U.S. patent number 3,769,627 [Application Number 05/314,512] was granted by the patent office on 1973-10-30 for ink jet printing system using ion charging of droplets.
This patent grant is currently assigned to A B Dick Company. Invention is credited to Joseph J. Stone.
United States Patent |
3,769,627 |
Stone |
October 30, 1973 |
INK JET PRINTING SYSTEM USING ION CHARGING OF DROPLETS
Abstract
There is described an arrangement for charging with ions the
drops in an ink drop printing apparatus, in place of the present
induction charging techniques which are employed.
Inventors: |
Stone; Joseph J. (Northbrook,
IL) |
Assignee: |
A B Dick Company (Chicago,
IL)
|
Family
ID: |
23220250 |
Appl.
No.: |
05/314,512 |
Filed: |
December 13, 1972 |
Current U.S.
Class: |
347/76; 361/228;
346/74.2 |
Current CPC
Class: |
B41J
2/085 (20130101) |
Current International
Class: |
B41J
2/085 (20060101); B41J 2/075 (20060101); G01d
015/18 () |
Field of
Search: |
;346/75,74ES ;317/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hartary; Joseph W.
Claims
What is claimed is:
1. In an ink drop printing system of the type wherein drops of ink
are formed in a serial stream, and are emitted along a path toward
a recording medium, said drops have charges applied to them in
accordance with signals from a video source at a charging position
along said path, said drops thereafter passing between two
deflection electrodes which deflect the drops a distance determined
by the amplitude of the charges thereon, and said drops finally
coming to rest upon said recording medium, the improvement in
charging said drops comprising:
a source of ions,
means for establishing a field for bombarding each drop with ions
as it passes through said charging position, and
means for applying signals from said video source to said means for
establishing a field for controlling said field for determining the
amount of charge on each drop.
2. In an ink drop printing system as recited in claim 1 wherein
there is included:
means responsive to the presence of ink drops at a location prior
to said charging position for generating timing signals responsive
thereto, and
means for timing the application of signals for controlling said
field responsive to said timing signals.
3. In an ink drop printing system as recited in claim 1 wherein
said means for establishing a field comprises:
blocking means interposed between said source of ions and the path
of said drops at said charging position to block the access of ions
from said source from said path of said drops,
said blocking means having an aperture therethrough sized to afford
ions access to a drop at a time, and
a first conductive means surrounding said aperture on the side of
said blocking means adjacent said source of ions,
said means for applying signals from said video source to said
means for establishing a field includes:
means for applying said signals between said source of ions and
said first conductive means surrounding said aperture.
4. In an ink drop system as recited in claim 3 wherein said means
for establishing a field for bombarding each drop with ions further
includes:
a second conductive means surrounding said aperture on the side of
said blocking means, adjacent the path of said drops,
a third conductive means positioned opposite said second conductive
means and spaced therefrom to permit said stream of drops to pass
therebetween, and
means for biasing said second and third conductive means relative
to said first conductive means to establish fields which direct
ions entering said aperture at the path of said drops.
5. In an ink drop system as recited in claim 1 wherein said means
for bombarding each drop with ions as it passes through said
charging position includes:
a blocking means interposed between said source of ions and the
path of said drops at said charging position to block the access
from said source from said path of said drops,
said blocking means having a plurality of apertures therethrough
and spaced along the path of said drops and sized to afford ions
access successively to a drop as it moves along said path through
said charging position, and
a separate first conductive means surrounding each of said
plurality of apertures on the side of said blocking means adjacent
said source of ions,
said means for applying said signals from said video source to said
means for establishing a field includes,
analog-to-digital means for converting each of said signals from
said video source into a binary code having as many bit signals as
there are apertures in said blocking means, and
means for applying the bit signals representative of a video signal
between said source of ions and each of said separate first
conductive means successively to charge a drop passing through said
charging position.
6. In an ink drop system as recited in claim 5 wherein said means
for applying the bit signal representative of a video signal
between said source of ions and each of said separate first
conductive means successively includes:
a shift register for each of said plurality of apertures,
means for applying the output of each shift register to a separate
one of said first conductive means,
means for applying each bit signal to the input of a different one
of said shift registers,
means for detecting the presence of a drop prior to its entrance
into said charging position, and producing a timing signal
representative thereof, and
means for applying said timing signal to each of said shift
registers to cause them to advance responsive thereto.
7. In an ink drop printing system of the type wherein drops of ink
are formed in a serial stream, and are emitted along a path toward
a recording medium, said drops have charges applied to them in
accordance with signals from a video source at a charging position
along said path, said drops thereafter passing between two
deflection electrodes which deflect the drops a distance determined
by the amplitude of the charges thereon, and said drops finally
coming to rest upon said recording medium, the improvement in
charging said drops comprising:
a source of ions,
conductive grid means interposed between the source of ions and
said charging position, and
means for applying signals from said video source to said
conductive grid means for controlling responsive thereto the amount
of ions which can pass through said conductive grid means to charge
a drop passing through said charging position.
8. In an ink drop system as recited in claim 7 wherein said
conductive grid means comprises:
an insulating blocking means having an aperture therethrough,
and
conductive means surrounding said aperture on each surface of said
insulating blocking means.
9. In an ink drop system as recited in claim 7 wherein said
conductive grid means comprises:
an insulating blocking means having an aperture therethrough,
a separate conductive means surrounding each aperture on the
surface of said insulating blocking means adjacent said ion source,
and
a conductieve means surrounding each aperture on the other
side.
10. In an ink drop system as recited in claim 9 wherein said means
for applying signals from said video source to said conductive grid
means comprises:
means for converting each of said signals from said video source
into a binary code having as many bit signals as there are
apertures in said insulating blocking means,
means for applying the bit signals representative of a video signal
between said source of ions and each of said separate conductive
means successively to charge a drop passing through said charging
position.
11. In an ink drop system as recited in claim 10 wherein said means
for applying the bit signals representative of a video signal
between said source of ions and each of said separate conductive
means successively includes:
means responsive to the presence of drops prior to entering said
charging position for generating timing signals,
a separate delay means for each aperture, each delay means having
its input connected to receive one of the bit signals in a binary
code representative of a video signal and its output connected to
apply a bit signal to a separate one of said separate conductive
means, and
means for applying said timing signals to each of said separate
delay means to enable said separate delay means to successively
apply a bit signal to a conductive means as a drop passes the
aperture surrounded by said conductive means.
12. In an ink drop system as recited in claim 8 wherein there is
included a further conductive means positioned opposite said
insulating blocking means at said charging position to permit drops
to pass therebetween, and
means for applying a potential between said further conductive
means and said conductive means surrounding the apertures of said
insulating means to establish an electric field therebetween for
enabling ions passing through said aperture to bombard a drop
opposite said aperture.
13. In an ink drop system as recited in claim 9 wherein there is
included a further conductive means positioned opposite said
insulating blocking means at said charging position to permit drops
to pass therebetween, and
means for applying a potential between said further conductive
means and said conductive means on the side of said insulating
means adjacent said drop charging position to establish an electric
field therebetween to enable ions passing through said apertures to
bombard a drop.
Description
BACKGROUND OF THE INVENTION
This invention relates to ink drop printing apparatus, and more
particularly, to an improved arrangement for charging ink
drops.
Present ink drop printing systems, such as described by Sweet in
his U.S. Pat. No. 3,596,275, use selectively charged droplets,
which are deflected by a high voltage deflection field to form
images on a recording medium. These droplets form at a very regular
rate by squirting pressurized ink through a small orifice.
Ultrasonic energy, superimposed on the supply pressure for the ink,
velocity modulates the emitter stream. As a result of this
modulation, the stream forms into droplets at the frequency of the
ultrasonic source.
Selective drop charging involves the induction of charges in the
drop being formed by a surrounding charged electrode. The induced
charge varies in accordance with the inducing voltage until the
instant in time at which the droplet physically separates from the
stream. From that time on, the induced charge is trapped and
remains with the drop. It is obvious, therefore, that the charging
process must be carefully synchronized with the timing of the drop
break off. This involves the use of complex phasing control sensors
and loops. This in turn, increases the cost of the equipment.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to provide an ink drop charging
system which does not depend upon a synchronization of the carging
charging with the break off time.
It is another object of this invention to produce an ink drop
charging system, which charges drops after they break off from the
ink jet stream.
Another object of the present invention is the provision of a
simpler and less complex ink drop charging system than has been
used heretofore.
These and other objects of the invention may be achieved by an
arrangement wherein drops, after they separate fron the ink jet
stream, are detected and charged by ions to a level indicated by
the video signals, which is determined by the location on the paper
on which it is desired to deposit the drop. The drops, after
charging, pass through an electric field which deflects each drop
by an amount determined by the amplitude of the charge thereon.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a schematic and fragmentary view of an ink drop printing
system which illustrates an embodiment of the invention.
FIG. 2 is an enlarged isometric view of a control aperture.
FIG. 3 is a schematic view of a single control aperture embodiment
of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a schematic diagram of a portion of an ink jet printer.
The portion shown in the ink drop charging and deflecting
arrangement, which is in accordance with this invention. The reason
why an entire ink drop printing system is not shown is because,
aside from the charging portion which is in accordance with this
invention, these printing systems are well known, are commercially
available, and are described in a number of patents, besides the
Sweet patent referred to previously herein.
A pressurized ink supply, not shown, causes ink to flow through a
nozzle 10. The nozzle has a small opening 12 through which an ink
jet is emitted. An oscillator 14 applies electrical energy at a
suitable ultrasonic frequency to a transducer 16. The transducer
converts this electrical energy to mechanical energy and usually
squeezes the nozzle at a rate determined by the oscillator
frequency. As a result, the stream 18 of ink, which is emitted,
forms into drops such as 29 through 34. Light from a source 40 is
focused by a lens 42 at the region through which the drops pass.
The drop 22 is in position to intercept or block the light. Another
lens 44 focuses light from the region through which the drops pass
onto a photocell 46. The photocell output is applied to a pulse
generator 48, which generates a pulse each time the light is
blocked by a drop. The output of the pulse generator 48 is used for
timing and control purposes in such a manner that one pulse occurs
for each drop passing the detection zone, or the region at which
light is focused by the line 42.
It should be noted that the ink jet stream breaks up into a series
of uniformly spaced, equally sized drops, moving at a constant
velocity toward the recording medium. The initial ink stream
pressure directly determines the drop velocity and this can be
regulated within close limits.
Immediately following the photocell detector, each drop passes over
a series of charging apertures 50, 52, 54, 56 and 58. Each of these
apertures permits charges to be placed on a drop by means of
gaseous ions emitted from a positive corona source 60. Control
voltages which determine whether or not ions can pass through one
of the apertures 50 through 58, are received from amplifiers,
respectively 62 through 70, which are applied to conductive layers
adjacent each aperture. Details of the control of each aperture
will be described in connection with FIG. 2, subsequently
herein.
Each of the amplifiers 62 through 70 is driven by the output stage
of the respective shift registers 72 through 80. Each one of the
shift registers is one or more bits in length and shifts, in
response to shift pulses received from an adjustable time delay
circuit 82. The adjustable time delay circuit is driven by the
output of the pulse generator 48 and not only provides shift
pulses, but provides timing pulses to the remainder of the system.
The adjustable time delay is used to delay the output of the pulse
generator 48, which is applied thereto for whatever interval is
required to insure that a drop is positioned over each one of the
respective apertures 50 through 58. Once this interval is set,
since the drops occur at regular intervals and are regularly
spaced, it need not be adjusted again, unless either the ink jet
pressure or the oscillator frequency is altered.
In order to block the flow of gaseous ions through an aperture, a
negative voltage is applied to the conductive layer 82, which
surrounds an aperture. Otherwise, a positive voltage is applied to
this conductive layer.
Let it be assumed that it is desired to charge a drop with three
increments of charge as it passes over the five holes. This will
require that, for example, when drop 26 is over aperture 50, a one
representative control voltage is applied to the conductive layer
around the hole 50. Similarly, when drop 26 is over the holes 52
and 54, one representative voltage should be applied to the
conductive layer surrounding each of these holes. When drop 26 then
successively passes over the holes 56 and 58, zero representative
voltages should be applied to the conductive layers surrounding
openings 56 and 58. The zero representative layers will be negative
signals and the one representative layers will be positive signals.
This will require that one representative signals be at the output
stages of shift registers 72, 74 and 76, when ink drop 26
successively passes over openings 50, 52 and 54. This further
requires that zero representative signals be at the output stages
of shift registers 78 and 80, when ink drop 26 is opposite the
respective openings 56 and 58.
Since the shift pulses are applied to cause the shift registers to
shift as each drop passes between the lenses 42 and 44, the loading
of the shift registers with the signals which are to control the
charging of drop 26, (and other drops also), must be as follows.
Assuming that the shift registers are five stage registers, and the
respective stages from output to input are numbered from zero
through four, a one representative signal is in stage zero of shift
register 72, a one representative signal is in stage one of shift
register 74, a one representative signal is in stage two of shift
register 76, a zero representative signal is in stage three of
shift register 78, and a zero representative signal is in stage
four of shift register 80.
The loading of signals into the shift registers for controlling the
charging of drops must be done in the staggered manner described,
so that a drop is properly charged as it passes by each one of the
five openings. One way of achieving this type of loading is by
having suitable different delay lines in front of the shift
registers. Another preferred way is to make the shift registers
have different lengths so that although they are loaded in
parallel, the control voltage for charging a drop will arrive at
the shift register output stages properly timed as the drop
successively passes each charging aperture. A third way is to have
the shift registers the same length, say one stage, but to have a
counter count the output of the adjustable time delay and apply the
first count output to shift register 72; the second count output is
applied to shift register 74; the third count output is applied to
shift register 76; the fourth count output is applied to shift
register 78 and the fifth count output is applied to shift register
80.
Thus, for each droplet, a number of shift pulses must be provided
equal to the number of apertures to be controlled. The time between
pulses should equal the flight time of the individual droplets
between apertures, and the start of the pulse train should occur at
the time the detected drop reaches the first aperture.
The output of the adjustable time delay circuit 82 is not only
applied to the shift registers to provide shift pulses, but is also
applied to a drop charge control source 84, which is driven by
signals from a data source 86. The data source and the drop charge
control source function in the manner of the circuit used in
presently manufactured drop charging systems in that they function
to produce a sequence of charging voltages for each character to be
printed having amplitudes which, when applied to the drops will
cause the drops to be deposited in a pattern representative of a
character. All that is needed to produce a pattern of control
voltages for controlling the apertures 50 through 58 for ion
charging is an analog-to-digital converter 85, which converts the
analog charging voltages into five digital control voltages. These
are applied to the five shift registers 72 through 80.
The system shown may also be used for printing curves or lines,
since in that case, the data source will provide succession of
signals which the drop charge control source will convert into
voltages that are then converted into digital aperture control
signals by the analog-to-digital converter, whereby a drop will be
charged and thereafter deflected by a distance representative of
that voltage.
In the event that the system is used for printing characters, then
the output of the adjustable time delay circuit is applied to a
counter 88. Since a character in order to be printed requires a
number of drops, the counter counts the number of drops passing
between the lenses 42 and 44, representative of the maximum number
of drops for printing a character, and then applies an output to
the data source 86 to apply the next set of signals representing a
character to be printed to the drop charge control source. The drop
charge control source in response to the timing pulses generates a
sequence of voltages required to charge drops in the induction type
of charging for depositing the drops in the form of a character. In
the present invention, this voltage sequence is applied to the
analog-to-digital converter as described above.
It will be appreciated that where purely a curve or line printing
system is desired, that is where a single ink drop is to represent
each data signal, as opposed to where a plurality of drops are
required, then, the counter 88 is omitted.
After the drops have received charges in passing over the apertures
50 through 58, they pass between two spaced parallel electrodes
respectively 90, 92. These two electrodes are connected to a source
of potential, with the lower electrode 92 being connected to ground
and the upper electrode 90, being connected to a negative high
voltage source to establish an electric field between the
electrodes. Drops which are not charged are not deflected and move
along in the path into which they were initially projected. These
drops are finally deflected by a catcher 94, into a reservoir 96,
from which they may be pumped back to the initial reservoir used
for this system. The other drops, which bear charges, are deflected
by the field by an amount determined by the amplitude of the
charge. The drops finally fall on the recording medium 98. Suitable
mechanisms are provided for moving the recording medium, in a well
known manner, to insure that the pattern in which the drops fall
thereon forms either characters or curves, as desired.
FIG. 2 is an enlarged cross sectional view of the region around one
of the apertures, such as the aperture 50. The lower conductor 82,
which serves as a control electrode, surrounds the aperture and a
control voltage is applied thereto from an amplifier 62. The lower
conductor 82 is separated from the deflection plate 92, by a
suitable insulator 100. The deflecting electrode 92 is connected to
ground. The amplifier 62 applies a negative voltage relative
thereto when it is desired to block the passage of ions through the
opening, and a positive voltage relative therethrough, when it is
desired to permit the passage of ions through the opening.
The positive corona source 60 generates positive ions. A field
E.sub.1 may be established between the positive corona source and
the control electrode 82 such that these ions are accelerated
toward control electrode 82. When the control electrode is
positive, ions are urged through the opening and when the control
electrode is negative, ions are not urged through the opening. A
field E.sub.2 is established by the relative potentials between the
electrode 92 and the conductor 82. When the conductor 82 is
negative with respect to the conductor 92, this field blocks the
ions through the opening. A third field E.sub.3 is established
between the electrode 92 and the electrode 90 which projects ions
out of the opening and toward the electrode 90. Any ink drops that
is in the space between electrodes 90 and 92, and that is over an
opening through which the ions pass, will be bombarded with ions
and thus, will assume a positive charge.
The system shown in FIG. 1 is a digital charging system, that is,
each drop receives a unit of charge (or not), as it passes over
each one of the charging holes. By varying the amplitude of the
control signal applied to the conductor 82 surrounding the opening,
the amplitude of charge applied to a drop may also be varied to
achieve the results similar to the results obtained for the
apparatus described in FIG. 1. FIG. 3 is a schematic diagram which
incorporates the structures of FIG. 1 to show an arrangement for
charging drops with different amplitude, using a single hole. The
structures in FIG. 3, which perform the same function as the
structures in FIG. 1, bear the same reference numerals. The change
between the drawing of FIG. 1 and that of FIG. 3 is in the omission
of the analog-to-digital converter 85 and the five registers 72
through 80. The output of the Drop Charge Control Source is a
signal whose amplitude is determined by a signal from the video
data source. This apparatus is the same as is used presently for
the inductor charging of drops. The output of the drop charge
control apparatus is applied to the amplifier 62, which after
amplification, applies it to the control electrode 82. Only a
single opening 50 is used. The amount of ion charge on a drop
passing adjacent opening 50 is determined by the amplitude of the
voltage applied to the control electrode 82. As was previously the
case, the distance of the deflection of the drop from the
trajectory of an uncharged drop.
It should be appreciated that in FIG. 1, the five charging holes
which are shown are by way of example. More or less may be used as
desired. Also, the system illustrated herein uses a positive corona
source. Those skilled in the art will appreciate that a negative
corona source may also be used, by reversing all the voltage
polarities shown in FIG. 1.
There has accordingly been described and shown herein a novel and
useful arrangement for charging drops with ions.
* * * * *