US Patent 7380824 Wheelchair suspension

A side frame assembly for an electric wheelchair suspension includes a supporting frame unit with a rider-supporting frame, a front caster frame, an upper link having a front end connected pivotally to the front caster frame, and a lower link disposed under the upper link and having a front end connected pivotally to the front caster frame. A drive wheel frame has a front lower end connected pivotally to a pivot portion of the supporting frame unit. A connecting frame has an upper pivot portion connected pivotally to a rear end of the upper link, a lower pivot portion connected pivotally to a rear end of the lower link, and a rear pivot portion connected pivotally to the rear upper end of the drive wheel frame.