EP4659968A1

EP4659968A1 - Mechanical pencil

Info

Publication number: EP4659968A1
Application number: EP24749951.0A
Authority: EP
Inventors: Hirotake Izawa; Yusuke Koizumi; Tsutomu Ikeda
Original assignee: Mitsubishi Pencil Co Ltd
Current assignee: Mitsubishi Pencil Co Ltd
Priority date: 2023-01-31
Filing date: 2024-01-17
Publication date: 2025-12-10
Also published as: KR20250139270A; CN120265469A; JP2024108694A; WO2024161997A1; TW202444582A

Abstract

A mechanical pencil 1 comprises: a barrel 5 that has a rear shaft 3 and a front shaft 2 provided with a front end opening 2a from which a writing lead can protrude; a rotation member that has a chuck unit 10 which allows advancement of the writing lead but prevents retraction thereof, a relay member 9 that surrounds the chuck unit, and a slider 7; and a rotation driving mechanism 30 which has a rotor 40 and which drives rotation of the rotor in one direction upon receiving an axial direction retraction operation due to writing pressure received by the writing lead held by the chuck unit and an axial direction advancement operation due to release of the writing pressure. The rotor is connected to a rear end part of the relay member. The slider is removably connected to a front end part of the relay member. The rotation member is configured such that the writing lead held by the chuck unit rotates due to rotation upon receiving a rotational driving force of the rotor. The front shaft is configured as a single component.

Description

FIELD

The present invention relates to a mechanical pencil.

BACKGROUND

Known in the art is a mechanical pencil comprised of a shaft barrel having a front shaft and a rear shaft detachably connected to a rear end part of the front shaft; a rotation member having a chuck unit allowing advance of a writing lead and stopping retraction thereof, a relay member surrounding the chuck unit and a slider; and a rotation drive mechanism having a rotor and receiving an axial direction retracting operation due to writing pressure received by the writing lead gripped by the chuck unit and an axial direction advancing operation due to release of the writing pressure so as to drive the rotor to rotate in one direction; and configured so that the rotor is connected to a rear end part of the relay member, the slider is detachably connected to a front end part of the relay member, and the rotation member rotates receiving rotation drive force of the rotor whereby the writing lead gripped by the chuck unit rotates (PTL 1). In the mechanical pencil according to PTL 1, a separate part comprising a tip member formed in a substantially tapered shape is screwed together with the front end part of the cylindrical front shaft formed by substantially the same outside diameter.

[CITATION LIST]

[PATENT LITERATURE]

[PTL 1] Japanese Unexamined Patent Publication No. 2013-107263

SUMMARY

[TECHNICAL PROBLEM]

In this regard, in general, in a mechanical pencil, the impact at the time of being dropped sometimes causes the writing lead to break inside of the mechanical pencil. The writing lead which becomes short due to the break or other factors and can no longer be fed out by a click operation, has to be removed in order for the mechanical pencil to continue to be used.
In the mechanical pencil described in PTL 1, to remove the writing lead no longer able to be fed out due to the lead becoming shorter at the inside of the slider etc., the tip member has to be detached from the front shaft and then the slider removed from the relay member. The slider is shorter in length in the axial direction as compared with the total length of the mechanical pencil, therefore is relatively difficult to grip.
If the slider has been strongly snap fit with the relay member, even if twisting the slider with respect to the relay member to try to detach it, due to the structure of the rotation drive mechanism, the relay member itself ends up rotating together with the slider making the slider difficult to detach. Furthermore, in the case of a mechanical pencil provided with a rotation drive mechanism of a type where the slider and the relay member are not snap fit, but are screwed together, the relay member itself rotates together with the slider, so unscrewing becomes difficult and therefore the slider is more difficult to detach. In these cases, it is possible to use a click operation to press the operating part arranged at the rear end part of the mechanical pencil to the front and maintain that state to thereby stop rotation of the relay member. However, using one hand to maintain a pressed state of the operating part while using another hand to make the slider rotate is hard to describe as "good maintenance ability".
Therefore, even if detaching not only the tip member but also the front shaft from the rear shaft to expose the relay member and directly grip it and making the slider rotate to try to remove it, part or all of the component parts of the rotation drive mechanism arranged inside the rear shaft are liable to end up dropping off from the rear shaft. If part or all of the component parts end up dropping off, the component parts are liable to be lost or to be mistakenly reassembled, so this is not preferable
The present invention has as its object the provision of a mechanical pencil improved in maintenance ability with respect to broken writing leads etc.

[SOLUTION TO PROBLEM]

According to one aspect of the present invention, there is provided a mechanical pencil comprising a shaft barrel having a front shaft provided with a front end opening through which a writing lead can project and a rear shaft detachably connected to a rear end part of the front shaft; a rotation member having a chuck unit allowing advance of the writing lead and prohibiting retraction, a relay member surrounding the chuck unit and a slider; and a rotation drive mechanism having a rotor and receiving a retracting operation in an axial direction due to writing pressure received by the writing lead held by the chuck unit and an advancing operation in the axial direction due to release of the writing pressure so as to drive rotation of the rotor in one direction; the rotor being connected to the rear end part of the relay member while the slider being detachably connected to the front end part of the relay member, the rotation member being configured to rotate by receiving rotation drive force of the rotor whereby the writing lead held by the chuck unit rotates, and the front shaft being configured by a single part.
The rotation drive mechanism may be arranged inside the rear shaft and have a support member configured to prevent the rotation drive mechanism from dropping off from the rear shaft in a state after detachment of the front shaft. The slider may be formed with a female thread, the relay member formed with a male thread, and the slider and the relay member detachably connected by screwing.

[ADVANTAGEOUS EFFECTS OF INVENTION]

According to the aspects of the present invention, the common effect is exhibited of provision of a mechanical pencil improved in maintenance ability with respect to broken writing leads etc.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a vertical cross-sectional view of a mechanical pencil according to an embodiment of the present invention.
FIG. 2 is an enlarged cross-sectional view of a front half of the mechanical pencil of FIG. 1.
FIG. 3 is an enlarged cross-sectional view of a center part of the mechanical pencil of FIG. 1.
FIG. 4 is a schematic view for explaining a rotation drive operation of a rotor of a rotation drive mechanism.
FIG. 5 is a schematic view for explaining a rotation drive operation of a rotor continuing from FIG. 4.
FIG. 6 is a perspective view of the mechanical pencil of FIG. 1 in the state with the front barrel detached.
FIG. 7 is a perspective view of the mechanical pencil of FIG. 1 in the state with the slider detached further from the state shown in FIG. 6.

DESCRIPTION OF EMBODIMENTS

Below, while referring to the drawings, embodiments of the present invention will be explained in detail. Throughout the figures, corresponding component elements will be assigned common reference notations.
FIG. 1 is a vertical cross-sectional view of a mechanical pencil 1 according to an embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a front half of the mechanical pencil 1 of FIG. 1.
The mechanical pencil 1 has a front shaft 2, a rear shaft 3 detachably screwed over the outer circumferential surface of the rear end part of the front shaft 2, and an inside barrel 4 snap fit in an inner circumferential surface of the rear end part of the rear shaft 3 and provided with a clip. The front shaft 2 and the rear shaft 3 form the shaft barrel 5. Note that, including also the inside barrel 4, these are also called the "shaft barrel 5". The mechanical pencil 1 is configured so that the writing lead projects out from the front end of the shaft barrel 5. Specifically, the mechanical pencil 1 is configured so that the writing lead can project out from a front end opening 2a of the front shaft 2. In this Description, in the axial direction of the mechanical pencil 1, the writing lead side is defined as the "front" side while the side opposite to the writing lead side is defined as the "rear" side.
The front shaft 2 is a tubular member formed in substantially the same outside shape. The vicinity of the front end part is formed in a substantially tapered shape. At the front end part of the front shaft 2, a front end opening 2a is formed. Therefore, the outside shape of the front shaft 2 is similar to the front shaft of a conventional mechanical pencil. The front shaft 2 has a grip part 2b formed by a material softer than the front shaft 2 so that the user can easily grip the mechanical pencil 1. At the inside of the front end part of the front shaft 2, a slider 7 having a front end pipe 6 for guiding the writing lead is arranged to be able to slide in the axial direction and to be able to rotate about its axis.
The slider 7 is formed in a cylindrical shape with an outside diameter becoming narrower in stages toward the front. The front end part of the slider 7 sticks out together with the front end pipe 6 from the front end opening 2a of the front shaft 2. Inside the slider 7 at the rear of the front end pipe 6, a holding chuck 8 formed with a through hole at its center is arranged. The through hole of the holding chuck 8 acts to slidingly contact the outer circumferential surface of the writing lead and temporarily hold the writing lead.
At the rear end part of the slider 7, a relay member 9 formed in a cylindrical shape is screwed. That is, at the inner circumferential surface of the rear end part of the slider 7, a female thread 7a is formed, while at the outer circumferential surface of the front end part of the relay member 9, a male thread 9a is formed. At the insides of the slider 7 and relay member 9, a chuck unit 10 and lead case 13 gripping the writing lead are arranged. The chuck unit 10 has a chuck body 11 and a fastener 12 formed in a cylindrical shape so as to surround the front end part of the chuck body 11. At least the front half of the chuck body 1 is divided into three chuck pieces 11a along the axial direction, and the through hole for the writing lead is formed along the center axis. The chuck pieces 11a are formed so that their front end parts are separated from each other. The lead case 13 is formed into a cylindrical shape and houses the writing lead inside it. At the inside of the front end part of the lead case 13, the rear end part of the chuck body 11 is inserted and snap fit.
A coil spring 14 is arranged so as to surround the chuck body 11. The front end of the coil spring 14 is supported by a step part formed at the inner circumferential surface of the relay member 9, while the rear end of the coil spring 14 abuts against the front end face of the lead case 13. Therefore, the coil spring 14 biases the lead case 13 and chuck body 11 to the rear. By having the chuck body 11 biased to the rear be held in the fastener 12, the front end parts approach each other and the state of gripping the writing lead can be maintained. Further, if writing pressure is applied to the writing lead, the chuck body 11 retracts more and is housed in the fastener 12, while the writing lead is gripped by the chuck body 11. Due to this, retraction of the writing lead is prevented. On the other hand, if force acts pulling the writing lead out to the front, the chuck body 11 is not acted on by the fastener 12, so it is possible to pull the writing lead out to the front without resistance. That is, the chuck unit 10 acts to allow advance and prevent retraction of the writing lead, but so long as this action is exhibited, it may also be another chuck unit, for example, a ball chuck.
The outer circumferential surface of the fastener 12 is snap fit with the inner circumferential surface of the front end part of the relay member 9. Therefore, the slider 7, relay member 9, and chuck unit 10 can move inside the shaft barrel 5 in the axial direction. The rear end part of the relay member 9 is connected to a later explained rotation drive mechanism 30.
At the rear end part of the shaft barrel 5, specifically the rear end part of the inside barrel 4, as a click member, a tubular click member 20 is provided to be able to move back and forth with respect to the shaft barrel 5. The click member 20 is biased to the rear by the coil spring 21. At the inside of the front end part of the click member 20, the lead case 13 is inserted. At the inside of the rear end part of the click member 20, a rubber eraser 22 is attached in a detachable manner. At the outer circumferential surface of the rear end part of the click member 20, a click cover 23 is attached in a detachable manner whereby the rubber eraser 22 is protected from getting dirty etc.
The lead case 13 advances by a click operation pressing the click member 20 or the click cover 23 forward. Due to this, the chuck body 11 is pushed out to the front. Along with this, it acts to make the writing lead gripped by the chuck body 11 also advance and feed out the writing lead from the front end pipe 6. If releasing the pressure due to the click operation, due to the biasing force of the coil spring 21, the click member 20 retracts and returns to the original position. At this time, the chuck body 11 retracts due to the biasing force of the coil spring 14. On the other hand, the writing lead is held by a holding chuck 8 arranged inside the slider 7, so, as the action of the chuck unit 10, the writing lead is pulled out from the chuck body 11 without resistance. As a result, the writing lead is fed out from the front end pipe 6, so each time repeating this click operation, the writing lead can be fed out by a predetermined amount.
FIG. 3 is an enlarged cross-sectional view of a center part of the mechanical pencil 1 of FIG. 1. The rotation drive mechanism 30 is arranged in the inside space of the rear shaft 3. The rotation drive mechanism 30 is connected to the rear end part of the relay member 9. The lead case 13 runs through the insides of the relay member 9 and rotation drive mechanism 30 to move away from the rotation drive mechanism 30. The rotation drive mechanism 30 is biased to the rear by a shaft spring 31. That is, the front end of the shaft spring 31 is supported by the support member 32 formed in the cylindrical shape, while the rear end of the shaft spring 31 is supported by the front end face of the rotation drive mechanism 30. Due to this, the rotation drive mechanism 30 is biased to the rear.
The support member 32 has a ring-shaped support surface 32a facing the rear formed by a projection provided at the inner circumferential surface and a locking projection 32b provided in a ring shape at the outer circumferential surface of the rear end part. The support surface 32a, as explained above, is configured to support the front end of a shaft spring 31. The locking projection 32b is configured to lock with a ring-shaped projecting part 3a provided at the inner circumferential surface of the rear shaft 3. That is, in the assembly of the mechanical pencil 1, the rotation drive mechanism 30 is placed inside the rear shaft 3, then the support member 32 is inserted into the rear shaft 3. At this time, the locking projection 32b of the support member 32 rides over the projecting part 3a of the rear shaft 3 by elastic deformation and the locking projection 32b and projecting part 3a become locked in state. As a result, forward movement of the support member 32 is restricted and the support member 32 is fixed at the vicinity of the open end of the rear end of the rear shaft 3.
The rotation drive mechanism 30 has a rotor 40 formed in a cylindrical shape, an upper cam forming member 41 as a first cam forming member formed in a cylindrical shape, a lower cam forming member 42 as a second cam forming member formed in a cylindrical shape, a cylinder member 43 formed in a cylindrical shape, a torque canceller 44 formed in a cylindrical shape, and a coil-shaped cushion spring 45. The rotation drive mechanism 30 is made the unit of these members combined.
At an inner circumferential surface of the front end part of the rotor 40, an outer circumferential surface of the rear end part of the relay member 9 is snap fit. The vicinity of the front end part of the rotor 40 has a part formed in a flange shape of a just slightly larger diameter. At the rear end face of that part, a first cam face 40a is formed. At the front end face of the part, a second cam face 40b is formed.
The upper cam forming member 41 surrounds the rotor 40 at the back of the first cam face 40a of the rotor 40 to be able to turn. The lower cam forming member 42 is snap fit at the outer circumferential surface of the front end part of the upper cam forming member 41. At the front end face of the upper cam forming member 41 facing the first cam face 40a of the rotor 40, the first fixed cam face 41a is formed. At the inside surface of the front end part of the lower cam forming member 42 facing the second cam face 40b of the rotor 40, the second fixed cam face 42a is formed.
At the outer circumferential surface of the rear end part of the upper cam forming member 41, a cylinder member 43 formed into a cylindrical shape is snap fit. At the rear end part of the cylinder member 43, a through hole 43a through which the lead case 13 can be inserted is formed. Inside the cylinder member 43, a torque canceller 44 formed into a cylindrical shape and able to move in the axial direction is arranged. Between the inside surface of the front end part of the torque canceller 44 and the inside surface of the rear end part of the cylinder member 43, a cushion spring 45 is arranged. The cushion spring 45 biases the rotor 40 to the front through the torque canceller 44.
Here, the relay member 9 transmits the retracting operation and advancing operation (cushion operation) of the writing lead due to a writing operation to the rotation drive mechanism 30, that is, the rotor 40, and transmits the rotational motion of the rotor 40 in the rotation drive mechanism 30 occurring due to the cushion operation to the chuck unit 10 in the state gripping the writing lead. Therefore, due to rotation of the relay member 9, the writing lead gripped by the chuck unit 10 also rotates.
Other than when writing by the mechanical pencil 1, that is, when writing pressure is not being applied to the writing lead, the rotor 40 is positioned at the front due to the biasing force of the cushion spring 45 through the torque canceller 44. Therefore, the second cam face 40b of the rotor 40 is rendered a state abutting and engaged with the second fixed cam face 42a. When writing by the mechanical pencil 1, that is, when writing pressure is being applied to the writing lead, the chuck unit 10 retracts against the biasing force of the cushion spring 45. Along with this, the rotor 40 also retracts. Therefore, the first cam face 40a of the rotor 40 is rendered a state abutting and engaged with the first fixed cam face 41a. The writing lead and the rotor 40 advance, retract, or rotate integrally.
FIG. 4 is a schematic view for explaining a rotation drive action of the rotor 40 of the rotation drive mechanism 30, while FIG. 5 is a schematic view for explaining a rotation drive action of the rotor 40 continuing from FIG. 4. In FIG. 4 and FIG. 5, a first cam face 240a formed into a continuous sawtooth shape along the circumferential direction is formed in a ring shape at a rear end face of a surface at the upper side of the rotor 40, while a second cam face 40b formed into a continuous sawtooth shape along the circumferential direction is also formed in a ring shape at a front end face of a surface at the lower side of the rotor 40.
At the ring-shaped end face of the upper cam forming member 41 facing the first cam face 40a of the rotor 40, a first fixed cam face 41a formed into a continuous sawtooth shape along the circumferential direction is formed. At the ring-shaped end face of the lower cam forming member 42 facing the second cam face 40b of the rotor 40 as well, a second fixed cam face 42a formed into a continuous sawtooth shape along the circumferential direction is formed. The cam faces of the first cam face 40a and second cam face 40b formed at the rotor 40 and the cam faces of the first fixed cam face 41a formed at the upper cam forming member 41 and the second fixed cam face 42a of the lower cam forming member 42 are formed so that the pitches in the circumferential direction become substantially the same as each other.
FIG. 4(A) shows the relationship of the rotor 40 advancing in the state where writing pressure is not applied to the writing lead, upper cam forming member 41, and lower cam forming member 42. In this state, the second cam face 40b formed at the rotor 40 abuts against the second fixed cam face 42a of the lower cam forming member 42 due to the biasing force of the cushion spring 45. At this time, the first cam face 40a of the rotor 40 and the first fixed cam face 41a of the upper cam forming member 41 are set to a relationship offset in the axial direction by half a phase with respect to one tooth of the cam.
FIG. 4(B) shows the initial state where writing pressure is applied to the writing lead for writing by the mechanical pencil 1. In this state, the rotor 40 retracts while compressing the cushion spring 45 along with retraction of the chuck unit 10. Due to this, the rotor 40 moves to the upper cam forming member 41 side and abuts against the first fixed cam face 41a.
Next, FIG. 4(C) shows the state where writing pressure is further applied to the writing lead and the rotor 40 abuts against the first fixed cam face 41a of the upper cam forming member 41 and slides against it while retracting. That is, the rotor 40 receives a rotation drive action corresponding to half a phase of one tooth of the first cam face 40a. In this state, the first cam face 40a of the rotor 40 engages with the first fixed cam face 41a of the upper cam forming member 41.
Note that, the circle mark drawn at the center part of the rotor 40 in FIG. 4 and FIG. 5 shows the amount of rotational movement of the rotor 40. Further, in the state shown in FIG. 4(C), the second cam face 40b of the rotor 40 and the second fixed cam face 42a of the lower cam forming member 42 are set so as to a relationship offset in the axial direction by half a phase with respect to one tooth of the cam.
Next, FIG. 5(D) shows the initial stage where writing by the mechanical pencil 1 ends and the writing pressure on the writing lead is released. In this state, the rotor 40 advances due to the biasing force of the cushion spring 45. Due to this, the rotor 40 moves to the lower cam forming member 42 side and abuts against the second fixed cam face 42a.
Next, FIG. 5(E) shows the state where the rotor 40 abuts against the second fixed cam face 42a of the lower cam forming member 42 due to the biasing force of the cushion spring 45 and slides against it while advancing. That is, the rotor 40 again receives a rotation drive action corresponding to half a phase of one tooth of the second cam face 40b. In this state, the second cam face 40b of the rotor 40 engages with the second fixed cam face 42a of the lower cam forming member 42.
Therefore, as shown by the circle mark drawn at the center part of the rotor 40 at FIG. 5, along with reciprocating motion in the axial direction of the rotor 40 receiving writing pressure, that is, front-back motion, the rotor 40 receives a rotation drive action corresponding to one tooth of the first cam face 40a and second cam face 40b. Through the chuck unit 10, the writing lead gripped by this is driven to rotate in the same way. Therefore, due to one front-back motion in the axial direction of the rotor 40 due to writing, the rotor 40 receives a rotation drive action corresponding to one tooth of the cam. By repeating this, the writing lead is successively driven to rotate. For this reason, it is possible to prevent the writing lead from being unevenly worn along with progress in writing and possible to prevent the thickness of the written lines and the darkness of the written lines from greatly changing.
Note that, the torque canceller 44 receiving the biasing force of the cushion spring 45 and pushing out the rotor 40 to the front causes sliding between the front end face and the rear end face of the rotor 40 and prevents rotational motion of the rotor 40 from being transmitted to the cushion spring 45. That is, due to the torque canceller 44, rotational motion of the rotor 40 is prevented from being transmitted to the cushion spring 45. Due to this, untwisting of the cushion spring 45 (torque) obstructing rotational motion of the rotor 40 is prevented from being generated.
Due to the above, the mechanical pencil 1 has a rotation member having a chuck unit 10 allowing advance of the writing lead and prohibiting retraction, a relay member 9 surrounding the chuck unit 10 and a slider 7, and a rotation drive mechanism 30 having a rotor 40 and receiving a retracting operation in an axial direction due to writing pressure received by the writing lead held by the chuck unit 10 and an advancing operation in the axial direction due to release of the writing pressure so as to drive rotation of the rotor 40 in one direction. Further, it is configured so that the rotor 40 is connected to the rear end part of the relay member 9, the slider 7 is detachably connected to the front end part of the relay member 9, and the rotation member rotates receiving the rotation drive force of the rotor 40, whereby the writing lead held by the chuck unit 10 is rotated.
FIG. 6 is a perspective view of the mechanical pencil 1 of FIG. 1 in the state with the front barrel 2 detached, while FIG. 7 is a perspective view of the mechanical pencil 1 of FIG. 1 in the state with the slider 7 detached further from the state shown in FIG. 6.
In the mechanical pencil 1, at the inside of the slider 7 etc., to remove writing lead no longer able to be fed out due to the lead becoming short, the front shaft 2 is detached from the rear shaft 3 (FIG. 6). Next, the relay member 9 is gripped and the slider 7 is made to rotate to unscrew it (FIG. 7). Due to this, the user can access the insides of the chuck unit 10 and slider 7 and can remove the writing lead at the inside of the slider 7 etc.
In the mechanical pencil 1, the front shaft 2 is configured as a single part from the front end opening 2a through which the writing lead can project to the rear end opening connected to the rear shaft 3. Therefore, by just detaching the front shaft 2 from the rear shaft 3, the relay member 9 is exposed in the axial direction by exactly a sufficient length. Further, the user can directly grip the exposed relay member 9 while making the slider 7 rotate, therefore the slider 7 can be easily detached. Therefore, according to the mechanical pencil 1, it is possible to improve the maintenance ability with respect to broken writing leads etc.
Further, the support member 32 is arranged near the opening end of the rear shaft 3, therefore even if the front shaft 2 is in a state detached from the rear shaft 3, part or all of the component parts of the rotation drive mechanism 30 can be prevented from falling off from the rear shaft 3. Due to this, the component parts of the rotation drive mechanism 30 can be prevented from being lost etc.
Here, if, like in a conventional mechanical pencil, configured so that the tip member is connected to the front shaft, the inside space near the connection part becomes narrower by the amount of the thicknesses of the two members superposed in the diametrical direction due to the snap fitting or screwing at the connection part. As a result, it is necessary to make the outside diameter of the part of the slider corresponding to the connection part smaller. Due to this, the slider becomes harder to grip.
On the other hand, in the mechanical pencil 1 according to an embodiment of the present invention, the front shaft 2 is formed by a single part. The front shaft 2 is configured so as to surround not only the relay member 9, but also the slider 7. In the mechanical pencil 1, there is no connection part like a conventional mechanical pencil, so it is possible to make the space around the slider 7 broader than the past and make the outside diameter of the slider 7 larger. As a result, the slider 7 becomes easier to grip when detached.
If, like in the mechanical pencil according to PTL 1, the slider and the relay member are connected not by screwing, but by snap fitting, too strong a snap fit would not be desirable considering maintenance to deal with broken writing leads etc. On the other hand, if making the snap fit looser to a certain extent, at the time of writing, the writing lead will not be firmly held, but will rattle about, so the feeling in writing of the user will be detracted from. That is, due to the friction with the writing surface by writing, the writing lead receives a force in the diametrical direction. On the other hand, the front end pipe and in turn the slider also receive force in the diametrical direction. At this time, if the snap fit of the slider and the relay member is loose, the slider will move in the diametrical direction with respect to the relay member and the user gripping the relay member through the shaft barrel will feel the writing lead is rattling about. This rattling feeling becomes a cause of poorer feeling in writing.
On the other hand, in the mechanical pencil 1 according to an embodiment of the present invention, the slider 7 and the relay member 9 are connected by screwing. Therefore, compared with the case, like in the mechanical pencil described in PTL 1, where the slider and relay member are connected by snap fitting, it is possible to realize stronger connection. Further, the feeling in writing is also not detracted from.
Further, in the mechanical pencil 1, the female thread 7a is formed at the inner circumferential surface of the rear end part of the slider 7 and the male thread 9a is formed at the outer circumferential surface of the front end part of the relay member 9. Therefore, compared with the case where the male thread is formed at the slider and the female thread is formed at the relay member, the outside diameter of the slider can be made larger. As a result, the slider 7 becomes easier to grip when detached.
Note that the front shaft 2 is configured as a single part, so it is possible to make the inside space of the front end part broader than in the past. Accordingly, it is possible to make the axial lengths of the female thread of the slider 7 and the male thread of the relay member 9 longer and realize more reliable connection. Since a longer connection part can be secured, the slider and the relay member may also be connected not by screwing, but by snap fitting.
In the above embodiment, a mechanical pencil provided with a rotation drive mechanism was explained, but the embodiment of the present invention may also be applied to a mechanical pencil not provided with the rotation drive mechanism but with a slider able to be attached and detached at the front of the chuck unit.

REFERENCE SIGNS LIST

1 mechanical pencil
2 front shaft
2a front end opening
2b holding part
3 rear shaft
4 inner barrel
5 shaft barrel
6 front end pipe
7 slider
8 holding chuck
9 relay member
10 chuck unit
11 chuck body
13 lead case
14 coil spring
20 click member
21 coil spring
22 rubber eraser
23 click cover
30 rotation drive mechanism
31 shaft spring
32 support member
40 rotor

Claims

A mechanical pencil comprising:
a shaft barrel having a front shaft provided with a front end opening through which a writing lead can project and a rear shaft detachably connected to a rear end part of the front shaft;

a rotation member having a chuck unit allowing advance of the writing lead and prohibiting retraction, a relay member surrounding the chuck unit and a slider; and

a rotation drive mechanism having a rotor and receiving a retracting operation in an axial direction due to writing pressure received by the writing lead held by the chuck unit and an advancing operation in the axial direction due to release of the writing pressure so as to drive rotation of the rotor in one direction;

the rotor being connected to the rear end part of the relay member while the slider being detachably connected to the front end part of the relay member,

the rotation member being configured to rotate by receiving rotation drive force of the rotor whereby the writing lead held by the chuck unit rotates, and

the front shaft being configured by a single part.
The mechanical pencil according to claim 1, wherein the rotation drive mechanism is arranged inside the rear shaft and has a support member configured to prevent the rotation drive mechanism from dropping off from the rear shaft in a state after detachment of the front shaft.
The mechanical pencil according to claim 1 or 2, wherein the slider is formed with a female thread, the relay member is formed with a male thread, and the slider and the relay member are detachably connected by screwing.