JPS6026570Y2 - Three-point hitch device for agricultural tractors - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a pressure point hit device for an agricultural tractor.

The three-point hitch device that supports and raises and lowers the agricultural machinery of an agricultural tractor is shown in Figure 1, and consists of two left and right lower links a and b and one top link C. Agricultural machinery such as subsoilers and plows attached to the three-point hit device is raised and lowered by rotating the lift lever d connected to a and b with the lifting cylinder device e in the vertical direction. .

However, the conventional three-point hit device has the following problems due to its structural defects.

In other words, the hydraulic circuit of the elevating cylinder device e is as shown in Fig. 2.
1. f2. f3. Each state is controlled by operating the lever f on the operating valve f, but when this operating valve f is set to "hold" envoy 2, the elevating cylinder device e is in the locked state. For this reason, if there is an obstacle while working with a subsoiler or plow with the operation valve f set to "main" 2, it will be pushed up by these agricultural machines, placing a heavy load on the agricultural machinery and lifting equipment, and causing breakdowns. Cause.

Note that g is a fixed throttle valve. The present invention was developed in consideration of the above-mentioned issues, and even if there is an obstacle during work with agricultural machinery such as a subsoiler or plow with the main switching valve set to the "hold" position, the agricultural machinery will be lifted up by the uplifting force of the subsoiler or plow. An object of the present invention is to provide a three-point hit device for an agricultural tractor that can prevent large loads from being applied to agricultural tractors and protect the agricultural machinery.

The configuration will be explained below based on the embodiment shown in FIG.

In FIG. 3, 1 in the figure is a lifting cylinder, and this lifting cylinder 1 has a piston rod 3 connected to a lift lever 2.
It has a double-acting double-piston type having a first pin 4 having a second piston 4 and a second piston 5 fitted in a free state on the bottom side of the first piston 4.

The intermediate chamber 6 between the first piston 4 and the second piston 5 is constantly drained through an oil hole 7 provided in the piston rod 3.

The rod side chamber 8 and bottom side chamber 9 of the lifting cylinder 1 are
It is connected to a hydraulic power source 11 via a main switching valve 10 having respective positions 10a, 10b, and 10c of the "floating" position.

The "up" position 10a of the main switching valve 10 communicates between the hydraulic power source 11 and the bottom chamber 9, and the drain circuit and the rod side chamber 8, and the "hold" position 10b closes the bottom chamber 9. At the same time, the rod side chamber 8 is communicated with the hydraulic power source 11 and the drain circuit, and the "floating" position 1
0c is a hydraulic source 11 that connects the rod side chamber 8 and the bottom side chamber 9 to each other.
and the drain circuit.

In addition, the bottom side circuit 12 connecting the bottom side chamber 9 and the hydraulic power source 11 has an upper circuit and a lower circuit connected in parallel with the main switching valve 10.
Interposed is a lowering switching valve 13 having a position 13a and a "drain" position 13b.

The "lower" position 13a of this lowering switching valve 13 communicates the bottom side circuit 12 with the drain circuit, and closes the drain circuit from the main switching valve 10.
Position 13b closes the bottom side circuit 12 and communicates with the drain circuit from the main switching valve 10.

The lowering switching valve 13 is normally in the "drain" position 13.
b, and when the main switching valve 10 is in the "hold" position 10b, it can be switched to the "lower" position it 13a.

The main switching valve 10 and the lowering switching valve 13 may be either electromagnetic valves or manual type.

A check valve 14a1 and a variable throttle valve 1 are installed in the bottom side circuit 12.
A lift response control valve 14 consisting of 4b and 4b is interposed.

15 is a three-point hitch installed at the rear of the tractor and raised and lowered by the lift lever 2; 16 is a lower link;
17 is a top link, 18 is an adjustment link, and 19 is a plow that is an example of an agricultural machine attached to the three-point hitch 15.

In the above configuration, the agricultural machine is raised or lowered by switching the main switching valve 10, but when the main switching valve 10 is in the "floating" position, that is, when it is lowering, the lifting cylinder 1 is in a free state over the entire stroke, and the agricultural machine is moved. It descends due to its own weight.

On the other hand, when the main switching valve 10 is set to "Hold", the bottom side chamber 9 of the lifting cylinder 1 is closed and the movement of the second piston 5 toward the bottom is stopped, and the first piston 4 is moved to the second piston 5.
The end of the stroke in the downward direction is determined by .

Therefore, the lowering position of the agricultural machine is determined by the position of the second piston 5, and the plowing depth remains constant.

Also, in this state, the first piston 4 is in a free state between the second piston 5 and the cylinder rond side, so
If an upward force greater than a downward force due to its own weight is applied to the agricultural machine due to an obstacle or the like during work, the agricultural machine is upwardly moved by the stroke of the first piston 4, thereby avoiding the excessive traction.

Further, when the lowering switching valve 13 is set to the "lower" position 13a while the main switching valve 10 is in the "hold" position 10b, the lifting cylinder 1 is forcibly shortened and the agricultural machine is forcibly lowered.

The present invention is as described above, and consists of a lower link 16, a top link 17, and an adjustment link 18, and the agricultural tractor is moved up and down via the lift lever 2 by extending and contracting these elevating cylinder devices 1. In the three-point hit device, the lifting cylinder device 1 includes a first piston 4 having a piston rod 3 connected to a lift lever 2, and a second piston 5 located in a free state on the bottom side of the first piston 4. has a first piston 4
and the second piston 5 is always connected to the tank side, and between the lifting cylinder device 1 and the hydraulic power source 11, the hydraulic power source 11 and the bottom side chamber 9 of the lifting cylinder device 1 are connected. In addition, the "upper" position 10a communicates the drain circuit and the rod side chamber 8, and the bottom side chamber 9 is not closed.
A "hold" position 10b where the rod side chamber 8 is communicated with the hydraulic power source 11 and the drain circuit, and a "floating" position 1 where the rod side chamber 8 and the bottom side chamber 9 are communicated with the hydraulic power source 11 and the drain circuit.
A main switching valve 10 having a 0C is interposed between the bottom side chamber 9 of the lifting cylinder device 1 and the hydraulic power source 11 and the drain circuit, and the bottom side chamber 9 and the drain circuit are communicated with each other. Close the drain circuit from valve 10 ``
"lower" position 13a, and "drain" position 13b, which closes the bottom side chamber 9 and communicates the drain from the main switching valve 10.
Since the three-point hit device of the agricultural tractor is constructed by interposing the lowering switching valve 13 having A free state is established between the piston 5 and the rond side of the cylinder, and the stroke end in the shortening direction is determined by the second piston 5, whereby the agricultural machine is determined at the position of the second piston 5. It becomes a free state upward from a predetermined plowing depth position.

Therefore, even if there is an obstacle during work with agricultural machinery such as a subsoiler or plow with the main switching valve 10 set to the "hold" position 10b, the agricultural machinery will be lifted by the uplifting force and will be prevented from being subjected to a large load. Agricultural machinery can be protected.

[Brief explanation of the drawing]

Figure 1 is a side view showing the three-point hit device of an agricultural tractor;
FIG. 2 is a conventional hydraulic circuit diagram, and FIG. 3 is a hydraulic circuit diagram showing an embodiment of the present invention. 1 is a lifting cylinder device, 2 is a lift lever, 3 is a piston rod, 4 is a first piston, 5 is a second piston, 6 is an intermediate chamber, 8 is a rod side chamber, 9 is a bottom side chamber, 10 is a main switching valve, 10a , 10b, 10c are respective positions, and 11 is a hydraulic power source.

Claims (1)

[Scope of utility model registration request] In a three-point hit device for an agricultural tractor, the lower link 16, top link 17, and adjustment link 18 are raised and lowered via a lift lever 2 by telescoping the lifting cylinder device 1. 1 has a first piston 4 having a piston rod 3 connected to a lift lever 2, and a second piston 5 located in a free state on the bottom side of the first piston 4. The intermediate chamber 6 between the piston 5 and the piston 5 is always connected to the tank side, and between the lifting cylinder device 1 and the hydraulic power source 11, the hydraulic source 11 and the bottom side chamber 9 of the lifting cylinder device 1 are connected, and a drain is connected between the hydraulic power source 11 and the bottom side chamber 9 of the lifting cylinder device 1. an "upper" position 10a where the circuit and the rod side chamber 8 are communicated with each other, a "hold" position 10b where the bottom side chamber 9 is closed and the rod side chamber 8 is communicated with the hydraulic power source 11 and the drain circuit, and a rod side chamber 8.
and a "floating" position 10c that communicates the bottom side chamber 9 with the hydraulic power source 11 and the drain circuit. In between, the bottom side chamber 9 and the drain circuit are communicated with each other and the drain circuit from the main switching valve 10 is closed. do"
A three-point hit device for an agricultural tractor, characterized in that a lowering switching valve 13 having a drain position 13b is installed.