Patent Publication Number: US-7898130-B2

Title: Control servo

Description:
BACKGROUND OF THE PRESENT INVENTION 
     1. Field of Invention 
     The present invention relates to a control servo or control device, and more particularly to a control servo having a simple structure, relatively light weight and high integration for controlling a remote-controlled model aircraft. 
     2. Description of Related Arts 
     A conventional model aircraft is remotely controlled to take-off, land and turn via the movement of the aerofoil surfaces by means of the rudder or other steering device. For larger aircraft, weight is not the main issue as there is sufficient power for a wide choice of servos. However, with the demand for entertainment, the development of small scale and micro scale model aircraft is growing rapidly. The small scale and micro aircraft has a critical requirement in its weight. The conventional model aircraft servos are complicated and required to include a complex gear reduction system so it is hard to reduce the overall weight and size of the servo and in turn the weight of the aircraft. In other words, the structure of the servo restricts the development of the small-scale model aircraft from further miniaturization. 
     SUMMARY OF THE PRESENT INVENTION 
     An object of the present invention is to provide a control servo which has simple structural configuration and light weight. 
     Accordingly, in order to accomplish the above objective, the present invention provides a control servo, which comprises a supporting frame, a motor, a driving shaft and a control slider. The supporting frame comprises a mount and a slider cavity, wherein the motor is supported in the mount of the supporting frame. In order to transmitting power between the motor and the driving shaft , a driving gear provided at an output end of the motor and a driven gear provided at one end of the driving shaft. The driving shaft is positioned longitudinally through the slider cavity. The driven gear is to mesh with the driving gear such that when the driving gear is driven to rotate by the motor, the driving shaft is rotated by the driven gear. The driving shaft penetrates through the control slider while an upper portion of the control slider extends out of the slider cavity in such a manner that the control slider moves along the slider cavity when the driving shaft is rotated. An electric brush is provided underneath the control slider. 
     According to the present invention, the control circuit board of the control servo has drive circuit provided thereon, wherein the supporting frame has at least an affixing hole for affixing the supporting frame to the control circuit board via an affixing means. 
     The control circuit board has an elongated carbon film and an elongated silver film spaced apart printed thereon, wherein the electric brush is in electrical contact with the carbon and silver films when the supporting frame is mounted on the control circuit. 
     The control servo further comprises a retention bushing attached at the opposite end of the driving shaft. 
     The control slider has a longitudinal sliding slot where the driving shaft passes therethrough, so that the outer threaded portion of the threaded driving shaft is engaged with the inner threaded portion of the control slider so as to make the control slider to slide when the threaded shaft is rotated. 
     A plurality of coupling holes is provided at the upper portion of the control slider for coupling with moving parts of the aerofoil. 
     Accordingly, the difference between the present invention and the conventional art is that the present invention does not require any traditional potentiometer and eliminates the complex gear reduction box and the traditional circuit board. The present invention also simplifies the structural configuration by integrating the carbon film of the potentiometer with the circuit board. Therefore, the present invention provides a control servo having the features of simple structural configuration, relatively light weight, and high integration. Most importantly, the weight of the control servo can be significantly reduced so as to be incorporated within smaller and micro scale aircraft so as to advance the development of such model aircraft. 
     These and other objectives, features, and advantages of the present invention will become apparent from the following detailed description, the accompanying drawings, and the appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a control servo according to a preferred embodiment of the present invention. 
         FIG. 2  is a top view of the control servo according to the above preferred embodiment of the present invention. 
         FIG. 3  is a perspective view of the supporting frame of the control servo according to the above preferred embodiment of the present invention. 
         FIG. 4  is a perspective view of the control slider of the control servo according to the above preferred embodiment of the present invention. 
         FIG. 5  is a bottom view of the control servo according to the above preferred embodiment of the present invention. 
         FIG. 6  is a perspective view of the electric brush of the control servo according to the above preferred embodiment of the present invention. 
         FIG. 7  is a perspective view of the control servo according to the above preferred embodiment of the present invention, illustrating the supporting frame being mounted on the control circuit board. 
         FIG. 8  is an exploded perspective view of the control servo according to the above preferred embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to  FIGS. 1 and 2  of the drawings, a control servo for a model aircraft according a preferred embodiment of the present invention is illustrated, wherein the control servo comprises a supporting frame  10 , a motor  20  which is embodied as an electric motor, a driving shaft  30  which is an elongated shaft having an outer threaded portion, and a control slider  40 . Further referencing  FIG. 3 , the supporting frame  10  comprises a mount  11  and a slider cavity  12 , wherein the mount  11  has a round hoop structure so that the motor  20  is supported by the supporting frame  10  via the hoop structure of the mount  11 . Accordingly, the mount  11  and the slider cavity  12  are positioned side-by-side such that the mount  11  is parallel to the slider cavity  12  to form a one-piece integral structure of the supporting frame  10 . The slider cavity  12  has two side-openings  14  formed at both ends of the supporting frame  10  respectively, wherein the threaded driving shaft  30  is longitudinally extended through the slider cavity  12  at a position so that two ends of the threaded driving shaft  30  are extended out of the slider cavity  12  through the side-openings  14 . The control slider  40  has a bottom portion slidably coupled with the threaded driving shaft  30  within the slider cavity  12 . 
     As shown in  FIG. 4 , the control slider  40  has a longitudinal sliding slot  41  having an inner threaded portion provided along the surrounding wall thereof, wherein the threaded driving shaft  30  is extended through the sliding slot  41  at a position that the outer threaded portion of the threaded driving shaft  30  is engaged with the inner threaded portion of the control slider  40  so as to drive the control slider  40  to slide when the threaded driving shaft  30  is rotated. 
     The upper portion of the control slider  40  is extended out of the slider cavity  12 . A plurality of coupling holes  42 , in which three coupling holes  42  are shown in  FIG. 4 , is spacedly provided at the upper portion of the control slider  40  for coupling with the moving parts of the aerofoil, such as rudder or steering device, through one or more control cables (not shown in Figures). Therefore, when the control slider  40  is driven to slide along the slider cavity  12 , the moving parts of the aerofoil are moved correspondingly to steer the model aircraft. It is worth mentioning that the number of coupling holes  42  can be selectively added or reduced and the diameter of each of the coupling holes  42  can be selectively modified according to the actual operation of the aerofoil. 
     Referring to  FIGS. 1 and 2 , a driving gear  50  and a driven gear  60  is provided for transmitting power. An output end of the motor  20  is coupled with the driving gear  50  so that the driving gear  50  is driven to rotate by the motor  20 . One end of the threaded driving shaft  30  is coupled with the driven gear  60  which is mesh with the driving gear  50  such that when the driving gear  50  is rotated, the driving shaft  30  is driven to be rotated through the driven gear  60 . A gear diameter of the driving gear  50  is smaller than that of the driven gear  60  so as to reduce the speed from the motor  20  to the driving shaft  30 . In order to prevent the driving shaft  30  from being disengaged from the supporting frame  10  during the rotational operation, a retention bushing  31  is coupled at the other end of the driving shaft  30 . In other words, the two ends of the threaded shaft  30  are coupled with the driven gear  60  and the retention bushing  31  respectively such that the driving draft  30  is securely retained at the slider cavity  12  of the supporting frame  10 . 
     As shown in  FIG. 5 , the control servo of the present invention further comprises an electric brush  70  which is provided at the bottom side of the control slider  40 . As shown in  FIG. 6 , the electric brush  70  comprises a contacting side  71  and a brushing side  72 , wherein the brushing side  72  is inclinedly extended from the contacting side  71  at an acute angle. The electric brush  70  is made of a thin copper piece which is flexible and electrically conductive. The contacting side  71  of the electric brush  70  is coupled at the bottom side of the control slider  40  while the brushing side  72  is downwardly and inclinedly extended from the bottom side of the control slider  40 . 
     As shown in  FIGS. 1 and 2 , the supporting frame  10  has at least an affixing hole  13 . Preferably two or more affixing holes  13  are spacedly provided at the peripheral side of the supporting frame  10 . As shown in  FIGS. 7 and 8 , the supporting frame  10  is mounted at a control circuit board  80  through the affixing holes  13  by the affixing means such as screws. Accordingly, the control circuit board  80  has a drive circuit printed thereon. In order to retain the position of the electric brush  70 , the control circuit board  80  has two conductive films spacedly printed on the control circuit board  80  at the area for positioning the supporting frame  10 . wherein the two conductive films can be an elongated carbon film  81  and an elongated silver film  82  respectively. In other words, when the supporting frame  10  is mounted at the control circuit board  80 , the brushing side  72  of the electric brush  70  is electrically contacted with the carbon film  81  and the silver film  82 , so as to provide a brush structure similar to the sliding potentiometer. 
     According to the present invention as disclosed above, the control servo of the present invention does not require any traditional potentiometer and eliminates the complex gear reduction box and the traditional circuit board. The present invention also simplifies the structural configuration by integrating the carbon film of the potentiometer with the circuit board, so that the control servo of the present invention provides the features of simple structural configuration, relatively light weight, and high integration. Most importantly, the weight of the control servo can be significantly reduced so as to be incorporated within smaller and micro scale aircraft to advance the development of such model aircraft. 
     One skilled in the art will understand that the embodiment of the present invention as shown in the drawings and described above is exemplary only and not intended to be limiting. It will thus be seen that the objects of the present invention have been fully and effectively accomplished. The embodiments have been shown and described for the purposes of illustrating the functional and structural principles of the present invention and is subject to change without departure from such principles. Therefore, this invention includes all modifications encompassed within the spirit and scope of the following claims.