GB2564633A

GB2564633A - Improvements in or relating to a mobility vehicle

Info

Publication number: GB2564633A
Application number: GB1707510.2A
Authority: GB
Inventors: Sterry Hawley Ross John
Original assignee: Igan Ltd
Current assignee: Igan Ltd
Priority date: 2017-05-10
Filing date: 2017-05-10
Publication date: 2019-01-23
Anticipated expiration: 2037-05-10
Also published as: GB2564633B; GB201707510D0

Abstract

A mobility vehicle 20 has a seat 22 with a variable orientation with respect to a chassis 32. Adjustment of the angle of the seat 22 in at least one axis, for example compensating for pitch or roll of the vehicle 20, is enacted by a control system that operates a variable position support system, which in turn forms part of a pivotable mounting 24 that fixes one end of a mast 31 to the frame 32. The other end of the column 31 is attached to the seat 22. The control system includes a sensor 33 which determines an angle of the chassis to a reference, and adjusts the mast 31 in response to this angle. At least some of the control system is housed in the chassis 32. The vehicle 20 moves using ground contact means such as a pair of tracks or three or more wheels.

Description

Improvements In or Relating to a Mobility Vehicle

Field of the Invention [001] The invention relates to mobility vehicles. In particular the present invention relates to a system that is operable to enable speed control of a mobility vehicle and to support an occupant of such a mobility vehicle with consideration to terrain.

Background to the Invention [002] Mobility vehicles, mobility assistance vehicles, mobility scooters or - in the simplest sense possible - powered wheelchairs are terms that refer to a vehicle adapted for use by an individual having a disability, infirmity, injury or illness whereby the vehicle enables or, at the very least greatly assists the person to move on their own. In the eighteenth century, with the advent of the industrial revolution, wheel chairs were initially produced for assistance with the taking of the infirm to the waters of that town to bathe in the baths. Incidentally, the chair - an example of which is shown in Figure 1 gained in popularity and by the 1830's had replaced the sedan chair as a conventional means of transport - for those with money. Whilst in the nineteenth century, wheelchairs were typically constructed of wood and wicker designs, by the twentieth century steel-tubed wheelchairs became commonplace and were fitted with a pair of large wheels that were fitted at the rear with a pair of small and typically castor mounted wheels at the front. Bicycle technology was borrowed to provide pneumatic tyres to provide a minimal amount of comfort when pushed by a nurse or carer although a rim outside of the wheel was developed to enable self-propulsion for those with sufficiently strong arms. However, it was not until after the second world war that powered wheelchairs were developed to become commercially viable, and mobility vehicles developed therefrom, having a larger wheelbase and track to support a battery sufficient for a duration of an hour or more; the vehicle also became larger as the advantage of a platform to support baggage such as groceries and other goods was generally beneficial.

[003] Whilst the push-wheelchair is typically very compact, with a wheelbase of 30 - 50cm not being too different from the track, the type of vehicle being the subject of the present invention, a mobility vehicle, will however be powered and have a short wheelbase and a narrow track, not too dissimilar to the wheelchair. With a centre of mass - when laden - being approximately 0.7 m above the ground, the stability of the vehicle can be an issue of concern. It is also to be noted that a user of such a vehicle generally speaking is not in the best of health and in the event of a stability incident, would not be able to jump clear, meaning that the issue of stability of the vehicle needs to be taken into account at all times during use. Equally it must be made clear that the present invention is not concerned with larger vehicles such as cars which have been adapted for use by people having disabilities, where handling issues - such as stability correspond to the handling of a base car that has been adapted to permit access for the person having a disability, injury or illness and are not, ordinarily, an issue of concern as such. Further, it is essential - in the event of a loss of power and/or a loss of control - that the mobility vehicle can reduce speed and come to a standstill safely at all times, without any specific intervention from the user or items that are susceptible to failure, such as electrical controls - unless such controls are fail-safe.

[004] Many wheelchair stability assessment methods involve positioning a wheelchair and occupant on an inclined platform whereby to determine an angle at which the wheelchair tips over. Typically, in the United Kingdom, this angle is 12° for attendant pushed wheelchairs, and 16° for occupant propelled or electric powered wheelchairs. As will be appreciated, as an occupant of a mobility vehicle traverses an incline, the occupant is likely to be subject to a degree of stress and worry.

[005] As is known to all vehicle designers, to prevent any tipping of any vehicle, a projection of the centre of gravity must lie within the footprint of the vehicle, as defined by the points of engagement of the vehicle with a ground support surface by way of wheels, tracks or otherwise. Mobility vehicles are typically electrically powered and motive power electrical cells are ordinarily placed as low as possible. However, the weight distribution of the occupant can have a significant effect; for example an occupant with one or more above femoral amputations will raise a centre of mass of the mobility vehicle and a suggestion that the occupant could sit lower is likely to reduce the occupant's visibility and the visibility of others with respect to the occupant whereby to cause further problems. Notwithstanding this, any mobility vehicle must have a satisfactory braking system which, in addition to normal operation, must be effective in the event of a total loss of power and of any control functions.

[006] R.U2510347 provides an automatic brake for wheelchairs adapted for motion over stairways, where the brake system comprises levers with thrust rollers at their free ends. The levers are pivoted ahead of wheels and change from an upper idle position to a lower operational position whereby to permit the wheelchair to roll over steps or other surfaces ahead of wheels and to allow dropping down by gravity and holding up above the following step. Other types of mobility vehicles are collapsible to obviate the issue of certain slopes, flights of steps and stairways, as exemplified by GB2473833 (Evac & Chair Int.I Ltd.), which provides a wheelchair comprising a collapsible main frame and a system is provided to assist in movement over stairs attached to the rear of the frame.

[007] US8851213 (Bradley) provides a motorized wheelchair equipped with a safety system for bringing the wheelchair to a stop if a wheelchair user should experience an emergency situation which renders the user unable to safely control the wheelchair while in use. The safety system utilizes at least one switch mounted to an upright backrest for sensing whether or not the user's back is in contact with the backrest. If the user's back is in contact with the backrest, the wheelchair is operative and may be controlled in a normal manner. If the user's back moves out of contact with the backrest, whether voluntarily or because of an emergency situation, the safety system operates to disable operation of motors which operably propel drive wheels of the wheel chair, thus causing the wheel chair to be inoperative and bringing the wheel chair to a stop if in motion. Whilst in principle this provides a safe system for limited circumstances, the systems does not take into account passage over undulating territory, where the back may move out of contact with the backrest causing inconvenience to the user at the very least. Moreover, the present invention seeks to provide a mobility vehicle that will comfortably exceed the 16° slope capability for mobility vehicles, whereby to provide comfortable, stress-free transportation despite any particular type of adverse terrain and the traversal of inclines both in the direction of a climb or descent, such as 40° in pitch and up to 10° in roll but also transverse with respect the direction of a slope.

Object of the Invention [008] The present invention therefore seeks to provide a solution that addresses the issues of the prior art. The present invention seeks to provide a mobility vehicle that provides an automatic correction for undulations and slopes of a surface upon which the mobility vehicle is seeking to traverse. In particular, the present invention seeks to provide a system for a mobility vehicle whereby, in addition to pitch control, roll control of the vehicle is provided whereby traversal of slopes, steps and stairs not previously considered passable can be safely traversed by a mobility vehicle in accordance with the present invention, whilst maintaining a composure/orientation/comfort of the user at all times. The present invention also seeks to provide an improved mobility vehicle and to provide an improved usability of the vehicle as such.

Statement of Invention

In accordance with a first aspect of the invention, there is provided a mobility vehicle comprising a seat, a chassis, ground contact means, and control system; wherein the seat is supported by a mast with respect to the chassis, operable to support a user of the mobility vehicle, the mast being attached to the seat at a first end and being attached to the chassis by means of a pivotable mounting including a variable position support system, operable to permit the mast to move with respect to the chassis about an arc in at least one axis; wherein the chassis is supported by the ground contact means for movement with respect to a ground support surface, the chassis having a longitudinal axis and housing the control system; wherein the ground contact means contact the ground support surface by way of points of contact, which points of ground contact define a footprint of the vehicle; wherein the mast is supported by a variable position support system, operable to permit the mast to move with respect to the chassis about an arc in at least one axis; wherein the control system includes sensors operable to determine an angle of the chassis and an angle of the seat to a reference angle; and, wherein the variable position support system is operable to adjust the mast in correspondence with the reference angle.

Thus the mobility vehicle is provided with at least one means to maintain a seat squab at the same level, conveniently permitting the seat base to be maintained in a nominal horizontal position, despite undulations of terrain and differences in slope. Notwithstanding this, the mast / seat assembly can be variable in height not only to cater for differences in stature, but also to assist in comfort, when uphill terrain is encountered. The pivotable mounting is preferably arranged such that it is operable to permit the mast to move with respect to the chassis to compensate for at least one of pitch and roll of the mobility vehicle as it moves across terrain, nevertheless, whilst the system can be arranged such that it permits the mast to move with respect to the chassis to compensate for roll of the mobility vehicle, it is preferred that the system is arranged such that it permits the mast to move with respect to the chassis to compensate for pitch and roll of the mobility vehicle as it moves across terrain. Preferably the reference angle is horizontal.

Conveniently, the ground contact means comprises a pair of continuous tracks, although the ground contact means comprises a set of wheels. The mobility vehicle may be a wheelchair having four wheels, and for example a wheelchair having a pair of front wheels of relatively large diameter and a pair of rear wheels of relatively small diameter. However, the mobility vehicle may have a different number of wheels such as six or eight. Equally, the principle of operation of the present invention means that it is also applicable to three wheeled mobility vehicles.

Conveniently one or more drive motors operable to cause the mobility vehicle are provided whereby to move and are preferably provided with a speed control operable as a function of the determined angle of the chassis to the reference angle. Conveniently a brake system operable to enable the mobility vehicle to control speed and/or turn is controlled as a function of the determined angle of the chassis to the reference angle. Furthermore, the control system is preferably operable to limit the amount of initial braking force that can be applied upon an application of the brake as a function of the determined angle of the chassis to the reference angle.

The brakes can be provided by drum brakes, discs brakes, band brakes or other types of braking system. It is preferred that directional brakes such a band brakes are employed since the use of such - which increases the amount of braking effect in one sense and allows hill starts to be simply accomplished.

Preferably the mobility vehicle is provided with bodywork. Operator controls for the mobility vehicle are conveniently provided by way of joystick system - which joystick controls are provided by one of a seat armrest control, a chassis mounted joystick or by a wireless remote handset.

A mobility vehicle in accordance with the present invention is conveniently electrically powered but for safety reasons any braking system must be effective in the event of total loss of power and of any control functions. The usual means of doing this would be by using spring-energised braking which is released, in normal operation, by an electrical solenoid system.

Brief Description of the Figures

For a better understanding of the present invention, reference will now be made, by way of example only, to the Figures as shown in the accompanying drawing sheets, wherein :Figure la is a perspective view of an eighteenth century wheelchair;

Figure lb shows a prior art wheelchair being manoeuvred down a set of steps;

Figure lc shows a prior art wheelchair changing an angle of the seat, ready for a descent;

Figure Id shows a prior art standing wheelchair;

Figure 2 is a side view of a first embodiment mobility vehicle in accordance with the invention;

Figures 3a is a perspective view of a seat support in accordance with a first aspect of the invention;

Figure 3b is a perspective view of a seat support in accordance with a second aspect of the invention; and,

Figure 4 is a perspective view of a seat support in accordance with a third aspect of the invention.

Detailed description of the Preferred Embodiments

There will now be described, by way of example only, the best mode contemplated by the inventor for carrying out the present invention. In the following description, numerous specific details are set out in order to provide a complete understanding to the present invention. It will be apparent to those skilled in the art, that the present invention may be put into practice with variations of the specific.

Inventors have studied the issues surrounding mobility vehicle usage and their stability, in particular in relation to the tackling of pathway undulations, the presence of steps and, in particular, the use of a mobility vehicle when proceeding - with respect to a direction of travel - up and down a steep slope or at an obtuse angle with respect a slope. Inventors have determined that roll correction is required when the user is traversing across a slope e.g. up to a 10° slope and also when tackling wide steps at a small angle to the fall line, parallel with the angle of the slope. There have been numerous accidents when conditions have proved to be insurmountable, allowing the user to become unseated with unfortunate consequences. Whilst the prior art, as discussed above, teaches of some systems that compensate for pitch correction, none are particularly helpful, given that an angle of the seat will move to a degree but the centre of mass is not moved to any great degree, limiting any benefit. Moreover, the prior art is silent with regard to the matter of roll correction.

With reference to Figure 2, there is shown a first embodiment of the invention. The mobility vehicle 20 comprises a tracked vehicle, which is supported upon a ground surface by way of by a set of tracks 27 arranged in a parallel spaced apart fashion, which in turn supports a chassis (not detailed)upon which a body 21 is mounted. A seat 22 is mounted either upon the chassis or the body and the seat is provided with controls such as a finger-joystick (not detailed) similar to a computer games controller as are widely available and conveniently associated with an armrest 23 although such controls could also be provided upon a control stick as upstanding from one of the chassis or the body 21. Given that an occupant of the mobility vehicle will tend to be one with limited physical mobility and may have difficulties in manoeuvring and sitting down, the control could also comprise a separate unit, akin to a computer games controller, using, for example, automobile keyless technology for access control. The mobility vehicle is provided with a seat 22 that is mounted to provide compensation for pitch and/or roll and the seat is mounted such that it pivots about a point 24 at least with respect to pitch at a point distal to the seat cushion 25. To enable secure orientation, a triangulation variable length support system 26 is provided.

The tracks 27 - or wheels in an alternative embodiment - of the mobility vehicle are arranged in a parallel spaced apart fashion whereby to provide, for a given width of mobility vehicle an appropriate degree of stability. The mobility vehicle is conveniently powered by an electric motor 28, given the benefits of the associated battery packs ordinarily being easily charged at home and other places using mains electricity. Whilst it is not advantageous to have a significant mass associated with a mobility vehicle, given that electrical storage cells sufficient to provide a decent range will weigh between 10 - 20 Kilograms, it is beneficial to mount the electrical motor and electrical storage cells at a low point within the platform (chassis). The use of internal combustion engines is of little value given that mobility vehicles are frequently employed indoors and enclosed areas, such as shopping malls etc.. Whilst it is possible to configure a liquid petroleum gas engine, this has not been performed and in any event carbon monoxide emissions can be an issue if the motor is not set up properly.

The power train has been arranged such that the electrical motor 28 drives a continuous track, also commonly referred to as a tank tread or caterpillar track. Such a system of vehicle propulsion depends upon a continuous band of tread that is conveniently driven by a rear drive-wheel 29. This band is typically made of synthetic rubber reinforced with steel wires as is frequently employed in robotic vehicles and also in the case of lighter agricultural or construction vehicles. The motor can conveniently drive the rear wheel by an in-hub motor or a direct gear coupling, for example, as will be known to the skilled man.

Mobility vehicles are frequently provided with caterpillar tracks since they can mount pavement kerbstones and the like relatively easily since they can be arranged to present a surface to obstacles whereby they climb the obstacles, this sort of configuration requiring a front caterpillar pulley wheel 31 to be set above and before the first ground running pulley wheel, whereby to present a front climbing feature by the track 27. In contrast a wheeled device would not be able to mount a kerbstone if the height of the kerbstone approached one half of the diameter of the wheel - noting that if a pneumatic tyre were to be employed, then the axis of the wheel will be below half height, taking into account compression of the tyre in use. For completeness, however, it ought to be mentioned that sets of three wheels (or more) can be carried about a rotatable assembly, but these systems suffer from being overly large and does not provide smooth operation for a user. Additionally, it is well known that the large surface area of the continuous tracks distributes the weight of the vehicle better than three or four wheels as might be provided by alternative types of steel or rubber tyres on an equivalent mobility vehicle, enabling a continuous tracked vehicle to traverse carpets and soft ground with a reduced likelihood of making a mark or damaging an internal flooring - or becoming stuck due to sinking when the mobility vehicle is not on a prepared path. Notwithstanding this, the present invention is neither dependent upon a mobility vehicle's method of propulsion nor upon how such a mobility vehicle makes contact with a ground surface.

Referring to Figure 3a, there is shown a first seat - mobility vehicle arrangement, wherein seat 22 is supported by means of a support mast 31 which connects with an underside of the seat cushion on the one hand and with the mobility vehicle platform or chassis 32 that supports the body 21 of the mobility vehicle on the other hand. The support mast locates via a pivot 24 which enables angular movement of pitch P of the seat with respect to the mobility vehicle platform 32. At least one of the seat and the mast are also supported by variable length support means 34 to enable the mast to be moved whereby the seat remains operationally horizontal within a pre-determined range of pitch angle, P°. Given that in this embodiment only pitch is taken into account, i.e. the pivot base enables a single axis movement, the axis being perpendicular to a front-rear axis of the mobility vehicle, then in addition to the mast 31, only a single variable length support 34 is required. By placement of the pivot axis 24 as low as is possible - effectively the ground clearance (which could be variable by virtue of variable height dampers, for example) plus the space required for mounting the pivot. The space required for mounting the pivot can be of the order of 2cm, dependent upon the thickness of the base of the vehicle and the fact that the pivot will be a main weight bearing part of the vehicle and will need to be sufficiently strong. Applicants have demonstrated functionality with the pivot axis being closer to a top surface of the body of the mobility vehicle, - effectively 30cm from the ground - but the advantages of the invention are reduced.

Associated with the seat or mast 31, there is provided an orientation sensor 33 (a tilt sensor), receptive to deviations from the a reference angle, operable to provide signals proportional to a degree of pitch, which signals can be employed to control the operational length OL of the variable length support 34 - and thus, the angle of pitch of the mast with respect to the chassis 32. The variable length support can be configured in a number of fashions. For example, the support could comprise a hydraulic fluid pump which drives a hydraulic ram which is associated with or comprises the variable length support; the support could comprise a linear actuator driven by an electric motor; a screw-thread system or similar, but it will be appreciated that certain actuators may not provide a required speed of response when a mobility vehicle is used to traverse undulating terrain. It will be appreciated that an orientation sensor could be attached to the chassis; the particular placement is not of great concern - it can be placed to provide a balanced weight distribution and needs to be capable of ensuring that the mast 31 is oriented to ensure that that the seat is oriented in a nominal horizontal plane, noting that a preferred orientation of the seat may actually slope forwardly, backwardly or otherwise to accommodate a particular disability of a user of the mobility vehicle. Conveniently, the seat unit also comprises a foot plate arrangement 35, whereby to prevent any orientation/condition of the foot/leg of the user of the mobility vehicle causing a fouling with respect to a desired movement of the mast/seat assembly with respect to the chassis 32 or body 21 of the vehicle.

Referring to Figure 3b, there is shown a second seat - mobility vehicle arrangement, wherein - as with the first embodiment - seat 22 is supported by means of a support mast 31 which connects with an underside of the seat cushion on the one hand and with the mobility vehicle platform or chassis 32. In contrast to the first embodiment, however, pivot 24 provides movement with respect to a longitudinal axis of the vehicle, whereby to compensate for angular movement of roll of the seat with respect to the mobility vehicle platform 32. Again, in correspondence with the first example, at least one of the seat and the mast are also supported by variable length support means 34 to enable the mast to be moved whereby the seat remains operationally horizontal within a predetermined range of roll. Given that in this embodiment only roll is taken into account, i.e. the pivot base enables a single axis movement, the axis being parallel with a longitudinal axis of the mobility vehicle, then in addition to the mast 31, only a single variable length support 34 is required, which single io variable length support could be alternatively configured as would be apparent to the skilled man. In common with the tilt sensor as discussed above, there is provided a tilt sensor 33, operable to provide signals proportional to a degree of roll, which signals can be employed to control the operational length of the variable length support 34.

Referring now to Figure 4, there is shown a further embodiment of mobility vehicle. In this case, the seat 22 is supported by means of a support mast 31 via a multi-axis pivot 24 which enables angular movement of pitch and roll of the seat with respect to the mobility vehicle platform 32. The pivot 24 is effectively a universal joint allowing movement in two axes (pitch and roll) but fixed with respect to the third axis (yaw). Given that the movement is not limited to only one arc, at least one of the seat and the mast must also be supported by two support members 34; conveniently the support members are each variable in length (or mounted upon moveable fastenings), whereby to enable the mast to be simply fastened with respect to the seat and not require any alternative hinge or swivel mechanism to enable the attitude of the seat to remain effectively constant in use. That is to say a further support is required to provide triangulation support, to cater for the two degrees of freedom.

It will be appreciated that whilst the seat is described as being supported by a mast and is shown as being a generally columnar body and positioned centrally, it will be appreciated that it need not be so oriented. For example, it could be considered generally, as an inverted L and be mounted to one side of the chassis. In a further alternative, it has been disclosed, in relation to a pitchonly system that the mast has a single axis of movement, with the axis of pitch generally being in correspondence with a general fore-aft axis of the mobility vehicle. To provide a second degree of movement, the base of the seat squab could be provided with a tilt mechanism, whereby only attachments of the seat with respect to the chassis are necessary, simplifying the mechanical support system to a degree. It will be appreciated that by having a mast, the forces arising from the seat can act with respect to the pivot 24, whereby to reduce the effective centre of mass - the centre of mass is the mean position of the mass in an object; the centre of gravity, which is the point where gravity appears to act. For many objects, these two points are in exactly the same place. It will also be appreciated, that having the drive components relating to the variable length supports placed as low as is possible in the chassis, the centre of the mass is lowered, which assists vis-a-vis the overall stability of the mobility vehicle.

The orientation of a user upon a seat is, however, not the only feature of the present invention that is of significance. Given that the orientation of the user seat can be determined, then the system will be aware of a change in the position of the centre of mass of the vehicle and will be able to take the weight and centre of mass into account with regard to the maximum angle of slope that can be accomplished by the user (leaving a sensible margin for error, given that the exact height of the centre of mass will never be known, given that it can arise from the physique of the user (short legs, heavy torso; long legs; small torso; weight arising from clothing - including, for example, a helmet - and any goods that may be carried by the user or arranged about the seat. It will also be pertinent to note that whilst it will not be recommended that bags etc. are draped about the mobility vehicle, such bags etc. could interfere with any corrective motion applied as determined by the inclination sensors. In the event that the slope was of a particular level, then the mobility vehicle's electronics could determine that it would not be safe to progress up or down such a slope and cease operation of the drive motors. In the alternative, the mobility vehicle's electronics could determine that a certain reduced maximum speed may be permitted.

Additionally, given the orientation of the user seat and weight - conveniently determined by way of a weight sensor associated with the seat base - weighting or bias can be applied to the left and right brakes of the mobility vehicle, not just in terms of maximum braking force to be applied, but also in terms of how rapidly the brakes are applied. Drum and disc brakes are well known from automobiles and no specific detail of such will be given in relation to these types of brakes, given that the brakes employed are band brakes, wherein the brakes are in the form of band that applies a friction force with respect to a radial surface, the surface being at a reduced radius relative to the rear drive wheels at the rear of the mobility vehicle. A proprietary friction material (e.g. FTL 156 from Friction Technology) is conveniently used on the inner face of these bands, which bands are typically manufactured from a stainless steel. Because the method of operation is directional, there are two bands operating on each wheel, one clockwise and the other anticlockwise. By using the maximum possible arc (e.g. 310°) the required braking effect can be produced by a modest tension at the tail end of the band. Typically, a 100 N force on the tail end gives a braking force of 600 N if the direction of rotation tightens the band. If the opposite rotation applies with the direction of rotation slackening the band, the braking force is an order of magnitude lower; this can be a benefit. Directional band braking systems are preferred for mobility vehicles since they provide security for hill starts; a band brake in operation, for example in an upwardly hill facing orientation, will prevent movement downwards, but will not prevent or interfere with a movement up the hill. Such band braking systems are analogous to a ratchet system in that they are effective in preventing rotation in a first direction, but effectively do not prevent rotation in the other direction.

Calculations have been made which anticipate that the braking force needed on level ground to give a retardation force equivalent to one eighth of the force of gravity (12.5% G - 1.23 ms’²) is 208 N, which would be a value that can easily be tolerated by the user and from a maximum speed of 1.5 ms ¹ (3.3 mph) this would give a stopping distance of 0.9 m, and a stopping time of 1.2 sec. If the mobility vehicle were to be on a 40 degree slope, crawl mode would apply and the braking force needed is 1070 N; if such a force were to be applied on level ground then the retardation would be 64 % G and it would generally be considered to be dangerous: an elderly or disabled user and vehicle would come to grief in no uncertain manner.

To address such scenarios, the braking force must be tailored to suit the slope, without using any electrical control.

Conveniently, the present invention is programmed so as to ensure that the seat maintained in a nominal horizontal position - that is to say that the base seat squab is maintained at the same orientation despite any sloping nature of the terrain over which the mobility vehicle moves. The term nominal horizontal is employed given that all users will not necessarily desire the seat to be horizontal, noting that the angle of the mast relates to an angle subtended from the base of the seat to the pivot on the chassis rather than, necessarily, being the angle of a mast member. Indeed, by reason of, for example, a limited availability of space for functional items, the mast may not itself be necessarily orthogonally oriented with respect to the chassis / flat ground support surface or indeed comprise an elongate member. Specifically, the present invention can be programmed such that upon reaching a limit of angular movement to maintain the seat horizontal, the mobility vehicle may prevent further forward (or rearward) movement whereby to provide a degree of safety, to ensure that the mobility vehicle with passenger does not approach a position of instability. Typically, in such circumstances, at least one of: the data relating to the weight of the person, the height of the mast, the angle between the mast and the chassis can be used to apply the necessary braking force to the tail end of the appropriate brake band, as shall be discussed below.

Conveniently, the drive system is provided by two drive motors; each drive motor working with respect to the wheels or caterpillar track of one side. As discussed above, by the use of a brake band braking system, each drive wheel is also provided with two brake bands, one for forward motion and the other for reverse, each brake band having a tail end tensioned by a spring, which tension can be released by a solenoid actuator, whereby to make the system fail-safe. In one embodiment, a movement of the mast relative to the chassis can be transferred by Bowden cables to the springs whereby to cause increased tension in the bands, which would occur automatically, in use, however, such tension could also be controlled electronically, although this would not be effective in a loss of power/loss of control situation.

In operation of the mobility vehicle, the system can be arranged such that upon reaching a particular angle of rising or falling slope, it will adjust its speed of movement - for example to a crawl speed or to a range of reduced speeds relative to a range of angles of slope - which speeds may be different as to whether the movement is forward or rearward.

The following description covers the movement of a mobility vehicle as it travels in an uphill fashion, but similar principles will be employed to provide a similar effect when going downhill, noting that due to, for example, the weight distribution, the system may need to operate at a different speed in different direction for the same slope, although the same physical principles relating to speed, weight distribution etcetera shall apply.

As the chassis tilts to meet the rising slope, the mast is controlled by the variable length support arms such that the seat remains horizontally disposed and the uphill braking Bowden cables are tensioned and so apply a proportional force, via a spring, to the tail end of the uphill braking band. This causes only a small braking effect in forward motion because the band is being slackened, but in reverse motion (backing down the slope) the band would tend to tighten and therefore would provide the necessary braking force.

If the mobility vehicle were to come to a stop on the slope, then a brake solenoid would be de-activated and the mobility vehicle would be held in position by the uphill braking bands. In the event that forward motion was to be resumed, then the motors and the solenoids would be energised, the band would be slackened so that any braking effect would be negligible. Notwithstanding the comment above, in the unlikely event that motion downhill were to be desired following a stop, then the motors would need to be energised such that they overcome the uphill braking force before the mobility vehicle would be caused to move.

It will be appreciated that in the calculation of braking forces, not only must the speed and angular degree and orientation of the terrain be known, but the values of a number of operating variables associated with the mobility vehicle and its components and user must be known whereby to permit safe control . These values can therefore take into account at least some of the following; the weight of the person be determined - or otherwise a permitted maximum value would be employed as a default: height of the mast/seat, the weight of the vehicle, together with the effective wheelbase and track of the vehicle; operational characteristics of the vehicle, namely: Suspension spring data including: free length; extended length; max load; initial status I Rate I Initial tension) together with anticipated loads acting on main and auxiliary springs; Vehicle braking characteristics such as tension factors for uphill and downhill brake bands; the radius of brake band surface; the radius of track, with account taken of factors such as, inter alia: the degree of movement in cables; uphill & downhill tail end loads; uphill & downhill fixed end loads; net load of brake band and net load of band at track. Other factors also need to be taken into account; the electric drive motors could operate with a free-wheel mechanism - otherwise inertial forces when not active would need to be taken onto account.

By the use one set of simple, off-the-shelf solenoids, it has been shown that, once connected and pulsed using 36 V supply, a force of 45N can readily be produced, which is sufficient to overcome the spring tensions in both the uphill and downhill cables at a slope of less than 12° (equivalent to a 1 in 4 slope). In normal use, this allows the brakes to be released by way of energising of a solenoid (i.e. fail safe) on slopes of less than 12 °. For reasons of safety, movement of the mobility vehicle is restricted to a crawl mode on any slope of more than 8° (equivalent to a 1 in 7 slope); for similar reasons the controls have been arranged such that reverse movement of the mobility vehicle will always be in crawl mode.

It will be appreciated that the single pivot element could be replaced by an elongate hinge if only pitch or roll were to be taken into consideration. It will also be conceivable that a single axis pivot could address the issue of pitch, for example, and that the seat be mounted about a hinge axis to stabilize a user with regard to roll - and vice versa. It will be appreciated that by having a pivot being operable with respect to pitch and roll, and at the lowest possible height above the ground, the best solution for maintenance of a centre-of mass within a footprint of a vehicle is provided.

Claims

1 A mobility vehicle comprising a seat, a chassis, ground contact means, and control system;

Wherein the seat is supported by a mast with respect to the chassis, operable to support a user of the mobility vehicle, the mast being attached to the seat at a first end and being attached to the chassis by means of a pivotable mounting including a variable position support system, operable to permit the mast to move with respect to the chassis about an arc in at least one axis;

Wherein the chassis is supported by the ground contact means for movement with respect to a ground support surface, the chassis having a longitudinal axis and housing at least some of the control system;

wherein the ground contact means contact the ground support surface by way of points of contact, which points of ground contact define a footprint of the vehicle;

wherein the mast is supported by a variable position support system, operable to permit the mast to move with respect to the chassis about an arc in at least one axis;

wherein the control system includes a sensor operable to determine an angle of the chassis to a reference; and, wherein the variable position support system is operable to adjust the mast in correspondence with the reference angle.

2 A mobility vehicle according to claim 1, wherein the ground contact means comprises a pair of continuous tracks.

3 A mobility vehicle according to claim 1, wherein the ground contact means comprises three or more wheels.

4 A mobility vehicle according to any one of claims 1-3, wherein the pivotable mounting is operable to permit the mast to move with respect to the chassis to compensate for pitch of the mobility vehicle.

5 A mobility vehicle according to any one of claims 1-3, wherein the pivotable mounting is operable to permit the mast to move with respect to the chassis to compensate for roll of the mobility vehicle.

6 A mobility vehicle according to any one of claims 1-3, wherein the pivotable mounting is operable to permit the mast to move with respect to the chassis to compensate for pitch and roll of the mobility vehicle.

7 A mobility vehicle according to any one of claims 1-6, wherein the reference plane is horizontal.

8 A mobility vehicle according to any one of claims 1-7, wherein the pivotable mounting is operable to permit the mast to enable the seat to be maintained in a nominal horizontal position.

9 A mobility vehicle according to any one of claims 1-8, wherein the seat is supported by a variable height mast.

10 A mobility vehicle according to any one of claims 1-9, wherein a drive motor operable to cause the mobility vehicle to move has a speed control as a function of at least one of: the determined angle of the chassis to the reference angle; the angle of the seat to the chassis; the weight of the user; and, the height of the seat.

11 A mobility vehicle according to any one of claims 1 - 10, wherein a brake system operable to enable the mobility vehicle to control speed and/or turn is limited as a function of at least one of: the determined angle of the chassis to the reference angle; the angle of the seat to the chassis; the weight of the user; and, the height of the seat.

12 A mobility vehicle according to any one of claims 1 - 11, wherein the control system is operable to limit the amount of initial braking force that can be applied upon an application of the brake as a function of at least one of: the determined angle of the chassis to the reference angle; the angle of the seat to the chassis; the weight of the user; and, the height of the seat.

13 A mobility vehicle according to any one of claims 1 - 12, wherein the chassis further comprises bodywork.

14 A mobility vehicle according to any one of claims 1 - 13, wherein there is further provided operator controls by way of joystick system.

15 A mobility vehicle according to claim 14, wherein the joystick controls are provided by one of a seat armrest control, a chassis mounted joystick or by a

5 wireless remote handset.

16 A mobility vehicle according to any one of claims 1 - 15, wherein the seat is supported by one or more variable length support members, which variable support member operable to receive signals from the control with regard to the orientation sensor, which signals can be employed to control the operational io length OL of variable length supports whereby the angle of pitch and/ or roll of the seat post with respect to the chassis can be controlled.

17 A mobility vehicle according to claim 16, wherein the variable length support is provided by one of: a hydraulic support member, which operably receives hydraulic fluid from a pump under the control of the controller, a linear

15 actuator driven by an electric motor, or, a screw-thread system.