Patent Publication Number: US-6908246-B2

Title: Mechanical pencil

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mechanical pencil and, more particularly, to a mechanical pencil in which a lead can be used effectively and the remainder lead can be shortened. 
     2. Description of the Related Art 
     In a conventional mechanical pencil having a barrel, a lead feeding mechanism disposed in the barrel to tighten and feed a lead, a lead holder disposed on the tip end side of the lead feeding mechanism to hold the lead penetrating therethrough, and an operating part for causing the lead feeding mechanism to feed the lead, the lead is normally tightened by the lead feeding mechanism. Thus, the lead is prohibited from moving. 
     When the lead is projected from the tip end of the barrel at the time of writing, the operating part is operated to cause the lead feeding mechanism to feed the lead. At this time, since the lead is held by the lead holder, the lead that has been fed a predetermined amount during the lead feeding operation by the lead feeding mechanism, is prevented from retreating (e.g., retracting) together with the lead feeding mechanism when the lead feeding mechanism returns. Since the lead feeding mechanism tightens the lead after returning, the lead projecting from the tip end of the barrel is used for writing without being retreated (retracted) by a writing force. 
     However, in the above-mentioned conventional mechanical pencil, when the lead is consumed, and thus the length thereof becomes shorter than a distance from the lead feeding mechanism to the tip end of the barrel, the lead is undesirably released from the tightening of the lead feeding mechanism. Thus, there arises a problem in that the consumed lead cannot be used effectively. 
     Specifically, for example, when the consumed lead is fed, the next lead is fed by the lead feeding mechanism so that the consumed lead is pushed out by using the next lead. However, since the next lead is not held by the lead holder, the feeding of lead is not performed completely, so that the consumed lead cannot be pushed out surely in some cases. In particular, when the lead is fed in an upward position of the pencil, such a phenomenon often occurs. 
     As a result, the lead that has become shorter than the distance from the lead feeding mechanism to the tip end of the barrel cannot be used sufficiently, and therefore becomes a remainder lead, which leads to a waste of resources. 
     SUMMARY OF THE INVENTION 
     In view of the foregoing and other problems, drawbacks, and disadvantages of the conventional structures, an object of the present invention is to provide a mechanical pencil in which the length of remainder lead can be decreased greatly. 
     To achieve the above and other objects, a mechanical pencil according to the present invention includes a barrel, a lead feeding mechanism disposed in the barrel to tighten and feed a lead, and an operating part for causing the lead feeding mechanism to feed the lead. The holding portions for holding the lead are provided in at least two places between the lead feeding mechanism and the tip end of the barrel spacedly (e.g., in a spaced configuration) in the axial direction. 
     When the lead is consumed, and thus the length thereof becomes shorter than a distance between the lead feeding mechanism and the tip end of the barrel, the holding portion provided at the front in the axial direction of the holding portions provided in at least two places holds the consumed lead, and the holding portion provided at the rear in the axial direction holds the next lead. 
     Thus, when the next lead is fed by the lead feeding mechanism, the next lead is surely fed by the holding portion provided at the rear. Hence, the next lead fed surely pushes out the consumed lead, so that the consumed lead is surely fed. Thus, the consumed lead can be used sufficiently. Specifically, as long as at least the holding portion provided at the front can hold the consumed lead, the consumed lead can be used, so that the length of remainder lead can be decreased greatly. 
     Also, in the mechanical pencil, a lead holder having a through hole through which the lead penetrates can be provided closer to the tip end than the lead feeding mechanism in the barrel, and the holding portions are provided on the lead holder. 
     By providing the holding portions on the lead holder, the mechanical pencil can be manufactured without increasing the number of parts. Also, since at least two holding portions are provided on the lead holder spacedly in the axial direction, the axial length of the lead holder increases resultantly, so that the length of the penetrating lead surrounded by the lead holder increases. Therefore, unintended decentering of the lead can be prevented, and thus the lead is prevented from being broken. 
     The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-3113, filed on Jan. 10, 2001, which is expressly incorporated herein by reference in its entirety. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other purposes, aspects and advantages of the present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not limiting the present invention, wherein: 
         FIG. 1  is a longitudinal sectional view of an essential portion of a mechanical pencil in accordance with an embodiment of the present invention; 
         FIG. 2  is an enlarged sectional view of a tip end member  14  and a slider  50 ; and 
         FIG. 3  is a plan view of FIG.  2 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION 
     An embodiment of the present invention will now be described with reference to the accompanying drawings.  FIGS. 1  to  3  show an embodiment of the present invention. 
     Referring to  FIG. 1 , a mechanical pencil has mainly a barrel  10 , a lead feeding mechanism  20  (e.g., writing medium feeding mechanism) disposed in the barrel  10  to tighten and feed a lead (e.a., a writing medium), a lead holder  50  (e.g., writing medium holder) disposed on the tip end side of the lead feeding mechanism  20  to hold the lead penetrating therethrough, and an operating part (not shown) for causing the lead feeding mechanism  20  to feed the lead. 
     The barrel  10  includes a front barrel  12 , a tip end member  14  screwed into the front barrel  12 , and a rear barrel (not shown). A gripper  18  made of an elastic material is mounted on the outer peripheral face of the front barrel  12 . The front barrel  12 , the tip end member  14 , and the rear barrel can be formed integrally (e.g., a unitary construction), or can be formed of more parts than in this embodiment. An opening  14   a  at the tip end of the tip end member  14  serves as an opening at the tip end of the barrel  10  to allow the lead to pass through. 
     The lead feeding mechanism  20  can have any construction. In this embodiment, the lead feeding mechanism  20  includes a lead containing cylinder  22  for containing the lead, a chuck  24  fixed at the tip end of the lead containing cylinder  22  to tighten and feed the lead, a chuck ring  26  located around the outer periphery of the chuck  24  to tighten the chuck  24 , a sleeve  28  for preventing the rearward movement of the chuck ring  26 , and a chuck spring  30  located between the sleeve  28  and the lead containing cylinder  22  to urge the lead containing cylinder  22  and the chuck  24  rearward. 
     To the rear end of the lead containing cylinder  22  is detachably connected a rear end pushbutton, which is the operating part. By knocking the rear end pushbutton, the lead containing cylinder  22 , the chuck  24 , and the chuck ring  26  of the lead feeding mechanism  20  are advanced, by which the lead is fed a predetermined amount. The operating part is not limited to the rear end pushbutton, and can be a side lever provided on the side face of the barrel  10 . 
     The tip end member  14  contains a slider  50  (e.g., which may be single-piece lead holder or single-piece writing medium holder), and a tip  52 . In this embodiment, the tip  52  and the slider  50  can be slid in the axial direction, and the tip  52  and the slider  50  can be projected together with the lead from the opening  14   a  at the tip end member or can be retreated (retracted) into the opening  14   a  at the tip end. It is a matter of course that the tip  52  and the slider  50  need not be slidable in the axial direction, and that they can be applied to a mechanical pencil of a type such that the tip and the slider are not slidable in the axial direction. 
     As shown in greater detail in  FIGS. 2 and 3 , the slider  50  has a substantially cylindrical body  50   b  formed with a through hole  50   a  through which the lead penetrates, an outside cylinder  50   c  provided concentrically on the outside of the body  50   b  at the rear end part of the body  50   b , and a connecting part  50   d  for connecting the outside cylinder  50   c  to the body  50   b  in the radial direction. 
     In the front end part of the body  50   b , at least one blade  50   e  projecting in the inside diameter direction is formed, and also in the rear end part of the body  50   b , a rib  50   f  projecting in the inside diameter direction is formed on the inner peripheral face of the through hole  50   a . Also, a slit  50   h  is formed in a portion in which the rib of  50   f  is absent at the rear end part of the body  50   b  formed with the rib  50   f  of the slider  50 . Thus, the rib  50   f  can be displaced elastically in the radial direction. Therefore, the blade  50   e  and the rib  50   f  form holding portions at two or more locations along an axial length of the writing medium holder  50 . 
     Similarly, on the outer peripheral face of the outside cylinder  50   c , a rib  50   g  projecting in the outside diameter direction is formed, and a slit  50   i  is formed in a portion in which the rib  50   g  of the outside cylinder  50   c  is absent. Thus, the rib  50   g  can be displaced elastically in the radial direction into contact with the inner surface of the (tip end member) of the barrel. 
     The blade  50   e  and the rib  50   f  come into contact with the lead passing through the through hole  50   a , and thereby hold the lead with a proper holding force. Also, a contact portion includes the rib  50   g  of the outside cylinder  50   c  that comes into contact with the inner peripheral face of the tip end member  14 , and thereby maintains the positional relationship with the tip end member  14  with a proper holding force. The blade  50   c  may be replaced with a rib similar to the rib  50   f.    
     Although the slits  50   h  and  50   i  are not necessarily needed, a stable holding force can be obtained by the provision of slits  50   h  and  50   i . The maximum static friction force generated between the rib  50   g  and inner peripheral face of the tip end member  14  is set to be larger than a sum of the maximum static friction force generated between the blade  50   e  and the lead, and the maximum static friction force generated between the rib  50   f  and the lead. 
     In the above-described mechanical pencil, when the lead is not consumed, the lead is held by the blade  50   e  and the rib  50   f  of the slider  50  in portions located ahead of a portion in which the lead is tightened by the chuck  24  of the lead feeding mechanism  20 . The rest of the configuration of the pencil is the same as that of the conventional mechanical pencil, so that the explanation thereof is omitted. 
     When the lead is consumed, and thus the length thereof becomes shorter than a distance between the chuck  24  of the lead feeding mechanism  20  and the opening  14   a  at the tip end of the tip end member  14  as shown in  FIGS. 1 and 2 , a consumed lead L 1  is held by the blade  50   e  of the slider  50 , and the next lead L 2  is held by the rib  50   f  of the slider  50 . Therefore, the consumed lead L 1  is prevented from dropping by the blade  50   e.    
     When the operating part is operated in this state to feed the next lead L 2  using the lead feeding mechanism  20 , since the next lead L 2  is held by the rib  50   f  of the slider  50 , the lead L 2  is surely fed by a predetermined amount without being pulled back together with the chuck  24  when the chuck  24  returns. Therefore, the consumed lead L 1  is pushed out according to the fed amount, so that the consumed lead L 1  can be fed surely. Even if the next lead L 2  is fed in an upward position of the pencil, the consumed lead L 1  is fed surely in the same way. 
     Since the consumed lead L 1  can be used in this manner, the length of remainder lead can be decreased significantly (e.g., almost completely as shown in FIG.  2 ). Preferably, an axial distance between the blade  50   e  and the rib  50   f  is set as long as possible to hold the consumed lead L 1  and the next lead L 2 . In this case, as a result, the length of the slider  50  is increased. Therefore, even if the lead is not consumed, the lead is protected against unintended decentering by the slider  50 , so that the lead is prevented from being broken. It is noted that, instead of providing the blade  50   e  and the rib  50   f  on one component as holding portions as in the above-described embodiment, each of these elements can be provided on an individual separate component. 
     As explained earlier, the slider  50  is axially slidable within the tip end member  14  of the barrel  10  and, as is clearly illustrated in  FIG. 1 , the rib  50   b  on the outside cylinder  50   c  maintains frictional contact throughout the entire axially slidable extent. In other words, the slider  50  always maintains a stable holding force within the tip end member  14  of the barrel. It is at least this feature that ensures that the lead L 2  is surely fed by a predetermined amount without being pulled back together with the chuck  24  when the chuck  24  returns as described above. 
     With the invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art intended to be included within the scope of the following claims. 
     For example, while the above described embodiment has been exemplarily described with respect to a mechanical pencil having a lead, other writing instruments having a consumable writing medium and which rely on the consumable writing medium being held by a holding portion, could find great benefit with the invention.