Abstract:
A coaxial dual-rotor model helicopter system includes a power control mechanism, a transmission mechanism, a control mechanism and a rotor mechanism. The rotor mechanism includes an upper rotor and a lower rotor coaxially installed on an upper side and a lower side of a main shaft and controlled by an inner shaft and an outer shaft for rotating. The control mechanism includes a Bell self-balance mechanism to control the upper rotor and a Bell-Hiller control structure to control the lower rotor. The power control mechanism controls the rotor mechanism through the transmission mechanism and the control mechanism. The present invention achieves balance effect through the upper rotor by employing the Bell self-balance mechanism that has a great stability to provide automatic control. The lower rotor aims to control direction and employs the Bell-Hiller control structure that has a high maneuverability to perform active control.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a coaxial dual-rotor model helicopter and particularly to a dual-rotor model helicopter control system to provide improved stability and maneuverability. 
       BACKGROUND OF THE INVENTION 
       [0002]    Conventional coaxial dual-rotor model helicopters such as those disclosed in PCT patent No. WO 02/064425 A2 and China publication No. CN1496923A include two rotors installed on a shaft, one for veer control and another for balance control. Maneuverability and stability mainly depend on whether the balance mechanism adopts balance paddles (WO 02/064425 A2) or balance weights (CN1496923A). Those adopted the balance paddle mechanism have superior balance and veer control but inferior stability, while those adopted the balance weight mechanism have improved stability but poor maneuverability, which are more suitable for novices at aviation models. However, both of the aforesaid structures have a great number of elements, malfunction frequently occurs. Moreover, design for coordination of upper and lower rotors is more sophisticated, and more adjustment parameters are needed and adjustment is complicated. Thus the costs are higher and usability is lower. 
         [0003]    As the performances of the aforesaid toy helicopters vary in extremes, either has a great stability or a great maneuverability, they are suitable only for novices or players with experience or professional skills, but not desirable for midrange players who have limited experience but not yet reach the professional level. In short, there is still a need for a midrange model helicopter both in terms of stability and maneuverability in the present market that yet to be fulfilled. 
       SUMMARY OF THE INVENTION 
       [0004]    The primary object of the present invention is to overcome the shortcomings of the conventional techniques by providing a dual-rotor model helicopter control system to offer improved stability and maneuverability. 
         [0005]    In order to achieve the foregoing object, the dual-rotor model helicopter control system according to the present invention comprises a power control mechanism, a transmission mechanism, a control mechanism and a rotor mechanism. The rotor mechanism includes an upper rotor and a lower rotor coaxially installed on an upper side and a lower side of a main shaft and controlled respectively by an inner shaft and an outer shaft for rotating. The present invention provides an improved structure in the control mechanism that includes a Bell self-balance mechanism to control the upper rotor and a Bell-Hiller control structure to control the lower rotor. The power control mechanism controls the rotor mechanism through the transmission mechanism and the control mechanism. The present invention achieves balance effect through the upper rotor and employs the Bell self-balance mechanism that has a great stability to provide automatic control. The lower rotor aims to control direction and employs the Bell-Hiller control structure that has a high maneuverability to perform active control. In a non-active control situation, the Bell self-balance mechanism can automatically correct interferences caused by external factors such as airflow and the like to maintain desired stability. In an active control condition, such as veering, the higher maneuverable Bell-Hiller control structure provides sufficient and desired maneuverability to the helicopter. 
         [0006]    The present invention provides mechanisms with different functions on the two rotors so that the helicopter can fly in a stable condition and also can be controlled and maneuvered flexibly. Aiming such a goal, the Bell self-balance mechanism may also be installed on the lower rotor and the Bell-Hiller control structure installed on the upper rotor. The Bell self-balance mechanism or Bell-Hiller control structure may be installed respectively on an upper side or lower side of the rotor mechanism. 
         [0007]    The foregoing, as well as additional objects, features and advantages of the invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]      FIG. 1  is a schematic view of the structure of the present invention. 
           [0009]      FIG. 2  is a schematic view of an internal structure according to  FIG. 1 . 
           [0010]      FIG. 3  is an exploded view according to  FIG. 1 . 
           [0011]      FIG. 4  is a fragmentary enlarged view of segment A in  FIG. 2 . 
           [0012]      FIG. 5  is an exploded view according to  FIG. 4 . 
           [0013]      FIG. 6  is a fragmentary enlarged view of segment B in  FIG. 2 . 
           [0014]      FIG. 7  is an exploded view according to  FIG. 6 . 
           [0015]      FIG. 8  is a schematic view showing vibration conditions of axle of the Bell-Hiller control structure. 
           [0016]      FIG. 9  is a schematic view of a structure driving the Bell-Hiller control structure. 
           [0017]      FIG. 10  is a schematic view of a control structure of the lower rotor. 
           [0018]      FIG. 11  is a side view according to  FIG. 1 . 
           [0019]      FIG. 12  is a schematic view of the main shaft power system. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0020]    Please refer to  FIG. 1 , the dual-rotor model helicopter according to the present invention includes a fuselage  6  with an ornamental casing  9  at a front end, a tail assembly  7  at a rear end and a main shaft  8  in the middle to drive a balance system  1  and a veering system  2  to rotate in opposite directions as marked by the arrows in the drawing. Also refer to  FIG. 2  for the structure with the ornamental housing  9  removed and  FIG. 3  for detailed elements. The entire dual-rotor model helicopter can be divided into eight portions: the balance system  1  comprising an upper rotor  12  and a Bell self-balance mechanism  11 , the veering system  2  comprising a lower rotor  22 , a Bell-Hiller control structure  21  and a slant rotary disk  23 , a power control mechanism  3  comprising three rudder sets  31 ,  32  and  33  evenly disposed on a same circle and spaced from each other at an angle of 120 degrees, an aviation power mechanism  4  comprising an electric apparatus  41  and a speed changing mechanism  42 , a circuit system  5  comprising a wireless transceiver circuit  51  and a battery  52 , the fuselage  6  comprising a left chassis  61 , a right chassis  62 , a landing gear  63  and linkage structures bridging them, the tail assembly  7  comprising a tail wing shaft  71 , a propeller  72 , a horizontal stabilizer  73 , a vertical fin  74  and bracing bars  75 , and the main shaft  8  comprising an inner shaft  81  and an outer shaft  82  coupled together. 
         [0021]    Refer to  FIGS. 4 and 5  for the balance system  1 . The Bell self-balance mechanism  11  includes a balance bar  111  and balance weights  112  located at two ends of the balance bar  111 . The upper rotor  12  includes an upper rotor clip  121  and two upper blades  122  clamped by two ends of the upper rotor clip  121 . The Bell self-balance mechanism  11  and upper rotor  12  are installed on an upper portion of the inner shaft  81  through spindles  113  and  123  that are perpendicular to the main shaft  8 , and are located on different planes and connected by self-balance bar  13 . The spindles  113  and  123  of the Bell self-balance mechanism  11  and upper rotor  12  are parallel with each other and revolve independently in a tilted manner about their own axes as marked by the arrows in  FIG. 4 . The upper rotor clip  121  has a frame  124  in the middle that is coupled on the inner shaft  81  through the spindle  123  and turnable. The inner shaft  81  has a shaft holder  811  at the top end with a notch  812  formed thereon in the middle. The Bell self-balance mechanism  11  has a middle portion mounted onto the shaft holder  811  through the spindle  113  and is movable up and down in a tilted manner. The balance bar  111  is slidable in the notch  812 . The self-balance bar  13  has two ball sleeves  131  and  132  at two ends that are respectively connected to two ball fasteners  133  and  134  located respectively on the Bell self-balance mechanism  11  and upper rotor  12 . The Bell self-balance mechanism  11  and upper rotor  12  are bridged by the self-balance bar  13  so that they are moveable synchronously in the tilted manner during flying. In the event that the main shaft  8  is tilted against the upper rotor due to external interference during flying, the Bell self-balance mechanism  11  can correct the angle between the main shaft  8  and upper rotor  12  through centrifugal principle so that both of them remain perpendicular with each other. Thereby a stable effect can be achieved. Please refer to China patent No. CN1496923A for detailed operation principle if desired. 
         [0022]    Refer to  FIGS. 6 and 7  for the Bell-Hiller control structure  21 . It comprises a direction control bar  211  and blades  212  installed on two ends of the direction control bar  211 , the lower rotor  22  and the Bell-Hiller control structure  21  that are installed on a lower portion of the outer shaft  82  through axles  223  and  213  that are perpendicular to the main shaft. They are perpendicular with each other and coupled with the power control mechanism  3  through a transmission mechanism. The axles  223  and  213  of the lower rotor  22  and the Bell-Hiller control structure  21  are parallel with and perpendicular to each other. The axle  223  coincides with the axis of the lower rotor  22 . The lower rotor  22  revolves about its axis as marked by the arrows in  FIG. 6 . The Bell-Hiller control structure  21  can revolve about the axle  213  in a tilted manner as marked by the arrows in  FIG. 6 . 
         [0023]    The lower rotor  22  includes two lower rotor clips  221  and two lower blades  222 . Each of the lower rotor clips  221  has a front end clipping the lower blade  222  and a distal end inserted into the axle  223  of the lower rotor  22 . The lower rotor clip  221  has an eccentric control end  224  at one side, and an upper disk  232  of the slant rotary disk  23  coupled with the eccentric control end  224  through a linkage bar mechanism to control revolving of the lower rotor  22  about the axle  223 . The direction control bar  211  of the Bell-Hiller control structure  21  has a middle portion coupled on the main shaft  8  through a frame for rotating. The frame includes an inner frame  214  and an outer frame comprising frame elements  215  and  216 . The inner frame  214  rotates about the axle  213  of the Bell-Hiller control structure  21  in a vibration manner, while the outer frame rotates about the axis of the direction control bar  211  in a vibration manner. The directions that the inner and outer frames rotate are perpendicular to each other as shown in  FIG. 8 . The direction control bar  211  is fixed on the outer frame and inserted into the inner frame  214  is a turnable manner. The outer frame can be turned to drive the direction control bar  211  to turn. The slant rotary disk  23  is coupled with two ends of the outer frame through a linkage bar mechanism to control the angle of the blades  212  at the distal end of the direction control bar. 
         [0024]    The transmission mechanism includes three linkage bar mechanisms  24 ,  25  and  26  and a slant rotary disk. The slant rotary disk is coupled with the outer shaft  82  of the main shaft  8  through a ball coupler  234  in a turnable manner, and includes an upper disk  232  and a lower disk  231  that are rotated about the ball coupler  234  through a spring  233  wedged in the center of the slant rotary disk. The lower disk  231  has three ball coupler nodes and a direction fixing bar  238  at one side extended outwards. The direction fixing bar  238  is fixed in a direction fixing trough  239  formed on the fuselage and slidable longitudinally in the trough as shown in  FIGS. 3 and 11 . The ball coupler nodes of the lower disk  231  are connected to the rudder set  33  through the first linkage bar mechanism  26  (including three linkage bars). The upper disk  232  has four ball coupler nodes at one side extended outwards that are perpendicular to each other. Two opposing ball coupler nodes thereof form one set, and are connected to the eccentric control end  224  of the lower rotor  22  through the second linkage bar mechanism  25 , and connected to the frame element  215  of the outer frame in the middle of the direction control bar  211  through the third linkage bar mechanism  24 . 
         [0025]    The third linkage bar mechanism  24  bridges the upper disk  232  and the frame element  215 , and includes a lower linkage bar  242  connecting to the upper disk  232 , an upper linkage bar  241  connecting to the frame element  215  and a first lever mechanism  243  which has a short arm connecting to the lower linkage bar  242  and a long arm connecting to the upper linkage bar  241 . The first lever mechanism  243  has a first fulcrum  244  located on the outer shaft  82  as shown in  FIG. 9  which illustrates only one set of mechanism to facilitate viewing. When the upper disk  232  is tilted, the lower linkage bar  242  is moved downwards to amplify and transmit the tilted movement of the upper disk  232  through the first lever mechanism  243  to the upper linkage bar  241 , then the upper linkage bar  241  drives the outer frame to rotate, thereby to change the thread pitch of the blade  212 . To improve maneuverability, the present invention utilizes the first lever mechanism  243  to amplify the movement of the slant rotary disk  23 , so that the slant rotary disk  23  has higher sensitivity. 
         [0026]    The second linkage bar mechanism  25  bridges the upper disk  232  and the eccentric control end  224  of the lower rotor  22 , and includes a lower linkage bar  252  connecting to the upper disk, an upper linkage bar  251  connecting to the eccentric control end  224  and a second lever mechanism  253  which includes a long arm connecting to the lower linkage bar  252  and a short arm connecting to the upper linkage bar  251 . The second lever mechanism  253  has a second fulcrum  254  located on the outer shaft  82  as shown in  FIG. 10  which illustrates only one set of mechanism to facilitate viewing. When the upper disk  232  is tilted, the lower linkage bar  252  is moved downwards to shrink and transmit the tilted movement of the upper disk  232  through the second lever mechanism  253  to the upper linkage bar  251 , the upper bar  251  drives the eccentric control end  224  to change the thread pitch of the lower rotor  22 . During flying, alteration of the thread pitch of the lower rotor  22  is smaller than that of the blade  212 . In order to control alterations of two thread pitches through the same slant rotary disk  23 , the present invention shrinks the movement of the slant rotary disk  23  through the second lever mechanism  253 , thus the structure is simplified and also more stable. By means of the foregoing structure, the present invention provides great maneuverability same as that of WO 02/064425 A2 with a simpler structure but greater stability. 
         [0027]    In order to make the first lever mechanism  243  to be rotated synchronously with the main shaft, the present invention provides two detent struts  28  located between the outer shaft  82  and the third linkage bar mechanism  24  which bridges the slant rotary disk  23  and the outer frame and extended in the direction along the main shaft  8 . 
         [0028]    Referring to  FIG. 11 , the Bell self-balance mechanism  11  generates a centrifugal force through rotation to drive the upper rotor  12  to move synchronously in the tilted manner, and automatically correct unbalanced conditions of the helicopter during flying to maintain stability of the fuselage. Through the up and down moving of the slant rotary disk  23 , alteration of the thread pitch of the blades of the lower rotor  22  and Bell-Hiller control structure  21  can be controlled to control movements of ascending, descending and spiraling of the helicopter. 
         [0029]    The inner and outer shafts  81  and  82  of the main shaft  8  are rotated in opposite directions by driving of the electric apparatus  41  through the speed changing mechanism  42  as shown in  FIG. 12 . The speed changing apparatus  42  comprises a main active gear  421  fixed on the spindle of the electric apparatus, a belt gear including a pinion  422  and a small pulley  423  that rotate coaxially, a large gear  424  fixed on the outer shaft  82 , a large pulley  425  and a synchronous belt  426  fixed on the inner shaft  81 . The large gear  424  is engaged with the pinion  422 , the synchronous belt  426  is coupled on the large pulley  425  and the small pulley  423 , and the main active gear  421  drives the large gear  424  and the large pulley  425  to rotate in opposite directions through the belt gear.