Print unit

Details Print unit Print unit

1999-06-30

2001-06-26

Hilten, John S. (Department: 2854)

Printing

Special article machines

Rotary

C400S649000

Reexamination Certificate

active

06250218

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a print unit. In particular, the invention relates to a print unit suitable for use in cigarette packaging machines, to which the following text refers, although without limiting the scope of the invention, for printing a code on wrapping material blanks used in the packaging machine.
Known cigarette packaging machines normally comprise a print unit for printing a code on the blanks, allowing identification, for example, of the date and/or place of production of the relative packet.
In the above-mentioned packaging machines, the print unit in turn comprises a seat designed to hold a blank and mounted on a rotary wheel which moves the blank forward along a path which passes through a print station. The print station houses an actuator which moves a print head away from and towards the seat, so as to print the above-mentioned code on a blank held in the seat.
The above-described print unit is normally equipped with a deformable elastic element, which is inserted between the above-mentioned actuator and the print head, or between the seat and the wheel, and can be adjusted to calibrate the force with which the print head acts upon the blank.
In operation, the above-described print unit subjects the wheel shaft supports to relatively high levels of stress, particularly in modern packaging machines, which have very high operating speeds (over 500 packets per minute). Since they must stand such stress, the shaft supports and corresponding seats must be very strong and are, therefore, expensive.
Moreover, in the above-mentioned print unit, it is very difficult to precisely calibrate the force with which the print head acts upon the blank, since said force depends on the elastic characteristics of the deformable element, on the reciprocal position of the print head and the seat, and on the actuator travel.
The aim of the present invention is to provide a print unit which has none of the above-mentioned disadvantages and, at the same time, is simple and economical to produce.
SUMMARY OF THE INVENTION
Accordingly, the invention provides a print head comprising a print head housed in a print station for printing a graphic symbol on a sheet; an electromagnet housed in the print station; an armature made of a ferromagnetic material which moves away from and towards the print head due to the action of a magnetic field produced by the electromagnet; feed means for feeding the sheet to the print station in a position between the armature and the print head; and control means designed to activate the electromagnet, so as to attract the armature against the print head.


REFERENCES:
patent: 3995730 (1976-12-01), Kwan et al.
patent: 4098389 (1978-07-01), Kwan
patent: 5002267 (1991-03-01), Brecy
patent: 5048986 (1991-09-01), Czesnik et al.
patent: 961245 (1950-05-01), None

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