Patent ID: 7037393

Claim:
A method of constructing a desiccant pot by trapping a low density membrane of spun bonded plastics between opposed touching surfaces of two separate parts constituting the pot lid and the pot body, these two separate parts being made of high density plastic, and then fusing the membrane and the separate parts together by ultrasonic welding,wherein one of the separate parts is provided with a fine protuberance in the form of one or more ridges or points extending from its touching surface towards the touching surface of the other separate part to space the touching surfaces slightly apart, and pressing the two parts together with the membrane trapped between the touching surfaces so that the membrane is compressed at the point of contact with the protuberance thereby increasing its density at the point such that, at the time of ultrasonic welding, the protuberance acts as an energy directing protrusion, and the ultrasonic vibrations pass from the protuberance on the one part through the membrane at the point where it is compressed to increase its density to the other part.