Abstract:
A personal flight device including: a housing securable to the pilot; at least one pair of ducted fans, one fan of each pair mounted to each side of the housing; wherein each fan rotates about an axis of rotation to draw air through the corresponding duct; wherein the axis of rotation of each fan is fixed relative to the housing; at least one engine mounted on the housing for driving the fans, wherein both fans rotate in the same direction for producing thrust; three pairs of control surfaces, with one control surface of each pair mounted below each fan of the one or each pair of fans; such that air leaving said fan impact on said control surface; one pair of control surfaces being configured to control yaw, one pair to control pitch, and one pair to control roll; control means for controlling the orientation of said control surfaces relative to said fans.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a vertical take-off and landing personal flight device, i.e. a device which can be secured to the pilot rather like a jet belt, and which gives the pilot controllable powered flight. 
       BACKGROUND OF THE INVENTION 
       [0002]    It should be noted that any discussion of the prior art throughout the specification is not an admission that such prior art is widely known or forms part of the common general knowledge in the field. 
         [0003]    Personal flight devices were developed in the 1960&#39;s and 1970&#39;s, but were essentially rocket based devices (jet belts) which gave extremely short flight times (typically about 26 seconds) and were difficult to control. Further, these devices were fuelled by rocket fuel which is intrinsically dangerous. 
         [0004]    In a related type of device fuel is fed to a catalyst bed to produce hot gas which is distributed between two spaced counter-rotating turbines to generate vertical thrust from the turbine exhausts. The device is steered by shrouds or deflector rings pivoted to the base of each turbine. 
         [0005]    More recently, a number of personal flight devices have been proposed which use ducted fans as their means of propulsion:—for example a device which includes a pair of ducted fans and which is steered by tilting the ducted fans relative to the pilot. 
         [0006]    A broadly similar type of design has been proposed, using shrouded propellers rather than ducted fans. 
         [0007]    As the terms are used in this specification, the distinction between a ‘shrouded propeller’ and a ‘ducted fan’ essentially is that a ducted fan comprises one or more rotating aerofoils or fans (single or multi-bladed) mounted completely within a duct; the duct increases the overall efficiency of the fan. A shrouded propeller comprises a rotating aerofoil or propeller which is surrounded by a shroud, the only function of the shroud being to protect the propeller—the shroud does not appreciably affect the efficiency of the propeller. 
         [0008]    A further proposal describes a device which includes a pair of ducted fans. In this device, the fans are rigidly secured to the supporting harness, and steering is achieved by control flaps mounted adjacent to the outlet of each fan. However, in this design the two fans are contra-rotating and thus have to be driven via a gearbox using a relatively complex rigid transmission system; this adds considerable weight to the device. 
         [0009]    Other prior art proposals have been for single shrouded propellers or ducted fans. Single propeller/fan devices have the drawback that the propeller/fan has to be extremely large to provide adequate lift, and to balance the devices the pilot generally has the propeller/fan above or below him, which is far from ideal from a safety point of view. A further drawback is that the thrust from a single propeller/fan has to be split in some way to give steering and this tends to result in high frictional losses in the steering tubes or ducts. 
       SUMMARY OF INVENTION 
       [0010]    An object of the present invention is a personal flight device which overcomes the disadvantages of the prior art devices described above, and which provides a lightweight yet powerful personal flight device which is comparatively safe to use. 
         [0011]    The present invention provides a personal flight device which includes:
       a housing which is securable to the pilot;   at least one pair of ducted fans, one fan of the pair mounted to one side of the housing, and the other fan of the pair mounted to the other side of the housing;   wherein each fan rotates about an axis of rotation so as to draw air through the corresponding duct from an entry end of the duct to an exit end of the duct;   and wherein the axis of rotation of each fan is fixed relative to the housing;   at least one engine mounted on the housing for driving the fans, wherein both fans rotate in the same direction for producing thrust;   three pairs of control surfaces, with one control surface of each pair mounted below one fan of the one or each pair of fans, and the other control surface of each pair being mounted below the other fan of the or each pair of fans, such that air leaving said fan impact on said control surface;   one pair of control surfaces being configured to control yaw, one pair of control surfaces being configured to control pitch, and one pair of control surfaces being configured to control roll;   control means for controlling the orientation of said control surfaces relative to said fans.       
 
         [0020]    It is envisaged that the device probably would use only a single engine and a single pair of fans, since it is important for most applications to keep the overall weight of the device as low as possible. However, it would be possible to use more than one pair of fans, each pair driven by its own engine or both/all pairs driven by a single engine. If more than one pair of fans is used, then, depending upon how the fans are arranged, each fan may have a separate set of control surfaces (for yaw, pitch and roll) or, if the fans are arranged so that air leaving both or all of the fans on one side of the housing impacts upon a single area (for example if the sets of fans are stacked vertically on each side of the housing) than a single set of control surfaces may be used on each side of the housing. Preferably, the housing is securable to a pilot by means of a harness, and includes protective shielding between the pilot and the engine and fans. 
         [0021]    The engine may be any suitable reliable, robust, lightweight engine e.g. a two-stroke or a four-stroke internal combustion engine, rotary engine, or a gas turbine. 
         [0022]    The drive means may be any reliable lightweight drive means e.g. a chain drive, a fluid drive or a belt drive. Preferably, the drive means is a flexible belt drive, most preferably a toothed belt drive or a micro-V belt drive. A belt drive is preferred because a belt drive may easily be inspected by a pilot to check for wear or damage, and modern belt drives give a low-weight high-efficiency drive. For additional security, two or more drive means may be used in parallel. 
         [0023]    Preferably, each of the or each pair of control surfaces configured to control yaw is mounted diametrically across the exit end of each duct, being configured to be pivotable about an axis substantially perpendicular to the axis of rotation of the corresponding fan, such that movement of said yaw control surfaces by said control means yaws the device. 
         [0024]    Preferably also, each of the or each pair of control surfaces configured to control pitch is mounted below the exit end of the corresponding duct, being supported such that in a neutral position when no steering control is applied by said control means, each said control surface lies in a substantially vertical plane; each said control surface being configured to be pivoted about an axis substantially perpendicular to the longitudinal axis of the corresponding fan, such that movement of said pitch control surfaces by said control means pitches the device. 
         [0025]    Preferably also, each of the or each pair of control surfaces configured to control roll is mounted below the exit end of the corresponding duct, each said control surface being configured to be pivoted about an axis substantially perpendicular to the longitudinal axis of the corresponding fan, such that movement of said roll control surfaces by said control means rolls the device. 
         [0026]    Most preferably, each of the or each pair of control surfaces configured to control roll is mounted below the exit end of the corresponding duct, with each said control surface being formed as two co-planar vanes mounted one on each side of the corresponding pitch control surface; each said roll control surface being configured to be pivoted about an axis substantially perpendicular to the longitudinal axis of the corresponding fan and substantially perpendicular to the pivot axis of the corresponding pitch control surface, such that movement of said roll control surfaces by said control means rolls the device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    By way of example only, a preferred embodiment of the present invention is described in detail with reference to the accompanying drawings in which: 
           [0028]      FIG. 1  is a diagrammatic front view of a device in accordance with the present invention; 
           [0029]      FIG. 2  is a plan view from above of the device of  FIG. 1 ; 
           [0030]      FIG. 3  is a side view of the device of  FIG. 1 ; 
           [0031]      FIG. 4  is a view of one ducted fan from below; 
           [0032]      FIG. 5  is a side view of the fan of  FIG. 4 ; 
           [0033]      FIG. 6  is a diagram of the drive arrangement; 
           [0034]      FIG. 7  is a diagram of part of the control system; 
           [0035]      FIG. 8   a  and  b  are diagrams of two different versions of stators; 
           [0036]      FIG. 9  is a plan view of a stator of  FIG. 8   b  on a larger scale; 
           [0037]      FIG. 10  is a view in the direction of Arrow A of  FIG. 9 ; and 
           [0038]      FIG. 11  is a plan view from above of one set of pitch/roll controls. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    Referring to the drawings, a personal flight device  1  includes a pair of ducted fans  2 , 3  which are supported and spaced apart by a central housing  4 , which also supports an engine  6  and a fuel tank (not visible). 
         [0040]    The ducted fans  2 , 3  are of known design and consist of a central multi-blade fan  7 , 8  mounted on, and rotatable with, a hub  7   a , 8   a,  inside a concentric cylindrical duct  9 , 10 . The ducts  9 , 10  are rigidly mounted on the housing  4  by mounting brackets  4   a  (visible in  FIG. 2  only) and are oriented such that in the “at rest” position shown in  FIGS. 1 and 3 , (i.e. when the device is resting on the ground) the axis of rotation of each fan is substantially vertical. The ends of the ducts  9 , 10  are depicted as open, but may in fact be covered by a protective grill or mesh. 
         [0041]    The fans  7 , 8  are driven from the engine  6  by a drive means in the form of a pair of toothed drive belts  11   a , 11   b  to the corresponding hub  7   a , 8   a.  The toothed belt drive is shown (diagrammatically) in  FIGS. 4 and 6 . As shown in  FIG. 6 , the engine  6  drives a drive pulley  6   a  through a flexible coupling  6   b,  to dampen torsional vibration from the engine  6 . Two drive belts  11   a , 11   b  are engaged with the drive pulley  6   a,  one belt alongside the other. 
         [0042]    The first drive belt  11   a  passes around the pulley  6   a,  through an aperture  9   b  in the duct  9  and around the hub  7   a  to drive the fan  7 . The second drive belt  11   b  passes around the pulley  6   a,  through an aperture  10   b  in the duct  10 , and around the hub  8   a  to drive the fan  8 . In use, both fans  7 , 8  are rotated in the same direction, but the airflow from the bottom  9   a , 10   a,  of each duct  9 , 10  is made linear (i.e. substantially parallel to the longitudinal axis of the corresponding fan) by the use of a row of stators  12 . The stators  12  are spaced, and extend radially around the inner circumference of each duct  9 , 10  below the corresponding fan  7 , 8 . Each stator  12  is a ‘spoke’ which extends radially from the inner wall of the duct towards the hub. 
         [0043]      FIG. 8   a  shows the simplest arrangement of stators, in which each stator is a flat parallel-sided plate, with the length of each plate extending radially from the inner wall of the duct towards the hub. 
         [0044]      FIGS. 8   b , 9  and  10  illustrate a more aerodynamically efficient design of stator  12   b,  in which each stator  12   b  is a curved aerofoil cross-section plate, one end of which is secured to the inner wall of the duct and the other end of which is secured to the hub. As shown in  FIGS. 9 and 10 , each stator  12   b  twists along its longitudinal axis from the hub to the duct. Stators of this design have a higher efficiency than the simple flat stators  12   a , but are more expensive to produce and to fit. 
         [0045]    The housing  4  is slightly wider than the shoulder width of the pilot, and approximately the same height as the pilot. In the “at rest” position shown in  FIGS. 1 and 3  of the drawings, the device rests on a support  1   a  which may be of any suitable type. 
         [0046]    The housing  4  provides head shields  13  and armrests  14 , 15  ( FIGS. 1 and 2 ). 
         [0047]    The device is provided with controls for controlling yaw, pitch and roll; all of these controls can be operated by the pilot by means of control handles built into the armrests, as described below. 
         [0048]    Yaw is the angular rotation of the device about a vertical axis; this is controlled by a pair of control vanes  50 , 51 , one vane in each pair being mounted diametrically across the exit end of each of the ducts  9 , 10 , and arranged to pivot about an axis substantially perpendicular to the axis of rotation of the corresponding fan and hub. Each vane  50 , 51  has an aerofoil cross-section. Each vane projects partly below the lower edge of the corresponding duct, as shown in  FIGS. 5 and 6 , and is made in two sections, one section lying on each side of the lower part of the hub. The two sections of each vane move together as a single unit. 
         [0049]    The control vanes  50 , 51  can be moved by cables (not shown) connected to a control lever  17  mounted on the corresponding armrest  14  ( FIG. 7 ). Alternatively, a nonmechanical control system can be used, using, e.g. an electric actuator controlled by movement of the control lever to move the control vanes. The control system is always set so that the movement of one control vane  50  in one direction (e.g. the direction indicated by Arrow A in  FIG. 7 ) produces an equal movement of the control vane  51  in the opposite direction (e.g. the direction indicated by Arrow B in FIG.  7 ):—this movement would yaw the device to the left; moving the vanes in the opposite direction would yaw the device to the right. The extent to which the control vanes are moved governs the degree of yaw. 
         [0050]      FIGS. 1 and 7  show a single pair of control vanes  50 ,  51 , but it also is possible to use multiple pairs of control vanes  50 ,  51 , mounted in parallel as shown in  FIG. 3 . The multiple pairs of vanes are used in the same manner as the single pair of vanes. 
         [0051]    Pitch and roll are governed by aerofoil-cross-section control surfaces  60 / 61  and  70 / 71  respectively. Pitch is the angular motion of the device in a vertical plane about a lateral axis; roll is the revolution of the device about a horizontal axis. From the point of view of the pilot of the device, yaw is swinging from side to side about a vertical axis, roll is leaning to one side or the other in a vertical plane, and pitch is leaning forwards or leaning backwards. 
         [0052]    The control surfaces  60 / 61  and  70 / 71  are arranged as two sets of control surfaces in a cruciform configuration, with one set  60 / 70  on one side of the housing and the other set  61 / 71  on the other side of the housing. Both sets of control surfaces are supported by a support beam  72  which extends at right angles to the longitudinal axis of the device and is mounted across the lower portion of the housing, so that one set of control surfaces lies below the exit end of one duct, and the other set lies below the exit end of the other duct. 
         [0053]    The control surfaces  60 / 61  which govern pitch are mounted on the support beam  72 , with the longitudinal axis of the surface parallel to that of the support beam  72 , and in the neutral position lie in a substantially vertical plane. The control surfaces  60 / 61  are moved by pivoting the support beam  72  in its bearings (not shown); this movement moves the lower end of the surfaces  60 / 61  in the directions indicated by the arrows C and D ( FIG. 3 ). If the control surfaces  60 / 61  move in the direction of Arrow C, the air coming from the exit ends of the ducts  9 , 10  tends to pitch the device as shown in  FIG. 3  anticlockwise. If the control surfaces  60 / 61  move in the direction of Arrow D, the device as shown in  FIG. 3  is pitched clockwise. 
         [0054]    Because of the cruciform arrangement of the control surfaces, surfaces  70 / 71  move with the surfaces  60 / 61 , but in the pitching movement described in the preceding paragraph, the surfaces  70 / 71  remain at a constant angle to the airflow from the ducts and thus do not alter the orientation of the device. 
         [0055]    The control surfaces  70 / 71  are each constructed as two equal parts, one on each side of the corresponding surface  60 , 61 . The control surfaces  70 / 71  can pivot relative to the corresponding surfaces  60 / 61  as shown in broken lines in  FIG. 1 ; this pivoting movement is controlled by a control rod  73  which moves the control surfaces  70 / 71  on bearings  74  mounted on the surfaces  60 / 61 . To roll the device to the left, the control surfaces  70 , 71  are pivoted in the direction of Arrow E ( FIG. 1 ); to roll the device to the right, the control surfaces  70 / 71  are pivoted in the direction of Arrow F. 
         [0056]    The movements of the control surfaces  60 / 61 ,  70 / 71  are controlled by movements of the control handle  19 , mounted on the armrest  15 ; 
         [0057]    The armrest  14  also incorporates a twist grip throttle which is connected to the engine  6  and is used to control the acceleration of the engine in known manner. 
         [0058]    Movements of all of the control surfaces  50 / 51 ,  60 / 61  and  70 / 71 , as well as movement of the throttle, may be by means of control cables or rods or using electronic actuators to operate any of a wide range of known hydraulic or electrical servos to act on the control surfaces/throttle. The controls/throttle may be manually controlled by the pilot, or may be remotely controlled via an interface with a microcomputer (the so-called “fly by wire” system). Another possibility is for the device to be primarily manually controlled, but with a safety override provided by computer control, so that if the device is at an unsafe attitude or speed, the override automatically cuts in. 
         [0059]    In use, the pilot stands in the space  20  ( FIG. 2 ) and is strapped to the device by means of a parachute type a harness (not shown) which is mounted on the housing  4 . Once strapped in, the pilot starts the engine  6  to rotate the fans  7 , 8  within the ducts  9 , 10  to give vertical lift to the device. The amount of lift is governed by the acceleration of the engine  6 , which is controlled by the throttle. Pitch, roll and yaw are controlled as described above. 
         [0060]    Rotating both fans  7 , 8  in the same direction means that the fans can be driven directly from the engine and there is no need for a gearbox to alter the direction of drive. This saves a great deal of additional weight, and also eliminates a component which would need maintenance and be a possible source of failure. Rotating both fans in the same direction would impart torque to the device, making the device difficult or impossible to steer, were it not for the stators which render the airflow leaving the fans  2 , 3  substantially linear. 
         [0061]    The device is fitted with a parachute (not shown) which in emergencies can be opened by the pilot to bring the device and the pilot together safely to the ground. 
         [0062]    It is envisaged that the primary use of the above-described device would be a one-person transport. However, it would be possible to substitute any of a range of remote-control devices for the pilot, and to operate the device remotely.