Abstract:
An underwater turbine arrangement is herein described. The water driven turbine comprises a housing having a shaft mounted for rotation about an axis therein. The shaft includes a plurality of flights arranged to drive rotation of the shaft. Mounted onto the housing is a funnel having a mouth greater in size than the housing and a discharge of similar size as the housing. Thus, water entering the funnel is constricted before being passed onto the housing, thereby increasing the force with which the shaft is rotated, thereby increasing the amount of energy produced.

Description:
U.S. Pat. No. 4,219,303 teaches an underwater power plant which includes electrical generators and machine rooms within the device. Clearly, a device such as this is simply too large for use in streams or rivers and is suitable only for use in ocean currents. 
    
    
     BACKGROUND OF THE INVENTION 
     There are a number of devices taught in the prior art for converting energy from the flow of a fluid (such as air or water) to electrical energy. 
     For example, U.S. Pat. No. 4,412,417 teaches a turbine arranged to be anchored on the surface of a body of water for converting “wave energy” to electrical energy. The device includes a shaft having a helical flight displaced therearound, The flight is not enclosed and the waves passing along the flight causes the shaft to rotate, thereby generating electrical power. U.S. Pat. No. 4,849,647 teaches a similar floating turbine that floats on and is exposed to a body of water. 
     U.S. Pat. No. 5,664,418 teaches a turbine arrangement including vanes for concentrating the wind. 
     One difficulty faced by devices such as these is that the flow intensity of the fluid, whether wind or wave, is highly variable and dependent upon weather conditions. That is, in conditions wherein there is little or no wind, the above-described device would not produce much power, whereas a strong wind could lead to conditions which would damage the device. As such, these devices are impractical, as the amount of electrical power generated at a given time is highly variable and unpredictable. This is not the case with underwater currents, which are generally more constant both in terms of intensity and direction, making underwater currents more suitable as potential sources for electrical power. 
     U.S. Pat. No. 4,219,303 teaches an underwater power plant which is includes electrical generators and machine rooms within the device. Clearly, a device such as this is simply too large for use in streams or rivers and is suitable only for use in ocean currents. 
     U.S. Pat. No. 4,025,220 teaches a turbine for use in water or air which includes a “flexible fluid current collector” for increasing the flow of a fluid, the device being arranged for use in either air or water. It is of note that the collector described is composed of fabric. 
     Clearly, a device that is arranged for generating electrical power from underwater currents that can also be used in streams and rivers and the like is needed. 
     SUMMARY OF THE INVENTION 
     According to the invention, there is provided a water driven turbine for converting the energy of an underwater current comprising: a hollow tubular open ended housing, said housing having an entry end for accepting the water and an exit end for releasing the water; a shaft mounted within the housing, said shaft arranged to rotate within the housing about an axis of rotation; connection means on the shaft for operably linking the shaft to a generator such that rotation of the shaft generates electrical power; blade means arranged about the shaft, said blade means extending along a length of the shaft; and a funnel mounted onto the entry end of the housing, said funnel having a mouth and a discharge, said mouth having a diameter greater than the diameter of the housing, said discharge having a diameter approximately equal to the diameter of the housing, wherein the discharge of the funnel is mounted onto the entry end of the housing such that the water entering the funnel at the mouth passes through the housing and contacts the blade means, thereby rotating the shaft and generating electrical power. 
     The generator may be positioned behind the exit end of the housing relative to the mouth of the funnel. 
     The diameter of the mouth may be approximately 50% greater than the diameter of the discharge. 
     The water driven turbine may include fins mounted on an upper surface and a lower surface of the housing for preventing twisting of the water driven turbine. 
     The fins may be mounted on the housing proximal to the exit end of the housing. 
     The water driven turbine may include buoyancy means mounted on the water driven turbine. 
     The buoyancy means may be mounted within the fins. 
     There may be three blade means or two blade means. 
     The water driven turbine may include tether means mounted within the funnel for stabilizing the water driven turbine. 
     One embodiment of the invention will now be described in conjunction with the accompanying drawings in which: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a side view in cross-section of the turbine. 
     FIG. 2 is a cross-sectional view along line  2 — 2  in FIG.  1 . 
     FIG. 3 is a front view of an alternative arrangement of the flight. 
     FIG. 4 is a side view in cross-section of an alternative arrangement of the turbine. 
    
    
     In the drawings like characters of reference indicate corresponding parts in the different figures. 
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to the drawings, a water driven turbine  1  for converting an underwater current into electrical power comprises a housing  10 , a funnel  12  and a generator  34 . 
     As shown in FIG. 1, the housing  10  is tubular, open-ended and hollow, comprising an inner surface  14 , an outer surface  16 , a shaft  18 , an entry end  22  and an exit end  24 . The shaft  18  is mounted within the housing  10  such that the shaft  18  rotates within the housing  10  about an axis of rotation, as described below. The shaft  18  includes flights  20  which extend about the shaft  18  along the length of the shaft  18 . It is of note that there may be several flights  20  arranged about the shaft, depending upon conditions and the intended use. For example, FIGS. 1 and 2 show an embodiment of the invention wherein there are two flights whereas FIG. 3 shows an embodiment having three flights. As will be apparent to one knowledgeable in the arts, the three flight shaft will have a larger surface area than the two flight shaft. In the embodiment shown in FIG. 1, the flights  20  extend around the shaft  18  in a helical or twisted arrangement. Specifically, the flights  20  are struck by a flow of water passing through the housing  10  which in drives rotation of the shaft  18 , as described below. However, it is of note that other suitable arrangements of flights  20  known in the art may also be used. It is of note that the shaft  18  may be mounted within the housing  10  in a hub such that the shaft  18  can rotate freely. The hub is mounted to the housing by a plurality of legs, the legs being arranged so as to minimize their interference with water flow through the water driven turbine  1 . 
     The funnel  12  is composed of a rigid material and comprises a mouth  26  and a discharge  28 . It is of note that the mouth  26  is arranged to be of a greater diameter than the discharge  28  for increasing the velocity and inertial force in the flow of water as it passes through the funnel  12  compared to the current as described below. Furthermore, as can be seen in FIG. 1, the decrease in diameter between the mouth  26  and the discharge  28  is gradual, so that water is not forced out of the water driven turbine  1 , as water diverted away from the water driven turbine  1  cannot be used to drive the shaft  18  and is in effect wasted energy. Furthermore, as can be seen in FIG. 1, the mouth  26  includes a lip  27  that is of a fixed diameter and acts to retain incoming water flow, as described below. Specifically, in the embodiment shown in FIG. 1, the diameter of the mouth  26  is approximately 50% greater than that of the discharge  28 . As a result of this arrangement, the surface area at the mouth  26  of the funnel  12  is greater than the surface area at the discharge  28 . Furthermore, as shown in FIG. 1, the discharge  28  is of a similar diameter as the entry end  22  of the housing  10 . It is of note that other ratios may also be utilized, according to the conditions in which the water driven turbine  1  is to be used. 
     In the embodiment shown in FIG. 1, tether means  30  are connected to the funnel  12  for anchoring the water driven turbine  1  in the waterway. Specifically, the tether means  30  comprises side cables  36  and top and bottom cables  38  which are mounted to the front face of the lip  27 , as shown in FIG.  1 . The cables  38  are connected to a support structure (not shown) for securing and stabilizing the water driven turbine  1  in the underwater current, as described below. In addition, in the embodiment shown in FIG. 1, the water driven turbine  1  includes fins  32  for further stabilizing the position of the water driven turbine  1  in the waterway. In the embodiment shown in FIG. 1, the fins  32  are mounted on the outer surface  16  of the housing  10  above and below the shaft  18 , proximal to the exit end  22 . Thus, as a result of the tethering means  30  and the fin  32 , the water driven turbine  1  will not rotate, twist or turn when exposed to the water current, meaning that maximum efficiency is retained. That is, the water driven turbine  1  remains positioned within the water flow such that the maximum flow of water is directed through the water driven turbine  1 . As will be appreciated by one knowledgeable in the art, other tether means  30  or fins  32  at other locations along the water driven turbine  1  may also be used for stabilizing the water driven turbine  1 . 
     As can be seen in FIG. 1, the shaft  18  is operably linked to the generator  34 . The details of the generator are not shown as these will be well known to one knowledgeable in the art. It is of note that in the embodiment shown in FIG. 1, the shaft  18  is connected directly to the generator  34  and the generator  34  is mounted to the housing  10  behind the exit end  22 . Specifically, the generator  34  is mounted to the exit end  22  of the housing  10  by support bars such that the shaft  18  is connected to the generator in a straight line. In other embodiments, the generator  34  may be located at a distance to the water driven turbine  1 . It is of note that in some embodiments the generator  34  may be positioned in a non-linear arrangement relative to the shaft  18  using means known in the art. 
     It is of note that in the embodiment shown in FIG. 1, the fins  32  include buoyancy means  40  within the fins  32  for counter-acting the weight of the generator  34 . That is, as discussed above, the fins  32  are mounted proximal to the exit end  22  and therefore proximal to the generator  34 , for counter-balancing the weight of the generator  34 . As a result of this arrangement, the water driven turbine  1  does not tilt when in use. 
     For use, the funnel  12  is mounted onto the housing  10  such that the entry end  22  of the housing  10  contacts the discharge  28  of the funnel  12 . The water driven turbine  1  is then lowered into the body of water, below the surface of the body of water and the water driven turbine  1  is positioned such that the water current flows through the water driven turbine  1  as described below. Specifically, the water driven turbine  1  is positioned such that the current in the body of water directs the flow of water directly into the mouth  26  of the funnel  12 . It is of note that the shaft  18  is operably linked to the generator  34 , as described below. 
     In use, as discussed above, the water driven turbine  1  is positioned such that the current in the body of water directs water to flow into the mouth  26  of the funnel  12  at the lip  27 . As discussed above, the diameter of the mouth  26  of the funnel  12  is greater than the diameter of the discharge  28  of the funnel. As a result of this arrangement, the velocity and inertial force of the water flow increases as it passes through the funnel  12  from the mouth  26  to the discharge  28 . In this manner, the inertial force and velocity of the water is increased relative to the water flow caused by the natural current in the body of water. As noted above, the lip  27  is of a fixed diameter and acts to prevent backflow of the water once it enters the funnel  12 . Furthermore, once water enters the funnel  12 , it must exit through the exit end  24  of the housing  10  and the funnel  12 . Thus, the flow of water passes through the housing  10  at the entry end  22  and exits the housing  10  through the exit end  24 . As the water passes through the housing  10 , the water strikes the flights  20 , thereby driving rotation of the shaft  18 . Rotation of the shaft  18  in turn generates electrical power at the generator  34 . It is of note that the flights  20  are fitted within the housing  10  for maximum surface area and minimum clearance within the housing  10  so that the shaft  18  rotates freely within the housing  10 . That is, the flights  20  are arranged to have maximum surface area and are arranged about the shaft  18  to maximize contact with the flow of water, so that electrical power generation is more efficient. Specifically, once the flow of water enters the water driven turbine  1 , it must pass over the flights  20 . Furthermore, the funnel  12  increases the velocity of the flow of water and passes the flow of water directly to the housing  10  without allowing water to flow back out of the funnel and escape, as discussed above. 
     In an alternative embodiment, the water driven turbine  1  includes a cone  42  mounted to the housing  10  and extending past the exit end  24 , as shown in FIG.  4 . Specifically, the cone  42  is connected to and extends outwardly and rearwardly from a position on the housing  10  past the exit end  24 . Furthermore, the cone  42  may be connected to the housing at positions proximal to the exit end  24 , as shown in FIG.  4 . It is also of note that the cone  42  increases in diameter while extending rearwardly from the housing  10 , such that the cone  42  is most narrow at the point that is mounted to the housing  10  and most wide at the distal end of the cone  42  relative to the housing  10 . As a result of this arrangement, water exiting avoids the turbulence and restraining effect which would result from contact with the flow of water passing outside the device at the immediate exit, and the expanded volume available to the exiting water will enhance the velocity of flow throughout the device by eliminating some back pressure. Further, the cone will increase the velocity of flow of the water passing outside of the cone, which in turn will have a pulling effect on the water exit from inside the cone, enhancing its velocity of flow. 
     Thus, the above-described water driven turbine  1  is arranged for converting underwater currents to electrical power. Furthermore, the design is such that the water driven turbine  1  can be used in bodies of water such as lakes, streams and rivers, where prior art water driven turbines are not suitable or impractical. Specifically, the water driven turbine is arranged to increase velocity in a natural water flow and to direct the water over a plurality of flights. Water passing over the flights drives rotation of a shaft which is in turn linked to a generator, resulting in the production of electrical power. 
     While the preferred embodiments of the invention have been described above, it will be recognized and understood that various modifications may be made therein, and the appended claims are intended to cover all such modifications which may fall within the spirit and scope of the invention.