Refills for mechanical pencils and writing instruments

Abstract

The simple structure prevents the sliding pipe from easily retracting. [Solution] A mechanical pencil lead comprising a tip 50 and a slide pipe 60 fitted to the inner circumferential surface of the tip 50 so as to extend and retract from the front end of the tip 50, wherein the lead x is advanced and inserted into the slide pipe 60, the inner circumferential surface of the tip 50 is provided with a diameter reduction portion 54 that reduces the inner diameter, and the outer circumferential surface of the slide pipe 60 is provided with an inclined surface portion 62b that is directed forward diagonally toward the pipe lead side, and when the slide pipe 60 advances, the inclined surface portion 62b is fitted to the pipe lead side end 54a of the diameter reduction portion 54 and fixed, and when it retracts due to an external force, the inclined surface portion 62b is detached from the pipe lead side end 54a and released.

Description

TECHNICAL FIELD

[0001] The present invention relates to a mechanical pencil refill in which a lead core is inserted through a slide pipe that protrudes and retracts from the front end of a tip metal, and a writing instrument provided with the mechanical pencil refill. BACKGROUND ART

[0002] Conventionally, for this type of invention, there is a slide pipe type mechanical pencil in which a pipe for inserting and protecting a lead core at the tip end side is provided so as to be slidable back and forth with respect to the tip metal. According to this slide pipe type mechanical pencil, as the lead core is shortened by rubbing against a paper surface or the like during writing, the front end of the slide pipe abuts against the paper surface or the like and retracts, so writing can be continued while protecting the tip end portion of the lead core. In addition, since the slide pipe retracts under impact such as dropping or abutment, it is possible to prevent the slide pipe from being damaged due to abutment against a floor, an object or the like, and prevent the slide pipe from damaging an object, skin or the like. However, in such a slide pipe type mechanical pencil, the slide pipe may unintentionally retract into the tip metal, which may interfere with the lead feeding operation and writing operation, or cause lead breakage.

[0003] For example, as shown in FIGS. 6(a) to (c), when the chuck 210 is repeatedly advanced and retracted by a rear end knocking operation or the like for feeding out the lead, the lead core x also retracts due to friction with the chuck 210 when the chuck retracts, and the slide pipe 260 may also retract due to friction with the retracting lead core x. Such a phenomenon is particularly remarkable when the forward force of the slide pipe due to its weight cannot be obtained, for example, when a user performs a knocking operation for centering by pointing the tip end of the slide pipe sideways or upward in order to check the tip end of the protruding lead core. Therefore, for example, in the conventional technology described in Patent Document 1, an inner convex portion is provided on the mouthpiece, and the retraction of the slide pipe member is suppressed by the inner convex portion. PRIOR ART DOCUMENTS [Patent Documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 9-207490 [Overview of the project] [Problems that the invention aims to solve]

[0005] However, the conventional technology described above requires the creation of internal protrusions or grooves in the nozzle, which is difficult to process. [Means for solving the problem]

[0006] In view of these challenges, one aspect of the present invention comprises the following configuration. A mechanical pencil lead comprising a tip and a slide pipe fitted to the inner surface of the tip so as to extend and retract from the front end of the tip, wherein the lead is advanced and inserted into the slide pipe, the inner surface of the tip has The device is provided with a pipe sliding hole portion into which the slide pipe can be fitted to move forward and backward, a flat, reduced-diameter portion extending radially inward from the front end of the pipe sliding hole portion, and a straight, cylindrical, small-diameter hole portion extending forward from the pipe core-side end of the reduced-diameter portion, the pipe core-side end of the reduced-diameter portion being the corner where the reduced-diameter portion and the small-diameter hole portion intersect. The outer surface of the slide pipe is provided with an inclined surface portion that extends forward toward the pipe core, and when the slide pipe moves forward, the inclined surface portion is corner It is fitted and fixed in place, and when it retracts due to an external force, the inclined surface portion corner A lead refill for mechanical pencils characterized by its ability to detach and be released from its base. Another aspect of the present invention comprises the following configuration. A mechanical pencil lead comprising a tip and a slide pipe fitted to the inner circumferential surface of the tip so as to extend and retract from the front end of the tip, wherein the lead is advanced and inserted into the slide pipe, the inner circumferential surface of the tip is provided with a diameter-reducing portion that reduces the inner diameter, and the outer circumferential surface of the slide pipe is provided with an inclined surface portion that is directed forward diagonally toward the pipe lead side, the inclined surface portion of the slide pipe is fitted to the pipe lead side end of the diameter-reducing portion when the slide pipe is advanced and fixed, and the inclined surface portion is fitted to the pipe lead side when it is retracted by an external force The slide pipe is detached from its side end and released, and a chuck is provided at the rear of the slide pipe to advance the lead core by a reciprocating motion. A pressure-relieving member, made of an elastic material and pressure-relieving against the outer surface of the lead core, is integrally provided on the slide pipe. The advancing chuck contacts the pressure-relieving member, pushing the pressure-relieving member and the slide pipe together, causing the inclined surface to fit onto the side end of the pipe core, and the impact during contact is mitigated by the elasticity of the pressure-relieving member. Refill for mechanical pencils. [Effects of the Invention]

[0007] As described above, the present invention is configured in such a way that its simple structure can prevent the slide pipe from easily retracting. [Brief explanation of the drawing]

[0008] [Figure 1] This is a longitudinal cross-sectional view showing an example of a lead for a mechanical pencil according to the present invention. [Figure 2] This is a close-up, partially cross-sectional view of the key part showing how the slide pipe is assembled to the tip. [Figure 3] This is a magnified view of the main part of the lead for the mechanical pencil. (a) shows the slide pipe retracted into the tip, and (b) shows the slide pipe protruding due to being pushed by the advancing chuck, with the inclined surface fitted into the end of the pipe lead. [Figure 4] The images show enlarged views of the main components of the lead for the mechanical pencil; (c) shows the slide pipe extended and the chuck retracted, and (d) shows the chuck moving forward and backward to extend the lead out of the slide pipe. [Figure 5] The following are enlarged views of the main parts of a writing instrument equipped with the lead for the mechanical pencil: (a) shows the protruding lead in contact with the writing surface with the inclined surface fitted to the end of the pipe lead, and (b) shows the inclined surface detaching from the end of the pipe lead and retracting as the lead wears down due to writing, as the sliding pipe is pushed against the writing surface. [Figure 6] This is a vertical cross-sectional view showing an example of a mechanical pencil lead without an inclined surface on the slide pipe. (a) shows the slide pipe retracted into the tip, (b) shows the slide pipe protruding due to the advancing chuck, and (c) shows the slide pipe and lead retracted due to the retraction of the chuck. [Modes for carrying out the invention]

[0009] Next, embodiments of the present invention will be described in detail with reference to the drawings. Figure 1 shows an example of a lead for a mechanical pencil according to the present invention. This mechanical pencil lead 1 comprises a chuck 10 that grips and releases the lead x with multiple claws 11, a clutch 20 that fits annularly onto the multiple claws 11 from the rear, a retractable tube 30 that is annularly placed over and connected to a cylindrical part 12 at the rear end of the chuck 10, a support tube 40 that covers the rear side of the chuck 10 and the front side of the retractable tube 30 in a cylindrical shape behind the clutch 20, a tip 50 that is detachably connected to the outer circumference of the front end of the support tube 40, and a front part that extends and retracts from the front end of the tip 50 inside the tip 50. The device comprises a slide pipe 60 fitted to slide backward, a pressure-relieving member 70 fitted to the rear end of the slide pipe 60 and gently press-fitting against the outer surface of the lead core x, a compression coil spring 80 mounted annularly on the reciprocating pipe 30 with its front end in contact with the support pipe 40, a receiving member 90 fixed to the outer surface of the reciprocating pipe 30 in a way that prevents it from retracting, and a cylindrical core tank 100 connected to the reciprocating pipe 30 behind the receiving member 90.

[0010] This mechanical pencil lead 1 is installed inside the barrel of a writing instrument such as a multi-function writing instrument or a mechanical pencil. When this mechanical pencil lead 1 is installed in the writing instrument, the rear end knock mechanism (not shown) is operated, causing the lead tank 100, receiving member 90, and chuck 10 to reciprocate in the front-to-back direction, thereby advancing the lead x held in the chuck 10 forward.

[0011] More specifically, when the chuck 10 moves forward due to the aforementioned knocking operation, the lead core x held by the chuck 10 also moves forward. As the chuck 10 moves forward, it disengages from the clutch 20, which restricts its forward movement, thereby releasing the clamping force on the lead core x. After this, the chuck 10 retracts due to the biasing force of the compression coil spring 80. During this retraction, the lead core x is held elastically by the pressure-relieving member 70, and therefore its retraction is prevented. Through the repetition of these actions, the lead lead x advances further and protrudes from the tip 50.

[0012] The tip 50 is formed into a roughly cylindrical shape with a tapered tip by appropriately processing a hard metal material (for example, brass or stainless steel). An inner peripheral surface of the front tip 50 includes: a clutch sliding hole portion 51 that fittingly receives the clutch 20 so as to allow the clutch 20 to move forward and backward; a pipe sliding hole portion 52 that fittingly receives a slide pipe 60 so as to allow the slide pipe 60 to move forward and backward, the pipe sliding hole portion 52 being located on a front side relative to the clutch sliding hole portion 51; and a small-diameter hole portion 53 having a reduced diameter and located on a front side relative to the pipe sliding hole portion 52.

[0013] The clutch sliding hole portion 51 is an inner wall surface of a cylindrical hole continuous in the front-rear direction, and is formed so as to be in sliding contact with an outer peripheral surface of the clutch 20. A boundary between the clutch sliding hole portion 51 and the pipe sliding hole portion 52 has a stepped reduced diameter to restrict forward movement of the slide pipe 60 (see FIGS. 3(a) and 3(b)). The clutch 20 slides a predetermined amount between the stepped portion and a front end portion of the support tube 40.

[0014] The pipe sliding hole portion 52 is an inner wall surface of a cylindrical hole that has a smaller diameter than the clutch sliding hole portion 51 and is continuous in the front-rear direction, and is formed to allow a large-diameter cylindrical portion 61 of the slide pipe 60 to move forward and backward by a predetermined amount. A length of the pipe sliding hole portion 52 in the front-rear direction is set such that the slide pipe 60 can move forward and backward between: a position where a front end of the slide pipe 60 is retracted into the front tip 50 (see FIG. 3(a)); and a position where a front end side of the slide pipe 60 protrudes from the front tip 50 by a predetermined amount and an inclined surface portion 62b of the slide pipe 60 is fitted to a pipe core side end portion 54a of the front tip 50 (see FIG. 3(b)).

[0015] The small-diameter hole portion 53 is an inner wall surface of a cylindrical hole that has a smaller diameter than the pipe sliding hole portion 52 and is continuous in the front-rear direction. A diameter-reduced portion 54 that reduces an inner diameter is provided at a boundary between the pipe sliding hole portion 52 and the small-diameter hole portion 53.

[0016] The diameter-reduced portion 54 is an annular surface continuous from a front end of the pipe sliding hole portion 52 to a rear end of the small-diameter hole portion 53, and is a surface substantially perpendicular to a pipe core (a center of the slide pipe 60). According to the illustrated example, the pipe core side end portion 54a of the diameter-reduced portion 54 is a corner portion. That is, the pipe core side end portion 54a is a corner portion where the diameter-reduced portion 54, which is an annular surface, intersects the small-diameter hole portion 53, which is a cylindrical inner wall surface.

[0017] The slide pipe 60 is formed into a cylindrical shape with a gradually decreasing diameter at the tip by appropriately processing a hard metal material (for example, brass or stainless steel). This slide pipe 60 is housed in the range from the pipe sliding hole portion 52 to the small diameter hole portion 53 of the tip plate 50.

[0018] This slide pipe 60 integrally comprises a large-diameter cylindrical section 61 located at the rear end, a medium-diameter cylindrical section 62 whose outer diameter is reduced in front of the large-diameter cylindrical section 61, and a small-diameter cylindrical section 63 whose outer diameter is reduced in front of the medium-diameter cylindrical section 62 (see Figure 2).

[0019] The outer diameter and length of the large-diameter cylindrical portion 61 are set so that it is close to or sliding against the pipe sliding hole portion 52 of the tip metal 50 (see Figure 3) and moves back and forth within the pipe sliding hole portion 52 by a predetermined amount (see Figure 3). Furthermore, the inner diameter surface of the large-diameter cylindrical portion 61 is formed in the shape of a stepped hole. The pressure-relieving member 70 elastically contracts and fits into this inner diameter surface.

[0020] The medium-diameter cylindrical portion 62 is formed in a roughly cylindrical shape with a smaller outer diameter than the large-diameter cylindrical portion 61. The inner diameter surface of this medium-diameter cylindrical portion 62 has a slight gap with respect to the outer diameter surface of the lead core x (see Figure 3). Furthermore, the outer diameter surface of the medium-diameter cylindrical portion 62 is provided with a straight cylindrical portion 62a that is substantially parallel to the inner diameter surface of the small-diameter hole portion 53 of the tip 50, and an annular inclined surface portion 62b connected to the rear end of this straight cylindrical portion 62a (see Figures 2 and 3).

[0021] The outer diameter of the straight cylindrical portion 62a is set so that it moves back and forth within the small-diameter hole 53, approaching or sliding against the inner circumferential surface of the small-diameter hole 53 of the slide pipe 60.

[0022] The inclined surface portion 62b is an inclined surface that slopes linearly toward the front diagonal pipe core side, and is provided in an annular shape around the entire circumference of the medium diameter cylindrical portion 62 (see Figure 2). The angle α and length L of this inclined surface portion 62b are appropriately set so that when the slide pipe 60 moves forward relative to the tip 50, it fits and is fixed around the entire circumference to the pipe core end 54a of the reduced diameter portion 54 (see Figure 3(b)), and when the slide pipe 60 moves backward due to an external force (see Figure 5(b)), it detaches from the pipe core end 54a and is released.

[0023] More specifically, the angle α of the inclined surface portion 62b with respect to the pipe core (see Figure 2) is set within the range of 2 to 6°, and according to a preferred example of this embodiment, it is within the range of 3 to 5°, and is set to approximately 4°. Furthermore, the length L in the front-to-back direction of this inclined surface portion 62b is set to approximately 1 mm.

[0024] The inclined surface portion 62b of the above configuration can be easily integrally machined onto the outer surface of the slide pipe 60 by, for example, cutting the outer diameter surface using a lathe or the like.

[0025] The inner circumferential surface of the medium-diameter cylindrical portion 62 is a continuous cylindrical shape in the front-to-back direction, and a slight gap is maintained between it and the outer circumferential surface of the lead core x (see Figure 3). In this example, the outer diameter of the lead core x is set to 0.5 mm.

[0026] The small-diameter cylindrical portion 63 is formed in a substantially cylindrical shape with a smaller outer diameter than the medium-diameter cylindrical portion 62. The inner circumferential surface of the small-diameter cylindrical portion 63 is a continuous cylindrical shape in the front-rear direction, and its outer diameter is set so that it is close to or slidingly in contact with the outer circumferential surface of the lead core x. When this small-diameter cylindrical portion 63 moves forward relative to the tip 50, it protrudes from the front end of the tip 50 (see Figure 3(b)), and when it moves backward, it is retracted into the tip 50 (see Figure 3(a)).

[0027] Furthermore, the pressure-relieving member 70 is formed from an elastic material such as rubber or elastomer resin into a single stepped cylindrical shape having a cylindrical large-diameter portion 71 and a small-diameter portion 72 connected to the front of the large-diameter portion 71.

[0028] The large-diameter portion 71 fits into the inner circumferential surface of the large-diameter cylindrical portion 61 of the slide pipe 60 and is held in place so as not to come off easily. The rear end surface of the large-diameter portion 71 faces the front end of the chuck 10 and is formed to abut against the front end of the advancing chuck 10.

[0029] The smaller diameter portion 72 has a reduced outer diameter so that it gradually moves away from the inner circumferential surface of the slide pipe 60 towards the front. The inner diameter surface of this reduced diameter portion is elastically pressed against the outer circumferential surface of the lead core x through which it is inserted.

[0030] <Effects and Effects> Next, the characteristic effects and benefits of the lead refill 1 for mechanical pencils with the above configuration will be explained in detail. The lead refill 1 for the mechanical pencil is installed inside the barrel of a writing instrument such as a multi-function writing instrument or a mechanical pencil. In this state, when the chuck 10 moves forward or backward due to a rear-end knock operation, the lead x in the lead tank 100 is supplied into the chuck 10.

[0031] Figure 3(a) shows the state in which the slide pipe 60 is immersed within the tip 50 and the lead core x is held in place within the chuck 10. As the chuck 10 moves forward from this position, the jaws 11 of the chuck 10 disengage from the clutch 20, causing the chuck 10 to elastically expand radially outward. As shown in Figure 3(b), the front end of the chuck 10 comes into contact with the pressure release member 70, pushing the pressure release member 70 and the slide pipe 60 forward. The impact of this contact is mitigated by the elasticity of the pressure release member 70.

[0032] Then, as described above, the slide pipe 60 is pushed by the chuck 10, causing it to protrude from the tip 50, and within the tip 50, the inclined surface portion 62b is pressed against the pipe core end portion 54a (corner portion) of the reduced diameter portion 54 over its entire circumference and fitted into place.

[0033] Subsequently, the chuck 10 retracts due to the biasing force of the compression coil spring 80, engages with the clutch 20, and closes radially inward to clamp the lead core x (see Figure 4(c)). As the chuck 10 retracts as described above, friction with the retracting chuck 10 causes a rearward force to act on the lead core x, and a rearward force also acts on the pressure-relieving member 70 that elastically holds the lead core x, and on the slide pipe 60 which is integrated with the pressure-relieving member 70.

[0034] Therefore, if the conventional configuration without the inclined surface portion 62b (see Figure 6) is adopted, as described in the background technology above, the slide pipe 60 may also retract as the lead core x retracts.

[0035] However, according to the lead refill 1 for mechanical pencils, which is an example of the present invention, as described above, the inclined surface portion 62b fits into the pipe lead end portion 54a and the slide pipe 60 is fixed to the tip 50, so the slide pipe 60 does not easily retract.

[0036] Subsequently, as shown in Figure 4(d), even if the chuck 10 is repeatedly moved forward and backward due to rear-end knocking operations, the slide pipe 60 remains fixed to the tip 50 and does not retract, allowing the lead lead x to advance. Therefore, even if, for example, the tip of the slide pipe 60 is pointed sideways or upward when the knocking operation is performed, the slide pipe 60 does not retract, and the lead lead x can be fed out stably.

[0037] The state in which the slide pipe 60 is fixed to the tip 50 as described above is released when a rearward external force is applied to the slide pipe 60. For example, when writing is performed with the lead x extended (see Figure 5(a)), as the lead x rubs against the writing surface such as paper and wears down, the front end of the slide pipe 60 comes into contact with the writing surface, and the slide pipe 60 receives a rearward force from the writing surface. As a result, the inclined surface portion 62b separates from the pipe lead side end portion 54a (corner portion) (see Figure 5(b)), and the slide pipe 60 is released from its fixed state.

[0038] After this, as the lead x wears down due to writing, the slide pipe 60 retracts relatively, allowing writing to continue while protecting the tip of the lead x. In Figure 5, reference numeral 200 denotes the tip portion of the barrel of the writing instrument into which the lead refill 1 for the mechanical pencil is installed.

[0039] Furthermore, if the slide pipe 60 comes into contact with the floor or other surface when it falls, the force of the contact will cause the slide pipe 60 to retract into the tip 50, thus protecting the slide pipe 60. In addition, if the slide pipe 60 comes into contact with an object or skin, the backward force caused by the contact will cause the slide pipe 60 to retract, preventing the protruding slide pipe 60 from damaging the object or skin.

[0040] In other words, with the mechanical pencil lead 1 having the above configuration, and the writing instrument equipped with the mechanical pencil lead 1, the sliding pipe 60 protruding from the tip 50 cannot be easily retracted by the rear end knocking operation, etc., by a simple structure.

[0041] <Variation> According to the above embodiment, the pipe core side end 54a of the reduced diameter portion 54 is made into a corner. However, as another example of this pipe core side end, it is also possible to make it a chamfered portion with an R-shaped or C-shaped chamfer formed at the part where the reduced diameter portion 54 and the small diameter hole portion 53 intersect.

[0042] According to the above embodiment, a stepped reduced-diameter portion 54 is formed between the small-diameter hole portion 53 and the pipe sliding hole portion 52. However, as another example of this reduced-diameter portion, it is also possible to form it in a mortar shape that gradually reduces the inner diameter of the small-diameter hole portion 53. In this other example, the inclined surface portion 62b can be pressed against and fitted into the pipe core end of the diameter-reducing portion that is shaped like a mortar, and then fixed in place.

[0043] According to the above embodiment, the inclined surface portion 62b is formed in an annular shape over the entire circumference. However, other examples of this inclined surface portion include multiple inclined surfaces spaced apart in the circumferential direction, or a single inclined surface portion partially formed in the circumferential direction.

[0044] According to the above embodiment, in one particularly preferred example, the front end of the advancing chuck 10 is brought into contact with the pressure-relieving member 70 which is integrated with the slide pipe 60, thereby advancing the slide pipe 60. However, in another example, the front end of the advancing chuck 10 is brought into direct contact with the rear end of the slide pipe 60, thereby advancing the slide pipe 60.

[0045] Furthermore, the present invention is not limited to the specific configurations described above, and can be modified as appropriate without altering the essence of the invention.

[0046] <Summary> As described above, the above embodiment discloses the following invention. (1) A mechanical pencil lead comprising a tip and a slide pipe fitted to the inner circumferential surface of the tip so as to extend and retract from the front end of the tip, wherein the lead is advanced and inserted into the slide pipe, the inner circumferential surface of the tip is provided with a diameter-reducing portion that reduces the inner diameter, and the outer circumferential surface of the slide pipe is provided with an inclined surface portion that is directed forward towards the pipe lead side, and the slide pipe is fixed by fitting the inclined surface portion to the pipe lead side end of the diameter-reducing portion when it advances, and the inclined surface portion is released by detaching from the pipe lead side end when it retracts due to an external force (see Figures 1 to 5). (2) The lead for a mechanical pencil according to (1), characterized in that the end of the pipe core is a corner (see Figures 1 to 5). (3) The lead for a mechanical pencil according to (1) or (2) (see Figure 2), characterized in that the inclined surface portion is integrally machined with the slide pipe. (4) A chuck is provided behind the slide pipe to advance the lead by a reciprocating motion, and the slide pipe is fixed by fitting the inclined surface portion to the end of the pipe lead when pushed forward by the chuck, as described in any of (1) to (3) (see Figure 3). (5) The lead for a mechanical pencil according to (4) (see Figure 3), wherein the slide pipe is integrally provided with a pressure-relieving member that is in pressure-relieving contact with the outer surface of the lead core, and the slide pipe advances when the pressure-relieving member is pushed by the chuck. (6) A writing instrument equipped with a lead refill for a mechanical pencil as described in any of (1) to (5) (see Figure 5). [Explanation of Symbols]

[0047] 1 Refill for mechanical pencil 10 Chuck 11. Nail area 20 Clutch 30 Advance / retreat pipe 40 Support tube 50 Gold Tip 51 Clutch sliding hole 52 Pipe sliding hole 53 Small diameter hole 54 Reduced diameter part 54a Pipe core end 60 Slide pipe 62b Slope section 80 Compression coil springs 100-core tank x lead core

Claims

1. A mechanical pencil lead comprising a tip and a slide pipe fitted to the inner surface of the tip so as to extend and retract from the front end of the tip, wherein the lead is advanced and inserted into the slide pipe, The inner circumferential surface of the tip is provided with a pipe sliding hole portion for fitting the slide pipe so that it can move back and forth, a flat, reduced-diameter portion extending radially inward from the front end of the pipe sliding hole portion, and a straight, cylindrical, small-diameter hole portion extending forward from the pipe core end of the reduced-diameter portion. The end of the reduced diameter portion on the pipe core side is the corner where the reduced diameter portion and the small diameter hole portion intersect. The outer surface of the slide pipe is provided with an inclined surface portion that extends forward toward the pipe core. The lead for a mechanical pencil is characterized in that the sliding pipe is fixed by fitting the inclined surface portion into the corner portion when it moves forward, and the inclined surface portion detaches from the corner portion and is released when it moves backward due to an external force.

2. The mechanical pencil lead according to Claim 1, characterized in that the reduced diameter portion is formed in the shape of a flat surface substantially perpendicular to the pipe core.

3. The aforementioned tip and the aforementioned slide pipe are both formed from brass or stainless steel. The lead for a mechanical pencil according to claim 1, characterized in that the inclined surface portion is integrally machined with the slide pipe.

4. A mechanical pencil lead comprising a tip and a slide pipe fitted to the inner surface of the tip so as to extend and retract from the front end of the tip, wherein the lead is advanced and inserted into the slide pipe, The inner circumferential surface of the tip is provided with a diameter-reducing portion that reduces the inner diameter. The outer surface of the slide pipe is provided with an inclined surface portion that extends forward toward the pipe core. The aforementioned slide pipe is fixed by fitting the inclined surface portion to the pipe core end of the reduced diameter portion when it moves forward, and when it moves backward due to an external force, the inclined surface portion detaches from the pipe core end and is released. A chuck is provided behind the slide pipe that advances the lead core by moving back and forth. The slide pipe is integrally provided with a pressure-relieving member, which is made of rubber or elastomer resin and is pressure-relievingly pressed against the outer surface of the lead core. The advancing chuck comes into contact with the pressure-relieving member, pushing the pressure-relieving member and the slide pipe together, so that the inclined surface fits onto the end of the pipe core. A lead for a mechanical pencil, characterized in that the impact during contact is mitigated by the elasticity of the pressure-relieving member.

5. A writing instrument comprising a lead for a mechanical pencil as described in any one of Claims 1 to 4.

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