Title of Invention

METHOD AND APPARATUS FOR EJECTING INK

Abstract The invention relates to an inkjet printhead having a plurality of drop generators responsive to drive current and address signals for dispensing ink, the inkjet printhead comprising a plurality of subgroups of at least first and second drop generators (42, 42') disposed on the printhead (24) that together form a group of drop generators with each drop generator (42, 42') of the group of drop generators configured for connection to a drive current source (P1 - P16) wherein within each subgroup, the first and second drop generators (42) are configured to receive address signals (A1 - A13) from a common address source, and wherein each subgroup of at least first and second drop generators (42) is configured for connection to a different source of address signals; and a first switching device (48) connected between the common address source (46) and each of the first and second drop generators (42) of a subgroup, the switching device (48) responsive to enable signals for selectively providing the address signal to only one of the first and second drop generators (42) of the subgroup.
Full Text METHOD AND APPARATUS FOR EJECTING INK
BACKGROUND OF THE INVENTION
This invention relates to inkjet printing devices, and more particularly to an
inkjet printing device that includes a printhead portion that receives drop activation
signals for selectively ejecting ink.
Inkjet printing systems frequently make use of an inkjet printhead mounted to
a carriage which is moved back and forth across print media such as paper. As the
printhead is moved across the print media, a control device selectively activates each
of a plurality of drop generators within me printhead to eject or deposit ink droplets
onto the print media to form images and text characters. An ink supply that is either
carried with the printhead or remote from the printhead provides ink for replenishing
the plurality of drop generators.
Individual drop generators are selectively activated by the use of an activation
signal that is provided by the printing system to the printhead. In the case of thermal
inkjet printing, each drop generator is activated by passing an electric current through
a resistive element such as a resistor. In response to the electric current the resistor
produces heat, that in turn, heats ink in a vaporization chamber adjacent the resistor.
Once the ink reaches vaporization, a rapidly expanding vapor front forces ink within
the vaporization chamber through an adjacent orifice or nozzle. Ink droplets ejected
from the nozzles are deposited on print media to accomplish printing.
The electric current is frequently provided to individual resistors or drop
generators by a switching device such as a field effect transistor (FET). The
switching device is activated by a control signal that is provided to the control
terminal of the switching device. Once activated the switching device enables the
electric current to pass to the selected resistor. The electric current or drive current
provided to each resistor is sometimes referred to as a drive current signal. The
control signal for selectively activating the switching device associated with each
resistor is sometimes referred to as an address signal.
In one previously used arrangement, a switching transistor is connected in
series with each resistor. When active, the switching transistor allows a drive current
to pass through each of the resistor and switching transistor. The resistor and
switching transistor together form a drop generator. A plurality of these drop
generators are then arranged in a logical two-dimensional array of drop generators
having rows and columns. Each column of drop generators in the array are connected
to a different source of drive current and with each drop generator within each column
connected in a parallel connection between the source of drive current for that
column. Each row of drop generators within the array is connected to a different
address signal with each drop generator within each row connected to a common
source of address signals for that row of drop generators. In this manner, any
individual drop generator within the two-dimensional array of drop generators can be
individually activated by activating the address signal corresponding to the drop
generator of row and providing drive current from the source of drive current
associated with the drop generator column. In this manner, the number of electrical
interconnects required for the printhead is greatly reduced over providing drive and
control signals for each individual drop generator associated with the printhead.
While the row and column addressing scheme previously discussed is capable
of being implemented in relatively simple and relatively inexpensive technology
tending to reduce printhead manufacturing costs, this technique suffers from the
disadvantage of requiring relatively large number of bond pads for printheads having
large numbers of drop generators. For printheads having in excess of three hundred
drop generators, a number of bond pads tend to become a limiting factor when
attempting to minimize the die size.
Another technique that has been previously been used makes use of
transferring activation information to the printhead in a serial format. This drop
generator activation information is rearranged using shift registers so that the proper
drop generators can be activated. This technique, while greatly reducing the number
of electrical interconnects, tends to require various logic functions as well as static
memory elements. Printheads having various logic functions and memory elements
require suitable technologies such as CMOS technology and tend to require a constant
power supply. Printheads formed using CMOS technology, which tend to be more
costly to manufacturer than printheads using NMOS technology. The CMOS
manufacturing process is a more complex manufacturing process than the NMOS
manufacturing process that requires more masking steps that tend to increase the costs
of the printhead. In addition, the requirement of a constant power supply tends to
increase the cost of the printing device that must supply this constant power supply
voltage to the printhead.
There is an ever present need for inkjet printheads that have fewer electrical
interconnects between the printhead and the printing device thereby tending to reduce
the overall costs of the printing system as well as the printhead itself. These
printheads should be capable of being manufactured using a relatively inexpensive
manufacturing technology that allows the printheads to be manufactured using high
volume manufacturing techniques and have relatively low manufacturing costs.
These printheads should allow information to be transferred between die printing
device and the printhead in a reliable manner thereby allowing high print quality as
well as reliable operation. Finally, these printheads should be capable of supporting
large numbers of drop generators to provide printing systems that are capable of
providing high print rates.
SUMMARY OF THE INVENTION
One aspect of the present invention is an inkjet prinuiead having a plurality of
drop generators responsive to drive current and address signals for dispensing ink.
The inkjet printhead includes first and second drop generators disposed on the
prinuiead with each of the first and second drop generators configured to receive
drive current from a drive current source. Each of die first and second drop
generators is configured to receive address signals from a common address source.
The inkjet printhead further includes a switching device connected between the
common address source and each of the first and second drop generators. The
switching device is responsive to enable signals for selectively providing the address
signal to only one of the first and second drop generators.
Another aspect of die present invention is that the first drop generator includes
a first switching device connected between the source of drive current. The first
switching device is responsive to address active signals for selectively activating the
first drop generator. Included with the second drop generator is a second switching
device connected between the source of drive current. The second switching device is
responsive to address active signals for selectively activating the second drop
generator.
Yet another aspect of the present invention is that the switching device
includes a third and fourth switching device. The third switching device is connected
between the source of address signals and the first switching device and the fourth
switching device is connected between the source of address signals and the second
switching device. The third switching device is responsive to enable signals for
selectively providing address signals to the first switching device. The fourth
switching device is responsive to enable signals for selectively providing address
signals to the second switching device.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Fig. 1 depicts a printing system of the present invention that incorporates an
inkjet print cartridge of the present invention for accomplishing printing on print
media shown in a top perspective view.
Fig. 2 depicts the inkjet print cartridge shown in Fig. 1 in isolation and viewed
from a bottom perspective view.
Fig. 3 is a simplified block diagram of the printing system shown in Fig. 1 that
includes a printer portion and a printhead portion.
Fig. 4 is a block diagram showing further detail of one preferred embodiment
of a print control device associated with the printer portion and the printhead shown
with 16 groups of drop generators.
Fig. 5 is a block diagram showing further detail of one group of drop
generators having 26 individual drop generators.
Fig. 6 is a schematic diagram showing further detail of one preferred
embodiment of one individual drop generator of the present invention.
Fig. 7 is a schematic diagram showing two individual drop generators for the
printhead of the present invention shown in Fig. 5.
Fig. 8 is a timing diagram for operating the printhead of the present invention
shown in Fig. 4.
Fig. 9 is an alternative timing diagram for operating the printhead of the
present invention shown in Fig. 4.
Fig. 10 is a detailed view of the timing for timeslots 1 and 2 of the timing
diagram shown in Fig. 8.
Fig. 11 is a detailed view of the timing for timeslots 1 and 2 of the alternative
timing diagram shown in Fig. 9.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Fig. 1 is a perspective view of one exemplary embodiment of an inkjet
printing system 10 of the present invention shown with its cover open. The inkjet
printing system 10 includes a printer portion 12 having at least one print cartridge 14
and 16 installed in a scanning carriage 18. The printing portion 12 includes a media
tray 20 for receiving media 22. As the print media 22 is stepped through a print zone,
the scanning carriage 18 moves the print cartridges 14 and 16 across the print media. '
The printer portion 12 selectively activates drop generators, within a printhead portion
(not shown) associated with each of the print cartridges 14 and 16 to deposit ink on
the print media to thereby accomplish printing.
An important aspect of the present invention is a method for which the printer
portion 12 transfers drop generator activation information to the print cartridges 14
and 16. This drop generator activation information is used by the printhead portion to
activate drop generators as the print cartridges 14 and 16 are moved relative to the
print media. Another aspect of the present invention is the printhead portion that
makes use of the information provided by the printer portion 12. The method and
apparatus of the present invention allows information to be passed between the printer
portion 12 and the printhead with relatively few interconnects thereby tending to
reduce the size of the printhead. In addition the method and apparatus of the present
invention allows the printhead to be implemented without requiring clocked storage
elements or complex logic functions thereby reducing the manufacturing costs of the
printhead. The method and apparatus of the present invention will be discussed in
more detail with respect to Figs. 3-11.
Fig. 2 depicts a bottom perspective view of one preferred embodiment of the
print cartridge 14 shown in Fig. 1. In the preferred embodiment, the cartridge 14 is a
3 color cartridge containing cyan, magenta, and yellow inks. In this preferred
embodiment, a separate print cartridge 16 is provided for black ink. The present
invention will herein be described with respect to this preferred embodiment by way
of example only. There are numerous other configurations in which the method and
apparatus of the present invention is also suitable. For example, the present invention
is also suited to configurations wherein the printing system contains separate print
cartridges for each color of ink used in printing. Alternatively, the present invention
is applicable to printing systems wherein more than 4 ink colors are used such as in
high-fidelity printing wherein 6 or more ink colors are used. Finally, the present
invention is applicable to various types of print cartridges such as print cartridges
which include an ink reservoir as shown in Fig. 2, or for print cartridges which are
replenished with ink from a remote source of ink, either continuously or
intermittently.
The ink cartridge 14 shown in Fig. 2 includes a printhead portion 24 that is
responsive to activation signals from the printing system 12 for selectively depositing
ink on media 22. In the preferred embodiment, the printhead 24 is defined on a
substrate such as silicon. The printhead 24 is mounted to a cartridge body 25. The
print cartridge 14 includes a plurality of electrical contacts 26 that are disposed and
arranged on the cartridge body 25 so that when properly inserted into the scanning
carriage, electrical contact is established between corresponding electrical contacts
(not shown) associated with the printer portion 12. Each of the electrical contacts 26
is electrically connected to the printhead 24 by each of a plurality of electrical
conductors (not shown). In this manner, activation signals from the printer portion 12
are provided to the inkjet printhead 24.
In the preferred embodiment, the electrical contacts 26 are defined in a
flexible circuit 28. The flexible circuit 28 includes an insulating material such as
polyimide and a conductive material such as copper. Conductors are defined within
the flexible circuit to electrically connect each of the electrical contacts 26 to
electrical contacts defined on the printhead 24. The printhead 24 is mounted and
electrically connected to the flexible circuit 28 using a suitable technique such as tape
automated bonding (TAB).
In the exemplary embodiment shown in Fig. 2, the print cartridge is a 3 color
cartridge containing yellow, magenta, and cyan inks within a corresponding reservoir
portion. The printhead 24 includes drop ejection portions 30, 32 and 34 for ejecting
ink corresponding, respectively, to yellow, magenta, and cyan inks. The electrical
contacts 26 include electrical contacts associated with activation signals for each of
the yellow, magenta, and cyan drop generators 30,32, 34, respectively.
In the preferred embodiment, the black ink cartridge 16 shown in Fig. 1 is
similar to the color cartridge 14 shown in Fig. 2 except the black cartridge makes use
of two drop ejection portions instead of three shown on the color cartridge 14. The
method and apparatus of the present invention will be discussed herein with respect to
the black cartridge 16. However, the method and apparatus of the present invention is
applicable to the color cartridge 14 as well.
Fig. 3 depicts a simplified electrical block diagram of the printer portion 12
and one of the print cartridges 16. The printer portion 12 includes a print control
device 36, a media transport device 38 and a carriage transport device 40. The print
control device 36 provides control signals to the media transport device 38 to pass the
media 22 through a print zone whereupon ink is deposited on the print media 22. In
addition, the print control device 36 provides control signals for selectively moving
the scanning carriage 18 across the media 22, thereby defining a print zone. As the
media 22 is stepped past the printhead 24 or through the print zone the scanning
carriage 18 is scanned across the print media 22. While the printhead 24 is scanned
the print control device 36 provides activation signals to the printhead 24 to
selectively deposit ink on print media to accomplish printing. Although, the printing
system 10 is described herein as having the printhead 24 disposed in a scanning
carriage there are other printing system 10 arrangements as well. These other
arrangements involve other arrangements of achieving relative movement between the
printhead and media such as having a fixed printhead portion and moving the media
past the printhead or having fixed media and moving the printhead past the fixed
media.
Fig. 3 is simplified to show only a single print cartridge 16. In general, the
print control device 36 is electrically connected to each of the print cartridges 14 and
16. The print control device 36 provides activation signals to selectively deposit ink
corresponding to each of the ink colors to be printed.
Fig. 4 depicts a simplified electrical block diagram showing greater detail of
the print control device 36 within the printer portion 12 and the printhead 24 within
the print cartridge 16. The print control device 36 includes a source of drive current,
an address generator, and an enable generator. The source of drive current, address
generator and enable generator provide drive current, address and enable signals
under control of the control device or controller 36 to the printhead 24 for selectively
activating each of a plurality of drop generators associated therewith.
In the preferred embodiment, the source of drive current provides 16 separate
drive current signals designated P (1-16). Each drive current signal provides
sufficient energy per unit time to activate the drop generator to eject ink. In the
preferred embodiment, the address generator provides 13 separate address signals
designated A (1-13) for selecting a group of drop generators. In this preferred
embodiment the address signals are logic signals. Finally, in the preferred
embodiment, the enable generator provides 2 enable signals designated E (1-2) for
selecting a subgroup of drop generators from the selected group of drop generators.
The selected subgroup of drop generators is activated if drive current provided by the
source of drive current is supplied. Further detail of the drive signals, address signals
and enable signals will be discussed with respect to Figs. 9-11.
The printhead 24 shown in Fig. 4 includes a plurality of groups of drop
generators with each group of drop generators connected to a different source of drive
current. In the preferred embodiment, the printhead 24 includes 16 groups of drop
generators. The first group of drop generators is connected to the source of drive
current labeled P(l), the second group of drop generators are each connected to the
source of drive current designated P(2), the third group of drop generators is
connected to the source of drive current designated P(3), and so on with the sixteenth
group of drop generators each connected to the source of drive current designated
P(16).
Each of the groups of drop generators shown in Fig. 4 are connected to each of
the address signals designated A(l-13) provided by the address generator on the print
control device 36. In addition, each of the groups of drop generators are connected to
the two enable signals designated E(1-2) provided by the address generator on the
print control device 36. Greater detail of each of the individual groups of drop
generators designated will now be discussed with respect to Fig. 5.
Fig. 5 is a block diagram representing a single group of drop generators from
the plurality of groups of drop generators shown in Fig. 4. In the preferred
embodiment, the single group of drop generators shown in Fig. 5 is a group of 26
individual drop generators each connected to a common source of drive current. The
group of drop generators shown in Fig. 5 are all connected to the common source of
drive current designated P(1) of Fig. 4.
The individual drop generators within the group of drop generators are
organized in drop generator pairs with each pair of drop generators connected to a
different source of address signals. For the embodiment shown in Fig. 5, the first pair
of drop generators are connected to a source of address signals designated A(1), the
second pair of drop generators are connected to a second source of address signals
designated A(2), the third pair of drop generators are connected to a source of address
signals designated A(3) and so on with the thirteenth pair of drop generators
connected to the thirteenth source of address signals designated A(13).
Each of the 26 individual drop generators shown in Fig. 5 is also connected to
the source of enable signals. In the preferred embodiment, the source of enable
signals is a pair of enable signals designated E(1-2).
The remaining groups of drop generators shown in Fig. 4 that are connected to
the remaining sources of drive current designated P(2) through P(16) are connected in
a manner similar to the first group of drop generators shown in Fig. 5. Each of the
remaining groups of drop generators are connected to a different source of drive
current as designated in Fig. 4 instead of the source of drop current P(1) shown in
Fig. 5. Greater detail of each individual drop generator shown in Fig. 5 will now be
discussed with respect to Fig. 6.
Fig. 6 shows one preferred embodiment of an individual drop generator
designated 42. The drop generator 42 represents one individual drop generator shown
in Fig. 5. As shown in Fig. 5 two individual drop generators 42 make up a pair of
drop generators 42 that is each connected to a common source of address signals. The
individual drop generator shown in Fig. 6 represents one of the pair of drop
generators 42 connected to address source 1 designated A(1) of Fig. 5. All sources of
signals such as address signals A(1) and enable signals E(1-2) discussed with respect
to Figs. 6 and 7 are signals that are provided between the corresponding source of
signals and the common reference point 46. In addition, the source of drive current is
provided between the corresponding source of drive current designated P(1) and the
common reference point 46.
The drop generator 42 includes a heating element 44 connected between the
source of drive current. For the particular drop generator 42 shown in Fig. 6 the
source of drive current is designated P(1). The heating element 44 is connected in
series with a switching device 48 between the source of drive current P(1) and the
common reference point 46. The switching device 48 includes a pair of controlled
terminals connected between the heating element 44 and the common reference point
46. Also included with the switching device 48 is a control terminal for controlling
the controlled terminals. The switching device 48 is responsive to activation signals
at the control terminal for selectively allowing current to pass between the pair of
controlled terminals. In this manner, activation of the control terminals allows drive
current from the source of drive current designated P(1) to pass through the heating
element 44 thereby producing heat energy that is sufficient to eject ink from the
printhead 24.
In one preferred embodiment, the heating element 44 is a resistive heating
element and the switching device 48 is a field effect transistor (FET) such as an
NMOS transistor.
The drop generator 42 further includes a second switching device 50 and a
third switching device 52 for controlling activation of the control terminal of the
switching device 48. The second switching device has a pair of controlled terminals
connected between a source of address signals and the control terminal of switching
device 48. The third switching device 52 is connected between the control terminal of
switching device 48 and the common reference point 46. Each of the second and
third switching devices 50 and 52, respectively, selectively control the activation of
the switching device 48.
The activation of switching device 48 is based on each of the address signal
and enable signal. For the particular drop generator 42 shown in Fig. 6 the address
signal is represented by A(1), the first enable signal represented by E(1) and a second
enable signal represented by E(2). The first enable signal E(1) is connected to the
control terminal of the second switching device 50. The second enable signal
represented by E(2) is connected to the control terminal of the third switching device
52. By controlling the first and second enable signals, E(1-2), and the address signal,
A(1), the switching device 48 is selectively activated to conduct current through the
heating element 44 if drive current is present from, the source of drive source P(1).
Similarly, the switching device 48 is inactivated to prevent current from being
conducted through the heating resistor 44 even if the source of drive current P(1) is
active.
The switching device 48 is activated by the activation of the second switching
device 50 and the presence of an active address signal at the source of address signals,
A(1). In the preferred embodiment where the second switching device is a field effect
transistor (FET) the controlled terminals associated with the second switching device
are source and drain terminals. The drain terminal is connected to the source of
address signals A(1) and the source terminal is connected to the controlled terminal of
the first switching device 48. The control terminal for the FET transistor switching
device 50 is a gate terminal. When the gate terminal, connected to the first enable
signal E(1), is sufficiently positive relative to the source terminal and the source of
address signals, A(1), provides a voltage at the drain terminal that is greater than the
voltage at the source terminal then the second switching device 50 is activated.
The second switching device, if active, provides current from the source of
address signals A(1) to the control terminal or gate of the switching device 48. This
current, if sufficient, activates the switching device 48. The switching device 48, in
the preferred embodiment, is a FET transistor having a drain and source as the
controlled terminals with the drain connected to the heating element 44 and the source
connected to the common reference terminal 46.
In the preferred embodiment, the switching device 48 has a gate capacitance
between the gate and source terminals. Because this switching device 48 is relatively
large to conduct relatively large currents through the heating device 44, then the gate
to source capacitance associated with the switching device 48 tends to be relatively
large. Therefore, to enable or activate the switching device 48, the gate or control
terminal must be charged sufficiently so that the switching device 48 is activated to
conduct between the source and drain. The control terminal is charged by the source
of address signals A(1) if the second switching device 50 is active. The source of
address signals A(1) provides current to charge the gate to source capacitance of the
switching device 48. It is important that the third switching 52 be inactive when the
switching device 48 is active to prevent a low resistance path from being formed
between the source of address signals A(1) and the common reference terminal 46.
Therefore, the enable signal E(2) is inactive while the switching device 48 is active or
conducting.
The switching device 48 is inactivated by activating the third switching device
52 to reduce the gate to source voltage sufficiently to inactivate me switching device
48. The third switching device 52 in the preferred embodiment is a FET transistor
having drain and source as the controlled terminals with the drain connected to the
control terminal of switching device 48. The control terminal is a gate terminal that is
connected to the second source of enable signals E(2). The third switching device 52
is activated by activation of the second enable signal E(2) that provides a voltage at
the gate that is sufficiently large relative to a voltage at the source of the third
switching device 52. Activation of the third switching device 52 causes the controlled
terminals or drain and source terminals to conduct thereby reducing a voltage between
the control terminal or gate terminal of the switching device 48 and the source
terminal of the switching device 48. By sufficiently reducing the voltage between the
gate terminal and the source terminal of the switching device 48 the switching device
48 is prevented from being partially turned on by capacitive coupling.
While the third switching device 52 is active, the second switching 50 is
inactive to prevent sinking large amounts of current from the source of address
signals, A(1), to the common reference terminal 46. The operation of the individual
drop generator 42 will be discussed in more detail with respect to the timing diagrams
shown in Figs. 8 through 11.
Fig. 7 shows greater detail of a pair of drop generators that are formed by the
drop generator designated 42 and a drop generator designated 42'. Each of the drop
generators 42 and 42' that form the pair of drop generators are identical to the drop
generator 42 discussed previously with respect to Fig. 6. The pair of drop generators
is each connected to a source of address signals represented by A(1) shown in Fig. 5.
Each of the drop generators 42 and 42' are connected to a common source of drive
current P(1) and common source of address signals A(1). However, the first and
second enable signals E(1) and E(2), respectively, are connected differently in drop
generator 42' from drop generator 42. In drop generator 42', the first enable signal
E(1) is connected to the gate or control terminal of the third switching device 52' in
contrast to drop generator 42 in which the first enable signal E(1) is connected to the
gate or control terminal of the second switching device 50. Similarly, the second
enable signal E(2) is connected to the gate or control terminal of the second switching
device 50' in the drop generator 42' in contrast to the drop generator 42 where the
second enable signal E(2) is connected to the gate or control terminal of the third
switching device 52.
The connection of the first and second enable signals El and E2 for the pair of
drop generators 42 and 42' ensures that only a single drop generator of the pair of
drop generators will be activated at a given time. As will be discussed later, it is
important that within the group of drop generators that are connected to a common
source of drive current that no more than one of these drop generators is active at the
same time. The drop generators that are connected to a common source of drive
current tend to be positioned near each other on the prinmead. Therefore, by ensuring
that no more than one of the drop generators that are connected to a common source
of drive current of these is active at the same time tends to prevent fluidic crosstalk
between these proximatly positioned drop generators.
In the preferred embodiment, each of the pairs of drop generators shown in
Fig. 5 are connected in a manner similar to the pair of drop generators shown in Fig.
7. In addition, each of the groups of drop generators connected to a common source
of drive current shown in Fig. 4 are connected in a manner similar to the group of
drop generators shown in Fig. 5.
Fig. 8 is a timing diagram illustrating the operation of printhead 24. The
printhead 24 has a cycle time or period of time for each of the drop generators on the
printhead 24 can be activated. This period of time is represented by a time T shown
in Fig. 8. The time T can be divided into 29 intervals of time with each interval
having the same duration. These intervals of time are represented by time slots 1
through 29. Each of the first 26 time slots represents a period in which a group of
drop generators can be activated if the image to be printed so requires. Time slots 27,
28 and 29 represent intervals of time during a printhead cycle in which no drop
generators are activated. The time slots 27,28, and 29 are used by the printing system
10 to perform a variety of functions such as resynchronize the carriage 18 position
and drop generator activation data and transfer activation data from the printer portion
12 to the printhead 24, to name a couple.
The 13 different sources of address signals represented by A(1) through A(13)
are each shown. In addition, each of the first and second enable signals represented
by E(1) and E(2) are also shown. Finally, each of the sources of drive current P (1-
16) are also shown, grouped together. It can be seen from Fig. 8 that the address
signals are each activated periodically with the period of activation for each address
signal being equal to the cycle time T of the printhead 24. In addition, no more than
one address signal is active at the same time. Each address signal is active during two
consecutive time slots.
Each of the enable signals E(1) and E(2) are periodic signals having a period
that is equal to two time slots. The enable signals E(1) and E(2) each have a duty
cycle that is less than or equal to 50%. Each of the enable signals are out of phase
with each so that only one of enable signal E(1) or E(2) are active at the same time.
In operation, repeating patterns of address signals provided by each of the 13
sources of address signals A( 1-13) is provided to the printhead 24 by the print control
device 36. In addition, repeating patterns of enable signals for the first and second
enable signals, E(1) and E(2), respectively, are also provided by the print control
device 36 to the printhead 24. Both the address and enable signals are generated
independent of the image description or image to be printed. Each of the 16 sources
of drive current designated P (1-16) are selectively provided during each of the 26
time slots for each complete cycle for the inkjet printhead 24. The source of drive
current P( 1 -16) is selectively applied based on the image description or the image to
be printed. During the first time slot, the sources of drive current P(l-16) may all be
active, none of them active or any number of them active, depending upon the image
to be printed. Similarly, for time slots 2- 26, each of the sources of drive current P (1-
16) are individually selectively activated as required by the print control device 36 to
form the image to be printed.
Fig. 9 is a preferred timing for each of the sources of drive current P (1-16),
sources of address signals A (1-13) and enable signals E (1-2) for the printhead 24 of
the present invention. The timing in Fig. 9 is similar to the timing of Fig. 8 except
that each source of address signals A(l-13) instead of remaining active over the entire
two consecutive time slots shown in Fig. 8, each address is active for only a portion of
each of the two time slots shown in Fig. 9. In this preferred embodiment, each of the
address signals A(l-13) are active at the beginning of each time slot the address signal
is active. In addition, the duty cycle of each of the first and second enable signals
reduced from the nearly 50% duty cycle shown in Fig. 8. Further detail of the timing
of the address enable and drive current will now be discussed with respect to Figs. 10
and 11.
Fig. 10 shows greater detail of time slots 1 and 2 for the timing diagram of
described in Fig. 8. Because the only active address signal during time slot 1 and 2 is
A(1) only the address signal A(1) need be shown in Fig 10. As discussed previously,
it is important that the first and second enable signals, E(1) and E(2) respectively, not
be active at the same time to prevent providing a low resistance path to the common
reference point 46 thereby sinking current from the source of address signals A(l-13).
Therefore, the duty cycle of each of the first and second enable signals, E(1) and E(2)
respectively, should be less than 50%. In Fig. 10 the time interval labeled Te between
the transition from active to inactive for the first enable signal E(1) and the transition
from inactive to active for the second enable signal E(2) should be greater than zero.
The enable signal should be active before drive current is provided by the
source of drive current to ensure that the gate of capacitance of the switching
transistor 48 is sufficiently charged to activate the drive transistor 48. The time
interval labeled Ts represents the time between the first enable E(1) active and the
application of the drive current by the sources of drive current P(l-16). A similar
time interval is required for the time between the second enable E(2) active and the
application of the drive current by the sources of drive current P( 1 -16).
The enable signal E(1) should remain active for a period of time after the
source of drive current P( 1 -16) transitions from active to inactive as designated Th-
This period of time Th referred to as hold time is sufficient to ensure that drive
current is not present at the switching device 48 when the switching device 48 is
inactivated. Inactivating the switching device 48 while the switching device 48 is
conducting current between the controlled terminals can damage the switching device
48. The hold time Th provides margin to ensure the switching device 48 is not
damaged. The duration of the drive current signal P(l-16) is represented by time
interval labeled To. The duration of drive current signal P(l-16) is selected to be
sufficient to provide drive energy to the heating element 44 for optimum drop
formation.
Fig. 11 shows further detail of the preferred timing for time slots 1 and 2 for
the timing diagram of Fig. 9. As shown in Fig. 11 for time slot 1 the source of
address signals A(1) and the source of enable signals E(1) does not remain active the
entire duration that the source of drive current remains active. Once the gate
capacitance of the switching transistor 48 and 48' shown in Fig.7 is charged, the
transistor 48 and 48' remain conducting the remaining duration that the source of
drive current remains active. In this manner, the gate capacitance of the switching
device 48 and 48' acts as a storage device or memory device that retains an activated
state. The source of drive signals designated P(l-16) then provides the drive energy
that is necessary for optimum drop formation.
Similar to Fig. 10 the time interval labeled Ts represents the time between the
first enable E(1) active and the application of the drive current by the sources of drive
current P(l-16). An interval of time labeled Tah represents a hold time the source of
address signals A(1) must remain active after the first enable signal E(1) is inactive to
ensure the gate capacitance for transistor 48' is in the proper state. If the source of
address signals were to change state before the first enable signal E(1) signal becomes
inactive the wrong state of charge can exist at the gate of transistors 48 and 48'.
Therefore, it is important that the time interval labeled Tah be greater than 0. An
interval of time labeled Teh represents a hold time the second enable signal E(2) must
be active after the source of drive current P(l-16) becomes active. During the time
interval transistor 52 in Fig. 7 is activated by the second enable signal E(2) to
discharge the gate capacitance of transistor 48. If this duration is not sufficiently long
to discharge the gate of transistor 48 the heating element 44 may improperly be
activated or partially activated.
Operation of the inkjet printhead 24 using the preferred timing shown Fig. 11
has important performance advantages over the use of the timing shown in Fig. 10. A
minimum time required for each drop generator 42 activation for the timing shown in
Fig. 10, is equal to the sum of time intervals Ts, To, Te and Th. In contrast, the timing
shown in Fig. 11 has a minimum time that is required for each drop generator 42
activation that is equal to the sum of time intervals Ts, and To. Because Tp and Ts is
the same for each of the timing diagrams, the minimum time required for activation of
a drop generator 42 is less in Fig. 11 than in Fig. 10. Both the address hold time Tah
and the enable hold time Teh do not contribute to the minimum time interval for drop
generator 42 activation in the preferred timing shown in Fig. 11 thereby allowing each
time slot to be a smaller time interval than in Fig. 10. Reduction of the time interval
required for each time slot reduces the cycle period designated T in Figs. 8 and 9
thereby increasing the printing rate for the printhead 24.
The method and apparatus of the present invention allows 416 individual drop
generators to be individually activated using 13 address signals, two enable signals,
and 16 sources of drive current. In contrast, the use of previously used techniques
whereby an array of drop generators having 16 columns and 26 rows would require
26 individual addresses to individually select each row with each column being
selected by each source of drive current. The present invention provides significantly
fewer electrical interconnects to address the same number of drop generators. The
reduction of electrical interconnects reduces the size of the printhead 24 thereby
significantly reducing the costs of the printhead 24.
Each individual drop generator 42 as shown in Fig. 6 does not require a
constant power supply or bias circuit but instead relies on the input signals such as
address, source of drive current, and enable signals to supply power or activate the
drop generator 42. As discussed previously with respect to the timing of the signals,
it is important that these signals be applied in the proper sequence in order to have
proper operation of the drop generator 42. Because the drop generator 42 of the
present invention does not require constant power, the drop generator 42 can be
implemented in relatively simple technology such as NMOS which requires fewer
manufacturing steps then more complex technology such as CMOS. Use of a
technology that has lower manufacturing costs further reduces the costs of the
printhead 24. Finally, the use of fewer electrical interconnects between the printer
portion 36 and the printhead 24 tends to reduce the costs of the printer portion 36 as
well as increase the reliability of the printing system 10.
Although the present invention has been described in terms of a preferred
embodiment that makes use of 13 address signals, two enable signals, and 16 sources
of drive current to selectively activate 416 individual drop generators other
arrangements are also contemplated. For example, the present invention is suitable
for selectively activating different numbers of individual drop generators. The
selective activation of different numbers of individual nozzles may require different
numbers of one or more of the address signals, enable signals, and sources of drive
current to properly control different numbers of drop generators. In addition, there
are other arrangements of address signals, enable signals, and sources of drive current
to control the same number of drop generators as well.
CLAIMS:
1. An inkjet printhead (24) having a plurality of drop generators responsive to drive
current and address signals for dispensing ink, the inkjet printhead comprising:
a plurality of subgroups of first (42) and second (42') drop generators disposed
on the printhead that together form a group of drop generators with each drop generator
of the group of drop generators configured for connection to a drive current source
wherein within each subgroup, the first and second drop generators are configured to
receive address signals from a common address source, and wherein each subgroup of
first and second drop generators is configured for connection to a different source of
address signals;
a first switching device (50, 50') connected between the common address source
and each of the first and second drop generators of a subgroup, the switching device
responsive to enable signals for selectively providing the address signal to only one of
the first and second drop generators of the subgroup;
a plurality of drive current contacts each configured for connection to a source of
drive current source;
a plurality of address contacts each configured for connection to a source of
address signals;
a plurality of enable contacts each configured for connection to a source of
enable signals;
a plurality of groups of drop generators with each group electrically connected to
one of the plurality of drive current contacts, with each of the plurality of drive current
contacts connected to a different source of drive current, with each group of drop
generators having a plurality of the subgroups of first and second drop generators;
wherein the plurality of groups is equal to the plurality of drive current contacts
and wherein the size of each of the plurality of groups is equal to the plurality of address
contacts multiplied by the plurality of enable contacts; and
wherein the plurality of drive current contacts is equal to 16 and wherein 16 drop
generators can be activated at the same time.
2. The inkjet printhead of claim 1 wherein each of the first and second drop
generators include a heating device (44, 44') for selectively heating ink to eject ink from
the printhead.
3. The inkjet printhead of claim 1 or claim 2 wherein each of the first and second
drop generators include a second switching device (48, 48') connected in a current path
between a pair of drive current conductors coupled to the source of drive current, the
second switching device responsive to address signals for selectively allowing drive
current to pass therethrough.
4. The inkjet printhead of claim 2 wherein each of the first and second drop
generators include a second switching (48, 48') device connected in series with the
heating device between a pair of drive current conductors coupled to the source of drive
current, the second switching device responsive to address signals for selectively
allowing drive current to pass through the heating device associated with one of the first
and second drop generators.
5. The inkjet printhead of claim 1 wherein within each subgroup, the first drop
generator includes a second switching device (48) connected between a pair of drive
current conductors coupled to the source of drive current, the second switching device
responsive to address active signals for selectively activating the first drop generator and
wherein the second drop generator includes a third switching device (48') connected
between the pair of drive current conductors, the third switching device responsive to
address active signals for selectively activating the second drop generator.
6. The inkjet printhead of claim 5 wherein the first switching device comprises a
fourth (50) and fifth (50') switching device with the fourth switching device connected
between the source of address signals and the second switching device and with the fifth
switching device connected between the source of address signals and the third
switching device wherein the fourth switching device is responsive to enable signals for
selectively providing address signals to the second switching device and wherein the
fifth switching device is responsive to enable signals for selectively providing address
signals to the third switching device.
7. The inkjet printhead of any preceding claim wherein the first switching device
comprises a transistor.
8. The inkjet printhead of any preceding claim wherein the first switching device
comprises an NMOS transistor.
9. The inkjet printhead of claim 2 wherein:
each of the first and second drop generators include a second switching device
(48, 48') having a pair of controlled terminals connected in series with the heating
device between a pair of drive current conductors and a control terminal, the second
switching device responsive to an actuation signal at the control terminal for conducting
current between the controlled terminals to activate the heating device; and
the first switching device (50, 50') comprises a third switching device having a
pair of controlled terminals connected between an address terminal and the control
terminal of one of the second switching devices and a control terminal configured for
connection to a source of first enable signals, the third switching device responsive to the
first enable signals for selectively allowing address signals at the address terminal to be
provided to the control terminal of the one of the second switching devices.
10. The inkjet printhead of claim 9 wherein the first switching device (50, 50')
further comprises a fourth switching device (52, 52') having a pair of controlled
terminals connected between the control terminal of the one of the second switching
devices and one of the pair of drive current conductors and a control terminal configured
for connection to a source of second enable signals, the fourth switching device
responsive to the second enable signals for selectively conducting current between the
control terminal of the one of the second switching devices and one of the pair of drive
current conductors.
11. The inkjet printhead of claim 9 wherein the first switching device further
comprises:
a fourth switching device (50') having a pair of controlled terminals connected
between the address terminal and the control terminal of a second one of the second
switching devices and a control terminal configured for connection to a source of second
enable signals, the fourth switching device responsive to the second enable signals for
selectively allowing address signals at the address terminal to be provided to the control
terminal of the second one of the second switching devices for actuating the second one
of the switching devices; and
wherein the third and fourth switching devices are configured to activate only
one of the second switching devices at the same time.
12. The inkjet printhead of any of claims 1 to 11 wherein the plurality of address
contacts include A address contacts, the plurality of enable contacts include E enable
contacts, and the plurality of drive contacts include D drive current contacts, and
wherein the plurality of drop generators include (A x E x D) drop generators.
13. The inkjet printhead of any of claims 1 to 11 wherein the plurality of address
contacts is equal to 13 and wherein the plurality of enable contacts is equal to 2.
14. The inkjet printhead of any of claims 1 to 11 wherein the number of plurality of
drop generators in the printhead is equal to the number of plurality of address contacts
multiplied by the number of plurality of enable contacts multiplied by the number of
plurality of drive current contacts.
15. The inkjet printhead of any one of claims 1 to 11 wherein a ratio of the plurality
of address contacts to the plurality of enable contacts is approximately 6.5 to 1.

The invention relates to an inkjet printhead having a plurality of drop generators
responsive to drive current and address signals for dispensing ink, the inkjet
printhead comprising a plurality of subgroups of at least first and second drop
generators (42, 42') disposed on the printhead (24) that together form a group
of drop generators with each drop generator (42, 42') of the group of drop
generators configured for connection to a drive current source (P1 - P16)
wherein within each subgroup, the first and second drop generators (42) are
configured to receive address signals (A1 - A13) from a common address source,
and wherein each subgroup of at least first and second drop generators (42) is
configured for connection to a different source of address signals; and a first
switching device (48) connected between the common address source (46) and
each of the first and second drop generators (42) of a subgroup, the switching
device (48) responsive to enable signals for selectively providing the address
signal to only one of the first and second drop generators (42) of the subgroup.

Documents:

450-KOLNP-2003-(22-03-2012)-CORRESPONDENCE.pdf

450-KOLNP-2003-(22-03-2012)-PA-CERTIFIED COPIES.pdf

450-kolnp-2003-abstract.pdf

450-kolnp-2003-assignment 1.1.pdf

450-kolnp-2003-assignment.pdf

450-kolnp-2003-claims.pdf

450-kolnp-2003-correspondence 1.1.pdf

450-kolnp-2003-correspondence.pdf

450-kolnp-2003-description (complete).pdf

450-kolnp-2003-drawings.pdf

450-kolnp-2003-examination report 1.1.pdf

450-kolnp-2003-examination report.pdf

450-kolnp-2003-form 1.pdf

450-kolnp-2003-form 13 1.1.pdf

450-kolnp-2003-form 13.pdf

450-kolnp-2003-form 18 1.1.pdf

450-kolnp-2003-form 18.pdf

450-kolnp-2003-form 2.pdf

450-kolnp-2003-form 3 1.1.pdf

450-kolnp-2003-form 3.pdf

450-kolnp-2003-form 5 1.1.pdf

450-kolnp-2003-form 5.pdf

450-KOLNP-2003-FORM-27.pdf

450-kolnp-2003-gpa 1.1.pdf

450-kolnp-2003-gpa.pdf

450-kolnp-2003-granted-abstract.pdf

450-kolnp-2003-granted-claims.pdf

450-kolnp-2003-granted-description (complete).pdf

450-kolnp-2003-granted-drawings.pdf

450-kolnp-2003-granted-form 1.pdf

450-kolnp-2003-granted-form 2.pdf

450-kolnp-2003-granted-specification.pdf

450-kolnp-2003-priority document 1.1.pdf

450-kolnp-2003-reply to examination report 1.1.pdf

450-kolnp-2003-reply to examination report.pdf

450-kolnp-2003-specification.pdf

450-kolnp-2003-translated copy of priority document.pdf


Patent Number 243360
Indian Patent Application Number 450/KOLNP/2003
PG Journal Number 41/2010
Publication Date 08-Oct-2010
Grant Date 07-Oct-2010
Date of Filing 10-Apr-2003
Name of Patentee HEWLETT-PACKARD COMPANY
Applicant Address M/S 20 BN. 3000, HANOVER STREET, PALO ALTO, CA
Inventors:
# Inventor's Name Inventor's Address
1 CROWGER BRUCE 2040 NE CONIFER BOULEVARD, CORVALLIS, OR 97330
2 TORGERSON, JOSEPH, M. 24901 HIDDEN VALLEY ROAD, PHILOMATH, OR 97370
3 HURST, DAVID, M. 560 NW LEPRECHAUN LANE, CORVALLIS, OR 97330
4 MACKENZIE, MARK H. 1448 SW BIRDIE DRIVE, CORVALLIS, OR 97330
PCT International Classification Number B41J 2/00
PCT International Application Number PCT/US2001/46245
PCT International Filing date 2001-10-29
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 09/702,231 2000-10-30 U.S.A.