Note: Descriptions are shown in the official language in which they were submitted.
'7
ROTARY PRINTING DEVICE WITH IDENTIFYING MEANS AND
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~IETI10~ ~ND APPAR~TUS FOR IN SITU IDENTIFICATION
This lnvention relates to an improved rotary
~rintillg devlce, such as a daisy-type prlntwheel or a
cup-sh~ped prlntlng element, Eor use in an impact
r~ priJlter. The printwheel ls provided with
identi~ication Eeatures thereon which~ in one form,
serve to locate a "home" or reference position. In
anotller form, the ldentlfication features provide to
the printer, in addition to locating a "home" position,
informatiotl regarding the font style, language, pltch,
poin~ Si ze and other characteristlcs. Thls lnformatlon
~nables tlle prlnter to select the deslred characters,
to incremerlt -the carriage by the correct amount, and to
impact the prlntwheel at the proper energy level. A
lr~ method and apparatus for in situ identification of the
rotary prlntlng device is also comprehended in this
invention.
In impact printers utlll~ing dalsy-type
printwheels or printcups, i.e. printing devices having
a plurality of radlally extending spo]ces or petals each
bearlng one or more characters thereon, it is deslrable
to readlly substltute one prlnt element for another ln
order to simply and quickly change the prlnted output.
To this end, the mechanics of removing one devlce and
~5 replacing it with another have been greatly simplified.
For example, the printwheel shown in United States
Patent No. 4,037,706 (assigned to the instant assignee)
is provided with a handling cap. In assignee's
companion United States Patent No. 3,954,163 a similar
printt~heel provided with a handling cap is shown
mounted in a printer. Another approach to simplify
prlntwheel manipulation is shown ln United States
Patent Nos. 4,127,335 and 4,209,262 (both also assigned
to the instant assignee) wherein the printwheels are
-~, cartridge-loaded and the printer is provided with a
suitable mechanism to accept it.
Beyond the mere mechanlcs of quickly and easily
substituting one printing device with another, lt ls
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desirable to "arm" today's intelligent printers with
necessary inEormation about the loaded printwheel or
printcup in order that the printer wlll know the
loca-tion of each character, the proper impact energy
level to be applied to eaeh charaeter, and the lateral
distanee by which the printer earriage must be moved.
Printing device identification to the printer may be
provided directly by the user through a keyboard entry
or the printer may "read" this information directly
from the loaded device. Onee the identifying
ln information has been reeeived, the printer will make
the neeessary control adjustments. This may be
aeeomplished, as taught in United ~tates Paten-t No.
~,074,798 (also assigned to the instant assignee), by
any number of embodiments of read-only memory, in the
form of optical or magnetie indieia, arranged in a
eircular manner on the printwheel hub. Alternatively,
Xerox Diselosure Journal, Vol. 1, Nos. 9/10, Sept./Oct.
1976, p.25 discusses, in general terms, the
desirability of plaeing a eode upon each petal to
control the impaet force for that character. Also, IBM
Teehnieal Diselosure Bulletin, Vol. 22, No. 11, April
1980 teaehes the use of optical indieia placed upon the
end portion of printwheel petals for identifying the
printwheel font.
It is also necessary, when loading a printing
device on the printer carriage, to provide some means
for locating a reference position in order that, upon
the operator 1 5 selection of a charaeter on the
keyboard, the spoke bearing that eharaeter will be
aligned with the hammer for impaetion. This is
required since eaeh character is allocated a unique
number representing its position relative to the
reference position. An optical arrangement for ~eroing
in, or loeating, the "home" position of a printwheel,
or a printeup, in an impaet printer is taught in U.S.
Patent No. 3,651,916~ Therein, there is disclosed a
printwheel having a peripheral aperture defined by the
absenee of print petals. A photoeleetrie cell and
2a ~3~
cooperating light sou~ce identify the home position
when the aperture passes between the light source and
sensor.
Several mechanical "home" positioning
conflg~lrations are taught in the aforementioned U.S.
Patent Nos. ~,037,706 and 4,127,335, and also in U.S.
Ratent No. 4,161,373. In each, the printwheel is
provided with an opening in the form of a keyway into
which a locating key is positioned, upon mounting of
the printwheel relative to its rotatable drive shaft.
The keyway is fabricated to establish, within desired
tolerances, the precise location of the "home"
posi-tion.
Another optical or magnetic home position sensor
is taught in Figure 5 of the aforementioned U.S. Patent
No. 4,209,262. Magnetically or optically readab]e
indicia upon the printwheel may be accessed through an
aperture in the loading cartridge, by a suitable
magnetic or optical sensor. By use of this marking and
detection method, the home position of the wheel may be
sensed. In addition, this patent teaches that a
predetermined pattern of similar indicia may be used to
define a code to indicate the type of character font
used.
The above-described mechanical arrangements for
locating the printwheel at its home position are not
foolproof as they require some degree of manual
dexterity to manipulate the wheel relative to the
carriage and drive shaft. On the other hand, the
provision of a printwheel cartridge does result in a
foolproof referenced mounting of the printwheel.
However, it should be apparent that the cartridge
approach is expensive, as it requires, in addition to
the cartridge, a suitable receiving structure.
On its face, it would appear that the optical
indicia and sensor approach to the dual problem of
locating a reference position and identifying the
printwheel characteristics appears to be quite
satisfactory. However, the facts belie this
conclusion. The impact printer environment generally
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becomes so dirty as to greatly interfere with correct
optical sensing. This results from the fact that the
paper record member is a bonded composite material made
up of diverse particulate ingredients. These include:
the bulk particles of small discrete cellulosic fibers
of wood pulp, fillers such as clay, sizing such as
rosin, coloring dyes, and bonding agents such as
starches~ When the paper is repeatedly impacted at
high speeds and energy t clouds of particles are beaten
off this composite material resulting in a
ln contamination of the interior of the printer. ~learly,
the particulates will de-tract from the effectiveness of
the optical sensing devices and may even render them
totally inoperative after a period of prolonged usage.
A further drawback of the sensed indicia approach
resides in the increased manufacturing costs of the
printwheel bearing the optical or magnetic indiciaO
Affixing the indicia, in the form of reflective
stripes, requires integrally molding them or adhering
them to the wheel by some other means. Both approaches
are costly. Similarly, the use of magnetic indicia in
conjunction with magnetic sensors also elevates the
cost of the printwheel elements.
The novel rotary printing device oE the present
invention is provided with mounting means for coupling
the printing device to a drive shaft, without regard to
angular alignment, "home" position identifying means
and characteristic identifying means, comprising two
precisely located protrusions. In an alternative, more
simple, form of the invention, the device only includes
the "home" position identifying means. ~ foolproof
method and apparatus for the in situ interpretation of
both identifying means is also comprehended. Once
mou~ted in the printer, on the drive shaft, the device
is manipulated to locate the "home" reference position
and to determine the included angle between the
protrusions to "arm" the printer with location and
characteristics information. In the case of a device
of the alternative form, the manipulation will solely
locate the "home" or reEerence position.
g
Many of the attendant advantages and the mode of
operation of this invention will becorne rncre readily
appreciated upon review of the ~ollowing detailed
descri.ption and with reference to the drawings, in
which:
5Figure 1 i5 a plan view of a printer embodyiny the
present invention;
Figure 2 is an enlarged cross-sectional view taken
substantially along line 2-2 of Figure l;
Figure 3 is an enlarged plan view of the novel
printing device of this invention, showing a detector
device in the angle ~ zone;
Figure 4 is a side, partial sectional, view of the
printing device of Figure 3 showing the detector device
i.n more detail;
15Figure 5 is an enlarged plan view of the novel
printing device of this invention, showing a detector
device in the angle ~ zone;
Figure 6 is an enlarged plan view of an
alternative embodiment of the novel printing device of
this invention, showing identification protrusions on
both sides;
Figure 7 is a side, partial sectional, view of -the
printing device of Figure 6 showing the detec-tor device
in more detail;
25Figure 8 is an enlarged plan view of another
embodiment of the novel pri.nting device of this
invention, showing three identification protrusions;
Figure 9 is an enlarged plan view of yet another
embodiment o~ the novel printing device of this
invention, showing a single identification protrusion;
and
Figure 10 is a schematic block diagram showing the
printer control electronics.
Turnlng now, more specifically, to the drawings,
thexe is illustrated in Figuxes 1 and ~ an overall view
of a representative printer with which one form of the
novel printing device of this invention may ~e used.
The illustrated printer provides one suitable
environment for supporting, rGtatiny, sensing and
impacting the device. It should be clear that the
novel printing device of this invention may be in the
Eorm of a disk-shaped printwheel (as illustrated), a
cup-shaped element (as referred to above), or any other
suitable construction, and may be used in conjunction
with any suitable impact printer mechanism.
External support for the printer is provided by
rectangular frame 10 which carries a cylindrical platen
12 having end knobs 14 and 16 for manually rotating the
0 platen to advance and retract a paper record member
wrapped thereon. Spanning the long dimension of the
frame 10 are smooth, parallelly aligned support rods 18
and 20 upon which carriage 22 is mounted for
reciprocating linear movement from one end of the frame
to the other end, on low friction roller assemblies 24
and 26.
The motive force for carriage 22 is provided by
carriage motor 28 secured to frame 10 by suitable
fastening members. The motor 28 has drive shaft 30
extending outwardly therefrom upon which is mounted a
drive pulley 32, in the form of a capstan. Anchored to
the pulley 32 are left cable segment 34 and right cable
segment 36, each counterwound thereon. Cable segment
34 passes to idler pulleys 38 and ~0, then over a
portion of carriaye pulley ~2 (see Figure 2) and is
firmly secured to tensioning anchor 44 mounted upon the
frame 10. Likewise, cable segment 36 passes to idler
pulleys ~6 and ~8, over a portion of carriage pulley ~2
(in the opposite direction) and has its end ~irmly
secured to anchor 50 mounted upon the opposite frame
wall. Accurate control of the energization of carriage
motor 28, by the machine logic circuitry, enables the
carriage to be moved incrementally, either to the left
or to the right (as viewed in Figure 1), by the desired
amount and at the desired speed.
A paper feed motor 52, fixed to the right wall of
frame 10 (as viewed in Figure 1), drives the platen 12
through a gear train 54. Thus, by controlling the
6 ~ 7
motor 52 through the machine logic circuitry, paper may
be advanced incrementally.
~ ounted upon the reciprocable carriage 22, for
latera] movement therewith, is a printwheel drive motor
5fi, to which is secured a printwheel 58, a hammer
assemb1y 60, and a ribbon cartridge 62~ Inked ribbon
64, stored within and advanced by the ribbon cartridge,
is interposed between the printwheel type elements and
the paper 66 wrapped upon platen 1~.
The printwheel drive motor 56 has a central axial
1~) shaft 68 extending outwardly beyond the motor, both
Eorwardly and rearwardly. The forward end of shaft 68
comprises a splined printwheel engaging and clriving
head 70 upon which the printwheel 58 may be mounted for
being positively driven thereby. At the rearward end
of shaft 68 there is located a transducer 72 including
a rotatable disk 74, mounted upon and for rotation with
shaft 68, and a fixed disk 76~ secured to the motor
housing. ~he transducer provides position signals
representative of the rotational position o~ shaft 68
(and thus printwheel 58) to the printer control
electronics in a known manner, as more specifically set
forth in U.S. Patent No. 3,839,665 entitled "Apparatus
Measuring Relative Velocity of Movable Members
Including Means to Detect Velocity from the Position
Encoder", and U.S. Patent No. 3,95~,163 entitled "High
~peed Printer With Intermittent Print Wheel And
Carriage Mo~ement", both by Andrew Gabor and assigned
to the same assignee as the instant application.
There is illustrated in Figures 2-5 one form of
the printwheel 58. It includes a central hub portion
78 from which a plurality o~ spokes 80 extend radially
outwardly, each spoke terminating in a pad 82 upon
which a character element is formed. The material of
which the printwheel i5 fabricated is of no import in
the context of this invention. Preferably, it is
molded of a suitable plastic material, however, heavy
duty composite (iOe. plastic and metal combination)
printwheels are also prevalent today and may be
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constructed to incorporate the instant invention.
Typically, the prin-twheel includes a handllng cap 8~,
secured to one side of the printwheel, and having a
central cavity 86 in axial alignment with a central
openillg in hub 78. The cavity 86 is illus-trated as
'; being splined for receiving splined head 76 of drive
shaft 68. Of course, any positive drive configuration
may be used, such as a common square or hexagonal
mating arrangement. In this manner, mounting and
withdrawal o~ the printwheel from the shaft 68 is a
1~ simple and casual manual operation for the operator,
since no attention need be paid to proper alignment of
the printwheel, as heretofore required. It should be
understood that cap 8~ may be eliminated entirely, i-t
being sufficient to provide the printwheel hub with
some suitable mating arrangement for receiving the
drive shaft.
Extending axially from the hub 78, are a pair of
protrusions or identi-fication pins 88A and 88B.
Although the protrusions are illustrated as being of
circular cross-section, it should be understood that
they may be of any desired shape. They are preferably
disposed on a common circle and are spaced from one
another by a predetermined identification angle ~ ,
which must be less than 180 (i-ts complementary angle
is designated as ~ ). One of the pins (88A for the
sake of this description), is the home position
indicator. Dashed line "R", tangent to the pin 88A,
will be the reference position from which the angular
rotation to each of the characters is counted. The
included angle ~, between the pins, will identify to
the printer all the informat on necessary to properly
operate that particular printwheel. Thus, once the
angle has been determined, font style ~viz. Pica, OCR,
Emphasis), pitch (viz. 10, 12, PS) and font language
(viz. French, German, English) will have been
identified by the printer microprocessor and the
location of each character and its required impact
level will be known. A11 the foregoing information is
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simply and inexpensively integrated into the printwheel
dnrin~ fahrication, by the addition of the two
plotrusions or pins spaced from one another by a known
-In~le. In the molded plastic wheels, provision may be
mad~ :itl the molding tool, for each different type of
-~ wlleel, for including properly spaced protrusions.
Since the protrusions are relatively small they will
add li-ttle to the cost of the novel printwheel.
In order to obtain relevant information regarciing
the location of ~:he pins and the included angle N, a
l~ suitab]e detector device is required. One such
detector embodlment 90 i5 disclosed in Figures 2 and 4.
It includes a selectively movable interposer 92 which
m~y be moved by solenoid actuator 94 mounted upon
carriage 2~, or any other suitable device. When a
1~ printwheel is to be identified, such as, when a new
wheel is loaded, or at the initiation of operation
àfter power -to the printer has been turned off, a
detection cycle is effected. Since prudent practice
dictates deenergizing the printer when the cover is
opened for replacement of the printwheel, the detection
cycle may be included in the usual power-up sequence.
A representative detection cycle may include the
following steps: first, the printwheel drive motor 56
is energized to rotate the printwheel at a slow speed,
i.e. less than one and one-half revolutions per second
(as compared to its normal print speed, i.e.
approximately five to fifteen revolutions per second~;
second the interposer 92, of detector 90, is moved by
means of the solenoid 94 into interference relationship
itl~ the pins 88A and 88B; third, the printwheel drive
motor is stopped when one of the pins 88 contacts the
interposer 92, stopping the drive motor and arresting
the train of signals from the transducer, fourth, the
direc.ion of printwheel motor 56 is reversed and
,, p~intwheel 58 will be slowly rotated until the other of
the pins 88 contacts the interposer 92, again stopping
the drive motor and arresting the train of signals from
the transducer; and finally, the interposer is
9 ~ 2'7
retrac-ted by the solenold 94. The angle between pins
88A and 88B can easily be ascertained by counting -the
number of transducer generated zero crossing signals
t:ransmitted during the reverse rotation of the
printwhcel motor. Rotation of the printwheel during
the first step of the detection cycle (i.e. beEore
introduction of the interposer 92) is eEfected to
prevent jamming or locking of the drive motor, which
could result if one of the pins were in direct
a:Lignment with the interposer at the time the solenoid
actuator 94 is energized, and the interposer is urged
agairlst a pin. Of course, the drive motor and the
in-terposer solenoid may be energized simultaneously
rather than sequen-tially, as set forth aboveO
As stated above, the printwheel 58 may be mounted
upon the shaft 68 without regard to aligning it at a
home position. Thus, as illustrated in Figures 3 and
5, the interposer may measure either the angle ~ or the
angle ~. For the purposes of this invention, it is of
no import which angle is measured since the printer
2Q control electronics is programmed to identify an angle
between 0 and 180. In the event that an angle
greater than 180 is measured, that angle is merely
subtracted from 360 to determine the printwheel
characteristic identification angle. Alternatively,
the printer control electronics may be programmed to
generate the same output identification for the ~ or
3 angle~
The printwheel "home" or reference position l''R'')
may be arbitrarily selected to be adjacent to pin 88A
8(! in the ~ zone. Therefore, it is determined by the
ju~taposition of wall "r" of interposer 92 and pin 88A.
Clearly, if the measured angle is ~ , the opposite
walls of interposer 92 and pin 88A will be in contact,
thus, the printer control electronics must also be
progran~ed to compensate for the pin and interposer
dimensions, to correctly determine the angle ~ and to
locate the home posi-tion, in the event that angle ~ is
measured.
Another embodiment of the detector device and
detection cycle will now be described (but will not be
illustrated in the drawings). In this form, a
detector, including a fixed interposer, is mounted on
the left frame element (as viewed in Figure l) adjacent
a carriage stop, also mounted upon the left frame
element. A-t the initiation of the power-up sequence,
the carriage will be moved fully to -the left until it
abuts the ~top. Prior to contacting the stop, the
printwheel drive motor will begin to rotate the wheel
1~ a~ the slow detection speed. Thus, when the carriage
arrives at the stop, the interposer will be in a
position to interfere with the free rotation of the
printwheel, but because of the premature rotation, the
drive motor will not jam, if they happen to be in
direct alignment. The subsequent detection cycle steps
as se-t forth above may then be carried out, namely, the
printwheel is rotated in a first direction until it
hits one of the pins, then the printwheel is rotated in
the opposite direction until it is again stopped by the
other pin. The measured angle ~ or ~ is determined
and the printer control electronics is armed with all
the information necessary for proper utilization of the
new printwheelO As it is sometimes required to change
printwheels during the production of a tas~, it is
desirable, with this embodiment, that the printer
control electronics restore the carriage to its
previous location relative to the platen (and document)
after the printwheel has been identified, so that the
tas~ may be completed.
Q An alternative embodiment of the unique printing
device is identified as 58' in Figures 6 and 7 wherein
the protrusions 88A' and 88s' are on opposite sides of
the printwheel and the interposer 92' is in the form of
a U-shaped element. It is contemplated that this form
of the printing device be utilized with the detector
device and detection cycle described in the preceding
paragraph, wherein the interposer 92' is fixed on the
printer frame and the printwheel carriage is brought
1 ] ~ '7
into interference rela-tionship with the interposer
cluring the detection cycle. It should be apparent that
this emhodiment will only be practical with a
disk-shaped printing device.
As it becomes desirable to identify a larger
number of printing devices than can be determined from
the 1&0 region allotted to identification, as
described above, a further embodiment of the printing
device is suggested. By providiny the printwheel 58"
illustrated in Figure 8, having protrusions 88A and 88B
1~ on one side (as in Figure 3) and a third protrusion 88C
located on the opposite side, a further identification
region of substantially 360 becomes possible. The
identification region, defined by the angle ~ between
protrusion 88C and reference position ("R"), may be
measured by a second interposer 93 moved into
interference relationship with the protruslon 88C at
the appropriate time. ~hile the interposer 93 has been
shown in Figure 8 at the 3 o'clock position, it should
be understood that it may be mounted in any
advantageous location as long as it is able to perform
its desired function. The method of in situ
identification will follow the series oE steps set
forth above, with respect to the Figure 3 embodiment,
with the addition of the further steps of removing
interposer 92, rotating the printwheel at the slow
speed, and moving the interposer 93 into interference
position. Since the printer electronics would have
already determined the location of the reEerence
position it is a simple matter to measure the angle (up
to 360) between that position and the third
protrusion, in either direction. Therefore, it is a
matter of choice to rotate the printwheel in the first
direction or in the second direction.
Although the novel rotary printing device of the
present invention has been described as beiny provided
with means for identifying a "home" position and for
identifying the printing device characteristics, the
present invention also contemplates a printing device
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]2
provided solely with "home" position identifying means.
Such a device is illustrated in Figure 9, as 58''', and
is provided with a single protrusion 88. In use, the
printer will rotate the printing device in one
direction only, un-til the movable interposer 92 abuts
the protrusion 88 and stops the drive motor. When this
occurs, the reference position "R" has been de-termined
and the printer control electronics will be "armed".
Reference is now made to Figure lO for a graphic
representation of the printer control electronics
1~ capable of carrying out the in situ identification of
the embodirnent illustrated in Figures l through 5.
During the identification cycle, as described above,
the printwheel dr~ve motor 56 rotates the printwheel 58
relative to the interfering interposer 92. Each time
one of the printwheel protrusions 88 contacts the
interposer, the printwheel and its drive motor will be
stopped. The transducer 72, also carried on the shaft
of the drive motor 56, generates a cyclical signal, as
the drive shaft rotates, whose cycles are sensed by the
processor 96 as an indication of a predetermined
incremental rotation of the printwheel. The processor
96 may be similar to the processor 76 disclosed in U.S.
Patent ~o. ~,05~,195 by Fravel et al (assigned to the
same assignee as the instant invention) and found in
the HyType II serial printer manu~actured by Diablo
Systems, Inc. of Hayward, California.
The cyclical signal train is used by the control
elements of the processor 96, referred to generally as
the controller 98 to increment a counter defined in a
s-torage location of a random access memory (RAM) lO0,
within the processor 96. The counter will be reset by
the controller, during the identification cycle, upon
the first incidence of arrested movement of the drive
motor, indicating that the first ~rotrusion has been
contacted. Continued rotation of the drive motor will
again allow the transducer to generate cyclical
position signals~ Each cycle is then counted by the
RAM counter until the second incidence of arrested
movement stops the train of signals, at which -tirne the
counter is also stopped by the controller. The value
stored in the RAM counter indicates the number of
cycles, of the cyclical signal train, between
protrusions 88A and 88~. Then, the stored value is
applied as an address to a table read-only-memory (ROM)
102 which contains all the characterizing data for each
printwheel to be used with the printer. It should be
noted, that the table ROM will also be programmed to
generate -the same characteriziny data for a stored RAM
n value indicative of the ~ angle or ~ angle. Each of
the other alternative embodiments, of the present
invention, described above will require a similar
identification cycle control program.
It is to be understood that the present disclosure
of an improved printwheel and the method of its use has
been made only by way of example, and that numerous
changes in process steps, details of construction and
the combination and arrangement of parts may be
resorted to without departing from the true spirit and
scope of the invention as hereinafter claimed.
