GB2619934A

GB2619934A - A battery-powered four-way load handling vehicle

Info

Publication number: GB2619934A
Application number: GB2209094.8A
Authority: GB
Inventors: Turnbull Kevin
Original assignee: Cargotec Engineering Ireland Ltd
Current assignee: Cargotec Engineering Ireland Ltd
Priority date: 2022-06-21
Filing date: 2022-06-21
Publication date: 2023-12-27
Also published as: GB202209094D0

Abstract

A battery-powered four-way load handling vehicle has a chassis with a pair of front wheels 101, 103 and a rear wheel (105, Figure 1), with the rear wheel and at least one front wheel being powered by a wheel motor with a wheel motor controller for controlling the wheel motors. The vehicle is operable in a forwards/backwards mode of operation and a sideways mode of operation. In the sideways mode of operation, when a front steering wheel 101 is turned so that the rear wheel is on the inside of the turn, the wheel motor controller slows the rear wheel gradually with increasing degree of turn until the front steering wheel reaches a critical angle at which the rear wheel is stopped, and the rear wheel is placed into a freewheeling mode in which it can move in reverse. In the forwards/backwards mode a front wheel on the inside of the turb may similarly be made to freewheel at a critical angle.

Description

"A battery-powered four-way load handling vehicle"

Introduction

This invention relates to a battery-powered four-way load handling vehicle.

More specifically, the invention relates to a steering management control system and methodology for a load handling vehicle capable of operating in a forwards/backwards mode of operation and a sideways mode of operation.

Battery-powered four-way load handling vehicles are particularly suited for transporting goods in and around factories and warehouses. Due to the enhanced manoeuvrability of the four-way load handling vehicle, it is capable of navigating warehouses with relatively narrow aisles. As the four-way load handling vehicle can travel sideways in the direction of the long load on its lifting mechanism, its width is not dictated by the length of the load, as is the case with two-way machines. Accordingly, the warehouse may be arranged more efficiently and with higher density than was otherwise possible with many other types of load handling vehicles. The four-way load handling vehicle is not limited to use in warehouses and may be used in other areas where enhanced manoeuvrability is advantageous. In addition, the battery-powered load handling vehicle is suitable for working in low emissions zones where emissions from an internal combustion engine would be an impediment to their operation.

One such machine is that described in European Patent No. EP2,956,350 in the name of Combilift (Registered Trade Mark, 0) Limited.

Another similar type of load handling vehicle that is particularly useful is the Moffett 0 M4 four-way, as sold by Cargotec 0 Ireland Limited. The Moffett 0 M4 four-way is a diesel engine powered machine and is a special type of vehicle, a so-called piggyback forklift truck that is designed to be transported to and from customer's premises on the rear of a carrying vehicle so that the forklift truck can be used to load and/or unload goods at the customer's premises, thereby obviating the need for the customer to have their own load handling vehicle. -2 -

There are however some problems with some of the known offerings and indeed there are aspects of those offerings that could be improved upon. For example, a problem with practically all battery-powered four-way load handling vehicles is limited battery life. For certain machines, a full charge from a 1.8kW socket takes approximately 6-7 hours to complete. Providing additional battery packs on a piggyback forklift truck in particular is not practical as it would increase the weight of the piggyback forklift truck which is entirely contrary to several of the design requirements of piggyback forklift trucks. Therefore, it is advantageous, indeed necessary, to preserve battery power during normal operation as much as possible.

Secondly, it is desirable to provide a smooth drive without sudden changes in acceleration/deceleration. Sudden changes in acceleration/deceleration can cause instability to the carried load which is highly disadvantageous. Sudden changes in acceleration/deceleration is particularly an issue during turning of the load handling vehicle as these can cause the load handling vehicle to "jump", which can be both disconcerting to the driver and dangerous.

Thirdly, it is preferable to reduce the wear and tear on components of the vehicle during normal operation of the vehicle. In this way, it is possible to reduce maintenance costs and vehicle downtime when repairs have to be carried out to the vehicle.

Fourth, in order to provide a good driver experience and promote uptake, it may be preferable for the load handling vehicle to have handling characteristics similar to the existing four-way diesel machines.

It is an object of the present invention to provide a battery-powered four-way load handling vehicle that overcomes at least one of these problems. It is a further object of the present invention to provide a battery-powered four-way load handling vehicle that offers a useful choice to the consumer. -3 -

Statements of Invention

According to the invention there is provided a battery-powered four-way load handling vehicle comprising: a chassis having a pair of front wheels and a rear wheel located behind and intermediate the pair of front wheels, the rear wheel powered by a rear wheel motor and at least one of the front wheels powered by a front wheel motor, a wheel motor controller for controlling one or more of the wheel motors, and in which there is provided a driver's station, a battery pack for powering the wheel motors, and a lifting mechanism mounted on the chassis; the four-way load handling vehicle is operable in a forwards/backwards mode of operation and a sideways mode of operation, in which: during the forwards/backwards mode of operation, the front wheels and the rear wheel are oriented substantially parallel to the longitudinal axis of the load handling vehicle when in a neutral steering angle position, and the load handling vehicle is steered by the rear wheel; and during a sideways mode of operation, the front wheels and the rear wheel are oriented substantially perpendicular to the longitudinal axis of the load handling vehicle when in a neutral steering angle position, and the load handling vehicle is steered by at least one of the front wheels; characterized in that when the four-way load handling vehicle is operated in a sideways mode of operation, when the front steering wheel is turned so that the rear wheel is on the inside of the turn, the wheel motor controller is operated to slow the rear wheel gradually with increasing degree of turn until the front steering wheel reaches a critical angle at which the rear wheel is stopped, and placed into a freewheeling mode, so that on further turning of the front steering wheel, the driven rear wheel is free to rotate in reverse.

By having such a vehicle, the battery power to the driven rear wheel is temporarily cut so that the driven rear wheel is no longer draining resources from the battery. It is envisaged that this may be advantageous for the battery life of the vehicle. In addition, -4 -as the rear wheel is not driven in reverse, there will be no sudden "jump" of the load handling vehicle as the rear wheel is positively powered in reverse. This will lead to a more stable operation. By not operating the rear wheel in reverse, it is envisaged that this will lead to less wear and tear of the rear wheel motor, resulting in lower operating costs and reduced downtime. Finally, it is envisaged that the handling of the load handling vehicle will more closely mimic that of an existing diesel machine, improving operator experience.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which when the four-way load handling vehicle is operated in a forwards/backwards mode of operation, when the rear steering wheel is turned, the wheel motor controller is operated to slow the driven front wheel on the inside of the turn gradually with increasing degree of turn until the rear steering wheel reaches a critical angle at which the front wheel is stopped and placed into a freewheeling mode, so that on further turning of the rear steering wheel, the driven front wheel on the inside of the turn is free to rotate in reverse.

By having such a vehicle, the battery power to the driven front wheel is temporarily cut so that the driven front wheel is no longer draining resources from the battery. It is envisaged that this will save energy. Furthermore, at the front wheel is not driven in reverse, there will be no sudden "jump" of the load handling vehicle as the front wheel transitioned to being positively powered in reverse. This will lead to a more stable operation of the vehicle. By not operating the front wheel in reverse, it is envisaged that this will lead to less wear and tear of the front wheel motor, resulting in lower operating costs and reduced downtime. Finally, it is envisaged that the handling of the load handling vehicle will more closely mimic that of an existing diesel machine, improving operator experience.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which when the four-way load handling vehicle is operated in a forwards/backwards mode of operation, when the rear steering wheel is turned, the wheel motor controller is operated to slow the driven front wheel on the inside of the turn gradually with increasing degree of turn until the rear steering wheel reaches a critical angle at which the front wheel is stopped and placed into reverse, so that on further turn -5 -of the rear steering wheel, the driven front wheel on the inside of the turn is driven in reverse. In this way, the driving characteristics of the four-way machine will operate in much the same way as a two-way machine when in a forward/backwards mode of operation. This familiarity may be preferable for the drivers.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which when the driven front wheel on the inside of the turn is driven in reverse, it is driven at a speed proportional to the degree of turn beyond the critical angle.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which both of the front wheels are each provided with a front wheel motor and both of the front wheels are driven.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which the freewheeling mode comprises a towing mode.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which the chassis comprises a U-shaped chassis having a pair of forwardly projecting side bars connected by a rear bridging member, and in which one of the pair of front wheels is located at the forwardmost end of one of the side bars, the other of the pair of front wheels is located at the forwardmost end of the other of the side bars, and the rear wheel is located centrally on the rear bridging member. This configuration is particularly suitable for a piggyback forklift truck.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which the lifting mechanism is mounted on the chassis intermediate the side bars.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which the lifting mechanism is mounted on a carriage that is moveable forwards and backwards on the chassis intermediate the side bars. This is seen as a particularly useful embodiment that will be able to pick up and put down loads forward of the front wheels. -6 -

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which there are provided a plurality of wheel position sensors in communication with the wheel motor controller.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which there is provided a steering wheel position sensor in communication with the wheel motor controller.

In one embodiment of the invention there is provided a battery-powered four-way load handling vehicle in which the battery pack is configured to receive a trickle charge from a carrying vehicle for charging the battery pack during transit of the load handling vehicle on the carrying vehicle. This is seen as particularly useful. By being able to trickle charge the battery during transit, the load handling vehicle will have its battery topped up when it is being transported to customer's premises. This will significantly lengthen the amount of operational time of the piggyback forklift truck enabling more deliveries to be carried out between full charges.

Detailed Description of the Invention

The invention will now be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings, in which:-Figures 1(a) to 1(c) are diagrammatic representations of a steering management methodology of a two-way load handling vehicle known in the art; Figures 2(a) to 2(c) are diagrammatic representations of a steering management methodology of a four-way load handling vehicle according to the invention, Figures 3(a) to 3(c) are diagrammatic representations of a steering management methodology of a four-way load handling vehicle according to the invention; and Figure 4 is a perspective view of a four-way load handling vehicle according to the invention. -7 -

Referring to Figures 1(a) to 1(c), there is shown a diagrammatic representation of a two-way load handling vehicle known in the art, indicated generally by the reference numeral 100, comprising a pair of front wheels 101, 103 and a steerable rear wheel 105. The pair of front wheels 101, 103 are arranged substantially parallel to a longitudinal axis 107 of the load-handling vehicle and the rear wheel 105 is operated to steer the vehicle.

Typically, as the load handling vehicle begins to turn, the front wheel on the inside of the turn, in this case the front wheel 101 for a left hand turn, is gradually slowed in order to prevent wheel spin and maintain traction.

In Figure 1(a), the angle of the turn (i.e. the angle of the rear wheel relative to the longitudinal axis 107 of the load-handling vehicle) is at approximately 45°. Put another way, the transverse axis 109 of the rear wheel 105 is "outside" the front wheel 101. As the angle of turn is increased, the front wheel 101 is slowed further as the transverse axis of the rear wheel 105 approaches the front wheel 101.

The front wheel 101 is slowed until the angle of turn reaches a critical angle, as illustrated in Figure 1(b), in which the steering radius of the load handling vehicle approximately matches the distance between the front wheel 101 and the rear wheel 105. In the embodiment shown, the angle of the turn (i.e. the angle of the rear wheel relative to the longitudinal axis 107 of the load-handling vehicle) is at approximately 57°.

In other words, at this point, the transverse axis 109 of the rear wheel 105 intersects the front wheel 101.

Referring now to Figure 1(c), the rear steering wheel 105 of the load handling vehicle has been turned further still so that the transverse axis 109 of the rear wheel 105 is "inside" the front wheel 101. In the embodiment shown, the angle of the turn (i.e. the angle of the rear wheel relative to the longitudinal axis 107 of the load-handling vehicle) is at approximately 70°. In this mode, as the vehicle is turned, the front wheel 101 will travel in reverse.

In a diesel-powered machine known in the art, in which the wheels are powered by hydraulic motors, hydraulic fluid is delivered to all three wheels 101, 103, 105 or is delivered simply to both of the front wheels 101, 103. As the load handling vehicle 100 begins to turn, the pressure on the hydraulic fluid being delivered to the inside front -8 -wheel 101 (for a left hand turn) will begin to increase. As the hydraulic fluid will follow the path of least resistance, the flow of hydraulic fluid to the front wheel 101 on the inside of the turn will be reduced, and more hydraulic fluid will be delivered to the other wheel(s) 103, 105. As the steering wheel 105 is turned further, at the critical angle as shown in Figure 1(b), the build-up of pressure on the hydraulic fluid being delivered to the front wheel 101 will reach a point where the front wheel 101 will stop. Further turning of the rear steering wheel and further turning of the load handling vehicle, as shown in Figure 1(c) will cause the front wheel 101 to overcome the hydraulic fluid pressure and the front wheel will effectively be dragged in reverse. However, this is hard wearing on the load handling vehicle equipment.

In a battery powered machine, it will be understood that this automatic adjustment to inside wheel speed and direction based on the effect of turning angle on the hydraulic fluid pressure is not applicable. Instead, the front wheel 101 is positively slowed by slowing the electric motor driving that front wheel 101 until the steering angle reaches the critical angle as shown in Figure 1(b) and after that angle, with increasing angle of turn, the front wheel 101 is driven in reverse at a speed proportional to the angle of turn. Although less hard wearing on the tyres and other components of the load handling vehicle, the motor being driven in reverse is still consuming battery power and there will be wear and tear from changing the direction of the motor and operating the motor in reverse. In addition, it has been found that at the cross-over point where the motor begins to be operated in reverse, the load handling vehicle has a tendency to "jump" once the motor on the front wheel kicks in to reverse. This can be disconcerting from the operator's viewpoint and can destabilize a load on the lifting mechanism (not shown).

Referring now to Figures 2(a) to 2(c) inclusive and 3(a) to 3(c) inclusive, there is shown a diagrammatic representation of a four-way load handling vehicle according to the invention, indicated generally by the reference numeral 200, where like parts have been given the same reference numeral as before. Referring specifically to Figures 2(a) to 2(c), the four-way load handling vehicle 200 is shown in a forwards/backwards mode of operation in which the front wheels 101, 103 and the rear wheel 105 are oriented substantially parallel to the longitudinal axis 107 of the load handling vehicle 200 when in a neutral steering angle position, and the load handling vehicle is steered by the rear wheel 105. Referring specifically to Figures 3(a) to 3(c), the four-way load handling -9 -vehicle 200 is shown in a sideways mode of operation in which the front wheels 101, 103 and the rear wheel 105 are oriented substantially perpendicular to the longitudinal axis 107 of the load handling vehicle when in a neutral steering angle position (not shown), and the load handling vehicle 200 is steered by at least one of the front wheels 101, 103.

Referring once again to Figures 2(a) to 2(c), the load handling vehicle is shown turning to the left, similar to the embodiment shown in Figures 1(a) to 1(c) above. In Figure 2(a), the angle of the turn (i.e. the angle of the rear wheel 105 relative to the longitudinal axis 107 of the load-handling vehicle) is again at approximately 45°. Put another way, the transverse axis 109 of the rear wheel 105 is "outside" the front wheel 101. As the angle of turn of the rear wheel 105 is increased (i.e. as the transverse axis of the rear wheel 105 approaches the front wheel 101), the front wheel 101 is slowed proportional to the angle of turn by slowing the motor powering that front wheel 101.

The front wheel 101 is slowed until the angle of turn reaches the critical angle, as illustrated in Figure 2(b), in which the steering radius of the load handling vehicle approximately matches the distance between the front wheel and the rear wheel. In the embodiment shown, the angle of the turn (i.e. the angle of the rear wheel relative to the longitudinal axis 107 of the load-handling vehicle) is at approximately 57°. In other words, at this point, the transverse axis of the rear wheel intersects the front wheel 101.

The precise angle at which the critical angle is reached will depend in part on the geometry of the load handling vehicle. At this point, when the steering reaches the critical angle, the front wheel 101 is stopped and thereafter placed into a freewheeling mode, so that on further turning of the rear steering wheel 105, the driven front wheel 101 is no longer driven and is free to rotate in reverse.

Referring now to Figure 2(c), the rear steering wheel 105 of the load handling vehicle has been turned further still so that the transverse axis 109 of the rear wheel 105 is "inside" the front wheel 101. In the embodiment shown, the angle of the turn (i.e. the angle of the rear wheel relative to the longitudinal axis 107 of the load-handling vehicle) is at approximately 70°. In this mode, as the vehicle is turned, the front wheel 101 will be able to freewheel in reverse. The wheel is neither dragged not powered in reverse, thereby leading to less wear and tear and not using energy from the battery.

-10 -Referring once again to Figures 3(a) to 3(c) inclusive, the four-way load handling vehicle 200 is shown in a sideways mode of operation. In a sideways mode of operation, the load handling vehicle is configured to move in a direction perpendicular to the longitudinal axis 107 of the load handling vehicle. The front wheels 101, 103 and the rear wheel 105 are oriented perpendicular to the longitudinal axis 107 of the load handling vehicle when in a neutral steering angle position (not shown), so that the load handling vehicle can move sideways, as is understood in the art. In the sideways mode of operation, the load handling vehicle 200 is steered by at least one of the front wheels 101, 103. In the embodiment shown, both of the front wheels operate to steer the load-handling vehicle and the load handling vehicle is making a left hand turn, placing the driven rear wheel 105 on the inside of the turn.

In Figure 3(a), the front wheel 103 is shown at a steering angle of 25°. More specifically, the direction of the front wheel 103 is at an angle of 25° to a transverse axis 201 of the load handling vehicle. At this point, a transverse axis 203 of that front wheel 103 intersects an extension of the longitudinal axis 107 of the load handling vehicle at a point 205 that is outside the rear wheel 105. As the front wheel 103 is steered, the rear wheel 105, that is on the "inside" of the turn, is gradually slowed by slowing the motor driving the rear wheel 105. Preferably, the rear wheel 105 is slowed proportional to the degree of turn of the front wheel.

Referring now specifically to Figure 3(b), the front wheel 103 has been steered further, to a critical angle, indicated by the reference A, at which point the transverse axis 203 of the front wheel 103 intersects the rear wheel. The critical angle will be dependent on the geometry of the load handling vehicle but in the present case, the critical angle A for the load handling vehicle is an angle of 36.1°. At this critical angle, the steering radius of the machine matches the distance to the rear wheel from the driven front wheel and at this steering angle, the rear wheel 105 is stopped (is no longer driven). The rear wheel 105 is thereafter placed in a freewheeling mode so that upon further steering of the front wheel, increasing the angle of turn, the rear wheel 105 will freely rotate in reverse.

Referring now to Figure 3(c), the front wheel 103 has been steered further beyond the critical angle A, so that the transverse axis 203 of the front wheel 103 intersects the longitudinal axis 107 of the load handling truck at point 207, which is inside the rear wheel 105. As the load handling truck is moved forwards, in the direction of the arrow shown, the rear wheel 105 will rotate in reverse. In this way, as the rear wheel is not dragged or driven in reverse, there will be less wear and tear, less battery consumption, and there will be no "jump" to destabilize the load caused by a wheel motor to the rear wheel 105 operating in reverse, thereby leading to a smoother more efficient operation.

Referring now to Figure 4, there is shown a perspective view of a battery-powered four-way load handling vehicle 200 according to the invention, where like parts have been given the same reference numeral as before. The load handling vehicle 200 comprises a chassis 300 having a pair of front wheels 101, 103 and a rear wheel (not shown) located behind and intermediate the pair of front wheels. The rear wheel is powered by a rear wheel motor and the front wheels are each powered by their own front wheel motor 301, 303. There is further provided a driver's station 305, a battery pack 307 for powering the wheel motors, and a lifting mechanism 309 mounted on the chassis. The battery pack 307 is configured to receive a trickle charge from a carrying vehicle (not shown) for charging the battery pack during transit of the load handling vehicle 200 on the carrying vehicle. The lifting mechanism comprises an upright mast 311, which may be a simplex or a multi-stage mast, mounted on a carriage 313 that is slidably moveable forwards and backwards on the chassis 300. The chassis is a U-shaped chassis with a pair of side bars 315, 317 bridged by a rear cross bar 319.

The four-way load handling vehicle is operable in a forwards/backwards mode of operation and a sideways mode of operation as outlined above. A wheel motor controller for controlling the wheel motors is provided. There are provided at least one of a wheel position sensor on one or more of the steered wheels, in communication with the wheel motor controller, and a steering wheel position sensor in communication with the wheel motor controller. In this way, the wheel motor controller knows the angle of turn of the load carrying vehicle and can dictate the relative speeds of the wheel motors powering the wheels. Other sensors may be provided including a throttle sensor. Data from the throttle sensor may be fed to the wheel motor controller for aiding in the subsequent control of the speed of the wheel motors.

-12 -In this specification the terms "comprise, comprises, comprised and comprising" and the terms "include, includes, included and including" are deemed interchangeable and should be afforded the widest possible interpretation.

The invention is not solely limited to the embodiment hereinbefore described but may be varied in both construction and detail within the scope of the appended claims.

Claims

-13 -Claims: (1) A battery-powered four-way load handling vehicle comprising: a chassis having a pair of front wheels and a rear wheel located behind and intermediate the pair of front wheels, the rear wheel powered by a rear wheel motor and at least one of the front wheels powered by a front wheel motor, a wheel motor controller for controlling one or more of the wheel motors, and in which there is provided a driver's station, a battery pack for powering the wheel motors, and a lifting mechanism mounted on the chassis; the four-way load handling vehicle is operable in a forwards/backwards mode of operation and a sideways mode of operation, in which: during the forwards/backwards mode of operation, the front wheels and the rear wheel are oriented substantially parallel to the longitudinal axis of the load handling vehicle when in a neutral steering angle position, and the load handling vehicle is steered by the rear wheel; and during a sideways mode of operation, the front wheels and the rear wheel are oriented substantially perpendicular to the longitudinal axis of the load handling vehicle when in a neutral steering angle position, and the load handling vehicle is steered by at least one of the front wheels; characterized in that when the four-way load handling vehicle is operated in a sideways mode of operation, when the front steering wheel is turned so that the rear wheel is on the inside of the turn, the wheel motor controller is operated to slow the rear wheel gradually with increasing degree of turn until the front steering wheel reaches a critical angle at which the rear wheel is stopped, and placed into a freewheeling mode, so that on further turning of the front steering wheel, the driven rear wheel is free to rotate in reverse.(2) A battery-powered four-way load handling vehicle as claimed in claim 1 in which when the four-way load handling vehicle is operated in a forwards/backwards mode of operation, when the rear steering wheel is turned, the wheel motor -14 -(3) (4) (5) (6) (7) controller is operated to slow the driven front wheel on the inside of the turn gradually with increasing degree of turn until the rear steering wheel reaches a critical angle at which the front wheel is stopped and placed into a freewheeling mode, so that on further turning of the rear steering wheel, the driven front wheel on the inside of the turn is free to rotate in reverse.A battery-powered four-way load handling vehicle as claimed in claim 1 in which when the four-way load handling vehicle is operated in a forwards/backwards mode of operation, when the rear steering wheel is turned, the wheel motor controller is operated to slow the driven front wheel on the inside of the turn gradually with increasing degree of turn until the rear steering wheel reaches a critical angle at which the front wheel is stopped and placed into reverse, so that on further turn of the rear steering wheel, the driven front wheel on the inside of the turn is driven in reverse.A battery-powered four-way load handling vehicle as claimed in claim 3 in which when the driven front wheel on the inside of the turn is driven in reverse, it is driven at a speed proportional to the degree of turn beyond the critical angle.A battery-powered four-way load handling vehicle as claimed in any preceding claim in which the freewheeling mode comprises a towing mode.A battery-powered four-way load handling vehicle as claimed in any preceding claim in which both of the front wheels are each provided with a front wheel motor and both of the front wheels are driven.A battery-powered four-way load handling vehicle as claimed in any preceding claim in which the chassis comprises a U-shaped chassis having a pair of forwardly projecting side bars connected by a rear bridging member, and in which one of the pair of front wheels is located at the forwardmost end of one of the side bars, the other of the pair of front wheels is located at the forwardmost end of the other of the side bars, and the rear wheel is located centrally on the rear bridging member.-15 - (8) A battery-powered four-way load handling vehicle as claimed in claim 7 in which the lifting mechanism is mounted on the chassis intermediate the side bars.(9) A battery-powered four-way load handling vehicle as claimed in claim 8 in which the lifting mechanism is mounted on a carriage that is moveable forwards and backwards on the chassis intermediate the side bars.(10) A battery-powered four-way load handling vehicle as claimed in any preceding claim in which there are provided a plurality of wheel position sensors in communication with the wheel motor controller.(11) A battery-powered four-way load handling vehicle as claimed in any preceding claim in which there is provided a steering wheel position sensor in communication with the wheel motor controller.(12) A battery-powered four-way load handling vehicle as claimed in any preceding claim in which the battery pack is configured to receive a trickle charge from a carrying vehicle for charging the battery pack during transit of the load handling vehicle on the carrying vehicle.