JP2017061787A - Head for drilling expanded hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a head for drilling an expanded hole that enables opening/closing operation of an expansion vane with a simple structure and that can detect whether the expansion vane is expanded.SOLUTION: In a head for drilling an expanded hole, a lower shaft is inserted in a shaft hole of an upper shaft 2 for connection in a manner of being rotatable in forward and inverse directions at a predetermined angle. A shaft part 16 for supporting an expansion vane 15 arranged to face each other in the diameter direction so as to be rotatable within the predetermined angle is installed in an upper bracket 12a and a lower bracket 12b, and the upper bracket and the lower bracket are fitted to the lower shaft. An expansion vane operating member 20 for expanding the diameter of the expansion vane 15 is fitted to the upper shaft 2. A shear pin 13 for inspecting expansion of the diameter of the expansion vane 15 is installed between the upper and lower brackets 12a and 12b.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an enlarged hole excavation head, and more particularly to an enlarged hole excavation head used when constructing a foundation steel pipe pile or a concrete pile having a bulb portion in civil engineering work.

  In order to construct a foundation steel pipe pile or concrete pile, a ground hole or a screw auger is used to excavate an underground hole, and the foundation steel pipe pile or concrete pile is built. At this time, in order to increase the supporting force of the foundation steel pipe pile or the like, the bottom portion of the underground hole is subjected to diameter expansion excavation at a required depth position, and the lower end portion of the underground hole is expanded into a bulb shape.

  As described above, as means for forming the bulb-shaped widened portion at the lower end portion of the underground hole, for example, a drilling head having an expanded drilling blade as disclosed in Japanese Patent Laid-Open No. 11-350473, There is an enlarged hole drilling device disclosed in Japanese Patent Publication No. 1-75194.

  In the invention disclosed in Japanese Patent Laid-Open No. 11-350473, when the tip of the steel pipe pile reaches the support layer, the auger screw inserted into the steel pipe pile is reversed and contracted to the lower end of the auger screw. This is a method of expanding the portion where the tip of the steel pipe pile is located by expanding the diameter of the expansion bit inserted in the diameter state and simultaneously moving it up and down.

  Further, the enlargement excavation apparatus disclosed in Japanese Utility Model Laid-Open No. 1-75194 reverses the excavation rod after entraining the excavation blades into the ground and constrains the rotation so that the tip of the pressing knock faces the rear end of the enlargement blade. The expansion blade is forcibly rotated outward by pushing it out and pressing it, so that the expanded expansion blade is used for the expansion excavation.

  In these excavation heads and expansion excavators, in order to excavate an expansion hole, the operation must be changed from forward rotation (clockwise direction) to reverse rotation (counterclockwise direction). In that case, since the tip of the auger head and the excavation blades rotate in the opposite direction, the ability to excavate the bottom of the underground hole is significantly reduced, and the work efficiency is also significantly reduced. Further, in the expansion excavator, there is no means for locking the expansion blade during the forward rotation of the excavation rod, so that rocks or the like enter between the expansion blade and the press knock during the normal rotation, and rotate the expansion blade, There is also a risk of inadvertently drilling an enlarged hole.

  Therefore, the inventors, as in the inventions described in Japanese Patent No. 2711236 and Japanese Patent No. 4945603, can also perform the forward rotation when excavating the enlarged hole, can form the enlarged hole to a desired depth, An expansion hole excavation head that prevents the expansion blade from being inadvertently expanded during normal rotation has been proposed. That is, in the enlarged hole excavation head described in Japanese Patent No. 2711236, when the enlarged hole is excavated, when the excavator blade is bitten into the bottom of the hole and the outer cylinder is fixed, the drive shaft is reversely rotated. Within the range in which the key portion and the key groove are loosely fitted, the kick pin is detached from the enlarged blade, and is expanded by pushing the enlarged blade outward in the radial direction.

  Then, when the drive shaft is rotated forward, the expanding blade receives the resistance of the soil and fully expands, and excavates the soil together with the excavating blade. After drilling the excavation hole of a predetermined depth, when the drive shaft is pulled upward while rotating in reverse, the enlargement blade is folded while rotating due to the resistance of the soil, and the kicking pin is engaged with the enlargement blade. At the same time, the original state is restored.

  Further, in the enlarged hole excavation head described in Japanese Patent No. 4945603, when the enlarged hole is excavated, the enlarged blade is held in a reduced state within the radius of the excavating blade by the enlarged blade operating member. The release of the expansion blade and the expansion blade are kicked outward to expand the diameter almost simultaneously, so that the expansion blade can be reliably contracted and expanded, and the expansion blade can be operated during the reverse rotation of the upper shaft. The kicking part of the member forcibly spreads the expanding blade outward until the tip of the expanding blade protrudes from the radius of the drilling blade, so that the radius of the drilling blade can be increased even in the case of viscous ground. The diameter can be reliably expanded until it is located outside.

  Further, when the expanding blade is expanded to a predetermined angle, the inner surface in the vicinity of the shaft portion of the expanding blade comes into contact with the stopper, so that the expanded blade is expanded to a predetermined angle and the expanded diameter is maintained, and the desired diameter is maintained. It is assumed that the enlarged hole can be drilled reliably.

Japanese Patent Laid-Open No. 11-350473 Japanese Utility Model Publication No. 1-75194 Japanese Patent No. 2711236 Japanese Patent No. 4945603

  However, in the above invention, the structure corresponding to the viscous ground is made, so the structure of the enlarged hole excavation head is complicated. There were restrictions on use, such as the need to repair the excavation head. Moreover, inconveniences such as the difficulty of excavation itself have occurred in a gravelly ground having a high N value and high excavation resistance (N value).

  In order to overcome the drawbacks of the prior art as described above, the present invention can realize the operation of expanding and reducing the diameter of the expanding blade with a simple structure, and also improves the durability. An object of the present invention is to provide an enlarged hole excavation head capable of reliably forming an enlarged hole even in a ground having a large excavation resistance.

In order to achieve the above object, according to a first aspect of the present invention, a lower shaft is connected to a lower end portion of an upper shaft provided with a connecting portion connected to a drive shaft at an upper end portion so as to be able to rotate forward and backward by a predetermined angle. Then,
The lower shaft is provided with an enlarged blade supporting member composed of an upper bracket and a lower bracket that pivotally support the enlarged blade so as to be rotatable within a predetermined angle at at least two positions opposed to each other in the diameter direction.
At the time of forward rotation of the upper shaft, one end is in contact with the rear end portion near the shaft portion of the expansion blade, and the expansion blade is folded within the radius of the excavation blade attached to the lower shaft. As a torque transmission part to hold, and at the time of reverse rotation, the other end collides with the tip of the enlargement blade, and the enlargement blade is forced to a position where the tip of the enlargement blade protrudes from the radius of the excavating blade. An expansion hole excavation head equipped with expansion blade operation members each functioning as a kicking-out portion that expands outward in the direction,
As a stopper to prevent the enlargement blade from expanding its diameter by abutting the diameter-expansion side shaft portion of the enlargement blade during forward rotation of the upper shaft, and during the reverse rotation of the upper shaft, The enlarged blade detecting means functioning as a detecting portion for detecting the enlarged diameter of the enlarged blade is provided between the upper bracket and the lower bracket of the enlarged blade supporting member. An enlarged hole excavation head characterized in that it is provided.

  Further, in the invention according to claim 2 of the present application, the expanding blade detecting means is a bolt in which upper and lower ends are respectively fixed to the upper bracket and the lower bracket of the expanding blade support member, and the diameter of the expanding blade is increased. A shear guide groove is provided at two upper and lower portions across a height interval larger than the thickness of the vicinity of the side shaft portion.

  In the invention according to claim 3 of the present application, when the enlarged blade expands to a predetermined angle, the enlarged blade contacts the outer surface on the reduced diameter side in the vicinity of the shaft portion of the expanded blade and increases the diameter more than the predetermined angle. A stopper member for blocking is provided on the reduced diameter side near the shaft portion of the enlarged wing.

  Further, in the invention according to claim 4 of the present application, the excavation blade mounted on the lower shaft is provided with an auxiliary expansion blade composed of a blade expansion portion and a positioning member that expands substantially to the outer diameter of the pile. Features.

  In the present invention, the stopper that prevents the expansion blade from expanding its diameter by contacting the upper bracket and the lower bracket of the expansion blade support member with the vicinity of the shaft portion on the diameter expansion side of the expansion blade during the forward rotation of the upper shaft. Further, when the upper shaft rotates in the reverse direction, the shaft portion near the diameter expansion side of the expansion blade abuts and is sheared to break, and each of the detection means functions as a detection unit that detects the diameter expansion of the expansion blade. The structure provided with the enlarged blade operating member can simplify the structure, and as a result, the thickness of the constituent member can be increased to increase the durability.

  Further, in the present invention, it is possible to confirm that the diameter of the expansion wing is surely expanded by observing the expansion wing detection means, and that the expansion hole having a predetermined diameter is drilled in the expanded state.

  Further, in the present invention, the expansion blade detection means is a bolt having upper and lower ends fixed to the upper bracket and the lower bracket of the expansion blade support member, respectively, in the vicinity of the shaft portion on the diameter expansion side of the expansion blade. By adopting a configuration in which two shear guide grooves are provided at the upper and lower portions with a height interval larger than the thickness, when the bolt receives pressure, the bolt is reliably sheared at the position of the shear guide groove, The diameter expansion is not hindered, and the diameter can be reliably increased when it is desired to increase the diameter of the expansion blade.

  In the invention, when the enlarged blade expands to a predetermined angle, a stopper member that abuts the outer surface of the shaft portion near the reduced diameter side of the expanded blade and prevents the expanded diameter by a predetermined angle or more is provided. Since the structure is provided on the reduced diameter side near the shaft portion of the blade, the rotating radius of the enlarged blade can be kept constant, and the drilling hole of the desired diameter is reliably drilled at the lower part of the underground hole can do.

  Further, according to the present invention, the excavation resistance is provided on the excavation blade attached to the tip of the lower shaft by providing the auxiliary expansion blade composed of the expansion portion and the positioning member that expands to the outer diameter of the pile substantially. The excavation of the expansion hole becomes easy even in gravelly ground with a large N value.

It is a front view of the head for enlarged hole excavation concerning the present invention. It is a right view of the expansion hole excavation head. It is a front view in the state where the auxiliary expansion blade of the expansion hole excavation head expanded in diameter. It is CC sectional view taken on the line of FIG. It is the BB sectional view taken on the line of FIG. It is CC sectional view taken on the line of FIG. 1 at the time of the diameter expansion operation start of an expansion blade. It is the BB sectional drawing of FIG. 1 at the time of the diameter expansion operation start of the expansion blade. It is CC sectional view taken on the line of FIG. 1 at the time of the diameter expansion operation 1st stage of the expansion blade. It is the BB sectional view taken on the line of FIG. 1 at the time of the 1st step of diameter expansion operation of the expansion blade. It is CC sectional view taken on the line of FIG. 1 at the time of the diameter expansion operation 2nd stage of the expansion blade. It is CC sectional view taken on the line of the state which the same expansion blade expanded to the maximum. It is a bottom view of the state where the auxiliary expansion wing is expanded to the maximum. It is an enlarged view of D section of FIG. It is an enlarged view after the shear pin shearing of D section of FIG. It is longitudinal cross-sectional explanatory drawing at the time of expansion hole excavation.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in FIGS. In the figure, reference numeral 1 denotes an enlarged hole excavation head according to the present invention, and reference numeral 2 denotes an upper shaft having a connecting portion 3 with a drive shaft 101 at the upper end. Reference numerals 4 and 4 denote key grooves formed on the inner peripheral surface of the shaft hole 5 of the upper shaft 2. The key grooves 4 and 4 extending in the axial direction A are opposed to each other in the diameter direction of the upper shaft 2. Are formed respectively. In the figure, reference numeral 6 denotes a spiral excavating blade provided on the lower outer peripheral surface of the upper shaft 2.

  Reference numeral 8 denotes a lower shaft. On the outer peripheral surface of the upper end portion thereof, key portions 9 and 9 that are loosely fitted and engaged with the key grooves 4 and 4 in the shaft hole 5 of the upper shaft 2 are provided at the lower portion of the lower shaft 9. Helical excavating blades 10 are provided on the outer peripheral surface, and the upper end of the lower shaft 8 is inserted into the shaft hole 5 at the lower portion of the upper shaft 2 to connect the shafts 2 and 8 together. Yes.

  The upper shaft 2 and the lower shaft 8 are within a range in which the key groove 4 and the key portion 9 are loosely fitted. For example, in this embodiment, the upper shaft 2 has a central angle of 60 with respect to the lower shaft 8. The structure allows forward rotation (clockwise) and reverse rotation (counterclockwise) within a range of degrees. In the figure, reference numeral 11 denotes a plurality of excavation blade tips provided in a row at the lower end of the excavation blade 10.

  Reference numeral 12 denotes an enlarged wing support member fixed to the upper portion of the lower shaft 8, and is composed of an upper bracket 12a and a lower bracket 12b having a rectangular shape in plan view, which are mounted apart from each other in the vertical direction. Insertion holes 14 for attaching bolts 13 to be described later are formed at two positions opposite to each other in the diametrical direction of the lower shaft 8 near the side surfaces 12c at both ends of 12a and 12b.

  Reference numeral 15 denotes an enlarged wing, which is composed of an arm portion 18 having a large width and thickness to enhance durability, and a tip blade 19 provided at the tip thereof, on the inner side surface 18 a side of the arm portion 18. In the vicinity of the bent rear end portion, it is installed so as to be rotatable by cylindrical shaft portions 16 and 16 in the vicinity of both end portions between the upper and lower brackets 12a and 12b.

  Reference numeral 20 denotes an enlargement blade operating member mounted on the upper shaft 2 via a plate 21, and the front view of the outer surface 21 a of the plate 21 that hangs down from a position facing each other in the diameter direction of the upper shaft 2 is a horizontal platform. Each side end 20a faces the rear end face 18b side of the arm portion 18 of one of the enlarged blades 15 and the other side end 20b faces the tip blade 19 side of the other enlarged blade 15 respectively. It is fixed to the plate 21 and is installed so as to be rotatable in the circumferential direction around the upper shaft 2.

  With the above configuration, the upper shaft 2 is rotated forward, and the one end 20a of the expanding blade operating member 20 is brought into contact with the rear end surface 18b of the arm portion 18 of the one expanding blade 15, whereby the axis of the expanding blade 15 It is possible to prevent rotation in the diameter increasing direction around the portion 16. Further, by causing the other side end 20 b of the expansion blade operation member 20 to abut against the inner portion 19 a of the tip blade 19 of the other expansion blade 15, the diameter of the expansion blade 15 is forcibly expanded about the shaft portion 16. Can do.

  Reference numeral 13 denotes a function as a stopper for preventing the enlarged blade 15 from inadvertently expanding the diameter, and a shear pin that functions as an enlarged blade detecting means for detecting the expanded blade 15 when the diameter is increased. The bolt 13a is formed with two shear guide grooves 13c and 13c spaced apart from each other at a distance slightly larger than the thickness in the vicinity of the shaft portion on the diameter expansion side of the expansion blade 15. In the figure, reference numeral 13b denotes a nut screwed onto the bolt 13a from the lower surface side of the lower bracket 12a, and the shear pin 13 is fixed so as to span between the upper and lower brackets 12a and 12b.

  A stopper member 22 is mounted on the side surface 12c near both ends of the upper and lower brackets 12a and 12b, and is disposed in the vicinity of the outer diameter surface 18c on the reduced diameter side of the shaft portion vicinity portion 7 of the expanding blade 15. When two stopper members 22 are arranged at positions opposed to each other in the diameter direction of the lower shaft 8, they are fixed so as to bridge between the upper and lower brackets 12a and 12b. .

  With the above configuration, when the enlarged blade 15 is first folded within the radius R of the excavating blades 6, 10, the outer side surface 18c on the reduced diameter side of the shaft portion vicinity portion 7 of the enlarged blade 15 is the stopper. The contact with the inclined surface 22a of the member 22 restricts the movement of the enlarged blade 15 to reduce the diameter of the lower shaft 8 more than necessary around the shaft portion 16, and the enlarged blade 15 enters the lower shaft 8 side. It ’s not too much.

  In addition, when the expanding blade 15 expands outward with the shaft portion 16 as a center, and the shear pin 13 receives a strong pressure by the inner surface 18a on the expanded diameter side of the arm portion 18 of the expanding blade 15, the shear pin 13 13 is sheared between the two upper and lower shear guide grooves 13c, 13c, and it can be detected that the enlarged blade 15 has expanded its diameter. After the shear pin 13 is sheared, the arm portion 18 of the expansion wing 15 can pass freely.

  When the rear end portion of the arm portion 18 passes between the shear pins 13 and 13 remaining in both the upper and lower brackets 12a and 12b, and when the expanding blade 15 expands to the maximum extent around the shaft portion 16, that is, When the diameter of each of the two expanding blades 15, 15 is increased to a linear position facing each other across the shaft portion 16, the outer surface 18 c of the shaft portion vicinity portion 7 of the expanding blades 15, 15 is in contact with the stopper member 22. Abutting on the tip surface 22b, the movement of the expanding blade 15 in the diameter expansion is stopped, and further expansion of the expanding blade 15 around the shaft portion 16 is prevented.

  Reference numeral 23 denotes an auxiliary enlarged wing provided near the outer periphery of the excavating blade 10 of the lower shaft 8. Bolts 25 a and 25 a are provided on both sides so as to sandwich the excavating blade 10 inside an L-shaped bracket 24 that is a positioning member. The nut 25b is rotatably supported. The auxiliary expanding blade 23 is centered on the bolt 25a from the state where the auxiliary expanding blade 23 is folded within the radius R of the excavating blade 10 to the state where the side surface portion 23a of the auxiliary expanding blade 23 contacts the upper side portion 24a of the bracket 24. The diameter can be expanded, and the expanded holes can be excavated in the lower part of the underground hole 111 by the two auxiliary expanded blades 23 and 23 whose diameters are increased.

  Further, normally, the auxiliary expanding blade 23 is fixed to the excavating blade 10 by spot welding in a folded state so as not to inadvertently expand the diameter. The length of the auxiliary expansion blade 23 is such that the rotation radius r1 when the diameter of the auxiliary expansion blade 23 is expanded to the maximum is slightly smaller than the rotation radius r2 when the expansion blade 15 is expanded to the maximum. Is set.

  Next, the operation of the enlarged hole excavation head 1 will be described. When excavating the underground hole 111 having a predetermined depth from the ground, the drive shaft 101 is rotated in the forward direction (clockwise) so that the drive shaft The upper shaft 2 connected to 101 via the connecting portion 3 and the enlarged blade operating member 20 attached to the upper shaft 2 via the plate 21 rotate in the same direction.

  When the enlargement blade operation member 20 rotates forward, one side end 20a of the hanging portion of the enlargement blade operation member 20 comes into contact with the rear end surface 18b of the arm portion 18 of the enlargement blade 15 as shown in FIGS. . As a result, the outward movement (expansion) of the expansion blade 15 around the shaft portion 16 is prevented, and the expansion blade 15 is held in a state of being folded within the radius R of the excavating blades 6 and 10. .

  At the same time, the outer side surface 18c of the rear end portion of the arm portion 18 of the expanding blade 15 contacts the inclined surface 22a of the stopper member 22, and further movement in the lower shaft 8 side direction around the shaft portion 16 of the expanding blade 15 ( Reduction in diameter) is also prevented. As a result, the expanding blade 15 cannot rotate around the shaft portion 16 and is fixed in a state where it is folded within the radius R of the excavating blades 6, 10.

  Here, due to some trouble, the upper shaft 2 rotates in the reverse direction, and as shown in FIGS. 6 and 7, one end 20 a of the enlarged blade operating member 20 is slightly separated from the rear end surface 18 b of the arm portion 18 of the enlarged blade 15. Even in this case, the inner side surface 18a of the rear end portion of the arm portion 18 of the expansion blade 15 abuts against the shear pin 13, and the rotation of the expansion blade 15 in the diameter expansion direction is prevented. The folded state within the radius R of the blade 10 is maintained.

  The upper wing operating member 20 mounted on the upper shaft 2 and the upper shaft 2 via the plate 21 rotates in the forward direction, and as shown in FIG. 5, the key groove 4 of the shaft hole 5 of the upper shaft 2 is in the positive rotation direction side. The end surface 4 a of the lower end 8 abuts on the key portion 9 of the lower shaft 8. When the upper shaft 2 further rotates forward, the lower shaft 8 rotates forward together with the upper shaft 2.

  As a result, the excavating blades 6 and 10 and the excavating blade tip 11 mounted on the outer peripheral surfaces of the upper shaft 2 and the lower shaft 8 rotate in the same direction, so that the drive shaft 101 causes the lower shaft 8 to pass through the upper shaft 2 with respect to the lower shaft 8. By applying the pushing force in the axial direction A, the underground hole 111 having a predetermined depth can be excavated in the ground 113.

  Next, when the expansion hole 112 is formed below the underground hole 111 after the underground hole 111 reaches a predetermined depth from the ground, the drive shaft 101 is stopped once the rotation of the drive shaft 101 is stopped. By applying a pushing force in the axial direction A to the lower shaft 8 via the upper shaft 2, the excavation blade tip 11 provided at the lower end of the excavation blade 10 of the lower shaft 8 is caused to bite into the hole bottom 114, The lower shaft 8 is fixed to the hole bottom 114.

  Then, with the lower shaft 8 fixed to the hole bottom 114, the drive shaft 101 is rotated in the reverse direction (rotated counterclockwise), and the upper shaft 2 connected to the drive shaft 101 is rotated in the reverse direction. That is, the upper shaft 2 is within the range where the key groove 4 of the upper shaft 2 and the key portion 9 of the lower shaft 8 are loosely fitted from the state shown in FIGS. 4 and 5, for example, within the range of 60 degrees in this embodiment. By rotating the upper shaft 2 in the reverse direction, the end surface 4b of the key groove 4 of the upper shaft 2 on the reverse rotation direction side abuts against the key portion 9 of the lower shaft 8 in the state shown in FIG.

  When the upper shaft 2 rotates in the reverse direction, one side end 20a of the hanging portion of the expanding blade operating member 20 attached to the upper shaft 2 via the plate 21 is set to the rear end surface 18b of the arm portion 18 of the one expanding blade 15. And the state shown in FIG. Then, by continuing the reverse rotation of the upper shaft 2, the enlarged blade operating member 20 approaches the other enlarged blade 15 while drawing an arc, and as shown in FIG. The side end 20b is in contact with the inner portion 19a of the tip blade 19 of the magnifying blade 15.

  Then, when the upper shaft 2 is reversely rotated even after the state shown in FIG. 9 in which the end surface 4b on the reverse rotation direction side of the key groove 4 of the upper shaft 2 collides with the key portion 9 of the lower shaft 8, the enlarged blade operating member The other end 20b of the drooping portion 20 moves to the position of the inner portion 19a of the tip blade 19 of the expanding blade 15 (see FIG. 8). Accordingly, the tip blade 19 of the magnifying blade 15 is forcibly pushed out by the magnifying blade operation member 20 and rotated counterclockwise about the shaft portion 16, so that the outer portion 19 b of the tip blade 19 becomes the digging blades 6, 10. It moves (expands) to a position protruding outside the radius R.

  As described above, the enlargement blade 15 is expanded outward by the enlargement blade operation member 20 around the shaft portion 6, so that the rear end portions of the arm portions 18 of the two enlargement blades 15 and 15 also have the shaft portion 16. It rotates counterclockwise as the center. As a result, as shown in FIG. 13, the shear pin 13 fixed so as to be passed between the upper and lower brackets 12a and 12b receives pressure by the inner side surface 18a of the arm portion 18, and as shown in FIG. Shearing is performed at the positions of the shear guide grooves 13c and 13c. Then, the rear end portion of the expanding blade 15 can freely pass between the shear guide grooves 13c and 13c of the shear pin 13 remaining in both the upper and lower brackets 12a and 12b, and the diameter can be increased.

  Next, the drive shaft 101 is rotated forward from the state shown in FIG. Along with this, the upper shaft 2 connected to the drive shaft 101 also rotates in the same direction, and the end surface 4a on the positive rotation direction side of the key groove 4 contacts the key portion 9 of the lower shaft 8 as shown in FIG. . When the drive shaft 101 is further rotated forward, the lower shaft 8 rotates in the same direction as the drive shaft 101 via the upper shaft 2 connected to the drive shaft 101.

  The forward rotation of the lower shaft 8 causes the tip blade 19a of the expanding blade 15 that has moved to a position protruding outside the radius R of the excavating blades 6, 10 to receive the resistance of the excavating soil, The diameter gradually increases around the portion 16 (see FIGS. 8 and 10). Then, the rear end portion of the arm portion 18 of the expanding blade 15 passes between the shear guide grooves 13c and 13c of the shear pin 13 remaining in the upper and lower brackets 12a and 12b as described above, and as shown in FIG. At the position opposite to each other in the diametrical direction of the upper shaft 2, the two enlarged wings 15, 15 are expanded until their arm portions 18, 18 are aligned.

  At this time, since the outer side surface 18c of the rear end portion of the arm portion 18 of the expansion blade 15 contacts the tip surface 22b of the stopper member 22, further diameter expansion of the expansion blade 15 is prevented. Therefore, by digging while maintaining the forward rotation of the drive shaft 101, the enlarged hole 112 is excavated by the tip blade 19 of the enlarged blade 15 at the lower part of the underground hole 111 at a desired depth, as shown in FIG. Can do.

  When the operation of excavating the enlarged hole 112 at the lower part of the underground hole 111 having a desired depth is completed, the drive shaft 101 is rotated in reverse. Accordingly, since the upper shaft 2 connected to the drive shaft 101 also rotates in the same direction, the end surface 4b on the reverse rotation direction side of the key groove 4 of the upper shaft 2 is the key portion of the lower shaft 8 as shown in FIG. 9, the lower shaft 8 gradually reversely rotates in the same direction as the upper shaft 2.

  The tip blade 19 of the enlarged wing 15 whose diameter is expanded to a position protruding outside the radius R of the excavating blades 6 and 10 by the reverse rotation of the lower shaft 8 is the outer surface 18c of the arm portion 18. Receives the resistance of the excavated soil, and the enlarged blade 15 gradually rotates rightward (reduced diameter) about the shaft portion 16 and rotates to the inside of the radius R of the excavating blades 6 and 10.

  As described above, when the tip blade 19 of the expanding blade 15 rotates and moves to the inside of the radius R of the excavating blades 6 and 10, the drive shaft 101 is now rotated forward. Accordingly, the upper shaft 2 connected to the drive shaft 101 also rotates in the same direction, and one side end 20a of the hanging portion of the expanding blade operating member 20 comes into contact with the rear end surface 18b of the arm portion 18 of the expanding blade 15. As a result, the outward movement (expansion) of the expansion blade 15 around the shaft portion 16 is prevented, and the expansion blade 15 is held in a state of being folded within the radius R of the excavating blades 6 and 10. .

  Here, since the shear pin 13 for detecting the expansion of the diameter of the expansion blade 15 is fixed to the upper and lower brackets 12a and 12b as shown in FIGS. 13 and 14, the expansion hole 112 is excavated. After the work is completed, it is possible to detect whether or not the enlarged blade 15 has been expanded by pulling the enlarged hole excavation head 1 upward and observing the state of the shear pin 13.

  Therefore, even if the enlarged blade 15 is folded when the enlarged hole excavation head 1 is pulled upward, if the shear pin 13 is sheared at the position of the shear guide groove 13c, It can be detected that the enlarged blade 15 has actually expanded in diameter during excavation, and it can be understood that the enlarged hole 112 has been excavated below the underground hole 111.

  Further, when it is determined that the excavation of the expansion hole 112 is difficult only by the expansion blade 15 due to the test ground, the auxiliary expansion blade 23 is released from the spot welding. As a result, when the lower shaft 8 rotates forward together with the drive shaft 101, the tip of the auxiliary expanding blade 23 is removed from the state shown in FIG. 2 where the auxiliary expanding blade 23 is folded within the radius R of the excavating blades 6, 10. 23b receives the resistance of the excavated soil and gradually expands around the bolt 25a.

  And since the auxiliary expansion blade 23 expands to the state shown in FIG. 3 and FIG. 12 where the side surface portion 23a of the auxiliary expansion blade 23 contacts the upper side portion 24a of the bracket 24, the expansion hole 112 can be excavated. .

  Further, when the excavation work of the enlarged hole 112 is completed and the enlarged hole excavation head 1 is pulled upward, the lower shaft 8 rotates in reverse with the drive shaft 101 as described above, so that the auxiliary enlarged blade 23 is made of excavated soil. It receives resistance and gradually closes, and returns to a state where it is folded within the radius R of the excavating blades 6 and 10, as shown in FIG.

  Here, if the auxiliary expansion blade 23 is not folded by biting earth and sand while the expansion hole excavation head 1 is pulled up, the thickness of the excavation blade 10 at the position where the auxiliary expansion blade 23 is fixed is as follows. As described above, since the structure is thin compared to other positions and is weak against the resistance in the vertical direction, the enlarged hole excavation head 1 is forcibly pulled up while breaking the thin position of the excavation blade 10.

  Moreover, you may use the bolt 25a with weak tensile resistance for the volt | bolt 25a which supports the auxiliary | assistant expansion blade 23 to the excavation blade 10 so that rotation is possible. By doing so, when the earth and sand are bitten and the auxiliary expansion wing 23 is not folded, the expansion hole excavation head 1 is forcibly pulled upward to break the bolt 25a, and the auxiliary expansion wing 23 is removed from the excavation blade 10. The enlarged hole excavation head 1 can be lifted upward while dropping.

DESCRIPTION OF SYMBOLS 1 Expansion hole excavation head 2 Upper shaft 3 Connection part 4 Key groove 5 Axis hole 6 Excavation blade 7 Axis part vicinity 8 Lower shaft 9 Key part 10 Excavation blade 11 Excavation blade tip 12 Expanding blade support member 12a Upper bracket 12b Lower part Bracket 12c Side surface 13 Shear pin 13a Bolt 13c Shear guide groove 14 Insertion hole 15 Expansion blade 16 Shaft portion 18 Arm portion 18a Inner side surface 18b Rear end surface 19 Tip blade 19a Inner side surface 20 Expanding blade operation member 20a One side end 20b Other side end 21 Plate 22 Stopper member 22a Slope 22b Tip surface 23 Auxiliary expansion wing 24 Bracket

Claims (4)

When the lower shaft is connected to the lower end of the upper shaft, which is connected to the drive shaft at the upper end, so that it can rotate forward and reverse by a predetermined angle,
The lower shaft is provided with an enlarged blade supporting member composed of an upper bracket and a lower bracket that pivotally support the enlarged blade so as to be rotatable within a predetermined angle at at least two positions opposed to each other in the diameter direction.
At the time of forward rotation of the upper shaft, one end is in contact with the rear end portion near the shaft portion of the expansion blade, and the expansion blade is folded within the radius of the excavation blade attached to the lower shaft. As a torque transmission part to hold, and at the time of reverse rotation, the other end collides with the tip of the enlargement blade, and the enlargement blade is forced to a position where the tip of the enlargement blade protrudes from the radius of the excavating blade. An expansion hole excavation head equipped with expansion blade operation members each functioning as a kicking-out portion that expands outward in the direction,
As a stopper to prevent the enlargement blade from expanding its diameter by abutting the diameter enlargement side shaft portion of the enlargement blade at the time of forward rotation of the upper shaft, and at the time of reverse rotation of the upper shaft, The enlarged blade detecting means functioning as a detecting portion for detecting the enlarged diameter of the enlarged blade, respectively, by contacting an enlarged portion of the enlarged blade supporting member with the upper bracket and the lower bracket of the enlarged blade. An enlarged hole excavation head characterized by having a gap between them.   The expanding blade detecting means is a bolt having upper and lower ends fixed to the upper bracket and the lower bracket of the expanding blade support member, respectively, and having a height interval larger than the thickness of the shaft portion near the diameter expansion side of the expanding blade 2. The enlarged hole excavation head according to claim 1, wherein shear guide grooves are provided at two positions on the upper and lower sides of the groove.   When the diameter of the expansion blade is increased to a predetermined angle, a stopper member that contacts the outer surface on the reduced diameter side near the shaft portion of the expansion blade and prevents diameter expansion beyond a predetermined angle is provided near the shaft portion of the expansion blade. The expansion hole excavation head according to claim 1, wherein the expansion hole excavation head is provided on a reduced diameter side of the portion.   4. An auxiliary expanding blade comprising a blade expanding portion and a positioning member that expands substantially to the outer diameter of the pile is provided on the excavating blade provided at the tip of the lower shaft. An enlarged hole excavation head according to claim 1.

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