A stair climbing conveyance

Abstract

Stair climbing conveyances are described including: first and second bogies; each bogie includes a first pair of spaced apart wheels at one end of the bogie and a second pair of spaced apart wheels at the other end of the bogie, the wheels defining a ground contacting footprint; at least one of the pairs of wheels of each bogie are driven wheels; the conveyance further includes first and second crank arms located at either side of the conveyance; the first and second bogies are mounted to the respective first and second crank arms at pivotable joints; when in use in a stair climbing operation, as the crank arms rotate, the conveyance is supported and balanced alternately by the first and second bogies as it ascends or descends a flight of stairs.

Description

[0001] A STAIR CLIMBING CONVEYANCE

[0002] Technical Field

[0003] The invention relates to stair climbing conveyances such as might be used by wheelchair users to allow them to successfully negotiate a flight of stairs.

[0004] Background to the Invention

[0005] 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.

[0006] To address the problem faced by wheelchair users of negotiating stairs various types of stair climbing conveyances have been devised. For example, the device described in KR10118862 has an arrangement of legs stowed beneath the passenger’s chair. The legs have joints akin to knees and ankles to enable the chair to “walk” up or down the stairs. However, this device is constrained in that the passenger must face in the direction of travel.

[0007] Stairclimbing conveyances with seats that face down the stair, have the following disadvantages:

[0008] - passengers look down the stair as they descend, which can be frightening.

[0009] - passengers face backwards as they ascend the stair. It can feel unnatural to travel backwards.

[0010] - passengers cannot see where they are going.

[0011] - if a passenger falls off the seat, they may fall down the stair.

[0012] One example of a stair climbing conveyance is disclosed in WO2019090385A1 which is attributed to the present applicant and the entire contents of this document are incorporated herein by reference. One version of that device made provision for the conveyance having a rotating seat which could be turned sideways at the time of travelling up or down a flight of stairs.

[0013] A stairclimbing conveyance with a seat facing sideways has the following advantages:

[0014] - a balustrade of the staircase is always in front of the passenger, so they feel secure.

[0015] - the balustrade can prevent a passenger from falling off the chair.

[0016] - there already exist fixed stair-climbers that travel on rails, with seats facing sideways so travelling on a stair facing sideways is familiar and commonly accepted.

[0017] However, the stair width in houses, small commercial premises and fire escape stairs is often narrow. The width is commonly one metre or less. The device described in W02019090385A1 is too wide to negotiate a stairway of this type with the seat facing sideways.

[0018] There remains a need for improved stair climbing conveyances.

[0019] Summary of the Invention

[0020] In a first aspect the present invention provides a stair climbing conveyance including first and second bogies; each bogie includes a first pair of spaced apart wheels at one end of the bogie and a second pair of spaced apart wheels at the other end of the bogie, the wheels defining a ground contacting footprint; at least one of the pairs of wheels of each bogie are driven wheels; the conveyance further includes first and second crank arms located at either side of the conveyance; the first and second bogies are mounted to the respective first and second crank arms at pivotable joints; when in use in a stair climbing operation, as the crank arms rotate, the conveyance is supported and balanced alternately by the first and second bogies as it ascends or descends a flight of stairs.

[0021] The pairs of wheels may be mounted at transverse beam portions of each bogie.

[0022] The transverse beam portions may house wheel motors for driving the wheels.

[0023] All of the wheels of each bogie may be driven wheels.

[0024] The wheel motors of each bogie may be configured to drive one of the pairs of wheels at a lower speed than the other pair of wheels.

[0025] The conveyance may operate in a mode in which it is supported on the ground by four wheels being one pair of wheels of the first bogie and one pair of wheels of the second bogie.

[0026] The operating height of the conveyance may be adjusted by varying the distance between the pairs of ground contacting wheels.

[0027] The crank arms may be mounted at either end of a common axle which extends across the width of the conveyance.

[0028] The common axle may be mounted inside a pair of first and second hollow drive axles, each drive axle being connected to and driven by a drive motor.

[0029] Each hollow drive axle may be connected to its respective drive motor via a reduction gearbox.

[0030] Each of the first and second drive axles may be coupled to the first and second bogies by a drive arrangement associated with each crank arm to enable the attitude of the bogie with respect to the crank arm about the pivotable joint to be controlled.

[0031] The conveyance may further include a centrally disposed planetary gear arrangement including: a sun gear which is mounted to the common axle; a set of planetary gears which are mounted in a carrier; and a ring gear. The conveyance may further include first and second clutches which are operable to engage or disengage the first and second hollow drive axles with the carrier.

[0032] The conveyance may further include a carrier locking arrangement to lock the carrier from rotating in relation to the ring gear.

[0033] Each drive motor may include a cylindrical aperture extending through the central axis of the motor and both of the common axle and a drive axle are located within the aperture of each motor.

[0034] The crank arms may be fixedly mounted at either end of a substantially cylindrical casing which extends across the width of the conveyance and the cylindrical casing rotates during a stair climbing operation.

[0035] The conveyance may further include a load carrying saddle which rotates with respect to the casing to keep the saddle level during a stair climbing operation.

[0036] The conveyance may further include a saddle brake that may lock the saddle with respect to the external casing.

[0037] The conveyance may further include a left motor and gear reducer, able to rotate the left bogie with respect to the left crank arm; a right motor and gear reducer, able to rotate the right bogie with respect to the right crank arm.

[0038] The conveyance may further include a middle motor and gear reducer able to level the saddle by counter-rotating the saddle when the external casing rotates with respect to the ground.

[0039] The conveyance may further include a disc brake inside each crank arm that may lock each bogie with its respective the crank arm.

[0040] The conveyance may further include a seat. The seat may be pivotable about a vertical axis to enable the seat to either face in the direction of movement or transversely to the direction of movement of the conveyance.

[0041] Brief Description of the Drawings

[0042] An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying diagrammatic drawings, in which:

[0043] Figure 1 is a side view of a wheelchair;

[0044] Figure 2 is an underside view of the wheelchair of figure 1;

[0045] Figure 3 is a perspective view of the wheelchair of figure 1;

[0046] Figure 4 is a cross sectional view of the wheelchair of figure 1;

[0047] Figure 5 is a cross sectional view through the central drive unit of the wheelchair of figure 1 ;

[0048] Figure 6 is a detailed view of the mid-portion of the drive unit of figure 5;

[0049] Figure 7 is a perspective view of the central drive unit of figure 5;

[0050] Figure 8 is an exploded view of the central drive unit of figure 7;

[0051] Figure 9 shows a clutch arrangement of the drive unit of figure 7;

[0052] Figure 10 is an exploded view of figure 9;

[0053] Figure 11 shows the wheelchair of figure 1 negotiating a flight of stairs;

[0054] Figures 12 to 15 illustrate a sequence of movements of the wheelchair of figure 11;

[0055] Figures 16 to 18 shows the wheelchair of figure 1 in use in various scenarios at various heights;

[0056] Figure 19 illustrates the chair of the wheelchair of figure 1 being levelled when travelling on a slope;

[0057] Figure 20 shows the wheelchair of figure 1 prepared for a reclining manoeuvre;

[0058] Figure 21 shows the wheelchair of figure 20 in a reclining manoeuvre;

[0059] Figure 22 is a cross-sectional view of a second embodiment of a conveyance;

[0060] Figure 23 is a perspective view of the central drive unit of the conveyance of figure 22;

[0061] Figure 24 is an exploded view of the central drive unit of figure 23;

[0062] Figure 25 is another exploded view of the central drive unit of figure 23; and

[0063] Figure 26 is a cross-sectional view through the central drive unit of figure 23.

[0064] Detailed Description of Preferred Embodiments

[0065] Embodiments of the invention are aimed at achieving a stair climbing ability with a compact stair-climbing mechanism. Embodiments have the following features:

[0066] 1) having only two bogies to stay balanced, one mounted at either side of the wheelchair;

[0067] 2) each bogie having two transverse beam regions for stiffness and stability;

[0068] 3) each bogie having a pivotal joint;

[0069] 4) a crank arm attached and able to be driven at each pivotal joint; 5) a compact central drive-unit for climbing motion and scissoring motion;

[0070] 6) drive-units for the wheels are contained within the bogie transverse beam regions;

[0071] 7) the above components coordinated to interleave without collision, during climbing, rolling and scissoring up and down.

[0072] Having one bogie mounted at each side of the mechanism, means load is transferred to the ground asymmetrically, as the mechanism balances on one bogie then the other, during climbing. The central drive-unit is stiff enough to act as a cantilevered transverse beam and able to transfer load across to one side of the mechanism and down through the bogie on that side. The bogie’s two transverse beams then transfer the load to the wheels and thence the ground.

[0073] By their coordination the following elements effect an interleaving motion of the bogies:

[0074] 1 Each bogie joint traces an arc about the other bogie joint, because each is the fulcrum point for lifting the other;

[0075] 2 Each transverse beam traces an arc about its own, local bogie joint;

[0076] 3 The resultant path through space of each transverse beam is the combination of the two arcs: about its local bogie joint and about the other bogie joint;

[0077] 4. The particular shape and size of the four transverse beams;

[0078] 5. The particular shape and size of the central drive unit;

[0079] 6 The attitude of the bogie in the air, which is controllable;

[0080] 7 The motion sequence for stair climbing and scissoring up and down.

[0081] The interleaving motion of the bogies is best seen in the cross-sectional diagrams in Figures 12 to 18. The interleaving motion allows the bogies’ paths through space to intersect, enabling a more compact arrangement than the conveyance disclosed in WO2019090385A1, which shows bogies with non-intersecting paths through space.

[0082] Two versions of the central drive unit are herewith presented:

[0083] A first version of the central drive-unit consists of two sets of motor, gearbox and clutch, placed either side of a central planetary gear. The central planetary gear keeps the payload level during climbing, using a similar principle to that shown in WO2019090385A1.

[0084] A second version of the central drive-unit consists of two sets of motor and gearbox, placed either side of a third motor and gearbox. The third motor keeps the payload level during climbing. An electronic gyroscope helps control the third motor.

[0085] The first version of the central drive-unit is in the description below. The second version is described later.

[0086] The first version of the central drive-unit is a novel donut-shaped arrangement. The donut shape allows a concentric double axle to pass through the middle.

[0087] The clutch engages and disengages using a screw-driven ring mounted rotatably within the cylindrical case.

[0088] The drive-units for the wheels, consist of a motor and gearbox. Two such units are inside each bogie transverse beam - one for each wheel - to achieve differential steering.

[0089] Each bogie has two transverse beams, fore and aft. One transverse beam contains low speed, high torque drive units. The other transverse beam contains higher speed, lower torque drive units. By selecting which transverse beam connects with the ground, a choice between slow or fast motion is provided. Slow, high torque motion is particularly useful for adjusting position on a stair. Fast motion is useful for travelling across a floor surface.

[0090] Referring to figures 1 to 3, a stair climbing conveyance is shown in the form of wheelchair 10 which includes a first bogie 20 connected at the right hand side of the wheelchair (from the perspective of a passenger sitting in chair 10) and a second bogie 30 which is connected at the left hand side of the wheelchair.

[0091] As best seen in figure 2, bogie 20 includes a first pair of spaced apart wheels 22 located at one end of the bogie 20 and a second pair of spaced apart wheels 24 at the other end of the bogie.

[0092] As best seen in figure 3, a control panel 110 is provided for the passenger to control operations of the wheelchair and batteries (not visible) are integrated into the arms of the seat 100 to power the electronic systems of the wheelchair.

[0093] Chair 10 is coupled to a drive unit of the wheelchair by way of a chair mounting mechanism which allows movement of the chair with respect to the remainder of the wheelchair in two modes which can be controlled by user input at the control panel 110 as follows:

[0094] 1. The chair 10 is able to be controlled to rotate at least 90 degrees about a vertical axis. This allows the passenger to face sideways on the chair when ascending or descending stairs; and

[0095] 2. The chair is able to move laterally forwards and backwards with respect to the direction of movement of the chair. This enables the user to influence the centre of gravity of the combination of the wheelchair and the passenger which can be useful when carrying out certain manoeuvres.

[0096] Referring to figure 4, wheelchair 10 includes a centrally located drive unit 40 which includes a rotating common axle 42 which extends across the width of the conveyance and includes first and second crank arms 28, 38 located at each end of the common axle 42. The crank arms 28, 38 are oriented in opposite directions by being angularly offset from one another by 180 degrees. The first and second bogies 20, 30 are mounted to the respective first and second crank arms 28, 38 at pivotable joints 26, 36.

[0097] Wheels 22 are mounted to a transverse beam portions 24 of bogie 20 which houses wheel motors in the form of drive units 25 for the wheels 22 in the form of an electric motor and reduction gearbox combinations. All other sets of wheels 24, 32, 34 are mounted in the same fashion so there are a total of eight drive units 25 in total, one for each wheel. The beam portions 24 are structurally stiff and contribute to the overall stiffness of the stairclimbing mechanism of the wheelchair 10. They also provide protection for the drive units 25 for the wheels.

[0098] Referring to figures 5 to 10, the central drive unit 40 is an assembly contained within an external casing 41 and includes an arrangement of drive motors and clutches and a planetary gear arrangement to control the operations of the wheelchair 10. The central drive unit 40 is generally symmetrical about a centre line and matching components are located on either side of this line. The central drive unit has a high degree of stiffness which is aided by its cylindrical form. The central drive unit acts as a transverse structural beam in the wheelchair and thereby plays an important role in enabling a stair-climbing ability of the wheelchair during which the chair is alternately supported on one bogie, then the other as will be later described.

[0099] Common axle 42 is located centrally in the unit. Crank arms 28, 38 are fixed at either end of axle 42. Hollow drive axles 46a, 46b are located on the common axle 42. Drive axle 46a is coupled to cog 21 of bogie 20 via cog 47a and a set of idler gears 29. Drive axle 46b is coupled to cog 31 of bogie 30 via cog 47b and a set of idler gears 39. Drive axles 46a, 46b are permanently coupled to the rotors of hollow cylindrical motors 44a, 44b via hollow cylindrical reduction gearboxes 45 a, 45b.

[0100] Suitable motors include the Torque QTR-A 133 series from Tecnotion BV. Suitable hollow reduction gearboxes include the SD-BRC Zero Backlash series from

[0101] Hsoar.

[0102] A planetary gear arrangement includes a sun gear 56 which is fixed to common axle 42, an outer ring gear 54 which is affixed to the inside of casing 41, and a carrier 53. The carrier 53 houses an arrangement of planetary gears 58 which mesh with both of the sun gear 56 and the ring gear 54. The carrier 53 is selectively engageable with the hollow drive shafts 46a, 46b by two clutches 50a, 50b. The carrier is lockable with respect to the casing 41 by a carrier lock actuator 63.

[0103] The principal of operation of both clutches 50a, 50b is the same and will be described in detail in relation to clutch 50b which is shown in exploded detail in figures 9 and 10. The operation of clutch 50b is controlled by a clutch actuator motor 60b which turns a cog 61b which is meshed with screw drive ring 66b which has cog teeth on the outside and a screw thread on the inside. The screw thread on the inside of the screw drive ring engages with clutch engagement ring 67b which can move from side to side, guided by linear guide posts which fit into apertures spaced around the clutch engagement ring 67b. The guide posts are best seen in figure 10 and extend around the periphery of plate 68b. The plate is affixed to the casing 41.

[0104] Moveable clutch plate 52b is retained by, but free to rotate with respect to, the clutch engagement ring 67. Fixed clutch plate 5 lb is affixed to the hollow drive axle 46b. The moveably and fixed clutch plates 52b, 5 lb are provided with a series of radially oriented ridges and grooves which serve to key the clutch plates together. In addition, magnets embedded in the clutch plates 52b and 5 lb keep them locked together when they mate, to operate as a “power-off” clutch system.

[0105] Moveable clutch plate 52b is keyed to a small cylindrical extension of the carrier and free to move a short distance along this extension, being moved by the screw drive ring 66b to move between an extended position and a retracted position. In the extended position the clutch plates 52b, 5 lb engage together and lock the hollow drive shaft 46b into engagement with carrier 53. In the retracted position, the hollow drive shaft 46b can rotate with respect to the carrier 53. The extended or retracted positions are selected by operation of the clutch motor 60b in one direction or the other.

[0106] The wheelchair can operate in the following operational modes with the given mechanical settings:

[0107] Mode 1 - Stair Climbing

[0108] Engage both clutches 50a, 50b, turn both motors 44a, 44b in the same direction.

[0109] Referring to figures 11 to 15, wheelchair 10 is shown negotiating a flight of stairs 200. Commencing at figure 12, the wheelchair 10 is shown partway up the stairs. Both motors 44a, 44b are actuated with both of clutches 50a, 50b engaged which causes the crank arms to rotate. The bogie 20 becomes lifted from the stairs and the chair 10 moves progressively up the staircase. As the crank arm rotates, the idler gears 29 maintain the attitude of the bogie as it rotates about its pivotal joint 21.

[0110] Beyond the position shown in figure 15, the bogie 20 will come to rest on the next stair up the staircase and continued rotation will cause bogie 30 to become lifted and moved to the next stair. During the times when one of the bogies is free from the ground the other bogie may make a small adjustment by moving forwards or backwards on the stairs. Proximity sensors are mounted in the transverse beam portions of the bogies to detect features of the staircase such as the stair treads, noses and risers to enable appropriate positioning of the wheels on the stairs.

[0111] As the sequence continues, as the crank arms rotate, the wheelchair 10 is supported and balanced alternately by the first and second bogies as it ascends or descends the stairs.

[0112] Mode 2 - Adjust Attitude of Bogie in Air Whilst Climbing

[0113] Engage one clutch and disengage other clutch, use one motor to climb, use other motor to adjust attitude of bogie in air. At some times, it may be desirable to adjust the attitude of one of the bogies whilst it is in the air. In a stair climbing operation, this will occur at the stages where the wheelchair moves from level ground onto the stairs, or moves from the stairs onto level ground.

[0114] The overall principal of operation and sequence of movements made in a stair climbing operation including the stages of moving onto or off the stairs is otherwise as described in applicant’s prior published application W02019090385A1.

[0115] Mode 3 - Rolling on Flat Ground

[0116] Engage carrier lock, engage both clutches, turn off both motors

[0117] In this mode, wheelchair can be freely rolled along the ground.

[0118] Mode 4 - Scissor Lift Motion - Up and Down

[0119] Engage carrier lock, disengage both clutches, turn each motor in opposite directions.

[0120] The Wheelchair 10 can scissor upwards or downwards to set the seat of the wheelchair at a range of heights to assist the passenger in negotiating various situations.

[0121] At figure 16, the wheelchair is shown at a normal height, suitable from transfer to or from a bed.

[0122] At figure 17 the wheelchair 10 is shown in a lowered configuration, suitable for transfer to or from a toilet.

[0123] At figure 18, the wheelchair is shown at an elevated height suitable for sitting at a kitchen worktop. Mode 5 - Tilt to Level Seat

[0124] Engage carrier lock, disengage both clutches, turn motors incrementally in same direction.

[0125] Referring to figure 19, the mechanism can tilt the seat to keep it horizontal whilst travelling on a hill.

[0126] Mode 6 - Recline

[0127] Disengage carrier lock, disengage both clutches, turn motors in same direction.

[0128] Wheelchair users commonly recline twice an hour, to improve blood circulation and avoid pressure sores. Referring to figures 20 and 21 the wheelchair is prepared for a reclining movement by scissoring down to a lowered position with both bogies having four-wheel contact with the ground. In addition to reclining, the mechanism can turn clockwise and anticlockwise repeatedly, to produce a rocking motion.

[0129] Referring now to figures 22 to 26, a second embodiment of a conveyance 110 will be described which incorporates a modified version of central drive unit 140.

[0130] Central drive unit 140 includes a cylindrical external casing 141 made up of attached casing sections 141a, 141b and 141c which protects internal components and is able to act as a stiff transverse beam across the width of the conveyance. Left and right crank arms 138, 128 are fixed rigidly to the ends of the external casing 141. A saddle 150 for mounting the payload, such as a chair 100, is rotatable with respect to the external casing 141.

[0131] A right motor and gear reducer 145a is able to rotate the right bogie connector 120 (and hence the right bogie when connected) with respect to the right crank arm 128. A left motor and gear reducer 145b is able to rotate the left bogie connector 130 with respect to the left crank arm 138. A middle motor and gear reducer 153 which, as best seen in figure 25 is able to level the saddle 150 by counter-rotating the saddle under the control of 150 via motor and reducer 153 and gearset 154 utilising the input of an electronic gyroscope (not shown) located in the saddle, as the external casing 141 rotates with respect to the ground.

[0132] As best seen in figure 24, a planetary gearset 129 and an idler gear 126 inside each crank arm engages each bogie connector with its respective motor 145. The sun gear 129a of the planetary gearset 129 turns the planet gears 129b held in the carrier 129c. The carrier 129c is fixed to the crank arm 128. The planet gears 129b turn the ring gear 129d that is keyed to the inside of bogie connector 120 by a series of notches provided around its periphery.

[0133] The planetary gearset 129 acts as a form of reduction gearbox to transmit high torque to the bogie connector 120, and hence the bogie, and the loads of the various operating forces are spread across the teeth of the four planetary gears 129b.

[0134] The saddle 150 includes cleats 151 for attachment of the chair 100. The saddle optionally includes a motor that drives a pinion gear 152 to adjust the position of the chair 100.

[0135] As best seen in figure 26, a disc brake 170a, 170b inside each crank arm may lock each bogie connector 120, 130 with respect to its respective crank arm 138, 128. A saddle brake 155 may lock the saddle with respect to the external casing by way of engaging with a brake pad located on the outside of the casing 141. A system of slip rings 160 transfers electrical power and communications between the rotatable components.

[0136] This second version of the central drive unit 140 achieves the same operational modes as the first version, without need of a clutch system, by use of a motor dedicated to levelling the seat.

[0137] Using the second version of the central drive unit, the wheelchair can operate in the following operational modes with the given mechanical settings:

[0138] Mode 1 - Stair Climbing

[0139] Release both disc brakes 170a, 170b, release saddle brake 155, use one motor 145 to lift the chair, use the opposite motor to control the attitude of the bogie in the air, use the middle motor 153 to keep the saddle level.

[0140] Mode 2 - Adjust Attitude of Bogie in Air Whilst Climbing

[0141] Release the disc brake 170 associated with the bogie 20, 30. Use the motor 145 associated with the bogie to adjust the attitude of the bogie.

[0142] Mode 3 - Rolling on Flat Ground

[0143] Apply both disc brakes 170a, 170b, apply the saddle brake 155, turn off all motors 145, 153.

[0144] Mode 4 - Scissor Lift Motion - Up and Down

[0145] Release both disc brakes, 170a, 170b apply saddle brake 155, turn the left and right motors 145a, 145b in opposite directions, turn saddle motor 153 off.

[0146] Mode 5 - Tilt to Level Seat

[0147] Apply both disc brakes 170a, 170b, release the saddle brake 155, turn off the left and right motors 145a, 145b, use the saddle motor 153 to tilt the seat.

[0148] Mode 6 - Recline

[0149] Apply both disc brakes, 170a, 170b, release the saddle brake 155, turn off the left and right motors 145a, 145b, use the saddle motor 153 to recline the seat. In either embodiment the speed of each wheel can be controlled individually. This allows the wheelchair to perform differential steering operations. An explanation of differential steering and examples of wheel structures suitable for differential steering may be found in applicant’s prior published specification WO2024 / 152087, the entire contents of which are incorporated herein by reference.

[0150] The drive units in each bogie are specified to provide a set of wheel drive units at one end of each bogie configured for low speed / high torque movement, and to provide wheel drive units at the other end of each bogie configured for high speed / low torque movement. For standard everyday movement, the bogies are rotated so that the two pairs of high speed wheels are in contact with the ground. For precision motion, or for precision movements during stair climbing operations, the bogies are rotated so that the low speed wheels are used.

[0151] Any reference to prior art contained herein is not to be taken as an admission that the information is common general knowledge, unless otherwise indicated.

[0152] It is to be appreciated that the invention may also be used for purposes other than a wheelchair. Examples of other purposes are described in W02019090385A1.

[0153] It can be seen that embodiments of the invention have at least one of the following advantages:

[0154] • The two-leg device is more compact in width than the three-leg device, due to the removal of one leg.

[0155] • The compact width allows the seat to be rotated sideways, for safer climbing of stairs. The user faces the balustrade, which is safer than facing down the stair.

[0156] • The compact width improves manoeuvrability. The turning circle is reduced and the device more easily passes through doorways.

[0157] • The two-leg design is less insect-like than its three-leg predecessor. It feels less like a contraption and more like a lifestyle product. The sleeker aesthetic improves inclusivity for the user.

[0158] • The compact width causes less interference to others. For example, it takes up less space on a footpath and fits more neatly on public transport. The user consequently feels less awkward or self-conscious.

[0159] • Removal of one leg simplifies the drive unit. There is less duplication of components and fewer components, compared to the three-legged version.

[0160] Finally, it is to be appreciated that various alterations or additions may be made to the parts previously described without departing from the spirit or ambit of the present invention.

Claims

CLAIMS:

1. A stair climbing conveyance including: first and second bogies; each bogie includes a first pair of spaced apart wheels at one end of the bogie and a second pair of spaced apart wheels at the other end of the bogie, the wheels defining a ground contacting footprint; at least one of the pairs of wheels of each bogie are driven wheels; the conveyance further includes first and second crank arms located at either side of the conveyance; the first and second bogies are mounted to the respective first and second crank arms at pivotable joints; when in use in a stair climbing operation, as the crank arms rotate, the conveyance is supported and balanced alternately by the first and second bogies as it ascends or descends a flight of stairs.

2. A conveyance according to claim 1 wherein each bogie includes two transverse beam portions.

3. A conveyance according to claim 2 wherein the bogies have an interleaving motion.

4. A conveyance according to claim 2 wherein the pairs of wheels are mounted at the transverse beam portions of each bogie.

5. A conveyance according to claim 2 wherein the transverse beam portions house wheel motors for driving the wheels.

6. A conveyance according to any preceding claim wherein all of the wheels of each bogie are driven wheels.

7. A conveyance according to claim 5 wherein the wheel motors of each bogie are configured to drive one of the pairs of wheels at a lower speed than the other pair of wheels.

8. A conveyance according to any preceding claim which can operate in a mode in which it is supported on the ground by four wheels being one pair of wheels of the first bogie and one pair of wheels of the second bogie.

9. A conveyance according to claim 8 wherein the operating height of the conveyance can be adjusted by varying the distance between the pairs ofground contacting wheels.

10. A conveyance according to any preceding claim wherein the crank arms are mounted at either end of a common axle which extends across the width of the conveyance.

11. A conveyance according to claim 10 wherein the common axle is mounted inside a pair of first and second hollow drive axles, each drive axle being connected to and driven by a drive motor.

12. A stair climbing conveyance according to claim 11 wherein each hollow drive axle is connected to its respective drive motor via a reduction gearbox.

13. A stair climbing conveyance according to either of claims 11 or 12 wherein each of the first and second drive axles are coupled to the first and second bogies by a drive arrangement associated with each crank arm to enable the attitude of the bogie with respect to the crank arm about the pivotable joint to be controlled.

14. A stair climbing conveyance according to any preceding claim further including a centrally disposed planetary gear arrangement including: a sun gear which is mounted to the common axle; a set of planetary gears which are mounted in a carrier; and a ring gear.

15. A stair climbing conveyance according to claim 14 further including first and second clutches which are operable to engage or disengage the first and second hollow drive axles with the carrier.

16. A stair climbing conveyance according to claim 15 further including a carrier locking arrangement to lock the carrier from rotating in relation to the ring gear.

17. A stair climbing conveyance according to any one of claims 11 to 16 wherein each drive motor includes a cylindrical aperture extending through the central axis of the motor and both of the common axle and a drive axle are located within the aperture of each motor.

18. A stair climbing conveyance according to any one of claims 1 to 9 wherein the crank arms are fixedly mounted at either end of a substantially cylindrical casing which extends across the width of the conveyance and the cylindrical casing rotates during a stair climbing operation.

19. A stair climbing conveyance according to claim 18 further including a load carrying saddle which rotates with respect to the casing to keep the saddle level during a stair climbing operation.

20. A stair climbing conveyance according to claim 19 further including a saddle brake that may lock the saddle with respect to the external casing.

21. A stair climbing conveyance according to any one of claims 18 to 20 further including: a left motor and gear reducer, able to rotate the left bogie with respect to the left crank arm; a right motor and gear reducer, able to rotate the right bogie with respect to the right crank arm.

22. A stair climbing conveyance according to any one of claims 18 to 21 further including: a middle motor and gear reducer able to level the saddle by counter-rotating the saddle when the external casing rotates with respect to the ground.

23. A stair climbing conveyance according to any one of claims 18 to 22 further including a disc brake inside each crank arm that may lock each bogie with its respective the crank arm.

24. A stair climbing conveyance according to any preceding claim further including a seat.

25. A stair climbing conveyance according to claim 24 wherein the seat is pivotable about a vertical axis to enable the seat to either face in the direction of movement or transversely to the direction of movement of the conveyance.

Images