A character applying device which is controlled by a separate signal processor can be manually moved across a writing surface while the characters are being applied. A single-tipped marking instrument is moved with a prescribed motion parallel to the surface as the device is moved across the surface to create a relatively dense array of line patterns. Simultaneously, received control signals cause the tip to move in and out of contact with the surface for, in effect, masking the array to produce characters represented by those signals.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to recording instruments, and more particularly to 
devices and methods for applying characters to a surface. 
2. Description of the Prior Art 
Due to the innovations of modern technology, it is now possible and 
practical to store alpha-numeric data in a variety of ways other than the 
standard approach using printed memoranda on a paper recording medium. 
Examples of such storage techniques include magnetic tape recorders, 
computer disc files, and semiconductor memories in computers and 
calculators. In order to use data stored in these ways, it is often 
necessary to have a way to reduce the data to humanly readable form. 
Methods for accomplishing this important task include the use of 
television screens (as are often used in airports for plane schedule 
monitors), teletypewriters, ticker tape machines, "X-Y" plotters, and also 
movable printers that apply the data characters to a writing surface as 
the printer is drawn across the surface. Two types of such movable 
printers known in the prior art are the matrix print head rolling printer 
and the ink jet moving printer. 
One matrix print head rolling printer is described "Selectable Area 
Television Printer/Plotter" by S. Kambic, IBM Technical Disclosure 
Bulletin, Vol. 17, No. 2, July 1974, pages 565-567. That printer uses a 
printing mechanism in which many marking tips are arranged in a 
rectangular array. These tips are separately controlled in their vertical 
movement with respect to the printing surface so as to approximate any 
alpha-numeric symbols when they strike the surface in a variety of 
patterns as the printer is rolled across the surface. Although this matrix 
approach is suitable for its purpose, it is relatively complex and 
expensive. 
An ink jet moving printer is shown in U.S. Pat. No. 3,656,169 to T. Kashio 
and has an ink depositing mechanism which controls an electrostatically 
charged stream of ink with deflection electrodes in a manner similar to 
the technique for controlling an electron beam in a cathode ray tube. 
Responsive to the changing voltage levels on the control electrodes, the 
stream of ink traces out characters on a printing surface as the printer 
is being moved across the surface. The ink stream control mechanism of 
this type of printer is useful for some applications, but it is a costly 
precision device requiring fine alignment and adjustment. 
Objects of the present invention include simplifying movable printers and 
rendering them more reliable and less costly movable printers than those 
of the prior art. 
SUMMARY OF THE INVENTION 
The invention is directed to a movable printer employing a single-tipped 
marking device which is driven with a prescribed motion parallel to a 
writing surface as the printer is being moved across the surface. The 
contact of the tip of the marking device with the writing surface is 
controlled by a print control actuator which is responsive to received 
signals defining information to be printed. 
It is one feature of the invention that an indexing mechanism is coupled to 
one of the printer wheels. This indexer provides an indication of the 
extent of displacement of the printer as it moves across the writing 
surface so that information characters being applied will be properly 
spaced. 
In one embodiment of the present invention, the marking tip is oscillated 
essentially parallel to the writing surface and perpendicular to the 
direction of motion of the printer across the surface. The combination of 
the oscillations and printer motion thus cause the marking tip to describe 
a set of almost vertical closely spaced lines as the printer moves across 
the surface. Easily readable characters are generated by controlling the 
tip contact with the surface and thereby appropriately interrupting those 
lines. 
In another embodiment of the instant invention, the marking tip is moved in 
a circular pattern parallel to the writing surface as the printer is moved 
across the surface. A set of partially overlapping almost circular loops 
are thus traced out on the writing surface. The actuator raises the tip 
off the writing surface to interrupt the loops at appropriate times to 
print a desired pattern of characters. A desirable feature of this 
embodiment is that the almost circular patterns are generated with less 
lateral mechanical vibration than in the first-mentioned embodiment. 
With both embodiments, easily distinguishable characters are produced in a 
reliable and relatively inexpensive manner. 
A feature of the instant invention is that it may employ one of a broad 
variety of marking devices (e.g., a ball-point pen tip, an oscillating 
wire-end "hammer" striking through an inking ribbon, a felt-tipped marker, 
a nylon-tipped marker, a brush tip, etc.). 
Another feature of this invention is that it may be adapted for the use of 
more than one type of writing medium (e.g., ink, paint, pencil lead, 
chalk, etc.). 
Yet another feature of the instant invention is that it may be adapted to 
apply characters to various writing surfaces such as paper, wood, leather, 
glass, concrete, etc.

DETAILED DESCRIPTION 
FIG. 1 shows a hand-held version of the invention. In this figure a printer 
200 is responsive to signals received through a cable 220 from a source 
100 for applying characters to a surface 101. Source 100 is advantageously 
a portable calculator programmed to perform predetermined well-known forms 
of logic operations of types to be outlined. Such a calculator supplies 
data directly from its own operations or from an internal store loaded 
from those operations or from an external source. For example, the 
calculator can be acoustically or electrically coupled to a telephone 
station set to load that internal store from a callable remote data 
source. 
FIG. 2 shows an embodiment of the invention in which a marking tip 201 of 
any appropriate type is caused to oscillate essentially parallel to the 
writing surface 101 in a direction perpendicular to the horizontal motion 
as depicted by arrow 219 of the printer 200 across the surface. A pair of 
field coils 202 and 203 are energized from source 100 by way of wires (not 
separately shown) through cable 220. Those coils are thus provided with a 
constant frequency alternating current, and the resulting magnetic field 
causes a permanent magnet 204 to be vibrated back and forth. A guide tube 
205 extends through, and is secured to the magnet 204. The marking tip 201 
is secured to a shaft 210 which passes through the tube 205 and is secured 
to a magnetic disc 211 in an electromagnetic actuator. Tip 201 has a close 
sliding fit in the lower end of tube 205. 
The actuator includes two solenoids 208 and 209 within a housing 225 to 
which are secured pivots, such as the pivot 221, rotatably mounted in the 
printer 200 outer housing. Tip shaft 210 advantageously extends through 
both solenoids, and the disc 211 extends into a space between those 
solenoids so that the shaft and disc are free to move to a limited extent 
in a direction parallel to the length of the shaft. Guide tube 205 is 
secured to solenoid housing 225. Thus, the assembly including housing 225, 
tube 205, and tip 201 swings as a unit on the pivots 221 as the magnet 204 
is driven back and forth. 
As tip 201 reciprocates, it makes an oscillatory trace on surface 101 
between limiting positions 206 and 207. A similar trace for no character 
control signals is shown in FIG. 3A. The extent of excursion between those 
positions is determined by a coil spring 212 which engages a shoulder in 
the upper end of housing 225 and nominally has a longitudinal axis 
approximately colinear with the longitudinal axis of the tip driving 
apparatus. Spring 212 is held under adjustable compression by a cap 222 
engaging the upper end thereof to provide a limited toggle function. The 
cap and spring are held in position by two screws 213 and 214 which are in 
threaded engagement with a head member 223 secured to the housing of 
printer 200. Those screws are on an axis perpendicular to the axis of 
pivotal motion. When the screws are adjusted to cause compression or allow 
extension of spring 212, the extent of the arc through which the upper end 
of housing 225 can move is correspondingly shortened or lengthened. 
Consequently, the distance between limiting positions 206 and 207 is 
similarly shortened or lengthened. Since two screws are employed, the cap 
222 can be held in a tilted position to bias the path described by tip 
201. For example, in one application the bias was made sufficient to 
require electromagnetic drive power in only alternate half cycles of the 
tip sweep leaving the intermediate half cycles to be return powered by 
spring 212. 
In an embodiment for printing characters of about the size of conventional 
typewriter type, the distance from pivot 221 to the surface 101 was about 
three inches. Consequently, there was no substantial difference in trace 
density on surface 101 between the central and end regions of sweep. 
Solenoids 208 and 209 are alternatively energized from source 100 by 
control signals transmitted by wires (not shown) through cable 220. Those 
signals cause the marking tip shaft 210 to move up or down within the 
guide tube, hence causing the marking tip to move in or out of contact 
with the writing surface 101. This has the effect of partially masking 
recurrences of the tip pattern trace to produce desired information 
characters. The disc 211 serves as a pole piece for the solenoids 208 and 
209. When solenoid 208 is energized it creates a magnetic field which 
causes the magnetic disc 211 and marking tip shaft 210 to which it is 
attached to be pulled up so that the marking tip 201 is out of contact 
with the writing surface. When solenoid 208 is unenergized, solenoid 209 
is energized; and the magnetic disc 211 and the shaft 210 are pulled down 
so that the marking tip 201 contacts the writing surface. 
Fine adjustment of the height of tip 201 is advantageously effected by 
adjusting the positions of wheels 218 on the housing of printer 200. When 
properly adjusted, tip 201 is in stable marking engagement with surface 
101 while solenoid 209 is energized but before disc 211 has moved downward 
sufficiently to be held against that solenoid. In applications where tip 
201 is a wire-end "hammer", the energizing signals for solenoid 209 have 
an oscillatory signal superimposed thereon to cause the tip to make a 
series of dots rather than tracing a continuous line. 
In order to synchronize the up and down motion of the marking tip with the 
motion of the printer across the writing surface, it is necessary to have 
an indexing mechanism which produces a signal indicating the linear 
displacement of the printer. Such an arrangement is shown as elements 215 
through 218 of FIG. 2. A photodiode electronic switching device 216 is 
used to sense the rotation of a slotted disc 215 which is to be driven by 
a guide wheel 218 through an idler wheel 217. In this manner the 
displacement of the printer is measured in small steps as shown in FIG. 3C 
where the pulses indicate passage of a slot in disc 215 past the device 
216. This displacement information is transmitted from device 216 by wires 
(not separately shown) in cable 220 to signal source 100 which receives it 
as an input signal to be used in combination with the stored data signals 
to generate control signals for the solenoids 208 and 209 in order to 
properly position the marking tip 201 as the printer 200 is moved across 
the marking surface 101. Consequently, as the solenoids 208 and 209 are 
energized, the stored characters are applied to the writing surface. An 
illustrative character "B" is shown in FIG. 3B. 
Various logic arrangements can be employed in source 100 for providing the 
solenoid control signals in response to the printer displacement index 
signals of FIG. 3C. For example, a character field can be considered to be 
divided into rows and columns of area units, e.g., 7.times.14 units. For 
each field the vertical coordinates correspond to units of time for a 
single sweep in either direction by tip 201, and the horizontal 
coordinates represent units of displacement of the printer relative to the 
surface as presented by index signals of FIG. 3C. A table is constructed 
in memory for the anticipated character set and having in each bit 
position a bit indicating by its binary signal state which of solenoids 
208 or 209 is to be energized for a particular unit area of a particular 
character. Then by counting sweep time units and character field index 
pulses, and combining those counts with data signals representing 
respective characters, the successive address signal sets are produced to 
address the table to read out the respective solenoid control signals for 
each segment of each pattern traced by tip 201. 
FIGS. 3D through 3F show a typical set of control signals for generating 
the letter "B" with the embodiment of FIG. 2. FIG. 3D shows the 
triangular-waveform field coil voltage which causes the guide tube 205 to 
oscillate as previously described. FIG. 3E shows the marking tip "pickup" 
control signals for pickup control solenoid 208. FIG. 3F shows the marking 
tip "print" control signals for solenoid 209. The dots on the waveform in 
FIG. 3D show the points at which the marking tip is raised or lowered to 
produce the "B" of FIG. 3B. It should be noted that these two solenoid 
control signals are complementary so that the marking tip is constrained 
to be in either a "pickup" or "print" position. Considering FIGS. 3B 
through 3F together, the correlation is evident. For example, in FIG. 3E 
the pulse pair 301 corresponds to the two tip-lift operations as tip 201 
makes its first sweep up through a portion of the letter "B" involving the 
two internal openings in that letter. Similarly, the FIG. 3E signal 
excursions 302 represent the sweep of tip 201 to define the right-hand 
edge of the character of FIG. 3B. 
FIG. 4 shows a second embodiment of the invention in which a marking tip 
401 for a printer 400 is caused to revolve in a circular motion parallel 
to the writing surface 101 as the printer is rolled across the surface. 
This embodiment is characterized by less lateral vibration than is the 
embodiment of FIG. 2. FIG. 5A illustrates a typical trace with no 
character information. In the FIG. 4 embodiment, signals are coupled 
between source 100 and printer 400 by way of a cable 420 as before. 
Similarly, a linear indexing arrangement including a photodiode detector 
device 409 cooperating with a slotted disc 408 driven through an idler 
wheel 410 from a printer wheel 411 provides signals to source 100 
indicating printer displacement as shown in FIG. 5C. Also, the tip 401 is 
coupled through a shaft 404 extending through a guide tube 403, to a 
magnetic disc 407 that is actuated by lift and print signals applied from 
source 100 to solenoids 405 and 406. In this embodiment shaft 404 is 
flexible for a reason to be discussed. Solenoid housing 414 is mounted to 
the printer housing by way of square supports such as the support 415 to 
represent a rigid relationship in this embodiment between the solenoids 
and the printer housing. 
Rotation of tip 401 is achieved by having the guide tube 403 secured to the 
armature of an electric motor 402 that is fixedly mounted by a bracket 417 
to the housing of printer 400. For example, in an embodiment using a fine 
shaft 404 or a wire-end "hammer" type of marker, the motor 402 is 
advantageously a No. 2112-N903 type of motor manufactured commercially by 
the HICO Horizons International Co., of Menlo Park, California. The motor 
is energized for continuous operation by direct current supplied from 
source 100 by way of cable 402. 
In FIG. 4, the guide tube 403 has a dog-leg bend 418 in the lower portion 
thereof to place tip 401 at an appropriate offset, i.e., one half of 
character height, from the axis of rotation of the tube 403. Tip shaft 404 
extends through the tube 403 and the armature of motor 402. As shown in 
FIG. 4, tube 403 is substituted for the motor drive shaft to facilitate 
the mentioned arrangement of shaft 404. Shaft 404 is advantageously 
coupled to the lower end of a further shaft 416 supported in bearings in 
the solenoid housing 414 and secured to disc 407. In some applications, 
rotation of tube 403 by motor 402 simply deflects the lower portion of 
shaft 404 without actually causing that shaft and shaft 416 and disc 407 
to rotate, except as to relative angular displacement between shaft 404 
and tube 403. However, in other applications as the motor 402 drives tube 
403 in rotation, tip 401 and shafts 404 and 416 are correspondingly driven 
through the engagement of shaft 404 with tube 403 at the dog-leg bend 418. 
Energization of solenoids 405 and 406 actuates disc 407 to drive the shafts 
416 and 404 and the tip 401 up and down within tube 403 to be either out 
of or in marking engagement with the marking surface 101. In applications 
where shaft 404 rotates with tube 403, the coupling for disc 407 to shaft 
416 should be made through thrust bearings (not shown) to permit the 
vertical drive function without risking rotational dragging of disc 407 on 
the solenoids. 
In order to facilitate production of the solenoid control signals for FIG. 
4, an additional indexing arrangement is provided to supply source 100 
with angular position information regarding tip 401. To this end a 
photodiode detector device 413, mounted on the printer housing, cooperates 
with a single-slot disc 412 secured to rotate with tube 403. Any 
predetermined angular orientation of the slot with respect to the position 
of bend 418 is satisfactory. On each complete rotation, device 413 
produces one pulse to source 100 as shown in FIG. 5D. Logic in source 100 
uses those signals in cooperation with the linear displacement signals of 
FIG. 5C to determine, in a manner analogous to that already described in 
connection with FIGS. 2 and 3B-3F, when to produce lift signals and print 
signals for the solenoids. However, in the case of the FIG. 4 embodiment, 
the storage of solenoid control signals is advantageously predistorted to 
reflect the fact that tip 401 is moving in a circular fashion instead of a 
linear reciprocating fashion. The angular index pulses of FIG. 5D are used 
with at least the field vertical coordinate time counting to provide tip 
time position information. Also the horizontal coordinate set is split 
into two subsets to reflect the fact that the basic tip pattern is 
nonlinear, and symmetrical in this case, so that the tip follows a 
different path in each half of a full pattern cycle. Traces for a letter 
"B" produced in manner of FIG. 4 are shown in FIG. 5B. 
While the invention has been explained and described with reference to two 
particular embodiments thereof, other realizations will be apparent to 
those skilled in the art without departing from the spirit and scope of 
the invention.