Method of measuring leak rates

Claim 1

A method of measuring leak rates from a cavity in test pieces of the same configuration, comprising the steps of: placing the cavity of each of a series of sample test pieces in communication with a fluid pressure source to initiate a test cycle; monitoring the flow rate to each of said cavities after placing each of said cavities in communication with said fluid pressure source; determining the time after initiation of said test cycle when said flow rates become repeatable for successive test pieces; measuring the flow rate from said fluid pressure source to said cavity at a predetermined time after initiating of said test cycle, after said time determined to produce repeatable flow rates, but prior to the achievement of steady state flow conditions, for two sample test pieces having differing effective leak rates; determining the corresponding steady state flow rates for said two sample test pieces; generating a calibration function of the form: y=A+Bx where y is the steady state flow rate to a test piece cavity placed in communication with a fluid pressure source, x is the flow rate measured at an earlier time in the test cycle, and A and B are constants calculated from the testing of the two sample test pieces; placing the cavities of successive test pieces in communication with said fluid pressure source; measuring the flow rate to said cavities at said predetermined time in said test cycle; converting said measured flow rates into corresponding steady state flow rates by application of said calibration function to determine the leak rates from said cavities, whereby said test cycle for determining said leak rates is shortened by measuring said flow rates at said predetermined time.

Claim 2

A method of measuring leak rates from a cavity in test pieces of the same configuration, comprising the steps of: placing the cavity of each of a series of sample test pieces in communication with a fluid pressure source to initiate a test cycle; monitoring the flow rate to each of said cavities after placing each of said cavities in communication with said fluid pressure source; determining the time after initiation of said test cycle when said flow rates become repeatable for successive test pieces; measuring the flow rate from said fluid pressure source to said cavity at a predetermined time after initiating of said test cycle, after said time determined to produce repeatable flow rates, but prior to the achievement of steady state flow conditions, for two sample test pieces having differing effective leak rates; determining the corresponding steady state flow rates for said two sample test pieces; generating a calibration function of the form: y=A+Bx where y is the steady state flow rate to a test piece cavity placed in communication with a fluid pressure source, x is the flow rate measured at an earlier time in the test cycle, and A and B are constants calculated from the testing of the two sample test pieces; placing the cavities of successive test pieces in communication with said fluid pressure source; measuring the flow rate to said cavities at said predetermined time in said test cycle; converting said measured flow rates into corresponding steady state flow rates by application of said calibration function to determine the leak rates from said cavities, whereby said test cycle for determining said leak rates is shortened by measuring said flow rates at said predetermined time.