236 secures the first piston head 212 against a second seat 240. For example, the second retainer 236 can include snap rings, circlips, piston pins, etc. The second seat 240 is a ledge formed in the piston rod 160. In other examples the first piston head 212 and the piston rod 160 can be coupled in other ways, including being formed with the piston rod 160.

The second piston head 216 is positioned within the second interior space 202. The second piston head 216 subdivides the second interior space 202 to define a third chamber 232 between the second piston head 216 and the first wall 192 and a fourth chamber 260 between the second piston head 216 and the third wall 200. For example, the third chamber 232 can increase in size as the second piston head 216 moves in the first direction with the piston rod 160 and can decrease in size as the second piston head 216 moves in the second direction with the piston rod 160, or vice versa. Correspondingly, the fourth chamber 260 can decrease in size as the first piston head 212 moves in the first direction and can increase in size as the first piston head 212 moves in the second direction, or vice versa. The second piston head 216 is shown being monolithically formed with the piston rod 160. In other examples, the second piston head 216 can be attached to the piston rod 160 by a fastener, press-fit connection, threaded connection, etc.

Seals can be used to prevent leakage between chambers of a hydraulic actuator. Here, the first piston head 212 includes a seal 224 (e.g., a first seal) to seal against the cylinder 152 wall to prevent leakage between the first chamber 228 and the second chamber 229. Similarly, the second piston head 216 includes a seal 220 (e.g., a second seal) to seal against the cylinder 152 wall to prevent leakage between the third chamber 232 and the fourth chamber 260. The seals 220 and 224 may be O-rings, hydraulic seals, or guide rings. The piston rod 160 extends through the first piston head 212 and the first wall 192.

The first chamber 228 and the third chamber 232 are fluidly coupled to one another. FIGS. 3-4 show an illustrated example in the piston assembly. A first passage 244 is defined between the first chamber 228 and the third chamber 232. The first passage 244 is located within the piston rod 160. The first passage 244 port in the first chamber 228 can be located next to the second retainer 236, as may ensure the passage 244 port remains in the first chamber 228. The first passage 244 port in the third chamber 232 can be located next to the second piston head 216, as may ensure the passage 244 port remains in the third chamber 232. The first passage 244 can be a high-pressure communication line. The first chamber 228 is in fluid communication with a pump passage 248. The pump passage 248 can pump hydraulic fluid into the first chamber 228. For example, as hydraulic fluid is pumped into the first chamber 228, pressure begins to increase in the first chamber 228. The pressure of the hydraulic fluid acts on the surface area of the first chamber 228 generating a force. The force moves the piston assembly (i.e., the piston rod 160, the first piston head 212, and the second piston head 216) in the first direction. In other examples, the first passage 244 connecting the first chamber 228 to the third chamber 232 can positioned differently, for example, in the cylinder 152 or as external hose connection.

The hydraulic cylinder arrangement includes the second chamber 229. The second chamber 229 is defined within the first interior space 201. The second chamber 229 is between the first wall 192 and the first piston head 212. In some examples, the second chamber 229 is a first flooded chamber that retains hydraulic fluid. For example, as the piston assembly moves in a first direction (e.g., towards the third wall 200), the second chamber 229 decreases in volume. As the second chamber 229 decreases in volume, fluid pressure needs to be relieved to allow continued movement of the piston.

The hydraulic cylinder arrangement includes the fourth chamber 260. The fourth chamber 260 is defined within the second interior space 202. The fourth chamber 260 is between the second piston head 216 and the third wall 200. In some examples, the fourth chamber 260 is a second flooded chamber that retains hydraulic fluid. The fourth chamber 260 is in fluid communication with a tank passage 256. As the piston assembly moves in the first direction (e.g., towards the third wall 200), the fourth chamber 260 decreases in volume. As fourth chamber 260 is decreasing in volume, pressure is relieved by hydraulic fluid flowing through the tank passage 256.

Referring again to the illustrated examples in FIG. 3 and FIG. 4, the second chamber 229 and the fourth chamber 260 are fluidly coupled to one another. A second passage 264 is defined between the second chamber 229 and the fourth chamber 260. The second passage 264 is located within the piston rod 160. The second passage 264 port in the second chamber 229 is located on the piston rod 160 between the first piston head 212 and the first wall 192. The second passage 264 port for the fourth chamber 260 is located on the second piston head 216. The second passage 264 can be a low-pressure communication line. For example, as the second chamber 229 builds up pressure when the piston assembly moves in the first direction (e.g., towards the third wall 200), hydraulic fluid enters the second passage 264 and flows to the fourth chamber 260. Further, as the pressure increases in the fourth chamber 260 the hydraulic fluid enters the tank passage 256. The hydraulic fluid flows to the pump passage 248 and is repumped into the first chamber 228. This process may continue until the piston assembly has completed motion in the first direction. In some cases, motion in the first direction corresponds to retraction of the piston assembly, and a second direction corresponds to extension of the piston assembly, or vice versa. In other examples, the second passage 264 connecting the second chamber 229 to the fourth chamber 260 can positioned differently, for example, in the cylinder 152 or as external hose connection.

In some examples, a first spring 268 is optionally disposed within the fourth chamber 260. In some examples, a second spring 272 is optionally disposed within the second chamber 229. For example, as the piston assembly moves in the first direction, the first spring 268 and the second spring 272 are compressed. As the first spring 268 and the second spring 272 are compressed, they store potential energy. The potential energy is converted into kinetic energy to move the piston assembly in the second direction. As the first spring 268 and second spring 272 move the piston assembly in the second direction, the third chamber 232 decreases in size and builds up pressure. The pressure in the third chamber 232 is relieved through the first passage 244. The hydraulic fluid flows through the first passage 244 to the first chamber 228. The hydraulic fluid flows back through the pump passage 248 to the tank passage 256 and enters the fourth chamber 260. Additionally, hydraulic fluid flows from the fourth chamber 260 to the second chamber 229 through the second passage 264 to replenish the hydraulic fluid that was evacuated during the movement in first direction. This process is continued until the first spring 268 and second spring 272 are fully extended and the piston assembly has returned to the starting position.

FIG. 5 illustrates an example hydraulic actuator 300, which is another example of the hydraulic actuator 136 for use with the hydraulic tool 100 of FIG. 1. To that end, features of the hydraulic actuator 300 described below include reference numbers that are similar to those used in FIGS. 1-4, and discussion above applies to similar named and numbered items below, unless otherwise noted or required. For example, the hydraulic actuator 300 includes a piston 156 that is received in a hydraulic cylinder 152. The piston 156 includes a first piston head 212 and a second piston head 216.

In some examples, a hydraulic cylinder can be formed from multiple cylinder portions for easier assembly. For example, the hydraulic actuator 300 includes the cylinder 152 formed from a first cylinder 304 and a second cylinder 308 that are coupled together. The first cylinder 304 defines a first end 312 of the hydraulic actuator 300. More specifically, the first cylinder 304 includes an open end 316 and a closed end 320 (e.g., end wall). Correspondingly, the first cylinder 304 defines the first interior space 201 to receive the first piston head 212. The second cylinder defines a second end 324 of the hydraulic cylinder 152. More specifically, the second cylinder 308 includes an open end 328 and a closed end 332 and defines the second interior space 202 to receive the second piston head 216. The open end 328 contacts the second wall 196 of the hydraulic cylinder 152 and the closed end 332 corresponds with the first wall 192. The open end 316 of the first cylinder 304 includes a flange 336 to couple (e.g., by treads, press-fit, snap rings, etc.) to the closed end 332 of the second cylinder 308. The closed end 332 of the second cylinder 308 defines an opening 340 through which the piston rod 160 is received.

The piston 156 is movably received in the interior space 188 of the hydraulic cylinder 152. The piston 156 includes the piston rod 160, the first piston head 212, and the second piston head 216. The first piston head 212 is positioned in the first interior space 201 to form the first chamber 228 and the second chamber 229. The second piston head 216 is positioned in the second interior space 202 to form the third chamber 232 and the fourth chamber 260. The first chamber 228 and the third chamber 232 are fluidly coupled with one another. More specifically, the first chamber 228 and the third chamber 232 are coupled by a first passage 244. In the illustrated example, the first passage 244 is defined in the piston rod 160. The first passage 244 can be also positioned elsewhere (e.g. external to the cylinder 152 or in the cylinder wall).

In some examples, a piston can be formed as a multi-piece piston to facilitate assembly. A piston can be formed from a first piston and a second piston that are coupled together and that each include a respective piston head and a piston rod. For example, the piston 156 of the hydraulic actuator 300 is formed from a first piston 344 and a second piston 348 that are coupled together. In the illustrated example, the first piston 344 and the second piston 348 are coupled by a fastener 349. In some cases, the first piston 344 can define a channel 372 and the fastener 349 can be positioned in the channel to couple to the second piston 348. In other examples, other methods of fastening can be used, for example, threading of the first piston 344 to the second piston 348, a pinned connection, press-fit, etc.

The first piston 344 includes the first piston head 212 that is formed as a single piece with a first piston rod 352. The second piston 348 includes the second piston head 216 that is formed as a single piece with a second piston rod 356. The first piston rod 352 is fixedly coupled to the second piston head 216 or the second piston rod 356 so the first piston 344 and the second piston 348 move together. The first piston rod 352 extends though the opening 340 in the first wall 192 (e.g., the closed end 332 of the second cylinder 308). Correspondingly, the first wall 192 includes an annular groove 360 to receive a piston seal 364 to seal against the first piston rod 352. The second piston rod 356 extends out of the cylinder 152 (e.g., through the second wall 196) to engage with and operate a working head of the hydraulic tool 100.

In some examples, a hydraulic cylinder or piston can be configured to allow for two-stage movement to modulate the speed or force output. In some cases, a first stage of extension can be high-speed and low-force while a second stage of extension can be low-speed and high force, or vice versa. For example, a first stage of movement (e.g., extending to a workpiece or retracting from a workpiece) correlates to high speed with low force extension or retraction of the piston, while a second stage of movement (e.g., performing an action on the workpiece) correlates to low speed with high force extension or retraction of the piston. In some examples, the piston can switch between the first stage and second stage when the piston reaches the workpiece.

To allow for different stages of extension, a hydraulic cylinder can include a conduit tube that is fixed to an end wall of the hydraulic cylinder. The conduit tube can direct fluid from a pump (e.g., pump 132) to a channel to define a single chamber or subset of chambers of a hydraulic actuator to enable higher speed extension for a given flow rate of fluid. For the second stage, fluid can be supplied from the pump to some or all of the remaining chambers. To allow switching between stages, the hydraulic actuator can include a valve system (e.g., one or more of a sequence valve, check valve, shear seal valve, etc.).

Still referring to FIG. 5, a conduit tube 368 is fixedly coupled to the first wall 192 of the first cylinder 304. The conduit tube 368 is received in the channel 372 that is defined in the piston rod 160 (e.g., in the first piston rod 352). The channel 372 is configured as a closed channel so that the channel 372 forms a chamber (e.g., a pre-chamber or fifth chamber). Fluid can be supplied to the channel 372 via the conduit tube 368 to cause movement of the piston 156. A seal 384 can be provided between the piston rod 160 and the conduit tube 368 to prevent leakage out of the channel 372 and into the second chamber 229. In the illustrated example, the channel 372 defines an annular groove 380 that receives the seal 384 to seal against the conduit tube 368. In other examples, the seal can be positioned differently (e.g., to be coupled to the conduit tube).

A hydraulic cylinder can include a sequence valve to control fluid flow from the pump to various chambers to control extension. In the illustrated example, the hydraulic actuator 300 includes a sequence valve 396. The sequence valve 396 is moveable between a first position (e.g., closed) and a second position (e.g., open). In the first position, the sequence valve 396 allows fluid to be supplied from the pump 132 through a first inlet 400 to the channel 372, while a second inlet 408 is blocked. In the second position, the sequence valve 396 allows fluid through the first inlet 400 to the channel 372, as well as through second inlet 408 to the first chamber 228. Fluid supplied to the first chamber 228 is also supplied to the third chamber 232 via the first passage 244.

With a sequence valve in a first position, a first stage of fluid flow is provided to a chamber having less than a total acting surface area of a piston so that a piston extends at a higher rate because fluid is supplied to a volume with a smaller cross-sectional area. Therefore, for a given flow rate the piston extends at a higher rate to account for the change in volume. The piston rod 160 defines the channel 372 and the conduit tube 368 is in the channel 372 to define a passage 404 between the first inlet 400 and the channel 372. On a first stage of extension, the sequence valve 396 is in the first position so that the first inlet 400 is open and the second inlet 408 is closed (e.g., by selective blocking of the sequence valve 396). The pump 132 provides fluid through the first inlet 400 into the channel 372 (via the conduit tube 368). As a result, the first piston 344 and the second piston 348 move together in the first direction (e.g., extension toward a workpiece), which increases the volume of the first chamber 228 and the third chamber 232. To prevent a vacuum and equalize pressure in the first chamber 228 and the third chamber 232 that would oppose movement, a check valve 412 can be provided to allow hydraulic fluid to be drawn in from the reservoir 148 by movement of the piston 156. As shown in FIG. 5, in some cases, the check valve 412 is located in the first chamber 228, and opens when the pressure in the first chamber 228 is below a pressure of in the reservoir 148 to allow fluid to flow freely into the first chamber 228 from the reservoir 148. That is, the check valve 412 allows fluid to flow from the reservoir 148 into the first chamber 228 and through the first passage 244 to third chamber 232. In some cases, the piston 156 can continue to move rapidly via the first stage of extension until pressure in the chambers 228 and 232 increases above a threshold level, as may occur upon contacting a workpiece. A dump valve 416 can be provided to allow fluid to flow out when the piston 156 moves in a second direction (e.g., retraction of the piston).

In some cases, it may be beneficial to switch from a first stage of extension to a second stage of extension when a piston reaches a workpiece. To do so, the sequence valve 396 moves from the first position to the second position when the sequence valve 396 detects the workpiece (e.g., via a pressure change, manual activation, or other control signal), thereby switching the first stage of extension to a second stage of extension. In the second stage, the first inlet 400 remains open and the second inlet 408 is also opened to allow fluid into the first chamber 228. Fluid is pumped through the second inlet 408 to the first chamber 228 through the first passage 244 to the third chamber 232, in addition to the first inlet 400 to the channel 372 via the conduit tube 368. The piston 156 extends at a slower rate because the fluid fills a volume with a larger cross-sectional area defined by the first piston head 212 and the second piston head 216 (i.e., in the first chamber 228 and the third chamber 232). While the rate of movement is decreased (e.g., extension or retraction depending on the particular configuration), the force applied by the piston 156 is increased because the fluid is acting on a larger cross-sectional area (e.g., the channel 372, the first piston head 212 and the second piston head 216), as compared with the first stage. The second stage of extension may correspond with performing an action (e.g., a crimp, cut, punch) on a workpiece that requires a larger force.

In some cases, a piston assembly can include relief valve. For example, still referring to FIG. 5, a relief valve is positioned in a passage defined in the second piston 348 (e.g., in the second piston rod 356. The relief valve selectively couples the passage with the channel 372. So, when pressure in fifth chamber reaches a crack pressure of the relief valve, the relief valve can open to allow hydraulic fluid to bleed through the second piston 356.

In some cases, a hydraulic actuator can have fluid passages that are configured differently to allow for a more compact actuator. FIGS. 6 and 7 illustrate an example hydraulic actuator 500, which is another example of a hydraulic actuator 136 according to aspects of the disclosure for use with the hydraulic tool 100 of FIG. 1. To that end, features of the hydraulic actuator 500 described below include reference numbers that are generally similar to those used in FIGS. 1-5, and discussion applies to similar named and numbered items below, unless otherwise noted or required.

In some cases, fluid passages within a hydraulic cylinder can be arranged differently to achieve multi-stage extension. For example, a first chamber defined in a cylinder by a piston can be filled for a first stage of extension, while a first chamber and a second chamber defined in the cylinder by the piston can be filled for a second stage of extension. Put more generally, a set of chambers can correspond with a stage of movement when filled, while a subset of the set of chambers can correspond with another stage of movement when filled. In the illustrated example, the hydraulic actuator 500 includes cylinder 152 that is formed from a first cylinder 304 and a second cylinder 308, and a piston 156. The first piston rod 352 defines a channel 372 to receives the conduit tube 568. The channel 372 is configured as an open channel to allow fluid to flow from the pump 132 and into the third chamber 232.

For the first stage extension in the hydraulic actuator 500, fluid is pumped through the first inlet 400 into the channel 372 via the conduit tube 568 to the third chamber 232. The piston 156 extends rapidly because full pump flow is supplied to the third chamber 232. To equalize pressure in the first chamber 228, fluid can be drawn into the first chamber 228 from the reservoir 148 via opening of the sequence valve 396.

For a second stage of extension, fluid is pumped through a second inlet to a first chamber, in addition to a second chamber, thereby dividing flow between the two chambers. For example, for the second stage of extension in the hydraulic actuator 500, the sequence valve 396 is in the second position allowing fluid to be pumped through both the first inlet 400 and the second inlet 408. The piston 156 extends at a slower rate because the fluid fills both chambers, which has the effect of filling a volume with a larger cross-sectional area defined by both the first piston head 212 and the second piston head 216 (i.e., in the first chamber 228 and the third chamber 232). While the rate of movement is decreased, the force applied by the piston 156 is increased because the fluid is acting on a larger cross-sectional area (e.g., the pre-chamber, the first piston head 212 and the second piston head 216), as compared with the first stage.

In some cases, a piston assembly can include relief valve. For example, still referring to FIG. 6, a relief valve is positioned in a passage defined in the second piston 348 (e.g., in the second piston rod 356. The relief valve selectively couples the passage with the channel 372. So, when pressure in the third chamber 232 or the channel 372 reaches a crack pressure of the relief valve, the relief valve can open to allow hydraulic fluid to bleed through the second piston 356.

In some cases, a hydraulic cylinder can have external flow to simplify piston geometries. FIG. 8 illustrates an example hydraulic actuator 600, which is another example of the hydraulic actuator 136 according to aspects of the disclosure for use with the hydraulic tool 100 of FIG. 1. To that end, features of the hydraulic actuator 600 described below include reference numbers that are generally similar to those used in FIGS. 1-7, and discussion applies to similar named and numbered items below, unless otherwise noted or required.

A first inlet and a second inlet can be configured in a different arrangement to provide fluid to chambers to achieve multi-stage extension. In some cases, a first chamber defined in a cylinder by a piston can be filled for a first stage of extension via a first inlet, while a first chamber and a third chamber defined in the cylinder by the piston can be filled for a second stage of extension via a first inlet and a second inlet, respectively. For example, the hydraulic actuator 600 includes a cylinder 152 that defines a first inlet 601 and a second inlet 608. As shown in FIG. 8, the second inlet 608 is external to the hydraulic actuator 600. The hydraulic actuator 600 also includes a first passage 668 (e.g., a pre-fill passage) that is external to the piston 156. The first passage 668 includes a check valve 672 to allow filing from the reservoir 148.

For a first stage of extension, fluid is pumped through a first inlet into a first chamber. For example, for the first stage of extension in the hydraulic actuator 600, fluid is pumped through the first inlet 601 into the first chamber 228 to move the piston 156 in the first direction. The check valve 672 allows hydraulic fluid to be drawn in from the reservoir 148 and through the first passage 668 in response to movement of the piston 156. As shown in FIG. 8, in some cases, the check valve 672 opens when the pressure in the third chamber 232 is below a pressure in the reservoir 148 to allow fluid to freely flow into the third chamber 232.

For a second stage of extension, fluid is pumped through a second inlet to a second chamber in addition to a first inlet to a first chamber. For example, for the second stage of extension in the hydraulic actuator 600, fluid is pumped through the second inlet 608 to the third chamber 232 in addition to the first inlet 601 to the first chamber 228.

In some cases, a hydraulic cylinder can include hydraulic fluid backfill to simplify the piston geometry. FIG. 9 illustrates an example hydraulic actuator 700, which is another example of a hydraulic actuator 136 according to aspects of the disclosure for use with the hydraulic tool 100 of FIG. 1. To that end, features of the hydraulic actuator 700 described below include reference numbers that are generally similar to those used in FIGS. 1-8, and discussion applies to similar named and numbered items below, unless otherwise noted or required.

In the illustrated example, the hydraulic actuator includes a first inlet 601 to supply fluid to the first chamber 228, a second inlet 608 to supply fluid to the third chamber 232, and a third inlet 768 to supply fluid to the second chamber 229. As described further below, fluid can be selectively pumped (e.g., via operation of a valve system) into the first chamber 228 and the third chamber 232 via the first inlet 601 and the second inlet 608, respectively. A check valve 772 (e.g., a refill valve) can positioned to allow fluid into the second chamber 229 from the reservoir 148. A passage 776 is provided to supply fluid from the second chamber 229 to the third chamber 232. In this case, the passage 776 is provided in the cylinder 152, however, it can be positioned differently in other examples, (e.g., in the piston 156). In some cases, a check valve (e.g., a prefill valve 779 can be positioned along the passage 776 to block flow to the third chamber 232 from the second chamber 229, as may prevent pump flow from entering the third chamber 232, which could inhibit movement of the piston 156.

In some cases, a hydraulic actuator can include chambers pre-filled (e.g., flooded) with hydraulic fluid. For example, the second chamber 229 is a flooded chamber that is pre-filled with hydraulic fluid. For a first stage of extension, fluid is pumped into a first chamber. Fluid is pumped into the hydraulic actuator 700 through the first inlet 601 into the first chamber 228. As the piston 156 moves in the first direction, the prefill check valve 779 opens when the pressure in the third chamber 232 is below a pressure in the second chamber 229 to allow fluid to freely flow into the third chamber 232.

For a second stage of extension of the hydraulic cylinder 700, fluid is pumped through the first inlet 601 into the first chamber 228 and the second inlet 608 into the third chamber 232 to move the piston in the first direction. Similar to the first stage of extension, as the piston 156 moves in the first direction, and hydraulic fluid in the second chamber 229 flows through the prefill check valve 779 into the third chamber 232. Accordingly, fluid is supplied to the first chamber 228 from the pump 132 and fluid is supplied to the third chamber 232 from both the pump 132 and the second chamber 229.