JPH0140324Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Technical Field) The present invention relates to a cushion device when a single-acting hydraulic cylinder is extended or cut.

(Technical Background) A conventional single-acting hydraulic cylinder is constructed as shown in FIG. 3 in order to absorb shock during extension.

1 is a cylinder body, 2 is a cylinder head, 3 is a piston, and 4 is a piston rod, which communicate with upper and lower oil chambers 5 and 6 through a communication path formed in the piston rod 4.

Further, in parallel to this passage 7, a check valve 8 is provided in the piston 3.

Pressure oil is supplied to and discharged from the cylinder body 1 through a supply and discharge port 9 provided in a lower oil chamber 6.

During the expansion side operation, when pressure oil is sent from the port 9 to the oil chamber 6, the piston 3 moves upward due to the difference in pressure receiving area corresponding to the cross-sectional area of the piston rod 4.

Note that from the upper oil chamber 5 which is contracting, there is a communication passage 7.
Oil flows into the oil chamber 6 below through. When the piston rod 4 reaches its maximum extension, the communication between the communication passage 7 and the oil chamber 5 is cut off by the cylinder head 2, and the oil chamber 5 enters an oil lock state, preventing the piston rod 4 from starting to extend and causing the piston 3 to slightly
Leakage escaping from the sliding gap causes cushioning action.

On the other hand, when the cylinder is contracted, when the port 9 is connected to the tank to create a low pressure, the oil in the lower oil chamber 6 is discharged due to the weight or load of the piston rod 4, and the piston 3 begins to lower, at the same time becoming in an oil lock state. Oil is sucked into the upper oil chamber 5 via a check valve 8.

In such a conventional device, the cushioning action when the piston rod 4 is fully extended is due to the piston 3
The cushioning characteristics depend on the resistance leaking through the sliding gap of the piston rod 4 and the sliding gap of the piston rod 4, so the cushion characteristics tend to fluctuate significantly due to variations in the sliding gap due to manufacturing errors and viscosity changes due to changes in oil temperature. , and the sealing member 1 of the piston rod 4
An excessively high pressure acts directly on the cylinder 0, and the cylinder body 1 also needs to have a structure that can withstand the high pressure.

(Purpose of the invention) The object of the invention is to solve the above-mentioned problem by applying braking without relying on the oil lock when the piston rod is extended or released.

(Disclosure of the invention) The present invention is a single-acting hydraulic cylinder equipped with a passage that constantly communicates two oil chambers on the rod side and the piston side, in which a supply/discharge port is formed to communicate with the oil chamber on the rod side, The port is closed by the piston or the piston rod when the piston rod reaches near its maximum extension.

(Example) In the first embodiment shown in Fig. 1, the supply/discharge port 9
is provided in the upper part of the cylinder body 1, communicating with the upper rod-side oil chamber 5.

A cushion ring 12 provided on the piston rod 4 is freely fitted into an inner circumferential gap 11 of the cylinder head 2, and a port 13 communicating with the supply/discharge port 9 opens in the inner circumferential gap 11.

Other parts that are the same as those in Figure 3 are given the same reference numerals.
Next, the action will be explained.

When the cylinder is extended, pressurized oil is sent from the intake/exhaust port 9 through the passage 7 that constantly communicates from the rod-side oil chamber 5 to the lower piston-side oil chamber 6, and the piston rod 4 moves upward. It starts to grow.

When the maximum extension is reached, the port 13 that communicates with the supply/discharge port 9 is connected to the piston 3 before the communication path 7.
The cushion ring 12 that rises at the same time narrows the flow of oil into the oil chambers 5 and 6, reducing the piston rising speed.

When the port 13 is completely closed, the piston 3 will no longer move toward the extension side.
It stops at the fully extended position.

Therefore, when the piston rod 4 stops at the fully extended position, the pressure oil is gradually squeezed and braking is applied, and when the piston rod 4 stops, the oil chamber 5 is not locked as in the conventional case. The pressure does not suddenly rise to a certain peak value,
No impact pressure is applied to the oil seal member 10.

Note that the piston 3 is held at the extended position while high pressure is applied to the supply/discharge port 9.

Next, during the contraction operation, the pressure of the supply/discharge port 9 is released to the tank side.

As a result, the piston 3 is lowered by the weight of the piston rod 4, and the oil in the oil chamber 6 flows into the oil chamber 5.
Furthermore, the excess amount due to the entry of the piston rod 4 flows out from the supply/discharge port 9.

FIG. 2 shows a second embodiment, in which the supply/discharge port 9 is directly opened and closed by a piston ring 15 fitted around the outer circumference of the piston 3, and has the same effect as above. arise.

Since the oil chamber 5 is communicated with the supply/discharge port 9 via the check valve 16, hydraulic oil can be sucked in via the check valve 16 during the piston contraction start stroke, making it easier to lower the piston.

(Effects of the invention) As described above, according to the invention, since braking is applied by restricting the supply of pressure oil to the oil chamber when the piston rod is fully extended, the cushion characteristics are always stable without being affected by oil temperature, etc. At the same time, it is possible to protect the sealing member and reduce the pressure resistance of the cylinder.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a first embodiment of the present invention, FIG. 2 is a sectional view of a second embodiment, and FIG. 3 is a sectional view of a conventional device. 1...Cylinder body, 2...Cylinder head, 3...
Piston, 4...Piston rod, 5, 6...Oil chamber,
7...Communication path, 9...Supply/discharge port, 12...Cushion ring, 13...Port.

Claims (1)

[Scope of utility model registration request] In a single-acting hydraulic cylinder, a piston that can freely slide in the cylinder body defines two oil chambers on both sides, and a communication path that constantly communicates these oil chambers.The hydraulic oil supply and discharge port is connected to the piston rod. A cushioning device for a single-acting hydraulic cylinder, characterized in that the piston or the piston rod is provided with means that opens to communicate with a side oil chamber and narrows and closes the opening near the maximum extension of the piston rod.