JP2744568B2 - Backhoe - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure for preventing a backhoe from contacting an outer frame covering an outermost portion of a driving section with a bucket.

[0002]

2. Description of the Related Art Japanese Patent Laid-Open Publication No. Hei 2-256722 discloses an example of a structure of a backhoe that avoids contact between an outer frame covering an outermost portion of a driving unit and a bucket. In this structure, a check surface (a second set position in FIG. 3 of the above-mentioned publication) which is separated by a predetermined distance from an external frame (3 in FIG. 3 of the above-mentioned publication) which covers the outermost part of the driving unit. Is set in the space, and a position sensor for detecting the position of the bucket (8 in FIG. 3 of the above publication) of the backhoe device is provided. Then, when the bucket attempts to enter the driving section side beyond the check surface based on the detection of the position sensor, the control valve of the hydraulic cylinder for driving the backhoe device is forcibly returned to the neutral position, and the backhoe device is stopped. Means. With the above configuration, when the operator of the driving unit is operating the backhoe device, even if the bucket is erroneously brought close to the driving unit side so as to collide with the external frame, the bucket is not moved to the outside. Upon reaching the restraining surface outside the frame, the backhoe device automatically stops and contact is avoided.

[0003]

In the above-mentioned structure, as shown in FIG.
When only the arm (9 in FIG. 3 of the above-mentioned publication) is squeezed to the operation unit side while the 10) in the figure is relatively lowered and stopped, the bucket reaches the check surface and the arm stops. Will be operated. Assume that the operation is interrupted and the backhoe is left as it is for a long time in a state where the boom is relatively lowered and the arm is operated to the scraping side so that the bucket reaches the check surface. In this case, the control valve of the hydraulic cylinder for driving the boom is operated to the neutral position,
Although the boom should have stopped at that position, the boom may gradually descend due to its own weight due to hydraulic oil leaking from a control valve or the like of the hydraulic cylinder. This boom descends while drawing an arc trajectory around the support point of the swivel, so when the boom descends from the horizontal to the lower side, the bucket approaches the driving unit, and the bucket is restrained. There is a case where it gets into the driving section side beyond the surface.

[0004] Therefore, even if an attempt is made to resume the operation in a state where the bucket has entered the check surface, the operation of the boom and the arm cannot be performed due to the action of the check means. It is necessary to perform an operation such as releasing the action of the check means, and there is room for improvement in operability. The present invention relates to a backhoe in which the tread surface is set in space as described above, and when the backhoe is left for a long time, when the boom or the like descends by its own weight and the bucket enters the tread surface, the work is performed. The purpose is to make it easy to resume.

[0005]

The feature of the present invention resides in the following configuration of the above-mentioned backhoe. In other words, a setting means for setting a tread surface separated by a predetermined distance in front of the external frame covering the outermost part of the driving unit provided on the swivel base in space, and a position sensor for detecting the position of the bucket of the backhoe device. Arm restraint means for stopping the hydraulic cylinder for driving the arm in the backhoe device to prevent restraint when the bucket attempts to cross the restraint surface and enter the driving section based on the detection of the position sensor; and a position sensor. When the bucket attempts to enter the operation section side over the tread surface based on the detection of the boom, the boom drive hydraulic cylinder in the backhoe device is stopped, and the boom check means for stopping the tuck is prevented. In the range of the tread surface below the predetermined position, the position where the bucket enters the operation section side beyond the tread surface Are a boom allowable operating means for enabling operation of the boom in the direction of movement to restrain side.

[0006]

For example, as shown in FIG. 3, in a state where the boom 4 is relatively lowered and stopped, only the arm 5 is squeezed to the operation unit side, and the bucket 6 (bucket pin 6a) reaches the check surface A1. Thus, it is assumed that the arm 5 has been stopped. Then, in this state, the backhoe is left as it is for a long time, and the boom 4 is gradually lowered by its own weight due to the leakage of hydraulic oil from the control valve of the hydraulic cylinder, and the predetermined position D
It is assumed that the bucket 6 (bucket pin 6a) has entered the operation unit side beyond the tread surface A1 in the range of the tread surface A1 below the lower limit. In such a state, in the conventional structure, as described above, the operation of the boom, the arm, and the like cannot be performed due to the action of the restraint means.

On the other hand, when configured as in the present invention,
Even in the state as shown in FIG. 3, the boom operation permitting means can operate the boom 4 in the direction in which the bucket 6 (bucket pin 6) moves toward the restraint surface A1 (in a direction away from the operating unit). The bucket 6 (bucket pin 6a) that has entered the driving unit side beyond the check surface A1 is
It can be moved in the opposite direction from that position and can be moved outward from the restraining surface A1. If the bucket 6 (bucket pin 6a) can be taken out of the restraint surface A1 as described above, the operation of the boom restraint means and the arm restraint means disappears, so that the boom 4 and the arm 5 can be operated as usual. (See the state of FIG. 2). Then, in a range above the predetermined position D, as shown in FIG.
When the bucket 6 (bucket pin 6a) reaches the restraint surface A1, the action of the boom restraint means and the arm restraint means causes
The operation of the boom 4 and the arm 5 in which the bucket 6 (bucket pin 6a) attempts to enter the operation unit side beyond the restraint surface A1 is blocked as usual.

[0008]

As described above, even if the boom descends little by its own weight and the bucket crosses the tread surface and enters the driving section side, at least the boom in the direction of extending the bucket outward from the tread surface. Operation can be performed, and normal operation can be restored. This eliminates the need to perform an operation such as stopping the engine once and releasing the action of the check means as in the conventional structure, thereby improving the operability of the backhoe.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. (1) FIG. 7 shows the entire side surface of the backhoe. A swivel base 2 is supported by a traveling device 1 of a rubber crawler type, and a backhoe device 3 is provided at a front part of the swivel base 2. The backhoe device 3 includes a boom 4 that is driven to swing up and down by a hydraulic cylinder 11, an arm 5 that is driven to swing back and forth by a hydraulic cylinder 12, and a bucket 6 that is driven to be swung and swung by a hydraulic cylinder 13. It is configured.

The boom 4 in the backhoe 3 is shown in FIG.
As shown in the figure, the first boom part 4 is driven to swing up and down.
a, a second boom portion 4b swingably connected around an axis P1 at a front end of the first boom portion 4a, and a swingably connected around an axis P2 at a front end of the second boom portion 4b. It is constituted by a support bracket 4c, and the arm 5 is connected to the support bracket 4c. And the first
The link 4 is erected between the boom part 4a and the support bracket 4c to form a parallel quadruple link. The arm 5 and the bucket 6 are parallelized by swinging the second boom part 4b by the hydraulic cylinder 7. To the left and right.

As shown in FIGS. 4 and 7, in the swivel 2, a backhoe device 3 is disposed on the right side, and a driving section 15 including a driver's seat 14 and right and left operation levers 9 and 10 is disposed on the left side. Are located. A vertical partition plate 16 with a window (corresponding to an outer frame that covers the outermost portion of the driving unit 15) is provided at the left and right centers of the swivel 2 to partition the backhoe device 3 and the driving unit 15. A semicircular upper partition plate 17 (corresponding to an outer frame that covers the outermost portion of the operation unit 27) is fixed to the upper end of the partition plate 16 along the outside of the swivel 2.

(2) Next, the hydraulic circuit structure of the backhoe, the operation structure of the backhoe device 3, the swivel 2 and the like will be described. As shown in FIG. 6, the control valve 26 for the traveling device 1 on the right side of the first pump 18 and the first boom portion 4a
The control valve 21 for the hydraulic cylinder 11 of the (boom 4) and the control valve 23 for the hydraulic cylinder 13 of the bucket 6 are connected in parallel. The control valve 28 for the traveling device 1 on the left side of the second pump 19, the first boom portion 4a (boom 4)
The auxiliary control valve 25 for the hydraulic cylinder 11, the control valve 22 for the hydraulic cylinder 12 of the arm 5, and the control valve 29 for the service port (not shown) are connected in parallel. The hydraulic motor 30 of the swivel 2 with respect to the third pump 20
Control valve 24, hydraulic cylinder 7 of second boom portion 4b
And a control valve 32 for a hydraulic cylinder (not shown) for raising and lowering the dozer 31 shown in FIG. 7.

The control valves 21, 22, 23, 24, 26, 2
7, 28, 29, 32 and the auxiliary control valve 25 are of the center bypass type, and the control valve 2
6, 28, the control port 29 for the service port, and the control valve 32 for the dozer 31 are mechanically operated and neutral return type operated by operation levers (not shown). And the first
A control valve 21 and an auxiliary control valve 25 for the boom portion 4a, a control valve 22 for the arm 5, a control valve 23 for the bucket 6, a control valve 24 for the swivel 2 and a control valve 27 for the second boom portion 4b are provided. It is a hydraulically operated pilot operated neutral return type.

As shown in FIG. 5, a pilot valve 41 for generating a pilot pressure by operating the right operating lever 9 back and forth and a pilot valve 42 for generating a pilot pressure by operating the right and left are provided. Left operating lever 10
A pilot valve 43 for generating a pilot pressure by the front-rear operation and a pilot valve 44 for generating a pilot pressure by the left-right operation. The pilot pressure is supplied to each of the pilot valves 41, 42, 43, 44. A pilot pump 33 is provided. And FIG.
As shown in FIG. 6, the pilot oil passage 35 from each of the pilot valves 41 to 44 is connected to the control valve 2 for the first boom portion 4a.
1 and an auxiliary control valve 25, a control valve 22 for the arm 5, a control valve 23 for the bucket 6, and a control valve 24 for the swivel 2.

With the above structure, when the right operating lever 9 is operated back and forth, the control valve 21 and the auxiliary control valve 25 are operated by the pilot pressure from the pilot valve 41, and the first boom portion 4a is driven to swing up and down. (The auxiliary control valve 25 operates only when the first boom portion 4a is raised.) When the right operation lever 9 is operated left and right, the control valve 23 is operated by the pilot pressure from the pilot valve 42, and the bucket 6
Are driven to swing back and forth. When the left operating lever 10 is operated back and forth, the control valve 22 is operated by the pilot pressure from the pilot valve 43, the arm 5 is driven to swing back and forth, and when the left operating lever 10 is operated left and right, the pilot valve 44 is operated. Then, the control valve 24 is operated by the pilot pressure from, and the turntable 2 is driven to the right and left turning sides. As shown in FIG. 6, an operation pedal 48 is provided at a lower portion on the front side of the driving unit 15, and an electromagnetic proportional valve 46 which is operated based on a signal from a potentiometer 45 for detecting an operation position of the operation pedal 48 is provided. The pilot oil passage 34 from the electromagnetic proportional valve 46 is connected to the control valve 27 for the second boom portion 4b. As a result, the second boom portion 4b is operated to the right and left swing sides by depressing the operation pedal 48 left and right.

In the above structure, the more the right and left operation levers 9, 10 and the operation pedal 48 are operated from the neutral position, the larger the pilot pressure generated in the pilot valves 41 to 44 and the electromagnetic proportional valve 46 becomes. Have been. Thus, as the right and left operation levers 9, 10 and the operation pedal 48 are operated from the neutral position, the pilot pressure of the pilot valves 41 to 44 and the electromagnetic proportional valve 46 increases, and the control valves 21 to 24, 27 and the auxiliary The control valve 25 is operated to the large flow rate side. That is, the right and left operation levers 9,
10. The hydraulic cylinders 11 to 13, 7 and the hydraulic motor 30 are configured to operate at a higher speed as the operation pedal 48 is operated larger.

(3) Next, the front restraint surface A1, the lateral restraint surface A2, and the like set for the swivel 2 will be described. FIG.
As shown in FIG. 4, a front restraint surface A <b> 1 separated by a predetermined distance ahead of the vertical partition plate 16 and a lateral restraint surface A <b> 2 separated by a predetermined distance rightward from a side surface of the vertical partition plate 16 on the backhoe device 3 side. Are set in the control device 52 (see FIG. 5) (corresponding to setting means).

In this case, as shown in FIG. 2, the bucket pin 6a connecting the bucket 6 to the tip of the arm 5 moves the bucket 6 closest to the driving section 15 when the bucket pin 6a is on the front restraint surface A1. The vertical divider 1
The front restraint surface A1 is set so that the tip of the bucket 6 is located on a trajectory C1 separated by a predetermined distance from the track 6. FIG.
As shown in FIG. 5, the left lateral side of the bucket 6 is placed on the vertical partition plate 16 with the bucket pin 6a on the lateral restraint surface A2.
The lateral restraint surface A2 is set so as to be on a trajectory C2 separated by a predetermined distance from. Also, the front and side restraint surfaces A1,
A plane that is separated by a predetermined distance forward or to the right from A2 is set, and the space between this space and the front and side restraint surfaces A1 and A2 is defined as a front restraint area B1 and a side restraint area B2 in the control device 52. Is set. The front and side restraint surfaces A1 and A2 and the front and side restraint areas B1 and B2 as described above are set with respect to the swivel base 2. They move together.

(4) When the bucket pin 6a is operated toward the operation section 15 over the front and lateral restraint surfaces A1 and A2, the operation is prevented from being restrained. Next, the restraint will be described. I do. As shown in FIG. 7, an angle sensor 3 for detecting a vertical angle of the first boom portion 4a with respect to the swivel 2 is provided at a connection between the swivel 2 and the first boom 4a.
6 (corresponding to a position sensor), and a connecting portion between the first and second boom portions 4a and 4b is provided with an angle sensor 37 (a position sensor) for detecting a left-right angle of the second boom portion 4b with respect to the first boom portion 4a. Equivalent) is provided.
Then, at the connecting portion between the support bracket 4c and the arm 5,
An angle sensor 38 (corresponding to a position sensor) for detecting the front-rear angle of the arm 5 with respect to the second boom portion 4b is provided, and detection signals from the angle sensors 36 to 38 are input to the control device 52.

As shown in FIG. 6, the pilot oil passage 35a for operating the control valve 21 and the auxiliary control valve 25 for the first boom portion 4a on the ascending side has two positions, an unload position and an unload stop position. A control valve 39 (corresponding to a boom restraint means) urged toward the unload stop position by a spring is connected to a switching type electromagnetically operated type. The two-position switching electromagnetic operation type of the unload position and the unload stop position is applied to the pilot oil passage 35b for operating the control valve 22 for the arm 5 to the squeezing side by a spring. Is connected to the control valve 40 (corresponding to an arm restraint means).

By controlling the control valves 39, 40 to the two positions at high speed by the control device 52 to change the duty ratio, the pilot oil passages 35a, 35
5b is operated to reduce the pilot pressure (the maximum pressure is the value set by the right or left operating levers 9 and 10), regardless of the operating position of the right or left operating levers 9 and 10. The opening degree of the valve 25 on the rising side (the first boom portion 4a
(The extension speed of the hydraulic cylinder 11 for the arm 5) and the degree of opening of the control valve 22 on the squeezing side (the extension speed of the hydraulic cylinder 12 for the arm 5) can be arbitrarily changed to the closed side (the low speed side). I have. The control device 52 controls the electromagnetic proportional valve 4 of FIG.
6, the pilot pressure is reduced (the maximum pressure is the value set by the operation pedal 48), and the control valve 2 is controlled regardless of the operation position of the operation pedal 48.
7, the opening degree on the left swing side (the speed at which the second boom portion 4b operates to the left swing side) can be arbitrarily changed to the low swing side.

As shown in FIG. 1, in the control device 52, a first signal based on detection signals from the angle sensors 36 to 38 is provided.
The vertical angle of the boom portion 4a, the horizontal angle of the second boom portion 4b, the front-rear angle of the arm 5, the first boom portion 4a,
The position of the bucket pin 6a is constantly calculated from the second boom portion 4b and the length of the arm 5 (step S).
1). As a result, when the bucket pin 6a enters the front or lateral restraint areas B1 and B2 shown in FIGS. 2 and 4 (step S2), the switching operation of the control valves 39 and 40 and the opening of the electromagnetic proportional valve 46 as described above. Due to the change, the operating speed of the first boom part 4a to the ascending side, the operating speed of the arm 5 to the scraping side, and the second boom part irrespective of the operating positions of the right and left operating levers 9, 10 and the operating pedal 48. The operation speed of the left swinging side of 4b is decelerated (step S3). In this case, the bucket pin 6a is moved to the front and side restraint areas B1, B
2, that is, as the bucket pin 6a approaches the front and lateral restraint surfaces A1 and A2, the speed of the deceleration operation is increased.

As shown in FIG. 5, the pilot oil passage 35a for operating the control valve 21 and the auxiliary control valve 25 for the first boom portion 4a on the ascending side, and the control valve 22 for the arm 5 on the scraping side. In the pilot oil passage 35b, pressure sensors 49 and 50 are provided at right and left operation levers 9 and 10 relative to the control valves 39 and 40, and a detection signal of the pressure sensors 49 and 50 is input to the control device 52. ing. Thereby, based on the detection signals of the pressure sensors 49 and 50 and the detection value of the potentiometer 45 of the operation pedal 48, the direction in which the bucket pin 6a approaches the front or lateral restraint surfaces A1 and A2 in the front or lateral restraint areas B1 and B2. (Step S4), the buzzer 4 in FIG.
7 is sounded (step S5) to notify the operator of the driving unit 15 of the alarm.

Next, it is assumed that the bucket pin 6a has reached the front restraint surface A1 (step S6). In this case, even if the left operation lever 10 is operated to the squeezing side of the arm 5 or the operation pedal 48 is operated to the left swing side of the second boom portion 4b, the control valve 40 and the electromagnetic proportional valve 46 Is held at the unload position, the pilot pressure on the control valves 22 and 27 disappears, the control valves 21 and 27 return to the neutral position, and the arm 5 and the second boom portion 4b are stopped (step S).
7, S8). When the bucket pin 6a is positioned on the front restraint surface A1, the operation of the hydraulic cylinder 13 of the bucket 6 can be performed, and an operation in which the bucket pin 6a moves on the front restraint surface A1 can be performed at an extremely low speed.

As shown in FIG. 2, the first boom portion 4a
A predetermined position D at the same height as the support point 51 at which the (boom 4) is swingably connected to the swivel base 2 is set for the swivel base 2. Thereby, in a state where the bucket pin 6a has reached the front restraint surface A1, the tip of the support bracket 4c of the boom 4 (the angle sensor 3) as shown in FIG.
8 is higher than the predetermined position D (step S9), the right operating lever 9 is moved to the first boom portion 4
a, the control valve 39 is maintained at the unload position, the pilot pressure on the control valve 21 and the auxiliary control valve 25 disappears, the control valve 21 and the auxiliary control valve 25 return to the neutral position, and the first The stop operation of the boom part 4a is performed (step S10).

Conversely, the state in which the bucket pin 6a has reached the front restraint surface A1 or that the bucket pin 6a has moved beyond the front restraint surface A1
In the state of being inserted into the side, the end of the support bracket 4c of the boom 4 (the angle sensor 38) as shown in FIG.
Is located at the same position as the predetermined position D or at a position lower than the predetermined position D (step S9), even if the right operation lever 9 is operated to the rising side of the first boom portion 4a, the control valve 39
Is held at the unload stop position without being operated to the unload position, the control valve 21 and the auxiliary control valve 25 are switched to the ascending side, and the first boom portion 4a is ascended (boom operation permitting means). Equivalent).

When the bucket pin 6a is at the same position as the predetermined position D or lower than the predetermined position D and the first boom portion 4a is raised, the bucket pin 6a is moved to
As it moves diagonally forward and upward from 5,
The bucket pin 6a does not come into contact with the driving unit 15 or the like. Conversely, even if the right operation lever 9 is operated to lower the first boom portion 4a in this state, the first boom portion 4a is not operated to lower. This is because when the first boom portion 4a is lowered in this state, the bucket pin 6a moves obliquely downward and approaches the driving unit 15.

Next, it is assumed that the bucket pin 6a has reached the lateral restraint surface A2 (step S6). In this case, even if the operation pedal 48 is operated to the left swing side of the second boom portion 4b,
The electromagnetic proportional valve 46 is held at the unload position and the control valve 2
7, the control valve 27 returns to the neutral position, and the second boom portion 4b is stopped (step S11). When the bucket pin 6a is located on the lateral restraint surface A2, the operation of the hydraulic cylinder 13 of the bucket 6 can be performed, and the bucket pin 6a can be moved on the lateral restraint surface A2. When the bucket pin 6a is operated in a direction away from the front and side restraint surfaces A1 and A2 in a state where the bucket pin 6a is located in the front and side restraint areas B1 and B2, the control valve as described above is used. The deceleration operation by the 39, 40 and the electromagnetic proportional valve 46 does not act, and the first boom portion 4a and the like operate at the normal speed set by the right and left operation levers 9, 10 and the operation pedal 48.

[Alternative Embodiment] In the above-described embodiment, the predetermined position D in FIG. 2 is set to the position of the support point 51 of the first boom portion 4a. It may be set at an upper position or a slightly lower position. Further, the predetermined position D may be arbitrarily changed up and down. In the above-described embodiment, only the first boom portion 4a can be raised when the state shown in FIG. 3 is reached. However, when the state shown in FIG. In addition to the lifting operation, the arm 5 may be configured to be operated in a direction opposite to the rubbing side.

In the above-described embodiment, as shown in FIGS. 2 and 4, the front and lateral restraint surfaces A1 and A2 are set based on the position of the bucket pin 6a.
An angle sensor (not shown) is also installed at the position a, so that the front and side restraint surfaces A1, A2
May be configured to be set. In this case, FIG.
And the trajectories C1 and C2 shown in FIG. 4 are the front and side restraint surfaces of the present invention.

In the above-described embodiment, the pilot valves 41 to 44 are directly mechanically operated by operating the right and left operation levers 9 and 10, and the control valves 21 to 24 are operated by the pilot pressure from the pilot valves 41 to 44. This is a type of switching operation, and the present invention is applied to this type. However, the present invention may be applied to a backhoe of the following type. That is, the operating positions of the right and left operating levers 9, 10 and the operating pedal 48 are electrically detected by a potentiometer (not shown), and a pilot valve (not shown) of an electromagnetic proportional pressure reducing valve type is operated to operate the pilot type. Models for switching the control valves 21 to 24, 27 and the auxiliary control valve 25, and the right and left operation levers 9,
10. An operation position of the operation pedal 48 is electrically detected by a potentiometer (not shown), and a control valve (not shown) of an electromagnetic proportional pressure reducing valve type is operated based on the detected value.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a diagram showing a flow of control in front and side restraint surfaces, and in front and side restraint areas.

FIG. 2 is a side view showing a front restraint surface and a front restraint area in a state where a boom is raised.

FIG. 3 is a side view showing a front restraint surface and a front restraint area and a state in which the boom is lowered.

FIG. 4 is a plan view showing front and side restraint surfaces, front and side restraint areas, and the like.

FIG. 5 is a hydraulic circuit diagram showing right and left operation levers, a pilot valve, a pilot oil passage, and the like.

FIG. 6 shows each hydraulic cylinder, control valve,
Hydraulic circuit diagram showing pilot and pilot oil passages

FIG. 7 is an overall side view of the backhoe.

[Explanation of symbols]

 Reference Signs List 2 swivel base 3 backhoe device 4 boom 5 arm 6 bucket 11 hydraulic cylinder for driving boom 12 hydraulic cylinder for driving arm 15 operating unit 16, 17 external frame 36, 37, 38 position sensor 39 boom restraining means 40 arm restraining means A1 Checking surface D Predetermined position

 ────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-306535 (JP, A) JP-A-4-333730 (JP, A) JP-A-5-272155 (JP, A) JP-A-3-302 156037 (JP, A) JP-A-3-228929 (JP, A)

Claims (1)

(57) [Claims] An operating unit (1) provided on a swivel (2).
Setting means for setting in space a restraining surface (A1) spaced a predetermined distance forward from the outer frames (16), (17) covering the outermost surface of (5), and a bucket (6) of the backhoe device (3); Position sensor (36) for detecting the position of
(37), (38), and based on the detection of the position sensors (36), (37), (38), the bucket (6) moves over the check surface (A1) and the driving unit (15). ) Side, an arm restraint means (40) for stopping a hydraulic cylinder (12) for driving the arm (5) in the backhoe device (3) and preventing the brake thereof, and the position sensor (36), Based on the detection of (37) and (38), when the bucket (6) attempts to enter the operation section (15) side beyond the tread surface (A1), the boom (4) of the backhoe device (3) is driven. Boom restraining means (39) for stopping the hydraulic cylinder (11) for use and stopping the brake, and the restraining surface (39) below a predetermined position (D) set with respect to the swivel (2). Range of A1) Oite, the bucket (6) is operated portion beyond the restraining surface (A1) (1
5) A backhoe including boom operation permitting means for enabling the operation of the boom (4) in a direction in which the boom (4) moves from the position where it enters the side toward the restraint surface (A1).