Working vehicle

Abstract

A working vehicle which hydraulic circuit 108 is supplied by multiple pumps 322 each driven by electric motor 344 via gearbox 370. Inverters 346 drive the motors at predetermined speed according to ac

Description

FIELD The present disclosure relates to a working vehicle including a hydraulic pump system. BACKGROUND Working vehicles such as excavators, backhoe loaders, telehandlers, skid-steer loaders, dumpers and the like often have one or more hydraulically actuated devices such as working arm actuators, track motors, bucket actuators etc. Such hydraulically actuated devices operate by receiving a flow of hydraulic fluid from a hydraulic pump. Typically, the hydraulic pump of a working vehicle receives hydraulic fluid from the reservoir via a first pipe and supplies hydraulic fluid to a hydraulic system via a second pipe. When the hydraulic pump is to be removed / replaced for maintenance or repair, the first and second pipes are disconnected and the hydraulic pump is de-mounted from the working vehicle. Such an arrangement is therefore time-consuming and awkward to maintain and replace. Furthermore, energy losses along the length of the first pipe reduce the efficiency of the hydraulic system. In standard working vehicles driven by an internal combustion engine (ICE), the hydraulic pump is typically driven by the ICE. That is, the hydraulic pump includes a drive shaft which is coupled (either directly, or via a gearbox) to an output shaft of the ICE, so that the hydraulic pump outputs a flow of hydraulic fluid whenever the ICE is running. Since a flow of hydraulic fluid is not required by the hydraulically actuated device(s) of the working vehicle at all times when the ICE is running, excess output from the hydraulic pump is returned to the hydraulic reservoir via a bypass circuit / relief valve. Alternatively, a swash angle of the pump is altered to reduce the output of hydraulic fluid from the hydraulic pump. In either case, the ICE-driven pump arrangement leads to reduced efficiency of the hydraulic system, since the pump is being driven unnecessarily when no flow of hydraulic fluid is required. The present disclosure seeks to overcome, or at least mitigate, one or more problems of the prior art. SUMMARY Aspects and embodiments of the invention provide a working vehicle as claimed in the amended claims. According to a first aspect of the disclosure a working vehicle is provided. The working vehicle may comprise a plurality of hydraulic actuators. The working vehicle may comprise a hydraulic pump system. The hydraulic pump system may comprise a housing defining a tank for containing hydraulic fluid in use. The hydraulic pump system may also comprise one or more (e.g., a plurality of) pump modules, each pump module for driving one of the plurality of hydraulic actuators. Each pump module may comprise a hydraulic pump for supplying hydraulic fluid from the tank to a hydraulic system. Each pump module may also comprise an electric motor. Each pump module may also comprise a gear arrangement coupled between the electric motor and the hydraulic pump, such that the hydraulic pump is driven by the electric motor via the gear arrangement. The hydraulic pump system may also comprise at least one inverter configured to drive each of the electric motors at a predetermined speed in accordance with a demand for the respective actuator. The hydraulic pump system may also comprise a mounting arrangement, wherein each pump module is mounted to the housing by the mounting arrangement. The working vehicle may also comprise a hydraulic circuit for directing hydraulic fluid supplied by each pump module to a respective one of the hydraulic actuators. Providing a gear arrangement for each of the pump modules allows the size of the motor and inverter to be reduced to provide improved packaging within the working machine. In particular, such a gear arrangement removes the need for the electric motor to match the torque requirements of the hydraulic pump. For example, the torque requirement of the electric motor may be reduced, which may allow smaller electric motor and inverter to be used. Such an arrangement may also allow manufacturing costs to be lower. Optionally, the gear arrangement comprises a single stage gearbox. A single stage gearbox (e.g., a gearbox having a fixed gearbox ratio) provides a simpler, cheaper and more compact gear arrangement than alternatives, such as variable speed gearboxes. Optionally, the gear arrangement comprises a first gear coupled to an output shaft of the electric motor for rotation with the output shaft, and a second gear coupled to an input shaft of the hydraulic pump for rotation with the input shaft. Optionally, the first gear and second gear are in permanent mesh with each other. This provides a simple, cheap and compact gear arrangement. Optionally, the gear arrangement comprises a parallel shaft gearbox in which the first and second gears are positioned side-by-side. In other words, the output shaft of the electric motor may be parallel to, but offset from, the input shaft of the hydraulic pump. This may be simpler to construct and have a lower height than alternatives, such as planetary gearboxes. Optionally, the gear arrangement comprises a planetary gearbox. This may have a narrower width than alternatives, such as parallel shaft gearboxes. In applications which are have lateral packaging constraints, this may facilitate a higher gearbox ratio. Optionally, the gear arrangement comprises a gearbox ratio corresponding to a faster rate of rotation of the first gear than the second gear. In this way, the torque requirement of the electric motor may be reduced, which may allow a cheaper and smaller electric motor to be used. Optionally, the gearbox ratio is in a range of about 1.5:1 to about 6:1; optionally, in a range of about 2:1 to about 4:1. Such a range of gear ratios may offer a particularly good trade-off between decreasing motor size / cost and increasing size of the gear arrangement. Optionally, the gear arrangement of each pump module is the same as the gear arrangement of the other pump modules. Optionally, the hydraulic pump system comprises a plurality of pump modules each having a hydraulic pump, electric motor and gear arrangement. Optionally, the hydraulic pump system comprises three or more pump modules. This allows fluid (e.g. hydraulic fluid) to be supplied to multiple circuits more efficiently than if a single pump and flow sharing valves were used. Optionally, the hydraulic pump of each pump module comprises a body. Optionally, the body extends at least partially into the tank. Optionally, the body is located entirely within the tank. This provides a compact arrangement (since at least part of the body of the pump is within an interior of the housing) which is useful in space-constrained environments, such as mobile vehicles (e.g. working vehicles). In addition, this may reduce transmission of noise generated by the pump to the external environment. Optionally, the gear arrangement comprises a gearbox which is positioned external to the tank. This may inhibit gear debris generated by the gear arrangement from contaminating the hydraulic fluid within the tank. In addition, this may provide easier access to the gear arrangement for maintenance, etc. Optionally, the mounting arrangement comprises a mounting plate having an interior surface and an exterior surface, wherein the gearbox is mounted to the exterior surface of the mounting plate. This provides a simple means for externally mounting the gearbox, whilst also allowing the gearbox and pump to be mounted / dismounted as a single unit via the mounting plate. Optionally, the electric motor is mounted to the gearbox. This provides a simple and compact means of mounting the electric motor. Optionally, the gear arrangement comprises a gearbox which extends at least partially into the tank. Optionally, the gearbox is located entirely within the tank. Optionally, the mounting arrangement comprises a mounting plate having an interior surface and an exterior surface, wherein the gearbox is mounted to the interior surface of the mounting plate. This may facilitate cooling and / or lubrication of the gear arrangement using hydraulic fluid contained within the tank. Optionally, the hydraulic pump system is provided within an enclosure in a machine body of the working vehicle. Optionally, the working vehicle is an excavator and the hydraulic pump system is provided within an enclosure in a superstructure of the excavator. Optionally, the hydraulic pump system comprises a cover for covering components of the hydraulic pump system which are provided external to the tank. According to a further aspect of the disclosure, a pump system is provided, the pump system comprising: a housing defining a tank for containing fluid (e.g. hydraulic fluid) in use; and one or more pump modules each comprising a pump for supplying fluid from the tank to a fluid system (e.g. hydraulic system); a mounting arrangement; wherein the or each pump module is mounted to the housing by the mounting arrangement. Mounting the pump module(s) (i.e. as attachable / detachable self-contained units) to the housing provides a self-contained pumping assembly and reduces or removes the length of piping needed to connect the pump(s) to fluid (e.g. hydraulic fluid) contained in the tank. This reduces the complexity of the system and reduces or removes energy losses which would occur along such piping. This is particularly beneficial for working vehicles, such as battery-powered working vehicles where reduced energy losses result in increased battery life, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. In addition, this arrangement is more compact than prior art systems in which the pump(s) are provided separate from the tank. Furthermore, having pump modules (i.e. attachable / detachable self-contained units) allows the pump modules to be installed or removed from the pump system without having to connect / disconnect interconnected components within the module. This simplifies the procedure for removal / replacement of pumps for repair or maintenance. Optionally, the pump system is a hydraulic pump system for supplying hydraulic fluid from the tank to a hydraulic system. Optionally, the pump system comprises a plurality of pumps, optionally three pumps. Having a plurality of pumps allows fluid (e.g. hydraulic fluid) to be supplied to multiple circuits more efficiently than if a single pump and flow sharing valves were used. Optionally, the mounting arrangement comprises a single mounting portion (e.g. mounting plate) and each pump is mounted to the housing via the single mounting portion. Having such a single mounting portion provides a simple means to install / remove the pumps together from the housing (e.g. for access to an interior of the housing for cleaning / maintenance). Optionally, the mounting portion (e.g. mounting plate) comprises a lid for the housing. Optionally, the mounting arrangement comprises a plurality of mounting portions and each pump is mounted to the housing via one of the mounting portions Optionally, the or each pump module comprises a mounting portion and is mounted to the housing by said mounting portion. Optionally, the or each pump comprises a body, and wherein the body extends at least partially into the tank. Having a body of the pump(s) extending at least partially into the tank (i.e. into an interior region defined by the housing) provides a compact arrangement (since at least part of the body of the pump is within an interior of the housing) which is useful in space-constrained environments, such as mobile vehicles (e.g. working vehicles). Optionally, the housing comprises an outer casing and an inner liner spaced apart from the outer casing to define a cavity therebetween. Such a cavity in a two-part housing reduces the transmission of sound generated by the one or more pumps from within the tank to an exterior of the housing. It will be understood that the liner of such a housing defines an interior wall of the tank. Optionally, the cavity contains sound absorbing material. Such sound absorbing material further reduces the amount of noise generated by the one or more pumps that is transmitted to the exterior of the tank. Optionally, the outer casing comprises an inwardly extending projection (e.g. flange) and / or the inner liner comprises an outwardly extending projection (e.g. flange) configured to space the liner from the outer casing. Such projection(s) facilitate correct alignment of the inner liner within the casing (e.g. so that a width of the cavity is approximately equal around a perimeter of the housing). Furthermore, such projection(s) being provided on the outer casing and / or inner liner removes the need for separate spacing components. Optionally, one or more spacers are provided within the cavity between the inner liner and the outer casing. Such spacer(s) facilitate correct alignment of the inner liner within the casing (e.g. so that a width of the cavity is approximately equal around a perimeter of the housing). Optionally, the outer casing comprises an open end comprising a rim and the inner liner comprises an end comprising an outwardly extending projection (e.g. flange) for engaging the rim. Such an arrangement provides a simple means for constructing the two-part housing. Optionally, the rim comprises an inwardly extending projection (e.g. flange), and the outwardly extending projection of the inner liner engages the inwardly extending projection of the outer casing. In this way, the inwardly-extending projection of the outer casing acts to space the liner from an outer wall of the outer casing, whilst also provided a greater surface area for contact with the outwardly extending projection of the inner liner (e.g. to provide an increased surface area for welding or for receiving one or more bolts therethrough). Optionally, the outer casing is formed of plastics material or metallic material (e.g. steel or aluminium). Optionally, the inner liner is formed of plastics material or metallic material (e.g. steel or aluminium). The housing components can be easily formed from such materials. These materials have also been found to be suitable for reducing noise in tanks in combination with the cavity and / or sound absorbing material above. Optionally, the housing defines one or more apertures for receiving the one or more pump modules. Having one or more apertures for receiving the pump modules, provides a simple means for mounting the pump modules to the housing. Optionally, the mounting arrangement comprises one or more plates or flanges each for at least partially surrounding a perimeter of one of said one or more apertures of the housing. Having a plate or flange which surrounds a perimeter of one of said apertures of the housing allows the aperture to be completely covered by the plate or flange (which is useful for preventing ingress of dirt or debris, and / or leakage of fluid from the aperture). Such a plate or flange also provides an abutment surface which indicates when the pump module has been correctly positioned relative to the housing. Optionally, the mounting arrangement (e.g. a single mounting plate, or a plurality of mounting plates / flanges) is mounted to the housing via a releasable fastening. Having a releasable fastening allows the pump module(s) to be easily removed / installed for maintenance or replacement purposes. Optionally, one of the mounting arrangement and housing comprises one or more through-holes or threaded holes and the other of the mounting portion and housing comprises a corresponding one or more threaded holes or through-holes, wherein the or each through-hole and threaded hole is provided for receiving a bolt to couple said mounting arrangement to the housing. Having an arrangement which is suitable for coupling via one or more bolts provides a simple means of releasably mounting the pump module(s) to the housing via the mounting arrangement. Optionally, the pump system further comprises one or more seals for sealing the one or more apertures. The apertures being sealed allows the pump assembly to be used in any orientation (e.g. pump modules can be mounted on a top, side or lower surface of the housing) without leakage of fluid (e.g. hydraulic fluid). This provides a more flexible range of uses for the pump assembly. Furthermore, being sealed also prevents leakage in mobile applications where fluid may move around within the tank (e.g. in a working vehicle due to acceleration forces or inclined surfaces). Optionally, the mounting arrangement comprises one or more mounting plates or flanges which at least partially surround a respective aperture of said one or more apertures of the housing, and wherein the or each mounting plate or flange further comprises a seal surface and / or seal provided on said mounting plate or flange for sealing said aperture. A seal (e.g. a compressible seal such as a gasket) offers a reliable means of sealing an aperture, particularly under pressure (e.g. a bolting pressure exerted on the compressible seal when the mounting portion is secured to the housing via one or more bolts). Optionally, each of the one or more pump modules comprises a body comprising an inlet portion which defines a pump inlet, and wherein the inlet portion of the body extends into the tank such that the pump inlet is immersed in fluid (e.g. hydraulic fluid) contained in the tank in use; and / or wherein the pump system further comprises a filter or strainer arrangement coupled to the pump inlet, wherein the inlet portion of the body extends into the tank such that the filter or strainer arrangement is immersed in fluid (e.g. hydraulic fluid) contained in the tank in use. Having a pump inlet of the pump body immersed in fluid (e.g. hydraulic fluid) in the tank removes the need for pipework connecting the pump inlet to the fluid in the tank. This reduces the complexity of the system and reduces or removes energy losses which would occur along such piping. This is particularly beneficial for working vehicles, such as battery-powered working vehicles where reduced energy losses result in increased battery life, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. Optionally, each of the one or more pump modules comprises a pump outlet, and wherein the hydraulic pump system further comprises one or more fluid supply lines (e.g. hydraulic supply lines) connected to the one or more pump outlets for channelling fluid (e.g. hydraulic fluid) supplied by the one or more pump modules out of the housing. Such a fluid supply line(s) allows fluid (e.g. hydraulic fluid) supplied by the pump(s) to be used outside the tank (e.g. to move actuators in a hydraulic system for a working vehicle). Optionally, each of the fluid supply lines is coupled to the mounting arrangement, so that said fluid supply lines can be attached / detached from the pump system with the respective pump modules. Each of the fluid supply lines being coupled to the mounting arrangement allows simple removal / replacement of pump modules with the mounting arrangement without having to connect / disconnect the fluid supply line from the associated pump outlet. Optionally, the mounting arrangement comprises one or more fluid supply ports each coupled to a respective fluid supply line for connection to a fluid system (e.g. hydraulic system) in order to supply fluid (e.g. hydraulic fluid) from the pump module to the fluid system, wherein the fluid supply port is arranged to be external to the tank. Such a fluid supply port allows the pump module(s) to be easily connected to a fluid system (e.g. to a hydraulic system for moving hydraulic actuators in a hydraulic system for a working vehicle). Furthermore, the one or more fluid supply ports being provided on or by the mounting arrangement allows the pump(s) to be removed with the mounting arrangement without having to disconnect the fluid supply line(s) and / or downstream fluid connections (e.g. as opposed to having the port(s) on a fixed part of the housing, which would necessitate disconnecting the fluid supply line(s) from the respective port(s) and / or pump(s) when removing the pump(s) and mounting arrangement from the housing. Optionally, each of the one or more pump modules further comprises an electric motor for driving the pump. In embodiments with multiple pump modules, having an electric motor for each pump module allows flow of fluid from each module to be controlled independently of the other modules. This allows optimal pump flow rates to be set for each pump module, in contrast to prior art hydraulic systems that are driven by an internal combustion engine (ICE) which results in the hydraulic pump(s) outputting hydraulic fluid whenever the ICE is running (even if not required by hydraulically actuated devices of the hydraulic system). In other words, having an electric motor for each pump module leads to improved efficiency of the pump system, which is particularly beneficial for working vehicles, such as battery-powered working vehicles where increased pump system efficiency results in increased battery life, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. Optionally, the output of fluid (e.g. hydraulic fluid) from the pump of each of the one or more pump modules is controlled via rotation speed of the electric motor of said pump module; optionally, wherein the pump system further comprises one or more inverters for controlling frequency of power supplied to the one or more pump modules; optionally, wherein the one or more inverters are each mounted to the mounting arrangement or to a respective pump module, so that said one or more inverters can be attached / detached from the pump system with said one or more pump modules. Having the pump(s) controlled via rotation speed of the electric motor(s) allows an optimal pump flow rate to be set for each pump module. This reduces the need for restrictions in downstream fluid systems (e.g. downstream hydraulic systems), which improves the efficiency of the associated fluid system. Such an inverter arrangement enables variable speed control of the electric motor(s) and DC to AC power smoothing / conversion. This is useful in applications where the electric motors are powered by a DC electricity source (e.g. a battery on an electric working vehicle or a fuel cell on a fuel cell powered working vehicle). Optionally, the pump system further comprises a controller configured to set the rotation speed of the or each electric motor based on one or more user inputs and / or one or more sensor inputs such as pump pressure and system temperature. Such a controller allows an optimal pump flow rate to be set for each pump module, which leads to increased efficiency of a fluid system (e.g. hydraulic system) incorporating the pump system. Optionally, the electric motor of each of the one or more pump modules is connected to the pump of said pump module by a common drive shaft or a gearbox. Connecting a pump to an electric motor via a common drive shaft offers a simple and reliable means for driving the hydraulic pump by the electric motor. Connecting a pump to an electric motor via a gearbox allows the electric motor and pump to each be run in their optimal rotational speed ranges (which may differ), which increases the efficiency of the pump system. Optionally, the electric motor and / or inverter of at least one of the one or more pump modules is arranged to be positioned external to the tank. Arranging the electric motor(s) to be external to the tank protects electrical components from short-circuiting or other damage caused be contact with hydraulic fluid. Optionally, the pump system comprises a cover for said electric motor(s) and / or inverter(s). Such a cover provides two functions. Firstly, the cover protects the external components (i.e. electric motor(s) and / or inverter(s)) from being damaged by impact or dirt / debris. Secondly, the cover reduces the transmission of noise generated by the external components, which results in a quieter pump system. Optionally, the cover comprises sound-absorbing material (e.g. lined on an inside of the cover). Such sound-absorbing material further reduces the transmission of noise from the pump system. Optionally, the cover is formed of plastics material or metallic material (e.g. steel or aluminium). The cover can be easily formed from such materials. These materials have also been found to be suitable for reducing noise transmission through the cover. Optionally, the pump of each of the one or more pump modules is a fixed displacement pump. Having an electric motor driving a fixed displacement pump eliminates the need for variable swash control to vary pump output, which allows an infinite range of output flow rates without inefficiency of partial displacement associated with variable swash plate piston pumps. Optionally, the pump of each of the one or more pump modules is a bent axis piston pump. Bent axis piston pumps have been found to offer a high displacement ratio due to large swash angles (>40°), which results in a power dense package in comparison to axial piston pumps. This provides a high volumetric efficiency, which leads to an increased overall efficiency of the pump system. Optionally, the pump system further comprises a filter arrangement for filtering fluid (e.g. hydraulic fluid) input to the tank (e.g. hydraulic fluid returning to the tank from a hydraulic system). Having such a filter arrangement removes debris entrained in the fluid prior to entering the tank (e.g. debris formed via erosion of components in a hydraulic system) which improves the efficiency of the associated fluid system and reduces the likelihood of damage to components such as the pump. Optionally, the filter arrangement is mounted on the housing or the mounting arrangement; optionally, wherein the filter arrangement extends at least partially into the tank. Having the filter arrangement mounted on the housing and extending into the tank provides a compact and self-contained arrangement. According to a further aspect of the disclosure, a working vehicle is provided, the working vehicle comprising a pump system as disclosed herein. Optionally, the working vehicle is an electric working vehicle (e.g. a battery powered working vehicle). Optionally, the working vehicle is a fuel cell powered working vehicle (e.g. comprising a hydrogen fuel cell for powering the working vehicle). Optionally, the working vehicle is a hybrid working vehicle of the kind having an electric source of power and an alternative source of power. The pump systems disclosed herein are particularly compact and efficient. This provides significant benefits when applied to a working vehicle (where space is restricted and power is of limited capacity), particularly electric working vehicles where increased efficiency results in increased battery life and periods of use between charging, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. Optionally, the working vehicle is an excavator, backhoe loader, telehandler, skid-steer loader, dumper, forklift truck or other type of working vehicle having one or more hydraulically-actuated devices. According to a further aspect of the disclosure, a pump module is provided, the pump module comprising a pump, an electric motor for driving the pump, and a mounting portion for mounting the pump module to a housing of a fluid tank in use. Such a pump module (i.e. an attachable / detachable self-contained unit) is suitable for mounting directly to a housing of a fluid tank, which provides a compact arrangement. Furthermore, such an arrangement allows easy removal / replacement / maintenance of such modules. Optionally, the pump is a hydraulic pump. Optionally, the mounting portion is positioned such that a portion of the pump extends into said fluid tank when the pump module is mounted to said housing by the mounting portion in use. Optionally, the mounting portion comprises a flange for surrounding a perimeter of an aperture of said housing when the pump module is mounted to said housing by the mounting portion in use. Having a flange which surrounds a perimeter of an aperture of the housing allows the aperture to be completely covered by the mounting portion (which is useful for preventing ingress of dirt or debris, and / or leakage of fluid from the aperture). Such a flange also provides an abutment surface which indicates when the pump module has been correctly positioned relative to the housing. Optionally, the mounting portion comprises a releasable fastening for releasably mounting the hydraulic pump module to said housing in use. Having a releasable engagement formation provides a simple means of releasably mounting the pump module to the housing. This allows the pump module to be removed for maintenance or replaced easily. Optionally, the mounting portion comprises a seal surface and / or seal configured to seal an aperture of said housing when the pump module is mounted to said housing by the mounting portion in use. A seal (e.g. a compressible seal such as a gasket) offers a reliable means of sealing an aperture, particularly under pressure (e.g. a bolting pressure exerted on the compressible seal when the mounting portion is secured to the housing via one or more bolts). Furthermore, this allows the pump module to be fitted a housing of a fluid tank in any orientation (e.g. to a top, side or bottom surface) without leakage of fluid (e.g. hydraulic fluid). Optionally, the electric motor is arranged to be positioned external to said fluid tank when the pump module is mounted to said housing by the mounting portion in use. Arranging the electric motor to be external to the tank in use protects electrical components from short-circuiting or other damage caused be contact with fluid. Optionally, the pump comprises a pump inlet and a pump outlet, wherein the pump module further comprises a fluid supply line connected to the pump outlet for channelling fluid (e.g. hydraulic fluid) supplied by the pump to a fluid system (e.g. a hydraulic system). Having a fluid supply line as part of the pump module allows simple removal / replacement of the pump module from a housing of a tank without having to connect / disconnect the fluid supply line from the pump outlet. Optionally, the fluid supply line is coupled to the mounting portion, so that said hydraulic supply lines can be attached / detached from said housing with the pump. The fluid supply line being coupled to the mounting portion allows simple removal / replacement of the pump module without having to connect / disconnect the fluid supply line from the pump outlet. Optionally, the mounting portion further comprises a fluid supply port coupled to the fluid supply line for connection to a fluid system (e.g. hydraulic system) in order to supply fluid from the pump module to the fluid system, wherein the fluid supply port is arranged to be external to said fluid tank when the pump module is mounted to said housing by the mounting portion in use. Having a fluid supply port allows the pump module to be easily connected to a fluid system (e.g. a hydraulic system for moving hydraulic actuators of a working vehicle). Optionally, the output of fluid from the pump is controlled via rotation speed of the electric motor. Having the pump controlled via rotation speed of the electric motor allows an optimal pump flow rate to be set for the pump module. This reduces the need for restrictions in downstream fluid systems (e.g. valves in hydraulic circuits), which improves the efficiency of the associated fluid system. Optionally, the pump module further comprises an inverter to control frequency of power supplied to the electric motor. Having an inverter arrangement enables variable speed control of the electric motor(s) and DC to AC power smoothing / conversion. This is useful in applications where the electric motors are powered by a DC electricity source (e.g. a battery on an electric working vehicle, or a fuel cell in a fuel cell powered working vehicle). Optionally, the electric motor is connected to the pump by a common drive shaft or a gearbox. Connecting the pump to the electric motor via a common drive shaft offers a simple and reliable means for driving the pump by the electric motor. Connecting the pump to the electric motor via a gearbox allows the electric motor and pump to each be run in their optimal rotational speed ranges (which may differ), which increases the efficiency of the pump module. Optionally, the pump is a fixed displacement pump. Having an electric motor driving a fixed displacement pump eliminates the need for variable swash control to vary pump output, which allows an infinite range of output flow rates without inefficiency of partial displacement associated with variable swash plate piston pumps. Optionally, the pump is a bent axis piston pump. Bent axis piston pumps have been found to offer a high displacement ratio due to large swash angles (>40°), which results in a power dense package in comparison to axial piston pumps. This provides a high volumetric efficiency, which leads to an increased overall efficiency of the pump module. According to a further aspect of the disclosure, a pump module is provided, the pump module comprising a pump and a mounting portion for mounting the pump module to a housing of a hydraulic fluid tank in use, wherein the mounting portion is configured to at least partially surround an aperture of said housing, and wherein the mounting portion comprises a seal surface and / or seal configured to seal said aperture when the pump module is mounted to said housing in use. Such a pump module (i.e. an attachable / detachable self-contained unit) is suitable for mounting directly to a housing of a hydraulic fluid tank, which provides a compact arrangement. Furthermore, such an arrangement allows easy removal / replacement / maintenance of such modules. In addition, a seal (e.g. a compressible seal such as a gasket) offers a reliable means of sealing an aperture, particularly under pressure (e.g. a bolting pressure exerted on the compressible seal when the mounting portion is secured to the housing via one or more bolts). Optionally, the mounting portion is positioned such that a portion of the pump extends into said fluid tank when the pump module is mounted to said housing by the mounting portion in use. Optionally, the mounting portion comprises a flange for surrounding a perimeter of said aperture when the pump module is mounted to said housing by the mounting portion in use; Having a flange which surrounds a perimeter of an aperture of the housing allows the aperture to be completely covers by the mounting portion (which is useful for preventing ingress of dirt or debris, and / or leakage of fluid from the aperture). Such a flange also provides an abutment surface which indicates when the pump module has been correctly positioned relative to the housing. Optionally, the mounting portion comprises a releasable fastening for releasably mounting the pump module to said housing in use. Having a releasable engagement allows the pump module to be easily removed / installed to a housing for maintenance or replacement purposes. According to a further aspect of the disclosure a fluid system is provided, the fluid system comprising: a housing defining a tank for containing fluid in use; and one or more components each comprising a body extending at least partially into the tank; wherein the housing comprises an outer casing and an inner liner spaced apart from the outer casing to define a cavity therebetween. Such a cavity in a two-part housing reduces the transmission of sound generated by the one or more components from within the tank to an exterior of the housing. For example, where the one or more components are pumps, any noise generated by the pumps would be reduced by the two-part tank construction. It will be understood that the liner of such a housing defines an interior wall of the tank. Optionally, the cavity contains sound absorbing material. Such sound absorbing material further reduces the amount of noise generated by the one or more components that is transmitted to the exterior of the tank. Optionally, the outer casing comprises an inwardly extending projection (e.g. flange) and / or the inner liner comprises an outwardly extending projection (e.g. flange) configured to space the liner from the outer casing. Such projection(s) facilitate correct alignment of the inner liner within the casing (e.g. so that a width of the cavity is approximately equal around a perimeter of the housing). Furthermore, such projection(s) being provided on the outer casing and / or inner liner removes the need for separate spacing components. Optionally, one or more spacers are provided within the cavity between the inner liner and the outer casing. Such spacer(s) facilitate correct alignment of the inner liner within the casing (e.g. so that a width of the cavity is approximately equal around a perimeter of the housing). Optionally, the outer casing comprises an open end comprising a rim and the inner liner comprises an end comprising an outwardly extending projection (e.g. flange) for engaging the rim. Such an arrangement provides a simple means for constructing the two-part housing. Optionally, the rim comprises an inwardly extending projection (e.g. flange), and the outwardly extending projection of the inner liner engages the inwardly extending projection of the outer casing. In this way, the inwardly-extending projection of the outer casing acts to space the liner from an outer wall of the outer casing, whilst also provided a greater surface area for contact with the outwardly extending projection of the inner liner (e.g. to provide an increased surface area for welding or for receiving one or more bolts therethrough). Optionally, the outer casing is formed of plastics material or metallic material (e.g. steel or aluminium). Optionally, the inner liner is formed of plastics material or metallic material (e.g. steel or aluminium). The housing components can be easily formed from such materials. These materials have also been found to be suitable for reducing noise in tanks in combination with the cavity and / or sound absorbing material above. It will be appreciated that the features of any aspect of the disclosure outlined above may be combined with features of any other aspect of the disclosure outlined above. All combinations have not been recited for brevity. BRIEF DESCRIPTION OF THE DRAWINGS Embodiments are now described by way of example only with reference to the accompanying drawings, in which: Figure 1 is an exploded perspective view of a hydraulic pump system having three pump modules; Figure 2 is a cross-sectional side view of the hydraulic pump system of Figure 1 taken along line A-A of Figure 1; Figure 3 is a cross-sectional side view of the hydraulic pump system of Figures 1 and 2 connected to inverters and a control system; Figure 4 is a cross-sectional side view of a hydraulic pump module according to an embodiment; Figure 5 is a perspective view of a further hydraulic pump system having three pump modules; Figure 6 is an exploded cross-sectional perspective view of the mounting arrangement and housing of the hydraulic pump system of Figure 5; Figure 7 is a cross-sectional side view of the hydraulic pump system of Figures 5 and 6; Figure 8 is a side view of the pump module of the pump system of Figures 5 to 7; Figure 9 is a side view of a working machine including the hydraulic pump system of Figures 1 to 3 or 5 to 7; Figure 10 is a schematic diagram of a further hydraulic pump system for the working vehicle of Figure 9, according to an embodiment of the invention; and Figure 11 is an enlarged view of a single pump module of the hydraulic pump system of Figure 10. DETAILED DESCRIPTION Referring firstly to Figures 1 to 4, a hydraulic pump system is indicated at 10. The hydraulic pump system 10 includes a housing 12 defining a tank 14 for containing hydraulic fluid 16 in use. In the illustrated configuration, the hydraulic pump system also includes three pump modules 18 (one of which is obscured by the exploded / removed pump module 18 at the front of the figure). In alternative configurations, more or fewer than three pump modules 18 are provided. Each pump module 18 includes a mounting portion 20 and a hydraulic pump 22 for supplying hydraulic fluid 16 from the tank 14 to a hydraulic system (e.g. a hydraulic system of a working vehicle). Each pump module 18 is mounted to the housing 12 by the mounting portion 20. Having pump modules 18 (i.e. attachable / detachable self-contained units) mounted to the housing 12 provides a self-contained hydraulic pump system 10 and reduces or removes the length of piping needed to connect the pumps 22 to the hydraulic fluid 16 contained in the tank 14. This reduces the complexity of the system and reduces or removes energy losses which would occur along such piping. This is particularly beneficial for working vehicles, such as battery-powered working vehicles where reduced energy losses result in increased battery life, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. In addition, this arrangement is more compact than prior art systems in which the hydraulic pump(s) 22 are provided separate from the tank 14. It will be understood that the pump modules 18 are each attachable to and detachable from the housing as a self-contained unit. In other words, the pump modules 18 can each be installed or removed from the hydraulic pump system 10 without having to connect / disconnect interconnected components within the pump module 18. Each hydraulic pump 22 includes a body 24 having a pump inlet 26 and a pump outlet 28. In the illustrated configuration, the body 24 extends into the tank 14 so that the pump inlet 26 is immersed in hydraulic fluid 16 contained in the tank 14 in use. In alternative configurations, the body 24 extends partially into the tank 14. For example, in some configurations part of the body 24 (e.g. an inlet portion) extends into the tank and another part of the body 24 is located external to the tank 14. In some configurations, the pump inlet 26 is not immersed in hydraulic fluid 16 contained in the tank 14 in use. Having a body 24 extending at least partially into the tank 14 (i.e. into an interior region defined by the housing 12) provides a compact arrangement, since at least part of the body 24 of the hydraulic pump 22 is within an interior of the housing 12, which is useful in space-constrained environments, such as mobile vehicles (e.g. working vehicles). The housing 12 defines three apertures 30 for receiving the pump modules 18. The mounting portion 20 of each pump module 18 is configured for mounting the pump module 18 around a respective aperture 30 of the housing 12. It will therefore be understood that where the number of pump modules 18 is more or less than in the illustrated configuration, the number of apertures 30 differs accordingly. Having one or more apertures 30 for receiving the pump modules 18, and a mounting portion 20 on each pump module 18 provides a simple means for mounting the pump modules 18 to the housing 12. In the illustrated configuration, the mounting portion 20 of each pump module 18 includes a flange 32 for surrounding a perimeter of an aperture 30 of the housing 12 when the pump module 18 is coupled to the housing 12 in use. Having a flange 32 which surrounds a perimeter of an aperture 30 of the housing 12 allows the aperture 30 to be completely covered by the mounting portion 20 (which is useful for preventing ingress of dirt or debris, and / or leakage of fluid from the aperture 30). Such a flange 32 also provides an abutment surface which indicates when the pump module 18 has been correctly positioned relative to the housing 12. In alternative configurations, the mounting portion 20 of each pump module 18 includes a flange which only partially surrounds a perimeter of an aperture 30 of the housing 12. In alternative configurations, the mounting portion 20 includes a plurality of projections or flanges arranged circumferentially around an aperture 30 of the housing 12 in use. In the illustrated configuration, the mounting portion 20 of each pump module 18 is mounted to the housing 12 via a releasable fastening. Having a releasable fastening allows the pump modules 18 to be easily removed / installed for maintenance or replacement purposes. In particular, the mounting portion 20 includes a plurality of through-holes 34 and the housing 12 includes a corresponding plurality of threaded holes 36. Each through-hole 34 and threaded hole 36 is provided for receiving a bolt (not shown) to couple the pump module 18 to the housing 12 in use. In alternative configurations, the housing 12 includes a plurality of through-holes 34 and the mounting portion 20 includes a corresponding plurality of threaded holes 36. In alternative configurations, any other combination of through-holes and / or threaded holes suitable for receiving a fastener is used (e.g. a plurality of through-holes on the housing 12 and a corresponding plurality of through-holes on the mounting portion 20, or a plurality of threaded holes on the housing 12 and a corresponding plurality of threaded holes on the mounting portion 20). It will be understood that the term "through-hole" shall be interpreted as a non-threaded hole, and the term "threaded hole" shall be interpreted as a blind or through-hole comprising threads. Having an arrangement which is suitable for coupling via one or more bolts provides a simple means of releasably mounting the pump modules 18 to the housing 12. In alternative configurations, the mounting portion 20 of each pump module 18 is fixedly attached to the housing 12 (e.g. via welding or adhesive). Fixedly attaching the mounting portions 20 to the housing 12 ensures a robust connection and can contribute to sealing of the apertures 30 in which the pump modules 18 are received. As will be described in more detail below, the hydraulic pump system 10 includes seals for sealing the apertures 30 to prevent leakage of hydraulic fluid 16 from the tank 14. The apertures 30 being sealed in use allows the hydraulic pump system 10 to be used in any orientation (e.g. pump modules 18 can be mounted on a top, side or lower surface of the housing 12) without leakage of hydraulic fluid 16. This provides a more flexible range of uses for the hydraulic pump system 10. Furthermore, being sealed also prevents leakage in mobile applications where hydraulic fluid 16 may move around within the tank 14 (e.g. in a working vehicle due to acceleration forces or travelling over inclined surfaces). In the illustrated configuration, the mounting portion 20 of each pump module 18 includes a seal 38 for sealing a respective aperture 30 when the pump module 18 is coupled to the housing 12 in use. A seal 38 (e.g. a compressible seal such as a gasket) offers a reliable means of sealing an aperture 30, particularly under pressure (e.g. a bolting pressure exerted on the compressible seal 38 when the mounting portion 20 is secured to the housing 12 via one or more bolts). In the illustrated configuration, the seal 38 of each pump module 18 is provided on a lower surface of the mounting portion 20, so that the seal 38 is provided between the flange 32 and a portion of the housing 12 surrounding the aperture 30. In alternative configurations, the mounting portion 20 of each pump module 18 includes a seal surface instead of, or in addition to, the seal 38. For example a flat metal surface intended to form a metal-to-metal seal with the housing when the mounting portion 20 is fixed to the housing under pressure (e.g. bolting pressure). The hydraulic pump system 10 also includes a plurality of hydraulic supply lines 40 each connected to a respective pump outlet 28 of the pump modules 18 for channelling hydraulic fluid 16 supplied by the pump modules 18 out of the housing 12. Such hydraulic supply lines 40 allow hydraulic fluid 16 supplied by the hydraulic pumps 22 to be used outside the tank 14 (e.g. to move actuators in a hydraulic system for a working vehicle). In the illustrated configuration, each pump module 18 includes one of the hydraulic supply lines 40 so that the hydraulic supply lines 40 can be attached / detached from the hydraulic pump system 10 with the respective pump module 18. Each of the hydraulic supply lines 40 being part of a respective pump module 18 allows simple removal / replacement of pump modules 18 without having to connect / disconnect the hydraulic supply line 40 from the associated pump outlet 28. In the illustrated configuration, each pump module 18 includes a hydraulic supply port 42 coupled to the hydraulic supply line 40 of the pump module 18 for connection to a hydraulic system in order to supply hydraulic fluid 16 from the pump module 18 to the hydraulic system. Each of the hydraulic supply ports 42 is arranged to be external to the tank 14 when its respective pump module 18 is mounted to the housing 12. Such a hydraulic supply port 42 allows the hydraulic pump modules 18 to be easily connected to a hydraulic system (e.g. for moving hydraulic actuators in a hydraulic system for a working vehicle). In alternative configurations, the hydraulic supply ports 42 are provided on the housing 12 rather than the respective pump modules 18. In the illustrated configuration, each of the pump modules 18 also includes an electric motor 44 for driving the hydraulic pump 22 of the pump module 18. In configurations with multiple pump modules 18 such as that illustrated, having an electric motor 44 for each pump module 18 allows flow of hydraulic fluid 16 from each module 18 to be controlled independently of the other modules 18. This allows optimal pump flow rates to be set for each pump module 18, in contrast to prior art hydraulic systems that are driven by an internal combustion engine (ICE) which results in the hydraulic pump(s) outputting hydraulic fluid whenever the ICE is running (even if not required by hydraulically actuated devices of the hydraulic system). In other words, having an electric motor for each pump module leads to improved efficiency of the hydraulic pump system 10, which is particularly beneficial for working vehicles, such as battery-powered working vehicles where increased pump system efficiency results in increased battery life, or fuel cell powered working vehicles where reduced energy losses result in reduced fuel consumption. Referring still to Figure 3, the output of hydraulic fluid 16 from the hydraulic pump 22 of each of the pump modules 18 is controlled via rotation speed of the electric motor 44 of the pump module 18. Having the hydraulic pumps 22 controlled via rotation speed of the electric motors 44 allows an optimal pump flow rate to be set for each pump module 18. This reduces the need for restrictions in downstream hydraulic systems, which improves the efficiency of the associated hydraulic system. In the illustrated configuration, the hydraulic system also includes three inverters 46 to control frequency of power supplied to the electric motors 44 of the pump modules 18. Such an inverter arrangement enables variable speed control of the electric motors 44 and DC to AC power smoothing / conversion. This is useful in applications where the electric motors 44 are powered by a DC electricity source (e.g. a battery on an electric working vehicle or a fuel cell on a fuel cell powered vehicle). In some configurations, the inverters 46 are each part of a respective pump module 18 so that the inverter 46 can be attached / detached from the hydraulic pump system 10 with said pump module 18. In alternative configurations, the inverters 46 are provided separate to the pump modules 18. In alternative configurations, the electric motors 44 are DC motors and the inverters 46 are omitted. The hydraulic pump system 10 also includes a controller 48 configured to set the rotation speed of the electric motors 44 based on one or more user inputs 50 (such as an operating lever position) and / or one or more sensor inputs 52 (such as pump pressure and system temperature). Such a controller 48 allows an optimal pump flow rate to be set for each pump module 18, which leads to increased efficiency of a hydraulic system incorporating the hydraulic pump system 10. Referring again to Figure 1, the electric motor 44 of each pump module 18 is connected to the hydraulic pump 22 of the pump module 18 by a common drive shaft 54. Connecting a hydraulic pump 22 to an electric motor 44 via a common drive shaft 54 offers a simple and reliable means for driving the hydraulic pump 22 by the electric motor 44. In alternative configurations, the electric motor 44 of each pump module 18 is connected to the hydraulic pump 22 of the pump module 18 by a gearbox. Connecting a hydraulic pump 22 to an electric motor 44 via a gearbox allows the electric motor 44 and hydraulic pump 22 to each be run in their optimal rotational speed ranges (which may differ), which increases the efficiency of the hydraulic pump system 10. In the illustrated configuration, the electric motor 44 of each pump module 18 is arranged so that it is positioned external to the tank 14. Arranging the electric motors 44 to be external to the tank 14 protects electrical components from short-circuiting or other damage caused be contact with hydraulic fluid 16 located within the tank 14 in use. In some configurations, the hydraulic pump 22 of each pump module 18 is a fixed displacement pump. For example, in some configurations the hydraulic pumps 22 are bent axis piston pumps. Having an electric motor 44 driving a fixed displacement pump 22 eliminates the need for variable swash control to vary pump output, which allows an infinite range of output flow rates without inefficiency of partial displacement associated with variable swash plate piston pumps. Furthermore, bent axis piston pumps have been found to offer a high displacement ratio due to large swash angles (>40°), which results in a power dense package in comparison to axial piston pumps. This provides a high volumetric efficiency, which leads to an increased overall efficiency of the hydraulic pump system 10. In alternative configurations, the number of electric motors 44 is less than the number of pump modules 18, so that one or more pump modules are driven by a common electric motor 44. In alternative configurations, the electric motors 44 are omitted and the pump modules 18 are driven by an internal combustion engine. In some configurations where the pump modules 18 are driven by an internal combustion engine, the output of hydraulic fluid 16 from the hydraulic pumps 22 of the pump modules 18 is variable for a given rotation rate of the common electric motor 44 or internal combustion engine (e.g. by using a variable swash-plate pump). In such configurations, a controller is provided to set the swash-plate angle (or similar displacement-changing property of the hydraulic pumps) based on one or more user inputs 50 and / or sensor inputs 52. In the illustrated configuration, the hydraulic pump system 10 also includes a filter arrangement 56 for filtering hydraulic fluid 16 input to the tank 14 (e.g. hydraulic fluid 16 returning from one or more hydraulically-actuated devices of a working vehicle). Having such a filter arrangement 56 removes debris entrained in the hydraulic fluid 16 prior to entering the tank 14 (e.g. debris formed via erosion of components in a hydraulic system) which improves the efficiency of the hydraulic system and reduces the likelihood of damage to components such as the hydraulic pump 22. In the illustrated configuration, the filter arrangement 56 is mounted on the housing 12 and extends partially into the tank 14 similarly to the pump modules 18, which provides a compact and self-contained arrangement. In alternative configurations, the filter arrangement 56 is provided external to the housing 12 (e.g. as a separate unit connected to the tank 14 via a pipe). The hydraulic pump system 10 may be used in different applications with different pump requirements. For example, in some configurations only two pump modules 18 are required. In some configurations where only two pump modules 18 are required, the housing 12 still includes three apertures 30 for receiving three pump modules 18. Therefore, one of the apertures 30 will not be covered by a pump module 18. In such configurations, the aperture 30 which is not covered by the pump module 18 is covered by a cover plate of similar shape and size as the mounting portion 20 of the pump modules 18. In this way, the aperture 30 which is not covered by a pump module 18 is covered (and sealed, if the cover plate includes a seal) to prevent influx of debris to the tank 14 or leakage of hydraulic fluid 16 from the tank 14. Such a hydraulic pump system 10 is therefore configurable to meet the requirements of a particular application, by using the same basic integers (i.e. housing 12, pump modules 18 and cover plate). Referring now to Figures 5 to 8, a hydraulic pump system according to a further configuration is indicated at 210. Common features between the hydraulic pump system of Figures 1 to 4 and this configuration are given the prefix "2", and only differences between the configurations will be discussed in detail. The housing 212 includes an outer casing 212a and an inner liner 212b which defines an interior wall of the tank 214. The inner liner 212b is spaced apart from the outer casing 212a to define a cavity 213 therebetween (as best illustrated in Figures 6 and 7). The cavity 213 reduces the transmission of sound generated by the pumps 222 from within the tank 214 to an exterior of the housing 212. In some configurations, the cavity 213 contains sound absorbing material to further reduce the amount of noise generated by the pumps 222 that is transmitted to the exterior of the housing 212. In the configuration of Figures 5 to 8, the outer casing 212a has an open end defining a rim 258 and the inner liner 212b has an outwardly extending flange 260 for engaging the rim 258. In this way, the outwardly extending flange 260 prevents the inner liner 212b from dropping to the base of the outer casing 212a, so that the cavity 213 extends underneath the inner liner 212b. In alternative configurations, the inner liner 212b has a different type of outwardly extending projection instead of the flange 260 (e.g. a series of outwardly extending projections distributed around the inner liner 212b). The rim 258 of the outer casing 212a defines an inwardly extending flange which is configured to space the inner liner 212b from the side walls 262a of the outer casing 212a. In this way, the inwardly extending flange of the rim 258 extends to and abuts against the side walls 262b of the inner liner 212b, which ensures correct alignment of the inner liner 212b within the outer casing 212a. In alternative configurations, the rim 258 has a different type of inwardly extending projection instead of a flange (e.g. a series of inwardly extending projections distributed around the rim 258). In alternative configurations, separate spacing components are provided within the cavity 213 to facilitate spacing between the liner 212b and the outer casing 212a (e.g. in addition to, or instead of, the inwardly extending flange / projection(s) of the rim 258). In the configuration of Figures 5 to 8, the rim 258 is box shaped (i.e. formed of box sections welded to the side walls 262) and also extends outwardly from the side walls to provide a greater contact area for the flange 260 of the inner liner 212b and for the mounting plate 220. In alternative configurations, the inwardly extending flange of the rim 258 is formed by bending the side walls 262 inwards. The housing has an open upper end which defines an aperture 230 for receiving the pumps 222, as will be described in more detail below. The aperture 230 is closed by a mounting plate 220. In other words, the mounting plate 220 acts as a lid for the tank 214. The mounting plate 220, flange 260 of the inner liner 212b and / or the rim 258 of the outer casing 212a can be clamped or welded together. While not shown in the illustrated configuration, mounting plate 220, flange 260 of the inner liner 212b and / or the rim 258 of the outer casing 212a can also be attached by fasteners (e.g. bolts) provided in complementary through-holes or threaded holes in the mounting plate 220, flange 260 of the inner liner 212b and / or rim 258 of the outer casing 212a. It will be understood that in some configurations with such through-holes or threaded holes, the outwardly extending portion of the rim 258 is extended to provide space for the holes to receive the fasteners. In some configurations, a seal (not shown) is provided between the mounting plate 220 and the housing 212. For example, in some configurations a compressible seal such as a gasket is attached to an underside of the mounting plate 220 or attached to a top of the flange 260 of the inner liner 212b. Alternatively, in some configurations a compressible seal is provided as a separate component that is placed between the mounting plate 220 and housing 212 during assembly. In some configurations where a seal is provided between the mounting plate 220 and the housing 212, the seal also has holes aligned with through-holes or threaded holes of the mounting plate 220 and housing 212 to receive a fastener (e.g. bolt) therethrough. The outer casing 212a can be formed of plastics material, metallic material (e.g. steel or aluminium) or any other suitable material. Similarly, the inner liner 212b can be formed of plastics material, metallic material (e.g. steel or aluminium) or any other suitable material. In the configuration of Figures 5 to 8, the mounting plate 220 is configured to mount all of the pumps 222 to the housing 212. In other words, the pump module 218 includes the mounting plate 220, the three pumps 222, and their respective motors 244 and inverters 246, so that all the pumps 222, motors 244 and inverters 246 are installed / removed from the housing 212 together. The hydraulic supply lines 240 each extend from a respective pump outlet 228 to a respective port 242 provided on the common mounting plate 220. In alternative configurations, the pumps 222 and their respective motors 244 and inverters 246 are additionally releasably mounted to the mounting plate 220 so that they can be removed / replaced independently of each other. For example, in some configurations, several pump modules 18 are attached to a common mounting plate 220 by individual mounting portions 20, in the same way that the pump modules 18 of the configuration of Figures 1 to 4 above are attached to an upper surface of the housing 12. As best illustrated in Figures 5 and 6, the mounting plate 220 extends beyond the area defined by the open end of the housing 212 (e.g. behind the housing 212). In this way, the mounting plate 220 provides a shoulder 264 which can be used to mount the hydraulic pump system 210 to a vehicle. The portion of the mounting plate 220 which extends beyond the area defined by the open end of the housing 212 also provides space for mounting additional components such as electronics, filters or the like. In the configuration of Figures 5 to 8, a cover 266 is provided for the components which are external to the tank 214 (i.e. electric motors 244, inverters 246 and other electronics). The cover 266 protects such components from impact, dirt and debris, and also reduces the transmission of noise generated by these components, which results in a quieter pump system 210. Although not illustrated, it will be understood that the cover 266 would include one or more suitable apertures, cutaways or the like for access to the hydraulic ports 242 (e.g. to connect hoses thereto). In some configurations, the cover 266 includes sound-absorbing material (e.g. lined on an inside of the cover 266). The cover 266 can be formed of plastics material, metallic material (e.g. steel or aluminium) or any other suitable material. As illustrated in Figure 6, the mounting plate 220 includes a slot 268 for allowing airflow inside the cover 266 (e.g. for cooling the electronic components located therein). In alternative configurations, such a slot 268 is provided in the cover 266, or a plurality of such slots 268 are provided in the mounting plate 220 and / or cover 266. Referring now to Figure 9, a working vehicle according to an configuration is indicated at 100. The working vehicle 100 includes a working arm 102 controlled by a plurality of hydraulic actuators 104. The working vehicle 100 also includes a pair of left and right tracks 106 for moving the working vehicle 100. The left and right tracks 106 are driven by respective hydraulic motors. A set of user inputs 50 (e.g. joy-sticks, levers, buttons, pedals etc.) are provided on the working vehicle 100 for controlling movement of the working vehicle 100 and the working arm 102. The working vehicle 100 also includes a hydraulic pump system 10 as described above in relation to Figures 1 to 4 or a hydraulic pump system 210 as described above in relation to Figures 5 to 8. The hydraulic pump system 10, 210 is provided to supply hydraulic fluid 16 to the hydraulic actuators 104 and left / right track motors of the working vehicle 100. As has been outlined above, the hydraulic pump systems 10, 210 of Figures 1 to 4 and 5 to 8 are particularly compact and efficient. This provides significant benefits when applied to a working vehicle 100 (where space is restricted and power is of limited capacity), particularly when the working vehicle 100 is an electric working vehicle where increased efficiency results in increased battery life and periods of use between charging, or a fuel cell powered working vehicle where reduced energy losses result in reduced fuel consumption. In the illustrated configuration, the working vehicle 100 is of the type known as an excavator. In alternative configurations, the working vehicle is a different type of vehicle. For example, in some configurations the working vehicle is a backhoe loader, telehandler, skid-steer loader, dumper, forklift truck or other type of working vehicle having one or more hydraulically-actuated devices. In alternative configurations, the hydraulic pump system 10, 210 is part of a hydraulic system of a static application rather than a mobile application such as a working vehicle (e.g. the hydraulic pump system 10, 210 is part of an industrial hydraulic system in a manufacturing or processing plant). Referring now to Figures 10 and 11, an alternative hydraulic pump system for the working vehicle 100 of Figure 9 is indicated at 310. The hydraulic pump system 310 of Figures 10 and 11 is similar to previous hydraulic pump systems 10, 210 of Figures 1 to 8. Therefore, common features between the hydraulic pump system 310 of Figures 10 to 11 and the hydraulic pump systems 10, 210 of Figures 1 to 8 are given the prefix "3", and only differences are discussed in detail below. Similar to the previous configurations, the hydraulic pump system 310 has a housing 312 defining a tank 314 for containing hydraulic fluid in use. The hydraulic pump system 310 also has a plurality of pump modules 318 (in particular three pump modules 318), each pump module 318 for driving one of the plurality of hydraulic actuators 14 of the working vehicle 100. However, in the embodiment of Figures 10 and 11, the pump modules 318 have a different configuration. In the illustrated embodiment, each pump module 318 has a hydraulic pump 322 for supplying hydraulic fluid from the tank 314 to a hydraulic system. Each pump module 318 also has an electric motor 344 for driving the hydraulic pump 322, similar to the previous configurations of Figures 1 to 8. Similar to the previous configurations of Figures 1 to 8, the hydraulic pump system 310 also has a mounting arrangement 320, each pump module 318 being mounted to the housing 312 by the mounting arrangement 320. The mounting arrangement 320 is indicated schematically in Figures 10 and 11, but may be similarto the individual mounting portions 20 of Figures 1 to 4 or to the common mounting plate 220 of Figures 5 to 8. Similar to the previous configurations of Figures 1 to 8, the hydraulic pump system 310 has three inverters 346 configured to drive the electric motors 344 at a predetermined speed in accordance with a demand for the respective actuator 104 of the working vehicle 100. In the illustrated configuration, the inventers 346 are mounted on a plate 347 above the electric motors 344, similar to the configuration of Figure 3. However, other mounting positions of the inverters 346 may be used in alternative embodiments. In Figure 10, a portion of a hydraulic circuit 108 for directing hydraulic fluid supplied by the pump modules 318 to the respective hydraulic actuators 104 of the working vehicle 100 is also shown. In particular, the hydraulic pumps 322 of the pump modules 318 are connected via hydraulic lines 107 to inputs 109A of a valve block 109. The valve block 109 also has outputs 109B for connection via further hydraulic lines (not shown) to the hydraulic actuators 104 of the working vehicle 100. The main difference between the pump modules 318 of Figures 10 and 11 and the pump modules 18, 218 of the previous configurations is that each pump module 318 has a gear arrangement 370 coupled between the electric motor 344 and the hydraulic pump 322, such that the hydraulic pump 322 is driven by the electric motor 344 via the gear arrangement 370. In other words, the gear arrangement 370 replaces the common drive shaft 54 of the previous configurations. This allows the size of the electric motors 344 and inverters 346 to be reduced to provide improved packaging within the working machine 100. In particular, the gear arrangement 370 removes the need for the electric motors 344 to match the torque requirements of the hydraulic pumps 322. For example, the torque requirements of the electric motors 344 may be reduced, which may allow smaller electric motors 344 and inverters 346 to be used. Referring now to Figure 11, a single pump module 318 is illustrated in more detail, but it will be understood that the other pump modules 318 have the same configuration. In other words, the gear arrangement 370 of each pump module 318 is the same as the gear arrangement 370 of the other pump modules 318. Therefore, only one pump module 318 and gear arrangement 370 will be described in detail below. In the illustrated embodiment, the gear arrangement 370 has a first gear 374 coupled to an output shaft 354A of the electric motor 344 for rotation with the output shaft 354A. The gear arrangement 370 also has a second gear 376 coupled to an input shaft 354B of the hydraulic pump 322 for rotation with the input shaft 354B. In the illustrated embodiment, the first gear 374 and second gear 376 are in permanent mesh with each other. In particular, the gear arrangement 370 is in the form of a parallel shaft gearbox 372 in which the first and second gears 374, 376 are positioned side-by-side. In other words, the output shaft 354A of the electric motor 344 is parallel to, but offset from, the input shaft 354B of the hydraulic pump 322. The illustrated gear arrangement 370 is an example of a single stage gearbox 372. In other configurations, the gear arrangement 370 may be a planetary gearbox (e.g., a single stage planetary gearbox, as another example of a single stage gearbox). Such a planetary gearbox may have aligned input and output shafts 354A, 354B. In some embodiments, the gear arrangements 370 of the pump modules 318 differ (e.g., one of the gear arrangements 370 being a planetary gearbox and another of the gear arrangements 370 being a parallel shaft gearbox). The gear arrangement 370 may have a gearbox ratio corresponding to a faster rate of rotation of the first gear 374 than the second gear 376. In this way, the torque requirement of the electric motor 344 may be reduced, which may allow a cheaper and smaller electric motor 344 to be used. For example, the gearbox ratio may be in a range of about 1.5:1 to about 6:1, e.g., in a range of about 2:1 to about 4:1. For example, in the illustrated parallel shaft gearbox 372, the gearbox ratio may be around 2:1. In a planetary gearbox configuration, the gearbox ratio may be around 4:1. It will be understood that the gearbox ratios discussed above allow a faster rate of rotation of the electric motor for a given rotational speed of the hydraulic pump. For example, if the gearbox ratio is 2:1 then, for a given output from the hydraulic pump 322, the electric motor 344 would rotate at roughly twice the rate of an electric motor in a direct drive arrangement (e.g., of the kind illustrated in Figures 1 to 8). Although the hydraulic pump 322 is illustrated schematically in Figures 10 to 11, it will be appreciated that each hydraulic pump 322 has a body which extends at least partially into the tank 314 (e.g., entirely within the tank 314) in a similar manner to the previous configurations of Figures 1 to 8. In the illustrated embodiment, the gearbox 372 is positioned external to the tank 314. In particular, the mounting arrangement 320 includes a mounting plate (e.g., similar to the individual mounting portions 20 of Figures 1 to 4, or the common mounting plate 220 of Figures 5 to 8). The mounting plate 320 has an interior surface 320A and an exterior surface 320B. The gearbox 372 is mounted to the exterior surface 320B of the mounting plate 320. In the illustrated configuration, the hydraulic pump 322 is mounted to the interior surface 320A of the mounting plate 320. This provides a simple means for externally mounting the gearbox 372, whilst also allowing the gearbox 372 and hydraulic pump 322 to be mounted / dismounted as a single unit via the mounting plate 320. In the illustrated embodiment, the electric motor 344 is mounted to the gearbox 372. In particular, the gearbox 372 has a casing 378 which houses the first and second gears 374, 376, and the electric motor 344 is mounted to an upper surface of the casing 378. A lower surface of the casing 378 sits on the exterior surface 320B of the mounting plate 320 to mount the gearbox 372 to the exterior surface 320B. In alternative embodiments, the gearbox 372 may extend at least partially into the tank 314 (e.g., entirely within the tank 314). For example, the gearbox 372 may be mounted to the interior surface 320A of the mounting plate 320. In such embodiments, an upper surface of the casing 378 of the gearbox 372 may be mounted to the interior surface 320A of the mounting plate 320, and the hydraulic pump 322 may be mounted to a lower surface of the casing 378 of the gearbox 372. In some embodiments, the hydraulic pump system 310 of Figures 10 and 11 may have a cover for covering the components which are external to the tank 314. For example, a cover similar to the cover 266 of Figure 5 may be provided. The hydraulic pump system 310 may be provided within an enclosure 105 in a machine body 103 of the working vehicle 100. For example, in the excavator 100 of Figure 9, the hydraulic pump system 310 may be provided within an enclosure 105 in a superstructure 103 of the excavator 100. Although the hydraulic pump system 310 of Figures 10 and 11 is only indicated schematically, it will be understood that any of the features of the hydraulic pump systems 10, 210 may be included in the hydraulic pump system of Figures 10 and 11, provided that they are compatible with the addition of the gear arrangement 370. For example, a non-exhaustive list of potential features which could be included in the hydraulic pump system of Figures 10 and 11 includes: hydraulic supply lines 40, 240 may be provided within the tank 314 outside of the body of the pump 322 to channel hydraulic fluid out of the tank 314; hydraulic supply ports 42, 242 may be provided through the mounting arrangement 320 connected to the hydraulic supply lines 40, 240 so that the pump modules 318 can be installed / removed from the housing 312 as a self-contained unit; the hydraulic pumps 322 may have the same configuration of the body 24, 224, inlet 26, 226 and outlet 28, 228 illustrated in Figures 1 to 8; the pump modules 318 may each be mounted to the housing 312 individually (i.e., through respective apertures 30 in the housing 312) as illustrated in Figures 1 to 4, or via a common mounting plate 220 as illustrated in Figures 5 to 8; the mounting arrangement 320 may be releasably attached (e.g., via through-holes 34 and / or threaded holes 36 of the kind illustrated in Figures 1 to 4) or fixedly attached to the housing 312; seals 38 similar to those illustrated in Figures 1 to 4 may be provided; a controller 48 similar to that described in relation to Figures 1 to 4 may be provided to control the hydraulic pump system 310; a filter arrangement 56 of the kind described above in relation to Figure 1 may be provided; the hydraulic pumps 322 may be fixed displacement pumps (e.g., bent-axis piston pumps) of the kind described in relation to Figures 1 to 8; the housing 312 may have an outer casing 312a and an inner liner 312b (e.g., with sound absorbing material therebetween) similar to those illustrated in Figures 5 to 8. The term "module" used throughout this description is to be interpreted as an attachable / detachable self-contained unit comprising components that can be installed in or removed from the hydraulic pump system 10 as a single unit, i.e. without having to connect / disconnect interconnected components of the module to or from one another. Although the disclosure has been described in relation to one or more configurations, it will be appreciated that various changes or modifications can be made without departing from the scope defined by the appended claims. For example: the pump system 10, 210, 310 may be configured for supplying fluid different to a hydraulic fluid to a different type of fluid system, e.g. the pumps may be cooling oil / water pumps for pumping cooling oil / water in a cooling fluid system; the number of pumps 22, 222, 322 and pump modules 18, 218, 318 may be more or less than in the illustrated embodiments; the pump modules 18, 218, 318 may be entirely contained within the tank 14, 214, 314 (e.g. electric motors 44, 244, 344 may be located within an interior of the tank with only power / signal cables and hydraulic supply ports 42, 242 passing through the housing 12, 212, 312); the mounting portions 20, 220, 320 may be of different shape and / or configuration; the inverters 46, 246, 346 may be integral to the pump modules 18, 218, 318, or may be part of a separate assembly operably coupled to the pump modules 18, 218, 318; the electric motors 44, 244, 344 may be DC motors and the inverters 46, 246, 346 may be omitted; the hydraulic pumps 22, 222, 322 of the pump modules 18, 218, 318 may be of any suitable type (e.g. of different type or configuration to the bent axis piston pumps described above); the pump modules 18, 218, 318 may be mounted to the housing 12, 212, 312 via a different means to the through-holes 34 and threaded holes 36 (e.g. via welding or adhesive); and the filter arrangement 56 may be external to the housing 12, 212, 312 (e.g. as a separate unit connected to the tank 14, 214, 314 via a pipe). It should also be noted that whilst the appended claims set out particular combinations of 5 features described above, the scope of the present disclosure is not limited to the particular combinations hereafter claimed, but instead extends to encompass each feature herein disclosed in isolation, as well as any combination of features herein disclosed.

Claims

1. A working vehicle comprising:a plurality of hydraulic actuators;a hydraulic pump system comprising:a housing defining a tank for containing hydraulic fluid in use;a plurality of pump modules each pump module for driving one of the plurality of hydraulic actuators comprising:a hydraulic pump for supplying hydraulic fluid from the tank to a hydraulic system;an electric motor; and,a gear arrangement coupled between the electric motor and the hydraulic pump, such that the hydraulic pump is driven by the electric motor via the gear arrangement;at least one inverter configured to drive each of the electric motors at a predetermined speed in accordance with a demand for the respective actuator;a mounting arrangement, wherein each pump module is mounted to the housing by the mounting arrangement; and,a hydraulic circuit for directing hydraulic fluid supplied by each pump module to a respective one of the hydraulic actuators.

2. The working vehicle of claim 1, wherein the gear arrangement comprises a single stage gearbox.

3. The working vehicle of claim 2, wherein the gear arrangement comprises a first gear coupled to an output shaft of the electric motor for rotation with the output shaft, and a second gear coupled to an input shaft of the hydraulic pump for rotation with the input shaft.

4. The working vehicle of claim 3, wherein the first gear and second gear are in permanent mesh with each other.

5. The working vehicle of claim 3 or 4, wherein the gear arrangement comprises a parallel shaft gearbox in which the first and second gears are positioned side-by-side.

6. The working vehicle of claim 3 or 4, wherein the gear arrangement comprises a planetary gearbox.

7. The working vehicle of any of claims 3 to 6, wherein the gear arrangement comprises a gearbox ratio corresponding to a faster rate of rotation of the first gear than the second gear.

8. The working vehicle of claim 7, wherein the gearbox ratio is in a range of about 1.5:1 to about 6:1.

9. The working vehicle of claim 8, wherein the gearbox ratio is in a range of about 2:1 to about 4:1.

10. The working vehicle of any preceding claim, wherein the gear arrangement of each pump module is the same as the gear arrangement of the other pump modules.

11. The working vehicle of any preceding claim, wherein the hydraulic pump system comprises three or more pump modules.

12. The working vehicle of any preceding claim, wherein the hydraulic pump comprises a body, and wherein the body extends at least partially into the tank.

13. The working vehicle of claim 12, wherein the body is located entirely within the tank.

14. The working vehicle of claim 12 or 13, wherein the gear arrangement comprises a gearbox which is positioned external to the tank.

15. The working vehicle of claim 14, wherein the mounting arrangement comprises a mounting plate having an interior surface and an exterior surface, wherein the gearbox is mounted to the exterior surface of the mounting plate.

16. The working vehicle of claim 15, wherein the mounting plate defines a lid for the tank; optionally a removable lid.

17. The working vehicle of claim 14, 15 or 16, wherein the electric motor is mounted to the gearbox.

18. The working vehicle of claim 12 or 13, wherein the gear arrangement comprises a gearbox which extends at least partially into the tank.

19. The working vehicle of claim 18, wherein the gearbox is located entirely within the tank.

20. The working vehicle of claim 19, wherein the mounting arrangement comprises a mounting plate having an interior surface and an exterior surface, wherein the gearbox is mounted to the interior surface of the mounting plate.

21. The working vehicle of claim 20, wherein the mounting plate defines a lid for the tank; optionally a removable lid.

22. The working vehicle of any preceding claim, wherein the hydraulic pump system is provided within an enclosure in a machine body of the working vehicle.

23. The working vehicle of claim 22, wherein the working vehicle is an excavator and wherein the hydraulic pump system is provided within an enclosure in a superstructure of the excavator.

24. The working vehicle of any preceding claim, wherein the hydraulic pump system comprises a cover for covering components of the hydraulic pump system which are provided external to the tank.40Application No: GB2414481.8 Examiner: Ian ChoiClaims searched: 1-24 Date of search: 27 February 2025Patents Act 1977: Search Report under Section 17Documents considered to be relevant:Category Relevant to claims Identity of document and passage or figure of particular relevance X X X X A A 1-15, 17, 22-24 1-17, 22-24 1-14, 17, 22-24 1-15, 17, 22-24 JP 2010013879 A (SUMITOMO CONSTR MACHINERY MFG) See especially figures 1-7, and paragraphs 8, 12, 14, 16, 20, 27, 41-47. GB 2604609 A (BAMFORD EXCAVATORS LTD) See especially figures, page 13 lines 21-32, and page 17 lines 19-24. WO 2020 / 074340 Al (AGCO INT GMBH) See especially figures and page 5 lines 13-20. CN 104859439 A (XINGGUANG AGRICULTURAL MACHINERY CO LTD) See especially US 2018 / 0202367 Al (SUCIU et al.) See especially figures 4-6 and paragraphs 46-63. EP 4033038 Al (BAMFORD EXCAVATORS LTD) See especially figures and paragraphs 68-70, 85-101.Categories: X Document indicating lack of novelty or inventive step A Document indicating technological background and / or state of the art. Y Document indicating lack of inventive step if combined with one or more other documents of same category. P Document published on or after the declared priority date but before the filing date of this invention. & Member of the same patent family E Patent document published on or after, but with priority date earlier than, the filing date of this application.Field of Search:Search of GB, EP, WO &US patent documents classified in the following areas of the UKCX :Worldwide search of patent documents classified in the following areas of the IPC_____________E02F; F04B; F04C; F04D; F15B______________________________________The following online and other databases have been used in the preparation of this search report SEARCH-PATENTInternational Classification:Subclass Subgroup Valid From F04C 0015 / 00 01 / 01 / 2006 E02F 0009 / 22 01 / 01 / 2006 F04B 0009 / 02 01 / 01 / 2006 F04B 0017 / 03 01 / 01 / 2006 F04D 0013 / 02 01 / 01 / 2006 F04D 0013 / 06 01 / 01 / 2006 F15B 0015 / 18 01 / 01 / 2006

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