Abstract: A vacuum heat treating furnace includes a pressure vessel having a wall that defines a chamber wherein metal parts are vacuum heat treated. A fan is disposed inside the chamber for circulating a cooling gas therein. An electric motor is mounted externally to the pressure vessel for driving the fan. A drive shaft interconnects the fan and the electric motor through an opening in the wall of the pressure vessel. The vacuum furnace incorporates a dual seal for providing a vacuum-tight seal and a gas-tight seal where the drive shafts passes through the pressure vessel wall. The dual seal includes an inflatable seal surrounding the drive shaft for providing a vacuum-tight seal around said drive shaft when the furnace chamber is evacuated to a subatmospheric pressure.

Abstract: A hybrid furnace includes a vacuum furnace for heat treating a workpiece and a transportable oven removably attached to the vacuum furnace for holding the workpiece and maintaining it at an elevated temperature. The workpiece is transferred from the vacuum furnace to the transportable oven under an inert atmosphere to prevent the workpiece from being exposed to an oxidizing atmosphere or from undergoing a phase transition. The transportable oven is adapted to be detached from the vacuum furnace and transported to a work station for further processing of the workpiece. Heating means is provided in the transportable oven to maintain the temperature of the workpiece above a preselected warming temperature while the workpiece is waiting to be processed.

Abstract: A heat treating furnace has a hot zone enclosure with a substantially rectangular cross section. The floor of the hot zone enclosure is formed such that it is removable independently of the remainder of the hot zone enclosure. The heat treating furnace has a heating element with a novel support element that is readily mounted on and removed from the hot zone enclosure and which adjusts to accommodate a wide range of heating element thicknesses and insulation shield thicknesses. The electrically insulating components of the support element are formed to resist electrical shorting resulting from metallization and to resist cracking from thermally induced stress. The heat treating furnace further includes a cooling gas injection nozzle formed to reduce turbulence in the injected gas stream and to be readily attached to or removed from the hot zone enclosure.

Abstract: An electrode for a plasma carburizing furnace is disclosed which is adapted to provide a dynamic gas shroud for inhibiting the buildup of carbon soot on the insulating elements of the electrode. The reduction of carbon soot buildup on the insulating components dramatically reduces the frequency of electrical short-circuits across the insulating component, thereby increasing the availability of the furnace for processing of workpieces.

Abstract: A cooling system for a processing furnace provides improved cooling efficiency in a more compact arrangement than known furnace cooling systems. In the system a blower is situated within the cooling gas plenum but has its intake exterior thereto. The plenum wall and the furnace outer wall define a recirculation channel which is relatively large and free of obstructions. Heat exchanger coils are disposed within the recirculation channel adjacent the blower intake thereby providing a less restricted flow path for the cooling gas.

Abstract: A vent cap for a heat treating furnace provides bidirectional pressure relief. The cap is weighted and balanced over the furnace vent such that the vent is closed as long as the furnace has a slightly positive internal pressure. If the internal pressure exceeds a preselected upper limit the cap opens the vent to relieve the overpressure. The vent cap has a controlled inlet which opens to equalize the pressure differential if the internal pressure falls below a preselected lower limit below the ambient pressure outside the furnace. Such controlled equalization prevents the formation of undesirable combustible mixtures of air and treating gas in the furnace.

Abstract: A heat-insulating box houses a telemetry system of high accuracy for use within a high-temperature vacuum furnace. The container includes an inner box formed by a block of rigid heat-insulating material having a cavity which contains a telemetry system chassis and its components, including such items as batteries, transmitters, switches, thermocouple elements including transition tubes, isothermal double-layer terminal strips, and the like. A plurality of very fine thermocouple conductors of dissimilar metal extend from the thermocouple junction tips on work pieces outside of the box through the heat-insulating inner block to the thermocouple transition tubes, and then, by way of the isothermal double-layer terminal strip to the transmitters. An antenna lead is carried through the wall of the box to a transmitting antenna mounted on the front wall of the box. Pressure switches in the cavity within the box control the ON-OFF condition of the transmitters.

Abstract: The electric resistance heating elements of a heat treating furnace are suspended within a work chamber by hanger rods threaded into nuts which are welded to the inside of the outer wall of the chamber to avoid the need for forming holes through the outer wall. Spacers are supported by adjacent hanger rods and hold thin radiation shields in spaced relation over the entire span extending from rod-to-rod.

Abstract: A heat treating furnace in which an electrical resistance heating element is disposed in a chamber and is energized by way of a power feed through conductor which extends slidably through the wall of the furnace. An insulating washer and a retaining washer may be installed on and removed from the inner end portion of the feed through conductor from inside the furnace without either removing the conductor from the furnace wall or disconnecting the conductor from the heating element. A power terminal block and inlet and outlet lines for cooling water are adapted to be quickly and easily disconnected from the outer end portion of the feed through conductor to permit the conductor to be easily pulled inwardly through the furnace wall for servicing.

Abstract: A nozzle for delivering cooling gas into the work chamber of a heat treating furnace. The nozzle is formed by a resiliently yieldable metal tube having an overlapping seam and adapted to be contracted radially for insertion through a hole in the wall of the work chamber. After being inserted through the hole, the tube springs outwardly into frictional engagement with the edge of the hole to retain itself in place. Flares on the ends of the tube prevent the tube from shifting endwise relative to the chamber wall.

Abstract: A heat treating furnace having a work chamber of circular cross-section and having banks of electric resistance heating elements formed by rigid and elongated graphite bars. The graphite bars of each bank are interconnected so as to form an octagon located closely adjacent the circular wall of the work chamber and closely approximating the circular shape of the chamber. As a result of the octagonal arrangement, ring-like banks of rigid graphite elements may be space longitudinally along the circular work chamber to enable front-to-rear temperature trim zones to be established in the chamber.