US Patent 11834302 Stairlift

A stairlift includes a rail and a carriage. The carriage includes a frame, a central drive unit mounted to the frame, the central drive unit including a drive motor and a drive gear, a yoke assembly pivotably mounted to the frame, and a first bogie unit attached to the yoke assembly and a second bogie unit attached to the yoke assembly, wherein each bogie unit includes a bogie socket mounted to the yoke assembly, and a bogie ball spherically pivotable within the bogie socket, the bogie ball including a plurality of bogie ball rollers configured to hold the bogie ball to the rail, and further wherein the plurality of bogie ball rollers are configured to maintain the bogie ball in a generally perpendicular travel orientation relative to the rail.