Control apparatus for producing uniform thickness corrugated tubing

Apparatus for producing thermoplastic corrugated tubing having a substantially uniform thickness throughout comprising an extruder forming a hollow smooth-walled extrudate, corrugating means immediately adjacent the extruder arranged to receive the extrudate and to form corrugations therein, the corrugating means including continuously moving cooperating mold blocks configured to form alternating annular peak portions, valley portions and interconnecting side wall portions in the extrudate, and blow means urging the extrudate into intimate engagement with the configured mold blocks, motivating means for selectively moving the corrugating means relative to the extruder along the line of travel of the tubing, and timing means connected to the motivating means arranged to cause the extruder and the corrugating means to slightly move away from one another during formation of the annular valley portions and to slightly move toward one another during formation of the annular peak and interconnecting side wall portions.