A telescopic ball-point pen includes a tubular body, including a sliding axial tube, which in turn includes a refill tank. An interior surface of the body and an exterior surface of the sliding axial tube are threaded to form a driver screw portion, and an interior surface of the sliding axial tube and an exterior surface of the refill tank are threaded to form a follower screw portion. A pitch of the follower screw portion is greater than that of the driver screw portion so that the amount of front-and-back movement of the refill tank is greater than that of the sliding axial tube per rotation. A rear end of the sliding axial tube is fixed to a sheath. When the sheath and the body are rotated, the tip of a ball-point pen refill removably received within the refill tank is projected beyond, or received within, the pen.

FIELD OF THE INVENTION

The present invention is related to a telescopic ball-point pen.

BACKGROUND OF THE INVENTION

With a conventional telescopic ball-point pen, when the pen is not in use, its frontal axial portion and rear axial portion are moved closer together, thereby engageably striking an internal push rod with a sliding tip portion, so that the sliding tip portion is projected to a position to thereby conceal a tip of a ball-point pen refill. When the pen is in use, the frontal axial portion and the rear axial portion are moved away from each other, thereby disengaging the push rod from the sliding tip portion, so that the sliding tip portion is retracted to a position to expose the tip of a ball-point pen refill.

Construction of this type of telescopic ball-point pen requires high-precision machining, with a relatively low yield. Further, the assembly work required tends to be complex and costly.

SUMMARY OF THE INVENTION

The present invention provides a telescopic ball-point pen in which the telescopic motion is effected by rotating components that are screwed or threaded onto each other, so as to permit high-yield machining and relatively easy assembly of the pen.

A telescopic ball-point pen includes a tubular body, to one end of which a mouth ring is removably attached. The tubular body includes therein a sliding axial tube, which in turn includes a refill tank. An interior surface of the body and a corresponding exterior surface of the sliding axial tube are threaded to form a driver screw portion, which permits the sliding axial tube to slide back and forth within the body. An interior surface of the sliding axial tube and a corresponding exterior surface of the refill tank are threaded to form a follower screw portion, which permits the refill tank to slide back and forth within the sliding axial tube. The pitch of the follower screw portion is greater than that of the driver screw portion so that the amount of front-and-back movement of the refill tank is greater than that of the sliding axial tube per rotation. A ball-point pen refill is removably received within a refill tank so that its pen tip can be projected beyond, or received within, a distal end of the mouth ring. At a rear end of the sliding axial tube, a sheath and a head cap are provided, both of which are configured to rotationally slide along a connection portion of the body. When the sheath and the body are rotated, they are moved away from each other or closer together and, at the same time, the pen tip of the ball-point pen refill within the refill tank is projected beyond or received within the mouth ring.

Accordingly, the present invention provides a telescopic ball-point pen in which the telescopic motion is effected by simply rotating components that are screwed or threaded onto each other, and thus the pen can be readily put to use for writing. Further, the threaded construction permits high-yield machining and relatively easy assembly of the pen.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A telescopic ball-point pen includes a body2, to one end of which a mouth ring1is removably attached. An interior surface of the body2and a corresponding exterior surface of a sliding axial tube3form a driver screw portion4, which permits the sliding axial tube to slide back and forth within the body2. An interior surface of the sliding axial tube3and a corresponding exterior surface of a refill tank6form a follower screw portion7, which permits the refill tank6to slide back and forth within the sliding axial tube3. The pitch of the follower screw portion7is greater than that of the driver screw portion4so that the amount of front-and-back movement of the refill tank6is greater than that of the sliding axial tube3per rotation. A ball-point pen refill5is removably received within the refill tank6so that its pen tip5′ can be projected beyond, or received within, a distal end of the mouth ring1. At a rear end of the sliding axial tube3, a sheath9and a head cap10are provided, both of which are configured to rotationally slide along a connection portion8of the body2. When the sheath9and the body2are rotated, they are moved away from each other, or closer together, and at the same time, the pen tip5′ of the ball-point pen refill5within the refill tank6is projected beyond, or received within, the mouth ring1.

In one embodiment, the ratio between the pitch of the driver screw portion4and the pitch of the follower screw portion7is set as 1:1.4. When a telescopic ball-point pen is shortened or retracted as shown inFIG. 1, a user can rotate the body2and the sheath9so as to separate the body2and the sheath9away from each other to thereby extend the pen, as shown inFIG. 2.

The beginning end and the terminal end of an internal thread11of the driver screw portion4include slightly bossed flat lock portions12and12′, respectively. An external thread13, which corresponds to the internal thread11, includes a projection14. When the pen is shortened, the projection14is received by the beginning end lock portion12of the internal thread11, and when the pen is extended the projection14is received by the terminal end lock portion12′ of the internal thread11, so as to stabilize the pen when it is shortened or extended and to prevent inadvertent extension or shortening of the pen.

The refill tank6and the body2include a projection15and a groove16, respectively, which are engageable so as to relatively move the refill tank6and the body2only in the front-and-back direction.

When the pen is extended, a ring18strikes a stopper17so as to stop the extension movement, and at that time the projection14of the external thread13is engaged with the terminal end lock portion12′ of the internal thread11to prevent any inadvertent extension or shortening movement.

A stop screw19fixed to a rear end of the sliding axial tube3is provided to fasten the sheath9and the head cap10.

According to the construction described above, all of the main structural components, such as the body2, the sliding axial tube3, and the refill tank6, are tubular, and can be constructed by simply applying threads on their exterior or interior surfaces or portions thereof. Therefore, the construction permits high-yield machining and relatively easy assembly of the pen.