JPH0925779A - Two-stage expanding head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To quickly conduct an excavation by providing a half-open coupling section coupled with a coupled section above an expanding blade and holding the blade at the half-open state and a full-open coupling section coupled with a coupled section below the blade and holding the blade at the full-open state. SOLUTION: The expanding blade 4 of a two-stage expanding head A is set to the half-open state, a spiral auger 8 is rotated forward, and a nonsupport layer is excavated nearly to the diameter of an existing pile. When the tip section of the head A reaches a support layer, the auger 8 is stopped and slightly lifted. The upper face of the blade 4 is coupled with the lower face of the existing pile, the blade 4 and a rod 1 are lifted, and a coupled section 4a above the blade 4 is separated from the half-open coupling section 6a of a flange section 6. When the auger 8 is rotated forward, the blade 4 is not moved, the rod 1 is rotated together with the auger 8, a slide tube section 12 is rotated together with the rod 1, and the coupled section 4b below the blade 4 is coupled with a full-open coupling section 12a above the slide tube section 12 into the full-open state. The auger 8 is further rotated forward, and the support layer is excavated to provide a cavity for a bulb.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-stage enlarged head used for excavation in a middle excavation enlargement method, which is a type of embedding method for ready-made piles.

[0002]

2. Description of the Related Art For the construction of ready-made piles, various low-pollution methods have been generally developed instead of the driving method from the viewpoint of preventing pollution such as noise and vibration. The low-pollution method is roughly classified into low-pollution driving method and embedding method. Conventionally, based on the provisions of Article 93 of the Building Standard Act, the cement milk method by pre-boring, which is a type of embedding method for piles (also referred to as piles) indicated in Notification No. 1623 of the Ministry of Construction in 1978 ( The drilling blade of the drilling head attached to the tip of the spiral auger in the pre-boring method was not used.

[0003] However, in the conventional cement milk method, a drilling hole slightly larger than a pile diameter of a pile to be used is first opened in the ground with a spiral auger. Even without opening and closing movements, the intended use could be sufficiently achieved. However, since the cement milk method is slightly higher in noise and vibration and has more residual soil than the middle digging method, the middle digging method is advantageous to low pollution methods. It is increasingly adopted by.

Therefore, a one-stage enlarged head (B) as shown in FIGS. 15 and 16 has been proposed as a one-stage enlarged head (B) for the mid-digging method. That is, as shown in the drawing, the conventional one-stage enlarged head (B) has an outer flange (9) having a rectangular planar shape formed at the upper end of the rod (1). Two screws (2) are formed around the rod (1). At the lower end of the screw (2), a drilling bracket (13) with a hard drilling bit (13a) protrudes in parallel with the rod (1).

At the upper end of the rod (1), a small-diameter mounting shaft (1) inserted and fixed to the lower end of the spiral auger (8).
a) is provided, and rods (1) are provided at both ends of the outer collar (9).
A blade mounting groove (7) formed symmetrically with respect to the center axis of the blade is recessed, and the rear end of the one-stage enlarged blade (4) is rotatably pivoted by the support shaft (3). ing.

[0006] By rotating (turning clockwise) the one-stage enlarged head (B) mounted on the tip of the spiral auger (8), the enlarged blade (4) of the one-stage enlarged head (B) is opened. Then, the excavation metal fitting (13) attached to the tip penetrates the ground (non-support layer (16)) at the tip of the ready-made pile (18) and excavates to the upper part of the support layer (not shown). Along with this excavation, the ready-made pile (18) into which the spiral auger (8) is inserted is pushed into the excavated portion. When the upper layer of the support layer (not shown) which is harder than the non-support layer (16) is sufficiently excavated to form the cavity for the bulb (not shown), the spiral auger (8) is reversed. The expansion blades (4) are closed, and a rooting material (not shown) is jetted into the bulb cavity (not shown), and then a spiral auger (8) is formed between the cavity and the ready-made pile (18). Repeatedly moving up and down between them to stir the root solidification material and the surrounding earth and sand or gravel, and to fill and densify the excavated part of the root solidification material with the stirring member for the root solidification material and earth and sand. This allows
A block (not shown) for a bulb will be formed in the cavity at the tip of the embedded pile (18). Finally, the rotation of the spiral auger (8) is stopped, and the entire one-stage enlarged head (B) is pulled up into the hollow portion (18a) of the ready-made stake (18) while ejecting the stiffening material (5).

Here, since the conventional enlarged blade (4) of the one-stage enlarged head (B) is only one-stage switching between closing and opening, the diameter of the enlarged blade (4) when opened is determined by the diameter of the ready-made pile. (18) It cannot be made larger (in other words, the expanded blade when opened
If the diameter of (4) is larger than that of the ready-made pile (18), the diameter of the borehole increases, the amount of excavation increases, and the amount of excavated soil remaining increases. As a result, the diameter of the hollow part of the bulb-forming part and the diameter of the ready-made pile (18) are almost the same, and the bulb part does not wrap the tip of the ready-made pile (18), and the supporting strength There was a problem that was small.

The method of constructing the ready-made pile (18) is illustrated as follows.

[0009]

The problem to be solved by the present invention is as follows.
By making the expanded blades expandable in two stages during excavation work, when excavating the unsupported layer, the ground at the tip of the embedding is approximately the same diameter as the ready-made pile and the generation of residual soil is minimized. In the part where the bulb is formed from the lower part of the non-support layer to the upper part of the support layer, the excavation is excavated with a diameter larger than that of the existing pile. The purpose is to remarkably improve the support strength.

[0010]

According to a first aspect of the present invention, a two-stage enlarged head (A) comprises a rod (1) attached to a tip of a spiral auger (8), and a rod (1). Collars protruding from both sides and having bearing through holes (10) formed in each
(6) and is attached slidably in the axial direction of the rod (1) without rotating with respect to the rod (1) below the collar (6),
A support shaft that is slidably inserted into the bearing through-hole (10).
The slide cylinder (12) to which (3) is attached is disposed between the flange (6) and the slide cylinder (12), and is rotatably supported by the support shaft (3). Enlarged blade (4) that expands and closes, and is formed on the lower surface of flange (6), and the upper surface of enlarged blade (4) is engaged when slide cylinder (12) approaches flange (6). Part (4a) is engaged with the half-open engagement part (6a) that holds the enlarged blade in a half-open state, and is formed on the upper surface of the slide cylinder part (12), and the slide cylinder part (12) is a flange part (6). From the engaged portion (4) on the lower surface of the enlarged blade (4)
b) is engaged with the fully open engaging portion (12a) for holding the enlarged blade (4) in the fully opened state.

According to this, the hollow portion (18a) of the ready-made pile (18)
The spiral auger (8) is inserted through and a two-stage enlarged head (A) is attached to the tip of the spiral auger.
By rotating (8) forward (clockwise), the engaged portion (4a) on the upper surface of the enlarged blade (4) of the two-stage enlarged head (A) is partially engaged with the lower surface of the flange (6). The expanded blade (4) is held half-open by engaging with 6a), and in this state, the unsupported layer (16) of soft ground is excavated with the same diameter as the existing pile (18). Hard support layer (1
7) It becomes close and switches to excavation of the hollow part (20) for bulbs. After stopping the spiral auger (8), slightly raise the spiral auger (8). As a result, the upper surface of the half-open enlarged blade (4) engages the lower surface of the ready-made pile (18), so that when the spiral auger (8) is slightly lifted, the enlarged blade (4) and the lower portion of the enlarged blade (4) The rod (1), on which the flange (6) is protruded, is lifted, leaving the slide cylinder (12) disposed on the upper surface of the enlarged blade (4) and the lower surface of the flange (6). A gap (h) is generated between the engaged portions (4a) on the upper surface of the expanding blade (4).
Is disengaged from the half-open engagement portion (6a) of the flange portion (6). When the spiral auger (8) is rotated forward slightly again in this state, the expanded blade
Only (4) does not move in contact with the excavated soil in the cavity (20),
The rod (1) rotates with the spiral auger (8). At the same time, the slide cylinder (12) slides with respect to the rod (1) but does not rotate, and thus rotates with the rod (1). As a result, the upper surface of the slide cylinder (12) is slid and the fully open engagement
The engaged portion (4b) on the lower surface of the enlarged blade (4) is engaged, and the engaged portion (4b) is fully opened when the engaged portion is engaged. Excavate to the upper part of the support layer (17), which is a hard ground. In this excavation, a hollow portion (20) having a diameter larger than that of the existing pile (18) is obtained because the enlarged blade (4) is fully opened.

When the bulb-forming cavity (20) is formed, a root consolidation material (5) is injected, and at the same time, the spiral auger (8) is reversed to close the enlarged blade (4), and the cavity is formed. (20) to the hollow part (18a) of the ready-made pile (18), the two-stage magnifying head (A) is moved up and down to fill the hollow part (20) with the stiffener (5), and finally the spiral auger (8) ), The two-stage enlarged head (A) is pulled out from the hollow portion (18a) of the ready-made pile (18) with the enlarged blade (4) closed. By the above series of operations, a bulb block (19) is formed in a portion from the bottom of the non-support layer (16), which is soft ground, to the upper layer of the support layer (17), which is hard ground, and this bulb block (19) The tip of the ready-made pile (18) is wrapped around, so that the ready-made pile (18) can be firmly supported.

According to a second aspect of the present invention, in addition to the first aspect, a "rod (1) attached to the tip of the spiral auger (8),
A flange (6) protruding from both side surfaces of (1) and having a through hole (10) for a bearing formed therein, and a rod below the flange (6).
A support shaft (3) is slidably attached in the axial direction of the rod (1) without rotating with respect to (1), and a support shaft (3) is slidably inserted into the bearing through-hole (10). Slide barrel part (12)
And an enlarged blade (4) disposed between the flange portion (6) and the slide cylinder portion (12) and rotatably supported by the support shaft (3) to expand and close, and a flange portion ( 6) formed on the lower surface of the slide cylinder (1
A half-open engaging portion (6a) that engages the engaged portion (4a) on the upper surface of the enlarged blade (4) when the 2) approaches the flange portion (6) side and holds the enlarged blade in a half-open state, Formed on the upper surface of the slide tube (12), the enlarged blade (4) when the slide tube (12) is separated from the flange (6).
A fully open engagement portion (12a) that engages with the engaged portion (4b) on the lower surface of the rod to hold the enlarged blade (4) in a fully open state, and an outer periphery of the rod (1) below the enlarged blade (4). Screw spirally wound around
(2)

In a second aspect of the present invention, in addition to the first aspect, the ground immediately below the rod (1) and its surroundings are excavated with a spiral screw (2), and when the enlarged blade (4) is opened, the screw (2) is opened. Since the ground around the excavated part will be excavated further,
The excavation of the bulb part cavity (20) can be performed more quickly.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. The cross section of the two-stage enlarged head (A) according to the present invention is shown in FIGS.
As shown in the figure, the rod (1) has
2) is a hollow body having an opening, and the upper end portion of the rod (1) is formed to have a small diameter, and this portion is a mounting shaft portion (1a), and this mounting shaft portion (1a) Is inserted into and fixed to the lower end of the spiral auger (8). As can be seen from FIG. 4, the mounting shaft (1a) is formed in a hexagonal cross section, and a mounting hole (8) having a hexagonal cross section at the lower end of the spiral auger (8).
a). (15) is the mounting shaft (1a)
Is a fixing pin for fixing the to the mounting hole (8a).

A pair of flanges (6) protrude from both side surfaces of the rod (1), and the flange (6) is formed with a through hole (10) for a bearing. The lower surface of the collar portion (6) is cut off in a step shape to form a half-open engagement portion (6a). Flange of rod (1)
The portion protruding downward from (6) is formed in a hexagonal column (of course, a quadrangular column or other irregular cross-section, as long as a slide cylinder (12) described later slides but does not rotate). This portion is referred to as a slide pillar (1c).

The rod (1) is a hollow body having a hollow portion (1f) formed therein (the hollow portion (1f) is a hollow hole (8b) of a spiral auger (8)).
Is in communication with ), The root material discharge hole (22) is open at the bottom. The consolidation discharge hole (22) can also discharge compressed air and compressed water, including the consolidation material (5).
(The compressed air is injected to discharge the excavated earth and sand from the hollow part (18a) of the existing pile (18). Compressed water is injected when the excavation ground is hard to facilitate excavation. It is for.)

The sliding column (1) extends downward from the lower surface of the flange (6).
The slide column (1c) is slidably inserted into a hexagonal slide hole (12b) formed in the slide cylinder (12). In this case, slide column (1
Since c) and the slide hole (12b) are hexagonal (of course, they are not limited to hexagons and may be irregular shapes), they slide in the axial direction but do not rotate. Therefore, it slides with respect to the rod (1) but rotates together. Slide tube
At the upper part of (12), a lower flange (12c) protrudes in the same direction as the flange (6). The outer shape of the lower flange (12c) is substantially the same oval shape as the flange (6), and the upper surface of the lower flange (12c) is formed in a stepped shape to form a fully open engaging portion (12a). As can be seen from FIG. 4, the position of the fully open engaging portion (12a) is formed rearward with respect to the expanding direction of the expanding blade (4), and the expanding blade (6a) is first provided with the expanding blade (6a). 4) engages, and then engages the full-open engagement part (12c). A support shaft (3) is fixed and erected on the lower flange (12c), and a rotating hole (4c) of the enlarged blade (4), a flange (6)
It is inserted through a bearing through-hole (10) formed in the hole.

An enlarged blade (4) is provided between the flange (6) and the slide cylinder (12), and the support shaft (3) is rotated by the rotation of the enlarged blade (4) as described above. Penetrated through the hole (4c)
The (4) is adapted to rotate around the support shaft (3). The support shaft (3) may be a fixed type, but may be insertable / removable, in which case, by expanding the support shaft (3), the expansion blades (4)
Can be replaced. As can be seen from FIG. 4, the enlarged blade (4) has a substantially rectangular shape, and has a pivot hole (4c) formed at one end, and the outer periphery thereof is rounded in accordance with the pivot hole (4c). The other end is formed at an acute angle to be a digging end, and a hard digging claw (4d) is protruded downward from the tip as needed.

Since the excavation claw (4d) protrudes downward from the tip of the enlarged blade (4), when the spiral auger (8) is rotated forward and the enlarged blade (4) is rotated, the soft unsupported layer is formed.
Of course, the excavation claw (4d) can easily penetrate and excavate even on the ground of the hard support layer (17). In addition, the digging depth (= cavity (20)) of the support layer (17), which is usually made of hard earth and sand, must be at least 3.0 times the outer diameter of the ready-made pile (18). . Also, the amount of insertion of the ready-made pile (18) into the support layer (17) must be at least the outer diameter of the ready-made pile (18).

A lower cylindrical body (1d) is provided below the rod (1).
Is fixed with rivets (21), and this lower cylinder (1d)
The outer periphery of the screw (2) is spirally formed with two screws (the number is not limited to two, but may be one or more or three or more). A hard screw claw (2a) is attached to the lower end of the screw (2). The tip of the screw claw (2a) is shaped like a chisel to facilitate excavation.

FIGS. 1 (a) to 1 (f) show two examples according to the present invention.
It is sectional drawing which shows the enforcement example of one Example of the middle digging expansion root compaction method of a step expansion head (A), and FIGS. 2-14 are the front view which shows the state of the two step expansion head (A) of each stage, side view It is a figure, a sectional view, and a perspective view, and explains the effect of the present invention according to these. (18) is a hollow prefabricated pile, in which a spiral auger (8) is inserted through a hollow portion (18a), and a two-stage enlarged head (A) is attached to the tip of the spiral auger (8). When excavating the non-supporting layer (16) from the ground to the hard supporting layer (17), as shown in FIG. 1 (a) or FIG.
The expanding blade (4) of the step expanding head (A) is half-opened, the spiral auger (8) is rotated forward, and excavation is performed according to the diameter of the existing pile (18). At this time, the central part of the drilling hole was excavated with the screw claw (2a) of the screw (2) screwed to the lower cylinder (1d), and the peripheral part was half-opened.
As described above, the non-support layer (16) is pierced with the same diameter as the existing pile (18) with the excavation claw (4d) at the tip of the hole. And ready-made pile (18) into which spiral auger (8) is inserted
Will be pushed into the excavated part with excavation.
The ground of the non-support layer (16) is softer than the support layer (17) and cannot support the ready-made pile (18). Therefore, the excavation is performed up to the upper part of the hard soil support layer (17).

When the excavation reaches just above the support layer (17) made of hard earth and sand, this is detected and the enlarged blade (4) is fully opened, and the excavation diameter is enlarged to excavate the upper layer of the support layer (17). I will go on. Here, the relationship between the enlarged blade (4) and the rod (1) when excavating with the enlarged blade (4) half open will be described. As shown in FIG. 4, the engaged portion (4a) formed on the upper surface of the enlarged blade (4)
Engages with a half-open engagement portion (6a) formed on the lower surface of the flange portion (6), and the half-open state is maintained. In this case, as shown in FIGS. 2 and 3, the earth and sand generated by the excavation existing in the hollow portion (20) formed by the excavation pushes up the expanding blade (4) and the slide cylinder portion (12), and the collar portion ( The pivoting end of the expansion blade (4) is sandwiched between 6) and the lower collar (12c) to maintain the above-mentioned half-open engagement state. Therefore, in this case, the lower cylinder (1
There is a gap (H) between the upper surface of (d) and the lower surface of the slide cylinder (12). Also, as described above, the slide cylinder (12)
Is raised by the earth pressure in the hollow portion (20), so that the support shaft (3) erected on the lower flange (12c) has a through hole (10) for a bearing.
Is pushed all the way up. Thus expanded feather (4)
When the spiral auger (8) is rotated forward with the half open state, the enlarged blade (4) has its upper surface engaged portion (4a) engaged with the half open engagement portion (6a) on the lower surface of the flange portion (6). While maintaining the state, it will be excavated by rotating in a half-open state together with the spiral auger (8).

FIG. 1 (b) shows a support layer (17) which is a harder ground.
In a state where it is dug to the lower part of the non-supporting layer (16) in the vicinity (in this case, the tip of the two-stage enlarged head (A) has reached the supporting layer (17)), and from this point on, the expanding blade With (4) fully opened, excavation is performed in the forward rotation. Figure 1 (c)
Is a cross-sectional view of the case where the lower part of the non-support layer (16) penetrates into the upper part of the support layer (17) and the excavation is continued with the expansion blades (4) wide open, and the spiral auger ( 8) Rotate forward to fully excavate the upper part of the support layer (17) from the bottom of the non-support layer (16) to make a cavity (20) for the bulb with a diameter larger than the outer diameter of the existing pile (18). To form.

Here, the case where the above-mentioned enlarged blade (4) is changed from the half-open state to the fully-open state will be described with reference to FIGS. In the previous stage {FIG. 1 (a)}, the upper surface engaged portion (4a) of the enlarged blade (4) engages with the half-open engagement portion (6a) on the lower surface of the flange portion (6a) to be in a half-open state. However, the spiral auger (8) is temporarily stopped from this state, and then the spiral auger is stopped.
(8) is raised slightly. As a result, the upper surface of the half-open enlarged blade (4) engages with the lower surface of the ready-made pile (18), so when the spiral auger (8) is pulled up, the enlarged blade (4) and the enlarged blade (4)
The collar section leaving the slide cylinder section (12) arranged below
The rod (1) provided with (6) is raised, and a gap (h) is generated between the upper surface of the expanding blade (4) and the lower surface of the flange portion (6),
The engaged portion (4a) on the upper surface of the enlarged blade (4) is disengaged from the half-open engaging portion (6a) of the flange (6). Spiral auger in this state again
When (8) is rotated forward, only the enlarged blade (4) comes into contact with the excavated soil in the cavity (20) and does not move, and the rod (1) rotates together with the spiral auger (8).

At the same time, the slide cylinder (12) slides with respect to the rod (1) but does not rotate, so that it rotates with the rod (1). As a result, the fully open engagement portion (12a) on the upper surface of the slide tube portion (12) is engaged with the engaged portion (4b) on the lower surface of the expansion blade (4) to be in a fully open state, and normally rotate in that state. As a result, the lower part of the non-supporting layer (16) is excavated and penetrated to the upper part of the supporting layer (17) which is a harder earth and sand ground. In this excavation, a hollow part (20) having a larger diameter than the existing pile (18) is obtained because the enlarged blade (4) is fully opened.
(c)).

When the bulb-forming cavity (20) is formed, a root consolidation material (5) is injected, and at the same time, the spiral auger (8) is reversed to close the enlarged blade (4), and the cavity is formed. From the (20) to the hollow portion (18a) of the ready-made pile (18), the two-stage enlarged head (A) is moved up and down to fill the hollow portion (20) with the root compaction material (5) while the root compaction material (5). And the surrounding earth and sand are stirred to fill the excavated part with the stirring member and make it denser (FIG. 1 (d)). Then, the ready-made pile (18) is driven to a predetermined depth (FIG. 1 (e)). ) Finally, with the spiral auger (8) closed, the enlarged blades (4) are closed, and the two-stage enlarged head (A) is pulled out from the hollow portion (18a) of the ready-made pile (18) (Fig. 1 (f)). . As a result, a bulb block (19) is formed in the cavity (20) at the embedding tip of the ready-made pile (18).
In FIG. 1 (e), the rotation of the spiral auger (8) is stopped, and the expanded blade
(4) is closed, and the entire two-stage enlarged head (A) is pulled up in the hollow portion (18a) of the ready-made pile (18). It is important that the root stiffener (5) does not tear.

FIG. 1 (f) is a sectional view showing a state in which the spiral auger (8) is extracted from the ready-made pile (18) and the bulb block (19) is fixedly formed at the tip of the ready-made pile (18). FIG. By the above series of operations, a bulb block (19) is formed in a portion from the bottom of the non-support layer (16), which is soft ground, to the upper layer of the support layer (17), which is hard ground, and this bulb block (19) The tip of the ready-made pile (18) is wrapped around, so that the ready-made pile (18) can be firmly supported.

Here, the case where the above-mentioned enlarged blade (4) is switched from the fully opened state to the closed state will be described with reference to FIGS. When the excavation of the bulb cavity (20) is completed,
Invert the spiral auger (8) {Fig. 1 (d)}. At this time, only the expanding blade (4) is also stopped due to the earth pressure resistance, and the spiral auger (8), the rod (1) and the slide cylinder (12) are reversed. Thereby, the engaged portion (4b) on the lower surface of the enlarged blade (4) is separated from the fully-opened engaged portion (12a), closed around the support shaft (3), and as shown in FIG.
(4) comes along the collar (6) and the lower collar (12c). This results in a diameter that can be stored in the hollow portion (18a) of the existing pile (18).

[0030]

According to the present invention, the expansion blade of the two-stage expansion head attached to the tip of the spiral auger can be switched between three stages: a closed state, a half-opened state, and a fully-opened state. In the case of excavation, it is possible to excavate with almost the same diameter as the existing pile with the expanded blade half open, thus minimizing the amount of excavated soil left over, When excavating a hollow part for a bulb from the support layer to the supporting layer, the expanded blade is fully opened and excavation is made larger than the diameter of the existing pile. Will be wrapped in the bulb part, and the bearing capacity of the existing pile will be improved. Furthermore, since the screw is spirally wound around the outer circumference of the rod below the enlarged blade, when excavating the ground, the center of the drill hole is excavated with the screw, and the surrounding area is further enlarged. Since the excavation is performed by the blade, there is an advantage that rapid excavation is possible.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing the steps of a middle digging and expanding root consolidation method according to the present invention.

FIG. 2 is a front view of the two-stage enlarged head of the present invention when the enlarged blade is half-opened.

FIG. 3 is a side view of FIG.

FIG. 4 is a plan view of FIG. 2;

FIG. 5 is a sectional view of FIG. 2;

FIG. 6 is a front view of the two-stage enlarged head of the present invention when the enlarged blades are fully opened.

FIG. 7 is a side view of FIG. 6;

FIG. 8 is a plan view of FIG. 6;

9 is a sectional view of FIG.

FIG. 10 is a front view of the two-stage enlarged head of the present invention in a state where an enlarged blade is closed.

FIG. 11 is a side view of FIG.

12 is a plan view of FIG.

FIG. 13 is a perspective view of a half-open state of an enlarged blade of the two-stage enlarged head of the present invention.

FIG. 14 is a perspective view of the expansion blade of the two-stage expansion head of the present invention in a fully opened state.

FIG. 15 is a cross-sectional view showing a state in which a conventional head is closed.

FIG. 16 is a cross-sectional view showing a state where a conventional head is opened and excavated.

[Explanation of symbols]

 (A) ... two-stage enlarged head (1) ... rod (1b) ... slide cylinder (3) ... support shaft (4) ... enlarged blade (4a) ... engaged part on the upper surface of enlarged blade (4b) ... enlarged Engaged part on lower surface of blade (6)… Flange part (6a)… Semi-open engagement part (8)… Spiral auger (10)… Bearing hole (12)… Slide cylinder part (12a)… Fully open engagement Department

Front page continuation (72) Inventor Hiroaki Tanaka 3-3-22 Nakanoshima, Kita-ku, Osaka City, Kansai Electric Power Co., Inc. (72) Shinji Goda 5-14 Nishitenma 5-chome, Kita-ku, Osaka Kinki Concrete Industrial Co. (72) Inventor Wakone Soneda 14-15 Nishitenma, Kita-ku, Osaka City Kinki Concrete Industry Co., Ltd.

Claims (2)

[Claims] 1. A rod attached to the tip of a spiral auger, a flange protruding from both side surfaces of the rod and having bearing through holes formed therein, and a rod below the flange. A sliding cylinder portion, which is slidably attached in the axial direction of the rod without rotating, and has a support shaft attached to be slidably inserted into the bearing through-hole, and a flange portion and a sliding cylinder portion. An enlarged blade that is disposed between the blades and that is rotatably supported by the support shaft and that expands and closes; and an upper blade that is formed on the lower surface of the flange portion and that is covered by the upper surface of the enlarged blade when the slide cylinder portion approaches the flange side. A half-opening engagement portion that engages with the engagement portion to hold the enlarged blade in a half-open state; and an engaged portion formed on the upper surface of the slide tube portion and on a lower surface of the expansion blade when the slide tube portion is separated from the flange portion. Are engaged with each other to hold the enlarged blade in a fully open state. Features a two-stage enlarged head. 2. A rod attached to a tip of a spiral auger, a flange protruding from both side surfaces of the rod and having bearing through holes formed therein, and a rod below the flange. A sliding cylinder portion, which is slidably attached in the axial direction of the rod without rotating, and has a support shaft attached to be slidably inserted into the bearing through-hole, and a flange portion and a sliding cylinder portion. An enlarged blade that is disposed between the blades and that is rotatably supported by the support shaft and that expands and closes; and an upper blade that is formed on the lower surface of the flange portion and that is covered by the upper surface of the enlarged blade when the slide cylinder portion approaches the flange side. A half-opening engagement portion that engages with the engagement portion to hold the enlarged blade in a half-open state; and an engaged portion formed on the upper surface of the slide tube portion and on a lower surface of the expansion blade when the slide tube portion is separated from the flange portion. Are engaged with each other to hold the enlarged blade in a fully open state, and at a position below the enlarged blade. A two-stage enlarged head characterized by comprising a screw spirally wound around an outer periphery of a rod.