Patent ID: 6036796
Filing Date: 2000-03-14
Classification: B06B,B23K,B29C

Abstract:
The method of ultrasonically welding thermoplastic sheet material comprising:feeding the material to be welded through a weld station comprising an anvil and an oppositely disposed horn rendered resonant at an ultrasonic frequency for coupling ultrasonic energy into the material as the material is fed through said station between said horn and anvil, and providing a force for urging said anvil and horn toward mutual engagement for causing said horn to be in forced engagement with the material;providing a first signal commensurate with a predetermined energy density to be present in the material when welded at said station, a second signal responsive to the feed speed of the material through said station, and a third signal responsive to the ultrasonic power coupled by said horn to the material;processing said first, second and third signals by multiplying said first signal by said second signal to cause a multiplication product signal; subtracting said third signal from said multiplication product signal to produce an error signal, and processing said error signal in a proportional-integration circuit for minimizing the loop and steady-state errors of said error signal, whereby to obtain a control signal; andusing said control signal for controlling the ultrasonic power coupled by said horn to the material for causing the energy density in the material to be commensurate with said first signal.