Measuring piston displacement in hydraulic working cylinder - determining flow of hydraulic medium through cylinder from pressure difference measurement across choke

摘要

The piston (58) displacement is determined by measuring the hydraulic medium flowing through the working cylinder (20). The press. of the medium flowing in a line towards the cylinder is measured on both sides of a choke aperture (30) in the line (26). The vol. flow per unit time is derived from the difference in the measured press. values and integrated to determine the vol. of medium flowing into the cylinder. The piston displacement is derived from the vol. The start and end of the integration corresp. to the switching of a valve controlling the flow to the cylinder. USE/ADVANTAGE - Esp. for monitoring working cylinders at coal face. Enables displacement of piston in single thrust cycle to be more accurately measured, using retrofitted arrangement.