Hydraulic system for a lift vehicle

Abstract

A hydraulic system for a lift device, such as a lift vehicle, is provided. A first fluid circuit includes a first pump drivingly connected to at least one motor, and a first hydraulic actuator receiving fluid flow from the first pump via a first pressure galley. A second fluid circuit includes a second pump drivingly connected to the at least one motor, and a second hydraulic actuator receiving fluid flow from the second pump via a second pressure galley. A crossover valve is provided to fluidly connect the first pressure galley to the second pressure galley in an open position, and isolate the first pressure galley from the second pressure galley in a closed position. A lift device, and a method of controlling the hydraulic system of the lift device are also included.

Description

HYDRAULIC SYSTEM FOR A LIFT VEHICLECROSS-REFERENCE TO RELATED APPLICATIONS[00011 This application claims the benefit of U.S. provisional application Serial No. 63 / 741,313 filed January 2, 2025, the disclosure of which is hereby incorporated in its entirety by reference herein.TECHNICAL FIELD

[0002] Various embodiments relate to a hydraulic system for a vehicle such as a lift vehicle.BACKGROUND[00031 Examples of hydraulic systems for vehicles may be found in U.S. Pat. Pub. No.2020 / 0386101 Al, U.S. Pat. Pub. No. 2022 / 0275601 Al, U.S. Pat. No. 11,022,153 B2, U.S. Pat. Pub. No. 2022 / 0098017 Al, and U.S. Pat. No. 8,978,798 B2.SUMMARY

[0004] According to an example, a hydraulic system for a lift device is provided. The hydraulic system has at least one motor. The hydraulic system has a first fluid circuit comprising a first pump drivingly connected to the at least one motor, and a first hydraulic actuator receiving fluid flow from the first pump via a first pressure galley. The hydraulic system has a second fluid circuit comprising a second pump drivingly connected to the at least one motor, and a second hydraulic actuator receiving fluid flow from the second pump via a second pressure galley. A crossover valve fluidly connects the first pressure galley to the second pressure galley in an open position, and isolate the first pressure galley from the second pressure galley in a closed position.

[0005] According to another example, a hydraulic system for a lift device is provided. The hydraulic system has a first fluid circuit comprising a first pump, s first relief valve, and a first hydraulic actuator receiving fluid flow from the first pump via a first check valve in a first pressuregalley. The hydraulic system has a second fluid circuit comprising a second pump, a second relief valve, and a second hydraulic actuator receiving fluid flow from the second pump via a second check valve in a second pressure galley. The hydraulic system has a third fluid circuit comprising a third pump, a third relief valve, and a third hydraulic actuator receiving fluid flow from the third pump via a third check valve in a third pressure galley. A first crossover valve is provided to fluidly connect the first pressure galley to the second pressure galley in an open position, and isolate the first pressure galley from the second pressure galley in a closed position. A second crossover valve is provided to fluidly connect the second pressure galley to the third pressure galley in an open position, and isolate the second pressure galley from the third pressure galley in a closed position.[0(106] According to yet another example, a method of controlling a hydraulic system in a lift device is provided. A first pump in a first fluid circuit is operated to provide flow to a first pressure galley connected to a first actuator. In response to receiving a request for flow in the first pressure galley above a threshold associated with the first pump, a second pump is operated in a second fluid circuit with a second pressure galley connected to a second actuator A pressure setting of a relief valve positioned upstream of a check valve in the second pressure galley to fluidly couple the second pressure galley to a return line for the second pump. A crossover valve positioned downstream of the check valve is opened to fluidly connect the second pressure galley to the first pressure galley. The pressure setting of the relief valve is controlled to direct flow from the second pressure galley into the first pressure galley such that flow in the first pressure galley is above the threshold.BRIEF DESCRIPTION OF THE DRAWINGS

[0007] FIGURE 1 is a perspective view of an aerial lift vehicle according to an embodiment, illustrated in a partially extended position;10008] FIGURE 2 is a perspective view of an aerial lift vehicle according to another embodiment, illustrated partially extended;

[0009] FIGURE 3 is a hydraulic schematic according to an embodiment and for use with the vehicles of Figure 1 or 2;

[0010] FIGURE 4 is a partial view of the hydraulic schematic of Figure 3, illustrating an alternative motor arrangement;

[0011] FIGURE 5 is a flow chart for a method of controlling a hydraulic system; and

[0012] FIGURE 6 is a hydraulic schematic according to another embodiment and for use with the vehicles of Figure 1 or 2, and / or method of Figure 5.DETAILED DESCRIPTION

[0013] Reference will now be made in detail to embodiments, examples of which are illustrated in the accompanying drawings. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the various described embodiments. However, it will be apparent to one of ordinary skill in the art that the various described embodiments may be practiced without these specific details. In other instances, well-known methods, procedures, components, circuits, and networks have not been described in detail so as not to unnecessarily obscure aspects of the embodiments.

[0014] It is to be understood that the disclosed embodiments are merely exemplary and that various and alternative forms are possible. The figures are not necessarily to scale; some features may be exaggerated or minimized to show details of particular components. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a representative basis for teaching one skilled in the art to variously employ embodiments according to the disclosure.

[0015] It will also be understood that, although the terms first, second, etc. are, in some instances, used herein to describe various elements in order of introduction, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first valve could be termed a second valve, and, similarly, a second valve could betermed a first valve, without departing from the scope of the various described embodiments. The first valve and the second valve are both valves, but they are not the same valve.(0016] The terminology used in the description of the various described embodiments herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used in the description of the various described embodiments and the appended claims, the singular forms “a”, “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that the term “and / or” as used herein refers to and encompasses any and all possible combinations of one or more of the associated listed items. It will be further understood that the terms “includes,” “including,” “comprises,” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0017] As used herein, the term “if’ is, optionally, construed to mean “when” or “upon” or “in response to determining” or “in response to detecting,” depending on the context. Similarly, the phrase “if it is determined” or “if [a stated condition or event] is detected” is, optionally, construed to mean “upon determining” or “in response to determining” or “upon detecting [the stated condition or event]” or “in response to detecting [the stated condition or event],” depending on the context.|0018| The terminology controller may be provided as one or more controllers or control modules for the various components and systems. The controller 88 and control system may include any number of controllers, and may be integrated into a single controller, or have various modules. Some or all of the controllers may be connected by a controller area network (CAN) or other system. It is recognized that any controller, circuit, or other electrical device disclosed herein may include any number of microprocessors, integrated circuits, memory devices (e.g., FLASH, random access memory (RAM), read only memory (ROM), electrically programmable read only memory (EPROM), electrically erasable programmable read only memory (EEPROM), or other suitable variants thereof) and software which co-act with one another to perform operation(s)disclosed herein. In addition, any one or more of the electrical devices as disclosed herein may be configured to execute a computer-program that is embodied in a non-transitory computer readable medium that is programmed to perform any number of the functions as disclosed herein.10019] Aerial lift assemblies provide an operator platform on a linkage assembly that rotates, pivots and / or translates to lift the operator platform to an elevated worksite. Aerial lift assemblies include various adjustable structures to lift an operator platform to a height for performing a work operation. The aerial lift assemblies often include a stack linkage assembly. The aerial lift assemblies often include an articulated boom assembly, which may be provided by a four-bar linkage mechanism or an extending riser type linkage. Aerial lift assemblies are often provided on land vehicles for transportation of operator platform to the worksite.

[0020] Figure 1 illustrates a lift device 20 or utility vehicle 20 or aerial lift assembly 20 according to a first example and for use with the present disclosure. The lift device 20 may be used in a commercial or industrial environment and may include lift equipment, including a portable material lift, aerial work platform, telehandler, scissor lift, rough terrain telescopic load handler, and telescopic and articulating boom. The lift device 20 may be mobile on an underlying support surface, and the lift equipment may be retracted, collapsed, or otherwise stowed for transportation. The lift device 20 may be transportable for towing and transport upon a trailer behind a truck. In Figure 1, the lift device 20 is illustrated as a telescopic and articulating boom according to a nonlimiting example.

[0021] As shown, the lift device 20 is expandable or raised by operator control to lift an operator to an elevated worksite. The lift device may further include rotational movements in addition to translational movements to move the operator to the elevated worksite. The lift device 20 is configured for lifting a load, such as a person, tools, cargo, and the like, with respect to a support surface 22 or the underlying terrain, such as paved or unpaved ground, a road, an apron such as a sidewalk or parking lot, an interior or exterior floor of a structure, or other surfaces.

[0022] The lift device 20 includes a lift structure that provides significant stability and performance characteristics by elevating a worker to a selected position for reach while providing stability. The lift device 20 includes a chassis 24 to support the lift device 20 upon the ground 22or any support surface. The chassis 24 is supported upon a plurality of wheels 26 that contact the ground 22 for support and mobility of the lift device 20.(0023] A lift mechanism 28 is connected to the chassis 24 to extend and retract from the chassis 24. A lift platform 30 is provided on the lift mechanism 28 with a perimeter railing 32. According to one embodiment, the lift mechanism 28 includes a plurality of linkages with an extendable boom. At least one actuator assembly 34 may be provided to pivot the linkages and the extendable boom, and another actuator assembly 36 may be provided to extend the boom. Furthermore, an the lift platform 30 and lift mechanism 28 may be supported by a swing chassis 38 that is rotatably connected to the chassis 24, with an associated actuator assembly 38 to rotate the swing chassis 38 relative to the chassis 24.

[0024] The lift device 20 may have a propulsion system with one or more motors to propel the wheels. In one example, the lift device has an electric propulsion system that acts to propel the vehicle, with one or more electric motors rotating the wheels. In a further example, each wheel may be provided with an associated electric motor to rotate the wheel, e.g. in a direct drive or hub motor configuration. The electric motor for propulsion of the wheel may be drivingly coupled to at least one wheel supported by the chassis to propel the lift vehicle. In other examples, the lift device 20 may be propelled via an internal combustion engine, or via a hybrid powered propulsion system.

[0025] The lift device 20 also has a hydraulic system that operates the work function, such as actuator assemblies associated with the lift platform and lift mechanism 28, as well as actuators associated with other vehicle systems such as steering and / or oscillating axle(s). Examples of hydraulic systems for use with the lift device 20 are described below in further detail with respect to Figure 3-5.(0026] The operator for the lift device 20 inputs commands to the lift device 20 via an operator input or user input 40, e.g., on a control panel. The operator input 40 may control the propulsion system to control the speed of the wheels. The operator input 40 also provides for steering input, operator control of the position of the lift platform 30 relative to the chassis 24 via the lift mechanism 28, and the like.

[0027] Figure 2 illustrates a lift device 50 according to another embodiment and for use with the present disclosure. Elements that are the same as or similar to those described above with respect to Figure 1 are given the same reference number for simplicity.

[0028] In Figure 2, the lift device 50 is illustrated as a stack linkage lift according to another nonlimiting example. The lift device 50 is utilized to lift the platform 30 and workers to elevated work locations to perform work operations. A linkage assembly 52 is connected to the chassis 24 to extend and retract from the chassis 24. A lift platform 30 is provided on the linkage assembly 28 to extend and retract from the chassis 24. The linkage assembly 52 is a stack linkage assembly 52, with a series of pivotally connected stack links that retract to collapse and stack upon the chassis 24 for compactness for storage and transportation. The lift device 50 also includes an actuator assembly 54 to extend and retract the linkage assembly 52 and consequently, extend and retract the platform 30. The platform 30 includes perimeter railing 32 extending upward from the platform 30 to enclose an operator workspace upon the platform 30.

[0029] The lift device 50 may additionally have a propulsion system as described above with respect to Figure 1. The lift device 50 has a hydraulic system that operates the work functions or load functions, such as lift actuator assembly(ies) 54 associated with the lift platform and lift linkage assembly 52, as well as actuators associated with other vehicle systems such as steering and / or oscillating axle(s). Examples of hydraulic systems for use with the lift device 50 are described below in further detail with respect to Figures 3-5. The operator for the lift device 50 inputs commands to the lift device 20 via an operator input or user input 40, e.g., on a control panel, as described above with respect to Figure 1.

[0030] Figures 3 and 5 illustrate examples of hydraulic systems 100, 300 for use with a lift vehicle or lift device. Figure 4 illustrates an alternative motor and pump arrangement for use with the hydraulic system 100 of Figure 3. In various non-limiting examples, the hydraulic systems of Figures 3-5 may be implemented on the lift vehicle 20 or lift vehicle 50 as disclosed herein.|00311 Generally, the hydraulic systems 100, 300 as disclosed herein run multiple pumps in a parallel configuration to meet the power specifications for the hydraulic system, which allows for use of use lower power, lower voltage pump motors in comparison to a single pump system. Withthe disclosed use of more than one pump, and optional use of more than one motor, smaller pumps may also be used, as the hydraulic systems 100, 300 allow for two or more pumps to be fluidly connected together to achieve the needed flow to a function to the extent it exceeds the output available from one of the motor and pump combinations, e.g. when a pump threshold is reached. Additionally, the hydraulic systems 100, 300 as disclosed herein provide for dedicated single pumps for single functions or groups of functions, which can further realize increases in efficiency since a pump speed (which may be controlled via a motor speed) may be used to meter fluid flow at a load pressure, opposed to metering the flow hydraulically via a valve assembly which introduces pressure or flow losses. For example, the hydraulic system 100 may be operating at or near a maximum efficiency when metering or control valves in valve assemblies 114 are wide open and the function 114 speed is controlled by a speed of the pump 106. With the disclosure herein, multiple pumps are provided, and flow may be combined via crossover valves when a pump cannot meet the requirements of the active functions that are connected to it. Additionally, and with the use of smaller motors and / or pumps, the motors and pumps may operate on an electrical system that is rated at a lower voltage than would be required for a single motor and pump system, for example, as a 48 Volt system and components versus a 60 Volt system and components, which allows for reduced costs associated with batteries and other electrical components such as motor controllers.

[0032] Conversely, in other systems with only a single motor and pump combination for the hydraulic system, use of a higher battery voltage would be likely required as well as a higher pump flow output to meet the requirements of the functions collectively, which may be less efficient that the hydraulic systems according to the present disclosure. For example, with a single motor, single pump system, if a first function is operated (with a large actuator and low pressure requirement) at the same time as a second function (with a smaller actuator and high pressure requirement), the single pump would need to operate at the higher pressure requirement for the second function while also supplying the large flow required by the first function, which would require the flow to be restricted (or metered) to the first function, which inherently creates inefficiencies via pressure loss and fluid heating. In the present disclosure, and as described below, the hydraulic system 100, 300 may operate two motors and two pumps to provide separate flows to each of the first andsecond functions, with the motors and pumps controlled to output based on each function’s flow and pressure requirements.(0033] Referring to Figure 3, the hydraulic system 100 is shown schematically. The hydraulic system 100 has at least one motor 102. In the non-limiting example shown, the hydraulic system 100 has a first motor 102a and a second motor 102b. Each motor 102 may be provided by an electric machine or electric motor. In other examples, and as further described below, one or more of the motors 102 may be provided as or include an internal combustion engine. For electric motors, each electric motor 102 may be connected to a battery that is on-board the lift device, via a motor controller to allow control over the motor speed. In various examples, the electric motors 102 may be operated as motors to provide torque output to drive associated pumps 106, or as generators to provide current to charge the battery, such as a traction or other battery on-board the device 20, 50. In the examples shown, the motors 102 are dedicated for use with the hydraulic system 100, and the motor shafts are not coupled or drivingly connected to wheels 26 of the device 20, 50. As described above with respect to Figures 1 and 2, the wheels 26 may be propelled using separate motor systems on-board the device 20, 50.

[0034] In one example, one motor 102 is drivingly connected to two pumps 106, with each pump 106 fluidly connected to its own pressure galley 112 (or supply line or manifold) and associated fluid circuit 104. Each pressure galley 112 provides pressurized fluid to one or more loads 114. In another example, one motor 102 is drivingly connected to a first pump 106 and a second motor 102 is drivingly connected to a second pump 106, with each pump 106 fluidly connected to its own separate associated pressure galley 112. In a further example, and as shown in Figure 3, a combination is provided with one motor 102 is drivingly connected to two pumps 106, with each pump 106 fluidly connected to its own pressure galley 112 and associated fluid circuit 104, and another motor 102 drivingly connected to a third pump 106 and its associated pressure galley 112. In further examples, additional combinations of motors 102 and pumps 106 for various pressure galleys 112 and fluid circuits 104 may be provided within the spirit and scope of the disclosure.

[0035] The hydraulic system 100 as shown also has a first fluid circuit 104a, a second fluid circuit 104b, and a third fluid circuit 104c. Although three fluid circuits are shown by way of example,in other examples, the hydraulic system 100 may be provided with two fluid circuits, or with more than three fluid circuits. Each fluid circuit 104 has an associated fluid pump 106 that provides fluid flow to a pressure galley 112 with a relief valve assembly 108 and a check valve 110, with the pump 104 and associated pressure galley 112 providing flow to one or more associated loads 114 for the fluid circuit. Each load 114 may include one or more actuator assemblies 116 to control a function of the lift device 20, as well as one or more associated valve assemblies 118 and other associated flow control elements for the actuator assembly, e.g. for hydraulic-based pressure compensation via a pressure compensated flow control valve in the valve assembly 118 or with an electronic-based pressure compensation via a motion sensor on the load 114 for speed control via the controller 130. For example, if two loads 114 are fluidly connected to the same pressure galley or fluid source, pressure compensation may be needed for both loads 114 to operate in parallel and with different flow and pressure requirements.

[0036] Each actuator assembly 116 may be provided with its own valve assembly 118 as shown. Each valve assembly 118 may include one or more valve elements as appropriate for the load 114 and hydraulic actuator 116 such as a holding valve, flow directional control valve or metering valve, function enable valve, or the like. A function enable valve is operable to block flow from the actuator or redirect fluid flow back to the return line 140, e.g. to prevent movement of the actuator 116 is a primary control valve in the valve assembly 118 will not close.|0037| At least two of the fluid circuits 104 may be selectively fluidly connected to one another via an associated crossover valve assembly 120. In the example shown, the hydraulic system 100 has a first crossover valve 120a to connect the first and second fluid circuits 104a, b, and a second crossover valve 120b to connect the first and second fluid circuits 104b, c.

[0038] The hydraulic system 100 is also connected to a controller 130. The controller 130 may be integrated or in communication with a controller or control system for the lift device 20, 50. The controller 130 is in communication with the operator input 40, as well as the various controllable components of the hydraulic system 100, and any sensors associated with the hydraulic system 100, including pressure sensors, and angular or linear sensors associated with actuators 116 in the loads 114. The controller may also receive other inputs from other sensors orsystems on-board the device 20, for example, such as a pressure sensor 132. Although only one sensor 132 is shown associated with the first fluid circuit 104a, additional pressure sensors may also be provided, e.g. for one or more of the other fluid circuits. The controller 130 may control: the electric motors 102, the pumps 106, the relief valves 108, the crossover valves 120, and the valve assemblies 118 associated with the loads 114.

[0039] More specifically, and with reference to the example in Figure 3, the first fluid circuit 104a has a first motor 102a drivingly connected to a first pump 106a. The first pump 106a is fluidly coupled to a first pressure galley 112a or first pressure manifold. The first pressure galley 112a has sequentially: a first relief valve 108a that fluidly connects the first pressure galley to a return line 140, a first check valve 110a that is positioned to prevent flow from returning to the first pump 106a via the first pressure galley, a first crossover valve 120a connected to an adjacent pressure galley of another fluid circuit (such as pressure galley 112b), and a first load 114a. In other examples, the first fluid circuit 104a may be provided with more than one load 114a. Flow from the load 114a flows through the return line 140 to a reservoir 142 for the first pump 106a.

[0040] The second fluid circuit 104b has a second motor 102b drivingly connected to a second pump 106b. The second pump 106b is fluidly coupled to a second pressure galley 112b or second pressure manifold. The second pressure galley 112b has sequentially: a second relief valve 108b that fluidly connects the second pressure galley to a return line 140, a second check valve 110b that is positioned to prevent flow from returning to the second pump 106b via the second pressure galley, the first crossover valve 120a and a second crossover valve 120b, and a second load 114b. The first and second crossover valves 120a, b are each connected to adjacent pressure galleys of other fluid circuits (such as pressure galleys 112a, 112c, respectively). In other examples, the second fluid circuit 104b may be provided with more than one load 114b. Flow from the load 114b flows through the return line 140 to a reservoir 142 for the second pump 106b.[00411 The third fluid circuit 104c has the second motor 102b drivingly connected to a third pump 106c. The third pump 106c may be coaxial and piggybacked onto the second pump 106b, e.g. such that one motor is drivingly connected to two pumps, with the second motor rotating both the second and third pumps as shown. In other examples, the third fluid circuit 104c may beprovided with a separate third motor to drive the third pump 106c. The third pump 106c is fluidly coupled to a third pressure galley 112c or third pressure manifold. The third pressure galley 112c has sequentially: a third relief valve 108c that fluidly connects the third pressure galley to a return line 140, a check valve 110c that is positioned to prevent flow from returning to the third pump via the third pressure galley, the second crossover valve 120b, and three associated loads 114c for different device functions. In other examples, the third fluid circuit 104c may be provided with one or two loads 114c, or any other numbers of loads 114c. Flow from the loads 114c flows through the return line 140 to a reservoir 142 for the third pump 106c.[00421 The first, second, and third pressure galleys 112 a-c are generally maintained to be fluidly independent from one another; however, they may be connected in certain circumstances or operating conditions via valving as described herein to combine flows from two or more pumps 106 for a load 114. The return lines 140 and reservoirs 142 for each of the first, second, and third fluid circuits 104a-c may be the same elements as shown in Figure 3, or may be separately provided.[0043| Each of the pumps 106 may be provided as a fixed displacement pump, such as a gear pump, or a variable displacement pump. For a fixed displacement pump, the speed of the associated motor 102 controls the speed of the pump, which in turn controls the flow output of the pump (e.g. the volumetric flow rate from the pump) from a minimum flow output up to a maximum flow output from that associated pump. Each of the motors 102 may therefore be provided as variable speed electric motors according to an example. For a variable displacement pump 106, the motor 102 speed as well as the pump 106 displacement may be controlled via the controller 130 to control the flow output of the pump 106 from a minimum or zero flow output up to a maximum flow output from that associated pump. The pump 106 is provided with predetermined pump specifications that may be used to determine thresholds for the pump, including a pump curve chart, which indicates the pump volumetric flow output based on pressure and speed of the pump. In various examples, all of the pumps 106 may be provided as fixed displacement pumps, variable displacement pumps, or a combination thereof. Each pump 106 may have an inlet connected to the reservoir 142, and an output connected to the pressure galley 112 for its associated fluid circuit 104.

[0044] The controller 130 may be programmed or configured to independently control a speed of each motor 102 thereby controlling a speed of the associated pump(s) 106 and associated flow to the pump’s associated pressure galley 112. In the example shown, the first pump 106a has the highest displacement volume to provide high flow to the first pressure galley 112a, and at the lowest pressure compared to the other pumps 106b-c. The third pump 106c has the lowest displacement volume to provide low flow to the third pressure galley 112c, and at the highest pressure compared to the other pumps 106a-b. The second pump 106b has a displacement volume between the first and second pumps 106a, c to provide flow to the second pressure galley 112b. In other examples, the pumps 106 may be provided with other displacements relative to one another, or two or more pumps may be identical to one another.

[0045] As shown, each pump 106 and each fluid circuit 104 may be provided with its own filter 122, and with the filter located upstream or downstream of the associated pump 106 as shown. By having a separate filter 122a-c for each fluid circuit 104a-c, the flow can remain separated between the circuits while still being filtered. In other examples, filter 122 may alternatively or additionally be provided in the return line 140.

[0046] Each of the relief valves 108 may be a proportional relief valve, and may further be provided as an adjustable valve, e.g. as an electrically adjustable valve controlled by the controller 130. The relief valve 108 may be a normally open coil actuated proportional relief valve, or may be another type of relief valve such as a pilot actuated or dump valve. In the example shown, each fluid circuit 104 may be provided with one relief valve 108 connecting its pressure galley 112 to the return line 140. Each relief valve 108 may be separately adjusted from zero or near zero pressure to a predetermined maximum system 100 pressure. The controller 130 controls the relief valve 108 to change the pressure setting, with the relief valve 108 opening to fluidly connect the associated pressure galley 112 to the return line 140 when the pressure in the associated pressure galley 112 adjacent to the relief valve 108 exceeds the pressure setting for the relief valve. The controller 130 may therefore control the pressure and / or the flow in a pressure galley 112 by controlling the pressure setting for the associated relief valve 108. The controller 130 may control the pressure setting of the relief valve 108 to change it during system 100 operation as described below by way of various examples. For example, the controller 130 may control the pressuresetting of a relief valve 108 such that the valve 108 is open and flow from the associated pump 106 returns to the return line 140 when a load 114 is inactive and the pump is rotating. The controller 130 may control the relief valve 108 to another pressure setting to at least partially close the valve 108 and direct flow towards the associated loads 114 when the loads are active, e.g. for movement of the actuators 118. The relief valve 108 may further be set at zero psi (pounds per square inch) to provide a “function enable valve” such that any pressure above zero psi in the associated pressure galley 112 opens the relief valve 108 and fluid flows into the associated return line 140.

[0047] According to an example, each relief valve 108 allows flow from the associated pump to 106 pass directly back to the reservoir 142 when not energized, e.g. when the valve 108 is a normally open coil actuated proportional relief valve. When a control signal is applied by the controller 130 to the valve 108, the pressure is increased in the associated pressure galley, thereby causing fluid flow to flow to the hydraulic valve(s) 118 and load(s) 114. If an associated crossover valve 120 is open, the controller 130 may control the relief valves 108 in connected pressure galleys (e.g. those associated with each pump 106 that is contributing to combined flow) to the same or substantially the same pressure settings, e.g. a pressure setting which allows active functions 114 to operate with sufficient pressure. In further examples, the relief valve 108 may provide a function enable valve, which may be used to prevent movement in an actuator 116 of an associated load 114, which further may eliminate the need for additional valving downstream or provide redundancy in the system.

[0048] In the example shown, the first relief valve 108a fluidly connects the first pressure galley 112a upstream of the first crossover valve 120a to the return line 140 in response to a pressure in the first pressure galley 112a exceeding a first pressure setting. The second relief valve 108b fluidly connects the second pressure galley 112b upstream of the first crossover valve 120a and second crossover valve 120b to the return line 140 in response to a pressure in the second pressure galley 112b exceeding a second pressure setting. The third relief valve 108c fluidly connects the third pressure galley 112c upstream of the second crossover valve 120b to the return line 140 in response to a pressure in the third pressure galley 112c exceeding a third pressure setting. The controller 130 may set the first, second, and third pressure settings, which may be the same as oneanother, or may be different than one another, to control flow through the relief valves 108a-c. The controller 130 may further control or modify the first, second, and / or third pressure settings during operation of the hydraulic system 100.|0049] Crossover valves 120 are provided to connect adjacent pressure galleys 112 of two different fluid circuits to fluidly couple two or more of the pressure galleys 112. Each of the crossover valves 120 may be in communication with the controller 130, and may be controlled between an open position such that fluid flows therethrough between the two associated pressure galleys 112 and circuits 104, or a closed position to prevent fluid flow therethrough and isolate the two associated pressure galleys 112 and circuits 104 from one another. For systems 100 with multiple crossover valves 120, the controller 130 may selectively open one crossover valve 120 to fluidly connect two fluid circuits 104 to one another, or may open more than one or all of the crossover valves 120 to fluidly connect more than two fluid circuits 104 to one another. In the example, shown the controller 130 may open the first crossover valve 120a to fluidly connect the first and second pressure galleys 112a-b and first and second fluid circuits with the second crossover valve 120b closed, may open the second crossover valve 120b to fluidly connect the second and third pressure galleys 112b-c and second and third fluid circuits with the first crossover valve 120a closed, or may open both the first and second crossover valves 120a-b to fluidly connect first, second and third pressure galleys 112a-c and associated fluid circuits. The controller 130 may open a crossover valve 120 to permit flow from multiple pumps 106 to be combined or shared as needed, e.g. when a pump 106 cannot meet the demand from one or more loads 114 on its fluid circuit 104, or to provide redundancy in the system 100. The controller 130 may close a crossover valve 120 to prevent fluid flow through the crossover valve and isolate the two associated pressure galleys 112 and fluid circuits 104 from one another. For example, the first crossover valve 120a may be closed to isolate the first pressure galley 112a from the second pressure galley 112b, and the second crossover valve 120b may be closed to isolate the second pressure galley 112b from the third pressure galley 112c.

[0050] A check valve 110, or one-way valve, is shown as being positioned between the relief valve 108 and the crossover valve 120 for each fluid circuit 104. Each check valve 1 lOa-c may be positioned to prevent fluid flow in the associated pressure galley 112a-c from flowing frompressure galley adjacent to the crossover valve 120 through the check valve 110 and towards the pump 106, e g. such that fluid may only flow through the check valve 110 from the pump 106 towards the crossover valve 120 and load for the associated pressure galley 112 and fluid circuit 104.[00511 In the example shown, the first fluid circuit 104a and first pressure galley 112a is connected to a first load 114a, with a first actuator assembly 116 and a first valve assembly 118. The second fluid circuit 104b and second pressure galley 112b is connected to a second load 114b, with a second actuator assembly 116 and a second valve assembly 118. The third fluid circuit 104c and third pressure galley 112c is connected to third, fourth, and fifth loads 114c, each with an associated actuator assembly 116 and valve assembly 118. Each valve assembly 118 may include a metering valve, a holding valve, and / or a direction control valve. According to a nonlimiting example, the actuator assembly 116 of the first load 114a is a lift cylinder for the lift platform, the actuator assembly 116 of the second load 114b is an extension cylinder for the boom, the actuator assemblies 116 for the third load(s) 114c are a turntable or platform rotation actuator, a jib boom actuator, and one or more steering cylinders. In other examples, the actuator assemblies 116 may control other work functions of the device 20 such as another turntable or platform rotation actuator, a platform leveling cylinder, axle oscillate cylinders, or greater or fewer actuator assemblies may be provided.100521 The actuator assembly 116 of the first load 114a may be a larger actuator or cylinder than the actuator assemblies associated with the second or third loads 114b-c such that the first pump 106a is selected for its ability to provide high flow at low pressure. The actuator assemblies for the third loads 114c may be smaller but operate at a higher pressure, such that the third pump 106c is selected for its ability to provide low flow at high pressure (e g. relative to the first pump 106a). In the non-limiting example shown, the maximum flow output of the first pump 106a is greater than the maximum flow output of the second pump 106b, which in turn, is greater than the maximum flow output of the third pump 106c.

[0053] Each pump 106 may be provided to generally meet pressure requirements for the associated loads 114 on its fluid circuit 104; however, the pump 106 may not be able to meet flowrequirements for its associated fluid circuit 104 and load under certain circumstances, as described below and when the pump 106 and / or motor 102 associated with that fluid circuit 104 cannot be operated at a higher speed, at which point, the controller 130 may operate a crossover valve 120 and other elements of the system 100 to combine flow from multiple pumps 106 and direct flow from the multiple pumps 106 to the load 114 with the higher flow and / or pressure requirement.

[0054] Figure 4 illustrates a partial schematic view of an alternative motor 102 and pump 106 arrangement for use with the hydraulic system 100 in Figure 3. In Figure 4, the first pump 106a is connected to a first motor 102a that is provided by an internal combustion engine 150 and associated clutch 152. The clutch 152 may be provided as a one-way overrunning clutch, or other clutch or torque transfer device, such as a torque converter. The first motor 102a may additionally include an electric motor 154 drivingly connected to the pump 106a, with the internal combustion engine 150 connected to the electric motor 154 via the clutch 152. The controller 130 is in communication with the internal combustion engine 150, the clutch 152, and the electric motor 154 (if present) to control the speed of the input shaft for the first pump 106a. For example, the controller 130 may control the clutch 152 engagement and slip to control the speed difference between the internal combustion engine 150 and the pump 106a input shaft. Additionally or alternatively, the controller 130 may control a relief valve 108a to control the flow into an associated pressure galley 112a to avoid the need to change the engine 150 speed or clutch 152 operation, e.g. for an internal combustion engine running at a generally constant speed. To the extent that the clutch 152 is an overrunning clutch, the electric motor 154 connected to the clutch may be operated independently of the engine 150, and the motor 154 speed may be controlled via the controller 130, e.g. at a higher speed if needed to control and increase pump 106a flow output. Alternatively, the electric motor 154 may be operated as a generator to charge an associated battery. The second and third pumps 106b-c are connected to a second motor 102b, which may be an electric motor, as described above. In other examples, the second and third pumps 106b-c may alternatively be driven by motors 102 that include internal combustion engines, alone or in combination with electric motors.|0055| The controller 130 may implement a method 200 of controlling a hydraulic system in a lift vehicle, such as the hydraulic systems 100, in accordance with the steps listed below, and withreference to Figure 5. These steps may be performed generally in sequential order. In other examples, some steps may be performed simultaneously or at overlapping times. In further examples, steps may be added or omitted. The first and second fluid circuits 104a-b are used by way of example; however, the controller 130 may combine flows from the second and third fluid circuits 104b, c , or all three fluid circuits 104a-c in other examples and as disclosed herein.

[0056] In operation, and at step 202, the controller 130 operates a first pump 106a in a first fluid circuit to provide flow to a first pressure galley 112a connected to a first actuator or first load 114a. The controller 130 is programmed or configured to: to, in response to a request for increased flow in the first pressure galley 112a above a threshold associated with the first pump 106a, operate the first pump 106a and the second pump 106b, e.g. by also operating the second pump 106b in a second fluid circuit with a second pressure galley 112b connected to a second load 114b. At step 204, the controller 130 is also programmed or configured to, in response to the request for increased flow in the first pressure galley 112a above the threshold associated with the first pump 106a, adjust or control the first pressure setting of the first relief valve 108a to prevent fluid flow in the first pressure galley 112a from flowing to the return line 140 therethrough. The request for increased flow in the first pressure galley 112a may be based on the load 114a associated with the first fluid circuit. The controller 130 may also be programmed or configured to adjust or control a second pressure setting of the second relief valve 108b to fluidly couple the second pressure galley 112b to a return line 140 for the second pump 106b. The controller 130 may use a threshold associated with each pump that is based on the associated pump’s capability, e.g. based on the pump curve, and in some examples, may be based on a pressure or flow upper threshold for the pump output, or a upper threshold for a motor speed and resulting pump speed.]0057[ At step 206, the controller 130 then is programmed or configured to open the first crossover valve 120a to fluid connect the second pressure galley 112b to the first pressure galley 112a with the second pressure setting set to fluidly connect the second pressure galley 112b to the return line 140 via the second relief valve 108b. At step 208, the controller 130 is programmed or configured to restrict flow through a metering valve 118 associated with the hydraulic actuator 116 in the second load 114b in response to the request for increased flow in the first pressure galley 112a above the threshold associated with the first pump 106a to increase flow from the secondpressure galley 112b into the first pressure galley 112a via the first crossover valve 120a. The controller 130 is then programmed or configured to adjust the second pressure setting of the second relief valve 108b to control flow from the second pressure galley 112b into the first pressure galley 112a, e.g. by directing flow from the second pressure galley 112b into the first pressure galley 112a, such that flow in the first pressure galley 112a is above the first threshold.

[0058] Referring back to Figures 3-4, and according to various examples, the hydraulic system 100 as disclosed herein is provided with at least one motor 102 (including more than one electric motor) to rotate or spin at least two pumps 106, with fluid flow from each of the pump 106 remaining separated in their respective fluid circuits 104 and loads 114 for operation of different actuators 116 and associated functions. In the example shown in Figure 3, there are two electric motors 102a-b turning three pumps 108a-c total, with three separate fluid circuits and associated pressure galleys 112a-c, and each fluid circuit 102 and pressure gallery 112 receiving fluid flow from a respective one of the pumps 106.|0059] According to the various examples disclosed herein, the check valves HOa-c are positioned downstream of the relief valves 108a-c in each pressure galley. This positioning of the check valves 110 prevents fluid flow from an adjacent open crossover valve 120 from backflowing to the associated pump 106. This positioning of the check valves 110 also allows pressure to be equalized prior to a pump 106 flow being combined with another pump flow, e.g. via control of the relief valve 108 pressure settings for each fluid circuit 102, and further provides variable flow ranges to a pressure galley 112 and load 114 when combining flows from more than one pump 106 via a crossover valve 120 without an abrupt pressure or flow change, e.g. to provide a smooth transition for flow.

[0060] According to an example of the disclosure, and when the device 20, 50 is driving, the third pump 106c associated with the third fluid circuit 102c of the hydraulic system 100 is operated to supply fluid flow needed for loads 114c such as those containing the steering cylinders and any axle oscillate cylinders. However, the third pump 106c may be sized to provide fluid flow such that these loads 114c are responsive, and certain use cases may exceed the capability of the third pump 106c (e.g. the upper flow output or another threshold for the third pump 106c), where therequest for flow in the third pressure galley 112c is above a threshold associated with the third pump 106c (e.g. if the pump and / or associated motor is at its upper speed limit). When the request for flow in the third pressure galley 112c is above a threshold associated with the third pump 106c, the second pump 106b may be connected to the third pressure galley 112c and third fluid circuit to provide the additional required fluid flow to meet the request. By selectively operating and fluidly connecting the second pump 106b only when the request exceeds the request for flow in the third pressure galley 112c is above a threshold associated with the third pump 106c, the hydraulic system 100 may be operated for extended periods of time with only the third pump 106c operating to provide fluid flow to the third pressure galley 112c, which is more efficient than a system that operates a larger pump at all times while the vehicle or device is driving. In various examples, the controller 130 may determine that the request for flow in the third pressure galley 112c is above a threshold associated with the third pump 106c based on a pressure gauge measurement associated with the third galley 112c, or via a sensor associated with the load 114c to indicate additional flow or pressure is needed, e.g. an angle sensor or linear sensor, such as a steering sensor to show movement beyond a predetermined angle, a user input requesting a turn that requires a steering angle change above a predetermined angle, or the like. In certain examples, not all loads may be provided with an associated sensor.|0061| The system 100 may also be operated such that certain loads 114 are associated with certain fluid circuits 102. For example, loads 114 typically requiring a higher flow at a lower pressure may be on one fluid circuit, and loads 114 typically requiring a higher pressure at a lower flow may be on another fluid circuit. This provides for the pump 106 on that circuit 102 to be sized to operate near or at the pressure required by the associated loads 114 under typical operating conditions, and flow can be combined from multiple circuits 102 as described herein when a pressure or flow requirement for a load 114 exceeds that available from its associated fluid circuit 102.

[0062] Referring to Figures 3-4, various examples are provided for the disclosure for operation of the hydraulic system 100, and are not intended as being limiting, but as disclosing the capability of the system 100 and various implementations for control and operation.

[0063] According to a first example, the controller 130 determines that the load 114b on the second pressure galley 112b needs to be operated at a pressure above the second pump 106b output, e.g. in response to a sensor associated with the load 114b, and / or a pressure sensor associated a pressure galley 112b of the hydraulic system 100. The controller 130 operates the system 100 to selectively join the flow from the third pump 106c to the second pressure galley 112b as follows based on the sensor input(s). The controller 130 closes the second relief valve 108b to fluidly connect the second pump 106b to the second pressure galley 112b, and opens the third relief valve 108c to connect the third pressure galley 112c to the return line 140 (note that the second and third check valves 1 lOb-c prevent back flow towards each pump 106b-c). The controller 130 opens the second crossover valve 120b to fluidly connect the second and third pressure galleys 112b-c (note that the first crossover valve 120a remains closed to isolate the first pressure galley 112a). The controller 130 may then open the third relief valve 108c to join the flow from the third pump 106c and third pressure galley 112c into the second galley 112b via the second crossover valve 120b, and the controller 130 may further proportionally open the second crossover valve 120b, or may open it at a slow rate. The controller 130 may additionally close metering valves 118 for the various loads 114c connected to the third pressure galley 112c and third fluid circuit such that all of the flow from the third pump 106c is directed to the second galley 112b along with flow from the second pump 106b. By providing second and third relief valves 108b-c and second and third check valves 1 lOb-c prior to the second crossover valve 120b, the fluid flow from two pumps 106b-c may be generally equalized and joined smoothly, thereby avoiding or limiting clunking or other effects caused by abrupt pressure changes. Likewise, the controller 130 may close the second crossover valve 120b and separate the second and third pressure galleys 112b-c based on sensor inputs and the load 114b on the second pressure galley able to be operated at a pressure at or below the second pump output 106b. Alternatively, the controller 130 may join or separate the first and second pressure galleys, or the first, second and third pressure galleys using a control algorithm and method similar to that described herein.|0064| According to a second example, the second pump 106b is operating a load on the second pressure galley 112b, and the second relief valve 108b is set to an appropriate value higher than the load pressure such that it remains closed to prevent flow to the return line 140. All of the flow from the second pump 106b is therefore going to its associated load 114b, and the second pump106b is operating at or near its load pressure. The second motor 102b driving the second pump 106b is at or near its associated speed threshold, or upper speed limit, but the controller 130 determines, e.g. based on a sensor or other input, that the actuator 116 of the second load 114b needs to go faster. The controller 130 controls the hydraulic system 100 such that the third pump 106c adds flow to the second pressure galley 112b to meet the request or requirement for the load 114b on the second pressure galley 112b. Since the second and third pumps 106b-c are both operating as they are driven by the second motor 102b and its output shaft, the flow from the third pump 106c can be re-directed to add to the second pump 106b flow. The controller 130 may open the second crossover valve 120b to fluidly connect the third pressure galley 112c to the second pressure galley 112b, control or ramp the third relief valve 108c to match the setting of the second relief valve 108b, and also reduce the second motor 102b speed such that the second and third pumps 106b-c together provide generally the same flow output as the second pump 106b was previously making when the second motor 102b was operating at or near its upper speed threshold. The controller 130 may additionally adjust or increase the pressure setting for the third relief valve 108c, e.g. to its maximum pressure, so only one relief valve 108 is likely to open (in this case, the second relief valve 108b would open prior to the third relief valve 108c). Likewise, the controller 130 may close the second crossover valve 120b and separate the second and third pressure galleys 112b-c based on sensor inputs and changing requests for the load 114b on the second pressure galley 112b.

[0065] According to a third example, the first pump 106a is operating to supply flow to the load 114a on the first pressure galley 112a, and the third pump 106c is operating to supply flow to at least one of the loads 114c on the third pressure galley 112c. The second pump 106b is rotated by the second motor 102b as the third pump 106c is supplying fluid flow; however, the flow from the second pump 106b and second pressure galley 112b may be directed to the return line 140 and reservoir 142 via the pressure setting of the second relief valve 108b, e.g. with a pressure setting of zero psi. While the hydraulic actuator 116 on the first load 114a is being operated, it may require additional flow to increase its speed beyond what is available from the first pump 106a with the first motor 102a at its upper speed threshold, so the controller 130 operates the hydraulic system 100 to provide additional flow to the first pressure galley 112a and associated load 114a, using flow from the second pump 106b in this instance. As the second pump 106b is alreadyrotating or spinning with its connection to the second motor 102b and third pump 106c, the controller 130 opens the first crossover valve 120a to fluidly connect the first and second pressure galleys 112a-b, and also increases the pressure setting on the second relief valve 108b such that the second relief valve 108b closes to prevent fluid flow therethrough to the return line 140, and may increase the pressure setting up to the maximum pressure setting for the second relief valve 108b. The controller 130 also controls the speeds of the first and second motors 102a-b such that the first and second pump 106a-b volumetric flow output is the generally the same as the first pump 106a output was at the upper speed threshold of the first motor 102a, and then controls or increases the speeds of the first and second motors 102a-b to increase the total flow from the first and second pumps 106a-b to the load 114a on the first fluid circuit 104a to meet the flow request. As the third pump 106c speed may also be increased based on the speed of the second motor 102b needed for the second pump 106b, excess flow may be generated from the third pump 106c; however, the third relief valve 108c pressure setting may be controlled to direct any excess flow beyond that required by the third load(s) 114c to the return line 140. Likewise, the controller 130 may close the first crossover valve 120a and separate the first and second pressure galleys 112a-b based on sensor inputs and changing requests for the load 114a on the first pressure galley.

[0066] Figure 6 illustrates a hydraulic system 300 according to another embodiment of the disclosure. Elements that are the same as or similar to those described above with respect to Figures 1-4 are given the same reference number for convenience, and reference may be made to the disclosure above and below with respect to operation and control of the elements in the system 300. The system 300 may furthermore be used with method 200 as described above.

[0067] The system 300 has a first fluid circuit 104a and a second fluid circuit 104b, and three fluid pumps 106a-c driven by two motors 102a-b.

[0068] The first fluid circuit 104a has a first pressure galley 112a that receives fluid flow from a second pump 106b and a third pump 106c. The second pump 106b is driven by a first motor 102a, and the third pump 106c is driven by a second motor 102b. Note that check valves 302 may be provided upstream of a junction 304 joining flow from the two pumps 106b-c to prevent back flow to each of the second and third pumps 106b-c. In the non-limiting example shown, the first motor102a is a combination of an internal combustion engine 150, clutch 152, and electric motor 154, and the second motor 102b is an electric motor only. In other examples, other motor 102 configurations may also be provided.

[0069] The second fluid circuit 104b has a second pressure galley 112b that receives fluid flow from a first pump 106a. The first pump 106a is driven by the first motor 102a, and the second pump 106b may be coaxial to and piggybacked onto the first pump 106a as shown.

[0070] The first pressure galley 112a has sequentially, and downstream of the flow junction 304 from the second and third pumps 106b-c, an optional filter 122a, a first relief valve 108a connecting the first pressure galley 112a to a return line 140, a check valve 110a, a crossover valve 120 connected to the second pressure galley 112b, and one or more loads 114a (with associated actuators 116 and valve assemblies 118).

[0071] The second pressure galley 112b has sequentially, an optional filter 122b, a second relief valve 108b connecting the second pressure galley 112b to the return line 140, a check valve 110b, the crossover valve 120 connected to the first pressure galley 112a, and one or more loads 114b (with associated actuators 116 and valve assemblies 118).

[0072] A controller 130 is provided and controls the operation of the various motor(s), pump(s), valve(s) and loads of the system 300 based on sensor and other inputs 40 as described herein. Note that sensors may be provided as described above, and are not shown in Figure 6 for simplicity.

[0073] According to various examples, and for use with the hydraulic systems 100, 300 as described herein, multiple pumps 106 may be operated in separate fluid circuits 104 to provide flow to separate pressure galleys 112, with each pump 106 and associated pressure galley 112 dedicated to specific vehicle loads 114 or functions, and configured to generally operate in a parallel flow configuration. In certain circumstances, e.g. when a pressure or flow requirement for a load 114 in a fluid circuit 104 exceeds that available from the associated pump 106, the controller 130 may control one or more crossover valves 120 and other elements of the system 100, 300 to merge or combine flow from two or more pressure galleys 112 to meet the requirement for the load 114. With the systems 100, 300 as described herein, components of the hydraulic system100, 300, such as motors 102, the associated motor controllers, and the like, may be configured for use with a lower voltage system, e.g. a 48 Volt system, on the device 10 while still meeting the requirements for the loads 114 across the various operating conditions by combining flow from different fluid circuits 104 as needed, opposed needing to a higher voltage system (e.g. 60 Volts or higher) and associated components. This may result in the ability to use low voltage standards, reduce cost, use common parts across different platforms, and increase ease of service and maintenance.

[0074] In the present disclosure, as each pump 106 primarily provides flow to only its associated pressure galley 112 and load(s) 114, the speed of the motor 102 associated with the pump 106 may be controlled to control the pump 106 speed and flow output to limit or minimize the flow control needed by any metering valves downstream of that pump, such as valves 118. Of course, flow from multiple pumps 106 may be combined into a single pressure galley 112 based on the flow or pressure required by a load 114 exceeding the flow or pressure available from the associated fluid circuit 104 and pump 106, according to the various examples and disclosure herein.

[0075] In contrast, other conventional devices may use multiple pumps that are always in fluid communication with a single pressure galley (and that may be driven by one or more than one motors), with metering valves controlling flow to different loads connected to the pressure galley. With this system, the pressure galley needs to be maintained and controlled based on the load with the highest pressure requirement even though other loads connected to the pressure galley may have lower pressure requirements, and controlling the metering valves for the different loads may result in losses or inefficiencies, e.g. via waste heat introduced by the metering valves for those loads.

[0076] By interconnecting the pressure galleys 112, redundancy is increased in the system 100, 300, e.g. in the event of a motor or pump operating below its expected performance standard due to a maintenance or other requirement. Furthermore, the system 100, 300 may be operated in an auxiliary function in the event that one battery in the device 20, 50 has insufficient charge to operate functions on the vehicle. The second motor 102b and small third pump 106c can be connected to and independently operated on an auxiliary backup battery, and the valves 108, 120,118 may be controlled to connect the third pressure galley 112c to the first and second galleys 112a-b, for example, to operate a load 114a-b on the first and / or second galley 112a-b.(0077] Similarly, the first pressure galley 112a may be joined with the second pressure galley 112b to provide flow to any load 114a-b on the first and / or second pressure galleys 112a-b. Likewise, the first, second, and third pressure galleys 112a-c may be combined to provide flow to any load 114a-c in the hydraulic system 100, 300.(0078| While exemplary embodiments are described above, it is not intended that these embodiments describe all possible forms of the disclosure and / or invention. Rather, the words used in the specification are words of description rather than limitation, and it is understood that various changes may be made without departing from the spirit and scope of the disclosure and invention. Additionally, the features of various implementing embodiments may be combined to form further embodiments of the disclosure and invention.

Claims

WHAT IS CLAIMED IS:

1. A hydraulic system for a lift device, the hydraulic system comprising: at least one motor;a first fluid circuit comprising a first pump drivingly connected to the at least one motor, and a first hydraulic actuator receiving fluid flow from the first pump via a first pressure galley;a second fluid circuit comprising a second pump drivingly connected to the at least one motor, and a second hydraulic actuator receiving fluid flow from the second pump via a second pressure galley; anda first crossover valve to fluidly connect the first pressure galley to the second pressure galley in an open position, and isolate the first pressure galley from the second pressure galley in a closed position.

2. The hydraulic system of claim 1 further wherein the first fluid circuit further comprises a first relief valve fluidly connecting the first pressure galley upstream of the first crossover valve to a return line in response to a pressure in the first pressure galley exceeding a first pressure setting; andwherein the second fluid circuit further comprises a second relief valve fluidly connecting the second pressure galley upstream of the first crossover valve to the return line in response to a pressure in the second pressure galley exceeding a second pressure setting.

3. The hydraulic system of claim 2 wherein the first fluid circuit further comprises a first check valve positioned in the first pressure galley between the first relief valve and the first crossover valve to prevent fluid flow from the first pressure galley adjacent to the first crossover valve to the first pump; andwherein the second fluid circuit further comprises a second check valve positioned in the second pressure galley between the first relief valve and the first crossover valve to prevent fluid flow from the second pressure galley adj cent to the first crossover valve to the second pump.

4. The hydraulic system of claim 3 further comprising a controller to, in response to a request for increased flow in the first pressure galley above a threshold associated with the first pump, (i) operate the first pump and the second pump, (ii) open the first crossover valve to fluid connect the second pressure galley to the first pressure galley with the second pressure setting set to fluidly connect the second pressure galley to the return line via the second relief valve, and (iii) adjust the second pressure setting of the second relief valve to control flow from the second pressure galley into the first pressure galley such that flow in the first pressure galley is above the threshold.

5. The hydraulic system of claim 4 wherein the controller is further configured to, in response to the request for increased flow in the first pressure galley above the threshold associated with the first pump, adjust the first pressure setting of the first relief valve to prevent fluid flow in the first pressure galley from flowing to the return line therethrough.

6. The hydraulic system of claim 4 wherein the second fluid circuit comprises a valve assembly associated with the second hydraulic actuator; andwherein the controller is further configured to restrict flow through the valve assembly in response to the request for increased flow in the first pressure galley above the threshold associated with the first pump to increase flow from the second pressure galley into the first pressure galley via the first crossover valve.

7. The hydraulic system of claim 3 wherein an inlet for the first pump and an inlet for the second pump are each fluidly connected to the return line via a reservoir.

8. The hydraulic system of claim 1 wherein the at least one motor further comprises a first motor drivingly connected to the first pump and the second pump.

9. The hydraulic system of claim 8 wherein the hydraulic system further comprises a second motor;a third fluid circuit comprising a third pump drivingly connected to the second motor, and a third actuator receiving fluid flow from the third pump via a third pressure galley; anda second crossover valve assembly to fluidly connect the second pressure galley to the third pressure galley in an open position, and isolate the second pressure galley from the third pressure galley in a closed position.

10. The hydraulic system of claim 1 wherein the at least one motor further comprises a first motor drivingly connected to the first pump, and a second motor drivingly connected to the second pump.

11. The hydraulic system of claim 1 further comprising a controller in communication with the at least one motor to control a speed of the at least one motor thereby controlling a speed of the first pump and associated flow to the first pressure galley, and controlling a speed of the second pump and associated flow to the second pressure galley.

12. The hydraulic system of claim 1 wherein the at least one motor comprises at least one electric motor.

13. A lift vehicle comprising:a chassis;a lift platform supported by the chassis; andthe hydraulic system of claim 1 supported by the chassis.

14. The lift vehicle of claim 13 wherein one of the first and second hydraulic actuators comprises a steering cylinder or an oscillate cylinder connected to at least one wheel of the vehicle; andwherein the other of the first and second hydraulic actuators comprises a cylinder connected to the lift platform to raise or rotate the lift platform relative to the chassis.

15. The lift vehicle of claim 13 further comprising at least one electric motor drivingly coupled to a wheel supported by the chassis to propel the lift vehicle.

16. A hydraulic system for a lift device, the hydraulic system comprising: a first fluid circuit comprising a first pump, a first relief valve, and a first hydraulic actuator receiving fluid flow from the first pump via a first check valve in a first pressure galley;a second fluid circuit comprising a second pump, a second relief valve, and a second hydraulic actuator receiving fluid flow from the second pump via a second check valve in a second pressure galley;a third fluid circuit comprising a third pump, a third relief valve, and a third hydraulic actuator receiving fluid flow from the third pump via a third check valve in a third pressure galley;a first crossover valve to fluidly connect the first pressure galley to the second pressure galley in an open position, and isolate the first pressure galley from the second pressure galley in a closed position; anda second crossover valve to fluidly connect the second pressure galley to the third pressure galley in an open position, and isolate the second pressure galley from the third pressure galley in a closed position.

17. The hydraulic system of claim 16 wherein the first fluid circuit has sequentially arranged downstream of the first pump: the first relief valve, the first check valve, the first crossover valve, and the first hydraulic actuator;wherein the second fluid circuit has sequentially arranged downstream of the second pump: the second relief valve, the second check valve, the first crossover valve and the second crossover valve, and the second hydraulic actuator; andwherein the third fluid circuit has sequentially arranged downstream of the third pump: the third relief valve, the third check valve, the second crossover valve, and the third hydraulic actuator.

18. The hydraulic system of claim 16 further comprising:a first motor drivingly connected to the first pump; anda second motor drivingly connected to at least one of the second pump and the third pump.

19. A method of controlling a hydraulic system in a lift device, the method comprising:operating a first pump in a first fluid circuit to provide flow to a first pressure galley connected to a first actuator;in response to receiving a request for flow in the first pressure galley above a threshold associated with the first pump, operating a second pump in a second fluid circuit with a second pressure galley connected to a second actuator;controlling a pressure setting of a relief valve positioned upstream of a check valve in the second pressure galley to fluidly couple the second pressure galley to a return line for the second pump;opening a crossover valve positioned downstream of the check valve to fluidly connect the second pressure galley to the first pressure galley; andcontrolling the pressure setting of the relief valve to direct flow from the second pressure galley into the first pressure galley such that flow in the first pressure galley is above the threshold.

20. The method of claim 19 further comprising restricting flow through a valve assembly associated with the second actuator in the second fluid circuit in response to receiving the request for flow in the first pressure galley above the threshold associated with the first pump.

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