×

Electronic typewriter

  • US 4,480,931 A
  • Filed: 03/09/1982
  • Issued: 11/06/1984
  • Est. Priority Date: 03/16/1981
  • Status: Expired due to Fees
First Claim
Patent Images

1. 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 line position;

    a plurality of line index registers each for storing a count indicative of a print line position;

    control means to maintain in said index registers counts corresponding to sequential print lines which include at least one character printed independently of whether said sequential print lines contain an error;

    indicator means for indicating the presence of characters printed in and hence automatically deletable from the current print line on the record sheet; and

    said control means being responsive to operation of said line indexing mechanism successively comparing the contents of said line index registers with the contents of said line position register and for activating said indicator means if coincidence is reached.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×