Slider for mechanical pencil

Abstract: A slider (9) for a mechanical pencil comprises: a slider body (9b) provided with a through bore (9d) through which a lead is passed and disposed in the tip (2) of a barrel (1) so as to be axially slidable in a predetermined range; a lead guide (10) concentrically fixed to the slider body so as to let the lead slide therethrough; a sliding part (9c) concentrically connected to the outer circumference of the rear end of the slider body so as to extend forward and to be able to slide against a predetermined frictional resistance relative to the inner circumference of the tip (2); and a lead guiding part (9e) disposed in one end of the slider body and capable of expansion and of applying a frictional resistance smaller than that applied to the sliding part by the inner circumference of the tip, to the lead.

Description: BACKGROUND OF THE INVENTION Field of the Invention The present invention relates to a slider for a mechanical pencil and, more particularly, to a slider for a mechanical pencil provided with a lead guide which is forced to slide to project the lead. Description of the Related Art Generally, in a mechanical pencil having a tip member and a lead guide comprising a pipe and a chip and fixed to the front end of the tip member, the length of a portion of the lead projecting from the front end of the lead guide is limited to prevent the breakage of the lead. Therefore, when writing for a long time, a push head provided on the rear end of a lead tank must be frequently pushed as the lead wears to feed the lead. Since the grip on the mechanical pencil must be changed to push the push head for a lead feed operation, the lead feed operation reduces writing efficiency. A slide type mechanical pencil provided with a lead guide which is operated for sliding when the lead wears and a mechanical pencil capable of feeding a desired length of the lead by pressing the lead against the writing paper or the like without requiring the change of grip on the mechanical pencil have been proposed to solve such a problem. For example, the applicant of the present patent application proposed in JP-U-3-47907 a lead feed slider formed by concentrically arranging a larger tubular member and a smaller tubular member having a diameter different from that of the larger tubular member toward the rear, in which the larger tubular member is placed surely in sliding contact with the inner circumference of the tip member of a mechanical pencil so that a large frictional resistance acts thereon, and the smaller tubular member holds the lead securely so that a fixed frictional resistance acts on the lead. Referring to Figs. 1 to 3 showing this prior art lead feed slider, in a slider for a mechanical pencil, comprising a lead guide 11 disposed within the tip of a barrel so as to be axially slidable in a predetermined range, and a sliding member 12 fixed to the rear end of the lead guide 11, having an inner circumference capable of applying a fixed frictional resistance to the lead to hold the lead and an outer circumference in sliding contact with the inner circumference of the tip and capable of sliding against a frictional resistance greater than the frictional resistance acting on the lead, the sliding member 12 has a smaller tubular portion 13 and a larger tubular portion coaxial with the smaller tubular portion 13 and having a diameter larger than that of the smaller tubular portion 13, a plurality of axial recesses 15 are formed in the smaller tubular portion 13, the sliding member 12 is provided with an inner sliding piece 16 tapered toward a lead guiding part to hold the lead that slides through the lead guide by a frictional resistance, a plurality of recesses 17 formed in the larger tubular portion 14, and an outer sliding piece in sliding contact with the inner circumference of the tip and capable of sliding against a frictional resistance greater than the aforesaid frictional resistance. In the prior art slider thus formed, the larger tubular portion and the smaller tubular portion are formed concentrically backward in a single body, and an annular gap opening toward the rear is formed in the rear end through which the lead is fed. Therefore, when inserting the lead in the slider, the lead is liable to enter the gap and hence it is difficult to guide the lead forward. Consequently, there is the possibility that the lead is broken. Furthermore, particles of leads, fragments of leads and residual leads accumulated in the gap make the reliable action of the slider impossible. EP-A-0 210 280 representing the closest prior art from which the invention proceeds discloses a slider which has first and second axial tubular sections and a writing lead passageway extending through the coaxial tubular section. The second tubular section has an outer diameter larger than that of the first tubular section, and a double-walled structure comprising an outer tubular wall and an inner tubular wall. The tubular wall of the second tubular section is formed with first axially extending notches, each of which is opened at the rear end thereof. Similarly, the outer tubular wall of the second tubular section is formed with second axially extending notches, each of which is opened at the rear end thereof. Each of the first and second axially extending notches is opened at the rear end thereof as mentioned above, so that when a writing lead is fed toward the writing lead passageway by the writing lead feeding mechanism, a leading portion of the writing lead accidentially can enter anyone of the first and second axially extending notches of the slider and is liable to be caught in the notches. When the tip portion of the writing lead is caught in a notch, there is a possibility that the writing lead will be broken. In addition, when fragments of the broken writing lead are accumulated in the notches, reliable action of the slider will be prevented. EP-A-271 249 discloses a similar slider having the same disadvantages as mentioned above. SUMMARY OF THE INVENTION The present invention has been made to solve the foregoing problems and it is therefore an object of the present invention to provide a slider for a mechanical pencil, capable of preventing the breakage of the lead, of avoiding being stopped up with particles of the lead, of reliably guiding, holding and feeding the lead, and of enabling writing for a long time without changing the grip on the mechanical pencil. With the aforesaid object in view, the present invention provides a slider for a mechanical pencil, said pencil including a feeding mechanism for advancing a writing lead toward the slider and actuating means for actuating the feeding mechanism, said slider comprising a slider body provided with a through bore through which the lead is passed and disposed in the tip of a barrel so as to be adapted to be axially slid in a predetermined range by the feeding mechanism when the feeding mechanism is actuated by the actuating means, a lead guide concentrically fixed to the slider body so as to let the lead slide therethrough; a sliding part concentrically connected to the outer circumference of the slider body so as to be able to slide against a predetermined frictional resistance relative to the inner circumference of the tip, and a lead guiding means disposed in one end of the slider body and capable of expansion and of applying to the lead a frictional resistance smaller than that applied to the sliding part by the inner circumference of the tip, characterized in that the sliding part is concentrically connected to the outer circumference of the rear end of the slider body so as to extend forward. Further advantageous embodiments are defined in the dependent claims. According to the present invention, the sliding part formed concentrically on the outer circumference of the sliding body of the slider is able to be held in sliding contact with the inner circumference of the tip by a sufficiently large frictional resistance, the slider is able to hold the lead securely by the lead guiding means provided on the sliding body by the agency of the predetermined frictional resistance, any gap is not formed because the rear end of the slider body and the rear end of the sliding part are jointed together and hece particles of lead, broken leads and residual leads are not accumulated and the lead can be smoothly guided toward the tip. Since the lead guiding means is flexible to facilitate the advancement of the lead, the lead can be reliably guided, held and advanced. US-A-4 281 939 discloses a lead protective device provided in the mechanical pencil, but not a slider in the meaning of the present invention. Namely, such lead protective device is not disposed in the tip of a barrel like the slider according to the present invention, but extends out of an insertion hole at a forward end tube of a pencil body. The lead protective device is slidably mounted in the forward end tube and slidably in and out of the insertion hole. At the rearward end of a lead insertion tube of such lead protective device there is a lead guide having a funnel-shaped lead guide hole and an integral check flange provided on the outside thereof. Such flange is not engaged with the inner surface of the front cavity in the forward end tube over the most part of the axial length of such cavity since the diameter of the most part of the cavity is larger than that of the flange. So, the flange cannot be subject to a whatsoever frictional resistance by the inner circumference of the forward end tube in accordance with the teaching of the present invention. Rather, the flange serves as a stop both in the forward and rear-ward end positions of the lead protective device in order to prevent the lead protective device from fully slipping out of or into the forward end tube resulting in a malfunction of the mechanical pencil. Namely, the flange is fixedly mounted to the lead insertion tube of the lead protective device. Therefore, the flange has no resilient characteristics at all, which is a further reason for that the flange is not able to have the function of the sliding part in accordance with the teaching of the present invention. Further, whereas in accordance with the teaching of the present invention the slider and, thus, the sliding part cooperates with the feeding mechanism for advancing the lead toward the slider, the lead protective device of US-A-4 281 939 is provided separately from and independently upon the feeding mechanism. This is because the lead protective device has not the function to guide the lead within the barrel of the pencil, but to preclude the lead from slipping out due to its own weight when released from the lead sustaining and feeding mechanism thereby minimizing the loss of lead. After all, the present invention is not obvious from US-A-4 281 939. BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following description taken in connection with the accompanying drawings, in which: Fig. 1 is a front view of a slider included in a conventional mechanical pencil; Fig. 2 is a right end view of the slider of Fig. 1; Fig. 3 is a sectional view of the slider taken on line D-D in Fig. 1 Fig. 4 is a longitudinal sectional view of an essential portion of a mechanical pencil provided with a slider in a first embodiment according to the present invention; Fig. 5 is an enlarged front view of a slider shown in Fig. 4, in which lead guide is removed; Fig. 6 is a left end view of the slider of Fig. 5; Fig. 7 is a right end view of the slider of Fig. 5; Fig. 8 is a longitudinal sectional view of the slider of Fig. 5; Fig. 9 is a sectional view of the slider taken on line A-A in Fig. 5; Fig. 10 is a front view of a slider in a second embodiment according to the present invention; Fig. 11 is a left end view of the slider of Fig. 10; Fig. 12 is a right end view of the slider of Fig. 10; Fig. 13 is a sectional view of the slider taken on line B-B in Fig. 10; Fig. 14 is a sectional view of the slider taken on line C-C in Fig. 10; and Fig. 15 is a longitudinal sectional view of an essential portion of a mechanical pencil, showing the slider of Fig. 10 in an operating state. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figs. 4 to 8 show a slider in a first embodiment according to the present invention. Referring to Fig. 4, a tip 2 is formed on the front end of a barrel 1 integrally with the barrel 1. A lead tank 3 is inserted in the barrel 1 coaxially for sliding movement, and a lead chuck 4 is fixedly attached to the front end of the lead tank 3. A knocking cap, not shown, is detachably put on the rear end of the lead tank 3 so as to slide relative to the barrel 1. A chuck ring 5 is put loosely on the front end of the lead chuck 4. The rear end of the chuck ring 5 faces an inside flange 6a formed on the inner surface of the front end of a cushion sleeve 6 axially movable within the barrel 1. The cushion sleeve 6 is an elastically deformable member and has a generally cylindrical shape. The rear end of the cushion sleeve 6 is expanded to form a stopping part 6c having a diameter greater than the outside diameter of the body part 6b. A radial recess 6d is formed in the body part 6b and an axial recess 6e is formed in the rear end to enable the stopping part 6c to produce a resilient force relative to the body part 6b. The stopping part 6c is formed in a shape so that the stopping part 6c can be surely and smoothly fitted in a stopping hole 1a formed in the barrel 1 when the cushion sleeve 6 is inserted together with a lead feed mechanism in the barrel 1 by a simple pushing action and the stopping part 6c will not rattle in the stopping hole 1a. The body part 6b moves elastically in a range corresponding to the axial gap G of the recess 6d relative to the stopping part 6c held in the stopping hole 1a. Normally, the body part 6b is biased forward. A chuck spring 7 is interposed between the front end of the lead tank 3 and the flange 6a of the cushion sleeve 6 to bias the lead tank 3 backward. The front portion of the tip 2 is tapered toward the front in the shape of a circular cone. A tapered stopping step 8 is formed between portions of different diameters of the inner circumference of the front portion of the tip 2. A slider 9 having stopping parts 9a is axially slidably fitted in the front portion of the tip 2. The forward movement of the slider 9 is limited by the step 8. As shown in Figs. 5 to 9, the slider 9 has a substantially cylindrical slider body 9b, and a sliding part 9c. The respective rear ends of the slider body 9b and the sliding part 9c are joined together in an integral piece. The slider 9 is an integral member formed of a synthetic resin, such as an ABS resin or a polyacetal resin. The front portion of the slider 9 is pressed in a lead guide 10 for surely guiding the lead, i.e., a tip member. The lead guide 10 is neither abraded nor damaged even if the same strikes on a paper sheet or the like during writing. Since the lead is held by the front portion of the slider 9 and only the outer surface of the slider body 9b is available for attaching, the lead guide 10 as shown in Fig. 4 is a suitable tip member. A lead guiding part 9e for holding the lead is formed in the front portion of the slider body 9b. More specifically, the lead guiding part 9e is provided with a bore tapering toward the front, a plurality of slits 9f extending backward from the front end, and lead holding protrusions 9g on the inner surface of the front end. The rear end of the slider body 9b and the rear ends of the sliding part 9c are joined concentrically in an integral piece. In this embodiment, the sliding part 9c has two sliding lugs extending toward the front and capable of radially and elastically strained. In a free state, i.e., in a state before the slider 9 is inserted in the tip 2, the outside diameter of the rear end of the sliding part 9c is greater than the inside diameter of the tip 2. Protrusions 9h are formed on the outer circumference of the sliding part 9c. A frictional resistance that acts on the outer circumference of the sliding part 9c when the sliding part 9c is brought into contact with the inner surface of the tip 2 is far greater than a frictional resistance applied to the lead by the inner surfaces of the lead holding protrusions 9g. The operation of the slider in this embodiment will be described hereinafter with reference mainly to Fig. 4. In a state where any external force is not applied to the rear end of the lead tank 3, the cushion sleeve 6 is held at the front end of the range of its movement, and the lead is held firmly by the front end of the lead chuck 4 because the lead chuck 4 is biased backward relative to the chuck ring 5 as shown in Fig. 4. When the knocking cap, not shown, is knocked to push the lead tank 3 forward in this state, the lead chuck 4 is moved forward together with the chuck ring 5, and then the chuck ring 5 is disengaged from the lead chuck 4 and only the lead chuck 4 advances further to release the lead after the chuck ring 5 has been brought into contact with a step 2a formed in the inner surface of the tip 2. When the force applied to the knocking cap is removed, the lead tank 3 is moved backward together with the lead chuck 4, the chuck ring 5 comes into contact with the front end of the cushion sleeve 6 and squeezes the front end of the lead chuck 4 to hold the lead, and then the lead tank 3 stops. This lead feed operation is repeated to feed the lead stepwise. The length of the lead by which the lead is fed by one cycle of the lead feed operation is approximately equal to the distance between the front end of the chuck ring 5 and the step 2a. When the lead feed operation is performed to advance the lead, the lead advances through the lead guide 10 because the frictional resistance applied to the lead by the protrusions 9g of the lead guiding part 9e is smaller than the frictional resistance applied to the protrusions 9h of the sliding part 9c by the inner circumference of the tip 2. Then, the mechanical pencil, similarly to the ordinary mechanical pencil, is used for writing. When the tip of the lead is abraded or broken during writing, the remaining part of the lead is pressed against the paper sheet or the like without changing the hold on the barrel 1. Then, a backward force acts on the lead chuck 4 holding the lead and the lead tank 3 to move the lead chuck 4 and the lead tank 3 together with the chuck ring 5 and the cushion sleeve 6 backward against the resilience of the stopping part 6c. The range of backward movement is about 0.5 to about 1.0 mm. Since the stopping parts 9a formed at the front end of the sliding part 9c are in contact with the step 8 of the barrel 1, the size of the range for the backward movement of those components is G at the maximum. When the lead is moved backward to the front end of the lead guide 10, the paper sheet applies a pressure to the lead guide 10 and the lead guide 10 moves backward together with the slider 9. When the lead is moved to the rear end of the range of its movement, the position of the lead coincides with that of the lead guide 10. When the pressure pressing the barrel 1 toward the paper sheet is removed, the resilience of the flexed stopping part 6c moves the body part 6b of the cushion sleeve 6 forward to the front end of the moving range and, consequently, the chuck ring 5 advances together with the lead chuck 4 and the lead held by the lead chuck 4 to its original position. However, the lead guide 10 is restrained from advancement by the large frictional resistance applied by the inner circumference of the tip 2 to the protrusions 9h of the sliding part 9c and hence the front end of the lead projects from the tip of the lead guide 10 by a length corresponding to the distance by which the lead guide 10 has been moved backward. The same operation can be repeated until the lead guide 10 reaches the rear end of its moving range. If it is desired to further project the lead from the lead guide 10 after the lead guide 10 has reached the rear end of its moving range, the lead tank 3 is pushed axially for lead feed operation. When the lead tank 3 is pushed axially, the lead chuck 4 advances releasing the lead, the lead chuck 4 comes into contact with the rear end of the slider 9 and moves the slider 9 to the front end of its moving range. Then, the lead advances together with the slider 9 and hence the front end of the lead remains at the tip of the lead guide 10. When the force applied to the lead tank 3 is removed, lead chuck 4 moves backward leaving the lead and the lead guide 10 at the same position, and stops after engaging with the chuck ring 5. The lead can be advanced gradually by a predetermined distance at a time by repeating the lead feed operation. In the slider in the first embodiment, the lead guiding part 9e is at the front end of the slider body 9b, any projection is not formed in the surface of a through bore 9d formed in the slider body 9b and the through bore 9d is a straight bore extending from the rear end of the slider body 9b to the lead guiding part 9e. Therefore, the lead dropping by gravity can readily advance and can be readily guided through the through bore 9d. Figs. 10 to 15 show a slider 9 in a second embodiment according to the present invention. While the slider 9 in the first embodiment holds the lead by its front end, the slider 9 in the second embodiment holds the lead by its rear end. A slider 9b is provided with a through bore 9d through which the lead moves. The slider 9 is fitted in the tip 2 of a barrel 1 so as to be axially movable in a predetermined range. A lead guide 10 is fixed concentrically to the front end of the slider body 9b, and the lead slides through the lead guide 10. The slider 9 has a sliding part 9c concentrically joined to the outer circumference of the rear end of the slider body 9b so as to extend forward, provided with a plurality of axial slits 9f and in sliding contact with the inner circumference of the tip 2 and held in place by a frictional resistance, and lead holding pieces 9i for applying a frictional resistance smaller than the frictional resistance applied to the sliding part 9c by the inner circumference of the tip 2 to the lead. The rear end of a lead guiding part 9e formed on the inner circumference of the rear end of the slider body 9b is joined to the rear end of the sliding part 9c, and has a plurality of connecting pieces 9k (Fig. 13), and a plurality of lead holding pieces 9i (Fig. 14) tapered backward, separated from the connecting pieces 9k by a plurality of slits 9f extending from the rear toward the front and having rear ends not connected to the sliding part 9c. The connecting pieces 9k and the lead holding pieces 9i are separated from each other by the slits 9f and are arranged alternately on a circle. An arcuate lead holding protrusion 9g protrudes inward from the rear end of each lead holding piece 9i. The lead holding pieces 9i are formed so that the diameter of a circle circumscribed about the lead holding pieces 9i is equal to or greater than the diameter of a lead guiding opening 9j formed in the rear end of the lead guiding part 9e to prevent the lead being stopped when inserting the lead into the slider 9 from the rear end of the slider 9; that is, the outer surfaces of the lead holding pieces 9i are on the circumference of a circular cylinder corresponding to the inner circumference of the lead guiding opening 9j or on the circumference of a circular cylinder greater than the inner circumference of the lead guiding opening 9j. Since the lead can be easily guided into the lead guiding opening 9j without being caught and the rear ends of the lead holding pieces 9i are free, the lead holding pieces 9i can be easily bent radially outward and the lead can be automatically held. The operation of the slider 9 in the second embodiment having the lead guiding part 9e at its rear end is substantially similar to that of the slider 9 in the first embodiment having the lead guiding part 9e at its front end. In this embodiment, the lead guide 10 may be a chip or a pipe. The slider body 9b and the lead guide 10 may be separate members or may be formed integrally. Naturally, the number of the slits 9f formed in the lead guiding part 9e of the slider body 9b need not be limited to three or four as shown in the drawings, and the number of the sliding pieces of the sliding part 9c need not be limited to two.

Claims: A slider for a mechanical pencil, said pencil including a feeding mechanism for advancing a writing lead toward the slider (9) and actuating means for actuating the feeding mechanism, said slider (9) comprising: a slider body (9b) provided with a through bore (9d) through which the lead is passed and disposed in the tip (2) of a barrel (1) so as to be adapted to be axially slid in a predetermined range by the feeding mechanism when the feeding mechanism is actuated by the actuating means; a lead guide (10) concentrically fixed to the slider body (9b) so as to let the lead slide therethrough; a sliding part (9c) concentrically connected to the outer circumference of the slider body (9b) so as to be able to slide against a predetermined frictional resistance relative to the inner circumference of the tip (2); and a lead guiding means (9e) disposed in one end of the slider body (9b) and capable of expansion and of applying to the lead a frictional resistance smaller than that applied to the sliding part (9c) by the inner circumference of the tip (2), characterized in that the sliding part (9c) is concentrically connected to the outer circumference of the rear end of the slider body (9b) so as to extend forward. The slider according to claim 1, wherein the lead guiding means (9e) is disposed in the front end of the slider body (9b). The slider according to claim 2, wherein the lead guiding means (9e) is tapered toward the front, has an open front end, and is provided with a plurality of axial slits (9f). The slider according to claim 3, wherein lead holding protrusions (9g) are formed on the front end of the lead guiding means (9e) so as to protrude inward. The slider according to claim 1, wherein the lead guiding means (9e) is disposed on the rear end of the slider body (9b). The slider according to claim 5, wherein the lead guiding means (9e) is provided with a plurality of connecting pieces (9k) having rear ends connected to the sliding part (9c) and a plurality of lead holding pieces (9i) each tapered toward the rear and having a cut rear end, the plurality of connecting pieces (9k) and the plurality of lead holding pieces (9i) are arranged alternately, and the diameter of a circle circumscribed about the outer surfaces of the rear ends of the lead holding pieces (9i) is equal to or greater than that of a lead guiding opening. The slider according to claim 6, wherein the lead holding pieces (9i) is provided on its rear end with an inwardly protruding arcuate lead holding protrusion (9g). The slider according to any one of claims 5 to 7, wherein the slider body (9b) and the lead guide are formed in a single member.

Inventors: NOGUCHI YOSHIO, NOGUCHI, YOSHIO, Noguchi, Yoshio, c/o Kotobuki &amp; Co., Ltd.
Applicants: KOTOBUKI & CO LTD, KOTOBUKI & CO., LTD.
Application year: 1995
Main classification: B43K21
IPC codes: B43K21