JPH0114639Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an emergency circuit for an aerial work vehicle.

In aerial work vehicles that use hydraulic actuators to raise, extend, retract, or bend the boom, safety valves such as holding valves are installed on each hydraulic actuator, so even if the operating valve is operated in the event of a failure of the hydraulic power source, The hydraulic actuator will not operate, and if the operating valve is a solenoid valve and the electrical system fails, the hydraulic actuator will not operate and the boom in the working position will be lowered and the worker on the work platform It was not possible to lower it to the ground.

The present invention was developed in view of the above circumstances, and has an emergency circuit for aerial work vehicles that has a simple structure and can easily lower the boom naturally in the event of a failure of the hydraulic power source or electrical system. The purpose is to provide

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the working posture of a bendable and extendable aerial work vehicle, in which the base end of a lower boom 3 is pivotally supported on a turntable 2 provided on a vehicle body 1, and the lower boom 3 is raised and lowered by the expansion and contraction of a raising and lowering cylinder 4. An atsupa boom 5 is pivotally attached to the tip of the lower boom 3, and the atsupa boom 5 bends and stretches by the expansion and contraction of a bending cylinder 6.
A workbench 7 is held in balance at the tip of the Atsupah boom 5.

FIG. 2 shows the hydraulic circuit of the bending cylinder 6, and shows the main pumps 9 and 4 driven by the engine 10.
The port 3 position electromagnetic directional control valve 11 is connected by a conduit 24, and the bottom side and rod side of the electromagnetic directional control valve 11 and the bending cylinder 6 are connected to the conduit 13 and the conduit 1.
A holding valve 12 is provided in the conduit 13, and a pilot conduit 15 of the holding valve 12 is connected to the conduit 14. A shuttle valve 16 is inserted into the pilot line 15, and the shuttle valve 16 is connected by a line 17 to an emergency hand pump 18 having a variable throttle valve 26 in parallel. Conduit 13 and Conduit 1
4 are connected by a pipe 19 having a pilot check valve 20 and a check valve 21 in opposite directions, and a pipe 13 between the holding valve 12 and the electromagnetic directional control valve 11 is connected to the pilot check valve 23 by a pipe 22. connected to the reservoir 8 via
The pilot lines of the pilot check valve 20 and the pilot check valve 23 are both connected to a line 17 that connects the hand pump 18 and the shuttle valve 16.

With the above configuration, normally, that is, when the engine and electrical system are normal, the electromagnetic directional control valve 1
1, the bending cylinder 6 is extended, and when it is contracted, pressure is built up in the pilot pipe 15, the shuttle valve 16 is in the state shown in FIG. 2, the holding valve 12 is opened, and the bending cylinder 6 is contracted. do. If the engine breaks down during work and the main pump 9 stops, or if the electrical system breaks down and the electromagnetic directional control valve 11 does not operate, the aerial work vehicle should be moved so that the atsupah boom 5 is in the upper position as shown in Figure 1. Therefore, the worker on the workbench 7 cannot get down to the ground. Therefore, when the variable throttle valve 26 is closed and the hand pump 18 is operated to send pressure oil, pressure is built up in the pipe line 17, the shuttle valve 16 is switched, and pressure oil is sent to the pilot pipe line 15. When the holding valve 12 is opened, the pilot check valve 20 and the pilot check valve 23 are also opened. Then, since a compressive force is applied to the bending cylinder 6 due to the weight of the atsupah boom 5 and the like, the bending cylinder 6 contracts, and the oil on the bottom side of the bending cylinder 6 passes through the holding valve 12 and the bending cylinder 6 is compressed. The amount of oil necessary to fill the rod side is supplied from the conduit 14 to the rod side of the bending cylinder 6 through the check valve 21 and the pilot check valve 20 in the conduit 19, and the excess oil is supplied from the conduit 22 to the pilot check valve 20. 23 and returns to the reservoir 8. Therefore, the boom 5 is lowered, and the worker on the work platform 7 can descend to the ground. When the contraction of the bending/extending cylinder 6 is stopped, the variable throttle valve 26 of the hand pump 18 is opened to reduce the pressure in the pipe line 17, causing the holding valve 12 and the pilot check valve 20 to decrease.
Then, the pilot check valve 23 closes, and the contraction of the bending/extending cylinder 6 is stopped.

As described above, the present invention provides an emergency circuit for an aerial work vehicle that can naturally lower a boom located above with a small amount of effort, and the present invention has a simple structure. Effective for improving functionality.

[Brief explanation of drawings]

The drawings show an embodiment of the present invention, and FIG. 1 is a side view of a bending type aerial work vehicle, and FIG. 2 is a hydraulic circuit diagram of the bending cylinder. 6...Bending cylinder, 11...Solenoid directional control valve, 12...Holding valve, 15...Pilot line, 16...Shuttle valve, 18...Emergency hand pump, 20, 23...Pilot check valve , 21...Check valve.

Claims (1)

[Scope of utility model registration request] In a circuit in which a holding valve is provided in one pipe line connecting the directional control valve and the hydraulic cylinder, and a pilot pipe line of the holding valve is connected to the other pipe line connecting the directional control valve and the hydraulic cylinder, the holding valve Insert a shuttle valve into the pilot line of the valve, connect an emergency pump to this shuttle valve, and connect the pilot check valve and check valve in opposite directions between both lines connecting the directional control valve and hydraulic cylinder. Connected by a conduit equipped with
The pipes between the holding valve and the directional control valve are connected to the reservoir by pipes equipped with pilot check valves, and the pilot pipes of these pilot check valves are connected to the pipes connecting the emergency pump and the shuttle valve. An emergency circuit for an aerial work vehicle, characterized in that the holding valve is opened by pressure from an emergency pump.