Patent Publication Number: US-2022219815-A1

Title: Unmanned Aerial Drone Crane

Description:
BACKGROUND OF THE INVENTION 
     The present invention pertains to multi rotor unmanned aerial vehicles (UAVs) capable of lifting heaving payloads. UAVs are becoming increasingly common. UAVs are employed in many different industries and, as explained below, are needed in some cases to replace cranes in a construction site. 
     Typically, UAVs have four rotatable propellers and are designed for vertical takeoff. However, some UAVs have fixed wings and other UAVs have additional rotatable propellers. Each propeller is usually powered by a separate motor attached to a central frame. The frame carries a controller that is electronically connected to each motor and is also connected to a communications system that receives control instructions from a ground-based controller or a user interface. The UAV can, therefore, be controlled remotely by someone who is on the ground employing the user interface. In other words, there is no need to have a pilot physically on board. The UAV is controlled from the ground and in some cases the UAV has a certain degree of autonomous control. For example, the UAV is often able to hover on its own without continuous input from the user interface. 
     Controlling UAVs is accomplished by varying the speed of each motor which in turn varies the speed of each propellor. The propellors on one side of the vehicle usually counterrotate versus the propellors on the opposite side, while the propellors on the same side of the UAV rotate in the same direction. Hovering in place is achieved by having the propellors rotate at the same speed with just enough lift to counter the weight of the vehicle. Roll, pitch and yaw are controlled by changing the speeds of each propellor. Various protocols for moving a UAV by adjusting individual rotor speed are known in the art. 
     The motors are often brushless direct current motors since such motors have a high power to weight ratio and are relatively easy to control. Power for the motors is provided by a battery mounted on the central frame. The batteries are usually made of lithium due to weight considerations. 
     Some UAVs are provided with cameras and are therefore able to capture video that cannot otherwise easily be obtained. Diverse groups from law enforcement, oil platform workers and the military all take advantage of the ability of UAVs to take pictures while flying. The safety of the workers is improved as the UAV can enter a dangerous area to take pictures so that a person no longer has to do so. For example, instead of hanging on a rope off of an oil drilling platform to take pictures while searching for structural damage, a UAV can be sent instead. UAVs are also now being used to deliver packages or payloads. However, there is a demand in the industry for delivering payloads not only from central distribution points to customers but also in a construction site to a desired location. The payloads involved tend to be heavy and, therefore, most UAV designs simply cannot lift sufficient weight to meet the demands of industry. While helicopters have been used in place of cranes, such helicopters have particularly large rotors to enable them to lift heavy loads. 
     Vertical takeoff and landing (VTOL) vehicles are aircraft that can take off like a helicopter but fly like a plane, which improves long distance efficiency and airspeed. A helicopter or multirotor is not very efficient in getting from point A to point B, and they are especially not fast at it. Hundreds of organizations have developed various VTOL aircraft concepts. Some though simply adapt lifting surfaces (wings) to existing multirotor frames and add a ‘pusher motor’ to propel the aircraft forward; the multirotor rotors stop once the aircraft&#39;s forward speed creates enough lift on its lifting surfaces. By contrast most UAVs are designed to take advantage of four small propellers that provide agility at a relatively inexpensive cost. 
     Accordingly, there is a need in the art for a UAV that can carry large amounts of weight especially one that can lift a payload to a desired location in a construction site. 
     SUMMARY OF THE INVENTION 
     Preferably a drone crane is provided with an H-Frame setup that is provided with two parallel longitudinally extending supports or beams with a cross beam. The rotors are mounted along the longitudinal extending supports, with one rotor mounted at each end and one rotor mounted at the cross beam. Alternatively, additional cross beams may be added at the ends of the longitudinal beams and the motors can be placed at the ends of the laterally extending cross beams. The subject unmanned aerial drone crane preferably will have a minimum of 6 rotors. Larger versions of the drone crane will preferably have 6 or possibly 8 rotors. Such an arrangement is more efficient than a helicopter of similar disk size and is more efficient than a traditional hex rotor setup with a circular pattern of rotors. 
     For example, in one preferred embodiment, the drone crane comprises a frame including a pair of longitudinal beams each having a first end, a second end, an upper surface and a lower surface. A first lateral beam is connected to the lower surface of the longitudinal beams at the first end. A second lateral beam is connected to the lower of the longitudinal beams at the second end. A third lateral beam is connected to the upper surface of the longitudinal beams between the first end and the second end. The drone crane also comprises a first propulsion unit mounted to an end of the first lateral beam. The propulsion unit includes a first motor configured to operate at a plurality of speeds, a shaft rotated by the motor and a first propeller mounted above the first lateral beam and rotatably coupled to the first motor via the shaft. The propulsion unit has a first hub and a first plurality of blades mounted on the hub. The blades have a pitch that is varied. A second propulsion unit is mounted to an end of the second lateral beam of the frame and includes a second propeller with a second set of blades, mounted above the second lateral beam and rotatably coupled to a second motor. A third propulsion unit is mounted to an end of the third lateral beam of the frame and includes a third propeller mounted above the third lateral beam. A third plurality of blades from the third propeller has blade tips configured to create blade tip vortices that act on the first and second plurality of blades of the first and second propellers. 
     The first propulsion unit further comprises a servo motor driving a pinion mounted for connection with a rack gear, whereby rotation of the servo motor varies the pitch of the first plurality of blades. The first propulsion unit further comprises a pitch slider connected to the rack gear and a plurality of pitch links extending between the pitch slider and a plurality of pitch levers. The pitch levers are configured to rotate the blades in response to movement of the pitch slider thus providing dramatically varying the lift. 
     The center pair of rotors is preferably positioned above the outer two pairs for two purposes: this arrangement allows the center beams to carry a load, with the two frame beams beneath the center beam, and the two outer beams beneath the longitudinal beams so that all lifting forces are translated against the beams/frames rather than relying on the strength of any fasteners. This arrangement also allows for a more efficient aircraft since the blade tip vortices from the center pair of rotors will act on both pairs of outboard rotors. This arrangement will increase the lift on the outer rotors, interrupt and reduce their own tip vortices, and reduce drag on the outer rotors therefore increasing efficiency. The drone cranes will be tethered to their payload via a sling or cable and have fixed landing gear on the frame. Such UAVs, when adapted, act as unmanned aerial drone cranes and are able to lift heavy payloads to desired locations within the construction site. 
     Additional objects, features and advantages of the present invention will become more readily apparent from the following detailed description of preferred embodiments when taken in conjunction with the drawings wherein like reference numerals refer to corresponding parts in the several views. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of drone crane having a frame supporting multiple propellor assemblies constructed in accordance with the present invention; 
         FIG. 2  is a schematic view of a control system for the drone crane of  FIG. 1 ; 
         FIG. 3  is a prospective view of one of the propellor assemblies of the unmanned aerial vehicle of  FIG. 1 . 
         FIG. 4  is a side view of the propellor assembly of  FIG. 3 ; 
         FIG. 5  is an exploded view of the propellor assembly of  FIG. 4   
         FIG. 6  is a close-up view of the propellor assembly of  FIG. 3 , with the frame removed for clarity; 
         FIG. 7  is an exploded view of the propellor mount of the propeller assembly of  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Detailed embodiments of the present invention are disclosed herein. However, it is to be understood that the disclosed embodiments are merely exemplary of the invention that may be embodied in various and alternative forms. The figures are not necessarily to scale, and some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting but merely as a representative basis for teaching one skilled in the art to variously employ the present invention. 
     When a feature or element is herein referred to as being “on” another feature or element, it can be directly on the other feature or element or intervening features and/or elements may also be present. In contrast, when a feature or element is referred to as being “directly on” another feature or element, there are no intervening features or elements present. It will also be understood that, when a feature or element is referred to as being “connected”, “attached” or “coupled” to another feature or element, it can be directly connected, attached or coupled to the other feature or element or intervening features or elements may be present. In contrast, when a feature or element is referred to as being “directly connected”, “directly attached” or “directly coupled” to another feature or element, there are no intervening features or elements present. Although described or shown with respect to one embodiment, the features and elements so described or shown can apply to other embodiments. It will also be appreciated by those of skill in the art that references to a structure or feature that is disposed “adjacent” another feature may have portions that overlap or underlie the adjacent feature. 
     Spatially relative terms, such as “under”, “below”, “lower”, “over”, “upper” and the like, may be used herein for ease of description to describe one element or feature&#39;s relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if a device in the figures is inverted, elements described as “under” or “beneath” other elements or features would then be oriented “over” the other elements or features. Thus, the exemplary term “under” can encompass both an orientation of over and under. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. Similarly, the terms “upwardly”, “downwardly”, “vertical”, “horizontal” and the like are used herein for the purpose of explanation only unless specifically indicated otherwise. 
     Although the terms “first” and “second” may be used herein to describe various features/elements (including steps), these features/elements should not be limited by these terms, unless the context indicates otherwise. These terms may be used to distinguish one feature/element from another feature/element. Thus, a first feature/element discussed below could be termed a second feature/element, and similarly, a second feature/element discussed below could be termed a first feature/element without departing from the teachings of the present invention. 
     Throughout this specification and the claims which follow, unless the context requires otherwise, the word “comprise”, and variations such as “comprises” and “comprising” means various components can be co-jointly employed in the methods and articles (e.g., compositions and apparatuses including device and methods). For example, the term “comprising” will be understood to imply the inclusion of any stated elements or steps but not the exclusion of any other elements or steps. 
     As used herein in the specification and claims, including as used in the examples and unless otherwise expressly specified, all numbers may be read as if prefaced by the word “about” or “approximately,” even if the term does not expressly appear. The phrase “about” or “approximately” may be used when describing magnitude and/or position to indicate that the value and/or position described is within a reasonable expected range of values and/or positions. Any numerical values given herein should also be understood to include about or approximately that value, unless the context indicates otherwise. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. 
     The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. Instead, the illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into another embodiment unless clearly stated to the contrary. While the disclosure is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular illustrative embodiments described. On the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the disclosure. 
     With initial reference to  FIG. 1  there is shown an unmanned aerial vehicle (UAV) or drone crane  10  in accordance with a preferred embodiment of the invention. Drone crane  10  has a main frame  20  that is formed with first and second longitudinal beams  31  and  32  and three lateral beams  41 ,  42  and  43 . More specifically, frame  20  includes a longitudinal beam  31  having a first end  51 , a second end  52 , an upper surface  53  and a lower surface  54 . First lateral beam  41  is connected to lower surface  54  of longitudinal beam  31  at first end  51 . A second lateral beam  42  is connected to lower surface  54  longitudinal beam  31  at second end  52 . A third lateral beam  43  is connected to upper surface  53  of longitudinal beam  31  between first end  51  and second end  52 . 
     Drone crane  10  also comprises a first propulsion unit  61  mounted to an end  62  of first lateral beam  41 . First propulsion unit  61  includes a first motor  64  configured to operate at a plurality of speeds. Motor  64  is securely attached to first lateral beam  41  with a mounting plate  65 . A first propeller  66 , mounted above first lateral beam  41  is rotatably coupled to first motor  64 . First propeller  66  has a first hub  67  and a first plurality of blades  68  mounted on hub  67 . First plurality of blades  68  has a pitch that is varied. A second propulsion unit  71  is mounted to an end  72  of second lateral beam  42 . Second propulsion unit  71  includes a second motor  75  configured to operate at a plurality of speeds, a second propeller  76 , mounted above second lateral beam  42  and rotatably coupled to second motor  75  and having a second hub  77  and a second plurality of blades  78  mounted on second hub  77 . A third propulsion unit  81  is mounted to an end  82  of third lateral beam  43  and includes a third motor  85  configured to operate at a plurality of speeds. A third propeller  86  is mounted above third lateral beam  43  and is rotatably coupled to third motor  85  and having a third hub  87  and a third plurality of blades  88  mounted on the third hub and having blade tips  89  configured to create blade tip vortices  90  that act on the first and second plurality of blades  68 ,  78 . 
     Second longitudinal beam  32  also has a first end  151 , a second end  152 , an upper surface  153  and a lower surface  154 . Second longitudinal beam  32  connected to first lateral beam  41 , second lateral beam  42  and third lateral beam  43 . Upper surface  155  of first lateral beam  41  supports lower surface  154  of second longitudinal beam  32  and upper surface of second lateral beam  42  supports the lower surface of second longitudinal beam  32 . The first, second and third plurality of blades  68 ,  78 , and  88  are configured to cause blade tip vortices  90  of third plurality of blades  88  to reduce blade tip vortices  190 ,  191  formed by the first and second plurality of blades  68 ,  78 . 
     Referring back to  FIG. 1 , there are shown three additional propulsion units  361 ,  371  and  381  which are similar to the first second and third propulsion units  61 ,  71  and  81 , and preferably include similar or identical features (e.g., power sources, numbers of poles, whether the motors included therein are synchronous or asynchronous) or operational capacities (e.g., angular velocities, torques, operating speeds or operating durations). Each of such propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381  may be operated individually or in tandem with one another, for any purpose. For example, two or more of the propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381  may be operated to provide both lift and thrust in the form of a thrust vector that changes as the drone cranes&#39;s attitude changes, while two or more of propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381  may be operated to provide forward motion. Motor  64  may be any type or form of motor (e.g., electric, gasoline-powered or any other type of motor) capable of generating sufficient rotational speeds of the corresponding to provide lift and/or thrust forces to drone crane  10  and any engaged payload  400  supported by payload bracket  401 , and to aerially transport the engaged payload  400 . For example, motor  64  preferably includes a brushless direct current (DC) motor. 
     The drone is equipped with landing gear  410 . As shown landing struts  411  are located in a rectangular pattern and are attached to the laterally first and second extending beams  41 ,  42 . As shown landing struts  411  are fixed. Preferably, landing struts  411  are long enough so that load  400  carried by drone crane  10  will not touch the ground when drone crane  10  has landed. However, the landing struts  411  could be shorter for when drone crane  10  will pick up and drop off payload  400  supported by a sling while flying. Landing struts  411  could also be retractable. Details of such a landing gear can be found in U.S. Patent Application Publication No. 2018/0281933 incorporated herein by reference. 
     A power source or battery  415  is also provided. Battery  415  may be centrally located on longitudinal beams  31 ,  32  and contains a plurality of stacks of lithium battery cells  420 . Alternatively, battery  415  is comprised of multiple smaller cells (not shown) each located on lateral beams  41 ,  42  to reduce the length of cable from the cells to the propulsions unit, thus providing redundancy while increasing efficiency and decreasing weight. Preferably battery  415  is a rechargeable smart battery having a controller  421  that tracks battery usage, charging and temperature. More details of a rechargeable battery for a drone are found in U.S. Patent Application Publication No. 2019/0233100 incorporated herein by reference. 
     Frame  20  preferably supports a control unit  510  in addition to, propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381 , battery  415  payload securing bracket  401 , and other components.  FIG. 2  schematically illustrates components of a control unit  510  and associated components mounted on frame  20 . Control unit  510  has a central processing unit  520  one or more radio antennas  522  and sensors  523 . Central processing unit  520  includes executable instructions to control flight and other operations of drone crane  10 . In some embodiments, the central processing unit  520  is operationally connected to payload bracket  411  and landing struts  411  to allow drone crane  10  to release a payload. Processor  520  is powered from battery  415 . Central processing unit  520  is preferably coupled to a motor control system  524  that is configured to manage propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381 . 
     Through control of the individual propulsion units  61 ,  71 ,  81 ,  361 ,  371 , and  381 , drone crane  10  is controlled in flight. In the central processor  520  there is located a navigation controller  525  configured to determine the present position and orientation of drone crane  10 , the appropriate course towards a destination, etc. 
     Optionally a camera apparatus  526  is coupled to drone crane  10  for providing image data to an image processing system  526  within or coupled to the processor  520 . Image processing system  526  is preferably a separate image processor, such as an application specific integrated circuit, configured for processing images, such as stitching together images. Alternatively, image processing system  526  is implemented in software executing within the processor  520 . 
     Control unit  510  preferably includes one or more transceivers  530 , which may be coupled to an antenna  522 . Transceiver  530  is preferably capable of communication with other drones, smart phones, a drone controller and other devices or electronic systems. Transceiver  530  may include a GPS receiver configured to provide position information to navigation unit  525  and include a GNSS receiver configured to provide three-dimensional coordinate information to drone crane  10  by processing signals received from three or more GNSS satellites. Navigation controller  525  may use an additional or alternate source information from processed images to determine speed and direction of travel and attitude information by processing images of the ground. 
     An avionics component  540  of navigation controller  525  may be configured to provide flight information, such as altitude, attitude, airspeed, heading and similar information that may be used for navigation purposes. Navigation controller  525  may include or be coupled to sensors  523  configured to supply data to navigation controller  525 . For example, sensors  523  could include one or more accelerometers or gyroscopes to provide information to the navigation unit. Sensors  523  could also include barometers, thermometers, audio sensors, motion sensors, etc. Sensors  523  may provide information regarding accelerations and orientation (e.g., with respect to the gravity gradient and earth&#39;s magnetic field) to enable navigation controller  525  to perform navigational calculations of drone crane  10  during flight. A barometer may provide ambient pressure readings used to approximate elevation level (e.g., absolute elevation level) of drone crane  10 . 
     The details of propulsion unit  61  can be best seen in  FIGS. 3-6 . First propulsion unit  61  has first and second pinions  600 ,  601  driven by a first and second pinion motors  610 ,  611 . First and second pinion motors  610 ,  611  are each preferably an electric servo motor mounted on end  62  of first lateral beam  41 . Preferably pinion motors  610 ,  611  are provided with splined output shafts. Each output shaft has splines that mate with corresponding internal splines located on mounting horns (not separately shown). The horns have a standard bolt pattern to allow pinions  600 ,  601  to be secured on the shafts so that motors  610 ,  611  can drive pinions  600 ,  601 . First pinion  600  is drivingly connected with a first rack gear  615  and second pinion  601  is connected with a second rack gear  616  ( FIG. 4 ). Specifically, teeth (not separately labelled) are formed on pinions  600 ,  601  and are engaged with teeth (not separately labelled) on gear racks  615 ,  616  whereby rotation of pinions  600 ,  601  move rack gears  615 ,  616  up or down relative to drone crane  10 . Pinions  600 ,  601  are preferably made of aluminum alloy. Rack gears  615 ,  116  are preferably made of a high-density polymer to eliminate wear between pinions  600 ,  601  and rack gears  615 ,  116 . Alternatively, rack gears  615 ,  116  could be made from bronze or brass instead of a polymer. The interaction between the polymer and aluminum allows for a long mechanism life, without any loss of precision from wear. Rack gears  615 ,  116  are connected to pitch slider  620  which in turn is connected to a plurality of pitch links, one of which is labelled  625 . Pitch link  625  is connected to a pitch lever  630 . First propulsion unit  61  further comprises a pitch slider  620  connected to rack gear  615  and a plurality of pitch links  625  extending between pitch slider  620  and a plurality of pitch levers  630  connected to blades  66 . Pitch lever  630  is configured to rotate the pitch of blades  68  as shown by arrow  631  ( FIG. 4 ) in response to movement of pitch slider  620  while motor  64  is connected to hub  67  by shaft  650  so as to rotate blades  68  so that blades  68  can provide lift for drone crane  10 . Rack gears  615 ,  116  pinion motors are rotary servos, when rotary servos fail, they spin freely. In addition, each servo pinion motor  610 ,  611  is configured to be powerful enough to be able to move pitch slider  620  even when only one of pinion motors  610  and  611  are working. In other words, the pinion motors have enough power to overcome drag caused by a failed motor and still drive pitch slider  620 . By contrast if linear actuators were employed and one failed, pitch slider  620  would not be able to move as the failed linear actuate would lock up and not move. Rack gears  615 ,  116  are configured to prevent pitch slider  620  from rotating with hub  67 . The polymer composition of rack gears  615 ,  116  allows a sliding connection between rack gears  615 ,  116  and frame  20 . Essentially the polymer allows rack gears  615 ,  116  to act as a bushing. Rack gears  615 ,  116  have a curved shape as does pitch slider  620 . The curved shape forces rack gears  615 ,  116  into alignment with pitch slider  620 . 
       FIG. 3  showing a side view and  FIGS. 5 and 6  showing exploded views of propulsion unit  61  to make clearer the details of how pitch link  625  is connected to a pitch lever  630  and also how motor  64  is connected to hub  67  and a shaft  650 . Motor  64  has a stationary portion  652  attached to plate  65  and a rotary portion  653  attached to shaft  650  which can rotate as shown by arrow  651  ( FIG. 3 ). With reference to  FIG. 5 , gear racks  615 ,  616  are both connected to pitch slider assembly  620  which is connected to several pitch links including pitch link  625  which is a turnbuckle linkage having Hiem joints located at each end, an upper hiem joint  700  and lower hiem joint  701 . Upper hiem joint  700  has a hiem ball  710  which connects pivotably to pitch lever  630 , which in turn is mounted on blade cuff and spacer assembly  715 . Motion of pitch slider assembly  620  is transferred by pitch links  625  to pitch lever  630  and then to blades  66 . Spacer assembly  715  is fastened to hub  67  by fasteners  750  and supports one of the blades  66 , best seen in  FIG. 4 . 
     Turning back to  FIGS. 5 and 6 , a threaded fastener  751  is configured to pass through a hub cap  760  and into shaft  650  and thereby secure hub  67  to shaft  650 . A phasing plate  770  is connected to pitch links  625  and is secured to hub  67  by fasteners  775 . Phasing plate  770  ensures that pitch links  625  and pitch lever arms  630  all work in unison to provide blades  66  with the same amount of pitch. Plate  770  also traps pitch links  625  to keep them rotating in unison with the rest of the propeller. Otherwise, the pitch of one of the blades  66  could be altered by just the spinning of hub  67 . 
     A hub coupler  785  is connected to shaft  650  by hub retaining pins  765 . Hub  67  is trapped between hub cap  760  and hub coupler  785 . Shaft  650  is provided with motor coupler retaining pin holes  785 . When assembled, shaft  650  passes through motor  64  motor coupler retaining pins pass into a motor coupler and then into the motor coupler retaining pin holes  785  to secure the motor to shaft  650 . Shaft  650  is connected to hub  67  which supports blades  66  by a blade cuff and spacer assembly  715 . 
     Blade cuff and spacer assembly  715  is one of three assemblies mounted on hub  67 . Blade cuff and spacer assembly  715  is shown separated from hub  67  at the upper right of  FIG. 6  with pitch arm  630  spaced away from hub  67 . In  FIG. 7 , blade cuff and spacer assembly  715  is rotated so that pitch arm  630  is located to the left. With reference to both  FIGS. 6 and 7 , blade cuff and spacer assembly  715 , lever pitch arm  630  is provided with fasteners  790  that mount lever pitch arm  630  to blade cuff  800 . Blade  66  is removed for clarity but can be seen in  FIG. 4 . Blade cuff  800  is rotatably mounted in radial bearings  801  and  802  so as to be rotatably secured in cuff spacer  803 . A thrust bearing  820  is held in place by a thrust retainer plate  830  and fasteners  835 . Preferably retainer plate  830  is made of steel and fasteners  835  are  8  bolts which pass through retainer plate  830  and into cuff  800 . As such steel retainer plate  830  sits against thrust bearing  820  in assembly  715  followed by radial bearing  802 . All three of these pieces sit flush against a hub side of blade cuff  800  and are sized to be inserted into rotor hub  67  by a tight fit. On the side of blade cuff and spacer assembly  715  facing away from rotor hub  67 , preferably fasteners  790  are four bolts that mount pitch arm  630 . Radial bearing  801  is pressed into cuff spacer  803 . Preferably blade  66  is made from a composite material employing carbon fiber. Blade  66  is adhered to the inside of blade cuff  800  with adhesive and three titanium pins, not shown. Since radial bearing  802  is free to slide on blade cuff  800 , blade cuff  800  acts as a spacer between bearings  801  and  802  so that the need for shims is reduced. Also, alignment pins between blade cuff  800  and hub  67  are needed as bearings  801 ,  802  and  820  force blade cuff  800  into proper alignment with hub  67  This arrangement allows motor  64  to drive blades  66  in a rotational manner to provide lift for drone crane  10  while also allowing blades  66  to vary their pitch angle. 
     The examples and illustrations included herein show, by way of illustration and not of limitation, specific embodiments in which the subject matter may be practiced. As mentioned, other embodiments may be utilized and derived there from, such that structural and logical substitutions and changes may be made without departing from the scope of this disclosure. Such embodiments of the inventive subject matter may be referred to herein individually or collectively by the term “invention” merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept, if more than one is, in fact, disclosed. Thus, although specific embodiments have been illustrated and described herein, any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. This disclosure is intended to cover any and all adaptations or variations of various embodiments. Combinations of the above embodiments, and other embodiments not specifically described herein, will be apparent to those of skill in the art upon reviewing the above description. 
     For example, with minor modifications, namely a specific non-slung payload mount, drone crane has the potential to be an extremely powerful and nimble aircraft. The drone crane can support a 400 lb payload with a 2.0× safety factor. This safety factor could not only be drastically reduced for military use, but simply reducing the payload carried would allow the aircraft to operate at far greater speeds than in ‘crane configuration’. Alternative rotor blades could also be designed that have a symmetrical airfoil. The total lifting capacity would be slightly reduced, but the drone would then have the ability to fly inverted and perform maneuvers that create immense G-Forces that most other aircraft and pilots cannot withstand. This still allows the entire aircraft and payload to weigh at least as much as 400 lbs. A VTOL aircraft with this mass would become one of the largest and most capable in its class. 
     Although various illustrative embodiments are described above, any of a number of changes may be made to various embodiments without departing from the scope of the invention as described by the claims. For example, the order in which various described method steps are performed may often be changed in alternative embodiments, and in other alternative embodiments one or more method steps may be skipped altogether. Optional features of various device and system embodiments may be included in some embodiments and not in others. Therefore, the foregoing description is provided primarily for exemplary purposes and should not be interpreted to limit the scope of the invention as it is set forth in the claims. 
     As can be seen from the above description a drone crane has been described that can lift a large payload at a worksite with low risk to work crews working at the site. The drone takes advantage of rotor placement to increase lift and payload capacity. The drone also provides a mechanism to rotate blade pitch which also increases payload capacity.