Mechanical separation type double-rod linear actuator

Abstract

The hydraulic circuit includes a first cylinder having a first rod and a second cylinder having a second rod. Further, the hydraulic circuit includes: a primary energy source common to both the first cylinder and the second cylinder, the primary energy source sized to perform an intended work of the circuit; and a secondary energy source common to both the first cylinder and the second cylinder, the secondary energy source sized to compensate for parasitic losses of the loop. The first cylinder and the second cylinder are electronically and fluidly coupled such that when the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder with an equal and opposite movement to the first rod movement.

Description

Technical Field

[0001] The invention relates to a mechanically decoupled double-rod linear actuator. Background Art

[0002] Certain pump applications, including but not limited to hydraulic fracturing or "hydraulic fracturing," require fluid pumps that provide large volumes of fluid flow at high fluid pressures. Figure 1 As shown, in the hydraulic fracturing market, some conventional pumps 100 consist of a mechanical plunger device 102 that moves linearly in the fluid end, displacing volume forward and backward through a crankshaft 104 to increase the pressure of an aqueous solution called slurry. Specifically, the pressure is increased from the charge pressure in the suction line 106 to the required formation fracturing pressure, which is determined by the formation operating through the cap 108. The pump 100 is limited in stroke length and force, which can be generated by the mechanical limitations of the power end 110. Therefore, in order to increase the flow rate, the pump 100 (also known as a "short stroke pump") can be operated at a higher speed, thereby bringing high maintenance costs to the operation. In order to reduce operating and maintenance costs and improve the durability and reliability of the pump, it is desirable to reduce the opening and closing frequency of the valve 112 incorporated into the fluid end 114. In addition, it is desirable to reduce the impact force on the fluid end 114 through a longer and slower stroke. For reference, the stroke length of many commercially available fluid ends 114 is 8 inches. Summary of the invention

[0003] Referring to Figure 2, in order to provide a pump with a longer stroke, a linear actuator can be used. In this case, the actuator 201 is a hydraulic cylinder having a variable and bidirectional hydraulic energy source 203. The energy source 203 directs a fluid such as oil between chambers 202 and 208 through a first pipeline 206 to generate a force Fe and form a pumping action in chamber 207. In this example, chamber 207 corresponds to the fluid end. In this simplified representation, those skilled in the art will recognize that there is a differential volume between chambers 202 and 208. The differential volume must be managed during the advancement and retraction of rod 210, but is not shown as there are many existing circuits to handle this situation. The actuator 201 can be a ball screw or any other device capable of transmitting the required energy. To achieve these purposes, with Figure 1 The new device requires a lower number of strokes per minute for a given flow rate than the device in FIG. 2. The fluid end 207 may be different from the one present in FIG. Figure 1The fluid end in a conventional fracturing pump in is roughly the same as in, but not limited to, this configuration. The idea and purpose of the linear long stroke is to provide a longer, more gradual stroke and displace a greater volume of fluid per stroke, for example, displacing approximately 5 times the volume per stroke. The design shown in FIG2 is a very compact design in which the rod 210 of the actuator 201 acts as a plunger into the fluid end 207. In this case, the rod 210 displaces volume to create a pumping action. This can be a disadvantage because material from the slurry present in the fluid end 207 can be drawn back into the chamber 208, contaminating the system.

[0004] Referring to FIG. 3 , an alternative linear pump 300 functions the same as the pump 200 of FIG. 2 , with the following differences. In FIG. 3 , the actuator 201 is a hydraulic cylinder having a rod 310 that is divided into a first rod portion 313 and a second rod portion 309 . The first and second rod portions 309 , 313 are coupled together in such a manner that the distance between the fluid end 207 and the actuator 201 ensures that the chance of slurry material entering the rod side chamber 208 is minimized. This is a less compact embodiment, but may be more robust. An energy source 312 supplies fluid through a valve 311 to ensure that system pressure is maintained at all times. This is standard in all of the illustrated embodiments and will be understood by those skilled in the art.

[0005] One disadvantage of the pumps 200, 300 shown in Figures 2 and 3 is that no work is done when the actuator 201 is retracted, i.e., when fluid is moving from the first port 204 to the second port 205. This means that the hydraulic energy source 203 is engaged, but no useful work is being done, causing dead time in the cycle for this important valuable substance.

[0006] See also Figure 4 , another alternative linear pump 400 solves the above problems by using a double-acting cylinder. In this embodiment, the actuator 201 includes a piston 214 having a first rod 210(1) protruding from a first side thereof and a second rod 210(2) protruding from a second side thereof. This involves mounting an additional (e.g., second) fluid end 407 that engages with the second rod 210(2), but as the fluid moves from the first port 204 to the second port 205, the second fluid end 407 is pumping and the first fluid end 207 is filling with fluid. When the end of the stroke is reached and the energy source 203 reverses direction, fluid flows from the second port 205 to the first port 204. This causes the first fluid end 207 to pump and the second fluid end 407 to fill with fluid. In this case, the energy source 203 is fully utilized 100% of the time, thereby reducing the dead time to the time it takes to reverse direction. It should be appreciated that the plunger rod orientation shown in Figure 3 can also be used Figure 4. One limitation of the dual rod cylinder approach is that the orientation of the first fluid end 207 and the second fluid end 407 are fixed at 180 degrees from each other (e.g., linearly aligned and pointing in opposite directions). In some applications, it is desirable to achieve the same utilization of the energy source 203 without being limited by the linear alignment orientation imposed by this dual rod cylinder design.

[0007] See also Figure 5 , hoping to achieve while breaking the physical connection of the rod Figure 4 Advantages of the system. Because the actuator rods are separate, there are no restrictions on the relative orientation of the rods. That is, the rods can be coaxial, parallel and offset, perpendicular, or at an acute angle.

[0008] In some aspects, the hydraulic circuit includes a first cylinder having a first rod and a second cylinder having a second rod. In addition, the hydraulic circuit includes a primary energy source common to both the first cylinder and the second cylinder, which is sized to perform the intended work of the circuit, and a secondary energy source common to both the first cylinder and the second cylinder.

[0009] The first cylinder is electronically and fluidly coupled to the second cylinder such that when the primary energy source drives the first rod to move relative to the first cylinder, the second rod moves relative to the second cylinder in a motion pattern that alternates with the motion of the first rod.

[0010] When the primary energy source induces motion in the first cylinder, causing the first rod to advance, the second rod retracts, because the rod side of each of the first and second cylinders is associated with a common fixed volume. Similarly, when the primary energy source induces motion in the second cylinder, causing the second rod to advance, the first rod will retract. Throughout the cycle defined by the advancement and retraction motion of the first rod, the secondary energy source can adjust the relative motion of the first and second cylinders relative to the motion applied by the primary energy source if required for a particular application.

[0011] In some aspects, the hydraulic circuit includes a first cylinder including a first rod, a second cylinder including a second rod, and a primary energy source. The primary energy source is fluidly connected to both the first cylinder and the second cylinder and is sized to perform the intended work of the circuit. The hydraulic circuit includes a secondary energy source, which is fluidly connected to both the first cylinder and the second cylinder and is configured to regulate the relative movement of the first cylinder and the second cylinder relative to the movement applied to the first cylinder and the second cylinder by the primary energy source. The first cylinder is electronically and fluidly coupled to the second cylinder so that when the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder in an alternating motion, wherein the first rod advances when the second rod retracts, and the second rod advances when the first rod retracts.

[0012] In some embodiments, when the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder in a motion opposite and equal to the motion of the first rod.

[0013] In some embodiments, when the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder in a motion that is opposite and substantially equal to the motion of the first rod relative to the first cylinder.

[0014] In some embodiments, when the primary energy source causes movement in the first cylinder so that the first rod advances, the secondary energy source compensates for parasitic losses in the hydraulic circuit so that the second rod retracts a distance equal to the stroke of the first rod, and when the primary energy source causes movement in the second cylinder so that the second rod advances, the secondary energy source compensates for parasitic losses in the hydraulic circuit so that the first rod retracts a distance equal to the stroke of the second rod.

[0015] In some embodiments, the hydraulic circuit includes a charge pump configured to compensate for parasitic losses in the hydraulic circuit.

[0016] In some embodiments, the first cylinder includes a first piston that separates the first cylinder into a first chamber and a second chamber. A first rod is fixed to the first piston and is at least partially disposed in the second chamber, and one end of the first rod is disposed outside the first cylinder and is configured to be connected to a first load. The first rod is isolated from the first chamber by a seal between the first piston and the first cylinder. In addition, the second cylinder includes a second piston that separates the second cylinder into a third chamber and a fourth chamber. A second rod is fixed to the second piston and is at least partially disposed in the fourth chamber, and one end of the second rod is disposed outside the second cylinder and is configured to be connected to a second load. The second rod is isolated from the third chamber by a seal between the second piston and the second cylinder.

[0017] In some embodiments, the hydraulic circuit includes a first fluid line allowing communication between the main energy source and the first chamber, a second fluid line allowing communication between the main energy source and the third chamber, a third fluid line allowing communication between the second chamber and the fourth chamber, and a fourth fluid line allowing communication between each of the first fluid line and the second fluid line and the third fluid line. The fluid flow in the fourth fluid line flows in only one direction, so as to flow from the third fluid line to the first fluid line or from the third fluid line to the second fluid line.

[0018] In some embodiments, a filter is disposed in the fourth fluid line.

[0019] In some embodiments, the hydraulic circuit includes a control device disposed in the fourth line and configured to control fluid flow between the second and first chambers or between the fourth and third chambers.

[0020] In some embodiments, the control device is selected from a group of control devices including a control valve, a pressure control valve, and a variable displacement pump.

[0021] In some embodiments, the hydraulic circuit includes a first fluid line allowing communication between the primary energy source and the first chamber, a second fluid line allowing communication between the primary energy source and the third chamber, a third fluid line allowing communication between the second chamber and the fourth chamber, and a fourth fluid line allowing communication between the third fluid line and the secondary energy source. The fluid flow in the fourth fluid line is controlled by a first valve disposed in the fourth fluid line between the secondary energy source and the third fluid line.

[0022] In some embodiments, the hydraulic circuit includes a hydraulic accumulator connected to the third fluid line via a second valve and configured to allow expansion and contraction of volumes defined within the second chamber, the fourth chamber, and the third fluid line.

[0023] In some embodiments, the first rod is coaxial with the second rod.

[0024] In some embodiments, the first rod extends parallel to the second rod and is offset relative to the second rod.

[0025] In some embodiments, the first rod is perpendicular to the second rod.

[0026] In some embodiments, the first rod is at an acute angle relative to the second rod.

[0027] In some embodiments, the first rod has a first orientation in space, the second rod has a second orientation in space, and the first and second cylinders are configured such that determination of the second orientation is not constrained based on the first orientation.

[0028] In some embodiments, the energy generation capacity of the primary energy source is greater than the energy generation capacity of the secondary energy source.

[0029] In some aspects, the hydraulic circuit includes a main energy source configured to generate a flow of hydraulic fluid within the hydraulic circuit. The main energy source includes a main energy source A port and a main energy source B port. The hydraulic circuit includes a first actuator having a first cylinder and a first piston side port in the first cylinder. The first piston side port is connected to the main energy source A port through a first fluid pipeline. The first actuator includes a first rod side port in the first cylinder and a first piston disposed in the first cylinder. The first piston divides the internal space of the first cylinder into a first chamber connected to the first piston side port and a second chamber connected to the first rod side port. In addition, the first actuator includes a first rod disposed in the second chamber, the first rod having a first rod first end connected to one side of the first piston and a first rod second end configured to be connected to a first load. The hydraulic circuit includes a second actuator having a second cylinder and a second piston side port in the second cylinder. The second piston side port is connected to the main energy source B port through a second fluid pipeline. The second actuator includes a second rod side port in the second cylinder. The second rod side port is connected to the first rod side port through a third fluid pipeline. The second actuator includes a second piston disposed in the second cylinder, the second piston separating the internal space of the second cylinder into a third chamber connected to the second piston side port and a fourth chamber connected to the second rod side port. In addition, the second actuator includes a second rod disposed in the second chamber, the second rod having a second rod first end connected to one side of the second piston and a second rod second end configured to be connected to a second load. The hydraulic circuit includes a secondary energy source connected to the third fluid line through a fourth fluid line, the secondary energy source being configured to maintain a predetermined minimum fluid pressure in the hydraulic circuit. In addition, the hydraulic circuit includes a valve disposed in the fourth fluid line between the secondary energy source and the third fluid line. The fluid sub-volume in the hydraulic circuit is defined by the second chamber, the third line, and the fourth chamber. When the main energy source causes motion in the first cylinder, the first rod advances or retracts (one of the advances and retracts) through a first distance, and the second rod retracts or advances (the other of the advances and retracts) through a second distance. Due to the fluid volume in the sub-volume when the motion is caused, the second distance is equal to the first distance. The secondary energy source is configured to provide fluid to the sub-volume through a valve, and the valve is configured to adjust an amount of fluid in the sub-volume to allow movement of the second rod to lag or lead movement of the first rod.

[0030] In some embodiments, the first rod has a first orientation in space, the second rod has a second orientation in space, and the first and second cylinders are configured such that determination of the second orientation is not constrained based on the first orientation.

[0031] In some embodiments, the energy generation capacity of the primary energy source is greater than the energy generation capacity of the secondary energy source.

[0032] In some embodiments, the hydraulic circuit includes a charge pump configured to compensate for parasitic losses in the hydraulic circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 is a diagram of a prior art fracturing pump.

[0034] FIG. 2 is a schematic diagram of a linear pump.

[0035] FIG. 3 is a schematic diagram of a linear pump with an isolated chamber.

[0036] Figure 4 It is a schematic diagram of a double-acting hydraulic cylinder.

[0037] Figure 5 Schematic diagram of a split hydraulic cylinder.

[0038] Figure 6 is a schematic diagram of a hydraulic circuit including a twin-rod linear actuator in which the rods are separated.

[0039] Figure 7 is a schematic diagram of an alternative embodiment hydraulic circuit including a dual rod linear actuator in which the rods are separated.

[0040] Figure 8 yes Figure 7 Schematic diagram of a hydraulic circuit showing the release lever in an alternative relative orientation.

[0041] Fig. 9 yes Figure 7 Schematic diagram of a hydraulic circuit showing the release lever in another alternative relative orientation.

[0042] Fig.10 yes Figure 7 Schematic diagram of a hydraulic circuit showing the release lever in another alternative relative orientation. DETAILED DESCRIPTION

[0043] See also Figure 4-Figure 6 , the hydraulic circuit 650 includes a twin-rod linear actuator 600, in which rods 616, 618 are separated. In the separated twin-rod linear actuator 600, a first main energy source 603 provides power to the two hydraulic actuators 601, 602, and drives the two hydraulic actuators 601, 602 to advance and retract the rods 616, 618. The main energy source 603 can be, for example, a variable speed bidirectional pump. The two hydraulic actuators 601, 602 are mechanically separated, such as Figure 5 shown, but due to the hydraulic scheme they will operate and work as a single actuator, as Figure 4As shown. In addition, the hydraulic circuit 650 includes a secondary energy source 608, which is used to adjust the relative movement of the hydraulic actuators 601, 602, so as to allow one rod to relatively lead or lag in movement relative to the other rod. Since the hydraulic actuators are not coupled, the main energy source 603 can be fully utilized while providing a degree of freedom to independently orient the rods 616, 618 and the corresponding fluid ends 207, 407 as needed. In addition, the secondary energy source 608 allows the relative alternating movement of the rods 616, 618 to be adjusted. The split dual-rod linear actuator 600 will now be described in detail.

[0044] The first actuator 601 includes a first cylinder 624 and a first actuator piston side port 606 in the first cylinder 624. The first actuator piston side port 606 is connected to the first energy source A port through a first fluid line 1. The first actuator 601 includes a first actuator rod side port 609 disposed in the first cylinder 624 and a first piston 614 disposed in the first cylinder 624. The first piston 614 forms a seal with the inner surface of the first cylinder 624 and divides the internal space of the first cylinder 624 into a first chamber 604 (1) connected to the first actuator piston side port 606 and a second chamber 604 (2) connected to the first actuator rod side port 609. In addition, the first cylinder 624 includes a first rod 616 disposed in the second chamber 604 (2). The first rod 616 has a first rod first end connected to one side of the first piston 614, and a first rod second end configured to be connected to a first load (e.g., the first fluid end 207).

[0045] The second actuator 602 includes a second cylinder 626 and a second actuator piston side port 607 in the second cylinder 626. The second actuator piston side port 607 is connected to the first energy source B port through the second fluid line 2. The second actuator 602 includes a second actuator rod side port 610 in the second cylinder 626, and the second actuator rod side port 610 is connected to the first actuator rod side port 609 through the third fluid line 3. The second actuator 602 includes a second piston 615 disposed in the second cylinder 626. The second piston 615 forms a seal with the inner surface of the second cylinder 626 and divides the internal space of the second cylinder 626 into a third chamber 605 (1) connected to the second actuator piston side port 607 and a fourth chamber 605 (2) connected to the second actuator rod side port 610. In addition, the second cylinder 626 includes a second rod 618, which is arranged in the fourth chamber 605 (2) and has a second rod first end connected to one side of the second piston 615, and a second rod second end configured to be connected to a second load (e.g., the second fluid end 407).

[0046] The hydraulic circuit 650 includes a secondary energy source 608. The secondary energy source 608 can be, for example, a variable speed one-way pump. The secondary energy source 608 can draw fluid from the reservoir 620 and be connected to the third fluid line 3 at a position between the piston side ports 609, 610 of the first and second actuators 601, 602. The secondary energy source 608 can be a supply pump that operates to maintain a predetermined minimum fluid pressure in the circuit even with parasitic losses. Compared with the main energy source 603, the secondary energy source 608 provides a relatively small amount of energy to the hydraulic circuit. In addition to filling the circuit, the secondary energy source 608 also controls the flow of fluid in the hydraulic circuit 650 in conjunction with the control valve 611 to keep the cylinders 624, 626 moving sequentially or allowing a slight lead or lag in relative motion, as discussed in detail below.

[0047] The control valve 611 is disposed in the fourth fluid pipeline 4. The fourth fluid pipeline 4 connects the third fluid pipeline 3 (and therefore the output of the secondary energy source 608) to the first fluid pipeline 1 through a first one-way check valve, and connects the third fluid pipeline 3 to the second fluid pipeline 2 through a second one-way check valve. Figure 6 In the drawings, reference numeral 612 is used to collectively refer to one-way check valves.

[0048] In order to achieve the orientation freedom of the actuator 600, the first and second hydraulic actuators 601, 602 constituting the actuator 600 must be as follows: Figure 6 However, it is desirable to use the primary energy source 603 to generate motion so that motion in the first actuator 601 generates a corresponding motion in the second actuator 602. In the illustrated embodiment, the primary energy source 603 and the secondary energy source 608 operate in concert to achieve relative alternating motion of the actuators 601, 602 so that an advance-retract motion in the first actuator 601 generates a corresponding retract-advance motion in the second actuator 602. Since the second chamber 604(2) is connected to the fourth chamber 605(2) via the third fluid line 3, and since these structures together define a fixed volume, relative alternating motion naturally occurs.

[0049] When the primary energy source 603 induces motion in the first cylinder 624, the first rod 616 is advanced and the second rod 618 is retracted, because the rod side of each of the first and second cylinders 624, 626 is associated with a common fixed volume. Similarly, when the primary energy source 603 induces motion in the second cylinder 626, the second rod 618 is advanced and the first rod 616 is retracted. Throughout the cycle defined by the advancement and retraction motion of the first rod 616, the secondary energy source 608 can adjust the relative motion of the first and second cylinders 624, 626 relative to the motion applied by the primary energy source 603 if required for a particular application.

[0050] In some embodiments, movement in the first actuator 601 produces a corresponding movement in the second actuator 602 that is opposite and equal (e.g., "180 degrees out of phase") to the movement of the first actuator 601. As used herein, the term "opposite" refers to retraction compared to advancement, rather than any particular absolute direction, keeping in mind that the rods may not be parallel or aligned in their separated state. In other embodiments, the corresponding movement in the second actuator 602 may be opposite and substantially equal to the movement of the first actuator 601. As used herein, the term "substantially equal" means that within the relative size range of the secondary energy source 608 compared to the primary energy source 603, the movement of the second actuator 602 may be 180 degrees out of phase with the first actuator 601, or alternatively may lead or lag the first actuator for a period of time within a given advancement and retraction cycle of a given rod 616 or 618. The amount of lead or lag that can be achieved depends on the size of the secondary energy source 608 and is determined by the requirements of the particular application. In some embodiments, the amount of lead or lag may be very small, for example, in the range of one percent to ten percent of the distance traveled by the actuator rods 616, 618 during forward motion. Advantageously, because the amount of lead or lag may be very small relative to the distance traveled by the actuator rods 616, 618, the secondary energy source 608 may be small relative to the primary energy source 603.

[0051] Throughout the motion, the actuators 601, 602 are controlled by the secondary energy source 608 to be in opposite, or alternatively to be ahead or behind each other. However, after a complete cycle, the second actuator 602 will be 180 degrees out of phase with the first actuator 601. This is because the secondary energy source 608 is very small relative to the primary energy source 603.

[0052] With this configuration, from a motion perspective, the actuator 600 behaves similarly to Figure 4 , and has the further advantage of being able to achieve "substantially equal" motion. In operation, the hydraulic circuit 650 operates with the first or main energy source 603 to transmit fluid power between the first actuator piston side port 606 of the first actuator 601 and the second actuator piston side port 607 of the second actuator 602. During the operation of transmitting power to the first actuator 601, the main energy source 603 draws fluid from the second actuator piston side port 607 and compresses it into the first actuator piston side port 606. As a result, the rod 616 of the first actuator 601 extends (e.g., advances), thereby displacing the volume in the first fluid end 207.

[0053] If there are no leaks in the hydraulic circuit 650, the rod 618 of the second actuator 602 will retract at the same rate as the rod 616 of the first actuator 601 extends. Again, this will cause a certain amount of fluid to leave the first port 607 of the second actuator 602 and supply fluid to the main energy source 603 to push it into the first port 606 of the first actuator 601. Unfortunately, all hydraulic systems have leaks that are intentionally created to allow lubrication and cooling. These leaks are called parasitic losses. Therefore, of the certain amount of fluid that leaves ports 609 and 607, a portion will return to the reservoir 620. As a result, unless the lost fluid is replenished, the rod 618 of the second actuator 602 will not retract synchronously with the advancement of the rod 616 of the first actuator 601.

[0054] When used in a conventional hydraulic circuit, a charge pump is not usually used as part of a control circuit, but rather replenishes the discharged fluid in an uncontrolled manner. Figure 6 In the hydraulic circuit 650 shown, the secondary energy source 608 is used as a supply pump and also as part of the control circuit. The primary energy source 603 is connected in a closed loop with the position feedback device on the first actuator 601, while the secondary energy source 608 is connected in a closed loop with the feedback device on the second actuator 602. Position / speed control of the second actuator 602 is implemented by the secondary energy source 608, ensuring that all fluid leaving the hydraulic circuit 650 (for example, due to parasitic losses) is exactly replenished by the secondary energy source 608 drawn from the reservoir 620. This enables the secondary energy source 608 to accurately deliver sufficient flow to control the valve 611 and the one-way check valve 612, so that the volume entering the port 610 and leaving the piston-side port 607 is approximately equal to the volume leaving the rod-side port 609 and entering the first port 606, thereby synchronizing the movement of the two actuators 601 and 602.

[0055] To control the movement, the control valve 611 sets the pressure difference between the rod side port 610 and the piston side port 607 of the second actuator 602 so that the second actuator 602 will retract when the fluid is evacuated from the piston side port 607. The check valve 612 ensures that the fluid leaving the control valve 611 will enter the low pressure side of the main energy source 603.

[0056] In some embodiments, a filter module 622 is provided on the fourth fluid line 4 in the control valve 611 (shown) or the check valve 612 to ensure that any contaminants entering the hydraulic circuit 650 from the fluid end slurry can be captured before entering the main circuit. This can be applied to any application where the working stroke is in one direction and needs to be continuous.

[0057] In the hydraulic circuit 650 , the primary energy source 603 causes movement in the first cylinder 624 , causing the first rod 616 to advance while the second rod 618 retracts a distance equal to the stroke of the first rod 616 , as parasitic losses of the hydraulic circuit 650 are compensated by the secondary energy source 608 .

[0058] See also Figure 4-Figure 5 and Figure 7 , an alternative embodiment hydraulic circuit 750 includes a twin-rod linear actuator 700 in which rods 716, 718 are separated. In the separated twin-rod linear actuator 700, a first main energy source 703 provides power to the two hydraulic actuators 701, 702 and drives the two hydraulic actuators 701, 702 to advance and retract the rods 716, 718. The main energy source 703 can be, for example, a variable speed bidirectional pump. The two hydraulic actuators 701, 702 are mechanically separated, such as Figure 5 shown, but due to the hydraulic scheme they will operate and work as a single actuator, as Figure 4 As shown. In addition, the hydraulic circuit 750 includes a secondary energy source 708 and a control valve 711, which are used to adjust the relative movement of the hydraulic actuators 701, 702, so as to allow one rod to relatively lead or lag in movement relative to the other rod. Since the hydraulic actuators are not coupled, the main energy source 703 can be fully utilized while providing a degree of freedom to independently orient the rods 716, 718 and the corresponding fluid ends 207, 407 as needed. In addition, the secondary energy source 708 and the control valve 711 cooperate to allow the relative alternating movement of the adjustment rods 716, 718. The split dual-rod linear actuator 700 will now be described in detail.

[0059] The first actuator 701 includes a first cylinder 724 and a first actuator piston side port 706 in the first cylinder 724. The first actuator piston side port 706 is connected to the first energy source A port through a first fluid line 1. The first actuator 701 includes a first actuator rod side port 709 in the first cylinder 724 and a first piston 714 disposed in the first cylinder 724. The first piston 714 forms a seal with the inner surface of the first cylinder 724 and divides the internal space of the first cylinder 724 into a first chamber 704 (1) connected to the first actuator piston side port 706 and a second chamber 704 (2) connected to the first actuator rod side port 709. In addition, the first cylinder 724 includes a first rod 716 disposed in the second chamber 704 (2). The first rod 716 has a first rod first end connected to one side of the first piston 714, and a first rod second end configured to be connected to a first load (e.g., the first fluid end 207).

[0060] The second actuator 702 includes a second cylinder 726 and a second actuator piston side port 707 in the second cylinder 726. The second actuator piston side port 707 is connected to the first energy source B port through the second fluid line 2. The second actuator 702 includes a second actuator rod side port 710 in the second cylinder 726, and the second actuator rod side port 710 is connected to the first actuator rod side port 709 through the third fluid line 3. The second actuator 702 includes a second piston 715 disposed in the second cylinder 726. The second piston 715 forms a seal with the inner surface of the second cylinder 726, and divides the internal space of the second cylinder 726 into a third chamber 705 (1) connected to the second actuator piston side port 707 and a fourth chamber 705 (2) connected to the second actuator rod side port 710. In addition, the second cylinder 726 includes a second rod 718, which is disposed in the fourth chamber 705 (2) and has a second rod first end connected to one side of the second piston 715, and a second rod second end configured to be connected to a second load (e.g., the second fluid end 407).

[0061] The hydraulic circuit 750 includes a supply pump 730 that pumps fluid into the first and second fluid lines 1, 2 through the check valve 712, thereby operating to maintain a predetermined minimum fluid pressure in the hydraulic circuit 759 despite parasitic losses. The supply pump 730 may be a single speed, unidirectional pump and draws fluid from the reservoir 720.

[0062] The hydraulic circuit 750 includes a secondary energy source 708. The secondary energy source 708 may be, for example, a variable speed one-way pump. The secondary energy source 708 may draw fluid from the reservoir 720 and be connected to the third fluid line 3 at a position between the piston side ports 709, 710 of the first and second actuators 701, 702. The secondary energy source 708 is combined with a control valve 711 to control the flow of fluid in the hydraulic circuit 750 to keep the cylinders 724, 726 moving in sequence, or to allow a slight lead or lag in relative motion, as discussed in detail below.

[0063] The secondary energy source 708 is in fluid communication with the third fluid line 3 via the fourth fluid line 4. A control valve 711 is provided in the fourth fluid line 4 at a position between the secondary energy source 708 and the third fluid line 3. The control valve 711 controls the flow of fluid from the secondary energy source 708.

[0064] In order to achieve the orientation freedom of the actuator 700, the first and second hydraulic actuators 701, 702 constituting the actuator 700 must be as follows: Figure 7As shown, the first and second actuators 701 and 702 are mechanically separated. However, it is desirable to use the main energy source 703 to generate motion so that the motion in the first actuator 701 generates a corresponding motion in the second actuator 702. In the illustrated embodiment, the main energy source 703 and the secondary energy source 708 cooperate to achieve relative alternating motion of the actuators 701 and 702, so that the advance-retract motion in the first actuator 701 generates a corresponding opposite motion, for example, the retract-advance motion in the second actuator 702. Since the second chamber 704 (2) is connected to the fourth chamber 705 (2) via the third fluid line 3, and since these structures together define a fixed volume, relative alternating motion naturally occurs. This fixed volume will be referred to as the rod-side chamber 780, which includes the sum of the fluid volumes in the second chamber 704 (2), the fourth chamber 705 (2) and the third fluid line 3.

[0065] When the primary energy source 703 induces motion in the first cylinder 724, causing the first rod 716 to advance, the second rod 718 to retract, because the rod side of each of the first and second cylinders 724, 726 is associated with a common fixed volume defined within the rod side chamber 780. Similarly, when the primary energy source 703 induces motion in the second cylinder 726, causing the second rod 718 to advance, the first rod 716 retracts. Throughout the cycle defined by the advancement and retraction motion of the first rod 716, the secondary energy source 708 can adjust the relative motion of the first and second cylinders 724, 726 relative to the motion applied by the primary energy source 703, if required for a particular application.

[0066] In some embodiments, movement in the first actuator 701 produces a corresponding movement in the second actuator 602 that is opposite and equal (e.g., "180 degrees out of phase") to the movement of the first actuator 601. In other embodiments, the corresponding movement in the second actuator 602 may be opposite and substantially equal to the movement of the first actuator 601. As previously described, the term "substantially equal" means that within the relative size range of the secondary energy source 708 relative to the primary energy source 703, the movement of the second actuator 702 may be 180 degrees out of phase with the first actuator 701, or alternatively may lead or lag the first actuator 701 for a period of time within a given advancement and retraction cycle of a given rod 716 or 718. The amount of lead or lag that can be achieved depends on the size of the secondary energy source 708 and is determined by the requirements of the particular application. In some embodiments, the amount of lead or lag may be very small, for example, in the range of one percent to ten percent of the distance traveled by the actuator rods 716, 718 during the advancement movement. Advantageously, the secondary energy source 708 can be small relative to the primary energy source 703 because the amount of lead or lag can be very small relative to the distance traveled by the actuator rods 716, 718.

[0067] Throughout the motion, the actuators 701, 702 are controlled by the secondary energy source 708 to be in opposite, or alternately leading or lagging each other. However, after a complete cycle, the second actuator 702 will be 180 degrees out of phase with the first actuator 701. This is because the secondary energy source 708 is very small relative to the primary energy source 703.

[0068] With this configuration, from a kinematic perspective, the actuator 700 behaves similarly to Figure 4 . In operation, the hydraulic circuit 750 operates with the first or main energy source 703, operating to transmit fluid power between the first actuator piston side port 706 of the first actuator 701 and the second actuator piston side port 707 of the second actuator 702. During the operation of transmitting power to the first actuator 701, the main energy source 703 draws fluid from the second actuator piston side port 707, compressing it into the first actuator piston side port 706. As a result, the rod 716 of the first actuator 701 extends (e.g., advances), thereby displacing the volume in the first fluid end 207.

[0069] If there is no leakage in the hydraulic circuit 750, the total volume of fluid in the rod side chamber 780 remains unchanged. Therefore, the rod 718 of the second actuator 702 will retract at the same rate as the rod 716 of the first actuator 701 extends. Similarly, this will cause a certain volume of fluid to leave the first port 707 of the second actuator 702 and supply fluid to the main energy source 703 to push into the first port 706 of the first actuator 701. Unfortunately, all hydraulic systems have leaks that are intentionally generated to allow lubrication and cooling, such as parasitic losses. Most of these leaks occur in the main energy source 703. In this embodiment, the volume loss in the first and second fluid pipelines 1, 2 is compensated by the check valve 712 and the supply pump 730.

[0070] exist Figure 7 In the illustrated hydraulic circuit 750 , the secondary energy source 708 is separate from the supply pump 730 and is used as part of the control circuit. The secondary energy source provides a relatively small amount of energy to the hydraulic circuit 750 compared to the primary energy source 703 .

[0071] In the hydraulic circuit 750, the main energy source 703 is connected in a closed loop with the position feedback device on the first actuator 701, and the auxiliary energy source 708 is connected in a closed loop with the feedback device on the second actuator 702 through the control valve 711. The position / speed control of the second actuator 702 is implemented through the auxiliary energy source 708 and the control valve 711 to ensure that the fluid volume of the rod side chamber 780 is controlled and the synchronization between the first and second actuators 701 and 702 is maintained.

[0072] Alternatively, it may be desirable to control the first and second actuators 701, 702 so that the relative motion is opposite and equal or substantially equal. In the hydraulic circuit 750, this can be achieved in a variety of ways. Figure 7 , the control valve 711 can be used to discharge fluid from the third fluid line 3 to the reservoir 720, thereby reducing the total volume of the rod side chamber 780. This allows the first actuator 701 to extend a greater distance than the second actuator 702 to retract. Using the control valve 711 and the second energy source 708, the volume of the rod side chamber 780 can be increased to return the actuators 701 and 702 to a previously set synchronization, or to allow the actuator 702 to retract a greater distance than 701 extends. In this example, equal or substantially equal synchronization is maintained between the actuators 701 and 702.

[0073] In a second example, by employing a hydraulic accumulator 740 in the hydraulic circuit 750, opposite and equal or substantially equal movement between the two actuators 701, 702 can be achieved. The hydraulic accumulator 740 is connected to the third fluid line 3 via a valve 741. This configuration allows the volume of fluid within the rod side chamber 780 to expand and contract, thereby allowing differential movement between the actuators 701 and 702. This is particularly useful for decompression. When the actuator 701 reaches the end of its forward stroke, the actuator 702 is fully retracted. Under load, the fluid in the first chamber 704 (1) must be decompressed before the first rod 716 and the first piston 714 can begin to retract. This decompression is achieved by moving a certain volume of fluid from the first chamber 704 (1) to the third chamber 705 (1). To achieve this, the second piston 715 and the second rod 718 must be slightly extended. Since the first rod 716 and the first piston 714 cannot retract yet, the volume of fluid within the rod side chamber 780 must be allowed to decrease. The volume of fluid in the rod side chamber 780 can be temporarily reduced by displacing a small volume of fluid into the accumulator 740. After decompression and system equilibration, the volume of fluid in the rod side chamber 780 will return to its original state and the fluid that flowed out of the accumulator 740 will re-enter the rod side chamber 780.

[0074] In About Figure 6 and Figure 7 In the hydraulic circuits 650 and 750 described above, the rods 616, 618, 716 and 718 of the actuators 600 and 700 are separated, and therefore, the relative orientation of the rods 616, 618, 716 and 718 is not limited. For example, in some embodiments, the cylinders 624, 626, 724 and 726 are arranged so that the first rod 616 and 716 are coaxial with the second rod 618 and 718 ( Figure 8In other embodiments, the cylinders 624, 626, 724, 726 are arranged such that the first rod 616, 716 extends parallel to the second rod 618, 718 and is not coaxial with the second rod 618, 718 ( Fig. 9 In yet other embodiments, the cylinders 624, 626, 724, 726 are arranged such that the first rod 616, 716 is angled relative to the second rod 618, 718, wherein the angle may be an acute angle ( Fig.10 ), normal angle or obtuse angle. Although in the orientation shown here, the rods 616, 618, 716, 718 are coplanar, they are not limited to this configuration.

[0075] Although the hydraulic circuit has been described herein as having an application in hydraulic fracturing, the hydraulic circuit is not limited to this application. For example, the hydraulic circuit can be used in many other applications, including but not limited to being a driver for a cryogenic fluid pump, a gas compressor, a mud pump, or any application driven by a crankshaft connected to a piston. Furthermore, the hydraulic circuit is not limited to applications requiring high fluid flow and / or high pressure. Advantages of the hydraulic circuit include but are not limited to the ability to allow for a reduction in strokes per minute to reduce wear, to change the discharge frequency of the pumping pulses, and to change the motion profile of the pump stroke.

[0076] Although the exemplary primary energy source is described as a variable speed, bidirectional pump, and the secondary energy source is described as a variable speed, unidirectional pump, the energy source is not limited to these types of pumps. The type of pump employed will be determined by the specific application. In addition, other energy sources may be used, such as a hydraulic motor (e.g., when operating in reverse).

[0077] Selective illustrative embodiments of the hydraulic circuit are described in detail above. It should be understood that only the structures considered necessary to illustrate the hydraulic circuit are described herein. Other conventional structures of the hydraulic circuit and the structures of the auxiliary and accessory components are considered to be known and understood by those skilled in the art. In addition, although the working examples of the hydraulic circuit are described above, the hydraulic circuit is not limited to the above working examples, but various design changes can be made without departing from the hydraulic circuit set forth in the claims.

Claims

1. A hydraulic circuit comprising: A first cylinder including a first rod, a second cylinder including a second rod, and a primary energy source fluidly connected to both the first cylinder and the second cylinder and sized to perform the intended work of the circuit, and a secondary energy source fluidly connected to both the first cylinder and the second cylinder and configured to adjust relative motion of the first cylinder and the second cylinder relative to motion imparted on the first cylinder and the second cylinder by the primary energy source, in The first cylinder is electronically and fluidly coupled to the second cylinder so that when the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder in an alternating motion wherein the first rod advances when the second rod retracts and the second rod advances when the first rod retracts.

2. The hydraulic circuit according to claim 1, wherein When the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder with a movement opposite and equal to the movement of the first rod.

3. The hydraulic circuit according to claim 1, wherein When the first rod moves relative to the first cylinder, the second rod moves relative to the second cylinder in a motion that is opposite and substantially equal to the motion of the first rod relative to the first cylinder.

4. The hydraulic circuit according to claim 1, wherein When the primary energy source causes movement in the first cylinder, causing the first rod to advance, the secondary energy source compensates for parasitic losses in the hydraulic circuit, causing the second rod to retract a distance equal to the stroke of the first rod, and When the primary energy source causes movement in the second cylinder, causing the second rod to advance, the secondary energy source compensates for parasitic losses in the hydraulic circuit, causing the first rod to retract a distance equal to the stroke of the second rod.

5. The hydraulic circuit of claim 1, comprising a charge pump configured to compensate for parasitic losses in the hydraulic circuit.

6. The hydraulic circuit according to claim 1, wherein The first cylinder includes a first piston, the first piston dividing the first cylinder into a first chamber and a second chamber, a first rod fixed to the first piston and at least partially disposed in the second chamber, One end of the first rod is disposed outside the first cylinder and is configured to be connected to a first load, The first rod is isolated from the first chamber by a seal between the first piston and the first cylinder, The second cylinder includes a second piston, which divides the second cylinder into a third chamber and a fourth chamber, a second rod fixed to the second piston and at least partially disposed in the fourth chamber, One end of the second rod is disposed outside the second cylinder and is configured to be connected to a second load, and The second rod is isolated from the third chamber by a seal between the second piston and the second cylinder.

7. The hydraulic circuit according to claim 6, comprising: a first fluid line allowing communication between the primary energy source and the first chamber, a second fluid line allowing communication between the primary energy source and the third chamber, a third fluid line allowing communication between the second chamber and the fourth chamber, and a fourth fluid line allowing communication between each of the first fluid line and the second fluid line and the third fluid line, in, The fluid flow in the fourth fluid line flows in one direction only, so as to flow from the third fluid line to the first fluid line or from the third fluid line to the second fluid line.

8. The hydraulic circuit of claim 7, wherein a filter is provided in the fourth fluid line.

9. The hydraulic circuit according to claim 7, comprising a control device provided in the fourth pipeline, the control device being configured to control the fluid flow between the second chamber and the first chamber or between the fourth chamber and the third chamber.

10. The hydraulic circuit according to claim 9, wherein: The control device is selected from a group of control devices including a control valve, a pressure control valve and a variable displacement pump.

11. The hydraulic circuit according to claim 6, comprising a first fluid line allowing communication between the primary energy source and the first chamber, a second fluid line allowing communication between the primary energy source and the third chamber, a third fluid line allowing communication between the second chamber and the fourth chamber, and a fourth fluid line allowing communication between the third fluid line and a secondary energy source, in, Fluid flow in the fourth fluid line is controlled by a first valve disposed in the fourth fluid line between the secondary energy source and the third fluid line.

12. The hydraulic circuit of claim 11, comprising a hydraulic accumulator connected to the third fluid line via the second valve and configured to allow expansion and contraction of volumes defined within the second chamber, the fourth chamber, and the third fluid line.

13. The hydraulic circuit of claim 1, wherein the first rod is coaxial with the second rod.

14. The hydraulic circuit of claim 1, wherein the first rod extends parallel to the second rod and is offset relative to the second rod.

15. The hydraulic circuit of claim 1, wherein the first rod is perpendicular to the second rod.

16. The hydraulic circuit of claim 1, wherein the first rod is at an acute angle relative to the second rod.

17. The hydraulic circuit according to claim 1, wherein: The first rod has a first orientation in space, the second rod has a second orientation in space, and the first and second cylinders are configured such that determination of the second orientation is not constrained based on the first orientation.

18. The hydraulic circuit of claim 1, wherein the energy generation capacity of the primary energy source is greater than the energy generation capacity of the secondary energy source.

19. A hydraulic circuit comprising: a primary energy source configured to generate a flow of hydraulic fluid within the hydraulic circuit, the primary energy source comprising a primary energy source A port and a primary energy source B port; The first actuator includes First cylinder, A first piston side port in the first cylinder, the first piston side port being connected to a main energy source A port through a first fluid pipeline, The first rod side port in the first cylinder, a first piston provided in the first cylinder, the first piston dividing the inner space of the first cylinder into a first chamber connected to the first piston side port and a second chamber connected to the first rod side port, and A first rod disposed in the second chamber, the first rod having a first rod first end connected to one side of the first piston, and a first rod second end configured to be connected to a first load; a second actuator comprising The second cylinder, A second piston side port in the second cylinder, the second piston side port being connected to the main energy source B port through a second fluid pipeline, a second rod side port in the second cylinder, the second rod side port being connected to the first rod side port through a third fluid line, a second piston provided in the second cylinder, the second piston dividing the inner space of the second cylinder into a third chamber connected to the second piston side port and a fourth chamber connected to the second rod side port, and a second rod disposed in the second chamber, the second rod having a second rod first end connected to one side of the second piston, and a second rod second end configured to be connected to a second load; a secondary energy source connected to the third fluid line through a fourth fluid line, the secondary energy source configured to maintain a predetermined minimum fluid pressure in the hydraulic circuit; as well as a valve disposed in a fourth fluid line between the secondary energy source and the third fluid line, in a sub-volume of fluid in the hydraulic circuit is defined by the second chamber, the third line, and the fourth chamber, and When the primary energy source causes movement in the first cylinder, causing the first rod to one of advance and retract through a first distance, the second rod is advanced and retracted the other of through a second distance, wherein the second distance is equal to the first distance due to the volume of fluid in the subvolume when the motion is induced, and The secondary energy source is configured to provide fluid to the subvolume through the valve, and the valve is configured to adjust an amount of the fluid in the subvolume to allow movement of the second rod to lag or lead movement of the first rod.

20. The hydraulic circuit of claim 19, wherein the first rod has a first orientation in space, the second rod has a second orientation in space, and the first and second cylinders are configured such that determination of the second orientation is not constrained based on the first orientation.

21. The hydraulic circuit of claim 19, wherein the energy generation capacity of the primary energy source is greater than the energy generation capacity of the secondary energy source.

22. The hydraulic circuit of claim 19, comprising a charge pump configured to compensate for parasitic losses in the hydraulic circuit.

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