Dual hydraulic actuator

Abstract

The actuator includes a primary piston and a secondary piston axially movable together within a cylinder assembly; a plurality of chambers having a first chamber, a second chamber, a third chamber and a fourth chamber, where a flow of fluid into the first chamber causes the primary piston to advance and a flow of fluid into the second chamber causes the primary piston to retract, and where a forward fluid force applied by the fluid in the third chamber to advance the secondary piston is different from a retracting fluid force applied by the fluid in the fourth chamber to retract the secondary piston; and a force balancing chamber configured to receive fluid from the third chamber or the fourth chamber and apply a balancing force to the secondary piston to resist or add to the fluid force acting on the secondary piston, thereby compensating for a difference between the forward fluid force and the retracting fluid force.

Description

[Technical field]

[0001] (CROSS REFERENCE TO RELATED APPLICATIONS) This application claims priority to U.S. Provisional Patent Application No. 63 / 310,679, filed February 16, 2022, the entire contents of which are incorporated by reference herein as if fully set forth herein. [Background technology]

[0002] A hydraulic cylinder actuator includes a cylinder that uses hydraulic force to facilitate mechanical operation. Specifically, a hydraulic cylinder actuator includes a hollow cylindrical tube within which a piston can slide. The piston can divide the cylinder into two chambers. Supply of pressurized fluid to one chamber causes the piston to move. A double-acting actuator has a piston that can move in both directions. Any fluid pressure difference between the two sides of the piston causes the piston to move within the cylinder.

[0003] Hydraulic actuators may be used in a variety of applications, such as controlling implements on hydraulic machinery (e.g., excavators, loaders, etc.) and moving aircraft control surfaces. For example, aircraft typically include a number of flight control surfaces (fixed-wing aircraft) or one or more cyclic pitch control swashplates (rotorcraft) that guide the motion of the aircraft when steerably positioned.

[0004] In some important applications, for example aircraft flight control systems, it may be desirable to provide redundant control, for example multiple actuators for moving a control surface, so that if control of one actuator is lost, another actuator can safely move the control surface. Furthermore, the forces of these actuators are additive, thereby increasing the force that the actuators can apply.

[0005] In some applications, for example military applications, it may be further desirable to configure the actuator to be ballistic resistant so that the actuator can continue to operate even if a portion of the actuator is damaged. It may be desirable to make the actuator ballistic resistant without substantially increasing the weight of the actuator.

[0006] It is with respect to these and other issues that the disclosure herein is presented for consideration. Summary of the Invention

[0007] This disclosure describes embodiments relating to a dual hydraulic actuator.

[0008] In a first exemplary embodiment, the present disclosure describes an actuator including a primary piston at least partially disposed within a cylinder assembly, a secondary piston at least partially disposed within the cylinder assembly, the primary piston and the secondary piston configured to move axially together within the cylinder assembly, and a plurality of chambers formed within the cylinder assembly, including (i) a first chamber, where a flow of fluid into the first chamber advances the primary piston, (ii) a second chamber, where a flow of fluid into the second chamber retracts the primary piston, and (iii) a third chamber, where a flow of fluid into the third chamber advances the primary piston, and (iv) a second chamber, where a flow of fluid into the third chamber advances the primary piston. the secondary piston advances; and (iv) a fourth chamber, in which the secondary piston retracts when fluid flows into the fourth chamber, wherein a forward fluid force applied by the fluid in the third chamber to advance the secondary piston is different from a retraction fluid force applied by the fluid in the fourth chamber to retract the secondary piston; and a force balancing chamber configured to receive fluid from the third chamber or the fourth chamber and apply a balancing force to the secondary piston to resist or add to the fluid force acting on the secondary piston, thereby compensating for the difference between the forward fluid force and the retraction fluid force.

[0009] In a second exemplary embodiment, the present disclosure describes a method of operating the actuator of the first exemplary embodiment.

[0010] In a third exemplary embodiment, the present disclosure describes a hydraulic system including a fluid source, a fluid reservoir, an actuator of the first exemplary embodiment, and one or more manifolds that control fluid flow from the fluid source to the actuator and from the actuator to the fluid reservoir.

[0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, embodiments and features described above, further aspects, embodiments and features will become apparent by reference to the drawings and the detailed description that follows.

[0012] The novel features believed characteristic of the illustrative examples are set forth in the appended claims. However, the illustrative examples, as well as the preferred modes of use, further objects and the description thereof, can best be understood by reference to the following detailed description of illustrative examples of the present disclosure, read in conjunction with the accompanying drawings. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view of an actuator in accordance with an exemplary embodiment; [Diagram 2] 2 is a cross-sectional side view of the actuator of FIG. 1 according to another exemplary embodiment. [Diagram 3] 2 is another cross-sectional side view of the actuator of FIG. 1 in accordance with an exemplary embodiment. [Figure 4] 1 is a flowchart of a method for actuating an actuator in accordance with an illustrative embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] The present disclosure relates to dual hydraulic actuators. In some applications, multiple hydraulic cylinder actuators may be used to increase the force that can be applied to a member being controlled by the actuator (e.g., a rotor on a helicopter or a control surface on a fixed-wing aircraft) as well as to provide redundancy in case control of one actuator is lost.

[0015] In one example, an actuator may include two trains staggered in-line such that a long cylinder houses multiple pistons, e.g., two pistons coupled to a common rod. However, such a configuration may make it difficult to armor such a long cylinder to protect the pistons against ballistic damage. Additionally, such actuators may be subject to damage to one train propagating to the other train, resulting in loss of control of the entire actuator.

[0016] In another example, the actuator may include three separate pistons, with a central piston controlled by one system and two outer pistons on either side of the central piston controlled by a second system. In this example, if the system assigned to the central piston does not operate, the second system will operate the other two pistons, thereby allowing the actuator to continue to operate. Although damage to one system will not propagate to the other system, such an arrangement leads to a large structure, which may not be desirable in some applications. Furthermore, armoring three separate cylinders may make the actuator significantly heavier.

[0017] Furthermore, in such a three-piston configuration, the pistons are connected to a common yoke. The two outer pistons have an indirect load path acting on the yoke. This reduces stiffness and can make the actuator more susceptible to vibration-based damage. Additionally, force imbalance between the outer pistons can lead to bending and side loads.

[0018] It may therefore be desirable to have a dual-path hydraulic actuator that provides redundancy. Additionally, it may be desirable for such a dual-path actuator to prevent the propagation of damage from one path to the other, so that if one path fails, the other path can continue to operate. It may also be desirable to construct such a dual-path actuator with a smaller structure (e.g., smaller end-to-end length) as compared to a three-piston configuration. Such actuators have a higher stiffness, which may improve vibration performance.

[0019] 1 illustrates a perspective view of an actuator 100 according to an exemplary embodiment. The actuator 100 may include a cylinder assembly 102 and a piston rod 104. The piston rod 104 is slidably received within the cylinder assembly 102. The term "slidably received" is used herein to indicate that a first component (e.g., a piston) is positioned with sufficient clearance relative to a second component (e.g., a cylinder) to allow the first component to move proximally and distally relative to the second component.

[0020] The proximal end of the cylinder assembly 102 has a connecting portion 106 having a through hole 107 in which a pin may be disposed for coupling the cylinder assembly 102 to a frame or structure (e.g., the frame of an aircraft). Similarly, the distal end of the piston rod 104 has a connecting portion 108 having a through hole 109 in which a pin may be disposed for coupling the piston rod 104 to a moveable member, such as a control surface of an aircraft or a rotor blade of a helicopter.

[0021] In the exemplary embodiment, the cylinder assembly 102 may include a primary cylinder 200 and a secondary cylinder 202. The primary cylinder 200 is separate from the secondary cylinder 202.

[0022] The primary cylinder 200 may have a flange 204 and the secondary cylinders 202 may have respective flanges 206. The flanges 204 are coupled to the flanges 206 via a number of fasteners (e.g., bolts), such as fasteners 208, arranged in a circular array about the cylinder assembly 102. Advantageously, because the cylinder assembly 102 comprises two separate cylinders, if one of the two cylinders (e.g., the primary cylinder 200) is damaged, the other cylinder (e.g., the secondary cylinder 202) can continue to operate.

[0023] Figure 2 illustrates a cross-sectional side view of an exemplary embodiment of actuator 100, and Figure 3 illustrates another cross-sectional side view of actuator 100, according to an exemplary embodiment. The cross section in Figure 3 is along a plane that is perpendicular to the plane of the cross section in Figure 2.

[0024] The actuator 100 includes a central gland 300 located at the interface between the primary cylinder 200 and the secondary cylinder 202. In one example, the central gland 300 may include two portions, a first gland portion 302 and a second gland portion 304. The central gland 300 separates the primary cylinder 200 and the secondary cylinder 202 and is coupled to the primary cylinder 200 and the secondary cylinder 202 via fasteners (e.g., fasteners 208) that couple the primary cylinder 200 to the secondary cylinder 202.

[0025] The central gland 300 acts as a seal support. For example, the central gland 300 may have a number of internal annular grooves in which seals (e.g., O-rings, T-seals, etc.) may be placed. This allows for the movement of a slidable component, e.g., a piston, relative to the central gland 300 while sealing the fluid chambers from one another. Additionally, as described in more detail below, the central gland 300 isolates a first system that controls the primary piston from a second system that controls the secondary piston.

[0026] The primary cylinder 200 and the secondary cylinder 202 together define an internal cylindrical cavity within which a primary piston 306 and a secondary piston 308 are at least partially disposed. The primary piston 306 and the secondary piston 308 are axially movable within the cylinder assembly 102.

[0027] Both the primary piston 306 and the secondary piston 308 are hollow. In particular, the primary piston 306 has a cylindrical longitudinal cavity formed therein within which a portion of the secondary piston 308 is disposed, and through which a portion of the piston rod 104 is disposed.

[0028] The secondary piston 308 is coupled to the piston rod 104 such that the secondary piston 308 and the piston rod 104 move together. For example, the piston rod 104 may have a thread formed on its outer surface at its proximal end, and the secondary piston 308 may have a corresponding thread formed on its inner surface at its distal end. Thus, the piston rod 104 may be threadedly coupled to the secondary piston 308 at a threaded region 309.

[0029] Additionally, a proximal end of the primary piston 306 rests against or is coupled to a shoulder 310 formed by the secondary piston 308, while a distal end of the primary piston 306 is coupled to the piston rod 104. Thus, the primary piston 306, the secondary piston 308, and the piston rod 104 move together. In particular, when a force is applied to the primary piston 306, such force is also transferred to the secondary piston 308 and the piston rod 104. When a force is applied to the secondary piston 308, such force is also transferred to the primary piston 306 and the piston rod 104.

[0030] The primary piston 306 has a piston head 312 against which a fluid acts (i.e., applies a fluid force) to move the primary piston 306. The primary piston 306 is slidably received within the primary cylinder 200 such that the piston head 312 slides along the inner surface of the primary cylinder 200 as the primary piston 306 moves axially.

[0031] As shown in Figures 2-3, a first chamber 314 is defined between or by an outer circumferential surface of the secondary piston 308 and an inner circumferential surface of the primary cylinder 200, and between the piston head 312 and the first gland portion 302. The first chamber 314 is an annular chamber as shown. When pressurized fluid is supplied to the first chamber 314, the primary piston 306 advances. The term "advance" or "advancement" is used herein to refer to motion in a distal direction (e.g., to the right as viewed in Figures 2-3), whereas the term "retract" or "retraction" is used herein to refer to motion in a proximal direction (e.g., to the left as viewed in Figures 2-3).

[0032] Furthermore, a second chamber 316 is defined between or by the outer circumferential surface of the primary piston 306 and the inner circumferential surface of the primary cylinder 200, and between the piston head 312 and the end gland 318. This second chamber 316 is also an annular chamber. When pressurized fluid is supplied to the second chamber 316, the primary piston 306 retracts.

[0033] The end gland 318 is disposed between the primary piston 306 and the primary cylinder 200 at the distal end of the primary cylinder 200. The end gland 318 may have an internal annular groove in which a seal is disposed. Thus, the primary piston 306 can move or slide axially relative to the end gland 318 while the seal prevents leakage from the second chamber 316 to the environment outside the actuator 100. The second chamber 316 is referred to as a retract chamber because when pressurized fluid is supplied to the second chamber 316, the primary piston 306 retracts.

[0034] The actuator 100 includes a first port 320 formed in the primary cylinder 200 and configured to supply fluid to and receive fluid from the first chamber 314. The actuator 100 also includes a second port 322 formed in the primary cylinder 200 and configured to supply fluid to and receive fluid from the second chamber 316.

[0035] For example, when pressurized fluid is supplied from a fluid source (e.g., a pump) through the first port 320 to the first chamber 314, the fluid exerts a fluid force in a distal direction on the piston head 312, advancing (moving distally) the primary piston 306. Fluid expelled from the second chamber 316 as the primary piston 306 advances flows through the second port 322, for example, to a fluid reservoir.

[0036] On the other hand, when pressurized fluid is supplied from the fluid source through the second port 322 to the second chamber 316, the fluid exerts a fluid force on the piston head 312 in a proximal direction, allowing the primary piston 306 to retract (i.e., move in a proximal direction) until it reaches the first gland portion 302 of the central gland 300 (i.e., bottoming of the primary piston 306 during retraction occurs when the primary piston 306 reaches the first gland portion 302).

[0037] Fluid expelled from the first chamber 314 as the primary piston 306 retracts flows to the fluid reservoir through the first port 320. As described above, movement of the primary piston 306 causes movement of the piston rod 104 and secondary piston 308 with the primary piston 306.

[0038] 3, the outer diameter of the piston head 312 of the primary piston 306 (or the inner diameter of the primary cylinder 200) is designated "D1," while the outer diameter of the remainder of the primary piston 306 is designated "D2." The outer diameter of the secondary piston 308 through the portion defining the first chamber 314 is also equal to D2. With this configuration, the annular surface area of ​​the primary piston 306 in the first chamber 314 against which fluid acts to advance the primary piston 306 is equal to the annular surface area of ​​the primary piston 306 in the second chamber 316 against which fluid acts to retract the primary piston 306.

[0039] Thus, the primary piston 306 is balanced, i.e., the fluid force acting on the primary piston 306 when advancing is equal to the fluid force acting on the primary piston 306 when retracting. The pressure level of the supply fluid supplied to the first chamber 314 is defined as P S , the return fluid in the second chamber 316 (fluid discharged from the second chamber 316) is P R Assuming that, whether the primary piston 306 is moving forward or backward, the fluid force acting on the primary piston 306 is

number

[0040] The primary cylinder 200, primary piston 306 and assigned fluid chambers can be considered as a first system that controls the advancement and retraction of the piston rod 104. The actuator 100 further includes a second system that includes a secondary piston 308 and assigned fluid chambers that (via the secondary piston 308) control the advancement and retraction of the piston rod 104. Thus, the actuator 100 is a dual system actuator in that if one system is not operational, the other system can still safely operate the moveable member (e.g., an aircraft control surface or rotor) controlled by the actuator 100.

[0041] The secondary piston 308 has a piston head 324 against which the fluid acts (i.e., applies a fluid force) to move the secondary piston 308. The secondary piston 308 is slidably received within the secondary cylinder 202 such that the piston head 324 slides along the inner surface of the secondary cylinder 202 as the secondary piston 308 moves axially.

[0042] The secondary piston 308 is hollow and includes a cylindrical longitudinal cavity formed therein, as shown in Figures 2-3. The actuator 100 includes a balance tube 326, an inner cylinder 328, and a stationary piston 330, each of which is at least partially contained within the cylindrical longitudinal cavity of the secondary piston 308.

[0043] The stationary piston 330 is coupled to the secondary cylinder 202 such that the stationary piston 330 remains fixed or immovably disposed within the secondary cylinder 202. For example, the proximal end of the stationary piston 330 may be threaded into the secondary cylinder 202 or may be retained in the secondary cylinder 202 by a retaining ring.

[0044] The balance tube 326 is coupled to the stationary piston 330 via a retaining ring 332 (e.g., a wire ring or a retaining O-ring), which also keeps the balance tube 326 stationary. The inner cylinder 328 is slidable around the outer surface of the stationary piston 330. In particular, the inner cylinder 328 is slidably received between the balance tube 326 and the stationary piston 330 such that the inner cylinder 328 can move axially relative to the balance tube 326 and the stationary piston 330.

[0045] A force balance chamber 334 is formed between the outer circumferential surface of the stationary piston 330 and the inner circumferential surface of the inner cylinder 328, between the enlarged distal end 335 of the stationary piston 330 and the proximal end 336 of the inner cylinder 328. The proximal end 336 of the inner cylinder 328 has an outer groove and an inner groove in which a seal can be placed to prevent fluid leakage from the force balance chamber 334 as the inner cylinder 328 moves axially around the outer surface of the stationary piston 330. As shown in Figures 2-3, the balance tube 326 is interposed (radially) between the inner cylinder 328 and the secondary piston 308. The secondary piston 308 is configured to move axially around the outer surface of the balance tube 326 as the secondary piston 308 advances or retreats.

[0046] 2-3, a third chamber 338 is defined between or between the outer circumferential surface of the balance tube 326 and the inner circumferential surface of the secondary cylinder 202, and between the piston head 324 and the inner proximal surface of the secondary cylinder 202. A fourth chamber 340 is defined between or between the outer circumferential surface of the secondary piston 308 and the inner circumferential surface of the secondary cylinder 202, and between the piston head 324 and the second gland portion 304 of the central gland 300.

[0047] Both the third chamber 338 and the fourth chamber 340 are annular. When pressurized fluid is supplied to the third chamber 338, the secondary piston 308 advances. On the other hand, when pressurized fluid is supplied to the fourth chamber 340, the secondary piston 308 retracts.

[0048] The piston head 324 may have an exterior annular groove in which a seal is disposed such that the secondary piston 308 can move or slide axially while preventing leakage between the fourth chamber 340 and the third chamber 338.

[0049] The actuator 100 further includes a third port 342 defined in the secondary cylinder 202 and configured to supply fluid to and receive fluid from the third chamber 338. The actuator 100 also includes a fourth port 344 defined in the secondary cylinder 202 and configured to supply fluid to and receive fluid from the fourth chamber 340.

[0050] When pressurized fluid is supplied to the third chamber 338 through the third port 342, the fluid exerts a fluid force on the piston head 324 in a distal direction, causing the secondary piston 308 to advance (move distally). The secondary piston 308 may advance (i.e., move distally) until it reaches the second gland portion 304 of the central gland 300 (i.e., bottoming of the advancing secondary piston 308 occurs when the secondary piston 308 reaches the second gland portion 304). Fluid expelled from the fourth chamber 340 as the secondary piston 308 advances flows through the fourth port 344 to the fluid reservoir.

[0051] On the other hand, when pressurized fluid is supplied to the fourth chamber 340 through the fourth port 344, the fluid exerts a fluid force in a proximal direction on the piston head 324, causing the secondary piston 308 to retract (move proximally). Fluid expelled from the third chamber 338 as the secondary piston 308 retracts flows through the third port 342 to the fluid reservoir. As described above, movement of the secondary piston 308 causes movement of the piston rod 104 and primary piston 306 with it.

[0052] 3, the outer diameter of the piston head 324 of the secondary piston 308 (or the inner diameter of the secondary cylinder 202) is designated "D1" and the outer diameter of the remainder of the secondary piston 308 is designated "D2". The outer diameter of the balance tube 326 is designated "D3" which is smaller than D2. This configuration allows the annular surface area of ​​the secondary piston 308 in the third chamber 338 against which fluid acts to advance the secondary piston 308 to be greater than the annular surface area of ​​the secondary piston 308 in the fourth chamber 340 against which fluid acts to retract the secondary piston 308. Thus, the forward fluid force exerted by the fluid in the third chamber 338 to advance the secondary piston 308 is different from the retraction fluid force exerted by the fluid in the fourth chamber 340 to retract the secondary piston 308.

[0053] The pressure level of the fluid supplied to the third chamber 338 to advance the secondary piston 308 is defined as P S , the pressure level in the fourth chamber 340 is P R Assuming that, the forward fluid force acting on the secondary piston 308 in the distal direction is:

number

number

[0054] Since D2 is greater than D3, the forward fluid force is greater than the backward fluid force, i.e., F 2E >F 2R However, the actuator 100 must be configured to balance the secondary piston 308 by F 2E >F 2R The present invention is configured to offset or compensate for the difference between the

[0055] The stationary piston 330 has a first set of cross holes 346, a longitudinal passageway 348 formed therein, and a second set of cross holes 350. The term "hole" is used generally herein to refer to a hollow location (e.g., a cavity) in, for example, a solid object or surface. The term "cross hole" is used herein to include any type of opening (e.g., slot, window, hole, etc.) that intersects the path of or is formed transversely to another hole, cavity, or passageway.

[0056] With this configuration, fluid provided to the third chamber 338 is communicated to the force balancing chamber 334 through the first set of cross holes 346, the longitudinal passage 348, and the second set of cross holes 350. Thus, when the pressurized fluid in the third chamber 338 exerts a fluid force in a distal direction on the secondary piston 308, it also exerts a force in a proximal direction on the inner cylinder 328. The inner cylinder 328 is coupled to the secondary piston 308, such that a force acting on the inner cylinder 328 in a proximal direction is transferred to the secondary piston 308, which resists a fluid force acting on the secondary piston 308 in a distal direction.

[0057] The inner cylinder 328 is locked to the secondary piston 308. Any locking or coupling mechanism may be used. Thus, an axial force applied to the inner cylinder 328 is transferred to the secondary piston 308 and vice versa. Additionally, the actuator 100 may have an anti-rotation feature (e.g., a pin) that prevents the primary piston 306 from rotating relative to the secondary piston 308 when both pistons move axially within the cylinder assembly 102.

[0058] Referring again to Figure 3, the inner diameter of the inner cylinder 328 is designated "D4" and the outer diameter of the stationary piston 330 is designated "D5." Referring together to Figures 2-3, during forward movement of the secondary piston 308, the fluid communicated to the force balancing chamber 334 exerts a fluid force in a proximal direction on the proximal end 336 of the inner cylinder 328. The fluid force acting in a proximal direction on the inner cylinder 328 is sometimes referred to as a balancing force,

number

[0059] In particular, the inner cylinder 328 and the stationary piston 330 are balanced by D4 and D5, respectively. B F 2E and F 2R In other words, F B =F 2E -F 2R It is.

[0060] Thus, the secondary piston 308 is balanced. As the secondary piston 308 advances, a balancing force F B is the forward force F 2E This resists the F 2E is reduced, and the retraction force F 2R is equal to

[0061] In the exemplary embodiment shown in the drawings, pressurized fluid provided to the third chamber 338 is communicated to the force balance chamber 334 to resist forward movement of the secondary piston 308, although other configurations are possible. For example, rather than communicating fluid from the third chamber 338 to the force balance chamber 334, the actuator 100 may be configured such that fluid from the fourth chamber 340 is communicated to the force balance chamber 334. In this example, as the secondary piston retracts, a counterbalance force F applied to the inner cylinder 328 via the fluid in the force balance chamber 334 is B The retraction force F of the fluid in the fourth chamber 340 2R This results in an additive force that is added to F B +F 2R =F 2E It becomes.

[0062] Thus, the actuator 100 may be configured to supply fluid to the force balancing chamber 334 from the third chamber 338 or the fourth chamber 340. In the first case, the force acting on the inner cylinder 328 is proportional to the forward force F acting on the secondary piston 308. 2E In the second case, the force acting on the inner cylinder 328 resists the retraction force F acting on the secondary piston 308. 2R is added to.

[0063] Thus, the actuator 100 is configured as a dual-path actuator. If the first path stops working under some conditions, the second path can continue to work to move the piston rod 104. Thus, the actuator 100 provides redundancy. Furthermore, the force applied to the secondary piston 308 is added to the force applied to the primary piston 306. In other words, to advance both the primary piston 306 and the secondary piston 308, pressurized fluid can be simultaneously supplied to the first chamber 314 and the third chamber 338, whereby the forces applied to the piston rod 104 by both pistons 306, 308 are added together. Similarly, to retract both the primary piston 306 and the secondary piston 308, pressurized fluid can be simultaneously supplied to the second chamber 316 and the fourth chamber 340, whereby the forces applied to the piston rod 104 by both pistons 306, 308 are added together.

[0064] The configuration of the actuator 100 may provide numerous advantages over existing actuators. For example, the actuator 100 has two systems for redundancy. A first hydraulic system (e.g., first chamber 314, second chamber 316, first port 320, second port 322, etc.) actuates a primary piston 306 to move the piston rod 104. At the same time, a second hydraulic system (e.g., third chamber 338, fourth chamber 340, third port 342, fourth port 344, etc.) actuates a secondary piston 308 coupled to the piston rod 104 and the primary piston 306. If one system is damaged, the other system can continue to operate, thus providing a redundant configuration.

[0065] Furthermore, the actuator 100 is constructed such that damage to one system cannot propagate to the other system. For example, the primary cylinder 200 is separate from the secondary cylinder 202. Therefore, damage to one cylinder will not damage the other cylinder. In particular, if there is a crack in one cylinder, such a crack will not propagate to the other cylinder because the two cylinders are separated by the central gland 300, which is composed of two separate parts (i.e., the first gland part 302 and the second gland part 304). In other words, the crack is blocked. Similarly, the primary piston 306 is a separate component from the secondary piston 308. Therefore, if there is damage or a crack in one piston, such a crack will not propagate to the other piston.

[0066] In one example, the end gland 318 may be configured as a frangible gland or component. Thus, if the end gland 318 is damaged when the primary piston 306 moves, the end gland 318 may be disrupted (e.g., crushed) so that the primary piston 306 does not get stuck. Even if the end gland 318 is damaged, causing leakage and failure of the hydraulic system controlling the primary piston 306, the hydraulic system controlling the secondary piston 308 continues to operate, thereby allowing the secondary piston 308 to safely position the piston rod 104. Similarly, the first gland portion 302 and the second gland portion 304 of the central gland 300 may be formed as frangible components.

[0067] In one example, one of the cylinders 200, 202 may be armored (e.g., formed from thick-walled hardened steel capable of withstanding ballistic objects) to provide additional protection against ballistic fragments that may damage the actuator 100. By armoring one cylinder instead of both cylinders, the weight of the actuator 100 is reduced. At the same time, if the unarmored cylinder is damaged, the armored cylinder can continue to protect its respective piston and hydraulic system, thereby allowing the actuator 100 to continue functioning.

[0068] Additionally, the configuration of actuator 100 with at least partially concentric pistons allows actuator 100 to be stiffer as compared to actuators having three side-by-side pistons. The higher stiffness allows actuator 100 to be more vibration resistant. Additionally, actuator 100 does not suffer from side load or bending problems associated with three-piston actuators.

[0069] 4 is a flow chart of a method 900 for actuating an actuator according to an example embodiment. For example, the method 900 may be used to actuate the actuator 100.

[0070] Method 900 may include one or more operations or actions as illustrated by one or more of blocks 902-906. Although the blocks are illustrated in a sequential order, the blocks may be performed in parallel and / or in a different order than described herein. Also, various blocks may be combined with one another to form fewer blocks, divided into additional blocks, and / or removed based on the desired embodiment. It will be appreciated that, for the above and other processes and methods disclosed herein, the flow chart illustrates the functions and operations of one possible embodiment of the example. Included within the scope of the examples of the present disclosure are alternative embodiments in which functions may be performed in a different order than illustrated or discussed, such as substantially concurrently or in reverse order, depending on the functionality involved, as would be apparent to one of ordinary skill in the art.

[0071] In block 902, the method 900 includes supplying fluid to a first chamber 314 and a third chamber 338 of an actuator 100 to advance a piston rod 104 of the actuator 100, the actuator 100 comprising a primary piston 306 and a secondary piston 308, the secondary piston 308 coupled to the piston rod 104, the primary piston 306 being fixed to the secondary piston 308 and the piston rod 104, such that the primary piston 306, the secondary piston 308 and the piston rod 104 move axially together, and supplying fluid to the first chamber 314 advances the primary piston 306, and supplying fluid to the third chamber 338 applies a forward fluid force to advance the secondary piston 308.

[0072] In block 904, the method 900 includes supplying fluid to the second chamber 316 and the fourth chamber 340 of the actuator 100 to retract the piston rod 104 of the actuator 100, where by supplying fluid to the second chamber 316, the primary piston 306 is retracted and by supplying fluid to the fourth chamber 340, a retracting fluid force different from the forward fluid force is applied to retract the secondary piston 308.

[0073] In block 906, the method 900 includes supplying fluid from the third chamber 338 or the fourth chamber 340 to the force balancing chamber 334 to apply a balancing force to the secondary piston 308 to resist or add to the fluid forces acting on the secondary piston 308, thereby compensating for the difference between the forward and reverse fluid forces.

[0074] The method may include other operations as described herein.

[0075] In the above detailed description, various features and operations of the disclosed system are explained with reference to the accompanying drawings. The illustrative embodiments described herein are not meant to be limiting. Certain aspects of the disclosed system may be arranged and combined in a wide variety of configurations, all of which are contemplated herein.

[0076] Moreover, unless the context suggests otherwise, features shown in each drawing may be used in combination with one another. Thus, the drawings should be considered generally as component aspects of one or more overall embodiments, and it should be understood that not all illustrated features are required for each embodiment.

[0077] Moreover, any recitation of elements, blocks, or steps in the specification or claims is for the purpose of clarity, and thus such recitation should not be construed as requiring or implying that these elements, blocks, or steps be adhered to in a particular arrangement or performed in a particular order.

[0078] Further, the device or system may be used or configured to perform the functions presented in the figures. In some cases, the components of the device and / or system may be configured to perform the functions, whereby the components are in fact configured and organized (with hardware and / or software) to enable such performance. In other examples, the components of the device and / or system may be adapted to perform a function, enable performance of a function, or be arranged such that they are suitable for performing a function, e.g., when operated in a particular manner.

[0079] The term "substantially" means that the recited characteristic, parameter or numerical value need not be achieved exactly, but rather deviations or variations including, for example, tolerances, measurement errors, measurement accuracy limits and other factors known to those skilled in the art may occur to an extent that does not interfere with the effect that the characteristic is intended to provide.

[0080] The arrangements described herein are for purposes of example only. Thus, one of ordinary skill in the art will recognize that other arrangements and other elements (e.g., machines, interfaces, operations, sequences and groupings of operations, etc.) may be used instead, and some elements may be omitted entirely, depending on the results desired. Furthermore, many of the described elements are functional entities that may be configured as separate or distributed components or in any suitable combination and location with other components.

[0081] Although various aspects and embodiments have been disclosed herein, other aspects and embodiments should be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for illustrative purposes only and are not intended to be limiting, with the true scope being set forth in the following claims and the full scope of equivalents to which such claims are entitled. Additionally, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting.

[0082] Accordingly, embodiments of the present disclosure may relate to one of the exemplary embodiments (EEE) listed below.

[0083] The EEE1 is an actuator including a primary piston at least partially disposed within a cylinder assembly, a secondary piston at least partially disposed within the cylinder assembly, the primary and secondary pistons configured for axial movement together within the cylinder assembly, and a plurality of chambers formed within the cylinder assembly, the plurality of chambers including: (i) a first chamber, where a flow of fluid into the first chamber advances the primary piston, (ii) a second chamber, where a flow of fluid into the second chamber retracts the primary piston, and (iii) a third chamber, where a flow of fluid into the third chamber advances the secondary piston, and and (iv) a fourth chamber, in which a flow of fluid into the fourth chamber causes the secondary piston to retract, wherein a forward fluid force exerted by the fluid in the third chamber to advance the secondary piston is different from a retraction fluid force exerted by the fluid in the fourth chamber to retract the secondary piston; and a force balancing chamber configured to receive fluid from the third chamber or the fourth chamber and apply a balancing force to the secondary piston to resist or add to the fluid force acting on the secondary piston, thereby compensating for a difference between the forward fluid force and the retraction fluid force.

[0084] EEE2 is an actuator as described in EEE1, wherein the cylinder assembly comprises a primary cylinder and a secondary cylinder coupled to the primary cylinder, the primary and secondary cylinders forming a cylindrical longitudinal cavity within which the primary and secondary pistons can move axially.

[0085] EEE3 is an actuator as described in EEE2, wherein the primary cylinder has a flange, the secondary cylinders have respective flanges, and the actuator further comprises a central gland disposed between the flange of the primary cylinder and each of the flanges of the secondary cylinder, and a plurality of fasteners connecting the flange of the primary cylinder, the flanges of each of the secondary cylinders, and the central gland to one another.

[0086] EEE4 is an actuator as described in EEE3, in which the central gland comprises a first gland portion which interacts with a flange of the primary cylinder and a second gland portion separate from the first gland portion which interacts with each flange of the secondary cylinder.

[0087] EEE5 is the actuator of any one of EEE1 to 4, wherein the actuator further comprises a piston rod coupled to a secondary piston partially disposed within the cylinder assembly, and the primary piston is fixed between the secondary piston and the piston rod, whereby the primary piston, secondary piston and piston rod move together in the axial direction.

[0088] EEE6 is the actuator of any one of EEE1 to 5, wherein the actuator further comprises a stationary piston coupled to the cylinder assembly so as to remain fixed, and an inner cylinder coupled to the secondary piston and slidable around an outer surface of the stationary piston, and a force balancing chamber is formed between the outer surface of the stationary piston and the inner surface of the inner cylinder, whereby a balancing force is applied to the inner cylinder, which transmits the balancing force to the secondary piston.

[0089] EEE7 is the actuator described in EEE6, wherein the force balancing chamber is fluidly connected to the third chamber via a longitudinal passage and one or more intersecting holes formed in the stationary piston, whereby as the secondary piston advances the force balancing chamber receives fluid from the third chamber and the fluid in the force balancing chamber applies a balancing force to the secondary piston to resist the forward fluid force being applied to the secondary piston by the fluid in the third chamber.

[0090] EEE8 is the actuator of EEE6 or 7, wherein the force balancing chamber is fluidly connected to the fourth chamber, whereby as the secondary piston retracts, the force balancing chamber receives fluid from the fourth chamber and the fluid in the force balancing chamber applies a balancing force to the secondary piston as an additive force to the retraction fluid force being applied to the secondary piston by the fluid in the fourth chamber.

[0091] EEE9 is the actuator of any one of EEE6 to 8, wherein the actuator further comprises a balance tube radially interposed between the inner cylinder and the secondary piston coupled to the stationary piston, the secondary piston being configured to move axially around the outer surface of the balance tube when the secondary piston advances or retracts.

[0092] EEE10 provides a method for advancing a piston rod of an actuator by supplying fluid to a first chamber and a third chamber, the actuator comprising a primary piston and a secondary piston, the secondary piston coupled to the piston rod, the primary piston being fixed to the secondary piston and the piston rod, whereby the primary piston, secondary piston and piston rod move together in an axial direction, and by supplying fluid to the first chamber, the primary piston is advanced, and by supplying fluid to the third chamber, an advancing fluid force is applied to advance the secondary piston. supplying fluid to a second chamber and a fourth chamber of the actuator to retract a piston rod of the actuator, where supplying fluid to the second chamber retracts a primary piston and supplying fluid to the fourth chamber applies a retracting fluid force different from the forward fluid force to retract the secondary piston; and supplying fluid from the third or fourth chamber to a force balancing chamber to apply a balancing force to the secondary piston to resist or add to the fluid forces acting on the secondary piston, thereby compensating for a difference between the forward and retracting fluid forces.

[0093] EEE11 is the method of EEE10, wherein the actuator further comprises: (i) a cylinder assembly capable of axially moving the primary and secondary pistons therein; (ii) a stationary piston coupled to the cylinder assembly such that it remains fixed; and (iii) an inner cylinder coupled to the secondary piston and slidable around an outer surface of the stationary piston; and wherein applying a counterbalancing force to the secondary piston includes applying a counterbalancing force to the inner cylinder, which transmits the counterbalancing force to the secondary piston.

[0094] EEE12 is the method of EEE11, wherein supplying fluid to the force balancing chamber includes supplying fluid from the third chamber to the force balancing chamber through one or more intersecting holes and longitudinal passages formed in the stationary piston as the secondary piston advances, and applying a balancing force to the secondary piston to resist a forward fluid force being applied to the secondary piston by the fluid in the third chamber.

[0095] EEE13 is the method of EEE11 or 12, wherein supplying fluid to the force balancing chamber includes supplying fluid from a fourth chamber to the force balancing chamber when the secondary piston retracts, and applying a balancing force to the secondary piston as an additive force to the retraction fluid force being applied to the secondary piston by the fluid in the fourth chamber.

Claims

1. An actuator, a primary piston disposed at least partially within the cylinder assembly; a secondary piston disposed at least partially within the cylinder assembly, the primary piston and the secondary piston configured for axial movement together within the cylinder assembly; a plurality of chambers formed within the cylinder assembly, the plurality of chambers comprising: (i) a first chamber, wherein a flow of fluid into the first chamber advances the primary piston; (ii) a second chamber, wherein a flow of fluid into the second chamber advances the primary piston; (iii) a third chamber, wherein a flow of fluid into the third chamber advances the secondary piston; and (iv) a fourth chamber, wherein a flow of fluid into the fourth chamber advances the secondary piston; and wherein a forward fluid force exerted by fluid in the third chamber to advance the secondary piston is different from a backward fluid force exerted by fluid in the fourth chamber to retract the secondary piston; a force balancing chamber configured to receive fluid from the third chamber or the fourth chamber and apply a balancing force to the secondary piston to resist or add to the fluid forces acting on the secondary piston, thereby compensating for a difference between the forward fluid force and the reverse fluid force; An actuator comprising:

2. The cylinder assembly includes: A primary cylinder; a secondary cylinder coupled to the primary cylinder; Equipped with the primary cylinder and the secondary cylinder defining a cylindrical longitudinal cavity within which the primary piston and the secondary piston may move axially; The actuator of claim 1.

3. the primary cylinder having a flange and the secondary cylinder having respective flanges; The actuator comprises: a central gland disposed between the flange of the primary cylinder and each of the flanges of the secondary cylinder; a plurality of fasteners connecting the flange of the primary cylinder, each of the flanges of the secondary cylinder, and the central gland together; The actuator of claim 2 further comprising:

4. The central gland is a first gland portion that interfaces with the flange of the primary cylinder; a second gland portion separate from the first gland portion, the second gland portion interacting with each of the flanges of the secondary cylinder; The actuator of claim 3 comprising:

5. 2. The actuator of claim 1, further comprising a piston rod coupled to the secondary piston disposed partially within the cylinder assembly, the primary piston being fixed between the secondary piston and the piston rod such that the primary piston, the secondary piston and the piston rod move axially together.

6. The actuator comprises: a stationary piston coupled to said cylinder assembly so as to remain fixed; an inner cylinder coupled to the secondary piston and slidable on an outer surface of the stationary piston; Further equipped with the force balancing chamber is formed between the outer surface of the stationary piston and the inner surface of the inner cylinder, whereby the balancing force is applied to the inner cylinder, which in turn transmits the balancing force to the secondary piston; The actuator of claim 1.

7. 7. The actuator of claim 6, wherein the force balancing chamber is fluidly connected to the third chamber through a longitudinal passageway and one or more cross holes formed in the stationary piston, whereby as the secondary piston advances, the force balancing chamber receives fluid from the third chamber and the fluid in the force balancing chamber exerts the balancing force on the secondary piston to resist the forward fluid force being exerted on the secondary piston by the fluid in the third chamber.

8. 7. The actuator of claim 6, wherein the force balancing chamber is fluidly connected to the fourth chamber, whereby as the secondary piston retracts, the force balancing chamber receives fluid from the fourth chamber and the fluid in the force balancing chamber applies the balancing force to the secondary piston as an additive force to the retraction fluid force being applied to the secondary piston by the fluid in the fourth chamber.

9. 7. The actuator of claim 6, further comprising a balance tube coupled to the stationary piston and radially interposed between the inner cylinder and the secondary piston, the secondary piston configured to move axially on an outer surface of the balance tube as the secondary piston advances or retracts.

10. supplying fluid to a first chamber and a third chamber of an actuator to advance a piston rod of the actuator, the actuator comprising a primary piston and a secondary piston, the secondary piston coupled to the piston rod, the primary piston fixed to the secondary piston and the piston rod, whereby the primary piston, the secondary piston and the piston rod move axially together, supplying fluid to the first chamber advances the primary piston, and supplying fluid to the third chamber applies an advancing fluid force to advance the secondary piston; supplying fluid to a second chamber and a fourth chamber of the actuator to retract the piston rod of the actuator, where supplying fluid to the second chamber retracts the primary piston and supplying fluid to the fourth chamber applies a retracting fluid force different from the forward fluid force to retract the secondary piston; supplying fluid from the third chamber or the fourth chamber to a force balancing chamber to apply a balancing force to the secondary piston to resist or add to the fluid forces acting on the secondary piston, thereby compensating for a difference between the forward fluid force and the reverse fluid force; A method comprising:

11. the actuator further comprises: (i) a cylinder assembly capable of axially moving the primary piston and the secondary piston therein; (ii) a stationary piston coupled to the cylinder assembly so as to remain fixed; and (iii) an inner cylinder coupled to the secondary piston and slidable on an outer surface of the stationary piston; applying the balancing force to the secondary piston includes applying the balancing force to an inner cylinder, the inner cylinder transmitting the balancing force to the secondary piston. The method of claim 10.

12. Providing a fluid to the force balancing chamber comprises: supplying fluid from the third chamber through one or more cross holes and longitudinal passages formed in the stationary piston to the force balance chamber as the secondary piston advances; applying a counterbalancing force to the secondary piston to resist the forward fluid force being applied to the secondary piston by the fluid in the third chamber. The method of claim 11 , comprising:

13. Providing a fluid to the force balancing chamber comprises: supplying fluid from the fourth chamber to the force balancing chamber when the secondary piston retracts; applying the balancing force to the secondary piston as an additive force to the retracting fluid force being applied to the secondary piston by the fluid in the fourth chamber. The method of claim 11 , comprising:

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