EP3406448A1

EP3406448A1 - Cleaning cylinder arrangement for intaglio printing machine

Info

Publication number: EP3406448A1
Application number: EP18172471.7A
Authority: EP
Inventors: Maurizio Ripamonti
Original assignee: Officina Riparazioni Macchine Grafiche- Ormag- SpA
Current assignee: Officina Riparazioni Macchine Grafiche- Ormag- SpA
Priority date: 2017-05-24
Filing date: 2018-05-15
Publication date: 2018-11-28
Anticipated expiration: 2038-05-15
Also published as: EP3406448B1; IT201700056347A1

Abstract

It is disclosed a cleaning cylinder arrangement in an intaglio printing machine, comprising a cleaning cylinder (2) mounted in rotation, against a printing cylinder (3), above a recovery tray (1), and a flexible cleaning element (5, 6) consisting of a porous cloth (5) maintained in contact with a lower portion of the surface of said cleaning cylinder (2), extended at least on a 45° arc, by means of a flexible support element (6) provided with downward ink outflow openings, said flexible cleaning element (5, 6) being attached at leading and trailing edges on attachment means, one of which is adjustable in position, wherein said attachment means consist of a front holding unit (20) and a rear holding unit (21) opposed to each other in respect to a symmetrical axis (Z-Z), provided with blocking devices (20e, 21e) respectively of a leading edge and of a trailing edge of said flexible cleaning element (5, 6) and wherein said blocking devices (20e, 21e) are sliding driven at least according to different displacement axes (X-X;Y-Y) that are substantially parallel to axes tangential to the surface of the cleaning cylinder (2) by means of first and second pneumatic actuators (20c, 21c).

Description

Field of the Invention

The present invention relates to a cleaning cylinder arrangement for a printing machine, in particular a cylinder configuration with a corresponding abrasive cloth for the removal of the ink.

Technical background

It is well known that the intaglio printing technique involves conducting the printing process by adhering a sheet to be printed to an engraved plate. In particular, on an engraved copper or nickel (zinc) plate, a uniform layer of ink is applied, which is then cleaned in such a way that the ink remains only in the microcavities of the engravings. The sheet to be printed is adhered with pressure to the plate, so that the ink present in the microcavities is transferred onto the sheet.
Originally this process was carried out with an intaglio press, but in the most modern systems, for example for printing value papers, it is provided the use, instead of a press, of a rotary printing cylinder on which the engraved plate is fixed.
In such a system, in order to carry out the calibrated cleaning of the engraved plate, a cleaning cylinder of suitable softness - for example made of PVC, rubber or other plastic material - which is mounted counter-rotating in respect to the printing drum and with its surface kept in contact with that of the printing drum, removing the excess ink deposited on it.
Since the amount of removed ink is still relevant, the cleaning cylinder must also undergo a cleaning operation.
According to the prior art, the use of a special porous or widely perforated cleaning cloth, kept in contact with the cleaning cylinder, has been proposed: the ink is scraped off the cleaning cylinder, passes through the porosity of the cloth and precipitates downwards into a recovery tray. The cloth has a special shape, because it must be soft enough not to wear the cleaning cylinder and also sufficiently porous to let the ink fall downwards: a typical suitable product is described in US 5,390,598 and marketed with the name SCOTCH BRITE ® by the company 3M.
EP 1,055,516 describes an arrangement wherein a cleaning cloth is held against a cleaning cylinder upstream of another device provided with a finishing brush. The cleaning cloth is fixed at its ends to a pressure device that pushes it locally against the cleaning cylinder: to obtain uniform pressure, the cloth is spread over a rather small circumference arc, for example, on a circle arc path quite lesser than 30°. To obtain a substantial cleaning with this configuration it is necessary to apply a significant pressure of the cloth against the cylinder, which produces a superficial erosion.
Another example is described in EP 2,007,580 , which represents the preamble of the attached main claim. In this case, a Scotch Brite® cloth is laid on a flexible perforated curved plate, keeping it pushed into contact with the surface of the cleaning cylinder, in particular on a segment of an arc of the cleaning cylinder lower surface well above 45°, for example in the order of 90°. This configuration also has spraying nozzles, with which a diluent solution is sprayed towards the porous cloth, so as to favour the process of removing the ink from the cleaning cylinder and percolating it downwards into a recovery tray.
Since the porous cloth must be kept adherent to the cylinder in a calibrated manner, even upon progressive wear, the supporting plate has a capacity of adjustment with respect to the cleaning cylinder. For this purpose, the flexible perforated plate is mounted at two supporting attachments arranged parallel to the rotation axis of the cleaning cylinder, a first attachment being positioned fixed, at short distance from the surface of the cleaning cylinder, and a second is mounted integral with arc guides that move according to an arc of circle with the center on the rotation axis of the cleaning cylinder.
This arrangement has proved to be quite effective but has at least two drawbacks. On the one hand, the movement of the second attachment along an arc of a circle requires a rather complex driving mechanism, having problems in adjustment and accessibility during maintenance step. On the other hand, the displacement of one end of the supporting plate, although occurring on a circular arc, does not allow a perfect adjustment of the cleaning cloth to the surface of the cylinder, thus the flexible plate with its cleaning cloth ends up assuming a position not yet in continuous abutment on the cleaning cylinder, but rather moving away from such surface, starting from the first attachment point and moving towards the second attachment point; hence, substantially, not all the surface of the cleaning cloth is effective for the cleaning.

Summary of the invention

The problem underlying the invention is therefore to propose an arrangement of the cleaning cylinder which overcomes the aforementioned drawbacks, and which is more economical in manufacture and maintenance, and more effective in use. This scope is achieved by the features mentioned in claim 1. The dependent claims describe preferred features of the invention.

Brief description of the drawings

Further features and advantages of the invention will anyhow be more evident from the following detailed description of a preferred embodiment, given by mere way of nonlimiting example and illustrated in the accompanying drawings, wherein:

Fig. 1 is a cross-sectional view of a cleaning arrangement according to the invention;
Fig. 2A and 2B are, respectively, a front elevation view and a plan view of a rinsing device according to the invention;
Fig. 3 is a partial plan view of the cleaning cylinder and of the rear attachment device; and
Fig. 4 is a plan view of an example embodiment of the cleaning cloth spread over a plane.

Detailed description of a preferred embodiment

For a better comprehension of the invention, a cleaning arrangement for an intaglio printing machine is described below, without illustrating the cylinder with the engraved plate and the rest of the machine (which are well known to a person skilled in the art).
A cleaning arrangement generally makes use of a washing tray 1 cooperating with a cleaning cylinder 2, kept in contact with a printing cylinder, of suitable material (PVC, rubber or other plastic materials).
In a manner known per se, the cleaning cylinder 2 is rotatably mounted above the washing tray 1 and is kept in contact, in the lower part, to a flexible porous cloth 5 - such as a Scotch Bride® cloth - which in turn is held in position by a flexible support element 6. The latter is preferably in the form of a network of plastic material, placed underneath and made integral with the porous cloth 5.
The flexible porous cloth is in contact with the cleaning cylinder 2 on an arc of circumference greater than 45°, for example about 90°.
The system further comprises a nebulizer 4 for spraying a cleaning solution against the surface of the cleaning cylinder 2 - preferably on the upstream side (on the left in Fig. 1) at the contact point between the cloth 5 and the cylinder 2 - in order to remove the ink with increased efficacy. The cleaning solution and the ink present on the surface of the cylinder 2, are effectively removed by the mechanical action of the cloth 5 on the cylinder 2, percolate through the cloth 5 and fall downwards until they are collected on the washing tray 1.
According to the present invention, the flexible support element 6 supports the porous cloth 5 from below and is fixed on the leading side (upstream) and on the trailing side (downstream) of the cleaning cylinder 2 by means of two respective front attachment/holding unit 20 and rear attachment/holding unit 21 both equipped with blocking devices.
In particular, the front attachment/holding unit 20 comprises a support body 20a, on which a slide 20b is movably mounted, driven by a pneumatic actuator 20c, which carries a stem 20d for driving a blocking body 20e wherein the leading edge 6' of the flexible support element 6 is blocked and retained (for example with holding heads not shown).
The drive stem 20d of the actuator 20c moves along an axis X-X which is obliquely oriented, so as to be substantially tangent to the periphery of the cylinder 2 at the attachment point of the blocking body 20e.
The rear attachment/holding unit 21 is similarly constructed, but almost specular to the front unit 20 relative to an intermediate symmetry axis Z-Z. In particular, it comprises a support body 21a on which a slide 21b is movably mounted, driven by a pneumatic actuator 21c which carries a clamping device 21e in which the trailing edge 6'' of the flexible support element 6 is clamped and retained.
The Y-Y axis along which the actuator 21c and the gripping device 21e move, is also oriented in oblique direction, as said in a specular way to the axis X-X, i.e. in such a way as to be substantially tangent to the periphery of the cylinder 2 in the attachment point of the clamping device 21e.
Here, it is important to note that the pneumatic actuators 20c and 21c of the two units 20 and 21 are driven by compressed air, with pressure values that can be different from one to the other. Thus, the actuators can exert a differentiated drive pressure, so as to allow a precise control of the pressure action of the support element 6 against the porous cloth 5, depending on the types of ink, the speed of the machine and the quality of the cleaning fluid.
Note that, though in the cross-section view of Fig. 1 only two actuators 20c and 21c are shown, actually two arrays of actuators 20c and 21c are provided, aligned longitudinally parallel to the rotation axis of the cleaning cylinder 2 (see Fig. 3), so as to constrain and support the two front and rear edges of the flexible support element 6. With this arrangement, possibly the clamping device 21e can also be constituted by a single piece which extends over the entire length of the cleaning cylinder 2.
Due to this arrangement, in which the position is controlled (according to a stroke along the axes X-X and Y-Y) of both the leading and trailing edges of the support element 6, it is obtained that the whole surface of the cleaning cloth 5 can be made to contact perfectly, with the desired pressure, against the surface of the cleaning cylinder 2. On the other hand, this arrangement allows to move away the support element 6 from the cylinder surface 2 along with the cloth 5 in a fast and easy manner, for maintenance and washing operations or for the substitution of the cloth 5.
As illustrated in fig. 4, the cloth 5 is in fact simply provided with a series of holes 6a along the leading edge, with which it can be hooked by insertion into holding elements of the blocking unit 20e. The smooth trailing edge of the cloth 5 is instead held by clamping by the clamping device 21e.
According to an advantageous feature of the present invention, the support element 6 is in the form of a carbon fibre net, allowing the fluid passage, in particular of the washing fluid which passes through the cloth 5, much more effectively than the perforated metal plates of the prior art.
Conventionally, a cleaning solution adduction system is also provided, by means of nozzles 23 injecting the liquid into a first contact area between the porous cloth 5 and the cleaning cylinder 2.
According to a further feature of the invention, it is envisaged to associate to the described cleaning system, also a rinsing assembly 22, comprising a rinsing tray 22a and a pair of rinsing solution adduction connectors 22e. As well represented in figs. 2A and 2B, the tray 22a extends over a good part of the length of the cylinder 2, in a vertically underlying position in respect to the cylinder 2 and ends with the two connectors 22e. Inside the tray 22a a shaped brush body 22f is housed, provided with brushing elements which are inserted through the porous cloth 5 and come into contact with the cleaning cylinder 2. For this purpose, the cloth 5 preferably has cut-outs 5a in which said brushing elements are apt to be inserted.
The brush body 22f is carried by a plurality of mounting stems 22d, movable along a substantially vertical axis, which are connected to respective pneumatic actuators 22c belonging to lower control units 22b. The plurality of pneumatic actuators 22a performs the task of precisely controlling the pressure of the brushes 22f against the cloth 5 and the cleaning cylinder 2. This system performs the task of providing a fresh cleaning solution towards the cloth 5 and the cylinder 2, in cooperation with the solution coming from the nozzles 23, so as to carry out a rinsing of the cloth 5, with the removal of the ink removed from the cylinder 2.
The actuation with pneumatic actuators of the two leading and trailing edges of the cleaning cloth 5, as well as of the underlying shaped brush body 22f, allows to obtain a beneficial precise adjustment of the pressure of the cloth 5 both longitudinally and circumferentially to the cylinder 2.
The pneumatic control is also easily controllable with conventional driving techniques. According to a preferred embodiment, the system is further provided with a camera (not shown) which captures the image of the cylinder 2 downstream of the cleaning cloth 5. Depending on the captured image, it is possible to determine how much ink is still left on the surface and consequently increase or reduce the pressure of the cloth 5 on the cylinder 2 acting on the control of the pneumatic actuators. In this way it is possible to create a feedback control system, so as to optimize the cleaning of the cylinder 2 without applying an oversized pressure which would end up causing a premature wear of the cloth 5 and of the surface of the cylinder 2.
As can be understood from the above description, the arrangement of the invention allows to fully achieve the purposes stated in the introduction. In particular, by means of pneumatic drive, that can be easily controlled with compressed air available on board of the machine and with little space, it is possible to obtain a perfect adjustment of the pressure of the porous cloth against the cleaning cylinder. Due to an optimal distribution of the pressure, concentrated abrasion areas are avoided and, ultimately, lower maintenance costs are obtained.
With the same technique it is possible to obtain a brushing and a rinsing in the lower part of the cleaning cylinder, allowing for a more efficient cleaning process and therefore, ultimately, leading to a lower consumption of cleaning solution and therefore less pollution.
It is understood, however, that the invention is not to be considered as limited by the particular arrangement illustrated above, which represents only an exemplary embodiment of the same, but different variants are possible, all within the reach of a person skilled in the art, without departing from the scope of the invention itself, as defined by the following claims.

Claims

Cleaning cylinder arrangement in an intaglio printing machine, comprising a cleaning cylinder (2) rotatably mounted, against a printing cylinder (3), above a recovery tray (1), and a flexible cleaning element (5, 6) consisting of a porous cloth (5) maintained in contact with a lower portion of the surface of said cleaning cylinder (2), spreading over at least on a 45° arc, by means of a flexible support element (6) provided with downward ink outflow openings, said flexible cleaning element (5, 6) being fastened at leading (6') and trailing (6") edges on attaching means, one of which is adjustable in position,
wherein said attaching means consist of a front holding unit (20) and a rear holding unit (21) opposed to each other with respect to a symmetrical axis (Z-Z), provided with blocking devices (20e, 21e) respectively of a leading edge (6') and of a trailing edge (6") of said flexible cleaning element (5, 6)
characterized in that said blocking devices (20e, 21e) are sliding driven at least according to different displacement axes (X-X;Y-Y) that are substantially parallel to axes tangential to the surface of the cleaning cylinder (2) by means of first and second pneumatic actuators (20c, 21c) .
Arrangement as in 1, wherein said displacement axes (X-X, Y-Y) are substantially parallel to axis tangential to the surface of the cleaning cylinder (2) in the area of the leading edge and of the trailing edge of said flexible cleaning element (5, 6), respectively.
Arrangement as in 1 or 2, wherein each holding unit (20, 21) comprises a support body (20a, 21a) whereon a stem is movably mounted, actuated by a respective pneumatic actuator (20c, 21c), which carries a clamping device (20e, 21e) wherein it is retained an edge of said flexible support element (6).
Arrangement as in 1, 2 or 3, wherein said first and second pneumatic actuators are arranged as arrays of actuators distributed along the length of said cleaning cylinder (2), driven by compressed air also in a differentiated way in order to obtain a precise control of the cloth (5) pressure on the cleaning cylinder along its longitudinal axis.
Arrangement as in any one of the preceding claims, wherein between said front holding unit (20) and the cleaning cylinder (2) there are installed spray nozzles (23) of a cleaning solution.
Arrangement as in any one of the preceding claims, wherein it is furthermore provided a rinsing assembly (22) vertically underlying said porous cloth (5), comprising at least a rinsing tray (22a) wherein it is housed a shaped brush body (22f) apt to contact said porous cloth (5) and said cleaning cylinder (2).
Arrangement as in 6, wherein said porous cloth (5) is provided with cut-outs (5a) in correspondence with said shaped brush body (22f).
Arrangement as in 6 or 7, wherein said shaped brush body (22f) is driven in position according to a vertical axis by means of third pneumatic actuators (22).
Arrangement as in any one of the preceding claims, wherein a camera is also provided apt to acquire an image of said cleaning cylinder (2) downstream of said flexible cleaning element (5, 6), said first, second and third pneumatic actuators being controlled by a feedback based on said acquired image.