Abstract:
A boat propeller system, consisting of propeller blades attached to the forwardmost portion of a cylindrical housing extending aftward from the propeller blades for increasing the propulsion of the propeller system.

Description:
BACKGROUND 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates generally to a water propulsion system, and more particularly to a boat propeller including a cylindrical casing for augmenting propeller thrust that improves propulsion. 
         [0003]    2. Description of the Related Art 
         [0004]    There is a compelling need for an improved propeller system for boats. Previous propellers are wasteful of energy. The high pressure fluid leaving a propeller immediately encounters a much lower pressure in the medium it operates in and dissipates in that direction. 
         [0005]    It is well known in the art to propel boats by engaging blades of a propeller in water. Typically, the angular nature of the blades acting on water propels the watercraft. While this method of forward propulsion is effective, the efficiency of the system is generally low. The radial movement of the blades about the longitudinal shaft causes water to be thrown off centrifugally, which results in a radially exerted force. This effect reduces the forward longitudinal propulsion. The force intended for forward propulsion is wasted by the blades radially and tangentially agitating the surrounding water, which in turn causes cavitation. 
         [0006]    Cavitation is the rapid formation and collapse of vapor pockets in a flowing liquid in regions of very low pressure caused by the axial movement of the propeller blades. Cavitation results from propeller blades spinning so fast that the water pressure against the blades decreases, causing the water to boil. The resulting bubbles of water collapsing onto the surface of the blades causes metal blades to be eaten away, which is a common cause of structural damage to propellers. 
         [0007]    Previous attempts to improve thrust of propellers, such as those described in U.S. Pat. No. 5,213,525, have resulted in only marginal improvements in trust. 
         [0008]    Therefore, it is desired to provide a boat propeller that improves forward thrust that is producible at a reduced cost. 
       SUMMARY OF THE INVENTION 
       [0009]    To achieve the foregoing, and in accordance with the purposes of the present invention as embodied and broadly described herein, it is an object of this invention to provide an improved propeller system including a simple cylinder attached at the tips of the blades and extending aft. The propeller system of the present invention defeats dissipation. Elimination of flow from the tips of the blade enhances rotation speed and reduces the incidence of cavitation, thereby preventing physical damage. 
         [0010]    In a preferred embodiment, the cylinder is attached to the outside edges of the propeller blades, allowing the cylinder to rotate with the propeller blades. This configuration reduces drag and requires no external support so that it is self-supporting. The design of the present invention allows all of the displaced fluid to produce propulsion. 
         [0011]    Known propeller systems, such as those shown in U.S. Pat. No. 5,213,525, include a thrust jacket to increase safety by including the propeller blades aft of the forwardmost portion of a cylinder. However, the aft placement of propeller blades reduces the propulsion  6 f the propeller system. 
         [0012]    Therefore, the present invention provides a propeller assembly that operates a higher efficiency and greater speeds than known designs while reducing cavitation and preventing physical damage to the system. 
     
     
       BRIEF DESCRIPTION OF THE DRAWINGS/FIGURES 
         [0013]    The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention and to enable a person skilled in the relevant art to make and use the invention: 
           [0014]      FIG. 1  shows a perspective view of the propeller of the present invention. 
           [0015]      FIG. 2  shows a front view of the propeller of the present invention. 
           [0016]      FIG. 3  shows a side view of the propeller of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0017]    The present invention will now be described with reference to the accompanying drawings. In the drawings, like reference numbers indicate identical or functionally similar elements. While specific configurations and arrangements are discussed, it should be understood that this is done for illustrative purposes only. A person skilled in the relevant art will recognize that other configurations and arrangements can be used without departing from the spirit and scope of the invention. It will be apparent to a person skilled in the relevant art that this invention can also be employed in a variety of other devices and applications. 
         [0018]    The propeller system  10  of the present invention includes a plurality of helical propeller blades  20  radially attached to a hub  12 . Blades  20  are coupled to a cylindrical housing  30  having an inner surface  32  and an outer surface  34 . In a preferred embodiment, blades  20  are coupled to the forwardmost portion of cylindrical housing  30 , as shown in  FIGS. 1-3 , allowing propeller system  10  to be self-supporting. 
         [0019]    In a preferred embodiment, blades  20  are welded to cylindrical housing  30 , although, in alternate embodiments, other coupling methods may be used, as would be known to one skilled in the relevant art. 
         [0020]    In a preferred embodiment, the hub  12  is substantially conventional in design. In the embodiment shown in  FIGS. 1-3 , propeller system  10  has three blades  30 , however, in alternate embodiments, propeller system could have four, five, six, or any number of blades, as would be known to one skilled in the relevant art. 
         [0021]    The cylindrical housing  30  and propeller blades  20  are formed as a single unit, such that the present invention increases the propulsion of the propeller system  10  while avoiding the bulkiness, drag, and water friction of the prior devices. The length of the cylinder is determined by rotation speed of the propeller and energy applied. 
         [0022]    While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention or any embodiment thereof. It will be apparent to a person skilled in the relevant art that this invention can also be employed in a variety of other devices and applications. All patents, patent applications and publications cited herein are fully incorporated by reference herein in their entirety.