JPH0423988Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to an enlarged bit used for excavation in a ready-made pile embedding method.

[Conventional technology]

Various construction methods for ready-made piles have been developed, but low-pollution construction methods are required in urban areas. One of the low-pollution construction methods for such pre-fabricated piles is to perform pre-boring to enlarge the area that will become the tip of the pile, sink the pre-fabricated pile, and then inject cement milk into the enlarged area to ensure high bearing capacity. There is a construction method. In this method, a hole about the diameter of a pile is excavated to the desired depth, and after reaching the specified depth, the auger is reversed, so that the closed blades of the bit at the bottom of the auger receive resistance from the side walls and bottom of the hole. This is a construction method that allows the hole to be opened and enlarged. As a device used for this purpose, there is a device described in Japanese Utility Model Application Publication No. 54-16201.

[Problem that the invention attempts to solve]

However, in most places where piles are constructed, there is a soft clay layer or silt layer above the supporting layer. When conventional bits are used in such strata, the clay or silt adheres to the bits and rods due to their own adhesive force, completely enveloping the bits and rods, and forming a hole between the bit part with the enlarged blades and the hole. Contact with the side wall and bottom surface is broken, and the blade cannot provide any resistance for expansion. Therefore, there is a drawback that it becomes impossible to enlarge the enlarging blade and it becomes impossible to form a predetermined enlarged excavated portion at the tip of the excavated hole.

[Means for solving problems]

In the present invention, an enlarged blade whose rear end is pivotably supported by a pin near the outer periphery of the screw provided around the rod is attached 2 along the screw.
The rod is provided with an ejection port for spouting fluid at the central portion near the tip of the expansion blade when the expansion blade is in a closed state, and the rod is provided with a spout port for spouting fluid at the center of the expansion blade when the expansion blade is in a closed state. has a curved surface that receives the fluid at right angles even when the expanding blade expands, and furthermore, the cutting edge surface of the expanding blade has a predetermined angle θ with respect to a line drawn from the tip toward the center of the rod. This is an enlarged bit characterized by the following.

〔Example〕

The present invention will be explained below with reference to the drawings.

FIG. 1 is an enlarged view of the expansion blade of one embodiment of the present invention, and FIG. 2 is a view of the expansion blade of the second embodiment of the invention in a closed state.

In the enlarged bit shown in these two drawings, an enlarged blade 4 whose rear end is pivotally supported by a pin 3 and can be opened and closed is located near the outer periphery of a screw 2 provided around the rod 1. Two or more rods are installed along the screw 2, and the rod 1
A spout 6 is provided at. Furthermore, as shown in FIG.
When the expansion blade 4 is in the closed state, the spout 6 faces toward the center of the expansion blade 4 near the tip.

Of course, the expansion bit has a joint 9 at its top so that it can be spliced onto other rods.

When drilling a hole with this expansion bit in the state shown in FIG. 2 with the expansion blade 4 closed, clay and silt adhere to the area around the expansion blade 4, making it difficult to expand the expansion blade 4. In the enlarged bit of the invention, when the enlarged blade 4 is in the closed state, the ejection port 6 is directed toward the center near the tip of the enlarged blade 4, so when the fluid is ejected from the ejection port 6, The expanding blade 4 is about to be expanded by the ejected energy of the fluid, and at the same time, the clay and silt attached around the expanding blade 4 are removed by the fluid, and the expanding blade 4 is easily expanded. Ru. In order to utilize the ejected energy of the fluid more effectively when the enlarging vane 4 is expanded, the ejected fluid is designed to always act at right angles to the enlarging vane 4 even while the enlarging vane 4 is being expanded. . That is, as shown in FIG.
When the blade is in the closed state, the tangent at the center portion 8 from the tip of the enlarged blade 4 is perpendicular to the line connecting the center portion 8 and the jet nozzle 6.

Furthermore, when the expansion blade 4 is expanded, in order to effectively utilize the resistance of the side wall of the borehole in order to sufficiently expand the expansion blade 4, as shown in FIG. 2, the expansion blade 4 is closed. The cutting edge surface 5 of the enlarged blade 4 at a certain time
A predetermined angle such that the line extended from the point is inside the line drawn from the tip of the expanding blade 4 toward the center of the rod (the angle is inside as shown as θ in Figure 2). It has a structure with an acute angle at the tip to give it a shape. With this structure, when the expansion blade 4 expanded by the fluid from the jet port 6 rotates in the direction in which the expansion blade 4 expands by reversing the rod 1, the tip of the expansion blade 4 touches the hole wall. It becomes easier to dig in, and the reaction force of the wall is also expanded.
It can be effectively used for expansion.

[Effect of idea]

The expansion blades of conventional excavation bits have a structure that expands due to earth pressure resistance, and with such a structure, when excavating clay layers or silt layers, the expansion blades often do not expand. Using the energy of the fluid ejected from the spout, it is possible to easily expand the expanding blade, and the mutual action of the fluid and the expanding blade removes clay and silt attached to the expanding blade. It becomes even easier to expand. Furthermore, in this invention, the rod-side surface of the expansion blade is curved so that it receives the fluid at right angles even when the expansion blade expands, so the energy of the fluid ejected during expansion is transferred to the rod-side surface. can be continuously directed towards. Further, since the tip of the enlarging blade has an acute angle, the tip of the enlarging blade easily bites into the hole wall, and the reaction force of the wall can also be effectively used to expand the expanding blade.

Therefore, even in the ground where there is a clay layer or silt layer, it is possible to reliably excavate an enlarged portion of the specified diameter at the location where the pile tip will be, increasing the reliability of construction and furthermore providing high bearing capacity. This can serve as a pile foundation, further increasing the reliability of the method of embedding ready-made piles, and at the same time increasing the design safety of the method.

[Brief explanation of the drawing]

FIG. 1A is an enlarged perspective view of the expansion blade of the first embodiment of the present invention, FIG. 1B is a sectional view taken along the line A-A of FIG. 1A, and FIG. 2A is the present invention. A perspective view of the second embodiment of the magnifying blade in a closed state;
Figure B is a sectional view taken along the line BB in Figure 2A. 1 is a rod, 2 is a screw, 3 is a pin, 4 is an enlarged blade, 5 is a cutting edge surface, 6 is a spout, 7 is a side surface,
8 indicates the center part near the tip, and 9 indicates the joint.

Claims (1)

[Scope of utility model registration request] Two or more enlarged wings, the rear end of which is rotatably supported by a pin, are attached near the outer periphery of the screw provided around the screw, and the enlarged wings are attached to the rod. When the blade is in the closed state, a jet port is provided in the center of the expanding blade near the tip, and the rod-side surface of the expanding blade is configured to eject the fluid at right angles even when the expanding blade is expanded. 1. An enlarged bit having a curved surface so as to be received by the rod, and further characterized in that the cutting edge surface of the enlarged blade has a predetermined angle θ with respect to a line drawn from the tip toward the center of the rod.