Differential pressure indicators of controlled response to flow surges and filter assemblies including the same

Claim 1

A DIFFERENTIAL PRESSURE INDICATOR RELATIVELY INSENSITIVE TO FLOW SURGES IN A FIRST SOURCE OF FLUID PRESSURE, COMPRISING, IN COMBINATION, A HOUSING; FIRST AND SECOND FLUID LINES ASSOCIATED WITH HOUSING AND COMMUNICATING WITH FIRST AND SECOND SOURCES OF FLUID PRESSURE, RESPECTIVELY; INDICATING MEANS MOUNTED IN THE HOUSING BETWEEN THE FIRST AND SECOND FLUID LINES FOR MOVEMENT TO AND FROM AN INDICATING POSITION IN RESPONSE TO A PREDETERMINED STATIC PRESSURE DIFFERENTIAL BETWEEN THE FLUID LINES; AND A FLOW CONTROL PASSAGE HAVING A CONSTRICTED PORTION FOR FLOW OF FLUID OF THE FIRST SOURCE OF FLUID PRESSURE THERETHROUGH, AND DIMENSIONED TO INCREASE VELOCITY HEAD AND DECREASE STATIC HEAD OF SUCH FLOW; SAID FIRST FLUID LINE COMMUNICATING WITH THE FIRST SOURCE OF FLUID PRESSURE AT THE CONSTRICTED PORTION OF THE FLOW CONTROL PASSAGE, TO TAP ONLY SUCH DECREASED STATIC PRESSURE TO THE INDICATING MEANS, THEREBY PREVENTING RESPONSE OF THE INDICATOR TO FLOW SURGES.