How to use an excavator

Abstract

To provide an excavator provided with an excavation attachment capable of statically crushing without using vibration.SOLUTION: An excavator 1 comprises: a traveling body 10 moving along a rail 91 installed on a ceiling of a work room 90; a revolving body 11 revolving with respect to the traveling body 10; a boom 12 standing and lying with respect to the revolving body 11; and a ripper 2 or ripper bucket 3 as an excavation attachment detachably attached to a tip 121 of the boom 12. Furthermore, the tip 121 of the boom 12 is configured to be rotatable around an axis line of the boom 12.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an excavator used in a pneumatic caisson construction method. [Background technology]

[0002] Conventionally, in the pneumatic caisson construction method, an overhead excavator is known for excavating the ground in the working chamber at the bottom of the caisson. For this overhead excavator, excavation attachments have been developed to handle a variety of ground conditions, from soft to rock.

[0003] Known excavation attachments include, for example, (usually) buckets, breakers, and drifters. Among these, breakers are designed to crush and excavate rock by continuously striking the rock with a chisel (for details on excavators, see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2015-108245 A Summary of the Invention [Problem to be solved by the invention]

[0005] However, the breakers that were previously used placed a heavy burden on the excavator due to repeated vibrations, and sometimes were unable to crush the rock effectively depending on the direction of the joints.

[0006] SUMMARY OF THE PRESENT DISCLOSURE ... An object of the present invention is to provide an excavator equipped with an excavation attachment capable of static crushing without using vibration. [Means for solving the problem]

[0007] In order to achieve the above-mentioned objective, the excavator of the present invention is an excavator used in the pneumatic caisson construction method, and is equipped with a running body that moves along rails installed on the ceiling of a workroom, a rotating body that rotates relative to the running body, a boom that rises and falls relative to the rotating body, and a ripper or ripper bucket as an excavation attachment that is detachably attached to the tip of the boom. Effect of the Invention

[0008] In this way, the excavator of the present invention includes a traveling body, a rotating body, a boom, and a ripper or a ripper bucket as an excavation attachment, and is therefore an excavator equipped with an excavation attachment that can crush material statically without using vibration. [Brief description of the drawings]

[0009] [Figure 1] FIG. 1 is a side view of an excavator equipped with a ripper according to a first embodiment. [Diagram 2] FIG. 2 is an explanatory diagram of a ripper, (a) being a side view and (b) being a front view. [Diagram 3] FIG. 11 is a side view of an excavator equipped with a ripper bucket according to a second embodiment. [Figure 4] FIG. 1 is an explanatory diagram of a ripper bucket, in which (a) is a side view and (b) is a front view. [Diagram 5] FIG. 1 is a side view of an excavator in a state where an area under the cutting edge is being excavated using a ripper. [Figure 6] FIG. 1 is a side view of a conventional excavator being used to dump dirt into a soil dump bucket. [Figure 7] FIG. 1 is a side view showing an embodiment of the excavator being used to dump soil into a soil dumping bucket. [Figure 8] 1 is an explanatory diagram for explaining an outline of an experiment in Example 3, in which (a) is a side view and (b) is a front view. [Figure 9]Photographs of the experiment in Example 3. (a) shows the excavator used in the experiment, (b) shows the state of excavation by the bucket, (c) shows the state of excavation by the ripper bucket, and (d) shows the state of excavation by the ripper. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the components described in the following embodiments are merely examples, and are not intended to limit the technical scope of the present invention to those alone. Below, an excavator having a ripper will be described in Example 1, and an excavator having a ripper bucket will be described in Example 2. Furthermore, in Example 3, a demonstration experiment of the excavation performance of the excavator will be described. EXAMPLES

[0011] (composition) First, the overall configuration of an excavator 1 having a ripper 2 as an excavation attachment of this embodiment will be described with reference to Figure 1. As shown in Figure 1, the excavator 1 of this embodiment is an overhead traveling type excavator 1 used in the pneumatic caisson construction method. Although not shown, the pneumatic caisson is mainly composed of a side wall portion, a work chamber ceiling slab, a cutting edge (92), etc. In addition, the pneumatic caisson is equipped with a material shaft, a material lock, a manlock, etc. as equipment.

[0012] 1, the excavator 1 of this embodiment is equipped with a traveling body 10 that moves along rails 91 installed on the ceiling of a work chamber 90, a rotating body 11 that rotates relative to the traveling body 10, a boom 12 that rises and falls relative to the rotating body 11, and a ripper 2 as an excavation attachment that is detachably attached to the tip 121 of the boom 12. In this way, the excavator 1 of this embodiment is an overhead traveling type excavator that excavates the ground below by using a reaction force against the ceiling slab (the pneumatic caisson itself).

[0013] Moreover, in the excavator 1 of this embodiment, the tip 121 of the boom 12 is configured to be able to freely rotate 360 ​​degrees around the axis of the boom 12. That is, unlike a normal excavator (such as a backhoe) that travels on the ground, the rotation of the tip 121 of the boom 12 allows the excavation attachment attached to the tip 121 to freely rotate 360 ​​degrees.

[0014] The ripper 2, as an excavation attachment, can cut rocks and boulders according to the direction and angle of the joints, enabling effective static crushing (crushing without using vibration). Specifically, the ripper 2 is an excavation attachment that crushes consolidated hard ground and soft rocks, etc., to enable excavation with a bucket. The ripper 2 causes less impact and vibration than a breaker, and is known to have higher crushing efficiency than a breaker depending on the ground conditions.

[0015] As shown in Figures 2(a) and (b), the ripper 2 of this embodiment is manufactured by processing (cutting, welding, etc.) a steel plate, and is composed of a main body portion 20 curved in a V-shape (shallow J-shape; arc shape) and a mounting bracket portion 21 that is integral with the main body portion 20 and is connected to one end of the V-shaped main body portion 20.

[0016] The main body 20 is formed into a rounded V-shape (arc-like shape) from a steel plate of a specified thickness, and a replaceable tip 20a is attached to the tip of the pointed shape. The ripper 2 is attached to the tip 121 of the boom 12 via the mounting bracket 21 in such a direction that the center of curvature of the curved main body 20 is located toward the front (i.e., so that the concave portion opens toward the front). In other words, the ripper 2 of this embodiment is oriented in such a way that it operates like a power shovel (swinging from the front side to the far side), unlike a backhoe.

[0017] The mounting bracket portion 21 is formed in a U-shape by one bottom plate and two side plates. The main body portion 20 is connected to the one bottom plate, and two mounting holes 21a, 21b are provided in each of the two side plates. The mounting bracket portion 21 is attached (connected) to the tip 121 of the boom 12 via bolts inserted into the mounting holes 21a, 21b. The tip 121 of the boom 12 is configured to swing by extending and retracting a cylinder 122, so that the ripper 2 also swings (rotates; swings).

[0018] (How to use) Next, a method of using the excavator 1 equipped with the ripper 2 of this embodiment will be described with reference to Fig. 5. Below, a case where an area under the cutting edge is excavated will be described, but it is of course possible to excavate an area other than the area under the cutting edge.

[0019] The method of using the excavator 1 of this embodiment is as follows: 1) a step of moving the excavator 1 to the vicinity of a cutting edge; 2) a step of rotating the tip 121 of the boom 12 to lay down the ripper 2 as an excavation attachment; 3) A process of thinly scraping out the ground under the cutting edge from the side using a ripper 2 as an excavation attachment, as shown in FIG. 5; 4) A process of moving and loading (discharging) the excavated soil using another excavator (1) equipped with a regular bucket; It is equipped with:

[0020] Of these, in the raking out process 3), by raking out the soil with the ripper 2 laid on its side, the thickness of the ground to be excavated is the thickness of the main body 20 of the ripper 2, so the ground can be excavated thinly. In other words, while the action of raking the bottom of the blade from below significantly is limited in depth by law (50 cm or less), by raking from the side by the thickness of the ripper 2, excavation can be performed with almost no digging in the depth direction.

[0021] Furthermore, it is also preferable to repeat this "3) scraping process" several times to excavate the ground little by little. In other words, in one scraping operation with the ripper 2, the ground is excavated by the thickness of the ripper 2, but by repeating the scraping operation while checking the state of subsidence, it becomes possible to control the subsidence more safely and with higher accuracy.

[0022] (effect) Next, the effects of the excavator 1 of this embodiment will be listed and explained.

[0023] (1) As described above, the excavator 1 is equipped with the running body 10 which moves along the rails 91 installed on the ceiling of the working chamber 90, the rotating body 11 which rotates relative to the running body 10, the boom 12 which rises and falls relative to the rotating body 11, and the ripper 2 as an excavation attachment which is detachably attached to the tip 121 of the boom 12. Therefore, the excavator 1 is equipped with an excavation attachment which can crush rock statically without using vibration.

[0024] (2) The ripper 2 as an excavation attachment has a curved main body 20 and is detachably attached to the tip 121 of the boom 12 in a direction such that the center of curvature of the main body 20 is located toward the front. This makes it easier to cut through the joints in the rock or boulders by hooking the ripper 2 on them using a reaction force from the ceiling slab.

[0025] (3) Furthermore, the tip 121 of the boom 12 is configured to be rotatable around the axis of the boom 12, making it easier to align the direction of the ripper 2 with the joints in the rock or boulders, making it easier to cut through the rock or boulders. It also makes it possible to scrape out the area under the cutting edge of the pneumatic caisson from the side. The rotation angle can be freely changed according to the target.

[0026] (4) The method of using the excavator 1 described above includes the steps of moving the excavator 1 to the vicinity of the cutting edge, rotating the tip 121 of the boom 12 to lay the ripper 2 as an excavation attachment, and using the ripper 2 as an excavation attachment to scrape out the ground beneath the cutting edge. By using the excavator 1 in this manner, the ripper 2 can be laid down to scrape out a thin layer of the ground beneath the cutting edge.

[0027] (5) The process of scraping out the ground from under the cutting edge using the ripper 2 as an excavation attachment can be repeated multiple times to excavate the ground under the cutting edge little by little while checking the state of subsidence, enabling delicate control of subsidence. EXAMPLES

[0028] Hereinafter, an excavator 1 having a ripper bucket 3 as an excavation attachment will be described with reference to Figures 3, 4 and 5. Note that the same or equivalent parts as those described in the first embodiment will be described with the same reference numerals.

[0029] (composition) 3, the excavator 1 of this embodiment includes a traveling body 10, a rotating body 11, a boom 12, and a ripper bucket 3 as an excavation attachment that is detachably attached to the tip 121 of the boom 12. In the excavator 1 of this embodiment, the tip 121 of the boom 12 is configured to be able to freely rotate 360 ​​degrees around the axis of the boom 12.

[0030] The ripper bucket 3 as an excavation attachment of this embodiment can cut rocks and boulders according to the direction and angle of the joints, similar to the ripper 2, and therefore enables effective static crushing (crushing without using vibration). This ripper bucket 3 is an excavation attachment that has the functions of both a ripper (described in the first embodiment) and a normal bucket. In other words, similar to the ripper 2, consolidated hard ground and soft rock I can be crushed with the ripper part (31), and then moved and carried out with the bucket part (32). In this way, crushing and excavation can be performed without changing the excavation attachment.

[0031] As shown in Figures 4(a) and (b), the ripper bucket 3 is manufactured, for example, by processing (cutting, welding, etc.) a steel plate, and is composed of a main body portion 30 consisting of a ripper portion 31 and a bucket portion 32, and a mounting bracket portion 33 that is attached to the bucket portion 32 and is integral with the bucket portion 32 (main body portion 30).

[0032] The ripper portion 31 is formed into a rounded C-shape (arc-like shape) from a steel plate of a specified thickness, and a replaceable tip 31a is attached to the tip of the pointed shape. The ripper bucket 3 is attached to the tip 121 of the boom 12 via a mounting bracket portion 33 in such a direction that the center of curvature of the curved ripper portion 31 is located toward the front (i.e., so that it opens forward).

[0033] The bucket section 32 is formed of steel plates in a box shape with an opening, and the ripper section 31 is attached to the center of the left and right sides. That is, the volume of the bucket section 32 is divided into halves by the ripper section 31. Therefore, the bucket section 32 is capable of storing excavated soil and sand equivalent to its content integral, excluding the volume of the ripper section 31. Furthermore, claws similar to those of the ripper section 31 are attached to both left and right ends of the opening of the bucket section 32, enabling it to excavate the ground. However, the tip 31a of the ripper section 31 protrudes longer than the claws at both ends of the bucket section 32, making it easier for the ripper section 31 to exert its cutting action.

[0034] The mounting bracket portion 33 is formed by two parallel side plates. Two mounting holes 33a, 33b are provided in each of the two side plates. The mounting bracket portion 33 is attached (connected) to the tip 121 of the boom 12 via bolts inserted into the mounting holes 33a, 33b. The tip 121 of the boom 12 is configured to swing by extending and retracting a cylinder 122, so that the ripper bucket 3 also swings (rotates; oscillates).

[0035] (How to use) Next, a method of using the excavator 1 equipped with the ripper bucket 3 of this embodiment will be described with reference to Fig. 5. First, a case of excavating below the cutting edge will be described below, but it is of course possible to excavate a position other than the usual position below the cutting edge.

[0036] The method of using the excavator 1 in this embodiment for excavating the area under the cutting edge is as follows: 1) a step of moving the excavator 1 to the vicinity of a cutting edge; 2) a step of rotating the tip 121 of the boom 12 to lay down the ripper bucket 3 as an excavation attachment; 3) A process of thinly scraping out the ground under the cutting edge from the side using a ripper bucket 3 as an excavation attachment, as shown in FIG. 5; 4) a process of moving and loading (discharging) the excavated soil by the same ripper bucket 3; It is equipped with:

[0037] In this way, by using the ripper bucket 3, the same excavator 1 can perform both ripper and normal bucket operations.

[0038] Next, a method of using an excavator 1 equipped with the ripper bucket 3 of the embodiment and having a boom 12 that rotates around an axis will be described when dumping soil into the soil dump bucket 80.

[0039] First, for comparison, a method of dumping soil into a soil dumping bucket 80 using a conventional excavator 1 in which the boom 12 does not rotate around its axis will be described with reference to Fig. 6. This conventional excavator 1 has a configuration in which the boom 12 rises and falls relative to the traveling body 10 but cannot rotate around its axis.

[0040] 6, when dumping soil from the bucket 4 into the soil dumping bucket 80, the dumping must be performed by raising and lowering the boom 12 and rotating the bucket 4 in the opening direction. In this case, due to the relationship between the height at which the soil dumping bucket 80 is placed and the height of the excavator 1, it is necessary to operate the bucket 4 to open by retracting the bucket cylinder while raising the tip of the boom 12.

[0041] Even if these operations are attempted, it is difficult to dump the excavated soil properly because there is a risk of interference between the soil dump bucket 80 and the bucket 4 of the excavator 1. In particular, it is difficult to perform such dumping operations within the space of the work chamber 90, which has a limited height.

[0042] In contrast, the method of using the excavator of this embodiment is as shown in FIG. 1) a step of attaching a ripper bucket 3 as an excavation attachment to a tip 121 of a boom 12; 2) a step of excavating the ground by a ripper bucket 3; 3) a step of scooping up the excavated soil with a ripper bucket 3; 4) moving the excavator 1 so that the ripper bucket 3 is positioned above the soil dumping bucket 80; 5) rotating the ripper bucket 3 around the axis of the boom 12 to dump excavated soil into the soil discharge bucket 80; It is equipped with:

[0043] In particular, in the above-mentioned steps 2) and 3), the ground is excavated with the ripper bucket 3 and the excavated soil is scooped up, and then, in step 5), the ripper bucket 3 is rotated around the axis of the boom 12 to dump the excavated soil into the soil disposal bucket 80. This is an important point in this method of use.

[0044] That is, the excavator 1 of this embodiment is equipped with the ripper bucket 3 and the boom 12 rotates about its axis, so that earth and sand can be quickly and easily dumped into the soil removal bucket 80 even in a narrow work chamber 90 with little height. In this way, compared to the conventional type, there is no need to raise and lower the boom 12 more than necessary, and there is also no need to retract the bucket cylinder to open the ripper bucket 3.

[0045] Furthermore, it is extremely important that the excavator 1 of this embodiment can perform the three steps of excavation, scooping and dumping using the same excavator 1. In other words, while the number of excavators 1 in the working room 90 is limited, performing the three steps using one excavator 1 can greatly contribute to shortening the construction period compared to using multiple excavators with different roles.

[0046] (Action and effect) Next, the effects of the excavator 1 of this embodiment will be listed and explained.

[0047] (1) As described above, the excavator 1 is equipped with the running body 10 which moves along the rails 91 installed on the ceiling of the working chamber 90, the rotating body 11 which rotates relative to the running body 10, the boom 12 which rises and falls relative to the rotating body 11, and the ripper bucket 3 as an excavation attachment which is detachably attached to the tip 121 of the boom 12. Therefore, the excavator 1 is equipped with an excavation attachment which can crush rock statically without using vibration.

[0048] Therefore, the burden on the main machine caused by various repeated vibrations such as those of a breaker or a road header is reduced, preventing breakdowns. Furthermore, high-pressure work can also be reduced. In addition, there is no noise compared to vibrating crushers such as breakers. This is because the inside of the work chamber of a pneumatic caisson is a high-pressure, closed space, and it is necessary to prevent as much as possible the burden on the ears and semicircular canals in particular. Furthermore, when a drifter is used as an attachment, vibrations are generated because the drilling location is charged and blasted, but if a ripper bucket 3 is used as in this embodiment, no vibrations are generated.

[0049] (2) Furthermore, since the tip 121 of the boom 12 is configured to be rotatable around the axis of the boom 12, it becomes easier to align the direction of the ripper bucket 3 with the joints in the rock or boulders, making it easier to cut through the rock or boulders. It also becomes possible to scrape out the area under the cutting edge of the pneumatic caisson from the side.

[0050] Since the excavator 1 moves along the rails 91, its position is determined, but with a conventional breaker it was difficult to align it with the direction of the "joints" in the rock mass. On the other hand, with the present invention, it is possible to align it with the direction of the joints by rotating it.

[0051] A normal bucket has approximately the same vertical and horizontal dimensions, so the excavation height does not change even if it is laid down and used for shoveling. On the other hand, the ripper 2 and ripper bucket 3 of this embodiment have a narrow width, so the digging height can be lowered by laying them down and using them for shoveling.

[0052] Furthermore, dumping soil into the soil dump bucket becomes easier by rotating the ripper bucket 3. This is because the ripper part 31 in the center of the ripper bucket 3 protrudes significantly, and when dumping soil into the soil dump bucket, if the ripper bucket is a fully rotating bucket, by inverting it, soil can be dumped without interference between the ripper part 31 and the top of the soil dump bucket.

[0053] (3) The method of using the excavator 1 described above includes the steps of moving the excavator 1 to the vicinity of the cutting edge, rotating the tip 121 of the boom 12 to lay the ripper bucket 3 as an excavation attachment, and using the ripper bucket 3 as an excavation attachment to scrape out the ground beneath the cutting edge. By using the excavator 1 in this manner, the ripper bucket 3 can be laid down to scrape out a thin layer of ground beneath the cutting edge. Furthermore, consolidated hard ground or soft rock I can be crushed by the ripper portion 31, and then excavated by the bucket portion 32. In this manner, crushing and excavation can be performed without changing the excavation attachment.

[0054] In this way, particularly when excavating near the cutting edge (below the cutting tip), extremely delicate and efficient subsidence work is possible by using the ripper portion 31 of the ripper bucket 3 to perform a jerking motion below the cutting edge in a lying position and by using the bucket portion 32 of the ripper bucket 3 to scrape up the excavated soil.

[0055] Furthermore, in excavation using the pneumatic caisson method, the number of excavators 1 is limited, so the fact that one ripper bucket 3 can perform two roles is significant. In addition, there is also the effect of reducing the number of excavation attachment replacement operations, which are performed under high pressure.

[0056] (4) Furthermore, the method of using the excavator of this embodiment is as follows: a step of attaching a ripper bucket 3 as an excavation attachment to the tip of the boom; - excavating the ground by a ripper bucket 3; a step of scooping up the excavated soil by a ripper bucket 3; a step of moving the excavator 1 so that the ripper bucket 3 is positioned above the soil dumping bucket; and a step of rotating the ripper bucket 3 about the axis of the boom 12 to dump the excavated earth into the soil dump bucket. By using the excavator 1 in this manner, when loading excavated earth into the soil dump bucket, a loading operation can be performed by rotating the ripper bucket 3 on the soil dump bucket.

[0057] Other configurations and effects are substantially the same as those in the first embodiment, and therefore description thereof will be omitted. EXAMPLES

[0058] 8 and 9, a description will be given of a demonstration experiment of the excavation performance of the excavator 1 described in Examples 1 and 2. Note that the same reference numerals will be used to denote the same or equivalent parts as those described in Examples 1 and 2. 1.1 Experiment location The performance tests were conducted on land north of the planned site for the construction of a technical research institute in the northeast part of the Central Equipment Center site of Taito Construction Co., Ltd. in Ibaraki Prefecture. 1.2 Implementation period June 24th ~ September 13th, 2019 1.3 Drilling performance verification method The performance test of the rock excavation equipment was verified by excavating the test ground using the actual DREAM II. Based on the results of the performance test, the shape of the equipment, the installation method, and the operation method will be reviewed and improved as necessary (see Figure 8). 2. Test ground In order to approximate the target rock mass, the test ground is made mainly of broken granite and consolidated with air mortar. -Target strength setting The soil survey results show that the uniaxial compressive strength of the conglomerate is 0.08MN / m 2 ~3.6MN / m 2 Average value: 0.78 MN / m 2 (No.3), 0.82 MN / m 2 (No.8) The maximum value is 3.6 MN / m 2 Therefore, the target strength is 3.6 MN / m 2 (3.6N / mm 2 ) was used as the basis. 3. Drilling equipment The excavation equipment is an attachment to the DREAM II that can be attached in place of a bucket. A ripper and ripper bucket were used for the equipment, taking into consideration the nature of the rock, excavation efficiency, and the load on the DREAM body. 4. Measurement (1) Check the crushing status 1 Bucket and ripper The bucket and ripper are used to excavate the same location on each test ground, and the excavation shape (width, depth, length, area) is measured. Excavation is performed in one operation, twice, shifting the location. The excavation shape is photographed and converted into three dimensions using a 3D photo-based measurement system. (2) Crushing status check 2 Bucket and ripper The bucket and ripper are used to continuously excavate a specified area of ​​each test ground (5 minutes x 2), and the excavation status is checked. The excavation shape is photographed and converted into three dimensions using a 3D photo-based measurement system. (3) Checking drilling performance The entire test ground is crushed using the ripper bucket and the ripper. After crushing, the crushed test ground debris is loaded using the ripper bucket and the bucket. The time required for both tasks is measured (see Figure 9). 5. Results The results are as shown below.

[0059] The crushing situation was such that the excavation volume was larger when using a ripper or ripper bucket than when using a (normal) bucket. The excavation volumes of the ripper and ripper bucket were roughly the same, but the ripper bucket was slightly larger.

[0060] The crushing volume per hour was about seven times larger with the ripper and ripper bucket than with the (normal) bucket. The crushing volume (crushing efficiency) of the ripper and ripper bucket was roughly the same, but the ripper was slightly larger.

[0061] On the other hand, the loading volume per hour with the (normal) bucket was greater than that with the ripper bucket. The loading volume (loading efficiency) of the (normal) bucket was approximately 1.5 times that of the ripper bucket.

[0062] Other configurations and effects are substantially the same as those of the previously described embodiment, and therefore will not be described here.

[0063] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configurations are not limited to these embodiments, and design changes that do not deviate from the gist of the present invention are included in the present invention. [Explanation of symbols]

[0064] 1. Excavator 10 Running body 11 Rotating body 12. Boom 121 Tip 2 Lipa 20 Main body 20a Chip 21 Mounting bracket part 21a Mounting hole 21b Mounting hole 3 Ripper bucket 30 Main body 31 Ripper Department 31a Chip 32 Bucket section 33 Mounting bracket part 4 Buckets (conventional) 80 Soil Removal Bucket 90 Work Room 91 Rail 92 Blade mouth

Claims

1. An excavator for use in a pneumatic caisson construction method, A running body that moves along a rail installed on the ceiling of the workroom; A rotating body that rotates relative to the traveling body; A boom that rises and falls relative to the rotating body; A ripper or a ripper bucket as an excavation attachment detachably attached to the tip of the boom, A method of using an excavator, wherein the tip of the boom is configured to be rotatable about an axis of the boom, moving the excavator to a position adjacent to a cutting edge; A step of rotating the tip of the boom to lay down the ripper or the ripper bucket as an excavation attachment; A method of using an excavator comprising the steps of: scraping out the ground beneath a cutting edge of the ripper or the ripper bucket as an excavation attachment.

2. 2. A method for using an excavator according to claim 1, wherein the step of scraping out the ground beneath the cutting edge by the ripper or the ripper bucket as an excavation attachment is repeated a number of times.

3. An excavator for use in a pneumatic caisson construction method, A running body that moves along a rail installed on the ceiling of the workroom; A rotating body that rotates relative to the traveling body; A boom that rises and falls relative to the rotating body; A ripper or a ripper bucket as an excavation attachment detachably attached to the tip of the boom, A method of using an excavator, wherein the tip of the boom is configured to be rotatable about an axis of the boom, Attaching the ripper bucket to a tip of the boom as an excavation attachment; Excavating the ground with the ripper bucket; A step of scooping up excavated soil and sand with the ripper bucket; moving the excavator so that the ripper bucket is positioned above a soil dump bucket; and rotating the ripper bucket about the axis of the boom to dump excavated soil into the soil disposal bucket.

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