Device for controlling the movement of a web through a printing

Details Device for controlling the movement of a web through a printing Device for controlling the movement of a web through a printing

1980-12-09

1983-02-08

Heinz, A. J.

Printing

Rolling contact machines

Rotary

226143, B41F 1354

Patent

active

043722067

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a process for controlling the format to be printed of a web which feeds, without tension, a printing machine with a rotary printing cylinder, this machine operating in successive cycles, each cycle being defined as one rotation of the printing cylinder and involving the printing of one area of the web in the said format.
The object of the invention is to permit easy changing of the format, that is to say of the length of web which moves through the machine for each cycle.
This is achieved, according to the invention, by determining this format by means of the take-up speed of the web during the cycle.
In a typical embodiment of the invention, the web is caused to move forward during each cycle, alternately at the printing speed during printing and at a take-up speed which is at most equal to the printing speed, the excess length arising from the difference between the printing speed and the take-up speed, in the case where the latter is less than the printing speed, being re-absorbed by pulling the web backwards without stopping the web between the movement at the take-up speed and the movement at the printing speed.
According to the invention, successive starting and stopping movements are thus avoided.
The invention applies to all printing processes (letterset, dry offset, wet offset and gravure) and it makes it possible to use paper in the form of webs of widely varying substance and quality.
The invention also relates to devices for carrying out the process of the invention.


BRIEF DESCRIPTION OF THE DRAWINGS

These devices will be described with reference to the figures of the attached drawings, in which:
FIG. 1 schematically illustrates one embodiment of a printing machine according to the present invention during a portion of a printing cycle in which a web is being pulled back through the machine;
FIG. 2 is a view of the printing machine of FIG. 1 at the end of pulling back of the web;
FIG. 3 is a view of the printing machine of FIG. 1 at the start of a printing operation;
FIG. 4 is a view of the printing machine of FIG. 1 during a printing operation;
FIG. 5 is a view of the printing machine of FIG. 1 at the end of a printing operation; and
FIG. 6 schematically illustrates a modification of the printing machine of FIG. 1.
The device shown in FIGS. 1 to 6 comprises a printing machine 1 represented schematically by a printing cylinder 2, possessing a printing surface 3 which, in the example, will be assumed to cover three-quarters of the surface of the cylinder, and by an impression cylinder 17. For the clarity of the drawing, the other accessories of the printing device have not been shown. The printing cylinder acts on the web 4 when there is contact between this web and the printing surface, by virtue of the pinching of the web between the printing surface 3 and a counterpart surface 18 of the cylinder 17.
The device shown comprises, downstream of the printing machine, in the direction of movement of the web shown by the arrow 5, a device 6 for drawing the web in the direction of the arrow 5 at a speed equal to the printing speed, and a device 7 for drawing the web in the direction of the arrow 5 at a take-up speed.
The device also comprises, upstream of the machine 1, a pulling-back device 8 for pulling the web back in the opposite direction to the normal direction of movement 5.
The device 6 is designed to convey the web in synchronisation with the printing, that is to say that the beginning and the end of this conveying coincide with the beginning and the end of the printing, and that the conveying speed coincides with the tangential speed of the printing cylinder, the latter speed having been referred to as the "printing speed".
The device 6 consists, for example, of a cam, the surface of which has the same shape and the same angular dimensions as the printing surface, this cam being caused to rotate at the same speed as the printing cylinder, and the angular positions of this cam and of the printing surface being identical in order to obtain the desired coincidences

REFERENCES:
patent: 2039236 (1936-04-01), Meisel
patent: 2845021 (1958-07-01), Pinckert et al.
patent: 3420158 (1969-01-01), Kobiella
patent: 3548747 (1970-12-01), D'Amato
patent: 3762322 (1973-10-01), Vines

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