JP5293490B2 - Threaded joint structure of drilling tools - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prolong the life of a tool by preventing a sharp edge from being formed at an incomplete thread part even if the wear of a screw is advanced to some degree as well as before the wear, while suppressing the premature promotion of the wear of the screw. <P>SOLUTION: In this screw joint structure of an excavating tool in which a male screw part is formed on a screw shaft and a female screw part 1 is formed in a screw hole, the male screw part and the female screw part 1 have respective cross sections of isosceles trapezoidal shapes in which the threads 3 at the complete thread part has a pair of slopes 3A, 3B and a flat part 3C at the crest part. The threads 3 at the incomplete thread part of at least one screw part 1 are configured so that the slope 3A thereof in contact with the other screw part is arranged continuously with the slope 3A thereof at the same inclination angle and twist angle as the slope 3A of the thread 3 at the complete thread part which faces the same side. The crest part crosses the bottom surface 4 of the thread with the height of the thread 3 lowered while the flat part 3C arranged continuously with the flat part 3C at the incomplete thread part is formed. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention connects a drilling bit for excavating the ground and a drilling rod for transmitting a striking force and a rotational force from a drilling device to the drilling bit, or a coupling for connecting the drilling rod and the drilling rod to each other. Therefore, the present invention relates to a threaded joint structure of a drilling tool having a threaded shaft formed with a male threaded portion and a threaded hole formed with a female threaded portion.

  As a thread of a male and female thread part in the threaded joint structure of these excavation tools, a so-called T thread in which a complete thread part has a trapezoidal shape with a cross section having a flat part on a pair of oblique sides and a peak part is known. Even in a general screw such as a T screw, an incomplete screw portion at both ends of the male and female screw portions is chamfered or notched so as to be crushed so that the cross section has an acute angle. An edge that forms the following is formed. And especially in the threaded joints of excavation tools where rotational force, striking force and thrust act during excavation, stress concentration is generated by such sharp edges coming into contact with the other thread of the male and female threaded parts. The tool life will be reduced.

  Therefore, for example, in Patent Document 1, in such a threaded joint of an excavating tool having a thread with an isosceles trapezoidal cross section, an end portion, that is, an incomplete thread portion, in which the thread width and height of the female thread portion are reduced. It has been proposed to maintain an essentially invariant screw profile, i.e., a cross-sectional shape, by removing, so that no sharp edges are formed as described above. Further, Patent Document 2 discloses a sharp shape with a different slope by changing the incomplete screw portion to a cross-sectional shape in which the thread is rounded against a complete screw portion having an isosceles trapezoidal shape in cross section. Some have been proposed in which the edge is not formed on the incomplete threaded portion.

JP 62-125192 A Special table 2002-507686 gazette

  Among these, in the screw joint described in Patent Document 1, since the incomplete screw portion is removed, a sharp edge is not formed in the incomplete screw portion. However, on the other hand, if the incomplete screw portion is removed in this way, an edge is formed at the intersection ridge line portion of the removal surface from which the incomplete screw portion is removed and the slope of the screw thread. As a result, stress concentration occurs on the thread slope of the other screw portion of the male and female screw portions, resulting in a reduction in tool life.

  Moreover, even if it is incomplete, removing the screw part which contributes somewhat to securing the contact area of the male and female screw parts as described in Patent Document 1 promotes early screw wear. This is not preferable. This is also the case with the screw joint described in Patent Document 2, that is, the inclined surface of the incomplete screw portion comes into contact with the other male and female screw portions because the inclined surface is different between the complete screw portion and the incomplete screw portion. There is nothing, and it is difficult to suppress the early wear of the screw.

  The present invention has been made under such a background, and it is possible to prevent the thread wear from being promoted at an early stage. It is an object of the present invention to provide a threaded joint structure for an excavating tool that can prevent a sharp edge from being formed and extend the tool life.

  In order to solve the above-described problems and achieve such an object, the present invention provides a screw formed with a male screw portion that connects a drill bit and a drill rod, drill rods, or a drill rod and a coupling. A threaded joint structure of a drilling tool with a shaft and a threaded hole formed with a female threaded portion, wherein the male threaded portion and the female threaded portion have a threaded portion in a complete threaded portion with a flat portion on a pair of slopes and peak The screw thread in the incomplete screw portion of at least one of the male screw portion and the female screw portion has an inclined surface on the side in contact with the other screw portion. The thread has a slope and a twist angle equal to the slope facing the same side of the thread in the section, and is continuous with the slope. The lower the screw valley And characterized by being crossed in.

  In the screw joint structure configured as described above, the at least one screw portion of the male and female screw portions first has a slope on the side contacting the other screw portion of the incomplete screw portion in the complete screw portion. It has an inclination angle and a twist angle equal to those of the slope facing the same side of the screw thread and is continuous with the slope, and the slope of this complete thread portion is extended as it is along the direction of twist. For this reason, the contact area with the slope of the screw thread in the other screw portion can be increased, and the progress of screw wear can be suppressed.

  Then, the thread crest at the incomplete threaded portion of the at least one threaded portion that intersects the slope has a lower threaded height while the flat portion connected to the flat portion of the complete threaded portion is formed. It intersects with the bottom of the valley, that is, it has a certain width over its entire length so that a crossing ridge line of a predetermined length is formed even at the intersection with the bottom of the screw valley. . Therefore, the crossing angle between the flat portion and the slope can be made obtuse, and it is possible to avoid the formation of a sharp edge on the incomplete screw portion, and thus the flat portion at the peak portion has a certain width. Therefore, even if the inclined surface is retreated due to the progress of screw wear, the crossing angle between the flat portion and the inclined surface can be maintained at an obtuse angle within this width.

  Here, in order to form the flat part formed at the top of the thread in the incomplete thread part of the at least one thread part so as to intersect the bottom face of the thread valley with a certain width. First, the flat portion may be made to intersect with the bottom surface of the screw valley by gradually lowering the screw thread height while keeping the width equal to the flat portion of the screw thread in the complete screw portion. In this case, the width of the flat portion in the incomplete screw portion is the same as that of the complete screw portion over the entire length. It is possible to maintain a state where the crossing angle is obtuse and no sharp edge is formed.

  Second, the screw thread in the incomplete screw part of the at least one screw part has the same thread height as that of the complete screw part, and the width of the flat part formed in the peak part is the complete screw part. The width gradually decreases to be smaller than the width of the flat portion of the portion, and then the screw thread height gradually decreases while the flat portion is kept constant at this small width so that the peak portion intersects the bottom surface of the screw valley. May be formed. In this case, since the contact area with the other screw portion can be ensured at a portion where the screw thread height is equal to the complete screw portion, the progress of screw wear can be effectively suppressed.

  In this case, the constant width formed by the flat portion when the top of the screw thread in the incomplete screw portion of the at least one screw portion intersects the bottom surface of the screw valley is the width of the flat portion of the complete screw portion. It is desirable that it is 1/3 or more. That is, if the constant width of the flat portion of the incomplete screw portion is smaller than 1/3 of the width of the flat portion of the complete screw portion, it is relatively fast even if the progress of screw wear can be suppressed. There is a possibility that the flat portion of the incomplete screw portion disappears at a time and a sharp edge is formed.

  As described above, according to the present invention, premature screw wear is suppressed by maintaining the contact of the inclined surface even in the incomplete screw portion, and, of course, even if the wear progresses to some extent, this defect is not caused. It is possible to avoid the formation of a sharp edge in the complete threaded portion, thereby preventing stress concentration from occurring on the slope of the other threaded portion and extending the life of the excavating tool.

It is the schematic which shows the opening part of the screw hole in which the internal thread part 1 to which the threaded joint structure of the excavation tool of this invention is applied. It is sectional drawing along the axis line O in FIG. 1 which shows the 1st Embodiment of this invention. (A) AA sectional view in FIG. 1, (b) BB sectional view in FIG. 1, (c) CC sectional view in FIG. 1, (d) DD sectional view in FIG. is there. It is a figure equivalent to sectional drawing in alignment with the axis O in FIG. 1, which shows the 2nd Embodiment of this invention. 2A shows a second embodiment of the present invention, (a) a view corresponding to the AA cross section in FIG. 1, (b) a view corresponding to the BB cross section in FIG. 1, and (c) equivalent to a CC cross section in FIG. FIG. 4D is a diagram corresponding to the DD cross-sectional view in FIG. It is a figure equivalent to sectional drawing in alignment with the axis O in FIG. 1, which shows the 3rd Embodiment of this invention. 3A shows a third embodiment of the present invention, (a) a view corresponding to the AA cross section in FIG. 1, (b) a view corresponding to the BB cross section in FIG. 1, and (c) equivalent to a CC cross section in FIG. FIG. 4D is a diagram corresponding to the DD cross-sectional view in FIG.

  1 to 3 show a first embodiment of the present invention, in which the present invention includes a male screw portion that connects a drill bit and a drill rod, drill rods, or a drill rod and a coupling. The present invention is applied to a threaded joint having a threaded hole in which a female threaded part is formed in a threaded joint structure of a drilling tool having a formed screw shaft and a threaded hole in which a female threaded part is formed. That is, the female thread portion 1 is a cylindrical portion formed on the rear end side of the bit body or the rod body in the drill body 2 such as the bit body of the drill bit, the rod body of the drill rod, or the body of the coupling. In the coupling in which the main body itself is formed in a cylindrical shape, it is formed on at least one inner peripheral portion on the front end side and the rear end side.

  The thread 3 of the female thread portion 1 in this embodiment has a pair of slopes 3A, 3B and a flat portion 3C at the top of the thread 3 and is a cross section along the axis O of the female thread portion 1. Are so-called T-screws having an isosceles trapezoidal shape. However, the intersecting ridge line portion where the pair of slopes 3A and 3B intersect with the flat surface of the peak is rounded so as to form a convex curve smoothly contacting the slopes 3A and 3B and the flat portion 3C in the cross section. .

  Then, the thread 3 of the female screw portion 1 forms a trapezoidal trapezoidal shape having a constant size and shape in the complete screw portion, and is twisted around the axis O with a constant twist angle. On the other hand, in the incomplete screw part formed at the opening side end part of the inner peripheral part of the excavation tool main body 2 which is the start end or the end of the female screw part 1, a pair of inclined surfaces 3A, 3B Of these, a slope 3A on the side in contact with a male screw portion (the other screw portion) (not shown) that is screwed into the female screw portion 1 is continuous with the slope 3A at an inclination angle equal to the slope 3A of the complete screw portion and the twist angle. The crest portion is formed so that the height of the crest 3 is lowered while the flat portion 3C connected to the crest portion 3C of the crest portion in the complete screw portion is formed. It is formed so as to intersect with the screw valley bottom 4 That.

  Here, in this embodiment, the flat portion 3C of the screw thread 3 in the incomplete screw portion has a width L in the axis O direction as shown in FIG. The fixed width L is equal to the width L, and the height of the screw thread 3 is gradually lowered while intersecting the screw valley bottom surface 4 while maintaining the constant width L. Therefore, an intersecting ridge line having the length of the width L is formed at a portion where the flat portion 3C and the thread valley bottom surface 4 intersect.

  Of the slopes 3A and 3B of the thread 3 in the incomplete thread portion, the slope 3B opposite to the slope 3A has a flat portion 3C having the width L on the thread 3 in the incomplete thread portion. In this way, the thread is chamfered or notched so as to be crushed, and the height of the thread 3 gradually decreases at the incomplete thread as described above, and the male thread Never touch the thread.

  Therefore, in the threaded joint structure of an excavation tool formed by screwing the male thread portion formed on the outer periphery of the threaded shaft of the excavation rod into the female thread portion 1 formed in this way, the thread 3 Since the slope 3A in contact with the male screw portion is extended at an inclination angle and a twist angle equal to the slope 3A of the complete screw portion, the slope 3A is brought into contact with the male screw portion over the entire surface, thereby contacting the surface area. Can be secured. For this reason, since the load which acts on the internal thread part 1 from an external thread part at the time of excavation can be disperse | distributed, it can suppress the progress of the abrasion which arises in this slope 3A from a complete thread part to an incomplete thread part by this load. it can.

  Further, the thread 3 in the incomplete thread portion is formed so as to intersect the thread valley bottom surface 4 with the height of the thread 3 being lowered with the flat portion 3C remaining at the top of the thread. 3A and the flat portion 3C also intersect at an obtuse angle over the entire length of the incomplete screw portion in the same manner as the complete screw portion, and the intersecting ridge line portion is rounded in a convex curve shape. That is, since there is no portion with an acute edge formed in the incomplete screw portion, according to the screw joint structure configured as described above, the screw thread of the male screw portion is stressed by contacting such an edge. Concentration does not occur, and it is possible to prevent a situation in which a tool life is shortened due to damage to the excavation tool starting from the portion where stress concentration occurs in this way.

  Further, since the flat portion 3C is left and the incomplete screw portion is formed in this way, even if wear occurs on the slope 3A due to long-term excavation, while the flat portion 3C remains, It is possible to maintain a large contact area of the inclined surface 3A with the male screw portion, and it is possible to prevent wear from being accelerated at an early stage. Therefore, according to the threaded joint structure having the above-described configuration, damage due to stress concentration is prevented as described above, wear of the inclined surface 3A is suppressed, and further, even if wear occurs, the promotion thereof is prevented. In combination with this, it is possible to greatly extend the tool life.

  In particular, in the first embodiment, the flat portion 3C of the screw thread 3 in the incomplete screw portion is extended until it intersects the screw valley bottom surface 4 with a width L equal to the flat portion 3C in the complete screw portion. Until the thread 3 is worn down to the depth of the width L, that is, until the female screw portion 1 disappears, the contact area of the slope 3A with the male screw portion in the incomplete screw portion can be maintained. Actually, since the excavation tool reaches the end of its life due to other factors while the wear progresses to that extent, as a result, the present embodiment provides a threaded joint structure in which the contact area does not vary due to wear. It becomes possible.

  Next, FIGS. 4 to 7 show the second and third embodiments of the present invention, and the same reference numerals are used for the parts common to the first embodiment shown in FIGS. The explanation is omitted. That is, in the first embodiment, the thread 3 in the incomplete thread portion is formed so that the flat portion 3C has a width L equal to the flat portion 3C of the complete thread portion, and the height gradually decreases. On the other hand, in the second and third embodiments, the thread 3 of the incomplete thread portion has a height equal to that of the complete thread portion from the complete thread portion, and the width of the flat portion 3C is equal to that of the complete thread portion. The width of the screw thread 3 is gradually reduced so that the width M is gradually smaller than the width L of the flat portion 3C, and the flat portion 3C is kept constant at the small width M. The flat portion 3 </ b> C is formed so as to intersect the screw valley bottom surface 4. Here, in the second embodiment, the width M is set to 1/3 of the width L of the flat portion of the screw thread 3 in the complete screw portion, and is set to 1/2 in the third embodiment.

  Accordingly, also in the second and third embodiments, the inclined surface 3A of the thread 3 of the incomplete thread portion has an equal inclination angle and twist angle so as to be on the extension of the inclined surface 3A of the complete thread portion. In particular, until the flat portion 3C reaches the width M, the height of the screw thread 3 is also equal to the complete screw portion. Therefore, it is possible to suppress wear by securing a large contact area with respect to the male screw portion which is the other screw portion. it can. Further, after reaching the width M, the flat portion 3C maintains a constant width and gradually decreases in height so as to intersect the screw valley bottom surface 4, and the intersecting ridge line having a length of width M is formed at the intersecting portion. Therefore, since the slope 3A and the flat portion 3C are made to intersect at an obtuse angle over the entire length of the incomplete screw portion, stress concentration on the male screw portion can be prevented. In the range of the width M, even if the inclined surface 3A is worn, the flat portion 3C and the obtuse angle are maintained, so that the tool life can be extended as in the first embodiment. .

  However, the flat portion 3C of the screw thread 3 in the incomplete screw portion is directed to the intersection portion from the complete screw portion to the screw valley bottom surface 4 so that the width L of the complete screw portion becomes a smaller width M. If the width M is too small and then reaches the intersection, the slope 3A is worn and retracted to the opposite slope 3B side. Sometimes, the flat portion 3C having a certain width M is crushed relatively early, the receding slope 3A and the slope 3B on the opposite side intersect, and a sharp edge is formed at the intersecting ridge line portion, and the male screw There is a risk of stress concentration in the part. For this reason, the width M is desirably up to 1/3 of the width L of the flat portion 3C in the complete screw portion as in the second embodiment, and 1 / of the width L as in the third embodiment. It is more desirable that the number is about 2.

  In the first to third embodiments, the case where the screw joint structure of the present invention is applied to the female screw portion 1 formed in the screw hole in the inner peripheral portion of the cylindrical portion of the excavation tool main body 2 has been described. However, you may apply to the external thread part of the screw shaft screwed in to this internal thread part 2, and may apply to both of these external thread parts. However, in the state where the screw shaft is screwed into the screw hole and the drill bit and drill rod of the drilling tool, the drill rods are connected, or the drill rod and the coupling are connected, for example, the male screw part exceeds the incomplete screw part of the female screw part. When the is extended, the present invention may not be applied to the male screw portion, that is, the present invention may be applied to at least one of the female and male screw portions.

1 Female thread (at least one thread)
2 Excavation tool body 3 Thread of female thread part 1 3A Slope of screw thread 3 (in the incomplete thread part, the slope on the side in contact with the other thread part)
3B Slope of the thread 3 3C Flat part of the thread 3 4 Bottom face of the thread valley of the female thread part 1 Axis of the female thread part 1 Width of the flat part 3A of the thread 3 at the complete thread part M Width at the incomplete thread part Width of flat portion 3A made smaller than L

Claims (4)

  This is a threaded joint structure of a drilling tool that includes a threaded shaft formed with a male thread and a threaded hole formed with a female thread, which connects the drilling bit and the drilling rod, the drilling rods, or the drilling rod and the coupling. The male threaded portion and the female threaded portion have a cross-section isosceles trapezoidal shape in which the thread in the complete threaded portion has a pair of slopes and a flat portion on the peak, and the male threaded portion and the female threaded portion are The thread in the incomplete thread part of at least one of the thread parts has an inclined angle and a twist angle equal to a slope of the side in contact with the other thread part that faces the same side of the thread in the complete thread part. An excavation tool that is continuous with the slope and has a crest that intersects the bottom of the screw valley with a lower screw thread height while a flat portion connected to the flat portion of the complete screw portion is formed. Screw joint structure.   The flat part formed at the top of the thread in the incomplete thread part of the at least one thread part has a width that is the same as the flat part of the thread in the complete thread part, and the thread height is gradually reduced. The threaded joint structure for an excavating tool according to claim 1, wherein the threaded joint bottom surface intersects the bottom surface of the thread valley.   The thread in the incomplete thread part of the at least one thread part has the same thread height as the complete thread part, and the width of the flat part formed at the top of the thread is the width of the flat part of the complete thread part. The width of the screw thread is gradually reduced to be smaller than the width of the screw thread, and then the height of the thread is gradually lowered while the flat part is kept constant with this small width. The threaded joint structure for an excavation tool according to claim 1.   The threaded joint structure for an excavation tool according to claim 3, wherein the constant width is １ ／ or more of the width of the flat portion of the complete threaded portion.

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