U.S. patent number 3,641,588 [Application Number 05/044,953] was granted by the patent office on 1972-02-08 for electrostatic printer.
This patent grant is currently assigned to Teletype Corporation. Invention is credited to Jack L. Metz.
United States Patent |
3,641,588 |
Metz |
February 8, 1972 |
ELECTROSTATIC PRINTER
Abstract
A stream of ink drops is electrostatically moved in a printing
course from each of a plurality of supply nozzles toward an ink
receiving carrier which is moved vertically in a straight path
transversely of said course. A sweep voltage associated with each
nozzle is repeatedly generated across a first pair of parallel
electrodes which are generally horizontally spaced laterally of
said course, and has a magnitude adapted for deflecting the
associated stream generally horizontally in repeated lines
extending transversely of the path of carrier travel and the course
between the nozzle and the carrier. The movement of the carrier is
adapted to generate one dimension of a two dimensional character
from each stream, the sweep of the trace made by the associated
"horizontally" deflected ink stream generating the other dimension.
A print or nonprint mode is produced by selected of a pair of
voltages applied across a second pair of parallel electrodes which
are disposed about the course of each stream and generally
vertically spaced. In the print mode, each stream remains in its
printing course by clearing the edge of a mask. In the nonprint
mode, each stream is deflected generally vertically from its course
onto the mask and prevents printing. Accordingly, character
definition is obtained. The edge of the mask is a sawtooth
configuration having sloping segments, each of which is associated
with one stream. To produce characters which are "squared" to the
carrier, the electrodes of each first pair are nonparallel to the
direction of the path of carrier movement. Their angle of tilt from
a parallel condition is a function of the speed of the carrier such
that a line trace resulting from a single sweep of an associated
stream of ink drops will mark the carrier normal to the path of
carrier movement; and the edge of the mask is parallel to the line
along which each ink stream is "horizontally" deflected when
printing.
Inventors: |
Metz; Jack L. (Des Plaines,
IL) |
Assignee: |
Teletype Corporation (Skokie,
IL)
|
Family
ID: |
21935213 |
Appl.
No.: |
05/044,953 |
Filed: |
June 10, 1970 |
Current U.S.
Class: |
347/77 |
Current CPC
Class: |
G06K
15/10 (20130101); B41J 2/09 (20130101) |
Current International
Class: |
B41J
2/09 (20060101); B41J 2/075 (20060101); G06K
15/02 (20060101); G06K 15/10 (20060101); G01d
015/18 () |
Field of
Search: |
;346/75,140,1 |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Gamblin et al., Orthogonalization of Electrostatic Printing, IBM
Technical Disclosure Bulletin, Vol. 11, No. 10, March 1969, pp.
1292-3..
|
Primary Examiner: Hartary; Joseph W.
Claims
I claim:
1. In an electrostatic printer for simultaneously printing a
plurality of two dimensional characters and being of the type
adapted to generate one dimension of each two dimensional character
by movement in a straight path of a carrier toward which ink drops
in a stream are directed over a course from across a span relative
ink applying means and the other dimension of each character is
generated by application of changing voltages across a pair of
parallel first electrodes disposed in said span at an angle other
than parallel to said course and spaced apart transversely thereof
for deflecting said stream in a succession of sweeps transversely
of said straight path and at an angle other than perpendicular to
the direction of said straight path, the improvement characterized
by:
an array of horizontally aligned nozzles, each of said nozzles
associated with a pair of parallel first electrodes for
simultaneously providing a plurality of streams of ink;
a mask construction disposed downstream of said nozzles and defined
by a sawtooth edge configuration with a plurality of segments
extending longitudinally of nozzle alignment, said configuration
comprised of edges respectively associated with said nozzles, each
edge extending parallel to the sweeps of the stream of ink from an
associated nozzle, and
a pair of parallel second electrodes associated with each nozzle
for providing character definition by stream deflection, each pair
of second parallel electrodes spaced transversely of the spacing of
associated first electrodes and extending transversely of though at
an angle other than perpendicular to an associated straight path,
each pair of said second electrodes having a first condition in
which an associated stream impinges said carrier during any portion
of a sweep and a second condition in which such stream is prevented
by said mask construction from reaching said carrier during any
portion of its sweep.
2. A combination according to claim 1 wherein said mask
construction has a window opening limited by said
configuration.
3. A combination according to claim 2 wherein said sawtooth
configuration has a plurality of slopes each thereof parallel to
the others and to the path of the sweeps of an associated nozzle.
Description
FIELD OF THE INVENTION
The present invention relates to printing. Particularly the
invention relates to line raster printers. Specifically, the
invention relates to an electrostatic raster printer.
BACKGROUND OF THE INVENTION
Raster printing is an art in which one dimension of a two
dimensional character is generated by repeatedly applying an ink
trace on a carrier or ink receiving medium with ink sweeping means.
The other dimension of the character is generated by relative
movement of a succession of sweeps and the carrier in a path
transversely of each sweep. Character definition is provided by
selectively preventing ink deposition during selected sweeps.
Electrostatic printing, of one type, is an art in which a stream of
ink droplets is moved across a span from a nozzle to a carrier on
which intelligence is printed. Character formation in said art is
effected through the agency of voltages which are generated about
the ink droplets in the span selectively to deflect the drops.
In one form of the marriage of the aforesaid arts, which heretofor
has been consummated, the carrier moves continuously during
printing. Accordingly, resulting characters are slanted; and that
phenomenon is considered, in some circumstances, to be undesirable.
Character slanting may be obviated by printing while the carrier is
stationary, with successive line traces in each character raster
being advanced or stepped, one at a time, relative the stationary
carrier and transversely of each sweep until a character is
completed. But, to follow the last procedure requires the addition
of electrical components for advancing line traces which are not
required when the carrier moves continuously during ink
application.
It is an object of the present invention to provide an improved
printing process and apparatus.
It is another object of the invention to provide an improved raster
printing process and apparatus.
It is a further object of the invention to provide an improved
electrostatic printing process and apparatus.
It is an additional object of the invention that the lines of a
raster and the direction of carrier movement are orthogonal in a
raster printing art in which the character is continuously moving
during the printing.
It is yet a further object of the invention to generate characters
squared to a continuously moving carrier in a raster printing art,
particularly in which the recording material is an
electrostatically impelled stream of droplets.
SUMMARY OF THE INVENTION
To effect the foregoing, and other objects of the invention which
will become apparent from the ensuing description, one dimension of
a two dimensional character is generated by moving a carrier in a
path relative ink applying means in a raster printing process. The
other character dimension is generated through a repeated sweep
force for applying successive linear ink traces transversely of
said path. Character definition is produced by preventing selected
ink portions from being effective for printing. Means are provided
for sloping each linear sweep at an angle other than perpendicular
to the path of carrier movement.
From another aspect, said objects are achieved in a printer of the
type adapted to generate one dimension of a two dimensional
character by moving a carrier on which ink is applied in a straight
path. The other dimension of the character is generated by means
for directing the ink in repeated sweeps transversely of the
straight path in response to changing electrical effects. Means are
provided for sloping each ink sweep at an angle other than normal
to the straight path. A mask having an edge parallel to the sweeps
and beyond which printing is effected is adapted to intercept
selected portions of ink deflected from a course toward the carrier
to provide character definition.
BRIEF DESCRIPTION OF THE DRAWINGS
In the ensuing detailed description reference is had to the
accompanying drawings which:
FIG. 1 is a scheme, in perspective, of apparatus embodying the
present invention;
FIG. 2 is an enlarged detailed view looking downstream through an
electrode assembly comprising said apparatus;
FIG. 3 is a graphic representation of a voltage sweep across a pair
of the electrodes comprising said assembly; and
FIG. 4 is an elevational view of a modified embodiment of the
invention looking upstream through its electrode assembly.
DETAILED DESCRIPTION OF THE INVENTION
Referring now more particularly to FIG. 1 of the drawings, shown is
a single printing assembly 10 which includes a reservoir 12 as a
source for a recording material or ink. The reservoir is fluidally
connected through a conduit 14 to an electrically conductive head
16 having ink applying means comprised of a delivery nozzle 18. In
the illustrated embodiment, sufficient head pressure is maintained
for producing a meniscus from the downstream end of the nozzle to
produce an intrusion of ink in a gap 20 generated by spacing an
electrically conductive platen 22 downstream from and in printing
alignment with the nozzle.
A carrier or ink receiving medium 24 is arranged to be moved in a
straight path 25 at constant and uniform velocity over the upstream
face of platen 22 by motive means shown herein as a motor 26. To
that end motor output is coupled through a drive train, which may
include a pulley 28, to a sprocket wheel 30, the teeth of which are
proportioned for feeding engagement in marginal apertures 32 of
carrier 24. Path 25 is considered vertical, as shown in the
drawings relative which all terms of orientation in the
specification is made.
Charging means which may be of conventional construction and of
which terminals 34 and 36 are shown respectively connected to head
16 and platen 22 provide a potential difference in gap 20, charge
platen 22 and produce an electrostatic charge on ink as it passes
through head 16. A valving electrode 38 is connected to a charge
generator, only terminal 40 of which is shown, and is disposed
downstream of nozzle 18. It is adapted to generate an electrostatic
field of sufficient magnitude to draw ink into a stream of drops 42
and initiate ink movement in a course 41 toward carrier 24. The
valving electrode has an aperture 39 which is coaxially aligned
with the bore of nozzle 18, and through which the stream will
continuously flow under sufficient impelling force to reach the
carrier.
Parallel electrodes 43 and 44 of a first or "vertical" pair thereof
are spaced downstream of valving electrode 38 and are generally
vertically spaced apart about course 41 permitting passage
therebetween of the stream of drops. Charging means of which only
terminals 45 and 46 are shown, are adapted for imposing selected of
two voltage conditions across said last electrodes. In a first of
the conditions, assembly 10 is in an "on" or print mode and drops
42 are not affected. In the second condition, assembly 10 is in a
nonprint or "off" mode and the drops are deflected "vertically"
from course 41 to a course 48.
A mask 50 is disposed in intercepting or catching association with
path 48 downstream of electrodes 43 and 44 between platen 22 and
parallel electrodes 51 and 52 of a second or "horizontal" pair
thereof. The last mentioned electrodes are parallel to each other
and are generally horizontally spaced apart, being disposed about
path 41 downstream of electrodes 43 and 44.
A sweep generator 54 is connected to electrodes 51 and 52 through a
pair of leads 55 and 56 for repeatedly deflecting drops 42 in a
generally horizontal direction transversely of path 25 and course
41. By means which may be known, the sweep generator is adapted to
charge left electrode 51 decreasingly from a high to a base value
while simultaneously increasing the charge on the right electrode
52 from such base value to a high value (FIG. 3), and after each
voltage sweep to restore itself for a repeat sweep. In consequence
thereof, drops 42 which are passing between the horizontal
electrodes and are in course 41 (not having been deflected into
course 48) will be moved from the left to the right in a manner
such that a straight line of ink dots will be traced or printed on
carrier 24 transversely of the path 25 for each voltage sweep.
Accordingly, one dimension of any visual two dimensional design,
such as an alphanumeric character, can be generated on carrier 24
by reason of the "horizontal" sweep of the ink stream. The other
dimension of such design can be generated in consequence of
movement of the carrier. The result of the combined effect is a
line raster. Character definition is added by applying "vertically"
deflecting voltages such that selected drops 42 from groups thereof
which would be associated with selected line traces, if printed,
will be directed against mask 50. Control of the "vertical"
electrodes through terminals 45 and 46 can be in accordance with
programming which may be conventional.
A trough 58 is arranged in draining association with mask 50 and is
adapted for collecting fluid which is directed in stream 48.
Suitable means, such as a pump 60, which is fluidally connected to
trough 58 is adapted to return ink caught on mask 50 to reservoir
12. The foregoing construction precludes the requirement for
shutting off ink flow from nozzle 18 during the printing operation
and thereby minimizes the likelihood of nozzle cloggage which
occasionally occurs in systems which do not maintain continuous
flow from the nozzle during printing.
If, as in heretofor known devices, the direction of spacing of the
"horizontal" electrodes is normal to path 25, each line of a raster
traced on carrier 24 will slope in a manner such that the
characters which are formed will not be "squared" to the carrier;
and resulting printing will be slanted. In accordance with the
present invention, such result can be obviated. That is to say, the
lines of each raster and path 25 can be orthogonal. To that end,
the path of deflection of stream 41 during each voltage sweep is
required to be at an angle to path 25 which is other than normal;
the angle from normal through which the stream is horizontally
deflected being a function of carrier velocity.
Particularly, means for producing the result comprises electrodes
51 and 52 disposed in a general lateral condition to the path 41;
however, rotated (FIG. 2) slightly about the axis of the bore of
nozzle 18 such that the direction of spacing of said "horizontal"
electrodes is at an angle other than normal to path 25. Said
"horizontal" electrodes when thusly disposed are aptly and
variously characterized as means for sloping the path along which
ink is deposited on the carrier at an angle other than normal to
the direction of the path of carrier movement, and means for
sloping each sweep of the ink stream or each ink trace on carrier
24 at an angle other than perpendicular to the direction of path
25.
Mask 50 has a straight edge 64 (FIG. 2) which is disposed adjacent
path 41 such that when a print mode is effected in assembly 10,
drops 42 will clear or pass above edge 64 for impinging carrier 24.
However, when a nonprint mode is effected, the drops will be
directed below said edge. According to another aspect of the
invention, edge 64 extends parallel to the slope of the path taken
by the drops during "horizontal" deflection, means for deflecting
selected portions of the drops against said mask to prevent
impingement on said carrier comprising electrodes 43 and 44.
According to yet another aspect of the invention, the direction of
spacing of electrodes 43 and 44 and the direction of spacing
between electrodes 51 and 52 are orthogonal. Accordingly, the
direction of the spacing of electrodes 43 and 44 forms an angle
with path 25 which is equal to the angle formed by the direction of
the spacing of electrodes 51 and 52 with the perpendicular to said
path.
A modified embodiment of the invention has an assembly 110 (FIG. 4)
for simultaneously printing a plurality of designs or characters
and comprises a horizontal array 118 of nozzles, each of which is
similar to nozzle 18. The nozzles in the array are mounted in a
framework 119 which also supports a plurality of electrode
assemblies 170 each of which is associated with a nozzle and
disposed relative thereto in the manner illustrated for the
electrodes in assembly 10.
A unitary mask 150 is associated with and disposed downstream of
all of the nozzles in the array. The mask has a window opening 151
with a saw-toothed edge comprised of a plurality of segments 164
each of which corresponds to a mask edge 64. That is to say, each
segment 164 extends parallel to the direction of "horizontal"
deflection or sweep of an ink stream of an associated nozzle when
such stream is in a printing mode. By suitably selecting the number
of nozzles in array 118 all of the horizontal segments in a line of
intelligence can be printed simultaneously.
In the illustrated embodiment, each nozzle is adapted to provide a
stream for printing two alphanumeric characters at one time. That
is to say, assuming an "on" print mode the stream issuing from one
nozzle will be swept from left to right with respect to FIG. 1,
first to impinge the carrier along segment I of row A continuing
the sweep along segment II of row A following a programmed
interruption to enable proper character spacing. Thereafter during
an ensuing sweep and following rapid retrace during which a
nonprint mode is effected, a line would be traced on segment I of
row B and thereafter, on segment II of row B. Successive rows could
be traced in a like manner until a pair of characters will have
been completed, preventing ink from reaching selected areas of the
carrier by control of voltage across electrodes 43 and 44.
An operating embodiment of the illustrated apparatus is adapted to
print characters each of which has a matrix of 0.080 inch by 0.100
inch with character spacing 0.020 inch. Although two matrices are
shown traced in FIG. 1 for illustration, in practice they are not
traced on carrier 24. Only desired designs are traced, upper
portions of two thereof being shown in FIG. 1. Each matrix has 80
dot positions for each character arranged in 10 rows and eight
columns, each dot position comprising a square adapted for
reception of a plurality of drops 42, and each character matrix
being spaced two columns from an adjacent thereof. Accordingly,
each adjoining horizontal pair of characters made from one nozzle
will require 10 horizontal sweeps. These can be made in said
operative embodiment in 50.14 milliseconds. Restated, each sweep
requires 4.36 milliseconds. Retrace time requires 0.654
milliseconds.
In said embodiment a hydrostatic head of 0.718 inch of ink is
maintained as an operating condition. The inside diameter of the
bore of nozzle 18 is 0.0065 inch, its outside diameter being 0.010
inch. The diameter of aperture 39 is 0.030 inch and the
accelerating electrode is spaced 0.0435 inch from the downstream
end of said nozzle.
"Vertical" electrodes 43 and 44 are spaced 0.045 inch (center to
center) from the valving electrode 38; and "horizontal" electrodes
51 and 52 are spaced a like distance (center to center) from the
"vertical" electrodes. Mask 50 is spaced 0.103 inch downstream from
the "horizontal" electrodes (center to center) and said mask is
spaced 0.240 inch from platen 22. The thickness of each of the
electrodes and of said mask is 0.010 inch, the valving electrode,
the pair of "vertical" electrodes and the pair of "horizontal"
electrodes each being disposed in a plane parallel to the planes of
the others and to the plane of mask 50.
Moreover, each electrode of each "vertical" and "horizontal" pair
thereof is spaced a distance from course 41 equal to the distance
that the other electrode of such pair is spaced from said course.
Furthermore, the spacing between the "vertical" electrodes is 0.020
inch and the spacing between the "horizontal" electrodes is 0.025
inch.
An ink which has been used effectively in the operative embodiment
has the parameters of viscosity and resistivity which are set forth
in the copending application of Robert J. Dunlavey and Charles R.
Winston, Ser. No. 853,825, filed Aug. 28, 1969, and assigned to the
assignee of the present application. An adequate jet printing
stream which is controllable in the manner herein described is
drawn from nozzle 18 by an electrostatic field generated by
imposing -3,500 volts on nozzle 18 and -1,000 volts on valving
electrode 38. By applying +10,000 volts to platen 22, the ink
stream, when in a print mode, will have sufficient impetus to
impinge on carrier 24 for printing.
During operation of the apparatus the uppermost electrode 44 of the
"vertical" pair thereof is maintained at reference or ground
potential when either a print or a nonprint mode prevails. To
effect a print mode -450 volts is applied to the lower electrode 43
of said pair. This is sufficient under the conditions in the
apparatus to deflect the ink stream along path 48 into mask 50,
when the latter is maintained at +4,000 volts. During each voltage
sweep, voltage on left electrode 51 is reduced from +1,600 volts to
0 while the voltage on the right electrode 52 increases from 0 to
+1,600 volts and will produce a single line of the raster.
The spacing between the upper edge 64 of the mask and path 41 is
merely 0.006 inch; the angles .theta. and .gamma. (FIG. 2) are
2.degree. 351/2 minutes.
Under the conditions identified, printing can be effected which is
"squared" to carrier 24 while it is continuously driven at a
velocity of 1.944 inch per second.
As many modifications in the described construction and process
could be conceived, and as many changes could be made therein
without departing from the spirit and scope of the claims, it is
intended that all matter contained in the accompanying
specification shall be considered as illustrative only and not in a
limiting sense.
* * * * *