阅读说明：本技术 自动铅笔 (Propelling pencil ) 是由 阴山秀平 于 2018-04-10 设计创作，主要内容包括：本发明提供具备将以不同的弹簧常数进行缓冲动作的多个缓冲动作区域不会跳跃地连接的缓冲弹簧的自动铅笔。一实施方式的自动铅笔具备：轴筒；夹头机构,其是收纳于该轴筒内的夹头机构,能够把持及送出笔芯；以及第一缓冲弹簧及第二缓冲弹簧,其相对于该轴筒在轴线方向上弹性支撑该夹头机构,通过组合该第一缓冲弹簧及第二缓冲弹簧,形成具有第一弹簧常数的第一缓冲动作区域和具有第二弹簧常数的第二缓冲动作区域,该第一缓冲动作区域及第二缓冲动作区域不会跳跃地连接。(The invention provides a mechanical pencil with a buffer spring which connects a plurality of buffer action areas which perform buffer action with different spring constants without jumping. A mechanical pencil according to one embodiment includes: a shaft cylinder; a cartridge mechanism housed in the shaft tube and capable of holding and feeding the refill; and a first buffer spring and a second buffer spring that elastically support the chuck mechanism in the axial direction with respect to the shaft tube, and form a first buffer operation region having a first spring constant and a second buffer operation region having a second spring constant by combining the first buffer spring and the second buffer spring, the first buffer operation region and the second buffer operation region being connected without jumping.)

1. A mechanical pencil is characterized by comprising:

a shaft cylinder;

A cartridge mechanism which is accommodated in the shaft tube and can hold and feed out the pen refill; and

A first buffer spring and a second buffer spring for elastically supporting the chuck mechanism in an axial direction with respect to the shaft tube,

By combining the first and second buffer springs, a first buffer operation region having a first spring constant and a second buffer operation region having a second spring constant are formed, and the first and second buffer operation regions are connected without jumping.

2. The mechanical pencil of claim 1,

The first and second buffer springs are integrally formed as a coil spring having a first winding portion and a second winding portion.

3. the mechanical pencil according to claim 1 or 2,

The first and second buffer springs are attached to have a free length.

4. The mechanical pencil according to any one of claims 1 to 3,

When the first and second buffer operation regions are applied with a pen pressure within a range of 150 + -50 g, the combined first and second buffer springs are connected at one operation point where the combined first and second buffer springs contract within a range of 0.45 + -0.15 mm.

5. The mechanical pencil according to any one of claims 1 to 4,

The second buffer operation region includes an operation point at which the combined first buffer spring and second buffer spring are contracted within a range of 0.8 + -0.11 mm when the pen pressure is applied within a range of 350 + -50 g.

Technical Field

The present invention relates to a mechanical pencil which is provided with a holder for holding a lead and can output the lead by a knock operation.

Background

At present, there is known a mechanical pencil including: a core container slidably provided in the shaft tube; a chuck fixedly disposed at a front end portion of the core container; a collet ring which is loosely fitted to the collet; the sleeve is arranged between the shaft barrel and the chuck; an elastic body abutting against the sleeve and having a part thereof attached by pressure-bonding to the core container; and an operation unit that compresses the elastic body to move the core container in the axial direction (see, for example, patent document 1).

Disclosure of Invention

problems to be solved by the invention

According to the mechanical pencil disclosed in patent document 1, the stroke of the push-out slider can be sufficiently obtained by a simple structure in which the chuck fastening spring and the buffer spring are integrated. However, there is a demand for a mechanical pencil including a buffer spring capable of connecting a plurality of buffer operation regions performing buffer operation with different spring constants without jumping, such as one region performing buffer operation with one spring constant for absorbing excessive writing pressure and another region performing buffer operation with another spring constant different from the one spring constant for preventing breakage of a writing lead.

The invention aims to provide a mechanical pencil which is provided with a buffer spring which connects a plurality of buffer action areas which carry out buffer action with different spring constants in a jumping-free way.

Means for solving the problems

in one aspect of the mechanical pencil of the present invention, the mechanical pencil includes: a shaft cylinder; a cartridge mechanism which is accommodated in the shaft tube and can hold and feed out the pen refill; and a first buffer spring and a second buffer spring that elastically support the chuck mechanism in the axial direction with respect to the shaft tube, and form a first buffer operation region having a first spring constant and a second buffer operation region having a second spring constant by combining the first buffer spring and the second buffer spring, the first buffer operation region and the second buffer operation region being connected without jumping.

Effects of the invention

In some aspects of the present invention, a mechanical pencil can be provided that includes a buffer spring that connects a plurality of buffer operation regions that perform buffer operations with different spring constants without jumping.

Drawings

Fig. 1 is a partial cross-sectional view of a mechanical pencil according to an embodiment of the present invention, showing a front portion and a rear portion without an intermediate portion.

Fig. 2 is a diagram showing an output load with respect to displacement of the combined damper spring of the mechanical pencil according to the embodiment of the present invention.

Fig. 3 is a partial sectional view showing a front side portion and a rear side portion of a mechanical pencil according to another embodiment of the present invention, with a middle portion omitted.

Detailed Description

hereinafter, a plurality of embodiments of the present invention will be described based on the drawings. The mechanical pencil 1 of the present embodiment shown in fig. 1 is a rear-end-knock type mechanical pencil in which a lead T is projected by being fed out from the front end of a nib 3 by a knock operation of a knock button 5. In the following description, the side of the mechanical pencil 1 on which the writing tip 3 is disposed is the front side in the central axis direction (axial direction) extending in the longitudinal direction of the mechanical pencil 1, and the side on which the knock button 5 is disposed is the rear side.

The mechanical pencil 1 includes a substantially cylindrical shaft main body 2 and a substantially tapered cylindrical writing tip 3. The shaft tube is formed to include a shaft tube main body 2 and a nib 3. The nib 3 is disposed in front of the barrel main body 2. The rear portion of the nib 3 is formed in a double-barrel shape having an outer barrel 3a and an inner barrel 3 b. The nib 3 is fixed to the barrel body 2 by screwing a male screw portion 2a formed on the outer peripheral surface of the distal end portion of the barrel body 2 and a female screw portion 3a1 formed on the inner peripheral surface of an outer cylinder 3a behind the nib 3.

A knock button 5 formed in a bottomed tubular shape is detachably attached to a rear end of a core tube 11 described later in detail disposed inside the shaft tube main body 2. The inner peripheral surface of the front end opening of the knock button 5 is detachably fitted to the outer peripheral surface of the rear end of the core tube 11. The outer peripheral surface of the front portion of the rubber holder 4 formed in a substantially cylindrical shape is detachably fitted to the inner peripheral surface of the rear end of the core tube 11. The rubber holder 4 has a front small diameter portion 4a and a rear large diameter portion 4 b. The rubber holder 4 is assembled by detachably fitting the outer peripheral surface of the rubber 6 to the inner peripheral surface of the large diameter portion 4 b.

The core tube 11, which accommodates the lead T therein, is formed in a substantially cylindrical shape and is disposed in the shaft body 2. A collet 12 is assembled at the front of the core tube 11. The cartridge 12 is formed such that when cartridge pieces each having a tip divided into three in the circumferential direction are elastically deformed toward the center axis, the pen refill T can be gripped by being radially pinched. The chuck 12 has: a base 12a inserted and fixed to the rear end of the core tube 11; a beam-shaped portion 12b extending forward from the base portion 12 a; and a bulging portion 12c formed at the tip of the beam-like portion 12 b. A clip ring 13 is attached to the outer periphery of the bulging portion 12c so as to be freely fitted and removed. The sleeve 7 is disposed on the outer periphery of the front portion of the core tube 11 and the outer peripheries of the base portion 12a and the beam-shaped portion 12b of the collet 12 as shown in the drawing.

The sleeve 7 is formed in a substantially cylindrical shape. An annular wall 7a is formed on the inner circumferential surface of the distal end portion of the sleeve 7 so as to protrude radially inward. On the other hand, an annular projecting portion 7b is formed on the outer peripheral surface of the front portion of the sleeve 7 so as to project radially outward. An annular projecting portion 2b is formed on the inner peripheral surface of the shaft tube main body 2 so as to project radially inward so as to face the projecting portion 7b of the sleeve 7 in the axial direction. A composite damper spring 18, which is a compression coil spring compressed in the axial direction, is disposed between the projecting portion 7b of the sleeve 7 and the projecting portion 2b of the shaft cylinder main body 2. The axial front end of the combined damper spring 18 is supported in contact with the projecting portion 7b of the sleeve 7, and the axial rear end is supported in contact with the projecting portion 2b of the cylinder main body 2. In this way, the combined damper spring 18 is disposed between the sleeve 7 and the shaft cylinder main body 2 so as to extend in the axial direction. The sleeve 7 is biased forward relative to the shaft body 2 by the composite damper spring 18.

The combined damper spring 18 is formed so that the number of turns of the coil per unit length differs between a region S1 on the front side and a region S2 on the rear side. In the present embodiment, the first wound portion 18-1 functioning as a first damper spring is formed in the region S1, and the second wound portion 18-2 functioning as a second damper spring is formed in the region S2. The composite damper spring 18 is formed by combining a first damper spring and a second damper spring, and is formed integrally as a coil spring having a first wound portion 18-1 and a second wound portion 18-2. The spring constant of the first winding portion 18-1 of the region S1 having more turns per unit length than the region S2 is smaller than the spring constant of the second winding portion 18-2 of the region S2 having less turns per unit length than the region S1. This is because, by the first winding portion 18-1 having more turns per unit length than the second winding portion 18-2, the angle of inclination of the extending direction (helical winding direction) of the wire of the coil spring with respect to the axial direction becomes large, and thereby the first winding portion 18-1 is more easily deflected with respect to the axial direction. In the present embodiment, the first wound portion 18-1 is wound at a pitch of about 0.1 mm.

a collet spring 15 as a coil spring is assembled between the outer peripheral surface of the beam-shaped portion 12b of the collet 12 and the inner peripheral surface of the sleeve 7. The collet spring 15 has a front end abutting against the rear surface of the annular wall 7a of the sleeve 7 and a rear end abutting against the front end surface of the core tube 11. The collet spring 15 is assembled in a state compressed in the axial direction between the sleeve 7 and the core tube 11. Since the core tube 11 and the collet 12 are biased rearward with respect to the sleeve 7 by the biasing force of the collet spring 15, the collet ring 13 fitted to the collet 12 is also biased with respect to the sleeve 7, and as shown in the drawing, the rear end surface of the collet ring 13 abuts against the front surface of the annular wall 7a of the sleeve 7.

A plurality of ribs 3b1 extending in the axial direction are formed in the circumferential direction on the inner circumferential surface of the inner cylinder 3b of the nib 3. The front end surface of the sleeve 7 abuts against the rear end surface of the rib 3b1 in a state biased forward by the composite damper spring 18.

A step portion 3b2 is formed at a substantially central position in the axial direction of the rib 3b1, and the tip end surface of the clip ring 13 can abut against the step portion when moving forward. When the front end surface of the clip ring 13 abuts against the step 3b2 of the rib 3b1 formed in the inner cylinder of the nib 3, the clip ring 13 is disengaged rearward from the clip 12, and the refill T is disengaged from the grip of the clip 12. The series of output operations of the mechanical pencil 1 will be described in detail later.

The guide pipe 31 is disposed at a position in front of the distal end surface of the chuck 12 so as to be movable in the axial direction. The duct 31 has: a disc-shaped base end 31 b; the refill T is inserted through the central hole along the axis direction; and a plurality of insertion legs 31a formed around the center hole so as to protrude forward from the base end portion 31 b. The tip of the insertion leg 31a is formed into a hook shape as shown in the drawing, and is engaged with a slit 32a formed in a core holder 32 described later in detail, thereby being locked to the core holder 32 so as to be movable in the front-rear direction.

A stepped portion is formed on the outer peripheral edge of the proximal end portion 31b of the catheter 31. Further, a stepped portion of the inner periphery of the nib 3 is formed on the inner periphery of the nib 3 facing the stepped portion of the base end 31b of the conduit 31 in the axial direction. A return spring 36 as a compression coil spring for biasing the guide tube 31 rearward in the axial direction with respect to the nib 3 is disposed between the base end portion 31b of the guide tube 31 and the stepped portion on the inner periphery of the nib 3. In a state where the guide tube 31 is biased rearward by the return spring 36, the rear end surface of the base end portion 31b of the guide tube 31 approaches the front end surface of the cartridge 12 from the front. When the cartridge 12 advances, the rear end surface of the guide tube 31 comes into contact with the front end surface of the cartridge 12 from the front. The rear end surface of the guide tube 31 supports the pen core T protruding from the front end surface of the cartridge 12 in a direction orthogonal to the axial direction in a state of being approached from the front or being in contact with the front end surface of the cartridge 12. Therefore, the bending moment acting on the position on the distal end surface of the cartridge 12 in the axial direction of the pen core T held by the cartridge 12 can be reduced, and the pen core T can be prevented from breaking at the position of the distal end surface of the cartridge 12.

A core holder 32 is disposed at a position forward of the duct 31 so as to be movable in the axial direction. The core holder 32 is formed with a plurality of slits 32a extending in the front-rear direction. The tip of the insertion leg 31a of the above-described catheter 31 formed in a hook shape is slidably engaged in the slit 32 a. Thereby, the duct 31 is locked to the core holder 32 so as to be movable in the front-rear direction. A center hole through which the pen core T is inserted is formed in the core holder 32 in the axial direction. A holding portion for holding the lead T radially inward is formed at the tip of the center hole of the lead holder 32. A substantially tapered tubular tip pipe 30, which will be described in detail later, is disposed in front of the core holder 32, and the tip pipe 30 has an outer peripheral surface that slides on the inner peripheral surface of the opening 3c of the nib 3 and is configured to be movable in the axial direction. The core holder 32 is inserted into the front end pipe 30 from the rear and assembled to the front end pipe 30.

A flange portion is formed at the rear end of the front end pipe 30. An O-ring 38 that elastically supports the tip pipe 30 and the core holder 32 in a direction orthogonal to the axis L direction is assembled to the outer periphery of the flange portion. The O-ring 38 is configured to provide an appropriate sliding resistance to the forward and backward movement of the distal end pipe 30 and the core holder 32. Here, the appropriate sliding resistance means the following sliding resistance: the tip end tube 30 and the core holder 32 can be held so as to be able to hold the fed pen core T in the axial direction. In addition, the following sliding resistance is indicated: the movement of the tip pipe 30 and the core holder 32 can be allowed so that the tip pipe 30 can protrude from the nib 3 or the tip pipe 30 can be housed in the nib 3 when a larger pressing force in the axial direction is applied to the tip pipe 30 and the core holder 32. The forward movement of the tip pipe 30 and the core holder 32 is restricted by the flange portion of the tip pipe 30 abutting against a step portion formed on the inner peripheral surface of the opening 3c of the nib.

The cartridge mechanism capable of gripping and feeding the refill T includes a cartridge 12, a cartridge ring 13, a sleeve 7, and a cartridge spring 15, and is housed in the shaft tube. In the present embodiment, the combined damper spring 18 as a coil spring that elastically supports the chuck mechanism in the axial direction is attached with a free length. With this configuration, writing can be performed by absorbing excessive writing pressure according to the spring constant of the first buffer spring (first wound portion 18-1) of the combined buffer spring 18, and therefore writing with high quality reflecting the spring constant of the first wound portion 18-1 functioning as the first buffer spring of the combined buffer spring 18 can be performed. On the other hand, when an excessive pen pressure is applied to the writing lead T gripped by the chuck mechanism, the second winding portion 18-2 of the composite buffer spring 18 having a large spring constant, which functions as a second buffer spring, is deflected, and the writing lead T can be prevented from being broken.

The feeding of the writing lead T of the mechanical pencil 1 will be described. By the knocking operation of pressing the knock button 5, the core tube 11, the cartridge 12 fitted with the cartridge ring 13, and the cartridge T held by the cartridge 12 advance against the urging force of the cartridge spring 15. The guide pipe 31 abutting against the chuck 12 after the advance is also pressed forward, and advances against the biasing force of the return spring 36. When the guide tube 31 advances, the core holder 32 and the tip tube 30 pressed by the guide tube 31 advance and protrude from the nib 3. When the cartridge 12 and the cartridge ring 13 move by a predetermined interval, the front end surface of the cartridge ring 13 engages with the abutment surface of the stepped portion 3b2 formed on the inner peripheral surface of the nib 3, and the cartridge ring 13 is separated rearward from the expanded portion 12c of the cartridge 12. When the clip ring 13 is disengaged, the clip pieces of the clip 12 are respectively opened radially outward by elasticity, and the pen core T is released. The writing lead T is discharged and releases a predetermined feeding amount per one knocking operation of the mechanical pencil 1. When the knock button 5 is released and the chuck mechanism is released from the knocking operation, the pen core T held by the core holder 32 is left at the position where the pen core is fed and released, the chuck 12 and the chuck ring 13 are retreated, and the pen core T is held again at a position rearward of the position before the knocking operation. When the chuck mechanism is released from the knocking operation and the chuck 12 and the chuck ring 13 retreat, the guide pipe 31 is urged to retreat by the return spring 36.

The mechanical pencil 1 can write in a state where a predetermined amount of the lead T protrudes from the tip tube 30. A load (so-called pressure) generated in the axial direction by writing is applied to the writing lead T, the collet 12 holding the writing lead T, the collet ring 13, and the sleeve 7. The synthetic damper spring 18 is elastically deformed by the pressure, and generates a damping operation in which the cartridge T, the cartridge 12, the cartridge ring 13, and the sleeve 7 are retracted rearward with respect to the shaft tube body 2.

The buffering operation of the present embodiment will be described with reference to fig. 2. Fig. 2 shows a specific example of the relationship between the writing pressure (load) during the cushioning operation of the mechanical pencil 1 and the amount of displacement of the chuck 12 that is elastically supported by the combined cushioning spring 18 to retract (the amount of compression or the amount of operation of the combined cushioning spring 18). When a writing pressure is applied to the writing lead T, the first wound portion 18-1, which is the first buffer spring, of the combined buffer spring 18 is compressed more greatly at the initial stage, and the second wound portion 18-2, which is the second buffer spring, is also compressed slightly. At this time, the combined damper spring 18 operates in the first damper operation region CR1 indicated by a line from the point O to the point P in fig. 2. When about 150g of pen pressure is applied, the resultant buffer spring 18 contracts by about 0.45 mm. When the stroke pressure exceeds about 150g, the first winding portion 18-1 serving as the first spring is immediately operated in the second damping operation region CR2 indicated by a line after point P in fig. 2 in which only the second winding portion 18-2 serving as the second spring is operated. When about 350g of pen pressure is applied, the resultant damping spring 18 contracts by about 0.8 mm.

The combined damper spring 18 has a first spring constant in the first damper operation region CR1 and a second spring constant different from the first damper operation region CR1 in the second damper operation region CR 2. By combining the first and second cushion springs that compose the cushion spring 18, a first cushion operation region CR1 having a first spring constant and a second cushion operation region CR2 having a second spring constant are configured. The first buffer operation region CR1 and the second buffer operation region CR2 are continuous as shown in the figure and are connected without jumping. In other words, the compression amount and the output of the combined damper spring 18 at the end point of the first damper operation region CR1 match the compression amount and the output at the start point of the second damper operation region CR 2. With this configuration, the user can use the mechanical pencil 1 without being aware of a transition between a plurality of buffer operation regions having different spring constants.

The pen core T is usually used in a range of 0.45 ± 0.15mm projecting from the front end tube 30. If the combined shock spring 18 is configured to contract in the range of 0.45 ± 0.15mm when the pen pressure is applied in the range of 150 ± 50g as in the present embodiment, the normal writing state in which the pen core T protrudes from the tip tube 30 can be made to substantially coincide with the first shock absorbing operation region CR1 of the combined shock spring 18, which is preferable. In this case, when the pen pressure is applied within the range of 150 ± 50g, the first and second damping operation regions CR1 and CR2 are connected without jumping at one operating point at which the combined first and second damping springs contract within the range of 0.45 ± 0.15 mm. Further, for example, it is more preferable that the combined damper spring 18 is configured to contract in a range of 0.45 ± 0.09mm when the pen pressure is applied in a range of 150 ± 30g, and it is most preferable that the combined damper spring 18 is configured to contract in a range of 0.45 ± 0.03mm when the pen pressure is applied in a range of 150 ± 10 g. When the amount of movement (amount of compression) of the combined shock spring 18 is larger than the amount of protrusion of the writing lead T from the front end tube 30, the front end tube 30 and the core holder 32, the front end of which is in contact with the writing surface, are retracted as far as possible, and the front end tube 30 and the core holder 32 are retracted, so that the amount of movement (amount of compression) of the combined shock spring 18 can be secured. The distal end tube 30 and the core holder 32 are retracted while protecting the core T, and when the writing pressure is removed and the combined buffer spring 18 returns to its free length, the core T protrudes from the distal end tube 30 again.

Further, as shown in the present embodiment, when the pen pressure is applied in the range of 350 ± 50g, the combined damper spring 18 may be configured to contract in the range of 0.8 ± 0.11 mm. In this case, the end point assumed for the normal writing in the second damping operation region CR2 of the combined damping spring 18 can be set to a displacement amount at which the user can easily perceive an increase in the damping stroke, and the writing pressure at which the writing lead T is prevented from being broken can be set, which is suitable. In this case, the second damping operation region CR2 includes an operation point at which the combined first and second damping springs contract within a range of 0.8 ± 0.11mm when the pen pressure is applied within a range of 350 ± 50 g. Further, for example, it is more preferable that the combined damper spring 18 is contracted in a range of 0.8 ± 0.07mm when the pen pressure is applied in a range of 350 ± 30g, and it is most preferable that the combined damper spring 18 is contracted in a range of 0.8 ± 0.02mm when the pen pressure is applied in a range of 350 ± 10 g.

in another embodiment, the spring constant of the second damping operation region CR2 may be set to be smaller than that of the present embodiment, and the resultant damping spring 18 may be positioned at an end point assumed for normal writing in the second damping operation region CR2 when compressed by about 1.5 mm. In this case, the user can perform writing with high quality reflecting the spring constant of the second damper spring (the second winding portion 18-2) of the combined damper spring 18 while preventing breakage of the pen core T in the second damper operation region CR2 having a longer damper stroke.

Thus, the mechanical pencil having the buffer springs for connecting the plurality of buffer operation regions performing the buffer operation with different spring constants without jumping can be provided. The composite buffer spring 18 is formed integrally as a coil spring having the first winding portion 18-1 and the second winding portion 18-2 having different numbers of turns, and therefore, the number of parts can be reduced and it can be formed appropriately. Further, since the combined damper spring 18 is attached with a free length, as shown in fig. 2, the damping operation can be performed over the entire operation region of the combined damper spring 18 including the O point.

A mechanical pencil 1A according to another embodiment of the present invention is described with reference to fig. 3. The mechanical pencil 1A has the same structure as the mechanical pencil 1 described above except for the structure of the combined buffer spring 18A. Therefore, only the synthetic damper spring 18A will be described for the mechanical pencil 1A, and redundant description will be omitted. The combined damper spring 18A of the mechanical pencil 1A has a first damper spring 18A-1 having a relatively small diameter and a second damper spring 18A-2 having a relatively large diameter disposed on the outer periphery of the first damper spring 18A-1, which are formed separately from each other. In this way, the combined damper spring 18A may be configured by arranging the first damper spring 18A-1 and the second damper spring 18A-2, which are formed separately, in parallel. On the other hand, in the combined damper spring 18 of the mechanical pencil 1 according to the above-described embodiment, the first damper spring (the first wound portion 18-1) and the second damper spring (the second wound portion 18-2) are arranged in series.

the first damper spring 18A-1 and the second damper spring 18A-2 of the combined damper spring 18A of the present embodiment have different spring constants. The first buffer spring 18A-1 wound at a predetermined equal interval has its axial front end supported in contact with the projecting portion 7b of the sleeve 7 and its rear end supported in contact with the projecting portion 2b of the column body 2. The second buffer spring 18A-2 wound at another predetermined equal interval is arranged such that the rear end in the axial direction thereof is supported in a state of being bonded to the front surface of the projecting portion 2b of the shaft tube main body 2 and the front end thereof does not abut against the projecting portion 7b of the sleeve 7. With this configuration, only the first damper spring 18A-1 operates at the initial stage of the operation of the combined damper spring 18A. When the pen pressure is further applied, the front end of the second buffer spring 18A-2 abuts against the rear surface of the projection 7b of the sleeve 7 after the first buffer spring 18A-1 is elastically deformed by a predetermined amount. When a further pen pressure is applied, the first buffer spring 18A-1 and the second buffer spring 18A-2 are elastically deformed and operate. Therefore, it is possible to provide a mechanical pencil including a buffer spring in which a plurality of buffer operation regions performing buffer operations with different spring constants are connected without jumping.

The relationship between the pen pressure (load) during the cushioning operation of the combined cushioning spring 18A and the amount of displacement by which the chuck 12 elastically supported by the combined cushioning spring 18A is retracted (the amount of compression or operation of the combined cushioning spring 18A) in the present embodiment is the same as in the case of the mechanical pencil 1 shown in fig. 2 described above. When a writing pressure is applied to the writing lead T, only the first buffer spring 18A-1 is compressed at the initial stage of the synthetic buffer spring 18A, and the second buffer spring 18A-2 does not operate. At this time, the combined damper spring 18A operates in the first damper operation region CR1 indicated by a line from the point O to the point P in fig. 2. When pen pressure is applied to about 150g, the resultant damping spring 18A contracts about 0.45 mm. When the pen pressure exceeds about 150g, the second damper spring (the second wound portion 18-2) operates together with the first damper spring (the first wound portion 18-1), and therefore the combined damper spring 18A operates in the second damper operation region CR2 shown by a line after point P in fig. 2. The spring constant in the second damping operation region CR2 of the combined damping spring 18A is configured to be larger than the spring constant in the first damping operation region CR 1. Therefore, the user can easily grasp the operation of the combined damper spring 18A in the second damper operation region CR2 from the rate of increase (spring constant) of the pen pressure during writing. When about 350g of pen pressure is applied, the resultant damping spring 18A contracts about 0.8 mm.

While the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and can be implemented with various modifications. For example, in the above-described embodiment, a case where one coil spring having the first wound portion 18-1 and the second wound portion 18-2 is provided as the combined damper spring 18 has been described. However, the present invention is not limited to this, and a composite damper spring may be configured by arranging a first damper spring and a second damper spring, which are separately formed, in series. For example, the spring constant of the first wound portion 18-1 may be larger than the spring constant of the second wound portion 18-2. Thus, the first and second damper springs arranged in series can be arranged in any desired manner by exchanging the springs. Further, the present invention is not limited to the first and second cushion springs, and a composite cushion spring may have two or more arbitrary plural cushion springs and operate in combination. Further, the case where the composite damper spring is formed as a coil spring has been described, but the composite damper spring is not limited to this, and may be formed of elastic resin, rubber, or the like into an arbitrary shape.

Description of the symbols

1. 1A-a mechanical pencil, 2-a barrel body, 2 a-an external screw thread portion, 2 b-a protrusion, 3-a nib, 3 a-an external barrel, 3a 1-an internal screw thread portion, 3 b-an internal barrel, 3b 1-a rib, 3b 2-a step portion, 3 c-an opening portion, 4-a rubber holder, 4 a-a small diameter portion, 4 b-a large diameter portion, 5-a knock button, 6-a rubber, 7-a sleeve, 7 a-an annular wall, 7 b-a protrusion, 11-a core tube, 12-a cartridge, 12 a-a base, 12 b-a beam portion, 12 c-a bulge portion, 13-a cartridge ring, 15-a cartridge spring, 18-a synthetic buffer spring, 18-1-a first winding portion, 18-2-a second winding portion, 18A-a synthetic buffer spring, 18A-1-a first buffer spring, 18A-2-a second buffer spring, 30-a tip tube, 31-a guide tube, 31A-an insertion foot, 31 b-base end, 32-core holder, 32 a-slit, 36-return spring, 38-O-ring.