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AssigneeSchenck Pegasus Corporation
InventorsEndre A. Meyer, Robert D. Kachman
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Electrohydraulic servovalve structure and method. The servovalve structure has minimum oil passage length and oil volume and a high response force motor with a light weight armature and a stiff flexible tube and includes a second stage pilot valve having an axially movable metering spool therein and a non contacting, electromagnetic, proximity type sensor positioned adjacent one end of the spool for converting axial spool position to an electrical signal. In modifications, a quartz or ceramic window is placed between the one end of the spool and sensor and electronics are placed on the servovalve adjacent the sensor for providing a low impedance spool position output signal from the servovalve. In accordance with the method of the invention, the axial position of the spool is sensed by the eddy current sensor and an electrical signal is provided representative of the position of the spool for use in controlling the electrohydraulic servovalve. In a modification, the position representative signal is converted to a low impedance signal at the servovalve.
A high frequency response electrohydraulic servovalve including a first stage, high response force motor, a second stage, pilot valve, and a third stage, metering valve connected in series so that the force motor controls the pilot valve and the pilot valve controls the metering valve, means for providing a first electrical signal representing a demand flow through the third stage metering valve, a first differential amplifier, a second differential amplifier and a third amplifier in series between the means for providing the first electrical signal and the force motor for passing the first signal, modified in the differential amplifiers to the force motor, said second stage;
A method of providing an electrical signal representative of the axial position of a pilot valve metering spool in an electrohydraulic servovalve including a force motor, a pilot valve and a metering valve, comprising converting the pilot valve metering spool position to an electrical signal with a non contacting, electromagnetic, proximity type sensor positioned adjacent one end of the pilot valve metering spool and converting the electrical signal to a low impedance electrical signal at the electrohydraulic servovalve.
A high frequency response electrohydraulic servovalve comprising a force motor first stage, a pilot valve second stage and a metering valve third stage, an external electrical input signal for the force motor first stage, two differential amplifiers in series between the external electrical input signal and the force motor first stage of the electrohydraulic servovalve, said pilot valve stage including an unbiased metering spool with a longitudinal axis movable axially to meter fluid through the pilot valve stage to control the metering valve stage, a non contacting, electromagnetic, proximity type sensor positioned adjacent one end of the pilot valve stage metering spool for converting pilot valve metering spool axial position into a pilot valve electrical signal and means for feeding the pilot valve electrical signal to the second differential amplifier, said metering valve stage also including a metering spool with a longitudinal axis movable axially to meter fluid through the metering valve stage and a linear voltage differential transformer operably associated with the metering valve metering spool for providing a metering valve electrical signal and means for feeding the metering valve electrical signal to the first differential amplifier.
A high frequency response electrohydraulic servovalve including a pilot valve stage having a metering spool with a longitudinal axis movable axially to meter fluid through the servovalve and no biasing spring acting on the metering spool and a non contacting, electromagnetic, proximity type sensor positioned adjacent one end of the pilot valve stage metering spool for converting pilot valve metering spool axial position into an electrical signal wherein the electrohydraulic servovalve includes an end cap adjacent the one end of the metering spool having an opening therethrough on the axis of the metering spool and a window in the opening and wherein the sensor is on the other side of the window from the one end of the metering spool.
A high frequency response electrohydraulic servovalve including a pilot valve stage having a metering spool with a longitudinal axis movable axially to meter fluid and no biasing spring acting on the metering spool, a non contacting, electromagnetic, proximity type sensor positioned adjacent one end of the pilot valve metering spool for converting pilot valve metering spool axial position into an electrical signal and electronic means immediately adjacent the sensor on the electrohydraulic servovalve and connected to the sensor for reducing the impedance of the electrical signals from the electrohydraulic servovalve.
Dependencies are inferred from the claim text.