Patent Description:
Conveyances in the form of wheelchairs are known for conveying persons with limited mobility. A traditional wheelchair is a well-known arrangement and includes two larger rear wheels which the occupant can turn with their hands and two smaller front wheels which are able to swivel. It is also well known that traditional wheelchairs are unsuitable for ascending or descending staircases.

It has become common practice when designing a building or public space to provide access ramps alongside or in place of staircases to enable access by wheelchair users. Nonetheless, there remain scenarios where a person using a traditional wheelchair will be faced with a staircase or other obstacle that they cannot negotiate including for instance a staircase in a building with no elevator, a doorstep or a kerb.

It has been tried to provide alternative types of conveyances to enable persons with limited mobility to negotiate staircases. Previous attempts include conveyances which utilise a track based drive system. One or more tracks are provided with outer teeth. The tracks are driven, and the teeth press on the corners of steps to lift the conveyance up the stairs, or control descent down the stairs. However, such systems can cause significant damage to the corners of the stairs.

It has also been tried to provide conveyances with wheel clusters which include multiple wheels uniformly distributed in the same plane around a common centre. The cluster is driven to rotate to ascend or descend the staircase. However, a wheel cluster alone lacks stability when travelling on stairs. It needs an appendage to prevent tipping. Also, wheel cluster systems are optimally suited to stairs within a particular geometric range and are prone to damaging stairs outside that range.

<CIT> discloses a stair travel vehicle a left and right pair of first and second axes; first and second arms; and a pair of first motors for rotating respective first arms around the first axes. A pair of second motors rotates the second arms around the second axes.

There remains a need to provide improved conveyances for surmounting obstacles.

The present invention provides a conveyance for surmounting obstacles as set forth in claim <NUM>.

The forwardly disposed portion and the rearwardly disposed portion of at least one of the ground engaging arrangements may be spaced apart from one another by being mounted at opposite ends of a beam.

The first and second ground engaging arrangements may be joined to a rotating linkage which effects the alternating movement of the ground engaging arrangements.

The rotating linkage may include at least one epicyclic gear set.

The rotating linkage may include at least one epicyclic gearset which is associated with a chassis of the conveyance and another epicyclic gearset which is associated with at least one of the ground engaging arrangements.

The attitude of the ground engaging arrangements may be adjustable.

At least some of the wheels may be steerable wheels.

The conveyance may further include a seat to convey a person.

The conveyance may further include a pair of manually propelled wheels.

The manually propelled wheels may be removable.

The conveyance may be controllable to adopt a range of different operating heights.

The conveyance may be controllable to adopt a range of differently sized footprints.

The conveyance may be adjustable to tilt to compensate for travel on sloping ground.

The conveyance may be substantially symmetrical about a centre line parallel to the direction of travel of the conveyance.

Referring to <FIG>, a conveyance for surmounting obstacles is shown in the form of motorised wheelchair <NUM>. Wheelchair <NUM> includes a first ground engaging arrangement in the form of outer bogies <NUM>, <NUM> and a second ground engaging arrangement in the form of inner bogie <NUM>. The first and second ground engaging arrangements are operable to move in an alternating sequence of movements to enable the conveyance to surmount obstacles such as stairs as will be later described.

Wheelchair <NUM> further includes a seat <NUM> and a user control panel <NUM>. The control panel includes a joystick and other controls to allow the wheelchair occupant to control the movements of the wheelchair. Seat <NUM> is mounted on a chassis by attaching to drive units <NUM>, <NUM>. Seat is attached to the chassis by way of an adjustable mechanism which allows the position seat <NUM> to be adjusted forwards or backwards with respect to the chassis to enable control over the centre of gravity of the combination of the wheelchair and the occupant.

As best seen in <FIG>, outer bogie <NUM> includes a forwardly disposed portion in the form of a steerable driven wheel <NUM> and a rearwardly disposed portion in the form of passive wheel <NUM>. Wheels <NUM>, <NUM> are spaced apart from one another by being mounted at opposite ends of a curved beam <NUM>. The curvature of the beam <NUM> defines an obstacle accommodating region below the beam located between the wheels <NUM>, <NUM> which accommodates a portion of an obstacle being surmounted, such as a stair, as will become apparent.

Similarly, inner bogie <NUM> includes a forwardly disposed portion in the form of a pair of passive wheels <NUM> and a rearwardly disposed portion in the form of a pair of steerable driven wheels <NUM>. Wheels <NUM>, <NUM> are spaced apart from one another by being mounted on cross members attached at opposite ends of curved beam <NUM>. The curvature of the beam <NUM> defines an obstacle accommodating region below the beam located between the wheels <NUM>, <NUM> which accommodates a portion of an obstacle being surmounted.

Referring now to <FIG>, beam <NUM> is mounted to a carrier arm of drive unit <NUM> by way of epicyclic gearset <NUM>. Similarly, beam <NUM> is mounted to a carrier arm of drive unit <NUM> by way of epicyclic gearset <NUM>. Drive units <NUM>, <NUM> both contain double pinion epicyclic gearsets. Each of the epicyclic gearsets is associated with two clutches to control operation of the gearsets as will be described. Suitable clutches include electromagnetic type clutches for robotic use as may be obtained from manufacturer Ogura Industrial Corp (www. ogura-clutch.

Referring now to <FIG> and <FIG>, drive unit <NUM> includes a motor A and a motor B. Each motor includes an internal worm drive reduction gearbox which drives an output gear <NUM>. The output gear <NUM> of motor B is visible in <FIG>. Each output gear drives an associated main gear <NUM> which is free to rotate on the central axle of the double pinion epicyclic gearset. The axle of the double pinion epicyclic gearset is provided with teeth to form a sun gear <NUM>. Ring gear <NUM> is affixed to the inside of the case of drive unit <NUM>. Planets <NUM>, 47a are mounted on a carrier which is selectively engageable with the main gear <NUM> by way of a clutch. Arm <NUM> is integrally formed with the sun gear <NUM>. Arm <NUM> also carries a bogie gear <NUM> which is rotatably mounted to arm <NUM> and which meshes with main gear <NUM>.

Due to the double pinion nature of the gearset, the ring gear <NUM> and sun gear <NUM> rotate in opposite directions. Also, the double-pinion gearset is configured so that the ring gear <NUM> and the sun gear <NUM> rotate equally in opposite directions. That is to say, a reduction ratio of one to minus one. The gears of the double-pinion epicyclic gearset are configured as follows:.

Referring now to <FIG>, the bogie gear <NUM> is integrally formed with the axle of epicyclic gearset <NUM> which is provided with teeth to form sun gear <NUM> of epicyclic gearset <NUM>. Ring gear <NUM> is affixed to beam <NUM>. Planets <NUM> are mounted on a carrier. The carrier can be rotationally fixed with respect to beam <NUM> by way of clutch a. This allows the wheelchair to be statically balanced on a bogie when it is engaged with the ground. The carrier can be rotationally fixed with respect to arm <NUM> by way of clutch b. This allows for adjustment of the pitch of a bogie, at a suitable output torque. The epicyclic gearset is dimensioned to provide an effective reduction ratio of two to one between the ring gear <NUM> and the sun gear <NUM>. The ratio aims to halve the rotational speed, to double the output torque. The gears of the epicyclic gearset <NUM> are configured as follows:.

The epicyclic gearset <NUM> associated with beam <NUM> is of similar construction to epicyclic gearset <NUM>. It is controlled by operation of clutches k and m. Drive unit <NUM> is of identical construction to drive unit <NUM>. It includes motors C and D and clutches i and j. Beam <NUM> of the central bogie is associated with two epicyclic gearsets which are of similar construction to the epicyclic gearsets <NUM>, <NUM>. They are associated with operation of clutches e, f, g, and h. The epicyclic gearsets associated with beam <NUM> may be omitted.

Wheelchair <NUM> includes a lidar system which detects the presence, shape and location of obstacles in use and is used to control the movements of the wheelchair. Wheelchair <NUM> further includes an onboard power supply in the form of a rechargeable battery for operating the electronic and electrical components of the wheelchair. The electronic components include a computer based control system which is programmed to conduct sequences of movements of the wheelchair in response to user inputs. The electrical components include motors, clutches and steering devices.

Referring now to <FIG>, height and footprint adjustment of the wheel chair will be described. At <FIG>, wheelchair <NUM> is shown in its default mid height configuration with default size footprint (the footprint being the area of the region defined by the ground contacting wheels). This configuration is used for normal travel along footpaths. To adjust the height and footprint of the wheelchair clutches b, e, h and k are engaged and all other clutches are disengaged. The motors B, D are operated together to turn in one direction and the motors A, C are operated together to turn in the opposite direction. This causes the mechanism to scissor upwards or downwards, depending upon the direction of rotation of the pairs of motors. Worm drives within the motors prevent slippage.

The scissor movement allows the wheelchair to move from the configuration shown in <FIG> to a high height configuration with a smaller footprint shown in <FIG>. This configuration is good for bars or retail counters and for negotiating narrow spaces such as turning a corner in a narrow corridor. Alternatively, the wheelchair can move to a low height configuration with a larger footprint as shown in <FIG>. This configuration is good for use with standard height desks. It is also the position that the wheelchair adopts at the commencement of a stair climbing operation.

Referring to <FIG>, wheelchair <NUM> is shown in a sequence of steps which are used to carry out a stair climbing operation. The occupant of the wheelchair is not shown for ease of illustration. At step <NUM> the wheelchair <NUM> has arrived near the top of a staircase and the wheelchair occupant wishes to descend the stairs. The wheelchair occupant selects the relevant operation from the user control panel. This causes the onboard control system to conduct a sequence of movements.

The wheelchair firstly moves to the low configuration of <FIG>. The wheelchair then moves forwards until the lidar system indicates that the front wheels <NUM> are a predetermined distance away from the edge of the top stair as shown at step <NUM>.

The outer bogies <NUM>, <NUM> are then raised slightly off the ground. This is achieved by engaging clutches b, d, f, g, i and k and driving motors A and C. With the outer bogies off the ground, the attitude of the bogies can be adjusted by adjusting their pitch by driving motors B and D. Depending upon the direction of drive of motors B, D the pitch of the outer bogeys can be adjusted in either a clockwise or anti-clockwise direction. With the outer bogies lifted off the ground, the powered wheels <NUM> of the inner bogey are driven to move the wheelchair forwards until the lidar system indicates that the wheels <NUM> of the inner bogey are a predetermined distance away from the edge of the top stair as shown at step <NUM>.

The outer bogies <NUM>, <NUM> are then lowered by driving motors A, C, and their pitch adjusted by driving motors B, D until it is detected that wheels <NUM> have come into contact with the second stair and wheels <NUM> have come into contact with the top stair as shown at step <NUM>. The top stair is accommodated within the region beneath the beam <NUM> and between the wheels <NUM>, <NUM> of the outer bogies.

At all times when the outer bogies <NUM>, <NUM> are lifted clear of the ground the wheelchair is statically balanced by the inner bogie <NUM>. The centre of gravity of the combination of the wheelchair and occupant lies within the boundaries of the footprint defined by the pairs of wheels <NUM>, <NUM> of the inner bogie.

The purpose of engaging clutches d and i during the lifting sequence, is to operate the double pinion epicyclic gearsets, which turn the drive units <NUM> and <NUM> in reverse to the rotation of the arm. This "neutralises" the rotation, keeping the drive units and the passenger seat level.

The clutches are now actuated in preparation for lifting the inner bogie <NUM>. Clutches a, c, e, h, j and m are engaged, and the remaining clutches are released. Motors B, D now control the raising or lowering of the inner bogie <NUM> whilst motors A, C control the pitch of the inner bogie <NUM>. The inner bogie <NUM> is lifted and the driven wheels <NUM> of the outer bogies are driven forwards until the lidar system indicates that wheels <NUM> are a predetermined distance away from the edge of the second stair.

Continued rotation of motors B, D causes the inner bogie <NUM> to "step over" the outer bogies <NUM>, <NUM> and to lower the inner bogie <NUM> so that wheels <NUM> come into contact with the third stair, and wheels <NUM> come into contact with the top stair as shown at step <NUM>. The top stair and the second stair are accommodated within the region beneath the beam <NUM> and between the wheels <NUM>, <NUM> of the inner bogie.

Again, at all times when the inner bogie <NUM> is lifted clear of the ground the wheelchair is statically balanced by the outer bogies <NUM>, <NUM>. The centre of gravity of the combination of the wheelchair and occupant lies within the boundaries of the footprint defined by the pairs of wheels <NUM>, <NUM> of the outer bogies.

Again, the double pinion epicyclic gearsets, turn the drive units <NUM> and <NUM> in reverse to the arms' rotation, to keep the drive units and the passenger seat level.

The wheelchair now continues a repeated sequence of movements in which the bogies operate alternately stepping one over the other to descend the staircase. As part of each stepping operation, the bogie that is in contact with the ground drives forward to the edge of the stair that it is resting upon. During steps <NUM> to <NUM> adjustments to the pitch of the bogies are made as the wheelchair progressively steps onto flat ground.

At step <NUM> the wheelchair has finished descending the stairs and is on flat ground in the lowered configuration of <FIG>. The wheelchair is then raised to the normal height configuration of <FIG> and the occupant can continue to travel on the flat ground in a usual manner.

During the stair descending operation the forward and rearward movement of the seat is controlled to move the occupant forwards or backwards to influence the location of the centre of gravity of the combination of the wheelchair and the occupant.

The operation of climbing a staircase is the reverse of the descent operation. The wheelchair occupant controls the wheelchair to bring the wheelchair up to the base of a staircase so that the back of the seat faces the stairs. The stair climbing operation can then be initiated and the wheelchair climbs the stairs backwards, with the occupant facing outwards.

Referring to <FIG>, wheelchair <NUM> is shown in a sequence of movements surmounting an obstacle in the form of a hob barrier. The movements made are similar as for the stair climbing operation. The lidar system detects the shape and location of the hob barrier and the bogies are controlled in sequence to step over the obstacle.

Referring to <FIG>, wheelchair <NUM> is shown in a sequence of configurations to illustrate a tilt adjust function when travelling on sloping ground. With clutches a, b, e, f, g, h, k, m engaged and clutches c, d, i, j released then if all of motors A, B, C D are operated in the same direction this has the effect of adjusting the tilt of the seat of the wheelchair with respect to the wheels. The seat is tilted forwards or backwards depending upon the direction in which the motors are driven. This mode of adjustment compensates for travel on sloping ground and allows for the occupant of the wheelchair to remain sitting upright when travelling either uphill or downhill.

Referring to <FIG>, optionally, a pair of larger hand operable wheels <NUM> may be attached to the wheelchair to convert the wheelchair to a hybrid manual wheelchair. The wheelchair is first moved to the high configuration shown in <FIG>. Wheels <NUM> may then be attached to the outer bogies <NUM>, <NUM>. Wheelchair <NUM> is then lowered so that wheels <NUM> come into contact with the ground. The manually operable wheels allow the occupant to propel the wheelchair by hand to conserve battery life.

Referring to <FIG>, an alternative wheelchair <NUM> is shown. It differs in that the seat is pivotally mounted to the chassis. The user can swivel the seat to enable them to face sideways whilst ascending or descending a staircase or surmounting other types of obstacles.

Although the invention has been described with reference to a wheelchair, the invention has application in other types of conveyance. For instance, the conveyance could be designed to carry loads, rather than an occupant. The conveyance could be autonomously controlled to deliver goods or other items or to carry items around. The conveyance could be used in exploration over rough terrain. The conveyance could be used for mounting other equipment such as a robotic arm. The conveyance could, in a miniature form, be a toy.

A double pinion epicyclic gearset was associated with the chassis of the conveyance and a single pinion epicyclic gearset was associated with at least one of the ground engaging arrangements. A single pinion epicyclic gearset may be associated with the chassis of the conveyance. An idler gear may be provided between the main gear and the bogey gear.

It can be seen that the invention have at least one of the following advantages:.

Claim 1:
A conveyance (<NUM>) for surmounting obstacles including
a first ground engaging arrangement (<NUM>, <NUM>); and
a second ground engaging arrangement (<NUM>);
each ground engaging arrangement (<NUM>, <NUM>; <NUM>) includes a forwardly disposed portion (<NUM>) and a rearwardly disposed portion (<NUM>) which are spaced apart from one another;
each ground engaging arrangement (<NUM>, <NUM>; <NUM>) further includes an obstacle accommodating region (<NUM>, <NUM>) located between the forwardly disposed portion (<NUM>) and the rearwardly disposed portion (<NUM>) which can accommodate a portion of an
obstacle being surmounted in use;
characterised in that
the first and second ground engaging arrangements (<NUM>, <NUM>; <NUM>) are operable to move in an alternating sequence of movements to enable the conveyance (<NUM>) to surmount obstacles; and
the ground engaging arrangements (<NUM>, <NUM>; <NUM>) include wheels (<NUM>, <NUM>) at least some of the wheels are driven wheels (<NUM>);
the wheels of each ground engaging arrangement (<NUM>, <NUM>, <NUM>) define a footprint when in contact with the ground; and
at all times when one of the ground engaging arrangement (<NUM>, <NUM>; <NUM>) is lifted clear of the ground the centre of gravity of the conveyance (<NUM>) lies within the boundaries of the footprint defined by the other ground engaging arrangement (<NUM>, <NUM>; <NUM>) so that the conveyance (<NUM>) is statically balanced alternately by one then the other of the ground engaging arrangements (<NUM>, <NUM>; <NUM>) throughout the sequence of movements.