TECHNICAL FIELD
[0001] The present invention relates to a pen point made of an inorganic material to be
used for writing.
BACKGROUND ART
[0002] A porous pen point is exemplarily proposed in the Japanese Patent Laid-open No.112497/1985.
[0003] The conventional porous pen points, including the above pen point, are highly resistant
to wear and solvent due to the structure thereof such that the continuous air holes
among the particles in a metallic cylindrical body is used as an ink passage to supply
ink to the pen point.
DISCLOSURE OF THE INVENTION
[0004] Concerning ink viscosity, pigments contained in ink and buckling strength, some restrictions
are imposed on the conventional ones due to the employment of the continuous air holes
as ink passage.
[0005] In other words, in case of a higher ink viscosity or a larger size of pigment particle,
ink movement cannot be expected unless the diameter of air hole is larger in proportion
with the viscosity or the particle size. Furthermore, the filtration of the pigment
particles may occur, causing blinding.
[0006] On the contrary, an enlarged diameter of air holes inevitably involves the reduction
of buckling strength; if there is prepared a pen point provided with a required degree
of buckling strength, there are imposed restrictions on ink, including a lower viscosity
of ink and a smaller size of the particle diameter of a pigment in ink.
[0007] A wide variety of differences are also found among the diameters of individual air
holes of the continuous air holes, which is disadvantageous from the point that a
uniform supply of ink in each cylindrical body can hardly be expected.
[0008] The present invention has been carried out under such circumstances. It is the object
of the present invention to completely resolve the contradictory problems regarding
the ink viscosity and pigments in ink and the buckling strength thereof, to provide
a pen point made of an inorganic material, with excellent buckling strength and high
resistance to wear and solvent and capable of mass production at low coat.
[0009] For the object, the pen point of an inorganic material in accordance with the present
invention is characterized by the structure wherein a mixture of fine particles of
metal or ceramic with a binder is extruded, degreased, and sintered to form a continuous
piece having a uniform cross-section and provided along its axis with a through ink
passage in the form of holes of various profiles and grooves, permitting capillary
movement of ink, with one end thereof forming a part of the writing surface sharpened
at its tip.
[0010] More specifically, there are proposed as ink passage, a mode of holes of various
profiles to be formed in the individual ribs each extending from the outer circumferential
portion toward the central direction; a mode of grooves to be formed in the individual
ribs each extending radially from the center; a mode of holes of various profiles
and grooves, to be formed in the sub ribs extending from the individual ribs; and
other optional modes.
[0011] The metal is preferably corrosion resistant such as stainless steel, which is also
effective for rust prevention.
[0012] General ceramic materials known may be used as the ceramic. Preferably, the fine
particle of metal or ceramic is nearly in spherical form and of a diameter of 0.1
- 10 µm, whereby the closest packing of the fine particle and the fluidity resistance
thereof at extrusion are improved, leading to the relative density of 92 to 97%, so
that the buckling strength and the frictional coefficient of the surface of a pen
point are improved.
[0013] The binder for these particles includes known thermoplastic resins such as polypropylene,
a blend of polypropylene and polyacetal and the like, and waxes such as paraffin,
etc., to be selected appropriately.
[0014] The diameter of a pen point ranges from 0.3 to 2.5 m⌀.
The following effects are obtained;
[0015]
1. Because the extruded ink passage extends along its axis under the controlling conditions
of its form to be through holes of various profiles and grooves, so as to control
and regulate the amount of ink by means of the passage of holes of various profiles
and grooves, the pen point of itself is not required to be made porous and the relative
density of the fine particles of metal or ceramic can be freely increased up to the
degree of a desired numerical figure, so that the pen point has excellent entire properties
in terms of buckling strength, rigidity and wear resistance.
2. The ink passage in the form of the holes of various profiles and grooves under
control contributes to the ink introduction suitable for individual inks with different
viscosities.
3. Because the surface of the ink passage of holes of various profiles and grooves
is formed with fine irregular surfaces caused by the fine particles, leading to good
leakage resistance and yield of ink, drop or drain bag won't be caused.
4. The pen point has a structure such that it can be produced in large scale and inexpensively.
BRIEF DESCRIPTION OF DRAWINGS
[0016] Fig.1 is a side elevation representing an embodiment of the pen point of the present
invention; Fig.2 is an enlarged transverse cross section; and Figs. 3 to 6 are enlarged
transverse cross sections representing other individual embodiments.
BEST MODE OF CARRYING OUT THE INVENTION
[0017] One embodiment of the present invention will be explained in detail with reference
to drawings hereinbelow.
[0018] In the figures, A is a pen point; the pen point A is made of metal or ceramic, which
is extruded, degreased and sintered to be polished into a desirable form as a pen
point.
The pen point A has a through ink passage 1, along its axis, permitting capillary
movement of ink, and the ink passage 1 forms a part of the writing surface 2 sharpened
at its tip. The final end of the pen point A is in the form of a smaller diameter,
in order to be easily inserted in an ink absorber 3, and that ink can make capillary
movement from the ink absorber 3 through the ink passage 1 to the writing surface
2.
[0019] The width of the ink passage 1 is appropriately determined depending on the viscosity
of ink, etc., which is about 0.01 to 0.10 mm.
[0020] Specific examples are now illustrated.
[0021] In the cross-sectional view of the pen point A illustrated in Fig. 2, long, medium
and short-sized ribs 5 each extend from the inner face of the outer circumferential
portion 4 toward the central direction, respectively making an equal angle with each
other, and the ink passage 1 is in the center and in the form of mutually connecting
holes of various profiles.
[0022] In the cross-sectional view of the pen point A illustrated in Fig. 3, each of the
ribs 5 of an identical length extends from the outer circumferential portion 4 toward
the central direction, respectively making an equal angle with each other, and the
ink passage 1 is in the center and in the form of mutually connecting holes of various
profiles.
[0023] In the cross-sectional view of the pen point A illustrated in Fig. 4, long and short-sized
ribs 5 each extend from the inner face of the outer circumferential portion toward
the central direction, respectively making an equal angle with each other, and the
ink passage 1 is in the center and in the form of mutually connecting holes of various
profiles.
[0024] In the cross-sectional view of the pen point A illustrated in Fig.5, ribs 5 extend
radially from the center and respectively making an equal angle with each other, involving
the subribs 6 concentrically elongated from each rib 5, whereby the ink passage 1
is largely divided in each rib 5 and is in the form of groove communicating mutually
in the subribs 6, within the divisions of holes of various profiles.
[0025] In the cross-sectional view of the pen point A illustrated in Fig. 6, ribs 5 extend
radially from the center and respectively making an equal angle with each other, where
the ink passage 1 is in the form of groove formed nearly radially between adjacent
individual ribs 5.
The cross-sectional structure of the pen point A is not limited to the examples illustrated,
and the pen point A may be formed into a preferable form including the form of the
writing surface 2, on taking into account of ink viscosity, writing angle, orientation
and the like.
[0026] An example of producing a pen point A in accordance with the present invention is
described in the embodiment made of metal illustrated in Fig. 2. A kneading mixture
of nickel-made fine particle of a particle diameter of 1 to 5 m∅ and paraffin having
the melting point of about 56 °C is placed in a hopper of an extruder, which is then
extruded in a desired cross-sectional form of the cylindrical body and is stretched
down to an appropriate diameter. Subsequently the body is cut off in an appropriate
length after cooling and solidification.
[0027] Then, the cylindrical body is put into a pressure chamber. The pressure chamber is
filled with an inert gas of an absolute pressure of about 70 kg f/cm² at a temperature
of about 230 °C, while the temperature inside is relatively linearly heated from ambient
temperature up to about 230 °C and kept at the temperature about two hours. The cylindrical
body is then transferred from the pressure chamber to a cooling room and is gradually
cooled in the cooling room maintained at about 20 °C, the condensed product being
collected. The removing of the binder is continued until the increase in the amount
of the condensed product reaches zero.
[0028] Subsequently, the cylindrical body is transferred into a sintering furnace and the
temperature inside the furnace is heated from ambient temperature to 1260 °C over
six hours, in a relatively linear manner. After the body is left in the furnace at
the same temperature and under the atmosphere of the inert gas for about two hours,
the temperature is gradually lowered. After sintering by such manner, the body was
polished to be finally made into a pen-point form of a diameter of 2.0 mm⌀.
[0029] The pen point A made of ceramic may be also produced, basically following the same
procedure as in the aforementioned producing example, wherein the particle diameter
of ceramic fine particle is 1 to 5 µm⌀; the main binder is polypropylene; the temperature
and time period for removing off binder is normal temperature to 250 °C for 10 hours;
and that of the sintering is normal temperature to 1160 °C for 8 hours.