JP2011038271A - Screw joint structure of excavating tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a screw joint structure of an excavating tool capable of preventing such events as seizure, separation, and stress concentration, which may lower the life of the tool, from occurring at an incomplete thread part and of maintaining the stable connection even if the wear of the screw is advanced. <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 is formed in a screw hole, the thread 3 of at least one screw part 2 among the male screw part and the female screw part at the incomplete thread part is configured so that, in a cross section along the axis of one screw part 2, at least a part of the slope 3A thereof facing the other screw part has the same inclination angle as the slope 3A of the threads 3 at the complete thread part which faces the same side as the part of the slope 3A, and the slope 3A at the complete screw part is recessed from an extension surface X extending along the twist angle thereof. <P>COPYRIGHT: (C)2011,JPO&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.

  Beginning with the threaded joint structure of these drilling tools, even in general screws, incomplete threaded parts at both ends of the male and female threaded parts are chamfered or notched so as to be crushed. In addition, the contact area between the inclined surfaces of the thread of the male and female screw portions is smaller than that of the complete screw portion. Therefore, on the contrary, the pressure applied to the slope of the thread at this imperfect thread is high, and this is especially the case for threaded joints of drilling tools where large forces such as rotational force, striking force and thrust force are applied during drilling. The phenomenon of seizure and peeling is likely to occur due to the increase of.

  Here, for example, in Patent Document 1, in a screw joint of an excavation tool having a thread with an isosceles trapezoidal cross section called a so-called T-screw, a terminal portion where the thread width and height of the female thread portion are reduced. That is, an invariant screw profile, that is, a cross-sectional shape is maintained by removing an incomplete screw portion. Further, Patent Document 2 also has a shape in which the slope is different by changing the incomplete screw portion into a cross-sectional shape in which the screw thread is rounded against the complete screw portion having an isosceles trapezoidal shape in cross section. Proposed.

JP 62-125192 A Special table 2002-507686 gazette

  Among these, in the threaded joint described in Patent Document 1, since the incomplete thread portion is removed, no pressure acts on the slope of the incomplete thread portion, but the corresponding pressure is the complete thread portion. As a result, premature screw wear is caused. In addition, if the incomplete screw portion of one of the male and female screw portions is removed in this way, a sharp edge is formed at the intersection ridge line portion between the removal surface from which the incomplete screw portion is removed and the slope of the thread. As a result of the above high pressure acting from this edge, stress concentration occurs on the thread slope of the other threaded part of the male and female threaded parts, resulting in a shortened tool life. Become.

  On the other hand, in the screw joint described in Patent Document 2, since the thread of the incomplete thread portion has a different shape from the thread of the complete thread portion, the thread wear progresses and the contact surface of the thread portion of the male and female thread portions. Is spread to the incomplete threaded portion, the male and female threaded portions are in partial contact with the incomplete threaded portion at a position different from the complete threaded portion. Therefore, when the thread wear progresses in this way, the contact state of the male and female screw parts changes, so the fastening must be unstable, and the contact area between the slopes of the thread in the incomplete thread part is Since it remains small, it is still difficult to reliably prevent seizure and peeling.

  The present invention has been made under such a background, and prevents occurrence of a phenomenon that reduces tool life such as seizure or peeling at an incomplete screw portion or stress concentration, and is stable even if screw wear proceeds. It is an object of the present invention to provide a threaded joint structure for an excavation tool that can maintain the fastened connection.

  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 in which a female threaded portion is formed, wherein the thread in the incomplete threaded portion of at least one of the male threaded portion and the female threaded portion is the other And at least a part of the slope on the side facing the threaded portion has an inclination angle equal to the slope facing the same side of the thread in the complete threaded portion in the cross section along the axis of the one threaded portion. The slope of the portion is formed to be recessed with respect to the extended surface extending along the twist angle.

  In the threaded joint structure configured in this way, since the incomplete thread portion is left first, the contact area of the male and female thread portions is increased to some extent to disperse the pressure and prevent premature screw wear. it can. In addition, since it is possible to avoid the formation of a sharp edge on the inclined surface, it is possible to prevent stress concentration from occurring on the inclined surface of the other screw portion and resulting in breakage.

  And the thread in the incomplete thread part of at least one thread part of this male and female thread part has at least a part of the slope on the side facing the other thread part equal to the slope of the thread thread in this complete thread part. Since it is inclined and is recessed with respect to the extended surface of the inclined surface of the complete screw part, it is uniform even if the screw wear progresses and reaches the incomplete screw part while preventing seizure and peeling due to increased pressure. If worn, the entire slope can be brought into contact with the other threaded portion in the height direction of the thread. For this reason, it can suppress that the contact state of a male and female screw part changes a lot, and it becomes possible to ensure a larger contact area.

  Here, in order to dent the inclined surface of the incomplete screw portion with respect to the extended surface while keeping the inclination angle equal to the inclined surface of the complete screw portion, for example, the inclined surface of the incomplete screw portion is changed to the complete screw portion. However, in this case, if the step of the step is large, the stress concentration due to the edge of the step and the early stage are similar to those of the screw joint structure described in Patent Document 1. This will cause screw wear.

  Therefore, the thread in the incomplete screw portion of the at least one screw portion is such that at least a part of the inclined surface on the side facing the other screw portion has a constant twist angle different from the twist angle in the complete screw portion. It is desirable to be formed so as to be gradually recessed with respect to the extended surface, thereby avoiding the formation of sharp edges as described above. In addition, since the change in the contact state of the male and female screw portions due to the progress of screw wear becomes continuous, more stable fastening can be achieved.

  Moreover, as such a threaded joint of an excavation tool, the screw thread in the complete thread part of the said male thread part and a female thread part is made into a pair of slope and peak part similarly to what was described in patent document 1,2. It is possible to use a so-called T-screw that has a flat isosceles trapezoidal cross-section, and in this case, at the top of the thread in the incomplete thread of the at least one thread, It is desirable that at least a part on the side of the complete screw part is formed with a flat part connected to the flat part of the screw thread in the complete screw part. Since the crossing at an obtuse angle, it is possible to more reliably prevent the stress concentration from occurring at the other threaded portion due to the sharp edge.

  Further, when the T screw is used in this way, the thread in the incomplete thread part of the at least one thread part is formed on the top of the thread while the thread height is equal to the complete thread part. The width of the flat portion is gradually reduced so as to be smaller than the width of the flat portion in the complete screw portion, and then the screw thread height is gradually lowered while the flat portion is kept constant with this small width. It is desirable that the portion is formed so as to intersect the bottom surface of the thread valley of the at least one screw portion. By configuring in this way, it is possible to more reliably prevent a sharp edge from being formed by maintaining the flat portion until the incomplete screw portion disappears, and incomplete even if screw wear progresses. In the portion where the screw thread height on the complete screw portion side is equal to the complete screw portion, the change in the contact state with the other screw portion can be further suppressed.

  As described above, according to the present invention, it is possible to prevent the contact state of the male and female screw portions from changing significantly even if screw wear progresses while preventing seizure, peeling, and stress concentration in the incomplete screw portion. This makes it possible to perform efficient excavation while maintaining stable fastening while preventing a reduction in tool life.

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 by the plane containing the axis line O in FIG. 1 which shows the 1st Embodiment of this invention. (A) A cross-sectional view of the plane including the axis O at the position of the straight line A (complete screw portion) in FIG. 2, (b) at the position of the straight line B in FIG. 2 (boundary between the complete screw portion and the incomplete screw portion). 2 is a cross-sectional view of the plane including the axis O, (c) a cross-sectional view of the plane including the axis O at the position of the straight line C (incomplete screw portion) in FIG. 2, and (d) the position of the straight line D in FIG. It is sectional drawing by the plane containing the axis line O in a thread part. It is sectional drawing by the plane containing the axis line O in FIG. 1 which shows the 2nd Embodiment of this invention. (E) A cross-sectional view of the plane including the axis O at the position of the straight line E (complete screw portion) in FIG. 4, (f) at the position of the straight line F in FIG. 4 (boundary between the complete screw portion and the incomplete screw portion). 4 is a cross-sectional view of the plane including the axis O, (g) a cross-sectional view of the plane including the axis O at the position of the straight line G (incomplete screw portion) in FIG. 4, and (h) the position of the straight line H in FIG. It is sectional drawing by the plane containing the axis line O in a thread part.

  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 Among them, the slope 3A on the side facing the male screw part (the other screw part) (not shown) that is screwed into the female screw part 1 has an inclination angle equal to the slope 3A in the complete screw part in the cross section along the axis O (for example, The inclined surface 3A of the complete threaded portion is formed so as to be recessed with respect to the extended surface X extending along the constant twist angle.

  Here, in this embodiment, the thread 3 in the incomplete threaded portion of the female threaded portion 1 has a slope 3A on the extended surface X with a constant twist angle different from the twist angle of the slope 3A in the complete threaded portion. In the first embodiment in which the present invention is applied to the female screw portion 1, the torsion angle of the inclined surface 3A in the incomplete screw portion is larger than the torsion angle of the inclined surface 3A in the complete screw portion. Becomes smaller.

  Further, in the present embodiment in which the screw thread 3 has a pair of slopes 3A and 3B and a flat part 3C at the peak and is formed in an isosceles trapezoidal cross section, even in an incomplete screw part, A flat portion 3C that is continuous with the flat portion 3C of the screw thread 3 in the complete screw portion is formed at the peak portion. In this embodiment, the flat portion 3C of the incomplete screw portion has the same height as the flat portion 3C of the complete screw portion, that is, the diameter from the axis O, in the present embodiment. At the same time, the thread 3 is chamfered at the incomplete screw portion or is cut out so that the pussies are attached, so that the width of the slope 3A is gradually reduced from the complete screw portion. The width is reduced to 0 at the intersecting portion.

  Of the slopes 3A and 3B of the thread 3 in the incomplete thread portion, the slope 3B opposite to the slope 3A is thus chamfered or crushed in the incomplete thread portion. By being cut out, the screw thread of the male screw part is prevented from contacting.

  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, first, the incomplete thread portion is not removed. Since the remaining portion of the slope 3A of the incomplete screw portion is brought into contact with the male screw portion to ensure a contact area, a certain portion on the side of the complete screw portion can disperse the pressure. The progress of wear of the thread portion can be suppressed. In addition, since a sharp edge is not formed at the portion in contact with the male screw portion, it is possible to prevent a situation in which stress concentration occurs on the slope of the male screw portion and causes damage.

  Further, the inclined surface 3A on the side facing the male screw portion in the incomplete screw portion has the same inclination angle as the inclined surface 3A facing the same side of the screw thread 3 in the complete screw portion and in contact with the male screw portion. 3A. In other words, the incomplete threaded portion is formed in a recessed portion relative to the pitch P of the female threaded portion 1 in the complete threaded portion shown in FIG. 3B. As shown in (c), the slope 3A of the incomplete screw portion maintains the same cross-sectional shape as the extension surface X, although the pitch is larger by the dent amount A than the extension surface X of the slope 3A of the complete screw portion. Have been to.

  Accordingly, the portion of the inclined surface 3A of the incomplete screw portion that is in contact with the above-described male screw portion on the complete screw portion side to some extent is the male screw over the entire height direction of the thread 3 like the complete screw portion. In other words, since the slope 3A of the incomplete thread portion does not partially contact the male thread portion, it is possible to prevent seizure or peeling. Even if the screw wear progresses and reaches the inclined surface 3A of the incomplete screw portion, the wear is uniform over the entire height direction of the screw thread 3, so that the contact state with the male screw portion is remarkable. There is no change, and stable fastening can be maintained. For this reason, according to the threaded joint structure having the above-described configuration, even if the wear is prevented while preventing the seizure and peeling, or the damage of the external thread due to the progress of wear and stress concentration as described above, and suppressing the decrease in the tool life. Even if advancing, the contact state of the male and female screw portions can be stably maintained, and smooth and efficient excavation can be achieved.

  In particular, in the present embodiment, the slope 3A of the thread 3 of the incomplete thread portion is different from the slope 3A facing the same side of the complete thread portion with a twist angle different from the twist angle formed by the slope 3A of the complete thread portion. Since the inclined surface 3A of the complete screw portion and the incomplete screw portion intersects an obtuse angle as shown in FIG. 2, the sharpness as described above is caused. As a result, it is possible to more reliably prevent the formation of a sharp edge, and it is possible to make the change in the contact state more gradual when the screw wear progresses.

  However, instead of changing the twist angle so that the inclined surface 3A of the incomplete screw portion is moved backward with respect to the extended surface X, for example, the inclined surface 3A of the incomplete screw portion is changed with respect to the extended surface X. It may be formed in a staircase shape that is recessed stepwise while parallel to the direction of the twist angle. Even in such a case, if the step difference of the recessed step is sufficiently small, the twist angle is changed. And substantially the same effect can be obtained.

  In the present embodiment, the screw thread 3 in the complete thread portion is a T-thread with a trapezoidal cross-sectional shape having a flat portion 3C at the peak, and the flat portion 3C is a screw thread of the incomplete screw portion. 3 is also extended to intersect the slope 3A. For this reason, even in this incomplete threaded part, until the inclined surface 3A is recessed from the extended surface X by a certain amount of dent A, the top of the inclined surface 3A is formed to intersect with the flat portion 3C at an obtuse angle. In other words, since it is possible to avoid the formation of a sharp edge, it is possible to more reliably prevent stress concentration on the male screw portion.

  However, in the first embodiment, the height of the flat portion 3C is constant from the complete screw portion to the incomplete screw portion, while the thread 3 is chamfered or attached to the incomplete screw portion. In this case, the width is gradually narrowed so that the chamfered portion or the portion where Nussumi and the inclined surface 3A intersect with each other has a width of 0. After the width of 3C becomes 0, the inclined surface 3A and the chamfer and the nudity directly intersect with each other, and the intersecting ridge line portion has a sharp and sharp shape as shown in FIG. Of course, the inclined surface 3A is incompletely threaded and recessed with respect to the extended surface X. Therefore, it is unlikely that the intersecting ridge line part directly contacts the male threaded part and causes stress concentration. If the portion remains, the intersecting ridge portion may be crushed and easily deformed, which may hinder smooth attachment / detachment of the male and female screw portions.

  Therefore, in such a case, as in the second embodiment of the present invention shown in FIGS. 4 and 5, the screw thread 3 in the incomplete screw portion of the female screw portion 1 is moved from the screw valley bottom surface 4. The width of the flat portion 3C is gradually narrowed so that the width of the flat portion 3C is smaller than the width of the flat portion 3C in the complete screw portion while the height is equal to the complete screw portion. Alternatively, the height of the screw thread 3 may be gradually lowered, and the peak portion may be formed so as to intersect the thread valley bottom surface 4 of the female screw portion 1 while maintaining this constant width. In the second embodiment, the same reference numerals are assigned to the parts common to the first embodiment shown in FIGS. 1 to 3, and the description thereof is omitted.

  Therefore, in such a second embodiment, the incomplete screw portion is submerged in the screw valley bottom surface 4 while the flat portion 3C is left between the chamfered surface and the chamfer 3A and the chamfer or the nudity in the incomplete screw portion. Therefore, the intersecting ridge line portion having the sharp edge as described above is not formed, and the male and female screw portions can be attached and detached more smoothly. Further, since the height of the flat portion 3C is equal to the height of the complete screw portion on the complete screw portion side of the incomplete screw portion, a contact state that is the same as the male screw portion is maintained even if screw wear proceeds. be able to.

  However, the flat portion 3C of the screw thread 3 in the incomplete screw portion is directed toward the intersecting portion from the complete screw portion to the screw valley bottom surface 4 so that the width of the complete screw portion becomes smaller than this. In the case of gradually decreasing the width and then reaching the intersecting portion as a constant width with this width, if the constant width is too small, the inclined surface 3A sandwiching the flat portion 3C and chamfering There is also a possibility that the distance between and the top of the screw thread 3 cannot be prevented from being deformed. For this reason, it is desirable that the constant width of the flat portion 3C in the portion intersecting the screw valley bottom surface 4 is set to 1/3 of the width of the flat portion 3C in the complete screw portion, and more desirably the flat portion in the complete screw portion. The width is about ½ of the width of 3C.

  In the first and second 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.

  In addition, when the present invention is applied to the male screw portion, when the twist angle of the slope of the incomplete screw portion is recessed with respect to the extended surface as a constant twist angle different from that of the complete screw portion, the slope of the incomplete screw portion is reduced. The twist angle is made larger than the twist angle of the extended surface of the slope of the complete thread portion. Furthermore, the slope 3A of the thread 3 of the incomplete thread portion should be at least partially recessed with respect to the extended surface X at an inclination angle equal to the slope 3A of the complete thread portion, that is, in the first embodiment. The position of the straight line B in FIG. 2 in the embodiment and the position of the straight line F in FIG. It may begin to dent from the middle, or may begin to dent in the middle of the incomplete screw part. Further, the inclination angle may not be the same as that of the inclined surface 3A in the complete screw portion over the entire inclined surface 3A thus formed. For example, even if screw wear proceeds, there is little possibility of contact with the male screw portion. On the side where the incomplete screw portion is immersed in the bottom surface of the screw valley, the angle of inclination does not necessarily have to be the same.

1 Female thread (at least one thread)
2 Excavation tool body 3 Thread of female thread part 1 3A Slope of thread 3 (slope on the side facing the other thread part in incomplete thread part)
3B Slope of the thread 3 3C Flat part of the thread 3 4 Bottom surface of the thread valley of the female thread 1 O Axis of the female thread 1 X Extension surface P extending the slope 3A of the thread 3 in the complete thread P Female thread 1 The pitch of the thread 3 in the complete thread portion of the screw A A Indentation amount relative to the extended surface X of the slope 3A of the thread 3 in the incomplete thread portion

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 thread in the incomplete threaded portion of at least one of the male threaded portion and the female threaded portion is such that at least a part of the slope facing the other threaded portion of the one threaded portion is In the cross section along the axis, it forms an inclination angle equal to the inclined surface facing the same side of the screw thread in the complete screw portion, and the inclined surface of this complete screw portion is formed to be recessed with respect to the extended surface extending along the twist angle A threaded joint structure for an excavating tool.   The thread in the incomplete thread part of the at least one thread part is such that at least a part of the slope on the side facing the other thread part has a constant twist angle different from the twist angle in the complete thread part and the extension surface. The threaded joint structure for an excavating tool according to claim 1, wherein the threaded joint structure is formed so as to be gradually recessed with respect to the surface.   The male screw portion and the female screw portion are formed in an isosceles trapezoidal shape in which the screw thread in the complete screw portion has a pair of inclined surfaces and a flat portion on the peak portion, and the screw in the incomplete screw portion of the at least one screw portion. 3. A flat portion connected to the flat portion of the screw thread in the complete screw portion is formed at a part of at least a portion of the complete screw portion on the peak portion of the mountain. A threaded joint structure for a drilling tool as described in 1.   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 on the top of the thread is the flat part in the complete thread part. The width of the screw thread gradually decreases so that the width becomes smaller than the width of the screw thread, and then the screw thread height gradually decreases while the flat part is kept constant with this small width, and the peak part is the bottom surface of the thread valley of the at least one screw part. The threaded joint structure for an excavation tool according to claim 3, wherein

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