JP6843433B2 - chisel - Google Patents

Description

The present invention relates to a chisel, and more particularly to a chisel with a protective member capable of protecting the user's hand and the cutting edge of the chisel.

Traditionally, chisel has been used as a teaching material for drawing work in primary education. As a chisel that can be safely used by young people who are unfamiliar with blades, those equipped with a protective member that surrounds the blade are known.

As an example of such a chisel, there is a chisel disclosed in Patent Document 1.
In the chisel disclosed in Patent Document 1, a protective member is movably attached to the handle portion. Then, it is possible to switch between a state in which the protective member protrudes from the handle member and covers the periphery of the cutting edge, and a state in which the protective member is housed inside the handle member.

That is, a user who is unfamiliar with the handling of a cutting tool can use it safely by using it in a state where the protective member covers the periphery of the cutting edge.
On the other hand, a skilled user may find the protective member located around the cutting edge in the way. In such a case, the user can use the protective member in the same manner as a chisel without the protective member by storing the protective member inside the handle member.

That is, the chisel disclosed in Patent Document 1 can be comfortably used by various users having different skill levels by changing the position of the protective member.
Further, unlike the structure in which the protective member is attached to and detached from the handle member, the removed protective member is not lost, which is preferable.

Japanese Unexamined Patent Publication No. 2013-091304

By the way, the chisel disclosed in Patent Document 1 has room for further improvement from the viewpoint of further facilitating the engraving work and further improving the usability.

Further, the chisel disclosed in Patent Document 1 has room for further improvement from the viewpoint of making the protective member more difficult to break.
That is, as described above, the chisel is expected to be used by a young person, and may be used unexpectedly. Then, the protective member may be damaged by using the chisel in an unexpected posture and forcibly applying force.
Here, since the protective member is a member for safety for the purpose of protecting the hand or the like, it is preferable that the protective member is more resistant to breakage. That is, a protective member that is less likely to be damaged has been desired.

That is, a conventional chisel having a protective member has been desired to improve usability and safety.

Therefore, the present invention makes it possible to provide a chisel that is easy to use and has a good usability.

The invention according to claim 1 for solving the above problems includes a handle portion, a blade portion attached to the handle portion, and a protective member, and a blade formed on the blade portion is used as a target surface. A chisel that can be used in contact with the guard, and the protective member has a guard portion that can be arranged at least around the blade body portion, and the guard portion is in a protective posture in which the guard portion is located around the blade portion. A curved surface extending from the lower surface to the front surface is formed on the front end side of the guard forming piece, and in the protective posture, the longitudinal direction of the handle portion is inclined with respect to the target surface. The blade can be brought into contact with the target surface by setting the direction and tilting at a predetermined angle, and at least the guard portion has the angle at which the blade and the target surface can come into contact with each other. The range is regulated, and when the angle formed by the virtual line extending in the longitudinal direction of the handle portion and the target surface is in the range of 15 degrees or more and 40 degrees or less in the protective posture, the blade is attached to the target surface. When the angle formed by the guard is within the range of 15 degrees or more and 40 degrees or less, the state in which the guard portion does not contact the target surface and the state in which the guard portion contacts the target surface are described. The chisel is characterized in that the curved surface is in contact with the target surface in a state where the guard portion is in contact with the target surface together with the blade, which is switched according to the angle of the formed angle .
The "target surface" here is a surface to be engraved, such as the surface of plywood, and is the surface of the object to be engraved with which the blade is brought into contact when using the chisel.

By the way, when carving a target surface (a surface to be engraved) with a general chisel, it may be difficult to carve depending on how the blade is brought into contact with the target surface. Therefore, as a result of the sensory tests conducted by the present inventors on various people, the posture was set so that the angle between the longitudinal direction of the chisel (the longitudinal direction of the handle) and the target surface exceeded 40 degrees. At one point, it turned out to be difficult to work with. In addition, it was found that the work became difficult as soon as the posture was laid down above 15 degrees.
Therefore, in the chisel of the present invention, when the blade is brought into contact with the target surface (for example, the surface of the wood block), the blade comes into contact when the inclination of the chisel (handle portion) with respect to the target surface is within the above range. It is said. That is, the structure is such that the blade does not come into contact with the target surface when the posture is upright beyond the above range or when the posture is laid down beyond the above range.
In this way, if the posture is such that the blade is in contact with the target surface when the work is easy to perform, and the blade is not in contact with the posture when the work is difficult to perform, the blade is brought into contact with the target surface during use. Becomes a posture that makes it easy to work naturally. Therefore, it is possible to provide a chisel that is comfortable to use and easy to use even if it is used by a person who is unfamiliar with the work.
In addition, if a user who is unfamiliar with the work continues to use the chisel of the present invention, it can be expected that the user will naturally learn how to apply the blade to the target surface.
Further, since the guard portion functions as an angle regulating member, the posture can be restricted without unnecessarily increasing the number of parts. That is, it is possible to reduce the manufacturing cost, and the feeling of use does not deteriorate due to reasons such as the newly provided parts becoming an obstacle during use.

According to the second aspect of the present invention, when the longitudinal direction of the handle portion is the front-rear direction and the blade portion side is the front side, the front-rear direction from the front end portion of the guard portion to the blade in the protective posture. A virtual line when the blade and the guard portion are connected by a virtual line segment extending in the vertical direction in a state where the distance in the direction is L2, the protective posture is set, and the front-back direction is parallel to the horizontal plane. The first aspect of claim 1, wherein the L2 is 4.0 mm or more and 8.0 mm or less, and the L3 is 1.0 mm or more and 3.0 mm or less, where L3 is the length of the line segment. It is a chisel.

According to this configuration, the blade is sufficiently hidden in front view and side view, and the guard portion does not interfere with the work (during engraving work), so that the chisel has high safety and good usability. Can be provided. In addition, the guard portion has a natural shape, and the above-mentioned posture can be restricted.
The "front view" referred to here is a plan view seen from the front. The "side view" is a plan view seen from the side, and is a side view when the engraving target surface side is the lower side and the opposite side is the upper side when the blade is in contact with the engraving target surface. is there.

The invention according to claim 3 is one end side in a direction orthogonal to the front-rear direction, with the longitudinal direction of the handle portion as the front-rear direction and the blade portion side as the front side, and the blade is the target surface as the protection posture. When the target surface side is the lower side and the opposite side is the upper side in the state of being in contact with the guard portion, the lower end of the handle portion is located below the lower end of the guard portion, and the lower end portion of the handle portion is located. The chisel according to claim 1 or 2, wherein the portion around the front end side is also regulated in the range of the angle.

According to such a configuration, by making the guard portion and the handle portion function as the angle regulating member, the chisel can be made into a more natural shape and the above-mentioned posture can be restricted.

The invention according to claim 4 is one end side in a direction orthogonal to the front-rear direction, with the longitudinal direction of the handle portion as the front-rear direction and the blade body portion side as the front side, and the blade is the target surface as the protection posture. When the target surface side is the lower side and the opposite side is the upper side in the state of being in contact with the guard portion, the guard portion extends by connecting the two guard forming pieces and the front end sides of the two guard forming pieces. It has a guard connecting piece and extends continuously in a semi-annular manner on the outside of the front end and both side ends of the blade body portion in the protective posture, and the guard forming piece is the blade body in the protective posture. a chisel as claimed in any one of claims 1 to 3, characterized in that laterally outer parts is a portion extending in the front-rear direction.

According to such a configuration, when the blade is brought into contact with the target surface, even if the guard portion comes into contact with a different portion of the target surface, the guard portion does not easily interfere with the engraving work, which is preferable.

The invention according to claim 5 is one end side in a direction orthogonal to the front-rear direction, with the longitudinal direction of the handle portion as the front-rear direction and the blade body portion side as the front side. When the target surface side is the lower side and the opposite side is the upper side in the state of being in contact with the guard portion, the guard portion has two guard forming pieces, and in the protective posture, the two guard forming pieces The blade body portion is located between them, and the guard forming piece extends in the front-rear direction on the lateral outer side of the blade body portion, and the guard forming piece extends in the front-rear direction and the rear end side portion extending in the front-rear direction. It has a tip-side portion that extends upward as it goes toward, and the tip-side portion of the guard forming piece is formed with a constricted portion that is more constricted than the other portions, and the guard is formed. The chisel according to any one of claims 1 to 4, wherein the tip end side portion of the piece can be elastically deformed.

In such a configuration, a constricted portion is formed on the tip end side portion of the guard portion, and when a force is applied to the tip end side portion of the guard portion for some reason, the guard portion is deformed to prevent damage to the guard portion. it can.

The invention according to claim 6 is the chisel according to claim 5, wherein the constricted portion is formed in a portion from the rear end of the distal end side portion of the guard forming piece.

In such a configuration, a constricted portion is formed in a portion from the rear end on the base end side in the protruding direction, and the entire portion can be deformed so as to be enlarged, so that the guard portion can be prevented from being damaged. Therefore, it is more preferable.

In the invention according to claim 7, the average moment of inertia of area of the cross section of the constricted portion is 100 mm ⁴ or more and 300 mm ⁴ or less, and the geometrical moment of inertia of the cross section in the rear end side portion of the guard forming piece is secondary. The chisel according to claim 5 or 6, wherein the moment is smaller than the minimum value.

According to such a configuration, it is possible to form a structure in which the guard portion is deformed so as to be bent while ensuring a certain level of strength and resistance to deformation.
Specifically, from the viewpoint of preventing the guard portion from being destroyed when a large force is unexpectedly applied, it is preferable that the guard portion is easily deformed by a certain amount or more and the elastic range is widened. However, on the other hand, from the viewpoint of ensuring safety during normal use, it is preferable that the material does not deform even when a light force is applied. Therefore, with the above configuration, it is possible to form a suitable guard portion both when a large force is unexpectedly applied and during normal use.

In the invention according to claim 8, the rear end portion of the constricted portion is located on the rear side in the front-rear direction with respect to the blade, and the front end portion of the constricted portion is located on the front side in the front-rear direction with respect to the blade. The chisel according to any one of claims 5 to 7, characterized in that it is located.

In such a configuration, when the guard portion is pressed against the object and deformed, the guard portion is deformed so as to be formed from the rear end portion of the constricted portion located behind the blade. From this, it is possible to form a structure in which the blade (front end of the blade body portion) easily comes into contact with the object when the guard portion is deformed. Then, by bringing the blade into contact with the object, it is possible to prevent further deformation of the guard portion and prevent damage to the guard portion.

According to the ninth aspect of the present invention, the handle portion is formed with an in-handle space capable of accommodating at least a part of the guard portion, and the in-handle space is located on the front side of the handle portion. It has an opening portion, and the upper end portion of the opening portion is located slightly above the upper end portion of the guard portion, or the upper end portion of the guard portion and the upper end portion in the vertical direction are the same. The protective member is attached so as to be movable relative to the handle portion, and by moving the protective member, the protective posture and at least a part of the guard portion are said. It is possible to switch between the storage posture in which the handle is stored in the handle space, and in the storage posture, there is a slight gap between each part of the upper surface of the guard portion located in the handle space and the upper surface of the handle space. The chisel according to any one of claims 5 to 8, characterized in that they are facing each other or are in contact with each other.

According to this configuration, even if the guard portion is deformed beyond the elastic range for some reason, it can be restored to its original shape (or a shape close to the original shape) by performing an operation of switching to the storage posture. It becomes possible.

The invention according to claim 10 is characterized in that the protective member is a resin molded body formed of polyacetal and polyamide as main raw materials, and the guard portion is integrally molded with the protective member. The chisel according to any one of claims 1 to 9.

With such a configuration, it is possible to inexpensively and easily form a guard portion that is difficult to be deformed to a sufficient extent to function as an angle regulating member and is easily deformed to a preferable degree to be deformed in response to a strong force applied unexpectedly. Is.
The term "main raw material" as used herein means that a sufficient amount is contained in order to exert a function. Further, "using polyacetal and polyamide as main raw materials" here means that the ratio of polyacetal and polyamide to the total raw materials is 50% or more.

A related invention of the present invention is a chisel provided with a handle, a blade attached to the front end side of the handle, and a protective member, and the protective member is at least around the blade. It has a guard portion that can be arranged, a blade is formed on the blade body portion, and the guard portion can be in a protective posture located around the blade, and the guard in the protective posture. A virtual line segment extending the blade and the guard portion in the vertical direction, with the distance from the front end portion of the portion to the blade in the front-rear direction being L2, the protective posture, and the front-rear direction being parallel to the horizontal plane. When the length of the virtual line segment connected by is L3, the L2 is 4.0 mm or more and 8.0 mm or less, and the L3 is 1.0 mm or more and 3.0 mm or less. It is a chisel to do.

Even in a chisel having such a configuration, the posture can be restricted as described above after the guard portion has a natural shape.

According to the present invention, it is possible to provide a chisel that is easy to use and has a good usability.

It is a perspective view which shows the chisel which concerns on embodiment of this invention, (a) shows a protective posture, (b) shows a stowed posture. It is an exploded perspective view which shows the chisel of FIG. It is a partially cutaway perspective view which shows the handle part of FIG. It is a side view which shows the vicinity of the front end of the chisel of FIG. 1 (a). In the chisel of FIG. 4, the guard portion is broken at the central portion in the width direction, and one side in the width direction is omitted. 4A and 4B are cross-sectional views showing a chisel, FIG. 4A is a cross-sectional view taken along the line AA, and FIG. 4B is a cross-sectional view taken along the line BB. It is explanatory drawing which shows the state which the front end side of the chisel of FIG. 1 is directed downward and is pressed against the flat surface on the lower side, (a) shows the state before pressing, and (b) shows the state after pressing. It is explanatory drawing which shows typically the front end side part of the handle part and the protection member of FIG. 1, and is the figure which shows the state when the handle part is broken and a part is omitted, and it shifts from a protection posture to a storage posture. The transition is shown in the order of (a) to (c). It is explanatory drawing which shows typically the front end side part of the handle part and the protection member of FIG. 1, the handle part is broken and a part is omitted, and after the guard part is deformed so that it warps, it shifts from a protection posture to a storage posture. It is a figure which shows the state at the time of this, and shows the state of transition in the order of (a) to (c). It is explanatory drawing which shows the state that the chisel of FIG. 1 is brought into contact with a plane located on the lower side, and is the figure which shows how the angle formed by a virtual line extending along the longitudinal direction of a chisel and a plane is varied. It is shown that the angle formed in the order of (a) to (c) is increased. Following FIG. 10, it is a diagram showing a state in which the angle formed by the virtual line extending along the longitudinal direction of the chisel and the plane is further increased, and the angle formed in the order of (a) and (b) is increased. Shown. 2A and 2B are views showing a protective member, FIG. 2A is a perspective view seen from different directions and is a partially enlarged view, and FIG. 2B is a plan view showing an enlarged portion of FIG. 2A. .. 2 is a view showing a rear end side portion of the second handle forming piece of FIG. 2, where FIG. 2A is a perspective view and FIG. 2B is a plan view. It is explanatory drawing which shows the state when the protective member is moved to the rear side and shifts to a storage posture in the chisel of FIG. The transition is shown in the order of (a) to (c). It is explanatory drawing which shows typically the state of performing the durability test of the guard part with respect to the chisel of Example 1. FIG. It is a graph which shows the result of the durability test performed on Example 1, Comparative Example 1, and Comparative Example 2.

Hereinafter, embodiments of the present invention will be described in detail.
In the following description, unless otherwise specified, the longitudinal direction of the chisel 1 is the front-rear direction, one end side in the longitudinal direction in which the blade is located is the front side, and the other end side of the pair is the rear side.
Unless otherwise specified, the vertical direction in the following description is a direction orthogonal to the longitudinal direction of the chisel 1, and is the height direction in FIG.
Furthermore, unless otherwise specified, the width direction in the following description shall be a direction orthogonal to the above-mentioned vertical direction and front-back direction.

In addition to the above vertical direction, the chisel 1 in the present embodiment is a flat sword, and it is assumed that the blade surface is positioned on the side of the engraving object such as a woodblock during normal use. .. Therefore, the vertical direction of the chisel 1 of the present embodiment is the same as the vertical direction in the posture of lying down with the blade surface facing downward. In other words, it is in the same direction as the vertical direction in the posture in which the portion of the blade front and the blade back that is located on the side of the object to be engraved during normal use is laid down.
The "laid-down posture" here is a posture in which the front-back direction is parallel to the horizontal plane.

As shown in FIG. 1, the chisel 1 of the present embodiment has a structure including a handle portion 2, a blade portion 3, and a protective member 4.
The chisel 1 has a protective posture in which the guard portion 6 which is a part of the protective member 4 covers the periphery of the blade body portion 3 (see FIG. 1A), and the guard portion 6 is inside the handle portion 2. The posture can be changed from the stored posture (see FIG. 1B). That is, by moving the operating portion 7 exposed to the outside in the front-rear direction, the entire protective member 4 moves in the front-rear direction, and the guard portion 6 moves in the front-rear direction accordingly. Then, in the stowed posture, the guard portion 6 moves away from the periphery of the blade portion 3. That is, the storage posture is a posture in which the periphery of the blade body portion 3 is opened.

As shown in FIG. 2, the handle portion 2 includes a first handle forming piece 10 located on the upper side and a second handle forming piece 11 located on the lower side, and these are overlapped and integrated. It is a part formed by.
The first handle forming piece 10 is formed with a window portion 10a for exposing the operating portion 7. The window portion 10a is a through hole penetrating the outer surface (upper surface) and the inner side surface (lower surface) of the first handle forming piece 10, and is an elongated hole extending in the front-rear direction.

As shown in FIG. 3, a blade mounting portion 18 and a guide protrusion 19 are formed inside the handle portion 2. These are the portions of the internal space of the handle portion 2 that are formed on the central side in the width direction.

The blade mounting portion 18 is a massive portion formed so as to connect the inner side surface (lower surface) of the first handle forming piece 10 and the inner side surface (upper surface) of the second handle forming piece 11, and has a plan view shape. It has a substantially rectangular parallelepiped shape and is a part that extends in the front-back direction.
A mounting hole for mounting the blade body 3 is formed on the front end surface of the blade body mounting portion 18. Then, a handle-side engaging recess 18a is formed in the lower end side portion of the blade mounting portion 18.

The handle-side engaging recess 18a is a portion that is recessed inward in the width direction. In the present embodiment, one handle-side engaging recess 18a is formed on each of the one-side end portion and the other-side end portion in the width direction of the blade mounting portion 18. In other words, the other handle-side engaging recess 18a is formed at a position separated from one handle-side engaging recess 18a in the width direction, and the lower end side portion of the blade mounting portion 18 is wider than the upper portion thereof. The length of the direction is shortened.
By engaging with a part of the protective member 4, the handle-side engaging recess 18a functions as a guide portion when the protective member 4 moves.

The guide protrusion 19 is formed by two guide forming pieces 19a and 19b located behind the blade mounting portion 18.
The two guide forming pieces 19a and 19b are both vertical wall-shaped portions, are arranged at intervals in the width direction, and extend in the front-rear direction so as to be parallel to each other. The guide forming pieces 19a and 19b project upward from the inner side surface of the second handle forming piece 11 and extend downward from the inner side surface (lower surface) of the first handle forming piece 10. That is, a space is formed between the upper end portions of the two guide forming pieces 19a and 19b and the inner side surface (lower surface) of the first handle forming piece 10.

That is, the handle portion 2 is a tubular body whose rear end side is closed, and the handle inner space 20 which is an internal space thereof is a space having an opening portion 20a on the front end side.
The handle interior space 20 can store most of the protective member 4. Specifically, a portion located on one end side in the width direction of the blade mounting portion 18 and the guide protrusion portion 19, a portion located on the other end side in the width direction of the blade body mounting portion 18, and above the guide protrusion portion 19. The located portion serves as a space for arranging and moving the protective member 4.

The blade body portion 3 is a plate-shaped portion formed of an appropriate metal such as steel, and the shape of the blade (blade edge) located at the front end portion is a flat shape extending in the width direction. That is, the chisel 1 of the present embodiment is a so-called flat sword.
In addition, the blade of the blade body portion 3 is a portion serving as a boundary between the upper surface and the lower surface of the blade body portion 3, and is a portion formed by thinly and sharply processing the portion. Therefore, the blade of the blade body portion 3 is a very thin surface or side located on the front end side of the blade body portion 3.

The protective member 4 is a member formed by using an appropriate resin as a raw material, and in the present embodiment, it is a resin molded body formed by using polyacetal and polyimide as main raw materials. Therefore, the protective member 4 is a member having flexibility (elasticity).

As shown in FIG. 2, the protective member 4 includes a guard portion 6, a connecting portion 25, an internal sliding body 26, and an operating portion 7, and these are integrally formed.

The guard portion 6 is a portion that is located in front of the front end of the handle portion 2 and is exposed to the outside when in a protective posture (see FIG. 1A), and is connected to the two guard forming pieces 30 and 31 by a guard. It has a structure including one piece 32.
More specifically, the guard portion 6 is integrally molded with the protective member 4, and is a semi-annular continuous portion on the front end side of the protective member 4. Then, a guard that connects the standing wall-shaped guard forming piece 30 located on one end side in the width direction, the other guard forming piece 31 located on the other end side, and the front end sides of the two guard forming pieces 30 and 31. The connecting piece 32 is integrally formed, and the overall plan view shape is substantially U-shaped.
The guard portion 6 is a characteristic portion of the present embodiment, and will be described in detail later.

The connecting portion 25 is a portion formed by the two connecting piece portions 25a and 25b.
The two connecting pieces 25a and 25b are both portions having a substantially "L" -shaped cross section and extending in the front-rear direction, and a part of the lower end side of the standing wall-shaped portion is bent inward (inside in the width direction). It has a shape like that. That is, the two connecting piece portions 25a and 25b are portions extending so as to be parallel to each other at positions separated in the width direction, and have a flat plate shape protruding in a direction approaching each other on the lower end side of the inner side surfaces facing each other. Part is formed.
Of the two connecting piece portions 25a and 25b, one front end portion extends continuously and integrally with the rear end portion of one guard forming piece 30. Further, the other front end portion extends continuously and integrally with the rear end portion of the other guard forming piece 31. Then, each rear end portion is continuous with the front end side portion of the internal sliding body 26.

The internal sliding body 26 has a structure including a top plate portion 26a and two standing plate portions 26b and 26c hanging downward from both ends of the top plate portion 26a in the width direction.
That is, on the lower side of the top plate portion 26a, an engaging recess 35 surrounded by the top plate portion 26a and two standing plate portions 26b and 26c that are separated and opposed in the width direction is formed. The engaging recess 35 is a recess into which the guide protrusion 19 can be fitted.

The operation portion 7 has a structure provided with an operation protrusion 7a and a front locking piece portion 7b, and is a portion in which these are integrally formed.

The operation protrusion 7a is a protrusion portion having a substantially oval shape (track shape) in a plan view.
The "oval shape (track shape)" referred to here is a shape in which two short sides of a rectangle are replaced with semicircles.

The front locking piece portion 7b has a shape including a flat plate-shaped portion that protrudes further forward from the vicinity of the front lower end portion of the operation protrusion 7a and a protruding portion that protrudes upward near the protruding end of the flat plate-shaped portion. There is.

Here, the top plate portion 26a of the internal sliding body 26 is formed with a through hole that penetrates the top plate portion 26a in the thickness direction (vertical direction) at an appropriate portion. Most of the front side of the operation unit 7 is arranged at a position where it overlaps with the through hole of the top plate portion 26a in a plan view. That is, only the rear end portion of the operation portion 7 is connected to the top plate portion 26a, and is a portion extending in a cantilever shape.
Therefore, when the operation protrusion 7a is pressed downward, the front locking piece portion 7b also moves downward.

Here, the guard portion 6 will be described in detail.
As described above, the guard portion 6 is a portion formed by integrally forming the two guard forming pieces 30 and 31 and the guard connecting piece 32 (see FIG. 1A and the like).
Here, the two guard forming pieces 30 and 31 have the same shape and are arranged so as to overlap each other in a plan view with the line-of-sight direction as the width direction. They are distantly opposed to each other in the width direction and extend so as to be parallel to each other.
In the following description, one guard forming piece 30 (first guard forming piece 30) will be described in detail, and the other guard forming piece 31 (second guard forming piece 31) having the same shape will be duplicated. Detailed explanation will be omitted.

As shown in FIG. 4, the guard forming piece 30 is a portion divided into a guard base end portion 38, a constriction portion 39, and a front end side portion 40 in this order from the rear end side.
That is, in the guard forming piece 30, the guard base end portion 38 forms the rear end side portion, and the constricted portion 39 and the front end side portion 40 form the front end side portion. The tip end side portion extends from the front end of the guard base end portion 38 toward the front upper side.
In the front end side portion of the guard forming piece 30, the constricted portion 39 forming the rear side portion is formed to be thinner than most of the front end side portion 40 forming the front side portion.

The upper surface of the guard base end portion 38 is a plane parallel to the horizontal plane, and the front side portion thereof becomes a portion that becomes thinner toward the front side.

The constricted portion 39 becomes thinner toward the front upper side, and becomes thicker toward the front upper side from the thinnest portion. The rear end portion of the constricted portion 39 is located on the rear side in the front-rear direction as compared with the blade of the blade body portion 3. Further, the front end portion of the constricted portion 39 is positioned on the front side in the front-rear direction as compared with the blade of the blade body portion 3.
The upper surface of the constricted portion 39 is a curved surface recessed in an oblique direction (lower front side).

The tip side portion 40 is a portion that becomes a curved surface that is rounded so that the upper surface is convex upward.

Here, the lower surface of the guard forming piece 30 extends from a portion of the lower surface of the guard base end portion 38 that is from the front side to a portion that is from the rear side of the lower surface of the front end side portion 40 via the lower surface of the constricted portion 39. A series of gently extending inclined surfaces are formed between them. A curved surface portion 45 is formed on a portion located on the front side of the inclined surface.
The curved surface portion 45 forms a curved surface extending from a portion of the lower surface of the front end side portion 40 that is from the front side to the front end surface of the guard forming piece 30. That is, on the front end side of the guard forming piece 30, a curved surface extending from the front end side on the lower surface to the lower side on the front surface is formed.

Here, the minimum value L1 of the thickness of the constricted portion 39 is preferably 1.5 mm or more and 4.0 mm or less, more preferably 1.5 mm or more and 3.0 mm or less, and 2.0 mm or more and 2. It is more preferably 5 mm or less.
The "thickness of the constricted portion 39" is the distance from the upper surface to the lower surface of the constricted portion 39, and is the length in the direction orthogonal to the extending direction of the constricted portion 39 in a plan view with the width direction as the line-of-sight direction. Is. Further, the "degree" referred to here includes an error of several percent, and the same applies to the description described later.

In addition, the minimum value L1 of the thickness of the constricted portion 39 is smaller than the minimum value of the thickness of the guard base end portion 38. Further, in the present embodiment, the minimum value L1 of the thickness of the constricted portion 39 is set to about 2.3 mm.

Further, the distance L2 (see FIG. 4) from the front end portion of the guard portion 6 to the blade in the front-rear direction is preferably 4.0 mm or more and 8.0 mm or less, and preferably 6.3 mm or more and 7.52 mm or less. More preferably, it is 6.5 mm or more and 7.0 mm or less.
It should be noted that this distance L2 is also the length of the front-rear direction component of the line segment (virtual line segment) connecting the front end portion of the guard portion 6 and the blade in the side view with the line-of-sight direction as the width direction. In other words, it is also the length of the component in the front-rear direction (longitudinal direction of the chisel 1) of the shortest line segment among the line segments (virtual line segments) connecting the front end portion of the guard portion 6 and the blade.

Further, when the shape of the blade is a so-called flat sword as in the present embodiment, the distance L2 is preferably 4.0 mm or more and 8.0 mm or less, and 6.0 mm or more and 7.0 mm or less. Is more preferable. In the present embodiment, this distance L2 is set to about 6.59 mm.

Further, in the side view with the line-of-sight direction as the width direction, the length L3 (see FIG. 4) of the line segment when the blade and the guard portion 6 are connected by a line segment (virtual line segment) extending in the vertical direction is 1. It is preferably 0.0 mm or more and 3.0 mm or less. Further, it is more preferably 1.25 mm or more and 1.37 mm or less, and further preferably 1.30 mm or more and 1.35 mm or less.
The length L3 is also the distance from the portion of the guard portion 6 directly above the blade to the blade in the side view with the line-of-sight direction as the width direction.

Further, when the shape of the blade is a so-called flat sword as in the present embodiment, the length L3 of this line segment is preferably 1.0 mm or more and 3.0 mm or less, and 1.0 mm or more and 2. It is more preferably 0 mm or less. In the present embodiment, the length L3 of this line segment is about 1.26 mm.

Here, as shown in FIG. 5, the guard connecting piece 32 is a portion that connects the ends of the two guard forming pieces 30 and 31 (one of which is not shown in FIG. 5) in the protruding direction, and is a guard portion. Most of the front end surface and the upper end surface of No. 6 are formed.

The distance L4 (see FIG. 5) in the vertical direction from the lower surface of the guard connecting piece 32 to the blade is preferably 2.0 mm or more and 5.0 mm or less, and preferably 2.5 mm or more and 4.5 mm or less. More preferably, it is 3.0 mm or more and 4.0 mm or less.
The distance L4 is also the length of the vertical component of the line segment (virtual line segment) connecting the lower surface of the guard connecting piece 32 and the blade in the side view with the line-of-sight direction as the width direction.
In the present embodiment, this distance L4 is set to about 3.67 mm.

Further, the average value of the moment of inertia of area of the cross section of the constricted portion 39 ^{is preferably 100 mm 4} or more and 300 mm ⁴ or less, ^{more preferably 150 mm 4} or more and 250 mm ⁴ or less, and 160 mm ⁴ or more and 200 mm ⁴ or less. It is more preferable to have.
The "cross section" referred to here is a cross section cut in a direction perpendicular to the extending direction (thickness direction of the constricted portion 39).

Here, the cross section of the front end portion of the guard base end portion 38 (see FIG. 6A) is the portion of the cross section of the guard base end portion 38 where the value of the moment of inertia of area is the smallest. .. The value of the moment of inertia of area at the front end portion is about ^{405.35 mm 4.}
That is, the average value of the moment of inertia of area in the cross section of the constricted portion 39 is lower than the value of the moment of inertia of area at the front end portion of the guard base end portion 38.
Further, the cross section of the narrowest portion of the constricted portion 39 (see FIG. 6B) is the portion of the cross section of the constricted portion 39 in which the value of the moment of inertia of area is the smallest. The value of the moment of inertia of area in this portion is about ^{181.98 mm 4.}

In the present embodiment, by forming the blade body portion 3 and the guard portion 6 as described above, the guard portion 6 is bent and deformed even if a force is applied to the guard portion 6, and the guard portion 6 is not easily damaged.
More specifically, as shown in FIG. 7, the chisel 1 is in an upright posture with the guard portion 6 facing downward in the protective posture, and is moved vertically downward and pressed against the lower flat surface. In this case, the guard portion 6 is not damaged even if the blade is pressed until it hits a flat surface.
The "upright posture" referred to here is a posture in which the longitudinal direction of the chisel 1 (the above-mentioned front-back direction) is the vertical direction.

That is, in the chisel 1 of the present embodiment, the front end portion of the guard portion 6 can be deformed so as to warp upward (left side in FIG. 7). Then, when deformed in this way, the front end portion of the guard portion 6 after deformation and the blade of the blade body portion 3 are in the same position in the front-rear direction (the state shown in FIG. 7B). In FIG. 7, it is possible to set the vertical direction).
Then, even if the guard portion 6 is deformed to such a state, the guard portion 6 is returned to its original shape by putting the guard portion 6 in a natural state (a state in which an external force is not applied and is separated from a flat surface). It is supposed to return.
As described above, when the guard portion 6 is deformed within the elastic range, the front end portion of the deformed guard portion 6 and each of the blades of the chisel 1 are on the same plane (orthogonal to the longitudinal direction of the chisel 1). It is possible to position it on the virtual surface). More specifically, elastic deformation is possible to warp a little more from this state.

That is, when the user uses the chisel 1 in an unusual posture and usage, and an unreasonable force is applied to the guard portion 6 due to this, another object (for example, the surface of the plywood to be engraved) or , The top plate of the desk, etc.) is likely to be pressed.
Therefore, in the present embodiment, even if the guard portion 6 is pressed against some surface, the guard portion 6 bends and deforms, and as a result, a portion different from the guard portion 6 (such as the blade of the blade body portion 3) comes into contact with the guard portion 6. It has a structure that contacts the surface. As a result, the guard portion 6 is prevented from being deformed by a certain amount or more, and the guard portion 6 can be prevented (suppressed) from being damaged. This means that in addition to the upright posture as described above, the posture in which the chisel 1 is tilted with respect to the contact surface (the angle between the virtual line extending in the longitudinal direction of the chisel 1 and the contact surface is 90 degrees or less). The same applies when pressed as a posture).

Further, in addition to the above-mentioned deformation such that the upper end of the guard portion 6 is warped, elastic deformation such that the upper end of the guard portion 6 moves downward is also possible.
That is, even when the chisel 1 is turned upside down and the chisel 1 presses the vicinity of the cutting edge against a flat surface in an inclined posture with respect to the contact surface, the guard portion 6 is deformed and the blade body portion 3 comes into contact with the flat surface. It has a structure to do.
The maximum deformation amount in the elastic range of the deformation in which the upper end of the guard portion 6 moves downward is smaller than the maximum deformation amount in the elastic range of the deformation in which the upper end moves upward.

However, even with the chisel 1 formed in this way, when the front end portion of the guard portion 6 is deformed so as to warp upward, it is conceivable that the chisel 1 will be deformed beyond the elastic range for some reason. Be done.

Therefore, the chisel 1 of the present embodiment has a structure capable of restoring the guard portion 6 to the original shape (or a shape close to the original shape) by shifting from the protective posture to the storage posture. There is. That is, even if the guard portion 6 is plastically deformed so as to warp upward, it can be restored to its original shape.

First, the chisel 1 in a normal state will be described. In the present embodiment, as shown in FIG. 8, the upper end portion of the guard portion 6 is located below the upper end portion of the handle inner space 20. Therefore, when the chisel 1 is shifted from the protective posture to the storage posture, the guard portion 6 does not come into contact with the front end surface of the handle portion 2.

In the front end side portion of the handle inner space 20, the shape of the upper part of the inner peripheral surface thereof is a shape substantially along the upper surface of the guard portion 6, and is a curved surface having a gentle downward slope toward the rear side. ..
Therefore, as shown in FIG. 8C, when the chisel 1 is in the retracted posture, the inner surface of the first handle forming piece 10 located above the guard portion 6 and the upper surface of the guard portion 6 are Some of them are in contact with each other, and most of the others are separated and opposed to each other. In the portions facing each other, the distance between the inner surface of the first handle forming piece 10 and the upper surface of the guard portion 6 in each portion is substantially the same.
This interval is 10% or less of the length of the guard portion 6 in the vertical direction, is a fine interval of several mm (for example, 3 mm) or less, and is an interval of 1 mm or less in the present embodiment.

On the other hand, as shown in FIG. 9A, when the upper end portion of the guard portion 6 is plastically deformed so as to warp, the upper end portion of the guard portion 6 is above the upper end portion of the in-handle space 20. Will be located in. That is, as described above, the guard portion 6 can be elastically deformed so that the front end portion after deformation and the blade have the same position in the front-rear direction. Therefore, when the guard portion 6 is deformed so as to warp beyond the elastic range, the upper end portion of the guard portion 6 is inevitably located above the upper end portion of the in-handle space 20.

In this state, when the chisel 1 is shifted from the protective posture to the stowed posture, the upper end portion of the guard portion 6 is in contact with the front end surface of the handle portion 2, as shown in FIG. 9B.
Then, if the operation of moving the guard portion 6 to the rear side is performed as it is, the guard portion 6 is in a state of being pressed against the front end surface and the upper part of the inner peripheral surface of the handle portion 2, and further to the rear side with respect to the guard portion 6. The force to go is added. For this reason, the guard portion 6 is subjected to a force in the direction in which the warp is corrected by the reaction force received from the handle portion 2.

Further, in the chisel 1 of the present embodiment, the blade of the chisel 1 is operated when the work of carving an object to be engraved such as a woodblock is performed by forming the blade body portion 3 and the guard portion 6 as described above. It is possible to bring it into contact with the object to be engraved in an easy-to-use posture (angle). In other words, the chisel 1 of the present embodiment regulates the contact angle of the blade in the protective posture so that the blade does not come into contact with the object to be engraved at an angle that is difficult to engrave.

That is, as shown in FIGS. 10 and 11, when the blade of the chisel 1 is brought into contact with the plane (target surface) located on the lower side, the virtual line extending along the longitudinal direction of the chisel 1 and the plane form a flat surface. The structure is such that the blade contacts the flat surface only when the angle α is within a predetermined range.
This predetermined range (range of the angle α formed) is preferably 15.0 degrees or more and 40.0 degrees or less, and particularly preferably 15.0 degrees or more and 35.0 degrees or less. Then, it is more preferably 16.05 degrees or more and 31.68 degrees or less, and further preferably 20.0 degrees or more and 30.0 degrees or less.

Further, when the shape of the blade is a so-called flat sword as in the present embodiment, the range of the angle α formed is preferably 17.16 degrees or more and 30.26 degrees or less, and 20.0 degrees or more. It is more preferably 30.0 degrees or less. In the present embodiment, this predetermined range is 17.16 degrees or more and 30.26 degrees or less.

Here, the range of the angle α formed is a range determined based on a sensory test or the like conducted in advance.
Specifically, as a result of the sensory tests conducted by the present inventors on various people, if the angle α formed exceeds 40.0 degrees and the chisel is erected, it is difficult for the majority of people to perform the work. It turned out to feel.
In addition, when the angle α to be formed is laid down at an angle lower than 15.0 degrees, problems such as the cutting edge slipping on the surface occur, and the work is immediately more difficult than when the angle is 15.0 degrees or more. It turned out to be.
Then, in the range where the formed angle α is 15.0 degrees or more, when the formed angle α is 35.0 degrees or less, many people feel that the work is easier than when the angle exceeds 35.0 degrees. It turned out that Furthermore, it was found that when the angle α formed is in the range of 20.0 degrees or more and 30.0 degrees or less, the majority of people feel that the work is easier to do.
Further, the range of the angle α formed is the range when the guard portion 6 maintains the shape (normal shape) in the natural state, and as a matter of course, the guard portion 6 is bent by forcibly applying a force. This is not the case.

Based on the above test results, in the chisel 1 of the present embodiment, when the angle α formed above falls below 17.16 degrees, the handle portion 2 comes into contact with the target surface as shown in FIG. 10 (a). The structure is such that contact with the target surface of the blade is prevented.

Then, when the angle α formed is within the above range, the blade comes into contact with the target surface as shown in FIGS. 10 (b), 10 (c), and 11 (a), respectively. In the postures shown in FIGS. 10 (b), 10 (c), and 11 (a), the respective angles α formed are 17.16 degrees, 22.0 degrees, and 30.26 degrees. ..

Here, in the chisel 1 of the present embodiment, as shown in FIGS. 10 (b) and 10 (c), when the formed angle α is set to a preferable range, the guard portion 6 is the target surface in most cases. It has a structure that does not come into contact with. For this reason, the guard portion 6 is preferable because it does not get in the way during engraving work.
Further, as shown in FIG. 11A, even when the blade and the guard portion 6 each come into contact with the target surface, the curved surface portion 45 is formed as described above, and the guard portion 6 and the target surface are formed. The contact area can be reduced. Therefore, when the blade is moved while being in contact with the target surface, the guard portion 6 does not hinder the movement of the blade, which is preferable.

Further, when the angle α formed above exceeds 30.26 degrees, as shown in FIG. 11B, the guard portion 6 prevents the blade from coming into contact with the target surface, and the blade does not come into contact with the target surface. It has become.

Therefore, when the chisel 1 was laid down on a flat surface and the chisel 1 was erected so that the value of the formed angle α gradually increased, the formed angle α became 17.16 degrees. The blade comes into contact with the flat surface in this state. Then, the blade remains in contact with the flat surface until the angle α formed is 30.26 degrees, and when the angle exceeds 30.26 degrees, the blade is separated from the flat surface.

That is, in the chisel 1 of the present embodiment, the contact angle of the blade can be regulated by the handle portion 2 and the guard portion 6. In other words, the guard portion 6 of the present embodiment not only functions as a protective member that protects the user's fingers and the like, but also functions as a regulating member that regulates the contact angle of the blade.

Here, as described above, the guard portion 6 of the present embodiment is capable of being deformed by a certain amount or more when a strong force is unexpectedly applied, and has a structure that prevents or suppresses damage to the guard portion 6 due to the deformation. It has become. Therefore, it is necessary to lower the elastic modulus by a certain amount or more and widen the elastic range by a certain amount or more.
On the other hand, since the guard portion 6 also functions as a regulating member for regulating the contact angle, it is necessary that the guard portion 6 is not deformed by a light force. Therefore, it is necessary to increase the elastic modulus by a certain level or more.
From this, the guard portion 6 of the present embodiment is a member having a high elastic modulus, an appropriate elastic modulus, and a wide elastic range by being formed as described above, as compared with the case where the guard portion 6 is formed by using rubber or the like as a raw material. It has become. That is, by using the above-mentioned main raw material and setting it within the above-mentioned L1 range, it is preferable to achieve both strength and safety.
Further, by setting the range of L2, L3, and L4 described above, the angle limitation described above is possible, and the guard portion is kept out of the way during work while keeping the blade sufficiently hidden. In other words, it is preferable in order to achieve both safety and good usability.

By the way, the chisel 1 of the present embodiment has a structure in which the handle portion 2 and the protective member 4 are engaged with each other to maintain the protective posture and the storage posture.

Specifically, the front locking piece portion 7b (see FIG. 2) of the protective member 4 engages with a recess (not shown) formed on the inner side surface (lower surface) of the first handle forming piece 10. , The structure is such that the protective posture is maintained.
That is, these front locking piece portions 7b and the recesses are portions that function as the first posture maintaining portion for maintaining the protective posture, and are in an engaged state during the protective posture when the protective member 4 is moved. It will be in a disengaged state in the stowed position.

On the other hand, the rear engaging protrusion 50 (see FIG. 12) formed on the rear side of the protective member 4 and the handle-side engaging protrusion 53 (see FIG. 13) formed on the second handle forming piece 11 , It is a part that functions as a second posture maintenance unit for maintaining the storage posture.

As shown in FIG. 12, the rear engaging protrusion 50 is a protruding portion formed on each of the two standing plate portions 26b and 26c of the protective member 4.
Here, in each of the two standing plate portions 26b and 26c, a groove portion 51 is formed at a position slightly forward of the rear end portion. In other words, each of the two standing plate portions 26b and 26c is a wall-shaped portion in which a part on the rear end side is missing.

The groove portion 51 is a notched groove-shaped portion extending from the lower end (upper end in FIG. 12) of the standing plate portions 26b and 26c to the upper end, and penetrates the standing plate portions 26b and 26c in the thickness direction. That is, the groove portion 51 divides the standing plate portions 26b and 26c into a majority on the front side and a part on the rear end side.

A rear engaging protrusion 50 is formed on the inner side surface of a part of the standing plate portions 26b, 26c on the rear end side. That is, the rear engaging protrusion 50 is formed at a position on the rear side of the groove 51.
The rear engaging protrusion 50 is a protruding portion formed so as to project inward in the width direction, and the portion on the protruding end side has a rounded shape. In other words, the rear engaging protrusion 50 is a protrusion-like portion having a substantially semicircular shape in a plan view and extending in the vertical direction.

Here, the two groove portions 51 formed in the two standing plate portions 26b and 26c are groove-shaped portions having the same shape, respectively, and are located at positions facing each other in the width direction (the width direction of the chisel 1 and the internal sliding body 26). It is formed in each. That is, each of the two groove portions 51 has the same position in the front-rear direction.
Further, the two rear engagement protrusions 50 are protrusion-like portions having the same shape, are formed at positions separated and opposed to each other in the width direction, and project in a direction approaching each other. Therefore, each of the two rear engaging protrusions 50 also has the same position in the front-rear direction.

As shown in FIG. 13, the handle-side engaging protrusion 53 is a protruding portion formed on the guide protrusion 19, and is formed on each of the two guide forming pieces 19a and 19b, both of which are guide forming pieces. It projects further outward from the outer surface in the width direction of 19a and 19b.

Each of the handle-side engaging protrusions 53 has a substantially semicircular shape in a plan view and extends in the vertical direction, and is formed slightly forward of the rear end.
That is, the two handle-side engaging projections 53 have the same shape, are formed at positions that are separated and opposed to each other in the width direction, and project in directions that are separated from each other. That is, each of the two handle-side engaging protrusions 53 has the same position in the front-rear direction.

Then, when shifting the chisel 1 from the protective posture to the stowed posture, as shown in FIG. 14A, when the protective member 4 is moved to the rear side (right side in FIG. 14), two The rear engaging projection 50 is in contact with the different handle-side engaging projections 53 from the front side.

Specifically, in the chisel 1 of the present embodiment, the protective member 4 is inserted in the front-rear direction with the guide protrusion 19 fitted in the engaging recess 35 (see FIGS. 2, 12, etc.) of the protective member 4. It has a structure to move to.
That is, the structure is such that the operating protrusion 7a is inserted into the window portion 10a, and the guide protrusion 19 is fitted into the engaging recess 35, thereby restricting the movement of the protective member 4 in the left-right direction.
That is, the set consisting of the window portion 10a and the operating protrusion 7a and the set consisting of the engaging recess 35 and the guide protrusion 19 all function as guides when moving the protective member 4 in the front-rear direction.

Here, by fitting the guide protrusions 19 into the engaging recesses 35, as shown in FIG. 14, the two guide forming pieces 19a and 19b are positioned between the two standing plates 26b and 26c. It has become.
That is, the outer surface of one guide forming piece 19a in the width direction and the inner surface of one of the standing plate portions 26b in the same direction are separated and opposed to each other with a fine gap. Further, the outer surface of the other guide forming piece 19b and the inner surface of the other standing plate portion 26c are also in a state of being separated and opposed to each other with a fine gap.

Therefore, when the protective member 4 is moved to the rear side, one rear engaging projection 50 abuts on one handle side engaging projection 53 from the front, and the other rear engaging projection 50 comes into contact with the other. It is in a state of being in contact with the handle side engaging protrusion 53 from the front (see FIG. 14A).
Then, by further moving the protective member 4 to the rear side from this state, each of the two rear engagement protrusions 50 is located outside in the width direction of the two handle side engagement protrusions 53. (See FIG. 14 (b)).

That is, the two guide forming piece portions 19a and 19b have groove portions 51 formed as described above (see FIG. 12), and can be elastically deformed so that parts on the rear end side move away from each other. It has become. Further, as described above, both the rear engaging protrusion 50 and the handle side engaging protrusion 53 have a rounded shape.
Therefore, when a force toward the rear side is further applied to the protective member 4 in a state where the rear side engaging protrusion 50 is in contact with the handle side engaging protrusion 53 from the front, the rear side engaging protrusion 50 is engaged with the handle side. It moves so as to get over the handle side engaging protrusion 53 while maintaining the state of contact with the joint protrusion 53.

That is, the rear engaging protrusion 50 is located on the outside of the handle-side engaging protrusion 53 (outside in the width direction of the chisel 1) from the state of being located in front of the handle-side engaging protrusion 53, and is on the handle side. It is in a state of riding on the engaging protrusion 53.
That is, the rear end portions of the two guide forming pieces 19a and 19b are elastically deformed so as to move away from each other, and the rear end side portions of the two guide forming pieces 19a and 19b are opened more than usual. It becomes a state. Then, one rear engaging projection 50 is located outside the one handle-side engaging projection 53 in the width direction, and the other rear engaging projection 50 is located outside the other handle-side engaging projection 53. It is in a state of being located on the outside in the width direction (see FIG. 14B).

Further, by moving the protective member 4 to the rear side, the two rear engaging projections 50 get over the different handle-side engaging projections 53 and are located behind the handle-side engaging projections 53 (). (See FIG. 14 (c)), the shift to the storage posture.

In this state, the protective member 4 is locked by the two handle-side engaging protrusions 53, and the two handle-side engaging protrusions 53 are protected unless the protective member 4 is moved forward by a certain force or more. Prevents the member 4 from moving forward. That is, the two handle-side engaging protrusions 53 function as stoppers to prevent the two rear-side engaging protrusions 50 from moving forward, thereby unintentionally changing the posture from the stowed posture to the protective posture. Is blocked.
When changing from the stowed posture to the protective posture, by moving the protective member 4 forward with a force equal to or higher than a certain level, the two rear engaging protrusions 50 move in the opposite direction to the above, and the handle side. The engaging protrusion 53 is overcome from the rear side.

In the above embodiment, an example of restricting the range of the angle α formed by the handle portion 2 and the guard portion 6 is shown, but the shape of the guard portion 6 and the like are changed to regulate the range of the angle α formed only by the guard portion 6. You may.

In the above-described embodiment, the example in which the chisel 1 is a flat sword has been described, but the shape of the blade portion 3 may be changed as appropriate. That is, the shape is not limited to the so-called flat sword, but may be a so-called stamped sword (cutting sword), round sword, shallow round sword, triangular sword, flat round sword, round curved sword, or the like.
When the blade has a shape extending in a direction including a front-rear direction component like a so-called stamp sword, the position of the blade in the front-rear direction at the above-mentioned distance L2 or the like is assumed to be the front end portion.
Further, when the blade has a shape extending in a direction including a vertical component like a so-called triangular sword, the position of the blade in the vertical direction with the above-mentioned line segment length L3 or the like is the lower end portion. And.

Here, the chisel 1 of the above-described embodiment is assumed to have the blade surface positioned on the engraving object side during normal use. However, for example, in a chisel having a blade shaped like a so-called stamp sword, it is assumed that the back of the blade is located on the side of the object to be engraved in normal use. That is, the chisel formed is not limited to the one in which the blade surface is located on the lower side as in the above-described embodiment, and the blade back may be located on the lower side.

When the shape of the blade is a so-called triangular sword, the above-mentioned distance L2 is preferably 4.0 mm or more and 8.0 mm or less, and more preferably 6.0 mm or more and 7.0 mm or less.
Further, it is particularly preferable that the distance L2 is about 6.3 mm.

Further, when the shape of the blade is a so-called triangular sword, the length L3 of the above-mentioned line segment is preferably 1.0 mm or more and 3.0 mm or less, and more preferably 1.0 mm or more and 2.0 mm or less. preferable. Further, it is particularly preferable that the length L3 of the line segment is about 1.25 mm.

When the shape of the blade is a so-called triangular sword, the range of the above-mentioned angle α is preferably 15 degrees or more and 40 degrees or less, and more preferably 21 degrees or more and 31.68 degrees or less.

When the shape of the blade is a so-called round sword, the above-mentioned distance L2 is preferably 4.0 mm or more and 8.0 mm or less, and more preferably 6.0 mm or more and 7.0 mm or less.
Further, it is particularly preferable that the distance L2 is about 6.79 mm.

Further, when the shape of the blade is a so-called round sword, the length L3 of the above-mentioned line segment is preferably 1.0 mm or more and 3.0 mm or less, and more preferably 1.0 mm or more and 2.0 mm or less. preferable. Further, it is particularly preferable that the length L3 of the line segment is about 1.37 mm.

When the shape of the blade is a so-called round sword, the range of the above-mentioned angle α is preferably 15 degrees or more and 40 degrees or less, and more preferably 17.25 degrees or more and 29.78 degrees or less. ..

When the shape of the blade is a so-called small round sword, the above-mentioned distance L2 is preferably 4.0 mm or more and 8.0 mm or less, and more preferably 6.0 mm or more and 8.0 mm or less.
Further, it is particularly preferable that the distance L2 is about 7.52 mm.

Further, when the shape of the blade is a so-called small round sword, the length L3 of the above-mentioned line segment is preferably 1.0 mm or more and 3.0 mm or less, and more preferably 1.0 mm or more and 2.0 mm or less. preferable. Further, it is particularly preferable that the length L3 of the line segment is about 1.33 mm.

When the shape of the blade is a so-called small round sword, the range of the above-mentioned angle α is preferably 15 degrees or more and 40 degrees or less, and more preferably 16.05 degrees or more and 29.77 degrees or less. ..

Subsequently, Examples and Comparative Examples of the present invention will be described.
As an example and a comparative example, a durability test was carried out on a chisel according to the above-described embodiment and a commercially available chisel, and the durability performance of the guard portion was compared.
(Example 1)

A chisel was prepared according to the above embodiment and a durability test was carried out.
In the test, as shown in FIG. 15, the guard portion was placed upright with the guard portion facing upward, and the lower end portion was fixed with a vise. That is, the chisel was fixed in a posture in which the front-back direction was along the vertical direction. Further, as shown in FIG. 15, the lower end surface of the sensor is brought into contact with the front end portion (upper end portion at the start of the test) of the guard portion, and this lower end surface is moved downward at a speed of 50 mm / min. Bending strength and bending strength were measured.
The lower end surface of the sensor is a surface parallel to the horizontal plane. Further, the area of the lower end surface of the sensor was set to be sufficiently larger than the plan view area of the chisel in the upright posture, and the test was started from a state where the guard portion was in contact with the vicinity of the center thereof.
Then, when the lower end surface of the sensor came into contact with the blade, the measurement was completed.

The relationship between the moving distance of the front end portion of the guard portion and the load applied to the guard portion until the end of the measurement is as shown in the graph of FIG. In addition, when the chisel was put into a natural state after the test was completed, the guard part was restored to its original shape.
In this durability test, the shape of the guard portion is deformed so as to warp, whereas the load is always applied to the lower side in the vertical direction. Therefore, despite the deformation within the elastic range, the maximum value of the load (about 4.5 kgf) is measured when the moving distance is about 3 mm, and then it is measured even if the moving distance increases. The value of the load does not change significantly.
Therefore, the substantial strength is at or above the point A corresponding to the moving distance when the blade hits on the line segment obtained by extending the slope of the graph at the initial stage of the experiment as it is.
(Comparative Example 1)

A chisel equipped with a commercially available protective member was prepared. Then, a part of the protective member covered the periphery of the blade, and the same durability test as in Example 1 was carried out.
The result of the test is as shown in the graph of FIG. Further, when the moving distance was about 4.5 mm, the maximum value of the load (about 6.6 kgf) was measured (see point B in the figure), and the protective member was broken and damaged. That is, the protective member was broken and damaged before the blade came into contact with the sensor.
(Comparative Example 2)

A commercially available chisel equipped with a protective member, and a chisel having a different manufacturer and shape from Comparative Example 1 was prepared. Then, a part of the protective member covered the periphery of the blade, and the same durability test as in Example 1 was carried out.
The result of the test is as shown in the graph of FIG. In the chisel of Comparative Example 2, when the protective member was deformed until the blade abuted on the sensor, the protective member was plastically deformed and could not be restored.

1 Chisel 2 Handle 3 Blade 4 Protective member 20 Handle space 20a Opening 30, 31 Guard forming piece 32 Guard connecting piece 38 Guard base end 39 Constriction 40 Tip side 45 Curved angle α

Claims (10)

A chisel that includes a handle, a blade attached to the handle, and a protective member, and can be used by bringing the blade formed on the blade into contact with the target surface.
The protective member has a guard portion that can be arranged at least around the blade body portion.
The guard portion can be in a protective posture located around the blade.
A curved surface extending from the lower surface to the front surface is formed on the front end side of the guard forming piece.
In the protective posture, the longitudinal direction of the handle portion is set to be inclined with respect to the target surface, and the blade can be brought into contact with the target surface by setting the posture to be tilted at a predetermined angle.
At least the guard portion regulates the range of the angle at which the blade and the target surface can come into contact with each other.
In the protective posture, the blade comes into contact with the target surface when the angle formed by the virtual line extending in the longitudinal direction of the handle portion and the target surface is in the range of 15 degrees or more and 40 degrees or less .
When the angle formed is within the range of 15 degrees or more and 40 degrees or less, the state in which the guard portion does not contact the target surface and the state in which the guard portion contacts the target surface depend on the angle of the angle formed. A chisel characterized in that, in a state where the guard portion is in contact with the target surface together with the blade, the curved surface is in contact with the target surface. When the longitudinal direction of the handle is the front-back direction and the blade side is the front side,
The distance from the front end portion of the guard portion to the blade in the front-rear direction in the protective posture is L2.
The length of the virtual line segment when the blade and the guard portion are connected by a virtual line segment extending in the vertical direction in the state where the protective posture is set and the front-back direction is parallel to the horizontal plane is L3. When you do
The chisel according to claim 1, wherein the L2 is 4.0 mm or more and 8.0 mm or less, and the L3 is 1.0 mm or more and 3.0 mm or less. The longitudinal direction of the handle is the front-back direction, and the blade side is the front side.
When it is one end side in a direction orthogonal to the front-rear direction, and the target surface side is the lower side and the opposite side is the upper side when the blade is in contact with the target surface as the protective posture.
The lower end of the handle is located below the lower end of the guard.
The chisel according to claim 1 or 2, wherein a portion of the lower end portion of the handle portion that is around the front end side also regulates the range of the angle. The longitudinal direction of the handle is the front-back direction, and the blade side is the front side.
When it is one end side in a direction orthogonal to the front-rear direction, and the target surface side is the lower side and the opposite side is the upper side when the blade is in contact with the target surface as the protective posture.
The guard portion has two guard forming pieces and a guard connecting piece extending by connecting the front end sides of the two guard forming pieces to each other, and in the protective posture, the front end and both side ends of the blade portion. It extends continuously in a semi-annular shape on the outside,
The guard forming piece, the chisel according to one of claims 1 to 3, characterized in that in the protective position is a portion extending longitudinally in laterally outward of said blade body portion. The longitudinal direction of the handle is the front-back direction, and the blade side is the front side.
When it is one end side in a direction orthogonal to the front-rear direction, and the target surface side is the lower side and the opposite side is the upper side when the blade is in contact with the target surface as the protective posture.
The guard portion has two guard forming pieces.
In the protective posture, the blade body portion is located between the two guard forming pieces, and the guard forming piece extends in the front-rear direction on the lateral outer side of the blade body portion.
The guard forming piece has a rear end side portion extending in the front-rear direction and a front end side portion extending in the upward direction toward the front.
The tip end side portion of the guard forming piece is formed with a constricted portion that is more constricted than the other portions, and the tip end side portion of the guard forming piece can be elastically deformed. The chisel according to any one of claims 1 to 4. The chisel according to claim 5, wherein the constricted portion is formed in a portion of the guard forming piece from the rear end of the distal end side portion. The average value of the moment of inertia of area of the cross section of the constricted portion is 100 mm ⁴ or more and 300 mm ⁴ or less, which is smaller than the minimum value of the moment of inertia of area of the cross section at the rear end side portion of the guard forming piece. The chisel according to claim 5 or 6. The rear end portion of the constricted portion is located on the rear side in the front-rear direction with respect to the blade, and the front end portion of the constricted portion is located on the front side in the front-rear direction with respect to the blade. The chisel according to any one of claims 5 to 7. The handle portion is formed with an internal space inside the handle that can store at least a part of the guard portion.
The space inside the handle has an opening portion on the front side of the handle portion, and the upper end portion of the opening portion is located slightly above the upper end portion of the guard portion, or the guard It is formed so that the upper end of the part and the vertical position are the same.
The protective member is attached so as to be movable relative to the handle portion.
By moving the protective member, it is possible to switch between the protective posture and the storage posture in which at least a part of the guard portion is stored in the space inside the handle.
In the storage posture, each portion of the upper surface of the guard portion located in the inner space of the handle and the upper surface of the inner space of the handle face each other or are in contact with each other with a slight gap. The chisel according to any one of claims 5 to 8. The protective member is a resin molded body formed of polyacetal and polyamide as main raw materials.
The chisel according to any one of claims 1 to 9, wherein the guard portion is integrally molded with the protective member.

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