Grab bucket

Abstract

To provide a grab bucket capable of discharging mud water at the time of lifting soil.SOLUTION: In a grab bucket 1, at a first bucket 61 and a second bucket 62, a dewatering screen 7 is provided, at a first opening part 618 opening in a horizontal direction or a vertically downward direction in a closing position, capable of discharging water content (mud water) contained in sediment stored in a storage space, while suppressing flowing out of the sediment stored in the storage space. Thereby, the water content (mud water) contained in the sediment in the storage space can be discharged via the dewatering screen 7 into the lifting soil. Thereby, a mud water amount stored in the storage space can be reduced by an amount dewatered via the dewatering screen 7, and discharge of the mud (industrial waste) at the time of underwater excavation can be suppressed.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a grab bucket used for the subsidence excavation of a shaft related to, for example, a press-in open caisson method or an urban ring method, and for the lifting of excavated earth and sand.

Background Art

[0002] As a conventional grab bucket, for example, the one described in Patent Document 1 below is known.

[0003] Briefly explained, this grab bucket has a pair of left and right buckets provided so as to be openable and closable, and on the side wall of the bucket, there are provided through holes for air venting and an opening / closing valve capable of opening and closing these through holes. Thus, when the bucket is open, the opening / closing valve functions to open the through hole, so the air inside the bucket escapes to the outside through the through hole. On the other hand, when the bucket is closed, the through hole is blocked by the opening / closing valve, so the air inside the bucket is suppressed from rising and causing the earth and sand to fly up.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the case of the conventional grab bucket, the through hole is blocked by the opening / closing valve when the bucket is closed. Therefore, it is impossible to discharge muddy water during lifting, leaving room for improvement in that it is difficult to reduce the discharge of the muddy soil (industrial waste) containing the muddy water.

[0006] This invention was devised in view of the aforementioned technical problems, and aims to provide a grab bucket capable of discharging muddy water during soil removal. [Means for solving the problem]

[0007] In one embodiment, the excavator according to the present invention comprises: a support body suspended vertically via a wire so as to be able to move up and down; a pair of arms supported by the support body; a pair of buckets rotatably supported by the pair of arms, configured to open and close between an open position where they are furthest apart from each other and a closed position where they are in close contact, with the connection portion with the arms as the pivot point, forming a storage space for containing soil and sand inside in the closed position; a connecting shaft rotatably connecting the pair of buckets to each other; an opening provided on one or both of the pair of buckets, which opens horizontally or vertically downward in the closed position; and a dewatering screen provided in the opening, which suppresses the outflow of soil and sand contained inside the storage space while discharging moisture contained in the soil and sand contained inside the storage space.

[0008] As described above, according to the present invention, a dewatering screen is provided at an opening that opens horizontally or vertically downward when the bucket is in the closed position. This screen suppresses the outflow of soil contained in the bucket's storage space while simultaneously discharging the moisture contained in the soil contained in the bucket's storage space. As a result, during soil lifting, moisture (slurry water) contained in the bucket's storage space can be discharged through the dewatering screen.

[0009] Furthermore, because the dewatering screen is installed on the bucket, when the bucket is submerged in water during underwater drilling, the dewatering screen is automatically washed by the water resistance caused by the submersion. This suppresses clogging of the dewatering screen due to the discharge of muddy water (where sediment contained in the muddy water clogs the dewatering screen), avoids frequent maintenance of the dewatering screen, and allows for more efficient drilling operations with the grab bucket.

[0010] Furthermore, in another embodiment of the grab bucket, it is desirable that the opening be located at the vertical upper end of the bucket in the closed position.

[0011] In this way, by positioning the opening at the vertical upper end of the bucket in the closed position, water accumulating on the supernatant of the soil (mud) contained in the bucket's storage space can be efficiently discharged.

[0012] Furthermore, in yet another embodiment of the grab bucket, the pair of buckets preferably have a bottom wall and a pair of side walls rising from both side edges of the bottom wall, and the opening is located in the bottom wall.

[0013] Thus, by providing the opening in the bottom wall, which is set to be relatively wide relative to the pair of side walls, it becomes possible to secure a wider opening, thereby improving the efficiency of water drainage.

[0014] Furthermore, the vertical upper end of the bottom wall where the opening is located is on the opposite side from the vertical lower end, which may come into contact with soil during excavation. Therefore, there is no risk of contact with soil during excavation, which helps to suppress problems such as deformation of the opening and damage to the dewatering screen.

[0015] Furthermore, in yet another embodiment of the grab bucket, it is desirable that the opening be located at the vertical lower end of the bucket in the closed position.

[0016] In this way, by positioning the opening at the vertical lower end of the bucket in the closed position, moisture accumulating at the bottom of the soil (mud) contained in the bucket's storage space can be efficiently discharged.

[0017] Furthermore, in yet another embodiment of the grab bucket, the pair of buckets has a bottom wall and a pair of side walls rising from both side edges of the bottom wall, wherein the pair of side walls has a thickened portion provided on the closing side in the opening and closing direction of the pair of buckets, and a thinned portion provided on the opening side in the opening and closing direction of the pair of buckets, which is formed to be thinner than the thickened portion and whose outer surface is recessed in a stepped manner relative to the thickened portion, and the opening is preferably located in the thinned portion.

[0018] In this way, the opening is positioned in a stepped, concave thin-walled section located on the opening side of the bucket. This means that the thin-walled section where the opening is located is formed in a stepped, concave shape relative to the thick-walled section that directly contacts the ground (soil) during excavation. As a result, the thin-walled section does not directly contact the ground (soil) during excavation, which helps to suppress problems such as deformation of the opening and damage to the dewatering screen.

[0019] Furthermore, in yet another embodiment of the grab bucket, it is preferable that the dewatering screen comprises a mesh-like screen member and a fixing frame detachably provided in the opening for fixing the screen member to the opening.

[0020] Thus, the dewatering screen is composed of screen members that can be attached to and detached from the opening via a fixed frame, making it maintainable. Therefore, if the screen members become clogged or damaged, the screen members can be replaced, thereby maintaining the soil collection performance and water discharge performance of the dewatering screen for a long period of time.

[0021] When performing maintenance on the above-mentioned dewatering screen, it is possible to replace only the screen component that functions as a screen, or to replace the entire dewatering screen assembly, including the fixed frame.

[0022] Also, as yet another aspect of the grab bucket, the screen member includes a first screen member formed of a relatively thick grid and having a relatively coarse mesh, and a second screen member formed of a grid finer than the first screen member and having a mesh finer than the first screen member, and it is desirable that the first screen member and the second screen member are overlapped.

[0023] Thus, by overlapping the first screen member with high rigidity formed of a relatively thick grid and the second screen member with low rigidity formed of a relatively thin grid, it becomes possible to reinforce the second screen member that functions as a substantial screen with the first screen member. Thereby, while ensuring the collection performance of the screen member, the durability can be improved.

[0024] Also, as yet another aspect of the grab bucket, it is desirable that the second screen member is set to 10 to 30 mesh.

[0025] Thus, by setting the second screen member that functions as a substantial screen to 10 to 30 mesh, it becomes possible to reduce clogging while collecting a relatively large amount of earth and sand, and it is possible to achieve both the collection performance of earth and sand and the life of the screen.

Effect of the Invention

[0026] According to the present invention, the moisture contained in the accommodation space of the bucket can be discharged into the lifted soil by the dehydration screen provided in the bucket. Thereby, the amount of muddy water in the accommodation space of the bucket can be reduced by the amount of dehydration through the dehydration screen, and the discharge of mud (industrial waste) during underwater excavation can be suppressed.

Brief Description of the Drawings

[0027] [Figure 1] It is a schematic view of the grab bucket according to the present invention and the crawler crane for suspending the grab bucket. [Figure 2] This is a perspective view showing the open state of a grab bucket according to the first embodiment of the present invention. [Figure 3] A side view showing the open state of a grab bucket according to the first embodiment of the present invention, where (a) is a view taken from direction A in Figure 2, and (b) is a view taken from direction B in Figure 2. [Figure 4] This is a perspective view showing the closed state of a grab bucket according to the first embodiment of the present invention. [Figure 5] A side view showing the closed state of a grab bucket according to the first embodiment of the present invention, wherein (a) is a view taken from direction C in Figure 4, and (b) is a view taken from direction D in Figure 4. [Figure 6] Figure 4 is an enlarged view of the main part, which is an exploded perspective view of the dewatering screen. [Figure 7] Figure 6 shows a perspective view of the screen members of the dewatering screen, with (a) showing the assembled state and (b) showing the disassembled state. [Figure 8] Figure 6 shows a graph illustrating the results of the dewatering measurement test for the second screen member. [Figure 9] This is a perspective view showing the open state of a grab bucket according to a second embodiment of the present invention. [Figure 10] A side view showing the open state of a grab bucket according to a second embodiment of the present invention, where (a) is a view taken from direction E in Figure 9, and (b) is a view taken from direction F in Figure 9. [Figure 11] This is a perspective view showing the closed state of a grab bucket according to a second embodiment of the present invention. [Figure 12] A side view showing the closed state of a grab bucket according to a second embodiment of the present invention, where (a) is a view taken from direction G in Figure 11, and (b) is a view taken from direction H in Figure 11. [Figure 13] Figure 11 is an enlarged view of the main part, showing an exploded perspective view of the dewatering screen. [Figure 14] Figure 13 shows a graph illustrating the results of the dewatering measurement test for the second screen member. [Modes for carrying out the invention]

[0028] Hereinafter, embodiments of the grab bucket according to the present invention will be described in detail with reference to the drawings. In the embodiments described below, an example of the present invention being applied to a press-in type open caisson construction method will be shown.

[0029] [First Embodiment] Figures 1 to 8 show a first embodiment of the grab bucket according to the present invention.

[0030] (Grab bucket configuration) Figure 1 shows a schematic diagram of the grab bucket 1 and the crawler crane that suspends the grab bucket 1 according to this embodiment. In Figure 1, the symbol G represents the ground, and the symbol WT represents the water level underground.

[0031] As shown in Figure 1, the grab bucket 1 is suspended vertically via a first wire W1 supported by the jib 22 of a crawler crane 21, which is a lifting machine located on the ground (ground G). It is used for excavating a shaft underground in conjunction with the press-in and sinking of the caisson 3, and for lifting the excavated soil obtained from the shaft excavation. The soil lifted by the grab bucket 1 is transported to a soil pit (not shown) located on the ground (ground G).

[0032] Specifically, the grab bucket 1 includes a support body 4 suspended from the jib 22 of the crawler crane 21 via a first wire W1, a pair of arms supported by the support body 4, namely a first support arm 51 and a second support arm 52, a pair of buckets rotatably supported via the first support arm 51 and the second support arm 52, namely a first bucket 61 and a second bucket 62, and a connecting shaft 60 linked to the support body 4, which connects the first bucket 61 and the second bucket 62 so that they can be opened and closed.

[0033] Figure 2 shows a perspective view of the grab bucket 1 in the open position. Figure 3 is a side view of the grab bucket 1 shown in Figure 2, where (a) is the view from direction A in Figure 2 and (b) is the view from direction B in Figure 2. Figure 4 shows a perspective view of the grab bucket 1 in the closed position. Figure 5 is a side view of the grab bucket 1 shown in Figure 4, where (a) is the view from direction C in Figure 4 and (b) is the view from direction D in Figure 4.

[0034] The support structure 4 consists of a first support structure 41 and a second support structure 42, which are a pair of upper and lower support structures formed in the shape of rectangular blocks, with a roughly rectangular shape in plan view, as shown in Figures 2 and 4. The first support structure 41 is fixed in position, while the second support structure 42 is positioned opposite the first support structure 41 so as to be able to move relative to it (approach or move away from it) in the vertical direction. The first support structure 41 is suspended from the jib 22 via a first wire W1, and the second support structure 42 is suspended from the jib 22 via a second wire W2.

[0035] The first support 41 is positioned vertically above the second support 42. A pair of first support arms 511 and 512 are rotatably connected to the end of the first side portion 411, which is one end of the first support 41, while a pair of second support arms 521 and 522 are fixedly connected to the second side portion 412, which is the other end of the first support 41. The first support 41 is also provided with a first wire connection portion 410 near the upper center, to which the first wire W1 is connected. That is, the first support 41 moves vertically upward when the first wire W1 is wound up, and moves vertically downward when the first wire W1 is wound down. The first support 41 also has a second wire through-hole (not shown) formed vertically in a position adjacent to the first wire connection portion 410, through which the second wire W2 can pass.

[0036] On the other hand, the second support 42 is provided with a second wire connection portion 420 near the upper central position, and the second wire W2, which passes through the second wire through hole (not shown) of the first support 41, is connected to this second wire connection portion 420. The second support 42 is also provided with a connecting shaft 60 that connects the first bucket 61 and the second bucket 62 and supports them so that they can rotate relative to each other. As a result, when the second wire W2 is wound up, the second support 42 moves in a direction approaching the first support 41 (vertically upward), so that the first bucket 61 and the second bucket 62 form a closed state, while when the second wire W2 is wound down, the second support 42 moves in a direction away from the first support 41 (vertically downward), so that the first bucket 61 and the second bucket 62 form an open state.

[0037] The first support arms 511 and 512 are prism-shaped or cylindrical in shape, and one end of each in the longitudinal direction is connected to the end of the first side portion 411 of the first support body 41 via a first link (not shown), thereby rotatably supporting the first support body 41. The other ends of the first support arms 511 and 512 in the longitudinal direction are connected to the first supported portions 613 and 614 provided on the first bucket 61 via a second link (not shown), thereby rotatably supporting the first bucket 61.

[0038] The second support arms 521 and 522 are prism-shaped or tubular in shape, and one end of each in the longitudinal direction is fixedly connected to a support extension portion 43 extending from the second side portion 412 of the first support 41 by a predetermined fixing means, such as welding. The other end of each of the second support arms 521 and 522 in the longitudinal direction is connected to the first supported portions 623 and 624 provided on the second bucket 62 via a third link (not shown), thereby rotatably supporting the second bucket 62.

[0039] The first bucket 61 has a bottom wall 610 formed in a curved shape that bulges radially outward, and a pair of left and right side walls 611 and 612 that rise from both side edges of the bottom wall 610 and are generally fan-shaped. The upper end of the bottom wall 610 is provided with first supported portions 613 and 614 that are supported by first support arms 511 and 512. On the other hand, the tops of the side walls 611 and 612 are provided with second supported portions 615 and 616, respectively, which are used for connection with the connecting shaft 60. In addition, a plurality of (three in this embodiment) claw-shaped first blade portions 617 are provided at generally equal intervals in the width direction of the bottom wall 610 at the lower end of the bottom wall 610. In the open state, the first blade portion 617 is directed vertically downward, as shown in Figures 2 and 3, enabling excavation. In the closed state, as shown in Figures 4 and 5, it intersects with the second blade portion 627 in an alternating manner, allowing the inner end faces of the first bucket 61 and the second bucket 62 to be in close contact with each other.

[0040] Similarly, the second bucket 62 has a bottom wall 620 formed in a curved shape that bulges radially outward, and a pair of left and right side walls 621, 622 that rise from both side edges of the bottom wall 620 and are generally fan-shaped. The upper end of the bottom wall 620 is provided with first supported portions 623, 624 that are supported by second support arms 521, 522. On the other hand, the tops of the side walls 621, 622 are provided with second supported portions 625, 626, respectively, for connection with the connecting shaft 60. In addition, a plurality (three in this embodiment) of claw-shaped second blade portions 627 are provided at generally equal intervals in the width direction of the bottom wall 620 at the lower end of the bottom wall 620. Furthermore, in the open state, the second blade portion 627 is directed vertically downward, as shown in Figures 2 and 3, enabling excavation. In the closed state, as shown in Figures 4 and 5, it intersects with the first blade portion 617 in an alternating manner, allowing the inner end faces of the first bucket 61 and the second bucket 62 to be in close contact with each other.

[0041] Thus, the first bucket 61 is configured to open and close between an open position where they are furthest apart from each other (see Figures 2 and 3) and a closed position where they are in close contact (see Figures 4 and 5), with the connection points with the first support arms 511 and 512 (first supported parts 613 and 614) as pivot points, and the second bucket 62 is configured to open between an open position where they are furthest apart from each other (see Figures 2 and 3) and a closed position where they are in close contact (see Figures 4 and 5), with the connection points with the second support arms 521 and 522 (first supported parts 623 and 624) as pivot points. In the closed position, the inner end faces of the first bucket 61 and the second bucket 62 are in close contact, forming a storage space for soil and sand inside the first bucket 61 and the second bucket 62.

[0042] Furthermore, the upper end of the bottom wall 610 of the first bucket 61 is provided with a first opening 618 that opens horizontally or vertically downward when in the closed position. Similarly, the upper end of the bottom wall 620 of the second bucket 62 is also provided with a second opening (not shown) that opens horizontally or vertically downward when in the closed position. The first opening 618 and the second opening (not shown) are each provided with a dewatering screen 7 that suppresses the outflow of soil contained in the storage space while discharging moisture (muddy water) contained in the soil contained in the storage space.

[0043] Furthermore, the first opening 618 and the second opening (not shown) only need to be provided in the bottom walls 610 and 620, and are not limited to being located at the upper end of the bottom walls 610 and 620. In other words, the first opening 618 and the second opening (not shown) can be located not only at the upper end of the bottom walls 610 and 620, but also, for example, at the lower end of the bottom walls 610 and 620. In this configuration, there is the advantage of being able to efficiently drain the water (mud) that accumulates at the bottom of the soil (mud) contained in the containment space.

[0044] (Dehydration screen configuration) Figure 6 is an enlarged view of the main part of Figure 4, showing an exploded perspective view of the dewatering screen. Figure 7 shows a perspective view of the screen members of the dewatering screen shown in Figure 6, where (a) shows the assembled state and (b) shows the disassembled state. For convenience, in the following description, only the dewatering screen 7 placed in the first bucket 61 will be explained by referring to Figure 6. However, on the second bucket 62 side, a dewatering screen 7 is also provided in the same configuration as the first bucket 61, in a second opening (not shown) provided in the bottom wall 620 of the second bucket 62 (see Figures 2 to 5).

[0045] As shown in Figure 6, the dewatering screen 7 consists of a mesh-like screen member 70 and a fixing frame 73 for fixing the screen member 70 to the first opening 618. In other words, the screen member 70 has a two-piece structure in which the screen member 70 and the fixing frame 73 are separate, and is configured to be detachably attached to the first opening 618 via the fixing frame 73.

[0046] As shown in Figure 6, the first opening 618 in which the screen member 70 is placed has a bottom wall 610 with a stepped recess on its outer surface, and a number of roughly rectangular opening windows are formed near the center of the bottom. Specifically, four first opening windows 618a are opened in parallel in the width direction of the first opening 618 at the bottom of the first opening 618. In addition, two first through holes 618b are formed on each side of the outer ends of the first opening windows 618a at both ends in the width direction of the first opening 618, for attaching the fixing frame 73 which will be described later.

[0047] The screen member 70 is set to a width dimension corresponding to the formation area of ​​the first opening window 618a in the width direction of the first opening 618. As shown in Figure 7, it is constructed by overlapping a pair of first screen members 71, 71 made of a relatively coarse mesh and a second screen member 72 made of a finer mesh than these first screen members 71, 71. In other words, the screen member 70 is constructed by placing the pair of first screen members 71, 71 on both sides of the second screen member 72, sandwiching the second screen member 72 between the pair of first screen members 71, 71. The pair of first screen members 71 and second screen members 72 each have the same width dimension and are configured to overlap each other without excess or deficiency. As a result, the screen member 70 is constructed such that the second screen member 72, which has a relatively fine mesh and low rigidity, is reinforced by the first screen members 71, 71, which have a relatively coarse mesh and are relatively more rigid than the second screen member 72.

[0048] Specifically, it is desirable that the first screen member 71 be set to approximately 3 mesh. However, it is sufficient that the first screen member 71 has sufficient rigidity to reinforce the second screen member 72, and is not limited to the aforementioned 3 mesh. On the other hand, it is desirable that the second screen member 72 be set to approximately 10 to 30 mesh. However, since the optimal number of meshes for the second screen member 72 differs depending on the size of the soil particles lifted by the grab bucket 1, it is not limited to the aforementioned 10 to 30 mesh, and can be arbitrarily selected according to the size of the soil particles being lifted.

[0049] The fixing frame 73 is formed to be wider than the screen member 70 and consists of a frame body 74 for sandwiching and holding the screen member 70 between itself and the first opening 618, and a pair of backing plates 75, 75 for fixing the frame body 74 to the first opening 618. The frame body 74 and the pair of backing plates 75, 75 are fastened to the first opening 618 via bolts 76 and nuts 77. In this way, the fixing frame 73 is fastened to the first opening 618, for example, via fastening means consisting of bolts 76 and nuts 77, thereby detachably fixing the screen member 70 to the first opening 618. Note that the pair of backing plates 75, 75 can be omitted.

[0050] The frame 74 is made of a metal material and has a generally rectangular plate shape corresponding to the bottom of the first opening 618, and is formed in a shape that overlaps the bottom of the first opening 618 with approximately no excess or deficiency. Specifically, the frame 74 has multiple (four in this embodiment) frame opening windows 741 that overlap the first opening window 618a with approximately no excess or deficiency, and two frame through holes 742 are provided on each side of the widthwise ends of the frame 74, which match the first through holes 618b of the first opening 618.

[0051] The pair of backing plates 75 are formed from a metal material into rectangular plates of the same shape, and each has a pair of plate through-holes 750, 750 that correspond to a pair of frame through-holes 742, 742 on one side. That is, the pair of backing plates 75, 75 are positioned at both ends of the frame 74 and are fixed together with the frame 74 to the first opening 618 by fastening together with a plurality (four sets in this embodiment) of bolts 76 and nuts 77. Specifically, the nuts 77 are screwed onto the shaft portion (male thread portion) of the bolts 76 that pass through the frame through-holes 742 and plate through-holes 750, respectively, with the bolts inserted into the first through-holes 618b, thereby fastening the frame 74 and the pair of backing plates 75, 75 together to the first opening 618.

[0052] (Test to measure the amount of water removed from the screen material) Figure 8 shows a graph illustrating the results of the dewatering measurement test of the second screen member 72 shown in Figure 6. This graph shows the dewatering amount measured over 8 minutes for each mesh number (number of steel wires placed in 25.4 mm) for a 200 mm x 200 mm square mesh, with the horizontal axis representing the mesh number and the vertical axis representing the dewatering amount (cm³). 3 This indicates that...

[0053] The screen member 70 is composed of first screen members 71, 71, which serve as reinforcing materials to reinforce the second screen member 72, which has relatively low rigidity, and the second screen member 72, which functions as an effective screen. Therefore, in selecting the mesh to be applied to the second screen member 72, which functions as an effective screen, the amount of water removed was measured for second screen members 72 with mesh sizes from 10 to 50, and the optimal mesh for the second screen member 72 was analyzed based on the test results shown in Figure 8.

[0054] As shown in Figure 8, the amount of dewatering remained almost unchanged for the 40-mesh and 50-mesh meshes, while for the 10-30 mesh meshes, it clearly increased compared to the 40-mesh and 50-mesh meshes, and increased inversely proportionally to the mesh count. From these results, it was concluded that, as mentioned above, it is desirable to set the second screen member 72 to 10-30 mesh.

[0055] On the other hand, if the mesh count of the second screen member 72 is set to a small number, the amount of water that can be discharged (dewatered) will increase, but the amount of soil particles passing through the second screen member 72 will also increase. Therefore, it is desirable to select the mesh count of the second screen member 72 within the range of 10 to 30 meshes, according to the soil type (size of soil particles) of the ground to be excavated.

[0056] (Effects of this embodiment) The characteristic effects and benefits of the grab bucket 1 according to this embodiment will be described in detail below.

[0057] The conventional grab bucket described above has a configuration in which the through-hole is closed by an opening / closing valve when the bucket is closed. As a result, muddy water cannot be discharged during soil lifting, making it difficult to reduce the discharge of muddy soil (industrial waste) containing this muddy water, leaving room for improvement.

[0058] In contrast, the grab bucket 1 according to this embodiment is provided with a first opening 618 in the first bucket 61 and the second bucket 62 that opens horizontally or vertically downward when closed. This opening 7 is capable of discharging water (mud) contained in the soil contained in the storage space while suppressing the outflow of the soil contained in the storage space. As a result, water (mud) contained in the soil in the storage space can be discharged through the dewatering screen 7 during excavation. This reduces the amount of mud contained in the storage space by the amount of water dewatered through the dewatering screen 7, thereby suppressing the discharge of mud (industrial waste) during underwater excavation.

[0059] It should be noted that the dewatering screen 7 only needs to be provided in at least one of the first bucket 61 and the second bucket 62, and is not limited to the configuration in which it is provided in both the first bucket 61 and the second bucket 62, as in this embodiment. On the other hand, by providing the dewatering screen 7 in both the first bucket 61 and the second bucket 62, as in this embodiment, it is possible to efficiently discharge the moisture (mud) contained in the soil in the storage space, and to discharge a larger amount of moisture (mud) in a shorter time.

[0060] Furthermore, because the dewatering screen 7 is provided on the first bucket 61 (and the second bucket 62), when the grab bucket 1 is submerged in water during underwater excavation, the dewatering screen 7 is automatically washed by the water resistance caused by the submersion. This suppresses clogging of the dewatering screen 7 due to the discharge of muddy water (where sediment contained in the muddy water clogs the dewatering screen 7 as the muddy water is discharged), making it possible to avoid frequent maintenance of the dewatering screen 7 and enabling more efficient excavation work with the grab bucket 1.

[0061] Furthermore, in this embodiment, the first opening 618 (second opening, not shown) is positioned at the vertical upper end of the first bucket 61 (second bucket 62) in the closed position. This allows for efficient discharge of moisture that accumulates on top of the soil (mud) contained in the storage space.

[0062] Furthermore, in this embodiment, the first opening 618 (second opening, not shown) is provided in the bottom wall 610 (bottom wall 620), which is set to be relatively wider than the pair of side walls 611 and 612 (side walls 621 and 622). As a result, it is possible to secure a wider first opening 618 (second opening, not shown), and the efficiency of draining water (mud water) can be improved.

[0063] Furthermore, the upper vertical end of the bottom wall 610 (bottom wall 620) where the first opening 618 (second opening not shown) is located is the end opposite to the first blade portion 617 and the second blade portion 627 that come into contact with the ground during excavation. Since there is no risk of contact with soil during excavation, problems such as deformation of the first opening 618 (second opening not shown) and damage to the dewatering screen 7 can be suppressed.

[0064] Furthermore, in this embodiment, the dewatering screen 7 is composed of a screen member 70 that can be attached to and detached from the first opening 618 (a second opening not shown) via a fixed frame 73, making it maintainable. Therefore, if the screen member 70 becomes clogged or damaged, the screen member 70 can be replaced, thereby maintaining the soil collection performance and moisture (mud water) discharge performance of the dewatering screen 7 for a long period of time.

[0065] Furthermore, in this embodiment, the screen member 70 is constructed by overlapping a first screen member 71 with a relatively coarse mesh and a second screen member 72 with a finer mesh than the first screen member 71. This makes it possible to reinforce the second screen member 72, which functions as an effective screen, with the first screen member 71, thereby improving the durability of the screen member 70 while ensuring its collection performance.

[0066] Furthermore, in this embodiment, the second screen member 72, which functions as an effective screen, is set to a mesh size of 10 to 30. This makes it possible to collect a relatively large amount of sediment while reducing clogging of the second screen member 72, thereby achieving a balance between sediment collection performance and lifespan for the second screen member 72.

[0067] [Second Embodiment] Figures 9 to 14 show a second embodiment of the grab bucket according to the present invention. This embodiment is a modification of the arrangement of the dewatering screen 7 in the first embodiment, and the other components are the same as in the first embodiment. For this reason, components that are the same as in the first embodiment are denoted by the same reference numerals, and their descriptions are omitted.

[0068] (Grab bucket configuration) Figure 9 shows a perspective view of the grab bucket 1 in the open position. Figure 10 is a side view of the grab bucket 1 shown in Figure 9, where (a) is a view from direction E in Figure 9 and (b) is a view from direction F in Figure 9. Also, Figure 11 shows a perspective view of the grab bucket 1 in the closed position. Figure 12 is a side view of the grab bucket 1 shown in Figure 11, where (a) is a view from direction G in Figure 11 and (b) is a view from direction H in Figure 11.

[0069] In this embodiment, as shown particularly in Figures 9 and 11, the grab bucket 1 has both side walls 611 and 612 of the first bucket 61 configured as thick-walled portions 611a and 612a at the lower end in the open position, and thin-walled portions 611b and 612b at the upper end in the open position. As a result, in the grab bucket 1 according to this embodiment, the outer surfaces of the upper end of both side walls 611 and 612 of the first bucket 61 at the open position have a stepped shape that is recessed inward.

[0070] Similarly, the second bucket 62 is configured with thick-walled sections 621a and 622a at the lower end in the open position, and thin-walled sections 621b and 622b at the upper end in the open position. As a result, in this embodiment, the grab bucket 1 has a stepped shape on the outer surfaces of the upper end of both side walls 621 and 622 of the second bucket 62 that are recessed inward.

[0071] Thus, in this embodiment, the lower end of the open position of the first bucket 61 and the second bucket 62 is reinforced by forming a thicker wall on the lower end of the open position of both side walls 611, 612 of the first bucket 61 and 621, 622 of the second bucket 62. As a result, when the first bucket 61 and the second bucket 62 of the grab bucket 1 come into contact with the ground, they can adequately withstand the forces received from the ground due to excavation.

[0072] Furthermore, the thin-walled portions 611b and 612b of both side walls 611 and 612 of the first bucket 61 are provided with a first opening 619 that opens in a roughly rectangular window shape at a position corresponding to the lower end of the closed position, allowing communication between the inside and outside of the first bucket 61. Similarly, the thin-walled portions 611b and 612b of both side walls 621 and 622 of the second bucket 62 are provided with a second opening (not shown) that opens in a roughly rectangular window shape at a position corresponding to the lower end of the closed position, allowing communication between the inside and outside of the second bucket 62. Dewatering screens 7 are provided in the first opening 619 and the second opening (not shown), respectively, to suppress the outflow of soil contained in the storage space while discharging moisture (muddy water) contained in the soil contained in the storage space.

[0073] The first opening 619 and the second opening (not shown) are provided in the thin-walled portions 611b, 612b of the side walls 611, 612 and the thin-walled portions 611b, 612b of the side walls 621, 622, respectively, and are not limited to being located at positions corresponding to the lower ends of the closed positions in the thin-walled portions 611b, 612b of the side walls 611, 612 and the thin-walled portions 611b, 612b of the side walls 621, 622. In other words, with respect to the first opening 619 and the second opening (not shown), in addition to being located at a position corresponding to the lower end of the closed position of the thin-walled portions 611b, 612b of the side walls 611, 612 and the thin-walled portions 611b, 612b of the side walls 621, 622, it is also possible to extend them to, for example, the upper end of the closed position of the thin-walled portions 611b, 612b of the side walls 611, 612 and the thin-walled portions 611b, 612b of the side walls 621, 622, or to be located at a position corresponding to the upper end of the closed position. With such a configuration, there is an advantage in that moisture accumulating on the supernatant of the soil (mud) contained in the containment space can be efficiently discharged.

[0074] (Dehydration screen configuration) Figure 13 is an enlarged view of the main part of Figure 11, showing an exploded perspective view of the dewatering screen. In the following description, as with the first embodiment, for convenience, only the dewatering screen 7 placed in the first bucket 61 will be described by referring to Figure 13. However, on the second bucket 62 side, a dewatering screen 7 is also provided in the same configuration as in the first bucket 61, in a second opening (not shown) provided in the side walls 621, 622 (see Figures 9 to 12) of the second bucket 62.

[0075] As shown in Figure 13, the dewatering screen 7 consists of a mesh-like screen member 70 and a fixing frame 73' that fixes the screen member 70 to the first opening 619 and the second opening (not shown). In other words, the screen member 70 has a two-piece structure in which the screen member 70 and the fixing frame 73' are separate, and is configured to be detachably attached to the first opening 619 and the second opening (not shown) via the fixing frame 73'.

[0076] The fixed frame 73' is fixed to the outer surfaces of the thin-walled portions 611b and 612b of the side walls 611 and 612 of the first bucket 61 by welding or the like, and consists of a rectangular U-shaped first frame 78 that opens vertically upward in the closed position, and a rectangular annular (rectangular O-shaped) second frame 79 that is fixed to the outer surface of the first frame 78 by welding or the like, and has an opening window 790 that opens at the central position without interruption around its entire circumference.

[0077] The first frame 78 is formed to surround three sides of the screen member 70 with a thickness slightly greater than that of the screen member 70, and has a notch 780 on the inside that is slightly larger than the outer shape of the screen member 70. On the other hand, the second frame 79 is formed to be wider than the first frame 78, and in a plan view, its inner edge overlaps with the outer edge of the screen member 70, and has an opening window 790 in the center that is slightly smaller than the outer shape of the screen member 70.

[0078] With this configuration, the fixed frame 73' is attached to the outer surfaces of the thin-walled portions 611b and 612b of the side walls 611 and 612 of the first bucket 61, thereby defining a screen housing portion (not shown) between the first frame 78 and the second frame 79 that can accommodate the screen member 70. That is, the fixed frame 73' receives the screen member 70 through the notch 780 of the first frame 78, and holds the screen member 70 in a clamped state by sandwiching it between the thin-walled portions 611b and 612b of the side walls 611 and 612 of the first bucket 61 and the second frame 79.

[0079] Thus, in the grab bucket 1 according to this embodiment, instead of attaching and detaching the screen member 70 by attaching and detaching the fixing frame 73 to the first bucket 61 and the second bucket 62 as in the first embodiment, the fixing frame 73' remains fixed to the first bucket 61 and the second bucket 62, respectively, and the screen member 70 can be attached and detached only by inserting and removing the screen member 70 through the notch 780 of the first frame body 78 into the fixing frame 73' which is configured in a slot shape.

[0080] (Test to measure the amount of water removed from the screen material) Figure 14 shows a graph illustrating the results of a dewatering measurement test of the second screen member 72 shown in Figure 13. This graph shows the dewatering amount measured over 8 minutes for each mesh number (number of steel wires placed in 25.4 mm) for a 200 mm x 200 mm square mesh, under the same conditions as in the first embodiment. The horizontal axis represents the mesh number, and the vertical axis represents the dewatering amount (cm³). 3 This indicates that...

[0081] As shown in Figure 14, the amount of dewatering remained almost unchanged for the 40-mesh and 50-mesh meshes, while for the 10-30 mesh meshes, it clearly increased compared to the 40-mesh and 50-mesh meshes, and increased inversely proportionally to the mesh count. From these results, it was concluded that, in this embodiment as well, it is desirable to set the second screen member 72 to 10-30 mesh.

[0082] Furthermore, referring to Figures 8 and 14, a comparison of the dewatering amount measurement results according to this embodiment with the dewatering amount results according to the first embodiment shows that in this embodiment, where the dewatering screen 7 is arranged on the side walls 611, 612 of the first bucket 61 and the side walls 621, 622 of the second bucket 62, the dewatering amount increased by approximately 20% compared to the first embodiment, where the dewatering screen 7 is arranged on the bottom walls 610, 620 of the first bucket 61 and the second bucket 62.

[0083] In this embodiment as well, similar to the first embodiment, if the number of meshes of the second screen member 72 is set to a small number, the amount of water that can be discharged (dewatered amount) will increase, while the amount of soil particles passing through the second screen member 72 will also increase. Therefore, it is desirable to select the number of meshes of the second screen member 72 within the range of 10 to 30 meshes, according to the soil type (size of soil particles) of the ground to be excavated.

[0084] (Effects of this embodiment) As described above, in this embodiment, the first opening 619 (second opening, not shown) is located at the vertical lower end of the closed position of the first bucket 61 (second bucket 62). Therefore, moisture accumulating at the bottom of the soil (mud) contained in the storage space of the grab bucket 1 can be efficiently discharged.

[0085] Furthermore, in this embodiment, the first opening 619 (second opening not shown) is located in the stepped, concave thin-walled portions 611b, 612b (thin-walled portions 621b, 622b) on the opening side of the side walls 611, 612 of the first bucket 61 (side walls 621, 622 of the second bucket 62). Thus, the outer surfaces of the side walls 611, 612 of the first bucket 61 (side walls 621, 622 of the second bucket 62) are configured such that the thin-walled portions 611b, 612b (thin-walled portions 621b, 622b) where the first opening 619 (second opening not shown) is located are recessed in a stepped manner relative to the thick-walled portions 611a, 612a (thick-walled portions 621a, 622a) that directly contact the ground (soil) during excavation. As a result, the thin-walled sections 611b, 612b (and 621b, 622b) do not come into direct contact with the ground (soil) during excavation, which helps to suppress problems such as deformation of the first opening 619 (and a second opening not shown) and damage to the dewatering screen.

[0086] (modified version) The present invention is not limited to the configurations exemplified in the above embodiments, and can be freely modified according to the specifications of the target application, etc., without departing from the spirit of the present invention.

[0087] Furthermore, although the above embodiment illustrates a rope-type configuration in which the first bucket 61 and the second bucket 62 are opened and closed via a second wire W2, the power source for opening and closing the first bucket 61 and the second bucket 62 is not limited to the rope type. For example, any power source may be adopted depending on the specifications of the grab bucket 1, such as a hydraulic system in which the first bucket 61 and the second bucket 62 are opened and closed by a hydraulic cylinder, or an electric system in which the first bucket 61 and the second bucket 62 are opened and closed by an electric motor. [Explanation of Symbols]

[0088] 1… Grab bucket 21... Crawler crane 22... Jib 3… Caisson 4...Support part 41...First support part (support part) 42...Second support part (support part) 511...First support arm (a pair of arms) 512...First support arm (a pair of arms) 521...Second support arm (a pair of arms) 522...Second support arm (a pair of arms) 60...Connection shaft 61…First bucket (a pair of buckets) 610...Bottom wall 611... Side wall (a pair of side walls) 611a...Thick wall part 611b…Thin wall part 612... Side wall (a pair of side walls) 612a...thick wall part 612b…Thin wall part 618...First opening (opening) 619...First opening (opening) 62...Second bucket (a pair of buckets) 620...Bottom wall 621... Side wall (a pair of side walls) 621a...Thick wall part 621b…Thin wall part 622... Side wall (a pair of side walls) 622a...thick wall part 622b…Thin wall part 628...Second opening (opening) 629...Second opening (opening) 7…Dehydration screen 70…Screen components 71…First screen member 72...Second screen component 73, 73'... Fixed slots 74...Frame (fixed frame) 75... Backing plate (fixing frame) 76... Volts 77... Nut 78...First frame (fixed frame) 79...Second frame (fixed frame) W1…First wire (wire) W2...Second wire (wire)

Claims

1. A support structure suspended vertically via a wire, A pair of arms supported by the aforementioned support, Each of the pair of arms is rotatably supported, and the connection point with the arms is configured to open and close between an open position where they are furthest apart from each other and a closed position where they are tightly pressed together, and in the closed position a pair of buckets form a storage space for containing soil and sand inside, A connecting shaft that rotatably connects the pair of buckets, An opening provided in one or both of the pair of buckets, which opens horizontally or vertically downward when in the closed position, A dewatering screen is provided in the opening and, while suppressing the outflow of soil and sand contained within the containment space, discharges the moisture contained in the soil and sand contained within the containment space. Equipped with, The dewatering screen comprises a mesh-like screen member and a fixing frame that is detachably provided in the opening and for fixing the screen member to the opening. The screen member includes a first screen member and a second screen member. The first screen member is composed of a grid with a thicker grid than the second screen member and has a coarser mesh than the second screen member. The second screen member is composed of a grid with a finer grid than the first screen member and has a finer mesh than the first screen member. The first screen member and the second screen member are superimposed on each other, so that the second screen member is reinforced by the first screen member. A grab bucket characterized by the following features.

2. A grab bucket according to claim 1, The opening is located at the vertical upper end of the bucket in the closed position. A grab bucket characterized by the following features.

3. A grab bucket according to claim 2, The pair of buckets have a bottom wall and a pair of side walls rising from both side edges of the bottom wall. The opening is located in the bottom wall, A grab bucket characterized by the following features.

4. A grab bucket according to claim 1, The opening is located at the vertical lower end of the bucket in the closed position. A grab bucket characterized by the following features.

5. A grab bucket according to claim 4, The pair of buckets have a bottom wall and a pair of side walls rising from both side edges of the bottom wall. The pair of side walls have a thickened portion provided on the closing side in the opening and closing direction of the pair of buckets, and a thinned portion provided on the opening side in the opening and closing direction of the pair of buckets, which is formed to be thinner than the thickened portion and whose outer surface is recessed in a stepped manner relative to the thickened portion. The aforementioned opening is located in the thin-walled portion. A grab bucket characterized by the following features.

6. A grab bucket according to claim 1, The second screen member is set to 10 to 30 mesh. A grab bucket characterized by the following features.

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