Printer having an ink ribbon shift apparatus

A printer having an ink ribbon shift apparatus includes a carrier unit having a printer head and a ribbon guide which is movable upwardly and downwardly. Up and down shift means are provided to shift an ink ribbon cassette up and down. A shaft is disposed parallel to a platen and extends along the entire range of movement of the carrier unit. The shaft shifts up and down together with the ink ribbon cassette and is engaged with the said ribbon guide. The up and down shift means moves the ink ribbon cassette up and down and the ribbon guide is thereby shifted up and down via the shaft so that a predetermined color band of an ink ribbon is positioned on a printing line.

Background of the Invention 
The present invention relates to a printer having an ink ribbon apparatus, 
and more particularly, to a printer using a ribbon cassette having a color 
ink ribbon with a plural number of bands of different colors. 
In an impact printer such as a wire dot printer and the like, a color ink 
ribbon that is divided across its width into bands of different colors is 
used in order to perform color printing. 
Color printing using such a color ink ribbon requires that the area of the 
color ink ribbon having the desired color be positioned above the printing 
line on the platen, and therefore requires an ink ribbon shift mechanism 
to do this. 
As a conventional ink ribbon shift mechanism, for example, U.S. Pat. No. 
4,695,175, discloses a mechanism wherein a rotation mechanism swings an 
ink ribbon cassette, which in turn causes a lever on a carriage to rotate 
thereby to move a ribbon guide up and down. 
In such a mechanism, the ribbon frame and the lever are connected by a 
connecting mechanism, which is adapted to keep the rotational position of 
the lever as it is while the carridge moves along the platen. 
Also, West German Patent Laid Open Pubilication No. 3,538,761 discloses 
another conventional ink ribbon shift mechanism. This is a mechanism in 
which an ink ribbon cassette can swing around a single support point, 
where a ribbon guide can rotate around a separate support point, and where 
a cam mechanism having first cam members for the ink ribbon cassette and 
second cam members for the ribbon guide is provided parallel to a platen. 
The first cam members move the ink ribbon cassette and the second cam 
members move the ribbon guide separately. 
In the mechanism disclosed in U.S. Pat. No. 4,695,175, however, the lever 
on the carriage and the connecting mechanism cause the problems of the 
mechanism becoming complex and of there being many places for adjustment. 
In the apparatus disclosed in West German Patent Laid Open Publication No. 
3,538,761, the second cam members must be adapted to move together with 
the carridge along the platen and so the mechanism becomes complex and 
adjustment also becomes difficult. 
SUMMARY OF THE INVENTION 
Accordingly, it is a general object of the present invention to provide a 
novel and useful printer having an ink ribbon shift mechanism in which the 
problems described heretofore are eliminated. 
Another object of the present invention is to provide a printer having an 
ink ribbon shift mechanism with a configuration wherein a shaft engaged 
with a ribbon guide is provided parallel to a platen so that the up and 
down movement of the ribbon cassette also moves the shaft up and down, 
which in turn moves the ribbon guide up and down. 
According to the present invention, because the ribbon guide is almost 
directly moved up and down according to the up and down movement of the 
ribbon cassette, and because the ribbon guide has the position to which it 
is moved and held by only the shaft, the number of parts is reduced and 
the mechanism and its adjustment become simple. 
Other objects and further features of the present invention will be 
apparent from the following detailed description when read in conjunction 
with the accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1, FIG. 2 and FIG. 3 indicate a schematic configuration of a printer 
10 according to the present invention. 
A rotatable platen 11 is provided between side plates 13a and 13b at the 
right and left of a base unit 12. The platen 11 is rotated by a 
feed mechanism (not indicated in the figure) and feeds printing paper 14 in 
the direction indicated by the arrow A. 
A carrier unit 15 carries a printing head 16 and is supported by a guide 
shaft 17 provided between the side plates 13a and 13b so as to be movable 
therealong. A carrier unit drive mechanism 18 drives the carrier unit 15 
in a reciprocating manner in the longitudinal direction of the platen 11. 
A ribbon guide 20 engages with and is supported by studs 21 and 22 provided 
upright in the carrier unit 15, and is movable up and down. The ribbon 
guide 20 guides the ink ribbon of the ink ribbon cassette to be described 
later. 
Towards the rear side of the carrier unit 15, an ink ribbon cassette 
support frame 25 is supported so as to be swingable about pivot pins 26, 
27 on the side plates 13a and 13b. 
The frame 25 has, at the right and left sides thereof, arm portions 28 and 
29 which extend forwardly. Between the ends of these arm portions 28 and 
29 is provided a shaft 30 parallel to the platen 11. 
On both sides of the lower side portion of the ribbon guide 20, are 
provided U-shaped cutout portions or brackets 31 and 32 opening so as to 
face the frame 25. Sleeves 33 and 34 made of synthetic resin are engaged 
with and held in the cutout portions 31 and 32, and the shaft 30 passes 
through these sleeves 33 and 34. 
The ribbon guide 20 and the shaft 30 are thereby in a mechanical 
relationship such that they are not restricted in the longitudinal 
direction of the shaft 30 but are restricted with each other in the up and 
down direction. 
Accordingly, with respect to the up and down shift of the shaft 30, the 
ribbon guide 20 is shifted together with the shaft 30 in the up and down 
direction. In addition, the ribbon guide 20 moves 
along the entire length of the platen 11 together with the carrier unit 15 
while its height position is regulated by the shaft 30. 
To the rear side of the frame 25 is provided an arm part 35 having a gear 
portion 35a. 
A stepping motor 36 is provided on the side plate 13b and a gear 37 on its 
spindle engages with said gear portion 35a. 
As is indicated in FIG. 4 and in FIG. 5, an ink ribbon cassette 40 is 
loaded on the frame 25. 
The ink ribbon cassette 40 has a configuration in which an ink ribbon 44 is 
accommodated in a cassette unit 43 having arm poritions 41 and 42 on both 
sides thereof, and a part of the ink ribbon 44 extends in a loop between 
the arm portions 41 and 42. 
When the ink ribbon cassette 40 is loaded on the frame 25, the ink ribbon 
44 is parallel to the platen 11 and at the position of the carrier unit 
15, is positioned between the printing head 16 and the platen 11 and is 
guided by the ribbon guide 20. 
As indicated in FIG. 5, the ink ribbon 44 has in the order from bottom to 
top across its width, a yellow band 45, a magenta band 46, a cyan band 47 
and a black band 48. 
The following is a description of the operation of an apparatus having the 
configuration described above. 
In the state indicated in FIG. 5 where the black band 48 is positioned on a 
printing line 50, and for example, a color specification signal specifying 
the color magenta is input, a predetermined number of pulses are applied 
to the stepping motor 36 until the magenta band 46 comes onto the printing 
line 50. By so doing, as indicated in FIG. 6, the stepping motor 36 
rotates in the counterclockwise direction and the frame 25 rotates via the 
gear 37 and the gear portion 35a, around the shafts 26 and 27, over a 
predetermined rotational angle, and stops at that position. 
By the above described rotation of the frame 25, firstly the ink ribbon 
cassette 40 is rotated to the desired position. 
Secondly, the shaft 30 moves together with the frame 25 in the 
counterclockwise direction and pushes the ribbon guide 20 in an upward 
direction. 
The ribbon guide 20 is guided by the studs 21 and 22 to move linearly 
upwardly. The rotational movement of the shaft 30 is converted into linear 
movement and causes the ribbon guide 20 to displace in a linear manner so 
that it is positioned at a predetermined height position. 
The ink ribbon 44 at the portion guided by the ribbon guide 20 is shifted 
together with the ribbon guide 20 in the direction of the width of the ink 
ribbon, and the magenta band 46 is positioned on the printing line 50 on 
the platen 11, as indicated in FIG. 6. 
The ribbon guide 20 moves along the full length of the platen 11 in the 
state where the above described height position is maintained by the shaft 
30. 
In addition, the shaft 30 extends for the full range of the movement of the 
carrier unit 15. Therefore, the ribbon guide 20 moves up and down by the 
shaft 30 irrespective of the position of the carrier unit 15. 
The following is a description of another embodiment according to the 
present invention, with reference to FIG. 7 through FIG. 12. 
In the figure, those portions that correspond to portions of FIG. 1 through 
FIG. 6 are indicated with the same numerals, and the corresponding 
descriptions of them are eliminated. 
This embodiment is adapted to compensate for deviation between the height 
of the ribbon guide 20 and that of the ink ribbon 44 in the ink ribbon 
cassette 40, which deviation occurs inevitably when the ribbon frame 25 is 
rotated. 
A protrusion 28a is provided on the arm portion 28 in FIG. 10A and FIG. 
10B. A hole 28b is provided at a distal end of the arm portion 28. 
As indicated in FIG. 8A and FIG. 8B, a slide lever 53 has a slide groove 
53a, a protrusion 53b and a stepped groove 53c. 
As indicated in FIG. 9A and FIG. 9B, a turn lever 54 has a protrusion 54a, 
a support hole 54b and a hole 54c. 
The side plate 13a (refer to FIG. 2) has formed in it a guide groove 80 as 
indicated in FIG. 7. 
The turn lever 54 is mounted at the hole 54c thereof to the mounting hole 
28b by a nut and bolt, and pivots around the hole 54b, as indicated in 
FIG. 10A and FIG. 10B. 
As indicated in FIG. 11A and FIG. 11B, the slide lever 53 is incorporated 
in such a manner that the slide groove 53a engages with the protrusion 28a 
and the stepped groove 53c engages with the protrusion 54a, and further 
that the protrusion 53b engages with the groove 80. 
Accordingly, the slide lever 53 can slide while being regulated by the 
groove 80 and the slide groove 53a. The stepped groove 53c controls the 
rotation with respect to the support hole 54b of the turn lever 54. 
The shaft 30 is fixed in the hole 54c at a distal end of the turn lever 54. 
As indicated in FIG. 7, in the state where the uppermost portion (i.e. 
black band 48) of the ink ribbon 44 corresponds to the printing line 50, 
the protrusion 53b is at the lowermost position of the groove 80, and the 
slide lever 53 is thereby at the left end with respect to the arm portion 
28. 
Accordingly, the protrusion 28a is at the right end of the groove 53a, and 
the protrusion 54a is also at the right end of the groove 53c. 
When the ink ribbon cassette support frame 25 is rotated in the 
counterclockwise direction, as indicated in FIG. 12, the slide lever 53 is 
regulated by the groove 80 and the protrusion 28a and advances in the 
forward direction of the arm portion 28. 
Because of this, the protrusion 54a of the turn lever 54 is positioned at a 
stepped portion of the stepped groove 53c corresponding to the amount of 
movement of the slide lever 53, and the turn lever 54 is thereby rotated 
in the counterclockwise direction to move the shaft 30 upwardly. 
Accordingly, the ribbon guide 20 is moved upwardly by a predetermined 
amount in which an amount of turning movement of the turn lever 53 is 
added to an amount of turning movement of the arm portion 28 of the frame 
25, and compensation for deviation between the height position of the ink 
ribbon 44 and that of the ink ribbon guide 20 is therefore performed. 
That is, in this embodiment, as the ribbon guide 20 is shifted upwardly, 
there occurs an insufficiency in the amount of linear movement of the 
ribbon guide 20 corresponding to the same amount of rotation of the motor 
36 (refer to FIG. 3). Accordingly, the embodiment is arranged in such 
that, as the frame 25 rotates in the counterclockwise direction to swing 
upwardly, the stepped groove 53c lowers the protrusion 54a to turn the 
lever 54 in the counterclockwise direction to raise the shaft 30. 
In this embodiment, two levers are provided to perform compensation of the 
amount of rotational and linear movement, and can be realized with only a 
slight addition of parts. 
According to this embodiment, it is possible to always determine the ideal 
position of the ribbon guide 20 no matter what position the ink ribbon 
cassette 40 is in the up and down direction. Accordingly, there is no 
color slip even in the case where the color bands of the ink ribbon are 
very narrow. 
Moreover, in this embodiment, the shaft 30 is mounted on the ribbon frame 
25, but the present invention is not limited to this, for example, the 
shaft 20 may be attached to the ink ribbon cassette 40 itself. In this 
case, the ribbon frame 25 described above is no longer necessary and the 
ink ribbon cassette 40 itself can be swingably supported between the side 
plates 13a and 13b of the ink ribbon cassette 40, whereby the ink ribbon 
cassette 40 itself rotates in accordance with the input of the color 
specification signals. 
In addition, the present invention is not limited to the above embodiment 
in which there is rotational movement of the ribbon frame, but it can also 
be configured so that the ribbon frame 25 moves linearly in the up and 
down direction. 
Furthermore, the present invention is not limited to these embodiments, but 
various variations and modifications may be made without departing from 
the scope of the present invention.