Retractable writing instrument

Abstract

We provide a retractable writing instrument with a more reliable retractable mechanism. [Solution] The retractable writing instrument 1 comprises a barrel 4, a refill 6 disposed inside the barrel, a spring 7 that biases the refill backward, a plurality of outer cams 20, a knock member 30 having a cam surface 32 with a plurality of first peaks 33 and first valleys 34 formed on its front end surface, and a rotor 40 having a cam receiving surface 42 with a plurality of second peaks 43 and second valleys 44 formed on its rear end surface and configured to cooperate with the outer cam and cam surface, wherein the rotor is rotated by the cam surface pressing against the cam receiving surface, and the writing state and non-writing state can be switched, wherein the opening angle of the first peaks 33 is the first angle α, and the opening angle of the second peaks 43 is the second angle β, and the first angle and the second angle are different from each other.

Description

Technical Field

[0001] The present invention relates to a knock-type writing instrument.

Background Art

[0002] A so-called knock-type writing instrument is known, which has a knock member at the rear end of a barrel and performs a knock operation to press the knock member forward against the biasing force of a spring disposed within the barrel, thereby switching between a writing state in which a writing portion, which is a pen tip, protrudes from the tip of the barrel and a non-writing state in which the writing portion is immersed within the barrel (for example, Patent Document 1). Regarding the switching operation between the writing state and the non-writing state by the knock mechanism in a general knock-type writing instrument as shown in Patent Document 1, an explanation will be given while referring to FIGS. 8 to 11. In these figures, the upper side is the rear of the knock-type writing instrument, and the lower side is the front of the knock-type writing instrument.

[0003] The knock-type writing instrument has a knock mechanism 100, and the knock mechanism 100 includes an outer cam 120 provided on the inner peripheral surface of the barrel, a knock member 130 formed in a cylindrical shape, and a rotor 140 disposed in front of the knock member 130. The rotor 140 is constantly biased rearward by the biasing force of a spring via a refill, which is a writing body.

[0004] Figure 8 is a side view of a conventional retractable writing instrument with the retractable member 130 and rotor 140 combined, and Figure 9 is a schematic diagram of the retractable mechanism 100 of a conventional retractable writing instrument. Specifically, Figure 9 is a schematic diagram of the retractable mechanism 100, which has an outer cam 120, a retractable member 130, and a rotor 140, unfolded in the circumferential direction. Figure 10 is a schematic diagram of the retractable mechanism 100 showing the switching from the writing state to the non-writing state of a conventional retractable writing instrument, and Figure 11 is a schematic diagram of the retractable mechanism 100 showing the switching from the non-writing state to the writing state of a conventional retractable writing instrument. Specifically, Figures 10 and 11 are schematic diagrams showing the positional relationship between the retractable member 130 and the rotor 140, showing the positions of the locking projection 131 of the retractable member 130 and the inner cam 141 of the rotor 140 with respect to the outer cam 120 unfolded in the circumferential direction. Since the rotor 140 rotates around its central axis with each knock operation, it moves from right to left in Figures 10 and 11.

[0005] In detail, four external cams 120 are provided at equal intervals in the circumferential direction at the rear end of the inner circumferential surface of the shaft cylinder. Adjacent external cams 120 define four first guide grooves 121 that extend in the front-rear direction. Each external cam 120 consists of a first projection 122, a second projection 123, and a third projection 124 that extend in the front-rear direction and are arranged continuously in the circumferential direction. The third projection 124, located in the middle, has a radial thickness that is thinner than the first projection 122 and the second projection 123. Therefore, a second guide groove extending in the front-rear direction is formed between the first projection 122 and the second projection 123.

[0006] Eight locking projections 131 are provided at equal intervals in the circumferential direction on the front outer circumferential surface of the knock member 130. Each of the locking projections 131 is positioned within the first guide groove 121 between adjacent outer cams 120, or above the third projection 124, i.e., within the second guide groove between the first projection 122 and the second projection 123. Each of the locking projections 131 is configured to move in the front-rear direction within the first guide groove 121 or the second guide groove by the knock operation. A cam surface 132 is formed on the front end surface of the knock member 130. The cam surface 132 has eight first peaks 133 and first valleys 134.

[0007] Four internal cams 141, each consisting of projections extending in the front-rear direction, are provided at equal intervals in the circumferential direction on the outer circumferential surface of the rotor 140. A cam receiving surface 142 is formed on the rear end surface of the rotor 140, which cooperates with and has a complementary shape to the cam surface 132 of the knocking member 130. The cam receiving surface 142 has eight second peaks 143 and second valleys 144, similar to the cam surface 132 of the knocking member 130. When the rotor 140 rotates around its central axis due to a knocking operation, the internal cams 141 engage with the outer cams 120 or are positioned within the first guide groove 121 between the outer cams 120. When the internal cams 141 are positioned within the first guide groove 121 between the outer cams 120, the outer cams 120 are positioned between the internal cams 141.

[0008] The knocking operation is performed by pressing the knocking member 130 forward against the biasing force of the spring to advance it to a predetermined position, and then releasing the pressure. As the knocking member 130 advances due to the knocking operation, the rotor 140 is pressed and moves forward within the barrel. The knocking operation switches between a writing state in which the rotor 140 is engaged with the outer cam 120 and a non-writing state in which the rotor 140 is disengaged from the outer cam 120.

[0009] Referring to Figure 10, in the writing state (Figure 10(A)), the knock member 130 is advanced until the inner cam 141 of the rotor 140 passes over the first projection 122 of the outer cam 120 of the barrel (Figure 10(B)). As a result, the cam surface 132 and the cam receiving surface 142, which are positioned out of phase, cooperate, and the rotor 140 rotates until the cam surface 132 and the cam receiving surface 142 coincide (Figure 10(C)). Next, when the force applied to the knock member 130 is released, the knock member 130 and the rotor 140 retract due to the biasing force of the spring, and the rear end surface of the inner cam 141 and the front end surface of the outer cam 120 come into contact (Figure 10(D)). Under the biasing force of the spring, the rear end surface of the inner cam 141 and the front end surface of the outer cam 120 cooperate to rotate the rotor 140 until the inner cam 141 enters the first guide groove 121 (Figure 10(E)). As a result, the click-type writing instrument enters a non-writing state (Figure 10(F)).

[0010] Referring to Figure 11, in the non-writing state (Figure 11(A)), the knock member 130 is advanced until the inner cam 141 of the rotor 140 passes over the second projection 123 of the outer cam 120 of the barrel (Figure 11(B)). As a result, the cam surface 132 and the cam receiving surface 142, which are positioned out of phase, cooperate, and the rotor 140 rotates until the cam surface 132 and the cam receiving surface 142 coincide (Figure 11(C)). Next, when the force applied to the knock member 130 is released, the knock member 130 and the rotor 140 retract due to the biasing force of the spring, and the rear end surface of the inner cam 141 and the front end surface of the outer cam 120 come into contact (Figure 11(D)). Under the biasing force of the spring, the rear end surface of the inner cam 141 and the front end surface of the outer cam 120 cooperate to rotate the rotor 140 until the inner cam 141 contacts the side surface of the first projection 122 of the outer cam 120 (Figure 11(E)). As a result, the inner cam 141 engages with the front end surface of the third projection 124, and the click-type writing instrument enters the writing state (Figure 11(F)). [Prior art documents] [Patent Documents]

[0011] [Patent Document 1] Japanese Patent Publication No. 2015-003443 [Overview of the project] [Problems that the invention aims to solve]

[0012] Even after releasing the pressure from the knocking operation, the knocking member 130 and rotor 140 may not retract immediately, despite the biasing force of the spring, but may retract with a delay. This will be explained with reference to Figure 12.

[0013] Figure 12 is a schematic diagram showing the force acting on the knocking mechanism 130 in a conventional retractable writing instrument. Figure 12 corresponds to Figure 10(E) when switching from the writing state to the non-writing state. The following explanation can also be applied to the diagram corresponding to Figure 11(E) when switching from the non-writing state to the writing state.

[0014] When the rear end surface of the inner cam 141 and the front end surface of the outer cam 120 work together to rotate the rotor 140, the cam receiving surface 142 of the rotor 140 presses against the cam surface 132 of the knock member 130 due to the biasing force of the spring. If this pressing force is denoted as pressing force F2, then pressing force F2 acts in a direction perpendicular to the inclined surface of the cam surface 132. The pressing force F2 can be considered as being divided into an axial component f21 that retracts the knock member 130 and a rotational component f22 that rotates the knock member 130 around its central axis.

[0015] The rotational force component f22 presses the locking projection 131 of the knock member 130 against the side surface of the outer cam 120, specifically the side surfaces of the first projection 122 and the second projection 123. When the knock member 130 retracts in this state, the locking projection 131 of the knock member 130 and the side surface of the outer cam 120 slide against each other and rub against each other. If the frictional resistance at this time increases, it may hinder or delay the retraction of the knock member 130.

[0016] Furthermore, friction causes wear on the locking projection 131 of the knock member 130 and the side surface of the outer cam 120, generating wear particles, which are fine powder-like particles. Similarly, during the series of switching between writing and non-writing states, the cam surface 132 of the knock member 130 and the cam receiving surface 142 of the rotor 140 slide and rub against each other as the rotor 140 rotates. This friction also generates wear particles. The generated wear particles penetrate between parts such as the knock member 130 and the rotor 140, increasing the frictional resistance of the moving parts. As a result, this may hinder the operation of the knock member 130 and the rotor 140, for example, the retraction of the knock member 130.

[0017] As a result, even when the pressure from the knocking operation is released, the knocking member 130 and rotor 140 may not retract immediately despite the biasing force of the spring, but may retract with a delay. In this case, the user may feel that the knocking member 130 is not reacting well to the knocking operation. In the worst case, if the knocking member 130 does not retract completely due to frictional resistance and stops midway, it may become impossible to switch between writing and non-writing states as a knock-type writing instrument.

[0018] The present invention aims to provide a retractable writing instrument equipped with a more reliable retractable mechanism. [Means for solving the problem]

[0019] According to one aspect of the present invention, there is provided a knock-type writing instrument including: a shaft cylinder; a writing body disposed within the shaft cylinder; a spring that biases the writing body rearward; a plurality of outer cams each including a protrusion provided on an inner surface of the shaft cylinder, the protrusions extending in a front-rear direction and being arranged in a circumferential direction, and a guide groove extending in the front-rear direction being defined between the plurality of outer cams; a knock member having a locking protrusion configured to be movable in the front-rear direction within the guide groove and provided on an outer peripheral surface thereof, the knock member having a cam surface formed on a front end surface and including a plurality of first ridges and first valleys; and a rotor having an inner cam configured to be movable in the front-rear direction within the guide groove and provided on an outer peripheral surface thereof, the rotor having a cam receiving surface formed on a rear end surface and including a plurality of second ridges and second valleys and being configured to cooperate with the outer cams and the cam surface. The cam surface rotates the rotor by pressing the cam receiving surface, and the writing instrument is configured to be capable of switching between a writing state in which the inner cam engages with the outer cams and a non-writing state in which the inner cam is accommodated within the guide groove. The opening angle of the first ridges is defined as a first angle, and the opening angle of the second ridges is defined as a second angle, and the knock-type writing instrument is characterized in that the first angle and the second angle are different from each other.

[0020] The first angle may be larger than the second angle. The first angle may be larger than 120 degrees and smaller than 150 degrees.

Advantages of the Invention

[0021] According to an aspect of the present invention, there is a common advantage of providing a thermochromic writing instrument capable of switching between a writing state and a non-writing state by a simple mechanism without using an elastic member such as a spring.

Brief Description of the Drawings

[0022] [Figure 1] FIG. 1 is a longitudinal sectional view of a knock-type writing instrument according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of a state in which a knock member and a rotor of the knock-type writing instrument of FIG. 1 are combined. [Figure 3]FIG. 3 is a schematic diagram of the knock mechanism of the knock-type writing instrument of FIG. 1. [Figure 4] FIG. 4 is a schematic diagram showing the force acting on the knock member in the knock-type writing instrument of FIG. 1. [Figure 5] FIG. 5 is a diagram showing the relationship between the load applied to the knock member and the displacement of the knock member according to the shape of the knock member. [Figure 6] FIG. 6 is a diagram showing the relationship between the load applied to the knock member and the displacement of the knock member before and after the repeated test in the knock-type writing instrument of FIG. 1. [Figure 7] FIG. 7 is a diagram showing the relationship between the load applied to the knock member and the displacement of the knock member before and after the repeated test in a conventional knock-type writing instrument. [Figure 8] FIG. 8 is a side view of a state in which the knock member and the rotor of a conventional knock-type writing instrument are combined. [Figure 9] FIG. 9 is a schematic diagram of the knock mechanism of a conventional knock-type writing instrument. [Figure 10] FIG. 10 is a schematic diagram of the knock mechanism showing the switching from the writing state to the non-writing state of a conventional knock-type writing instrument. [Figure 11] FIG. 11 is a schematic diagram of the knock mechanism showing the switching from the non-writing state to the writing state of a conventional knock-type writing instrument. [Figure 12] FIG. 12 is a schematic diagram showing the force acting on the knock member in a conventional knock-type writing instrument.

Embodiments for Carrying Out the Invention

[0023] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. Throughout the drawings, common reference numerals are assigned to corresponding components.

[0024] Figure 1 is a longitudinal cross-sectional view of a retractable writing instrument 1 according to an embodiment of the present invention. The retractable writing instrument 1 comprises a barrel 4 formed in a cylindrical shape and having a front barrel 2 and a rear barrel 3, a refill 6 which is a writing body disposed inside the barrel 4 and having a writing section 5 at one end, a spring 7 which biases the refill 6 backward, and a knock mechanism 10 located at the rear end of the barrel 4. In this specification, in the axial direction of the retractable writing instrument 1, the side with the writing section 5 is defined as the "front" side, and the side opposite to the writing section 5 is defined as the "rear" side.

[0025] The knock mechanism 10 includes an outer cam 20 (Figure 3) provided on the inner circumferential surface of the barrel 4, a cylindrical knock member 30, a rotor 40 positioned in front of the knock member 30, and a fitting member 50 equipped with a connecting portion 51 for connecting the clip 52. The fitting member 50 is fitted to the rear end of the knock member 30. The rotor 40 is always biased rearward by the biasing force of the spring 7 via the refill 6. A notch 8 is formed on the rear end surface of the rear barrel 3, cut out toward the front. The connecting portion 51 is configured to move in the front-rear direction within the notch 8 when the knock operation is performed.

[0026] Figure 2 is a side view of the retractable writing instrument 1 of Figure 1 with the knock member 30 and rotor 40 combined. Figure 3 is a schematic diagram of the knock mechanism 10 of the retractable writing instrument 1 of Figure 1, and corresponds to Figure 9, which was referenced for a conventional retractable writing instrument. Therefore, Figure 3 is a schematic diagram of the knock mechanism 10 having the outer cam 20, knock member 30, and rotor 40 of the barrel 4, unfolded in the circumferential direction.

[0027] Four protruding outer cams 20 are provided at equal intervals in the circumferential direction on the rear end of the inner circumferential surface of the shaft cylinder 4. Adjacent outer cams 20 define four first guide grooves 21 that extend in the front-rear direction. Each outer cam 20 consists of a first projection 22, a second projection 23, and a third projection 24 that extend in the front-rear direction and are arranged continuously in the circumferential direction. The third projection 24, located in the middle, has a thinner radial thickness than the first projection 22 and the second projection 23. Therefore, a second guide groove extending in the front-rear direction is formed between the first projection 22 and the second projection 23.

[0028] Eight locking projections 31 are provided at equal intervals in the circumferential direction on the front outer circumferential surface of the knock member 30. Each of the locking projections 31 is positioned within a first guide groove 21 between adjacent outer cams 20, or above a third projection 24, i.e., within a second guide groove between a first projection 22 and a second projection 23. Each of the locking projections 31 is configured to move in the front-rear direction within the first guide groove 21 or the second guide groove by the knocking operation. A cam surface 32 is formed on the front end surface of the knock member 30. The cam surface 32 has eight first peaks 33 and first valleys 34.

[0029] Four internal cams 41, each consisting of projections extending in the front-rear direction, are provided at equal intervals in the circumferential direction on the outer circumferential surface of the rotor 40. A cam receiving surface 42 is formed on the rear end surface of the rotor 40, configured to cooperate with the cam surface 32 of the knocking member 30. The cam receiving surface 42 has eight second peaks 43 and second valleys 44, similar to the cam surface 32 of the knocking member 30. When the rotor 40 rotates around its central axis due to a knocking operation, the internal cams 41 engage with the outer cams 20 or are positioned within the first guide grooves 21 between the outer cams 20. When the internal cams 41 are positioned within the first guide grooves 21 between the outer cams 20, the outer cams 20 are positioned between the internal cams 41.

[0030] The knocking operation is performed by pressing the knocking member 30 forward against the biasing force of the spring 7 to advance it to a predetermined position, and then releasing the pressure. As the knocking member 30 advances due to the knocking operation, the rotor 40 is pressed and moves forward inside the barrel 4. The knocking operation switches between a writing state in which the rotor 40 is engaged with the outer cam 20 and a non-writing state in which the rotor 40 is disengaged from the outer cam 20. The switching between the writing state and the non-writing state by the knocking operation is performed in the same way as conventional knock-type writing instruments, as described above with reference to Figures 10 and 11, so a detailed explanation is omitted.

[0031] In conventional retractable writing instruments, the cam surface 132 of the retractable member 130 and the cam receiving surface 142 of the rotor 140 are formed complementaryly. Specifically, in Figure 9, which shows the cam surface 132 and the cam receiving surface 142 unfolded in the circumferential direction, the opening angle defined by the ridge of the first peak 133 is defined as the first angle α, and the opening angle defined by the ridge of the second peak 143 is defined as the second angle β. The opening angle is an angle smaller than 180 degrees. In conventional retractable writing instruments, the first angle α of the first peak 133 and the second angle β of the second peak 143 are the same. The opening angles between the first valley 134 of the retractable member 130 and the second valley 144 of the rotor 140 are also the same. The first angle α and the second angle β are, for example, 120 degrees. The opening angle may be specified in the unfolded view as shown in Figure 4 or Figure 9, or it may be specified by the surface constituting the first peak or the second peak.

[0032] In contrast, in the retractable writing instrument 1, the cam surface 32 of the retractable member 30 and the cam receiving surface 42 of the rotor 40 are not formed complementaryly. Specifically, in Figure 3, which shows the cam surface 32 and the cam receiving surface 42 unfolded in the circumferential direction, the opening angle defined by the ridge of the first peak 33 is defined as the first angle α, and the opening angle defined by the ridge of the second peak 43 is defined as the second angle β. In the retractable writing instrument 1, the first angle α of the first peak 33 and the second angle β of the second peak 43 are formed to be different from each other. Specifically, the first angle α of the first peak 33 is larger than the second angle β of the second peak 43. Furthermore, the first angle α of the first peak 33 of the retractable writing instrument 1 is formed to be larger than the first angle α of the first peak 133 of a conventional retractable writing instrument.

[0033] By forming the first angle α of the first peak 33 and the second angle β of the second peak 43 to be different from each other, it is possible to provide a retractable writing instrument 1 with a more reliable retractable mechanism 10. This will be explained with reference to Figure 4.

[0034] Figure 4 is a schematic diagram showing the force acting on the knocking member 30 in the retractable writing instrument 1 of Figure 1. Figure 4 corresponds to Figure 10(E) when switching from the writing state to the non-writing state. The following explanation can also be applied to the diagram corresponding to Figure 11(E) when switching from the non-writing state to the writing state.

[0035] When the rear end surface of the inner cam 41 and the front end surface of the outer cam 20 work together to rotate the rotor 40, the cam receiving surface 42 of the rotor 40 presses against the cam surface 32 of the knock member 30 due to the biasing force of the spring 7. If this pressing force is denoted as pressing force F1, then pressing force F1 acts in a direction perpendicular to the slope of the cam surface 32. Pressing force F1 can be considered as being divided into an axial component f11 that retracts the knock member 30 and a rotational component f12 that rotates the knock member 30 around its central axis.

[0036] As described above, the first angle α of the first peak 33 of the retractable writing instrument 1 is formed to be larger than the first angle α of the first peak 133 of a conventional retractable writing instrument. Therefore, the direction in which the pressing force F1 acts is closer to parallel with respect to the front-back direction than the direction in which the pressing force F2 (Figure 12) acts, by the amount of the difference in angle. When the pressing forces F1 and F2 are the same, the axial component force f11 of the pressing force F1 is larger than the axial component force f21 of the pressing force F2, and the rotational component force f12 of the pressing force F1 is smaller than the rotational component force f22 of the pressing force F2.

[0037] Because the rotational component f12 of the pressing force F1 is smaller than the rotational component f22 of the pressing force F2, the pressing force on the side surface of the outer cam 20, specifically the side surfaces of the first projection 22 and the second projection 23, by the locking projection 31 of the knock member 30 is reduced. As a result, the frictional resistance between the locking projection 31 of the knock member 30 and the side surface of the outer cam 20 when the knock member 30 is retracted is also reduced. In addition, because the axial component f11 of the pressing force F1 is larger than the axial component f21 of the pressing force F2, the force that retracts the knock member 30 becomes greater. In short, with the knock-type writing instrument 1, the frictional resistance when the knock member 30 is retracted is further reduced, and the force that retracts the knock member 30 becomes greater, thus preventing delays or stops in the retraction of the knock member 30. Therefore, a more reliable knock mechanism can be realized.

[0038] Furthermore, the frictional resistance between the locking projection 31 of the knock member 30 and the side surface of the outer cam 20 is reduced when the knock member 30 retracts, thereby reducing wear on the locking projection 31 and the outer cam 20, and also reducing the generation of wear particles. In addition, the difference in the angles of the first angle α of the first peak 33 and the second angle β of the second peak 43 reduces the contact area between the cam surface 32 of the knock member 30 and the cam receiving surface 42 of the rotor 40. As a result, the generation of wear particles due to sliding between the cam surface 32 and the cam receiving surface 42 as the rotor 40 rotates is also reduced. Since the generation of wear particles is reduced, the increase in frictional resistance of movable parts caused by wear particles is suppressed, and the operation of the knock member 30 and the rotor 40, such as the retraction of the knock member 30, becomes smoother. Therefore, a knock mechanism that operates more reliably can be realized.

[0039] As described above, in conventional retractable writing instruments, it has been common practice to form the cam surface 132 of the retractable member 130 and the cam receiving surface 142 of the rotor 140 in a complementary manner. However, contrary to this common practice, the present invention deliberately forms the cam surface 32 and the cam receiving surface 42 with different shapes. Specifically, the first angle α of the first peak 33 and the second angle β of the second peak 43 are formed to be different from each other. Hereinafter, embodiments of the present invention will be described with reference to Figures 5 to 7, which demonstrate the effect of this invention.

[0040] Figures 5 to 7 are graphs showing the relationship between the load L applied to the knocking member and the displacement S of the knocking member. The load L applied to the knocking member includes not only the load when the knocking member is pressed forward by the user, but also the load due to the backward biasing force of the spring. In the graphs shown in Figures 5 to 7, the vertical axis is the load L [N] applied to the knocking member, and the horizontal axis is the displacement (stroke) S [mm] of the knocking member in the front-to-back direction. Specifically, Figures 5 to 7 show the relationship when switching from a non-writing state to a writing state. In each graph, starting from the point where the load L=0 and displacement S=0 in the non-writing state, the switch to the writing state is made through section a, section b, ..., section f.

[0041] The correspondence between each section of the graphs shown in Figures 5 to 7 and each figure in Figure 11, a schematic diagram of the knock mechanism showing the switching from the non-writing state to the writing state, will be explained. When the knocking operation is started by pressing the knocking member forward from a load L=0 and displacement S=0 (Figure 11(A)), the load L rises sharply to start the compression of the spring. Next, when the spring compression starts, the load L increases in accordance with the displacement S (section a), and the knocking member is advanced until the inner cam of the rotor passes the second projection of the outer cam of the barrel (section b and Figure 11(B)). As a result, the cam surface and the cam receiving surface, which are positioned in phase with each other, cooperate, and the rotor rotates until the cam surface and the cam receiving surface coincide (section c and Figure 11(C)). Next, when the force applied to the knocking member is released, the knocking member and rotor retract due to the biasing force of the spring, and the rear end surface of the inner cam and the front end surface of the outer cam come into contact (section d and Figure 11(D)). Under the biasing force of the spring, the rear end face of the inner cam and the front end face of the outer cam cooperate to rotate the rotor until the inner cam engages with the first projection of the outer cam (section e and Figure 11(E)). As a result, the click-type writing instrument enters the writing state (section f and Figure 11(F)).

[0042] Figure 5 shows the relationship between the load L applied to the knocking member and the displacement S of the knocking member, depending on the shape of the knocking member. Specifically, Figure 5 shows four examples, each with a different first angle α of the first peak of the cam surface of the knocking member. Line P shows the case where the first angle α is 120 degrees as a reference example, which is an angle widely used in conventional knock-type writing instruments. Line T1 shows the case where the first angle α is 130 degrees, line T2 shows the case where the first angle α is 140 degrees, and line T3 shows the case where the first angle α is 150 degrees. The second angle β of the second peak of the rotor is 120 degrees.

[0043] As shown in Figure 5, the load L in sections a and e differs from each other depending on the first angle α. Specifically, as the first angle α increases, the load L in section a decreases. In short, a larger first angle α allows the knock member to be advanced with less force. Also, as the first angle α increases, the load L in section e increases. In short, a larger first angle α increases the force that retracts the knock member due to the biasing force of the spring, i.e., the axial component force.

[0044] From the above, a larger first angle α allows the user to advance the knocking mechanism with less force, while also ensuring that the knocking mechanism retracts more reliably after the user releases the force applied to it. On the other hand, a larger first angle α is not always preferable. A larger first angle α results in a larger axial force component, while the rotational force component decreases accordingly. As a result, the rotor may not rotate reliably, potentially leading to a malfunction. If the rotor malfunctions, the switching between writing and non-writing states will not function correctly. Rotor malfunctions are more likely to occur due to wear and tear on the components caused by repeated knocking operations. This will be explained with reference to Figures 6 and 7.

[0045] Figure 6 shows the relationship between the load L applied to the knock member 30 and the displacement S of the knock member 30 before and after repeated testing in the knock-type writing instrument 1 of Figure 1. Specifically, a knock member 30 with a first angle α of 140 degrees is used. Figure 7 shows the relationship between the load L applied to the knock member 130 and the displacement S of the knock member 130 before and after repeated testing in a conventional knock-type writing instrument. Specifically, a knock member 130 with a first angle α of 120 degrees is used. The second angle β of the second peak of the rotor is 120 degrees.

[0046] Referring first to Figure 7, which shows a conventional retractable writing instrument, line P1 shows the relationship between load L and displacement S before the repeated test, and is the same as line P shown in Figure 5. Line P2 shows the relationship between load L and displacement S after the repeated test of 10,000 knock operations. Comparing lines P1 and P2 before and after the repeated test, in particular at section e, the load L decreased from approximately 0.8 N before the repeated test to approximately 0.5 N. In short, this means that after the repeated test, the axial component force f21 (Figure 12), which is the force that retracts the knocking member due to the biasing force of the spring, has decreased significantly.

[0047] Next, referring to Figure 6 for the retractable writing instrument 1, line T21 shows the relationship between load L and displacement S before the repeated test, and line T22 shows the relationship between load L and displacement S after the repeated test involving 10,000 knock operations. Comparing lines T21 and T22, which are before and after the repeated test, particularly in section e, the load L decreased from approximately 1.2 N before the repeated test to approximately 1.0 N. In short, this means that after the repeated test, the axial component force f11 (Figure 4), which is the force that retracts the knock member 30 due to the biasing force of the spring 7, has decreased. However, the rate of decrease in load L shown in Figure 6 is smaller than the rate of decrease in load L for the conventional retractable writing instrument shown in Figure 7, and the load L itself is larger. Therefore, the knock member can be reliably retracted when the first angle α is 140 degrees than when the first angle α is 120 degrees.

[0048] Next, we will explain the results of repeated tests in which knocking operations were performed 10,000 or 30,000 times depending on the first angle α. In the repeated tests, the pressing force applied to the knocking member was released, and the presence or absence of a delay in the knocking member's immediate retraction was visually confirmed. In addition, in the repeated tests, it was visually confirmed whether the switching between the writing state and the non-writing state was performed normally. The number of samples was N, and the number of samples in which a defect occurred was counted out of N. The second angle β of the second peak 43 of the rotor 40 is 120 degrees.

[0049] In the 10,000-cycle test, the knocking operation was performed once per second. The test results showed that delays were observed in 17% (N=24) of the samples when the first angle α was 120 degrees, 6% (N=17) when the first angle α was 130 degrees, 0% (N=30) when the first angle α was 140 degrees, and 0% (N=17) when the first angle α was 150 degrees. Switching between writing and non-writing states was performed normally in all samples.

[0050] In the 30,000-cycle test, three knocking operations were performed per second. The test results showed that delays were observed in 33% (N=15) of samples when the first angle α was 120 degrees, 0% (N=10) when the first angle α was 130 degrees, 0% (N=10) when the first angle α was 140 degrees, and 0% (N=10) when the first angle α was 150 degrees.

[0051] Furthermore, in one sample (10%) where the rotor did not rotate sufficiently when the first angle α was 150 degrees, the switching between writing and non-writing states did not function properly. As explained with reference to Figure 4, this was because a larger first angle α resulted in a smaller rotational force component, and as a result, the knocking member was unable to rotate the rotor sufficiently.

[0052] Based on the above, the first angle α is preferably greater than 120 degrees and less than 150 degrees, and more preferably greater than 130 degrees and less than 150 degrees. In particular, the first angle α is preferably 140 degrees.

[0053] As described above with reference to Figure 4, the pressing force F1 exerted by the cam receiving surface 42 of the rotor 40 against the cam surface 32 of the knock member 30 acts in a direction perpendicular to the slope of the cam surface 32. Therefore, the second angle β can be arbitrarily chosen as long as the first angle α of the first peak 33 of the knock member 30 and the second angle β of the second peak 43 of the rotor 40 are different from each other.

[0054] In the embodiment described above, the first angle α of the first peak 33 of the knock member 30 is configured to be greater than the second angle β of the second peak 43 of the rotor 40. However, the first angle α of the first peak 33 may be configured to be smaller than the second angle β of the second peak 43. In this case as well, the second angle β is preferably greater than 120 degrees and less than 150 degrees, and more preferably greater than 130 degrees and less than 150 degrees. In particular, it is preferable that the first angle α is 140 degrees.

[0055] Refill 6 may be a ballpoint pen, or other type of writing instrument such as a marking pen, stylus, or eraser. Furthermore, part or all of the fitting member 50 may be an erasing section for erasing writing made with a retractable writing instrument.

[0056] Refill 6 may be a ballpoint pen containing thermochromic ink. Here, thermochromic ink refers to ink that maintains a predetermined color (first color) at room temperature (e.g., 25°C), changes to a different color (second color) when heated to a predetermined temperature (e.g., 60°C), and then returns to its original color (first color) when cooled to a predetermined temperature (e.g., -5°C). In thermochromic writing instruments using thermochromic ink, the second color is made colorless, and the process of heating the line written with the first color (e.g., red) to make it colorless is referred to here as "erasing." Therefore, friction heat is generated by rubbing the writing surface on which the line is written with the friction member, which is the erasing part, and thereby changing the line to colorless, i.e., erasing it. Of course, the second color may be a color other than colorless. [Explanation of symbols]

[0057] 1. Retractable writing instrument 4 shaft cylinder 5 Writing section 6 refills 7 Springs 10. Knock mechanism 20 external cam 21 First guide groove 22 1st protrusion 23 Second protrusion 24 Third protrusion 30 Knock Member 31 Locking protrusion 32 Cam surface 33. First Mountain Section 34. First Valley 40 rotors 41 Internal cam 42 Cam bearing surface 43. Second Mountain Section 44 Second Valley α 1st angle β second angle

Claims

1. The barrel and, A cursive writing element is placed inside the barrel, A spring that biases the writing instrument backward, A plurality of outer cams comprising projections provided on the inner surface of the shaft cylinder, wherein the projections extend in the front-rear direction and are arranged in the circumferential direction, and guide grooves extending in the front-rear direction are defined between the plurality of outer cams, A knock member having a locking projection on its outer circumferential surface that is configured to move in the front-rear direction within the guide groove, wherein the knock member has a cam surface formed on its front end surface that has a plurality of first peaks and first valleys, A rotor having an inner cam on its outer circumferential surface that is configured to move in the front-rear direction within the guide groove, the rotor having a cam receiving surface formed on its rear end surface that has a plurality of second peaks and second valleys and is configured to cooperate with the outer cam and the cam surface, It is equipped with, A retractable writing instrument in which the rotor is rotated by the cam surface pressing against the cam receiving surface, and the writing state in which the inner cam engages with the outer cam and the non-writing state in which the inner cam is housed in the guide groove are switchable, A retractable writing instrument characterized in that the opening angle of the first peak is defined as the first angle, and the opening angle of the second peak is defined as the second angle, and the first angle and the second angle are different from each other.

2. The retractable writing instrument according to claim 1, wherein the first angle is greater than the second angle.

3. The retractable writing instrument according to claim 2, wherein the first angle is greater than 120 degrees and less than 150 degrees.

Images