Retractable writing instrument

Abstract

To provide a retractable writing instrument having a quieter retracting mechanism, capable of addressing the problem of a retractable writing instrument disclosed in a patent document 1, specifically easy radial backlash against a shaft inner wall surface with an annular projection as a supporting point to increase an operation sound of a cam mechanism.SOLUTION: This retractable writing instrument is configured such that a projected state of a writing part provided at the front end of a writing instrument body is set by locking a locking projection provided on the outer wall surface of the writing instrument body to a cam provided on a cam cylinder inner wall.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a so-called retractable writing instrument in which a writing instrument body having a writing portion at the front end is disposed inside a barrel so as to be movable back and forth, and the writing portion can protrude from and retract into the front end opening of the barrel. Hereinafter, the direction in which the writing portion protrudes is defined as the front, and the direction in which the writing portion retracts is defined as the rear. Further, the state in which the writing portion protrudes from the front end opening of the barrel and can be used for writing is defined as the protruding state, and the state in which the writing portion retracts into the barrel is defined as the retracted state.

Background Art

[0002] As a retractable writing instrument, there is known one in which a so-called cam mechanism is adopted in at least a part of the retracting mechanism. In the cam mechanism in the retractable writing instrument, a locking projection is provided on the writing instrument body so that the writing instrument body can be locked at different positions in the front-rear direction inside the barrel. A cam portion is provided inside the barrel as the locking destination of the locking projection. The cam portion is displaced in the circumferential direction as the writing instrument body moves back and forth, and enables the writing portion to protrude and retract in a continuous single operation only by moving the writing instrument body back and forth. In such a retractable writing instrument, in order to form the protruding state, the writing instrument body is advanced until the locking projection is positioned in front of the cam portion. Thereafter, the writing instrument body is retracted by a force such as the biasing force of an elastic member, and the locking projection is locked to the cam portion, so that the retraction of the writing instrument body stops and the protruding state can be formed.

[0003] For example, Patent Document 1 (Japanese Utility Model Publication No. 54-38980) discloses a retractable writing instrument in which a writing instrument body biased rearward by an elastic member and a cam cylinder rotatable around the outer periphery of the writing instrument body are disposed inside a barrel.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the retractable writing instrument disclosed in Patent Document 1, a cam portion, which is a part of the cam cylinder and receives a force for rotating the cam cylinder by contacting either the writing body as the writing instrument body moves back and forth, is provided at both front and rear ends of the cam cylinder in the front-rear direction. Since the cam portion is also the locking destination of the locking projection, it is necessary to limit the movement of the cam cylinder in the front-rear direction inside the shaft cylinder to a certain extent. Therefore, an annular projection protruding radially outward is provided on the outer wall surface of the cam cylinder. The movement of the cam cylinder in the front-rear direction is restricted by the side wall of the annular projection coming into contact with a part inside the shaft cylinder in the front-rear direction. Since the annular projection is shorter in the front-rear direction than the cam portion, there is a problem that radial play with respect to the inner wall surface of the shaft cylinder easily occurs with the annular projection as a fulcrum, and the operating sound of the cam mechanism becomes large.

[0006] An object of the present invention is to provide a retractable writing instrument with a retractable mechanism that operates quietly.

Means for Solving the Problems

[0007] The present invention is a retractable writing instrument in which at least a writing instrument body and a cam cylinder are disposed inside a shaft cylinder. The writing instrument body is disposed so as to be movable back and forth by a forward force by operating a knock portion exposed outside the shaft cylinder and a backward biasing force by an elastic member. The cam cylinder is disposed so as to be at least rotatable around the outer periphery of the writing instrument body as the writing instrument body moves back and forth. The locking projection provided on the outer wall surface of the writing instrument body locks to the cam portion provided on the inner wall surface of the cam cylinder, so that at least a protruding state of the writing portion provided at the front end of the writing instrument body from the front end opening of the shaft cylinder is formed. This is the first gist of the retractable writing instrument.

[0008] Also, a retractable writing instrument in which both front and rear ends of the cam cylinder in the front-rear direction are held between stepped portions protruding from the inner wall surface of the shaft cylinder and are thus immovable back and forth is the second gist.

[0009] Furthermore, the third gist is an emerging and retracting writing instrument that is rotatably arranged such that a sliding rib provided on the inner wall surface of the barrel or the outer wall surface of the writing instrument body slides along a sliding groove extending in the front-rear direction provided on the outer wall surface of the writing instrument body or the inner wall surface of the barrel.

Advantages of the Invention

[0010] In the emerging and retracting writing instrument of the present invention, since the cam portion is provided on the inner wall surface of the cam barrel, the outer wall surface of the cam barrel can be made longer in the front-rear direction than the cam portion. Since there is no need to provide a portion on the outer wall surface of the cam barrel that can serve as a fulcrum for causing radial play with respect to the inner wall surface of the barrel, it is possible to provide an emerging and retracting writing instrument in which the operating sound of the cam mechanism constituting the emerging and retracting mechanism is quiet.

[0011] Also, in the second gist, since both the front and rear ends of the cam barrel in the front-rear direction are sandwiched by stepped portions protruding from the inner wall surface of the barrel and are thus immovable in the front-rear direction, the operating sound of the cam barrel is less likely to occur in addition to the collision sound between the locking projection and the cam portion accompanying the front-rear movement of the writing instrument body, and it is possible to provide an emerging and retracting writing instrument with a quieter emerging and retracting mechanism.

[0012] Furthermore, in the third gist, since the writing instrument body is non-rotatable, it is possible to prevent loss of force for rotating the cam barrel, and the user does not need to operate the knock portion with excessive force, and it is possible to provide an emerging and retracting writing instrument with a quieter emerging and retracting mechanism.

Brief Description of the Drawings

[0013]

Figure 1

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Figure 12

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Figure 18

Embodiments for Carrying Out the Invention

[0014] The present invention is a writing instrument such as a ball pen, a mechanical pencil, a brush pen, a felt pen, a marking pen, etc., and can be implemented as a retractable writing instrument in which a writing part such as a ball pen tip can protrude and retract from the front end opening of the shaft cylinder. Hereinafter, embodiments of the present invention will be described with reference to the drawings.

[0015] Fig. 1 is an external view of a ball pen 1 which is a retractable writing instrument according to an embodiment of the present invention, and Fig. 2 is a cross-sectional view taken along the line A-A' of Fig. 1. The ball pen 1 has a writing instrument body 3, a cam cylinder 4, and a coil spring 5 as an elastic member disposed inside a hollow cylindrical shaft cylinder 2.

[0016] The shaft tube 2 is composed of a front shaft 2a and a rear shaft 2b. The rear opening end of the front shaft 2a is inserted into the front end opening of the rear shaft 2b. Screw portions are provided on the outer wall surface of the rear opening end of the front shaft 2a and the inner wall surface of the front opening end of the rear shaft 2b respectively, and the front shaft 2a and the rear shaft 2b can be coupled by screw engagement. By releasing the screw engagement, the writing instrument body 3, the cam tube 4, etc. can be easily arranged and replaced.

[0017] The shaft tube 2 can adopt other configurations than those that can release the connection between the front shaft and the rear shaft in the middle of the front-rear direction as in this embodiment. For example, it can be configured as a single part extending in the front-rear direction, with an opening provided at the rear end for arranging each member inside, and a tail plug for closing the opening is detachably attached.

[0018] The front shaft 2a is a so-called two-color molded product. The primary side located on the inner side in the radial direction of the front shaft 2a is a member made of polypropylene resin, and the secondary side located on the outer side in the radial direction of the front shaft 2a is a member made of styrene-based triethyl phosphate resin. The outer wall surface of the front shaft 2a is subjected to satin finish processing and functions as a grip that is easy for the user to hold by hand.

[0019] In addition to being a two-color molded product as in this embodiment, the front shaft 2a can be configured in a desired shape by a known method. It can also be configured such that the grip is a separate member and covers the outer wall surface of the front shaft 2a.

[0020] As the material of the front shaft 2a, polypropylene resin, polycarbonate resin, acrylic resin, polyethylene resin, polyamide resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polyethylene naphthalate resin, vinyl chloride resin, ethylene vinyl alcohol copolymer, polyacrylonitrile resin, fluororesin, polyacetal resin, polyethylene terephthalate resin, polystyrene resin, ABS resin, silicone resin, elastomer, or a composite material containing these resins can be appropriately selected in consideration of moldability, durability, etc. Also, the molding method is not limited to two-color molding as in this embodiment, and various known methods can be appropriately selected.

[0021] On the rear side wall of the rear shaft 2b, a window hole 2ba is provided that extends in the front-rear direction and penetrates between the inside and outside of the rear shaft 2b. The writing instrument body 3 is connected via the window hole 2ba to a clip 6 which is a knock part exposed outside the shaft cylinder 2. When the clip 6 is operated from the rear to the front along the window hole 2ba, the writing instrument body 3 moves forward inside the shaft cylinder 2 in conjunction, which is a so-called side slide type.

[0022] The knock part only needs to be interlocked with the writing instrument body 3, and it can also be a so-called rear-end knock type in which it is exposed from the rear end of the rear shaft 2b and pressed forward to form a protruding state.

[0023] The rear shaft 2b is a member made of polycarbonate resin. As other materials for the rear shaft 2b, considering moldability, durability, etc., polypropylene resin, acrylic resin, polyethylene resin, polyamide resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polyethylene naphthalate resin, vinyl chloride resin, ethylene vinyl alcohol copolymer, polyacrylonitrile resin, fluororesin, polyacetal resin, polyethylene terephthalate resin, polystyrene resin, ABS resin, silicone resin, elastomer, or a composite material containing these resins can be appropriately selected.

[0024] The writing instrument body 3 is composed of a ball pen refill 3a and a slider 3b. The ball pen refill 3a is composed of a ball pen tip 3aa as a writing part and a pipe 3ab in which ink is stored inside. The ink inside the pipe 3ab is discharged onto the writing surface through the ball pen tip 3aa, and characters, pictures, etc. can be written and drawn.

[0025] The rear end of the ball pen refill 3a is inserted into a bottomed cylindrical part from the front end opening of the slider 3b. The ball pen refill 3a is not fixed inside the cylindrical part of the slider 3b and is loosely fitted so as to be rotatable in the circumferential direction.

[0026] The ballpoint pen refill 3a can be advanced by advancing the clip 6 inside the shaft cylinder 2 as described above. In front of the inner wall surface of the front shaft 2a, a stepped portion 2aa, which is an annular protrusion continuous in the circumferential direction, is provided. When the front end surface of the pipe 3ab abuts against the stepped portion 2aa, the advancement of the writing instrument body 3 stops.

[0027] On the outer wall surface of the pipe 3ab, two protrusions 3aba for the rear end of the coil spring are provided at equal intervals in the circumferential direction to abut against the rear end of the coil spring 5. Also, on the inner wall surface of the front shaft 2a, six ribs 2ab for the front end of the coil spring, which abut against the front end of the coil spring 5, are provided at equal intervals in the circumferential direction (two of the six are shown). The coil spring 5 is clamped between the protrusion 3aba for the rear end of the coil spring and the rib 2ab for the front end of the coil spring in a state of being contracted from its natural state, and constantly biases the writing instrument body 3 backward.

[0028] On the outer wall surface of the slider 3b, an operating protrusion 3ba and a locking protrusion 3bb are provided. By each protrusion abutting against the cam portion 4a of the cam cylinder 4 described later, the ballpoint pen tip can be projected and retracted from the front end opening of the shaft cylinder 2.

[0029] In this embodiment, the writing instrument body 3 is composed of the ballpoint pen refill 3a and the slider 3b. However, for example, by directly providing protrusions corresponding to the operating protrusion 3ba and the locking protrusion 3bb on the pipe 3ab, etc., the writing instrument body 3 can also be formed.

[0030] Figs. 3(a) and (b) are external perspective views of the cam cylinder 4. Fig. 3(b) shows the outer wall of the cam cylinder 4 transparently and shows a part of the cam portion 4a provided on the inner wall surface by a dotted line. The cam cylinder 4 is a cylindrical member provided with a through hole penetrating in the front-rear direction. The writing instrument body 3 is inserted into the through hole. A cam portion 4a is provided on the inner wall surface of the cam cylinder 4. When the writing instrument body 3 moves back and forth, the operating protrusion 3ba and the locking protrusion 3bb abut against the cam portion 4a, and the cam cylinder 4 can rotate around the outer periphery of the writing instrument body 3. The cam portion 4 is a member whose back-and-forth movement is restricted inside the shaft cylinder 2.

[0031] By providing the cam portion 4a on the inner wall surface of the cam cylinder 4, the degree of freedom in the design of the outer wall surface of the cam cylinder 4 is increased. In the present embodiment, the outer wall surface of the cam cylinder 4 can be made longer in the front-rear direction than the cam portion 4a. In other words, both front and rear end portions of the cam portion 4a in the front-rear direction are not exposed in the front-rear direction from both opening end portions of the through hole and are within the range in the front-rear direction of the inner wall surface of the cam cylinder 4. It is not necessary to provide other irregularities on the outer wall surface of the cam cylinder 4 for causing the cam cylinder 4 to function as a part of the cam mechanism. Therefore, it is not necessary to provide a portion that can serve as a fulcrum for causing rattling in the radial direction with respect to the inner wall surface of the shaft cylinder that abuts against the outer wall surface. As a result, the operating noise of the cam mechanism constituting the retracting mechanism can be made quiet, which is preferable.

[0032] The slider 3 and the cam cylinder 4 are members made of polyacetal resin. As other materials for the slider 3 and the cam cylinder 4, polypropylene resin, polycarbonate resin, acrylic resin, polyethylene resin, polyamide resin, polybutylene terephthalate resin, polybutylene naphthalate resin, polyethylene naphthalate resin, vinyl chloride resin, ethylene vinyl alcohol copolymer, polyacrylonitrile resin, fluororesin, polyethylene terephthalate resin, polystyrene resin, ABS resin, silicone resin, elastomer, or a composite material containing these resins can be appropriately selected in consideration of moldability, durability, etc.

[0033] Hereinafter, with reference to FIGS. 4 to 9, the cam mechanism constituting the retracting and extending mechanism in the present embodiment will be described. FIGS. 4 to 9 illustrate the slider 3 and the cam cylinder 4 developed in the circumferential direction so that the contact relationship between the slider 3 and the cam cylinder 4 can be visually recognized. Also, to facilitate understanding of the contact relationship between the slider 3 and the cam cylinder 4, the two members that are originally oriented radially toward each other are illustrated on the same plane. Specifically, it is illustrated from the viewpoint that the operating protrusion 3ba and the locking protrusion 3bb protrude from the back side to the front side of the drawing. Therefore, the cam portion 4a is illustrated from the outside of the cam cylinder 4, in other words, from the base side of the cam portion 4a (the hatching of the cam portion 4a is omitted for improved visibility). Hereinafter, the direction toward the right side of the drawing, which is the rotation direction of the cam cylinder 4, is defined as the front in the rotation direction, and the direction opposite to the front in the rotation direction and toward the left side of the drawing is defined as the rear in the rotation direction.

[0034] FIG. 4 is a developed view of the cam mechanism in the retracted state. This state is the state where the writing instrument body 3 is retracted the most inside the shaft cylinder 2. The locking protrusion 3bb and the cam portion 4a are provided at four locations each at equal intervals in the circumferential direction on the outer wall surface of the slider 3 and the inner wall surface of the cam cylinder 4, respectively. In the retracted state, the locking protrusions 3bb are alternately positioned between the cam portions 4a. The operating protrusion 3ba is provided at two locations at equal intervals in the circumferential direction on the outer wall surface of the slider 3.

[0035] FIG. 5 is a view of the writing instrument body 3 advanced from the state of FIG. 4. An operating surface 3baa is provided on the front end surface of the side wall of the operating protrusion 3ba. A front operating surface 4aa that contacts the operating surface 3baa is provided on the rear end surface of the side wall of the cam portion 4a and in the front in the rotation direction. The operating surface 3baa and the front operating surface 4aa are planes facing each other that are inclined rearward in the front-rear direction as they go forward in the rotation direction and forward in the front-rear direction as they go backward in the rotation direction.

[0036] Figure 6 is a view in which the writing instrument body 3 is advanced from the state of Figure 5. This state is the state in which the writing instrument body 3 has advanced the most inside the shaft cylinder 2. When the writing instrument body 3 is further advanced from the state of Figure 4 where the operating surface 3baa and the front operating surface 4aa are in contact, the cam cylinder 4 receives a circumferential force from the operating surface 3baa via the front operating surface 4aa and rotates forward in the rotational direction. Since the locking projection 3bb moves forward away from the cam portion 4a, it does not interfere with the rotation. When the front end surface of the pipe 3ab contacts the stepped portion 2ab and the advancement of the writing instrument body 3 stops, the rotation of the cam cylinder 4 also stops, and the state shown in Figure 6 is reached. At this time, since the coil spring 5 is compressed the most as the writing instrument body 3 advances, the biasing force acting on the writing instrument body 3 in the rearward direction becomes the maximum.

[0037] Figure 7 is a view in which the writing instrument body 3 is retracted from the state of Figure 6. A locking surface 3bba is provided on the rear end surface of the side wall of the locking projection 3bb. A protruding locking surface 4ac that contacts the locking surface 3bba is provided on the front end surface of the side wall of the cam portion 4a and in the forward direction of the rotational direction. The locking surface 3bba and the protruding locking surface 4ac are opposing planes that are inclined forward in the front-rear direction as they go forward in the rotational direction and inclined rearward in the front-rear direction as they go backward in the rotational direction.

[0038] Figure 8 is a view in which the writing instrument body 3 is retracted from the state of Figure 7 and is a developed view of the cam mechanism in the protruding state. When the writing instrument body 3 is further retracted from the state of Figure 6 where the locking surface 3bba and the protruding locking surface 4ac are in contact, the cam cylinder 4 receives a circumferential force from the locking surface 3bba via the protruding locking surface 4ac and rotates forward in the rotational direction. Since the operating projection 3ba moves rearward away from the cam portion 4a, it does not interfere with the rotation. There is a portion that forms a wall along the front-rear direction behind the protruding locking surface 4ba in the rotational direction. When the rear end surface of the side wall of the locking projection 3bb in the rotational direction contacts this portion, the retraction of the writing instrument body 3 and the rotation of the cam cylinder 4 stop, and the state shown in Figure 8 is reached.

[0039] Fig. 9 is a view showing the writing instrument body 3 advanced from the state of Fig. 8. At the rear end face of the side wall of the cam portion 4a and on the rear side in the rotation direction, a rear operating surface 4ab that contacts the operating surface 3baa is provided. The operating surface 3baa and the rear operating surface 4ab are opposing planes that are inclined rearward in the front-rear direction as they go forward in the rotation direction and forward in the front-rear direction as they go backward in the rotation direction. When the writing instrument body 3 is advanced from the state of Fig. 8, the operating surface 3baa and the rear operating surface 4ab come into contact. When the writing instrument body 3 is further advanced, the cam cylinder 4 receives a circumferential force from the operating surface 3baa via the rear operating surface 4ab and rotates forward in the rotation direction. Since the locking projection 3bb is separated forward from the cam portion 4a, it does not interfere with the rotation. When the front end face of the pipe 3ab contacts the stepped portion 2ab and the advancement of the writing instrument body 3 stops, the rotation of the cam cylinder 4 also stops.

[0040] When the writing instrument body 3 is retracted from the state of Fig. 9, it returns to the immersed state shown in Fig. 4. At the front end face of the side wall of the cam portion 4a and on the rear side in the rotation direction, an immersion guide surface 4ad that contacts the locking surface 3bba is provided. The immersion guide surface 4ad is a plane that faces the locking surface 3bba and is inclined forward in the front-rear direction as it goes forward in the rotation direction and rearward in the front-rear direction as it goes backward in the rotation direction. When the writing instrument body 3 is retracted from the state of Fig. 8, the locking surface 3bba and the immersion guide surface 4ad come into contact. When the writing instrument body 3 is further retracted, the cam cylinder 4 receives a circumferential force from the locking surface 3bba via the immersion guide surface 4ad and rotates forward in the rotation direction. When the cam cylinder 4 rotates until the immersion guide surface 4ad and the locking surface 3bba no longer contact each other, the locking projections 3bb are in an immersed state where they are alternately positioned between the cam portions 4a. The above is the cam mechanism in this embodiment, which is a mechanism that returns from the immersed state through the protruding state to the immersed state.

[0041] FIG. 10 is an enlarged cross-sectional view of the vicinity of the joint portion of the ballpoint pen refill 3a and the slider 3b. As described above, the cam cylinder 4 is a member whose forward and backward movement is restricted inside the shaft cylinder 2, and in the present embodiment, it is arranged so as not to be able to move forward and backward. On the inner wall surface of the rear shaft 2b, ribs 2bb extending in the front-rear direction are provided. Four ribs 2bb are provided at equal intervals in the circumferential direction. The front end surfaces of the respective ribs 2bb and the rear end surface of the front shaft 2a are in contact with both end surfaces of the cam cylinder 4 in the front-rear direction in the state where the shaft cylinder 2 is assembled, and function as a stepped portion for sandwiching the cam cylinder 4. Thereby, the cam cylinder 4 is arranged inside the shaft cylinder 2 so as not to be able to move forward and backward. Note that the inability to move forward and backward implies not only a state where the cam cylinder 4 does not move at all in the front-rear direction inside the shaft cylinder 2, but also a state where it moves forward and backward by the amount of clearance caused by molding tolerances and slight wear due to use.

[0042] Since the cam cylinder 4 is arranged inside the shaft cylinder 2 so as not to be able to move forward and backward, it is possible to make the ballpoint pen 1 with a retractable mechanism quieter, as the operating sound of the retractable mechanism is less likely to occur other than the collision sound between the locking surface 3bba, which is the operating sound of the cam mechanism, and the protruding locking surface 4ac. Specifically, when the cam cylinder 4 rotates as the writing instrument body 3 moves forward and backward, since the cam cylinder 4 does not move forward and backward, it does not collide with any of the inner wall surfaces of the shaft cylinder 2 and only collides with the writing instrument body 3. The forward and backward movement of the writing instrument body 3 is performed only by the biasing force backward by the coil spring 5 and the operation of the clip 6 by the user against the biasing force. When the writing instrument body 3 is in the advanced state, if the user releases the hand, particularly the finger, from the clip 6 or weakens the forward force while keeping the finger on the clip 6 to a level weaker than the biasing force backward by the coil spring 5, the writing instrument body 3 retreats. It is preferable that the retractable mechanism can be operated quietly regardless of the method of retreating the writing instrument body 3.

[0043] Figure 11 is an external perspective view of the slider 3. On the outer wall surface of the slider 3, there are provided sliding grooves 3bc extending in the front-rear direction. Two sliding grooves 3bc are provided at equal intervals in the circumferential direction. Among the four ribs 2bb provided on the inner wall surface of the rear shaft 2b, two ribs 2bb facing each other in the circumferential direction and corresponding to the sliding grooves 3bc have sliding ribs 2bba protruding radially inward from the front end surface toward the rear from the middle in the front-rear direction. The sliding ribs 2bba are inserted into the sliding grooves 3bc. When the front end surface of the sliding rib 2bba abuts against the front end surface of the sliding groove 3bc, the backward movement of the writing instrument body 3 stops. Further, as the sliding rib 2bba slides along the sliding groove 3bc, the slider 3 is disposed in a non-rotatable manner inside the shaft cylinder 2. Consequently, the writing instrument body 3 is disposed in a non-rotatable manner inside the shaft cylinder 2. Note that non-rotatable means not only a state where the slider 3 does not move at all in the circumferential direction inside the shaft cylinder 2, but also includes a state where the slider 3 rotates in the circumferential direction by a gap caused by molding tolerances or slight wear due to use. In the present embodiment, the ballpoint pen refill 3a is not fixed inside the cylindrical portion of the slider 3b and is loosely fitted so as to be rotatable in the circumferential direction. Since only the rotation of the slider 3 in the circumferential direction is restricted, for example, due to some impact accompanying the protrusion and retraction of the writing portion, only the ballpoint pen refill 3a may rotate slightly. However, even in such a case, it is considered that the writing instrument body 3 is non-rotatable in the present invention.

[0044] By disposing the writing instrument body 3 in a non-rotatable manner inside the shaft cylinder 2, it is possible to prevent loss of the force for the writing instrument body 3 to rotate the cam cylinder 4 during the operation of the cam mechanism. The cam cylinder 4 converts the front-rear movement of the writing instrument body 3 into a rotational direction and rotates. Conversely, the writing instrument body 3 receives a certain amount of reaction force from the cam cylinder 4. If the writing instrument body 3 rotates backward in the rotational direction due to this reaction force, the force for rotating the cam cylinder 4 is lost, and it becomes necessary to move the writing instrument body 3 back and forth with a greater force. By preventing such loss of force, the user does not need to operate the knock portion with an excessive force, and a ballpoint pen with a quieter protrusion and retraction mechanism can be obtained, which is preferable.

[0045] An annular projection 3bd is provided at the front end of the outer wall surface of the slider 3b that constitutes the writing instrument body 3. The rear of the annular projection 3bd is continuous with the front of the locking projection 3bb. The annular projection 3bd projects in a flange shape toward the outer side in the radial direction. When the rear of the slider 3 is inserted from the front of the through hole of the cam cylinder 4 provided with the cam portion 4a on the inner wall surface, the front end surface of the side wall of the cam portion 4a protruding radially inward finally abuts against the rear end surface of the side wall of the annular projection 3bd. Therefore, the cam cylinder 4 cannot be removed from the front of the slider 3.

[0046] The slider 3b that constitutes the writing instrument body 3 is disposed inside the rear shaft 2b within the rear shaft 2b. The slider 3b is connected to the clip 6 via the window hole 2ba. Since the connection portion intersects the front of the edge forming the window hole 2ba, the forward movement of the clip 6 is restricted. Therefore, the slider 3b is also restricted in forward movement inside the shaft cylinder 2 and cannot be removed from the front end opening of the rear shaft 2b.

[0047] Due to such a configuration, when the user replaces the ballpoint pen refill 3a due to ink consumption or ink color change, even if the screw engagement between the front shaft 2a and the rear shaft 2b is released, the slider 3b and the cam cylinder 4 will not accidentally fall off from the front end opening of the rear shaft 2b, and the user can easily replace the ballpoint pen refill 3a, which is preferable.

[0048] FIG. 12 is a longitudinal cross-sectional perspective view of the cam cylinder 4. It is a cross-sectional view of the cam cylinder 4 in the front-rear direction, showing a configuration in which the rear of the cam cylinder 4 is inclined toward the back side of the drawing and the front of the cam cylinder 4 is inclined toward the front side of the drawing. The radial heights of the protruding locking surface 4ac and the recessed guiding surface 4ad of the cam portion 4a are different, and the recessed guiding surface 4ad is lower than the protruding locking surface 4ac. From the rear in the rotation direction of the protruding locking surface 4ac, a protrusion provided with the recessed guiding surface 4ad on the front end surface extends forward in the front-rear direction. The protrusion itself is radially lower than the protruding locking surface 4ac over the front-rear direction, and a rear operating protrusion guiding surface 4ae continuous with the protruding locking surface 4ac is provided radially outward from the root portion of the protrusion. Similar to the protruding locking surface 4ac, the rear operating protrusion guiding surface 4ae is a plane inclined forward in the front-rear direction as it faces forward in the rotation direction and inclined rearward in the front-rear direction as it faces rearward in the rotation direction.

[0049] While referring to FIGS. 13 to 16, the state in which the slider 3b is inserted into the through hole of the cam cylinder 4 will be described in detail. FIGS. 13 to 16, similar to FIGS. 4 to 9, illustrate the slider 3 and the cam cylinder 4 developed in the circumferential direction so that the contact relationship between the slider 3 and the cam cylinder 4 can be visually recognized.

[0050] When inserting the rear of the slider 3b from the front of the through hole of the cam cylinder 4, depending on the circumferential positional relationship between the cam cylinder 4 and the slider 3b, there are cases where the operating protrusion 3ba contacts the cam portion 4a and cases where the operating protrusion 3ba does not contact the cam portion 4a and directly enters the space between the adjacent cam portions 4a in the circumferential direction.

[0051] FIG. 13 is a view showing the case where the operating protrusion 3ba contacts the cam portion 4a. The rear of the side wall of the operating protrusion 3ba is composed of two inclined surfaces, a front guiding surface 3bab in the forward rotation direction and a rear guiding surface 3bac in the rearward rotation direction. The front guiding surface 3bab is inclined forward in the front-rear direction as it faces forward in the rotation direction and inclined rearward in the front-rear direction as it faces rearward in the rotation direction, and is a plane facing the protruding locking surface 4ac and the rear operating protrusion guiding surface 4ae.

[0052] FIG. 14 is a view in which the cam cylinder 4 is advanced from the state of FIG. 13. The front guide inner surface 3bab abuts against any surface extending from the protruding locking surface 4ac to the rear operating projection guide surface 4ae. When the front guide inner surface 3bab abuts against the protruding locking surface 4ac, as the cam cylinder 4 advances, the cam cylinder 4 rotates forward in the rotational direction along their surfaces. Here, the radial height at the rear of the side wall of the operating projection 3ba is lower than the radial height of the projection provided with the recessed guide surface 4ad on the front end surface. In other words, the radial top surface at the rear of the side wall of the operating projection 3ba and the radial top surface of the projection provided with the recessed guide surface 4ad on the front end surface are dimensioned so as not to contact each other. As a result, even when the advancement and forward rotation in the rotational direction of the cam cylinder 4 proceed, the rear of the operating projection 3ba and the front in the rotational direction of the projection provided with the recessed guide surface 4ad on the front end surface do not collide. Furthermore, even when the advancement and forward rotation in the rotational direction of the cam cylinder 4 proceed, the front guide inner surface 3bab can smoothly abut against the rear operating projection guide surface 4ae. The cam cylinder 4 receives a circumferential force from the protruding locking surface 4ac and the rear operating projection guide surface 4ae via the front guide inner surface 3bab and rotates forward in the rotational direction.

[0053] Here, the radial height of the side wall of the operating projection 3ba is different between the front side provided with the operating surface 3baa and the rear side provided with the front guide inner surface 3bab and the rear guide inner surface 3bac, and the front side is higher. As a result, when the actuator 3 is inserted into the through hole of the cam cylinder 4, the rear side of the side wall of the operating projection 3ba can smoothly proceed with the insertion without being caught by the front side of the cam portion 4, and as described above, the operating surface 3baa can abut against the cam portion 4 and function as a cam mechanism, which is preferable.

[0054] FIG. 15 is a view in which the cam cylinder 4 is advanced from the state of FIG. 14. When the cam cylinder 4 is advanced from the state of FIG. 14, the contact with the cam portion 4a against which the operating projection 3ba was in contact at the time of the state of FIG. 14 is released. The operating projection 3ba is guided between the cam portion 4a and a cam portion 4a located rearward in the rotational direction from the cam portion 4a. When the cam cylinder 4 is further advanced, the state shown in FIG. 3 is reached, and the insertion of the slider 3b into the through hole of the cam cylinder 4 is completed.

[0055] FIG. 16 shows a case where the operating projection 3ba does not contact the front end surface of the side wall of the cam cylinder 4, unlike FIG. 13. On the side wall of the cam portion 4a with which the operating projection 3ba contacts in the state of FIG. 16, a front operating projection guide surface 4af is provided in front of the projection that extends farthest forward in the rotational direction among the cam portions 4a. A front operating surface 4aa is provided behind the front operating projection guide surface 4af in the front-rear direction. The rear guide surface 3bac and the front operating projection guide surface 4af are opposing planes that are inclined forward in the front-rear direction as they go rearward in the rotational direction and rearward in the front-rear direction as they go forward in the rotational direction.

[0056] When the rear guide surface 3bac and the front operating projection guide surface 4af come into contact, the cam cylinder 4 receives a circumferential force from the rear guide surface 3bac via the front operating projection guide surface 4af and rotates rearward in the rotational direction. Then, the operating projection 3ba is guided between the cam portion 4a and the cam portion 4a located forward of the cam portion 4a in the rotational direction, and the same state as in FIG. 15 is achieved. When the cam cylinder 4 is further advanced, the state shown in FIG. 3 is reached, and the insertion of the slider 3b into the through hole of the cam cylinder 4 is completed.

[0057] FIG. 17 is an external view of the clip 6 on the side of the shaft cylinder 2. A gate position 6a at the time of molding is provided on the side wall of the clip 6, which is a molded product of polycarbonate resin. On the outer wall surface of the clip 6 on the side of the shaft cylinder 2, a rib 6b that branches into three is provided. The gate position 6a is sandwiched in the front-rear direction by the ends of two of the three branches of the rib 6b, and the remaining one rib extends in a direction orthogonal to the front-rear direction, and the gate position 6a is located on the extension line thereof. By the rib 6b serving as a beam, the strength of the clip 6 is improved, and it is preferable that it is resistant to cracking and breaking even when bent.

[0058] FIG. 18 is an external view of the shaft cylinder 2 side of the clip 6 according to another embodiment. Similar to FIG. 17, the clip 6 is a molded product of polycarbonate resin. A gate position 6a at the time of molding is provided on the side wall of the clip 6. On the outer wall surface of the shaft cylinder 2 side of the clip 6, a rib 6b divided into four branches is provided. One of the four branches of the rib 6b is formed thick in the front-rear direction, and the gate position 6a is designed to fit within the front-rear direction range. With such a configuration, the thickness in the vicinity of the gate position 6a becomes large, and it is particularly preferable that it is resistant to cracking and breaking starting from the vicinity of the gate position 6a. Generally, the larger the thickness of a resin molded product, the more likely it is to generate so-called sink marks, which are unintended unevenness on the surface of the molded product. In the present embodiment, since the gate position 6a where the resin flows into the mold is arranged at the location where the thickness of the clip 6 increases, a sufficient amount of resin is filled in that location, making it less likely to generate sink marks, which is preferable. Also, in the present embodiment, since there is one more rib extending in a direction orthogonal to the front-rear direction than the rib 6b in FIG. 17, the strength of the clip 6 in the torsional direction is improved, which is preferable.

Description of reference numerals

[0059] 1 Ballpoint pen 2 Shaft cylinder 2a Front shaft 2aa Step portion 2ab Rib for the front end of the coil spring 2b Rear shaft 2ba Window hole 2bb Rib 2bba Sliding rib 3 Writing instrument body 3a Ballpoint pen refill 3aa Ballpoint pen tip 3ab Pipe 3aba Projection for the rear end of the coil spring 3b Slider 3ba Actuating projection 3baa Actuating surface 3bab Inner guiding surface in the front direction 3bac Inner guiding surface in the rear direction 3bb Locking projection 3bba Locking surface 3bc Sliding groove 3bd annular protrusion 4 cam barrel 4a cam portion 4aa front operating surface 4ab rear operating surface 4ac protruding locking surface 4ad recessed guiding surface 4ae rear operating protrusion guiding surface 4af front operating protrusion guiding surface 5 coil spring 6 clip 6a gate position 6b rib

Claims

1. A retractable writing instrument in which at least a writing instrument body and a cam cylinder are disposed inside a shaft cylinder, wherein the writing instrument body is disposed so as to be movable back and forth by a forward force by operation of a knock portion exposed outside the shaft cylinder and a backward biasing force by an elastic member, the cam cylinder is disposed so as to be at least rotatable around the outer periphery of the writing instrument body as the writing instrument body moves back and forth, and a locking projection provided on an outer wall surface of the writing instrument body locks to a cam portion provided on an inner wall surface of the cam cylinder, whereby at least a protruding state of a writing portion provided at a front end of the writing instrument body from a front end opening of the shaft cylinder is formed, and the writing instrument body has an operating projection provided on the outer wall surface of the writing instrument body so as to be located rearward of the locking projection, in the protruding state, the cam portion is configured to be located between the locking projection and the operating projection in the front-rear direction retractable writing instrument.

2. The retractable writing instrument according to claim 1, wherein both front and rear ends of the cam cylinder in the front-rear direction are sandwiched by stepped portions protruding from an inner wall surface of the shaft cylinder, so that the cam cylinder cannot move back and forth.

3. The retractable writing instrument according to claim 1 or claim 2, wherein the writing instrument body is disposed so as not to be rotatable by a sliding rib provided on an inner wall surface of the shaft cylinder or an outer wall surface of the writing instrument body sliding along a sliding groove extending in the front-rear direction provided on the outer wall surface of the writing instrument body or the inner wall surface of the shaft cylinder.

4. The cam cylinder has a plurality of cam portions provided with a front operating projection guide surface inclined with respect to the front-rear direction at the rear, the writing instrument body includes a slider having the locking projection and the operating projection provided with a rear guide surface inclined with respect to the front-rear direction at the rear, when the slider is inserted into the cam cylinder, the front operating projection guide surface provided at the rear of the plurality of cam portions abuts against the rear guide surface of the operating projection, and as the cam cylinder rotates in the circumferential direction, each of the operating projections is configured to be guided between a pair of circumferentially adjacent cam portions among the plurality of cam portions. The retractable writing instrument according to claim 1 or 2.

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