JPH0418567B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a safety device for safely lowering a cargo box in a dump vehicle.

[Prior Art] Generally, in a dump vehicle, a rear end of a cargo box is tiltably supported at a rear end of a vehicle frame, and a hydraulic actuator is connected between the vehicle frame and the cargo box. When the dump lever in the driver's cab is pulled up, the hydraulic pump is activated.
Pressure oil is supplied to the hydraulic actuator to extend the piston rod and tilt the cargo box. Conversely, when the dump lever is pushed down, the oil in the hydraulic actuator is returned to the oil tank, and the cargo box is placed on the vehicle frame by its own weight.

If the remote cable connecting the dump lever and the hydraulic unit is accidentally pulled when performing maintenance, inspection, or servicing of various parts with the cargo box tilted,
There is a danger that the cargo box will fall.

In the dump vehicle disclosed in Japanese Utility Model Publication No. 58-43527, in order to prevent the above-mentioned accidents, a telescoping rod is connected between the vehicle frame and the cargo box, and when the telescoping rod is extended, the latch is released. A mechanism locks the telescoping rod into position. However, since the above-mentioned device supports the load of the cargo box by engaging the telescopic rod and the latch, the device becomes large and
The cost of manufacturing and assembling parts increases.

[Problems to be Solved by the Invention] In view of the above-mentioned problems, it is an object of the present invention to have a simple structure, to be able to be attached to any vehicle, and to provide a system that prevents accidental damage to the hydraulic pressure during maintenance of the vehicle body by tilting the cargo box. To provide a safety device for a dump vehicle that prevents a cargo box from being lowered even if a remote cable for actuating an actuator is pulled.

[Means for Solving the Problems] In order to achieve the above object, the present invention has a structure in which a normally closed electromagnetic on-off valve is inserted and connected to a pipe connecting a hydraulic actuator for tilting a cargo box and a hydraulic pump. An up/down switch is installed inside the cab that is closed when the dump lever is operated from the neutral position, and a manually operable lowering safety switch that is opened by spring force when the dump lever is in the neutral or lowered position is installed outside the cab. A vertical switch and a downward safety switch are inserted and connected in series to the energizing circuit of a normally closed electromagnetic on-off valve.

[Operation] When the dump lever inside the cab is pulled up from the neutral position, the upper switch closes, the normally closed electromagnetic on-off valve inserted and connected to the pipe connecting the hydraulic actuator and the hydraulic pump opens, and the cargo box is tilted by the hydraulic actuator. It will be done. When the dump lever is returned to the neutral position, the normally closed electromagnetic on-off valve closes and the cargo box stops at that position.

When lowering a cargo box, not only do you simply pull down the dump lever and close the lower switch, but also operate the lowering safety switch located in a position where you can monitor the underside of the cargo box (such as on the outside wall of the cab). Otherwise, the normally closed electromagnetic on-off valve will not open and the hydraulic actuator will not operate.

[Embodiment of the Invention] As shown in FIG. 1, in a dump vehicle, the rear end of a cargo box 18 is rotatably supported by a support shaft 39 at the rear end of a vehicle frame 22. The hydraulic actuator 14 connected between the two is extended to tilt the cargo box 18.

According to the present invention, the lowering safety switch 12 is disposed at a position where the lower side of the cargo box 18 can be monitored when the cargo box 18 is lowered (in the illustrated example, on the right side wall of the cab 31).

As shown in FIG. 3, the lowering safety switch 12 is housed inside a housing 34 fixed to the cab 31.
An operating rod 15 that can be operated from the outside of the cab 31
The contact piece 5c of the switch 5 is elastically supported at the inner end of the operating rod 15 via a spring 32.
The operating rod 15 is projected outward from the cab 31 by a spring 28 interposed between the piston 15a connected to the operating rod 15 and the end of the housing 34. Chamber 3 partitioned by piston 15a
3 is normally open to the atmosphere, but the solenoid switching valve 6
Pressurized air can be supplied through the

A plunger 8 that is attracted by the electromagnetic coil 7 is supported on the peripheral wall of the housing 34 .
The force of the spring 36 makes it possible to engage the groove 25 provided in the operating rod 15. A pair of terminals 5a and 5b are disposed at the inner end of the housing 34 via an insulating material, and can be electrically connected by the contact piece 5c described above.

As shown in FIG. 2, the hydraulic actuator 14
Inside the cylinder, chambers 26 and 26a are partitioned by a piston to which a piston rod 24 is connected, and the upper chamber 26a is connected to an oil tank 21. The lower chamber 26 is connected to a port 29a of the hydraulic unit 16 via a normally closed electromagnetic on-off valve 9, and to a discharge port of the hydraulic pump 13 via a check valve 23.

The hydraulic unit 16 is connected to ports 20, 29, 29a by a spool 10 fitted into a housing 17.
The hydraulic pump 13 is provided with a neutral position closed type directional switching valve that switches the connection state of the hydraulic pump 13. Spool 1
In the illustrated neutral position at 0, the ball 19 is biased into engagement by the spring into the recess of the spool 10. When the spool 10 is pulled to the left, the ball of the switch 3 is pushed out and the circuit is closed, and when the spool 10 is pushed to the right, the ball of the switch 4 falls into the above-mentioned recess and opens the circuit.

One end of a lever 37 is connected to the spool 10 by a pin 35. The lever 37 has an intermediate portion attached to the support shaft 3.
8 on the vehicle frame side, and the other end is connected via a remote cable 30 to an arm of a dump lever 11 disposed inside a cab 31. Dump lever 1
1 is rotatably supported in the vehicle compartment by a support shaft 27,
When the dump lever 11 is pulled up from the neutral position shown by the solid line, the upper switch 1 closes and the cargo box 18 tilts.
Conversely, when the dump lever 11 is pushed down, the lower switch 2 is closed and the cargo box 18 can be lowered.

As shown in Fig. 4, each switch 1, 2, 3,
4 and 5 are connected to a power battery 40. In the figure, 6 is an electromagnetic switching valve, 9 is a normally closed electromagnetic on-off valve, 7 is an electromagnetic coil, and 41 is a start switch.

Next, the operation of the device of the present invention will be explained. Normally, even if the start switch 41 is closed, the cargo box 18
is locked in the lowered position shown. That is, when the dump lever 11 is in the position shown by the solid line in FIG. 2, the ball 19 is engaged with the recess of the spool 10. Therefore, as shown in FIG. 4, switches 1, 2, and 3 are open. Since the switch 4 is closed, the electromagnetic coil 7 is energized and the plunger 8 is pulled out of the groove 25 of the operating rod 15. The operating rod 15 is pushed back to the right by the spring 28, and the switch 5 is open. Since the switch 5 is open, the electromagnetic on-off valve 9 is demagnetized and closed, the hydraulic circuit of the hydraulic actuator 14 is locked, and the cargo box 18 is held in the lowered position.

When the cargo box 18 is to be tilted, the start switch 41 is closed, the dump lever 11 is pulled up, and the upper switch 1 is closed. In FIG. 2, the spool 10 is pulled to the left, the switch 3 is closed, and the electromagnetic switching valve 6 is energized to connect the chamber 33 to the air pressure source, supplying pressurized air to the chamber 33 of the lowering safety switch 12. Ru. In FIG. 3, the operating rod 15 is pushed to the left, the switch 5 is closed, and the electromagnetic on-off valve 9 is energized and opened.

As shown in FIG. 5, by moving the spool 10 to the left, the port 20 connected to the oil tank 21 and the port 29 connected to the hydraulic pump 13 are cut off.
Therefore, the oil in the oil tank 21 is supplied by the hydraulic pump 13 to the lower chamber 26 of the hydraulic actuator 14 via the port 29, the check valve 23, and the electromagnetic on-off valve 9, and the piston rod 24 tilts the cargo box 18.

When the cargo box 18 reaches the required inclination, the dump lever 11 is returned to the neutral position and the spool 10 is returned to the neutral position shown in FIG. 2, and the upper switch 1 opens.
The electromagnetic on-off valve 9 is demagnetized and closed, the hydraulic actuator 14 is stopped at that position, and the cargo box 18 is maintained in an inclined state. Accidentally disconnect remote cable 30
Even if the user pulls , the electromagnetic on-off valve 9 is closed, so the cargo box 18 will not fall unexpectedly.

At the same time, the switch 3 is opened, the electromagnetic switching valve 6 is demagnetized, and the chamber 33 is opened to the atmosphere. Operation rod 1
5 is pushed to the right by the spring 28, and the switch 5 opens.

Next, when lowering the cargo box 18, the lower switch 2 is closed by pushing down the dump lever 11 from the neutral position shown in FIG. When the spool 10 is pushed to the right, the port 29a is connected to the electromagnetic on-off valve 9.
is connected to a port 20 connected to an oil tank 21.

At the same time, the switch 4 opens due to leftward movement of the spool 10, the electromagnetic coil 7 is demagnetized, and the spring 36 is demagnetized.
The plunger 8 is pushed by this force and hits the operating rod 15 of the lowering safety switch 12.

When the operating rod 15 of the lowering safety switch 12 in the outer wall of the cab 31 is depressed, the plunger 8, biased by the spring 36, engages the groove 25 in the operating rod 15 and maintains the switch 5 in the closed position.

When the switch 5 closes, the electromagnetic on-off valve 9 is energized and opens. The piston rod 24 is pushed down by the weight of the cargo box 18, and the oil in the lower chamber 26 of the hydraulic actuator 14 flows into the electromagnetic on-off valve 9 and the port 29.
a, 20 and then returned to the oil tank 21.

The driver can ensure safety by pressing the operating rod 15 of the lowering safety switch 12 while checking whether there is a worker under the cargo box 18.

In the above-described embodiment, the upper switch 1 and the lower switch 2 are separately configured as upper and lower switches operated by the dump lever, but a single changeover switch may be used.

Furthermore, instead of driving the operating rod when the cargo box is tilted using air pressure in the above-described embodiment, electromagnetic force may be used.

[Effects of the Invention] As described above, the present invention opens a normally closed electromagnetic on-off valve inserted and connected to the high pressure circuit of a hydraulic actuator by manual operation of a lowering safety switch disposed on the outer wall of the cab. The lowering safety switch is small, easy to install in any vehicle, and inexpensive to manufacture.

By operating the lowering safety switch while checking the underside of the cargo box, worker safety can be ensured when lowering the cargo box.

Even if a worker enters the underside of the cargo box while the cargo box is tilted and accidentally gets caught in the remote cable, the hydraulic circuit of the hydraulic actuator will not switch, allowing inspection work to be carried out safely.

[Brief explanation of drawings]

FIG. 1 is a side view showing an outline of a dump vehicle according to the present invention, FIG. 2 is a side sectional view of a hydraulic unit that drives a hydraulic actuator, and FIG. 3 is a side view of a lowering safety switch that lowers a cargo box. Fourth
This figure is the same electric circuit diagram, and FIG. 5 is a side sectional view showing the operating state of the hydraulic unit when the cargo box is tilted. 1: Upper switch, 2: Lower switch, 3-5: Switch, 6: Solenoid switching valve, 7: Solenoid coil, 8:
Plunger, 9: Normally closed electromagnetic on-off valve, 11: Dump lever, 12: Lowering safety switch, 13: Hydraulic pump, 14: Hydraulic actuator, 18: Loading box, 31: Cab.

Claims (1)

[Claims] 1 Insert and connect a normally closed electromagnetic on-off valve into the pipe connecting the hydraulic actuator that tilts the cargo box and the hydraulic pump,
Inside the cab is a vertical switch that is closed when the dump lever is operated from the neutral position, and outside the cab is a manually operable lowering safety switch that is opened by spring force when the dump lever is in the neutral and lowered positions. A safety device for a dump vehicle, characterized in that an up/down switch and a down safety switch are inserted and connected in series to the energizing circuit of a normally closed electromagnetic on-off valve.