Device and method for controlling a printing machine, particular

Printing – Processes – Position or alignment

Patent

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Details

101216, 101232, 101 91, B41J 132

Patent

active

058133470

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

The invention concerns controlling a printing machine, particularly controlling a drum type franking machine.
These machines use a rotary print drum to print a mark on envelopes.
In this type of machine the periphery of the print drum receives the postal marks to be printed on the envelope.
The principle of drum printing is as follows. The drum is initially stopped. When an envelope is introduced into the machine the print drum is put in motion and then contacts the envelope to be marked. For the marking to be of good quality the tangential speed of the print drum and the speed at which the envelope moves must be identical when the ink is transferred to the envelope. When the printing phase is finished the print drum is decelerated to a full stop. The speed profile of the movement of the drum is of the trapezoidal type and comprises three phases, constant acceleration, rotation at fixed speed and constant deceleration. This state of the art is perfectly described in document EP-A-0 177 057.
As this type of machine operates at high speed, it is imperative for the unit driving the print drum to be able to accelerate the latter very rapidly. The drive units are currently electric motors of various types; they must have a high torque in order to accelerate said drum as required.
It has already been proposed to reduce the drive torque of the drive unit in order to reduce its price, its size and the noise level of the machine in operation, since the noise level and the torque are closely related. Various parameters can be modified in order to reduce the drum torque: for example, reducing the inertia of the drum or not stopping the movement of the drum between two consecutive print operations (cf. EP-A-0 545 769).


SUMMARY OF THE INVENTION

The aim of the invention is to propose a different approach, based on a dynamic study of the movement of the drum which shows that the torque needed to accelerate the latter is inversely proportional to the angle of acceleration of the drum.
The invention also concerns a method of controlling a print drum enabling a substantial reduction in the drive torque based on reversing the direction of rotation of the drum in the operating cycle of the latter in order to increase the acceleration angle.
The invention also concerns a device for controlling a machine for printing articles "on the fly", particularly for franking envelopes, of the type including: print drum carrying an active print part on a portion of its surface; articles in contact with said print means at a given transport speed Vt and extracting the printed articles; tangential speed of said print drum is maintained equal to said transport speed Vt during a printing phase corresponding to the time period for which an article is in contact with said active print part and, outside the printing phase, reduced during a deceleration phase following the printing phase, and increased to the speed Vt during an acceleration phase preceding the next printing phase,
characterised in that said control means are adapted to impart a negative speed to the drum after (preferably immediately after) the deceleration phase (and therefore before the next acceleration phase).
Advantageously, the speed is reduced linearly from Vt to a minimal negative speed and then increased linearly from the latter to Vt during the next printing operation.
The invention also concerns a method of controlling a printing machine having a rotary drum, particularly for franking envelopes, of the type in which after each printing operation at constant rotation speed in a given direction the rotation speed of the drum is decreased and, before each next printing operation, the rotation speed of the drum is increased in the same direction up to said constant speed, characterised in that the rotation direction of the drum is reversed after reducing the rotation speed after each printing operation.
The features and advantages of the present invention will emerge from the following description of one embodiment shown in the appended draw

REFERENCES:
patent: 3756149 (1973-09-01), Bishop et al.
patent: 4023489 (1977-05-01), Beery
patent: 4220084 (1980-09-01), MacLean et al.
patent: 4232217 (1980-11-01), Juziuk et al.
patent: 4579054 (1986-04-01), Buan et al.
patent: 4665353 (1987-05-01), Salazar et al.
patent: 4909498 (1990-03-01), Rutishauser
patent: 5018443 (1991-05-01), Bolger
patent: 5471928 (1995-12-01), Dimur et al.

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