JP2008031672A - Excavation head of diametrically expanding excavator for constructing foundation pile - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excavation head of an excavator for constructing a foundation pile, superior in excavation performance, capable of securing the quality of a foot protection expanded bulb, and capable of suppressing an earth removal quantity when pulling up, in the excavator in the form of gradually diametrically expanding an expanding blade by a spline structure. <P>SOLUTION: This excavation head 1 has a hollow driving shaft 2 and an excavation shaft 3 relatively movably stored in the axial direction inside its shaft. The expanding blade 4 joined by a pin to the driving shaft 2 side is expanded and contracted via a diametrically expanding plate 5 on the excavation shaft 3 side by using these relative movements. A spline is formed of a U-shaped key way 6 on the inner surface side of the driving shaft 2 and a key 7 on the outside surface side of the excavation shaft 3. The key way 6 is formed in a U shape out of a guide part 6a in the vertical direction, a first locking lock part 6b in which the key 7 is engaged in the circumferential direction when normally rotating the driving shaft 2 in the diametrically contracted state of the expanding blade 4, and a second locking lock part 6c in which the key 7 is engaged in the peripheral direction when normally rotating the driving shaft the a diametrically expanding state of the expanding blade 4. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a structure of a drilling head of a diameter-extended excavator for foundation pile construction used in the case of forming a root-enlarged bulb part by a medium digging method or the like.

  In order to secure the tip bearing capacity of the foundation pile, it is often practiced to create a root-enlarged bulb part, and as an expansion drilling device for that purpose, an enlargement provided on the excavation head when creating the enlarged bulb part Various types have been developed in which the wings are expanded to expand the diameter, and the diameter is reduced again when the blades are pulled up.

  As a principle of expansion / contraction of the expansion blade, there are one that expands / contracts by operation of a hydraulic device, another that expands / contracts mechanically, and one that utilizes resistance from the ground.

  As such a diameter expanding excavator, for example, Patent Documents 1 and 2 disclose excavation treatment for foundation pile construction in which the diameter expansion amount can be set large while preventing sudden resistance from the ground during diameter expansion. As a tool, the diameter can be increased by being supported by the drive shaft, the excavation shaft splined to the drive shaft, the shaft digging blade provided at the tip of the excavation shaft, and the drive shaft and the excavation shaft. An excavation jig for constructing a foundation pile including an expansion blade with an expansion excavation blade attached thereto, wherein the drive shaft and the excavation shaft are spline-coupled in a vertically displaceable manner, and the expansion blade The upper end portion of the expansion wing is connected to the drive shaft so as to be rotatable in the vertical direction, and the lower end portion of the expansion wing or the intermediate position in the extending direction is connected to the upper end portion of the auxiliary link so as to be rotatable in the vertical direction. The lower end of can be rotated up and down with respect to the drilling shaft Drilling jig for foundation piles construction, characterized in that the sintering is described.

  That is, in the inventions described in Patent Documents 1 and 2, the drive shaft and the excavation shaft at the tip can be moved relative to each other in the axial direction via the keyway and the key constituting the spline, and are provided on the drive shaft side. The expansion blade expands and contracts via an auxiliary link that connects the expansion blade and the excavation shaft.

  As other background art, Patent Document 3 discloses a data collection / pipe system for grasping the situation of forming an enlarged bulb part, and Patent Documents 4 and 5 describe an elastic structure using a spline composed of a key groove and a key. Patent Document 6 describes a means for expanding the diameter of an expansion blade using a horizontal auxiliary diameter expansion plate and a main diameter expansion plate.

JP 2003-106082 A JP 2005-023561 A JP-A-2005-240284 Japanese Examined Patent Publication No. 56-047355 Japanese Patent No. 3330850 JP 2004-076384 A

  In the conventional diameter expansion drilling device that forms a root-enlarged bulb part, the drive shaft is excavated in the forward direction (direction in which it is screwed into the ground as the screw at the tip rotates), and reversed by the root-enlarged bulb part. Most devices expanded the expanded wing and excavated the expanded bulb by reversing it.

  In particular, in a device that gradually expands the diameter of an enlarged blade due to a spline structure, the shape of the spline is a Z-shape as shown on the left side of FIG. 4 (corresponding to those described in Patent Documents 1 and 2 as a conventional example). As a result, I had to drill in reverse.

  That is, as shown as a conventional example on the left side of FIG. 4, when excavating while the diameter of the enlarged blade is reduced and rotating in the middle digging method or the like (state A), the key is a Z-shaped key in the figure. When it is locked to the locking part at the top of the groove and starts expanding the diameter of the enlarged bulb (state B), the key is unlocked by reversing the key, and the key is locked in the reverse direction. The expanding blade gradually opens and expands in diameter while moving along the tapered surface opposite to the position (state C).

  When the diameter expansion is completed from that state, the key is locked to the engaging portion at the lower part of the Z-shaped key groove while being reversed, and the enlarged bulb part is created while moving the excavation head up and down (state D). At that time, a curable filler such as cement milk is injected into the enlarged bulb portion through piping provided inside the drive shaft and the excavation shaft, and mixed with earth and sand.

  After the formation of the enlarged bulb part is completed, the locked state of the key is released by normal rotation and pulled up by normal rotation (not shown).

  In the conventional example on the left side of FIG. 4, the keyway is on the drive shaft side and the key is on the excavation shaft side, but the opposite case (the example of the present invention on the right side in FIG. 4 is the opposite case). ), The relationship between the keyway and the key is reversed.

  The construction of the procedures such as forward excavation (state A), reverse diameter expansion (states B and C), reverse root consolidation enlarged bulb portion excavation (state D), and forward pulling have the following problems. is there.

(1) At the tip of the excavator, there is usually a screw-shaped excavation blade, which is cut in the direction of the screw propelled by normal rotation. Excavation can be carried out, but excavation becomes difficult in the case of reverse rotation.

(2) The excavated soil may accumulate at the bottom of the bulb. Insufficient stirring and mixing may cause difficulty in creating a uniform enlarged bulb portion.

(3) The sediment deposited on the upper screw in the medium digging method is consolidated in the steel pipe, and an excessive load is applied to the auger. In addition, the earth and sand deposited on the upper part of the screw may fall into the root-enlarged bulb portion, which may adversely affect the quality of the root-solidification.

(4) When the excavation head is lifted up, it rotates in the forward direction, so that negative pressure is applied and the root-setting liquid such as cement milk in the root-enlarged bulb may be pulled up. Further, since the head is lifted while rotating in the direction of raising the soil, the amount of soil removal may increase.

(5) In the Z-shaped spline shape, the rotation direction after the key is released from the lock at the time of expansion blade contraction is one direction. Therefore, the third stage on the left side of FIG. ), The key may hit the corner at the position indicated by a black circle, and the key may be damaged.

  The present invention is an excavator of a type in which the diameter of the enlarged wing is gradually expanded by the spline structure, and by devising the shape of the spline, it is excellent in excavability, can secure the quality of the rooted enlarged bulb, It aims at providing the excavation head of the excavator for foundation pile construction which can suppress the amount of earth removal.

  The invention according to claim 1 of the present application includes a hollow drive shaft that constitutes an excavation head, and an excavation shaft that is accommodated inside the drive shaft so as to be relatively movable in the axial direction. A foundation pile in which an enlarged wing whose one end is pivotally supported on the drive shaft side can be expanded and contracted by means of a diameter expanding means provided on the excavation shaft side. In the excavation head of the construction excavator, the key provided on one of the drive shaft and the excavation shaft is relatively movable in the axial direction and the circumferential direction of the excavation head in the key groove provided on the other, The keyway is a longitudinal guide portion that induces relative movement of the drive shaft and the excavation shaft in the axial direction, and extends in the circumferential direction from the guide portion when the drive shaft is rotated forward in a reduced diameter state of the enlarged blade. A first locking portion for engaging the key in a circumferential direction; and the guide portion. And a second locking lock portion that is engaged with the key in the circumferential direction when the drive shaft is rotated forward in a diameter-enlarged state of the expansion blade. .

  Using the relative movement in the axial direction of the drive shaft and the excavation shaft, the expansion wing whose one end is pivotally supported on the drive shaft side can be expanded and contracted via a diameter expanding means provided on the excavation shaft side. This is the same as that using the conventional spline structure. In this case, the rotation direction of the drive shaft during excavation and the rotation direction of the excavation shaft are the same direction.

  In the inventions described in Patent Documents 1 and 2, the spline shape is Z-shaped, whereas in the present invention, the spline shape, that is, the key groove shape is placed above and below the vertical guide portion, and the key is rotated during normal rotation of the drive shaft. By making the U-shaped having the first and second locking lock portions engaged in the circumferential direction, the enlarged wings are expanded in diameter by reversing the drive shaft, and then the enlarged bulb portions are fixed by normal rotation. Can be created.

  Therefore, as described in the section of the problem to be solved by the invention, the problem in the case of excavating and building the root-enlarged bulb portion by reversing the drive shaft is solved, and excavability is excellent, and the root-enlarged bulb portion Quality is ensured, and the amount of soil discharged during lifting can be reduced.

  According to a second aspect of the present invention, in the excavation head of the excavator for foundation pile construction according to the first aspect, a taper is provided on a side of the guide portion of the keyway that comes into contact with the key when the drive shaft is reversed. It is a feature.

  The direction of the taper is that when the diameter of the expansion blade is increased when the drive shaft is reversed, the vertical component of the force acting between the key and the key groove provided with the taper pulls the drive shaft and the excavation shaft in the axial direction. The direction.

  When the keyway is provided on the drive shaft side and the key is provided on the outer surface side of the excavation shaft, the key is pulled out from the first locking lock portion located on the lower side due to the reverse rotation of the drive shaft. The guide part is moved upward along the taper located on the side, and after the diameter of the enlargement blade is increased, it is engaged with the second locking lock part located on the upper side by the forward rotation of the drive shaft. By rolling, excavation and creation of an enlarged bulb part is carried out.

  When the keyway is provided on the outer surface side of the excavation shaft and the key is provided on the inner surface side of the drive shaft, the vertical and horizontal directions are reversed.

  According to a third aspect of the present invention, in the excavation head of the excavator for foundation pile construction of the diameter expansion excavator according to the first or second aspect, the lubricating oil is put into the key groove, and between the inner surface of the drive shaft and the outer surface of the excavation shaft. It is characterized by having a sealed structure.

  Lubricating oil moves in the spline to prevent vacuum and prevent soil from being pulled in from the outside of the spline. Further, the lubricant is spread over the entire area of the key groove, so that the key is hardly damaged.

  The amount of lubricating oil sealed in the spline is desirably about the volume of the upper and lower first and second locking portions, that is, about 70% of the volume in the spline, and about 50 to 80%.

  In a test conducted by changing the amount of the lubricating oil, when the lubricating oil was added to nearly 100% of the volume in the spline, the key stopped moving, and when it was about 70%, the key moved smoothly and no negative pressure was generated.

  According to a fourth aspect of the present invention, in the excavation head of the excavator for foundation pile construction of the large-diameter excavator according to the first, second, or third aspect, the diameter-expanding means is horizontal or substantially horizontal provided on the outer periphery of the excavation shaft. It is made of an enlarged plate, and the lower surface of the enlarged blade comes into contact with the outer peripheral portion of the enlarged plate by the relative movement of the drive shaft and the excavating shaft in the axial direction, and the enlarged blade expands and contracts around the shaft support portion. It is characterized by being made.

  As for the diameter expansion means of the expansion blade using the relative movement in the axial direction of the drive shaft and the excavation shaft, a link is used as in Patent Documents 1 and 2, and a horizontal expansion plate is used as in Patent Document 6. Various structures are conceivable, but those using a diameter expansion plate have a simple structure and are less likely to cause malfunctions.

  Note that the expansion blade has a problem that it becomes difficult to open the blade if the soil enters between the blade and the receiving member on the drive shaft side during expansion. By adopting a free structure with a margin in the receiving member, it is possible to make it difficult to cause malfunction due to the entry of soil.

  In the present invention, by changing the spline shape of the excavation head from the Z shape to the U shape, excavation is performed by forward rotation, and the diameter of the expansion blade is expanded by reverse rotation. The agitation of the bulb part can be made normal.

  In this case, since the roots are rotated forward at the time of the expanded excavation, a force that pushes the soil upwards acts, and there is little accumulation of excavated earth and sand at the lower end of the expanded bulb portion, thereby improving the excavability.

  In addition, when the excavation head is lifted, the rotation is reversed, so that the rooting liquid of the enlarged bulb is not pulled up, and the soil is placed under the reverse rotation, so the amount of soil removed is also suppressed. Can do.

  In addition, by making the spline shape U-shaped, in the process of expanding the expanding blade, depending on whether the key is provided on the excavation shaft side or the drive shaft side, it rises all the way up or down to the bottom Since the key rotates along the upper or lower part of the key groove in the process of falling down to the normal rotation and locking forward, the key does not hit the corner and damage to the key can be suppressed.

  FIG. 1 shows the position of a key and an enlarged blade in a key groove from the start of excavation by normal rotation in a reduced diameter state to excavation of an enlarged bulb portion by normal rotation in an enlarged diameter state and stirring in one embodiment of the present invention. The positional relationship of is shown.

  The excavation head 1 has a hollow drive shaft 2 and an excavation shaft 3 accommodated therein so as to be relatively movable in the axial direction. In this example, the excavation head 1 performs relative movement in the axial direction of the drive shaft 2 and the excavation shaft 3. Utilizing the enlarged wing 4 whose one end is pivotally supported by a pin joint on the drive shaft 2 side so as to be rotatable in the vertical direction, the auxiliary enlarged diameter plate 5a and the main enlarged diameter plate 5b provided on the excavation shaft 3 side are used. Can be scaled.

  In the drawing, the portion protruding from the upper portion of the drive shaft 2 is a connecting portion 8 to the upper portion of the excavator, and a rod having spiral blades on the outer periphery is usually connected to this portion.

  In this example, although not visible from the outer surface, a U-shaped key groove 6 is formed on the inner surface side of the drive shaft 2. On the outer surface side, the key 7 projects from the key groove 6 to form a spline. This spline portion is made watertight by interposing packing or the like between the inner surface of the drive shaft 2 and the outer surface of the excavation shaft 3 to prevent the entrainment of earth and sand, and 70% of the spline volume inside. A certain amount of lubricant should be sealed.

  The keyway 6 formed on the inner surface side of the drive shaft 2 extends in the circumferential direction from a longitudinal guide portion 6a that induces relative movement of the drive shaft 2 and the excavation shaft 3 in the axial direction, and a lower end of the guide portion 6a. A first locking lock portion 6b that engages the key 7 in the circumferential direction when the drive shaft 2 is rotated forward in the reduced diameter state of the expansion blade 4, and the expansion blade 4 extends in the circumferential direction from the guide portion 6a. When the drive shaft 2 is rotated forward in the diameter state, the key 7 is U-shaped from the second locking portion 6c engaged in the circumferential direction (in this example, it is U-shaped when viewed from the back of the paper). Is formed.

  FIG. 1 (a) shows a state where the drive shaft 2 is rotated forward while the enlarged blade 4 is in a reduced diameter state, and at this time, the key 7 is a first locking lock portion at the lower end of the key groove 6. FIG. The rotation of the drive shaft 2 is transmitted to the excavation shaft 3 while being engaged with 6b.

  (b) is a state in which the excavation head 1 reaches the enlarged bulb formation position at a predetermined depth and starts to expand the diameter of the expansion blade 4 by reversing the drive shaft 2. It abuts against the surface opposite to the stop lock portion 6b.

  At this time, rotation in the reverse direction is transmitted to the excavation shaft 3 at this contact portion. Further, in this example, the auxiliary diameter-expanding plate 5a whose diameter is gradually increased is provided horizontally on the excavation shaft 3, and due to the reverse rotation of the excavation shaft 3, the expanding blade 4 extends along the outer edge of the auxiliary diameter-expanding plate 5a. Open while sliding.

  (c) shows a state in which the key 7 has moved up the guide portion 6a of the key groove 6 to the upper end of the guide portion 6a with the drive shaft 2 reversed.

  The guide portion 6a is provided with a taper, and the vertical component of the force acting on the key 7 from the guide portion 6a of the key groove 6 pushes the key 7 upward by rotating the drive shaft 2 in the reverse direction. At this time, the expansion blade 4 is pushed upward by the auxiliary diameter expansion plate 5a due to relative displacement in the axial direction.

  From this state, by rotating the drive shaft 2 forward, the key 7 enters and engages with the second locking lock portion 6c as shown in (d).

  At that time, the expansion blade 4 is in a substantially horizontal expansion state by riding on the main diameter expansion plate 5b located at the lower end on the drive shaft 2 side, and this state is maintained during normal rotation.

  A spiral blade 9 is attached to the lower end of the excavation head 1 (illustration of this portion is omitted for (b) and (c) in FIG. 1), and a plurality of excavation blades 10 are attached to the lower end of the spiral blade 9. It has been. In the present invention, since the enlarged bulb portion is excavated and stirred by forward rotation with the enlarged blade 4 expanded in diameter, the functions of the spiral blade 9 for forward rotation and the excavating blade 10 attached in the forward direction are maximized. Can be used.

  Usually, the excavating blade 11 on the lower surface side of the expanding blade 4 is also attached so as to function in the normal direction. However, in the illustrated example, the excavating blade 12 is also attached to the upper surface side of the expanding blade 4 so that excavation can be performed upward. I have to.

  FIG. 2 shows the positions of the enlarged blade and the enlarged plate from the start of excavation by forward rotation in the reduced diameter state to the excavation of the enlarged bulb portion by forward rotation in the enlarged diameter state and stirring in another embodiment of the present invention. It shows the relationship. In (b) to (d), the spiral wing 9 at the tip is not shown.

  The basic structure and function are the same as in the case of FIG. 1, but the resistance is reduced by minimizing the cross section of the auxiliary enlarged plate 5a as much as possible. Further, a rib 5c is provided on the outer peripheral portion of the auxiliary diameter expanding plate 5a, and the upper portion of the rib 5c is in direct contact with the lower surface of the expanding blade 4 to push up the expanding blade 4. By providing an inclination on the upper part of the rib 5c, the enlarged blade 4 can be pushed up smoothly.

  Further, in the process of expanding the diameter of the expansion blade 4 from (d) to (e) in FIG. 2, when the rotation of the drive shaft 2 changes to normal rotation, the expansion blade 4 is detached from the diameter expansion plate 5 and contracted. The end of the rib 5c and the base of the enlarged wing 4 are engaged so as not to stir (see cross section AA in (d)).

  FIG. 3 is an enlarged wing and drilling water or hardened filling from the start of excavation by forward rotation in the reduced diameter state to excavation of the enlarged bulb portion by forward rotation in the expanded diameter state and stirring in another embodiment of the present invention. The positional relationship with the flow path for injecting a material is shown.

  As in the present invention, in a diameter expansion excavator that forms a root-enlarged bulb part, in order to confirm the expansion of the expansion blade, conventionally, a double pipe is used for the rod, and confirmation is performed using hydraulic pressure or water pressure. Although there is a method to do so, it is very costly to use a double pipe.

  In addition, there is a method of confirming on the ground using electromagnetic waves or the like when the wings expand, but electromagnetic waves may flow to other places and may not be confirmed reliably.

  On the other hand, in this type of large-diameter excavator, construction is generally performed while injecting curable filler such as drilling water or cement milk through a pipe line penetrating the inside, and the embodiment of FIG. 3 is expanded. In order to confirm the expanded state of the blade 4, the relative movement of the drive shaft 2 and the excavation shaft 3 with respect to the pipe for injecting excavation water and cement milk provided inside the drive shaft 2 and the excavation shaft 3 The diameter expansion state of the expansion blade 4 is confirmed from the increase or decrease in the fluid injection pressure accompanying the change in the fluid resistance of the pipe line.

  More specifically, in FIG. 3, the use of the fact that the excavation head 1 expands and contracts when the diameter of the expansion blade 4 is expanded, and in the processes (a) to (c), a space 21 is formed between the upper and lower pipe lines 22 and 23. In the stage where the expanded blade 4 is greatly expanded in diameter by the relative displacement in the axial direction in the reverse state as shown in (d) from the state in which the drilling water or cement milk is injected in a state where resistance is low, the drilling head The space 21 is eliminated by the reduction of 1 and the pipe line 22 on the drive shaft 2 side and the pipe line 23 on the excavation shaft 3 side are in contact with each other so that the flow path is narrowed and the resistance is increased (see the enlarged view of the same A). After the enlargement, in the forward rotation state of (e), the pipe 22 on the drive shaft 2 side fits in the opening of the pipe 23 on the excavation shaft 3 side (see the enlarged view of A), and the flow path is the original size. Thus, the resistance is reduced.

  In addition, a structure in which the flow channel area during excavation is suppressed and the flow channel becomes wider when expanding is also conceivable.

  In this way, it is possible to confirm that the diameter of the expansion blade 4 has expanded due to an increase or decrease in the pressure of the drilling water or cement milk.

  FIG. 4 shows excavation and agitation of an enlarged bulb portion by forward rotation in the diameter-expanded state from the start of excavation by forward rotation in the diameter-reduced state for the conventional Z-type spline and the U-shaped spline in the present invention. This shows the positional relationship between the key position in the keyway and the position of the enlarged wing.

  The case of the conventional Z-shaped spline is as described in the section of the problem to be solved by the invention. Briefly speaking, the state A is forward excavation, the states B and C are reverse diameter expansion, State D is during excavation of the inversion root and expanded bulb.

  There is no significant difference between states A and B, but in the case of the conventional Z-shaped spline shape, the rotation direction is the same in the process from state C to D, and the surface where the key and the key groove abut (see FIG. 4). Since the key is about to be engaged with the second locking portion located on the contact surface side while the right side surface of the key remains unchanged, a state in which the contact area temporarily decreases occurs. For this reason, the problem of damage due to corner contact of the key occurs. On the other hand, in the present invention, in the process from state C to D, the key is engaged with the second locking portion of the key groove by switching the rotation from the reverse rotation to the normal rotation. The contact area does not decrease and there is no problem with corner contact.

  Also in the state D, in the case of the conventional Z-shaped spline shape, excavation and agitation of the enlarged bulb portion are performed by reversing, which may cause problems of excavability, problems of soil removal, sedimentation of excavated soil, etc. While there is a problem of the quality of the root-enlarged bulb portion, the excavation head according to the present invention performs the normal rotation, so that all these problems are solved.

  5 to 8 show the effects of forward excavation and reverse excavation during the excavation of the enlarged bulb part in comparison with the prior art and the present invention.

  In FIG. 5, in the conventional example of (a), the rotation of the excavation head 1 during the expanded excavation is reverse, whereas in the present invention of (b), the rotation is normal.

  Therefore, in FIG. 6, in the conventional example of (a), the force of dropping the sediment deposited on the screw of the rod 31 connected to the upper part of the excavation head 1 acts downward as shown by the arrow, In the present invention, since it is normal rotation, the excavated soil is subjected to a force that pushes it upward, and there is little sediment on the lower end of the enlarged bulb.

  Further, in FIG. 7, in the conventional example of (a), excavated earth and sand may accumulate at the lower end of the enlarged bulb part, so that it becomes difficult to re-excavate to the ground once excavated as described above. Since stirring and mixing with the root-setting liquid at the lower end is insufficient, it may be difficult to create a uniform root-enlarged bulb portion. Moreover, the earth and sand deposited on the screw 32 of the rod 31 connected to the upper part of the excavation head 1 may be consolidated inside the steel pipe, and an excessive negative pressure may be applied to the auger. On the other hand, in the present invention of (b), since the accumulation of excavated soil is small, it is easy to excavate again.

  In FIG. 8, in the conventional example of (a), when the excavation head 1 is recovered, a negative rotation is applied, and there is a possibility that the root-setting liquid of the root-enlarged bulb part is pulled up, and the amount of soil is also increased. Increase. On the other hand, in the present invention of (b), when the excavation head 1 is recovered, there is no possibility of pulling up the root-setting liquid of the root-enlarged bulb, and it is possible to create a healthy enlarged bulb It can also reduce the amount of soil discharged.

In the embodiment of the present invention, the positional relationship between the position of the key and the expansion blade in the key groove from the start of excavation by normal rotation in the reduced diameter state to the excavation and stirring of the enlarged bulb portion by normal rotation in the expanded diameter state. It is the shown front view and horizontal sectional view. In the other embodiment of the present invention, the positional relationship between the expansion blade and the expansion plate from the start of excavation by normal rotation in the reduced diameter state to the excavation of the expanded bulb portion by normal rotation in the expanded diameter state and stirring is shown. It is a front view and a horizontal sectional view. In another embodiment of the present invention, from the start of excavation by normal rotation in the reduced diameter state to the excavation of the enlarged bulb portion by normal rotation in the diameter-expanded state, the expansion blade and the drilling water or the curable filler from the stirring are injected. It is the front view and horizontal sectional view which showed the positional relationship with the flow path for this. For the conventional Z-shaped spline and the U-shaped spline in the present invention, the keyway from the start of excavation by normal rotation in the reduced diameter state to the excavation of the expanded bulb portion by normal rotation in the expanded diameter state and stirring FIG. 6 is a front view and a development view of a spline portion showing the positional relationship between the key position and the enlarged blade in the inside. It is the vertical cross section which showed the influence by the normal rotation excavation and reverse rotation excavation at the time of expansion bulb part excavation contrasting with respect to a prior art and this invention. It is the vertical sectional view which showed the influence by an expansion bulb part excavation, the normal rotation excavation at the time of agitation, and reverse rotation excavation in contrast with the prior art and this invention. It is the vertical sectional view which showed the influence by an expansion bulb part excavation, the normal rotation excavation at the time of agitation, and reverse rotation excavation in contrast with the prior art and this invention. It is the vertical sectional view which showed the influence by the normal rotation excavation and reverse rotation excavation at the time of raising of an excavation head as contrasted with the prior art and this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Excavation head, 2 ... Drive shaft, 3 ... Excavation shaft, 4 ... Expansion blade, 5a ... Auxiliary diameter expansion plate, 5b ... Main diameter expansion plate, 6 ... Key groove, 6a ... Guide part, 6b ... 1st engagement Stop lock portion, 6c ... second locking lock portion, 7 ... key, 8 ... connecting portion, 9 ... spiral wing, 10, 11, 12 ... excavation blade, 21 ... space, 22, 23 ... piping, 31 ... rod 32 ... Screw, 41 ... Expanding bulb part

Claims (4)

  A hollow drive shaft that constitutes the excavation head; and an excavation shaft that is accommodated inside the drive shaft so as to be relatively movable in the axial direction, and uses relative movement in the axial direction of the drive shaft and the excavation shaft. In the excavation head of the foundation pile construction excavator, one end of which is pivotally supported on the drive shaft side so as to be rotatable can be expanded / contracted via a diameter expanding means provided on the excavation shaft side. A key provided on one of the drive shaft and the excavation shaft can be relatively moved in a key groove provided on the other in the axial direction and the circumferential direction of the excavation head, and the key groove corresponds to the drive shaft and the excavation shaft. A longitudinal guide portion that induces relative movement in the axial direction, and the key is engaged in the circumferential direction when the drive shaft is rotated forward in a reduced diameter state of the enlarged blade extending in the circumferential direction from the guide portion. A first locking portion and a circumferentially extending portion from the guide portion; It said key drilling head of the foundation pile construction for an excavator, characterized in that it comprises the a second lock portion to be engaged in the circumferential direction when the radial state to forward the drive shaft.   The excavation head of the excavator for foundation pile construction according to claim 1, wherein a taper is provided on a side of the guide portion of the key groove where the key abuts when the drive shaft is reversely rotated.   The excavator for foundation pile construction of a diameter-expanded excavator according to claim 1 or 2, wherein lubricating oil is put in the keyway and sealed between the inner surface of the drive shaft and the outer surface of the excavation shaft. Drilling head. The diameter expansion means is a horizontal or substantially horizontal diameter expansion plate provided on the outer periphery of the excavation shaft, and the lower surface of the expansion blade is moved to the diameter expansion plate by relative movement in the axial direction of the drive shaft and the excavation shaft. 4. An excavator for foundation pile construction of a diameter-expanding excavator according to claim 1, wherein the expanding blade abuts on the outer peripheral portion of the shaft and expands and contracts around the shaft support portion. Drilling head.

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