Technical Field
[0001] The present invention relates to a mechanical pencil.
Background Art
[0002] Conventionally, there are known mechanical pencils with a lead breakage
preventing function that are configured to allow a lead to retract into a pipe when
excessive writing pressure is applied to the lead. To make the lead hard to break, this
type of mechanical pencil is provided with a chuck that holds the lead in such a manner
as to be movable rearward against the biasing force of a spring (see, for example, P1Ll).
[0003] However, the conventional configuration constantly causes the lead breakage
preventing function to operate during writing. In other words, the biasing force of the
spring is constantly applied to the lead in the conventional mechanical pencils with the
lead breakage preventing function.
[0004] Therefore, due to the constant application of the spring biasing force onto the
lead, the conventional mechanical pencils with the lead breakage preventing function
make users feel difficulty in writing.
Citation List
Patent Literature
2
[0005]
[PTL 1] Japanese Patent Application Publication No. 2011-37227
Summary oflnvention
Technical Problem
[0006] The present invention has been devised in view of the circumstances described
above and aims to provide a mechanical pencil that can suitably reduce a problem that
makes the user feel difficulty in writing due to the constant action of the lead breakage
preventing function.
Solution to Problem
[0007] That is, the present invention is configured as follows:
[0008] An invention according to claim 1 is a mechanical pencil including a lead
breakage preventing mechanism that operates to make a lead hard to break when
excessive writing pressure is applied to the lead, wherein the lead breakage preventing
mechanism is configured to be switchable between an operating state and a nonoperating
state based on a length of the lead protruding from a lead pipe provided at a
tip of the mechanical pencil.
[0009] An invention according to claim 2 is a mechanical pencil including a lead
breakage preventing mechanism that operates to make a lead hard to break when
excessive writing pressure is applied to the lead, wherein the lead breakage preventing
mechanism is configured to be switchable from an operating state to a non-operating
state based on a retraction operation of a lead pipe provided at a tip of the mechanical
pencil.
3
[0010] An invention according to claim 3 is the mechanical pencil according to claim 1,
wherein the lead breakage preventing mechanism is set not to operate if a length of the
lead is smaller than or equal to a predetermined value, and the lead breakage preventing
mechanism is set to be operable if a length of the lead is larger than the predetermined
value.
[0011] An invention according to claim 4 is the mechanical pencil according to claim 1,
2, or 3, wherein the lead breakage preventing mechanism is configured to enable a
chuck holding the lead to be movable rearward against a biasing force of a spring.
[0012] An invention according to claim 5 is the mechanical pencil according to claim 1,
2, 3, or 4, further including: operation restricting means for restricting an operation of
the lead breakage preventing mechanism, wherein the operation restricting means
includes the lead pipe that is supported at a tip of a writing shaft so as to be movable
forward and rearward and is configured to be operable only when the lead pipe is
pressed against a writing surface and retracts.
[0013] An invention according to claim 6 is the mechanical pencil according to claim 5,
wherein the operation restricting means is provided with a movement restricting
member that is capable of changing a posture thereof between a first posture, which is a
posture when not engaged with the lead pipe, and a second posture, which is a posture
when engaged with the lead pipe and is different from the first posture, and the
movement restricting member is capable of restricting retraction of the chuck holding
the lead in the second posture.
[0014] An invention according to claim 7 is the mechanical pencil according to claim 6,
wherein the lead pipe includes: a pipe portion extending in a front-back direction and
into which the lead is inserted; and a slider portion integrally provided at a base end of
4
the pipe portion and having a larger outer diameter than the pipe portion, and the
movement restricting member is capable of changing a posture thereof from the fust
posture to the second posture when the lead pipe retracts, causing a rear end of the slider
portion to engage with the movement restricting member.
[00 15] An invention according to claim 8 is the mechanical pencil according to claim 7,
further including: a chuck holding member externally fitted to the chuck and capable of
. opening and closing the chuck by moving relative to the chuck in a front-back direction,
wherein the chuck holding member has a flange portion provided at an outer
circumference thereof, the movement restricting member has an engagement claw
capable of engaging with the flange portion in the second posture, and retraction of the
chuck is limited via the chuck holding member by causing the engagement claw to
engage with the flange portion.
[0016] An invention according to claim9 is the mechanical pencil according to claim 5,
6, 7, or 8, wherein the writing shaft is configured such that an interior of a part of or the
entire writing shaft is allowed to be visually recognized from an outside, and operating
states of the lead breakage preventing mechanism and the operation restricting means
are allowed to be confirmed visually from an outside.
Advantageous Effects of Invention
[0017] As described above, the present invention can provide the mechanical pencil that
can suitably reduce a problem that makes the user feel difficulty in writing due to
constant action of the lead breakage preventing function.
Brief Description of Drawings
5
[0018]
Fig. 1 is a side view illustrating an embodiment of the present invention.
Fig. 2 is a side view illustrating a cut portion in the same embodiment.
Fig. 3 is an explanatory diagram of the operation of a lead breakage preventing
mechanism in the same embodiment.
Fig. 4 is an explanatory diagram of the operation of an operation restricting
means in the same embodiment.
Fig. 5 is an explanatory diagram of the operation of an operation restricting
means in the same embodiment.
Fig. 6 is a cross-sectional view corresponding to Fig. 4(a).
Fig. 7 is a cross-sectional view corresponding to Fig. 4(b ).
Fig. 8 is an explanatory diagram of a component (lock frame) in the same
embodiment.
Fig. 9 is an explanatory diagram of a component (a locking sleeve) in the same
embodiment.
Description of Embodiments
[0019] An embodiment of the present invention will be described below with reference
to Figs. 1 to 9.
[0020] This embodiment is directed to a knock-type mechanical pencil to which the
present invention is applied. The mechanical pencil has a lead breakage preventing
mechanism C that operates to make a lead S hard to break when excessive writing
pressure is applied to the leadS due to a user's writing operation on a writing surface M.
[0021] The mechanical pencil includes: a writing shaft A serving as a portion to be
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grasped by the user; a lead feed mechanism B mainly including a chuck 2 disposed in
the writing shaft A; the lead breakage preventing mechanism C that operates the chuck
2 holding the lead S (the lead S with a thickness of 0.3 mm which is applied in this
embodiment) against a biasing force of a spring, specifically a cushion spring v2; and an
operation restricting means D capable of restricting the operation of the lead breakage
preventing mechanism C.
[0022] The lead feed mechanism B includes a lead case b 1 provided inside the writing
shaft A and capable of housing the lead S, the chuck 2 connected in front of the lead
case b 1, and a chuck holding member 3 externally mounted on the chuck 2. The chuck
holding member 3 opens and closes the chuck 2 by moving relative to the chuck 2 in the
front-back direction.
[0023] The lead breakage preventing mechanism C is configured to enable the chuck 2
provided in the writing shaft A and holding the lead S to move rearward against the
biasing force of the cushion spring v2.
[0024] The operation restricting means D is configured to be capable of restricting the
operation of the lead breakage preventing mechanism C by restricting the retraction of
the chuck 2 provided in the writing shaft A and holding the lead S.
[0025] Hereinafter, this mechanical pencil will be described in detail.
[0026]

The writing shaft A serves as a case in which an internal mechanism of the
mechanical pencil is housed. The writing shaft A includes a shaft tip a!, a front shaft
portion a2, and a rear shaft portion a3. The shaft tip a! has, at its tip, a holding hole j
into which a pipe portion 11 of a lead pipe I can be inserted. The shaft tip a! is capable
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of holding the lead pipe 1 so that the lead pipe 1 can advance or retract in the front-back
direction. The front shaft portion a2 forms a cylinder and is connected to a rear part of
the shaft tip al. The rear shaft portion a3 forms a cylinder and has its front end coupled
to a rear part of the front shaft portion a2 and its rear end opened.
[0027] The shaft tip al includes a conical portion all, a front cylindrical portion al2,
and a rear cylindrical portion al3. The conical portion all has a substantially conical
shape tapered gradually forward in the side view. The conical portion all has, at its
front end, a holding hole j 1 capable of holding the pipe portion 11 of the lead pipe 1 so
that the pipe portion ll can advance and retract. The holding hole j 1 extends in the
front-back direction. The front cylindrical portion al2 is continuously provided behind
the conical portion all and has a larger diameter than the conical portion all. The rear
cylindrical portion a13 is continuously provided behind the front cylindrical portion al2
and has a larger diameter than the front cylindrical portion al2.
[0028] The shaft tip al holds a locking sleeve 4 having therein the operation restricting
means D and a lock frame 5 holding the locking sleeve 4 so that the locking sleeve 4
and the lock frame 5 do not move forward and rearward. The shaft tip al is made of a
synthetic resin that is transparent or translucent in its entirety and configured such that
its interior is allowed to be visually recognized from the outside.
[0029] The front shaft portion a2 is coupled to the shaft tip al by being externally fitted
to the rear part of the shaft tip al. Note that the shaft tip al is inserted from the rear end
of the front shaft portion a2, causing the front cylindrical portion al2 and the rear
cylindrical portion al3 to be internally fitted to a front part of the front shaft portion a2
at predetermined respective positions. The front shaft portion a2 is made of a synthetic
resin that is transparent or translucent in its entirety and configured such that its interior
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is allowed to be visually recognized from the outside.
[0030] A front recess a21 that is recessed inward is provided on an outer
circumferential surface of a part of the front shaft portion a2 which part is adjacent to an
engagement claw t of a movement restricting member 41 constituting the operation
restricting means D. Further, a rear recess a22 that is recessed inward is provided on an
outer circumferential surface of a part of the front shaft portion a2 which part is adjacent
to a gap sk constituting the lead breakage preventing mechanism C.
[0031] The front recess a21 serves as a concave lens that makes it easier to see the
interior. The front recess a21 also makes it easier for the user to visually recognize
whether the operation restricting means D is operating.
[0032] The rear recess a22 serves as a concave lens that makes it easier to see the
interior. The rear recess a22 also makes it easier for the user to visually recognize
whether the lead breakage preventing mechanism C is operating.
[0033] The rear shaft portion a3 is coupled to the front shaft portion a2 by being
screwed into an inner circumferential surface of the rear part of the front shaft portion
a2. A cap b2 attached .to a rear end of the lead case b1 housed therein is protruded from
a rear end of the rear shaft portion a3. The cap b2 constitutes the lead feed mechanism
B and functions as a knocking portion that the user presses forward to feed out the lead
s.
[0034] A front end edge of the rear shaft portion a3 abuts against a rear surface of a
collar c21 provided at a rear end of a rear spring-receiving sleeve c2 housed in the front
shaft portion a2. A rear end edge of a middle sleeve c3 abuts against a front surface of
the collar c21 in the rear spring-receiving sleeve c2. A step c32 provided on an outer
circumferential surface of a front portion of the middle sleeve c3 is connected to a rear
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end edge of the rear cylindrical portion a13 in the shaft tip al.
[0035] That is, the middle sleeve c3 and the rear spring-receiving sleeve c2 are located
. while being sandwiched between the shaft tip al and the rear shaft portion a3, and their
movements in the front-back direction are restricted. In other words, the middle sleeve
c3 and the rear spring-receiving sleeve c2 are positioned not to move forward and
rearward with respect to the writing shaft A. The locking sleeve 4 and the lock frame 5
which are disposed between the middle sleeve c3 and the shaft tip al are also positioned
not to move forward and rearward with respect to the writing shaft A.
[0036] Meanwhile, the lead pipe 1, the chuck 2, the lead case bl, the cap b2, the chuck
holding member 3, and a front spring-receiving sleeve cl are housed so as to be
movable forward and rearward with respect to the writing shaft A.
[0037] Next, the lead feed mechanism B, the lead breakage preventing mechanism C,
and the operation restricting means D, which are provided in the writing shaft A, will be
described in detail.
[0038]

The lead feed mechanism B is configured such that by pressing the cap b2,
which is the knocking portion provided at its rear end, forward against the biasing force
of a chuck spring vl, the chuck 2 can be relatively moved forward relative to the chuck
holding member 3 whose forward movement is restricted, thereby making it possible to
feed out the lead S forward. That is, the lead feed mechanism B causes the chuck 2 to
alternately take a posture of holding the lead S and a posture of not holding the lead S
through the relative movement between the chuck 2 and the chuck holding member 3 in
the front-back direction, thereby feeding out the leadS.
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[0039] The lead feed mechanism B includes the chuck 2, the chuck holding member 3,
the lead case b I, the cap b2, and the chuck spring vI. The chuck 2 is provided with a
· lead passage 21 provided on an axis part of the chuck, and it has a known configuration
that is capable of taking the posture of holding the lead S and the posture of not holding
the lead S. The chuck holding member 3 has a chuck insertion hole 32 into which the
chuck 2 is inserted. The chuck holding member 3 is externally fitted to the chuck 2 and
capable of opening and closing the chuck 2 by moving relative to the chuck 2 in the
front-back direction. The lead case b1 is integrally coupled to the chuck 2 while the
axis of the lead case is coincident with a rear end of the chuck 2. The lead case b 1 is
capable of housing the lead S therein. The cap b2 is detachably mounted at the rear end
of the lead case bl. The chuck spring v1 is a spring interposed between the lead case b1
and the front spring-receiving sleeve cl so as to feed the lead S.
[0040] The chuck 2 has a known configuration and is made of brass with a threepronged
tip formed.

Claims
Claim I
A mechanical pencil comprising a lead breakage preventing mechanism that
operates to make a lead hard to break when excessive writing pressure is applied to the
lead,
wherein the lead breakage preventing mechanism is configured to be switchable
between an operating state and a non-operating state based on a length of the lead
protruding from a lead pipe provided at a tip.
Claim2
A mechanical pencil comprising a lead breakage preventing mechanism that
operates to make a lead hard to break when excessive writing pressure is applied to the
lead,
wherein the lead breakage preventing mechanism is configured to be switchable
from an operating state to a non-operating state based on a retraction operation of a lead
pipe provided at a tip.
Claim 3
The mechanical pencil according to claim 1,
wherein the lead breakage preventing mechanism is set not to operate if a length
of the lead is smaller than or equal to a predetermined value, and
wherein the lead breakage preventing mechanism is set to be operable if a length
of the lead is larger than the predetermined value.
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Claim 4
The mechanical pencil according to claim 1, 2, or 3, wherein the lead breakage
preventing mechanism is configured to enable a chuck holding the lead to move
rearward against a biasing force of a spring.
Claim 5
The mechanical pencil according to claim 1, 2, 3, or 4, further comprising:
operation restricting means for restricting an operation of the lead breakage preventing
mechanism,
. wherein the operation restricting means includes the lead pipe that is supported
at a tip of a writing shaft so as to be movable forward and rearward, the operation
restricting means being configured to be operable only when the lead pipe is pressed
against a writing surface and retracts.
Claim 6
The mechanical pencil according to claim 5,
wherein the operation restricting means is provided with a movement restricting
member that is capable of changing a posture thereof between a first posture, which is a
posture when not engaged with the lead pipe, and a second posture, which is a posture
when engaged with the lead pipe and is different from the first posture, and
wherein the movement restricting member is capable of restricting retraction of
the chuck holding the lead in the second posture.
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Claim 7
The mechanical pencil according to claim 6,
wherein the lead pipe includes: a pipe portion extending in a front-back direction
and into which the lead is inserted; and a slider portion integrally provided at a base end
of the pipe portion and having a larger outer diameter than the pipe portion, and
wherein the movement restricting member is capable of changing a posture
thereof from the frrst posture to the second posture when the lead pipe retracts, causing
a rear end of the slider portion to engage with the movement restricting member.
Claim 8
The mechanical pencil according to claim 7, further comprising: a chuck holding
member externally fitted to the chuck and capable of opening and closing the chuck by
moving relative to the chuck in the front-back direction,
wherein the chuck holding member has a flange portion provided at an outer
circumference thereof,
wherein the movement restricting member has an engagement claw capable of
engaging with the flange portion in the second posture, and
wherein retraction of the chuck is limited via the chuck holding member by
causing the engagement claw to engage with the flange portion.