JPH0619199B2 - Dashiyu Pot - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dash pot that utilizes flow pressure loss, and more particularly to a dash pot structure that requires high accuracy in the stroke dependence of piston resistance.

BACKGROUND OF THE INVENTION Examples of installing a dashpot for the purpose of preventing a water hammer phenomenon by suppressing a rapid operation of a valve body are widely used inside a check valve incorporated in a piping system. Known, for example, RS Care and SMM
Chiyo "Hydroistic Performance of Chilting Disk Ticks Buffbus" American Society Civil Engineering 102,
1 (1976) [RSKare and SMCho. “Hydraulic Performance of Tilting Disk Ckeck Valv
es ", Am. Soc. Civil. Eng. 102, 1 (1976)], shows an example of use in the primary main cooling system piping of the fast breeder test reactor FFTF in the United States.

The basic structure in these examples of use is shown in FIG. In FIG. 2, a valve pig 2 is attached to an upper portion of a casing 1, and a valve body 3 is rotatably supported on the valve pig. The flow direction of the fluid flowing through the casing 1 is normally as shown by the arrow in FIG. 2, and the valve body 3 is maintained at the opening degree by the fluid force. When the flow is stopped and the back pressure is applied to the valve body 3, the valve body 3 is pressed against the valve seat of the casing 1 and the check performance is obtained. At this time, the arm 4 attached to the valve body 3 presses against the head of the piston 6 incorporated in the dump rod cylinder 5, so that a reaction force is generated between the arm 4 and the piston 6. ,
As a result, the depressing force acts on the rotational movement until the valve body 3 closes the valve seat, and the occurrence of the water hammer phenomenon due to the rapid valve closing is prevented.

FIG. 3 shows a structural diagram of the dust pot. Piston 6
Is supported by the cover 7 and the cylinder 5 and slides in the axial direction. Piston rings 8 and 9 are attached to the sliding surface to reduce fluid leakage from the sliding portion.
The inside of the cylinder 5 is divided into a low pressure chamber 10 and a high pressure chamber 11 by the piston cylinders 8 and 9. When the pushing force is applied to the piston 6 and the piston 6 is displaced in the direction of the arrow in FIG.
The fluid is sucked from the inflow port 12 provided on the circumference of. On the other hand, the internal fluid of the high pressure chamber 11 is
After passing through the communication port 13 provided in the lower part of the piston 6 to the hollow portion of the piston 6, passing through the orifice 14 provided inside the piston 6, it is finally discharged to the outside. At this time, the internal pressure of the high-pressure chamber 11 becomes a positive pressure corresponding to the pressure loss of the orifice 14, and as a result, a reaction force against the pushing is generated in the piston 6, and the rotational movement of the valve body 3 of the check valve is suppressed. Has the effect of However, the fact that a sudden reaction force is generated at the same time as the operation of the piston 6 is caused by the arm 4 of the valve body 3
Since a violent collision occurs between the heads of the pistons 6, it is not preferable in terms of soundness of the structure. Therefore, a buffer orifice 15 is provided on the circumference of the cylinder 5 to promote the discharge of fluid from the high pressure chamber 11 and prevent a large reaction force from being generated by the orifice 14 at the same time when the piston 6 starts operating. . At this time, as the piston 6 advances, the piston rings 8 and 9 pass through the opening of the buffer orifice 15, and thereafter, the high pressure chamber 1
Since the fluid No. 1 is not discharged from the buffer orifice 15, it will flow out exclusively through the orifice 14.
The reaction force increases from that point.

However, in the structure as described above, in the region before and after the piston rings 8 and 9 pass through the buffer orifice 15, the pressure side chamber of the fluid passing through the buffer orifice 15 becomes complicated due to its relative positional relationship. Since there is a possibility of displacement, there is a problem that it is difficult to accurately predict the transient change of the reaction force generated in the piston 6 and keep the characteristics within an appropriate accuracy.

[Object of the Invention]

An object of the present invention is to provide a dump pot in which a reaction force generated is transiently changed, and the reaction force transits to a sharp state so that a low reaction force region and a high reaction force region can be clearly distinguished. To do.

[Outline of Invention]

FIG. 3 shows the transient transition characteristics of the piston reaction force with the progress of the piston 6 regarding the dump point shown in FIG. 2 and the mutual positional relationship between the piston 6, the piston rings 8 and 9, and the buffer orifice 15. Shown with.

In FIG. 3, the horizontal axis represents the stroke of the piston 6, and the vertical axis represents the reaction force generated in the piston 6. From this figure,
It can be seen that the reaction force of the piston 6 is divided into two parts, a low range and a high range, depending on the stroke. That is, as described in the explanation of FIG. 2, the low region is a region where the internal fluid of the high pressure chamber 11 is discharged from both the buffer orifice 15 and the orifice 14 inside the piston 6, and the high region is As the stroke progresses, the buffer orifice 15 is closed by the piston rings 8 and 9, and the internal fluid of the high-pressure chamber 11 is discharged exclusively from the orophus 14.

The situation of the reaction force transition will be sequentially described below. In a region before the front edge of the piston 6 reaches the buffer orifice 15, a relatively low reaction force is kept constant. When the leading edge of the piston 6 reaches the trailing edge of the buffer orifice 15, the reaction force starts to increase as shown by in FIG. Since the fitting tolerance between the piston 6 and the cylinder 5 is small, the piston ring 8 passes through the buffer orifice 15 even before the piston ring 8 reaches the buffer orifice 15 as shown in FIG. The flowing fluid is
This is because the pressure loss occurs when passing through the gap between the piston 6 and the cylinder 5, and that amount contributes to the reaction force of the piston 6.

After that, the increase of the reaction force is as shown in in FIG.
Continue until the leading edge of the piston ring 8 reaches the leading edge of the cylinder orifice 15.

That is, the region from to in FIG. 3 is a region where the reaction force transits, and if the stroke range of this region is narrowed, a sharp transition characteristic can be obtained.

However, it can be seen that the reaction force of the piston 6 gradually increases even in the region after the point in FIG. This means that there is leakage of fluid between the piston rings 8 and 9 and the inner wall surface of the cylinder 5 even in the region after the point, and the leaked fluid flows out from the buffer orifice 15. At this time, the pressure loss of the fluid increases as the distance from the front edge of the piston 6 to the buffer orifice 15, that is, the aircraft that the fluid should pass through before it flows out from the buffer orifice 15, becomes longer. Therefore, it is considered that the reaction force of the pushstone 6 gradually increases as the stroke progresses. Therefore, in order to eliminate this man-made tendency and flatten the characteristics in the high reaction force region, the pressure loss of the fluid leaking through the gap between the piston 6 and the cylinder 5 increases as the stroke progresses. Take measures not to do so, namely the piston ring 8
It is important that the amount of leakage from 9 and 9 remains constant and does not decrease.

The present invention embodies the above measures and reflects them in the structure.

Example of Invention

An embodiment of the present invention will be described below with reference to FIG. Fourth
The figure is a detailed view of the piston 6, and the piston rings 8 and 9 are attached to the sliding surface of the piston 6 by cutting a groove.
At the front edge of the sliding surface of the piston 6, the buffer orifice 1
A notch is provided in accordance with the position of 5. Therefore, the transitional region corresponding to ~ in FIG. 3 does not exist because the front edge of the piston 6 is cut out, and a sharp transition characteristic can be obtained.

Next, another embodiment of the present invention will be described with reference to FIG. Fifth
The figure is a detailed view of the piston 6 and the cylinder 5 and the buffer orifice 15 around it. In this embodiment, the third
In order to narrow the stroke range of the region (1) to (4) in the figure, the buffer orifice is formed into a slit shape 17. However, since only the slit shape 17 is structurally unfulfilled, the outer surface side of the cylinder 5 is similar to that shown in FIG.
A small hole is left on the circumference of the cylinder 5. When the slit shape 17 is used as the buffer aurifoss 15 as in this example, not only is the width of the transition region narrowed to provide sharp characteristics, but processing using a lathe is also possible. This has the effect of improving the positional accuracy in the cylinder axis direction.

Next, still another embodiment of the present invention will be described with reference to FIG. FIG. 6 is a detailed view of the piston 6, the cylinder 5 around it, and the buffer orifice 15. In this embodiment, the inner surface of the cylinder 5 after the buffer orifice 15 is formed into a taper shape 18 in order to make the characteristic of the reaction force after that in FIG. When the taper shape 18 is adopted, as the stroke progresses,
Since the inner diameter of the cylinder 5 increases, the contact surface pressure of the piston rings 8 and 9 against the inner surface of the cylinder 5 decreases.
As a result, the amount of leakage from the piston rings 8 and 9 gradually increases as the stroke progresses, so that the pressure loss of the fluid is kept constant by subtraction and the reaction force characteristic is flattened.

Next, still another embodiment of the present invention will be described with reference to FIG. In this embodiment, in order to make the characteristic of the reaction force after that in FIG. 3 a flat characteristic that does not gradually increase, the number increases on the inner surface of the cylinder 5 after the buffer orifice 15 as the stroke progresses. As shown in FIG.
When the grooves 19 are provided, the amount of leakage from the piston cylinders 8 and 9 increases, and the amount increases with the number of the grooves 19, so that the pressure loss of the fluid is kept constant by subtraction. The pressure characteristic has the effect of becoming flat.

〔The invention's effect〕

According to the first embodiment of the present invention, since there is no effect of pressure loss of fluid due to the fitting structure from the piston leading edge to the piston ring, the sharpening determined only by the relative position of the piston ring and the buffer orifice. There is an effect that various characteristics can be obtained.

According to the second embodiment of the present invention, since the width of the buffer orifice can be reduced by the slit shape, the stroke distance that the piston ring passes on the buffer orifice is shortened, so that the sharp characteristic can be obtained. is there.

According to the third embodiment of the present invention, since the contact surface pressure of the piston ring gradually decreases with the stroke due to the taper structure of the inner surface of the piston, there is an effect that the reaction force characteristic becomes constant subtraction.

According to the fourth embodiment of the present invention, since the amount of leakage from the piston ring increases due to the groove processing in which the number of piston inner surfaces gradually increases, there is an effect that the reaction force characteristic becomes constant subtraction.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a check valve incorporating a dump port,
FIG. 2 is a cross-sectional view of the dump pot, FIG. 3 is a relationship diagram of the stroke of the dump pot and the reaction force of the piston, and FIGS. 4 to 7 are cross-sectional views around the piston of the dump pot. 1 ... Casing, 2 ... Valve pig, 3 ... Valve body, 4 ...
Arm, 5 ... Cylinder, 6 ... Piston, 7 ... Cover, 8 ... Piston ring, 9 ... Piston ring, 1
0 ... Low pressure chamber, 11 ... High pressure chamber, 12 ... Inlet port, 13
...... Communication opening, 14 ...... Olihuis, 15 ...... Butfu Aorifuisu, 16 ...... Notch, 17 ...... Slit, 18 ......
Taper, 19 ... Groove.

Claims (4)

[Claims] Claim: What is claimed is: 1. A piston having an orifice for causing flow resistance therein, a cylinder for supporting the piston via a piston ring attached to the piston, and a wall of the cylinder closed along with sliding of the piston. A tashpot made of a buffer orifice, characterized in that a notch is provided at the front edge of the piston that supports the piston ring. 2. The dashpot according to claim 1, wherein the shape of the buffer orifice provided on the cylinder wall surface is a slit shape on the cylinder inner surface side, and the cylinder outer surface side is a small hole contacting the outside of the slit. Dash pot with a shape. 3. The dashpot according to claim 1, wherein the cylinder sliding surface behind the buffer orifice provided in the middle of the stroke of the piston has a taper structure, and the inner diameter of the cylinder sliding portion is closer to the rear end of the stroke. Datsuyupot characterized by increasing the. 4. A dashpot according to claim 1, wherein a groove gradually increasing in number is provided on the cylinder sliding surface rearward of the buffer orifice provided in the middle of the stroke of the piston. Datsuyu pot.