A stair climbing device as well as a method of using the device. The device in a preferred embodiment is a wheelchair. The chair is mounted on a floating chassis having a wheel assembly (150, 200) at each corner, each wheel assembly (150, 200) consisting of a pair of wheels (160, 170, 180, 190) mounted on arms (161, 171, 211, 221), the wheels (160, 170, 180, 190) being drivable about their own axes (169, 179, 219, 229) and the arms (161, 171, 211, 221) being drivable about the common axis (121, 141) by which they are connected to the floating chassis. The chair portion is connected to the chassis via pivots at the front end of the device and by extensible cylinders (400) at the rear end of the device so that the chair can be kept horizontal whilst the chassis can become inclined as the wheelchair goes up and down stairs. The arrangement is such that the device can also be used to raise and lower the chair relative to the chassis while the chassis is remaining horizontal. Thus the front pivoted connection is via a linkage arm. The method of ascending and descending stairs is that the chair rolls along, preferably backwards, when the device is ascending stairs, until the rearmost wheel contacts the riser of the first step, this producing a signal in suitable sensors, and then the drive mechanism is arranged to rotate the arm of the then rearmost wheel of this first wheel assembly that contacts the first riser so that the arm rotates around the common axis to bring the wheel onto the tread of the first step and as soon as this contact is sensed this wheel is driven into the riser of the first step until contact is again sensed, the arm of this wheel is then rotated towards a vertical position which draws the now trailing wheel of this assembly up the step and then the rotating movement is carried out again. This sequence is carried out in turn with the front and rear assemblies and the front and rear wheels of each assembly until the device has reached the top of the stairs and all wheels sense only upward pressures.
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