Abstract:
A dam with a flexible cover atached to a bottom sheet by fittings with corrugations formed between the fittings so that upon deflation the cover conforms to the surface of the corrugations, minimizing any floating cover portion. The corrugations may be formed as pipe-like members, as molded portions integral with the bottom sheet or as part of the concrete foundation. Preferably the length between the fittings measured along the corrugation surface sis at least 1.1 times the linear length therebetween. The corrugations are also preferably recessed to extend no higher than the bottom of the riverbed.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an erecting/lying-down dam or sluice gate made of a flexible sheet. 
     Erecting/lying-down dams or sluice gates are typically made of a flexible film (for example, rubberized fabric) attached on a riverbed at least in a direction intersecting the river flow with a fluid such as air, water or the like acting as an expanding medium. The medium is discharged from the cover to make the cover lay down through a pumping pipe communicating with the inside of the cover. Such devices are described in Japanese Patent Publication Nos. 40-11702 and 44-2371. 
     FIG. 1(a) shows such a prior art erecting/lying-down dam or sluice gate made of a flexible film as described above. In the drawing, reference numeral 1 designates a flexible film forming a cover, 2 a foundation of concrete, 3 a watertight sheet forming a base, 4 fittings connecting cover 2 and base 3, 5 air or water inflating the gate, and 6 a stream of water in a river or the like. 
     Where water exists also at the downstream side, film cover 1 does not completely lay down on foundation 2 when deflating; that is, a floating film F is produced as shown in FIG. 1(c). Of course film 2 does not float if there is no water or little water at the downstream side. FIG. 1(b) shows a midway state where fluid is being discharged. 
     When the foregoing dam is inflated as an estuary dam, a temporary shut-up dam, a lock gate, or the like, of course the dam prevents a ship from navigating. However, navigation is not always possible even when the dam is deflated. There is a possibility of damage of a floating film as described above by a ship by its body or screw. Even if the floating film is lying down, there is another possibility of damage by being rolled up by a screw. 
     SUMMARY OF THE INVENTION 
     According to the present invention, an erecting/lying-down dam or sluice gate is made with a cover of the flexible film attached by two rows of fittings at least onto a bottom portion of a river or the like in a direction intersecting a stream of the river and air or water is pumped into and out of the inside of the cover to expand and deflate it. Corrugations are provided on the lower interior surface between the rows of fittings so that the flexible film of the cover contacts the surface of the corrugations to minimize or eliminate the length of any floating film portion of the cover when the dam or sluice gate lies down. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a transverse cross-section illustrating the conventional prior art erecting/lying-down dam or sluice gate made of a flexible film. FIG. 1(a), (c) and (b) show the state where the cover is expanded, the state where the cover is deflated, and the state midway between states (a) and (c). 
     FIG. 2(a) and (b) and FIG. 3 are cross-sections illustrating an erecting/lying-down dam or sluice gate made of a flexible film according to the first and second embodiments of the present invention, respectively. FIG. 2(a) and (b) show the state where the cover is expanded and the state where the cover is deflated respectively. 
     FIG. 4(a) and (b) and FIG. 5 are cross-sections for illustrating an erecting/lying-down dam or sluice gate made of a flexible film according to the third and fourth embodiments of the present invention, respectively. FIG. 4(a) and (b) show the state where the cover is expanded and the state where the cover is deflated respectively. 
     FIG. 6 is a diagram for explaining that there is no effect in the case where the cover attaching is made in a single row even if corrugations are provided according to the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preferred embodiments of the present invention will be described with reference to the accompanying drawings. 
     FIG. 2(a) and (b) show an embodiment according to the present invention. Reference numeral 1 designates a flexible film such as a rubberized fabric forming a cover, 2 a foundation of concrete, 3 a watertight sheet forming a base, 4 fittings connecting cover 1 and sheet 3, 5 air or water inflating the base, 6 a stream of water in a river or the like, and 7 a mouth for pumping. 
     According to the first embodiment of the present invention, the dam is specifically made in the following manner. First, attaching lines forming fittings are arranged in two rows A and B. Next, corrugation forming members 9 are placed on the watertight sheet 3 between the attaching lines A and B, so that the members 9 and the sheet 3 constitute in combination a watertight sheet integrally provided with a corrugated upper surface D. 
     As the above-mentioned corrugation forming member, a cylindrical member such as a pipe (for example, an iron pipe, a pipe of vinyl chloride, a rubber pipe, or the like), a rod, or the like, having rigidity which is large enough not to be crushed down by the depth of water at a dam location can be used. In FIG. 2, reference numeral 10 designates a holder for holding the corrugation forming member in place on base sheet 3. Further, the foregoing corrugations D are usually formed parallel to the above-mentioned attaching direction. 
     As described above, according to the first embodiment of the present invention, corrugation forming members are disposed on the surface of a watertight sheet to form corrugations thereon, so that the actual length (represented by AB) measured along the surface of corrugations between A and B is longer than the linear distance or linear length between A and B (represented by AB). Accordingly, it is possible to shorten or obviate the floating length of a flexible film in the conventional art because the flexible film lies along the surface AB owing to the external pressure against the cover which is higher than the internal pressure of the same when the dam lies down. This state is shown in FIG. 2(b). 
     To achieve satisfactory shortening or elimination of the floating length of the film the condition AB≧1.1X AB should be at least satisfied. 
     If the attaching line is provided only by one row, the cover may take such an attitude as shown in FIG. 6 when the dam has laid down, so that there is no action of pressing down the cover. 
     The construction of FIG. 2, was tested with the cover deflated (air was used as the expanding medium) with the length (H) of the cover 1 as 1.8 m, the attaching interval (L) between A and B was 3.74 m, the diameter (d) of each of the corrugation forming member 9 (pipes were used) was 0.3 m φ (four members 9 are disposed equidistantly, and the distance (M) was 0.45 m). The film of the cover fitted well on the surface of the corrugations, so that no floating film was generated. 
     FIG. 3 shows a second embodiment of the present invention. Elements corresponding functionally to those in the first embodiment are designated by like reference numerals or characters. In this embodiment, instead of arranging the corrugation forming members on the watertight sheet as shown in FIG. 2, the corrugations D are provided by molded rubber or plastic raised portions 8 formed as a separate member or integrally with the rubber- or plastic-coated fabric of the watertight sheet 3. Furthermore, since the dam is recessed below the riverbed with the corrugated surface portion extending no higher than the riverbed, there is no risk of damage to the film by a screw or the like because the deflated film does not extend beyond the surface S of the body of the foundation concrete. 
     FIG. 4 (a) and (b) show a third embodiment of the present invention. Elements corresponding functionally to those in the first and second embodiments are designated by like reference numerals or characters. 
     According to the third embodiment of the present invention, first, attaching lines constituted by fittings are arranged in two rows A and B, as described in the first and second embodiments. Next, corrugations D are formed on the upper surface of the foundation concrete between the attaching lines A and B. Usually, the corrugations D are made to be parallel with the above-mentioned attaching direction. 
     Thus, corrugations are formed on the foundation concrete, so that the actual length (represented by AB) measured along the surface of corrugations between A and B is longer than the linear distance or linear length between A and B (represented by AB). Accordingly, it is possible to shorten or obviate the floating length of a flexible film in the conventional art because the flexible film lies along the AB direction owing to the external pressure against the cover which is higher than the internal pressure of the same when the dam lies down. This is shown in FIG. 4(b). 
     As above, to achieve satisfactory shortening or elimination of the floating length of the film the condition AB≦1.1 X AB should be satisfied. Further, the watertight sheet 3 is always kept in the state where it is in close contact with the surface of corrugation D by the internal pressure of the cover when the cover is in its expanded state and by the external pressure against the cover when the cover is in its deflated state. 
     If the attaching line is provided only by one row, the cover may take such an attitude as shown in FIG. 6 when the dam has lain down, so that there is no action of pressing down the cover. 
     FIG. 5 shows a fourth embodiment of the present invention. Elements corresponding functionally to those in the first through fourth embodiments are designated by like reference numerals or characters. The phantom line indicates the state when the cover is deflated. 
     In this embodiment, instead of forming the corrugation on the foundation concrete in such a manner as shown in FIG. 4, alternatively, corrugation forming members 9 are disposed on the foundation concrete so as to provide corrugations, in combination with the foundation concrete, on the upper surface integrated with the foundation concrete. 
     As above, a pipe (for example, an iron pipe, a pipe of vinyl chloride, a rubber pipe, or the like), a rod, or the like, having rigidity which is large enough not to be crushed down by the depth of water at a dam location can be used. Furthermore, since the portion between attaching intervals where the corrugated surface portion integrally provided on the foundation concrete is arranged is dug down in the main body of the foundation concrete, there is no risk of damage of the film by a screw or the like because the film does not extend beyond the surface S of the body of the foundation concrete. 
     As described above, according to the present invention, it is possible to obtain an erecting/lying-down dam or sluice gate in which no floating film of a cover occurs, the film does not prevent a ship from navigating, and the film is never injured by a ship, even if the dam or sluice gate is used as an estuary dam, a temporary shutup dam, a lock gate, or the like.