US 4,587,619 AGranted

Method and apparatus for electronic leak testing

AssigneeScans Associates, Inc.

InventorsVernon G. Converse, III, James M. Bordato, Theodore R. Bott, Charles E. Foerster, Jr., Desra N. Herbst, Jr., Ronald K. Mudge, Richard L. Smith, Frank R. Young

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Abstract

The specification discloses an electronic dynamic balance leak testing system utilizing a "live zero", wherein a source of test medium at a predetermined desired pressure or vacuum is connected to a part to be tested, and after the part is filled with the test medium, and an interval is provided for the system to stabilize the affects due to wave front oscillations, the test part is momentarily isolated from said test media and a microcomputer system is utilized, both to cause said isolation, and to measure the differential pressure existing at two points during the test. In a modification of our system which can dynamically project leak and accept or reject parts much sooner because of this projection feature, the rate of change of the differential pressure transducer is examined and is compared to a curve which is characteristic of the rate of change of a volume which is experiencing a predominately leak based change of pressure. When the rate of change is determined to be predominately a leak based change, the rate of change is determined to be a "Qualified Leak" or a qualified curve. In this case, after a predetermined sample time elapses from the point at which the curve was qualified, a reading of leakage is taken, such reading is then extrapolated to a full test time reading and compared to limits to see if a part is to be accepted or rejected.

Claims73

Dependent claims

A method of electronically testing a part for leakage, said method including the steps of:

(a) providing a source of test medium at a predetermined desired pressure or vacuum;
(b) connecting a test part to said source of test medium;
(c) momentarily isolating said test part from said source of test medium;
(d) measuring the differential pressure existing between said source of test medium and said test part;
(e) calculating the change in differential pressure while said test part is isolated, wherein the step of calculating the change in differential pressure includes the steps of:
(aa) starting said leak test;
(bb) interposing an exhaust valve between said fill valve and said test part;
(cc) closing said exhaust valve;
(dd) opening said fill valve, thereby permitting said test medium from said source to equalize with (i.e. vacuum or pressure) said test part;
(ee) obtaining a reading from said fill pressure transducer, comparing said reading to predetermined limits and proceeding with said leak tests only if said reading is within said limits;
(ff) closing said balance valve, thereby isolating said test part from said source;
(gg) introducing the balance delay time;
(hh) obtaining at least one differential pressure reading from said differential pressure transducer, wherein the steps of obtaining differential pressure readings include the steps of:
(a) providing a microcomputer system;
(b) providing a test program to operate said microcomputer system;
and
(c) utilizing said test program and said microcomputer system to obtain said differential pressure reading;
(ii) introducing a test delay time;
(jj) obtaining at least one additional differential pressure reading from said differential pressure transducer and proceeding with said leak test if said one additional reading is not beyond the range of said differential pressure transducer;
and
(kk) calculating the change in differential pressure between said additional differential pressure reading obtained after said test delay time, and said differential pressure reading obtained prior to said test delay time;
(f) utilizing said differential pressure and said change in differential pressure to determine if said test part is acceptable, or unacceptable, or whether the test was faulty.

19 more elements

A leak testing system including:

(a) means to provide a source of test medium at a predetermined desired pressure or vacuum;
(b) means to connect a test part to said source of test medium, said means to connect including a fill valve;
(c) means to isolate said test part from said source of test medium, said means to isolate including a balance valve;
(d) means to measure the differential pressure existing between said source of test medium and said test part, said means to measure including a differential pressure transducer;
(e) means to calculate the change in differential pressure while said test part is isolated, wherein said means to calculate the change in differential pressure while said test part is isolated include a microcomputer system connected to said fill valve, said bypass valve, and said differential pressure transducer to calculate the change in differential pressure while said test part is isolated;
and
(f) means to utilize said differential pressure measurement and said change in differential pressure to determine if said test part is acceptable, or unacceptable, or whether the test was faulty.

4 more elements

A method of testing a part for leakage, said method including the steps of:

(a) providing a source of test medium at a predetermined desired pressure or vacuum;
(b) connecting a test part to said source of test medium;
(c) momentarily isolating said test part from said source of test medium;
(d) measuring the differential pressure existing between said source of test medium and said test part;
(e) calculating a projected change in differential pressure while said test part is isolated;
and
(f) utilizing said projected change in differential pressure to determine if a test part is acceptable or unacceptable or whether the test conditions are invalid.

4 more elements

Apparatus for leak testing a part using a selected test medium from a selected source including:

(a) means for control;
(b) means for subjecting the part to a predetermined test medium pressure, said means for subjecting is connected to said means for control;
(c) means for isolating the part from the source of test medium pressure while continuing to subject the part to pressure, said means for isolating is connected to said means for control;
(d) means for sensing a selected pressure at the part being tested including electronic means for generating a digital representation of the sensed selected pressure, said means for sensing and said electronic means for generating are connected to said means for control;
(e) said means for control to cause said means for subjecting and said means for isolating to subject the part to be tested to the predetermined test medium then to isolate the part from the source of test medium and to cause said means for sensing and said means for generating to generate a digital representation of a first sensed selected pressure;
(f) means for storage connected to said control means to store the digital representation of the first sensed selected pressure,
(g) means to determine that a selected time interval has elapsed;
(h) said means for control to cause said means for sensing and said means for generating to generate a digital representation of a second sensed selected pressure when the selected time interval has passed;
(i) means for forming a difference, said means for forming connected to said means for control to form a difference between the digital representations of said first and second sensed selected pressures and to generate a selected binary representation of that difference;
and
(j) means for comparing connected to said means for control to compare said difference between the first and second sensed selected pressures to a predetermined value and to generate an electrical signal corresponding to the results of said comparison indicating acceptance or rejection of the part.

8 more elements

Dependencies are inferred from the claim text.