JP2014189991A - Screw joint structure of excavation tool, and excavation tool - Google Patents

Abstract

An object of the present invention is to provide a threaded joint structure for an excavating tool that can easily recognize a use limit of a screw in a threaded joint structure without requiring skill of an operator and reliably prevent damage to the tool, and an excavating tool using the same. To provide.
A male screw having a male screw part and a female screw having a female screw part are connected to connect a drilling bit and a drilling rod, two drilling rods, two or three, or a drilling rod and a coupling. 21 is a threaded joint structure 1 of an excavating tool that is screwed together with a female screw 21. The female screw 21 has a peripheral wall portion 23 having a female screw portion 22 formed on the inner periphery, and the peripheral wall portion 23 has a first index. A portion 31 is provided, and the second indicator portion 32 is disposed on the male screw 5 so that the position of the first indicator portion 31 in the circumferential direction is different from that of the first indicator portion 31 when the male screw 5 is screwed with the female screw 21. When the screw is worn and the male screw 5 and the female screw 21 are relatively rotated in the circumferential direction, the positions along the circumferential direction of the first indicator portion 31 and the second indicator portion 32 are overlapped. Is done.
[Selection] Figure 3

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. Further, the female screw has a cylindrical peripheral wall portion (skirt portion) in which a female screw portion is formed on the inner periphery, and the peripheral wall portion has a drill bit and a female screw portion (on the female screw side). It is formed in a drilling rod or 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. In the threaded joint structure of an excavation tool, the female screw has a peripheral wall portion in which the female screw portion is formed on an inner periphery, and the peripheral wall portion is provided with a first indicator portion, The male screw is provided with a second indicator portion arranged so that its position in the circumferential direction is different from that of the first indicator portion in a state where the male screw is screwed with the female screw. When the male screw and the female screw are relatively rotated in the circumferential direction, the positions along the circumferential direction of the first indicator portion and the second indicator portion are set to overlap each other.
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 having the same according to the present invention, the first index portion is provided on the cylindrical peripheral wall portion forming the peripheral wall of the internal thread (internal thread hole), and the internal thread The male indicator (male screw shaft) that is screwed into the second indicator portion is provided with a circumferential position different from that of the first indicator portion in a state in which the female screw and the male screw are screwed together. When the screw is worn by excavation (drilling) and the male screw and the female screw are rotated relative to each other in the circumferential direction (when they are screwed in by the wear amount), the circumferential position between the first and second indicator portions Are set to overlap (at least partially match), the following effects can be obtained.

That is, when the male screw part and the female screw part are worn by excavation and the screw reaches the use limit, the circumferential positions of the first and second index parts can be set to overlap each other.
Specifically, the screw wears, the first and second indicator parts move closer to each other in the circumferential direction, and the circumferential position of each other overlaps to confirm that the screw joint structure has reached the use limit. Can be easily recognized (visually recognized). As the simplest configuration as such first and second indicator portions, for example, it is possible to provide marks on the outer periphery of the peripheral wall portion and the outer periphery of the male screw (portions not covered by the peripheral wall portion). .

  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 of an excavation tool of the present invention, the male screw has a large diameter portion that is larger in diameter than the male screw portion, and the second index portion is provided in the large diameter portion, In a state where the male screw and the female screw are screwed together, an end surface of the large-diameter portion facing the peripheral wall portion side and an end surface of the peripheral wall portion facing the large-diameter portion side may abut.

  In this case, since the screw joint structure is connected by a so-called shoulder drive (per shoulder contact) in which the peripheral wall portion of the female screw and the large-diameter portion of the male screw are in contact, it is easy to ensure the rigidity of the screw joint structure. In particular, breakage of the male screw can be effectively 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. The first indicator portion and the second indicator portion are formed in a groove shape, a hole shape, or a notch shape through which fluid can flow, and communicate with the female screw portion. One of the first index part and the second index part is communicated between the male thread part and the female thread part, and the other of the first index part and the second index part is the threaded joint structure It is good also as being able to communicate between the said external thread part and the said internal thread part through said one.

  In this case, when the screw reaches the use limit, the circumferential positions of the first and second indicator portions overlap and communicate with each other, so that the fluid flowing in the fluid circulation hole flows into the male screw portion and the female screw. It flows out of the threaded joint structure through the inside of the first and second indicator parts from between the parts. Thereby, 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. Moreover, according to this structure, since the operator can visually recognize that the screw has reached the wear limit without approaching the excavation hole, safety is ensured.

  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 the (a) front view and the (b) side sectional view of the excavation rod of the external thread side connected by the screw joint structure of the excavation tool concerning one embodiment of the present invention. It is the (a) side sectional view and (b) front view of the excavation rod by the side of an internal thread connected by the screw joint structure of the excavation tool concerning one embodiment of the present invention. It is a sectional side view which shows the threaded joint structure of the excavation tool which concerns on one Embodiment of this invention. It is a sectional side view which expands and shows the B section of FIG. 3, and is a figure explaining the abrasion state of a screw. (A) A diagram for explaining the relative positions along the circumferential direction of the first and second indicator portions in the initial stage of use of the threaded joint structure of the excavating tool, (b) the first when the screw is worn and reaches the use limit, It is a figure explaining the relative position along the circumferential direction of a 2nd parameter | index part. It is a figure which expands and shows the C section of FIG. It is a figure explaining the modification 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 part and a female screw formed with a female screw part (for connecting a drilling bit and a drilling rod, drilling rods or between a drilling rod and a coupling). In this embodiment, a drilling rod 2 having a male screw 5 (on the male screw side) and a female screw 21 are provided. The threaded joint structure 1 and the excavation tool 10 that are formed by screwing the excavation rod 3 (on the female screw side) that are provided will be described.

The excavation tool 10 of the present embodiment is mounted on an excavator and drills an excavation hole in the ground. An excavation bit (not shown) disposed at the tip of the excavation tool 10 and excavates the ground, A plurality of excavating rods 2 and 3 are connected to the base end side (excavator side) of the excavation bit and transmit thrust, striking force and rotational force from the excavator to the excavation bit. 1 to 3, the excavation rod 2 on the male screw side and the excavation rod 3 on the female screw side are separately described, but these excavation rods 2 and 3 are made of the same member. (That is, the same excavation rod having the male screw 5 and the female screw 21 at both ends may be used). Further, in the illustrated example, only one excavation rod 2 and 3 is shown, but these excavation rods 2 and 3 are successively connected in accordance with the depth of the excavation hole to be drilled. It is like that.
As shown in FIG. 3, the excavation rods 2 and 3 are disposed coaxially with the axis (center axis) O of the male screw 5 as a common axis. In this specification, the side of the excavation rod 3 on the female screw side (left side in FIG. 3) along the axis O direction is the tip side, and the side of the excavation rod 2 on the male screw side along the axis O direction (right side in FIG. 1) is based. It is called the 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 rods 2 and 3 are rotated by the excavator during excavation is referred to as the tool rotation direction.

  As shown in FIGS. 1 (a) and 1 (b), the excavation rod 2 extends along the direction of the axis O, and the rod main body 4 whose cross section perpendicular to the axis O is circular or polygonal, for example. It has a male screw 5 that is disposed at the tip of the main body 4 (left side in FIG. 1B) and extends with the axis O as a central axis.

  The male screw 5 includes a male screw portion 6 whose outer periphery is processed with a male screw, and a large-diameter portion 9 that is positioned on the proximal end side of the male screw portion 6 and has a larger diameter than the male screw portion 6. ,have. In the illustrated example, the male screw portion 6 has a smaller diameter than the outer diameter of the rod main body 4, and the large diameter portion 9 has the same outer diameter as the rod main body 4. In the present embodiment, the annular end surface 13 facing the front end side of the large-diameter portion 9 is formed in a planar shape perpendicular to the axis O. Further, a non-screw part 14 having a slightly smaller diameter than the male screw part 6 is formed between the end face 13 and the male screw part 6 on the outer periphery of the male screw 5.

  A fluid circulation hole 11 is formed inside the excavation rod 2 along the direction of the axis O. The fluid circulation hole 11 penetrates the excavation rod 2 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 open to a front end face 12 facing the direction of the axis O in the male screw 5. 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. In the illustrated example, the distal end portion of the male screw 5 is formed in a tapered shape that gradually decreases in diameter toward the distal end surface 12.

  In a longitudinal sectional view of the male screw 5 shown in FIG. 4, the screw thread 7 of the male screw portion 6 has a top portion 7 a that protrudes outward in the radial direction (the lower side in FIG. 4), and an axis O of the top portion 7 a. A pair of inclined surfaces 7b and 7c that are continuous with both ends along the direction and extend gradually inward in the radial direction (upper side in FIG. 4) as they are separated from the top 7a in the axis O direction (left-right direction in FIG. 4). 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 (right side in FIG. 4) is the inclined surface 7b and faces the distal end side in the axis O direction (left side in FIG. 4). The surface is a slope 7c. In the present embodiment, in the longitudinal sectional view shown in FIG. 4, 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. 4, the thread 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 FIGS. 2A and 2B, the excavation rod 3 extends along the direction of the axis O, and the rod body 4 whose cross section perpendicular to the axis O forms, for example, a circular shape or a polygonal shape, and the rod. The main body 4 includes a female screw 21 that is disposed at the base end portion (right side in FIG. 2A) and that opens toward the base end side and extends along the axis O direction.

  The female screw 21 has a cylindrical peripheral wall portion 23, and a female screw portion 22 is formed by performing female screw processing on the inner periphery of the peripheral wall portion 23. As shown in FIG. 3, the male screw 5 is inserted into the peripheral wall portion 23, and the female screw portion 22 and the male screw portion 6 are screwed together, so that the excavating rods 2 and 3 are connected to each other in the axis O direction. It has become so.

  In the example shown in FIG. 2A, the outer diameter of the peripheral wall portion 23 is the same as the outer diameter of the rod body 4. In addition, the annular end surface 15 facing the base end side in the peripheral wall portion 23 is formed in a planar shape perpendicular to the axis O corresponding to the shape of the end surface 13 of the male screw 5. Further, a non-screw part 16 having a slightly larger diameter than the female screw part 22 is formed between the end face 15 and the female screw part 22 on the inner periphery of the female screw 21.

  The peripheral wall portion 23 has a bottomed cylindrical shape, and is located between the bottom surface 24 located at the distal end portion of the peripheral wall portion 23 and facing the base end side, and the female screw portion 22 as shown in FIG. A dull portion 17 having a concave curve shape in the longitudinal sectional view shown is formed.

  As shown in FIG. 3, in the present embodiment, the distance from the end surface 15 along the axis O direction of the female screw 21 to the bottom surface 24 is the distance from the end surface 13 along the axis O direction of the male screw 5 to the front end surface 12. Has been bigger than. Therefore, in a state where the male screw 5 and the female screw 21 are screwed together, the end surface 13 facing the peripheral wall portion 23 side of the large diameter portion 9 and the end surface 15 facing the large diameter portion 9 side of the peripheral wall portion 23 are in close contact with each other. Abut.

2A and 2B, a fluid circulation hole 11 is formed in the excavation rod 3 along the direction of the axis O. The fluid circulation hole 11 passes through the excavation rod 3 in the direction of the axis O, and the base end of the fluid circulation hole 11 opens to the bottom surface 24 and communicates with the female screw 21.
As shown in FIG. 3, in the state where the male screw 5 is inserted into the peripheral wall portion 23, the fluid flow hole 11 that opens to the front end surface 12 of the male screw 5 of the excavation rod 2 and the bottom surface 24 of the excavation rod 3 are formed. The fluid circulation holes 11 that are open communicate with each other. That is, these fluid circulation holes 11 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 these fluid circulation holes 11 are formed at the tips of the male screws 5. The male screw portion 6 and the female screw portion 22 communicate with each other through the surface 12 and the bottom surface 24 of the female screw 21.

  In a longitudinal sectional view of the peripheral wall portion 23 shown in FIG. 4, the screw thread 25 of the female screw portion 22 has a top portion 25 a that protrudes inward in the radial direction (upper side in FIG. 4), and an axis O direction of the top portion 25 a. And a pair of slopes 25b and 25c extending gradually outward in the radial direction (downward in FIG. 4) as they are separated from the top 25a in the axis O direction (left-right direction in FIG. 4). doing. In the illustrated example, of the pair of inclined surfaces 25b and 25c, the surface facing the base end side (right side in FIG. 4) in the axis O direction is the inclined surface 25b and faces the distal end side (left side in FIG. 4) in the axis O direction. The surface is a slope 25c. In the present embodiment, in the longitudinal sectional view shown in FIG. 4, 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. 4, the thread 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.

Then, as shown in FIGS. 2A and 2B, a first indicator portion 31 is provided on the peripheral wall portion 23 of the female screw 21. In the present embodiment, the first indicator portion 31 is formed in a groove shape through which a fluid can flow, and is open to the inner non-threaded portion 16 and the end surface 15 of the peripheral wall portion 23, There is no opening at the outer periphery of the peripheral wall portion 23. Specifically, the first indicator portion 31 has a rectangular groove shape with a rectangular cross section, and the groove depth (length along the axis O direction) of the first indicator portion 31 is outside from the inside in the radial direction. It is made smaller gradually toward
In the state where the male screw 5 and the female screw 21 are screwed together as shown in FIG. 3, the first indicator portion 31 is communicated between the male screw portion 6 and the female screw portion 22, while these screws 5, In an initial stage (such as a state before being used for excavation) in which 21 is screwed, it is blocked by the tip of the large diameter portion 9 and is not communicated to the outside of the threaded joint structure 1.

Further, as shown in FIG. 5A, the male screw 5 is arranged so that its position in the circumferential direction is different from that of the first indicator portion 31 in a state where the male screw 5 is screwed with the female screw 21. The second indicator portion 32 is provided. As shown in FIGS. 1A and 1B, in the present embodiment, the second indicator portion 32 is provided in the large-diameter portion 9 of the male screw 5 and has a groove shape capable of circulating a fluid therein. And is open to the outer periphery of the large-diameter portion 9 and the end face 13. Specifically, the second indicator portion 32 has a rectangular groove shape with a rectangular cross section, and the groove depth (length along the axis O direction) of the second indicator portion 32 is from the radially outer side to the inner side. It is made smaller gradually toward
In the state where the male screw 5 and the female screw 21 are screwed together as shown in FIG. 3, the second indicator portion 32 is exposed to the outside of the screw joint structure 1, while these screws 5 and 21 are screwed together. In the initial stage, the base end portion of the peripheral wall portion 23 is blocked and the male screw portion 6 and the female screw portion 22 are not communicated with each other.

As shown in FIG. 5B, in the threaded joint structure 1 of the present embodiment, when the screw is worn by excavation and the male screw 5 and the female screw 21 are relatively rotated in the circumferential direction, the first The positions along the circumferential direction of the index part 31 and the second index part 32 are set to overlap.
As shown in FIG. 6, in the present embodiment, the first indicator portion 31 is opened on the end surface 15, the second indicator portion 32 is opened on the end surface 13, and the radially outer end of the first indicator portion 31 is shown. The portion is disposed on the radially outer side with respect to the radially inner end of the second indicator portion 32. As a result, when the male screw 5 and the female screw 21 are relatively rotated around the axis O as shown in FIG. 5B, the circumferential positions of the first and second indicator portions 31 and 32 overlap with each other. 1 and 2nd index parts 31 and 32 can communicate.

  Specifically, according to the amount of wear of the screw, the male screw 5 and the female screw 21 are screwed (tightened) while being rotated in the tool rotation direction by the excavator, and the screw reaches the use limit. The first and second indicator portions 31 and 32 are set to communicate with each other. That is, the second indicator portion 32 can communicate with the male screw portion 6 and the female screw portion 22 through the first indicator portion 31 when the screw reaches the use limit.

  Here, the angle (center angle) indicated by the symbol θ in FIG. 5B is the rotation until the first index part 31 and the second index part 32 are relatively rotated around the axis O and are communicated with each other. Represents a corner. Such an angle θ corresponds to the amount of wear of the screw shown in FIG. 4 (the amount of wear at which the screw becomes the limit of use) A, the pitch P of the screw, and the lead L of the screw (the example shown in FIG. 4 is for a double screw) Can be roughly calculated by the formula: (360 × A) / PorL, for example.

  In FIG. 4, when only the female screw portion 22 of the male screw portion 6 and the female screw portion 22 is worn by the wear amount A in the direction of the axis O, the rotational force of the tool causes the female screw portion 22 to move. The state in which the male screw portion 6 is tightened and moved in the direction of the axis O is indicated by a two-dot chain line, but the manner of wear of the screw is not limited to the illustrated example. That is, the wear state of the screw shown in FIG. 4 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 caused by these screw portions 6. , 22 will proceed.

  According to the screw joint structure 1 of the excavating tool and the excavating tool 10 including the excavating tool according to the present embodiment described above, the first index portion 31 is provided on the cylindrical peripheral wall portion 23 that forms the peripheral wall of the female screw 21. The male indicator 5 that is screwed into the female screw 21 has a second indicator portion so that the circumferential position of the first indicator portion 31 is different from that of the first indicator portion 31 when the female screw 21 and the male screw 5 are screwed together. 32 is provided, and when the screw is worn by excavation (drilling) and the male screw 5 and the female screw 21 are rotated relative to each other in the circumferential direction (when screwed by the amount of wear), the first and second indices Since the circumferential positions of the portions 31 and 32 are set to overlap (at least partially match), the following effects can be 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 first and second indicator portions 31 are used. , 32 can be set so that their circumferential positions overlap each other.
Specifically, the screw wears, the first and second indicator portions 31 and 32 move toward each other in the circumferential direction, and the circumferential position of each other overlaps, so that the screw joint structure 1 reaches the use limit. The operator can easily recognize (visually recognize) that this has occurred.

  In the present embodiment, when the screw reaches the use limit, the circumferential positions of the first and second indicator portions 31 and 32 overlap with each other, and the fluid flowing through the fluid circulation hole 11 flows. Then, from between the male screw portion 6 and the female screw portion 22, it flows out of the screw joint structure 1 through the insides of the first and second indicator portions 31 and 32 as indicated by arrows in FIG. 6. Thereby, 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. Moreover, according to this structure, since the operator can visually recognize that the screw has reached the wear limit without approaching the excavation hole, safety is ensured.

  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 this embodiment is the screw joint structure 1 connected by what is called a shoulder drive (per shoulder contact) in which the peripheral wall portion 23 of the female screw 21 and the large-diameter portion 9 of the male screw 5 abut, It becomes easy to ensure the rigidity of the joint structure 1, and in particular, breakage of the male screw 5 can be effectively prevented.

  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 threaded joint structure 1 of the excavation tool is described using the external thread side excavation rod 2 and the internal thread side excavation rod 3 that are continuously provided in the direction of the axis O in the excavation tool 10. However, the present invention is not limited to this. That is, the present invention is formed by screwing a drilling bit disposed at the tip of the drilling tool 10 to drill the ground and a drilling rod 2 connected to a peripheral wall portion (skirt portion) 23 of the drilling bit. A screw that can be employed in a threaded joint structure, or a screw formed by screwing a drilling rod 2 having a male screw 5 and a coupling having a cylindrical peripheral wall portion 23 having a female screw portion 22 formed on the inner periphery thereof. You may employ | adopt for a joint structure.

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. 4, the tops and the pair of inclined surfaces of the screw threads 7 and 25 form a wavy curve as a whole, meandering in the radial direction (vertical direction in FIG. 4), 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.

  In the above-described embodiment, the end surface 13 of the large-diameter portion 9 of the male screw 5 and the end surface 15 of the peripheral wall portion 23 of the female screw 21 are both annular planes perpendicular to the axis O. However, the present invention is not limited to this. That is, these end surfaces 13 and 15 are only required to be in contact with each other in a state in which the male screw 5 and the female screw 21 are screwed together. For example, the end surfaces 13 and 15 are inclined so as to be opposite to each other with respect to the axis O. It may be an inclined surface that can be contacted.

  Further, the non-threaded portion 14 of the male screw 5 and the non-threaded portion 16 of the female screw 21 may not be provided.

  In the above-described embodiment, the first indicator portion 31 and the second indicator portion 32 are each formed in a groove shape. However, the shapes of the first and second indicator portions 31 and 32 are as follows. It is not limited. Specifically, for example, the first and second indicator portions 31 and 32 may be formed in a hole shape or a notch shape through which a fluid can flow. Further, the shape of the first indicator portion 31 and the shape of the second indicator portion 32 may be different from each other.

In the above-described embodiment, as shown in FIG. 3, in the state where the male screw 5 and the female screw 21 are screwed together and in the initial stage where these screws 5 and 21 are screwed together, the first indicator portion 31 is communicated between the male threaded portion 6 and the female threaded portion 22, while not communicating with the exterior of the threaded joint structure 1, and the second indicator 32 is disposed outside the threaded joint structure 1. On the other hand, it is assumed that the male screw part 6 and the female screw part 22 are not communicated with each other, but the present invention is not limited to this.
Here, what is shown in FIG. 7 is a modification of the threaded joint structure 1 described in the above embodiment. In this example, the groove-shaped first indicator portion 41 of the peripheral wall portion 23 is opened to the outer periphery and the end surface 15 of the peripheral wall portion 23, while being opened to the non-threaded portion 16 on the inner periphery of the peripheral wall portion 23. Not. Further, the groove-shaped second indicator portion 42 of the large diameter portion 9 is opened on the end face 13, but is not opened on the outer periphery of the large diameter portion 9. Further, the radially inner end of the first indicator portion 41 is disposed radially inward with respect to the radially outer end of the second indicator portion 42. Thus, when the screw is worn and the male screw 5 and the female screw 21 are relatively rotated in the circumferential direction, the circumferential positions of the first and second indicator portions 41 and 42 are overlapped, and the first and second The indicator portions 41 and 42 can communicate with each other.
Also in this modification, the same effect as the screw joint structure 1 using the first and second index portions 31 and 32 and the excavation tool 10 described above can be obtained. That is, in a state where the male screw 5 and the female screw 21 are screwed together, any one of the first index parts 31 and 41 and the second index parts 32 and 42 is between the male screw part 6 and the female screw part 22. The other one of the first indicator portions 31 and 41 and the second indicator portions 32 and 42 is exposed to the outside of the threaded joint structure 1, and the male screw portion 6 and the female screw portion 22 are passed through the one. It is only necessary to be able to communicate with each other.

Moreover, although the fluid can be circulated in the first index parts 31 and 41 and the second index parts 32 and 42, the present invention is not limited to this. Specifically, when the screw wears, the first indicator portions 31 and 41 and the second indicator portions 32 and 42 move closer to each other in the circumferential direction, and the circumferential positions of each other overlap (match), It is only necessary that the operator can recognize that the screw joint structure 1 has reached the use limit.
As the simplest configurations of the first and second indicator portions (31, 41), (32, 42), for example, the outer periphery of the peripheral wall portion 23 and the outer periphery of the large-diameter portion 9 (covering the peripheral wall portion 23). For example, it is possible to provide a mark on each of the unexposed portions.

  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 Thread joint structure of a drilling tool 2 Drilling rod on the male screw side 3 Drilling rod on the female screw side 5 Male screw 6 Male screw part 9 Large diameter part 10 Drilling tool 11 Fluid flow hole 13 End face of large diameter part 15 End face of peripheral wall part 21 female screw 22 female screw portion 23 peripheral wall portion 31, 41 first indicator portion 32, 42 second indicator portion O-axis

Claims (4)

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 peripheral wall part in which the female screw part is formed on the inner periphery, and the first index part is provided on the peripheral wall part,
The male screw is provided with a second indicator portion arranged so that a position in the circumferential direction is different from the first indicator portion in a state where the male screw is screwed with the female screw.
When the screw wears and the male screw and the female screw rotate relative to each other in the circumferential direction, the positions along the circumferential direction of the first indicator portion and the second indicator portion are set to overlap. Features a screw joint structure for excavating tools. The threaded joint structure for an excavation tool according to claim 1,
The male screw has a large-diameter portion that is larger in diameter than the male screw portion, and the second indicator portion is provided in the large-diameter portion,
In a state where the male screw and the female screw are screwed together, an end surface of the large-diameter portion facing the peripheral wall portion side and an end surface of the peripheral wall portion facing the large-diameter portion side are in contact with each other. Screw joint structure for drilling tools. A threaded joint structure for an excavation tool according to claim 2,
Inside the threaded joint structure, a fluid circulation hole is formed along the axial direction of the male screw, and the fluid circulation hole communicates between the male screw part and the female screw part,
The first indicator portion and the second indicator portion are formed in a groove shape, a hole shape, or a notch shape through which a fluid can flow.
Either one of the first indicator portion and the second indicator portion is communicated between the male screw portion and the female screw portion,
The other of the first indicator portion and the second indicator portion is exposed to the outside of the screw joint structure, and can be communicated between the male screw portion and the female screw portion through the one. A threaded joint structure for an excavating tool.   An excavation tool comprising the threaded joint structure for an excavation tool according to any one of claims 1 to 3.

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