AN APPARATUS AND METHOD FOR CHANGING A BLADE OF A ROTARY DIE CUTTER, PARTICULARLY FOR FLEXOGRAPHIC PRINTING MACHINES

Technical field of the invention

The present invention relates to an apparatus and a method for changing a blade of a rotary die cutter particularly for flexographic and offset printing machines.

Background of the invention

It is known, in particular in the sector of flexographic printing, that there exists the problem of replacing the rotary die cutters when there is variation in shape and size of labels and or of any printed image to be die-cut.

At present, in fact, the replacement of rotary die-cutters, for changing the blade which allows cutting-to-size of the labels or the printed images requires more or less prolonged machine downtimes, depending on the complexity of the replacement operations which must be performed. An example thereof is provided in the document EP 2 484 498 A1, which discloses an apparatus and a method according to the preamble of claims 1 and 5.

Summary of the invention

The main task of the present invention is to provide an apparatus and a method for changing a blade of a rotary die cutter which overcomes the drawbacks and the limitations of the prior art.

Within the scope of this task, an object of the present invention is to provide an apparatus and a method which allow the blade of the rotary die cutter to be replaced in a much more rapid and efficient manner.

Another object of the invention is to provide an apparatus and a method which may also be completely automated.

Another object of the invention is to provide an apparatus and a method which may be applied to any already existing rotary die-cutting system.

Another object of the invention is to provide an apparatus and a method which allow different sequences of die-cutting operations to be obtained for different printing jobs using a single rotary die cutter.

A further object of the invention is to provide an apparatus and a method which are able to ensure greater guarantees in terms of reliability and safety during use. Another object of the invention is to provide an apparatus which is easy and inexpensive to produce and a method which is competitive from an economic point of view when compared to the prior art.

The tasks described above, along with the objects mentioned and others which will appear more clearly below, are achieved by an apparatus and a method for changing a blade of a rotary die cutter, particularly for flexographic printing machines, according to claims 1 and 5.

Brief description of the drawings

Further characteristic features and advantages will become clearer from the description of a preferred, but non-exclusive embodiment of an apparatus for changing a blade of a rotary die cutter, illustrated by way of a non-limiting example with reference to the attached drawings in which:

• Figure 1 is a perspective view of an embodiment of an apparatus, according to the invention;
• Figures 2 to 4 show a sequence of steps for application of a first blade of a rotary die cutter to a magnetic cylinder, by means of the apparatus according to the invention;
• Figures 5 to 12 show a sequence of steps for replacing, on a magnetic cylinder, a first blade with a second blade, by means of the apparatus according to the invention.

Detailed description of the Invention

With reference to the figures mentioned, the apparatus for changing a blade of a rotary die cutter, particularly for flexographic printing machines, denoted overall by the reference number 1, comprises a magnetic cylinder 3, configured to receive and support a die-cutting blade 5, 5'.

According to the invention, the apparatus 1 comprises a station 7 for inserting a blade 5, which comprises retention means 70 configured to retain the blade 5 in the insertion station 7, and guiding means 71 configured to guide the blade 5 from the insertion station 7 toward the magnetic cylinder 3; and a station 9 for extracting the blade 5, which comprises extraction means 90 configured to remove the blade 5 from the magnetic cylinder 3. The extraction means 90 comprise an oscillating body 91 which comprises an end 92 adapted to detach the blade 5 from the magnetic cylinder 3. The oscillating body 91 oscillates in fact between an inactive configuration, in which its end 92 is spaced from the magnetic cylinder 3, and therefore also from the blade 5 wrapped around the magnetic cylinder 3, and a configuration for removal of the blade 5, in which the end 92 of the oscillating body 91 is adapted to engage the blade 5 and detach it from the magnetic cylinder 3.

In Figures 2 to 5, 11 and 12, the oscillating body 91 is shown in its inactive configuration, while in Figures 6 to 10 the oscillating body is shown in the configuration for removal of the blade 5, 5'.

Advantageously, moreover, in the removal configuration, the end 92 of the oscillating body 91 is adapted to be inserted between the blade 5, 5' wrapped around the magnetic cylinder 3 and the magnetic cylinder 3 itself so that the rotation of the magnetic cylinder 3 about its rotation axis 30 causes detachment of the blade 5, 5' from the magnetic cylinder 3.

The blade 5, 5' has a size such as to be wrapped substantially around the whole of the lateral surface of the magnetic cylinder 3. As shown in particular in Figure 6, oscillation of the extraction means 90 may be synchronized with the rotation of the magnetic cylinder 3 so that the oscillating body 91 is positioned in the configuration for removal of the blade 5, 5' precisely at the point where the ends of the blade 5 face each other. In this way it is possible to ensure that the end 92 of the oscillating body 91 is inserted between the blade 5, 5' and the magnetic cylinder 3, causing detachment of the blade 5, 5' from said magnetic cylinder 3.

The oscillating body 91 is advantageously hinged on a portion of the extraction station 9 and may comprise actuating means which cause oscillation thereof from the inactive configuration into the removal configuration and vice versa.

Advantageously, the guiding means 71 comprise a pair of guiding cylinders 72, 73 which face each other and between which the blade 5, 5' is guided. Furthermore, the guiding means 71 may also comprise a sliding channel 75 for the blade 5, 5', adapted to seat the blade 5, 5' while on standby waiting to be applied onto the magnetic cylinder 3.

Advantageously the retention means 70 comprise a retention arm 74 which can move between a retention configuration, in which said arm 74 is adapted to support the blade 5, 5', and a release configuration, in which this arm 74 is adapted to release the blade 5, 5' toward the magnetic cylinder 3. By way of example, in Figure 2, the retention arm 74 is shown in the retention configuration, while in Figure 3 it is shown in the release configuration. Advantageously the blade 5, 5', when the retention arm 74 is in the release condition, tends to slide, owing to the force of gravity, downwards, while being guided by the guiding means 70 until it is attracted, and made to rotate, by the magnetic cylinder 3. The retention means 70 comprise advantageously actuating means which cause the displacement of the retention arm 74 from the retention configuration into the release configuration and vice versa.

The method for changing a blade of a rotary die cutter, by means of the apparatus 1, comprises the steps of:

• detaching and removing, in the extraction station 9, a first blade 5 from the magnetic cylinder 3 around which it is wrapped, using the extraction means 90 which cooperate, in order to perform detachment and removal of the blade 5, with the magnetic cylinder 3 made to rotate about its rotation axis 30;
• inserting a second blade 5' in the insertion station 7;
• guiding the second blade 5' from the insertion station 7 toward the magnetic cylinder 3, via the guiding means 71, following deactivation of the retention means 70;
• wrapping the second blade 5' around the magnetic cylinder 3, by means of rotation of the magnetic cylinder 3 about its rotation axis 30.

The step of detaching and removing the first blade 5 from the magnetic cylinder 3 comprises the step of engaging the first blade 5 and the step of detaching the first blade 5 from the magnetic cylinder 3 using the extraction means 90 which are configured to remove the first blade 5 from the magnetic cylinder 3, penetrating between said first blade 5 and the magnetic cylinder 3, together with rotation of the magnetic cylinder 3 about its rotation axis 30.

Advantageously, moreover, the method of changing a blade of a rotary die cutter comprises a step of automatic preparation of the blade 5, 5' in the insertion station 7. In this way, the blade 5' located in the insertion station 7 is already ready to replace the blade 5 which will be detached and removed from the magnetic cylinder 3.

The method may also comprise a step of automatic storage of the blades 5, 5' exiting the extraction station 9.

Furthermore the steps of detaching and removing the first blade 5 from the magnetic cylinder 3, guiding the second blade 5' toward the magnetic cylinder 3 and wrapping the second blade 5' around the magnetic cylinder 3 are advantageously automated.

Once the blade 5, 5' is positioned in the insertion station 7, it remains on standby waiting to be applied onto the magnetic cylinder 3. Insertion of the blade 5, 5' onto the magnetic cylinder 3 may be performed automatically, by means of a signal from said apparatus 1, or manually, by means of an operator. Owing to the retention means 70, which retain the blade 5, 5' in the insertion station 7, a blade 5, 5' can be inserted into the insertion station at any time so that the latter is ready, if necessary, to replace the blade which is momentarily applied to the magnetic cylinder 3. Activation of the extraction means 90 may also be automatic or manual.

Advantageously, operation of the retention means 70, the guiding means 71, the extraction means 90 and the actuating means for rotation of the magnetic cylinder 3 about its rotation axis 30 is synchronized so as to ensure correct insertion of the blade 5, 5' onto the magnetic cylinder 3 and correct removal of the blade 5, 5' from the magnetic cylinder 3 without damaging it.

Moreover change-over of the blade 5, 5' from the standby condition in the insertion station 7 to the operating condition on the magnetic cylinder 3 and then to the condition for expulsion via the extraction station 9 may be performed entirely automatically, depending on the series of operations to be performed by the die-cutting machine, or semi-automatically, in the case where there is an operator who sets the times for change-over from one working condition of the rotary die cutter to another.

Advantageously, moreover, automatic change-over from one die cutting condition to another is performed always on the same single magnetic cylinder so that it is possible to obtain different sequences of die-cutting operations for the different printing jobs using a single die-cutting machine.

The apparatus and the method for changing a blade of a rotary die cutter, according to the present invention, performs the task and also achieves the predefined objects since it allows changing of the blade rapidly, efficiently and also automatically.

Another advantage of the apparatus according to the invention consists in the fact that it may be applied to any existing rotary die-cutting system.

A further advantage of the apparatus and the method according to the invention consists in fact that replacement of the die-cutting blades is performed in a smooth, efficient and delicate manner.