Patent Publication Number: US-8523627-B2

Title: Model helicopter with improved reduction gear mechanism

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to radio-controlled helicopters and more particularly to a model helicopter having a motor with a motor shaft being coaxial with a main shaft of a main rotor and an improved reduction gear mechanism. 
     2. Description of Related Art 
     Major components of a drive mechanism of a typical type of model helicopter are shown in  FIGS. 1 and 2  and comprise a motor (e.g., battery powered servo motor)  10 , a small gear  12  fixed to a motor shaft of the motor  10 , a main gear  11  in mesh with the small gear  12 , a main shaft  1  fixed to the main gear  11 , and a main rotor  13  at a top of the main shaft  1  and co-rotated therewith. 
     It is understood that the more powerful of the motor  10  the larger of the main gear  11  will be (i.e., greater diameter). One type of model helicopter having a main gear  11  with a diameter of 120 mm is available. However, greater diameter of main gear is not desired since it can adversely affect maneuverability, shorten the useful life of components, and greatly consume energy. 
     The invention is intended to obviate the above drawbacks by providing a model helicopter having a motor with a motor shaft being coaxial with a main shaft of a main rotor. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a model helicopter comprising a drive mechanism, the drive mechanism comprising a battery powered motor comprising a toothed motor shaft; a main rotor comprising a main shaft aligned with the motor shaft, the main shaft including a main gear; and a reduction gear assembly comprising a lower section including four first gears arranged around the motor shaft, and four second gears smaller than the first gears, each second gear fixed to top of the first gear; an upper section including four third gears and four fourth gears each being smaller than the third gear and fixed to top of the third gear, the fourth gears being meshed with the main gear; and four shafts each axially passing through the fourth gear, the third gear, the second gear, and the first gear so that a revolution of the motor shaft rotates the main shaft via the first gears, the fourth gears, and the main gear. 
     The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of major components of a drive mechanism of a typical model helicopter; 
         FIG. 2  is a top plan view of  FIG. 1  with the main rotor removed for clarity; 
         FIG. 3  is a perspective view of major components of a drive mechanism of a model helicopter according to the invention with a main rotor and a substantial portion of a main shaft removed; 
         FIG. 4  is a top plan view of a lower section of the reduction gear assembly of  FIG. 3 ; and 
         FIG. 5  is a perspective view of the major components of the drive mechanism of the model helicopter according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 3 to 5 , a drive mechanism of a model helicopter according to the invention is shown. A tail rotor and its associated components are not the subject of the invention and are not shown and described for brevity. 
     Major components of the drive mechanism comprise a motor (e.g., battery powered servo motor)  2 , and a reduction gear assembly  3 . A toothed motor shaft (only a portion being shown in  FIG. 3 )  21  of the motor  2  has a portion disposed in the reduction gear assembly  3 . The reduction gear assembly  3  includes a circular base  32 ; a lower section mounted on the base  32  and having four large gears  31  arranged as four corners of a virtual square, and four small gears  34  each fixed to top of the large gear  31 ; an upper section having four large gears  35  arranged as four corners of a virtual square, and four small gears  36  each fixed to top of the large gear  35 ; and four shafts  33  each passing through the upper small gear  36 , the upper large gear  35 , the lower small gear  34 , and the lower large gear  31  at the same corners of the squares and fixed thereto. The large gears  31  of the lower section are meshed with the toothed motor shaft  21  of the motor  2 . The reduction gear assembly  3  is enclosed by a reduction gear box (not numbered). 
     It is noted that the number of each of the gears  31 ,  34 ,  35 ,  36  and shafts  33  can be different from four in other embodiments (e.g., three). 
     Major components of the drive mechanism comprise further comprise a main shaft  4 , a main gear  41  fixed to the main shaft  4  and meshed with the four upper small gears  36 , a plate member  5  disposed on top of the reduction gear assembly  3 , and a main rotor  6  fixed to top end of the main shaft  4  and co-rotated therewith. 
     The revolution of the toothed motor shaft  21  of the motor  2  will rotate the main shaft  4  via the lower large gears  31 , the upper small gears  36 , and the main gear  41 . Eventually, the main rotor  6  rotates at the number of revolution determined by the gear reduction ratio of the toothed motor shaft  21  to the large gear  31  and that of the small gear  36  to the main gear  41 . 
     It is envisaged by the invention that maneuverability and stability can be improved, the useful life of components can be prolonged, and energy consumption can be reduced because the motor shaft of the motor is aligned with the main shaft of the main rotor and the provision of the reduction gear assembly. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.