Patent Publication Number: US-6705789-B2

Title: Mechanical pencil

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a mechanical pencil in which a tubular shaft has at its front portion a slide member having a passage for a writing lead, and a lead advancement means axially slidably disposed in the tubular shaft. 
     2. Background Information 
     An example of the mechanical pencil of the type described which is shown in Japanese Pre-examined Utility Model Publication No. 56-44191 has a tubular shaft and an axially movable lead tank in the tubular shaft, and a chuck body is fixedly provided in front of the lead tank for the purpose of advancing the writing lead in the forward direction. At a front portion of the chuck body, a chuck ring is positioned around the chuck body to open/close the chuck body. 
     Further, a front member is fixed to the front end portion of the tubular shaft, and the front member has a passage for permitting the lead to move therethrough and, in addition, a slide member to which an anti-retraction member for the lead is press-fitted is arranged so that the slide member can project from an end of the front member. 
     In the known structure of the mechanical pencil described above, there is generally produced a gap or space between a rear end of a shortened residual lead (hereinafter referred to as a “remaining lead”) which has been positioned out of the chuck body and a front end of a succeeding (or, following) new lead (hereinafter referred to as a “succeeding lead”). This is caused by the following mechanism. Namely, the chuck body is closed by a chuck ring immediately before a retracting movement of the chuck body ends and is retracted grasping the succeeding lead. At this moment, however, the shortened remaining lead is positioned independent of the succeeding new lead and slightly held by the anti-retraction member in the front member so that the shortened lead is prevented from being retracted. 
     Once a gap as the gap described is produced, the remaining lead is retracted unexpectedly by a writing pressure in a writing operation and this results in a failure of writing and consequently a growth of feeling of wrongness. 
     Further, some users who dislike the above phenomena try to remove the remaining lead out of a lead guide member and operate to advance the next new lead. This will be a burden to an effective use of the shortened remaining leads. 
     SUMMARY OF THE INVENTION 
     In view of the above, it is an object of the present invention to provide a mechanical pencil which can abolish the disadvantages and difficulties appearing in the conventional structure described above and permits an effective use of the remaining leads. 
     According to a first aspect of the present invention, there is provided a mechanical pencil which comprises a tubular shaft having at its front portion a slide member having a passage for a writing lead, and a lead advancement means axially slidably disposed in the tubular shaft, wherein the slide member and at least one element of the lead advancement means are co-acted and interlocked with each other. 
     According to a second aspect of the invention, there is provided a mechanical pencil comprising a first chuck body at the rear portion of a second chuck body, the second chuck body grasping lead and releasing the same, the second chuck body having an anti-retraction member for softly holds the lead, wherein the first chuck body and the second chuck body are co-acted (interlocked) in the retraction movement thereof such that the retraction movement is conducted by a retraction of the first chuck body. 
     According to a third aspect of the invention, a slide member having a lead passage is disposed at a front portion of the tubular shaft, and a lead advancement (feeding) means is axially moveably disposed in the tubular shaft, wherein a knocking actuator member is provided to have a contact portion such that the contact portion is contacted with the slide member and the lead advancement (feed) member. 
     According to a fourth aspect of the invention, a slide member having a lead passage is disposed at a front portion of the tubular shaft and a lead advancement (feeding) means is axially moveably disposed in the tubular shaft, wherein the slide member is retracted by pushing a part of the tubular shaft. 
     In the structure of the mechanical pencil according to the invention, when the slider is retracted, a remaining (residual) lead is retracted with contacting with a succeeding lead. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a longitudinal sectional view of a part of a mechanical pencil according to a first embodiment of the invention. 
     FIG. 2 is an enlarged perspective view of a part of the pencil shown in FIG.  1 . 
     FIG. 3 is a longitudinally sectional view of a part of a mechanical pencil according to a second embodiment of the invention. 
     FIGS. 4 and 5 show an operation of the mechanical pencil of the second embodiment. 
     FIG. 6 is a longitudinally sectional view of a part of a mechanical pencil according to a third embodiment of the invention. 
     FIG. 7 is a longitudinally sectional view of a part of a mechanical pencil according to a fourth embodiment of the invention. 
     FIG. 8 is an enlarged perspective view, partly sectioned, of the structure shown in FIG.  7 . 
     FIG. 9 is a longitudinally sectional view of a part of a mechanical pencil according to a fifth embodiment of the invention. 
     FIG. 10 is an enlarged perspective view, partly sectioned, of a part of a mechanical pencil according to a sixth embodiment of the invention. 
     FIG. 11 is a perspective view of a slide member shown in the structure of FIG.  10 . 
     FIG. 12 is an enlarged perspective view, partly sectioned, of a part of a mechanical pencil according to a seventh embodiment of the invention. 
     FIG. 13 is a longitudinally sectional view of a part of a mechanical pencil according to a eighth embodiment of the invention. 
     FIG. 14 is an enlarged perspective view, partly sectioned, of the structure shown in FIG.  13 . 
     FIG. 15 is a sectional view of a part of the pencil according to a ninth embodiment of the invention. 
     FIG. 16 is a sectional view of a slide member according to a tenth embodiment of the invention. 
     FIG. 17 is a diagram showing the slide member according to a eleventh embodiment of the invention. 
     FIG. 18 is a longitudinally sectional view of a mechanical pencil to according to a twelfth embodiment of the invention. 
     FIG. 19 is an enlarged perspective view, partly sectioned, of the structure shown in FIG.  18 . 
     FIGS. 20 to  25  show an operational mode of the mechanical pencil. 
     FIG. 26 is a longitudinally sectional view of a pencil according to a thirteenth embodiment of the invention. 
     FIG. 27 is an enlarged perspective view, partly sectioned, of the structure shown FIG.  26 . 
     FIG. 28 is a diagram which shows a state that a writing lead is grasped or held. 
     FIG. 29 shows an operational mode of the pencil. 
     FIGS. 30,  31  and  32  show an example of a slide member. 
     FIG. 33 is a longitudinally sectional view of a mechanical pencil according to a fourteenth embodiment of the invention. 
     FIGS. 34 to  36  are enlarged views of elements shown in FIG.  33 . 
     FIGS. 37 and 38 are sectional views showing an operational mode of a lead holding mechanism. 
     FIGS. 39 to  42  are sectional views showing an operation of the lead holding mechanism. 
     FIG. 43 shows a structure of the slide member. 
     FIG. 44 shows a modification of the slide member shown in FIG.  43 . 
     FIG. 45 is a diagram showing an operation of the slide member. 
     FIGS. 46 and 47 show modifications of the slide member. 
     FIGS. 48 to  51  show examples of a chuck body adapted to the mechanical pencil of the invention. 
     FIG. 52 is a diagram showing a method of assembly of the chuck body. 
     FIG. 53 is a longitudinally sectional view of a mechanical pencil according to a fifteenth embodiment of the invention. 
     FIGS. 55 to  58  are sectional views showing an operation of the pencil according to the fifteenth embodiment of the invention. 
     FIG. 59 is a longitudinally sectional view of a mechanical pencil according to a sixteenth embodiment of the invention. 
     FIGS. 60 to  63  are diagrams showing an example of a molding device for forming a chuck body according to the present invention. 
     FIG. 64 is a longitudinally sectional view of a mechanical pencil according to a seventeenth embodiment of the invention. 
     FIGS. 65 to  67  are enlarged views of the part shown in FIG. 64, showing an operational mode. 
     FIG. 68 is a sectional view of a part of the mechanical pencil according to a eighteenth embodiment of the invention. 
     FIG. 69 shows a modification of the chuck body of the seventeenth embodiment of the invention. 
     FIGS. 70 to  73  show further modifications of the chuck body according to the seventeenth embodiment of the invention. 
     FIG. 74 is a longitudinally sectional view of a mechanical pencil according to a nineteenth embodiment of the invention. 
     FIG. 75 is a sectional view of the portion shown in FIG.  74 . 
     FIGS. 76 to  79  are sectional views showing an operational mode of the structure of the nineteenth embodiment of the invention. 
     FIG. 80 is a sectional view showing a modification of the nineteenth embodiment shown in FIG.  74 . 
     FIG. 81 is a sectional view showing another modification of the nineteenth embodiment of the invention. 
     FIG. 82 is a sectional view of a mechanical pencil according to a twentieth embodiment of the invention. 
     FIGS. 83 to  86  show an operational mode of the pencil of the twentieth embodiment shown in FIG.  82 . 
     FIGS. 87 to  89  show a structure according to a twenty-first embodiment of the invention, wherein FIG. 87 is an enlarged sectional view, FIG. 88 a transversal sectional view, and FIG. 89 is a diagram explaining the operational mode. 
     FIGS. 90 to  93  are sectional views showing the structure according to a twenty-second embodiment and also showing an operation thereof. 
     FIGS. 94 to  99  are sectional views of a part of a mechanical pencil, showing a modification of the twenty-second embodiment of the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     A first embodiment of the invention will be described with reference to FIGS. 1 and 2. A tubular shaft  1  has a lead tank  2  which is moveable axially (or, in the frontward/backward direction) in the tubular shaft, and the lead tank  2  has at its front end a chuck body  5  which is fixed thereto and can be opened through an intermediate joint member  3  and a lead guide member  4 . The chuck body has, around its front portion, a chuck ring  6  which serves to open/close the chuck body  5 . 
     On the front end of the tubular shaft  1  is provided a front member  9  which is releasably engaged with the front end through a press member  7  and a connecting member by a threaded engagement means or the like. The front member  9  can be formed integral with the tubular shaft  1 . A slide member  10  is axially moveably disposed in the front member  9  and has an anti-retraction member  11  which is made of a suitable rubber material and press-fitted in the slide member  10  for providing a light and soft holding of a writing lead to prevent the lead from retracting. Reference numeral  12  denotes a lead protection tube of a metal which is press-fitted to a front end of the slide member  10 , and the lead protection tube  12  can be made integral with the slide member  10 . 
     In the illustration of FIG. 1, reference character “S” represents a resilient member such as a coil spring for biasing the chuck body  5  as well as the lead tank  2  in a backward direction. The tubular shaft  1  is made of a transparent material and similarly the other elements such as the slide member  10  and the anti-retraction member  11  can be made of a transparent material so that actuation and movement of the writing lead can be visually observed by a user. 
     The chuck body  5  and the slide member  10  will be explained. On a front outer portion of the chuck body  5  is provided an outer flange portion  13 . At the rear portion of the slide member  10  is provided a tubular portion  14  which extends from the rear portion and has an inner flange portion  15  which contacts the outer flange portion  13  of the chuck body  5 . 
     The chuck body  5  is of so-called collet-type having two-split, three-split or four-split chuck leaves and has a structure that when it is firmly closed with no lead being held therein, the outer flange portion  13  of the chuck body  5  is released from the inner flange portion  15  of the slide member  10 . In other words, the chuck body  5  and the slide member  10  are separable from each other and can be assembled when necessary. 
     The slide member  10  is movably inserted into the front member  9  but a friction force (i.e., resistance) can be added between the elements  9  and  10  so that a soft engagement is established. However, it is noted that the friction force is set smaller than a friction force of the anti-retraction member  11  relative to the writing lead. By preventing the slide member  10  from moving while the lead is not grasped, generation of a moving sound of the slide member  10  can be prevented, wherein the moving sound is a noise which is likely to be produced when a middle step portion of the slide member  10  abuts against an inner step of the front member  9  and is produced when the pencil is shaken. 
     On the inner front portion of the front member  9 , there is provided an inner step portion  17  to which a front end  16  of the slide member  10  is contacted to limit an advance distance of the slide member  10 . 
     An operation will now be described. FIG. 2 shows a state in which a shortened residual lead A left from the chuck body  5  is held by the anti-retraction member  11  and a succeeding lead B is being held by the chuck body  5 . When the lead tank  2  is pressed forward in this state, the chuck body  5  is advanced along with the chuck ring  6 , so that the succeeding lead B is also advanced together. Then, along with the advance of the succeeding lead B, the residual lead A is pushed forward but, in this state, the residual lead A is held by the anti-retraction member  11  and, consequently, the slide member  10  is advanced together with the residual lead A. In this state, when the middle step portion  16  of the slide member  10  is contacted with the inner step portion  17  of the front member  9 , this restricts an advancing movement of the slide member  10 . By the operation described, the lead protection tube  12  fixed to the slide member  10  is advanced relative to the front member  9  and, therefore, a projection length of the lead protection tube  12  projecting from the front member  9  becomes larger than a length of an initial position. 
     When the lead tank  2  is advanced further, the residual lead A is pushed forward by the succeeding lead B and advanced in the lead protection tube  12  which is prevented from moving so that the succeeding lead B is projected from the end of the lead protection tube  12 . In a short time, the chuck ring  6  comes into contact with a rear end of the slide member  10  and limited its further advancing movement, so that the chuck body is released to open its engagement (grasping) portion to thereby release the succeeding lead B. 
     In this state, when the advancing movement of the lead tank  2  is released, the chuck body  5  is retracted with the succeeding lead B being released. During this retraction of the chuck body  5 , the outer flange  13  of the chuck body  5  is contacted with the inner flange  15  of the slide member  10  so that the slide member  10  as well is retracted. At this moment, the residual lead A is softly held by the anti-retraction member  11  of the slide member  10  and, therefore, it is retracted together with the slide member  10  with its projecting state being maintained, and this serves to retract the succeeding lead B which has been released from the chuck body  5 . 
     Then, the chuck body  5  is closed by the chuck ring  6  to grasp and retract the succeeding lead B, but since the residual lead A is retracted together with the slide member  10  as described above, no gap or space is generated between the residual lead A and the succeeding lead B. 
     Although the residual lead A is retracted by the operation described above, it is retracted together with the slide member  10  relative to the front member  9  and, therefore, the residual lead A does not retract relative to the lead protection tube  12  (slide member  10 ). As a result, a projecting length of the residual lead A from the lead protection tube  12  is not decreased but maintained. 
     A second embodiment of the invention will be described with reference to FIGS. 3 to  5 . This is a modification of an interlocking mechanism of the chuck body and the slide member in the first embodiment described above. In this embodiment, a chuck body  18  does not have a portion like the flange portion  13  of the first embodiment but, instead, it has a structure that a frictional resistance is added to the inner flange  15  of the slide member  10 . As an example of providing such a frictional resistance to the inner flange  15 , an outer diameter of the front outer circumference of the chuck body  18  is made slightly larger than an inner diameter of the inner flange portion  15  of the slide member  10  and, in another alternative, a resilient material such as rubber can be coated on at least one of the contacted portions. Alternatively, embossing or graining can be used. 
     An operation will be explained. In an initial stage of operation wherein the chuck body  18  is gasping the lead (see FIG.  3 ), the chuck body  18  contacts at its front outer circumference to an inside of the inner flange portion  15  of the slide member  10 . At this moment, when the chuck body  18  is advanced together with the chuck ring  6 , the slide member  10  as well is advanced because the chuck body  18  and the inner flange portion  15  are frictionally engaged with each other. It is a matter of course that the residual lead A grasped by the anti-retraction member  11  and the succeeding lead B held by the chuck body  18  are advanced as well. 
     Further, when the chuck body  18  and the slide member  10  are advanced, the middle step  16  of the slide member  10  is contacted with the inner step portion  17  of the front member  9  similarly as the case of the first embodiment, and the forward movement of the slider member  10  is prevented (see FIG.  4 ). However, the chuck body  18  can be advanced further, and a contact between the chuck body  18  and the inner flange  15  of the slide member  10  is released against the frictional force. Since the chuck body is further advanced, the residual lead A is advanced in the lead protection tube  12 . 
     Then, the chuck ring  6  is contacted with the rear end of the slide member  10  and the chuck body  18  is opened to release the succeeding lead B as shown in FIG.  5 . Now, when the advancing movement of the chuck body  18  is released, the chuck body  18  is retracted by the resilient member “S”, the front outer circumference of the chuck body  18  is again contacted with the inner flange  15  of the slider member  10 , and by the frictional resistance of the contact the slide member  10  as well is retracted. By the retraction of the slide member  10 , the residual lead A held by the anti-retraction member  11  is also retracted but this residual lead A serves to retract the succeeding lead B which was released from the chuck body  18 . 
     Then, the chuck body  18  is closed by the chuck ring  6  to grasp the succeeding lead B and retract the same. In the case, since the residual lead A is retracted together with the slide member  10 , no gap of space is produced between the residual lead A and the succeeding lead B. 
     In the second embodiment of the invention as well as the first embodiment, in the state that the chuck gasps no lead at all, an outer diameter of the front outer circumference of the chuck body becomes smaller than an inner diameter of the inner flange of the slide member, an easy assembling of the chuck body to the slide member is realized. In the case that the parts and elements are assembled by an automatic assembling machine, it is possible to make the front portion of the chuck body have a constant diameter and, therefore, a parts-feeding machine can be used effectively. 
     A third embodiment of the invention will be described with reference to FIG. 6, in which an outer flange portion  20  is formed on a rear outer circumference of the slide member  19  and an inner flange portion  23  is formed on the front end of the chuck body  21  through a tubular portion  22 . 
     By making the chuck body be positioned outside the slide member, an easy assembly of these parts can be realized. Namely, in the first and second embodiment of the invention, an amount of diameter-reduction of the chuck body is restricted by a width of a slit which is formed on the chuck body. By contrast, however, in this third embodiment of the invention the chuck body is dilated outwardly and an assembly is made in this outwardly dilated state and, therefore, no restriction is required as the restriction described above. 
     In the third embodiment, the slide member can efficiently be retracted in the tubular portion and, therefore, the lead protection tube can be housed in the front member after use. 
     FIGS. 7 and 8 show a fourth embodiment of the invention which is substantially similar to that of the first embodiment except the anti-retraction member. Specifically, the anti-retraction member  24  in this embodiment is coated on an inner surface of the lead protection tube  12 . The anti-retraction member  24  is made of a rubber-like resilient material such as silicone rubber and NBR. 
     The anti-retraction member  24  can be inserted into the lead protection tube. In alternatives, electroforming can be applied to provide iron ions to a surface of the anti-retraction member so that the lead protection tube  12  is formed around the anti-retraction member  24 . 
     As described above, the anti-retraction member  24  is disposed on the lead protection tube  12  so that the lead can be held even when the residual lead becomes very short and, therefore, the lead can be used up effectively. 
     As a means for effectively use the residual lead A, the lead protection tube can be press-fitted into the front member  9  as shown in the four embodiment, and in another alternative, the lead protection tube  25  can be formed integral with the front member  9  (fifth embodiment shown in FIG.  9 ). In either cases, if the distance between the anti-retraction member  26  and the lead protection tube  12  is made short, the shortened residual lead A can still be held or grasped firmly so that the lead can be used up effectively to the very point of the minimum remaining length. 
     A sixth embodiment of the invention will be described with reference to FIGS. 10 and 11. In this embodiment, the anti-retraction member and the lead protection tube are formed integral with the slide member. More specifically, anti-retraction member  29  comprised of a plurality of divided leaves is formed on an inner middle portion of the slide member  28 , and a trapezoidal projection  30  for actually holding the lead is formed on the inner surface of the anti-retraction member  29 . At a rear of the slide member  28 , confronting engaging members  31  projecting in the rearward direction is formed and an inner flange portion  32  is formed on a rear inner surface of the engaging members  31 . The inner flange portion  32  contacts the outer flange  13  of the chuck body to co-acts with the latter. 
     On a front portion of the slide member  28 , a lead protection tube  33  is also formed in integral. On a front portion of the thus formed lead protection tube  33 , a tapered portion  34  which is tapering toward a front end is formed. In writing, a tip of the writing lead can be viewed well so that a correct writing can be accomplished. 
     By integrally forming the anti-retraction member and the lead protection tube with the slide member, cost reduction in manufacturing parts and assembly thereof can be attained. Further, if the rear end portion of the slide member is diverged to provide split-type engagement leaves, an easy assembly operation can be made between the chuck body and the slide member. 
     FIG. 12 shows a seventh embodiment of the invention which is a modification of the sixth embodiment. A slit if formed on the lead protection tube  36  of the slide member  35  and a projection  38  is formed on the inner surface of the lead protection tube  36  to hold the lead. In other words, the anti-retraction member (that is, projection  38 ) is formed on the lead protection tube  36  and this structure permits a reliable holding of the residual lead after it is extremely shortened by use, so that a residual lead can be used up effectively to an extremity. 
     FIGS. 13 and 14 show an eighth embodiment of the invention. In this embodiment, the tubular portion of the slide member in the first embodiment is separately and independently formed relative to the slide member and these elements are frictionally engaged with each other but slidable with each other. Specifically, on the rear outer surface of the slide member  39 , an O-ring  40  of a rubber-like resilient material is fitted and a tubular member  41  is fitted at a rear portion of the slide member  39 . The O-ring  40  is made separate from the slide member but they are made in a unitary structure by, for example, forming circumferential rib on an outer circumference of the slide member. On an inner rear surface of the tubular member  41 , an inner flange  42  is formed such that it contacts the outer flange  13  of the chuck body  5 . An operational mode of this embodiment is substantially same as that of the first embodiment and, in this embodiment, if the lead protection tube  12  is contacted with a writing surface when the lead is retracted for rest after writing is finished, the lead protection tube  12  is completely encased within the front member  9 . This is because the slide member to which the lead protection tube is fixed can be slid or moved in the rearward direction within the tubular member  41  against a frictional resistance of the O-ring. 
     Reference numeral  43  is a restriction ring which serves to prevent drop of the slide member  39  from the tubular member  41 , which ring  43  can be omitted if the aforementioned O-ring has a sufficient frictional resistance force. In a case that no restriction ring  43  is provided, assembly and disassembly of the slide member and the tubular member can be made easily and an adjustment can be made easily when the tube should be blocked with the lead. 
     FIG. 15 shows a ninth embodiment of the invention. On the surface of both the outer flange portion  13  of the chuck body  5  of the first embodiment and the inner flange portion  15  of the slide member  10 , a male thread  44  and a female thread  45  are formed. When the chuck body  5  and the slide member  10  are assembled together, the chuck body  5  is firmly closed to fit it to the slide member  10  and, on the other hand, when they are disassemble, the chuck body is rotated relative to the slide member to release the threaded engagement between them. 
     FIG. 16 (tenth embodiment of the invention) and FIG. 17 (eleventh embodiment) show structures which facilitate assembly and disassembly of the chuck body and the slide member. In FIG. 16, a slit is formed at a tubular portion  47  of the slide member  46  so that the tubular portion  47  can be opened easily by the slit  48 , with the result that assembly and disassembly of the chuck body relative to the slide member can be made easily. This is somewhat similar with the structure of the sixth embodiment shown in FIG.  11 . In FIG. 16 reference numeral  49  represents an inner flange portion which contacts with an outer flange of the chuck body. 
     Further, in the embodiment of FIG. 17, the slit  48  is formed larger than that of FIG. 16 so that the aforementioned tubular portion is formed into bar-shaped structure having arms  50  with a recess  51  being formed at a middle of the slide member  46 , and a longitudinal groove is formed on an inner surface of the front member  9  so that it is engaged with the recess  51 . When the front member  9  is released from the tubular shaft  1 , the slide member is urged to be released from the front member  9  along with the chuck body, but actually, the slide member  46  which is engaged with the front member  9  is not fully released from the front member  9  and, as a result, the arms  50  of the slide member  46  are dilated or opened. Consequently, the slide member is released from the chuck body. This will facilitates maintenance working when the writing lead should be broken in pieces in the slide member. 
     A twelfth embodiment of the invention will be described with reference to FIGS. 18 and 19. A description with reference to the structure and elements which are similar with those of the previous first embodiment will be omitted for clarification. On an outer circumference of the slide member  10 , an O-ring  52  of a rubber-like resilient material is slidably press-fitted to an inner surface of the front member  9 . This O-ring can be replaced by a projection or the like which is formed integrally on the slide member  9 . A sliding resistance force of the slide member  10  relative to the front member  9  is set to be larger than a sliding resistance of the lead relative to the anti-retraction member  11 . In other words, when the residual lead A is urged to be pushed by the succeeding lead B, the slide member  10  as well is urged to be pushed out together, but the sliding resistance between the slide member  10  and the front member  9  is strong enough and, consequently, the slide member is maintained still and, on the other hand, the residual lead A is pushed out. 
     The chuck body  5  is a so-called collet chuck which has a two-split, three-split or four-split leaves structure so that if it is forcibly closed while it has no writing lead grasped therein, the outer flange portion  13  of the chuck body  5  is taken out of the inner flange portion  15  of the slide member  10 . In other words, the chuck body  5  and the slide member  10  can be assembled and disassembled with each other. 
     The middle step portion  17  of the slide member  10  is contacted with the front inner surface of the front member  9  and an inner step portion  18  is formed for limiting a forward movement of the slide member  10 . 
     An operation mode will be described. FIGS. 18 to  20  show a state that a residual lead A which has left from the chuck body  5  is maintained by the anti-retraction member  11  and the succeeding lead B is held or gasped by the chuck body  5 . When the lead tank  2  is pushed forward in this state, the chuck body  5  is advanced in the tubular portion  14  together with the chuck ring  6  so that the succeeding lead B which is grasped by the chuck body  5 . Along with the advance of the succeeding lead B, the residual lead A is pushed and urged to be advanced, but since the residual lead A is held by the anti-retraction member  11 , the slide member  10  is also urged to be advanced. Actually, however, a sliding resistance force of the slide member  10  relative to the front member  9  is set to be larger than a sliding resistance force of the lead relative to the anti-retraction member  11  and, therefore, the residual lead A is advanced with the slide member  10  being maintained still in a rested position, so that the residual lead A project from a tip of the slide member  10  (that is, from an end of the lead protection tube  12 ). Incidentally, if the aforementioned relationship of the sliding resistance forces is made reversed, there is an outcome that the slide member is advanced in the first place and then the lead is belatedly projected from the end of the slide member  10  and, therefore, it gives some feeling of wrongness. 
     When a further advance is made with respect to the chuck body  5  and the chuck ring  6 , etc., the front end of the chuck ring  6  is contacted with a rear end of the slide member  10  to thereby restrict the chuck ring  6  from moving forward (advance) as shown in FIG.  21 . 
     However, since the chuck body  5  is advanced further, it is released from the chuck ring  6  so that, at this moment, the engagement between the chuck body  5  and the succeeding lead B is released. 
     In this state, when the chuck body  5  is further advanced until the front end of the chuck body  5  is contacts the inner step portion  10   a  of the slide member  10 , the chuck body  5  serves to advance the slide member  10 . At this moment, since the residual lead A is softly held by the anti-retraction member  11 , the residual lead A is advanced according to the advance of the slide member  10 . However, since the succeeding lead B is released from the chuck body  5 , the succeeding lead B is advanced with maintaining its contact with the residual lead A like a drop by gravity (FIG.  22 ). 
     Then, when the middle step portion  16  of the slide member  10  is contacted with the inner step portion  17  of the front member  9 , the advance X or forward movement of the slide member  10  is limited. This is shown in FIG.  23 . 
     By the operation described above, the leads (that is, the succeeding lead B and the residual lead A) and the lead protection tube  12  which is fixed by slide member  10  are advanced relative to the front member  9  so that a length of the lead projecting from the front member  9  is increased relative to the projecting length of the same at the initial stage. 
     Now, when the advancing movement of the lead tank  2  is released, the chuck body  5  which releases the succeeding lead B and the outer flange portion  14  which contacts nothing in the tubular portion  14  move in a backward direction. If a contact resistance between the slide member  10  and the front member  9  is made larger than a contact resistance between the chuck body  5  and the slide member  10 , the outer flange portion  13  can be moved in a contacted state. In other words, it is sufficient that the chuck body  5  is moved backward while the slide member is standing still. When the outer flange portion  13  of the slide member  10  comes into contact with the inner flange portion  15  of the slide member  10  in this backward movement, the slide member  10  is retracted and, at a little moment later, the chuck body  5  is closed by the chuck ring  6  and holds or grasps again the succeeding lead B (FIG.  24 ). By the operation described above, the residual lead A is softly held by the anti-retraction member  11  of the slide member  10  and, therefore, the residual lead A is retracted together with the slide member  10  with the projected length thereof being maintained. Further, the succeeding lead B which is held by the chuck body  5  is retracted together with the chuck body  5 . 
     By the operation described above, the succeeding lead B and the residual lead A which are retracted together with the slide member  10  relative to the front member  9  are not retracted relative to the lead protection tube  12  (slide member  10 ) and, accordingly, there is no case that the projecting length of the lead from the lead protection tube  12  is decreased, see FIG.  25 . 
     Further, the slide member  10  is press-fitted into and contacted with an inner surface of the front member  9  by the O-ring  52 , the position of the slider member  10  is maintained after the pressing operation is released, no space is formed between the succeeding lead B and the residual lead A, the space being likely to be produced when the lead drops by gravity. 
     FIGS. 26 and 27 show a thirteenth embodiment of the invention. Description of the structure and elements which are substantially similar to those of the first embodiment will be omitted for simplification only. Between a rear end of the slide member  10  and the connecting member  8  is provided a resilient member  53  such as a coil spring which urges or biases the slide member  10  in the forward direction. A spring force of the resilient member  53  for biasing the slide member in the forward direction is larger than a slide-contact force of the outer flange portion  13  relative the an inner surface of the tubular portion  14  of the slide member  10  when the chuck body  5  is opened. In other words, the slide member  10  is always biased in the forward direction whether or not the slide member  10  is movably contacted with, or movably inserted into, the inner surface  14  of the outer flange portion  13 . 
     The chuck body can be used so that the outer flange portion of the chuck body does not contact the tubular portion of the slide member. In case that a chuck body is made of a resin, it is general that the expansion or dilation is designed to be larger in view of the defects by the time. Thus, it sometimes contacts the inner surface of the slide member. Thus, it may be possible to make the inner diameter of the tubular portion larger so that the outer flange portion does not contact the inner surface of the tubular portion but this will require a larger dimension of the outer surface of the tubular portion and, as a result, size of the front member becomes larger. Further, in that case, the opening or dilating dimension of the chuck body is large so that if the lead is even slightly curved or slightly smaller than the requirement, the lead is then gripped at its unfair portion apart from the holding position of the chuck body (FIG.  28 ), and therefore, it possibly provides misdirection of the lead feeding operation. Thus, in this embodiment, a tubular portion of the slide member is made smaller and, at the same time, the outer flange of the chuck body is contacted with the inner surface of the tubular portion so that the opening degree of the chuck body is restricted to thereby permit the lead to be gripped by and at the predetermined correct position of the chuck body. 
     An operation will be described except for the advancing operation of the chuck body and the slide member which is substantially same as that of the first and twelfth embodiments described above. When the advance movement (forward movement) of the lead tank  2  is released, the chuck body  5  is retracted with is gripping mouth opened and its outer flange portion  13  being frictionally slid along the inner surface of the tubular portion  14 , but since the slide member  10  having the tubular portion  14  is forwardly biased by the resilient member  53 , the slide member  10  does not proceed retraction. Then, the chuck body  5  contacts at its outer flange portion  13  with the inner flange portion  15  of the slide member  10  and, from at this moment, the slide member  10  starts its retraction (see FIG.  29 ). This of course occurs against a spring force of the resilient member  53 . 
     The chuck body  5  is forcibly closed by the chuck ring  6  to hold again the succeeding lead B and, at this moment, the chuck body  5  will be slightly retracted in a similar manner as the conventional prior art structure but also the slide member  10  is retracted. Therefore, no space or gap is produced between the succeeding lead B and the residual lead A. 
     Although the succeeding lead B and the residual lead A are retracted by the operation described above, the lead is retracted together with the slide member  10  relative to the front member  9  and, therefore, it does not retract relative to the lead protection tube  12  (that is, slide member  10 ), so that a projecting length of the lead from the lead protection tube  12  is not decreased. 
     The slide member  10  engaged with the outer flange portion  13  of the chuck body  5  and its retracting position is maintained after the pushing operation is released and, therefore, any gap or space is not produced between the succeeding lead B and the residual lead A by, for example, a drop of the lead by gravity or a biasing force of the resilient member  53 . 
     In the preceding examples described above, the resilient member and the slide member are made of different members and assembled with each other but if necessary, an elastic member is formed by an injection molding method or the like at a rear portion of the slide member, as shown in FIGS. 30 and 32. More specifically, this structure of the elastic portion which can be deformed, a tubular portion  55  is formed at the rear portion of the slide member  54  and the tubular portion  55  has its rear end an elastically deformable portion  56  of net shape. 
     FIG. 31 shows an example of production of the slide member  54  and the chuck body  57  in which both of the members  54  and  57  are made of a resin material by an injection molding method. As described above, the resin-made chuck  57  is, at its opened state, contacted at its outer circumference to the inner circumference of the tubular portion  55  so that its opening degree is restricted. Specifically, the opening degree is made slightly smaller than a diameter of the writing lead. This of course is made for the purpose of hold the lead at the regular position thereof. 
     In this embodiment the elastic, deformable portion is provided at the rear portion of the slide member but, if desired, a tension spring can be provided at a front portion of the slide member. In an alternative method, a magnet is used for biasing the slide member forwardly. 
     FIGS. 33 to  36  show a fourteenth embodiment of the invention. In this embodiment, a lead tank  59  is axially slidably disposed in the tubular shaft  58 , and a chuck body  60  which can be opened and closed at the front end of the lead tank  59 . At the front portion of the lead tank  59  is provided a chuck ring  61  which serves to open/close the chuck body  60 . A base portion  62   a  of a clip  62  is press-fitted to a rear portion of the tubular shaft  58 , and a rubber eraser  63  is detachably fitted to a rear portion of the lead tank  59 . Reference numeral  54  is a end cap which is detachably fitted to the rear portion of the lead tank  59  for covering the rubber eraser  63 . 
     A front member  65  is detachably fitted to a front end of the tubular shaft  58  by means of threaded engagement or the like, and a grip  66  made of a rubber material is coated in such a manner that it is laid across and extended between the tubular shaft  58  and the front member  65  so that the elements  65  and  58  should not be removed from each other inadvertently or accidentally. The slide member  67  is axially movably disposed in the front member  65 , and an anti-retraction member  68  made of a rubber or synthetic resin material is press-fitted to the interior of the slide member  57  for softly holding the writing lead. If necessary, a lead guide member made of a suitable resin can be disposed at the rear portion of the anti-retraction member. Reference numeral  69  represents a lead protection tube which is formed integral with an end of the slide member  67 . The lead protection tube  69  can be formed of a metal pipe and press-fitted. Reference character “S” represents a coil spring which spring-biases the chuck body  60  and the lead tank  59  in the rearward direction. 
     A further description will be made with reference to the chuck body  60  and the slide member  67 . The chuck body  60  has, at its front end surface, projections  70 ,  70  in an opposed relation. At the rear portion of the slide member  67  is provided a tubular portion  71  which has at a middle portion thereof an engagement hole  72  to which the projections  70 ,  70  of the chuck body  60  (FIGS. 35A,  35 B and  35 C). The tubular portion  71  has an inclined surface  73  which slants gradually toward the front end as illustrated in FIG. 36, so that it facilitates a smooth insertion of the projections  70 ,  70  of the chuck body  60  into the engagement hole  72 . In other words, this makes it easy to assembly the chuck body  60  to the slide member  67 . 
     A resilient member  74  such as a coil spring is provided between a rear end of the slide member  67  and the tubular shaft  58  to spring-bias the slide member  67  in the forward direction. A spring force of the resilient member  74  for spring-biasing the slide member  67  is larger than a sliding frictional force of the edge portion  75  except the projections  70 ,  70  at the time when the edge portion  18  is slidably contacted with an inner surface of the tubular portion  71  of the slide member  67 . Namely, the slide member  67  is always urged to move forward, irrespective of the state whether or not the edge portion  75  of the chuck body  60  is slidably contacted with the inner surface of the tubular portion  71 . 
     Again, the chuck body  60  is of collet type chuck mechanism having two-split, three-split or four-split configuration. A middle step portion  76  of the slide member  57  is contacted with the inner front portion of the front member  65 , and an inner step portion  77  is formed to limit the advancing distance of the slide member  67 . 
     An assembly procedure of the chuck body  60  to the slide member  67  will be described. In the state that no lead is grasped by the chuck body (in the state of FIG.  37 ), the projections  70 ,  70  of the chuck body  60  is pressed against the rear end of the slide member  69  (that is, tubular portion  71 ), a head of the chuck body  60  is reduced in its diameter (FIG. 38) On the inner front portion of the front member  65 , and in a short time the projections  70 ,  70  are moved to the engagement hole  72  and, at time moment, the projections  70 ,  70  of the chuck body  60  are released so that the hed of the chuck body  60  is dilated. Thus, the projections  70 ,  70  of the chuck body  60  are freely inserted into the engagement hole  72  so that they are placed into a somewhat inseparable state (that is, the state of FIG.  33 ). 
     The anti-retraction member  68  for preventing the lead from moving back or retracting to a rear position will be described. The anti-retraction member  68  has, along its length, a lead passage  68   a  with a diameter a slightly larger than a diameter of a writing lead but not so large as to permit two leads to pass at a time. At the front portion of the lead passage  68   a,  the anti-retraction portion  68   b  which has a hole of a diameter slightly smaller than a diameter of the lead to be used. The anti-retraction member  68   b  holds the lead softly and serves to prevent the lead from retracting or moving backward. In the state that the lead is held by the anti-retraction member  68   b,  the lead is held at a ridge portion so that this can prevent the residual lead from rotating at the time of writing. The lead passage  68   a  is provided with a groove portion  68   c  in a confronting relation relative to an axial direction, the groove portion  68   c  being smaller than a diameter of the lead, and the groove portion  68   c  is formed along the entire length of the anti-retraction member  68 . Further, at the area adjacent to the anti-retraction portion  68   b,  the groove portion  68   c  is formed extending until an outer circumference of the anti-retraction member  68 . In other words, the groove portion  68   c  adjacent the anti-retraction portion  68   b  is of slit-shape configuration. A resilient effect is added to the anti-retraction portion  68   b  which serves to actually hold the lead so that a dispersion of the lead diameter can be absorbed. The groove portion  68  is shown to be provided at two spots in the illustrated embodiment but it may be provided radially at three sports or four spots. Further, it may be formed such that it is a groove having a triangular cross section. The lead passage  68   a  has at its upper portion a cone shaped portion  68   d  for reliably guiding the lead to the lead passage  68   a.    
     Further, the anti-retraction member  68  is formed of a resin material. The position of a gate (that is, a hole for cavity) at the time of injection molding is provided at right angles relative to an axial line of the lead passage  68   a  and at the position where the aforementioned groove portion  68   c  is formed (FIGS. 35A to  35 C). By providing a flow of the resin material from the position where a core pin has more strength, the core pin is prevented from being bent or broken. Further, the groove portion  68   c  serves to absorb scattering or dispersion of the diameter of the leads when the anti-retraction member  68  is press-fitted to the slide member  67  and also serves to maintain a suitable strength of fixture. In other words, an elastic deformation of the anti-retraction member  68 , which is effected by the groove portion  68   c,  is utilized effectively. In this embodiment, the lead passage  68   a  and the anti-retraction portion  68   b  are formed in a unitary structure but they may be formed independently or separately from each other so that the anti-retraction portion may be positioned at a front of the member which has the lead passage as shown by, for example, FIG.  53 . 
     An operation mode will then be described. FIGS. 33 and 34 show the state in which the residual lead A left from the chuck body  60  is held by the anti-retraction member  68  and the succeeding lead B is held by the chuck body  60 . The slide member  67  is spring-biased forwardly by the resilient member  74  but, since the rear end of the engagement hole  72  of the tubular portion  71  is in an abutment engagement with the projections  70  of the chuck body  60 , the slide member  67  is restricted from advancing movement. 
     When the lead tank  59  is pushed froward in the state described above, the chuck body  60  is advanced in a non-contact state in the tubular portion  71  together with the chuck ring  61  but, since the slide member  67  is spring-biased by the resilient member  74 , also the slide member  67  is advanced with the engagement between the engagement hole  72  and the projection  71  being maintained. Consequently, the succeeding lead B held by the chuck body  60  and the residual lead A held by the anti-retraction member  68  is advanced together with the guide member  67 . 
     In a short time, the middle step portion  76  of the slide member  67  abuts against the inner step portion  77  of the front member  65  to stop the advancing movement of the slide member  67  (FIG.  39 ). However, the projections  70  of the chuck body  60  are freely inserted into the engagement hole  72 . Although the chuck body  60 , the chuck ring  61  and the succeeding lead B as well as the residual lead A are advanced further, the chuck ring  61  is prevented from moving further at the time when the chuck ring  61  abuts against the rear end of the tubular portion  71  of the slide member  67 . Then, at this moment, the chuck body  60  is dilated or opened to release the succeeding lead B and the edge portion  75  of the chuck body  60  contacts the inner surface of the tubular portion  71  of the slide member  67  (FIG.  40 ). 
     When the advancing movement of the lead tank  59  is released, the chuck body  60  is retraced with its holding portion being opened and with edge portion  75  being frictionally slid along an inner surface of the tubular portion  71  but, since the slide member  67  having the tubular portion  71  is spring-biased by the resilient member  7 , the slide member  67  is not retracted. When the projections  70  are contacted with the rear end of the engagement hole  72  of the slide member  67 , the slide member  67  starts its retracting movement (FIG.  41 ). This is done against a spring force of the resilient member  74 . 
     Then, the chuck body  60  is closed by the chuck ring  61  to hold again the succeeding lead B (FIG.  42 ). In this case, the chuck body  60  is slightly retracted in a similar manner as the prior art device with the succeeding lead B being grasped but, since the slide member  67  as well is retracted, no gap or air space is produced between the residual lead A and the succeeding lead B. 
     By the operation described above, the succeeding lead B and the residual lead A are retracted, but the leads A and B are retracted together with the slide member  76  relative to the front member  65 . Consequently, the leads A and B are not retracted relative to the lead protection tube  69  (slide member  67 ) and, therefore, a projecting length of the lead from the lead protection tube  69  is not decreased. 
     Further, the slide member  67  is engaged with the projections  70  of the chuck body  60  similarly as the previous embodiments and maintains its retracting position after the pushing operation is released, no space is formed between the succeeding lead B and the residual lead A due to, for example, a drop of the lead by gravity. 
     The resilient member and the slide member which are formed of separate members in the embodiment described above but they may be formed in a unitary structure by a suitable method as an injection molding as illustrated in FIG.  43 . With respect to the elastically deformed portion in the present embodiment, an elastically deformable portion  79  of a shrinkable net shape is formed at a back of the slide member  78 . 
     A modified structure will be explained with reference to FIG.  44 . In this modification, an engagement hole  82  is formed on a tubular portion of the slide member  80  and a slit  83  narrower than the projections  70  of the chuck body  60  are formed. On the rear end of the tubular portion  81 , an inclined surface  84  is formed for facilitating adoption or fitting of the projections  70  to the engagement hole  82 . 
     When the projections  70  of the chuck body  60  are pushed against the inclined surface  84 , the tubular portion  81  is elastically deformed at the center of the slit  83  (see FIG.  45 ), so that the projections  70  are reliably introduced into the engagement hole  82 . 
     Further, the engagement hole  82  is provided, at its inner surface, with an inclined surface  85  in a confronting relation with the aforementioned inclined surface  84 . The inner inclined surface  85  permits the chuck body  60  be removed from the slide member  67 . In other words, maintenance can be done by separation of the two members  60  and  67  from each other when the lead in the slide member should be broken. 
     A modification of the engagement hole will be described with reference to FIG.  46 . The slide member  86  has an engagement hole  88  on a tubular portion  87  in a similar manner as the previous embodiment, and in this modification, an L-shaped guide groove  89  is formed in continuation with the engagement hole  88 . The guide groove  89  is extended to the end of the tubular portion  87 . In this modification, the chuck body  60  and the slide member  86  are assembled by rotating the one relative to the other (FIG.  47 ). This permits an easy assembly operation and an easy disassembly of the chuck body and the slide member when the lead is broken in the slide member. 
     In the embodiment described above, since the projecting length of the chuck body from the chuck ring is small and there is a distance for the resilient member to be closely contacted, assembly must be made by rotating the slide member while a knock cap is pushed to urge the chuck body for a some distance. In this point, if the chuck body is formed longer, the slide member can be assembled without moving the chuck body in the forward direction. 
     In the embodiment described above, the engagement portion is formed in the form of the through-hole and, therefore, its working can be made easily and, especially when the slide member is formed by injection molding, the molding dies can be made at a low cost and dimensional accuracy can be obtained. 
     A fan shaped expansion portion  90  is formed on a front end of the chuck body  60  so that the fan shape corresponds to the shape of the chuck body  60  (FIGS.  48  and  49 ). The expansion portion  90  serves as a pusher portion when the lead tank  59  is press-fitted to the lead tank  59 . A method of the press-fitting will be described later. In the present embodiment of the invention, in stead of the fan-shaped expansion portion, a hill-shaped raised portion is formed at a center of the front surface of the chuck body  60  as shown in FIG.  50  and in a further modification, a front end of the chuck body  60  is continuously extended forward from the projections  70  as shown in FIG.  51 . 
     Assembly of the chuck body  60  to the lead tank  59  will be described with reference to FIG.  52 . In the first place the lead tank is positioned in an upright posture and the resilient member S is inserted from forward position into the lead tank  59 . Then, the tubular shaft  58  is fitted from above of the lead tank  60  and, after that, the chuck ring  61  is mounted from above on the tubular shaft  58 , followed by insertion of the chuck body  60  of the present embodiment. Next, the pusher member  91  is contacted against the expansion portion  90  of the chuck body  60  to provide a downward force upon the pusher member  91 . Thus, chuck body  60  receives a force of the pusher member  91  through the expansion member  90  and the lower portion of the chuck body  60  is press-fitted to lead tank  59 . At this moment, when an excessive force is added to the chuck body  60  by the pusher member  91 , the expansion member  90  at the front end of the chuck body  60  is deformed inwardly or outwardly so that deformation of the front portion of the chuck body is restricted. In other words, a regular assembly can be accomplished with the predetermined shape being maintained, without deformation of the front portion of the chuck body, wherein the front portion is to be contacted with the chuck ring  61 . 
     In the embodiment described above, the projections  70  are formed on the outer circumference of the chuck body  60  and the projections  70  are engaged with the slide member  67 , so that the slide member  67  is retracted to thereby remove a gap between the residual lead A and the succeeding lead B. In other words, the shape of the projections  70  is an important factor. Accordingly, if the projections  70  are deformed, retracting positions of the slide member  67  becomes different and scattered and, as a result, a projecting length of the lead will become scattered. In some cases, the projections  70  are damaged or broken and, in that case, it is impossible to retract the slider to the predetermined position. For the purpose of avoiding such disadvantages, it is desired to form the expansion portion  90  as described above. 
     FIGS. 53-58 show a fifteenth embodiment of the invention. The same reference numerals are used for the same or similar parts and structures of the fourteenth embodiment. The lead tank  59  is axially movably disposed in the tubular shaft  58  and the chuck body  60  is fixedly positioned at the front end of the lead tank  59 . The chuck ring  61  is disposed at the front portion of the chuck body  60  to open/close the chuck body  60 . The resilient member S such as a coil spring is disposed between the lead tank  50  and the inner step portion  93  of the tubular shaft  58  to spring-bias the elements such as the chuck body. Thus, a lead feed mechanism  94  is constituted by such elements as the lead tank  59 , chuck body  60 , chuck ring  61  and the resilient member S. 
     Further, at the front portion of the tubular shaft  58 , the front member  65  is releasably engaged by a thread engagement or the like, and the slide member  67  is slidably positioned to the front member  65  such that the slide member  67  projects from the end of the front member  65 . In the slide member  67 , the lead guide member  95  and the anti-retraction member  96  of a resilient member such as a silicone, NBR or the like for holding softly the lead and prevent the retraction of the lead are provided. The lead guide member  95  and the anti-retraction member  96  may be formed integral with the front member  65 . Further, the tubular portion  71  is formed at the rear portion of the slide member  67 , and a window  72  is formed on the tubular portion  71  in an opposed relation. The tubular portion has a slit in continued relation with the window  72  so that if an external force is added to the tubular portion  71 , it can be opened by elastic deformation. The projections  70  which are formed on the outer circumference of the chuck body  60  are movably inserted to the window  72 . 
     A step portion  97  is formed on the inner rear portion of the front member  65  for the purpose of serving as a restriction portion which limits a forward movement of the chuck ring  61 . When the chuck ring  61  is contacted with the step portion  97 , the chuck body  60  is dilated to release the lead which was grasped therein. 
     A distance V between the chuck ring  61  and the step portion  97  is determined that it (V) is smaller than a distance W between the projection  70  of the chuck body  60  and the front end of the window  72  of the slide member  67 . In other words, the chuck ring  61  is contacted with the step portion  97  to open the chuck body  60  and, after that, the projections  70  of the chuck body  60  is then contacted with the front end of the window  72 . More specifically, the distance V is determined to be smaller by 0.1 mm than the distance W. If this difference is between 0.05 mm and 1.0 mm, the structure will work well. If the difference is 1.0 mm, however, the structure works but a length of the projecting lead becomes large and, therefore, it will be difficult to regulate the projection length of the lead. 
     Between the portion adjacent to the tubular portion  71  of the slide member  67  and the tubular shaft  58 , there is provided a gap X which is determined to be smaller than an engagement distance Y between the chuck body  60  and the slide member  67 . In other words, when the projections  70  of the chuck body  60  are inserted into (or fitted to) the window  72  of the slide member  67 , the tubular portion  71  adjacent to the window  72  is dilated or opened but, after the front member  65  is fitted to the tubular shaft  58 , the opening movement of the tubular portion  71  is restricted so that the movably inserted relation of the projections  70  relative to the window  72  can be maintained. In other words, the projections  70  are secured in the window  72  and does not fall out of the window  72 . Further, the slide member of this embodiment has a slit  83  in a similar manner as the modified structure of the fourteenth embodiment, and the slit  83  has a width such that when the slit is dilated by fitting the slide member to the front member, the projections of the chuck body do not fall out. Namely, the difference between the width of the projections  70  of the chuck body  60  and the width of the slit  83  is larger than the difference between an inner diameter of the front member  65  and the outer diameter of the tubular portion of the slide member  67 . 
     The O-ring  98  of a rubber-like material is disposed between the inner surface rib  65   a  of the front member  65  and the slide member  67  to provide a sliding frictional resistance force. The resistance force of the slide member  67  relative to the front member  65  is determined to be larger than a resistance force of the lead relative to the anti-retraction member  96 . In other words, when the lead is advanced together with the chuck body  60 , the slide member  67  is restricted from moving relative to the front member  65 . Incidentally, a lead holding force of the anti-retraction member is preferably selected to be in the range of from 20 gf to 100 gf. A value below the range (less than 20 fg) will result in sliding drop of the lead whereas a value above the range (more than 100 gf) provides difficulties in lead feed operation. In the embodiment of the invention described above, the O-ring  98  is slidably contacted with the inner rib  65   a  of the front member  65 . Instead of the inner rib  65   a,  the O-ring  98  can be contacted with the inner surface of the tubular portion, but in view of unexpected deformation of the O-ring and compression by air, it will be desirable to provide a rib structure. 
     A base portion  62   a  of the clip  62  is press-fitted to the rear portion of the tubular haft  58  and a rubber eraser  63  is releasably fitted to the rear portion of the lead tank  59 . A knock cap  64  which covers the rubber eraser  63  is releasably disposed at the lead tank  59 . A grip member  66  is mounted on the front portion of the tubular shaft  58  such that the grip member  66  rides over, and extends between, a recess  58   a  of the tubular shaft  58  and a recess  65   b  of the front member  65 . This prevents a looseness or incomplete fitness of the front member  65  relative to the tubular shaft  58  and, at the same time, permits a full finger-gripping manipulation to the front member  65 . This structure is substantially the same as the fourteenth embodiment of the invention. 
     An operation will be described. FIG. 53 shows the state that the residual lead A left from the chuck body  60  is held by the anti-retraction member  96 , and the succeeding lead B is held by the chuck body  60 . The slide member  67  is pulled rearward by the projections  70  of the chuck body  60 . 
     When the lead tank  59  is pushed forward, the chuck body  60  and the chuck ring  61  as well as the succeeding lead B held by the chuck body  60  and the residual lead A are moved forward, wherein the residual lead A is pushed by the succeeding lead B. At this moment, the residual lead A is softly held by the anti-retraction member  96  of the slide member  67  and therefore also the slide member  67  is urged to advance together but, since the sliding frictional resistance of the slide member  67  relative to the front member  65  is determined to be relatively large and, therefore, the slide member stands still without movement, and the residual lead A is slidably moved in the anti-retraction member  96 , so that the residual lead A projects from the end of the slide member  67 . Thereafter, the chuck ring  61  comes into contact with the step portion  97  of the front member  65  to thereby restrict its forward movement. At this moment, a gap “Z” (FIG. 55) is formed between the projection  70  of the chuck body  60  and the front end of the window  72  of the slide member  67 . If the lead tank  59  is advanced further, the chuck body  60  advances slightly the succeeding lead B (and the residual led A) and at the same time the projections  70  of the chuck body  60  is forcibly contacted with the front end of the window  72  (FIG.  56 ). At this moment, the chuck body  60  is dilated or opened to release the succeeding lead B which was held. If necessary, however, it can be designed such that the chuck body  60  is dilated immediately after the chuck ring  61  contacts the step portion  97 . 
     When the lead tank  59  is advanced further, the projections  70  of the chuck body  60  serve to move the slide member  67  forward. The forward movement of the slide member  67  continues until the middle step portion  76  of the slide member  67  abuts against the rear end  77  of the inner face rib  65   a  of the front member  65  (FIG.  57 ). 
     When the forward movement of the lead tank  59  is released, the chuck body  60  is retracted in its opened state, but the slide member  67  which receives a resistance by the O-ring  98  is not retracted. Soon after that, the projections  70  of the chuck body  60  contact the rear end of the window  72  of the slide member  67  (FIG. 58) to thereby start a retracting movement of the slide member  67 . 
     In a short time, the chuck body  60  is forcibly closed by the chuck ring  61  to grip or hold again the succeeding lead B (FIG.  53 ). At this time, although the chuck body  60  is retracted slightly with holding the succeeding lead B therein in a similar manner as the conventional prior art, the slide member  67  as well is forcibly retracted and, therefore, no gap of air space is formed between the succeeding lead B and the residual lead A. 
     The succeeding lead B and the residual lead A which are retracted as described above are retracted together with the slide member  67  relative to the front member  65  but not retracted relative to the slide member  67  and, therefore, a projecting length of the lead from the slide member  67  is not decreased at all. 
     Further, since the window  72  of the slide member  67  is engaged with the projections  70  of the chuck body  60 , its retracting position is maintained even after the release of the knocking or pushing operation and, therefore, no gap or air space is produced between the succeeding lead B and the residual lead A due to, for example, a drop of the lead by gravity. 
     In the embodiment described above, the projections  70  of the chuck body  60  are contacted with the front end of the window  72  after the contact between the chuck ring  61  and the step portion  97 , that is, after opening of the chuck body  60 . Therefore, the chuck body  60  can be opened without receiving any restriction and, consequently, a pleasant “click” sound of the chuck ring can be obtained by the user. 
     FIG. 59 shows a sixteenth embodiment of the invention, in which the tubular portion of the slide member  67  is made of a separate member. The tubular member  99  has a window  100  for receiving freely the projections  70  of the chuck body  60 . The tubular member  99  is press-fitted into the body portion of the slide member  67 , and the press-fitting distance can be determined optionally. 
     An operation of the structure described above can be considered to be substantially same as that of the fifteenth embodiment and will be omitted for simplification but, in this embodiment, a press-fitting distance of the tubular member  99  to the body portion of the slide member  67  can be varied. Therefore, dimensional unevenness or scattering of the products and a projection length of the lead can be determined by the press-inserting distance of the tubular member to the slide member  67 . 
     In the fifteenth and sixteenth embodiments of the invention, the rear end of the slide member is positioned in a forward position relative to the stepped portion  97  of the front member  65 , and a gap is formed between the rear end of the slide member and the front end of the chuck ring. However, it may be possible that the rear end of the slide member is positioned in a rearward position relative to the stepped portion of the front member and the gap is formed between the rear end of the slide member and the front end of the chuck ring. In brief, it will be sufficient that there is a gap for retraction of the slide member while the chuck body is holding the succeeding lead. Unless the gap is formed, the chuck body is not permitted to be retracted by a normal writing pressure and, consequently, a wedging force for gripping the lead is weakened to result in an unfavorable and unexpected retraction of the lead. 
     An example of a molding device for forming the chuck body will be explained with reference to FIGS. 60 to  63 . The mold  101  contains therein a cavity  102  which is divided into plural portions for forming an outer shape of the chuck body  60 , and a core pin (mold pin)  103  for forming an inner shape of the chuck body  60 . The plural-divided cavity  102  is constituted with a cavity portion  102   a  for forming a rear portion  60   a  and a front portion  60   c  of the chuck body  60 , and a cavity portion  102   b  for an inclined surface  60   b  contacting with the chuck ring  61 . More specifically, a through hole  102   d  is formed at the portion where the inclined surface  60   b  of the cavity portion  102   a  is formed, and the cavity portion  102   b  which forms the inclined surface  60   b  is fitted to the through hole  102   d  (FIG.  62 ). In other words, the cavity portion  102   b  for forming at least the inclined surface  60   b  of the chuck body  60  can be changed or replaced. When it is desired to regulate the outer shape of the inclined surface  60   b,  only the cavity portion  102   b  is removed and replaced by another one by modifying or correcting the same. 
     In the embodiment described above, the cavity portion  102   a  which forms the rear portion  60   a  and the front portion  60   b  of the chuck body  60  is formed in a unitary structure, but it can be formed in a separate manner as shown in FIG.  60 . Specifically, it may be comprised of a cavity portion  102   a  for forming the rear portion  60   a  of the chuck body  60 , a cavity portion  102   b  for forming the inclined surface  60   b  and a cavity portion  102   c  for forming the front portion  60   c.  Namely, it can be constructed such that the cavity portion  102   a  is divided into two. 
     In the structure that the chuck body and the slide member are operationally interconnected with each other as described above, the timing is very important between the time when the chuck body is retracted to retract the slide member and the time when the chuck body is closed by the chuck ring. Therefore, an accuracy of the inclined surface of the chuck body is required. In this respect, the chuck body which is made by the mold described above will provide an accurate regulation of the inclined surface of the chuck body quite easily and economically. 
     FIGS. 64 and 65 show a seventeenth embodiment of the invention in which a lead gripping member is provided at an end of the slide member. In the tubular shaft  104 , the lead tank  105  having a first chuck body  106  at its front end is axially movably disposed. At the front of the first chuck body  106  is provided a chuck ring  107  which serves to close/open the chuck body  106 . 
     A front member  108  is releasably engaged with the end of the tubular shaft  104  by means of, for example, a threading engagement means but the front member  108  can be integrally formed with the tubular shaft  105 . The chuck body  108  contains therein a second chuck body  109  which is axially movable in the front member  108 . The second chuck body  109  has a lead holding portion  110  having on its inner surface a lead griping portion  111  for softly hold the lead. The lead gripping portion  111  is formed integral with or otherwise separately from the second chuck body  109 . In other words, when the second chuck body  109  is fully closed, it holds or grasps firmly the lead and, on the other hand, when it is opened, it holds the lead softly. Incidentally, if the lead gripping portion  111  is formed in a unitary structure, the lead holding portion  110  can be processed with embossing or tapping on the inner surface thereof and, if it is formed of different members, a resilient material such as a silicone rubber, NBR or the like is adhered thereto. 
     The second chuck body  109  has a front portion which projects from the end of the front member  108 , and the end portion of the front member  108  serves as a chuck ring  112  for opening/closing the second chuck body  109 . 
     In FIG. 64 of the drawing reference character “S” represents a resilient member such as a coil spring for spring-biasing the first chuck body and the lead tank  105 . 
     A further description will be made with respect to the first chuck body  106  and the second chuck body  109 . The first chuck body  106  has, on its front outer circumference, an outer flange portion  113 . The second chuck body  109  has at its rear portion a tubular portion in a continued manner, and the tubular portion  114  has, at its inner rear end, an inner flange portion  115  which contacts with the outer flange portion  113  of the first chuck body  106 . The second chuck body  109  has, on its front outer circumference, a middle stepped portion  116  so that it ( 116 ) contacts the inner stepped portion  117  of the front member  108 . 
     The first chuck body  106  is of collet type having two-split, three-split or four-split structure in which if it is forcibly and firmly closed while it grasps no, lead at all, the outer flange portion  113  of the first chuck body  106  is released out of the inner flange portion  115  of the of the second chuck body  109 . In other words, the first chuck body  106  and the second chuck body  109  can be assembled with, and disassembled from, each other. 
     An operation will be described. FIG. 65 shows the state that a residual lead A which has been left from the first chuck body  106  is held by the second chuck body  109 . Further, the succeeding lead B is held by the first chuck body  106 . When the lead tank  105  is pushed forward, the first chuck body  106  is advanced together with the chuck ring  107  so that also the succeeding lead B is advanced. Along with the advance of the succeeding lead B, the residual lead A is pushed forward. However, since the residual lead A is held by the holding portion  110  of the second chuck body  109 , and since the inner flange portion  115  of the second chuck body  109  is contacted with the outer surface of the first chuck body  106 , the second chuck body  109  is advanced together with the residual lead A. 
     At this moment, when the second chuck body  109  is advanced a little (that is, more or less), the second chuck body  109  is opened but, since the lead is held softly by the lead holding portion  109  even when the second chuck body  109  is opened and, therefore, the second chuck body  109  is advanced by the advancing movement of the residual lead A. Incidentally, when the middle stepped portion  116  of the second chuck body  109  is contacted with the inner stepped portion  117  of the front member  108 , the second chuck body  109  is restricted from its further advancing movement. 
     When a further advancing movement is made by the lead tank  105 , the residual lead A is pushed by the succeeding lead B and further slidably advanced through the lead gripping portion  111  of the second chuck body  109  which has been restricted from its movement so that the residual lead A is projected from the end of the lead gripping portion  111 . In a short time, the chuck ring  107  is contacted with the rear end of the second chuck body  109  and its further advancing movement is limited, so that the first chuck body  106  is opened to release the succeeding lead B (FIG.  66 ). 
     When the advancing movement of the lead tank  105  is released (that is, terminated), the first chuck body  106  is retracted releasing the succeeding lead B and, in the process of the retraction, the outer flange portion  113  of the first chuck body  106  is contacted with the inner flange portion  115  of the second chuck body  109  to thereby retract also the second chuck body  109 . In this state, since the residual lead A is softly held by the lead gripping portion  111  of the second chuck body  109 , it is retracted together with the second chuck body  109  with the projected position of the residual lead A being maintained, and the residual lead B which is released from the first chuck body  106  is retracted (FIG.  67 ). 
     Then, the first chuck body  106  is closed by the chuck ring  107  to retract the succeeding lead B. 
     By the operation described above, the residual lead A is retracted relative to the front member  108  but, since the residual lead A is retracted together with the second chuck body  109 , a projecting length of the residual lead A is not decreased. 
     FIG. 58 shows an eighteenth embodiment of the invention. A conical angle  121  of an outer circumference of a first chuck body  118  which contacts an inner flange portion  120  of a second chuck body  119  is determined to be larger than an conical angle  122  of the outer circumference of the end portion of the second chuck body  119 . By varying the conical angles of the first chuck body and the second chuck body as described above, unevenness of the holding positions of the lead by each of the chuck bodies can be absorbed. For example, when the first chuck body is made of a resin material, an outer diameter of the first chuck body is decreased due to elasticity fatigue, etc. and, as a result, the second chuck body which is positioned at a relatively forward position is retracted more than an initially determined position. Consequently, it provides a bad effect on the lead gripping force. This problem has been solved by changing the conical angles of the first chuck body and the second chuck body in the present embodiment. 
     With respect to the conical angles described above, it may be possible that the conical angle relation in the eighteenth embodiment described above be changed in the opposite relation. Namely, the conical angle of the first chuck body  118  is set smaller and the conical angle of the second chuck body  119  is set larger. The eighteenth embodiment will work effectively if the first chuck body is made of a metal and the second chuck body is made of a resin material. This will permit that a lead gripping force of the second chuck body becomes larger than the first chuck body, so that a shake or swing of the lead at its extended tip portion can be prevented. 
     FIG. 69 shows another example in which the second chuck body  123  has, on its inner flange portion  124 , a conical portion  125  so that it contacts with the outer flange portion  127  of the first chuck body  126 . It is the matter of course that the conical angle  128  of the first chuck body  126  is different from the conical angle  129  of the second chuck body  123 . There will be many other modifications. In an example of FIG. 70, the second chuck body  131  is provided, at its middle of the tubular portion  132 , with a flexible stitch portion  133  which, however, can be replaced by rubber-like resilient body  134  (FIG. 71) by a two-color molding technique (molding technique of different material). Further, as shown in FIG. 72, a bellows-like structure  135  can be formed. In another alternative, as shown in FIG. 73, a slit is formed at a tip of the front member  108  so that the slit portion can be opened, and the closed position of the second chuck body is made changeable to thereby absorb the unevenness or scattering of the gripping position of the lead. 
     In the various examples described above, the slide member (and second chuck body) is retracted by the chuck body (and first chuck body) but other features can be applied. 
     Hereinafter, a nineteenth embodiment of the invention will be described with reference to FIGS. 74 and 75, for example. The tubular shaft  137  contains therein an axially displaceable lead tank  138  which has at its front end a chuck body  139 . On the front end portion of the chuck body  139  is provided a chuck ring  140  for opening/closing the chuck body. A resilient member  5  such as a coil spring is disposed between the lead tank  138  and the inner stepped portion  142  of the tubular shaft  137  for the purpose of spring-biasing the elements such as the chuck body  139 . Thus, a lead feed mechanism  143  of the present invention will be composed of these elements such as the lead tank  138 , chuck body  149 , chuck ring  140  and the resilient member  141 . 
     A front member  148  is threadedly engaged with the front portion of the tubular shaft  137 , and the front member  148  contains therein an axially movable slide member  149  projecting from the end of the front member  148 . The slide member  149  has, independently or otherwise unitarily, an anti-retraction member  150  which prevents the lead from retracting. On the outer surface of the two confronting spots of the slide member  149 , a groove portion  151  is formed. The groove portion  151  is not extended to the rear end of the slide member  149  but terminated en route or on the half way, and a stop portion  151   a  is formed as illustrated in FIGS. 74 and 76, for example. 
     The lead tank  138  has at its front portion an arm portion  152  in an opposed relation and the arm portion  152  has an inner projection  153  at its front end portion. In the illustrated embodiment, the arm portion  152  and the lead tank  138  are made of separate members but they can be made in a unitary structure if desired. The inner projection  153  comes into a slidable engagement with the groove  151  of the slide member  149 . The arm portion  152  is slidably fitted into a slit  155  on an inner reduced-diameter portion  154  of the tubular shaft  137 , so that swinging or bending in a circumferential direction can be prevented (see particularly FIG.  75 ). 
     A resilient member  156  such as a coil spring is disposed between the tubular shaft  137  and the slide member  149  for spring-biasing the slide member  149  all the time. 
     An operation will be described. FIG. 74 shows the state that the residual lead A left from the chuck body  139  is held by the anti-retraction member  150  and the succeeding lead A is held by the chuck body  139 . The slide member  149  is spring-biased forwardly by the resilient member  156  but, since the inner projection  153  of the arm member  152  from the lead tank  138  is contacted with the rear portion of the groove portion  151  of the slide member  149 , a forward movement of the slide member  149  is restricted. 
     When the lead tank  138  is pushed forward, the chuck body  139  is retracted together with (lie chuck ring  140 . However, since the slide member  149  is spring-biased by the resilient member  156 , the slide member  149  is advanced with the engagement being maintained between the inner projection  153  of the arm portion  152  and the rear portion of the groove portion  151 . Consequently, the succeeding lead B held by the chuck body  139  and the residual lead A held by the anti-retraction member  150  are advanced together with the slide member  149 . Then, the middle stepped portion  157  of the slide member  149  is contacted with the inclined wall  158  of the front member  148  to limit the further advancing movement (FIG.  76 ). 
     Now, the inner projections  153  of the arm portion  152  is movably inserted into the groove portion  151  of the slide member  149  and therefore the inner projection  153  of the arm portion  152 , the chuck body  139 , the chuck ring  140 , the succeeding lead B and the residual lead A which are held by the chuck body  139  can be advanced further (FIG.  77 ). However, the chuck ring  140  is restricted from further movement at the time when it abuts against the rear end of the slide member  149 . At this moment, the chuck body  139  is opened so that the engagement of the succeeding lead B is released (FIG.  78 ). 
     When the forward movement (i.e., advance) of the lead tank  138  is released, the chuck body  139  is retracted while it is opened, and the slide member  149  which is spring-biased by the resilient member in the forward direction is not retracted. When the inner projection  153  of the arm portion  152  is contacted with the stop portion  151   a  of the groove portion  151  of the slide member  149 , the slide member  149  starts retracting (FIG. 79) against a resilient force of the resilient member  156 . 
     In a short time, the chuck body  139  is closed by the chuck ring  140  to grasp the succeeding lead B again (FIG.  74 ). At this moment, chuck body  139  will be retracted with holding therein the succeeding lead B in a similar manner as the conventional prior art technique. However, also the slide member  149  is retracted and therefore no gap is produced between the succeeding lead B and the residual lead A. 
     Although the succeeding lead and the residual lead are retracted by the operation described above, but the leads are retracted together with the slide member  149  relative to the front member  148  and, therefore, they are not retracted relative to the slide member  149 . Consequently, a lead projection length from the end of the slide member  149  is not at all decreased. 
     Further, the slide member  149  which is engaged with the inner projection  153  of the arm portion  152  maintains its retracting position even after release of the pushing operation and, therefore, no space or gap is produced between the succeeding lead B and the residual lead A due to, for example, drop by gravity. 
     A modification of the nineteenth embodiment of the invention will be described with reference to FIG.  80 . Although in the previous embodiment the arm portion is fixed to the lead tank to thereby provide an interlocking relation, in the present embodiment of FIG. 80, the slide member is interconnected by the resilient member  141 . Specifically, a forwardly bent arm portion  159  is extended from a rear end of the resilient member  141 , and a front end portion (inner projection  160 ) of the arm portion  159  is engaged with a stop portion  151   a  of the groove portion  151 . By working or processing the resilient member itself, the arm portion can be formed and, therefore, an easy and economical assembly can be attained. A further description of the operation will be omitted for simplification only since it is considered to be substantially same as the previous embodiments. 
     FIG. 81 shows a further modification in which an arm portion  162  is extended rearward from the slide member  161  and the arm portion  162  is slidably engaged with a slit  164  of the lead tank  163  to thereby provide an interconnecting relation. 
     An operation will be described except the operational mode that is substantially same as the previous (nineteenth) embodiment. When the lead tank  163  is pushed, the chuck body  139  and the chuck ring  140  are advanced and at this moment the slide member  161  is advanced by a resilient force of the resilient member  156 . When the advance of the slide member  161  is released, only the chuck body  139  and the chuck ring  140  are advanced and, in a short time, the chuck body  139  is opened. At this moment, the slit  164  of the lead tank  163  is slidably advanced relative to the inner projection  165  of the arm portion  162 . When the pushing operation of the lead tank  163  is released, not only the lead tank  163  but also the chuck body  139  start their retraction. At this moment, the slider member  161  is not moved rearward by the resilient member  156  but, in a moment of so, the arm portion  165  is contacted with the front portion of the slit  164  of the lead tank  163  and, by this contact, the slide member  161  is forcibly retracted. 
     FIG. 82 shows a twentieth embodiment of the present invention in which the invention is applied to a so-called side knock type mechanical pencil having a knocking or pushing operational button on the side of the tubular shaft of the pencil. A tubular shaft  166  has a lead tank portion  167  at the rear portion but the lead tank portion may be formed at a rear of a lead feeding mechanism which will be described. 
     In a front inner portion of the tubular shaft  166 , a tapered slide member  168  is axially slidably disposed. A chuck ring  170  is provided around a front portion of the chuck body  169  for opening/closing the chuck body  169 . At the rear end of the tapered slide member  168 , a lead receiving member  171  is fixed to, or unitarily formed with, the rear end of the tapered slide member so that the leads can be divided one by one and received the lead receiving member  171 . An inner diameter of a lead passage  172  of the tapered slide member  1698  is determined to be larger than the diameter of the lead, so that any obstruction against passing of the lead, which is caused by curvature of the tapered slide member of curvature of the lead, can be prevented effectively. 
     A resilient member  173  such as a coil spring which spring-biases the tapered slide member  168  and the chuck body, etc. in the rearward direction is disposed between the tapered slide member  168  and the inner stepped portion  174  of the tubular shaft  166 . These elements such as the tapered slide member  168 , chuck body  169 , chuck ring  170  and resilient member  173  constitute the lead feed mechanism  175  of the present invention. 
     A front member  176  is releasably engaged with a front portion of the tubular shaft  166  by, for example, a threaded engagement. The front member  176  has a slide member  178  which is slidably disposed in the front member and projects from an end of the front member  176 . The slide member  178  has therein an anti-retraction member  179  which holds the lead softly for preventing the lead from dropping. The anti-retraction member  179  may be formed integral with the slide member  178 . 
     The tapered slide member  168  has an inclined surface  180  on an outer surface of the middle portion thereof. An arm portion  181  is fixed to a rear portion of the slide member  178  and the arm portion  181  has at its rear portion an inclined surface  182  which is shorter than the inclined surface  180 . A knock member  183  is rotatably positioned at a middle portion of the tubular shaft  166  and the knock member  183  has a first contact portion  184  and a second contact portion  185  which will contact with the inclined surfaces  180 ,  182 , respectively. Incidentally, the contact portions  184 ,  185  of the knock member  183  are formed to ride over the tapered slide member  168  so that they can contact with the inclined surfaces  180 ,  182 . 
     Reference numeral  186  represents a resilient member such as a coil spring which is disposed between the front member  176  and the slide member  178  for spring-biasing the slide member  178  in the rearward direction. 
     Further, reference numeral  187  represents a grip member of a rubber-like material which is coated extending from a front portion of the tubular shaft  166  to a rear portion of the front member  176 . At the middle portion where the grip member  187  meets with the tubular shaft  166 , a window  188  is formed for permitting the knock member  183  to rotate about, as a fulcrum, the front end thereof. 
     An operation will be explained. FIG. 82 shows the state that the residual lead A which has been left from the chuck body  169  is held by the anti-retraction member  179  and the residual lead B is held by the chuck body  169 . The slide member  178  is spring-biased in the rearwardly by resilient member  186 , and its rear end (that is, the inclined surface  182 ) is contacted with the second contact portion  185  of the knock member  183  and, therefore, a retraction of the slide member  178  is restricted. Incidentally, the first contact portion  184  of the knock member  183  is, in a normal condition, not contacted with but spaced from the inclined surface  180  of the tapered slide member  178 . By forming the spaced relation as described above, a reliable grasping force of the chuck body relative to the lead can be maintained even if there is an inadvertent or unexpected dimensional reduction of the lead during the production steps of the lead. On the other hand, if the tapered slide member is always placed in a close contact position relative to the knock member, the gripping force becomes lowered and, therefore, it is likely that the lead is unfavorably depressed in the writing operation. 
     When the knock member  183  is pushed inside of the tubular shaft in the radially inwardly, the second contact portion  185  of the knock member  183  pushes the inclined surface  182  of the slide member  178  so that the slide member is advanced. At this moment, the residual lead A is held by the anti-retraction member  179  of the slide member  178  and, therefore, the residual lead A is retracted together with the slide member  178 . When the knock member  183  is pushed further, the first contact portion  184  of the knock member  183  comes into contact with the inclined surface  180  of he tapered slide member  168  to thereby start an advancing movement of the tapered slide member  168 . At this moment, however, the second contact  185  of the knock member  183  has over-ridden a top of the inclined surface  182  of the slide member  178  and, therefore, the slide member is not permitted to advance further. Thus, even if the knock member  183  is pushed further, the position of the knock member is unchanged (FIG.  83 ). 
     When the advancing movement of the tapered slide member starts, the chuck body  169  which holds the succeeding lead B and the chuck ring  170  are moved forward. In the forward movement of the chuck body  169 , the succeeding lead B held by the chuck body  169  contacts and immediately pushes the residual lead A, so that the residual lead A is advanced relative to the slide member  178  (FIG.  84 ). In a short time, the chuck ring  170  contacts the rear end of the slide member  178  to open the chuck body  169  so that the engagement with the succeeding lead is released. Although in this step the slide member  178  is spring-biased by the resilient member in the rearward direction but retraction of the slide member  178  is restricted because the top of the inclined surface  182  is contacted with the second contact portion  185  of the knock member  183 . 
     An advancing movement distance of the tapered slide member  168  by the first contact portion  184  of the knock member  183  is larger than an advancing movement of the slide member  178  by the second contact portion  185 . In other words, it is designed that the tapered slide member advances more than the slide member. Specifically, a length of the inclined surface  180  of the tapered slide member  168  is made longer than a length of the inclined surface  182  of the slide member  178  so that the advancing distance is longer as described above. 
     When the pushing operation of the knock member  183  is released, the tapered slide member  168  is retracted in the first place, so that the chuck body  169  and the chuck ring  170  are retracted and hold again the succeeding lead B to finish the retracting operation. However, since the second contact portion  185  of the knock member  183  is in the state of pushing the inclined surface  182 , the slide member  178  maintains its advanced position. At this moment, the succeeding lead B is held immediately before the chuck body  169  is completely closed and retracted and, therefore, it will retract slightly so that, as a result, a gap is produced relative to the residual lead A (FIG.  85 ). 
     When the pushing operation of the knock member  183  is released, the second contact portion  185  of the knock member  183  rides over again the top of the inclined surface  182 , and also the slide member  178  is retracted together with the residual lead A by a resilient force of the resilient member  186 . At this moment, the rear end of the residual lead A is contacted with the front end of the succeeding lead B (FIG.  86 ). 
     In this embodiment, the tapered slide member starts moving to open the chuck body after the advancing movement of the slide member is restricted. It may be possible that the tapered slide member starts in the process of the advance of the slide member, and the chuck ring catches up the rear end of the slide member to thereby open the chuck body. 
     In other words, it can be determined that the slide member is retracted for at least a distance which is equal to the lead-retraction length or more, after the chuck is closed, when the chuck body hold the lead. This will be able to omit a means or mechanism which restricts the advancing movement of the slide member. 
     FIGS. 87 and 88 show a twenty first embodiment of the invention, in which the slide member is retracted by pushing a grip member which is provided on the tubular shaft. The grip member  190  made of a rubber-like resilient material is mounted on the front outer circumference of the tubular shaft  189 . A front member  191  is threadedly engaged with a front end of the tubular shaft  189  and a slide member  193  having therein an anti-retraction member  192  is axially slidably disposed in the front member  191 . An arm portion  194  is formed on the rear portion of the slide member  193  such that the arm portion  194  is slidably engaged with a slit  198   a  of the tubular shaft  198 , and the arm portion  194  has an engagement hole  195  at is rear end. The engagement hole  195  has an inclined surface  195   a  on its rear portion. A through hole  196  is formed on the tubular shaft  189  at a confronting position of the engagement hole  195 , and an inner projection  197  of the grip member  190  is movably inserted into the through hole  196 . A chuck body  199  is fixed to the front end of a lead tank  198 . 
     An operation will be described. FIG. 87 shows the state that the lead tank  198  is pushed to proceed a lead feed operation. Similarly to the prior art structure, a space or gap  200  is formed between the residual lead A and the succeeding lead B. When the grip member  190  is grasped for writing purposes, the grip member  190  is inwardly deformed or depressed by the grasping force of the user, and the inner projection  197  serves to retract the arm portion  194  by sliding along the inclined surface  195   a  of the arm portion  194 . At this moment, also the slide member  193  is retracted and consequently the rear end of the residual lead A is contacted with the front end of the succeeding lead B (FIG. 89) 
     FIG. 90 shows a twenty second embodiment of the invention which is a modification of the fifteenth embodiment. In this embodiment, a distance P of the movement until the chuck ring contacts the stepped portion is made larger than a distance Q of the movement until the projection of the chuck body contacts the front end of the window of the slide member. Similarly to the fifteenth embodiment of the invention, the slide member  201  has at its rear end a window  202  which freely receives therein a projection  205  of the chuck body  204 . 
     On the inner surface of the front member  65  fixed to the front end of the tubular shaft  58 , a stepped portion  97  to which the chuck ring  61  contacts is provided. A movement distance P of the chuck ring  61  is determined to be larger than a movement distance  0  until the projection  205  of the chuck body  204  contacts the front end of the window  202  of the slide member  201 . Further, a sliding resistance force of the slide member  201  relative to the front member  65  is determined to be larger than a sliding resistance force of the lead relative to the anti-retraction member  96 . 
     An operation will be described. When the lead tank  59  is pushed, the chuck body  204  is pushed together with the succeeding lead B and, by this movement, the residual lead A is also pushed forward. In a short time, the projection  205  of the chuck body  204  is contacted with the front end of the window of the slide member  201  (FIG. 91) to thereby makes the slide member  201  move forward. (FIG.  92 ). Further, when the lead tank  59  is pushed, the chuck ring  61  is contacted with the stepped portion  97  and the chuck body  204  urges the slide member in the forward direction and, at the same time, open the chuck body  204  to thereby release the engagement of the succeeding lead B (FIG.  93 ). 
     When the pushing force of the lead tank is released, the chuck body  204  is retracted and, with some delay time, the chuck body  204  is further retracted together with the slide member  201  so that the chuck body is closed by the effect of the chuck ring  61 . 
     FIGS. 94 to  99  show a modification of the twenty second embodiment described above, in which the slide member  201  has at its rear portion a window  202  having an inclined surface  203  at the front end portion of the window  202 . A projection  205  of the chuck body  204  is freely inserted into the window  202 , and the window  202  has at its front end an inclined surface  206  which slidably contacts the inclined surface  203  of the window  202 . 
     On the inner surface of the front member  65  fitted to the front end of the tubular shaft  58 , a stepped portion  97  to which the chuck ring  61  contacts is provided. A moving distance P of the chuck ring  61  is determined to be larger than a distance Q of the movement until the projection  205  of the chuck body  204  is contacted with the front end of the window  202  of the slide member  201 . 
     An operation will be described When the lead tank  59  is pushed, the chuck body  204  is pushed together with the succeeding lead B and, by the movement, also the residual lead A is pushed forward. In a short time, the inclined surface  206  of the chuck body  204  is contacted with the inclined surface  203  of the slide member  201  (FIG. 95) to thereby advance the slide member  201  as well (FIG.  96 ). Further, when the lead tank  59  is pushed, the chuck ring  61  is contacted with the stepped portion  97  and, at the same time, the chuck body  204  is opened by the effect of the inclined surfaces so that, at this moment, the engagement to the succeeding lead B is released. 
     In other words, in this modification the two inclined surfaces are made to thereby positively open or dilate the chuck body so that a reliable operation of the chuck body is enhanced. 
     As described above, the present invention provides an improvement of the mechanical pencil which provides a favorable feeling of writing and an effective use of the writing lead.