Patent Publication Number: US-2020276066-A1

Title: A conveyance for surmounting obstacles

Description:
TECHNICAL FIELD 
     The present invention relates to a conveyance for surmounting obstacles. Embodiments of the invention find a particular application in conveying persons up and down staircases. However, the invention is not limited to this application. 
     BACKGROUND TO THE INVENTION 
     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. 
     There remains a need to provide improved conveyances for surmounting obstacles. 
     SUMMARY OF THE INVENTION 
     In a first aspect the present invention provides a conveyance for surmounting obstacles including: a first ground engaging arrangement; and a second ground engaging arrangement; the first and second ground engaging arrangements are operable to move in an alternating sequence of movements to enable the conveyance to surmount obstacles; the conveyance is statically balanced alternately by one then the other of the ground engaging arrangements throughout the sequence of movements; each ground engaging arrangement includes a forwardly disposed portion and a rearwardly disposed portion which are spaced apart from one another; and each ground engaging arrangement further includes an obstacle accommodating region located between the forwardly disposed portion and the rearwardly disposed portion which can accommodate a portion of an obstacle being surmounted in use. 
     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 beam may be curved. 
     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. 
     The ground engaging arrangements may include wheels. 
     At least some of the wheels may be driven wheels. 
     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. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An embodiment of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: 
         FIG. 1  is a perspective view of a motorised wheelchair; 
         FIG. 2  is an underside perspective view of the wheelchair of  FIG. 1 ; 
         FIG. 3  is a side view of the wheelchair of  FIG. 1 ; 
         FIG. 4  is an underside view of the wheelchair of  FIG. 1 ; 
         FIG. 5  is a detail view of one of the drive units of the wheelchair of  FIG. 1 ; 
         FIG. 6  is a cut away view of the drive unit of  FIG. 5 ; 
         FIG. 6A  is a perspective cut-away view of the epicyclic gear arrangement of the drive unit of  FIG. 5 . 
         FIG. 7  is a schematic view of the chassis of the wheelchair of  FIG. 1  with cut away views of the epicyclic gearsets; 
         FIGS. 8 a  to 8 c    illustrate the wheelchair of  FIG. 1  adjusted at different working heights; 
         FIG. 9  shows a sequence of movements of the wheelchair of  FIG. 1  descending a staircase; 
         FIG. 10  shows a sequence of movements of the wheelchair of  FIG. 1  stepping over a hob barrier; 
         FIG. 11  shows a sequence of configurations illustrating a tilt adjustment function of the wheelchair of  FIG. 1 ; 
         FIG. 12  is a sequence of views illustrating attaching a pair of manually propelled wheels to the wheelchair of  FIG. 1 ; and 
         FIG. 13  is a perspective view of an alternative embodiment of a wheelchair with a swivelling seat. 
     
    
    
     DETAILED DESCRIPTION OF EXAMPLE OF AN EMBODIMENT 
     Referring to  FIGS. 1 to 3 , a conveyance for surmounting obstacles is shown in the form of motorised wheelchair  10 . Wheelchair  10  includes a first ground engaging arrangement in the form of outer bogies  20 ,  22  and a second ground engaging arrangement in the form of inner bogie  30 . 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  10  further includes a seat  50  and a user control panel  52 . The control panel includes a joystick and other controls to allow the wheelchair occupant to control the movements of the wheelchair. Seat  50  is mounted on a chassis by attaching to drive units  40 ,  42 . Seat is attached to the chassis by way of an adjustable mechanism which allows the position seat  50  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. 3 , outer bogie  22  includes a forwardly disposed portion in the form of a steerable driven wheel  26  and a rearwardly disposed portion in the form of passive wheel  28 . Wheels  26 ,  28  are spaced apart from one another by being mounted at opposite ends of a curved beam  24 . The curvature of the beam  24  defines an obstacle accommodating region below the beam located between the wheels  26 ,  28  which accommodates a portion of an obstacle being surmounted, such as a stair, as will become apparent. 
     Similarly, inner bogie  30  includes a forwardly disposed portion in the form of a pair of passive wheels  38  and a rearwardly disposed portion in the form of a pair of steerable driven wheels  36 . Wheels  36 ,  38  are spaced apart from one another by being mounted on cross members attached at opposite ends of curved beam  34 . The curvature of the beam  34  defines an obstacle accommodating region below the beam located between the wheels  36 ,  38  which accommodates a portion of an obstacle being surmounted. 
     Referring now to  FIG. 4 , beam  24  is mounted to a carrier arm of drive unit  42  by way of epicyclic gearset  60 . Similarly, beam  21  is mounted to a carrier arm of drive unit  40  by way of epicyclic gearset  62 . Drive units  40 ,  42  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.com). 
     Referring now to  FIGS. 5, 6 and 6A , drive unit  40  includes a motor A and a motor B. Each motor includes an internal worm drive reduction gearbox which drives an output gear  43 . The output gear  43  of motor B is visible in  FIG. 5 . Each output gear drives an associated main gear  45  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  48 . Ring gear  49  is affixed to the inside of the case of drive unit  40 . Planets  47 ,  47   a  are mounted on a carrier which is selectively engageable with the main gear  45  by way of a clutch. Arm  46  is integrally formed with the sun gear  48 . Arm  46  also carries a bogie gear  63  which is rotatably mounted to arm  46  and which meshes with main gear  45 . 
     Due to the double pinion nature of the gearset, the ring gear  49  and sun gear  48  rotate in opposite directions. Also, the double-pinion gearset is configured so that the ring gear  49  and the sun gear  48  rotate equally in opposite directions. That is to say, a reduction ratio of one to minus one. In this embodiment the gears of the double-pinion epicyclic gearset are configured as follows: 
     Main gear  45 —has 130 teeth 
     Planet gear  47 —is a compound gear including gears of 12 teeth and 48 teeth joined together on a common axis. 
     Planet gear  47   a —has 26 teeth 
     Sun gear  48 —has 66 teeth 
     Ring gear  49 —has 132 teeth 
     Bogie gear  63 —has 130 teeth 
     Referring now to  FIG. 7 , the bogie gear  63  is integrally formed with the axle of epicyclic gearset  60  which is provided with teeth to form sun gear  68  of epicyclic gearset  60 . Ring gear  69  is affixed to beam  24 . Planets  67  are mounted on a carrier. The carrier can be rotationally fixed with respect to beam  24  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  46  by way of clutch b. This allows for adjustment of the pitch of a bogie, at a suitable output torque. In this embodiment epicyclic gearset is dimensioned to provide an effective reduction ratio of two to one between the ring gear  69  and the sun gear  68 . The ratio aims to halve the rotational speed, to double the output torque. In this embodiment the gears of the epicyclic gearset  60  are configured as follows: 
     Planet gear  67 —has 20 teeth 
     Sun gear  68 —has 40 teeth 
     Ring gear  69 —has 80 teeth 
     The epicyclic gearset  62  associated with beam  21  is of similar construction to epicyclic gearset  60 . It is controlled by operation of clutches k and m. Drive unit  40  is of identical construction to drive unit  42 . It includes motors C and D and clutches i and j. Beam  34  of the central bogie is associated with two epicyclic gearsets which are of similar construction to the epicyclic gearsets  60 ,  62 . They are associated with operation of clutches e, f, g, and h. In some embodiments one of the epicyclic gearsets associated with beam  34  may be omitted. 
     Wheelchair  10  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  10  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. 8 , height and footprint adjustment of the wheel chair will be described. At  FIG. 8 a   , wheelchair  10  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. 8  to a high height configuration with a smaller footprint shown in FIG.  8   b . 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. 8 c   . 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. 9 , wheelchair  10  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  01  the wheelchair  10  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. 8 c   . The wheelchair then moves forwards until the lidar system indicates that the front wheels  26  are a predetermined distance away from the edge of the top stair as shown at step  02 . 
     The outer bogies  20 ,  22  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  36  of the inner bogey are driven to move the wheelchair forwards until the lidar system indicates that the wheels  38  of the inner bogey are a predetermined distance away from the edge of the top stair as shown at step  03 . 
     The outer bogies  20 ,  22  are then lowered by driving motors A, C, and their pitch adjusted by driving motors B, D until it is detected that wheels  26  have come into contact with the second stair and wheels  28  have come into contact with the top stair as shown at step  04 . The top stair is accommodated within the region beneath the beam  24  and between the wheels  26 ,  28  of the outer bogies. 
     At all times when the outer bogies  20 ,  22  are lifted clear of the ground the wheelchair is statically balanced by the inner bogie  30 . 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  36 ,  38  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  40  and  42  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  30 . 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  30  whilst motors A, C control the pitch of the inner bogie  30 . The inner bogie  30  is lifted and the driven wheels  26  of the outer bogies are driven forwards until the lidar system indicates that wheels  26  are a predetermined distance away from the edge of the second stair. 
     Continued rotation of motors B, D causes the inner bogie  30  to “step over” the outer bogies  20 ,  22  and to lower the inner bogie  30  so that wheels  38  come into contact with the third stair, and wheels  36  come into contact with the top stair as shown at step  05 . The top stair and the second stair are accommodated within the region beneath the beam  34  and between the wheels  36 ,  38  of the inner bogie. 
     Again, at all times when the inner bogie  30  is lifted clear of the ground the wheelchair is statically balanced by the outer bogies  20 ,  22 . 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  26 ,  28  of the outer bogies. 
     Again, the double pinion epicyclic gearsets, turn the drive units  40  and  42  in reverse to the arms&#39; 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  09  to  13  adjustments to the pitch of the bogies are made as the wheelchair progressively steps onto flat ground. 
     At step  14  the wheelchair has finished descending the stairs and is on flat ground in the lowered configuration of  FIG. 8 c   . The wheelchair is then raised to the normal height configuration of  FIG. 8 a    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. 10 , wheelchair  10  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. 11 , wheelchair  10  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. 12 , optionally, a pair of larger hand operable wheels  70  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. 8 b   . Wheels  70  may then be attached to the outer bogies  20 ,  22 . Wheelchair  10  is then lowered so that wheels  70  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. 13 , an alternative embodiment of a wheelchair  100  is shown. This embodiment differs from the embodiment described above 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. An embodiment of the conveyance could, in a miniature form, be a toy. 
     In the embodiment described above 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. In other embodiments a single pinion epicyclic gearset may be associated with the chassis of the conveyance. In such an embodiment an idler gear may be provided between the main gear and the bogey gear. 
     It can be seen that embodiments of the invention have at least one of the following advantages:
         Whilst surmounting obstacles the conveyance remains statically balanced at all times by at least one of the ground engaging arrangements. This allows for very gentle, controlled movements to avoid damage to stairs and the like. It also allows the conveyance to stop moving at any time whilst also remaining stable and upright.   The conveyance is able to maintain the stability of a load carried on the conveyance by controlling the orientation of the chassis.   The conveyance is substantially symmetrical about a centre line parallel to the direction of travel of the conveyance. This contributes to balance and stability and may also reduce torsional stress.   Wheelbase can fold to a compact four-wheel form when not deployed for surmounting obstacles. This improves agility, particularly in confined indoor spaces, so the conveyance can avoid hitting furniture and the like.   Height adjustable to suit a range of different uses   Tilt adjustable to compensate for travel on sloping ground.   Aesthetically discreet. Is compact and has visual cues to everyday normal furniture. The feeling of familiarity improves social inclusivity for the user.   May be converted to a hybrid manual wheelchair eliminating the need for two chairs and the inconvenience of moving between different chairs.       

     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. 
     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.