Abstract:
An ornithopter with two set of opposed wings maintains powered flight by flapping each set of wings. To dampen vibration, each set of wings move 180 degrees out of phase. To further dampen vibration, the empennage and cockpit are articulated to move vertically in response to the movement of the wings. Changes of flight direction result from wing warping and changing the center of gravity of the ornithopter.

Description:
RELATED APPLICATIONS 
     This application is related to U.S. patent application Ser. No. 10/164,751 and Ser. No. 10/172,413 both of which are incorporated herein by reference. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to the field of ornithopters which develop lift and thrust through vertical movement of the wings to develop high aerodynamic propulsive efficiency. Further, the invention includes provision for damping the vibration resulting from movement of the wings. 
     1. Background of the Invention 
     There is a long history of aerial vehicles which attain flight through the movement of the wings. Of course, the most successful derivation of this concept is the helicopter. Modern helicopters and conventional aircraft have comparable characteristics of speed, lifting capacity and passenger comfort. These characteristics of the helicopter result from the rotary wing design wherein the wings or blades rotate in a plane parallel with the longitudinal axis of the fuselage. 
     In attaining the level of performance of current models, the helicopter has become a very complex machine requiring highly trained pilots. One of the most notable features of the helicopter is the balancing of dynamic rotational forces to attain controllable flight. The torque generated by the rotary wing acting against the fuselage must be managed by the pilot to attain straight and level flight. In addition, the pilot must simultaneously manipulate other flight controls similar to an airplane. Further, if the helicopter loses the function of the vertical tail rotor or ducted fan, which provides critical anti-rotational force, controlled flight is impossible. 
     Ornithopters also use a wing drive for flight. In contrast to the rotary wing of the helicopter, the ornithopter has reciprocating wings which move in a plane normal to the longitudinal axis of the fuselage. The ornithopter eliminates the complexity required for overcoming dynamic rotational forces of flight at the expense of flight speed and incidence of reciprocal vibration. However, the lifting capacity of the ornithopter can be substantial and flight operation is less complex than a helicopter. 
     Because of the reciprocating movement of the wings, ornithopters suffer from harmonic vibration. The power input and resulting differential moments result in vibratory accelerations in the vertical plane. These vibrations are translated to the fuselage and payload unless damped out or reduced in some manner. 
     Ornithopters can be useful in specialized tasks requiring slow moving observation or lifting or remote flight found in construction, forestry, oil and gas industry, and the military. 
     2. Description of the Prior Art 
     U.S. Pat. No. 6,206,324 to Smith discloses an ornithopter with multiple sets of computer controlled wings which may be programmed to reciprocate in various combinations. The angle of attack of the wings is controlled throughout each reciprocation to provide optimal lift and minimal drag. 
     The Michelson patent, U.S. Pat. No. 6,082,671, is an attempt to teach the concept of a mechanical insect. The wings are twisted, to optimize lift, during reciprocation by rotation of the wing spar. 
     A toy ornithopter is disclosed in U.S. Pat. No. 4,155,195. The two sets of wings of the device are mounted on the fuselage in a vertically overlapping design. The sets of wings are reciprocated by crank arms oriented at 90 degrees to each other and powered by a rubber band. The sets of wings reciprocate out of phase with each other in that as one set moves downwardly the other set is moving upwardly. The flight path is preset by adjusting the empennage before flight. 
     What the prior art lacks is an ornithopter with a simple system for damping vibrations resulting from power inputs. 
     SUMMARY OF THE INVENTION 
     Accordingly, it is an objective of the instant invention to teach an ornithopter having vertically moving wings for developing lift and thrust and a movable tail for directional control. 
     It is a further objective of the instant invention to teach the use of a vibration damping system to reduce vibration in the fuselage and cockpit or load carrying compartment. 
     It is yet another objective of the instant invention to teach damping vertical vibration by counterbalancing the forces generated by the wings by a fully articulating empennage. 
     It is a still further objective of the invention to teach the vibratory isolation of the payload compartment from the wing section. 
     It is another objective to teach the controllability of the vehicle at slow speeds, well below stall speed of fixed wing aircraft and below the speed at which a conventional empennage is effective, by moving the center of gravity in flight. 
     It is another objective of the invention to teach that the force required to support the lift of the front set of wings is counterbalanced by the force of the aft set of wings and directional control is affected by controlling the shape and angle of attack of the wings. 
     Other objects and advantages of this invention will become apparent from the following description taken in conjunction with the accompanying drawings wherein are set forth, by way of illustration and example, certain embodiments of this invention. The drawings constitute a part of this specification and include exemplary embodiments of the present invention and illustrate various objects and features thereof. 
    
    
     BRIEF DESCRIPTION OF THE FIGURES 
     FIG. 1A is a perspective of the ornithopter of this invention; 
     FIG. 1B is a front view of the wing spars and stationary shaft with the wing at the lower limit of the stroke; 
     FIG. 1C is a front view of FIG. 1B with the wing at the upper limit of the stroke; 
     FIG. 2A is a side view, partly in section, of the power train and articulating empennage in downward damping movement; 
     FIG. 2B is a side view of FIG. 2A showing upward damping of the articulating empennage; 
     FIG. 3 is a side view, partly in section, showing the vibration damping connection of the cockpit and the damping arm; 
     FIG. 4 is a top plan view of the flight controls in the yaw axis; 
     FIG. 5 is a top plan view of FIG. 4 showing lateral movement of the cockpit and empennage in phantom lines; 
     FIG. 6A is a top plan view of the ornithopter showing lateral movement of the cockpit for flight control; 
     FIG. 6B is a top plan view of the ornithopter showing coordinated movement of the cockpit and empennage for flight control; and 
     FIG. 7 is a plan view of a wing of the ornithopter. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The ornithopter  10  has a fuselage  11 , wings  12 , landing gear  13 , and cockpit  100  as shown in FIG.  1 . The fuselage  11  has a rigid forward portion  14  and a flexible empennage  15 . The fuselage  14  has a central support beam extending along the roll axis to reinforce and rigidify the fuselage section. A passenger compartment  100  and/or a load carrying apparatus is attached to the rigid forward fuselage  14  by an articulating connection  101 . The vertical movement of the wings  12  is shown in FIGS. 1B and 1C which illustrates the journals  38  and  39  at the base of the spars  40  and  41 . FIGS. 1B and 1C also illustrate the stabilizing links  78  and  79  between the wings and the fuselage. Each link is rotatably attached at one end to the wing spar by a pin  80  and rotatably attached to the fuselage  14  by another pin  81 . In this manner, the wing spar may rotate about the attachment and the link may wobble between both pins during the power strokes. 
     As shown in FIG. 1A, the flight control system  200  includes the wing warping device  202 . A change of direction in the pitch and roll axes is partially controlled by the movement of the foot of the wing. A vertical post  203  is mounted in the fuselage and supports a horizontal bar  204 . Control rods  205  and  206  extend from each end of the bar to a respective foot of opposite wings, as shown in FIG.  1 A. As shown in FIGS. 3 and 4, the bar  204  has two movements executed by different control inputs. The bar  204  can move along post  203  to change the angle of attack of both wings equally or the bar pivots about a horizontal axis perpendicular to post  203  to simulate the action of ailerons. The wing warping is only shown on one set of wings but it may be on both sets. This wing warping may be integrated with control inputs to the downhaul  76  and vang  77  to further change the shape of the flexible wings  12 . The wing warping may be integrated with the lateral movement of the empennage and cockpit through a control stick in the cockpit or it may be a separate control input. 
     The cockpit or payload compartment  100  is mounted on the fuselage  14  through an articulating joint  101 . Extending the cockpit  100  from the fuselage  14  acts as passive dampening of the vertical vibrations by moving a mass further from the center of gravity to increase the inertia of the vehicle. The joint  101  has movement in the pitch and yaw axes of the ornithopter. The movement in the pitch axis serves to passively and actively dampen the vibratory oscillations inherent in the ornithopter as a reaction to the flapping of the wings. As shown in FIG. 3, the cockpit or payload compartment moves vertically parallel to the front of the fuselage  14  by a pair of wishbone shaped pivot arms. The wishbones  102  maintains approximate equal space between the cockpit and the fuselage. A tubular member  103  is vertically attached to the rear of the cockpit. The apexes of the wishbones  102  have pins  104  attached to the tubular member  103  so as to move in opposite response to the vibrations caused by the power stroke and flapping wings. The opposite ends  105  of the wishbone are pivotally attached to the fuselage wall to absorb some of the vertical forces on the wishbone. The tubular member  103  and the aperture  104  also function in the flight control system, to permit the cockpit to pivot in the yaw axis. Of course, this installation could be reversed, with the opposite ends of the wishbone connected to the cockpit and the apex connected to the fuselage. Further, the bar could be replaced with a channel and the wishbone apex could have a pivoting shuttle sliding in the channel. 
     To further smooth and absorb the vibratory motion of the cockpit, a spring  106  and shock absorber  107  are mounted between the cockpit and fuselage. The ends of the spring and shock absorber are attached to the fuselage and cockpit by a pin and bushing to provide more flexibility. A more sophisticated system (not shown) can include accelerometers input computer controlled to operate the movement of the wishbone and spring mechanism or a hydraulic or electrical powered vibration dampening system. 
     A power source  16 , by way of illustration, as shown in FIGS. 2A,  2 B, and  3 , is mounted within the fuselage  14 . However, the power source may be mounted in other locations on the vehicle. Also, the power source is shown as a generator but any type of motor may be used, including fuel burning reciprocating engines, turbines, fuel cells, batteries or others. 
     The power source  16  drives a fly wheel  17  through a belt  18  and cooperating pulleys  19  and  20 . Of course, the belt could be a chain and the pulleys could be sprockets, as a matter of choice. Also, a drive shaft could be used in place of the belt, with bevel gears, to drive the fly wheel  17 . 
     The fly wheel  17  has an eccentrically mounted pin  21  connected to a drive link  22 . Journal  23  permits drive link  22  to rotate around the pin  21  during rotation of the fly wheel. Another journal  24  is in the other end of the drive link  22 . Journal  24  rotatably connects the drive link to the power beam  25 . This arrangement results in reciprocation of the power beam in response to the rotation of the fly wheel. As an alternative (not shown), the power beam could be reciprocated by solenoids acting on the end(s) of the beam. 
     The power beam  25  is mounted on the rigid forward fuselage by a pin  26  located intermediate the length of the beam. As the drive link  22  reciprocates, the power beam  25  pivots about pin  26 . As can be seen in FIGS. 2A and 2B, the drive link  22  attaches by journal  24  to the power beam  25  nearer one end to provide the reciprocation of the beam. A pin  27  is located on power beam  25  near the journal  24 . The pin fits into a rotating journal on connecting link  28 . Connecting link  28  rotatably connects power beam  25  and wing mount  29  through journal  30 . This link smoothly transfers the reciprocating force of power beam  25  to the front set of wings  31 . 
     The other end of power beam  25  includes pin  32  journaled into rear connecting link  33  for rotational movement. The rear connecting link  33  is rotatably connected to journal  34  on rear wing mount  35  by pin  36 . Rear wings are connected to the wing mount  35 . As power beam  25  pivots about pin  26 , the front set of wings move in one direction while the rear set of wings move in the opposite direction. The opposite movement of the sets of wings counterbalances the reciprocating forces on the fuselage and provides smooth flight. As can be seen by a comparison of FIGS. 2A and 2B, the distance of the throw of the ends of power beam  25  is equal. However, the additional linkage on the front wings dampens the transition of the change of direction of the wings. 
     Stationary shaft  37  is mounted on the forward fuselage  14  between the forward set of wings and extends vertically normal to the longitudinal axis of the fuselage. The wing mount  29  slidably engages the shaft  37  by a linear bearing and moves along its length during reciprocation of the wings. The wing mount  29  carries journals  38  and  39  which rotatably connect to wing spars  40  and  41  of forward wings  42  and  43 . 
     Rear stationary shaft  44  is mounted on the forward fuselage between the rear set of wings and extends vertically normal to the longitudinal axis of the fuselage. The wing mount  35  slidably engages the shaft  44  and moves along its length during reciprocation of the wings. The wing mount  44  carries journals  45  and  46  which rotatably connect to wing spars  47  and  48  of the rear wings  49  and  50 . 
     The lift force of the forward set of wings supported by pin  27  of beam  25  is counterbalanced by the lift force of the rear wings at pin  32  of beam  25 . 
     Both the rear and front sets of wings have a rotating connections  38 ,  39 ,  45  and  46  to the wing mounts  29  and  35 , respectively, which also smooth out the reciprocating vibration forces. 
     In this manner, the pivoting of the power beam  25  drives the wing mounts  29  and  35 , in opposite directions, translating the vertical movement to the flapping of the forward wings  42  and  43  with the rear wings  49  and  50 . 
     As shown in FIGS. 1A and 3, the vertical or pitch vibration damping system also provides active damping to the empennage through rigid damping bar  108 , shown in FIG. 3, having one end rotatably and eccentrically connected on opposite sides of beam  25 . As beam  25  rotates about pin  26 , the damping bar moves longitudinally along the roll axis. The aft ends of the damping bar is rotatably connected to a vibration plate ill by pin and bearing  110 , shown in FIG. 3. A bracket  112  is attached to the fuselage  14  and extends toward the tail of the craft. The aft end of the bracket has a journal through which a pin  113  extends horizontally. The pin  113  is rotatably connected to the vibration plate  111 . The aft edge of the vibration plate is rigidly connected to the empennage  15 . This mechanism provides a direct mechanical harmonic movement of the empennage attuned to the vertical power strokes of the wings. The coordinated movement of the cockpit and empennage, in the same plane as the vibration, serves to dampen vehicle vibration and produce a smooth ride. 
     FIGS. 5,  6 A and  6 B, illustrate another component of the control system  200 . The deflection of the flexible empennage  15  is illustrated as a lateral movement of the free end of the empennage in the yaw axis of the vehicle. In the slow flight regime of the ornithopter, a shift in the center of gravity coupled with asymmetrical increased drag will change the flight path. Longitudinal actuators  201  and  202  are mounted in the fuselage and controlled by crank  258  moving crank arms. As shown in FIG. 4, the longitudinal actuators are crossed at  210  to permit the empennage and payload compartment to simultaneously move to the same side of the yaw axis upon actuation of the crank arms  208  and  209 . The actuators may be cable or segmented control rods. For example, as crank arm  209  moves toward the cockpit the empennage will be forced to shorten by actuator  201  while the longitudinal actuator  202  gives slack to the cockpit connection. Simultaneously, the crank arm  208  is shortening actuator  201  to pivot the cockpit. In this manner the payload compartment and the empennage and, therefore, the center of gravity, are shifted to the same side of the yaw axis resulting in a change in flight direction. 
     The deflection of the flexible longeron  51  is not severe enough to cause permanent bending or structural damage of the empennage. The empennage will tend to return to the longitudinal axis upon relief of the control input. The empennage is made up of a central longeron  51  made of a material with a desired moment of elasticity and strength. The longeron  51  may be in the form of a thin plate with vertical bending zones  57 , shown in profile in FIGS. 1A,  2 A,  2 B and  3 . The bending zones may be reduced thickness of the plate or spring biased hinges. The longeron is connected at one end  52  to the rigid fuselage  14  and the free end  53  is connected to the surrounding control elements  201 ,  202  and  57 . 
     As shown in FIGS. 4,  5 , and  6 A and B, the control bar or crank  258  has a center pin  260  which forms a rotatable connection. Control input may be applied through the center pin  260  or through the ends of the control bar  258 . In the Figures, the bar  258  is rotatably connected at arms  208  and  209  to the longitudinal actuators  201  and  202 , respectively, for deflection in the yaw axis. To maintain spatial orientation of the control elements and the longeron  51 , a series of brackets  63  are attached along the length of the longeron  51 . The brackets have apertures through which the control elements pass. 
     As can be seen in the drawings, the empennage is hinged at  113  for movement in the pitch axis for active vibration damping and bendable in the yaw axis for flight control. 
     In order to more closely mimic the efficiency of a bird&#39;s wing, the ornithopter has control of the angle of attack and the twist of the wings through each cycle. Each of the wings  12  of the ornithopter  10  has a flexible wing surface  67  in the nature of a sail. The wings surface  67  has a leading edge  68 , a foot  69 , and a trailing edge  70 . The leading edge and the trailing edge intersect at the tip  71  opposite the foot  69 . The leading edge of the wing surface is attached to the wing spars of the of the wings  12 . As shown in FIG. 7, the wings surface  67  is attached to wing spar  41  of the front set of wings. The foot  69  of the wing surface forms the wing root and includes a batten  72  extending from the leading edge  68  to the trailing edge  70  for stiffening the wing surface material. To provide more shaping to the wing surface, battens  73 ,  74  and  75  are spaced from the foot to the tip. The battens may be made from any light weight material that has the requisite flexibility and strength to reinforce and hold the desired shape of the wing surface. 
     To provide adjustability of the chord in the wings a down haul  76  is attached to the foot of the wing surface and extends parallel to the spar. Added tension on the down haul  76  tends to flatten the wing surface longitudinally. Such a control input is related to an increase in the relative wind speed. A vang  77  is attached to the batten  72  near the trailing edge of the wing surface and extends to the spar. By increasing the tension on the vang  77 , the chord of the wing is flattened laterally. By attaching the boom van tension to the spar keeps wing warping forces out of the wing drive mechanism. These control inputs could be set before flight or operated by flight controls during flight. In any event, the angle of attack of the wings and the drag may be adjusted by adjusting the twist of the wings. 
     It is to be understood that while a certain form of the invention is illustrated, it is not to be limited to the specific form or arrangement of parts herein described and shown. It will be apparent to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown and described in the specification and drawings.