Internally coating plastics or similar thin tube - involves maintaining liquid column at constant level inside ascending tube length

摘要

A method of maintaining constant the level of coating liquid inside a continuously moving tube of plastics or similar material is used for a vertical length of tube travelling upwards along its own axis. A rhythmical cycle of pressure is applied to the sides of the tube comprising three stages: (1) opposite sides of the tube are squeezed inwards towards its axis with a simultaneous forward movement in the same direction as the tube; (2) when the sides have been pressed together, the forward movement is continued, the sides being kept squeezed together; (3) the squeezing pressure is released while the forward movement of the pressure point still continues to travel with the tube. Used esp. for coating cellulsoe hydrate tubes. Process results in uniform application of drying heat to the coated.