Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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1 D RIPTION OF THE INVENTION
The present invention relates to a printer. More
particularly, the present invention relates to a printer
of the type in which the ~uality of printed letters is
significantly influenced by a slight change of the space
between the top end of a printing head and the surfa~e of
a recording paper, such as a dot printer.
In the conventional printer of the type in which a
printing head is reciprocatively shifted along a platen,
the paper thickness is changed when the number of recording
papers is increased or decreased or when a chit or the like
is selectively inserted in ordinary recording papers and
printing is carried out in this state. In this case, it is
A desired that the quality of printed letters should be ~}~-
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f _ lby changina and adjusting the relative position
of the printing head to the platen. This can be achieved by
detecting the paper thickness and determining the position
of the printing head according to the detected thickness.
Various means have been proposed and adopted for attaining
this purpose. For example, U.S. Patent No. 3,988,984 diS-
closes a printer provided with such means. The printer dis-
closed in this U.S. Patent is not different from the con-
ventional printer in that a printing head is disposed reci-
procatively movably on the front face of a cyclindrical platen
horizontally located, but in this printer, a detecting roller
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1 ~ engaging with recordina papers wound around the pla~cl.~ is
attac:hed to a lever in the lower portion of the platen.
This lever is connected to a lever on the side of the print-
ing head through a rotary shaft or other connecting lever,
so that the position of the printing head is determined by
the movement of this lever. In short, in this printer, since
the paper thickness-detecting portion is much spaced from
the position of the printing head and the operation directions
of these two members are opposite to each other, a complicated
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lever mechanism shoul~ inevitably be interposed. Therefore,
the number of connecting and coupling members is very large
and the structure is much-complicated, and hence, it is very
difficult to precisely grasp the relation between the value
of the change of the paper thickness and the quantity of the
movement of the printing head. Accordingly, in order to
attain the intended object effectively, it is necessary to
pr~ c~ S~
manufacture respective parts with very high prcoi~ion3.
Furthermore, adjustment at the assembling step is very dif-
~ ficult, and it is very difficult to maintain certain capacities
in the printer.
It is a primary object of the present invention to providea printer in which the position of a printing head can precisely
be determined according to the thickness of recording papers.
Another object of the present invention is to provide a
printer in which a paper pressing roller is used as means for
detecting the thickness of recording papers and this paper
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1 pressing roller and a printing head are disposed on the
same levers, whereby the structure is simplified and adjust-
ment of the position can be accomplished very precisely.
Still another object of the present invention is to
provide a printer in which on insertion of a chit or the
like, the insertion position can assuredly be maintained in
the open state and on feedlng of papers, the paper pressing
state can assuredly be restored.
A further object of the present invention is to provide
a printer in which an arrangement is made so that no print-
ing driving signal is emitted unless the paper pressing state
is maintained, whereby an erroneous operation is prevented.
The present invention will now be described in detail
with reference to the accompanying drawings, in which:
Fig. 1 is a paerspective view showing one embodiment
of the printer of the present invention in the state where
a printing head is taken out; Fig. 2 is an enlarged view of
the printer in the state where a frame is dismounted; Fig. 3
is a top plan view showing a part of the printer shown in
Fig. 2; and Fig. 4 is a fragmentary perspective view illust-
rating a part of a mechanism for driving a carrier.
One embodiment illustrated in the accompanying drawings
will now be described. A pair of confronting frames 1 are
disposed on the left and right sides, respectively, and
levers 2 and 3 are held on the outer surfaces of the frames
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1 1 so t~lat the levers can turn along the frames 1 with shafts
8 being the centers. Both the ends of a guide shaft 6
slidably supporting a carrier S having a printing head
4 for a dot printer stationarily assembled thereon are
supported on the levers 2 and 3. Both the ends of another
guide shaft 7 are supported on the frames 1 in the state
where the shaft 7 is gripped by the rear portion of the
carrier 5.
Fig. 2 is a side view in which the frames 1 are
omitted to show arrangement of parts. A motor 9 is secured
to one frame 1 and gears 11, 12, 13, 14, 15 and 16 are
positioned to reduce the rotation speed of the motor 9 and
transmit the reduced rotation speed to a cam 10. A paper
feed cam 17 is disposed so that the cam 17 rotates coaxially
with the gear 12. The cam 10 has a drum-like shape, and on
the periphery of the cam 10, there is formed an endless spiral
groove 18~starting from one end, extending to the other
end and returning to said one end. A cam follower 19 to
be engaged with this groove 18 is supported on the carrier
5 and is rotatably mounted around the vertical axis.
A guide plate 21 is disposed between said frames 1
to guide a long recording paper 20 to a platen 25, and shafts
24 having paper feed rollers 22 and 23 fixed thereon are
~; rotatably supported between the frames 1. A paper pressing
roller 26 confronting the upper paper feed roller 22 is
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1 fitted in and held on a shaft 27 having both the ends
supported on the levers 2 and 3. A pinch roller 28 as a
pressing member confronting the lower paper feed roller 23
is supported by another lever 29. Ratchets 30 are fixed to
one end of the shafts 24 of the paper feed rollers 22
and 23, respectively.
A seesaw lever 31 having one end confronting the
paper feed cam 17 is attached to one frame 1 while the
seesaw lever 31 is rotatably urged by a return spring 32.
A stop lever 33 and a magnet 34 are held on one frame 1
so that the other end of the seesaw lever 31 is locked.
Feed levers 35 to be engaged with the above-mentioned
ratchets 30 are connected to the seesaw lever 31.
A stopper 36 for regulating the range of the
turning movement of the lever 2, a switch 37 as detecting
means, which is put off by movement of the lever 2:in the
counterclockwise direction to open a printing driving
circuit, and a toggle spring 38 for urging the lever 2
in the clockwise direction or counterclockwise direction
every time the lever 2 turns from one side to the other
side with the neutral position being as the center are
attached to the frame 1.
A printing ribbon 40 having both the ends held
by spools 39 is pulled out and located on the front face
of the platen 25.
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1 In the printer having the above-mentioned structure,
the rotation of the motor 9 is transmitted to the cam 10
through the gears 11 through 16, and the carrier 5 having
the cam follower 19 engaged with the groove 18 of the
rotating cam 10 makes a reciprocative movement along the
guide shafts 6 and 7 while the carrier 5 holds the printing
head 4 thereon. During this process, the printing operation
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is performed. -Wh~ the other cam 17 is being rotated, the
seesaw lever 31 is pressed by a high part of the cam 17 and
turned in the counterclockwise direction, and at this point,
the magnet 34 is energized to attract the stop lèver 23 in
the counterclockwise direction. Accordingly, at the point
when the high part of the cam 17 passes away, the seesaw
lever 31 is turned in the clockwise direction by the force
of the spring 32 to bring down the feed lever 35 and
intermittently turn the ratchet 30, and the paper feed rollers
22 and 23 feed the recording paper 20 by one pitch.
When the printing operation is performed on a chit 41,
the levers 2 and 3 are brought down in the counterclockwise
direction. In this state, the levers 2 and 3 are urged in
the bring-down direction by the to~gle spring 38 but their
positions are determined by the stopper 36. Accordingly, the
guide shaft 6 is allowed to shift along a locus with the shaft
8 being as the center, and the printing head 4, together with
the carrier 5, is separated from the platen 5. At this point,
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1 the rear portion of the carrier 5 slides in a direction
perpendicular to the other guide shaft 7, and therefore,
the retreating movement of the carrier 5 from the platen
25 is not inhibited by the guide shaft 7. Furthermore, by
virtue of an arrangement in which on both the ends of the
cam 10, the groove 18 is extended in a direction perpendi-
cular to the axis of the cam 10, only the movement of the
carrier 5 and printing head 4 in a direction separating
from (or approaching to) the platen 25 is allowed while
the movement of the carrier 5 and printing head 4 along
the platen 25 is inhibited. Accordingly, the chit 41 can
easily be inserted on the front face of the platen 25.
Then, the levers 2 and 3 are returned in the clockwise
direction and the paper press roller 26 is brought into
engaging contact with the paper feed roller 22 by the
force of the toggle spring 38. By this stopping action
of the paper press roller 26, a clearance between the top
end of the printing head 4 (i.e. the end facing the platen)
and the platen 25 can be adjusted to a predetermined size
~ by a one-touch operation. While the chit 41 is set in
the above-mentioned manner, the switch 37 detects the position
of the lever 2 to put off the printing driving circuit, and
therefore, an erroneous operation can effectively be
prevented. The printed chit 41 is fed upwardly by the upper
paper feed roller 22.
Incidentally, if the feed speed of the upper
paper feed roller 22 is made slightly larger than that
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1 of the~paper feed roller 23 in printing the printing paper
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20,1even when the recording paper 20 ~ slackened between
the paper feed rollers 22 and 23, an upward tension is given
to the recording paper 20 and the slack can be eliminated.
Accordingly, by this arran~ement, the recording paper 20
can be set on the platen 25 horizontally and catching of a
dot needle can be prevented.
In the foregoing embodiment, the levers 2 and 3 are
moved by a manual operation. In the present invention,
however, there may be adopted a modification in which the
levers 2 and 3 are moved by an electrical driving system
using solenoids or the like. In this modification, the top
ends of the levers 2 and 3 are not protruded from a cabinet
and an operation switch button or the like is attached. It
is preferred that a display device be disposed to indicate
whether the levers 2 and 3 are located at positions capable
of receiving a chit 41 or the like or they are in the paper-
pressing state.
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