Patent ID: 6957721

Claim:
A hydraulic elevator comprising: a hydraulic drive including a piston displaceable in a cylinder; a pressure accumulator; a charging pump for charging said pressure accumulator with hydraulic oil from a tank, said charging pump being driven by an electric motor; a constant displacement main pump connected between said pressure accumulator and said cylinder for producing a flow of hydraulic oil between said pressure accumulator and said hydraulic drive; a main motor for driving said main pump, said main motor for driving said main pump being operated by a power output stage on the basis of signals from a control and regulating unit; an accumulator line connecting said main pump to said pressure accumulator; a cylinder line connecting said main pump to said hydraulic drive; and an electrically actuated open-closed type valve in said cylinder line, wherein said main motor drives said main pump when a pressure differential in one direction between said pressure accumulator line and said cylinder line is positive, and said main motor operates as a generator when said pressure differential between said pressure accumulator line and said cylinder line in said one direction is negative.