JPS6233125Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION This invention relates to a hydraulic cylinder having a cylinder chamber divided into two parts by a piston.

FIG. 1 is a diagram showing a conventional hydraulic cylinder and its hydraulic circuit. In the figure, 1 is a hydraulic cylinder, 2
is the outer cylinder of the hydraulic cylinder 1, 3 is the piston provided in the outer cylinder 2, and 4a and 4b are the two pistons provided by the piston 3.
Cylinder chamber divided into parts, 5a, 5b are pipes connected to cylinder chambers 4a, 4b, 6a, 6b
are pilot check valves provided in the conduits 5a, 5b, and the pilot check valves 6a, 6b are opened when the pressure in the conduits 5b, 5a exceeds a predetermined value. Reference numerals 7a and 7b are a pair of relief valves provided between the conduits 5a and 5b to face each other.

In this hydraulic cylinder, for example, the pipe line 5
When pressure oil is supplied to a, the pressure oil is sent to the cylinder chamber 4a, and the pilot check valve 6b is opened, so that the piston 3 moves to the right. Furthermore, even if an external force F in the direction of the arrow acts on the piston 3 while the supply of pressure oil is stopped, the piston 3 will not move to the left because the pilot check valve 6a is provided. . moreover,
When the external force F becomes excessive and the pressure in the cylinder chamber 4a becomes higher than the set pressure of the relief valve 7a,
Since the relief valve 7a is opened, it is possible to prevent the pressure in the pipe line 5a from becoming excessive and damaging the equipment.

However, the pipes 5a, 5 leading from the cylinder chambers 4a, 4b to the pilot check valves 6a, 6b.
When relief valves 7a and 7b are provided between b.
Pilot check valve 6 for the pipes 5a and 5b
The length up to a and 6b increases, and the pipe 5
Since the volumes of a and 5b become large, the apparent compressibility of the oil cannot be ignored, and for example, even when a normal amount of external force is applied in the direction of the arrow, the piston 3 moves somewhat to the left. It ends up.

This invention was made in order to solve the above-mentioned problems, and its purpose is to provide a hydraulic cylinder in which the amount of movement of the piston is small when an external force of a normal size is applied.

In order to achieve this purpose, in this invention, in a hydraulic cylinder having a cylinder chamber divided into two parts by a piston, a hole is provided inside the piston, and a head is provided in the hole to face each other. a pair of poppets, a first spring provided between the poppets and the piston, a pair of movable seats provided between the poppets, and a second spring provided between the movable seats. A spring and a movement restricting means provided between the poppet and the movable seat are provided.

FIG. 2 is a sectional view showing a hydraulic cylinder according to this invention, and FIG. 3 is a sectional view taken along line AA in FIG. In the figure, 8a and 8b are a pair of relief valves disposed opposite to each other inside the piston 3, 9 is a hole provided inside the piston 3, and 10 and 10b are the cylinder chambers 4a and 4b and the hole 9. a communicating oil passage;
Reference numerals 11a and 11b are protrusions that protrude into the hole 9, and the protrusions 11a and 11b constitute movement regulating means. 12a, 12b are poppets provided in the hole 9 with their heads facing each other; 13a, 13b are poppets 1;
2a, 12b. Under normal conditions, the poppets 12a, 12b are biased by the spring 13.
a, 13b are pressed against the protrusions 11a, 11b. 14a, 14b are movable seats, 15
is a spring provided between the movable seats 14a and 14b, and in a normal state, the movable seats 14a and 14
b is connected to the poppets 12a and 12 by the spring 15.
b, and the protrusions 11a, 1
There is a gap 1 between 1b and movable sheets 14a and 14b.
6a and 16b are formed. A valve body 17 is attached to the outer cylinder 2, and pilot check valves 6a and 6b are provided within the valve body 17.

In this hydraulic cylinder, for example, the pipe line 5
When pressure oil is supplied to a, the pressure acts on the left end surface of the movable seat 14b, the movable seat 14b moves to the right against the spring 15, and the pressure in the cylinder chamber 4a increases between the movable seats 14a, Poppet 12
However, when the external force F is small, the pressure inside the cylinder chamber 4a does not become very high, so the movable seat 14a and poppet 12a do not move.
Further, when the external force F is somewhat large and the pressure inside the cylinder chamber 4a becomes somewhat high, the movable seat 14
a, the poppet 12a moves to the right against the spring 13a, but the movable seat 14a
After coming into contact with 1a, the poppet 12 is released due to pressure.
The force acting on a is the product of this pressure and the cross-sectional area of the head of the poppet 12a, and since the cross-sectional area is small, the poppet 12a will not move any further to the right. In these cases, that is, when pressure oil is supplied to the pipe line 5 and the external force F is small or somewhat large, the pilot check valve 6b is opened by the pressure in the cylinder chamber 4a, and the pressure in the cylinder chamber 4a is reduced to the piston 3. , the piston 3 moves to the right and a propulsion operation is performed. and,
When the normal external force F acts while the propulsion operation is stopped, the pilot check valve 6a is closed and the relief valve 8a is closed as described above, so the piston 3 does not move, but the external force F is When the pressure in the cylinder chamber 4a reaches the set pressure of the relief valve 8a, that is, the product of the pressure in the cylinder chamber 4a and the cross-sectional area of the head of the poppet 12a, that is, the force due to the pressure exceeds the force of the spring 13a. When the size increases, the poppet 12a moves to the right against the spring 13a, and the relief valve 8a opens, so that the oil in the cylinder chamber 4a moves to the cylinder chamber 4b.
The pressure inside a never exceeds the set pressure of the relief valve 8a, and damage to the equipment can be prevented.

As explained above, in the hydraulic cylinder according to this invention, since the relief valve is arranged inside the piston, the length of the pipeline from the cylinder chamber to the pilot check valve can be shortened, so that external force is not applied. Since the displacement of the piston due to the apparent compressibility of the oil can be made very small, the load can be held reliably. In addition, since there is no need to arrange an external relief valve, the device can be made compact, so when the hydraulic cylinder according to this invention is used in a drilling machine, for example, the device can be placed in a small space. It is possible. in this way,
The effect of this idea is remarkable.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a conventional hydraulic cylinder and its hydraulic circuit, FIG. 2 is a sectional view showing a hydraulic cylinder according to this invention, and FIG. 3 is a sectional view taken along line AA in FIG. DESCRIPTION OF SYMBOLS 1...Hydraulic cylinder, 2...Outer cylinder, 3...Piston, 4a, 4b...Cylinder chamber, 6a, 6b...
...Pilot check valve, 8a, 8b...Relief valve, 11a, 11b...Protrusion, 12a, 12
b...Poppet, 13a, 13b...Spring, 14a, 14b...Movable seat, 15...Spring, 16a, 16b...Gap.

Claims (1)

[Scope of utility model registration request] A hydraulic cylinder having a cylinder chamber divided into two parts by a piston, a hole provided inside the piston, a pair of poppets provided in the hole with their heads facing each other, and the poppet and the piston. a first spring provided between the poppets, a pair of movable seats provided between the poppets, and a second spring provided between the movable seats.
A hydraulic cylinder comprising: a spring; and a movement regulating means provided between the poppet and the movable seat.