JP2018089812A - mechanical pencil - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a mechanical pencil which can surely avoid breakage of a writing lead when higher writing pressure is added to the writing lead, and has a smoother writing feeling than that of a conventional one.SOLUTION: A mechanical pencil 100 comprises: a barrel 10 having a barrel contact part 32; a barrel inner tube 40b having a barrel inner tube contact part 40e contacting with the barrel contact part 32; a lead-delivering unit 40 which is supported in the barrel 10 and holds a writing lead 70; and a mouthpiece 52. The lead-delivering unit 40 is relatively moved in an axial direction of the barrel 10 by a component of writing pressure in an axial direction of the barrel 10, and the mouthpiece 52 is relatively moved in a radial direction of the barrel 10 by a component of the writing pressure in a radial direction of the barrel 10. A value obtained by dividing a length between a contact part between the barrel contact part 32 and the barrel inner tube contact part 40e and a front end part of the mouthpiece 52 along the axial direction of the barrel 10 by a length from the contact part between the barrel contact part 32 and the barrel inner tube contact part 40e to an axis line of the barrel 10 is 2-5.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a mechanical pencil capable of writing by drawing a writing core by a predetermined amount from the tip of a base by a knocking operation or the like.

  A conventional mechanical pencil has a problem that when a high writing pressure is applied to the writing core during writing, the writing core exposed from the tip of the base easily breaks. When the writing pressure is constant, the writing core breaks down as the angle between the axial direction of the mechanical pencil barrel and the paper surface becomes smaller (so that the barrel is laid down) or exposed from the tip of the base. The longer the length is, the more conspicuous.

  With respect to such a problem, in Patent Document 1 (Japanese Patent Application Laid-Open No. 2015-123687), when a high writing pressure is applied to the writing core, the writing pressure component in the axial direction of the shaft cylinder is orthogonal to the axial direction. A mechanical pencil is described in which the writing pressure component in the direction is absorbed by different mechanisms to reduce the breakage of the writing core.

Specifically, in the mechanical pencil of Patent Document 1, the base is supported by a shaft cylinder via an elastic body (spring), and the base gradually decreases in diameter toward the rear in the axial direction of the shaft cylinder. have. Further, the shaft cylinder is formed with a pressing portion that presses the cam inclined surface forward in the axial direction of the shaft cylinder. With such a configuration, the cam inclined surface of the base is pressed forward in the axial direction of the shaft cylinder by the pressing portion due to a component of the writing pressure in the direction orthogonal to the axial direction of the shaft cylinder (force in the outer direction of the shaft diameter). Then, the base slides forward (jumps out) from the tip of the shaft tube. Thereby, the length of the writing core exposed from the front-end | tip of a nozzle | cap | die is reduced.
Further, in the mechanical pencil of Patent Document 1, the core feeding unit for feeding out the writing core is urged forward in the axial direction by the elastic body (spring) (the front end direction of the base in the axial direction). Are supported by the shaft cylinder in a state of being relatively movable. Then, the core feeding unit including the writing core relatively moves rearward in the axial direction of the shaft cylinder, so that the axial component of the writing pressure is absorbed. As a result, the length of the writing core exposed from the tip of the base is further reduced, and the breakage of the writing core is reduced.

  In the mechanical pencil described in Patent Document 1, when a high writing pressure is applied to the writing core, the base is stretched all at once over the maximum length (stroke) that allows the base to slide forward with respect to the barrel. It is designed to slide (jump out).

  On the other hand, when the high writing pressure is applied to the writing core, the inventors of the present invention slide the base in the radial direction of the shaft cylinder, and the writing core is behind the base. Was developed as an international application PCT / JP2016 / 068863. In such a mechanical pencil, breakage of the writing core can be effectively avoided, but it has been demanded to provide a better writing feeling in order to further improve the completeness.

Japanese Patent Laying-Open No. 2015-123689

  As a result of extensive studies, the present inventor has found that setting the length of the base to a specific dimension is effective in improving the writing feeling.

  The present invention is based on the above knowledge, and its purpose is to reliably avoid breakage of the writing core when a high writing pressure is applied to the writing core, and to achieve a smoother writing feeling. Is to provide a mechanical pencil.

The present invention provides a shaft tube having a shaft tube contact portion;
A shaft cylinder inner cylinder having a shaft cylinder inner cylinder abutting portion that is biased forward in the axial direction with respect to the shaft cylinder in the shaft cylinder, and abuts on the shaft cylinder abutting portion;
A lead feeding unit which is supported in the shaft cylinder and holds a writing lead;
A base having an opening that is supported by the shaft cylinder so as to be exposed from the shaft cylinder in the axial direction forward of the shaft cylinder and through which the writing core held by the core feeding unit can pass;
The core feeding unit is relatively moved in the axial direction of the shaft cylinder with respect to the shaft cylinder by a component of the pen pressure in the axial direction of the shaft cylinder, and the base is the shaft cylinder of the writing pressure. Is moved relative to the axial cylinder in the radial direction of the axial cylinder,
In a state where the base is not relatively moved in either the axial direction or the radial direction of the shaft tube, the contact portion between the shaft tube contact portion and the shaft tube inner tube contact portion and the front end portion of the base tube The length along the axial direction of the shaft tube between the contact portion between the shaft tube contact portion and the shaft tube inner tube contact portion and the axis line of the shaft tube is divided by A mechanical pencil having a value of 2 or more and 5 or less.

  According to the present invention, when a high writing pressure is applied to the writing core, the lead feeding unit and the base move relative to the shaft cylinder in a predetermined direction. Breakage of the writing core can be avoided reliably. Further, the length along the axial direction of the shaft tube between the contact portion between the shaft tube contact portion and the shaft tube inner tube contact portion and the front end portion of the base is determined as the shaft tube contact portion and the shaft tube. By setting the value divided by the distance from the contact portion with the inner tube contact portion to the axis of the shaft tube to be 2 or more and 5 or less, it is possible to provide a mechanical pencil with a smoother writing feeling. it can.

  At least one of the shaft tube inner tube contact portion and the shaft tube contact portion may be a tapered surface that gradually increases in diameter toward the rear in the axial direction of the shaft tube.

  In this case, with a simple configuration, the base can be relatively moved in the radial direction of the shaft cylinder by a writing pressure component in the radial direction of the shaft cylinder.

  The above mechanical pencil may further include an elastic body disposed in a compressed state between the lead feeding unit and the base.

  Further, in the above mechanical pencil, the writing core and the core feeding unit are moved relative to the shaft tube in the axial direction rearward with respect to the shaft tube by the writing pressure, and the base is moved by the elastic body. However, it may move relatively forward in the axial direction with respect to the lead feeding unit.

  In these cases, the relative position of the base in the axial direction of the shaft cylinder can be kept constant regardless of the relative position of the core feeding unit in the axial direction of the shaft cylinder. For this reason, a writing feeling is not impaired by the relative movement of the lead feeding unit.

  The core feeding unit may be deformable or tiltable with respect to the axial direction of the shaft tube.

  In particular, the lead feeding unit may have a lead pipe that can be bent and deformed. In this case, the relative movement of the writing core in the radial direction of the shaft cylinder is smooth.

  According to the present invention, when a high writing pressure is applied to a writing core, breakage of the writing core can be reliably avoided, and a mechanical pencil with a smoother writing feeling can be provided.

It is a schematic longitudinal cross-sectional view which shows the mechanical pencil by one embodiment of this invention. It is a schematic longitudinal cross-sectional view which shows the components structure of the mechanical pencil shown in FIG. FIG. 2 is a partial schematic longitudinal sectional view of the mechanical pencil of FIG. 1 when a force (writing pressure) larger than a predetermined value is not applied to the writing core, for explaining a method of setting the length of the base It is also a figure. It is a partial schematic longitudinal cross-sectional view of the mechanical pencil of FIG. 1 in case the force (writing pressure) larger than a predetermined value is applied with respect to the writing core. The length Lq along the axial direction of the shaft tube between the contact portion Q of the shaft tube inner tube contact portion and the first shaft tube contact portion and the front end portion of the base is changed from the contact portion Q to the shaft tube. It is a graph which shows the result of having evaluated the operativity and visibility of a nozzle | cap | die with respect to several mechanical pencil from which the value (Lq / Rq) which remove | divided by distance Rq to the axis | shaft of this differs.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic longitudinal sectional view showing a mechanical pencil 100 according to an embodiment of the present invention, and FIG. 2 is a schematic longitudinal sectional view showing a component configuration of the mechanical pencil 100 shown in FIG. 3 is a partial schematic longitudinal section of the mechanical pencil 100 of FIG. 1 when a force (writing pressure) larger than a predetermined value is not applied to the writing core 70 in the radial direction of the shaft cylinder 10. It is a figure and is also a figure for demonstrating the setting method of the length of the nozzle | cap | die 52. FIG.

  As shown in FIGS. 1 to 3, the mechanical pencil 100 of the present embodiment includes a shaft tube 10, a core feeding unit 40 that is supported in the shaft tube 10 and holds a writing core 70, and an axis of the shaft tube 10. And a base 52 having an opening that is supported by the shaft tube 10 so as to be exposed from the shaft tube 10 forward in the direction and through which the writing core 70 held by the core feeding unit 40 can pass.

  The shaft cylinder 10 is made of polycarbonate, and includes a rear shaft 20 and a front shaft 30 disposed in front of the rear shaft 20 in the axial direction. In the present embodiment, a female screw portion is provided in the rear region of the front shaft 30, and a male screw portion is provided in the front region of the rear shaft 20. The front shaft 30 is fixed to the rear shaft 20 by screwing the female screw portion and the male screw portion together. Further, the inner surface of the front region of the rear shaft 20 has a first projecting portion 21 projecting inward in the radial direction of the shaft tube 10. As will be described later, the first protrusion 21 is used to urge the core feeding unit 40 forward in the axial direction with respect to the shaft tube 10.

  The core feeding unit 40 includes a core feeding unit main body 40a whose front end is surrounded by a base 52, which will be described later, a shaft cylinder inner tube 40b for holding the base 52 in a state of being prevented from being detached from the core feeding unit main body 40a, have. The core feeding unit main body 40a is made of a polypropylene core pipe 41 extending in the axial direction of the shaft tube 10 inside the shaft tube 10, and made of brass fixed to the front end portion of the core pipe 41 via a connector 49. The chuck 43, a brass tightening ring 42 fitted in the front area of the chuck 43, an outer cylinder 45 surrounding the chuck 43, and a return spring for urging the core pipe 41 axially rearward with respect to the outer cylinder 45 44.

  As shown in FIG. 1 to FIG. 3, the outer cylinder 45 has a flange portion 45 c that supports the chuck 43 on the inner peripheral surface of the front region and projects outward in the radial direction of the shaft tube 10 on the outer surface of the rear region. It has a rear cylinder 45a and a front cylinder 45b that is fitted and fixed to the front region of the rear cylinder 45a and extends forward in the axial direction of the shaft cylinder 10 beyond the front end portion of the chuck 43. A second spring 60 that can be expanded and contracted is disposed in a compressed state between the flange 45 c and the first projecting portion 21 of the rear shaft 20, and the core feeding unit 40 has an axis line with respect to the shaft cylinder 10. It is biased forward in the direction.

  1 to 3, the chuck 43 is fastened by a fastening ring 42 to pinch the writing core 70 so as not to retreat. The front cylinder 45b has an abutting step portion 45e for restricting the forward movement of the fastening ring 42 in the middle on the inner peripheral surface in the axial direction of the shaft cylinder 10 with respect to the fastening ring 42.

  Further, a predetermined gap is provided between the side peripheral surface of the flange portion 45 c of the outer cylinder 45 and the inner surface of the front shaft 30, whereby the core feeding unit 40 is fixed to the shaft cylinder 10 by a certain amount. Only tilting is allowed.

  The shaft tube inner tube 40b has a shaft tube inner tube contact portion 40e at the front end. As shown in FIG. 3 in particular, the shaft tube inner tube contact portion 40e of the present embodiment is configured as a tapered surface that gradually increases in diameter toward the rear in the axial direction of the shaft tube 10. Further, the shaft cylinder 10 (front shaft 30) has a first shaft cylinder contact portion 32 projecting inward in the radial direction of the shaft cylinder 10 on the inner peripheral surface of the front region. In the present embodiment, as shown in FIGS. 1 to 3, the first shaft cylinder contact portion 32 and the shaft tube inner tube contact portion 40e are in contact with each other. As will be described later, when the lead feeding unit 40 tilts, the first shaft tube contact portion 32 moves the shaft tube inner tube contact portion 40e, that is, the core feed unit 40 moves with respect to the shaft tube 10. Relative movement is made backward in the axial direction.

  As shown in FIG. 1 to FIG. 3, the mechanical pencil 100 according to the present embodiment is disposed in the front end region of the lead feeding unit 40 and can be moved relative to the lead feeding unit 40 in the axial direction of the barrel 10. 52. As described above, the front end portion of the lead feeding unit main body 40 a is surrounded by the base 52.

  As shown in the figure, the base 52 connects a cylindrical front region 52a for guiding the writing core 70, a sleeve-shaped rear region 52b having a diameter larger than the front region 52a, and the front region 52a and the rear region 52b. A base abutting portion 52c. Further, the rear region 52b includes a front small diameter portion 52d and a rear large diameter portion 52e, and a tapered portion 52f that connects the small diameter portion 52d and the large diameter portion 52e.

  As described above, the base 52 is attached to the tip region of the core feeding unit main body 40a while being prevented from being detached by the shaft tube inner tube 40b and being slidable in the axial direction of the shaft tube 10. Specifically, as shown in FIGS. 1 to 3, the shaft cylinder inner tube 40b is fitted into a cylindrical main body portion 40c surrounding the rear region 52b of the base 52 and a rear end region of the cylindrical main body portion 40c. An annular stopper 40d. And the nozzle | cap | die 52 is hold | maintained in the clearance gap between the axial cylinder inner cylinder 40b and the outer cylinder 45 so that the axial direction of the said outer cylinder 45 is slidable, and the undesired drop-off from the core feeding unit main body 40a is prevented. . Further, the front end of the cylindrical main body 40c is an opening, and the front region 52a of the base 52 projects forward from this opening.

  The base 52 of the present embodiment is urged forward in the axial direction of the shaft tube 10 by a first spring 55 disposed in a compressed state between the base 52 and the core feeding unit main body 40a. Specifically, the outer cylinder 45 of the core feeding unit body 40a has a flat surface 45f facing the front in the axial direction of the shaft cylinder 10 on the outer surface. The first spring 55 that can be expanded and contracted is disposed in a compressed state between the flat surface 45f and the tapered portion 52f of the base 52, whereby the base 52 is urged forward with respect to the core feeding unit main body 40a. ing.

  As shown in FIG. 1 to FIG. 3, the shaft tube 10 (front shaft 30) has a second shaft tube contact portion on the inner peripheral surface of the shaft tube 10 in the axial direction front direction than the front end portion of the rear region 52 b of the base 52. 33, the inner diameter of the shaft tube 10 (front shaft 30) is smaller than the outer diameter of the rear region 52 b of the base 52 in the second shaft tube contact portion 33. That is, the second shaft cylinder contact portion 33 and the base contact portion 52c are in contact with each other, so that the relative movement of the base 52 in the axial direction relative to the shaft tube 10 is restricted. In other words, the second shaft cylinder contact portion 33 and the base contact portion 52c are in contact with each other, so that the lead feeding unit 40 is prevented from coming off from the shaft tube 10.

  With the configuration as described above, the contact state between the base 52 and the second shaft tube contact portion 33 of the shaft tube 10 even when the core feeding unit 40 is relatively moved rearward in the axial direction with respect to the shaft tube 10. Is to be maintained. Further, when the lead feeding unit 40 including the writing lead 70 is relatively moved axially rearward with respect to the shaft tube 10, the length of the writing lead 70 exposed from the front end portion of the base 52 is reduced. It has become.

  Further, as shown in FIG. 3, the front cylinder 45 b of the core feeding unit 40 includes a front region 45 b 1 having an outer surface that is slidably contacted with the inner surface of the base 52 so as to be relatively movable in the axial direction of the shaft cylinder 10. In the present embodiment, in the state of FIG. 3 in which the base 52 is not relatively moved in either the axial direction or the radial direction of the shaft tube 10, the shaft tube inner tube contact portion 40e and the front shaft of the shaft tube inner tube 40b. The length Lq along the axial direction of the shaft tube 10 between the contact portion Q of the first shaft tube contact portion 32 of the 30 and the front end portion of the base 52 is defined as the axis of the shaft tube 10 from the contact portion Q. The size of the base 52 is determined so that the value divided by the distance Rq, that is, the value (ratio) of Lq / Rq is 2.88.

The reason for focusing on the ratio between the length Lq and the distance Rq will be briefly described as follows. That is, when the radial component of the shaft tube 10 increases in the writing pressure acting on the writing core 70, the core feeding unit 40 is placed around the deflection start position M of the core pipe 41 located on the axis of the shaft tube 10. A moment to rotate clockwise is generated. More specifically, referring to FIG. 3, the force due to the pen pressure component acting on the front end portion A of the writing core 70 along the direction perpendicular to the line segment MA is F1, and the contact portion Q Assuming that the force acting from the single-shaft cylinder abutting portion 32 to the inner-cylindrical cylinder abutting portion 40e is F1, the moment around the starting position M of the bending due to the force F1 and the surrounding of the starting position M of the bending due to the force F2 The following relationship holds for moments. The front end portion A of the writing core 70 is a portion corresponding to the front end of the writing core 70 on the axis a1 of the shaft cylinder.
[Formula 1]
F1 ・ MA = F2 ・ MQ
Here, MA and MQ represent the lengths of the line segment MA and the line segment MQ, respectively.

By the way, when the coefficient of friction between the first shaft tube contact portion 32 and the shaft tube inner tube contact portion 40e is μ, it is between the first shaft tube contact portion 32 and the shaft tube inner tube contact portion 40e. The frictional force (Fk + F2) · μ is generated by the resultant force of the force Fk provided to the first shaft contact portion 32 by the elastic force of the two springs 55 and 60 and the aforementioned force F2. If the frictional force in the direction along the taper of the first shaft contact portion 32 becomes smaller than the force Ft in the direction acting on the first shaft contact portion 32 due to the writing pressure, the base 52 Moves relative to the inner cylinder 40b. That is, the condition for the base 52 to move relative to the shaft tube inner tube 40b is expressed by the following equation, considering [Equation 1].
[Formula 2]
(F1 · (MA / MQ) + Fk) · μ <Ft

  According to [Formula 2], it can be said that the smaller the value of MA / MQ, the easier the inner cylinder 40 b moves relative to the main cylinder 10. In other words, as the MA is relatively small and the MQ is relatively large, the shaft tube inner tube 40 b is easily moved relative to the shaft tube 10. That is, the base 52 is easy to move relative to the shaft tube inner tube 40b. Here, referring to the drawings, if the length Lq decreases, the MA decreases. Further, it is understood that MQ is relatively increased as the distance Rq is increased. Accordingly, when attention is paid to the value (ratio) of Lq / Rq instead of the value (ratio) of MA / MQ, the smaller the value, the easier the base 52 tends to move relative to the shaft cylinder inner tube 40b. Conceivable.

  FIG. 5 is a chart showing the results of evaluating the operability and visibility of the base 52 for a plurality of mechanical pencils having different values of Lq / Rq. In FIG. 7, the column of “operability” is a result of evaluating whether or not the base 52 is easy to move relative to the shaft tube inner tube 40b. “◯” is good and “◎” is very good. It shows that it was. The column “Visibility” is the result of evaluating the visibility of written characters, etc., and “◯” indicates good and “◎” indicates very good, respectively. Although the lengths of MA and MQ are also shown in FIG. 5, since the starting position M of the deflection of the core pipe 41 changes depending on the writing situation, these values are reference values under specific writing conditions.

  In view of the above evaluation results, the operability and visibility were good or very good when the value of Lq / Rq was in the range of 2 to 5. When the value of Lq / Rq is greater than 5, the base 52 is less likely to move relative to the inner cylinder 40b, so that when the writing pressure applied to the writing core 70 increases, It breaks. On the other hand, when the value of Lq / Rq is smaller than 2, the base 52 relatively moves in the radial direction of the shaft tube 10 even with a weak writing pressure, and the visibility of written characters and the like decreases. End up. Considering the above, 2.88 is adopted as the value of Lq / Rq in the present embodiment.

  Further, the rear shaft 20 has a second projecting portion 22 projecting radially inward of the shaft tube 10 on the inner surface of the rear region. In the shaft cylinder 10, a weight body 90 is disposed between the second projecting portion 22 and the connector 49 so as to surround the core pipe 41. The inner diameter of the rear shaft 20 is smaller than the outer diameter of the weight body 90 at the second protrusion 22. Further, the outer shape of the rear end portion of the connector 49 is larger than the inner diameter of the weight body 90. With such a configuration, the weight body 90 can move between the second projecting portion 22 and the connector 49 in the axial direction of the shaft tube 10. As the weight body 90 of the present embodiment, a metal pipe is employed. Further, in the present embodiment, when the base 52 is relatively moved in the radial direction of the shaft tube 10, the weight body 90 and the inner surface of the shaft tube 10 do not interfere with each other.

  Further, as shown in FIG. 1, the core feeding unit 40 further includes a knock portion 48 that is attached to the rear end of the core pipe 41 and presses the core pipe 41 forward in the axial direction against the outer cylinder 45. doing. The knock portion 48 of the present embodiment is provided with a sleeve portion 48a fitted on the rear end region of the core pipe 41 on the front side in the axial direction of the axial cylinder 10, and further on the rear side in the axial direction of the axial cylinder 10 with a cylindrical shape. A holder portion 48b for detachably holding the eraser 80 is provided. The internal space of the sleeve portion 48a and the internal space of the holder portion 48b are communicated by an opening. Thus, by removing the eraser 80 from the holder portion 48b, the writing core 70 can be put into the core pipe 41 from the opening. A dome-shaped knob 81 that covers the back of the eraser 80 is detachably fitted to the holder portion 48b.

  Furthermore, in the present embodiment, the head crown 23 is fixed to the rear end region of the rear shaft 20. The crown 23 has a bulging portion 23 a that bulges radially inward of the shaft tube 10 on the inner surface thereof. Further, a flange portion 48c is formed on the outer periphery of the holder portion 48b, and an elastic spring 48d is disposed in a compressed state between the flange portion 48c and the bulging portion 23a.

  Next, the operation of the mechanical pencil 100 according to the present embodiment will be described.

  First, prior to writing on the paper, if necessary, the knob 81 and the eraser 80 are removed from the holder portion 48b, and the writing core 70 is formed through an opening that connects the sleeve portion 48a and the holder portion 48b. It is put into the core pipe 41. The eraser 80 and the knob 81 are attached to the holder portion 48b, and the knock portion 48 (knob 81) is pressed (knocked) forward in the axial direction with the front end of the base 52 directed downward. As a result, the core pipe 41, the connector 49, the chuck 43 and the fastening ring 42 are advanced against the urging force of the return spring 44. In the middle of this forward movement, only the fastening ring 42 comes into contact with the contact step 45e formed on the front cylinder 45b of the outer cylinder 45. As a result, the fastening ring 42 is removed rearward from the chuck 43, the chuck 43 is released, and the writing core 70 is fed out. At the time of pressing (knocking), an appropriate resistance feeling is brought about by the biasing force of the spring 48d disposed between the flange portion 48c of the knock portion 48 and the bulging portion 23a of the head crown 23.

When the pressing state of the knock portion 48 (knob 81) is released, the core pipe 41 is retracted together with the chuck 43 by the urging force of the return spring 44. Along with this, the fastening ring 42 is fitted again to the front region of the chuck 43, and the chuck 43 is fastened.
Thereby, the writing core 70 is pinched so as not to retreat, and the state where the writing core 70 is extended is maintained. Then, by repeating this series of pressing operations as appropriate, the writing core 70 is exposed (drawn) from the tip of the base 52 by a desired length (see FIG. 3). The shaft cylinder 10 is gripped by the user, and writing is performed by moving the shaft cylinder 10 as desired while bringing the writing core 70 into contact with the paper surface.

  In writing, the shaft tube 10 is generally gripped so that the axial direction forms an acute angle with respect to the paper surface (see FIG. 3). For this reason, the writing pressure including the component perpendicular to the axial direction of the barrel 10 and the component in the axial direction is applied to the writing core 70. In the mechanical pencil 100 according to the present embodiment, when a high writing pressure is applied to the writing core 70 during writing, as will be described in detail with reference to FIG. Each component of the direction is absorbed, and breakage of the writing core 70 exposed from the tip of the base 52 is avoided.

  4 is a partial schematic longitudinal sectional view of the mechanical pencil 100 of FIG. 1 when a force (writing pressure) larger than a predetermined value is applied to the writing core 70 in the radial direction of the shaft cylinder 10. is there. When high writing pressure is applied to the writing core 70, as shown in FIG. 4, the front region of the core feeding unit 40 is tilted by the component of the writing pressure along the direction orthogonal to the axial direction of the shaft tube 10, and the front shaft The shaft inner cylinder abutting portion 40 e is pressed rearward in the axial direction of the shaft cylinder 10 by the first shaft cylinder abutting portion 32 of 30. Accordingly, the lead feeding unit 40 including the writing lead 70 is relatively moved rearward in the axial direction of the shaft tube 10 against the urging force of the second spring 60. On the other hand, since the base 52 is pressed forward with respect to the shaft tube inner tube 40 b by the urging force of the first spring 55, it is not relatively moved rearward in the axial direction of the shaft tube 10. As a result, the length of the writing core 70 exposed from the tip of the base 52 is reduced.

  The core feeding unit 40 is prohibited from relatively moving in the radial direction of the shaft tube 10 by a certain amount or more by the side peripheral surface of the flange portion 45 c of the outer tube 45 coming into contact with the inner surface of the shaft tube 10. Thus, even when the base 52 is relatively moved over the maximum length in the radial direction of the shaft tube 10, the weight body 90 and the inner surface of the shaft tube 10 do not interfere with each other, and the base 52 Is not undesirably prevented from moving in the radial direction.

  Further, as shown in FIG. 4, the writing core 70 is pressed against the axial tube 10 backward in the axial direction by the component of the writing pressure along the axial direction of the axial tube 10. Thereby, the core feeding unit 40 including the writing core 70 is further moved relative to the rear in the axial direction against the urging force of the second spring 60. Also at this time, since the base 52 is pressed forward against the inner cylinder 40 b by the urging force of the first spring 55, it is not relatively moved rearward in the axial direction of the axial cylinder 10. As a result, the length of the writing core 70 exposed from the tip of the base 52 is further reduced, and breakage of the writing core 70 is avoided.

  In the present embodiment, by adopting 2.88 as the value of Lq / Rq, when writing is performed in a state where the axis of the shaft tube 10 is 55 ° with respect to the paper surface, the paper surface with respect to the writing core 70 is used. When a 3N writing pressure is applied in a direction orthogonal to the base tube 52, the base 52 starts to be relatively moved in the radial direction of the shaft tube 10. That is, the base 52 starts to move relative to the inner cylinder tube 40b. Note that when the angle between the writing surface and the axis of the shaft cylinder 10 increases, the component of the writing pressure along the axis direction of the shaft cylinder 10 increases. In this case, the base 52 is not relatively moved in the radial direction of the shaft tube 10, and only the core feeding unit 40 including the writing core 70 is moved rearward in the axial direction of the shaft tube 10 by compressing the second spring 60. Will be.

  When the writing pressure applied to the writing core 70 is weakened, the lead feeding unit 40 including the writing core 70 is pushed back in the axial direction of the axial tube 10 by the urging force of the second spring 60. As a result, the initial state (see FIG. 3) is restored.

  The mechanical pencil 100 according to the present embodiment can feed out the writing core 70 by swinging the shaft tube 10 back and forth. That is, when the shaft cylinder 10 is swung back and forth by the user, the weight body 90 moves back and forth inside the space portion. At this time, the weight body 90 abuts on the connector 49 in the front in the axial direction. At the time of the contact, the connector 49 is advanced in the axial direction by the inertial force of the weight body, and the writing core 70 is drawn out. Even when such a swing-type lead feeding unit is employed, the same effect as that obtained when the knock-type lead feeding unit 40 is employed can be obtained. Further, the writing core 70 is quickly drawn out without performing a knocking operation.

  According to the present embodiment as described above, when a high writing pressure is applied to the writing core 70, the front region of the core feeding unit 40 is axially driven by the component of the writing pressure orthogonal to the axial direction of the shaft tube 10. It is tilted in the cylinder 10. As a result, the lead feeding unit 40 including the writing lead 70 is moved relative to the axial tube 10 in the axial direction against the urging force of the second spring 60, so that the writing lead exposed from the tip of the base 52. The length of 70 is reduced. Furthermore, the lead feeding unit 40 including the writing lead 70 is further moved relative to the shaft tube 10 in the axial direction rearward against the urging force of the second spring 60 by the axial component of the writing pressure. The length of the writing core 70 exposed from the tip is further reduced. For these reasons, when a high writing pressure is applied to the writing core 70, breakage of the writing core 70 is reliably avoided. Furthermore, since the value of Lq / Rq is 2.88 (corresponding to Example 1 in FIG. 7), the mechanical pencil 100 having a smoother writing feeling without sacrificing the visibility of the writing core 70 is provided. can do.

  In the mechanical pencil 100 described above, the writing core 70 and the core feeding unit 40 are moved relative to the axial cylinder 10 in the axial direction rearward with respect to the axial cylinder 10 by the writing pressure, and the base 52 is moved by the first spring 55. It moves relative to the core feeding unit 40 in the axial direction of the shaft cylinder. For this reason, irrespective of the relative position of the lead feeding unit 40 in the axial direction of the barrel 10, the relative position of the base 52 in the axial direction can be kept constant, and the writing feeling is felt by the relative movement of the lead feeding unit 40. There is no damage.

  Moreover, since the lead feeding unit 40 has the lead pipe 41 that can be bent and deformed, the relative movement of the writing lead 70 in the radial direction of the shaft tube 10 is smooth.

  In the mechanical pencil 100 described above, in order to improve writing feeling, it is also important to set the urging forces of the two springs 55 and 60 appropriately. Here, the biasing force is a state in which the first spring 55 is located at both ends of the first spring 55 in a state where the base 52 is not relatively moved in either the axial direction or the radial direction of the shaft tube 10. 52 and the force applied to the outer cylinder 45. In the second spring 60, the second spring 60 is a force applied to the shaft cylinder 10 and the outer cylinder 45 located at both ends thereof.

  As a result of evaluating the writing feeling of the mechanical pencil in which the urging forces of the springs 55 and 60 are changed to various values, the ratio of the urging force W2 of the second spring 60 to the urging force W1 of the first spring 55 is W2-W1. It was revealed that it is preferably 0.5N or more and 5N or less. When the value of W2-W1 is 5 or more, the bases 52, 252, and 352 are difficult to relatively move in the axial direction or the radial direction of the shaft tube 10. For this reason, when a high writing pressure is applied to the writing core 70, the writing core 70 is easily broken. On the other hand, when the value of W2-W1 is 0.5 or less, the base 52 easily moves relative to the axial direction or the radial direction of the shaft tube 10. For this reason, even if a low writing pressure is applied to the writing core 70, the caps 52, 252, and 352 move relative to each other in the axial direction or the radial direction of the shaft tube 10, and the writing feeling is deteriorated.

  The spring constants of the springs 55 and 60 are relative movements when the caps 52, 252, and 352 move relative to the shaft tube 10 by a writing pressure when a certain writing pressure is applied to the writing core 70. It is related to the amount, and is preferably 500 N / m or more and 2000 N / m or less. That is, when the spring constant of each of the springs 55 and 60 is greater than 2000 N / m, the relative movement amount when the bases 52, 252, and 352 move relative to the shaft tube 10 due to the writing pressure applied to the writing core 70. Is relatively small, and the writing core 70 is easily broken. On the other hand, when the spring constants of the springs 55 and 60 are smaller than 500 N / m, the relative movement amount when the caps 52, 252, and 352 move relative to the shaft tube 10 by the writing pressure applied to the writing core 70. Is relatively large, and the writing feeling is reduced.

  Based on the above, in each embodiment, the value of W2-W1 is set to 2N. Specifically, the biasing force W1 of the first spring 55 is 4N, and the biasing force W2 of the second spring 60 is 6N. The spring constant of the first spring 55 is 1500 N / m, and the spring constant of the second spring 60 is also 1500 N / m. The mechanical pencil 100 has a good writing feeling in combination with the appropriate setting of the length of the base 52 by setting the urging forces W1 and W2 of the two springs 55 and 60 in this way. Can be provided.

DESCRIPTION OF SYMBOLS 10 Shaft cylinder 20 Rear axis | shaft 21 1st protrusion part 22 2nd protrusion part 23 Head crown 23a bulging part 30 Front shaft 32 1st axis cylinder contact part 33 2nd axis cylinder contact part 40 Core feeding unit 40a Core feeding unit Main body 40b Shaft cylinder inner cylinder 40c Tubular main body part 40d Stopper 40e Shaft cylinder inner cylinder contact part 41 Core pipe 42 Tightening ring 43 Chuck 44 Return spring 45 Outer cylinder 45a Rear cylinder 45b Front cylinder 45b1 Front area 45c Flange part 45e Contact Step portion 45f Flat surface 48 Knock portion 48a Sleeve portion 48b Holder portion 48c Flange portion 48d Spring 49 Connector 52 Base 52a Front region 52b Back region 52c Base contact portion 52d Small diameter portion 52e Wide diameter portion 52f Taper portion 55 First spring 60 First 2 Spring 70 Writing core 80 Rubber 81 Knob 90 Weight body 100 Mechanical pencil

Claims (6)

A shaft tube having a shaft tube contact portion;
A shaft cylinder inner cylinder having a shaft cylinder inner cylinder abutting portion that is biased forward in the axial direction with respect to the shaft cylinder in the shaft cylinder, and abuts on the shaft cylinder abutting portion;
A lead feeding unit which is supported in the shaft cylinder and holds a writing lead;
A base having an opening that is supported by the shaft cylinder so as to be exposed from the shaft cylinder in an axially forward direction of the shaft cylinder, and through which the writing core held by the core feeding unit can pass;
With
The core feeding unit is relatively moved in the axial direction of the shaft cylinder with respect to the shaft cylinder by a component of the pen pressure in the axial direction of the shaft cylinder, and the base is the shaft cylinder of the writing pressure. Is moved relative to the axial cylinder in the radial direction of the axial cylinder,
In a state where the base is not relatively moved in either the axial direction or the radial direction of the shaft tube, the contact portion between the shaft tube contact portion and the shaft tube inner tube contact portion and the front end portion of the base tube The length along the axial direction of the shaft tube between the contact portion between the shaft tube contact portion and the shaft tube inner tube contact portion and the axis line of the shaft tube is divided by A mechanical pencil having a value of 2 or more and 5 or less. 2. The tape cylinder according to claim 1, wherein at least one of the inner cylinder tube contact portion and the shaft tube contact portion is a tapered surface that gradually increases in diameter toward the rear in the axial direction of the shaft tube. mechanical pencil. The mechanical pencil according to claim 1, further comprising an elastic body disposed in a compressed state between the core feeding unit and the base. Due to the writing pressure, the writing core and the core feeding unit move relative to the shaft tube in the axial direction rearward of the shaft tube, and the base is moved to the axis line with respect to the core feeding unit by the elastic body. The mechanical pencil according to claim 3, wherein the mechanical pencil moves relative to the front in the direction. The mechanical pencil according to any one of claims 1 to 4, wherein the core feeding unit is capable of bending deformation or tilting with respect to an axial direction of the shaft cylinder. The mechanical pencil according to any one of claims 1 to 5, wherein the lead feeding unit includes a lead pipe that can be bent and deformed.