EP1364783B1

EP1364783B1 - High-speed printing machine with flexo printing matrix for sheets transported via a continuous suction belt conveyor

Info

Publication number: EP1364783B1
Application number: EP03425316A
Authority: EP
Inventors: Maria Teresa Cintio
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-05-20
Filing date: 2003-05-16
Publication date: 2006-11-22
Anticipated expiration: 2023-05-16
Also published as: DE60309773D1; CY1107340T1; ATE345931T1; DE60309773T2; ES2255891T1; ES2255891T3; EP1364783A3; PT1364783E; SI1364783T1; ITAP20020005A1; DK1364783T3; EP1364783A2

Abstract

The present invention refers to a printing machine with flexo printing matrix (03) for sheets, panels, plates and/or similar items of fibre-wood, MDF, plywood, cardboard, ceramic and any other material. The printing machine of the invention allows for using fast-drying inks that are more environmental friendly than water inks. The printing machine comprises a roll (01) with flexo printing matrix, an inking assembly (26,28) with inking roll (02) in contact with the flexo printing matrix and a perforated conveyor belt (04) that moves on a suction-operated surface (05) to transport the items to be printed to the printing stations by means of the force generated between the item and the belt thanks to air suction through the belt holes. <IMAGE>

Description

The present invention refers to a high-speed printing machine with flexo printing matrix for sheets, panels, plates and/or similar items of fibre-wood, MDF, plywood, cardboard, ceramic and any other material, which uses fast-drying inks that are more environmental friendly than water inks.
The minimum layout comprises a roll with flexo printing matrix, an inking assembly with inking roll in contact with flexo printing matrix around the matrix roll and a closed-loop perforated conveyor belt that moves on a suction-operated surface to transport the items to be printed.
The movement of the items to the printing stations is ensured by the force generated between the items and the perforated belt, thanks to the depression caused by air suction through the belt holes.
The invention can be advantageously applied on printing machines for sheets and/or panels in general, and in particular in the sector of plywood, MDF, fibre-wood and/or cardboard fruit and vegetable packaging.
An important advantage is represented by the possibility of realising high-speed 4-colour printing on these materials and on the entire sheet surface with excellent results.
As it is known, printing machines used to print panels/sheets of this type are generally made up of multiple printing groups for multiple colours, with fixed closed distances between printing groups.
These printing machines normally use inking assemblies for oil ink, which comprise a series of rolls to grind, mix, spread and transfer ink to the rigid printing matrix.
Rolls are generally made of steel and/or rubber and have a smooth external surface on which ink adheres because of viscosity and is then transferred onto the matrix with approximately uniform layer.
Oil ink dries very slowly and is absorbed very slowly by the aforementioned materials, and it is not possible to use drying stations due to lack of time caused by the reduced space between printing machines and by the speed of the sheets. In view of the above, the limits of this type of printing machines appear evident as regards quality printing.
Inking assemblies have numerous disadvantages since they are characterised by very large volume and complex operation, due to the large number of rolls needed to spread ink. They do not allow for multiple colour printing due to the problems related with roll cleaning when passing from one colour to another. Moreover, oil inks are not environmental friendly, since their components are not biodegradable and are sometimes very polluting. Moreover, ink waste requires expensive disposal.
Printing machines with water-based ink and flexo printing matrix fixed to the printing roll have been devised. Sheets and/or panels are moved to the printing stations by means of chain-mounted elements. These machines, however, are penalised by numerous problems.
The transportation system of the sheets to the printing stations does not allow for keeping colour register on sheets during printing.
As it is known, the roll-mounted cliché does not have dimensional variations on development; the elements used to transport the sheets to the printing stations suffer from chain wear, thus changing the movement speed of the sheet to the printing stations. This causes continuous colour out-of-register situations, which cannot be controlled, resulting in poor printing quality.
Other printing machines have been devised to transport the sheets/panels to the printing stations with driving rolls.
This system is not suitable for printing the aforementioned materials, since it does not print the entire surface of sheets/panels.
The driving rolls must be in contact with the two sides of the sheet/panel, including the printed side.
It appears evident that the roll and/or driving ring located on the printing side is in direct contact with the surface of the sheet being printed.
Apart from preventing printing on the entire sheet surface, this system requires a long time to place the driving rings in the areas where the sheet is not printed.
It is also known that fruit and vegetable distributors require pleasant packing to attract the consumer's attention.
For this reason, most packing manufacturers are forced to glue printed paper on panels, being unable to obtain acceptable printing quality on these materials. This solution, however, has some drawbacks.
Firstly, an increase of cost due to paper, glue and labour for the application of paper on panels.
Secondly, paper tends to come off from panels during the following operations and transportation in refrigerated vehicles.
The printing machines that are currently used are not capable of providing acceptable printing quality on materials such as plywood, MDF, fibre-wood, cardboard, etc. Moreover, in view of their low absorption capacity, these materials require fast-drying ink, such as water ink, and a precise, reliable system to transport sheets and/or panels to the printing stations to print the entire surface.
The purpose of the invention is to realise a printing machine with flexo printing matrix that uses fast-drying ink, including water ink, to colour print sheets and/or panels of different materials, provided with a transportation system of the sheets to the printing stations characterised by simple operation, speed, safety and accuracy, in order to eliminate the aforementioned drawbacks, as well as ecological problems.
The aforementioned purpose is achieved by the present invention, which refers a printing machine with flexo printing matrix for sheets, panels, plates and/or similar items of fibre-wood, MDF, plywood, cardboard, ceramic and similar materials, transported via a suction-operated continuous conveyor belt with at least a roll with flexo printing matrix, an inking assembly realised in different constructive modes, always including an inking roll in contact with the flexo printing matrix around the matrix roll, and a closed-loop perforated conveyor belt that moves on a suction-operated surface to transport the items to be printed.
The movement of the items to the printing stations is ensured by the force generated between the items and the perforated belt, thanks to the depression caused by air suction through the belt holes, through a suction unit located in a second area of the roll with flexo printing matrix.
The cylindrical external surface of the inking roll is provided with micro-incisions and is partially immersed in water ink that can be contained in a small tank, channel or chamber.
US patent No. 5531313 describes a device for conveying a continuous shingled or overlapping sheet or copy stream to a rotary printing press, with a conveying table, at least one endless, revolvingly drivable conveyor belt surrounding the conveying table, and at least one suction box disposed beneath the conveying table and being connected through suction openings with the underside of the conveyor belt, the conveyor belt being formed with through-perforated suction holes, the suction box being formed with at least two suction chambers subjectible to negative pressure or vacuum independently of one another.
The conveyor belt described in said US patent operates as a simple feeding device enslaved to a rotary printing press which must be provided with means for the collection and printing of each sheet, one by one.
US patent No. 5531313 neither provides any description of a continuous rotary printing press nor specifies whether said conveyor belt cooperates with the cliché of the rotary machine.
It is pointed out that the purpose of the present invention is to realise a colour printing machine, with high-speed flexo printing matrix, of the type described In EP patent No. 0941843 which has the peculiarity of being provided with innovative means of transport allowing for the fast and accurate transfer through the subsequent printing station of the sheets/panels to be printed in more colours.
In order to perform a fast and accurate transfer the printing machine according to the invention has been equipped with a perforated conveyor belt moving on a suction plane, equipped with at least one suction chamber, and supporting the sheets/panels during printing.
The speed of said perforated conveyor belt is identical to the peripheral speed of the flexographic matrix, thus allowing for a perfect synchronised contact of the sheets/panels to the matrix.
For major clarity the description of the invention continues with reference to the enclosed drawings, which are intended for purposes of illustration and not in a limiting sense, whereby:

Fig. 1 is a diagrammatic view of a printing machine according to the invention that uses an inking assembly with ink chamber;
Fig. 2 is a diagrammatic view of a printing machine according to the invention that uses an inking assembly with ink tank;
Fig. 3 is a diagrammatic view of a printing machine according to the invention that uses an inking assembly with ink channel.

Fig. 1 is a diagrammatic view of a high-speed flexo printing machine with two printing machines, especially suitable to print panels of wood, fibre-wood, plywood, MDF, cardboard, ceramic and similar materials.
Every printing machine comprises a roll (01) that supports a flexo printing matrix (03) wound on the roll (01) and a closed-loop perforated conveyor belt (04) that moves on a suction-operated surface (05) to transport the item (06) to be printed.
The movement of the item to the printing stations is ensured by the force generated between the item (06) and the perforated belt (04) thanks to the depression caused by air suction through the holes of the belt (04) by means of a suction unit (25) connected to the belt with a pipe (24).
The suction-operated conveyor belt (04), which is moved by the motor roll (22) and return roll (23), is driven into continuous rotation at the same speed as the peripheral speed of the flexo printing matrix (03) mounted on the roll (01).
In addition to transport it, the conveyor belt (04) positioned around the roll (01) can push the sheet-panel to be printed against the matrix (03) in perfect contact to obtain good graphic quality.
Moreover, each printing machine comprises an inking assembly with different construction.
Fig. 1 is a diagrammatic view of a two-colour flexo printing machine with two inking assemblies (26) composed of a ink chamber (07) next to the cylindrical external surface of the inking roll (02), with doctors (08) used to remove excessive ink from the surface of the inking roll (02) before transferring the ink to the matrix (03).
The ink is taken from a container (10) with a pump (11), pushed through an abduction duct (12) inside the chamber (07) and poured into the container (10) through the overflow duct (13).
Fig. 2 is a diagrammatic view of a part of a printing machine with inking assembly (27) comprising a small tank (09) that contains the ink taken from the container (10) with the pump (11).
The ink is maintained at constant level through an abduction duct (12) and an overflow duct (13).
A doctor (14) acts on the inking roll (02) in order to engage its border with the roll surface.
The doctor (14) is used to remove excessive ink from the surface of the inking roll (02) before transferring the ink to the matrix (03).
Fig. 3 is a diagrammatic view of a part of a printing machine with inking assembly (28) comprising a longitudinal contact channel between a roll (15) covered with elastomeric material and the external surface of the inking roll (02).
The contact between the two rolls creates a sort of hydrodynamic doctor means, apart from containing and spreading the ink.
This version is provided with a tank (16) in higher position than the channel fed by the tank (16) by means of controlled fall through a duct (17).
The tank (16) has an abduction duct (12) and an overflow duct (13) so that the ink is taken from a container (10) with a pump (11) and maintained at constant level by pouring excessive ink into the container (10).
The ends of the rolls (15 and 02) house two tanks (18) to recover the ink and convey it into the container (10) through the duct (31).
To remove excessive ink form the surface of the roll (02) before transferring it to the matrix (03), a doctor (19) is applied parallel to the roll (02) in such a way that its border engages with the surface of the roll (02) in an area comprised between the contact of the two rolls (15 and 02) and the contact with the matrix (03).
The cylindrical external surface of the inking roll (02) is provided with micro-incisions and partially immersed in ink stored in different types of containers, as shown in Figs. 1, 2 and 3.
The ink transported by the micro-incisions is a calibrated reserve sufficient to ink the relief parts of the matrix (03) uniformly and constantly. As a matter of fact, the ink adheres to the surface of the relief parts and is immediately transferred to the panel (06) in the contact area on the pressure counter-roll (21). The peripheral speed of the inking roll (02), the speed of the relief parts of the flexo printing matrix and the speed of the suction-operated belt (04) must be perfectly identical in order not to cause dragging.
Since fruit and vegetable packages are printed with different colours, in order to complete the printing, the machine is provided with other printing devices same as the machine shown in Fig. 1, 2, or 3.
Because of the different thickness of plywood, MDF, fibre-wood and cardboard sheets/panels, a polymeric shock-absorbing cushion (20) with lower hardness than the matrix (03) is mounted next the matrix (03). The cushion compensates planarity errors and thickness differences of the sheets, to ensure necessary uniformity of pressure and adherence of the flexo printing matrix (03) when the matrix (03) comes into contact with the sheet/panel (06) to transfer the print ink, in order to avoid deformation of the relief parts of the flexo printing matrix (03).
Because of dust on the sheets/panels, a brush with suction unit is installed before the printing stations to remove dust and/or saw dust.
Hot air jets are provided and then evacuated in the areas immediately after each printing group, in order to realise high-speed chromatic effect printing.
The sheets/panels are fed in synchronisation with the movement of the perforated conveyor belt and with the printing groups.
At the end of the printing process, one of the printing groups as illustrated above can be used to apply overprint paint with suitable drying unit to provide glossy finish to the item, which can be either transported to the next machining stations or collected.
Perfect synchronisation between the suction-operated conveyor belt (04) that transports the sheets/panels and the printing machines and between the printing machines is needed to obtain excellent printing quality.
According to the invention, synchronisation is ensured by means of electrical axles driven by electronic devices; or by means of mechanic and/or hydraulic and/or electric and/or electronic devices.
Tests carried out with inking assemblies on sheets/panels transported by a suction-operated continuous conveyor belt as illustrated above have given excellent results compared to printing obtained with known machines of the same type.
Characters and images are clear, profiles have no burr even in the case of sheets/panels with non-calibrated thickness thanks to the shock-absorbing cushion (20).
The perfect synchronisation of the rolls (01 and 02) combined with the movement of the sheet/panel (06) transported by a suction-operated continuous conveyor belt (04) allows for increased speed, with excellent printing results.
The printing machine of the invention is much simpler and cheaper than currently used machines; the replacement of ink with a different colour is much easier and faster compared to a group with oil ink; consequently, cleaning is simpler and quicker.
The use of water inks requires no waste treatment, since water ink is soluble in water, with no environmental pollution.
The roll (01) with flexo printing matrix is devised for replacement of the sleeve with flexo printing matrix (03) by simple air pressure, allowing for axially removal of the sleeve. In view of the frequent changes of printing matrixes (03), the system of the invention considerably reduced setup and shutdown time.
The suction-operated conveyor belt (04) used to move the sheets/panels (06) is especially accurate in positioning the panels next to the matrix (03); it is reliable, economically convenient and requires minimum maintenance.
The present invention can be advantageously used in the field of printing machines for sheets and/or panels of plywood, wood, fibre-wood, MDF, cardboard, ceramic and/or similar materials for all uses and especially in the field of customised fruit and vegetable packaging.
The invention is not limited to specific shapes, dimensions, geometrical arrangements, aesthetics, or materials in the different embodiments of printing machines. Likewise, the invention is not limited to specific inks and/or sheets/panels. Modifications and improvements can be made on the printing machine of the invention within the scope of the claims.
For example, the counter-roll (21) may wind the belt (04) and act as matrix roll (22); it may act as belt return roll (23), or it may be replaced by extending the surface (05) where the suction-operated belt (04) moves.
Each printing group may have its own suction-operated continuous conveyor belt (04) and the counter-roll (21) may come into direct contact with the sheet (06).
It appears evident that in Fig. 2 the roll (02), instead of taking ink directly, may receive it from at least one absorbing roll parallel and in contact with the surface of the roll, which must be at least partially immersed in ink.
In Fig. 2 it appears evident that a roll covered with elastomeric material parallel and in contact with the surface of the roll (02) may be installed in the area where the doctor (14) is engaged to replace the doctor.
Ink can be fed in different ways other than illustrated above, as well as manually.

Claims

High-speed flexo printing machine comprising:
- at least one flexo printing matrix (03) supported by a roll (01);

- at least a counter-roll (21) that co-operates with said roll (01) with matrix;

- at least an inking assembly (26, 27, 28) comprising an inking roll (02) in contact with the flexo printing matrix (03) wherein the cylindrical external surface of the inking roll (02) is provided with micro-incisions and partially immersed in water or solvent ink contained in a chamber (07), a small tank (09) or a channel;
machine characterised in that it comprises at least one continuous perforated conveyor belt (04) wound around a motor roll (22) and a return roll (23) that moves on a suction-operated surface (05), said conveyor belt (04) being capable of supporting the sheets/panels (06) while moving forward through matrix (03) of said roll (21).
High-speed flexo printing machine as defined in the previous claim characterised in that said conveyor belt (04) moves forward through matrix (03) of said roll (21).
Machine as defined in claims 1 and 2, characterised in that ink is contained in a small tank (09), the surface of the roll (02) being partially immersed in said ink, and in that doctors (14) or rolls remove excessive ink from the surface of the roll (02) before transfer to the flexo printing matrix (03).
Machine as defined in claims 1 and 2 characterised in that the ink is contained in a chamber (07) and doctors (08) remove excessive ink from the surface of the roll (02) before transfer to the flexo printing matrix (03).
Machine as defined in claims land 2 characterised in that the ink is contained in a channel formed by the longitudinal contact between a roll (15) and the external surface of the inking roll (02).
Machine as defined in claim 5 characterised in that doctors (19) remove excessive ink from the surface of the roll (02) before transfer to the flexo printing matrix (03).
Machine as defined in one of the previous claims characterised in that the cylindrical external surface of the inking roll (02) and is provided with micro-incisions, doctors and/or rolls to remove excessive ink from the surface before transfer to the matrix (03).
Machine as defined in claim 7 characterised in that the conveyor belt (04) is autonomously organised on every printing group.
Machine as defined in claims 1 and 8 characterised in that the suction-operated surface (05) has a case-shaped form and the wall in contact with the conveyor belt (04) is perforated for air passage, the case being connected to a suction unit (25) by a pipe (24) to create depression on the conveyor belt (04).
Machine as defined in claims 1 to 6 characterised in that the ink is a fast-drying ink, comprising at least one pigment dissolved in water or water solution, or in any case any type of low viscosity ink.
Machine as defined in claims 1and 2 characterised in that the flexo printing matrix (03) is of flexible polymeric material or of any other material.
Machine as defined in claims 1 and 8 characterised in that synchronisation between the suction-operated conveyor belt (04) that transports the sheet-panel and the printing machines and/or between the printing machines is ensured by electrical axles driven by suitable electrical-electronic devices.
Machine as defined in claims 1 and 8 characterised in that synchronisation between the suction-operated conveyor belt (04) and the printing machines and/or between the printing machines is ensured by mechanical and/or hydraulic and/or electric and/or electronic and/or optical devices.
Machine as defined in claims 1 to 6 characterised in that the inking assemblies (26, 27, 28) can be removed and replaced by an inking assembly for oil ink in working position.
Machine as defined in claims 1and 2 characterised in that the flexo printing matrix (03) is in contact with a shock-absorbing cushion (20) having a lower hardness than the flexo printing machine, capable of yielding to pressure to return immediately into its operating position for the next printing cycle.
Machine as defined in claim 1 characterised in that the roll (01) with flexo printing matrix is provided with holes for pressurised air to allow for rapid installation of the sleeve with matrix (03) with shock-absorbing cushion (20).
Machine as defined in claims 1 and 2 characterised in that the counter-printing roll (21) acts as motor roll for the belt (04), or as return roll for the belt (04).
Machine as defined in claims 1 and 2 characterised in that the counter-printing roll (21) comes into direct contact with the sheets/panels (06) during printing.