JPS6020805Y2 - hydraulic cylinder - Google Patents

Description

[Detailed description of the invention] This invention relates to a hydraulic cylinder, and more specifically to a forklift truck that uses a cushion when fully extended to prevent vibrations and shocks from being applied to cargo on a support platform connected to a piston rod. This invention relates to a single-acting hydraulic cylinder suitable for use in cargo handling equipment, etc.

In general, the cargo handling equipment of forklift trucks uses a single single-acting hydraulic cylinder or a multi-stage extension cylinder in which multiple single-acting hydraulic cylinders are connected in a multi-stage manner, and these hydraulic cylinders are connected to a work platform and a support platform. Normally, cargo is moved up and down by connecting hydraulic cylinders, but when the piston collides with the cylinder head when the hydraulic cylinder is fully extended, large vibrations and shocks are generated, and these vibrations are transmitted to the support base. This can cause the load on the support stand to fall or shift, which is very dangerous and may even damage the load.

Therefore, the purpose of the present invention is to provide a hydraulic cylinder suitable for use in forklift truck cargo handling equipment, etc., which uses a cushion to reduce the speed of piston rod extension when the piston rod is fully extended, thereby preventing vibrations and shocks from being applied to the cargo. It is to provide.

An embodiment of the present invention will be described below with reference to the drawings.

In a single-acting hydraulic cylinder, a hollow piston rod 3 is movably inserted into a cylinder tube 1 via a piston 2, and seals 4 and 5 are interposed between the piston 2 and the cylinder tube 1. The cylinder tube 1 is divided into two upper and lower oil chambers 6.7, the piston rod 3 is divided into an oil chamber 8, and above the oil chamber 8, a gas chamber 9 for air gas, etc. is formed. There is.

A cylinder head 11 is connected to the upper end of the cylinder tube 1, and a piston rod 3 passes through this cylinder head 11 and is guided to be vertically movable. ring 12
, a seal 13 is interposed.

A passage 15 is bored in the bottom portion 14 of the lower end of the cylinder tube 1, and this passage 15 connects the lower oil chamber 7 to a hydraulic pressure source of a pump or a tank.

An oil filler column 16 is provided at the upper end of the piston rod 3, and when injecting oil, this stopper is removed and the oil is normally sealed.

One or more through holes 17, 18, 19... are bored in the lower part of the piston rod 3, and the heights of these through holes 17, 18, 19 are made to be different.

When the hydraulic cylinder is used in a lifting device for a forklift truck, a support base is connected to the upper end of the piston rod 3 via a sheave, wire, etc., so that a load can be placed thereon.

According to the single-acting hydraulic cylinder of the present invention, in the extension operation, high pressure is introduced from the passage 15 to the lower oil chamber 7 to raise the piston 2 and piston rod 3, and at this time, the upper oil chamber 6 is contracted to discharge the oil. It flows out into the oil chamber 8 in the piston rod via the through holes 17, 18, 19.

However, near the maximum extension, the passages 17, 18, and 19 gradually close one by one on the inner periphery of the cylinder head 11 from the upper passage hole 17, so that the hydraulic oil flowing out from the oil chamber 6 is throttled. As the flow resistance increases, the cushion becomes effective.

Therefore, when the piston 2 is fully extended, the cylinder head 11
Since a sudden collision with the piston rod 3 is prevented, no large impact is generated, and no vibration or impact is applied to the support base or cargo connected to the piston rod 3.

Also, during compression, when the passage 15 is connected to the tank side, the piston rod 3 and the piston 2 descend due to their own weight, and at this time, the upper oil chamber 6 expands and the hydraulic oil in the oil chamber 8 in the piston rod flows into the through hole 17. 18. 19 into the upper oil chamber.

However, when it is fully extended, hydraulic oil is supplied to the oil chamber 8, so the gas chamber 9 is compressed accordingly and the pressure is higher than the gauge pressure, and the same pressure is also applied to the upper oil chamber 6. Therefore, even when compression is started, the upper oil chamber 6 is not vacuumed and the compression operation is performed smoothly.

Next, FIG. 2 relates to another embodiment of the present invention.

This is a passage 20 that communicates with the oil chamber 8 in the piston rod and the upper oil chamber 6 on the base end side of the piston rod 3 or the piston 2, and a ball valve or other similar check valve 21 in the middle of this passage 20 can be opened and closed. be placed in
During compression operation, the oil in the oil chamber 8 pushes open the check valve 21 so that it can flow into the upper oil chamber 6.

In this case, negative pressure in the upper oil chamber 6 is completely prevented during compression operation from the maximum extension.

Furthermore, FIG. 3 shows another embodiment of the present invention, in which a through hole 22 for opening the gas chamber 9 to the outside is bored at the upper end of the piston rod 3 or other similar positions, and a ball is inserted in the middle of the through hole 22. A relief valve 25 consisting of a valve body 23 and a spring 24, such as a valve or other similar valve body, is arranged to be openable and closable.

This occurs when hydraulic oil enters the upper oil chamber 6 from the lower oil chamber 7 and the amount of oil increases, or when air enters the gas chamber 9 from the outer circumference of the piston rod 3, the internal pressure of the gas chamber 9 becomes abnormal. When the abnormal pressure rises, the valve body 23 resists the spring 24 and releases this abnormal pressure to the outside.

As described above, the present invention has one or more through holes bored in the base end of the hollow piston rod, and these through holes communicate the piston upper oil chamber with the oil chamber inside the piston rod, and the cylinder head near the maximum extension. Since the opening area is narrowed down, the cushion is effective near the maximum extension, and the extension speed of the piston rod is reduced, so even when the piston hits the cylinder head at the maximum extension, large vibrations and shocks do not occur, making it safe. be.

Furthermore, since the piston rod is made hollow and only has a through hole provided at its base end, the structure is simple and compact, and is highly economical.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional side view of a hydraulic cylinder according to one embodiment of the present invention, and FIGS. 2 and 3 are partially cutaway longitudinal sectional side views of hydraulic cylinders according to other embodiments. 1... Cylinder tube, 2... Piston, 3... Piston rod, 6, 7...
...Oil chamber, 8...Oil chamber, 9...Gas chamber, 17. 18. 19...through hole, 20...
...Through hole, 21...Check valve, 25.
·····Relief valve.

Claims (2)

[Scope of utility model registration request] (1) A hollow piston rod is movably inserted into a cylinder tube connected to a cylinder head via a piston, and the piston defines two upper and lower oil chambers within the cylinder tube, and an oil chamber and an oil chamber within the piston rod. A gas chamber is formed, one or more through holes are bored in the lower part of the piston rod, and the upper oil chamber and the oil chamber in the piston rod are communicated through the through holes until the piston rod reaches its maximum extension. When the hydraulic cylinder moves, the opening area of the through hole is reduced by the cylinder head to provide a cushioning effect. (2) A hydraulic cylinder according to claim 1, in which the plurality of through holes have different heights.