Plastic case having improved ultrasonic welds between halves thereof and method for producing same

A method for producing a plastic case comprising the steps of:

• providing two case halves, one of said case halves having a projection formed thereon, and the other of said case halves having a recess formed for receiving a distal face of said projection, said projection having a diameter slightly greater than the diameter of said recess, a gap being formed between the bottom of said recess and an end face of said distal face of said projection when said projection is inserted into said recess defining an internal space, and at least one air hole is provided in at least one of said projection and recess communicating with said internal space;
• assembling said two case halves with said distal face of said projection received in and abutting said recess;
• applying ultrasonic vibration energy to abutting portions of said projection and recess to weld said projection to said recess;
• and
• simultaneously with said step of applying ultrasonic vibration energy, applying suction to said air hole to apply suction to said internal space to thereby draw out through said air hole particulate material formed during welding of said projection and recess.