Multi-color flexographic rotary machine with main drum and independent separate color units

A flexographic rotary printing machine has a supporting structure provided with two lateral shoulders, an impression roller over which a material in sheet form to be printed passes, at least one printing element or assembly arranged adjacent to the impression roller and having an inking unit, a printing plate cylinder and an anilox roller, which are sleeve cylinders, and a drive for transmitting motion between the impression roller and each printing assembly. At each shoulder there is at least one lateral support device for the advancement-retraction of the sleeve cylinders, adapted to move them between a retracted or resting position, in which a respective sleeve can be inserted or removed, and an advanced or active position, in which the cylinders are kept in contact with, and operatively connected to, the impression roller.

BACKGROUND OF THE INVENTION 
The present invention relates to a multi-colour rotary flexographic machine 
of the narrow-web type. 
As it is known, replacement of the printing plate cylinder and the anilox 
roller in each printing unit of a conventional flexographic rotary machine 
is a troublesome operation which requires long machine downtimes. 
SUMMARY OF THE INVENTION 
The main object of the present invention is to provide a new flexographic 
rotary machine with separate printing units in which changing of printing 
and/or printing colours can be made in a quick and easy way. 
Another object of the present invention is to provide a high performance 
flexographic rotary machine which is highly reliable and precise. 
These and other objects which will become better apparent hereinafter are 
achieved by a flexographic rotary printing machine according to the 
invention, which comprises a supporting structure, an impression roller on 
which a sheet material to be printed passes, at least one printing unit 
arranged adjacent to said impression roller and having a closed-chamber 
doctor-blade inking group, a printing plate cylinder and an anilox roller, 
which are of sleeve cylinder type, motion transmission means between said 
impression roller and each printing assembly, and at least one lateral 
support device for forward and backward movements of said sleeve cylinders 
which is arranged to move them between a retracted or resting position, in 
which a respective sleeve can be inserted or removed, and an advanced or 
printing position, in which they are kept in contact with, and operatively 
connected to, said impression roller. 
Advantageously, said lateral support device comprises at least one slide 
provided with recirculating ballscrew sliding blocks and a guide of 
antifriction material.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
In the accompanying drawings, identical or similar parts or components have 
been designated by the same reference numerals. 
With reference to FIGS. 1 to 10 and 15, it will be noted that a printing 
machine according to the invention has a supporting structure, generally 
designated by the reference numeral 1. An impression roller or printing 
drum 2, around which a sheet or web material to be printed passes and is 
partly wound, is mounted for rotation on the structure 1. On the opposite 
side with respect to the vertical axis of the impression roller 2 there is 
provided a plurality of printing assemblies or color units 3, e.g. eight 
printing units, which extend substantially in radial direction with 
respect to the impression roller. 
The supporting structure 1 comprises in particular two cast-iron shoulders 
1a and 1b of large thickness to ensure maximum stability and lack of 
vibrations and thus optimum printing quality control. 
Each printing unit 3 comprises, as usual in the art, a closed-chamber 
doctor-type inking group, generally designated by SI, an anilox roller 4, 
and a printing plate cylinder 5, which can be operatively connected to 
each other and to the impression roller 2 by suitable motion transmission 
means, usually gears, as further explained hereinafter. 
The printing plate cylinder 5 and the anilox roller 4 of each printing unit 
are sleeve cylinders, since engraving is also provided on a tubular 
element 6, whereby both the printing plate 7 and the tubular element 6 
constitute "sleeves" insertable on, and removable from, a respective 
cylinder 5 or 4. This makes it possible to considerably simplify printing 
or color changing operations, since it is no longer necessary to replace 
the cylinders 4 and 5 but simply to change or replace their respective 
sleeves, which is a much simpler operation that can be performed in a very 
short time, as no heavy loads or loads which might be dangerous for the 
safety of the personnel and for the components of the machine need to be 
handled. 
Each printing unit 3 has at one shoulder of the machine (preferably the 
front shoulder 1b ) a supporting device, generally designated by the 
reference numeral 8, arranged to cause the sleeve cylinders 4 and 5 to 
move back and forward between a retracted or resting position, in which 
their respective sleeve 6, 7 can be inserted or removed, and an advanced 
or printing position, in which it is kept in contact and operatively 
connected to said impression roller. 
More particularly, each supporting device 8 is mounted at a respective 
large opening or slot 9 formed in the front shoulder 1b of the printing 
machine for easy loading and unloading of the ceramic anilox sleeve 6 and 
the printing plate sleeve 7 of the sleeve cylinders 4 and 5. A supporting 
device 8 comprises a slide 10, one or more lower linear prismatic guides 
11 which are fixed to the supporting structure 1, an upper linear guide 12 
for the linear sliding of the slide 10, and control means for actuating 
the slide 10, e.g. constituted by a screw 13 driven by an electric motor 
14 supported by the shoulder 1b and controlled by a respective encoder 15, 
and by a female thread 16, secured to the slide 10, the screw 13 being 
rotated by a wheel or pulley 17 which is keyed thereon and by a toothed 
transmission belt 18 which is driven by the motor 14. 
Preferably, the or each prismatic guide 11 is engaged by a respective 
sliding block 19, which is fixed to the slide 10 and mates with the 
prismatic guide 11, and is constituted by a suitable antifriction material 
having a low coefficient of friction, e.g. a material commercially known 
as "Turcite" and marketed by Swedish company Shamban, which besides having 
a very low coefficient of friction can also absorb the vibrations that 
might occur during printing. 
At its upper part, the slide 10 has two recirculating-ballscrew sliding 
locks 20 to ensure good smoothness and high resistance to overturning 
moments which might occur during a sleeve changing operation. 
To the side of the slide 10 there is a second slide or sliding block 100 
which is designed to support the cylinder 4 and can be actuated by an 
assembly comprising an electric motor 22, an encoder 23, a toothed belt 24 
and a pulley 25 and arranged to rotate a screw 26 in a female thread 27 
carried by the slider 10. 
At the upper guide 12 registering wedges 21 are also provided which are 
arranged to eliminate any play between the slider 10 and 100 and the 
shoulders of the supporting structure 1 and to apply a given preloading to 
the lower guide or guides 11, thereby ensuring greater and constant 
rigidity of the system during printing operations. 
The slide 10 has a through slot 30 which extends longitudinally and 
parallel to the guides 11 and 12 and has such dimensions as to ensure easy 
passage of an anilox sleeve 6 for the anilox cylinder 4. 
The distal end of the slide or sliding block 100 is equipped, i.e. it has a 
substantially semicircular receiving cradle or seat 31 whose inlet has 
chamfered edges 32 and 33 to constitute guiding surfaces for the entry of 
the end 34 of the cylinder 4. 
Advantageously, the lower portion of the cradle 31 is constituted by a 
separate part which is articulated at a pivot 35 which has a horizontal 
axis in order to resiliently yield and assist the inlet-exit of the end 34 
into and from the cradle 31. 
At the distal end of the slide 10, a recess 36 delimits a cradle or seat 
for receiving an end 37 of the cylinder 5. At the upper portion of the 
cradle 36 there is provided a removing holding device 38 which is further 
explained with reference to FIGS. 7 to 10. 
Most of the upper portion of the cradle 36 is formed by a holding lever or 
cap element 39, which is articulated about a pivot 40 located in an upper 
region above the cradle 36, in a backward position close to the slot 30, 
thereby allowing the holding element 39 to oscillate on a plane parallel 
to the plane on which the slide 10 moves. 
As shown more clearly in FIG. 8, the holding element 39 can be a U-shaped 
in cross-section and is slidingly inserted from below onto the upper end 
of the cradle 36. Moreover, the lever element 39 is resiliently loaded, 
e.g. by one or more helical springs 45 which urge it to its closed 
position. 
Articulation movements of the holding element 39 are prevented by an 
axially movable pivot 41 which has a frustum-shaped tip and is located in 
a lateral seat or recess 42 formed in one wing of the holding element and 
terminating with a frustum-shaped portion 43 provided in the slider 10. 
The pivot 41 is actuated by a linear actuator 44, e.g. a solenoid, a jack 
or the like, and is preferably kept slightly axially offset (FIG. 8) with 
respect to the axis of its seat 42 for safer holding effect in its locked 
position. 
With this configuration, when the slider 10 is moved against the end 37 of 
the cylinder 5 towards its working position, after the pivot 41 has been 
moved backwards from the frustum-shaped seat 43 by the actuator 44, the 
cap 39 rises automatically, thereby allowing easy insertion of the end 37 
into the cradle 36 and then it returns to its locking position, firmly 
holding in position the cylinder end 37 and therefore the cylinder 5. At 
the same time, the cradle 31 on the slide 100 engages with the end 34 of 
the cylinder 4, which is in turn held in its working position. 
In the embodiment shown in FIGS. 11 to 14, the holding device or cap 39, 
instead of rotating about a pivot, can perform a translatory motion so as 
to be raised when the end 37 moves therethrough in contrast with the force 
of one or more loading springs 45, which react against an abutment block 
46 secured to the slide 10, e.g. by means of bolts 47. 
At the rear shoulder 1a (FIGS. 1 and 5) a plate-like slide 50 is mounted 
movable along a lower guide 51 and an upper guide 52 which are entirely 
similar to the guides 11 and 12. Sliding blocks 20 slide on the upper 
guides 52. The slide 50 rotatably supports the other end of the sleeve 
cylinder 5 and can be actuated, similarly to the slide 10, by a motor 
which, by means of a transmission belt 18, drives a pulley 17 which is 
keyed to a screw 13 screwed into a female thread 16 secured to the slide. 
The revolutions of the screw 13 are controlled by an encoder 15. 
A slide or sliding block 500, similar to the sliding block 100 on the front 
shoulder 1b, is also provided on the rear shoulder 1a and is arranged to 
move parallel to the side of the slide 50. Its movements are likewise 
controlled by an electric motor 22 through a transmission comprising a 
toothed belt 24 and a pulley 25 which is keyed on a screw 26 provided with 
an encoder 23. 
The screws 13 and 26 are preferably high-precision recirculating 
ballscrews. A pneumatic brake 53 is located axially aligned on each screw 
is to ensure effective locking in position of the slides. 
As more clearly shown in FIGS. 1 and 6, the ends 34 and 37 of the cylinders 
4 and 5 are mounted on the slide 50 and 500 by means of a respective 
sleeve 54 and 55 with the interposition of friction reduction means, i.e., 
bearings 56, whereby allowing its respective cylinder to perform limited 
angular oscillations (as shown by arrow A in FIG. 6) during sleeve 
changing operations, and limited longitudinal movements for the necessary 
transverse alignment of said cylinders (arrow B). 
In order to minimize the free bending length of the cylinder 5, at the ends 
37 of the cylinder 5 two additional roller bearings 56A (see FIG. 6A) can 
be provided which are seated in the sleeve 54 on one side and in the 
sleeve 61 on the other side. This arrangement has also the advantage of 
eliminating angular oscillations indicated by double arrow A in FIG. 6. 
FIG. 6 also illustrates the front end of the cylinder 5 which, like the 
front end 34 of cylinder 4, is provided with a cap 60 which is screwed 
onto a sleeve 61 for resting on the cradle 36 in the slide 10, the sleeve 
61 being loaded by one or more springs 62 for transverse registering 
movements. 
The spring or springs 62 are designed to keep or automatically return the 
sleeve 61 to its centered position during sleeve changing operations. As 
more clearly shown in FIG. 6, a second sleeve 65 is slideably mounted 
inside the sleeve 54 and protrudes from the sleeve 54 with a widened end 
portion which internally receives the bearings 56. 
An oval external flange 66 is fixed to the sleeve 65 and to an acme-thread 
screw 67 secured to the oval flange 66. The screw 67 can be screwed into a 
female thread 68 which can be rotated by a toothed pulley 69 which is in 
turn driven by a toothed belt 70 wound on a driving pulley 71 which is 
directly rotated by an electric motor 72. By causing the electric motor 72 
to turn in one direction or in the other the screw 67 and thus the sleeve 
66 and the cylinder 5 are caused to traverse, thereby performing the 
precision transverse registering of the printing plate cylinder 5. 
It will be noted that in a printing machine as described above a very 
simple, quick and safe change the sleeves 6 and 7 can be performed through 
the openings 9 with no need of replacing the sleeve cylinders 4 and 5. In 
practice, it has been found that in a color printing machine according to 
the invention an average sleeve changing time is on the order of a few 
minutes, in contrast with color changing time of a few hours required with 
conventional printing machines. 
The above described invention is susceptible of numerous modifications and 
variations within the scope as defined by the appended claims. 
Thus, for example, as shown in FIGS. 16 and 17, the above described 
embodiment of a printing machine can be applied to printing machines with 
a central drum (FIG. 15), to printing machines with separate color units 
(FIG. 16) and to printing machines with twin stacked color units (also 
known as "stack" machines in the art) see FIG. 17. 
The disclosures in Italian Patent Application No. VR98A000037 from which 
this application claims priority are incorporated herein by reference.