Mechanical pencil

Abstract

In order to provide a mechanical pencil that can appropriately suppress the problem that the user may feel difficult to write because the core break prevention function always works, in a mechanical pencil having a core break prevention mechanism (C) that can retract the core (S) when an excessive writing pressure is applied to the core (S), it is configured to be able to switch between the case where the core break prevention mechanism (C) works and the case where the core break prevention mechanism (C) does not work based on the length (w3) of the core (S) protruding from the core tube (1) provided at the tip. Also, it is set that the core break prevention mechanism (C) does not work when the length (w3) of the core (S) is equal to or less than a predetermined value, and it is set that the core break prevention mechanism (C) can work when the length (w3) of the core (S) is greater than the predetermined value.

Description

Technical Field

[0001] The present invention relates to a mechanical pencil. Background Art

[0002] Conventionally, there has been known a mechanical pencil having a function of preventing the lead from breaking, which is configured such that when an excessive writing pressure is applied to the lead, the lead can retract into the tube. In order to make it difficult for the lead to break, the chuck holding the lead is provided so as to be movable rearward against the force of a spring (for example, see Patent Document 1).

[0003] However, in the mechanical pencil having the conventional configuration, the function of preventing the lead from breaking always operates during writing. In other words, in the conventional mechanical pencil having the function of preventing the lead from breaking, the force of the spring always acts on the lead.

[0004] Therefore, in the conventional mechanical pencil having the function of preventing the lead from breaking, the user feels difficulty in writing because the force of the spring always acts on the lead.

[0005] Prior Art Documents

[0006] Patent Documents

[0007] Patent Document 1: Japanese Patent Application Laid-Open No. 2011-37227 Summary of the Invention

[0008] Problems to be Solved by the Invention

[0009] The present invention has been made in view of the above circumstances, and provides a mechanical pencil capable of appropriately suppressing the problem that the user feels difficulty in writing because the function of preventing the lead from breaking always operates.

[0010] Means for Solving the Problems

[0011] That is, the present invention has the following configuration.

[0012] According to one embodiment of the present invention, there is provided a mechanical pencil including a lead break prevention mechanism that operates in such a manner as to make it difficult for the lead to break when an excessive writing pressure is applied to the lead, and the mechanical pencil is configured to be able to switch between a state in which the lead break prevention mechanism operates and a state in which the lead break prevention mechanism does not operate based on the length of the lead protruding from a lead tube provided at the tip.

[0013] According to another embodiment of the present invention, there is provided a mechanical pencil including a lead break prevention mechanism that operates in such a manner as to make it difficult for the lead to break when an excessive writing pressure is applied to the lead, and the mechanical pencil is configured to be able to switch from a state in which the lead break prevention mechanism operates to a state in which the lead break prevention mechanism does not operate based on a retraction operation of the lead tube provided at the tip.

[0014] According to the mechanical pencil described above, the mechanical pencil is set such that the core breakage prevention mechanism does not operate when the length of the core is below a predetermined value, and the mechanical pencil is set such that the core breakage prevention mechanism can operate when the length of the core is greater than the predetermined value.

[0015] According to the mechanical pencil described above, the core breakage prevention mechanism is configured to be able to move the chuck holding the core rearward against the force of a spring.

[0016] According to the mechanical pencil described above, the mechanical pencil is provided with an operation restriction unit that restricts the operation of the core breakage prevention mechanism. The operation restriction unit includes the core tube supported at the tip of the writing shaft so as to be able to move back and forth, and is configured to be able to operate only when the core tube is pressed by the writing surface and retracts.

[0017] According to the mechanical pencil described above, the operation restriction unit is provided with a movement restriction member that can change its posture between a first posture and a second posture. The first posture is a posture in which it does not engage with the core tube, and the second posture is a posture different from the first posture in which it engages with the core tube. The movement restriction member can restrict the backward movement of the chuck holding the core in the second posture.

[0018] According to the mechanical pencil described above, the core tube includes a tube portion extending in the front-rear direction and having the core inserted therein, and a slider portion integrally provided at the base end of the tube portion and having an outer diameter larger than that of the tube portion. When the core tube retracts and the rear end portion of the slider portion engages with the movement restriction member, the movement restriction member can change its posture from the first posture to the second posture.

[0019] According to the mechanical pencil described above, the mechanical pencil includes a chuck holding member that is externally fitted to the chuck and can open and close the chuck by relative movement in the front-rear direction. The chuck holding member is provided with a flange portion on its outer periphery. The movement restriction member includes an engagement claw that can engage with the flange portion in the second posture. By the engagement of the engagement claw with the flange portion, the backward movement of the chuck is restricted via the chuck holding member.

[0020] According to the mechanical pencil described above, all or a part of the writing shaft is configured such that its internal structure can be visually confirmed from the outside, and the operating states of the core breakage prevention mechanism and the operation restriction unit can be visually confirmed from the outside.

[0021] Advantages of the Invention

[0022] As described above, according to the present invention, it is possible to provide a mechanical pencil that can appropriately suppress the problem that the user may feel difficult to write because the core break prevention function always works. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 FIG. 1 is a side view showing an embodiment of the present invention.

[0024] Figure 2 FIG. 2 is a partially cut-away side view of the embodiment.

[0025] Figure 3 FIG. 3 is an explanatory view of the operation of the core break prevention mechanism in the embodiment.

[0026] Figure 4 FIG. 4 is an explanatory view of the operation of the operation restricting unit in the embodiment.

[0027] Figure 5 FIG. 5 is an explanatory view of the operation of the operation restricting unit in the embodiment.

[0028] Figure 6 FIG. 6 is Figure 4 a corresponding cross-sectional view of (a).

[0029] Figure 7 FIG. 7 is Figure 4 a corresponding cross-sectional view of (b).

[0030] Figure 8 FIG. 8 is an explanatory view of a component (locking frame) in the embodiment.

[0031] Figure 9 FIG. 9 is an explanatory view of a component (locking sleeve) in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0032] Hereinafter, an embodiment of the present invention will be described with reference to Figures 1 - 9 the accompanying drawings.

[0033] In this embodiment, the present invention is applied to a push-type mechanical pencil. The mechanical pencil includes a core break prevention mechanism C that operates in such a way that the core S is difficult to break when an excessive pen pressure is applied to the core S due to the writing operation of the user with respect to the writing surface M.

[0034] The mechanical pencil includes a writing shaft A that constitutes a part held by the user, a core pushing mechanism B mainly composed of a chuck 2 disposed inside the writing shaft A, a core break prevention mechanism C that causes the chuck 2 holding the core S (in this embodiment, a core with a thickness of 0.3 mm is used for the core S) to operate against the acting force of a buffer spring v2 as a spring, and an operation restricting unit D that can restrict the operation of the core break prevention mechanism C.

[0035] The core pushing-out mechanism B is disposed inside the writing shaft A, and has a core housing b1 capable of accommodating the core S, a chuck 2 connected to the front of the core housing b1, and a chuck holding member 3 externally mounted on the chuck 2 and configured to open and close the chuck 2 by relative movement in the front-rear direction with respect to the chuck 2.

[0036] The core break prevention mechanism C is disposed inside the writing shaft A and is configured to enable the chuck 2 holding the core S to move rearward against the force of the buffer spring v2.

[0037] The operation limiting unit D is disposed inside the writing shaft A and is configured to limit the operation of the core break prevention mechanism C by restricting the backward movement of the chuck 2 holding the core S.

[0038] Hereinafter, this mechanical pencil will be described in detail.

[0039] <Writing shaft A>

[0040] The writing shaft A serves as a housing for accommodating the internal mechanism of the mechanical pencil. The writing shaft A includes: a shaft tip portion a1 having a holding hole j at the tip through which the tube portion 11 of the core tube 1 can be inserted, and capable of holding the core tube 1 in a manner that allows forward and backward movement; a shaft front portion a2 having a cylindrical shape and connected to the rear of the shaft tip portion a1; and a shaft rear portion a3 having a cylindrical shape, with its front end connected to the rear of the shaft front portion a2 and its rear end open.

[0041] The shaft tip portion a1 includes: a conical portion a11 having a generally conical shape that tapers gradually forward in a side view, and having a holding hole j1 extending in the front-rear direction at the front end for holding the tube portion 11 of the core tube 1 in a manner that allows forward and backward movement; a front cylindrical portion a12 continuously provided after the conical portion a11 and having a diameter larger than that of the conical portion a11; and a rear cylindrical portion a13 continuously provided after the front cylindrical portion a12 and having a diameter larger than that of the front cylindrical portion a12.

[0042] The shaft tip portion a1 internally holds the locking sleeve 4 constituting the operation limiting unit D and the locking frame 5 holding the locking sleeve 4 in a non-movable manner in the front-rear direction. The entire shaft tip portion a1 is made of a transparent or semi-transparent synthetic resin and is configured to allow visual confirmation of the internal structure from the outside.

[0043] The shaft front portion a2 is connected to the shaft tip portion a1 by being externally fitted to the rear of the shaft tip portion a1. In addition, the shaft tip portion a1 is inserted from the rear end of the shaft front portion a2, and the front cylindrical portion a12 and the rear cylindrical portion a13 are internally fitted to the front of the shaft front portion a2 at predetermined positions. The entire shaft front portion a2 is made of a transparent or semi-transparent synthetic resin and is configured to allow visual confirmation of the internal structure from the outside.

[0044] On the front portion a2 of the shaft, a front recessed portion a21 that is recessed inward is provided on the outer peripheral surface at a position close to the engaging claw t of the movement restricting member 41 that constitutes the operation restricting unit D. Further, on the front portion a2 of the shaft, a rear recessed portion a22 that is recessed inward is provided on the outer peripheral surface at a position close to the gap sk of the core break prevention mechanism C.

[0045] The front recessed portion a21 serves as a concave lens that makes it easy to see inside. The front recessed portion a21 allows the user to easily visually confirm whether the operation restricting unit D is operating.

[0046] The rear recessed portion a22 serves as a concave lens that makes it easy to see inside. The rear recessed portion a22 allows the user to easily visually confirm whether the core break prevention mechanism C is operating.

[0047] The rear portion a3 of the shaft is connected to the front portion a2 by being threadedly engaged with the inner peripheral surface of the rear portion of the front portion a2 of the shaft. A cap b2 assembled to the rear end portion of the core housing b1 housed inside protrudes from the rear end portion of the rear portion a3 of the shaft. The cap b2 constitutes the core pushing mechanism B and serves as a push portion for the user to press forward in order to push out the core S.

[0048] The front edge of the rear portion a3 of the shaft abuts against the rear surface of the convex shoulder portion c21 provided at the rear end portion of the rear spring receiving sleeve c2 housed inside the front portion a2 of the shaft. The rear edge of the intermediate sleeve c3 abuts against the front surface of the convex shoulder portion c21 of the rear spring receiving sleeve c2. A stepped portion c32 provided on the outer peripheral surface of the front portion of the intermediate sleeve c3 is connected to the rear edge of the rear cylindrical portion a13 of the shaft tip portion a1.

[0049] That is to say, the intermediate sleeve c3 and the rear spring receiving sleeve c2 are sandwiched between the shaft tip portion a1 and the rear portion a3 of the shaft and are located therebetween, and their forward and backward movement is restricted. In other words, the intermediate sleeve c3 and the rear spring receiving sleeve c2 are positioned so as not to move forward and backward with respect to the writing shaft A. The locking sleeve 4 and the locking frame 5 disposed between the intermediate sleeve c3 and the shaft tip portion a1 are also positioned so as not to move forward and backward with respect to the writing shaft A.

[0050] On the other hand, the core tube 1, the chuck 2, the core housing b1, the cap b2, the chuck holding member 3, and the front spring receiving sleeve c1 are housed so as to be able to move forward and backward with respect to the writing shaft A.

[0051] Next, the core pushing mechanism B, the core break prevention mechanism C, and the operation restricting unit D provided inside the writing shaft A will be described in detail.

[0052] <Core Pushing Mechanism B>

[0053] The core ejection mechanism B can push the core S forward by pressing the cap b2, which is a pressing part provided at the rear end, forward against the force of the chuck spring v1, so that the chuck 2 can move forward relative to the chuck holding member 3 whose forward movement is restricted, and thus push the core S forward. That is, the core ejection mechanism B makes the chuck 2 alternately assume a posture of holding the core S and a posture of not holding the core S by the relative movement of the chuck 2 and the chuck holding member 3 in the front-rear direction, and ejects the core S.

[0054] The core ejection mechanism B includes: a chuck 2, which is a known structure having a core passage 21 provided in the axial center part and capable of assuming a posture of holding the core S and a posture of not holding the core S; a chuck holding member 3, which has a chuck insertion hole 32 for inserting the chuck 2, is externally fitted to the chuck 2, and can make the chuck 2 perform an opening and closing action by the relative movement in the front-rear direction with respect to the chuck 2; a core housing b1, which is integrally connected to the rear end part of the chuck 2 so that the axial centers are aligned, and can house the core S inside; a cap b2, which is detachably installed at the rear end part of the core housing b1; and a chuck spring v1, which is a spring for ejecting the core S and is interposed between the core housing b1 and the front spring receiving sleeve c1.

[0055] The chuck 2 is a known structure and is a brass member with a trident-shaped tip.

[0056] The chuck holding member 3 is provided with a chuck insertion hole 32 penetrating in the front-rear direction at the axial center part. At the tip part of the chuck insertion hole 32 in the chuck holding member 3, a chuck ring cr is provided to make the tip part of the chuck 2 perform an opening and closing action corresponding to the front-rear movement of the chuck 2. A gap is formed on the tip side of the chuck ring cr, which is the protruding margin of the core S during pressing.

[0057] The chuck holding member 3 includes a cylindrical flange part 31 provided at the outer periphery of the front part and a cylindrical positioning part 33 provided at the outer periphery of the rear part behind the flange part 31 in a convex shoulder shape. The front end face of the positioning part 33 engages with the convex shoulder part c31 provided at the front end part of the intermediate sleeve c3, restricting the forward movement of the chuck holding member 3.

[0058] The positioning part 33 is internally fitted into the recessed part c13 provided at the front end part of the front spring receiving sleeve c1. The chuck holding member 3 can move integrally backward with the front spring receiving sleeve c1 against the force of the buffer spring v2 when the core breaking prevention mechanism C comes into play.

[0059] The core housing b1 has a space formed inside that can accommodate the core S, and is shaped such that the accommodated core S can be introduced into the core passage 21 of the chuck 2. A cylindrical chuck connection portion b11 for connecting the rear end portion of the chuck 2 is provided at the front end portion of the core housing b1. A spring receiving step portion b12, which is a spring receiving portion for receiving the rear end portion of the chuck spring v1, is formed on the outer periphery of the chuck connection portion b11.

[0060] <Chip breakage prevention mechanism C>

[0061] When an excessive writing pressure is applied to the core S due to the writing operation of the user, the chip breakage prevention mechanism C can cause the core S to retreat against the acting force of the buffer spring v2. The chip breakage prevention mechanism C is configured such that the core S protruding forward from the tip st of the core tube 1 receives stress from the writing surface M due to the writing pressure based on the writing operation of the user, and can elastically retreat backward (buffer backward) against the acting force of the buffer spring v2.

[0062] The chip breakage prevention mechanism C includes: a chuck 2 that can hold the core S; a chuck holding member 3 that is externally fitted to the chuck 2 holding the core S and can perform a retreating action together with the chuck 2; a front spring receiving sleeve c1 that is connected to the rear end portion of the chuck holding member 3 and can move forward and backward integrally with the chuck holding member 3; a buffer spring v2 that is interposed between the front spring receiving sleeve c1 that can move forward and backward relative to the writing axis A and the rear spring receiving sleeve c2 that does not move forward and backward relative to the writing axis A; and an intermediate sleeve c3 that has a shoulder portion c31 as a movement restricting portion that can restrict the forward movement of the chuck 2, the chuck holding member 3, and the front spring receiving sleeve c1 applied with the force of the buffer spring v2, and can allow the chuck 2, the chuck holding member 3, and the front spring receiving sleeve c1 holding the core S to move backward within a certain range against the acting force of the buffer spring v2.

[0063] The front spring receiving sleeve c1 includes a front cylindrical portion c11 provided with a recessed portion c13 externally fitted to the positioning portion 33 of the chuck holding member 3 at the front end portion, and a rear cylindrical portion c12 that is continuously provided after the front cylindrical portion c11 and has a larger diameter than the front cylindrical portion c11.

[0064] A spring receiving flange c14, which is a spring receiving portion for receiving the front end portion of the chuck spring v1, is formed at the rear portion of the recessed portion c13 of the front cylindrical portion c11. In addition, a spring receiving step portion c15, which is a spring receiving portion for receiving the front end portion of the buffer spring v2, is formed on the inner peripheral surface of the front end portion of the rear cylindrical portion c12.

[0065] The rear spring receiving sleeve c2 has a cylindrical body c22 with a spring receiving flange c23 provided on the inner peripheral surface of the front portion as a spring receiving portion for receiving the rear end portion of the buffer spring v2, and a shoulder portion c21 formed at the rear end portion of the cylindrical body c22.

[0066] The intermediate sleeve c3 has a front cylindrical portion c33 provided with a shoulder portion c31 at the front end portion and a rear cylindrical portion c34 continuously provided at the rear portion of the front cylindrical portion c33 and having a diameter larger than that of the front cylindrical portion c33.

[0067] The front cylindrical portion c11 of the front spring receiving sleeve c1 is disposed inside the front cylindrical portion c33 of the intermediate sleeve c3, and positioning of the front spring receiving sleeve c1 in the vertical and horizontal directions, which can move back and forth relative to the intermediate sleeve c3, is performed. The rear cylindrical portion c12 of the front spring receiving sleeve c1 and the cylindrical body c22 of the rear spring receiving sleeve c2 are housed inside the rear cylindrical portion c34 of the intermediate sleeve c3.

[0068] A gap sk is provided between the rear end edge e1 of the front spring receiving sleeve c1 and the front end edge e2 of the rear spring receiving sleeve c2. That is, a gap sk that can allow the backward movement of the front spring receiving sleeve c1 constituting the broken core prevention mechanism C is provided between the rear end edge e1 of the front spring receiving sleeve c1 and the front end edge e2 of the rear spring receiving sleeve c2 located inside the intermediate sleeve c3.

[0069] A buffer spring v2 is provided between the front spring receiving sleeve c1 and the rear spring receiving sleeve c2, and both are urged in a separating direction. The front spring receiving sleeve c1 and the rear spring receiving sleeve c2 are separated and disposed with a gap sk having a predetermined width dimension w1 that allows compression of the buffer spring v2.

[0070] Then, the mechanical pencil of this embodiment is configured to be able to switch between a state (ON state) where the broken core prevention mechanism C operates and a state (OFF state) where the broken core prevention mechanism C does not operate based on the length w3 of the core S protruding from the tip st of the core tube 1.

[0071] That is, the mechanical pencil is set such that the broken core prevention mechanism C does not operate when the length w3 of the core S protruding from the tip st is below a predetermined value. In addition, the mechanical pencil is set such that the broken core prevention mechanism C can operate when the length w3 of the core S protruding from the tip st is larger than the predetermined value.

[0072] In addition, the "predetermined value" of the length w3 of the core S is a value at which the tip st of the core tube 1 and the tip sn of the core S can simultaneously contact the writing surface M. The length w3 of the core S protruding from the tip st of the core tube 1 is set to be approximately 0.06 mm in the case of writing at an angle of 60° with respect to the writing surface M as in the example of Figure 5 above.

[0073] The mechanical pencil is configured to be able to switch from the state (ON state) in which the core break prevention mechanism C operates to the state (OFF state) in which the core break prevention mechanism C does not operate based on the retraction operation of the core tube 1 that can move back and forth relative to the writing axis A.

[0074] If a more specific configuration is described, a working restriction unit D that restricts the operation of the core break prevention mechanism C is provided in the mechanical pencil. The working restriction unit D can operate in association with the core tube 1 provided at the tip of the writing axis A.

[0075] <Working restriction unit D>

[0076] The working restriction unit D includes the core tube 1 supported in a holding hole j1 at the tip portion a1 of the shaft in the writing axis A so as to be able to move back and forth, and is configured to be able to operate only when the core tube 1 is pressed by the writing surface M and retracts to a predetermined position that is a predetermined distance w2 behind the most forward position (G) and is located at the retracted position (H).

[0077] The working restriction unit D includes: a core tube 1 through which the core S is inserted in the central portion and can move forward and backward relative to the writing axis A; a locking sleeve 4 having a movement restricting member 41 that can engage with the core tube 1 to change the posture; a locking frame 5 that supports the locking sleeve 4 so as not to move back and forth relative to the writing axis A; and a chuck holding member 3 provided with a flange portion 31 that can engage with the movement restricting member 41 in the second posture (F).

[0078] The core tube 1 includes a tube portion 11 that extends in the front-rear direction and in which the core S is inserted, and a slider portion 12 integrally provided at the base end of the tube portion 11 and having an outer diameter larger than that of the tube portion 11. An unillustrated check member made of synthetic resin that engages with the core S is provided inside the slider portion 12. When the core tube 1 retracts rearward by abutting against the writing surface M and is in the retracted position (H), the rear end portion of the slider portion 12 can engage with the movement restricting member 41 of the locking sleeve 4.

[0079] The locking sleeve 4 includes: a movement restricting member 41 that can change the posture between the first posture (E) in which it does not engage with the core tube 1 and the second posture (F) in which it engages with the slider portion 12 of the core tube 1; an arm portion 42 that extends in the front-rear direction, and the rear end portion as one end is connected to the central portion in the front-rear direction of the movement restricting member 41; and a writing axis connecting portion 43 to which the front end portion as the other end of the arm portion 42 is connected and is embedded in the inner surface of the tip portion of the tip portion a1.

[0080] The movement restricting member 41 extends in the front-rear direction. The movement restricting members 41 are arranged in pairs above and below with the chuck holding member 3 therebetween. The movement restricting member 41 can act in a seesaw shape between a first posture (E) and a second posture (F) through elastic deformation of the arm portion 42 in the up-down direction.

[0081] On the inner surface side of the front end portion of the movement restricting member 41, a projection k having a cam surface km capable of engaging with the slider portion 12 of the core tube 1 is provided. In addition, on the inner surface side of the rear end portion of the movement restricting member 41, an engaging claw t capable of engaging with the flange portion 31 of the chuck holding member 3 in the second posture (F) to restrict the backward movement of the chuck holding member 3 is provided.

[0082] When the core tube 1 retreats from the foremost position (G) to the retreat position (H) and the rear end portion of the slider portion 12 engages with the cam surface km of the projection k of the movement restricting member 41, the movement restricting member 41 can change its posture from the first posture (E) to the second posture (F). In this embodiment, the distance w2 from the foremost position (G) to the retreat position (H) is set to 0.5 mm.

[0083] The cam surface km of the projection k abuts against the rear end peripheral portion 12a of the slider portion 12 in the core tube 1 that is pressed by the writing surface M and retreats from the foremost position (G) to the retreat position (H).

[0084] When the cam surface km of the projection k in the movement restricting member 41 in the first posture (E) abuts against the rear end peripheral portion 12a of the slider portion 12 in the core tube 1, due to the guiding action of the cam surface km, the front portion of the projection k moves outward (in the direction opposite to the axial direction), and the rear portion having the engaging claw t moves inward (axial direction), that is, toward the chuck holding member 3, and the movement restricting member 41 changes to the second posture (F).

[0085] The engaging claw t does not engage with the chuck holding member 3 in the first posture (E). On the other hand, the engaging claw t can engage with the flange portion 31 provided on the outer periphery of the chuck holding member 3 in the second posture (F).

[0086] The chuck holding member 3 restricts the backward movement of the chuck 2 holding the core S. Therefore, if the movement restricting member 41 is in the second posture (F) and the engaging claw t engages with the flange portion 31, the backward movement of the chuck holding member 3 is restricted, and the backward movement of the chuck 2 holding the core S via the chuck holding member 3 is also restricted.

[0087] That is, based on the movement of the core tube 1 that can move back and forth relative to the writing axis A from the foremost position (G) to the retracted position (H), the movement restricting member 41 that constitutes the working restriction unit D changes its posture from the first posture (E) to the second posture (F), and the chuck holding member 3 is switched from the state where it can retract to the state where it cannot retract. Thus, it is possible to switch from the state where the core break prevention mechanism C operates (ON state) to the state where the core break prevention mechanism C does not operate (OFF state).

[0088] The locking frame 5 is used to hold the locking sleeve 4 at a predetermined position within the shaft tip portion a1. The locking frame 5 includes: an annular portion 51 provided at the rear end portion; and left and right side walls 52 that project forward from the left and right side portions of the annular portion 51, and a pair of left and right fitting protrusions 52a that are fitted into the engaging concave portions 43a at the left and right side portions of the writing axis connecting portion 43 provided in the locking sleeve 4 are provided at the front end portion.

[0089] Positioning protrusions 51a that project outward and can engage with the rear edge of the front cylindrical portion a12 in the shaft tip portion a1 are formed at the upper and lower end portions of the annular portion 51.

[0090] Next, an example of the operation of the mechanical pencil having the above-described configuration will be described.

[0091] If the user presses the cap b2, which is the pressing portion, forward, then by the action of the core pushing mechanism B, the core S accommodated in the core tube 1 is pushed forward through the core passage 21 within the chuck 2. The core tube 1 disposed within the shaft tip portion a1 of the writing axis A moves forward together with the core S pushed forward by the core pushing mechanism B and is located at the foremost position, that is, the foremost position (G).

[0092] The mechanical pencil can, as in the example of Figure 5 write continuously with the core S slightly protruding from the tip st of the core tube 1 and in a state where core breakage is suppressed by the tube portion 11 of the core tube 1.

[0093] That is, as the writing continues and the core S gradually wears, the core tube 1 moves backward relative to the writing axis A. At this time, the tip st of the core tube 1 and the tip sn of the core S contact the writing surface M simultaneously, as in the example of Figure 5 .

[0094] On the other hand, in the case where the core S protrudes too much from the tip st of the core tube 1, as in the example of Figure 3 , the tip st of the core tube 1 cannot contact the writing surface M during writing. In the example of Figure 3 , the tip st of the core tube 1 does not contact the writing surface M, and only the tip sn of the core S held by the chuck 2 contacts the writing surface M. In this case, the core break prevention mechanism C of the mechanical pencil can operate.

[0095] That is, when an excessive pen pressure is applied to the core S due to the writing operation of the user on the writing surface M, the core break prevention mechanism C operates. If stress from the writing surface M is received relative to the core S, the chuck 2 holding the core S, the core housing b1, the cap b2, the chuck holding member 3 holding the chuck 2, the chuck spring v1, and the front spring receiving sleeve c1 connected to the chuck holding member 3 can move rearward against the acting force of the buffer spring v2.

[0096] A gap sk with a predetermined size w1 is provided between the front spring receiving sleeve c1 and the rear spring receiving sleeve c2. The core break prevention mechanism C can buffer (elastically retreat) the core S against the acting force of the buffer spring v2 by the gap sk with the predetermined size w1 provided between the front spring receiving sleeve c1 and the rear spring receiving sleeve c2.

[0097] In addition, in this embodiment, the size w1 of the gap sk is set to 0.85 mm. Through the core break prevention mechanism C, the core S can be buffered rearward by 0.85 mm.

[0098] In the case where the core tube 1 moves from the foremost position (G) to the retracted position (H) as the core S wears due to the user's continued writing on the writing surface M or when the core tube 1 is moved from the foremost position (G) to the retracted position (H) at the user's discretion, a working restriction unit D that can restrict the operation of the core break prevention mechanism C can function.

[0099] If the writing operation is continued in a state where the tip st of the core tube 1 abuts on the writing surface M, the core tube 1 that is in the foremost position (G) in the initial state before writing gradually moves rearward following the wear of the core S.

[0100] If the core tube 1 moves rearward by a certain size w2 (0.5 mm in this embodiment) from the foremost position (G) and reaches the retracted position (H), the rear peripheral edge portion 12a of the slider portion 12 in the core tube 1 abuts on the protrusion k of the movement restricting member 41 provided in the locking sleeve 4 in the first posture (E).

[0101] If the core tube 1 presses the cam surface km of the protrusion k rearward, then through the guiding action of the cam surface km, the front portion of the movement restricting member 41 provided with the protrusion k rotates about the fulcrum st in a direction opposite to the axial direction by the elastic deformation of the arm portion 42, and the rear portion of the movement restricting member 41 provided with the engaging claw t rotates about the fulcrum st in the axial direction by the elastic deformation of the arm portion 42, and the movement restricting member 41 changes its posture from the first posture (E) to the second posture (F).

[0102] When the movement restricting member 41 assumes the second posture (F), the engaging claw t provided at the rear portion of the movement restricting member 41 engages with the flange portion 31 of the chuck holding member 3, thereby being able to restrict the backward movement of the chuck holding member 3.

[0103] If the backward movement of the chuck holding member 3 is restricted, the chuck 2 embedded in the chuck holding member 3 cannot move backward either. As a result, the buffer spring v2 is not compressed via the front spring receiving sleeve c1, and thus the operation of the core break prevention mechanism C is restricted.

[0104] The core S does not receive the acting force of the buffer spring v2 and is not in a state where it can compress the buffer spring v2. That is to say, the operation of the core break prevention mechanism C is switched to the OFF state, and the phenomenon of "the core S bouncing" does not occur.

[0105] At this time, the core tube 1 is not restricted from moving backward by the movement restricting member 42 of the locking sleeve 4. The protrusion k of the movement restricting member 42 can move in the direction opposite to the axial direction as the core tube 1 retracts. Therefore, the core tube 1 can move backward relative to the writing shaft A even in a state where the operation restricting unit D is functioning. The core tube 1 can follow the movement of "the user writes on the writing surface M, and the tip sn of the core S wears and retracts".

[0106] The user can use the mechanical pencil to write in a state where the operation restricting unit D is operating and the operation of the core break prevention mechanism C is restricted until the tip st of the tube portion 11 is inserted into the shaft tip portion a1.

[0107] As described above, the mechanical pencil according to the present embodiment includes a core break prevention mechanism C that can retract the core S when an excessive writing pressure is applied to the core S. And the mechanical pencil is configured to be able to switch between the case where the core break prevention mechanism C operates and the case where the core break prevention mechanism C does not operate based on the length of the core S protruding from the core tube 1 provided at the tip.

[0108] Therefore, in the case of the mechanical pencil according to the present embodiment, it is possible to appropriately suppress the adverse situation that it is easy to cause writing difficulties for the user because the core break prevention function always functions.

[0109] Moreover, since it is configured to be able to switch between the case where the core break prevention mechanism C operates and the case where the core break prevention mechanism C does not operate based on the length of the core S protruding from the core tube 1 provided at the tip, the ON / OFF of the core break prevention mechanism C can be automatically switched without the user having to perform a switching operation arbitrarily.

[0110] It is set that when the length w3 of the core S is equal to or less than a predetermined value, the core break prevention mechanism C does not operate, and it is set that when the length w3 of the core S is greater than the predetermined value, the core break prevention mechanism C can operate.

[0111] Therefore, when the core S protrudes too much from the tip st of the core tube 1, it is possible to prevent core breakage by the action of the core break prevention mechanism C.

[0112] On the other hand, when the core S does not protrude too much from the tip st of the core tube 1, that is, when the length w3 of the core S is equal to or less than the predetermined value and the tip st of the core tube 1 and the tip sn of the core S are in contact with the writing surface M at the same time, the operation restricting unit D operates, and it is possible to prevent the core S from bouncing (elastically retracting).

[0113] The core break prevention mechanism C is configured to be able to move the chuck 2 holding the core S backward against the acting force of the buffer spring v2 serving as a spring.

[0114] Therefore, by elastically retracting the core S by compressing the buffer spring v2, it is possible to impart a certain buffering property to the core S that contributes to difficult breakability.

[0115] An operation restricting unit D for restricting the operation of the core break prevention mechanism C is provided. The operation restricting unit D includes a core tube 1 supported at the tip of the writing shaft A so as to be able to move back and forth, and is configured to be able to operate only when the core tube 1 is pressed by the writing surface M and retracts.

[0116] Therefore, it is possible to restrict the operation of the core break prevention mechanism C in association with the core tube 1.

[0117] The operation restricting unit D is provided with a movement restricting member 41 capable of changing its posture between a first posture (E) and a second posture (F). The first posture (E) is a posture in a case of not engaging with the core tube 1, and the second posture (F) is a posture different from the first posture (E) in a case of engaging with the core tube 1. The movement restricting member 41 can restrict the backward movement of the chuck 2 holding the core S in the second posture (F).

[0118] Therefore, it is possible to restrict the backward movement of the chuck 2 by the movement restricting member 41 whose posture is changed to the second posture (F) by engaging with the core tube 1.

[0119] The core tube 1 includes a tube portion 11 extending in the front-rear direction and having the core S inserted therethrough inside, and a slider portion 12 integrally provided at the base end of the tube portion 11 and having an outer diameter larger than that of the tube portion 11. When the core tube 1 retracts relative to the writing shaft A and the rear end peripheral portion 12a of the slider portion 12 as the rear end portion engages with the movement restricting member 41, the movement restricting member 41 can change its posture from the first posture (E) to the second posture (F).

[0120] Therefore, the posture of the movement restricting member 41 can be appropriately changed from the first posture (E) to the second posture (F) by the retracting movement of the core tube 1.

[0121] There is provided a chuck holding member 3 that is externally fitted to the chuck 2 and can open and close the chuck 2 by relative movement in the front-rear direction. The chuck holding member 3 is provided with a flange portion 31 on its outer periphery. The movement restricting member 41 has an engaging claw t that can engage with the flange portion 31 in the second posture (F). By the engagement of the engaging claw t with the flange portion 31, the retraction of the chuck 2 is restricted via the chuck holding member 3.

[0122] Therefore, the movement restricting member 41 can appropriately restrict the retraction of the chuck 2 via the chuck holding member 3.

[0123] A part of the writing shaft A is configured such that its internal structure can be visually confirmed from the outside. Also, the operating states of the core break prevention mechanism C and the operation restricting unit D can be visually confirmed from the outside.

[0124] Therefore, the user can use the mechanical pencil pleasantly and comfortably by being able to visually confirm the operating states of the core break prevention mechanism C and the operation restricting unit D.

[0125] In addition, the present invention is not limited to the embodiments described in detail above.

[0126] The core break prevention mechanism only needs to operate in such a way that the core is difficult to break when an excessive writing pressure is applied to the core, and its specific configuration is not limited to the configuration shown in the above embodiments. For example, it may be configured to advance the core tube when an excessive writing pressure is applied to the core.

[0127] Specific configurations that are configured to be able to switch between the case where the core break prevention mechanism operates and the case where the core break prevention mechanism does not operate based on the length of the core protruding from the core tube (core protruding size) can adopt various configurations.

[0128] The length of the core below a predetermined value set in such a way that the core break prevention mechanism does not operate and the length of the core greater than the predetermined value set in such a way that the core break prevention mechanism can operate can vary depending on the angle of writing on the writing surface by the user, the shape of the tip of the core tube, the thickness of the core, etc.

[0129] The writing shaft may be configured such that not only a part but also the whole of it can be visually confirmed from the outside. In addition, the configuration that allows the internal structure to be visually confirmed from the outside is not limited to using transparent components. For example, it may be configured to be able to visually confirm the inside from the outside by providing window holes.

[0130] In addition, as a configuration that allows the internal structure to be visually confirmed from the outside, convex portions at the front and rear that serve as convex lenses may be provided instead of the concave portions at the front and rear.

[0131] In addition, the specific configurations of the respective parts are not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

[0132] Explanation of Reference Numerals

[0133] A... Writing shaft

[0134] B... Core pushing mechanism

[0135] C... Core breakage prevention mechanism

[0136] D... Operation restriction unit

[0137] 1... Core tube

[0138] 2... Chuck

[0139] 3... Chuck holding member

[0140] 4... Chuck sleeve

[0141] 5... Locking frame

Claims

1. An automatic pencil, which is provided with a core break prevention mechanism that operates in such a way that the core is difficult to break when an excessive writing pressure is applied to the core. The automatic pencil is configured to be able to switch between a state in which the core break prevention mechanism operates and a state in which the core break prevention mechanism does not operate based on the length of the core protruding from the core tube provided at the tip. The core break prevention mechanism is configured to be able to move the chuck holding the core backward against the force of a spring. The automatic pencil is provided with an operation restriction unit that restricts the operation of the core break prevention mechanism. The operation restriction unit includes the core tube supported at the tip of the writing shaft so as to be able to move back and forth, and is configured to be able to operate only when the core tube is pressed by the writing surface and moves backward. The operation restriction unit is provided with a movement restriction member that can change its posture between a first posture and a second posture. The first posture is a posture when not engaged with the core tube, and the second posture is a posture different from the first posture when engaged with the core tube. The movement restriction member can restrict the backward movement of the chuck holding the core in the second posture.

2. An automatic pencil, which is provided with a core break prevention mechanism that operates in such a way that the core is difficult to break when an excessive writing pressure is applied to the core. The automatic pencil is configured to be able to switch from a state in which the core break prevention mechanism operates to a state in which the core break prevention mechanism does not operate based on the backward movement of the core tube provided at the tip. The core break prevention mechanism is configured to be able to move the chuck holding the core backward against the force of a spring. The automatic pencil is provided with an operation restriction unit that restricts the operation of the core break prevention mechanism. The operation restriction unit includes the core tube supported at the tip of the writing shaft so as to be able to move back and forth, and is configured to be able to operate only when the core tube is pressed by the writing surface and moves backward. The operation restriction unit is provided with a movement restriction member that can change its posture between a first posture and a second posture. The first posture is a posture when not engaged with the core tube, and the second posture is a posture different from the first posture when engaged with the core tube. The movement restriction member can restrict the backward movement of the chuck holding the core in the second posture.

3. The automatic pencil according to claim 1. The automatic pencil is set such that the core break prevention mechanism does not operate when the length of the core is equal to or less than a predetermined value. The automatic pencil is set such that the core break prevention mechanism can operate when the length of the core is greater than the predetermined value.

4. The automatic pencil according to claim 3. The predetermined value is a value at which the tip of the core tube and the tip of the core can simultaneously contact the writing surface.

5. The automatic pencil according to claim 1 or 2. The core tube includes a tube portion that extends in the front-rear direction and in which the core is inserted, and a slider portion integrally provided at the base end of the tube portion and having an outer diameter larger than the outer diameter of the tube portion. When the core tube retreats and the rear end portion of the slider portion engages with the movement restricting member, the movement restricting member can change from the first posture to the second posture.

6. The mechanical pencil according to claim 5, The mechanical pencil includes a chuck holding member that is externally fitted to the chuck and can open and close the chuck by relative movement in the front-rear direction. The chuck holding member is provided with a flange portion on its outer periphery. The movement restricting member includes an engaging claw that can engage with the flange portion in the second posture. By the engagement of the engaging claw with the flange portion, the retreat of the chuck is restricted via the chuck holding member.

7. The mechanical pencil according to claim 1 or 2, All or a part of the writing shaft has a structure that allows the internal components to be visually confirmed from the outside. The operating states of the broken lead preventing mechanism and the operation restricting unit can be visually confirmed from the outside.

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