Patent Document

BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a lead cartridge for replenishing a writing tool with leads or replacing leads in a writing tool and to a writing tool into which the lead cartridge is to be incorporated. 
         [0003]    2. Description of the Related Art 
         [0004]    When replenishing a writing tool with leads, a user for the writing tool usually removes an eraser from an eraser receptacle engaged with the rear part of a lead tank disposed within the body of the writing tool, extracts leads from a lead case which is a separate product from the writing tool and contains spare leads, and insert the leads into the lead tank through the eraser receptacle. 
         [0005]    As alternative way of replenishing a writing tool with leads, it is also known that a lead cartridge containing leads is replaced, and such a lead cartridges is described in Japanese Utility Model Publication Laid-Open No. 64-17784. According to the publication, an open pipe is fixed to a leading guide of a writing tool, an opening/closing mechanism having an elastic opening/closing part is disposed at the tip of the lead cartridge, and the elastic opening/closing part is opened when it is in its position of engagement with the leading guide by the open pipe or is closed when it is in a position of non-engagement with the leading guide. 
       SUMMARY OF THE INVENTION 
       [0006]    Although the lead cartridge according to the publication or any other lead cartridge now commercially distributed may be equipped at its rear end with a rod-shaped eraser, the equipped eraser is usually small and has to be replaced earlier than the lead cartridge is. As a result, it is necessary to replace or replenish the leads and the eraser respectively. 
         [0007]    An object of the present invention, attempted in view of this problem, is to provide a lead cartridge which is capable of holding a rod-shaped object of a sufficient length and allowing the replacement of leads and the rod-shaped object at the same time and a writing tool in to which the lead cartridge is to be incorporated. 
         [0008]    In order to achieve the object stated above, a lead cartridge according to the invention including a tank for containing leads and adapted to be detachably incorporated into a writing tool to supply leads, further comprises a rod-shaped object feeding mechanism for propelling a rod-shaped object by a turning manipulation. 
         [0009]    According to the invention, equipping the lead cartridge with a rod-shaped object feeding mechanism for propelling a rod-shaped object enables the rod-shaped object to have a sufficient length in the axial direction and thereby to extend the exhaustion of the rod-shaped object until the replacement timing for the lead cartridge and accordingly to dispense with separate replacement of the lead and of the rod-shaped object. 
         [0010]    The rod-shaped object feeding mechanism can comprises a spiral groove formed in the inner circumferential surface of a case comprising the tank, a guide sleeve which is disposed within the case so as to be unmovable in the axial direction and rotatable relative to the case and is formed with a guide hole extending in the axial direction, and a receptacle for holding a rod-shaped object, which is slidably fitted into the guide hole of the guide sleeve and has a male thread screwing into the spiral groove. When the lead cartridge is incorporated into the writing tool, the case is unrotatable relative to an outer sleeve of the writing tool and part of the guide sleeve protrudes from the writing tool to be subjected to the turning manipulation. By forming of the spiral groove for propelling the rod-shaped object on the inner circumferential surface of the case constituting the tank enables the rod-shaped object feeding mechanism to be integrally incorporated into the lead cartridge. When the lead cartridge is incorporated into a writing tool, the rod-shaped object can be propelled from the writing tool by turning the guide sleeve partly protruding from the writing tool. 
         [0011]    Alternatively, the rod-shaped object feeding mechanism can comprise a guide sleeve which is coupled to a case constituting the tank so as to be unmovable in the axial direction and unrotatable relative to the case and is formed with a guide hole extending in the axial direction, a spiral sleeve which is arranged outside of the guide sleeve so as to be unmovable in the axial direction and rotatable relative to the guide sleeve and is formed in an inner circumferential surface with a spiral groove, and a receptacle for holding a rod-shaped object, which is slidably fitted into the guide hole of the guide sleeve and has a male thread screwing into the spiral groove. When the lead cartridge is incorporated into the writing tool, the case is unrotatable relative to an outer sleeve of the writing tool, and part of the spiral sleeve protrudes from the writing tool to be subjected to the turning manipulation. By coupling of the guide sleeve to the case constituting the tank enables the rod-shaped object feeding mechanism to be integrally incorporated into the lead cartridge. When the lead cartridge is incorporated into a writing tool, the rod-shaped object can be propelled from the writing tool by turning the spiral sleeve partly protruding from the writing tool. By decoupling the case and the guide sleeve, the rod-shaped object feeding mechanism is enabled to be used as an independent unit as well. 
         [0012]    Alternatively, the rod-shaped object feeding mechanism can comprise a spiral sleeve which is coupled to a case constituting the tank so as to be unmovable in the axial direction and unrotatable relative to the case and is formed in an inner circumferential surface with a spiral groove, a guide sleeve which is arranged inside of the guide sleeve so as to be unmovable in the axial direction and rotatable relative to the spiral sleeve and is formed with a guide hole extending in the axial direction, and a receptacle for holding a rod-shaped object, which is slidably fitted into the guide hole of the guide sleeve and has a male thread screwing into the spiral groove. When the lead cartridge is incorporated into the writing tool, the case is unrotatable relative to an outer sleeve of the writing tool, and part of the guide sleeve protrudes from the writing tool to be subjected to the turning manipulation. By coupling of the spiral sleeve to the case constituting the tank enables the rod-shaped object feeding mechanism to be integrally incorporated into the lead cartridge. When the lead cartridge is incorporated into a writing tool, the rod-shaped object can be propelled from the writing tool by turning the guide sleeve partly protruding from the writing tool. By decoupling the case and the spiral sleeve, the rod-shaped object feeding mechanism is enabled to be used as an independent unit as well, 
         [0013]    The guide sleeve can engage with an engaging portion formed on the circumferential surface of the case comprising the tank to be held so as to be unmovable in the axial direction within the case. Alternatively, the spiral sleeve can engage with an engaging portion formed on the circumferential surface of the case comprising the tank to be held so as to be unmovable in the axial direction within the case. When the rod-shaped object feeding mechanism is to be assembled to the case, it can be easily accomplished by engaging the engaging portion. When the rod-shaped object feeding mechanism is desired to be removed from the case, it can be easily taken out of the case by disengaging the engaging portion. 
         [0014]    Preferably, a display part on which lead information regarding leads contained in the tank is displayed can be provided on the outer circumferential part of the lead cartridge. The display part can provide information on the contained leads and the lead cartridge can be appropriately incorporated into the writing tool. 
         [0015]    Preferably, at least part of the case comprising the tank is composed of a transparent material which makes visible an inside of the tank. As the inside of the tank is made visible, it is possible to check from outside the state of accommodation of leads in the tank or the other status. 
         [0016]    Preferably, in a writing tool into which the lead cartridge is to be incorporated, the lead cartridge is made visible through at least part of an outer sleeve of the writing tool. It is possible to check from outside of the writing tool, lead information and the state of accommodation of leads in the tank by visually inspecting the lead cartridge through the outer sleeve of the writing tool in a state in which the lead cartridge is incorporated into the writing tool 
         [0017]    At least part of the outer sleeve of the writing tool is composed of a transparent material and the part composed of the transparent material functions as a lens. It is possible to check from outside of the writing tool, lead information and the state of accommodation in the tank in an enlarged view by utilizing the lens function of part of the outer sleeve 
         [0018]    The present disclosure relates to subject manner contained in Japanese Patent Application Nos. 2006-77084 filed on Mar. 20, 2006, and 2007-030886 filed on Feb. 9, 2007, which is expressly incorporated herein by reference in its entirety. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0019]      FIG. 1  shows an overall view of a lead cartridge, which is a preferred embodiment of the present invention; 
           [0020]      FIG. 2  is a longitudinal sectional view of the lead cartridge shown in  FIG. 1 ; 
           [0021]      FIG. 3  is a longitudinal sectional view of a case; 
           [0022]      FIG. 4A  is a plan view, and  FIG. 4B  a sectional view, of a guide sleeve; 
           [0023]      FIG. 5  is a plan view,  FIG. 5B  a front view and  FIG. 5C  a sectional view, of an eraser receptacle; 
           [0024]      FIG. 6  is a sectional view showing a state in which the lead cartridge shown in  FIG. 1  is incorporated into a mechanical pencil; 
           [0025]      FIG. 7  is a longitudinal section of the body of an outer sleeve; 
           [0026]      FIG. 8  is a longitudinal sectional view of a chuck joint; 
           [0027]      FIG. 9  is a sectional view of a variation of the chuck joint; 
           [0028]      FIGS. 10A and 10B  are sectional views showing the procedure of linking the lead cartridge with the chuck joint; 
           [0029]      FIG. 11  shows another side view of a mechanical pencil into which the lead cartridge is incorporated; 
           [0030]      FIG. 12  is a longitudinal sectional view of a lead cartridge, according to another preferred embodiment of the invention; 
           [0031]      FIG. 13  shows an exploded view of the lead cartridge shown in  FIG. 12 ; 
           [0032]      FIG. 14  is an exploded longitudinal sectional view of the lead cartridge shown in  FIG. 12   
           [0033]      FIG. 15  is a sectional view showing a state in which the lead cartridge shown in  FIG. 12  is incorporated into a mechanical pencil; and 
           [0034]      FIG. 16  is a longitudinal sectional view of a lead cartridge, according to still another preferred embodiment of the invention; 
           [0035]      FIG. 17  shows an exploded view of the lead cartridge shown in  FIG. 16 ; and 
           [0036]      FIG. 18  is a sectional view showing a state in which the lead cartridge shown in  FIG. 16  is incorporated into a mechanical pencil. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0037]    Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. 
         [0038]      FIG. 1  shows an overall view of a lead cartridge according to a preferred embodiment of the invention, and  FIG. 2  shows a longitudinal sectional view of this lead cartridge. 
         [0039]    Referring to the drawings, a lead cartridge  10  comprises a case  12 , a packing  13 , a guide sleeve  14 , and an eraser receptacle  16  to hold an eraser  18  which is a rod-shaped object. 
         [0040]    The case  12  is a hollow cylinder as shown in  FIG. 3 , comprising a lead tank  12   a  in its central portion to contain a plurality of leads for replenishment or replacement. The case  12  is provided on the front side of the lead tank  12   a  with a detachable coupling  12   b  having a reduced diameter than that of the portion defining lead tank  12   a . A contracted part  12   c , reduced in bore, is formed on the boundary between the lead tank  12   a  and the detachable coupling  12   b . The packing  13 , composed of an elastic material, is so inserted into the detachable coupling  12   b  from its tip as to protrude toward the contracted part  12   c . The central aperture  13   a  of the packing  13  is smaller in its natural state than the diameter of a lead, and in this state no lead in the lead tank  12   a  can pass the central aperture  13   a  and is prevented from escaping from the detachable coupling  12   b.    
         [0041]    A plurality of ribs  12   d  for preventing rotation are provided on the outer circumference of the case  12 . The case  12  is also provided on the circumferential surface on the rear side of the lead tank  12   a  with a pair of engaging pieces  12   e  as engaging portions. The engaging pieces  12   e  axe surrounded by a U-shaped slit  12   f  formed in the circumferential surface of the case  12 , and are thereby enabled to be elastically displaced in the radial direction. Engaging stubs  12   g  are formed on the inner circumferential surface of the engaging pieces  12   e . Further, a spiral groove  12   h  is formed in the inner circumferential surface positioned to rearward of the engaging pieces  12   e  of the case  12 . 
         [0042]    Preferably, a display part  12   i  on which some items of lead information such as the diameter, hardness and color of leads contained therein are printed, is provided on the outer surface of the case  12 . This would facilitate appropriate choice of a lead cartridge  10  by the user. 
         [0043]    The guide sleeve  14  is arranged within the case  12  so as to correspond to the engaging pieces  12   e  and the spiral groove  12   h  of the case  12  described above. As shown in  FIG. 4 , an annular groove  14   a  as an engaging portion is formed in the outer circumferential surface of the front end of the guide sleeve  14 , and the engaging stubs  12   g  of the engaging pieces  12   e  engage with the inside of this annular groove  14   a . This engagement enables the guide sleeve  14  to rotate relative to the case  12  but it is unable to move in the axial direction relative to the case  12 . A pair of guide holes  14   b  extending in the axial direction are formed in the central portion of the guide sleeve  14 , and a manipulating part  14   c  expanded in diameter is formed at the rear end of the guide sleeve  14 , The manipulating part  14   c , arranged outside the case  12 , is in contact with the rear end surface of the case  12 . 
         [0044]    In assembling the guide sleeve  14  into the case  12 , as the engaging pieces  12   e  permit elastic displacement, when the guide sleeve  14  is inserted into the case  12 , the guide sleeve  14  is enabled to be easily engaged with the case  12  by the deformation of the engaging pieces  12   e . In addition, when it is desired to remove the guide sleeve  14  from the case  12  after assembly, the guide sleeve  14  can be easily taken out of the case  12  by deforming the engaging pieces  12   e  from outside outward in the radial direction by using a jig or the like. Therefore, even if a wrong kind or the wrong number of leads are loaded at the time of assembly and that error is revealed after the guide sleeve  14  is assembled into the case  12 , the error can be corrected by removing the guide sleeve  14  from the case  12 . It has to be noted that, instead of engaging the engaging pieces  12   e  as engaging portions with the annular groove  14   a  of the guide sleeve  14  as engaging portion, annular concave rib and convex rib formed as engaging portions between the inner circumferential surface of the case  12  and the outer circumferential surface of the guide sleeve  14  can as well be engaged, and fitting these concave and convex ribs together enables the guide sleeve  14  to be turnably engaged with the case  12 . 
         [0045]    The eraser receptacle  16  is arranged within the guide sleeve  14  to be slidable in the axial direction relative to the guide sleeve  14  and to be turnable relative to the case  12 . As shown in  FIG. 5 , the eraser receptacle  16  has a bottom part  16   a  receiving the bottom surface of the eraser  18  and a pair of pinching pieces  16   b  extending backward from the bottom part  16   a  to pinch the eraser  18  between them. The pinching pieces  16   b , fitted into the guide holes  14   b  of the guide sleeve  14 , can slide in the guide holes  14   b  in the axial direction. Further, a male thread  16   c  is formed on the outer circumferential surface of the pinching pieces  16   b , and screws into the spiral groove  12   h  of the case  12 . 
         [0046]    The spiral groove  12   h  of the case  12 , the guide sleeve  14  and the eraser receptacle  16  constitute a rod-shaped object feeding mechanism which is to be integrated with the lead cartridge  10 . 
         [0047]      FIG. 6  shows a state in which the lead cartridge  10  configured as described above is incorporated into a mechanical pencil  20 , which is a writing tool. This mechanical pencil  20  has an outer sleeve  22  and a lead feeding mechanism  24  built into the outer sleeve  22 . 
         [0048]    The outer sleeve  22  comprises a body  30 , a tip element  32  screwed on the tip of the body  30  and a grip element  34  fitted to the grip portion of the body  30 . As shown in  FIG. 7 , grooves  30   a  for preventing rotation are formed in the inner circumferential surface of the body  30 . Engagement of the ribs  12   d  of the case  12  of the lead cartridge  10  with these grooves  30   a  prevents the case  12  and the outer sleeve  22  from relatively turning. 
         [0049]    The lead feeding mechanism  24  has a chuck joint  36 , a lead chuck  38  which, with its rear end pressed into the chuck joint  36 , fastens and feeds out a lead, a chuck ring  40  which, fitted on the outer circumferential side of the chuck portion of the lead chuck  38 , can fasten the chuck portion of the lead chuck  38 , a sleeve  42  which restricts the backward movement of the chuck ring  40 , a chuck spring  44  which, positioned between the sleeve  42  and the chuck joint  36  urges the chuck joint  36  and the lead chuck  38  backward, a slider  46  which is movably disposed within the tip element  32 , and a lead pipe  48 . 
         [0050]    The chuck joint  36 , as shown in  FIG. 8  on an enlarged scale, has a chuck fitting hole  36   a  into which the rear end of the lead chuck  38  is pressed, a cartridge fitting hole  36   b  to which the detachable coupling  12   b  of the case  12  of the lead cartridge  10  is detachably coupled, and a lead feeding hole  36   c  communicating the chuck fitting hole  36   a  and the cartridge fitting hole  36   b  for guiding lead to penetrate one by one. A guide pipe  37  is fixedly inserted into the lead feeding hole  36   c . Alternatively, this guide pipe  37  may be molded integrally with the chuck joint  36  as shown in  FIG. 9 . 
         [0051]    The coupling of the lead cartridge  10  and the chuck joint  36  is accomplished by inserting the detachable coupling  12   b  of the case  12  of the lead cartridge  10  into the cartridge fitting hole  36   b  as shown in  FIG. 10 . This causes the ridged surface of the outer circumferential surface of the detachable coupling  12   b  and the ridged surface of the inner circumferential surface of the cartridge fitting hole  36   b  to mesh with each other to cause the case  12  and the chuck joint  36  to be coupled to each other. At the same time, the guide pipe  37  is forcedly inserted into the central aperture  13   a  of the packing  13  to enlarge the central aperture  13   a  to enable a lead in the lead tank  12   a  to pass the central aperture  13   a  and the lead feeding hole  36   c . In this way, a lead in the lead tank  12   a  is fed to the lead chuck  38 . When the lead cartridge  10  is to be taken off, it can be easily accomplished by drawing the case  12  out of the outer sleeve  22 . 
         [0052]    When the lead cartridge  10  is incorporated into the mechanical pencil  20  as described above, the rear end portion of the lead cartridge  10  including the manipulating part  14   c  of the guide sleeve  14  protrudes from the rear end of the outer sleeve  22 . When the rear end portion of this lead cartridge  10  is knocked, the chuck joint  36 , the lead chuck  38  and the chuck ring  40  move ahead together with the lead cartridge  10 , resulting in lead feeding as is well known to make the lead available for use in writing. 
         [0053]    Further, when the eraser is to be used, the manipulating part  14   c  in the rear end portion is turned in a state in which the outer sleeve  22  is fixed. Since the outer sleeve  22  and the case  12  are prevented from relatively turning, the eraser receptacle  16  which turns integrally with the guide sleeve  14  turns relative to the case  12 . Then, as the male thread  16   c  of the eraser receptacle  16  moves along the spiral groove  12   h , the eraser  18  is let out. When the manipulating part  14   c  is turned in the other direction, the eraser  18  is retreated into the case  12 , 
         [0054]    Since the eraser  18  can be propelled in this way, a sufficient length in the axial direction can be secured for the eraser  18  until the lead cartridge  10  is up for replacement, making it unnecessary for the leads and the eraser to be replaced on separate occasions, 
         [0055]    Further it is possible to provide a transparent shaft  30 ′ in part of the body  30  of the outer sleeve  22  as shown in  FIG. 11 . If the position of this transparent shaft  30 ′ is matched with that of the display part  12   i  of the case  12  of the lead cartridge  10  in the axial direction within the body  30 , information on the lead and other items can be conveniently seen from outside even after the lead cartridge  10  is incorporated. By appropriately varying the wall thickness of the transparent shaft  30 ′ and shaping the inner sectional profile of the transparent shaft  30 ′ in a polygon to give the transparent shaft  30 ′ a lens effect, the display part  12   i  of the case  12  can be displayed on an enlarged scale for further convenience. Alternatively, it is also possible to provide a through hole in part of the outer sleeve  22  instead of the transparent shaft  30 ′. 
         [0056]    It is further possible to configure either the whole or part of the case  12  of transparent resin to make it a transparent shaft. This makes it possible to see leads in the lead tank  12   a  visible from outside and to know the state of accommodation of leads in the tank and the number of leads currently contained and accordingly the need, if any, to replace the lead cartridge  10 . 
         [0057]      FIG. 12  is a longitudinal sectional view of a lead cartridge according to another preferred embodiment of the present invention. The same or similar members as or to the foregoing embodiment will be assigned respectively the same reference signs, and their description will be dispensed with. 
         [0058]    A lead cartridge  50  of this embodiment has a case  52 , a packing  13 , a guide sleeve  54 , a spiral sleeve  56  and an eraser receptacle  16  to hold an eraser  18  which is a rod-shaped object. 
         [0059]    The case  52  is a hollow cylinder as shown in  FIG. 13  and  FIG. 14 , comprising a lead tank  52   a  in its central portion to contain a plurality of leads for replenishment or replacement. The case  52  is provided on the front side of the lead tank  52   a  with a detachable coupling  52   b  having a reduced diameter than that of the portion defining the lead tank  52   a . A contracted part  52   c , reduced in bore, is formed on the boundary between the lead tank  52   a  and the detachable coupling  52   b . The packing  13 , composed of an elastic material, is so inserted into the detachable coupling  52   b  from its tip as to protrude toward the contracted part  52   c    
         [0060]    A plurality of ribs  52   d  for preventing rotation are provided on the outer circumferential surface of the case  52 , to be meshed with the grooves  30   a  for preventing rotation of the body  30  of the outer sleeve  22  of the writing tool  20 . The inner circumferential surface of the case  52  on the rear side of the lead tank  52   a  constitutes a polygonal hole portion  52   e  whose sectional profile is a polygon, and an annular concave rib  52   f  is formed as an engaging portion in the inner circumferential surface to rearward of the polygonal hole portion  52   e.    
         [0061]    A guide sleeve  54  engages with the polygonal hole portion  52   e  and the annular concave rib  52   f  of the case  52 . Thus, the outer circumferential surface of the front of the guide sleeve  54  constitutes a polygonal part  54   a  whose sectional profile is shaped polygonal, and an annular convex rib  54   d  is formed as an engaging portion on the outer circumferential surface behind this polygonal part  54   a . This polygonal part  54   a  is fitted into the polygonal hole portion  52   e  of the case  52 , and the annular convex rib  54   d  engages with the annular concave rib  52   f  of the case  52 . This engagement causes the guide sleeve  54  to be coupled to the case  52  so as to be unrotatable nor unmovable in the axial direction relative to the case  52 . A pair of guide holes  54   b  extending in the axial direction are formed in the central portion of the guide sleeve  54 , and an expanded-diameter part  54   c  is formed at the rear end of the guide sleeve  54 . 
         [0062]    Further, a pair of engaging pieces  54   e  axe formed on the outer circumferential surface of the guide sleeve  54 . The engaging pieces  54   e  are surrounded by a U-shaped slit  54   f  formed in the circumferential surface of the guide sleeve  54 , and are thereby enabled to be elastically displaced in the radial direction. 
         [0063]    The spiral sleeve  56 , held between the expanded-diameter part  54   c  and the engaging pieces  54   e  of the guide sleeve  54 , is so arranged on the outer circumferential side of the guide sleeve  54  as to be unable to move in the axial direction but able to turn relative to the guide sleeve  54 . A spiral groove  56   a  is formed in the inner circumferential surface of the spiral sleeve  56 . 
         [0064]    The eraser receptacle  16  is arranged within the guide sleeve  54  to be slidable in the axial direction relative to the guide sleeve  54  and to be turnable relative to the spiral sleeve  56 . The pinching pieces  16   b  of the eraser receptacle  16  are fitted into the guide holes  54   b  of the guide sleeve  54  to be able to slide in the axial direction in the guide holes  54   b , and at the same time the male thread  16   c  of the eraser receptacle  16  screws into the spiral groove  56   a  of the spiral sleeve  56 , 
         [0065]    The guide sleeve  54 , the eraser receptacle  16  and the spiral sleeve  56  described above constitute a rod-shaped object feeding mechanism which is to be integrated with the lead cartridge  50 . 
         [0066]      FIG. 15  shows a state in which the lead cartridge  50  configured as described above is being incorporated into the mechanical pencil  20 , which is a writing tool. This lead cartridge  50  can be fitted or removed in the same way as in the first preferred embodiment. When the lead cartridge  50  is incorporated into the mechanical pencil  20 , the expanded-diameter part  54   c  of the guide sleeve  54  and part of the spiral sleeve  56  protrude from the rear end of the outer sleeve  22 . When the rear end portion of this lead cartridge  50  is knocked, the chuck joint  36 , the lead chuck  38  and the chuck ring  40  move ahead together with the lead cartridge  50 , resulting in lead feeding as is well known to make the lead available for use in writing. 
         [0067]    Further, when the eraser is to be used, the spiral sleeve  56  in the rear end portion is turned in a state in which the outer sleeve  22  is fixed. Since the outer sleeve  22  and the case  52  are prevented from relatively turning and the case  52  and the guide sleeve  54  are also prevented from turning, the eraser receptacle  16  which turns integrally with the guide sleeve  54  turns relative to the spiral sleeve  56 . Then, as the male thread  16   c  of the eraser receptacle  16  moves along the spiral groove  56   a , the eraser  18  is let out. When the spiral sleeve  56  is turned in the other direction, the eraser  18  is retreated into the spiral sleeve  56   
         [0068]    Since the eraser  18  can be propelled in this way, a sufficient length in the axial direction can be secured for the eraser  18  until the lead cartridge  50  is up for replacement, making it unnecessary for the leads and the eraser to be replaced on separate occasions. 
         [0069]    In this preferred embodiment, as the binding force between the case  52  and the chuck joint  36  is weaker than that between the case  52  and the guide sleeve  54 , when the lead cartridge  50  is to be removed from the mechanical pencil  20 , pulling the guide sleeve  54  of the lead cartridge  50  backward enables the whole lead cartridge  50  to be pulled out of the outer sleeve  22 . 
         [0070]    Also, when the remainder of the eraser  18  is still usable after the lead tank  52   a  runs out of leads and the cartridge  50  is pulled out of the mechanical pencil  20 , it is possible to use the remaining eraser  18  by applying a strong force to disengage the engaging portions to release the case  52  and the guide sleeve  54  from each other and leaving only the rod-shaped object feeding mechanism. 
         [0071]      FIG. 16  is a longitudinal sectional view of a lead cartridge according to still another preferred embodiment of the present invention. The same or similar members as or to the foregoing embodiment will be assigned respectively the same reference signs, and their description will be dispensed with 
         [0072]    A lead cartridge  60  of this embodiment has a case  62 , a packing  13 , a guide sleeve  64 , a spiral sleeve  66  and an eraser receptacle  16  to hold an eraser  18  which is a rod-shaped object. 
         [0073]    The case  62  is a hollow cylinder as shown in  FIG. 17 , comprising a lead tank  62   a  in its central portion to contain a plurality of leads for replenishment or replacement. The case  62  is provided on the front side of the lead tank  62   a  with a detachable coupling  62   b  having a reduced diameter than that of the portion defining the lead tank  62   a . A contracted part  62   c , reduced in bore, is formed on the boundary between the lead tank  62   a  and the detachable coupling  62   b . The packing  13 , composed of an elastic material, is so inserted into the detachable coupling  62   b  from its tip as to protrude toward the contracted part  62   c.    
         [0074]    A plurality of ribs  62   d  for preventing rotation are provided on the outer circumferential surface of the case  62 , to be meshed with the grooves  30   a  for preventing rotation of the body  30  of the outer sleeve  22  of the writing tool  20 . The outer circumferential surface of the case  62  on the rear side of the lead tank  62   a  is formed with engaging slots  62   e  as an engaging portion. 
         [0075]    A spiral sleeve  66  engages with the engaging slots  62   e  of the case  62 . Thus, the outer circumferential surface of the front of the spiral sleeve  66  is formed with engaging protrusions  66   b  as engaging portions, which engage with the engaging slots  62   e  of the case  62 . This engagement causes the spiral sleeve  66  to be coupled to the case  62  so as to be unrotatable nor unmovable in the axial direction relative to the case  62 , A spiral groove  66   a  is formed in the inner circumferential surface of the spiral sleeve  66  and engaging slots  66   c  are formed in the inner circumferential surface of the spiral sleeve  66  on the front side of the spiral groove  66   a.    
         [0076]    The guide sleeve  64  is inserted into the spiral sleeve  66  from the rear. An engaging tube  64   a  is formed at the front end of the guide sleeve  64 , a pair of guide holes  64   b  extending in the axial direction are formed in the central portion of the guide sleeve  64 , and a manipulating part  64   c  expanded in diameter is formed at the rear end of the guide sleeve  64 . The manipulating part  64   c  may be provided with a decorating ring  65 . The engaging tube  64   a  is adapted to be engaged with the engaging slots  66   c  of the spiral sleeve  66  when the guide sleeve  64  is inserted into the spiral sleeve  66 . 
         [0077]    The engagements between manipulating part  64   c  and the engaging elements  64   a  of the guide sleeve  64  and the spiral sleeve  66  allow the guide sleeve  64  to be arranged on the inner circumferential side of the spiral sleeve  66  so as to be unable to move in the axial direction but able to turn relative to the guide sleeve  66 , 
         [0078]    The eraser receptacle  16  is arranged within the guide sleeve  64  to be slidable in the axial direction relative to the guide sleeve  64  and to be turnable relative to the spiral sleeve  66 . The pinching pieces  16   b  of the eraser receptacle  16  are fitted into the guide holes  64   b  of the guide sleeve  64  to be able to slide in the axial direction in the guide holes  64   b , and at the same time the male thread  16   c  of the eraser receptacle  16  screws into the spiral groove  66   a  of the spiral sleeve  66 . 
         [0079]    The guide sleeve  64 , the eraser receptacle  16  and the spiral sleeve  66  described above constitute a rod-shaped object feeding mechanism which is to be integrated with the lead cartridge  60 . 
         [0080]      FIG. 18  shows a state in which the lead cartridge  60  configured as described above is being incorporated into the mechanical pencil  20 , which is a writing tool. This lead cartridge  60  can be fitted or removed in the same way as in the first preferred embodiment. When the lead cartridge  60  is incorporated into the mechanical pencil  20 , the manipulating part  64   c  of the guide sleeve  64  and part of the spiral sleeve  66  protrude from the rear end of the outer sleeve  22 . When the rear end portion of this lead cartridge  60  is knocked, the chuck joint  36 , the lead chuck  38  and the chuck ring  40  move ahead together with the lead cartridge  60 , resulting in lead feeding as is well known to make the lead available for use in writing. 
         [0081]    Further, when the eraser is to be used, the manipulating part  64   c  of the guide sleeve  64  in the rear end portion is turned in a state in which the outer sleeve  22  is fixed. Since the outer sleeve  22  and the case  62  are prevented from relatively turning and the case  62  and the spiral sleeve  66  are also prevented from relatively turning, the eraser receptacle  16  which turns integrally with the guide sleeve  64  turns relative to the spiral sleeve  66 . Then, as the male thread  16   c  of the eraser receptacle  16  moves along the spiral groove  66   a , the eraser  18  is let out. When the manipulating part  64   c  is turned in the other direction, the eraser  18  is retreated into the spiral sleeve  66 . 
         [0082]    Since the eraser  18  can be propelled in this way, a sufficient length in the axial direction can be secured for the eraser  18  until the lead cartridge  60  is up for replacement, making it unnecessary for the leads and the eraser to be replaced on separate occasions. 
         [0083]    In this preferred embodiment, as the binding force between the case  62  and the chuck joint  36  is weaker than that between the case  62  and the spiral sleeve  66 , when the lead cartridge  60  is to be removed from the mechanical pencil  20 , pulling the spiral sleeve  66  of the lead cartridge  60  backward enables the whole lead cartridge  60  to be pulled out of the outer sleeve  22   
         [0084]    Also, when the remainder of the eraser  18  is still usable after the lead tank  62   a  runs out of leads and the cartridge  60  is pulled out of the mechanical pencil  20 , it is possible to use the remaining eraser  18  by applying a strong force to disengage the engaging portions to release the case  62  and the guide sleeve  66  from each other and leaving only the rod-shaped object feeding mechanism. 
         [0085]    While the principles of the invention have been described above in connection with specific embodiments, and particular modifications thereof, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of invention.

Technology Category: 7