The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 23, 2001
Filed:
Apr. 20, 2000
Kabushiki Kaisha Pilot, Tokyo-To, JP;
Abstract
A retractable ballpoint pen is free from leakage of ink from its tip and ink back-flow attributable to shocks produced by retractable operation, and is capable of satisfactory writing performance. The retractable ballpoint pen has a ballpoint pen refill (,) having a ballpoint pen tip (,) disposed in a forward end of an ink-accommodating tube (,), a ball (,) held for free rotation in a forward end part of the ballpoint pen tip (,). The retractable ballpoint pen is provided with a retracting mechanism (,) for projecting a forward end of the ballpoint pen tip (,) and retracting the same through an open forward end (2a) of a barrel (,). A water-based ink (,) contained in the ink-accommodating tube (,) contains a thixotropic agent and has a viscosity at a rate of shear of 1.9 sec,at 20° C. in the range of 900 to 2500 mPa·s. A restricting passage (,) is formed in a passage for the water-based ink (,) contained in the ink-accommodating tube (,) to flow to the ball (,) and has a cross-sectional area measured perpendicular to the axis of the ink-accommodating tube (,) in the range of 0.4 to 0.8 mm,. The restricting passage (,) limits the flow of the water-based ink (,).