Working machinery

Abstract

The actuator raises the bucket, which is then stopped at the designated position. [Solution] The working device 5 of the deep foundation excavator 1 includes an arm 10, a sheave mounting member 14 that moves by an actuator, a first lifting sheave 19 attached to the sheave mounting member 14, a second lifting sheave 23 provided on the arm 10 at a distance from the first lifting sheave 19, a lifting rope 38 wound around the first lifting sheave 19 and the second lifting sheave 23, and a clamshell bucket 9 supported by the lifting rope 38 that moves up and down in accordance with the change in the distance between the first lifting sheave 19 and the second lifting sheave 23. The deep foundation excavator 1 also includes a sensor that detects the position of the first lifting sheave 19, and a speed limiting device that limits the movement speed of the first lifting sheave 19 by the actuator when the position of the first lifting sheave 19 detected by the sensor reaches a predetermined position.

Description

Technical Field

[0001] The present disclosure relates to a working machine suitably used for shaft excavation work and the like.

Background Art

[0002] As a working machine including a self-propelled vehicle body and a working device provided on the vehicle body, a deep foundation excavator that performs shaft excavation work is known. The working device of the deep foundation excavator usually includes a boom whose proximal end is rotatably attached to the vehicle body, an arm rotatably attached to the distal end side of the boom, and a bucket (clam shell bucket) provided so as to be able to move up and down with respect to the arm. The deep foundation excavator lowers the bucket into the shaft with the tip of the arm arranged above the shaft, and opens and closes the bucket to excavate earth and sand.

[0003] Here, the working device of the deep foundation excavator includes a first sheave provided so as to be movable in the longitudinal direction of the arm, a second sheave provided on the arm at a distance from the first sheave, a hoisting rope wound around the first sheave and the second sheave, and a hoisting cylinder that changes the distance between the first sheave and the second sheave. One end of the hoisting rope is attached to the arm, and the other end of the hoisting rope is attached to the bucket via a guide sheave attached to the tip of the arm. Therefore, the bucket can be raised and lowered by expanding and contracting the hoisting cylinder to change the distance between the first sheave and the second sheave.

[0004] In this case, the length of the hoisting rope is adjusted so that the bucket reaches the stop position (a position close to the guide sheave at the front end of the arm) when the hoisting cylinder is in the fully extended state. Thereby, even if the bucket is raised to the stop position, the bucket does not contact the guide sheave or the like. Further, a plurality of sheaves are provided on the bucket (clam shell bucket), and the bucket is opened and closed by winding and unwinding an opening and closing rope wound around these plurality of sheaves. Therefore, when the bucket is raised and lowered by the hoisting rope, it is necessary to wind and unwind the opening and closing rope together with the hoisting rope.

[0005] By the way, the opening and closing ropes that are wrapped around the bucket sheaves are prone to deterioration due to the accumulation of excavated mud and other debris. When the opening and closing ropes deteriorate, they are often shortened by cutting the deteriorated portion, allowing for continued use. In this way, when the opening and closing ropes are shortened by cutting, the lifting ropes also need to be shortened by the same length. However, if the lifting cylinder is fully extended while both the lifting ropes and opening and closing ropes are shortened, the lifting ropes may become over-wound, potentially causing the bucket to exceed its stopping position and come into contact with the guide sheaves or other components.

[0006] Here, for example, in a hydraulic crane in which a hook for lifting loads is attached to the end of a lifting rope, a hook overwinding prevention device has been proposed to prevent the hook from coming into contact with a guide sheave or the like due to excessive winding of the lifting rope. For example, a hook overwinding prevention device has been proposed that includes a weight movably attached to the lifting rope having a through hole through which the lifting rope is inserted, a suspension rope that suspends the weight between the guide sheave and the hook, and a sensor that detects the tension of the suspension rope (Patent Document 1).

[0007] The hook overwinding prevention device described in Patent Document 1 prevents the hook from being overwinded by detecting, via a sensor, that the tension of the suspension rope has decreased when the hook rises and collides with the weight, and by stopping the winding operation of the lifting rope. Furthermore, the hook overwinding prevention device described in Patent Document 1 is configured to stop the winding operation of the lifting rope after a predetermined time has elapsed since the sensor detected that the tension of the suspension rope has decreased. This avoids the problem of the sensor malfunctioning due to the impact when the hook collides with the weight, which would prevent it from accurately stopping the winding operation of the lifting rope.

[0008] On the other hand, other conventional hook overwinding prevention devices consist of two weights, one above and one below, that are movably attached to the lifting rope, two suspension ropes that suspend these two weights with a gap between the hook and the guide sheave, and two sensors that detect the tension of the two suspension ropes (Patent Document 2). The hook overwinding prevention device according to Patent Document 2 is configured to reduce the winding speed of the lifting rope when the rising hook collides with the lower weight, and to stop the winding operation of the lifting rope when the hook collides with the upper weight. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 3926907 [Patent Document 2] Patent No. 3434401 [Overview of the project] [Problems that the invention aims to solve]

[0010] However, in the hook overwinding prevention device described in Patent Document 1, the winding operation of the lifting rope stops after a predetermined time has elapsed since the sensor detected a decrease in the tension of the lifting rope. As a result, the timing of stopping the winding operation is delayed, and there is a possibility that the hook may come into contact with the guide sheave or the like. Also, if the winding speed of the lifting rope is high, the tension of the lifting rope may decrease due to friction between the weight and the lifting rope, and the sensor may mistakenly detect that the hook and the weight have collided. On the other hand, in the overwinding prevention device described in Patent Document 2, if the winding speed of the lifting rope is high, the sensor may mistakenly detect a decrease in the tension of the lifting rope due to friction between the weight and the lifting rope.

[0011] In particular, in deep foundation drilling machines equipped with a lifting cylinder for winding and unwinding the lifting rope, the lifting rope that suspends the bucket is wrapped around multiple first sheaves and multiple second sheaves whose spacing is changed by the lifting cylinder. Therefore, the winding speed of the lifting rope when raising the bucket by the lifting cylinder increases as the number of sheaves increases. Consequently, deep foundation drilling machines equipped with a lifting cylinder typically have a higher winding speed of the lifting rope compared to cranes that use a winch to wind and unwind the lifting rope.

[0012] Therefore, if a hook overwinding prevention device, such as those described in Patent Documents 1 and 2, which consist of a weight, suspension rope, and sensor, were to be applied to a deep foundation excavator equipped with a lifting cylinder, there would be a problem of frequent false detections by the sensor due to friction between the weight and the lifting rope. Moreover, because the deep foundation excavator moves the bucket, which is gripping the soil, up from the shaft at a high speed, the bucket may come to a sudden stop at the stopping position, causing the bucket to vibrate violently and potentially spill the soil. In response to this, the operator of the deep foundation excavator needs to fine-tune the operation to extend the lifting cylinder in order to decelerate the bucket before it reaches the stopping position, which reduces the work efficiency when operating the lifting cylinder.

[0013] The object of the present invention is to provide a work machine that can stably stop the bucket at a stopping position when raising the bucket using an actuator. [Means for solving the problem]

[0014] The present invention relates to a work machine comprising a self-propelled vehicle body and a work device provided on the vehicle body, wherein the work device comprises an arm rotatably mounted on the vehicle body, a sheave mounting member that moves in the longitudinal direction of the arm by an actuator provided on the arm, a first sheave attached to the sheave mounting member, a second sheave provided on the arm spaced apart from the first sheave, a lifting rope wound around the first sheave and the second sheave with one end attached to the arm, and a bucket supported at the other end of the lifting rope that moves up and down relative to the arm in accordance with the change in the distance between the first sheave and the second sheave which are moved by the actuator, and further comprising a sensor for detecting the position of the first sheave, and a speed limiting device that limits the speed at which the actuator moves the first sheave when the position of the first sheave detected by the sensor reaches a predetermined position. [Effects of the Invention]

[0015] According to the present invention, the position of the first sheave when the bucket rises to the stopping position is set as a predetermined position, and the movement speed is limited when the first sheave reaches the predetermined position, thereby enabling the bucket to be stably stopped at the stopping position. [Brief explanation of the drawing]

[0016] [Figure 1] This is a left side view showing a deep foundation drilling machine to which the first embodiment of the present invention is applied. [Figure 2] This is a left side view showing the bucket lifting and opening / closing mechanism. [Figure 3] This is a plan view showing the bucket lifting and opening / closing mechanism. [Figure 4] This is a diagram of the arm after it has been disassembled. [Figure 5] This is a cross-sectional view taken from the direction of arrow VV in Figure 2, showing the lifting cylinder, sheave mounting member, first lifting sheave, first opening / closing sheave, buckling prevention member, buckling prevention pin, etc. [Figure 6]It is a cross-sectional view seen from the direction of arrow VI-VI in FIG. 5 showing a buckling prevention member, a buckling prevention pin, a switch pressing plate, etc. [Figure 7] It is a perspective view showing an arm, a sheave attachment member, a first limit switch, a second limit switch, a position adjustment mechanism, etc. [Figure 8] It is a perspective view showing a first limit switch, a second limit switch, a position adjustment mechanism, etc. [Figure 9] It is a cross-sectional view showing a sheave attachment member, a buckling prevention pin, a switch pressing plate, a first limit switch, a second limit switch, etc. [Figure 10] It is a cross-sectional view similar to FIG. 9 when the first limit switch is in the OFF state. [Figure 11] It is a cross-sectional view similar to FIG. 9 when the first limit switch and the second limit switch are in the OFF state. [Figure 12] It is a hydraulic circuit diagram including a lifting cylinder, a first limit switch, a second limit switch, a supply amount limiting device, etc. [Figure 13] It is a hydraulic circuit diagram according to the second embodiment of the present invention. [Figure 14] It is a hydraulic circuit diagram according to the third embodiment of the present invention.

Mode for Carrying Out the Invention

[0017] Hereinafter, a deep foundation excavator will be taken as an example of a working machine according to an embodiment of the present invention, and it will be described in detail according to the accompanying drawings. In the embodiment, the traveling direction of the deep foundation excavator is defined as the front-rear direction, and the direction perpendicular to the traveling direction is defined as the left-right direction for explanation. [[ID=—33]]

[0018] FIGS. 1 to 12 show the first embodiment of the present invention. The deep foundation excavator 1 is manufactured based on, for example, a crawler-type hydraulic excavator. The deep foundation excavator 1 includes a self-propelled crawler-type lower traveling body 2, an upper revolving body 3 that is rotatably mounted on the lower traveling body 2, and a working device 5 described later provided on the upper revolving body 3. The lower traveling body 2 and the upper revolving body 3 constitute the vehicle body of the deep foundation excavator 1.

[0019] The cab 4 is located on the left front side of the upper rotating body 3. The cab 4 forms the operator's cabin, where the operator who operates the deep foundation drilling machine 1 sits. Inside the cab 4 is the operator's seat 4A, and around the operator's seat 4A are various control devices for operating the travel of the lower traveling body 2, the rotation of the upper rotating body 3, and the work equipment 5.

[0020] The working device 5 has a boom 6 rotatably mounted on the upper slewing body 3, and the boom 6 rotates relative to the upper slewing body 3 in accordance with the extension and retraction operation of the boom cylinder 7. An arm 10, which will be described later, is provided at the tip of the boom 6, and the arm 10 rotates relative to the boom 6 in accordance with the extension and retraction operation of the arm cylinder 8. A bucket lifting / lowering and opening / closing device 17, which will be described later, is provided on the arm 10, and a clamshell bucket 9 is suspended from the front end of the arm 10.

[0021] The clamshell bucket 9 is suspended from the front end of the arm 10 so as to be able to move up and down using a lifting rope 38, which will be described later. The clamshell bucket 9 has a bucket support section 9A, a pair of buckets 9B that are openable and closable and provided below the bucket support section 9A, a connecting bracket 9C to which the pair of buckets 9B are rotatably connected, and a pair of opening and closing arms 9D that connect the bucket support section 9A and the pair of buckets 9B. The bucket support section 9A is provided with a plurality of upper sheaves 9E, and the connecting bracket 9C is provided with a plurality of lower sheaves 9F that are vertically opposed to the upper sheaves 9E.

[0022] The other end 38B of the lifting rope 38 is attached to the bucket support portion 9A of the clamshell bucket 9. The opening and closing rope 40, which will be described later, is wound alternately around the upper sheave 9E and the lower sheave 9F of the clamshell bucket 9. One end 40A of the opening and closing rope 40 is attached to the arm 10 via the right stay 41, which will be described later (see Figure 3), and the other end 40B of the opening and closing rope 40 is attached to the bucket support portion 9A of the clamshell bucket 9.

[0023] The arm 10 is rotatably mounted at the tip of the boom 6. As shown in Figures 2 to 4, the arm 10 is divisible, consisting of an arm body 11 formed from a hollow rectangular tube and extending in the front-rear direction, a pair of guide arms 12 and 13 attached to the rear side of the arm body 11, and a sheave mounting member 14 movably attached to the guide arms 12 and 13.

[0024] The arm body 11 is the base of the arm 10 and is formed as a rectangular tube with a rectangular cross-sectional shape. The arm body 11 is surrounded by a left side panel 11A and a right side panel 11B, an upper panel 11C that connects the upper ends of the left side panel 11A and the right side panel 11B, and a lower panel 11D that connects the lower ends of the left side panel 11A and the right side panel 11B.

[0025] The front end 11E of the arm body 11 is closed, and the rear end 11F of the arm body 11 is open. On the upper plate 11C of the arm body 11, a stepped surface 11G is formed in the part located in front of the center in the front-rear direction, which is lower in height (distance from the lower plate 11D) than the part located behind the center. An intermediate guide sheave 37, which will be described later, is provided on the stepped surface 11G. The lower plate 11D of the arm body 11 is provided with a boom mounting bracket 11H and a cylinder mounting bracket 11J. The boom mounting bracket 11H is rotatably connected to the tip of the boom 6 via a connecting pin 11K (see Figure 1). The cylinder mounting bracket 11J is pin-connected to the tip of the arm cylinder 8, whose base end is attached to the boom 6. Therefore, the arm body 11 rotates vertically around the connecting pin 11K in accordance with the extension and retraction movement of the arm cylinder 8.

[0026] Two pin insertion holes 11L and 11M are formed on the rear end 11F side of the left side panel 11A and the right side panel 11B, spaced apart in the vertical direction and penetrating in the horizontal direction. Connecting pins 12B and 13B, which will be described later, are inserted through these pin insertion holes 11L and 11M.

[0027] Guide arms 12 and 13 are detachably attached to the rear side of the arm body 11 in a pair in the vertical direction. Each guide arm 12 and 13 is formed as a rectangular tubular body with a rectangular cross-section and extends in the front-to-back direction. Cylindrical portions 12A and 13A extending in the left-to-right direction are fixed to the front ends of each guide arm 12 and 13. A connecting pin 12B is inserted through the inner circumference of the cylindrical portion 12A of guide arm 12, and both ends of the connecting pin 12B are inserted through the pin insertion holes 11L of the arm body 11. A connecting pin 13B is inserted through the inner circumference of the cylindrical portion 13A of guide arm 13, and both ends of the connecting pin 13B are inserted through the pin insertion holes 11M of the arm body 11. On the other hand, the rear ends of guide arms 12 and 13 are connected via a connecting member 13C. As a result, the guide arms 12 and 13 extend rearward from the rear end 11F of the arm body 11 while maintaining a constant distance between them in the vertical direction.

[0028] The sheave mounting member 14 is movably attached to a pair of guide arms 12 and 13. With the first lifting sheave 19 and the first opening / closing sheave 21 (described later) attached to the sheave mounting member 14, it moves in the front-rear direction along the guide arms 12 and 13. The sheave mounting member 14 is formed as a rectangular tube having a rectangular cross-sectional shape equivalent to that of the arm body 11, and surrounds the guide arms 12 and 13 from the outside. The sheave mounting member 14 is formed as a short rectangular tube surrounded by a left plate 14A, a right plate 14B, an upper plate 14C, and a lower plate 14D.

[0029] As shown in Figures 4 and 5, pin insertion holes 14E, which penetrate in the left-right direction, are concentrically formed in the front portions of the left plate 14A and the right plate 14B that constitute the sheave mounting member 14. The second connecting pin 18F, which will be described later, is inserted through these two pin insertion holes 14E. As shown in Figure 5, a left shaft mounting hole 14F, which penetrates in the left-right direction, is formed in the center of the left plate 14A that constitutes the sheave mounting member 14, and the first lifting sheave shaft 20, which will be described later, is attached to the left shaft mounting hole 14F. A right shaft mounting hole 14G, which penetrates in the left-right direction, is formed in the center of the right plate 14B that constitutes the sheave mounting member 14, and the first opening / closing sheave shaft 22, which will be described later, is attached to the right shaft mounting hole 14G.

[0030] Slide plates 15 are provided between the inner surfaces of the left plate 14A, right plate 14B, and upper plate 14C of the sheave mounting member 14 and the guide arm 12, and the slide plates 15 are in slidable contact with the guide arm 12. Slide plates 16 are provided between the inner surfaces of the left plate 14A, right plate 14B, and lower plate 14D of the sheave mounting member 14 and the guide arm 13, and the slide plates 16 are in slidable contact with the guide arm 13. These slide plates 15 and 16 are fixed to the sheave mounting member 14 using bolts or the like, and allow the sheave mounting member 14 to move smoothly relative to the guide arms 12 and 13.

[0031] The bucket lifting and opening / closing device 17 is installed on the arm 10. The bucket lifting and opening / closing device 17 controls various operations, including the lifting and lowering and opening / closing operations of the clamshell bucket 9. The bucket lifting and opening / closing device 17 consists of a lifting cylinder 18, a first lifting sheave 19, a first opening / closing sheave 21, a second lifting sheave 23, a second opening / closing sheave 30, an opening / closing cylinder 31, an intermediate guide sheave 37, a lifting rope 38, an opening / closing rope 40, a slack adjustment sheave 47, and a slack adjustment cylinder 48, which are described later.

[0032] The lifting cylinder 18, acting as an actuator, is located within the arm body 11 that constitutes the arm 10 and extends in the longitudinal direction (front-to-back direction) of the arm body 11. The lifting cylinder 18 raises or lowers the clamshell bucket 9 by extending or retracting in response to the operation of a lifting operation device 65, which will be described later and is located inside the cab 4. The lifting cylinder 18 has a tube 18A, a piston (not shown) inserted inside the tube 18A, and a rod 18B whose base end is attached to the piston and whose tip protrudes from the tube 18A.

[0033] As shown in Figure 4, a mounting flange 18C is fixed to the tip side (rod 18B side) of the tube 18A of the lifting cylinder 18. The mounting flange 18C is pin-connected to the rear end 11F side of the arm body 11 using a first connecting pin 18D. As a result, the tube 18A of the lifting cylinder 18 is attached to the arm body 11 so as to be able to swing around the first connecting pin 18D.

[0034] On the other hand, as shown in Figures 5 and 6, a rectangular mounting eye 18E is provided at the tip of the rod 18B of the lifting cylinder 18. A second connecting pin 18F is inserted through the pin insertion hole 14E of the sheave mounting member 14 and the mounting eye 18E. As a result, the rod 18B of the lifting cylinder 18 is connected to the sheave mounting member 14 via the second connecting pin 18F. Furthermore, a buckling prevention member 50, which will be described later, is attached to the mounting eye 18E.

[0035] Thus, the tube 18A of the lifting cylinder 18 is attached to the arm body 11 via the first connecting pin 18D, and the rod 18B is attached to the sheave mounting member 14 via the second connecting pin 18F. Therefore, by extending and retracting the lifting cylinder 18, the sheave mounting member 14 moves in the front-rear direction along the guide arms 12 and 13.

[0036] The first lifting sheave 19, which functions as the first sheave, is attached to the outer surface of the left plate 14A that constitutes the sheave mounting member 14 via the first lifting sheave shaft 20. Multiple first lifting sheaves 19 are provided in a row (for example, five) arranged in the axial direction of the first lifting sheave shaft 20, and are supported by the sheave mounting member 14 so as to be rotatable about the first lifting sheave shaft 20. These multiple first lifting sheaves 19 are covered by a sheave cover 19A fixed to the left plate 14A of the sheave mounting member 14.

[0037] As shown in Figure 5, the axial middle portion of the first lifting sheave shaft 20 is fixed to the left shaft mounting hole 14F of the sheave mounting member 14 (left side plate 14A). One end 20A of the first lifting sheave shaft 20 protrudes outward from the sheave mounting member 14 (left side plate 14A). The portion of the first lifting sheave shaft 20 that protrudes outward from the left side plate 14A rotatably supports the first lifting sheave 19. The other end 20B of the first lifting sheave shaft 20 protrudes inward from the left side plate 14A towards the inside of the sheave mounting member 14.

[0038] The first opening / closing sheave 21 is attached to the outer surface of the right side plate 14B of the sheave mounting member 14 via the first opening / closing sheave shaft 22. One end of the first opening / closing sheave shaft 22 is fixed to the right shaft mounting hole 14G of the sheave mounting member 14 (right side plate 14B), and the other end protrudes to the right from the sheave mounting member 14. Multiple first opening / closing sheaves 21 are provided in an axial order (for example, 5) on the other end of the first opening / closing sheave shaft 22, and are rotatably supported on the sheave mounting member 14 about the first opening / closing sheave shaft 22. These multiple first opening / closing sheaves 21 are covered by a sheave cover 21A fixed to the right side plate 14B of the sheave mounting member 14.

[0039] The second lifting sheave 23, acting as a second sheave, is provided on the arm body 11 spaced apart from the first lifting sheave 19 and fixed to the arm 10 in the longitudinal direction. The second lifting sheave 23 is attached to the outer surface of the left side panel 11A that constitutes the arm body 11 via the second lifting sheave shaft 24. One end of the second lifting sheave shaft 24 is fixed to the middle of the arm body 11 (left side panel 11A) in the longitudinal direction, and the other end protrudes to the left from the arm body 11. Multiple second lifting sheaves 23 are provided in the axial direction of the second lifting sheave shaft 24 (for example, four), and are rotatably supported relative to the arm body 11 about the second lifting sheave shaft 24.

[0040] Therefore, as the sheave mounting member 14 moves in accordance with the extension and retraction movement of the lifting cylinder 18, the first lifting sheave 19 attached to the sheave mounting member 14 moves closer to and further away from the second lifting sheave 23. In this embodiment, the rod 18B of the lifting cylinder 18, the sheave mounting member 14, and the second connecting pin 18F constitute the first sheave movable part that changes the position of the first lifting sheave 19 relative to the second lifting sheave 23.

[0041] The opening / closing sheave movement mechanism 25 is located in the middle of the arm body 11 in the front-rear direction and is provided on the right side panel 11B. As shown in Figure 3, the opening / closing sheave movement mechanism 25 consists of a guide rail 26, a sliding member 27, a frame member 28, and a second opening / closing sheave shaft 29, and supports the second opening / closing sheave 30 so that it can move in the front-rear direction.

[0042] The guide rail 26 is fixed to the right side panel 11B of the arm body 11. The slide member 27 is engaged with the guide rail 26 so as to be slidable in the front-rear direction. The frame member 28 is attached to the slide member 27 using bolts or the like. A rod mounting pin 28A extending in the left-right direction is attached to the frame member 28, and the rod 31B of the opening / closing cylinder 31, which will be described later, is attached to the rod mounting pin 28A. In addition, a second opening / closing sheave shaft 29 extending in the left-right direction is attached to the frame member 28 adjacent to the rod mounting pin 28A.

[0043] The second opening / closing sheave 30 is rotatably mounted on the second opening / closing sheave shaft 29. Specifically, the second opening / closing sheave 30 is provided on the outer surface of the right side plate 11B that constitutes the arm body 11, so as to be movable in the front-rear direction via the opening / closing sheave moving mechanism 25. Multiple (for example, four) second opening / closing sheaves 30 are provided in the axial direction of the second opening / closing sheave shaft 29, which is provided on the opening / closing sheave moving mechanism 25, and are rotatably supported on the arm body 11 around the second opening / closing sheave shaft 29.

[0044] The opening / closing cylinder 31 is located on the rear end 11F side of the arm body 11 and is provided on the right side panel 11B. The opening / closing cylinder 31 extends in the front-rear direction and moves the second opening / closing sheave 30 closer to and further away from the first opening / closing sheave 21. The opening / closing cylinder 31 has a tube 31A and a rod 31B whose tip protrudes from the tube 31A. The bottom side of the tube 31A is attached to the rear end 11F side of the right side panel 11B of the arm body 11 via a bracket 31C. The tip of the rod 31B is attached to the frame member 28 of the opening / closing sheave moving mechanism 25 via a rod mounting pin 28A. Therefore, the second opening / closing sheave 30 attached to the opening / closing sheave moving mechanism 25 moves in the front-rear direction in accordance with the extension and retraction operation of the opening / closing cylinder 31, and moves closer to and further away from the first opening / closing sheave 21.

[0045] The guide sheave support shaft 32 is provided on the front end 11E side of the arm body 11. One end of the guide sheave support shaft 32 is fixed to the front end 11E side of the left side panel 11A, and the other end of the guide sheave support shaft 32 protrudes to the left from the left side panel 11A. The guide sheave support shaft 32 rotatably supports the lifting guide sheave 33 and the opening / closing guide sheave 34.

[0046] The lifting guide sheave 33 and the opening / closing guide sheave 34 are provided on the left side panel 11A of the arm body 11 via the guide sheave support shaft 32. The lifting guide sheave 33 and the opening / closing guide sheave 34 have the same diameter. The lifting guide sheave 33 guides the lifting rope 38, which is wound around the first lifting sheave 19 and the second lifting sheave 23, to the clamshell bucket 9. The opening / closing guide sheave 34 guides the opening / closing rope 40, which is wound around the first opening / closing sheave 21, the second opening / closing sheave 30, and the intermediate guide sheave 37 and slack adjustment sheave 47 (described later), to the clamshell bucket 9. As a result, as shown in Figure 1, for example, while the arm 10 is held horizontally to the ground, the clamshell bucket 9 can be raised and lowered vertically using the lifting rope 38 wound around the lifting guide sheave 33.

[0047] The intermediate guide sheave shaft 35 is provided on the stepped surface 11G located on the front end 11E side of the arm body 11. A frame member 36, which is bent into a U-shape in cross-section, is fixed to the stepped surface 11G of the arm body 11. The intermediate guide sheave shaft 35 extends upward from the stepped surface 11G, with one end attached to the stepped surface 11G and the other end attached to the frame member 36.

[0048] The intermediate guide sheave 37 is rotatably mounted on the stepped surface 11G of the arm body 11 via the intermediate guide sheave shaft 35. The intermediate guide sheave 37 is interposed between the opening / closing guide sheave 34, which is provided on the left side plate 11A of the arm body 11, and the looseness adjustment sheave 47, which will be described later, provided on the right side plate 11B of the arm body 11. The opening / closing rope 40 extending from the looseness adjustment sheave 47 is wound around the intermediate guide sheave 37, guiding the opening / closing rope 40 to the opening / closing guide sheave 34.

[0049] The lifting rope 38 is provided between the arm 10 and the clamshell bucket 9, and supports the clamshell bucket 9 so that it can be raised and lowered. The lifting rope 38 is made of wire rope, and one end 38A of the lifting rope 38 is attached to a left stay 39 that protrudes from the left side plate 11A of the arm body 11. The other end 38B of the lifting rope 38 is attached to the bucket support part 9A of the clamshell bucket 9, and supports the clamshell bucket 9 (see Figure 1). The middle section of the lifting rope 38 is alternately wound around multiple first lifting sheaves 19 and multiple second lifting sheaves 23.

[0050] The opening / closing rope 40 is provided between the arm 10 and the clamshell bucket 9 and opens and closes a pair of buckets 9B of the clamshell bucket 9. The opening / closing rope 40 is made of wire rope, and one end 40A of the opening / closing rope 40 is attached to a right stay 41 that protrudes from the right side plate 11B of the arm body 11. The other end 40B of the opening / closing rope 40 is attached to the bucket support part 9A of the clamshell bucket 9 (see Figure 1). The middle section of the opening / closing rope 40 is alternately wound around multiple first opening / closing sheaves 21 and multiple second opening / closing sheaves 30. The other end 40B of the opening / closing rope 40 is alternately wound around multiple upper sheaves 9E and multiple lower sheaves 9F that make up the clamshell bucket 9.

[0051] The clamshell bucket 9 descends when the lifting cylinder 18 retracts, causing the first lifting sheave 19 to move closer to the second lifting sheave 23, and rises when the lifting cylinder 18 extends, causing the first lifting sheave 19 to move away from the second lifting sheave 23. On the other hand, the clamshell bucket 9 opens when the opening / closing cylinder 31 retracts, causing the second opening / closing sheave 30 to move closer to the first opening / closing sheave 21, and closes when the opening / closing cylinder 31 extends, causing the second opening / closing sheave 30 to move away from the first opening / closing sheave 21.

[0052] The loosening adjustment sheave moving mechanism 42 is located on the front end 11E side of the arm body 11 and is provided on the right side panel 11B. The loosening adjustment sheave moving mechanism 42 supports the loosening adjustment sheave 47 so that it can move in the front-rear direction. As shown in Figure 3, the loosening adjustment sheave moving mechanism 42 is composed of a guide rail 43, a slide member 44, a frame member 45, and a loosening adjustment sheave shaft 46.

[0053] The guide rail 43 is fixed to the right side panel 11B of the arm body 11. The slide member 44 is engaged with the guide rail 43 so as to be slidable in the front-rear direction. The frame member 45 is attached to the slide member 44 using bolts or the like. A rod mounting pin 45A extending in the left-right direction is attached to the frame member 45, and the rod 48B of the loosening adjustment cylinder 48, which will be described later, is attached to the rod mounting pin 45A. In addition, a loosening adjustment sheave shaft 46 extending in the left-right direction is attached to the frame member 45 adjacent to the rod mounting pin 45A.

[0054] The loosening adjustment sheave 47 is rotatably mounted on the loosening adjustment sheave shaft 46 of the loosening adjustment sheave moving mechanism 42. That is, the loosening adjustment sheave 47 is provided on the right side faceplate 11B of the arm body 11 so as to be movable in the front-rear direction via the loosening adjustment sheave moving mechanism 42. The loosening adjustment sheave 47 consists of a single sheave and is rotatably supported on the arm body 11 around the loosening adjustment sheave shaft 46.

[0055] The opening / closing rope 40, wound around multiple first opening / closing sheaves 21 and multiple second opening / closing sheaves 30, is sequentially wound around a slack adjustment sheave 47, an intermediate guide sheave 37, and an opening / closing guide sheave 34. The other end 40B of the opening / closing rope 40 wound around the opening / closing guide sheave 34 is wound around the upper sheave 9E and lower sheave 9F of the clamshell bucket 9, and the other end 40B of the opening / closing rope 40 is attached to the bucket support 9A.

[0056] The loosening adjustment cylinder 48 is located in front of the opening / closing sheave movement mechanism 25 and is provided on the right side panel 11B of the arm body 11. The loosening adjustment cylinder 48 extends in the front-rear direction and moves the loosening adjustment sheave 47 closer to or further away from the second opening / closing sheave 30. The loosening adjustment cylinder 48 has a tube 48A and a rod 48B whose tip protrudes from the tube 48A. The bottom side of the tube 48A is attached to the right side panel 11B of the arm body 11 via a bracket 48C. The tip of the rod 48B is attached to the frame member 45 of the loosening adjustment sheave movement mechanism 42 via a rod mounting pin 45A.

[0057] Therefore, the loosening adjustment sheave 47 attached to the loosening adjustment sheave moving mechanism 42 moves in the forward and backward directions in accordance with the extension and retraction operation of the loosening adjustment cylinder 48, moving closer to and further away from the second opening / closing sheave 30. As a result, for example, when excavating a shaft using the deep foundation drilling machine 1, when the clamshell bucket 9 lands on the ground and the opening / closing rope 40 is loosened, the loosening adjustment cylinder 48 can be extended to move the loosening adjustment sheave 47 away from the second opening / closing sheave 30, thereby removing the looseness of the opening / closing rope 40.

[0058] The buckling prevention mechanism 49 is provided between the rod 18B of the lifting cylinder 18 and the sheave mounting member 14. The buckling prevention mechanism 49 consists of a buckling prevention member 50 and a buckling prevention pin 53, and when a large load is applied in the contraction direction of the lifting cylinder 18, it restrains the rotational displacement of the lifting cylinder 18 relative to the sheave mounting member 14, thereby suppressing a decrease in the buckling load of the lifting cylinder 18 and preventing the lifting cylinder 18 from buckling.

[0059] The buckling prevention member 50 is fixed to a mounting eye 18E provided at the tip of the rod 18B of the lifting cylinder 18. The buckling prevention member 50 has a mounting base 51 attached to the mounting eye 18E and two buckling prevention plates 52 fixed to the mounting base 51. As shown in Figure 6, a pin hole 52A is formed in the buckling prevention plate 52 that penetrates in the left-right direction, and a buckling prevention pin 53 is inserted through the pin hole 52A. The pin hole 52A is formed in the shape of an elongated hole extending in the longitudinal direction of the buckling prevention plate 52, and a virtual line extending parallel to the buckling prevention plate 52 through the center of the pin hole 52A coincides with the center line OO of the lifting cylinder 18.

[0060] The buckling prevention pin 53 is integrally formed on the portion of the first lifting sheave shaft 20 that protrudes inward from the left plate 14A of the sheave mounting member 14. The buckling prevention pin 53 has two radially opposing flat surfaces 53A. These two flat surfaces 53A slidably contact the inner circumferential surface of the pin hole 52A when the buckling prevention pin 53 is inserted through the pin hole 52A of the buckling prevention plate 52.

[0061] A switch pressing plate 54 is attached to the buckling prevention pin 53. The switch pressing plate 54 is a rectangular plate extending in the front-rear direction and is fixed to the flat surface 53A of the two flat surfaces 53A of the buckling prevention pin 53 that faces the guide arm 13 in the vertical direction. The switch pressing plate 54 is positioned between the two buckling prevention plates 52 and protrudes rearward from the buckling prevention pin 53. In this way, the switch pressing plate 54 is attached to the rod 18B of the lifting cylinder 18 via the buckling prevention mechanism 49 and moves in the front-rear direction together with the sheave mounting member 14 as the lifting cylinder 18 extends and retracts. An inclined surface 54A that is tilted diagonally upward is formed on the protruding end side of the switch pressing plate 54, and this inclined surface 54A can smoothly press the rotating lever 55A of the first limit switch 55 and the rotating lever 56A of the second limit switch 56, which will be described later.

[0062] Next, the first limit switch 55 and the second limit switch 56, which serve as sensors (protrusion length sensors) for detecting the position of the first lifting sheave 19, will be described with reference to Figures 7 to 11.

[0063] The first limit switch 55 and the second limit switch 56 are arranged side by side in the front-to-back direction on the rear side (connecting member 13C side) of the guide arm 13. The first limit switch 55 has a rotating lever 55A, and the second limit switch 56 has a rotating lever 56A. While the lifting cylinder 18 is extended and the clamshell bucket 9 is raised to the stop position (upper limit position), the switch pressing plate 54 sequentially presses the rotating lever 55A of the first limit switch 55 and the rotating lever 56A of the second limit switch 56, as shown in Figures 10 and 11.

[0064] In this embodiment, a deceleration position is set to reduce the upward speed of the rising clamshell bucket 9 before it reaches the stopping position. The stopping position of the clamshell bucket 9 is the position before the rising clamshell bucket 9 interferes with the lifting guide sheave 33, the front end 11E of the arm body 11, etc.

[0065] Specifically, when the clamshell bucket 9 reaches the deceleration position, as shown in Figure 10, the switch pressing plate 54 presses the rotating lever 55A of the first limit switch 55, and the extension speed of the lifting cylinder 18 is reduced. At this time, the protrusion length of the rod 18B relative to the tube 18A of the lifting cylinder 18 is set as the first protrusion length L1 (a predetermined value). Furthermore, when the clamshell bucket 9 reaches the stop position, as shown in Figure 11, the switch pressing plate 54 presses the rotating lever 56A of the second limit switch 56, and the extension operation of the lifting cylinder 18 stops. At this time, the predetermined value of the protrusion length of the rod 18B relative to the tube 18A of the lifting cylinder 18 is set as a second protrusion length L2 (a predetermined value) which is greater than the first protrusion length L1 (L2 > L1). In this way, the position of the first lifting sheave 19, which is raised by the lifting cylinder 18, that is, the protrusion length of the rod 18B relative to the tube 18A of the lifting cylinder 18, is detected by the first limit switch 55 and the second limit switch 56.

[0066] Here, the first limit switch 55 is a normally closed (B-contact) switch with a rotating lever 55A. It remains electrically ON when the rotating lever 55A is not pressed (state in Figure 9) and remains electrically OFF when the rotating lever 55A is pressed (states in Figures 10 and 11). The second limit switch 56 is also a normally closed (B-contact) switch with a rotating lever 56A and is located behind the first limit switch 55. The second limit switch 56 remains electrically ON when the rotating lever 56A is not pressed (states in Figures 9 and 10) and remains electrically OFF when the rotating lever 56A is pressed (state in Figure 11).

[0067] A position adjustment mechanism 57 is provided between the first limit switch 55 and the second limit switch 56 and the guide arm 13 that constitutes the arm 10. The position adjustment mechanism 57 is composed of a plurality of screw seats 58 and a switch support member 59, and adjusts the mounting positions of the first limit switch 55 and the second limit switch 56 with respect to the direction of movement of the first lifting sheave 19.

[0068] Multiple screw seats 58 are fixed to the upper surface of the guide arm 13 (the surface facing the guide arm 12 in the vertical direction) by means of welding or other means. Each screw seat 58 consists of a rectangular plate extending in the left-right direction, and female screw holes are formed at both ends in the length direction, penetrating in the thickness direction. The multiple screw seats 58 are arranged continuously on the rear side of the guide arm 13, maintaining a constant distance from each other in the front-rear direction.

[0069] The switch support member 59 is detachably attached to a plurality of screw seats 58 while supporting the first limit switch 55 and the second limit switch 56. As shown in Figure 8, the switch support member 59 has a rectangular flat plate bottom plate 59A that extends in the front-rear direction and flat plate-shaped side plates 59B that rise vertically from the bottom plate 59A. The bottom plate 59A is attached to the screw seats 58, and the first limit switch 55 and the second limit switch 56 are attached to the side plates 59B using bolts or the like.

[0070] The lower plate 59A has two elongated grooves 59C that extend in the front-to-back direction while maintaining a constant distance between them in the left-to-right direction. The distance between the two elongated grooves 59C corresponds to the distance between the female screw holes provided in the screw seat 58, and the switch support member 59 is attached to the guide arm 13 by screwing a bolt 59D inserted through the elongated grooves 59C into the female screw holes of the screw seat 58. Therefore, the switch support member 59 can be adjusted significantly in the front-to-back direction within the range in which multiple screw seats 58 of the guide arm 13 are fixed, and can also be adjusted finely in the front-to-back direction within the range of the elongated grooves 59C formed in the lower plate 59A.

[0071] In this way, the position adjustment mechanism 57 adjusts the mounting positions of the first limit switch 55 and the second limit switch 56, which are attached to the side plate 59B of the switch support member 59, over a wide range with respect to the direction of movement of the first lifting sheave 19. Therefore, even if the length of the lifting rope 38 changes, the protruding length of the rod 18B of the lifting cylinder 18 (first protruding length L1 and second protruding length L2) can be appropriately changed according to the length of the lifting rope 38 by adjusting the mounting positions of the first and second limit switches 55 and 56 using the position adjustment mechanism 57.

[0072] The side plate 59B is provided with a plurality of bolt holes 59E spaced apart in the front-rear direction for mounting the first limit switch 55 and the second limit switch 56. By selecting any of these bolt holes 59E, the distance between the first limit switch 55 and the second limit switch 56 mounted on the switch support member 59 (the distance between the deceleration position and the stop position) can be appropriately changed. In this case, the rotation lever 55A of the first limit switch 55 and the rotation lever 56A of the second limit switch 56 must be spaced apart so that the switch pressing plate 54 can be pressed simultaneously.

[0073] Next, the hydraulic circuit that drives the lifting cylinder 18 and other components of the bucket lifting and opening / closing device 17 will be explained with reference to Figure 12.

[0074] The hydraulic pump 60, together with the tank 61, constitutes a hydraulic power source. A pilot pump 62 is connected to the hydraulic pump 60, and both the hydraulic pump 60 and the pilot pump 62 are driven by a prime mover. The hydraulic fluid (pressurized oil) discharged from the hydraulic pump 60 is supplied to the lifting cylinder 18, etc., through the main pipeline 63. The main pipeline 63 has a lifting pump pipeline 63A that supplies hydraulic fluid from the hydraulic pump 60 to the lifting cylinder 18, and a tank pipeline 63B that is connected to the tank 61.

[0075] The lifting / lowering control valve 64 is located between the hydraulic pump 60 and the lifting / lowering cylinder 18. The lifting / lowering control valve 64 is connected to the rod-side oil chamber 18G of the lifting / lowering cylinder 18 via the rod-side conduit 64A, and the lifting / lowering control valve 64 is connected to the bottom-side oil chamber 18H of the lifting / lowering cylinder 18 via the bottom-side conduit 64B. When the lifting / lowering control valve 64 is switched from the neutral position to the switching position (a), it supplies hydraulic fluid from the hydraulic pump 60 to the rod-side oil chamber 18G of the lifting / lowering cylinder 18 through the rod-side conduit 64A. On the other hand, when the lifting / lowering control valve 64 is switched from the neutral position to the switching position (b), it supplies hydraulic fluid from the hydraulic pump 60 to the bottom-side oil chamber 18H of the lifting / lowering cylinder 18 through the bottom-side conduit 64B.

[0076] The lifting control device 65 is located inside the cab 4 of the deep foundation excavator 1. The lifting control device 65 consists of a pressure reducing valve type pilot operating valve having a retraction-side pressure reducing valve section 65A and an extension-side pressure reducing valve section 65B, and has a pedal 65C that is operated by the operator by pressing it. When the pedal 65C of the lifting control device 65 is operated to the retraction side, pilot pressure discharged from the pilot pump 62 is supplied to the lifting switching valve 64 from the retraction-side pressure reducing valve section 65A through the retraction-side pilot pipeline 66A, etc. This switches the lifting switching valve 64 to the switching position (a), causing the lifting cylinder 18 to retract and the clamshell bucket 9 to descend. On the other hand, when the pedal 65C of the lifting control device 65 is operated to the extension side, pilot pressure is supplied to the lifting switching valve 64 from the extension-side pressure reducing valve section 65B through the extension-side pilot pipeline 66B, etc. As a result, the lifting valve 64 is switched to the switching position (b), the lifting cylinder 18 extends, and the clamshell bucket 9 rises.

[0077] The extension-side pilot conduit 66B branches into a first pilot conduit 66B1 and a second pilot conduit 66B2, which are connected in parallel. A shuttle valve 67 is provided at the junction of the first pilot conduit 66B1 and the second pilot conduit 66B2 with the extension-side pilot conduit 66B, which is connected to the lift-down control valve 64. The input side of the shuttle valve 67 is connected to the first pilot conduit 66B1 and the second pilot conduit 66B2, and the output side of the shuttle valve 67 is connected to the lift-down control valve 64 via the extension-side pilot conduit 66B.

[0078] In the first pilot conduit 66B1, a first on-off valve 68 is provided between the extension-side pressure reducing valve section 65B of the lifting operation device 65 and the shuttle valve 67. The first on-off valve 68 opens when a signal is input to the electromagnetic pilot section 68A, opening the first pilot conduit 66B1, and closes when the signal to the electromagnetic pilot section 68A is stopped, blocking the first pilot conduit 66B1. In the second pilot conduit 66B2, a second on-off valve 69 is provided between the extension-side pressure reducing valve section 65B of the lifting operation device 65 and the shuttle valve 67. The second on-off valve 69 opens when a signal is input to the electromagnetic pilot section 69A, opening the second pilot conduit 66B2, and closes when the signal to the electromagnetic pilot section 69A is stopped, blocking the second pilot conduit 66B2.

[0079] A pressure reducing valve 70 is provided between the shuttle valve 67 and the second on-off valve 69 in the second pilot pipeline 66B2. The pressure reducing valve 70 is a variable pressure reducing valve that can adjust the set pressure (degree of pressure reduction). When the second on-off valve 69 is open, the pilot pressure flowing through the second pilot pipeline 66B2 is reduced in pressure by the pressure reducing valve 70 and supplied to the lift-down switching valve 64 via the extension-side pilot pipeline 66B.

[0080] A first relay 72 is provided between the electromagnetic pilot unit 68A of the first on-off valve 68 and the battery 71. The first relay 72 is energized when the first limit switch 55 is ON, and electrically connects the battery 71 and the electromagnetic pilot unit 68A. A second relay 73 is provided between the electromagnetic pilot unit 69A of the second on-off valve 69 and the battery 71. The second relay 73 is energized when the second limit switch 56 is ON, and electrically connects the battery 71 and the electromagnetic pilot unit 69A.

[0081] As shown in Figure 9, when the switch pressing plate 54 is not pressing the rotating lever 55A of the first limit switch 55, that is, before the rising clamshell bucket 9 reaches the deceleration position, both the first limit switch 55 and the second limit switch 56 are in the ON state. In this case, the electromagnetic pilot section 68A of the first on-off valve 68 and the battery 71 are connected by the first relay 72, and the electromagnetic pilot section 69A of the second on-off valve 69 and the battery 71 are disconnected by the second relay 73. As a result, the first on-off valve 68 opens, and the pilot pressure is supplied to the lift-down switching valve 64 through the first pilot line 66B1 of the extension-side pilot line 66B and the shuttle valve 67. Therefore, the clamshell bucket 9 rises at a speed corresponding to the operation of the pedal 65C of the lift-down operating device 65.

[0082] Furthermore, as shown in Figure 10, when the switch pressing plate 54 presses only the rotating lever 55A of the first limit switch 55, that is, when the clamshell bucket 9 reaches the deceleration position, the first limit switch 55 switches to the OFF state and the second limit switch 56 remains in the ON state. In this case, the connection between the electromagnetic pilot section 68A of the first on-off valve 68 and the battery 71 is interrupted by the first relay 72, and the connection between the electromagnetic pilot section 69A of the second on-off valve 69 and the battery 71 is connected by the second relay 73. As a result, the second on-off valve 69 opens, and the pilot pressure is supplied to the lift-down switching valve 64 in a reduced state through the second pilot line 66B2 of the extension-side pilot line 66B, the pressure reducing valve 70, and the shuttle valve 67. Consequently, the extension operation of the lift-down cylinder 18 is decelerated, and the lifting speed of the clamshell bucket 9 is reduced.

[0083] Furthermore, as shown in Figure 11, when the switch pressing plate 54 presses both the rotating lever 55A of the first limit switch 55 and the rotating lever 56A of the second limit switch 56, that is, when the clamshell bucket 9 reaches the stopping position, both the first limit switch 55 and the second limit switch 56 are turned OFF. In this case, the connection between the electromagnetic pilot unit 68A of the first on-off valve 68 and the battery 71 is interrupted by the first relay 72, and the connection between the electromagnetic pilot unit 69A of the second on-off valve 69 and the battery 71 is interrupted by the second relay 73. As a result, both the first on-off valve 68 and the second on-off valve 69 are closed, and the supply of pilot pressure from the extension-side pressure reducing valve unit 65B of the lifting operation device 65 to the lifting switching valve 64 is stopped. Consequently, the lifting cylinder 18 stops, and the upward movement of the clamshell bucket 9 stops.

[0084] As described above, in this embodiment, the protrusion length sensor for detecting the protrusion length of the rod 18B of the lifting cylinder 18 is composed of a first limit switch 55 and a second limit switch 56. When the protrusion length of the rod 18B reaches a predetermined position (first protrusion length L1, second protrusion length L2) set by the first and second limit switches 55 and 56, the movement speed of the first lifting sheave 19 by the lifting cylinder 18 is limited. In this case, the movement speed of the first lifting sheave 19 is limited by a supply amount limiting device 74 that reduces the amount of hydraulic fluid supplied to the lifting cylinder 18. The supply amount limiting device 74 is composed of a shuttle valve 67, a first on-off valve 68, a second on-off valve 69, a pressure reducing valve 70, a first relay 72, a second relay 73, etc.

[0085] The deep foundation excavator 1 according to this embodiment has the configuration described above, and the operation of excavating a shaft using the deep foundation excavator 1 will be described below.

[0086] The operator, seated in the cab 4, extends the boom cylinder 7 to lift the tip of the boom 6 upward, as shown in Figure 1, for example, and extends and retracts the arm cylinder 8 to hold the arm 10 in a horizontal position relative to the ground. Next, the clamshell bucket 9 is positioned above the ground where the shaft is to be excavated, and then the lifting cylinder 18 is retracted. As a result, the sheave mounting member 14 moves forward along the guide arms 12 and 13, the first lifting sheave 19 approaches the second lifting sheave 23, and the first opening / closing sheave 21 approaches the second opening / closing sheave 30. Consequently, the lifting rope 38 and the opening / closing rope 40 are fed out from the arm 10, and the clamshell bucket 9 descends.

[0087] As the clamshell bucket 9 approaches the ground, the operator retracts the opening / closing cylinder 31. This causes the second opening / closing sheave 30, attached to the opening / closing sheave moving mechanism 25, to approach the first opening / closing sheave 21, and the opening / closing rope 40 is fed out from the arm 10, causing the pair of buckets 9B of the clamshell bucket 9 to open fully. With the clamshell bucket 9 fully open, the operator retracts the lifting cylinder 18, causing the pair of buckets 9B of the clamshell bucket 9 to sink into the ground under their own weight.

[0088] Next, before closing the clamshell bucket 9, the operator extends the slack adjustment cylinder 48, separating the slack adjustment sheave 47, which is attached to the slack adjustment sheave moving mechanism 42, from the second opening / closing sheave 30. As a result, the lifting rope 38 remains slack, while only the slack in the opening / closing rope 40 is removed. In this state, the operator extends the opening / closing cylinder 31, separating the second opening / closing sheave 30, which is attached to the opening / closing sheave moving mechanism 25, from the first opening / closing sheave 21, thereby pulling the opening / closing rope 40 towards the arm 10. This causes the clamshell bucket 9 to close while sinking into the ground under its own weight, allowing it to scoop up a large amount of soil and sand.

[0089] After closing the clamshell bucket 9 and scooping up the soil, the operator extends the lifting cylinder 18. This causes the first lifting sheave 19 attached to the sheave mounting member 14 to separate from the second lifting sheave 23, and the lifting rope 38 to be pulled up toward the arm 10. At the same time, the first opening / closing sheave 21 separates from the second opening / closing sheave 30, and the opening / closing rope 40 to be pulled up toward the arm 10. As a result, the lifting rope 38 and the opening / closing rope 40 are pulled up together toward the arm 10, and the clamshell bucket 9, holding the soil, is lifted and raised by the lifting rope 38 and the opening / closing rope 40.

[0090] After raising the clamshell bucket 9 to the outside of the shaft, the upper rotating body 3 is rotated, for example, to move the clamshell bucket 9 above the bed of a dump truck (not shown). In this state, the operator retracts the opening / closing cylinder 31, bringing the second opening / closing sheave 30, which is attached to the opening / closing sheave moving mechanism 25, closer to the first opening / closing sheave 21. As a result, the opening / closing rope 40 is pulled out from the arm 10, and the clamshell bucket 9 opens, allowing the excavated soil to be discharged onto the bed of the dump truck.

[0091] Here, the other end 40B of the opening / closing rope 40, which is wrapped around the upper sheave 9E and lower sheave 9F of the clamshell bucket 9, deteriorates due to the accumulation of excavated mud and other debris. Instead of replacing the entire opening / closing rope 40, the deteriorated portion of the rope 40 may be cut off, allowing the shortened rope 40 to be used continuously. When the opening / closing rope 40 is shortened, the lifting rope 38 also needs to be shortened by the same length. However, if the lifting cylinder 18 is fully extended with the lifting rope 38 shortened, the lifting rope 38 may become over-wound between the first lifting sheave 19 and the second lifting sheave 23, potentially causing the clamshell bucket 9 to interfere with the lifting guide sheave 33, the front end 11E of the arm body 11, etc.

[0092] In contrast, in this embodiment, the protruding length of the rod 18B when the clamshell bucket 9 reaches the deceleration position is preset as the first protruding length L1, and the protruding length of the rod 18B when the clamshell bucket 9 reaches the stopping position is preset as the second protruding length L2. The first limit switch 55 is positioned at the position corresponding to the first protruding length L1, and the second limit switch 56 is positioned at the position corresponding to the second protruding length L2. Specifically, a switch support member 59 to which the first limit switch 55 and the second limit switch 56 are attached is fixed to the screw seats 58 of the plurality of screw seats 58 that correspond to the first protruding length L1 and the second protruding length L2.

[0093] As described above, in this embodiment of the deep foundation excavator 1, when the lifting rope 38 and opening / closing rope 40 are shortened, a first limit switch 55 and a second limit switch 56 are positioned on the guide arm 13 via a position adjustment mechanism 57. As a result, when the clamshell bucket 9 that has excavated soil rises to a deceleration position near the stopping position, the switch pressing plate 54 presses the rotating lever 55A of the first limit switch 55, thereby decelerating the upward speed of the clamshell bucket 9. Then, when the decelerated clamshell bucket 9 reaches the stopping position, the switch pressing plate 54 presses the rotating lever 56A of the second limit switch 56, thereby stopping the clamshell bucket 9.

[0094] In other words, before the switch pressing plate 54 presses the rotating lever 55A of the first limit switch 55, the first limit switch 55 and the second limit switch 56, which are B-contacts, remain in the ON state. As a result, the electromagnetic pilot section 68A of the first on-off valve 68 is connected to the battery 71 by the first relay 72, and the first on-off valve 68 opens. On the other hand, the electromagnetic pilot section 69A of the second on-off valve 69 is disconnected from the battery 71 by the second relay 73, and the second on-off valve 69 closes. As a result, pilot pressure from the extension-side pressure reducing valve section 65B of the lifting operation device 65 is supplied to the lifting switching valve 64 through the first pilot line 66B1 of the extension-side pilot line 66B and the shuttle valve 67, and the clamshell bucket 9 rises at a speed corresponding to the operation of the pedal 65C of the lifting operation device 65.

[0095] Next, when the clamshell bucket 9 reaches the deceleration position and the switch pressing plate 54 presses the rotating lever 55A of the first limit switch 55, as shown in Figure 10, the first limit switch 55 turns OFF. As a result, the connection between the electromagnetic pilot section 68A of the first on-off valve 68 and the battery 71 is interrupted by the first relay 72, and the first on-off valve 68 closes. On the other hand, since the second limit switch 56 remains ON, the connection between the electromagnetic pilot section 69A of the second on-off valve 69 and the battery 71 is made by the second relay 73, and the second on-off valve 69 opens. Consequently, the pilot pressure is supplied to the lift-down switching valve 64 in a reduced state through the second pilot line 66B2 of the extension-side pilot line 66B, the pressure reducing valve 70, and the shuttle valve 67. As a result, regardless of the operation of the pedal 65C of the lifting control device 65, the amount of hydraulic fluid supplied to the lifting cylinder 18 (bottom oil chamber 18H) is limited, and the clamshell bucket 9 rises towards the stopping position at a reduced speed.

[0096] Furthermore, when the clamshell bucket 9 reaches its stopping position and the switch pressing plate 54 presses both the rotating lever 55A of the first limit switch 55 and the rotating lever 56A of the second limit switch 56, as shown in Figure 11, both the first limit switch 55 and the second limit switch 56 are turned OFF. As a result, the connection between the electromagnetic pilot unit 68A of the first on-off valve 68 and the battery 71 is interrupted by the first relay 72, and the connection between the electromagnetic pilot unit 69A of the second on-off valve 69 and the battery 71 is interrupted by the second relay 73. Consequently, both the first on-off valve 68 and the second on-off valve 69 are closed, and the supply of pilot pressure to the lift-down switching valve 64 is stopped. As a result, the extension operation of the lift-down cylinder 18 is stopped, and the clamshell bucket 9 can be stopped at the stopping position.

[0097] As described above, in this embodiment, when the switch pressing plate 54 presses the rotating lever 56A of the second limit switch 56, the supply of hydraulic fluid to the lifting cylinder 18 is stopped when it is detected that the protruding length of the rod 18B of the lifting cylinder 18 has reached a second protruding length L2 corresponding to the stopping position of the clamshell bucket 9. As a result, even when the lifting rope 38 is shortened, the extension operation of the lifting cylinder 18 prevents the lifting rope 38 from becoming over-wound between the first lifting sheave 19 and the second lifting sheave 23, and prevents the clamshell bucket 9 from interfering with the lifting guide sheave 33, the front end 11E of the arm body 11, etc.

[0098] Furthermore, the switch pressing plate 54 presses the rotating lever 55A of the first limit switch 55 in front of the second limit switch 56, allowing detection that the clamshell bucket 9 has reached a deceleration position close to the stopping position. When this state is detected by the first limit switch 55, the amount of hydraulic fluid supplied to the lifting cylinder 18 is limited, and the upward speed of the clamshell bucket 9 can be reduced before it stops at the stopping position. As a result, it is possible to prevent the excavated soil from spilling out due to the clamshell bucket 9 suddenly stopping and vibrating at the stopping position.

[0099] In this case, since the lifting rope 38 is wrapped around the first lifting sheave 19 and the second lifting sheave 23 multiple times (five times in this embodiment), the extension and retraction speed of the lifting cylinder 18 is 1 / 10 of the lifting speed of the clamshell bucket 9. Therefore, even when the upward speed of the clamshell bucket 9 is high, the clamshell bucket 9 can be stopped precisely at the stopping position. Moreover, the complicated operation of fine-tuning the amount of pressure applied to the pedal 65C of the lifting operating device 65 near the stopping position of the clamshell bucket 9 is eliminated, improving the operability of the deep foundation excavator 1.

[0100] Furthermore, the deep foundation drilling machine 1 according to this embodiment can determine whether or not the clamshell bucket 9 has reached the stopping position by detecting the protruding length of the rod 18B of the lifting cylinder 18 using the first limit switch 55 and the second limit switch 56. Therefore, it is possible to prevent the malfunction of the overwinding prevention device exemplified as a prior art device, which erroneously detects the tension of the rope suspending the weight due to friction between the weight and the lifting rope, and mistakenly determines that the hook has risen to the stopping position and collided with the weight.

[0101] Furthermore, in this embodiment, a plurality of screw seats 58 are arranged on the upper surface of the guide arm 13, and the switch support member 59 to which the first limit switch 55 and the second limit switch 56 are attached is fixed to any of the plurality of screw seats 58 using a bolt 59D. This allows the switch support member 59 to be fixed at any position according to the shortened length (amount cut of the initial lifting rope 38) when the lifting rope 38 is used in a shortened state, and the mounting positions of the first limit switch 55 and the second limit switch 56 with respect to the direction of movement of the sheave mounting member 14 can be adjusted. Moreover, by changing the mounting position of the switch support member 59 with respect to the screw seats 58 within the range of the elongated groove holes 59C provided in the lower plate 59A of the switch support member 59, the mounting positions of the first limit switch 55 and the second limit switch 56 with respect to the direction of movement of the sheave mounting member 14 can be adjusted even more precisely.

[0102] Furthermore, in this embodiment, the side plate 59B of the switch support member 59 is provided with a plurality of bolt holes 59E spaced apart in the front-rear direction, and the first limit switch 55 and the second limit switch 56 can be attached to any selected bolt hole 59E. This allows the distance between the rotating lever 55A of the first limit switch 55 and the rotating lever 56A of the second limit switch 56 to be appropriately changed. As a result, the distance from when the first limit switch 55 is turned OFF and the clamshell bucket 9 decelerates until when the second limit switch 56 is turned OFF and the clamshell bucket 9 stops can be appropriately changed.

[0103] Thus, the deep foundation drilling machine 1 according to this embodiment consists of a self-propelled vehicle body and a work device 5 provided on the vehicle body. The work device 5 includes an arm 10 rotatably mounted on the vehicle body, a sheave mounting member 14 that moves in the longitudinal direction of the arm 10 by an actuator provided on the arm 10, a first lifting sheave 19 attached to the sheave mounting member 14, a second lifting sheave 23 provided on the arm 10 spaced apart from the first lifting sheave 19, a lifting rope 38 wound around the first lifting sheave 19 and the second lifting sheave 23 with one end 38A attached to the arm 10, and a clamshell bucket 9 supported by the other end 38B of the lifting rope 38, which moves up and down relative to the arm 10 as the distance between the first lifting sheave 19 and the second lifting sheave 23 changes as the actuator moves. Furthermore, the deep foundation drilling machine 1 is equipped with a sensor that detects the position of the first lifting sheave 19, and a speed limiting device that limits the movement speed of the first lifting sheave 19 by the actuator when the position of the first lifting sheave 19 detected by the sensor reaches a predetermined position.

[0104] With this configuration, the position of the first lifting sheave 19 when the clamshell bucket 9 rises to the stopping position is set as a predetermined position, and when the first lifting sheave 19 reaches the predetermined position, the movement speed of the first lifting sheave 19 by the actuator is limited, thereby allowing the clamshell bucket 9 to be stably stopped at the stopping position.

[0105] In this embodiment, the actuator is a lifting cylinder 18 that raises and lowers the clamshell bucket 9 by changing the distance between the first lifting sheave 19 and the second lifting sheave 23 by expanding and contracting in accordance with the amount of hydraulic fluid supplied, and the speed limiting device is a supply amount limiting device 74 that limits the amount of hydraulic fluid supplied to the lifting cylinder 18. With this configuration, the position of the first lifting sheave 19 when the clamshell bucket 9 reaches the stop position is set as a predetermined position, and when the first lifting sheave 19 reaches the predetermined position, the supply amount limiting device 74 limits the amount of hydraulic fluid supplied to the lifting cylinder 18, thereby stopping the clamshell bucket 9 at the stop position.

[0106] In this embodiment, the sensor is a protrusion length sensor that detects the protrusion length of the rod 18B relative to the tube 18A of the lifting cylinder 18, and the supply amount limiting device 74 limits the amount of hydraulic fluid supplied to the lifting cylinder 18 when the protrusion length of the rod 18B detected by the protrusion length sensor reaches a predetermined value. With this configuration, by setting the protrusion length of the rod 18B when the clamshell bucket 9 rises to the stop position as a predetermined value, the supply amount limiting device 74 can limit the amount of hydraulic fluid supplied to the lifting cylinder 18 when the protrusion length of the rod 18B exceeds the predetermined value, thereby stopping the clamshell bucket 9 at the stop position.

[0107] In this embodiment, the predetermined protrusion length of the rod 18B of the lifting cylinder 18 has a first protrusion length L1 and a second protrusion length L2 which is greater than the first protrusion length L1. The supply amount limiting device 74 reduces the amount of hydraulic fluid supplied to the lifting cylinder 18 when the protrusion length of the rod 18B reaches the first protrusion length L1, and stops the supply of hydraulic fluid to the lifting cylinder 18 when the protrusion length of the rod 18B reaches the second protrusion length L2. With this configuration, when the rod 18B reaches the first protrusion length L1, the speed at which the lifting cylinder 18 extends is reduced, and then when the rod 18B reaches the second protrusion length L2, the operation of the lifting cylinder 18 can be stopped. As a result, the upward speed can be reduced before the clamshell bucket 9 stops at the stopping position, thus preventing the clamshell bucket 9 from suddenly stopping and vibrating at the stopping position.

[0108] In this embodiment, the predetermined value of the protruding length of the rod 18B can be changed according to the length of the lifting rope 38. With this configuration, for example, when a portion of the lifting rope 38 is cut and used, the predetermined value of the protruding length of the rod 18B (first protruding length L1, second protruding length L2) can be changed according to the shortened length of the lifting rope 38, thereby allowing the clamshell bucket 9 to be decelerated at the deceleration position and stopped at the stop position, regardless of the length of the lifting rope 38.

[0109] In this embodiment, the lifting cylinder 18 has one of its tubes 18A and rod 18B connected to the arm 10 via a first connecting pin 18D, and the sheave mounting member 14 is connected to the other of the tube 18A and rod 18B via a second connecting pin 18F. The rod 18B or tube 18A of the lifting cylinder 18, the sheave mounting member 14, and the second connecting pin 18F constitute a first sheave movable part that moves the first lifting sheave 19 relative to the second lifting sheave 23. The protrusion length sensor is positioned on either the arm 10 or the first sheave movable part, and detects the protrusion length of the rod 18B according to the position of the first sheave movable part relative to the arm 10. With this configuration, since the first sheave movable part moves relative to the arm 10 in accordance with the extension and retraction operation of the lifting cylinder 18, the protrusion length of the rod 18B can be detected by positioning the protrusion length sensor on either the arm 10 or the first sheave movable part.

[0110] In this embodiment, the protrusion length sensor is attached to the arm 10, and a position adjustment mechanism 57 is provided between the arm 10 and the protrusion length sensor to adjust the mounting position of the protrusion length sensor with respect to the direction of movement of the first lifting sheave 19. With this configuration, even if the length of the lifting rope 38 changes, the predetermined values ​​of the protrusion length of the rod 18B of the lifting cylinder 18 (first protrusion length L1, second protrusion length L2) can be appropriately changed according to the length of the lifting rope 38 by adjusting the mounting position of the protrusion length sensor with the position adjustment mechanism 57.

[0111] In this embodiment, the protrusion length sensor is composed of a first limit switch 55 and a second limit switch 56 arranged side by side in the longitudinal direction of the arm 10. The first limit switch 55 is operated by the first sheave movable part to detect when the rod 18B of the lifting cylinder 18 reaches a first protrusion length L1, and the second limit switch 56 is operated by the first sheave movable part to detect when the rod 18B of the lifting cylinder 18 reaches a second protrusion length L2. With this configuration, the first limit switch 55 and the second limit switch 56 can sequentially detect when the rod 18B has reached the first protrusion length L1 and the second protrusion length L2, respectively.

[0112] Next, Figure 13 shows a second embodiment of the present invention, which is characterized by using a stroke sensor 75 as a sensor for detecting the position of the first lifting sheave 19. In this embodiment, the same reference numerals are used for the same components as in the first embodiment, and their descriptions are omitted.

[0113] In the figure, the stroke sensor 75 is used in this embodiment as a sensor to detect the position of the first lifting sheave 19, replacing the first and second limit switches 55 and 56 used in the first embodiment. The stroke sensor 75 consists of, for example, a wire-type stroke sensor externally attached to the lifting cylinder 18 and is connected to the input side of the controller 76.

[0114] The stroke sensor 75 comprises a spool rotatably mounted within a casing, a rotary sensor attached to the rotation axis of the spool, and a wire rope wound around the spool (none of which are shown). The casing of the stroke sensor 75 is attached to the tube 18A of the lifting cylinder 18, and the end of the wire rope is attached to the rod 18B. The wire rope is unwound from the spool by the amount (stroke) that the rod 18B protrudes from the tube 18A, and the voltage value output from the rotary sensor changes linearly with the rotation of the spool at this time. Therefore, the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 corresponds to the protrusion length of the rod 18B, and decreases as the protrusion length of the rod 18B increases, for example.

[0115] A monitor 77 located inside the cab 4 is connected to the input side of the controller 76. A monitor operating device 78 is connected to the monitor 77, and by operating the monitor operating device 78, the first protrusion length L1 of the rod 18B corresponding to the deceleration position of the clamshell bucket 9 and the second protrusion length L2 of the rod 18B corresponding to the stopping position of the clamshell bucket 9 can be output to the controller 76 via the monitor 77 and stored in the controller 76. Therefore, when the lifting rope 38 is shortened, the first protrusion length L1 and the second protrusion length L2 of the rod 18B can be set according to the deceleration position and stopping position of the clamshell bucket 9 by operating the monitor operating device 78. Specifically, by operating the monitor operating device 78 when the clamshell bucket 9 is raised to the deceleration position and stopping position, the voltage value corresponding to the first protrusion length L1 and the voltage value corresponding to the second protrusion length L2 of the rod 18B can be stored in the controller 76, respectively.

[0116] The output side of the controller 76 is connected to the electromagnetic pilot section 68A of the first on-off valve 68 and the electromagnetic pilot section 69A of the second on-off valve 69. Based on the detection signal from the stroke sensor 75, the controller 76 determines the protruding length of the rod 18B of the lifting cylinder 18. For example, if the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 is greater than the voltage value corresponding to the first protruding length L1, the controller 76 determines that the clamshell bucket 9 has not risen to the deceleration position and outputs a signal to the electromagnetic pilot section 68A of the first on-off valve 68. As a result, only the first on-off valve 68 opens, and the pilot pressure from the extension-side pressure reducing valve section 65B of the lifting operating device 65 is supplied to the lifting switching valve 64 through the first pilot pipeline 66B1 of the extension-side pilot pipeline 66B and the shuttle valve 67. As a result, the clamshell bucket 9 rises at a speed corresponding to the operation of the pedal 65C of the lifting operating device 65.

[0117] When the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 falls below the voltage value corresponding to the first protrusion length L1, the controller 76 determines that the clamshell bucket 9 has reached the deceleration position. At this time, the controller 76 stops outputting a signal to the electromagnetic pilot unit 68A of the first on-off valve 68 and outputs a signal to the electromagnetic pilot unit 69A of the second on-off valve 69. As a result, only the second on-off valve 69 opens, and the pilot pressure is supplied to the lift-down switching valve 64 through the second pilot line 66B2 of the extension-side pilot line 66B, the pressure reducing valve 70, and the shuttle valve 67. As a result, regardless of the operation of the pedal 65C of the lift-down operating device 65, the amount of hydraulic fluid supplied to the lift-down cylinder 18 is limited, and the lifting speed of the clamshell bucket 9 can be reduced.

[0118] When the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 falls below the voltage value corresponding to the second protrusion length L2, the controller 76 determines that the clamshell bucket 9 has reached its stop position. At this time, the controller 76 stops outputting signals to the electromagnetic pilot section 68A of the first on-off valve 68 and the electromagnetic pilot section 69A of the second on-off valve 69. As a result, both the first on-off valve 68 and the second on-off valve 69 close, and the supply of pilot pressure to the lift-down switching valve 64 is stopped. Consequently, the extension operation of the lift-down cylinder 18 stops, and the clamshell bucket 9 can be stopped at the stop position.

[0119] Thus, in the second embodiment as well, the upward speed of the clamshell bucket 9 can be reduced at the deceleration position and the clamshell bucket 9 can be stably stopped at the stopping position. However, in the second embodiment, a stroke sensor 75 is used as a sensor to detect the position of the first lifting sheave 19, and the protruding length of the rod 18B of the lifting cylinder 18 is detected based on the voltage value of the detection signal output from the stroke sensor 75 to the controller 76.

[0120] In the second embodiment, when the clamshell bucket 9 is raised to the deceleration position and the stopping position, the monitor operating device 78 can be operated to store in the controller 76 the voltage value corresponding to the first protrusion length L1 and the voltage value corresponding to the second protrusion length L2 of the rod 18B, respectively. Therefore, when the lifting rope 38 is cut and used, even if the deceleration position and stopping position of the clamshell bucket 9 change according to the shortened length of the lifting rope 38, the monitor operating device 78 can easily store (update) in the controller 76 the voltage value corresponding to the new first protrusion length L1 and the voltage value corresponding to the new second protrusion length L2 of the rod 18B.

[0121] Next, Figure 14 shows a third embodiment of the present invention, which is characterized in that a stroke sensor 75 is used as a sensor for detecting the position of the first lifting sheave 19, and a proportional solenoid valve 79 is provided in the extension-side pilot pipeline 66B connecting the lifting operating device 65 and the lifting switching valve 64. In this embodiment, the same reference numerals are used for the same components as in the second embodiment, and their descriptions are omitted.

[0122] In the diagram, the proportional solenoid valve 79 is installed in the extension-side pilot pipeline 66B, which connects the extension-side pressure reducing valve section 65B of the lifting operating device 65 to the lifting / lowering switching valve 64. The electromagnetic pilot section 79A of the proportional solenoid valve 79 is connected to the output side of the controller 76. The proportional solenoid valve 79 linearly changes the valve opening in accordance with the voltage value of the signal output from the controller 76 to the electromagnetic pilot section 79A, and controls the pilot pressure supplied from the extension-side pressure reducing valve section 65B to the lifting / lowering switching valve 64.

[0123] The controller 76 determines that the clamshell bucket 9 has not risen to the deceleration position if the voltage value of the detection signal from the stroke sensor 75 is greater than the voltage value corresponding to the first protrusion length L1. As long as the voltage value of the detection signal from the stroke sensor 75 is greater than the voltage value corresponding to the first protrusion length L1, the controller 76 maintains the voltage of the signal output to the electromagnetic pilot section 79A of the proportional solenoid valve 79 at the voltage value at which the proportional solenoid valve 79 is fully open. As a result, the clamshell bucket 9 rises at a speed corresponding to the operation of the pedal 65C of the lifting operation device 65.

[0124] When the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 falls below the voltage value corresponding to the first protrusion length L1, the controller 76 determines that the clamshell bucket 9 has reached the deceleration position. At this time, the controller 76 reduces the voltage of the signal output to the electromagnetic pilot section 79A of the proportional solenoid valve 79 from the voltage value at which the proportional solenoid valve 79 is fully open, in accordance with the stroke of the lifting cylinder 18 (protrusion length of the rod 18B). As a result, the valve opening of the proportional solenoid valve 79 decreases, and the amount of hydraulic fluid supplied to the lifting cylinder 18 gradually decreases, thereby gradually reducing the lifting speed according to the raised position of the clamshell bucket 9.

[0125] When the voltage value of the detection signal output from the stroke sensor 75 to the controller 76 falls below the voltage value corresponding to the second protrusion length L2, the controller 76 determines that the clamshell bucket 9 has reached the stop position. At this time, the controller 76 reduces the voltage of the signal output to the electromagnetic pilot section 79A of the proportional solenoid valve 79 to the voltage value at which the proportional solenoid valve 79 is fully closed. As a result, the proportional solenoid valve 79 closes the extension-side pilot pipeline 66B, and the supply of pilot pressure to the lift-down switching valve 64 is stopped. As a result, the extension operation of the lift-down cylinder 18 is stopped, and the clamshell bucket 9 can be stopped at the stop position.

[0126] Thus, in the third embodiment, as in the first and second embodiments, the upward speed of the clamshell bucket 9 can be reduced at the deceleration position and the clamshell bucket 9 can be stably stopped at the stopping position. However, in the third embodiment, the deceleration of the clamshell bucket 9 at the deceleration position and the stopping at the stopping position can be controlled by a single proportional solenoid valve 79 provided in the extension-side pilot pipeline 66B. Therefore, compared to the case where the first on-off valve 68 and the second on-off valve 69 are used as in the first and second embodiments, the configuration of the hydraulic circuit can be simplified, and this can also contribute to reducing manufacturing costs.

[0127] In this embodiment, an example is shown in which a lifting cylinder 18, which is a hydraulic cylinder, is used as the actuator for moving the first lifting sheave 19. However, the present invention is not limited to this, and a ball screw mechanism driven by an electric motor or the like may also be used as the actuator.

[0128] Furthermore, in the embodiment, the tube 18A of the lifting cylinder 18 is connected to the arm body 11 constituting the arm 10 via a first connecting pin 18D, and the rod 18B is connected to the sheave mounting member 14 via a second connecting pin 18F. However, the present invention is not limited to this, and for example, the rod 18B may be connected to the arm body 11 and the tube 18A may be connected to the sheave mounting member 14.

[0129] Furthermore, the first embodiment illustrates a case in which the first and second limit switches 55 and 56, which serve as protrusion length sensors, are attached to the guide arm 13 that constitutes the arm 10. However, the present invention is not limited to this, and may also be configured to be attached to, for example, the rod 18B of the lifting cylinder 18 that constitutes the first sheave movable part, the sheave mounting member 14, the second connecting pin 18F, etc. [Explanation of symbols]

[0130] 1. Deep foundation drilling machine 2. Lower running body (vehicle body) 3. Upper rotating body (vehicle body) 5. Working equipment 9. Clamshell Bucket (Bucket) 10 Arms 14 Sheave mounting component 18. Lifting cylinder (actuator) 18A Tube 18B Rod 18D First connecting pin 18F Second connecting pin 19. First lifting sheave (first sheave) 23. Second lifting sheave (second sheave) 38 Lifting rope 38A one end 38B Other end 55. First limit switch (sensor, protrusion length sensor) 56. Second limit switch (sensor, protrusion length sensor) 57 Position adjustment mechanism 74. Supply limiting device (speed limiting device) 75 Stroke Sensor (Sensor, Protrusion Length Sensor)

Claims

1. It consists of a self-propelled vehicle body and a work device installed on the vehicle body. The aforementioned work device includes an arm that is rotatably mounted relative to the vehicle body, A sheave mounting member that moves in the longitudinal direction of the arm by an actuator provided on the arm, The first sheave attached to the sheave mounting member, A second sheave is provided on the arm, spaced apart from the first sheave, A lifting rope is wound around the first sheave and the second sheave, with one end attached to the arm, In a work machine comprising a bucket supported at the other end of the lifting rope and moving relative to the arm by a change in the distance between a first sheave and a second sheave, which are moved by the actuator, A work machine characterized by comprising a sensor for detecting the position of the first sheave, and a speed limiting device for limiting the movement speed of the first sheave by the actuator when the position of the first sheave detected by the sensor reaches a predetermined position.

2. The actuator is a lifting cylinder that raises and lowers the bucket by changing the distance between the first sheave and the second sheave by expanding and contracting in accordance with the amount of hydraulic fluid supplied. The work machine according to claim 1, characterized in that the speed limiting device is a supply amount limiting device that limits the amount of hydraulic fluid supplied to the lifting cylinder.

3. The sensor is a protrusion length sensor that detects the protrusion length of the rod relative to the tube of the lifting cylinder, The work machine according to claim 2, characterized in that the supply amount limiting device limits the amount of hydraulic fluid supplied to the lifting cylinder when the protruding length of the rod detected by the protruding length sensor reaches a predetermined value set in advance.

4. The predetermined value of the protruding length of the rod has a first protruding length and a second protruding length that is greater than the first protruding length. The work machine according to claim 3, characterized in that the supply amount limiting device reduces the amount of hydraulic fluid supplied to the lifting cylinder when the protruding length of the rod reaches the first protruding length, and stops the supply of hydraulic fluid to the lifting cylinder when the protruding length of the rod reaches the second protruding length.

5. The work machine according to claim 3, characterized in that the predetermined value of the protruding length of the rod can be changed according to the length of the lifting rope.

6. The lifting cylinder is connected to the arm via a first connecting pin, with one of the tube and the rod being connected to the arm. The sheave mounting member is connected to the other of the tube and the rod via a second connecting pin. The rod or tube of the lifting cylinder, the sheave mounting member, and the second connecting pin constitute a first sheave movable part that moves the first sheave relative to the second sheave. The work machine according to claim 4, wherein the protrusion length sensor is disposed on either the arm or the first sheave movable part, and the protrusion length of the rod is detected according to the position of the first sheave movable part relative to the arm.

7. The protruding length sensor is attached to the arm, The work machine according to claim 3, characterized in that a position adjustment mechanism is provided between the arm and the protrusion length sensor for adjusting the mounting position of the protrusion length sensor with respect to the direction of movement of the first sheave.

8. The protrusion length sensor is composed of a first limit switch and a second limit switch arranged side by side in the longitudinal direction of the arm. The first limit switch is operated by the first sheave movable part to detect when the rod of the lifting cylinder reaches the first protruding length. The working machine according to claim 6, characterized in that the second limit switch is operated by the first sheave movable part to detect when the rod of the lifting cylinder has reached the second protruding length.

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