JP5567512B2 - Deep excavator - Google Patents

Description

  The present invention relates to a deep excavator constructed by attaching a telescore to a self-propelled vehicle via a boom or the like and attaching a clamshell bucket to the tip thereof.

  For excavating vertical holes, etc., a boom is attached to a self-propelled vehicle so that it can be raised and lowered, and a telescore (which combines multiple stages of arms that can be extended and retracted by a hydraulic cylinder, etc.) that can extend downward is attached to this boom. There is known a deep excavator constructed by attaching a clamshell bucket that is opened and closed by a hydraulic cylinder to the lower end of the telescore (see, for example, Patent Document 1).

  In such a deep excavator, in order to meet a demand for excavating a deeper vertical hole, a work is performed by adding a suspension bracket for deep excavation between the telescore and the clamshell bucket. .

Japanese Patent Publication No. 03-012179

  However, when such a suspension bracket is added, when the clamshell bucket is lifted to the ground and positioned on the truck bed, and when the clamshell bucket is opened and excavated sediment is loaded on the bed, the level of the clamshell bucket and the bed Since the difference becomes small and it is difficult to secure a sufficient loading amount, it is not possible to add a very long suspension bracket. For this reason, according to the addition of the suspension bracket, an increase in the excavation depth cannot be expected so much.

  In view of the above problems, an object of the present invention is to provide a deep excavator that can achieve an increase in excavation depth and can ensure loading into a truck.

The deep excavator of the present invention is
In a deep excavator configured to attach a boom to a self-propelled vehicle so as to be able to undulate, attach a telescoreme to the boom so as to be tiltable, and attach a clamshell bucket to a lower end of the telescore,
An extension cylinder is provided between the telescoreme and the clamshell bucket to lower the clamshell bucket by extension and to raise by contraction,
A control valve that serves both as the telescopic cylinder and the bucket cylinder for opening and closing the clamshell bucket;
A first pipe line connected to one secondary port of the control valve, an open side pipe line connected to the open side chamber of the bucket cylinder, and an extension side pipe line connected to the bottom chamber of the telescopic cylinder; And connect
A second conduit connected to the other secondary port of the control valve; a closed conduit connected to the closed chamber of the bucket cylinder; and a contracted conduit connected to the rod chamber of the telescopic cylinder And connect
When the hydraulic oil is supplied to the first pipe line by the switching operation to one side of the control valve, the opening of the bucket is preceded and the telescopic cylinder is extended after the bucket is opened. An opening operation sequence valve in which operating pressure is set is provided in the extension side pipe of the telescopic cylinder,
When the hydraulic oil is supplied to the second pipe line by the switching operation to the other side of the control valve, the bucket closing operation is preceded by the contraction of the telescopic cylinder, and the bucket is closed after the bucket is closed. A closing operation sequence valve in which operating pressure is set is provided in the contraction side pipe of the expansion cylinder so as to contract the expansion cylinder,
In the contraction side conduit of the expansion cylinder between the rod chamber of the expansion cylinder and the closing operation sequence valve, the flow from the rod chamber of the expansion cylinder to the closing operation sequence valve side is prevented , A check valve is provided to return the hydraulic oil from the rod chamber only to the bottom chamber side when the telescopic cylinder is extended ,
The expansion cylinder between the bottom chamber of the expansion cylinder and the sequence valve for opening operation is prevented from flowing from the bottom chamber of the expansion cylinder to the sequence valve for opening operation; A pilot check valve that opens the hydraulic pressure between the check valve and the closing sequence valve as a pilot pressure is provided.
The contraction side pipe line between the check valve and the rod chamber of the extension cylinder and the extension side pipe line between the pilot check valve and the bottom chamber of the extension cylinder are bypass pipes. connection,
Wherein the bypass line is closed during contraction of the telescopic cylinder, Bei give a freewheeling sequence valve to open when extended refluxing the working oil of the rod chamber to the bottom chamber,
The recirculation sequence valve and the pilot check valve are respectively connected to the contraction side pipe line between the check valve and the closing operation sequence valve by a pilot pipe line .

  According to the present invention, when excavation is performed by operating the control valve to the bucket opening side, when hydraulic oil is supplied to the first pipeline, first, the sequence valve provided on the contraction side pipeline side of the telescopic cylinder The telescopic cylinder does not extend by the action, and the bucket opens. Then, after the bucket is opened, the hydraulic pressure on the primary side of the sequence valve is increased due to the increase in the hydraulic pressure of the first pipe, the sequence valve is opened, and the telescopic cylinder is extended. In this way, when the bucket is opened and the telescopic cylinder is extended, the telescore is extended to reach the bottom of the vertical hole, and then the control valve is switched to supply the hydraulic oil to the second pipe. By the sequence valve provided in the extension side pipe line of the cylinder, the bucket closing operation precedes and the telescopic cylinder contracts after the bucket is closed.

  If the bucket is lifted to the ground with the telescopic cylinder contracted in this way and discharged on the truck bed, etc., the telescopic cylinder is in a contracted state. In addition, the soil can be discharged and the loadability on the truck can be secured. That is, when excavating, the telescopic cylinder can be extended for excavation, and when excavating, the telescopic cylinder can be shortened for excavation. This restriction is relaxed and deeper excavation is possible.

The telescopic cylinder of the present invention can also be used as a hydraulic hose and a control valve as it is without increasing the hydraulic hose attached to the telescoreme of the existing deep excavator. It can be implemented at a low cost and can be provided at low cost.
Also, when the telescopic cylinder is extended, the operation of the rod chamber of the telescopic cylinder is caused by the action of a check valve provided between the rod chamber of the telescopic cylinder and the sequence valve for closing operation in the contraction side pipe of the telescopic cylinder. Since oil is recirculated to the bottom chamber of the expansion cylinder through a sequence valve provided in the bypass line, the expansion cylinder can be extended at high speed.

In addition, since the pilot check valve allows the reaction force during excavation to be received by the telescopic cylinder, the excavation force is maintained.

It is a side view which shows one Embodiment of the deep excavation machine by this invention in a excavation operation state. In the deep excavation machine of this Embodiment, it is a side view which shows the state which has loaded earth and sand on the truck. It is a block diagram which shows an example of the telescore of this Embodiment. It is a side view which shows the connection structure of the expansion-contraction cylinder and bucket of this Embodiment. It is a side view which shows the structure of the bucket of this Embodiment. It is a hydraulic circuit diagram for bucket opening and closing and telescopic cylinder expansion and contraction of the present embodiment. It is a hydraulic circuit diagram including the other example of the bucket to which this invention is applied.

  FIG. 1 and FIG. 2 are side views showing an embodiment of a deep excavator according to the present invention in an excavation state and a state in which sediment is loaded on a truck, respectively. In FIGS. 1 and 2, reference numeral 1 denotes a lower traveling body, and 3 an upper revolving body installed on the lower traveling body 1 via a revolving device 2. The upper swing body 3 is configured by mounting a hydraulic power unit 4, a cab 5, a counterweight 6, and the like on a swing frame 3a. The lower traveling body 1 and the upper turning body 2 constitute an excavator body that is a self-propelled vehicle. As shown in FIG. 1, the cab 5 can be moved back and forth, and the cab 5 is moved forward during excavation work so that an operator in the cab 5 can visually observe the excavation site in the vertical hole 7. ing.

  Reference numeral 8 denotes a boom attached to the revolving frame 2a by a boom cylinder 9 so as to be raised and lowered. Reference numeral 10 denotes a telescore, and in this example, the telescore 8 is directly attached to the boom 8, but the telescore 10 may be attached via a non-expandable arm (not shown).

  This telescoreme 10 is configured by combining an outer arm 10a, a center arm 10b, and an inner arm 10c in a telescopic manner. As shown in FIG. 2, the telescore 10 has an outer arm 10 a connected to the tip of the boom 8 by a pin 11, and both ends connected to the outer arm 10 a and the boom 8 by pins 12 and 13. The inclination angle with respect to the boom 8 can be changed by the expansion and contraction of the arm cylinder 14.

  Reference numeral 16 denotes a clamshell bucket, and reference numeral 17 denotes a telescopic cylinder additionally provided according to the present invention between the inner arm 10 c of the telescoreme 10 and the clamshell bucket 16. The telescopic cylinder 17 is attached to the inner arm 10c by a pin 19.

  FIG. 3 shows a configuration example of the telescoreme 10. The telescore 10 of this example has a built-in telescopic cylinder 20, the rod of the telescopic cylinder 20 is connected to the upper end of the outer arm 10a by a pin 21, and the upper part of the tube is connected to the center arm 10b by a pin 22. A rope 23 pulls up the inner arm 10c with respect to the center arm 10b when the telescopic cylinder 20 is contracted. One end of the pulling rope 23 is connected to the outer arm 10a by the connecting portion 24, the intermediate portion is hooked on the sheave 25 attached to the top of the center arm 10b, and the other end is connected by the connecting portion 26 provided on the top of the inner arm 10c. And install.

  A rope 28 pushes down the inner arm 10c with respect to the center arm 10b when the telescopic cylinder 20 is extended. One end of this push-down rope 28 is connected to the outer arm 10a by a connecting portion 29, the intermediate portion is hooked on a sheave 30 attached to the lower end portion of the center arm 10b, and the other end is connected to a connecting portion 31 provided on the top portion of the inner arm 10c. Connected and mounted. With this configuration, the telescope 10 expands and contracts by interlocking the ropes 23 and 28 and the sheaves 25 and 30 due to the expansion and contraction of the expansion cylinder 20. The pulling rope 23 is provided with a hydraulic hose (not shown) for flowing hydraulic oil for opening and closing the bucket 16 and expanding and contracting the telescopic cylinder 17. In the inner arm 10c, only a hydraulic hose 32 for flowing hydraulic oil for opening / closing the bucket 16 and expanding / contracting the telescopic cylinder 17 is provided.

  In addition to the telescore structure, for example, two hydraulic cylinders are combined such that the rods protrude in opposite directions, and the tubes of the two hydraulic cylinders are connected to the center arm 10b, and one of the hydraulic cylinders is connected. The telescore which has other expansion-contraction means can be used not only in FIG. 3, such as the rod connected to the outer arm 10a and the rod of the other hydraulic cylinder connected to the inner arm 10c. 2 or 4 or more.

  FIG. 4 is an enlarged side view showing the structure of a clamshell bucket (hereinafter referred to as a bucket) 16 and the telescopic cylinder 17 added according to the present invention. As shown in FIG. 4, the upper bracket 33 is connected to the telescopic cylinder 17 by a pin 33 a directed to the left and right, and the upper bracket 33 is connected to the upper end of the bucket 16 by a pin 35 a. The bucket 16 is attached to the telescopic cylinder 17 so as to be swingable back and forth and left and right by being connected by the pin 34 directed. When the telescopic cylinder 17 is contracted, the bottom of the bucket 16 is in the raised position indicated by H, and when the telescopic cylinder 17 is extended, it is in the lowered position indicated by L, and the deep excavation with the length of the telescopic cylinder 17 added. It becomes possible.

  FIG. 5 shows the structure of the bucket 16. The bucket 16 of this embodiment is provided with a bucket cylinder 36 at the center. The bucket cylinder 36 is externally fitted so that a tube 36c can be moved up and down with respect to a rod 36b having a piston 36a fixed to an intermediate portion. It has a structured. A pin hole 37 connected to the pin 35a shown in FIG. 4 is provided at the upper end of the rod 36b. The rod 36b also serves as a support for the shell 41 described later. The bucket cylinder 36 has an open side chamber (oil chamber that supplies hydraulic oil when opening the bucket) 36d and a closed side chamber (hydraulic fluid when closing the bucket) that are sealed above and below the piston 36a in the tube 36c. Oil chamber) 36e.

  The frame 40 is fixed to the lower end of the rod 36b of the bucket cylinder 36 by welding or the like. A pair of shells 41 and 41 are pivotally attached to the frame 40 by pins 42 and 42 so as to be opened and closed. 43 is a connecting arm that opens and closes the shell 41 by the vertical movement of the tube 36c. These connecting arms 43 are connected to the tube 36c by a pin 44 and the lower end is connected to the shell 41 by a pin 45.

  FIG. 6 is a hydraulic circuit diagram for expanding and contracting the telescopic cylinder 17 and opening and closing the bucket 16. In FIG. 6, 47 is a main hydraulic pump included in the hydraulic power unit 4 mounted on the swing frame 3a of the ground excavator body, and 48 is a pilot hydraulic pump. Reference numeral 50 denotes a control valve that opens and closes the bucket 16. In the present invention, the control valve 50 is also used for expansion and contraction of the telescopic cylinder 17. 51 is a pilot valve for operating this control valve 50, and has an operation pedal 51a.

  53 is a first pipe connected to one secondary side port A of the control valve 50, and 54 is a second pipe connected to the other secondary side port B. The first pipeline 53 branches into a pipeline 53A and a pipeline 53B. The pipe line 53 </ b> A is an open side pipe line connected to the open side chamber 36 d of the bucket cylinder 36. The pipe line 53B is an extension side pipe line connected to the bottom chamber 17a of the telescopic cylinder 17.

  The second pipeline 54 branches into a pipeline 54A and a pipeline 54B. The pipe line 54 </ b> A is a closed side pipe line connected to the closed side chamber 36 e of the bucket cylinder 36. Reference numeral 54B denotes a contraction side pipe line connected to the rod chamber 17b of the telescopic cylinder 17. Reference numerals 56 and 57 denote relief valves for setting the maximum hydraulic pressures of the first pipeline 53 and the second pipeline 54, respectively.

  58A is a sequence valve for opening operation provided in the extension side pipe line 53B of the telescopic cylinder 17, and 59A is a check valve provided in parallel with the sequence valve 58A. The sequence valve 58A switches the control valve 50 to the left position so that hydraulic fluid is supplied to the open side chamber 36d of the bucket cylinder 36 of the bucket 16 and the bottom chamber 17a of the telescopic cylinder 17 via the first conduit 53. When supplied simultaneously, the bucket 16 is opened first.

  58B is a closing operation sequence valve provided in the contraction side pipe 54B of the expansion / contraction cylinder 17, and 59B is a check valve provided in parallel with the sequence valve 58B. The sequence valve 58B operates the switching operation of the control valve 50 to the right position so that hydraulic oil is supplied to the closing side chamber 36e of the bucket cylinder 36 of the bucket 16 and the rod chamber 17b of the telescopic cylinder 17 via the second conduit 54. When supplied simultaneously, the closing of the bucket 16 is preceded.

  Reference numeral 60 denotes a bypass pipe connecting the bottom chamber 17a of the expansion cylinder 17 and the rod chamber 17b, and 58C denotes a sequence valve provided in the bypass pipe 60. When the expansion cylinder 17 is extended, the rod chamber 17b is actuated. This is for returning the oil to the bottom chamber 17a. 59C is a check valve provided in parallel with the sequence valve 58C. A check valve 62 is provided between the rod chamber 17b of the expansion cylinder 17 and the sequence valve 58B. When the expansion cylinder 17 is extended, the hydraulic oil from the rod chamber 17b is recirculated only to the bottom chamber 17a side. Is for.

  61 is a pilot line of the sequence valve 58C, and this pilot line 61 is located between the sequence valve 58B and the check valve 62 in the contraction side pipe 54B of the expansion cylinder 17 and between the pilot chamber of the sequence valve 58C. Connect. This pilot line 61 secures the hydraulic pressure applied to the rod chamber 17b by increasing the operating pressure of the recirculation sequence valve 58C when the telescopic cylinder 17 is contracted, and reliably contracts the telescopic cylinder 17. Provided for.

  A pilot check valve 65 is provided between the sequence valve 58 </ b> A and the bottom chamber 17 a of the expansion cylinder 17 in the expansion side pipe 53 </ b> B of the expansion cylinder 17. Reference numeral 66 denotes a pilot pipe line of the pilot check valve 65. The pilot pipe line 66 uses the hydraulic pressure between the sequence valve 58B and the check valve 62 provided in the contraction side pipe 54B of the expansion cylinder 17 as a pilot pressure. In addition to the pilot chamber of the pilot check valve 65, the flow of hydraulic oil in the reverse direction in the pilot check valve 65 is allowed when there is hydraulic pressure in the pilot line.

  When excavating with this deep excavator, the control valve 50 is switched to the left position by operating the pilot valve 51 shown in FIG. As a result, the hydraulic oil discharged from the main hydraulic pump 47 is supplied to the first pipeline 53, and is first supplied to the open side chamber 36d of the bucket cylinder 36 via the pipeline 53A. 41 and 41 rotate upward as indicated by a two-dot chain line around the pins 42 and 42, and the bucket 16 opens.

  Here, since the operation pressure is set so that the sequence valve 58A is not opened at the hydraulic pressure required when the bucket is opened, the sequence valve 58A is not opened and the telescopic cylinder 17 is not expanded. When the bucket 16 is opened to the maximum opening, the sequence valve 58A is opened due to the increase in the hydraulic pressure of the first pipe 53, and the telescopic cylinder 17 is extended. For this reason, when excavating the deep part of the vertical hole 7 shown in FIG. 1, first, the telescopic cylinder 17 extends with the bucket 16 opened. In this manner, the telescore 10 is extended with the telescopic cylinder 17 extended, thereby pressing the bucket 16 against the bottom of the vertical hole 7.

  When the telescopic cylinder 17 is extended, the hydraulic oil in the rod chamber 17b of the hydraulic cylinder 17 is returned to the bottom chamber 17a through the sequence valve 58C by the action of the check valve 62, so that the telescopic cylinder 17 is extended at high speed. be able to.

  Next, when the operator in the cab 5 operates the pilot valve 51 to switch the control valve 50 to the right position, the hydraulic oil discharged from the main hydraulic pump 47 is supplied to the second conduit 54. Here, in normal excavation, the operating pressure of the sequence valve 58B is set so as not to open at the hydraulic pressure required when closing the bucket 16, so the sequence valve 58B is not opened, and the telescopic cylinder 17 is Does not shrink. For this reason, from the bucket open state where the tube 36c of the bucket cylinder 36 is raised, the tube 36c is lowered, the shells 41 and 41 are rotated downward about the pins 42 and 42, the bucket 16 is closed and excavation is performed. .

  When the bucket 16 is closed, the sequence valve 58B is opened due to the increase in the hydraulic pressure of the second pipe 54, and accordingly, the pilot check valve 65 is also opened. At the same time, the pilot chamber of the sequence valve 58C enters the pilot chamber 66 from the pilot pipe 66. The pilot pressure is applied, the operating pressure of the sequence valve 58C increases, the flow of hydraulic oil through the sequence valve 58C is blocked, the hydraulic oil is introduced into the rod chamber 17b, and the hydraulic oil in the bottom chamber 17a passes through the pilot check valve 65. The expansion cylinder 17 contracts out.

  Thus, when the earth and sand are accommodated in the bucket 16 and the telescopic cylinder 17 is in a contracted state, the control valve 50 is returned to the neutral position, the telescore 10 is contracted, and the track as shown in FIG. By positioning the bucket 16 on the load bed 63 and switching the control valve 50 to the left position again, the bucket 16 can be opened while the telescopic cylinder 17 is closed, and the earth and sand in the bucket 16 can be loaded on the load bed 63.

  As described above, in this embodiment, the bucket 16 is attached to the lower end of the telescore 10 via the telescopic cylinder 17, and the telescopic cylinder 17 can be extended during excavation. On the other hand, excavation is possible, and the earth can be discharged without the bucket 16 being held by the loading platform 63 or the earth and sand 64 on the loading platform 63 because the expansion and contraction cylinder 17 can be removed in a short time during the soil removal. That is, as compared with the conventional suspension bracket, the restriction on the bucket height in the soil removal is relaxed, and excavation can be performed at a deeper location.

  Moreover, since the hydraulic lines 53 and 54 for operating the telescopic cylinder 17 and the control valve 50 are also used for the bucket 16, the hydraulic pressure attached to the telescore 10 of the existing deep excavator. Since the hose and the control valve 50 can also be used as they are, they can be implemented by a slight modification of an existing deep excavator and can be provided at low cost.

  When excavating with the bucket 16 closed as described above, the hydraulic pressure applied to the rod chamber 17b of the telescopic cylinder 17 is increased when the hydraulic pressure of the second pipe 54 rises due to reasons such as rocks being included in the excavation target. By the rise, the telescopic cylinder 17 contracts and slightly rises from the object to be excavated, and the bucket 16 is switched to the closing direction again due to the decrease in the hydraulic pressure of the second pipeline 54. By such an operation, excavation can be performed while avoiding excessive excavation resistance, so that efficient excavation can be performed.

  In this embodiment, the sequence valve 58B provided in the contraction side conduit 54B of the expansion cylinder 17 between the sequence valve 58A in the extension side conduit 53B of the expansion cylinder 17 and the bottom chamber 17a of the expansion cylinder 17 is provided. Since the pilot check valve 65 that opens the hydraulic pressure between the cylinder chamber 17 and the rod chamber 17b of the expansion cylinder 17 as a pilot pressure is provided, the reaction force at the time of excavation can be received by the expansion cylinder 17 and the excavation force can be secured. it can.

  FIG. 7 shows another example of a bucket to which the hydraulic circuit of FIG. 6 is applied. The basic configuration of the hydraulic circuit of FIG. 7 is the same as that of FIG. A bucket 16 </ b> A shown in FIG. 7 has a pin hole 37 for connecting the telescopic cylinder 17 to the upper end of the center rod 38 by the pin 34. Further, the frame 40 is fixed to the lower end of the rod 38, and the shells 41 and 41 are pivotally attached to the frame 40 around the pins 42 and 42. The bucket cylinder 36 that opens and closes the shell 41 has one end connected to the rod 38 by a pin 44 and the other end connected to the shell 41 by a pin 45.

  The bucket 16 </ b> A is closed as shown by a solid line by extension of the bucket cylinder 36, and is opened as shown by a two-dot chain line by contraction of the bucket cylinder 36. In the hydraulic circuit of FIG. 7 as well, the operating pressure of the sequence valve 58A is set so that the opening of the bucket 16A precedes the extension of the telescopic cylinder 17. Further, the operating pressure of the sequence valve 58B is set so that the closing of the bucket 16A precedes the contraction of the telescopic cylinder 17. Even when the bucket 16A is configured in this manner, the same operational effects as described above can be exhibited.

  Although the present invention has been described above by the embodiments, the present invention is not limited to the above-described embodiments, and various modifications and additions can be made without departing from the gist of the present invention.

DESCRIPTION OF SYMBOLS 1: Lower traveling body, 2: Turning apparatus, 3: Upper turning body, 3a: Turning frame, 4: Hydraulic power unit, 5: Cab, 6: Counterweight, 7: Vertical hole, 8: Boom, 9: Boom cylinder, 10 : Telescore: 10a: outer arm, 10b: center arm, 10c: inner arm, 14: arm cylinder, 16, 16A: clamshell bucket, 17: telescopic cylinder, 20: telescopic cylinder, 23: lifting rope, 25: sheave, 28: Push-down rope, 30: Sheave, 32: Hydraulic hose, 36: Bucket cylinder, 36a: Piston, 36b: Rod, 36c: Tube, 36d: Open side chamber, 36e: Closed side chamber, 40: Frame, 41: Shell, 43 : Connection arm, 47: Main hydraulic pump, 48: Pilot hydraulic pump, 50: Control 51: Pilot valve, 53: First pipe, 53A: Open side pipe, 53B: Extension side pipe, 54: Second pipe, 54A: Close side pipe, 54B: Contraction side pipe Road, 58A-58C: Sequence valve, 59A-59C: Check valve, 60: Bypass pipe, 61: Pilot pipe, 62: Check valve, 63: Truck bed, 64: Sediment, 65: Pilot check valve , 66: Pilot pipeline

Claims (1)

In a deep excavator configured to attach a boom to a self-propelled vehicle so as to be able to undulate, attach a telescoreme to the boom so as to be tiltable, and attach a clamshell bucket to a lower end of the telescore,
An extension cylinder is provided between the telescoreme and the clamshell bucket to lower the clamshell bucket by extension and to raise by contraction,
A control valve that serves both as the telescopic cylinder and the bucket cylinder for opening and closing the clamshell bucket;
A first pipe line connected to one secondary port of the control valve, an open side pipe line connected to the open side chamber of the bucket cylinder, and an extension side pipe line connected to the bottom chamber of the telescopic cylinder; And connect
A second conduit connected to the other secondary port of the control valve; a closed conduit connected to the closed chamber of the bucket cylinder; and a contracted conduit connected to the rod chamber of the telescopic cylinder And connect
When the hydraulic oil is supplied to the first pipe line by the switching operation to one side of the control valve, the opening of the bucket is preceded and the telescopic cylinder is extended after the bucket is opened. An opening operation sequence valve in which operating pressure is set is provided in the extension side pipe of the telescopic cylinder,
When the hydraulic oil is supplied to the second pipe line by the switching operation to the other side of the control valve, the bucket closing operation is preceded by the contraction of the telescopic cylinder, and the bucket is closed after the bucket is closed. A closing operation sequence valve in which operating pressure is set is provided in the contraction side pipe of the expansion cylinder so as to contract the expansion cylinder,
In the contraction side conduit of the expansion cylinder between the rod chamber of the expansion cylinder and the closing operation sequence valve, the flow from the rod chamber of the expansion cylinder to the closing operation sequence valve side is prevented , A check valve is provided to return the hydraulic oil from the rod chamber only to the bottom chamber side when the telescopic cylinder is extended ,
The expansion cylinder between the bottom chamber of the expansion cylinder and the sequence valve for opening operation is prevented from flowing from the bottom chamber of the expansion cylinder to the sequence valve for opening operation; A pilot check valve that opens the hydraulic pressure between the check valve and the closing sequence valve as a pilot pressure is provided.
The contraction side pipe line between the check valve and the rod chamber of the extension cylinder and the extension side pipe line between the pilot check valve and the bottom chamber of the extension cylinder are bypass pipes. connection,
Wherein the bypass line is closed during contraction of the telescopic cylinder, Bei give a freewheeling sequence valve to open when extended refluxing the working oil of the rod chamber to the bottom chamber,
The deep excavation, wherein the reflux sequence valve and the pilot check valve are connected to the contraction side pipe line between the check valve and the closing operation sequence valve by a pilot pipe line, respectively. Machine.

Images