Propelling pencil

Abstract

A mechanical pencil (1) has a first cam surface (140a) provided with first cam teeth (140aa), a second cam surface (140b) provided with second cam teeth (140ba), a first fixed cam surface (141a) that rotates a rotating body in cooperation with the first cam surface, and a second fixed cam surface (142a) that rotates the rotating body in cooperation with the second cam surface. The first fixed cam surface is provided with first fixed cam teeth (141aa) cooperating with the first cam teeth, the second fixed cam surface is provided with second fixed cam teeth (142aa) cooperating with the second cam teeth, and in the first cam teeth, the length of the bottom side located on the rear side relative to the rotation direction of the rotating body (140) is set to be X with respect to a perpendicular line led out from the apex, and X is the length of the bottom side located on the rear side relative to the perpendicular line led out from the apex. The first cam teeth are configured so as to satisfy the relationship 0 < Y < X, where Y is the length of the bottom side on the front side with respect to the rotation direction of the rotating body.

Description

Technical Field

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

[0002] There is known a mechanical pencil comprising: a rotating member including a slider having a chuck, the chuck allowing a writing lead to move forward and preventing the writing lead from moving backward; and a rotation drive mechanism having a rotating body, and receiving a moving backward motion in the axial direction caused by a writing pressure applied to the writing lead held by the chuck and an moving forward motion in the axial direction caused by release of the writing pressure, and driving the rotating body to rotate in one direction, wherein the chuck rotates in response to the rotational driving force of the rotating body, thereby rotating the writing lead (Patent Documents 1 and 2).

[0003] In the mechanical pencil with a rotation drive mechanism described in Patent Document 1, in order to rotate the lead, the lead generally moves forward and backward, albeit slightly. The series of forward and backward movements of the lead are collectively referred to as "buffering movements". In the mechanical pencil described in Patent Document 1, the user is provided with the ability to freely switch the rotation drive mechanism on and off, with a view to the problem that such buffering movements, especially the backward movement of the lead, are annoying when taking shorthand, for example. For the buffering movement of the rotation drive mechanism, refer to Fig.12 and Fig.13 Provide explanation.

[0004] Fig.12 2 is a schematic diagram for explaining the rotational drive of the rotating body 240 of the conventional rotational drive mechanism. Fig.13 Then Fig.12 Schematic diagram for explaining the rotational drive of the rotating body 240. The rotational drive mechanism includes the rotating body 240 formed in a cylindrical shape, an upper cam forming member 241 formed in a cylindrical shape, and a lower cam forming member 242 formed in a cylindrical shape. Fig.12 and Fig.13 In the figure, a first cam surface 240a is formed in a circular ring shape on the upper surface of the rotating body 240, i.e., the rear end surface, and the second cam surface 240b is formed in a circular ring shape on the lower surface of the rotating body 240, i.e., the front end surface, and the second cam surface 240b is formed in a circular ring shape and the second cam surface 240b is formed in a circular ring shape and the second cam surface 240b is formed in a circular ring shape and the second cam surface 240b is formed in a circular ring shape.

[0005] The first fixed cam surface 241a which is continuously sawtoothed along the circumferential direction is also formed on the annular end surface of the upper cam forming member 241 which is opposite to the first cam surface 240a of the rotating body 240. The second fixed cam surface 242a which is continuously sawtoothed along the circumferential direction is also formed on the annular end surface of the lower cam forming member 242 which is opposite to the second cam surface 240b of the rotating body 240. The cam surfaces of the first cam surface 240a and the second cam surface 240b formed on the rotating body 240 and the cam surfaces of the first fixed cam surface 241a formed on the upper cam forming member 241 and the second fixed cam surface 242a formed on the lower cam forming member 242 are formed so that the pitch in the circumferential direction is substantially the same as each other.

[0006] The rotary drive mechanism converts the retracting and advancing movements (buffering movements) of the pen core based on the writing movement transmitted to the rotary drive mechanism into the rotary motion of the rotating body 240. The rotary motion of the rotating body 240 is transmitted to the chuck unit holding the pen core, and thus the pen core held by the chuck unit also rotates.

[0007] Fig.12 (A) shows the relationship between the rotating body 240, the upper cam forming member 241 and the lower cam forming member 242 in a state where no writing pressure is applied to the pen core. In this state, the second cam surface 240b formed on the rotating body 240 abuts against the second fixed cam surface 242a of the lower cam forming member 242 under the force of a spring not shown. At this time, the first cam surface 240a of the rotating body 240 and the first fixed cam surface 241a of the upper cam forming member 241 are set to be offset in the axial direction by half a phase relative to one tooth of the cam.

[0008] Fig.12 (B) shows the initial state in which writing pressure is applied to the lead by writing with a mechanical pencil. In this state, the rotating body 240 retreats as the chuck unit retreats, overcoming the force of the spring. As a result, the rotating body 240 moves toward the upper cam forming member 241 and abuts against the first fixed cam surface 241a.

[0009] then, Fig.12 (C) shows a state where the writing pressure is further applied to the pen core, causing the rotating body 240 to slide and retreat while contacting the first fixed cam surface 241a of the upper cam forming member 241. That is, the rotating body 240 is driven to rotate by half the phase of one tooth of the first cam surface 240a. In this state, the first cam surface 240a of the rotating body 240 is meshed with the first fixed cam surface 241a of the upper cam forming member 241.

[0010] In addition, Fig.12 and Fig.13 The circle mark drawn in the center of the rotating body 240 shows the rotational movement amount of the rotating body 240. Fig.12 In the state shown in (C), the second cam surface 240b of the rotating body 240 and the second fixed cam surface 242a of the lower cam forming member 242 are set to be offset in the axial direction by half a phase relative to one cam tooth.

[0011] then, Fig.13 (D) shows the initial state in which writing with the mechanical pencil is completed and the writing pressure on the lead is released. In this state, the rotating body 240 moves forward under the force of the spring. As a result, the rotating body 240 moves toward the lower cam forming member 242 and abuts against the second fixed cam surface 242a.

[0012] then, Fig.13 (E) shows a state where the rotating body 240 moves forward while sliding against the second fixed cam surface 242a of the lower cam forming member 242 under the action of the spring. That is, the rotating body 240 is again driven by a rotation corresponding to half the phase of one tooth of the second cam surface 240b. In this state, the second cam surface 240b of the rotating body 240 is meshed with the second fixed cam surface 242a of the lower cam forming member 242.

[0013] Therefore, as indicated by the circle mark drawn in the center of the rotating body 240, the rotating body 240 receives a rotational drive corresponding to one tooth of the first cam surface 240a and the second cam surface 240b as the rotating body 240 receives the writing pressure and moves back and forth in the axial direction, that is, moves forward and backward, and the pen lead held by the chuck unit is also driven to rotate in the same manner by the chuck unit. Therefore, by using the one forward and backward movement of the rotating body 240 in the axial direction caused by writing, the rotating body 240 receives a rotational movement corresponding to one tooth of the cam, and by repeating the above-mentioned action, the pen lead is driven to rotate in sequence. As a result, it is possible to prevent the pen lead from being unevenly worn as writing proceeds, and it is possible to prevent the thickness and depth of the writing line from changing to a large extent.

[0014] Prior art literature

[0015] Patent Literature

[0016] Patent Document 1: Japanese Patent Application Publication No. 2022-073560

[0017] Patent Document 2: International Publication No. 2007 / 142135 Summary of the invention

[0018] Problem that the invention aims to solve

[0019] As described above, in Patent Document 1, the problem of the writing feeling being reduced due to the annoyance of the buffering action is addressed, and the rotation drive mechanism is provided to be turned off as needed so that the buffering action itself cannot be performed. However, in Patent Document 1, no reexamination of the problem of the buffering action itself is found. The forward movement of the lead is performed as the lead moves away from the writing surface during writing, so it is hardly noticed by the user. On the other hand, as for the backward movement of the lead, when writing is desired, although the lead is brought into contact with the writing surface, the main body of the mechanical pencil moves forward, in other words, the lead moves relatively backward, so there is a situation where the user feels unnatural visually or tactilely.

[0020] In this regard, the inventors of the present invention conducted a survey to collect negative or positive opinions on a mechanical pencil equipped with a rotation drive mechanism for rotating the lead, and the results showed that among the 21.4% of negative opinions, 44.8% of users actually cited the retreat of the lead as the reason for the negative opinion. On the other hand, 78.6% of users gave a positive evaluation of such a mechanical pencil, and therefore the function of rotating the lead was highly evaluated. Therefore, the inventors of the present invention thought that a buffer action is required in order to rotate the lead by the rotation drive mechanism, but the amount of the buffer action is further reduced, especially the retreat amount of the lead is reduced to the limit.

[0021] Reference Fig.12 (A) describes the amount of buffering action or the amount of retraction of the writing lead. The height of the cam tooth is set as distance h, and the moving distance until the top of the cam tooth of the first cam surface 240a contacts the first fixed cam surface 241a by the retraction of the rotating body 240 is set as distance d. The distance s in the axial direction between the rear end of the first cam surface 240a of the rotating body 240, that is, the top of the tooth top of the cam tooth and the tooth bottom of the cam tooth of the first fixed cam surface 241a of the upper cam forming member 241, corresponds to the amount of retraction of the writing lead in the buffering action.

[0022] exist Fig.12 In (A), since the second cam surface 240b of the rotating body 240 is meshed with the second fixed cam surface 242a of the lower cam forming member 242, in order to release the meshing, at least the top of the cam teeth of the second cam surface 240b must pass over the top of the cam teeth of the second fixed cam surface 242a. In other words, it is necessary to make the rotating body 240 and the pen core retreat by an amount corresponding to the distance h of the cam teeth. When the distance d is less than the distance h, the rotation of the rotating body 240 is hindered by the first fixed cam surface 241a or the second fixed cam surface 242a, and therefore cannot function as a rotation drive mechanism. Therefore, when the rotating body 240 passes the distance h of the cam teeth and retreats further, a distance equivalent to the distance dh indicates that there is room to reduce the retreat amount of the pen core.

[0023] An object of the present invention is to provide a mechanical pencil having a rotation drive mechanism for rotating a writing lead, in which the amount of retreat of the writing lead is further reduced.

[0024] Solutions for solving problems

[0025] According to one technical solution of the present invention, there is provided a mechanical pencil, characterized in that the mechanical pencil comprises: a pen barrel; a chuck unit which allows the pen lead to advance and prevents the pen lead from retreating; and a rotation drive mechanism which comprises a rotating body, the rotation drive mechanism receiving a retreating action in the axial direction caused by the writing pressure on the pen lead held by the chuck unit and an advancing action in the axial direction caused by the release of the writing pressure, and drives the rotating body to rotate in one direction, the rotation drive mechanism comprising: an annular first cam surface which is formed on the rear end surface of the rotating body ; a second annular cam surface formed on the front end surface of the rotating body; a first fixed cam surface provided on the side of the pen holder and cooperating with the first cam surface to rotate the rotating body; and a second fixed cam surface provided on the side of the pen holder and cooperating with the second cam surface to rotate the rotating body, the mechanical pencil being configured such that, by utilizing the retreating action of the chuck unit caused by the writing pressure, the first cam surface of the rotating body abuts against the first fixed cam surface to mesh with the rotating body while rotating, and by utilizing the release of the writing pressure, the rotation of the rotating body is The second cam surface abuts against the second fixed cam surface so that the rotating body is meshed while rotating, and when the first cam surface of the rotating body is meshed with the first fixed cam surface, the second cam surface and the second fixed cam surface are set to be offset in the axial direction by half a phase relative to one tooth of the cam, and when the second cam surface of the rotating body is meshed with the second fixed cam surface, the first cam surface and the first fixed cam surface are set to be offset in the axial direction by half a phase relative to one tooth of the cam, The first cam surface includes a first cam tooth, the second cam surface includes a second cam tooth, the first fixed cam surface includes a first fixed cam tooth cooperating with the first cam tooth, and the second fixed cam surface includes a second fixed cam tooth cooperating with the second cam tooth. In the first cam tooth, when the length of the base located at the rear side with respect to the rotation direction of the rotating body is set to X and the length of the base located at the front side with respect to the rotation direction of the rotating body is set to Y with respect to a perpendicular line drawn from the vertex, the first cam tooth is constructed in a manner to achieve a relationship of 0<Y<X.

[0026] According to another embodiment, the first cam tooth and the second cam tooth are configured to satisfy a relationship of X / Y≥1.72.

[0027] According to another embodiment, the first cam tooth and the second cam tooth are configured to satisfy a relationship of X / Y≥2.0.

[0028] According to another embodiment, in a state where the second cam surface of the rotating body is meshed with the second fixed cam surface, the apex of the first cam tooth and the apex of the first fixed cam tooth are separated from each other by 0.1 mm or more in the circumferential direction.

[0029] According to another embodiment of the present invention, the first fixed cam surface and the second fixed cam surface are arranged at a minimum distance that does not hinder the rotation of the rotating body.

[0030] According to another embodiment of the present invention, the mechanical pencil is configured such that the chuck unit receives a rotational driving force from the rotating body and rotates, thereby rotating the writing lead.

[0031] Effects of the Invention

[0032] According to the technical aspects of the present invention, there is provided a common effect of providing a mechanical pencil including a rotation drive mechanism for rotating a writing lead, in which the amount of retreat of the writing lead is further reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a longitudinal sectional view of the mechanical pencil which concerns on embodiment of this invention.

[0034] Figure 2 yes Figure 1 An enlarged cross-sectional view of the front half of a mechanical pencil.

[0035] Figure 3 yes Figure 1 An enlarged cross-sectional view of the central portion of a mechanical pencil.

[0036] Figure 4 It is a partial enlarged view of the rotary drive mechanism.

[0037] Figure 5 The diagrams sequentially illustrate the rotational drive of the rotating body of the rotational drive mechanism.

[0038] Figure 6 The diagram is a schematic diagram for sequentially explaining the rotational drive of the rotating body of the rotational drive mechanism.

[0039] Figure 7 It is a schematic diagram for explaining the relationship between the cams of the rotation drive mechanism.

[0040] Figure 8 It is a diagram for explaining the offset of the rotating body.

[0041] Fig. 9It is a diagram for explaining a rotation failure of a rotating body.

[0042] Fig.10 It is a schematic diagram for explaining the relationship between the cams of another rotation drive mechanism.

[0043] Fig.11 It is described in order Fig.10 Schematic diagram of rotational driving of a rotating body of a rotational driving mechanism.

[0044] Fig.12 This is a schematic diagram for explaining the rotational drive of a rotating body in a conventional rotational drive mechanism.

[0045] Fig.13 Then Fig.12 A schematic diagram illustrating the rotational drive of a rotating body. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. In all the drawings, corresponding components are denoted by common reference numerals.

[0047] Figure 1 1 is a longitudinal sectional view of a mechanical pencil 1 according to an embodiment of the present invention. Figure 2 yes Figure 1 An enlarged cross-sectional view of the front half of the mechanical pencil 1.

[0048] The mechanical pencil 1 comprises a front barrel 2, a rear barrel 3 threadedly coupled to the outer circumferential surface of the rear end of the front barrel 2, and an inner barrel 4 fitted to the inner circumferential surface of the rear end of the rear barrel 3 and provided with a clip. The front barrel 2 and the rear barrel 3 constitute a barrel 5. In addition, the barrel 5 may be referred to as the barrel 5 including the inner barrel 4. The mechanical pencil 1 is configured such that the lead protrudes from the top end of the barrel 5. The vicinity of the top end of the barrel 5 is covered by a top end tube 6 for guiding the lead. In this specification, in the axial direction of the mechanical pencil 1, the lead side is defined as the "front" side, and the side opposite to the lead side is defined as the "back" side.

[0049] Inside the front end of the pen barrel 5, the slider 7 is arranged in a manner that can slide in the axial direction and rotate around the axis. The slider 7 is formed into a cylindrical shape whose outer diameter tapers in a step-like manner toward the front. The above-mentioned top tube 6 is installed at the front end of the slider 7. In addition, a retaining chuck 8 with a through hole formed in the center is arranged behind the top tube 6. The through hole of the retaining chuck 8 is in sliding contact with the outer peripheral surface of the pen core, and plays a role in temporarily retaining the pen core.

[0050] A cylindrical relay member 9 is threadedly connected to the rear end of the slider 7. A chuck unit 10 and a refill shell 13 for holding the refill are arranged inside the slider 7 and the relay member 9. The chuck unit 10 has a chuck body 11 and a fastener 12 formed in a cylindrical shape so as to surround the front end of the chuck body 11. At least the front half of the chuck body 11 is divided into three chuck pieces 11a along the axial direction, and a through hole for the refill is formed along the central axis. The chuck pieces 11a are each formed in a manner that the front end is separated from each other. The refill shell 13 is formed in a cylindrical shape and accommodates the refill inside. The rear end of the chuck body 11 is inserted and fitted into the interior of the front end of the refill shell 13.

[0051] The coil spring 14 is arranged to surround the chuck body 11. The front end of the coil spring 14 is supported by the step formed on the inner peripheral surface of the relay member 9, and the rear end of the coil spring 14 abuts against the front end surface of the refill shell 13. Therefore, the coil spring 14 applies force to the refill shell 13 and the chuck body 11 backward. The chuck body 11, which is applied force backward, is accommodated in the fastener 12, and the front ends are close to each other, so that the state of holding the refill can be maintained. In addition, when writing pressure is applied to the refill, the chuck body 11 further retreats and is accommodated in the fastener 12, and the refill is held by the chuck body 11. As a result, the refill is prevented from retreating. On the other hand, when a force is applied to pull the refill forward, the chuck body 11 is not affected by the fastener 12, so the refill can be pulled forward without resistance. That is, the chuck unit 10 functions to allow the writing lead to move forward and to prevent the writing lead from moving backward, but other chuck units, such as a ball chuck, may be used as long as they fulfill this function.

[0052] The outer peripheral surface of the fastener 12 fits with the inner peripheral surface of the front end of the relay member 9. Therefore, the slider 7, the relay member 9 and the chuck unit 10 can move in the axial direction in the pen barrel 5. The rear end of the relay member 9 is connected to the rotation drive mechanism 30 described below.

[0053] A cylindrical push member 20 as a push member is provided at the rear end of the pen barrel 5, specifically, at the rear end of the inner tube 4 so as to be movable forward and backward relative to the pen barrel 5. The push member 20 is urged backward by a coil spring 21. A refill case 13 is inserted into the interior of the front end of the push member 20. An eraser 22 is detachably mounted inside the rear end of the push member 20. A push cover 23 is detachably mounted on the outer peripheral surface of the rear end of the push member 20, and the push cover 23 protects the eraser 22 from contamination, etc.

[0054] By performing a push operation of pressing the push member 20 or the push cover 23 forward, the refill case 13 moves forward. As a result, the chuck body 11 is pushed forward. Along with this, the refill held by the chuck body 11 also moves forward, and acts to deliver the refill from the top tube 6. When the push operation is released, the push member 20 retreats and returns to its original position by the force of the coil spring 21. At this time, the chuck body 11 retreats by the force of the coil spring 14. On the other hand, the refill is held by the holding chuck 8 arranged in the slider 7, so that the refill is pulled out from the chuck body 11 without resistance as the chuck unit 10 functions. As a result, the refill is delivered from the top tube 6, so that the refill can be delivered in a predetermined amount each time the push operation is repeated.

[0055] Figure 3 yes Figure 1 An enlarged cross-sectional view of the central portion of the mechanical pencil 1, Figure 4 : is a partial enlarged view of the rotation drive mechanism 30. The rotation drive mechanism 30 is arranged in the internal space of the rear pen barrel 3. The rotation drive mechanism 30 is connected to the rear end of the relay member 9. An axial spring 31 is arranged between the rear end surface of the front pen barrel 2 and the front end surface of the rotation drive mechanism 30 to apply force to the rotation drive mechanism 30 in the rear direction. The refill case 13 penetrates the interior of the relay member 9 and the rotation drive mechanism 30, and the refill case 13 is separated from the rotation drive mechanism 30.

[0056] The rotary drive mechanism 30 includes a cylindrical rotating body 40, a cylindrical upper cam forming member 41 as a first cam forming member, a cylindrical lower cam forming member 42 as a second cam forming member, a cylindrical cylinder member 43, a cylindrical torque canceller 44, and a helical buffer spring 45. These components of the rotary drive mechanism 30 are integrated and unitized.

[0057] The outer peripheral surface of the rear end of the relay member 9 is fitted into the inner peripheral surface of the front end of the rotating body 40. The rotating body 40 has a flange-shaped portion with a slightly larger diameter near the front end, and a first cam surface 40a is formed on the rear end surface of the portion, and a second cam surface 40b is formed on the front end surface of the portion.

[0058] The upper cam forming member 41 surrounds the rotating body 40 behind the first cam surface 40a of the rotating body 40 so that the rotating body 40 can rotate. The lower cam forming member 42 is fitted into the outer peripheral 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 opposite to the first cam surface 40a of the rotating body 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 opposite to the second cam surface 40b of the rotating body 40.

[0059] The first cam surface 40a includes a plurality of first cam teeth 40aa, the second cam surface 40b includes a plurality of second cam teeth 40ba, the first fixed cam surface 41a includes a plurality of first fixed cam teeth 41aa, and the second fixed cam surface 42a includes a plurality of second fixed cam teeth 42aa. The first cam teeth 40aa and the first fixed cam teeth 41aa have the same shape and the same orientation. The first cam teeth 40aa and the second cam teeth 40ba have the same shape but are line-symmetrical. The first cam teeth 40aa, the second cam teeth 40ba, and the first fixed cam teeth 41aa are continuously arranged without gaps along the circumferential direction on the corresponding cam surfaces. On the other hand, the second fixed cam teeth 42aa of the second fixed cam surface 42a are of similar shape larger than the first cam teeth 40aa, the second cam teeth 40ba, and the first fixed cam teeth 41aa. In addition, the second fixed cam teeth 42aa are separated from each other along the circumferential direction and arranged at equal intervals on the second fixed cam surface 42a. The first cam surface 40a is formed in a sawtooth shape by a plurality of first cam teeth 40aa, the second cam surface 40b is formed in a sawtooth shape by a plurality of second cam teeth 40ba, and the first fixed cam surface 41a is formed in a sawtooth shape by a plurality of first fixed cam teeth 41aa.

[0060] The cylinder member 43 formed in a cylindrical shape is fitted to the outer peripheral surface of the rear end portion of the upper cam forming member 41. A through hole 43a through which the refill case 13 can pass is formed at the rear end portion of the cylinder member 43. A torque canceller 44 formed in a cylindrical shape and movable in the axial direction is arranged in the cylinder member 43. A buffer spring 45 is arranged between the inner surface of the front end portion of the torque canceller 44 and the inner surface of the rear end portion of the cylinder member 43. The buffer spring 45 applies force to the rotating body 40 forward via the torque canceller 44.

[0061] Here, the relay member 9 transmits the backward movement and forward movement (buffering movement) of the writing lead based on the writing movement to the rotation drive mechanism 30, that is, the rotating body 40, and the relay member 9 transmits the rotational motion of the rotating body 40 of the rotation drive mechanism 30 caused by the buffering movement to the chuck unit 10 in the state of holding the writing lead. Therefore, the writing lead held by the chuck unit 10 is also rotated by the rotation of the relay member 9.

[0062] When writing is not performed with the mechanical pencil 1, that is, when writing pressure is not applied to the lead, the rotating body 40 is located forward by the force of the buffer spring 45 through the torque canceller 44. Therefore, the second cam surface 40b of the rotating body 40 abuts against the second fixed cam surface 42a and is in meshing state. When writing is performed with the mechanical pencil 1, that is, when writing pressure is applied to the lead, the chuck unit 10 overcomes the force of the buffer spring 45 and moves backward, and the rotating body 40 also moves backward. Therefore, the first cam surface 40a of the rotating body 40 abuts against the first fixed cam surface 41a and is in a state. The lead and the rotating body 40 move forward, backward or rotate integrally.

[0063] Figure 5 1 is a diagram for sequentially explaining the rotational drive of the rotating body 40 of the rotational drive mechanism 30. Figure 6 The diagram is a schematic diagram for sequentially explaining the rotational drive of the rotating body 40 by the rotational drive mechanism 30 . Figure 6 (A) to Figure 6 (E) is related to Figure 5 (A) to Figure 5 's (E) respectively correspond to the schematic diagrams. Further, Figure 5 (A) to Figure 5 (E) and Figure 6 (A) to Figure 6 (E) and Fig.12 (A) to Fig.12 (C) and Fig.13 (D) and Fig.13 ’s (E) correspond respectively. Figure 6 The cam teeth of the rotating body 40 are shown as shown in FIG. 1 , and the cam teeth of the rotating body 40 are shown as shown in FIG. 1 . Figure 4 A cam tooth unit U surrounded by an imaginary line is described.

[0064] The second fixed cam teeth 42aa have a similar shape to the other cam teeth, and therefore are substantially equivalent to cam teeth arranged continuously in the same shape from a functional point of view. Figure 6 and the following Figure 7 In order to facilitate Fig.12 and Fig.13For comparison, the second fixed cam tooth 42aa is schematically shown as a cam tooth that is continuously arranged in the same shape as other cam teeth. In addition, the second fixed cam tooth 42aa may be set to the same shape as other cam teeth and continuously arranged along the circumferential direction. In addition, the first cam tooth 40aa, the second cam tooth 40ba, and the first fixed cam tooth 41aa are each continuously arranged along the circumferential direction, but may be separately arranged along the circumferential direction, and may have a shape similar to other cam teeth from a functional point of view.

[0065] Figure 5 (A) and Figure 6 (A) shows the relationship between the moving rotating body 40, the upper cam forming member 41, and the lower cam forming member 42 when no writing pressure is applied to the writing lead. In this state, the second cam surface 40b formed on the rotating body 40 abuts against the second fixed cam surface 42a of the lower cam forming member 42 under the force of the buffer spring 45. At this time, the first cam surface 40a of the rotating body 40 and the first fixed cam surface 41a of the upper cam forming member 41 are set to be offset in the axial direction by half a phase relative to one tooth of the cam.

[0066] Figure 5 (B) and Figure 6 (B) shows an initial state in which writing pressure is applied to the lead due to writing with the mechanical pencil 1. In this state, the rotating body 40 retreats as the buffer spring 45 contracts with the retreat of the chuck unit 10. As a result, the rotating body 40 moves to the upper cam forming member 41 side and abuts against the first fixed cam surface 41a.

[0067] then, Figure 5 (C) and Figure 6 (C) shows a state where the writing pressure is further applied to the pen core, and the rotating body 40 is brought into contact with the first fixed cam surface 41a of the upper cam forming member 41, while sliding and retreating. That is, the rotating body 40 is driven to rotate by half the phase of one tooth of the first cam surface 40a. In this state, the first cam surface 40a of the rotating body 40 is meshed with the first fixed cam surface 41a of the upper cam forming member 41.

[0068] In addition, Figure 5 The circle mark drawn in the center of the rotating body 40 indicates the rotational movement amount of the rotating body 40. Figure 5 In the state shown in (C), the second cam surface 40b of the rotating body 40 and the second fixed cam surface 42a of the lower cam forming member 42 are set to be offset in the axial direction by half a phase with respect to one cam tooth.

[0069] then, Figure 5(D) and Figure 6 (D) shows an initial state in which writing with the mechanical pencil 1 is completed and the writing pressure on the writing lead is released. In this state, the rotating body 40 moves forward under the force of the buffer spring 45. As a result, the rotating body 40 moves toward the lower cam forming member 42 and abuts against the second fixed cam surface 42a.

[0070] then, Figure 5 (E) and Figure 6 (E) shows a state where the rotating body 40 slides and moves forward while contacting with the second fixed cam surface 42a of the lower cam forming member 42 under the force of the buffer spring 45. That is, the rotating body 40 is again driven by a rotation corresponding to half the phase of one tooth of the second cam surface 40b. In this state, the second cam surface 40b of the rotating body 40 is meshed with the second fixed cam surface 42a of the lower cam forming member 42.

[0071] Therefore, if Figure 5 As shown by the o mark drawn in the center of the rotating body 40, the rotating body 40 receives a rotational drive corresponding to one tooth of the first cam surface 40a and the second cam surface 40b as the rotating body 40 receives the writing pressure and moves back and forth in the axial direction, that is, moves forward and backward, and the pen lead held by the chuck unit 10 is also rotationally driven in the same manner. Therefore, by using the one forward and backward movement of the rotating body 40 in the axial direction caused by writing, the rotating body 40 receives a rotational movement corresponding to one tooth of the cam, and by repeating the above-mentioned action, the pen lead is rotationally driven in sequence. As a result, it is possible to prevent the pen lead from being unevenly worn as writing proceeds, and it is possible to prevent the thickness and depth of the written line from changing greatly. In addition, the following description can also be applied to a mechanical pencil having a rotational drive mechanism but not configured to rotate the pen lead.

[0072] In summary, the rotation drive mechanism 30 includes a first annular cam surface 40a formed on the rear end surface of the rotating body 40, a second annular cam surface 40b formed on the front end surface of the rotating body 40, a first fixed cam surface 41a provided on the side of the pen barrel 5 and rotating the rotating body 40 in cooperation with the first cam surface 40a, and a second fixed cam surface 42a provided on the side of the pen barrel 5 and rotating the rotating body 40 in cooperation with the second cam surface 40b. The rotation drive mechanism 30 is configured such that, by the retreating action of the chuck unit 10 caused by the writing pressure, the first cam surface 40a of the rotating body 40 abuts against the first fixed cam surface 41a, so that the rotating body 40 is meshed while rotating, and by the release of the writing pressure, the second cam surface 40b of the rotating body 40 abuts against the second fixed cam surface 42a, so that the rotating body 40 is meshed while rotating. When the first cam surface 40a of the rotating body 40 is meshed with the first fixed cam surface 41a, the second cam surface 40b and the second fixed cam surface 42a are set to be offset in the axial direction by half a phase relative to one tooth of the cam. When the second cam surface 40b of the rotating body 40 is meshed with the second fixed cam surface 42a, the first cam surface 40a and the first fixed cam surface 41a are set to be offset in the axial direction by half a phase relative to one tooth of the cam.

[0073] Furthermore, the torque canceller 44, which receives the force of the buffer spring 45 and pushes the rotating body 40 forward, slides between its front end surface and the rear end surface of the rotating body 40, thereby preventing the rotational motion of the rotating body 40 from being transmitted to the buffer spring 45. That is, the torque canceller 44 prevents the rotational motion of the rotating body 40 from being transmitted to the buffer spring 45, thereby preventing the buffer spring 45 from generating reverse twisting (torque) that hinders the rotational motion of the rotating body 40.

[0074] As described above, the mechanical pencil 1 includes the chuck unit 10 and the rotating body 40, and is configured so that the writing lead can be released and held by the forward and backward movement of the chuck unit 10, so that the writing lead can be sent forward, the chuck unit 10 is held in the pen barrel 5 so as to be rotatable around the central axis in a state of holding the writing lead, and the rotating body 40 is rotated by the forward and backward movement of the chuck unit 10 under the writing pressure of the writing lead, and the rotational motion of the rotating body 40 is transmitted to the writing lead via the chuck unit 10.

[0075] Figure 7 is a schematic diagram for explaining the relationship between the cams of the rotation drive mechanism 30, and is Figure 6The first cam tooth 40aa of the first cam surface 40a has a first inclined surface 40aa1 and a vertical surface 40aa2 corresponding to the second inclined surface, and the first cam surface 40aa1 and the vertical surface 40aa2 of the adjacent first cam teeth 40aa are used to make the first cam surface 40a become a continuous sawtooth shape. The first inclined surface 40aa1 is a surface inclined at an inclination angle θ relative to the transverse direction perpendicular to the axial direction, and the vertical surface 40aa2 is a surface parallel to the axial direction, that is, a surface perpendicular to the transverse direction. As described above, the second cam tooth 40ba of the second cam surface 40b and the first fixed cam tooth 41aa of the first fixed cam surface 41a also have the same shape.

[0076] The height of the first cam tooth 40aa and the second cam tooth 40ba and the height at which the second fixed cam tooth 42aa substantially meshes with the second cam tooth 40ba are equal to Fig.12 The length of the vertical surface 40aa2 of the first cam tooth 40aa is equal to the height of the first cam tooth 40aa, and is therefore equal to the distance H. The moving distance of the top end of the first cam tooth 40aa until it contacts the first fixed cam tooth 41aa by retreating the rotating body 40 is equal to Fig.12 The distance d of (A) corresponds to the distance D. The length of the first cam tooth 40aa along the circumferential direction is referred to as the length L of the cam tooth.

[0077] Furthermore, the first cam teeth 40aa have a thickness in the radial direction corresponding to the member of the rotating body 40 formed in a cylindrical shape. Figure 6 and Figure 7 The state where the rotating body 40, the upper cam forming member 41, and the lower cam forming member 42 are expanded in the circumferential direction is schematically shown. However, for the first cam tooth 40aa, which part within the range of the thickness in the radial direction is expanded, strictly speaking, the angle and size are slightly different. Figure 6 and Figure 7 In other descriptions of this specification, it is assumed that the outermost portion of the rotating body 40 having a predetermined outer diameter is expanded in the circumferential direction to define angles and distances such as θ and L and positional relationships of other members.

[0078] In the rotation drive mechanism 30 of the mechanical pencil 1, the first fixed cam surface 41a and the second fixed cam surface 42a are arranged at a minimum distance that does not hinder the rotation of the rotating body 40. Therefore, the height at which the second cam tooth 40ba and the second fixed cam tooth 42aa are substantially meshed, that is, the distance H and the distance D in the axial direction between the tip of the first cam tooth 40aa and the first fixed cam tooth 41aa are configured to be equal.

[0079] In detail, in Figure 5 (A) and Figure 6 (A) equivalent Figure 7 In the state in which the rotating body 40 is in a state in which the second cam teeth 40ba of the second cam surface 40b are locked with the second fixed cam teeth 42aa of the second fixed cam surface 42a, the rotation of the rotating body 40 is restricted. When the rotating body 40 is retracted by a distance H due to the retraction of the writing lead from this state, the locking of the second cam teeth 40ba and the second fixed cam teeth 42aa is released, thereby releasing the restriction on the rotation of the rotating body 40. In addition, when the rotating body 40 is retracted by a distance D, the first inclined surface 40aa1 of the rotating body 40 abuts against the first fixed cam teeth 41aa, thereby enabling the rotating body 40 to rotate.

[0080] In short, it can be said that the state in which the restriction on the rotation of the rotating body 40 is released and the first cam surface 40a and the first fixed cam surface 41a are in contact with each other at the same time, that is, the state in which the distance H and the distance D are equal (D=H), is the state in which the first fixed cam surface 41a and the second fixed cam surface 42a are arranged at the minimum distance that does not hinder the rotation of the rotating body 40. In other words, when the distance H and the distance D are equal, the retreat amount m of the writing lead becomes the minimum. It is also possible to configure the distance D to be slightly longer than the distance H in consideration of tolerances during manufacturing and the like. The minimum distance is determined on the basis of considering tolerances during manufacturing and not considering wear during use of the mechanical pencil, as long as the intention of designing so as not to hinder the rotation of the rotating body is clear objectively or in appearance.

[0081] As described above, the first cam surface 40a and the first fixed cam surface 41a are arranged to be offset by half a phase relative to one tooth of the cam. Figure 5 (B) and Figure 6 The state shown in (B) is Figure 5 (C) and Figure 6 In the state shown in (C), the reel rotates by a distance of 1 / 2L and retreats by a distance of 1 / 2H. In short, in a series of buffering actions, the reel retreats by a distance of 3 / 2H (= 1 / 2H + H), which is the minimum retreat amount m of the reel as the rotation drive mechanism 30. The minimum retreat amount m obtained geometrically in this way is set as the minimum retreat amount M. Of course, the rotating body 40 is in the retreated state ( Figure 5 (C) and Figure 6 (C)) to the forward state ( Figure 5 (E) and Figure 6 The amount of movement in the axial direction, i.e., the amount of advance, of (E) is the same distance as the minimum amount of retreat M, 3 / 2H.

[0082] Furthermore, when focusing on the movement of the tip of the tooth tip of the second cam tooth 40ba of the second cam surface 40b, it moves along a trajectory T1 when it first retreats, and moves along a trajectory T2 by subsequent rotation and retreat. The first cam tooth 40aa of the first cam surface 40a also moves along the same trajectory.

[0083] The distance H depends on the inclination angle θ of the first cam tooth 40aa and the length L in the circumferential direction, and is in the relationship of H=Ltanθ. Therefore, by further reducing the length L of the cam tooth or further reducing the inclination angle θ, the distance H can be reduced, and as a result, the minimum retreat amount M can be further reduced. Then, the design of the inclination angle θ and the length L of the cam tooth will be described.

[0084] The tilt angle θ is a major factor that determines the ease of sliding between the cam teeth. That is, if the tilt angle θ is too small, for example, if the tilt angle θ is smaller than the friction angle, the cam teeth do not slide, and the rotating body 40 does not rotate. If the tilt angle θ is too large, the distance H becomes larger, and the minimum retreat amount M also becomes larger. In addition, considering the materials used as the components of the writing tool as a whole, the tilt angle θ is preferably within the range of 8° to 25°.

[0085] Generally speaking, the structural components of writing tools such as mechanical pencils are mostly formed of resins such as polypropylene and polyacetal. In particular, the internal components such as the cam structures of the rotating body 40, the upper cam forming member 41, and the lower cam forming member 42, which have complex shapes and do not affect the appearance, are basically not formed of metal materials. The cooperative action of each cam tooth formed in these components, specifically, the action of the rotating body 40 sliding and rotating while contacting with the upper cam forming member 41 or the lower cam forming member 42, is more reliable in consideration of friction resistance. Therefore, an inclination angle θ greater than the friction angle is required in each cam tooth. For example, the rotating body 40, the upper cam forming member 41, and the lower cam forming member 42 are made of polyacetal, and the friction angle is 10.2°. That is, when the inclination angle θ is less than 10.2°, the cam teeth do not slide against each other, and thus the rotating body 40 cannot be rotated.

[0086] The length L of the cam teeth is calculated by calculating the length of the entire circumference (outer diameter×π) from the outer diameter of the rotating body 40 and dividing it by the number of cam teeth. An example of the dimensional design of the outer diameter of the rotating body 40 is described. According to the Japanese Industrial Standard JIS specification S6005 for mechanical pencil leads, a 0.5 mm lead is allowed to have an outer diameter of 0.58 mm. In the case where a plurality of leads can be accommodated in the lead case 13, the inner diameter of the lead case 13 needs to be at least 1.8 mm, for example, for three leads. From the viewpoint of strength, the wall thickness of the cylindrical portion of the resin member is set to at least 0.5 mm. Therefore, the wall thickness of the lead case 13, the wall thickness of the rotating body 40 surrounding the lead case 13, and the wall thickness of the portion where the cam teeth are formed are set to 0.5 mm respectively. Considering these wall thicknesses and the inner diameter of the lead case 13, the outer diameter of the first cam surface 40a and the second cam surface 40b of the rotating body 40 becomes 4.8 mm.

[0087] The number of cam teeth of the first cam surface 40a, that is, the number of cam teeth of the corresponding second cam surface 40b, is preferably 20 to 90. The number of cam teeth determines the rotation angle of the pen core in one buffering action. For example, when the number of cam teeth is 90, 360° is divided by 90 to obtain 4°, so the rotating body 40 rotates 4° in one buffering action. Therefore, when writing 90 strokes, the pen core rotates once.

[0088] If the number of cam teeth is more than 90, the rotation angle becomes smaller, and the next writing is done by the worn part of the lead. Therefore, the original purpose of the mechanical pencil with a rotation drive mechanism, which is to prevent uneven wear of the lead, cannot be achieved. On the other hand, if the number of cams is less than 20, the length L of the cam teeth becomes larger. Therefore, according to the above-mentioned relationship of distance H = Ltanθ, the height of the cam teeth, that is, the distance H, becomes larger, resulting in a larger minimum retreat amount M. Therefore, the number of cam teeth is preferably 20 to 90.

[0089] When the outer diameter of the rotating body 40 is set to 4.8 mm, the number of cam teeth is set to 90, and the inclination angle θ is set to 10.3° which is larger than the friction angle 10.2°, the length L of the cam teeth is about 0.17 mm according to 4.8×π / 90. Therefore, the height of the cam teeth, that is, the distance H, is 0.03 mm according to the relationship of Ltanθ. As a result, the minimum retreat amount M is 0.05 mm according to the relationship of 3 / 2H.

[0090] As described above, when the retreat amount m of the writing lead is less than 0.05 mm, which is the minimum retreat amount M, the inclination angle θ of the cam teeth becomes smaller, so that the cam teeth do not slide against each other and a rotation failure may occur, or the rotation angle of the rotating body 40 becomes smaller, so that the original purpose of the mechanical pencil having a rotation drive mechanism may not be achieved. Therefore, it is preferable that the retreat amount m is not less than 0.05 mm, which is the minimum retreat amount M.

[0091] On the other hand, the retreat amount m is preferably 0.3 mm or less. If the retreat amount m is larger than 0.3 mm, the user may feel unnatural due to the retreat of the writing lead.

[0092] The inventors of the present invention conducted the following investigation: 23 students were asked to write with a mechanical pencil having a setback m of 0.15 mm and a mechanical pencil having a setback m of 0.3 mm without being informed in advance that there was a difference in the setback m, and the following results were obtained: All students noticed the difference. In short, it was found that even a slight difference of 0.15 mm can be felt by the user. The setback m of the lead is preferably smaller, but as mentioned above, if the setback m is too small, it may cause poor rotation, etc. In order to reliably realize the rotation of the rotating body 40 and the lead while the user does not feel the unnaturalness of the setback of the lead as much as possible, the setback m is preferably less than 0.3 mm.

[0093] As described above, the mechanical pencil 1 comprises: the pen barrel 5; the chuck unit 10 which allows the writing lead to move forward and prevents the writing lead from moving backward; and the rotation drive mechanism 30 which has the rotating body 40 which receives the moving backward motion in the axial direction caused by the writing pressure applied to the writing lead held by the chuck unit 10 and the moving forward motion in the axial direction caused by the release of the writing pressure, and drives the rotating body 40 to rotate in one direction. In the mechanical pencil 1, the moving backward amount m of the writing lead is preferably within the range of 0.05 mm to 0.3 mm.

[0094] As described above, when the number of cam teeth is set to 90, a buffering action is used to rotate 4°. In the case of a user with a high writing pressure, the amount of wear of the pen core due to one writing is also large, so there is a case where a rotation of 4° is not enough. In order to increase the rotation angle of the pen core using a buffering action, the number of cam teeth is more preferably 20 to 40. For example, when the number of cam teeth is 40, 360° is divided by 40 to become 9°, so the rotating body 40 rotates 9° using a buffering action. Therefore, when writing 40 strokes, the pen core rotates one circle.

[0095] When the outer diameter of the rotating body 40 is set to 4.8 mm as described above, the number of cam teeth is set to 40, and the inclination angle θ is set to 10.3°, the length L of the cam teeth is about 0.38 mm according to 4.8×π / 40. Therefore, the height of the cam teeth, that is, the distance H, is 0.07 mm according to the relationship of Ltanθ. As a result, the minimum retreat amount M is 0.1 mm according to the relationship of 3 / 2H.

[0096] As described above, when the amount of retreat m is 0.1 mm or more, sufficient rotation of the lead can be obtained even in the case of a user with a strong writing pressure, and thus it is more preferable. In addition, there is a case where some users write with the mechanical pencil 1 extremely tilted relative to the writing surface. In such a case, a method with a larger amount of retreat m, that is, a method with a longer length L of the cam teeth or a larger tilt angle θ, is preferable because each cam tooth can cooperate reliably. For this reason, the amount of retreat m is more preferably 0.1 mm or more.

[0097] In addition, when writing smaller characters, the tip of the pen core is focused and the feeling is more acute, so the retreat amount m is more preferably less than 0.2 mm. In addition, even with the same buffer amount, the feeling felt when writing with a 0.5 mm pen core is different from the feeling felt when writing with a 0.3 mm pen core. That is, for the feeling felt when writing with a 0.3 mm pen core, the distance that the tip of the pen core moves forward and backward is relatively large relative to the thickness of the pen core, so it is easier to feel unnatural. For this reason, the retreat amount m is more preferably less than 0.2 mm.

[0098] As described above, the retreat amount m of the writing lead is more preferably within the range of 0.1 mm to 0.2 mm.

[0099] In addition, the amount of retreat m can also be changed according to the core diameter of the lead, and is more preferably less than about half of the outer diameter of the lead. For example, according to the Japanese Industrial Standard JIS specification S6005 for mechanical pencil leads, for example, a 0.5 mm lead is specified as 0.55 mm to 0.58 mm. Therefore, in the case of a 0.5 mm lead, the amount of retreat m is preferably less than 0.3 mm. Similarly, a 0.3 mm lead is specified as 0.37 mm to 0.39 mm. Therefore, in the case of a 0.3 mm lead, the amount of retreat m is preferably less than 0.2 mm.

[0100] In addition, the cam teeth may not be continuous throughout the entire circumference. When the number of cam teeth is considered, even if the cam teeth are not continuous throughout the entire circumference but are arranged separately, the number of virtual cam teeth can be calculated by dividing the length of the entire circumference by the length L of one representative cam tooth in the circumferential direction. For the sake of design efficiency, the number of cam teeth is preferably 20, 40, 60, and 90 relative to 360° of the rotating body 40, and is most preferably 40 from the viewpoint of reducing the retreat amount m.

[0101] In the above-mentioned embodiment, the minimum retreat amount M and the retreat amount m of the writing lead are described based on an example of the outer diameter of the rotating body 40, the number of cam teeth, and the inclination angle, but the above-mentioned preferred range of the retreat amount m of the writing lead can also be applied to mechanical pencils having other outer diameters, the number of cam teeth, etc. That is, according to the above-mentioned embodiment, in the mechanical pencil 1 having the rotation drive mechanism for rotating the writing lead, the retreat amount of the writing lead can be further reduced.

[0102] In addition, further shortening the length L of the first cam tooth 40aa means reducing the proportion of the first cam tooth 40aa in the length of the entire circumference. In other words, further shortening the length L can increase the number of cam teeth. When the length L is further shortened, the cam teeth arranged at positions corresponding to the direction orthogonal to the offset direction may not be fully engaged due to the fact that the relative positional relationship of the rotating body 40 with respect to the upper cam forming member 41 and the lower cam forming member 42 is offset in the radial direction, that is, the center axes of each other are offset. As a result, improper rotation of the rotating body 40 may occur. Regarding this point, refer to Figure 8 and Fig. 9 Provide explanation.

[0103] Figure 8 4 is a diagram for explaining the offset of the rotating body 40. Fig. 9 It is a diagram for explaining a rotation failure of the rotating body 40 . Figure 8 The rotation drive mechanism 30 is viewed from the axial direction and is schematically depicted with the scale bar omitted and slightly exaggerated. Figure 8 , the rotating body 40 is shown to be shifted upward by a distance g relative to the upper cam forming member 41 and the lower cam forming member 42. That is, since the upper cam forming member 41 and the lower cam forming member 42 are provided on the pen barrel 5 side, their central axes coincide with each other, but only the central axis of the rotating body 40 is shifted by a distance g.

[0104] Fig. 9 (A) shows the position of the rotating body 40 at the maximum radial offset, i.e. Figure 8 The relationship between the various cams of part P1. Fig. 9(B) shows the position of the rotating body 40 at the maximum circumferential offset, i.e. Figure 8 That is, the portion P1 is a portion located in the direction in which the rotating body 40 is offset, and the portion P2 is a portion located in a direction orthogonal to the offset direction. Since the cam teeth of each cam are arranged along the circumferential direction, in the portion P1, the cam teeth are arranged along the left-right direction in the figure, and in the portion P2, the cam teeth are arranged along the up-down direction in the figure.

[0105] Reference Fig. 9 (A), and Figure 6 Compared with the state shown in (A) of FIG. 1 , the cam teeth of the rotating body 40 are offset by a distance g in the radial direction of the rotating body 40, that is, in the direction perpendicular to the paper surface in the figure, relative to the cam teeth of the upper cam forming member 41 and the lower cam forming member 42. Therefore, in the portion P1, there is no phase shift of the cam teeth, and thus there is almost no influence on the rotational drive of the rotating body 40.

[0106] On the other hand, refer to Fig. 9 (B), and Figure 6 Compared with the state shown in (A), the cam teeth of the rotating body 40 are offset by a distance g along the circumferential direction of the rotating body 40, i.e., the right direction in the figure, relative to the cam teeth of the upper cam forming member 41 and the lower cam forming member 42. Generally speaking, when the rotating body 40 moves backward due to writing, the first cam surface 40a of the rotating body 40 contacts the first fixed cam surface 41a of the upper cam forming member 41 over half the length of the first inclined surface 40aa1 of the rotating body 40. That is, as Figure 6 As shown in (B), the length of the abutting portion in the circumferential direction, i.e., the hooking amount E, is 1 / 2L.

[0107] On the other hand, since the rotating body 40 is offset by the distance g, the hooking amount E is reduced by a corresponding amount. Therefore, the first cam surface 40a and the first fixed cam surface 41a cannot cooperate reliably, which may cause a rotational defect in which the rotating body 40 does not rotate. Fig. 9 As shown in (C), when the distance g is greater than half of the length L of the cam tooth of the first cam tooth 40aa, that is, when the phase is shifted by more than half relative to one cam tooth, the first cam surface 40a cannot abut against the corresponding first fixed cam surface 41a that should abut. As a result, even if a rotational driving force is generated in other parts, the rotation is restricted by the parts, and a rotational defect occurs in which the rotating body 40 does not rotate.

[0108] In short, the smaller the length L of the cam teeth is relative to the distance g that the rotator 40 is offset in the radial direction, the higher the possibility of rotation failure. Therefore, considering the radial offset of the rotator 40, the length L of the cam teeth and the number of the cam teeth are appropriately determined within the range that can achieve the above-mentioned retreat amount m of the writing lead.

[0109] In addition, the radial offset of the rotating body 40 depends largely on the gap between the outer peripheral surface of the top end portion of the slider 7 connected to the rotating body 40 via the relay member 9 and the inner peripheral surface of the front pen barrel 2 surrounding the outer peripheral surface. The gap is caused by the tolerance during manufacturing, so in order to be able to process with higher precision, at least the slider 7 is preferably made of metal.

[0110] The first cam tooth 40aa of the rotating body 40 in the above-mentioned embodiment has a first inclined surface 40aa1 and a vertical surface 40aa2 corresponding to the second inclined surface. Therefore, the first cam surface 40a is formed into a continuous so-called sawtooth shape. Other cam teeth also have the same shape. For example, the mechanical pencil described in Patent Document 1 also has the same shape. Even if the cam teeth are not sawtooth-shaped, the rotating body can be driven to rotate. The shape of another cam tooth is described below.

[0111] Fig.10 is a schematic diagram illustrating the relationship between the cams of another rotary drive mechanism, and is Figure 7 The corresponding figure. Fig.10 The illustrated rotary drive mechanism includes a rotary body 140 , an upper cam forming member 141 , and a lower cam forming member 142 , and is replaceable with the rotary body 40 , the upper cam forming member 41 , and the lower cam forming member 42 of the rotary drive mechanism 30 described above.

[0112] The first cam tooth 140aa of the first cam surface 140a has a first inclined surface 140aa1 and a second inclined surface 140aa2, and the first cam surface 140a forms a continuous mountain shape using the first inclined surface 140aa1 and the second inclined surface 140aa2 of the adjacent first cam teeth 140aa. The first inclined surface 140aa1 is a surface inclined at an inclination angle θ with respect to the transverse direction orthogonal to the axial direction. The second cam tooth 140ba of the second cam surface 140b, the first fixed cam tooth 141aa of the first fixed cam surface 141a, and the second fixed cam tooth 142aa of the second fixed cam surface 142a also have the same shape as the first cam tooth 140aa.

[0113] Fig.11 It is described in order Fig.10 Schematic diagram of the rotation drive mechanism for rotationally driving the rotating body 140. Fig.11 (A) to Fig.11 (E) is related to Figure 6 (A) to Figure 6 (E) respectively correspond to the schematic diagrams, and the basic actions are the same. Fig.11 The rotating body 140, the upper cam forming member 141 and the lower cam forming member 142 are partially shown in a state where they are spread out in the circumferential direction. Figure 6 Likewise, the description is made using a unit U consisting of one cam tooth.

[0114] Fig.11 (A) shows the relationship between the moving rotating body 140, the upper cam forming member 141, and the lower cam forming member 142 when no writing pressure is applied to the pen core. In this state, the second cam surface 140b formed on the rotating body 140 abuts against the second fixed cam surface 142a of the lower cam forming member 142 under the force of the buffer spring 45. At this time, the first cam surface 140a of the rotating body 140 and the first fixed cam surface 141a of the upper cam forming member 141 are set to be offset in the axial direction by half a phase relative to one tooth of the cam.

[0115] Fig.11 (B) shows an initial state in which writing pressure is applied to the lead due to writing with the mechanical pencil 1. In this state, the rotating body 140 retreats as the buffer spring 45 contracts with the retreat of the chuck unit 10. As a result, the rotating body 140 moves to the upper cam forming member 141 side and contacts the first fixed cam surface 141a.

[0116] then, Fig.11 (C) shows a state where the writing pressure is further applied to the pen core, causing the rotating body 140 to slide and retreat while contacting the first fixed cam surface 141a of the upper cam forming member 141. That is, the rotating body 140 is driven to rotate by half the phase of one tooth of the first cam surface 140a. In this state, the first cam surface 140a of the rotating body 140 is meshed with the first fixed cam surface 141a of the upper cam forming member 141.

[0117] then, Fig.11 (D) shows an initial state in which writing with the mechanical pencil 1 is completed and the writing pressure on the writing lead is released. In this state, the rotating body 140 moves forward under the force of the buffer spring 45. As a result, the rotating body 140 moves toward the lower cam forming member 142 side and abuts against the second fixed cam surface 142a.

[0118] then, Fig.11(E) shows a state where the rotating body 140 moves forward while sliding against the second fixed cam surface 142a of the lower cam forming member 142 under the force of the buffer spring 45. That is, the rotating body 140 is again driven by a rotation corresponding to half the phase of one tooth of the second cam surface 140b. In this state, the second cam surface 140b of the rotating body 140 is meshed with the second fixed cam surface 142a of the lower cam forming member 142.

[0119] Therefore, as the rotating body 140 subjected to the writing pressure reciprocates in the axial direction, that is, moves forward and backward, the rotating body 140 is rotationally driven by one tooth of the first cam surface 140a and the second cam surface 140b, and the writing lead held by the chuck unit 10 is also rotationally driven by the chuck unit 10. In short, whether the shape of the cam teeth is a sawtooth shape or a mountain shape, the basic rotational driving action of the rotational driving mechanism is the same.

[0120] Reference Fig.10 , explaining the calculation of the minimum retreat amount M. Figure 7 The height of the sawtooth cam teeth shown is the distance H, relative to which Fig.10 The height of the cam teeth of the mountain shape shown is set to a distance H'. Fig.10 In the figure, the imaginary line shows Figure 7 The sawtooth-shaped cam teeth shown. The moving distance until the top end of the first cam tooth 140aa contacts the first fixed cam tooth 141aa by retreating the rotating body 140 is set as distance D. The length of the first cam tooth 140aa along the circumferential direction is set as the length L of the cam tooth. Considering the triangle shape of the first cam tooth 140aa, when a perpendicular line is drawn from the vertex to the base and the length L is divided, the length of the base located at the rear side relative to the rotation direction of the rotating body 140 (left direction in the figure) is set as X, and the length of the base located at the front side relative to the rotation direction of the rotating body 140 is set as Y.

[0121] The distance H between the sawtooth cam teeth and the distance H' between the mountain-shaped cam teeth are geometrically related by H'=HX / (X+Y). Fig.10 The distance D of the multiple auxiliary lines J of the second cam tooth 140ba is D=H-2H(Y / (X+Y))=H(XY) / (X+Y). Therefore, the minimum retraction amount M is M=1 / 2H+D=1 / 2H+H(XY) / (X+Y)=H(3X-Y) / {2(X+Y)}=H'(3X-Y) / (2X). Therefore, the relationship of the minimum retraction amount M=3 / 2H'-H'Y / (2X) is obtained. Figure 7In the case of the sawtooth-shaped cam teeth whose height is a distance H shown, Y is zero. Therefore, according to this relational expression, the minimum retraction amount M=3 / 2H is obtained as described above.

[0122] Furthermore, when focusing on the movement of the tip of the tooth tip of the second cam tooth 140ba of the second cam surface 140b, it moves along a trajectory T3 when it first retreats, and moves along a trajectory T4 during subsequent rotation and retreat. The first cam tooth 140aa of the first cam surface 140a also moves along the same trajectory.

[0123] The first cam tooth 140aa forms an isosceles triangle when X=Y. Such a cam tooth is disclosed in Patent Document 2. Figure 4 In this case, according to the relationship of minimum retreat amount M = 3 / 2H'-H'Y / (2X), the minimum retreat amount M = H', and the minimum retreat amount M becomes the minimum. However, referring to Fig.10 Considering the case of X=Y, it is clear that the vertex of the first cam tooth 140aa and the vertex of the first fixed cam tooth 141aa are arranged at opposite positions. Therefore, the amount of hooking E is small or point-shaped, and a slight deviation of the rotating body 140 in the radial direction may cause rotation failure.

[0124] Therefore, Y is preferably smaller than X. In addition, according to the above relationship, when the first cam tooth 140aa is not Figure 7 In the case of the first cam tooth 40aa having a right triangle shape, that is, a sawtooth shape, it is possible to further reduce the minimum retreat amount M. Therefore, it is preferable that Y is greater than zero.

[0125] As described above, it is preferable that the first cam tooth 140aa and the second cam tooth 140ba are configured so as to satisfy the relationship of 0<Y<X, when the length of the bottom side located at the rear side with respect to the rotation direction of the rotating body 140 is X and the length of the bottom side located at the front side with respect to the rotation direction of the rotating body 140 is Y with respect to the top of the first cam tooth 140aa or the top of the second cam tooth 140ba. Furthermore, it is preferable that the first fixed cam surface 141a and the second fixed cam surface 142a are configured so as to be arranged at the minimum distance that does not hinder the rotation of the rotating body 140. Thereby, the minimum retreat amount M and the retreat amount m of the writing core can be further reduced, and the required hooking amount E can be ensured to a greater extent.

[0126] In addition, considering the tolerance during manufacturing, the amount of hooking E is preferably 0.1 mm or more (E ≥ 0.1 mm). In this regard, the number of cam teeth is set to 40, and the outer diameter of the first cam surface 140a and the second cam surface 140b of the rotating body 140 is 4.8 mm as described above. In addition, various dimensions are described in correspondence with the rotation angle around the central axis of the mechanical pencil 1 or the rotating body 140.

[0127] When the number of cam teeth is 40, the rotation angle α corresponding to half the phase of one cam tooth is 360 / 40 / 2 = 4.5°. According to the relationship of 4.8 mm × π × β / 360 = 0.1, the rotation angle β corresponding to the hanging amount E of 0.1 mm is 2.4°. Fig.10 Regarding the base of the first cam tooth 140aa, in consideration of an isosceles triangle with X=Y, the vertex of the first cam tooth 140aa is offset 1.2° to the left in the figure, and the first fixed cam tooth 141aa is offset 1.2° to the right in the figure, which is a relative rotation angle of 2.4° in total, and the amount of hooking E is 0.1 mm. Regarding the length of the base of the first cam tooth 140aa at this time, the rotation angle corresponding to X is 9.0 / 2+1.2=5.7° based on the rotation angle corresponding to one cam tooth of 9.0°, and the rotation angle corresponding to Y is 9.0 / 2-1.2=3.3°. Therefore, in order to make the amount of hooking E ≥ 0.1 mm, it is preferred that X / Y ≥ 5.7 / 3.3=1.72.

[0128] As described above, it is preferable to configure the first cam tooth 140aa and the second cam tooth 140ba so as to satisfy the relationship of X / Y ≥ 1.72. In order to more reliably prevent rotation failure due to radial deviation of the rotating body 140, it is more preferable to configure the first cam tooth 140aa and the second cam tooth 140ba so as to satisfy the relationship of X / Y ≥ 2.0. Even in the case of the cam teeth in the above-mentioned relationship of X and Y, as described above, the retraction amount of the writing lead caused by the retraction action is preferably within the range of 0.05 mm to 0.3 mm, and more preferably within the range of 0.1 mm to 0.2 mm.

[0129] In the above embodiment, a preferred cam tooth shape, that is, the relationship between X and Y, is described based on an example of the outer diameter of the rotating body 140, the number of cam teeth, and the inclination angle, but the above relationship between X and Y can also be applied to mechanical pencils having other outer diameters, the number of cam teeth, etc. That is, according to the above embodiment, in the mechanical pencil 1 having the rotation drive mechanism for rotating the writing lead, the amount of retreat of the writing lead can be further reduced.

[0130] Description of Reference Numerals

[0131] 1. Mechanical pencil; 5. Pen barrel; 10. Chuck unit; 20. Push member; 31. Shaft spring; 40. Rotating body; 40a. First cam surface; 40aa. First cam tooth; 40b. Second cam surface; 40ba. Second cam tooth; 41. Upper cam forming member; 41a. First fixed cam surface; 41aa. First fixed cam tooth; 42. Lower cam forming member; 42a. Second fixed cam surface; 42aa. The second fixed cam tooth; 140, rotating body; 140a, the first cam surface; 140aa, the first cam tooth; 140b, the second cam surface; 140ba, the second cam tooth; 141, the upper cam forming member; 141a, the first fixed cam surface; 141aa, the first fixed cam tooth; 142, the lower cam forming member; 142a, the second fixed cam surface; 142aa, the second fixed cam tooth; M, the minimum retreat amount.

Claims

1. A mechanical pencil, characterized in that: This mechanical pencil has: pen; a chuck unit that allows the cartridge to advance and prevents the cartridge from retreating; and a rotation drive mechanism having a rotating body, the rotation drive mechanism receiving a retreating motion in the axial direction caused by the writing pressure on the pen core held by the chuck unit and an advancing motion in the axial direction caused by the release of the writing pressure, and driving the rotating body to rotate in one direction; The rotary drive mechanism comprises: a first annular cam surface formed on the rear end surface of the rotating body; a second annular cam surface formed on the front end surface of the rotating body; a first fixed cam surface provided on the pen holder side and cooperating with the first cam surface to rotate the rotating body; and a second fixed cam surface provided on the pen holder side and cooperating with the second cam surface to rotate the rotating body. The mechanical pencil is configured such that, by the retreating action of the chuck unit caused by the writing pressure, the first cam surface of the rotating body abuts against the first fixed cam surface, so that the rotating body meshes while rotating, and by the release of the writing pressure, the second cam surface of the rotating body abuts against the second fixed cam surface, so that the rotating body meshes while rotating. In a state where the first cam surface of the rotating body is meshed with the first fixed cam surface, the second cam surface and the second fixed cam surface are set to be offset in the axial direction by half a phase relative to one tooth of the cam, and in a state where the second cam surface of the rotating body is meshed with the second fixed cam surface, the first cam surface and the first fixed cam surface are set to be offset in the axial direction by half a phase relative to one tooth of the cam, The first cam surface includes a first cam tooth, the second cam surface includes a second cam tooth, the first fixed cam surface includes a first fixed cam tooth cooperating with the first cam tooth, and the second fixed cam surface includes a second fixed cam tooth cooperating with the second cam tooth. In the first cam tooth, when the length of the base located on the rear side with respect to the rotation direction of the rotating body is set to X, and the length of the base located on the front side with respect to the rotation direction of the rotating body is set to Y, with respect to the perpendicular line drawn from the vertex, the first cam tooth is constructed in a manner to achieve a relationship of 0<Y<X.

2. The mechanical pencil according to claim 1, wherein: The first cam teeth and the second cam teeth are configured so as to satisfy the relationship of X / Y≥1.

72.

3. The mechanical pencil according to claim 2, wherein: The first cam teeth and the second cam teeth are configured so as to satisfy the relationship of X / Y≥2.

0.

4. The mechanical pencil according to any one of claims 1 to 3, wherein In a state where the second cam surface of the rotating body meshes with the second fixed cam surface, the apex of the first cam tooth and the apex of the first fixed cam tooth are separated from each other by 0.1 mm or more in the circumferential direction.

5. The mechanical pencil according to any one of claims 1 to 3, wherein The first fixed cam surface and the second fixed cam surface are configured to be arranged at a minimum distance that does not hinder the rotation of the rotating body.

6. The mechanical pencil according to any one of claims 1 to 3, wherein The mechanical pencil is configured such that the chuck unit receives the rotational driving force of the rotating body and rotates, thereby rotating the writing lead.

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