Coating implements with material supply – Including ball – roller or endless-belt tool – With flow-regulator
Reexamination Certificate
2000-04-20
2001-10-23
Walczak, David J. (Department: 3751)
Coating implements with material supply
Including ball, roller or endless-belt tool
With flow-regulator
C401S209000
Reexamination Certificate
active
06305865
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a retractable ballpoint pen provided with a ballpoint pen refill having an ink-accommodating tube containing water-based ink and having a ballpoint pen tip capable of being projected from and retracted into a barrel through an open forward end of the barrel by operating a retracting mechanism.
BACKGROUND ART
A well-known retractable ballpoint pen is provided with a ballpoint pen refill having a ballpoint pen tip capable of being projected from and retracted into a barrel through an open forward end of the barrel. This retractable ballpoint pen has a ballpoint pen refill containing writing ink which is inserted in the barrel for sliding movement in the barrel and biased toward the rear end of the barrel by a spring. This retractable ballpoint pen has a retracting mechanism for projecting the ballpoint pen tip from and retracting the same into the barrel through the open forward end of the barrel.
A retractable ballpoint pen with a ballpoint pen refill having an ink-accommodating tube containing water-based ink has been marketed in recent years.
The ballpoint pen tip of the retractable ballpoint pen with the ballpoint pen refill having the ink-accommodating tube containing water-based ink is pointed downward when the retractable ballpoint pen is held in a pocket of clothes with a clip. Consequently, problems are liable to arise due to leakage or back-flow of ink. Back-flow of ink is a phenomenon in which the ink flows rearward from the ballpoint pen tip into the ink-accommodating tube due to shocks caused by the operation of a retracting mechanism or dropping.
The present invention has been made in view of the above-mentioned problems. It is therefore an object of the present invention to provide a retractable ballpoint pen with a ballpoint pen refill having an ink-accommodating tube containing water-based ink inserted in a barrel. The pen is free of ink leakage from its tip and free of ink back-flow due to shocks caused by retractable operation, and the pen is also satisfactory in writing performance.
SUMMARY OF THE INVENTION
To achieve the object, the present invention provides a retractable ballpoint pen comprising: a ballpoint pen refill having an ink-accommodating tube, a ballpoint pen tip disposed in a forward end of the ink-accommodating tube, and a ball held for free rotation in a forward end of the ballpoint pen tip; a barrel having an open forward end and containing the ballpoint pen refill; a retracting mechanism for projecting and retracting a forward end of the ballpoint pen tip through an open forward end of the barrel; a water-based ink contained in the ink-accommodating tube, the water-based ink containing a thixotropic agent and having a viscosity at a rate of shear of 1.9 sec
−1
at 20° C. in the range of 900 to 2500 mPa·s; and a restricting passage for restricting a flow of the water-based ink. The restricting passage is formed in a passage so that the water-based ink contained in the ink-accommodating tube can flow to the ball, and a sectional area of the restricting passage measured perpendicular to an axis of the ink-accommodating tube is in a range of 0.4 to 0.8 mm
2
.
Preferably, the retractable ballpoint pen further comprises a tip holder attached to a forward end part of the ink-accommodating tube. The tip holder holds a rear end of the ballpoint pen tip in the forward end part, and the tip holder is provided with an ink passage. The restricting passage is formed by reducing at least a part of the ink passage. Preferably, the restricting passage is formed in a rear end of the ink passage.
Preferably, the ink passage is tapered from a front end of the tip holder toward a rear end of the tip holder, and the restricting passage is formed at a narrowest rear end of the ink passage.
Preferably, the retractable ballpoint pen comprises a coil spring pressing the ball forward to press the ball closely against an inner surface of the forward end part of the ballpoint pen tip. The tip holder has an aperture at its forward end part, and a rear end of the ballpoint pen tip is fitted in the aperture. The aperture of the tip holder is connected to the ink passage, and is formed to have a diameter greater than a diameter of the ink passage so as to form a shoulder at a joint of the aperture and the ink passage to hold a rear end of the coil spring thereon.
Preferably, the retractable ballpoint pen further comprises a tip holding part formed integrally with a forward end of the ink-accommodating tube. The tip holding part is provided with an ink passage, and the restricting passage is formed by reducing at least a part of the ink passage of the tip holding part.
Preferably, the retractable ballpoint pen further comprises a flow control member with an ink passage, wherein the ink-accommodating tube has a small-diameter section formed at the forward end, and a large-diameter section formed behind the small-diameter section. The large-diameter section has a diameter larger than a diameter of the small-diameter section, and the ballpoint pen tip is attached to a forward end of the small-diameter section. The flow control member is fitted in the small-diameter section, and the restricting passage is formed by setting the smallest cross-sectional area of the ink passage of the flow control member at a value in a range of 0.4 to 0.8 mm
2
.
Preferably, the ballpoint pen tip is attached directly to a forward end of the ink-accommodating tube or to a forward end of a tip holder attached to the forward end of the ink-accommodating tube, and the restricting passage is formed in the ballpoint pen tip. The restricting passage can be formed by bending a rear edge of the ballpoint pen tip inwardly. Alternatively, the restricting passage can be formed by reducing a diameter of a rear end of the ballpoint pen tip along a predetermined length. The restricting passage can also be formed by forming a projection projecting inwardly from an inner surface of a rear end part of the ballpoint pen tip.
Preferably, the retractable ballpoint pen further comprises a flow control member fitted in an open rear end part of the ballpoint pen tip, wherein the restricting passage is formed in the flow control member. The restricting passage can be a continuous hole or a continuous groove extending from a forward end of the flow control member to a rear end thereof, and the hole or the groove has a minimum sectional area in the range of 0.4 to 0.8 mm
2
. The restricting passage can also be formed by a projection formed on an inner surface of a continuous hole or a continuous groove extending from a forward end of the flow control member to a rear end thereof.
Preferably, the thixotropic agent is a mixture of a crosslinking acrylic acid polymer, a xanthan gum and a succinoglycan. The concentration of the thixotropic agent in the ink is in the range of 0.2 to 0.8% by weight.
The retracting mechanism of the present invention is a well-known writing tip operating mechanism employing a rotary cam, a mechanism that holds a projection in a hole or a mechanism employing a heart cam groove. The retracting mechanism of the present invention may be any one of various mechanisms capable of projecting a forward end of a ballpoint pen tip of a ballpoint pen refill contained in a barrel from an open forward end of the barrel and retracting the same into the barrel when a knocking head is pressed.
The restricting passage according to the present invention may be an aperture of a predetermined length along the direction of the axis of the ink-accommodating tube or may be a local, small part not having the predetermined length. There is no particular restriction on the sectional shape of the restricting passage. The sectional shape of the restricting passage may be either circular or noncircular.
The ink passage according to the present invention may be a straight passage extending along the direction of the axis of the ink-accommodating tube, a meandering passage or a zigzag passage.
There is no particular restriction on the sectional shape of the connecting aperture
Ohno Takashi
Sasaki Kazuhiko
Yoshii Kazuhiro
Kabushiki Kaisha Pilot
Nguyen Tuan
Walczak David J.
Wenderoth , Lind & Ponack, L.L.P.
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