Device for processing workpieces

A device for processing a workpiece using ultrasound, the device comprising:

• a resonant system having an input, an ultrasound generator communicating with said input, an ultrasound sonotrode communicating with said ultrasound generator an anvil and an output, wherein the workpiece is processed between said anvil and said ultrasound sonotrode;
• a feedback signal path communicating with said resonant system output to transmit a feedback signal;
• a regulation means having a regulation member, said regulation means having an input receiving said feedback signal and an output emitting a regulation signal;
• connecting means having a first input communicating with said output of said regulation means for receiving said regulation signal and an output communicating with said input of said resonant system, said connecting means also having a second input, wherein said resonant system, said feedback signal path, said regulation means and said connecting means are connected together in series within a closed feedback resonant circuit;
• and
• means for generating a process variable signal in response to processing of the workpiece and in dependence on a processing procedure, said process variable signal being extracted outside of said resonant system and being substantially insensitive to high frequency fluctuations of mechanical and electrical variables within said resonant system, said processing variable generating means having an output from which said process variable signal is passed to said second input of said connecting means, wherein said process variable signal and said regulation signal thereby enter said connecting means in parallel, said connecting means then combining said process variable and said regulation variable to generate a modified regulation variable which is passed from said connecting means output to said resonant system input, thereby preventing or damping feedback related oscillations thereof.