Fluid pump system for a fluid-driven actuator, system and lifting platform

Abstract

Fluid pump system (10) for supplying fluid-driven actuators (100) with a pressurized fluid, wherein the fluid pump system (10) comprises: • an electrical machine (12); • a fluid pump unit (14) adapted to be driven by the electric machine (12); • a flow divider (25); • a valve (26); wherein the fluid pump unit (14) is fluidically connected to the flow divider (25) via a first fluid path (20) and the flow divider (25) is configured to divide a first fluid flow received via the first fluid path (20) in a defined ratio, and wherein the valve (26) is arranged in the first fluid path (20).

Description

[0001] This disclosure relates to a fluid pump system for a fluid-driven actuator, a system, and a lifting platform.

[0002] Fluid pump systems are often used to drive fluid actuators. In lifts, for example, such actuators are often used to selectively deploy stabilizers or outriggers to stabilize the lift on a floor surface. Typically, a fluid pump unit supplies pressurized fluid to a plurality of fluid actuators, e.g., at least one fluid actuator per stabilizer. It has been found that, in such a setup, pressure differences can occur between the fluid volumes supplied to the stabilizers. This can lead to instability and / or require additional adjustments to safely support the lift on the floor.

[0003] It is therefore an object of the present invention to improve existing fluid pump systems, particularly with regard to pressure differences supplied to a plurality of actuators.

[0004] This objective is achieved by a fluid pumping system for supplying pressurized fluid to fluid-driven actuators, the fluid pumping system comprising: • an electrical machine; • a fluid pump unit adapted to be driven by the electric machine; • a flow divider; • a valve;wherein the fluid pump unit is fluidly connected to the flow divider via a first fluid path and the flow divider is configured to divide a first fluid flow received via the first fluid path according to a defined ratio, and wherein the valve is arranged in the first fluid path.

[0005] The flow divider can divide the received fluid flow into at least two separate fluid flows, each of which can be supplied to a connected fluid-driven actuator. In one example, the split ratio of the first fluid flow can be set such that each of the separate fluid flows has the same pressure.

[0006] The fluid can be compressed air or a pressurized fluid, such as hydraulic oil. Accordingly, the fluid pump system can, in particular, be a hydraulic pump system.

[0007] The electric machine can be operated as an electric motor to drive the fluid pump unit to pressurize the fluid. According to the embodiments described below, it can also be used as a generator to generate electrical energy.

[0008] The electric machine may be mechanically coupled to the fluid pump unit. For example, an output shaft of the electric machine may be coupled to the fluid pump unit to drive it and / or to be driven by it when the electric machine is operated as a generator.

[0009] The fluid pump unit, which may also be referred to as a pump head, may comprise, in addition to the electric machine, the parts that generate a fluid flow and / or pressurise the fluid. The fluid pump unit may, for example, comprise parts that are driven (i.e., moved) by the electric machine and are, for example, directly or indirectly connected to the output shaft of the electric machine. Depending on the design principle of the fluid pump unit, these parts may include, for example, an impeller, a gear set or at least one piston. In general, the fluid pump unit may comprise the parts in which the fluid is sucked in, pressurised and then discharged into the first fluid flow path, at least in the first operating state described below.

[0010] The valve can help improve the controllability of the generated, and in particular the split, fluid flow. According to the embodiments described below, it can also help enable regenerative operation of the fluid pumping system.

[0011] According to one embodiment, the fluid pump system is operable in a first state in which the fluid pump unit is driven by the electric machine, which operates as an electric motor to generate the first fluid flow. In this first state, the valve can be configured to assume an open state. This first state can be activated when the actuator is to be actively driven, for example, to perform a defined movement and / or generate forces.

[0012] Furthermore, the fluid pump system can be operated in a second state in which the fluid pump is driven by a second fluid flow flowing along the first fluid path in a direction opposite to the first fluid flow, and in which the electric machine operates as an electric generator. The second state can resemble a regenerative operation of the fluid pump system. The second fluid flow can cause the fluid pump unit to rotate the electric machine in the opposite direction compared to the first state, so that the machine operates as a generator and generates electrical energy. In this second state, the valve can also assume an open state. The second set can be implemented, for example, when the actuators are depressurized or when the actuators contain and maintain a pressurized fluid, e.g.by closing directly enclosed valves, wherein the first fluid path is still at least partially filled with a previously pressurized fluid volume.

[0013] Additionally or alternatively, the fluid pump system can be operated in a third state in which the fluid pump is not driven by the electric machine to generate the first fluid flow, and in which the valve is configured to assume a closed state. This third state can be realized if the actuators are not to be actively driven, but rather a pressure supplied to the actuators is to be maintained.

[0014] The mention of a first, second, and third state does not necessarily mean that these states must be provided in a specific order, i.e., from the first state through the second state to the third state. However, according to certain embodiments, such a sequence may also be realized.

[0015] In one example, the valve is a two-position valve. This may include the valve being switchable only between two states, namely an open state, in particular fully open, and a closed state, in particular fully closed.

[0016] Additionally or alternatively, the valve can be a two-way valve. For example, it can have an inlet and an outlet, but no other fluid connections. Each of the inlets and outlets can be connected to a different section of the first fluid path, e.g., one section leading to the fluid pump unit and one to the flow divider.

[0017] In one embodiment, the flow splitter, the valve, and the fluid pump unit are comprised in an integrated arrangement. The integrated arrangement may be a stand-alone unit that can be handled as an integrated unit, for example, during assembly and / or maintenance. The integrated arrangement may, for example, provide that the flow splitter, the valve, and the fluid pump unit are directly mechanically connected to one another, such that movement of one of these elements results in simultaneous movement of the other elements. The integrated arrangement may be a compact unit in which the flow splitter, the valve, and the fluid pump unit each directly contact at least one of the other elements, i.e., another element of the flow splitter, the valve, and the fluid pump unit.

[0018] The integrated assembly may have a common outer shell or outer housing, and the flow splitter, valve, and fluid pump unit may each comprise at least a portion of the outer shell or outer housing. In one embodiment, at least two of the flow splitter, valve, and fluid pump unit comprise at least a portion of an outer housing of the integrated assembly.

[0019] In one example, the valve is arranged in a flange part that is arranged adjacent to and in particular in direct, opposing contact with at least one of the flow divider, the valve and the fluid pump unit.

[0020] Additionally or alternatively, the flow divider, the valve (or a flange portion in which the valve is arranged), and the fluid pump unit may be enclosed between the other two parts of the flow divider, the valve (or the flange portion), and the fluid pump unit. This may involve direct contact with at least one of the adjacent elements.

[0021] Additionally or alternatively, the flow divider, the valve, and the fluid pump unit may be rigidly connected to one another, in particular, directly attached to one another. This may include a fastening element (e.g., a tie rod), a fastening connection, or a fastening joint being directly attached to and / or extending through and / or connected to the respective connected elements.

[0022] According to one example, the fluid pumping system includes at least one tie rod or other fastening element, e.g., an elongated screw, whose sections are respectively received in the flow splitter, the valve, and the fluid pumping unit. The connecting rod or fastening element can, for example, extend through a recess or opening, such as a through-hole, in each of the flow splitter, the valve, and the fluid pumping unit.

[0023] The disclosure also relates to a system that includes: • a fluid pump system according to any of the aspects disclosed herein; and • a fluid-driven actuator.

[0024] The fluid-driven actuator can be, for example, a hydraulic jack or a hydraulic cylinder. Additionally or alternatively, the hydraulic actuator can be a stabilizer or boom, particularly for leveling and / or stabilizing lifting platforms or other vehicles.

[0025] Furthermore, the disclosure also relates to a lifting platform comprising a system described above. As is generally known, a lifting platform, which may also be referred to as a cherry picker or bucket truck, may be a type of vehicle typically equipped with a platform or bucket at the end of an extendable arm. It may be used to raise the bucket or platform to higher areas so that workers on or in the bucket or platform can perform tasks such as maintenance, construction, or utility work.

[0026] Embodiments within the meaning of this disclosure are discussed below with reference to the accompanying schematic figures. In the figures, identical or similar features may be provided with the same reference numerals. Fig. 1 is a schematic view of a fluid pump system according to a first embodiment in a first operating state. Fig. 2 is a schematic view of the fluid pump system according to the first embodiment in a second operating state. Fig. 3 is a schematic view of the fluid pump system according to the first embodiment in a third operating state. Fig. 4 is a sectional view similar to a construction drawing of the fluid pump system according to the first embodiment. Fig. 5 is an exploded view of the Fig. 4 shown fluid pump system.

[0027] Fig. 1 shows a schematic representation of a hydraulic fluid pump system 10 according to a first embodiment. In Fig. 1, the fluid pump system 10 operates in a first state in which a hydraulic fluid is actively pressurized to supply it to the hydraulically driven actuators 100.

[0028] The actuators 100 and the fluid pump system 10 together form a system 120 within the meaning of this disclosure. The system 120 is located in a vehicle (not shown), e.g., a lifting platform. The actuators 100 are configured to selectively extend and retract stabilizers (in other words, legs) for stabilizing and, in particular, for leveling the lifting platform. There may be more actuators 100 than shown, e.g., four actuators 100.

[0029] The fluid pump system 10 comprises an electric machine 12 configured to generate a torque for rotating an output shaft 11, at least when operated in the first state. The output shaft 11 is connected to a fluid pump unit 14 configured to suck in a volume of fluid, pressurize it, and then discharge it, at least when the electric machine 12 operates as an electric motor. The fluid pump unit 14 is connected via a connection to a fluid reservoir 18 and via another connection to a first fluid path 20. The first fluid path 20 branches into two sections 22, each of which is fluidically and physically connected to an output chamber 24 of a flow divider 25. These output chambers 24 conduct fluid flows of equal pressure to the actuators 100.Accordingly, the first fluid path 20 runs at least between the fluid pump unit 14 and the flow divider 25, which fluidically connects these units.

[0030] The fluid pump system 10 also includes a two-way valve 26. This two-way valve 26 is arranged on and physically connected to a portion of the first fluid path 20 extending between the fluid pump unit 14 and the branching portions 22.

[0031] In the first operating state shown by Fig. 1, the two-way valve 26 assumes an open state. The first fluid flow from the reservoir 18 to the actuators 100 is indicated by corresponding arrows. This fluid flow results in the actuators 100 being supplied with pressurized fluid to deploy the associated stabilizers (not shown).

[0032] Fig. Figure 2 illustrates a second operating state of the fluid pump system 10. In this second state, the actuators 100 no longer draw in any more pressurized fluid. Rather, they contain an already drawn-in volume of pressurized fluid, for example, to hold the extended stabilizers in a current position. In this second state, the valve 26 also assumes its open state, but the fluid flow is reversed.

[0033] In particular, as indicated by the correspondingly aligned arrows, a second fluid flow is generated along the first fluid path 20, through which the fluid remaining in the first fluid path 20 is discharged into the reservoir 18. The second fluid flow flows through the fluid pump unit 14 to and into the reservoir 18. As a result, the fluid pump unit 14 rotates in the opposite direction compared to the first state and drives the electric machine 12, which operates as a generator. In this way, electrical energy is generated, which can be stored, for example, in a battery (not shown).

[0034] Fig. Figure 3 illustrates a third operating state of the fluid pump system 10. In the third state, the actuators 100 also no longer draw in any further pressurized fluid, but instead maintain the previously provided pressurized fluid volume. The electric machine 12 is switched off. The valve 26 is closed. In this way, the system 120 is configured to keep the stabilizers in an extended state for long periods of time, e.g., several hours.

[0035] The first through third states can be activated sequentially, starting with the first, second, and third states. Following the third state, the pressure from the actuators 100 can be released by opening the valve 26. The electric machine 12 can again operate as a generator during the release.

[0036] In none of the Fig. 1 to 3, a control device, in particular an electronic control unit, is specifically illustrated. This control unit is configured to control the operation of one of the units discussed in one of the described ways to transition between the first and third states. The control unit may be an integrated unit or a distributed system. The control unit may include data and / or signal lines to the electric machine 12, the valve 26, and the actuators 100. The control unit may be configured to control the operation of the valve 26 so that it transitions between its open and closed states. Furthermore, the control unit may be configured to actuate the actuators 100 to draw in, discharge, or maintain a pressurized fluid volume.The control unit may be configured to control the electric machine 12 to operate as a generator or motor, and in particular to control the generated torque and / or rotational speed.

[0037] As in the Fig. 1-3, the flow divider 25, the valve 26, and the fluid pump unit 14 form the first fluid path 20 of an integrated assembly 30. Accordingly, the first fluid path 20 is a non-flexible and / or non-tubular fluid path. Rather, it is formed by internal fluid channels within the integrated assembly 30, wherein the channels are formed, for example, by through-holes, drilled channels, or other free spaces. Accordingly, the channels may be defined by solid and / or non-flexible and / or rigid material volumes. As can be seen from the Fig. 1-3, this means that the fluidic connection between the flow divider 25 and the fluid pump unit 14 is internally comprised by the integrated assembly 30, thereby improving compactness.

[0038] Fig. 4 is a cross-sectional view of an exemplary integrated assembly 30 resembling a construction drawing. Fig. 5 shows an exploded view of the integrated assembly 30. The Fig. 3 and Fig. 4 are largely discussed together below.

[0039] In these figures, the fluid pump unit 14 is shown. It comprises an input shaft section 15 which is arranged to be connected to the output shaft 11 of Fig. 1. Furthermore, a flange part 32 is shown, which includes the valve 26, see Fig. 5. A portion of the first fluid path 20, which extends over the flange part 32 and through the valve 26, at least when the latter is open, runs through a through-bore 33 in the flange part 33. Furthermore, the flow divider 25 is shown, which comprises the outlet chambers 24.

[0040] The Fig. 4 and Fig. 5 shows that the integrated assembly 30 is elongated and substantially cylindrical in shape. It extends along a longitudinal axis L. The flange portion 32 is disposed axially between the fluid pump unit 14 and the flow divider 25. It contacts both the fluid pump unit 14 and the flow divider 25.

[0041] In addition, the flange part 32, the fluid pump unit 14, and the flow divider 25 are fastened to one another. Specifically, they are held and clamped together by a plurality of tie rods (not shown). These tie rods are located outside the sectional plane of Fig. 4. Fig. Figure 5 shows through holes 34 in each of the outer parts of the integrated assembly 30, into which the anchored rods can be inserted. There are four tie rods and four through holes 34 each, which are in Fig. 5 are marked with a corresponding reference symbol for only one of the components. This component is an optional spacer plate between the output chambers 24. In Fig. 5, two exemplary axes A are marked, which indicate an alignment of selected through holes 34. The tie rods not shown extend along these axes A, ie along four axes A, of which in Fig. 5 only two are shown. The axes A run parallel to the longitudinal axis L.

[0042] The pump unit 14 and the flow divider 25 are, going back to Fig. 4, according to known examples, with gear sets 36 formed by intermeshing gear shafts 37. In the flow divider 25, each output chamber 24 contains a gear set 36. The gear sets 36 of the output chambers 24 are connected to one another by a connecting element 40, e.g., a connecting sleeve, to enable pressure-compensating common rotation. The first fluid path 20 is in Fig. 4 is not specifically shown, but extends in a generally known manner along the gear sets 36.

[0043] In Fig.5 also shows the fluid outlet connections 38 of the fluid pump unit 14 and the flow divider 25. Furthermore, bearings 42, e.g., in the form of rolling bearings, of the gear sets 36 are marked. Furthermore, it can be seen that the fluid pump unit 14 and the outlet chambers 24 each comprise a housing section 44, which, like the flange part 32, is part of an outer housing 13 of the integrated assembly 30. The integrated assembly 30 also comprises end plates 46 at its axially opposite ends, which are also part of the outer housing 13.

Claims

[1] Fluid pump system (10) for supplying fluid-driven actuators (100) with a pressurized fluid, wherein the fluid pump system (10) comprises: • an electrical machine (12); • a fluid pump unit (14) adapted to be driven by the electric machine (12); • a flow divider (25); • a valve (26); wherein the fluid pump unit (14) is fluidically connected to the flow divider (25) via a first fluid path (20) and the flow divider (25) is configured to divide a first fluid flow received via the first fluid path (20) in a defined ratio, and wherein the valve (26) is arranged in the first fluid path (20). [2] The fluid pump system (10) of claim 1, wherein the fluid pump system (10) is operable in a first state in which the fluid pump unit (14) is driven by the electric machine (12) operating as an electric motor to generate the first fluid flow, and in which the valve (26) assumes an open state. [3] The fluid pump system (10) of claim 2, wherein the fluid pump system (10) is operable in a second state in which the fluid pump unit (14) is driven by a second fluid flow flowing along the first fluid path (20) in a direction reverse to the first fluid flow, and wherein the electric machine (12) operates as an electric generator. [4] Fluid pump system (10) according to one of the preceding claims, wherein the fluid pump system (10) is operable in a third state in which the fluid pump unit (14) is not driven by the electric machine (12) to generate the first fluid flow, and wherein the valve (26) is configured to assume a closed state. [5] Fluid pump system (10) according to one of the preceding claims, wherein the valve (26) is a two-position valve. [6] Fluid pump system (10) according to one of the preceding claims, wherein the flow divider (25), the valve (26) and the fluid pump unit (14) are comprised in an integrated arrangement (30). [7] The fluid pumping system (10) of claim 6, wherein at least two of the flow divider (25), the valve (26) and the fluid pumping unit (14) comprise at least a portion of an outer housing (13) of the integrated assembly (30). [8] A fluid pump system (10) according to any one of claims 2 or 3, wherein the valve (26) is disposed in a flange portion (32) disposed adjacent to at least one of the flow divider (25), the valve (26) and the fluid pump unit (14). [9] A fluid pump system (10) according to any one of the preceding claims, wherein one of the flow divider (25), the valve (26) or the flange part (32) according to claim 8 and the fluid pump unit (14) is arranged between the other two of the flow divider (25), the valve (26) or the flange part (32) according to claim 8 and the fluid pump unit (14). [10] Fluid pump system (10) according to one of the preceding claims, wherein the flow divider (25), the valve (26) and the fluid pump unit (14) are attached to one another. [11] A fluid pump system (10) according to claim 10, comprising at least one tie rod or other fastening element, portions of which are respectively received in the flow divider (25), the valve (10) and the fluid pump unit (14). [12] System (120) comprising: • a fluid pump system (10) according to any one of the preceding claims; and • at least two fluid-driven actuators (100). [13] Lifting platform comprising a system (120) according to claim 12.

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