Note: Descriptions are shown in the official language in which they were submitted.
1 BACKGROUND OF THE INVENTION
This invention relates to a ball-point pen tip and a
ball-point pen provided with the same, and more particularly, to
a type thereof which uses an aqueous solution based low viscosity
ink.
According to the conventional ball-point pen, a tip
portion includes a socket formed of plastic material or metal
such as brass and nickel silver, and a steel or rubby-ball rota-
tably disposed in the tip portion of the socket. Further, an
ink guide stem is inserted in the rear portion of the socket, and
an ink passage is formed between a ball seat and the ink guide
stem.
In this type of the pen tip, the socket must stably
hold the ball, even when large writing force is applied to the
pen t;p. Further, in order to provide comfortable writing for
long duration, the ball seat must sustain frictional wear due to
the rotational surface contact with the rigid ball. Furthermore,
ink must be constantly supplied into the ball seat and the ink -
passage in conformity with consumption amount of the ink, so that
the ink passage must provide sufficient cross-sectional area so
as to permit the ink to pass therethrough and must create
capillary acti.on for retaining the low viscosity ink therein so
as to prevent the ball-point pen from failing to write or skip-
ping.
In case the socket made. of plastic material is used, it
i.s possible to produce axial channels, as the ink passages, hav-
ing compl~cated cross sectional shape by molding in order to
create s.u~ficient capillary actIon. However, the ball seat is
extremely worn due to rotati.onal contact with the ball, to thus
degrade writing performance for long duration. Further, the
33
1 plastic socket does not provide sufficient force for holding the
ball therein ln comparison with the metal socket, so that ball
may be accidentally released or disengaged from the ball seat
during writing.
On the other hand, in case the socket made of metal is
used, it would be difficult to produce a plurality of axial
channels, as the ink passages, to create capillary action.
Generally used are copper alloys such as brass and nickel silver
those being easily subject to machining or cutting. However, it
is yet difficult to produce axial capillary channels by machining,
and resultant socket is costly with low productivity. Further,
since brass and nickel silver are apt to be corroded by the
aqueous solution ink, the ink to be used must be selected in light
of its characteristics such as pH and Cl-ion content, resulting
in reducing variety of the aqueous solution ink.
Another type of socket of ball-point pen is proposed
in U.S. patent 3,781,123, wherein a central axial bore having
simplified circular cross-section is formed instead of the
plurality of axial channels for capillary action. The central
bore has one end in communication with radial grooves each having
capillary dimension and radially spreading in the surface of the
ball seat. However, according to this type, in case the central
bore.has relat~.vely large diameter so as to supply large amount
of ink., reduced is the capillarity for maintaining capillary
acti`.on of the a~ueous solution based lo~ viscosity ink, and there-
fore., such.socket may not be appreciated as a ball-point pen tip
which.use.s aqueous solution ink.
SU~AR~ OF THE INVENTION
-
I:t i.s therefore an object of the present invention to
overcome the above-nlentioned draw~acks and to provide an improved
1 ball-point pen tip and the ball point pen provided with the tip
which uses an aqueous solution based low viscosity ink, wherein
a socket provides excellent ball retainability and su~tains
frictional wear due to rotational contact between the ball seat
and the ball, yet providing smooth introduction of the ink into
the ball seat by the axial capillary channels, to thereby prevent
the ball-point pen from failing to write or skipping.
These and other objects are attained in accordance with
the present invention by providing a socket comprising a holder
formed with openings and a tubular ink guide portion made of
metal whose hollow space is in communication with one of the
openings of the holder. The tubular ink guide portion is formed
with a plurality of protrusions radially inwardly bent toward the
central axis of the tube at the same circumferential position
thereof by the pressing deformation of the metal tube. Between
the neighbouring protrusions, ink passages are radially-provided
for capillary action. The ball is rotatably supported between
the walls of the inwardly bent protrusions and tip end of the
tubular ink guide portion with a part of the ball surface ~eing
exposed to the atmosphere. Further, the other opening of the
holder allows insertion of an ink supply stem therethrough. The
ink supply stem is in contact with one end of an ink guide stem
disposed in the tubular ink guide portion. The other end of the
ink guide stem is in contact with at least one of the protrusions
radially inwardly extended.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings;
Fig. 1 is a longitudinal cross-sectional view of a ball-
point pen tip according to a first embodiment of the present
invention;
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I Fig. 2 is a longitudinal cross-sectional view of a ball-
point pen tip according to a second embodiment of the present
invention;
Fig. 3 is a longitudinal cross-sectional view of a ball-
point pen tip according to a third embodiment of the present
invention;
Fig. 4 is a transverse cross-sectional view taken along
the line IV-IV of Fig. l;
Fig. 5 is a transverse cross-sectional view taken along
the line V-V of Fig. 2;
Figs. 6 through 10 are longitudinal cross-sectional view
of various examples of protrusions extending radially inwardly
according to the present invention;
Fig. 11 is a transverse cross-sectional view taken along
the line XI-XI of Fig. 2;
Figs. 12 and 13 are transverse cross-sectional view
showing another embodiments of ink guide stems, and
Fig. 1~ shows a longitudinal cross-sectional view show-
ing a ball-point pen provided with a ball-point pen tip according
to the present invention.
DETAILED DESCRIPTION OF THE PREFERRED E~ODIMENTS
Referring now to the drawings, and initially to Fig. 1,
an ink guide portion 2 is integrally formed with a holder portion
3 to define a metal socket 1. An ink supply stem 7 is inserted
into a rear opening of the holder 3 and is contacted with an ink
guide stem 6 disposed in the ink guide portion 2. The tubular
ink guide portion 2 made of metal is formed with a plurality- of
projections 5 extending radially inwardly. These projections 5
are lormed by radially inwardly bending the metal tube 2 at the
same circumferential position thereof. A ball 4 is rotatably
1 supported between a ball seat 9 defined by side walls of the pro-
trusions S and a tip end of the tubular ink guide portion 2. The
tip end is radially inwardly bent.
As shown in Fig. 4, three radially inwardly bent pro-
jections 5 define ink passages 8 (capillary channel) therebetween
for capillary action.
A second embodiment according to the present invention
is shown in Fig. 2, wherein like parts and components are desig-
nated by the same reference numerals as those shown in the first
embodiment. According to the second embodiment, a tubular ink
guide portion 2' made of metal is independently formed w;th
respect to a holder 3' to provide a socket 1' by the combination
thereof. A plurality of projections 5 are formed which radially
extend into the central axis of the tube 2'. As shown in Fig. 5
the projections 5' are defined by four radially inwardly bent
portions between which ink passages 8 are provided. Further, in
the tubular ink yuide portion 2, a rod having complicated cross-
section as sho~n in Figs. 11 through 13 is disposed as an ink
guide stem 6'~6",6"'2. The rod is formed with axial clearances
to permit ink for creating capillary action.
A third embodiment of this invention is shown in Fig.
3, wherein a tubular ink guide portion 2 is formed integral with
a holder 3 to provide an integral socket 1, and further, the ink
suppl~ stem is integral with the ink guide stem to provide an
integral ink supply stem 7'.
As mentioned above, the socket 1 or 1' of the
present invention can be provided in integral structure, or by
connecting the tubular ink guide portion to the holder independ-
ently formed relative to the tubular ink guide portion. However,
in both cases, at least the tubular ink guide portion should be
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1 formed of metal, while the holder is formed of either synthetic
resin or metal. Since ink guide portion of the socket is formed
in the metal pipe, the ball 4 is sufficiently supported therein,
and the ball seat 9 has sufficient wear resistance against
rotational contact of the ball for long duration. Further,
capillary channels 8 in fluid communication with the ball seat
9 are easily provided by pressing deformation of the metal tube
2 radially inwardly at.the same circumferential portion thereof
to provide projections 5 extending radially inwardly. The metal
for use in the tube 2 is for example, copper alloy such as brass
and nickel silver, those being subject to easy machining, or
stainless steel which has been considered to be difficult to use
due to dificulty in machining
By the formation of the radial projections 5, radial
ink pass.ages 8 (capillary passages 8) are defined, so that ink
supply amount can be increased, and ink retainability is enhanced
to th.us provide uniform ink supplying function into the ball seat
wi.thout causing any disadvantages such as skipping.
The size and numbers of the protrusions 5 are determin-
~ ed b.y th.e dia.meter of the metal pipe 2, the diameter beingdetermi.nati.ve by the diameter of the ball 4. Specifically, in
order to create capillary action conducted in the spaces between
. the projecti.ons 5, three to six projections are formed, pre-
ferrab.ly, three to four projections. The. distance between the
- projecti.ons (~i.dth.of the pas-sages 8~. is in a range o~ about
Q.Qlmm to Q.6mm, pre~errably O..Q2mm to Q.4mm.
Further, the ball 4 i.s an ordinary steel ball o~ rubby
ball. The diameter of the ball 4 i5 in a range of Q~5mm to
1.5mm. A~on~ these, widely-used are.t~e balls having diameters
of Q.Smm, Q.7mm, Q.8mm and l.O~m. The ball 4 is rotatabl~
33
1 supported between the ball seats 9 defined by the projections 5
and a tip end of the metal tube 2 radially inwardly bent.
The ink guide stem 6(6') which serves to supply ink
into the capillary channels 8 is formed of resin finished
fascicular synthetic fibers, or foamed plastic stem or synthetic
resin stem. The ink guide stem is preferrably formed of plastic
stem in light of easiness of molding. In this case, since the
ink is flown through the spaces defined be~ween the inner peri-
pheral surface of the metal tube 2' and the ink guide stem 6' as
shown in Fig. 2, the plastic ink guide stem 6' is formed with
capillary grooves as at 10 (Figs. 11 to 13~ along the axial
direction of the stem 6' in order to ensure introduction of the
ink into the capillary passage 8. These grooves 10 are provided
by forming the outer surface of the stem 6' in complicated con-
figuration. Such plastic stem 6' is produced by extruding
plast;c materials such as polyacetal, nylon and cellulose
derivat;ves.
~ s shown in Fig. 14, a ball-point pen includes a tip
portion 11, a pen shaft 12 and an ink reservoir 13. When the
ball-point pen tip of the present invention is accommodated in
the ball-point pen which uses aqueous solution ink, the ink
supply stem 7 serves to introduce the ink from the ink reservoir
13 to the ink guide stem 6, so that the ink supply stem is re-
quired to provide sufficient function for supplying sufficient
amount of ink in accordance with writing speed. In view of the
above, the diameter of the ink supply stem 7 is larger than that
of the ink guide stem 6, and the ink supply stem 7 is rod shape,
and is formed of resin finished fascicular fibers or formed of
plastic molded articles having continuous bubbles therein, or
plastic molded article formed with a plurality of axial bores
~S~ 3
therein. Since the ink guide stem 7 is formed with a plurality
of generally straight axial bores from one end to the other, the
stem of the resin-finished fascicular fibers is the most advan-
tageous in terms of the ink transferring speed and supply amount
thereof. Such resin finished fascicular fibers is produced by
partially bonding fibers with resins, those fibers being nylon
or acrylic or polyester synthetic fibers having denier number of
3 to lOd. These fibers are in the form of fascicular oriented
along axial direction of the stem 7.
Such ink supply stem has one end inserted into the rear
opening of the socket l in order to provide surface contact with
the ink guide stem 6. Alternatively, the rear end portion of the
ink guide stem 6 is thrusted into the ink supply stem 7, or
minute clearance is provided between the ink supply stem and the
ink guide stem 6.
Further, as shown in Fig. 3, the ink supply stem 7 can
be formed integral with the ink guide stem 6 so as to gradually
reduce the diameter toward the pen tip. The integral materiaL
is, for example/ resin finished fascicular fibers or plastic
molded article formed with continuous bubbles.
Figs~. 6 through lQ show embodiments showing the various
shape of the projections 5 and the ball seat 9. According to
the em~odiment shown in Fig. 6, the ball seat 9 provides point
contact with the ball 4, whereas according to the embodiment
shown in Fig. 7 the ball seat 9' provides line contact therewith.
Further, according to the embodiment of Fig. 9, the ball seat
~"' provldes surface contact with the hall 4, as in the case of
the embodiment shown in Fig. 8 wherein a ball seat 9" provide
surface contact with the ball 4. In case light or smooth writing
performance is required, the contacting area between the ball
1 and the ball seat should be minimized. On the other hand, if the
ball-point pen is put much weight on continuous ink lay-down,
contacting area between the ball and the ball seat should be
large.
Fig. 10 shows still another embodiment of the protru-
sions 5, wherein axial length of one of the projections 5' is
longer than that of the remaining projections 5 with respect to
their rear faces. In this case, since the ink guide stem 6 is
contacted with the side face of the longer projections 5',
clearance space is formed between the ink guide stem 6 and non-
contacting projections 5, so that ink is accumulated in the
space.. This ink accumulation provi.des smooth ink supplying
action to the ball, to thus avoid ink separation in the ink
passages.
~ hile the invention has been described in detail and
with.reference to specific embodiments thereof, it will be appar-
ent to one skilled in the art that various changes and modifica-
t;ons can be made therein without departing from the spirit and
scope thereof.
