Preventing Buckling For Downhole Linear Actuator

TECHNICAL FIELD

The present disclosure relates to oilfield operations generally and more specifically to downhole linear actuators.

BACKGROUND

Downhole linear actuators are used inside wellbores to provide push and pull forces to accommodate different mechanical tasks. These tools can contain a power rod that is pushed and pulled by various systems, such as electro-mechanical or hydraulic systems. The pushing strength of these rods can be limited due to buckling for a given rod size (e.g., diameter and length). The force able to be applied through a power rod before it buckles changes with respect to the diameter of the power rod and the unsupported length of the power rod.

BRIEF DESCRIPTION OF THE DRAWINGS

The specification makes reference to the following appended figures, in which use of like reference numerals in different figures is intended to illustrate like or analogous components

FIG. 1 is a schematic diagram of a wellbore including a linear actuator according to certain aspects of the present disclosure.

FIG. 2A is a partial cross-sectional diagram depicting a linear actuator in a retracted position according to certain aspects of the present disclosure.

FIG. 2B is a partial cross-sectional diagram depicting a linear actuator in an extended position according to certain aspects of the present disclosure.

FIG. 3A is a partial cross-sectional diagram depicting a linear actuator with slidable bearings in a retracted position according to certain aspects of the present disclosure.

FIG. 3B is a partial cross-sectional diagram depicting a linear actuator with slidable bearings in an extended position according to certain aspects of the present disclosure.

FIG. 4A is a partial cross-sectional diagram depicting a linear actuator with hydraulically-motivated slidable bearings in a retracted position according to certain aspects of the present disclosure.

FIG. 4B is a partial cross-sectional diagram depicting a linear actuator with hydraulically-motivated slidable bearings in an extended position according to certain aspects of the present disclosure.

FIG. 5A is a partial cross-sectional diagram depicting a linear actuator with rotatable braces in a retracted position according to certain aspects of the present disclosure.

FIG. 5B is a partial cross-sectional diagram depicting a linear actuator with rotatable braces in an extended position according to certain aspects of the present disclosure.

FIG. 6 is a cross-sectional view of a linear actuator having four rotatable braces according to certain aspects of the present disclosure.

FIG. 7 is a cross-sectional view of a linear actuator having three rotatable braces according to certain aspects of the present disclosure.

FIG. 8 is a cross-sectional view of a linear actuator having multiple sets of rotatable braces according to certain aspects of the present disclosure.

DETAILED DESCRIPTION

Certain aspects and features of the present disclosure relate to a linear actuator having a power rod supported by movable supports. The movable supports are designed to provide support to the power rod to avoid buckling of the power rod when large compressive forces are imparted on the power rod. The movable supports are designed to move towards (e.g., by a biasing mechanism) a first position that minimizes the unsupported length of the power rod, but are capable of being displaced by the power rod during extension of the power rod. Examples of movable supports include slidable bearings (e.g., axially slidable) or rotating braces (e.g., rotatable form a supporting position to an out-of-the-way position). Examples of suitable biasing mechanisms include springs and spring members. In some embodiments, hydraulic force is used to move the movable supports.

A linear actuator for use in downhole environments is disclosed herein. The linear actuator includes a power rod that interacts with a downhole tool. An example linear actuator includes a motor that drives a lead screw, which axially moves the power rod. In other embodiments, a hydraulic piston can be used. Other types of linear actuating mechanisms can be used to axially drive the power rod. In many downhole environments, it can be desirable to use a small-diameter power rod for various reasons, such as space limitations and pressure considerations. For example, a non-pressure compensated linear actuator, the power rod exiting the actuator housing would be pushed back into the actuator by the surrounding high-pressure environment, and thus a small diameter power rod may be desirable to lower the force of the pressure that is effectively pushing the rod back into the actuator. However, as the diameter of a power rod lessens, the amount of force necessary to cause buckling (“buckling load”) decreases, meaning less force can be pushed through that power rod.

Additionally, the buckling load decreases as the unsupported span of the power rod increases. The unsupported span includes any distance of the power rod that is not supported, such as by bearings that displace radial forces to a housing. Therefore, it may be desirable to decrease the unsupported span of a power rod in order to increase the amount of compressive force that can be applied to the power rod without the power rod buckling. However, the use of internal supports can reduce the stroke length of the power rod. Additionally, in downwell environments, it can be necessary for a power rod to have a smooth surface finish for sealing purposes. Therefore, any supports used cannot be attached to the power rod itself.

Various aspects of the present disclosure relate to movable supports that are capable of returning to a supporting position that minimizes the unsupported span of the power rod after being displaced by the power rod in order to maximize the stroke length of the power rod. The movable supports can be biased back to the supporting position by biasing mechanisms such as springs and spring members. In some embodiments, the movable supports can be moved into the supporting position through the use of pressurized fluids. Examples of suitable movable supports include slidable bearings and rotatable braces, while other movable supports can be used. Multiple movable supports can be used in a single linear actuator. The movable supports can be located entirely within the housing of the linear actuator.

In an example, a movable support can be a slidable bearing. The bearing can be positioned within the housing of the linear actuator and the power rod can pass through the bearing. The bearing does not need to be rotationally or axially fixed and can pass radial forces from the power rod to the housing, thus preventing buckling. The bearing can be coupled to other bearings and the housing through biasing mechanisms that are springs or spring members. Example biasing members can include elastomeric bellows or springs. As the power rod extends, features of the power rod, such as a rear flange, can contact the slidable bearings and push them towards the distal end of the housing where they collected together (e.g., thus maximizing the stroke length of the power rod). However, as the power rod retracts, the biasing mechanisms can push or pull the slidable bearings back to their first position (supporting position). The biasing mechanisms can be selected to have lengths that would position the slidable bearings equally within the housing to minimize the lengths of the unsupported spans of the power rod.

In another example, the slidable bearings are moved using pressurized fluid. The housing can be filled with a fluid (e.g., hydraulic fluid) and the slidable bearings can form seals with the housing and the power rod, thus separating the housing into two or more chambers, depending on the number of slidable bearings. A valve or piston can provide the distal-most chamber with high pressure from the surrounding high-pressure environment. As the power rod extends, the slidable bearing can be pushed to the distal end of the housing. As the power rod retracts, the high pressure from the surrounding high-pressure environment can push the slidable bearing back into its supporting position. A mechanical stop (e.g., a flange or track of the housing that engages the slidable bearing) can stop the slidable bearing from being pushed beyond its supporting position.

In another example, the movable support can be a brace that is rotatably coupled to the housing. Multiple braces can be used to provide support to the power rod from various directions. For example, two or more braces can be used and spaced equally around the power rod (e.g., spaced at 120° when three braces are used, or spaced at 90° when four braces are used). Each brace can be hinged to move from a supporting position where the brace is perpendicular to the power rod and provides support to carry radial forces from the power rod to the housing, to an out-of-the-way position where the brace is no longer perpendicular to the power rod. In some embodiments, the out-of-the-way position can be generally parallel to the power rod. The brace can be biased (e.g., through a spring or spring mechanism) to rotate in a first direction and the brace can include a step that engages the housing to stop the brace from rotating in the first direction once the brace is in the supporting position. The brace can then be displaced into the out-of-the-way position by the power rod as the power rod extends.

Various linear actuators as described herein can provide increased force (e.g., load) and increased stroke length over linear actuators without movable supports. The increased force and increased stroke length can allow a single linear actuator to perform more actions in a single run than a linear actuator without movable supports, thus decreasing the number of runs necessary to perform certain actions for a particular wellbore. The movable supports disclosed herein do not require the use of complicated latches or rails. The movable supports disclosed herein can be easily adaptable to multiple rod sizes.

These illustrative examples are given to introduce the reader to the general subject matter discussed here and are not intended to limit the scope of the disclosed concepts. The following sections describe various additional features and examples with reference to the drawings in which like numerals indicate like elements, and directional descriptions are used to describe the illustrative embodiments but, like the illustrative embodiments, should not be used to limit the present disclosure. The elements included in the illustrations herein may be drawn not to scale.

FIG. 1 is a schematic diagram of a wellbore 102 including a linear actuator 106 according to certain aspects of the present disclosure. The wellbore 102 can penetrate a subterranean formation 104 for the purpose of recovering hydrocarbons, storing hydrocarbons, disposing of carbon dioxide, or the like. The wellbore 102 can be drilled into the subterranean formation 104 using any suitable drilling technique. While shown as extending vertically from the surface in FIG. 1, in other examples the wellbore 102 can be deviated, horizontal, or curved over at least some portions of the wellbore 102. Portions of the wellbore 102 can be cased, open hole, contain tubing, and can include a hole in the ground having a variety of shapes or geometries.

A service rig, such as a drilling rig, a completion rig, a workover rig, or other mast structure or combination thereof can support a workstring 108 in the wellbore 102, but in other examples a different structure can support the workstring 108. For example, an injector head of a coiled tubing rigup can support the workstring 108. In some aspects, a service rig can include a derrick with a rig floor through which the workstring 108 extends downward from the service rig into the wellbore 102. The servicing rig can be supported by piers extending downwards to a seabed in some implementations. Alternatively, the service rig can be supported by columns sitting on hulls or pontoons (or both) that are ballasted below the water surface, which may be referred to as a semi-submersible platform or rig. In an off-shore location, a casing may extend from the service rig to exclude sea water and contain drilling fluid returns. Other mechanical mechanisms that are not shown may control the run-in and withdrawal of the workstring 108 in the wellbore 102. Examples of these other mechanical mechanisms include a draw works coupled to a hoisting apparatus, a slickline unit or a wireline unit including a winching apparatus, another servicing vehicle, and a coiled tubing unit.

The workstring 108 can include a tubular attached to a linear actuator 106. In some embodiments, the linear actuator 106 can be supported by a wireline or can be otherwise embodied in a downhole tool supported by a wireline or a tubular. The linear actuator 106 can be coupled to a downhole tool 110 that is operable through linear motion. The linear actuator 106 can extend and retract its power rod. As the power rod is extended and retracted, different operations of the downhole tool 110 can be actuated.

In an example the downhole tool 110 can include components that need to be shifted, set, or latched. A user from the surface can send an actuation signal (e.g., an electrical signal or a pressure signal or other) to the linear actuator 106. Upon receiving the actuation signal, the linear actuator 106 can extend its power rod to a first, extended position to perform one of the shifting, setting, or latching tasks of the downhole tool 110. A second actuation signal can be sent from the surface and then received by the linear actuator 106, which causes the linear actuator 106 to extend the power rod to a second extended position to perform another of the shifting, setting, or latching tasks of the downhole tool 110. A third actuation signal can be sent from the surface and then received by the linear actuator 106, which causes the linear actuator 106 to retract the power rod to a refracted position. In some embodiments, retraction of the power rod can perform yet another of the shifting, setting, or latching tasks of the downhole tool 110. In other embodiments, any number of extended positions and retracted positions can be used. In other embodiments, any suitable tasks can be performed by the downhole tool 110 in response to axial movement of the power rod.

FIGS. 2A-2B are partial cross-sectional diagrams depicting a linear actuator 200 without movable supports. FIG. 2A depicts the linear actuator 200 when retracted and FIG. 2B depicts the linear actuator 200 when extended. The linear actuator 200 includes a housing 202 and a driving mechanism for axially moving the power rod 212 from the retracted position, as seen in FIG. 2A, to the extended position, as seen in FIG. 2B. The driving mechanism can be electric, hydraulic, or other. FIGS. 2A-2B depict a simple version of an electric driving mechanism, having a motor 204 that drives a screw 206. Rotation of the screw 206 causes the sleeve 208 to extend or retract. Other driving mechanisms can be used.

The housing 202 can include a stationary support 210, which can support the power rod 212 or sleeve 208. As seen in FIGS. 2A-2B, the stationary support 210 supports the sleeve 208. The power rod 212 can be coupled to the sleeve 208, such that movement of the sleeve 208 in an axial direction (e.g., left-to-right or right-to-left as seen in FIGS. 2A-2B) causes movement of the power rod 212 in the axial direction. The sleeve 208 can include a flange 214. The power rod 212 can be supported (e.g., radially supported) by a seal or other feature of the housing 202 where the power rod 212 exits the housing. The length where the power rod 212 is not supported (e.g., radially supported, such as by a stationary support 210 or the housing 202) can be known as the unsupported span 218. The largest unsupported span 218 is the first likely place where buckling can occur as increased compression forces are applied to the power rod 212. As the largest unsupported span 218 decreases in length, the amount of force necessary for buckling of the power rod 212 (e.g., buckling load) increases. In other words, with shorter unsupported spans 218, more compressive force can be applied through the power rod 212 without the power rod 212 buckling.

The power rod 212 can be extended from a refracted position (e.g., as seen in FIG. 2A) to an extended position (e.g., as seen in FIG. 2B). The distance the distal end of the power rod 212 (e.g., that end towards the right of the figure as seen in FIGS. 2A-2B) travels between the furthest retracted position and the furthest extended position can be known as the stroke length 216. As described above, long stroke lengths can be desirable, such as to enable a downhole tool to perform more functions on a single run in the well. Additionally, long stroke lengths 216 may be necessary to operate certain downhole tools.

FIGS. 3A-3B are partial cross-sectional diagrams depicting a linear actuator 300 with slidable bearings 326 according to certain aspects of the present disclosure. FIG. 3A depicts the linear actuator 300 when retracted and FIG. 3B depicts the linear actuator 300 when extended. Slidable bearings 326 are located within the housing to provide support to the power rod 312. The slidable bearings 326 are able to move between a first position (e.g., a supporting position, as seen in FIG. 4A) and a second position (e.g., an out-of-the-way position, as seen in FIG. 4B). The slidable bearings 326 may still supply some support to the power rod 412 when in the out-of-the-way position. The power rod 312 can pass through a central aperture of each slidable bearing 326. In some embodiments, a slidable bearing 326 is round in shape, similar to a washer or a round spacer. As seen in FIGS. 3A-3B, the slidable bearings 326 are located between the stationary support 310 and the distal wall of the housing 302 (e.g., the wall to the right of the figure as seen in FIGS. 3A-3B). However, the slidable bearings 326 can be located anywhere within the housing 302 where they may provide support to the power rod 312, irrespective of whether or not a stationary support 310 is used.

The slidable bearings 326 provide radial support to the power rod 312. The slidable bearings 326 can be rotationally free within the housing 302, or can be keyed or otherwise rotationally fixed. When the power rod 312 is in a retracted position (e.g., as seen in FIG. 3A), biasing mechanisms cause the slidable bearings 326 to be positioned at certain locations between the distal wall of the housing 302 and the stationary support 310. More specifically, connecting members 328 can be located between adjacent slidable bearings 326, between a slidable bearing 326 and the housing 302, between a slidable bearing 326 and the sleeve 308, or between any combination thereof.

In some embodiments, the connecting member 328 are elastomeric bellows or other connectors that are collapsible, but that are capable of pulling the slidable bearings 326 into a supporting position (e.g., as seen in FIG. 3A) upon refraction of the sleeve 308. Refraction of the sleeve 308 can pull on the proximal-most slidable bearing 326 via the connecting member 328, which can then pull on the next most proximal slidable bearing 326, until all slidable bearings 326 are pulled into the appropriate position, which can be dictated by the length of the connecting members 328. The connecting members 328 can be coupled to other features (e.g., the flange 314) that move along with the power rod 312 during retraction or extension of the power rod 312.

In other embodiments, the connecting members 328 are spring members, which are capable of being compressed, but which then expand to provide a biasing force on the slidable bearings 326. Such connecting members 328 can be loose or can be coupled to the slidable bearings 326 or housing 302. When the connecting member 328 are spring members, there is no need for a connecting member 328 to couple a slidable bearing 326 to the sleeve 308, as retraction of the sleeve 308 will necessarily allow the slidable bearings 326 to move into the supporting position (e.g., as seen in FIG. 3A) due to expansion of the spring members. The connecting members 328 provide a biasing force to the slidable bearings 326 to separate the slidable bearings 326 to a certain extent. The extent to which the slidable bearings 326 are separated can depend on the length of the connecting members 328.

Connecting members 328 cause the slidable bearings 326 to be spaced out between the stationary support 310 and the distal wall of the housing 302. In some embodiments, the slidable bearings 326 are spaced equidistant from one another. The presence of movable supports results in several unsupported spans 318, 320, 322, 324. The connecting members 328 can be selected to position the slidable bearings 326 at distances from one another, from the stationary support 310, and from the distal wall of the housing 302, such that each of the unsupported spans 318, 320, 322, 324 is minimized. Other arrangements can be used.

As the power rod 312 is extended towards the extended position, the flange 314 or other feature can interact with the slidable bearings 326 and begin to compress them towards the distal end of the housing 302. When the power rod 312 is in an extended position (e.g., as seen in FIG. 3B), the slidable bearings 326 can be compressed towards the distal end of the housing 302, thus compressing the connecting members 328. As the power rod 312 is retracted towards the retracted position, the connecting members 328 will cause the slidable bearings 326 to separate from one another and provide support to the power rod 312 to reduce the length of unsupported spans 318, 320, 322, 324.

The power rod 312 is able achieve a long stroke length 316 since the slidable bearings 326 can collect at the distal end of the housing 302, as opposed to using additional stationary bearings, which would reduce the stroke length 316, as additional stationary bearing would act as a stop for the flange 314.

In some embodiments, additional slidable bearings 326 can be located around the sleeve 308, such as between the stationary support 310 and the flange 314, in order to provide additional radial support to the sleeve 308.

FIGS. 4A-4B are partial cross-sectional diagrams depicting a linear actuator 400 with a hydraulically-motivated slidable bearing 420 according to certain aspects of the present disclosure. FIG. 4A depicts the linear actuator 400 when retracted and FIG. 4B depicts the linear actuator 400 when extended. Slidable bearing 420 is located within the housing 402 to provide support to the power rod 412. The slidable bearing 420 is able to move between a first position (e.g., a supporting position, as seen in FIG. 4A) and a second position (e.g., an out-of-the-way position, as seen in FIG. 4B). The slidable bearing 420 may still supply some support to the power rod 412 when in the out-of-the-way position. The power rod 412 can pass through central apertures of the slidable bearing 420. The slidable bearing 420 can separate a subset of the housing 402 into a first chamber 424 (e.g., between the stationary support 410 and slidable bearing 420) and a second chamber 428 (e.g., between the slidable bearing 420 and the distal end of the housing 402). A seal can be included in the central aperture of the slidable bearing 420 to limit the flow of fluid across the slidable bearing 420 (e.g., from one chamber 424, 428 to another). In some embodiments, fewer or more slidable bearings can be used, thus separating a portion of the housing 402 into fewer or more fluidly-isolated chambers.

The slidable bearing 420 provides radial support to the power rod 412. The slidable bearing 420 can be rotationally free within the housing 402, or can be keyed or otherwise rotationally fixed. When the power rod 412 is in a retracted position (e.g., as seen in FIG. 4A), differences in fluid pressure between the chambers 424, 428 can bias the slidable bearing 420 towards the proximal end of the housing 402 (e.g., left, as seen in FIGS. 4A-4B). The slidable bearing 420 can engage a stop 430 to retain the slidable bearing 420 in an appropriate locations (e.g., to minimize the unsupported spans 418). In some embodiments, instead of using a stop 430, other features can be used to stop the travel of the slidable bearing 420 at the appropriate locations. In an example, a compressible material (e.g., a flexible ribbon) or structure (e.g., two struts connected to one another with a hinge) can be used to couple the slidable bearing 420 to the housing 402 or to another slidable bearing to limit travel of the slidable bearing 420. When the power rod 412 is in a retracted position, the compressible material or structure keeps the slidable bearing 420 from moving too far towards the proximal end of the housing 402, and when the power rod 412 is in the extended position (e.g., as seen in FIG. 4B), the compressible material or structure compresses or folds adjacent the slidable bearing 420, allowing the slidable bearing 420 to collect near the distal end of the housing 402.

As the power rod 412 moves from a retracted position (e.g., as seen in FIG. 4A) to an extended position, the flange 414 can interact with the slidable bearing 420, causing it to be forced towards the distal end of the housing 402. As slidable bearing 420 moves, the pressure in the first chamber 424 may drop, as the pressure in the second chamber 428 may rise. Continued movement of slidable bearing 420 can cause pressure in the second chamber 428 to be released through valve 434. Valve 434 can be an opening or aperture in the housing that is in fluid communication with the surrounding environment 440. In some embodiments, valve 434 is a piston that retains fluid isolation between the second chamber 428 and the surrounding environment 440, but allows pressure equalization between the second chamber 428 and the surrounding environment 440. Eventually, slidable bearing 420 is able to collect at the distal end of the housing 402, in an out-of-the-way position, as seen in FIG. 4B.

During retraction of the power rod 412, the flange 414 moves towards the proximal end of the housing 402, thus allowing slidable bearing 420 to move in the same direction because of the relatively low pressure in the first chamber 424, as compared to the relatively high pressures in the second chamber 428 and surrounding environment 440. The slidable bearing 420 can continue to move towards the proximal end of the housing, being biased in that direction due to the relatively low pressure of the first chamber 424 and the relatively high pressure of the surrounding environment 440. Eventually, the slidable bearing 420 will be pressed up against stop 430, or otherwise held at their appropriate locations, as described above.

The power rod 412 is able achieve a long stroke length 416 since the slidable bearing 420 can collect at the distal end of the housing 402, as opposed to using additional stationary bearings, which would reduce the stroke length 416, as additional stationary bearing would act as a stop for the flange 414.

In some embodiments, additional slidable bearings can be located around the sleeve 408, such as between the stationary support 410 and the flange 414, in order to provide additional radial support to the sleeve 408.

In embodiments where multiple slidable bearings are used, some slidable bearing may contain check valves to regulate pressure build-up in chambers between adjacent slidable bearings. When multiple slidable bearings are used, all but the most proximal (e.g., towards the left as seen in FIGS. 4A-4B) slidable bearing may require a set of check valves.

FIGS. 5A-5B are partial cross-sectional diagrams depicting a linear actuator 500 with braces 530, 532, 534 supporting a dual-diameter power rod 512 according to certain aspects of the present disclosure. FIG. 5A depicts the linear actuator 500 when retracted and FIG. 5B depicts the linear actuator 500 when extended. Braces 530, 532, 534 are located within the housing to provide support to the power rod 512. The power rod 512 is a dual-diameter power rod 512, having a larger diameter section 526 within the housing 502 and a smaller diameter section 528 that exits the housing. Such power rods 512 can be useful in certain applications.

Braces 530, 532, 534 are able to rotate between a first position (e.g., a supporting position, as seen in FIG. 4A) and a second position (e.g., an out-of-the-way position, as seen in FIG. 4B). The braces 530, 532, 534 may still supply some minimal support to the power rod 412 when in the out-of-the-way position. In some embodiments, the pivot point 538, size of a brace 530, 532, 534, or both can be used provide support to both the smaller diameter section 528 and larger diameter section 526, depending on how far extended the power rod 512 may be. As seen in FIGS. 5A-5B, the braces 530, 532, 534 are located between the stationary support 510 and the distal wall of the housing 502 (e.g., the wall to the right of the figure as seen in FIGS. 5A-5B). However, the braces 530, 532, 534 can be located anywhere within the housing 502 where they may provide support to the power rod 512, irrespective of whether or not a stationary support 510 is used. In some embodiments, braces 530, 532, 534 can be located in recesses of the housing 502 and can be rotated into recesses of the housing 502.

The braces 530, 532, 534 provide radial support to the power rod 512. Each brace 530, 532, 534 can be coupled to the housing 502 at a pivot point 538. When the power rod 512 is in a retracted position (e.g., as seen in FIG. 5A), biasing mechanisms cause the braces 530, 532, 534 to rotate to a supporting position (e.g., the brace being perpendicular to the power rod 512). More specifically, spring members 536 can be located between each brace 530, 532, 534 and the housing 502. The spring members 536 can bias each brace 530, 532, 534 to rotate in a first direction (e.g., from the position depicted in FIG. 5B towards the position depicted in FIG. 5A). The housing 502 can include recesses into which the braces 530, 532, 534 can rotate. The housing 502 can include stops 542 that act to halt rotation of the braces 530, 532, 534, due to the biasing forces of the spring members 536, past the supporting position (e.g., perpendicular with the power rod 512). In alternate embodiments, other biasing mechanisms can be used to cause rotation of the braces 530, 532, 534, such as hydraulic pistons.

The braces 530, 532, 534 can be installed in the housing 502 to create desirable or optimal unsupported spans 518, 520, 522, 523. A set of braces can be positioned, in a single lateral plane, around the power rod 512 in various configurations, as described in further detail herein.

As the power rod 512 is extended towards the extended position, the flange 514, larger diameter section 526 or other feature can interact with braces 530, 532, 534 and displace each brace 530, 532, 534 to rotate about its respective pivot point 538 to compress its respective spring member 536. As the power rod 512 is retracted back towards the retracted position, the spring members 536 cause their respective braces 530, 532, 534 to pivot back to the supporting positions.

The power rod 512 is able achieve a long stroke length 516 since the braces 530, 532, 534 can rotate to an out-of-the-way position, as opposed to using additional stationary bearings, which would reduce the stroke length 516, as additional stationary bearing would act as a stop for the flange 514 or the larger diameter section 526 of the power rod 512.

In some embodiments, additional braces can be located around the sleeve 508, such as between the stationary support 510 and the flange 514, in order to provide additional radial support to the sleeve 508. Such braces may rotate in a direction opposite the rotational direction of braces 530, 532, 534.

FIG. 6 is a cross-sectional view of a linear actuator 600 having four rotatable braces 606 according to certain aspects of the present disclosure. The cross-sectional view is taken from a plane located adjacent the distal end of the housing 604 of the linear actuator 600. The power rod 602 is supported by four movable supports that are rotatable braces 606. Each brace 606 is positioned directly across a diameter of the power rod 602 from another brace 606. Each brace 606 is positioned 90° offset from one another.

FIG. 7 is a cross-sectional view of a linear actuator 700 having three rotatable braces 706 according to certain aspects of the present disclosure. The cross-sectional view is taken from a plane located adjacent the distal end of the housing 704 of the linear actuator 700. The power rod 702 is supported by three movable supports that are rotatable braces 706. Each brace 706 is positioned equidistant around the power rod 702 from one another. Each brace 606 is positioned 120° offset from one another.

Any number of braces can be used and with any spacing.

FIG. 8 is a cross-sectional view of a linear actuator 800 having multiple sets of rotatable braces 806, 808 according to certain aspects of the present disclosure. The cross-sectional view is taken from a plane located adjacent the distal end of the housing 804 of the linear actuator 800. The cross-sectional view depicts a first set of rotatable braces 806 in the plan of the page. The first set of rotatable braces 806 can include three braces that are each positioned 120° offset from one another. The cross-sectional view also depicts a second set of rotatable braces 808 that lies in a plane below the page (e.g., is axially offset from the first set of rotatable braces 806 along an axis of the power rod 802). The second set of rotatable braces 808 can also include three braces that are each positioned 120° offset from one another. The first set of rotatable braces 806 and the second set of rotatable braces 808 can be rotationally offset from one another (e.g., out of phase from one another). As seen in FIG. 8, the first set of rotatable braces 806 is 180° offset from the second set of rotatable braces 808. This rotational offset between axially displaced, but adjacent sets of braces can provide beneficial support to the power rod 802. Other suitable rotational offsets and numbers of braces per set can be used.

The foregoing description of the embodiments, including illustrated embodiments, has been presented only for the purpose of illustration and description and is not intended to be exhaustive or limiting to the precise forms disclosed. Numerous modifications, adaptations, combinations and uses thereof will be apparent to those skilled in the art.

As used below, any reference to a series of examples is to be understood as a reference to each of those examples disjunctively (e.g., “Examples 1-4” is to be understood as “Examples 1, 2, 3, or 4”).

Example 1 is an assembly comprising a housing; a power rod at least partially contained within the housing, the power rod being retractable and extendable; and a movable support within the housing, the movable support being movable to a first position in response to the power rod retracting for displacing radial force from the power rod into the housing, and being movable to a second position in response to the power rod extending.

Example 2 is the assembly of example 1, wherein the movable support includes a spring member for biasing the movable support towards the first position, and wherein the power rod includes a feature for displacing the movable support into the second position in response to the power rod extending.

Example 3 is the assembly of example 2, wherein the movable support further includes a slidable bearing for receiving the power rod therethrough, the slidable bearing being axially slidable between the first position and the second position, and wherein the spring member is positioned for biasing the slidable bearing towards the first position.

Example 4 is the assembly of examples 2 or 3, wherein the movable support further includes a brace rotatably coupled to the housing, wherein the brace is perpendicular to the power rod when in the first position and not perpendicular to the power rod when in the second position.

Example 5 is the assembly of example 4, wherein the spring member is positioned for biasing the brace to rotate in a first direction; and wherein the brace includes a step for contacting the housing when the brace is in a first position and for blocking the brace from rotating further in the first direction.

Example 6 is the assembly of examples 4 or 5, wherein the movable support further includes a second brace and a third brace, each rotationally spaced about the power rod 120° apart from the brace.

Example 7 is the assembly of examples 1-6, wherein the movable support is movable to the first position in response to pressure of a fluid within the housing, and wherein the power rod is axially movable for changing the pressure of the fluid within the housing.

Example 8 is the assembly of examples 1-7, wherein the power rod is retractable at least partially into the housing.

Example 9 is a method comprising extending a power rod of a linear actuator by axially moving the power rod from a refracted position to an extended position; displacing a movable support from a first position to a second position in response to extending the power rod; retracting the power rod by axially moving the power rod from the extended position to the retracted position; moving the movable support from the second position to the first position in response to refracting the power rod; and displacing radial force from the power rod into a housing of the linear actuator by the movable support in the first position.

Example 10 is the method of example 9, wherein the moving the movable support from the second position to the first position includes a biasing element of the movable support moving the movable support towards the first position.

Example 11 is the method of examples 9 or 10, wherein displacing the movable support includes sliding a slidable bearing from the first position to the second position; wherein the power rod passes through the slidable bearing; and wherein moving the movable support includes a spring member moving the slidable bearing from the second position to the first position.

Example 12 is the method of examples 9-11, wherein displacing the movable support includes rotating a brace from the first position to the second position, wherein the brace is perpendicular to the power rod when in the first position; and wherein moving the movable support includes a spring member rotating the brace from the second position to the first position.

Example 13 is a linear actuator comprising a housing; a power rod at least partially contained within the housing; a motor; a lead screw coupled to the motor and the power rod for retracting and extending the power rod; a movable support within the housing, the movable support being movable to a first position in response to the power rod retracting for displacing radial force from the power rod into the housing, and being movable to a second position in response to the power rod extending.

Example 14 is the linear actuator of example 13, wherein the movable support includes a biasing member for biasing the movable support towards the first position, and wherein the power rod includes a feature for displacing the movable support into the second position in response to the power rod extending.

Example 15 is the linear actuator of example 14, wherein the movable support further includes a slidable bearing for receiving the power rod therethrough, the slidable bearing being axially slidable between the first position and the second position, and wherein the biasing member is positioned for biasing the slidable bearing towards the first position.

Example 16 is the linear actuator of examples 14 or 15, wherein the movable support further includes a brace rotatably coupled to the housing, wherein the brace is perpendicular to the power rod when in the first position and not perpendicular to the power rod when in the second position.

Example 17 is the linear actuator of example 16, wherein the biasing member biases the brace to rotate in a first direction; and wherein the brace includes a step for contacting the housing when the brace is in a first position and for blocking the brace from rotating further in the first direction.

Example 18 is the linear actuator of examples 16 or 17, wherein the movable support further includes a second brace and a third brace, each rotationally spaced about the power rod 120° apart from the brace.

Example 19 is the linear actuator of examples 13-18, wherein the movable support is movable between the first position and the second position in response to pressure of a fluid within the housing, and wherein the power rod is axially movable for changing the pressure of the fluid within the housing.

Example 20 is the linear actuator of examples 13-19, wherein the power rod is retractable at least partially into the housing.

Preventing Buckling For Downhole Linear Actuator

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