention is to provide improvements over prior art. This object, and other objects that will appear from the following description, have now been achieved by the technique defined in the appended independent claims; certain embodiments being set forth in the related dependent claims.
In a first aspect, there is provided a roll of cleaning fabric for cleaning printing cylinders of a printing system. The cleaning fabric comprises a liquid absorbable material soaked with a cleaning liquid which comprises a polar additive containing either a glycol ether or a long-chain alcohol or both. The polar additive is configured to make the cleaning liquid polar. The cleaning fabric is wrapped or wound around a core to form the roll. An advantage with a cleaning fabric soaked with a polar cleaning liquid is that the liquid is easily dissolved in water which is beneficial during a printing process. Thus, remaining cleaning liquid from the cleaning process integrated with the water mitigate the problems with toning leading to reduced waste of prints.
Preferably, the polar additive is a compound comprising 10-16 carbon atoms. When the long-chain alcohol option is employed, it is preferred to use a 10-16 carbon atom compound. Cleaning fabrics soaked with cleaning liquid of this structure has proven to be particularly efficient. It is also preferred that the cleaning liquid comprises the polar additive in a range of 50-90 m/m %.
Depending on the circumstances under which cleaning is to take place, the cleaning fabric may be soaked with the cleaning liquid either before or after being wrapped or wound around the core for forming the roll.
In an embodiment, the roller of cleaning fabric is inserted into a removable sealing bag configured to seal around the roll in order to prevent the cleaning liquid from evaporating before use. The sealing bag secures proper operation when the cleaning fabric is to be used. The roll of cleaning fabric is preferably vacuum packed in the bag.
In a second aspect, there is provided a cleaning cassette which comprises means configured to support a roll of cleaning fabric of the type described above, and a collecting roller around which used cleaning fabric is configured to be wrapped or wound. This cassette is beneficial since it constitutes a compact and robust unit which is easy to incorporate in the printing system. Preferably, the supporting means is a rotatable shaft which is spaced from and parallel to the rotatable collecting roller.
In an embodiment, the cleaning cassette is arranged in the printing system in such a way that it is movable between an idle position in which the cleaning fabric is out of contact with any printing cylinder, and an active position in which the cleaning fabric is in contact with a printing cylinder to be cleaned. By this design, an efficient cleaning operation is achieved since the cleaning fabric is in cleaning contact only when required.
The cleaning cassette may comprise a pad configured to press the cleaning fabric against a printing cylinder to be cleaned. Hereby, a favourable press action of the cleaning fabric against the cylinder to be cleaned is achieved. The pad may be provided with an elastic element on the pad surface which is adapted to be press the cleaning fabric against the cylinder to be cleaned.
In a third aspect, there is provided a printing system comprising a cleaning cassette which is of the type described above and which preferably is movable between an idle position and a cleaning position. The printing system may comprise printing cylinders, inking rollers, damping rollers, an ink source and a damping source. Hence, this improved printing system incorporates an efficient cleaning function.
In a fourth aspect, there is provided method for cleaning printing cylinders of a printing system by means of a cleaning cassette of the design described above and including a roll of cleaning fabric as described above. The method comprises the steps of (i) unwinding from the roll at least a portion of the cleaning fabric soaked with a cleaning liquid; and (ii) placing said at least portion of the cleaning fabric in contact with a cylinder to be cleaned. This method makes it possible to clean printing cylinders in a more efficient manner than what has been possible in the art hitherto.
Preferably, used cleaning fabric is wound around the collecting roller included in the cleaning cassette which makes the cleaning procedure smooth and functional.
It is also preferred that the cleaning cassette—when cleaning is to be performed in accordance with the present cleaning method—is moved from an idle position in which the cleaning fabric is out of contact with any printing cylinders, to an active position in which the cleaning fabric is in contact with a printing cylinder to be cleaned.
In a fifth aspect, it is proposed to use a cleaning fabric for cleaning printing cylinders of a printing system, in which the cleaning fabric is soaked with a cleaning liquid which comprises a polar additive containing either a glycol ether or a long chain alcohol or both. Use of such a fabric ensures cleaning which is improved over prior art.
Embodiments of the invention will be described in the following, reference being made to the appended diagrammatic drawings which illustrate non-limiting examples of how the inventive concept can be reduced into practice and in which:
With reference to
When the printing system 1 is performing printing work, water is firstly transported via the damping rollers 6 from the damping source 9 towards the cylinders. The water is then present at the non-pressured surfaces occurring between the cylinders 2, 3, 4. Secondly, ink is then transported by means of the ink rollers 5 from the ink source 8 towards the cylinders 3, 4, 5. The print is then transferred to the blanket cylinder 3 and the material, e.g. paper, receiving the print is arranged between the blanket cylinder 3 and the impression cylinder 2 where the printing work is conducted and the print is transferred from the rubber sheet to the material. The set up of the cylinders and rollers shown and described herein is only an example of a set up.
More or less often the printing cylinders have to be cleaned. This is made by means of a cleaning machine or cassette 10 which houses a cleaning device or roll 12 with a cleaning fabric 13, also referred to as a cleaning cloth. Before the cleaning process begins, the cleaning roll 12 is taken out of its package or bag 15 (see
The cleaning roll 12 shown in
The cleaning fabric 13 consists of a liquid or solvent absorbable material, such as a non-woven material, which is adapted to be soaked with a cleaning liquid before starting a cleaning process. Preferably, the cleaning fabric 13 is soaked with the cleaning liquid before being packed and stored or transported, i.e. it can be soaked long before it is to be used in a cleaning process. Further, the cleaning fabric 13 can be soaked either before or after being wrapped around the core 14.
The cleaning liquid includes a polar additive or polar compound which is configured to make the cleaning liquid polar. Since liquids with similar polarity dissolve in each other, the polar additive is water soluble. By adding the polar additive to the cleaning liquid, this liquid is thus provided with a desired polar ability. This desired feature will be further explained below.
The polar additive includes glycol ether, for example butyl ether, and/or a long chain alcohol. The long chain alcohol is an alcohol with a carbon chain preferably between ten and sixteen carbon.
Further, the cleaning liquid includes the polar additive in a range of 50-90 m/m %, can also be expressed as 50-90 wt %. To clarify, the amount of polar additive in respect of the total amount of liquid is between 50-90%.
Other possible compounds of the cleaning liquid with different abilities can be aliphatic hydrocarbon for cleaning power, vegetable ester for cleaning power and reduction of evaporation, corrosion inhibitor for preventing corrosion and emulsifier for emulsification with water.
An advantage with a polar liquid is that it is water soluble, since water is also a polar liquid. A non-polar liquid is not water soluble and would instead—if brought into contact with water—gather on its surface, and form a layer on top of the water surface.
During a cleaning process of a printing system as shown in
The residue of the non-polar cleaning liquid on the printing surfaces is the reason why toning occurs on the printed paper. In order to reduce the amount of waste due to toning after a cleaning process, different types of cleaning liquids have been tried in the past with poor results. However, tests conducted by the inventors of the present patent application have surprisingly shown that if the cleaning liquid is made polar it will dissolve in the water of the water bath 9 and thus create a situation where a reduced amount of cleaning liquid is transferred back to the cylinders. In turn, this surprisingly results in reduced waste of printed paper due to toning. In order to create a polar cleaning liquid either glycol ether or long chain alcohol is used in the described embodiment. However, there may be other suitable compositions that can be used to provide the cleaning liquid with the same desired abilities; for instance both glycol ether and long-chain alcohol.
As shown in
The cleaning roll 12 is vacuum packed until the bag 15 is broken before a cleaning process starts. Preferably, the bag 15 is tubular and built up by a multi-layer plastic film. A suitable plastic film for this purpose is a three-layer film based on a first layer of polyethylene (PE) providing a fluid barrier, a second mid layer of polyamide (PA) providing strength and a third layer of polyethylene (PE) providing a fluid barrier and a sealing layer. This three-layer plastics film has proven to be favourable in practical tests. The thickness of the sealing film is designed in such a way that it is easy to remove from the roll 12, as is shown in
In
Furthermore, the cassette 10 includes mounting means in the shape of a transverse shaft 11 configured to support the core 14 of the roll 12 of cleaning fabric 13 (shown in bold in
At the free transverse end portion of the cassette 10, there is a front pad 17 configured to press the cleaning fabric 13 against a cylinder to be cleaned. At its front surface, the pad 17 has a transverse element 18 of elastic material, preferably rubber, which serves to press the cleaning fabric 13 against the cylinder to be cleaned with a suitable pressure. The elongate elastic element 18 protrudes somewhat from the surface of the pad 17 where it is fastened.
The cassette 10 also includes a transverse return roller or collecting roller 16 around which used cleaning fabric 13 is wrapped after been in cleaning contact with a cylinder. In this way, used cleaning fabric 13 can easily be collected and handled after a cleaning process. The shaft 11 and the collecting roller 16 are spaced apart and parallel. The collecting roller 16 is also referred to as a take-up roller since the free end of the cleaning fabric 13 is fastened to this roller before the cleaning process is initiated.
In operation, collecting roller 16 and the shaft 11 are rotated—preferably stepwise—so that fresh portions of the cleaning fabric 13 are applied to the rotating cylinder to be cleaned. This rotational movement of the cleaning fabric 13 is illustrated diagrammatically by arrows in
As shown by a double arrow in
Hence, the cleaning equipment is operated in accordance with a method for cleaning printing cylinders of a printing system 1 with a cleaning roll 12 including the steps of:
A cleaning fabric for cleaning printing cylinders of a printing system comprises a liquid absorbable material which is configured to be soaked with a cleaning liquid before starting the cleaning. The cleaning liquid has a polar additive, in order to make the cleaning liquid polar. An advantage with a polar cleaning liquid is that it easily mixes with water which is an important part during a printing process. Thus, remaining cleaning liquid from the cleaning process integrated with the water mitigate the problems with toning leading to reduced waste of prints.
In an embodiment the cleaning liquid comprises the polar additive in a range of 50-90 m/m %. Tests have shown that a cleaning liquid containing the polar additive within that range has a surprisingly positive effect on the result.
In another embodiment the polar additive comprises a glycol ether and/or a long chain alcohol. Also here, tests have shown that these two alternatives prove to have a surprisingly positive effect on the result.
A cleaning device for cleaning printing cylinders of a printing system comprises a cleaning fabric with a liquid absorbable material which is configured to be soaked with a cleaning liquid before starting the cleaning. The cleaning liquid comprises a polar additive in order to make the cleaning liquid polar. Further, the cleaning device has a core around which the cleaning fabric is wrapped. The described cleaning device provides a device which has the same benefits as described above.
The cleaning fabric may be soaked with the cleaning liquid either before being wrapped around the core or after being wrapped around the core. This facilitates already existing assembling processes without changing the cleaning result of the soaked cleaning fabric.
Further, the roll of cleaning fabric may be provided with a removable sealable bag configured to seal around the core and cleaning fabric in order to prevent the cleaning liquid from evaporating. By adding the sealable bag, the cleaning device can be stored away for a long time and still provide the same desired cleaning result during a cleaning process.
In order to even more improve the storing of the device, the cleaning device may be vacuum packed.
There is also provided a method for cleaning printing cylinders of a printing system with a cleaning device as described above. The method includes the steps of:
Finally, although the inventive concept has been described above with reference to specific embodiments, it is not intended to be limited to the specific form set forth herein. Rather, the invention is limited only by the accompanying claims and other embodiments than the specific above are equally possible within the scope of these appended claims.
Number | Date | Country | Kind |
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1750145-3 | Feb 2017 | SE | national |
Filing Document | Filing Date | Country | Kind |
---|---|---|---|
PCT/EP2018/053719 | 2/14/2018 | WO | 00 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2018/149890 | 8/23/2018 | WO | A |
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Number | Date | Country | |
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20190358680 A1 | Nov 2019 | US |