JP2022014228A - mechanical pencil - Google Patents

Abstract

To provide a mechanical pencil of a swing type that can extend a writing core with a compact operation and with a light force.SOLUTION: A mechanical pencil 1 includes: a chuck unit 11 having a weight body 10 arranged so as to be movable back and forth inside a barrel 6, a spring 25 that urges the weight body rearward with respect to the barrel, a chuck body portion 14 that grips a writing core 8, and a knock transmission cylinder 15 arranged separately from the chuck body portion; and a holding chuck 9 arranged in front of the chuck unit and configured to hold the writing core. At the time of the extending operation, the weight body advances against the urging force of the spring, and as the weight body advances, only the chuck body portion advances and the writing core is extended. At the time of knock operation, the knock transmission cylinder advances to hold the rear end of the chuck body portion, and the chuck body portion and the knock transmission cylinder advance to extend the writing core.SELECTED DRAWING: Figure 2

Description

The present invention relates to mechanical pencils.

A so-called mechanical pencil that draws out a writing core by swinging the shaft back and forth using the movement of a weight body (heavy body) that is movably arranged inside the shaft cylinder is known. There is (for example, Patent Document 1). In the mechanical pencil described in Patent Document 1, the movement of the weight body back and forth is configured to stop by colliding with elastic pieces arranged in front of and behind the weight body. The impact of the weight colliding with the front elastic piece causes the chuck to move forward, thereby feeding out the writing core. Since the impact of the weight body at the time of collision is absorbed by the elastic piece, the collision sound is reduced to some extent.

Japanese Unexamined Patent Publication No. 2012-240407

Generally, in a mechanical pencil of a swing-out type, it is necessary to move the weight at a predetermined speed or more in order to reliably extend the writing core, that is, to transmit an impact of a certain level or more to the chuck. Therefore, the user must first pull the axle cylinder backward and then immediately swing it back forward. It is desirable that this series of drawing operations can be performed in a compact manner, that is, with a short stroke and a light force, so that anyone of all ages can reliably extend the writing core.

Further, since the weight body is arranged so as to be freely movable back and forth inside the barrel, even the mechanical pencil described in Patent Document 1 has a large momentum immediately before it comes into contact with the elastic piece. Collision noise cannot be completely reduced. In addition, it is desirable to reduce the sliding contact sound with the inner surface of the barrel due to the movement of the weight body.

An object of the present invention is to provide a mechanical pencil of a swing-out type that can extend a writing core with a compact operation and with a light force.

According to one aspect of the present invention, a shaft cylinder, a weight body movably arranged inside the shaft cylinder, a spring that urges the weight body rearward with respect to the shaft cylinder, and writing. A chuck unit having a chuck main body that grips the lead and a knock transmission cylindrical body that is arranged separately from the chuck main body, and is configured to allow the writing lead to move forward and prevent it from moving backward. A mechanical pencil that is arranged in front of the chuck unit and is configured to hold the writing core, and is a mechanical pencil capable of feeding out the writing core by a swinging operation and a knocking operation. Occasionally, the weight body advances against the urging force of the spring, and only the chuck body portion advances with the advancement of the weight body so that the writing core is extended, and during a knock operation, the writing core is extended. The knock transmission cylinder advances to hold the rear end of the chuck body, and the chuck body and the knock transmission cylinder move forward to extend the writing lead. A mechanical pencil characterized by being provided is provided.

The chuck unit may further include a relay member formed in a cylindrical shape, and the weight body may be urged by the spring via the relay member. The chuck unit is a fastener that surrounds the chuck main body portion, and the fastener has a tapered surface that expands forward on the inner peripheral surface, and the tapered surface of the fastener and the chuck main body portion. It has a ball arranged between the outer surface of the fastener and a chuck spring that urges the chuck main body rearward with respect to the fastener, and the relay member is fitted to the outer peripheral surface of the fastener. You may. A locking mechanism that prevents the movement of the weight body may be further provided. The outer peripheral surface of the weight may be provided with a protrusion that is in sliding contact with the inner peripheral surface of the barrel when the weight is moved. The spring constant of the spring may be in the range of 0.001 to 0.1 N / mm. The mass of the weight may be in the range of 2 to 20 g.

According to the aspect of the present invention, there is provided a mechanical pencil of a swing type capable of feeding out a writing core with a compact operation and with a light force. Further, according to the aspect of the present invention, it is possible to reduce the collision sound and the sliding contact sound due to the movement of the weight body.

FIG. 1 is a perspective view of a mechanical pencil according to an embodiment of the present invention. FIG. 2 is a vertical cross-sectional view of the mechanical pencil of FIG. FIG. 3 is a vertical cross-sectional view of the front half of the mechanical pencil of FIG. FIG. 4 is a diagram illustrating an unlocked state of the weight body. FIG. 5 is a diagram illustrating a locked state of the weight body. FIG. 6 is a vertical cross-sectional view of the mechanical pencil immediately after the drawing operation. FIG. 7 is a vertical cross-sectional view of a mechanical pencil showing a stepwise knock operation in an unlocked state of the weight body. FIG. 8 is a vertical cross-sectional view of a mechanical pencil illustrating a knock operation in a locked state of a weight body.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. A common reference code is attached to the corresponding components throughout the drawing.

1 is a perspective view of a mechanical pencil 1 according to an embodiment of the present invention, FIG. 2 is a vertical sectional view of the mechanical pencil 1 of FIG. 1, and FIG. 3 is a front half of the mechanical pencil 1 of FIG. It is a vertical sectional view.

The mechanical pencil 1 has a front shaft 2, a rear shaft 3, a connecting member 4 connecting the front shaft 2 and the rear shaft 3, and a mouth member 5 screwed to the inner peripheral surface of the front end portion of the front shaft 2. are doing. A grip portion 2a composed of a plurality of grooves is formed on the front half portion of the outer peripheral surface of the front shaft 2 as a non-slip when gripping the mechanical pencil 1. The connecting member 4 is a cylindrical member, the front end portion of the connecting member 4 is fitted to the inner peripheral surface of the rear end portion of the front shaft 2, and the rear end portion of the connecting member 4 is the front end portion of the rear shaft 3. Fits with the inner peripheral surface. The front shaft 2, the rear shaft 3, and the connecting member 4 form a shaft cylinder 6. In addition, the shaft cylinder 6 may be referred to including the mouth member 5. A tip pipe 7 is attached to the tip of the mouth member 5, and the writing core 8 projects from the tip pipe 7. Behind the tip pipe 7, a rubber holding chuck 9 having a through hole formed in the center is arranged. The through hole of the holding chuck 9 is configured to be in sliding contact with the outer peripheral surface of the writing core 8 to temporarily hold the writing core 8. In the present specification, in the axial direction of the mechanical pencil 1, the tip pipe 7 side is defined as the "front" side, and the side opposite to the tip pipe 7 side is defined as the "rear" side.

Inside the shaft cylinder 6, particularly the front shaft 2, a weight body 10 that is movable back and forth and is formed in a cylindrical shape, and a chuck unit 11 that grips the writing core 8 are arranged. The chuck unit 11 is a ball chuck in this embodiment. The chuck unit 11 includes a relay member 12 formed in a cylindrical shape, a fastener 13 formed in a cylindrical shape, a chuck main body portion 14 arranged in the fastener 13, and a knock transmission formed in a cylindrical shape. It has a cylindrical body 15, a plurality of balls 16, an annular stopper member 17, and a chuck spring 18.

The relay member 12 is fitted to the outer peripheral surface of the rear end portion of the fastener 13 by press fitting. The relay member 12 and the fastener 13 are integrally arranged so as to be movable back and forth in the barrel 6. A tapered surface that expands toward the front is formed on the inner peripheral surface of the front end portion of the fastener 13. The chuck main body 14 is formed with a through hole for the writing core 8 along the central axis, and the front end portion of the chuck main body 14 is divided into a plurality of parts along the axial direction. The knock transmission cylinder 15 is arranged separately from the chuck main body 14 in the initial state in which no operation is performed, and does not hold the chuck main body 14. The plurality of balls 16 are arranged between the outer surface of the chuck main body 14 and the tapered surface of the fastener 13. The chuck main body 14 can move in the axial direction with respect to the fastener 13.

When writing pressure is applied to the writing core 8, the chuck main body 14 abuts on the tapered surface in the cylindrical fastener 13 together with the ball 16, so that the writing core 8 is gripped by the chuck main body 14. As a result, the retreat of the writing core 8 is prevented. On the other hand, when the force for pulling out the writing core 8 works, the chuck main body 14 is not affected by the fastener 13, so that the writing core 8 can be pulled out forward without resistance. That is, the chuck unit 11 is configured to allow the writing core 8 to move forward and prevent it from moving backward. The stopper member 17 is fitted into the inner peripheral surface of the front end portion of the fastener 13 to prevent the ball 16 from falling off.

The chuck spring 18 is arranged so as to surround the chuck main body portion 14. The rear end portion of the chuck spring 18 is fitted to the outer surface of the chuck main body portion 14, and the front end portion of the chuck spring 18 is supported by a step portion formed on the inner peripheral surface of the fastener 13. The chuck spring 18 urges the chuck main body 14 rearward against the fastener 13, and as a result, the chuck unit 11 can maintain the state in which the writing core 8 is gripped.

The front end of the core case 19 is fitted to the rear end of the knock transmission cylinder 15. The core case 19 is formed in a cylindrical shape, and the writing core 8 is housed inside. A cylindrically formed joint member 20 is fitted so as to cover the fitting portion of the knock transmission cylinder 15 and the core case 19 and the front end portion of the core case 19.

A knock member 21 is provided at the rear end of the shaft cylinder 6 so as to be movable back and forth with respect to the shaft cylinder 6. The knock member 21 is urged rearward by the knock spring 22. An eraser 23 is detachably attached to the inside of the rear end portion of the knock member 21 as an erasing member. A knock cover 24 is detachably attached to the outer peripheral surface of the rear end portion of the knock member 21 to protect the eraser 23 from dirt and the like. The knock member 21 is fitted via a joint member 19a provided at the rear end of the core case 19.

A spring 25 is arranged as a coil spring surrounding the relay member 12 in the axle cylinder 6 in front of the weight body 10. An O-ring 26 made of an elastic material is arranged inside the connecting member 4. The connecting member 4 constitutes a part of the lock mechanism 30 that prevents the weight body 10 from moving. The lock mechanism 30 includes a cam forming member 31 arranged on the outer peripheral surface of the connecting member 4 and formed in a cylindrical shape, an annular recess 32 formed on the outer peripheral surface of the rear end portion of the weight body 10, and the inside of the recess 32. It has a cam member 33 arranged in the above, and an operation member 34 arranged on the outer peripheral surface of the cam forming member 31 and formed in a cylindrical shape.

Referring to FIG. 3, a flange portion 12a is formed in the central portion of the relay member 12 in the axial direction. The front end portion of the spring 25 is arranged on the inner wall of the barrel 6, that is, the inner wall of the mouth member 5, and the rear end portion of the spring 25 is arranged near the flange portion 12a of the relay member 12.

As will be described later, when the weight body 10 is in the unlocked state in the lock mechanism 30, the weight body 10 can move back and forth in the barrel 6. Therefore, the weight body 10 is integrally urged rearward by the contact between the rear end surface of the flange portion 12a of the relay member 12 urged rearward by the spring 25 and the front end surface of the weight body 10. There is. In other words, the weight body 10 is urged rearward via the relay member 12. The retreat of the weight 10 and the relay member 12 is regulated by the O-ring 26 as described above. On the outer peripheral surface of the weight body 10, two annular protrusions 10a arranged apart from each other in the axial direction are provided (FIG. 2). Since the weight body 10 is provided with the annular protrusion 10a, the protrusion 10a is in sliding contact with the inner peripheral surface of the barrel 6 when the weight body 10 is moved, and frictional resistance and sliding contact with the inner peripheral surface of the barrel 6 are provided. Sound is reduced. In addition, instead of the annular protrusion, a plurality of protrusions provided at equal intervals along the circumferential direction, rib-shaped protrusions provided at equal intervals along the circumferential direction, and extending in the axial direction may be used. That is, as long as the contact area between the inner peripheral surface of the barrel 6 and the outer peripheral surface of the weight body 10 can be reduced and the frictional resistance can be reduced, protrusions having an arbitrary shape are provided on the outer peripheral surface of the weight body 10. May be good. Further, instead of providing the protrusion on the outer peripheral surface of the weight body 10, a similar protrusion may be provided on the inner peripheral surface of the barrel 6.

The locking mechanism 30 of the weight body 10 will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram for explaining the unlocked state of the weight body 10, and FIG. 5 is a diagram for explaining the locked state of the weight body 10. 4 (A) and 5 (A) are perspective views in which the operating member 34 is omitted, and FIGS. 4 (B) and 5 (B) are vertical cross-sectional views of the lock mechanism 30. be.

Referring to FIGS. 4A and 4B, the cam member 33 has a parallel quadrilateral cam portion 33a exposed on the surface of the cam forming member 31 and a slide arranged in the recess 32 of the weight body 10. It has a moving portion 33b. The cam forming member 31 is provided with a cam groove 31a in which the cam portion 33a of the cam member 33 is movably formed in a complementary shape. As shown in FIG. 4A, the cam groove 31a is formed so as to extend diagonally backward along the circumferential direction and then extend backward along the axial direction. Referring to FIG. 5A, the connecting member 4 is formed with a rectangular elongated hole 4a extending in the axial direction. In the cam member 33, the cam portion 33a is arranged in the cam groove 31a via the elongated hole 4a in a state where the sliding portion 33b is arranged in the recess 32.

The operating member 34 is integrally fitted with the cam forming member 31. Therefore, when the operating member 34 is rotated around the central axis with respect to the barrel 6, the cam forming member 31 also rotates integrally. When the operating member 34 is rotated from the state shown in FIG. 4, the cam portion 33a relatively moves along the cam groove 31a. As the cam portion 33a moves along the cam groove 31a, the sliding portion 33b moves rearward in the recess 32. As a result, the cam member 33 moves rearward along the elongated hole 4a, and the locking mechanism 30 is in the locked state shown in FIG.

At this time, as shown in FIG. 5B, the sliding portion 33b is arranged at the rear end in the recess 32. Therefore, the weight body 10 is sandwiched between the sliding portion 33b in the recess 32 and the O-ring 26 that abuts on the rear end portion of the weight body 10, and the weight body 10 is locked. Even if the swinging operation is performed in this state, the writing core 8 cannot be fed out because the weight body 10 does not move. By rotating the operation member 34 in the opposite direction, the cam member 33 moves forward along the elongated hole 4a, and the lock mechanism 30 is in the unlocked state shown in FIG. 4 (FIG. 4).

The drawing of the writing core 8 by the drawing operation will be described with reference to FIG. FIG. 6 is a vertical cross-sectional view of the mechanical pencil 1 immediately after the drawing operation. The swinging operation is performed by grasping the shaft cylinder 6 of the mechanical pencil 1 with a finger from the state shown in FIG. 3, first pulling the shaft cylinder 6 backward, and then immediately swinging the shaft cylinder forward. As will be described later, the initial movement of pulling the axle cylinder 6 backward may be omitted. When the movement of the mechanical pencil 1 swung forward is stopped, the state shown in FIG. 6 is achieved due to the inertial force acting on the weight body 10.

Specifically, when the weight body 10 advances with respect to the barrel 6 due to the inertial force, the relay member 12 resists the urging force of the spring 25 via the flange portion 12a that is in contact with the front end surface of the weight body 10. And move forward. At this time, the fastener 13 fitted to the relay member 12, the chuck main body 14, the ball 16, the stopper member 17, and the chuck spring 18 are integrally advanced. In short, in the chuck unit 11, the members other than the knock transmission cylinder 15 move forward integrally. The writing core 8 is held by the holding chuck 9 in front of the chuck unit 11, but as described above, the chuck unit 11 is configured to prevent the writing core 8 from retracting. Therefore, the writing core 8 gripped by the chuck main body 14 moves forward together with the chuck unit 11. The advance of the chuck unit 11 is stopped when the front end surface of the chuck unit 11, that is, the front end surface of the stopper member 17 comes into contact with the step portion 5a provided on the inner peripheral surface of the mouth member 5.

When the advance of the chuck unit 11 by the swinging operation is stopped, the relay member 12 and the weight body 10 via the flange portion 12a start to retract due to the urging force of the spring 25. At this time, in the chuck unit 11, the members other than the knock transmission cylinder 15 are integrally retracted. As described above, since the chuck unit 11 is configured to allow the writing core 8 to advance, the writing core 8 is held by the holding chuck 9 without retracting together with the chuck unit 11. Therefore, the writing core 8 is relatively drawn out from the chuck unit 11, that is, from the chuck main body 14. The retreat of the chuck unit 11 is stopped by the weight body 10 colliding with the O-ring 26 via the relay member 12.

From the above, the writing core 8 is drawn out by the amount of the stroke in the axial direction of the chuck unit 11 by the swinging operation. That is, each time the drawing operation is repeated, the writing core 8 can be drawn out by a predetermined amount. Since the knock transmission cylinder 15 is arranged separately from the chuck main body portion 14, it does not move in the shaft cylinder 6 in the swinging operation.

The extension of the writing core 8 by the knock operation in the unlocked state of the weight body 10 will be described with reference to FIG. 7. FIG. 7 is a vertical cross-sectional view of the mechanical pencil 1 showing the knock operation in the unlocked state of the weight body 10 stepwise. The knock operation is performed by pressing the operating portion of the mechanical pencil 1, that is, the knock cover 24, the eraser 23, or the knock member 21 forward against the urging force of the knock spring 22.

When the operation unit is pressed by the knock operation from the state shown in FIG. 3, the core case 19 fitted to the knock member 21 advances as shown in FIG. 7 (A). By moving the core case 19, the knock transmission cylinder 15 fitted to the front end portion of the core case 19 moves forward and is connected to the rear end portion of the chuck main body portion 14.

When the operation unit is further pressed, as shown in FIG. 7B, the entire chuck unit 11 resists the urging force of the spring 25 in a state where the knock transmission cylinder 15 and the chuck body 14 are connected to each other. Advance. Therefore, when the relay member 12 advances and the front end portion of the mechanical pencil 1 faces downward, the weight body 10 advances together with the relay member 12 due to gravity. The advance of the chuck unit 11 is stopped when the front end surface of the chuck unit 11, that is, the front end surface of the stopper member 17 comes into contact with the step portion 5a provided on the inner peripheral surface of the mouth member 5. At this time, the chuck spring 18 is not compressed.

Then, when the operation portion is further pressed, as shown in FIG. 7C, the chuck main body portion 14 and the knock transmission cylinder 15 holding the writing core 8 resist the urging force of the chuck spring 18. Advance with respect to the fastener 13. At this time, the knock transmission cylinder 15 further deeply receives the rear end portion of the chuck main body portion 14. Here, a tapered surface 15a extending forward is formed on the inner peripheral surface of the knock transmission cylinder 15. When the rear end of the chuck body 14 is pressed against the tapered surface 15a of the knock transmission cylinder 15 by advancing the knock transmission cylinder 15, the rear end of the chuck body 14 moves inward in the radial direction. On the other hand, the front end portion of the chuck main body portion 14 expands radially outward, and the writing core 8 is released. The advancement of the knock transmission cylinder 15 is stopped when the front end surface of the joint member 20 fitted to the knock transmission cylinder 15 comes into contact with the step portion 12b provided on the inner peripheral surface of the relay member 12.

Next, when the pressing of the operation portion by the knock operation is released, the knock member 21 retracts and returns to the original position by the urging force of the knock spring 22. Along with this, the chuck main body 14 retracts due to the urging force of the chuck spring 18, and the entire chuck unit 11 retracts due to the urging force of the spring 25. As described above, since the chuck unit 11 is configured to allow the writing core 8 to advance, the writing core 8 is held by the holding chuck 9 without retracting together with the chuck unit 11. Therefore, the writing core 8 is relatively drawn out from the chuck unit 11, that is, from the chuck main body 14. The retreat of the chuck unit 11 is stopped by the weight body 10 colliding with the O-ring 26 via the relay member 12.

From the above, the writing core 8 can pay out the writing core 8 by a predetermined amount each time the knocking operation is repeated. As shown in FIG. 7C, when the writing core 8 is released from the chuck main body 14, the writing core 8 drawn out from the tip pipe 7 can be pushed back by a fingertip or the like.

Therefore, the mechanical pencil 1 is a mechanical pencil in which the writing core can be extended by a swinging operation and a knocking operation. During the swinging operation, the weight body 10 advances against the urging force of the spring 25, and the weight body 10 moves forward. Only the chuck main body 14 moves forward along with the advance so that the writing lead is extended, and during the knock operation, the knock transmission cylinder 15 advances to hold the rear end portion of the chuck main body 14. , The chuck main body 14 and the knock transmission cylinder 15 are configured to move forward so that the writing core 8 is extended.

With reference to FIG. 8, the extension of the writing core 8 by the knock operation in the locked state of the weight body 10 will be described. FIG. 8 is a vertical cross-sectional view of the mechanical pencil 1 for explaining the knocking operation in the locked state of the weight body 10. The state of the knock operation in FIG. 8 corresponds to the state of the knock operation in FIG. 7 (C).

The knock operation in the locked state of the weight body 10 differs only in that the weight body 10 does not move forward due to gravity as compared with the case of the knock operation in the unlocked state of the weight body 10 described with reference to FIG. 7. Therefore, in FIG. 8, the front end surface of the weight body 10 and the rear end surface of the step portion 12b of the relay member 12 are not in contact with each other and are separated from each other. Since the other points in the knock operation are as described above with reference to FIG. 7, the description thereof will be omitted.

In order to reliably extend the writing core 8 by the drawing operation, the acceleration of the weight body 10 by the drawing operation, the mass of the weight body 10, the spring constant of the spring 25, and the like are important factors.

The rearward urging force of the spring 25 against the relay member 12 is Fs, the resistance force of the holding chuck 9 against the retreat of the writing core 8 is Fh, and the force required to pull out the writing core 8 from the chuck unit 11 is Fp. .. Further, the inclination angle of the sharp pencil 1 with respect to the vertical direction is θ, the mass of the weight body 10 is m, and the gravitational acceleration is g, which acts between the outer peripheral surface of the weight body 10 and the inner peripheral surface of the barrel 6. When the dynamic friction coefficient is μ, the force acting on the weight body 10 by gravity is mg · cosθ = Fg, and the frictional force acting on the weight body 10 when the weight body 10 moves is μ · mg · sinθ. = Ff. Further, when the spring constant of the spring 25 is k and the compression amount of the spring 25 from the initial state (FIG. 3), that is, the stroke amount of the chuck unit 11 is x, the minimum required for feeding the writing core 8 is The acceleration a of the weight body 10 is obtained.

Since the resistance force Fh against the retreat of the writing core 8 by the holding chuck 9 is larger than the force Fp required to pull out the writing core 8 from the chuck unit 11, the writing core 8 is pulled out from the chuck unit 11 as described above. It becomes possible.

For example, the condition for advancing the writing core 8 by a predetermined amount is that the spring 25 is compressed until the state shown in FIG. 6 is obtained by a swinging operation or the like performed with the front end of the mechanical pencil 1 facing downward. It is expressed by the following equation (1).
(Fs + kx) + Fh + Ff ≦ Fg + (m × a) ・ ・ ・ (1)

Further, the condition for the spring 25 to return to the initial state shown in FIG. 3 while pulling out the writing core 8 is expressed by the following equation (2).
Fs ≧ Fp + Fg + Ff ・ ・ ・ (2)

From the equations (1) and (2), the acceleration a can be obtained by the following equation (3).
a ≧ (Fs + kx + Fh-Fg + Ff) / m = (Fh + Fp + kx + 2Ff) / m ... (3)

As is clear from the equation (3), by setting Fh, Fp, Ff and k to be smaller and m to be larger, the writing core 8 is extended by a smaller acceleration a, that is, a smaller drawing operation. Is possible.

Specifically, as an embodiment, the urging force Fs by the spring 25 is 0.12N, the resistance force Fh by the holding chuck 9 is 0.04N, and the force Fp required to pull out the writing core 8 is 0.03N. The tilt angle of the sharp pencil 1 with respect to the vertical direction is set to 0 ° for θ, that is, vertically downward with the writing part facing straight down, and the force Fg acting on the weight body 10 by gravity is 0.08N, which acts on the weight body 10. When the frictional force Ff to be applied is 0N, the spring constant k of the spring 25 is 0.003N / mm, the stroke amount x of the chuck unit 11 is 0.5mm, and the mass m of the weight body 10 is 8g, the writing core is written. The acceleration a of the weight body 10 required to feed the 8 is about 1.1 G from the above equation (3).

The spring constant k is preferably in the range of 0.001 to 0.1 N / mm, more preferably 0.001 to 0.01 N / mm, from the viewpoint of feeding out the writing core 8 with a lighter force. It is in the range of 0.001 to 0.005 N / mm, more preferably 0.001 to 0.005 N / mm. Further, from the same viewpoint, and further, from the viewpoint that the weight of the entire mechanical pencil 1 is within the range of the weight of a general writing instrument, the mass m of the weight body 10 is preferably in the range of 2 to 20 g. More preferably, it is in the range of 3 to 10 g.

According to the mechanical pencil 1 according to the embodiment of the present invention, the acceleration a of the drawing operation required to extend the writing core 8 can be made smaller than that of the conventional mechanical pencil of the drawing type. Therefore, the writing core 8 can be extended with a smaller stroke amount, that is, a more compact operation and a lighter force. As a result, it is possible to reduce the collision sound due to the movement of the weight body 10 and the sliding contact sound with the inner peripheral surface of the barrel 6.

Further, the writing core 8 can be extended without pulling the mechanical pencil 1 backward, which is the initial movement of the drawing operation. That is, in the mechanical pencil 1, since the weight body 10 is urged rearward with respect to the barrel 6 by the spring 25, the weight with respect to gravity is particularly high when the front end portion of the mechanical pencil 1 faces downward. It can be said that the body 10 is elastically supported. Therefore, the user simply moves the mechanical pencil 1 forward and stops it from the stationary state in which the mechanical pencil 1 is gripped, and an inertial force for advancing the weight body 10 acts to advance the chuck unit 11 and thereafter. The writing core 8 can be extended.

For example, the user can extend the writing core 8 by a wrist snapping motion performed from a writing posture in which the mechanical pencil 1 is gripped, that is, a swinging operation by a supination motion or a supination motion of the forearm. Further, by applying vibration to the mechanical pencil 1, the writing core 8 can be extended. For example, the mechanical pencil 1 may be vibrated by scraping the grip portion 2a formed of a plurality of grooves formed on the front shaft 2 in the axial direction with the fingernail of the index finger that grips the mechanical pencil 1. Further, a small battery and a motor may be mounted on the mechanical pencil 1, and the mechanical pencil 1 may be vibrated by the rotation of the motor.

While the mechanical pencil 1 can extend the writing core 8 with such a light force or vibration, it has a locking mechanism 30, so that the writing core 8 is unintentionally placed in a pencil case or the like in a bag. It is possible to prevent the feeding from being performed. Further, as described above, the writing core 8 can be extended by the knock operation even in the locked state of the weight body 10.

In the mechanical pencil 1, in the initial state, the chuck main body 14 that grips the writing core 8 and the knock transmission cylinder 15 are arranged separately. Therefore, in the swinging operation, the knock transmission cylinder 15, the core case 19 connected to the knock transmission cylinder 15, the knock member 21, and the like do not move relatively in the shaft cylinder 6. In other words, in the mechanical pencil 1, the chuck unit 11 and the core case 19 are arranged separately. As a result, it becomes easier to set the center of gravity of the mechanical pencil 1 to the front, so that it is possible to reliably extend the mechanical pencil even by a small swinging operation such as a wrist snapping operation as described above.

Further, since the chuck main body 14 and the knock transmission cylinder 15 are arranged separately, it is possible to reduce the influence of the change in the weight of the member including the weight 10 which affects the swinging operation. Specifically, it is possible to reduce the influence on the swinging operation due to the difference in the amount of the writing core housed in the core case 19 connected to the knock transmission cylinder 15. Further, as a result, since the spring load of the spring 25 that supports the weight body 10 can be set more strictly, the spring load can be made smaller so that the writing core 8 can be extended with a lighter swinging operation.

In the above-described embodiment, the chuck unit 11 is a ball chuck, but it may be other than the ball chuck as long as it allows the writing core to move forward and prevents it from moving backward. Further, the relay member 12 and the fastener 13 may be integrally formed.

1 Sharp pencil 2 Front shaft 3 Rear shaft 4 Connection member 5 Mouth member 6 Shaft tube 7 Tip pipe 8 Writing core 9 Holding chuck 10 Weight 11 Chuck unit 12 Relay member 13 Fastener 14 Chuck body 15 Knock transmission cylinder 16 Ball 17 Stopper member 18 Chuck spring 19 Core case 20 Joint member 21 Knock member 22 Knock spring 23 Eraser 24 Knock cover 25 Spring 26 O-ring 30 Lock mechanism 31 Cam forming member 32 Recess 33 Cam member 34 Operation member

When the operation unit is pressed by the knock operation from the state shown in FIG. 3, the core case 19 fitted to the knock member 21 advances as shown in FIG. 7 (A). By advancing the core case 19, the knock transmission cylinder 15 and the joint member 20 fitted to the front end of the core case 19 are advanced. By advancing the joint member 20, the protrusion at the rear end of the joint member 20 and the protrusion at the rear end of the relay member 12 engage with each other .

When the operation unit is further pressed, as shown in FIG. 7B, the entire chuck unit 11 advances against the urging force of the spring 25 in a state where the relay member 12 and the joint member 20 are engaged with each other. Therefore , when the front end portion of the mechanical pencil 1 faces downward, the weight body 10 advances together with the relay member 12 due to gravity. The advance of the chuck unit 11 is stopped when the front end surface of the chuck unit 11, that is, the front end surface of the stopper member 17 comes into contact with the step portion 5a provided on the inner peripheral surface of the mouth member 5. At this time, the chuck spring 18 is not compressed.

Then, when the operation portion is further pressed, as shown in FIG. 7C, the protrusion at the rear end portion of the joint member 20 gets over the protrusion at the rear end portion of the relay member 12 and is disengaged, and the joint member is disengaged. 20 advances with respect to the relay member 12. As the joint member 20 advances, the knock transmission cylinder 15 advances and comes into contact with the chuck main body 14. Further, the chuck main body 14 holding the writing core 8 and the knock transmission cylinder 15 move forward with respect to the fastener 13 against the urging force of the chuck spring 18. At this time, the knock transmission cylinder 15 deeply receives the rear end portion of the chuck main body portion 14 inside. Here, a tapered surface 15a extending forward is formed on the inner peripheral surface of the knock transmission cylinder 15. When the rear end of the chuck main body 14 is pressed against the tapered surface 15a of the knock transmission cylinder 15 by advancing the knock transmission cylinder 15, the rear end of the chuck main body 14 moves inward in the radial direction. On the other hand, the front end portion of the chuck main body portion 14 expands radially outward, and the writing core 8 is released. The advancement of the knock transmission cylinder 15 is stopped when the front end surface of the joint member 20 fitted to the knock transmission cylinder 15 comes into contact with the step portion 12b provided on the inner peripheral surface of the relay member 12.

Claims (7)

With the shaft tube
A weight body that is movable back and forth inside the barrel,
A spring that urges the weight rearward with respect to the barrel,
A chuck having a chuck main body that grips the writing core and a knock transmission cylinder that is arranged separately from the chuck main body, and is configured to allow the writing core to move forward and prevent it from moving backward. With the unit,
A mechanical pencil provided with a holding chuck arranged in front of the chuck unit and configured to hold the writing core, and capable of feeding out the writing core by a swinging operation and a knocking operation.
At the time of the swinging operation, the weight body advances against the urging force of the spring, and only the chuck main body advances with the advancement of the weight body so that the writing core is extended.
At the time of knock operation, the knock transmission cylinder advances to hold the rear end of the chuck main body, and the chuck main body and the knock transmission cylinder advance to advance the writing core so that the writing core is extended. A mechanical pencil characterized by being configured. The mechanical pencil according to claim 1, wherein the chuck unit further has a relay member formed in a cylindrical shape, and the weight body is urged by the spring via the relay member. The chuck unit is a fastener that surrounds the chuck main body portion, and the fastener has a tapered surface that expands forward on the inner peripheral surface, and the tapered surface of the fastener and the chuck main body portion. It has a ball arranged between the outer surface of the fastener and a chuck spring that urges the chuck main body rearward with respect to the fastener, and the relay member is fitted to the outer peripheral surface of the fastener. The sharp pencil according to claim 2. The mechanical pencil according to any one of claims 1 to 3, further comprising a locking mechanism for preventing the movement of the weight body. The mechanical pencil according to any one of claims 1 to 4, wherein the outer peripheral surface of the weight is provided with a protrusion that is in sliding contact with the inner peripheral surface of the barrel when the weight is moved. The mechanical pencil according to any one of claims 1 to 5, wherein the spring constant of the spring is in the range of 0.001 to 0.1 N / mm. The mechanical pencil according to any one of claims 1 to 6, wherein the weight of the weight is in the range of 2 to 20 g.

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