JPS624199A - Safety equipment for aerial work vehicles - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a safety device for an aerial work vehicle, particularly for an aerial work vehicle equipped with a crane device.

(Prior art) Generally, aerial work vehicles have a work platform installed at the tip of the boom.
The boom is extended and contracted and raised and lowered to move the workbench to an appropriate location in the space.

In such aerial work vehicles, there is a range in which work can be done safely, a so-called safe work range, and within the safe work range set by the boom extension/contraction length and the hoisting angle, the boom can be freely extended, contracted, and raised. However, extension and lowering of the boom are restricted outside the set safe work range.

In other words, assuming that the variation in the load acting on the workbench is zero,
(For example, Japanese Unexamined Patent Application Publication No. 50-8
(See Publication No. 245).

On the other hand, in response to the diversification of aerial work vehicles, vehicles equipped with a crane device in addition to a work platform at the tip of the boom have recently been used for electrical work.

(Problems to be Solved by the Invention) If we consider the case where a range restriction device is provided to the above-mentioned aerial work vehicle equipped with a crane device, the load will vary if the object to be lifted by the crane device differs. Therefore, it is not possible to set a safe work range that corresponds to the load by simply regulating the range.

Specifically, there is no means to detect the load, so even if the boom length and luffing angle are the same, there is a risk of overturning if the load increases, and even if the load is smaller than the rated load, the rated load The disadvantage is that it is not possible to exceed the safe working range set by

The present invention has been made in view of the above points, and it sets a safe work range that differs depending on the magnitude of the load acting on the boom, and when the boom attempts to deviate from the safe work range, the operation is immediately stopped to ensure safety. The present invention provides a safety device for a vehicle for working at heights that enables work at heights to be carried out.

(Means for Solving the Problems) The present invention provides a workbench with an operating section for controlling at least the extension, contraction and elevation of the boom and the lifting and lifting of the crane device, and a rotating platform that controls at least the extension and contraction and elevation of the boom. An operating unit is provided to control the vehicle, and an overload detection device is installed to detect when the aerial work vehicle has reached a certain load state, and the boom is extended, laid down, and lifted by the crane device. Safety valves are installed in the hydraulic piping to the telescopic cylinder, the luffing cylinder, and the winch hydraulic motor, and when the overload detection device is activated, all of the safety valves are switched, regardless of the operation from the operating section. It has a configuration that stops the extension and lowering of the telescopic boom and the lifting operation of the crane device.

(Example) The structure of the present invention will be described below based on the drawings using an example.

FIG. 1 shows an overall side view of an example of an aerial work vehicle, and FIG. 2 shows its hydraulic circuit diagram.

A swivel base 2 is pivoted to the upper rear part of the vehicle body l of the aerial work vehicle so that it can rotate horizontally around a vertical axis, and a boom 3 is mounted on the swivel base z.
The base end of the boom 3 is pivoted to allow it to be raised and lowered, and the telescopic boom 4 of the boom 3 is telescopically telescopic in multiple stages at the same time. A crane device 6 and a workbench 7 are attached to the tip of the front boom 5.

The boom-related operations of the work vehicle are performed by a hydraulic drive device, and the swivel base 2 is rotated by a swivel motor (not shown), and is undulated and extended by a hoisting cylinder 8 installed between the boom 3 and the swivel base 2. The boom 4 is extended and contracted by a telescoping cylinder 9 (see Figure 2) installed therein, and the front boom 5 is extended and contracted by a rotating cylinder (not shown) installed between it and the telescoping boom 4.
The work platform 7 is extended and supported in front of the telescopic boom 4 and is folded and stored, and the work platform 7 is transformed into a storage position and a horizontal position by a storage/balance hydraulic cylinder 10 installed between it and the front boom 5 to raise and lower the boom 3. In cooperation with other balance cylinders 11 that are linked to the angle, the horizontal working posture is maintained in the boom hoisting position, and the work platform 7 is roughly swung around the vertical axis by a swing motor (not shown), and the crane device 6 is a hydraulic motor 12 (
(see Figure 2).

These hydraulic drive devices are incorporated and operated in the hydraulic circuit shown in FIG.

The hoisting cylinder 8 has a switching valve 13, 13' connected in parallel.

The telescopic cylinder 9 is piped so as to supply oil discharged from the hydraulic pump 15 by switching operation of the switching valves 14 and 14' connected in parallel to perform the hoisting and telescoping operations of the boom 3. The -1 switching valves 15' and 14' are provided in the operating section 16 on the swivel table z side, and the -1 switching valves 15' and 14' are provided in the operating section 17 on the work table 7, respectively.

A balanced hydraulic cylinder 10 connected to the workbench 7 is connected to the swivel table 2.
Piping is arranged so that the work platform 7 can be horizontally raised and retracted by operating the switching valve 18 of the side operation section 16. A balance cylinder 11 connected to the boom 3 is connected in parallel to the balance cylinder 10, and the work platform 7 can be raised and retracted. After that, the piping to these balance cylinders to and tt is closed with cocks 19 and 19, and both cylinders 10 and 11 are interlocked to maintain the horizontal posture of the workbench 7 even if the boom is raised and lowered.

Pyro check valves 20, 21 and 22 are provided in the piping leading to the piston back pressure side oil chambers of the aforementioned hydraulic cylinders 8, 9 and 10, respectively, to prevent return flow from the piston back pressure side oil pressure. However, when supplying pressurized oil to the piston rod side oil chamber, the pilot pressure switches the pressure oil and allows return flow.

On the other hand, safety valves 23 are provided in the luffing cylinder and the telescopic cylinder 8.9, respectively, which switch the supply direction of pressure oil when an overload is detected to stop operation toward the dangerous side, that is, boom lowering and boom extension. .24 is installed.

Furthermore, the winch hydraulic motor 12 is controlled by a switching valve 36 provided on the operating section 17 on the workbench 7, and a counterbalance valve 25 and a hydraulic piping between the switching valve 36 and the hydraulic motor 12 are provided. A safety valve 26 is provided.

The safety valve 26 is connected to a power unit 27 on the vehicle body side.
It is activated by pilot pressure from the winch, and is piped to stop normal rotation by the winch, that is, the lifting operation of the crane device 6.

In this way, no electrical wiring is required during the boom.

FIG. 3 shows an electric circuit for advance detection of an overload condition in the safety device of the present invention, and FIG. 5 shows a setting chart thereof.

In FIG. 3, an electric contact 29 for detecting a certain length extension state of the boom 3 is connected to the power source 28, for example, one of the boom
A limit switch that switches the contact point when the boom is extended by /6 and an electric contact 30 that detects the undulation state of the boom at a certain angle, for example, a limit switch that switches the contact point when the boom undulation angle is 15 degrees, are connected.

The circuit from these boom state detection switches 29 is equipped with a changeover switch 31 that switches to the upper contact when the boom is in the upright position and to the lower contact when the boom is in the down position, and various points of these switches are set. Pressure switch Psi with different pressures
, connected to PS2 and PS3, and also a common relay 3
2 and then ground.

The contacts 33 that are closed when the relay 32 is energized are connected to the electric motor starting solenoid 34 of the power unit 27 that controls the solenoids 34 of the safety valves 23 and 24 described above and the safety valve 26 of the winch hydraulic motor 12.
It is inserted into the circuit connecting 5.

The pressure switches Psi, PS2, and PS3 are used to determine the overturning moment, which varies depending on the boom's extension state, hoisting state, and actual load.As shown in FIG. The operating pressure is set, and depending on the size of the load and the amount of extension of the boom,
Furthermore, it is operated by pressure oil acting on the piston back pressure side oil chamber of the undulation cylinder, which varies depending on the magnitude of the undulation angle.

That is, if the boom's extension and contraction and undulation are controlled so as to obtain a constant working radius when a constant load is lifted, the pressure acting on the undulation cylinder 8 changes as shown in the characteristic curve shown in FIG. 4.

In the embodiment of the present invention, when the rated load (200 kg) is lifted, the characteristic curve becomes substantially constant at an undulation angle of about 15 degrees or more, and the pressure PL is set as the set pressure of the pressure switch PSl.

Further, when the undulation angle is 15 degrees or less, the pressure acting on the undulation cylinder 8 increases, and the pressure switch PS
If all angle ranges are restricted with 1, it will be impossible to work below 15 degrees, so in response to this, the pressure switch PS
Pressure switch PS3 with a set pressure P2 greater than l
is provided! The set pressure of the pressure switch PS3 is set to an appropriate pressure that is generated in the luffing cylinder 8 at a working radius that does not cause overturning even when the rated load is lifted at a luffing angle of 15 degrees or less.

On the other hand, the pressure switch PS2 connected to the boom tilting operation side of the changeover switch 31 is also connected to the piston rod side oil chamber of the hoisting cylinder 8, and detects the differential pressure with the piston back pressure side oil chamber. ing.

This is because the pilot pressure from the pilot check valve 20 acts extra on the piston rod side oil chamber when the boom is down, so it is not possible to obtain an accurate load support pressure unless this amount is subtracted.Therefore, the pressure switch PS
2 is designed to be connected only when the boom is laid down.

Further, the changeover switch 31, which is disposed between the boom state detection switch and the pressure switch and is switched when the boom is raised or lowered, is used to control the pilot check valve 20 interposed in the hydraulic circuit to the hoisting cylinder 8. It is possible and desirable to automatically select the contact switching by pressure or by pilot pressure to a pilot check valve 22 interposed in the hydraulic circuit of the balance cylinder 10.

Considering the operating source of the changeover switch 31, the changeover valves 13 and 13' of the hoisting cylinder 8 are located on both the swivel platform and the workbench, so they must be able to be detected at the single-car work position. Detection can be achieved by installing a detection electrical contact on the operation part of the switching valve 13, 13', but this requires wiring to the work platform 7, which poses a problem in terms of insulation, so it is not possible to raise or lower the boom as described above. The contact of the changeover switch 31 is automatically switched by using the pilot pressure applied to the pilot check valve 20 of the luffing cylinder 8 or the pilot check valve 22 of the work platform balancing cylinder 10, which sometimes causes the presence or absence of pilot pressure.

Next, the operation of this embodiment will be explained.

After the balance cylinder 10 is extended and raised from the running state shown by the solid line in FIG. 1, a rotating cylinder (not shown) is controlled to extend the front boom 5 to the tip of the telescopic boom 4.

In this case, since the boom 3 is in a substantially horizontal state and a fully retracted state, the limit switch 29 is switched to the lower contact point, and the limit switch 30 is switched to the upper contact point.

Therefore, the current from power supply 28 is applied to pressure switch PS3.
When the pressure in the hoisting cylinder 8 generated by the load acting on the aerial work vehicle reaches the set pressure, for example, if a large load greater than the rated load is lifted and the elongation is within 1/6, the pressure will increase. Switch PS3 is closed and relay 3
2 is energized.

As a result, the solenoid 34 is energized via the contact 33,
At the same time, the safety valves 23 and 24 are switched to stop the contraction operation of the luffing cylinder 8 and the extension operation of the telescopic cylinder 9, and at the same time, the power unit 27 is further activated to switch the safety valve 26 to stop the normal rotation operation of the winch hydraulic motor 12. .

That is, the extension operation and lowering operation of the boom 3 and the hoisting operation of the crane device 6 are stopped even if each switching valve is operated from the operation section 16.17.

In this case, the retraction of the boom 3, the hoisting and the crane device 6
Suspended operation of is permissible.

Also, set the boom 3 from the approximately horizontal position to the fully retracted position.
When the workbench 7 is moved to a suitable position in the space by being extended by more than 176 degrees or by being raised or lowered by more than 15 degrees, the limit switch 29 is set to the upper contact point, and the limit switch 30 is moved to the upper contact point.
are respectively switched to the lower contacts, and the pressure switch PS1 or PS2 is switched via the changeover switch 31.
Either one of them is energized.

At this time, the load is lifted by the crane device 6 and the boom 3
When raising the switch 31, the changeover switch 31 is switched to the upper contact point, and the pressure switch PS1 is turned on via the contact point.
is energized.

Therefore, the load acting on the work vehicle is the pressure switch PS
When the pressure that activates the boom 3 is reached, the further extension operation, lowering operation of the boom 3, and lifting operation of the crane device 6 are stopped in the same manner as described above.

On the other hand, when lifting a load with the crane device 6 and further lowering the boom 3, the changeover switch 31 is switched to the lower contact point by the pilot pressure of the pilot check valve 20, and the switch 31 is switched to the lower contact point via the contact point to the pressure switch PS2. Power is on.

When the load acting on the aerial work vehicle reaches a set pressure that activates the pressure switch PS2, the further extension operation and lowering operation of the boom 3 and the lifting operation of the crane device 6 are stopped. .

As described above, the boom 3 is in the extended state and in the up-and-down state.

When the varying pressure in the luffing cylinder reaches the set pressure of the pressure switch due to the winch load, one of the pressure switches Psi, PS2 . PS3 closes, which causes relay 3
Current flows through 2, closing contact 33 and energizing solenoid 34, activating safety valves 23, 24 and 26 to stop boom extension, lowering and winching.

Therefore, it is possible to work safely within these limits without the risk of falling.

FIG. 5 shows the relationship between lift height and working radius according to the present invention in comparison with FIG. 1, and the relationships are X for rated load, large load, and small load, respectively.

It becomes as shown in Y and Z.

In other words, in the present invention, a switch is installed in series with the boom condition detection limit switch to detect the pressure in the luffing cylinder that fluctuates depending on the load, and to regulate it based on the magnitude of the pressure. The radius becomes smaller, and when the load is smaller than the rated load, a larger working radius can be used, and the working radius is automatically set according to load fluctuations.

In the embodiment of the present invention, the boom is composed of a telescoping boom and a front boom, and the work platform is provided on the front boom.
A work platform may be mounted directly on the telescoping boom.

Further, although a plurality of pressure switches are used as the overload detection means, the present invention is not limited to this.

(Effects of the Invention) As described above, in the present invention, the safe work range is automatically changed depending on the load acting on the aerial work vehicle, and the work platform can be freely moved to the appropriate space only within the safe work range. It can be moved and safely perform work at heights according to the load.

[Brief explanation of drawings]

The drawings illustrate an embodiment of the present invention, and FIG. 1 is an overall side view showing an example of an aerial work vehicle, FIG. 2 is a hydraulic circuit diagram thereof, FIG. 3 is an electric circuit diagram thereof, and FIG. 5 is a pressure-up and down angle characteristic curve, and FIG. 5 is a head-working radius characteristic curve. 3...boom, 6...crane device,
7... Workbench, 8... Lifting cylinder,
16.17...Operation unit, 23,24.26...
...Safety valve, Psi, PS2, PS3...
pressure switch.

Claims (1)

[Claims] In an aerial work vehicle equipped with a work platform and a crane device at the tip of a telescoping boom, an operating section for controlling at least the extension and contraction of the boom, the raising and lowering of the boom, and the lifting and lifting of the crane device is provided on the work platform side, and a swivel platform is provided. At least an operation section for controlling the boom's extension/contraction and elevation is provided on the side, and an overload detection device is installed to detect when the aerial work vehicle reaches a certain load state. Safety valves that regulate the overturning operation and the hoisting operation of the crane device are installed in the hydraulic piping to the telescopic cylinder, the hoisting cylinder, and the winch hydraulic motor, and all of the safety valves are switched when the overload detection device is activated. 1. A safety device for an aerial work vehicle, characterized in that the boom extension, lowering and lifting operations of a crane device are stopped regardless of operations from an operating section.