JP2014189990A - Screw joint structure of excavation tool, and excavation tool - Google Patents

Abstract

A screw joint structure for an excavating tool that can easily recognize the use limit of a screw in a threaded joint structure without requiring skill of an operator and reliably prevent damage to the tool, and uses the same. Providing drilling tools.
A male screw 5 formed with a male screw portion 6 and a female screw 21 formed with a female screw portion 22 for connecting a drill bit and a drill rod, the drill rods or between the drill rod and a coupling are provided. In the screw joint structure 1 of an excavating tool screwed together, the female screw 21 has a skirt portion 23 in which the female screw portion 22 is formed on the inner periphery, and the skirt portion 23 includes the skirt portion 23. A detection hole 27 is formed in the outer periphery of the portion 23 and extends toward the female screw portion 22, and a bottom surface 28 of the detection hole 27 approaches the female screw portion 22 without opening in the female screw 21. It is arranged.
[Selection] Figure 2

Description

  The present invention relates to a drilling bit for excavating the ground and a drilling rod for transmitting thrust, striking force and rotational force from the drilling device to the drilling bit, or a coupling for connecting the drilling rods, or the drilling rod and the drilling rod. The present invention relates to a screw joint structure of an excavation tool in which a male screw formed with a male screw part and a female screw formed with a female screw part are screwed together, and an excavation tool using the same. .

  As an excavation tool for excavating the ground, a drill bit provided with a plurality of button tips made of a hard material such as cemented carbide at the tip, and a drill rod connected to the base end side of the drill bit It has been known. The excavation tool digs through the ground by transmitting the thrust, striking force, and rotational force from the excavator to the excavation bit at the tip via a plurality of excavation rods (see, for example, Patent Document 1 below) ).

  In such a drilling tool, a male screw (male screw shaft) and a female screw part are formed to connect a drilling bit and a drilling rod, between drilling rods, or a drilling rod and a coupling. It has a screw joint structure in which a female screw (female screw hole) is screwed together. The female screw has a cylindrical skirt portion having a female screw portion formed on the inner periphery, and the skirt portion has a drill bit, a drill rod (on the female screw side) having a female screw portion, or Formed in the coupling.

JP 2007-162220 A

However, the conventional drilling tools have the following problems.
In the threaded joint structure of an excavation tool, the external thread part and the internal thread part are worn by excavation. The most ideal form of screw life is to replace the tool when the thread is worn and the connection by screwing cannot be maintained. However, it is difficult to judge whether or not the use limit has been reached even if the wear state of the thread is visually confirmed, and skill is required. In reality, it is often used continuously in a state where the usage limit is exceeded. In this case, generally, a crack is generated on the bottom surface of the screw valley, and the crack propagates in the circumferential direction to break the screw.

  When the screw breaks in this way, a sudden load caused by the break is applied to the tool, not only damaging the excavation tool, but also applying a load to the excavator body as well. In addition, when a fracture occurs in the drilling hole, the tool from the fractured part is left in the drilling hole, and it is necessary to collect the fractured part, or the drilled drilling hole itself is wasted. May be frustrated.

  The present invention has been made in view of such circumstances, and makes it possible to easily recognize the use limit of a screw in a screw joint structure without requiring skill for an operator, and reliably prevent damage to a tool. An object of the present invention is to provide a threaded joint structure for a drilling tool, and a drilling tool using the same.

In order to solve such problems and achieve the above object, the present invention proposes the following means.
That is, according to the present invention, a male screw formed with a male screw part and a female screw formed with a female screw part, which connect the drilling bit and the drilling rod, the drilling rods, or the drilling rod and the coupling, are screwed together. A threaded joint structure for an excavation tool, wherein the female screw has a skirt portion having the female screw portion formed on an inner periphery thereof, and the skirt portion opens to an outer periphery of the skirt portion. A detection hole extending toward the female screw portion is formed, and a bottom surface of the detection hole is arranged close to the female screw portion without opening in the female screw.
Moreover, the excavation tool of the present invention is characterized by including the above-described screw joint structure for an excavation tool.

  According to the threaded joint structure for an excavation tool and the excavation tool including the excavation tool according to the present invention, the cylindrical skirt portion forming the peripheral wall of the female screw (female screw hole) is open to the outer periphery of the skirt portion. Since the inner peripheral female screw portion is provided with a detection hole-like detection hole that does not penetrate and the bottom surface of the detection hole is disposed close to the female screw portion, the following effects can be obtained.

That is, it can be set so that the bottom surface of the detection hole opens into the female screw when the male screw portion and the female screw portion are worn by excavation and the screw reaches the use limit.
Specifically, the screw wears out, and the detection hole opens into the female screw portion to become a through hole. For example, the inside of the fluid coupling hole formed along the axial direction of the male screw inside the screw joint structure. A fluid such as water (drilling water) flowing through the pipe flows from the space between the male screw portion and the female screw portion to the outer periphery of the skirt portion through the detection hole (through hole). As the fluid flows out of the detection hole in this manner, the operator can visually recognize from the outside that the threaded joint structure has reached the use limit.
In addition, when the screw between the female screw and the male screw is released with the excavation tool pulled out from the excavation hole, the operator looks into the inside of the detection hole and whether the bottom surface is open in the female screw. It is possible to determine whether or not the screw has reached the use limit by confirming whether or not.

  Then, by replacing the threaded joint structure that has reached the limit of use with another new threaded joint structure, it is possible to avoid a situation where the screw breaks, so that the broken tool part can be removed from the drilled hole. It is possible to prevent the work to be collected or the drilling hole itself from being wasted. Moreover, since the great load applied to the excavation tool and the load applied to the excavator main body when the screw is broken can be prevented, the effect of extending the life of the excavation tool and the excavator can be expected.

  As described above, according to the present invention, the use limit of the screw in the threaded joint structure can be easily recognized without requiring skill for the operator, and the breakage of the tool can be surely prevented.

  Further, in the threaded joint structure for an excavation tool according to the present invention, a fluid circulation hole is formed in the threaded joint structure along the axial direction of the male screw, and the fluid circulation hole is connected to the male threaded portion. It is good also as communicating between the said internal thread part.

  In this case, when the screw reaches the use limit, the detection hole opens into the female screw to become a through hole, and the fluid flowing in the fluid circulation hole is inserted between the male screw portion and the female screw portion. Since it flows out to the outer periphery of the skirt part through the (through hole), the operator can recognize from the outside that the screw joint structure has reached the use limit of the screw without disassembling the screw joint structure. .

  Further, in the threaded joint structure for an excavation tool according to the present invention, in the longitudinal sectional view of the skirt portion, the thread of the female screw portion protrudes toward the inside in the radial direction perpendicular to the axial direction of the male screw. And a pair of slopes that are continuous with both ends of the top portion along the axial direction and gradually extend outward in the radial direction from the top portion in the axial direction, and a bottom surface of the detection hole May be arranged radially outside the top and arranged between the pair of slopes.

In this case, the screw thread of the female screw part and the screw thread of the male screw part screwed to the female screw part are also screws having a top part and a pair of inclined surfaces, respectively.
Since the bottom surface of the detection hole is disposed radially outside the top of the thread of the female screw portion and between the pair of inclined surfaces, the screw does not reduce the rigidity of the screw thread by the detection hole. When the thread comes into contact with the thread of the male thread and wears, the bottom surface of the detection hole is easily opened into the female thread reliably.

  Further, in the threaded joint structure for an excavation tool according to the present invention, the top portion has a flat surface parallel to the axial direction in the longitudinal cross-sectional view of the skirt portion, and the pair of inclined surfaces are respectively linear. It is good.

  In this case, the screw thread of the female screw part and the screw thread of the male screw part engaged with the female screw part are also trapezoidal screws (so-called T screws) each having a flat surface (top) and a pair of inclined surfaces.

  In the threaded joint structure for an excavation tool according to the present invention, the top portion and the pair of slopes may have a wavy curved shape as a whole in a longitudinal sectional view of the skirt portion.

  In this case, the screw thread of the female screw part and the screw thread of the male screw part screwed to the female screw part are also round screws (so-called rope screws) each having a cross-sectionally curved waveform.

  According to the threaded joint structure and the drilling tool of the excavating tool of the present invention, it is possible to easily recognize the use limit of the screw in the threaded joint structure without requiring the skill of an operator, and reliably prevent the tool from being damaged. it can.

It is a side view of a excavation bit and a excavation rod connected by the screw joint structure of an excavation tool concerning one embodiment of the present invention. It is the sectional side view to which the A section in FIG. 1 was expanded. FIG. 3 is a diagram for explaining a state in which a screw is worn and reaches a use limit in the threaded joint structure of the excavating tool of FIG.

  Hereinafter, a threaded joint structure 1 for a drilling tool and a drilling tool 10 using the same according to an embodiment of the present invention will be described with reference to the drawings. The present invention relates to a male screw (male screw shaft) formed with a male screw portion and a female screw formed with a female screw portion, which connects a drill bit and a drill rod, drill rods or between a drill rod and a coupling. The screw joint structure of the excavation tool and the excavation tool in which the female screw hole) is screwed, and in this embodiment, the screw joint structure 1 and the excavation tool formed by screwing the excavation bit 2 and the excavation rod 3 10 will be described.

The excavation tool 10 of this embodiment is mounted on an excavator and drills an excavation hole in the ground. As shown in FIG. 1, excavation that is disposed at the tip of the excavation tool 10 and excavates the ground. A bit 2 and a drill rod 3 connected to the base end side (excavator side) of the excavator bit 2 and transmitting thrust, striking force, and rotational force from the excavator to the excavator bit 2 are provided. In the illustrated example, only one excavation rod 3 is shown, but a plurality of excavation rods 3 are successively added according to the depth of the excavation hole to be drilled. .
Here, the excavation bit 2 and the excavation rod 3 are disposed coaxially with an axis O of a male screw 5 described later as a common axis. In this specification, the excavation bit 2 side (left side in FIG. 1) along the axis O direction is referred to as a distal end side, and the excavation rod 3 side (right side in FIG. 1) along the axis O direction is referred to as a proximal end side. A direction orthogonal to the axis O is referred to as a radial direction, and a direction around the axis O is referred to as a circumferential direction. Of the circumferential directions, the direction in which the excavation rod 3 is rotated by the excavator during excavation is referred to as the tool rotation direction.

  The excavation rod 3 extends along the direction of the axis O, and is disposed at a rod body 4 having a cross section orthogonal to the axis O, for example, a hexagonal shape, and a tip portion (left side in FIG. 1) of the rod body 4, And an external thread 5 extending about the axis O as a central axis. The male screw 5 has a smaller diameter than the outer diameter of the rod body 4.

  A fluid circulation hole 11 is formed inside the excavation rod 3 along the direction of the axis O. The fluid circulation hole 11 penetrates the excavation rod 3 in the direction of the axis O and extends over the rod body 4 and its male screw 5. The front end of the fluid circulation hole 11 is opened on the end face of the male screw 5 facing the direction of the axis O. In this embodiment, the front end face 12 of the male screw 5 is opened. In the fluid circulation hole 11, a fluid such as water (perforated water) is circulated from the proximal end side to the distal end side.

A male screw portion 6 is formed on the outer periphery of the male screw 5.
In the longitudinal cross-sectional view of the male screw 5 shown in FIG. 2, the screw thread 7 of the male screw part 6 has a top part 7a projecting outward in the radial direction (upper side in FIG. 2), and the axis O direction of the top part 7a. And a pair of slopes 7b, 7c extending gradually toward the inner side (lower side in FIG. 2) in the radial direction as they are separated from the top portion 7a in the axis O direction (left-right direction in FIG. 2). doing. In the illustrated example, of the pair of inclined surfaces 7b and 7c, the surface facing the base end side in the axis O direction (the right side in FIG. 2) is the inclined surface 7b and faces the distal end side in the axis O direction (the left side in FIG. 2). The surface is a slope 7c. In the present embodiment, in the longitudinal sectional view shown in FIG. 2, the top portion 7a has a flat surface parallel to the direction of the axis O, and the pair of inclined surfaces 7b and 7c are linear. Moreover, in this longitudinal cross sectional view, the connection part of the top part 7a and the pair of slopes 7b, 7c in the screw thread 7 is formed in a convex curve shape.

  Further, a screw valley bottom surface 8 is formed between the screw threads 7 adjacent to each other in the axis O direction in the male screw portion 6. In the longitudinal sectional view shown in FIG. 2, the thread valley bottom surface 8 is a flat surface parallel to the axis O direction, and one of the screw threads 7 adjacent to each other in the axis O direction is located on the proximal end side. The slope 7c of the screw thread 7 is connected to the slope 7b of the other screw thread 7 located on the tip side. In this longitudinal cross-sectional view, the connecting portions of the thread valley bottom surface 8 and the pair of inclined surfaces 7b and 7c sandwiching the thread valley bottom surface 8 from the axis O direction are each formed in a concave curve shape.

  As shown in FIG. 1, the outer shape of the excavation bit 2 is formed in a substantially cylindrical shape, and the tip side portion thereof is a cutting edge portion 13 that directly collides with the ground and drills the ground. The cutting edge portion 13 is formed such that the outer diameter increases toward the distal end side, and a circular face surface 14 perpendicular to the axis O is formed on the distal end surface portion, and the face surface 14 A gauge surface 15 is formed which is connected to the outer peripheral side to form a ring shape, and is inclined toward the base end side as it goes radially outward.

  The face surface 14 is made of a hard material such as cemented carbide, and a plurality of button chips 16 each having a hemispherical tip portion and a columnar shape other than the tip portion are disposed. The button chip 16 has a central axis orthogonal to the face surface 14 and is embedded in the face surface 14 with the tip projecting from the face surface 14. The face surface 14 is formed with a plurality of openings (not shown) of fluid flow holes 17 communicating with female screws 21 described later.

  On the gauge surface 15, a plurality of large-diameter button chips 18 made of a hard material such as cemented carbide and having an outer diameter one step larger than that of the button chip 16 embedded in the face surface 14 are arranged. The large-diameter button chip 18 has a hemispherical tip portion and a cylindrical portion other than the tip portion, and is embedded in the gauge surface 15 with the tip portion protruding from the gauge surface 15. Yes. The central axis of the large-diameter button chip 18 is disposed so as to be orthogonal to the gauge surface 15.

  In the example shown in FIG. 1, the gap between the large-diameter button chips 18 adjacent in the circumferential direction on the gauge surface 15 includes a wide portion and a narrow portion, which are alternately arranged in the circumferential direction. . A first portion of the gap between the large-diameter button chips 18 adjacent in the circumferential direction is formed with a first cutting waste discharge groove 19 that is recessed inward in the radial direction and extends toward the proximal end side. Is formed with a second drilling waste discharge groove 20 having a depth smaller than that of the first drilling waste discharge groove 19 and a short length in the direction of the axis O.

  The excavation bit 2 is formed with a female screw 21 that opens toward the proximal end and extends along the axis O direction. The female screw 21 is formed at a portion other than the cutting edge portion 13 of the excavation bit 2. The female screw 21 has a cylindrical skirt portion 23 in which a female screw portion 22 is formed on the inner periphery. The male screw 5 is inserted into the skirt portion 23, and the female screw portion 22 and the male screw portion 6. And the excavation rod 3 and the excavation bit 2 are connected.

  The skirt portion 23 has a bottomed cylindrical shape, and the distal end surface 12 of the male screw 5 of the excavation rod 3 is in contact with the bottom surface 24 that is located at the distal end portion of the skirt portion 23 and faces the proximal end side. ing. Further, in the state where the male screw 5 is inserted into the skirt portion 23 in this way, the fluid flow hole 11 opened to the front end surface 12 of the male screw 5 and the portion other than the skirt portion 23 (the cutting edge portion) of the excavation bit 2 13) The fluid circulation holes 17 that extend along the axis O direction and open to the bottom surface 24 communicate with each other. That is, the fluid circulation holes 11 and 17 are continuously provided so as to extend along the direction of the axis O in the threaded joint structure 1 of the present embodiment, and the fluid circulation holes 11 and 17 are provided with the male screw 5. The male screw portion 6 and the female screw portion 22 communicate with each other through the front end surface 12 and the bottom surface 24 of the female screw 21.

  In a longitudinal sectional view of the skirt portion 23 shown in FIG. 2, the screw thread 25 of the female screw portion 22 has a top portion 25 a that protrudes radially inward (lower side in FIG. 2), and an axis O of the top portion 25 a. A pair of slopes 25b and 25c extending toward the outer side in the radial direction (upper side in FIG. 2) as they are separated from each other in the direction in the direction of the axis O (left and right direction in FIG. 2). doing. In the illustrated example, of the pair of inclined surfaces 25b and 25c, the surface facing the base end side in the axis O direction (right side in FIG. 2) is the inclined surface 25b and faces the distal end side in the axis O direction (left side in FIG. 2). The surface is a slope 25c. In the present embodiment, in the longitudinal sectional view shown in FIG. 2, the top portion 25a has a flat surface parallel to the direction of the axis O, and the pair of inclined surfaces 25b and 25c are linear. Moreover, in this longitudinal cross sectional view, the connection part of the top part 25a and the pair of slopes 25b, 25c in the screw thread 25 is formed in a convex curve shape.

  Further, a thread valley bottom surface 26 is formed between the thread threads 25 adjacent to each other in the axis O direction in the female thread portion 22. In the longitudinal sectional view shown in FIG. 2, the screw valley bottom surface 26 is a flat surface parallel to the axis O direction, and one of the screw threads 25 adjacent to each other in the axis O direction is located on the proximal end side. The slope 25c of the screw thread 25 is connected to the slope 25b of the other screw thread 25 located on the tip side. In this longitudinal cross-sectional view, the connecting portion of the thread valley bottom surface 26 and a pair of inclined surfaces 25b, 25c sandwiching the thread valley bottom surface 26 from the axis O direction is formed in a concave curve shape.

  The male screw portion 6 and the female screw portion 22 of the present embodiment each have a top portion 7a, 25a and a pair of inclined surfaces (7b, 7c), (25b, 25c) each having a flat surface, and are formed in an isosceles trapezoidal shape in cross section. A trapezoidal screw (a so-called T screw) is formed.

  As shown in FIGS. 1 and 2, the skirt portion 23 of the female screw 21 is formed with a stop hole-like detection hole 27 that opens to the outer periphery of the skirt portion 23 and extends toward the female screw portion 22. The bottom surface 28 of the detection hole 27 is arranged close to the female screw portion 22 without opening in the female screw 21. In the example shown in the drawing, the detection hole 27 extends along the radial direction, and is disposed at the tip side portion along the axis O direction of the skirt portion 23 of the female screw 21.

  2, the bottom surface 28 of the detection hole 27 is disposed on the radially outer side of the top portion 25a of the screw thread 25, and is disposed between the pair of inclined surfaces 25b and 25c. Specifically, the bottom surface 28 of the detection hole 27 is located radially inward of the screw valley bottom surface 26, and the axis O between the inclined surfaces 25b and 25c is spaced from the pair of inclined surfaces 25b and 25c at equal intervals. It is arranged at the center of the direction. The cross-sectional shape of the detection hole 27 is circular, and the bottom surface 28 of the detection hole 27 is gradually reduced in diameter toward the inner side in the radial direction of the skirt portion 23.

  The depth of the detection hole 27 (the depth drilled from the outer periphery toward the inner periphery) is determined when the male screw portion 6 and the female screw portion 22 are worn by excavation and the screw reaches the use limit. As shown in FIG. 3, the bottom surface 28 of the detection hole 27 is set to open into the female screw 21.

  According to the threaded joint structure 1 of the excavating tool and the excavating tool 10 having the same according to the present embodiment described above, the cylindrical skirt portion 23 that forms the peripheral wall of the female screw 21 is provided on the outer periphery of the skirt portion 23. While the opening is provided with a detection hole 27 in the form of a stop hole that does not penetrate through the internal thread portion 22 on the inner periphery, and the bottom surface 28 of the detection hole 27 is disposed close to the internal thread portion 22, the following An effect is obtained.

That is, by using this configuration, as described in the present embodiment, when the male screw portion 6 and the female screw portion 22 are worn by excavation and the screw reaches the use limit, the bottom surface 28 of the detection hole 27 is the female It can be set to open into the screw 21.
Specifically, as shown in FIG. 3, the screw wears out, and the detection hole 27 opens into the female screw portion 22 to form a through hole, so that the screw joint structure 1 is along the axis O direction. A fluid such as water (drilling water) flowing in the formed fluid circulation holes 11 and 17 passes through the detection hole 27 (through hole) from between the male screw part 6 and the female screw part 22, and the skirt. It flows out to the outer periphery of the part 23. Thus, when the fluid flows out from the detection hole 27, the operator can visually recognize from the outside that the screw joint structure 1 has reached the use limit.
Further, when the screwing of the female screw 21 and the male screw 5 is released in a state where the excavating tool 10 is pulled out from the drilling hole, the operator looks into the inside of the detection hole 27 and the bottom surface 28 is inside the female screw 21. It is also possible to determine whether or not the screw has reached the use limit by checking whether or not it is open.

  Then, by replacing the threaded joint structure 1 that has reached the use limit with another new threaded joint structure 1, it is possible to avoid a situation in which the screw breaks. It is possible to prevent the portion from being collected and the excavation hole itself from being wasted. Moreover, since a great load applied to the excavation tool 10 and a load applied to the excavator main body when the screw is broken can be prevented, an effect of extending the life of the excavation tool 10 and the excavator can be expected.

  As described above, according to the present embodiment, the use limit of the screw in the threaded joint structure 1 can be easily recognized without requiring skill for the operator, and the breakage of the tool can be surely prevented.

  Moreover, since the fluid flow holes 11 and 17 formed in the threaded joint structure 1 communicate with each other between the male screw portion 6 and the female screw portion 22, when the screw reaches the use limit, The detection hole 27 opens into the female screw 21 to form a through hole, and the fluid flowing through the fluid circulation holes 11 and 17 passes between the male screw portion 6 and the female screw portion 22 in the detection hole (through hole) 27. Since the fluid flows out to the outer periphery of the skirt portion 23, the operator can recognize from the outside that the screw joint structure 1 has reached the use limit of the screw without disassembling the screw joint structure 1.

Further, the screw thread 25 of the female screw part 22 and the screw thread 7 of the male screw part 6 that is screwed to the screw thread 25 also have screws 7a, 25a and a pair of inclined surfaces (7b, 7c), (25b, 25c), respectively. It is said that.
Since the bottom surface 28 of the detection hole 27 is disposed on the outer side in the radial direction of the top portion 25a of the thread 25 of the female screw portion 22 and between the pair of inclined surfaces 25b, 25c, the screw hole 25 is formed by the detection hole 27. When the thread 25 comes into contact with the thread 7 of the male threaded portion 6 and wears out without reducing the rigidity, the bottom surface 28 of the detection hole 27 is easily opened into the female thread 21 reliably.

  The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

  For example, in the above-described embodiment, the screw joint structure 1 of the excavation tool has been described using the excavation bit 2 and the excavation rod 3 of the excavation tool 10, but the present invention is not limited to this. That is, the present invention includes the excavation rod 3 (on the male screw side) provided with the male screw 5 and the female screw 21 that are connected to each other in the axis O direction among the plural excavation rods 3 of the excavation tool 10 ( It can also be used in a threaded joint structure in which a drilling rod 3 (on the female screw side) is screwed together, or a drilling rod 3 having a male screw 5 and a cylindrical skirt in which a female screw part 22 is formed on the inner periphery. You may employ | adopt for the threaded joint structure formed by screwing the coupling provided with the part 23. FIG.

In the above-described embodiment, the male screw portion 6 and the female screw portion 22 have the top portions 7a and 25a formed of flat surfaces and a pair of inclined surfaces (7b and 7c) and (25b and 25c) that form a straight cross section. The trapezoidal screw (so-called T screw) formed in the shape of an isosceles trapezoidal cross section has been described, but the present invention is not limited to this, and a normal screw that does not have a flat surface on the tops 7a and 25a. It does not matter.
Alternatively, in the longitudinal cross-sectional view in FIG. 2, the tops and the pair of inclined surfaces of the threads 7 and 25 form a wavy curved shape as a whole, meandering in the radial direction (vertical direction in FIG. 2), and the direction of the axis O It may be a round screw (so-called rope screw) extending in the left-right direction in FIG.

Further, in the above-described embodiment, the detection hole 27 extends in the skirt portion 23 along the radial direction, and the detection hole 27 is arranged at the tip side portion along the axis O direction of the skirt portion 23. It is not limited to this. That is, for example, the detection hole 27 may open to the outer periphery of the skirt portion 23 and gradually extend toward the distal end side or the proximal end side in the axis O direction as it goes radially inward. Moreover, the detection hole 27 may be arrange | positioned in the base end side part and center part other than the front end side part along the axis | shaft O direction of the skirt part 23. FIG.
In addition, in order to accurately detect that the detection hole 27 is opened in the female screw 21 (that is, to make it easy to visually recognize that the fluid flows out from the detection hole 27 that is a through hole), More preferably, the detection hole 27 is arranged in the central portion of the skirt portion 23.

Further, in the above-described embodiment, the bottom surface 28 of the detection hole 27 is positioned radially inward from the thread valley bottom surface 26 of the female screw portion 22, and these are spaced equidistant from the pair of inclined surfaces 25b and 25c. Although it has been arranged in the central portion along the axis O direction between the slopes 25b, 25c, it is not limited to this. In other words, the wear of the screw may proceed so as to slightly increase the diameter of the bottom surface 26 of the female threaded portion 22, and in anticipation of this, the bottom surface 28 of the detection hole 27 is moved outward in the radial direction of the bottom surface 26 of the thread valley. It is good also as arranging close. However, as described in the above-described embodiment, the bottom surface 28 of the detection hole 27 is disposed between the pair of inclined surfaces 25b and 25c of the screw thread 25 and protrudes radially inward from the screw valley bottom surface 26. It is more preferable because the detection hole 27 can be easily opened in the female screw 21 when the screw is worn. In this case, the intervals along the axis O direction between the bottom surface 28 of the detection hole 27 and the pair of inclined surfaces 25b and 25c may be set differently.
Further, the shapes of the detection hole 27 and the bottom surface 28 thereof are not limited to those described in the above embodiment.

  In the above-described embodiment, the front end surface 12 of the male screw 5 and the bottom surface 24 of the female screw 21 are in contact with each other. However, the present invention is not limited to this. That is, a space may be provided between the front end surface 12 of the male screw 5 and the bottom surface 24 of the female screw 21. Specifically, instead of the front end surface 12 of the male screw 5 and the bottom surface 24 of the female screw 21 being in contact with each other, the male screw is provided on the proximal end portion of the male screw 5 in the rod body 4 of the excavation rod 3. A ring-shaped contact surface that has a diameter larger than 5 and faces the distal end side may be provided, and an end surface 29 facing the proximal end side of the skirt portion 23 may be in contact with the contact surface.

  Further, the wear state of the screw described with reference to FIG. 3 is shown in a simplified manner in order to explain the progress of the wear. Actually, the wear of the male screw portion 6 and the female screw portion 22 is shown in these figures. It progresses by both the screw parts 6 and 22.

  In addition, in the range which does not deviate from the meaning of this invention, you may combine each structure (component) demonstrated by the above-mentioned embodiment, a modified example, a note, etc., addition of a structure, omission, substitution, others It can be changed. Further, the present invention is not limited by the above-described embodiments, and is limited only by the scope of the claims.

DESCRIPTION OF SYMBOLS 1 Screw joint structure of a drilling tool 2 Drilling bit 3 Drilling rod 5 Male screw 6 Male screw part 10 Drilling tool 11, 17 Fluid flow hole 21 Female screw 22 Female screw part 23 Skirt part 25 Female thread part thread 25a Top part 25b, 25c Slope 27 Detection hole 28 Bottom of detection hole O-axis

Claims (6)

An excavation tool for connecting an excavation bit and an excavation rod, excavation rods or between an excavation rod and a coupling, wherein a male screw formed with a male screw and a female screw formed with a female screw are screwed together. A threaded joint structure,
The female screw has a skirt portion in which the female screw portion is formed on the inner periphery,
The skirt portion is formed with a detection hole that opens to the outer periphery of the skirt portion and extends toward the female screw portion.
The screw joint structure for an excavation tool, wherein the bottom surface of the detection hole is arranged close to the female screw portion without opening in the female screw. The threaded joint structure for an excavation tool according to claim 1,
A fluid circulation hole is formed in the threaded joint structure along the axial direction of the male screw, and the fluid circulation hole communicates between the male screw part and the female screw part. Threaded joint structure for excavating tools. A threaded joint structure for an excavation tool according to claim 1 or 2,
In the longitudinal sectional view of the skirt portion, the thread of the female screw portion is
A top portion projecting inward in the radial direction perpendicular to the axial direction of the male screw;
A pair of inclined surfaces that are continuous with both ends of the top portion along the axial direction, and gradually extend from the top portion toward the outside in the radial direction as they are spaced apart in the axial direction;
The screw joint structure for an excavation tool, wherein a bottom surface of the detection hole is disposed on a radially outer side of the top and is disposed between the pair of inclined surfaces. A threaded joint structure for an excavation tool according to claim 3,
The screw joint structure for an excavation tool, wherein the top portion has a flat surface parallel to the axial direction in the longitudinal cross-sectional view of the skirt portion, and the pair of inclined surfaces are each linear. A threaded joint structure for an excavation tool according to claim 3,
The screw joint structure for an excavation tool, wherein the top portion and the pair of inclined surfaces as a whole have a corrugated curved shape in a longitudinal sectional view of the skirt portion.   An excavation tool comprising the threaded joint structure for an excavation tool according to any one of claims 1 to 5.

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