Method and apparatus for acoustic testing of armatures

Apparatus for testing the quality of a fused joint between a commutator tang and a commutator bar in a commutator of an armature of a dynamoelectric machine, said commutator bar having first and second opposed substantially parallel commutator bar surfaces, said tang having first and second opposed substantially parallel tang surfaces, said fused joint being formed between said first commutator bar surface and said first tang surface without melting any of said surfaces, said apparatus comprising:

• an acoustic beam emitter for directing an acoustic beam comprising at least one pulse toward a portion of said second tang surface along an axis substantially perpendicular to said portion of said second tang surface, at least a portion of each said pulse passing through said tang and reflecting off one or more gaps formed during fusing, said gaps being between said first commutator bar surface and said first tang surface at said joint;
• an acoustic receiver for measuring said reflected portion of each of said at least one pulse to determine a reflected amplitude of each of said at least one pulse;
• and
• an analysis unit for deriving from said reflected amplitude an indication of the quality of said joint, said quality of said joint being representative of the quantity and size of said gaps.

In a manufacturing line for dynamoelectric machine armatures, an armature testing station for testing the quality of a fused joint between a commutator tang and a commutator bar in a commutator of an armature, said commutator bar having first and second opposed substantially parallel commutator bar surfaces, said tang having first and second opposed substantially parallel tang surfaces, said fused joint being formed between said first commutator bar surface and said first tang surface without melting any of said surfaces, said armature testing station comprising:

• an acoustic beam emitter for directing an acoustic beam comprising at least one acoustic pulse toward a portion of said second tang surface along an axis substantially perpendicular to said portion of said second tang surface, at least a portion of said at least one pulse passing through said tang and reflecting off one or more gaps formed during fusing, said gaps being between said first commutator bar surface and said first tang surface at said joint;
• an acoustic receiver for measuring said reflected portion of each of said at least one pulse to determine a reflected amplitude of said pulse;
• and
• an analysis unit for deriving from said reflected amplitude an indication of the quality of said joint, said quality of said joint being representative of the quantity and size of said gaps.

A method for testing the quality of a plurality of fused joints of a commutator of an armature of a dynamoelectric machine in succession, each of said fused joints being between a commutator tang and a commutator bar of said commutator, said armature having a longitudinal axis and being gripped by a gripper, said joints being disposed circumferentially around said longitudinal axis of said armature, each of said commutator bars having first and second opposed substantially parallel commutator bar surfaces, each of said tangs having first and second opposed substantially parallel tang surfaces, each of said fused joints being formed between each of said first commutator bar surfaces and each of said first tang surfaces without melting any of said surfaces, said method comprising:

• directing an acoustic beam comprising a plurality of pulses from said emitter substantially perpendicular to and substantially toward said longitudinal axis of said armature, at least a portion of one of said plurality of pulses passing through one of said second tang surfaces and reflecting off one or more gaps formed during fusing, said gaps being between said first commutator bar surface and said first tang surface at one of said joints;
• rotating said armature around said longitudinal axis of said armature;
• measuring said reflected portion of said pulse for each of said joints during said rotating to determine a reflected amplitude profile, said profile having a plurality of maxima;
• correlating each of said profile maxima with each of said fused joints;
• comparing each of said profile maxima with a predetermined threshold amplitude;
• characterizing each of said correlated joints as unacceptable if said correlated profile maximum exceeds said threshold amplitude.

Apparatus for testing the quality of a plurality of fused joints of a commutator of an armature of a dynamoelectric machine in succession, each of said fused joints being between a commutator tang and a commutator bar of said commutator, said armature having a longitudinal axis, said joints being disposed circumferentially around said longitudinal axis of said armature, each of said commutator bars having first and second opposed substantially parallel commutator bar surfaces, each of said tangs having first and second opposed substantially parallel tang surfaces, each of said fused joints being formed between each of said first commutator bar surfaces and each of said first tang surfaces without melting any of said surfaces, said apparatus comprising:

• an acoustic beam emitter for directing an acoustic beam comprising a plurality of pulses from said emitter substantially perpendicular to and substantially toward said longitudinal axis of said armature, at least a portion of one of said pulses passing through one of said second tang surfaces and reflecting off one or more gaps formed during fusing, said gaps being between said first commutator bar surface and said first tang surface at one of said joints;
• a gripper for gripping said armature and for rotating said armature around said longitudinal axis of said armature;
• an acoustic receiver for measuring said reflected portion of said pulse for each of said joints during said rotating to determine a reflected amplitude profile, said profile having a plurality of maxima;
• an analysis unit for correlating each of said profile maxima with each of said fused joints, comparing each of said profile maxima with a predetermined threshold amplitude, and characterizing each of said correlated joints as unacceptable if said correlated profile maximum exceeds said threshold amplitude.

A method for testing the quality of a fused joint between a commutator tang and a commutator bar in a commutator of an armature of a dynamoelectric machine, said commutator bar having first and second opposed substantially parallel commutator bar surfaces, said tang having first and second opposed substantially parallel tang surfaces, said fused joint being formed between said first commutator bar surface and said first tang surface without melting any of said surfaces, said method comprising:

• directing an acoustic beam comprising at least one pulse having a frequency of about 20 MegaHertz toward said second tang surface along an axis substantially perpendicular to said second tang surface, at least a portion of said pulse passing through said tang and reflecting off one or more gaps formed during fusing, said gaps being between said first commutator bar surface and said first tang surface at said joint;
• measuring said reflected portion of said pulse to determine a reflected amplitude;
• comparing said reflected amplitude to a predetermined threshold amplitude;
• and
• characterizing said joint as having at least one gap having a depth greater than about 0.005 mm in a direction perpendicular to the plane of the joint if said reflected amplitude exceeds said threshold amplitude.