JPH0322486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a floating automatic cutoff device for a front loader, which operates a control valve for raising and lowering the boom to a floating state when a work implement is lifted with a load exceeding a predetermined load. The floating circuit is cut off to prevent sudden falls.

In a front loader equipped with a working tool such as a bucket at the tip of the boom, a control valve for raising and lowering the boom is provided with a floating function so that leveling work and the like can be performed in a floating state.
However, this type of control valve can be operated arbitrarily at any time, so for example, when a bucket full of earth and sand is being transported by raising the boom high,
If the control valve were mistakenly switched to the floating state, there was a risk that the bucket would suddenly fall to the wrong side and cause an accident.

The present invention has been provided for the purpose of solving these conventional problems, and is characterized by a front loader in which a control valve for raising and lowering the boom has a floating function. In the control device, there is a position detector that detects that the work implement at the tip of the boom is in the raised position, a load detector that detects that the load on the work implement is above a predetermined value, and the detection of these detectors. The main feature is that it is equipped with a shutoff valve that sometimes shuts off the floating circuit.

Hereinafter, the present invention will be described in detail with reference to the illustrated embodiment. FIG. 1 shows a bucket type front loader for a tractor device, where 1 is a tractor, 2 is a mounting frame, and 3 is a pair of left and right booms, which are attached to the mounting frame 2. It is pivoted so that it can be raised and lowered, and can be raised and lowered by a pair of left and right boom cylinders 4. 5 is Bucket,
It is pivotally supported at the tip of the boom 3 and can be rotated by a pair of left and right bucket cylinders 6. 7 is a three-point link mechanism, and 8 is a hydraulic device for raising and lowering the working machine attached via the three-point link mechanism 7.

Figure 2 shows the hydraulic circuit, 9 is a hydraulic pump,
Driven by an engine. Reference numeral 10 designates a control valve for the boom cylinder 4, which can be switched to neutral, ascending, and descending positions using an operating lever 11, and has a floating portion 10a, and when operated to this floating portion 10a, the boom cylinder 4
Both cylinder chambers are in communication with each other. 1
Reference numeral 2 denotes a control valve for the bucket cylinder 6, which can be operated by an operating lever 13, and these control valves 10,
12 is connected in series between the hydraulic pump 9 and the hydraulic device 8. Note that the hydraulic device 8 is, of course, connected to a dedicated control valve. 14 and 15 are check valves, and 16 is a relief valve. Reference numeral 17 denotes an electromagnetic shutoff valve, which is interposed between the control valve 10 and the boom cylinder 4 so as to shut off the floating circuit. 18 is a load detector, which is composed of a pressure switch and is connected to a hydraulic pump 9 and a control valve 10.
It is connected between the bucket belt 5 and detects whether a load of a predetermined value or more is acting on the bucket 5 based on a change in the pressure on the discharge side of the hydraulic pump 9.

FIG. 3 shows a control circuit for the cutoff valve 17, which is driven by a valve drive circuit 19. The valve drive circuit 19 includes a position detector 20 for detecting the rise of the bucket 5, the aforementioned load detector 18, and the control valve 1.
Signals from the detectors 21 that detect states other than floating at 0 are inputted to the detectors 18 and 2, respectively.
When 0 operates, the shutoff valve 17 is energized and shut off,
Further, when the detector 21 is activated, the shutoff valve 17 is demagnetized and released. The position detector 20 is attached to the pivot portion of the boom 3 and is configured to detect the rise of the bucket cart 5 through the vertical movement of the boom 3.

In the above configuration, when the control valve 10 is in a state other than floating, the detector 21 interlocked with the control valve 10 operates and the cutoff valve 17 is in the released state. Therefore, by switching the control valves 10 and 12, the boom cylinder 4 and the bucket cylinder 6 can be freely expanded and contracted, allowing normal work to be carried out and also allowing use in a floating state.

When the boom cylinder 4 is extended after the bucket 5 is filled with earth and sand, etc., if the load on the bucket 5 is greater than a predetermined value, the load detector 18 is activated by the discharge pressure of the hydraulic pump 9. When the bucket 5 rises to a certain height, the position detector 20 operates via the boom 3. For this reason, the valve drive circuit 19 operates, and the cutoff valve 17 is energized to cut off the connection between the control valve 10 and the boom cylinder 4. Therefore, even if the control valve 10 is switched to the floating part 10a side by mistake, the flow The testing circuit remains cut off. Therefore, it is possible to prevent the boom 4 from descending and the bucket cart 5 to suddenly fall, improving safety, and eliminating the need to pay special attention during operation, resulting in good operability. Moreover, if the bucket cart 5 is suddenly stopped in the middle of falling, excessive stress will be applied to the vehicle body, front axle, etc. of the tractor 1, but such a problem can be prevented.

The working tool may be a fork or the like other than the bucket 5. The raised position does not necessarily have to be the upper limit of the working tool, and can be set at an intermediate position for safety reasons.

According to the present invention, when the work tool rises to the raised position with a load greater than a predetermined value being applied, the floating valve is used to shut off floating, so that the work tool does not fall suddenly due to incorrect operation of the control valve. This improves safety and operability.

4 to 8 disclose a control device other than the one according to the present invention, in which FIG. 4 shows a solenoid valve type hydraulic circuit, 22 is a solenoid valve for controlling the boom cylinder 4, 23 are solenoid valves for controlling the bucket cylinder 6, which are connected in series with the solenoid valve 22 at the front stage and the solenoid valve 2 at the rear stage. Solenoid valve 2
2 is a rising solenoid 24 and a descending solenoid 2
5, and the solenoid valve 23 has a dump solenoid 2.
6 and a rollback solenoid 27.
A pressure detector 28 is connected to a hydraulic circuit between the solenoid valve 22 and the hydraulic pump 9. The pressure detector 28 generates an output when the circuit pressure rises to a cracking pressure that is slightly lower than the relief pressure of the relief valve 16. Reference numeral 29 denotes an operation detector for the hydraulic system 8, which is composed of a pressure switch. Note that this operation detector 29 may be constituted by a limit switch that is interlocked with a hydraulic control lever that controls the hydraulic device 8.

FIG. 5 shows a control circuit, 30 is an operation switch for raising the boom, 31 is an operation switch for lowering the boom, 32 is an operation switch for bucket dumping,
Reference numeral 33 denotes an operation switch for the bucket trawler, which can be selectively operated for the boom or the bucket in conjunction with, for example, one operation lever. 34 and 35 are OR circuits, 36 to 38 are
NAND circuit, 39 is an RS flip-flop circuit consisting of NAND circuit, 40 and 41 are NOT circuits,
42 to 48 and 53 are AND circuits. 49-5
2 is a transistor for driving each solenoid 24-27.

In the configurations shown in FIGS. 4 and 5, the excavation and loading work of earth and sand is possible by expanding and contracting the boom cylinder 4 and the bucket cylinder 6 under the control of the electromagnetic valves 22 and 23.

During such work, the control circuit operates as follows and drives each electromagnetic valve 22, 23 according to a signal. For example, when rolling back the bucket 5, when the operation switch 33 is operated, a bucket rollback signal is generated, and the AND circuit 48
The transistor 52 operates via the solenoid valve 23.
The solenoid 27 is energized, and the solenoid valve 23 is operated in the rollback direction. Therefore, the bucket cylinder 6 contracts and the bucket 5 rolls back.

When dumping the bucket 5, operate the operation switch 32.
generates a bucket dump signal, AND circuit 47,
The solenoid 26 of the electromagnetic valve 23 is energized via the transistor 51, the electromagnetic valve 23 operates in the dumping direction, the bucket cylinder 6 extends, and the bucket 5 dumps.

When the boom 3 is raised or lowered, the operation switch 30 or 31 generates a boom up signal or a boom down signal, and the solenoid 24 or 25 of the solenoid valve 23 is energized via the AND circuit 45 or 46 and the transistor 49 or 50. The solenoid valve 22 operates in the upward or downward direction, the boom cylinder 4 extends or contracts, and the boom 3 rises or descends.

When operating the operating switches 30 and 33 simultaneously to raise the boom 3 while rolling back the bucket 5, the solenoid valves 22 and 23 operate as described above, and the boom cylinder 4 is connected to the hydraulic pump 9.
The bucket cylinder 6 is supplied with pressure oil from the boom cylinder 4, and each cylinder 4, 6 is operated. Note that each cylinder 4,
6 has the same diameter and the same volume. At this time, if the circuit pressure detected by the pressure detector 28 is below the cracking pressure, no pressure detection signal is generated, so the output of the NAND circuit 37 is at H level, so the output of the flip-flop circuit 39 is in the previous state, That is, keeping the L level, the NOT circuit 41,
AND circuits 45 and 4 via AND circuits 43 and 44
8 works. Of course, the output of the AND circuit 53 is also H.
level. When an overload is applied for some reason and the circuit pressure reaches the cracking pressure, the pressure detector 28 operates and generates a pressure detection signal, so all the inputs of the NAND circuit 37 become H level, and its output becomes Change to L level. Therefore, the output of the flip-flop circuit 39 becomes H level, and the output of the flip-flop circuit 39 goes to the AND circuit 43,
44 is closed, each electromagnetic valve 22, 23 returns to neutral, and both cylinders 4, 6 interrupt their expansion and contraction operations. In other words, the work is suspended and remains in that state even if the circuit drops below the cracking pressure.
Therefore, when either the operation switch 30 or 33 is returned, the output of the AND circuit 53 changes to the L level, so the output of the flip-flop circuit 39 changes to the L level, and the NOT circuit 41 and the AND circuit 4
3, 44, only one of the electromagnetic valves 22, 23 is operated via the AND circuits 45, 48, and the other is inoperable. That is, once the circuit pressure rises to the cracking pressure, the solenoid valves 22 and 23 will maintain a neutral state unless one of the signals is cut off, and the interruption will be canceled only when one of them is selected, and the next signal will be released. It is possible to move into action. Therefore, even though the solenoid valves 22 and 23 are connected in series, a large back pressure such as cracking pressure does not act on the solenoid valve 22 at the previous stage.

On the other hand, if the hydraulic device 8 is used during work with the front loader, the pressure on the hydraulic device 8 side will increase to the solenoid valve 2.
There was a fear that the front loader side would not operate and would fall due to back pressure acting on 2 and 23. Furthermore, the seals of the solenoid valves 22 and 23 were sometimes damaged.

However, at this time, the operation detector 29 detects the operation of the hydraulic device 8, and the L level signal obtained by inverting the signal in the NOT circuit 40 enters the flip-flop circuit 39 via the AND circuit 42, so that the solenoid valve 22 is inverted as described above. , 23 can be returned to neutral, thus preventing problems caused by back pressure and improving safety. These actions are the sixth
The flowchart shown in Figure.

For example, the solenoid valves 22 and 23 are connected to one operating lever 5.
4, if the operating direction is cross-shaped as shown in FIG. Operation confirmation light emitting elements 60 to 63 are provided in each of the apparatuses, and the commands from the operating lever 54 and the operations of the electromagnetic valves 22 and 23 can be visually confirmed by the display of the light emitting elements, thereby enabling safe and efficient work. Note that the display board 55 may be provided with a pressure display light emitting element 64 and a bucket position display light emitting element 65.

When the solenoid valves 22 and 23 are operated by two levers, one lever may be provided for each lever as shown in FIG.

[Brief explanation of drawings]

1 to 3 show one embodiment of the present invention, in which FIG. 1 is a side view, FIG. 2 is a hydraulic circuit diagram, FIG. 3 is a block diagram, and FIGS. 8
The figures show a control device different from the present invention, FIG. 4 is a hydraulic circuit, FIG. 5 is an electric circuit diagram, and FIG. 6 is a flow chart.
FIG. 7 and FIG. 8 are diagrams showing the display board. DESCRIPTION OF SYMBOLS 1... Tractor, 3... Boom, 4... Boom cylinder, 5... Bucket, 6... Bucket cylinder, 10, 12... Control valve, 10a... Floating part, 17... Shutoff valve, 18 ...Load detector, 20...Position detector.

Claims (1)

[Claims] 1 In a front loader control device in which the control valve for raising and lowering the boom has a floating function, there is a position detector that detects that the work tool at the tip of the boom is in the raised position, and a position detector that detects when the work tool at the tip of the boom is in the raised position. An automatic floating shutoff device for a front loader, comprising a load detector that detects the above, and a shutoff valve that shuts off a floating circuit when these detectors detect the above.