EP0226554B1

EP0226554B1 - A flexographic machine

Info

Publication number: EP0226554B1
Application number: EP86830357A
Authority: EP
Inventors: Luigi Sergio Carraro; Giovanni Gessaghi
Original assignee: GRAPHIC MACHINE SERVICE Srl
Current assignee: GRAPHIC MACHINE SERVICE Srl
Priority date: 1985-12-19
Filing date: 1986-11-28
Publication date: 1989-05-10
Also published as: EP0226554A1; ATE42929T1; DE3663231D1; ES2010193B3; IT1200910B; IT8523279A0

Abstract

A flexographic machine (1), affording unusual rapidity of printing plate cylinder (10) replacement, comprises a drive (20) for simultaneously and synchronously moving a printing plate cylinder (10) toward and away from an impression cylinder (8), and a screened cylinder (16) toward and away from the printing plate cylinder (10), as well as a motor (28) for powering said drive (20), a detector (38) confronting the printing plate cylinder (10) to emit a signal on its becoming engaged therewith, and a motor (28) shut-off means (29) activated by said signal.

Description

This invention relates to a flexographic machine of a type which comprises a framework; an impression cylinder journalled to said framework; a printing plate cylinder supported at the ends on a pair of slides mounted slidingly on the framework to shift the printing plate cylinder toward and away from the impression cylinder; a screened cylinder supported at the end by a shoe pair, each shoe being mounted slidingly on a respective one of said slide pair to shift the screened cylinder toward and away from the printing plate cylinder; and a drive comprising a motor for moving the slides and shoes simultaneously and synchronously toward and away from the impression cylinder and the printing plate cylinder, respectively.
As is known, flexographic machines require frequent replacement of the printing plate cylinders owing to the patterns to be printed varying. It should be also noted that the various printing plate cylinders equipping a machine differ from one another not only by their printing plates but also by their diameters, in accordance with recurrence pitches at which the patterns are to be printed.
Whenever a printing plate cylinder requires replacement, the slide pair which support it must be moved away from the impression cylinder, to bring the printing plate cylinder a distance away from the impression cylinder and, accordingly, remove the shoe pair from the printing plate cylinder, thereby the screened cylinder can be set aside with respect to the printing plate cylinder. On this state being achieved, the printing plate cylinder can be easily replaced with another cylinder from the set equipping the machine.
In order to restore the machine to its operative condition, the printing plate cylinder must be moved back to a position close to the impression cylinder, and the screened cylinder to a position close to the printing plate cylinder. This is done manually by acting on the mechanical drive, being careful that engagement of the printing plate cylinder with the impression cylinder occurs at a desired mutual pressure, as disclosed for example in FR-A-2 280 503 and 2 271 931.
The above procedure is a troublesome one and timeconsuming, and requires, every time that a cylinder must be changed, the availability of skilled personnel possessing the necessary dexterity which standard tuning up of the machine involves.
To overcome this drawback, it has been suggested of driving the slides and shoes through a numeric control apparatus, as disclosed for example in EP-A-96 646 and 51 037. Such an approach, which in theory would be effective to fully automate the operation, is nonetheless a source of different-kind problems, it resulting in a more complicated construction of the machine and higher cost thereof. Consequently, it has met with unfavorable acceptance by the user.
The problem underlying this invention is to provide a flexographic machine of the type indicated, which has such constructional and functional features as to fill the abovementioned need, while overcoming the problems posed heretofore by conventional flexographic machines.
The solutive idea of this invention is that of using the printing plate cylinder itself as a reference for a detector operative to halt the cylinder approaching movement.
Based upon said solutive idea and to solve the aforesaid technical problem, this invention provides a flexographic machine of the type specified above, which is characterized in that it comprise a detector mounted on a shoe at a position to face the printing plate cylinder for emitting a signal when engaged with said cylinder, and motor shut-off means activated by said signal.
Further features and advantages of the flexographic machine according to this invention will become apparent from the following description of a preferred embodiment thereof, given by way of illustration and not of limitation with reference to the accompanying drawings, where:

Figure 1 is a side elevation view showing schematically a flexographic machine according to the invention;
Figure 2 is a side elevation view, drawn to an enlarged scale, of a detail of the machine of Figure 1, as incorporating a printing station;
Figure 3 shows, to a further enlarged scale, a detail of the printing station of Figure 2; and
Figure 4 is a plan view of the detail shown in Figure 3, taken in the direction of the arrow IV.

With reference to the drawing figures, the numeral 1 designates comprehensively a flexographic machine according to this invention, for printing a material 2, such as a plastics film.
The machine 1 comprises, within a framework 3, a decoiler 4 for the material to be printed, a printing assembly 5, a drying stove 6, and a rewinding assembly 7 for the printed and dried material.
The printing assembly 5 comprises an impression cylinder 8 of large diameter which is journalled to the framework 3 and subjected to the action of said motor means, not shown because quite conventional, and six printing stations, comprehensively designated 9, which are arranged peripherally around the cylinder 8.
Since the stations 9 are all substantially alike, only one of them will be discussed in detail hereinafter.
In particular, said stations 9 comprise a printing plate cylinder 10 each, which printing plate cylinder has a platen 11 carrying a printing plate, not shown, and opposingly located journals..12 and 13 at its ends.
The printing plate cylinder 10 is journalled to a pair of slides 14 and 15, wherein the journals 12 and 13 are respectively accommodated in a rotatable and readily removable manner.
The slides 14 and 15 are mounted on a frame 3 for sliding movement in a substantially radial direction X - X to the impression cylinder 8, thereby the printing plate cylinder 10 can be moved toward and away from the aforesaid impression cylinder 8.
The printing assembly 5 further comprises a screened cylinder 16 which is journalled at its opposed ends to a pair of shoes 17 and 18.
The shoes 17 and 18 are mounted on the slides 14 and 15, respectively, for sliding movement in the direction X - X and shift the screened cylinder 16 toward and away from the printing plate cylinder 10. Indicated at 19 is an inker roll, also journalled to the shoe pair 17 and 18, to ink the screened cylinder.
The reference numeral 20 designates a drive, known per se, operative to simultaneously and synchronously drive the slide pair 14, 15 and shoe pair 17, 18. In particular, the drive 20 is connected to a single input drive shaft 21 which extends between two gear boxes 22 and 23, respectively attached to the slides 14 and 15.
Out of the gear box 22 there extend two screws 24 and 25, drivingly connected inside the box 22 to the shaft 21, said screws threadingly engaging respective screw nuts 26 and 27, the screw nut 26 being rigid with the shoe 17, and the screw nut 27 being rigid with the frame 3.
In a likewise fashion, two screws extend out of the gear box 23 which are connected drivingly to the shaft 21, said screws engaging threadingly with respective screw nuts rigid with the shoe 15 and the frame 3, respectively.
It should be noted that the aforesaid screw nuts are made fast with their respective shoes and respective slides through micrometric adjustment assemblies, comprehensively designated 20a, which are known per se and provided with respective knobs 20b for fine tuning manual adjustment purposes.
The machine 1 of this invention comprises a motor means 28, such as an electric motor, operative to power the drive 20. In particular, the motor 28 is attached to the gear box 22 to drive the shaft 21 rotatively, and is associated with a shut-off means 29, such as a remote-controlled switch.
The machine 1 further comprises a detector 30, advantageously in the class of an induction-type proximity switch, said detector being mounted on the shoe 18. Specifically, the detector 30 fits into a small block 31 cartridge-fashion, said block being fastened to the shoe 18 by screws 31 a so as to occupy a position facing the printing plate cylinder 10 and, more specifically, facing a reference portion 32 formed coaxially in the cylinder 10 at the journal 13 thereof. It should be noted that the reference portion 32 has a set diameter, which is equal to the diameter of the platen 11 of the cylinder 10, or which is in a set reference thereto, e. g. it differs from it by a set given quantity.
The detector 30 emits a signal on its engaging with said reference portion 32 of the printing plate cylinder 10. In the instance considered, wherein the detector 30 is of the proximity kind, that engagement would occur on a gap of a preset magnitude being developed between the detector 30 and the reference portion 32.
Indicated at 33 is a cable connecting the detector 30 to the shut-off means 29 for the motor 28.
As regards the rotative entrainment of the printing plate cylinder 10 and the screened cylinder 16 by the impression cylinder 8, gears 34, 35 and 36 are provided in quite a conventional manner. In particular, the printing plate cylinder 10, screened cylinder 16, and impression cylinder 8 comprise the gears 34, 35 and 36, respectively, which are rotatively rigid therewith. The gear 35 meshes with the gear 34, and the latter is in mesh engagement with the gear 36.
It should be noted that the gear 34, made rigid rotatively with the cylinder 10, is shiftable axially between a first operating position where it mesh engages with the gears 35 and 36, and a second, inoperative position where it is disengaged. The gear 34 is first moved into its inoperative position when the printing plate cylinder is to be controlled to move closer to the impression cylinder, and the screened cylinder closer to the printing plate cylinder.
The operation of the flexographic machine according to the invention will be now described with reference to a starting condition as that shown in the drawing, in which the flexographic machine is operative to print on a material 2, the cylinder 10 being engaged on one side with the impression cylinder 8 and on the other side with the screened cylinder 16.
Should the printing plate cylinder require a change, it will be sufficient to operate the motor 28 so as to cause the printing plate cylinder 10 to move simultaneously and synchronously away from the impression cylinder 8, until a condition is attained such as that shown in dash lines in Figure 3.
At this stage, the motor 28 would be stopped automatically, and the cylinder 10 replaced with another cylinder. The newly installed cylinder 10 also has a portion 32 whose diameter is equal to the diameter of the new cylinder, or differs therefrom by the same given set quantity mentioned above.
At this stage, the motor 28 is operated in the reverse direction, so as to cause the screened cylinder 16 to move toward the new printing plate cylinder 10, and said cylinder 10 toward the impression cylinder 8.
During that approaching movement, the detector 30 would be moved toward the reference portion 32. On the detector 30 engaging with said portion 32, it will output a signal which is supplied to, over the cable 33, and activates the shut-off means 29 which brings the motor 28 to a stop.
Thus, an operative condition is re-established for the machine. In the event that the new cylinder 10 has the same diameter as the previous cylinder, that operative condition would be quite identical of the starting condition. If the new cylinder has instead a different diameter, e. g. a larger diameter, the new operative condition would provide for the shoes to be further away from the printing plate cylinder, and concurrently therewith, for the slides to be further removed from the impression cylinder. The reverse would apply if the new cylinder has a smaller diameter.
In any case, simultaneous mutual engagement of the cylinders is achieved as desired, and specifically of the screened cylinder with the printing plate cylinder and the printing plate cylinder with the impression cylinder.
It should be noted that in the example considered, a flexographic machine has been discussed which has a plurality of printing stations, all of wich act on a single, large-size impression cylinder; however, the invention equally applies to flexographic machines wherein each printing station is arranged to act on a respective, small-diameter impression cylinder.
It should be further noted that on the flexographic machine just described, the screened cylinder may be replaced with a cylinder engraved for rotogravure, engaging with a flat platen type of printing plate cylinder.
The main advantage of the inventive machine resides in the unusually short time it requires to replace the printing plate cylinder, thanks to the cylinder re-positioning being effected automatically in relation to the new cylinder.
An additional advantage of the machine according to the invention resides in its simple construction, which affords prospects of reliable and constant operation overtime.
Also within the scope of this inventive concept, a modified embodiment of the flexographic machine according to the invention will be described herein below with reference to Figure 5, where parts with the same structure and/or mode of operation as those shown in Figures 1 to 4 carry the same reference numerals and, for convenience of illustration, will be no further described herein.
In the flexographic machine of Figure 5, the gear 34 roatively rigid with the cylinder 10 has a reference portion 37 formed integrally therewith which is quite similar to the reference portion 32.
A detector 38, quite similar to the detector 30, is adapted to become engaged with the reference portion 37, with the gear 34 in its inoperative position. The detector 38 is mounted on the end of a bracket 39 rigidly attached to the shoe 18.
The flexographic machine of this modified embodiment affords the important practical advantage that it can accommodate the standard printing plate cylinders which equip flexographic machines.
Of course, the skilled person in the art may choose, in order to meet specific contingent requirements, to introduce several modifications in the machine embodiments described above, and it is intended that such modifications would fall within the protection scope of the invention as set forth in the appended claims.

Claims

1. A flexographic machine of a type which comprises a framework (3); an impression cylinder (8) journalled to said framework; a printing plate cylinder (10) supported at the end of a slide pair (14,15), mounted slidingly on the framework to shift the printing plate cylinder toward and away from the impression cylinder; a screened cylinder supported at the end by a shoe pair (17, 18), each shoe being mounted slidingly on a respective one of said slide pair to shift the screened cylinder toward and away from the printing plate cylinder; and a drive (20) comprising a motor (28) for moving the slides and shoes simultaneously and synchronously toward and away from the impression cylinder, and the printing plate cylinder, respectively; characterized in that it comprises a detector (30) mounted on a shoe (18) at a position to face the printing plate cylinder (10) for emitting a signal when engaged with said cylinder (10); and a motor shut-off means (29) activated by said signal.

2. A flexographic machine according to Claim 1, characterized in that the printing plate cylinder (10) comprises, at a journal thereof, a coaxial cylindrical reference portion adapted to be engaged by the detector (30).

3. A flexographic machine according to Claim 2, characterized in that said detector (30) is a proximity-type detector operative to emit a signal on reaching a set limited distance from said reference portion (32) of the journal.

4. A flexographic machine according to Claim 1, characterized in that the printing plate cylinder (10) comprises, at a gear (34) totatively rigid therewith, a coaxial cylindrical reference portion (37) adapted to be engaged by the detector (30).

5. A flexographic machine according to Claim 4, characterized in that said detector (30) is a proximity-type detector operative to emit a signal on reaching a set limited distance from said reference portion (37) of the gear (34).

6. A flexographic machine of type which comprises a framework (3); an impression cylinder (8) journalled to said framework; a printing plate cylinder (10) supported at the end of a slide pair (14, 15) mounted slidingly on the framework to shift the printing plate cylinder toward and away from the impression cylinder; a screened cylinder (16) supported at the end by a shoe pair (17, 18), each shoe being mounted slidingly on a respective one of said slide pair to shift the screened cylinder toward and away from the printing plate cylinder; and a drive (20) comprising a motor (28) for moving the slides and shoes toward and away from the impression and printing plate cylinders, respectively; characterized in that it comprises a detector (30) mounted movably with respect to the printing plate cylinder (10) at a position facing the printing plate cylinder (10) to emit a signal when engaged with said cylinder; and a means (29) of shutting off said motor means (28) being activated by said signal.