Patent Publication Number: US-2023149825-A1

Title: Boomerang

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of the serial number of U.S. patent application Ser. No. 17/426,083, filed on Apr. 8, 2021, entitled Boomerang, the entire disclosure of which is incorporated herein 
    
    
     TECHNICAL FIELD 
     The present invention relates to the technical field of boomerangs, in particular to a boomerang. 
     BACKGROUND 
     The moment to the supporting point generated by the gyro rotating at high speed by gravity will not make it topple, but process at a small angle, which is the gyro effect. Simply put, the gyro effect means that the rotating object has inertia to keep its rotating direction. 
     Gyro effect is widely used in technical fields such as scientific and technological progress, and its practical application can be seen from aerospace to deep-sea stealth. In our daily life, a flying toy that can fly back after being thrown is one of the most representative practical applications of gyro effect. 
     Most of the rotary flying toys in the prior art adopt two pairs of propellers which are arranged in parallel and rotate in opposite directions to offset the torque generated by the rotation of the propellers, so as to provide the lifting force of the flying toys and increase the stability of the flying toys. U.S. Pat. No. 6,843,699 discloses a directional controllable aircraft and a propeller structure for realizing the same, which comprises a main propeller connected to a central hub, the main propeller including a pair of propeller fins extending from a propeller shaft, a plurality of hub fins fixed to the central hub and extending outward and downward from the central hub, the main propeller and the plurality of hub fins rotating in opposite directions caused by torque of a motor structure for rotating the main propeller, The hub fins extend from the central hub to the outer ring, and the main propeller extends downward from the central hub and is positioned below the hub fins so that the tail end of the main propeller is located inside the outer ring. The propeller also includes a pair of connections connecting the propeller to the propeller shaft fixed to the drive shaft. When the torque of the rotor structure changes, the pitch and height of the propeller fins also change so as to substantially offset the tail end tilt. 
     However, although the flying toy adopting this scheme has controllable direction and good stability in flight, it requires the operator to control the inclination and height of the propeller wing by using the remote control unit, so as to control the flying direction of the flying toy. For a flying toy, the remote control unit is added, and the cost of the flying toy will be higher. On the other hand, it is necessary to learn how to operate the remote control unit, which also limits the popularization audience of the flying toy. Furthermore, the flying toy fails to effectively protect the propeller component and the operator. When the flying toy collides with an obstacle, the propeller component has a great probability of being damaged, which leads to the loss of the flying ability of the flying toy. At the same time, the residual blades of the propeller wings flying out due to the damage also have a great probability of hurting the operator. In the more extreme case, the flying toy flies out of control directly to the operator, resulting in more serious situations. Any of the above problems is not ideal for the flying toy. 
     The prior art also discloses a flying toy which does not use a remote control unit and simultaneously provides a protective shell for the propeller. The U.S. patent application No. 20200238188 discloses a miniature finger gyro gyroplane, which comprises a main body casing, a fan blade arranged in the main body casing, a mandrel arranged in the center of the fan blade, and a shiatsu upper cover and a shiatsu lower cover arranged at the upper and lower sides of the main body casing through both ends of the mandrel. The main body casing, the shiatsu upper cover and the shiatsu lower cover can rotate independently around the mandrel, and are arranged in the main body casing. 
     Although the flying toy adopting this technical scheme does not need a remote control unit and is provided with a main body shell capable of protecting the propeller, when in use, it is necessary to first rotate the main body shell and the fan blades, and the rotation direction of the main body shell and the fan blades is opposite to offset the torsion force generated by the relative rotation between the main body shell and the fan blades, so as to obtain sufficient lift force, and then the flying toy is thrown out, and the flying toy flies back by the gyro effect. To throw the flying toy, you need to press the upper cover and the lower cover with your hands first, and then throw the flying toy at an appropriate throwing angle. On the one hand, this throwing method limits the flying angle of the flying toy; on the other hand, because the main body shell is a part of the rotating flying component, the high-speed rotating shell may hurt the skin of the contact person, and even cut your eyes in severe cases. At the same time, the flying component falling from high altitude will be broken if there is no protection on the outside of the flying component. In addition, the high-speed rotating shell is also the main body of its gyro effect. This design only leaves two small finger pressure upper and lower covers. The products produced by this technology are extremely difficult to operate and have poor user experience. Besides adults, the audience of flying toys is also a large number of operators. In the cognition of the majority of children, they do not know the principle of rotary flying toys. They only know that it is a toy that will fly back when thrown out. Therefore, it is necessary to throw out the flying toys by pressing the cover, which further increases the difficulty for children to use the flying toys. On the one hand, because the size of flying toys is fixed, it can&#39;t be suitable for children of different ages, such as the palm of younger children. 
     Based on the above, it is necessary to provide a flying toy with full enclosure isolation, which can isolate the flying components rotating at high speed from the skin of the contact person, and at the same time, realize the technology of controlling different flight trajectories of the aircraft by preset throwing angles, which will make users have an incredible experience. When the flying toy falls from high altitude, the fully enclosed net shell can also protect the core flying components. 
     SUMMARY 
     The present invention provides a boomerang. The boomerang includes a flight component, wherein the flight component comprises at least one rotating device and a driving device; the maximum diameter rotating plane formed by the rotation of the rotating device defines the outer perimeter of the flight component, and the rotating device rotates coaxially around the center axis of the maximum diameter rotating plane; a central shaft penetrating the center axis, wherein two ends of the central shaft are respectively connected with a first base and a second base, and the first base and the second base are respectively separated from the upper and lower ends of the flight component; a protective device arranged around the flight component, wherein the protective device is composed of a plurality of ribs connected with each other, and an inner diameter of the protective device corresponding to the outer perimeter of the flight component is larger than the outer perimeter. 
     In some embodiments, the center of the first base extends out of the first receiving part and receives the first end of the central shaft, and the center of the second base extends out of the second receiving part to receive the second end of the central shaft. In order to improve the protection effect of the ribs on the boomerang, the ribs are configured to be made of elastic materials. In order to make the boomerang have excellent rotary flying performance, the boomerang is configured to have two pairs of propellers which are arranged in parallel and rotate in opposite directions, and the propeller assemblies are started so that the boomerang can gain lift to fly. 
     At least one embodiment of the present invention relates to a boomerang. The boomerang comprises a first base, a second base, a luminous component, a plurality of ribs extending outwards to connect the first base and the second base, and a central shaft connecting the flight component to the first base and the second base, wherein the ribs surround the flight component, the first base and the second base respectively receive the first end and the second end of the central shaft, and the luminous component and the flight component are electrically connected. 
     At least one embodiment of the present invention relates to a boomerang. The boomerang comprises a flight component, a central shaft and a protective device, wherein the flight component comprises at least one rotating device, a driving device and a bracket with a cavity; the central shaft runs through the center axis of the maximum diameter plane formed when the rotating device rotates; and one end of the central shaft is connected with a first base which is separated from the upper and lower ends of the flight component; and the protective device is formed by connecting a plurality of ribs. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       In order to explain the technical scheme of this application more clearly, the following will briefly introduce the drawings that need to be used in the embodiments. Obviously, the drawings in the following description are only some embodiments of this application. For those of ordinary skill in this field, other drawings can be obtained according to these drawings without any creative effort. 
         FIG.  1    is a schematic diagram of a preferred embodiment of the present invention; 
         FIG.  2    is an explosion diagram of a preferred embodiment of the present invention; 
         FIG.  3    is a schematic diagram of the first base and ribs; 
         FIG.  4    is a schematic diagram of a second base and ribs; 
         FIG.  5    is a schematic diagram of the central axis; 
         FIG.  6    is a schematic diagram of the preferred embodiment of the present invention without flight components; 
         FIG.  7    is the explosion diagram of the flight component; 
         FIG.  8    is a schematic diagram of other extension tracks of ribs; 
         FIG.  9    is another schematic diagram of other extension tracks of ribs; 
         FIG.  10    is a schematic diagram of the use of other disclosed technologies; 
         FIG.  11    is a schematic diagram of the preferred embodiment of the present invention; 
         FIG.  12    is a schematic diagram of the center of gravity and the center of lift of the preferred embodiment of the present invention; 
         FIG.  13    is a schematic diagram of a boomerang with a light emitting assembly according to the present invention; 
         FIG.  14    is a schematic diagram of a light emitting assembly; 
         FIG.  15    is a schematic diagram of the light emitting assembly of the present invention arranged on the propeller blade; 
         FIG.  16    is another schematic diagram of the central axis of the present invention; 
         FIG.  17    is a schematic diagram of the boomerang of the present invention in flight; 
         FIG.  18    is a schematic diagram of the flight trajectory of the boomerang of the present invention; 
         FIG.  19    is another schematic diagram of the flight trajectory of the boomerang of the present invention; 
         FIG.  20    is another operation mode of the boomerang of the present invention; 
         FIG.  21    is a schematic diagram of a light source frame; 
         FIG.  22    is another embodiment of the boomerang of the present invention; 
         FIG.  23    is another embodiment of the boomerang of the present invention. 
     
    
    
     In the figures: 
       1 . First base;  11 . First receiving part;  2 . Second base;  21 . Second receiving part;  3 . Rib;  4 . Flight component;  401 . Rotating device;  402 . Driving device;  41 . Propeller component;  42 . Motor;  43 . Motor base;  44 . Power supply;  45 . Sensor;  46 . Circuit board;  47 . Transmission gear;  48 . Bracket;  411 . First propeller;  412 . Second propeller;  4121 , Outer ring;  4122 . Installation table;  5 . Central axis;  51 . First end;  52 . Second end;  53 . Shaft sleeve;  6 . Luminous component;  61 . Light bar;  62 . Light source frame;  7 . Accommodation space;  8 . Protective device; G, center of gravity; F, Lift center; F 1 , Thrust; F 2 , Wind power; F 3 , Lifting force; F 4 , offset force; S 1 , Flight trajectory; S 2 , Flight trajectory. 
     DESCRIPTION OF EMBODIMENTS 
     The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the drawings in the embodiments of this application. Obviously, the described embodiments are only part of the embodiments of this application, but not all of them. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without creative labor are within the scope of protection in this application. 
     The reference to “an embodiment” or “an implementation” here means that a specific feature, structure or characteristic described in connection with an embodiment or an implementation can be included in at least one embodiment of this application. The appearance of this phrase in various places in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment mutually exclusive with other embodiments. It is understood explicitly and implicitly by those skilled in the art that the embodiments described herein can be combined with other embodiments. 
       FIGS.  1  and  2    show a preferred embodiment of a boomerang, which includes a flight component  4  and a protective device  8  arranged around the flight component  4 . The flight component  4  includes at least one rotating device  401  and a driving device  402 . The maximum diameter rotation plane formed by the rotation of the rotating device  401  defines the outer perimeter of the flight component  4 , and the rotating device  401  rotates coaxially around the center axis of the maximum diameter rotation plane. 
     The boomerang also includes a central shaft  5  (see  FIG.  2   ) penetrating through the center axis of the maximum diameter rotating plane formed by the rotation of the rotating device  401 . Two ends of the central shaft  5  are connected with the first base  1  and the second base  2 , and the first base  1  and the second base  2  are separated from the upper and lower ends of the flight component  4 . 
     Among them, the first base  1  extends from the center out of the first receiving part  11  (see  FIG.  3   ), and the first receiving part  11  is configured to receive the first end  51  of the central shaft  5  (see  FIG.  5   ); The second base  2  extends from its center out of the second receiving part  21  (see  FIG.  4   ), and the second receiving part  21  is configured to receive the second end  52  of the central shaft  5  (see  FIG.  5   ). 
     In this preferred embodiment, the central shaft  5  is preferably a single through shaft with a cylindrical surface. In other embodiments, the central shaft  5  may also have surfaces of other shapes, such as rectangular or prismatic, and the central shaft  5  may also be composed of two or more mandrels through coupling. As shown in  FIG.  16   , the central shaft  5  is composed of two coaxial mandrels, one end of which is respectively received by the first receiving part  11  and the second receiving part  21 , and the other end is rotatably connected with the bracket  48 . 
     As shown in  FIG.  1    and  FIG.  2   , the protective device  8  arranged around the flight component  4  is composed of a plurality of ribs  3  connected to each other, and its inner diameter is larger than the outer periphery of the flight component  4 . 
     In this preferred embodiment, between the first base  1  and the second base  2  receiving the central shaft  5 , an accommodation space  7  (see  FIG.  6   ) is formed in the longitudinal axis direction of the central shaft  5 , and the accommodation space  7  is designed to accommodate the flight component  4 . The accommodation volume of the accommodation space  7  depends on the extension track of the ribs  3 . Similarly, the accommodation volume of the accommodation space  7  will also limit the size of the flight component  4 . In order to make the ribs  3  completely protect the flight component  4 , the size of the flight component  4  is designed to be smaller than the accommodation volume of the accommodation space  7 . 
       FIG.  7    shows the main components of the flight component  4  of the present invention, including a rotating device  401  and a driving device  402 . The rotating device  401  is composed of a propeller component  41 , which includes a first propeller  411  and a second propeller  412 . The driving device  402  is composed of a motor  42 , a motor base  43 , a power supply  44 , a sensor  45 , a circuit board  46  and a transmission gear  47 , and the components of the driving device  402  are all built in a bracket  48  with a cavity. 
     The second propeller  412  is fixedly connected to the motor base  43 , the motor  42 , the power supply  44  and the circuit board  46  are fixedly mounted on the motor base  43 , and the sensor  45  is electrically connected to the circuit board  46 . The sensor  45  feeds back signals to the circuit board  46 , and the circuit board  46  controls the operation of the motor  42 . The driving shaft of the motor  42  is in transmission connection with the first propeller  411  through a transmission gear  47 . 
     The motor  42  drives the first propeller  411  to rotate, and the reaction force generated when the first propeller  411  rotates will push the motor base  43  to rotate, thus driving the bracket  48  and the second propeller  412  fixedly connected with the motor base  43  to rotate. At this time, the rotation direction of the bracket  48  and the second propeller  412  is opposite to that of the first propeller  411 , so that the torsional forces between the first propeller  411  and the second propeller  412  are mutually offset, and at the same time, the upward lift force is generated, so that the boomerang can fly. At the same time, under the action of the thrown external force, the boomerang first flies in the throwing direction for a certain distance. After the thrown external force disappears, the flying angle of the boomerang will remain unchanged due to the gyro effect generated by the rotation of the support  48  and the propeller, and the boomerang will continue to fly in the direction of this angle. Users can preset the throwing angle of the boomerang to obtain different flight trajectories. 
     In order to make the flight component  4  fly with sufficient lift, besides increasing the RPM of the motor, it is also a preference to make the blades of the propeller more similar. Increasing the size of the propeller blades also increases the size of the flight component  4 , which leads to the increase of the accommodating volume of the accommodating space  7 . 
     Increasing the accommodation volume of the accommodation space  7  can be achieved by increasing the extension length of the ribs  3 . However, if the accommodation volume of the accommodation space  7  is simply increased by increasing the extension length of the ribs  3 , the cost of the boomerang will undoubtedly increase greatly, which is obviously not ideal. 
     On the premise of not increasing the extension length of the ribs  3 , in order to make the accommodation space  7  have the largest accommodation volume, the extension track of the ribs  3  in this preferred embodiment is configured as y=±√{square root over ((r 2 −x 2 ))} or x=±√{square root over ((r 2 −y 2 ))}. According to Euclidean geometry, when the circumference is the same, the surface area of a circle is the largest, and when the surface area is the same, the volume of a sphere is the largest. The demonstration process of this basis is the existing academic knowledge, so it will not be discussed in this paper. 
     In some embodiments, the extension track of the ribs  3  can be other shapes, as shown in  FIG.  8   , the extension track of the ribs  3  is y=ax 2 +bx+c: as shown in  FIG.  9   , the extension tracks of the ribs  3  are y=kx+b and 
     
       
         
           
             y 
             = 
             
               
                 k 
                 x 
               
               ⁢ 
               
                 
                   ( 
                   
                     k 
                     ≠ 
                     0 
                   
                   ) 
                 
                 . 
               
             
           
         
       
     
     By analogy, the extension track of the rib  3  can be any desired shape. 
     As a preferred embodiment of the present invention, the extension track of the rib  3  is configured as y=±√{square root over (r 2 −x 2 ))} or x=±√{square root over ((r 2 −y 2 ))}. With this configuration, the outer contour of the boomerang is closer to a regular sphere, and the operation is more in line with the usage habits of operators. 
     As shown in  FIG.  10   , the boomerang disclosed in U.S. patent application No. 20200238188 adopts the operation mode of pressing the upper cover and the lower cover with two fingers and then throwing them out. In this operation mode, only the upper and lower covers of the boomerang are pressed by fingers, and the force can&#39;t be consistent when thrown, so that the flight trajectory of the thrown boomerang has great uncertainty and can&#39;t run according to the expected flight trajectory, which greatly reduces the operator&#39;s actual use experience. Similarly, the number of optional flight trajectories of the boomerang is limited due to the limitation of wrist joints. 
     As a preferred embodiment of the present invention, the present invention provides a boomerang, which throws the boomerang out of flight by grasping the boomerang with the palm. As shown in  FIG.  11   , when in use, the palm of the operator grasps the boomerang which forms an approximate sphere. At this time, five fingers and palms are evenly distributed on the surface of the boomerang. The central shaft  5  installed on the first base  1  and the second base  2  of the protective device  8  will balance the thrown external force on the central shaft  5 , so as to ensure that the external force acting on the protective device  8  will not change its angular momentum when the flight component  4  rotates at a high speed. That is, when the boomerang provided by the present invention is thrown. Furthermore, with the grasping throwing form, there are more throwing paths that can be selected, more flight trajectories of boomerangs, and a better user experience. 
     As shown in  FIG.  17   , when the boomerang provided by the present invention tilts around the central axis  5 , the flight component  4  generates wind force F 2  as shown in the figure, which can be divided into two parts: an offset force F 4  and an ascending force F 3 ; The offset F 4  will make the boomerang drift in one direction; The gyro effect generated by the first propeller  411  and the second propeller  412  of the flight component  4  keeps the deflection angle of the flight toy about the central axis  5  from changing, and the flight toy will always fly in this direction under the action of the deflection force F 4 . 
       FIG.  18    shows the flight trajectory of the boomerang provided by the present invention after being thrown out. When the operator preset the included angle with the central axis  5  as the axis, and the direction of the thrust F 1  is opposite to that of the offset force F 4 , the boomerang is pushed out by the thrust F 1 . The gyro effect generated by the first propeller  411  and the second propeller  412  of the flight component  4  keeps the offset angle of the boomerang with the central axis  5  unchanged. When the thrust force F 1  is greater than the offset force F 4 , the boomerang first flies along the flight path S 1  in the direction of the thrust force F 1 , until the thrust force F 1  disappears, and the boomerang flies along the flight path S 2  at the corresponding offset angle under the action of the offset force F 4 . 
       FIG.  19    shows another flight trajectory of the boomerang of the present invention. When the operator preset the included angle about the central axis  5 , and the direction of the thrust F 1  is the same as that of the offset force F 4 , the boomerang is pushed out by the thrust F 1 . The gyro effect generated by the first propeller  411  and the second propeller  412  of the flight component  4  keeps the offset angle of the boomerang about the central axis  5  unchanged, and the pushed thrust F 1  is superimposed with the offset force F 4 , and the boomerang will fly in the direction of the thrust F 1 . 
     In order to better protect the flight components  4  covered by the ribs  3 , the ribs  3  are configured to be made of elastic materials and distributed crosswise. When the boomerang collides with an obstacle, the ribs  3  made of elastic materials can produce elastic deformation, absorb the corresponding collision energy, and provide buffer protection for the flight component  4 ; Similarly, the cross distribution of the ribs  3  further enhances the structural strength and reduces the probability of fracture or damage of the ribs  3 . At the same time, the ribs  3  can also protect the operator, preventing the wings of the flight component from flying out and causing harm to the operator. 
     In order to make the boomerang have better flying performance, the ribs  3  are configured in a hollow grid shape to reduce the weight of the ribs  3 , and the grid pattern can be configured in any pattern shape; The propeller component  41  is configured as two pairs of first propellers  411  and second propellers  412 , which are arranged in parallel and rotate in opposite directions, so as to counteract the torsional force generated when the propellers rotate; The rotating shafts of the first propeller  411  and the second propeller  412  are arranged coaxially with the central shaft  5 , so that the center of lift generated by the propeller component  41  is on the same axis as the center of gravity of the boomerang. 
     The first propeller  411  is driven by the motor  42 , and the reaction force generated when the first propeller  411  rotates will push the motor base  43  to rotate, and then drive the bracket  48  and the second propeller  412  fixedly connected with the motor base  43  to rotate. At this time, the rotation direction of the bracket  48  and the second propeller  412  is opposite to that of the first propeller  411 , so that the torsional forces between the first propeller  411  and the second propeller  412  are mutually offset, and at the same time, lift force is generated, so that the boomerang can fly. 
     During the flying process of boomerangs, the position of the center of gravity is also a factor affecting the flying stability. Once the center of gravity shifts, it will lead to unstable flight trajectory, and make the boomerang run on an unsatisfactory flight trajectory. 
     As a preferred embodiment of the present invention, the central shaft  5  is configured to be coaxial with the rotating shafts of the first propeller  411  and the second propeller  412 . This has the advantage that the center of gravity of the boomerang can be kept on the same axis as the center of lift generated by the propeller component  41 , and the angular momentum generated when the first propeller  411  and the second propeller  412  rotate will not change, so that the boomerang in operation will have a gyro effect. After the boomerang is thrown, the flying angle of the boomerang remains unchanged due to the gyro effect generated by the rotation of the bracket  48  and the propeller, and the boomerang will continue to fly along the direction of this angle. The user can preset the throwing angle of the boomerang, so as to obtain different flight trajectories. 
     According to the teaching of U.S. Pat. No. 6,843,699, when the center of gravity is above the center of lift, the flying effect of boomerangs will increase. As shown in  FIG.  12   , the propeller component  41  of the present invention is arranged below the motor base  43 , and the lifting force F 3  generated by the propeller component  41  pushes the boomerang upward. At this time, the center of gravity G of the boomerang is above the lifting force center F generated by the propeller component  41 , thus making the boomerang more stable in flight. 
       FIG.  13    shows another exemplary embodiment of a boomerang provided by the present invention, which has all the technical features of the preferred embodiment of the present invention. In order to make it more ornamental and playable, the boomerang also includes a light emitting component  6 . 
     As shown in  FIG.  14   , the light emitting assembly  6  is configured as a light bar  61 , which can be a flexible LED light bar, and is electrically connected with the circuit board  46  in the flight component  4 . In order to make the boomerang more enjoyable and playable, the bracket  48  is further provided with a light source bracket  62 , which is designed to fix the light bar  61 . The outer periphery of the second propeller  412  is formed with an outer ring  4121 , and the outer ring  4121  is formed with a mounting platform at its end edge. The mounting table  4122  is also designed to fix the light bar  61 , wherein the light bar  61  is designed to rotate synchronously with the bracket  48 , and the radius of rotation coincides with the maximum rotation radius of the rotating device  401 . At the same time, the circuit board  46  can control different light-emitting units on the light bar  61 , so as to realize stereoscopic light picture display during rotation. 
     Specifically, as shown in  FIGS.  14  and  21   , the light source bracket  62  is arranged below the first propeller  411  and sleeved on the central shaft  5 . One end of the light bar  61  is electrically connected with the circuit board  46 , the other end is fixedly connected with the light source bracket  62 , and the middle part is fixedly connected with the mounting table  4122 . The light source bracket  62  can rotate relative to the axis of the central shaft  5 , so when the bracket  48  rotates, the bracket  48  will drive. 
     In this embodiment, the outer periphery of the second propeller  412  is formed with an outer ring  4121 , the radius of which is larger than the rotation radius of the blades of the second propeller  412 , and the outer ring  4121  is fixedly connected with the bracket  48  through the blades of the second propeller  412 . On the one hand, the outer ring  4121  can protect the blades of the second propeller  412  and increase the safety of the flight component  4 ; on the other hand, the outer ring  4121  fixedly connected with the bracket  48  can also increase the flight rotation of the boomerang. 
     In order to make the boomerang have other types of light and shadow effects, the position of the lighting assembly  6  can be set according to the actual requirements.  FIG.  15    shows that the lighting assembly  6  is arranged on the propeller blade, which also adopts the LED light bar made of flexible material, which can also make the boomerang have dynamic light and shadow visual effects. As shown in  FIG.  16   , the position of the light-emitting component  6  can also be arranged on the rib  3 . As the light-emitting component  6  is arranged on the outer surface of the rib  3 , the light emitted by the light-emitting component  6  is not blocked by the rib  3 . The boomerang has more realistic visual effect and better appreciation. In addition, the light-emitting components  6  can be configured in various ways, including but not limited to thermal radiation light sources, gas discharge light sources, electroluminescent light sources, etc., and their positions can also be arranged inside or outside the ribs  3  according to the actual use requirements, and the number of them can also be configured in multiple ways, or their light-emitting effects can be controlled independently, without linkage with the flight components  4 . 
     Now, referring to  FIG.  20   , the boomerang provided by the present invention has other playing methods besides the throwing method. The user can place the boomerang on the palm of his hand. When the wind F 2  of the boomerang puts pressure on the palm of his hand, the palm of his hand also gives the boomerang a reaction force, so that the boomerang can be suspended above the palm of his hand. 
       FIG.  22    shows another embodiment of the present invention. As shown in  FIG.  21   , the boomerang includes a flight component  4 , a central shaft  5  and a protective device  8 . The flight component  4  includes at least one rotating device  401 , a driving device  402  and a bracket  48  with a cavity, wherein the maximum diameter rotating plane formed by the rotating device  401  when rotating defines the outer perimeter of the flight component  4 , and the rotating device  401  rotates coaxially around the center axis defined by the maximum diameter rotating plane. The center shaft  5  coincides with the center axis, and one end of the center shaft  5  is connected with the first base  1 , which is separated from the upper and lower ends of the flight component  4 ; The protective device  8  is composed of a plurality of ribs  3  connected to each other, and is arranged around the flight component  4 , wherein the inner diameter of the protective device  8  is larger than the outer periphery of the flight component  4 . 
     Different from the preferred embodiment of the present invention, in this embodiment, the second end  52  of the central shaft  5  is not received by the second base  2 , but a sleeve  53  is sleeved on the second end  52 . The sleeve  53  is tightly connected with the second end, and the sleeve  53  can keep the rotating shaft of the rotating device  401  coaxial with the central shaft  5 . The boomerang adopting this scheme also has good flying performance and can also protect the flight component  4 . 
       FIG.  23    shows another embodiment of the present invention, which adopts the same main structure as the embodiment shown in  FIG.  22   , and the difference is the design angle of the second propeller  412  blade. As shown in  FIG.  23   , the concave surface of the blade of the second propeller  412  of the rotating device  401  faces the driving device  402 . This arrangement can also make the boomerang have better flying performance and playability. 
     The technical means disclosed in the scheme of the present invention is not limited to the technical means disclosed in the above embodiments, but also includes the technical scheme composed of any combination of the above technical features. It should be pointed out that for those of ordinary skill in the technical field, several improvements and embellishments can be made without departing from the principle of the present invention, and these improvements and embellishments are also regarded as the protection scope of the present invention.