Mechanical pencil unit and writing utensil with the mechanical pencil unit

A mechanical pencil unit is provided which includes: a holding tube; a holder which is inserted into a front side opening portion of the holding tube and which protrudes forward from a front end of the holding tube, and moreover which is supported so as to be back and forth movable relative to the holding tube; a pencil lead delivering mechanism which delivers forward a pencil lead x inserted into the holder; and a movement direction conversion mechanism which causes the holder to go forward relative to the holding tube and the pencil lead x by using a force applied in a radial direction from the pencil lead x to the holder, wherein the pencil lead delivering mechanism is provided at a position further toward a rearward side than the holder and the movement direction conversion mechanism.

TECHNICAL FIELD

The present invention relates to a mechanical pencil unit that constitutes a mechanical pencil refill, a mechanical pencil, and the like and to a writing utensil with the mechanical pencil unit.

BACKGROUND ART

Conventional examples of a mechanical pencil configured to prevent a pencil lead from breaking by excessive writing pressure or the like include an invention described in PTL 1. According to the conventional invention, there are provided: a shaft tube; an approximately tubular holder which is inserted into a front side opening portion of the shaft tube and which protrudes forward from a front end of the shaft tube; and a pencil lead which is inserted into the holder and which protrudes forward, wherein movement direction converting means which causes the holder to go forward by using a force applied in a radial direction to the holder is provided between the shaft tube and the holder, and a pencil lead urge member is provided inside the shaft tube so as to urge a chuck clipping the pencil lead forward relative to the shaft tube.

According to the mechanical pencil, when a force is applied in a radial direction by writing pressure or the like to a part of the pencil lead protruding from the holder, since the holder goes forward relative to the shaft tube and the pencil lead, a front side of the pencil lead can be covered by the holder and damage to the pencil lead and the like can be prevented.

In addition, when a rearward compressing force along an axial direction is applied to the protruding pencil lead, since the chuck clipping the pencil lead moves backward against an urging force of the pencil lead urge member, damage to the pencil lead and the like can be further prevented.

CITATION LIST

Patent Literature

SUMMARY OF INVENTION

Technical Problem

However, according to the prior art described above, since the chuck clipping the pencil lead, a tubular member housing the chuck, and the like are provided so as to overlap with each other in the radial direction inside the holder, an outer diameter is likely to increase and an application as a mechanical pencil refill to a retractable writing utensil (for example, refer to PTL 2) and the like in which each refill is relatively slim is difficult.

Solution to Problem

In consideration of the problem described above, the present invention provides the following configuration.

A mechanical pencil unit, including: a holding tube; a holder which is inserted into a front side opening portion of the holding tube and which protrudes forward from a front end of the holding tube, and moreover which is supported so as to be back and forth movable relative to the holding tube; a pencil lead delivering mechanism which delivers forward a pencil lead inserted into the holder; and a movement direction conversion mechanism which causes the holder to go forward relative to the holding tube and the pencil lead using a force in a radial direction being applied from the pencil lead to the holder, wherein the pencil lead delivering mechanism is provided at position toward a rearward side than the holder and the movement direction conversion mechanism.

DESCRIPTION OF EMBODIMENTS

A present embodiment discloses the following features.

A first feature includes: a holding tube; a holder which is inserted into a front side opening portion of the holding tube and which protrudes forward from a front end of the holding tube, and moreover which is supported so as to be back and forth movable with relative to the holding tube; a pencil lead delivering mechanism which delivers forward a pencil lead inserted into the holder; and a movement direction conversion mechanism which causes the holder to go forward relative to the holding tube and the pencil lead by using a force applied in a radial direction from the pencil lead to the holder, wherein the pencil lead delivering mechanism is provided at a position further toward a rearward side than the holder and the movement direction conversion mechanism (refer toFIGS. 1 to 16).

According to this configuration, an outer diameter can be reduced as compared to prior part and, for example, an application as a detachable mechanical pencil refill of a retractable writing utensil or the like can be facilitated.

In a second feature, in order to effectively transmit a force in a radial direction from a pencil lead to a holder, in addition to the first feature described above, on an inner circumference face of the holder, a pencil lead sliding contact surface which slidingly contacts an outer circumference face of the pencil lead on a front end side of the inner circumference face and a pencil lead guide surface which is adjacent to the outer circumference face of the pencil lead at a position further toward a rear side than the pencil lead sliding contact surface are formed.

In a third feature, in order to improve productivity, in addition to the first or second feature described above, the holding tube includes a first tube portion immanent so as to cause the holder to protrude forward and a second tube portion connected to a rearward side of the first tube portion, wherein the holder and the movement direction conversion mechanism are provided inside the first tube portion and the pencil lead delivering mechanism is provided inside the second tube portion.

In a fourth feature, in addition to any of the first to third features described above, the pencil lead delivering mechanism includes a pencil lead breaker which is loosely pressure contacted by the outer circumference face of the pencil lead being delivered forward.

In a fifth feature, in order to mitigate impact when a holder moves backward, in addition to the fourth feature described above, the pencil lead breaker receives from a rearward side thereof the holder by a front end side part made of an elastic material and the pencil lead breaker is supported inside the holding tube.

In a sixth feature, in order to prevent slippage of a pencil lead breaker or the like, in addition to the fifth feature described above, an annular projected portion which protrudes in a radially inner direction is provided inside the holding tube, and the pencil lead breaker is formed in an approximately tubular shape having an annular recessed portion in an outer circumference portion thereof and causes the annular recessed portion to fit with the annular projected portion (refer toFIGS. 11A to 14B).

In a seventh feature, in order to absorb excessive writing pressure in an axial direction, in addition to the fourth to sixth features described above, the pencil lead delivering mechanism includes a chuck portion which delivers forward a clipped pencil lead by a prescribed operation, the pencil lead delivering mechanism is immanent in the holding tube and the holding tube holds the chuck portion so as to be back and forth movable, the seventh feature further including: a pencil lead tank portion which is connected to the holding tube so as to supply a pencil lead to the pencil lead delivering mechanism from a rearward side; and a first urge member which urges the chuck portion forward relative to the pencil lead tank portion with an urging force set in advance which is stronger than writing pressure.

In an eighth feature, in order to improve performance when absorbing excessive writing pressure in an axial direction, in addition to the seventh feature described above, the holding tube is connected to the pencil lead tank portion so as to go back and forth by a prescribed amount, and a second urge member which urges the holding tube forward relative to a front end portion of the first urge member and the urging force of which is smaller than that of the first urge member is provided.

In a ninth feature, in order to improve both performance when absorbing excessive writing pressure in an axial direction and performance during pencil lead deliver, in addition to the eighth feature described above, the pencil lead delivering mechanism includes: the chuck portion which elastically deflects in a radially inner direction and which clips a pencil lead; a clutch ring which fits with the chuck portion in a clipping state and, when going forward together with the chuck portion, touches a touched portion of an inner face of the holding tube and disengages from the chuck portion; a clutch receiver which is provided so as to go back and forth by a prescribed amount inside the holding tube and which receives the clutch ring from a rearward side; the pencil lead breaker which is positioned on a further forward side than the clutch ring; and a third urge member which urges the chuck portion rearward relative to the clutch receiver, wherein an urging force of the third urge member is set larger than an urging force of the first urge member, and the pencil lead tank portion and the chuck portion are provided so as to have a space in a back and forth direction and are provided so that one of the pencil lead tank portion and the chuck portion touches the other of the pencil lead tank portion and the chuck portion by narrowing the space.

In a tenth feature, in order to prevent clogging of a pencil lead or the like, in addition to the ninth feature described above, a rear end side of the chuck portion is provided with a touching portion which touches a front end portion of the pencil lead tank portion when the space is narrowed and a pencil lead introducing portion which is provided so as to extend rearward from the touching portion and which is inserted into the pencil lead tank portion on a rear side of the space (refer toFIGS. 12A to 14B).

In an eleventh feature, in order to prevent urge members from interfering with each other, in addition to the ninth or tenth feature described above, the clutch receiver is formed in a tubular shape, and the second urge member and the third urge member are respectively provided on an outer side and an inner side of a side wall of the clutch receiver in a radial direction thereof (refer toFIGS. 12A to 14B).

In a twelfth feature, in order to further improve performance when absorbing excessive writing pressure in an axial direction, in addition to any of the ninth to eleventh features described above, an urging force of the second urge member is set larger than a resistance force in a back and forth direction between the pencil lead breaker and a pencil lead.

In a thirteenth feature, in order to prevent clogging of a broken pencil lead or the like, in addition to any of the first to twelfth features described above, the holding tube is provided with a hard annular protrusion which is adjacent to or which contacts an outer circumference face of a pencil lead delivered by the pencil lead delivering mechanism (refer toFIGS. 15 and 16).

In a fourteenth feature, a writing utensil is configured so as to include the mechanical pencil unit with any of the first to thirteenth features described above (refer toFIG. 4).

First Embodiment

Next, specific embodiments having the features described above will be described in detail based on the drawings. Moreover, in the present specification, an axial direction refers to a direction in which a central line of a holding tube or a shaft tube extends. In addition, “front” refers to one side of the axial direction which is a direction in which a pencil lead is delivered. Furthermore, “rear” refers to a side of an opposite direction to the one side of the axial direction. In addition, a “radial direction” refers to a direction perpendicular to the axial direction. Furthermore, a “radially outer direction” refers to a direction separating from an axial center along the radial direction. A “radially inner direction” refers to a direction approaching the axial center along the radial direction.

A mechanical pencil unit1shown inFIG. 1includes: a holding tube10; a holder20which is inserted into the holding tube10and protrudes forward from a front end of the holding tube10and which is supported so as to be back and forth movable relative to the holding tube10; a pencil lead delivering mechanism M2which delivers a pencil lead x clipped by a chuck portion40with a back and forth movement; a movement direction conversion mechanism M1which causes the holder20to go forward relative to the holding tube10and the pencil lead x using a force in a radial direction being applied to the holder20between the holding tube10and the holder20; a pencil lead tank portion60which supplies the pencil lead x from a rearward side to the pencil lead delivering mechanism M2; and the like.

The holding tube10is constituted in an integral tubular shape by a first tube portion11being immanent so as to cause the holder20to protrude forward, a second tube portion12coaxially connected to a rear end side of the first tube portion11, and a third tube portion13coaxially connected to a rear end side of the second tube portion12.

The first tube portion11is a cylindrical member having front and rear end portions opened, and the movement direction conversion mechanism M1, a holder urge member23, and the like are immanent therein.

A stepped locking portion11bfor locking a front end portion of the holder urge member23is provided on an inner circumference face of the first tube portion11.

A locking stepped portion11cfor locking the first tube portion11to a front end opening edge of a shaft tube a1(refer toFIG. 4) of the retractable writing utensil is formed on a front end side of an outer circumference face of the first tube portion11.

The holder urge member23is a compression coil spring according to the illustrated example, and urges the holder20rearward by touching the locking portion11bwith a front end portion thereof and touching a receiver22with a rear end portion thereof.

The holder20is integrally constituted by a holder main body portion21and the receiver22connected to a rear side of the holder main body portion21, and is supported so as to be back and forth movable relative to the holding tube10.

The holder main body portion21is an approximately cylindrical member which is inserted into the holding tube10and which protrudes forward from a front side opening portion11aof the holding tube10. An annular cam slope21awhich slidingly contacts a front end opening edge of the first tube portion11is provided in an outer circumference portion of the holder main body portion21.

According to the illustrated example, the cam slope21ais formed in a conical face shape of which a diameter increases forward, and constitutes the movement direction conversion mechanism M1which moves the holder20forward relative to the holding tube10and the pencil lead x using a force in a radial direction being applied to the holder20.

In addition, a pencil lead sliding contact surface21bwhich slidingly contacts an outer circumference face of the pencil lead x on a front side of the cam slope21aand a pencil lead guide surface21cwhich is adjacent across a small space to the outer circumference face of the pencil lead x on a rear side of the pencil lead sliding contact surface21bare formed on an inner circumference face of the holder main body portion21.

Furthermore, the receiver22which receives a rear end of the holder urge member23is integrally connected to a rear end side of the holder main body portion21.

The receiver22is formed in an approximately cylindrical shape having a stepped portion22awhich receives the holder urge member23on an outer circumference face thereof. An annular inclined face22b(refer toFIG. 10A) of which a diameter gradually decreases forward is formed on a center side of a rear end face of the receiver22. The annular inclined face22bguides the front end portion of the pencil lead to a central portion of the receiver22when the pencil lead x is inserted from the rearward side, and when the receiver22moves backward, the annular inclined face22btouches a front end portion of a pencil lead breaker31to be described later.

Moreover, while the receiver22is a separate member from the holder main body portion21according to the illustrated example, as another example, the receiver22may be configured as a portion integrally formed on a rear end side of the holder main body portion21.

In addition, the second tube portion12is a cylindrical member connected to a rear end side of the first tube portion11by connecting means such as screwing, fitting, and the like. An annular projected portion12awhich protrudes in a radially inner direction is formed near a front end on an inner circumference face of the second tube portion12.

The pencil lead breaker31is formed in an approximately cylindrical shape of an elastic material, loosely pressure contacts the outer circumference face of the inserted pencil lead x with an inner circumference face thereof, and receives the holder20having moved backward with a front end face thereof.

A reduced diameter portion31aof which a diameter is reduced stepwise is formed on a front half portion side on an outer circumference face of the pencil lead breaker31. The reduced diameter portion31ais fitted to and inserted into an inner circumference face of the annular projected portion12aon a front end side of the second tube portion12. In addition, a front end side of the reduced diameter portion31aprotrudes more forward than the front end of the second tube portion12.

Furthermore, a large diameter part on a rear side of the reduced diameter portion31aon the outer circumference face of the pencil lead breaker31elastically fits with the second tube portion12to prevent the pencil lead breaker31from moving backward relative to the second tube portion12.

In addition, in the second tube portion12, a chuck portion40supported so as to be back and forth movable and a clutch ring33annularly fitted with the chuck portion40are provided on a rear side of the pencil lead breaker31.

The chuck portion40is integrally constituted by a chuck main body41and a receiver42connected to a rear end side of the chuck main body41.

The chuck main body41is constructed by integrally coupling a plurality of (for example, about two to four) elongated pieces arranged annularly at intervals in a circumferential direction on rear end sides of the elongated pieces. In addition, the chuck main body41causes the plurality of elongated pieces to elastically deform in a radially inner direction and clips the pencil lead x with claw portions on a front end side of the elongated pieces.

The clutch ring33fits with the chuck main body41in a clipping state and, when having gone forward together with the chuck main body41, touches a stepped locking portion12con an inner face of the holding tube10and disengages from the plurality of claw portions and releases a front end side of the chuck main body41. Structures of the chuck main body41and the clutch ring33are approximately similar to known structures.

The chuck portion40, the clutch ring33, the locking portion12c, the pencil lead breaker31, and the like described above constitute the pencil lead delivering mechanism M2.

The pencil lead delivering mechanism M2is provided in the second tube portion12at a position further toward a rearward side than the holder20and the movement direction conversion mechanism M1.

In addition, in the second tube portion12, an approximately cylindrical clutch receiver34is provided on a rear side of the clutch ring33so as to go back and forth by a prescribed amount in the second tube portion12.

The clutch receiver34has the chuck main body41loosely inserted on a center side thereof.

An annular protruding portion34ais provided on an outer circumference portion of the clutch receiver34so as to protrude in a radially outer direction from near center in a front and rear direction. The annular protruding portion34atouches, from the rearward side, a stepped touched portion12don an inner circumference face of the second tube portion12. By being touched, the touched portion12drestricts forward movement of the entire clutch receiver34.

A rear end portion of the annular protruding portion34areceives a front end portion of a third urge member51bto be described later.

In addition, a frontmost end portion of the clutch receiver34receives a rear end portion of the clutch ring33.

Moreover, the clutch receiver34need only be provided so as to go back and forth by a prescribed amount in the holding tube10, be configured to receive the clutch ring33from a rearward side, and be urged forward by the third urge member51b, and a shape other than that of the illustrated example can be adopted.

In addition, the receiver42is an approximately cylindrical member and has a stepped portion42awhich receives the third urge member51bon a rear end side of an outer circumference face of the receiver42. The receiver42integrally goes back and forth together with the chuck main body41in the holding tube10.

Moreover, while the receiver42is configured as a separate member from the chuck main body41according to the illustrated example, the receiver42may also be configured as a portion integrally formed on a rear end side of the chuck main body41.

Furthermore, as exemplified inFIGS. 2A and 2B, the third tube portion13is an approximately elongated cylindrical member having front and rear end portions opened. More specifically, the third tube portion13is constituted by a cylindrical tube portion main body13aand an engaging portion13bwhich protrudes in a radially inner direction from a rear end edge of the tube portion main body13a.

The engaging portion13bis provided in plurality at intervals in a circumferential direction. According to the example shown inFIGS. 2A and 2B, each engaging portion13bis formed in a linear protruding piece-shape which is approximately parallel to a tangent of a circumferential circle of the tube portion main body13a. The engaging portion13bengages with a connector61of the pencil lead tank portion60to be described later so as to go back and forth.

A plurality of urge members provided in the second tube portion12and the third tube portion13will now be described in detail.

A chuck portion urge member51which urges the chuck portion40forward and rearward with different urging forces and a second urge member52are provided in the second tube portion12and the third tube portion13.

The chuck portion urge member51in the illustrated example is a two-stage spring integrally constituted by a first urge member51aand the third urge member51bwhich continues to a front side of the first urge member51a.

Alternatively, as will be described later as another example, the first urge member51aand the third urge member51bcan also be respectively configured as independent springs.

An urging force of the first urge member51ais set so as to urge, relative to the pencil lead tank portion60, the chuck portion40forward with an urging force set in advance which is stronger than writing pressure. The writing pressure is a rearward force applied to the pencil lead x in an ordinary writing posture and is obtained in advance by an experiment, a calculation, or the like.

An outer diameter of a coil spring that constitutes the first urge member51ais set larger than an outer diameter of a coil spring that constitutes the third urge member51b, and an urging force of the third urge member51bis set larger than an urging force of the first urge member51a.

A rear end portion of the first urge member51atouches the pencil lead tank portion60to be described later. In addition, the first urge member51aengages a front end side part thereof with the receiver42and urges the receiver42forward.

A rear end portion of the third urge member51bis received by the stepped portion42aof the receiver42, a front end portion of the third urge member51btouches the annular protruding portion34aof the clutch receiver34, and the third urge member51burges the chuck portion40rearward relative to the clutch receiver34.

In addition, the second urge member52is a coil spring with a smaller urging force than the first urge member51a. The urging force of the second urge member52is set larger than a resistance force in a back and forth direction by friction and the like between the pencil lead breaker31and the pencil lead x.

By touching a stepped portion (specifically, the rear end portion of the second tube portion12) on an inner face of the holding tube10with a front end portion and touching a front end portion of the first urge member51awith a rear end portion, the second urge member52urges the entire holding tube10forward relative to the front end portion of the first urge member51a.

Furthermore, the pencil lead tank portion60is configured in an approximately tubular shape having a front end portion opened and is connected so as to be back and forth movable to a rear end side of the holding tube10so as to supply the pencil lead x from a rearward side to the pencil lead delivering mechanism M2.

The pencil lead tank portion60is integrally constituted by the connector61and a tank main body62connected to a rear end side of the connector61.

As exemplified inFIGS. 3A and 3B, the connector61is an approximately cylindrical member and has, on a rear portion side of an outer circumference face thereof, an engaged portion61awhich engages with the engaging portion13b(refer toFIGS. 2A and 2B) of the third tube portion13so as to be back and forth movable.

The engaged portion61aincludes a flat face-shaped guide surface61a1provided so as to extend back and forth and a front side restricting portion61a2which protrudes in a radially outer direction from a front end of the guide surface61a1and which restricts forward movement of the engaging portion13b.

In addition, an inner circumference face of a rear portion side of the connector61is formed in a cylindrical shape which fits with an outer circumference face of a front end side of the tank main body62. InFIGS. 3A and 3B, a reference sign61bdenotes a protruding portion61bwhich is touched with pressure by an outer circumference face of the tank main body62, and a reference sign61cdenotes a guide hole which guides the pencil lead x forward one by one.

According to the connector61with the shape described above, since a plurality of the guide surfaces61a1are formed in a polygonal shape (a triangular shape according to the example shown inFIG. 3B), compared to a hypothetical case in which the guide surface61a1is formed in a cylindrical face shape, an area where the engaging portion13bis hooked can be increased, and thin-wall parts can be reduced to realize a structure with high strength.

Alternatively, as another example, the engaging portion13bcan be configured as a partial protrusion which protrudes in a radially inner direction and the engaged portion61acan be configured as a groove which fits with the protrusion and which guides the protrusion in a front and rear direction.

The tank main body62is an elongated cylindrical member having front and rear end portions opened, and a front end side of the tank main body62is inserted to the connector61to be fitted with and fixed by the connector61.

Moreover, while the connector61and the tank main body62are constituted by separate members in the illustrated example, as another example, the connector61and the tank main body62can also be constituted by an integrated member.

In addition, the mechanical pencil unit1configured as described above can be mounted to, for example, a multi-function retractable writing utensil A shown inFIG. 4.

By an operation for selectively causing a plurality of pieces a2and a3which are to be exposed to the outside on a rear end side of the shaft tube a1to go forward, the multi-function retractable writing utensil A causes a front end writing portion of a refill connected to the piece a2(or a3) having gone forward to protrude forward from a front end of the shaft tube a1. According to the illustrated example, the refill is the mechanical pencil unit1or a ballpoint pen refill2.

For example, as shown inFIG. 4, when the piece a2having a clip a6with an opening and closing function is operated so as to go forward against an urging force of a coil spring a4and the front end writing portion of the mechanical pencil unit1(a refill) connected to the piece a2protrudes forward from a front end opening portion of the shaft tube a1, the piece a2is locked by a locking portion a5on a circumferential wall of the shaft tube a1and this protruding state is maintained.

In this protruding state, by performing a prescribed operation (specifically, an operation causing the clip a6to go forward or an operation causing a tail plug a7to go forward), the pencil lead x is delivered from a front end of the mechanical pencil unit1.

Moreover, a basic structure of the multi-function retractable writing utensil A is approximately similar to that described in PTL 2.

Next, characteristic operational effects of the mechanical pencil unit1and the multi-function retractable writing utensil A will be described.

First, an operation when delivering the pencil lead x will be described in detail based onFIGS. 5A, 5B, 6C, and 6D.

When the piece a2is caused to go forward in a protruding state of a writing portion shown inFIG. 4, as shown inFIG. 5A, the locking stepped portion11con the front end side of the holding tube10is locked by the front end opening edge of the shaft tube a1and forward movement of the holding tube10is restricted.

When the piece a2is caused to go further forward in this restricted state, as shown inFIG. 5B, the pencil lead tank portion60(a hatched part) integrally goes forward with the piece a2. During going forward, a position of the chuck portion40is held by a rearward urging force of the third urge member51band only the first urge member51awith a smaller urging force than the third urge member51bcontracts.

Therefore, a space W between the chuck portion40and the pencil lead tank portion60decreases and a front end of the pencil lead tank portion60touches a rear end of the chuck portion40.

Next, when the pencil lead tank portion60goes further forward by an operation performed on the piece a2, as shown inFIG. 6C, the chuck portion40clipping the pencil lead x is compressed by the pencil lead tank portion60and goes forward and the clutch ring33touches the locking portion12c.

Subsequently, when the chuck portion40goes further forward, as shown inFIG. 6D, the clutch ring33touching the locking portion12cdisengages from the claw portions on the front end side of the chuck portion40and the chuck portion40elastically opens to release the pencil lead x. Since the released pencil lead x is loosely pressure contacted by the pencil lead breaker31, the pencil lead x is held without moving back and forth.

Next, when a compressing force on the pencil lead tank portion60is removed, the chuck portion40moves backward, fits with the clutch ring33, and clips the pencil lead x to restore the state shown inFIG. 5A.

Accordingly, the pencil lead can be delivered by a back and forth movement of the pencil lead tank portion60.

Next, an operation when an excessive rearward compressing force is applied to the pencil lead x will be described in detail based onFIGS. 7A and 7B.

FIG. 7Ashows a state (refer toFIG. 4) where the mechanical pencil unit1is locked while protruding from the shaft tube a1. In this protruding state, the pencil lead tank portion60is held by the piece a2of the multi-function retractable writing utensil A so as to be incapable of moving backward.

When an excessive rearward force along an axial direction is applied to the pencil lead x by writing or the like in this protruding state, as shown inFIG. 7B, the pencil lead x and the chuck portion40clipping the pencil lead x cause the first urge member51ato contract and, at the same time, cause the second urge member52to extend by elastic restoration and then move backward. Therefore, breakage and damage of the pencil lead x can be prevented.

Moreover, in a favorable example of the present embodiment, since the holding tube10is urged forward relative to the chuck portion40by the second urge member52having an urging force smaller than that of the first urge member51a, the holding tube10is prevented from moving backward in association with the backward movement of the chuck portion40and the pencil lead x having moved backward can be reliably housed inside the holder20and the holding tube10.

In addition, an amount of backward movement of the chuck portion40is to be restricted as the receiver42of the chuck portion40touches the connector61of the pencil lead tank portion60.

Next, an operation when an excessive compressing force in a radial direction is applied to the pencil lead x will be described in detail based onFIGS. 8A and 8B.

FIG. 8Ashows a state (refer toFIG. 4) where the mechanical pencil unit1is locked while protruding from the shaft tube a1in a similar manner toFIG. 7A.

When an excessive force in the radial direction is applied to the pencil lead x by writing and the like in this protruding state, as shown inFIG. 8B, the cam slope21aof the holder20slidingly contacts the front side opening portion11aof the holding tube10and causes the holder20to go forward while being slightly tilted. Therefore, the holder20having gone forward covers a front end side of the pencil lead x being clipped by the chuck portion40and prevents breakage, damage, and the like of the pencil lead x.

In addition, when an excessive compressing force in a rearward direction and a radial direction is applied to the pencil lead x, both the operation shown inFIGS. 7A and 7Band the operation shown inFIGS. 8A and 8Bare to be performed.

In other words, as shown inFIGS. 9A and 9B, the pencil lead x and the chuck portion40move backward and, at the same time, the holder20goes forward to cover the front end side of the pencil lead x. Therefore, breakage, damage, and the like of the pencil lead x can be prevented.

Furthermore, when an excessive compressing force in the radial direction applied to the pencil lead x causes the holder20to go forward (refer toFIGS. 8A to 9B), when the excessive compressing force in the radial direction is subsequently removed, as shown inFIGS. 10A and 10B, the holder20is to move backward by an urging force of the holder urge member23.

In doing so, since the receiver22on a rear end side of the holder20touches a protruding part31bon a front end side of the pencil lead breaker31and the pencil lead breaker31elastically deforms, a sound created by touching can be reduced.

Alternatively, as another example of the pencil lead breaker31, a configuration of a pencil lead breaker31′ exemplified inFIGS. 11A and 11Bmay be adopted.

With the pencil lead breaker31′, by forming an increased diameter portion31cin a part of the pencil lead breaker31which protrudes from the front end of the holding tube10, an outer circumference portion on a rear side of the increased diameter portion31con the front end side of the pencil lead breaker31constitutes an annular recessed portion31dand the annular recessed portion31dis fitted with the annular projected portion12aon the side of the holding tube10.

According to the mechanical pencil unit1and the multi-function retractable writing utensil A using the pencil lead breaker31′, as shown inFIGS. 11A and 11B, the pencil lead breaker31′ is prevented by the increased diameter portion31cfrom dropping off rearward from the holding tube10and, at the same time, a silencing effect can be improved by the increased diameter portion31cwith a relatively large outer diameter.

In addition, according to the embodiment described above, while the mechanical pencil unit1is applied with respect to a multi-function retractable writing utensil including a plurality of refills to a part of the plurality of refills, as other examples, a mode in which the mechanical pencil unit1is applied with respect to a retractable writing utensil configured with a single retractable refill to the single refill, a mode in which the mechanical pencil unit1is applied with respect a mechanical pencil configured with a non-retractable refill to the refill, and the like can be adopted.

Furthermore, according to the embodiment described above, while the holding tube10is integrally constituted by three independent tube portions (the first tube portion11, the second tube portion12, and the third tube portion13), as another example, a part of or all of the tube portions may be constructed as a single integrated member. As yet another example, the holding tube10can be integrally constituted by four or more independent members.

In addition, according to the embodiment described above, while the first urge member51aand the third urge member51bare integrally configured as a two-stage spring as a favorable mode with particularly preferable productivity, as another example, the first urge member51aand the third urge member51bcan also be respectively configured as separate coil springs.

In this case, the first urge member51aengages with the receiver42integrated with the chuck portion40so as to urge the chuck portion40forward. This engagement structure can be applied to, for example, a mode which causes a front end portion of the first urge member51ato engage with the receiver42, a mode which provides a flange on the receiver42and which causes the front end portion of the first urge member51ato touch a rear end face of the flange and, at the same time, causes a rear end portion of the second urge member52to touch a front end face of the flange, and the like.

Furthermore, according to the embodiment described above, while the holder20which is moved backward by the movement direction conversion mechanism M1is configured to touch the pencil lead breaker31, as another invention, in a mechanical pencil structure having a holder (including a pipe-like holder) which goes back and forth without including the movement direction conversion mechanism M1, a configuration can be adopted in which the holder is caused to touch the pencil lead breaker31to reduce a sound created by the touching.

In addition, according to the embodiment described above, while the entire pencil lead breaker31is formed of an elastic material as a particularly favorable mode, as another example, a mode can be adopted in which only a front end side part of the pencil lead breaker31is partially formed of an elastic material.

Furthermore, as a favorable configuration to be added to the embodiment described above, a guide member which protrudes rearward and which slidably fits with the connector61of the pencil lead tank portion60can be provided on a rear end side of the receiver42of the chuck portion40in order to further improve straight-advancing stability of the chuck portion40.

Second Embodiment

Next, another embodiment of a mechanical pencil unit according to the present invention will be described. Since the embodiment described below represents a partial modification of the first embodiment described above, modified parts of the embodiment will be mainly described in detail and parts with similar functions will be denoted by same reference signs and overlapping detailed descriptions thereof will be omitted.

The main modifications of a mechanical pencil unit2shown inFIGS. 12A and 12Bfrom the mechanical pencil unit1described above include the clutch receiver34being replaced with a clutch receiver34′, the chuck portion40being replaced with a chuck portion40′, the clutch urge member51(the first urge member51aand the third urge member51b) which is a two-stage spring being replaced with a first urge member51a′ and a third urge member51b′ which are respectively separate bodies, and the pencil lead tank portion60being replaced with a pencil lead tank portion60′.

The clutch receiver34′ is a tubular member having the chuck main body41loosely inserted on a center side thereof.

A front end face of the clutch receiver34′ is locked by the stepped touched portion12din the holding tube10.

In addition, a locking protrusion34a′ which protrudes outward in a radial direction is provided on an outer circumference face on a rear end side of the clutch receiver34′.

A front end face of the locking protrusion34a′ receives a rear end seat portion of the second urge member52. In addition, a rear end face of the locking protrusion34a′ receives a front end seat portion of the first urge member51a′.

Furthermore, a diameter of a front end side of an inner circumferential portion of the locking protrusion34a′ is reduced, and a rear face of the reduced diameter portion constitutes a locking portion34b′ for locking the third urge member51b′.

In addition, the clutch receiver34′ is positioned so as to provide a partition between the second urge member52on an outer side in a radial direction and the third urge member51b′ on an inner side in the radial direction.

The chuck portion40′ is constituted by the chuck main body41and a receiver42′ connected to a rear end side of the chuck main body41.

The receiver42′ is constituted by a tubular sleeve42a′ annularly connected to the rear end side of the chuck main body41and a pencil lead tank guiding portion42b′ which is connected to a rear end side of the sleeve42a′ and which is inserted into the pencil lead tank portion60′. Alternatively, the sleeve42a′ and the pencil lead tank guiding portion42b′ can be configured as a single member formed integrally in advance.

The sleeve42a′ is a cylindrical member, and a rear end side of the chuck main body41is inserted into and fitted with a front end side of an inner circumference face of the sleeve42a′. In addition, a front end face of the sleeve42a′ receives a rear end portion of the third urge member51b′.

The pencil lead tank guiding portion42b′ is a tubular member inserted and fixed to a rear end side of the sleeve42a′, and includes a touching portion42b1′ which touches a front end portion of the pencil lead tank portion60′ when a space W between the front end of the pencil lead tank portion60′ and the touching portion42b1′ is reduced and a pencil lead introducing portion42b2′ which is provided so as to extend rearward from a portion on a radially inner direction side of the touching portion42b1′, which is inserted into the pencil lead tank portion60′, and which introduces the pencil lead x from a rearward side.

The touching portion42b1′ is formed in an annular shape so as to cause a rear end face of the touching portion42b1′ to touch a front end face of the pencil lead tank portion60′ in a state where a front end face of the touching portion42b1′ contacts a rear end face of the sleeve42a′.

The pencil lead introducing portion42b2′ is formed in a tubular shape with a smaller outer diameter than the touching portion42b1′, and an outer circumference face on a rear portion side of the pencil lead introducing portion42b2′ slidingly contacts or is adjacent with an inner circumference face of the pencil lead tank portion60′.

A rear end side of an inner circumference face of the pencil lead introducing portion42b2′ is chamfered in a mortar shape so as to enable the pencil lead x to be introduced.

The pencil lead tank portion60′ integrally includes a connector61′ and the tank main body62connected to a rear end side of the connector61′ and is configured in an approximately tubular shape having a front end portion opened.

The connector61′ is an approximately cylindrical member and is provided with, on a rear portion side of an outer circumference face thereof, an engaged portion61a′ of which a diameter has been reduced to enable engagement with an engaging portion13b′. The engaging portion13b′ represents a modification of the engaging portion13b(refer toFIGS. 2A and 2B) described above to an inward-facing annular protrusion.

In addition, a locking stepped portion61b′ with a cylindrical face shape for receiving the first urge member51a′ is provided on an outer circumference portion on a front end side of the connector61′.

Alternatively, the engaging portion13b′ and the locking stepped portion61′ can be formed in a polygonal shape in a similar manner to the engaging portion13band the engaged portion61a(FIGS. 2A to 3B) described earlier.

In addition, the first urge member51a′ and the second urge member52are respectively independent and separate coil springs.

An urging force of the first urge member51a′ is set so as to urge, relative to the pencil lead tank portion60′, the chuck portion40′ forward with an urging force set in advance which is stronger than writing pressure, and the urging force of the first urge member51a′ is larger than an urging force of the second urge member52but smaller than an urging force of the third urge member51b′.

Moreover, the urging force of the second urge member52is larger than the urging force of the holder urge member23.

A front end portion of the first urge member51a′ touches the locking protrusion34a′ on the rear end side of the clutch receiver34′, and a rear end portion of the first urge member51a′ touches the locking stepped portion61b′ on the front end side of the pencil lead tank portion60′.

A front end portion of the third urge member51b′ touches the locking portion34b′ of the clutch receiver34′, and a rear end portion of the third urge member51b′ touches a front end of the receiver42′.

The mechanical pencil unit2configured as described above is mounted to the multi-function retractable writing utensil A (refer toFIG. 4) in a similar manner to the mechanical pencil unit1described earlier, and produces operational effects approximately similar to those produced by the mechanical pencil unit1.

For example, when the piece a2is caused to go forward in the protruding state of the writing portion shown inFIG. 4, as shown inFIG. 12B, the pencil lead tank portion60′ (a hatched part) goes forward. During going forward, a position of the chuck portion40′ is held by a rearward urging force of the third urge member51b′ and only the first urge member51a′ with a smaller urging force than the third urge member51b′ contracts.

Therefore, a space W between the chuck portion40′ and the pencil lead tank portion60′ decreases and a front end of the pencil lead tank portion60′ touches the chuck portion40′ (more specifically, the touching portion42b1′) (refer toFIG. 12B).

Next, when the pencil lead tank portion60′ goes further forward, as shown inFIG. 13C, the first urge member51a′ and the third urge member51b′ contract, the chuck portion40′ clipping the pencil lead x goes forward, and the clutch ring33touches the locking portion12c.

Subsequently, when the chuck portion40′ goes further forward, as shown inFIG. 13D, the first urge member51a′ and the third urge member51b′ further contract, the clutch ring33touching the locking portion12cdisengages from the claw portions on the front end side of the chuck portion40′, and the chuck portion40′ elastically opens to release the pencil lead x. Since the released pencil lead x is loosely pressure contacted by the pencil lead breaker31′, the pencil lead x is held without moving back and forth.

Next, when a compressing force on the pencil lead tank portion60is removed, the pencil lead tank portion60moves backward by the urging force of the third urge member51b′, the first urge member51a′ extends, and the chuck portion40′ fits with the clutch ring33and clips the pencil lead x to restore the state shown inFIG. 12A.

Accordingly, the pencil lead can be delivered by a back and forth movement of the pencil lead tank portion60′.

Next, an operation when an excessive rearward compressing force is applied to the pencil lead x will be described in detail based onFIGS. 14A and 14B.

In a state where the mechanical pencil unit2protrudes from the shaft tube a1(refer toFIG. 14A), the pencil lead tank portion60′ is held by the piece a2of the multi-function retractable writing utensil A so as to be incapable of moving backward.

When an excessive rearward force along an axial direction is applied to the pencil lead x by writing or the like in this protruding state, as shown inFIG. 14B, the pencil lead x and the chuck portion40′ clipping the pencil lead x cause the first urge member51a′ to contract and, at the same time, cause the second urge member52to extend by an elastic restoring force and then move backward. Therefore, breakage and damage of the pencil lead x can be prevented.

In addition, in the ballpoint pen refill2, when an excessive compressing force in a radial direction is applied to the pencil lead x, the holder20covers and protects a front end side of the pencil lead x in a similar manner to the mechanical pencil unit1(refer toFIGS. 8A and 8B) described earlier.

Therefore, the mechanical pencil unit2is capable of performing a smooth delivery operation of the pencil lead x, providing protection for the pencil lead x, and the like in a similar manner to the mechanical pencil unit1described earlier. In addition, since an outer diameter can be reduced as compared to conventionally-structured mechanical pencil units, the mechanical pencil unit2is useful as a detachable mechanical pencil unit to be included in the multi-function retractable writing utensil A and the like.

Furthermore, with the mechanical pencil unit2, the pencil lead introducing portion42b2′ on the rear end side of the chuck portion40′ prevents an occurrence of a situation where, for example, a broken pencil lead x or the like gets caught by the first urge member51a′.

Moreover, the second urge member52and the third urge member51b′ can be prevented from interfering with each other by a side wall of the clutch receiver34′ positioned between the second urge member52and the third urge member51b′.

Third Embodiment

Next, a third embodiment of a ballpoint pen refill according to the present invention will be described (refer toFIGS. 15 and 16).

The main modifications of the ballpoint pen refill3from the mechanical pencil unit1described earlier include the holding tube10being replaced with a holding tube10′ and the pencil lead breaker31being replaced with a pencil lead breaker32.

The holding tube10′ is configured by replacing the second tube portion12in the holding tube10described earlier with a second tube portion12′.

The second tube portion12′ is formed in an elongated, approximately cylindrical shape of a hard material such as metal and is detachably connected to the first tube portion11by a screw connection or the like. A frontmost tip portion of the second tube portion12′ is provided with an annular protrusion12b′ which is adjacent to or which contacts the outer circumference face of the pencil lead x being clipped by the chuck main body41.

The annular protrusion12b′ is an annular protrusion which protrudes in a radially inner direction from a front end portion of the second tube portion12′ and which is continuous over an entire circumference.

An inner diameter of a smallest diameter part of the annular protrusion12′ is set to a slightly larger diameter than an outer diameter of the pencil lead x so that the pencil lead x can be loosely inserted into the annular protrusion12′ and that the annular protrusion12′ contacts the outer circumference face of the pencil lead x when the pencil lead x deflects.

In addition, a front end of a smallest part of the annular protrusion12′ is provided with a corner12b1′ (refer toFIG. 16) so as to encourage breaking of a touching pencil lead x.

In addition, the pencil lead breaker32is formed in an approximately cylindrical shape of an elastic material such as an elastomer resin or rubber. The pencil lead breaker32is fitted into and fixed in the second tube portion12′, and an inner circumference face of the pencil lead breaker32loosely pressure contacts the outer circumference face of the inserted pencil lead x.

Unlike the pencil lead breaker31described earlier, the pencil lead breaker32is not provided with a part which protrudes forward from the second tube portion12′.

Therefore, according to the ballpoint pen refill3configured as described above, when an excessive compressing force is applied to a portion protruding forward from the second tube portion12′ in the pencil lead x as a result of attaching or detaching the first tube portion11(refer toFIG. 16) to or from the second tube portion12′ and the like, the protruding part can be caused to touch the annular protrusion12b′ to be severed on an outer side of the second tube portion12′ (refer to dashed-two dotted line inFIG. 16). Therefore, a broken pencil lead can be prevented from clogging inside the second tube portion12′.

In addition, situations such as the pencil lead x breaking and tilting inside the second tube portion12′ and the tilted broken pencil lead obstructing a pencil lead from going forward subsequently can also be prevented.

While embodiments of the present invention have been described in detail above, it is to be understood that specific configurations of the present invention are not limited to these embodiments and that various design modifications and the like may be made without departing from the spirit and scope of the invention. In addition, the embodiments described above may be implemented so as to combine respective techniques thereof as long as no contradictions, problems, and the like arise in an object, a configuration, and the like of such implementations.

REFERENCE SIGNS LIST