Mechanical pencil

Abstract

To provide a mechanical pencil configured to reduce rattling in a radial direction of a writing lead.SOLUTION: There is provided a mechanical pencil including: a barrel 5; a rotary member with a chuck unit 10 capable of gripping and releasing a writing lead and a slider having a holding portion, the rotary member having a part protruding from a front end of the barrel; and a rotation drive mechanism 30 having a rotor 40 connected to the rotary member, and configured to drive the rotor to rotate in one direction in response to an axial retraction movement caused by a writing pressure applied to the writing lead held by the chuck unit and an axial advancement movement caused by a release of the writing pressure. The rotary member rotates in response to a rotational driving force of the rotor, causing the writing lead held by the chuck unit to rotate, and a viscous fluid 70 is applied between an inner surface of the front end of the barrel and an outer surface of the holding portion.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a mechanical pencil. [Background technology]

[0002] A mechanical pencil is known which is equipped with a barrel, a rotating member equipped with a chuck unit and a slider capable of gripping and releasing a writing lead, and a rotational drive mechanism which has a rotor and drives the rotor to rotate in one direction in response to the axial backward movement caused by the writing pressure applied to the writing lead gripped by the chuck unit and the axial forward movement caused by the release of the writing pressure, and in which the chuck unit rotates in response to the rotational drive force of the rotor, causing the writing lead to rotate (Patent Document 1).

[0003] In general, in a mechanical pencil configured to rotate the writing lead, a clearance based on manufacturing tolerances exists between the inner surface of the front end of the barrel and the outer surface of the slider due to the rotation and axial movement of the slider. However, the presence of the clearance can cause the slider to wobble in the radial direction perpendicular to the central axis of the mechanical pencil. Depending on the user, the radial wobble of the slider during writing may be bothersome as the tip of the writing lead wobble. In addition, the radial wobble of the slider may cause the slider to collide with the barrel, resulting in an unpleasant impact sound.

[0004] In the mechanical pencil described in Patent Document 1, rattling is reduced by implanting a large number of short fibers on the inner surface of the front end of the barrel or on the outer surface of the slider. In other words, the large number of short fibers reduces the movement of the slider relative to the barrel, and prevents or buffers collisions between the slider and the barrel. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2013-132843 A Summary of the Invention [Problem to be solved by the invention]

[0006] In the mechanical pencil described in Patent Document 1, there is a risk that the short fibers will wear out or fall off and decrease over time or with repeated use. In addition, if a user has a habit of always holding the pencil in the same position while writing, and only short fibers in specific locations are repeatedly subjected to load, there is a risk that the short fibers provided around the entire circumference will wear out or decrease unevenly. If the short fibers decrease or wear out, the effect of reducing rattling will also decrease.

[0007] An object of the present invention is to provide a mechanical pencil that is configured to reduce radial wobble of the writing lead. [Means for solving the problem]

[0008] According to one aspect of the present invention, there is provided a mechanical pencil comprising a rotating member having a barrel, a chuck unit capable of gripping and releasing a writing lead, and a slider equipped with a holding portion, the rotating member having a portion protruding from the front end of the barrel, and a rotor connected to the rotating member, the rotating drive mechanism rotating the rotor in one direction in response to an axial backward movement due to writing pressure applied to the writing lead gripped by the chuck unit and an axial forward movement due to the release of the writing pressure, the rotating member being configured to rotate the writing lead gripped by the chuck unit by receiving the rotational drive force of the rotor, and a viscous fluid being applied between the inner surface of the front end of the barrel and the outer surface of the holding portion.

[0009] The barrel may have a front barrel including the front end portion and detachable from the barrel, and the retaining portion may be configured to come off the rotating member together with the front barrel when the front barrel is removed from the barrel. The rotating member may further have a cylindrical sleeve including the retaining portion and detachable from the slider. The front end portion of the sleeve may be tapered or formed with a smaller diameter than the rear portion. The rear end portion of the sleeve may be provided with an annular flange portion. At least one recess may be provided in the front end surface of the flange portion. A locking portion that locks the retaining portion against retraction may be provided within the front barrel. The locking portion may be a separate member from the front barrel. Effect of the Invention

[0010] According to the aspects of the present invention, a common effect is achieved of providing a mechanical pencil configured to reduce rattling of the writing lead in the radial direction. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a vertical sectional view of a mechanical pencil according to a first embodiment of the present invention. [Diagram 2] FIG. 2 is an enlarged cross-sectional view of the front end of the mechanical pencil of FIG. [Diagram 3] FIG. 3 is an enlarged cross-sectional view of the central portion of the mechanical pencil of FIG. [Figure 4] FIG. 4 is a schematic diagram illustrating the rotational drive of the rotor of the rotational drive mechanism. [Diagram 5] FIG. 5 is a schematic diagram illustrating the rotational drive of the rotor, following FIG. [Figure 6] FIG. 6 is a perspective view of a sleeve of the mechanical pencil of FIG. [Figure 7] FIG. 7 is a front view of the sleeve of FIG. [Figure 8] FIG. 8 is a longitudinal sectional view of the sleeve of FIG. [Figure 9] FIG. 9 is a perspective view of another sleeve. [Figure 10] 10 is an enlarged cross-sectional view of the front end portion for explaining the knocking operation of the mechanical pencil of FIG. 1 in stages. [Figure 11] FIG. 11 is a partially enlarged cross-sectional view of the mechanical pencil of FIG. 1 with the front shaft removed. [Figure 12] FIG. 12 is a partial exploded perspective view of a mechanical pencil according to a second embodiment of the present invention. [Figure 13] 13 is an enlarged cross-sectional view of the front end of the mechanical pencil of FIG. [Figure 14] FIG. 14 is a partially enlarged cross-sectional view of the mechanical pencil of FIG. 11 with the tip member removed. [Figure 15] FIG. 15 is an enlarged cross-sectional view of a front end portion of a mechanical pencil according to a third embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Corresponding components are designated by common reference numerals throughout the drawings.

[0013] FIG. 1 is a vertical cross-sectional view of a mechanical pencil 1 according to a first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a front end portion of the mechanical pencil 1 of FIG.

[0014] The mechanical pencil 1 has a front shaft 2, a rear shaft 3 connected to the front shaft 2, an inner tube 4 fitted to the inner surface of the rear end of the rear shaft 3 and equipped with a clip, and a tip member 6 screwed to the inner surface of the front end of the front shaft 2. The front shaft 2, the rear shaft 3, and the tip member 6 constitute a barrel 5. The barrel 5 may be collectively referred to as the barrel 5 including the inner tube 4. The tip member 6 may be integrally formed with the front shaft 2. The tip member 6, or the front shaft 2 when the tip member 6 is integrally formed, constitutes a tip shaft. In this case, the tip shaft is detachable from the barrel 5. The mechanical pencil 1 is configured such that a writing core (not shown) protrudes from the tip of the barrel 5. In this specification, in the axial direction of the mechanical pencil 1, the writing core side is defined as the "front" side, and the opposite side to the writing core side is defined as the "rear" side.

[0015] The front barrel 2, the rear barrel 3 and the inner cylinder 4 are cylindrical members formed with approximately the same outer diameter. The tip member 6 is a cylindrical member formed in an approximately tapered shape tapering toward the front. Inside the front end of the barrel 5, specifically inside the front end of the tip member 6, a slider 7 having a tip pipe 15 that guides the writing lead is arranged so as to be slidable in the axial direction and rotatable about the axis. A sleeve 50 is loosely fitted onto the outer surface of the slider 7. A locking ring 60 is fitted onto the inner surface of the tip member 6 behind the sleeve 50 so as to surround the slider 7.

[0016] The front axle 2 and the rear axle 3 are connected via a cylindrical support member 32. That is, a male thread is formed on the outer surface of the support member 32, and a female thread is formed on the inner surface of the rear end of the front axle 2 and the inner surface of the front end of the rear axle 3. The female thread on the rear end of the front axle 2 screws into the male thread on the front end of the support member 32, and the female thread on the front end of the rear axle 3 screws into the male thread on the rear end of the support member 32. As a result, the front axle 2 and the rear axle 3 are connected. An annular support protrusion 32a that protrudes radially inward is formed on the inner surface at the rear of the support member 32.

[0017] The slider 7 is formed in a cylindrical shape with an outer diameter that tapers in stages toward the front. The front end of the slider 7, together with the tip pipe 15, protrudes from the front end of the barrel 5, i.e., the tip member 6. Alternatively, only the tip pipe 15 may protrude from the front end of the barrel 5. A retaining chuck 8 with a through hole formed in the center is disposed inside the slider 7 behind the tip pipe 15. The through hole of the retaining chuck 8 comes into sliding contact with the outer surface of the writing lead, and acts to temporarily hold the writing lead.

[0018] A cylindrical relay member 9 is screwed to the rear end of the slider 7. An annular engagement protrusion 9a is provided on the outer surface of the rear of the relay member 9. A chuck unit 10 for gripping a writing lead and a lead case 13 are arranged inside the slider 7 and the relay member 9. The chuck unit 10 has a chuck main body 11 and a fastener 12 formed in a cylindrical shape so as to surround the front end of the chuck main body 11. At least the front half of the chuck main body 11 is divided into three chuck pieces 11a along the axial direction, and a through hole for the writing lead is formed along the central axis. Each of the chuck pieces 11a is formed so that the front ends are spaced apart from each other. The lead case 13 is formed in a cylindrical shape, and a writing lead is accommodated inside. The rear end of the chuck main body 11 is inserted into the front end of the lead case 13 and fitted therein.

[0019] The coil spring 14 is disposed so as to surround the chuck body 11. The front end of the coil spring 14 is supported by a step formed on the inner surface of the relay member 9, and the rear end of the coil spring 14 abuts against the front end surface of the lead case 13. Therefore, the coil spring 14 biases the chuck body 11 and the lead case 13 rearward. The chuck body 11 biased rearward is accommodated in the fastener 12, so that the front ends approach each other and the writing lead can be maintained in a gripped state. In addition, when writing pressure is applied to the writing lead, the chuck body 11 moves back further and is accommodated in the fastener 12, and the writing lead is gripped by the chuck body 11. This prevents the writing lead from moving back.

[0020] The outer surface of the fastener 12 fits into the inner surface of the front end portion of the relay member 9. Therefore, the slider 7, the relay member 9 and the chuck unit 10 are movable in the axial direction within the barrel 5. The rear end portion of the relay member 9 is connected to a rotation drive mechanism 30, which will be described later.

[0021] A cylindrical knock member 20 is provided at the rear end of the barrel 5, specifically at the rear end of the inner barrel 4, so as to be movable back and forth relative to the barrel 5. The knock member 20 is biased rearward by a coil spring 21. The lead case 13 is inserted inside the front end of the knock member 20. An eraser 22 is removably attached inside the rear end of the knock member 20. A knock cover 23 is removably attached to the outer surface of the rear end of the knock member 20 to protect the eraser 22 from dirt and the like.

[0022] By performing a knock operation to press the knock member 20 or the knock cover 23 forward, the lead case 13 advances. This causes the chuck body 11 to be pushed forward and escape from the fastener 12. Accordingly, the writing lead held by the chuck body 11 also advances, and the chuck body 11 releases the writing lead. In short, the chuck unit 10 acts to feed the writing lead from the tip pipe 15 by being able to hold and release the writing lead. When the pressure caused by the knock operation is released, the knock member 20 retreats and returns to its original position due to the biasing force of the coil spring 21. At this time, the chuck body 11 retreats due to the biasing force of the coil spring 14. On the other hand, the writing lead is held by the holding chuck 8 arranged in the slider 7. As a result, the writing lead is fed out from the tip pipe 15, and the writing lead can be fed out a predetermined amount each time the knock operation is repeated. The chuck unit 10 may be another chuck unit, for example, a ball chuck.

[0023] 3 is an enlarged cross-sectional view of the center portion of the mechanical pencil 1 of FIG. 1. The rotation drive mechanism 30 is disposed in the internal space of the rear shaft 3. The rotation drive mechanism 30 is connected to the rear end of the relay member 9. The lead case 13 passes through the interior of the relay member 9 and the rotation drive mechanism 30 and is spaced apart from the rotation drive mechanism 30. The rotation drive mechanism 30 is biased rearward by the shaft spring 31. That is, the front end of the shaft spring 31 is supported by the support protrusion 32a of the support member 32, and the rear end of the shaft spring 31 is supported by the front end face of the rotation drive mechanism 30, so that the rotation drive mechanism 30 is biased rearward.

[0024] The rotation drive mechanism 30 has a rotor 40 formed in a cylindrical shape, an upper cam forming member 41 which is a first cam forming member formed in a cylindrical shape, a lower cam forming member 42 which is a second cam forming member formed in a cylindrical shape, a cylinder member 43 which is formed in a cylindrical shape, a torque canceller 44 which is also formed in a cylindrical shape, and a coil-shaped cushion spring 45. The rotation drive mechanism 30 is a unit formed by integrating these members.

[0025] The outer surface of the rear end of relay member 9 is fitted onto the inner surface of the front end of rotor 40. The rotor 40 has a flange-shaped portion with a slightly larger diameter near the front end, with a first cam surface 40a formed on the rear end surface of said portion and a second cam surface 40b formed on the front end surface of said portion.

[0026] The upper cam forming member 41 rotatably surrounds the rotor 40 behind the first cam surface 40a of the rotor 40. The lower cam forming member 42 fits onto the outer surface of the front end portion of the upper cam forming member 41. A first fixed cam surface 41a is formed on the front end surface of the upper cam forming member 41 facing the first cam surface 40a of the rotor 40. A second fixed cam surface 42a is formed on the inner surface of the front end portion of the lower cam forming member 42 facing the second cam surface 40b of the rotor 40.

[0027] A cylindrically shaped cylinder member 43 is fitted onto the outer surface of the rear end of the upper cam forming member 41. An insertion hole 43a through which the lead case 13 can be inserted is formed in the rear end of the cylinder member 43. A cylindrically shaped torque canceller 44 that is movable in the axial direction is disposed within the cylinder member 43. A cushion spring 45 is disposed between the inner surface of the front end of the torque canceller 44 and the inner surface of the rear end of the cylinder member 43. The cushion spring 45 urges the rotor 40 forward via the torque canceller 44.

[0028] Here, the relay member 9 transmits the backward and forward movements (cushioning movement) of the writing lead based on the writing action to the rotation drive mechanism 30, i.e., the rotor 40, and also transmits the rotational motion of the rotor 40 in the rotation drive mechanism 30 caused by the cushioning movement to the chuck unit 10 holding the writing lead. Therefore, the rotation of the relay member 9 also rotates the writing lead held by the chuck unit 10.

[0029] When the mechanical pencil 1 is not being used for writing, i.e., when no writing pressure is being applied to the writing lead, the rotor 40 is positioned forward by the urging force of the cushion spring 45 via the torque canceller 44. Therefore, the second cam surface 40b of the rotor 40 abuts against the second fixed cam surface 42a and is brought into an engaged state. When the mechanical pencil 1 is used for writing, i.e., when writing pressure is being applied to the writing lead, the chuck unit 10 moves backward against the urging force of the cushion spring 45, and the rotor 40 also moves backward accordingly. Therefore, the first cam surface 40a of the rotor 40 abuts against the first fixed cam surface 41a and is brought into an engaged state. The writing lead and the rotor 40 move forward, backward, or rotate together.

[0030] Fig. 4 is a schematic diagram for explaining the rotational drive of the rotor 40 of the rotational drive mechanism 30, and Fig. 5 is a schematic diagram for explaining the rotational drive of the rotor 40 subsequent to Fig. 4. In Figs. 4 and 5, a first cam surface 40a having a continuous sawtooth shape along the circumferential direction is formed in an annular shape on the rear end surface, which is the upper surface of the rotor 40, and a second cam surface 40b having a continuous sawtooth shape along the circumferential direction is formed in an annular shape on the front end surface, which is the lower surface of the rotor 40.

[0031] A first fixed cam surface 41a having a continuous sawtooth shape along the circumferential direction is also formed on an annular end face of the upper cam forming member 41 facing the first cam surface 40a of the rotor 40, and a second fixed cam surface 42a having a continuous sawtooth shape along the circumferential direction is also formed on an annular end face of the lower cam forming member 42 facing the second cam surface 40b of the rotor 40. The cam surfaces of the first cam surface 40a and the second cam surface 40b formed on the rotor 40 and the cam surfaces of the first fixed cam surface 41a formed on the upper cam forming member 41 and the second fixed cam surface 42a formed on the lower cam forming member 42 are formed so that the pitches are substantially the same.

[0032] 4(A) shows the relationship between the advanced rotor 40, the upper cam forming member 41, and the lower cam forming member 42 when no writing pressure is applied to the writing lead. In this state, the second cam surface 40b formed on the rotor 40 abuts against the second fixed cam surface 42a of the lower cam forming member 42 by the biasing force of the cushion spring 45. At this time, the first cam surface 40a of the rotor 40 and the first fixed cam surface 41a of the upper cam forming member 41 are set to be shifted by half a phase (half a pitch) with respect to one tooth of the cam in the axial direction.

[0033] 4(B) shows the initial state in which writing pressure is applied to the writing lead for writing with the mechanical pencil 1. In this state, the rotor 40 retracts by contracting the cushion spring 45 as the chuck unit 10 retracts. As a result, the rotor 40 moves toward the upper cam forming member 41 and comes into contact with the first fixed cam surface 41a.

[0034] 4(C) shows a state in which further writing pressure is applied to the writing core, causing the rotor 40 to slide back while abutting against the first fixed cam surface 41a of the upper cam forming member 41. In other words, the rotor 40 receives a rotational drive equivalent to a half phase (half pitch) of one tooth of the first cam surface 40a. In this state, the first cam surface 40a of the rotor 40 meshes with the first fixed cam surface 41a of the upper cam forming member 41.

[0035] 4 and 5, a circle drawn in the center of the rotor 40 indicates the amount of rotational movement of the rotor 40. In the state shown in Fig. 4(C), the second cam surface 40b of the rotor 40 and the second fixed cam surface 42a of the lower cam forming member 42 are set to have a relationship shifted by half a phase (half a pitch) with respect to one tooth of the cam in the axial direction.

[0036] 5(D) shows the initial state in which writing with the mechanical pencil 1 has finished and the writing pressure on the writing lead has been released. In this state, the rotor 40 advances due to the biasing force of the cushion spring 45. As a result, the rotor 40 moves toward the lower cam forming member 42 and comes into contact with the second fixed cam surface 42a.

[0037] 5(E) shows a state in which the rotor 40 advances while sliding against the second fixed cam surface 42a of the lower cam forming member 42 due to the biasing force of the cushion spring 45. That is, the rotor 40 is again subjected to a rotational drive equivalent to a half phase (half pitch) of one tooth of the second cam surface 40b. In this state, the second cam surface 40b of the rotor 40 is engaged with the second fixed cam surface 42a of the lower cam forming member 42.

[0038] 4 and 5, as the rotor 40 reciprocates in the axial direction when subjected to writing pressure, that is, moves back and forth, the rotor 40 is rotationally driven by one tooth (one pitch) of the first cam surface 40a and the second cam surface 40b, and the writing lead held by the rotor 40 is also rotationally driven via the chuck unit 10. Therefore, the rotor 40 undergoes a rotational motion corresponding to one tooth of the cam by one back and forth movement of the rotor 40 in the axial direction due to writing, and by repeating this, the writing lead is sequentially rotationally driven. Therefore, it is possible to prevent uneven wear of the writing lead as writing proceeds, and to prevent a large change in the thickness and darkness of the drawn lines.

[0039] The torque canceller 44, which pushes the rotor 40 forward by receiving the biasing force of the cushion spring 45, generates a slip between its front end face and the rear end face of the rotor 40, preventing the rotational motion of the rotor 40 from being transmitted to the cushion spring 45. In other words, the torque canceller 44 prevents the rotational motion of the rotor 40 from being transmitted to the cushion spring 45, thereby preventing the cushion spring 45 from twisting back (torque) that would impede the rotational motion of the rotor 40.

[0040] As described above, the mechanical pencil 1 comprises a chuck unit 10 capable of gripping and releasing a writing lead, a rotating member having an intermediate member 9, a slider 7, and a tip pipe 15 surrounding the chuck unit 10, and a rotation drive mechanism 30 having a rotor 40, which drives the rotor 40 to rotate in one direction in response to an axial backward movement due to writing pressure applied to the writing lead gripped by the chuck unit 10 and an axial forward movement due to the release of the writing pressure. The rotor 40 is connected to the rear end of the intermediate member 9, and the slider 7 is detachably connected to the front end of the intermediate member 9, and the rotating member is configured to rotate by receiving the rotational drive force of the rotor 40 and thereby rotate the writing lead gripped by the chuck unit 10.

[0041] 6 is a perspective view of the sleeve 50 of the mechanical pencil 1 of FIG. 1, FIG. 7 is a front view of the sleeve 50 of FIG. 6, and FIG. 8 is a vertical cross-sectional view of the sleeve 50 of FIG.

[0042] The sleeve 50 is a cylindrical member. The inner surface of the sleeve 50 is formed into a cylindrical surface shape with approximately the same inner diameter along the axial direction. The sleeve 50 has a sleeve body 51 formed into a cylindrical shape with approximately the same outer diameter, a flange portion 52 formed on the outer surface of the rear end portion of the sleeve body 51, a first tapered portion 53 provided in front of the sleeve body 51, a second tapered portion 54 provided in front of the first tapered portion 53, and three protrusions 55 provided on the inner surface of the front end portion of the sleeve 50. The three protrusions 55 are protrusions with convex curved surfaces. The three protrusions 55 are arranged at equal intervals along the circumferential direction.

[0043] The first taper portion 53 and the second taper portion 54 are tapered toward the front. The outer diameter of the rear end of the first taper portion 53 is slightly smaller than the outer diameter of the sleeve body 51. Therefore, the first taper portion 53 is connected to the sleeve body 51 via a ring-shaped step 51a facing forward. The rear end of the second taper portion 54 is connected to the front end of the first taper portion 53. The taper angle of the second taper portion 54 is larger than the taper angle of the first taper portion 53. The outer surface of the flange portion 52 is formed with a third taper portion 52a tapered toward the front. The sleeve 50 may extend the sleeve body 51 without having the first taper portion 53 and the second taper portion 54. The sleeve 50 may not have the third taper portion 52a.

[0044] The flange portion 52 is provided with four recesses 56 at equal intervals along the circumferential direction. Each of the recesses 56 has a bottom surface 56a perpendicular to the central axis and a curved side surface 56b perpendicular to the bottom surface 56a by cutting out the front periphery of the flange portion 52. A flat portion 57 is provided in a part of the flange portion 52 as if scraped off along a plane parallel to the axial direction. The sleeve 50 may have at least one recess 56 or may not have any recesses 56.

[0045] As shown in FIG. 2, the sleeve 50 is fitted to the outer surface of the slider 7 near the front end. Specifically, a slider body 7a having approximately the same outer diameter is formed near the front end of the slider 7. The inner diameter of the sleeve 50 is the same as the outer diameter of the slider body 7a of the slider 7 or is slightly larger than the outer diameter of the slider body 7a of the slider 7. On the other hand, the diameter of the inscribed circle of the three protrusions 55 of the sleeve 50 is slightly smaller than the outer diameter of the slider body 7a of the slider 7. Therefore, the sleeve 50 is loosely fitted to the slider 7 by the three protrusions 55 engaging with the slider body 7a of the slider 7 while elastically deforming. Thereby, the sleeve 50 can move forward, backward, or rotate integrally with the slider 7. Therefore, the sleeve 50 may be referred to as a rotating member. The sleeve 50 may be configured in any way as long as it can be loosely fitted to the slider 7.

[0046] For example, the sleeve may be configured as a sleeve 150 shown in FIG. 9. FIG. 9 is a perspective view of another sleeve 150. The sleeve 150 has the same basic outer shape as the sleeve 50 described above, and differs from the sleeve 50 only in the shape of the inner surface. The inner surface of the sleeve 150 is provided with three locking surfaces 158 that are flat along the axial direction so as to thicken the cylindrical inner surface. The three locking surfaces 158 are disposed at equal intervals along the circumferential direction. Three protrusions 155 are provided on the inner surface of the front end of the sleeve 150 and between adjacent locking surfaces 158. The three protrusions 155 are convex curved protrusions. The three protrusions 155 are disposed at equal intervals along the circumferential direction.

[0047] The sleeve 150 is also fitted to the outer surface of the slider 7 near the front end, similarly to the sleeve 50 described above. The diameter of the inscribed circle of the three locking surfaces 158 of the sleeve 150 is formed to be the same as the outer diameter of the slider body 7a of the slider 7 or slightly smaller than the outer diameter of the slider body 7a of the slider 7. On the other hand, the diameter of the inscribed circle of the three projections 155 of the sleeve 150 is formed to be slightly smaller than the outer diameter of the slider body 7a of the slider 7. Therefore, the sleeve 150 is loosely fitted to the slider 7 by the three projections 155 or the three locking surfaces 158 being engaged with the slider body 7a of the slider 7 while being elastically deformed. Thereby, the sleeve 150 can move forward, backward, or rotate integrally with the slider 7. Therefore, the sleeve 150 may also be called a rotating member.

[0048] Referring again to FIG. 2, the locking ring 60 is a series of annular members. The cross section of the locking ring 60 is approximately square. The outer diameter of the locking ring 60 is slightly larger than the inner diameter of the corresponding prong member 6. Thus, the locking ring 60 fits against the inner surface of the prong member 6 behind the sleeve 50. The inner diameter of the locking ring 60 is larger than the outer diameter of the corresponding slider 7, and the locking ring 60 surrounds the slider 7.

[0049] The inner surface of the front end of the tip member 6 is provided with a support surface 6a formed in a cylindrical shape with approximately the same inner diameter along the axial direction. The rotation and axial movement of the rotating member rotated by the rotation drive mechanism 30, specifically, the slider 7 via the relay member 9 connected to the rotor 40 of the rotation drive mechanism 30, and further the sleeve 50 fitted to the slider 7, are directly or indirectly supported by the support surface 6a of the tip member 6. In detail, the support surface 6a of the tip member 6 not only contacts and directly supports the sleeve 50, but also indirectly supports the sleeve 50 via a viscous fluid 70 described later.

[0050] A viscous fluid 70 is applied between the support surface 6a of the tip member 6 and the outer surface of the sleeve 50, specifically the outer surface of the sleeve body 51. That is, the viscous fluid 70 is applied at least over the contact surface between the support surface 6a and the outer surface of the sleeve 50. At least a part of the outer surface of the sleeve body 51 of the sleeve 50 constitutes a holding portion in that it holds the viscous fluid 70. Furthermore, since the sleeve 50 is fitted into the slider 7, it can be said that the slider 7 has a holding portion. The viscous fluid 70 is silicone oil, silicone grease, or the like, and for example, silicone grease G501 manufactured by Shin-Etsu Chemical Co., Ltd. is used.

[0051] FIG. 10 is an enlarged cross-sectional view of the front end for explaining the knock operation of the mechanical pencil 1 of FIG. 1 in stages. In FIG. 10, the writing lead is omitted. FIG. 10(A) shows the state before the knock operation is performed. From the state shown in FIG. 10(A), the knock member 20 or the knock cover 23 is pressed forward to start the knock operation. The knock operation advances the relay member 9 together with the lead case 13. The advance of the relay member 9 is restricted by the engagement protrusion 9a of the relay member 9, which is disposed in the central portion of the mechanical pencil 1, engaging with the support protrusion 32a of the support member 32. At this time, the sleeve 50, which advances together with the relay member 9, is restricted by the engagement of the flange portion 52 with the engagement surface 6b facing backward inside the tip member 6 (FIG. 10(B)).

[0052] When the knock member 20 or the knock cover 23 is further pressed forward by the knock operation, the chuck body 11 is pushed forward while gripping the writing lead (not shown) as described above (FIG. 10(C)). When the pressure by the knock operation is released, the chuck body 11 retreats due to the urging force of the coil spring 14, and the writing lead is advanced. The relay member 9, the slider 7, the sleeve 50, etc. also retreat and return to their original positions (FIG. 10(A)). Note that, when a writing load is applied to the writing lead during a writing operation from the state shown in FIG. 10(A), the relay member 9, the slider 7, and the sleeve 50 retreat slightly as a unit as a part of the cushioning action (FIG. 10(D)). When the relay member 9 retreats, the rotor 40 receives a rotational drive equivalent to a half phase (half pitch) of one tooth of the first cam surface 40a and rotates, and therefore the slider 7 and the sleeve 50 also rotate together around the central axis. In addition, it is preferable that the fitting force between the slider 7 and the sleeve 50, in other words, the force required to remove the sleeve 50 from the slider 7, is less than the spring load of the coil spring 14 that biases the chuck body 11 and the lead case 13 backward.

[0053] As described above, generally, in a mechanical pencil configured with a rotating writing lead, due to the rotation and axial movement of the slider, there is a clearance based on manufacturing tolerances, etc. between the inner surface of the front end of the barrel and the outer surface of the slider.

[0054] In the mechanical pencil 1, the clearance is filled with the viscous fluid 70. Therefore, even if radial rattle occurs in the tip of the writing lead and the sleeve 50, the rattle is mitigated by the viscosity of the viscous fluid 70. Furthermore, even if radial rattle causes the sleeve 50 to collide with the inner surface of the barrel 5, the collision is mitigated by the viscosity of the viscous fluid 70, and the collision sound is also minimized.

[0055] Furthermore, the viscous fluid 70 is effective not only against radial rattles, but also against the cushioning action of the rotation drive mechanism 30. In other words, in a conventional rotation drive mechanism required to rotate a writing lead, the minute backward and forward movements (cushioning actions) of the writing lead based on the writing action as described above may be bothersome to some users as rattles in the axial direction. With the mechanical pencil 1, the viscous fluid 70 has the effect of mitigating rattles in the axial direction as well as rattles in the radial direction.

[0056] In short, by disposing the viscous fluid 70 between the inner surface of the front end of the barrel 5 and the sleeve body 51 of the sleeve 50, which is a retaining part included in the rotating member, the rattling of the writing lead, the slider 7, and the sleeve 50 in the radial and axial directions is mitigated. As a result, the user can feel a good writing feeling, a heavy feeling, or a luxurious feeling when writing with the mechanical pencil 1.

[0057] The viscous fluid 70 is selected so as to have both high viscosity so as not to drip outward even when various posture changes occur during writing or transportation, and low viscosity so as not to impede the rotation and axial movement of the rotating member. In other words, low viscosity so as not to impede the rotation and axial movement of the rotating member means that if the viscosity is too high, the axial movement of the rotating member is not performed properly, and as a result, the cams of the rotor 40, the upper cam forming member 41, and the lower cam forming member 42 do not cooperate properly, and the rotating member cannot be rotated properly. Therefore, the viscous fluid 70 has low viscosity so as not to impede the rotation and axial movement of the rotating member.

[0058] Generally, when the lead breaks inside the mechanical pencil, specifically between the retaining chuck and the chuck unit, due to the mechanical pencil being dropped or the like, the broken lead may close the retaining chuck, making it impossible to advance the lead. In this case, it is necessary to disassemble the mechanical pencil in order to remove the lead between the retaining chuck and the chuck unit.

[0059] Fig. 11 is a partially enlarged cross-sectional view of the mechanical pencil 1 in Fig. 1 with the front shaft 2 removed. For example, in order to access between the holding chuck 8 and the chuck unit 10 to remove a broken writing lead, it is first necessary to remove the front shaft 2 or the tip member 6 from the mechanical pencil 1, and then remove the slider 7 that screws into the relay member 9. As shown in Fig. 11, when the front shaft 2 is removed, the tip member 6 that screws into the front end of the front shaft 2 and the sleeve 50 disposed inside the tip member 6 are removed together.

[0060] That is, when the front shaft 2 is removed, the sleeve 50 loosely fitted to the slider 7 is removed from the slider 7 by abutting and locking against the locking ring 60, and remains in the tip member 6. Similarly, when the tip member 6 is removed from the front shaft 2 while the front shaft 2 is still connected to the rear shaft 3, the sleeve 50 abuts and locks against the locking ring 60, and remains in the tip member 6. In detail, when the front shaft 2 or the tip member 6 is removed, the sleeve 50 retreats together with the slider 7 relative to the tip member 6, but the rear end surface of the sleeve 50 abuts against the front end surface of the locking ring 60, and the sleeve 50 is removed from the slider 7. Therefore, the fitting force of the sleeve 50 to the slider 7 is smaller than the fitting force of the locking ring 60 to the tip member 6.

[0061] The locking ring 60 constitutes a locking portion that locks the sleeve 50 including the retaining portion from retracting. The locking ring 60 is a continuous annular member, but may be a C-shaped annular member with some parts spaced apart, and may have a circular or rectangular cross-sectional shape. In addition to the separate locking ring 60, the locking portion may be a locking protrusion integrally provided on the inner surface of the tip member 6. In this case, the locking protrusion may be provided annularly on the inner surface of the tip member 6, and may be a single protrusion, or multiple protrusions arranged along the circumferential direction.

[0062] With the rear end surface of the sleeve 50 in contact with the front end surface of the locking ring 60, the front end surface of the sleeve 50 is located at the same position as or behind the front end surface of the tip member 6 in the axial direction. In other words, the sleeve 50 in this state does not protrude from the tip member 6. Therefore, even if the front shaft 2 or the tip member 6 with the sleeve 50 remaining therein is dropped from the front end onto the ground such as a floor surface, the sleeve 50 will not collide with the ground. Therefore, no force that would cause the sleeve 50 and further the locking ring 60 to be removed backward acts on the sleeve 50. In other words, the axial length of the sleeve 50 and the fitting position of the locking ring 60 in the axial direction of the tip member 6 are determined so that the sleeve 50 does not protrude from the front end of the barrel 5 at the retreat limit.

[0063] As described above, the viscous fluid 70 is applied between the support surface 6a of the tip member 6 and the outer surface of the sleeve 50, but since the sleeve 50 remains in the tip member 6, the viscous fluid 70 is held in the tip member 6 and is not applied to the outer surface of the slider 7 or flows out to the outside. Therefore, even if the mechanical pencil 1 is disassembled, such as when removing a broken writing lead, the viscous fluid 70 does not stain the hands or clothes. In addition, when assembling the mechanical pencil 1, the slider 7 attached to the relay member 9 can be easily refitted by inserting it into the sleeve 50.

[0064] As described above, the first tapered portion 53 having a smaller diameter is provided in front of the sleeve body 51 of the sleeve 50 via the step 51a, and the second tapered portion 54 is provided further in front of it. By providing the step 51a and the first tapered portion 53, and further by the surface tension of the viscous fluid 70, the viscous fluid 70 applied to the outer surface of the sleeve body 51 is prevented from diffusing beyond the step 51a to the first tapered portion 53 and further to the second tapered portion 54. Furthermore, by providing the step 51a, the first tapered portion 53, and further the second tapered portion 54, even when assembling the mechanical pencil 1 after removing a broken writing lead, the viscous fluid 70 is prevented from being applied to unnecessary parts of the sleeve 50. The flange portion 52 of the sleeve 50 is provided with four recesses 56. The sleeve 50 has the recess 56, which temporarily stores the viscous fluid 70 that flows with the relative movement of the sleeve 50 with respect to the tip member 6, thereby preventing the viscous fluid 70 from diffusing to the outside, etc. The shape of the recess 56 may be arbitrarily configured as long as it is capable of temporarily storing the viscous fluid 70.

[0065] According to the mechanical pencil 1, the amount of the viscous fluid 70 can be adjusted according to the clearance, so the tolerance of the dimensions between the parts is high. Even if the clearance is biased, the fluidity of the viscous fluid 70 fills the clearance according to the bias. Since the viscous fluid 70 is present during the rotation and radial and axial movements of the slider 7 and the sleeve 50 relative to the shaft tube 5, i.e., the tip member 6, there is no wear due to friction between the parts, and the mechanical pencil 1 can be used for a long time. Since the user does not come into contact with the viscous fluid 70, the viscous fluid 70 is unlikely to deteriorate during long-term use, and the same performance and effect can be maintained for a long time.

[0066] Fig. 12 is a partially exploded perspective view of a mechanical pencil 100 according to a second embodiment of the present invention, Fig. 13 is an enlarged cross-sectional view of the front end of the mechanical pencil 100 of Fig. 11, and Fig. 14 is an enlarged cross-sectional view of the mechanical pencil 100 of Fig. 11 with the tip member 106 removed. The mechanical pencil 100 differs from the mechanical pencil 1 according to the first embodiment in that it does not have a sleeve and in the shapes of the tip member, slider, and relay member. The mechanical pencil 100 has a tip member 106, a slider 180, and a relay member 190.

[0067] An annular protrusion, that is, a locking portion 106c, is provided on the inner surface of the tip member 106, instead of the locking ring 60 of the mechanical pencil 1 according to the first embodiment. A support surface 106a formed in a cylindrical shape with approximately the same inner diameter along the axial direction is provided on the inner surface of the front end portion of the tip member 6.

[0068] The slider 180 of the mechanical pencil 100 is formed in a cylindrical shape with an outer diameter that tapers in a step toward the front. The slider 180 has a slider body 181 formed in a cylindrical shape with approximately the same outer diameter near the front end, a flange portion 182 formed on the outer surface of the rear end of the slider body 181, and a slider rear portion 183 with a larger diameter provided behind the flange portion 182. Two rectangular cutout portions 184 are provided at the rear end of the slider 180, i.e., the rear end of the slider rear portion 183. The two cutout portions 184 are provided on opposite sides of the central axis of the slider 180. The front end of the slider 180, together with the tip pipe 15, protrudes from the front end of the shaft tube 5, i.e., the tip member 106. It is to be noted that only the tip pipe 15 may protrude from the front end of the shaft tube 5.

[0069] The relay member 190 has two restricting protrusions 191 provided on a side surface near the front end, two claw portions 192 extending forward beyond the chuck unit 10, and a claw protrusion 193 provided on the inner surface of the front end of each of the claw portions 192. The two restricting protrusions 191 are provided on opposite sides to each other with respect to the central axis of the relay member 190. Similarly, the two claw portions 192 are provided on opposite sides to each other with respect to the central axis of the relay member 190. The restricting protrusions 191 and the claw portions 192 are aligned in the axial direction, but they do not have to be aligned.

[0070] In the assembled state of the mechanical pencil 100, the restricting protrusion 191 of the relay member 190 is disposed in the corresponding notch 184 of the slider 180. As a result, the slider 180 is locked in the rotational direction relative to the relay member 190, and the slider 180 can rotate integrally with the relay member 190. On the other hand, the restricting protrusion 191 of the relay member 190 is not locked in the axial movement with the corresponding notch 184 of the slider 180. The inner surface of the slider rear part 183 of the slider 180 is loosely fitted to the outer surface of the front end part of the relay member 190. Therefore, the slider 180 can move forward or backward integrally with the relay member 190. The fastener 12, which has been advanced together with the chuck body part 11 by the knock operation, is locked with the claw protrusion 193 of the claw part 192. As a result, the chuck body 11 together with the writing lead can be advanced further relative to the fastener 12, and the writing lead can be advanced.

[0071] A viscous fluid 70 is applied between the support surface 106a of the tip member 106 and the outer surface of the slider 180, specifically, the outer surface of the slider body 181. That is, the viscous fluid 70 is applied at least over the contact surface between the support surface 106a and the outer surface of the slider 180. At least a part of the outer surface of the slider body 181 of the slider 180 constitutes a holding portion in that it holds the viscous fluid 70.

[0072] The mechanical pencil 100 has the viscous fluid 70, and thus has the same effect as the mechanical pencil 1 according to the first embodiment. That is, the radial and axial rattles caused by the clearance between the inner surface of the tip member 106 and the outer surface of the slider 180 can be mitigated.

[0073] In the mechanical pencil 100, in order to access between the holding chuck 8 and the chuck unit 10 to remove the broken writing lead, it is first necessary to remove the front shaft 2 or the tip member 106 from the mechanical pencil 100, and then remove the slider 180 that screws into the relay member 109. As shown in Fig. 14, when the tip member 106 is removed, the slider 180 arranged inside the tip member 6 is also removed together with it.

[0074] That is, the slider 180 loosely fitted to the relay member 190 is removed from the relay member 190 and remains in the relay member 106 when the front shaft 2 or the tip member 106 is removed. In detail, when the tip member 106 is removed, the slider 180 retreats together with the relay member 190 relative to the tip member 106, but the flange portion 182 of the slider 180 and the locking portion 106c of the tip member 106 come into contact with each other, and the slider 180 is removed from the relay member 190.

[0075] At this time, as described above, the restricting protrusion 191 of the relay member 190 does not lock with the corresponding notch portion 184 of the slider 180 in terms of axial movement, and therefore removal of the slider 180 is not hindered. The slider 180 and the relay member 190 may be configured in any manner as long as they are locked in the rotational direction but not in the axial direction. For example, only one restricting protrusion 191 and one notch portion 184 may be provided, or three or more may be provided. Also, the slider may have a groove extending in the axial direction on the outer surface, rather than a notch penetrating the wall thickness.

[0076] By the slider 180 remaining in the tip member 106, the viscous fluid 70 is held within the tip member 106 and does not flow out. Therefore, even if the mechanical pencil 1 is disassembled, for example to remove a broken writing lead, the viscous fluid 70 does not stain the hands or clothes. Furthermore, when assembling the mechanical pencil 1, the relay member 9 can be easily refitted by inserting it into the slider 180.

[0077] According to the mechanical pencil 100, the amount of the viscous fluid 70 can be adjusted according to the clearance, so the tolerance of the dimensions between the parts is high. Even if the clearance is biased, the fluidity of the viscous fluid 70 fills the clearance according to the bias. Since the viscous fluid 70 is present during the rotation and radial and axial movement of the slider 180 relative to the barrel 5, i.e., the tip member 106, there is no wear due to friction between the parts, and the mechanical pencil 100 can be used for a long time. Since the user does not come into contact with the viscous fluid 70, the viscous fluid 70 is unlikely to deteriorate during long-term use, and the same performance and effect can be maintained for a long time.

[0078] In short, according to the mechanical pencil 1 of the first embodiment and the mechanical pencil 100 of the second embodiment, the barrel has a tip shaft, i.e., a front shaft or tip member, that is detachable from the barrel, and the holding portion that holds the viscous fluid 70, i.e., the sleeve 50 or slider 180, is configured to come off the rotating member together with the tip shaft when the tip shaft is removed from the barrel.

[0079] 15 is an enlarged cross-sectional view of the front end of a mechanical pencil 200 according to a third embodiment of the present invention. The mechanical pencil 200 is similar to a conventional mechanical pencil configured to rotate a writing lead, except that it has a viscous fluid 70. The slider 7, relay member 9, chuck unit 10, etc. are substantially the same as those of the mechanical pencil 1 according to the first embodiment. The mechanical pencil 200 does not have a tip member, and the front end of the slider 7 protrudes from the front end of the front shaft 202 equipped with a gripping portion 202a.

[0080] As described above, the slider 7 is formed in a cylindrical shape with an outer diameter tapering in a stepwise manner toward the front. The slider 7 has a slider body 7a formed in a cylindrical shape with approximately the same outer diameter near the front end. The inner surface of the front end of the front shaft 202 is provided with a support surface 202b formed in a cylindrical shape with approximately the same inner diameter along the axial direction.

[0081] A viscous fluid 70 is applied between the support surface 202b of the front shaft 202 and the outer surface of the slider 7, specifically, the outer surface of the slider main body 7a. That is, the viscous fluid 70 is applied at least over the contact surface between the support surface 106a and the outer surface of the slider 7. At least a part of the outer surface of the slider main body 7a of the slider 7 constitutes a holding portion in that it holds the viscous fluid 70.

[0082] The mechanical pencil 200 has the viscous fluid 70, and thus has the same effect as the mechanical pencil 1 according to the first embodiment. That is, the radial and axial rattles caused by the clearance between the inner surface of the front shaft 202 and the outer surface of the slider 7 can be mitigated.

[0083] According to the mechanical pencil 200, the amount of the viscous fluid 70 can be adjusted according to the clearance, so the tolerance of the dimensions between the parts is high. Even if the clearance is biased, the fluidity of the viscous fluid 70 fills the clearance according to the bias. Since the viscous fluid 70 is present during the rotation and radial and axial movement of the slider 7 relative to the shaft tube 5, i.e., the front shaft 202, there is no wear due to friction between the parts, and the mechanical pencil 200 can be used for a long time. Since the user does not come into contact with the viscous fluid 70, the viscous fluid 70 is unlikely to deteriorate during long-term use, and the same performance and effect can be maintained for a long time.

[0084] From the above, the mechanical pencil according to the embodiment described above is a rotating member having a barrel, a chuck unit capable of gripping and releasing a writing lead, and a slider equipped with a holding portion, and is equipped with a rotating member having a portion protruding from the front end of the barrel, and a rotation drive mechanism having a rotor connected to the rotating member, which drives the rotor to rotate in one direction in response to the axial backward movement due to the writing pressure applied to the writing lead gripped by the chuck unit and the axial forward movement due to the release of the writing pressure, and is configured so that the writing lead gripped by the chuck unit rotates when the rotating member rotates in response to the rotational drive force of the rotor, and a viscous fluid is applied between the inner surface of the front end of the barrel and the outer surface of the holding portion. [Explanation of symbols]

[0085] 1 mechanical pencil 2 front axle 3 rear axle 4 Inner cylinder 5 shaft cylinder 6 Tip member 6a Support surface 6b Engagement surface 7 Slider 7a Slider body 8 Holding chuck 9 Intermediate parts 10 Chuck unit 13 Lead case 14 Coil spring 15 Tip pipe 50 Sleeve 51 Sleeve body 51a Step 52 Flange 60 Locking ring 70 Viscous fluid

Claims

1. A shaft cylinder, A rotating member having a chuck unit capable of gripping and releasing a writing lead and a slider having a holding portion, the rotating member being configured so that a portion of the rotating member protrudes from a front end portion of the barrel; a rotation drive mechanism having a rotor connected to the rotating member, which drives the rotor to rotate in one direction in response to an axial retreat movement caused by a writing pressure applied to the writing lead gripped by the chuck unit and an axial advance movement caused by the release of the writing pressure; The rotating member is rotated by receiving the rotational driving force of the rotor, thereby rotating the writing lead held by the chuck unit, A mechanical pencil in which a viscous fluid is applied between the inner surface of the front end of the barrel and the outer surface of the holder.

2. 2. The mechanical pencil according to claim 1, wherein the barrel has a tip shaft that includes the front end and is detachable from the barrel, and the holding portion is configured to come off the rotating member together with the tip shaft when the tip shaft is removed from the barrel.

3. 3. The mechanical pencil according to claim 2, wherein the rotating member further includes a cylindrical sleeve that is provided with the holding portion and is detachable from the slider.

4. 4. The mechanical pencil according to claim 3, wherein the front end of the sleeve is tapered or has a smaller diameter than the rear end.

5. 4. The mechanical pencil according to claim 3, wherein the sleeve has a rear end provided with an annular flange portion.

6. The mechanical pencil according to claim 5, wherein at least one recess is provided on a front end surface of the flange portion.

7. The mechanical pencil according to claim 2 , wherein a locking portion for locking the holding portion against retraction is provided inside the front barrel.

8. The mechanical pencil according to claim 7, wherein the locking portion is a separate member from the front shaft.

Images