JP3918227B2 - Backflow prevention type water drain valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backflow prevention type water drain valve, and more particularly to a water drain valve that further ensures backflow prevention.
[0002]
[Prior art]
Conventionally, this type of drain valve has been easily repaired and inspected, such as those in which a backflow prevention valve is accommodated in the inlet and outlet of the valve box or Japanese Patent Application No. 6-79480 by the same applicant. Various types have been used, such as one in which a backflow prevention valve pressed by a spring is attached to the small diameter portion of the piston. However, in the case of the above, there is no means to prevent backflow when the packing of the backflow prevention valve is damaged or foreign matter is caught in the packing, especially for directly connected water supply. There was a problem with reliability to use as.
[0003]
[Problems to be solved by the invention]
Therefore, an object of the present invention is to provide a more reliable backflow prevention type drain valve that is less likely to cause backflow even if the packing is damaged.
[0004]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a piston having a communication path extending from the inlet side upstream of the backflow prevention valve to the drain port, and a large-diameter sliding surface on the inlet side in the middle of the piston. Has a drain valve seat with a small diameter, and forms a drainage chamber that communicates with the outflow port through a lateral introduction hole. The drainage chamber is fitted inside the sliding surface and the drain valve seat is closed. If a negative pressure is generated due to water breakage or the like on the main side, the drain valve opens the drain valve seat due to the outflow side pressure due to the area difference between the sliding surface and the drain valve seat. In addition, the water in the outlet side pipe can be discharged from the drain port.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment, an example is shown in which a backflow prevention valve is mounted on the piston, but this can also be accommodated in the outlet as in Japanese Utility Model Publication No. 60-5310 in the same application.
[0006]
Although the piston is lowered to be drained, the reverse flow prevention valve can also have a water stop function by raising the piston and draining it.
[0007]
Instead of moving the operating rod up and down with a screw, it can be moved up and down with a cam, a lever, etc. to reduce the number of rotations of the handle, and it can be electrically operated remotely using a motor. If a check valve that prevents the backflow of sewage from the ground is installed at the drain, it can also be used as a valve box for an antifreeze hydrant.
[0008]
【Example】
The embodiment will be described with reference to the drawings. In FIG. 1, reference numeral 1 denotes a valve box, which has an inlet 2 and an outlet 3 on a side wall, and a drain outlet 4 on a lower end. Inside, the cylinder 5 is formed above the inflow port 2, the cylinder 6 is formed between the inflow port 2 and the outflow port 3, and the cylinder 7 is formed coaxially between the outflow port 3 and the drainage port 4.
[0009]
An operation unit body 8 is connected and fixed to the upper end, and an operation rod 10 having an operating male screw 9 is accommodated therein. A piston 11 is rotatably connected to the lower end of the operation rod 10, and a handle 12 is attached to the upper end. Install.
[0010]
The piston 11 is fitted with annular packings 13, 14, and 15 that slide on the cylinders 5, 6, and 7, respectively, and a small-diameter portion 16 formed between the annular packings 14 and 15 has an outer check packing 17 and an inner packing. While installing the check packing 18, a check valve body 20 pressed upward by the spring 19 is provided to form a check valve 21. The outer non-return packing 17 and the inner non-return packing 18 use a one-way sealable packing having a Y-shaped cross section so as to make the sliding resistance as small as possible.
[0011]
A communication passage 22 extending from between the annular packing 14 and the backflow prevention valve 21 to the drainage port 4 is bored in the piston 11, and is connected to the outflow port 3 through the introduction hole 23 in the middle thereof, and has a large diameter on the internal inflow port side. A drainage chamber 26 having a small-diameter drainage valve seat 25 is formed on the drainage port side, and an upper annular packing 27 having a Y-shaped cross section that is in close contact with the sliding surface 24 and a lower end thereof. A drain valve 29 to which a drain packing 28 that is in close contact with the drain valve seat 25 is mounted is accommodated. Reference numeral 30 denotes a protrusion that serves as a stopper when the piston 11 is lowered.
[0012]
The figure shows a state in which the faucet at the end of the downstream side pipe is closed, that is, a water stoppage state. When the faucet is opened in this state, water from the inflow port 2 compresses the spring 19 to check the valve body. 20 is pushed down, and flows out from the outflow port 3 through the gap between the cylinder 6 and the small diameter portion 16 to an outflow side pipe (not shown). At this time, the annular packings 13 and 15 are in close contact with the cylinders 5 and 7 and the drainage packing 28 is in close contact with the drainage valve seat 25, so there is no outflow to other places.
[0013]
When negative pressure is generated due to water breakage or the like on the main pipe side in the water flow state, the check valve body 20 immediately rises due to the restoring force of the spring 19, and the inner check gasket 18 is placed on the small diameter portion 16 on the outer check. The packing 17 is in close contact with the cylinder 6 to prevent backflow, but at the same time, the inside of the communication path 22 is also in a negative pressure state, so that the drain valve 29 is introduced into the introduction hole 23 due to the area difference between the sliding surface 24 and the drain valve seat 25. The drainage packing 28 is separated from the drainage valve seat 25 and discharges the water in the outflow side pipe from the drainage port 4. Of course, at this time, the water in the outflow side pipe does not flow back to the inlet 2 side by the upper annular packing 27. That is, the backflow toward the main pipe can be effectively prevented even when foreign matter is caught or damaged in the check packings 17 and 18. When the negative pressure state is eliminated, the drain valve 30 receives the pressure water from the communication passage 22 and closes the drain valve seat 25 again.
[0014]
Next, when draining water in the pipe in winter, the handle 12 may be rotated from the state shown in the figure, and the operating rod 10 is lowered while being rotated by the operating male screw 9, and the piston 11 is rotated accordingly. First, the annular packing 14 comes into close contact with the cylinder 6 to block water from the inlet 2. Thereafter, the annular packing 15 is detached from the cylinder 7 and further descends so that the lower end of the piston 11 comes into contact with the protrusion 30 to stop the descending, and the water in the outflow side pipe passes through the gap between the cylinder 7 and the outer periphery of the piston 11. Since the water is discharged from the drain port 4 and the inside of the pipe is emptied, freezing is prevented.
[0015]
In winter, when the water is forgotten to drop and the inside of the pipe freezes and an abnormal pressure is generated, the backflow prevention valve 21 prevents the abnormal pressure from escaping to the main pipe, resulting in damage to the pipe. However, in this embodiment, the pressure in the outflow side pipe increased, and the force to lift the drain valve 29 overcome the force to lower the drain valve on the inlet 2 side. At that time, the drainage packing 28 is detached from the drainage valve seat 25 and the abnormal pressure is released to the drainage port 4, so that the above-mentioned accident does not occur.
[0016]
FIG. 2 shows another embodiment of the drainage valve of the present invention. The drainage valve 29 has upper and lower packings 27 and 28 provided with the same O-rings at the upper and lower ends. However, this may be mounted on the piston side (in this case, the O-ring serves as a valve seat), and in some cases, the upper annular packing 27 can be omitted.
[0017]
【The invention's effect】
As described above, in the drain valve of the present invention, when negative pressure is generated on the main pipe side, the drain valve opens, and the water in the outflow side pipe is discharged to the drain port. Even in the case of damage, the possibility that sewage will be sucked into the main pipe will be reduced, and the reliability will be improved. It also has the advantage that it can be prevented from being damaged.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view in a water stop state showing an embodiment of the present invention.
FIG. 2 is a longitudinal sectional view of an essential part showing another embodiment of the drain valve of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Valve box 2 Inlet 3 Outlet 4 Drain outlet 5, 6, 7 Cylinder 8 Operation part main body 9 Actuation male screw 10 Operation rod 11 Piston 12 Handle 13, 14, 15 Annular packing 16 Small diameter part 17 Outer non-return packing 18 Inner check packing 19 Spring 20 Check valve body 21 Check valve 22 Communication passage 23 Introduction hole 24 Sliding surface 25 Drain valve seat 26 Drain chamber 27 Upper annular packing 28 Drain packing 29 Drain valve 30 Protrusion

Claims (1)

In the drain valve where the piston moves up and down, the stop valve is located in the valve box that houses the backflow prevention valve inside the inlet and outlet, and the drain outlet at the lower end. Open a communication path from the inlet side upstream of the backflow prevention valve to the drainage port, and in the middle of it, have a large-diameter sliding surface on the inlet side and a small-diameter drainage valve seat on the drainage side. A backflow prevention type drainage valve comprising a drainage chamber which is connected to an outlet through an introduction hole, and a drainage valve which fits the sliding surface and closes the drainage valve seat therein.

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