Throat and Mouthpiece Heaters
The mouth and throat heaters are clamped in close contact with the outside of the crucible throat to keep the metal at the operating temperature while being pumped from the crucible to the mold. The throat heater extends the full length of the pot throat and is held in close contact with it. The mouth heater is clamped tightly to the pot mouth. Both heaters are surrounded with heat insulating material and are held in close contact with the pot throat and mouth by a U-shaped clamp under the throat unit and a plate over the mouth unit, drawn tight by two nuts.
The mouth and throat heaters are always connected in “series,” one set being used for 100-volt to 125-volt and another set for 200-volt to 250-volt.
The heat for the throat and mouth units are controlled by a manually controlled rheostat moving from the left to the right, and fastened to the front of the control panel under and at the rear of the keyboard.
The rheostat is connected directly to the mouth and throat heater and is not controlled by the dynamic thermometer.
The crucible heaters are intended for heating the metal to the proper temperature, and the mouth and throat heaters are only intended to keep the metal at the proper temperature while being forced from the crucible to the mold.
If the voltage is irregular and remains too high for some time, or a speedy operator casts large slugs at a rapid rate continuously, the mouthpiece is apt to become heated and the slugs will have hollow backs. In this case it will be necessary to turn rheostat knob left-handed, but if the voltage remains low for some length of time, or a slow operator casts small slugs slowly, the mouthpiece may become cold and the slugs will have poor faces, in which case the rheostat knob should be turned right-handed.
When casting large slugs in rapid succession the mold is apt to become heated, but attempting to regulate the temperature of the metal in the crucible to overcome the heating of the mold will fail, because the electric pot is a heating unit only and will not cool the mold.
The control panel consists of a magnet switch mounted on a slate panel enclosed in a steel cabinet. The cabinet also has a suitable fuse cut-out and the switches which control both the pot and the electric motor (if used) and places all controls within easy reach of the operator. Connection is made between the pot proper, the dynamic thermometer, and the control panel by suitable wiring enclosed in a flexible conduit.