Error correcting system for an electronic typewriter

Claim 2

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, a print buffer for storing therein character data being printed on the record sheet, and an automatic correction mechanism for addressing said print buffer and for deleting printed characters on the record sheet, comprising: storage memory means for storing therein coded data representative of characters being deleted by said correction mechanism; a manually operable print enabling key; and addressing means responsive to said key for successively addressing said storage memory to recall the character data stored therein and for causing said printing mechanism to print on the record sheet a character or characters in accordance with the character data thus recalled.

Claim 3

A typewriter as claimed in claim 1, further comprising a no-print key for preventing printing operation of said printing mechanism while allowing character data to be stored in said print buffer, a first operation of said print enabling key after preceding depression of said no-print key invalidating the effect of said no-print key - whereas a second operation of said print enabling key may render said addressing means operative.

Claim 4

A typewriter as claimed in claim 1, further comprising a no-print key for preventing a deleting operation of said correction mechanism, while allowing said print buffer to be addressed by said correction mechanism and allowing coded character data to be stored in said storage memory means, a first operation of said print enabling key after a preceding depression of said no-print key invalidating the effect of said no-print key whereas a second operation of said print enabling key will render said addressing means operative.

Claim 5

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, bidirectional feeding means for feeding said printing mechanism relative to said platen, a bidirectional line indexing mechanism, a print buffer for storing therein character data being printed on the record sheet, said print buffer being capable of storing therein a predetermined number of lines of characters last printed, and an automatic correction mechanism for addressing said print buffer and for deleting printed characters from the record sheet, comprising: a line position register responsive to operation of said line indexing mechanism for storing a count indicative of a current print line position; a plurality of line index registers each for storing a count indicative of a print line position corresponding to a print line which includes at least one character printed; indicator means for indicating the presence of characters printed in and hence automatically deletable from the current print line on the record cheet; and means responsive to operation of said line indexing mechanism for successively comparing the contents of said line index registers with the contents of said line position register and for activating said indicator means if a coincidence is reached.

Claim 6

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, bidirectional feeding means for feeding said printing mechanism relative to said platen, a bidirectional line indexing mechanism, a print buffer for storing therein character data being printed on the record sheet, said print buffer being capable of storing therein a predetermined number of lines of characters last printed, and an automatic correction mechanism for addressing said print buffer and for deleting printed characters from the record sheet, comprising: a line position register responsive to operation of said line indexing mechanism for storing a count indicative of a current print line position; a plurality of line index registers each for storing a count indicative of a print line position corresponding to a print line which includes at least one character printed; indicator means for indicating the presence of characters printed in and hence automatically deletable from the current print line on the record cheet; and means responsive to operation of said line indexing mechanism for successively comparing the contents of said line index registers with the contents of said line position register and for activating said indicator means if a coincidence is reached.

Claim 7

A typewriter as claimed in claim 4, wherein the printing point defined by and between said platen and said printing mechanism is backspaced within the current print line each time a printed character or a space is deleted.

Claim 8

A typewriter as claimed in claim 4 or 5, further comprising a plurality of line format registers each corresponding to one of said line index registers for storing data representative of the first and end print positions for a given print line, activation of said correction mechanism when the current print point is at the first print position for a print line resulting in indexing of said platen to the preceding print line if available and then feeding of said printing mechanism to the end print position for the thus indexted print line thereby to enable subsequent succeeding automatic deletion of printed characters for the print line by said correction mechanism.

Claim 9

A typewriter as claimed in claim 4, 5 or 6, further comprising storage memory means for storing therein coded data representative of characters being deleted by said correction mechanism, a manually operable print enabling key; and addressing means responsive to said key for successively addressing said storage- memory to recall the character data stored therein and for causing said printing mechanism to print on the record sheet a character or characters in accordance with the character data thus recalled.

Claim 10

A typewriter as claimed in any one of claims 4 to 7, further comprising a no-print key for preventing printing operation of said printing mechanism while allowing character data to be stored in said print buffer, a first operation of said print enabling key after a preceding depression of said no-print key invalidating the effect of said no-print key whereas a second operation of said print enabling key will render said addressing means operative.

Claim 11

A typewriter as claimed in any one of claims 4 to 7, further comprising a no-print key for preventing deleting operation of said correction mechanism while allowing said print buffer to be addressed by said correction mechanism and the coded character data to be stored in said storage memory means, a first operation of said print enabling key after a preceding depression of said no-print key invalidating the effect of said no-print key whereas a second operation of said print enabling key will render said addressing means operative.

Claim 12

A typewriter as claimed in any one of claims 4 to 9, further comprising an error correction key manually operable to activate said automatic correction mechanism, said indicator means including a light emitting element which is associated with said correction key.

Claim 13

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, feeding means for moving said printing mechanism relative to said platen to define successive print points, means for setting a left margin, and a left margin register for storing therein a count indicative the left margin thus set to which said printing mechanism is to return by carrier return operation, comprising: tab stock means for storing therein counts each indicative of a tab point; means for providing a tabulating instruction; tabulating means responsive to a tabulating instruction for searching said tab stock means for a following next tab point and for causing said printing mechanism to be moved to the following next tab point; and a key independent of the providing means and manually operable to provide a tabulating -instruction to said tabulating' means and to cause a count indicative of the following next tab point to be stored in said left margin register.

Claim 14

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, feeding means for moving said printing mechanism relative to said platen to define successive print points, means for setting a left margin, and a left margin register for storing therein a count indicative the left margin thus set to which said printing mechanism is to return by carrier return operation, comprising: tab stock means for storing therein counts each indicative of a tab point; means for providing a tabulating instruction; tabulating means responsive to a tabulating instruction for searching said tab stock means for a following next tab point and for causing said printing mechanism to be moved to the following next tab point; and a key independent of the providing means and manually operable to provide a tabulating -instruction to said tabulating' means and to cause a count indicative of the following next tab point to be stored in said left margin register.

Claim 15

A typewriter as claimed in claim 11, further comprising a left margin save register for storing the count of the left margin set by the margin setting means so as to enable, upon a second operation of said key, the thus set left margin count to be stored in said left margin register again.

Claim 16

A typewriter as claimed in claim 11 or 12, further comprising indicator means for indicating that said printing mechanism is to return to a point other than the left margin set by the margin setting means.

Claim 17

A typewriter as claimed in claim 13, wherein said indicator means includes a light emitting element which is associated with said key.

Claim 18

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, feeding means for moving said printing mechanism relative to said platen to define successive print positions, a right margin register for storing therein a count indicative of a prescribed right margin for a print line, a left margin register for storing therein a count indicative of a left margin for the print line, and a margin release key, comprising: selector means having first and second positions; and control means responsive to said selector means in the second position for invalidating said right margin thereby to enable said printing mechanism to print characters successively beyond the right margin position.

Claim 19

A typewriter having a platen, a printing mechanism for printing characters on a record sheet supported on said platen, feeding means for moving said printing mechanism relative to said platen to define successive print positions, a right margin register for storing therein a count indicative of a prescribed right margin for a print line, a left margin register for storing therein a count indicative of a left margin for the print line, and a margin release key, comprising: selector means having first and second positions; and control means responsive to said selector means in the second position for invalidating said right margin thereby to enable said printing mechanism to print characters successively beyond the right margin position.

Claim 20

A typewriter as claimed in claim 15, further comprising a control zone register for storing therein a count representative of the leftward extreme end of a control zone, said control means being responsive to a first spacing or hyphenation instruction during printing at a position at or rightwardly of the position represented by the leftward extreme end of said control zone for activating said feeding means to automatically return said printing mechanism to the left margin print position. /