Integrated printhead

Details Integrated printhead Integrated printhead

2002-01-11

2003-05-20

Nguyen, Thinh (Department: 2853)

Incremental printing of symbolic information

Ink jet

Controller

C347S150000

Reexamination Certificate

active

06565175

ABSTRACT:

TECHNICAL FIELD
This invention relates to an integrated printhead comprising an array of groups of ink jet elements in M rows and L columns wherein each group has a single row and column address, first addressing means P
J
associated with the array of groups for selecting one of the M rows of the array of groups of ink jet elements in M rows and L columns, second addressing means X
K
associated with the array of groups for selecting one of the L columns of the array of groups of ink jet elements in M rows and L columns, and third addressing means A
I
associated with the array of groups for selecting one ink jet element in each group of ink jet elements.
In particular, this invention relates to a thermal ink jet head of the IDH type (Integrated Drive Head) wherein a plurality of thermal resistances or resistors are selectively activated by an external control circuit to produce the emission of droplets of ink through nozzles placed in correspondence with the resistors.
BACKGOUND ART
An IDH integrated printhead is known from the U.S. Pat. No. 5,644,342 wherein addressing of the various resistors is effected via three-dimensional (or 3-D) addressing.
The known head
10
(
FIG. 1
) comprises a plurality of resistors
11
each connected to a power transistor
12
. The activation of the resistors
11
is controlled by means of an external control circuit connected to the head
10
itself through two corresponding flexible circuits (head flat cable and printer flat cable) having a plurality of contact points A
I=1−N
, P
J=1−M
, GND
K=1−L
where:
N is the number of resistors
11
or addresses A
I
that can be selected inside an activating group
14
;
M is the number of pairs of primitives P
J
that can be selected; and
L is the number of ground contacts GND
K
or columns that can be selected.
For example, a head of 624 nozzles can be produced, according to the known art, from an integrated circuit comprising 24 pairs (M) of activating groups
14
with 13 (N) resistors
11
and associated transistors
12
.
Accordingly:
M+N+L=39 contacts allows the external circuit to control the selective activation of
24*13*2=624 nozzles
by activating the ground connection of a column of primitives through a ground contact GND
K=1−L
(Ground Select);
by activating, for a determined time and by means of the transistors
12
, a first address A
I
(Address Line Select);
by electrically powering, within the column activated, with predefined current pulses and by means of the contacts P
J
(Primitive Select), a predefined configuration of primitives corresponding to the first address A
I
;
by activating in sequence a second address A
I
(Address Line Select) and the relative transistors
12
;
by electrically powering, within the column activated, with predefined current pulses and by means of the contacts P
J
(Primitive Select), a second predefined configuration of primitives corresponding to the second address A
I
;
and so on in successive steps until activation of the N addresses is complete, and then continuing in similar fashion after de-activating the ground connection of the first column of primitives and activating that of the second column of primitives.
As is known, with 3-D addressing it is possible to limit the number of contact points between head and control circuit when the number of nozzles is very high. This is very important since, as is known, integrated heads are economically advantageous and reliable only if the number of contacts is limited to 50-60; indeed, it is only by limiting the number of contacts that it is possible to limit the surface of the integrated circuit constituting the head, the surface of the head flat cable and/or of the head flat cable/printer flat cable area of contact.
For example, as will be apparent to those acquainted with the sector art, the head with 624 nozzles of
FIG. 1
, if made with 2-D addressing, would not be economically advantageous as it would require:
2*24 (M)+13 (N)+24 (GND)=85 contacts.
But 3-D form addressing made in the known way of
FIG. 1
presents a certain number of technical problems compromising its reliability and use possibilities.
A first problem consists of the fact that the intensity of current in the contact points GND
K=1−L
between head flat cable and printer flat cable, being directly proportional to the primitives P
J
powered simultaneously, may assume extremely variable values, for example between 250 mA and 6 Ampere (24*250 mA), assuming naturally that the minimum activating current of a resistor
11
is 250 mA. As will be obvious to those acquainted with the sector art, head flat cable/printer flat cable pressure contacts with these current values are not reliable or repeatable over time.
A second technical problem lies in the fact that the switches in the external control circuit for the ground contacts GND
K
must be over-sized so as to be capable of supporting, for example, peak current values of magnitude 6 Ampere with very low resistances for closing the switches in question.
A third technical problem lies in the fact that the layout of this 3D type integrated head is very critical with regard to the ground conductors, which must support variable and very high peak currents in the head flat cable/printer flat cable contacts, and which have high parasitic resistances, with variable paths and high and variable voltage drops.
A fourth technical problem lies in the fact that the head flat cable/printer flat cable pressure contacts, with regard in particular to the contact points GND
K=I−L
, may cause sparks and electric discharges in the presence of high peak currents.
In short, the known 3-D integrated heads, due to the grouping of the ground connections, imply technical problems that are difficult to solve and signify poor reliability, production difficulties and variability of the power supplied to the resistors
11
for activating the emission of ink from the nozzles.
DISCLOSURE OF THE INVENTION
The object of this invention is to overcome the technical problems outlined above with an innovative integrated head layout which, at the same time, has the advantages of 3-D addressing and, unlike the known art, is easy to produce and reliable.
This object is attained by the integrated printhead characterised by logic means associated with each group of ink jet elements and with the second addressing means X
K
and suitable for being activated by logic signals for selecting one of the L columns of the array of groups of ink jet elements.
According to another characteristic of this invention, the integrated printhead, to advantage, may be driven by the control circuit via a four-dimensional, or 4-D, form of addressing.


REFERENCES:
patent: 5644342 (1997-07-01), Argyres
patent: 6402279 (2002-06-01), Torgerson et al.
patent: 6431677 (2002-08-01), Anderson et al.
patent: 0 388 073 (1990-03-01), None
patent: 0 592 221 (1993-10-01), None

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