APPARATUS FOR INJECTING AIR OR GAS INTO A BLOWER FILM BUBBLE

摘要

To maintain an air or gas bubble forming in a moving tube of plastics material between pairs of squeeze rollers, an air or gas injecting needle is mounted to pivot substantially in a plane containing centreline of the tube. The needle pierces the tube wall of the bubble when in one rotary position, moves with the tube while pivoting through an arc depending on the depth of needle penetration and is withdrawn from the bubble in a second rotary position.