Patent ID: 8092631

Claim:
An apparatus for welding a first plastic sheet to a second plastic sheet, the apparatus comprising: a) a die comprising an elongate body made of a conductive material which extends between opposed first and second ends, a welding face for engaging the first plastic sheet, and a die channel extending longitudinally along the welding face between the first and second ends, the die channel having a depth, the die channel being open at the first and second ends, and the die further comprising a thinned portion at one of the first and second ends, the thinned portion being formed by a widening of the die channel; b) a plate made of a conductive material comprising a welding face for engaging the second plastic sheet, wherein the die and the plate are operable to compress the first and second plastic sheets in an overlapping arrangement between their respective welding faces; c) a high frequency alternating current generating means for generating a high-frequency alternating electromagnetic field between the die and the plate, wherein the high-frequency alternating electromagnetic field and the compression of the first and second plastic sheets are operable to weld the first and second plastic sheets to one another; and wherein the depth of the die channel prevents the formation of an electromagnetic field that is strong enough to weld the first and second plastic sheets in an area between the die channel and the plate.