EP1997625A1

EP1997625A1 - Image forming automatic apparatus, in particular for printing lithographic plates

Info

Publication number: EP1997625A1
Application number: EP07425334A
Authority: EP
Inventors: Paolo Spano; Fabiano Tuccillo; Antonello Vannucci; Felice Pignatiello
Original assignee: Andromeda Srl
Current assignee: Andromeda Srl
Priority date: 2007-06-01
Filing date: 2007-06-01
Publication date: 2008-12-03
Also published as: WO2008145764A1

Abstract

An image forming apparatus (1), in particular for printing plates suitable to be used in lithography processes, allows a completely automatic management of the plates inside the apparatus and comprises: a stacking station (2) of the plates on a plurality of plate supporting trays (7), having: means for the vertical translation (17) of the supporting trays (7); means for blocking (22, 23) the supporting trays (7) at a predetermined height; a punching device (24) for the plates; and a storing section (25) of the printed plates, an exposure station (3) of the plates, having: a cylindrical drum (30), apt to receive photosensitive plates on the outer surface thereof through a feeding plane; and securing means (31) for said photosensitive plates on the cylindrical drums (30); catching and releasing means (40) of said plates, arranged so as to draw the plates from said supporting trays (7) and to translate them vertically and horizontally in said stacking station (2) and from and to said exposure station (3).

Description

The present invention is related to an automatic image forming apparatus, in particular in the field of the printing of plates suitable to be used in lithography processes, wherein the image printed in the plate is transferred and reproduced on other media, using the plate as a master.
According to a known typology of image forming apparatuses, the plate is arranged on the outer surface of a rotating cylindrical drum, and one or more exposure heads are used to expose the moving plate by means of optical means like a laser beam operating in the infrared field, in the ultraviolet field, in the violet light field and in other wavelength fields which can be considered suitable for this task.
The plates are coated with a layer in a technopolymer photosensitive to the light beam projected onto the surface of the plate itself, in this way achieving the image reproduction.
The plates, intended to be printed on the drum, have to be provided continuously and in a certain amount at the image forming station, and then they have to be stored. The handling of plates has to be carried out very precisely and an operation of punching has also to be carried out on the plates, to form, at an edge of the plates, some reference holes which are used un subsequent operations.
In the known apparatuses, all these steps are not carried out automatically by the apparatus, but require the intervention of an operator.
The technical problem underlying the present invention is to provide an image forming apparatus allowing to obviate to the drawbacks mentioned with reference to the prior art.
Such a problem is solved by an apparatus as above specified comprising:

* a stacking station of the plates on a plurality of plate supporting trays, having:
- o means for the vertical translation of the supporting trays;
- o means for blocking the supporting trays at a predetermined height;
- o a punching device for the plates; and
- o a storing section of the printed plates,
* an exposure station of the plates, having:
- o a cylindrical drum, apt to receive photosensitive plates on the outer surface thereof through a feeding plane; and
- o securing means for said photosensitive plates on the cylindrical drums;
* catching and releasing means of said plates, arranged so as to draw the plates from said supporting trays and to translate them vertically and horizontally in said stacking station and from and to said exposure station.

The main advantage of the apparatus according to the present invention lies in allowing a completely automatic management of the plates inside the apparatus.
The present invention will be hereinafter disclosed according to a preferred embodiment thereof, provided to an exemplificative and non-limitative purpose, with reference to the annexed drawings wherein:

* Figure 1 shows a schematic perspective view of an image forming apparatus according to the invention;
* Figures 2A, 2B and 2C show perspective views of a detail of the apparatus of Figure 1, i.e. a stacking station;
* Figures 3A, 3B and 3C show perspective views of an enlarged detail of the stacking station of Figures 2A, 2B and 2C;
* Figure 4 shows a perspective view of a further details of the stacking station of Figures 2A, 2B and 2C;
* Figures 5A and 5B show perspective top and bottom views of a detail of the apparatus of Figure 1; i.e. of the catching and releasing means of the plates;
* Figures 6A and 6B show perspective views of details of the stacking station of Figures 2A, 2B and 2C;
* Figure 7 shows a partially sectioned perspective view of the stacking station of Figures 2A, 2B and 2C;
* Figure 8 shows a partial perspective view of a detail of the apparatus of figure 1; and
* Figure 9A and 9B show perspective views of supporting trays used in the apparatus of figure 1.

With reference to the figures, an automatic image forming apparatus is indicated as 1. It is substantially divided into a stacking station indicated as 2, and into an exposure station, indicated as 3.
In the stacking station 2, all the handling operations of the photosensitive plates, indicated as 4, are carried out: storing before the exposure, drawing, punching, feeding to the exposure station 3, storing after the exposure.
The exposure station 3 is instead provided for the step of exposing the plates, which will be detailed hereinafter.
Ideally, the two station are structurally independent to each other and they can be coupled for realising an image forming apparatus.
The stacking station 2 comprises a frame structure 5, made of tubular frame members 6 in the form of a parallelepiped cage. In the present embodiment, the frame structure 5 is made by drawn solid tubular members in FE360B, producing a stiffening of the structure.
As it will be apparent from the following description, the frame structure 5 permits the installation of a number of supporting trays 7, e.g. three, and the housing of all the electric, pneumatic and electronic components. Interface plates on the tray member 6 are further arranged on the frame structure, suitably flattened by machining with a flatness and parallelism of predetermined tolerance of about 0,1 mm, for assuring, in the coupling step of the stations 2, 3, a correct alignment of the whole system.
On the frame structure 5, a further frame module 8 can be mounted, having the same size and the same constructional features of the frame structure 5. It is prepared for supporting an additional number of supporting trays 7, e.g. five.
Between structure 5 and module 8, a system of mechanical joints 9 of the module 8 is provided, intended to be fitted into suitable notches 10 formed at the top of the structure 5, with consequent locking by self-locking grips (Figures 3A, 3B and 3C). Thus, the additional module 8 is inserted directly into the frame structure 5 (Figures 2A, 2B and 2C).
The trays can be stacked one onto each other (Figure 4) and each of them contains a drawer 11 suitable to receive a number even relevant, about a hundred, of plates of the same format. The trays 7, rectangular-shaped like the plates, are divided by spacer members 12, placed at the corners of the trays 7. Thanks to them, the trays can be superimposed one onto each other, determining a structure apt to be self-supporting and preventing to interfere with the plates in the drawers 11.
Being superimposed (Figure 4), the trays permit to save vertical space, and to limit the height of the stacking station 2, improving the stability thereof and reducing the making and transport costs.
The trays is designed to support on the surface thereof the drawer 11 and, in the lower section thereof, the trays has a drawer-covering flat member 13, supported by a C-section indicated as 14 (Figure 6B) wherein projecting pins 15 pf the flat member 13 are inserted, the latter therefore being horizontally extractable.
Inside the drawer 11, the plates are aligned by a mechanical system allowing to keep them compacted. The drawer 11 laterally shows rubber wheel 21 to ease the insertion inside the tray 7 (Figure 9A).
In the above described structure, the weight of the whole assembly of stacked trays 7 with the plates is at least partially released on the spacer members 12 (Figure 4), making the weight and the inertia directly converge on the arms 16 of a vertical lifting system 17 inside the stacking station 2 (Figure 7).
The vertical lifting system 17 has a pair of posts 18 located at the side of the stacking station 2 opposite to the exposure station 3.
Each post 18 has a respective slide 19 inserted into a linear guide, driven through an endless screw shaft connected to a motor 20.
The above described vertical lifting system 17 constitutes means for the vertical translation of the supporting trays 7 inside the stacking station 2.
Furthermore, blocking means for the trays at a predetermined height is provided, i.e. with respect to frame members of the frame structure 5. Such means comprises retractable pins 22 provided pair by pair on the opposite sides of the frame structure 5, i.e. those left free by the lifting system 17 and by the exposure station 3.
Such pins 22 are intended to engage with suitable anchoring member provided pair by pair on opposite sides of the trays 7, in positions corresponding to those of the pins 22.
In such a way, a part of trays can remain secured in the upper section of the frame structure 5, while another part is vertically translated by the lifter 17. The top tray 7 of this latter part of trays has a drawer 11 left uncovered by the covering flat member 13 thereof, which is kept anchored to the above towering tray. In the gap dividing the two tray assemblies it is possible to insert an element for handling the plates, which will be hereinafter detailed.
Further, in the stacking station, a punching device 24 of the plates is provided, laterally placed with respect to the stacking station 2 and faced to the exposure station 3. In such a way, the plate edge which is punched is already facing the exposure station 3.
At the bottom section thereof, the stacking station 2 finally comprises a storage section 25 of the printed plates.
The exposure station 3 comprises a frame member, not shown, supporting a cylindrical drum 30, apt to receive photosensitive plates on the outer surface thereof.
The exposure station further comprises fixing means for said plates, generally indicated as 31. The definition of the present invention does not depend upon the typology of the fixing means of the plates.
The frame member supporting the drum 30 is arranged inside a further frame structure 32 cage-shaped like the preceding one, but structurally independent.
In this station, an exposure head is provided, laterally placed with respect to the drum 30 and mobile along a direction parallel to the axis of the drum 30. Thus, on the frame member, means for rotating the drum 30 are supported, at a predetermined rotation rate depending upon the type of plate and upon the corresponding exposure head. A leading sheave wheel 33, connected to non-shown motor means, and a driven sheave wheel 34, integral to the drum 30, represent such means for rotating. The two sheave wheels 33, 34 are joined by a suitable belt 35.
The exposure head is associated to driving means (not shown), for driving said exposure head, fully supported by said frame member, according to a direction parallel to the axis of the cylindrical drum 30.
Such driving means comprises a respective supporting system for the exposure head. Such system is translated by a screw shaft rotated by a motor placed at one end of the screw shaft. The driving means further comprises straight guides 9, parallel to the drum axis.
With respect to the drum 30, a feeding plane is identified for the plate, which is substantially horizontal and extending so as to be tangential to the drum 30 on the upper side, between the latter and said stacking station 2.
Such feeding plane is embodied by catching and releasing means of the plates, positioned so as to remove the plates from said supporting trays 7 and to translate them vertically and horizontally inside said stacking station 2, to and from said exposure station 3.
Such catching and releasing means are composed by a handling device 40 having a horizontal guide extending between the two stations 2, 3, on the upper side of said feeding plane.
On this guide, a catch and release equipment 42 horizontally slides, supporting a vacuum plate 43 by means of variable length driving member 44, i.e. two hydraulic actuators (Figures 5A and 5B).
The vacuum plate is composed by a pair of separated micro-foraminated vacuum half-plates (Figure 5B), with separated vacuum circuits, apt to keep one plate 4 planar, without deforming it, ready to be placed onto the drum 30.
The handling device 40 can easily support the plate 4, even when it is punched.
In such a way, sliding planes for leading the plates to the punching and to the drums are not provided, reducing the overall length of the apparatus 1. Further, said handling device 40 can vacuum-keep the separation sheet provided between the plates, allowing the disposal thereof.
The apparatus herein described can be therefore operated according to the following loop:

(a) Step of tray loading, wherein the single drawer containing one format only of plates is inserted into a tray, and an operator can input the loaded plate number and the respective format through a not shown input unit, e.g. a touch-screen display;
(b) Step of moving the lifting system 17: in the loading, the lifting system has to raise and position the trays 7 at the drawer insertion height;
(c) Step of counting the drawer number: the system counts the drawer number present inside the stacking station, detecting which tray is empty;
(d) Step of drawing the plates from the last drawer: the lifting system is driven to the tray blocking level;
(e) Step of reaching the blocking height of the supporting trays 7;
(f) Step of inserting blocking pins 22 for keeping the trays 7 at a predetermined height: the pins are driven by a suitable actuator inside anchors 23 of the trays 7, designed to support even the above trays and filled drawers;
(g) Step of starting the lifting system to raise it at the puncher height;
(h) Intake of the handling device inside the stacking station;
(i) Drawing of one plate, lowering the vacuum plane;
(j) Punching of the plate: at this point the plate has been aligned with the punching system;
(k) Delivery of the plate inside the drum: the vacuum plane is placed at its top dead centre, and it aligned with the pins catching the plate and arranging it on the cylindrical drum;
(l) Gradual decreasing of the vacuum force: slowly the vacuum force of the vacuum plates is lead to zero, loading the plate on the drum;
(m) Catching of the plate separation sheet: the handling device inside the stacking station draws the plate separation sheet of the uncovered plate and bring it outside the station;
(n) Step of handling the trays in the upper section: the formerly lowered tray now it is raised so as to allow the intake of the handling device;
(o) Step of release of the separation sheet, which is let to fall inside a collection tray;
(p) Step of positioning of the handling device, which is positioned outside the stacking station, to start again the loop from (f).

To the above disclosed automatic image forming apparatus a man skilled in the art, to achieve further and contingent needing, can carry out additional changes and variants, all anyway embraced within the protection scope of the present invention, as defined by the annexed claims.

Claims

Image forming apparatus (1), in particular for printing plates suitable to be used in lithography processes, comprising:
* a stacking station (2) of the plates on a plurality of plate supporting trays (7), having:
o means for the vertical translation (17) of the supporting trays (7);

o means for blocking (22, 23) the supporting trays (7) at a predetermined height;

o a punching device (24) for the plates; and

o a storing section (25) of the printed plates,

* an exposure station (3) of the plates, having:
o a cylindrical drum (30), apt to receive photosensitive plates on the outer surface thereof through a feeding plane; and

o securing means (31) for said photosensitive plates on the cylindrical drums (30);

* catching and releasing means (40) of said plates, arranged so as to draw the plates from said supporting trays (7) and to translate them vertically and horizontally in said stacking station (2) and from and to said exposure station (3).
Apparatus (1) according to claim 1, wherein the stacking and exposure stations (2, 3) are structurally independent upon each other.
Apparatus (1) according to claim 2, wherein the stacking station (2) comprises a frame structure (5) provided with interface plates on respective frame member (6), appropriately flattened by machining with predetermined planarity and parallelism tolerances to have, in the coupling step of the stacking and exposure stations (2, 3), a correct alignment.
Apparatus (1) according to claim 1, wherein the stacking station (2) comprises a frame structure (5) on which a further frame module (8) can be mounted, provided for supporting an additional number of supporting trays (7).
Apparatus (1) according to claim 4, wherein a a system of mechanical joints (9) between the frame structure (5) and the frame module (8) is provided, intended to be fitted into suitable notches (10) formed at the top of the frame structure (5).
Apparatus (1) according to claim 1, wherein the trays (7) each contains a drawer (11) apt to receive a number of plates having the same format.
Apparatus (1) according to claim 1, wherein the trays (7) are separated by spacer members (12) so as to result in a self-supporting structure.
Apparatus (1) according to claim 7, wherein the tray 7, in its lower part, has a drawer-covering flat member (13).
Apparatus (1) according to claim 7, wherein the drawer (11) laterally has wheels (21) allowing to ease the introduction inside the tray (7).
Apparatus (1) according to claim 1, wherein the means for the vertical translation of the supporting trays (7) comprises a vertical lifting system (17) inside the stacking station (2) having a pair of posts (18) with a respective slide (19), inserted into a linear guide and driven by a screw shaft connected to a motor (20), from which a corresponding arm (16) projects.
Apparatus (1) according to claim 1, wherein the blocking means for the trays (7) at a predetermined height comprises retractable pins (22) arranged on the opposite sides of the stacking station (2), driven by actuators to engage with suitable anchoring members (23) provided on opposite sides of the trays (7), in a position corresponding to the pins (22).
Apparatus (1) according to claim 1, wherein the punching device (24) is provided laterally placed with respect to the stacking station (2), faced to the exposure station (3).
Apparatus (1) according to claim 1, wherein the storage section (25) of the stacking station (2) is placed at a bottom section thereof.
Apparatus (1) according to claim 1, wherein the catching and releasing means are composed by a handling device (40) having a horizontal guide (41) extending between the two stacking and exposure stations (2, 3), on the upper side of said feeding plane
Apparatus (1) according to claim 14, wherein the handling device (40) comprises a catch and release equipment (42) sliding along said guide (41) and supporting a vacuum plate (43) by variable length driving member (44).