Hydraulic driving systems for lowering and raising elevator cars which employ hydraulic jacks for supporting the weight of the elevator car and the passengers are well-known in the art. A typical hydraulic jack has a stroke of about 10 to about 80 feet and 1 to 8 stop positions. In such well-known hydraulic jacks, a hydraulic fluid, such as oil, in a jack cylinder is pressurized by a pump which pumps fluid from a reservoir through a filter, control valve, insulator coupling and piping connection to the jack cylinder. The pump is driven by an electric motor which is necessarily large sized, to carry a full load every time to move the elevator.
Systems for driving a hydraulic jack of the conventional elevator use a complicated control system with a large number of electrical and mechanical elements, which require frequent and troublesome maintenance. Large amounts of fluid pumped at high pressures through small restrictions causes high vibrations and noisy operation of the elevator system. Also the large size of the electrical motor necessary to drive a pump pressuring the fluid in the jack requires a substantially large amount of electrical energy.
In the conventional hydraulic elevator driving system, positioning of the elevator car is determined by microswitches at each floor sending signals to the flow regulating control valve, so that separate calibration for each floor is necessary.
The purpose of the present invention is to replace the sophisticated, elevator hydraulic driving system with above-described disadvantages by a simple, energy efficient, easy-to-maintain, and long-life reliable driving system for an elevator's hydraulic jack.