Boat propeller

Abstract

A boat propeller includes a gear box, an impeller, a stream-guiding ring, and a stream-shaping nozzle. The gear box has a casing and a transmission shaft partially received in the casing. The impeller has an impeller shaft and vanes. The impeller shaft has a hollow columnar outer shaft housing and a hollow columnar inner shaft housing. The inner and outer shaft housings are connected using a plurality of rib portions. The inner shaft housing is further connected to the transmission shaft of the gear box. The vanes are integrated formed on an outer peripheral surface of the outer shaft. The stream-guiding ring is assembled to the casing of the gear box to house the impeller. The stream-shaping nozzle is connected to a rear end of the stream-guiding ring for providing stream-shaping effects. Thereby, the boat propeller has its water inlet diameter maximized, which helps to improve propulsive efficiency.

What is claimed is: 
     
         1 . A boat propeller, comprising:
 a gear box, including a casing and a transmission shaft, wherein the transmission shaft is rotatably installed in the casing and has a front end thereof such received in the casing that a rear end thereof juts out the casing;   an impeller, including an impeller shaft and a plurality of vanes, wherein the impeller shaft has a hollow columnar outer shaft, a hollow columnar inner shaft housing, and a plurality of rib portions, in which the inner shaft housing is received in the outer shaft housing and coaxially connected to the transmission shaft of the gear box, and the rib portions are connected between the outer shaft housing and the inner shaft housing, while the vanes are integratedly connected to an outer peripheral surface of the outer shaft housing of the impeller shaft;   a stream-guiding ring, which is assembled to the casing of the gear box and houses the impeller; and   a stream-shaping nozzle, which is connected to a rear end of the stream-guiding ring.   
     
     
         2 . The boat propeller of  claim 1 , wherein the stream-shaping nozzle has a ring portion, a hollow axial portion, and a plurality of stream-shaping portions, in which the ring portion is connected to the rear end of the stream-guiding ring, and the hollow axial portion is defined in the ring portion and coaxially connected to the outer shaft housing of the impeller shaft of the impeller, while the stream-shaping portions are connected between the ring portion and the hollow axial portion and arranged equidistantly to circle the hollow axial portion. 
     
     
         3 . The boat propeller of  claim 2 , wherein the ring portion of the stream-shaping nozzle has a changing cross-sectional area that becomes smaller as the ring portion extends away from the stream-guiding ring. 
     
     
         4 . The boat propeller of  claim 1 , wherein the casing of the gear box has a tapered shaft, and an exhaust channel is formed between the tapered shaft and the impeller shaft of the impeller. 
     
     
         5 . The boat propeller of  claim 4 , wherein the casing of the gear box further has an upper wing, a lower wing, and an anti-swirl baffle, in which the upper wing and the lower wing are integratedly connected to top and bottom sides of the tapered shaft, and the anti-swirl baffle is integratedly connected to the upper wing so it is located above the stream-guiding ring; two upper supports being symmetrically fixed to a top edge of the outer peripheral surface of the stream-guiding ring for connecting the anti-swirl baffle, and a lower support being fixed to a bottom edge of the outer peripheral surface of the stream-guiding ring for connecting the lower wing. 
     
     
         6 . The boat propeller of  claim 5 , wherein the casing of the gear box further has a connecting portion that is integratedly connected to a top of the upper wing so as to be located above the anti-swirl baffle. 
     
     
         7 . The boat propeller of  claim 1 , wherein the inner shaft housing of the impeller is indirectly connected to the transmission shaft of the gear box through a bushing. 
     
     
         8 . The boat propeller of  claim 7 , wherein the inner shaft housing has an inner peripheral surface thereof provided with a positioning recess, and the bushing has an outer peripheral surface thereof provided with a positioning ridge, so that the positioning ridge of the bushing engages with the positioning recess of the inner shaft housing. 
     
     
         9 . The boat propeller of  claim 8 , wherein the bushing has a shock-absorbing layer and a metal layer wrapping the shock-absorbing layer, in which the shock-absorbing layer has an outer peripheral surface thereof provided with the positioning ridge, and the metal layer is connected to the transmission shaft.