US 6,883,983 B2 · Paper lateral edge detector for printer

Abstract

First and second light receiving windows are formed on a head cover of a thermal head. The first light receiving windows are disposed to cross the lateral edges of the first king-sized recording paper. The second light receiving windows are disposed to cross the lateral edges of the second large-sized recording paper. First and second phototransistors are provided on the thermal head so as to measure quantity of light passed through the first and second light receiving windows. When printing the first recording paper, the first light receiving windows are partially shielded with lateral edges of the first recording paper and the second light receiving windows are completely shielded with the recording paper. Positions of the lateral edges are determined from the difference between output signals of the two phototransistors. When printing the second recording paper, the first light receiving windows are shielded by light-tight shielding stickers.

Claims13

Dependent claims

A sheet lateral edge detector comprising:

a light receiving window having a region which a lateral edge of a recording sheet moves across;
a first photo sensor for measuring light passing through said light-receiving window partially shielded by said lateral edge of said recording sheet;
a second photo sensor disposed away from the first photo sensor in a widthwise direction of said recording sheet, for measuring dark current;
and
a judging device for judging the position of said lateral edge of said recording sheet from the difference signal between output signals of the first and second photo sensors.

2 more elements

A sheet lateral edge detector for a printer, said printer being capable of printing on first and second recording sheets, a width of said first recording sheet being larger than a width of said second recording sheet, said sheet lateral edge detector comprising:

a first light receiving window having a region while a lateral edge of said first recording sheet moves across during transport thereof;
a first photo sensor for receiving light passed through said first light receiving window partially shielded by said lateral edge of said first recording sheet;
a second light receiving window having a region which a lateral edge of said second recording sheet moves across during transport thereof;
a second photo sensor for receiving light passed through said second light receiving window partially shielded by said lateral edge of said second recording sheet;
a recording head for printing on said first or second recording sheet on line-by-line basis extending in said widthwise direction, said recording head having a length larger than said width of said first recording sheet;
a shielding device for shielding said second light receiving window in printing on said first recording sheet, and for shielding said first light receiving window in printing on said second receiving sheet;
and
a judging device for judging the position of said lateral edge of said first or second recording sheet from the difference signal between output signals of the first and second photo sensors.

5 more elements

Dependencies are inferred from the claim text.

Paper lateral edge detector for printer

Life of this patent

Paper lateral edge detector for printer

Life of this patent

Abstract

Claims13