Abstract:
Disclosed is a printer having a correction ribbon tape for correcting printed characters. A plurality of characters printed in the same print position can be corrected in one step of feed of the correction ribbon tape.

Description:
This application is a continuation of application Ser. No. 773,104, filed 9-6-85, now abandoned, which is a continuation of Ser. No. 537,576, filed 9-30-83, now abandoned. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a printer, and more particularly to a printer which has a correctable ink ribbon and a correction ribbon tape known in an electronic typewriter and can automatically or manually correct printed characters. 
     2. Description of the Prior Art 
     In a prior art printer such as an electronic typewriter, when a plurality of characters printed in the same print position such as a character with an underline as shown in FIG. 1 is to be erased, a new portion of a correction ribbon tape CT is fed each time one of the characters has been erased, as shown in FIG. 2(a). As a result, the consumption of the correction ribbon tape is large and a time to feed the correction ribbon tape is required each time when one character has been erased. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide a printer in which the correction operation is repeated with only one step of feed of the correction ribbon tape as shown in FIG. 2(b) when a plurality of characters printed in the same print position is to be corrected so that the correction ribbon tape is saved and the time to make corrections is shortened. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a printout on a paper, 
     FIG. 2 shows correction tapes after correction, in which FIG. 2(a) shows a tape in accordance with a prior art method and FIGS. 2(b), 2(c) and 2(d) show tapes in accordance with the present invention, 
     FIG. 3 shows a block diagram of one embodiment of the present invention, 
     FIG. 4 shows a keyboard, and 
     FIG. 5 shows a time chart for ports P1, P2 and P3 shown in FIG. 3 and a correction ribbon cassette. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 3 shows an embodiment of the present invention, in which numeral 1 denotes a keyboard, numeral 2 denotes a central processing unit (CPU), numeral 3 denotes a hammer driver, numeral 4 denotes a print hammer, numeral 5 denotes types, numeral 6 denotes a type wheel bearing the types 5, numeral 7 denotes a print paper, numeral 8 denotes a platen, numeral 9 denotes a cassette which contains a correction ribbon tape, and numeral 10 denotes a lever for moving the cassette 9 up and down. When the cassette 9 is moved up, the correction ribbon tape is fed. Numeral 11 denotes a drive circuit for the lever 10, numeral 12 denotes an OR circuit, numeral 13 denotes a motor for rotating the type wheel 6 and numeral 14 denotes a control circuit for the type wheel motor 13. 
     FIG. 4 shows a keyboard, in which SSW denotes a slide switch which selects a normal print mode when it is in a position XXX and selects an underlined print mode when it is in a position XXX, X  denotes a correction start key, and other keys are character keys. 
     The manual erasure of the printed character with underline &#34;A&#34; shown in FIG. 1 is now explained. An operator first sets the switch SSW to the position XXX and depresses the correction key  X . Thus, a correction start code is transferred from the keyboard 1 to the CPU 2. When the CPU 2 receives the correction start code, it renders the output port P3 to logic &#34;1&#34;. Thus, the OR circuit 12 produces a &#34;1&#34; output and the driver 11 for the lever 10 drives the lever 10 to lift the correction ribbon tape cassette 9. As a result, the correction ribbon tape is fed one step. Then, the operator depresses the key &#34;A&#34; corresponding to the printed character. Thus, the underline code and the character code are transferred from the keyboard 1 to the CPU 2. In response to the underline code, the CPU 2 renders the output port P2 to &#34;1&#34;. Then, it sends a signal to select the underline type to the type wheel motor control circuit 14 so that the circuit 14 selects the underline type. When an end of type selection signal is sent from the type wheel motor control circuit 14 to the CPU 2, the CPU 2 sends a print command signal P1 to the print hammer drive circuit 3. As a result, the print hammer drive circuit 3 drives the print hammer 4 so that the underline indicia is pressed against the correction tape CT as shown in FIG. 2(c) and the underline is erased. At the end of the energization of the print hammer 4, the CPU 2 renders the port P2 to &#34;0&#34;, but since the port P3 is &#34;1&#34; and the correction ribbon tape cassette 9 remains at the up position, the correction ribbon tape is not fed. When the CPU 2 receives the character code, it renders the port P2 to &#34;1&#34; and the port P3 to &#34;0 &#34;. Since the output of the OR circuit 12 is &#34;1&#34; at this time, the correction ribbon tape cassette remains at the up position. The CPU 2 sends a signal requesting selection of the type &#34;A&#34; to the type wheel motor control circuit 14 and the character &#34;A&#34; is erased as shown in FIG. 2(d) by the print command signal P1 in the same manner as described above. When the print hammer 4 is deenergized, the CPU 2 renders the port P2 &#34;0&#34;. Since both ports P2 and P3 are now &#34;0&#34;, the output of the OR circuit 12 changes to &#34;0&#34; and the correction ribbon cassette 9 is shifted down. 
     FIG. 5 shows levels of the ports P1, P2 and P3 and the correction ribbon cassette 9.  ○1  indicates the reception of the correction start code by the CPU 2,  ○2  and  ○4  indicate the reception of the underline code and the character code,  ○3  and  ○5 indicate the end of one character erasure. 
     As described herein above, in accordance with the present invention, when a plurality of characters are printed at the same print position, such as a character with underline, or a &#34; &#34; character which is composed by &#34;Y&#34; and &#34;=&#34;, the correction operation is carried out a plurality of times without feeding the correction ribbon tape so that the correction ribbon tape is saved and the correction time is shortened. While the manual erasure operation has been described above, the printed characters can be automatically erased by storing the printed characters in a memory such as a RAM and issuing a correction start signal.