Abstract:
A remotely controlled model airplane includes a receiver responsive to signals from a transmitter to control the direction of flight of the model airplane. The receiver, powered by a battery, demodulates the signal transmitted by the transmitter to selectively energize an electrical coil to generate a magnetic field of a first or second polarity. A rudder pivotally attached to the vertical stabilizer includes a magnet responsive to the magnetic fields generated and is urged in one direction or the other resulting in commensurate pivotal movement of the rudder. A hinge interconnecting the rudder and vertical stabilizer urges return to center of the rudder after it has been deflected left or right by the magnet responding to the magnetic field created as a result of a signal transmitted by the transmitter. An electric motor also under control of the transmitter and receiver may be incorporated to rotate a propeller to provide thrust and forward motion of the model airplane. By employing a transmitter to selectively transmit a plurality of signals, control surfaces of the model airplane can be deflected to provide 2-axis control to selectively alter the direction and pitch of the model airplane.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to control systems for remotely controlled model airplanes and, more particularly, to magnetically operated centrally biased control surfaces for a model airplane. 
   2. Description of Related Prior Art 
   Remotely controlled, and formerly referred to as radio controlled, model airplanes have been built and flown as a hobby since the 1940s when vacuum tube operated transmitters and receivers became available for use in model airplanes. With advances in the transmitter/receiver art, there have been significant size and weight reductions in the related equipment and there have been significant improvements in reducing the electrical power requirements. With such reductions in size and weight, smaller and lighter model airplanes became possible to be remotely controlled. 
   Initially, the control system actuated by a signal from the receiver was a rubber band driven escapement that provided left or right rudder deflection for directional control. Generally, such escapements lacked sufficient power to deflect the elevator to obtain a change in pitch or to deflect the ailerons to obtain a left or right rolling moment about the longitudinal axis. Moreover, control of the engine speed and operation was primarily limited to shutting down the engine, which engine was usually a single cylinder internal combustion engine. As technology advanced, several servo mechanisms were developed which had significant power to operate the various control surfaces and to provide a throttling capability for the engine. During the last ten years or so, the size of these servos has been significantly reduced. They also became capable of full proportional control to accurately deflect the respective control surface(s). 
   Through careful aerodynamic design of a model airplane, it is possible to control not only the direction of flight but also the pitch attitude of a model airplane using only deflection of the rudder. A skilled pilot can even do basic aerobatic maneuvers using only selected timed rudder deflection. For small sized lightweight model airplanes, a magnetic actuator for the rudder was available a number of years ago. This actuator included a coil to drive a linkage connected to the rudder of the model airplane. The signal transmitted by the transmitter and received by the receiver either energized the coil or de-energized the coil. The rudder was biased in one direction during the absence of a signal and upon transmission of a control signal, the coil was energized to cause deflection of the rudder in the other direction. By regulating the relative on/off periods of energizing the coil, directional control of the airplane could be maintained but a great deal of skill by the ground based pilot was required. Because of the low power output of the coil, the linkage connected to the rudder had to be very carefully adjusted, be essentially slop free and minimal friction was required. 
   With the advent of micro sized receivers, electric motors and small powerful batteries, small and light weight model airplanes can now be remotely controlled. As small and light weight model airplanes require relatively small forces to actuate control surfaces for controlling movement in the pitch, yaw and longitudinal axis, new and innovative low power servo mechanisms can be used for these purposes. 
   SUMMARY OF THE INVENTION 
   A conventionally configured model airplane that has a fuselage supporting a wing for generating lift, a fixed horizontal stabilizer for providing stability in the pitch axis and a vertical stabilizer for providing stability in the yaw axis includes a pivotally mounted rudder biased to the center position. A motor driven propeller for providing thrust may be included. A ground based transmitter includes a control to regulate left and right deflection of the rudder and may include a further control for the airplane motor to regulate the thrust. By such deflection of the rudder, the direction of travel of the model airplane can be controlled. A coil fixedly attached to the vertical stabilizer adjacent the hinge line with the rudder is energized to provide a magnetic field having a first or second polarity. A magnet attached to the rudder proximate the coil is responsive to each magnetic field generated and as a result of such response is urged to pivot to the left or the right. In response to the movement of the magnet, the rudder will be deflected left or right and the model airplane will change direction accordingly. On cessation of a signal actuating the coil, the hinges interconnecting the rudder with the vertical stabilizer bias the rudder to the center position. Thereby, the control signals generated by the transmitter and received by the receiver to actuate the coil provide left or right deflection of the rudder and a mechanical hinge automatically returns the rudder to the central position. 
   If the transmitter and receiver are appropriately configured, 2-axis control of the model airplane is possible. To implement such 2-axis control, the horizontal stabilizer includes an elevator actuated by the above described coil and magnet. For a model airplane having a V-tail, each of the control surfaces is actuated by such a coil and magnet to provide control in the yaw axis and the pitch axis. A flying wing may include elevons each of which is actuated by the same type of coil and magnet to provide control about the pitch axis and about the longitudinal axis. 
   It is therefore a primary object of the present invention to provide a lightweight control system for controlling the flight of a remotely controlled model airplane. 
   Another object of the present invention is to provide a selectively actuated coil for deflecting a control surface of a model airplane in one direction or the other. 
   Still another object of the present invention is to provide a rudder for a model airplane that is biased to the central position and deflectable left or right in response to a created magnetic field. 
   Yet another object of this invention is to provide a magnet mounted on a control surface of a model airplane responsive to a selectively actuated coil for controlling the direction of flight of the model airplane. 
   A further object of the present invention is to provide flexible hinges for a control surface of a model airplane to bias the control surface to the central position and yet accommodate movement of the control surface about the hinge line in response to a magnetic field acting upon a magnet secured to the control surface. 
   A still further object of the present invention is to provide a low cost operating system for selectively deflecting one or more control surfaces of a model airplane. 
   A yet further object of the present invention is to provide a magnetically actuated rudder for a model airplane. 
   A yet further object of the present invention is to provide a magnetically actuated elevator for a model airplane. 
   A yet further object of the present invention is to provide magnetically actuated control surfaces of a V-tail model airplane. 
   A yet further object of the present invention is to provide magnetically actuated elevons of a flying wing model airplane. 
   A yet further object of the present invention is to provide a method for magnetically controlling the deflection of a control surface of a model airplane. 
   These and other objects of the present invention will become apparent to those skilled in the art and the description there proceeds. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention will be described with greater specificity and clarity with reference to the following drawings, in which: 
       FIG. 1  is an isometric view of a remotely controlled model airplane incorporating the present invention; 
       FIG. 1A  is a representative view of a transmitter for transmitting control signals to the model airplane shown in  FIG. 1 ; 
       FIG. 2  is a side view of the model airplane; 
       FIG. 3  is a top view of a coil mounted on the vertical stabilizer and a magnet mounted on the rudder of a model airplane and taken along lines  3 — 3 , as shown in  FIG. 2 ; 
       FIG. 3A  is a further detailed view of the coil and magnet; 
       FIG. 4  is a partial side view of the interconnection between the vertical stabilizer and the rudder; 
       FIG. 5  is a cross sectional view taken along lines  5 — 5 , as shown in  FIG. 4 ; 
       FIG. 6  illustrates a flying wing having elevons as control surfaces; 
       FIG. 7  is a detail view of an elevon, illustrating a coil and a magnet for actuating the elevon; 
       FIG. 8  is a cross section taken along lines  8 — 8 , as shown in  FIG. 7 ; 
       FIG. 9  illustrates a conventional horizontal stabilizer with elevators and a vertical stabilizer with rudder forming the rear empennage of a model airplane; 
       FIG. 10  illustrates a V-tail of a model airplane having control surfaces; and 
       FIG. 11  illustrates a 2-axis transmitter for use with the model airplanes, as shown in  FIGS. 6 ,  9  and  10 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Referring to  FIG. 1 , there is shown a model airplane  10 . The airplane includes a fuselage  12  supporting a wing  14  for generating lift upon forward motion of the plane. A horizontal stabilizer  16  provides stability in the pitch axis and is generally in alignment with longitudinal axis  18 . However, for stability purposes, the horizontal stabilizer may have a small negative angle of attack. A vertical stabilizer  20  provides stability about the yaw axis of the model airplane. A propeller  22  is turned by a motor (see  FIG. 2 ) mounted within fuselage  12  and provides thrust for forward motion of the model airplane. A rudder  24  is hingedly attached to vertical stabilizer  20  and upon movement left or right, as depicted by dashed lines  26 ,  28 , the direction of flight of the airplane will change to the left or to the right, respectively. 
   Model airplane  10  is remotely controlled, sometimes referred to as radio controlled. Referring jointly to  FIGS. 1 ,  1 A and  2 , the remote control apparatus will be described. A transmitter  30  includes an antenna for radiating the transmitted signal. The transmitted signal is sensed by antenna  34  electrically connected to receiver  36  mounted within fuselage  12 . The transmitter includes several controls. A button  38 , or the like, on transmitter  30  provides an on/off function for motor  40  located in the nose of model airplane  10 . Typically, a gear box  42  interconnects the armature of motor  40  with propeller  22 . Also typically, electrical power to the motor is provided by battery  44  through electrical conductors  46  connected with the circuitry in receiver  36  and through electrical conductor  48  providing power to motor  40  upon actuation of button  38  in the transmitter. Thereby, transmitter  30  controls the thrust produced by propeller  22 . 
   When button  50  on transmitter  30  is depressed, a signal for a left turn is generated and transmitted. This signal is sensed by receiver  36  through antenna  34  and suitably demodulated by demodulator  52 , which demodulator may be a part of the circuitry of the receiver. The demodulator produces a control signal via electrical conductors  54 ,  56  to energize coil  58 . Upon applying electrical power to the coil, it will produce a magnetic field of a first polarity. Control of the magnetic polarity is a function of which of conductors  54 ,  56  conveys a greater positive voltage to the coil. Upon depressing button  60  on transmitter  30 , a further signal is transmitted via antenna  32  and sensed by receiver  36  through antenna  34 . Demodulator  52  demodulates this signal and produces a further control signal on electrical conductors  54 ,  56 . This further control signal is of the reverse polarity of the control signal on conductors  54 ,  56  when button  50  is depressed. Thus, the magnetic field produced by coil  58  is now reversed in polarity. As depicted by arrow  62  on transmitter  30 , button  50  corresponds with a left turn and button  60  corresponds with a right turn. 
   Additional indicators  64 ,  66  may be employed in the transmitter to indicate the voltage state of the circuitry driving the transmitter, the state of charge in the event battery  44  is charged by the transmitter upon moving the battery from the model airplane to a compartment within the transmitter. Other indicia for various purposes may also be incorporated. 
   Referring jointly to  FIGS. 2 ,  3 ,  3 A,  4  and  5 , details attendant the attachment of rudder  24  to vertical stabilizer  20  and operation of the rudder will be described. Coil  58  is mounted in vertical stabilizer  20  close to hinge line  70 , representatively shown as the trailing edge of the vertical stabilizer. Electrical conductors  54 ,  56  provide power to the coil and produce the above described magnetic field having a first or a second polarity. Rudder  24  is attached to the vertical stabilizer by a pair of segments of rubber bands  72 ,  74 . Typically, the end of each rubber band is inserted and glued within a slot at hinge line  70  of the vertical stabilizer  20  and similarly lodged and glued within corresponding slots in rudder  24 . As illustrated, a space exists between the rudder and the vertical stabilizer. The purpose of this space is to permit the rudder to deflect left and right relative to the vertical stabilizer without binding or otherwise contacting the hinge line or other part of the vertical stabilizer during the normal extension of rudder deflection left and right. A magnet  76  is secured to the leading edge of rudder  24  by a dab of glue, a strap  78 , as shown, or other device. 
   Upon energizing coil  58  by pushing button  50  on transmitter  30 , the coil will create a magnetic field to attract the left side of magnet  76 , hereinafter referred to as pole  80 . In response to such magnetic attraction, pole  80  will be drawn toward and move toward coil  58 . The resulting movement of the magnet will cause the rudder to deflect to the left, as shown in  FIG. 3A  and represented by dashed line  82 . With the rudder moved to the left, model airplane  10  will go into a left turn. Once button  50  is released, no further power is applied to coil  58 . Without such power, magnet  76  is no longer attracted to the coil. The resiliency of rubber bands  72 ,  74  will therefore urge the rudder to its central position, as depicted in  FIG. 3 ,  3 A which essentially aligns the rudder with the vertical stabilizer. With such alignment, model airplane  10  will travel essentially straight ahead. Upon depressing button  60  of transmitter  30 , a further control signal will be generated and conveyed to coil  58  through electrical conductors  54 ,  56 . This further control signal is of opposite polarity, as discussed above, and the magnetic field produced by the coil is of opposite polarity also. As a result, pole  84  of magnet  76  will be attracted to the coil. Such attraction will result in commensurate movement of the magnet and rudder  24  coupled with the magnet. The extent of movement is represented by dashed line  86 . With the rudder in this position, model airplane  10  will turn to the right. On release of button  60 , the magnetic field generated by coil  58  will cease and neither pole  80  or  84  of magnet  76  will be attracted to the coil. Hence, rudder  24  will once again will become essentially aligned with vertical stabilizer  20  in response to urging by rubber bands  72 ,  74 . As a result, the model airplane will once again fly straight ahead. 
   As illustrated in  FIG. 2 , the model airplane may include an undercarriage  90  to permit taxiing on a surface and to take off along a simulated runway. Similarly, the undercarriage will permit landing on a smooth surface in the manner of a conventional airplane. During such taxiing and take off, buttons  50  and  60  on transmitter  30  may be actuated to control the direction of movement of the model airplane during both taxiing and take off. 
   Referring to  FIG. 6 , there is illustrated a representative flying wing  100 . A model airplane of this type generally includes a center section  102 , sometimes referred to as a fuselage, for housing a remote control receiver and batteries. Although not shown, a motor driving a propeller may be mounted in nose  104  of the center section to provide thrust. Alternatively, such a motor and propeller may be mounted at tail  106 . Usually, one or more rudders  108  are provided for directional stability. Control of flying wing  100  about the pitch axis and the longitudinal axis is obtained by operation of elevons  110 ,  112 . When these elevons operate in concert, either up or down, the pitch attitude of the flying wing is changed. When these elevons operate in the opposite directions, that is, one elevon is deflected upwardly and the other elevon is deflected downwardly, forces are generated to cause the flying wing to rotate about its longitudinal axis. Such rotation results in the lift produced by the flying wing to be toward the inside of the bank and result in turning of the flying wing. 
   The structure and operation of the elevons will be described with specific reference to  FIGS. 6 ,  7  and  8 . Elevon  12  is pivotally attached to wing  114  by two or more segments of rubber bands  72 ,  74 , as described above. These segments of rubber bands will tend to bias the elevon in its neutral or central position. A coil  58  is mounted in wing  14  adjacent the hinge line between the wing and elevon  112 . This coil is of the type described above. A magnet  76  is attached to the leading edge of elevon  112  proximate coil  58 . As described above, energization of coil  58  with a first polarity will attract one pole of magnet  76  and result in commensurate movement of elevon  112 . When the polarity of the signal applied to coil  58  is reversed, the other pole of magnet  76  will be attracted and elevon  112  will be deflected in the opposite direction. As also described, a remote control receiver is mounted at an appropriate location within flying wing  100  to generate signals to coil  58  in response to signals transmitted from a transmitter. 
   Elevon  110  is similarly attached to wing  114  by segments of rubber bands  72 ,  74  and is actuated by a similar coil  58  selectively energized to attract magnet  76  to produce upward or downward deflection of the elevon. Elevons  110  and  112  may be deflected in concert upwardly or downwardly to produce a change in pitch attitude of the flying wing. Alternatively, they may be deflected in opposite directions to provide a left or right rolling movement about the longitudinal axis of the flying wing. 
   Referring to  FIG. 9 , there is illustrated the rear section of fuselage  12 , which may be part of the model plane shown in  FIGS. 1 and 2 . For this reason, common elements will be assigned corresponding reference numerals. Rudder  24  is pivotally attached to vertical stabilizer  20  through segments of rubber band  72 ,  74 . Upon actuation of coil  58 , a magnetic force will be created and magnet  76  responds thereto resulting in deflection of rudder  24  in one direction or the other as a function of the signal generated by a receiver mounted in fuselage  12 . Horizontal stabilizer  120  is attached to and supported by fuselage  12 . A single or a pair of elevators are pivotally attached to the horizontal stabilizer and deflection thereof, whether up or down, will result in a change in the pitch attitude of the model airplane. It is to be noted that elevators  122 ,  124  work in concert, that is, upon command, both elevators deflect either upwardly or downwardly. Elevator  122  is pivotally secured to horizontal stabilizer  120  by a pair of segments of rubber bands  126 ,  128 . These segments will bias the elevator into general alignment with the horizontal stabilizer and yet permit deflection in response to an imposed force. Similarly, elevator  124  is pivotally secured to the horizontal stabilizer by a pair of segments of rubber bands of which only rubber band  130  is illustrated. A coil  132  is mounted at hinge line  134  of horizontal stabilizer  120 . Magnet  136  is mounted at the leading edge of elevator  122  proximate to and under the influence of a magnetic field generated by coil  132 . Similarly, coil  138  is mounted proximate hinge line  140  of horizontal stabilizer  120 . Magnet  142  is mounted at the leading edge of elevator  124  proximate to and under the influence of a magnetic field generated by coil  138 . The function and operation of coil  132  and its magnet  136  and coil  138  and its magnet  142  are the same as that described above with respect to coil  58  and magnet  76 . Accordingly, a repetition of such function and operation need not be undertaken. 
   Upon transmission of a signal from a transmitter, coil  58  is selectively actuated to deflect rudder  24  to the left or right, as described above. Upon transmission of a further signal from the transmitter, coils  132 ,  138  are energized to create a magnetic field of one polarity or the other. Magnets  136 ,  142  will respond to such magnetic field and cause deflection of elevators  122 ,  124  either up or down as a function of the polarity of the magnetic fields created. Such deflection of the elevators will result in a change in the pitch attitude of the model airplane. 
     FIG. 10  illustrates the tail of a model airplane of which a part of fuselage  12  is illustrated. The rear empennage mounted on fuselage  12 , as shown in  FIG. 10 , is generally referred to as a V-tail. It includes two fixed stabilizers  150 ,  152 , each of which is set at an angle with respect to horizontal in the range of about 30–45°. Each of these stabilizers includes a pivotally connected control surface  154  and  156 . Upon deflection of these control surfaces upwardly or downwardly, the pitch attitude of the model airplane will change to cause the airplane to climb or descend, respectively. Directional control is achieved by having the control surfaces deflect in opposite directions; that is, one control surface is deflected upwardly and the other one downwardly relative to the respective stabilizer. This will cause the model airplane to turn in the direction of the upwardly deflecting control surface. Thereby, control in the pitch and yaw axis will be achieved. 
   In the previous discussions of different model airplane configurations, the control surfaces have been identified as either rudder, elevator or elevon; however, the term control surface would apply equally well to any of such elements. 
   Control surface  154  is secured to stabilizer  150  by segments of rubber bands  158 ,  160  to bias the control surface in generally planar alignment with the stabilizer and yet accommodate deflection of the control surface. Similarly, control surface  156  is secured to stabilizer  152  by segments of rubber bands  162 ,  164  accomplishing the same function and purpose. A coil  166  is mounted proximate hinge line  168  of stabilizer  150 . Magnet  170  is mounted at the leading edge of control surface  154  proximate coil  166  in order to be under the influence of a magnetic field created by the coil. Similarly, coil  172  is mounted proximate hinge line  174  of stabilizer  152 . Magnet  176  is mounted at the leading edge in sufficient proximity to coil  172  to be under any magnetic field generated by the coil. 
   In response to a signal from a transmitter and received by a receiver in the model airplane depicted in  FIG. 10 , coils  166  and  172  will be energized to create a magnetic field of a first polarity resulting in movement of magnets  170 ,  176  that will cause control surfaces  154 ,  156  to be deflected upwardly. As noted above, such upward deflection will result in a change in pitch attitude of the model airplane. By transmitting a further signal to energize these coils to create a magnetic field of the opposite polarity, the resulting movement of magnets  170 ,  176  will result in downward deflection of control surfaces  154 ,  156 . By transmitting a yet further signal to be received by the receiver in the model airplane, coil  166  will produce a magnetic field opposite in polarity to that of the magnetic field produced by coil  172 . This will result in movement of magnet  170  and its control surface  154  in a direction opposite to that of control surface  156  due to the correspondingly opposite movement of magnet  176 . Such movement of the control surfaces will result in a change in direction of the model airplane. By transmitting a yet further signal, the polarity of coils  166  and  172  will be reversed and result in opposite deflection of the respective control surfaces to achieve a change in direction of the model airplane in the opposite direction. 
   Referring to  FIG. 11 , there is shown representatively a transmitter  180 . This transmitter is similar to transmitter  30 , shown in  FIG. 1A , except that additional signals are selectively transmitted. A pivotally secured control stick  182  is pivotally attached to the transmitter by a screw or bolt  184 . Upon up and down pivoting of the control stick, one of switches  186 ,  188  will be engaged. Upon such engagement, a signal will be transmitted to the receiver in the model airplane and the receiver will decode the signal to energize coils  166 ,  176  to cause either upward or downward deflection of control surfaces  154 ,  156  and result in a change in pitch attitude of the model airplane. By deflecting control stick  182  to the left or right, switches  190 ,  192  will be engaged. Such engagement will result in transmission of a signal from transmitter  180  to the receiver within the model airplane and decoded to energize coils  166 ,  172  and create magnetic fields of different polarity to cause control surfaces  154 ,  156  to deflect in opposite directions. Such movement of the control surfaces will result in a change in direction, left or right, of the model airplane. Accordingly, transmitter  180  provides the capability for 2-axis control of a model airplane. Such 2-axis control can be used with any of the model airplanes shown in  FIG. 6 ,  9  or  10 .