Pressure differential piston locks for a linear actuator

Abstract

An example actuator includes a cylinder; a main piston movable within the cylinder; and a lock piston movable with the main piston, wherein the lock piston is configured to lock the main piston at a particular position, wherein a pressure differential acts on a first annular area to cause the lock piston to lock the main piston at the particular position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston.

Description

Pressure Differential Piston Locks for a Linear ActuatorCROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63 / 599,057, filed on November 15, 2023, the entire contents of which are herein incorporated by reference as if fully set forth in this description.BACKGROUND

[0002] A linear actuator may include a piston that is movable within a cylinder via pressurized fluid (e.g., hydraulic fluid, gas, or air). Some linear actuators have locking mechanisms that lock the piston in a fully-extended position and a fully-retracted position. Pressurized fluid is used to unlock the piston and allow it to move again.

[0003] Conventional locking mechanisms, however, may involve a component that rubs against an interior surface of the cylinder at a high pressure and force, causing rapid wear and galling of the cylinder. Further, some conventional locking mechanisms involve venting fluid to an atmosphere, and may thus require a large spring to prevent inadvertent unlocking from transient pressures.

[0004] It may thus be desirable to configure the locking and unlocking mechanism in a manner that reduces wear of the cylinder and prevents inadvertent unlocking, without using a large strong spring. It is with respect to these and other considerations that the disclosure made herein is presented.SUMMARY

[0005] The present disclosure describes implementations that relate to pressure differential piston locks for a linear actuator.

[0006] In a first example implementation, this disclosure describes an actuator including: a cylinder; a main piston movable within the cylinder between a fully-extended position and a fully- retracted position; a retract lock piston movable with the main piston, wherein the retract lock piston is configured to lock the main piston in the fully-retracted position; an extend lock piston movable with the main piston, wherein the extend lock piston is configured to lock the main piston in the fully-extended position; and a shuttle that is radially interposed between the retract lock piston and the extend lock piston. With this configuration, a pressure differential acts on a first annular area to cause the extend lock piston to lock the main piston in the fully-extended position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston and allow the main piston to retract. Also, the respective pressure differential acts on a third annular area to cause the retract lock piston to lock the main piston in the fully-retracted position, wherein the third annular area is smaller than a fourth annular area on which the pressure differential acts to release the main piston and allow the main piston to extend.

[0007] In a second example implementation, this disclosure describes a method of operating the actuator of the first example implementation.

[0008] In a third example implementation, this disclosure describes a system including a source of fluid, a fluid reservoir, and the actuator of the first example implementation.

[0009] In a fourth example implementation, this disclosure describes an actuator including: a cylinder; a main piston movable within the cylinder; and a lock piston movable with the mainpiston. The lock piston is configured to lock the main piston at a particular position. A pressure differential acts on a first annular area to cause the lock piston to lock the main piston at the particular position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston.

[0010] 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

[0011] 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.

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

[0013] Figure 2 illustrates a perspective cross-sectional view of the actuator of Figure 1, according to an example implementation.

[0014] Figure 3 illustrates a perspective view of a main piston of the actuator of Figure 1, according to an example implementation.

[0015] Figure 4 illustrates an enlarged perspective view of a piston head of the main piston of Figure 3, according to an example implementation.

[0016] Figure 5 illustrates a perspective view of a retract set of locking pawls and an extend set of locking pawls, according to an example implementation.

[0017] Figure 6A illustrates a partial perspective view of the main piston of Figure 3 with locking pawls mounted in annular grooves, according to an example implementation.

[0018] Figure 6B illustrates a perspective enlarged view of a locking pawl, according to an example implementation.

[0019] Figure 7 illustrates a partial cross-sectional view of the actuator of Figure 1 with the main piston in a fully-extended position, according to an example implementation.

[0020] Figure 8 illustrates a perspective cross-sectional view of a shuttle, according to an example implementation.

[0021] Figure 8A illustrates a partial cross-sectional view of an actuator with a shuttle configured as a quad seal, according to an example implementation

[0022] Figure 9A illustrates a partial cross-sectional view of the actuator of Figure 1 showing the main piston in the middle of its stroke, according to an example implementation.

[0023] Figure 9B illustrates a partial cross-sectional view of the actuator of Figure 1 showing the main piston in a fully-extended position, according to an example implementation.

[0024] Figure 10 illustrates a partial cross-sectional view of the actuator of Figure 1 showing an annular area on which fluid acts to release the main piston and allow it to retract, according to an example implementation.

[0025] Figure 11 illustrates a partial cross-sectional view of the actuator of Figure 1 showing an annular area on which fluid acts on a retract lock piston during retraction of the main piston, according to an example implementation.

[0026] Figure 12 illustrates a partial cross-sectional view of the actuator of Figure 1 with the main piston in a fully-retracted position, according to an example implementation.

[0027] Figure 13 illustrates a partial cross-sectional view of an actuator, according to an example implementation.

[0028] Figure 14 is a flowchart of a method for operating the actuator of Figure 1, according to an example implementation.DETAILED DESCRIPTION

[0029] Disclosed herein are actuators, assemblies, methods, and systems involving a linear actuator having a main piston movable within a cylinder. The actuator has a locking and unlocking mechanism that involves a pressure differential acting on a first annular area to unlock a main piston, while acting on a second annular area to lock the main piston, where the second annular area is smaller than the first annular area. This way, components (e.g., pawls) that are used to lock the main piston are not loaded with a high force against an inner bore of the cylinder, thereby reducing wear and galling of the cylinder.

[0030] Further, the locking system operates based on a pressure differential between an inlet pressure and an return pressure. This may prevent inadvertent unlocking when the linear actuator is subjected to high transient system return pressures. The disclosed configuration may also use a small, weak spring compared to conventional actuators in which the return pressure is vented to atmosphere and a strong, large spring may be necessary. Thus, weight savings may be achieved with the disclosed configuration.

[0031] Figure 1 illustrates a perspective view of an actuator 100, according to an example implementation. The actuator 100 can be a linear actuator that is operated by pressurized fluid. The actuator 100 includes a cylinder 102. The cylinder 102 may have a manifold 104 integrated therewith or mounted thereto. The manifold 104 has an extend port 106 and a retract port 108. The manifold 104 may also have various valves integrated therewith such as an anti -cavitation switching valve 110 and a flow control valve 112. Other valves, such as anti-cavitation valves could be used as well. In some examples, the extend port 106 and the retract port 108 can be formed in the cylinder 102 rather than the manifold 104.

[0032] In examples, the actuator 100 may also include a retract electric connector block 111 and an extend electric connector block 113. The retract electric connector blocks 111 includes a proximity switch or proximity sensor (or any other mechanical switch) that provides information (e.g., sensor signal) indicating whether a piston (e.g., main piston 114 described below) has reached a fully-retracted, locked position. Similarly, the extend electric connector blocks 113 includes a proximity switch or proximity sensor (or any other mechanical switch) that provides information (e.g., sensor signal) indicating whether the piston (e.g., main piston 114 described below) has reached a fully-extended, locked position.

[0033] The sensor information can be used as a safety feature. Particularly, an electronic controller of the actuator 100 having such sensor information might not shut off fluid flow to the actuator 100 prior to the piston reaching the end of its stroke, thereby avoiding having an implement coupled to and movable by the piston from moving (e.g., dropping) unintentionally.

[0034] Figure 2 illustrates a perspective cross-sectional view of the actuator 100, according to an example implementation. The actuator 100 has a main piston 114 that is axially or linearly movable within the cylinder 102. The main piston 114 has a piston head 116 and a piston rod 118 extending from the piston head 116 along a central longitudinal axis direction of the cylinder 102.

[0035] The piston head 116 divides the internal space of the cylinder 102 into a first chamber 120 (e.g., head-side or cap chamber) and a second chamber 122 (rod-side chamber). The second chamber 122 is annular and formed around the piston rod 118. Referring to Figures 1-2 together, when fluid is provided from a source of fluid (e.g., a pump) to the extend port 106 of the manifold 104, fluid is provided through the manifold 104 to the first chamber 120, causing the main piston 114 to extend (move in the distal direction). Fluid discharged from the second chamber 122, asthe main piston 114 extends, flows via a conduit 123 (shown in Figure 1) to the manifold 104, then through the retract port 108 to a fluid reservoir (a tank).

[0036] Conversely, when fluid is provided from the source of fluid (e g., a pump) to the retract port 108, fluid is provided through the manifold 104 to the second chamber 122, causing the main piston 114 to retract (move in the proximal direction). Fluid discharged from the first chamber 120, as the main piston 114 retracts, then flows through the manifold 104, and through the extend port 106 to the fluid reservoir.

[0037] Figure 3 illustrates a perspective view of the main piston 114, and Figure 4 illustrates an enlarged perspective view of the piston head 116 of the main piston 114, according to an example implementation. The piston head 116 has a first annular groove 124 and a second annular groove 126, spaced apart from each other along an axial length of the piston head 116.

[0038] The piston head 116 further includes an extend snubber surface 128 and piston ring 129. As described in more details below, the extend snubber surface 128 and the piston ring 129 operate to slow down the main piston 114 as it reaches an end of its extension stroke. The main piston 114 also includes a locking ring 130 at a distal end of the piston rod 118, and the locking ring 130 has a plurality of locking notches as shown in Figure 3.

[0039] As shown in Figure 4, the first annular groove 124 has a plurality of holes 125 disposed in a circular array about the piston head 116. Similarly, the second annular groove 126 has a respective plurality of holes 127 disposed in a circular array about the piston head 116. The plurality of holes of each annular groove are configured to receive respective locking pawls.

[0040] Figure 5 illustrates a perspective view of a retract set of locking pawls 132 and an extend set of locking pawls 134, according to an example implementation. The retract set of lockingpawls 132 is configured to be mounted in the first annular groove 124 of the piston head 116, and the extend set of locking pawls 134 is configured to be mounted in the second annular groove 126 of the piston head 116.

[0041] Figure 6A illustrates a partial perspective view of the main piston 114 with locking pawls mounted in the annular grooves 124, 126, and Figure 6B illustrates a perspective enlarged view of a locking pawl 136, according to an example implementation. The locking pawl 136 is generally T-shaped and has a curved or arcuate bar 138 that is configured to be disposed within the first annular groove 124 in the piston head 116. The arcuate bar 138 has inclined, ramped, or tapered edges such as tapered edge 139A and tapered edge 139B.

[0042] The locking pawl 136 further has a stem 140 protruding from the arcuate bar 138 and configured to move linearly within a hole of the plurality of holes 125 (see Figure 4). The stem 140 also has a tapered end 141.

[0043] Other locking pawls of the retract set of locking pawls 132 and the extend set of locking pawls 134 can be configured similar to the locking pawl 136. As such, reference to the locking pawl 136 herein is a general reference to any of the locking pawls of the retract set of locking pawls 132 and the extend set of locking pawls 134.

[0044] As depicted in Figure 5, the retract set of locking pawls 132 has a circular array of locking pawls. The locking pawls are independently movable or may be elastically coupled to allow them to move away from each other as they move radially outward. Locking pawls of the extend set of locking pawls 134 can be similarly configured.

[0045] Referring to Figures 4, 6A together, the piston head 116 further includes a third annular groove 142. The actuator 100 has a piston head seal 144 mounted in the third annular groove 142to seal against an interior bore of the cylinder 102 as the main piston 114 moves within the cylinder 102.

[0046] As shown in Figure 6A, a proximal ring 146 is mounted to the proximal end of the piston head 116. In examples, the proximal ring 146 may include a retract snubbing piston 147 integrated therewith. The retract snubbing piston 147 is configured to be received within a hole in the cylinder 102 when the main piston 114 is fully-retracted and is configured to slow down the main piston 114 as it approaches the retraction end stroke.

[0047] The actuator 100 further includes a locking configuration assembly that is embedded within, and movable with, the main piston 114. Particularly, the locking configuration assembly is substantially embedded within the piston head 116. The term substantially embedded is used herein to indicate the most of the components of the assembly are disposed within the piston head 116, with only a portion of one or more components extending outside the piston head 116 into the piston rod 118. The locking configuration assembly uses the retract set of locking pawls 132 and the extend set of locking pawls 134 to lock the main piston 114 in a fully-retracted position and a fully-extended position, respectively.

[0048] Figure 7 illustrates a partial cross-sectional view of the actuator 100 with the main piston 114 in a fully-extended position, according to an example implementation. Figure 7 labels extend and retract pressure chambers or regions within the actuator 100. The extend pressure regions are fluidly coupled to the extend port 106 via passages (e.g., unsealed spaces, drilled holes, etc.), while the retract pressure regions are fluidly coupled to the retract port 108 via respective passages (e.g., unsealed spaces, drilled holes, etc.).

[0049] The actuator 100 has an end cap 201 coupled to a distal end of the cylinder 102 such that the end cap 201 is mounted, at least partially, between the interior surface of the cylinder 102 andan exterior surface of the main piston 114. Several internal seals are mounted to the end cap 201 to prevent leakage of fluid to an external environment of the actuator 100.

[0050] The locking configuration assembly includes a retract lock piston 200 and an extend lock piston 202. The retract lock piston 200 and the extend lock piston 202 are disposed, at least partially, within the piston head 116. Further, the retract lock piston 200 can be mounted, at least partially, within the extend lock piston 202 as shown. Also, the retract lock piston 200 and the extend lock piston 202 are axially movable relative to each other, e.g., via slots (e.g., slot 203 shown in Figure 9A) in the extend lock piston 202 that allows it to slide axially relative to the retract lock piston 200 and vice versa.

[0051] The locking configuration assembly also has a shuttle 204 that is radially interposed between the retract lock piston 200 and the extend lock piston 202. The shuttle 204 is also axially interposed between a flange 206 of the retract lock piston 200 and a shoulder 208 of the extend lock piston 202. With this configuration, a fluid force acting on the shuttle 204 can be transferred to the retract lock piston 200 or the extend lock piston 202 based on direction of application of the fluid force (e.g., based on a net fluid force resulting from the differential pressure).

[0052] The extend lock piston 202 has a ramped surface 210 configured to interact with pawls of the extend set of locking pawls 134 to lock the main piston 114 in a fully-extended position as described below. Further, a tapered ring 212 is coupled to the retract lock piston 200 (e.g., via pins 213), and the tapered ring 212 has a ramped surface 214 that interacts with pawls of the retract set of locking pawls 132 to lock the main piston 114 in a fully-retracted position as described below.

[0053] In addition to the piston head seal 144 that seals between an exterior surface of the piston head 116 and an interior surface of the cylinder 102, the actuator 100 further includes an extend lock piston seal 216 disposed in an external annular groove formed in the extend lock piston 202.The extend lock piston seal 216 is configured to seal between an exterior surface of the extend lock piston 202 and an interior surface of the piston head 116.

[0054] The actuator 100 also includes a retract lock piston seal 218 disposed in an internal annular groove formed in a shoulder 219 (internal ring-shaped protrusion) of the piston head 116. The retract lock piston seal 218 is configured to seal between an exterior surface of the retract lock piston 200 and an interior surface of the piston head 116. The shoulder 219 also operates a stop for the retract lock piston 200 as depicted in Figure 7.

[0055] Figure 8 illustrates a perspective cross-sectional view of the shuttle 204, according to an example implementation. As shown, the shuttle 204 is configured as a ring mounted around the retract lock piston 200.

[0056] Referring to Figures 7-8 together, the shuttle 204 has an external annular groove in which a first shuttle seal 220 is disposed. The first shuttle seal 220 is configured to seal between an exterior surface of the shuttle 204 and an interior surface of the extend lock piston 202.

[0057] The shuttle 204 further has an internal annular groove in which a second shuttle seal 222 is disposed. The second shuttle seal 222 is configured to seal between an exterior surface of the retract lock piston 200 and an interior surface of the shuttle 204. Although the shuttle 204 is shown as a shuttle piston, other configurations are possible. For example, the shuttle 204, the first shuttle seal 220, and the second shuttle seal 222 can be replaced by a single seal having a large cross section such that its outer diameter is the outer diameter of the first shuttle seal 220 and its inner diameter is the inner diameter of the second shuttle seal 222.

[0058] Figure 8A illustrates a partial cross-sectional view of an actuator 800 with a shuttle configured as a quad seal 802, according to an example implementation. The actuator 800 issimilar to the actuator 100 and the common components are labeled with the same reference numbers.

[0059] The actuator 800 differs from the actuator 100 in that rather than using a shuttle piston as the shuttle, the shuttle of the actuator 800 is the quad seal 802. The quad seal 802, which may also be referred to as an X-ring seal, may be configured as a four-lobed rubber seal that is used to reduce friction. The quad seal 802 has a cross-like seal surface with double sealing surfaces, which provides greater seal protection and a larger sealing surface than an O-ring.

[0060] In an example, the actuator 800 may also include back-up rings disposed on sides of the quad seal 802. For example, the quad seal 802 may be sandwiched by a first back-up ring 804 and a second back-up ring 806. The back-up rings 804, 806 may include Polytetrafluoroethylene (PTFE) material, which is a synthetic fluoropolymer that has non-stick properties and can withstand high pressure levels. The back-up rings 804, 806 may be used when high pressure levels (e.g., over 1500 psi) are expected. In this case, the back-up rings 804, 806 may protect the quad seal 802 against spiraling as it shuttles axially.

[0061] Other seal configurations (other than quad seals) could be used as well. Regardless of the type of seal, as port pressure rises, the seal shuttles while the pressure is low and then once shuttled, the transient pressure builds to steady state pressure. This way, damage to the seal during the shuttling motion is avoided.

[0062] Although in the rest of the description below, the actuator 100 is used and the shuttle is shown as the shuttle 204 (e.g., a shuttle piston), it should be understood that the description is also applicable to the actuator 800. As such, the term “shuttle” is used herein to encompass other types of shuttling components such as seals (e.g., the quad seal 802).

[0063] Figure 9A illustrates a partial cross-sectional view of the actuator 100 showing the main piston 114 in the middle of its stroke, according to an example implementation. Four seals are relevant to operation of the locking configuration: the extend lock piston seal 216, the first shuttle seal 220, the second shuttle seal 222, and the retract lock piston seal 218. Each seal of the four seals has a particular diameter on which fluid acts. These particular diameters are: the outer diameter (DI) of the extend lock piston seal 216, the outer diameter (D2) of the first shuttle seal 220, the inner diameter (D3) of the second shuttle seal 222, and the inner diameter (D4) of the retract lock piston seal 218.

[0064] To extend the main piston 114, high pressure fluid is provided via the extend port 106 to the first chamber 120, thereby applying a pressure Psxt to the main piston 114 in the distal direction. Fluid in the second chamber 122 can be a low pressure fluid (as the second chamber 122 is fluidly coupled to a fluid reservoir via the retract port 108). Fluid in the second chamber 122 applies a pressure PRet on the main piston 114 in the proximal direction. Thus, a pressure differential PDiff_E = (Psxt - PRet) (i.e., the difference between the pressure level PExt and the pressure level PRet acts on the main piston 114 to cause it to extend (move in the distal direction, to the right in Figures 2, 9A).

[0065] Referring to Figures 7, 9A together, the same pressure differential PDiff_E = (PExt - PRet) acts or applies an extend lock force on the extend lock piston 202. Particularly, such extend lock force is equal to FExtend Lock = Poiff_E- \n:~^ ~where the annular areais the difference between an area defined by DI and an area defined by D2. As mentioned above, DI is the outer diameter of the extend lock piston seal 216, and D2 is the outer diameter of the first shuttle seal 220.

[0066] The extend lock piston 202 in turns applies the extend lock force FExtendLockonthe extend set of locking pawls 134. As the main piston 114 traverses its stroke (before reaching the end of the stroke), the ramped surface 210 of the extend lock piston 202 interacts with the pawls of the extend set of locking pawls 134, pushing them against the interior bore of the cylinder 102, causing friction. Such friction is correlated with the extend lock force FExtend Lock.

[0067] Figure 9B illustrates a partial cross-sectional view of the actuator 100 showing the main piston 114 in a fully-extended position, according to an example implementation. When the main piston 114 reaches the end of the extension stroke, the ramped surface 210 of the extend lock piston 202 interacts with the tapered end 141 of pawls (see Figure 6B) of the extend set of locking pawls 134, pushing them radially outward to an internal annular groove 300 formed in the cylinder 102 as shown in Figure 9B. In this position (radially outward position) of the pawls, they interact with the interior surfaces of the internal annular groove 300 of the cylinder 102 to lock the main piston 114 in the fully-extended position shown in Figure 9B.

[0068] In an example, the actuator 100 can include a spring 302 mounted in an annular slot 303 formed in the extend lock piston 202. The spring 302 is interposed between the shoulder 208 of the extend lock piston 202 and the tapered ring 212. This way, the spring 302 applies a biasing force on the extend lock piston 202 in the distal direction. Thus, the spring 302 biases the extend lock piston 202 to the locked position shown in Figure 9B.

[0069] Further, pawls of the extend set of locking pawls 134 interact (e g., via the tapered edges139A, 139B shown in Figure 6B) with the interior surface of the internal annular groove 300, causing the pawls to apply a radially inward force on the extend lock piston 202. This way, friction between the pawls and the extend lock piston 202 may facilitate maintaining the position of theextend lock piston 202 in the locked position until a release fluid force overcomes the various forces acting on the extend lock piston 202.

[0070] Notably, the end cap 201 has an inner tapered surface 304. Thus, as the main piston 114 traverses the last portion of its extend stroke, the inner tapered surface 304 squeezes the piston ring 129 into its groove. Further, the extend snubber surface 128 and the piston ring 129 interact with the inner tapered surface 304 as the main piston 114 extends to form a progressively smaller annular area due to the tapering of the inner tapered surface 304. This interaction effectively dampens, or slows down, the movement of the main piston 114 as fluid is squeezed through the progressively smaller annular area. This may prevent the main piston 114 from slamming into the end cap 201, which could damage an implement attached to the piston rod 118.

[0071] To retract the main piston 114, the main piston 114 is first released from the extend locked position shown in Figure 9B. Particularly, high pressure fluid is provided via the retract port 108 to the second chamber 122, thereby applying a pressure PRet to the main piston 114 in the proximal direction. In this case, fluid in the first chamber 120 can be a low pressure fluid (as the first chamber 120 can be fluidly coupled to the fluid reservoir via the extend port 106 in this case). Fluid in the first chamber 120 applies a pressure / E on the main piston 114 in the distal direction. Thus, a respective pressure differential PDiff_R = (PRet - PExt) acts on the main piston 114 in the proximal direction.

[0072] Figure 10 illustrates a partial cross-sectional view of the actuator 100 showing an annular area on which fluid acts to release (unlock) the main piston 114 and allow it to retract, according to an example implementation. The annular area is defined by the diameters DI and D3 as described below.

[0073] Referring to Figures 7, 10 together, the pressure differential between the high pressure acting in the retract regions (from the retract port 108) and the low pressure in the extend regions applies a fluid force on the shuttle 204 in the proximal direction against the extend lock piston 202. This way, the pressure differential Poiffji = (Paet - PEXI) acts or applies an unlocking or release force on the extend lock piston 202 in the proximal direction. Particularly, such release force is equal towhere DI and D3 are defined above (see Figure 9A) and are the outer diameter of the extend lock piston seal 216 and the inner diameter of the second shuttle seal 222, respectively.

[0074] The force FRetractRelease is applied to the extend lock piston 202, causing it to move in the proximal direction from underneath the pawls of the extend set of locking pawls 134. As the main piston 114 is also forced in the proximal direction, it applies a force on the pawls against the interior surface of the internal annular groove 300. Due to the interaction between the tapered edge 139A of the pawl with the interior surface of the internal annular groove 300, the pawls are pushed radially inward once the extend lock piston 202 has moved in the proximal direction, releasing the main piston 114 and allowing it to retract.

[0075] Thus, as the main piston 114 traverses its extension stroke (before reaching the end of the stroke shown in Figure 9B), the ramped surface 210 of the extend lock piston 202 interacts with the pawls of the extend set of locking pawls 134, pushing them against the interior bore of the cylinder 102, causing friction. Such friction is correlated with the extend lock force pExtend Lock However, to release the main piston 114 from the fully extendas described with respect to Figure 10. / D2D2

[0076] Notably, the differential area ( on which fluid acts to apply a force on theextend lock piston 202 as it moves in the distal direction to lock the main piston 114 in the extended position is smaller than the differential area on which fluid acts to apply a force onthe extend lock piston 202 in the proximal direction to release the main piston 114. Thus, advantageously, this configuration provides a larger unlocking annular area for fluid to act on to release the main piston 114, and a smaller engaging (locking pressure annular area) for fluid to act on when locking the main piston 114.

[0077] This way, the force dragging the pawls of the extend set of locking pawls 134 in the distal direction as the main piston 114 extends, and thus the friction with the inner bore of the cylinder 102, is reduced, thereby reducing wear and galling of the cylinder 102 during extension of the main piston 114. A similar advantage is achieved in the opposite direction as the main piston 114 retracts.

[0078] Figure 11 illustrates a partial cross-sectional view of the actuator 100 showing an annular area on which fluid acts on the retract lock piston 200 during retraction of the main piston 114, according to an example implementation. The annular area is defined by the diameters D3 and D4 as described below.

[0079] At the same time that the pressure differential PotffR = (PRet - PEM) acts or applies an unlocking or release force on the extend lock piston 202 in the proximal direction as described above with respect to Figure 10, such pressure differential also acts and applies a retract lock force on the retract lock piston 200. Particularly, such retract lock force is equal to FRetract Lock— PRet ~ where D3 and D4 are defined above and are the inner diameter ofthe second shuttle seal 222 and the inner diameter of the retract lock piston seal 218, respectively.

[0080] As the retract lock piston 200 moves with the main piston 114 in the proximal direction, it drags the pawls of the retract set of locking pawls 132 along, and pushes them against, the inner bore of the cylinder 102 via the tapered ring 212. However, the annular area is asmall annular area, and thus the force FRetract Lockis also small, causing friction with, and thus wear of, the cylinder 102 to be mitigated. When the main piston 114 reaches the end of its retraction stroke, it is locked via the retract lock piston 200 and the retract set of locking pawls 132.

[0081] Figure 12 illustrates a partial cross-sectional view of the actuator 100 with the main piston 114 in a fully-retracted position, according to an example implementation. When the main piston 114 reaches the end of the retraction stroke as depicted in Figure 12, the tapered ring 212 pushes the pawls of the retract set of locking pawls 132 radially outward into an internal annular groove 400 formed in the cylinder 102. The pawls are retained within the internal annular groove 400, and thus the main piston 114 is locked at the fully-retracted position.

[0082] At the fully-retracted position of the main piston 114, the proximal ring 146 operates as a stop for the extend lock piston 202. Further, as the extend lock piston 202 is stopped in the proximal direction, the spring 302 applies a biasing force on the tapered ring 212 in the proximal direction, to maintain the retract locked position.

[0083] Notably, the cylinder 102 has a blind cavity 402 formed at the end portion of the cylinder 102. The blind cavity 402 is bound by a tapered surface as shown. Thus, as the main piston 114 reaches the end of the retraction stroke, the retract snubbing piston 147 is received within the blind cavity 402, and the tapering of the surface bounding the cavity causes fluid to be progressivelysqueezed, slowing down the main piston 114. Fluid in the blind cavity 402 can be discharged or routed through channel 404 to the retract port 108.

[0084] To again extend the main piston 114 again (move it to the right in Figure 12), the main piston 114 is first released from the retract locked position shown. Particularly, high pressure fluid is provided via the extend port 106, thereby applying a pressure PEXI to the main piston 114 in the distal direction. In this case, fluid in the second chamber 122 can be a low pressure fluid (as the second chamber 122 can be fluidly coupled to the fluid reservoir via the retract port 108 in this case). Fluid in the second chamber 122 applies a pressure PRet on the main piston 114 in the proximal direction. Thus, a pressure differential Pntff_E = (Pp.xt - PRet) acts on the main piston 114 in the distal direction (to the right in Figure 12).

[0085] The pressure differential Pmff_E = (Pp t - PRet also acts or applies a release force on the retract lock piston 200 in the distal direction. Particularly, such release force is equal to^Extend Release (Ext ~ P^twhere D2 and D4 are defined above and are the outer diameter of the first shuttle seal 220 and the inner diameter of the retract lock piston seal 218, respectively.

[0086] The force pExtend Release is applied to the retract lock piston 200, causing it and the tapered ring 212 to move in the distal direction from underneath the pawls of the retract set of locking pawls 132. As the main piston 114 is also forced in the distal direction, it applies a force on the pawls against the interior surface of the internal annular groove 400. Due to the interaction between the tapered edge 139B of the pawl with the interior surface of the internal annular groove 400, a radially inward force component is applied to the pawls, pushing them radially inward,tracing the ramped surface of the tapered ring 212, thereby releasing the main piston 114 and allowing it to extend (move in the distal direction).

[0087] Notably, the differential area on which fluid acts to apply a force on theretract lock piston 200 as it moves in the proximal direction to lock the main piston 114 in the retracted position is smaller than the differential area on which fluid acts to apply aforce on the retract lock piston 200 in the distal direction to release the main piston 114. Thus, advantageously, this configuration provides a larger unlocking annular area for fluid to act on to release the main piston 114 and a smaller engaging (locking pressure annular area) for fluid to act on when locking the main piston 114. This way, the force dragging the pawls of the retract set of locking pawls 132 in the proximal direction as the main piston 114 retracts, and thus the friction with the inner bore of the cylinder 102, is reduced, reducing wear and galling of the cylinder 102 during retraction of the main piston 114.

[0088] Several variations can be implemented to the configuration shown in Figures 1-12, while maintaining the principle of operation where the annular area associated with applying pressure to lock the main piston 114 is smaller than the respective annular area associated with applying pressure to unlock the main piston 114. For example, the construction of the retract and extend lock pistons can be changed to change a location of the spring 302.

[0089] Figure 13 illustrates a partial cross-sectional view of an actuator 500, according to an example implementation. The actuator 500 also includes the cylinder 102 and the main piston 114. Some of the seals (e.g., the seals of the shuttle 204) are not shown in Figure 13 to reduce the visual clutter in the drawing.

[0090] The actuator 500 includes a retract lock piston 502 and an extend lock piston 504. The extend lock piston 504 does not have the annular slot 303 in which the spring 302 is disposed as in the extend lock piston 202. Rather, the spring 302 is located at a different portion of the actuator 100, but operates in a similar manner.

[0091] Also, rather than having the tapered ring 212 as a separate component, a ramped surface 506 is integrated into the retract lock piston 502. However, the actuator 500 operates in a similar manner to the actuator 100 and also defines four seal diameters to result in a smaller annular area for fluid to act on to lock the main piston 114 compared to the annular area on which fluid acts to lock the main piston 114.

[0092] Figure 14 is a flowchart of a method 600 for operating the actuator 100, according to an example implementation. The method 600 may include one or more operations, or actions as illustrated by one or more of blocks 602-608. 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.

[0093] At block 602, the method 600 includes applying a pressure differential PD^_E = (PEXI - PRSI) on a first annular area \ to cause the extend lock piston 202 to lock the main piston114 in a fully-extended position.

[0094] At block 604, the method 600 includes applying a respective pressure differential Potff_R = f D2D2\ PRet - PEXI) on a second annular area \ to release the main piston 114 and allow themain piston 114 to retract, wherein the first annular area is smaller than the second annular area.

[0095] At block 606, the method 600 includes applying the respective pressure differential PDiff_R = (PRet - PEXI) on a third annular area to cause the retract lock piston 200 to lock themain piston 114 in a fully-retracted position.

[0096] At block 608, the method 600 includes applying the pressure differential Poiff_E = (Psxt -PRet) on a fourth annular area to release the main piston 114 and allow the mainpiston 114 to extend, wherein the third annular area is smaller than the fourth annular area.

[0097] The method 600 can further include any of the steps described above.

[0098] Although the description above includes locking the main piston 114 in both direction (e.g., extend and retract directions), it is contemplated that in an example implementation, the main piston 114 may be locked in one direction. In other words, the differential pressure lock method described herein can be used to lock and unlock the piston at a single position (either retract or extend position). In this example embodiment, only one set of locking pawls (e.g., either the extend set of locking pawls 134 or the retract set of locking pawls 132) might be used. Also, in this example, only one locking piston (e.g., either the retract lock piston 200 or the extend lock piston 202) might be used.

[0099] 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.

[0100] 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 ascomponent aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[0101] 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.

[0102] 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.

[0103] 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.

[0104] 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.

[0105] 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.

[0106] Embodiments of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[0107] EEE 1 is an actuator comprising: a cylinder; a main piston movable within the cylinder between a fully-extended position and a fully-retracted position; a retract lock piston movable with the main piston, wherein the retract lock piston is configured to lock the main piston in the fully- retracted position; an extend lock piston movable with the main piston, wherein the extend lock piston is configured to lock the main piston in the fully-extended position; and a shuttle that is radially interposed between the retract lock piston and the extend lock piston such that (i) a pressure differential acts on a first annular area to cause the extend lock piston to lock the main piston in the fully-extended position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston and allow the main piston to retract, and (ii) the respective pressure differential acts on a third annular area to cause the retract lock piston to lock the main piston in the fully-retracted position, wherein the third annular area is smaller than a fourth annular area on which the pressure differential acts to release the main piston and allow the main piston to extend.

[0108] EEE 2 is the actuator of EEE 1, wherein the main piston comprises a piston head and a piston rod extending from the piston head, wherein the actuator further comprises: a piston headseal configured to seal between the piston head and the cylinder; a first shuttle seal mounted to the shuttle and configured to seal between the shuttle and the extend lock piston; a second shuttle seal mounted to the shuttle and configured to seal between the shuttle and the retract lock piston; and a retract lock piston seal configured to seal between the retract lock piston and the piston head.

[0109] EEE 3 is the actuator of EEE 2, wherein the first annular area comprises a difference between an area defined by an outer diameter of the piston head seal and a respective area defined by an outer diameter of the first shuttle seal, and wherein the second annular area comprises a difference between an area defined by the outer diameter of the piston head seal and a respective area defined by an inner diameter of the second shuttle seal.

[0110] EEE 4 is the actuator of any of EEEs 2-3, wherein the third annular area comprises a difference between an area defined by an inner diameter of the second shuttle seal and a respective area defined by an inner diameter of the retract lock piston seal, and wherein the fourth annular area comprises a difference between an area defined by an outer diameter of the first shuttle seal and a respective area defined by the inner diameter of the retract lock piston seal.

[0111] EEE 5 is the actuator of any of EEEs 2-4, wherein the first shuttle seal is disposed in an external annular groove of the shuttle, and wherein the second shuttle seal is disposed in an internal annular groove of the shuttle.

[0112] EEE 6 is the actuator of any of EEEs 1-5, further comprising: an extend set of locking pawls mounted to the main piston, wherein the extend lock piston comprises a ramped surface configured to interact with the extend set of locking pawls to lock the main piston in the fully- extended position.

[0113] EEE 7 is the actuator of EEE 6, wherein the cylinder comprises an internal annular groove, wherein the ramped surface of the extend lock piston pushes respective pawls of the extend set of locking pawls into the internal annular groove to lock the main piston in the fully-extended position.

[0114] EEE 8 is the actuator of any of EEEs 6-7, wherein the extend set of locking pawls comprises a plurality of pawls disposed in a circular array.

[0115] EEE 9 is the actuator of EEE 8, wherein a pawl of the plurality of pawls comprises (i) an arcuate bar disposed in an annular groove formed in the main piston, and (ii) a stem protruding from the arcuate bar and configured to move linearly within a hole formed in the annular groove of the main piston.

[0116] EEE 10 is the actuator of any of EEEs 1-9, further comprising: a retract set of locking pawls mounted to the main piston, wherein the retract lock piston comprises a tapered ring configured to interact with the retract set of locking pawls mounted to the main piston to lock the main piston in the fully-retracted position.

[0117] EEE 11 is the actuator of EEE 10, wherein the cylinder comprises an internal annular groove, wherein the tapered ring of the retract lock piston pushes respective pawls of the retract set of locking pawls into the internal annular groove to lock the main piston in the fully-retracted position.

[0118] EEE 12 is the actuator of any of EEEs 10-11, wherein the tapered ring is integrated into the retract lock piston.

[0119] EEE 13 is the actuator of any of EEEs 1-12, wherein the main piston divides an internal space of the cylinder into a first chamber and a second chamber, wherein the pressure differentialcomprises a difference between pressure level of fluid of the first chamber and pressure level of fluid of the second chamber when the main piston is to extend, and wherein the respective pressure differential comprises a difference between pressure level of fluid of the second chamber and pressure level of fluid of the first chamber when the main piston is to retract.

[0120] EEE 14 is the actuator of any of EEEs 1-13, wherein an assembly of the extend lock piston, the retract lock piston, and the shuttle are embedded within the main piston.

[0121] EEE 15 is the actuator of any of EEEs 1-14, wherein the extend lock piston is movable relative to the retract lock piston.

[0122] EEE 16 is the actuator of any of EEEs 1-15, further comprising: a spring configured to apply a biasing force on the extend lock piston.

[0123] EEE 17 is the actuator of EEE 16, wherein the spring is mounted in an annular slot formed in the extend lock piston.

[0124] EEE 18 is the actuator of any of EEEs 1-17, further comprising: an end cap coupled to a distal end of the cylinder such that the end cap is mounted, at least partially, between an interior surface of the cylinder and an exterior surface of the main piston; and one or more internal seals mounted to the end cap to prevent leakage of fluid to an external environment.

[0125] EEE 19 is the actuator of EEE 18, wherein the end cap has an inner tapered surface, wherein the main piston comprises an extend snubber surface and a piston ring such that as the main piston traverses a last portion of an extend stroke, the extend snubber surface and the piston ring interact with the inner tapered surface of the end cap to slow down the main piston.

[0126] EEE 20 is the actuator of any of EEEs 1-19, further comprising: a proximal ring mounted to the main piston, wherein the proximal ring includes a retract snubbing piston, wherein thecylinder comprises a blind cavity formed at a proximal end thereof, wherein the blind cavity is bound by a tapered surface, such that as the main piston reaches an end of a retraction stroke, the retract snubbing piston is received within the blind cavity, and wherein an interaction between the retract snubbing piston and the tapered surface slows down the main piston.

[0127] EEE 21 is a method of operating the actuator of any of EEEs 1-20.

[0128] EEE 22 is a system having a source of fluid, a fluid reservoir, and the actuator of any of EEEs 1-20.

[0129] EEE 23 is an actuator comprising: a cylinder; a main piston movable within the cylinder; and a lock piston movable with the main piston, wherein the lock piston is configured to lock the main piston at a particular position, wherein a pressure differential acts on a first annular area to cause the lock piston to lock the main piston at the particular position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston.

[0130] EEE 24 is the actuator of EEE 23, wherein the main piston comprises a piston head and a piston rod extending from the piston head, wherein the actuator further comprises: a piston head seal configured to seal between the piston head and the cylinder; a first shuttle seal mounted to a shuttle; and a second shuttle seal mounted to the shuttle.

[0131] EEE 25 is the actuator of EEE 24, wherein the first annular area comprises a difference between an area defined by an outer diameter of the piston head seal and a respective area defined by an outer diameter of the first shuttle seal, and wherein the second annular area comprises a difference between an area defined by the outer diameter of the piston head seal and a respective area defined by an inner diameter of the second shuttle seal.

[0132] EEE 25 is the actuator of any of EEEs 24-25, wherein the first shuttle seal is disposed in an external annular groove of the shuttle, and wherein the second shuttle seal is disposed in an internal annular groove of the shuttle.

[0133] EEE 26 is the actuator of any of EEEs 23-25, further comprising: a set of locking pawls mounted to the main piston, wherein the lock piston comprises a ramped surface configured to interact with the set of locking pawls to lock the main piston at the particular position.

[0134] EEE 27 is the actuator of EEE 26, wherein the cylinder comprises an internal annular groove, wherein the ramped surface of the lock piston pushes respective pawls of the set of locking pawls into the internal annular groove to lock the main piston at the particular position.

[0135] EEE 28 is the actuator of any of EEEs 26-27, wherein the set of locking pawls comprises a plurality of pawls disposed in a circular array.

[0136] EEE 29 is the actuator of EEE 28, wherein a pawl of the plurality of pawls comprises (i) an arcuate bar disposed in an annular groove formed in the main piston, and (ii) a stem protruding from the arcuate bar and configured to move linearly within a hole formed in the annular groove of the main piston.

[0137] EEE 30 is the actuator of any of EEEs 26-29, wherein the lock piston comprises a tapered ring configured to interact with the set of locking pawls mounted to the main piston to lock the main piston at the particular position.

[0138] EEE 31 is the actuator of EEE 30, wherein the cylinder comprises an internal annular groove, wherein the tapered ring of the lock piston pushes respective pawls of the set of locking pawls into the internal annular groove to lock the main piston at the particular position.

[0139] EEE 32 is the actuator of any of EEEs 30-31, wherein the tapered ring is integrated into the retract lock piston.

[0140] EEE 33 is the actuator of any of EEEs 23-32, wherein the main piston divides an internal space of the cylinder into a first chamber and a second chamber, wherein the pressure differential comprises a difference between pressure level of fluid of the first chamber and pressure level of fluid of the second chamber when the main piston is to move in a first direction, and wherein the respective pressure differential comprises a difference between pressure level of fluid of the second chamber and pressure level of fluid of the first chamber when the main piston is to move in a second direction, opposite the first direction.

[0141] EEE 34 is the actuator of any of EEEs 23-33, wherein the lock piston is embedded within the main piston.

[0142] EEE 35 is the actuator of any of EEEs 23-34, further comprising: a spring configured to apply a biasing force on the lock piston.

[0143] EEE 36 is the actuator of EEE 35, wherein the spring is mounted in an annular slot formed in the lock piston.

[0144] EEE 37 is the actuator of any of EEEs 23-36, further comprising: an end cap coupled to a distal end of the cylinder such that the end cap is mounted, at least partially, between an interior surface of the cylinder and an exterior surface of the main piston; and one or more internal seals mounted to the end cap to prevent leakage of fluid to an external environment.

[0145] EEE 38 is the actuator of EEE 37, wherein the end cap has an inner tapered surface, wherein the main piston comprises a snubber surface and a piston ring such that as the main pistontraverses a last portion of a stroke, the snubber surface and the piston ring interact with the inner tapered surface of the end cap to slow down the main piston.

[0146] EEE 39 is the actuator of any of EEEs 23-38, further comprising: a proximal ring mounted to the main piston, wherein the proximal ring includes a snubbing piston, wherein the cylinder comprises a blind cavity formed at a proximal end thereof, wherein the blind cavity is bound by a tapered surface, such that as the main piston reaches an end of a stroke, the snubbing piston is received within the blind cavity, and wherein an interaction between the snubbing piston and the tapered surface slows down the main piston.

[0147] EEE 40 is a method of operating the actuator of any of EEEs 23-39.

[0148] EEE 41 is a system having a source of fluid, a fluid reservoir, and the actuator of any ofEEEs 23-39.

Claims

CLAIMSWhat is claimed is:1 . An actuator comprising: a cylinder; a main piston movable within the cylinder between a fully-extended position and a fully- retracted position; a retract lock piston movable with the main piston, wherein the retract lock piston is configured to lock the main piston in the fully-retracted position; an extend lock piston movable with the main piston, wherein the extend lock piston is configured to lock the main piston in the fully-extended position; and a shuttle that is radially interposed between the retract lock piston and the extend lock piston such that (i) a pressure differential acts on a first annular area to cause the extend lock piston to lock the main piston in the fully-extended position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston and allow the main piston to retract, and (ii) the respective pressure differential acts on a third annular area to cause the retract lock piston to lock the main piston in the fully-retracted position, wherein the third annular area is smaller than a fourth annular area on which the pressure differential acts to release the main piston and allow the main piston to extend.

2. The actuator of claim 1, wherein the main piston comprises a piston head and a piston rod extending from the piston head, wherein the actuator further comprises: a piston head seal configured to seal between the piston head and the cylinder;a first shuttle seal mounted to the shuttle and configured to seal between the shuttle and the extend lock piston; a second shuttle seal mounted to the shuttle and configured to seal between the shuttle and the retract lock piston; and a retract lock piston seal configured to seal between the retract lock piston and the piston head.

3. The actuator of claim 2, wherein the first annular area comprises a difference between an area defined by an outer diameter of the piston head seal and a respective area defined by an outer diameter of the first shuttle seal, and wherein the second annular area comprises a difference between an area defined by the outer diameter of the piston head seal and a respective area defined by an inner diameter of the second shuttle seal.

4. The actuator of claim 2, wherein the third annular area comprises a difference between an area defined by an inner diameter of the second shuttle seal and a respective area defined by an inner diameter of the retract lock piston seal, and wherein the fourth annular area comprises a difference between an area defined by an outer diameter of the first shuttle seal and a respective area defined by the inner diameter of the retract lock piston seal.

5. The actuator of claim 2, wherein the first shuttle seal is disposed in an external annular groove of the shuttle, and wherein the second shuttle seal is disposed in an internal annular groove of the shuttle.

6. The actuator of claim 1 , further comprising: an extend set of locking pawls mounted to the main piston, wherein the extend lock piston comprises a ramped surface configured to interact with the extend set of locking pawls to lock the main piston in the fully-extended position.

7. The actuator of claim 6, wherein the cylinder comprises an internal annular groove, wherein the ramped surface of the extend lock piston pushes respective pawls of the extend set of locking pawls into the internal annular groove to lock the main piston in the fully-extended position.

8. The actuator of claim 6, wherein the extend set of locking pawls comprises a plurality of pawls disposed in a circular array.

9. The actuator of claim 8, wherein a pawl of the plurality of pawls comprises (i) an arcuate bar disposed in an annular groove formed in the main piston, and (ii) a stem protruding from the arcuate bar and configured to move linearly within a hole formed in the annular groove of the main piston.

10. The actuator of claim 1, further comprising: a retract set of locking pawls mounted to the main piston, wherein the retract lock piston comprises a tapered ring configured to interact with the retract set of locking pawls mounted to the main piston to lock the main piston in the fully-retracted position.

11. The actuator of claim 10, wherein the cylinder comprises an internal annular groove, wherein the tapered ring of the retract lock piston pushes respective pawls of the retract set of locking pawls into the internal annular groove to lock the main piston in the fully-retracted position.

12. The actuator of claim 10, wherein the tapered ring is integrated into the retract lock piston.

13. The actuator of claim 1, wherein the main piston divides an internal space of the cylinder into a first chamber and a second chamber, wherein the pressure differential comprises a difference between pressure level of fluid of the first chamber and pressure level of fluid of the second chamber when the main piston is to extend, and wherein the respective pressure differential comprises a difference between pressure level of fluid of the second chamber and pressure level of fluid of the first chamber when the main piston is to retract.

14. The actuator of claim 1, wherein an assembly of the extend lock piston, the retract lock piston, and the shuttle are embedded within the main piston.

15. The actuator of claim 1, wherein the extend lock piston is movable relative to the retract lock piston.

16. The actuator of claim 1, further comprising: a spring configured to apply a biasing force on the extend lock piston.

17. The actuator of claim 16, wherein the spring is mounted in an annular slot formed in the extend lock piston.

18. The actuator of claim 1, further comprising: an end cap coupled to a distal end of the cylinder such that the end cap is mounted, at least partially, between an interior surface of the cylinder and an exterior surface of the main piston; and one or more internal seals mounted to the end cap to prevent leakage of fluid to an external environment, wherein the end cap has an inner tapered surface, wherein the main piston comprises an extend snubber surface and a piston ring such that as the main piston traverses a last portion of an extend stroke, the extend snubber surface and the piston ring interact with the inner tapered surface of the end cap to slow down the main piston.

19. The actuator of claim 1, further comprising: a proximal ring mounted to the main piston, wherein the proximal ring includes a retract snubbing piston, wherein the cylinder comprises a blind cavity formed at a proximal end thereof, wherein the blind cavity is bound by a tapered surface, such that as the main piston reaches an end of a retraction stroke, the retract snubbing piston is received within the blind cavity, and wherein an interaction between the retract snubbing piston and the tapered surface slows down the main piston.

20. An actuator comprising: a cylinder; a main piston movable within the cylinder; anda lock piston movable with the main piston, wherein the lock piston is configured to lock the main piston at a particular position, wherein a pressure differential acts on a first annular area to cause the lock piston to lock the main piston at the particular position, wherein the first annular area is smaller than a second annular area on which a respective pressure differential acts to release the main piston.

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