JP2002147411A - Ram cylinder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a ram cylinder composed so as to effectively prevent occurrences of impact or noises when a piston starts to move following a contracting movement of a piston rod. SOLUTION: In the piston 15 provided in this ram cylinder 1, a plurality of pressure oil passages 2 are formed connectively communicating an end side oil pressure chamber 17 arranged between an end side end plate part 12 and the piston 15 and a rod side oil pressure chamber 18 arranged between a rod side end plate part 13 and the piston 15, and a spherical body 3 allowing a flow of pressure oil from the end side oil pressure chamber 17 to the rod side oil pressure chamber 18 and blocking a flow of the pressure oil from the rod side oil pressure chamber 18 to the end side oil pressure chamber 17 is movably integrated in at least one pressure oil passage 2a of the plurality of oil passages 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ram cylinder and, more particularly, to a cushion structure for reducing a shock generated when a piston rod starts a contraction operation.

[0002]

2. Description of the Related Art Conventionally, in loading and unloading vehicles such as picking forklifts and lift trucks, single-acting hydraulic cylinders, so-called ram cylinders, have been used as devices for raising and lowering a fork and a lifting mast. Kinds of ram cylinders are disclosed in JP-A-2000-5501.
It is generally disclosed in No. 0 and has a structure as shown in FIG. That is, the ram cylinder 11 has a cylinder tube 1 whose both ends are closed by the end-side end plate portion 12 and the rod-side end plate portion 13, respectively.
4, a piston 15 that moves in the cylinder tube 14, and a piston rod 1 that is connected to the piston 15 through the rod-side end plate portion 13 and protrudes to the outside.
6, the end-side end plate portion 12 and the piston 1
The piston rod 16 is extended in accordance with the supply of the pressure oil into the end-side hydraulic chamber 17 disposed between the piston rods 5 and, as a result, a load such as a fork or a lifting mast supported by the piston rod 16 is provided. The load (not shown) is configured to perform a rising operation.

At this time, a narrow slit 19 is provided between the piston 15 and the piston rod 16 and opens toward the rod-side hydraulic chamber 18 disposed between the rod-side end plate 13 and the piston 15. On the other hand, a plurality of, for example, six pressure oil flow paths 20 are formed for the piston 15, and each of the pressure oil flow paths 20 formed by selecting equally-spaced positions on concentric circles is formed. The end-side hydraulic chamber 17 and the rod-side hydraulic chamber 18 are connected to each other via the slit 19. Therefore, when the piston rod 16 is extended, the piston 15 is moved upward by the pressure oil supplied into the end-side hydraulic chamber 17, and at the same time, the rod-side hydraulic chamber 18 is compressed by the piston 15. Pressure oil will flow out, and
The outflowing pressure oil passes through the pressure oil flow path 20 from the slit 19 and then flows into the end-side hydraulic chamber 17.

Further, a hydraulic port 21 for supplying pressure oil is attached to an end-side end plate portion 12 that seals an end-side opening of a cylinder tube 14 provided in the ram cylinder 11, while a rod-side end thereof is provided. A pressure oil flow path 22 having an orifice structure, that is, a pressure oil flow path 22 functioning as a choke (throttle) of the pressure oil is formed in the rod-side end plate portion 13 closing the opening. And
The pressure oil flow path 22 connects the pressure oil flow path 20 of the piston 15 and the rod-side hydraulic chamber 18 to each other through the slit 19, and provides a cushion when the piston rod 16 is most extended. It is to function as a so-called stroke end cushion.

That is, in the ram cylinder having a normal configuration, the piston 15 directly collides against the rod-side end plate 13 at the time when the piston rod 16 has completed the extension operation, so that a large impact is generated. I will. However,
In the ram cylinder 11 in which the pressure oil flow path 22 having the orifice structure is formed as disclosed in Japanese Patent Application Laid-Open No. 2000-55010, the rod-side hydraulic pressure is closed immediately before the piston rod 16 completes the extension operation. The pressure oil that has flowed out of the chamber 18 is gradually narrowed while flowing through the pressure oil flow path 22 and then flows into the pressure oil flow path 20, so that the impact is reduced. A fork or a lifting mast as a load is attached to the piston rod 16 of the ram cylinder 11. When the supply of the pressure oil to the end-side hydraulic chamber 17 is stopped, the weight of the load is reduced. The piston rod 16 contracts.

[0006]

SUMMARY OF THE INVENTION However, Japanese Patent Application Laid-Open
In the ram cylinder 11 disclosed in Japanese Patent Application Publication No. 000-55010, as shown in FIG.
6, the side surface 15 of the piston 15 at the point in time immediately after starting to move downward in the cylinder tube 14
a, that is, the side surface 15a facing the rod side hydraulic chamber 18
Blocks the inflow port of the pressure oil flow path 22, the pressure oil in the end side hydraulic chamber 17 does not flow from the pressure oil flow path 22 and the slit 19 of the piston 15 into the rod side hydraulic chamber 18,
The inside of the rod-side hydraulic chamber 18 is almost in a vacuum state. Then, the piston rod 16 continues to contract, and the side surface 15a of the piston 15 is
2, the rod-side hydraulic chamber in which the slit 19 communicating with the pressure oil flow path 22 of the piston 15 is almost in a vacuum state as shown in FIG. When opening toward 18, the pressure oil that has passed through the slit 19 is ejected into the rod-side hydraulic chamber 18, and the ejected pressure oil collides with the wall surface of the cylinder tube 14. Shock and abnormal noise were to occur.

The present invention has been made in view of such inconvenience, and it is an object of the present invention to effectively prevent the generation of impact and abnormal noise immediately after the movement of a piston due to the contraction of a piston rod is started. The purpose of the present invention is to provide a ram cylinder capable of performing the following.

[0008]

According to a first aspect of the present invention, there is provided a ram cylinder having a cylinder tube whose both ends are closed by an end-side end plate and a rod-side end plate, and which moves in the cylinder tube. The piston includes a piston and a piston rod connected to the piston after passing through the rod-side end plate, and pressurized oil is supplied to an end-side hydraulic chamber disposed between the end-side end plate and the piston. Accordingly, the piston rod is configured to extend. The piston here has a plurality of pressure oil flow paths that connect and connect the rod-side hydraulic chamber and the end-side hydraulic chamber that are disposed between the rod-side end plate and the piston. In at least one of the pressure oil passages, the flow of the pressure oil flowing from the end side hydraulic chamber to the rod side hydraulic chamber is free while the pressure oil flowing from the rod side hydraulic chamber to the end side hydraulic chamber is provided. It is characterized in that the spherical body for preventing circulation is provided in a movable state.

A ram cylinder according to a second aspect of the present invention is the ram cylinder according to the first aspect, wherein the inlet of the pressure oil flow path in which the spherical body is provided is always connected to the end side hydraulic chamber. On the other hand, the outlet is on the side surface which is connected to the rod side hydraulic chamber at the same time that the side surface of the piston which has started to move with the contraction operation of the piston rod comes into contact with the rod side hydraulic chamber. It is characterized by being opened after selecting a position.

A ram cylinder according to a third aspect of the present invention is the ram cylinder according to the first or second aspect, wherein a pressure oil flow path formed in a piston and a rod-side hydraulic chamber are formed in a rod-side end plate. And a pressure oil flow path for connecting the pressure oil flow path and the pressure oil flow path having an orifice structure.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a simplified structure of a ram cylinder according to the present embodiment, FIG. 2 is an explanatory view showing an extension operation state of a piston rod, and FIG. 3 is an explanatory view showing a contraction operation state of a piston rod. In these figures, reference numeral 1 denotes a ram cylinder. Note that the overall configuration of the ram cylinder is basically the same as the conventional form,
In FIGS. 1 to 3, parts and portions that are the same as or correspond to those in FIGS. 4 and 5 are denoted by the same reference numerals.

As shown in FIG. 1, the ram cylinder 1 according to the present embodiment has a cylinder tube 14 whose both ends are closed by an end plate 12 and a rod plate 13.
And a piston 15 that moves inside the piston, and a piston rod 16 that is inserted through the rod-side end plate 13 and connected to the piston 15. The end-side end plate 12 and the piston 15 An end-side hydraulic chamber 17 is disposed between the rod-side end plate portion 13 and the piston 15.
A rod-side hydraulic chamber 18 is disposed between the two. And
The end-side hydraulic chamber 17 is supplied with pressure oil passing through a hydraulic port 21 attached to the end-side end plate portion 12. The rod 16, that is, the piston rod 16 that supports a load, such as a fork or a lifting mast, is to be extended.

A narrow slit 19 opening toward the rod-side hydraulic chamber 18 is provided between the piston 15 and the piston rod 16. For example, six pressure oil flow paths 2 are formed after selecting equal positions on the concentric circle of the piston 15. Therefore, each of these pressure oil flow paths 2 is connected to the end-side hydraulic chamber 1 through the slit 19.
7 and the rod side hydraulic chamber 18 are mutually connected and connected.

Further, the flow of the pressure oil from the end-side hydraulic chamber 17 to the rod-side hydraulic chamber 18 is free in one of the pressure oil flow paths 2a of the pressure oil The spherical body 3 that blocks the flow of the pressure oil from the side hydraulic chamber 18 to the end-side hydraulic chamber 17, that is, the spherical body 3 that functions as a check valve (check valve) can move in the vertical direction. It is decorated in the state. The inflow port of the pressure oil flow path 2a in which the spherical body 3 is housed is always opened at a position where it is connected to and communicates with the end side hydraulic chamber 17, while the outflow port is used for the contraction operation of the piston rod 16. The position at which the side surface 15a of the piston 15 that has started moving with the rod 15 comes into contact with the rod-side hydraulic chamber 19 at the same time that the side surface 15a comes into contact with the rod-side hydraulic chamber 19, specifically, the side surface 15a of the piston 15 The position on the side surface 15a closest to the end side hydraulic chamber 17 is selected and opened.

In this embodiment, the spherical body 3 is provided for one pressure oil flow path 2a. However, the invention is not limited to only one pressure oil flow path 2a. It is a matter of course that the spherical body 3 may be provided inside the passage 2 after forming the pressure oil passage 2a. Further, a pressure oil flow path 22 having an orifice structure similar to that of the related art is also formed in the rod-side end plate portion 13 that seals the rod-side opening of the cylinder tube 14 provided in the ram cylinder 1. In addition, the pressure oil flow path 22 connects the pressure oil flow path 2 of the piston 15 and the rod-side hydraulic chamber 18 to each other through a slit 19.

Next, the operation of the ram cylinder 1 according to the present embodiment will be described with reference to FIGS. That is, when the pressure oil that has passed through the hydraulic port 21 is supplied into the end-side hydraulic chamber 17 of the cylinder tube 14 provided in the ram cylinder 1, the piston 15 starts to move upward, and The piston rod 16 supporting a load, such as a fork or a lifting mast, starts to extend simultaneously. While the piston 15 is moving upward in the cylinder tube 14, the pressure oil that has been compressed by the piston 15 and has flowed out of the rod-side hydraulic chamber 18 passes through the slit 19 and the pressure oil flow path 2 of the piston 15. After passing, the end side hydraulic chamber 1
7, the piston rod 16 continues to extend smoothly, and the load supported by the piston rod 16 continues to be lifted.

Further, when the piston rod 16 reaches a point immediately before the end of the extension operation, the slit 19 between the piston 15 and the piston rod 16 is inserted into the rod-side end plate 1.
3 and the rod side hydraulic chamber 18 is hermetically closed. However, in the ram cylinder 1, the pressure oil flow path 22 having the orifice structure is formed by the rod-side end plate 1
As shown in FIG. 2, the pressure oil flowing out of the rod-side hydraulic chamber 18, which is closed immediately before the piston rod 16 completes the extension operation, is Is gradually narrowed down while passing through, and flows into the pressure oil flow path 2, and the pressure oil that has passed through the pressure oil flow path 2 flows into the end side hydraulic chamber 17, so that the generation of an impact is effective. Is prevented. In this case, the spherical body 3 provided inside the pressure oil flow path 2a is
From the rod-side hydraulic chamber 18 to the end-side hydraulic chamber 17 after passing through the pressure-oil flow path 2a. .

On the other hand, when the supply of the pressure oil to the end-side hydraulic chamber 17 is stopped, the weight of the load acts on the piston rod 16 so that the piston rod 16 contracts. 3 starts moving downward in the cylinder tube 14, FIG.
As shown in (a), the side surface 15 a of the piston 15, that is, the side surface 15 a facing the rod-side hydraulic chamber 18 closes the inlet of the pressure oil flow channel 22. However, piston 1
Immediately after the start of the downward movement of the piston 5, the side surface 15a of the piston 15 comes into contact with the rod-side hydraulic chamber 18, as shown in FIG. The outlet of the pressure oil flow passage 2a opened on the top 15a, that is, the outlet of the pressure oil flow passage 2a in which the spherical body 3 is provided, is simultaneously connected to the rod-side hydraulic chamber 18. Therefore, the end side hydraulic chamber 1
The spherical body 3 is pushed up and moved by the pressure oil flowing into the pressure oil flow path 2a from the inside.

When the spherical body 3 in the pressure oil flow path 2a is pushed up, the pressure oil flows from the end side hydraulic chamber 17 into the rod side hydraulic chamber 18 after passing through the pressure oil flow path 2a. And the inside of the rod side hydraulic chamber 18 is
It is filled with pressurized oil without reaching a state close to a vacuum. Therefore, after the piston rod 16 continues the contracting operation, it is formed between the piston 15 and the piston rod 16 and the pressure oil flow path 2 of the piston 15
The slit 19 connected to the rod side hydraulic chamber 1
Even if the opening is made toward 8, the pressurized oil does not erupt, and no large impact or abnormal noise is generated.

In the present embodiment, the ram cylinder 1 is a lifting device used in a cargo-handling vehicle. However, the ram cylinder 1 is not limited to the lifting device, but may be used as a moving device along a horizontal direction. Needless to say, the use destination is not limited to the cargo handling vehicle. In addition,
When the ram cylinder 1 according to the present embodiment is arranged along the horizontal direction, or when there is a possibility that the spherical body 3 may move freely due to the vibration of the cargo handling vehicle even in the vertical direction, the piston 15 It is preferable that the spherical body 3 is pressed and urged by an elastic body such as a coil spring so that the spherical body 3 contained in the pressure oil flow path 2a does not move carelessly.

[0021]

As described above, in the ram cylinder according to the present invention, when the piston moves along with the contraction of the piston rod, the spherical body is formed by the pressure oil flowing from the end side hydraulic chamber. The pressure oil is moved, and after passing through the pressure oil flow path opened with the movement of the spherical body, the pressure oil flows from the end side hydraulic chamber to the rod side hydraulic chamber. Therefore, the inside of the rod-side hydraulic chamber does not become nearly vacuum due to the contraction operation of the piston rod, and the inside is immediately filled with pressure oil, so that it is easy to generate large shocks and abnormal noises Is obtained.

Further, in the ram cylinder according to the present invention, a pressure oil flow path functioning as a cushion when the piston rod extends is formed in the rod-side end plate portion, and the cushion when the piston rod contracts. A pressure oil flow path containing a spherical body for realizing the function is formed for the piston. In other words, these cushion structures have independent structures, and the characteristics of each cushion structure can be individually managed. Therefore, there is also a practical advantage that dimensional accuracy can be easily managed. Secured.

[Brief description of the drawings]

FIG. 1 is a simplified sectional view showing a structure of a ram cylinder according to the present embodiment.

FIG. 2 is an explanatory view showing an extension operation state of a piston rod provided in the ram cylinder according to the present embodiment.

FIG. 3 is an explanatory diagram showing a contracting operation state of a piston rod provided in the ram cylinder according to the present embodiment.

FIG. 4 is a cross-sectional view showing a simplified structure of a ram cylinder according to a conventional embodiment.

FIG. 5 is an explanatory view showing a contracting operation state of a piston rod provided in a ram cylinder according to a conventional embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Ram cylinder 2 Pressure oil flow path 2a Pressure oil flow path 3 Spherical body 12 End side end plate part 13 Rod side end plate part 15 Piston 17 End side hydraulic chamber 18 Rod side hydraulic chamber

Claims (3)

[Claims] 1. A cylinder tube having both ends open and closed by an end-side end plate portion and a rod-side end plate portion, a piston moving in the cylinder tube, and a piston connected through the rod-side end plate portion. And a ram cylinder configured to extend the piston rod as pressure oil is supplied to the end-side hydraulic chamber disposed between the end-side end plate and the piston. The piston is formed with a plurality of pressure oil flow paths that connect and connect the rod-side hydraulic chamber and the end-side hydraulic chamber disposed between the rod-side end plate portion and the piston. In the at least one pressure oil flow path, the flow of pressure oil from the end side hydraulic chamber to the rod side hydraulic chamber is free while the flow of pressure oil from the rod side hydraulic chamber to the end side hydraulic chamber is restricted. Blocking Ram cylinder that spheroids characterized in that it is decorated in a movable state. 2. The inflow port of the pressure oil flow path in which the spherical body is provided is always opened at a position where it is in communication with the end side hydraulic chamber, while the outflow port is connected to the contraction operation of the piston rod. The side surface of the piston that has started to move and contacts with the rod-side hydraulic chamber is opened at the same time as the position on the side surface that is connected to and connected to the rod-side hydraulic chamber is selected. The ram cylinder described in. 3. A rod-side end plate is formed with a pressure-oil passage connecting a pressure-oil passage formed in the piston and the rod-side hydraulic chamber, and the pressure-oil passage is provided with an orifice. 3. The ram cylinder according to claim 1, wherein the ram cylinder has a structure.