JP2001040717A - Simplified built-up tank - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a built-up tank free from anxiety about creasing, breaking and water leakage, comprising an easily assembled cylindrical container and a bag body accommodated therein with bag shape formed along the inner surface and bottom face of the cylindrical container. SOLUTION: Ths simplified built-up tank is constituted by accommodating a bag body 3 formed by jointing the lower end of a cylindrical synthetic resin film 3a with a diameter substantially equal to the inner diameter of a cylindrical container 2, watertightly in the cylindrical container 2 built-up by jointing a large number of circularly curved metal wall elements 20, 21 in vertical and circumferential directions.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a relatively large, simple assembly tank suitable for storing rainwater falling on the roof of a house or an agricultural / horticultural house.

[0002]

2. Description of the Related Art Conventionally, groundwater is frequently used for solution cultivation and irrigation of plants, and groundwater is also frequently used for roof watering (watering for cooling) in summer.

However, groundwater may contain a large amount of salt and chemical fertilizers. If such groundwater is used for solution cultivation or irrigation, plants may be adversely affected,
There is a problem that fertilizer design does not go well. However, there is a problem that using tap water increases the cost and is not very good for plants because it contains chlorine.

On the other hand, rainwater does not contain salt, chemical fertilizer, chlorine, etc., and is therefore most suitable as water for plant cultivation. Attempts have been made to use it.

As such a tank for storing rainwater, the present applicant has previously proposed a simple assembling tank which is easy to assemble and can be constructed at low cost (Japanese Patent Application No. 11-91580). This simple assembly tank accommodates a bag inside a cylindrical container assembled by joining a large number of metal wall elements curved in an arc shape in the vertical and circumferential directions, and stores rainwater in the bag. It is something to do.

[0006]

However, the bag used in the above-mentioned simple assembling tank is formed by welding the lower end of a cylindrical synthetic resin film, and does not have a bag shape along the inner surface and the bottom surface of the cylindrical container. The lower part of the bag, from the bottom to the bottom, is folded and large wrinkles are formed, and a partial gap is easily created between the bag and the inner surface or bottom surface of the cylindrical container. There was a concern that the bag would break because of the direct action of the bag.

[0007] The present invention has been made in view of the above circumstances,
It is an object of the present invention to provide a simple assembling tank which has a bag shape along the inner surface and the bottom surface of a cylindrical container and accommodates a bag body which is free from wrinkling or tearing.

[0008]

In order to achieve the above object, a simple assembling tank according to a first aspect of the present invention includes a plurality of metal wall elements which are curved in an arc shape and are joined in a vertical direction and a circumferential direction. A tank in which a bag is accommodated inside a cylindrical container assembled by assembling, wherein the bag is formed on a peripheral portion of a circular bottom sheet made of synthetic resin or synthetic rubber and has substantially the same inner diameter as that of the cylindrical container. It is characterized in that the lower end of a cylindrical synthetic resin film having a diameter is joined in a watertight manner.

[0009] The simple assembling tank accommodating the above bag has a shape in which the cylindrical synthetic resin film of the bag is along the inner surface of the cylindrical container and the circular bottom sheet of the bag is along the bottom. Unlike a conventional bag, the bag does not fold and have large wrinkles, or a partial gap is formed between the inner surface and the bottom surface of the cylindrical container, so that the bag is not broken by water pressure. Further, since the peripheral edge of the circular bottom sheet and the lower end of the cylindrical synthetic resin film are joined in a watertight manner, there is no occurrence of water leakage.

[0010] Next, in the simple assembling tank according to claim 2 of the present invention, in the tank according to claim 1, a lower end portion of a cylindrical synthetic resin film is overlapped on a peripheral portion of the circular bottom sheet of the bag body, Further, a synthetic resin protective film is superposed thereon, and is fused and integrated in a watertight manner.

When the lower end of the cylindrical synthetic resin film is overlapped and fused on the peripheral portion of the circular bottom sheet, the lower end of the synthetic resin film becomes thinner or non-uniform in thickness, resulting in defective fusion or film failure. Although there is a possibility that partial breakage will occur, if the synthetic resin protective film is further laminated and integrated on the lower end of the cylindrical synthetic resin film as described above, the synthetic resin protective film Since the lower end portion of the cylindrical synthetic resin film is protected and the fused portion is reinforced, defective fusion and partial breakage of the film can be prevented, and watertightness can be secured.

[0013] Next, in the simple assembling tank according to claim 3 of the present invention, in the tank according to claim 1, the peripheral portion of the circular bottom sheet of the bag and the lower end portion of the cylindrical synthetic resin film are formed as follows.
It is characterized by being joined in a watertight manner via an annular joining member.

When the peripheral portion of the circular bottom sheet and the lower end portion of the synthetic resin film are fused, as the size of the bag increases, the fusing operation takes a long time and requires skill, but as described above, the annular joining member is used. The joining operation is relatively simple even when the size of the bag body is increased.

Next, a simplified assembly tank according to claim 4 is
The tank according to claim 3, wherein the annular joining member has an inner groove formed on the inner peripheral surface, an outer groove formed on the outer peripheral surface, and a ring receiving groove formed on the upper surface. , The peripheral edge of the circular bottom sheet is inserted in the inner groove,
A folded lower end portion of a cylindrical synthetic resin film and a wedge member are inserted into the outer groove, and a water-expandable ring is inserted into the ring receiving groove.

Such a joining member is easy to join, and when the water-expandable ring expands by absorbing water, the joining member is deformed in a direction in which the width of the inner groove and the outer groove is reduced. The peripheral edge portion of the circular bottom sheet inserted into the inner groove is tightened, and the folded end portion of the synthetic resin film inserted together with the wedge member into the outer groove is also tightened to be joined in a watertight manner.

Next, a simplified assembly tank according to claim 5 is
In the tank according to the third aspect, the annular joining member has an annular base having a U-shaped cross section with an inner opening, and an annular dovetail portion fixed on the annular base. The peripheral edge of the circular bottom sheet is inserted, and the folded lower end of a cylindrical synthetic resin film is inserted into the dovetail, and a water-expandable ring is inserted inside it. Things.

Such a joining member is also easy to join, and when the water-swellable ring absorbs water and expands, the folded end portion of the synthetic resin film comes into close contact with the inner surface of the dovetail portion and is joined in a water-tight manner.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a perspective view showing a simple assembly tank according to an embodiment of the present invention, FIG. 2 is a sectional view of the tank, and FIG.
(A) is a perspective view of a wall element used for a cylindrical container of the tank, FIG. 3 (b) is a perspective view of a lowermost wall element used for the cylindrical container, and FIG. 4 is an enlarged perspective view of an end of the wall element. FIG. 5 is an enlarged sectional view of a circumferentially joined portion of the wall element in the cylindrical container, and FIG. 6 is an enlarged sectional view of a vertically joined portion of the wall element in the cylindrical container. ) Shows a state before bending to the inside, and (b) shows a state after bending to the inside. FIG. 7 shows a partially enlarged bag body accommodated in the tank. It is an outline sectional view.

In FIGS. 1 and 2, reference numeral 1 denotes a concrete base, on which a cylindrical container 2 is fixed. A watertight bag 3 is accommodated inside the cylindrical container 2, and a lid 4 is detachably attached to the upper end opening of the cylindrical container.

The cylindrical container 2 is assembled by joining a metal wall element 20 curved in an arc shape shown in FIG. 3 (a) in the vertical direction and in the circumferential direction. The bottom of the container 2 is shown in FIG.
The wall element 21 shown in (b) is used.

The wall element 20 shown in FIG.
Is formed by bending an upper end and a lower end of a metal plate curved in an arc shape obtained by dividing a circumference into three parts outwardly at right angles, thereby forming an upper end flange portion 20a.
And a lower end flange portion 20b, respectively, and the tips of the flange portions 20a and 20b are further bent downward at a right angle, so that a short hanging edge 20c having a short vertical dimension is provided at the tip end of the upper end flange portion 20a rather than the hanging edge 20c. A long hanging edge 20d having a long vertical dimension is formed at the tip of the lower end flange portion 20b. As shown in FIGS. 3 (a) and 4, right and left ends of the wall element 20 are folded outward in a U-shape. The U-shaped folded portion 20e is formed, and the edge 5a of the joining member 5 having a substantially C-shaped cross section is engaged with the U-shaped folded portion 20e. The wall element 20 is manufactured by bending a zinc steel plate, an aluminum-plated steel plate, a stainless steel plate or the like having a thickness of preferably about 0.4 to 1 mm as described above.

The specific dimensions of the wall element 20 are not particularly limited, and may be appropriately determined in consideration of the size of the cylindrical container 2 to be assembled and the weight of the wall element. Container 2 has a diameter of 3 to 5
Since a size of about m is appropriate, the radius of curvature of the wall element 20 is preferably set to about 1.5 to 2.5 m, and the vertical dimension is preferably set to about 20 to 50 cm.

The wall element 21 of FIG. 3B used at the lowermost stage of the cylindrical container 2 is formed by bending the upper end flange portion 21a and the upper end flange portion 21a similarly to the wall element 20 of FIG. 3A. A short hanging edge 21 with a short top and bottom dimension
c, a wide lower end flange portion 21b, and a U-shaped folded portion 21e at both left and right ends, but a drooping edge is not formed at the tip of the lower end flange portion 21b. Is different from the wall element 20 of FIG.

As shown in FIG. 6A, the vertical joining of the wall element 20 is performed by connecting the lower end flange portion 20b of the upper wall element 20 to the upper end flange of the lower wall element 20. 6b, the lower part of the hanging edge 20d of the lower end flange portion 20b is folded upward so that the hanging edge 20c of the upper end flange portion 20a is embraced, and further, as shown in FIG. It is performed by bending and crimping. The wall element 20 and the lowermost wall element 2
1 is also vertically joined in the same manner as described above.

Further, as shown in FIG. 5, the wall elements 20 are joined to each other in the circumferential direction by connecting the wall elements 20, 20 in the circumferential direction.
0e, the edge 5 of the joining member 5 having a substantially C-shaped cross section described above.
a and 5a are engaged to caulk the engaging portion, or the engaging portion is adhered and fixed with an adhesive. The lowermost wall element 21 is joined in the circumferential direction in the same manner.

As described above, this cylindrical container 2
The wall elements 20 and 21 are not welded to each other in a watertight manner, and the respective hanging edges 20c and 20d of the upper flange portion 20a and the lower flange portion 20b are bent, and at the same time, the U-shaped folded portion 20e is formed using the joining member 5. , 20e
By simply connecting and fixing the wall elements, the wall elements 20, 21 are assembled by joining them in the vertical and circumferential directions, so that they can be assembled in a shorter time and at a lower cost than in the case of welding. Moreover, the wall element 20,
Since 21 is curved in an arc shape divided into three,
As in the case of the three-link mechanism, it is settled so as not to be deformed, and the shape of the cylindrical container can be maintained.

As shown in FIG. 1, the cylindrical container 2 has a lower end flange 21 of a lowermost wall element 21.
b is fixed on the concrete foundation 1 with several anchor bolts 7a and nuts 7b, so that there is no fear that the cylindrical container 2 will fall over even if a typhoon strikes or an earthquake occurs.

At the upper end opening of the cylindrical container 2, a flexible, lightweight and tough opaque covering material 4a such as canvas is stretched over a frame material 4b (frame). The lid 4 in the shape of a jinkasa is covered, and its peripheral edge is detachably attached to the upper end flange portion 20a of the uppermost wall element 20 of the cylindrical container 2 by the stopper 8. Therefore, since the light is blocked by the lid 4 so as not to enter the cylindrical container 2, it is possible to prevent the generation of algae in the rainwater stored in the bag 3 inside the container 2, There is no fear that the rainwater enters the bag 3 and contaminates the rainwater.

As shown in FIG. 7, the bag 3 accommodated in the cylindrical container 2 is substantially the same as the inner diameter of the cylindrical container 2 on the periphery of the circular bottom sheet 3b made of synthetic resin or synthetic rubber. The synthetic resin protective film 3c is formed by overlapping a lower end portion of a cylindrical synthetic resin film 3a having a diameter of, and a ring of synthetic resin protective films 3c thereon.

The cylindrical synthetic resin film 3a can be used as long as it has high flexibility and tear strength, for example, polyethylene, polypropylene, polyvinyl chloride, and the like.
A tubular inflation film (thickness of about 0.1 to 0.3 mm) such as nylon, a laminated film of various resins, a meshed film for reinforcement, and the like are preferably used. These synthetic resin films may be used in a stack of two sheets, and when such two sheets are stacked, even if one film is torn, there is an advantage that another film can prevent water leakage.

As the circular bottom sheet plate 3b, a sheet made of the same synthetic resin as the above-mentioned synthetic resin film 3a and having a thickness of about 0.5 to 1.5 mm, or an EP having good weather resistance
A sheet made of synthetic rubber such as DM and having a thickness of about 0.5 to 1.5 mm is preferably used.

As the synthetic resin protective film 3c, a film made of the same synthetic resin as the synthetic resin film 3a is used.

As means for fusion, conventionally known heat fusion,
It is possible to employ any of means of ultrasonic fusion and high frequency fusion, and for example, the synthetic resin film 3a, the circular bottom sheet 3b, and the synthetic resin protective film 3c are made of polyethylene or polypropylene having no polar group. If it is made of a material, thermal fusion or ultrasonic fusion may be used, and if it is made of polyvinyl chloride having a polar group, fusion may be made by using high frequency fusion.

When the synthetic resin protective film 3c is omitted and the peripheral edge of the circular bottom sheet 3b and the lower end of the cylindrical synthetic resin film 3a are fused, the fused lower end of the cylindrical synthetic resin film 3a becomes thinner. Although there is a possibility that the thickness of the film becomes uneven and the defective fusion or partial breakage of the film may possibly occur, as described above, the synthetic resin protective film 3a is further placed on the lower end of the cylindrical synthetic resin film 3a. Are laminated and fused and integrated, the lower end of the tubular synthetic resin film 3a is protected by the synthetic resin protective film 3c, and the fused portion is reinforced, thereby preventing defective fusion and partial breakage of the film. , Watertightness can be ensured.

When the bag 3 is accommodated in the cylindrical container 2, the cylindrical synthetic resin film 3 a of the bag 3 abuts along the inner surface of the cylindrical container 2 and the circular bottom sheet 3 b
Is placed along the bottom surface, so that it does not fold and have large wrinkles or a partial gap between the inner surface and the bottom surface of the cylindrical container 2. For this reason, the water pressure is applied to the inner surface and the bottom surface of the cylindrical container 2 via the bag body 3, so that the bag body 3 is not broken by the water pressure.
If there is a sharp protrusion or the like on the inner surface of the cylindrical container 2, there is a concern that the cylindrical synthetic resin film 3a of the bag body 3 may be damaged. However, since there is no protrusion or the like on the inner surface of the cylindrical container 2, That worry is useless.

As shown in FIG. 13, the upper end of the bag 3, that is, the upper end of the cylindrical synthetic resin film 3a, is wound around the flange 20a at the upper end of the cylindrical container 2, and the packer 32 is placed on the flange 20a. It is attached by fitting.

As shown in FIG. 2, a water guide pipe 11 for introducing rainwater falling on the roof of a house or an agricultural / horticultural house is inserted into the bag 3 from above through the cover 4. A soft tube or hose 11a is connected to the lower end of the water pipe 11. The lower part of this tube or hose 11 a is curved and contacts the bottom of the bag 3.

As described above, when the lower part of the tube or hose 11a connected to the water guide pipe 11 is bent and is in contact with the bottom of the bag 3, rainwater flows from the tip of the tube or hose 11a into the inside of the bag 3. Since the water is introduced sideways and quietly, there is no need to worry about the rainwater falling vigorously and vibrating the container 2 or damaging the bag 3 as in the case of only the water guide pipe 11.

As shown in FIG. 2, a bottom member 9 is laid on the base 1 at the bottom of the cylindrical container 2 to form a flat bottom surface. As the bottom member 9, a synthetic resin foam, a rubber foam, or the like is suitable, and preferably, a nonwoven fabric (not shown) or the like is stacked on the upper surface thereof. When the flat bottom surface is formed as described above, the circular bottom sheet 3 of the bag body 3 is formed.
There is no fear of breaking even if a large water pressure is applied to b.

As shown in FIGS. 7 and 12, plastic or metal reinforcing plates 3d, 3d are adhered to the upper and lower surfaces of the central portion of the circular bottom sheet 3b of the bag body 3 to connect the intake pipe. A mouth 3e is provided. And this connection port 3
e, a vertical short pipe 12a formed with a threaded portion of the water intake pipe 12 is inserted from below, and the reinforcing plates 3d, By tightening 3d, the intake pipe 1
The two vertical short tubes 12a are connected in a watertight manner. With such a connection structure, there is an advantage that the vertical short pipe 12a of the water intake pipe 12 can be firmly connected.

As shown in FIG. 2, the intake pipe 12 protrudes out of the tank through the inside of the foundation 1, and a faucet 13 is attached to the tip of the protruded intake pipe 12 as an opening / closing member. When the water intake pipe 12 passes through the inside of the foundation 1 in this manner, there is no possibility that the water intake pipe 12 will be damaged by water pressure or the like.
Rainwater can be taken out at any time.

In the simple assembling tank of the embodiment described above, the lower end of the cylindrical synthetic resin film 3a of the bag body 3 is fused to the peripheral portion of the circular bottom sheet 3b. The lower end of the synthetic resin film 3a and the periphery of the circular bottom sheet 3b may be joined.

FIG. 8 is a partial cross-sectional view showing a bag according to an embodiment using such a joining member, and FIG. 9 is a perspective view showing the joining member with a part cut away.

That is, the annular joining member 30 used for the bag body 3 of this embodiment is made of synthetic rubber such as EDPM as described above, and as shown in FIG. 30a, an outer groove 30b formed on the outer peripheral surface, and a ring receiving groove 30c formed on the upper surface.

As shown in FIG. 8, the peripheral edge of the circular bottom sheet 3b is inserted into the inner groove 30a, and the folded lower end of the tubular synthetic resin film 3a and the wedge member 30d are inserted into the outer groove 30b. Then, the periphery of the circular bottom sheet 3b and the lower end of the cylindrical synthetic resin film 3a are joined, and a water-swellable ring 30e made of water-swellable rubber is inserted into the ring receiving groove 3c. I have.

As the wedge member 30d, a plurality of plastic or metal curved plates which do not damage the cylindrical synthetic resin film 3a and have a thickness substantially equal to the width of the outer groove 30b are used. .

When the water-swellable ring 30e absorbs water and expands, the joining member 30 is deformed in such a manner that the ring receiving groove 3c is expanded and the width of the inner groove 30a and the outer groove 30b is reduced. Therefore, the periphery of the circular bottom sheet 3b inserted into the inner groove 30a is tightened, and the outer groove 30b is tightened.
The folded end portion of the cylindrical synthetic resin film 3a inserted together with the wedge member 30d is also fastened and joined in a watertight manner.

FIG. 10 is a partial sectional view showing a bag body according to an embodiment using another joining member, and FIG. 11 is a partial perspective view of the joining member.

The annular joining member 31 is made of metal or plastic. As shown in FIG. 11, an annular base 31a having a U-shaped cross section and an inner side opening is provided.
Is provided with an annular dovetail portion 31b fixed on the upper surface of the base.

Then, as shown in FIG. 10, the periphery of the circular bottom sheet 3b is inserted into the annular base 31a of the joining member 3 and fixed with the stopper 31c.
The folded lower end of the tubular synthetic resin film 3a is inserted, and a water-expandable ring 31d is inserted inside the folded lower end. The water-swellable ring 31d is made of the same water-swellable rubber as the water-swellable ring 30e.

When the water-swellable ring 31d expands by absorbing water, the joining member 31 is made of the synthetic resin film 3a.
The folded end of the circular bottom sheet 3b is in close contact with the inner surface of the dovetail groove 31b, and the peripheral edge of the circular bottom sheet 3b is also in close contact with the inner surface of the annular base 31a.

When the lower end portion of the tubular synthetic resin film 3a and the peripheral edge portion of the circular bottom sheet 3b are joined by using the annular joining members 30 and 31 as described above, a bag 3 having a large size is formed.
However, it can be manufactured relatively easily.

[0054]

The simple assembling tank of the present invention can assemble a cylindrical container by a simple assembling operation.
The bag body accommodated inside has a cylindrical synthetic resin film along the inner surface of the cylindrical container and a circular bottom sheet along the bottom surface, so it folds like a conventional bag and has large wrinkles. There is no gap between the inner surface and the bottom surface of the cylindrical container, so that the bag does not break due to water pressure, and the peripheral edge of the circular bottom sheet and the lower end of the cylindrical synthetic resin film. Are joined in a watertight manner, so that there is an effect that no water leakage occurs.

Then, the synthetic resin protective film is overlaid,
When a bag is used in which the lower end of the tubular synthetic resin film and the peripheral edge of the circular bottom sheet are fused, the fused portion is strong and does not have poor fusion or partial breakage. When using a member to join the lower end of the cylindrical synthetic resin film and the peripheral edge of the circular bottom sheet, the joining operation is simple and the bag can be relatively easily manufactured even if the size of the bag increases. To play.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a simple assembly tank according to an embodiment of the present invention.

FIG. 2 is a sectional view of the tank.

FIG. 3A is a perspective view of a wall element used for a cylindrical container of the same tank, and FIG. 3B is a perspective view of a lowermost wall element used for the cylindrical container of the same tank.

FIG. 4 is an enlarged perspective view of an end of the wall element.

FIG. 5 is an enlarged sectional view of a circumferentially connected portion of a wall element in the cylindrical container.

6A and 6B are enlarged cross-sectional views of a connecting portion of the wall element in the vertical direction in the cylindrical container, wherein FIG. 6A is a state before being bent inward, and FIG. This shows a later state.

FIG. 7 is a schematic cross-sectional view showing a partially enlarged bag body accommodated in the tank.

FIG. 8 is an enlarged partial sectional view showing another example of the bag.

FIG. 9 is a partially cutaway perspective view showing a joining member used for the bag body.

FIG. 10 is an enlarged partial sectional view showing still another example of the bag body.

FIG. 11 is a partial perspective view showing a joining member used for the bag body.

FIG. 12 is an enlarged sectional view showing a connection portion between a circular bottom sheet of the bag body and an intake pipe.

FIG. 13 is an explanatory view showing an attached state of an upper end portion of the tubular synthetic resin film of the bag body.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Concrete foundation 2 Cylindrical container 20, 21 Wall element 3 Bag body 3a Cylindrical synthetic resin film 3b Circular bottom sheet 3c Synthetic resin protective film 3d Reinforcement plate 3e Connection port 30, 31 Annular joining member 30a Outer groove 30b Inner groove 30c Ring receiving groove 30d Wedge member 30e, 31d Water-expandable ring 31a Annular base material 31b Dove groove 4 Lid 11 Water guide pipe 12 Water intake pipe 13 Faucet

Claims (5)

[Claims] 1. A tank in which a bag is accommodated in a cylindrical container assembled by assembling a plurality of metal wall elements curved in an arc shape in a vertical direction and a circumferential direction. The bag body is formed by joining a lower end of a cylindrical synthetic resin film having substantially the same diameter as the inner diameter of the cylindrical container to a peripheral portion of a circular bottom sheet made of synthetic resin or synthetic rubber in a watertight manner. A simple assembly tank characterized by the following. 2. A lower end portion of a cylindrical synthetic resin film is superimposed on a peripheral portion of the circular bottom sheet of the bag body, and a synthetic resin protective film is further superimposed on the lower end portion of the cylindrical synthetic resin film. The simple assembling tank according to claim 1, wherein: 3. The bag according to claim 1, wherein a peripheral portion of the circular bottom sheet of the bag and a lower end of the cylindrical synthetic resin film are water-tightly joined via an annular joining member. The simple assembly tank described. 4. An annular joint member having an inner groove formed on an inner peripheral surface thereof, an outer groove formed on an outer peripheral surface thereof, and a ring receiving groove formed on an upper surface thereof. The peripheral edge of the circular bottom sheet is inserted into the outer groove, the folded lower end of the cylindrical synthetic resin film and the wedge member are inserted into the outer groove, and the water-expandable ring is inserted into the ring receiving groove. 4. The simple assembly tank according to claim 3, wherein: 5. An annular joining member comprising: an annular base having an inner side open and having a U-shaped cross section; and an annular dovetail fixed to said annular base. 4. A dovetailed groove, wherein a folded lower end portion of a cylindrical synthetic resin film is inserted into the dovetail portion, and a water-expandable ring is inserted inside the folded lower end portion. The simple assembling tank described in.