US Patent 7215358 Motor-less automatic extraction device surveiling inside of furnaces

The present invention relates to a motor-less automatic retraction device that can insert a vision tube capable of monitoring the inside of a furnace to mange the internal state of the furnace and control the temperature of the furnace into the furnace and retract the vision tube from the furnace in a motor-less manner. A conventional retraction device is disadvantageous in that it is expensive, voluminous, difficult to install, thus requiring expert's help to install, and difficult to repair at the time of breakdown, and requires expensive repairing costs.