WO2025117009A1

WO2025117009A1 - Rotary actuator

Info

Publication number: WO2025117009A1
Application number: PCT/US2024/046839
Authority: WO
Inventors: Scott E. NEEL
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 2023-11-27
Filing date: 2024-09-16
Publication date: 2025-06-05
Anticipated expiration: 2026-05-27

Abstract

An example rotary actuator includes: a tube; an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity; a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube; a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed; and a primary sensor mounted in the primary sensor cavity of the endcap, wherein the primary sensor interacts with the sensor surface of the sensing target ring to provide sensor information indicating a rotary position of the sensing target ring and the shaft, and wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube.

Description

Rotary Actuator

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/602,874, filed on November 27, 2023, the entire contents of which are herein incorporated by reference as if fully set forth in this description.

BACKGROUND

[0002] Some rotary actuators involve using high pressure fluid to cause rotation of an output shaft. Such rotary actuators can be exposed to high moment, thrust, and radial loading because they are designed to be part of the structural load path in most applications. Particularly, existing rotary actuators configurations resolve axial forces developed from internal hydraulic pressure through either an end cap or shaft exclusively. It may thus be desirable to configure the rotary actuator in a manner that reduces stress on components of the rotary actuator.

[0003] In some applications, it may be desirable to measure the rotary position of the output shaft of a rotary actuator. However, standard encoders and position sensors are not designed to take the loading that the rotary actuator can be subjected to, and therefore such sensors cannot be placed in high load situations without additional support structure and space to operate.

[0004] It may thus be desirable to integrate a sensor within the pressure cavity of a rotary actuator to remove the sensor from the external loading. However, exposing the sensor to high pressure levels (e g., 5000 pounds per square inch) creates additional barriers to the use of some sensors. It may thus be desirable to have a position sensor configured to measure accurately the rotary position of an output shaft of a rotary actuator without regard to operational pressures in the actuator, external conditions, or internal loads under which the rotary actuator is operating. [0005] It is with respect to these and other considerations that the disclosure made herein is presented.

SUMMARY

[0006] The present disclosure describes implementations that relate to a rotary actuator.

[0007] In a first example implementation, the present disclosure describes a rotary actuator including: a tube; an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity; a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube; a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed; and a primary sensor mounted in the primary sensor cavity of the endcap, wherein the primary sensor interacts with the sensor surface of the sensing target ring to provide sensor information indicating a rotary position of the sensing target ring and the shaft, and wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube.

[0008] In a second example implementation, the present disclosure also describes a method of operating the rotary actuator of the first example implementation.

[0009] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES

[0010] The novel features believed characteristic of the illustrative examples are set forth in the appended claims. The illustrative examples, however, as well as a preferred mode of use, further objectives and descriptions thereof, will best be understood by reference to the following detailed description of an illustrative example of the present disclosure when read in conjunction with the accompanying Figures.

[0011] Figure 1 illustrates a perspective view of a rotary actuator, according to an example implementation.

[0012] Figure 2 illustrates a perspective view of an endcap of the rotary actuator of Figure 1, according to an example implementation.

[0013] Figure 3 illustrates a transparent front view of the endcap of Figure 2, according to an example implementation.

[0014] Figure 4 illustrates a perspective bottom view of the endcap of Figures 2-3, according to an example implementation.

[0015] Figure 5 illustrates a perspective cross-sectional side view of the rotary actuator of Figure 1, according to an example implementation.

[0016] Figure 6A illustrates an enlarged partial cross-sectional side view of the rotary actuator of Figure 5, according to an example implementation.

[0017] Figure 6B illustrates an enlarged partial cross-sectional side view of the rotary actuator 100 having an exclusion cap, according to an example implementation.

[0018] Figure 7 illustrates a perspective view of a ring of the rotary actuator of Figure 6A, according to an example implementation. [0019] Figure 8A illustrates a cross-sectional top view of the rotary actuator of Figure 1 with a piston sleeve extended, according to an example implementation.

[0020] Figure 8B illustrates a cross-sectional top view of the rotary actuator of Figure 1 with a piston sleeve retracted, according to an example implementation.

[0021] Figure 9 illustrates a perspective bottom view of the rotary actuator of Figure 1, according to an example implementation.

[0022] Figure 10A illustrates a perspective view of a sensor, according to an example implementation.

[0023] Figure 10B illustrates a top view of the sensor of Figure 10A, according to an example implementation.

[0024] Figure 10C illustrates a cross-sectional view of the sensor of Figures 10A-10B, according to an example implementation.

[0025] Figure 1 1 is a flowchart of a method for operating a rotary actuator, according to an example implementation.

DETAILED DESCRIPTION

[0026] Within examples, disclosed herein is a rotary actuator that enhances load bearing capability of the rotary actuator. The rotary actuator is also configured to be serviceable without full disassembly and without breaking into the pressure cavity of the rotary actuator.

[0027] In examples, the disclosed rotary actuator also provides a combination of integral rotary position sensors contained entirely within the rotary actuator footprint. The rotary actuator can include dual precision sensing target rings for the sensors, where the target rings are incorporated inside the rotary actuator and individually clocked to the rotation of the rotary actuator.

[0028] Further, in the disclosed actuator configuration, internal axial forces generated by hydraulic pressure are divided between a shaft and an endcap. This way, each component is subjected to a reduced stress level compared to conventional rotary actuators.

[0029] Figure 1 illustrates a perspective view of a rotary actuator 100, according to an example implementation. The rotary actuator 100 includes a tube 102 that operates as a housing for components of the rotary actuator 100. In an example, the tube 102 can be made of a high grade weldable steel material (such as A514 DOM or 4130 steel) with a honed inside diameter (ID) surface and machined attachment features (e.g., holes) on each end.

[0030] In an example, the tube 102 can be mounted to an enclosure 104 that supports the tube 102. The enclosure 104 can be made of thin sheet metal, for example. The enclosure 104 is secured to a first endcap 106 and a second endcap 108 (e.g., via screws) and is sealed along its perimeter that adjoins the endcaps 106, 108 and the tube 102. As described below with respect to Figure 9, the enclosure 104 can enclose electronic circuitry for sensors, where the output of such sensors is provided via a connector 109 (e.g., 12 pin connector) at a center of a side of the enclosure 104. [0031] The tube 102 is retained between the first endcap 106 and the second endcap 108. The endcaps 106, 108 can also be referred to as “feet” of the rotary actuator 100. The endcaps 106, 108 include machined features that allow the rotary actuator 100 to be mounted fixedly to a rigid ground structure and allow the endcaps 106, 108 to be coupled to the tube 102. The endcaps 106, 108 can be made of a high grade steel (such as 4140 steel), for example.

[0032] In the example implementation shown in the figures, the endcaps 106, 108 are configured as pillow blocks that facilitate mounting the rotary actuator 100 to a planar surface of a frame or fixture. The tube 102 along with the endcaps 106, 108 form a pressure vessel or enclosure for the rotary actuator 100. The endcaps 106, 108 also operate as axial stops for a piston as described below.

[0033] The rotary actuator 100 includes a first exclusion seal 110 at one end of the rotary actuator 100, and also includes a second exclusion seal 112 at the other end of the rotary actuator 100. The exclusion seals 110, 112 can be elastomeric seals, for example, and operate as primary seals that prevent debris (e.g., dust) and moisture from being ingested into the rotary actuator 100.

[0034] Figure 2 illustrates a perspective view of the first endcap 106, Figure 3 illustrates a transparent front view of the first endcap 106, and Figure 4 illustrates a perspective bottom view of the first endcap 106, according to an example implementation. The first endcap 106 has an endcap body 200 with a mounting base 202 integrated therewith.

[0035] The mounting base 202 has a first foot 204 and a second foot 206 for mounting the first endcap 106 to a planar surface, for example. For instance, as shown in Figure 3, the first foot 204 has a mounting hole 205 and the second foot 206 has a mounting hole 207. Fasteners (e.g., screws or bolts) can be mounted through the mounting holes 205, 207 to couple the first endcap 106 to a frame or other base components, for example. [0036] The endcap body 200 has a circular cavity 208 in which a sensing target ring and seal carrier is mounted as described below. Also, the first endcap 106 has a plurality of holes, such as hole 210, formed in a circular array about the outward facing side. The tube 102 of the rotary actuator 100 can have a corresponding set of holes such that fasteners can be mounted through the holes (e.g., the hole 210) of the first endcap 106 and the corresponding holes of the tube 102 to couple the first endcap 106 to the tube 102.

[0037] The endcap body 200 of the first endcap 106 defines or includes one or more ports such as first port 212 and second port 214. A source of fluid (e.g., a pump) can be fluidly coupled to the ports 212, 214 to provide fluid flow thereto. Fluid can then flow through lateral passages, such as lateral passage 216 and lateral passage 218 shown in Figure 3.

[0038] Referring to Figure 4, the lateral passages 216, 216 then communicate fluid to axial or longitudinal passage 219 and longitudinal passage 220, respectively. The longitudinal passages 219, 220 can then communicate fluid to a chamber within the tube 102 of the rotary actuator 100 to move a piston, as described below with respect to Figures 8A-8B.

[0039] As shown in Figures 3-4, the first endcap 106 further includes a primary sensor cavity 222. In examples, the first endcap 106 can also include a reference sensor cavity 224. The sensor cavities 222, 224 can be configured as counterbore pockets, for example, and respective sensors can be mounted in the primary sensor cavity 222 and the reference sensor cavity 224 to detect rotary shaft position as described in more details below. The endcap 106 further includes slot 223 extending from the primary sensor cavity 222, and includes slot 225 extending from the reference sensor cavity 224. The slots 223, 225 operate as wire-ways or conduits through which wires are routed from the sensors to the connector 109 at the center section of the enclosure 104. The second endcap 108 can be configured similar to the first endcap 106. [0040] Figure 5 illustrates a perspective cross-sectional side view of the rotary actuator 100, according to an example implementation. The rotary actuator 100 depicted in the example implementation of Figure 5 is a helical rotary actuator.

[0041] The rotary actuator 100 includes a shaft 300 disposed along a longitudinal axis of the rotary actuator 100. The shaft 300 of the rotary actuator 100 is coaxial with the tube 102 and is configured to rotate about the longitudinal axis of the rotary actuator 100.

[0042] In an example, the shaft 300 can be made of a high grade steel such as 4140 steel or Austempered Ductile Iron (ADI). The shaft 300 has a straight spline portion 301 (e.g., AGMA classified straight spline) that allows the shaft 300 to be rotatably coupled to an output hub 318. As depicted, the first exclusion seal 110 is mounted in a groove formed between the output hub 318 and the first endcap 106.

[0043] Particularly, the output hub 318 can include a machined straight spline (e.g., AGMA straight spline) mating with the straight spline portion 301 of the shaft 300 for transference of torque to the output hub 318. Thus, as the shaft 300 rotates, the output hub 318 rotates therewith. Other torque transference arrangements could be used such as a key-keyway arrangement or selfholding taper arrangement. As such, the shaft 300 is configured to transfer torque and maintain alignment of the output hub 318 (an a similar output hub at the other end of the rotary actuatorlOO). In an example, the output hub 318 can be made of high grade steel (such as 4140 steel) or ADI.

[0044] At each end of the shaft 300, the shaft 300 includes a first thread portion 303 and a second thread portion 305 machined into the shaft 300. In an example, the thread portions 303, 305 can have opposite handedness. For instance, the first thread portion 303 can be standard UN series right-handed (RH) major thread, and the second thread portion 305 can be a standard UN series left-handed (LH) minor thread. [0045] The helix of a thread can be configured to twist in two possible directions, and the configuration of the thread is referred to as the “handedness” of the thread. Threads that are oriented so that the threaded item (e.g., the first thread portion 303), when seen from a point of view on the axis through the center of the helix, moves away from the viewer when it is turned in a clockwise direction, and moves towards the viewer when it is turned counter-clockwise, are referred to as RH threads, as such configuration follows the right hand grip rule. Threads oriented in the opposite direction (e.g., the second thread portion 305) are referred to as LH threads

[0046] The shaft 300 further includes an external helical spline portion 307 machined in the shaft 300. For example, the external helical spline portion 307 can be a standard AGMA classified helical spline.

[0047] The rotary actuator 100 has an ring gear 302 projecting radially-inward from the tube 102 into a cavity 304 within the tube 102. The ring gear 302 can be welded, for example, to an internal surface of the tube 102. In an example, the ring gear 302 can be made of high grade weldable steel (such as A514 DOM or 4130 steel). The ring gear 302 includes internal helical splines 309 (e.g., AGMA helical spline) machined onto its inside diameter and projecting radially-inward within the cavity 304.

[0048] The rotary actuator 100 further includes a piston sleeve 306 (hollow, annular piston) mounted in the cavity 304 around the shaft 300. In other words, the piston sleeve 306 encircles the shaft 300, and is radially interposed between the shaft 300 and the interior surface of the ring gear 302 and the tube 102. The piston sleeve 306 has a piston head 308 and a piston rod 310. The piston head 308 can have an external groove and an internal groove in which radial seals are disposed to seal fluid between both sides of the piston head 308. In an example, the piston sleeve

306 can be made of a ductile iron material. [0049] The piston sleeve 306 has external helical splines 312 projecting radially-outward from the piston rod 310 and configured to engage with the internal helical splines 309 of the ring gear 302. The piston sleeve 306 also has internal helical splines 314 projecting radially-inward into a longitudinal cavity of the piston sleeve 306 to engage with the external helical spline portion 307 of the shaft 300.

[0050] The external helical splines 312 and the internal helical splines 314 of the shaft 300 can be AGMA helical splines, for example. They have opposite helical spline directions. For example, the internal helical splines 314 can be clockwise helical splines machined on the inside diameter of the piston rod 310, and the external helical splines 312 can be counter-clockwise helical splines machined on the outside diameter of the piston rod 310. The piston sleeve 306 is configured to convert its linear motion under hydraulic pressure into rotary motion of the shaft 300 via the opposing helical splines as described below with respect to Figures 8A-8B.

[0051] Figure 6A illustrates an enlarged partial cross-sectional side view of the rotary actuator 100, according to an example implementation. The output hub 318 can have a plurality of holes, such as hole 320, disposed in a circular array about the end face of the output hub 318. Fasteners can be mounted in such holes to couple the output hub 318 to a rotatable component of an application.

[0052] The output hub 318 is retained within the rotary actuator 100 via a retaining ring 322 and a lock ring 324. The retaining ring 322 and the lock ring 324 are threaded onto the shaft 300.

[0053] Particularly, the retaining ring 322 can have RH threads (e.g., UN series right hand threads on its inside diameter) to facilitate threaded engagement with the first thread portion 303 of the shaft 300. The retaining ring 322 interfaces with the output hub 318 as depicted to retain the output hub 318. In an example, the retaining ring 322 can be made of high grade steel (such as 4140 steel).

[0054] On the other hand, the lock ring 324 can have LH threads (e g., UN series left hand threads on its inside diameter) to facilitate threaded engagement with the second thread portion 305 of the shaft 300. The lock ring 324 interfaces with the retaining ring 322 as depicted. In an example, the lock ring 324 can be made of high grade steel (such as 4140 or 4340 steel).

[0055] The retaining ring 322 and the lock ring 324 retain the output hub 318 to the shaft 300 and prevent unintended unthreading or disassembly of the rotary actuator 100. Particularly, as mentioned above, threads of the retaining ring 322 can have handedness that is opposite to respective handedness of threads of the lock ring 324. Specifically, in the example implementation described above, the threads of the retaining ring 322 are RH threads, whereas threads of the lock ring 324 are LH threads. With this configuration, as the shaft 300 rotates, the locking ring 324 may be further tightened and prevents the retaining ring 322 and the output hub 318 from being unthreaded off the shaft 300.

[0056] Figure 6B illustrates an enlarged partial cross-sectional side view of the rotary actuator 100 having an exclusion cap 321, according to an example implementation. In one example implementation, the rotary actuator 100 can include the exclusion cap 321 at the end of the shaft 300 to completely enclose the shaft 300, the retaining ring 322, and the lock ring 324 from the external environment of the rotary actuator 100.

[0057] The exclusion cap 321 can have threads bounding a central hole 323 and aligned with a respective hole in the shaft 300 having respective threads. A flat-head flush-mounted fastener (not shown) can be screwed into the central hole 323 and the respective hole of the shaft 300 to couple the exclusion cap 321 to the shaft 300. A radial seal 325 can be mounted in a groove formed in the output hub 318 about the exterior surface of the exclusion cap 321. With this configuration, the shaft 300 is completely enclosed, protected, and sealed with a protective envelope defined by the exclusion cap 321.

[0058] Referring back to Figure 6A, the rotary actuator 100 includes a radial seal 326 (e.g., an elastomer seal) mounted in an annular groove formed in the output hub 318. The radial seal 326 operates as a secondary exclusion seal to the first exclusion seal 110 (primary exclusion seal) described above.

[0059] The rotary actuator 100 further includes a face seal 328 mounted in an annular groove formed at an end face of the output hub 318. The face seal 328 is also an exclusion seal and can be particularly beneficial in applications where the rotary actuator 100 is mounted vertically, where water, for example, can accumulate on an end face of the output hub 318.

[0060] The rotary actuator 100 further includes a wear ring 330 mounted radially between the output hub 318 and the first endcap 106. The wear ring 330 operates as a radial bearing or wear guide to facilitate rotation of the output hub 318 relative to the first endcap 106. The wear ring 330 can be made of a durable bronze allow material or a low friction composite material, as examples.

[0061] As mentioned above, the output hub 318 is configured to rotate a rotatable component, which is coupled to the output hub 318 via fasteners in the hole(s) 320. As the output hub 318 rotates and rotates the rotatable component therewith, the output hub 318 is subjected to a load. The load to which the output hub 318 is subjected is transferred to the wear ring 330, then to the first endcap 106, which is configured to be mounted to a fixed frame (ground). Thus, the wear ring 330 transfers radial forces from output hub 318 to the first endcap 106 in the load path from application to the fixed frame or ground.. [0062] This configuration of the rotary actuator 100, where the axial distance between the fasteners in the hole(s) 320 and the first endcap 106 is short, enhances the moment bearing capability of the rotary actuator 100. Particularly, the length of the moment arm between the fasteners and the first endcap 106 is small, and thus the moment is small. This substantially reduces the being moment to which the shaft 300 is subjected.

[0063] The rotary actuator 100 further includes a thrust bearing 332 mounted axially between the output hub 318 and the first endcap 106. The thrust bearing 332 can be a thrust washer or a thrust roller bearing and is configured to transfer thrust forces from the output hub 318 to the first endcap 106 in the load path from application to ground. As such, the thrust bearing 332 may increase the thrust (axial) loading capacity of the rotary actuator 100.

[0064] The thrust bearing 332 can be made of any number of materials or configurations. For example, low friction composite homogeneous material or a steel roller thrust bearing type could be used.

[0065] Advantageously, this configuration facilitates maintenance of the rotary actuator. Particularly, the output hub 318 can be removed to provide access to the thrust bearing 332, the wear ring 330, the retaining ring 322, the lock ring 324, the first exclusion seal 110, and the radial seal 326. The output hub 318, the thrust bearing 332, the wear ring 330, the retaining ring 322, the lock ring 324, the first exclusion seal 110, and the radial seal 326 can then be serviced or replaced without interrupting the cavity 304 (the pressure cavity of the rotary actuator 100), without introducing air, and without having to evacuate air out of the rotary actuator 100.

[0066] The rotary actuator 100 further includes a sensing target ring 334. The sensing target ring 334 is mounted to the shaft 300, at least partially within the first endcap 106 (in the circular cavity 208). Particularly, the sensing target ring 334 is radially interposed between the shaft 300 and the first endcap 106, and is rotatably coupled to the shaft 300. The sensing target ring 334 operates as a target ring to sensors mounted to the first endcap 106 and also operates as a seal carrier.

[0067] Figure 7 illustrates a perspective view of the sensing target ring 334, according to an example implementation. In an example, the sensing target ring 334 can be made of steel or aluminum.

[0068] The sensing target ring 334 can have internal splines 400 (e.g., machined AGMA straight spline) machined into its inside diameter and configured to engage corresponding splines or teeth in the shaft 300 such that as the shaft 300 rotates, the sensing target ring 334 rotates therewith.

[0069] The sensing target ring 334 can have timing marks, such as indentations 402, on its end face. Such timing marks facilitate mounting the sensing target ring 334 to the shaft 300 in a specific (repeatable or “clocked”) rotary position.

[0070] The sensing target ring 334 has a sensor surface 404 (e.g., a ramped surface or a cam surface) having a precision-machined specific profile that provides a continuously-varied radial surface position from the longitudinal axis of the shaft 300 (i.e., from a center of the sensing target ring 334) during rotary motion of the shaft 300 and the sensing target ring 334. A primary sensor mounted to the first endcap 106 interacts with the sensor surface 404 to sense the rotary position of the shaft 300 and the sensing target ring 334 as described below.

[0071] In examples, the rotary actuator 100 includes a reference sensor mounted to the first endcap 106 in the reference sensor cavity 224 described above with respect to Figures 3-4. In these examples, the sensing target ring 334 includes a cylindrical portion 406 that is concentric with the shaft 300. The cylindrical portion 406 has a circular surface 407, which operates as a reference surface that can render measurements of the primary sensor more accurate. [0072] The circular surface 407 of the cylindrical portion 406 has a constant radius, (i.e., points on the circular surface 407 are equidistant from a center of the shaft 300 and the sensing target ring 334). A reference sensor can interact with the cylindrical portion 406 to provide respective sensor information indicative of a location of the circular surface 407 of the cylindrical portion 406, which is concentric with the shaft 300. The circular surface 407 of the cylindrical portion 406 provides a baseline surface to measure via the reference sensor.

[0073] As shown in Figures 7, the sensing target ring 334 also includes a first annular groove 408 adjacent the cylindrical portion 406 and a second annular groove 410 that is axially spaced from the first annular groove 408. Referring to Figures 6-7 together, the rotary actuator 100 includes a first rotary pressure seal 338 disposed in the first annular groove 408 and a second rotary pressure seal 340 disposed in the second annular groove 410.

[0074] The rotary pressure seals 338, 340 seal the pressure cavity within the tube 102 from an external environment of the rotary actuator 100. Thus, the rotary pressure seals 338, 340 create a seal around the sensing target ring 334 as it rotates. Further, the rotary pressure seals 338, 340 isolate the sensor and the reference sensor mounted in the first endcap 106 from high pressure fluid in the cavity 304 within the tube 102.

[0075] The rotary pressure seals 338, 340 further divides axial hydraulic force between the first endcap 106 and the shaft 300. Particularly, a portion of the axial hydraulic/fluid force is applied to the first endcap 106, while a portion is applied to the shaft 300. This way, stress on the first endcap 106 and the shaft 300 can be reduced.

[0076] As depicted in Figure 5, the other side of the rotary actuator 100 (opposite the side shown in Figure 6A) can be configured similar to the side shown in Figure 6A. Thus, on such opposite side, the rotary actuator 100 similarly includes a respective output hub, respective retaining and lock rings, respective wear ring and thrust bearing, and a respective sensor target ring as shown in

Figure 5.

[0077] Figure 8A illustrates a cross-sectional top view of the rotary actuator 100 with the piston sleeve 306 extended, according to an example implementation. The second endcap 108 can include one or more ports such as port 500 and port 502 (similar to the ports 212, 214 of the first endcap 106). Fluid can be received from a source of fluid (e.g., a pump) through one or both of the ports 500, 502. Fluid received at the port 500 flows through lateral passage 504 and longitudinal passage 506 into a head chamber 508 in the cavity 304 within the tube 102. Similarly, fluid received at the port 502 flows through lateral passage 510 and longitudinal passage 512 into the head chamber 508.

[0078] Thus, when fluid is provided to one or both of the ports 500, 502, fluid flows to the head chamber 508 and applies a fluid force on the piston head 308 of the piston sleeve 306 in a distal axial direction (e.g., to the right in Figure 8A). The fluid force causes the piston sleeve 306 to move axially or longitudinally in the distal axial direction until it reaches the extended position shown in Figure 8 A where it is stopped by the first endcap 106.

[0079] Due to the engagement of the external helical splines 312 of the piston sleeve 306 with the internal helical splines 309 of the ring gear 302 (which is fixed), the piston sleeve 306 rotates as it translates linearly in the distal direction. Further, due to engagement of the internal helical splines 314 of the piston sleeve 306 with the external helical spline portion 307 of the shaft 300, as the piston sleeve 306 moves linearly in the distal direction and rotates, the shaft 300 rotates therewith in a first rotational direction. As the piston sleeve 306 moves, fluid is discharged from rod chamber 514 through the longitudinal passages 219, 220, the lateral passages 216, 218, and the ports 212, 214 of the first endcap 106. [0080] Figure 8B illustrates a cross-sectional top view of the rotary actuator 100 with the piston sleeve 306 retracted, according to an example implementation. When fluid is received at one or both of the ports 212, 214 of the first endcap 106, fluid is provided through the lateral passages 216, 218 and the longitudinal passages 219, 220 to the rod chamber 514 within the cavity 304 and applies a respective fluid force on the piston sleeve 306 in a proximal axial direction (e.g., to the left in Figure 5). The respective fluid force causes the piston sleeve 306 to move longitudinally in the proximal axial direction until it reaches the retracted position shown in Figure 8B where it is stopped by the second endcap 108.

[0081] Due to the engagement of the external helical splines 312 of the piston sleeve 306 with the internal helical splines 309 of the ring gear 302 (which is fixed), the piston sleeve 306 rotates as it translates linearly. Further, due to engagement of the internal helical splines 314 of the piston sleeve 306 with the external helical spline portion 307 of the shaft 300, as the piston sleeve 306 moves linearly in the proximal direction and rotates, the shaft 300 rotates therewith in a second rotational direction (opposite the first rotational direction). As the piston sleeve 306 moves, fluid is discharged from the head chamber 508 through the longitudinal passages 506, 512, the lateral passages 504, 510, and the ports 500, 502.

[0082] As such, reciprocal longitudinal movement of the piston sleeve 306 within the tube 102, in response to the selective application of fluid on either side of the piston sleeve 306, causes the shaft 300 to rotate clockwise or counterclockwise relative to the tube 102. The speed of rotation of the shaft 300 can depend on the pitch of the helical splines of the piston sleeve 306, for example. The rotational range of the shaft 300 corresponding to the stroke of the piston sleeve 306 can be 350 degrees, for example. [0083] Reference to “distal” and “proximal” is not intended to imply a specific orientation of components of the rotary actuator 100 relative to any surrounding environment. Instead, these directional terms are intended to facilitate a description of the interrelationship between the several components of the rotary actuator 100 and their function.

[0084] As mentioned above as the shaft 300 rotates, the sensing target ring 334 rotates therewith, a primary sensor detects rotary motion and rotary position of the shaft 300. A reference sensor may be added to provide a reference signal to compensate for any radial play or distortions. The rotary actuator 100 can further include a sensing target ring 516 (similar to the sensing target ring 334) mounted within the second endcap 108, and the second endcap 108 can have respective sensors that detect rotational position of the sensing target ring 516 for redundancy to enhance reliability.

[0085] Figure 9 illustrates a perspective bottom view of the rotary actuator 100, according to an example implementation. As shown, the rotary actuator 100 includes a primary sensor 600 mounted in the primary sensor cavity 222 to interact with the sensor surface 404 of the sensing target ring 334. The rotary actuator 100 may also include a reference sensor 602 mounted through the reference sensor cavity 224 in the first endcap 106 to interact with the cylindrical portion 406 of the sensing target ring 334. The reference sensor 602 is also shown in Figures 5-6.

[0086] In case the primary sensor 600 and/or the reference sensor 602 fail, the second endcap 108 can similarly include a primary sensor cavity 604 in which a primary sensor 606 is mounted to interact with a sensor surface (similar to the sensor surface 404) of the sensing target ring 516 mounted within the second endcap 108. The second endcap 108 can also include a reference sensor cavity 608 in which a reference sensor 610 is mounted to interact with a cylindrical portion (similar to the cylindrical portion 406) of the sensing target ring 516 of the second endcap 108. [0087] With this configuration, the rotary actuator 100 has sensor redundancy fully integrated inside the endcaps 106, 108. Further, as shown in Figure 9, the sensors are fully enclosed within the endcaps 106, 108, while being isolated from the pressure cavity (the cavity 304). There are no sensor parts sticking out, and there are no exposed wires. Electronics packaging of the sensors can thus be fully enclosed in the endcaps 106, 108 in weatherproof enclosures.

[0088] In one example, the primary sensors 600, 606 and the reference sensors 602, 610 can be contact-type sensors where a follower contacts a sensor surface or a circular surface of a respective sensing target ring. However, it is also contemplated herein that a non-contact sensor can be used. Such non-contact sensors can be configured to measure the position of the sensing target ring 334, for example, based on interacting with the sensor surface 404 without contacting it.

[0089] For instance, a sensor can include an optical sensor probe having an optical disc that operates as a window overseeing the sensor surface 404 of the sensing target ring 334. Such optical sensor can have a source of light that emits light through the optical disc. The optical sensor can also have a sensing element that receives the light reflected from the sensor surface 404 and converts light rays into electronic signals. Particularly, the sensing element can measure the distance to the sensor surface 404 and then converts the measurement into an electric signal indicative of the distance, and thus indicative of a rotary position of the sensing target ring 334.

[0090] As such, the term “interacting” with the sensor surface 404 (or the circular surface 407) is used herein to encompass both contacting the sensor surface 404 (or the circular surface 407) or having no contact with the sensor surface 404 (or the circular surface 407), yet being configured to determine a rotational position of the sensor surface 404 (or the circular surface 407). Thus, although a description is provided below for the primary sensor 600 as a contact-type sensor as an example, it should be understood that non-contact sensors can alternatively be used. [0091] Figure 10A illustrates a perspective view of the primary sensor 600, Figure 10B illustrates a top view of the primary sensor 600, and Figure 10C illustrates a cross-sectional view of the primary sensor 600, according to an example implementation. Figures 10A-10C are described together.

[0092] The primary sensor 600 includes an adapter 700. In an example, the adapter 700 can be configured as a hexagonal body as shown in Figure 10A. As an example, the adapter 700 can be made of machined stainless steel. The adapter 700 includes external threads 702 (e.g., Society of Automotive Engineers (SAE)-4 male threads) formed at its distal end and configured to engage corresponding internal threads in the first endcap 106 of the rotary actuator 100 to mount the primary sensor 600 to the rotary actuator 100.

[0093] The adapter 700 can also include internal threads 704 (e.g., a female SAE-4 threaded connection) at a proximal end of the adapter 700 as shown in Figure 10C. The adapter 700 is configured to operate as a guide for a follower 706 of the primary sensor 600. The follower 706 can also be referred to as a tracer, and is configured to move in an oscillating linear motion within the primary sensor 600 as described in more details below.

[0094] In an example, the follower 706 can be made from an injection molded thermoplastic material (e.g., Delrin®). In one example, the follower 706 can have a tip 707 at a distal end of the follower 706. The tip 707 is configured to be in contact with the sensor surface 404 of the sensing target ring 334, for example.

[0095] In an example, the tip 707 can be configured as a spherical tip. In this example, by being configured to have a spherical shape, the tip 707 may ensure smooth and consistent contact with the sensor surface 404 it follows. The spherical tip may also allow the follower 706 to maintain a consistent point of contact with the sensor surface 404 regardless of the orientation of the follower 706 or the position of the sensing target ring 334. This is because a sphere has the same curvature in all directions, which ensures that the contact point between the follower 706 and the sensor surface 404 remains constant, regardless of any small variations in the orientation of the follower 706 or the position of the sensing target ring 334.

[0096] The follower 706 has a cavity at its proximal end, and the primary sensor 600 includes a magnet 708 disposed in such cavity. As an example, the magnet 708 can be a rare earth magnet coupled to or retained within the cavity of the follower 706, and is configured to generate a magnetic field.

[0097] The primary sensor 600 also includes a tube 710 configured as a magnetic tube for the primary sensor 600. In an example, the tube 710 is a machined stainless steel component with external threads at its distal end (e.g., SAE-4 male threaded connection) configured to engage the internal threads 704 of the adapter 700 to couple the tube 710 to the adapter 700. As depicted in Figure 10C, the tube 710 has an open distal end through which the follower 706 is disposed and a closed distal end, such that the tube 710 and the adapter 700 form a longitudinal aperture 711 in which the follower 706 can oscillate in a linear motion.

[0098] The primary sensor 600 further includes a spring 712 (e.g., a steel spring) disposed in the longitudinal aperture 711. The spring 712 is compressed between an enlarged portion 713 (e.g., larger diameter section) of the follower 706 and an internal shoulder formed in tube 710 as depicted in Figure 10C. With this configuration, a proximal end of the spring 712 is fixed, while a distal end of the spring 712 rests against the enlarged portion 713 of the follower 706, thereby applying a biasing force on the follower 706 in the distal direction. This way, the spring 712 ensures that the tip 707 of the follower 706 remains in contact with a surface that the follower 706 traces during operation. The stroke of the follower 706 in the distal direction is limited as the enlarged portion

713 contacts an internal shoulder 714 at the distal end of the adapter 700.

[0099] The primary sensor 600 further includes an electronics module 716 mounted to an exterior surface of the tube 710. The electronics module 716 can also be referred to as a “read head,” and is configured to have a generally cylindrical body containing electronics that detect changes in magnetic field as the follower 706 and the magnet 708 move linearly, and thus determine the linear position of the follower 706.

[00100] For example, the electronics module 716 can include a printed circuit board (PCB) located within a molded frame, and such PCB can have electronics configured to resolve the magnetic field generated by the magnet 708 to determine the linear position of the follower 706. A PCB mechanically supports and electrically connects electronic components (e.g., microprocessors, integrated chips, capacitors, resistors, etc.) using conductive tracks, pads, and other features etched from one or more sheet layers of copper laminate onto and/or between sheet layers of a nonconductive substrate. Components are generally soldered onto the PCB to both electrically connect and mechanically fasten them to it.

[00101] In an example, the magnet 708 operates as a magnetic target for the electronics module 716, which is configured to measure changes in magnetic field intensity. As the follower 706 moves, the magnet 708 moves therewith, and the magnetic field intensity sensed or measured by the electronics module 716 changes. The position of the follower 706 to which the magnet 708 is attached can be correlated with the magnetic field intensity measured by the electronics module 716. Particularly, a processor of the electronics module 716 can receive the magnetic field intensity information as the magnet 708 moves, and can then determine the position of the follower 706 based on the magnetic field intensity information. [00102] In an example, the electronics module 716 has one or more coils that receive electric power, and responsively generate a magnetic field, which can interact with the magnetic field of the magnet 708. As the follower 706 and the magnet 708 move, the magnetic field changes, and such change is sensed by the coils of the electronics module 716. The coils of the electronics module 716 can then generate one or more voltage signal indicative of the change in the magnetic field, which is correlated with a linear position of the follower 706.

[00103] In an example, the primary sensor 600 can include a retaining ring 718 and a washer 720 mounted circumferentially around the tube 710 and configured to retain the electronics module 716 axially relative to the tube 710. As an example, the retaining ring 718 can be a steel snap ring mounted in a groove formed at the proximal end of the tube 710. The washer 720 can be a stainless steel flat washer used in conjunction with the retaining ring 718 to retain the electronics module 716 axially to the tube 710.

[00104] In one example, the primary sensor 600 can include a spring 722 interposed between the electronics module 716 and the tube 710. The spring 722 is depicted as a wave spring; however, other types of biasing devices could be used. The spring 722 is configured to apply a biasing force on the electronics module 716 in the proximal direction toward the retaining ring 718 and the washer 720 to fix the electronics module 716 at a particular repeatable position relative to the follower 706 to compensate for manufacturing tolerances in the follower 706 or the electronics module 716.

[00105] The primary sensor 600 further includes a first seal 726 (e g., an elastomeric O-ring seal) disposed about the exterior surface of the adapter 700. The first seal 726 is configured to seal the primary sensor cavity 222 in the first endcap 106 of the rotary actuator 100 in which the primary sensor 600 is disposed to prevent leakage from the fluid-filled cavity within the tube 102 or the first endcap 106 to an external environment of the rotary actuator 100. The primary sensor 600 an also include a second seal 728 disposed in an annular groove formed in the tube 710 to seal the connection between the adapter 700 and the tube 710, thereby rendering the longitudinal aperture 711 a pressure tight cavity in which the follower 706 reciprocates linearly.

[00106] Referring to Figures 6-7 and 10A-10C together, the follower 706 of the primary sensor 600 mounted in the primary sensor cavity 222 (see Figures 3-4) of the first endcap 106 contacts and traces the sensor surface 404 of the sensing target ring 334 within the rotary actuator 100 as the sensing target ring 334 rotates. The profile of the sensor surface 404 provides a continuously- varying radial surface position from the central axis of rotation of the shaft 300 of the rotary actuator 100. As the sensing target ring 334 rotates, rotary motion of the sensing target ring 334 translates into a reciprocal movement of the follower 706 of the primary sensor 600 due to the configuration of the sensor surface 404, and thus the linear position of the follower 706 indicates the rotary position of the shaft 300 of the rotary actuator 100.

[00107] As an example for illustration, the primary sensor 600 can be configured such that the total stroke of the follower 706 (e.g., the total axial motion of the follower between the highest position on the sensor surface 404 and the lowest position of on the sensor surface 404) is about 0.18 inches, which corresponds to 180 degrees of rotation of the sensing target ring 334. The primary sensor 600 can be configured to detect motions as small as one tenth of one thousandth of an inch (0.0001 inches). In this example, the primary sensor 600 can determine the rotational position of the sensing target ring 334 and the shaft 300 to an accuracy of 0.1 degrees.

[00108] In some examples, due to manufacturing tolerances, the assembly of the shaft 300, the piston sleeve 306, and the sensing target ring 334 may be offset from a center of the tube 102. As an example, there might be a clearance (e.g., 0.005-0.008 inches) between an exterior surface of the sensing target ring 334 (and an exterior surface of the piston head 308) and the interior surface of the tube 102). As such, there may be some radial “play” or movement in the assembly of the shaft 300, the piston sleeve 306, and the sensing target ring 334 within the cavity 304 of the tube 102.

[00109] In these examples, such radial play may cause the position of the follower 706 of the primary sensor 600 to provide an inaccurate indication of the rotational position of the shaft 300. For instance, if the assembly is shifted downward in the cavity 304, the follower 706 might extend into the cavity 304, which could indicate inaccurately or falsely that the sensor surface 404 has rotated.

[00110] In another example, due to high fluid pressures in the cavity 304 (e.g., pressure levels up to 5000 psi), the components of the rotary actuator 100, such as the tube 102, the sensing target ring 334, or the piston sleeve 306, might be distorted. For instance, the interior surface of the tube 102 might not remain circular under high pressures. Such distortions might also affect accuracy of the primary sensor 600 in indicating the rotary position of the shaft 300.

[00111] In these examples, it may be desirable to configure the rotary actuator 100 to have a reference sensor that provides a benchmark or reference value for where the internal assembly of the rotary actuator 100 is. Such reference value can be used to adjust or modify the rotary position determined by the primary sensor 600 to compensate for radial play or distortion. Particularly, the reference value may be subtracted from the measurement of the primary sensor 600 to nullify the effect of any radial play or distortion.

[00112] As such, the rotary actuator 100 can include the reference sensor 602 mounted within the first endcap 106 in the reference sensor cavity 224 and configured to interact with the cylindrical portion 406 of the sensing target ring 334. As mentioned above, the circular surface 407 of the cylindrical portion 406 has a constant radius, and points on the circular surface 407 are equidistant from a center of the shaft 300. A follower (similar to the follower 706) of the reference sensor 602 contacts the cylindrical portion 406, and thus the reference sensor 602 can measure and provide respective sensor information indicative of a location of the circular surface 407 of the cylindrical portion 406, which is concentric with the shaft 300.

[00113] In an example, the measurement or position of the circular surface 407 of the cylindrical portion 406 as detected by the follower of the reference sensor 602 can be subtracted from the measurement of the position of the follower of the primary sensor 600 to eliminate any inaccuracies resulting from unintended movement of the sensing target ring 334 (e.g., radial play). Elimination of such extraneous radial motion (when the sensing target ring 334 is subjected to radial deflection relative to the tube 102 from component assembly clearances or under heavy external loading) may produce a more accurate and repeatable angular position resolution for the shaft 300 as determined by the primary sensor 600.

[00114] Advantageously, as shown in Figure 7, the cylindrical portion 406 is located immediately adjacent to the sensor surface 404. Such closeness between the sensor surface 404 traced by the follower 706 of the primary sensor 600 and the circular surface 407 traced by the follower of the reference sensor 602 may render the determination of the rotary position of the shaft 300 after nullification of any radial play or distortion more accurate. In particular, having the sensor surface 404 immediately adjacent to the circular surface 407 and having both of them permanently fixed to the sensing target ring 334 allows a subtraction to be instantaneously performed on output values of the primary sensor 600 such that all positional variance of the sensing target ring 334 with respect to the tube 102 is nullified. [00115] Further, the rotary pressure seals 338, 340 isolate the primary sensor 600 and the reference sensor 602 mounted in the first endcap 106 from high pressure fluid in the cavity 304 within the tube 102. Respective rotary pressure seals of the sensing target ring 516 also isolate the primary sensor 606 and the reference sensor 610 (in the example where such sensors are mounted to the second endcap 108 for redundancy) from the high pressure fluid.

[00116] Figure 11 is a flowchart of a method 800 for operating the rotary actuator 100, according to an example implementation. The method 800 may include one or more operations, or actions as illustrated by one or more of blocks 802-808. Although the blocks are illustrated in a sequential order, these blocks may in some instances be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation.

[00117] In addition, for the method 800 and other processes and operations disclosed herein, the flowchart shows operation of one possible implementation of present examples. In this regard, some blocks may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor (e.g., a processor of the primary sensor 600 or a controller of the rotary actuator 100) for implementing specific logical operations or steps in the process. The program code may be stored on any type of computer readable medium or memory, for example, such as a storage device including a disk or hard drive. The computer readable medium may include a non-transitory computer readable medium or memory, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media or memory, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a computer readable storage medium, a tangible storage device, or other article of manufacture, for example. In addition, for the method 800 and other processes and operations disclosed herein, one or more blocks in Figure 11 may represent circuitry or digital logic that is arranged to perform the specific logical operations in the process.

[00118] At block 802, the method 800 includes providing fluid flow to the rotary actuator 100, wherein the rotary actuator 100 has: (i) the tube 102, (ii) the first endcap 106 coupled to an end of the tube 102, wherein the first endcap 106 has the primary sensor cavity 222, (iii) the shaft 300 disposed in the tube 102, wherein the shaft 300 is rotatable within the tube 102 upon providing fluid flow within the tube 102, (iv) the sensing target ring 334 rotatably coupled to the shaft 300, wherein the sensing target ring 334 has the sensor surface 404 and an annular groove (e.g., the first annular groove 408) in which the rotary pressure seal 338 is disposed, and (v) the primary sensor 600 mounted in the primary sensor cavity of the endcap to interact with the sensor surface.

[00119] At block 804, the method 800 includes, responsive to providing the fluid flow within the tube, causing the shaft to rotate, thereby causing the sensing target ring to rotate with the shaft.

[00120] At block 806, the method 800 includes generating, by the primary sensor, sensor information based on interaction with the sensor surface, wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube.

[00121] At block 808, the method 800 includes determining, based on sensor information from the primary sensor, a rotary position of the sensing target ring and the shaft.

[00122] The method 800 can further any of the operations described throughout herein. [00123] The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein.

[00124] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[00125] Additionally, any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order.

[00126] Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

[00127] By the term “substantially” or “about” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to those with skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide. [00128] The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

[00129] While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. Also, the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.

[00130] Embodiments of the present disclosure can thus relate to one of the enumerated example embodiment (EEEs) listed below.

[00131] EEE 1 is a rotary actuator comprising: a tube; an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity; a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube; a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed; and a primary sensor mounted in the primary sensor cavity of the endcap, wherein the primary sensor interacts with the sensor surface of the sensing target ring to provide sensor information indicating a rotary position of the sensing target ring and the shaft, and wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube. [00132] EEE 2 is the rotary actuator of EEE 1 , wherein the sensing target ring is disposed, at least partially, within the endcap such that the sensing target ring is radially interposed between the shaft and the endcap.

[00133] EEE 3 is the rotary actuator of any of EEEs 1-2, wherein the sensor surface of the sensing target ring provides a continuously-varied position from a center of the shaft as the sensing target ring rotates with the shaft.

[00134] EEE 4 is the rotary actuator of any of EEEs 1-3, wherein the sensing target ring further includes a circular surface that is concentric with the shaft, wherein the endcap further comprises a reference sensor cavity, and wherein the rotary actuator further comprises: a reference sensor mounted in the reference sensor cavity of the endcap, wherein the reference sensor interacts with the circular surface such that the reference sensor provides respective sensor information indicative of a location of the circular surface, and wherein the respective sensor information of the reference sensor is used to modify the sensor information of the primary sensor to determine the rotary position of the sensing target ring and the shaft.

[00135] EEE 5 is the rotary actuator of any of EEEs 1-4, wherein the endcap is a first endcap coupled to a first end of the tube, wherein the sensing target ring is a first sensing target ring, and wherein the rotary actuator further comprises: a second endcap coupled to a second end of the tube, wherein the second endcap has a respective primary sensor cavity; and a second sensing target ring rotatably coupled to the shaft, wherein the second sensing target ring has a respective sensor surface and a respective annular groove in which a respective rotary pressure seal is disposed.

[00136] EEE 6 is the rotary actuator of EEE 5, wherein the primary sensor is a first primary sensor, and wherein the rotary actuator further comprises: a second primary sensor mounted in the respective primary sensor cavity of the second endcap, wherein the second primary sensor interacts with the respective sensor surface of the second sensing target ring to provide sensor information indicating a respective rotary position of the second sensing target ring, and wherein the respective rotary pressure seal isolates the second primary sensor from high pressure fluid in the tube.

[00137] EEE 7 is the rotary actuator of any of EEEs 1-6, wherein the annular groove of the sensing target ring is a first annular groove, wherein the rotary pressure seal is a first rotary pressure seal, and wherein the sensing target ring has a second annular groove, axially spaced from the first annular groove, in which a second rotary pressure seal is disposed.

[00138] EEE 8 is the rotary actuator of any of EEEs 1-7, further comprising: an output hub rotatably coupled to the shaft; and a wear ring mounted radially between the output hub and the endcap such that the wear ring operates as a radial bearing to facilitate rotation of the output hub relative to the endcap.

[00139] EEE 9 is the rotary actuator of any of EEEs 1-8, further comprising: an output hub rotatably coupled to the shaft; and a thrust bearing mounted axially between the output hub and the endcap.

[00140] EEE 10 is the rotary actuator of any of EEEs 1-9, wherein the shaft has a first thread portion and a second thread portion formed into an end of the shaft, and wherein the rotary actuator further comprises: an output hub rotatably coupled to the shaft; a retaining ring that threadedly engages the first thread portion of the shaft and interfaces with the output hub; and a lock ring that threadedly engages the second thread portion of the shaft and interfaces with the retaining ring. [00141] EEE 11 is the rotary actuator of EEE 10, wherein the second thread portion has an opposite handedness compared to the first thread portion such that rotation of the shaft further tightens the lock ring and prevent the retaining ring and the output hub from being unthreaded.

[00142] EEE 12 is the rotary actuator of any of EEEs 1-11, wherein the endcap has (i) one or more ports for receiving fluid from a source of fluid, and (ii) one or more passages fluidly coupled to the one or more port for providing fluid received at the one or more ports to within the tube, and wherein the rotary actuator further comprises: a piston sleeve mounted to the shaft such that fluid provided within the tube applies a fluid force on the piston sleeve, causing the piston sleeve to move linearly within the tube, thereby rotating the shaft.

[00143] EEE 13 is the rotary actuator of EEE 12, further comprising: a ring gear coupled to the tube and having internal helical splines projecting radially-inward within the tube, wherein the piston sleeve comprises external helical splines engaging with the internal helical splines of the ring gear such that linear movement of the piston sleeve causes the piston sleeve to rotate relative to the tube.

[00144] EEE 14 is the rotary actuator of EEE 13, wherein the piston sleeve further includes respective internal helical splines engaging with an external helical spline portion formed in the shaft, such that rotation of the piston sleeve causes the shaft to rotate relative to the tube.

[00145] EEE 15 is the rotary actuator of any of EEEs 12-14, wherein the endcap operates as a stop for the piston sleeve.

[00146] EEE 16 is the rotary actuator of any of EEEs 12-15, wherein the endcap is a first endcap, wherein the piston sleeve divides a cavity within the tube into a head chamber and a rod chamber, and wherein the rotary actuator further comprises: a second endcap having (i) one or more respective ports for receiving fluid from the source of fluid, and (ii) one or more respective passages fluidly coupled to the one or more respective ports for providing fluid received at the one or more respective ports to within the tube, wherein: fluid received at the one or more ports of the first endcap is provided through the one or more passages to the head chamber, thereby driving the piston sleeve in a first direction until the piston sleeve reaches the second endcap, wherein fluid in the rod chamber is discharged through the one or more respective passages and the one or more respective ports of the second endcap, and fluid received at the one or more respective ports of the second endcap is provided through the one or more respective passages to the rod chamber, thereby driving the piston sleeve in a second direction until the piston sleeve reaches the first endcap, wherein fluid in the head chamber is discharged through the one or more passages and the one or more ports of the first endcap.

[00147] EEE 17 is the rotary actuator of any of EEEs 12-16, wherein the sensing target ring has one or more timing marks that facilitate mounting the sensing target ring to the shaft in a specific rotary position.

[00148] EEE 18 is a method of operating the rotary actuator of any of EEEs 1-17. For example, the method includes: providing fluid flow to a rotary actuator, wherein the rotary actuator has: (i) a tube, (ii) an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity, (iii) a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube, (iv) a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed, and (v) a primary sensor mounted in the primary sensor cavity of the endcap to interact with the sensor surface; responsive to providing the fluid flow within the tube, causing the shaft to rotate, thereby causing the sensing target ring to rotate with the shaft; generating, by the primary sensor, sensor information based on interaction with the sensor surface, wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube; and determining, based on sensor information from the primary sensor, a rotary position of the sensing target ring and the shaft.

[00149] EEE 19 is the method of EEE 18, wherein the sensing target ring further includes a circular surface that is concentric with the shaft, wherein the endcap further includes a reference sensor cavity, and wherein the rotary actuator further includes a reference sensor mounted in the reference sensor cavity of the endcap to interact with the circular surface, and wherein the method further comprises: generating, by the reference sensor, respective sensor information based on interaction with the circular surface, wherein the rotary pressure seal isolates the reference sensor from high pressure fluid in the tube; and adjusting, based on the respective sensor information generated by the reference sensor, the rotary position of the sensing target ring and the shaft determined by the sensor information from the primary sensor.

[00150] EEE 20 is the method of any of EEEs 18-19, wherein the endcap is a first endcap coupled to a first end of the tube, wherein the sensing target ring is a first sensing target ring, wherein the primary sensor is a first primary sensor, wherein the rotary actuator further includes: (i) a second endcap coupled to a second end of the tube, wherein the second endcap has a respective primary sensor cavity, (ii) a second sensing target ring rotatably coupled to the shaft, wherein the second sensing target ring has a respective sensor surface and a respective annular groove in which a respective rotary pressure seal is disposed, and (iii) a second primary sensor mounted in the respective primary sensor cavity of the second endcap to interact with the respective sensor surface, and wherein the method further comprises: generating, by the second primary sensor, sensor information based on interaction with the respective sensor surface, wherein the respective rotary pressure seal isolates the second primary sensor from high pressure fluid in the tube; and determining, based on sensor information from the second primary sensor, the rotary position of the second sensing target ring and the shaft.

Claims

CLAIMS What is claimed is:

1 . A rotary actuator comprising: a tube; an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity; a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube; a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed; and a primary sensor mounted in the primary sensor cavity of the endcap, wherein the primary sensor interacts with the sensor surface of the sensing target ring to provide sensor information indicating a rotary position of the sensing target ring and the shaft, and wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube.

2. The rotary actuator of claim 1, wherein the sensing target ring is disposed, at least partially, within the endcap such that the sensing target ring is radially interposed between the shaft and the endcap.

3. The rotary actuator of claim 1, wherein the sensor surface of the sensing target ring provides a continuously-varied position from a center of the shaft as the sensing target ring rotates with the shaft.

4. The rotary actuator of claim 1 , wherein the sensing target ring further includes a circular surface that is concentric with the shaft, wherein the endcap further comprises a reference sensor cavity, and wherein the rotary actuator further comprises: a reference sensor mounted in the reference sensor cavity of the endcap, wherein the reference sensor interacts with the circular surface such that the reference sensor provides respective sensor information indicative of a location of the circular surface, and wherein the respective sensor information of the reference sensor is used to modify the sensor information of the primary sensor to determine the rotary position of the sensing target ring and the shaft.

5. The rotary actuator of claim 1, wherein the endcap is a first endcap coupled to a first end of the tube, wherein the sensing target ring is a first sensing target ring, and wherein the rotary actuator further comprises: a second endcap coupled to a second end of the tube, wherein the second endcap has a respective primary sensor cavity; and a second sensing target ring rotatably coupled to the shaft, wherein the second sensing target ring has a respective sensor surface and a respective annular groove in which a respective rotary pressure seal is disposed.

6. The rotary actuator of claim 5, wherein the primary sensor is a first primary sensor, and wherein the rotary actuator further comprises: a second primary sensor mounted in the respective primary sensor cavity of the second endcap, wherein the second primary sensor interacts with the respective sensor surface of the second sensing target ring to provide sensor information indicating a respective rotary position of the second sensing target ring, and wherein the respective rotary pressure seal isolates the second primary sensor from high pressure fluid in the tube.

7. The rotary actuator of claim 1, wherein the annular groove of the sensing target ring is a first annular groove, wherein the rotary pressure seal is a first rotary pressure seal, and wherein the sensing target ring has a second annular groove, axially spaced from the first annular groove, in which a second rotary pressure seal is disposed.

8. The rotary actuator of claim 1, further comprising: an output hub rotatably coupled to the shaft; and a wear ring mounted radially between the output hub and the endcap such that the wear ring operates as a radial bearing to facilitate rotation of the output hub relative to the endcap.

9. The rotary actuator of claim 1, further comprising: an output hub rotatably coupled to the shaft; and a thrust bearing mounted axially between the output hub and the endcap.

10. The rotary actuator of claim 1, wherein the shaft has a first thread portion and a second thread portion formed into an end of the shaft, and wherein the rotary actuator further comprises: an output hub rotatably coupled to the shaft; a retaining ring that threadedly engages the first thread portion of the shaft and interfaces with the output hub; and a lock ring that threadedly engages the second thread portion of the shaft and interfaces with the retaining ring.

11. The rotary actuator of claim 10, wherein the second thread portion has an opposite handedness compared to the first thread portion such that rotation of the shaft further tightens the lock ring and prevent the retaining ring and the output hub from being unthreaded.

12. The rotary actuator of claim 1, wherein the endcap has (i) one or more ports for receiving fluid from a source of fluid, and (ii) one or more passages fluidly coupled to the one or more port for providing fluid received at the one or more ports to within the tube, and wherein the rotary actuator further comprises: a piston sleeve mounted to the shaft such that fluid provided within the tube applies a fluid force on the piston sleeve, causing the piston sleeve to move linearly within the tube, thereby rotating the shaft.

13. The rotary actuator of claim 12, further comprising: a ring gear coupled to the tube and having internal helical splines projecting radially-inward within the tube, wherein the piston sleeve comprises external helical splines engaging with the internal helical splines of the ring gear such that linear movement of the piston sleeve causes the piston sleeve to rotate relative to the tube.

14. The rotary actuator of claim 13, wherein the piston sleeve further includes respective internal helical splines engaging with an external helical spline portion formed in the shaft, such that rotation of the piston sleeve causes the shaft to rotate relative to the tube.

15. The rotary actuator of claim 12, wherein the endcap operates as a stop for the piston sleeve.

16. The rotary actuator of claim 12, wherein the endcap is a first endcap, wherein the piston sleeve divides a cavity within the tube into a head chamber and a rod chamber, and wherein the rotary actuator further comprises: a second endcap having (i) one or more respective ports for receiving fluid from the source of fluid, and (ii) one or more respective passages fluidly coupled to the one or more respective ports for providing fluid received at the one or more respective ports to within the tube, wherein: fluid received at the one or more ports of the first endcap is provided through the one or more passages to the head chamber, thereby driving the piston sleeve in a first direction until the piston sleeve reaches the second endcap, wherein fluid in the rod chamber is discharged through the one or more respective passages and the one or more respective ports of the second endcap, and fluid received at the one or more respective ports of the second endcap is provided through the one or more respective passages to the rod chamber, thereby driving the piston sleeve in a second direction until the piston sleeve reaches the first endcap, wherein fluid in the head chamber is discharged through the one or more passages and the one or more ports of the first endcap.

17. The rotary actuator of claim 12, wherein the sensing target ring has one or more timing marks that facilitate mounting the sensing target ring to the shaft in a specific rotary position.

18. A method comprising: providing fluid flow to a rotary actuator, wherein the rotary actuator has: (i) a tube, (ii) an endcap coupled to an end of the tube, wherein the endcap has a primary sensor cavity, (iii) a shaft disposed in the tube, wherein the shaft is rotatable within the tube upon providing fluid flow within the tube, (iv) a sensing target ring rotatably coupled to the shaft, wherein the sensing target ring has a sensor surface and an annular groove in which a rotary pressure seal is disposed, and (v) a primary sensor mounted in the primary sensor cavity of the endcap to interact with the sensor surface; responsive to providing the fluid flow within the tube, causing the shaft to rotate, thereby causing the sensing target ring to rotate with the shaft; generating, by the primary sensor, sensor information based on interaction with the sensor surface, wherein the rotary pressure seal isolates the primary sensor from high pressure fluid in the tube; and determining, based on sensor information from the primary sensor, a rotary position of the sensing target ring and the shaft.

19. The method of claim 18, wherein the sensing target ring further includes a circular surface that is concentric with the shaft, wherein the endcap further includes a reference sensor cavity, and wherein the rotary actuator further includes a reference sensor mounted in the reference sensor cavity of the endcap to interact with the circular surface, and wherein the method further comprises: generating, by the reference sensor, respective sensor information based on interaction with the circular surface, wherein the rotary pressure seal isolates the reference sensor from high pressure fluid in the tube; and adjusting, based on the respective sensor information generated by the reference sensor, the rotary position of the sensing target ring and the shaft determined by the sensor information from the primary sensor.

20. The method of claim 18, wherein the endcap is a first endcap coupled to a first end of the tube, wherein the sensing target ring is a first sensing target ring, wherein the primary sensor is a first primary sensor, wherein the rotary actuator further includes: (i) a second endcap coupled to a second end of the tube, wherein the second endcap has a respective primary sensor cavity, (ii) a second sensing target ring rotatably coupled to the shaft, wherein the second sensing target ring has a respective sensor surface and a respective annular groove in which a respective rotary pressure seal is disposed, and (iii) a second primary sensor mounted in the respective primary sensor cavity of the second endcap to interact with the respective sensor surface, and wherein the method further comprises: generating, by the second primary sensor, sensor information based on interaction with the respective sensor surface, wherein the respective rotary pressure seal isolates the second primary sensor from high pressure fluid in the tube; and determining, based on sensor information from the second primary sensor, the rotary position of the second sensing target ring and the shaft.