Apparatus and method for heat treating a plastic tube

摘要

An apparatus for heat-treating a tube of a synthetic organic thermoplastic polymer (which tube may subsequently be converted into a tubular film), by passage of the tube in a continuous manner through a heated liquid bath, comprises a tank for the bath, a guide sleeve extending through a wall of the tank into its interior, through which sleeve the tube can pass from the interior of the tank to the outside thereof, and means for moving at least the interior end of the sleeve between positions lying above and below a predetermined position in the tank corresponding, when in use, to the surface of the liquid in the tank. As shown in Figs. 1 and 2, a guide sleeve 1 is rigidly connected to a plate 2 which can be slid between an end wall 4 of the tank and a cover plate 5 and is provided with fixed guides 3. When starting the heat-treating operation, the sliding plate 2 is moved to its top position manually or by means of a servomotor, the guide sleeve 1 being thereby raised to a position above the surface of the liquid. The tube to be treated can now be passed through the sleeve 1 from the interior of the tank to the outside without the bath liquid flowing out. The tube is then inflated by the introduction of air or other gas into its interior sufficiently to cause the tube to press against the inner wall of the guide sleeve and the plate 2 is then moved to its bottom position against the stop 7, in order to submerge the tube in the bath liquid. The tube can now be drawn continuously through the bath and out through the sleeve without leakage of bath liquid from the tank. If the tube should burst in the tank or during further treatment after it has been withdrawn from the tank, the sliding plate is moved to its top position, thus preventing escape of the bath liquid from the tank. This movement of the plate is preferably effected automatically, as by means of a relay-controlled servomotor, when the gas pressure in the tube is released due to the bursting of the tube. As shown in Figs. 3 and 4, the guide sleeve 1 is mounted eccentrically in a circular plate 2 which can be rotated about its centre by a lever 8 and constitutes a wall of the tank. The edge of the plate moves in the annular channel formed by the flange 4 and the fixed annular members 3 and 5. Alternatively, as shown in Fig. 5, the sleeve may be centrally mounted in the plate and the portion of it within the tank may be curved. As shown in Fig. 6, the middle portion of the guide sleeve is flexible, thus allowing the rigid interior end portion 1 of the sleeve to be raised and lowered by means of a rod 9 which can be moved vertically by means of a relay-controlled geared motor 10.