After doing a little more patent digging I found that 2891180 is a vibration mount and is not the earliest such device The method for ultrasonic welding seems to be first mentioned in 2 522 082 in Feb 1945 Raytheon has a patent for a general vibration device 2 651 148 from Nov 1949 which they claim can be used for bonding plastics and other materials by localized heating among other things The first patent to use ultrasonic welding with respect to metals was Aeroprojects Sonobond in April 1956 but they do not seem to be the first to pioneer this process in any other regard I will continue to read up on patent searches and let you know how it goes 128 180 55 169