Hydraulic system with energy recovery from the reservoir and supply line supplement for machines that engage with a surface.

Abstract

An exemplary hydraulic system comprises: several unit cylinder actuators; a fluid source, wherein the source is fluidically coupled to the several unit cylinder actuators; and an amplifier, which is fluidically coupled to the several unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the several unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the several unit cylinder actuators, thereby replenishing fluid from the source.

Description

CROSS-REFERENCE TO RELATED REGISTRATION

[0001] This application claims priority over the preliminary US patent application No. 63 / 513,364 filed on July 13, 2023, and the preliminary US patent application No. 63 / 603,978 filed on November 29, 2023, the entire contents of which are incorporated by reference into this description as if they were fully contained therein. BACKGROUND

[0002] Conventional machines that engage with a surface (e.g., planters, seed drills, tillage machines, mowers, row cleaners for planters, rotating brooms / brushes that can remove debris from sidewalks, etc.) use springs, weights, or air cushions to maintain surface contact between a unit of the machine and the surface. Recent advances have led to these systems being equipped with fluid cylinders.

[0003] In an example, when an agricultural unit that engages the surface (e.g., the soil) travels across fields, it is difficult to maintain a constant engagement position (e.g., seeding depth) and other parameters using conventional methods, as soil conditions (soil type, moisture, surface elevation, etc.) change. This problem is exacerbated by the requirement for higher machine speeds. Therefore, it may be desirable to vary the downforce (downward force) to adapt to different soil conditions.

[0004] One solution to such a problem is to replace conventional methods of downforce (e.g., springs, weights, or airbags) with an active force control system. Such an active force control system can enable precise hydraulic control of the contact pressure.

[0005] Some machines can include multiple units engaging a surface (e.g., 16-48 units in a row). As the number of units and machine speed increase, dynamic flow requirements can become a limiting factor for machine productivity. For example, a machine's primary flow source may not be able to keep pace with the total flow demand. Furthermore, the energy wastage that occurs as the increasing exhaust fluid from each unit flows through restrictive tank lines increases with machine speed. This can render the machine's hydraulic system ineffective.

[0006] It may therefore be desirable to configure the hydraulic system in such a way that forces can be controlled with high precision at high machine speeds, while simultaneously improving the efficiency of the hydraulic system. This disclosure is presented with regard to these and other considerations. SUMMARY

[0007] This disclosure describes implementations relating to a hydraulic system with surge energy recovery and inlet supplementation for machines that engage with a surface.

[0008] In a first exemplary implementation, this disclosure describes a hydraulic system. The hydraulic system comprises: several unit cylinder actuators; a fluid source, wherein the source is fluidically coupled to the several unit cylinder actuators; and an amplifier, which is fluidically coupled to the several unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the several unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the several unit cylinder actuators, thereby replenishing fluid from the source.

[0009] In a second exemplary implementation, this disclosure describes a machine that engages with a surface and comprises the hydraulic system of the first embodiment.

[0010] In a third exemplary implementation, this disclosure describes a method for operating the hydraulic system of the first or second embodiment or the machine engaging a surface of the second embodiment.

[0011] The above summary is purely illustrative and is in no way intended to be limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become clear through reference to the figures and the following detailed description. BRIEF DESCRIPTION OF THE FIGURES Fig. Figure 1A illustrates a partial view of a machine intervening in the surface, according to an exemplary implementation. Fig. 1B illustrates a schematic view of a surface-engaging unit of the surface-engaging machine, from Fig. 1A after an exemplary implementation. Fig. Figure 2 illustrates a hydraulic system according to an exemplary implementation. Fig. Figure 3 is a flowchart of a process 300 for operating a hydraulic system of a machine that engages the surface, according to an exemplary implementation. DETAILED DESCRIPTION

[0012] This document discloses systems and methods that enable machines engaging with a surface to control the engagement forces (e.g., downward forces) with high precision and improved hydraulic system efficiency. The term "surface" is used throughout to refer to any vertical or horizontal plane or plane. Examples of surfaces include soil, earth, walls, roads, machine surfaces, etc. Other examples of machines engaging with a surface include seed drills or planters, tillage equipment, grass cutters, row cleaners for planters, road resurfacing machines, etc.

[0013] In particular, the systems, machines, and processes described herein enable cross-flow between the units of a surface-engaging unit to supplement the flow from a primary flow source when the primary source is unable to meet the flow demand. This process occurs passively via an amplifier, without active control management, additional hydraulic accumulators, or conversion of hydraulic energy into electrical or mechanical energy stored in energy storage devices.

[0014] Fig. Figure 1A illustrates a partial view of a machine 100 interlocking with a surface, according to an exemplary implementation. In the Fig. The surface-intervening machine shown in Figure 1A (100) could, for example, be a seed drill or planter attached to a tractor. A seed drill / planter is used here as an example. However, it should be understood that the systems, methods, and concepts discussed here are applicable to any surface-intervening machine, such as tillage equipment, mowers, row cleaners, rotary brooms / brushes that can remove dust from sidewalks, or any other machine that requires a device to engage with the surface.

[0015] The surface-penetrating machine 100 has several surface-penetrating row units (e.g., 16-48 units) such as row unit 102, row unit 104, row unit 106, row unit 108, and row unit 110. As the surface-penetrating machine 100 crosses a field, each row unit sows or plants seed in straight rows in raised or flat ground beds. Row unit 102 also includes rear wheels 114 that close the trench after the seed has been deposited.

[0016] Fig. Figure 1B illustrates a schematic view of the series unit 102 according to an exemplary implementation. With reference to the Fig. 1A and Fig. 1B, the surface-penetrating machine 100 can have a seed tank 109 for storing seed (e.g., corn, soybeans, etc.). With the aid of blowers, the seed can be conveyed from the seed tank 109 through seed hoses (not shown) to the row units 102-110.

[0017] The row unit 102 can have a surface-engaging device 111, including measuring wheels 112 (e.g. adjustable wheels attached to a plow or seed drill to control the penetration depth into the soil) and disc openers 113 (see Fig. 1A), which comprise metal discs that contact a surface 115 (e.g., the ground) to cut a trench at a specific depth for planting the seeds. The height of the measuring wheels 112 controls the height of the disc openers 113. Thus, for example, raising the measuring wheels 112 lowers the disc openers 113 to dig a deeper trench, and vice versa.

[0018] Since the depth of the trench excavated by the seed drill opener correlates with the height of the measuring wheels 112, it may be desirable to maintain contact between the measuring wheels 112 and the surface 115 while the machine 100, engaging the surface, traverses the field. To maintain such contact, it may be desirable for the individual row units to exert a certain downforce on their respective measuring wheels to maintain surface contact and compact the soil at the edges of the trench in which the seed is placed.

[0019] The series unit 102 can include a cylinder actuator 118, which is coupled to the surface-engaging device 111 and configured to exert a downward pressure on it. In one example, the cylinder actuator 118 can be coupled to the surface-engaging device 111 via a linkage 120. The cylinder actuator 118 is configured to exert a downward pressure on the surface-engaging device 111. Such downward pressure causes the measuring wheels 112 and the disc openers 113 to exert a respective downward force on the surface 115 and can thus influence the surface-engaging position of the disc openers 113. A fluid system 122 (e.g., as below with respect to Fig. 2 described) is used to control the fluid flow to and from the cylinder actuator 118 in order to change the force exerted by the cylinder actuator 118 on the device 111 engaging the surface.

[0020] In one example, the inline unit 102 also has an inline cleaner 116 in the form of a spiked wheel. The inline cleaner 116 is arranged in front of the measuring wheel 112 and the disc openers 113 and is designed to remove residues and lumps from the path of the disc openers 113 and the measuring wheels 112 so that they can operate smoothly and helps to prevent the unit from vibrating or bouncing.

[0021] In one example, the contact pressure of the row cleaner 116 can be controlled via a further cylinder actuator 124. The fluid system 122 can be used to control the fluid flow to and from the cylinder actuator 124 in order to change the force exerted by the row cleaner 116 on the surface 115 and thus the engagement position of the row cleaner 116.

[0022] Soil conditions can vary considerably. For example, the surface-penetrating machine 100 may encounter different soil types: sand, clay, rock, etc. Furthermore, the individual row units of the surface-penetrating machine 100 may be exposed to different soil conditions. Moisture, for instance, may not be uniform across the entire surface, meaning that different row units may have varying soil firmness. Additionally, the soil may be uneven, causing different row units to travel over different soil depths as the surface-penetrating machine 100 crosses the field. Therefore, it may be desirable to actively control the contact pressure applied to the measuring wheels (or row cleaner) of each row unit based on the soil conditions.

[0023] For example, in hard soil or aggressive organic material, it may be desirable to exert a positive downward pressure on the surface-engaging device 111 via the cylinder actuator 118, or a positive downward pressure on the row cleaner 116 via the cylinder actuator 124. Such a positive downward pressure, together with the weight of the surface-engaging device 111, can facilitate achieving a specific surface engagement position.

[0024] In other examples, however, the ground may be soft. In these examples, it may be desirable for the cylinder actuator 118, 124 to exert a small upward force, rather than a positive downward force, which is less than the weight of the device 111 engaging the surface or the row cleaner 116. In this way, a resultant or effective small downward force, corresponding to the difference between the weight of the device 111 engaging the surface or the row cleaner 116 and the upward actuating force, is exerted downward on the soft ground.

[0025] Therefore, it may be desirable to control the actuator's force with high precision to achieve a specific, desirable effective downward force, while the machine engaging the surface can traverse the field at high speeds. A hydraulic control system could enable such force control.

[0026] Fig. Figure 2 illustrates a hydraulic system 200 according to an exemplary implementation. The hydraulic system 200 is configured to control at least some of the surface-engaging units of the surface-engaging machine 100. For example, the hydraulic system 200 is configured to control a surface-engaging unit 202, a surface-engaging unit 204, a surface-engaging unit 206, and a surface-engaging unit 208. The surface-engaging units 202-208 can, for example, represent a subset of the series units 102-110 of the surface-engaging machine 100. Although in Fig. Since 2 four units penetrating the surface are shown, the hydraulic system 200 can be configured to control units that penetrate the surface to a greater or lesser extent.

[0027] The hydraulic system 200 includes a fluid source 210 capable of supplying fluid via the supply fluid line 212 over a wide pressure range, e.g., 80–3000 pounds per square inch (psi). In other words, the source 210 can be a variable-pressure fluid source.

[0028] The fluid source 210 can be a pump, an accumulator, another valve in a fluid system of the machine, a cylinder, etc. In one example, the source 210 can comprise a device for providing a fluid flow (e.g., a fixed- or variable-displacement pump) in combination with one or more valves configured to be electronically actuated by an electronic control unit to regulate the pressure level of the fluid provided by the source 210. For example, the control unit can be configured to send a signal to a solenoid of a valve to actuate the valve and achieve a specific pressure level for the fluid provided by the source 210.

[0029] The hydraulic system 200 also includes a fluid tank 214, which can store fluid at a low pressure level (e.g., atmospheric pressure or 0-50 psi). In an example where the fluid source 210 includes a pump, such a pump can draw fluid from the fluid tank 214 and then supply pressurized fluid to other components of the hydraulic system 200. The fluid tank 214 also receives return fluid via the tank line 211.

[0030] The surface-penetrating unit 202 includes a pressure control valve 216, which is configured to receive supply fluid via the unit's supply line 218. The pressure control valve 216 is configured to maintain the fluid at a specific pressure level or within a specific pressure level range downstream of the pressure control valve 216.

[0031] As in Fig. As symbolically represented in Figure 2, the pressure control valve 216 can, for example, be a hydromechanical pressure reducing and relief valve. A pressure reducing valve can provide a uniform pressure in a section of the hydraulic system 200 that operates at a pressure level lower than the normal system pressure (e.g., lower than the pressure level of the fluid supplied by source 210). A pressure reducing valve can be set to a desired reduced pressure within its design limits. For example, the pressure control valve 216 can receive fluid from source 210 at a pressure level in the range of 2800–3000 psi and supply fluid downstream at a reduced pressure level of 600 psi.

[0032] A pressure relief valve is a valve used to control or limit the pressure in a system. Otherwise, pressure can build up, potentially leading to component or system failure. The Pressure Control Valve 216 combines or integrates a pressure relief function with a pressure reduction function to maintain a substantially constant pressure level downstream. The term "substantially constant" is used here to indicate that the pressure level can be maintained within a threshold range (e.g., within 2% to 5%) of a desired pressure level. For example, if a desired pressure level is 600 psi, the Pressure Control Valve 216 can maintain the pressure level downstream in the range of 580–620 psi.

[0033] In the embodiment of Fig. 2. The pressure control valve 216 can have (ii) an inlet port 213 coupled to the supply line 218 of the unit, (ii) an outlet port 215 through which fluid is discharged downstream of the pressure control valve 216, and (iii) a drain port 217 coupled to the return line 219 of the unit. The term "fluidically coupled" is used throughout to indicate that fluid can flow or communicate between two fluid passages, chambers, ports, or openings.

[0034] In one example, the pressure regulating valve 216 can be a normally open pressure regulating valve configured to reduce a high pressure received at the inlet port 213 to a controlled lower pressure (reduced pressure) at the outlet port 215. The reduced pressure is determined by the preload force of a spring plus the pressure at the outlet port 217. The spring preload force can be adjustable (e.g., manually), as shown in Fig. 2 is represented symbolically.

[0035] The pressure regulating valve 216 further integrates the function of the pressure relief valve from the reduced pressure at the outlet port 215 to the drain port 217. In particular, the pressure regulating valve 216 enables the reduced pressure at the outlet port 215 to remain relatively constant under backflow conditions, e.g., when the backflow at the outlet port 215 is received at a higher pressure level than the set reduced pressure level. Such fluid with a higher pressure level at the outlet port 215 is diverted to the drain port 217 and the return line 219 in order to keep the pressure level at the outlet port 215 essentially constant.

[0036] The outlet port 215 of the pressure control valve 216 is fluidically coupled to a cylinder actuator 220. The unit cylinder actuator 220 can, for example, represent the cylinder actuator 118 or the cylinder actuator 124. The unit cylinder actuator 220 comprises a cylinder 222 and a piston 224, which is slidably (axially movable) mounted in the cylinder 222.

[0037] The piston 224 comprises a piston head 226 and a piston rod 228, which extends from the piston head 226 in the direction of a central longitudinal axis of the cylinder 222. The piston rod 228 can, for example, be coupled to the surface processing device 111 of the series unit 102 of the machine 100 that engages the surface.

[0038] The piston head 226 divides the interior of the cylinder 222 into a first chamber 230 and a second chamber 232. The pressure regulating valve 216 is, as in Fig. 2 shown, fluidically coupled to the second chamber 232 of the unit cylinder actuator 220.

[0039] The fluid can be drawn from the supply line 218 to the inlet port 213 of the pressure regulating valve 216, which reduces the pressure level and discharges the fluid through its outlet port 215 into the second chamber 232 of the cylinder actuator 220. In this way, a fluid with a specific pressure level (e.g., 600 psi) is supplied to the second chamber 232 by the pressure regulating valve 216.

[0040] The fluid in the second chamber 232 exerts a force on the piston 224 in a first direction (e.g. upwards). Fig. 2) Assuming that the diameter of the piston head 226 is D1, then a surface area of ​​the piston head 226 can be determined as A1=πD124. Assuming a diameter of the piston rod 228 is D2, then a surface area of ​​the piston 224, on which the fluid in the second chamber 232 acts, is the annular surface, which is considered A2=πD124−πD224 can be determined. Assuming the pressure level of the fluid in the second chamber 232 (which is controlled by the pressure regulating valve 216) is P2, then a fluid force F2 exerted by the fluid in the second chamber 232 on the piston 224 can be determined as follows. F2=P2⋅A2=P2⋅(πD124−πD224) Since the pressure control valve 216 P2 causes an essentially constant pressure level, the force F2 is an essentially constant fluid force.

[0041] The hydraulic system 200 further comprises a proportional pressure control valve 234, which can control the fluid flow and pressure level in the first chamber 230. The proportional pressure control valve 234 can have (i) an inlet port 231, which is coupled to the supply line 218 of the unit, (ii) an outlet port 233, which is coupled to the first chamber 230, and (iii) a return port 235, which is coupled to the return line 219 of the unit.

[0042] The proportional pressure control valve 234 can include a movable element (e.g., a slide, a valve disc, or a piston) arranged within it. The position of the movable element within the valve controls the size of a throttling point or flow range through the proportional pressure control valve 234.

[0043] The proportional pressure control valve 234 can be electrically actuated by a magnetic actuator 236. For example, the hydraulic system 200 can include a controller configured to send an electrical command signal to the magnetic actuator 236 to actuate the proportional pressure control valve 234. The controller can include one or more processors or microprocessors and a data storage medium (e.g., memory, transient computer-readable medium, non-transient computer-readable medium, etc.). Instructions can be stored in the data storage medium which, when executed by the controller's one or more processors, cause the controller to perform the operations described herein.

[0044] The proportional pressure control valve 234 can operate as a proportional pressure reducing valve. Specifically, the solenoid actuator 236 receives a valve command signal from the control unit and modulates (e.g., changes its position) the movable element of the proportional pressure control valve 234 to reduce the pressure level at the outlet port 233 relative to the pressure level at the inlet port 231, based on the magnitude of the command signal provided to the solenoid actuator 236. The smaller the command magnitude, the smaller the flow range of the proportional pressure control valve 234, and the pressure level at the outlet port 233 decreases. Conversely, as the magnitude of the valve command signal increases, the flow range of the proportional pressure control valve 234 and the pressure level at the outlet port 233 increase.

[0045] The outlet port 233 of the proportional pressure control valve 234 is fluidically coupled to the first chamber 230, so that the fluid, which has a pressure level at the outlet port 233, exerts a force on the piston 224 in a second direction (e.g. downwards). Fig. 2) acts in the opposite direction to the first. Assuming that the pressure level of the fluid in the first chamber 230 (which is controlled by the proportional pressure regulating valve 234) is P1, then a respective fluid force F1, which the fluid in the first chamber 230 exerts on the piston 224, can be determined as follows. F1=P1⋅A1=P1⋅πD124.

[0046] Therefore, the resulting or net fluid force acting on the piston 224 can be determined as follows: F net = F1 - F2 = P1 · A1 - P2 · A2. In the in Fig. In the exemplary implementation shown in Figure 2, the pressure level P2 in the second chamber 232, and thus the force F2, remains essentially constant due to the pressure regulating valve 216. By adjusting the valve command to the proportional pressure regulating valve 234, the pressure level P1 in the first chamber 230 and the force F1 can be changed to adjust the net fluid force F. net to adjust. The net fluid force F exerted on piston 224 net The force is transmitted to the device coupled to the piston 224 (e.g., the device 111 engaging the surface and thus the measuring wheels 112), and the device then exerts the force on the surface (e.g., the base). With this device, the downward force or the net fluid force F can be net The downward force exerted by the piston 224 on the surface engagement device can be adjusted by varying the valve command to the proportional pressure control valve 234 until a desired downward force is achieved.

[0047] For example, if the supply line 218 of the unit contains fluid at a specific pressure level of 3000 psi, the proportional pressure control valve 234 can proportionally vary the pressure in the first chamber 230 between 0 psi and approximately 3000 psi. Thus, the downward force F1 acting on the piston 224 can vary between a low and a high value. With this arrangement, the net fluid force F net vary in a continuum between a net downward force and a net upward force, based on the magnitude of the valve command signal to the magnetic actuator 236.

[0048] To facilitate the achievement of a desired net force, the unit cylinder actuator 220 can include one or more sensors configured to provide information about the actual net force F. netsupply the force exerted on the piston 224. The unit cylinder actuator 220 can, for example, include a force sensor. Various types of force sensors or force transducers can be used. Examples of force sensors include a load cell, a strain gauge force sensor, a piezoelectric force sensor, an inductive force sensor, a capacitive force sensor, a magnetostrictive force sensor, pressure sensors in each of the chambers 230, 232, etc. Therefore, the term "force sensor" is used throughout here to refer to one or more sensors capable of providing force sensor information that can be used to determine the actual force acting on the piston 224.

[0049] The force sensor can be coupled to the piston rod 228, to which a machine attachment (seed opener or measuring wheels) is mounted. The control unit communicates with the force sensor, receives sensor information from it, and determines the net force F accordingly. net , which is exerted on the piston 224 (and thus exerted on the surface by the device coupled to the piston 224). In examples, the force sensor or an additional force sensor can be coupled to the measuring wheels 112 so that the force sensor can take into account differences in the weight of the row unit, which may vary based on the brand, whether a full seed load is included, etc.

[0050] The control unit can receive input information, including input commands that specify a target net force F. netThe control unit specifies the desired force and also receives sensor information from the force sensor. It then sends a valve command signal to the proportional pressure control valve 234 (e.g., to the magnetic actuator 236) to change the pressure level in the first chamber 230 until the desired net force is reached.

[0051] In particular, the control system can display the actual net force F as indicated by the force sensor. net The system compares the net force with a target or desired net force and then adjusts the valve command signal (i.e., the magnitude of the electrical current or voltage) sent to the solenoid actuator 236 of the proportional pressure control valve 234 to achieve the target net force. Thus, the control unit can implement a closed-loop control system to achieve the target net force based on the feedback signal from the force sensor.

[0052] The proportional pressure control valve 234 operates not only as a pressure reducing valve, but also in a second operating mode as a pressure relief valve. In particular, if a pressure spike occurs in the first chamber 230 (at the outlet port 233 of the proportional pressure control valve 234), the proportional pressure control valve 234 releases fluid from the first chamber 230 to the return port 235, which is connected to the return line 219 of the unit.

[0053] The surface-interacting units 204-208 are similarly configured to the surface-interacting unit 202 and may have similar components.

[0054] The hydraulic system 200 can be operated in different modes, depending on whether the source 210 is able to meet the flow requirements of all units (and / or other hydraulic fluid consuming devices of the surface-penetrating machine 100) while maintaining a certain pressure level, such as 3000 psi.

[0055] A first operating mode of the hydraulic system 200 and the surface-engaging machine 100 can be described as a static mode. In this first operating mode, a target output for the surface-engaging units 202-208 is set to a specific value while the surface-engaging machine 100 (e.g., the tractor) is stationary (not moving). In this mode, the source 210 can provide fluid at a pressure of, for example, 3000 psi, while the respective proportional pressure control valves (e.g., proportional pressure control valve 234) can set the pressure level in the respective first chambers (e.g., first chamber 230) to, for example, 1500 psi. In this state or mode, all surface-interacting units 202-208 actively control this pressure level (e.g. 1500 psi in the first chambers), and the inlet pressure provided by source 210 has a margin above the target pressure.Source 210 is capable of maintaining such a margin. The pressure level in the return line 219 and / or the tank line 211 may be approximately 100 psi due to pressure losses resulting from line restrictions (e.g., couplings, fittings, pipes, hoses, etc.).

[0056] A second operating mode of the hydraulic system 200 and the surface-engaging machine 100 can be described as a dynamic mode with normal inlet pressure. In this dynamic state, a target output is set by adjusting a target pressure level (e.g., 1500 psi) in the first chambers, and the surface-engaging machine 100 (e.g., tractor) moves at a low speed, such as about 5 miles per hour (MPH), on stable ground conditions (e.g., essentially level ground and uniform soil texture). In this mode, the source 210 is also capable of supplying fluid at a pressure of 3000 psi (e.g., with a margin above the target pressure of 1500 psi).In this operating mode, with the essentially stable bottom conditions, some pistons of certain surface-engaging units might move upwards (push motion), while other pistons of other surface-engaging units might move downwards (recoil motion). However, the extent of out-of-phase movement is limited by the essentially flat bottom. Thus, the surface-engaging units with push (upward-moving) pistons can have first chambers (similar to first chamber 230) with a pressure level (e.g., 1600 psi) slightly higher than the target pressure, and these chambers can be relieved to the unit's return lines via respective proportional pressure control valves acting as pressure relief valves.On the other hand, the surface-engaging units with rebounding (downward-moving) pistons can have first chambers (similar to first chamber 230) with the target pressure level (e.g., 1500 psi). However, such imbalances are limited by stable soil conditions. In this mode, the pressure level in the return line 219 and / or the tank line 211 may be somewhat higher (e.g., about 300 psi) because some of the fluid is drawn off there from some of the surface-engaging units and the line constraints.

[0057] A third operating mode of the hydraulic system 200 and the surface-engaging machine 100 can be described as a dynamic mode with reduced inlet pressure. In this dynamic state, a target output is set by adjusting a target pressure level (e.g., 1500 psi) in the first chambers, and the surface-engaging machine 100 (e.g., a tractor) can move at a low speed, such as 5 MPH, but over highly variable ground conditions. Such highly variable ground conditions and other demands on the hydraulic system 200 mean that the source 210 is unable to supply a sufficient fluid flow to maintain a specific pressure level in the respective unit supply lines.

[0058] This operating mode can occur, for example, when the number of active surface-engaging units of the surface-engaging machine 100 increases. Under certain operating conditions, for instance, several surface-engaging units may simultaneously require high-pressure fluid to be supplied to their respective first chambers. Other fluid-consuming devices of the surface-engaging machine 100 may also request fluid from source 210. Under such conditions, source 210 may need to supply fluid at a pressure level higher than the pressure level intended to be supplied to the respective first chambers via the respective proportional pressure control valves, but may not be able to do so.For example, if the force required by the pistons necessitates a pressure level of approximately 1500 psi in the respective first chambers, Source 210 should provide fluid at approximately 3000 psi to compensate for any pressure losses in the fluid lines. However, if a sufficiently large number of devices require such a pressure level simultaneously, Source 210 may not be able to deliver enough flow to achieve the desired pressure level at the devices' supply lines, even if the controller fully opens the respective proportional pressure control valves. As an illustrative example, Source 210 may only be able to provide fluid at a pressure of 900 psi, which is insufficient to meet the needs of the various units.

[0059] In other words, in some cases, the hydraulic system 200, and in particular source 210, might not have sufficient capacity to supply enough fluid to maintain the desired pressure level and respective forces for all the actuators of the unit cylinders. This problem can be exacerbated by pressure losses in the numerous fluid lines (hoses, pipes, fittings, etc.) between source 210 and the various surface treatment units.

[0060] However, the hydraulic system 200 includes an amplifier 238, which is installed between the source 210 and the units engaging the surface, and the amplifier 238 can alleviate the problem of such insufficient capacity that can occur in this dynamic mode with an undersupplied source. In particular, the amplifier 238 is configured to use fluid from unit cylinder actuators with upward-moving pistons (push pistons) and to supply fluid to unit cylinder actuators with downward-moving pistons (recoil pistons) in order to compensate for the limited capacity of the source 210 under certain operating conditions.

[0061] Due to the varying ground conditions in this mode, the cylinder actuators of the respective ground-engaging units may be phase-shifted relative to each other. Specifically, the terrain on which the surface-engaging machine 100 operates in this mode is typically uneven, with crest sections (e.g., sections with rising or falling ground) and trough sections (e.g., sections with sloping or descending ground). Thus, a first subset of surface-engaging units may traverse crest sections, while a second subset of surface-engaging units may traverse trough sections.

[0062] The amplifier 238 utilizes such phase-shifted conditions to compensate for the limited flow capacity of the source 210. Specifically, the upward-moving pistons of the first subset of unit cylinder actuators force the fluid (from their respective first chambers) into the respective unit return lines, thus returning this fluid to the amplifier 238. The amplifier 238 then amplifies (increases) the pressure level of the fluid and supplies fluid at the amplified pressure level to the second subset of unit cylinder actuators, which require fluid (with downward-moving pistons). This replenishes the fluid from the source 210 and stabilizes the pressure level of the fluid supplied to the unit cylinder actuators. In other words, the amplifier 238 enables cross-flow or cross-feed from the first subset of cylinder actuators to the second group of cylinder actuators.

[0063] In the exemplary implementation from Fig. The amplifier 238 comprises an amplifier cylinder actuator 240 with an amplifier cylinder 242 and an amplifier piston 244, which is slidably (axially movable) mounted in the amplifier cylinder 242. The amplifier piston 244 comprises a piston head 246 and a piston rod 248, which extends from the piston head 246 along a central longitudinal axis of the amplifier cylinder 242. The piston head 246 divides the interior of the amplifier cylinder 242 into a head chamber 250 and a rod chamber 252.

[0064] As shown, the head chamber 250 is fluidically coupled to the tank line 211 and the rod chamber 252 to the supply fluid line 212. In this setup, the source 210 supplies fluid to the surface-engaging units via the rod chamber 252, and the fluid discharged by the surface-engaging units is delivered to the fluid tank 214 via the head chamber 250.

[0065] Assume that the piston head 246 has a diameter D H , the fluid in the head chamber 250 interacts with a cross-sectional area of ​​the piston head 246, which can be called the piston head area and is equal to AH=πDH24 Assume that the piston rod 248 has a diameter D R , the fluid in the rod chamber 252 interacts with an annular surface of the amplifier piston 244, which is called an annular piston surface ARingforming=πDH2−DR24 can be described.

[0066] Area A Ringförmig is smaller than the piston head area A H . Therefore, if the amplifier piston 244 extends within the amplifier cylinder 242 (e.g., in Fig. (moved downwards, 2) is the amount of fluid flow Q flowing into the head chamber 250. H greater than the amount of fluid flow Q exiting the rod chamber 252 Ringförmig , where the pressure level P aus in the rod chamber 252 relative to the pressure level P in of the fluid in the head chamber 250 by an area ratio AHA Ringforming is amplified (increased).

[0067] In particular, if the amplifier piston 244 moves at a certain speed V, then Q H = A H V greater than Q Ringförmig = A Ringförmig V and QH=AHARingforming Q RingförmigIn other words, the fluid exiting the rod chamber 252 has a flow rate that is, in relation to the fluid flowing into the head chamber 250, by the area ratio AHA Ringforming is reduced. On the other hand, the pressure level of the fluid in the rod chamber 252 is reduced by the same area ratio. AHA Ringforming relative to the pressure level in the head chamber, 250 is amplified or increased.

[0068] As in Fig. As shown in Figure 2, the respective return lines (similar to and including return line 219) are connected to a return channel 254, which is fluidly coupled to the head chamber 250 of the amplifier cylinder actuator 240. Conversely, the respective unit supply lines (similar to and including unit supply line 218) are connected to a supply channel 256, which is fluidly coupled to the rod chamber 252 of the amplifier cylinder actuator 240.

[0069] In this arrangement, when one or more of the surface-engaging units cross vertex sections and their respective pistons move upwards, the pressure in the respective first chambers of the unit's cylinder actuators can rise or increase for a short period (e.g., 50–100 milliseconds). This causes the pressure to also rise in the unit's return lines, the return channel 254 and the head chamber 250. Such a pressure spike is further amplified by the booster cylinder 240, as described above, so that fluid with an increased pressure level (but reduced flow rate) is delivered from the supply channel 256 to the respective unit supply lines. The booster 240 can include a check valve 258 that prevents fluid exiting the rod chamber 252 from flowing back to the source 210. Instead, the fluid from the rod chamber 252 is directed into the supply channel 256.

[0070] As an example to illustrate: If the area ratio AHAAnnular 4, and if the pressure of the fluid returning to the head chamber 250 via the unit's return lines is 500 psi, then the fluid exiting the rod chamber 252 has a pressure of approximately 2000 psi. This fluid is fed to the respective supply lines of the unit to ensure they have a sufficient pressure level if the source 210 is unable to supply an adequate fluid flow (e.g., if the source 210 supplies fluid at a pressure level such as 900 psi, which is insufficient to achieve the desired force levels). Thus, the energy recovered from the pressure peaks in the unit's return lines is transferred to the unit's supply lines via the amplifier 238, with pressure amplification and flow reduction.This allows the machine 100, which engages the surface, to travel at higher speeds under changing soil conditions, while precisely maintaining the downward forces for each individual cylinder actuator.

[0071] Furthermore, the amplifier 238 can be arranged near the cylinder actuators in certain examples. In this way, pressure losses due to fluid connections between the amplifier 238 and the actuators of the unit cylinder can be reduced.

[0072] For example, the booster cylinder 240, the check valve 258, various fluid passages, and respective connections linked to the surface-engaging units can be integrated into a connecting block or distributor 260. Furthermore, the hydraulic system 200 can include a supply pressure sensor 262 and a return pressure sensor 264. The pressure sensors 262 and 264 can be configured to provide the hydraulic system 200's control unit with sensor information indicating the pressure levels in the supply line 256 and the return line 254, enabling the control unit to monitor pressure spikes fed to the return line 254 and the fluid supplied to the supply line 256.

[0073] In examples, the surface-interacting machine 100 can have several amplifiers similar to amplifier 238, with each amplifier associated with a group of unit cylinder actuators. In the implementation of Fig. For example, amplifier 238 is associated with 4 unit cylinder actuators. Thus, a machine engaging with the surface with 48 surface-bearing units can have 12 amplifiers. This is only an illustrative example. Each amplifier can be associated with more or fewer units engaging with the surface. For instance, each amplifier can be associated with 6 units engaging with the surface.

[0074] At the in Fig. In the device shown in Figure 2, energy recovery from the fluid introduced into the return channel 254 occurs passively (automatically) via the amplifier 238. There is no active control management system, no additional hydraulic storage devices, and no conversion of hydraulic energy into electrical or mechanical energy stored in energy storage devices. Thus, the device can be operated by Fig. 2. Supplement source 210 and increase the efficiency of hydraulic system 200 at a lower cost.

[0075] Fig. Figure 3 is a flowchart of a procedure 300 for operating the hydraulic system 200 of the surface-engaging machine 100, according to an exemplary implementation. The procedure 300 can comprise one or more operations or actions, as illustrated in one or more of blocks 302-308. Although the blocks are illustrated in a sequential order, in some cases these blocks can be executed in parallel and / or in a different order than described here. Furthermore, the various blocks can be combined into fewer blocks, split into additional blocks, and / or removed, depending on the desired implementation.

[0076] In block 302, the method 300 comprises providing fluid from the fluid source 210 to several unit cylinder actuators (e.g., the unit cylinder actuator 220) of the surface-engaging machine 100, wherein each unit cylinder actuator has a respective piston (e.g., the piston 224) that is movable in a respective cylinder (e.g., the cylinder 222).

[0077] In block 304, the method 300 comprises the intake (e.g., in the head chamber 250 of the amplifier 238) of fluid from a first subset of unit cylinder actuators of the multiple unit cylinder actuators with pistons moving in a first direction (e.g., in Fig. 2 upwards).

[0078] In block 306, the method 300 comprises the amplification (e.g. by the amplifier cylinder actuator 240 of the amplifier 238) of the pressure level of the fluid received by the first subset of unit cylinder actuators.

[0079] In block 308, method 300 comprises the provision of fluid (e.g., from the rod chamber 252 of the booster cylinder actuator 240) with a boosted pressure level for a second subset of unit cylinder actuators of the multiple unit cylinder actuators with pistons moving in a second direction (e.g., in Fig. 2 downwards) as a supplement to fluid from source 210.

[0080] Procedure 300 may include all further steps described in this disclosure.

[0081] The detailed description above details various features and processes of the disclosed systems with reference to the accompanying figures. The illustrative implementations described here are not intended as limitations. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are considered herein.

[0082] Unless the context suggests otherwise, the elements illustrated in the individual figures can also be used in combination with one another. Therefore, the figures should generally be considered as component aspects of one or more overall implementations, and not all illustrated elements are required for every implementation.

[0083] Furthermore, any enumeration of elements, blocks, or steps in this description serves the purpose of clarity. Such an enumeration should therefore not be interpreted as meaning that these elements, blocks, or steps must or should be executed in a specific arrangement or order.

[0084] Furthermore, devices or systems can be used or set up to perform the functions shown in the figures. In some cases, the components of the devices and / or systems can be configured to perform the functions, such that the components are actually set up and structured (with hardware and / or software) to enable such performance. In other examples, the components of the devices and / or systems can be arranged to be adapted, capable, or suitable for performing the functions, such as when they are operated in a specific way.

[0085] The term “essentially” or “approximately” means that the specified element, parameter or value need not be achieved exactly, but that deviations or variations, such as tolerances, measurement errors, limitations in measurement accuracy and other factors known to those skilled in the art, may occur to an extent that does not preclude the intended effect of the feature.

[0086] The arrangements described here serve only as examples. Experts in the field know that other arrangements and elements (e.g., machines, interfaces, processes, sequences and groupings of processes, etc.) can be used instead, and some elements can be omitted entirely depending on the desired results. Furthermore, many of the described elements are functional units that can be implemented as discrete or distributed components, or in combination with other components, in any suitable combination and at any suitable location.

[0087] While various aspects and implementations have been disclosed herein, other aspects and implementations are obvious to those skilled in the field. The various aspects and implementations disclosed herein serve for illustrative purposes and are not to be understood as limiting, the true scope being specified by the following claims, together with the full scope of the equivalents to which such claims entitle. Furthermore, the terminology used herein serves only to describe certain implementations and is not to be understood as limiting.

[0088] Embodiments of the present disclosure may therefore refer to one of the exemplary embodiments (EEEs) listed below.

[0089] EEE 1 is a hydraulic system for a surface-engaging machine with multiple surface-engaging units, wherein the hydraulic system comprises: multiple unit cylinder actuators; a fluid source, wherein the source is fluidically coupled to the multiple unit cylinder actuators; and an amplifier, which is fluidically coupled to the multiple unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the multiple unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the multiple unit cylinder actuators, thereby replenishing fluid from the source.

[0090] EEE 2 is the hydraulic system of EEE 1, wherein the amplifier comprises: an amplifier cylinder actuator with an amplifier cylinder and an amplifier piston movable within the amplifier cylinder, the amplifier piston dividing an interior of the amplifier cylinder into a head chamber and a rod chamber, wherein fluid received by the first subset of unit cylinder actuators is received in the head chamber and wherein fluid supplied by the amplifier is supplied via the rod chamber.

[0091] EEE 3 is the hydraulic system of EEE 2, in which the source is fluidly coupled to the rod chamber of the amplifier, so that the source is fluidly coupled to the multiple unit cylinder actuators via the rod chamber of the amplifier.

[0092] EEE 4 is the hydraulic system of EEE 3, which further includes a check valve that allows fluid flow from the source to the rod chamber while preventing backflow from the rod chamber to the source.

[0093] EEE 5 is the hydraulic system of EEE 4, in which the booster and the check valve are integrated into a manifold which has respective ports that are in fluid contact with the multiple unit cylinder actuators.

[0094] EEE 6 is the hydraulic system of one of the EEEs 2-5, which further includes: a fluid tank which is fluidically coupled to the head chamber, so that the fluid tank is fluidically coupled to the multiple unit cylinder actuators via the head chamber of the amplifier.

[0095] EEE 7 is the hydraulic system of one of the EEEs 1-6, wherein each unit cylinder actuator of the multiple unit cylinder actuators (i) has a cylinder and (ii) a piston movable in the cylinder, wherein the first subset of the unit cylinder actuators has respective pistons moving in a first direction, and wherein the second subset of the unit cylinder actuators has respective pistons moving in a second direction.

[0096] EEE 8 is the hydraulic system of EEE 7, wherein the piston divides the cylinder into a first chamber and a second chamber, and wherein the hydraulic system further comprises: a proportional pressure control valve that fluidically couples the source to the first chamber.

[0097] EEE 9 is the hydraulic system of EEE 8 in which the proportional pressure control valve is electrically actuated, so that the pressure level of the fluid supplied in the first chamber varies based on the size of an electrical command to the proportional pressure control valve.

[0098] EEE 10 is the hydraulic system of one of the EEEs 8-9, further comprising: a pressure control valve that fluidically couples the source with the second chamber, so that the pressure control valve provides fluid to the second chamber at a substantially constant pressure.

[0099] EEE 11 is a surface-engaging machine with the hydraulic system of one of EEEs 1-10. The surface-engaging machine comprises, for example: several surface-engaging units, each surface-engaging unit having a respective unit cylinder actuator; a fluid source fluidically coupled to respective unit cylinder actuators of the several surface-engaging units; and an amplifier fluidically coupled to the respective unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the respective unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the respective unit cylinder actuators, thereby replenishing fluid from the source.

[0100] EEE 12 is the surface-engaging machine of EEE 11, wherein the amplifier comprises: an amplifier cylinder actuator with an amplifier cylinder and an amplifier piston movable within the amplifier cylinder, the amplifier piston dividing an interior of the amplifier cylinder into a head chamber and a rod chamber, fluid received by the first subset of unit cylinder actuators being received at the head chamber, and fluid supplied by the amplifier being supplied via the rod chamber.

[0101] EEE 13 is the surface-interacting machine of EEE 12, in which the source is fluidly coupled to the rod chamber of the amplifier, so that the source is fluidly coupled to the respective unit cylinder actuators via the rod chamber of the amplifier.

[0102] EEE 14 is the surface-penetrating machine, of EEE 13, which further includes a check valve that allows fluid flow from the source to the rod chamber while preventing backflow from the rod chamber to the source.

[0103] EEE 15 is the surface-penetrating machine of EEE 14, in which the amplifier and the check valve are integrated into a distributor which has respective connections that are fluidically connected to the respective unit cylinder actuators.

[0104] EEE 16 is the surface-interacting machine according to one of the EEEs 12 to 15, which further comprises: a fluid tank which is fluidically coupled to the head chamber, so that the fluid tank is fluidically coupled to the respective unit cylinder actuators via the head chamber of the amplifier.

[0105] EEE 17 is the surface-engaging machine, one of EEEs 11-16, wherein each unit cylinder actuator of the respective unit cylinder actuators (i) has a cylinder and (ii) a piston movable in the cylinder, wherein the first subset of unit cylinder actuators has respective pistons moving in a first direction, and wherein the second subset of unit cylinder actuators has respective pistons moving in a second direction.

[0106] EEE 18 is the surface-engaging machine of EEE 17, wherein the piston divides the cylinder into a first chamber and a second chamber, and wherein each surface-engaging unit comprises: a proportional pressure control valve fluidically coupling the source to the first chamber, wherein the proportional pressure control valve is electrically actuated such that the pressure level of the fluid supplied to the first chamber varies on the basis of the magnitude of an electrical command to the proportional pressure control valve.

[0107] EEE 19 is the surface-intervening machine of EEE 18, wherein the respective surface-intervening unit further comprises: a pressure control valve that fluidically couples the source to the second chamber, such that the pressure control valve provides fluid to the second chamber at a substantially constant pressure.

[0108] EEE 20 is a method for operating the hydraulic system of one of EEEs 1-10 or the surface-engaging machine of one of EEEs 11-19. The method comprises, for example: supplying fluid from a fluid source to several unit cylinder actuators of a surface-engaging machine, each unit cylinder actuator having a respective piston movable within a respective cylinder; receiving fluid from a first subset of unit cylinder actuators of the several unit cylinder actuators having pistons moving in a first direction; increasing the pressure level of the fluid received by the first subset of unit cylinder actuators; and supplying fluid with an increased pressure level to a second subset of unit cylinder actuators of the several unit cylinder actuators having pistons moving in a second direction, thereby replenishing fluid from the source. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] US 63 / 513,364

[0001] US 63 / 603,978

[0001]

Claims

[1] Hydraulic system for a machine engaging in a surface with several surface processing units, comprising the hydraulic system: several unit cylinder actuators; a fluid source, wherein the source is fluidically coupled to the multiple unit cylinder actuators; and an amplifier fluidically coupled to the multiple unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the multiple unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the multiple unit cylinder actuators, thereby replenishing fluid from the source. [2] Hydraulic system according to claim 1, wherein the amplifier comprises: an amplifier cylinder actuator comprising an amplifier cylinder and an amplifier piston movable within the amplifier cylinder, the amplifier piston dividing an interior of the amplifier cylinder into a head chamber and a rod chamber, fluid received by the first subset of unit cylinder actuators being received at the head chamber, and fluid supplied by the amplifier being supplied via the rod chamber. [3] Hydraulic system according to claim 2, wherein the source is fluidly coupled to the rod chamber of the amplifier, such that the source is fluidly coupled to the multiple unit cylinder actuators via the rod chamber of the amplifier. [4] Hydraulic system according to claim 3, further comprising: a check valve that allows fluid flow from the source to the rod chamber while preventing backflow from the rod chamber to the source. [5] Hydraulic system according to claim 4, wherein the amplifier and the check valve are integrated into a distributor which has respective connections which are fluidically connected to the multiple unit cylinder actuators. [6] Hydraulic system according to claim 2, further comprising: a fluid tank which is fluidly coupled to the head chamber, so that the fluid tank is fluidly coupled to the several unit cylinder actuators via the head chamber of the amplifier. [7] Hydraulic system according to claim 1, wherein each unit cylinder actuator of the multiple unit cylinder actuators (i) has a cylinder and (ii) a piston movable in the cylinder, wherein the first subset of the unit cylinder actuators has respective pistons that move in a first direction, and wherein the second subset of the unit cylinder actuators has respective pistons that move in a second direction. [8] Hydraulic system according to claim 7, wherein the piston divides the cylinder into a first chamber and a second chamber, and wherein the hydraulic system further comprises: a proportional pressure control valve that fluidically couples the source with the first chamber. [9] Hydraulic system according to claim 8, wherein the proportional pressure control valve is electrically actuated such that the pressure level of the fluid supplied to the first chamber changes based on the magnitude of an electrical command to the proportional pressure control valve. [10] Hydraulic system according to claim 8, further comprising: a pressure control valve that fluidically couples the source with the second chamber, so that the pressure control valve provides fluid to the second chamber at an essentially constant pressure. [11] Machine intervening into a surface, comprising: several units engaging with the surface, each unit engaging with the surface having a respective unit cylinder actuator; a fluid source coupled to the respective unit cylinder actuator of the multiple units engaging the surface; and an amplifier which is fluidically coupled to the respective unit cylinder actuators, wherein the amplifier (i) receives fluid from a first subset of unit cylinder actuators of the respective unit cylinder actuators and (ii) supplies fluid at an increased pressure level relative to the pressure level of the received fluid to a second subset of unit cylinder actuators of the respective unit cylinder actuators, thereby replenishing fluid from the source. [12] Machine engaging in a surface according to claim 11, comprising amplifier: an amplifier cylinder actuator comprising an amplifier cylinder and an amplifier piston movable within the amplifier cylinder, the amplifier piston dividing an interior of the amplifier cylinder into a head chamber and a rod chamber, fluid received by the first subset of unit cylinder actuators being received at the head chamber, and fluid supplied by the amplifier being supplied via the rod chamber. [13] Machine engaging in a surface according to claim 12, wherein the source is fluidly coupled to the rod chamber of the amplifier, such that the source is fluidly coupled to the respective unit cylinder actuators via the rod chamber of the amplifier. [14] Machine engaging in a surface according to claim 13, further comprising: a check valve that allows fluid flow from the source to the rod chamber while preventing backflow from the rod chamber to the source. [15] Machine engaging in a surface according to claim 14, wherein the amplifier and the check valve are integrated into a distributor which has respective connections which are fluidically connected to the respective unit cylinder actuators. [16] Machine engaging in a surface according to claim 12, further comprising: a fluid tank which is fluidically coupled to the head chamber, so that the fluid tank is fluidically coupled to the respective unit cylinder actuators via the head chamber of the amplifier. [17] Machine engaging in a surface according to claim 11, wherein each unit cylinder actuator of the respective unit cylinder actuators (i) has a cylinder and (ii) a piston movable in the cylinder, wherein the first subset of unit cylinder actuators has respective pistons that move in a first direction, and wherein the second subset of unit cylinder actuators has respective pistons that move in a second direction. [18] Machine engaging in a surface according to claim 17, wherein the piston divides the cylinder into a first chamber and a second chamber, and wherein each has a surface treatment unit: a proportional pressure control valve that fluidically couples the source to the first chamber, wherein the proportional pressure control valve is electrically actuated, so that the pressure level of the fluid supplied to the first chamber varies based on the size of an electrical command to the proportional pressure control valve. [19] Machine engaging in a surface according to claim 18, the respective surface treatment unit further comprising: a pressure control valve that fluidically couples the source with the second chamber, so that the pressure control valve provides fluid to the second chamber at an essentially constant pressure. [20] Procedures, including: Providing fluid from a fluid source to multiple unit cylinder actuators of a machine engaging a surface, wherein each unit cylinder actuator has a respective piston that is movable within a respective cylinder; Taking in fluid from a first subset of unit cylinder actuators of the multiple unit cylinder actuators with pistons moving in a first direction; Increasing the pressure level of the fluid received by the first subset of unit cylinder actuators; and Providing fluid with an increased pressure level for a second subset of unit cylinder actuators of the multiple unit cylinder actuators with pistons moving in a second direction, thereby supplementing fluid from the source.

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