RIBBON FORWARDING APPARATUS OF IMPACT TYPE PRINTER

Abstract: Disclosed is a ribbon forwarding apparatus of impact type printer for printing on a recording paper wound on a platen (1) by moving printing means (3) disposed at a specified position of a carrier (2) which moves along this platen to the printing position, and striking it by way of an ink ribbon, comprising, an elevation table (4) which is mounted on said carrier (2), has an ink ribbon cartridge (5) and a correction tape cartridge (6) mounted on the upper and lower parts thereof, and is moved up and down to position the ink ribbon (7) at said printing position when printing and the correction tape (8) when erasing, a ratchet wheel (9) which is mounted on this elevation table (4) and drives to selectively change over the ink ribbon feed in printing and ink ribbon feed in erasing, a slider (10) which is mounted on said elevation table (4) and has a feed pawl (11) engaged with said ratchet wheel (9); and a rocker arm (12) which is perpendicularly disposed on said carrier (2) with one end pivoted on and moves said slider (10) reciprocally, wherein said rocker arm (12) is disposed so that the abutting point of said slider (10) and rocker arm (12) may be shifted to the pivoting point (P) side of this rocker arm (12) along with the movement of said elevation table (4) when erasing to set the feed of the ink ribbon in erasing smaller than the feed of the ink ribbon in printing.

Description: This invention relates to a ribbon forwarding apparatus of an impact type printer for printing on a recording paper wound on a platen by moving printing means disposed at a specified position on a carrier which moves along this platen to a printing position, and striking it through an ink ribbon at the printing position. Conventionally, as a ribbon forwarding apparatus of impact type printer of this sort, for example, the structure shown in Fig. 3, was known. This ribbon forwarding apparatus is elevatably mounted on a carrier which has a printing unit and moves along a platen. A ratchet wheel 22 threaded in pitch C, corresponding to the feed rate of the ink ribbon, is pivoted on a lower face 21 of an elevation table having an ink ribbon cartridge and a correction ribbon cartridge mounted in its upper and lower faces. A feed pawl 23 is engaged with the ratchet wheel 22 and a slider 24 is reciprocally moved in the direction of arrow A in synchronism with the printing speed by drive means (not shown). In this way, the ratchet wheel 22 is rotated in the direction of arrow B by one pitch each, that is ϑc°, by the reciprocal motion of the slider 24 so as to forward the ink ribbon intermittently when printing. When erasing, on the other hand, the elevation table ascends to position the correction tape at the printing unit, and as the printing unit strikes the recording paper on the platen through the correction tape, the ink on the recording paper is picked up by the correction tape and thus erased. In this erasing action, it is not always necessary to forward the ink ribbon, but if the tape forwarding is null, when continuously erasing multiple letters, the ribbon may be loosened by vibrations to stick to the daisy wheel, or perfect transfer of the ink into the recording medium may not be achieved when printing. However, in said conventional ribbon forwarding apparatus, although forwarding of the ink ribbon in the erasing action is enough by a small amount necessary for preventing its looseness, the ink ribbon was actually forwarded in the erasing action by the same amount of the feed of the ink ribbon in printing action, the ink ribbon was wasted by the purposeless forwarding more than necessary for prevention of the loosening of the ribbon in the erasing action. From US-A-4,247,210 there is known a ribbon feed and lift mechanism for a typewriter, in which the ink ribbon and the correction ribbon are individually driven by respective ratchet wheels so that the ink ribbon is not advanced when the correction ribbon is used. The present invention aims to provide a ribbon forwarding apparatus capable in a simple and inexpensive structure, of forwarding the ink ribbon by a smaller feed in the erasing action than in the printing action, so as to eliminate waste of the ink ribbon. In accordance with one aspect of the present invention, a carrier assembly for use in an impact type printer including a printing device for striking against an ink ribbon to print or against a correction tape to erase and positioning means for selectively positioning either one of the ink ribbon and correction tape in position for striking by the printing device, is characterised by means for forwarding the ink ribbon at a first feed rate when printing and at a second feed rate slower than the first feed rate when erasing. In accordance with another aspect of the invention, a method for operating a ribbon forwarding apparatus in an impact type printer having an ink ribbon and a correction tape comprises the steps of: moving the ink ribbon a first predetermined incremental distance each time a character is to be printed; and moving the ink ribbon a second predetermined incremental distance each time a character is to be erased, said second predetermined incremental distance being shorter than said first predetermined incremental distance. The present invention will become more fully understood from the detailed described given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein: Fig. 1 is a schematic side elevation of an impact type printer having a ribbon forwarding apparatus of this invention; Fig. 2 is a plan showing the engaged state of ratchet wheel and feed pawl; and Fig. 3 is a plan showing principal parts of a conventional ribbon forwarding apparatus. This invention is described below in detail by referring to an illustrated embodiment. Fig. 1 is a schematic side elevation of an impact type printer having a ribbon forwarding apparatus of this invention, in which: numeral 1 is a platen which is stretched horizontally with a recording paper wound on the outer circumference thereof and is driven and rotated in the direction of arrow A along with printing; 2 is a carrier which is driven reciprocally in the vertical direction on the paper surface in the drawing along the platen 1; 3 is a printing device which is driven in the direction of arrow B to print, being disposed on this carrier 2 opposite to said platen 1; and 4 is an elevation table which is mounted on said carrier 2 with its rear end being pivoted, has an ink ribbon cartridge 5 and a correction tape cartridge 6 mounted on the upper face and lower face thereof respectively, and is inclined in the direction of arrow C when erasing so as to position the correction tape 8 at the front side of said printing device 3. Numeral 9 is a ratchet wheel which is disposed on the lower face of this elevational table 4 and feeds and drives the ink ribbon 7 selectively in two steps depending on printing and erasing motion; 10 is a slider which is slidably (see arrow D) mounted on the lower face of said elevation table 4, having a feed pawl 11 (see Fig. 2) engaging with this ratchet wheel 9 at its end; 12 is a rocker arm which is perpendicularly disposed to abut against the lower protruberance 10a of said slider, with its upper end pivoted on said carrier 2; 13 is a disc crank which is disposed in said carrier 2 to be driven and rotated at a speed corresponding to the printing speed; and 14 is a connecting rod which oscillates said rocker arm 12 in a specified amplitude as indicated by arrow E, with one end pinned to this disc crank 13 and the other end pinned to said rocker arm. Fig. 2 shows the engaged state of said ratchet wheel 9 and feed pawl 11, in which 16 ratchet teeth 15 are disposed on the outer circumference of the ratchet wheel 9 at a pitch d corresponding to the minimum feed of the ink ribbon. This pitch d is equal to the stroke of said slider 10 which is moved reciprocally by the rocker arm 12 when the lower protruberance 10a of the slider 10 abuts against the rocker arm 12 at the position indicated by double dot chain line in Fig. 1. On the other hand, in the printing state shown in Fig. 1, the lower protruberance 10a of the slider 10 abuts against the rocker arm 12 at a position at a double distance of the above from its pivoting point P, and it is structured so that the stroke of the slider 10 may be c or double the pitch d. The ribbon forwarding apparatus arranged in the above-described manner operates as follows. When printing, the elevation table 4 is in the state as shown in Fig. 1, and the ink ribbon 7 is positioned before the printing device 3. The lower protruberance 10a of the slider 10 mounted on the elevation table 4 abuts against the oscillation end side of the rocker arm 12, and the slider 10 moves reciprocally at a stroke of c = 2d as stated above, and is engaged with the ratchet wheel 9 on every other tooth to rotate it by ϑc° (45°) each, so that the ink ribbon 7 is forwarded intermittently at the printing feed. The printing device 3 strikes the recording paper on the platen 1 through said ink ribbon 7 which stops intermittently to print sequentially. Next, when erasing, the elevation table 4 is tilted in the direction of arrow C, and the correction tape 8 is positioned before the printing device 3. The lower protruberance 10a of the slider 10 of elevation table 4 moves its abutting point to the vicinity of pivoting point P of the rocker arm 12, and the slider 10 reciprocates at stroke d as mentioned above, and is engaged with the ratchet wheel 9 on every tooth to rotate it by ϑd° (22.5°) each, so that the ink ribbon 7 is intermittently forwarded at a feed rate of 1/2 that of the printing motion. The printing device 3 strikes the printed recorded paper on the platen through said correction tape 8 which stops intermittently to erase sequentially. Thus, in this embodiment, when erasing, the ink ribbon is forwarded at half feed of printing, and the consumption of the ink ribbon may be saved while preventing looseness of the ink ribbon and transferring the ink perfectly on the printing medium when printing. Whilst in the embodiment the forwarding speed of the ink ribbon in erasing motion is one half that of the ink ribbon in printing motion, by varying the pitch of the ratchet wheel teeth and the ratio of the distance from the pivoting point of the abutting point of the slider abutting against the rocker arm when printing and erasing, the forwarding speed of the ink ribbon in erasing motion may be set at 1/n (n = 3, 4, ...) that of the ink ribbon in printing motion. Thus, according to this invention, many benefits are brought about. For example, it is supposed that an ink ribbon cartridge is mounted on the upper part of the elevation table and a correction tape cartridge on the lower part thereof. When printing, said elevation table is at the lowest limit having the ribbon positioned at the printing point disposed at specified position of the carrier, and the slider mounted on this elevation table is reciprocated at a large amplitude, abutting against the oscillation end side of the rocker arm. The feed pawl of the slider is engaged with the ratchet wheel on every specified number of teeth by this reciprocal motion to rotate it, and the ink ribbon is forwarded by the feed amount corresponding to said number of teeth. The printing means strikes the platen through said ink ribbon which stops intermittently to print sequentially. When erasing, said elevation table ascends to the upper limit to position the correction tape to the printing point, and accordingly the slider on the elevation table moves its abutting point to the vicinity of the pivoting point of the rocker arm so as to be reciprocated at small amplitude. Accordingly, the feed pawl of the slider is engaged with the ratchet wheel on every tooth to rotate it, and the ink ribbon is intermittently forwarded by a smaller amount than when printing. The printing means strikes the printed recording paper on the platen through said correction tape which stops intermittently to erase sequentially. As clear from the description above, the ribbon forwarding apparatus according to this invention of an impact type printer for printing on a recording paper wound on a platen by moving printing means disposed at a specified position of a carrier which moves along this platen to the printing position, and striking it by way of an ink ribbon comprises an elevation table which is mounted on said carrier, has an ink ribbon cartridge and a correction tape cartridge mounted on the upper and lower parts thereof, and is moved up and down to position the ink ribbon at said printing position when printing and the correction tape when erasing, a ratchet wheel which is mounted on this elevation table and drives to selectively change over the ink ribbon feed in printing and ink ribbon feed in erasing, a slider which is mounted on said elevation table and has a feed pawl engaged with said ratchet wheel, and a rocker arm which is perpendicularly disposed on said carrier with one end pivoted on and moves said slider reciprocally, wherein said rocker arm is disposed so that the abutting point of said slider and rocker arm may be shifted to the pivoting point side of this rocker arm along with the movement of said elevation table when erasing to set the feed of the ink ribbon in erasing smaller than the feed of the ink ribbon in printing, so that the consumption of ink ribbon may be saved while preventing looseness of ink ribbon as experienced when there is no tape feed at all, thus avoiding troubles, and also transferring the ink perfectly on the recording medium.

Claims: A carrier assembly for use in an impact type printer including a printing device (3) for striking against an ink ribbon (7) to print or against a correction tape (8) to erase and positioning means for selectively positioning either one of the ink ribbon (7) and correction tape (8) in position for striking by the printing device (3), characterised in that the assembly comprises means (9, 10, 11, 12, 13, 14) for forwarding the ink ribbon at a first feed rate when printing and at a second feed rate slower than the first feed rate when erasing. A carrier assembly according to claim 1 wherein the positioning means comprises an elevation table adapted to carry the ink ribbon (7) and correction tape (8) on different parts thereof. A carrier assembly according to claim 1 or 2 wherein the forwarding means comprises a ratchet wheel having a series of teeth projecting radially therefrom, a slider which engages the teeth of said ratchet wheel and means for moving said slider reciprocally to intermittently engage said ratchet wheel on every specified number of teeth when printing and every tooth when erasing. A carrier assembly according to claim 3 wherein said specified number of teeth is two. A carrier assembly according to claim 3 or 4 wherein said means for moving said slider comprises a rocker arm which is oscillated at a rate corresponding to the striking rate of said printing device, wherein said slider abuts said rocker arm in one position when said ink ribbon is in position for striking by said printing device and in a second position when said correction tape is in position for striking by said printing device. A carrier assembly according to claim 5 wherein the first position is further from the point about which the rocker arm is oscillated than the second position. A carrier assembly according to any one of claims 1 to 6 wherein said forwarding means is operable to feed the ink ribbon intermittently. A carrier assembly according to claim 2 or any claim dependent thereon wherein the positioning means further comprises means for moving the elevational table between a printing and an erasing position. A carrier assembly according to claim 8 when dependent on claim 5 wherein the rocker arm is rotatable and disposed so that the slider abuts the arm at one point when the elevation table is in the printing position to reciprocate the slider a first distance and so that the slider abuts the arm at a second point closer to the point of rotation when the elevation table is in the erasing position to reciprocate the slider a second distance shorter than the first distance. A method for operating a ribbon forwarding apparatus in an impact type printer having an ink ribbon and a correction tape comprising the steps of: moving the ink ribbon a first predetermined incremental distance each time a character is to be printed; and moving the ink ribbon a second predetermined incremental distance each time a character is to be erased, said second predetermined incremental distance being shorter than said first predetermined incremental distance. The method of claim 9 wherein said predetermined incremental distance is 1/n times said first predetermined incremental distance, where n is an integer. A ribbon driving device for an impact printer of the type having an impact head (3) for impact printing through an ink ribbon (7) onto a target sheet supported on a platen (1), means (3, 6, 8) being provided for erasing characters or other markings so printed on said sheet, the device including means (9, 10, 11, 12, 13, 14) for advancing the ink ribbon between successive printing operations by the impact head, characterised in that the advancing means is arranged to advance the ink ribbon during operation of the erasing means, the degree of ink ribbon movement being less between successive erasing operations by the erasing means than between successive said printing operations by the impact head. A ribbon driving device according to claim 12 wherein said impact head (3) is mounted on a carriage (2) which is arranged to be driven relative to the platen for printing by the impact head or erasing by the erasing means at successive print locations on the target sheet, and wherein the erasing means includes means (4) for mounting an erasing tape on the carriage and for positioning said erasing tape adjacent the impact head, whereby erasing is effected by impact of the impact head (3) through the erasing tape (8). A ribbon driving device according to claim 13 wherein said means for mounting the erasing tape comprises a member (4) adapted also for mounting said ink ribbon, said member being displaceable between first and second positions for selectively positioning said ink ribbon or said erasing tape adjacent said impact head, the advancing means being arranged to vary said degree of ink ribbon movement in response to said displacement of said member. A ribbon driving device according to any of claims 12 to 14, wherein said advancing means is adapted for stepwise advancing said ink ribbon the steps being larger between successive printing operations than between successive erasing operations.

Inventors: IWAI, HIROJI, KADOYA, ATSUSHI
Applicants: SHARP KABUSHIKI KAISHA
Application year: 1987
Main classification: B41J33
IPC codes: B41J33, B41J35