Mechanical pencil

Abstract

We provide a mechanical pencil that reduces writing noise. [Solution] The mechanical pencil 1 comprises a cylindrical barrel 2 having an opening 5a, a mechanical pencil mechanism 28 positioned inside the barrel 2 such that its tip protrudes from the opening 5a, a cushioning member 80 provided on the outer surface of the mechanical pencil mechanism 28, and a knock mechanism 29 capable of positioning the mechanical pencil mechanism 28 between a retracted position and a first forward position forward of the retracted position. The cushioning member 80 does not contact the opening 5a when the mechanical pencil mechanism 28 is in the retracted position, but contacts the opening 5a in the axial direction when the mechanical pencil mechanism 28 is in the first forward position, and the modulus of elasticity of the cushioning member 80 is lower than the modulus of elasticity of the portion of the opening 5a that contacts the cushioning member 80.

Description

Technical Field

[0001] The present invention relates to a sharp pencil.

Background Art

[0002] In a quiet public place such as a library, the "writing sound" generated during the writing operation using a writing instrument often becomes a problem. For example, when one has to concentrate on studying for an exam, the loud writing sound of others may be distracting and prevent concentration. On the other hand, when one is writing oneself, there are cases where others point out that the writing sound is loud, disturbing the writing pace.

[0003] The causes of the writing sound during the writing operation can be mainly classified into "impact sound", "vibration sound", and "wear sound". The writing operation is an operation in which the writing part and the writing surface repeatedly separate and collide, and between the collision and separation, there is an operation accompanied by the sliding of the writing part on the writing surface. Therefore, an "impact sound" is generated when the writing part collides with the writing surface from a separated state, and then a "wear sound" is generated when the writing part slides on the writing surface. Also, during the separation, collision, and sliding of the writing part, a "vibration sound" is generated due to rattling caused by clearances between the components constituting the writing instrument. During the writing operation, the stronger the writing pressure, the greater the "impact sound", "vibration sound", and "wear sound".

[0004] By the way, there is known a sharp pencil mechanism having a chuck unit that allows the advancement of the lead and prevents the retraction, and a rotation drive mechanism having a rotor that is rotationally driven in one direction in response to an axial backward movement due to the writing pressure received by the lead held by the chuck unit and an axial forward movement due to the release of the writing pressure (Patent Document 1). The sharp pencil is configured such that the chuck unit rotates in response to the rotational driving force of the rotor, causing the lead to rotate.

[0005] In the mechanical pencil described in Patent Document 1, the clearance between the inner surface of an opening provided at the front end of the cylindrical barrel and the mechanical pencil mechanism protruding from the opening is configured to be as small as possible, thereby suppressing radial rattle of the mechanical pencil mechanism relative to the barrel. [Prior art documents] [Patent Documents]

[0006] [Patent Document 1] Japanese Patent Publication No. 2022-109748 [Overview of the project] [Problems that the invention aims to solve]

[0007] While suppressing radial play in the mechanical pencil mechanism relative to the barrel can reduce the aforementioned vibration noise, it cannot reduce impact noise. In other words, to reduce impact noise, it is necessary to mitigate the impact of the writing part against the writing surface, or in other words, the impact acting in the axial direction of the mechanical pencil. However, the mechanical pencil described in Patent Document 1 does not take into consideration the effect of impact on the writing surface of the writing part.

[0008] Even in mechanical pencils equipped with a mechanical pencil mechanism that does not have a rotational drive mechanism as described in Patent Document 1, problems such as vibration noise caused by radial rattle, as well as impact noise, can occur.

[0009] The present invention aims to provide a mechanical pencil that reduces writing noise. [Means for solving the problem]

[0010] According to one aspect of the present invention, a mechanical pencil is provided comprising: a cylindrical barrel with an opening; a mechanical pencil mechanism disposed inside the barrel such that its tip protrudes from the opening; a buffer provided on the outer surface of the mechanical pencil mechanism; and a position adjustment mechanism capable of positioning the mechanical pencil mechanism between a retracted position and a first forward position forward of the retracted position, wherein the buffer does not contact the opening when the mechanical pencil mechanism is in the retracted position, but contacts the opening in the axial direction when the mechanical pencil mechanism is in the first forward position, and the modulus of elasticity of the buffer is lower than the modulus of elasticity of the portion of the opening that contacts the buffer.

[0011] The position adjustment mechanism is capable of positioning the mechanical pencil mechanism between the retracted position, the first forward position, and the second forward position which is forward of the first forward position, and it is preferable that the cushioning portion contacts the opening in the axial direction and elastically deforms when the mechanical pencil mechanism is in the second forward position.

[0012] Preferably, the position adjustment mechanism includes a biasing member that biases the mechanical pencil mechanism backward; a cylindrical knock rotor positioned behind the mechanical pencil mechanism, having a cam receiving surface provided on its rear end surface and a protruding inner cam provided on its outer surface; a knock member positioned behind the knock rotor and having a cam surface that cooperates with the cam receiving surface to rotate the knock rotor; and an outer cam provided on the inner surface of the barrel so as to cooperate with the inner cam of the knock rotor, having a first engaging portion and a second engaging portion that can engage with the inner cam in the axial direction, wherein, in accordance with the rotation of the knock rotor, the inner cam sequentially engages with the first engaging portion to position the mechanical pencil mechanism in the first forward position, the inner cam engages with the second engaging portion to position the mechanical pencil mechanism in the second forward position, and the inner cam disengages from the outer cam to position the mechanical pencil mechanism in the retracted position.

[0013] It is preferable that the buffer portion is a separate, cylindrical buffer member made of a viscoelastic material.

[0014] Preferably, the cushioning member has a support member having a higher modulus of elasticity than the viscoelastic material and that can be fitted to the outer surface of the mechanical pencil mechanism, and the support member elastically deforms the cushioning member by sandwiching it between itself and the opening when the mechanical pencil mechanism is in the second forward position.

[0015] Preferably, the mechanical pencil mechanism includes a chuck unit that allows the writing lead to move forward and prevents it from moving backward, and a rotational drive mechanism equipped with a lead rotor, wherein the rotational drive mechanism is configured to rotate the lead rotor in one direction in response to the axial retraction movement caused by the writing pressure on the writing lead held by the chuck unit and the axial forward movement caused by the release of the writing pressure. [Effects of the Invention]

[0016] According to aspects of the present invention, a common effect is to provide a mechanical pencil that reduces writing noise. [Brief explanation of the drawing]

[0017] [Figure 1] Figure 1 is a side view of a mechanical pencil according to an embodiment of the present invention. [Figure 2] Figure 2 is a partial cross-sectional view of the mechanical pencil shown in Figure 1. [Figure 3] Figure 3 is a longitudinal cross-sectional view of the mechanical pencil shown in Figure 1. [Figure 4] Figure 4 is an enlarged longitudinal cross-sectional view of the front end of the mechanical pencil shown in Figure 1. [Figure 5] Figure 5 is an enlarged longitudinal cross-sectional view of the rotation drive mechanism and knock mechanism of the mechanical pencil shown in Figure 1. [Figure 6] Figure 6 is a schematic diagram illustrating the rotational drive of the rotor core of a rotary drive mechanism. [Figure 7] Figure 7 is a schematic diagram illustrating the rotational drive of the core rotor, following Figure 6. [Figure 8] Figure 8 is a longitudinal sectional view of the rear portion of the rear shaft. [Figure 9] Figure 9 is an enlarged perspective view of the knock mechanism. [Figure 10] Figure 10 is a longitudinal sectional view of the buffer member. [Figure 11] Figure 11 is an enlarged partial sectional view for explaining each position of the knock mechanism. [Figure 12] Figure 12 is a schematic diagram for explaining the operation of the knock rotor of the knock mechanism. [Figure 13] Figure 13 is a schematic diagram for explaining the operation of the knock rotor following Figure 12. [Figure 14] Figure

MODE FOR CARRYING OUT THE INVENTION

Mode for Carrying Out the Invention

[0018] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, common reference numerals are assigned to corresponding components.

[0019] Figure 1 is a side view of the sharp pencil 1 according to an embodiment of the present invention, Figure 2 is a partial sectional view of the sharp pencil 1 of Figure 1, Figure 3 is a longitudinal sectional view of the sharp pencil 1 of Figure 1, and Figure 4 is an enlarged longitudinal sectional view of the front end portion of the sharp pencil 1 of Figure 1.

[0020] The sharp pencil 1 has a cylindrical shaft tube 2. The shaft tube 2 has a front shaft 3 provided with a gripping portion 3a on the outer surface, a rear shaft 4 connected to the front shaft 3, and a tip member 5 connected to the front end portion of the front shaft 3. An inner tube 6 provided with a clip 6a is connected to the rear end portion of the rear shaft 4. The shaft tube 2 including the inner tube 6 may also be referred to. The tip member 5 may be integrally formed with the front shaft 3. In this specification, in the axial direction of the sharp pencil 1, the side of the writing core 7 is defined as the "front" side, and the side opposite to the side of the writing core 7 is defined as the "rear" side.

[0021] The front shaft 3, rear shaft 4, and inner cylinder 6 are cylindrical members formed with approximately the same outer diameter. The tip member 5 is a cylindrical member formed in a roughly tapered shape that narrows towards the front. Inside the front end of the shaft 2, specifically inside the front end of the tip member 5, a slider 9 having a tip pipe 8 for guiding the writing lead 7 is arranged to slide in the axial direction and rotate around the axis. A cylindrical cushioning member 80, which is a buffer, is fitted onto the outer surface of the slider 9.

[0022] Referring to Figure 4, the slider 9 is formed in a cylindrical shape, with its outer diameter tapering in a stepped manner towards the front. The front end of the slider 9, together with the tip pipe 8, protrudes from the opening at the front end of the barrel 2, that is, from the opening 5a at the front end of the tip member 5. Inside the slider 9 behind the tip pipe 8, a retaining chuck 10 with a through hole formed in the center is positioned. The through hole of the retaining chuck 10 slides against the outer surface of the writing lead 7 and acts to temporarily hold the writing lead 7.

[0023] A cylindrical connecting member 11 is screwed onto the rear end of the slider 9. Inside the slider 9 and the connecting member 11 are a chuck unit 12 for gripping the writing lead 7 and a lead case 13. The chuck unit 12 includes a chuck body member 14, a cylindrical chuck holding member 15 for gripping the rear end of the chuck body member 14, a cylindrical fastener 16 for surrounding the front end of the chuck body member 14, and a coil spring 17. The outer surface of the fastener 16 fits into the inner surface of the front end of the connecting member 11. The inner surface of the fastener 16 is formed in a conical shape, with the inner diameter continuously decreasing towards the rear. At least the front half of the chuck body member 14 is divided into three chuck pieces along the axial direction, and a through hole for the writing lead 7 is formed along the central axis. Each of the chuck pieces is formed so that the front ends are spaced apart from each other. The lead case 13 is formed in a cylindrical shape and houses the writing lead 7 inside. The rear end of the chuck holding member 15 is inserted into and fitted inside the front end of the core case 13.

[0024] A coil spring 17 is positioned to surround the chuck body member 14. The front end of the coil spring 17 is supported by a stepped portion formed on the inner surface of the connecting member 11, and the rear end of the coil spring 17 abuts against the front end surface of the chuck holding member 15. Therefore, the coil spring 17 biases the lead case 13 and the chuck body member 14 backward via the chuck holding member 15. When the chuck body member 14 is biased backward, its front ends move closer together as it is housed in the clamp 16, maintaining a grip on the writing lead 7. Furthermore, when writing pressure is applied to the writing lead 7, the chuck body member 14 retracts further and is housed in the clamp 16, and the writing lead 7 is gripped by the chuck body member 14. This prevents the writing lead 7 from retracting. On the other hand, when a force is applied to pull the writing lead 7 forward, the chuck body member 14 is not affected by the clamp 16, so the writing lead 7 can be pulled forward without resistance. In other words, the chuck unit 12 acts to allow the writing lead 7 to move forward and prevent it from moving backward. The chuck unit 12 may be any other chuck unit, such as a ball chuck, as long as it performs this function.

[0025] A cylindrical locking cylinder 18 is positioned to surround the chuck unit 12. The front end of the locking cylinder 18 is provided with an annular locking claw 18a that protrudes slightly radially inward. A cylindrical tail plug 19 is fitted to the rear end of the locking cylinder 18. The front end of a cylindrical intermediate member 20 is connected to the rear of the tail plug 19. The rear end of the intermediate member 20 is connected to a rotary drive mechanism 27, which will be described later. The core case 13 extends backward through the inside of the intermediate member 20. A coil spring 21 is positioned in the internal space of the locking cylinder 18, which is defined by the connecting member 11 and the tail plug 19, so as to surround the core case 13. The front end of the coil spring 21 abuts against the rear end surface of the connecting member 11, and the rear end of the coil spring 21 is supported by the front end surface of the tail plug 19. Therefore, the coil spring 21 biases the connecting member 11, and consequently the chuck unit 12, slider 9, and core case 13 forward.

[0026] The forward-biased slider 9, connecting member 11, chuck unit 12, and lead case 13 are integrally configured when a stepped portion on the outer surface of the slider 9 engages with the locking claw 18a of the locking cylinder 18. When the writing lead 7 retracts under writing pressure, the locking cylinder 18, and consequently the tail cap 19 and intermediate member 20, can also be retracted integrally with the slider 9. With the slider 9 and locking cylinder 18 locked, the rotational driving force from the rotational drive mechanism 27 (described later) is transmitted to the chuck unit 12 via the intermediate member 20, allowing the writing lead 7 to rotate. Furthermore, by knocking the operating member 50 (described later), the locking cylinder 18 can be advanced relative to the slider 9 and consequently to the chuck unit 12 against the biasing force of the coil spring 21, thereby releasing the lock between the slider 9 and the locking cylinder 18.

[0027] As shown in Figure 3, a cylindrical first knock member 22 is provided at the rear end of the barrel 2, specifically at the rear end of the inner cylinder 6, so as to be movable back and forth relative to the barrel 2. The first knock member 22 is biased rearward by a coil spring 23. A lead case 13 is inserted inside the front end of the first knock member 22. An eraser 24 is detachably mounted inside the rear end of the first knock member 22. A knock cover 25 is detachably attached to the outer surface of the rear end of the first knock member 22 to protect the eraser 24 from dirt and other contaminants.

[0028] By performing a knock operation, which involves pressing the first knock member 22 or the knock cover 25 forward, the lead case 13 moves forward. This pushes the chuck body member 14 forward, causing it to escape from the fastener 16. Consequently, the writing lead 7 held by the chuck body member 14 also moves forward, releasing the grip of the writing lead 7 from the chuck body member 14. In short, the chuck unit 12 acts to advance the writing lead 7 from the tip pipe 8 by being able to grip and release the writing lead 7. When the pressure from the knock operation is released, the first knock member 22 retracts and returns to its original position due to the biasing force of the coil spring 23. At this time, the chuck body member 14 retracts due to the biasing force of the coil spring 17. On the other hand, the writing lead 7 is held by the holding chuck 10 located inside the slider 9. As a result, since the writing lead 7 is advanced from the tip pipe 8, a predetermined amount of the writing lead 7 can be advanced each time the knock operation is repeated.

[0029] Figure 5 is an enlarged longitudinal cross-sectional view of the rotary drive mechanism 27 and the knock mechanism 29 of the mechanical pencil 1 shown in Figure 1. The rotary drive mechanism 27 constitutes part of the mechanical pencil mechanism 28. In short, the mechanical pencil mechanism 28 is a mechanism related to the advancement of the writing lead 7, such as the chuck unit 12 and the lead case 13, and includes a mechanism that can move back and forth integrally, and the rotary drive mechanism 27. The mechanical pencil mechanism 28 is arranged inside the barrel 2 such that the tip, i.e., the tip pipe 8, protrudes from the opening 5a of the tip member 5. The knock mechanism 29 will be described later.

[0030] The rotary drive mechanism 27 is located in the internal space of the rear shaft 4. The rotary drive mechanism 27 is connected to the rear end of the intermediate member 20. The lead case 13 passes through the interior of the intermediate member 20 and the rotary drive mechanism 27, and is spaced apart from the rotary drive mechanism 27. The rotary drive mechanism 27 is biased rearward by the shaft spring 26. That is, the front end of the shaft spring 26 is supported by the rear end of the front shaft 3, and the rear end of the shaft spring 26 abuts against the front end surface of the rotary drive mechanism 27. Therefore, the shaft spring 26 is a biasing member that biases the rotary drive mechanism 27, and by extension the mechanical pencil mechanism 28, rearward.

[0031] The rotary drive mechanism 27 includes a cylindrical core rotor 30, a cylindrical upper cam forming member 31 which is a first cam forming member, a cylindrical lower cam forming member 32 which is a second cam forming member, a cylindrical cylinder member 33, a cylindrical torque canceller 34, and a coil-shaped cushion spring 35. These components are integrated into a single unit for the rotary drive mechanism 27. A cylindrical identification member 36 is positioned on the outer surface of the cylinder member 33.

[0032] The outer surface of the rear end of the intermediate member 20 is fitted to the inner surface of the front end of the core rotor 30. Near the front end of the core rotor 30, there is a flange-like portion with a slightly larger diameter, a first cam surface 30a is formed on the rear end surface of this portion, and a second cam surface 30b is formed on the front end surface of this portion.

[0033] The upper cam forming member 31 rotatably surrounds the core rotor 30 behind the first cam surface 30a of the core rotor 30. The lower cam forming member 32 is fitted to the outer surface of the front end of the upper cam forming member 31. A first fixed cam surface 31a is formed on the front end surface of the upper cam forming member 31 facing the first cam surface 30a of the core rotor 30. A second fixed cam surface 34a is formed on the inner surface of the front end of the lower cam forming member 32 facing the second cam surface 30b of the core rotor 30.

[0034] A cylindrical cylinder member 33 is fitted to the outer surface of the rear end of the upper cam forming member 31. An insertion hole 33a is formed in the rear end of the cylinder member 33 through which the core case 13 can be inserted. A cylindrical torque canceller 34, which is movable in the axial direction, is arranged inside the cylinder member 33. A cushion spring 35 is arranged between the inner surface of the front end of the torque canceller 34 and the inner surface of the rear end of the cylinder member 33. The cushion spring 35 biases the core rotor 30 forward via the torque canceller 34.

[0035] Here, the intermediate member 20 transmits the retraction and advancement (cushioning) of the writing lead 7 based on the writing motion to the rotational drive mechanism 27, i.e., the lead rotor 30, and also transmits the rotational motion of the lead rotor 30 in the rotational drive mechanism 27, which is caused by the cushioning motion, to the chuck unit 12, which is holding the writing lead 7. Therefore, the writing lead 7 held by the chuck unit 12 also rotates as the intermediate member 20 rotates.

[0036] Except when writing with the mechanical pencil 1, that is, when no writing pressure is applied to the lead 7, the lead rotor 30 is positioned forward due to the biasing force of the cushion spring 35 via the torque canceller 34. Therefore, the second cam surface 30b of the lead rotor 30 contacts the second fixed cam surface 34a and engages with it. When writing with the mechanical pencil 1, that is, when writing pressure is applied to the lead 7, the chuck unit 12 retracts against the biasing force of the cushion spring 35, and the lead rotor 30 retracts accordingly. Therefore, the first cam surface 30a of the lead rotor 30 contacts the first fixed cam surface 31a and engages with it. The lead 7 and the lead rotor 30 move forward, backward, or rotate as a single unit.

[0037] Figure 6 is a schematic diagram illustrating the rotational drive of the core rotor 30 of the rotational drive mechanism 27, and Figure 7 is a schematic diagram illustrating the rotational drive of the core rotor 30 following Figure 6. In Figures 6 and 7, a first cam surface 30a, which is the rear end surface, which is the upper surface of the core rotor 30, is formed in an annular shape with continuously sawtooth teeth along the circumferential direction, and a second cam surface 30b, which is similarly formed in an annular shape with continuously sawtooth teeth along the circumferential direction, is formed on the front end surface, which is the lower surface of the core rotor 30.

[0038] A first fixed cam surface 31a, which is continuously serrated along the circumferential direction, is formed on the annular end face of the upper cam forming member 31 facing the first cam surface 30a of the core rotor 30, and a second fixed cam surface 34a, which is continuously serrated along the circumferential direction, is formed on the annular end face of the lower cam forming member 32 facing the second cam surface 30b of the core rotor 30. The cam surfaces of the first cam surface 30a and the second cam surface 30b formed on the core rotor 30, and the cam surfaces of the first fixed cam surface 31a formed on the upper cam forming member 31 and the second fixed cam surface 34a formed on the lower cam forming member 32 are formed so that their pitches are substantially the same.

[0039] Figure 6(A) shows the relationship between the advanced lead rotor 30, the upper cam forming member 31, and the lower cam forming member 32 when no writing pressure is applied to the lead 7. In this state, the second cam surface 30b formed on the lead rotor 30 is in contact with the second fixed cam surface 34a of the lower cam forming member 32 due to the biasing force of the cushion spring 35. At this time, the first cam surface 30a of the lead rotor 30 and the first fixed cam surface 31a of the upper cam forming member 31 are set to be offset by half a phase (half a pitch) with respect to one tooth of the cam in the axial direction.

[0040] Figure 6(B) shows the initial state when writing pressure is applied to the lead 7 for writing with the mechanical pencil 1. In this state, the lead rotor 30 retracts as the chuck unit 12 retracts, causing the cushion spring 35 to contract. As a result, the lead rotor 30 moves toward the upper cam forming member 31 and comes into contact with the first fixed cam surface 31a.

[0041] Next, Figure 6(C) shows the state in which further writing pressure is applied to the writing lead 7, causing the lead rotor 30 to contact the first fixed cam surface 31a of the upper cam forming member 31 and slide backward. That is, the lead rotor 30 receives rotational drive corresponding to half a phase (half a pitch) of one tooth of the first cam surface 30a. In this state, the first cam surface 30a of the lead rotor 30 is engaged with the first fixed cam surface 31a of the upper cam forming member 31.

[0042] The circles drawn in the center of the rotor 30 in Figures 6 and 7 indicate the amount of rotational movement of the rotor 30. In the state shown in Figure 6(C), the second cam surface 30b of the rotor 30 and the second fixed cam surface 34a of the lower cam forming member 32 are set to be offset by half a phase (half a pitch) with respect to one tooth of the cam in the axial direction.

[0043] Next, Figure 7(D) shows the initial state after writing with the mechanical pencil 1 has finished and the writing pressure on the lead 7 has been released. In this state, the lead rotor 30 moves forward due to the biasing force of the cushion spring 35. As a result, the lead rotor 30 moves toward the lower cam forming member 32 and comes into contact with the second fixed cam surface 34a.

[0044] Next, Figure 7(E) shows the state in which the core rotor 30 moves forward while sliding in contact with the second fixed cam surface 34a of the lower cam forming member 32 due to the biasing force of the cushion spring 35. That is, the core rotor 30 again receives rotational drive corresponding to half a phase (half a pitch) of one tooth of the second cam surface 30b. In this state, the second cam surface 30b of the core rotor 30 is engaged with the second fixed cam surface 34a of the lower cam forming member 32.

[0045] Therefore, as indicated by the circle drawn in the center of the lead rotor 30 in Figures 6 and 7, when the lead rotor 30 receives writing pressure, it reciprocates in the axial direction, i.e., moves back and forth, and the lead rotor 30 receives rotational drive corresponding to one tooth (one pitch) of the first cam surface 30a and the second cam surface 30b, and the writing lead 7 held by it via the chuck unit 12 is similarly driven to rotate. Thus, with each back and forth movement of the lead rotor 30 in the axial direction due to writing, the lead rotor 30 receives rotational movement corresponding to one tooth of the cam, and by repeating this, the writing lead 7 is sequentially driven to rotate. Therefore, it is possible to prevent uneven wear of the writing lead 7 as writing progresses, and to prevent large changes in line thickness and line darkness.

[0046] The torque canceller 34, which pushes the core rotor 30 forward under the biasing force of the cushion spring 35, generates slippage between its front end surface and the rear end surface of the core rotor 30, preventing the rotational motion of the core rotor 30 from being transmitted to the cushion spring 35. In other words, the torque canceller 34 prevents the rotational motion of the core rotor 30 from being transmitted to the cushion spring 35, thereby preventing the generation of torsional unwinding (torque) of the cushion spring 35 that would hinder the rotational movement of the core rotor 30.

[0047] Figure 8 is a longitudinal cross-sectional view of the rear of the rear axle 4. The outer surface of the rear of the rear axle 4 is provided with a recess 4a extending in the axial direction and a through hole 4b extending in the longitudinal direction within the recess 4a. Two outer cams 40, which constitute part of the knock mechanism 29, are provided on the inner surface of the rear of the rear axle 4 at equal intervals along the circumferential direction. Each of the outer cams 40 has a cam projection 41 extending in the axial direction. An axial groove 42 is defined by adjacent cam projections 41. The front end surface of the cam projection 41 is formed in a sawtooth shape along the circumferential direction. That is, the front end surface of the cam projection 41 consists of three inclined surfaces 43 along the circumferential direction and two vertical surfaces 44 connecting the three inclined surfaces 43. A concave first engagement portion 45 and a second engagement portion 46 are defined by adjacent inclined surfaces 43 and vertical surfaces 44. The second engagement portion 46 is located in front of the first engagement portion 45. A window hole 4c, which is a through hole extending in the circumferential direction, is provided on the side of the rear shaft 4 in front of the outer cam 40.

[0048] Figure 9 is an enlarged perspective view of the knock mechanism 29. The components of the knock mechanism 29 will be described with reference to both Figure 9 and Figure 5. The knock mechanism 29 includes the aforementioned outer cam 40, operating member 50, second knock member 60, and knock rotor 70. The lead case 13 penetrates the interior of the second knock member 60 and knock rotor 70, and is spaced apart from the knock mechanism 29. Note that the rear shaft 4 is omitted in Figure 9, and therefore the outer cam 40 is not shown.

[0049] The operating member 50 includes an operating knob 51, a plate portion 52, a connecting portion 53, and an annular ring portion 54. The operating knob 51 has a roughly triangular or roughly trapezoidal vertical cross-section and is connected to the plate portion 52 at the surface corresponding to its base. The plate portion 52 is boat-shaped and reduces frictional resistance during the knocking operation when the operating member 50 is slid back and forth in the recess 4a of the rear shaft 4, as will be described later. The operating knob 51 is connected to the connecting portion 53 via the plate portion 52, and further connected to the ring portion 54 via the connecting portion 53. The connecting portion 53 is positioned to contact the inner wall of the through hole 4b by passing through the through hole 4b, and restricts circumferential movement when the operating member 50 is slid back and forth.

[0050] The second knocking member 60 is a cylindrical member. The second knocking member 60 has a large diameter portion 61 and a small diameter portion 62 located behind the large diameter portion 61 and having a smaller diameter than the large diameter portion 61. Four sliding protrusions 63 are provided on the outer surface of the large diameter portion 61 of the second knocking member 60 at equal intervals along the circumferential direction. A cam surface 64 is formed on the front end surface of the second knocking member 60. The cam surface 64 has a plurality of peaks and valleys aligned along the circumferential direction. The ring portion 54 of the operating member 50 is fitted into the small diameter portion 62. As a result, when the operating member 50 slides back and forth, that is, when the operating member 50 is knocked, the operating member 50 and the second knocking member 60 can be moved back and forth as a single unit.

[0051] The knock rotor 70 is a cylindrical member. The knock rotor 70 has a cam portion 71 and an insertion portion 72 located behind the cam portion 71 and having a smaller diameter than the cam portion 71. Four inner cams 73, which are projections extending in the axial direction, are provided on the outer surface of the cam portion 71 at equal intervals along the circumferential direction. The inner cams 73 extend rearward beyond the rear end surface of the cam portion 71. The rear end surface of the inner cams 73 has a sloped cam receiving surface 74 that cooperates with the sloped surface 43 and vertical surface 44 of the outer cam 40 and the cam surface 64 of the second knock member 60. In other words, the striking and cam receiving surface 74 has a radial width or thickness so that it can cooperate with the sloped surface 43 and vertical surface 44 of the outer cam 40 and the cam surface 64 of the second knock member 60. The insertion portion 72 is inserted into the front end of the second knock member 60 and loosely fitted, and is used to align the second knock member 60 and the knock rotor 70.

[0052] The front end surface of the knock rotor 70 is in contact with the rear end surface of the rotational drive mechanism 27, specifically, the rear end surface of the cylinder member 33. As described above, the rotational drive mechanism 27 is biased rearward by the shaft spring 26. Therefore, the knock rotor 70, and consequently the second knock member 60, are also biased rearward by the shaft spring 26 via the rotational drive mechanism 27.

[0053] Figure 10 is a longitudinal cross-sectional view of the cushioning member 80. The cushioning member 80 is a cylindrical member. The cushioning member 80 has a cushioning body 81 and a support member 82. The cushioning body 81 has a base 83, a tip 84 provided in front of the base 83 and having a smaller diameter than the base 83, and a tapered portion 85 connecting the base 83 and the tip 84. The support member 82 is a cylindrical or annular member and is fitted onto the inner surface of the base 83 of the cushioning body 81. The support member 82 may be integrally formed with the cushioning body 81 by two-color molding or the like.

[0054] The cushioning body 81 of the cushioning member 80 is formed from a viscoelastic material or gel-like substance such as PTFE, polyethylene, or polypropylene. The support member 82 is formed from a hard plastic such as polycarbonate, ABS, PET, or PBT. The nozzle member 5 and slider 9 are also formed from a hard plastic such as polycarbonate, ABS, PET, or PBT. Therefore, the elastic modulus of the cushioning body 81 is lower than that of the opening 5a at the front end of the nozzle member 5 that contacts the cushioning body 81, as will be described later, and the elastic modulus of the support member 82 is higher than that of the cushioning body 81. The support member 82, the nozzle member 5, and the slider 9 may be formed from the same hard plastic or from different hard plastics.

[0055] As shown in Figure 4, the cushioning member 80 is fitted to the outer surface of the slider 9. Specifically, the cushioning member 80 is fitted to the outer surface of the slider 9 via the support member 82. When fitted to the slider 9, the tip portion 84 of the cushioning member 80 protrudes from the opening 5a of the mouth member 5. In addition, the inner surface of the cushioning body 81, supported by the support member 82, is spaced apart from the outer surface of the opposing slider 9 around its entire circumference.

[0056] Figure 11 is an enlarged partial cross-sectional view illustrating the various positions of the knock mechanism 29. In Figure 11, the right side is the rear side of the mechanical pencil 1. Figure 11(A) shows the state of the knock mechanism 29 in the retracted position, where the operating member 50 is in its most retracted position. Figure 11(B) shows the state of the knock mechanism 29 in the first forward position, where the operating member 50 has moved forward one step, and is further forward than the retracted position. Figure 11(C) shows the state of the knock mechanism 29 in the second forward position, where the operating member 50 has moved forward one more step, and is further forward than the first forward position. Figure 11(D) shows the state of the knock mechanism 29 in the full knock position, where the operating member 50 is in its most forward position.

[0057] In mechanical pencil 1, the knock mechanism 29 is sequentially switched between a retracted position, a first forward position, and a second forward position by performing a knock operation, which involves pressing the operating member 50 of the knock mechanism 29, specifically the operating knob 51, forward against the biasing force of the shaft spring 26. The limit of forward movement in the knock operation when switching back from the second forward position to the retracted position is the full knock position. The retracted position, first forward position, and second forward position of the knock mechanism 29 correspond to the retracted position, first forward position, and second forward position of the mechanical pencil mechanism 28. In other words, the knock mechanism 29 is a position adjustment mechanism that can position the mechanical pencil mechanism 28 at each position. The retracted position, first forward position, and second forward position of the mechanical pencil mechanism 28 correspond to the normal state, silent state, and fixed state of mechanical pencil 1, respectively, as described later.

[0058] Each state of the mechanical pencil 1 can be confirmed by the position of the mechanical pencil mechanism 28. Specifically, it can be confirmed by visually inspecting the identification member 36 inside the barrel 2 through a window hole 4c provided in the barrel 2. As shown in Figure 11(A), the identification member 36 is provided with a first identifier 36a, a second identifier 36b, and a third identifier 36c, which are formed in a ring shape and are assigned different colors to each other. The first identifier 36a, the second identifier 36b, and the third identifier 36c may be separate ring-shaped members or link-shaped colored members within the identification member 36.

[0059] In Figure 11(A), the first identifier 36a is visible through the window 4c. In Figure 11(B), the second identifier 36b is visible through the window 4c. In Figure 11(C), the third identifier 36c is visible through the window 4c. Note that in Figure 11(D), the cylinder member 33 of the rotary drive mechanism 27 is visible instead of the identification member 36, but as mentioned above, the state shown in Figure 11(D) is a temporary state during the switching process by the knock mechanism 29.

[0060] Next, the operation of the knock mechanism 29 will be explained with reference to Figures 12 and 13. Figure 12 is a schematic diagram illustrating the operation of the knock rotor 70 of the knock mechanism 29, and Figure 13 is a schematic diagram illustrating the operation of the knock rotor 70 following Figure 12. That is, Figures 12 and 13 are schematic diagrams showing the positional relationship between the outer cam 40, the second knock member 60, and the knock rotor 70, and show the positions of the sliding projection 63 of the second knock member 60 and the inner cam 73 of the knock rotor 70 with respect to the outer cam 40 unfolded in the circumferential direction. In the figures, the bottom is the front of the mechanical pencil 1, and the top is the rear of the mechanical pencil 1.

[0061] The knock rotor 70 is given rotational force by the cooperation of the cam surface 64 of the second knock member 60 and the cam receiving surface 74 of the knock rotor 70, and rotates around the central axis. Therefore, in Figures 12 and 13, the knock rotor 70 moves from right to left in the figures with each knock operation. In Figures 12 and 13, the shape and dimensions of each component are shown schematically.

[0062] The state of the knock mechanism 29 shown in Figure 12(A) corresponds to the retracted position shown in Figure 11(A). At this time, the inner cam 73 of the knock rotor 70, which is biased rearward by the shaft spring 26 via the rotation drive mechanism 27, is positioned in the groove 42 between the outer cams 40. The sliding projection 63 of the second knock member 60 is positioned in the groove 42. The second knock member 60 is biased rearward by the shaft spring 26 through contact with the inner cam 73 of the knock rotor 70. The cam surface 64 and the cam receiving surface 74 are positioned with a phase difference.

[0063] From the state shown in Figure 12(A), the second knocking member 60 and the knocking rotor 70 are advanced by performing a knocking operation on the operating member 50. At this time, the sliding projection 63 of the second knocking member 60 and the inner cam 73 of the knocking rotor 70 move forward within the groove 42. The second knocking member 60 and the knocking rotor 70 are subjected to circumferential force components in opposite directions via the inclined surfaces of the cam surface 64 and the cam receiving surface 74, but their circumferential movement is restricted by the contact between the sliding projection 63 and the side surface of the cam projection 41 of the outer cam 40.

[0064] As the second knock member 60 and the knock rotor 70 move further forward, the rear end of the inner cam 73 passes the front end of the outer cam 40, i.e., the cam projection 41, in the front-rear direction (Figure 12(B)). When the pressure of the operating member 50 is released from this state, the second knock member 60 and the knock rotor 70 retract due to the biasing force of the shaft spring 26. At this time, the knock rotor 70 receives component forces from the cam surface 64 of the second knock member 60 and the inclined surface 43 of the outer cam 40 and rotates around the central axis (Figure 12(C)). The inner cam 73 of the knock rotor 70 moves along the cam surface 64 and the inclined surface 43 until it contacts the vertical surface 44 of the outer cam 40, and the rotation of the knock rotor 70 stops (Figure 12(D)).

[0065] The state of the knock mechanism 29 shown in Figure 12(D) corresponds to the first forward position shown in Figure 11(B). In the knock mechanism 29 shown in Figure 12(D), the inner cam 73 of the knock rotor 70 is engaged with the first engagement portion 45 of the outer cam 40 in the axial direction.

[0066] From the state shown in Figure 12(D), the second knocking member 60 and the knocking rotor 70 are advanced by performing the knocking operation of the operating member 50 again. At this time, the sliding projection 63 of the second knocking member 60 moves forward within the groove 42. The second knocking member 60 and the knocking rotor 70 are subjected to circumferential force components in opposite directions via the inclined surfaces of the cam surface 64 and the cam receiving surface 74, but their circumferential movement is restricted by the contact between the sliding projection 63 and the side surface of the cam projection 41 of the outer cam 40, and by the contact between the inner cam 73 and the vertical surface 44 of the outer cam 40.

[0067] As the second knock member 60 and the knock rotor 70 move further forward, the rear end of the inner cam 73 crosses the vertical surface 44 of the outer cam 40 in the front-rear direction (Figure 12(E)). When the pressure of the operating member 50 is released from this state, the second knock member 60 and the knock rotor 70 retract due to the biasing force of the shaft spring 26. At this time, the knock rotor 70 receives component forces from the cam surface 64 of the second knock member 60 and the inclined surface 43 of the outer cam 40 and rotates around the central axis (Figure 13(F)). The inner cam 73 of the knock rotor 70 moves along the cam surface 64 and the inclined surface 43 until it contacts another vertical surface 44 of the outer cam 40, and the rotation of the knock rotor 70 stops (Figure 13(G)).

[0068] The state of the knock mechanism 29 shown in Figure 13(G) corresponds to the second forward position shown in Figure 11(C). In the knock mechanism 29 shown in Figure 13(G), the inner cam 73 of the knock rotor 70 is engaged with the second engaging portion 46 of the outer cam 40 in the axial direction. As described above, the second engaging portion 46 is located in front of the first engaging portion 45. Therefore, the knock rotor 70, and consequently the rotary drive mechanism 27, in the knock mechanism 29 shown in Figure 12(D) is located in front of the knock rotor 70, and consequently the rotary drive mechanism 27, in the knock mechanism 29 shown in Figure 13(G).

[0069] From the state shown in Figure 13(G), the second knocking member 60 and the knocking rotor 70 are advanced by performing the knocking operation of the operating member 50 again. At this time, the sliding projection 63 of the second knocking member 60 moves forward within the groove 42. The second knocking member 60 and the knocking rotor 70 are subjected to circumferential force components in opposite directions via the inclined surfaces of the cam surface 64 and the cam receiving surface 74, but their circumferential movement is restricted by the contact between the sliding projection 63 and the side surface of the cam projection 41 of the outer cam 40, and by the contact between the inner cam 73 and the vertical surface 44 of the outer cam 40.

[0070] As the second knock member 60 and the knock rotor 70 move further forward, the rear end of the inner cam 73 crosses the vertical surface 44 of the outer cam 40 in the front-rear direction (Figure 13(H)). The state of the knock mechanism 29 shown in Figure 13(H) corresponds to all knock positions shown in Figure 11(D). When the pressure of the operating member 50 is released from this state, the second knock member 60 and the knock rotor 70 retract due to the biasing force of the shaft spring 26. At this time, the knock rotor 70 rotates around its central axis, receiving component forces from the cam surface 64 of the second knock member 60 and the inclined surface 43 of the outer cam 40. The inner cam 73 of the knock rotor 70 moves along the cam surface 64 and the inclined surface 43 of the outer cam 40 until it contacts the side surface of the adjacent cam projection 41 of the outer cam 40, and the rotation of the knock rotor 70 stops (Figure 13(I)).

[0071] In this state, the inner cam 73 of the knock rotor 70 does not engage with the outer cam 40, and the inner cam 73 of the knock rotor 70 moves backward within the groove 42 together with the second knock member 60 due to the biasing force of the shaft spring 26 and stops (Figure 13(J)). Figure 13(J) is the same state as Figure 12(A), and the state of the knock mechanism 29 shown in Figure 13(J) corresponds to the retracted position shown in Figure 11(A).

[0072] Figure 14 is an enlarged longitudinal cross-sectional view of the front end of the mechanical pencil 1 in Figure 1 in each state. Specifically, Figure 14(A) shows the mechanical pencil mechanism 28 in the retracted position, at which point the mechanical pencil 1 is in its normal state. Figure 14(B) shows the mechanical pencil mechanism 28 in the first forward position, at which point the mechanical pencil 1 is silent. Figure 14(C) shows the mechanical pencil mechanism 28 in the second forward position, at which point the mechanical pencil 1 is fixed. Figure 14(D) shows the mechanical pencil mechanism 28 in the fully knocked position.

[0073] In the mechanical pencil 1 in its normal state as shown in Figure 14(A), the cushioning member 80 does not come into contact with the barrel 2, and therefore does not come into contact with the opening 5a of the tip member 5. Thus, the axial movement of the slider 9 is not obstructed by the cushioning member 80. In the mechanical pencil 1 in its normal state, when writing pressure is applied to the writing lead 7, the lead rotor 30 can be retracted via the slider 9 and the intermediate member 20, and the rotational drive mechanism 27 can be made to function as described with reference to Figures 6 and 7.

[0074] In a normal mechanical pencil 1, vibration noise is generated due to rattling caused by clearances between parts necessary for the operation of the rotation drive mechanism 27. In addition, impact noise is generated when the writing lead 7 collides with the writing surface from a position away from it.

[0075] In the silent mechanical pencil 1 shown in Figure 14(B), the mechanical pencil mechanism 28 is in the first forward position. Therefore, comparing the positions of the front ends of the slider 9, for example, the front end of the slider 9 in the first forward position is located a distance L1 forward relative to the tip member 5 than the front end of the slider 9 in the retracted position shown in Figure 14(A). As a result, the outer surface of the cushioning member 80 is in contact with the opening 5a of the tip member 5. Specifically, the tapered portion 85 of the cushioning member 80 is in contact with the rearward edge of the opening 5a. Even though the cushioning member 80 is in contact with the opening 5a of the tip member 5, the cushioning member 80 is hardly elastically deformed.

[0076] In the first forward position, the mechanical pencil mechanism 28 has the buffer member 80 in contact with the opening 5a, causing the slider 9, and consequently the intermediate member 20, to be slightly retracted relative to the rotation drive mechanism 27. Therefore, when no writing pressure is applied to the writing lead 7, the lead rotor 30 should be in contact with the lower cam forming member 32 further forward, as shown in Figure 6(A), but instead, as shown in Figure 6(C), it is in contact with the upper cam forming member 31 further rearward. As a result, the mechanical pencil mechanism 28 in the first forward position cannot rotate the lead rotor 30 by repeatedly moving it forward or backward based on the writing motion, as explained with reference to Figures 6 and 7. Therefore, in the silent state, the mechanical pencil 1 is in a rotation-locked state where the rotation drive mechanism 27 does not function.

[0077] In the silent state of the mechanical pencil 1, the rotational drive mechanism 27 does not function, thus reducing rattling caused by clearances between parts, and consequently reducing vibration noise. Furthermore, because the cushioning member 80 is in contact with the opening 5a in the axial direction, it has a cushioning effect against the axial movement of the mechanical pencil mechanism 28 relative to the barrel 2. In addition, because the inner surface of the cushioning part body 81, supported by the support member 82, is spaced apart from the outer surface of the opposing slider 9 around its entire circumference, it also has a cushioning effect against the radial movement of the mechanical pencil mechanism 28 relative to the barrel 2. Therefore, in the silent state of the mechanical pencil 1, not only vibration noise but also impact noise when the writing lead 7 collides with the writing surface from a state where it is separated from the writing surface is reduced.

[0078] Furthermore, as shown in Figure 14(B), the locking cylinder 18 has moved slightly forward relative to the slider 9 compared to the state shown in Figure 14(A). Therefore, the locking between the slider 9 and the locking cylinder 18 has been slightly released.

[0079] In the fixed mechanical pencil 1 shown in Figure 14(C), the mechanical pencil mechanism 28 is in the second forward position. Therefore, comparing the positions of the front ends of the slider 9, for example, the front end of the slider 9 in the second forward position is located a distance L2 forward of the front end of the slider 9 in the retracted position shown in Figure 14(A), and is located further forward than the front end of the slider 9 in the silent position shown in Figure 14(B). In other words, distance L2 is greater than distance L1. As a result, the cushioning member 80, particularly the tapered portion 85, is elastically deformed by the opening 5a of the tip member 5. Specifically, the cushioning body 81 of the cushioning member 80 is elastically deformed by being held between the support member 82. In short, the mechanical pencil 1 is configured such that the cushioning member 80 elastically deforms when it comes into contact with the opening 5a in the axial direction when the mechanical pencil mechanism 28 is in the second forward position.

[0080] In the fixed state of the mechanical pencil 1, the lead rotor 30 is in contact with the upper cam forming member 31 further rearward, as shown in Figure 6(C), similar to the silent state of the mechanical pencil 1. Therefore, in the fixed state of the mechanical pencil 1, the rotation drive mechanism 27 does not function, resulting in a rotation lock state and reduced vibration noise.

[0081] In the second forward position of the mechanical pencil mechanism 28, the cushioning body 81 of the cushioning member 80 is held by the support member 82 and undergoes elastic deformation, so the mechanical pencil mechanism 28 becomes like a single rigid body firmly connected to the barrel 2. As a result, the user can write stably without the writing lead 7 wobbling during the writing motion. On the other hand, because the barrel 2 and the mechanical pencil mechanism 28 are integrally constructed with high rigidity, the impact sound when the writing lead 7 collides with the writing surface from a position away from the writing surface is not reduced as much as in the case of the silent mechanical pencil 1.

[0082] In short, the normal state is the state in which the rotation drive mechanism 27 is functioning. The silent state is the state in which the impact noise and vibration noise during writing under the same conditions are reduced compared to the normal state and the fixed state. The fixed state is the state in which the slider 9, and by extension the writing lead 7, is more fixed to the barrel 2 compared to the normal state and the silent state, and radial movement is suppressed, resulting in a state in which stable writing is possible. In addition, the silent state and the fixed state are states in which the rotation is locked, resulting in a state in which stable writing is possible. With the mechanical pencil 1, the normal state, silent state and fixed state can be selectively switched by knocking the operating member 50 of the knock mechanism 29. Based on the above, the user can appropriately select the normal state, silent state and fixed state with the mechanical pencil 1 according to their preference, surrounding environment, mood and situation at the time.

[0083] Furthermore, as shown in Figure 14(C), the locking cylinder 18 has advanced further relative to the slider 9 compared to the state shown in Figure 14(B). Therefore, the locking between the slider 9 and the locking cylinder 18 has been released.

[0084] By the way, as explained with reference to Figure 13(H), in order to switch the knock mechanism 29 from the second forward position back to the retracted position, the second knock member 60 must be advanced so that the rear end of the inner cam 73 of the knock rotor 70 exceeds the vertical surface 44 of the outer cam 40 in the front-rear direction. On the other hand, in the mechanical pencil mechanism 28, the slider 9 is in contact with the tip member 5 via the buffer member 80. When the knock operation is performed with the operating member 50 in this state, the pressing force from the knock operation via the relay member 20 advances the locking cylinder 18 against the biasing force of the coil spring 21. As a result, the locking cylinder 18 advances relative to the slider 9 and, consequently, relative to the chuck unit 12, and the lock between the slider 9 and the locking cylinder 18 is completely released. At this time, the knock mechanism 29 is in the fully knocked position, and the rear end of the inner cam 73 of the knock rotor 70 can exceed the vertical surface 44 of the outer cam 40 in the front-rear direction.

[0085] Furthermore, the coil spring 21 is configured to allow the knock mechanism 29 to be moved to the fully knocked position in order to switch the knock mechanism 29 back from the second forward position to the retracted position. The coil spring 21 also has the effect of mitigating the impact when the writing lead 7 collides with the writing surface during writing, thereby preventing the writing lead 7 from breaking.

[0086] Using a mechanical pencil actually manufactured according to the embodiment of mechanical pencil 1 described above, the sound pressure level of the impact sound was experimentally measured in the normal state, silent state, and fixed state, and the results of converting them to sound pressure will be explained.

[0087] In the experiment, copy paper placed on a wooden desk was used as the writing surface. The writing method involved using a mechanical pencil tilted 60 degrees to the writing surface and applying a writing pressure of 1N. A Shure SM58 microphone was used to collect the writing sound. Measurements were taken with the microphone held 35cm vertically away from the writing position on the writing surface.

[0088] The experimental results showed that the sound pressure in the normal state was 20.4 mPa, the sound pressure in the fixed state was 15.7 mPa, and the sound pressure in the silent state was 6.7 mPa. In other words, the sound pressure in the silent state was reduced by approximately 67% compared to the normal state and by approximately 57% compared to the fixed state. Furthermore, the sound pressure in the fixed state was reduced by approximately 23% compared to the normal state. As described above, the effect of reducing writing noise by creating a silent state was confirmed.

[0089] In the above-described embodiment, the knock mechanism 29 was used as the position adjustment mechanism to switch between three positions of the mechanical pencil mechanism 28: the retracted position, the first forward position, and the second forward position. However, it is also possible to configure the mechanism to switch between only two positions: the retracted position corresponding to the normal state and the first forward position corresponding to the silent state. This configuration can be achieved by having only one engagement portion in the outer cam 40, which has two engagement portions, the first engagement portion 45 and the second engagement portion 46, as described above.

[0090] The outer cam 40 is provided on the inner surface of the barrel 2 so as to cooperate with the inner cam 73 of the knock rotor 70, and has a first engaging portion 45 and a second engaging portion 46 that can engage with the inner cam 73 in the axial direction. In accordance with the rotation of the knock rotor 70, the inner cam 73 engages with the first engaging portion 45 to position the mechanical pencil mechanism 28 in the first forward position, the inner cam engages with the second engaging portion 46 to position the mechanical pencil mechanism 28 in the second forward position, and the inner cam 73 disengages from the outer cam 40 to position the mechanical pencil mechanism 28 in the retracted position. The outer cam may be configured as such insofar as these conditions are met. For example, the second engaging portion of the outer cam may be positioned behind the first engaging portion. This allows for a change in the order in which the retracted position, the first forward position, and the second forward position are switched.

[0091] In the embodiment described above, the mechanical pencil mechanism had a rotational drive mechanism 27, but it does not have to have a rotational drive mechanism 27. In this case, the knock mechanism 29 is configured as a position adjustment mechanism that can position a normal mechanical pencil mechanism.

[0092] In the above-described embodiment, the knock mechanism 29 was used as the position adjustment mechanism to switch between the retracted position, the first forward position, and the second forward position of the mechanical pencil mechanism 28. However, any position adjustment mechanism can be used as long as it allows for switching or positioning of the mechanical pencil mechanism 28. Other position adjustment mechanisms may include, for example, a so-called rotary extension mechanism, or a simple manual sliding positioning mechanism.

[0093] In the cushioning member 80, the support member 82 may be omitted, and the cushioning body 81 may be directly fitted to the outer surface of the slider 9. The cushioning member 80 may also be a cushioning part integrally formed with the slider 9 by two-color molding or the like. [Explanation of Symbols]

[0094] 1. Mechanical pencil 2 shaft cylinder 3 Front axle 4 Rear axle 4c Window hole 5. Nozzle component 5a opening 9 Sliders 10 Retaining chuck 12 Chuck Units 13-core case 17 Coil Springs 18 Locking tube 18a Locking claw 19. Tail plug 20 Intermediate components 21 Coil Springs 26 Axle Spring 27 Rotary drive mechanism 28 Mechanical pencil mechanism 29. Knock mechanism 30-core rotor 35 cushion springs 36 Identification Member 40 External Cam 45 First engagement part 46 Second engagement part 50 Operating Member 60 Second knock member 70 Knock Rotor 80 Cushioning material 81 Buffer body 82 Support Member

Claims

1. A cylindrical shaft with an opening, A mechanical pencil mechanism is arranged inside the barrel so that its tip protrudes from the opening, A buffer portion provided on the outer surface of the mechanical pencil mechanism, The mechanical pencil mechanism comprises a position adjustment mechanism that can position the mechanical pencil between a retracted position and a first forward position that is forward of the retracted position. The buffer portion does not contact the opening when the mechanical pencil mechanism is in the retracted position, and contacts the opening in the axial direction when the mechanical pencil mechanism is in the first forward position. A mechanical pencil characterized in that the elastic modulus of the buffer portion is lower than the elastic modulus of the portion of the opening that comes into contact with the buffer portion.

2. The position adjustment mechanism is capable of positioning the mechanical pencil mechanism between the retracted position, the first forward position, and a second forward position that is further forward than the first forward position. The mechanical pencil according to claim 1, wherein the buffer portion contacts the opening in the axial direction and elastically deforms when the mechanical pencil mechanism is in the second forward position.

3. The position adjustment mechanism, A biasing member that biases the mechanical pencil mechanism to the rear, A cylindrical knock rotor positioned at the rear of the mechanical pencil mechanism, having a cam receiving surface on its rear end surface and a protruding inner cam on its outer surface, A knock member having a cam surface positioned behind the knock rotor and cooperating with the cam receiving surface to rotate the knock rotor, An outer cam provided on the inner surface of the barrel so as to cooperate with the inner cam of the knock rotor, the outer cam having a first engaging portion and a second engaging portion that can engage with the inner cam in the axial direction, wherein, in accordance with the rotation of the knock rotor, the inner cam sequentially engages with the first engaging portion to position the mechanical pencil mechanism in the first forward position, the inner cam engages with the second engaging portion to position the mechanical pencil mechanism in the second forward position, and the inner cam disengages from the outer cam to position the mechanical pencil mechanism in the retracted position.

4. The mechanical pencil according to claim 3, wherein the buffer portion is a separate cylindrical buffer member made of a viscoelastic material.

5. The mechanical pencil according to claim 4, wherein the cushioning member has a support member having a higher modulus of elasticity than the viscoelastic material and that can be fitted to the outer surface of the mechanical pencil mechanism, and the support member clamps the cushioning member between itself and the opening when the mechanical pencil mechanism is in the second forward position, thereby causing it to elastically deform.

6. The aforementioned mechanical pencil mechanism includes a chuck unit that allows the writing lead to move forward and prevents it from moving backward, and a rotary drive mechanism equipped with a lead rotor. The mechanical pencil according to any one of claims 1 to 5, wherein the rotational drive mechanism is configured to rotate the lead rotor in one direction in response to the axial retraction movement caused by the writing pressure received by the writing lead gripped by the chuck unit and the axial advance movement caused by the release of the writing pressure.

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