Patent Publication Number: US-11642909-B2

Title: Writing instrument

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-091605, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a writing instrument. 
     Description of Related Art 
     Conventionally, a water brush filled inside with water has been known. The water brush is used at the time of exercise of calligraphy or at the time of painting in watercolors at a place, for example, out of doors. 
     For example, JP 2019-209531 A describes a water brush including a brush tip part for applying water and a shaft part extending from the brush tip part, the shaft part including a coating liquid storage section for storing water. In the water brush described above, the coating liquid storage section includes a water through hole disposed at a tip end portion and a valve mechanism disposed at a rear end portion, and further includes an operation part for switching the valve mechanism between open state and close state. That is, according to such a water brush, a user presses the operation part to thereby cause the valve mechanism to come into open state so that the coating liquid storage section communicates with the external environment. Thus, water flows out from the water through hole to be supplied to the brush tip part. As seen from the above, the writing instrument of this type is demanded to supply an appropriate amount of water to the brush tip part at a timing intended by the user. This demand is required not only in the writing instrument including water but also in the writing instrument including ink. 
     However, the writing instrument described in JP 2019-209531 A is difficult to enable appropriate control of the supply amount of coating liquid such as water or ink only by means of operation of the operation part since the brush tip part and the coating liquid storage section are in constant communication with each other via the water through hole. Particularly in the case where the coating liquid has a low viscosity or low surface tension, the coating liquid may flow out from the water through hole even when the valve mechanism is in close state. Therefore, it is difficult to precisely control the supply amount of the coating liquid to the brush tip part. 
     Further, when the coating liquid is supplied to the brush tip part, it is necessary to prevent leakage of the coating liquid from any part other than the brush tip part. The water brush of JP 2019-209531 A, in which the valve mechanism and the operation part for opening the valve of the valve mechanism are arranged at the rear end portion, is provided with no measures to prevent leakage of the coating liquid from such a part. 
     SUMMARY OF THE INVENTION 
     In view of the aforementioned circumstances, it is an object of the present invention to provide a writing instrument that can more precisely control the supply amount of the coating liquid to the pen tip part, while preventing leakage of the coating liquid. 
     The following presents a simplified summary of the invention disclosed herein in order to provide a basic understanding of some aspects of the invention. This summary is not an extensive overview of the invention. It is intended to neither identify key or critical elements of the invention nor delineate the scope of the invention. Its sole purpose is to present some concepts of the invention in a simplified form as a prelude to the more detailed description that is presented later. 
     The writing instrument as an embodiment of the present invention includes: a pen tip part for applying a coating liquid; a coating liquid storage section for storage of the coating liquid; a cylindrical part having a cylindrical shape so as to cover the coating liquid storage section, and fixed to the pen tip part; a valve mechanism disposed at a tip end portion of the coating liquid storage section; an operation member fixed to the pen tip part and configured to open the valve mechanism and allow the coating liquid flowing out from the coating liquid storage section to flow toward a pen tip side via the valve mechanism; and a cylindrical elastic member being capable of expanding and contracting in an axial direction, and connecting the valve mechanism with the operation member to define a flow channel of the coating liquid between the valve mechanism and the operation member; in which the coating liquid storage section is relatively movable to the pen tip part in the axial direction, and the operation member is configured to open the valve mechanism in association with the relative movement of the coating liquid storage section to the pen tip part. 
     In the writing instrument, the operation member is preferably configured to bring the valve mechanism into open state by pressing the valve mechanism. 
     In the writing instrument, an end portion on one side of the cylindrical elastic member preferably covers the tip end portion of the coating liquid storage section, while covering the valve mechanism. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other features of the present invention will become apparent from the following description and drawings of an illustrative embodiment of the invention in which: 
         FIG.  1    schematically shows an internal structure of a writing instrument according to an embodiment. 
         FIG.  2    is an exploded view of the writing instrument of  FIG.  1   . 
         FIG.  3    shows an internal structure of a valve mechanism provided in the writing instrument of  FIG.  1   . 
         FIG.  4    is a view showing the valve mechanism provided in the writing instrument of  FIG.  1    as viewed from a rear end side in an axial direction. 
         FIG.  5    is a cross section view of a pressing member of the writing instrument of  FIG.  1   . 
         FIG.  6    is a view showing the pressing member of the writing instrument of  FIG.  1    as viewed from the rear end side in the axial direction. 
         FIG.  7    is a cross section view of a cylindrical elastic member of the writing instrument of  FIG.  1   . 
         FIG.  8    is a view of the cylindrical elastic member of the writing instrument of  FIG.  1    as viewed from one side in the axial direction. 
         FIG.  9    shows a relationship between the valve mechanism, the pressing member, and the cylindrical elastic member when the valve mechanism is in close state. 
         FIG.  10    shows a relationship between the valve mechanism, the pressing member, and the cylindrical elastic member when the valve mechanism is in open state. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     Hereinafter, a writing instrument according to an embodiment of the present invention will be described with reference to the attached drawings. 
     A writing instrument  1  according to this embodiment is filled with ink as a coating liquid. Further, the writing instrument  1  is configured to be refillable with ink when ink has been exhausted. 
     As shown in  FIG.  1    and  FIG.  2   , the writing instrument  1  according to this embodiment includes a pen tip part  2  for applying a coating liquid to an application target such as paper, and a shaft part  3  extending from the pen tip part  2 . The shaft part  3  includes a coating liquid storage section  31  for storage of the coating liquid, and a cylindrical part  32  having a cylindrical shape so as to cover the coating liquid storage section  31 . 
     In the description herein, a direction in which the writing instrument  1  extends is sometimes referred to as an axial direction, a direction orthogonal to the axial direction is sometimes referred to as a radial direction, and a direction rotating around a central axis of the writing instrument  1  is referred to as a circumferential direction. Also, a pen tip side in the axial direction is sometimes referred to as a tip end side, and the opposite side to the tip end side is referred to as a rear side. 
     In this embodiment, the pen tip part  2  includes an application part  21  configured to come into direct contact with an application target to apply the coating liquid to the application target, a retainer part  22  that retains the application part  21 , and a hollow part  23  having a cylindrical shape and extending from the retainer part  22  toward the rear end. 
     The application part  21  is formed by a hair bundle of a plurality of hairs with one end portion bound with adhesive. That is, the application part  21  has a bundled part with one end portion of the plurality of hairs bound with adhesive, and a non-bundled part in which the plurality of hairs are not bound with adhesive. The bundled part is disposed on the rear end side of the application part  21 , and the non-bundled part is disposed on the tip end side. A flow channel extending along the axial direction is formed in the bundled part. The coating liquid is supplied to the tip end portion  211  of the application part  21  via the flow channel. Specifically, the pen tip part  2  including the application part  21  is a brush tip part  2 . 
     Further, the application part  21  is formed to decrease in diameter from a rear end portion  212  toward the tip end portion  211 . Furthermore, the rear end portion  212  has an enlarged diameter part  213  that is formed to have a largest diameter in the application part  21 . 
     In this embodiment, the retainer part  22  is formed into a circular truncated cone shape decreasing in diameter from the rear end toward the tip end. The retainer part  22  has a through hole  221  extending along the axial direction. The through hole  221  has an inner diameter of such a dimension as not to allow the enlarged part  213  of the application part  21  to pass therethrough, while allowing the non-bundled part of the application part  21  to pass therethrough. 
     In this embodiment, the pen tip part  2  is fixed to the cylindrical part  32  in the hollow part  23 . The hollow part  23  is formed to be fitted onto a tip end portion  321  of the cylindrical part  32 . The hollow part  23  and the cylindrical part  32  are configured to be able to come into liquid-tight engagement with each other. In this embodiment, internal threads are formed on the inner peripheral surface of a rear end portion  232  of the hollow part  23 , and external thread capable of coming into threaded engagement with the internal threads are formed on the outer peripheral surface of the tip end portion  321  of the cylindrical part  32 . Thereby, the hollow part  23  and the cylindrical part  32  are configured to be capable of coming into threaded engagement with each other. 
     Further, a sealing member  4  having an annular shape is provided inside the hollow part  23 . The sealing member  4  is disposed to be sandwiched between a rear end portion  222  of the retainer part  22  and a tip end portion  321  of the cylindrical part  32  in the state where the pen tip part  2  is fixed to the cylindrical part  32 . The sealing member has an opening  41  allowing ink to pass therethrough. The inner diameter of the opening  41  is formed to be larger than the inner diameter of the flow channel in the application part  21  and smaller than the outer diameter of the enlarged diameter part  213  of the application part  21 . The sealing member  4  is disposed to allow the opening  41  to be in communication with the flow channel in the application part  21 . The sealing member  4  makes it easy to guide ink flowing out from the coating liquid storage section  31  into the flow channel via the opening  41 , and consequently makes it easy to supply ink to the pen tip part  2 . 
     The coating liquid storage section  31  has a bottomed cylindrical shape having a tip end portion  311  that is opened and a rear end portion  312  that is closed. The coating liquid storage section  31  has an internal space S for filling ink. The coating liquid storage section  31  includes a mixing member  314  having a ball shape and provided to accelerate the process of mixing of ink. The mixing member  314  has a smaller diameter than the inner diameter of the coating liquid storage section  31 , to thereby move in the internal space S in the axial direction by shaking of the writing instrument  1  in the axial direction. The mixing member  314  generally has a larger density than the density of ink. Thus, the mixing member  314  precipitates in ink. 
     Ink can be water-based ink or can be oil-based ink. 
     The cylindrical part  32  is formed into a cylindrical shape with the tip end portion  321  and a rear end portion  322  both being opened. The cylindrical part  32  is formed to be capable of housing the coating liquid storage section  31 . As shown in  FIG.  1   , the inner peripheral surface of the cylindrical part  32  and the outer peripheral surface of the coating liquid storage section  31  together form a gap G 1  therebetween. Thereby, the coating liquid storage section  31  is movable inside the cylindrical part along the axial direction. Also, the coating liquid storage section  31  can be relatively movable to the pen tip part  2  in the axial direction. The coating liquid storage section  31  can move inside the cylindrical part  32  so that part of the inner peripheral surface of the cylindrical part  32  and part of the outer peripheral surface of the coating liquid storage section  31  come into sliding contact with each other. 
     The cylindrical part  32  is formed to expose the rear end portion  312  of the coating liquid storage section  31  to the outside. With this configuration, the user can easily press the rear end portion  312  of the coating liquid storage section  31  (preferably, a rear end surface of the coating liquid storage section  31 ) by a thumb or the like and consequently can easily move the coating liquid storage section  31  toward the tip end side. 
     The writing instrument  1  further includes a valve mechanism  5  disposed at the tip end portion  311  of the coating liquid storage section  31 , and a pressing member  6  that is an operation member  6  configured to press the valve mechanism  5  to thereby open the valve mechanism  5 . The pressing member  6  of this embodiment is fixed to the tip end portion  321  of the cylindrical part  32 . In this embodiment, the pressing member  6  is directly fixed to the cylindrical part  32 . 
     The writing instrument  1  is configured to be capable of coming into close state and open state. In close state, the pressing member  6  does not press the valve mechanism  5  to bring the valve mechanism  5  into open state so that the valve mechanism  5  is in close state. In open state, the coating liquid storage section  31  is moved toward the tip end side so that the pressing member  6  presses the valve mechanism  5  so that the valve mechanism  5  is in open state. This configuration allows the valve mechanism  5  to be relatively movable to the pressing member  6  in the axial direction. In close state, a portion of the pressing member  6  that presses the valve mechanism  5  (specifically, protrusion  63  to be described later) can be in contact with the valve mechanism  5  or can be away from the valve mechanism  5 . In other words, allowance can be provided between the valve mechanism  5  and the portion of the pressing member  6  that presses the valve mechanism  5 , or no such allowance can be provided therebetween. 
     The writing instrument  1  includes a cylindrical elastic member  7  that connects the valve mechanism  5  with the pressing member  6 . 
     As shown in  FIG.  3    and  FIG.  4   , the valve mechanism  5  of this embodiment includes a valve main body  51  inside of which a flow channel  511  extending in the axial direction is formed, a valve body  52  that is movable in the flow channel  511  along the axial direction, a valve seat  53  with which the valve body  52  is in contact so that the flow channel  511  can be closed, and a spring member  54  that biases the valve body  52  toward the valve seat  53 . 
     The valve main body  51  is formed into a cylindrical shape extending along the axial direction so as to be capable of housing the valve body  52  and the valve seat  53 . The valve main body  51  further includes a locking part  512  having an annular shape for restricting the valve main body  51  from entirely entering the coating liquid storage section  31 . The valve main body  51  further includes an insertion part  513  that is formed to extend from the locking part  512  toward the rear end side and is disposed inside the coating liquid storage section  31 . 
     The outer diameter of the locking part  512  is formed to be larger than the inner diameter of the tip end portion  311  of the coating liquid storage section  31 . 
     The locking part  512  of this embodiment functions as a first elastic member connecting part  512  for connection of a rear end portion  72  of the cylindrical elastic member  7 . The outer diameter of the locking part  512  is formed to be smaller than the outer diameter of the tip end portion  311  of the coating liquid storage section  31 . With this configuration, the connection portion between the locking part  512  and the coating liquid storage section  31  gradually increases in diameter from the locking part  512  toward the tip end portion  311  of the coating liquid storage section  31 . 
     The insertion part  513  has a first extension part  513   a  that is formed to extend from the locking part  512  toward the rear end side and is formed to be in contact with the inner peripheral surface of the coating liquid storage section  31  along the circumferential direction. The insertion part  513  also has a second extension part  513   b  that is formed to extend from the first extension part  513   a  further toward the rear end side and is formed to decrease in diameter toward the rear end side. The second extension part  513   b  is disposed so that its outer peripheral surface is out of contact with the inner peripheral surface of the coating liquid storage section  31 . 
     The valve body  52  includes a contact part  521  that comes into contact with the valve seat  53 , a first valve rod part  522  that extends from the contact part  521  toward the tip end side, and a second valve rod part  523  that extends from the contact part  521  toward the rear end side. 
     The contact part  521  is disposed to come into contact with the valve seat  53  from the rear end side toward the tip end side (by moving from the rear end side toward the tip end side in the axial direction). The contact part  521  is formed into a circular truncated cone shape decreasing in diameter from the rear end side toward the tip end side and has a contact surface  521   a  that comes into contact with the valve seat  53  along the radial direction. 
     The first valve rod part  522  has a tip end portion  522   a  formed to protrude from the valve main body  51  in the state where the contact part  521  is in contact with the valve seat  53 . The first valve rod part  522  is formed into a cylindrical shape. 
     The second valve rod part  523  has a rear end portion  523   a  formed to protrude from the valve main body  51  in the state where the contact part  521  is away from the valve seat  53  while being close to the rear end side. The mixing member  314 , which may be able to close the flow channel  511  of the valve main body  51  from the rear end side, can be separated from the valve main body  51  by the second valve rod part  523 . 
     The valve seat  53  has a contacted part  531  with which the valve body  52  comes into contact. The contacted part  531  has a contacted surface  531   a  having a shape corresponding to the contact surface  521   a  of the valve body  52 . In other words, the contacted part  531  is formed to extend in the axial direction and formed into a circular truncated cone shape with the inner diameter increasing from the tip end side toward the rear end side. 
     The spring member  54  has a tip end portion in contact with the valve body  52  and a rear end portion in contact with the insertion part  513  of the valve main body  51 . The spring member  54  disposed in this manner comes into contracted state in which the spring member  54  is contracted in the axial direction in association with the movement of the coating liquid storage section  31  toward the tip end side. Specifically, the valve body  52  is pressed by the pressing member  6  in association with the movement of the coating liquid storage section  31  toward the tip end side, thereby the spring member  54  comes into contracted state in which the spring member  54  is contracted by receiving a pressure of the valve body  52  moving toward the rear end side. Further, the spring member  54  comes into expanded state in which the spring member  54  biases the valve body  52  toward the tip end side so as to cause the valve body  52  to be in contact with the valve seat  53  as the valve body  52  is released from the pressure by the pressing member  6  in association with the movement of the coating liquid storage section  31  toward the rear end side. 
     More specifically, the spring member  54  of this embodiment is a coil spring. 
     As shown in  FIG.  5    and  FIG.  6   , the pressing member  6  of this embodiment includes a locking part  61  having a cylindrical shape for restricting the locking part  61  from entirely entering the cylindrical part  32 , a second elastic member connecting part  62  having an annular shape formed to extend from the locking part  61  toward the rear end side and serving as a part for connection with a tip end portion  71  of the cylindrical elastic member  7 , a protrusion  63  having a rod shape formed to protrude toward the rear end side of the second elastic member connection part  62  and directly press the valve mechanism  5 , and a support part  64  for providing support to the protrusion  63  through the locking part  61  or the second elastic member connection part  62 . 
     The pressing member  6  is disposed to allow the locking part  61  to come into contact with the tip end portion  321  of the cylindrical part  32 . 
     The outer diameter of the second elastic member connection part  62  is formed to be smaller than the inner dimeter of the tip end portion  321  of the cylindrical part  32 . With this configuration, the outer peripheral surface of the second elastic member connection part  62  and the inner peripheral surface of the tip end portion  321  of the cylindrical part  32  together form a gap G 2  therebetween to dispose the cylindrical elastic member  7  therein, as shown in  FIG.  1   . 
     The protrusion  63  is formed to be insertable into the first valve rod part  522  of the valve body  52 . Thereby, the protrusion  63  comes into contact with the valve body  52  so as to be guided by the first valve rod part  522 . The protrusion  63  of this embodiment is disposed inside the first valve rod part  522  in both of close state and open state of the valve mechanism  5 . The protrusion  63  can be disposed outside the first valve rod part  522  when the valve mechanism  5  is in close state. 
     The support part  64  includes at least one or more of support pieces  641  formed to extend from a base end  631  of the protrusion  63  to the inner peripheral surface of the locking part  61  or the second elastic member connection part  62 . The support part  64  is formed to have a flow channel  642  of ink. The support part  64  of this embodiment is formed into a cross shape having four support pieces  641  radially extending in four directions respectively from the base end  631  of the protrusion  63 . Four flow channels  642  are formed between each adjacent support pieces  641 . 
     As shown in  FIG.  1   ,  FIG.  2   ,  FIG.  7   , and  FIG.  8   , the cylindrical elastic member  7  connects the valve mechanism  5  with the pressing member  6  so as to allow a tip end portion  71  to cover the second elastic member connection part  62  in the pressing member  6 , and allow a rear end portion  72  to cover the first elastic member connecting part  512  that is the locking part  512  in the valve mechanism  5 . The cylindrical elastic member  7  has a flow channel  73  that allows ink flowing out from the valve mechanism  5  to be moved from the valve mechanism  5  to the pressing member  6  when the valve mechanism  5  is brought into open state. 
     In the cylindrical elastic member  7  of this embodiment, the rear end portion  72  extends over the first elastic member connecting part  512  of the valve mechanism  5  to cover a part of the tip end portion  311  of the coating liquid storage section  31 . That is, the cylindrical elastic member  7  reinforces the fixing of the valve mechanism  5  to the coating liquid storage section  31 . The cylindrical elastic member  7  also covers the portion connecting the valve mechanism  5  with the coating liquid storage section  31  to prevent leakage of the coating liquid. 
     As shown in  FIG.  9    and  FIG.  10   , the cylindrical elastic member  7  that connects the valve mechanism  5  with the pressing member  6  forms, between the tip end portion  71  and the rear end portion  72 , an expansion-contraction part  74  that expands and contract in the axial direction. As shown in  FIG.  10   , the cylindrical elastic member  7  comes into contracted state in which the cylindrical elastic member  7  is contracted in the axial direction in association with the movement of the coating liquid storage section  31  toward the tip end side. Specifically, the cylindrical elastic member  7  receives the pressure in the axial direction from each of the valve mechanism  5  and the pressing member  6  as the valve mechanism  5  approaches the pressing member  6  upon the movement of the coating liquid storage section  31  toward the tip end side, to thereby cause the expansion-contraction part  74  to come into contracted state in which the expansion-contraction part  74  is contracted in the axial direction. Further, as shown in  FIG.  9   , the cylindrical elastic member  7  receives a tensile force in the axial direction from each of the valve mechanism  5  and the pressing member  6  as the valve mechanism  5  moves away from the pressing member  6  upon the movement of the coating liquid storage section  31  toward the rear end side, to thereby cause the expansion-contraction part  74  to comes into (from contracted state to) expanded state in which the expansion-contraction part  74  is expanded in the axial direction ( FIG.  9   ). 
     Further, the cylindrical elastic member  7  of this embodiment is configured to allow the expansion-contraction part  74  to come into the state of decreasing in diameter or warping in the radially inward direction, while the expansion-contraction part  74  is in contracted state, as shown in  FIG.  10   . The cylindrical elastic member  7  can be configured to allow the expansion-contraction part  74  to come into the state of increasing in diameter in the radially outward direction, while the expansion-contraction part  74  is in contracted state. 
     The cylindrical elastic member  7  of this embodiment is configured to allow the inner peripheral surface of the expansion-contraction part  74  to have a cylindrical shape to be substantially straight along the axial direction, while the expansion-contraction part  74  is in expanded state. 
     Examples of the material for forming the cylindrical elastic member  7  include a thermos plastic elastomer material. 
     As described above, the writing instrument  1  of this embodiment includes: a pen tip part  2  for applying a coating liquid; a coating liquid storage section  31  for storage of the coating liquid; a cylindrical part  32  having a cylindrical shape so as to cover the coating liquid storage section  31 , and fixed to the pen tip part  2 ; a valve mechanism  5  disposed at a tip end portion  311  of the coating liquid storage section  31 ; an operation member  6  fixed to the pen tip part  2  and configured to open the valve mechanism  5  and allow the coating liquid flowing out from the coating liquid storage section  31  to flow toward a pen tip side via the valve mechanism  5 ; and a cylindrical elastic member  7  being capable of expanding and contracting in an axial direction, and connecting the valve mechanism  5  with the operation member  6  to define a flow channel of the coating liquid between the valve mechanism  5  and the operation member  6 ; in which the coating liquid storage section  31  is relatively movable to the pen tip part  2  in the axial direction, and the operation member  6  is configured to open the valve mechanism  5  in association with the relative movement of the coating liquid storage section  31  to the pen tip part  2 . 
     According to the writing instrument  1  with the above configuration, the cylindrical elastic member  7  connecting the valve mechanism  5  with the operation member  6  can prevent leakage of the coating liquid from therebetween. Further, the coating liquid storage section  31  is relatively movable to the pen tip part  2  in the axial direction, and the operation member  6  causes the valve mechanism  5  to be opened in association with the relative movement of the coating liquid storage section  31 . Thereby, it is possible to supply the coating liquid to the pen tip part  2 , while discharging the coating liquid from the coating liquid storage section  31  via the valve mechanism  5  and the flow channel  73  of the cylindrical elastic member  7 . Furthermore, unintentional flowing out of the coating liquid from the tip end portion  311  toward the pen tip side can be suppressed since the tip end portion  311  of the coating liquid storage section  31  is closed by the valve mechanism  5  when the valve mechanism  5  is closed. Therefore, according to the above configuration, the user can relatively precisely control the supply amount of the coating liquid to the pen tip part  1  by operating the opening and closing of the valve mechanism  5  by moving the coating liquid storage section  31  toward the pen tip part  2 . 
     In the writing instrument  1  of this embodiment, the operation member  6  is configured to bring the valve mechanism  5  into open state by pressing the valve mechanism  5 . 
     According to the writing instrument  1  with the above configuration, the operation member  6  presses the valve mechanism  5  to bring the valve mechanism  5  into open state, which can achieve a relatively simple structure. 
     In the writing instrument  1  of this embodiment, an end portion on one side (i.e., rear end portion  72 ) of the cylindrical elastic member  7  covers the tip end portion  311  of the coating liquid storage section  31 , while covering the valve mechanism  5 . 
     According to the writing instrument  1  with the above configuration, an end portion on one side (i.e., rear end portion  72 ) of the cylindrical elastic member  7  covers both of the valve mechanism  5  and the tip end portion  311  of the coating liquid storage section  31 , which makes it possible to prevent leakage of the coating liquid from a gap that may occur between the valve mechanism  5  and the coating liquid storage section  31 . 
     In addition, according to the writing instrument  1  of this embodiment, since the coating liquid storage section  31  pressed toward the tip end side causes the expansion-contraction part  74  of the cylindrical elastic member  7  to come into contracted state, the coating liquid storage section  31  is movable together with the valve mechanism  5  toward the pressing member  6  by the distance by which the expansion-contraction part  74  is contracted. Then, the contact part  521  of the valve mechanism  5  is pressed by the protrusion  63  of the pressing member  6  to allow the valve mechanism  5  to come into open state. In association with this, ink discharged from the coating liquid storage section  31  is moved to the tip end side via the flow channel  511  of the valve mechanism  5 , the flow channel  73  of the cylindrical elastic member  7 , and the flow channels  642  of the pressing member  6 , to be supplied to the pen tip part  2 . 
     According to the writing instrument  1  of this embodiment, the valve mechanism  5  is in close state when the coating liquid storage section  31  is not pressed. Thus, even in the case where the coating liquid having a low viscosity or a low surface tension is used, the coating liquid does not flow out of the pen tip and it is possible to precisely control the supply amount of the coating liquid as desired by the user. 
     According to the writing instrument  1  of this embodiment, it is possible to prevent the ink leakage. Thus, it is unlikely to cause the ink stain so that the user can use it without care. 
     According to the writing instrument  1  of this embodiment, the portion connecting the coating liquid storage section  31  with the first elastic member connecting part  512  that is the locking part  512  has a diameter stepwisely increasing from the first elastic member connecting part  512  toward the tip end portion  311  of the coating liquid storage section  31 , which makes it possible to easily attach the cylindrical elastic member  7  to an area from the first elastic member connecting part  512  to the tip end portion  311 . 
     According to the writing instrument  1  of this embodiment, the cylindrical elastic member  7  covers an area from the first elastic member connecting part  512  to the tip end portion  311  of the coating liquid storage section  31 , which can prevent the ink leakage from a gap that may occur between the valve mechanism  5  and the coating liquid storage section  31 . Furthermore, unintentional detachment of the valve mechanism  5  from the coating liquid storage section  31  can be also prevented. 
     According to the writing instrument  1  of this embodiment, the expansion-contraction part  74  of the cylindrical elastic member  7  is configured to have the inner peripheral surface substantially straight along the axial direction when it is in expanded state, and thus allows ink to easily flow from the cylindrical elastic member  7  to the pressing member  6 . Thereby, ink is hardly left inside the cylindrical elastic member  7  to thereby be able to suppress adhesion of ink to the inner peripheral surface of the cylindrical elastic member  7 . Accordingly, smooth supply of ink to the pen tip part  2  can be maintained for a long term. This is suitable to the case where the writing instrument  1  is refillable with ink. 
     According to the writing instrument  1  of this embodiment, the pressing member  6  is directly fixed to the cylindrical part  32 . Thus, when the pen tip part  2  is detached from the cylindrical part  32 , the pressing member  6  comes into the state of being exposed on the tip end side of the cylindrical part  32 . When the rear end portion of the coating liquid storage section  31  is pressed in this state, the valve mechanism  5  is opened by the pressing member  6  fixed to the cylindrical part  32 . Thereby, the coating liquid storage section  31  can be refilled with ink via (the flow channel  642  of) the pressing member  6 . Since the pressing member  6  and the valve mechanism  5  are connected with each other by the cylindrical elastic member  7  also at the time of refilling ink, the ink leakage can be suppressed. 
     Although the writing instrument according to this embodiment is as described above, the present invention is not limited to the aforementioned embodiment and the design may be appropriately changed within the scope where the present invention is intended. Also, the functional effect of the present invention is not limited to the aforementioned embodiment. That is, the embodiments disclosed herein should be assumed as not limitations but exemplifications in all aspects. The scope of the present invention is described not by the above description but by the claims. Further, the scope of the present invention is intended to include the scope equivalent to the claims and all the changes in the claims. 
     For example, in the above embodiment, the writing instrument filled with ink as the coating liquid was described as an example, but the present invention is not limited thereto, and the writing instrument of the present invention can be filled with water, India ink, or the like as the coating liquid. 
     Further, in the above embodiment, the present invention was described by taking, for example, the form in which the valve mechanism  5  is relatively movable to the pressing member  6  in the axial direction, but the present invention is not limited thereto, and the pressing member  6  can be relatively movable to the valve mechanism  5  in the axial direction. 
     Further, the pressing member  6  can be indirectly fixed to the cylindrical part  32  to thereby be fixed to the cylindrical part  32 . In other words, the pressing member  6  can be indirectly fixed to the cylindrical part  32  by being fixed to a member or part other than the cylindrical part  32 . For example, the pressing member  6  can be fixed to the inside of the hollow part  23  of the pen tip part  2 . 
     Further, the cylindrical elastic member  7  can be formed into an accordion shape. Thereby, the expansion-contraction part  74  can easily expand and contract in the axial direction.