Wheelchair driver

Abstract

The wheelchair driver 100 for a wheelchair has a drive wheel 110, drive unit 120 for generating drive torque at the drive wheel, and a mount for mounting the driver proximate a rear wheel 15 of the wh

Description

Technical Field The present invention relates to a wheelchair driver. Embodiments of the present invention relate to a wheelchair driver for generating assistance torque for aiding an individual in pushing, pulling or otherwise manoeuvring a wheelchair, while also permitting folding of the wheelchair with the wheelchair driver in situ for easy transportation and storage. Background Wheelchairs can be of a variety of different types. Some wheelchairs are unpowered, and can be propelled either by the occupant of the wheelchair while seated in the wheelchair, or by another individual pushing the wheelchair from behind. In order for a wheelchair to be manually propelled by the person sat in it (its occupant), large rear wheels are provided, often with an attached rim for handling by the user. However, in the case of a wheelchair intended only to be propelled manually by another person, small wheels are generally provided front and rear. In almost all cases, handles are provided at the upper rear of the wheelchair to enable the wheelchair to be propelled and manoeuvred by an individual other than the occupant. Similarly, wheelchairs which are electrically propelled generally have relatively small wheels front and rear, typically with the rear wheels being electrically driven. It is known to retrofit electric wheelchair drivers onto unpowered wheelchairs. A variety of such solutions exist, but they generally come with substantial disadvantages. For example, Roma and TGA provide power pack drivers in which a motor and a pair of drive wheels are connected to the wheelchair by a bar that lowers onto brackets fixed to the wheelchair frame. A hand control lever fitted to the handle of the wheelchair controls the speed. These systems are very heavy (14kg overall with battery), and also not easy for an elderly person to fit and remove from the wheelchair. Also, they must be removed if the wheelchair is to be folded. Two other chairs have also recently been introduced which do not use extra wheels for the power assist. The Ypush wheelchair uses motors on each of the existing wheelchair wheels. It is heavy, with a weight of approximately 22kg. The efoldi powerchair has both driving with hand control and also an attendant control but uses twin motors similar to a conventual powerchair. Embodiments of the present invention seek to provide a wheelchair driver in which the above disadvantages are avoided, or at least ameliorated. Summary of the Invention According to an aspect of the present invention, there is provided a wheelchair driver for a wheelchair, the driver comprising: a drive wheel; a drive unit, for generating drive torque at the drive wheel; a mount, for mounting the wheelchair driver proximate a rear wheel of the wheelchair, at a position laterally offset from a halfway point between the rear wheels of the wheelchair. In use, the wheelchair driver is mounted to the wheelchair at one side only (laterally offset from the centre of the wheelchair). That is, the wheelchair driver is mounted closer to one side of the wheelchair, than to the other side of the wheelchair. In particular, the wheelchair driver is preferably mounted to the inside of the frame, in the area between the rear wheels of the wheelchair. As a result of the off-centre positioning of the wheelchair driver, the wheelchair may be folded while the wheelchair driver remains attached. Preferably, the wheelchair drive is mounted to a frame of the wheelchair in the vicinity of the rear wheel. The mount may comprise a mounting bracket, the drive unit being mounted to the mounting bracket and the mounting bracket being mounted to an inside of the frame of the wheelchair. The bracket may comprise a first side (arm) and a second side (arm), the bracket being mounted to the frame of the wheelchair at its first side, the drive unit and drive wheel being mounted between the first side and the second side. The drive unit may comprise an electric motor (for example a wheel hub motor, incorporated into the hub of a wheel, as typically used for electric scooters), powered by a battery. Preferably, the battery is disposed separately from the drive unit (for example mounted separately to the wheelchair, or retained in a pocket or compartment of the wheelchair) and connected to the drive unit via an electric cable. The battery may be a small, lightweight lithium battery, since this is adequate to power a hb motor, and can be retained in the pocket on the rear of the wheelchair even when the wheelchair is folded. Alternatively, the battery may be disconnected from the drive unit to be charged or transported separately. Preferably a controller is provided, for receiving a control input from a user to control the drive unit. The controller may be located at the drive unit, at the battery, or elsewhere. A user input device, such as a switch, lever or dial, is also preferably provided, mountable to the wheelchair separately from drive unit, and manipulable by the user to generate the control input. The controller and user input device may together allow a user to adjust the speed of the drive unit, for example with the user input device taking the form of a thumb (or finger) control mounted to a handle of the wheelchair. The controller may also permit switching between forwards and backwards rotation, enabling the wheelchair driver to assist both with pushing the wheelchair forwards, and pulling it backwards. Preferably, in order to minimise the width of the wheelchair driver, no more than one wheel is provided. Providing only a single drive wheel also minimises the weight of the wheelchair driver, and allows the controller to be less complicated to cope with turning. In particular, with two wheels it is generally necessary to have a transaxle or have a typical powerchair type set up / controller, whereas this is not required with one wheel. According to another aspect of the invention, there is provided a wheelchair comprising the wheelchair driver as per the above. Preferably, the wheelchair is foldable with the wheelchair driver mounted thereto. Preferably, wherein when the wheelchair is in an open state, no part of the wheelchair driver extends to the half-way point between the rear wheels. Generally, a maximum amount of torque deliverable by the wheelchair driver is insufficient to propel the wheelchair when occupied. In other words, the wheelchair driver is intended to provide assistance to an individual propelling the (occupied) wheelchair, not to propel the wheelchair without human propulsion. Accordingly, unlike prior wheelchair drivers, the present invention is not required to propel the wheelchair in the absence of a user pushing the wheelchair, but is instead merely intended to provide assistance torque. In other words, the wheelchair driver reduces the amount of effort required for a user to push the wheelchair. As a result of the continued involvement of an individual in pushing the wheelchair, it has been found that providing the drive wheel at a position offset from centre is acceptable. It will be appreciated that in a fully electrically driven solution that a single offset drive wheel would be unable to drive the wheelchair forwards, or backwards, in a straight line. Also, with a fully electrically driven solution an offset drive wheel makes turning difficult in one direction. The wheelchair can be folded with the wheelchair driver in situ due to the fact that (a) only a single drive wheel is provided, reducing the width required, and / or (b) the drive wheel is mounted at an offset position from the centre of the wheelchair -generally mounted to the frame of the wheelchair in the vicinity of one (and not both) of the rear wheels. For most wheelchairs, the clearance between the rear wheels in a folded state is sufficient to accommodate the width of the wheelchair driver, and since the wheelchair driver is attached directly to the (interior of the) wheelchair frame at only one side, no horizontal bar is required between the rear wheels of the wheelchair, such bar conventionally preventing folding of the wheelchair until it is removed. In addition, because the wheelchair driver is positioned away from the centre of the wheelchair, it represents less of a trip hazard for an individual pushing the wheelchair. In practical terms, the drive motor may be of the same type as use for an ebike or electric scooter. The system in some embodiments only adds approximately 3kg to the overall weight of the wheelchair. To summarise, existing designs of wheelchair drivers either provide a separate drive unit which is heavy, unwieldy and prevents folding, or directly drive the main wheelchair wheels. In contrast, embodiments of the present invention, with a single separate drive unit / wheel mounted to the frame at one side between the rear wheels of the wheelchair, represent a significant (and advantageous) advance over these. In particular, embodiments of the present invention are smaller, lighter, less likely to interfere with the pusher walking, and permits folding of the wheelchair without removing the drive unit. The provision of a single, offset, wheel would be expected to result in an uneven drive assist function, but surprisingly it has been found that this is not the case. Brief Description of the Drawings Embodiments of the present invention will now be described by way of example only with reference to the accompanying drawings where like parts are provided with corresponding reference numerals and in which: Figure 1 schematically illustrates a 3D view of a wheelchair, in an open configuration, with a wheelchair driver attached; Figure 2 schematically illustrates the wheelchair and wheelchair driver of Figure 1, from a rear view; Figure 3 schematically illustrates a 3D view of the wheelchair, in a closed configuration, with the wheelchair driver still attached; Figure 4 schematically illustrates the wheelchair and wheelchair driver of Figure 3, from a rear view; Figure 5 is a schematic exploded diagram illustrating attachment of the wheelchair drives to the wheelchair; Figure 6 is a further schematic exploded diagram illustrating attachment of the wheelchair driver to the wheelchair, with the wheel cut away to improve clarity; and Figure 7 schematically illustrates the wheelchair driver in side view. Detailed Description Referring to Figures 1 and 2, a wheelchair 1 is shown in an open (not folded) condition. When in the open condition, the wheelchair 1 can be sat in (occupied) by one individual, and pushed, pulled or otherwise manoeuvred while occupied, by another, different, individual. The wheelchair 1 has a seat portion 2, a back portion 3, a frame 4 comprising left and right lower horizontal members 5, 6 respectively, left and right rear upright (vertical) members 7, 8 respectively, left and right armrests 9, 10 respectively, left and right handles 11,12 respectively, left and right front wheels 13 (the front right wheel is obscured in Figures 1 and 2), and left and right rear wheels 14, 15 respectively. In use, an individual seated in the wheelchair 1 sits on the seat portion 2, rests their back against the back portion 3, and may rest their arms on the left and right armrests 9, 10. With this type of wheelchair, the occupant plays no role in propelling the wheelchair. A wheelchair drive assembly 100 is attached to the inside of the frame 4 of the wheelchair 1, in particular to the right lower horizontal member 6 and the right rear upright (vertical) member 8. That is, the drive assembly 100 is in the present implementation mounted proximate the right-hand rear wheel 15 of the wheelchair 1. However, the drive assembly 100 could equivalently be mounted proximate the lefthand rear wheel 14 of the wheelchair 1. In either case, the drive assembly 100 is located off-centre of the front-rear axis of the wheelchair 1 (that is, closer to one rear wheel than the other rear wheel). Generally, when the wheelchair 1 is in the open state shown in Figures 1 and 2, no part of the drive assembly 100 extends to / across the half-way point between the rear wheels. As a result of this off-centre positioning, and as a result of the relatively narrow width of the drive assembly 100 (which uses a single wheel and a hub motor), and as will be shown subsequently, the wheelchair 1 can be folded with the drive assembly 100 in situ (that is, attached to the wheelchair 1). The wheelchair 1 is otherwise unpowered. In particular, none of the wheels of the wheelchair 1 are powered (except indirectly via the drive assembly 100), and the wheelchair 1 is generally of the type which is pushed by one individual while another individual sits in the wheelchair 1. In particular, the wheelchair cannot be driven electrically by an individual sat in the wheelchair, since the wheels are not electrically driven / powered. Further, the wheelchair 1 cannot be moved manually by the individual seated in it, since it is not equipped with large rear wheels having a handling rim. In most cases, a maximum amount of torque deliverable by the drive assembly 100 is insufficient to propel the wheelchair 1 when occupied. In some implementations, the drive assembly 100 may be able to provide sufficient torque to move the wheelchair unaided, but even in this case it would not be able to control turning, since only one wheel is provided, and so does not provide equivalent capability to a conventional electrically propelled wheelchair. The drive assembly 100 comprises a wheel 110, a hub motor 120 integrated into the hub of the wheel 110, an axle 130 extending through the centre of the wheel 110 (and the hub motor 120), onto which the hub motor 120 is mounted, and a mounting bracket 140, which is mounted to the frame of the wheelchair 1. The axle 130 is mounted so as not to rotate with respect to the wheelchair 1, and the hub motor 120 rotates around the axle 130 to drive rotation of the wheel 110 to provide the required assistance torque. The axle 130 is a threaded rod axle (threaded at each end), fixedly mounted to the bracket using nuts 148. As can be seen more clearly in Figures 5 and 6, the mounting bracket 140 comprises a side plate 142 which in the present implementation is mounted to the horizontal member 6, and to the vertical members in the vicinity of the rear wheel 15. More specifically, the side plate 142 is mounted to or at the axle attachment point of the rear wheel 15. The side plate 142 comprises a perpendicular member 143 (at right angles to the side plate 142, and disposed horizontally) having a plurality of fixing holes. A U-shaped bracket 144 comprises a top part 144a and two legs 144b, 144c. The top part 144a comprises a plurality of fixing holes with a configuration matching the fixing holes of the perpendicular member 143. The U-shaped bracket 144 mounts underneath and to the perpendicular member 143 using the respective pluralities of fixing holes. In particular, fixings such as nuts and bolts may be used to secure the perpendicular member 143 and bracket 144 together via the fixing holes. Each of the legs 144b, 144c of the U-shaped bracket extends generally vertically, and comprises a slot, or cut-out, for receiving the axle 130 at a bottom portion thereof. The side plate 142 comprises a further plurality of fixing holes to permit its attachment to the horizontal member 6. Specifically, clamping part 150 mounts at both sides to the side plate 142, and clamps over the horizontal member 6 to trap it between the side plate 142 and the clamping part 150. The clamping part 150 comprises first and second fixing parts, to either side of the horizontal member 6, each provided with fixing holes for alignment with the further plurality of fixing holes on the side plate 142. Fixings such as nuts and bolts may be used to secure the side plate 142 and clamping part 150 together via the fixing holes. Having two separated mounting points (that is, to the horizontal member 6 and the vertical member 8) at which the bracket is fixed to the frame of the wheelchair prevents, or at least minimises, the wheelchair driver twisting upwards when the drive wheel comes into contact with the ground under load. It will be appreciated that the above structure for mounting the drive assembly 100 to the wheelchair 1 is specific to a particular form, or class, of wheelchair, and that for different wheelchairs a different mounting structure may be used. Also visible in Figure 1 is a control unit / power adapter 160 mounted higher up the wheelchair 1, in this case to or near the right vertical member 8 (it may be attached instead to the back portion 3 of the wheelchair), and a thumb control 170 mounted on the right hand handle 12 of the wheelchair 1. The control unit / power adapter 160 connects to a power supply (battery) 190 and draws power from it to power the hub motor 120, which in turn generates the assistance torque. The thumb control 170, which in a simple case may comprise a first switch for turning the assistance torque on and off, and a second switch for selecting a direction for the assistance torque (forwards or reverse), is electrically connected to the control unit 160, and selects whether and how electrical power is to be provided to the hub motor 120. The thumb control could instead be provided as a dial, which can be rotated from a first setting (off) to a second setting (on, forwards assistance torque) to a third setting (on, reverse assistance torque). Alternatively, different amounts of torque assistance could be set by the thumb control 170, and controlled via the control unit 160. For example, in each direction (or possibly just in the forwards direction) multiple levels of assistance torque could be provided, for example 50% and 100% (2 levels) or any other number of levels. This could be achieved by providing the thumb control 170 as a throttle lever or similar. The thumb control 170 is generally electrically connected (by wires) to the control unit 160, but in some implementations may instead by wirelessly connected, and powered with its own battery. Referring to Figures 3 and 4, the wheelchair 1 is shown in a folded state, useful for storage and transportation of the wheelchair. As can be seen from these figures, there is sufficient space between the rear wheels 14, 15 and the rear vertical members 7, 8 for the drive assembly 100 to remain in place while the wheelchair 1 is folded. Typically, the clearance between the left and right sides of a wheelchair frame when folded is between 100mm and 150mm (shown as dimension Z in Figure 4), and a single-wheeled drive assembly as per the current implementation, including its mounting structure, is able to fit within this clearance / gap, as can be seen from Figures 3 and 4. As can be seen from Figure 7, the wheel of the drive assembly 100 is preferably of smaller diameter than the rear wheel of the wheelchair 1. This helps keep the weight of the unit low. The wheel of the drive assembly 100 is in the present implementation set slightly forwards (towards the front of the wheelchair 1) of the rear wheels of the wheelchair 1. This helps to keep it out of the way of the feet of the individual pushing the wheelchair 1. This is different from many prior designs which utilised handle extensions. The extent to which the wheel is set forwards is constrained by the requirement that it and / or its mounting bracket should not conflict with the cross frame of the wheelchair 1. Preferably, the drive assembly 100 is mounted so that the bottom-most part of its wheel is slightly lower (preferably by approximately 5mm) than the rear wheels of the wheelchair 1. This is so that the drive assembly wheel remains engaged with the ground substantially at all times, and achieves good traction. The power supply (battery pack) 190, control unit / power adapter 160 and the thumb control 170 are provided physically separately from each other, and from the drive assembly 100. In particular, the battery 190 is housed in an additional pouch / pocket fixed to the rear 3 of the wheelchair 1. The wheelchair 1 can be folded with the battery 190 in place, although the battery pack is preferably also easy to remove for charging or lifting the wheelchair. The lithium battery intended weighs approximately 1.8kg. The drive assembly 100 includes the drive unit (motor, preferably hub motor), wheel and mount. The drive assembly 100, power supply 190, control unit 160 and thumb control 170 together define the wheelchair driver. The hub motor may be either direct drive (gearless) or indirect drive (geared). If a direct drive hub motor is used, the axle 130 is the axle of the motor itself, with the copper windings of the motor being fixed to the axle 130. If a geared hub motor is used, a planetary gear reduction system is provided between the motor and the axle 130. As a result, the motor can operate at higher, more efficient speeds. While direct drive hub motors are generally more powerful, they are also typically larger and heavier. Since size and weight are a greater consideration than available torque for the present application (since the wheelchair driver does not need to propel the wheelchair itself, merely generate assistance torque for aiding an individual in pushing or pulling the wheelchair), direct drive hub motors are less well suited for the present application. Preferably then, the hub motor is not direct drive, which also (in addition to the above advantages) enables the drive wheel to rotate freely when assistance torque is not being provided - this enables the wheelchair to be pushed freely, similarly to an e-bike. This is not possible with a direct drive hub motor. It will be appreciated that, while in the present implementation the user selects the amount (and direction) of assistance torque provided by the wheelchair driver (using the thumb throttle control), in alternative implementations the wheelchair driver may automatically determine how much, and what direction of, assistance torque to provide, based for example on a direction in which the wheelchair is being pushed or pulled, a speed at which the wheelchair is being pushed or pulled, a gradient on which the wheelchair is being manoeuvred, and whether the wheelchair is being pushed or pulled in a straight line, or turned. While the wheelchair driver may be provided separately from a wheelchair, and retrofitted to existing wheelchairs, it is also possible to provide a wheelchair which includes the wheelchair driver as a factory installed feature. In this case, embodiments of the invention may be considered to take the form of a wheelchair having a plurality of unpowered wheels, including left and right rear unpowered wheels, and a further powered wheel disposed at an off-centre position between the rear wheels of the wheelchair.

Claims

09 03 261. A wheelchair driver for a wheelchair, the driver comprising:a drive wheel;a drive unit, for generating drive torque at the drive wheel; anda mounting bracket, for mounting the wheelchair driver proximate a rear wheel of the wheelchair, at a position laterally offset from a halfway point between the rear wheels of the wheelchair, wherein the wheelchair driver is mountable to the wheelchair at one side only, wherein the wheelchair driver is mountable to a frame of the wheelchair in the vicinity of the rear wheel, wherein the drive unit is mountable to the mounting bracket and the mounting bracket is mountable to an inside of the frame of the wheelchair, wherein the mounting bracket comprises a first side and a second side, the mounting bracket being mountable to the frame of the wheelchair at its first side, the drive unit and drive wheel being mountable between the first side and the second side.

2. A wheelchair driver according to any preceding claim, wherein the drive unit comprises an electric motor, powered by a battery, and wherein the battery is disposed separately from the drive unit and connected thereto via an electric cable.

3. A wheelchair driver according to any preceding claim, comprising a controller, for receiving a control input from a user to control the drive unit.

4. A wheelchair driver according to any preceding claim, comprising a user input device, mountable to the wheelchair separately from drive unit, manipulable by the user to generate the control input.

5. A wheelchair driver according to any preceding claim, comprising no more than one drive wheel.

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