| 摘要 |
PURPOSE:To eliminate ununiformity in printed density in the feeding direction of a printing head and enhance printing quality, by a construction wherein the value obtained by dividing the diameter of a printing wire by the weaving pitch in the weft direction of an ink ribbon is an integer of at least 2. CONSTITUTION:A printing head 1 is mounted on a carrier 2, and printing wires are projected from a tip part 1a of the head 1 to impact against a paper through an ink ribbon 17. The ink ribbon 17 has a plain weave texture comprising warps 20 and wefts 21 intersecting alternately each other, and the length 2bt in the warp direction is the weaving pitch of the wefts. It is considered that the area P of the ribbon when the diameter bw of the printing wire 22 is projected on a model of section of the ribbon is substantially proportional to the printing pressure on the paper by the impact, and the ratio Pmin/Pmax of the minimum Pmin to the maximum Pmax of the area P represents the ununiformity in printed density. Namely, when Pmin/Pmax=1, the printing pressure is constantly fixed, and printed density is uniform. When an ink ribbon in which the ratio Aw=bw/2 bt of the diameter bw of the printing wire to the weaving pitch 2bt of the ribbon is an integer of at least 2 is used, a uniform printed density is obtained. |
