Abstract: A furnace includes an enclosure and a hearth plate within the enclosure for supporting combustible material. The furnace further includes a first heater element adjacent the hearth plate for initial combustion of the combustible material, a filter disposed above the hearth plate for filtering uncombusted products of combustion of the combustible material, and a second heater element adjacent the filter for final combustion of the uncombusted products of combustion filtered by the filter. A filter bypass path has an inlet located in a lower portion of the enclosure and an outlet located between the filter and the second heater.

Abstract: An electrically operated device and fastener assembly for establishing an electrical and mechanical connection on the device. The fastener assembly generally includes a fastener and a washer which may be permanently flattened against the device to establish an electrical connection to a piece of coated metal. Upon removal of the fastener, the washer remains permanently flattened against the device or piece of metal and mechanically connected thereto by a build-up of coating material on projections associated with the washer. Fastener assemblies may be constructed using, for example, sheet metal screws requiring only one of the washers in the assembly or machine screws which may require two of the washers.