Writing instrument

Abstract

To provide a writing instrument that can maintain a good writing feel to solve the problem that, in writing instruments using a chuck set, friction between the parts that come into contact with the ball prevents the chuck from moving back and forth properly, preventing the chuck from adequately gripping the lead, which can result in a poor writing feel, such as the lead unintentionally retracting when pressure is applied when using the writing instrument.SOLUTION: The gist of the present invention is a writing instrument in which a lubricant is applied to at least the portion of the ball surface and / or the chuck set that comes into contact with the ball.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a writing instrument.

Background Art

[0002] Conventionally, a writing instrument using a chuck set that enables the feeding out of a refill by repeatedly gripping or releasing the refill has been disclosed. For example, Patent Document 1 discloses an invention related to a Sharp pencil having a mechanism in which a chuck piece opens and closes as the chuck moves back and forth, and the refill is gripped or pulled forward.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] In a writing instrument using such a chuck set, due to the friction between the members in contact with the ball, the proper back-and-forth movement of the chuck is hindered, and the chuck cannot sufficiently grip the refill. For example, when using the writing instrument, there is a risk that the refill with pen pressure applied may unintentionally retreat, deteriorating the writing feel.

[0005] An object of the present invention is to provide a writing instrument that can maintain a good writing feel.

Means for Solving the Problems

[0006] The present invention relates to a writing instrument comprising at least a barrel and a chuck set disposed inside the barrel and constituting a feeding mechanism for a refill from the front-end opening of the barrel. The chuck set is at least composed of a cylinder, a chuck, a chuck spring, and a ball. The chuck is composed of a plurality of chuck pieces that are at least partially divided along the axial direction and can be opened and closed in the radial direction, and can grip the refill between the chuck pieces. The chuck is inserted into the cylinder and is arranged to be movable back and forth. The chuck spring biases the chuck backward. The ball is rotatable between the cylinder and the chuck while applying a pressing force inward in the radial direction to the chuck pieces so that the chuck pieces are in an open state as the chuck advances and in a closed state as the chuck retreats. The gist of the writing instrument is that a lubricant is applied to at least the surface of the ball and / or the portion of the chuck set that contacts the ball.

Advantages of the Invention

[0007] In the writing instrument according to the present invention, since a lubricant exists at least between the ball and the member in contact with the ball, the friction between the cylinder, the ball, and the chuck is reduced, so that the chuck can retreat sufficiently, the chuck can grip the refill more reliably, and a good writing feeling can be maintained.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Figure 13

Mode for Carrying Out the Invention

[0009] Hereinafter, with appropriate reference to the drawings, embodiments of the writing instrument according to the present invention will be described. The present invention is not limited to the dimensions and materials of the following embodiments, and various modifications can be made without departing from the gist of the present invention.

[0010] FIG. 1 is an external view of a Sharp pencil 1 which is an embodiment of the writing instrument according to the present invention, and FIG. 2 is a longitudinal cross-sectional view along the axial direction of the Sharp pencil 1. The Sharp pencil 1 is at least composed of a shaft cylinder 10 and a chuck set 100 disposed inside the shaft cylinder 10. In the present embodiment, a tip member 20, a cap 170, etc. are also disposed on the shaft cylinder 10. In this specification, when referring to the tip member 20 side along the center line F of the Sharp pencil 1, it may be expressed as "front", "forward", etc., and the opposite side, i.e., the cap 170 side, may be expressed as "rear", "rearward", etc. Also, the direction in which the center line F extends may be referred to as the axial direction, the direction orthogonal to the center line F as the radial direction, and the direction along a circle centered on the center line F as the circumferential direction, etc.

[0011] In the present embodiment, the writing instrument according to the present invention is described by taking the Sharp pencil 1 as an example, but as the writing instrument according to the present invention, it can also be implemented in any form such as a ballpoint pen, a marking pen, a retractable eraser, etc.

[0012] The shaft cylinder 10 is a hollow cylindrical member that penetrates in the axial direction. The shaft cylinder 10 is a member in which a brass outer cylinder 40 and a rear shaft 12 made of ABS resin are joined. At the front end of the shaft cylinder 10, a tip member 20 is arranged. The tip member 20 is a hollow conical member that penetrates in the axial direction. The tip member 20 is a brass member configured with an outer diameter that tapers forward in order to improve the visibility of the handwriting during writing. The shaft cylinder 10 and the tip member 20 are joined by screw-threading between a male screw portion formed on the outer wall surface of the front end of the shaft cylinder 10 and a female screw portion formed on the inner wall surface of the rear end of the tip member 20. The male screw portion and the female screw portion of both members may be interchanged. Also, the joining method of both members can be joined by any method such as press-fitting or fitting in addition to screw-threading.

[0013] A silicon grip 30 is arranged on the outer periphery of the shaft cylinder 10 and the tip member 20. The grip 30 is a hollow cylindrical member that penetrates in the axial direction. The grip 30 is arranged so as to cover a part in front of the shaft cylinder 10 and a part behind the tip member 20. Protrusions 31 are formed on the outer wall surface of the grip 30. A plurality of protrusions 31 are formed.

[0014] A brass outer cylinder 40 is arranged on the outer periphery of the grip 30. The outer cylinder 40 is a hollow cylindrical member that penetrates in the axial direction. Through holes 41 are formed in the outer cylinder 40. A plurality of through holes 41 are formed at positions corresponding to the protrusions 31 so that the protrusions 31 of the grip 30 protrude to the outside through the through holes 41.

[0015] A clip holder 50 made of ABS resin is arranged at the rear end of the shaft cylinder 10. An engagement hole 11 that penetrates inside and outside is formed behind the shaft cylinder 10. An engagement protrusion 51 formed on the outer wall surface of the clip holder 50 is engaged by being inserted into the engagement hole 11 from the radially inner side, and the clip holder 50 and the shaft cylinder 10 are joined. A clip 60 made of carbon tool steel is joined to the outer wall surface of the clip holder 50 by fitting. A clamping portion of the clip 60 is formed by the inner wall surface of the clip 60 and the outer wall surface of the shaft cylinder 10.

[0016] Inside the shaft cylinder 10, a core tank 70 made of polypropylene resin is arranged so as to be movable back and forth. The core tank 70 is a hollow cylindrical member that penetrates in the axial direction. The core tank 70 is a member for storing a writing core for a mechanical pencil inside. At the rear end of the core tank 70, an eraser 160 made of thermoplastic elastomer is detachably arranged. The core tank 70 and the eraser 160 are joined by fitting. By arranging the eraser 160, the rear end opening of the core tank 70 is closed. At the rear end of the core tank 70, further, a brass cap 170 is detachably arranged so as to cover the eraser 160. The rear of the cap 170 functions as a knock operation part 171 that is the target of the knock operation by the user of the mechanical pencil 1.

[0017] Inside the shaft cylinder 10, a spring 80 made of spring oil temper wire is arranged. The spring 80 is a member for biasing the core tank 70 backward. A stepped portion is formed on the inner wall surface of the shaft cylinder 10. On the outer wall surface of the core tank 70, a flange 71 that is an annular protrusion continuous in the circumferential direction is formed. The front end portion of the spring 80 contacts the rear end surface of the stepped portion of the shaft cylinder 10, and the rear end portion of the spring 80 contacts the front of the side wall of the flange 71, so that the spring 80 biases the core tank 70 backward. When the mechanical pencil 1 is not being knocked, the core tank 70 is prevented from coming off backward by the clip holder 50 with the flange 71.

[0018] Figure 3 is an enlarged front view of Figure 2, Figure 4 is an enlarged view of part A of Figure 3, and Figure 5 is an enlarged view of part B of Figure 3. In front of the core tank 70, an intermediate member 90 made of polyacetal resin is arranged. The intermediate member 90 is at least composed of a rear portion 91, a flange 92 that is an annular protrusion continuous in the circumferential direction, and a front portion 93. The core tank 70 and the intermediate member 90 are joined by the rear portion 91 being press-fitted into the front end opening of the core tank 70. The axial distance of the rear portion 91 press-fitted into the core tank 70 is restricted by the flange 92 contacting the front end surface of the core tank 0.

[0019] The front portion 93 is located on the side opposite to the rear portion 91 with the flange 92 interposed therebetween. The front portion 93 is at least composed of a raised portion 94, a recessed portion 95, and a pressing portion 96. The raised portion 94 is formed on the outer wall surface of the front portion 93. The relay member 90 and the chuck set 100 described later are joined by inserting the front portion 93 into the cylindrical body 110 of the chuck set 100 and fitting them with the raised portion 94. The chuck 120 of the chuck set 100 described later is inserted into the recessed portion 95. The pressing portion 96 is a portion for pressing the flange 121 of the chuck 120 forward during the knock operation. In front of the front portion 93, the recessed portion 95 is formed by being surrounded by the pressing portion 96. The protruding length of the pressing portion 96 from the bottom surface of the recessed portion 95 (the depth of the recessed portion 95) is larger than the length of the axially rearward portion of the flange of the chuck 120.

[0020] The chuck set 100 is disposed in front of the relay member 90. The chuck set 100 constitutes a mechanism for feeding out the core G of a sharp pencil, which is a refill, from the front end opening of the tip member 20. The chuck set 100 is at least composed of a cylindrical body 110, a chuck 120, a spring 139 which is a chuck spring, and a ball 140.

[0021] The cylindrical body 110 is a hollow cylindrical member made of polycarbonate resin that penetrates in the axial direction. An inclined portion 111 is formed on the inner wall surface at the rear of the cylindrical body 110. The inner diameter of the cylindrical body 110 decreases toward the front in the axial range where the inclined portion 111 is formed. The inner diameter of the cylindrical body 110 is constant at a distance H on the axially rearward side of the inclined portion 111 and is smaller than the distance H on the axially forward side of the inclined portion 111.

[0022] With the knocking operation, the front portion 93 is inserted forward while the raised portion 94 is in contact with the inclined portion 111, and the fitting force between the raised portion 94 and the rear end portion of the cylindrical body 110 increases. When the knocking operation amount reaches the maximum, the raised portion 94 overrides the inclined portion 111 and is inserted forward in the axial direction beyond the inclined portion 111. At this time, the fitting force between the raised portion 94 and the rear end portion of the cylindrical body 110 is the maximum. By forming such an inclined portion 111, it is possible to gradually switch the fitting force between the raised portion 94 and the rear end portion of the cylindrical body 110 according to the knocking operation amount.

[0023] On the outer wall surface of the front end portion of the cylindrical body 110, a flange 112, which is an annular protrusion continuous in the circumferential direction, is formed. When the rear side wall of the flange 112 comes into contact with the front end face of the rear shaft 12, the backward movement of the cylindrical body 110 is restricted. Also, when the end face 113 of the cylindrical body 110 comes into contact with the rear end face of the stepped portion formed on the inner wall surface of the front member 20, the forward movement of the cylindrical body 110 is restricted.

[0024] Inside the cylindrical body 110, a chuck 120 made of polyphenylene sulfide resin is housed. The chuck 120 is inserted through the cylindrical body 110 and is arranged so as to be movable back and forth relative to the cylindrical body 110. Also, a stainless steel spring 139 is arranged on the cylindrical body 110, biasing the chuck 120 backward. The chuck 120 is at least partially divided along the axial direction, and in this embodiment, it is composed of a first chuck piece 122 and a second chuck piece 123 that are divided throughout the axial direction. Note that the chuck 120 can also be divided into three or more pieces in part or all along the axial direction. The two chuck pieces can be opened and closed in the radial direction so that the gap between the first chuck piece 122 and the second chuck piece 123 changes. There are an open state in which the two chuck pieces are separated in the radial direction and the gap is large, and a closed state in which the two chuck pieces approach each other in the radial direction and the gap is small.

[0025] FIG. 6 is an external perspective view of the chuck set 100, FIG. 7 is a partial cross-sectional view of the chuck set 100, and FIG. 8 is a partial cross-sectional perspective view of the chuck set 100. The chuck 120 is formed with a gripping portion 124 for gripping the core G, a stepped portion 125 located axially rearward of the gripping portion 124, and a non-gripping portion 126 connected to the gripping portion 124 via the stepped portion 125. The gripping portion 124 is formed with a groove having a width smaller than the diameter of the writing core G. The groove is composed of a pair of inclined portions 127 and an edge portion 128 of the groove. The width of the groove is defined by the distance between the edge portions 128.

[0026] In the closed state of the chuck 120, the chuck 120 can grip the core G by the inclined portions 127 of the first chuck piece 122 and the inclined portions 127 of the second chuck piece 123 contacting the core G at four locations on the radially outer side.

[0027] The stepped portion 125 is defined by a plane along the radial direction. The pair of inclined portions 127 constituting the gripping portion 124 have the position of the stepped portion 125 as the axial rearward end. Grooves are formed in the first chuck piece 122 and the second chuck piece 123 rearward of the stepped portion 125, and the grooves are at least composed of a pair of edge portions 129. The distance between the pair of edge portions 129 is larger than the distance between the pair of edge portions 128 constituting the gripping portion 124 due to the presence of the stepped portion 125. Thus, in the non-gripping portion 126 located on the axially opposite side of the gripping portion 124 with the stepped portion 125 interposed therebetween, the pair of edge portions 129 are located radially outside the pair of edge portions 128 constituting the gripping portion 124. Therefore, the non-gripping portion 126 is configured not to contact the core G gripped by the gripping portion 124 in the closed state.

[0028] On the non-gripping portion 126, a convex portion 130 is formed for guiding the core G to the gripping portion 124. The convex portion 130 is formed to protrude radially inward from the surface of a groove having a pair of edge portions 129 of the non-gripping portion 126. The convex portion 130 gradually increases in the amount of protrusion from the surface of the non-gripping portion 126 toward the front in the axial direction and reaches a ridge line 131. The position of the ridge line 131 is the position where the amount of protrusion of the convex portion 130 from the surface of the non-gripping portion 126 is maximum. The portion in front of the ridge line 131 in the axial direction is cut down so as to be substantially flat and is connected to the surface of the non-gripping portion 126. When the core G inserted from the rear in the axial direction passes through the non-gripping portion 126 during replenishment of the core G and the core G comes into contact with the convex portion 130, the core G is guided radially inward by the convex portion 130. Therefore, it is preferable to suppress a defect in which the core G is locked to the stepped portion 125 and is not guided to the gripping portion 124. The portion behind the ridge line 131 of the convex portion 130 has a protruding curved surface shape so that the core G can be guided to the gripping portion 124 more smoothly.

[0029] The convex portions 130 may be provided continuously in the circumferential direction of the first chuck piece 122 and the second chuck piece 123, and any number of them may be provided. In the present embodiment, two convex portions 130 are separated at equal intervals (180°) in the circumferential direction, but they do not have to be at equal intervals.

[0030] The protruding amount of each convex portion 130 is formed such that the convex portion 130 is located radially outside the edge portion 128 with reference to the radial positions of a pair of edge portions 128 of the gripping portion 124 in the closed state. Therefore, even in the closed state, the ridge line 131 is located outside the outer wall surface of the core G, and the convex portion 130 does not come into contact with the core G.

[0031] On the outer wall surfaces of the first chuck piece 122 and the second chuck piece 123, recesses 132 that are recessed radially inward are formed as the rotation regions of the balls 140. The recess 132 is composed of a curved surface portion 133 and an edge portion 134 that is the outer edge of the curved surface portion 133.

[0032] At the front end of the cylinder body 110, a stainless steel ring 135 that forms part of the cylinder body 110 is arranged. The cylinder body 110 and the ring 135 are joined by press-fitting. The ring 135 is a cylindrical member that penetrates in the axial direction and is composed of an inclined portion 136 whose inner diameter increases from the rear to the front and a small-diameter portion 137 behind the inclined portion 136. In the present embodiment, the cylinder body 110 is composed of two parts with the ring 135, but the inclined portion 136 and the small-diameter portion 137 can also be provided directly in front of the cylinder body 110.

[0033] The ball 140 is a cemented carbide member held between the concave portion 132 and the ring 135. The ball 140 is in contact with the curved surface portion 133 on the radially inner side and the inclined portion 136 on the radially outer side. The ball 140 is rotatable between the ring 135 which is part of the cylinder body 110 and the first chuck piece 122 and the second chuck piece 123 which are the chuck 120. As the chuck 120 biased rearward by the spring 139 retracts, the ball 140 that attempts to retract simultaneously exhibits a wedge effect due to contact with the inclined portion 136. The first chuck piece 122 and the first chuck piece 123 are applied with a pressing force radially inward from the ball 140, and the chuck 120 is closed and enters a closed state.

[0034] A lubricant is applied to at least the surface of the ball 140 and / or the portion of the chuck set 100 that contacts the ball. The portion of the chuck set 100 that contacts at least the ball 140 includes the inclined portion 136 of the ring 135, the curved surface portion of the concave portion 132, and the like. By having a lubricant present at least between the ball 140 and the members that contact the ball 140, the friction between the ring 135, the ball 140, and the chuck 120 that constitute the cylinder body 110 is reduced, so that the chuck 120 can retract sufficiently, the chuck 120 can grip the core G more reliably, and a good writing feeling can be maintained.

[0035] As the lubricant, known ones such as lubricating oil and grease can be appropriately used, but fatty acids or fatty acid amides are preferred. Further, it is preferable that the fatty acid is any one of stearic acid, oleic acid, erucic acid, and palmitic acid. As the fatty acid amide, it is preferable that it is any one of stearic acid amide, oleic acid amide, erucic acid amide, and palmitic acid amide. These lubricants may consist only of these compositions, may contain one of these compositions as the main component and other additives, or may be a mixture of two or more of these compositions. In the present embodiment, a lubricant composed of powdery stearic acid is applied to the surface of the ball 140.

[0036] When the surface roughness (arithmetic mean height) of the ball 140 is 2 nm or more and 12 nm or less, while obtaining the friction required for rotation between the ball and the ring 135 and the chuck 120 in contact with the ball, the wettability with respect to the lubricant is also good, and even if the ball 140 rotates repeatedly, the lubricant can be sufficiently retained on the surface of the ball 140, so that a good writing feeling can be maintained. In the present embodiment, the surface roughness (arithmetic mean height) of the ball 140 is 3 nm.

[0037] As a method of applying a lubricant, it can be appropriately selected, such as directly applying, spraying, or dipping on a member including at least the portion in contact with the ball. If the lubricant was originally applied to the inner surface of the storage body that houses the members constituting the chuck set 100 in the process of assembling the mechanical pencil 1, and the lubricant is transferred to the surface of the members housed in the storage body, it is preferable that a mechanical pencil 1 can be manufactured that can maintain a good writing feel without separately providing a step of applying the lubricant because the lubricant is applied to an arbitrary surface during storage or transportation of the members. In the present embodiment, stearic acid is previously applied to the inner surface of a polyethylene resin bag serving as the storage body, and when the ball 140 is stored in the bag, stearic acid is transferred and applied to the surface of the ball 140. It is preferable that the lubricant applied to the inner surface of the bag can prevent the stored members from accidentally adhering or getting entangled. Also, it is preferable that when the surface roughness (arithmetic mean height) of the ball 140 is 2 nm or more and 12 nm or less, the ball 140 can sufficiently scrape off stearic acid from the surface of the polyethylene resin bag, which is a soft bag, and hold it on the surface.

[0038] By a knocking operation, the chuck 120 advances relative to the cylinder body 110 and the ring 135 against the spring 139 via the relay member 90. As the chuck 120 advances, when the ball 140 rolls forward on the inclined portion 136 within the curved surface portion 133, the pressing force decreases, the distance between the first chuck piece 122 and the first chuck piece 123 increases, the chuck 120 opens, and it becomes an open state.

[0039] A brass stopper 138 is arranged at the front end opening of the ring 135. The ring 135 and the stopper 138 are joined by press-fitting. A recess is formed on the rear end side of the stopper 138 so as not to inhibit the relative forward and backward movement of the chuck 120 with respect to the ring 135 and the stopper 138. When the chuck 120 advances relative to the cylinder body 110 and the ring 135, the front end portion of the chuck 120 enters the region of the recess.

[0040] Inside the front member 20, a slider 150 made of polyacetal resin is disposed so as to be positioned in front of the chuck set 100. Also, inside the front member 20 and on the outer peripheral side of the slider 150, a ring 151 made of polyacetal resin is fixed. The slider 150 is inserted through the ring 151 and is disposed so as to be movable back and forth relative to the ring 151.

[0041] On the outer wall surface of the slider 150, a tapered portion 152 whose outer diameter decreases from the front in the axial direction toward the rear is formed. The slider 150 is composed of a large-diameter portion on the front side in the axial direction and a small-diameter portion on the rear side in the axial direction with the tapered portion 152 interposed therebetween. When not knocking, the large-diameter portion on the front side of the tapered portion 151 is in a state of being fitted to the ring 151, and the ring 151 is loosely fixed to the slider 150 by frictional force.

[0042] Inside the front member 20, a stainless steel spring 153 is also disposed. The spring 153 is disposed between the ring 151 and the slider 150. The slider 150 is biased forward by the spring 153. The biasing force of the spring 153 is set to be smaller than the frictional force at the fitting portion between the large-diameter portion of the slider 150 and the ring 151. Therefore, when not knocking, even if the biasing force by the spring 153 acts, the fitting between the large-diameter portion of the slider 150 and the ring 151 is not released.

[0043] When the slider 150 is pressed forward as the relay member 90 and the chuck set 100 advance during a knock operation, the fitting between the large-diameter portion of the slider 150 and the ring 151 is released, and the slider 150 moves forward by the biasing force of the spring 153.

[0044] In the slider 150, a stainless steel core pipe 154 is arranged from the front by press-fitting, and a silicon core return prevention member 155 is arranged from the rear by press-fitting. The core pipe 154 and the core return prevention member 155 are fixed to the slider 150 and move along with the forward and backward movement of the slider 150. The core pipe 154 is a hollow cylindrical member penetrating in the axial direction. The core pipe 154 protrudes from the tip member 20 to protect the core G when the sharp pencil 1 is used. The core return prevention member 155 is also a member penetrating in the axial direction and can hold the core G by elastic force. Therefore, when the core G is drawn out by a plurality of knock operations, it is possible to prevent the core G from returning backward.

[0045] In the above-described embodiment, the loads (biasing forces) of the three types of springs arranged in the sharp pencil 1 are set to increase in the order of the spring 139, the spring 153, and the spring 80.

[0046] FIG. 9 is a cross-sectional view showing the front portion of the sharp pencil 1 during a knock operation, FIG. 10 is a cross-sectional view showing the front portion of the sharp pencil 1 in a state where writing is possible by a knock operation, FIG. 11 is a cross-sectional view taken along the line C - C' in FIG. 10 as viewed in the arrow direction, and FIG. 12 is a cross-sectional view taken along the line D - D' in FIG. 10 as viewed in the arrow direction.

[0047] When the sharp pencil 1 is not in use for writing, the cylindrical body 110 is not pressed by the relay member 90, and the cylindrical body 110 has retreated to a position where the flange 112 contacts the front end face of the rear shaft 12. At this time, the chuck 120 is not pressed by the relay member 90 either. Therefore, the chuck 120 is biased rearward by the biasing force of the spring 139 and has retreated relatively with respect to the cylindrical body 110 and the ring 135. At this time, since the chuck 120 is in a closed state, even if the core G enters the chuck 120 from the core tank 70, it stops behind the gripping portion 124.

[0048] In the Sharp pencil 1 during the knocking operation, the core tank 70 and the relay member 90 move forward due to the knocking operation. At this time, since the raised portion 94 is fitted with the portion behind the inclined portion 111 on the inner wall surface of the cylindrical body 110, the cylindrical body 110 and the ring 135 also move forward together with the relay member 90. The forward movement of the cylindrical body 110 and the ring 135 is restricted and stopped when the end face 113 contacts the wall surface of the front member 20.

[0049] As the cylindrical body 110 and the ring 135 move forward, the stopper 138 also moves forward. Therefore, the slider 150 is pressed forward via the stopper 138, and the fitting between the large-diameter portion of the slider 150 and the ring 151 is released. Thereby, the slider 150 moves forward by the biasing force of the spring 153, and the core pipe 154 protrudes from the front member 20.

[0050] If the knocking operation continues after the forward movement of the cylindrical body 110 stops (when knocking deeper), the pressing portion 96 of the front portion 93 of the relay member 90 presses the flange 121 of the chuck 120, and the chuck 120 moves forward relative to the cylindrical body 110 and the ring 135. Since the inner diameter of the cylindrical body 110 becomes smaller toward the front at the inclined portion 111, when the raised portion 94 moves over the inclined portion 111 and moves forward, the fitting between the cylindrical body 110 and the relay member becomes tighter.

[0051] Due to the relative forward movement of the chuck 120 with respect to the cylindrical body 110 and the ring 135, the contact position of the ball 140 with respect to the ring 135 shifts to the front portion of the inclined portion 136 where the inner diameter is large, and the chuck 120 is in an open state. In the open state, when the gap between the first chuck piece 122 and the second chuck piece 123 in the gripping portion 124 becomes larger, the core G can pass through the gripping portion 124. The core G that has passed through the gripping portion 124 falls by its own weight and stops behind the core return stopper member 155 disposed on the slider 150.

[0052] When the user releases their finger from the knock operation unit 171 and the knock operation ends, the core tank 70 and the relay member 90 begin to retract due to the biasing force of the spring 80. Since the raised portion 94 of the relay member 90 is tightly fitted with the cylindrical body 110 at a position in front of the inclined portion 111, it retracts together with the relay member 90. The retraction of the cylindrical body 110 and the ring 135 is restricted and stopped when the flange 112 of the cylindrical body 110 contacts the front end face of the rear shaft 12. After that, the relay member 90 continues to retract toward its position before the knock operation, the raised portion 94 moves behind the inclined portion 111, and the fit between the relay member 90 and the cylindrical body 110 becomes loose.

[0053] When the relay member 90 and the cylindrical body 110 begin to retract with the end of the knock operation, the chuck 120 also begins to retract due to the biasing force of the spring 139. The chuck 120 is in an open state, the core G is not restrained by the gripping portion 124, and the core G falls due to its own weight and remains stopped behind the core return stopper member 155.

[0054] When the retraction of the cylindrical body 110 and the ring 135 stops, the chuck 120 begins to retract relative to the cylindrical body 110 and the ring 135 due to the biasing force of the spring 139. At this time, the contact position of the ball 140 with respect to the ring 135 shifts to the rear portion of the inclined portion 136 where the inner diameter is small, and the chuck 120 becomes closed. Since the core G is inserted into the gripping portion 124, the decrease in the gap between the first chuck piece 122 and the second chuck piece 123 continues until the core G is gripped by the gripping portion 124. When the core G is gripped by the gripping portion 124, the decrease in the gap stops, and the retraction of the chuck 120 ends.

[0055] When the knocking operation is repeated again later, due to the operation described above, the core G is press-fitted into the core return stopper member 155 as the chuck 120 advances, and finally reaches the front end of the core pipe 154, entering a writable state. FIG. 9 shows the state during the knocking operation just before the Sharp pencil 11 enters the writable state. In this state, when the knocking operation ends, the core tank 70, the relay member 90, the cylindrical body 110, the ring 135, and the chuck 120 retreat, and the core G is gripped by the chuck 120, reaching the state shown in FIG. 10.

[0056] FIG. 13 is an enlarged view of part E of FIG. 10. In a cross-section along the center line F which is the axis of the cylindrical body 110, the angle J formed between the virtual straight line I extending forward axially from the small-diameter portion 137 and the inclined portion 136 on the inner wall surface of the ring 135 constituting the cylindrical body 110 is preferably 5° or more and 10° or less. When the angle J is 5° or more and 10° or less, the pressing force on both chuck pieces due to the wedge effect caused by the ball 140 and the inclined portion 136 of the ring 135 becomes appropriate with respect to the retraction amount of the chuck 120. Therefore, even when a high writing pressure is applied to the core G, the pressing force of the ball 140 on both chuck pieces does not become too high, preventing the core G from breaking and maintaining a good writing feeling.

[0057] When the angle J is 6° or more and 8° or less, even if the gripping force decreases due to deformation of both chucks during long-term use, or the core G becomes slippery with respect to the chuck 120 due to wear powder of the core G adhering to the gripping portions 124 of both chuck pieces, a high gripping force on the core G can be maintained because the space where the ball 140 can exist between the ring 135 constituting the cylindrical body 110 and both chuck pieces suddenly becomes small with respect to the retraction amount of the chuck 120, so a good writing feeling can be maintained, which is more preferable. In this embodiment, the angle J is 7°.

[0058] In a longitudinal cross-section including the deepest part 133a of the curved surface portion 133 along the center line F which is the axis of the two chuck pieces, it is preferable that the length K from the deepest edge part 134a, which is the part of the edge 134 located most radially outward, to the deepest part 133a is 45% or more and 55% or less of the ball diameter. When the length K is 45% or more and 55% or less of the ball diameter, the recess 132 has a sufficient depth with respect to the ball 140, so that the lubricant applied at least to the part in contact with the ball 140 hardly leaks out from the recess 132, the gripping force of the core G can be stabilized, and a good writing feeling can be maintained.

Explanation of Signs

[0059] 1 Sharp pencil 10 Shaft cylinder 11 Engagement hole 12 Rear shaft 20 Tip member 30 Grip 31 Protrusion 40 Outer cylinder 41 Through hole 50 Clip holder 51 Engagement protrusion 60 Clip 70 Core tank 71 Flange 80 Spring 90 Relay member 91 Rear part 92 Flange 93 Front part 94 Raised part 95 Recess 96 Pressing part 100 Chuck set 110 Cylindrical body 111 Inclined part 112 Flange 113 End face 120 Chuck 121 Flange 122 First chuck piece 123 Second chuck piece 124 Gripping part 125 Step part 126 Non-gripping part 127 Inclined part 128 Edge part 129 Edge part 130 Protruding part 131 Ridge line 132 Concave part 133 Curved surface part 133a Deepest part 134 Edge part 134a Edge deepest part 135 Ring 136 Inclined part 137 Small diameter part 138 Stopper 139 Spring 140 Ball 150 Slider 151 Ring 152 Taper part 153 Spring 154 Core pipe 155 Core return stopper member 160 Eraser 170 Cap 171 Knock operation part F Center line G Core H Distance I Virtual straight line J Included angle K Length

Claims

1. A writing instrument comprising at least a barrel and a chuck set disposed inside the barrel and constituting a feeding mechanism for the writing core from the front opening of the barrel, The chuck set is at least composed of a cylinder, a chuck, a chuck spring, and a ball, The chuck is composed of a plurality of chuck pieces that are at least partially divided along the axial direction and can be opened and closed in the radial direction, and can grip the writing core between the chuck pieces, and is inserted into the cylinder and arranged to be movable back and forth, The chuck spring biases the chuck backward, The ball is rotatable between the cylinder and the chuck while applying a pressing force radially inward to the chuck pieces so that the chuck pieces are in an open state as the chuck advances and in a closed state as the chuck retreats, A lubricant is applied to at least the portion of the ball surface and / or the chuck set that contacts the ball, Writing instrument.

2. The lubricant is a fatty acid or a fatty acid amide, The writing instrument according to claim 1.

3. The fatty acid is any one of stearic acid, oleic acid, erucic acid, and palmitic acid, The writing instrument according to claim 2.

4. The fatty acid amide is any one of stearic acid amide, oleic acid amide, erucic acid amide, and palmitic acid amide, The writing instrument according to claim 2.

5. The cylinder is at least composed of an inclined portion whose inner diameter increases from the rear to the front and a small-diameter portion behind the inclined portion, In a cross-section along the axis of the cylinder, the angle formed by the inner wall surface of the cylinder, a virtual straight line extending forward along the axial direction from the small-diameter portion, and the inclined portion is 5° or more and 10° or less, The writing instrument according to any one of claims 1 to 4.

6. The formed angle is 6° or more and 8° or less, The writing instrument according to claim 5.

7. A concave portion that is recessed radially inward is formed on the outer wall surface of the chuck piece as the rotation region of the ball, The concave portion is composed of a curved surface portion and an edge portion that is the outer edge of the curved surface portion, In a longitudinal section of the chuck piece along the axis and including the deepest part of the curved surface portion, the length from the outermost radially located portion of the edge portion to the deepest part is 45% or more and 55% or less of the ball diameter, The writing instrument according to any one of claims 1 to 4.

8. A concave portion that is recessed radially inward is formed on the outer wall surface of the chuck piece as the rotation region of the ball, The concave portion is composed of a curved surface portion and an edge portion that is the outer edge of the curved surface portion. In the longitudinal section of the chuck piece along the axis and including the deepest part of the curved surface portion, the length from the position of the edge portion that is the outermost in the radial direction to the deepest part is 45% or more and 55% or less of the ball diameter. The writing instrument according to claim 6.

9. The surface roughness (arithmetic mean height) of the ball is 2 nm or more and 12 nm or less. The writing instrument according to any one of claims 1 to 4.

10. The surface roughness (arithmetic mean height) of the ball is 2 nm or more and 12 nm or less. The writing instrument according to claim 6.

11. The lubricant is applied to the inner surface of a housing that houses the members constituting the chuck set, and is applied by being transferred to the surface of the members housed in the housing. The method for manufacturing a writing instrument according to any one of claims 1 to 4.

12. The lubricant is applied to the inner surface of a housing that houses the members constituting the chuck set, and is applied by being transferred to the surface of the members housed in the housing. The method for manufacturing a writing instrument according to claim 6.

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