Unmanned aircraft

Abstract

To provide an unmanned aircraft that can reduce the weight thereof.SOLUTION: An unmanned aircraft includes: a motor; an arm having an outer peripheral surface with different two first and second parts; and an attachment for connecting the motor to the arm. The attachment passes through the different two first and second parts.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to drones. [Background technology]

[0002] For example, in the drone disclosed in Patent Document 1, a motor and a propeller are attached to a propeller mounting portion, i.e., an attachment, which is attached to the tip surface of an arm. The attachment extends outward from the tip surface of the arm. Thrust and vibration are generated by the rotation of the propeller. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2019 / 146431 Summary of the Invention [Problem to be solved by the invention]

[0004] The moment of force caused by these thrusts and vibrations acts on the attachment. In order to withstand this moment of force, the attachment needs to have a certain level of strength. If ribs or other parts are added to ensure strength, the weight of the attachment, i.e., the weight of the drone, increases.

[0005] Therefore, one of the objectives of the present invention is to provide an unmanned aircraft that can be made lighter. [Means for solving the problem]

[0006] A drone according to one embodiment of the present invention comprises a motor, an arm having an outer surface having two distinct first and second parts, and an attachment connecting the motor and the arm, the attachment passing through the two distinct first and second parts. [Brief description of the drawings]

[0007] [Figure 1] 1 is a perspective view showing a schematic structure of an unmanned vehicle 1 according to a first embodiment of the present invention. [Diagram 2] 1 is a perspective view showing a schematic structure of an unmanned vehicle 1 according to a first embodiment of the present invention. [Diagram 3] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. [Figure 4] FIG. 1 is a perspective view showing a schematic structure of an attachment 3 according to one specific example. [Diagram 5] FIG. 1 is a perspective view showing a schematic structure of an attachment 3 according to one specific example. [Figure 6] 1 is an oblique view showing a schematic structure of an unmanned vehicle 1A according to a second embodiment of the present invention. [Figure 7] FIG. 13 is a perspective view showing a schematic structure of an attachment 3A according to another specific example. [Figure 8] 11 is an oblique view showing a schematic structure of an unmanned vehicle 1B according to a third embodiment of the present invention. FIG. [Figure 9] FIG. 13 is a perspective view showing a schematic structure of an attachment 3B according to another specific example. [Figure 10] 13 is an oblique view showing a schematic structure of an unmanned vehicle 1C according to a fourth embodiment of the present invention. FIG. [Figure 11] 13 is a perspective view showing a schematic structure of an attachment 3C according to another specific example. FIG. [Figure 12] 13 is an oblique view showing a schematic structure of an unmanned aerial vehicle 1D according to a fifth embodiment of the present invention. FIG. [Figure 13] 13 is an oblique view showing a schematic structure of an unmanned aerial vehicle 1D according to a fifth embodiment of the present invention. FIG. [Figure 14] 14 is a cross-sectional view taken along line 14-14 in FIG. 12. [Figure 15] 13 is an oblique view showing a schematic structure of an unmanned aerial vehicle 1E according to a sixth embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0008] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIGS. 1 and 2 are perspective views that show a schematic structure of a drone 1 according to a first embodiment of the present invention. The drone 1 is a so-called multicopter equipped with a plurality of propulsion devices. The drone 1 includes a main body (not shown), a plurality of arms 2, an attachment 3 disposed at the tip of each arm 2, a motor 4 attached to the attachment 3, and a propeller (not shown) attached to the motor 4. The motor 4 and the propeller constitute the propulsion device of the drone 1. Note that the tip of one arm 2 is shown enlarged in FIGS. 1 and 2.

[0009] The drone 1 has a main body that incorporates a control device for controlling the operation of the drone 1, a battery, various sensors, a camera, and other components. From this main body, a plurality of arms 2, for example, three, four, six, or eight arms 2, extend, for example, radially. In this example, the arms 2 are formed of a cylindrical metal material centered on a central axis x1. The ends of the arms 2 are open. Wiring (not shown) and the like are housed in the internal space of the arms 2. The arms 2 may have a shape other than cylindrical. Furthermore, it is not necessary for one arm 2 to extend directly from the main body, and for example, a T-shaped arm having two ends, such as an H-shape, may be used.

[0010] An attachment 3 is attached to the tip of the arm 2. The attachment 3 has an annular ring 10, a disk-shaped mounting base 11, a first flange 12, and a second flange 13. The ring 10 is attached to the outer peripheral surface 2a of the arm 2. The mounting base 11 is integrally formed at the upper end of the ring 10. A motor 4 defining a rotation axis x2 is supported on a surface (hereinafter referred to as the "support surface") 11a defined on the upper surface of the mounting base 11. The rotation axis x2 of the motor 4 intersects with the central axis x1 of the arm 2. In this example, the rotation axis x2 is perpendicular to the central axis x1. A propeller is supported at the upper end of the motor 4 so as to be rotatable around the rotation axis x2. Details of the attachment 3 will be described later.

[0011] FIG. 3 is a cross-sectional view taken along line 3-3 in FIG. 2. Referring to FIGS. 1 to 3 together, the motor 4 has a holder 40 constituting a base of the motor 4. A plurality of screw holes (not shown) are formed in the holder 40. The holder 40 is attached to the mounting base 11 by screwing fastening members 14 such as bolts into the screw holes of the holder 40 from the underside of the mounting base 11 through through holes (not shown) formed in the mounting base 11. The holder 40 is integrally formed from a metal material such as aluminum or a non-magnetic material including a resin material. A stator 41 is fixed to the outer circumferential surface of the cylindrical holder 40 centered on the rotation axis x2. The stator 41 has a stator core 42, a plurality of coils 43, and a plurality of insulators 44.

[0012] As is well known, the stator core 42 is formed from a laminate of magnetic material such as silicon steel plates, and functions as a yoke for the stator 41. A coil 43 is wound around each of a plurality of teeth of the stator core 42, which extend radially outward in a direction perpendicular to the rotation axis x2. An insulator 44 is disposed between the teeth and the coil 43. The insulator 44 is formed from an insulating material. In this way, electrical insulation is established between the stator core 42 and the coil 43. A magnetic pole portion (not shown) is formed at the outer circumferential end of each tooth of the stator core 42. The magnetic pole portion radially faces a magnet, which will be described later.

[0013] On the other hand, the holder 40 has a cylindrical inner peripheral surface centered on the rotation axis x2, and holds outer rings of two bearings 45, 46 arranged along the rotation axis x2. The bearings 45, 46 are fitted into the inner peripheral surface of the holder 40 and fixed to the inner peripheral surface by adhesive. The bearings 45, 46 are, for example, ball bearings. However, the bearings 45, 46 may be other bearings such as sleeve bearings. A part of the rotor 47 is held in the inner rings of the bearings 45, 46. In this way, the rotor 47 is supported by the holder 40 via the bearings 45, 46 so as to be rotatable around the rotation axis x2. The rotor 47 has a cover 48, a yoke 49, and a magnet (permanent magnet) 50.

[0014] The cover 48 covers the holder 40, the stator core 42, the coil 43, and the insulator 44 from above. The cover 48 is supported by the inner rings of the bearings 45 and 46 at its cylindrical portion on the inner periphery side. A propeller (not shown) is attached to the upper end of the cylindrical portion of the cover 48 by a fastening member such as a bolt. A cylindrical yoke 49 is attached to the outer periphery end of the cover 48. A cylindrical magnet 50 is attached to the inner periphery surface of the yoke 49. The inner periphery surface of the magnet 50 faces the magnetic pole portion of the stator core 42 in the radial direction with a predetermined magnetic gap. The motor 4 constitutes, for example, an outer rotor type motor. Note that the above configuration is one example of the motor 4, and the motor 4 may be an inner rotor type motor or other motor having another configuration.

[0015] 4 and 5 are perspective views that show a schematic structure of an attachment 3 according to a specific example. Referring to FIGS. 1 to 5 together, the attachment 3 has a ring 10, a mounting base 11, a first flange 12, and a second flange 13, as described above. The mounting base 11 has a plurality of through holes 11b for receiving the fastening member 14 described above. The ring 10 has a body 19 that defines an inner circumferential surface 15, an outer circumferential surface 16, an outer side surface 17, and an inner side surface 18. The inner circumferential surface 15 is cylindrically defined along the outer circumferential surface 2a of the arm 2. The central axis of the inner circumferential surface 15 coincides with the central axis x1. The outer circumferential surface 16 faces away from the inner circumferential surface 15. On the other hand, the outer side surface 17 is defined on the tip side of the arm 2 and extends along a virtual plane perpendicular to the central axis x1. In this example, as shown in FIG. 3, the outer side surface 17 coincides with the tip of the arm 2. The inner surface 18 is defined parallel to the outer surface 17 and faces away from the outer surface 17 .

[0016] A first flange 12 and a second flange 13 are formed on the inner surface 18. The first flange 12 and the second flange 13 protrude parallel to each other from the inner surface 18 along the central axis x1. The first flange 12 defines an inner surface 12a that is continuous with the inner circumferential surface 15 of the main body 19. The inner surface 12a is a partial cylindrical surface along the outer circumferential surface 2a of the arm 2. Similarly, the second flange 13 defines an inner surface 13a that is continuous with the inner circumferential surface 15 of the main body 19. The inner surface 13a is a partial cylindrical surface along the outer circumferential surface 2a of the arm 2. The inner surfaces 12a and 13a face each other. The first flange 12 and the second flange 13 are formed integrally with the main body 19. The first flange 12 is further formed integrally with the mounting base 11. Meanwhile, the mounting base 11 is formed integrally with the main body 19.

[0017] As shown in FIG. 3, the inner peripheral surface 15 of the main body 19 and the inner surface 12a of the first flange 12 at least partially contact the first portion 2a1 defined on the upper side of the outer peripheral surface 2a of the arm 2. On the other hand, the inner peripheral surface 15 of the main body 19 and the inner surface 13a of the second flange 13 at least partially contact the second portion 2a2 defined on the lower side of the outer peripheral surface 2a opposite to the upper side. In this example, the first portion 2a1 corresponds to the upper region of the outer peripheral surface 2a divided by a virtual plane that includes the central axis x1 and is perpendicular to the rotation axis x2. On the other hand, the second portion 2a2 corresponds to the lower region of the outer peripheral surface 2a divided by the virtual plane. The motor 4 faces the first portion 2a of the arm 2 via the attachment 3. In addition, the rotation axis x2 of the motor 4 passes through the main body 19 of the ring 10.

[0018] The first flange 12 has a screw hole 12b formed parallel to the rotation axis x2. The second flange 13 has a hole (hereinafter referred to as a "through hole") 13b formed parallel to the rotation axis x2. The screw hole 12b and the through hole 13b are formed on a virtual line perpendicular to the central axis x1. Similarly, the arm 2 has a pair of through holes 2b, 2b formed corresponding to the screw hole 12b and the through hole 13b. The attachment 3 has a rod 20 that passes through the through hole 13b and the pair of through holes 2b, 2b from the underside of the second flange 13 and is screwed into the screw hole 12b. The rod 20 has a length greater than the radial size (outer diameter) of the arm 2. The rod 20 passes through the first portion 2a1 and the second portion 2a2 of the arm 2. One form of the rod 20 is, for example, a bolt. With such a rod 20, it is possible to reliably prevent the attachment 3 from falling off the arm 2.

[0019] The ring 10 has a protruding portion 21 that protrudes downward from the lower end of the main body 19. A slit 22 is formed in the main body 19 and the protruding portion 21 parallel to the central axis x1 from the outer surface 17 toward the inner surface 18. The rotation axis x2 passes through the slit 22. The slit 22 enters from the main body 19 and the protruding portion 21 into the second flange 13. The slit 22 divides a part of the main body 19 and the protruding portion 21 into a first block 23 and a second block 24. In this example, a through hole (not shown) that penetrates the first block 23 and a screw hole (not shown) formed in the second block 24 are formed in a tangential direction of the inner peripheral surface 15 and a direction perpendicular to the rotation axis x2. A fastening member 25 such as a bolt is screwed into a screw hole in the second block 24 from the through hole in the first block 23.

[0020] Next, assume that the motor 4 is connected to the arm 2. First, the motor 4 is attached to the attachment 3. Specifically, with the screw hole of the holder 40 of the motor 4 and the through hole 11b of the mounting base 11 of the attachment 3 aligned with each other, the fastening member 14 is screwed into the screw hole of the motor 4 through the through hole 11b of the mounting base 11. As a result, the motor 4 is attached to the mounting base 11. Thereafter, the attachment 3 with the motor 4 attached is attached to the tip of the arm 2. First, the tip of the arm 2 is inserted into the ring 10 of the attachment 3. The position of the through hole 2b of the arm 2 is aligned with the position of the screw hole 12b of the first flange 12 and the position of the through hole 13b of the second flange 13.

[0021] With the through hole 2b, the screw hole 12b, and the through hole 13b aligned with each other, the rod 20 is screwed into the screw hole 12b from the lower side of the attachment 3 through the through hole 13b and the through holes 2b, 2b. As the rod 20 is screwed in, the inner surface 12a of the first flange 12 and the inner surface 13a of the second flange 13 are tightened against the first portion 2a1 and the second portion 2a2 of the outer circumferential surface 2a, respectively. In this way, the rod 20 is connected to the first flange 12 and the second flange 13. At the same time, the first flange 12 is fixed to the first portion 2a1, while the second flange 13 is fixed to the second portion 2a2. That is, the first flange 12 and the second flange 13 clamp the outer circumferential surface 2a of the arm 2 by screwing the rod 20 in.

[0022] Furthermore, the fastening member 25 is screwed into the screw hole of the second block 24 from the through hole of the first block 23 of the main body 19 of the ring 10. As the fastening member 25 is screwed in, the first block 23 and the second block 24 are drawn toward each other along the axial direction of the fastening member 25 (the circumferential direction of the inner peripheral surface 15 of the main body 19). The size of the slit 22 decreases in the axial direction of the fastening member 25. In this way, the inner peripheral surface 15 of the main body 19 of the ring 10 is tightened to the outer peripheral surface 2a of the arm 2. When the fastening member 25 is sufficiently screwed into the screw hole of the second block 24, the main body 19 of the ring 10 is fixed to the arm 2. That is, the ring 10 is fixed to the first portion 2a1 and the second portion 2a2 of the outer peripheral surface 2a of the arm 2. The attachment 3 is attached to the arm 2. In this way, the attachment 3 connects the arm 2 and the motor 4.

[0023] In the drone 1 as described above, in the attachment 3 that connects the motor 4 to the arm 2, at least the ring 10 passes through the different first and second portions 2a1 and 2a2 of the outer circumferential surface 2a of the arm 2. In this manner, the ring 10 is attached to the outer circumferential surface 2a of the arm 2. With this configuration, the attachment 3 does not need to have a portion that extends outward from the tip of the arm 2, so that the moment of force acting on the attachment 3 due to thrust and vibration generated by the rotation of the propeller can be reduced. As a result, the attachment 3 does not need to have excessive strength, so that the attachment 3 can be made lighter.

[0024] In particular, in the drone 1 according to the first embodiment, the rotation axis x2 of the motor 4 passes through the ring 10 of the attachment 3. Therefore, the force moment from the motor 4 to the attachment 3 can be substantially zero. Such a configuration further contributes to reducing the weight of the attachment 3. In addition, the first flange 12 and the second flange 13 protruding from the inner surface 18 of the main body 19 of the ring 10 are fixed to the first portion 2a1 and the second portion 2a2 of the outer circumferential surface 2a of the arm 2, respectively. That is, the first flange 12 and the second flange 13 clamp the outer circumferential surface 2a of the arm 2. Such clamping reinforces the clamping of the inner circumferential surface 15 of the main body 19 of the ring 10 to the outer circumferential surface 2a of the arm 2.

[0025] FIG. 6 is a perspective view that shows a schematic structure of a drone 1A according to a second embodiment of the present invention. In FIG. 6, the motor 4 is omitted for convenience of explanation. In this drone 1A, an attachment 3A is incorporated in place of the attachment 3 described above. FIG. 7 is a perspective view that shows a schematic structure of an attachment 3A according to another specific example. With reference to both FIG. 6 and FIG. 7, in the attachment 3A, the formation of the first flange 12 and the second flange 13 described above is omitted. That is, the attachment 3A is clamped to the outer peripheral surface 2a of the arm 2 only by the main body 19 of the ring 10. According to such an attachment 3A, it is possible to achieve even lighter weight than the attachment 3. The other configurations of the drone 1A are the same as those of the drone 1 described above, so that a duplicated description here will be omitted.

[0026] FIG. 8 is a perspective view showing a schematic structure of a drone 1B according to a third embodiment of the present invention. In FIG. 8, the motor 4 is omitted for convenience of explanation. An attachment 3B, which is a modified example of the attachment 3A described above, is incorporated in this drone 1B. FIG. 9 is a perspective view showing a schematic structure of the attachment 3B according to another specific example. Referring to both FIG. 8 and FIG. 9, in the attachment 3B, a protrusion 21 is formed on the lateral side, which is an intermediate position between the upper and lower sides, rather than on the lower side of the main body 19 of the ring 10. According to this configuration, the fastening member 14 for the motor 4 and the fastening member 25 for the ring 10 can be screwed in the same direction along the rotation axis x2. The other configurations of the drone 1B are the same as those of the drone 1A described above, so that a duplicated description here will be omitted.

[0027] FIG. 10 is a perspective view that shows a schematic structure of a drone 1C according to a fourth embodiment of the present invention. In FIG. 10, the motor 4 is omitted for convenience of explanation. An attachment 3C, which is a modified version of the attachment 3B described above, is incorporated in this drone 1C. FIG. 11 is a perspective view that shows a schematic structure of the attachment 3C according to another specific example. Referring to both FIG. 10 and FIG. 11, in the attachment 3C, a pair of protrusions 21 are formed on both sides of the body 19 of the ring 10, which is not on the lower side but is located at a midpoint between the upper and lower sides. That is, the body 19 of the ring 10 is divided into an upper part 19A and a lower part 19B. The other configurations of the drone 1C are the same as those of the drone 1B described above, so that a duplicated description will be omitted here.

[0028] 12 and 13 are perspective views that show a schematic structure of an unmanned vehicle 1D according to a fifth embodiment of the present invention. In FIG. 12 and FIG. 13, the motor 4 is omitted for ease of explanation. An attachment 3D, which is a modified example of the attachment 3 described above, is incorporated in this unmanned vehicle 1D. FIG. 14 is a cross-sectional view taken along line 14-14 in FIG. 12. Referring to FIG. 12 to FIG. 14 together, in the attachment 3D, a cylindrical portion (hereinafter referred to as "cylindrical portion") 26 is formed on the inner surface 18 of the main body 19 of the ring 10 instead of the first flange 12 and the second flange 13. An inner circumferential surface 26a of the cylindrical portion 26 is continuous with the inner circumferential surface 15 of the main body 19 (see FIG. 14).

[0029] A through hole 26b is formed on the upper side of the cylindrical portion 26, and a screw hole 26c is formed on the lower side of the cylindrical portion 26. A pair of through holes 2b, 2b corresponding to the through hole 26b and the screw hole 26c are formed on the arm 2. In this example, the through hole 26b, the screw hole 26c, and the pair of through holes 2b, 2b are formed on a virtual straight line perpendicular to the central axis x1 and parallel to the rotation axis x2. As shown in FIG. 14, a rod 27 is screwed into the screw hole 26c from the upper side of the attachment 3D through the through hole 26b and the through holes 2b, 2b. By screwing the rod 27, the inner peripheral surface 26a of the cylindrical portion 26 is tightened against the outer peripheral surface 2a of the arm 2. As a result, the cylindrical portion 26 is clamped to the outer peripheral surface 2a of the arm 2 by its inner peripheral surface 26a.

[0030] Also, in the attachment 3D, unlike the attachment 3, the mounting base 11 is formed as a separate body from the main body 19 of the ring 10. In this example, the mounting base 11 has a pair of protruding portions 11c, 11c extending in a direction perpendicular to the rotation axis x2. Correspondingly, a pair of protruding portions 19a, 19a is formed in a direction perpendicular to the rotation axis x2 from the upper end of the main body 19 of the ring 10. The protruding portions 11c, 11c and the protruding portions 19a, 19a are formed at the same position around the rotation axis x2. In this example, the protruding portion 19a has a through hole 19b formed therein, while the protruding portion 11c has a screw hole 11d corresponding to the through hole 19b formed therein. The mounting base 11 is attached to the main body 19 of the ring 10 by screwing a fastening member (not shown) such as a bolt into the screw hole 11d through the through hole 19b. The other configurations of the drone 1D are the same as those of the drone 1 described above, so that a duplicated description will be omitted here.

[0031] FIG. 15 is a perspective view that shows a schematic structure of an unmanned vehicle 1E according to a sixth embodiment of the present invention. In FIG. 15, the motor 4 is omitted from the illustration for the sake of convenience. The attachment 3E, which is a modified example of the attachment 3, is incorporated in the unmanned vehicle 1E. In the attachment 3E, the main body 19 of the ring 10 is divided into two parts, a first part 19C and a second part 19D, in a direction along the central axis x1. In the division, a slit 28 is formed in the main body 19 along a virtual plane perpendicular to the central axis x1. The slit 28 is formed continuously around the central axis x1. That is, the protrusion 21 is also divided according to the first part 19C and the second part 19D. The first part 19C and the second part 19D each constitute a clamp.

[0032] In this example, the fastening member 25 is screwed into the first portion 19C and the second portion 19D. That is, a pair of through holes and a screw hole are formed in each of the first block 23 and the second block 24. The pair of through holes and screw holes are arranged along the central axis x1, sandwiching the rotation axis x2. That is, the fastening member 25 is screwed into the first portion 19C, whereby the first portion 19C is fastened to the outer peripheral surface 2a of the arm 2. Similarly, the fastening member 25 is screwed into the second portion 19D, whereby the second portion 19D is fastened to the outer peripheral surface 2a of the arm 2. The other configurations of the drone 1E are the same as those of the drone 1 described above, so that a duplicated description here will be omitted. The configuration of the attachment 3E incorporated into the drone 1E may be incorporated into the drones 1 to 1D described above.

[0033] Although the present invention has been described above through the above embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments. It is clear to those skilled in the art that various modifications or improvements can be made to the above embodiments. It is clear from the claims that such modifications or improvements can also be included in the technical scope of the present invention.

[0034] The above-described embodiments are intended to facilitate understanding of the present invention, and are not intended to limit the present invention. The components of the above-described embodiments, as well as their arrangements, materials, conditions, shapes, sizes, etc., are not limited to those illustrated, and can be modified as appropriate. Furthermore, components shown in different embodiments can be partially substituted or combined with each other within the scope of technical inconsistency. [Explanation of symbols]

[0035] 1 to 1E drone, 2 arm, 2a outer peripheral surface, 2a1 first portion, 2a2 second portion, 2b through hole, 3 to 3E attachment, 4 motor, 10 ring, 11 mounting base, 11a surface (support surface), 11b through hole, 11c protrusion, 11d screw hole, 12 first flange, 12a inner surface, 12b screw hole, 13 second flange, 13a inner surface, 13b hole portion (through hole), 14 fastening member, 15 inner peripheral surface, 16 outer peripheral surface, 17 outer surface, 18 inner surface, 19 main body, 19a protrusion, 19b through hole, 19A upper portion, 19B lower portion, 19C first portion, 19D second portion, 20 rod, 21 protrusion, 22 slit, 23 first block, 24 second block, 25 Fastening member, 26 cylindrical portion, 26a inner peripheral surface, 26b through hole, 26c screw hole, 27 rod, 28 slit, 40 holder, 41 stator, 42 stator core, 43 coil, 44 insulator, 45 bearing, 46 bearing, 47 rotor, 48 cover, 49 yoke, 50 magnet, x1 central axis, x2 rotation axis

Claims

1. A motor; an arm having an outer circumferential surface with two distinct first and second portions; an attachment that connects the motor and the arm; The attachment passes through the two distinct first and second portions.

2. The drone of claim 1 , wherein the attachment comprises a rod passing through the two distinct first and second portions.

3. The drone of claim 2 , wherein the motor faces the first portion via the attachment.

4. the attachment comprises a first flange secured to the first portion and a second flange secured to the second portion; The drone of claim 3 , wherein the rod is connected to the first flange and the second flange.

5. the attachment comprises a ring; The drone of claim 4 , wherein the ring is attached to an outer circumferential surface of the arm.

6. The drone of claim 5 , wherein the motor is coupled to the first flange.

7. The drone of claim 5 , wherein the motor's axis of rotation passes through the ring.

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