Incremental printing of symbolic information – Ink jet – Controller
Reexamination Certificate
2000-12-01
2002-10-15
Vo, Anh T. N. (Department: 2853)
Incremental printing of symbolic information
Ink jet
Controller
C347S078000
Reexamination Certificate
active
06464322
ABSTRACT:
DOMAIN OF THE INVENTION
The present invention relates to ink jet printers in which ink jets are formed and electrically charged and then deviated to strike a print substrate. It relates to a process designed to simplify the mechanical assembly of print heads and a printer applying this process.
TECHNOLOGICAL BACKGROUND
It is known that a pressurized ink jet ejected through a print nozzle can be broken into a series of individual droplets, each droplet being individually charged in a controlled manner. Constant potential electrodes along the path of these individually charged droplets deviate the droplets by a variable amount depending on their charge. If it is not required that a droplet should reach the print substrate, its charge is controlled such that it is deviated to an ink recovery reservoir. The operating principle of this type of ink jet printer is well known, and for example is described in U.S. Pat. No. A-4,160,982. As described in this patent and as shown in
FIG. 1
, this type of printer comprises a reservoir
11
containing electrically conducting ink
10
that is distributed through a distribution duct
13
to a droplets generator
16
. The role of the droplets generator
16
is to form a set of individual droplets starting from the pressurized ink in the distribution duct
13
. These individual droplets are electrically charged by means of a charge electrode
20
powered by a voltage generator
21
. The charged droplets pass through a space between two deviation electrodes
23
,
24
and are deviated by a variable amount depending on their charge. The least deviated or undeviated droplets are directed to an ink recovery reservoir
22
, whereas deviated droplets are directed to a substrate
27
. The successive droplets in a burst reaching the substrate
27
can thus be deviated to an extreme low position, an extreme high position and any number of intermediate positions, the set of droplets in the burst forming a line with height &Dgr;X approximately perpendicular to a relative direction of advance between the print head
25
and the substrate. The print head consists of the droplet generator
16
, the charge electrode
20
, the deviation electrodes
23
,
24
and the recovery reservoir
22
. In general, this head
25
is enclosed in a casing not shown. The deviation movement applied to the charged droplets by the deviation electrodes
23
,
24
is complemented by a movement along a Y axis perpendicular to the X axis, between the print head and the substrate. The time elapsed between the first and last droplets in a burst is very short. The result is that despite continuous movement between the print head
25
and the substrate, it can be assumed that the substrate has not moved with respect to the print head during the time of a burst. Bursts are fired at regular intervals in space. If all droplets in each burst were directed towards the substrate, then a sequence of lines with height &Dgr;X would be printed. In general, only some droplets in the burst are directed towards the substrate. Under these conditions, the combination of the relative movement of the head and the substrate, and the selection of the droplets in each burst that are directed towards the substrate, is a means of printing any pattern such as that shown in
28
in FIG.
1
. If the line that is drawn with the droplets in a burst is in a direction X, the relative movement of the head and the substrate in the plane of the substrate is in a direction Y perpendicular to X. The undeviated droplets are directed to the recovery reservoir along a path Z perpendicular to the x, y plane of the substrate. Printed droplets reach the substrate by following paths slightly deviated from direction Z.
If the relative movement of the head and the substrate takes place continuously along the largest dimensions of the substrate, there will usually be several print heads printing bands parallel to each other. One example of this type of use is shown in
FIGS. 1 and 2
in the patent issued to IBM, as number FR 2 198 410.
If the relative movement of the print head and the substrate in the Y direction takes place along the smallest dimension of the substrate, printing is done band by band, with the substrate performing an intermittent advance movement in the X direction after each scanning. The relative movement of the print head and the substrate is called the “scanning movement”. The scanning movement is thus composed of a forward and return movement between a first edge of the substrate and a second edge of the substrate. The movement between one edge and the other edge of the substrate is a means of printing a band of height L, or frequently a part of the band of height &Dgr;X
b
where &Dgr;X
b
is usually a sub-multiple of L, without stopping. All bands printed in sequence thus form the pattern to be printed on the substrate. Each time that a band or a part of band is printed, the substrate is advanced by the distance between two bands or parts of bands to print the next band or part of band. Printing may be done during the forward movement only, or during the forward and return movements of the print head with respect to the substrate.
When the pattern to be printed is colored, the different shades of colors are the result of ink impacts from nozzles supplied by inks of different colors being superimposed and placed adjacent to each other. The system for relative displacement of the substrate with respect to the print heads is achieved such that a given point on the substrate is presented in sequence under each of the different colored ink jets.
Usually, the print system comprises several jets of the same ink operating simultaneously, either by multiple heads being adjacent to each other or by the use of multi-jet heads, or finally by the combination of these two types of heads in order to achieve high print speeds. In this case, each ink jet prints a limited part of the substrate. Known means of controlling the different jets will now be described with reference to FIG.
2
.
The pattern to be printed is described by a numeric file. This file may be formed using a scanner, a calculator aided graphic creation pallet (CAD) transmitted using a calculator data exchange network, or it may simply be read from a peripheral reading a numeric data storage medium (optical disk, CD-ROM). The numeric file representing the colored pattern to be printed is firstly split into several binary patterns (or bitmaps) for each ink. Note that the case of the binary pattern is a non-limitative example; in some printers, the pattern to be printed is of the “contone” type, in other words each position may be printed by a variable number of droplets from 1 to M for each ink. Part of the binary pattern is extracted from the file for each jet corresponding to the width of the band that will be printed.
FIG. 2
, which shows the control electronics of a jet, shows a memory
1
in which the numeric pattern cut into bands is stored, this storage memory containing information about a color. For printing each band, an intermediate memory
2
contains the data necessary for printing the band with the said color. Descriptive data for the band to be printed are then input into a calculator
3
that calculates the charge voltages of the different drops that will form the band for this color. These data are input into the calculator in the form of a sequence of frame descriptions that, when combined, will form the band. The calculator
3
that calculates droplet charge voltages is often in the form of a dedicated integrated circuit. This calculator
3
calculates the sequence of voltages to be applied to the charge electrodes
20
, in real time, in order to print a given frame defined by its frame description, as loaded from the intermediate memory
2
. An output side electronic circuit
4
, called the “droplet charge sequencer”, synchronizes the charge voltages firstly with the times at which droplets are formed, and secondly with the relative advance of the print head and the substrate. The advance of the substrate with respect to the print head
Imaje S.A.
Mouttet Blaise L
Pearne & Gordon LLP
Vo Anh T. N.
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