JPS5944521B2 - hydraulic cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hydraulic cylinder that operates in a double-acting manner for a part of its expansion and contraction strokes and as a single-acting cylinder for the rest of the stroke.

For example, a double-acting cylinder may be used as a hydraulic cylinder for raising and lowering a boom in an aerial work vehicle.

This is because when a single-acting cylinder is used, the angle of depression of the boom is large, and when the boom exceeds the so-called get point where it does not move down due to its own weight, it is inconvenient to apply external force to the boom until it moves down due to its own weight. It is.

However, on the other hand, when a double-acting cylinder is used, the external force from the cylinder acts on the boom until the boom moves down and returns to its original state, so when the boom collides with an obstacle, the collision force is extremely large. There was a risk of damaging the boom, etc., and there were drawbacks such as a lack of safety during work.

Therefore, in such applications, the hydraulic cylinder acts as a double-acting cylinder until the boom moves downwards due to its own weight, and then returns to its original state due to the boom's own weight.If it is a hydraulic cylinder that acts as a single-acting cylinder, the boom will move downwards. When moving,
The development of such a hydraulic cylinder has long been desired in the industry because even if it collides with an obstacle, the collision is small and safety is high.

The present invention has been made in response to the above-mentioned needs, and is intended to provide a hydraulic cylinder that is most suitable for lowering the boom of an aerial work vehicle, lowering the ladder of a ladder vehicle, and the like.

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

Reference numeral 1 denotes a hydraulic cylinder body, which is equipped with an in-shaft oil supply and drainage connection part 2, 2' that communicates with a hydraulic pressure generating part or an oil tank (not shown) at its base end; the main body 10 is connected to an in-shaft oil supply and drainage connection part 2 at its base end. An oil supply port 3 is provided at the tip of the cylinder chamber on the head side, and an oil drain port 4 is provided at the tip of the head side cylinder chamber, and the oil drain port 4 and the oil drain connection portion 2 are provided.
' are connected by a pipe 5.

A piston 1 slides within a cylinder chamber 6 and has a piston rod 8 on the head side, and the rod 8 passes through a sliding hole 10 in a head 9 and projects outward.

Reference numeral 11 indicates an opening provided at the base end of the piston 70 facing the proximal side cylinder chamber, and reference numeral 12 indicates an opening provided in the head side cylinder chamber at the base of the condo 80 and at a position to be inserted into the head sliding hole 10 at the extension end position of the cylinder. Both openings 11 and 12 are communicated with each other through a communicating hole 13 through openings facing each other.

A check valve 14 is interposed in the communication hole 13 to allow flow only from the rod-side opening 12 to the piston-side opening 11.

Note that the check valve 14 is a known one.

Next, a description will be given of the operation mode when the hydraulic cylinder 1 configured as described above is used as the fill (immediate drive device) of the boom 15 of an aerial work vehicle shown in FIG.

First, to operate the boom, open the cylinder chamber 6 from the fuel filler port 3.
When the piston 7 is refueled, the check valve 14 is closed and the piston 7
is slid toward the tip side, and the piston rod 8 is extended.

At this time, the oil is drained from the oil drain port 4 on the tip side through the pipe 5.

Then, the piston 7 comes into contact with the head 9 and the extension of the rod ends, but in this state the rod-side opening 12 is located within the head sliding hole 10 and the opening 12 is closed.

Next, the boom is lowered, and in order to return to its original state, pressurized oil is passed through the pipe 5 from the oil drain port 4 into the head side cylinder chamber 6 between the piston 7 and the head 9, and the piston 7 is slid toward the base end. The rod begins to contract.

This operation, that is, the operation as a double-acting cylinder, continues until the rod side opening 12 is pulled out from the head sliding hole 10, and when the rod side opening 12 is exposed in the cylinder chamber 6, the communication hole 13 is opened from the opening 12. Pressure oil enters the check valve 1
4 is opened and pressure oil flows into the proximal cylinder chamber through the piston-side opening 11 to establish communication, so the oil pressure from the oil drain port 4 does not act on the piston 7 and it operates as a single-acting cylinder.

Therefore, the boom 15 is at the so-called dead point.
The boom 15 is lowered by the double-action hydraulic cylinder 1 until it exceeds the point ), but after that, the hydraulic cylinder 1 becomes single-action, so the boom 15 slowly lowers due to its own weight and returns to its original state. Even if the boom 15 comes into contact with an obstacle, there is little risk of the boom or the like being damaged and it is safe.

However, in the hydraulic cylinder of the present invention, in an expansion cylinder having an oil supply port at the base end and an oil drain port at the tip, the piston base end opening facing the base end side cylinder chamber and the piston rod base opening are communicated. A check valve is installed in the communication hole to allow flow only from the rod-side opening to the piston-side opening, and at the end of the rod extension, The rod base opening is inserted into the cylinder head and closed, and during that time it is possible to operate as a double-acting cylinder, so that it can be operated as a double-acting hydraulic cylinder from the extension end position of the hydraulic cylinder in the initial stroke of the start of contraction. The present invention can be used in a wide range of special applications, and can also be used as a hydraulic cylinder for lifting the boom of an aerial work vehicle as described above, thereby effectively exhibiting the effects of the present invention.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a partially omitted front view, FIG. 2 being a partially omitted vertical sectional view in a contracted state, and FIG. 3 being a partially omitted longitudinal sectional view in an extended state. FIG. 4 is a longitudinal sectional view, FIG. 4 is an overall schematic oblique view, and FIG. 5 is an explanatory view showing a state in which the hydraulic cylinder of the present invention is mounted on a vehicle for aerial work. 1... Hydraulic cylinder body, 2, 2'...
...Oil supply/drain connection, 3...Oil filler port, 4...
...Drain port, 5...Pipe, 6...Cylinder chamber, 7...Piston, 8...
Piston rod, 9...Head, 10...
...Head sliding hole, 11...Piston side opening,
12... Rod side opening, 13... Communication hole, 14... Check valve, 15... Boom.

Claims (1)

[Claims] 1. In a hydraulic cylinder having an oil supply port at the base end of the cylinder body and an oil drain port at the tip of the body, the piston base end opening facing the base end side cylinder chamber and the piston 70 base opening communicate with each other. A check valve is installed in the communicating hole to allow flow only from the rod side to the piston side, and the connecting hole connects the proximal end side and the distal end side of the cylinder chamber to communicate with each other. Hydraulic cylinder where the rod side opening fits into the cylinder head and is closed.