Patent ID: 7611300
Filing Date: 2009-11-03
Classification: B43K

Abstract:
1. A double-head writing instrument, comprising: a barrel formed by injection molding of transparent synthetic resin, the barrel opened at first and second ends thereof, the barrel having a partition formed therein; first and second ink-tanks provided inside the barrel and defined by the barrel and the partition so as not to communicate each other, the first and second ink-tanks opened at the first and second ends of the barrel, respectively; a first ink-retaining member connected with a first nib provided on an opening of the first ink-tank; a first ink reserved inside a first ink-reservoir which is provided inside the first ink-tank and at a rear of the first ink-retaining member; a second ink-retaining member connected with a second nib provided on an opening of the second ink-tank; and a second ink reserved inside a second ink-reservoir which is provided inside the second ink-tank and at a rear of the second ink-retaining member, wherein the first and second ink-retaining members retain temporarily the first and second ink spilled in accordance with an increase in pressure inside the first and second ink-reservoirs, respectively, the partition is extended in an axial direction of the writing instrument so as that the first and second ink-reservoirs overlap each other in a radial direction, and thickness C of the partition and thickness D of a side wall of the barrel connected with the partition satisfy a relation of 0.2≦C/D≦2.5, wherein a first guiding core supplying the first ink from the first ink-reservoir to the first nib is inserted at an axial center of the first ink-retaining member, a rear end of the first guiding core projects posterior to a rear end of the first ink-retaining member so as to contact with the first ink when the first nib is pointed upward, a second guiding core supplying the second ink from the second ink-reservoir to the second nib is inserted at an axial center of the second ink-retaining member, and a rear end of the second guiding core projects posterior to a rear end of the second ink-retaining member so as to contact with the second ink when the second nib is pointed upward.