Mechanical pencil

Abstract

This mechanical pencil comprises: a shaft cylinder (5); a rotary member including a chuck unit (10), capable of gripping and releasing a writing lead, and a slider including a holding part, the rotary member partly protruding from a front end part of the shaft cylinder; and a rotary drive mechanism (30) which has a rotor (40) connected to the rotary member and which, in response to a backward motion in an axial direction due to a writing pressure received by the writing lead held by the chuck unit and a forward motion in the axial direction due to a release of the writing pressure, rotationally drives the rotor in one direction. The mechanical pencil is configured such that the writing lead gripped by the chuck unit rotates as a result of rotation of the rotary member due to rotational driving force of the rotor. A viscous fluid (70) is provided between an inner surface of the front end part of the shaft cylinder and an outer surface of the holding part.

Description

mechanical pencil

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

[0002] A known mechanical pencil is equipped with a barrel, a rotating member equipped with a chuck unit and slider that can grip and release a writing lead, and a rotation drive mechanism that has a rotor and drives the rotor to rotate in one direction in response to axial backward movement due to writing pressure applied to the writing lead gripped by the chuck unit and axial forward movement due to the release of the writing pressure, and is configured so that the writing lead rotates when the chuck unit rotates due to the rotational drive force of the rotor (Patent Document 1).

[0003] Generally, in mechanical pencils with a rotating lead, a clearance 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, based on manufacturing tolerances, etc. However, the presence of this 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 it causes the tip of the lead to wobble. Furthermore, the radial wobble of the slider may cause the slider to collide with the barrel, resulting in an unpleasant impact noise.

[0004] In the mechanical pencil described in Patent Document 1, rattle 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. That is, 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.

[0005] JP 2013-132843 A

[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 become reduced over time or with repeated use. Furthermore, 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 arranged around the entire circumference will wear out or become reduced unevenly. When the short fibers are reduced or worn out, the rattle-mitigating effect will also be reduced.

[0007] An object of the present invention is to provide a mechanical pencil configured to reduce radial rattle of the writing lead.

[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 rotary drive mechanism rotating the rotor in one direction in response to axial backward movement due to writing pressure applied to the writing lead gripped by the chuck unit and axial forward movement due to the release of writing pressure, the mechanical pencil being configured such that the writing lead gripped by the chuck unit rotates when the rotating member receives 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.

[0009] The barrel may have a front barrel that includes the front end and is 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 that includes the retaining portion and is detachable from the slider. The front end of the sleeve may be tapered or formed with a smaller diameter than the rear end. The rear end of the sleeve may be provided with an annular flange portion. The front end surface of the flange may be provided with at least one recess. The front barrel may have a locking portion that locks the retaining portion against retraction. The locking portion may be a separate member from the front barrel.

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

[0011] FIG. 1 is a longitudinal cross-sectional view of a mechanical pencil according to a first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of the front end of the mechanical pencil of FIG. 1. FIG. 3 is an enlarged cross-sectional view of the central portion of the mechanical pencil of FIG. 1. FIG. 4 is a schematic diagram illustrating the rotational drive of a rotor of a rotation drive mechanism. FIG. 5 is a schematic diagram illustrating the rotational drive of the rotor, subsequent to FIG. 4. FIG. 6 is a perspective view of a sleeve of the mechanical pencil of FIG. 1. FIG. 7 is a front view of the sleeve of FIG. 6. FIG. 8 is a longitudinal cross-sectional view of the sleeve of FIG. 6. FIG. 9 is a perspective view of another sleeve. FIG. 10 is an enlarged cross-sectional view of the front end for explaining the knock operation of the mechanical pencil of FIG. 1 in stages. FIG. 11 is a partially enlarged cross-sectional view of the mechanical pencil of FIG. 1 with the front shaft removed. FIG. 12 is a partially exploded perspective view of a mechanical pencil 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 of FIG. 11. FIG. 14 is a partially enlarged cross-sectional view of the mechanical pencil of FIG. 11 with the tip member removed. FIG. 15 is an enlarged cross-sectional view of the front end portion of a mechanical pencil according to a third embodiment of the present invention.

[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 throughout the drawings are designated by common reference numerals.

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

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

[0015] The front barrel 2, rear barrel 3, and inner tube 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 that tapers 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 its 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, surrounding 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 threadably engages with 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 threadably engages with 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 within 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 threadedly engaged with the rear end of the slider 7. An annular engagement protrusion 9a is provided on the outer surface of the rear portion of the relay member 9. A chuck unit 10 for gripping a writing lead and a lead case 13 are disposed inside the slider 7 and the relay member 9. The chuck unit 10 includes a chuck main body 11 and a cylindrical fastener 12 that surrounds 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. The chuck pieces 11a are formed so that their front ends are spaced apart from each other. The lead case 13 is cylindrical and houses a writing lead. The rear end of the chuck main body 11 is inserted into and fitted into the front end of the lead case 13.

[0019] A coil spring 14 is disposed 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. When the chuck body 11 is biased rearward, its front ends approach each other as it is housed within the fastener 12, allowing it to maintain a grip on the lead. Furthermore, when writing pressure is applied to the lead, the chuck body 11 moves further back and is housed within the fastener 12, and the lead is gripped by the chuck body 11. This prevents the lead from moving backward.

[0020] The outer surface of the fastener 12 is fitted into the inner surface of the front end portion of the relay member 9. Therefore, the slider 7, relay member 9, and 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. A 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 knocking operation that presses the knock member 20 or the knock cover 23 forward, the lead case 13 advances. This pushes the chuck body 11 forward and escapes from the fastener 12. Accordingly, the writing lead held by the chuck body 11 also advances, and the chuck body 11 releases its grip on the writing lead. In short, the chuck unit 10, by being able to grip and release the writing lead, acts to feed the writing lead from the tip pipe 15. When the pressure generated by the knocking operation is released, the knock member 20 retracts and returns to its original position due to the biasing force of the coil spring 21. At this time, the chuck body 11 retracts due to the biasing force of the coil spring 14. Meanwhile, the writing lead is held by the retaining chuck 8 disposed within the slider 7. As a result, the writing lead is fed out from the tip pipe 15, and a predetermined amount of the writing lead can be fed out with each repeated knocking operation. The chuck unit 10 may be another chuck unit, for example, a ball chuck.

[0023] 3 is an enlarged cross-sectional view of the central portion of the mechanical pencil 1 in FIG. 1. The rotation drive mechanism 30 is disposed in the internal space of the rear barrel 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 an axial spring 31. That is, the front end of the axial spring 31 is supported by the support protrusion 32a of the support member 32, and the rear end of the axial spring 31 is supported by the front end surface of the rotation drive mechanism 30, thereby biasing the rotation drive mechanism 30 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 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 fits into the inner surface of the front end of rotor 40. Near the front end of rotor 40, there is a flange-shaped portion with a slightly larger diameter, and a first cam surface 40a is formed on the rear end surface of this portion, and a second cam surface 40b is formed on the front end surface of this 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 is fitted to 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 that faces 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 that faces 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 is formed in the rear end of the cylinder member 43, through which the lead case 13 can be inserted. 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 biases the rotor 40 forward via the torque canceller 44.

[0028] Here, the relay member 9 transmits the retreating and advancing movements (cushioning movements) 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 movement of the rotor 40 in the rotation drive mechanism 30, which is generated by the cushioning movement, to the chuck unit 10, which is 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 not writing with the mechanical pencil 1, i.e., when no writing pressure is being applied to the writing lead, the rotor 40 is positioned forward by the biasing 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 in an engaged state. When writing with the mechanical pencil 1, i.e., when writing pressure is being applied to the writing lead, the chuck unit 10 moves backward against the biasing 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 in an engaged state. The writing lead and rotor 40 move forward, backward, or rotate together.

[0030] Fig. 4 is a schematic diagram illustrating the rotational drive of rotor 40 of rotation drive mechanism 30, and Fig. 5 is a schematic diagram illustrating the rotational drive of 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 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 rotor 40.

[0031] A first fixed cam surface 41a having a continuous sawtooth shape along the circumferential direction is also formed on the annular end face of the upper cam forming member 41 that faces 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 the annular end face of the lower cam forming member 42 that faces 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, upper cam forming member 41, and 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 due to 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 so as 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 abuts against the first fixed cam surface 41a.

[0034] 4(C) shows a state in which further writing pressure is applied to the writing lead, 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 is subjected to a rotational drive equivalent to half the phase (half the pitch) of one tooth of the first cam surface 40a. In this state, the first cam surface 40a of the rotor 40 is engaged with the first fixed cam surface 41a of the upper cam forming member 41.

[0035] 4 and 5, the 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 in which they are 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 after 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 moves forward 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 abuts against 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 force equivalent to half the phase (half the 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, i.e., moves back and forth, under writing pressure, the rotor 40 is rotationally driven by a rotational force equivalent to one tooth (one pitch) of the first cam surface 40a and the second cam surface 40b, and the writing lead gripped by the rotor 40 is similarly rotationally driven via the chuck unit 10. Therefore, with one axial movement of the rotor 40 back and forth due to writing, the rotor 40 undergoes a rotational movement corresponding to one tooth of the cam, and by repeating this process, the writing lead is sequentially rotationally driven. This prevents uneven wear of the writing lead as writing progresses, and prevents large changes 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 slippage 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) which would hinder the rotational movement 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 intermediary member 9 surrounding the chuck unit 10, a slider 7, and a tip pipe 15, and a rotation drive mechanism 30 having a rotor 40, which drives the rotor 40 to rotate in one direction in response to axial backward movement due to writing pressure applied to the writing lead gripped by the chuck unit 10 and axial forward movement due to release of the writing pressure. The rotor 40 is connected to the rear end of the intermediary member 9, and the slider 7 is detachably connected to the front end of the intermediary member 9, and the rotating member is configured to rotate in response to the rotational drive force of the rotor 40, thereby rotating 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 with approximately the same inner diameter along the axial direction. The sleeve 50 has a sleeve main 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 of the sleeve main body 51, a first tapered portion 53 provided in front of the sleeve main 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 of the sleeve 50. The three protrusions 55 are convex curved protrusions. The three protrusions 55 are arranged at equal intervals along the circumferential direction.

[0043] The first tapered portion 53 and the second tapered portion 54 are tapered toward the front. The outer diameter of the rear end of the first tapered portion 53 is slightly smaller than the outer diameter of the sleeve body 51. Therefore, the first tapered portion 53 is connected to the sleeve body 51 via a forward-facing annular step 51a. The rear end of the second tapered portion 54 is connected to the front end of the first tapered portion 53. The taper angle of the second tapered portion 54 is larger than the taper angle of the first tapered portion 53. A third tapered portion 52a tapered toward the front is formed on the outer surface of the flange portion 52. Note that the sleeve 50 may extend the sleeve body 51 without including the first tapered portion 53 and the second tapered portion 54. Furthermore, the sleeve 50 may not include the third tapered portion 52a.

[0044] Four recesses 56 are provided in the flange portion 52 at equal intervals along the circumferential direction. Each recess 56 has a bottom surface 56a perpendicular to the central axis and a curved side surface 56b perpendicular to the bottom surface 56a, formed by cutting out the front periphery of the flange portion 52. A flat portion 57 is provided in a portion of the flange portion 52, as if it had been scraped off along a plane parallel to the axial direction. The sleeve 50 may have at least one recess 56, or may have no recesses 56.

[0045] As shown in FIG. 2 , the sleeve 50 is fitted onto the outer surface of the slider 7 near its front end. Specifically, a slider body 7a having approximately the same outer diameter as the slider body 7a is formed near the front end of the slider 7. The inner diameter of the sleeve 50 is the same as or slightly larger than the outer diameter of the slider body 7a of the slider 7. Meanwhile, 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 onto the slider 7 by the three protrusions 55 elastically deforming and engaging with the slider body 7a of the slider 7. This allows the sleeve 50 to move forward, backward, or rotate integrally with the slider 7. Therefore, the sleeve 50 may also be referred to as a rotating member. The sleeve 50 may be configured in any manner as long as it can be loosely fitted onto 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 external shape as the sleeve 50 described above, and differs from the sleeve 50 only in the shape of its inner surface. The inner surface of the sleeve 150 is provided with three axially flat locking surfaces 158 that thicken the cylindrical inner surface. The three locking surfaces 158 are arranged 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 convexly curved. The three protrusions 155 are arranged at equal intervals along the circumferential direction.

[0047] Like the sleeve 50 described above, the sleeve 150 also fits onto the outer surface near the front end of the slider 7. The diameter of the inscribed circle of the three locking surfaces 158 of the sleeve 150 is the same as 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 protrusions 155 of the sleeve 150 is slightly smaller than the outer diameter of the slider body 7a of the slider 7. Therefore, the sleeve 150 is loosely fitted onto the slider 7 by the three protrusions 155 or the three locking surfaces 158 elastically deforming to lock onto the slider body 7a of the slider 7. This allows the sleeve 150 to move forward, backward, or rotate integrally with the slider 7. Therefore, the sleeve 150 may also be referred to as a rotating member.

[0048] Referring again to Figure 2, the locking ring 60 is a continuous annular member. 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 proboscis member 6. As a result, the locking ring 60 fits against the inner surface of the proboscis 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] A support surface 6a 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 of the tip member 6. 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 the viscous fluid 70 described below.

[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 main body 51. That is, the viscous fluid 70 is applied over at least the contact surface between the support surface 6a and the outer surface of the sleeve 50. At least a portion of the outer surface of the sleeve main 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 also 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] Figure 10 is an enlarged cross-sectional view of the front end of the mechanical pencil 1 shown in Figure 1, illustrating the knock operation of the mechanical pencil 1 in stages. The writing lead is omitted from Figure 10. Figure 10(A) shows the state before the knock operation. From the state shown in Figure 10(A), the knock member 20 or knock cover 23 is pressed forward to initiate the knock operation. The knock operation advances the relay member 9 together with the lead case 13. The advancement of the relay member 9 is restricted by the engagement of the engagement protrusion 9a of the relay member 9, which is located in the central portion of the mechanical pencil 1, 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 rear-facing engagement surface 6b inside the tip member 6 (Figure 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 from the knock operation is released, the chuck body 11 retracts due to the biasing force of the coil spring 14, and the writing lead is advanced. The relay member 9, slider 7, sleeve 50, etc. also retract 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, slider 7, and sleeve 50 retract slightly together as a unit, essentially as part of a cushioning action ( FIG. 10(D) ). When the relay member 9 retracts, the rotor 40 receives a rotational drive equivalent to half a phase (half a pitch) of one tooth of the first cam surface 40a, and rotates. Therefore, the slider 7 and sleeve 50 also rotate together about the central axis. It is preferable that the engagement 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 mentioned above, in general, in mechanical pencils that are configured so that the writing lead rotates, 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 between the tip of the lead and the sleeve 50, the rattle is alleviated 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 alleviated by the viscosity of the viscous fluid 70, and the impact noise is also minimized.

[0055] Furthermore, the viscous fluid 70 is effective not only in reducing radial rattles but also in reducing the cushioning action of the rotation drive mechanism 30. In other words, in conventional rotation drive mechanisms required to rotate a lead, the slight backward and forward movements (cushioning actions) of the lead caused by the writing action, as described above, can be bothersome to some users as axial rattles. With the mechanical pencil 1, the viscous fluid 70 effectively reduces axial rattles as well as radial rattles.

[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 holding part included in the rotating member, rattles of the writing lead, slider 7, and sleeve 50 in the radial and axial directions are reduced. As a result, the user can feel a good writing sensation, a sense of solidity, and a sense of luxury 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 the writing surface is changed by various postures during writing or transportation, and low viscosity so as not to impede the rotation and axial movement of the rotating member. A 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 will not be performed properly, and as a result, the cams of the rotor 40, upper cam forming member 41, and lower cam forming member 42 will not cooperate properly, and the rotating member will not be able to rotate properly. Therefore, the viscous fluid 70 has a low viscosity so as not to impede the rotation and axial movement of the rotating member.

[0058] Generally, if the lead breaks inside the mechanical pencil, specifically between the retaining chuck and the chuck unit, due to dropping the mechanical pencil or other reasons, the broken lead may close the retaining chuck, preventing the lead from being extended. In this case, the mechanical pencil must be disassembled to remove the lead between the retaining chuck and the chuck unit.

[0059] Figure 11 is a partially enlarged cross-sectional view of the mechanical pencil 1 of Figure 1 with the front shaft 2 removed. For example, in order to access the space between the holding chuck 8 and the chuck unit 10 to remove a broken 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 onto the relay member 9. As shown in Figure 11, when the front shaft 2 is removed, the tip member 6 that screws onto the front end of the front shaft 2 is removed together with the sleeve 50 disposed inside the tip member 6.

[0060] That is, when the front shaft 2 is removed, the sleeve 50 that is loosely fitted to the slider 7 comes into contact with and locks onto the locking ring 60, and is removed from the slider 7, remaining in the tip member 6. Similarly, when the tip member 6 is removed from the front shaft 2 while the front shaft 2 remains connected to the rear shaft 3, the sleeve 50 comes into contact with and locks onto 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 moves back together with the slider 7 relative to the tip member 6, but the rear end surface of the sleeve 50 comes into contact with 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 retraction of the sleeve 50 including the retaining portion. The locking ring 60 is a continuous annular member, but may also be a C-shaped annular member with some parts spaced apart, or may have a circular or rectangular cross-sectional shape. In addition to the separate locking ring 60, the locking portion may also be a locking protrusion integrally provided on the inner surface of the prong member 6. In this case, the locking protrusion may be provided annularly on the inner surface of the prong 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 abutting against the front end surface of the locking ring 60, the front end surface of the sleeve 50 is positioned at the same position as or rearward of 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 tip member 6 with the sleeve 50 remaining therein is dropped from its front end onto the ground, such as a floor, the sleeve 50 will not collide with the ground. Therefore, no force that would cause the sleeve 50, or even the locking ring 60, to be removed rearward 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 retraction 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 because the sleeve 50 remains within the tip member 6, the viscous fluid 70 is retained within the tip member 6 and is not applied to the outer surface of the slider 7 or leaks out. Therefore, even if the mechanical pencil 1 is disassembled, for example to remove a broken writing lead, the viscous fluid 70 will not stain the hands, clothes, etc. Furthermore, when assembling the mechanical pencil 1, the slider 7 attached to the relay member 9 can be easily re-fitted by inserting it into the sleeve 50.

[0064] As described above, a smaller-diameter first tapered portion 53 is provided in front of the sleeve body 51 of the sleeve 50 via a step 51a, and a second tapered portion 54 is provided further forward of that. The provision of the step 51a and the first tapered portion 53, and the surface tension of the viscous fluid 70, prevent the viscous fluid 70 applied to the outer surface of the sleeve body 51 from spreading over the step 51a to the first tapered portion 53 and then to the second tapered portion 54. Furthermore, the provision of the step 51a, the first tapered portion 53, and the second tapered portion 54 prevents the viscous fluid 70 from being applied to unnecessary portions of the sleeve 50 when assembling the mechanical pencil 1, for example, after removing a broken writing lead. Four recesses 56 are provided in the flange portion 52 of the sleeve 50. The sleeve 50 has the recess 56, which temporarily stores the viscous fluid 70 that flows as the sleeve 50 moves relative to the tip member 6, thereby preventing the viscous fluid 70 from diffusing to the outside, etc. The shape of the recess 56 can be configured arbitrarily as long as it can temporarily store the viscous fluid 70.

[0065] The mechanical pencil 1 allows for high dimensional tolerance between components, as the amount of viscous fluid 70 can be adjusted according to the clearance. Even if the clearance becomes uneven, the fluidity of the viscous fluid 70 allows the clearance to be filled accordingly. Because the viscous fluid 70 is present during the rotation and radial and axial movement of the slider 7 and sleeve 50 relative to the barrel 5, i.e., the tip member 6, there is no wear due to friction between components, allowing the mechanical pencil 1 to be used for a long period of time. Because the user does not come into contact with the viscous fluid 70, the viscous fluid 70 is less likely to deteriorate over long-term use, and the same performance and effects can be maintained for a long period of 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 of 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] A locking portion 106c, which is an annular protrusion, 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, which is 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 of the tip member 6.

[0068] The slider 180 of the mechanical pencil 100 is cylindrical, with its outer diameter tapering toward the front. The slider 180 includes a slider body 181, which is cylindrical and has a substantially uniform outer diameter near its front end, a flange 182 formed on the outer surface of the rear end of the slider body 181, and a larger-diameter slider rear section 183 located behind the flange 182. Two rectangular cutouts 184 are provided at the rear end of the slider 180, i.e., the rear end of the slider rear section 183. The two cutouts 184 are located 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 barrel 5, i.e., the tip member 106. Alternatively, only the tip pipe 15 may protrude from the front end of the barrel 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 of the central axis of the relay member 190. Similarly, the two claw portions 192 are provided on opposite sides of 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] When the mechanical pencil 100 is assembled, the restricting protrusion 191 of the relay member 190 is disposed within the corresponding notch 184 of the slider 180. This allows the slider 180 to lock with the relay member 190 in the rotational direction, allowing the slider 180 to rotate integrally with the relay member 190. On the other hand, the restricting protrusion 191 of the relay member 190 does not lock with the corresponding notch 184 of the slider 180 in the axial direction. The inner surface of the slider rear portion 183 of the slider 180 is loosely fitted with the outer surface of the front end portion of the relay member 190. Therefore, the slider 180 can move forward or backward integrally with the relay member 190. The fastener 12, which moves forward together with the chuck body 11 by a knocking operation, locks with the claw protrusion 193 of the claw portion 192. As a result, the chuck body 11 can be moved further forward together with the writing lead relative to the fastener 12, and the writing lead can be advanced.

[0071] The 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 main body 181. That is, the viscous fluid 70 is applied over at least the contact surface between the support surface 106a and the outer surface of the slider 180. At least a portion of the outer surface of the slider main 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, which provides the same effect as the mechanical pencil 1 according to the first embodiment. That is, it is possible to reduce 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.

[0073] In the mechanical pencil 100, in order to access the area 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 106 from the mechanical pencil 100, and then remove the slider 180 that screws into the relay member 109. As shown in Figure 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, when the front shaft 2 or the tip member 106 is removed, the slider 180 loosely fitted to the relay member 190 is removed from the relay member 190 and remains in the tip member 106. In detail, when the tip member 106 is removed, the slider 180 moves back 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, and the slider 180 is removed from the relay member 190.

[0075] At this time, as described above, the restricting protrusions 191 of the relay member 190 do not lock with the corresponding notches 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 lock with each other in the rotational direction but not in the axial direction. For example, only one restricting protrusion 191 and one notch 184 may be provided, or three or more may be provided. Furthermore, the slider may have grooves extending in the axial direction on the outer surface rather than notches penetrating the wall thickness.

[0076] By leaving the slider 180 inside the tip member 106, the viscous fluid 70 is retained within the tip member 106 and does not leak out. Therefore, even if the mechanical pencil 1 is disassembled 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 inserted into the slider 180 for reassembly.

[0077] The mechanical pencil 100 allows for high dimensional tolerance between components, as the amount of viscous fluid 70 can be adjusted according to the clearance. Even if the clearance is uneven, the fluidity of the viscous fluid 70 allows the clearance to be filled accordingly. Because 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 components, allowing the mechanical pencil 100 to be used for a long period of time. Because the user does not come into contact with the viscous fluid 70, the viscous fluid 70 is less likely to deteriorate over long-term use, and the same performance and effects can be maintained for a long period of 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 includes a viscous fluid 70. Furthermore, the slider 7, relay member 9, chuck unit 10, etc. are substantially identical to 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, which is equipped with a gripping portion 202a.

[0080] As described above, the slider 7 is formed in a cylindrical shape with an outer diameter that tapers in stages toward the front. The slider 7 has a slider body 7a formed in a cylindrical shape with a substantially constant 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 a substantially constant 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 over at least the contact surface between the support surface 106a and the outer surface of the slider 7. At least a portion 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, which provides the same effect as the mechanical pencil 1 according to the first embodiment. That is, it is possible to reduce 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.

[0083] The mechanical pencil 200 has a high tolerance for dimensions between components, since the amount of viscous fluid 70 can be adjusted according to the clearance. Even if the clearance is uneven, the fluidity of the viscous fluid 70 fills the clearance accordingly. Because the viscous fluid 70 is present during the rotation and radial and axial movement of the slider 7 relative to the barrel 5, i.e., the front shaft 202, there is no wear due to friction between components, allowing the mechanical pencil 200 to be used for an extended period of time. Because the user does not come into contact with the viscous fluid 70, deterioration of the viscous fluid 70 is unlikely to occur over extended use, and the same performance and effects can be maintained for an extended period of time.

[0084] From the above, the mechanical pencil according to the above-described embodiment 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 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; the rotating member is configured to rotate in response to the rotational drive force of the rotor, thereby rotating the writing lead gripped by the chuck unit, 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.

[0085] REFERENCE SIGNS LIST 1 Mechanical pencil 2 Front shaft 3 Rear shaft 4 Inner tube 5 Shaft tube 6 Tip member 6a Support surface 6b Engagement surface 7 Slider 7a Slider body 8 Holding chuck 9 Relay member 10 Chuck unit 13 Lead case 14 Coil spring 15 Tip pipe 50 Sleeve 51 Sleeve body 51a Step 52 Flange portion 60 Locking ring 70 Viscous fluid

Claims

1. A mechanical pencil comprising: a barrel; a rotating member having a chuck unit capable of gripping and releasing a writing lead, and a slider equipped with a holding portion, the rotating member being configured so that a portion of the rotating member protrudes from the front end of the barrel; and a rotational 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 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; wherein 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.

2. A mechanical pencil as described in 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 from the rotating member together with the tip shaft when the tip shaft is removed from the barrel.

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

4. A mechanical pencil as claimed in claim 3, wherein the front end of the sleeve is tapered or has a smaller diameter than the rear end.

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

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

7. A mechanical pencil as claimed in any one of claims 2 to 6, wherein a locking portion for locking the retaining portion against retraction is provided within the tip barrel.

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

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