Apparatus for changing a ribbon-color of a printer

In a multi-color changing apparatus of a small-sized printer, a ribbon color of the printer can be changed by a novel structure highly suitable as a ribbon-cartridge converting apparatus for two colors not for four colors because of its simple structure to enhance productivity and lower manufacturing cost without a high-priced stepping motor. The apparatus includes a pair of side frames in right and left installed with parts for forming the small-sized printer while having supporting plates pair projecting to rear corners, a cartridge frame connected to be rotatable about a pin by inserting extending plates at the rear sides into the supporting plates while having a c-shaped cam guider extending to one side thereof, a driven shaft installed to the side frames while having a lead screw for transferring a print head and an externally-expanding one end, a shift cam placed into the inside of the cam guider of the cartridge frame by being fitted to run idling at the edge end of the driven shaft, a shift ratchet fixedly attached to the driven shaft onto the immediate inside of the shift cam while having hooking jaws onto the outer periphery thereof, a clutch spring inserted between the shift cam and shift ratchet while having both edge ends respectively fixed to the shift cam and shift ratchet, and a solenoid fixed to the side frames for catching an operating end to the hooking jaws of the shift ratchet. Here, the shift ratchet, clutch spring and shift cam are rotated along with the rotation of the driven shaft by a frictional force to swing up and down the cartridge frame by the shift cam.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to an apparatus for changing a ribbon-color 
of a printer, and more particularly to an ribbon-apparatus for changing a 
ribbon-color of a printer, wherein a ribbon of a cartridge is painted in 
two colors, and then the position of the cartridge is to ascend/descend 
for changing the color printed onto a sheet of paper. 
2. Description of the Prior Art 
A small-sized printer is generally employed for an electronic cash 
register, in which a sheet of paper that is curled up in the form of a 
roll is successively supplied between a printing plate and a cartridge 
ribbon, and a printer head prints the item name, amount and so on over the 
sheet of paper. 
Such a conventional small-sized printer is disclosed in U.S. Pat. No. 
4,773,777 as shown in FIG. 1 and U.S. Pat. No. 4,983,057 as shown in FIG. 
2. 
The multi-color changing apparatus shown in FIG. 1 enables a ribbon 
cartridge a1 to swing about a hinge pin a2, and the bottom plane of ribbon 
cartridge a1 is supported by a polygonal cam a4 which is fixedly attached 
to a driven shaft a3. Here, driven shaft a3 is rotated by a motive power 
of a motor by interposing a deceleration gear as a medium, and the 
instruction of operating the motor is produced from a separate control 
mechanism. The characteristic of the multi-color changing apparatus is in 
that a ribbon a5 is painted in four colors to allow for precisely 
regulating the height adjustment by four steps. 
The multi-color changing apparatus shown in FIG. 2 which enables a ribbon 
cartridge b1 to swing about a hinge pin 3 includes a supporting member b2 
extending down from the side of ribbon cartridge b1, and a semi-circular 
gear b3 furnished to underlie supporting member b2. In addition, a motive 
power transferring structure b4 is formed by a deceleration gear and a 
motor, and a control mechanism is provided for operating motive power 
transferring structure b4. Here, the height of ribbon cartridge b1 also 
can be adjusted by several steps, using the plurality of gears. 
However, since both the above-described conventional structures are of the 
color changing apparatus of the ribbon cartridge having four colors to 
involve a complicated operating mechanism, the multi-color changing 
apparatuses have drawbacks of incurring high cost in manufacturing, being 
difficult to be manufactured, etc. 
More specifically, in case of that shown in FIG. 1, an easily-controllable 
stepping motor should be employed for precisely rotating driven shaft a3 
fixedly attached with polygonal cam a4. Likewise, in case of that shown in 
FIG. 2, a high-priced stepping motor should be employed in order to 
operate semicircular gear b3 and motive power transferring structure b4 
while accurately controlling them. 
Additionally, those require a separate control equipment for accurately 
controlling the number of revolution of the aforementioned stepping motor 
to further increase the manufacturing cost, which are therefore unsuitable 
in realizing just two-color changing apparatus. 
SUMMARY OF THE INVENTION 
The present invention is devised to solve the foregoing problems of the 
prior arts. Therefore, it is an object of the present invention to provide 
an apparatus for changing a ribbon-color, wherein the main purpose is for 
changing a ribbon color of a small-sized printer, having a novel structure 
highly suitable as an apparatus for converting a ribbon cartridge just for 
two colors not for four colors because of its simple structure to be 
favorable for enhancing productivity and incurring low manufacturing cost 
without employing a high-priced part such as a stepping motor. 
To achieve the above object of the present invention, a characteristic 
construction of the present is an apparatus for changing a ribbon-color of 
a printer, which includes side frames installed with respective parts for 
forming said printer, and formed with a pair of supporting plates 
projecting to respective rear corners. A cartridge frame is connected to 
be rotatable about a pin by inserting both extending plates at the rear 
sides thereof into the supporting plates of both side frames, which has a 
cam guider positioned to one side thereof. Also, a driven shaft installed 
to the both side frames is formed with a lead screw for transferring a 
print head and a shift cam is fitted to run idling at the edge end of the 
driven shaft. In addition, a shift ratchet fixedly attached to the driven 
shaft onto the immediate inside of the shift cam has hooking jaws onto the 
outer periphery thereof, and a clutching means inserted between the shift 
cam and shift ratchet has both edge ends respectively fixed to the shift 
cam and shift ratchet. Furthermore, a hooking means is fixed to the side 
frames for leading an operating end thereof to be caught to the hooking 
jaws of the shift ratchet. By this construction, the shift ratchet, clutch 
spring and shift cam are rotated in accordance with the rotation of the 
driven shaft by a frictional force to be capable of swinging up and down 
the cartridge frame by the shift cam.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 3 is a side view showing a state of installing a ribbon-color changing 
apparatus of a small-sized printer according to the present invention, and 
FIG. 4 is an exploded perspective view showing a detailed construction of 
the ribbon-color changing apparatus according to the present invention. 
As shown in FIGS. 3 and 4, the ribbon-color changing apparatus is installed 
to side frames 1 of a printer main body that constitute the small-sized 
printer. 
Side frames 1 are the frame erected into both right and left of the main 
body, which are installed with a driven shaft 4 having a head-transferring 
lead screw 41, a guide shaft, a platen 10, a paper feed roller, and so on 
between them. Also, a plurality of gears (not shown) for driving the parts 
are installed to both sides of side frames 1. 
Especially, sides frames 1 of the present invention are formed with 
supporting plates 11 projecting upward at their corners of both rear 
sides, and supporting plates 11 are connected with a cartridge frame 2 of 
the present invention to be rotatable by means of a pin 3. 
In more detail, cartridge frame 2 is characterized by being formed with 
extending plates 21 at both rear sides thereof, so that it is connected to 
supporting plates 11 of side frames 1 by means of pin 3 while being formed 
with a cam guider 22 to one side thereof. 
Cam guider 22 has a horizontal part 22a obtained by horizontally extending 
the bottom portion of cartridge frame 2, a vertical part 22b obtained by 
bending from horizontal part 22a to extend downward, and a lower part 22c 
bent inward from vertical part 22b, thereby being provided in the shape of 
c. 
The middle portion of vertical part 22b is partially cut to bend inward to 
form a middle part 22d, so that middle part 22d and lower part 22c which 
will be described later become a substantial guider of a shift cam 5 to be 
described later. 
Driven shaft 4 having a lead screw 41 is installed between side frames 1 in 
a manner that a shaft end part 42 of driven shaft 4 protrudes through the 
side of side frames 1, and a shift ratchet 6, a clutch spring 7 and shift 
cam 5 are assembled to shaft end part 42 as shown in FIG. 5. 
Referring to FIG. 6, shift ratchet 6 is assembled to shaft end part 42 of 
driven shaft 4 neither loose-fitted nor tight-fitted, and has at least two 
hooking jaws 61 onto its outer periphery. Here, hooking jaws 61 function 
only when being rotated in one direction. 
Successive to shift ratchet 6, clutch spring 7 is fitted such that one end 
71 of clutch spring 7 is inserted into a discontinuous groove 62 of shift 
ratchet 6 and the other end 72 thereof is inserted into a discontinuous 
groove 52 of shift cam 5 to mutually connect them. 
Then, shift cam 5 follows clutch spring 7. After shift cam 5 is fitted into 
an edge end 43 stepped at driven shaft 4, an E-ring 9 is joined for 
fastening to avoid the escape of shift cam 5. 
More preferably, edge end 43 also project through a slit 22e formed in 
vertical part 22b of cam guider 22 to be joined with E-ring 9 at the end 
thereof to further inhibit the escape of cam guider 22. 
At one side of driven shaft 4 fixedly attached to shift ratchet 6, a 
solenoid 8 is attached to side frame 1, and an operating end 81 of 
solenoid 8 is to be caught by hooking jaws 61 of shift ratchet 6. 
In connection with the operation, the ribbon-color changing apparatus 
according to the present invention formed as above will be described 
below. 
In view of the operating state of the major parts, since hooking jaws 61 of 
shift ratchet 6 are supported by operating end 81 of solenoid 8 to inhibit 
the rotation of shift ratchet 6, clutch spring 7 cannot be rotated even 
though driven shaft 4 is rotated. Accordingly, shift cam 5 is not rotated 
to be incapable of ascending/descending cartridge frame 2. 
On the contrary, once solenoid 8 is operated to allow operating end 81 to 
be distanced from hooking jaws 61 of shift ratchet 6 while driven shaft 4 
is rotated, shift ratchet 6 can be rotated. Upon the rotation of shift 
ratchet 6, clutch spring 7 is rotated. In turn, when the rotational 
elasticity is accumulated onto clutch spring 7, shift cam 5 becomes 
successively rotated slightly later. 
When shift cam 5 is rotated, the preceding half part of cartridge frame 2 
is lift up as high as the top dead point since shift cam 5 is rotated at 
cam guider 22 of cartridge frame 2. 
Thereafter, once operating end 81 of solenoid 8 is moved again under the 
state that cartridge frame 2 is lifted up, it is caught by hooking jaws 61 
of shift ratchet 6 to impede the rotation of shift ratchet 6. Accordingly, 
the state that shift cam 5 lifts up cartridge frame 2 is continued. 
Now, the overall operating state will be described. 
When a user intends to print the black color on the sheet of printing paper 
in the normal time, it is used without performing any additional 
manipulation. Thus, at this time, the top dead center of shift cam 5 is 
moved downward while both extending plates 21 of cartridge frame 2 are 
connected to supporting plates 11 of side frames 1 by means of pin 3. Due 
to this fact, cartridge frame 2 maintains the horizontal state and, 
therefore, the black-colored portion of the ribbon is placed in front of 
the print head, thereby printing recording content in black. 
Contrarily, if the red color is needed to be printed (e.g., total amount, 
repayment and change), an unshown main control unit (e.g., CPU) of the 
printing apparatus operates solenoid 8. 
At this time, operating end 81 of solenoid 8 as shown in FIG. 3 is moved 
downward to permit the rotation of shift ratchet 6. In turn, shift ratchet 
6 rotates shift cam 5 via clutch spring 7, and shift cam 5 is rotated by 
180.degree. to ascend its top dead center. Then, cartridge frame 2 
including cam guider 22 is escalated with the consequence of placing the 
red-colored portion of the cartridge ribbon in front of the printer head, 
thereby enabling to print the red-colored characters. 
For reference, as shown in FIG. 4, the ascending/descending state of the 
cartridge ribbon is recognized by the interaction of a press plate 23 of 
cartridge frame 2 and a toggle switch 12 furnished to a substrate to be 
transmitted to the main control unit. 
As described above in detail, the ribbon-color changing apparatus according 
to the present invention is improved for printing respective two colors by 
using the cartridge ribbon consisting of two colors, in which cam guider 
22 is formed to cartridge frame 2, and shift cam 5 is rotated within cam 
guider 22 to ascend/descend the cartridge ribbon. As a result, the 
ribbon-color changing apparatus according to the present invention is 
favorable in its productivity and economizes the manufacturing cost 
resulting from the highly-simplified structure and facilitated operation 
thereof. 
While the present invention has been particularly shown and described with 
reference to particular embodiment thereof, it will be understood by those 
skilled in the art that various changes in form and details may be 
effected therein without departing from the spirit and scope of the 
invention as defined by the appended claims.