Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates to a dot matrix teleprinter
and in particular to a ribbon reversing mechanism to be used
therewith.
A dot matrix teleprinter prints information derived
from telecircuitry by means of a printing head which embodies
a plurality of needlelike printing wires operated selectively
in response to the pulses in the telecircuitry representing
the characters to be printed. One form of such printer is
disclosed in applicantls U.S. patent No. 3,670~861, issued
~une 20, 1972, where the printing head carriage, in the
course of printing a character, advances in a series of high
frequency increments, eight steps for each character, with
five steps devoted to actual printing and the remaining
three steps affording space between adjacent characters. In
each 9 tep one or more of the printing wires are actuated to
form a correspondlng number of dots as an incident to pressing
the paper against the supporting platen roll. High speed is
involved in that normal operation produces approximately ten
characters per second, meaning, in the example given,
approximately eighty steps per second.
In a&complishing this resort is had to a stepping
motor which rotates a timing balt to which the printing head
carriage is attached, the stepping motor being energi~ed by
the telegraph circuit whereby on the completion of one circuit
pulse in which the printing wires are excited, the printing
head matrix is advanced one step to continue the profile of
the dot character being printed on the next pulse.
The paper may be of the pressure responsive type in
which coloration is obtained as the result of wire impingement.
~0 The present invention is concerned with interposing a ribbon
between the printing head matrix and the sheet of paper so
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that the printing wires are effective to transfer ink from
the ribbon to the paper.
The teleprinter of the aforesaid patent has
; proven to be eminently satisfactory, and one object of the
present invention is to develop a ribbon reversin~ mechanis~
which can be readily mounted thereto, including a reversing
stepping motor energized by the teleprinter circuit. Other
objects of the invention are to employ sensors to detect
the end of ribbon pay-out and reverse the motor to start
~10 ribbon feed in the opposite direction; to step the ribbon
by an increment different from the increment of printing
head movement so that the ribbon will not be used repeatedly
at the same spot; and to develop unique mechanisms and
circuitry for reversing the stepping motor.
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The invention is used Ln combination with a high
speed teleprinter apparatus wherein characters are printed
bg a high speed printing head advancing in short high fre-
quency increments in response to a telegraph circuit, and
relates to a ribbon reversing mechanism comprising: a pair
of spools for supporting the ribbon, each spool having a
driven gear; a gear train including a pinion gear selectively
engageable with each of the driven gears to feed the ribbon
ln one direction or the other; a reversing stepping motor
energized by the telegraph circuit for incrementally rotating
the pinion gear; means to establish an increment of movement
of the ribbon different in dimension compared to the incremen$
of movement of ~he printing head, and means for reversing the
stepping motor after a predetermined length of ribbon has
been extended.
In the drawing:
Fig. 1 is a top plan view of the ribbon reversing
mechanism of the present inventiDn;
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Fig. 2 is a front elevation of the mechanism shown
in Fig. l;
Fig. 3 is an exploded view of the gear train;
Fig. 4 is a wiring diagram; and
Fig. 5 is a detail perspective view of a switch
operating lever.
Referring to Fig. l, the ribbon reversing mechanism
lS of the present invention is supported by an elongated ;;
mounting plate 16 having a pair of dependent support brackets
18 at opposed ends thereof adapted to be fastened to the
base 21 of the teleprinter disclosed in U.S. patent No.
3,670,861 as illustrative of a preferred embodiment of the
invention. When so mounted the support plate 16 is disposed
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in a horizontal plane.
The ribbon R, Figs. l and 2, is supplied by a pair
of spools 22 and 23. Depending upon the direction of
ribbon feed, one spool will constitute a supply spool and
the other spool will constitute a take-up spool.
To guide the ribbon, a pair of stationary guides ~4,
Figs. 1 and 2, of low friction plasti.c are supported in
vertical relation at opposite ends of the mounting plate 16.
To tension the ribbon, a pair of brake arms 25 are mounted
on posts 26 projecting upwardly from the upper sicle of the
mounting plate 16. Each brake arm is of S-form and includes
a front finger 28 serv.ing to apply a slight clampin~ force.
holdiny the ribbon against the related stationary guide~ A
coil spring 30 has one end anchored to a :Eixed stud ~:L bent
from a stud plate 32 secured to the underside o~ the mounting
plate, so as to project upwardly through an aperture in the
mounting plate. The opposite end of the spring 30 is secured
to a lug 33 projecting from the brake arm lever.25. The side
. of the brake arm 25 opposite the pressure applying finger 28 is
provided with a tab 34 permitting digital pressure to be
applied to release the brake if desired.
To feed the ribbon, each spool is provided with a
year, 22G and 23G, Figs. 1 and 2. In order tha-t the gears
may be neatly confined and accommoda-ted within narrow limits,
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the mounting plate 16l as shown in.Fig. 2, is dish~d at the
center, 16D. Each of the gears 22G and 23G is part of a
.~ one-piece plastic moulding which also afFords respec~ive
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bushings 2~B and 23B mounted for rotat.ion on spindles or
posts 35, Fig. 3, in turn secured in locating ape:rtures 36
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presented in the dished portion 16D of the mounting plate
16. Thus i~ will be seen, Figs. 2 and 3, that the ribbon
spools are mounted for rotation on vertical axes represented
by the posts 35~ Each post 35 is provi.ded with a bearing
surface 37 on which the related gear and bushing assembly is
free to turn.
In order to rotate and incrementally step one of the
- driven gears of the spools, a drive gear 40, Fig. 1, is
disposed between the gears 22G and 23G and is selectively
engageahle with one or the other depending upon the required
direction of ribbon feed. As shown in ~igO 2, gear 40 is
conveniently disposed within the space afforded by the dished
portion 16D of the mounking plate 16. Drive gear 40 is part
of a gear train which also includes an intermediate gear 41
co~molded therewith from plastic. Gear 41 in turn is driven
by a pinion gear 42 fastened to a shaft 43, Fig. 3, of a
reversing stepping motor 45.
; In order that gear 40 may be engagad with the driven
; gear o~ one of the spools, it is supported for pivotal movement
between the gears 22G and 23G, shifting from one to the other
when -the direction o:E motor xotation is reversed. A ~riction
device assures the gear will shift merely as an incldent to
motor reversal, as will be explained.
The drive gear 40 and the related gear 41 are mounted
for rotation at one end of a lever arm 50, Pig. 1, in turn
mounted for pivotal movement on a support bracket 52 fastened
to the dished portion of the mounting plate 16.
The support lever 50 is in the form o a U-shaped arm
as shown i.n Fig. 3. It is provided with apertures as 55 for
~eceivin~ a mounting screw 56 extendable through a support
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bushing 57 ~or lever 50 and secured in a tapped opening
in the support bracket 52.
A pair of bifururcations 59 in the support 52 register
with apertures 61 in the mounting plate so that mounting screws
may be employed to secure the support 52 in place.
The pivoting lever 50 has an ex-tended end in which a
- threaded stud 64 is mounted which rotatably supports the gear
assembly 40~41.
In order to sense the approaching end of ribbon pay-out
- 10 and to reverse the motor in a manner to be explained in more
detail, a pair of switches 70 and 71, Fig. 2, are located on
the underside of the mounting plate adjacent each end. Associated
w.ith each switch is a switch operating lever 73. Each swi.tch
operating lever has one arm provided with a ~inyer 75 in position
to engage the related switch contact button 76, Fig. 1.
The medial portion of each switch operating lever is
pivotally mounted on a post 77 at the underside of the
mounting plate 16~ The arm of each switch operating lever
opposite the switch contact finger 75 is provided with a
sensing finger 78 oE split ~orm projecting upwardly through an
aperture 7g in the mounting plate. The sensing ~inger thus
has two fingers af~ording a slot through which the ribbon is
extended, and each ribbon, ne~r the end thereof, is, provided
with a metal eyelet which is trapped in the slot of the sensing
~inger 78 to indicate the approaching end of ribbon pay-out.
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When the eyelet or metal element is thus presented to the~
sensing finger the next tug on the ribbon, tending to advance
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the ribbon, results in pivotal movement o~ the related switch
operating arm, causing the finger 75 to actuate the related
` ~ 30 switch button. When the switch is thus actuatecl,the cirauit
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to the reversing motor is reversed and the next driving
impulse results in gear 40 beiny displaced frcm one spool
gear to the other.
For example, gear 40, Fig. 1, is in position to
drive gear 22G so that spool 22 is the take-up spool; ribbon
feed is counter-clockwise. When the eyelet E on the ri~bon,
indicating the end of ribbon pay-out from spool 23~ is trapped
in the sensing finger 78, Fig. 5, the next tug on the ribbon
pivots the related switch operating arm 73 clockwise, finger
75 operates the button of switch 71, reversing the steppiny
motor 45 and gear 40 is shifted clockwise, Fig. 1, to engage
and drive gear 23G, whereupon spool 23 becomes the take-up
spool.
The reversing motor 45 is energized by the telegraph
circuit. This is equally true of the drive motor employed
to produce incremental spacing of the printing head as
disclosed in the aforesaid patent. The timing of the pulses
to the -two motors is therefore the same, and in order to step
the ribbon by an incremental distance different from that of
the printing head, the gear ratios are chosen so that this
dif~erence will prevail. The same effec~ could be realized
- by other means but doubtless at greater expense compared to
adjustment in the gear ~rain.
Circuitry-is shown in ~ig. 4 which is self-explanatory
for the most part. Motor 45, as already noted, is reversing.
The motor reversing contacts 45A and 45B are embodied in a
rela~ 80 which is also shown in Fig~ 2. One of the switches
~70) is normaIly closed; the other (71) i5 normaLly open.
However, when switch 71 is operated as explained above in
connection with Fig. 5, closing its related coIltacts, Fig. 4,
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a circuit from plus (+) to minus (-) is comple-ted for the
relay coil 80C. The contacts 45A and 45B are reversed,
reversing the motor. At the same time, a set of holding
contacts 80H for the relay coil are closed so that the
relay coil continue~ to be energized through normally
closed relay control switch 70, even though relay control
switch 71 once again returns to its normally open position
once the ribbon is reversed to displace the eyelet E, Fig . 5 .
Then, when the opposite end of ribbon pay-out is reached,
switch 70 is opened in the fashion explained in connection
with Fig. 5; the relay coil is de-energized and the motor
contacts 45A and 45B are reversed to reverse the motor. The
ribbon is reversed, and switch 70 is closed to condition the
circuit for reversal when the ribbon eyelet once more attains
the Fig. 5 position to produce operation of switch 71. It
will be appreciated that indicia other than the eyelets E
may be employed to identify the approaching end of ribbon
pay-out.
In order to effectively shift gear 40-41 as an
incident to reversing the motor, a riction device is adjusted
to prevent free wheeling of gear 40-41 on stud 41~ Conse-
quently, gear 41 uses gear 42 as a track and is not rotated
by gear 42 when ~he motor reverses; instead, gear 41 walks
on the teeth o~ gear 42 until gear 40 is engag2d with gear
22 or 23.
The device comprises a brake or friction plate 85,
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a washer-type spring 86 ana a lock nut 87 which secures the
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plate and spring to the threaded end of stud 64. Nut 87
is tightened suffiiently to prevent free wheeling of gear
assembly 40-41 on stud 64 while assuring that the gear
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assembly shifts from one ribbon feed gear to the other when
motor 45 is reversed. Once gear 40-41 is shifted to its
runniny position, it is held in place by the gear tooth loads
between gear 40-41 and whichever of gears 22 or 23 i5
engaged; -the gear tooth load overcomes the resistance of the
brake.
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