JPH1181368A - Excavator cutter bit for diaphragm wall - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify complicated exchange works maximally even at the time of usage for a prolonged term, and to prevent the induction of large damage by forming a stress concentration section to a bit for an excavator cutter bit for a diaphragm wall and constituting the cutter bit so that the stress concentration section is ruptured at the time of the working of overload. SOLUTION: A bit section for the cutter bit comprises an overload working section and an inserting section for mounting and demounting, and an annular notch ruptured when overloaded as a stress working section is formed between both the overload working section and the inserting section. The bit is fixed by inserting a pin into a pinhole bored to the inserting section for mounting and demoting and a pinhole formed to a base plate. Even when the cutter bit is overloaded at the time of operation, the annular notch section is broken and only the overload working section is slipped off, no load is applied to the base plate and mounting bolts, and damage can be prevented. Accordingly, complicated exchange works can be simplified maximally even at the time of usage for a prolonged term under conditions, in which boulder stones are mixed, and the induction of large damage can be obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cutter bit of an excavator used for excavating a ground to form a trench as a pre-process for constructing a continuous wall in the ground in civil engineering and construction work. It is.

[0002]

2. Description of the Related Art In constructing a continuous wall in the ground in civil engineering and construction work, a method of excavating a continuous groove in the ground and injecting cement milk into the groove to form a continuous wall in the ground has been attempted. ing.

[0003] As an excavator for performing such a method, for example, one disclosed in Japanese Patent Application Laid-Open No. 7-180154 is known. In this excavator, a bit with a tip having excellent wear resistance, such as a cemented carbide, brazed at its tip is attached to a base plate by welding to form a cutter bit. Are mounted with a plurality of bolts (mounting bolts) so as to cover the entire width of the excavation trench, and the cutter bit group including the plurality of types of cutter bits is connected to an endless chain that extends vertically toward the ground. It is configured so as to be continuously arranged at predetermined intervals.

[0004] In addition to the above-described digging apparatus, a digging apparatus for digging the ground with a digging bucket disposed on an endless chain and a bit protruding from the outer edge of the bucket. When cutting concrete, the bit is combined with a hard bit. There is also known an excavator configured to be replaceable (for example, Japanese Patent Application Laid-Open No. Hei 5-17946).

In these apparatuses, the cutter bit (or excavation bucket) is rotated, and the endless chain is driven. In such a state, the cutter bit is moved horizontally to excavate a continuous groove in the ground with the cutter bit. This is a basic configuration.

[0006]

However, the tip of the bit constituting the cutter bit of the excavator for underground continuous wall is always in contact with the ground during operation, so that the abrasion due to the contact with the ground is reduced. From the viewpoint of prevention, a cemented carbide having excellent wear resistance is often used as the material of the tip.

On the other hand, rocks, concrete shells and the like (hereinafter referred to as "boulders") may be mixed in the ground, and the cutter bit may collide with the boulders when excavating the trench for the underground continuous wall. is there. When the cutter bit collides with the boulder, the maximum load acts on the tip of the cutter bit. When the maximum load acts, the cutter bit and the mounting bolt are damaged.

The following are known as typical examples of such damage modes. Breaks at the weld between the bit and the base plate. The base plate (or excavation bucket) is greatly deformed. The mounting bolt is broken. Chip of cemented carbide is missing.

[0009] When the above-mentioned various types of damage occur, the following is the actual situation. In other words, when the above-mentioned damage occurs, loosen a plurality of mounting bolts, remove the cutter bit from the endless chain, send it back to a repair shop, etc., replace the damaged bit with a new bit, and replace it with the base plate. Weld. If the above damage occurs, loosen the plurality of mounting bolts, remove the cutter bit from the chain link, discard the damaged plate or drilling bucket, and assemble a spare plate or drilling bucket with the plurality of mounting bolts. I have to.

However, in the above-mentioned countermeasures, in any case, the labor for replacing and repairing the cutter bit becomes complicated, and several types of spare cutter bits and drilling buckets are always provided in order to smoothly perform the excavation work. And a large installation space is required.

On the other hand, when the above-mentioned damage occurs,
If only a few mounting bolts are broken, only the broken bolts need to be replaced, but if all the mounting bolts are broken, the entire cutter bit will fall into the ground, making it stronger than a boulder. This can cause significant damage to other cutter bits as a serious obstacle.

[0012] The present invention has been made in consideration of the above-mentioned circumstances, and its purpose is to perform a complicated replacement operation as long as it is used for a long time in a situation where rocks are mixed in the ground. An object of the present invention is to provide an excavator cutter bit for an underground diaphragm wall which can be simplified and does not cause significant damage.

[0013]

Means for Solving the Problems The underground continuous wall excavator cutter bit of the present invention which can solve the above problems (hereinafter, may be simply referred to as "cutter bit").
In the underground continuous wall excavator cutter bit consisting of a base plate and a bit, the bit is formed with a stress concentration portion, and the stress concentration portion is configured to break when an excessive load acts. It has.

The configuration of the cutter bit of the present invention is particularly useful when applied to a configuration in which the base plate and the bit are detachable. However, the present invention is not limited to this configuration, and the base plate and the bit are joined by welding. It is also useful to apply to what has been done.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is constructed as described above. In short, when the base plate collides with a boulder or the like, the bit is selectively applied with an excessive load smaller than a load that causes damage to the plate and the mounting bolt. The bit is formed with a stress concentration portion such as a notch or a wall thickness so as to be broken. By adopting such a configuration, when a boulder is encountered, the bit is selectively broken at a stress concentration portion such as a notch or a wall thickness, so that damage to the mounting bolt can be prevented and a load is applied to other portions. This prevents the other cutter bit from being damaged due to the cutter bit falling off.

The above-described configuration maximizes its effect when applied to a so-called detachable cutter bit in which the base plate and the bit are detachably configured. That is, when a bit provided with a stress concentration portion as described above is applied to a detachable cutter bit, only a damaged bit can be easily replaced, so that quick repair at a construction site is possible. What. The above-mentioned bit replacement can be easily performed at the construction site. However, as a bit spare part to deal with such a situation, it is necessary to hold various bits individually for each type of cutter bit. However, it is recommended to adopt a configuration in which the same bit is shared and used by several types of cutter bits.

As described above, forming the stress concentration portion on the bit prevents the cutter bit and the mounting bolt from being damaged by damaging only the bit, thereby exhibiting a function as destruction control. In addition, when such a function is applied to a detachable cutter bit, a damaged bit can be easily replaced, and a combination of these structures is extremely useful industrially. However, even in the case of a so-called integral type in which the bit is joined to the base plate by welding, providing a stress concentration portion near the mounting portion of the bit and performing destructive control requires that welding be performed when replacing the bit. Although the complexity remains, it is useful from the viewpoint that only the bit is damaged and the base plate is not significantly damaged, and such a configuration is also included in the technical scope of the present invention.

Next, the specific configuration of the cutter bit of the present invention will be described with reference to examples. However, the following examples are not intended to limit the present invention, and it is not possible to change the design in light of the above and subsequent points. All of them are included in the technical scope of the present invention.

[0019]

FIG. 1 is a schematic explanatory view showing the structure of a bit used in a cutter bit according to the present invention. This bit consists of an overload acting portion and a detachable insertion portion, between which an annular notch is formed as a stress acting portion, and this annular notch is designed to break when an overload is applied. Has become. And this pin has a pin hole in the insertion part for attachment and detachment so that it can be attached to and detached from the base plate,
The bit is fixed by inserting a pin through the pin hole and the pin hole formed in the base plate in a state where the insertion portion for detachment is inserted into the insertion hole of the base plate shown in FIG. At the same time, if the pin is removed, the bit can be easily removed from the base plate.

Such a bit is made of, for example, structural steel such as SCM435, and the annular notch can be formed by machining. However, for example, when the bit is manufactured by casting, it is necessary to prepare a casting mold. Of course, the annular notch may be formed in advance. Further, although the bit of FIG. 1 shows a configuration in which an annular notch is formed as a stress concentration portion, a linear notch or a partial thickness reduction is provided as long as the bit can function as a stress concentration portion. It may be a configuration.

The bit provided with the stress concentration portion as described above is
By being detachably mounted on the base plate shown in FIG. 2, even if an excessive load is applied to the cutter bit during operation, the annular notch portion breaks and only the excessive load acting portion falls off, so that the base plate and mounting bolts and the like are removed. Will not be loaded. That is, the load at which only the bit breaks (hereinafter, this load is referred to as a bit break setting load P _cr ) is appropriately set within a range where the base plate and the mounting bolt are not damaged when an excessive load is applied during operation. Thereby, damage to the base plate and the mounting bolts can be prevented.

Although FIGS. 1 and 2 show a construction in which the bit is detachable from the base plate, as shown in FIG. 3, a so-called integral cutter bit in which the bit is joined to the base plate by welding. Even in this case (in this case, no pin hole is formed in the bit), the same effect can be exerted by providing the above-mentioned stress concentration portion in the bit.

Incidentally, the excessive load differs depending on the operating conditions, and the above-mentioned bit break setting load may be selected in accordance therewith. Next, the selection criteria for the bit break setting load will be described.

For example, in the case of the integral cutter bit (material: for example, structural steel) shown in FIG. 3, damage is caused to the base plate and the mounting bolts. The calculation revealed that the base plate and the mounting bolts were damaged when the overload was 20 tonf or more. On the other hand, in normal operation in which no boulders are encountered, the load acting on one base plate is at least as small as about 2 tonf, and about 2 to 4 bits are mounted on each base plate. Only one tonf of load is applied to one bit.

Therefore, in the case of a cutter bit used under the above conditions, the bit breakage setting load (P _cr = P _cr = P so that the bit breaks when an excessive load of 10 tonf is applied.
10 tonf), and the above-mentioned annular notch is machined into the bit. Such a procedure is not limited to the one-piece cutter bit shown in FIG. 3, but is the same for the detachable cutter bit shown in FIG.

The notch bottom diameter (diameter of the portion where the annular notch is formed) and the breakage load (bit breakage setting load P _cr ) of the bit having the annular notch are determined by using the hardness of the bit material as a parameter. It has been found from finite element analysis and experiments that there is a relationship between the following equations (1) and (2). P _cr (tonf) = A · (Z / H) (1) Z = (π · d ³ ) / 32 (2) where A: constant (2.634 × 10 ⁵ , derived from finite element analysis method and experiment) ) H: Material hardness Z: Section modulus d: Notch bottom diameter (mm)

For example, in the cutter bit (material SCM435) shown in FIG. 1, the hardness is about Hv. 300 or more (according to JIS G4105, the breaking strength of SCM435 is described as 95 kgf / mm ² or more, and the hardness is 3% of the breaking strength.
Double the notch bottom diameter.
By setting the length to 3 mm, the set load P _cr for breaking the bit can be set to about 10 tonf.

In the above example, the case of setting the set load P _cr for breaking the bit in the annular notch is shown. However, when the linear notch is machined to provide the stress concentration portion, What is necessary is just to transform the coefficient Z into an equation corresponding to the cross section of the notch bottom at the time of processing into a linear notch. Further, in the above-described example, the case where the material of the bit is SCM435 is shown. However, the material of the bit is not limited to this, and other carbon steel, alloy steel, high tensile material, hard alloy (high chromium cast iron, Tool steel), cemented carbide, etc.
When the material of the bit is changed, the above formula may be applied as the value of the material whose hardness is changed.

[0029]

According to the present invention, as described above, complicated replacement work can be simplified as much as possible even when used for a long time under the condition that boulders are mixed in the ground, and large damage is caused. The excavator cutter bit for underground diaphragm wall without inducing is realized.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a configuration of a bit used in a cutter bit of the present invention.

FIG. 2 is a schematic explanatory view showing a configuration example of a detachable cutter bit.

FIG. 3 is a schematic explanatory view showing a configuration example of an integrated cutter bit.

Claims (3)

[Claims] An underground continuous wall excavator cutter bit comprising a base plate and a bit, wherein the bit is formed with a stress concentration portion, and the stress concentration portion is broken when an excessive load acts. An excavator cutter bit for an underground diaphragm wall. 2. The underground continuous wall excavator cutter bit according to claim 1, wherein the base plate and the bit are configured to be detachable. 3. The underground continuous wall excavator cutter bit according to claim 1, wherein the base plate and the bit are joined by welding.