Printer for monochrome and color printing

A printer for use with both monochrome and color ink ribbon cartridges has a cartridge holder which is rotatable to correctly position the ink ribbon of whichever cartridge is put in place in front of the print head. The cartridge holder and a transmission for driving it are mounted on a carriage which is movable in front of a platen. A driving motor for powering the transmission is placed on the carriage to convert the printer from monochrome so as to be able to use with either a monochrome or a color ink ribbon cartridge and a switch having two sets of contacts in a single circuit responds to the presence of a color ink ribbon cartridge to position the color ribbon in front of the printer at a color home position.

BACKGROUND OF THE INVENTION 
The present invention relates to printers. More particularly, the invention 
relates to printers useful for both monochromatic and multi-color printing 
and to an ink ribbon cartridge holder for use in such printers. 
In known printers, provision is made only for printing in one color. That 
is, monochromatic printers are not capable of driving a multi-color ink 
ribbon cartridge to permit use of the printer for multi-color printing. 
Also, known multi-color printers do not provide monochromatic printing 
even when a monochromatic ink ribbon cartridge is loaded. Thus, each 
printer has been specifically intended to be used for monochromatic or for 
color printing, and no printer has provided both. 
The color selecting mechanism of a known multi-color printer is shown in 
FIG. 15. In the printer of FIG. 15, a color-selecting motor 81 is located 
under the printer's paper guide 88. A motor 81 drives a barrel cam 82 and 
power therefrom is transmitted to one end of an oscillating lever 83. The 
other end of lever 83 moves vertically a cartridge holder 84 which carries 
an ink ribbon cartridge 85 to position that portion of a color ribbon (not 
shown) which has ink of a desired color in front of platen 87 for 
printing. Motor 81, together with other parts, is secured to the mechanism 
and neither the motor nor the driving unit, which includes the motor and 
its peripherals, can be removed easily by the user. 
Further, as mentioned above, a monochromatic printer of known type cannot 
be easily changed into a multi-color printer. Generally, therefore, if the 
purchaser of a monochrome printer comes to need multi-color printing, he 
must buy still another printer. 
Also, in known color printers accurate matching of the upper and the lower 
positions of the ink ribbon cartridge is performed by fine adjustment of 
an adjusting member which is attached to the print head carriage. Since 
the print head carriage is subject to vibration and to external shock, any 
set value is subject to change as the machine is used and is, therefore, 
unstable, with the result that the ink ribbon cartridge will often be 
incorrectly positioned. 
SUMMARY OF THE INVENTION 
The foregoing problems are solved in the present invention by a printer 
having a carriage which is conventionally movable in front of a platen. 
The carriage carries a print head which can be conventionally actuated to 
effect printing on paper which is held in front of the platen, and also 
carries a holder for a ribbon cartridge. The cartridge holder can 
interchangeably receive a monochrome ribbon cartridge and a color ribbon 
cartridge. A cartridge-shift drive motor is removably mounted on the 
carriage, and, when present on the carriage along with a color ribbon 
cartridge, provides motive power for moving the cartridge or a cartridge 
holder to position the color ink ribbon between the print head and the 
platen for printing a particular color. 
In one embodiment, a cartridge holder is pivotally mounted on the carriage 
so that a selected portion of the ribbon, if a color ribbon cartridge is 
present, can be positioned for printing by tilting the cartridge. Sensing 
switches may be provided which identify the type of cartridge which is 
mounted on the carriage and establish the "home" position of a color 
cartridge when such is used. According to one aspect of the invention, the 
two switches are combined into a single detector. 
In another embodiment, the ink ribbon cartridge is pivotally mounted on the 
carriage and the printer can be changed from a monochrome printer to one 
which uses either a monochrome ink ribbon cartridge or a color ink ribbon 
cartridge by positioning a drive unit on the carriage. When a monochrome 
ink ribbon cartridge is used, it is rotated on the pivots into position 
against a stop by a resilient spring so that the ink ribbon is located in 
front of the print head. When a color ink ribbon cartridge is used, the 
same spring urges the cartridge into engagement with the drive unit so 
that the drive unit can position a selected color band of the ink ribbon 
in front of the print head. The monochrome cartridge and the color 
cartridge are dimensioned differently so that the monochrome cartridge 
does not come into engagement with the motor drive unit and so that the 
color cartridge does not engage the stop. A mechanical stop on a cam in 
the drive unit can define the home position. 
According to another feature of the invention, the initial position of the 
color cartridge can be predetermined by means of an adjustable resistor. 
An object of the present invention is to provide an improved printer in 
which color or monochrome printing can be easily selected at any time. 
A further object of the invention is to provide differing structural 
features in one of a monochromatic ink ribbon cartridge and a multi-color 
ink ribbon cartridge to permit detection of the presence of one or the 
other in a printer. 
Still another object of the invention is to provide means by which 
detection of the home position of the ink ribbon cartridge is accurately 
performed. 
A still further object of the invention is to provide means by which the 
fine adjustment of the positions of an ink ribbon cartridge in a printer 
is securely performed. 
Still other objects and advantages of the invention will in part be obvious 
and will in part be apparent from the specification. 
The invention accordingly comprises the features of construction, 
combinations of elements, and arrangements of parts which will be 
exemplified in the constructions hereinafter set forth, and the scope of 
the invention will be indicated in the claims.

DETAILED DESCRIPTION OF THE INVENTION 
FIG. 1 is a plan view in partial cross-section of a printer carriage 5 
fabricated in accordance with the teachings of the present invention. 
Carriage 5 carries a print head 4 back and forth on a pair of guide shafts 
2 and 3 in front of and parallel to a platen 1 for printing on paper which 
is held thereon (not shown). Carriage 5 also carries a ribbon type 
detector 47. 
As can be seen in FIGS. 2 and 3, print head 4 is supported on and secured 
to carriage 5. Carriage 5 also supports a transmission gear 13 and an 
oscillatable lever 14 on separate axes and in engagement with each other. 
Space is provided between side walls 23 and 24 of carriage 5 for support 
of an ink ribbon cartridge holder 15, into which an ink ribbon cartridge 
18 can be readily inserted. A vertical arm 16, on the underside of 
cartridge holder 15 is movably received in, and can receive motion from, a 
slotted connector portion 28 of oscillatable lever 14. 
Carriage 5 is also provided with a pair of oppositely-facing upright claws 
21 and 22 for removably securing a color-selecting motor unit 19 in a 
predetermined position on carriage 5, and engaging a connector 25 for 
making electrical connection between motor unit 19 and the ink ribbon 
color selection control circuit of FIG. 11. When multi-color printing is 
to be done, motor unit 19 is inserted in carriage 5, being pushed down in 
the direction of arrow A so as to be held to carriage 5 by hooks 21 and 
22. When motor unit 19 has been emplaced, a drive gear 20, which protrudes 
downward from motor unit 19, meshes with inner teeth 30 of transmission 
gear 13, enabling power from motor unit 19 to be transmitted to ink ribbon 
cartridge holder 15. Also, when motor unit 19 is in place, it engages 
connector 25 and is connected to the electric circuit of the printer. 
As detailed in FIG. 4, transmission gear 13 has an axially-extending, 
peripheral rim, which carries a set of inward-projecting teeth 30, and a 
raised central portion which has a set of outward-projecting teeth 31. 
Both sets of teeth are centered around a gear shaft hole 32. Both sets of 
teeth are formed on the one gear body. 
As depicted in FIGS. 3-6, the fulcrum 29 of transmission lever 14 is 
oscillatable around a pivot 5a on carriage 5, being positioned so that its 
inner teeth 33 engage teeth 31 of transmission gear 13. 
When monochrome printing is selected, motor unit 19 is not mounted in the 
carriage and rotation of the transmission gear 30 is limited by a bridge 
or the like (not shown) so that oscillatable lever 14 can move no further 
than a predetermined position. 
The manner of switching ink ribbon 17 (FIG. 2) between ink colors is 
described with reference to FIG. 5. When gear 20 of motor unit 19 rotates 
in the direction of arrow F, its motion is transmitted to inner teeth 30 
of transmission gear 13 and thence to teeth 31 of transmission gear 13, 
which rotate in direction F. From teeth 31, power is transmitted to inner 
teeth 33 of rotatable lever 14, causing oscillatable lever 14 to rotate 
about pivot shaft 5a in the direction of arrow B. Vertical arm 16 on 
cartridge holder 15 is engaged in slotted connecting portion 28 (FIG. 2) 
of oscillatable lever 14 and is driven thereby to cause cartridge holder 
15 to rotate on pivots 26 and 27 in the direction shown by arrow C, 
lifting the ink ribbon in front of the print head. Shifting thus between 
the color bands of ink ribbon 17 is continued by rotating gear 20 of motor 
unit 19 until the desired color band is in front of the printing head 4. At 
this time, rotation of gear 20 of motor unit 19 is stopped. Now, when print 
head 4 is driven, the selected color will be printed on paper which is held 
in front of the print head on platen 8. 
To lower the ink ribbon, gear 20 of motor 19 rotates in the direction of 
arrow G, oscillatable lever 14 rotates around the fulcrum 29 in the 
direction of arrow D. Now, cartridge holder 15 rotates around pivot 
projections 26 and 27 in the direction of arrow E and cartridge holder 15 
rotates in the opposite direction from that when gear 20 is rotated in the 
direction of arrow F. 
In accordance with the present invention, the ink ribbon color is selected 
by using the reciprocal rotation of the motor which moves the oscillatable 
lever 14, as described above, in the direction of arrow B or of arrow D 
(FIG. 3) and, consequently, by rotating ink ribbon cartridge holder 15 in 
the direction of arrow C or of arrow E, respectively. Moreover, the 
invention provides, in one embodiment, that the mounting of motor unit 19 
on the carriage results in the arbitrary selection of multi-color 
printing. Thus, either monochromatic and multi-color ink ribbon cartridge 
can be used in the same printer. 
According to another feature of the invention, the addition of a detector 
or the like to a multi-color printer enables use of both a monochrome ink 
ribbon cartridge and the multi-color ink ribbon cartridge therein. 
Provision is made for detection of the kind of cartridge as well as for 
determining the home position of the cartridge. To this end, the apparatus 
of the invention is provided with a mechanism for detecting which kind of 
ink ribbon cartridge is present and for establishing the home position of 
the cartridge is now explained with reference to FIGS. 6 to 9. 
As depicted in FIG. 6, holes 8 are provided, on both sides of carriage 5, 
for receiving the laterally-projecting support pivots 26 of cartridge 
holder 15, about which the cartridge holder is oscillatable. Further, 
carriage 5 is provided with a vertically projecting member 9 for use in 
locating the color home position of cartridge holder 15. 
In the exploded view of FIG. 7, cartridge detector 47 is shown as having 
three parallel insulating members 40, 41, and 42, between which two 
conducting contact plates 43 and 44 are secured. An actuator 46 is 
rotatably fitted on portion 45 of insulating member 40, being supported 
from beneath, for example, by the surface of cartridge holder 15 on which 
detector 47 is seated. Contact plates 43, 44 respectively have contact 
portions 48, 49 and 50, 51. Contacts 48 and 50 are normally open, and 
contacts 49 and 51 are normally closed, thus forming a single-circuit 
switch having two sets of contacts. Detector 47 is held to cartridge 
holder 15 by claws extending from the lower portion of insulating member 
42. 
Generally speaking, a color typing ribbon is divided longitudinally into 
four colors: B (black), M (magenta), C (cyan) and Y (yellow) and has a 
width of about 1 inch, e.g. about 25 mm. On the other hand, a monochrome 
ink ribbon is only about 13 mm wide. Since the thickness of a color ink 
ribbon cartridge is different than that of a monochrome ink cartridge, the 
position at which the monochrome cartridge prints correctly will not be 
appropriate for a color cartridge. When these ribbon cartridges are used 
on the same printer, therefore, it is necessary to establish the home 
position of a color ribbon when it is loaded so that printing will always 
correctly use the center portion thereof. 
The foregoing problem is solved in the present invention by providing for 
initial positioning of the multi-color ink ribbon and the monochromatic 
ink ribbon at different levels. To this end, the type of ribbon, e.g. 
multi-color or monochromatic, is detected when the cartridge is loaded. 
For this purpose, the bottom of multicolor ink ribbon cartridge 18 (FIG. 
9) is provided with a pin or projection 53 for pushing down on tab 46' of 
actuator 46 in detector 47 when the multicolor cartridge is loaded on 
cartridge holder 15. The lower side of actuator tab 46' then engages and 
pushes down on the extended portion 49 of contact plate 43, moving it away 
from contact 51 and causing the normally closed switch contacts 49 and 51 
to open. In other words, when a multi-color ink ribbon cartridge has been 
loaded, switch contacts 49 and 51 are open; when a monochromatic ink 
ribbon cartridge has been loaded, switch contacts 49 and 51 are closed. 
Contacts 48 and 50, which control color home positioning, are normally 
open. When power from motor 19 (on carriage 5) is transmitted, at the 
outset, to ink ribbon cartridge holder 15, the outer portion of ink ribbon 
cartridge holder 15 moves lower, and an upward-extending color-positioning 
projection or post 9 on carriage 5 (FIG. 6) presses contact projection 48, 
closing contacts 48 and 50. In response to a contact closing signal, 
generated thereby, driving of oscillatable arm 14 by motor 19 is slowed 
and stopped. The position of ink ribbon cartridge holder 15 at this time 
is known as the "color home position". 
The operational sequence of cartridge holder 15 in ribbon detection and 
color home positioning is described below. 
First, cartridge holder 15 is moved upward, opening contacts 48 and 50. At 
this time, the condition of the switches in detector 47, shown as signal 
state (A) in FIG. 10, is read. If the signal state (A) indicates contacts 
"closed", the loaded ribbon is identified as monochrome and cartridge 
holder 15 is moved to a position such that the printing head is centered 
to strike the center of the monochrome ribbon and stays at that position. 
If signal state (A) indicates an "open" contact, the loaded ribbon is 
identified as multi-color. Cartridge holder 15 is then moved downward 
until contacts 48 and 50 close, being then positioned so that the printing 
head strikes the center of the total width of the multi-color ink ribbon. 
Subsequent movements of the cartridge holder for printing different colors 
now are all related to this "color home position". 
The foregoing method of the invention for adjusting for the optimum 
position of the cartridge, relative to the print head, is explained with 
reference to FIGS. 11 and 12. In FIGS. 11 and 12, carriage 5 positions a 
print head 4, in response to a print signal which is delivered from a host 
device (not shown) for printing information on paper which is supported on 
platen 1 in front of ink ribbon cartridge 18. Carriage 5 has an ink ribbon 
cartridge holder 63 which is coupled to a power transmission which includes 
an eccentric cam 62; turned by a motor 61, such as a stepping motor. When 
so turned, cartridge holder 63 pivots cartridge 18, moving the surface of 
the ink ribbon relative to printing head 4. 
As depicted in FIG. 12, the body 68 of the printer supports a semi-fixed 
resistor 67 in a location which can be reached by an appropriate 
instrument or tool which is inserted easily from the outside. Semi-fixed 
resistor 67 is receives a reference voltage V.sub.s (FIG. 11) and 
supplies, at tap terminal 67b, a voltage which is proportional to the 
amount of rotation of an adjusting knob 67a. The voltage from terminal 67b 
is fed to an analog-digital converter 69 where it is converted into a 
digital signal for use in controlling the initial elevation of the ink 
ribbon relative to print head 4. To this end, the digital signal is fed to 
an ink ribbon color-selecting circuit 70. Color selecting circuit 
subsequently responds to printing color designating signals from the 
external host device, or from an operational board of the printer (not 
shown) to actuate motor 61 and further set the elevation of the ink ribbon 
relative to printing head 4 to select a desired color for printing. 
In the illustrated embodiment, when the power switch of the printer is 
turned on, ink ribbon color-selecting circuit 70 is actuated so as to 
rotate drive motor 61 by an amount corresponding to the signal delivered 
from analog-digital converter 69, i.e., the amount which is preset into 
variable resistor 67, thereby adjusting the initial position of ink ribbon 
cartridge 18. Then, when a print color selecting signal is output from the 
host device, ink ribbon color-selecting circuit 70 responds appropriately, 
actuating motor 61 to elevate or depress the print head side of ink ribbon 
cartridge 18 until the ribbon section having the desired color faces print 
head 4. Cartridge 18 is maintained at that position until another color 
designating signal is received. 
Now, when the host device outputs print data and timing signals, print head 
carriage 5 moves along the platen in the printing direction, and print head 
4 prints on the paper character patterns corresponding to the data, using 
the selected color section of the ribbon. 
When, after lengthy use, the selection of printed colors becomes facilty, 
or when the position of the ink ribbon cartridge is to be adjusted at the 
factory, the adjustment is made by first operating the host device or the 
operating board of the printer to put out a print color designating 
signal. Holding a gauge, such as a ruler, at ink ribbon cartridge 18, the 
relative positions of the ink ribbon and of print head 4 are observed 
while terminal adjusting knob 67a of semi-fixed resistor 67 is turned by a 
screwdriver or other suitable tool. Sliding terminal 67b of variable 
resistor 67 outputs a voltage whose value is proportional to the degree of 
rotation of adjusting knob 67a and which is converted into a digital signal 
value by analog-digital converter 69 for supply to ink ribbon 
color-selecting circuit 70. Ink ribbon color selecting circuit 70 outputs 
a signal corresponding to the digital-converted value to motor 61 and ink 
ribbon cartridge holder 63 moves vertically relative to print head 4. By 
slow rotation of adjusting knob 67a, the desired color section of the ink 
ribbon is brought opposite print head 4. The adjustment is now complete, 
and the gauge is removed. After adjustment, the amount of the adjustment 
is stored as the resistance of the semi-fixed resistor 67, regardless of 
whether the power switch of the printer is turned on or off. 
FIG. 13 illustrates a circuit for converting the resistance of variable 
resistor 67 from analog to digital form in the printer of FIGS. 11 and 12. 
An analog/digital (A/D) converter 69 outputs the converted value in digital 
form into a register 71. When, for instance, register 71 is an 8-bit 
register, the resistance of variable resistor 67 is converted by A/D 
converter 69 into a value of from 0 to 255, and is then fed into register 
71. The value stored in register 71 is subsequently divided by a 
predetermined number n and the resulting number of pulses, corresponding 
to the quotient, is set into pulse number setting register 72. If, for 
example, the resistance is divided by 10 and the value set into and stored 
in the register 71 is between 0 and 19, the value 1 is set into register 
72. When the value is 20 to 39, the value 2 is set into register 72. 
The drive pulses 73 which drive step motor 61 are input to a counter 74. 
Every time that a pulse is input, the values of counter 73 and of register 
72 are compared, and, when the values coincide, an output pulse is fed into 
driving motor 61 to cause the driving motor to rotate. 
A flow chart illustrating the setting of the number of pulses into register 
72 after the power is turned on is shown in FIG. 14. 
When the printer power is turned on (step 1), the voltage corresponding to 
the preset resistance of variable resistor 67 is fed into A/D converter 69 
(step 2). The digital value corresponding to the resistance is then output 
into output register 71 (step 3). Finally, the value set into register 71 
is divided by the predetermined number n and the required number of 
driving pulses is calculated and set into register 72. 
This arrangement is advantageous in that, by presetting the value of the 
reference resistance into the A/D converter, the input resistance can be 
compared with the reference resistance and a negative number of pulses 
(that is, the requisite number of pulses to effect reverse rotation of the 
driving member 61) set into register 72. In this case, first the sign 
(positive or negative) of the value preset in register 72 is detected and 
then, depending upon the result, the direction of rotation of driving 
member 61 is determined. 
As described above, a printer fabricated in accordance with the teachings 
of the invention has the following advantageous effects. 
(a) A printer can easily be turned from a monochrome printer into a 
multi-color printer simply by attaching a motor unit, an arrangement which 
provides a great economic advantage for the user. Moreover, since the motor 
unit need only be pushed into place without use of an instrument or tool, 
the installation can easily be performed by the user. 
(b) The same printer can thus be used for both monochrome and multi-color 
printing. 
(c) Since the motor unit is mounted on the print head carriage, the 
conventional external dimensions of a monochrome printer need not be 
exceeded and thus a compact multi-color printer is obtained. 
(d) The two-contact, one-circuit detector switch which is provided in the 
ink ribbon cartridge holder, both detects whether a monochrome or a 
multi-color ink ribbon cartridge is present and effects the "home" 
positioning of the cartridge, an economical arrangement. Furthermore, the 
detector is compact and the electrical circuit is simple, all of which 
contributes to reducing the size of the printer as a whole. Further, due 
to the electrical detection of the color home position, accurate 
positioning of the ink ribbon cartridge is provided. 
(e) By mounting the adjustable resistor in the housing of the printer body, 
the signals therefrom can be output readily into the ink ribbon color 
selecting circuit and, at the same time, the adjusting member can be 
mounted at a position where the adjusting operation can be done easily. 
Therefore, a problem inherent in known color ribbon adjusting structures 
is eliminated, since the adjusting member is not mounted on the carriage 
and is therefore not subject to vibration and external shocks which would 
otherwise result in frequent readjustment. 
Reference is now made to FIGS. 16-21 where another embodiment of the 
present invention is depicted. As shown in FIG. 16, a print head carriage 
111 is mounted on parallel shafts 101, 102 for sliding movement back and 
forth in front of a cylindrical platen 125. A cartridge base 115 in which 
multi-color ink ribbon cartridge 18 (see FIG. 2) is supported, is mounted 
on carriage 111. The bottom surface of the rear portion of cartridge 18 
presses against a coil spring 114 on carriage 111 which urges the 
cartridge in a counter-clockwise direction. A removable motor unit 116 is 
supported in a recess 111a of carriage 111 and is connected by a 
self-contained connector 119b to a mating connector 119a mounted in recess 
111a to receive power from the electrical circuit. Motor 116 is releasably 
held in place by laterally displaceable hooks 107, 108. When the printer 
is to be used for multi-color printing, motor unit 116 is pushed downward 
from above into recess 111a in the direction of arrow H when no cartridge 
is in place. When motor unit 116 reaches the intended position, it is held 
by hooks 107, 108 and the parts of connector 119 are united to complete the 
electrical circuit. Cartridge base 115 and carriage 111 may be formed as 
one body. 
As depicted in FIG. 17, motor unit 116 includes a housing 120 supporting an 
electric motor 121 which provides the driving power for color selection. A 
motor drive gear 122a is supported on the motor shaft. An intermediate 
drive gear 122b and a cam drive gear 123c integrally formed on a spiral 
cam 123 are supported on housing 120. Spiral cam 123, as it turns, raises 
or lowers cam follower rod 124 in directions I and J, respectively. 
Multi-color ink ribbon cartridge 18, as detailed in FIG. 2, contains a 
multi-color ribbon 17 and has, mounted on the left and right sides 
thereof, in recesses, a pair of resilient members 18b. A laterally 
projecting axle pin 18a is mounted on each resilient member 18b for 
engaging a respective hole 126 in each lateral support member 115a on base 
115 (only one of two such supports is shown). The lower surface of 
multi-color ribbon cartridge 18 (FIG. 16) is provided with a downward 
opening groove 18c which provides clearance for a vertical positioning 
member 130 on cartridge base 115. Member 130 positions a monochrome ink 
ribbon cartridge which does not have such a groove when the printer is to 
be used for monochrome printing, (see FIG. 20). 
When a multi-color ribbon cartridge 18 is to be used, drive motor 116 being 
in place in carriage 111, the cartridge is emplaced in cartridge base 115 
by compressing resilient support members 18b so that projecting axle pins 
18a can be inserted in the holes in upward-projecting base side members 
115a. Cartridge 18 is now rotatably suspended in base 115 and is biased 
counter-clockwise, in the direction of arrow M (FIG. 16), by biasing 
spring 114. At the same time, the lower surface of cartridge 18 contacts 
cam follower rod 124, which extends upward from motor unit 116, and is 
positioned by it. Now, when color-selection motor 121 is rotated in the 
direction of arrow K (FIG. 17), cam follower rod 24 moves along the 
profile 123b of cam 123 and is raised in the direction of arrow I, causing 
multi-color ink ribbon cartridge 18 to rotate in the direction of arrow N 
raising the multi-color ribbon relative to print head 112. Rotation of the 
motor is stopped when the desired band of multi-color ink ribbon 17 (FIG. 
2) is positioned in front of print head 112 for printing. When print head 
112 is driven, the desired color will be printed on a recording medium 
(not shown) which is held between the print head and platen 125. 
To reach other color ribbon bands in the ribbon, motor 121 can be turned in 
the direction of arrow G so that cam follower rod 124 moves downward in the 
direction of arrow J (FIG. 17), rotating multi-color ink ribbon cartridge 
18 in the direction of arrow M. 
The home position of multi-color ink ribbon cartridge 18 is established as 
follows. As shown in FIG. 18, cam 123 has a profile 123b. If the motor is 
rotated continuously in the direction of arrow L (FIG. 17), cam follower 
rod 124 reaches an end positioning member 123a of cam 23, and the motor 
steps out. After detecting the step-out of the motor by the variety of the 
driving waveform or after driving at more pulse amount than that required 
for moving the cam follower rod 124 in the maximum range (a), the motor is 
stopped and then, the cam follower rod 124 is stopped in the home position 
(b). This is the home position from which multi-color ink ribbon cartridge 
13 can be rotated to select any of the colors of the multi-color ink 
ribbon. Thus, in the embodiment of FIG. 16, a home position which 
accurately positions the cartridge is provided without the need for any 
particular electrical device to detect and signal it. 
FIGS. 19a and 19b illustrate an alternative arrangement for securing motor 
unit 116 in carriage 111. In this embodiment, bottom wall 111b (see also 
FIG. 16) of carriage 111, in registration with recess 111a, is provided 
with a slotted opening 111c which receives a lock pin 127. Lock pin 127 is 
mounted in and passes through motor unit 116 and has, at its one end, a 
laterally extending lock portion 127a which is dimensioned to pass through 
slot 111a when motor 116 is being seated. Lock pin 127 has, at its other 
end, a lock lever 128 which is positioned on the exposed surface of motor 
116 for manual rotation of the lock pin 127 and lock portion 127a to bring 
lock portion 127a out of registration with slot 111a to retain motor unit 
116 in position. Slot 111c is defined by sloping surfaces 111c which 
extend from both surfaces of bottom wall 111b to permit engaging portion 
127a to rotate smoothly into position on bottom wall 111b. 
FIG. 20 depicts, in solid lines, the positioning of a monochrome ink ribbon 
cartridge 129 in carriage 115. Monochrome ink ribbon cartridge 129 is 
mounted therein in the same way as multi-color ink ribbon cartridge 13. 
However, cartridge 129 does not have the downward opening groove 118 with 
which the multi-color cartridge of FIG. 16 is provided. Therefore, 
monochrome cartridge 129 can pivot about its axis in holes 126 of carriage 
of 115 under the influence of biasing spring 114 only so far as contact of 
the upper end of positioning member 130 on its bottom surface will allow. 
FIG. 20 also illustrates, in dashed lines, the low and high positions 18l 
and 18h which can be attained by a multi-color ink ribbon cartridge as cam 
follower rod 124 is moved between positions 124l and 124h, respectively. 
Note that monochrome ink ribbon cartridge 129 is not as thick as 
multi-color ink cartridge 18, so that its lower surface does not come into 
contact with cam follower rod 124, regardless of the position of rod 124. 
Monochrome cartridge 129 therefore remains in one position. Thus, the 
embodiment of FIGS. 16-21 does not require a detector for determining 
whether monochrome or multi-color printing is to be carried out. 
FIG. 21 depicts a motor drive unit 116a which can be used in the apparatus 
of FIG. 16 in place of motor drive unit 116. In this unit, a drive motor 
121a is supported in housing 120a. A drive gear 122d is supported for 
driving on the motor shaft and is meshed with a round gear portion 122e of 
a double gear which is pivotably supported on housing 120a. A beveled 
portion 122f of the double gear meshes, in turn, with a beveled gear 122g 
which is connected to and rotates on shaft 122h. Shaft 122h is supported 
on housing 120a and supports and rotates a cam 123d which drives cam 
follower rod 124a up or down as indicated by arrow H. Cam 123d is an 
eccentrically mounted disk. As was the case with the drive on the 
periphery of cam 123d of FIG. 17, the up or down motion of cam follower 
rod 124a of FIG. 21, moves the multi-color ink ribbon cartridge up and 
down for the selection of a color ribbon band for printing by print head 
112. 
It will thus be seen that the objects set forth above, among those made 
apparent from the preceding description, are efficiently attained and, 
since certain changes may be made in the above construction without 
departing from the spirit and scope of the invention, it is intended that 
all matter contained in the above description or shown in the accompanying 
drawings shall be interpreted as illustrative and not in a limiting sense. 
It is also to be understood that the following claims are intended to cover 
all of the generic and specific features of the invention herein described 
and all statements of the scope of the invention which, as a matter of 
language, might be said to fall therebetween.