Information
-
Patent Grant
-
6318846
-
Patent Number
6,318,846
-
Date Filed
Monday, August 30, 199925 years ago
-
Date Issued
Tuesday, November 20, 200123 years ago
-
Inventors
-
Original Assignees
-
Examiners
- Tran; Huan
- Stephens; Juanita
-
CPC
-
US Classifications
Field of Search
US
- 347 12
- 347 13
- 347 42
- 347 145
- 347 180
- 347 181
- 347 182
-
International Classifications
-
Abstract
In a thermal ink jet print head, individually-controlled heating elements are separated into groups of heating elements. Redundant control lines for the separate groups of heating elements increase the print head's reliability by reducing the likelihood that a print head will be completely disabled by an electrical fault on the control lines that in prior art devices extended to all of the heating elements.
Description
FIELD OF THE INVENTION
The present invention relates generally to inkjet printing devices. In particular, the invention relates to an inkjet print head for thermal inkjet printing devices that incorporates multiple address bus demultiplexing circuitry for driving the drop ejector heater resistors.
BACKGROUND OF THE INVENTION
The art of inkjet printing technology is relatively well developed. Commercial products such as computer printers, graphics plotters, copiers, and facsimile machines successfully employ inkjet technology for producing hard copy printed output. The basics of the technology have been disclosed in various articles in the Hewlett-Packard Journal, Vol. 36, No. 5 (May 1985), Vol. 39, No. 4 (August 1988), Vol. 39, No. 5 (October 1988), Vol. 43, No. 4 (August 1992), Vol. 43, No. 6 (December 1992) and Vol. 45, No. 1 (February 1994) editions. Inkjet devices have also been described by W. J. Lloyd and H. T. Taub in Output Hardcopy Devices (R. C. Durbeck and S. Sherr, ed., Academic Press, San Diego, 1988, chapter 13).
A thermal inkjet printer for inkjet printing typically includes one or more translationally reciprocating print cartridges in which small drops of ink, are ejected by thermal energy from a drop generator, towards a medium upon which it is desired to place alphanumeric characters, graphics, or images. Such cartridges typically include a print head having an orifice member or plate that has a plurality of small nozzles through which the ink drops are ejected. Beneath the nozzles are ink firing chambers, which are enclosures in which ink resides prior to ejection through a nozzle. Ink is supplied to the ink firing chambers through ink channels that are in fluid communication with an ink reservoir, which may be contained in a reservoir portion of the print cartridge or in a separate ink container spaced apart from the print head.
Ink drop ejection through a nozzle employed in a thermal inkjet printer is accomplished by quickly heating the volume of ink residing within the ink firing chamber with a selectively energizing electrical pulse to a heater resistor ink ejector positioned in the ink firing chamber. At the commencement of the heat energy output from the heater resistor, an ink vapor bubble nucleates at sites on the surface of the heater resistor or its protective layers. The rapid expansion of the ink vapor bubble forces the liquid ink through the nozzle. Once the electrical pulse ends and an ink drop is ejected, the ink firing chamber refills with ink from the ink channel and ink reservoir.
Thermal inkjet ink can be corrosive. Prolonged exposure of electrical interconnections of an ink cartridge to the ink, will frequently result in a degradation and failure of the print head because the transistors that fire the heater resistors are effectively cut off from their source of power or from their control signals. In some print head designs, the transistors that fire the heater resistors are addressed (controlled) from a single electrical connector. If this one connector is electrically disabled because of chemical attack from the ink and its constituents, a large part (or all) of an ink cartridge can fail, adversely affecting print quality.
The heater resistors of a conventional inkjet print head comprise a thin film resistive material deposited on an oxide layer of a semiconductor substrate. Electrical conductors are patterned over the oxide layer and provide an electrical path to and from each thin film heater resistor. Since the number of electrical conductors can become large when a large number of heater resistors are employed in a high density (high DPI—dots per inch) print head, various multiplexing techniques have been introduced to reduce the number of conductors needed to connect the heater resistors to circuitry disposed in the printer. See, for example, U.S. Pat. No. 5,541,629 “Print head with Reduced Interconnections to a Printer” and despite its good conductivity, imparts an undesirable amount of resistance in the path of the heater resistor.
Individual transistors are typically addressed using combinations of electrical signals applied to the drain, source and gate terminals. These combinations of signals can effectively control when individual transistors will be in their “on” state, thereby allowing a droplet of ink to be ejected onto the print medium. Multiplexing the function of the various lines through the semiconductors allows a large number of individual transistors to be addressed using a relatively small number of address line conductors.
Multiplexing techniques have helped reduce the total number of conductors necessary to energize the heater resistors. Notwithstanding the improvements in addressing, more improvement is needed, however, to reliably address each transistor to avoid catastrophic failure of a print head caused by a single fault on an address bus. In addition, there is a need to provide printheads that have a flexibility to accept different input signal configurations.
SUMMARY OF THE INVENTION
A print head for an inkjet printer includes a substrate upon which is disposed a plurality of heater resistors. The heater resistors are electrically ordered into a first group and a second group; they are physically arranged about the opposing sides of an elongated slot (an ink aperture) through which ink flows from an ink reservoir to ink firing chambers of the ink jet print head. The resistors are heated by electrical current that is directed by switching devices such as three-terminal current switching field-effect transistors or FETs. Electrical control signals to the various FETs (which allow the heater resistors to be energized) are coupled into the print head using two (2) connectors on opposites of the substrate.
One electrical connector disposed on a first side of the substrate is provided with electrical paths between the contacts of the connector and the gate inputs of the various firing transistors that are electrically coupled to only a first group of ink firing elements (resistors) that coincidentally are proximate to a first portion of the ink aperture. A second electrical connector disposed on a second side of the substrate that is opposite the first side, is provided with electrical paths between the second connector and the gate inputs of a second group of transistors that are used to fire a second group of heater resistors.
Stated alternatively, the control inputs for the several transistors are divided into two groups where each group is electrically coupled to one of two edge connectors. A fault on one of the address lines controlling one of the transistors will disable only that transistor or other transistors coupled to that same address line. The control signals from the other connector, which are electrically isolated from the first connector, are not affected by ground (or other) faults adversely affecting signals on the opposite connector. Using two edge connectors to control inputs to the transistors significantly increases the print head reliability in that functionality of at least some of the ink ejectors is retained, even if a group of other ink ejectors is disabled.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1A
is a block diagram of a printing system employing the present invention.
FIG. 1B
is a simplified block diagram of the functional organization of the elements of a print head employing the present invention.
FIG. 2A
is an isometric drawing of an exemplary printing apparatus employing the present invention.
FIG. 2B
is an isometric drawing of a print cartridge carriage apparatus employed in the printer of FIG.
2
A.
FIG. 2C
is a schematic representation of the functional elements of the printer of FIG.
2
A.
FIG. 3
is a magnified isometric cross section of an ink drop generator employed in the print cartridge print head of the printer of FIG.
2
A.
FIG. 4
is a schematic diagram of a single FET, heater resistor and electrical connections of the FET employed in a “primitive” switching device that can be employed in the present invention.
FIG. 5A
is a topographic view of a print head of the present invention.
FIG. 5B
is an enlarged view of one ink aperture and the placement of heater resistors proximate to the ink aperture.
FIG. 6A
shows a topographic view of a major surface of a three-color ink jet print head.
FIG. 6B
illustrates the address activation sequence.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
FIG. 1A
is a block diagram of a printing system incorporating the present invention. The printing system
10
can be used for printing on any suitable material, such as paper media, transfer media, transparency media, photographic paper and the like. In general, the printing system communicates with a host system
12
, which can be a computer or microprocessor that produces print data. The printing system
10
includes a printer assembly
14
, which controls the printing system, a print head assembly
16
that ejects ink and a print head assembly transport device
18
that positions the print head assembly
16
as required.
The printer assembly
14
also includes a controller
20
, a print media transport device
22
and a print media
24
. The print media transport device
22
positions the print media
24
(such as paper) according the control instructions received from the controller
20
. The controller
20
provides control to the print media transport device
22
, the print head assembly
16
and the print head assembly transport device
18
according to instructions received from various microprocessors within the printing system
10
. In addition, the controller
20
receives the print data from the host system
12
and processes the print data into printer control information and image data. This printer control information and image data is used by the controller
20
to control the print media transport device
18
, the print head assembly
16
and the print head assembly transport device
18
. For example, the print head assembly transport device
18
positions the print head
30
over the print media
24
and the print head
30
is instructed to eject ink drops according to the printer control information and image data.
The print head assembly
16
is preferably supported by a print head assembly transport device
18
that can position the print head assembly
16
over the print media
24
. Preferably, the print head assembly
16
is capable of overlying any area of the print media
24
using the combination of the print head assembly transport device
18
and the print media transport device
22
. For example, the print media
24
may be a rectangular sheet of paper and the print head assembly transport device
18
may position the paper in a media transport direction while the print head assembly transport device
18
may position the print head assembly
16
across the paper in a direction transverse to the media transport direction.
The print head assembly
16
includes an ink supply device
26
that is fluidically coupled to the print head
30
for selectively providing ink to the print head
30
. The print head
30
includes a plurality of ink drop delivery systems, such as an array of inkjet nozzles or drop generators. The ink jet nozzles are comprised of orifices through an orifice plate through which ink is ejected when the ink is heated to boiling. As discussed further below, each ink drop delivery system forms a printed image by ejecting droplets of ink onto the print media
24
according to instructions from the controller
20
.
FIG. 3
shows an isometric view of the top of a substrate
313
on which is formed a barrier layer
315
that is shaped to direct ink to flow through a passage
307
into an ink firing chamber
301
. At the “bottom” of the ink firing chamber
301
is a thin film heater resistor
309
that is covered by a protective dielectric layer (not shown). When current is forced through the heater resistor
309
, ink in the firing chamber
301
is boiled causing the ink to be expelled through an orifice
303
in the orifice plate or top plate
305
that is placed over the barrier layer
315
. By capillary action, ink is retained in the firing chamber
301
until electrical current to the heater resistor heats the ink. The electrical current through the heater resistor therefore determines when ink is ejected from the orifice
303
.
FIG. 1B
is a simplified block diagram depicting print head or substrate
30
of the present invention in greater detail. For the purposes of the illustrative example in
FIG. 1B
, element
30
may be considered to be a semiconductor substrate such as a silicon substrate that incorporates inkjet drop generators and associated circuitry. Alternatively, clement
30
can represent a combination of a rigid semiconductor substrate and a flexible circuit for carrying signals between a printing system and the drop generators on print head
30
.
Substrate
30
is divided into two regions,
30
-
1
and
30
-
2
. Alternate embodiments of the invention disclosed herein would of course include a substrate divided into more than two regions. Each region shown in
FIG. 1B
contains a set of primitives. Hereinafter, a “primitive” is comprised of a collection of transistors (FETs) that are turned on (and oft) by voltages applied to (or removed from) control lines coupled to the FETs. All of the FETs in a primitive typically have their drain (or source) terminals coupled to a common ground; all of these FETs typically have their sources (or drains) coupled to a power source through individual and corresponding thin film heater resistors on the surface of the substrate. The power is a “primitive select” signal on a “primitive select” line discussed below. Alternate embodiments would also include using unique grounds for the FETs. Each FET then has its gate coupled to an address line, the voltages of which control the FET individually. The FETs, heater resistors and “lines” to and from the FETs and external connection points (connectors) all are considered to be fabricated “on” the substrate
30
. The “lines” are typically comprised of conductive traces fabricated on the substrate using appropriate semiconductor fabrication techniques.
One of the control lines to the primitive is considered to be a primitive control line—not shown in
FIG. 1B
but shown in
FIG. 4
as the primitive select lead
404
. This primitive control line (
404
in
FIG. 4
) applies V+ (or ground) to the source or drain terminals of the FETs in a primitive (through the heater resistor
400
in FIG.
4
). The other control line of an FET in a primitive is an address line coupled to the FET's gate, identified in
FIG. 4
by reference numeral
406
. The gate of each FET of a primitive is coupled to a unique address line permitting the FETs of a primitive to be individually activated. When the primitive control line to a primitive is active (primitive select line
404
in
FIG. 4
) and an address line (
406
in
FIG. 4
) to a FET gate in the same primitive is active, that FET (
402
in
FIG. 4
) will carry current through the corresponding heater resistor (
400
in FIG.
4
), causing ink to be ejected from the print head.
The sequence of turning “on” and “off” the transistors is important. If a transistor is “on” and conducting current, and thereafter the address line on the gate is turned “off” prior to the primitive control line being turned “off” the transistor can be damaged by avalanche breakdown, as well as other semiconductor failures. In the preferred embodiment, the address line is turned “on” prior to the primitive control line being turned “on.” The address line should stay “on” until after the primitive control line has been turned off to avoid semiconductor failures.
FIG. 4
shows a single FET switching device
402
of a “primitive” and which acts to control current flow through a heater resistor
400
used to eject ink onto a print medium. The FET
402
of
FIG. 4
is but one transistor of several such devices that make up a “primitive.” Several such FETs would be coupled together sharing a common ground and having their source coupled to V+ through a corresponding heater resistor. The relative direction and/or source of current through an FET is a design choice. Alternate embodiments would of course include coupling the FET source directly to V+ with the FET drain coupled to ground through the heater resistor. Still other embodiments would include coupling the FET source to ground through the heater resistor and coupling the FET drain to a negative-polarity voltage.
The address lead
406
corresponds to (and is connected to) the FET gate. In the embodiment shown, power is applied to the FET primitive select lead
404
, which in turn is connected to the FET through the heater resistor
400
. The ground connection
403
provides the return path for current through the FET
402
such that when the gate is active and power is applied to the primitive select lead
404
, current flows through the resistor, through the FET to ground. Only when both the primitive select and the address line on the gate are both active will the current flow through the resistor, through the FET to ground.
In a print head “primitive,” which is a group of FETs coupled to a primitive select lead
404
through separate heater resistors
400
on the substrate, all of the FETs have power applied to them simultaneously. The FETs in the group are all connected to the common ground but each of the FETs in the group has its gate
406
coupled to an address line. Individual FETs in a group or “primitive” can be fired separately if the FET's primitive select lead
404
and gate
406
are active at the same time. Accordingly, a combination of a primitive select lead
404
and an address select lead (gate)
406
individually control each FET in a matrix fashion.
An ink jet print head can be made more reliable when the several primitives on an ink jet print head substrate (which surround or are proximate to an ink aperture) are organized into groups or clusters and when these groups of primitives are addressed by electrically separate address and primitive control lines. In the preferred embodiment, the primitives on a substrate are divided in half along a line transverse to the ink aperture. Primitives on one side of this line are addressed by one address bus; primitives on the other side are addressed by a different address bus. A fault on one address bus will therefore not affect primitives controlled by the other address bus.
Although the depiction of
FIG. 1B
shows only two primitives per region, alternate embodiments would include virtually any number of primitives on a substrate. Moreover, the primitives might be organized into more than two groups. Three or more groups might be controlled by three electrically separate address busses.
Each primitive shown in
FIG. 1B
(P
1
-P
1
′) includes a plurality of heater resistors, also known in the art as drop generators D or D′, and associated multiplexing circuitry M or M′, including the FETs described above. The multiplexing circuitry receives signals from a plurality of power or primitive select or primitive control lines (not shown in
FIG. 1B
) and address select lines A or A′. The primitive control lines and the address lines together actuate the drop generators D or D′ by firing the FETs, the current of which acts to eject droplets of ink during a printing operation. In order to properly activate a particular drop generator, a combination of a primitive select lines and an address select lines that is unique to that drop generator must be activated. A primitive select line connects to the source/drain of each transistor by way of the drop generator within the primitive associated with the primitive select line. An address select line
32
or
32
′ connects to the gate of one transistor in each of the primitives within region
30
-
1
or
30
-
2
.
It is well known in the art that the gate of an FET can control when the device conducts. Alternate embodiments of the invention would include using other types of three-terminal current switching elements besides FETs including, but not limited to devices such as bi-polar transistors, SCRs, TRIACs and the like. In the case of a bi-polar transistor for example, controlling the base voltage would control when the device conducts.
FIG. 6A
is a schematic plan view of a major surface of a three-color print head. In operation, yellow, magenta and cyan inks would flow upward, i.e. out of, the plane of the FIG.
6
A through the ink apertures
670
,
672
and
674
into firing chambers (shown in
FIG. 3
) distributed along both sides of the ink apertures
670
,
672
and
674
. Shaded, rectangular areas on opposite sides of the ink apertures (
602
,
604
,
606
,
608
,
610
,
612
,
614
,
615
,
616
,
618
,
620
, and
622
) denote primitives. (Not shown in
FIG. 6A
, but existent in a preferred embodiment are twelve (12) additional primitives, each of which is adjacent to the enumerated primitives that are shown and the ink apertures, so as to provide a total of 24 primitives on the substrate. Each of the ink apertures therefore has eight primitives adjacent to it. Each of the eight primitives is comprised of 18 transistors) As shown, the ink aperture
670
has four primitives
602
,
604
,
615
and
616
that are located about the ink aperture
670
. One primitive,
615
, schematically depicts the several FETs and heater resistors connected to them, proximate to one end and adjacent to one side of the ink aperture
670
.
Each of the FETs of the primitive
615
is coupled to a ground bus
630
represented by a heavy line that can be seen on each of the primitive areas shown in the figure (
602
,
604
,
606
,
608
,
610
,
612
,
614
,
615
,
616
,
618
,
620
, and
622
).
A first address bus
640
is comprised of several conductors (individual conductors not shown), at least one of which is extended to each gate of each FET in the first set of primitives shown (
614
,
615
,
616
,
618
,
620
, and
622
) in the upper or top portion of the substrate
600
shown in
FIG. 6A. A
second address bus
650
is comprised of several conductors (individual conductors not shown) at least one of which is extended to each gate of each FET in the primitives shown (
602
,
604
,
606
,
608
,
610
,
612
) of a second set of primitives along the lower portion of the substrate
600
shown in FIG.
6
A. The first and second address busses
640
and
650
are electrically isolated from each other but are accessible from the connectors
660
and
662
on the edges of the substrate
600
.
In the preferred embodiment, each FET of a primitive has its gate terminal coupled to an address line
642
. There are therefore a number of address lines “N” in an address bus
640
,
650
that is equal to the number of drop generators (and FETs) in each of the primitives shown (
602
,
604
,
606
,
608
,
610
,
612
,
614
,
615
,
616
,
618
,
620
, and
622
). The address lines to the gates of the FETs of one set of primitives shown (
602
,
604
,
606
,
608
,
610
,
612
) are electrically isolated from the gates of the FETs of the other set of primitives shown (
614
,
615
,
616
,
618
,
620
, and
622
). (In an alternate embodiment, the two sets of address lines may be indirectly or directly coupled together.) The FETs in any set of primitives will not fire if those FETs are deactivated by their corresponding primitive control lines, depicted in
FIG. 6A
as the “P” lines
690
. The address lines are therefore effectively multiplexed to reduce the number of address lines needed to control numerous transistors in several primitives while allowing for individual selectability (addressability) of the drop generators. The only exception to this would be if one or more truncated primitives P (with less than N drop generators) is utilized. During a printing operation, the printing system cycles through the address lines such that only one of the address lines A
1
through AN is activated at a time. (See
FIG. 6B.
) Thus, within a primitive, only one drop generator can be activated at a time. However, all of the drop generators in the various primitives associated with a particular address can be fired simultaneously.
Referring back to
FIG. 1B
, each of the two regions
30
-
1
and
30
-
2
has its own set of separate address lines that control the firing of FETs in the corresponding region and which are preferably electrically isolated from each other so as to avoid a fault on one line affecting all of the primitives that it is connected to. Thus, region
30
-
1
has a first set of address lines A
1
, A
2
, . . . , AN, terminating on the substrate in a set of address pads
32
. Region
30
-
2
has a second set of addresses A
1
′, A
2
′, . . . , AN′, separate from the first set and terminating in a separate set of address pads
32
′.
As suggested earlier, one embodiment of print head
30
may be a combination of a silicon substrate and a flexible substrate.
In a first embodiment, the address pads
32
represent flexible circuit connections that connect to electronics in the printer assembly
14
when the print head assembly
16
is installed into printer assembly
14
. Alternatively, in a second embodiment, the address pads
32
represent the bond pads on a silicon substrate. Intermediary circuitry such as a flexible circuit can be used to connect the bond pads to circuitry in printer assembly
14
. One method for connection to such bond pads is known in the art as TAB bonding, or tape automated bonding.
In a third embodiment, the number of addresses A
1
, A
2
, . . . , AN in region
30
-
1
is equal to the number of addresses A
1
′, A
2
′, . . . , AN′ in region
30
-
2
(although alternate embodiments would include using different numbers of address lines in each region.) In the third embodiment, jumpers or conductive traces on print head
30
or a flexible circuit attached to the print head
30
electrically connect the address A
1
to address A
1
′ address A
2
to address A
2
′, . . . , address AN to AN′, etc. Thus, whenever address A is activated in section
30
-
1
, a corresponding address A′ is activated in section
30
-
2
. By providing these separate connections for each address pair A and A′, the crucial address connections are maintained even if a connection to one of them is lost. This assures that the proper signals are provided to print head
30
even if one of the address connections to print head
30
is lost.
In a fourth embodiment, the addresses in the sections
30
-
1
and
30
-
2
are electrically isolated. This allows the printer assembly to operate the print head in two modes. The printer can activate pairs of addresses A and A′ simultaneously, allowing for a higher printer speed. One way to do this is might include having the printer assembly circuitry electrically couple the address lines in pairs. Alternatively, the printer can operate the addresses A and A′ independently while combining primitives between region
30
-
1
and
30
-
2
in pairs. This lowers printer cost, but sacrifices speed.
An exemplary inkjet printing apparatus, a printer
101
, that may employ the present invention is shown in outline form in the isometric drawing of FIG.
2
A. Printing devices such as graphics plotters, copiers, and facsimile machines may also profitably employ the present invention. A printer housing
103
contains a printing platen to which an input print medium
105
, such as paper, is transported by mechanisms that are known in the art. A carriage within the printer
101
holds one or a set of individual print cartridges capable of ejecting ink drops of black or color ink. Alternative embodiments can include a semi-permanent print head mechanism that is sporadically replenished from one or more fluidically-coupled off-axis ink reservoirs, or a single print cartridge having two or more colors of ink available within the print cartridge and ink ejecting nozzles designated for each color, or a single color print cartridge or print mechanism; the present invention is applicable to a print head employed by at least these alternatives. A carriage
109
, which may be employed in the present invention and mounts two print cartridges
110
and
111
, is illustrated in FIG.
2
B. The carriage
109
is typically supported by a slide bar or similar mechanism within the printer and physically propelled along the slide bar to allow the carriage
109
to be translationally reciprocated or scanned back and forth across the print medium
105
. The scan axis, X, is indicated by an arrow in FIG.
2
A. As the carriage
109
scans, ink drops are selectively ejected from the print heads of the set of print cartridges
110
and
111
onto the medium
105
in predetermined print swatch patterns, forming images or alphanumeric characters using dot matrix manipulation. Conventionally, the dot matrix manipulation is determined by a user's computer (not shown) and instructions are transmitted to a microprocessor-based, electronic controller within the printer
101
. Other techniques of dot matrix manipulation are accomplished by the computer's rasterizing the data then sending the rasterized data as well as print commands to the printer. The printer interprets the commands and rasterized information to determine which drop generators to fire.
As can be seen in
FIG. 2C
, a single medium sheet is advanced from an input tray into a printer print area beneath the print heads by a medium advancing mechanism including a roller
207
, a platen motor
209
, and traction devices (not shown). In a preferred embodiment, the inkjet print cartridges
110
,
111
are incrementally drawn across the medium
105
on the platen by a carriage motor
211
in the X direction, perpendicular to the Y direction of entry of the medium. The platen motor
209
and the carriage motor
211
are typically under the control of a media and cartridge position controller
213
. An example of such positioning and control apparatus may be found described in U.S. Pat. No. 5,070,410 “Apparatus and Method Using a Combined Read/Write Head for Processing and Storing Read Signals and for Providing Firing Signals to Thermally Actuated Ink Ejection Elements”. Thus, the medium
105
is positioned in a location so that the print cartridges
110
and
111
may eject drops of ink to place dots on the medium as required by the data that is input to a drop firing controller
215
and power supply
217
of the printer. These dots of ink are formed from the ink drops expelled from the selected orifices in the print head in a band parallel to the scan direction as the print cartridges
110
and
111
are translated across the medium by the carriage motor
211
. When the print cartridges
110
and
111
reach the end of their travel at an end of a print swath on the medium
105
, the medium is conventionally incrementally advanced by the position controller
213
and the platen motor
209
. Once the print cartridges have reached the end of their traverse in the X direction on the slide bar, they are either returned back along the support mechanism while continuing to print or returned without printing. The medium may be advanced by an incremental amount equivalent to the width of the ink ejecting portion of the print head or some fraction thereof related to the spacing between the nozzles. Control of the medium, positioning of the print cartridge, and selection of the correct ink ejectors for creation of an ink image or character is determined by the position controller
213
. The controller may be implemented in a conventional electronic hardware configuration and provided operating instructions from conventional memory
216
. Once printing of the medium is complete, the medium is ejected into an output tray of the printer for user removal.
A single example of an ink drop generator found within a print head is illustrated in the magnified isometric cross section of FIG.
3
. As depicted, the drop generator comprises a nozzle, a firing chamber, and an ink ejector. Alternative embodiments of a drop generator employ more than one coordinated nozzle, firing chamber, and/or ink ejectors. The drop generator is fluidically coupled to a source of ink.
In
FIG. 3
, the preferred embodiment of an ink firing chamber
301
is shown in correspondence with a nozzle
303
and a segmented heater resistor or firing resistor
309
. Many independent nozzles are typically arranged in a predetermined pattern on the orifice plate
305
so that the ink drops are expelled in a controlled pattern. Generally, the medium is maintained in a position which is parallel to the plane of the external surface of the orifice plate. The heater resistors are selected for activation in a process that involves the data input from an external computer or other data source coupled to the printer in association with the drop firing controller
215
and power supply
217
. Ink is supplied to the firing chamber
301
via opening
307
to replenish ink that has been expelled from orifice
303
following the creation of an ink vapor bubble by heat energy released from the segmented heater resistor
309
. The ink firing chamber
301
is bounded by walls created by the orifice plate
305
, a layered semiconductor substrate
313
, and barrier layer
315
. In a preferred embodiment, fluid ink stored in a reservoir of the cartridge housing flows by capillary force to fill the firing chamber
301
.
A more-reliable ink jet print head of the present invention includes a substrate that supports heater resistors that provide heat pulses for ejecting droplets of ink onto a medium. As depicted schematically by
FIG. 4
, each heater resistor
400
is individually controlled by a separate switching device
402
, which is preferably a field effect transistor, or FET. Each switching device
402
has a primitive select lead
404
for transmitting power, and an address select lead
406
for opening and closing the switching device
402
through the FET gate to allow current to flow through the resistor
400
. Thus, in order to heat a particular resistor
400
, the particular resistor's associated switching device
402
must have its primitive lead
404
and address lead
406
active concurrently.
In the print head of the present invention, the resistors and associated FETs coupled to the resistors are arranged into groupings called primitives. There are several primitives on each substrate. Each primitive has a separate single primitive select lead that provides power to all of the resistors in the primitive. Each primitive has a ground lcad coupled to the ground connections of every switching device in the primitive. To reduce the required number of connections required to connect to the substrate, the same ground lead can be coupled to multiple primitives.
Each switching device (FET or other transistor device) within a particular primitive is coupled to an independent or separately energizable address select lead. During operation, the address leads are actuated one at a time in a sequence such that only a single switching device in a primitive is actuated at a time. To reduce the required number of connections to the substrate, address lines are shared between primitives.
The substrate of the present invention is divided into various topographic regions that each contain at least one primitive. Within each region, the address lines are shared; each primitive has its own unique primitive select line. Alternate embodiments however might provide each region on the die with its own separate set of address lines.
A schematic diagram of the present invention is illustrated in
FIG. 5A. A
substrate
500
has three ink feed slots or ink apertures
502
through which ink from an ink reservoir feeds to firing resistors adjacent to the feed slots. Alternate embodiments would include substrates providing only a single-color aperture or other colors as well. There are three ink feed slots, one slot
502
Y providing yellow, one slot
502
M providing magenta, and one slot
502
C providing cyan ink to the resistors. (The yellow feed slot
502
Y, shown greatly enlarged along with a few firing resistors numbered 1-5, is depicted in
FIG. 5B
) The resistors are arranged into 24 primitives along the feed slots
502
, indicated in the figure by the numbers 1-24. For example, along the ink feed slot providing yellow ink, primitives 2, 4, 6, and 8 are arranged along one side of the feed slot, and primitives 1, 3, 5, and 7 are arranged along an opposing edge of the feed slot
502
Y.
In the preferred embodiment, each primitive includes 18 firing resistors (with each coupled to a separate current-controlling FET) with a single primitive select line shared between the 18 resistors within each primitive. Alternate embodiments would of course include larger as well as smaller numbers of firing resistors and transistors per primitive. Thus, for the substrate of the present invention, there are 24 independent primitive select lines PS
1
to PS
24
(only PS
4
and PS
2
shown) corresponding to the 24 primitives.
Each primitive select line routes to a connector pad located along one of two outer edges
504
N or
504
S of the substrate. In order for each resistor within a particular primitive to be separately energized, each resistor is connected to a current-controlling transistor, each having a separate address line (not shown).
During a printing operation, the printer cycles through the addresses as depicted in
FIG. 6B
such that only a single one of the 18 firing resistors within a particular primitive is operated at a time, i.e. sequentially. However, resistors in different primitives may be operated simultaneously. For this reason, and to minimize a number of contacts required, primitives share address lines. Thus, for a given set of primitives sharing address lines, there are 18 address lines to allow for independent operation of addresses for a particular primitive.
To improve reliability and to allow multiple modes of operation, the primitives of the substrate are segregated into groups. One group of primitives is addressed by a first set of address lines for the primitives in the group. A second group of primitives is addressed by a separate set of address lines for the second group. The two groups of primitives are divided into regions that are designated as north
500
N and south
500
S for purposes of identification. In this example, half of the primitives are contained in region
500
N closest to substrate edge
504
N. The other half of the primitives are contained in region
500
S closest to the substrate edge
504
S. Alternate embodiments include dividing the primitives in uneven groups spread across the substrate in any ratio.
One set of 18 address select lines, referred to as A
1
N, A
2
N, . . . , A
18
N, provide address select signals to the switching devices in the region
500
N. Another set of 18 address select lines, referred to as A
1
S, A
2
S, . . . A
18
S provide address select signals to the switching devices in the region
500
S.
Providing separate north and south (or upper and lower) address leads to the transistors in the primitives in the north and south regions provides several benefits. First, the susceptibility to losing an address connection is reduced by one half. Second, by having independent sets of address leads for the separate groups of primitives, multiple firing modes are enabled for the same print head. As discussed before, print heads are operated by cycling through address lines as is indicated by FIG.
6
B. By having north and south primitives, the print head can be operated as having either 24 or having 12 primitives.
Address pairs of the north and south groups can be electrically or functionally “tied” together by appropriate circuitry so that combinations of transistors in any combination of groups can be fired together. In one such embodiment, each time a particular north address is activated (for example A
1
N), the corresponding south address is simultaneously activated (for example, A
1
S). This can be done by making A
1
N electrically common with A
1
S, A
2
N electrically common with A
2
S, etc. using any appropriate circuitry. This allows for higher speed or higher frequency printing, because it takes less time to cycle through the addresses (again view FIG.
6
B).
On the other hand, the print head can also be operated as having 12 primitives. This can be done by serially cycling through all of the south addresses and then all of the north addresses. Although slower, this provides the opportunity to make pairs of primitive select lines electrically common but keeping the address lines electrically isolated. This reduces the cost of the switching electronics required to energize the primitives, reducing the cost of the printing system.
Claims
- 1. An ink jet print head comprising:a substrate having a first major surface through which extends an ink aperture and on which is formed: a first primitive, said first primitive being comprised of a first set of current-controlling transistors, a first terminal of each transistor of said first set being coupled to at least one address line in a first set of address lines; a second primitive, said second primitive being comprised of a second set of current-controlling transistors, a first terminal of each transistor of said second set being coupled to at least one address line in a second set of address lines, said second set of address lines being electrically isolated from said first set of address lines; whereby each transistor in said first primitive can be activated independently of each transistor in that said second primitive by way of control signals on at least one address line of said first and second set of address lines.
- 2. The ink jet print head of claim 1 further comprising at least a third primitive, comprised of a third set of current-controlling transistors, a first terminal of each transistor of said third set of transistors being coupled to at least one address line of either of said first or second sets of address lines.
- 3. The ink jet print head of claim 1 further comprising at least one primitive control line for each primitive, said at least one primitive control line being coupled to a second terminal of each transistor of the respective primitive, said primitive control line applying a voltage of a predetermined magnitude and polarity.
- 4. The ink jet print head of claim 3 wherein said primitive control line applies a positive-polarity voltage to said second terminals of substantially each transistor of the corresponding primitive.
- 5. The ink jet print head of claim 3 wherein said primitive control line applies a predetermined voltage to said second terminal through a resistance.
- 6. The ink jet print head of claim 3 wherein said primitive control applies ground potential to said second terminals of each transistor of the respective primitive.
- 7. The ink jet print head of claim 1 wherein each transistor of both said first set and said second set of current-controlling transistors is a field-effect transistor (FET) and wherein said at least one terminal of each transistor of both said first set and said second set of current-controlling transistors is the FET gate.
- 8. The ink jet print head of claim 1 wherein each transistor of both said first set and said second set of current-controlling transistors is a bi-polar transistor and wherein said at least one terminal of each transistor of both said first set and said second said of current-controlling transistors is the transistor base.
- 9. The ink jet print head of claim 1 wherein each transistor of both said first set and said second set of current-controlling transistors is a triac or SCR.
- 10. The ink jet print head of claim 1 further including a plurality of address pads on said substrate.
- 11. The ink jet print head of claim 10 wherein said plurality of address pads on said substrate are formed using tape automated bonding.
- 12. The ink jet print head of claim 1 wherein a first transistor in said first set of current-controlling transistors and a second transistor in said second set of current controlling transistors are fired substantially simultaneously.
- 13. The ink jet print head of claim 1 wherein a first transistor in said first set of current-controlling transistors and a second transistor in said second set of current controlling transistors are fired sequentially.
- 14. An ink jet print head comprising:a substrate having an ink aperture through which ink from an ink reservoir flows to ink energizing elements; a first set of primitives, each primitive of said first set of primitives being comprised of a set of current-controlling transistors, a first terminal of each current-controlling transistor being coupled to an associated ink energizing element, a second terminal of each transistor being coupled to ground and a third terminal of each transistor being coupled to a predetermined address line in a first set of address lines; a second set of primitives, each primitive of said second set of primitives being comprised of a set of current-controlling transistors, a first terminal of each current-controlling transistor being coupled to an associated ink energizing element, a second terminal of each transistor being coupled to ground and a third terminal of each transistor being coupled to a predetermined address line in a second set of address lines, said first set of address lines being electrically isolated from said second set of address lines.
- 15. An ink jet print cartridge comprising:an ink reservoir; a substrate, having a first major surface that includes therein an ink aperture through which ink flows from said ink reservoir to a plurality of ink energizing elements; a first primitive comprised of a plurality of three-terminal current controlling elements on said substrate, a first terminal of each three-terminal current controlling element of said first primitive being electrically coupled to an associated ink energizing element on said substrate, a second terminal of each three-terminal current controlling clement being coupled to a first primitive control line and a third terminal of each three terminal current controlling element being coupled to an associated address line of a first set of address lines; a second primitive comprised of a plurality of three-terminal current controlling elements on said substrate, a first terminal of each three-terminal current controlling element of said second primitive being electrically coupled to an associated ink energizing element on said substrate, a second terminal of each three-terminal current controlling element being coupled to a second primitive control line and a third terminal of each three terminal current controlling element being coupled to an associated address line of a second set of address lines, said second primitive and said second set of address lines being electrically isolated from said first primitive and said first set of address lines; an orifice plate substantially covering said intc energizing elements and said primitives, said orifice plate having a plurality of openings through which ink is expelled; an electrical interface for coupling electrical control signals to said three-terminal current controlling elements from an external controller for said cartridge.
- 16. The inkjet print cartridge of claim 15 wherein said ink energizing elements are resistors.
- 17. The ink jet print cartridge of claim 15 wherein said substrate includes first and second edge connectors mounted on first and second edges, said first set of address lines being operatively coupled to said first edge connector and said second set of address lines being operatively coupled to said second edge connector.
- 18. The ink jet print cartridge of claim 15 further including wherein said first primitive control line is coupled to said first edge connector and said second primitive control line is coupled to said second edge connector.
- 19. An ink jet print head comprising:a substrate having an ink aperture through which ink from an ink reservoir flows to ink energizing elements; a plurality of primitives, each of which is physically adjacent to said ink aperture on said substrate, said plurality of primitives being subdivided into: a first subset of primitives, each primitive of said first subset of primitives being comprised of a set of current-controlling transistors, a first terminal of each current-controlling transistor being coupled to an associated ink energizing element, a second terminal of each transistor being coupled to ground and the third terminal of each transistor being coupled to a predetermined address line in a first set of address lines; a second subset of primitives, each primitive of said second subset of primitives being comprised of a set of current-controlling transistors, a first terminal of each current-controlling transistor being coupled to an associated ink energizing element, a second terminal of each transistor being coupled to ground and the third terminal of each transistor being coupled to a predetermined address line in a second set of address lines, said first set of primitives and said first set of address lines being electrically isolated from said second set of primitives and said second set of address lines.
- 20. An inkjet printing apparatus comprising:a printer housing; a platen; an input medium; at least one print cartridge having: a substrate including a first region and second region; a first set of primitives within said first region and a second set of primitives electrically isolated from said first set of primitives, within said second region, each primitive of said first and second sets of primitives comprising a plurality of electrically isolated resistors and associated multiplexing circuitry, the multiplexing circuitry directing electrical current through the resistors; and a first set of address conductors electrically coupled only to the multiplexing circuitry in the first region and a second set of address conductors electrically coupled only to the multiplexing circuitry in the second region, said first and second sets of address conductors extending to first and second sets of contacts pads on said substrate.
- 21. The inkjet printing apparatus of claim 20 further comprising: an ink feed slot through said substrate and at least partially extending through said first and second regions.
- 22. The inkjet printing apparatus of claim 20 wherein the number of address leads in each of said first and second sets of address conductors corresponds to the number of transistors in at least some of the primitives.
- 23. The inkjet printing apparatus of claim 20 wherein the number of address lines coupled to at least one of the primitives is at least as great as the number of transistors in said primitive.
- 24. The inkjet printing apparatus of claim 20 wherein said first and second sets of address conductors extending to first and second sets of contacts pads on said substrate are located on first and second edges of said substrate.
- 25. A printer comprised of:a controller; a print media transport; a print head assembly comprised of: a substrate having a first major surface through which extends an ink aperture and on which is formed: a first primitive, said first primitive being comprised of a first set of current-controlling transistors, a first terminal of each transistor of said first set being coupled to at least one address line in a first set of address lines; a second primitive, electrically isolated from said first primitive, said second primitive being comprised of a second set of current-controlling transistors, a first terminal of each transistor of said second set being coupled to at least one address line in a second set of address lines, said second set of address lines being electrically isolated from said first set of address lines; whereby each transistor in said first primitive can be activated independently of each transistor in that said second primitive by way of control signals on at least one address line of said first and second set of address lines.
US Referenced Citations (7)