U.S. patent number 3,813,676 [Application Number 05/295,302] was granted by the patent office on 1974-05-28 for non-sequential symbol generation system for fluid jet printer.
This patent grant is currently assigned to International Business Machines Corporation. Invention is credited to Bruce A. Wolfe.
United States Patent |
3,813,676 |
Wolfe |
May 28, 1974 |
NON-SEQUENTIAL SYMBOL GENERATION SYSTEM FOR FLUID JET PRINTER
Abstract
A fluid jet printing system includes a vibrating nozzle for
emitting a stream of fluid which is broken into a series of uniform
drops. The drops are charged by a voltage which is generated from a
symbol code input by a symbol generator which produces a charging
voltage representation for each drop of each symbol to be printed.
The symbol generator includes a symbol storage means having stored
in each location a representation of the charging voltage to be
applied to each fluid drop. Deflection electrodes which supply an
electric field for the purpose of deflecting charged fluid drops
are positioned at an angle with respect to a base line for a row of
symbols to provide greater flexibility and more accurate placement
of fluid drops on a record media surface.
Inventors: |
Wolfe; Bruce A. (Endicott,
NY) |
Assignee: |
International Business Machines
Corporation (Armonk, NY)
|
Family
ID: |
23137117 |
Appl.
No.: |
05/295,302 |
Filed: |
October 5, 1972 |
Current U.S.
Class: |
347/76;
347/77 |
Current CPC
Class: |
B41J
2/09 (20130101) |
Current International
Class: |
B41J
2/09 (20060101); B41J 2/075 (20060101); G01d
015/18 () |
Field of
Search: |
;346/75 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Gamblin et al.; Orthogonalization of Electrostatic Printing; IBM
Tech. Disc. Bulletin, Vol. 11, No. 10, March, 1969, pp.
1,292-1,293..
|
Primary Examiner: Hartary; Joseph W.
Attorney, Agent or Firm: Johnson; Kenneth P.
Claims
What is claimed is:
1. In a fluid jet printer having fluid reservoir means, fluid jet
means, transducer means for vibrating said fluid jet to produce a
stream of fluid droplets, means for applying a charging voltage to
individual ones of said droplets, and record means for receiving
the droplets thereon, in combination therewith;
means for generating a charging voltage signal representative of
the print position for each fluid droplet of each symbol, said
means comprising:
storage means having prestored therein individual droplet charging
voltages represented as digital values, the magnitude of said
digital values being time-independent values with respect to each
of a plurality of droplets for each symbol in a set of symbols;
decode means connected to said storage means and responsive to a
symbol code input signal for addressing said storage means to read
out in sequence said stored digital values for each droplet of one
of said pluralities for said symbol code; and
converting means connected to the output of said storage means for
converting each said digital value in said sequence into an analog
charging voltage signal for an ink droplet, with each charging
voltage signal being independent of charging voltage signals
applied to a preceding or succeeding droplet in said stream of
fluid droplets; and
means for deflecting each said droplet according to the charge
thereon, said deflection means being arranged so that said droplets
are deflected along a path angularly disposed with respect to the
relative motion of said record means and fluid jet means an amount
determined in part by the maximum number of drops used in a symbol
of said set.
2. Apparatus according to claim 1 further comprising means for
counting the number of drops to be printed for each symbol to
achieve maximum utilization of said storage means.
3. Apparatus according to claim 1 further comprising oscillator
means, connected to said means for generating a charging voltage
signal, for synchronizing generation of said charging voltage
signals with emission of fluid droplets from said fluid jet to
insure that the correct charge is applied to each fluid droplet.
Description
BACKGROUND OF THE INVENTION
The present invention relates to apparatus for controlling a fluid
jet printer and more particularly to apparatus for generating
symbols to be printed by a fluid jet printer.
In the prior art, symbol generators for fluid jet printers have
included symbol matrices which were scanned sequentially to produce
a video signal used to control the charging of fluid drops in the
printing apparatus. The information stored in the sequentially
scanned matrix was a binary value which indicated whether a
particular spot in the symbol matrix was to be printed (unblanked)
or not (blanked). The sequential binary video signal produced from
the prior art symbol generators was combined with a ramp voltage
signal in such a manner that a charging voltage was produced for
each video print signal with a charging voltage magnitude
determined by the instantaneous value of the ramp voltage
signal.
The sequential scanning of the symbol matrix of prior art systems
limits the flexibility of print drop placement to a small, fixed
number of locations in a normally rectangular matrix. This
limitation results in unsatisfactory printing of symbols employing
diagonal lines or graphics.
SUMMARY OF THE INVENTION
Therefore, it is an object of the present invention to efficiently
control the printing of symbols.
It is another object of the present invention to increase printing
speed in a fluid jet printer including a non-sequential symbol
generator.
It is yet another object of the present invention to increase fluid
drop utilization in a fluid jet printer.
A still further object of the present invention is to increase the
number of possible fluid drop positions on a record medium in a
fluid jet printer having a non-sequential matrix symbol generator
and having a pair of deflection electrodes precisely
positioned.
To achieve the foregoing objects, a fluid jet printing system
includes a fluid drop emitting subsystem including fluid supply,
pump, nozzle, and means for vibrating the nozzle to form uniform
fluid drops; a non-sequential symbol generation means for
converting a symbol code input into a series of voltage signals to
be applied to an electrode to charge individual fluid drops to a
potential representative of the print position in a given symbol;
and a deflection means positioned at an angle so as to provide a
greatly increased number of possible print positions for a given
symbol.
It is an advantage of the present invention that possible drop
locations are increased by a factor of 10 to 1 over prior art fluid
jet printers.
Another advantage of the present invention over the prior art is
that the record medium may be transported at a speed twice as fast
as the prior art.
A still further advantage of the present invention is that greater
precision can be obtained in printed symbols since separation
between available print positions is decreased.
Yet another advantage of the present invention over the prior art
is the elimination of "guard drops" used to compensate for drop
interaction.
Still another advantage of the present invention is the capability
of printing a wide variety of symbols, character sets and limited
graphics.
The foregoing and other objects, features and advantages of the
invention will be apparent from the following more particular
description of a preferred embodiment of the invention as
illustrated in the accompanying drawing.
FIG. 1 is an isometric diagram of a fluid jet printing apparatus
with deflection electrodes positioned according to the present
invention.
FIG. 2A is a block diagram of apparatus for converting an input
symbol code to a charging electrode potential.
FIG. 2B is a block diagram showing the logic elements of a
non-sequential symbol generator according to the present
invention.
FIG. 2C is a chart showing the magnitude in decimal and binary
notation for the charging voltage to be applied to each fluid drop
necessary to form the symbol 8.
FIG. 3A is a representation of a simbol 8 showing the placement of
each fluid drop.
FIG. 3B is a diagram showing the relative displacement of each drop
necessary to form the symbol 8 as a function of the binary coded
voltage representation.
FIG. 3C is a schematic representation showing the positioning of a
symbol 8 on a record medium relative to the angle of the deflection
electrodes.
DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIG. 1, a fluid jet printing system is shown
including the present invention. In fluid jet printing system 100,
fluid from reservoir and pump 114 is transmitted under pressure
through tube 112 to nozzle 110. A nozzle actuator transducer 120
which is driven by a transducer driver 122 vibrates nozzle 110
causing the fluid stream 102 to be broken into a uniform series of
droplets 104. A charging electrode 130 surrounds the fluid stream
at about the point of droplet separation. The charging electrode
charges each droplet to a potential determined by data source 132
which drives the charging electrode 130. The charged droplets pass
through an electric field which is created between deflection
electrodes 140. The deflection electrodes generate a constant
electric field due to an applied potential. The fluid droplets are
deflected while moving through the electric field formed by
deflection electrodes 140 an amount dependant upon the applied
charge for each droplet. For those droplets which are not to be
printed, a charge is applied which will cause them to strike gutter
150 which returns the fluid to reservoir 114.
Referring also to FIG. 3C, it should be especially noted that
deflection electrodes 140 are mounted at an angle to the direction
of record medium motion as shown by the arrow in FIG. 1. The
selected angle .PHI. (FIG. 3C) is adjusted to allow the maximum
usage of fluid droplets for printing and avoid the need for guard
drops or other means of compensation. In a preferred embodiment,
the angle .PHI. may be in the range of 20.degree. to 30.degree.
depending primarily on paper speed, drop separation and drop
size.
Referring now to FIGS. 2A and 2B, the data source and symbol
generation means will be described. A symbol code input
representing a symbol to be printed is presented to symbol code
buffer 310. Symbol code buffer 310 provides temporary storage for
the symbol code to enable synchronization of the input symbol code
data with a drop formation clock (not shown).
The symbol code data is presented to symbol generator 320 which is
shown in greater detail in FIG. 2B.
The symbol code contains n parallel bits, which for example, in a
symbol font having less than 64 symbols might be a six bit parallel
data path. The symbol code is decoded by symbol decode means 322
which has as a first output an address of a location in symbol
storage means 326 in which is stored the binary representation of
the charging voltage to be applied to the first fluid drop to be
printed for the symbol decoded. This address is loaded into address
counter 324 which controls the addressing of symbol storage means
326 via lines 323.
A second output of symbol decode means 322 is connected to symbol
drop count decode means 327 to set the symbol drop count to the
number of fluid drops to be printed for the particular symbol
decoded.
It should be noted that different symbols of the same symbol font
will be formed of a different number of fluid drops. For example,
referring to FIG. 2C it can be seen that the symbol 8 is formed of
14 drops. Some symbols may require less than 14 drops and some
symbols may require many more than 14 drops. Therefore, for most
efficient use of the symbol storage matrix 326 the drop count is
used to control the resetting of address counter 324 to eliminate
unnecessary storage access cycles.
It should be noted, referring to FIG. 2B that symbol storage means
326 is a three-dimensional matrix having K symbol locations where K
is the number of symbols in a particular font, each of which
contain L fluid drops to be printed where L is variable depending
upon the symbol to be printed, with m bits for each storage
location representing the charging potential to be applied to a
particular drop in a symbol.
The output of symbol storage means 326 which is m bits in parallel
is applied to symbol video code buffer 328 which provides a
temporary storage of the charging voltage representation for a
particular drop to be printed.
Referring again to FIG. 2A, the output of symbol generator 320
which is also the output of symbol video code buffer 328 is
connected to video decoder 330 which converts the binary digital
charging voltage representation into an analog voltage signal which
is amplified by video amplifier 340 which in turn is connected to
charging electrode 130 (see FIG. 1).
It should be especially noted that the symbol storage means 326
(FIGS. 2B) contains information regarding the exact charging
potential for each of the L drops for each of K symbols.
Referring now to FIGS. 2C, 3A, 3B and 3C, the printing of a
representative symbol 8 will be described.
FIG. 2C shows the decimal and binary code representations of the
charging voltage to be applied to each of the 14 drops to be
printed for the symbol 8. For example, drop L1 has a decimal code
voltage representation of 2 and a binary code voltage
representation of 010. Referring now to FIG. 3B, it can be seen
that drop L1 is positioned 2 voltage units above a base line. The
other drops required to form the symbol 8 are similarly positioned
a number of voltage units above a base line determined by the
binary code representation as shown in FIG. 2C. Referring now to
FIGS. 3A and 3C, the purpose and function of positioning deflection
electrodes 140 at angle .PHI. will be explained.
Deflection electrodes 140 are positioned at an angle of
approximately 26.5.degree. relative to the motion of the record
medium. In FIG. 3A, it can be seen that each fluid drop follows a
path which is along a line of (90 - .PHI.).degree. from a base
line. Each fluid drop may be positioned at any location along the
dotted line indicated in FIG. 3A as determined by the binary
voltage representation. Thus, taking drop L8 as an example, that
fluid drop could be positioned at any one of 7 positions along that
dotted line as determined by the binary code which was contained in
the appropriate location of symbol storage means 326. This is in
contrast to the prior art symbol generation techniques in which the
only information stored in a symbol storage matrix was the presence
or absence of a drop to be printed in a line scan sequential
manner.
It can be seen, therefore, that the present invention enables a
greater flexibility in the printing of symbols than does the prior
art. Further, no drop interaction compensation is required since
the effects of drop interaction can be considered in assigning the
binary representation for the charging voltage to be applied to
each fluid droplet to be printed. Therefore, guard drops can be
eliminated and every drop emanating from nozzle 110 (see FIG. 1)
can be utilized for printing.
The net result of the improvements due to the present invention are
that although the storage requirement is increased by a factor of
slightly more than 2.0, the number of possible drop locations on
the printing surface has increased by greater than 10 times and the
paper speed may be increased by a factor of two.
While the invention has been particularly shown and described with
reference to the preferred embodiment thereof, it will be
understood by those skilled in the art that various changes in form
and detail may be made therein without departing from the spirit
and scope of the invention.
* * * * *