Rotary actuator, hinged panel assembly, and fixed-wing aircraft

Abstract

A rotary actuator for an articulated panel assembly, such as for a fixed-wing aircraft, the rotary actuator including balls, an outer cylinder, a piston, and an inner shaft. The outer cylinder permits fluid pressure from a fluid pressure supply. The piston is externally received by the outer cylinder. The piston, outer cylinder, and balls together form an outer ball screw. The piston translates along a longitudinal central axis in response to the fluid pressure. The inner shaft is externally received by the piston, wherein the inner shaft, piston, and balls together form an inner ball screw coaxial with the outer ball screw. The ball screws form an interleaved ball circuit having one or more shared ball paths. Translation of the piston causes rotation of the piston and the inner shaft, thereby causing the balls to recirculate between the outer ball screw and the inner ball screw through the interleaved ball circuit.

Description

Technical Field

[0001] The present application relates to a rotary actuator including a recirculating ball screw and a hinged panel assembly and a fixed-wing aircraft having the rotary actuator. Background Art

[0002] Fluid power linear and rotary actuators are widely used in dynamic systems to apply torque and linear force to a driven load. A ball screw assembly is a common type of linear actuator. A typical ball screw assembly uses a relatively low pitch to achieve high linear force and translation in response to a relatively low input torque. A rotary actuator typically includes an electric motor that can be mechanically coupled to the driven load and can be selectively powered via a multi-cell battery pack or another power source. The powered electric motor responds by generating an output torque, which is then transferred to the coupled driven load. A rotary actuator can also be fluid actuated, such as in the case of a rotary vane and a rack and pinion actuator. A threaded-to-thread Acme screw assembly is another example of an actuator commonly used to apply force to a driven load. However, due to the high friction along the mating threads, Acme screws are more commonly used in applications where such friction and the resulting possible failure modes are relatively well tolerated. Summary of the Invention

[0003] Disclosed herein is a compact rotary actuator which, in its various embodiments, is configured to provide high torque efficiency and low friction relative to the conventional actuators generally described above. The rotary actuator can be used as an on-axis or off-axis solution to effectively drive the rotating hinge head of a hinged panel assembly. Representative hinged panel assemblies include, but are not limited to, pneumatic flight control surfaces / panels, such as flaps, ailerons, rudders, fairing fins, or struts disposed on the wings and tails of a fixed-wing aircraft (e.g., a thin-wing aircraft). Other aviation applications can benefit from this teaching, including but not limited to landing gear doors and cargo bay doors, and the described rotary actuator also has utility in other industries where compact / high-efficiency rotary actuation is required.

[0004] As elaborated in detail below, the rotary actuator of the present disclosure forms or defines two coaxial ball screws that share / recycle balls therebetween via interleaved ball circuits having one or more shared ball paths. One of the ball screws in the ball screw is radially located within the other ball screw relative to the longitudinal central axis of the rotary actuator, and thus, for greater clarity, the two ball screws are referred to herein as an outer ball screw and an inner ball screw.

[0005] In the disclosed embodiments, one or two pistons translate within the outer cylinder in response to fluid pressure permitted from an external pressure supply. When this occurs, the outer ball screw and the inner ball screw translate in opposite axial directions, and the translational movement and thus the rotation of one or more pistons ultimately cause the balls to recirculate between the inner ball screw and the outer ball screw. This occurs entirely within the housing of the outer cylinder, and thus the rotary actuator is characterized by having no external ball return path. Instead, the balls roll and translate along one or more shared ball paths, which may be implemented as a single continuous ball path or multiple shared ball paths, and the one or more shared ball paths together form the interleaved ball circuit described above. The rotation of the piston ultimately causes the inner shaft to rotate, which in turn is coupled to a driven load, such as but not limited to the aforementioned rotating hinge joint or articulated panel assembly.

[0006] The outer cylinder defines a set of helical or spiral grooves that form the internal threads of the outer ball screw. The piston that translates within the outer cylinder by means of a pressure differential across the piston face has an outer diameter that includes the external threads of the outer ball screw. The inner diameter of the piston includes the internal threads of the inner ball screw. The inner shaft circumscribed by the piston and the outer cylinder includes the external threads of the inner ball screw. Thus, the inner shaft rotates relative to the piston by the action of the inner ball screw.

[0007] The rotary actuator of the present disclosure may optionally be positioned coaxially with the rotating hinge joint of such an articulated panel assembly, which in the example of a thin-wing aircraft would eliminate the need to accommodate the associated crank assembly and mechanical linkage within a large lower-wing canoe fairing. Other configurations position the rotary actuator off-axis from the rotating hinge joint and connect the rotary actuator to the rotating hinge joint via one or more mechanical linkages.

[0008] In the disclosed non-limiting embodiments, the rotary actuator includes a plurality of balls, an outer cylinder, a piston, and an inner shaft. The outer cylinder has a plurality of fluid ports, each configured to permit fluid pressure from a fluid pressure supply. The piston is circumscribed by the outer cylinder. The piston, the outer cylinder, and the balls together form an outer ball screw. Additionally, the piston is configured to translate along the longitudinal central axis of the rotary actuator in response to fluid pressure. The inner shaft is circumscribed by the piston, wherein the inner shaft, the piston, and the balls together form an inner ball screw that is coaxial with the outer ball screw about the longitudinal central axis.

[0009] In this embodiment, the outer ball screw and the inner ball screw together form an interleaved ball circuit having one or more shared ball paths. The translation of the piston along the longitudinal central axis in response to fluid pressure has the dynamic effect of rotating the piston and the inner shaft, i.e., operatively rotating the piston and the inner shaft, which action causes the balls to recirculate between the outer ball screw and the inner ball screw through the interleaved ball circuit.

[0010] The present disclosure also discloses a hinged panel assembly. According to an illustrative embodiment disclosed, the hinged panel assembly includes a rotary actuator and a swivel joint that interconnects a first panel and a second panel and has a rotational axis. The rotary actuator is connected to the swivel joint and includes a rotatable inner shaft, a piston, an outer cylinder, and a plurality of balls. The inner shaft is connected to the rotational axis of the swivel joint. The piston circumscribes the rotatable inner shaft and is configured to translate along a longitudinal central axis of the rotary actuator in response to fluid pressure. The outer cylinder circumscribes the piston and has a plurality of fluid ports, each fluid port being configured to permit fluid pressure.

[0011] The rotatable inner shaft, the piston, and the outer cylinder are coaxially arranged relative to the longitudinal central axis to form two coaxial ball screws that together define the above-described interleaved ball circuit, wherein the balls are positioned within at least one shared ball path of the interleaved ball circuit. The piston, in response to permitting fluid pressure to enter the outer cylinder, operatively causes the balls to recirculate between the two coaxial ball screws via at least one shared ball path and causes the piston and the inner shaft to rotate, thereby actuating the swivel joint and changing the angular position of the first panel relative to the second panel.

[0012] The present disclosure also discloses a fixed-wing aircraft. A representative embodiment of the fixed-wing aircraft includes a pair of wings and a tail wing connected to a fuselage, a pneumatic flight control panel, and a rotary actuator, the pneumatic flight control panel being connected to one of the wings and / or connected to the tail wing via a swivel joint having a rotational axis, the rotary actuator being connected to the swivel joint and configured as described herein.

[0013] The foregoing summary is not intended to represent every embodiment or every aspect of the present disclosure. Rather, the foregoing summary merely provides examples of some novel concepts and features set forth herein. When taken in conjunction with the drawings and the appended claims, the above-described features and advantages, as well as other features and advantages, will become apparent from the following detailed description of the illustrated embodiments and representative modes for carrying out the present disclosure. Moreover, the present disclosure expressly includes any and all combinations and sub-combinations of the elements and features presented above and below. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic view of an exemplary fixed-wing aircraft having pneumatic flight control surfaces, each pneumatic flight control surface being actuatable via a corresponding compact rotary actuator of the type described herein.

[0015] Figure 2A and Figure 2B A schematic view of a representative hinged pneumatic flight control panel having a hinge axis powered by the rotary actuator of the present disclosure.

[0016] Figure 2C andFigure 2D Schematic view of a representative articulated pneumatic flight control panel having two hinge axes, each hinge axis being powered by a respective rotary actuator.

[0017] Figure 3 Partial cross-sectional perspective view of a rotary actuator according to a possible single piston embodiment.

[0018] Figure 4 is Figure 3 Schematic cross-sectional view of the rotary actuator shown.

[0019] Figure 5 Schematic perspective view of an exemplary interleaved ball circuit formed by a plurality of shared ball paths that can be incorporated into the construction of the rotary actuator disclosed herein.

[0020] Figure 6 is Figure 3 and Figure 4 Schematic cross-sectional view of an alternative dual piston embodiment of the rotary actuator shown.

[0021] The present disclosure may be extended to modified and alternative forms, with representative embodiments shown by way of example in the drawings and described in detail below. The inventive aspects of the present disclosure are not limited to the disclosed embodiments. Instead, the present disclosure is intended to cover modifications, equivalents, combinations, and alternative forms that fall within the scope of the present disclosure as defined by the appended claims. Detailed Description

[0022] The present disclosure is susceptible of implementation in many different forms. Representative embodiments of the present disclosure are shown in the drawings and will be described in detail herein. It should be understood that these embodiments are provided as examples of the disclosed principles and not as limitations on the broad aspects of the present disclosure. In this regard, elements and limitations described, for example, in the abstract, background, summary, and detailed description sections but not expressly set forth in the claims should not be incorporated into the claims singly or jointly by implication, inference, or otherwise. For the purposes of this detailed description, unless otherwise specified, the singular includes the plural and vice versa; for example, "a" means "at least one" or "one or more"; the words "and" and "or" should be both conjunctive and disjunctive; the words "any" and "all" should each mean "any and all"; and the words "comprising," "containing," "including," "having," etc. should each mean "including but not limited to." Further, approximate words such as "about," "almost," "substantially," "approximately," "around," "generally," etc. may each be used herein in the sense of, for example, "at, nearly, almost at" or "within 0 - 5% of" or "within acceptable manufacturing tolerances" or any logical combination thereof.

[0023] Referring to the accompanying drawings, in which like reference numerals refer to like features throughout several views, Figure 1 an exemplary aircraft 10 is depicted. The aircraft 10, such as the fixed-wing aircraft shown, includes a pair of main wings 12 and a tail wing 14 connected to the fuselage 16. As will be understood by those of ordinary skill in the art, the wings 12 and the tail wing 14 include various aerodynamic flight control surfaces or panels generally shown at 18. For example, each wing 12 may have one or more controllable flaps 18F and ailerons 18A, while the tail wing 14 includes a rudder 18R and an elevator 18E. Other aerodynamic flight control panels 18, not explicitly shown in Figure 1 but well known in the art, such as but not limited to spoilers, trim tabs, slats, etc., may be used at other locations on the aircraft 10, and thus the configuration and use of the aerodynamic flight control panels 18 may vary according to the application and configuration of the aircraft 10.

[0024] Each aerodynamic flight control panel 18 may be actuated independently via a respective compact rotary actuator 20 ( Figure 3 and 4 ) or 200 ( Figure 6 ). Each rotary actuator 20 and / or 200 used on the aircraft 10 is in fluid communication with a fluid pressure supply 15. In the exemplary aviation application shown, the fluid pressure supply 15 may optionally be implemented as a hydraulic fluid circuit of the aircraft 10, including a hydraulic fluid pump, valves, fittings, hoses, and fluid filters, all of which are not shown but are well known in the art.

[0025] Figure 1 The respective angular positions of the various aerodynamic flight control panels 18 shown are selectively changed by the pilot of the aircraft 10 or autonomously by an on-board flight control or avionics unit (not shown) by allowing fluid pressure from the fluid pressure supply 15 to enter the rotary actuator 20, as described below. Although the exemplary embodiments used herein to illustrate the teachings contemplate the use of hydraulic fluid pressure for this purpose, other embodiments may be envisioned in which the actuation of the aerodynamic flight control panels 18 is achieved in other ways, such as by using compressed air or gas / pneumatic actuation. For simplicity of illustration, the aerodynamic flight control surfaces 18 of the present disclosure are described below as hydraulically actuated, without limiting the actuation to such a form of movement.

[0026] In Figure 2A and 2B , a hinged panel assembly 19 is shown, in which a first panel (in this case one of the wings 12 of Figure 1 ) is connected to a second panel (in this case the flap 18F) via a swivel hinge joint 21, where the swivel hinge joint 21 has a rotational axis or hinge axis A 21 .Figure 2A And Figure 2B respectively depict the "flipped up" and "flipped down" configurations of a representative pneumatic flight control panel 18, such that Figure 1 the other panels 18 shown are similarly positioned in other embodiments. Figure 2C And 2D similarly depict the "flipped up" and "flipped down" configurations of another hinged panel assembly 190, with the significant difference being that Figure 2A and 2B the representative flap 18F shown in Figure 2C and 2D is replaced in

[0027] by two flap assemblies, namely a leading flap 18F-1 and a trailing flap 18F-2, where "leading" and "trailing" refer to the relative position with respect to the airflow over the wing 12. The corresponding leading flap 18F-1 and trailing flap 18F-2 may be rotatably interconnected via a rotating hinge joint 21B. Figure 2A - 2D In the configuration of 21 , the flap 18F and the leading flap 18F-1 may be rotatably connected to the wing 12 using the rotating hinge joints 21 or 21A, respectively. The advantage of the rotary actuator 20 is its compact size and high torque efficiency. This enables the rotary actuator 20 to be positioned on / coaxial with the hinge axis A Figure 2A of the hinge joints 21, 21A or 21B. For example, in the illustrated embodiment of 21 , the rotary actuator 20 is positioned on the hinge axis A 20 such that the longitudinal central axis A 21 of the rotary actuator 20 and the hinge axis A Figure 1 are coaxially aligned. This coaxial arrangement reduces the required packaging enclosures for the rotary actuator 20 and the various robotic arms or linkages (such as under the wing 12 of a large canoe fairing) that would otherwise be needed. Thus, when constructing an aircraft 10 using the rotary actuator 20 of the present invention

[0028] In Figure 2B , shown in dashed lines to represent an alternative off-axis configuration, the rotary actuator 20 may also be positioned at a short distance from the hinge axis A 21 and one or more mechanical linkages 23 may be used to connect the rotary actuator 20 to the hinged rotary joint 21. Such a configuration may also be used with Figure 2C and 2D the representative embodiments of Figure 1for use with other flight control panels 18. Thus, while the axial placement of the rotary actuator 20 provides the above and other possible advantages, the present rotary actuator 20 may be used off-axis within the scope of the present disclosure, for example, as a retrofit or aftermarket replacement for more efficient and less efficient actuators typically housed in the lower wing fairing as described above.

[0029] Referring Figure 3 and Figure 4 , the rotary actuator 20 includes two coaxial / outer ball screws and an inner ball screw to convert the linear motion of the reciprocating piston 24 into the rotational motion of the inner shaft 25. The inner shaft 25 may include a plurality of radial teeth or splines 125, as shown, to facilitate meshing engagement of the inner shaft 25 with a driven load, such as Figure 2A - 2D the swivel joints 21, 21A or 21B of

[0030] According Figure 3 to an exemplary embodiment of 20 , the rotary actuator 20 includes three main components: a piston 24, an inner shaft 25, and an outer cylinder 26, which are coaxially arranged with respect to the longitudinal central axis A 20 of the rotary actuator 20. Thus, the longitudinal central axis A Figure 3 is the longitudinal central axis of each of the piston 24, the inner shaft 25, and the outer cylinder 26. As described in more detail below, alternating fluid pressures, as indicated by arrows P1 and P2, are allowed to enter opposite ends of the outer cylinder 26. Such fluid pressures are allowed to selectively enter the outer cylinder 26 through corresponding fluid ports 41, Figure 3 one of which can be seen in a perspective view of

[0031] A plurality of fluid ports 41 of the outer cylinder 26 may be formed at accessible locations in the outer cylinder 26, i.e., as holes or apertures through the circumferential wall 26W of the outer cylinder 26. The inner diameter of the outer cylinder 26 defines / includes an internal thread 28 of the outer ball screw 29-O. The outer diameter of the piston 24 defines or includes an external thread 32 of the outer ball screw 29-O, and the inner diameter of the piston 24 defines or includes an internal thread 34 of the inner ball screw 29-I. Similarly, the outer diameter of the inner shaft 25 defines or includes an external thread 36 of the inner ball screw 29-I. The thread direction of the outer ball screw 29-O is opposite to the thread direction of the inner ball screw 29-I, which ensures the desired motion and reverse translation.

[0032] As shown, for example, the internal thread 28 and the external thread 32 of the outer ball screw 29-O are left-handed threads, while the internal thread 34 and the external thread 36 of the inner ball screw 29-I are right-handed threads. However, in other embodiments, the opposite can also be true, i.e., the internal thread 28 and the external thread 32 of the outer ball screw 29-O can be right-handed threads, while the internal thread 28 and the external thread 32 of the inner ball screw 29-I are left-handed threads.

[0033] The piston 24 is configured to separate the outer cylinder 26 into a plurality of pressure chambers, such as, for example, the pressure chambers 30A and 30B as Figure 4 shown. The plurality of fluid ports 41 of the outer cylinder 26 are configured to fluidly connect the fluid pressure supply unit 15 (see Figure 1 ) to the plurality of pressure chambers 30A and 30B. The position and configuration of the piston 24 thus form a barrier between the relatively arranged (nominally "right" and "left") fluid chambers 30A and 30B. The pressure difference across the piston 24 is used to drive the piston 24 along the longitudinal central axis A 20 in one of two possible axial directions, i.e., from Figure 3 and Figure 4 viewpoint to the right or left.

[0034] Generally, the construction of the rotary actuator 20 ensures that the translation of the piston 24 along the longitudinal central axis A 20 causes the piston 24 to rotate relative to the outer cylinder 26 and rotate radially within the outer cylinder 26. This rotation occurs through the action of the outer ball screw 29-O. By means of the inner ball screw 29-I and the translation of the piston 24, the inner shaft 25 is similarly rotated relative to the piston 24. In some configurations, the number of shared ball paths 40 of the inner ball screw 29-I is also equal to the number of shared ball paths 40 of the outer ball screw 29-O.

[0035] In Figure 3 and Figure 4 shown single-piston representative embodiment, the piston 24 circumscribes the inner shaft 25, wherein the axial ends E1 and E2 of the inner shaft 25 are supported by a set of thrust bearings 35 ( Figure 4 ), and the sliding seal 37 is located at the sliding interface between the outer cylinder 26, the piston 24, and / or the inner shaft 25. Similarly, static seals 39 are used at the static interfaces.

[0036] In some embodiments, as Figure 4The optional rotational position sensor 42 schematically shown therein may be connected to the inner shaft 25 adjacent to the end cap 44 of the rotary actuator 20, wherein the end cap 44 is configured to enclose the cavities 30A and 30B. The rotational position sensor 42 is configured to measure and report, for example, the angular position of the inner shaft 25 to an external electronic control unit (not shown). Various sensor types may be used for this purpose, including but not limited to a rotary variable differential transformer or a rotary encoder.

[0037] As described above, Figure 3 and Figure 4 the outer cylinder 26 shown surrounds / externally engages the piston 24 such that the inner shaft 25, the piston 24, and the outer cylinder 26 are coaxially arranged with respect to the longitudinal central axis A 20 to together form a coaxial inner ball screw 29-I and an outer ball screw 29-O. The inner ball screw 29-I and the outer ball screw 29-O together include one or more helical or spiral grooves that together define at least one shared ball path 40, such as a single continuous ball path 40 or multiple shared ball paths 40 that pass through and form an integral part of the inner ball screw 29-I and the outer ball screw 29-O, as Figure 5 shown. A plurality of balls 42 are located within one or more shared ball paths 40. Although the balls 42 are shown for simplicity of illustration as having approximately the same diameter, the balls 42 may have different diameters, e.g., having alternating larger and smaller ball diameters, and adjacent balls 42 rotate in different directions while translating in the same direction along one or more shared ball paths 40. The construction material of the balls 42 may also vary depending on the intended application, and exemplary steel or ceramic embodiments may be used in a wide range of applications.

[0038] As Figure 3 best shown in, a ball guide 46 is formed in the transition of one or more shared ball paths 40 to enable the balls 42 to be smoothly transferred from the outer ball screw 29-O to the inner ball screw 29-I. The translation of the piston 24 along the longitudinal central axis A 20 provides the motive force for recirculating the balls 42 within one or more shared ball paths 40 between the inner ball screw 29-I and the outer ball screw 29-O, respectively. The piston 24 is further configured to rotate about the longitudinal central axis A 20 as the piston 24 translates along the axis A 20 such that the longitudinal central axis A 20 becomes the axis of rotation of the piston 24 and the inner shaft 25.

[0039] Regarding the balls 42 and one or more shared ball paths 40, this particular aspect of the present disclosure ensures that the rotary actuator 20 is capable of recirculating the balls 42 between the respective outer ball screw 29 - O and the inner ball screw 29 - I while significantly reducing the friction during operation compared to a conventional thread - to - thread screw actuator. The balls 42 contacting the inner shaft 25 and the piston 24 recirculate radially within the outer cylinder 26 to contact the outer cylinder 26, where the balls 42 still maintain rolling contact with the piston 24. When this occurs, the rotation or angular velocity of the piston 24 is approximately half of the rotational speed of the inner shaft 25, and the friction caused by the rotation and translation of the piston 24 radially within the outer cylinder 26 causes the balls 42 to translate at a constant speed. That is, the translation speed of the plurality of balls 42 within the inner ball screw 29 - I is equal to the translation speed of the plurality of balls 42 within the outer ball screw 29 - O.

[0040] To further optimize the construction of the present invention, the rotary actuator 20 can use a relatively large pitch such that for every two inches or more of translation of the piston 24, the inner shaft 25 rotates a full turn. The large pitch is designed to ensure that the output torque provided on the inner shaft 25 remains high enough and the linear input force remains low enough. An advantage of the configuration of the rotary actuator 20 of the present invention is its ability to be reversely driven. For example, in the case of a jammed ball 42, if necessary, it can be reversely driven by applying a manual or electric torque to the inner shaft 25. The large pitch relative to a conventional ball screw also allows multiple thread / ball starts to be oriented around the piston 24, the outer cylinder 26, and the inner shaft 25.

[0041] In addition, more thread / ball starts allow for more balls 42 to carry a greater contact load. As a non - limiting illustrative example, up to eighteen (18) thread / ball starts can be used on each of the inner ball screw 29 - I and the outer ball screw 29 - O. Each thread / ball start can be rotated 20 degrees from the previous thread / ball start. However, based on the desired size of the rotary actuator 20 and the size of the balls 42, different numbers of thread / ball starts can also be used, and thus, the depicted embodiments represent the teachings of the present invention and are non - limiting.

[0042] Briefly refer to Figure 5, an exemplary interleaved ball circuit 50 includes at least six shared ball paths 40 having a total of twelve (12) different thread / ball starting points, which are nominally labeled S1 to S12 for clarity. As will be understood by those of ordinary skill in the art, the configuration shown is a false perspective / 3D representation of the ball paths 40 defined within the outer ball screw 29-O and the inner ball screw 29-I. Similarly, as described above, in an actual embodiment, the ball paths 40 shown will be completely filled with balls 42 such that the balls 42 in the outer ball screw / outer ball circuit will tend to push the balls 42 towards the inner ball screw / inner ball circuit. Similarly, the balls 42 in the inner ball screw 29-I will tend to push the balls 42 towards the outer ball screw 29-O, where the ball paths 40 extending between the corresponding inner ball screw 29-I and outer ball screw 29-O effectively form an internal ball return path.

[0043] In the illustrated embodiment, the ball paths 40 having ball starting points S1 and S7 are interconnected, and similarly the ball paths 40 having ball starting points S2 and S8 are continuous in this manner, i.e., S3 and S9, S4 and S10, S5 and S11, and S6 and S12. As Figure 5 shown, using multiple ball paths 40 increases redundancy and reduces sliding friction within the rotary actuator 20. That is, if Figure 3 and Figure 4 the balls 42 of Figure 5 happen to get stuck or aborted when translating through a given shared ball path 40 within the interleaved ball circuit 50 of

[0044] Figure 3 the ball guides 46 shown in Figure 5 form a transition between the shared ball paths 40 within the ball circuit 50, i.e., in the case where a given ball 42 moves from one shared ball path 40 to another shared ball path, such as when moving from the outer ball screw 29-O to the inner ball screw 29-I, these ball guides are formed as bends or turns. These turns should be designed to prevent the balls 42 from colliding. Given the complexity of the required surface geometries, additive manufacturing / 3D printing methods (such as selective laser melting) may be optimal when constructing the interleaved ball circuit 50 and its various ball guides 46. Within the scope of the present disclosure, other combinations or numbers of ball starting points and ball paths 40 are possible, for example, nine thread / ball starting points, and thus Figure 5 the embodiments are intended to illustrate the teachings of the present invention and are non-limiting.

[0045] To facilitate Figure 5The anti-blocking property of the balls 42 within the interleaved ball circuit 50 shown, particularly in Figure 3 and Figure 4 the rotary actuator 20 or Figure 6 the quick-acting embodiment of the double-piston rotary actuator 200 shown, as will be appreciated by those of ordinary skill in the art, more and / or shorter shared ball paths 40 may be used, and the curves and ball guides 46 may be configured to have gradually curved portions. If the rotary actuator 20 acts quickly, the translational speed of the captured balls 42 will tend to be higher, and thus the effect of inertia will increase. For example, if inertia causes a given ball 42 to stop rolling within the interleaved ball circuit 50 as the ball 42 translates therefrom, friction will increase and wear will occur, thereby reducing the working efficiency.

[0046] Referring to Figure 6 , as an alternative to the single-piston rotary actuator 20 of Figure 4 , a double-piston rotary actuator 200 may be constructed, which includes a first piston 124 and a second piston 224, an outer cylinder 126, and an inner shaft 225. An end cap 144 similar to the end cap 44 of Figure 3 is provided at the distal end E1. The rotary actuator 200 utilizes an internal fluid port 41(P I ), and a pair of external fluid ports 41(P O ) are located on the sides of the internal fluid port, wherein the internal fluid port 41(P I ) is located at or near the approximate axial midpoint of the rotary actuator 200. When fluid pressure is applied to the rotary actuator 200 via two external pressure ports (P O ) 41, the first piston 124 and the second piston 224 move towards each other as shown by the arrow II, wherein the internal pressure port 41(P I ) serves as an outlet port for discharging the captured fluid from the outer cylinder 126 in this case. Similarly, introducing fluid pressure into the internal fluid port 41(P I ) can drive the pistons 124 and 224 in the axially outward direction as shown by the arrow OO, wherein the external fluid port 41(P O ) serves as an outlet port.

[0047] Although at the cost of increased internal complexity, however, relative to the single-piston embodiments of Figure 3 and 4 , the exemplary double-piston embodiment of Figure 6 can best help balance the load on the rotary actuator 200. Therefore, Figure 6 the configuration of Figure 4the need for the thrust bearing 35 shown. To ensure proper fluid sealing and load support, a sliding seal 37 is maintained at the mating surface of any sliding or translating component, where a static seal 39 is provided at the static interface, and a journal bearing 55 is used to provide rotational support.

[0048] respectively shown in Figure 3 - 4 and 6, the exemplary rotary actuators 20 and 200 allow for a compact construction. In turn, a compact construction is desirable in a variety of applications such as, but not limited to Figure 1 actuation of the flight control panel 18, and for applications such as actuation of cargo bay doors or landing gear doors, it can be scaled up. By using the efficient inner ball screw 29-I and outer ball screw 29-O in place of the high-friction Acme screw, and the interleaved ball circuits 50 and one or more shared ball paths 40 illustrated in the Figure 5 , a large pitch solution becomes possible, such that the rotary actuator 20 or 200 can be selectively backdriven by applying torque through the inner shaft 25 ( Figure 3 and 4 ) or 225 ( Figure 6 ) as needed.

[0049] It may be desirable to have slightly different pitches respectively between the inner shafts 25 or 125 and the outer cylinders 26 or 126 in Figure 3 and Figure 6 , and other possible embodiments have the same pitch. Examples of relatively large pitches within the scope of the present disclosure include for a stroke of one or more pistons 24, 124 or 224 of two inches or more, the inner shaft 25 or 125 rotates one revolution, for example, in some embodiments, about 3 - 4 inches per revolution. Moreover, as allowed by the disclosed solution, using a large pitch allows for multiple thread starts, which in turn allows for more balls 42 (see Figure 3 and Figure 4 ) to carry the contact load between the respective components.

[0050] For example, nine thread / ball starts can be used on the respective inner ball screw 29-I and outer ball screw 29-O, each thread / ball start rotated 40 degrees from the previous one. In other embodiments, any number of starts can be used based on the size of the rotary actuator 20 or 200 and the size of the balls 42. Ideally, at least six and up to twelve thread or ball starts can be considered optimal without making the construction overly complex, and there is no limit to the number of thread or ball starts. When the pistons 24, 124 or 224 translate several inches as described above, such as two inches or more, this configuration can cause the inner shaft 25 or 225 to rotate about 60 degrees or more.

[0051] Accordingly, the rotary actuators 20 and 200 described above contemplate the use of coaxial inner ball screw 29-I and outer ball screw 29-O and recirculating balls 42 to convert the linear motion of one or more pistons, namely Figure 3 and 4 piston 24 of Figure 6 or the first piston 124 and the second piston 224 of Figure 1 into the rotational motion of the inner shaft 25 or 225. Among the many benefits disclosed herein, low friction and compactness make this teaching applicable to a wide range of applications external to the aircraft 10 used herein as an exemplary application. Similarly, the disclosed example dimensions, ranges, construction materials, etc. may vary within the scope of this disclosure to suit a particular application. For example, larger and / or more balls 42 and appropriately enlarged outer cylinders 26 or 126, one or more pistons 24, 124 or 224, and inner shafts 25 or 225 can be used to support rotational applications that need to actuate a driven load having an increased mass relative to

[0052] the flight control surface 18. Given the foregoing disclosure, those of ordinary skill in the art will readily recognize these and other benefits.

[0052] Aspects of the present disclosure have been described in detail with reference to the illustrated embodiments. However, those skilled in the art will recognize that certain modifications can be made to the disclosed structures and / or methods without departing from the scope of the present disclosure. The present disclosure is also not limited to the exact construction and composition disclosed herein. Modifications that are obvious from the foregoing description are within the scope of the present disclosure as defined by the appended claims. Moreover, this concept expressly includes combinations and sub-combinations of the foregoing elements and features.

Claims

1. A rotary actuator, comprising: A plurality of balls; An outer cylinder having a plurality of fluid ports, each fluid port configured to permit fluid pressure from a fluid pressure supply; A piston externally received by the outer cylinder, wherein the piston, the outer cylinder, and the plurality of balls together form an external ball screw, and wherein the piston is configured to translate along a longitudinal central axis of the rotary actuator in response to the fluid pressure; and An inner shaft externally received by the piston, wherein the inner shaft, the piston, and the plurality of balls together form an internal ball screw, the internal ball screw being coaxial with the external ball screw about the longitudinal central axis; Wherein the external ball screw and the internal ball screw together form an interleaved ball circuit having one or more shared ball paths, and wherein the piston operatively rotates the piston and the inner shaft in response to translation of the piston along the longitudinal central axis such that the plurality of balls are recirculated between the external ball screw and the internal ball screw through the interleaved ball circuit.

2. The rotary actuator according to claim 1, wherein, The inner diameter of the outer cylinder includes a plurality of internal threads of the external ball screw, the outer diameter of the piston includes a plurality of external threads of the external ball screw, the inner diameter of the piston includes a plurality of internal threads of the internal ball screw, and the outer diameter of the inner shaft includes a plurality of external threads of the internal ball screw.

3. The rotary actuator according to claim 2, wherein, The internal and external threads of the external ball screw are left-handed threads, and the internal and external threads of the internal ball screw are right-handed threads.

4. The rotary actuator according to claim 1, wherein, The piston is configured to separate the outer cylinder into a plurality of pressure chambers, and the plurality of fluid ports of the outer cylinder are configured to fluidly connect the fluid pressure supply to the plurality of pressure chambers.

5. The rotary actuator according to claim 1, further comprising a set of thrust bearings, wherein the piston is a single piston, and each respective thrust bearing of the set of thrust bearings is disposed at opposite distal ends of the inner shaft.

6. The rotary actuator according to claim 1, wherein, The piston includes a pair of pistons, and the plurality of fluid ports include an internal fluid port positioned at a substantially midpoint of the rotary actuator between the pair of pistons and include a pair of external fluid ports located on sides of the internal fluid port.

7. The rotary actuator according to claim 1, wherein, The one or more shared ball paths include at least six shared ball paths.

8. The rotary actuator according to claim 7, wherein, The one or more shared ball paths include ten or fewer shared ball paths.

9. The rotary actuator according to claim 1, wherein, The number of shared ball paths of the internal ball screw is equal to the number of shared ball paths of the external ball screw.

10. The rotary actuator according to claim 1, wherein, The rotary actuator is configured to rotate the inner shaft by approximately 60 degrees for each translation of the piston along the longitudinal central axis of two inches or more.

11. The rotary actuator according to claim 1, wherein, The interleaved ball circuit includes a single continuous ball path through the internal ball screw and the external ball screw, and includes at least nine ball starting points for the balls.

12. The rotary actuator according to claim 1, wherein, The translation speed of the plurality of balls within the internal ball screw is equal to the translation speed of the plurality of balls within the external ball screw.

13. A hinged panel assembly, comprising: A first panel; A second panel; A rotating hinge joint that interconnects the first panel and the second panel and has a rotation axis; and A rotary actuator as claimed in any one of claims 1 to 12, the rotary actuator being connected to the rotating hinge joint.

14. The hinged panel assembly according to claim 13, wherein, The rotation axis of the rotating hinge joint is coaxially aligned with the longitudinal central axis of the rotary actuator.

15. The articulated panel assembly according to claim 13, further comprising at least one mechanical link connecting the rotatable inner shaft to the rotating hinge joint.

16. The articulated panel assembly according to claim 13, wherein, The piston is configured to separate the outer cylinder into a plurality of pressure chambers, each pressure chamber being in fluid communication with a respective one of the fluid ports of the outer cylinder.

17. A fixed-wing aircraft, comprising: A fuselage; A pair of wings connected to the fuselage; A tail wing connected to the fuselage; An aerodynamic flight control panel connected to one of the wings and / or connected to the tail wing via a rotating hinge joint having a rotation axis; and A rotary actuator as claimed in any one of claims 1 to 12, the rotary actuator being connected to the rotating hinge joint.

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