The present invention relates to a side knock (click) type writing instrument.

A knock type writing instrument has a shaft barrel, a writing member arranged inside the shaft barrel and provided with a pen tip as a writing part, a knock member provided with an operating part and arranged at a rear of the writing member, and a spring biasing the knock member to the rear through the writing member. In a knock type writing instrument, by knocking the operating part against the biasing force of the spring arranged inside the shaft barrel, the knock type writing instrument enters a writing state where it projects out from the front end of the shaft barrel while by performing a release operation, the knock type writing instrument enters a nonwriting state where it retracts inside the shaft barrel. As a knock type writing instrument, in addition to a knock type writing instrument with an operating part arranged at the rear end part of the shaft barrel (below, referred to as a "rear end knock type writing instrument"), a knock type writing instrument with an operating part arranged at a side surface of the shaft barrel (below, referred to as a "side knock type writing instrument") is known (PTL 1 and PTL 2).

• [PTL 1] Japanese Unexamined Patent Publication 2017-41220
• [PTL 2] Japanese Unexamined Patent Publication 2011-56677

In a rear end knock type writing instrument, the knock operation (click operation) is performed by pressing the operating part arranged at the rear end of the shaft barrel toward the front. For this reason, at the rear end part of the shaft barrel, a rear end aperture is provided for allowing the operating part to project out. The rear end aperture of the shaft barrel is substantially equal in horizontal cross-sectional shape to the operating part. The size of the clearance around the operating part at the rear end aperture is substantially constant, regardless of the writing state and the non-writing state of the rear end knock type writing instrument.

On the other hand, in the side knock type writing instrument such as described in PTL 1 and PTL 2, the knock operation is performed by making the operating part arranged at the side surface of the shaft barrel slide to the front. For this reason, at the side surface of the shaft barrel, a window opening extending in the front-rear direction is provided corresponding to the movable range of the operating part. When the side knock type writing instrument is in the writing state, i.e., when the knock member is positioned more to the front in the window opening, the rear end part of the operating part or the rear end part of the knock member defines the clearance space communicating with the inside of the shaft barrel through the window opening. Therefore, along with long term use of the side knock type writing instrument, dust or other dirt gradually builds up at the rear end part of the knock member or inside the clearance space through the window opening and is liable to harm the appearance and harm the knock function.

The present invention has as its object the provision of a side knock type writing instrument free from harm to the appearance and knock function.

According to one aspect of the present invention, there is provided a side knock type writing instrument comprising a shaft barrel with a first window opening provided at a side surface, a writing member arranged inside of the shaft barrel, a knock member provided with a knock operating part exposed through the first window opening and arranged at the rear of the writing member, and a spring biasing the knock member to the rear through the writing member and configured so that the writing instrument enters a writing state by a knock operation making the knock operating part slide to the front and enters a non-writing state by a release operation, in which side knock type writing instrument, the knock member configured so that the first window opening is covered from the inside when the first window opening is viewed from the front in the writing state.

The knock member may have a cover part extending to the rear from the knock operating part. A second window opening may be provided at a side surface of the shaft barrel so as to face the first window opening, the knock member may be further provided with a release operating part with a second window provided at a side surface of the shaft barrel so as to face the first window opening, the knock member exposed through the second window opening and operated to be released, and the knock member may be configured so that the second window opening is covered from the inside when viewing the second window opening is viewed from the front surface in the writing state. The side knock type writing instrument may have a sliding part at which an outside surface of the knock member and an inside surface of the shaft barrel slide along with retraction of the knock member when switching from the writing state to the non-writing state, and the sliding part may be a slanted surface provided at the outside surface of the knock member or the inside surface of the shaft barrel.

According to the different aspects of the present invention, a common effect is exhibited of provision of a side clink writing instrument free from harm to the appearance and knock function.

• FIG. 1 is a perspective view of a non-writing state of a side knock type writing instrument according to a first embodiment of the present invention.
• FIG. 2 is a perspective view of a writing state of the side knock type writing instrument of FIG. 1.
• FIG. 3 is another perspective view of a non-writing state of the side knock type writing instrument of FIG. 1.
• FIG. 4 is another perspective view of a writing state of the side knock type writing instrument of FIG. 1.
• FIG. 5 is a vertical cross-sectional view of a writing state of the side knock type writing instrument of FIG. 1.
• FIG. 6 is a perspective view of a rear shaft of the side knock type writing instrument of FIG. 1.
• FIG. 7 is a side view of the rear shaft of FIG. 6.
• FIG. 8 is a vertical cross-sectional view of the rear shaft of FIG. 6.
• FIG. 9 is a cross-sectional view of the rear shaft along a line A-A of FIG. 7.
• FIG. 10 is a cross-sectional view of the rear shaft corresponding to a line B-B of FIG. 8.
• FIG. 11 is a perspective view of a knock member of the side knock type writing instrument of FIG. 1.
• FIG. 12 is a side view of the knock member of FIG. 11.
• FIG. 13 is another side view of the knock member of FIG. 11.
• FIG. 14 is a front view of the knock member of FIG. 11.
• FIG. 15 is a bottom view of the knock member of FIG. 11.
• FIG. 16 is a vertical cross-sectional view of a rear end part of the side knock type writing instrument of FIG. 1.
• FIG. 17 is another vertical cross-sectional view of a rear end part of the side knock type writing instrument of FIG. 1.
• FIG. 18 is a partial cross-sectional perspective view of the rear end part showing a non-writing state of the side knock type writing instrument of FIG. 1.
• FIG. 19 is a partial cross-sectional perspective view of the rear end part showing a writing state of the side knock type writing instrument of FIG. 1.
• FIG. 20 is a perspective view of a rear shaft of the side knock type writing instrument of a second embodiment of the present invention.
• FIG. 21 is a vertical cross-sectional view of the rear shaft of FIG. 20.
• FIG. 22 is a horizontal cross-sectional view of the rear shaft of FIG. 20.
• FIG. 23 is a perspective view of a knock member of the side knock type writing instrument of the second embodiment.
• FIG. 24 is a partial cross-sectional perspective view of the rear end part showing a non-writing state of the side knock type writing instrument according to the second embodiment.
• FIG. 25 is a partial cross-sectional perspective view of the rear end part showing a writing state of the side knock type writing instrument according to the second embodiment.

Below, while referring to the drawings, embodiments of the present invention will be explained in detail. Throughout the figures, corresponding component elements will be assigned common reference notations.

FIG. 1 is a perspective view of a non-writing state of a side knock type writing instrument 1 according to a first embodiment of the present invention, FIG. 2 is a perspective view of a writing state of the side knock type writing instrument 1 of FIG. 1, FIG. 3 is another perspective view of a non-writing state of the side knock type writing instrument 1 of FIG. 1, and FIG. 4 is another perspective view of a writing state of the side knock type writing instrument 1 of FIG. 1. Further, FIG. 5 is a vertical cross-sectional view of a writing state of the side knock type writing instrument 1 of FIG. 1.

The side knock type writing instrument 1 has a shaft barrel 2 provided with a front shaft 3 and a rear shaft 10 screwed with the outside surface of the rear end part of the front shaft 3, a writing member of a refill 4 arranged inside the shaft barrel 2 and provided with a writing part 4a at one end, a spring 5 biasing the refill 4 to the rear, a knock member 20 arranged at the rear of the refill 4, and a clip member 6 attached to a rear end part of the rear shaft 10.

In this Description, in the axial direction of the side knock type writing instrument 1, the writing part 4a side is defined as the "front" side while the opposite side to the writing part 4a is defined as the "rear" side. In the explanation of each member, the "front" side and the "rear" side are defined based on the state assembled with the side knock type writing instrument 1. In the side knock type writing instrument 1, the state where the writing part 4a sticks out from the shaft barrel 2 due to a knock operation is called the "writing state" (FIG. 2 and FIG. 4) and the state where the writing part 4a is retracted inside the shaft barrel 2 is referred to as the "non-writing state" (FIG. 1 and FIG. 3).

At the rear part of the shaft barrel 2, i.e., the side surface of the rear part of the rear shaft 10, a first window opening 11 and a second window opening 12 arranged so as to face the first window opening 11 are provided. The first window opening 11 and the second window opening 12 are arranged at positions exactly 90 degrees away from the clip member 6 in the rotational direction about the center axis. The knock member 20 has a knock operating part 21 and a release operating part 22 as operating parts. The knock operating part 21 is exposed to the outside through the first window opening 11 of the rear shaft 10. The release operating part 22 is exposed to the outside through the second window opening 12 of the rear shaft 10. As explained later, the side knock type writing instrument 1 is configured to be rendered a writing state by a knock operation making the knock operating part 21 slide to the front against the biasing force of the spring 5 and rendered a non-writing state by a release operation pressing the release operating part 22 inward in the radial direction.

FIG. 6 is a perspective view of the rear shaft 10 of the side knock type writing instrument 1 of FIG. 1, FIG. 7 is a side view of the rear shaft 10 of FIG. 6, FIG. 8 is a vertical cross-sectional view of the rear shaft 10 of FIG. 6, FIG. 9 is a cross-sectional view of the rear shaft 10 along a line A-A of FIG. 7, and FIG. 10 is a cross-sectional view of the rear shaft 10 corresponding to a line B-B of FIG. 8.

The rear shaft 10 is provided with a first flat surface 10a and a second flat surface 10b seemingly cut across the cylindrically shaped side surface along the axial direction. The first flat surface 10a and the second flat surface 10b are parallel with each other. The first flat surface 10a is provided with the above-mentioned first window opening 11, while the second flat surface 10b is provided with the above-mentioned second window opening 12. The first window opening 11 and the second window opening 12 are rounded corner rectangular shapes. The parts corresponding to the short sides are respectively formed into semicircular shapes. The rear end part of the rear shaft 10 is formed in a substantially semispherical shape. Part thereof is provided with a mounting part 10c including a hole for attaching a clip member 6.

At the inside surface of the rear shaft 10, a pair of rail projections 13 of projections extending from the rear end part to the front along the axial direction and sticking out inward in the radial direction are provided. The pair of rail projections 13 are respectively arranged so as to face each other. Further, the pair of rail projection 13 are respectively arranged at positions approximately 90 degrees away from the first window opening 11 and the second window opening 12 in the rotational direction about the center axis. In more detail, the pair of rail projections 13 are respectively arranged shifted just slightly closer to the first window opening 11 from positions exactly 90 degrees away from the first window opening 11 and the second window opening 12 in the rotational direction about the center axis. Therefore, strictly speaking, one rail projection 13 does not stick out inward in the radial direction, i.e., toward the center axis, but sticks out toward the other rail projection 13 arranged offset from it.

Each of the pair of rail projections 13 has an inside rail 14 extending to the front from the rear end part of the rear shaft 10 and an outside rail 15 extending to the front from the front end part of the inside rail 14. The inside rail 14 sticks out further from the inside surface of the rear shaft 10 than the outside rail 15. The horizontal cross-sectional shapes of the respective inside rail 14 and outside rail 15, i.e., the cross-sectional shapes perpendicular to the center axis of the rear shaft 10, are rectangular. The inside rail 14 and outside rail 15 are formed into step shapes along the axial direction. The pair of inside rails 14 have flat first top surfaces 14a facing each other and extending in the axial direction. Near the front end parts of the first top surfaces 14a, first stopping projections 14b are provided. At the rear of the facing first top surfaces 14a, limit slanted surfaces 14c slanted in directions approaching each other toward the rear are provided.

At the front end part of each inside rail 14, a first engaging part 16 is provided. The first engaging part 16 is formed in an acute angle shape comprised of a side surface of the inside rail 14 at the first window opening 11 side and a front end face slanted to the rear from the first window opening 11 toward the second window opening 12. At the front end part of each outside rail 15, a support part 17 is provided. The support part 17 is formed in an obtuse angle shape comprised of a side surface of the outside rail 15 at the first window opening 11 side and a front end face slanted to the front from the first window opening 11 toward the second window opening 12.

As shown in FIG. 10, the rear end part of the rear shaft 10 is formed partially thicker. Due to the resultant inside surface of the rear shaft 10 and the pair of rail projections 13, a rectangular first guide rail 18 and second guide rail 19 extending in the axial direction are defined. The first guide rail 18 is provided at the first window opening 11 side from the pair of rail projections 13, while the second guide rail 19 is provided at the second window opening 12 side from the pair of rail projections 13. As explained above, the pair of rail projection 13 are arranged just slightly at the first window opening 11, therefore the first guide rail 18 defines a narrower space than the second guide rail 19.

FIG. 11 is a perspective view of the knock member 20 of the side knock type writing instrument 1 of FIG. 1, FIG. 12 is a side view of the knock member 20 of FIG. 11, FIG. 13 is another side view of the knock member 20 of FIG. 11, FIG. 14 is a front view of the knock member 20 of FIG. 11, and FIG. 15 is a bottom view of the knock member 20 of FIG. 11. The knock member 20, in FIG. 11 to FIG. 13, is arranged inside the shaft barrel 2 so that the bottom becomes the front side of the side knock type writing instrument 1 and the top becomes the rear side of the side knock type writing instrument 1. FIG. 14 is a view of the knock member 20 seen from the front, while FIG. 15 is a view of the knock member 20 seen from the rear.

The knock member 20 has a first sliding member 23 and a second sliding member 24b of substantially rectangular plate shapes arranged substantially in parallel and a substantially plate shaped connecting member 25 connecting the first sliding member 23 and the second sliding member 24. The first sliding member 23 and the second sliding member 24 are arranged so as to face each other and have substantially the same lengths. The connecting member 25 has a length of substantially half of the first sliding member 23 and the second sliding member 24. The connecting member 25 is formed integrally so as to connect the rear halves of the first sliding member 23 and the second sliding member 24 perpendicularly to the first sliding member 23 and the second sliding member 24. Therefore, the rear half of the knock member 20 has a substantially H-shaped horizontal cross-sectional shape.

The above-mentioned knock operating part 21 is provided at the surface of the first sliding member 23. The above-mentioned release operating part 22 is provided at the surface of the second sliding member 24. The knock operating part 21 and the release operating part 22, like the corresponding first window opening 11 and second window opening 12, have rounded corner rectangular shapes. As shown in the later explained FIG. 16, the knock operating part 21 has a length in the longitudinal direction of about two-thirds of the first window opening 11. The release operating part 22 has a length in the longitudinal direction substantially the same as the second window opening 12. As particularly shown in the later explained FIG. 16(b), in the writing state of the side knock type writing instrument 1, it is possible to cover the entire second window opening 12. The knock operating part 21 has a length of about one-third of the length of the first sliding member 23, i.e., the length of the knock member 20. The knock operating part 21 is arranged at the surface of the first sliding member 23 at the center in the longitudinal direction. The release operating part 22 has a length of about two-thirds of the length of the second sliding member 24, i.e., the length of the knock member 20. The release operating part 22 is arranged at the surface of the second sliding member 24 closer to the rear.

The outside surface of the first sliding member 23 at the front from the knock operating part 21 and the outside surface of the second sliding member 24 are formed into cylindrical surface shapes. The outside surface of the first sliding member 23 at the rear from the knock operating part 21 is formed flat. In the first sliding member 23 and the second sliding member 24, the surfaces facing each other at the front halves of the parts in front of the connecting member 25, i.e., the inside surfaces, are formed in cylindrical surface shapes. Therefore, the front halves of the first sliding member 23 and the second sliding member 24 are formed to configure parts of a cylinder. The front halves of the first sliding member 23 and the second sliding member 24 and the front end face of the connecting member 25 configure a receiving part 26 open to the front. At the surfaces of the insides of the front end parts of the first sliding member 23 and the second sliding member 24 corresponding to the entrance of the receiving part 26, thin parts 26a becoming gradually thinner toward the front end parts are formed.

At the surface facing the second sliding member 24 at the center part of the first sliding member 23 in the longitudinal direction, a first guide projection 23a sticking out toward the second sliding member 24 is provided. The first guide projection 23a is provided across the width direction of the first sliding member 23 straddling the connecting member 25. At the surface of the first guide projection 23a facing the second sliding member 24, a flat first guide surface 23b is provided. At the rear end part of the first guide projection 23a, a second engaging part 27 is provided. The second engaging part 27 is formed into an acute angle shape comprised of the first guide surface 23b and a rear end face of the first guide surface 23b slanted from the rear end part toward the front. The second engaging part 27 has a horizontal cross-sectional shape of an acute angle shape substantially complementary with the first engaging part 16 of the rear shaft 10.

The first sliding member 23 has a pair of second guide projections 23c extending from the center part in the longitudinal direction toward the front and sticking out outward in the width direction. The surfaces of the second guide projections 23c facing the second sliding member 24 configure parts of the above-mentioned first guide surface 23b. At the front end part of each of the pair of the second guide projections 23c, a support projection 23d sticking out in the width direction of the first sliding member 23 is provided. The surface of the support projection 23d facing the second sliding member 24 configures part of above-mentioned first guide surface 23b. At the side surface at the rear side of the support projection 23d, a convex curved shape support surface 23e is provided. The surfaces near the rear end part of the first sliding member 23 are slanted by substantially the same angle and provided with narrow first taper parts 23f as a whole.

The second sliding member 24 has a pair of third guide projections 24a extending from the center part in the longitudinal direction to the rear end part and sticking out outward in the width direction. At the surfaces of the third guide projections 24a facing the first sliding member 23, flat second guide surfaces 24b are provided. The surfaces near the rear end part of the second sliding member 24 are slanted by substantially the same angle and provided with narrow second taper parts 24c as a whole.

At the surfaces near the rear end part of the connecting member 25, pairs of the second stopping projections 25a are provided in line shapes over the width direction. The surfaces of the connecting member 25 at the rear from the second stopping projections 25a are slanted by substantially the same angle and provided with narrow third taper parts 25b as a whole.

FIG. 16 is a vertical cross-sectional view of the rear end part of the side knock type writing instrument 1 of FIG. 1, while FIG. 17 is another vertical cross-sectional view of the rear end part of the side knock type writing instrument 1 of FIG. 1, Specifically, FIG. 16 is a cross-sectional view including the center axis of the side knock type writing instrument 1 and parallel to the flat surface of the connecting member 25, while FIG. 17 is a cross-sectional view corresponding to a cross-section rotated by exactly 90 degrees about the center axis from the cross-section in FIG. 16. FIG. 16(a) and FIG. 17(a) are cross-sectional views of the non-writing state of the side knock type writing instrument 1, while FIG. 16(b) and FIG. 17(b) are cross-sectional views of the writing state of the side knock type writing instrument 1. Further, FIG. 18 is a partial cross-sectional perspective view of the rear end part showing a non-writing state of the side knock type writing instrument 1 of FIG. 1, while FIG. 19 is a partial cross-sectional perspective view of the rear end part showing a writing state of the side knock type writing instrument 1 of FIG. 1. In FIG. 18 and FIG. 19, the rear end part of the rear shaft 10 is shown cutting open the part rotated to the first window opening 11 side by exactly 90 degrees about the center axis starting from the clip member 6 side including also part of a rail projection 13 from the cross-section corresponding to the line A-A of FIG. 7.

As shown in FIG. 18 and FIG. 19, in the side knock type writing instrument 1 in the assembled state, the knock member 20 is arranged inside the rear shaft 10 so that the first sliding member 23 is arranged inside the first guide rail 18 of the rear shaft 10 and the second sliding member 24 is arranged inside the second guide rail 19 of the rear shaft 10. At this time, as shown in FIG. 17, the connecting member 25 is arranged so as to be inserted between the pair of rail projections 13. The thickness of the connecting member 25 is set just slightly smaller than the distance between the inside rails 14. When inserting the knock member 20 inside the rear shaft 10, the second stopping projections 25a of the knock member 20 ride over the facing first stopping projections 14b of the pair of rail projections 13 while accompanied with elastic deformation. For this reason, for example, even in a state with no refill 4 such as at the time of replacement of the refill 4 etc., the second stopping projections 25a of the knock member 20 are stopped by the first stopping projections 14b of the rear shaft 10 whereby the knock member 20 is prevented from detaching from the rear shaft 10.

The refill 4 inserted from the front end aperture of the rear shaft 10 is inserted inside the receiving part 26 of the knock member 20. At this time, even if the refill 4 and knock member 20 are offset from each other in the radial direction, the rear end edge of the refill 4 abuts against the thin parts 26a of the receiving part 26 whereby the refill 4 is reliably guided to the inside of the receiving part 26. The rear end face of the refill 4 biased by the spring 5 abuts against the front end face of the connecting member 25 of the knock member 20 whereupon the knock member 20 is also biased to the rear. The knock member 20, as explained later, as shown in FIG. 16, moves relatively to the first window opening 11 side or the second window opening 12 side from the refill 4 by being switched between the writing state and the non-writing state. Therefore, the size of the receiving part 26, i.e., the distance between the first sliding member 23 and the second sliding member 24, is set so that the refill 4 is not interfered with by that movement of the knock member 20 with respect to the refill 4.

Here, the distance between the facing pair of inside rails 14 is set smaller than the width of the part of the first guide projection 23a of the knock member 20, i.e., the width of the first sliding member 23. The distance of the facing pair of outside rails 15 is set larger than the width of the part of the pair of the second guide projections 23c of the knock member 20 and is set smaller than the width of the part of the pair of the support projections 23d of the knock member 20. The width of the part of the pair of support projections 23d of the knock member 20, i.e., the maximum width of the first sliding member 23, and the width of the part of the pair of the third guide projections 24a, i.e., the maximum width of the second sliding member 24, are set to become equal. Furthermore, they are set to be just slightly smaller than the width of the first guide rail 18 and the width of the second guide rail 19. As a result, movement in the horizontal direction or rotational direction of the knock member 20 at the time of movement in the front-rear direction of the knock member 20 is limited by the support projections 23d abutting against the inside surface of the first guide rail 18 and by the third guide projections 24a abutting against the inside surface of the second guide rail 19. Therefore, at the time of a knock operation, the knock member 20 can be made to stably move in the front-rear direction. It should be noted that, the lengths of the outside rails 15 are set to be substantially equal to the lengths of the second guide projections 23c.

As shown in FIG. 16(a), the width of the rear end part of the knock member 20 including the connecting member 25 is just slightly smaller than the distance between the first window opening 11 and the second window opening 12 of the rear shaft 10. In this state, the knock operating part 21 of the knock member 20 sticks out just slightly from the first window opening 11 and is exposed through the first window opening 11. For this reason, the user becomes able to operate the knock operating part 21. As shown in FIG. 17(a), in the side knock type writing instrument 1 in the non-writing state, the biasing force of the spring 5 through the refill 4 causes the knock member 20 to retract together with the refill 4. At this time, the rear end face of the connecting member 25 of the knock member 20 abuts against the inside surface of the rear shaft 10 or the third taper parts 25b of the connecting member 25 of the knock member 20 are stopped by the limit slanted surfaces 14c of the rear shaft 10 whereby retraction of the knock member 20 is limited.

Referring to FIG. 16(a), FIG. 17(a), and FIG. 18 together with FIG. 1 and FIG. 3, a knock operation for switching from the non-writing state to the writing state will be explained. A knock operation is performed for making the knock operating part 21 slide to the front against the biasing force of the spring 5 from the non-writing state. When making the knock operating part 21 slide to the front, an inward force in the radial direction also acts on the knock member 20 pressed by a finger of the user. Due to the knock operation, the first sliding member 23 and the second sliding member 24 of the knock member 20 respectively slide along the first guide rail 18 and the second guide rail 19 of the rear shaft 10.

Specifically, the first guide projection 23a, the second guide projections 23c, and the first guide surface 23b of the support projection 23d of the first sliding member 23 slide along the side surface at the first window opening 11 side of the pair of rail projections 13. In other words, the first guide projection 23a and the second guide projections 23c of the first sliding member 23 slide with respect to the inside rail 14 while the support projection 23d slides with respect to the outside rail 15. It should be noted that, the partial cross-sectional perspective view of FIG. 18, as explained above, is shown with the rear shaft 10 and the rail projection 13 partially cut open. For this reason, in actuality, the first guide surface 23b of the knock member 20 abuts against the side surface of the rail projection 13.

If making the knock member 20 move by exactly a predetermined distance, at the first sliding member 23, the first guide projection 23a and the second guide projections 23c detach from the inside rail 14 and the support projection 23d detaches from the outside rail 15. Due to this, as shown in FIG. 16(b), FIG. 17(b), and FIG. 19, the knock member 20 moves to the second window opening 12 side, the knock operating part 21 retracts just slightly inside of the first window opening 11, and the release operating part 22 sticks out just slightly from the second window opening 12. Advance of the knock member 20 is limited by the front end of the release operating part 22 being stopped by the front end edge of the second window opening 12. At this time, the writing part 4a of the refill 4 sticks out from the front end aperture of the shaft barrel 2.

If the user releases the force which had been applied to the knock member 20 for the knock operation, the knock member 20 engages with the rear shaft 10 while retracting just slightly due to the biasing force of the spring 5 through the refill 4. In other words, due to the retraction of the knock member 20, as shown in FIG. 19, the acute angle shaped second engaging part 27 of the first sliding member 23 engages with the acute angle shaped first engaging part 16 of the rear shaft 10 and the support surface 23e of the support projection 23d of the first sliding member 23 is supported by the support part 17 of the rear shaft 10 in the radial direction. As a result, the side knock type writing instrument 1 enters the writing state (FIG. 2 and FIG. 4).

The writing state is switched to the non-writing state by pressing the release operating part 22 inward in the radial direction. According, when pressing the release operating part 22 inward in the radial direction, a force component in the axial direction is generated by the mutually abutting slanted surfaces of the first engaging part 16 and the second engaging part 27, which are acute angle shaped. The axial direction force component causes the knock member 20 to advance just slightly and the knock member 20 to move to the first window opening 11 side whereby the first engaging part 16 and the second engaging part 27 disengage. If the first engaging part 16 and the second engaging part 27 disengage, the biasing force of the spring 5 causes the knock member 20 to retract and the writing part 4a of the refill 4 to retract into the front end aperture of the shaft barrel 2. Further, at the time of retraction of the knock member 20, the second guide surface 24b of the second sliding member 24 slides along the side surface of the pair of rail projections 13 at the second window opening 12 side. As a result, the release operating part 22 retracts just slightly inside the second window opening 12 and the knock operating part 21 sticks out just slightly from the first window opening 11 whereby the side knock type writing instrument 1 enters the non-writing state (FIG. 1 to FIG. 3).

If the side knock type writing instrument 1 is in the non-writing state, when the first window opening 11 and the second window opening 12 are viewed from the front such as with the line of sight V1 shown in FIG. 16(a), as shown also in FIG. 1 and FIG. 3, the first window opening 11 and the second window opening 12 are substantially covered by the knock member 20 from the inside. Specifically, at the first window opening 11, the knock operating part 21 and the part of the first sliding member 23 at the front of the knock operating part 21 function as cover parts and cover the first window opening 11. At the second window opening 12, the release operating part 22 and the part of the second sliding member 24 at the front of the release operating part 22 function as cover parts and cover the second window opening 12.

On the other hand, if the side knock type writing instrument 1 is in the writing state, when the first window opening 11 and the second window opening 12 are viewed from the front such as with the line of sight V2 shown in FIG. 16(b), as shown also in FIG. 2 and FIG. 4, the first window opening 11 and the second window opening 12 are substantially covered by the knock member 20 from the inside. Specifically, at the first window opening 11, the knock operating part 21 and the part of the first sliding member 23 at the rear of the knock operating part 21 function as cover parts and cover the first window opening 11. At the second window opening 12, the release operating part 22 itself functions as a cover part and covers the second window opening 12.

Due to the above, in the side knock type writing instrument 1, the knock member 20 has cover parts extending further to the rear than the knock operating part 21 or the release operating part 22. For this reason, the first window opening 11 and the second window opening 12 are covered from the inside not only at the time of the non-writing state, but also at the time of the writing state, therefore dust etc. are prevented from entering inside of the shaft barrel 2. As a result, the knock function parts arranged inside of the shaft barrel 2 will not be harmed due to dust etc. along with time. Further, the appearance will not be harmed due to dust and other dirt.

In this regard, in general, not limited to a rear end knock type writing instrument, but in a side knock type writing instrument as well, when switching from the writing state to the non-writing state, the knock member moves with great force to the rear due to the biasing force of the spring then stops by striking the inside surface etc. of the rear shaft facing the rear. At this time, usually, the inside surface etc. of the rear shaft is formed as a surface perpendicular to the center axis, i.e., a perpendicular surface. Therefore, the knock member directly receives an impact in the axial direction, when striking it. The impact due to the knock member striking it is transmitted to the refill as well. If impact is applied to the refill, in particular if low viscosity ink or shear thinning ink is contained, the impact causes the ink to retract leading to the possibility of air entering the refill through the writing part. In this case, bubbles may form in the ink and poor writing performance is liable to be caused. Therefore, when switching from the writing state to the non-writing state, the smaller the impact applied to the knock member and in turn the refill, the more preferable.

In the side knock type writing instrument 1, the knock member 20 moved to the rear stops by sliding contact with the third taper parts 25b provided at the rear end part of the connecting member 25 and with the rear end part of the rear shaft 10, specifically the limit slanted surfaces 14c provided at the rear end parts of the rail projections 13. In other words, movement of the knock member 20 to the rear is gradually reduced by frictional resistance due to the sliding contact with the slanted surfaces of the third taper parts 25b and the slanted surfaces of the limit slanted surfaces 14c and the wedging grip between the facing slanted surfaces. Therefore, it is possible to ease the impact applied to the knock member 20 and in turn the refill 4 down to its minimum extent. In particular, the areas of the slanted surfaces of the third taper parts 25b and the slanted surfaces of the limit slanted surfaces 14c can be made larger by adjusting the slant angles and thereby the impact can be eased. By the impact being eased, it is also possible to reduce the impact noise when the knock member 20 stops and thereby also obtain a silencing effect.

In short, like the slanted surfaces of the third taper parts 25b and the slanted surfaces of the limit slanted surfaces 14c, slanted surfaces are provided at least at one of the outside surface of the knock member 20 or the inside surface of the rear shaft 10, i.e., the shaft barrel 2, while sliding contact parts for sliding contact with those slanted surfaces may be provided at the other. The sliding contact parts can be configured in any way so long as the outside surface of the knock member 20 and the inside surface of the shaft barrel slidingly contact along with retraction of the knock member 20 at the time of switching from the writing state to the non-writing state. Therefore, the slant angles of the slanted surfaces of the third taper parts 25b and the slant angles of the slanted surfaces of the limit slanted surfaces 14c are substantially the same, but the slant angles of the slanted surfaces of the third taper parts 25b may also be made larger while the slant angles of the slanted surfaces of the limit slanted surfaces 14c may be made smaller. Further, the slant angles of the slanted surfaces of the third taper parts 25b may also be made smaller while the slant angles of the slanted surfaces of the limit slanted surfaces 14c may be made larger. The rear end part of the connecting member 25 of the knock member 20 may also not be provided with the third taper parts 25b but made a right angle rear end edge and that rear end edge and the limit slanted surfaces 14c of the rear shaft 10 may be made to slidingly contact. On the other hand, instead of the limit slanted surfaces 14c of the rear shaft 10, projections sticking out inward in the radial direction may be provided and the projections and the third taper parts 25b of the knock member 20 may be made to slidingly contact.

FIG. 20 is a perspective view of a rear shaft 110 of the side knock type writing instrument according to a second embodiment of the present invention, FIG. 21 is a vertical cross-sectional view of the rear shaft 110 of FIG. 20, and FIG. 22 is a horizontal cross-sectional view of the rear shaft 110 of FIG. 20. FIG. 22 is a horizontal cross-sectional view corresponding to FIG. 8.

The side knock type writing instrument according to the second embodiment is not shown in its entirety, but has a shaft barrel provided with a front shaft and a rear shaft 110 screwed over the outside surface of the rear end part of the front shaft, a refill 4 of a writing member arranged inside the shaft barrel and provided with a writing part 4a at one end, a spring 5 biasing the refill 4 to the rear, a knock member 120 arranged at the rear of the refill 4, and a clip member 106 provided integrally at a side surface of the rear end part of the rear shaft 110. On this point, it is similar to the side knock type writing instrument 1 of the first embodiment. Further, as explained later, when the first window opening 111 is viewed from the front in the writing state, the knock member 120 is configured so that the first window opening 111 is covered from the inside. This point is similar to the side knock type writing instrument 1 according to the first embodiment. Therefore, in the side knock type writing instrument according to the second embodiment as well, similarly the above effect is exhibited that dust and other dirt will not gradually build up inside the rear end part or clearance space of the knock member through the window opening and the appearance will not be harmed and the knock function parts will not be harmed.

At a side surface of the rear shaft 110, a concave curved first curved surface 110a and concave curved second curved surface 110b are provided. The first curved surface 110a and the second curved surface 110b are arranged so as to face each other. The first curved surface 110a is provided with a first window opening 111, while the second curved surface 110b is provided with a second window opening 112. The first window opening 111 and the second window opening 112 are rounded corner rectangular shapes. The parts corresponding to the short sides are respectively formed into semicircular shapes. A clip member 106 is provided at a position about 90 degrees away from the first window opening 111 and the second window opening 112 in the rotational direction about the center axis.

At the inside surface of the rear shaft 110, a pair of rail projections 113 comprised of projections extending from the rear end part to the front along the axial direction and sticking out inward in the radial direction are provided. The pair of rail projections 113 are arranged so as to face each other. Further, the pair of rail projections 113 are respectively arranged at positions exactly 90 degrees away from the first window opening 111 and the second window opening 112 in the rotational direction about the center axis. Specifically, in the side knock type writing instrument 1 according to above-mentioned first embodiment, the pair of rail projections 13 are respectively arranged offset just slightly to the first window opening 11 from positions exactly 90 degrees away from the first window opening 11 and the second window opening 12 in the rotational direction about the center axis. On the other hand, in the present embodiment, the pair of rail projections 113 are arranged at positions of equal distances from the first window opening 111 and the second window opening 112.

Each of the pair of rail projections 113 has an inside rail 114 extending from the rear end part of the rear shaft 110 to the front and an outside rail 115 extending from the front end part of the inside rail 114 to the front. The inside rail 114 sticks out from the inside surface of the rear shaft 110 further than the outside rail 115. The horizontal cross-sectional shapes of the inside rail 114 and outside rail 115, i.e., the cross-sectional shapes perpendicular to the center axis of the rear shaft 110, are rectangular. The inside rail 114 and outside rail 115 are formed into step shapes along the axial direction.

At the front end part of each inside rail 114, a first engaging part 116 is provided. The first engaging part 116 is formed in a wedge shape with sides slanted toward each other from the side surfaces of the first window opening 111 side and the second window opening 112 side of the inside rail 114. At the front end part of the outside rail 115, a support part 117 is provided. The support part 117 is formed in a wedge shape with sides slanted toward each other from the side surfaces of the first window opening 111 side and the second window opening 112 side of the outside rail 115.

As shown in FIG. 22, the rear end part of the rear shaft 110 is formed partially thicker. The resultant inside surface of the rear shaft 110 and the pair of rail projections 113 define a rectangular first guide rail 118 and second guide rail 119 extending in the axial direction. The first guide rail 118 and the second guide rail 119 are formed as spaces having the same inside surfaces. In short, the rear shaft 110, unlike the rear shaft 10 of the side knock type writing instrument 1 according to the above-mentioned first embodiment, is formed symmetrically about the plane passing through the center axis.

FIG. 23 is a perspective view of a knock member 120 of the side knock type writing instrument according to the second embodiment. The knock member 120, in FIG. 23, is arranged inside the shaft barrel so that the bottom becomes the front side of the side knock type writing instrument and the top becomes the rear side of the side knock type writing instrument.

The knock member 120 has a first sliding member 123 and second sliding member 124 of substantially rectangular plate shapes arranged substantially in parallel and a substantially plate shaped connecting member 125 connecting the first sliding member 123 and the second sliding member 124. The first sliding member 123 and the second sliding member 124 are arranged so as to face each other and have substantially the same lengths. The connecting member 125 has substantially the same length as the first sliding member 123 and the second sliding member 124 and is integrally formed so as to connect the first sliding member 123 and the second sliding member 124 perpendicularly. Therefore, the knock member 120 has a substantially H-shaped horizontal cross-sectional shape.

At the surface of the first sliding member 123, a knock operating part 121 is provided. At the surface of the second sliding member 124, a release operating part 122 is provided. The outside surface of the first sliding member 123 and the outside surface of the second sliding member 124 are formed in cylindrical surface shapes. At the surface of the first sliding member 123 at the center part in the longitudinal direction facing the second sliding member 124, a first guide projection 123a sticking out toward the second sliding member 124 is provided. The first guide projection 123a is provided over the width direction of the first sliding member 123 straddling the connecting member 125. At the surface of the first guide projection 123a facing the second sliding member 124, a flat first guide projection 123b is provided. At the rear end part of the first guide projection 123a, a second engaging part 127 is provided. The second engaging part 127 is formed into an acute angle shape comprised of the first guide surface 123b and a rear end face slanted from a rear end part of the first guide surface 123b toward the front. The second engaging part 127 has a slanted surface of the same slant as the slanted surface of the first engaging part 116 of the rear shaft 110.

The first sliding member 123 has a pair of second guide projections 123c extending from the center part in the longitudinal direction toward the front end part and sticking out outward in the width direction. The surfaces of the second guide projections 123c facing the second sliding member 124 configure parts of the above-mentioned first guide surface 123b. At the front end part of each of the pair of the second guide projections 123c, a support projection 123d sticking out in the width direction of the first sliding member 123 is provided. The surfaces of the support projections 123d facing the second sliding member 124 configure parts of the above-mentioned first guide surface 123b. At the side surfaces of the rear sides of the support projections 123d, convex curve shaped support surfaces 123e are provided. The surfaces of the first sliding member 123 near the rear end part are slanted by substantially the same angles. Overall, narrow first taper parts 123f are provided.

The second sliding member 124 has a pair of third guide projections 124a extending across the longitudinal direction and sticking out outward in the width direction. At the surfaces of the third guide projections 124a facing the first sliding member 123, flat second guide surfaces 124b are provided. The surfaces of the second sliding member 124 near the rear end part are slanted by substantially the same angles. Overall, narrow second taper parts 124c are provided.

FIG. 24 is a partial cross-sectional perspective view of the rear end part showing a non-writing state of the side knock type writing instrument according to the second embodiment, while FIG. 25 is a partial cross-sectional perspective view of the rear end part showing a writing state of the side knock type writing instrument according to the second embodiment. In the partial cross-sectional perspective views of FIG. 24 and FIG. 25, the rear end part of the rear shaft 110, like in FIG. 18 and FIG. 19, is shown cut open and including also part of a rail projection 113.

As shown in FIG. 24 and FIG. 25, in the side knock type writing instrument in the assembled state, the knock member 120 is arranged inside the rear shaft 110 so that the first sliding member 123 is arranged inside the first guide rail 118 of the rear shaft 110 and the second sliding member 124 is arranged inside the second guide rail 119 of the rear shaft 110. At this time, the connecting member 125 is arranged so as to be inserted between the pair of rail projections 113. The refill 4 biased to the rear by the spring 5 abuts against the front end faces of the first sliding member 123, the second sliding member 124, and the connecting member 125 of the knock member 120. Therefore, the knock member 120 is biased to the rear by the biasing force of the spring 5 through the refill 4.

Here, the distance between the facing pair of inside rails 114 is set smaller than the width of the part of the first guide projection 123a of the knock member 120, i.e., the width of the first sliding member 123. The distance of the facing pair of outside rails 115 is set larger than the width of the part of the pair of the second guide projections 123c of the knock member 120 and is set smaller than the width of the part of the pair of the support projections 123d of the knock member 120. The width of the part of the pair of support projections 123d of the knock member 120, i.e., the maximum width of the first sliding member 123, and the width of the part of the pair of the third guide projections 124a, i.e., the maximum width of the second sliding member 124, are set to become equal. Furthermore, they are set to be just slightly smaller than the width of the first guide rail 118 and the width of the second guide rail 119. As a result, movement in the horizontal direction or rotational direction of the knock member 120 at the time of movement in the front-rear direction of the knock member 120 is limited by the support projection 123d abutting against the inside surface of the first guide rail 118 and by the third guide projections 124a abutting against the inside surface of the second guide rail 119. Therefore, at the time of a knock operation, the knock member 120 can be made to stably move in the front-rear direction. It should be noted that, the length of the outside rail 115 is set to be substantially equal to the length of the second guide projections 123c.

Referring to FIG. 24 and FIG. 25, the knock operation for switching from the non-writing state to the writing state will be explained. A knock operation is performed for making the knock operating part 121 slide to the front against the biasing force of the spring 5 from the non-writing state. When making the knock operating part 121 slide to the front, an inward force in the radial direction also acts on the knock member 120 pressed by a finger of the user. Due to the knock operation, the first sliding member 123 and the second sliding member 124 of the knock member 120 respectively slide along the first guide rail 118 and the second guide rail 119 of the rear shaft 110.

Specifically, the first guide projection 123a, the second guide projections 123c, and the first guide surface 123b of the support projection 123d of the first sliding member 123 slide along the side surface at the first window opening 111 side of the pair of rail projections 113. In other words, the first guide projection 123a and the second guide projections 123c of the first sliding member 123 slide with respect to the inside rail 114 while the support projection 123d slides with respect to the outside rail 115. It should be noted that, the partial cross-sectional perspective views of FIG. 24 and FIG. 25, as explained above, are shown with the rear shaft 110 and the rail projection 113 partially cut open. For this reason, in actuality, the first guide surface 123b of the knock member 120 abuts against the side surface of the rail projection 113.

If making the knock member 120 move by exactly a predetermined distance, at the first sliding member 123, the first guide projection 123a and the second guide projections 123c detach from the inside rail 114 and the support projection 123d detaches from the outside rail 115. If the user releases the force which had been applied to the knock member 120 for the knock operation, the knock member 120 engages with the rear shaft 110 while retracting just slightly due to the biasing force of the spring 5 through the refill 4. In other words, due to the retraction of the knock member 120, as shown in FIG. 25, the acute angle shaped second engaging part 127 of the first sliding member 123 engages with the wedge shaped first engaging part 116 of the rear shaft 110 and the support surface 123e of the support projection 123d of the first sliding member 123 is supported by the support part 117 of the rear shaft 110 in the radial direction. As a result, the side knock type writing instrument enters the writing state.

The writing state is switched from the writing state to the non-writing state by pressing the release operating part 122 inward in the radial direction. Specifically, if pressing the release operating part 122 inward in the radial direction, a force component in the axial direction is generated by the mutually abutting slanted surfaces of the first engaging part 116 and the second engaging part 127, which are acute angle shaped. The axial direction force component causes the knock member 120 to advance just slightly and the knock member 120 to move to the first window opening 111 side whereby the first engaging part 116 and the second engaging part 127 disengage. If the first engaging part 116 and the second engaging part 127 disengage, the biasing force of the spring 5 causes the knock member 120 to retract and the writing part 4a of the refill 4 to retract into the front end aperture of the shaft barrel. Further, at the time of retraction of the knock member 120, the second guide surface 124b of the second sliding member 124 slides along the side surface of the pair of rail projections 113 at the second window opening 112 side. As a result, the release operating part 122 retracts just slightly inside the second window opening 112 and the knock operating part 121 sticks out just slightly from the first window opening 111 and the side knock type writing instrument enters the non-writing state.

If the side knock type writing instrument is in the non-writing state, when the first window opening 111 and the second window opening 112 are viewed from the front such as with the line of sight V1 shown in FIG. 16(a), the first window opening 111 and the second window opening 112 are substantially covered by the knock member 120 from the inside. Specifically, at the first window opening 111, the knock operating part 121 and the part of the first sliding member 123 at the front of the knock operating part 121 function as cover parts and cover the first window opening 111. At the second window opening 112, the release operating part 122 and the part of the second sliding member 124 at the front of the release operating part 122 function as cover parts and cover the second window opening 112.

On the other hand, if the side knock type writing instrument is in the writing state, when the first window opening 111 and the second window opening 112 are viewed from the front such as with the line of sight V2 shown in FIG. 16(b), the first window opening 111 and the second window opening 112 are substantially covered by the knock member 120 from the inside. Specifically, at the first window opening 111, the knock operating part 121 and the part of the first sliding member 123 at the rear of the knock operating part 121 function as cover parts and cover the inside of the first window opening 111. At the second window opening 112, the release operating part 122 itself functions as a cover part and covers the second window opening 112.

Due to the above, in the side knock type writing instrument, due to the knock member 120 having cover parts extending to the rear from the knock operating part 121 or the release operating part 122, the first window opening 111 and the second window opening 112 are covered from the inside not only at the time of the non-writing state, but also at the time of the writing state, therefore dust etc. is prevented from entering inside of the shaft barrel. As a result, the knock function parts arranged inside of the shaft barrel will not be harmed due to dust etc. along with time. Further, the appearance will not be harmed due to dust and other dirt.

According to the side knock type writing instrument according to the second embodiment, compared to the rear shaft 10 of the side knock type writing instrument 1 according to the first embodiment, the rear shaft 110 is formed symmetrically. For this reason, it is possible to change the direction of insertion of the knock member 120 by exactly 180 degrees about the center axis in accordance with the preference of the user. In other words, rather than arranging the knock operating part 121 at the first window opening 111 side, the knock operating part 121 can be arranged at the second window opening 112 side. Due to this, it is possible to arrange the knock operating part 121 or the release operating part 122 with respect to the clip member 106 to enable easier operability. In particular the arrangement can be changed in accordance with properties of the user such as right handedness or left handedness.

In each of the above two side knock type writing instruments, the knock operating part and the release operating part can be readily identified by their shape, but the knock operating part and the release operating part may also be made different colors to enable them to be identified. In this case, the knock operating part and the release operating part may be made the same shape as a design having symmetry. Further, as the method for making the knock operating part and the release operating part different colors, they may be colored or attached with a seal etc. The knock operating part and the release operating part may also be shaped by a two-color process to make them different in color from each other.

In each of the above two side knock type writing instruments, the shaft barrel is provided with the first window opening and the second window opening, but the above configuration may also be applied to a side knock type writing instrument having a single window opening such as shown in PTL 2 or may be applied to a multi-core side knock type writing instrument having three or more window openings. In short, the cover parts of the knock member may be configured in any way so long as having parts extending to the rear from the window opening at the time of the non-writing state and covering the window opening at the time of the writing state.

The refill 4, in the embodiments explained above, is a ball pen type, but may also be another type of refill such as one for a marking pen, touch pen, eraser pen, etc. Further, part or all of the rear end part of the rear shaft may be made an eraser part for erasing writing by the side knock type writing instrument.

The refill 4 may also be a ball pen type in which a thermochromic ink is contained. Here, a "thermochromic ink" means an ink having the property of maintaining a predetermined color (first color) at ordinary temperature (for example, 25°C), changing to another color (second color) if made to rise in temperature to a predetermined temperature (for example, 60°C), then if made to cool to a predetermined temperature (for example, -5°C), again returning to the original color (first color). In a thermochromic type writing instrument using a thermochromic ink, making the second color a colorless one and raising the temperature of lines drawn by the first color (for example, red) to make them colorless will be referred to here as "erasure". Therefore, a writing surface etc. on which lines are drawn may be rubbed by an erasing part comprised of a friction member to generate heat of friction and thereby change the lines to colorless ones, i.e., erase them. It should be noted that, only naturally, the second color may also be another color rather than colorless.

• 1 side knock type writing instrument
• 2 shaft barrel
• 3 front shaft
• 4 refill
• 5 spring
• 10 rear shaft
• 11 first window opening
• 12 second window opening
• 13 rail projection
• 14 inside rail
• 15 outside rail
• 16 first engaging part
• 17 support part
• 18 first guide rail
• 19 second guide rail
• 20 knock member
• 21 knock operating part
• 22 release operating part
• 23 first sliding member
• 24 second sliding member
• 25 connecting member
• 26 receiving part
• 27 second engaging part