Patent Publication Number: US-2022219482-A1

Title: Retractable Writing Implement

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is the United States national phase of International Application No. PCT/JP2020/027427 filed Jul. 15, 2020, and claims priority to Japanese Patent Application No. 2019-136838 filed Jul. 25, 2019, the disclosures of which are hereby incorporated by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a retractable writing instrument configured to a pen point to be in a state of projecting from a barrel or to be in a state of being retracted into the barrel by sliding a clip in a longitudinal direction of the barrel. 
     Description of Related Art 
     Conventionally, retractable writing instruments have been known. A general retractable writing instrument includes a columnar operating portion at the rear end of a barrel. The pen point of the retractable writing instrument is in a state of projecting from the barrel or in a state of being retracted into the barrel by pressing the columnar operating portion forward. As a special embodiment, a retractable writing instrument is configured to cause a pen point to be in a state of projecting from a barrel by sliding a clip forward of the barrel. 
     JP 2005-111876 A discloses a retractable writing instrument provided with a clip allowing open/close operation. The clip allowing open/close operation is configured with a clip body, a first plunger, and a biasing member. The clip body is connected to the first plunger by the biasing member. The biasing member is a U-shaped sheet metal and produces a biasing force in a direction of closing the clip body. The clip body is provided with a pair of ball portions. The pair of ball portions extend parallel to a longitudinal direction of the clip body. The barrel is provided with a convex guide portion guiding the ball portions in the longitudinal direction of the barrel. When the pen point is in a state of being retracted into the barrel, the convex guide portion is engaged between the pair of ball portions. For example, a sandwiched object, such as paper and a notebook, is sandwiched between the convex guide portion and the ball portions by the biasing force of the biasing member. 
     JP 2007-055156 A discloses a retractable writing instrument has a barrel provided with a guide groove to guide a ball portion of a clip body. While the clip body slides, the ball portion moves in a longitudinal direction of the barrel along the guide groove. The guide groove has a bottom surface over the entire length. The entire length of the guide groove is slightly shorter than the moving distance of the ball portion. Accordingly, when moving most forward, the ball portion overrides a step at the front end of the guide groove. In this situation, a gap is formed between the ball portion and the bottom surface of the guide groove. 
     WO 2011/096357 A1 discloses a retractable writing instrument provided with a clip having a clip body, a ball portion, and a clip base integrally formed of a synthetic resin as a single piece. The instrument has a barrel provided with a guide groove to guide the ball portion. The guide groove has a bottom surface over the entire length. 
     JP 2017-024224 A discloses a retractable writing instrument that has an elastically deformable cantilever formed integrally with a front side of a clip body made of a synthetic resin as a single piece. The cantilever has flexural rigidity lower than the flexural rigidity of the clip body. For example, a sandwiched object, such as paper and a notebook, is sandwiched by a biasing force of the elastically deformed cantilever. When a pen point is in a state of projecting from a barrel, the cantilever abuts on a surface of the barrel to produce a biasing force. 
     PRIOR ART DOCUMENTS 
     Patent Document 
     Patent Document 1: JP 2005-111876 A 
     Patent Document 2: JP 2007-055156 A 
     Patent Document 3: WO 2011/096357 A1 
     Patent Document 4: JP 2017-024224 A 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     Conventional retractable writing instruments have a structural problem that a biasing force of a clip body interferes with rearward movement of a clip. For example, in the retractable writing instrument disclosed in JP 2005-111876 A, the biasing member produces the biasing force in the direction of closing the clip body. The biasing force of the biasing member causes the ball portion of the clip body to abut on the surface of the barrel to produce frictional resistance. Meanwhile, the clip is moved rearward of the barrel by the spring biasing a writing tool body rearward. If the biasing force of the spring is not more than the frictional resistance of the ball portion, the rearward movement of the clip is stopped by the frictional resistance of the ball portion. Similarly, the biasing force of the cantilever disclosed in JP 2017-024224 A also produces frictional resistance to stop the rearward movement of the clip. 
     With reference to  FIGS. 15A and 15B , mechanical relationship between the frictional resistance of the ball portion and the biasing force of the spring is described.  FIG. 15A  is a cross-sectional view illustrating a retractable writing instrument  100  in a state of a pen point projecting from a barrel  2 .  FIG. 15B  is a cross-sectional view illustrating the retractable writing instrument  100  in a state of the pen point being retracted into the barrel  2 . 
     As illustrated in  FIGS. 15A and 15B , in the barrel  2  of the retractable writing instrument  100 , a writing tool body  6  is housed. The writing tool body  6  is biased rearward of the barrel  2  by a first spring, not shown (refer to the reference sign “ 5 ” in  FIG. 2B ). An arrow P 1  indicates an elastic force of the first spring ( 5 ). Meanwhile, the retractable writing instrument  100  has a clip  4  provided with a second spring  44  biasing a front side of a clip body  41  in the direction of a surface of the barrel  2 . The second spring  44  has an elastic force causing a ball portion  42  of the clip body  41  to abut on a bottom surface  233  of a guide groove  23   f . An arrow P 2  indicates a biasing force of the clip body  41  pressed by the second spring  44 . 
     The biasing force P 2  of the clip body  41  causes the ball portion  42  to abut on the bottom surface  233  of the guide groove  23   f  to produce frictional resistance when the clip  4  moves rearward. The frictional resistance stops the rearward movement of the clip  4 . 
     The reason for stopping the rearward movement of the clip  4  is not only the biasing force P 2  of the clip body  41 . Variation of the elastic force P 1  in accordance with the expansion and contraction of the first spring ( 5 ) is also a reason for stopping the rearward movement of the clip  4 . That is, the elastic force P 1  of the first spring ( 5 ) becomes larger with the contraction of the first spring ( 5 ) and becomes smaller with the expansion of the first spring ( 5 ). The elastic force P 1  of the first spring ( 5 ) is thus maximum in the projected state of the pen point illustrated in  FIG. 15A  and minimum in the retracted state of the pen point illustrated in  FIG. 15B . In the process from the projected state to the retracted state of the pen point, if the elastic force P 1  of the first spring ( 5 ) is not more than the frictional resistance of the ball portion  42 , the rearward movement of the clip  4  is stopped by the frictional resistance of the ball portion  42 . 
     To solve such a problem, it is considered to increase the elastic force P 1  of the first spring ( 5 ). However, an increase in the elastic force P 1  of the first spring ( 5 ) causes a greater force to be used to slide the clip  4  forward of the barrel  2  and reduction in the operability to retract and project the pen point. Accordingly, the problem of stopping the rearward movement of the clip  4  is desirably solved not by increasing the elastic force P 1  of the first spring ( 5 ). 
     With reference to  FIG. 16 , a second problem caused by the biasing force of the clip body is then described.  FIG. 16  is a cross-sectional view illustrating a retractable writing instrument  200  including a plurality of writing tool bodies  6 A and  6 B. As illustrated in  FIG. 16 , the plurality of writing tool bodies  6 A and  6 B are housed in a barrel  2  of the retractable writing instrument  200 . The respective writing tool bodies  6 A and  6 B have a rear end attached to sliders  8 A and  8 B. Among them, the slider  8 A has a rear side formed integrally with a clip body  41  as a single piece. The clip body  41  has a front side formed integrally with a ball portion  42  as a single piece. The clip body  41  has a shape constantly producing a biasing force P 2  in a direction of a surface of the barrel  2 . 
     The writing tool body  6 A has a pen point in a state of projecting from the barrel  2 . Meanwhile, the writing tool body  6 B has a pen point in a state of being retracted into the barrel  2 . The projected state of the pen point of the writing tool body  6 A is retained by locking of a rear end portion  8   a  of the slider  8 A on a locking rib  2   a  provided in the barrel  2 . 
     However, the biasing force P 2  of the clip body  41  causes the second problem of facilitating removal of locking of the rear end portion  8   a  of the slider  8 A on the locking rib  2   a . That is, the ball portion  42  of the clip body  41  receives a reaction force (refer to gray arrow in  FIG. 16 ) in the direction opposite to the biasing force P 2  from the surface of the barrel  2 . The reaction force exerts a force in the direction of an arrow P 3  (force in a direction away from the surface of the barrel  2 ) on the rear end portion  8   a  of the slider  8 A. This facilitates removal of locking of the rear end portion  8   a  of the slider  8 A on the locking rib  2   a . Accordingly, the biasing force P 2  of the clip body  41  causes the pen point of the writing tool body  6 A to be in the retracted state from the projected state although unintended by a user of the retractable writing instrument  200 . 
     It is an object of the present invention to provide a retractable writing instrument where normal movement of a clip is securely performed to cause a pen point to be in a retracted state and a projected state of the pen point is securely retained. 
     Means to Solve the Problems 
     (1) To achieve the above object, a retractable writing instrument of the present invention includes a pen point, a barrel, and a clip, the pen point being configured to be in a state of projecting from the barrel or a state of being retracted into the barrel by sliding the clip in a longitudinal direction of the barrel, wherein the clip includes a clip body extending in the longitudinal direction of the barrel, a ball portion provided on a front side of the clip body and projecting in a direction of a surface of the barrel, and a clip base provided on a rear side of the clip body and is configured to produce a biasing force in a direction of a surface of the barrel, the surface of the barrel includes a guide groove extending in the longitudinal direction of the barrel and provided with a pair of side surfaces to restrict lateral movement of the ball portion, and the guide groove has a through groove capable of causing the ball portion to be in a noncontact state in a direction of the biasing force at least when the pen point is in the retracted state. 
     (2) It is preferred that, in the retractable writing instrument according to (1) above, the through groove of the guide groove has a length allowing the ball portion to be in the noncontact state in the direction of the biasing force during transfer of the pen point from the projected state to the retracted state. 
     (3) It is preferred that, in the retractable writing instrument according to (1) or (2) above, the barrel has a rear side provided with a slide hole to cause the clip base to slide in the longitudinal direction of the barrel, the slide hole includes a pair of side surfaces extending in the longitudinal direction of the barrel to restrict lateral movement of the clip base, and each side surface of the slide hole is continued to the corresponding side surface of the guide groove. 
     (4) It is preferred that, in the retractable writing instrument according to (3) above, the through groove of the guide groove is in communication with the slide hole. 
     (5) It is preferred that, in the retractable writing instrument according to (1) through (4) above, the guide groove has a bottom surface capable of receiving the biasing force from the clip by contacting the ball portion when the pen point is in the projected state. 
     (6) It is preferred that, in the retractable writing instrument according to (5) above, an inclined surface down to the through groove is formed at a rear end of the bottom surface of the guide groove. 
     (7) It is preferred that, in the retractable writing instrument according to (5) or (6) above, a second bottom surface separated from the bottom surface by the through groove is provided between the through groove of the guide groove and the slide hole. 
     (8) It is preferred that, in the retractable writing instrument according to (1) through (7) above, the clip includes a hinge connecting the clip base to the rear side of the clip body and a spring pressing the rear side of the clip body in a direction intersecting the barrel, and the clip body pressed by the spring produces the biasing force. 
     (9) It is preferred that, in the retractable writing instrument according to (1) through (7) above, the clip includes a leaf spring connecting the rear side of the clip body to the clip base and pressing in the direction of the surface of the barrel, and the clip body pressed by the leaf spring produces the biasing force. 
     (10) It is preferred that, in the retractable writing instrument according to (1) through (7) above, the clip body is configured with sheet metal, the rear side of the clip body is connected to the clip base, and the biasing force is produced by elasticity of the clip body. 
     (1) It is preferred that, in the retractable writing instrument according to (10) above, the clip body has a pair of side walls configured with the sheet metal. 
     (12) It is preferred that, in the retractable writing instrument according to (1) through (7) above, the clip body, the ball portion, and the clip base are formed of a synthetic resin, and 
     the biasing force is produced by elasticity of the clip body. 
     In the retractable writing instrument of the present invention, the term “front” is defined as the direction to the pen point and the term “rear” as the direction opposite to the pen point. 
     Effects of the Invention 
     The retractable writing instrument of the present invention allows secure performance of normal movement of the clip to cause the pen point to be in the retracted state and secure retention of the projected state of the pen point. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1A and 1B  illustrate a retractable writing instrument according to a first embodiment of the present invention, the retractable writing instrument being in a state of a pen point retracted into a barrel.  FIG. 1A  is a side view, and  FIG. 1B  is a cross-sectional view. 
         FIGS. 2A and 2B  illustrate the retractable writing instrument in a state of the pen point projecting from the barrel.  FIG. 2A  is a side view, and  FIG. 2B  is a cross-sectional view. 
         FIGS. 3A through 3F  illustrate a clip body configuring a clip of the retractable writing instrument.  FIG. 3A  is a plan view,  FIG. 3B  is a side view,  FIG. 3C  is a bottom view,  FIG. 3D  is a front view,  FIG. 3E  is a rear view, and  FIG. 3F  is a perspective view. 
         FIGS. 4A through 4F  illustrate a clip base configuring the clip of the retractable writing instrument.  FIG. 4A  is a plan view,  FIG. 4B  is a side view,  FIG. 4C  is a bottom view,  FIG. 4D  is a front view,  FIG. 4E  is a rear view, and  FIG. 4F  is a perspective view. 
         FIGS. 5A, 5B, and 5C  illustrate an intermediate barrel configuring the retractable writing instrument.  FIG. 5A  is a plan view of a rear side portion of the intermediate barrel.  FIG. 5B  is a perspective view of the rear side portion of the intermediate barrel.  FIG. 5C  is a cross-sectional view of the process of assembling the clip to the intermediate barrel. 
         FIGS. 6A and 6B  illustrate an internal configuration of the retractable writing instrument.  FIG. 6A  is a cross-sectional view illustrating the projected state of the pen point.  FIG. 6B  is a cross-sectional view illustrating the retracted state of the pen point. 
         FIGS. 7A, 7B, and 7C  illustrate an intermediate barrel configuring a retractable writing instrument according to a second embodiment of the present invention.  FIG. 7A  is a plan view of a rear side portion of the intermediate barrel.  FIG. 7B  is a perspective view of the rear side portion of the intermediate barrel.  FIG. 7C  is a cross-sectional view of the process of assembling a clip to the intermediate barrel. 
         FIGS. 8A and 8B  illustrate an internal configuration of the retractable writing instrument in the second embodiment.  FIG. 8A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 8B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIGS. 9A and 9B  illustrate an internal configuration of a retractable writing instrument according to a third embodiment of the present invention.  FIG. 9A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 9B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIGS. 10A and 10B  illustrate an internal configuration of a retractable writing instrument according to a fourth embodiment of the present invention.  FIG. 10A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 10B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIGS. 11A and 11B  illustrate an internal configuration of a retractable writing instrument according to a fifth embodiment of the present invention.  FIG. 11A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 11B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIGS. 12A, 12B, and 12C  illustrate an internal configuration of a retractable writing instrument according to a sixth embodiment of the present invention.  FIG. 12A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 12B  is a cross-sectional view illustrating a retracted state of the pen point.  FIG. 12C  is a cross-sectional view illustrating a clip of the retractable writing instrument. 
         FIG. 13A  is a plan view illustrating a rear side portion of an intermediate barrel configuring a retractable writing instrument according to a seventh embodiment of the present invention.  FIG. 13B  is a plan view illustrating a rear side portion of an intermediate barrel configuring a retractable writing instrument according to an eighth embodiment of the present invention. 
         FIGS. 14A and 14B  illustrate an internal configuration of a retractable writing instrument according to a ninth embodiment of the present invention.  FIG. 14A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 14B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIGS. 15A and 15B  illustrate an internal configuration of a conventional retractable writing instrument.  FIG. 15A  is a cross-sectional view illustrating a projected state of a pen point.  FIG. 15B  is a cross-sectional view illustrating a retracted state of the pen point. 
         FIG. 16  is a cross-sectional view illustrating an internal configuration of a conventional retractable writing instrument provided with a plurality of writing tool bodies. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     1. First Embodiment 
     With reference to  FIGS. 1A through 6B , a retractable writing instrument according to the first embodiment of the present invention is described below. In the embodiments described below, the retractable writing instrument is exemplified by a thermochromic writing instrument that allow handwriting in thermochromic ink to be thermochromic by frictional heat. However, the configuration of the present invention is not limited to a thermochromic writing instrument and is widely applicable to general retractable writing instruments. 
     1.1 Retractable Writing Instrument 
     The configuration of a retractable writing instrument  1  according to the first embodiment of the present invention is illustrated in  FIGS. 1A, 1B, 2A, and 2B . Double-pointed arrows in these drawings define the “front” and the “rear” of the retractable writing instrument  1 . The retractable writing instrument  1  includes a barrel  2 , a rotary member  3 , a clip  4 , a first spring  5 , a writing tool body  6 , and a friction unit  7 . 
     At first, the external configuration of the retractable writing instrument  1  is described. As illustrated in  FIG. 1A , the barrel  2  is configured with a tip  21 , a front barrel  22 , an intermediate barrel  23 , and a rear barrel  24 . The front barrel  22  has an outer peripheral surface on which an elastic grip  22   a  is mounted. The rear barrel  24  has an attachment hole  24   b  (refer to  FIG. 6A ) to fit the friction unit  7 . Meanwhile, the clip  4  is configured with a clip body  41 , a clip base  43 , and a second spring  44  (refer to  FIG. 5C ). Among the components configuring the appearance of the retractable writing instrument  1 , the tip  21  is formed by metal and the other components are formed by a synthetic resin. In the design of the entire retractable writing instrument  1 , the tip  21  made of metal markedly differs in the texture and the appearance from the other components made of a synthetic resin and thus is an eye-catching feature to users. A surface of the barrel  2  made of a synthetic resin, for example, a surface of the intermediate barrel  23  is decorated by adhering a transfer film. 
     The internal configuration of the retractable writing instrument  1  is then described. As illustrated in  FIG. 1B , the barrel  2  houses, in order from the front, the first spring  5 , the writing tool body  6 , the rotary member  3 , and a cylindrical portion  43   d  (refer to  FIG. 5C ) of the clip base  43 . 
     The writing tool body  6  includes a pen point  61 , an ink storage tube  62 , thermochromic ink  63 , a follower  64 , and an end plug  65 . The pen point  61  is attached to a front end of the ink storage tube  62 . The pen point  61  in the present embodiment is a ball-point pen tip while the configuration of the present invention is not limited to a ball-point pen and is widely applicable to retractable writing instruments, such as mechanical pencils and markers. The thermochromic ink  63  and the follower  64  are filled in the ink storage tube  62 . The end plug  65  is mounted in an opening at a rear end of the ink storage tube  62 . The end plug  65  is provided with a longitudinally extending air vent at the center. The thermochromic ink  63  forms handwriting on a paper surface and the friction unit  7  allows the handwriting to be thermochromic. The friction unit  7  produces frictional heat by abrasion on a paper surface. The frictional heat causes the handwriting in the thermochromic ink  63  to be thermochromic. The thermochromic ink  63  changes its color by heating, for example, from a first color to a second color or from being colored to being colorless. 
     A retractable mechanism causes the pen point  61  of the writing tool body  6  to be in a state of projecting from the barrel  2  or a state of being retracted into the barrel  2 . The retractable mechanism is configured with the first spring  5 , the rotary member  3 , and the clip base  43  housed in the barrel  2 , a slide hole  20 , a cam gear  23   a , and a cam groove  23   b  provided on a wall of the barrel  2  (refer to  FIG. 5C ). 
     As illustrated in  FIG. 1B , the first spring  5  is mounted in a front end portion of the writing tool body  6  and constantly biases the writing tool body  6  rearward. Rearward of the writing tool body  6 , the rotary member  3  and the clip base  43  are arranged. 
     The rotary member  3  is rotatably connected to the cylindrical portion  43   d  of the clip base  43  (refer to  FIG. 5C ). The rotary member  3  includes four longitudinally extending convex threads  31  (refer to  FIG. 6B ). The four convex threads  31  are evenly provided on an outer surface of the rotary member  3  at intervals of 90□. The convex threads  31  continue from a side surface to an upper surface of the rotary member  3 . Rear end portions of the convex threads  31  projecting from the upper surface of the rotary member  3  form inclined surfaces (cam gear) inclined in one direction. 
     The clip base  43  is longitudinally slidable along the slide hole  20  provided on a rear side of the barrel  2 . The clip base  43  is provided with a slider  43   a , a coupling portion  43   c , and the cylindrical portion  43   d  (refer to  FIG. 4B ). The slider  43   a  is located outside the barrel  2 . The cylindrical portion  43   d  is located inside the barrel  2 . To the slider  43   a , a rear side of the clip body  41  is turnably connected. The coupling portion  43   c  couples the slider  43   a  and the cylindrical portion  43   d  via the slide hole  20  of the barrel  2 . The cylindrical portion  43   d  is provided with a cam gear  43   e  at a front end (refer to  FIG. 4B ). The cam gear  43   e  of the cylindrical portion  43   d  engages with the rear end portions of the convex threads  31  of the rotary member  3 . 
     The barrel  2  has an inner wall surface provided with the cam gear  23   a  and the cam groove  23   b  described above (refer to  FIG. 5C ). The cam gear  23   a  and the cam groove  23   b  alternately engage with the convex threads  31  of the rotary member  3  (refer to  FIG. 6B ). This causes the pen point  61  of the writing tool body  6  to be in the projected state or the retracted state. That is, a user of the retractable writing instrument  1  slides the slider  43   a  of the clip base  43  together with the clip body  41  forward along the slide hole  20  of the barrel  2 . Then, in the barrel  2 , the rotary member  3  is pushed by the cylindrical portion  43   d  of the clip base  43  and moves forward more than the cam gear  23   a  and the cam groove  23   b . In this situation, the rotary member  3  rotates in one direction and the convex threads  31  engage with either one of the cam gear  23   a  or the cam groove  23   b . The engagement of the convex threads  31  with the cam gear  23   a  causes the rotary member  3  to be retained in the forwardly moved state. As a result, the pen point  61  of the writing tool body  6  is in a state of projecting from a front end hole  21   a  of the barrel  2 . In contrast, engagement of the convex threads  31  with the cam groove  23   b  causes rearward movement of the rotary member  3  along the cam groove  23   b . As a result, the pen point  61  of the writing tool body  6  is in the state of being retracted into the barrel  2 . 
     1.2 Clip 
     The retractable writing instrument  1  in the present embodiment includes the clip  4  allowing open/close operation. The configuration of the clip  4  is described below in detail. The clip  4  in the present embodiment is made with the clip body  41 , the clip base  43 , and the second spring  44  illustrated in  FIG. 5C . The clip body  41  and the clip base  43  are formed by a synthetic resin. The clip body  41  has a front side formed integrally with the ball portion  42  as a single piece. The rear side of the clip body  41  is turnably connected to the clip base  43  via a hinge. The second spring  44  is placed between the clip body  41  and the clip base  43 . By an elastic force of the second spring  44 , the rear side of the clip body  41  is pressed in a direction intersecting the barrel  2 . This causes the front side of the clip body  41  is biased in a direction of the surface of the barrel  2  (refer to biasing force P 2  in  FIG. 6A ). The clip body  41  may be opened in a direction away from the surface of the barrel  2  by a force greater than the elastic force of the second spring  44 . A sandwiched object, such as paper and a notebook, is held between the clip body  41  and the barrel  2 . 
     1.2.1 Clip Body 
       FIGS. 3A through 3F  illustrate the configuration of the clip body  41 . The clip body  41  is provided with an upper wall  41   a  extending in a longitudinal direction of the barrel  2 . A pair of side walls  41   b  are integrally formed as a single piece on both sides of the upper wall  41   a . The pair of side walls  41   b  has a length reaching the front of a rear end from a front end of the upper wall  41   a . The ball portion  42  described above is located on a front side of a back surface of the upper wall  41   a  and projects downward below the pair of side walls  41   b . On rear sides of the pair of side walls  41   b , a pair of bearing holes  41   c  are formed. The pair of bearing holes  41   c  configure the hinge described above to allow turning of the clip body  41 . Rearward of the bearing holes  41   c  on the back surface of the upper wall  41   a , a columnar projection  41   d  is integrally formed as a single piece. The projection  41   d  is inserted into an upper portion of the second spring  44  described above to retain the second spring  44 . 
     1.2.2 Clip Base 
       FIGS. 4A through 4F  illustrate the configuration of the clip base  43 . As already described, the clip base  43  is provided with the slider  43   a , the coupling portion  43   c , and the cylindrical portion  43   d . The slider  43   a  has a surface formed integrally with a pair of rotating shafts  43   b , a columnar projection  43   f , and a stopper  43   g  as a single piece. The pair of rotating shafts  43   b  are inserted into the pair of bearing holes  41   c  of the clip body  41  to configure the hinge described above. The clip body  41  is turnably connected to the clip base  43  with the pair of rotating shafts  43   b  as a fulcrum. The projection  43   f  is inserted into a lower portion of the second spring  44  to retain the second spring  44  described above. The stopper  43   g  is a vertical wall located at a front end of the slider  43   a . When the pen point is in the retracted state illustrated in  FIG. 6B , the stopper  43   g  abuts on a back surface of the clip  4  and blocks the pair of side walls  41   b  of the clip  4  from contacting the surface of the barrel  2  (intermediate barrel  23 ). At the front end of the cylindrical portion  43   d , the cam gear  43   e  is provided. The cam gear  43   e  engages with the rear end portions of the convex threads  31  of the rotary member  3 . 
     1.3 Guide Groove of Barrel 
       FIGS. 5A through 5C  illustrate the intermediate barrel  23  configuring the barrel  2 . On a rear side of the intermediate barrel  23 , the guide groove  23   f  with a narrow width and a first long hole  23   e  with a wide width are provided. The retractable writing instrument  1  in the present embodiment is characterized in the configuration of the guide groove  23   f . The guide groove  23   f  is a groove extending in the longitudinal direction of the barrel  2  and is configured with a bottom surface  233 , a pair of side surfaces  234 , and a through groove  235 . 
     As illustrated in  FIG. 6A , the bottom surface  233  of the guide groove  23   f  contacts the ball portion  42  of the clip body  41  when the pen point  61  is in the projected state. The bottom surface  233  receives the biasing force P 2  from the clip body  41  by contacting the ball portion  42 . Meanwhile, as illustrated in  FIG. 6B , when the pen point  61  is in the retracted state, the through groove  235  of the guide groove  23   f  causes the ball portion  42  to be in a noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 6A . The pair of side surfaces  234  of the guide groove  23   f  restrict lateral movement of the ball portion  42 . The guide groove  23   f  thus configured guides the clip  4  being slid to retract and project the pen point  61  in the longitudinal direction of the barrel  2  and moves the clip  4  straight. As already described, the surface of the intermediate barrel  23  is decorated by adhering the transfer film while the transfer film is not adhered to the guide groove  23   f.    
     As illustrated in  FIGS. 5A and 5B , the guide groove  23   f  in the present embodiment has the entire length more than a length for sliding of the clip  4 . The guide groove  23   f  includes a first region  231  on the front side and a second region  232  on the rear side. The second region  232  is in communication with a front end of the first long hole  23   e  provided on the rear side of the intermediate barrel  23 . The first long hole  23   e , together with a second long hole  24   a  in the rear barrel  24  illustrated in  FIG. 2B , configures the slide hole  20 . 
     The first region  231  of the guide groove  23   f  is used for sliding the clip  4  to retract and project the pen point  61 . That is, when the pen point  61  is retracted and projected, the ball portion  42  of the clip body  41  longitudinally moves in the range of a length of the first region  231 . 
     Meanwhile, the second region  232  of the guide groove  23   f  is used for assembling the clip  4  to the intermediate barrel  23 . As illustrated in  FIG. 5C , the clip  4  is assembled by inserting the cylindrical portion  43   d  of the clip base  43  into the intermediate barrel  23 . In the process of assembling the clip  4  to the intermediate barrel  23 , the ball portion  42  of the clip body  41  passes through the first long hole  23   e  and is guided from the second region  232  of the guide groove  23   f  to the first region  231 . This allows the clip  4  to be assembled to the intermediate barrel  23  without causing the ball portion  42  to contact the surface of the intermediate barrel  23  with a transfer film adhered thereto. 
     In this situation, the bottom surface  233  of the guide groove  23   f  is not an essential configuration but is formed in an area other than a rear half portion  231   b  of the first region  231  in the guide groove  23   f . The bottom surface  233  is preferably formed in a front half portion  231   a  of the first region  231  as in the present embodiment. In this case, the bottom surface  233  has substantially the same length as that of the front half portion  231   a . The bottom surface  233  in the present embodiment has a length slightly shorter than the entire length of the front half portion  231   a  of the first region  231 . That is, as illustrated in  FIG. 6A , the bottom surface  233  has a minimum length capable of contacting the ball portion  42  of the clip body  41  when the pen point  61  is in the projected state. 
     The through groove  235  of the guide groove  23   f  is formed at least in the rear half portion  231   b  of the first region  231 . The through groove  235  in the present embodiment is formed across the entire area from the first region  231  to the second region  232  excluding the bottom surface  233  and continues to the first long hole  23   e.    
     1.4 Technical Effects of Guide Groove 
     In the projected state of the pen point  61  illustrated in  FIG. 6A , the ball portion  42  of the clip body  41  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  42  is pressed against the bottom surface  233  of the guide groove  23   f  by the biasing force P 2  of the clip body  41 . As a result, frictional resistance is produced between the ball portion  42  and the bottom surface  233 . The biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  exhibit a preferred effect of inhibiting a rattle of the clip  4 . That is, the bottom surface  233  formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  4  in the projected state of the pen point 
     Then, the projected state of the pen point  61  illustrated in  FIG. 6A  is transferred to the retracted state of the pen point  61  illustrated in  FIG. 6B  by sliding the clip  4  forward of the barrel  2  (refer to  FIG. 2A ). In the process of transfer of the pen point  61  from the projected state to the retracted state, the clip  4  is slid rearward of the barrel  2  by the elastic force P 1  of the first spring  5  (refer to  FIGS. 1B and 2B ) mounted in the front end portion of the writing tool body  6 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  42  of the clip body  41  fits into the through groove  235  from above the bottom surface  233  in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  42  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This causes the pen point  61  to be in the completely retracted state illustrated in  FIG. 6B . 
     Meanwhile, the elastic force P 1  of the first spring  5  biasing the writing tool body  6  rearward (refer to  FIGS. 1B and 2B ) is maximum in the projected state of the pen point illustrated in  FIG. 6A  and minimum in the retracted state of the pen point illustrated in  FIG. 6B . 
     As illustrated in  FIG. 6B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  42  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 6A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  4  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 6B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  4  is securely performed to cause the pen point  61  to be in the retracted state. 
     As illustrated in  FIG. 5C , the through groove  235  formed in the second region  232  of the guide groove  23   f  is used when the clip  4  is assembled to the intermediate barrel  23 . In the process of assembling the clip  4  to the intermediate barrel  23 , the ball portion  42  of the clip body  41  passes through the first long hole  23   e  and is guided to the first region  231  by the through groove  235  formed in the second region  232  of the guide groove  23   f . This allows the clip  4  to be assembled to the intermediate barrel  23  without causing the ball portion  42  to contact the surface of the intermediate barrel  23  with a transfer film adhered thereto. 
     2. Second Embodiment 
     With reference to  FIGS. 7A through 8B , a retractable writing instrument according to the second embodiment of the present invention is then described. The retractable writing instrument according to the second embodiment is characterized in the configuration of the guide groove  23   f  illustrated in  FIGS. 7A through 8B  and has the other configurations same as those in the first embodiment described above. Accordingly, in the second embodiment below, identical reference signs are given to the same configurations as those in the first embodiment described above to omit detailed descriptions. 
       FIGS. 7A, 7B, and 7C  illustrate an intermediate barrel  23  of the retractable writing instrument according to the second embodiment. A guide groove  23   f  of the retractable writing instrument according to the second embodiment has a first bottom surface  233 A, a through groove  235 , and a second bottom surface  233 B. Similar to the first embodiment described above, the first bottom surface  233 A is formed in the front half portion  231   a  of the first region  231 . The second bottom surface  233 B is formed in the second region  232 . The through groove  235  is formed between the first bottom surface  233 A and the second bottom surface  233 B. The through groove  235  in the present embodiment has a length from a rear end of the first bottom surface  233 A, through the boundary between the first region  231  and the second region  232 , reaching a front end of the second bottom surface  233 B. The guide groove  23   f  in the present embodiment also exhibits technical effects similar to those in the first embodiment described above. 
     That is, in the projected state of the pen point  61  illustrated in  FIG. 8A , the ball portion  42  of the clip body  41  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  42  is pressed against the first bottom surface  233 A of the guide groove  23   f  by the biasing force P 2  of the clip body  41 . As a result, frictional resistance is produced between the ball portion  42  and the first bottom surface  233 A. The biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  exhibit a preferred effect of inhibiting a rattle of the clip  4 . That is, the first bottom surface  233 A formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  4  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  42  of the clip body  41  fits into the through groove  235  from above the first bottom surface  233 A in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  42  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This allows the pen point  61  to be in the completely retracted state illustrated in  FIG. 8B . 
     As illustrated in  FIG. 8B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  42  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 8A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  4  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 8B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  4  is securely performed to cause the pen point  61  to be in the retracted state. 
     As illustrated in  FIG. 7C , the second region  232  of the guide groove  23   f  is used when the clip  4  is assembled to the intermediate barrel  23 . In the process of assembling the clip  4  to the intermediate barrel  23 , the ball portion  42  of the clip body  41  passes through the first long hole  23   e  and is guided to the first region  231  by the second region  232  of the guide groove  23   f . This allows the clip  4  to be assembled to the intermediate barrel  23  without causing the ball portion  42  to contact the surface of the intermediate barrel  23  with a transfer film adhered thereto. 
     Moreover, formation of the second bottom surface  233 B in the second region  232  of the guide groove  23   f  improves the rigidity of the rear side portion of the intermediate barrel  23 . That is, in the rear side portion of the intermediate barrel  23 , the through groove  235  and the first long hole  23   e  are formed. As illustrated in  FIG. 5A , continuation of the through groove  235  and the first long hole  23   e  causes the rear side portion of the intermediate barrel  23  to have reduced rigidity and readily deflect. The second bottom surface  233 B illustrated in  FIG. 7A  breaks the continuation of the through groove  235  and the first long hole  23   e  to improve the rigidity of the rear side portion of the intermediate barrel  23 . This causes the rear side portion of the intermediate barrel  23  to be less likely to deflect and allows a transfer film to be efficiently adhered to the surface of the intermediate barrel  23 . 
     3. Third Embodiment 
     With reference to  FIGS. 9A and 9B , a retractable writing instrument according to the third embodiment of the present invention is then described. The retractable writing instrument according to the third embodiment is characterized in the configuration of a clip  410  illustrated in  FIGS. 9A and 9B  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the third embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIGS. 9A and 9B  illustrate the internal configuration of the retractable writing instrument in the third embodiment.  FIG. 9A  illustrates the projected state of the pen point  61  and  FIG. 9B  illustrates the retracted state of the pen point  61 . The clip  410  in the present embodiment is made with a clip body  411 , a clip base  413 , and a leaf spring  414 . The clip body  411  and the clip base  413  are formed by a synthetic resin. On a front side of the clip body  411 , a ball portion  412  is integrally formed as a single piece. A rear side of the clip body  411  is openably connected to the clip base  413  by the U-shaped leaf spring  414 . The rear side of the clip body  411  is pressed against a surface of the clip base  413  by elastic force of the leaf spring  414 . This causes the front side of the clip body  411  to be biased in the direction of the surface of the barrel  2  (refer to the biasing force P 2  in  FIG. 9A ). The clip body  411  may be opened in a direction away from the surface of the barrel  2  by a force greater than the elastic force of the leaf spring  414 . A sandwiched object, such as paper and a notebook, is held between the clip body  411  and the barrel  2 . 
     In this situation, the clip base  413  in the present embodiment supports the clip body  411  at a predetermined height. Specifically, the clip base  413  supports the clip body  411  at a height to cause the clip body  411  not to contact the surface of the barrel  2  in the retracted state of the pen point  61  illustrated in  FIG. 9B . This causes the surface of the barrel  2  not to be damaged. 
     In the projected state of the pen point  61  illustrated in  FIG. 9A , the ball portion  412  of the clip body  411  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  412  is pressed against the first bottom surface  233 A of the guide groove  23   f  by the biasing force P 2  of the clip body  411 . As a result, frictional resistance is produced between the ball portion  412  and the first bottom surface  233 A. The biasing force P 2  of the clip body  411  and the frictional resistance of the ball portion  412  exhibit a preferred effect of inhibiting a rattle of the clip  410 . That is, the first bottom surface  233 A formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  410  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  412  of the clip body  411  fits into the through groove  235  from above the first bottom surface  233 A in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  412  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This allows the pen point  61  to be in the completely retracted state illustrated in  FIG. 9B . 
     As illustrated in  FIG. 9B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  412  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 9A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  411  and the frictional resistance of the ball portion  412  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  410  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 9B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  410  is securely performed to cause the pen point  61  to be in the retracted state. 
     4. Fourth Embodiment 
     With reference to  FIGS. 10A and 10B , a retractable writing instrument according to the fourth embodiment of the present invention is then described. The retractable writing instrument according to the fourth embodiment is characterized in the configuration of a clip  420  illustrated in  FIGS. 10A and 10B  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the fourth embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIGS. 10A and 10B  illustrate the internal configuration of the retractable writing instrument in the fourth embodiment.  FIG. 10A  illustrates the projected state of the pen point  61  and  FIG. 10B  illustrates the retracted state of the pen point  61 . The clip  420  in the present embodiment is made with a clip body  421  and a clip base  423 . The clip body  421  is configured with sheet metal extending in the longitudinal direction of the barrel  2 . On a front side of the clip body  421 , a ball portion  422  is integrally formed as a single piece by bending the sheet metal. A rear side of the clip body  421  is connected to the clip base  423 . The clip body  421  produces a biasing force P 2  in the direction of the surface of the barrel  2  by the elasticity of its own. 
     The clip base  423  supports the clip body  421  at a predetermined height. Specifically, the clip base  423  supports the clip body  421  at a height to cause the clip body  421  not to contact the surface of the barrel  2  in the retracted state of the pen point  61  illustrated in  FIG. 10B . This causes the surface of the barrel  2  not to be damaged. 
     In the projected state of the pen point  61  illustrated in  FIG. 10A , the ball portion  422  of the clip body  421  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  422  is pressed against the first bottom surface  233 A of the guide groove  23   f  by the biasing force P 2  of the clip body  421 . As a result, frictional resistance is produced between the ball portion  422  and the first bottom surface  233 A. The biasing force P 2  of the clip body  421  and the frictional resistance of the ball portion  422  exhibit a preferred effect of inhibiting a rattle of the clip  420 . That is, the first bottom surface  233 A formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  420  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  422  of the clip body  421  fits into the through groove  235  from above the first bottom surface  233 A in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  422  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This allows the pen point  61  to be in the completely retracted state illustrated in  FIG. 10B . 
     As illustrated in  FIG. 10B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  422  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 10A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  421  and the frictional resistance of the ball portion  422  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  420  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 10B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  420  is securely performed to cause the pen point  61  to be in the retracted state. 
     5. Fifth Embodiment 
     With reference to  FIGS. 11A and 11B , a retractable writing instrument according to the fifth embodiment of the present invention is then described. The retractable writing instrument according to the fifth embodiment is characterized in the configuration of a clip  430  illustrated in  FIGS. 11A and 11B  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the fifth embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIGS. 11A and 11B  illustrate the internal configuration of the retractable writing instrument in the fifth embodiment.  FIG. 11A  illustrates the projected state of the pen point  61  and  FIG. 11B  illustrates the retracted state of the pen point  61 . The clip  430  in the present embodiment is made with a clip body  431  and a clip base  433 . The clip body  431  is configured by bending sheet metal, in a box shape, that extends in the longitudinal direction of the barrel  2 . On a front side of the clip body  431 , a ball portion  432  is integrally provided as a single piece by bending the sheet metal. On both sides of the clip body  431 , a pair of side walls  434  are integrally provided as a single piece by bending the sheet metal. A rear side of the clip body  431  is connected to the clip base  433 . The clip body  431  produces a biasing force P 2  in the direction of the surface of the barrel  2  by the elasticity of its own. 
     The clip base  433  supports the clip body  431  at a predetermined height. Specifically, the clip base  433  supports the clip body  431  at a height to cause the pair of side walls  434  of the clip body  431  not to contact the surface of the barrel  2  in the retracted state of the pen point  61  illustrated in  FIG. 11B . This causes the surface of the barrel  2  not to be damaged. 
     In the projected state of the pen point  61  illustrated in  FIG. 11A , the ball portion  432  of the clip body  431  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  432  is pressed against the first bottom surface  233 A of the guide groove  23   f  by the biasing force P 2  of the clip body  431 . As a result, frictional resistance is produced between the ball portion  432  and the first bottom surface  233 A. The biasing force P 2  of the clip body  431  and the frictional resistance of the ball portion  432  exhibit a preferred effect of inhibiting a rattle of the clip  430 . That is, the first bottom surface  233 A formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  430  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  432  of the clip body  431  fits into the through groove  235  from above the first bottom surface  233 A in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  432  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This allows the pen point  61  to be in the completely retracted state illustrated in  FIG. 11B . 
     As illustrated in  FIG. 11B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  432  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 11A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  431  and the frictional resistance of the ball portion  432  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  430  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 11B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  430  is securely performed to cause the pen point  61  to be in the retracted state. 
     6. Sixth Embodiment 
     With reference to  FIGS. 12A, 12B, and 12C , a retractable writing instrument according to the sixth embodiment of the present invention is then described. The retractable writing instrument according to the sixth embodiment is characterized in the configuration of a clip  440  illustrated in  FIGS. 12A, 12B, and 12C  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the sixth embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIGS. 12A, 12B, and 12C  illustrate the internal configuration of the retractable writing instrument in the sixth embodiment.  FIG. 12A  illustrates the projected state of the pen point  61  and  FIG. 12B  illustrates the retracted state of the pen point  61 .  FIG. 12C  illustrates the positional relationship between a ball portion  442  of a clip body  441  and the surface of the barrel  2 . 
     The clip  440  in the present embodiment has a configuration integrally formed of the clip body  441 , the ball portion  442 , and a clip base  443  by a synthetic resin as a single piece. As illustrated in  FIG. 12C , the clip body  441  is inclined at an angle to locate the ball portion  442  inward of the surface of the barrel  2  (intermediate barrel  23 ). This causes the clip body  441  to produce a biasing force P 2  in the direction of the surface of the barrel  2  by the elasticity of its own. 
     The clip base  443  supports the clip body  441  at a predetermined height. Specifically, the clip base  443  supports the clip body  441  at a height to cause the clip body  441  not to contact the surface of the barrel  2  in the retracted state of the pen point  61  illustrated in  FIG. 12B . This causes the surface of the barrel  2  not to be damaged. 
     In the projected state of the pen point  61  illustrated in  FIG. 12A , the ball portion  442  of the clip body  441  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  442  is pressed against the first bottom surface  233 A of the guide groove  23   f  by the biasing force P 2  of the clip body  441 . As a result, frictional resistance is produced between the ball portion  442  and the first bottom surface  233 A. The biasing force P 2  of the clip body  441  and the frictional resistance of the ball portion  442  exhibit a preferred effect of inhibiting a rattle of the clip  440 . That is, the first bottom surface  233 A formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  440  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  442  of the clip body  441  fits into the through groove  235  from above the first bottom surface  233 A in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  442  moves to the boundary between the second region  232  and the rear half portion  231   b  of the first region  231  along the through groove  235 . This allows the pen point  61  to be in the completely retracted state illustrated in  FIG. 11B . 
     As illustrated in  FIG. 12B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  442  to be in the noncontact state in the direction of the biasing force P 2  illustrated in  FIG. 12A  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  441  and the frictional resistance of the ball portion  442  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  440  from being stopped immediately before the pen point  61  is in the completely retracted state illustrated in  FIG. 12B  even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  440  is securely performed to cause the pen point  61  to be in the retracted state. 
     It should be noted that, as illustrated in  FIG. 12C , the clip  440  in the present embodiment has a configuration integrally formed of the clip body  441 , the ball portion  442 , and the clip base  443  by a synthetic resin as a single piece while not being limited to this configuration. For example, the clip body  441  and the clip base  443  may be two separate components made with a synthetic resin. Moreover, the clip body  441 , the ball portion  442 , and the clip base  443  may be three separate components made with a synthetic resin. These separate components may be fit to each other to configure the one clip  440 . 
     7. Seventh Embodiment 
     With reference to  FIG. 13A , a retractable writing instrument according to the seventh embodiment of the present invention is then described. The retractable writing instrument according to the seventh embodiment is characterized in the configuration of a guide groove  23   f  illustrated in  FIG. 13A  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the seventh embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIG. 13A  illustrates an intermediate barrel  23  of the retractable writing instrument according to the seventh embodiment. The guide groove  23   f  of the retractable writing instrument according to the seventh embodiment has no bottom surface  233  and is configured with a through groove  235  and a pair of side surfaces  234 . The through groove  235  in the present embodiment is formed across the entire area from the first region  231  to the second region  232  and continues to the first long hole  23   e.    
     The guide groove  23   f  illustrated in  FIG. 13A  constantly causes the ball portion  42  of the clip body  41  not to produce the biasing force P 2  regardless of the state of the pen point  61 . This also causes the frictional resistance between the ball portion  42  and the surface of the barrel  2  to be zero. Accordingly, the rearward movement of the clip  4  is prevented from being stopped. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  4  is securely performed to cause the pen point  61  to be in the retracted state. 
     The through groove  235  formed in the second region  232  of the guide groove  23   f  is used when the clip  4  is assembled to the intermediate barrel  23 . In the process of assembling the clip  4  to the intermediate barrel  23 , the ball portion  42  of the clip body  41  passes through the first long hole  23   e  and is guided to the first region  231  by the through groove  235  formed in the second region  232  of the guide groove  23   f . This allows the clip  4  to be assembled to the intermediate barrel  23  without causing the ball portion  42  to contact the surface of the intermediate barrel  23 . 
     8. Eighth Embodiment 
     With reference to  FIG. 13B , a retractable writing instrument according to the eighth embodiment of the present invention is then described. The retractable writing instrument according to the eighth embodiment is characterized in the configuration of a guide groove  23   f  illustrated in  FIG. 13B  and has the other configurations same as those in the first or second embodiment described above. Accordingly, in the eighth embodiment below, identical reference signs are given to the same configurations as those in the first or second embodiment described above to omit detailed descriptions. 
       FIG. 13B  illustrates an intermediate barrel  23  of the retractable writing instrument according to the eighth embodiment. The guide groove  23   f  of the retractable writing instrument according to the eighth embodiment only has a first region  231  and has no second region  232 . In a front half portion  231   a  of the first region  231 , a bottom surface  233  is formed. In a rear half portion  231   b  of the first region  231 , a through groove  235  is formed. The guide groove  23   f  in the present embodiment also exhibits technical effects similar to those in the first embodiment described above. 
     That is, in the projected state of the pen point  61 , the ball portion  42  of the clip body  41  is located in the front half portion  231   a  of the first region  231  of the guide groove  23   f . The ball portion  42  is pressed against the bottom surface  233  of the guide groove  23   f  by the biasing force P 2  of the clip body  41 . As a result, frictional resistance is produced between the ball portion  42  and the bottom surface  233 . The biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  exhibit a preferred effect of inhibiting a rattle of the clip  4 . That is, the bottom surface  233  formed in the front half portion  231   a  of the first region  231  of the guide groove  23   f  prevents a rattle of the clip  4  in the projected state of the pen point  61 . 
     In the process of transfer of the pen point  61  from the projected state to the retracted state, the ball portion  42  of the clip body  41  fits into the through groove  235  from above the bottom surface  233  in a position passing through the boundary between the front half portion  231   a  and the rear half portion  231   b  in the first region  231  of the guide groove  23   f . After that, the ball portion  42  moves rearward of the rear half portion  231   b  of the first region  231  along the through groove  235 . This causes the pen point  61  to be in the completely retracted state. 
     As illustrated in  FIG. 13B , formation of the through groove  235  in the guide groove  23   f  causes the ball portion  42  to be in the noncontact state in the direction of the biasing force P 2  during transfer of the pen point  61  from the projected state to the retracted state. This causes the biasing force P 2  of the clip body  41  and the frictional resistance of the ball portion  42  to be zero. Accordingly, the guide groove  23   f  in the present embodiment prevents the rearward movement of the clip  4  from being stopped immediately before the pen point  61  is in the completely retracted state even if the elastic force P 1  of the first spring  5  is reduced. That is, in the retractable writing instrument according to the present embodiment, normal movement of the clip  4  is securely performed to cause the pen point  61  to be in the retracted state. 
     Moreover, the guide groove  23   f  having no second region  232  breaks the continuation of the through groove  235  in the first region  231  and the first long hole  23   e . This improves the rigidity of the rear side portion of the intermediate barrel  23 . As a result, the rear side portion of the intermediate barrel  23  becomes less likely to deflect and allows a transfer film to be efficiently adhered to the surface of the intermediate barrel  23 . 
     9. Ninth Embodiment 
     Preferably, as illustrated in  FIG. 14A , an inclined surface  233   a  down to the through groove  235  is formed at a rear end of the bottom surface  233  (or the first bottom surface  233 A) of the guide groove  23   f . Such an inclined surface  233   a  allows the ball portion  42  of the clip body  41  to smoothly go up and down the bottom surface  233 . This allows smooth sliding operation of the clip  4  to retract and project the pen point  61 . 
     Preferably, as illustrated in  FIG. 14B , in the retracted state of the pen point  61 , a distance D is formed between the rear end of the bottom surface  233  of the guide groove  23   f  and the ball portion  42  of the clip body  41 . Due to the distance D, the ball portion  42  of the clip body  41  fits into the through groove  235  before the pen point  61  is in the completely retracted state and the biasing force P 2  of the clip body  41  becomes zero. Moreover, due to the distance D, the surface of the ball portion  42  does not contact the rear end of the bottom surface  233 , and in the process of transfer of the pen point  61  from the projected state to the retracted state, frictional resistance is not produced between the surface of the ball portion  42  and the rear end of the bottom surface  233 . Such a technical effect of the distance D more securely prevents the rearward movement of the clip  4  from being stopped. 
     10. Application to “Multi-Pen” Writing Instrument 
     The guide groove  23   f  in the seventh embodiment illustrated in  FIG. 13A  exhibits a particularly marked technical effect when applied to, for example, a retractable writing instrument  200  provided with a plurality of writing tool bodies  6 A and  6 B as illustrated in  FIG. 16 . 
     That is, when the guide groove  23   f  with no bottom surface  233  illustrated in  FIG. 13A  is applied to the retractable writing instrument  200  illustrated in  FIG. 16 , the biasing force P 2  of the clip body  41  is zero in the projected state of the pen point of the writing tool body  6 A. This causes the ball portion  42  of the clip body  41  not to receive a reaction force (refer to the gray arrow in  FIG. 16 ) in the direction opposite to the biasing force P 2  from the surface of the barrel  2 . As a result, a biasing force P 3  (force in a direction away from the surface of the barrel  2 ) in  FIG. 16  is not produced at the rear end portion  8   a  of the slider  8 A. This prevents accidental removal of the locking of the rear end portion  8   a  of the slider  8 A on the locking rib  2   a . In other words, the projected state of the pen point of the writing tool body  6 A is securely retained. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  Retractable Writing Instrument 
           2  Barrel 
           20  Slide Hole 
           21  Tip 
           21   a  Front End Hole 
           22  Front Barrel 
           22   a  Grip 
           23  Intermediate Barrel 
           23   a  Cam Gear 
           23   b  Cam Groove 
           23   e  First Long Hole 
           23   f  Guide Groove 
           231  First Region 
           231   a  Front Half Portion 
           231   b  Rear Half Portion 
           232  Second Region 
           233  Bottom Surface 
           233 A First Bottom Surface 
           233 B Second Bottom Surface 
           233   a  Inclined Surface 
           234  Side Surface 
           235  Through Groove 
           24  Rear Barrel 
           24   a  Second Long Hole 
           24   b  Attachment Hole 
           3  Rotary Member 
           31  Convex Thread 
           4  Clip 
           41  Clip Body 
           41   a  Upper Wall 
           41   b  Side Wall 
           41   c  Bearing Hole 
           41   d  Projection 
           42  Ball Portion 
           43  Clip Base 
           43   a  Slider 
           43   b  Rotating Shaft 
           43   c  Coupling Portion 
           43   d  Cylindrical Portion 
           43   e  Cam Gear 
           43   f  Projection 
           43   g  Stopper 
           44  Second Spring 
           5  First Spring 
           6  Writing Tool Body 
           61  Pen Point 
           62  Ink Storage Tube 
           63  Thermochromic Ink 
           64  Follower 
           65  End Plug 
           7  Friction Unit 
           410 ,  420 ,  430 ,  440  Clip 
           411 ,  421 ,  431 ,  441  Clip Body 
           412 ,  422 ,  432 ,  442  Ball Portion 
           413 ,  423 ,  433 ,  443  Clip Base 
           414  Leaf Spring 
           434  Side Wall 
         D Distance