JP7493441B2 - Pressurized writing implement - Google Patents

Description

The present invention relates to a pressure-type writing instrument.

Conventionally, pressurized writing implements capable of applying pressure to ink filled inside of writing implements such as ballpoint pens have been known. Patent Document 1 discloses a pressurized writing implement that includes a refill filled with ink in a barrel, a holder attached in an annular shape to the rear end side of the refill, a sealing member (valve body) such as an O-ring attached in an annular shape to the outer circumferential surface of the holder, and a cylinder that covers the holder from the rear and holds the holder so that it can be advanced and retreated, and that compresses a pressurized chamber that communicates with the rear end opening of the refill by retracting the holder. The inner circumferential surface of the cylinder has a large inner diameter portion located on the front side and a reduced diameter portion located rearward of the large inner diameter portion and reduced in diameter, and the large inner diameter portion and the reduced diameter portion are connected by an annular inclined surface.

In the pressurized writing instrument disclosed in Patent Document 1, when the refill retracts due to the writing part being pressed against the surface being written on, the holder also retracts together with the refill. As the holder moves rearward relative to the cylinder, its rear end approaches the inner bottom surface of the cylinder, narrowing the pressurized chamber. When the holder retracts, the air passage that connects the pressurized chamber to the outside is closed by a sealing member, and in this closed state the pressurized chamber is narrowed. The gas in the space from the pressurized chamber to the rear end side of the refill is compressed, and the resulting pressure presses the ink filled in the refill.

Patent No. 5558908

In the pressure-type writing instrument disclosed in Patent Document 1, when the holder retracts, the seal member needs to climb over a step (annular inclined surface) located between the large inner diameter portion and the reduced diameter portion of the inner circumferential surface of the cylinder. In this case, there is a risk that the seal member will be damaged as the seal member repeatedly climbs over this step as writing is repeated. In particular, in a pressure-type writing instrument in which pressure is applied and then released repeatedly for each stroke when writing, the increased number of times pressure is applied increases the possibility of the seal member being damaged.

The present invention was made with these points in mind, and aims to prevent damage to the sealing member that seals the pressure chamber in a pressure-type writing instrument.

The pressure-type writing instrument according to the present invention comprises:
A shaft cylinder,
a refill disposed within the barrel and having an ink reservoir filled with ink;
A pressure mechanism that applies pressure to the rear end of the ink,
The pressure mechanism includes:
a piston member having an outer step on an outer surface thereof;
a cylinder member having an inner step on an inner surface thereof, the inner step facing the outer step along an axial direction;
a first seal member that seals a gap between the piston member and the cylinder member forward of the outer step portion;
a second seal member that seals a gap between the piston member and the cylinder member rearward of the inner step portion;
a third seal member capable of sealingly closing a rear end opening of the piston member,
When the outer step moves toward the inner step, the rear end of the piston member abuts against the third seal member to form a pressurized chamber sealed by the first seal member, the second seal member and the third seal member, and the volume of the pressurized chamber decreases as the outer step approaches the inner step.

In the pressure-type writing instrument according to the present invention,
The outer surface of the piston member has a first large diameter portion and a first small diameter portion located rearward of the second large diameter portion,
The inner surface of the cylinder member has a second large diameter portion and a second small diameter portion located rearward of the second large diameter portion,
the outer step portion is located between the first large diameter portion and the first small diameter portion,
The inner step may be located between the second larger diameter portion and the second smaller diameter portion.

In the pressure-type writing instrument according to the present invention,
The piston member may have a through hole between the first seal member and the second seal member, the through hole connecting the inner surface and the outer surface.

In the pressure-type writing instrument according to the present invention,
At least a portion of the third seal member that comes into contact with the rear end opening may be made of an elastic material.

In the pressure-type writing instrument according to the present invention,
The housing may further include a resilient member that biases the third seal member forward.

In the pressure-type writing instrument according to the present invention,
The ink container further includes a tail plug attached to a rear end of the ink container.
At least a portion of the tail plug which comes into contact with the ink reservoir may be made of an elastic material.

The present invention makes it possible to prevent damage to the sealing member that seals the pressure chamber in a pressure-type writing instrument.

FIG. 1 is a vertical cross-sectional view showing a pressure-type writing instrument according to one embodiment of the present invention, and shows the pressure-type writing instrument in a state in which a ballpoint pen tip is retracted. FIG. 2 is a vertical cross-sectional view showing the pressure type writing instrument of FIG. 1 in a state where the ballpoint tip is protruded. FIG. 3 is an enlarged view of the pressure mechanism of the pressure-type writing instrument of FIG. FIG. 4 is an enlarged view of the pressure mechanism of the pressure-type writing instrument of FIG. FIG. 5 is a diagram for explaining the operation of the pressure mechanism. FIG. 6 is a diagram for explaining the operation of the pressure mechanism.

One embodiment of the present invention will now be described with reference to the drawings. Note that in the drawings attached to this specification, the scale and aspect ratios have been appropriately altered and exaggerated from those of the actual objects for the sake of ease of illustration and understanding.

In addition, terms used in this specification that specify shapes, geometric conditions, and the degree of those conditions, such as "parallel," "orthogonal," and "same," as well as values of lengths and angles, are not to be construed as being limited to their strict meanings, but rather are to be interpreted to include the range in which similar functions can be expected.

In this specification, the direction in which the central axis A of the writing implement extends (longitudinal direction, up and down direction in a longitudinal cross section) is referred to as the axial direction da, the direction perpendicular to the axial direction da is referred to as the radial direction, and the direction along the circumference around the central axis A is referred to as the circumferential direction. Additionally, along the axial direction da, the side that is close to the surface being written on, such as a piece of paper, when writing is referred to as the front, and the side that is away from the surface being written on is referred to as the rear. In other words, the side facing the pen tip is the front, and the side opposite the pen tip is the rear.

Figure 1 is a vertical cross-sectional view of a pressure-sensitive writing instrument 10 according to one embodiment of the present invention, showing the pressure-sensitive writing instrument 10 in a retracted state, and Figure 2 is a vertical cross-sectional view of the pressure-sensitive writing instrument 10 in a protruding state.

In this embodiment, an example will be described in which the pressure-type writing instrument 10 is a ballpoint pen. The pressure-type writing instrument 10 includes a barrel 20, a refill 30, and a pressure mechanism 50. In the pressure-type writing instrument 10 of this embodiment, the pressure mechanism 50 applies pressure to the rear end surface of the ink 31 contained in the refill 30, thereby increasing the amount of ink 31 ejected from the pen tip of the pressure-type writing instrument 10. This increases the density and width of the handwriting formed using the pressure-type writing instrument 10.

The barrel 20 has a front barrel 21, a grip member 25 arranged around the outer periphery of the front barrel 21, and a rear barrel 26 connected to the rear end of the front barrel 21. The front barrel 21 is a member having a substantially cylindrical shape, and has a front end opening 23 at its front end through which the tip of the ballpoint pen tip 34 described later can be inserted and removed. The grip member 25 is formed of an elastic material such as rubber or elastomer, and is intended to be grasped by the user's fingers when writing with the pressure-type writing instrument 10. The rear barrel 26 is a member having a substantially cylindrical shape arranged behind the front barrel 21. The front end of the rear barrel 26 is attached to the rear end of the front barrel 21, so that the rear barrel 26 is connected to the front barrel 21. As an example, the rear barrel 26 is connected to the front barrel 21 by screwing a female screw portion formed on the inner periphery of the front end of the rear barrel 26 into a male screw portion formed on the outer periphery of the rear end of the front barrel 21. The inner surface of the rear shaft 26 is provided with a protrusion that protrudes inward, and the front-facing surface of this protrusion forms an abutment portion 27 against which a step portion 74 of a cylinder member 70 described below can abut, and the rear-facing surface of this protrusion forms a receiving portion 28 that receives a resilient member 43 described below. The rear shaft 26 has a rear end opening 29 at its rear end into which a knock body 45 described below is inserted so as to be movable back and forth. Such front shaft 21 and rear shaft 26 are formed, for example, from resin.

A clip 12 is attached to the outer surface of the rear shaft 26. The clip 12 is configured so that any material (paper, cloth, etc.) can be sandwiched between the clip 12 and the outer surface of the rear shaft 26. The clip 12 is provided so as to be rotatable around an axis 14 relative to the rear shaft 26. The axis 14 extends so as to be positioned in a twisted position relative to the central axis A. More specifically, the axis 14 extends in a direction perpendicular to a straight line parallel to the central axis A. A resilient member 18 is disposed in a compressed state between a portion of the clip 12 located rearward of the axis 14 and the outer surface of the rear shaft 26. As a result, the front end of the clip 12 is pressed against the outer surface of the rear shaft 26. For example, a coil spring can be used as the resilient member 18. The clip 12 has a locked portion 16 at its front end to which a locking portion 75 of a cylinder member 70 described later is locked. In this embodiment, the engaging portion 75 is engaged with the engaged portion 16, thereby fixing the protruding state of the ballpoint pen tip 34 from the front end opening 23. In addition, the engaging portion 75 is disengaged from the engaged portion 16, thereby releasing the protruding state of the ballpoint pen tip 34 from the front end opening 23. That is, in this embodiment, the clip 12 also functions as a mechanism for fixing the protruding state of the ballpoint pen tip 34 from the front end opening 23 and releasing the protruding state.

The refill 30 is disposed within the barrel 20. In this embodiment, the refill 30 includes an ink storage tube 33 that stores ink 31 and an ink follower 32, and a ballpoint pen tip 34 attached to the front end of the ink storage tube 33.

As the ink 31, any ink that can be used in a writing instrument, such as an oil-based ink, a water-based ink, a gel ink, or a thermochromic ink, can be used without any particular restrictions. Among these inks, low-viscosity inks with an ink viscosity of 5000 (mPa·s) or less at a shear rate of 1.92 (sec ⁻¹ ) in a 20° C. environment are suitable for use in the writing instrument of this embodiment, since the ink discharge amount increases or decreases greatly due to pressure application, and the density, width, etc. of the handwriting change greatly due to pressure application. As an example, a thermochromic ink can be used as the ink 31. The thermochromic ink may be a reversible thermochromic ink. As the reversible thermochromic ink, various reversible thermochromic inks may be used alone or in combination, such as a thermal decolorization type that changes from a colored state to a decolored state by heating and changes from the decolored state to a colored state by cooling, a thermal coloring type that changes from a decolored state to a colored state by heating and changes from the colored state to the decolored state by cooling, or a color memory retention type that exhibits a specific color in a specific temperature range and changes color depending on temperature. For example, an ink containing a reversible thermochromic microencapsulated pigment may be used as the reversible thermochromic ink.

The ink follower 32 is provided to prevent the ink 31 from leaking out of the ink storage tube 33 and to suppress drying of the ink 31. The ink follower 32 is disposed in contact with the rear end of the ink 31. When the ink 31 is consumed and the rear end of the ink 31 moves forward, the ink follower 32 moves forward following the rear end of the ink 31. For example, a grease-like material can be used as such an ink follower 32.

The ink storage cylinder 33 is a member having a cylindrical shape extending in the front-rear direction. The ink storage cylinder 33 stores the ink 31 and the ink follower 32 inside. The ink storage cylinder 33 is formed, for example, from resin.

The ballpoint pen tip 34 includes a tip holder 35, a tip body 36, a ball 37, and a resilient member 38. The tip holder 35 is a member that holds the tip body 36. The rear end of the tip holder 35 is inserted into the front end of the ink storage tube 33, and the tip holder 35 is attached to the ink storage tube 33. Inside the tip holder 35, a through hole is provided that extends in the front-rear direction and guides the ink 31 in the ink storage tube 33 to the tip body 36. The ball 37 is held in a ball holding chamber formed in the front end of the tip body 36. Inside the tip body 36, a through hole is provided that extends in the front-rear direction and guides the ink 31 from the tip holder 35 to the ball 37. The resilient member 38 is arranged in a compressed state inside the through hole of the tip body 36 and urges the ball 37 forward. The force of the resilient member 38 presses the ball 37 against the front end opening of the ball holding chamber of the tip body 36. This makes it possible to prevent the ink 31 from leaking out from the gap between the ball 37 and the front end opening of the ball holding chamber when the ball 37 is not pressed against the writing surface. The resilient member 38 can be, for example, a coil spring.

Next, the pressure mechanism 50 will be described. FIG. 3 is an enlarged view of the pressure mechanism 50 of the pressure-type writing instrument 10 of FIG. 1. In the example shown in FIG. 3, the pressure mechanism 50 includes a piston member 60, a cylinder member 70, a first seal member 81, a second seal member 82, and a third seal member 83.

The piston member 60 is arranged in the barrel 20 behind the refill 30 so as to be movable back and forth. The piston member 60 has a through hole extending in the front-rear direction. The piston member 60 has an inner surface 61 that defines the through hole and an outer surface 63 that defines the outer shape of the piston member 60. The outer surface 63 has a first large diameter portion 63a and a first small diameter portion 63b located behind the first large diameter portion 63a. The first large diameter portion 63a and the first small diameter portion 63b both have a cylindrical shape whose central axis coincides with the central axis A, and the first large diameter portion 63a has a diameter larger than the diameter of the first small diameter portion 63b. An outer step portion 63c is formed between the first large diameter portion 63a and the first small diameter portion 63b. In the illustrated example, the outer step portion 63c is an inclined surface that is inclined in both the axial direction da and the radial direction. In particular, the outer step 63c is an inclined surface that slopes radially inward from the front to the rear. A rear end opening 65 is formed at the rear end of the piston member 60. The rear end opening 65 connects the inside and outside of the piston member 60. A first recess 63d is formed in the first large diameter portion 63a, in which a first seal member 81 is disposed. A second recess 63e is formed in the first small diameter portion 63b, in which a second seal member 82 is disposed. Both the first recess 63d and the second recess 63e extend annularly in the circumferential direction.

The piston member 60 has a through hole 67 between the first recess 63d and the second recess 63e that connects the inner surface 61 and the outer surface 63. The through hole 67 communicates the inside and the outside of the piston member 60. In the illustrated example, the through hole 67 is provided in the first small diameter portion 63b. In detail, the through hole 67 is provided in the first small diameter portion 63b between the outer step portion 63c and the second recess 63e. The through hole 67 extends along the radial direction. However, this is not limited to this, and the through hole 67 may be provided in the first large diameter portion 63a between the first recess 63d and the outer step portion 63c, or may be provided in the outer step portion 63c.

The piston member 60 further has a flange 69 disposed in front of the first large diameter portion 63a. The flange 69 has an outer diameter larger than the diameter (outer diameter) of the first large diameter portion 63a. The flange 69 has a first receiving portion 63f, which is a surface facing rearward. The first receiving portion 63f cooperates with a second receiving portion 71d (described later) of the cylinder member 70 to receive the elastic force of the elastic member 55.

The flange 69 engages with the refill holding member 51. The refill holding member 51 is a member that holds the refill 30. The rear end of the refill holding member 51 is inserted into the flange 69 and fixed to the flange 69. The rear end of the refill 30 is inserted into the front end of the refill holding member 51 and fixed to the refill holding member 51. This allows the refill 30 to move back and forth integrally with the piston member 60.

The tail plug 53 is disposed inside the flange 69 and the refill holding member 51. In the illustrated example, a protrusion provided on the outer periphery of the rear end of the tail plug 53 is located between the protrusion protruding inward from the inner surface of the refill holding member 51 and the flange 69. This fixes the tail plug 53 to the piston member 60 and the refill holding member 51. When the rear end of the refill 30 is inserted into the refill holding member 51, the front end of the tail plug 53 is attached to the rear end of the ink holding tube 33. At least the part of the tail plug 53 that contacts the ink holding tube 33 is formed of an elastic body so as to be in close contact with the ink holding tube 33. In particular, in this embodiment, the front end of the tail plug 53 is inserted into the rear end of the ink holding tube 33. In this case, at least the part of the tail plug 53 that contacts the inner surface of the ink holding tube 33 is formed of an elastic body. The outer diameter of the elastic body at the front end of the tail plug 53 when not inserted into the rear end of the ink reservoir 33 is larger than the inner diameter at the rear end of the ink reservoir 33. Such a tail plug 53 makes it possible to prevent air from leaking between the ink reservoir 33 and the tail plug 53. Preferably, the entire tail plug 53 is made of an elastic body. In this case, it is also possible to prevent air from leaking between the piston member 60 and the refill holding member 51. The tail plug 53 has a through hole that penetrates the tail plug 53 in the front-rear direction.

The cylinder member 70 is arranged in the shaft tube 20 so as to be movable back and forth. The cylinder member 70 is arranged radially outside the piston member 60 so as to surround the piston member 60. The cylinder member 70 has a through hole extending in the front-rear direction. The cylinder member 70 has an inner surface 71 that defines the through hole and an outer surface 73 that defines the outer shape of the cylinder member 70. The inner surface 71 has a second large diameter portion 71a and a second small diameter portion 71b located behind the second large diameter portion 71a. The second large diameter portion 71a and the second small diameter portion 71b both have a cylindrical shape whose central axis coincides with the central axis A, and the second large diameter portion 71a has a diameter larger than the diameter of the second small diameter portion 71b. An inner step portion 71c is formed between the second large diameter portion 71a and the second small diameter portion 71b. In the illustrated example, the inner step 71c is an inclined surface that is inclined in both the axial direction da and the radial direction. In particular, the inner step 71c is an inclined surface that is inclined radially inward from the front to the rear. The inner step 71c faces the outer step 63c of the piston member 60 along the axial direction da. A space S is formed between the outer step 63c and the inner step 71c, surrounded by the outer step 63c, the inner step 71c, the outer surface 63 of the piston member 60, and the inner surface 71 of the cylinder member 70.

The inner surface 71 has a second receiving portion 71d located forward of the second large diameter portion 71a. The second receiving portion 71d is a surface facing forward. A resilient member 55 is disposed between the first receiving portion 63f of the piston member 60 and the second receiving portion 71d of the cylinder member 70. The second receiving portion 71d cooperates with the first receiving portion 63f to receive the resilient force of the resilient member 55. For example, a coil spring can be used as the resilient member 55.

A step 74 is formed on the outer surface 73 of the cylinder member 70. The step 74 is the surface of the outer surface 73 of the cylinder member 70 facing rearward. When the cylinder member 70 moves rearward due to the resilient force of the resilient member 43 described below, the step 74 comes into contact with the abutment portion 27 of the rear axle 26. This restricts further rearward movement of the cylinder member 70.

The outer surface 73 of the front end of the cylinder member 70 is provided with a locking portion 75 that can be locked to the locked portion 16 of the clip 12. The locking portion 75 is formed as a protrusion that protrudes radially outward from the outer surface 73. When the cylinder member 70 moves forward and the locking portion 75 is positioned forward of the locked portion 16, the locking portion 75 is locked to the locked portion 16. This restricts the rearward movement of the cylinder member 70.

The cylinder member 70 has a front end 77 and a rear end 79. The front end 77 can come into contact with the flange portion 69 (first receiving portion 63f) of the piston member 60 when the resilient member 55 is compressed. The middle portion of the piston member 60 is located within the through hole of the cylinder member 70. The flange portion 69 of the piston member 60 is located forward of the front end 77 of the cylinder member 70. The rear end opening 65 of the piston member 60 is located rearward of the rear end 79 of the cylinder member 70. A retaining member 57 is provided at the rear end of the piston member 60. The retaining member 57 is fixed to the rear end of the piston member 60 and has a dimension that does not allow it to enter the inside of the cylinder member 70. As a result, the retaining member 57 functions as a so-called retainer that restricts the forward movement of the piston member 60 relative to the cylinder member 70.

The first seal member 81 and the second seal member 82 are both members that seal between the outer surface 63 of the piston member 60 and the inner surface 71 of the cylinder member 70. In particular, the first seal member 81 seals between the piston member 60 and the cylinder member 70 in front of the outer step portion 63c of the piston member 60. The second seal member 82 seals between the piston member 60 and the cylinder member 70 in rear of the inner step portion 71c of the cylinder member 70. The first seal member 81 is disposed in the first recess 63d of the piston member 60, and the second seal member 82 is disposed in the second recess 63e of the piston member 60. The first seal member 81 and the second seal member 82 are both elastic bodies that extend over the entire circumference. For example, an O-ring is used as the elastic body. The radial diameter of the first seal member 81 is larger than the radial diameter of the second seal member 82.

The third seal member 83 is disposed behind the piston member 60 and configured to be able to seal the rear end opening 65 of the piston member 60. In this embodiment, at least the portion of the third seal member 83 that contacts the rear end opening 65 is formed of an elastic material such as rubber or elastomer. However, this is not limited thereto, and for example, an elastic material may be disposed around the rear end opening 65 of the piston member 60, and the third seal member 83 may be formed of a hard material. In the illustrated example, the third seal member 83 is fixed to the holding member 85.

A locking member 59 is engaged with the rear end of the cylinder member 70. In particular, the locking member 59 is engaged with the outer surface 73 at the rear end of the cylinder member 70, thereby fixing the locking member 59 to the cylinder member 70. The locking member 59 has a first receiving portion 59a and a second receiving portion 59b. The first receiving portion 59a is a surface facing forward at a protruding portion protruding outward from the outer surface of the locking member 59, and the second receiving portion 59b is a surface facing rearward at a step portion provided on the inner surface of the locking member 59. A resilient member 43 is disposed between the receiving portion 28 of the rear axle 26 and the first receiving portion 59a of the locking member 59. The resilient member 43 may be disposed in a compressed state between the receiving portion 28 and the first receiving portion 59a. The first receiving portion 59a cooperates with the receiving portion 28 to receive the resilient force of the resilient member 43. The resilient member 43 can be, for example, a coil spring.

A knock body 45 is fixed to the rear end of the locking member 59. The knock body 45 is a member that the user touches when performing the pen tip extension/retraction operation in the pressure-type writing instrument 10. When the user presses the knock body 45 forward, the pen tip of the pressure-type writing instrument 10 protrudes and retracts from the front end opening 23. A resilient member 87 is disposed between the second receiving portion 59b of the locking member 59 and the inner surface of the knock body 45. The resilient member 87 biases the third seal member 83 forward via the retaining member 85. The resilient member 87 may be disposed in a compressed state between the second receiving portion 59b and the inner surface of the knock body 45. The second receiving portion 59b cooperates with the knock body 45 to receive the resilient force of the resilient member 87. For example, a coil spring can be used as the resilient member 87.

The knocking action of the pressure-type writing instrument 10 will be described with reference to Figures 1 to 4. Figure 1 shows the pressure-type writing instrument 10 with the ballpoint pen tip 34 retracted, and Figure 3 shows an enlarged view of the pressure mechanism 50 of the pressure-type writing instrument 10 of Figure 1. Figure 2 shows the pressure-type writing instrument 10 with the ballpoint pen tip 34 protruding, and Figure 4 shows an enlarged view of the pressure mechanism 50 of the pressure-type writing instrument 10 of Figure 2.

1 and 3, when the user presses the knock body 45 forward, the locking member 59 and the cylinder member 70 fixed to the locking member 59 move forward against the elastic force of the elastic member 43. This causes the piston member 60, the refill holding member 51 fixed to the piston member 60, and the refill 30 held by the refill holding member 51 to move forward via the elastic member 55. This causes the tip of the ballpoint pen tip 34 to protrude forward from the front end opening 23. At this time, when the locking portion 75 of the cylinder member 70 comes into contact with the locked portion 16 of the clip 12, the locking portion 75 moves forward against the elastic force of the elastic member 18 while lifting the locked portion 16. When the locking portion 75 moves forward of the locked portion 16, the elastic force of the elastic member 18 causes the locked portion 16 to contact the outer surface of the barrel 20 (rear barrel 26). When the user releases the forward pressure on the knock body 45 in this state, the elastic force of the elastic member 43 urges the cylinder member 70 rearward. At this time, when the locking portion 75 of the cylinder member 70 contacts the locked portion 16 of the clip 12 from the front, the locking portion 75 is locked to the locked portion 16, restricting the rearward movement of the cylinder member 70. In this way, the pressure-type writing instrument 10 can be brought into a protruding state as shown in Figures 2 and 4.

In the pressurized writing instrument 10 in the protruding state shown in Figures 2 and 4, when the user presses the rear end of the clip 12 toward the barrel 20 (rear barrel 26), the clip 12 rotates around the axis 14 against the resilience of the resilient member 18. As a result, the locked portion 16 of the clip 12 moves in a direction away from the barrel 20. When the distance between the tip of the locked portion 16 on the barrel 20 side and the barrel 20 becomes greater than the protruding height of the locking portion 75 of the cylinder member 70 from the outer surface of the barrel 20, the cylinder member 70 moves backward due to the resilience of the resilient member 43. At this time, the rear end 79 of the cylinder member 70 pushes the retaining member 57 backward, and as a result, the piston member 60 fixed to the retaining member 57, the refill holding member 51 fixed to the piston member 60, and the refill 30 held by the refill holding member 51 move backward. As a result, the tip of the ballpoint pen tip 34 retracts into the barrel 20 from the front end opening 23. When the step 74 of the cylinder member 70 abuts against the abutment portion 27 of the rear barrel 26, further rearward movement of the cylinder member 70 is restricted. In this manner, the pressure-type writing instrument 10 can be brought into a retracted state, as shown in Figures 1 and 3.

Note that the pen tip extension/retraction mechanism is not limited to the mechanism described above with reference to Figures 1 to 4.

Next, the method of applying pressure by the pressure mechanism 50 will be described with reference to FIG. 2 and FIG. 4 to FIG. 6. In the pressurized writing instrument 10 in the protruding state shown in FIG. 2 and FIG. 4, when a user presses the pen tip, more specifically the ball 37 of the refill 30, against a writing surface such as paper for writing, the refill 30 is pushed backward relative to the barrel 20, and the piston member 60 moves backward against the elastic force of the elastic member 55. At this time, the outer step 63c of the piston member 60 also moves backward. That is, the outer step 63c moves toward the inner step 71c of the cylinder member 70. Then, as shown in FIG. 5, the rear end of the piston member 60 comes into contact with the third seal member 83, and the rear end opening 65 of the piston member 60 is sealed by the third seal member 83. At this time, a pressurized chamber C sealed by the first seal member 81, the second seal member 82, and the third seal member 83 is formed. The pressure chamber C includes the space behind the ink follower 32 in the ink containing tube 33, the space inside the through hole of the tail plug 53, the internal space of the piston member 60, the through hole 67 of the piston member 60, and the space S formed between the outer step 63c and the inner step 71c. The space S and the through hole 67 are connected to each other via the gap between the outer surface 63 of the piston member 60 and the inner surface 71 of the cylinder member 70.

When the refill 30 moves further backward, as shown in FIG. 6, the outer step 63c of the piston member 60 moves further toward the inner step 71c of the cylinder member 70. At this time, the third seal member 83 moves backward against the resilience of the resilient member 87. When the outer step 63c approaches the inner step 71c, the volume of the space S decreases. That is, the volume of the pressurized chamber C decreases. During this time, the pressurized chamber C is sealed by the first seal member 81, the second seal member 82, and the third seal member 83, so the air inside the pressurized chamber C is pressurized. In other words, the pressure inside the pressurized chamber C increases. The increased pressure inside the pressurized chamber C pressurizes the rear end of the ink 31 through the ink follower 32. Therefore, the amount of ink 31 discharged from the pen tip of the pressurized writing instrument 10 increases.

When the user releases the pen tip from the writing surface, the piston member 60 moves forward together with the third seal member 83 due to the resilient force of the resilient member 87. The piston member 60 also moves forward relative to the cylinder member 70 due to the resilient force of the resilient member 55. At this time, the rear end of the piston member 60 moves away from the third seal member 83, the rear end opening 65 of the piston member 60 is released from the sealing, and the internal space of the piston member 60 is connected to the atmosphere. Therefore, the pressure on the rear end of the ink 31 is also released. This prevents the ink 31 from flowing out from the pen tip when the ball 37 is not pressed against the writing surface. More specifically, when the ball 37 is not pressed against the writing surface, the ink 31 is prevented from flowing out from the gap between the ball 37 and the front end opening of the ball holding chamber.

The pressurized writing instrument 10 of this embodiment comprises a barrel 20, a refill 30 arranged inside the barrel 20 and having an ink storage tube 33 filled with ink 31, and a pressurizing mechanism 50 that applies pressure to the rear end of the ink 31. The pressurizing mechanism 50 comprises a piston member 60 having an outer step 63c on its outer surface 63, a cylinder member 70 having an inner step 71c on its inner surface 71 that faces the outer step 63c along the axial direction da, a first seal member 81 that seals between the piston member 60 and the cylinder member 70 forward of the outer step 63c, and an inner The piston member 60 has a second seal member 82 that seals the gap between the piston member 60 and the cylinder member 70 behind the step 71c, and a third seal member 83 that can seal the rear end opening 65 of the piston member 60. When the outer step 63c moves toward the inner step 71c, the rear end of the piston member 60 abuts against the third seal member 83, forming a pressurized chamber C sealed by the first seal member 81, the second seal member 82, and the third seal member 83. The outer step 63c approaches the inner step 71c, reducing the volume of the pressurized chamber C.

When the pressurized writing instrument 10 is used, the first seal member 81 and the second seal member 82 slide on the inner surface 71 of the cylinder member 70 when the pressurized chamber C is pressurized, but do not overcome any steps. Therefore, damage to the seal members 81 and 82 can be effectively prevented when the pressurized writing instrument 10 is used for repeated writing.

In addition, when the pressurized writing instrument 10 is carried or stored, i.e., even when the pen tip is not pressed against the writing surface, the first seal member 81 and the second seal member 82 are in contact with the piston member 60 and the cylinder member 70, so that foreign matter such as dust can be prevented from being caught between the seal members 81, 82 and the piston member 60 and the cylinder member 70.

In the pressurized writing instrument 10 of this embodiment, the outer surface 63 of the piston member 60 has a first large diameter portion 63a and a first small diameter portion 63b located behind the first large diameter portion 63a, the inner surface 71 of the cylinder member 70 has a second large diameter portion 71a and a second small diameter portion 71b located behind the second large diameter portion 71a, the outer step portion 63c is located between the first large diameter portion 63a and the first small diameter portion 63b, and the inner step portion 71c is located between the second large diameter portion 71a and the second small diameter portion 71b.

With this type of pressure-type writing instrument 10, a space S is formed between the outer step 63c and the inner step 71c, surrounded by the outer step 63c, the inner step 71c, the outer surface 63 of the piston member 60, and the inner surface 71 of the cylinder member 70. By changing the volume of this space S, the volume of the pressure chamber C can be changed. Therefore, a mechanism for changing the volume of the pressure chamber C can be realized with a simple configuration.

In the pressurized writing instrument 10 of this embodiment, the piston member 60 has a through hole 67 between the first seal member 81 and the second seal member 82, which connects the inner surface 61 and the outer surface 63.

This type of pressure-type writing instrument 10 ensures that the space S and the internal space of the piston member 60 are in communication with each other. Therefore, by changing the volume of the space S, the pressure chamber C can be appropriately pressurized.

In the pressurized writing instrument 10 of this embodiment, at least the portion of the third seal member 83 that comes into contact with the rear end opening 65 is made of an elastic material.

With this type of pressurized writing instrument 10, the rear end opening 65 of the piston member 60 can be properly sealed by the third seal member 83.

The pressurized writing instrument 10 of this embodiment further includes a resilient member 87 that biases the third seal member 83 forward.

With this type of pressurized writing instrument 10, the third seal member 83 can keep the rear end opening 65 sealed in accordance with the rearward movement of the piston member 60.

The pressure-type writing instrument 10 of this embodiment further includes a tail plug 53 attached to the rear end of the ink reservoir 33,
At least the portion of the tail plug 53 which comes into contact with the ink containing tube 33 is made of an elastic material.

This type of pressurized writing instrument 10 can prevent air from leaking between the ink reservoir 33 and the tail plug 53.

10 Pressurized writing implement 12 Clip 14 Axis 16 Locked portion 18 Elastic member 20 Barrel 21 Front barrel 23 Front end opening 25 Grip member 26 Rear barrel 27 Contact portion 28 Receiving portion 29 Rear end opening 30 Refill 31 Ink 32 Ink follower 33 Ink storage barrel 34 Ballpoint pen tip 35 Tip holder 36 Tip body 37 Ball 38 Elastic member 43 Elastic member 45 Knocking body 50 Pressurizing mechanism 51 Refill holding member 53 Tail plug 55 Elastic member 57 Stopper member 59 Locking member 59a First receiving portion 59b Second receiving portion 60 Piston member 61 Inner surface 63 Outer surface 63a First large diameter portion 63b First small diameter portion 63c Outer step portion 63d First recess 63e Second recess 63f First receiving portion 65 Rear end opening 67 Through hole 69 Flange portion 70 Cylinder member 71 Inner surface 71a Second large diameter portion 71b Second small diameter portion 71c Inner step portion 71d Second receiving portion 73 Outer surface 74 Step portion 75 Locking portion 77 Front end 79 Rear end 81 First seal member 82 Second seal member 83 Third seal member 85 Holding member 87 Resilient member A Central axis C Pressurizing chamber S Space portion da Axial direction

Claims (6)

A shaft cylinder,
a refill disposed within the barrel and having an ink reservoir filled with ink;
A pressure mechanism that applies pressure to the rear end of the ink,
The pressure mechanism includes:
a piston member having an outer step on an outer surface thereof;
a cylinder member having an inner step on an inner surface thereof, the inner step facing the outer step along an axial direction;
a first seal member that seals a gap between the piston member and the cylinder member forward of the outer step portion;
a second seal member that seals a gap between the piston member and the cylinder member rearward of the inner step portion;
a third seal member capable of sealingly sealing a rear end opening of the piston member,
When the outer step moves toward the inner step, the rear end of the piston member abuts against the third seal member to form a pressurized chamber sealed by the first seal member, the second seal member and the third seal member, and the volume of the pressurized chamber decreases as the outer step approaches the inner step. The outer surface of the piston member has a first large diameter portion and a first small diameter portion located rearward of the first large diameter portion,
The inner surface of the cylinder member has a second large diameter portion and a second small diameter portion located rearward of the second large diameter portion,
the outer step portion is located between the first large diameter portion and the first small diameter portion,
The pressure-type writing instrument according to claim 1 , wherein the inner step is located between the second large diameter portion and the second small diameter portion. The pressurized writing instrument according to claim 1 or 2, wherein the piston member has a through hole between the first seal member and the second seal member that connects the inner surface and the outer surface. The pressure-type writing instrument according to any one of claims 1 to 3, wherein at least the portion of the third seal member that contacts the rear end opening is made of an elastic material. The pressure-type writing instrument according to any one of claims 1 to 4, further comprising a resilient member that biases the third seal member forward. The ink container further includes a tail plug attached to a rear end of the ink container.
6. The pressure type writing implement according to claim 1, wherein at least a portion of said tail plug which contacts said ink reservoir is made of an elastic material.