Abstract:
A color printer includes a carriage slidably movable on a printer frame. A print head is mounted on the carriage. A multiple-color ink ribbon having bands of color is stored in a cartridge which guides the multiple-color ink ribbon to the print head. A color selecting mechanism moves the cartridge and the multiple-color ink ribbon relative to the print head to select a color band for printing. An advancing mechanism winds the multiple-color ink ribbon in the storage member to tension the multiple-color ink ribbon after a color band has been selected and prior to printing.

Description:
BACKGROUND OF THE INVENTION 
     The present invention is generally directed to color printers and in particular to a color printer utilizing a multiple-color ink ribbon. Heretofore, conventional color printers utilizing multiple-color ink ribbons have used a ribbon shift mechanism for shifting the multiple-color ink ribbon to select a desired ink color. However, because the multiple-color ink ribbon has substantially no integral rigidity, the ribbon shift mechanism encounters problems in guiding the ink ribbon to a correct print position. The frictional forces imposed on the ink ribbon by the print head and the ribbon mask act to prevent the accurate positioning of the desired color band on the ribbon. Accordingly, a multiple-color ink ribbon color printer which accurately and reliably selects the proper ink color from a multiple-color ink ribbon is desired. 
     SUMMARY OF THE INVENTION 
     Generally speaking, in accordance with the instant invention, a color printer having a multiple-color ink ribbon is provided. The color printer has a frame and carriage slidably supported on the frame. A print head is supported on the carriage. A multiple-color ink ribbon having bands of color is stored in a cartridge which guides the multiple-color ink ribbon to the print head. A color selecting mechanism moves the cartridge and the multiple-color ink ribbon relative to the print head to select a color band for printing. An advancing mechanism winds the multiple-color ink ribbon in the storage member to tension the multiple color ink ribbon after a color band has been selected and prior to printing. 
     Accordingly, it is an object of the instant invention to provide an improved color printer utilizing a multiple-color ink ribbon. 
     Another object of the instant invention is to provide a color printer with a multiple-color ink ribbon which tensions the multiple-color ink ribbon after shifting for color selection and prior to printing. 
     A further object of the invention is to provide a color-printer using a multiple-color ink ribbon which accurately selects a desired color band on the ink ribbon for printing. 
     Yet another object of the invention is to provide a color printer using a multiple-color ink ribbon which because of reliable ink ribbon placement can consistently mix different colors on a recording medium which are separately present on the multiple-color ink ribbon. 
     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, combination of elements, and arrangement of parts which will be exemplified in the construction hereinafter set forth, and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a fuller understanding of the invention, reference is had to the following description taken in connection with the accompanying drawings, in which: 
     FIG. 1 is a partially cut away perspective view of a serial printer constructed in accordance with the present invention; 
     FIG. 2 is an exploded perspective view of an ink ribbon take-up mechanism constructed in accordance with a preferred embodiment of the invention; 
     FIG. 3 is an enlarged perspective view of a ribbon braking spring; 
     FIG. 4 is a front plan view of a ribbon shift mechanism constructed in accordance with a preferred embodiment of the invention; 
     FIG. 5 is an enlarged fragmentary front elevational view of a shift arm shaft constructed in accordance with the invention; 
     FIG. 6 is a diagram illustrating the relationship between the rotation of a shift cam and the selected color on a multiple-color ink ribbon; 
     FIG. 7 is a block diagram of the operation of a motor control system constructed in accordance with the invention; and 
     FIG. 8 is a timing chart of the operation of the motors referred to in FIG. 7. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Reference is made to FIG. 1 wherein a serial color printer, generally indicated as 100 constructed in accordance with the invention is depicted. Serial color printer 100 includes a carriage 1 slidably movable along a guide shaft 5 extending between a left side frame 2 and a right side frame 3, and parallel to a platen 4. Carriage 1 is also slidably movable along a second guide shaft 105. A print head 6 is supported on carriage 1. Carriage 1 supports a ribbon mask 7 positioned between print head 6 and platen 4, preventing a sheet of paper A (shown in fragmentary form in chain lines but extending around platen 4 in a conventional manner) from being smeared with ink. A four-color ink ribbon 8 is inserted between print head 6 and ribbon mask 7. Color ink ribbon 8 is stored in a ribbon cartridge 9 (see FIG. 2). Carriage 1 is driven by a stepping CR (carriage) motor 11 with a timing belt 10 located on the bottom of printer 100. Platen 4 is driven by a paper feeding motor 12 secured to right side frame 3. 
     Reference is made to FIG. 2 wherein the ink ribbon take-up mechanism is depicted. Timing belt 10, which engages carriage 1, is trained about a belt driven pulley 13 having a planetary lever 14 which supports a first planet gear 15 while pivoting about a support shaft 13a for pulley 13 and shaft 13a has a gear 13b which rotates with pulley 13 and which meshes with gear 15. Gear 13b pivots lever 14 and gear 15 between gears 16 and 17 depending on the rotational direction of pulley 13. Planet gear 15 is selectively turned as the carriage 1 is moved and transmits the rotation of pulley 13 to gear 15 which meshes with a planet transmission gear 16 in a first position and turns when the carriage moves to the right and meshes with a planet transmission gear 17 in a second position when the carriage 1 moves to the left (as shown dotted lines in FIG. 2). As the movement of carriage 1 changes directions, gear 15 shifts from meshing with gear 16 to meshing with gear 17 or vice versa. During the period of change, gear 15 is out of mesh with both gear 16 and gear 17. Planet transmission gear 17 is held in mesh with a planet transmission gear 18 at all times. Planet transmission gear 18 and planet transmission gear 16 are held in mesh by ribbon drive gear 19 at all times. 
     Color ink ribbon 8 is an endless ink ribbon stored in ribbon cartridge 9 which is composed of four differently colored horizontal stripes. In this embodiment, as depicted in FIG. 3, ink ribbon 8 has four colors, a black band or zone 8a, a magenta band or zone 8b, a cyan band or zone 8c and a yellow band or zone 8d. The independent and combined selection of these colors provides for significant color flexibility. Color ink ribbon 8 is sandwiched between a ribbon feed roller 20 and a ribbon presser roller 21 at the input side of ribbon cartridge 9, which in this embodiment is on the left side. Color ink ribbon 8 is fed along when portion 19a of ribbon drive gear 19, fitted into ribbon feed roller 20 is driven. To prevent color ink ribbon 8 from having slack, particularly in the region of print head 6, a ribbon braking spring 22 is placed in an outlet of ribbon cartridge 9 to maintain pressure against color ink ribbon 8. In this embodiment, ribbon braking spring 22 is present at the output side of ribbon cartridge 9 (the right side of FIG. 1). 
     Reference is next made to FIG. 3 wherein the operation of ribbon breaking spring 22 is depicted. Ribbon breaking spring 22 has three slits 22a, 22b, 22c positioned so as to align with the boundaries between the various colors. Slit 22a is positioned so as to be at the boundary between black zone 8a and magenta zone 8b. Slit 22b is positioned between the boundary between magenta zone 8b and cyan zone 8c. Slit 22c is positioned at the boundary between cyan zone 8c and yellow zone 8d. Slits 22a, 22b, and 22c are effective in preventing the penetration of color inks across the zone boundaries into adjacent ink zones, thereby successfully preventing mixed colors on the ribbon 8 under the pressure of ribbon breaking spring 22. Slits 22a, 22b and 22c are effective in relieving pressure on the boundaries between zones 8a, 8b, 8c, 8d where there is a danger that pressure would cause ink migration across the boundaries. The slits prevent application of pressure at the boundaries while allowing ribbon breaking spring 22 to maintain pressure against color ink ribbon 8. 
     Reference is next made to FIG. 4 wherein a ribbon shift mechanism generally indicated as 200, constructed in accordance with the invention is depicted. Ribbon cartridge 9 is supported in place by a pair of left and right cartridge holders 23L and 23R (see FIG. 1), which engage opposite ends of ribbon cartridge 9. A shift cam 24 is driven by a ribbon shift motor 25. In particular, a gear 25a coupled to ribbon shift motor 25 meshes with a gear 24e on shift cam 24. Shift cam 24 also has a cam groove 24f in which a shift arm 26 having a pin 26a adapted to fit within cam groove 24a slidably engages. Shift arm 26 is angularly rotated about a shift arm shaft 27 in response to the rotation of shift cam 24. Shift arm 26 is fixed to a shift adjustment arm 28 for adjusting the elevation of ribbon cartridge 9. Shift adjustment arm 28 has a projection 28a on the end of arm 28 furthest from its attachment with shift arm 26. Projection 28a engages a slide shaft 29. Slide shaft 29 has its upper end 29a fixed to cartridge holder 23L and is vertically slidable in a guide hole 30b in a slide shaft guide 30 which is mounted on side frame 2. A coil spring 31 is mounted between cartridge holder 23L and a spring seat 30a on slide shaft guide 30 for biasing cartridge holder 23L in a downward direction. 
     Reference is next made to FIG. 5 wherein the operation of shift arm shaft 27 is depicted. Shift arm shaft 27 is fixed by screws 32 to shfit arm 26 for rotation therewith. Shift arm shaft 27 extends through side frame 2 and 3 and is secured to a right shift arm 33 by a screw 32 outside of side frame 3 to drive a ribbon shift mechanism 200 composed of a shift adjustment arm 28, a slide shaft 29, a cartridge holder 23R, a slide shaft guide 30 and a coil spring 31 identical to those shown on guide frame 2 (FIG. 4). 
     Reference is made to FIG. 6 wherein the manner of selection of the colors on color ink ribbon 8 is depicted. The selection of colors on ink ribbon 8 is dependent on the angle of rotation of shift cam 24. Shift cam 24 has four stop points 24a, 24b, 24c and 24d about its outer periphery which are each spaced apart sixty degrees. As a result, a rotation of one hundred eighty degrees provides for the selection of all four colors. Arms 26 and 28 are adjusted so that when the angle of rotation of shift cam 24 is zero degrees (at stop point 24a), black zone 8a is located in the print position. The cam height at each stop point 24a--24d is amplified at the ink ribbon end 28a  by the leverage ratio of shift arm 26 and arm 28. When the angle of rotation is 60° (at stop point 24b), magenta zone 8b is located in the print position. Likewise, when the angle of rotation is 120° (at stop point 24c), cyan zone 8c is located in the print position. Finally, when the angle of rotation is 180° (at stop point 24d), yellow zone 8d is located in the print position. 
     The color selection is performed by rotating shift cam 24 to the appropriate angular position. To shift color ink ribbon 8 from black zone 8a to any of the other color zones, shift cam 24 is rotated clockwise (FIG. 6). Likewise, when shifting color ink ribbon 8 from yellow zone 8d to any of the black, magenta, or cyan zones, shift cam 24 is rotated counterclockwise (FIG. 6). 
     Color printer 100 is capable of printing characters and other indicia in the four colors referred to above and also in combinations of the four colors as green (yellow+cyan), orange (yellow+magenta) and violet (magenta+cyan) through double-strike or superimposed printing. Therefore, the color printer 100 can print characters in a total of seven colors with a four-color ink ribbon 8. 
     The operation of color printer 100 is now described in detail with reference to FIGS. 7 and 8. The motor control system of color printer 100 is controlled by a main CPU 36 which gives control commands directly to a ribbon shift motor control unit 34 and a paper feed motor control unit 35. Main CPU 36 outputs commands to slave CPU 38 which in turn directly controls CR (carriage) motor control unit 37. 
     The timing chart of FIG. 8 shows the operation of the various motors 11, 12 and 25 printing intervals, and directions of movement of the carriage 1 where print head 6 is moved from left frame 2 toward right frame 3 for printing, the paper A is fed for line feeding, and ink color selection. Thereafter, print head 6 is moved left to begin printing. While print head 6 is moving from left frame 2 to right frame 3, CR motor 11 is energized as indicated at 40. During this period belt driven pulley 13 (FIG. 2) is rotated clockwise as carriage 1 moves to the right and planet gear 15 meshes with planet transmission gear 16. As a result, planet gear 15 rotates counterclockwise and planet transmission gear 16 rotates clockwise. Ribbon drive gear 19 meshes with planet transmission gear 16 and rotates counterclockwise. Boss 19a of ribbon drive gear 19 engages ribbon feed roller 20 in ribbon cartridge 9. As a result, color ink ribbon 8 is advanced. 
     Next, paper feed motor 12 is energized as indicated at 41 in FIG. 8 to feed the paper A. Then, stepping CR motor 11 is energized as indicated at 42 to move carriage 1 to the left, resulting in the ink ribbon take-up gear train being released out of mesh. This reduces any frictional load generated between ribbon feed roller 20 and boss 19a of ribbon drive gear 19 when ribbon cartridge 9 is moved vertically. 
     Now, ribbon cartridge 9 can be lifted or lowered smoothly. When the ribbon take-up gear train does not mesh, ribbon shift motor 25 is energized at 43 to actuate the ribbon color selecting mechanism (by rotating shift cam 24 through the appropriate angle). When ribbon shift motor 25 is energized, shift cam 24 is rotated to swing shift arm 26, which slidably engages shift cam 24, to move ribbon cartridge 9 vertically with slide shaft 29 and cartridge holder 23L (and the corresponding elements on the right side of printer 100). When ribbon cartridge 9 moves downward, shift arm 26 also moves without disengaging from cam 24 under the biasing force of coil spring 31. When a desired color is selected, CR motor 11 is energized as indicated at 44 (FIG. 8) to move carriage 1 back to the right the same distance as carriage 1 previously moved to the left (42) in order to release the ink take-up gear train out of mesh. Thereafter, CR motor 11 is energized as indicated at 45 to reciprocate carriage 1. 
     Because the ink ribbon 8 is advanced when the carriage 1 moves to the right, ink ribbon 8 is advanced during the portion of interval 45 when carriage 1 is moving to the right. The subsequent left movement of carriage 1 during interval 45 returns carriage 1 to its initial position while ink ribbon 8 has been advanced. By advancing ink ribbon 8 after color selection has been completed, color ink ribbon 8 is placed under tension as it is advanced and any frictional resistance that was present between print head 6 and ribbon mask 7 which causes ink ribbon 8 not to be straight is overcome, thereby correctly aligning the proper color zone in the prescribed print position. Now, printer 100 is ready to print in the selected print color and CR motor 11 is turned on as indicated at 46 to move carriage 1 to the left to restart the printing operation. 
     As shown in FIG. 2, belt driven pulley 13 is rotated counterclockwise as carriage 1 is moved to the left and planet gear 15 engages with planet transmission gear 17. As a result, planet gear 15 rotates in a clockwise direction, planet transmission gear 17 rotates in a counterclockwise direction and planet transmission gear 18 rotates clockwise. Ribbon drive gear 19 which is held in mesh with planet transmission gear 18 is rotated counterclockwise, which causes color ink ribbon 8 to be wound up. 
     CR motor 11 has been described as being a stepping motor, however, CR motor 11 may be a different type of motor without a change in the functioning of the color printer 100. 
     As has been described above, any slack which is present in the color ink ribbon 8 after color selection has been performed is removed by winding the color ink ribbon 8 after color selection and before printing begins. By this method the color ink ribbon 8 is reliably guided to the appropriate color zone for printing without the need for additional parts and with much higher reliability than has heretofore been achieved. 
     Accordingly, a color printer 100 using a multiple-color ink ribbon 8 which reliably and precisely selects the appropriate color zone in the printing position is provided. 
     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 carrying out the above method and in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and 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.