| 摘要 |
PROBLEM TO BE SOLVED: To make a ball-rotation excellent, and facilitate the regulation to the most suitable flow rate of ink by setting the inner diameter of the ball house of a ball pen tip to a specific range of the dimension relative to the ball diameter, and bringing the ball to line contact with the seat surface of the ball house. SOLUTION: The inner diameter D of a ball house 18 is set in a range of 101.6-103.6% of the diameter (d) of the ball 15, and the opening diameter of the ball house is regulated so that the projection (h) of the ball 15 becomes approximately one thirds of the diameter of the ball 15. Therefore, the flow rate of ink becomes stable. In addition, the tip thereof is caulked with an interstice of the order of 0.005-0.011 mm provided between the opening end of the front bore and the ball 15. As a result, craters are not formed on the seat surface 21, and the ball 15 comes in line contact with the seat surface 21 of the ball retainer 18. Since the seat surface 21 of the ball house has no craters, the frictional resistance of the ball 15 is small, so that the ball rotates smoothly to enable a good writing. |
