Patent Publication Number: US-6698916-B2

Title: Underwater agitation pump

Description:
BACKGROUND OF THE INVENTION 
     (1) Field of the Invention 
     The present invention relates to an underwater agitation pump which can suck soil, sand or the like which contains block-like material or string-like material in a dredging site, civil engineering work site, a sewage treatment plant, a sedimentation pool or a pit within a plant, an inside of a manhole or the like while efficiently agitating such soil, sand or the like and can discharge such sand, soil or the like to a given place. 
     (2) Description of the Related Art 
     Conventionally, as an underwater agitation pump which is served for the above-mentioned usage, there has been known an underwater agitation pump  100  which has a constitution shown in FIG. 19, for example. 
     As shown in the drawing, in this underwater agitation pump  100 , an impeller casing  101  having a hollow disc-like shape is provided with a center suction opening portion  102  at a center portion of a lower surface thereof and a discharge opening portion  104  which is connected to a discharge pipe  103  at a peripheral portion thereof. In the inside of the impeller casing  101 , a disc-like impeller  105  is rotatably disposed. The impeller  105  is provided with a center suction opening portion  106  at a center portion of a lower surface thereof and forms a plurality of radial flow passages  107  in the inside thereof in a circumferentially spaced-apart manner. Further, the impeller  105  is fitted on and is connected to an output shaft  109  of a water-tight motor  108  which is mounted on an upper surface of the impeller casing  101 . 
     Further, a cylindrical strainer  111  having a bottom wall  110  is contiguously mounted on a lower portion of the impeller casing  101  and an annular support frame  112  is mounted on a lower surface of the cylindrical strainer  111 . 
     Still further, the output shaft  109  of the water-tight motor  108  to which the impeller  105  is fixedly secured is extended downwardly after passing through the center suction opening portion  106  of the impeller  105 , the center suction opening portion  102  of the impeller casing  101  and the cylindrical strainer  111  and forms an agitator mounting shaft  113 . An agitator (cutter fan)  114  which protrudes a plurality of blade members in the radial direction from an outer peripheral surface of a body thereof is fixedly secured to a distal end of the agitator mounting shaft  113 . 
     Due to such a constitution, when the watertight motor  108  is driven, the impeller  105  and the agitator  114  are integrally rotated so that a negative pressure is generated in the inside of the impeller casing  101  and soil, sand or the like which is piled up below the underwater agitation pump  100  is agitated by the agitator  114 . Accordingly, the agitated soil, sand or the like is sucked into the impeller casing  101  through the cylindrical strainer  111  and thereafter is discharged to a desired place through the discharge opening portion  104  and the discharge pipe  103 . 
     However, the above-mentioned underwater agitation pump  100  still has a following task to be solved. That is, as shown in FIG. 19, the agitator mounting shaft  113  which mounts the agitator  114  on the distal end thereof passes through the center suction opening portion  106  of the impeller  105  and the center suction opening portion  102  of the impeller casing  101 . Accordingly, as shown in FIG. 20, a soil/sand inflow effective area A 2  is formed of a narrow annular area which is defined between an inner peripheral surface of the center suction opening portion  106  or the center suction opening portion  102  and an outer peripheral surface of the agitator mounting shaft  113 . 
     Accordingly, when block-like material or string-like material is mixed in the soil, sand or the like, such string-like material or flexible cloths such as vinyl cloths or the like are entangled in the agitator  114 , the agitator mounting shaft  113 , the cylindrical strainer  111  or the like and the block-like material and the string-like material clog the soil/sand inflow effective area A 2 . As a result, the operation of the underwater agitation pump becomes difficult or impossible so that there is a possibility that the soil/sand suction operation becomes difficult or impossible. 
     The present invention has been made to solve such a drawback and it is an object of the present invention to provide an underwater agitation pump which can reliably and efficiently suck and discharge soil, sand or the like even when the sand, soil or the like includes block-like material or string-like material. 
     SUMMARY OF THE INVENTION 
     To achieve the above-mentioned object, according to a first aspect of the present invention, there is provided an underwater agitation pump which comprises an impeller casing in which an impeller driven by a motor is rotatably accommodated, an agitated material suction guide cylinder being constituted of a hollow cylinder which has one-end opening portion thereof integrally connected to a center suction opening portion of the impeller while passing through a center opening of the impeller casing and having the other-end opening portion thereof extended downwardly, the agitated material suction guide cylinder further forming an agitated material suction passage in the inside thereof, and an agitator which is mounted on an outer periphery of the other-end opening portion of the agitated material suction guide cylinder. 
     In the above-mentioned constitution, a proximal end of the agitated material suction guide cylinder which is formed of the hollow cylinder is directly communicably connected with the center suction opening portion of the impeller and the agitator is mounted on the outer peripheral portion of the distal end of the agitated material suction guide cylinder. Accordingly, it becomes possible to make an inner diameter of the agitated material suction guide cylinder substantially equal to an inner diameter of the center suction opening portion of the impeller and an agitator mounting shaft which has been necessary in a conventional underwater agitation pump is made unnecessary, whereby the agitated material suction passage formed in the inside of the agitated material suction guide cylinder can ensure a sufficiently wide agitated material inflow area. Accordingly, it becomes possible to sufficiently agitate soil, sand or the like in which block-like material or string-like material is mixed with use of the agitator and, at the same time, it is possible to smoothly suck such soil, sand or the like in which the block-like material or the string-like material is mixed into the impeller casing through the agitated material suction guide cylinder. 
     Further, since it becomes possible to make an outer diameter of the agitated material suction guide cylinder substantially equal to the inner diameter of the center suction opening portion of the impeller, compared to the agitator mounting shaft of the conventional underwater agitation pump which mounts an agitator on a distal end thereof, the outer diameter of the agitated material suction guide cylinder can be remarkably increased so that the winding or the wrapping of the string-like material around the agitated material suction guide cylinder can be reliably prevented. Further, compared to the agitator mounting shaft of the conventional underwater agitation pump, the outer diameter of the agitated material suction guide cylinder can be remarkably increased and hence, the section modulus can be remarkably increased so that the mechanical strength of the agitated material suction guide cylinder can be increased whereby it becomes possible to increase the agitator supporting strength and to prevent the rapture or the like of the agitated material suction guide cylinder reliably. 
     Still further, since the other-end opening portion of the agitated material suction guide cylinder which forms an suction opening of the agitated material is formed at a position which is downwardly protruded from the center suction opening portion of the impeller, such a suction opening can be located close to a waterbed compared to an agitated material suction opening of the conventional underwater agitation pump. Accordingly, it becomes possible to simultaneously perform the agitation and the suction of sediment (agitated material). In this manner, while ensuring the sufficiently wide agitated material inflow area in the inside of the agitated material suction guide cylinder, the suction efficiency of the sediment (agitated material) can be further enhanced. 
     Although the agitated material suction guide cylinder can be formed with the impeller by an integral molding, the agitated material suction guide cylinder can be formed as a body separate from the impeller and can be connected to the impeller by means of bolts. Further, the agitated material suction guide cylinder is formed as a body separate from the impeller, a female threaded portion is formed in the center suction opening portion of the impeller, a male threaded portion is formed in the one-end opening portion of the agitated material suction guide cylinder, and the agitated material suction guide cylinder is connected to the impeller by engaging the male threaded portion with the female threaded portion. In this manner, when the agitated material suction guide cylinder is constituted of a member separate from the impeller, the constitutions of the impeller and the agitated material suction guide cylinder can be simplified so that they can be manufactured at a low cost. 
     The agitated material suction guide cylinder may be comprised of a large-diameter body portion and a stepped distal-end narrowed-diameter portion which constitutes the other-end opening portion, and the agitator is formed by mounting a plurality of triangular agitator constituting members which are extended in the radial direction in a circumferentially spaced apart manner on a stepped portion of the stepped distal-end narrowed-diameter portion. In this case, the agitator constituting members plays a role of guides for the string-like material so that the entanglement of the string-like material in the agitator can be further reliably prevented. 
     Although the agitator may be mounted on the outer peripheral portion of the other-end opening portion of the agitated material suction guide cylinder by welding or the like, the agitator may be integrally formed with the agitated material suction guide cylinder by molding the other-end opening portion of the agitated material suction guide cylinder in a non-circular shape (triangular shape, quadrangular shape, polygonal shape, star-like shape or the like). In this case, since the agitator can be integrally formed with the agitated material suction guide cylinder, the agitator supporting strength can be increased. Further, since the agitated material suction guide cylinder and the agitator can be integrally formed, manufacturing steps can be decreased in number so that they can be manufactured at a low cost. 
     A helical feeding blade may be mounted on an inner surface of the agitated material suction guide cylinder. In this case, along with the rotation of the agitated material suction guide cylinder, the helical feeding blade is integrally rotated so as to generate a lifting force so that the suction efficiency of the underwater agitation pump can be enhanced. Accordingly, even when the agitated material may be made of material having a high-concentration (soil, sand, muddy water or the like of low fluidity having a small water content), the agitated material can be efficiently and reliably sucked. 
     A sub water supply pipe which has an upper inlet opening thereof opened in water may have a lower outlet opening thereof disposed in the vicinity of the agitator and directed toward the agitator. In this case, even when the concentration of the soil, sand or the like is excessively high, the soil, sand or the like can be diluted with the sub water so that the soil, sand or the like can be made to smoothly flow into the inside of the agitated material suction guide cylinder. 
     A peripheral wall for preventing collapsing and inflow of soil, sand or the like which concentrically surrounds the agitated material suction guide cylinder and has a lower end thereof opened may be contiguously connected to a lower portion of the impeller casing, a water reservoir space may be formed between the agitated material suction guide cylinder and the peripheral wall for preventing collapsing and inflow of soil, sand or the like, and a lower outlet opening of a sub water supply pipe which has an upper inlet opening thereof opened in water may be communicably connected to the water reservoir space. In this case, due to the presence of the peripheral wall for preventing collapsing and inflow of soil, sand or the like, it becomes possible to prevent soil, sand or the like from being collapsed and clogging the other-end opening portion of the agitated material suction guide cylinder which forms a suction opening of the agitated material. Further, due to the presence of the water reservoir space, the soil, sand or the like having a high-concentration can be agitated while being diluted with the sub water and thereafter can be made to smoothly flow into the inside of the agitated material suction guide cylinder. 
     Further, to achieve the above-mentioned object, according to a second aspect of the present invention, there is provided an underwater agitation pump which comprises an impeller casing in which an impeller driven by a motor is rotatably accommodated, an agitated material suction guide cylinder being constituted of a hollow cylinder which has one-end opening portion thereof integrally connected to a center suction opening portion of the impeller while passing through a center opening of the impeller casing and having the other-end opening portion thereof extended downwardly, the agitated material suction guide cylinder further forming an agitated material suction passage in the inside thereof, a strip-like agitator mounting member which spans the other-end opening portion of the agitated material suction guide cylinder, and an agitator which is fixedly secured to a center portion of the agitator mounting member, wherein portions which constitute the other-end opening portion of the agitated material suction guide cylinder and are disposed at both sides of the agitator mounting member are notched toward the impeller to form a pair of agitated material suction openings. 
     Also according to this aspect of the present invention, the agitation of soil, sand or the like by the agitator and the suction of the soil, sand or the like by the impeller can be simultaneously performed so that the suction and discharge efficiency can be enhanced. Further, since a pair of agitated material suction openings are formed at both sides of the agitator mounting member, the soil, sand or the like which contains the string-like material or the block-like material can be smoothly sucked into the impeller casing through the agitated material suction openings and thereafter can be discharged from the impeller casing. 
    
    
     BRIEF EXPLANATION OF THE DRAWINGS 
     FIG. 1 is a front view with a part in cross section of an underwater agitation pump according to the first embodiment of the present invention. 
     FIG. 2 is a bottom plan view as viewed from a line I—I of FIG. 1 in an arrow direction. 
     FIG. 3 is a perspective view of an impeller and an agitated material suction guide cylinder as viewed from below. 
     FIG. 4 is an explanatory view showing the connection state between the impeller and the agitated material suction guide cylinder. 
     FIG. 5 is an explanatory view showing the connection state between the impeller and the agitated material suction guide cylinder. 
     FIG. 6 is a front view of a modification of the agitator. 
     FIG. 7 is a bottom plan view of FIG. 6 as viewed from a line VII—VII in an arrow direction. 
     FIG. 8 is a front view of another modification of the agitator. 
     FIG. 9 is a bottom plan view of FIG. 8 as viewed from a line IX—IX in an arrow direction. 
     FIG. 10 is a front view of another modification of the agitator. 
     FIG. 11 is a bottom plan view of FIG. 10 as viewed from a line XI—XI in an arrow direction. 
     FIG. 12 is an explanatory view of an essential part of an underwater agitation pump according to the second embodiment of the present invention. 
     FIG. 13 is a front view with a part in cross section of an underwater agitation pump according to the third embodiment of the present invention. 
     FIG. 14 is a bottom plan view of FIG. 13 as viewed from a line XIV—XIV in an arrow direction. 
     FIG. 15 is a front view with a part in cross section of an underwater agitation pump according to the fourth embodiment of the present invention. 
     FIG. 16 is a front view of an agitator according to the fifth embodiment of the present invention. 
     FIG. 17 is a bottom plan view of FIG. 16 as viewed from a line XVII—XVII in an arrow direction. 
     FIG. 18 is a side view of FIG. 16 as viewed from a line VII—VII in an arrow direction. 
     FIG. 19 is a cross-sectional front view of a conventional underwater agitation pump. 
     FIG. 20 is an explanatory view showing a soil/sand inflow effective area in a conventional underwater agitation pump. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     The present invention is specifically explained hereinafter in reference to embodiments shown in attached drawings. 
     First Embodiment 
     An underwater agitation pump  10  according to the first embodiment of the present invention is shown in FIG. 1 to FIG.  3 . Here, FIG. 1 is a front view with a part in section of the underwater agitation pump  10  according to the first embodiment of the present invention, FIG. 2 is a cross-sectional view of FIG. 1 taken along a line I—I, and FIG. 3 is a perspective view showing an impeller, an agitated material suction guide cylinder and an agitator which constitute essential parts of the underwater agitation pump  10 . 
     First of all, to explain the whole constitution of the underwater agitation pump  10 , an impeller casing  11  having a hollow disc-like shape is provided with a circular center opening  12  at a center portion of a lower surface thereof and a discharge opening portion  14  which is connected to a discharge pipe  13  at a peripheral portion thereof. In the inside of the impeller casing  11 , a disc-like impeller  15  is rotatably disposed. The impeller  15  is provided with a circular center suction opening portion  16  at a center portion of a lower surface thereof and a plurality of radial passages  17  are formed in the inside of the impeller  15  in a circumferentially spaced-apart manner. Further, the impeller  15  is fitted on and connected to an output shaft  19  of a watertight motor  18  which constitutes a drive source and is mounted on an upper surface of the impeller casing  11 . Here, numeral  20  indicates a motor casing and numeral  21  indicates a support base having a mounting frame  21   a  which is served for mounting and supporting the underwater agitation pump  10  on a bottom surface  22  made of soil, sand or the like. 
     Further, an agitated material suction guide cylinder  23  which is constituted of a circular hollow cylinder is disposed concentrically below the impeller casing  11 . The agitated material suction guide cylinder  23  has one-end opening portion thereof pass through the center opening  12  of the impeller casing  11  and integrally and communicably connected with the center suction opening portion  16  of the impeller  15  and the other-end opening portion thereof extended downwardly. An agitated material suction passage  24  is formed in the inside of the agitated material suction guide cylinder  23 . 
     Further, an agitator  25  which is served for agitating the soil, sand or the like is mounted on an outer peripheral portion of the other-end opening portion of the agitated material suction guide cylinder  23 . 
     With respect to the agitated material suction guide cylinder  23  having the above-mentioned constitution, the diameter (inner diameter) of the agitated material suction guide cylinder  23  can be made substantially equal to the diameter (inner diameter) of the center suction opening portion  16  of the impeller  15  and hence, the agitated material suction guide cylinder  23  can form the agitated material suction passage  24  having the sufficiently large diameter (inner diameter), that is, the sufficiently wide space in the inside thereof. 
     Further, in this embodiment, the agitated material suction guide cylinder  23  is formed with the impeller  15  by an integral molding as shown in FIG.  1  and FIG.  3 . However, as shown in FIG. 4, the agitated material suction guide cylinder  23  can be mounted on the impeller  15  such that the agitated material suction guide cylinder  23  is formed as a body separate from the impeller  15 , a flange  26  is integrally mounted on an outer peripheral surface of one-end opening portion of the agitated material suction guide cylinder  23 , and the flange  26  is connected to the impeller  15  by means of bolts  27 . Further, as shown in FIG. 5, the agitated material suction guide cylinder  23  may be connected to the impeller  15  such that the agitated material suction guide cylinder  23  is formed as a body separate from the impeller  15 , a female threaded portion  28  is formed on the center suction opening portion  16  of the impeller  15 , a male threaded portion  29  is formed on one-end opening portion of the agitated material suction guide cylinder  23 , and the male threaded portion  29  is engaged with the female threaded portion  28 . 
     Further, according to this embodiment as shown in FIG. 1 to FIG. 3, the agitator  25  is constituted such that the agitated material suction guide cylinder  23  is comprised of a large diameter body portion  23   a  and a stepped distal-end narrowed-diameter portion  23   b  which constitutes the other-end opening portion, and a plurality of triangular agitator constituting members  30  which are extended in the radial direction in a circumferentially spaced-apart manner are formed on a stepped portion of the stepped distal-end narrowed-diameter portion  23   b . Further, the agitator constituting members  30  are respectively mounted with a fixed inclination angle in the circumferential direction. Here, the inner diameter of the stepped distal-end narrowed-diameter portion  23   b  still has a sufficiently large diameter so that the agitated material containing the string-like material or the block-like material can be smoothly sucked into the inside of the agitated material suction guide cylinder  23 . 
     The shape or structure of the agitator  25  is not limited to those shown in FIG. 1 to FIG.  5  and various shapes and structures can be adopted in view of the nature of soil, sand or the like which forms the bottom surface  22 . For example, the agitator  25  may take shapes or the structures shown in FIG. 6 to FIG.  11 . The agitator  25  shown in FIG.  6  and FIG. 7 is constituted such that a plurality of agitator constituting members  31  made of rectangular lugs are mounted on the outer peripheral surface of the other-end opening portion of the agitated material suction guide cylinder  23  which is made of a straight cylinder. The agitator  25  shown in FIG.  8  and FIG. 9 is constituted such that a flange  32  is mounted on the outer peripheral surface of the other-end opening portion of the agitated material suction guide cylinder  23  which is formed of a straight cylinder and a plurality of agitator constituting members  33  which are extended radially in a circumferentially spaced-apart manner are mounted on the flange  32 . Here, a plurality of agitator constituting members  33  are inclined in a circumferential direction. The agitator  25  shown in FIG.  10  and FIG. 11 is constituted such that a plurality of agitator constituting members  34  made of triangular lugs are mounted on the outer peripheral surface of the other-end opening portion of the agitated material suction guide cylinder  23  formed of a tapered cylinder which is narrowed toward a distal end thereof. 
     Further, although the agitator  25  can be mounted on the outer peripheral portion of the other-end opening portion of the agitated material suction guide cylinder  23  by welding or the like, the agitator  25  can be integrally formed with the agitated material suction guide cylinder  23  also by forming the other-end opening portion of the agitated material suction guide cylinder  25  in a non-circular shape (triangular shape, quadrangular shape, polygonal shape, star-like shape or the like). 
     Subsequently, the operation for sucking and discharging soil, sand or the like (hereinafter referred to as “soil sucking and discharging operation) using the underwater agitation pump  10  having the above-mentioned constitution is explained in conjunction with attached drawings, particularly in conjunction with FIG. 1 to FIG.  3 . 
     When the watertight motor  18  is driven, the impeller  15  and the agitator  25  which is integrally connected to the impeller  15  by way of the agitated material suction guide cylinder  23  are rotated together. Accordingly, the inside of the impeller casing  11  becomes a negative pressure and at the same time sand, soil or the like piled up on the bottom surface  22  below the underwater agitation pump  10  is agitated by the agitator  25  and hence, the agitated material is sucked into the inside of the impeller casing  11  through the agitated material suction passage  24  formed in the inside of the agitated material suction guide cylinder  23 . Thereafter, the sand, soil or the like is discharged to a desired location through the discharge opening portion  14  and the discharge pipe  13 . 
     In such a soil sucking and discharging operation, the inner diameter of the agitated material suction guide cylinder  23  can be made approximately equal to the inner diameter of the center suction opening portion  16  of the impeller  15  and the agitator mounting shaft of the conventional underwater agitation pump can be made unnecessary and hence, the agitated material suction passage  24  formed in the inside of the hollow cylinder can have the sufficiently wide agitated material inflow area. 
     Accordingly, the sand, soil or the like in which the block-like material or the string-like material is mixed can be sufficiently agitated with the agitator  25  and then can be sucked into the inside of the impeller casing  11  through the agitated material suction guide cylinder  23 . 
     Further, since the outer diameter of the agitated material suction guide cylinder  23  can be also made approximately equal to the inner diameter of the center suction opening portion  16  of the impeller  15 , the agitated material suction guide cylinder  23  can ensure the remarkably large outer diameter compared to that of the agitator mounting shaft of the conventional underwater agitation pump which mounts an agitator at a distal end thereof whereby the winding or the wrapping of the string-like material around the agitated material suction guide cylinder  23  can be prevented assuredly. 
     Further, the other-end opening portion of the agitated material suction guide cylinder  23  which forms the suction opening for the agitated material can be located at a position protruded downwardly from the center suction opening portion  16  of the impeller  15 . Accordingly, it becomes possible to make the other-end opening portion of the agitated material suction guide cylinder  23  face closer to the water bed compared to an agitated material suction opening of the conventional underwater agitation pump whereby the agitation and the suction of the sediment (agitated material) can be simultaneously performed. Coupled with the constitutional feature that the agitated material suction passage  24  can ensure the sufficiently wide agitated material inflow area, the suction efficiency of the sediment (agitated material) can be further enhanced. 
     Further, as shown in FIG. 1 to FIG. 5, in this embodiment, the agitator  25  is comprised of a plurality of triangular agitator constituting members  30  which are extended radially and hence, the agitator constituting members  30  play a role of guides for the string-like material whereby the winding or the wrapping of the string-like material around the agitator  25  can be prevented more assuredly. 
     Second Embodiment 
     As shown in FIG. 12, this embodiment is characterized by mounting a helical feeding blade  40  on an inner surface of the agitated material suction guide cylinder  23 . In this embodiment, along with the rotation of the agitated material suction guide cylinder  23 , the helical feeding blade  40  is integrally rotated so that a lifting force is generated whereby the suction efficiency of the underwater agitation pump  10  can be enhanced. Accordingly, even when the agitated material is formed of agitated material having a higher concentration (soil, sand, muddy water or the like which has a little water content and a low fluidity), the agitated material can be efficiently and reliably sucked. 
     Third Embodiment 
     As shown in FIG.  13  and FIG. 14, an underwater agitation pump  50  according to this embodiment is characterized in that the underwater agitation pump  10  according to the first embodiment is further provided with a sub water supply pipe  53  which has an upper-end inlet opening  51  thereof opened in water by way of a strainer  52  and has a lower-end outlet opening  54  thereof disposed in the vicinity of the agitator  25  and directed toward the agitator  25 . Here, constituents elements of the underwater agitation pump  50  which are identical with those of the underwater agitation pump  10  according to the first embodiment are indicated by same numerals. Further, in the drawing, numeral  55  indicates a mounting bracket for mounting the sub water supply pipe  53  to the underwater agitation pump  50 . 
     Due to the above-mentioned constitution, the underwater agitation pump  50  according to this embodiment can obtain, in addition to the advantageous effect obtained by the underwater agitation pump  10  according to the first embodiment that the soil, sand or the like can be smoothly sucked and discharged even when the string-like material or the block-like material is mixed into the soil, sand or the like, an advantageous effect that even when the concentration of the soil, sand or the like is excessively high, the soil, sand or the like can be diluted by the sub water and then is agitated so that the soil, sand or the like can be smoothly sucked into the agitated material suction guide cylinder  23 . 
     Fourth Embodiment 
     An underwater agitation pump  56  according to this embodiment relates to a modification of an underwater agitation pump  10  according to the third embodiment. To be more specific, as shown in FIG. 15, a peripheral wall  57  for preventing collapsing and inflow of soil, sand or the like which concentrically surrounds the agitated material suction guide cylinder  23  and has a lower end thereof opened is contiguously connected to the lower portion of the impeller casing  11 . The peripheral wall  57  may be preferably made of a solid wall having no apertures. A water reservoir space  58  is formed between the agitated material suction guide cylinder  23  and the peripheral wall  57  for preventing collapsing and inflow of soil. A sub water supply pipe  59  which has an upper-end inlet opening thereof opened in water by way of a strainer  59   a  has a lower-end outlet opening thereof communicably connected to the water reservoir space  58 . Here, constituent elements of the underwater pump  56  which are identical with those of the underwater pump  10  according to the third embodiment are indicated by same numerals. 
     In this case, with the provision of the peripheral wall  57  for preventing collapsing and inflow of soil, sand or the like, at the time of starting the operation of the underwater agitation pump  56 , it becomes possible to prevent the other-end opening portion of the agitated material suction guide cylinder  23  which forms the suction opening for the agitated material from being clogged by the collapsed soil, sand or the like. Simultaneously, with the provision of the water reservoir space  58 , it becomes possible to make the soil, sand or the like having a high concentration smoothly flow into the inside of the agitated material suction guide cylinder  23  after diluting such soil, sand or the like with sub water. 
     Fifth Embodiment 
     An underwater agitation pump according to this embodiment relates to a modification of the underwater agitation pump  10  according to the first embodiment. To be more specific, as shown in FIG. 16 to FIG. 18, this embodiment is characterized in that an agitator  60  is arranged at a center portion of the other-end opening portion of the agitated material suction guide cylinder  23 . That is, as shown in the drawings, a strip-like agitator mounting member  61  spans the other-end opening portion of the agitated material suction guide cylinder  23  and an agitator  60  is fixedly secured to a center portion of the agitator mounting member  61 . Further, portions which constitute the other-end opening portion of the agitated material suction guide cylinder  23  and are disposed at both sides of the agitator mounting member  61  are notched toward the impeller  15  to form a pair of agitated material suction openings  62 . 
     Also in this embodiment, the agitation of soil, sand or the like by the agitator  60  and the suction of the soil, sand or the like by the impeller  15  can be simultaneously performed so that the suction and discharge efficiency can be enhanced. Further, since a pair of agitated material suction openings  62  are formed at both sides of the agitator mounting member  61 , the soil, sand or the like which contains the string-like material or the block-like material can be smoothly sucked into the impeller casing  11  through the agitated material suction openings  62  and thereafter can be discharged from the impeller casing  11  to a desired location. 
     Further, by providing a constitution in which the agitator  60  is detachably mounted on the agitator mounting member  61  by means of bolts or the like, when the agitator  60  is worn, the agitator  60  can be easily exchanged. Further, it is unnecessary to exchange the agitator  60  together with the agitated material suction guide cylinder  23  and it is sufficient to exchange only the agitator  60  and hence, the maintenance fee can be reduced. 
     As has been described heretofore, according to the present invention, following advantageous effects can be obtained. 
     (1) In the present invention, the proximal end of the agitated material suction guide cylinder which is formed of the hollow cylinder is directly communicably connected with the center suction opening portion of the impeller and the agitator is mounted on the outer peripheral portion of the distal end of the agitated material suction guide cylinder. Accordingly, it becomes possible to make the inner diameter of the agitated material suction guide cylinder substantially equal to the inner diameter of the center suction opening portion of the impeller and the agitator mounting shaft which has been necessary in the conventional underwater agitation pump is made unnecessary, whereby the agitated material suction passage formed in the inside of the agitated material suction guide cylinder can ensure a sufficiently wide agitated material inflow area. Accordingly, it becomes possible to sufficiently agitate soil, sand or the like in which block-like material or string-like material is mixed with the use of the agitator and, at the same time, it is possible to smoothly suck such soil, sand or the like in which the block-like material or the string-like material is mixed into the inside of the impeller casing through the agitated material suction guide cylinder. 
     (2) Since it becomes possible to make an outer diameter of the agitated material suction guide cylinder substantially equal to the inner diameter of the center suction opening portion of the impeller, compared to the agitator mounting shaft of the conventional underwater agitation pump which mounts the agitator on a distal end thereof, the outer diameter of the agitated material suction guide cylinder can be remarkably increased so that the winding or the wrapping of the string-like material around the agitated material suction guide cylinder can be reliably prevented. 
     (3) Compared to the agitator mounting shaft of the conventional underwater agitation pump, the outer diameter of the agitated material suction guide cylinder can be remarkably increased and hence, the section modulus can be remarkably increased so that the mechanical strength of the agitated material suction guide cylinder can be increased whereby it becomes possible to increase the agitator supporting strength and to prevent the rapture or the like of the agitated material suction guide cylinder reliably. 
     (4) Since the other-end opening portion of the agitated material suction guide cylinder which forms an suction opening of the agitated material is formed at a position which is downwardly protruded from the center suction opening portion of the impeller, such a suction opening can be located close to the waterbed compared to an agitated material suction opening of the conventional underwater agitation pump. Accordingly, it becomes possible to simultaneously perform the agitation and the suction of sediment (agitated material). In this manner, while ensuring the sufficiently wide agitated material inflow area in the inside of the agitated material suction guide cylinder, the suction efficiency of the sediment (agitated material) can be enhanced. 
     (5) In the present invention, the strip-like agitator mounting member which spans the other-end opening portion of the agitated material suction guide cylinder, the agitator which fixedly secured to the center portion of the agitator mounting member, and portions which constitute the other-end opening portion of the agitated material suction guide cylinder and are disposed at both sides of the agitator mounting member are notched toward the impeller to form a pair of agitated material suction openings. Accordingly, the agitation of soil, sand or the like by the agitator and the suction of the soil, sand or the like by the impeller can be simultaneously performed so that the suction and discharge efficiency can be enhanced. 
     (6) Further, along with the advantageous effect (5), since a pair of agitated material suction openings are formed at both sides of the agitator mounting member, the soil, sand or the like which contains the string-like material or the block-like material can be smoothly sucked into the impeller casing through the agitated material suction openings and thereafter can be discharged from the impeller casing to the desired location. 
     (7) Further, along with the advantageous effect (5), by providing the constitution in which the agitator is detachably mounted on the agitator mounting member by means of bolts or the like, when the agitator is worn, the agitator can be easily exchanged. Further, it is unnecessary to exchange the agitator together with the agitated material suction guide cylinder and it is sufficient to exchange only the agitator and hence, the maintenance fee can be reduced. 
     Although the inventions have been explained specifically in conjunction with several embodiments, the present inventions are not limited to the above-mentioned embodiments and includes other embodiments and modifications without departing from the scope of the inventions defined by scope of patent claims. For example, the drive source of the underwater agitation pump is not limited to an electrically-operated motor and includes a hydraulic motor or the like. Further, although the underwater agitation pump is arranged such that the whole underwater agitation pump is immersed in water in the above-mentioned embodiments, the invention includes the underwater agitation pump which has a portion thereof such as a drive source, for example, disposed above a water level. In this case, it is unnecessary to use a watertight motor. Still, further, the underwater agitation pump may be used not only in the vertical posture as described in the embodiments but also in the inclined posture or in the horizontal posture depending on the use conditions.