JPH1151207A - Gate valve provided with intake or exhaust function - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of cavitation during a throttle operation in which a valve body is held at a small opening by perforating a vent hole in the wall part of a valve casing for a gate valve, which is opened and closed according to a forward/ backward movement of a valve element, connecting a vent pipe to the inlet of the vent hole, and arranging an intake or exhaust means in the inlet of the vent pipe. SOLUTION: In a lower half part in the just downstream position of a valve element seat in a wall part 2a of a valve casing 2, a plurality of intake holes 7 are perforated at equal intervals in the circumference direction, and intake pipes 8 are connected to the inlets of the intake holes 7. An intake means such as an air valve is arranged so as to be connected to the inlet of the intake pipe 8. During a throttle operation in which a valve element 1 is held at a small opening, a flow rate of water is increased in a contraction flow part, in which a passage cross section is shrunk, so that a pressure is lowered. Then, according to the pressure reduction, an intake valve serving as an intake means is opened, and air is sucked into a valve casing 2 through the intake pipes 8 and the intake holes 7, so that pressure is prevented from lowering below a vapor pressure at a water temperature at that time, and consequently, generation of cavitation can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gate valve having an intake or air supply function.

[0002]

2. Description of the Related Art As shown in FIGS. 4 and 5, a gate valve is mounted on a valve stem 3 having an axis C2 intersecting with an axis C1 of a valve box 2, and an axis of the valve stem 3 is provided. The valve body 2 is accommodated in the valve box 2 so as to be able to move up and down (movable forward and backward) in the direction C2.
The valve body sheet 4 of the valve body 1 comes into contact with and separates from the valve box sheet 5 on the inner surface of the valve box 2 to open and close. Note that the valve body 1 may be configured to move up and down together with the valve stem 3.

In a gate valve configured as described above, usually,
The valve body 1 is used while being held in a fully open state where the valve body 1 is raised from a fully closed position shown in FIG. 4 to a position shown in FIG. 5 and a fully closed state where the valve body 1 is lowered from this fully open position to a position shown in FIG.

However, as shown by the imaginary line in FIG. 5, when the valve element 1 is used in the throttle operation with the opening kept small, the flow velocity of the water increases in the contraction section 6 in which the passage cross-sectional area is reduced. To reduce pressure. When the pressure falls below the vapor pressure at the water temperature at that time, the water evaporates or the dissolved air in the water separates to generate bubbles (cavitation), and the bubbles are crushed and disappear on the downstream side where the pressure recovers In addition to generating noise and vibrations, if such a condition continues, the parts exposed to cavitation (the inner surface of the pipe wall)
Specific cavitation erosion will occur.

[0005]

That is, in the conventional gate valve, by performing the throttle operation with the valve body kept at a small opening, noise, vibration, cavitation erosion, etc. occur due to the occurrence of cavitation. Limited use in driving.

Accordingly, an object of the present invention is to provide a gate valve having an intake function capable of preventing cavitation even when used in a throttle operation in which a valve body is held at a small opening.

[0007]

In order to achieve the above-mentioned object, the present invention provides a valve element which is mounted on a valve stem having an axis intersecting the axis of a valve box, and which is movable in the axial direction of the valve stem. In a gate valve housed in a valve box and configured to open and close by moving a valve body forward and backward, a ventilation hole is provided through a wall of the valve box, and a ventilation pipe is connected to an inlet of the ventilation hole. And an air intake or air supply means communicating with the inlet of the ventilation pipe is provided.

According to the present invention, when the valve is used in the throttle operation in which the valve body is kept at a small opening, the flow rate in the contraction section is increased, and the pressure is reduced. Air is introduced into the valve box from the vent pipe and the route of the vent hole,
By preventing the pressure from falling below the vapor pressure at the water temperature at that time, it is possible to suppress the occurrence of cavitation.
Since bubbles generated by the introduction of air do not disappear on the downstream side, there is no occurrence of noise, vibration, or erosion of the inner surface of the tube wall. On the other hand, when the valve body is held at the full opening position or at a large opening near the full opening position, the operation of the intake or air supply means is stopped, so that the ventilation pipe, the passage of the ventilation hole into the valve box. The introduction of air is stopped, and the liquid passing through the valve box can be prevented from leaking outside from the vent through the vent pipe.

[0009]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view showing an embodiment of a butterfly valve according to the present invention, and FIG. 2 is a half sectional longitudinal front view. The same or corresponding parts as those in the conventional example shown in FIGS. 4 and 5 are denoted by the same reference numerals and described. FIG.
In FIG. 2 and FIG. 2, the gate valve is attached to a valve stem 3 having an axis C2 intersecting the axis C1 of the valve box 2 so that the valve body 1 can move up and down in the direction of the axis C2 of the valve stem 3 (movable forward and backward). The valve body sheet 4 of the valve body 1 is configured to be brought into contact with and separated from a valve box sheet 5 on the inner surface of the valve box 2 to open and close by opening and closing the valve body 1.

In the lower half of the wall 2A of the valve box 2 immediately downstream of the valve body sheet 4, a plurality of intake holes 7, 7... An intake pipe 8 is connected to an inlet of the intake pipe 7, and an intake means 9 formed by, for example, an air valve is provided in communication with the inlet of the intake pipe 8.

In the above-mentioned configuration, the gate valve is usually
In the same manner as in the conventional example described with reference to FIG. 5, the valve body 1 is raised from the fully closed position shown in FIG. 1 to the position shown in FIG. 2, and is lowered from this fully open position to the position shown in FIG. Used in the fully closed state.

Now, as shown in FIG. 3, when the valve element 1 is used in a throttle operation in which the valve body 1 is kept at a small opening degree, in the contraction section 6 having a reduced passage cross-sectional area, the flow rate of water increases and the pressure decreases. Lower. Along with this pressure drop, a well-known air valve constituting the intake means 9 is opened, and air is sucked into the valve box 2 through a path from the intake pipe 8 to the plurality of intake holes 7, 7,. Can be prevented from becoming lower than the vapor pressure at the water temperature, and the occurrence of cavitation can be suppressed. In addition, since the air bubbles generated by the intake air do not disappear on the downstream side, there is no occurrence of noise, vibration, erosion of the inner surface of the tube wall, or the like. Further, when the valve element 1 is held at the full open position shown in FIG. 1 or at a large opening degree in the vicinity thereof, the well-known air valve constituting the intake means 9 is closed, so that the intake means 9 The operation can be stopped, and the water passing through the valve box 1 can be prevented from leaking to the outside.

In the above-described embodiment, the intake holes 7, 7... Are provided through the wall 2A of the valve box 2, and the intake pipes 8 are connected to the inlets of the intake holes 7, 7,. Although the description has been given of the configuration in which the intake means 9 constituted by an air valve is provided in communication with the inlet of the intake pipe 8, air supply means such as a blower is provided in communication with the inlet of the intake pipe 8 instead of the intake means 9. , The intake pipe 8 functions as an air supply pipe,
Can function as air supply holes, the same operation and effect as in the above embodiment can be achieved.

[0014]

As described above, the present invention can suppress the occurrence of cavitation even when used in a throttle operation in which the valve body is held at a small opening. Therefore, noise, vibration, erosion of the inner surface of the tube wall, and the like do not occur.
In other words, even if the valve is used for operation with a small opening,
There is no inconvenience.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an embodiment of a gate valve according to the present invention.

FIG. 2 is a half sectional front view.

FIG. 3 is a vertical side view showing a state in which the gate valve of the present invention is held at a small opening.

FIG. 4 is a longitudinal sectional side view of a conventional example.

FIG. 5 is a vertical sectional side view showing a state in which a conventional gate valve is held at a fully opened state and a small opening degree.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Valve body 2 Valve box 2A Wall part of valve box 3 Valve rod 7 Intake hole (vent) 8 Intake pipe (vent pipe) 9 Intake means (intake or air supply means) C1 Axis of valve box C2 Axis of valve stem

Claims (1)

[Claims] A valve body is mounted on a valve stem having an axis intersecting with the axis of a valve box. The valve body is housed in a valve box movably in the axial direction of the valve stem. In the gate valve configured as described above, a ventilation hole is provided through the wall of the valve box, and a ventilation pipe is connected to an entrance of the ventilation hole, and intake or air supply communicating with the entrance of the ventilation pipe is provided. A gate valve having an intake or air supply function, characterized in that a means is provided.