JPH03186693A - Liquid inflow-preventing plug and mounting device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention is directed to, for example, when lining a buried pipe such as a sewer pipe with synthetic resin, a branch pipe branched from the buried pipe is connected to the buried pipe. The present invention relates to a predetermined liquid inflow prevention stopper that prevents liquid from flowing into the branch pipe or the buried main pipe at a communicating end thereof, and a liquid inflow prevention stopper attachment device used for mounting the liquid inflow prevention stopper.

(Prior Art) Metal pipes and humid pipes have been used for a long time as buried pipes used for water supply and sewerage systems.

Such buried pipes become obsolete due to long-term use, and there is a risk of damage due to corrosion, cracks, etc., resulting in water leakage. For this reason, recently, a synthetic resin type pipe is inserted into an aged buried pipe and the inner circumferential surface of the buried pipe is lined with the synthetic resin pipe.

Usually, a main underground pipe such as a sewer pipe has many branch pipes branching off, and sewage and the like flow into the main pipe from each branch pipe. For this reason, in the method of lining the main pipe with synthetic resin pipes as described above, the communication area between each branch pipe and the main pipe is sealed to prevent sewage, etc. flowing from each branch pipe from flowing into the main pipe. For example, Japanese Patent Application Laid-Open No. 61-38031
The publication discloses a method for stopping water in each branch pipe with a water stop valve using a rubber stopper, and a device for attaching the water stop valve to the branch pipe.

(Problem to be Solved by the Invention) However, when each branch pipe is water-stopped with a rubber stopper or the like, pressure from sewage or the like flowing through the branch pipe is applied to the rubber stopper. Main pipes lined with synthetic resin pipes are usually
Because it is buried at a depth of approximately 93 m below the ground surface, the stop valve installed in the branch pipe can hold up to 0.3 kg-f/
Water pressure of about am2 is applied. Therefore, a force is applied to the stop valve in the direction of pulling it out from the end of the branch pipe into the main pipe, and a part of the stop valve comes out of the branch pipe and protrudes into the main pipe. Or, in extreme cases, the stopcock may completely come off the branch pipe.

Further, when lining the main pipe with a synthetic resin pipe, a backfilling agent is filled between the main pipe and the synthetic resin pipe lining the main pipe. The backfilling agent is usually O,Skg
- Because it is filled with a pressure of about f/cm2, the water stop valve attached to the end of the branch pipe is forced into the branch pipe by a backfilling agent, contrary to the pressure of sewage, etc., which is being stopped. There is a risk that the force will be applied and the stopcock may be forced into the branch pipe.

In order to solve such problems, the applicant of the present application proposed in Japanese Patent Application No. 63-235857 that when installed in a branch pipe, sewage, etc. flowing through the branch pipe is only allowed to flow into the main pipe. We have proposed a liquid inflow prevention stopper that has a check valve that allows flow to flow, and a locking plate that locks onto the inner circumferential surface of the main pipe.

However, each branch pipe is not necessarily connected at right angles to the main pipe, but is usually at an angle with respect to the main pipe. Therefore, in the liquid inflow prevention stopper of the above specification, the stopper is approximately perpendicular to the locking plate, so when the stopper is installed in a branch pipe that is inclined with respect to the main pipe. , the locking plate becomes substantially perpendicular to the axis of the branch pipe, and a portion of the locking plate protrudes into the main pipe. If a part of the locking plate protrudes into the main pipe in this way, it will become a hindrance when inserting the synthetic resin pipe into the main pipe, and the synthetic resin pipe may be damaged by the locking plate. Otherwise, the synthetic resin pipe may not be completely inserted into the main pipe. Furthermore, if the locking plate gets caught on the synthetic resin pipe, there is a risk that the stopcock itself may fall off from the branch pipe.

In order to solve such problems, the inventors of the present application have developed a plug body that is fitted into the end of a branch pipe and is pressed into contact with the end of the branch pipe, and a plug body that is fitted into the end of the branch pipe and is attached to the end of the branch pipe. We have developed a liquid inflow prevention stopper that has a locking plate that locks onto the inner circumferential surface of the main pipe, which is the peripheral edge of the opening end of the stopper, and an extendable connecting body that connects the stopper and the locking plate. In this limb inflow prevention stopper, by pushing the stopper body into the inner side of the end of the branch pipe with the locking plate locked to the inner circumferential surface of the main pipe, the connecting body is expanded and locked. The plate is in a locked state in close contact with the inner peripheral surface of the main pipe, and there is no problem when inserting the lining pipe into the main pipe.

However, with such a liquid inflow prevention stopper, it is necessary to push the stopper into the innermost side of the end of the branch pipe while the locking plate is locked to the inner circumferential surface of the main pipe. However, it is not easy to push the stopper inserted into the branch pipe further into the branch pipe.

The present invention solves these problems, and its purpose is to provide a liquid inflow prevention stopper that can be easily and reliably attached to a branch pipe that is inclined with respect to the main pipe. It is in. Another object of the present invention is to provide a liquid inflow prevention stopper that is easy to carry into a main pipe and does not pose a problem when inserting a lining pipe into the main pipe. Still another object of the present invention is to provide a liquid inflow prevention stopper mounting device that can reliably attach the stopper body of the liquid inflow prevention stopper to a predetermined position at the end of a branch pipe from within the main pipe.

(Means for Solving the Problems) The liquid inflow prevention plug of the present invention is a liquid inflow prevention plug that covers the end of a branch pipe branched from a main pipe that communicates with the main pipe, and the liquid inflow prevention plug of the present invention are wound so as to be able to contract and expand in diameter along the inner peripheral surface of the main pipe while overlapping each other, and are large enough to cover the end of the branch pipe, with each side edge being expanded. The plug body is provided with a thin plate-like plug main body having a locking mechanism that locks in a movable state only in the radial direction, thereby achieving the above object.

Further, the liquid inflow prevention stopper mounting device of the present invention is a device for installing such a liquid inflow prevention stopper at a predetermined position in a main pipe, and has a cylindrical outer peripheral surface that is movable in an inward and outward direction. , is fitted into the stopper main body of the liquid inflow prevention stopper whose outer peripheral surface has been moved inward, and the diameter of the stopper main body is expanded by moving the outer circumferential surface outward. The above-mentioned object is achieved.

(Example) The present invention will be described below with reference to Examples.

As shown in FIG. 1, the liquid inflow prevention stopper of the present invention uses a branch pipe 82 that branches from the main pipe 81, for example, when lining the main pipe 81, which is an old sewer pipe, with a synthetic resin pipe.
It is attached to the end communicating with the main pipe 81 at.

As shown in FIGS. 1 and 2, the liquid inflow prevention stopper io of the present invention is constructed by using a thin plate made of, for example, transparent plastic, so that the mJR parts thereof overlap each other along the inner circumferential surface of the main pipe 81. The stopper main body part 11 is wound into a cylindrical shape.

The plug main body 11 has a thin plate shape large enough to cover the end of the branch pipe 82 that communicates with the main pipe 81 . A cylindrical rubbing portion 11a is provided approximately at the center of the stopper body portion 11 so as to protrude outward. The rubbing part 11a, branch pipe 1
It is sized to fit within the end of 1. An opening 11b is formed in the center of the stopper 11a, and a check valve 11c made of, for example, rubber is attached to the inner peripheral surface of the opening 11b to cover the opening 11b. ing. The check valve 11c allows liquid to flow only from the outside into the cylindrical stopper main body 11, and does not allow liquid to flow from the inside of the main body 11 to the outside.

Around the opening 11b on the outer surface of the rubbing part 11a, there is a detected object 1 for a sensor that detects the position of the rubbing part 11a.
2 is provided.

An annular seal member i3 is attached to the outer circumferential surface of the stopper main body 11 at an appropriate distance from the rubbing part 11a and concentrically with the rubbing part 11a. The seal member 13 has a diameter larger than the end opening of the branch pipe 82, and is made of rubber, sponge, or the like.

An engaging member 11d that forms a groove into which the other side is fitted is provided on the inner circumferential surface of each end of one side edge of the cylindrically wound plug body 11. .

The side edges of the cylindrically wound plug main body 11 that overlap each other are such that the overlapping portions are relatively movable only in the diameter expansion direction, and are relatively movable in the diameter contraction direction. A pair of locking mechanisms lie is provided to prevent movement. For example, as shown in FIG. 3, each locking mechanism 11e has a plurality of rectangular holes formed at predetermined intervals in the circumferential direction in a portion located on the outer peripheral side of the mutually overlapping side edges. It has an engaging hole 11f, and one claw portion 11g provided in a portion located on the inner circumferential side so as to protrude outward. The claw K I I g has a thickness that allows it to fit into each engagement hole Iff. The claw portion 11g has a tapered side surface in the direction in which the diameter increases, and each engagement hole t
When a force is applied in the direction of diameter expansion while the claw portion 11g is fitted into the tr, the claw portion 11g comes out of the engagement hole 11f along the tapered surface.

The liquid inflow prevention stopper 10 having such a configuration is used in a lining method for rehabilitating a main pipe 81, which is an old sewer pipe, using, for example, a synthetic resin spiral pipe. In this lining method, the liquid inflow prevention plug 10 is installed in the end of the branch pipe that communicates with the main pipe, prior to the step of inserting the spiral pipe into the main pipe 81.

When installing the liquid inflow prevention plug 10 into the branch pipe, the liquid inflow prevention plug attachment device of the present invention is used.

The liquid inflow prevention stopper attachment device has, for example, as shown in FIG. 4, a drive unit 20 that can move within the main pipe 81 along its axial direction. In the drive section 20, a turning motor 22 is mounted on a sled 21 that slides on the inner peripheral surface of the main pipe 81. A fixing member 23 is provided on the turning motor 22, and is made of, for example, an expandable bag made of rubber. The fixing member 23 is brought into pressure contact with the inner circumferential surface of the main pipe when air is supplied inside and expands, and the rotation motor 22
is fixed at a predetermined position within the main pipe 81.

A horizontal support shaft 31 is attached to the output shaft of the swing motor 22.
The proximal ends of the two are connected. The tip of the support shaft 31 is
The bearing is supported by the body 40. In the bearing body 40, a bearing 42 is provided on a sled 41 that slides on the inner peripheral surface of a main pipe 81, and the tip of the support shaft 31 is rotatably supported by the bearing 42. One end of a towing rope 50 is attached to the bearing body 40, and one end of the towing rope 50 is attached to the body 40.
As a result, the entire liquid inflow prevention stopper attachment device is moved within the main pipe 81.

A pair of cylindrical diameter-enlarging members 32 and 32 are attached to the support shaft 31 at appropriate intervals in the axial direction of the support shaft 31. Each diameter-expanding member 32 is, for example, an annular bag made of rubber, and by injecting air into each diameter-expanding member 32, the diameter-expanding member 32 expands and its outer peripheral surface moves outward. bulges out. The stopper main body portion 11 of the liquid inflow prevention stopper 1O of the present invention described above is installed across both the diameter expanding members 32.

A television camera 33 is installed between the two diameter-enlarging members 32 in order to monitor the state of the stopper body 11 of the liquid inflow prevention stopper 10 installed between both the diameter-enlarging members 32.
It is attached to L.

Cable connected to TV camera 33, each diameter expanding member 3
2 and the fixing member 22 extend from the drive unit 20 in a direction opposite to the pulling direction of the pulling lobe 50.

With the liquid inflow prevention attachment device of the present invention having such a configuration, the liquid inflow prevention plug 10 of the present invention is attached to a portion of the main pipe 81 to which the end of the branch pipe 82 is connected.

First, the liquid inflow prevention stopper IO is installed between each diameter expanding member 32 in the liquid inflow prevention stopper mounting device.

In this case, each expanding diameter member 32 is in a slightly contracted state, and the main body 11 of the liquid inflow prevention plug 10 is placed between both expanding diameter members 32.
is wound so that the frame portion 11a is on the upper side. At this time, the frame portion 11a is in a state facing the television camera 33 located between each of the diameter-expanding members 32. Then, one side edge portion of the main body portion 11 is fitted into the engagement member lid provided on the other side edge portion, and the body portions 11 are overlapped with each other. In this state, the claw portion 11g of each locking mechanism lie is brought into a reduced diameter state in close contact with the outer peripheral surface of each enlarged diameter member 32.
It is locked in a predetermined engagement hole 11f.

Thereby, the stopper main body portion 11 is held in a state where it is wrapped around each enlarged diameter portion 32.

In this state, the liquid inflow prevention plug attachment device is connected to the main pipe 81.
The main pipe 81 is pulled by the pulling lobe 50 and moved to the position where the branch pipe 82 branches. At this time, the position of the branch pipe 82 is confirmed by the TV camera 33 through the transparent plug main body 11 of the liquid inflow prevention plug 10, and the stopper of the liquid inflow prevention plug 10 wrapped around each diameter expanding member 32 is confirmed. The frame portion 11a in the main body portion 11 is
It is located below the end of the branch pipe 82. Next, air is injected into the fixing member 23 of the drive unit 20 to fix the fixing member 23.
expand. As a result, the fixing member 23 is pressed against the inner circumferential surface of the main pipe, and the entire drive section 20 is fixed within the main pipe 81.

When the entire drive unit 20 is fixed within the main pipe 81, the rotation motor in the drive unit 20 is monitored while the television camera 33 monitors the position of the opening of the branch pipe 82 and the frame 11a of the liquid inflow prevention plug 10. 22 to rotate its output shaft in a predetermined direction. As a result, the support shaft 31 is rotated in a predetermined direction, and the enlarged diameter portions 32 and the television camera 33 are rotated.
rotate integrally in a predetermined direction, and the liquid inflow prevention stopper lO attached to each diameter expanding member 32 moves in the circumferential direction with respect to the main pipe 81. Then, the frame portion 1 of the liquid inflow prevention plug lO
The swing motor 22 is driven until the frame portion 1a faces the opening of the branch pipe 82, and the frame portion 11a faces the opening of the branch pipe 82.

In this state, the rotation motor 22 is stopped, and air is injected into each diameter-expanding member 32. Each cylindrical expanding diameter member 32 expands so that its outer peripheral surface expands outward by injecting air into the inside. The plug main body 11 in close contact with the outer circumferential surface of each expanded diameter member 32 is
By expanding the diameter of each diameter-expanding member 32, each locking mechanism 1
The claw portion 11g of 1e is pulled out from the engagement hole 11f and sequentially fitted into the engagement hole 11f adjacent in the diameter expansion direction, thereby expanding the diameter. Then, as the diameter of each diameter-expanding member 32 increases, the main body portion 1
1 is enlarged in diameter, the frame portion 11 of the plug main body portion 11
a is fitted into the end opening of the branch pipe 81,
A sealing member 13 provided on the outer circumferential surface of the stopper main body 11 is in close contact with the inner circumferential surface of the main pipe 81, which is the peripheral edge of the branch pipe 81. At this time, the locking mechanism 11e in the plug body 11
Since the claw portion 11g is fitted into the predetermined engagement hole 11f, there is no risk that the diameter of the plug body portion 11 will be reduced.

In this state, the air in each expanding diameter member 32 and the air in the fixing member 23 in the driving section 20 are removed, and each expanding diameter member 32 and fixing member 23 are contracted.

Plug main body l of liquid inflow prevention plug 10! The locking mechanism lies
Since there is no risk of the diameter being reduced by
is fixed with the frame portion 11a fitted into the end opening of the branch pipe 82 and with the seal member 13 in close contact with the inner circumferential surface of the main pipe 81. Then, each diameter expanding member 32
When the fixing member 23 is contracted, the entire liquid inflow prevention stopper attachment device is pulled by the towing rope 50 and the main pipe 81 is pulled.
will be removed from.

At this time, if sewage is flowing through the branch pipe 82, the sewage flows through the check valve 11 from the opening 11b of the frame 11a.
It flows into the main pipe 81 through c. Therefore, the frame 11
If the check valve lie is provided in the branch pipe 82, the sewage flowing through the branch pipe 81 will not be stopped by the frame 11a installed in the branch pipe 82, and the sewage will not flow into the main pipe into the frame 11a. 81
This is preferable since there is no risk of pressure being applied inward.

In this way, when the liquid inflow prevention stopper lO is installed in the branch pipe 82, the sewage flowing through the branch pipe 82 passes through the check valve 11c of the liquid inflow prevention stopper lO into the main pipe 81. A synthetic resin spiral tube is inserted into the main pipe 81 in a state where the flow is conducted.

The spiral pipe is manufactured by a pipe making machine installed in a manhole to which one end of the main pipe 81 is connected.

Synthetic resin strips are sequentially introduced into the pipe-making machine, and the pipe-making machine spirally winds the introduced strips so that adjacent side edges of the wound strips meet each other. are locked by locking a wire rod between the side edges thereof, thereby manufacturing a spiral tube having a relatively small diameter compared to the inner diameter of the main tube 81. In the band,
Ribs with a T-shaped cross section are formed on the outer circumferential surface of the spiral tube at appropriate intervals along the axis. The spiral pipe manufactured by the pipe manufacturing machine is
It is directly inserted into the main pipe 81.

At this time, the liquid inflow prevention plug 10 attached to the branch pipe is
Since the frame part 11a is fitted into the branch pipe and the main body part 11 is in close contact with the inner circumferential surface of the main pipe via the seal member 13, the spiral pipe inserted into the main pipe does not fit into the main body part 11. It is inserted smoothly into the main pipe without getting caught. Sewage flows into the main pipe through the check valve 11c of the liquid inflow prevention stopper lO attached to the branch pipe, but the sewage is
There is no problem in inserting the spiral pipe into the main pipe. When the spiral pipe is inserted into the main pipe, the sewage that has flowed into the main pipe flows between the main pipe and the inserted spiral pipe.

When the small-diameter helical tube with the wire secured is pushed into the main pipe 81, a tube-making machine installed in the manhole is driven to sequentially feed the strips to the helical tube. The wire rods locked to the helical tube are sequentially removed from the tip of the helical tube. As a result, when the wire rod is removed from the spiral tube, the adjacent side edges of the strip forming the spiral tube are separated from each other.
A propulsive force is applied to the band-shaped body by a pipe-making machine, causing it to slide, and the diameter of the helical tube is gradually expanded from the part where the wire rod is detached. As a result, the spiral tube becomes a lining tube in which the ribs having a T-shaped cross section are in close contact with the inner peripheral surface of the main tube 81.

In this way, when the main pipe 81 is lined with a lining pipe that is in close contact with the inner circumferential surface of the main pipe 81, a sensor for detecting the detected object 12 attached to the liquid inflow prevention plug lO is provided in the lining pipe. A drilling machine is introduced. In the drilling machine, for example, a vertical drill rotated by a motor is attached to the tip of the main body so as to be movable up and down. The drilling machine is operated on the ground surface, and when the sensor attached to the drilling machine detects the detected object 12 attached to the liquid inflow prevention plug 10, the drilling machine is stopped. Then, the tip of the drill is opposed to the approximate center of the branch pipe 82 to which the liquid inflow prevention stopper IO is attached, and the drill is rotated and raised. Thereby, the drill drills a small hole in the lining pipe at a position substantially opposite to the axial center position of the branch pipe 82. The drill drills a small hole only in the lining pipe, and its tip does not come into contact with the liquid inflow prevention plug IO. Once the small hole has been drilled in this way, the drill is removed from the lining tube.

Next, a sealant injection machine is carried into the lining rod. The sealing material injector is run to the position of a small hole in the lining pipe that is bored substantially opposite to the axial center position of the branch pipe 82,
The sealant injection machine is stopped so that the tip of the injection nozzle faces a position near the small hole. In this state, the tip of the injection nozzle is inserted into the small hole, and a sealing material made of, for example, a thermosetting resin is discharged from the tip of the injection nozzle. Thereby, the sealing material is filled between the stopper body 11 of the liquid inflow prevention stopper 10 attached to the branch pipe 82 and the outer peripheral surface of the lining pipe.

Once the sealing material is filled in this way, the sealing material filling machine is carried out from the lining pipe, and after the sealing material has hardened, a hole drilling machine is carried into the lining pipe. Then, the hole drilling machine cuts the periphery of the small hole in the lining pipe to form an opening. At this time, at the same time, the sealing material that has entered and hardened into the frame 11a fitted in the branch pipe 82 of the liquid inflow prevention plug 10 is cut, and the frame 11a is also cut to remove the inside of the lining pipe. The branch pipe 82 is brought into communication via the opening. The opening of the lining pipe and the sealing material are cut along the inner peripheral surface of the branch pipe 82, and the liquid inflow prevention plug 10 is cut into the branch pipe 82.
When the lining tube 10 is removed from the lining tube 10, the area between the periphery of the opening formed in the lining pipe 10 and the periphery of the end face of the branch pipe 82 is sealed by the hardened sealing material.

As a result, the main pipe 81 is lined with a synthetic resin lining pipe, and the lining pipe and the branch pipe 82 communicate with each other while being sealed with a sealing material.

The locking mechanism lie of the liquid inflow prevention stopper 10 is composed of a square-shaped engagement hole 11f formed on one side of the stopper main body 11 and a claw portion 11g. It can also be a hole. Further, as shown in FIG. 5, a large number of serrated engagement grooves 11m are formed in the circumferential direction on the surface of one side edge, and each engagement groove 11m is formed in the engagement member 11n into which the side edge fits. A claw portion IIs that locks the groove 11m1 may be provided. Furthermore, the locking mechanism may be configured with a hook-and-loop fastener that slides in only one direction.

In the above embodiment, the liquid inflow prevention stopper attachment device had a configuration including two diameter-expanding members 32, but the diameter-expanding members 32
It may be one. In this case, the television camera 33
In this case, the bearing may be provided on the body 40. Also,
After the liquid inflow prevention stopper 10 is installed in the main pipe 81, a hole drilling machine for drilling a hole in the lining pipe may be integrally attached to the liquid inflow prevention stopper attachment device.

The diameter expanding member is not limited to a configuration in which it is expanded by air, but may have a configuration as shown in FIGS. 6 and 7, for example. The expanding diameter member 35 includes a cylindrical support member 35a supported concentrically on the support shaft 31, three air cylinders 35b supported by the support member 35a, and each air cylinder 35.
Holding plates 35c attached to the ends of the rods b
It has Each air cylinder 35b has support member 3
At the center of the rod 5a, the tips of the rods are disposed on the outside with equal intervals in the circumferential direction so that the mouths and throats of the rods can move along the radial direction. At the tip of each rod, a holding plate 35c having an arcuate shape forming a concentric cylinder is attached to the support member 35a. Each air cylinder 35b is integrally driven, and each air cylinder 3
By driving 5b, each holding plate 35c moves inward and outward. In this embodiment, components similar to those in the embodiment shown in FIG. 4 are denoted by the same reference numerals, and the description thereof will be omitted.

The stopper main body 11 of the liquid inflow prevention stopper IO is wrapped around each holding plate 35c and carried into the main pipe 81. Then, each air cylinder 35b is integrally driven at a predetermined position within the main pipe 81, and the outer circumferential surface of each holding plate 3Sc moves outward, thereby forming a cylinder formed by each holding plate 35c. is enlarged in diameter, and as a result, the liquid inflow prevention plug 1
0 is installed in the main pipe 81.

(Effects of the Invention) As described above, the liquid inflow prevention stopper for a branch pipe of the present invention has its cylindrical stopper main body expanded in diameter, so that it can be reliably installed at a predetermined position in the main pipe, and it can be installed in a predetermined position in the main pipe. Reliably prevent liquid from flowing into the main pipe. Moreover, when the main pipe is carried into the main pipe, the main body of the stopper can be in a reduced diameter state, so even if the main pipe has a small diameter, it can be installed without any problem.

The liquid inflow prevention plug attachment device of the present invention can reliably mount such a limb inflow prevention plug at a predetermined position within the main pipe.

4. Figure 1 is a partially cutaway side view showing an example of the liquid inflow prevention stopper of the present invention, Figure 2 is a cross-sectional view thereof, and Figure 3 is a cross-sectional view of its essential parts. , FIG. 4 is a side view showing an example of the limb inflow prevention plug attachment device of the present invention, FIG. 5 is a cross-sectional view of a main part of another example of the i & body inflow prevention plug, and FIG. 6 is a liquid inflow prevention plug attachment device. FIG. 7 is a sectional view taken along line A--A in FIG. 6.

10...Liquid inflow prevention stopper, 11... Stopper body, ll
a... Pillar portion, 11b... Opening, lie... Check valve, lle... Locking mechanism, llf... Engagement hole, l1g
...Claw part, 13...Sealing member, 20...Driving part, 32.35...Diameter expanding member.

that's all

Claims (1)

[Scope of Claims] 1. A liquid inflow prevention stopper that covers the end of a branch pipe branched from a main pipe that communicates with the main pipe, the inner circumferential surface of the main pipe with the side edges overlapping each other. It is wound so as to be able to contract and expand in diameter along the same direction, and has a size that can cover the end of the branch pipe, and locks each side edge so that it can move only in the direction of diameter expansion. A liquid inflow prevention stopper comprising a thin plate-like stopper body having a locking mechanism. 2. A device for mounting the liquid inflow prevention stopper according to claim 1 at a predetermined position in a main pipe, wherein the outer circumferential surface is cylindrical and movable inward and outward directions, and the outer circumferential surface is movable inwardly. A liquid inflow comprising a diameter expanding member that is fitted into the stopper main body which is in the reduced diameter state of the liquid inflow prevention stopper in a state where the stopper is in a reduced diameter state, and is capable of expanding the diameter of the stopper main body by moving the outer peripheral surface outward. Prevention plug installation device.