Patent ID: 7571815

Claim:
A sieve jigger for sorting solid material mixtures in a separating liquid bath according to density, comprising: a rocker mounted to pivot about a pivoting axis in the liquid bath and to carry the solid material mixtures; a hydraulic cylinder with a single working pressure chamber pivotally connected to the rocker to lift the rocker upwardly and to brake a downward movement of the rocker; a displacement measuring device operatively connected to a piston of the hydraulic cylinder and to generate a measuring signal; a displacement sensor arranged to receive the measuring signal from the displacement measuring device and to generate a displacement signal; a governor arranged to receive the displacement signal from the displacement sensor and to generate a control signal; a motor driven hydraulic oil pump; a hydraulic oil supply and evacuation conduit connected to the single working pressure chamber of the hydraulic cylinder; a proportional control valve communicating with the hydraulic oil supply and evacuation conduit and arranged to receive the control signal from the governor, the proportional control valve being configured to have a first lifting position in which the motor driven hydraulic oil pump is connected to the single working pressure chamber via the proportional control valve, a second free-fall position in which the single working pressure chamber is unrestrictedly connected to a hydraulic oil sump, and a third deceleration position in which the single working pressure chamber is closed off from the hydraulic oil pump and reservoir; the displacement measuring device being operatively connected via the governor to the proportional control valve in order to control the upward movement and the downward movement of the rocker, in a first lifting phase, a second free-fall phase and a third deceleration phrase, including controlling at least one of a lifting displacement and a lifting frequency.