Mechanical pencil

Abstract

Provided is a mechanical pencil capable of automatically feeding a writing lead while maintaining a constant view of the pen tip. The mechanical pencil according to the present invention is provided with: an automatic feeding mechanism J in which a writing lead sn is automatically fed forward on the basis of a retracting action of a ball chuck 3 caused by pressing the writing lead sn against a writing surface and an advancing action of the ball chuck 3 caused by stopping the pressing of the writing lead sn against the writing surface; a rotation member 4 that rotates in one direction on the basis of the retracting action and the advancing action of the ball chuck 3; and a ball-chuck forward movement mechanism B that moves the ball chuck 3 forward with respect to the rotation member 4 in conjunction with the rotating action of the rotation member 4.

Description

Sharp pencil

[0001] The present invention relates to a sharp pencil used for writing.

[0002] Conventionally, there has been known a sharp pencil configured such that the tip pipe retreats according to the wear of the refill while writing with the tip pipe abutted against the writing surface. In such a sharp pencil, by releasing the abutment of the tip pipe against the writing surface, the tip pipe that has been in contact with the writing surface advances, and the refill can be fed forward (see, for example, Patent Document 1).

[0003] However, in the conventional one, since the tip pipe moves back and forth with respect to the shaft cylinder, the tip of the pen does not have a constant appearance, and it is likely to cause a sense of discomfort to the user during use.

[0004] Japanese Unexamined Patent Application Publication No. 2020-203423

[0005] The present invention has been made paying attention to the above circumstances, and at least provides a sharp pencil in which the tip of the pen is easily maintained in a constant appearance and the refill can be automatically fed out.

[0006] That is, the present invention has the following configuration.

[0007] The invention according to claim 1 is a sharp pencil provided with an automatic feeding mechanism in which the refill is automatically fed forward based on the backward movement of the ball chuck caused by pressing the refill against the writing surface and the forward movement of the ball chuck caused by releasing the pressing of the refill against the writing surface, and is provided with a rotating member that rotates in one direction based on the backward movement and forward movement of the ball chuck, and a ball chuck forward movement mechanism that moves the ball chuck forward with respect to the rotating member in accordance with the rotation operation of the rotating member.

[0008] The invention described in claim 2 is the mechanical pencil according to claim 1, wherein the ball chuck forward movement mechanism comprises a forward-facing guide cam surface provided on the rotating member and a guide cam receiving surface provided on the ball chuck that engages with the guide cam surface.

[0009] The invention described in claim 3 is a mechanical pencil according to claim 2, wherein the guide cam surface is provided with a stepped portion that moves the ball chuck, which has been moved to the furthest forward position by the ball chuck forward movement mechanism, to the furthest backward position.

[0010] The invention described in claim 4 is a mechanical pencil according to claim 3, comprising a barrel having a lead-extending opening at its tip, a ball chuck and a rotating member disposed inside the barrel with their axes aligned, wherein the ball chuck is disposed so as to be able to move back and forth relative to the barrel but not to be able to rotate around its axis.

[0011] The invention described in claim 5 is a mechanical pencil according to claim 4, wherein the rotating member comprises a rotating member body that is generally cylindrical in shape and has a rear cam surface at its rear end and a front cam surface at its front end, the shaft has a rear fixed cam surface that engages with the rear cam surface and a front fixed cam surface that engages with the front cam surface, and the rotating member is configured to rotate by alternately repeating the engagement between the rear cam surface and the rear fixed cam surface in the retraction movement and the engagement between the front cam surface and the front fixed cam surface in the advance movement.

[0012] The invention described in claim 6 is a mechanical pencil according to claim 5, wherein the rotating member has an inward projection that protrudes from the inner circumferential surface of the rotating member body toward the axis, and the guide cam surface is provided on this inward projection.

[0013] The invention described in claim 7 is a mechanical pencil according to claim 6, wherein the ball chuck has a plurality of protrusions that protrude rearward at a certain interval in the circumferential direction, and the guide cam receiving surface is provided at the protruding ends of these protrusions.

[0014] The invention described in claim 8 is a mechanical pencil according to claim 4, wherein a spring is provided with the shaft cylinder as a base, and an annular member is interposed between the rotating member and the spring, which slides against the rotating member.

[0015] The invention described in claim 9 is a mechanical pencil according to claim 4, wherein an annular member is interposed between the ball chuck and a spring that uses the barrel as a base, a first rotation restricting means is provided between the annular member and the barrel to restrict the relative rotation of the annular member with respect to the barrel, and a second rotation restricting means is provided between the annular member and the ball chuck to restrict the relative rotation of the annular member with respect to the ball chuck.

[0016] The invention described in claim 10 is a mechanical pencil according to claim 9, wherein the first rotation restricting means is composed of a protrusion provided on either the annular member or the barrel and a recess provided on the other that engages with the protrusion, and the second rotation restricting means is composed of a protrusion provided on either the annular member or the ball chuck and a recess provided on the other that engages with the protrusion.

[0017] The invention described in claim 11 is a mechanical pencil according to claim 4, wherein the barrel comprises a barrel body and a lead pipe having a feeding opening and being supported so as to be movable back and forth relative to the barrel body, and the lead pipe is always biased forward by a lead pipe biasing spring interposed between the ball chuck and the lead pipe.

[0018] The invention described in claim 12 is a mechanical pencil according to claim 1, comprising a barrel that houses the ball chuck and the rotating member inside, wherein the barrel comprises a barrel body and a lead pipe having a lead-feeding opening at its tip for extending the writing lead and being supported to move back and forth relative to the barrel body, and the lead pipe and the ball chuck are configured to move backward relative to the barrel body while maintaining a constant distance from each other.

[0019] As described above, the present invention provides a mechanical pencil in which the pen tip is easily maintained at a consistent position and the writing lead can be automatically advanced.

[0020] A perspective view showing one embodiment of the present invention. A right side view of the same embodiment. A perspective view of the same embodiment. A right side view of the same embodiment. A central longitudinal section view of the same embodiment. An exploded perspective view of the same embodiment. An exploded perspective view of the same embodiment. An exploded right side view of the same embodiment. A perspective view of the same embodiment. A perspective view of the same embodiment. A front view of the same embodiment. A perspective view of the same embodiment. A front view of the same embodiment. A right side view of the same embodiment. A rear view of the same embodiment. A perspective view of the same embodiment. An operation diagram of the same embodiment. An operation diagram of the same embodiment. An operation diagram of the same embodiment. A schematic side view for illustrating another embodiment.

[0021] Hereinafter, one embodiment of the present invention will be described with reference to Figures 1 to 19.

[0022] The mechanical pencil is equipped with an automatic feed mechanism J that automatically feeds the lead sn forward based on the retraction movement of the ball chuck 3 relative to the barrel A caused by pressing the lead sn against the writing surface, and the forward movement of the ball chuck 3 relative to the barrel A caused by the release of the pressure on the writing surface of the lead sn.

[0023] Furthermore, the mechanical pencil is equipped with a knock mechanism (not shown) that, by pressing on a knock part 7 located at the rear end, causes the ball chuck 3 to move back and forth relative to the barrel A, thereby extending the writing lead sn forward.

[0024] The mechanical pencil comprises a barrel A having a lead dispensing port pm at its tip for extending the writing lead sn, a lead pipe biasing spring 2 positioned inside the barrel A with its axis aligned and positioned behind the lead pipe P that constitutes the barrel A, a ball chuck 3 positioned behind the lead pipe biasing spring 2 and positioned inside the barrel A with its axis aligned, a rotating member 4 positioned with its axis aligned to surround the outer circumference of the front part of the ball chuck 3 and rotating in only one direction by a cam mechanism provided between it and the barrel A while moving back and forth based on the retraction and advancement movements of the ball chuck 3, an annular member 5 interposed between the barrel A and the ball chuck 3 to restrict the rotation of the ball chuck 3 relative to the barrel A, and a spring 6 interposed between the annular member 5 and the barrel A.

[0025] The mechanical pencil is provided with a ball chuck forward movement mechanism B between the ball chuck 3 and the rotating member 4, which moves the ball chuck 3 forward relative to the rotating member 4 in accordance with the unidirectional rotational movement induced by the rotating member 4.

[0026] The mechanical pencil is provided with a first rotation restricting means D between the annular member 5 and the barrel A, which restricts the relative rotation of the annular member 5 with respect to the barrel A.

[0027] The mechanical pencil is provided with a second rotation restricting means G between the annular member 5 and the ball chuck 3, which restricts the relative rotation of the annular member 5 with respect to the ball chuck 3.

[0028] The mechanical pencil of this embodiment will be described in detail below.

[0029] <<Shaft Body A>> The shaft body A comprises a shaft body 1 and a lead pipe P that has an opening pm from which the writing lead sn is dispensed and is supported so as to be able to move back and forth relative to the shaft body 1.

[0030] <Shaft Body 1> The shaft body 1 comprises a front shaft section 11 and a rear shaft section 12 that is mounted on the rear of the front shaft section 11 with its axis aligned. The front shaft section 11 and the rear shaft section 12 are capable of housing a writing lead sn, a lead pipe biasing spring 2, a ball chuck 3, a rotating member 4, an annular member 5, and a spring 6 in their internal spaces.

[0031] [Front shaft cylinder portion 11] The front shaft cylinder portion 11 includes a tip portion 111 that holds the core pipe P so as to be movable back and forth and whose outer surface is formed in a conical shape, a cylindrical front cylindrical portion 112 connected behind the tip portion 111, and a rear cylindrical portion 113 connected behind the front cylindrical portion 112 and having an inner diameter longer than that of the front cylindrical portion 112.

[0032] The tip portion 111 is provided with a core pipe holding hole 1h, which is drilled in the front-rear direction with the axis aligned, and in which a core pipe P is disposed to move back and forth.

[0033] The rear of the tip portion 111 is provided with a restricting surface 1m that engages with a flange portion p2 provided on the core pipe P. The restricting surface 1m of the tip portion 111 restricts the movement of the core pipe P, which is biased forward by a core pipe biasing spring 2 that uses the ball chuck 3 as a base.

[0034] The front cylindrical portion 112 has a shorter inner diameter than the rear cylindrical portion 113. At the annular rear end of the front cylindrical portion 112, a front fixed cam surface 11m is provided, which constitutes a cam mechanism and is arranged in a sawtooth pattern, facing rearward. The front fixed cam surface 11m is inclined so that it gradually moves forward as viewed clockwise from the rear. The front fixed cam surface 11m provided on the front cylindrical portion 112 interacts with the front cam surface 4f, which faces forward and is provided on the front end of the rotating member 4.

[0035] The rear cylindrical portion 113 is designed to accommodate the rear axle cylinder portion 12 at its rear. The front portion of the rear axle cylinder portion 12 is inserted into the rear of the rear cylindrical portion 113 and fixed in a predetermined position so as not to rotate relative to it.

[0036] [Rear Axle Cylinder Section 12] The rear axle cylinder section 12 is cylindrical in shape. Multiple (four) rear fixed cam surfaces 12m, which constitute a cam mechanism, are arranged on the front end surface of the rear axle cylinder section 12 at regular intervals and facing forward. The rear fixed cam surfaces 12m are inclined so that they gradually move forward as viewed in a clockwise direction from the front. The rear fixed cam surfaces 12m provided on the rear axle cylinder section 12 are in relation to the rear cam surface 4r provided on the rear end of the rotating member 4, which faces backward.

[0037] The inner circumferential surface of the rear shaft cylinder portion 12 is provided with recesses d2 that extend along the axis at regular intervals. As will be described in detail later, the recesses d2 constitute a first rotation restricting means D that restricts the relative rotation of the annular member 5 with respect to the shaft cylinder A.

[0038] A spring support portion 121, which functions as a foothold for the spring 6, is provided protruding from the inner circumferential surface of the rear of the rear axle cylinder portion 12 toward the axis.

[0039] <Lead Pipe P> The lead pipe P comprises a lead pipe body p1 provided with a lead dispensing opening pm and a lead passage hole ph, and a flange portion p2 projecting from the rear end of the lead pipe body p1 toward the opposite axis. The front end of the lead pipe biasing spring 2 abuts against the rear end surface of the lead pipe P.

[0040] A chuck (not shown) is provided in the lead passage hole ph of the lead pipe P. This chuck is roughly cylindrical in shape and made of synthetic resin (elastomer) or the like, and restricts the backward movement of the lead sn relative to the lead pipe P. The chuck provided in the lead pipe P constitutes the automatic lead feeding mechanism J.

[0041] The core pipe P is constantly biased forward by a core pipe biasing spring 2 interposed between the core pipe P and the ball chuck 3.

[0042] <<Lead Pipe Biasing Spring 2>> The lead pipe biasing spring 2 is interposed between the lead pipe P, which constitutes the tip of the barrel A, and the ball chuck 3. The lead pipe biasing spring 2 is a coil spring. The lead pipe biasing spring 2 has a hollow section that extends in the front-rear direction along the axis and through which the writing lead sn can pass.

[0043] When the rotating member 4 biased by the spring 6 is in the foremost position engaged with the front fixing cam surface 11m of the shaft cylinder A, the core pipe biasing spring 2 biases the ball chuck 3 rearward and functions to bring it into close contact with the rotating member 4.

[0044] <<Ball chuck 3>> The ball chuck 3 holds the writing core sn. The ball chuck 3 is arranged to be movable back and forth with respect to the shaft cylinder A and non-rotatable around the axis. The ball chuck 3 acts to allow the forward movement of the writing core sn and prevent the backward movement.

[0045] An automatic feeding mechanism J is provided in the ball chuck 3 for automatically feeding the writing core sn forward based on its forward and backward movement.

[0046] Although not shown in detail, the automatic feeding mechanism J is configured to be able to automatically feed the writing core sn forward based on the backward movement of the ball chuck 3 caused by pressing the writing core sn against the writing surface and the forward movement of the ball chuck 3 caused by releasing the pressing of the writing core sn against the writing surface. The automatic feeding mechanism J is such that a chuck body part (not shown), a fastener, and a plurality of balls interposed between the chuck body part and the fastener that constitute the ball chuck 3 cooperate, and the gripping and release of the writing core sn by the chuck body part are alternately performed in relation to the forward and backward movement of the writing core sn, enabling the writing core sn to be automatically fed forward.

[0047] The ball chuck 3 is configured to cause a backward movement when the writing core sn is pressed against the writing surface. Specifically, when the ball chuck 3 is pressed backward through the writing core sn, it moves backward against the biasing force of the spring 6 that presses the ball chuck 3 forward through the annular member 5 and the rotating member 4.

[0048] The ball chuck 3 is configured such that when the pressing force against the writing surface of the refill sn is released, a forward movement is induced. When the pressing force against the refill sn is released, the ball chuck 3 moves forward together with the annular member 5 and the rotating member 4 according to the biasing force of the spring 6.

[0049] The ball chuck 3 is configured to be biased forward by a spring 6 that uses a spring receiving portion 121 provided on the shaft cylinder A as a base. In this embodiment, the biasing force of the spring 6 is transmitted in the order of the annular member 5, the rotating member 4, and the ball chuck 3.

[0050] The ball chuck 3 is directly engaged with the rotating member 4 and the core pipe biasing spring 2. The ball chuck 3 is provided with a guide cam receiving surface b2 that engages with a guide cam surface b1 provided on the rotating member 4. The guide cam receiving surface b2 provided on the ball chuck 3 constitutes a ball chuck forward movement mechanism B.

[0051] More specifically, the ball chuck 3 is provided with a plurality (four) of convex portions 3t at regular intervals in the circumferential direction. The plurality (four) of convex portions 3t protrude rearward longer than the step dimension of a step portion b3 provided on the rotating member 4. The guide cam receiving surface b2 is provided at the protruding end of the convex portion 3t, that is, at a position facing rearward.

[0052] <<Rotating Member 4>> The rotating member 4 includes a rotating member main body 41 having a rear cam surface 4r at the rear end and a front cam surface 4f at the front end, which is generally cylindrical, and an inward protruding portion 42 protruding from the inner peripheral surface of the rotating member main body 41 toward the axis.

[0053] The rotating member 4 is biased forward by the spring 6. The rotating member 4 biased forward by the spring 6 is configured such that it cannot move forward beyond the engagement with the front fixed cam surface 11m of the shaft cylinder A.

[0054] <Rotating Member Body 41> The annular rear end of the rotating member body 41 is provided with a rear cam surface 4r that forms a cam mechanism and is arranged in a sawtooth shape, facing backward. The rear cam surface 4r is inclined so that it gradually moves backward as viewed clockwise from the rear. The rear cam surface 4r provided on the rotating member body 41 interacts with the rear fixed cam surface 12m that faces forward and is provided on the front end of the rear shaft cylinder portion 12.

[0055] The annular front end of the rotating member body 41 is provided with a front cam surface 4f that forms a cam mechanism and is arranged in a sawtooth pattern, facing forward. The front cam surface 4f is inclined so that it gradually moves forward as viewed clockwise from the front. The front cam surface 4f provided on the rotating member body 41 interacts with the rearward-facing front fixed cam surface 11m provided on the front cylindrical portion 112 that constitutes the front shaft cylinder portion 11.

[0056] <Inner projection 42> The inner projection 42 is annular in shape as a whole. The inner projection 42 has a guide cam surface b1 on the side facing forward. The guide cam surface b1 on the inner projection 42 engages with the guide cam receiving surface b2 provided on the ball chuck 3.

[0057] The guide cam surface b1 provided on the inward projection 42 of the rotating member 4 constitutes the ball chuck forward movement mechanism B. The guide cam surface b1 is inclined so that it gradually moves forward as viewed clockwise from the front. The degree of inclination of the guide cam surface b1 with respect to a virtual plane perpendicular to the axis is set to be gentler than the degree of inclination of the rear fixed cam surface 12m and front fixed cam surface 11m in the shaft cylinder A, and the rear cam surface 4r and front cam surface 4f in the rotating member body 41.

[0058] The guide cam surface b1 is divided into four sections in the circumferential direction via stepped sections b3. Specifically, the guide cam surface b1 is provided with stepped sections b3 that move the ball chuck 3, which has been moved to its furthest forward position (F) by the ball chuck forward movement mechanism B, to its furthest retracted position (R).

[0059] <Regarding the rotational movement of the rotating member 4> Here, we will explain the rotational movement of the rotating member 4 around its axis.

[0060] The rotating member 4 retracts relative to the barrel A together with the ball chuck 3 that holds the writing lead sn when the writing lead sn is pressed against the writing surface.

[0061] The guide cam receiving surface b2 provided on the inward projection 42 of the rotating member 4 is in contact with the guide cam receiving surface b2 provided on the convex portion 3t of the ball chuck 3. Therefore, the rotating member 4 is pressed by the ball chuck 3, which retracts together with the writing lead sn, and moves backward together with the ball chuck 3.

[0062] At this time, the rear cam surface 4r provided on the rotating member body 41 of the rotating member 4 engages with the rear fixed cam surface 12m provided on the rear shaft portion 12 of the shaft cylinder A as the rotating member 4 moves backward. The engagement between the rear cam surface 4r and the rear fixed cam surface 12m that constitute the cam mechanism causes the rotating member 4 to rotate counterclockwise when viewed from the front.

[0063] When the writing lead sn is no longer pressed against the writing surface, the rotating member 4 moves forward relative to the barrel A by the biasing force of the spring 6, following the ball chuck 3 that holds the writing lead sn.

[0064] At this time, the front cam surface 4f provided on the rotating member body 41 of the rotating member 4 engages with the front fixed cam surface 11m provided on the front shaft portion 11 of the shaft A as the rotating member 4 moves forward. The engagement between the front cam surface 4f and the front fixed cam surface 11m, which constitute the cam mechanism, causes the rotating member 4 to rotate counterclockwise when viewed from the front.

[0065] In other words, the rotating member 4 in this embodiment is configured to rotate in one direction, that is, in a counterclockwise direction when viewed from the front, by alternately repeating the interaction between the rear cam surface 4r and the rear fixed cam surface 12m as the ball chuck 3 moves backward, and the interaction between the front cam surface 4f and the front fixed cam surface 11m as the ball chuck 3 moves forward.

[0066] <<Annular Member 5>> The annular member 5 is an annular shape overall and is interposed between the rotating member 4 and the spring 6.

[0067] The front end of a spring 6 is connected to the rear end of the annular member 5. The annular member 5 is constantly biased forward by the spring 6, which uses the spring receiving portion 121 provided on the shaft cylinder A as a base. The front end of the annular member 5 is connected to the rotating member 4.

[0068] The annular member 5 comprises a front annular portion 51 provided at the front and having no protruding parts on its outer circumferential surface, and a rear annular portion 52 provided behind the front annular portion 51 and having a longer outer diameter than the front annular portion 51. The inner diameters of the front annular portion 51 and the rear annular portion 52 are set to the same dimensions.

[0069] <Front annular portion 51> The front annular portion 51 is circular in shape. The front end surface of the front annular portion 51 abuts against the back surface of the inward projection 42 provided on the rotating member 4.

[0070] <Rear annular portion 52> The rear annular portion 52 has outer protrusions d1, which are convex portions, provided on its outer surface at regular intervals.

[0071] The outer projection d1 provided on the rear annular portion 52 of the annular member 5 constitutes the first rotation restricting means D. That is, the outer projection d1 provided on the annular member 5 engages with the groove-shaped recess d2 provided on the rear shaft portion 12 of the shaft cylinder A.

[0072] The inner circumferential surface of the annular member 5, that is, the inner circumferential surface smoothly and continuously formed by the front annular portion 51 and the rear annular portion 52, is provided with inner protrusions g1, which are convex portions that extend along the axis at regular intervals in the circumferential direction.

[0073] The inner protrusion g1 provided on the inner circumferential surface of the annular member 5 constitutes the second rotation restricting means G. That is, the inner protrusion g1 provided on the annular member 5 is related to the recess g2 provided on the ball chuck 3.

[0074] <<Spring 6>> Spring 6 is a coil spring.

[0075] The biasing force of spring 6 is set to be stronger than that of core pipe biasing spring 2. The rear end of spring 6 is supported by a spring receiving portion 121 provided on the rear shaft portion 12 of shaft cylinder A. The front end of spring 6 is engaged with the rear end of the rear annular portion 52 of annular member 5.

[0076] In other words, the spring 6 uses the spring receiving portion 121 provided on the shaft cylinder A as a base to bias the rear annular portion 52, the rotating member 4, the ball chuck 3, and the core pipe biasing spring 2 forward.

[0077] <<Ball Chuck Forward Movement Mechanism B>> The ball chuck forward movement mechanism B moves the ball chuck 3, which grips the writing lead sn, forward.

[0078] The ball chuck forward movement mechanism B comprises a forward-facing guide cam surface b1 provided on the inward projection 42 of the rotating member 4, and a guide cam receiving surface b2 provided on the convex portion 3t of the ball chuck 3 that engages with the guide cam surface b1.

[0079] The operation of the ball chuck forward movement mechanism B will be explained.

[0080] When a user holding the barrel A brings the writing lead sn into contact with the writing surface to write, the pressure from the writing surface on the writing lead sn causes the ball chuck 3 to move backward against the biasing force of the spring 6.

[0081] As the ball chuck 3 moves backward, the convex portion 3t of the ball chuck 3, which is provided with the guide cam receiving surface b2, presses backward against the inward projection 42 of the rotating member 4, which is provided with the guide cam surface b1. The rotating member 4, which is pressed backward by the ball chuck 3, moves backward together with the ball chuck 3 against the biasing force of the spring 6.

[0082] As the rotating member 4 moves backward, the rear cam surface 4r of the rotating member 4 engages with the rear fixed cam surface 12m provided on the rear shaft portion 12 of the shaft A, and the rotating member 4 rotates in one direction (counterclockwise when viewed from the front) due to the guiding action of the cam.

[0083] When the user temporarily separates the writing lead sn from the writing surface, the pressure from the writing surface on the writing lead sn is released, and the rotating member 4, which is connected to the spring 6 via the annular member 5, and the ball chuck 3, which is connected to the rotating member 4, move forward due to the biasing force of the spring 6.

[0084] As the rotating member 4 and the ball chuck 3 move forward, the front cam surface 4f of the rotating member 4 engages with the front fixed cam surface 11m provided on the front shaft portion 11 of the shaft A, and the rotating member 4 rotates in one direction (counterclockwise when viewed from the front) due to the guiding action of the cam.

[0085] The rotating member 4 rotates in only one direction (counterclockwise when viewed from the front) by repeatedly performing the forward and backward movements described above in accordance with the user's writing motion, which brings the writing lead sn into contact with and away from the writing surface.

[0086] The ball chuck 3 is configured to move back and forth relative to the shaft cylinder A, but is configured not to rotate around its axis relative to the shaft cylinder A due to its interaction with the annular member 5.

[0087] When the rotating member 4 rotates in one direction, the guide cam surface b1, which is an inclined surface provided on the rotating member 4, also rotates. The ball chuck 3, which is provided with a guide cam receiving surface b2 that engages with the guide cam surface b1, is gradually pushed forward as the rotating member 4 rotates in one direction due to the guiding action of the cam.

[0088] In other words, the ball chuck forward movement mechanism B moves the ball chuck 3 forward relative to the rotating member 4 in conjunction with the unidirectional rotational movement induced by the rotating member 4.

[0089] Furthermore, the guide cam surface b1 is provided with a stepped portion b3 that moves the ball chuck 3, which has been moved to its furthest forward position (F) by the ball chuck forward movement mechanism B, back to its furthest backward position (R). The ball chuck 3, which has been guided by the ball chuck forward movement mechanism B from its furthest forward position (R) to its furthest forward position (F), moves back to its furthest backward position (R) in one swift motion at the stepped portion b3, as if to reset the process of its forward movement.

[0090] Furthermore, even when the ball chuck 3 moves to its rearmost position (R), the lead pipe P is held by the internal chuck to prevent the writing lead sn from retracting. Since the lead pipe P is biased forward by the lead pipe biasing spring 2, the writing lead sn itself does not retract but moves forward relative to the lead pipe P.

[0091] As described above, the mechanical pencil according to this embodiment is equipped with an automatic feeding mechanism J that automatically feeds the writing lead sn forward based on the retraction movement of the ball chuck 3 caused by pressing the writing lead sn against the writing surface and the forward movement of the ball chuck 3 caused by the release of the pressure on the writing lead sn against the writing surface.

[0092] The mechanical pencil is equipped with a rotating member 4 that rotates in one direction based on the retraction and advancement movements of the ball chuck 3, and a ball chuck forward movement mechanism B is provided that moves the ball chuck 3 forward relative to the rotating member 4 in conjunction with the rotational movement of the rotating member 4.

[0093] Therefore, this embodiment provides a mechanical pencil in which the pen tip, i.e., the tip of the barrel A, is easily maintained in a consistent position and the writing lead sn can be automatically advanced.

[0094] In other words, due to the action of the ball chuck forward movement mechanism B, the writing lead sn moves forward while wearing down during writing. As a result, the degree to which the writing lead sn protrudes outward from the pen tip is easily maintained at a constant level, making it less likely to cause any visual discomfort to the user at the pen tip.

[0095] The ball chuck forward movement mechanism B comprises a forward-facing guide cam surface b1 provided on the rotating member 4 and a guide cam receiving surface b2 provided on the ball chuck 3 that engages with the guide cam surface b1.

[0096] Therefore, the cam action induced by the guide cam surface b1 and the guide cam receiving surface b2 causes the ball chuck 3 to move favorably forward as the rotating member 4 rotates.

[0097] A stepped portion b3 is provided on the guide cam surface b1, which moves the ball chuck 3, which has been moved to its furthest forward position (F) by the ball chuck forward movement mechanism B, to its furthest retracted position (R).

[0098] Therefore, the forward movement of the ball chuck 3 can be appropriately reset by the stepped portion b3.

[0099] The device comprises a barrel A having a lead dispensing port pm at its tip for extending the writing lead sn, and a ball chuck 3 and a rotating member 4 disposed inside the barrel A with their axes aligned. The ball chuck 3 is positioned to be movable back and forth relative to the barrel A but not rotatable around its axis, and is biased forward by a spring 6 that uses the barrel A as a base.

[0100] Therefore, the ball chuck 3 maintains a stable position without relative rotation to the shaft cylinder A, allowing for favorable forward and backward movement.

[0101] The rotating member 4 comprises a rotating member body 41 that is roughly cylindrical in shape and has a rear cam surface 4r at its rear end and a front cam surface 4f at its front end. The shaft cylinder A has a rear fixed cam surface 12m that engages with the rear cam surface 4r and a front fixed cam surface 11m that engages with the front cam surface 4f. The rotating member 4 is configured to rotate by alternately repeating the engagement between the rear cam surface 4r and the rear fixed cam surface 12m during reversal movement and the engagement between the front cam surface 4f and the front fixed cam surface 11m during forward movement.

[0102] Therefore, the rotating member 4 rotates appropriately around the axis by utilizing the cam action resulting from the interaction between the rear cam surface 4r and the rear fixed cam surface 12m, and the interaction between the front cam surface 4f and the front fixed cam surface 11m.

[0103] The rotating member 4 is equipped with an inward projection 42 that protrudes from the inner circumferential surface of the rotating member body 41 toward the axis, and a guide cam surface b1 is provided on this inward projection 42.

[0104] Therefore, by using the rear cam surface 4r and the front cam surface 4f provided on the rotating member body 41 that constitutes the rotating member 4, a cam action is performed to rotate the rotating member 4 around its axis, and by using the guide cam surface b1 provided on the inward projection 42 that constitutes the rotating member 4, a cam action is performed to move the ball chuck 3 forward. Thus, different functions can be suitably performed by a single rotating member 4.

[0105] The ball chuck 3 is equipped with a plurality of protrusions 3t that are spaced at regular intervals in the circumferential direction and protrude rearward for a length greater than the step dimension of the stepped portion b3, and a guide cam receiving surface b2 is provided at the protruding ends of these protrusions 3t.

[0106] Therefore, the protrusion 3t on the ball chuck 3, which is provided with the guide cam receiving surface b2, is suitably engaged with the guide cam surface b1 on which the stepped portion b3 is provided.

[0107] An annular member 5 is interposed between the rotating member 4 and the spring 6, and slides against the rotating member 4.

[0108] Therefore, the annular member 5 functions as a washer, reducing frictional resistance with the rotating member 4, thereby allowing the rotating member 4 to rotate smoothly.

[0109] An annular member 5 is interposed between the ball chuck 3 and the spring 6, a first rotation restricting means D is provided between the annular member 5 and the shaft cylinder A to restrict the relative rotation of the annular member 5 with respect to the shaft cylinder A, and a second rotation restricting means G is provided between the annular member 5 and the ball chuck 3 to restrict the relative rotation of the annular member 5 with respect to the ball chuck 3.

[0110] Therefore, the annular member 5 functions appropriately to prevent the ball chuck 3 from rotating around its axis relative to the shaft cylinder A.

[0111] The first rotation restricting means D is composed of an outer protrusion d1 which is a convex portion provided on the annular member 5, and a recess d2 provided on the shaft cylinder A that engages with the outer protrusion d1.

[0112] The second rotation restricting means G is composed of an inner protrusion g1, which is a convex portion provided on the annular member 5, and a recess g2 on the ball chuck 3 that engages with the inner protrusion g1.

[0113] Therefore, the first and second rotation restricting means G prevent the ball chuck 3 from rotating around its axis relative to the shaft cylinder A.

[0114] The shaft A comprises a shaft body 1 and a core pipe P having a discharge port pm and being supported so as to be movable back and forth relative to the shaft body 1. The core pipe P is always biased forward by a core pipe biasing spring 2 interposed between the ball chuck 3 and the core pipe P.

[0115] Therefore, the lead pipe P maintains a suitable predetermined position relative to the barrel body 1, and even when the writing lead sn is continuously worn down without being separated from the writing surface, the lead pipe P can retract appropriately as needed.

[0116] It should be noted that the present invention is not limited to the embodiments described in detail above. The mechanical pencil may be configured such that the lead pipe and the ball chuck move backward relative to the barrel body while maintaining a constant distance from each other.

[0117] Figure 20 shows a schematic representation of the main parts of another embodiment of a mechanical pencil.

[0118] The mechanical pencil of this embodiment comprises a ball chuck 3 that holds a writing lead sn, a rotating member 4 that moves back and forth in conjunction with the reciprocating movement of the ball chuck 3 and rotates around its axis, a lead pipe biasing spring 2 interposed between the ball chuck 3 and the lead pipe P, and a barrel A that houses the ball chuck 3 and the rotating member 4 inside.

[0119] The barrel A comprises a barrel body (not shown) and a lead pipe P having a lead dispensing port pm at its tip for dispensing the writing lead sn, and being supported to move back and forth relative to the barrel body. In this embodiment, an intermediate member N is interposed between the rotating member 4 and the lead pipe P, having a front engaging portion n1 that engages with the flange portion p2 of the lead pipe P and a rear engaging portion n2 that engages with the rotating member 4. The lead pipe P and the ball chuck 3 are configured to move backward relative to the barrel body while maintaining a constant distance due to the action of the intermediate member N.

[0120] In other words, when the ball chuck 3, which holds the writing lead sn, retracts, the rotating member 4 retracts together with the ball chuck 3, and the intermediate member N, which is engaged with the retracting rotating member 4, retracts the lead pipe P.

[0121] Even with such a configuration, it is possible to achieve the intended purpose.

[0122] It goes without saying that the present invention can be modified in various ways without departing from its spirit.

[0123] It goes without saying that the number of teeth and meshing configuration of the rotating member having a cam surface and the fixed cam surface corresponding to the cam surface of the rotating member can be set as appropriate, as long as the rotating member can be rotated smoothly. For example, one side of the rotating member and the shaft cylinder may have a cam surface (or fixed cam surface) around its entire circumference, while the other side may have fixed cam surfaces (or cam surfaces) intermittently spaced at regular intervals.

[0124] The ball chuck forward movement mechanism only needs to be capable of moving the ball chuck forward relative to the rotating member in conjunction with the rotational movement of the rotating member, and its specific configuration is not limited to that shown in the embodiments described above.

[0125] The ball chuck may be configured such that its rotation around the axis is restricted by its engagement with the shaft cylinder.

[0126] The first rotation restricting means can be configured to restrict the relative rotation of the annular member with respect to the shaft cylinder. For example, the first rotation restricting means may consist of a protrusion provided on the shaft cylinder and a recess provided on the annular member.

[0127] The second rotation restricting means can be configured to restrict the relative rotation of the annular member with respect to the ball chuck. For example, the second rotation restricting means may consist of a protrusion on the ball chuck and a recess on the annular member.

[0128] Furthermore, the specific configuration of each part is not limited to the above embodiments, and various modifications are possible without departing from the spirit of the present invention.

[0129] 1...Main barrel body 2...Lead pipe biasing spring 3...Ball chuck 4...Rotating member 5...Annular member 6...Spring A...Barrel B...Ball chuck forward movement mechanism P...Lead pipe sn...Writing lead

Claims

1. A mechanical pencil equipped with an automatic lead feeding mechanism that automatically feeds the lead forward based on the retraction of the ball chuck caused by pressing the lead against the writing surface and the forward movement of the ball chuck caused by the release of the pressure on the writing surface of the lead, wherein the mechanical pencil is equipped with a rotating member that rotates in one direction based on the retraction and forward movement of the ball chuck, and is equipped with a ball chuck forward movement mechanism that moves the ball chuck forward relative to the rotating member in conjunction with the rotation of the rotating member.

2. The mechanical pencil according to claim 1, wherein the ball chuck forward movement mechanism comprises a forward-facing guide cam surface provided on the rotating member and a guide cam receiving surface provided on the ball chuck that engages with the guide cam surface.

3. The mechanical pencil according to claim 2, wherein the guide cam surface is provided with a stepped portion that moves the ball chuck, which has been moved to the furthest forward position by the ball chuck forward movement mechanism, to the furthest backward position.

4. The mechanical pencil according to claim 3, comprising a barrel having a lead-extending opening at its tip, and the ball chuck and the rotating member disposed inside the barrel with their axes aligned, wherein the ball chuck is disposed so as to be able to move back and forth relative to the barrel but not to be able to rotate around its axis.

5. The mechanical pencil according to claim 4, wherein the rotating member comprises a rotating member body that is generally cylindrical in shape and has a rear cam surface at its rear end and a front cam surface at its front end, the shaft has a rear fixed cam surface that engages with the rear cam surface and a front fixed cam surface that engages with the front cam surface, and the rotating member is configured to rotate by alternately repeating the engagement between the rear cam surface and the rear fixed cam surface in the retraction movement and the engagement between the front cam surface and the front fixed cam surface in the advance movement.

6. The mechanical pencil according to claim 5, wherein the rotating member has an inward projection that protrudes from the inner circumferential surface of the rotating member body toward the axis, and the guide cam surface is provided on this inward projection.

7. The mechanical pencil according to claim 6, wherein the ball chuck has a plurality of protrusions that protrude rearward at regular intervals in the circumferential direction, and the guide cam receiving surface is provided at the protruding ends of these protrusions.

8. The mechanical pencil according to claim 4, wherein a spring is provided with the shaft cylinder as a base, and an annular member is interposed between the rotating member and the spring, which slides against the rotating member.

9. The mechanical pencil according to claim 4, wherein an annular member is interposed between the ball chuck and a spring that uses the barrel as a base, a first rotation restricting means is provided between the annular member and the barrel for restricting the relative rotation of the annular member with respect to the barrel, and a second rotation restricting means is provided between the annular member and the ball chuck for restricting the relative rotation of the annular member with respect to the ball chuck.

10. The mechanical pencil according to claim 9, wherein the first rotation restricting means is composed of a protrusion provided on either the annular member or the barrel and a recess provided on the other that engages with the protrusion, and the second rotation restricting means is composed of a protrusion provided on either the annular member or the ball chuck and a recess provided on the other that engages with the protrusion.

11. The mechanical pencil according to claim 4, wherein the barrel comprises a barrel body and a lead pipe having a feeding opening and being supported so as to be movable back and forth relative to the barrel body, and the lead pipe is always biased forward by a lead pipe biasing spring interposed between the ball chuck and the lead pipe.

12. A mechanical pencil according to claim 1, comprising a barrel that houses the ball chuck and the rotating member inside, wherein the barrel comprises a barrel body and a lead pipe having a lead dispensing opening at its tip and being supported to move back and forth relative to the barrel body, and the lead pipe and the ball chuck are configured to move backward relative to the barrel body while maintaining a constant distance from each other.

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