Incremental printing of symbolic information – Ink jet – Ejector mechanism
Reexamination Certificate
1999-08-10
2001-10-09
Barlow, John (Department: 2853)
Incremental printing of symbolic information
Ink jet
Ejector mechanism
C347S058000
Reexamination Certificate
active
06299292
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates generally to inkjet printers, and more particularly to driver circuitry for matrix inkjet printheads.
2. Related Art
Inkjet printheads for printers are generally classified in two categories: (1) passive and (2) active or “matrix” printheads. Passive printheads comprise a plurality of heater resistors all connected in common to a power supply. The heater resistors are turned on by independent “low” side transistor switches. By contrast, active or matrix type printheads comprise a row and column matrix, where “high” side transistors are provided to couple data to the columns, and a “low” side transistor is provided for each and every heater resistor.
An example of conventional driver circuitry for a matrix type printhead is shown in FIG.
1
. In this example, the printhead is a 13×16 heater resistor printhead. The plurality of heater resistors are driven in “columns” or groups
20
, each comprising 13 heater resistors on the printhead
30
. There are 16 groups in this example. The column driver circuit portion
10
comprises a plurality of high side transistors
12
that provide data to the groups
20
of heater resistors R in response to column data signals P
1
-P
16
. That is, data signal P
1
is assigned to the first group, data signal P
2
is assigned to the second group, etc. Heater resistors R in each group
20
are addressed by an associated low side field effect transistor (FET)
22
through another gating FET
24
in response to address signals A
1
-A
13
. That is, address signal A
1
is coupled to a first row of heater resistors across all of the groups
20
, the address signal A
2
is coupled to a second row of heater resistors across all of the groups
20
, etc. In operation, the printhead
30
is driven by stepping in time through the 13 different rows of heater resistors R and changing the column data signals for each time slice.
The architecture shown in
FIG. 1
requires high side transistors for each group
20
. These high side transistors require a low Vcesat that cannot vary substantially from a nominal value and furthermore must carry 400 mA. As a result, the column driver circuit portion
10
is relatively expensive. The address driver circuit portion, on the other hand, comprises FETs that are relatively simple (small and low current), inexpensive, and easily integrated on the printhead
30
.
It would be beneficial to provide the equivalent column driver signals in a manner similar to that provided by the address or “low” side driver circuit. Preferably, it would be desirable to eliminate the column drivers altogether to reduce driver circuitry costs.
SUMMARY OF THE INVENTION
Briefly, the present invention is directed to a driver circuit for an inkjet printhead having a plurality of heater resistors arranged in a matrix comprising a plurality of groups of heater resistors. The driver circuit comprises a plurality of first switches and a plurality of second switches. Each of the plurality of first switches is coupled to a heater resistor in each of the plurality of groups and is responsive to one of a plurality of first control signals to supply a current to the associated heater resistor. Each of the plurality of second switches is associated with one of the plurality of first switches, and comprises an input, an output and a gate. The input of each of the plurality of second switches is coupled to one of the plurality of first control signals, and the output of each of the plurality of second switches is coupled to the plurality of first switches for one of the plurality of groups of heater resistors. Each of the plurality of second switches is responsive to one of a plurality of second control signals coupled to the gate thereof to transfer one of the plurality of first control signals coupled to its input to an associated one of the plurality of first switches from its output, thereby driving one of the plurality of heater resistors in a group.
The above and other objects and advantages of the present invention will become more readily apparent when reference is made to the following description, taken in conjunction with the accompanying drawings.
REFERENCES:
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patent: 4719477 (1988-01-01), Hess
patent: 4947192 (1990-08-01), Hawkins et al.
patent: 5045870 (1991-09-01), Lamey et al.
patent: 5051755 (1991-09-01), Takahashi et al.
patent: 5081474 (1992-01-01), Shibata et al.
patent: 5122812 (1992-06-01), Hess et al.
patent: 5159353 (1992-10-01), Fasen et al.
patent: 5187500 (1993-02-01), Bohorquez et al.
patent: 5363134 (1994-11-01), Barbehenn et al.
patent: 5442381 (1995-08-01), Fukubeppu et al.
patent: 5638101 (1997-06-01), Keefe et al.
patent: 5644342 (1997-07-01), Argyres
patent: 5736997 (1998-04-01), Bolash et al.
Barlow John
Lexmark International Inc.
Needle & Rosenberg P.C.
Stephens Juanita
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