Patent ID: 7431896

Claim:
A method for making an exhaust treatment device, comprising: providing a housing assembly including an inner housing supporting an exhaust treatment device therein, and an outer housing enclosing the inner housing and defining an insulation cavity therebetween; providing an end cover adapted to mate with and enclose one end of the insulation cavity; mounting a temperature-activated variable insulation device on an interior side of the end cover for communication with the insulation cavity; applying solder to those portions of the end cover which mate with and abut the housing assembly to enclose the one end of the insulation cavity; providing an airtight chamber with an interior adapted to receive the housing assembly and the end cover therein; positioning a first heater adjacent a first portion of the chamber to heat the housing assembly when the same is positioned in the chamber; positioning a second heater a spaced apart distance from the first heater to heat the end cover when the same is positioned in the chamber; opening the chamber to access the interior thereof; positioning the housing assembly in the chamber at a location therein adjacent the first heater; positioning the end cover in the chamber at a location spaced apart from the housing assembly and the first heater; activating the first heater to heat the insulation cavity of the housing assembly to a predetermined bake-out temperature sufficient to drive off undesirable residue and gases from the insulation cavity, yet maintain the end cover at a temperature below the activation temperature of the variable insulation device to avoid premature activation of the same; drawing at least a partial vacuum in the chamber to create a predetermined vacuum in the insulation cavity for reduced heat transfer between the inner housing and outer housing; shifting the end cover into an abutting aligned relationship with the housing assembly, such that the solder on the mating portions of the end cover contacts the one end of the housing assembly; activating the second heater to melt the solder and fuse together the housing assembly and the end cover to define an exhaust treatment device; deactivating the first and second heaters; cooling the housing assembly and the end cover to a temperature sufficient to solidify the solder, and thereby form an airtight seal between the housing assembly and the end cover; and opening the chamber, and removing the exhaust treatment device from the chamber.