Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
1~83415
ck~round of the Invention
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In the field of high-speed printing devices which are
e~pecially suitable for use in connectlon wi~h electronic data
processing systems, the wire matrix type of printer has come
into increasing use. In this type of printer, letters, numbers
and symbols are formed from a series of dots producecl by the
impact of the ends of a plurality of wlre elements on record
media.
Since the wires employed in the matrix printer have
10 a short operating stroke, it is important that a uniEorm dis- -
tance be maintained between the print head and the upper surface
of the medium being printed upon. It is therefore important,
in those cases in which a plurality of differen~ thicknesses of
record media may be printed upon by a matrix printer, to pro-
vide a compensating device which acts to maintain the same
I relative distance between the print head and the upper surface --
~` of the record media regardless of changesin the thickness of
the record media.
Various compensation devices for maintaining a pre-
determined distance between the print head and the record mediaregardless of the thickne~.s of the record media are known in
the prior art. In some of these, print head guide rollers are
run along a flexlble tape secured at its ends. In another
arrangement, an axially reciprocable probe is used to determine
the position of the surface of the record media to be printed
upon, and controls a motor which positions the print head
accordingly.
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Summary of the Invention
This invention relates to an arrangement in a
printing device for controlling the distance between record
media and the printing elements of a print head by use of
sensing means which acts through a transducer to control motor
means operable to change the position of the print head.
According to one embodiment of the invention, a
printing device for printing on record media which may be of
different and varying thicknesses, ~aid record media being
introduced to the printing device in a given direction, com-
prises a carriage; a carrier operatively connected to the
carriage; a frame mounted on said carrier; a printer mounted
on said frame, said printer and said carriage being capable
of relative movement therebe~ween in a direction transverse
to the direction of introduction of the record media to the
` printing device; positioning means operatively connected to
the frame and the carrier and including a motor capable of
co~tinuously positively positioning the frame with respect to
the carrier in either of two directions so that the printer is
` 20 located a prede~ermined distance from the record media for
:~ proper printing thereon; circuit means including a Hall effect
transducer fixed to the frame, a comparator for comparing a
reference voltage with the voltage generated by the Hall
effect transducer and switching means controlled by the com-
parator for con~rolling said positioning means; and sensing
means pivotally mounted between its ends on said frame and
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including a feeler at one end, said sensing means being biased
to en~age the record media and to be continuously responsive
`I to variations in the thickness thereof, said sensing means
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also including magnetic means at its other end for coacting
with the Hall effect transducer for causing said circuit means
continuously to control the positioning means to alter the
position of the printer in accordance with movement of the
sensing means to maintain continuously said printer a predeter-
mined distance from the record media regardless of variations
in the thickness of said media.
It is accordingly an object of the present invention
to provide a printing device having a novel compensating means
for maintaining a given distance between a printing head and
the record media to be printed upon, regardless of the thick-
ness of said media.
Another object is to provide a printing device in
which sensing means acts through a transducer to control motor
means operable to change the position of a print head to main-
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tain a predetermined distance between said print head and the
record media being printed upon.
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A further object of the invention is to provide a
printing device in which sensing means acts through a Hall
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generator to control motor means operable to change the position
- of a print head to maintain a predetermined distance between
said print head and the record media being printed upon.
With these and other objects, which will become
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apparent from the following description, in view, the invention
includes certain novel features of construction and combination
of parts, a plurality of embodiment of which are hereinafter
described with reference to the drawings which accompany and
.j form a part of this specification.
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Brief Description of the_Drawing~
Fig. 1 is an elevation view of the printing device
of the present invention.
Fig. 2 is a partial perspective view of the printing
device shown in Fig. 1.
Fig. 3 is a block diagram of the control sy8tem of
the present invention.
Fig. 4 is a circuit diagram of the control system of
the present invention.
Fig. 5 is a perspective view of a modified form of
the presert invention.
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Description of the_Preferred Embodiments
Referring now to Fig. 1, the transport of one record
medium or several record media is accomplished by suitable
means, such as a platen 3. The thickness of the record medium
2 is sensed by a printing head distsnce feeler 8 so that, as
will hereinafter be described in detail, independent of the
thickness of the record medium 2, constant distance is main-
tained between the printing elements 13 (Figs. 2 and 5) of a
printing head 1 and the record medium 2. The prlnting head
distance feeler 8 is pivotally supported by a shaft 9, so that
upon a rocking movement of the left-hand part of the prin~ing ~-
head distance feeler 8 upwardly (Fig. 1) the right-hand part
thereof performs a rocking movement downwardly. By means of a
spring 10 the upper part of the printing head distance feeler
is caused to constantly rest upon the record medium 2 being
passed over the platen 3 9 and thi~ at a low bearing force of,
for instance, 20 dynes.
The right end (Fig. 1) of the printing head distance
feeler 8 has secured thereto a magnet 7 which acts upon a Hall
generator 6. Said Hall generator 6 is fa~tened to a suitable
support 14 on a pivotally mounted frame 50 which has arranged
thereon the printing head 1. The frame 50 and the printing
`, head 1 thereon are rockable around a centre of rotation 11
whenever suitable slgnals are being applied to the servomotor
4. The centre of rotation 11 and the servomotor 4 are pro- ,
vided on a carrier 51 which i8 movable transversely relative
to the transport direction of the record medlum 2. Caused by
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the rotation of the shaft of the servomotor 4, a bolt 5 havingan external thread and being secured to the shaft moves into an
element 43 having an opening with an internal thread and being
connected through the frame 50 to the prlnting head 1. By
rotation of the shaft of the servomotor 4, the bolt 5 thuR is
moved into or out of, respectively, the element 43, so that in
dependence upon the direction of rot~tion of the servomotor,
the printing head 1 is moved either away from or towards the
record medium 2.
The servomotor 4 i8 controlled for adjusting the dis-
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tance of the printing head 1 from the record medium 2 by means
of the Hall generator 6.
Fig. 2 is an enlarged view of the printing head dis-
tance feeler 8. The distance feeler 8 has a recess 42 through ~ -
which individual printing needles 13 of the printing head 1
can move to print on the record medium 2 which i8 guided over
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the platen 3 ~Fig. 1). By means of the spring 10 acting upon
the distance feeler 8 it is ensured that the latter rests with
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a light bearing force againct the platen 3, or respectively,
. 20 a record medium led thereover. In case of the thickness of the
-~ record medium changing, the distance feeler 8 is rocked around
~ the axle or shaft 9 extending through two guide elements 17 and
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18 (Fig. 2) on said feeler 8. Thereby the Hall generator 6,
belng fixed with respect to the printing head 1, is influenced ~ -
in proportional rel~ionship by the magnet 7 secured to the
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distance feeler 8. The parts lS and 14 (Fig. 2) are, as
already mentioned, fixed with respect to the printing head 1.
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In the present arrangement, the Hall generator 6 will
produce a voltage ranging, for instance, between 0.2 and 0.5V,
which represents a dimension for the local position of the
distance feeler 8 in relation to the record medium. The manner
in which the voltage as produced by the Hall generator 6 i9
utilized in an automatic control system for the purpose of
regulating the distance between the printing head 1 and a
record medium 2 (Fig. 1) or 2a and 2b (Fig. 5), respectively,
will now be described in connection with the block diagram of
Fig. 3. In a comparison means 44, a standard magnitude W in
the form of a nominal value voltage which is preadjusted by a
potentiometer 19 (Fig. 4) is compared with an actual value `~
voltage signal 52 as produced by the Hall generator 6. The re-
sult is a signal having a deviation of magnitude X which i~
supplied to a nominal value adJusting controller 12b, 12c, 12d,
which latter produces a control signal having magnitude Y,
acting upon the servomotor 4. A change is thereby produced,
in the manner previously described, in the distflnce of the ~ -
printing head 1 from the record media 29 which change, via the
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distance feeler 8, again influences the Hall generator 6, this
causing the automatic control system according to Fig. 3 to be
closed.
The electrical functioning of the automatic control
system a~ shown in Fig. 3 in ~ simplified m~nner will now be
explained with reference to Fig. 4.
Via a potentiometer 19, ~ controller 12a, formed as
a proportional/dlfferential controller (P/D-controller) h~
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supplied thereto a nominal value voltage. The functioning or
the characteristic, respectively, of said P/D-controller 12a
is determined in a known manner by resistors 22, 23, 24 and a
capacitor 25. The two lower terminals o~ the Hall generator 6
in Fig. 4 are connected to a base reference potential, shown
as ground, while the two upper terminals, via said resistors
23, 24 and the capacitor 25, or via the potentiometer 19,
respectively, are connected to the P/D-controller 12a compris-
ing two inputs. If a switch 22a, which connects the negative
input of the controller 12a to a base reference potential,
shown as ground, is closed, a correspondlng potential level
is applied to the negative input o~ the controller 12a. The
resulting output signal from the controller 12a is amplified
by an amplifier 12b, and causes a transistor 12c to conduct,
whereby the motor is, for instance, driven in a clockwise di-
rection. The "right-hand" rotary ~irection in this case means
l~ a rocking-away of the printing head 1 from the record medium 2.
; Said rocking-away movement i8 st~pped by a built-in throttle
switch 22b after the printing head's removal from the record
medium for a distance of approximately 6 millimeters. The
throttle switch 22b then opens to interrupt the motor branch
circuit. The rocking-away movement i~ of essential advantage
~ince a record medium can then easily be inserted through the
6 mm wide gap. By the subsequent opening of the switch 22a
the hitherto existing automatlc control system becomes effective
again. The relative potentials applied to the two inputs of the
controller 12a now cause transistor 12d to be rendered
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1~83415
conducting, thereby causing the mo~or 4 to be driven in a
counter-clockwise direction. The diode 22d is provided to -~
enable the motor branch circuit to bP completed for driving of ~ -
the motor 4 in one direction, counter-clockwise in the example
given, despite the switch 22b being open. The driving of the
motor in a counter-clockwise direction ceases when the desired
dist~nce i9 re~ched. As already mentioned, the Hall generator
as used here produces n voltage ranging between 0.2 and 0.5V.
In the embodiment as described, the magnitude of the voltage as
produced by the Hall generator depends on the position of the
distance feeler 8 and, thus, directly on ~he thickness o~ the
record medium used.
The result as produced in the controller 12a is
supplied via a resistor 26 to the amplifier 12b which is fed
back via a capacitor 27 and a resistor 28. The amplifier 12b
has a positive and a negative input. The positive input is
connected to a base reference po~ential, shown as ground, while
the previously mentioned signal, interpreting the deviation
from standard, i~ applied to the negative input.
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a 20 The output of the amplifier 12b is coupled over two
transistors 12c and 12d in a generally known manner to the
servomotor 4, this enabling the latter to be driven in counter-
clockwise or clockwise direction in dependence upon the pol~ri-
ty of the signal produced.
The supply voltages for the servomotor 4 to be driven
in counter-clockwise and clockwise directions are symbolically
lndicated by the two energy sources 20 and 21 In dependenoe upon
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the voltage as produced by the Hall generator 6, and the com-
parison voltage provided by the potentiometer 19, the P/D-
controller 12a produces a signal which, after having been amp-
lified, ls effective to drive the servomotor 4 in respective
manner either in counter-clockwise or clockwise direction,
this m~king the printing head 1 ad~ust itself in relation to
the record medium 2 in such a manner that a constant distance
between the printing needles 13 of the printing head 1 and the
record medium 2 is reached and held, respectively. The dimen-
sion of the said distance which is to be ~aintained can bedetermined by the adjustment of the potentiometer 19.
Shown in Fig. 5 is another embodiment of the present
invention illustrating one way in which the arrangement as per
the present invention can be used for the distance control in
a serial-type needle printer. In Fig. 5 the printing head 1
is arranged on a carrier 41 which is movable transversely to
the drawing-in direction of record media 2a and 2b. Through
an appropriate recess provided in the distance feeler 8 which
is resting lightly upon the record media 2a, 2b, the needle~
13 of the printing he~d 1 can be passed through in desired
series. Between the needles 13 and the record media 2a, 2b,
in a known manner, is guided the ink-ribbon of an ink-ribbon
means 29 The carrier 41 slides by means of rolls 38 on a
f~stening rod 36 which together with the rod 45 is fixed in
two side frame parts 30 snd 31. The energy supply and control
of the printing head BS well as of the au~omatic distance
control system is provided via a flexible conducting tape 37
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in generally known manner.
Both the magnet which i9 connected to the dlstance
feeler 8 and the Hall generator as used are not to be seen from
Fig. 5 since they are locsted behind the printing head 1. The
distance of the printing head 1 is controlled by ~he servomotor
4 in the previously described manner in dependence upon the
thickness of the record media 2a and 2b, respectively. The
carrier 41 is transported transversely to the drawing-in direc-
tion of the two record media, i.e. in line direction, by means
of a belt 35 which is guided over a deflection roll 40. The
belt 35 is driven via a motor 32 which, via a driving belt 34,
is effective to drive a roll 39. By the aid of a synchronizing
di~c 33 the po3itioning of the carrier 41 and the printing head
1, respectively, can be accompli~hed.
The two record media 2a and 2b of different thick-
nes~es can be drawn-in by means of 8 pulling-in mechanism, not -~
shown, the latter being for instance provided in the form of
grippers arranged transversely to the platen 3~ The record
medium 2a may be a ledger card and the record medlum 2b m~y be
a savings book. Through the distance feeler 8 lightly resting
upon the record media, the thickne~s of the latter is ascer-
tained. In depen~ence upon said thickness, the control of the
distance between the printing needles 13 and the surface of the
respective record medium opposite thereto to a deslred dimen-
sion, for instance to 0.3 mm, ig accomplished through the Hall
generator 6, the circuit of Fig. 4, and the servomotor 4, in
the manner previously described.
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Through the exact control of the printing head dis-
tance in accordance with the present invention it is ensured
that without the danger of the record medium's being damaged
or displaced, an exact and clean print can be obtained. This
i9 possible since the prin~ing needles 13 always strike at a
constant impact and after a constant track against the record
medium,
Since the printing speed of matrix printing heads is
highly dependent on the track of the needles, there is more- :
over possible a simple adjustment of the optimal track of the
printing needles, i.e. of the maximal printing speed.
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