US Patent 7090297 Heavy lift chair

A power-assisted heavy lift chair comprises a base assembly. A chair frame is supported on the base assembly. A lift mechanism communicates with the base assembly and the chair frame, and is operable to actuate the chair frame between first and second positions. A transformer provides electrical power to an electric motor. The electric motor provides rotational power to the lift mechanism at a first rate to lift and/or lower the chair frame. The electric motor draws current from the transformer according to a load upon the chair frame. The rate that the electric motor lifts and/or lowers the chair frame depends upon the voltage provided by the transformer. The transformer is operable to provide a generally constant voltage regardless of the current draw of the electric motor. Therefore, the electric motor lifts and/or lowers the chair at a constant rate independent of the load on the chair.