JPH058199Y2 - - Google Patents

Description

[Detailed Description of the Invention] Industrial Application Field The present invention relates to a hydraulic circuit for a device such as a dump truck that tilts a loading platform to discharge a load.

BACKGROUND ART FIG. 3 shows a dump truck, whose loading platform (body) a is tilted rearward by extending a hoist cylinder b so that the load c on the loading platform a is discharged rearward. It's summery.

A conventional hydraulic circuit for such a dump device is shown in Fig. 4, in which the lock chamber of the hoist cylinder b is directly connected to the hoist valve d, and the bottom chamber is connected to the hoist valve through a return throttle e. It is connected to a valve d, and after dumping is completed, the loading platform a is lowered by its own weight, and the lowering speed at this time is adjusted by a return throttle e.

Problems to be Solved by the Invention In the conventional hydraulic circuit described above, when dumping a load, if the dumping operation has to be stopped midway and the platform a has to be lowered with a considerable amount of the cargo remaining on the platform a, , if only the return aperture e is used, the loading platform a
The lowering speed of the loading platform (a) increases, and the shock at the end of the lowering of the loading platform (a) is large, which not only causes discomfort to the operator but also causes significant damage to the frame and the like.

Means and Effects for Solving the Problems The present invention was developed in consideration of the above-mentioned problems, and even when the loading platform is lowered with a considerable amount of cargo remaining on the loading platform, the shock at the end of the loading platform is reduced. The purpose is to provide a working hydraulic circuit for a dump device that can reduce the flow of water to the hoist cylinder 1 side. A drain circuit 11 is branched and connected between the above-mentioned throttle 9 and the hoist valve 9 in a circuit in which a check valve 10 is inserted in parallel to allow The hoist valve 8 is held in series when the hoist cylinder 1 is retracted, and by turning on the solenoid valve 12 and setting it to the continuous position, the hoist cylinder 1 is The return oil during the contraction movement is throttled by the two throttles 9 and 13, and its descending speed is reduced.
In addition, by switching the hoist valve 8 to lower (or float) and hold while the solenoid valve 12 is in the ON state, return oil can be drained through one throttle 9 and drained through two throttles 9 and 13. It is possible to have two different draining conditions, and two different lowering speeds can be obtained.

Embodiments The basic concept and specific embodiments of the present invention will be explained based on FIGS. 1 and 2.

Figure 1 shows the basic idea of this invention.
In the figure, 1 is the hoist cylinder, 2 is its rod chamber,
3 is a bottom chamber, 4 and 5 are circuits connected to each chamber 2 and 3, and a hoist valve 8 is interposed between each of these circuits 4 and 5 and a pump 6 and a tank 7. Further, in the circuit 5 connecting the hoist valve 8 and the bottom chamber 3, a throttle 9 and a check valve 10 allowing flow in the direction of the bottom chamber 3 are arranged in parallel.

Circuit 5a between the aperture 9 and hoist valve 8
A drain circuit 11 connected to the tank 7 is branch-connected to the drain circuit 11, and a solenoid valve 12 and a throttle 13 having disconnection and connection positions are interposed in the drain circuit 11. Normally, the solenoid valve 12 is in the disconnected position due to a spring, and is brought into the open position by energizing the solenoid 14. The solenoid 14 is connected to a power source via a switch 15.

In the above configuration, when the hoist valve 8 is lowered or floated to drain the pressure oil in the bottom chamber 3 of the hoist cylinder 1 via the circuit 5, if the lowering speed of the loading platform increases and becomes dangerous, the hoist valve 8 8 and turn on the switch 15 to set the solenoid valve 12 to the next position. In this way, the oil on the bottom side of the hoist cylinder 1 is sufficiently squeezed by the throttle 13 of the drain circuit 11, thereby reducing the lowering speed of the loading platform and reducing the shock at the end of the lowering of the loading platform.

In the above configuration and operation, when the lowering speed of the loading platform exceeds a predetermined speed, the hoist valve 8 may be held and the switch 15 may be turned on automatically.

In addition, in the above operation, by switching the hoist valve 8 between lowering (or floating) and holding with the solenoid valve 12 in the ON state, the return oil is diverted to one throttle 9.
There are two drain conditions: one in which the drain is drained through the diaphragm 9 and the other in which the drain is drained through the two apertures 9 and 13.
You will get the speed of descent of the street.

FIG. 2 shows a specific embodiment of the present invention. In this embodiment, the same members as those in FIG. 1 related to the above basic idea are given the same reference numerals, and the explanation thereof will be omitted.

In the figure, 20 is a hoist operating device for operating the hoist valve 8, and this part is the same as in the conventional example.

That is, 21 is a "lower, floating" switch 21a,
A dump switch consisting of a "hold" switch 21b and an "up" switch 21c, 22 is a controller, 23
is an operation drive device operated by this controller 22, 24a, 24b, 24c are air solenoid valves, 25a, 25b are air cylinders,
26 is a lever rod, and this lever rod 26 is connected to the hoist valve 8.

The operation of the hoist valve 8 by such a known hoist operating device 20 is performed as follows.
First, the hoist valve 8 is held in a "hold" position by a spring, and when the lever 26 swings clockwise, it goes "up", and when the lever 26 swings counterclockwise, it goes "down". They have a ``floating'' relationship. Therefore, (a) When the "Hold" switch 21b is operated, each air solenoid valve 24a, 24b, 24c becomes a drain state, and each air cylinder 25a, 25
Since b is in a free state, hoist valve 8
is held by a spring.

(b) When the "upper" switch 21c is operated, the intermediate air solenoid valve 24b is switched, air is supplied to the upper chamber of the right air cylinder 25b, and the lever moves downward, causing the lever 26 to swing clockwise. The hoist valve 8 is in the "up" position.

(c) When the "Down, Float" switch 21a is operated, the left air solenoid valve 24a switches, air is supplied to the upper chamber of the left air cylinder 25a, and the lever moves downward, causing the lever 26 to swing counterclockwise. The hoist valve 8 is moved to the "down" position.

(d) When the "down, float" switch 21a is operated again, the air solenoid valve 24c on the right side switches, air is supplied to the lower chamber of the air cylinder 25b on the right side, and the lever lever 26 moves upward. Further, the hoist valve 8 becomes "floating" by swinging counterclockwise.

The following hydraulic system is combined with such a hoist operating device 20.

A descent detection switch 28 is provided at a position facing the base end of the hoist cylinder 1, and is turned on via dogs 27a and 27b when the hoist cylinder 1 is retracted over a predetermined length. In addition, the circuit 5 on the bottom chamber 3 side of the hoist cylinder 1 is connected to the circuit 5 when the pressure inside the bottom chamber 3 exceeds a predetermined pressure.
A pressure switch 29 that is turned on is interposed. And the circuits 28a and 2 of the above-mentioned switches 28 and 29
Two relay switches 30, 31 are interposed in 9a, and both relays 30, 31 operate in the same way regardless of which of the switches 28, 29 is turned on. and each relay 3
0 and 31 both have normally closed contacts 30b and 31b for the first contacts 30a and 31a, and normally open contacts 30c and 31c to be connected in place of the first contacts 30a and 31a. Closed contact 30b is located in the "lower" circuit of controller 22, and normally open contact 30c is connected to solenoid 14 of solenoid valve 12. Also, the other relay 3
The first contact 31a and the normally closed contact 31b of the controller 22 are located in the "floating" circuit of the controller 22, and the normally open contact 31c is likewise connected to the solenoid 14 of the solenoid valve 12. 33 is a cancel switch.

In the above configuration, by operating the dump switch of the hoist operating device 20, each air solenoid valve 24a, 24 is operated via the controller 22.
b, 24c are operated, and the hoist valve 8 is switched to "up", "hold", "down", or "float" via the lever 26, and the hoist cylinder 1 is controlled according to the operation. Ru. At this time, each relay 3
0 and 31 are OFF and controller 22
The ``lower'' and ``floating'' circuits between the air solenoid valve and air solenoid valve are connected.

In the control of the hoist cylinder 1, when the hoist cylinder 1 is shortened over a predetermined length and the lowering detection switch 28 is turned on via the dogs 27a and 27b, each relay 30 and 31 is also turned on.
Therefore, the normally closed contacts 30b and 31b are opened, and the normally open contacts 30c and 31c are closed instead. As a result, the "lower" and "float" circuits of the controller 22 are cut off and the hoist valve 8 becomes "hold", and the solenoid 14 of the solenoid valve 12 is energized and turned on, and the return oil of the hoist cylinder 8 is The drain circuit 11 is sufficiently throttled by the throttle 13, so that the lowering speed of the loading platform is reduced, and the shock at the end of the lowering of the loading platform is reduced.

On the other hand, when the oil pressure on the bottom side of the hoist cylinder 1 becomes abnormally high and the pressure switch 29 is turned on, each relay 30, 31 is turned on and the same operation as when the hoist cylinder 1 is shortened is performed. The platform is lowered slowly. The operation at this time is canceled by the cancel switch 33.

Effects of the invention According to the invention, by turning on the solenoid valve 12 and switching the hoist valve 8, the state of throttling for return oil can be adjusted to regulate the descending speed of an empty loading platform and to control the rated load. Since it can be selected to restrict the descending speed of the loading platform when approximately 1/2 of the load is loaded, a descending speed that matches the loading capacity of the loading platform can be obtained from the beginning, thereby preventing undesirable shocks from occurring in the hydraulic circuit or the dumping device. There is no fear. In the unlikely event that a large amount of cargo remains on the loading platform and you forget to use the throttle with a higher degree of restriction when lowering the cargo, there is a sensor that detects the lowering speed of the loading platform and the increase in pressure in the hydraulic circuit. There is no danger because it can be automatically included by the action of Furthermore, if you are aware of the impact that may occur in the hydraulic circuit due to the addition of a high-restriction throttle midway through the process, and if you wish to shorten the operating cycle, you may want to proactively reduce the restriction even if a considerable amount of cargo remains. By setting only the lower throttle from the beginning, the lowering speed can be regulated only in the latter half of the lowering operation of the loading platform.

As described above, according to the present invention, an appropriate lowering condition of the loading platform can be selected by taking into consideration the loading condition, desired working speed, maintenance of the hydraulic circuit, etc.

[Brief explanation of drawings]

Figures 1 and 2 are circuit diagrams showing the basic concept and specific embodiments of the present invention, Figure 3 is a schematic side view of a dump truck, and Figure 4 is a circuit diagram of a conventional example. . 1 is a hoist cylinder, 3 is a bottom chamber, 8 is a hoist valve, 11 is a drain circuit, 12 is a solenoid valve, and 13 is a throttle.

Claims (1)

[Scope of utility model registration request] Bottom chamber 3 of hoist cylinder 1 of dump device
In the hydraulic circuit connecting the hoist valve 8 and the hoist valve 8, a throttle 9 for regulating the lowering speed of the empty loading platform and a check valve 10 for allowing flow to the hoist cylinder 1 side are installed in parallel. a throttle 13 that is branch-connected to the drain circuit 11 and regulates the descending speed of the loading platform loaded with approximately 1/2 of the rated load on the drain circuit 11;
A solenoid valve 12 having open and closed positions is interposed in series, a hydraulic sensor 29 for automatically operating the solenoid valve 12 is disposed, and the hoist valve 8 is switched when the hydraulic sensor 29 is operated. An operating hydraulic circuit for a dump device, characterized in that the solenoid valve 12 is turned on at the same time.