Process of producing a foamed plastic insulated conductor and an apparatus therefor

An apparatus for producing a foamed plastic insulated conductor comprising a gas injecting extruder to extrude a foamed resin insulation on a conductor wire travelling through a head thereof so as to cover said conductor wire with said foamed resin insulation;

• a gas flow rate regulator to determine a flow rate of a foaming gas to be injected into a molten resin in said gas foaming extruder;
• cooling trough means to cool said foamed insulation on said conductor wire, said cooling trough means including a movable trough which is movable axially of said foamed plastic insulated conductor toward and away from said head of said gas injecting extruder;
• a capacitance monitor to detect a value of a capacitance of said cooled and foamed plastic insulated conductor to be compared with a given or specified value thereof;
• and trough position adjusting means to adjust the position of said movable trough so as to eliminate a difference between said detected value and said given or specified one of said capacitance of said foamed plastic insulated conductor, characterized by further comprising trough position detecting means to electrically detect the positions of said movable trough adjacent to limit positions of the range of movement thereof;
• a gas flow rate regulator adjusting means to adjust said flow rate of said foaming gas to another value in accordance with an electrical signal from said trough position detecting means;
• and timer means to stop the adjustment of said gas flow rate regulator for a setting time after the adjustment of said gas flow rate regulator is completed.