Electromagnetic oscillating piston pump - uses large oil filled spaces above and below piston to minimise opposition to motion of piston

摘要

The volumes on either side of the piston of the pump are made large in relation to the piston displacement volume to reduce opposition to the motion of the piston. The piston is of magnetic material oscillating inside a cylinder. The alternating current supply is half-wave rectified and when the coil is energised the piston moves downward compressing a spring and deflecting an impermeable membrane, reducing the volume in the pumping chamber and forcing fluid out past an non-return valve. On the next half cycle the spring forces the piston upwards drawing in fluid through an non-return valve. The space above the piston is enlarged to be four or five times the piston displacement volume. This space is oil filled and communicates with the oil-filled space beneath the piston through grooves cut longitudinally in the piston outer wall.