JP7740924B2 - mechanical pencil - Google Patents

Description

The present invention relates to a mechanical pencil.

In a mechanical pencil, for example, by knocking the knocking part located at the rear end of the barrel, a fixed amount of lead is advanced by a tip member or slider attached to the front end of the barrel. Because the lead wears down with each writing action, it is necessary to perform the knocking operation after each writing action.

A mechanical pencil that can automatically and sequentially advance the lead using the writing pressure associated with the writing action is known (see Patent Document 1). The mechanical pencil described in Patent Document 1 has a ball chuck that holds the lead, a rotational drive mechanism that rotates a rotor in one direction in response to the axial backward movement caused by the writing pressure applied to the lead held by the ball chuck and the axial forward movement caused by the release of the writing pressure, and a lead advancing mechanism that includes a cam member and a retaining chuck that advances the lead forward in response to the rotational drive force of the rotor in the rotational drive mechanism. The ball chuck is configured to allow the lead to advance and prevent it from retracting.

Japanese Patent Application Laid-Open No. 2016-153246

Generally, after completing a series of writing actions, a user retracts the writing lead so that it does not protrude from the tip member or slider in order to protect it. Therefore, before starting the next writing action, it is necessary to perform at least one knocking operation to advance the writing lead in advance. Even with the mechanical pencil described in Patent Document 1, a writing action is required to automatically advance the writing lead, so it is necessary to perform at least one knocking operation to advance the writing lead in advance before starting a writing action. Therefore, if the writing lead is advanced without performing a knocking operation before starting a writing action, the writing action can be started more smoothly.

The objective of the present invention is to provide a mechanical pencil that allows for a new lead-advancing operation that differs from the conventional knock operation.

One aspect of the present invention provides a mechanical pencil comprising a barrel, a retaining chuck for holding a lead, a slider that holds the retaining chuck internally and is arranged within the barrel so as to be movable back and forth, with the lead that passes through the retaining chuck protruding from the tip, and a cap that has a lead feeding section and can be fitted to the front end of the barrel, wherein the lead feeding section presses against the slider, causing the slider to retract relative to the lead, when the cap is fitted to the barrel.

The lead advancing section may be provided with a recess capable of accommodating the tip of a writing lead. The lead advancing section may be provided inside the front end of the cap so that it can move back and forth. The pen may further be provided with a ball chuck that allows the writing lead to move forward and prevents it from moving backward.

These aspects of the present invention have the common effect of providing a mechanical pencil that allows for a new lead-advancing operation that differs from conventional knocking operations.

FIG. 1 is a vertical cross-sectional view of a mechanical pencil according to an embodiment of the present invention. FIG. 2 is a perspective view of a mechanical pencil. FIG. 3 is an enlarged cross-sectional view of the front half of the mechanical pencil. FIG. 4 is an enlarged cross-sectional view of the rear half of the mechanical pencil. FIG. 5 is a perspective view illustrating the internal structure of the mechanical pencil. FIG. 6 is an exploded perspective view of the clutch mechanism. FIG. 7 is an enlarged cross-sectional view of the rotation drive mechanism. FIG. 8 is a schematic diagram illustrating the rotational drive of the rotor of the rotational drive mechanism. FIG. 9 is a schematic diagram illustrating the rotational drive of the rotor, following FIG. FIG. 10 is a perspective view of the dial cam member. FIG. 11 is a perspective view of the rail cam member. FIG. 12 is another perspective view of the rail cam member. FIG. 13 is a perspective view of the dial cam member and rail cam member combined together. FIG. 14 is another perspective view of the combined dial cam member and rail cam member. FIG. 15 is a schematic diagram showing the feed cam surface. FIG. 16 is a perspective view of the input clutch cam. FIG. 17 is a perspective view of the output clutch cam. FIG. 18 is an enlarged perspective view illustrating the input clutch cam and the output clutch cam. FIG. 19 is a schematic diagram illustrating the operation of the clutch mechanism that cooperates with the rotary drive mechanism. FIG. 20 is a vertical cross-sectional view of the lead advancing member. FIG. 21 is an enlarged cross-sectional view of a mechanical pencil illustrating the extension of the writing lead. FIG. 22 is an enlarged perspective view of the cap. FIG. 23 is an enlarged perspective view of the barrel. FIG. 24 is a perspective view of the holding chuck. FIG. 25 is a vertical cross-sectional view of the holding chuck.

Embodiments of the present invention will be described in detail below with reference to the drawings. Corresponding components are designated by common reference symbols throughout the drawings.

Figure 1 is a longitudinal cross-sectional view of a mechanical pencil 1 according to an embodiment of the present invention, Figure 2 is a perspective view of the mechanical pencil 1, Figure 3 is an enlarged cross-sectional view of the front half of the mechanical pencil 1, Figure 4 is an enlarged cross-sectional view of the rear half of the mechanical pencil 1, Figure 5 is a perspective view illustrating the internal structure of the mechanical pencil 1, and Figure 6 is an exploded perspective view of the clutch mechanism 60.

Mechanical pencil 1 has a front shaft 2, a rear shaft 3 that screws onto the outer peripheral surface of the rear end of front shaft 2, and a tip member 4 that screws onto the outer peripheral surface of the front end of front shaft 2. The front shaft 2 and rear shaft 3 constitute a barrel 6. The barrel 6 may also include the tip member 4. As described below, mechanical pencil 1 is configured so that a writing lead 7 protrudes from the tip of slider 9. In this specification, in the axial direction of mechanical pencil 1, the side with the writing lead 7 is defined as the "front" side, and the side opposite the writing lead 7 is defined as the "rear" side.

Referring to Figure 3, a slider 9 is disposed inside the front end of the barrel 6 so that it can slide axially and rotate about its axis. The slider 9 is cylindrical, with an outer diameter that tapers in stages toward the front. A flange 9a is provided on the outer surface of the rear end of the slider 9. The writing lead 7 is guided by the slider 9 and can protrude from the tip of the slider 9. A holding chuck 10, which has a through hole 10a formed in its center, is disposed inside the slider 9. The through hole 10a of the holding chuck 10 makes sliding contact with the outer surface of the writing lead 7, acting to temporarily hold the writing lead 7.

A cylindrical dial cam member 50, which is the first cam member, and a ring-shaped rail cam member 52, which is the second cam member, are arranged on the outer peripheral surface of the slider 9, aligned in the axial direction. A roughly cylindrical gripping portion 8 is provided on the front end of the tip member 4 and the outer peripheral surface of the dial cam member 50. The tip of the slider 9 protrudes from the hole at the front end of the dial cam member 50. A ball chuck 11, specifically a fastener 13, that grips the writing lead 7 is fitted onto the inner peripheral surface of the rear end of the slider 9.

The ball chuck 11 has a cylindrical fastener 13, a chuck main body 14 disposed within the fastener 13, a cylindrical chuck holder 15, and multiple balls 16. The inner peripheral surface of the fastener 13 is formed with a tapered surface that widens toward the front. The chuck main body 14 has a through hole for the writing lead 7 formed along the central axis, and the front end of the chuck main body 14 is divided into multiple sections along the axial direction. The rear end of the chuck main body 14 is held by the chuck holder 15. The chuck main body 14 and the chuck holder 15 are movable in the axial direction relative to the fastener 13. The multiple balls 16 are disposed between the inner peripheral surface of the fastener 13 and the outer peripheral surface of the chuck main body 14.

When writing pressure is applied to the lead 7, the chuck body 14, together with the ball 16, abuts against the tapered surface inside the cylindrical fastener 13, and the lead 7 is gripped by the chuck body 14. This prevents the lead 7 from moving backward. On the other hand, when a force is applied to pull the lead 7 forward, the chuck body 14 is not affected by the fastener 13, so the lead 7 can be pulled forward without resistance. In other words, the ball chuck 11 acts to allow the lead 7 to move forward and prevent it from moving backward.

A coil spring 17 is arranged to surround the chuck main body 14. The rear end of the coil spring 17 is fitted onto the outer surface of the chuck main body 14, and the front end of the coil spring 17 is supported by a step formed on the inner surface of the fastener 13. The coil spring 17 urges the chuck main body 14 rearward, allowing the ball chuck 11 to maintain a grip on the lead 7. A cam abutment spring 18, which is also a coil spring, is arranged to surround the fastener 13. The cam abutment spring 18 urges the slider 9 forward. The front end of a lead case 19 is fitted onto the outer surface of the rear end of the chuck holding portion 15. The lead case 19 is cylindrical and contains the lead 7 inside.

An input clutch cam 61 of the clutch mechanism 60, which will be described later, is connected to the ball chuck 11. The input clutch cam 61 is cylindrical, and the outer peripheral surface of the rear end of the fastener 13 of the ball chuck 11 fits onto the inner peripheral surface of the front end of the input clutch cam 61. The outer peripheral surface of the front end of the cylindrical relay member 12 fits onto the inner peripheral surface of the rear end of the input clutch cam 61. As will be described later with reference to Figures 5 and 6, the clutch mechanism 60 has a protruding abutment 65c that protrudes forward. The abutment 65c is urged forward by the cam abutment spring 18 via the slider 9. Therefore, the slider 9, ball chuck 11, relay member 12, input clutch cam 61, and abutment 65c can move axially together within the shaft tube 6. The rear end of the relay member 12 is connected to the rotation drive mechanism 30, which will be described later.

Referring to Figure 4, a knock rod 20 serving as a knock portion is provided at the rear end of the barrel 6 so that it can move back and forth relative to the barrel 6. The knock rod 20 is biased rearward by a coil spring 21. A partition wall 20a equipped with a refill hole for the writing lead 7 is formed near the rear end of the knock rod 20. An eraser 22 is removably attached inside the rear end of the knock rod 20. A knock cover 23 is removably attached to the outer peripheral surface of the rear end of the knock rod 20 to protect the eraser 22 from dirt and the like. The knock rod 20 fits into the outer peripheral surface of the rear end of the lead case 19.

By performing a knocking operation that presses the knock bar 20 or knock cover 23 forward, the lead case 19 moves forward. This pushes the chuck body 14 forward via the chuck holding portion 15. Accordingly, the writing lead 7 held by the chuck body 14 also moves forward, acting to force the writing lead 7 out of the slider 9.

When the pressure exerted by the knock operation is released, the force of the coil spring 21 causes the knock rod 20 to retract and return to its original position. At this time, the chuck body 14 retracts due to the force of the coil spring 17. Meanwhile, the writing lead 7 is held by the retaining chuck 10 located within the slider 9, and the action of the ball chuck 11 causes the writing lead 7 to be pulled out of the chuck body 14 without resistance. As a result, the writing lead 7 is advanced from the slider 9, allowing the writing lead 7 to be advanced a predetermined amount with each repeated knock operation. If the knock rod 20 is moved forward by the knock operation and maintained in this state, the chuck body 14 protrudes from the fastener 13, releasing its grip on the writing lead 7. In this state, the writing lead 7 that has been advanced from the slider 9 can be pushed back with a fingertip or the like.

Figure 7 is an enlarged cross-sectional view of the rotation drive mechanism 30. The rotation drive mechanism 30 is disposed in the internal space of the rear axle 3. The rotation drive mechanism 30 is connected to the rear end of the relay member 12. An axle spring 31 is disposed between the rear end surface of the front axle 2 and the front end surface of the rotation drive mechanism 30, biasing the rotation drive mechanism 30 rearward. Rearward movement of the rotation drive mechanism 30 due to the biasing force of the axle spring 31 is restricted when the rear end surface of the rotation drive mechanism 30 abuts against a step provided on the inner surface of the axle tube 6. The lead case 19 passes through the interior of the relay member 12 and the rotation drive mechanism 30, and is separated from the rotation drive mechanism 30.

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

The inner peripheral surface of the front end of the rotor 40 is fitted with the outer peripheral surface of the rear end of the relay member 12. Near the front end of the 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, while a second cam surface 40b is formed on the front end surface of this portion.

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 peripheral surface of the front end of the upper cam forming member 41. A first fixed cam surface 41a, which serves as a first fixed cam surface, 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, which serves as a second fixed cam surface 42a, is formed on the inner surface of the front end of the lower cam forming member 42 facing the second cam surface 40b of the rotor 40.

A cylindrical cylinder member 43 is fitted onto the outer peripheral surface of the rear end of the upper cam forming member 41. An insertion hole 43a is formed at the rear end of the cylinder member 43, through which the lead case 19 can be inserted. A cylindrical 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.

Here, the relay member 12 transmits the backward and forward movement (cushioning movement) of the writing lead 7 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 ball chuck 11, which is holding the writing lead 7. Therefore, the writing lead 7 held in the ball chuck 11 also rotates.

When not writing with the mechanical pencil 1, i.e., when no writing pressure is being applied to the writing lead 7, 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 brought into meshing engagement. When writing with the mechanical pencil 1, i.e., when writing pressure is being applied to the writing lead 7, the ball chuck 11 retracts against the biasing force of the cushion spring 45, and the rotor 40 also retracts accordingly. Therefore, the first cam surface 40a of the rotor 40 abuts against the first fixed cam surface 41a and is brought into meshing engagement.

Figure 8 is a schematic diagram illustrating the rotational drive action of the rotor 40 of the mechanical pencil 1 of Figure 1 in sequence, and Figure 9 is a schematic diagram illustrating the rotational drive action of the rotor 40 following Figure 8. In Figures 8 and 9, the rear end face, or upper surface of the rotor 40, is formed with a first cam surface 40a in an annular shape that is continuously sawtoothed along the circumferential direction, and the front end face, or lower surface of the rotor 40, is formed with a second cam surface 40b in an annular shape that is similarly continuously sawtoothed along the circumferential direction.

A first fixed cam surface 41a having a continuous sawtooth pattern running circumferentially is formed on the 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 pattern running circumferentially is formed on the 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 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 approximately the same.

Figure 8 (A) shows the relationship between the rotor 40, upper cam forming member 41, and lower cam forming member 42 when no writing pressure is applied to the writing lead 7. In this state, the second cam surface 40b formed on the rotor 40 is engaged with 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 that they are shifted by half a phase (half a pitch) relative to one tooth of the cam in the axial direction.

Figure 8 (B) shows the initial state in which writing pressure is applied to the lead 7 when writing with the mechanical pencil 1. In this state, the rotor 40 retracts as the cushion spring 45 contracts as the ball chuck 11 retracts. This causes the rotor 40 to move toward the first fixed cam surface 41a of the upper cam forming member 41.

Next, Figure 8 (C) shows the state in which further writing pressure is applied to the writing lead 7, causing the rotor 40 to abut against the first fixed cam surface 41a of the upper cam forming member 41 and retract. 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. As a result, the rotor 40 is rotated by a distance equivalent to half the phase (half pitch) of one tooth of the first cam surface 40a.

Note that the triangle mark attached to the center of the rotor 40 in Figures 8 and 9 is used to indicate the amount of rotational movement of the rotor 40. In the state shown in Figure 8 (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 so that they are shifted by half a phase (half a pitch) relative to one tooth of the cam in the axial direction.

Next, Figure 9 (D) shows the initial state after writing with the mechanical pencil 1 has finished and the writing pressure on the writing lead 7 has been released. In this case, the rotor 40 moves forward due to the biasing force of the cushion spring 45. This causes the rotor 40 to move toward the lower cam forming member 42.

9(E) shows a state in which the rotor 40 has advanced by contacting the second fixed cam surface 42a of the lower cam forming member 42 due to the biasing force of the cushion spring 45. In this case, 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. As a result, the rotor 40 is again subjected to a rotational drive equivalent to half the phase (half pitch) of one tooth of the second cam surface 40b.

As indicated by the triangle mark in the center of the rotor 40, as the rotor 40 receives writing pressure and moves back and forth in the axial direction, i.e., moves back and forth, the rotor 40 is rotated by an amount equivalent to one tooth (one pitch) of the first cam surface 40a and the second cam surface 40b, and the writing lead 7 held by it is similarly rotated via the ball chuck 11. 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, the writing lead 7 is sequentially rotated. This prevents uneven wear of the writing lead 7 as writing progresses, and prevents large changes in the thickness and darkness of the drawn lines.

In short, the rotation drive mechanism has a first cam forming member and a second cam forming member, a rotor formed in an annular shape with a first cam surface and a second cam surface formed on one end face and the other end face in the axial direction, respectively, and a first fixed cam surface and a second fixed cam surface formed on the first cam forming member and the second cam forming member arranged to face the first cam surface and the second cam surface, respectively. When the writing pressure causes the ball chuck to retract, the first cam surface of the rotor abuts and meshes with the first fixed cam surface, and when the writing pressure is released, the second cam surface of the rotor abuts and meshes with the second fixed cam surface. When the first cam surface of the rotor is meshed with the first fixed cam surface, the second cam surface of the rotor and the second fixed cam surface are set in a phase-shifted relationship with respect to one tooth of the cam in the axial direction, and when the second cam surface of the rotor is meshed with the second fixed cam surface, the first cam surface of the rotor and the first fixed cam surface are set in a phase-shifted relationship with respect to one tooth of the cam in the axial direction.

The torque canceller 44, which pushes the rotor 40 forward under the 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.

As described above, the mechanical pencil 1 has a ball chuck 11 and a rotor 40, and is configured so that the ball chuck 11 moves back and forth to release and grip the writing lead 7, allowing the writing lead 7 to be advanced forward. The ball chuck 11 is held within the barrel 6 so that it can rotate around its central axis while gripping the writing lead 7, and the writing pressure of the writing lead 7 causes the rotor 40 to move back and forth via the ball chuck 11, causing the rotor 40 to rotate, and the rotational movement of the rotor 40 is transmitted to the writing lead 7 via the ball chuck 11.

The lead advancing mechanism and advancing amount adjustment mechanism will be described with reference to Figures 10 to 14. The lead advancing mechanism receives the rotational driving force of the rotor 40 of the rotation drive mechanism 30 and acts to advance the writing lead 7 from the slider 9.

Figure 10 is a perspective view of the dial cam member 50. In Figure 10, the dial cam member 50 is positioned so that the upper side is the rear side of the mechanical pencil 1. The dial cam member 50 is a cylindrical member and has a cam body 50a, a flange portion 50b formed on the outer peripheral surface of the cam body 50a, a fitting protrusion 50c formed on the rear end surface of the flange portion 50b, and a dial cam 51 formed on the rear end surface of the cam body 50a. The dial cam 51 has a flat first annular cam surface 51a located further forward and perpendicular to the central axis, and a flat second annular cam surface 51b located further rearward and perpendicular to the central axis. Furthermore, both ends of the first annular cam surface 51a and the second annular cam surface 51b are connected by a vertical wall 51c.

Figure 11 is a perspective view of the rail cam member 52, and Figure 12 is another perspective view of the rail cam member 52. The rail cam member 52 is positioned so that the upper side in Figures 11 and 12 is the rear side of the mechanical pencil 1. The rail cam member 52 is a member formed in an annular shape. An adjustment recess 52a is formed in the front end surface of the rail cam member 52. A plurality of mating recesses 52b are formed in the bottom surface of the adjustment recess 52a and are arranged in parallel at equal intervals along the circumferential direction.

A rail cam 53 is formed on the rear end surface of the rail cam member 52. The rail cam 53 has a flat first annular cam surface 53a located further forward and perpendicular to the central axis, a flat second annular cam surface 53b located further rearward and perpendicular to the central axis, and a sloped annular cam surface, an inclined surface 53c, that rises circumferentially to connect one end of the first annular cam surface 53a and one end of the second annular cam surface 53b. The other ends of the first annular cam surface 53a and the second annular cam surface 53b are connected by a vertical wall 53d.

Figure 13 is a perspective view of the combined dial cam member 50 and rail cam member 52, and Figure 14 is another perspective view of the combined dial cam member 50 and rail cam member 52. The dial cam member 50 and rail cam member 52 are positioned so that the upper side in Figures 13 and 14 faces the rear of the mechanical pencil 1. The annular rail cam member 52 is inserted into the rear end of the cam body 50a of the dial cam member 50 and engaged by the flange portion 50b, thereby combining them. That is, the front end surface of the rail cam member 52 abuts against the rear end surface of the flange portion 50b of the dial cam member 50. At this time, the mating protrusion 50c provided on the flange portion 50b of the dial cam member 50 fits into one of the mating recesses 52b in the adjustment recesses 52a of the rail cam member 52. The rail cam member 52 is positioned radially outward of the dial cam member 50.

When the dial cam member 50 and the rail cam member 52 are combined, the dial cam 51 of the dial cam member 50 is positioned adjacent to the rail cam 53 of the rail cam member 52. As a result, the dial cam 51 and the rail cam 53 cooperate to form a continuous, i.e., annular, circumferential extension cam surface 54.

As shown in Figure 3, the dial cam member 50 and rail cam member 52 are positioned outside the slider 9 in an assembled state. The outer surfaces of a portion of the dial cam member 50 and the rail cam member 52 are covered by the tip member 4 and the grip portion 8. The grip portion 8 engages with the outer surface of the dial cam member 50, allowing it to rotate around the central axis together with the dial cam member 50. A coil spring 56 is disposed between the inner surface of the front end of the tip member 4 and the flange portion 50b of the dial cam member 50. In addition, the abutment 65c, which is biased forward by the cam abutment spring 18 via the slider 9, remains in abutment against the delivery cam surface 54. The outer surface of the rail cam member 52 engages with the inner surface of the tip member 4, restricting rotation of the rail cam member 52 relative to the tip member 4 and, ultimately, the barrel 6.

The shape of the delivery cam surface 54 can be changed by rotating the dial cam member 50 and the rail cam member 52 relative to each other around their central axes. Specifically, the user rotates the dial cam member 50 around its central axis by holding the barrel 6 with one hand while rotating the gripping portion 8 with the other. Because the rail cam member 52 is engaged with the barrel 6, the dial cam member 50 rotates around its central axis relative to the rail cam member 52. The rotation of the dial cam member 50 relative to the rail cam member 52 is performed in stages so that the mating protrusions 50c of the dial cam member 50 move between and engage with the corresponding adjacent mating recesses 52b of the rail cam member 52. Therefore, the rotation of the dial cam member 50 around its central axis relative to the rail cam member 52 is performed in stages within the range of the adjustment recesses 52a of the rail cam member 52 within which the mating protrusions 50c of the dial cam member 50 can move. The relative positions of the dial cam 51 of the dial cam member 50 and the rail cam 53 of the rail cam member 52 change depending on the position of the mating recess 52b of the rail cam member 52 into which the mating projection 50c of the dial cam member 50 fits, thereby changing the shape of the payout cam surface 54. The dial cam member 50 is biased against the rail cam member 52 by the coil spring 56, and a clicking sensation is felt when the dial cam member 50 rotates in stages relative to the rail cam member 52.

Next, referring to Figure 15, we will explain how the lead 7 is advanced by the advancement cam surface 54. Figure 15 is a schematic diagram showing the advancement cam surface 54. Figure 15 shows the cylindrical surface around the central axis, including the advancement cam surface 54, expanded circumferentially to show the positional relationship between the dial cam member 50 and the rail cam member 52. In Figure 15, the top is the rear side of the mechanical pencil 1.

Referring to Figure 15, the dial cam member 50 is aligned with the rail cam member 52 so that the vertical wall 51c of the dial cam 51 and the sloped surface 53c of the rail cam 53 are radially overlapping. In Figure 15, the line (surface) located further rearward, i.e., higher in the figure, of the dial cam 51 and the rail cam 53 constitutes the payout cam surface 54. That is, the second annular cam surface 51b of the dial cam 51 and the second annular cam surface 53b and sloped surface 53c of the rail cam 53 cooperate to constitute the payout cam surface 54. Note that the height (height difference) of the axial step 55 (drop) formed by the second annular cam surface 51b of the dial cam 51 and the sloped surface 53c of the rail cam 53 on the payout cam surface 54 is referred to as the step height H.

When the dial cam member 50 and the rail cam member 52 are rotated relative to each other about the central axis so that the vertical wall 51c of the dial cam 51 is positioned on the side of the first annular cam surface 53a of the rail cam 53, the step height H becomes higher. On the other hand, when the dial cam member 50 and the rail cam member 52 are rotated relative to each other about the central axis so that the vertical wall 51c of the dial cam 51 is positioned on the opposite side of the first annular cam surface 53a of the rail cam 53, the step height H becomes lower.

As described below, the rotor 40 of the rotation drive mechanism 30 gradually rotates the abutment 65c based on the cushioning action of the writing lead 7. That is, when viewed from the tip of the slider 9, the abutment 65c rotates clockwise around the central axis. Due to this rotational movement, the abutment 65c, which is biased forward by the cam abutment spring 18, moves circumferentially in cooperation with the delivery cam surface 54. In other words, as the abutment 65c moves from right to left in Figure 15, it gradually rises along the slope 53c of the dial cam 51 that constitutes the delivery cam surface 54.

When the abutment 65c reaches the step 55, it is pressed by the biasing force of the cam abutment spring 18 and falls into the step 55. In other words, the abutment 65c moves forward from the second annular cam surface 51b of the dial cam 51 by the step height H of the step 55. At this time, as the abutment 65c advances, the slider 9 and, further, the holding chuck 10 disposed inside the slider 9 also move forward. As a result, the writing lead 7 held by the holding chuck 10 is pulled out of the ball chuck 11 and relatively extended from the tip of the slider 9 by the step height H. Therefore, the amount of writing lead 7 extended, i.e., the extension amount, is equal to the step height H.

Through the above operation, the lead 7 can be advanced from the slider 9 each time the abutment 65c makes one revolution along the advancement cam surface 54. By repeating this operation, the lead 7 is worn down with the writing action, and the lead 7 is advanced sequentially.

In short, the lead advancing mechanism is configured so that the abutment 65c moves along the advancing cam surface 54 in response to the rotation of the rotor 40, and the forward movement of the slider 9 when the abutment 65c drops into the step 55 on the advancing cam surface 54 causes the lead 7 held in the holding chuck 10 to be pulled out of the ball chuck 11. By utilizing the step 55 on the advancing cam surface 54, the lead advancing mechanism can convert the rotational driving force of the rotor 40 in the rotation drive mechanism 30 into an advancing motion for the lead 7. The configuration that creates a height difference on the advancing cam surface 54 is collectively referred to as a "drop."

The mechanical pencil 1 is configured so that the writing lead 7 held in the ball chuck 11 is also rotated by the rotational driving force of the rotor 40 in the rotation drive mechanism 30. This prevents uneven wear of the writing lead 7 as the writing progresses, and as a result, prevents significant changes in the thickness and darkness of the drawn lines. In short, the rotation drive mechanism 30 has a rotor 40, and drives the rotor 40 to rotate in one direction in response to the axial backward movement caused by the writing pressure applied to the writing lead 7 held in the ball chuck 11 and the axial forward movement caused by the release of the writing pressure.

As described above, the feed amount adjustment mechanism allows the step height H of the step 55 on the feed cam surface 54 to be changed simply by rotating the dial cam member 50 and the rail cam member 52 relatively around the central axis. This makes it possible to more easily and accurately adjust the amount of lead 7 fed by the lead feed mechanism.

By adjusting the amount of lead 7 extension so that it roughly matches the degree of wear on the lead 7 due to differences in writing pressure and lead 7 hardness used by different users, the amount of lead 7 protruding from the slider 9 can be kept constant even while writing is in progress. As a result, with the mechanical pencil 1, you can continue writing for a long time with just one knock operation. It is preferable to configure the dial cam 51 or rail cam 53 so that a step 55 is formed with a step height H that corresponds to a length that exceeds the normally expected degree of wear on the lead 7. This makes it possible to set the amount of lead 7 extension to suit the preferences of all users.

In the above-described embodiment, the dial cam member 50 was a cylindrical member serving as the first cam member, but it may also be an annular member. Furthermore, the rail cam member 52 was an annular member serving as the second cam member, but it may also be a cylindrical member. The first cam member may be provided with a rail cam 53, and the second cam member may be provided with a dial cam 51. In other words, a delivery cam surface may be formed by a ring-shaped or cylindrical first cam member and a ring-shaped or cylindrical second cam member arranged radially outward of the first cam member. Furthermore, the step height of the step may be adjusted by moving the first cam member and the second cam member back and forth relative to each other, i.e., by separating them in the axial direction.

The rail cam member 52 may be configured integrally with the dial cam member 50, with the dial cam member forming only a single payout cam surface 54. In this case, the payout amount cannot be adjusted as described above, but the number of parts is reduced, allowing for cost savings. To adjust the payout amount, multiple dial cam members with various step heights H may be provided. In this case, the user may be able to select and replace the dial cam member that achieves the payout amount that is optimal for them.

Next, the clutch mechanism 60 will be described with reference to Figures 3, 5, 6, and 16 to 19. The clutch mechanism 60 acts to convert the rotational motion of the rotor 40 in the rotation drive mechanism 30, which serves as an input, into the rotational motion of the abutment 65c, which serves as an output. The clutch mechanism 60 has an input clutch cam 61, which serves as an input member, an output clutch cam 62, which serves as an output member, a transmission cam 64, and an advance cam 65. The mechanical pencil 1 also has a clutch cam holder 66.

Figure 16 is a perspective view of the input clutch cam 61, Figure 17 is a perspective view of the output clutch cam 62, and Figure 18 is an enlarged perspective view explaining the input clutch cam 61 and output clutch cam 62. The input clutch cam 61 is positioned so that the upper side is the rear of the mechanical pencil 1 in Figure 16, and the output clutch cam 62 is positioned so that the upper side is the rear of the mechanical pencil 1 in Figure 17. In Figure 18, the upper side is the rear of the mechanical pencil 1.

The input clutch cam 61 is a cylindrical member, and a single cam protrusion 61a is provided on the annular rear end face 61b that forms the input cam surface. A flange portion 61c is provided on the outer peripheral surface of the rear end of the input clutch cam 61.

The output clutch cam 62 is positioned behind the input clutch cam 61. The output clutch cam 62 is a cylindrical member, and a flange portion 62a is provided on the outer peripheral surface near the front end of the output clutch cam 62. A clutch cam surface 63, which serves as the output cam surface, is provided on the annular front end surface of the output clutch cam 62. The clutch cam surface 63 is positioned opposite the cam protrusion 61a of the input clutch cam 61. The clutch cam surface 63 consists of multiple peaks 63a and multiple valleys 63b with flat bottoms provided between adjacent peaks 63a.

Referring to FIG. 18, the cam protrusion 61a of the input clutch cam 61 and the peak 63a of the output clutch cam 62 have substantially the same shape. The cam protrusion 61a of the input clutch cam 61 has a first engagement surface 61aa that is substantially perpendicular to the rear end surface 61b and a first inclined surface 61ab that is inclined. Similarly, the peak 63a of the output clutch cam 62 has a second engagement surface 63aa that is substantially perpendicular to the bottom surface of the valley 63b and a second inclined surface 63ab that is inclined. As described below, during operation of the clutch mechanism 60, the input clutch cam 61 and the output clutch cam 62 cooperate by engaging the first engagement surface 61aa of the input clutch cam 61 with the second engagement surface 63aa of the output clutch cam 62.

Referring to Figures 3, 5, and 6, the rear end of the transmission cam 64 is fitted onto the outer peripheral surface of the front end of the output clutch cam 62. The transmission cam 64 is inserted until the rear end surface of the transmission cam 64 abuts against the flange portion 62a of the output clutch cam 62. The transmission cam 64 is formed in a cylindrical shape, and its front end surface is provided with first engagement protrusions 64a that extend forward and are equally spaced along the circumferential direction. The circumferential side of the first engagement protrusions 64a is provided with first engagement walls 64b that extend along the axial direction. The inner peripheral surface of the transmission cam 64 is provided with an annular protrusion 64c.

The input clutch cam 61 is positioned within the transmission cam 64 so that the flange portion 61c is positioned between the clutch cam surface 63 of the output clutch cam 62 and the annular protrusion 64c of the transmission cam 64. In other words, the forward movement of the input clutch cam 61 is restricted by the flange portion 61c engaging with the annular protrusion 64c of the transmission cam 64. The backward movement of the input clutch cam 61 is restricted by the cooperation of the cam protrusion 61a and the clutch cam surface 63 of the output clutch cam 62.

A delivery cam 65 is disposed in front of the transmission cam 64. The delivery cam 65 is cylindrical, and its rear end face is provided with second engagement protrusions 65a that extend rearward and are spaced equally apart along the circumferential direction. The second engagement protrusions 65a have a shape complementary to the first engagement protrusions 64a of the transmission cam 64. A second engagement wall 65b is provided along the axial direction on the circumferential side of the second engagement protrusion 65a. The front end face of the delivery cam 65 is provided with the aforementioned protruding abutment 65c that protrudes forward. An annular protrusion 65d is provided on the inner circumferential surface of the front end of the delivery cam 65.

The slider 9 is inserted into the payout cam 65 from the rear, and the flange portion 9a can engage with the annular protrusion 65d of the payout cam 65. The cam contact spring 18 described above is positioned so that one end engages with the inner surface of the flange portion 9a of the slider 9 and the other end engages with the front end surface of the input clutch cam 61. The biasing force of the cam contact spring 18 urges the slider 9 forward, and the payout cam 65 is urged forward via the biased flange portion 9a of the slider 9. As a result, the abutment 65c is biased so as to abut against the payout cam surface 54, as described above. The payout cam 65 can move axially together with the slider 9, but can rotate independently about the central axis.

The clutch cam holder 66 is cylindrical and attached to the barrel 6, specifically the inner surface of the front barrel 2. A high-viscosity liquid lubricant, such as grease, is applied to the inner surface of the clutch cam holder 66. The output clutch cam 62 is inserted into the clutch cam holder 66, filling the gap between the outer surface of the output clutch cam 62 and the inner surface of the clutch cam holder 66 with liquid lubricant. As a result, the output clutch cam 62 and the connected transmission cam 64 are loosely held by the clutch cam holder 66, reducing sudden axial movement within the barrel 6 due to gravity and other factors. The clutch cam holder 66 may be integral with the barrel 6. In other words, a viscous fluid that suppresses axial movement of the output member is disposed between the output member and the barrel. The inclusion of the clutch cam holder 66 in the mechanical pencil 1 can absorb dimensional variations and frictional resistance among the components of the clutch mechanism 60. The clutch cam holder 66 may also be omitted.

Referring to Figure 3, as described above, the inner peripheral surface of the front end of the input clutch cam 61 is fitted with the outer peripheral surface of the rear end of the fastener 13 of the ball chuck 11, and the inner peripheral surface of the rear end of the input clutch cam 61 is fitted with the outer peripheral surface of the front end of the relay member 12. The rear end of the relay member 12 is connected to the rotor 40 (Figure 4). Therefore, the input clutch cam 61 is driven to rotate by the rotor 40 via the relay member 12 using the rotation drive mechanism 30. Furthermore, the input clutch cam 61 moves back and forth together with the rotor 40 via the relay member 12 based on the cushioning action of the writing lead 7. The relay member 12 penetrates the interior of the output clutch cam 62 and the transmission cam 64 and is separated from the relay member 12. Therefore, the rotational and forward/backward movement of the relay member 12 is not directly transmitted to the output clutch cam 62 and the transmission cam 64.

As described below with reference to Figure 19, the rotational motion of the input clutch cam 61 is transmitted to the output clutch cam 62 through cooperation between the cam protrusion 61a and the clutch cam surface 63 of the output clutch cam 62. The rotational motion of the output clutch cam 62 is transmitted to the delivery cam 65 via the connected transmission cam 64. That is, as the transmission cam 64 rotates, the first engagement wall 64b of the first engagement protrusion 64a engages with the second engagement wall 65b of the second engagement protrusion 65a in the circumferential direction, transmitting the rotational motion of the transmission cam 64 to the delivery cam 65. As a result, the abutment 65c moves along the delivery cam surface 54, as described above, and the writing lead 7 is delivered.

Figure 19 is a schematic diagram illustrating the operation of the clutch mechanism 60 in cooperation with the rotation drive mechanism 30. Figure 19 shows a circumferential development of a cylindrical surface around the central axis including each cam surface to illustrate the positional relationship between the rotor 40, upper cam forming member 41, and lower cam forming member 42 in the rotation drive mechanism 30 and the input clutch cam 61 and output clutch cam 62 in the clutch mechanism 60. In Figure 19, the top is the rear side of the mechanical pencil 1. The states of the rotation drive mechanism 30 shown in Figures 19(A) to (E) correspond to the states of the rotation drive mechanism 30 shown in Figures 8(A) to (C) and Figures 9(D) and (E), respectively. Triangle marks are attached to each of the rotor 40 and output clutch cam 62 to indicate the amount of rotational movement.

Figure 19 (A) shows the relationship between the rotation drive mechanism 30 and the clutch mechanism 60 when no writing pressure is applied to the writing lead 7. The rotation drive mechanism 30 corresponds to the state shown in Figure 8 (A). Therefore, 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. At this time, the cam protrusion 61a of the input clutch cam 61 and the clutch cam surface 63 of the output clutch cam 62 are separated in the axial direction and do not abut. The triangular marks on the rotor 40 and the output clutch cam 62 are aligned on the same line in the axial direction.

Next, Figure 19 (B) shows the initial state when writing pressure is applied to the writing lead 7. The rotation drive mechanism 30 corresponds to the state shown in Figure 8 (B). Therefore, in this state, the rotor 40 moves toward the upper cam forming member 41, and the input clutch cam 61 approaches the clutch cam surface 63 of the output clutch cam 62. At this time, the first engagement surface 61aa of the cam protrusion 61a of the input clutch cam 61 and the second engagement surface 63aa of the peak portion 63a of the output clutch cam 62 (Figure 18) are separated circumferentially; specifically, they are separated circumferentially by a distance D1.

Next, Figure 19(C) shows a state in which further writing pressure is applied to the writing lead 7, causing the first cam surface 40a of the rotor 40 to mesh with the first fixed cam surface 41a of the upper cam forming member 41. The rotation drive mechanism 30 corresponds to the state shown in Figure 8(C). Therefore, the rotor 40 is rotationally driven by an amount equivalent to half the phase (half the pitch) of one tooth of the first cam surface 40a. In other words, the rotor 40 rotates from the state shown in Figure 19(A) by an angle of rotation equivalent to the circumferential rotational movement distance L1. As the rotor 40 is rotated, the cam protrusion 61a of the input clutch cam 61 engages with the peak 63a of the output clutch cam 62, and the output clutch cam 62 is rotationally driven via the input clutch cam 61. As shown in Figure 19(B) immediately before this, the cam protrusion 61a of the input clutch cam 61 and the peak 63a of the output clutch cam 62 are spaced apart in the circumferential direction, so the amount of rotational movement of the output clutch cam 62 is less than the distance L1 of the input clutch cam 61, i.e., the rotational movement of the rotor 40. Specifically, the amount of rotational movement of the output clutch cam 62 is distance L2, obtained by subtracting distance D1 from distance L1, and therefore the output clutch cam 62 rotates by a second rotation angle equivalent to distance L2.

Next, Figure 19 (D) shows the initial state in which the writing pressure on the writing lead 7 is released. The rotation drive mechanism 30 corresponds to the state shown in Figure 9 (D). Therefore, in this state, the rotor 40 moves toward the lower cam forming member 42 due to the biasing force of the cushion spring 45, and the cam protrusion 61a of the input clutch cam 61 moves away from the clutch cam surface 63 of the output clutch cam 62.

Next, Figure 19(E) shows the state in which 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 due to the biasing force of the cushion spring 45. The rotation drive mechanism 30 corresponds to the state shown in Figure 9(E). Therefore, the rotor 40 again receives rotational drive equivalent to half a phase (half pitch) of one tooth of the second cam surface 40b. That is, the rotor 40, and further the input clutch cam 61 connected to the rotor 40, rotates from the state shown in Figure 19(A) by a first rotation angle corresponding to the rotational movement distance L3 equivalent to one phase (one pitch). However, because the cam protrusion 61a of the input clutch cam 61 and the peak portion 63a of the output clutch cam 62 are axially separated, the first engagement surface 61aa of the input clutch cam 61 and the second engagement surface 63aa of the output clutch cam 62 do not engage, and therefore the output clutch cam 62 is not rotationally driven. The input clutch cam 61 and output clutch cam 62 cooperate only at the first engagement surface 61aa of the input clutch cam 61 and the second engagement surface 63aa of the output clutch cam 62, and do not cooperate in any other areas.

When the rotor 40 moves back and forth in the axial direction due to writing, the rotor 40 and input clutch cam 61 undergo a rotational movement corresponding to one tooth of the rotary drive mechanism 30 cam, but the output clutch cam 62 undergoes a smaller rotational movement. In other words, the clutch mechanism 60 is configured to transmit the rotational movement of the input clutch cam 61 to the output clutch cam 62 so that when the input clutch cam 61 rotates by a first rotational angle, the output clutch cam 62 rotates by a second rotational angle smaller than the first rotational angle. The cam pitch in the clutch mechanism 60 is set smaller than the cam pitch in the rotary drive mechanism 30. Specifically, the output clutch cam 62 is rotationally driven by an angle (second rotational angle) that is the difference between the rotational angle (first rotational angle) corresponding to one tooth of the rotary drive mechanism 30 cam and the rotational angle (second rotational angle) corresponding to one tooth of the clutch mechanism 60 cam.

For example, suppose the number of teeth A of the rotary drive mechanism 30, such as the first cam surface 40a of the rotor 40, is 40, and the number of teeth B of the clutch cam surface 63 of the output clutch cam 62 is 46. The number of back and forth movements required for the rotor 40 to rotate once, i.e., the number of strokes, is 40. The rotation angle C of the rotor 40 per stroke is 360/A, so 360/40 = 9 degrees. The rotation angle D, which corresponds to the distance between adjacent peaks 63a of the output clutch cam 62, is 360/D, so 360/46 = 7.83 degrees. Then, as explained with reference to Figure 19, the rotation angle E of the output clutch cam 62 per stroke is C - D, so 9 - 7.83 = 1.17 degrees. Therefore, the number of strokes required for the output clutch cam 62 to rotate once is 360/1.17 = 307.7 strokes, or in other words, 308 strokes. Expressed as a reduction ratio, this becomes 1/(C/E) = 1/7.69.

The clutch mechanism 60 allows the number of strokes required for the output clutch cam 62, and therefore the abutting element 65c of the delivery cam 65, to rotate once more (e.g., 308 strokes) than the number of strokes required for the rotor 40 to rotate once (e.g., 40 strokes). Furthermore, by adjusting the number of teeth A of the cam of the rotation drive mechanism 30 and/or the number of teeth B of the cam of the clutch mechanism 60, the rotor 40 can be rotated once in any number of strokes, and the writing lead can be advanced in any number of strokes.

The output clutch cam 62 and the transmission cam 64 may be formed as a single unit. The output clutch cam 62, the transmission cam 64, and the delivery cam 65 may be collectively formed as an output member. The slider 9 and the delivery cam 65 may be formed as a single unit. The input clutch cam 61 has one cam protrusion 61a as the input cam surface, but may have multiple cam protrusions 61a. The input cam surface of the input clutch cam 61 and the clutch cam surface 63, which is the output cam surface of the output clutch cam 62, may be formed as desired, as long as they engage during circumferential movement but do not engage during axial movement, as with the relationship between the first engagement surface 61aa and the second engagement surface 63aa. Similarly, the transmission cam 64 and the delivery cam 65 may be formed as desired, as long as they engage during circumferential movement but do not engage during axial movement, as with the relationship between the first engagement wall 64b and the second engagement wall 65b.

In the above-described embodiment, meshing clutches, input clutch cam 61 and output clutch cam 62, are used as the input and output members, respectively. In other words, the clutch mechanism 60 is configured such that an input cam surface is formed on the input member and an output cam surface facing the input cam surface is formed on the output member, and the input cam surface and output cam surface engage only during part of the rotational motion of the rotor, transmitting the rotational motion of the rotor to the output member via the input member.

However, a friction clutch may also be used as the clutch mechanism. That is, the input and output members may be disk- or cone-shaped members facing each other, and frictional force may be used to rotate the rotor 40 via the relay member 12 such that when the input member rotates a first rotation angle, the output member rotates a second rotation angle smaller than the first rotation angle. The angle of rotation transmitted from the input member to the output member may be adjusted by changing the shape, material, surface roughness, etc. of the contact surface between the opposing disks or cones in the input and output members to adjust the frictional force. This allows the rotor 40 to rotate once in any number of strokes and the writing lead to be advanced in any number of strokes. The contact surface between the input and output members may be made of, for example, rubber or sandpaper. Any clutch mechanism other than a dog clutch or friction clutch may also be used.

In the above-described embodiment, the ball chuck 11 and the input clutch cam 61 were connected, and the ball chuck 11 was configured to rotate upon receiving the rotational driving force of the rotor 40 via the relay member 12 and the input clutch cam 61, thereby rotating the writing lead 7. However, the ball chuck 11 and the input clutch cam 61 do not have to be connected. In other words, the clutch mechanism may be applied to mechanical pencils that are not configured to rotate the writing lead.

After the writing lead 7 is pulled out of the ball chuck 11 by the knocking operation or the operation of the lead advancing mechanism, but before writing pressure is applied to the writing lead 7, the structure leaves room for the writing lead to further retract (backlash). Therefore, if the actual amount of lead 7 advancing is small, the advancing writing lead 7 may retract due to the backlash, and the writing lead 7 may not actually be advanced.

The clutch mechanism can delay the timing or frequency of the lead 7 being advanced by the lead advancement mechanism. Therefore, the clutch mechanism allows the lead 7 to be advanced more frequently after the lead 7 has worn down, preventing the lead 7 from effectively not being advanced due to backlash. The amount of lead advanced can be changed by adjusting the step height H of the lead advancement mechanism, as described above. Therefore, the above-described embodiment can provide a mechanical pencil equipped with a lead advancement mechanism that can more reliably advance the lead.

As shown in Figure 1, the mechanical pencil 1 further has a cap 70 that is equipped with a clip 70a and fits into the barrel 6. The cap 70 has a cover cap 71, a lead advancing member 72 that serves as the lead advancing portion, and a cushion spring 73. In this specification, the closed end side in the axial direction of the cap 70 is defined as the "front" side, and the open end side is defined as the "rear" side. A lead advancing mechanism that utilizes the lead advancing portion of the cap 70 will be described with reference to Figures 20 and 21.

As shown in Figures 1 and 21 (B), the cover cap 71 is a cap-shaped member with a closed front end. Attaching the cover cap 71 to the front end of the cap 70 forms the closed end of the cap 70. The lead advancing member 72 is arranged inside the front end of the cap 70 so that it can move back and forth. A cushion spring 73 is arranged between the cover cap 71 and the lead advancing member 72, and the cushion spring 73 urges the lead advancing member 72 rearward.

Figure 20 is a longitudinal cross-sectional view of the lead advancing member 72. The lead advancing member 72 is a cylindrical member. In Figure 20, the left side is positioned so that the front of the cap 70 is the left. The rear end surface of the lead advancing member 72 is provided with an insertion hole 72a, which is a circular opening into which the tip of the mechanical pencil 1, i.e., the slider 9, etc., is inserted. The bottom surface of the insertion hole 72a is provided with a storage recess 72b, which has a cylindrical inner surface with a depth D2 and an inner diameter R narrower than the entrance of the insertion hole 72a. A tapered surface 72c is provided behind the storage recess 72b. The inner diameter R of the storage recess 72b is set according to the outer diameter of the writing lead 7 used in the mechanical pencil 1. Specifically, the inner diameter R of the storage recess 72b is set slightly larger than the outer diameter of the writing lead 7 so that the tip of the writing lead 7 can be accommodated.

Figure 21 is an enlarged cross-sectional view of the mechanical pencil 1 illustrating the extension of the lead 7. Figure 21(A) shows the state of the mechanical pencil 1 before the lead 7 is extended and the cap 70 is not fitted onto the barrel 6, Figure 21(B) shows the state of the mechanical pencil 1 with the cap 70 fitted onto the barrel 6, and Figure 21(C) shows the state of the mechanical pencil 1 after the cap 70 has been removed from the barrel 6 and the lead 7 has been extended.

In Figure 21 (A), the writing lead 7 does not protrude from the slider 9. In other words, this shows the state in which the user has retracted the writing lead 7 after completing a series of writing actions so that it does not protrude from the slider 9 in order to protect the writing lead 7.

Next, as shown in Figure 21 (B), the cap 70 is fitted onto the barrel 6. At this time, the tip of the mechanical pencil 1, i.e., the tip of the lead 7 and the slider 9, are inserted into the insertion hole 72a of the lead advancing member 72. As described above, the inner diameter R of the accommodating recess 72b is set according to the outer diameter of the lead 7, so the accommodating recess 72b receives the tip of the lead 7. On the other hand, the outer diameter of the tip of the slider 9 is set larger than the inner diameter R of the accommodating recess 72b. Therefore, as the tip of the slider 9 is inserted into the cap 70, it engages with the tapered surface 72c without being accommodated in the accommodating recess 72b. As a result, the slider 9 retreats relative to the lead 7 within the barrel 6, and as a result, the lead 7 protrudes from the tip of the slider 9 within the cap 70 by a distance equal to the depth D2 of the accommodating recess 72b.

Next, as shown in Figure 21 (C), the cap 70 is removed from the barrel 6 to begin the next writing operation. At this time, the slider 9, which had been retracted, and the holding chuck 10 positioned inside the slider 9 are moved forward by the biasing force of the cam abutment spring 18. As a result, the writing lead 7 held by the holding chuck 10 is pulled out of the ball chuck 11 and relatively extended from the tip of the slider 9 by the depth D2 of the storage recess 72b. Therefore, the amount of writing lead 7 extended, i.e., the extension amount, is equal to the depth D2 of the storage recess 72b.

Generally, after a user has completed a series of writing actions, they retract the writing lead so that it does not protrude from the tip member or slider in order to protect it. Therefore, before starting the next writing action, it is necessary to perform at least one knocking operation to advance the writing lead in advance. Even in mechanical pencils equipped with the lead advancing mechanism described above, a writing action is required to automatically advance the writing lead, so it is necessary to perform at least one knocking operation to advance the writing lead in advance before starting a writing action.

With the lead advancing member 72, the lead 7 is advanced simply by attaching and detaching the cap 70 to the barrel 6. In other words, the lead can be advanced without performing a knocking operation before starting a writing action. This makes it possible to provide a mechanical pencil that allows for a new lead advancing operation that differs from conventional knocking operations.

Even if the cap 70 is fitted to the barrel 6 with the lead 7 protruding from the slider 9 longer than the depth D2 of the storage recess 72b, the amount of protrusion of the lead 7 does not change. In other words, in this state, the tip of the slider 9 does not engage with the tapered surface 72c, and therefore the slider 9 does not recede relative to the lead 7 within the barrel 6. At this time, the lead advancing member 72 is pressed by the tip of the lead 7 that protrudes further, but this pressure is absorbed by the lead advancing member 72 moving forward against the biasing force of the cushion spring 73.

The lead-advancing member 72 may be replaceable by removing the cover cap 71. In other words, the amount of protrusion of the lead 7 varies depending on the user's preference. For example, some users find it convenient for the lead 7 to protrude sufficiently, as it allows for longer writing, while others prefer a less protruding lead 7 because they do not need to worry about the lead 7 breaking. Therefore, lead-advancing members 72 with storage recesses 72b of various depths D2 may be prepared in advance and made replaceable according to user preference. The cushion spring 73 may be omitted, and the lead-advancing member 72 may be fixed and positioned inside the front end of the cap 70.

The lead advancing portion, which is the lead advancing member 72, may be configured in any way as long as it can press on the slider 9 and retract the slider 9 relative to the lead 7 when the cap 70 is fitted to the barrel 6. In other words, the shape of the accommodating recess 72b may be configured in any way as long as the tip of the lead 7 is received within the accommodating recess 72b when the cap 70 is fitted, and the tip of the slider 9 is not received within the accommodating recess 72b but is engaged and retracts. For example, the shape may be multiple inward-extending protrusions formed on the inner surface of the cap 70 so as to retract the slider 9 relative to the lead 7 when the cap 70 is fitted.

In the above-described embodiment, the slider 9 is biased forward by the cam abutment spring 18 to activate the lead-advancing mechanism. However, the lead-advancing member 72 of the cap 70 may also be applied to a mechanical pencil in which the slider is not biased forward. The mechanical pencil may or may not have a ball chuck. For example, the lead-advancing member of the cap may be applied to a pipe-slide mechanical pencil in which a pipe-shaped lead guide, which is a slider attached to the tip member, advances as the lead protrudes with the knock operation, and the lead guide retracts as the lead wears with writing.

Figure 22 is an enlarged perspective view of the cap 70. The inner peripheral surface of the cap 70, specifically the inner peripheral surface near the open end, is provided with multiple, specifically three, positioning recesses 70b arranged at equal intervals along the circumferential direction. The positioning recesses 70b are recesses that open toward the rear and are formed in a bell-shaped curve when viewed radially outward from the central axis. That is, a convex curved surface 70ba is formed on the inner surface on the front side of the positioning recess 70b, and a concave curved surface 70bb is formed on the inner surface on the rear side of the positioning recess 70b.

Figure 23 is an enlarged perspective view of the barrel 6. As shown in Figure 23 and also in Figure 2, the outer peripheral surface of the barrel 6 is provided with a plurality of positioning protrusions 6a, specifically three, arranged at equal intervals along the circumferential direction. The positioning protrusions 6a are protrusions that extend forward. A convex curved surface 6aa is formed on part of the outer surface on the front side of the positioning protrusion 6a. The convex curved surface 6aa of the positioning protrusion 6a is complementary to part of the convex curved surface 70ba of the positioning recess 70b. In other words, the positioning protrusions 6a and the positioning recess 70b have complementary portions.

As shown in Figures 1 and 21 (B), an annular magnet 80 is disposed inside the cap 70. The magnet 80 is, for example, a neodymium magnet. Instead of the annular magnet 80, multiple magnets may be disposed at equal intervals along the circumferential direction. On the other hand, the gripping portion 8 described above is a first magnetic body made of a magnetic material. The magnet 80 is disposed inside the cap 70 so that a magnetic attractive force acts between the magnet 80 and the gripping portion 8 when the cap 70 is fitted to the barrel 6.

When fitting the cap 70 to the barrel 6, the barrel 6 is typically held with one hand and the cap 70 with the other, and the open end of the cap 70 is inserted into the barrel 6. When the cap 70 is inserted to a predetermined depth into the barrel 6, the magnetic force acting between the gripping portion 8 and the magnet 80 pulls the cap 70 deeper. At this time, if the positioning protrusion 6a of the barrel 6 and the positioning recess 70b of the cap 70 are aligned along the axial direction, the positioning protrusion 6a and the positioning recess 70b will fit together without interfering with each other, and the barrel 6 and cap 70 will be fitted together. On the other hand, there are cases where the positioning protrusion 6a of the barrel 6 and the positioning recess 70b of the cap 70 are not aligned along the axial direction, i.e., they are misaligned circumferentially.

If the positioning protrusion 6a of the barrel 6 and the positioning recess 70b of the cap 70 are slightly misaligned in the circumferential direction, the magnetic attraction will cause the convex curved surface 6aa of the positioning protrusion 6a to come into contact with the concave curved surface 70bb of the positioning recess 70b. As a result, the positioning protrusion 6a and the positioning recess 70b work together to rotate the barrel 6 or cap 70 around the central axis so that the positioning protrusion 6a and the positioning recess 70b fit together, thereby fitting the barrel 6 and the cap 70 together.

If the positioning protrusion 6a of the barrel 6 and the positioning recess 70b of the cap 70 are significantly misaligned in the circumferential direction, the convex surface 6aa of the positioning protrusion 6a will not come into contact with the concave surface 70bb of the positioning recess 70b, even when subjected to magnetic attraction. Therefore, the positioning protrusion 6a and the positioning recess 70b will not cooperate, and the barrel 6 and cap 70 will not be mated. Now, hold the cap 70 with one hand and rotate the cap 70 around the central axis until the convex surface 6aa of the positioning protrusion 6a comes into contact with the concave surface 70bb of the positioning recess 70b. As a result, the positioning protrusion 6a and the positioning recess 70b cooperate to rotate the barrel 6 or cap 70 around the central axis so that the positioning protrusion 6a and the positioning recess 70b are mated, and the barrel 6 and cap 70 are mated.

The barrel and cap are typically fitted together in a snap-fit fashion, with a protrusion on the inner circumferential surface of the cap climbing over a protrusion on the outer circumferential surface of the barrel. According to the above-described embodiment, the barrel 6 and cap 70 are fitted together using magnetic attraction, eliminating the need to press the cap 70 firmly against the barrel 6. As a result, even if the cap 70 is inserted at an angle to the central axis of the barrel 6, there is no risk of the edge of the open end of the cap 70 damaging the outer circumferential surface of the barrel 6. Furthermore, even children or elderly people with weaker strength can easily fit the barrel 6 and cap 70 together.

Furthermore, if the outer surfaces of both the barrel 6 and the cap 70 are adorned with identifying marks, designs, such as symbols, letters, or patterns, or distinctive shapes, the barrel 6 and the cap 70 can be correctly positioned in the rotational direction around the central axis. In short, the above-described embodiment provides a writing instrument that allows the cap to be accurately fitted to the barrel. Furthermore, because the magnetic force tends to become stronger the closer the relative distance, the barrel 6 and the cap 70 collide with force when fitting is complete. As a result, the user can feel a pleasant clicking sensation and sound, and can confirm that the fitting has been completed securely.

As shown in Figures 1, 2, and 4, a second magnetic body 81 made from a magnetic material may be disposed at the rear end of the barrel 6, i.e., the rear end of the rear barrel 3. This allows for the use of magnetic attraction when fitting the cap 70 to the rear end of the barrel 6 for writing. In this case, a positioning protrusion 6a that cooperates with the positioning recess 70b of the cap 70 may be provided at the rear end of the barrel 6. In the above-described embodiment, the positioning protrusion 6a is formed on the outer peripheral surface of the barrel 6, and the positioning recess 70b is formed on the inner peripheral surface of the cap 70. However, a positioning recess may be formed on the outer peripheral surface of the barrel 6, and a positioning protrusion may be formed on the inner peripheral surface of the cap 70. The mechanical pencil 1 does not have to have the second magnetic body 81.

In the above-described embodiment, the magnet 80 is located on the cap 70 side, and the first magnetic body, which is not a magnet, is located on the barrel 6 side. However, it is also possible to locate the first magnetic body on the cap 70 side, and the magnet on the barrel 6 side, for example, inside the grip portion 8. However, because the grip portion 8 is exposed to the outside when the cap 70 is removed, it is preferable to locate the first magnetic body on the barrel 6 side, in order to prevent surrounding magnetic bodies, such as paper clips on a desk, from being attracted to the grip portion 8. Magnets may also be located on both the barrel 6 and the cap 70. The first magnetic body may also be provided in a part of the barrel 6 other than the grip portion 8.

In the above-described embodiment, three positioning protrusions 6a and three positioning recesses 70b are formed, but the number may be one, two, or four or more. The positioning protrusions 6a and the positioning recesses 70b may be configured in any manner as long as they cooperate with each other when slightly misaligned circumferentially, and the barrel 6 and the cap 70 are fitted together when the barrel 6 or the cap 70 is rotated around the central axis. For example, the positioning protrusion 6a shown in FIG. 23 may be formed to be completely complementary to the positioning recess 70b shown in FIG. 22.

The above-described fitting using magnetic attraction between the barrel and cap can be applied not only to mechanical pencils, but also to other writing instruments, such as ballpoint pens, felt-tip pens, marker pens, fountain pens, and thermochromic writing instruments. The positioning protrusions 6a and positioning recesses 70b may be omitted, and the fitting between the barrel and cap may simply be achieved using magnetic attraction.

Figure 24 is a perspective view of the holding chuck 10, and Figure 25 is a longitudinal cross-sectional view of the holding chuck 10. In Figure 25, the left side is positioned to be the front of the mechanical pencil 1. As described above, the holding chuck 10 has a through hole 10a extending along the axial direction. The holding chuck 10 has a cylindrical small-diameter portion 10b and a flange portion 10c provided on the outer surface of the rear end of the small-diameter portion 10b. Inside the front side of the through hole 10a is a lead holding portion 10d that is narrower than the rest of the hole. Inside the through hole 10a behind the lead holding portion 10d is a conical surface 10e that widens rearward.

As shown in Figure 24, the lead holding portion 10d of the through hole 10a is an elongated hole. Specifically, the cross-sectional shape of the lead holding portion 10d of the through hole 10a is a rounded rectangle. Note that the lead holding portion 10d of the through hole 10a may be any elongated hole, and therefore the cross-sectional shape of the lead holding portion 10d may be oval, specifically an ellipse or oval. The size of the elongated hole, for example, the length and aspect ratio in the case of a rounded rectangle, or the lengths of the major and minor axes in the case of an ellipse, is determined in advance through experiments, etc., depending on the outer diameter or composition of the writing lead 7 typically used in the mechanical pencil 1.

Because the lead holding portion 10d of the through hole 10a is an elongated hole, it is more susceptible to elastic deformation than a typical circular hole lead holding portion. That is, like a circular hole, an elongated hole is less susceptible to elastic deformation in the direction along the elongated shape, but is more susceptible to elastic deformation in the direction perpendicular to the elongated shape than a circular hole. Therefore, even if there is some variation during manufacturing in the outer diameter of the lead 7 or the size of the through hole in the holding chuck 10, this can be absorbed by elastic deformation in the direction perpendicular to the elongated shape. This makes it possible to provide a mechanical pencil in which the sliding resistance between the lead 7 and the holding chuck 10 can be more appropriately set.

In a typical mechanical pencil, sliding contact between the lead and the retaining chuck occurs only when the lead is advanced by knocking. On the other hand, as described above, in a mechanical pencil 1 equipped with a rotation drive mechanism and a lead advancing mechanism, sliding contact between the lead 7 and the retaining chuck 10 occurs not only when the lead 7 is advanced by knocking, but also during normal writing. Therefore, in order to ensure proper functioning of the rotation drive mechanism and the lead advancing mechanism, it is preferable to set the sliding resistance between the lead and the retaining chuck more precisely. In the mechanical pencil 1, the lead retaining portion 10d of the through-hole 10a is an elongated hole, which allows for more precise setting of the sliding resistance between the lead 7 and the retaining chuck 10.

The retaining chuck 10 is made from an elastic material such as NBR, EPDM, fluororubber, or silicone rubber. A retaining chuck 10 made from fluororubber is particularly preferable from the standpoint of creep resistance and chemical resistance. While the writing lead 7 contains some oil components, the effects of these oil components can be further reduced by making the retaining chuck 10 from fluororubber. As a result, various types of oil components and their blends can be selected for the writing lead 7, making it possible to manufacture a wider variety of writing leads. In this case, the lead retaining portion 10d does not have to be an elongated hole, and may have a typical circular cross-sectional shape.

In the above-described embodiment, the holding chuck 10 has a cylindrical small-diameter portion 10b, but the holding chuck may be formed with a tapered shape as a whole. In other words, the holding chuck 10 may have any external shape as long as the core-holding portion 10d of the through-hole 10a is an elongated hole.

1 Mechanical pencil 2 Front shaft 3 Rear shaft 4 Tip member 6 Shaft tube 6a Positioning protrusion 7 Writing lead 8 Grip (first magnetic body)
DESCRIPTION OF SYMBOLS 9 Slider 10 Holding chuck 10a Through hole 10d Lead holding portion 11 Ball chuck 12 Relay member 17 Coil spring 18 Cam contact spring 19 Lead case 20 Knock rod 21 Coil spring 30 Rotation drive mechanism 40 Rotor 50 Dial cam member 51 Dial cam 52 Rail cam member 53 Rail cam 54 Feeding cam surface 55 Step 56 Coil spring 60 Clutch mechanism 61 Input clutch cam 62 Output clutch cam 63 Clutch cam surface 64 Transmission cam 65 Feeding cam 65c Contact 66 Clutch cam holder 70 Cap 70b Positioning recess 71 Cover cap 72 Lead feeding member 72a Insertion hole 72b Storage recess 73 Cushion spring 80 Magnet 81 Second magnetic body

Claims (4)

A shaft cylinder and
a holding chuck for holding the writing lead;
a slider that holds the holding chuck therein and is arranged in the barrel so as to be movable back and forth, the slider being configured so that the writing lead that passes through the holding chuck protrudes from a tip end thereof;
a cap that is equipped with a lead-advancing portion and can be fitted onto the front end of the barrel;
The lead advancing portion is configured to press the slider and move the slider back relative to the writing lead when the cap is fitted to the barrel ,
The lead-advancing section is provided with a storage recess capable of storing the tip of the writing lead,
The mechanical pencil is configured so that the slider is retracted relative to the writing lead by a distance equal to the depth of the storage recess . 2. The mechanical pencil according to claim 1 , wherein the lead advancing portion is provided inside the front end of the cap so as to be movable back and forth. 3. The mechanical pencil according to claim 2, wherein the lead advancing portion is provided inside the front end of the cap so as to be movable back and forth when the cap is fitted onto the barrel. The mechanical pencil according to any one of claims 1 to 3 further comprises a ball chuck that allows the lead to move forward and prevents it from moving backward.