Systems and methods for controlling working fluid in hydraulic elevators
AssigneeTK Elevator Corporation
InventorAravind Samba Murthy
Life of this patent
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Abstract
A hydraulic elevator may comprise a bidirectional pump that controls up and down motion of an elevator car. A VVVF drive may cause the bidirectional pump to provide working fluid in a controlled manner to a hydraulic jack that supports the elevator car. A control valve may be disposed between the bidirectional pump and the hydraulic jack so that the control valve can be closed when the elevator car needs to be held in place. To avoid pressure waves that propagate when the control valve is opened with disparate pressures on the pump and jack sides of the control valve, the bidirectional pump may adjust the pressure on the pump side of the closed control valve to the pressure on the jack side of the control valve before the control valve is opened.
Claims8
A system for controlling working fluid in a hydraulic elevator, the system comprising:
- a hydraulic jack;
- a control valve in fluid communication with the hydraulic jack, wherein the control valve is configurable in an open position and in a closed position;
- a pump in fluid communication with the control valve, wherein the control valve is disposed between the pump and the hydraulic jack;
- a motor configured to generate a force for powering the pump;
- a controller, wherein when the control valve is in the closed position the controller causes the pump to at least one of adjust a first pressure on a pump side of the control valve to a second pressure on a hydraulic jack side of the control valve or maintain the first pressure at the second pressure;
- and
- a VVVF drive configured to provide electricity from a power source to the motor, and to operate in a speed-control mode when the controller causes the pump to adjust the first pressure to be within 1.0% of the second pressure, wherein a motor speed signal from the motor is provided as feedback to the VVVF drive.
Dependencies are inferred from the claim text.