U.S. patent number 3,681,778 [Application Number 05/139,409] was granted by the patent office on 1972-08-01 for phasing of ink drop charging.
This patent grant is currently assigned to A. B. Dick Company. Invention is credited to Robert I. Keur.
United States Patent |
3,681,778 |
Keur |
August 1, 1972 |
PHASING OF INK DROP CHARGING
Abstract
In a system wherein a stream of ink emitted from a vibrating
nozzle passes through a charging tunnel wherein the ink stream
breaks up into drops and the drops are charged by video signals, an
arrangement is provided for insuring that the ink drops formed
within the charging tunnel have the correct phase to receive a
proper video signal.
Inventors: |
Keur; Robert I. (Niles,
IL) |
Assignee: |
A. B. Dick Company (Chicago,
IL)
|
Family
ID: |
22486500 |
Appl.
No.: |
05/139,409 |
Filed: |
May 3, 1971 |
Current U.S.
Class: |
347/80 |
Current CPC
Class: |
B41J
2/115 (20130101) |
Current International
Class: |
B41J
2/115 (20060101); B41J 2/07 (20060101); G01d
018/00 () |
Field of
Search: |
;346/75 ;178/6.6R
;317/3 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Hartary; Joseph W.
Claims
1. In a system for printing with ink drops on a sheet of paper of
the type wherein ink is emitted from a vibrating nozzle in a stream
which next passes through a drop charging device wherein said
stream breaks up into drops whose formation is determined by the
frequency and phase of the vibrating nozzle, said drop printing
system including:
means for generating video pulses,
means for applying said video pulses to said drop charging device
for charging each drop, and
means for establishing an electric field through which charged
drops pass, after passing through said drop charging device, to be
deflected an amount determined by the charge on each drop, the
improvement comprising:
means for generating a test pulse immediately before and
immediately after the interval of each video pulse having an
amplitude greater than that of the largest video pulse,
means for applying the output of said means for generating a test
pulse to said drop charging device whereby a drop is charged with
either a video pulse or a test pulse,
drop interception means positioned beyond said electric field to
intercept a drop which is charged by a test pulse,
means for generating nozzle vibrating signals having one or the
other of two phases,
means responsive to interception of a drop by said drop
interception means to transfer said nozzle vibrating signals from
one to the other of said two phases, and
means for applying said nozzle vibrating signals to vibrate said
nozzle.
2. In an ink drop printing system as recited in claim 1 wherein
said drop interception means positioned beyond said electric field
includes a pair of conductive electrodes spaced apart a distance to
be bridged by an ink
3. In an ink drop system as recited in claim 1 wherein said means
for generating nozzle vibrating signals having one or the other of
two phases includes a toggle flip-flop having a first and a second
output and being driven to successively provide first one output
and then the other output in response to successive input
signals,
a first NAND gate having two inputs and one output,
a second NAND gate having two inputs and one output,
means respectively connecting said first and second toggle
flip-flop outputs to one of said respective first and second NAND
gate inputs,
a source of clock pulses,
means for applying clock pulses from said source to the other of
said first NAND gate inputs,
means for inverting clock pulses from said source to obtain
inverted clock pulses,
means for applying inverted clock pulses to the other of said
second NAND gate inputs,
means for applying said output signal to drive said toggle
flip-flop,
a third NAND gate having two inputs and an output and
means for applying the outputs of said first and second NAND gates
to the inputs of said third NAND gate whereby its output
constitutes nozzle
4. A system for printing with ink drops on a sheet of paper
comprising a source of ink under pressure,
nozzle means for emitting a stream of ink from said source of ink
toward said sheet of paper,
a source of clock pulses at a particular frequency,
means to which clock pulses are applied for generating nozzle
vibrating signals having one or the other of two phases,
means for applying said nozzle vibrating signals to said nozzle to
cause it to vibrate whereby said stream of ink breaks into a stream
of drops at a location downstream of said nozzle,
drop charging means positioned at the location where said stream of
ink breaks into a stream of drops,
electrode means extending along the path of said stream of drops
after they leave said charging means for establishing an electric
field transverse to said path,
means to which clock pulses are applied for generating video pulses
at a frequency responsive to the clock pulse frequency,
test pulse means for generating a test pulse just before and just
after each video pulse, said test pulses having an amplitude larger
than the largest video pulse,
means for applying said video pulses and test pulses to said drop
charging means,
test electrode means positioned adjacent an end of said electrode
means at a location for receiving only drops charged by a test
pulse and producing an output signal indicative thereof, and
means for applying output signals to said means for generating
nozzle vibrating signals to shift the phase thereof from one to the
other of said
5. A system as recited in claim 4 wherein said means to which clock
pulses are applied for generating nozzle vibrating signals includes
a toggle flip-flop having a first and a second output and being
driven to successively provide first one and then the other in
response to successive input signals,
a first NAND gate having two inputs and one output,
a second NAND gate having two inputs and one output,
means respectively connecting said first and second toggle
flip-flop outputs to one of said respective first and second NAND
gate inputs,
a source of clock pulses,
means for applying clock pulses from said source to the other of
said first NAND gate inputs,
means for inverting clock pulses from said source to obtain
inverted clock pulses,
means for applying inverted clock pulses to the other of said
second NAND gate inputs,
means for applying said output signal to drive said toggle
flip-flop,
a third NAND gate having two inputs and an output, and
means for applying the outputs of said first and second NAND gates
to the inputs of said third NAND gate whereby its output
constitutes nozzle vibrating signals of one or the other of two
phases.
Description
BACKGROUND OF THE INVENTION
This invention relates to ink drop printing systems and more
particularly to improvements therein.
In ink drop systems such as described in U.S. Pat. No. 3,465,350 a
conductive fluid is forced from an orifice which is vibrating at a
given rate and an appropriate amplitude to insure that the jet
emitted from the orifice will break up downstream into uniform
modular drops at the rate of vibration. Over the region at which
the drops separate from the jet, there is usually an arrangement,
such as a charging tunnel which applies a charging field to charge
the drops as they separate from the jet. In order to apply the
charge to the drops, the charging field must be maintained while
the drop separates. In order to place specific charges on given
drops one must know when drop separation is occurring. In U.S. Pat.
Nos. 3,465,350 and 3,465,351, systems for correcting phasing are
shown which requires the ink stream to strike a target prior to the
commencement of the writing of a line of characters. While these
systems are satisfactory, it would be better if drop phasing
corrections could be made during the writing time, since it can
happen that an out of phase condition may arise during such
interval and remain uncorrected until the end of the line. Also, if
phase correction can be made when necessary, during the writing
interval, then the time required to make the phase test is avoided,
and the writing process can therefore be speeded up.
OBJECTS AND SUMMARY OF THE INVENTION
It is an object of this invention to provide a system for testing
in an ink drop writer the phase of drop formation during writing
time.
It is another object of this invention to provide a phase testing
system for an ink drop writer which continuously tests for phase
correction and make corrections during writing time.
Yet another object of the present invention is the provision of a
novel and unique phase tester for an ink drop writer.
The novel features of this invention are set forth with
particularity in the appended claims. The invention will best be
understood from the following description when read in conjunction
with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a block schematic diagram of an embodiment of the
invention.
FIG. 2 is a waveform diagram indicating test pulses as well as
video signals.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 is a block schematic diagram of an ink drop printing system
which includes an embodiment of this invention for testing ink
drops to determine whether or not they are in proper phase with the
video signals. A source of video signals 10, desired to be printed,
is connected to a video processor 12. The video processor converts
the video signals into video pulses whose amplitude will determine
where a drop will be deposited on the paper on which writing
occurs. In other words, the video processor converts the incoming
video signals into signals of a type, which, when used to charge
the stream of drops, will result in the drop pattern deposited on
the paper having a form, be it letter or number or wave shape,
which is represented by the video signal. The video processor has
clock pulses for clocking the frequency of its pulse train output
which are derived from the second and third output counts of a
.div.4 counter 14. This counter is a cyclic counter which is driven
by clock signals from a source 16. The second and third count
outputs of .div.4 counter are applied through an OR gate 18 to the
video processor to serve as its clock signals. The first and fourth
count outputs of the .div.4 counter 14 are applied to an OR gate 20
which also has applied thereto a pulse train output of the video
processor 12.
The output of the OR gate will comprise a pulse wavetrain having
the waveform shown in FIG. 2. The first count from the .div.4
counter is represented by the pulse wave form 22. During the next
two count intervals, a video pulse 24 will occur, whose amplitude
is determined by the video signals. This amplitude will vary in
order to secure different deflections for the drops which are
charged in response thereto. The last high amplitude pulse 26
represents the last count of the counter. It should be noted that
the first and last counts of the counter as represented by the
pulses 22 and 26 have a much higher amplitude than any of the video
signals 24.
Referring back to FIG. 1, the output of the OR gate 20 is applied
to a video amplifier 28, whose output is applied to a charging
tunnel or ring 30.
Ink, from a source of ink under pressure 32, is applied to a nozzle
34. The nozzle is vibrated at clock frequencies by a tuned
amplifier and nozzle driver 36. As a result, the ink is emitted in
a stream 38, from the nozzle 34, in which the stream breaks down
into drops 40 within the charging tunnel, 30. The stream, because
of the pressure applied from the source, will pass out of the
tunnel and then between two charged plates, respectively 42, 44
onto writing paper 48. The plates have a voltage applied from a
high voltage source 46. The charged drops are now passing through
an electric field between the plates and are deflected in
accordance with the amplitude of the charge which has been applied
to them as they are formed in the ring 30. Drops then fall upon a
document 48, at a location determined by the deflection of the
drops during its transit through the field between the plates.
Those drops which are not used in writing on the document are
caught by a waste catcher 50.
Referring back to FIG. 2, it should be obvious that in order to
properly charge a drop, it should be formed in the video tunnel 30
during the interval of the video pulse applied to the tunnel. This
is illustrated in FIG. 2 as the video. However, the time at which
the drop will form, or more specifically the interval of drop
separation within the tunnel is not necessarily fixed in time but
can occur over an interval such as illustrated in FIG. 2, indicated
as the drop period. Thus, any drop which is formed within the
interval of the test pulse waveform 26 will not receive a video
pulse charge and would be lost as far as the writing process is
concerned.
The interval of drop formation is a function of the frequency and
phase with which the nozzle 34 is vibrated, which is determined by
the frequency and phase of the signal which drives the nozzle
driver 36. It should further be noted, that once the drops are
formed out of phase, the drops formed thereafter will stay out of
phase until the nozzle driver drifts back into phase with the video
signals.
The arrangement whereby phase corrections are made, in accordance
with this invention includes the pair of electrodes 52, 54, which
are placed between the printing material 48 and the high voltage
deflection plates 42, 44, and in line with the deflecting path of
drops which may be charged by any one of the test pulses 22, 26.
These are highly charged drops, higher than the highest video pulse
will charge a drop. The electrodes 52, 54 are spaced closely enough
so that they will be bridged by the test pulse charged drop. Plate
52 is grounded and plate 54 is connected to a transistorized switch
56. When a charged drop of conductive ink bridges the two
electrodes 52, 54, the base of the transistorized switch 56 is
grounded momentarily and thereby enables a pulse signal to pass to
a pulse shaper and amplifier 58. The output from the pulse shaper
and amplifier drives a toggle flip-flop 60.
The Q output of the toggle flip-flop is applied to a NAND gate 62.
The Q output of the toggle flip-flop is applied to a NAND gate 64.
The NAND gate 64 is enabled to pass clock pulses comprising the
output of NOR gate 18 in the presence of a Q input. These clock
pulses are also applied to a single input NAND gate 68, which acts
as an inverter. In the presence of the Q output of flip-flop 60,
NAND gate 62 is enabled to pass the output of NAND gate 66 which
occurs upon the occurrence of the fourth count of the .div.4
counter.
The output of the NAND gates 62 and 64 are applied to a NAND gate
66. The output of this NAND gate will either be pulses from NAND
gate 62 or pulses from NAND gate 64. That is, the output of NAND
gate 66 will either be clock pulses in phase with clock pulses
generated by counted 2 and 3 of counter 14 or clock pulses which
are out of phase with counts 2 and 3 generated by the counter 14.
The output of the NAND gate 66 drives the tuned amplifier nozzle
driver 36, which in turn drives the nozzle.
From the foregoing description it should be apparent that when
drops are formed during the video signal interval, the nozzle 34 is
being vibrated with the proper phase and frequency and no change is
made in the phase of the signal driving the nozzle driver. Should a
drop be formed at an interval outside of the video pulse interval,
then it will receive a high amplitude charge from a test pulse and
will activate the switching system described to cause a 1/2 drop
period 180.degree. phase shift in the signals driving the nozzle
driver 36. This will bring the drops formed thereafter into phase
with the video charging signals.
If desired, electrodes 52 and 54 may be cleared of a drop by making
electrode 52 somewhat porous and applying vacuum from a source 53
to the back thereof to suck away a bridging ink drop.
It will be appreciated that the system described will correct the
phase at which ink drops are formed at any time during the writing
interval that the drops may be formed out of phase and no extra
time for a phase test has to be devoted to this. The system can be
used with both stationary and moving writing heads because of the
constant phase checking, the uniformity and fidelity of the
printing is improved over that previously attainable. Finally, this
system is more economical to implement than those used
heretofore.
* * * * *