Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
2001-04-12
2003-04-08
Hsieh, Shih-wen (Department: 2861)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S029000
Reexamination Certificate
active
06543877
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention presented here involves a machine for direct printing by projection of ink drops onto a medium
2. Description of the Related Art
The ink jet technique is known from the prior-art.
It makes use of printing heads made of a piezo-electric ceramic having a chamber that, by deformation, projects the ink out of nozzles onto a medium. The projection of the ink can also be obtained, for certain types of ink, by heating that creates the formation of a gaseous bubble whose expulsion causes the ink jet.
These techniques are associated with microprocessor-controlled systems which make it possible to create, by ink projection, the desired image that can be, for example, a sign or an alphabetic letter or any other representation. These techniques are mainly used in office automation equipment.
In this equipment, the relative displacements of the printing head by the ink jets and the medium to be printed are low in amplitude, which does not harm the quality of the print. The necessary partial vacuum at the outlet of the projection nozzles is not affected by the low displacements. These technologies, however, are only suitable for certain types of specific inks and are not suitable for the projection of inks having a high corrosive capacity, the use of which is sought after for the quality of the printing obtained and for its unalterable adhesion on the medium or for inks to be developed by ultraviolet rays.
The invention intends to create a machine that allows equally the direct printing, by corrosive inks, i.e. having a solvent or ultraviolet base, on small formats or very large formats and on any type of medium, notably rigid, planar or formed The creation of a machine of this type that meets this definition is done by mastering a certain number of problems.
Since corrosive inks cannot be loaded into the known distributing cartridges of the HEWLETT PACKARD™ type or LEXMARK™. type, it is necessary to design a specific system for supplying ink using devices that make it possible to maintain a partial vacuum of 4 millibars at the level of the projection nozzles, without a variation in the pressure that would be detrimental to good printing, and this must be done independently of the given technique, by which the relative movements between the heads and the projection nozzles must be very fast. As an example, the heads and nozzles can be subjected to movement speeds of 800 millimeters per second and to accelerations of 5000 millimeters per second squared, which generates a pressure variation at the level of the nozzles.
Moreover, the nozzles functioning at a slight partial vacuum, with the variations mentioned above, are likely, in the course of the movement as a dynamic function, to pump out air bubbles.
This generates damage to their function that is causing stop of the projection, deflected jet, etc.
The invention presented here intends to provide a solution to this problem in creating a printing machine.
BRIEF SUMMARY OF THE INVENTION
For this purpose, the machine according to the invention for the direct printing functioning by projection of ink drops onto a medium, by one or more heads with projection nozzles, the machine being of a type having relative movements between the medium to be printed and the projection heads, each head being preferably dedicated to one color or to one ink, is characterized essentially in that:
the head(s) is or are carried by a mobile carriage above the medium to be printed along the three axes X, Y, and Z orthogonally in space,
each of the heads is equipped with a buffering reservoir carried by the mobile carriage, and
the head(s) and their buffering reservoir are kept at a partial vacuum and the buffering reservoirs are supplied under pressure from one or more stationary reservoirs.
According to another characteristic of the invention, the mobile carriage guides the heads and the nozzles cyclically on a system for cleaning and maintenance of the heads which cleans the nozzles and primes them by suction, evacuates the excess drops by doctoring, and makes it possible to keep the nozzles in a good functioning condition.
According to yet another characteristic of the invention, the internal volume of each loaded buffering reservoir is divided in order to reduce the amplitude of waves produced by the movements of the reservoirs.
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Aliaga Christophe
Boutet Alain
Harrison & Egbert
Hsieh Shih-wen
Siantec Sarl
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