JPS6030558B2 - Drafting machine drawing head and sharp pencil - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a drawing head for a drafting machine and a mechanical pencil that can always write with a constant pressure by springing a lead holder that holds the lead forward in the vertical direction with a constant pressure during writing.

The drawing head of the conventional drawing machine was JP-A-49-133125.
As described in the publication, a commercially available knock-type mechanical pencil holding a lead or an extrusion shaft that presses the lead downward is pressed downward at a constant pressure to feed the lead onto the paper surface. When the lead wore out a certain amount due to continuous writing, a limit switch was activated and a buzzer sounded to notify the user that the lead had worn out.

However, knock-type mechanical pencils with downward pressure are convenient because if one lead wears out, the next lead will follow, but on the other hand, if the lead protrudes longer than the tip of the knock-type mechanical pencil, Because it broke, it was not possible to protrude for a long time, and the writing distance was very short. For this reason, the limit switch would frequently activate and the buzzer would sound, and each time it would be necessary to press the knob to draw out the lead. As a drawing head for a drafting machine that has improved this point, the outer pipe and
The lead is held by a lead holder consisting of a chuck, a tightening ring, a middle pipe, and a chuck spring, and the lead holder is strongly held at the rear in the axial direction by the wedge action of the ball and the rear tapered part of the fastener. In front of the direction is the drawing machine's box head, which moves forward with very little resistance, but when it moves up and down at high speed like the drawing machine's drawing head, when the core hits the paper, Since there is a risk of damaging the surface of the outer pipe and the rear taper of the cotton fitting with the ball, these parts must be made of very hard material.
It had the disadvantage of being expensive. As for mechanical pencils, the mechanical pencil in which the lead is automatically drawn out by the length that has worn out was developed in 1983.
There are mechanical pencils described in JP-A-50-122326 and JP-A-50-122326, but in the mechanical pencil described in JP-U-50-151734, when the lead is pressed against the paper surface, the tailstock that supports the lead does not move. Because it is held by the wedge action of the ball and the small tool, writing can be performed without the lead retreating.As the lead wears out during writing, the cartridge body consisting of the tip, cartridge, lead holder, and tailstock holder retreats, while the lead When the cartridge is separated from the surface of the paper, the cartridge body is moved forward by an elastic body, gravity, magnetic force, etc., and the core and the tailstock are pulled forward. At this time, the wedge action between the fastener and the ball is released, and the tailstock rod is advanced without resistance. Therefore, while it has the advantage that the lead is automatically fed out, when one lead is used up, the cartridge body must be removed, a new lead stored, and then the cartridge body must be reattached to the mechanical pencil to write. It was extremely troublesome. Also, Tokuseki Sho 50-1223
The mechanical pencil described in Publication No. 26 holds the lead by pressing the protrusion of the collect chuck against the tapered surface of the connector using a spring after a slight elastic force, and when one lead is finished, Although there is an advantage that the next lead will follow just by opening the chuck, if the elastic force of the rear spring is too weak, the tapered surface of the coupling tool may be damaged by frequent writing, and the tapered surface of the coupling tool and the chuck may be damaged. The frictional resistance with the protrusion increases, making it difficult to close the chuck and making it impossible to hold the core.On the other hand, if the elastic force of the rear spring is strengthened in order to reliably move the chuck back and hold the core, , the resistance when the lead moves forward increases, and the holding force of the lead holder and the elastic force of the front spring have to be strengthened, and the force with which the lead guide pipe falls onto the paper surface becomes stronger, making it extremely difficult to write. It was difficult. A mechanical pencil that has improved this point holds the lead with a lead holder that the applicant invented before filing the application, which consists of an outer pipe, a chuck, a vertical ring, an inner pipe, and a chuck spring, and the lead holder is attached to a ball. There is a mechanical pencil that uses a wedge action to strongly hold the rear part of the shaft and advance it with very little resistance in the front part of the shaft. Compared to this, the durability of holding the lead is dramatically improved, but in order to reduce the pressure of the lead during writing by using the wedge action of the ball and the rear taper of the fastener, the rear taper of the fastener is used to hold the outer pipe. Since there is a risk that the surface of the outer pipe or outer pipe may be damaged by the ball, these members must be made of a very hard material, which has the disadvantage of being expensive like the drawing head of the drawing machine mentioned above. Ta. The present invention uses the outer pipe push spring having an elastic force set to the writing pressure or the own weight of the lead holder to hold the lead holder, which is composed of an outer pipe, a chuck, a tightening link, an inner pipe, and a chuck spring. The shaft is fired forward in all directions, and when carried, the core holder is moved forward by the wedge action of a tapered part of the vertical tool and the ball or a tapered part of the shaft and a steel ball in the case of a drawing head of a drawing machine. In the case of a mechanical pencil, the advancement of the lead holder is prevented by the wedge action of the tapered part of the shaft and the steel ball, and when writing, in the case of a drafting machine's drawing head, the ball or By separating the steel ball from the tapered part of the shaft, or in the case of a mechanical pencil by separating the steel ball from the rattan taper part, the lead holder can be pivoted by the elastic force of the outer pipe pushing spring or by the lead holder's own weight. Manko is pushed forward and the core is placed on the paper.

When you write in this state, you can write with a constant writing pressure and the lead holder moves forward as the lead wears, and the lead holder is only pushed forward in the direction of the central writing axis, just like the conventional one described above. The purpose is to provide drawing heads and mechanical pencils for drafting machines that have significantly improved durability because they are not held by a ball, and that when one lead ends, the next lead can easily follow. be. The configuration of this invention will be explained in detail based on the drawings.

As shown in FIG. 1, a lead guide pipe 1 is fixed to the tip of a shaft 4, and a lead holder 2 for lightly holding a lead 5 is built into the shaft 4 behind the lead guide pipe 1. The joint tube 3 is fixed to the shaft 4 by being located at the rear. Also, the outer pipe 6
Inside, an inner pipe 8 is fixed to a chuck 7 that holds the core 5, and a stepped portion 8A of the inner pipe 8 and an outer pipe 6 are connected to each other.
A chuck spring 9 is disposed between the chuck spring 9 and the inner stage 6A of the chuck 7, and the taper portion 7A of the chuck 7 is normally pressed against the cotton ring 10' by the elastic force of the chuck spring 9 to hold the core 5. There is. (Hereafter, outer pipe 6
, the chuck 7, the middle pipe 8, the chuck spring 9, and the vertical ring 10 are collectively referred to as a "core holder." ) Also, a spare core 11 for a textbook is built into the inner pipe 8, and the protrusion 3A of the joint pipe 3 and the protrusion 6B of the outer pipe 6 are configured to be combined with each other so that they can be moved. Then,
An outer pipe push spring 12 having an elastic force set to be equal to the writing pressure is installed between the recess 6C of the outer pipe 6 and the front end surface 13A of the fastener 13, and the elastic force of the outer pipe push spring 12 is The core 5 is pressed against the paper surface 14 by the force. I with stronger elastic force than chuck spring 9
A J-turn spring 15 is disposed between the stepped portion 4A of the shaft 4 and the front end surface 13A of the fastener 13, and a ball 16 is provided in the tapered portion 13B of the vertical member 13 with a ball 16 provided in the retainer 17, such as a horizontal hole. A part of the surface of the ball 16 protrudes outward from the outer diameter 17B of the IJ retainer 17, and a part of the other surface of the ball 16 protrudes inward from the inner diameter 17C of the retainer 17. Moreover, the direction of rotation toward the rear of the bag (C→○
The knob support 18 is mounted so that it can rotate (rotation here refers to being able to move more than 360 degrees) in the direction of rotating forward in all directions (D to C direction). Coil spring 1 attached between front end surface 18A and rear end 13C of cotton tool 13
9, the ball 16 is attached and the retainer 17 is pulled axially rearward (A→B direction) as described above, and is separated from the tapered portion 13B of the fastener 13. The rear end projection 17D of the retainer 17 is pressed against the front end surface 18A of the knob support 18 by the elastic force of the IJ retainer pressing spring 20 between the rear end projection 17D of the retainer 17 and the inner step 18B of the knob support 18. It is constructed according to the following. Further, a knob 21 is detachably attached to the knob support 18. A shaft support 22 that holds the shaft 4 is fixed to the shaft 4, and a shaft support 22 that holds the shaft 4 is fixed to the shaft 4.
The knob pusher shell 23 is configured to be able to slide through the upper hole 22A. Next, the operation of this invention will be explained.

First, in FIG. 1, for writing, move the shaft support 22 forward in the axial direction (direction B→A), position it so that the core guide pipe 1 and the paper surface 14 are at a certain distance, and then move the shaft support 22.
Stop 2. At this time, the knob pusher 23 moves the knob 21 from B to A.
By releasing the push in the direction, the elastic force of the coil spring 19 works, and the knob support 18 is pushed in the A → B direction, and at the same time, the rear end protrusion of the retainer 17 is pushed on the front end surface 18A of the knob support 18. The portion 17D is pulled, the retainer 17 moves in the direction A→B, and the balls 16 attached to the ball attachment portion 17A of the retainer 17 are separated from the tapered portion 13B of the fastener 13. Therefore, the lead holder 2 overcomes the force holding the lead 5, and the lead holder is pushed in the direction B→A by the elastic force of the outer pipe pushing spring 12, and the lead 5 is pressed against the paper surface 14 with a constant pressure, making it possible to write. Moreover, since the lead holder is pushed in the direction B→A, the lead 5 is gradually drawn out by the length worn out by writing. Next, when you want to stop writing, first the knob pusher 23 pushes the /button 21 in the direction B→A, then the knob support 1
Push 8 in the direction of B→A. As the knob support 18 moves in the B→A direction, the retainer 17 moves in the B→A direction, and the balls 16 are pressed against the tapered portion 13B' of the small tool 13 by the elastic force of the retainer pressing spring 20, and are tightened. Due to the wedge action of the tool 13 and the ball 16, the core holder is held with a force stronger than the elastic force of the outer pipe pushing spring 12, and cannot be moved in the direction B→A. Therefore, by moving the shaft support 22 in the A→B direction, even if the drawing head of the drawing machine moves in the A→B direction, the core 5 and the core holder cannot move in the B→A direction, and the shaft support Similarly to 22, it moves in the direction A→B and leaves the paper surface 14. In addition, the lead 5 is worn out due to long-term writing, and the lead holder is gradually drawn out, and the locking step 6D of the outer pipe 6 hits the rear end 3B of the joint pipe 3, and the lead holder moves from B to A direction. If it becomes impossible to do so, the knob support 18 is pushed by pushing the knob holder 23 in the B→A direction, and the front end surface 18A of the knob support 18 moves from B→A.
In order to move in the A direction, the retainer 17 is also
The ball 16 is moved in the direction B→A by the elastic force of the push spring 20, and the ball 16 is pressed against the tapered portion 13B of the fastener 13. As a result, the core holder can move in the A→B direction due to the wedge action of the fastener 13 and the pole 16, but cannot move in the B→A direction. By further pressing the button 21 in this state, the ball 16 pushes the tapered part 13B of the vertical fixture 13, and the competitive fixture 13 moves in the direction B→A. By pushing the fold/bump 21, the inner step 18B of the knob support I8 pushes the rear end 8B of the middle pipe 8. However, since the outer pipe 6 is in contact with the joint pipe 3 and cannot be moved in the B→A direction, the outer pipe 6 cannot be moved, and only the inner pipe 8 is pushed in the B→A direction. The chuck 7 comes off the inner surface of the tightening ring 10 and expands due to its own elasticity, releasing the lead 5 in the same manner as when a knock type mechanical pencil is knocked. Next, if the force for pressing the knob 21 is weakened, the core holder cannot move in the direction B→A due to the wedge action of the tapered part 13B of the fastener 13 and the ball 16, as described above, and therefore the fastener 13 is pushed and moved in the direction A→B by the elastic force of the return spring 15, the lead holder also moves in the direction A→B with the chuck 7 kept open. As the cotton tool 13 continues to move further, the rear end 13C of the cotton tool 13 hits the locking stage 4B of the shaft 4, and the cotton tool 13
can be stopped from moving in the A→B direction. Then, the knob support 18 is further moved by the elastic force of the coil spring 19.
→Move in the B direction, release the force pushing the middle pipe 8 in the B→A direction, and close the chuck 7. Furthermore, the knob support 18
moves from A to B direction, and the front end surface 18 of the knob support 18
A and the rear end protrusion 17D of the IJ tenor 17 hit,
By pulling the retainer 17 in the A→B direction, the ball 16 separates from the tapered part 13B of the fastener 13, and the outer stage 18C of the knob support 18 hits the rear stage 4C of the shaft 4, and the knob support 18 stops, and the second The figure returns to the state shown in FIG. In addition, when feeding out the spare lead 11, the ball 16 is inserted into the tapered part 13 of the fastener 13 by pushing the knob 21.
The outer pipe 6 is pressed against the clamp 13 and the ball 16
Due to the wedge action, it is impossible to move in the direction B→A, and the distance between the rear end 8B of the middle pipe 8 and the inner step 18B of the knob support 18 makes it difficult to move between the rear end 6E of the outer pipe 6 and the inner part of the knob support 18. Since the distance of the stepped portion 18B is longer, the fastener 13 does not move. Therefore, the outer pipe 6 cannot be moved, and by pushing the inner pipe 8 in the direction B→A, the spare lead 11 is replenished in the same manner as when knocking a conventional knock-type mechanical pencil. Next, referring to FIG. 3, an embodiment in which the present invention is applied to a mechanical pencil will be described.

First, the core guide pipe 31, the core holder 32, and the joint pipe 33.
The lead holder 32 lightly holds the lead 35. Further, the core guide pipe 31 is formed with a steel ball mounting portion 31A, such as a horizontal hole, and a part of the surface of the steel ball 54 is located outside the outer diameter 31B of the core guide pipe 31 in the steel ball mounting portion 31A. In addition, a part of the other surface of the steel ball 54 protrudes inward from the inner diameter 31C of the core guide pipe 31, and also rotates in the direction of rotation toward the rear of the ball direction (C→D direction) or the direction of the ball. It is attached so that it can rotate (rotation here means being able to move more than 3600 degrees) in the direction of rotation toward the front (D→C direction). Further, the steel ball 54 is pressed against the tapered surface 34B of the shaft 34 by the elastic force of a core guide pipe pressing spring 55 between the rear end 31D of the core guide pipe 31 and the protrusion 34A of the pith 34. The eraser 5 held in the eraser case 56 is mounted on the knob support 48.
7 are removably joined together. Next, to explain the operation of this embodiment, first, when writing, the core guide pipe 31 is pushed in the direction A→B by the paper surface 44, the steel ball 54 is separated from the tapered surface 34B of the shaft 34, and the steel ball 54 and the shaft 34 are
A constant writing pressure is always obtained by releasing the holding of the lead holder by the wedge action and pushing the lead holder in the direction from B to A by the elastic force of the outer pipe pushing spring 42.

When the lead holder is returned to its original position and the replacement of the spare lead 41, etc., operations are performed in exactly the same manner as in the embodiment of the drawing head of the drawing machine described above. FIG. 4 shows another embodiment relating to the drawing head of the drawing machine. The above-mentioned mechanical pencil shown in FIG. 3 is fixed to a shaft support 82 that is movable up and down relative to the paper surface 74 from the head body, and a knob pusher 83 is arranged so as to be slidable in the upper hole 82A of the shaft support 82.
A core guide pipe support 88 is always fixed to the head body at a certain distance from the paper surface 74, and the core guide pipe support 88 is configured to be movable parallel to the paper surface 74 together with the head body and the shaft support 82. Further, the core guide pipe support 88 is provided with a tip hole 88A, and the tip portion 61A of the core guide pipe 61 is configured to be able to slide inside the tip hole 88A. 89 is fixed. Next, to explain the operation of this embodiment, first, in order to write, the shaft support 82 is moved from B to A.
When moving in the direction, the shaft 64 also moves from B to A.
direction, and at the same time the core guide pipe 61 also moves from direction B to A, so the stopper 89 supports the core guide pipe support 8.
Hits 8.

Furthermore, by moving the shaft support 82 in the B→A direction, the shaft 64 also moves in the B→A direction, but the core guide pipe 6
1 cannot be moved because the stopper 89 is in contact with the core guide pipe support 88. Therefore, the core guide pipe pushing spring 85 is compressed, the steel ball 84 separates from the tapered surface 64A of the shaft 64, and the core holder is released from being held by the wedge action between the steel ball 84 and the shaft 64, and the outer pipe The elastic force of the spring 72 presses the lead holder and the lead 65 against the paper surface 74, and writing is performed. Next, if you stop writing and move the koji support 82 in the direction A→B, the stopper 89 will separate from the core guide pipe support 88, and the elastic force of the core guide pipe push spring 85 will cause the steel ball 84 to move toward the shaft 64.
The core holder is held by a force stronger than the elastic force of the outer pipe pushing spring 72 due to its wedge action, and writing is stopped. Further, the return operation of the lead holder in the direction A→B and the replenishment of the spare lead 71 are performed in the same manner as in the embodiment described above. FIG. 5 shows another embodiment of the mechanical pencil, and is a mechanical pencil having a structure in which the lead guide pipe push spring 55 of the embodiment shown in FIG. Pipe push spring 102
The elastic force pushes the lead holder in the B→A direction, causing the lead 95, lead holder 92, and lead guide pipe 91 to move from B→
Moving in the A direction, the steel ball 114 touches the tapered surface 94 of the shaft 94.
A, a wedge action acts between the steel ball 114 and the tapered surface 94A of the shaft 94 to overcome the elastic force of the outer pipe pushing spring 102 and hold the core holder.

As explained above, in the drawing head of a drafting machine, the present invention provides an outer pipe, a chuck, a tightening ring, and a
The lead holder consisting of the inner pipe and chuck spring is made to spring forward in the direction of the ball by the outer pipe push spring having an elastic force set to the writing pressure or by the weight of the lead holder, and when carried, the taper of the fastener is The wedge action between the part and the ball or the tapered part of the shaft and the steel ball prevents the lead holder from moving forward, and when writing, the lead holder is separated from the ball from the tapered part of the fastener or from the tapered part of the shaft. By arranging the writing so that the lead held by the lead is brought into contact with the paper surface, writing can be performed with constant writing pressure and with the lead holder gradually advancing as the lead wears.

Moreover, since the lead holder is only pushed forward in the writing axis direction and is not held at all, the structure is simple, and the outer pipe, which is a part of the lead holder, is used as a wedge between the pole and the fastener. The durability of the cotton utensil and outer pipe is significantly improved compared to those that are held while writing, and when one wick is finished, the next wick can easily follow by pressing the knob. It has a special effect.
On the other hand, in mechanical pencils, the lead holder consisting of an outer pipe, chuck, kneading ring, middle pipe, and chuck spring that holds the lead is moved in all directions by an outer pipe push spring with an elastic force set to the writing pressure. When carried forward, the lead holder is prevented from moving forward by the wedge action between the seven-part part of the shaft and the steel ball, and when writing, the lead guide pipe is pressed against the paper surface and retreated, allowing the steel ball to be released from the tapered part of the shaft. By separating the lead and writing with the lead held by the lead holder against the paper using only the elastic force of the outer pipe push spring, writing is always performed with a constant writing pressure. There are many things.

Moreover, since the lead holder is only pushed forward in the direction of the writing center axis, it is easier to write with a cotton holder than with a case where the outer pipe, which is a part of the lead holder, is held by the wedge action of a ball and a fastener. Moreover, the durability of the outer pipe is significantly improved.

[Brief explanation of the drawing]

FIG. 1 is a vertical cross-sectional view showing one embodiment of the first invention;
The figure is a vertical cross-sectional view showing the state in which writing is not performed in this invention, FIG. 3 is a vertical cross-sectional view showing an embodiment in which the invention is applied to a mechanical pencil, and FIG. FIG. 5 is a vertical cross-sectional view showing another embodiment of the mechanical pencil. 1, 31, 61, 91... Core guide pipe, 3
1A...Steel ball attachment part of core guide pipe 31, 31B
...Outer diameter of core guide pipe 31, 31C...
...Inner diameter of the core guide pipe 31, 31D...
Rear end of core guide pipe 31, 61A...Tip of core guide pipe 61, 2, 32, 92... Core holder, 3, 33... Joint pipe, 3A・・・・・・
...Protrusion of joint pipe 3, 3B. ．． ．． ．． ．． ．． Rear end of joint pipe 3, 4, 34, 64, 94...shaft, 4A...
・Step part of shaft 4, 4B... Locking step of shaft 4, 4C・
... Rear stage of shaft 4, 34A ... Protrusion of shaft 34, 34B ... Taper surface of shaft 34, 64A
...One tapered surface of the shaft 64, 94A...One tapered surface of the shaft 94, 5, 35, 65, 95... Core, 6...
...Outer pipe, 6A...Inner stage of outer pipe 6, 6B.
...Protrusion of outer pipe 6, 6C...Recess of outer pipe 6, 6D...Lock stage of outer pipe 6, 6
E...Rear end of outer pipe 6, 7...Chuck, 7A...Taper part of chuck 7, 8
...Medium pipe, 8A...Step part of middle pipe 8, 8B...
... Rear end of middle pipe 8, 9 ... Chuck spring, 10 ... Tightening ring, 11 ... Spare core, 1
2, 42, 72, 102... Outer pipe push spring, 13... Fastener, 13A... Front end surface of vertical member 13, 13B... Fastener Part of the taper of the odor 13, 13C... Rear end of the fastener 13, 14, 44, 7
4...paper surface, 15...return spring, 16...ball, 17...retainer, 17A...
...ball attachment part of retainer 17, 17B...outer diameter of retainer 17, 17C...retainer 17
Inner diameter of 17D...Rear end protrusion of retainer 17, 18, 48...Knob support, 18A.../pu support 18
front end surface of 18B, inner step of knob support 18,
18C... Outer stage of knob support 18, 19...
...Coil spring, 20...Retainer push spring, 21...Knob, 22, 82...Shaft support, 22A, 82A...Top of shaft support 22, 82 Hole, 23, 83... Knob pusher, 54, 84, 1
14... Steel ball, 55, 85... Core guide pipe push spring, 56... Eraser case, 57...
Eraser, 88... Core guide pipe support, 88
A... Tip hole of core guide pipe support 88, 89
······stopper. Figure 2 Figure 3 Figure 5 Figure 1 Figure 4

Claims (1)

[Scope of Claims] 1. In a drafting machine head body that can move parallel to the drawing board in any direction and move toward and away from the paper surface, a core holder is provided in front of the shaft of the head body and the core is held. A lead holder consisting of a chuck, a tightening ring, a chuck spring, an outer pipe, and an inner pipe is slidably installed inside the shaft, and the outer pipe is elastically pushed forward by the outer pipe pushing spring with an elastic force set to the writing pressure. A return spring with a stronger elastic force than the chuck spring is placed between the stepped part of the shaft and a fastener that can slide inside the shaft, and the fastener normally engages the shaft with the elastic force of the return spring. A ball rotatably attached to the ball attachment part of the retainer is attached to the tapered part of the fastener that is in contact with the stop and is configured to become narrower toward the front of the fastener. When pressed, the balls come into contact with the elastic force of the retainer pressing spring and are biased inward, and the balls contact the surface of the outer pipe, and a coil spring is provided between the fastener and the knob support, and the retainer and the ball are biased inward. A drawing head for a drafting machine, characterized in that a retainer pressing spring is provided between the knob support and the drawing head. 2. In a drafting machine head body that can move parallel to the drawing board in any direction and move toward and away from the paper surface, a core holder is provided in front of the shaft of the head body, and a chuck, tightening ring, and chuck for holding the core are provided. A lead holder consisting of a chuck spring, an outer pipe, and an inner pipe is provided so that it can slide inside the shaft using its own weight set to the writing pressure of the lead holder, and a return spring with a stronger elastic force than the chuck spring is attached to the shaft. It is placed between the step and a fastener that can slide inside the shaft, and the fastener usually comes into contact with the locking stage of the shaft due to the elastic force of the return spring, and becomes narrower toward the front of the fastener. When the knob is pressed forward in the axial direction, the ball, which is rotatably attached to the ball attachment part of the retainer, is brought into contact with the tapered part by the elastic force of the retainer pressing spring, and is inserted into the tapered part. 1. A drawing head for a drafting machine, characterized in that the ball is biased toward the outer pipe, the ball contacts the surface of the outer pipe, and a retainer pressing spring is provided between the fastener and the knob support. 3. A core guide pipe that has an internal core holder and a steel ball attachment part that rotatably attaches a steel ball that holds a core holder at the rear is slidably attached to the tip of the shaft, and A tapered part that narrows toward the shaft is configured so that it can come into contact with the steel ball, and a core holder consisting of a chuck, a tightening ring, a chuck spring, an outer pipe, and an inner pipe that holds the core is slid inside the shaft. The outer pipe is movable, and the outer pipe is elastically moved forward by a spring with an elastic force set to the writing pressure, and the return spring, which has an elastic force stronger than the chuck spring, slides on the stepped part of the shaft and inside the shaft. Normally, the fastener is brought into contact with the locking stage of the shaft by the elastic force of the return spring, and the tapered part of the fastener is configured to become narrower toward the front of the fastener. When the knob is pressed forward in the axial direction, the ball, which is rotatably attached to the ball attachment part of the retainer, comes into contact with the elastic force of the retainer pressing spring and is biased inward. A coil spring is provided in contact with the surface of the outer pipe and between the fastener and the knob support, and a retainer pressing spring is provided between the retainer and the knob support,
A sharp pencil characterized in that a knob protruding from the rear end of the shaft is detachably attached to the retainer pressing spring.