Abstract:
An improved propeller design is provided herein. One embodiment includes a propeller with a housing having a diameter sufficient to encloses at least a portion of the propeller blades. The housing may be secured to the ends of the propeller blades. The housing may include a forward facing edge that is flared outwardly. In addition, the housing generally tapers inward aft of the propeller blades reducing the diameter of the housing to form a general funnel shape. In one embodiment, the housing has a rear portion with a substantially constant diameter located aft of the end of the tapered section. Outer blades may be secured to the outer portion of the housing. These outer blades may be useful to, for example, provide additional rear thrust when the boat is shifted into reverse.

Description:
RELATED APPLICATIONS 
       [0001]    This application claims priority to, and any other benefit of U.S. Provisional Application Ser. No. 60/937,895, titled Improved Propeller, filed on Jun. 29, 2007. The entire disclosure of said provisional applications is hereby incorporated by reference in its entirety. 
     
    
       [0002]    This invention relates generally to power boats and more particularly to an improved propeller for power boats. 
       BACKGROUND 
       [0003]    Conventional propellers typically include three or more blades and have been used to propel boats through the water for many years. However, conventional propellers are inefficient and typical propellers have a slip of around 45%. 
       SUMMARY 
       [0004]    An improved propeller design is provided herein. One embodiment includes a propeller with a housing having a diameter sufficient to encloses at least a portion of the propeller blades. The housing may be secured to the ends of the propeller blades. The housing may include a forward facing edge that is flared outwardly. In addition, the housing generally tapers inward aft of the propeller blades reducing the diameter of the housing to form a general funnel shape. In one embodiment, the housing has a rear portion with a substantially constant diameter located aft of the end of the tapered section. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0005]      FIG. 1  is a prospective view of an embodiment of a propeller; 
           [0006]      FIG. 2  is a side perspective view of the propeller of  FIG. 1 ; 
           [0007]      FIG. 3  is a rear perspective view of the propeller of  FIG. 1 ; 
           [0008]      FIG. 4  is a side view of a propeller; 
           [0009]      FIG. 5  is a side view of propeller in the forward direction showing water and compressed air flow; 
           [0010]      FIG. 6  is a side view of propeller in the reverse direction showing water a flow; and 
           [0011]      FIG. 7  is an impeller having an attached housing; 
           [0012]      FIG. 8  is a prospective view of another embodiment of a propeller. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]      FIG. 1  illustrates an exemplary embodiment of an improved propeller  100 . The improved propeller  100  includes a inner propeller  110  having a plurality of blades  115 . Secured to the propeller  110  is a housing  120 . Housing  120  includes a flared out forward edge  130 , a longitudinal housing portion  125 , a tapered portion  140 , a rear portion  150  and a plurality of outer blades  160 . Tapered portion  140  may have a linear taper, as shown, a curved taper, or have any number of different shaped tapers that server to reduce the housing  120  from a first diameter to a second smaller diameter. Propeller  110  includes a forward hub  170  for fitting into a conventional outboard drive unit (not shown). The housing  120  and propeller  110  may have a unitary construction to form improved propeller  100 . Unitary construction, as used herein, does not mean it is formed of one solid piece, bur rather may be formed of multiple pieces that are joined or fastened together. Improved propeller  110  may be formed from aluminum, stainless steel, plastic, a composite, combinations of these materials, or any other suitable material(s). In one embodiment the propeller  110  is a conventional propeller, and housing  120  is modified so that it can be secured to the conventional propeller. For example, housing  120  may include pockets (not shown) for receiving blades of a conventional propeller, housing  120  may be mechanically fastened or welded to the conventional propellers. Slight modifications to the conventional propeller for securing it to the housing  110  is contemplated. Outer blades  160  are secured to rear portion  150 . Rear portion  150  may flare outward, have a constant diameter, or even taper inward. When the boat is shifted into reverse, housing  120  prevents some of the water that would normally flow over propeller  110  from contacting blades  115 . Outer blades  160  provide one means of creating additional thrust in the reverse direction. 
         [0014]    In operation, water enters the front of the housing  120 . The flared out forward flange  130  causes more water to contact the blades  115  of propeller  110  than would normally contact the blades  115 . As the propeller  110  turns, water is forced though the reduced portion of housing  120 . As the water travels through the housing  120 , it reaches the tapered portion  140 . Because water does not compress, the water is accelerated as it passes through the housing  120  and out the rear portion  150 . With the improved propeller  100 , all of the accelerated water is focused rearward verses with a conventional propeller where some of the water is directed outwardly. Focusing all of the accelerated water rearward increases forward thrust. 
         [0015]      FIG. 2  provides an additional prospective view of improved propeller  100 . This view is taken from the side and slightly behind the rear of the improved propeller  100 . Housing  120  includes flared out forward edge  130 , longitudinal housing portion  125 , tapered portion  140 , rear portion  150  and outer blades  160  are further illustrated in this view. 
         [0016]      FIG. 3  is a rear prospective view of the improved propeller  100 .  FIG. 3  illustrates the housing  120  having a tapered portion  140 , a rear portion  150  and outer blades  160 . Also shown is hub  300  and inner hub  310 . Inner hub  310  slides over the shaft of an outboard drive unit (not shown). Preferably, a nut (not shown) secures the improved propeller  100  to the drive unit just as it does a conventional propeller. 
         [0017]    In one embodiment, the tapered portion  140  reduces the diameter of the housing  120  down to the rear portion  150  so that the rear portion  150  has a cross sectional area that is less than the cross sectional area of the outside diameter of the inside blades  115  ( FIG. 1 ) minus the cross sectional area of hub  300 . The smaller cross sectional area of the rear portion  150  forces the water two accelerate through the rear portion  150 . 
         [0018]      FIG. 4  illustrates another embodiment of an improved propeller  400 . Improved propeller  400  is similar to improved propeller  100 . Improved propeller  400  includes a housing  405  having a flared out forward edge  410 , a longitudinal housing portion  420 , a tapered portion  430 , outer blades  440 , rear portion  450 , and forward hub  460 . These elements perform similar functions as their counter parts described above. 
         [0019]      FIG. 5  illustrates that path of water  510  through, and around, improved propeller  400 . Water  510  flows into the flared out forward edge  410 . As described briefly above, flared out forward edge  410  forces more water  510  to contact with the blades then normally would contact the conventional blades. As the blades spin, the blades (not shown) force the water  510  rearward through housing  405 . The water  510   a  accelerates as it flows through tapered portion  430 . Water is incompressible so as the water  510  is forced through rear portion  430  the water must accelerate. The accelerated water  510   b  passes through the rear portion  450  and creates additional thrust. In addition, often the drive units exhausts the engine fumes near the propeller  110  ( FIG. 1 ) and, as a result the exhaust gases are compressed in the tapered portion  430 . The compressed exhaust fumes  515  exit along with the accelerated water  510   b  and may cause enhanced performance. Water  510   a  flowing around the outside of housing  405  contacts outer blades  440  to provide additional thrust. Increases in the speed of the boat, increases the volume of water flowing into the housing, and results in increases in the efficiency of the improved propeller. 
         [0020]      FIG. 6  illustrates the path of water  610  when the improved propeller  400  is rotated in the reverse direction. Because of the reduced diameter at the housing  405 , the amount of water  610  that would otherwise contact the propeller that is inside housing  405  is reduced. Outer blades  440  contact the water  610  and force water  610   a  around housing  405  to provide additional reverse thrust. 
         [0021]      FIG. 7  is yet another embodiment of an improved propeller/impeller  700 . The improved impeller  700  includes a tapered housing  720 , an impeller  710  that includes mounting hubs  730  and  740 , and outer blades  750 . The operation of the impeller  700  is similar to the operation of the improved propellers discussed in detail above. 
         [0022]      FIG. 8  illustrates another exemplary embodiment of an improved propeller  800 . The improved propeller  800  includes a inner propeller  810  having a plurality of blades  815 . Secured to the propeller  810  is a housing  820 . Housing  820  includes a flared out forward edge  830 , a longitudinal housing portion  825 , a tapered portion  840 , and a rear portion  850 . Tapered portion  840  may have a linear taper, as shown, a curved taper, or have any number of different shaped tapers that server to reduce the housing  820  from a first diameter to a second smaller diameter. Propeller  810  includes a forward hub  870  for fitting into a conventional outboard drive unit (not shown). The housing  820  and propeller  810  may have a unitary construction to form improved propeller  800 . Unitary construction, as used herein, does not mean it is formed of one solid piece, bur rather may be formed of multiple pieces that are joined or fastened together. Improved propeller  810  may be formed from aluminum, stainless steel, plastic, a composite, combinations of these materials, or any other suitable material(s). In one embodiment the propeller  810  is a conventional propeller, and housing  820  is modified so that it can be secured to the conventional propeller  810 . For example, housing  820  may include pockets (not shown) for receiving blades of a conventional propeller, housing  820  may be mechanically fastened or welded to the conventional propellers. Slight modifications to the conventional propeller for securing it to the housing  810  is contemplated. Rear portion  850  may flare outward, have a constant diameter, or even taper inward. 
         [0023]    While the present invention has been illustrated by the description of embodiments thereof, and while the embodiments have been described in considerable detail, it is not the intention of the applicants to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications will readily appear to those skilled in the art. For example, the housing member may be integrally formed with, or secured to, a drive unit, and the propeller would rotate inside of the housing. Therefore, the invention, in its broader aspects, is not limited to the specific details, the representative apparatus, and illustrative examples shown and described. Accordingly, departures may be made from such details without departing from the spirit or scope of the applicant&#39;s general inventive concept.