Process for welding thermoplastic by injection

Claim 1

A process for welding a crack or junction line in a workpiece formed of thermoplastic material using a dispensing device comprising a barrel forming an internal chamber and having a nozzle forming a restrictive orifice outlet in its tip, said tip having a thickness greater than that of the crack or junction line, said device comprising means for forcing filler plastic into the chamber, and means for heating the barrel including its nozzle tip, comprising: (a) filling the chamber with filler plastic; (b) heating the chamber contents and nozzle sufficiently to render molten the plastic in the chamber and to render molten the workpiece plastic immediately adjacent the crack or junction line at the nozzle tip when the tip is applied thereto; (c) penetrating the hot nozzle tip into the workpiece at the crack or junction line to render molten said adjacent workpiece plastic and submerge the tip therein and simultaneously feeding additional filler plastic into the chamber at a rate sufficient to cause molten filler plastic to be injected at high pressure through the orifice outlet of the submerged tip into the molten workpiece plastic, to fuse therewith; and (d) drawing the tip along the crack or junction line while maintaining the steps and conditions of paragraph (c), to effect the weld.