JP6507012B2 - Double pipe drilling tool - Google Patents

Description

  The present invention provides a rotational force and a striking force by means of a double pipe consisting of an inner rod with a pilot bit mounted at its tip and an outer pipe casing with a ring bit rotatably mounted on its tip at its tip. BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotary impact double-tube drilling tool for drilling, and more particularly to a double-tube drilling tool characterized by an engagement structure between a ring bit and an outer tube casing.

  2. Description of the Related Art A rotary percussion method is widely known as a method of drilling a hole in the ground while applying drainage and boring, ground improvement, ground anchoring, etc., while applying rotational force and impact force. There is. This rotary percussion method has an advantage that drilling can be performed not only in the bedrock but also in the sand layer or the rock layer, because the rock is crushed by a striking force.

  The impact force application structure mounts a top hammer method in which the drill head has a hydraulic impact mechanism, and a down-the-hole hammer which applies an impact force by reciprocating the piston in the cylinder with compressed air at the tip of the inner tube rod. It is divided roughly into the down the hole method.

  On the other hand, the drilling method is roughly classified into a single tube drilling method and a double tube drilling method. The latter double tube drilling method is a method of drilling while protecting the hole wall by the outer tube casing in the case of a collapsible area where there is a possibility of hole wall collapse, and the inner side of the outer tube casing is inner With the rod inserted, drilling is performed while applying rotational force and striking force, and after drilling is completed, the outer tube casing (including the ring bit) is left, and the inner rod is pulled out and removed; After the inner rod is pulled out, the outer tube casing may be separated from the ring bit, and the outer tube casing may be pulled out for recovery.

  At present, various methods have been proposed for the double pipe drilling method, and as one of them, a ring bit method is known. In this construction method, a ring bit rotatably mounted on the axial center is attached to the tip of the outer pipe casing, and the rotational force and striking force given to the pilot bit are transmitted to the ring bit to rotate the outer pipe casing. While rotating the pilot bit (including the inner rod) and the ring bit, the ground is drilled by the rotation and striking of the pilot bit and the ring bit.

  As a prior art concerning the said ring bit construction method, the thing proposed by the following patent documents 1 and 2 can be mentioned, for example. In Patent Document 1 below, a ring bit is rotatably mounted on an end of a casing pipe around an axis, and an inner bit can be engaged on an end of an inner rod inserted in the casing pipe around an axis of the ring bit Attaching, inserting the casing pipe and the ring bit with the inner and outer peripheral surfaces facing each other, and forming the annular grooves extending around the axis on the mutually opposing inner and outer peripheral surfaces, these annular grooves being in agreement An excavating tool in which the ring bit is axially locked to the casing pipe by interposing a radially elastically deformable locking member with respect to the axis in an annular hole defined by Proposed.

  Further, in Patent Document 2 below, an annular ring bit is inserted rotatably around the axis of the casing pipe with the inner and outer peripheral surfaces facing each other at the tip of the cylindrical casing pipe, and these are opposed to each other Among the inner and outer peripheral surfaces, at least one of the peripheral surfaces has a recess extending in the axial direction in an annular shape around the axis, and the other peripheral surface is formed with a protrusion that can be accommodated in the recess. The ring bit is axially movably attached to the casing pipe while being axially engaged with the tip end of the ring bit by the locking means constituted by the inner bit and the inner bit is attached to the tip of the transmission member inserted into the casing pipe On the outer peripheral surface of the inner bit, the axial end of the outer peripheral surface of the inner pipe is in contact with the casing pipe side abutting portion provided in a projecting manner on the inner periphery of the front end portion Can be abutted toward the tip end in the axial direction to the first abutment portion that can abut toward the ring bit and the ring bit side abutment portion whose inner diameter is smaller than the casing pipe side abutment portion formed on the ring bit A second abutment portion is formed, and the inner bit is axially engageable with the ring bit by the engagement means, and the ring means is provided with the ring bit in the casing pipe. On the other hand, there has been proposed a drilling tool provided with a withdrawal mechanism for withdrawal on the axial tip side.

JP 2001-140578 A Unexamined-Japanese-Patent No. 2007-255106

  With regard to the engagement structure between the outer pipe casing and the ring bit, in the patent document 1, the casing pipe and the ring bit are interposingly engageable with a radially elastically deformable locking member between the inner and outer peripheral surfaces of each other. Thus, a structure in which the ring bit is axially locked to the casing pipe is adopted, and in the patent document 2, a male screw portion on the base end portion (closer to the casing pipe side) of the outer peripheral surface of the ring bit While providing a female screw at the end of the inner peripheral surface of the casing pipe, screw the ring bit from the base end side into the casing pipe, and then screw the male screw of the ring bit beyond the female screw of the casing pipe A structure is adopted in which the smooth peripheral surface on the tip side is pulled out (see FIG. 3 of the same document).

  In Patent Documents 1 and 2, the ring bit is prevented from falling off from the casing by adopting the above-mentioned engaging structure, and in a certain range, it can slide in the axial direction and can rotate around the axial center. And

  By the way, in the double pipe drilling method, in many cases, the ring bit and the casing are left in the ground, and the inner rod is removed together with the pilot bit. After the bit and the inner rod are pulled out and a manchette tube (water collection pipe) is inserted into the outer pipe casing, the outer pipe casing is separated from the ring bit and only the outer pipe casing is recovered. Moreover, after installing an anchor also in an anchor construction, removing an outer pipe | tube casing from a ring bit and collect | recovering only an outer pipe | tube casing is performed. In this regard, although the engagement structure between the casing and the ring bit according to Patent Document 1 does not presuppose the separation of the casing, the engagement structure between the casing and the ring bit according to Patent Document 2 is a screw type Therefore, by rotating the casing in the screw-out direction, it is separated from the ring bit and can be recovered on the ground side.

  However, in the double tube drilling method, drilling is performed while sequentially adding an outer tube casing of a predetermined length (about 1 to 1.5 m) and an inner rod, and in this case, at the rear end of the inner rod In order to add the next inner rod, the pi rod bit is once disengaged from the ring bit (unlocked), the inner rod is retracted with the pilot bit by a predetermined length, and the rod is added. Then, the pilot bit and the inner rod are again inserted into the outer pipe casing and repeated (relocking).

  In addition, when trouble such as jamming occurs in the middle of excavation, the pilot bit and the inner rod are temporarily retracted (unlocked), and flushing is performed to inject water from the discharge port of the pilot bit through the water supply hole of the inner rod. By doing this, after removing the earth and sand, fragments and the like, setting (relocking) of the pilot bit and the inner pipe rod is performed again.

  At the time of these unlocking (removal) and relocking (reconnection) work, the screw portion of the outer pipe casing and the screw portion of the ring bit may collide with each other, causing part of the screw thread to be deformed. . If such a defect occurs, even if it is attempted to recover the outer casing after drilling is complete, it can not be rotated midway through the screw due to deformation of the screw thread, and can not be separated from the ring bit. There was a problem that the pipe casing could not be recovered.

  In addition, when the outer pipe casing is separated from the ring bit and fine sand enters the screw groove, the outer pipe casing can not be rotated due to the bite of earth and sand, making it difficult to separate the outer pipe casing. Was a problem.

  Therefore, a main object of the present invention is to provide a double pipe drilling tool in which the outer tube casing can be reliably separated from the ring bit after drilling is completed and the outer tube casing can be reliably recovered.

In order to solve the above-mentioned problems, as the present invention according to claim 1, an inner rod having a pilot bit mounted at its tip and an outer pipe casing having a ring bit mounted at its tip so as to be rotatable around an axial center are mounted. A double pipe drilling tool having a striking force transmitting portion and a rotational force transmitting portion between the pilot bit and the ring bit in a state where the inner rod is inserted into the outer pipe casing and combined.
The engagement structure between the ring bit and the outer pipe casing forms a male thread over a predetermined range at an end position on the outer peripheral surface of the ring bit and near the outer pipe casing, while the outer pipe A pin-like protrusion is provided on the inner peripheral surface at the tip end side of the casing and engaged with the male screw portion, and screwed into the tip opening of the outer pipe casing while rotating the ring bit around the axial center. A double pipe drilling tool is provided which is characterized in that the hooked protrusion is pulled out of the male screw portion of the ring bit to the smooth outer peripheral surface.

  In the invention according to the first aspect, a male screw portion is formed over a predetermined range at an end position on the outer peripheral surface of the ring bit and near the outer pipe casing, and on the tip side of the outer pipe casing Pin-shaped projections that engage with the male screw portion on the inner peripheral surface, and screwing the ring-shaped bit into the opening of the distal end portion of the outer pipe casing while rotating the ring bit around the axial center, An engagement structure is obtained in which the smooth outer peripheral surface is removed beyond the male screw portion of the bit.

  When screws are provided on both the ring bit and the outer pipe casing as in Patent Document 2, the side surfaces of the screw threads are in continuous contact with each other. Since the generated deformation will affect the whole, if the side surfaces of the screw thread come into close contact with each other in the middle of the screw and can not be rotated, or if fine earth and sand enters the screw groove, this fineness Due to the influence of earth and sand, the side surfaces of the screw thread contact each other in the middle of the screw and can not be rotated. On the other hand, as in the present invention, while a male screw is formed on the ring bit side, when the outer tube casing side is a pin-like projection, the point contact is made with respect to the thread groove of the ring bit. Therefore, even if deformation occurs in part of the screw thread, if the pin-like projection passes over the place where the deformation occurs, the outer pipe casing can be rotated, and temporarily there is fine earth and sand in the screw groove As the outer pipe casing can be rotated if the pin-shaped projections rotate while the pin-shaped projections scrape out the earth and sand, or if the pin-shaped projections get over the earth and sand, the structure according to Patent Document 2 Also, the outer casing can be reliably separated from the ring bit.

  According to the present invention as set forth in claim 2, the pin-like protrusion is formed with a through hole on the peripheral surface of the outer pipe casing, and the shaft member is installed in the through hole so as to project inward. A dual pipe drilling tool according to claim 1 is provided which is fixed by welding.

  In the invention according to the second aspect, the first specific example of the structure of the pin-like projection is shown. In the present invention, the pin-shaped projection forms a through hole on the circumferential surface of the outer tube casing, and the shaft member is installed in the through hole so as to protrude to the inner side, and fixed by welding from the outer surface side.

  In the present invention according to claim 3, the pin-shaped projection forms a female screw hole in the peripheral surface of the outer tube casing, and a head of the pin-shaped protrusion has a screw groove shape of the ring bit from the inner surface side with respect to the female screw hole. The double pipe drilling tool according to claim 1 is provided, wherein the shaft portion of the bolt member matched with is screwed and fixed by welding from the outer surface side.

  In the invention according to the third aspect, the second specific example of the structure of the pin-like projection is shown. In the present invention, the pin-like protrusion forms a female screw hole in the peripheral surface of the outer tube casing, and a bolt member whose head conforms to the screw groove shape of the ring bit from the inner surface side with respect to the female screw hole. Screw the shaft part of and fix it by welding from the outer surface side.

  In the present invention according to claim 4, the male screw portion formed on the ring bit is formed as a single thread, and only one pin-like projection of the outer pipe casing is provided. A dual pipe drilling tool according to any one of 3) is provided.

  In the invention according to the fourth aspect, the first specific example of the male screw portion formed in the ring bit is shown. In the present invention, the male screw portion is formed as a single thread, and only one pin-like protrusion of the outer pipe casing is provided.

  According to a fifth aspect of the present invention, the male screw portion formed on the ring bit is formed as a multi-thread screw having 2 to 5 threads, and the pin-like protrusion provided on the outer pipe casing is The double pipe drilling tool according to any one of claims 1 to 3, wherein the number of threads according to the number of threads of the screw is distributed in the circumferential direction.

  In the invention according to the fifth aspect, the second specific example of the male screw portion formed in the ring bit is shown. In the present invention, the male screw portion is formed as a multi-threaded screw having 2 to 5 threads, and the pin-like projections provided on the outer pipe casing are circumferentially oriented according to the number of threads of the multi-threaded screw. It is distributed. If the ring bit is pushed forward by mistake when relocking after unlocking the engagement between the ring bit and the outer tube casing, depending on the direction, if the pin-like protrusion is one or two, the ring Since the bit may be angularly broken with respect to the shaft core O, in consideration of the stability of the engagement relationship between the ring bit and the outer pipe casing, the male screw portion is a multi-row screw of 3 to 5 threads. Is desirable. In this case, there are three to five pin-shaped projections, and contact at three to five points results in increased structural stability. Moreover, the circumferential length of each screw groove can be shortened, and the work of separating the outer pipe casing can be further improved.

  As described above, according to the present invention, the outer pipe casing can be reliably separated from the ring bit after drilling is completed, and the outer pipe casing can be reliably recovered.

It is a partially broken side view (at the time of drilling) of the double pipe drilling tool 1 according to the present invention. It is a longitudinal cross-sectional view of the double pipe drilling tool 1 according to the present invention. It is a front view of the double pipe drilling tool 1 according to the present invention. It is sectional drawing (IV-IV arrow directional view of FIG. 1) which shows the structure of the rotational force transmission part 9. As shown in FIG. The casing shoe 4 is shown, (A) is a longitudinal sectional view, and (B) is a front view. The ring bit 2 is shown, (A) is a longitudinal sectional view, (B) is a front view, and (C) is a rear view. The three-row groove formed in the surrounding surface of the ring bit 2 is shown, (A) is a side view, (B) is a rear view. The pilot bit 3 is shown, (A) is a side view, (B) is a front view. The example of the single groove formed in the surrounding surface of the ring bit 2 is shown, (A) is a side view, (B) is a rear view. The example of the double groove formed in the surrounding surface of a ring bit is shown, (A) is a side view, (B) is a rear view. It is a principal part expanded sectional view showing other forms of pin-like projection 17. It is a ground cross-sectional view which shows the operation | use point of a drainage and drainage boring work. It is a side view showing drilling machine 28. As shown in FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is procedure drawing (A)-(C) of drainage and drainage boring. BRIEF DESCRIPTION OF THE DRAWINGS It is procedure drawing (D)-(E) of the drainage drainage boring work.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  As shown in FIG. 1, the double pipe drilling tool 1 has an inner rod 6 with a pilot bit 3 mounted at its tip, and a ring bit 2 made rotatable around an axis O at its tip. It consists of an outer pipe casing 5, and in a state where the inner rod 6 is inserted into and combined with the outer pipe casing 5, a striking force transmitting portion 8 and a rotational force transmitting portion 9 are provided between the pilot bit 3 and the ring bit 2. It is possessed. In the figure, the device of reference numeral 7 externally fitted to the pipeline portion of the pilot bit 3 is a well-known down-the-hole hammer, which applies an impact force to the pilot bit 3. Further, the rotational force to the pilot bit 3 is given from the drifter through the inner rod 6.

  Hereinafter, it will be described in more detail. In the specification, the tip side refers to the tip side of the drilling rod, that is, the drilling surface side, and the base side refers to the original side of the drilling rod, that is, the drifter side.

  The ring bit 2 is a ring-shaped member as shown in FIG. 6 in detail, and a large number of carbide tips 10 are arranged along the circumferential direction at the outer peripheral portion of the tip. In the illustrated example, the carbide chips 10 are disposed along the circumferential direction along the three concentric circles on the outer circumference, the middle circumference, and the inner circumference. The outer peripheral portion of the ring bit 2 includes a large diameter outer peripheral portion 2A having the largest outer diameter, an intermediate outer peripheral portion 2B having an intermediate outer diameter, and a small diameter outer peripheral portion 2C having the smallest outer diameter in this order from the tip side. The male screw 13 described later is formed on the small diameter outer peripheral portion 2C. The male screw portion 13 is formed on the proximal end side of the small diameter outer peripheral portion 2C, that is, at an end position near the outer tube casing 5 over a predetermined range. It is a smooth outer peripheral surface 2c. The male screw portion 13 is formed as a multi-row screw with three threads, as shown in FIG. The multiple thread screw is a screw in which two or more parallel thread grooves are formed, and in the case of a triple thread screw, three insertion start points are provided in the circumferential direction. As shown in FIG. 7, the start point of the first thread thread 13a, the start point of the second thread thread 13b, and the start point of the third thread thread 13c are distributed at a central angle of 120 °. The circumferential length of each of the screw threads 13a to 13c is formed at least at a central angle over a range of 120 ° or more. In the illustrated example, the screw threads 13a to 13c are formed over a range of approximately 270 ° at the central angle.

  On the other hand, on the inner periphery of the ring bit 2, three impact force transmitting convex portions 11, 11... Receiving impact force from the pilot bit 3 are formed on the tip end side at intervals in the circumferential direction. Three rotational power transmission convex portions 12, 12... Are formed on the side at intervals in the circumferential direction.

  As shown in FIG. 1, the ring bit 2 is attached to the end of the outer tube casing 5 via a casing shoe 4. Generally, the casing shoe is a piece-like member and is often fixed to the end of the outer tube casing 5 by welding, but in this embodiment, the rod-shaped casing shoe 4 is screwed to the end of the outer tube casing 5 The ring bit 2 is attached to the casing shoe 4. The casing shoe 4 constitutes a part of the outer tube casing 5.

  The casing shoe 4 is a rod-like member, as shown in detail in FIG. 5, and includes a ring bit insertion portion 14 into which the base end side of the ring bit 2 is inserted at the tip end side. A striking force transmitting convex portion 15 which receives striking force from the pilot bit 3 is continuously formed in the circumferential direction on the base end side adjacent to the portion 14. Further, on the base end side, a female screw portion 16 for screw connection of the outer pipe casing 5 is formed. Three pin-shaped protrusions 17 are disposed on the inner peripheral surface of the outer pipe casing 5 at the tip end side of the outer pipe casing 5, that is, at an interval of 120 ° at a central angle along the circumferential direction. The pin-like projection 17 has a tip shape that engages with the male screw portion 13 formed on the ring bit 2. The ring bit insertion portion 14 includes a first engaging portion 14A having a relatively large inner diameter positioned at the distal end side and a first engaging portion 14B having a relatively small inner diameter positioned at the proximal end side, The inner diameter D2 of the first engaging portion 14A substantially matches the outer diameter of the intermediate outer peripheral portion 2B of the ring bit 2, and the outer diameter of the circle passing through the tip of the pin-like protrusion 17 in the second engaging portion 14B. D1 substantially matches the outer diameter of the smooth outer peripheral portion 2c of the small diameter outer peripheral portion 2C of the ring bit 2.

  The pin-like projection 17 has a through hole 4a formed on the peripheral surface of the outer pipe casing 15 (casing shoe 4), and is installed in the through hole 4a in a state in which the shaft member is projected inside. It is desirable to fix by welding. It is desirable that the pin-like projections 17 have a cylindrical shape, as shown in FIG. Since the screw of the male screw 13 formed on the ring bit 2 is shaped like a mountain, if the pin-shaped protrusion 17 has a cylindrical shape, a gap is formed between the pin-shaped protrusion 17 and the screw thread. As a result, it is possible to prevent biting of the pin and to easily get over the dirt.

  In order to attach the ring bit 2 to the tip of the outer tube casing 5 (casing shoe 4), the base end side of the ring bit 2 is applied to the tip opening of the casing shoe 4 and viewed from the tip side Screw in the ring bit 2 while rotating it counterclockwise around the axis O. At the same time from the insertion start point (3 points) of the male screw portion 13 of the ring bit 2, the pin-shaped projections 17, 17 ... of the casing shoe 4 enter and the pin-shaped projections 17, 17 ... ring It is made to slip out to the smooth outer peripheral surface 2 c beyond the male screw portion 13 of the bit 2. In this combined state, the ring bit 2 is rotatable around the axis O while the tip end surface of the pin-like projection 17 slides on the smooth outer peripheral surface 2 c of the ring bit 2. Further, the ring bit 2 can move the pin-like protrusion 17 within the range of the distance L of the smooth outer peripheral surface 2c in the longitudinal direction (axis O direction), and within this movable range, the axis O direction It is possible to slide on. In the drilled state shown in FIG. 1, the first engaging portion 14A of the casing shoe 4 is externally fitted in a sliding state with respect to the intermediate outer peripheral portion 2B of the ring bit 2, and the second engaging portion 14B of the casing shoe 4 The tip end surface of the pin-shaped projection 17 is in sliding contact with the outer surface of the small diameter outer peripheral portion 2C of the ring bit.

  On the other hand, as shown in detail in FIG. 8, the pilot bit 3 has a plurality of cemented carbide tips 10, 10. On the outer peripheral surface, in order from the front end side, a first striking force transmitting abutment portion 18 for giving a striking force to the ring bit 2, and a striking force transmission for giving a striking force to the ring bit 2 at the time of retreating Abutment portion 19, a rotational force transmitting abutment portion 20 for applying a rotational force to the ring bit 2, and a second striking force transmission for applying an impact force to the outer tube casing 5 (casing shoe 4) A collision part 21 is provided.

  The first striking force transmission abutment portion 18, the backward striking force transmission abutment portion 19, the rotational force transmission abutment portion 20 and the second striking force transmission abutment portion 21 are each formed along the circumferential direction. It is distributed and arranged so as to be discontinuous. Three abutment portions 18 to 21 are provided along the circumferential direction in the illustrated example. Further, the striking force transmission abutment portion 19 for reverse movement and the rotational force transmission abutment portion 20 are disposed so as to be displaced in the longitudinal direction of the member, and the abutment of the rotational force transmission abutment portion 20 is performed. When the rotational force transmitting convex portions 12, 12 of the ring bit 2 are positioned with respect to the position, the retreating impact force transmitting abutting portion 19 is positioned on the tip end side.

  Recesses 22 22 are formed in the pilot bit 3 at a central angle of 120 ° along the longitudinal direction of the member. By forming the recesses 22 22, the rotational force of the ring bit 2 is obtained. The pilot bit 3 can be inserted into the ring bit 2 while avoiding the transmission projections 12, 12.

  In the inside of the pilot bit 3, as shown in FIG. 2, a drilling water supply channel 23 is formed along the axial direction, and at the front end portion, a drilling front surface portion is formed by the channel 24 leading to the tip surface. It is supposed to be discharged. In addition, a part of the drilling water is supplied to the rotational force transmission unit 9 by the branch flow channel 25 and is supplied to the striking force transmission unit 8 by the branch flow channel 26 and is used as flushing water for preventing bite of earth and sand It has become so. The recess 22 in the longitudinal direction of the member formed on the outer peripheral surface of the pilot bit 3 constitutes a slime discharge passage 27 at the time of drilling.

  In order to lock the ring bit 2 by combining the pilot bit 3 with the pilot bit 3, the pilot bits 3 are made to pass through the recesses 22, 22. When the first striking force transmitting abutment portion 18 is inserted until it strikes the striking force transmitting convex portions 11, 11... Of the ring bit 2, as viewed from the proximal end, it turns counterclockwise. When it is rotated, the rotational force transmitting convex portions 12 of the ring bit 2 are positioned with respect to the adjacent position of the rotational force transmitting abutment portion 20. Further, the second striking force transmitting abutment portion 21 of the pilot bit 3 is in contact with the striking force transmitting convex portion 15 of the casing shoe 4. This state is the state shown in FIG. 1 and is in the locked state.

  In order to release the locked state, the pilot bit 3 is rotated clockwise as viewed from the base end side, and the concave portions 22 and 22 ... of the pilot bit 3 and the convex portions 12 and 12 for torque transfer of the ring bit 2 Can be separated from the ring bit 2 when the pilot bit 2 is pulled to the base end side.

[Other embodiment]
(1) In the embodiment described above, the male screw portion 13 consisting of three multi-thread threads is formed on the ring bit 2, but the male screw portion 13 is formed as shown in FIG. , Can be formed as a general single thread. In this case, only one pin-like projection 17 is provided on the casing shoe 4. Moreover, as shown in FIG. 10, it can also be formed as two multi-threaded screws 13a and 13b. In this case, a total of two pin-shaped protrusions 17 are provided on the casing shoe 4 in the direction of 180 °. In the case where the male screw portion 13 is a multi-threaded screw, it may be formed as a multi-threaded screw having 2 to 5 threads. In this case, the pin-shaped projections 17 formed on the casing shoe 4 are distributed in the circumferential direction in a number corresponding to the number of threads of the multi-threaded screw.

(2) In the embodiment described above, the pin-like protrusion 17 provided on the casing shoe 4 forms the through hole 4 a on the circumferential surface of the casing shoe 4, and the shaft member protrudes to the inside through the through hole 4 a. Although installed and fixed by welding from the outer surface side, as shown in FIG. 11, a female screw hole 4b is formed in the circumferential surface of the casing shoe 4, and the inner surface side with respect to the female screw hole 4b Alternatively, the shaft of the bolt member 27 whose head conforms to the thread groove shape of the external thread 13 of the ring bit 2 may be screwed together and fixed by welding from the outer surface side.

[Example of construction]
Next, a construction procedure (collection of water and drainage boring work) for installing a collection and drainage mansett tube in the ground by a drilling machine using the double pipe drilling tool 1 will be described in detail. Collecting drainage boring work is a work to remove ground water and to reduce the pore water pressure acting on the sliding surface and to reduce the moisture content of the sliding soil mass.

  As shown in FIG. 12, the drainage drainage boring machine forms a vertical shaft 29 for the target ground, places a drilling machine 28 at its bottom, and performs multiple horizontal borings toward the mountain side. For each drilling, a manset tube (collector / drain tube) is installed. Groundwater collected by the Mansett tube is drained to the drainage channel by pump-up.

  As shown in FIG. 13, in the drilling machine 28, the guide cell 32 is connected by a link and jacks 30, 31 to the base racket 29, so that the inclination angle of the guide cell 32 is made variable. A drifter 33 which can be advanced and retracted along the guide cell 32 is mounted. The double pipe drilling tool 1 according to the present invention is connected to the drifter 33 through the cleaning adapter 34 so that drilling is performed. Only the inner rod 6 is connected to the cleaning adapter 34, the outer pipe casing 5 is not connected, and the annular space between the inner rod 6 and the outer pipe casing 5 is a slime discharge flow path, and the outer pipe casing is It is discharged from the rear end opening of 5 to the outside.

  Hereinafter, the construction procedure will be described in detail based on FIGS. 14 and 15.

<During drilling>
As shown in FIG. 14 (A), the striking force given to the pilot bit 3 is the striking force transmitting convex of the ring bit 2 in contact with the first striking force transmitting abutment portion 18 of the pilot bit 3. The casing shoe 4 is transmitted to the ring bit 2 via the portion 15 and via the striking force transmitting convex portion 15 of the casing shoe 4 that is in contact with the second striking force transmitting abutment portion 21 of the pilot rod 3. It is transmitted to (the outer tube casing 5). Further, the rotational force applied to the pilot bit 3 is transmitted to the ring bit 2 via the rotational force transmitting convex portion 12 of the ring bit 2 adjacent to the rotational force transmitting abutment portion 20 of the pilot bit 3. Ru.

  In this drilling state, the position of the ring bit 2 is determined by the contact between the first striking force transmitting abutment portion 18 of the pilot bit 3 and the striking force transmitting convex portion 15 of the ring bit 2. (2) Since the position of the casing shoe 4 is determined by the abutment between the striking portion 21 for striking force transmission and the striking portion 15 for transmitting the striking force of the casing shoe 4, the pin-like projection 17 of the casing shoe 4 and the male screw of the ring bit 2 There is no interference with the part 13.

<Backward (Flushing)>
As shown in FIG. 14 (B), when bite of earth and sand occurs in the middle of drilling, the inner rod 6 is moved to the base end side together with the pilot bit 3, and the earth and sand is ejected by injection of drilling water. Try to wash it out. When the pilot bit 3 retreats, the abutment portion 19 for striking power transmission of the pilot bit 3 collides with the end side surface of the convex portion 12 for rotational force transmission of the ring bit 2 and makes the ring bit 2 retreat. When the end face on the rear end side collides with the side face on the tip side of the second striking force transmitting abutment part 21 of the pilot bit 3, the further movement is restricted. Also in this case, since the pin-shaped projections 17 of the casing shoe 4 are located within the range of the distance L of the smooth outer peripheral surface 2 c of the ring bit 2 in the longitudinal direction (axial O direction), the pin-shaped projections 17 and the ring bit There is no interference with the male screw portion 13 of 2. In addition, when the slime gets stuck in the gap between the outer pipe casing 5 and the hole wall and the outer pipe casing 5 can not move any further, the inner rod 6 is retreated in the locked state and the flushing water Although there is also a case where edge cutting with the hole wall is performed by injection, the positional relationship between the pin-like protrusion 17 and the male screw portion 13 of the ring bit 2 is also similar in this case.

<Removal of pilot bit 3 and inner rod 6>
As shown in FIG. 14C, when drilling is completed, the pilot bit 3 is rotated clockwise, and the projections 22 for the pilot bit 3 and the projections for transmitting the rotational force of the ring bit 2 are rotated. If the sections 12 and 12 are made to coincide with the axis O direction, the pilot bit 2 is pulled to the base end side, the pilot bit 3 is separated from the ring bit 2, and the pilot bit 3 is removed together with the inner rod 6. Do.

<Insertion of Manset tube>
As shown in FIG. 15 (D), a manset tube 35 (a polyvinyl chloride pipe having a large number of openings 35a formed therein) is inserted and installed inside the outer pipe casing 5.

<Removal of outer pipe casing 5>
When the rear end of the outer tube casing 5 is connected (screw connection) to the cleaning adapter 34, when the outer tube casing 5 is rotated clockwise while being retracted, the pin-like projection 7 of the casing shoe 4 is a ring bit The casing shoe 4 is inserted into the groove of the male screw 13 and rotated along the groove of the male screw 13 and separated from the ring bit 2 when the male screw 13 is released. After that, the outer pipe casing 5 is pulled out and removed.

  At the time of separation from the ring bit 2, the casing shoe 4 side is not a screw but a pin-like projection 17, so there is no biting of earth and sand, and the casing shoe 4 can be rotated smoothly and separated from the ring bit 2 .

  DESCRIPTION OF SYMBOLS 1 ... double pipe drilling tool, 2 ... ring bit, 2c ... smooth outer peripheral surface, 3 ... pilot bit, 4 ... casing shoe, 5 ... outer pipe casing, 6 ... inner rod, 7 ... down the hole hammer, 8 ... striking Force transmitting portion 9: rotational force transmitting portion 10: cemented carbide tip 11: convex portion for striking force transmission 12: convex portion for rotational force transmission 13: male thread portion 14: ring bit engaging portion 15 ... A striking force transmitting projection, 16 ... female screw, 17 ... pin-like projection, 18 ... first striking force transmitting abutment, 19 ... retraction striking power transmitting abutment, 20 ... rotational force transmitting The abutting portions 20, 21: second striking force transmitting abutting portions 21, 22: concave portions, 23: drilling water supply flow path, 28: drilling machine, 32: guide cell, 33: drifter, 34: cleaning adapter

Claims (5)

It consists of an inner rod with a pilot bit attached to the tip and an outer pipe casing with a ring bit attached to the tip, which is rotatable around an axis, and the inner rod is inserted into the outer pipe casing and combined A double pipe drilling tool having an impact force transmitting portion and a rotational force transmitting portion between the pilot bit and the ring bit;
The engagement structure between the ring bit and the outer pipe casing forms a male thread over a predetermined range at an end position on the outer peripheral surface of the ring bit and near the outer pipe casing, while the outer pipe A pin-like protrusion is provided on the inner peripheral surface at the tip end side of the casing and engaged with the male screw portion, and screwed into the tip opening of the outer pipe casing while rotating the ring bit around the axial center. A double pipe drilling tool characterized in that the projection is pulled out of the male screw portion of the ring bit to the smooth outer peripheral surface.   The pin-shaped projection is provided with a through hole on the circumferential surface of the outer tube casing, and the shaft member is installed in the through hole so as to project to the inner side, and fixed by welding from the outer side. The double pipe drilling tool according to 1.   The pin-shaped projection forms a female screw hole in the peripheral surface of the outer tube casing, and from the inner surface side with respect to the female screw hole, a shaft portion of a bolt member whose head matches the screw groove shape of the ring bit The double pipe drilling tool according to claim 1, wherein the two pipe drilling tools are screwed together and fixed by welding from the outer surface side.   The double pipe according to any one of claims 1 to 3, wherein the male screw formed on the ring bit is formed as a single thread, and only one pin-like protrusion of the outer pipe casing is provided. Drilling tool.   The external thread portion formed on the ring bit is formed as a multi-thread screw having 2 to 5 threads, and the pin-like projections provided on the outer pipe casing have a number corresponding to the number of threads of the multi-thread screw. The double pipe drilling tool according to any one of claims 1 to 3, which is distributed in the circumferential direction.

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