| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for detecting prestretch blow height and a method for setting prestretch blow height in a method for pressure forming by which the prestretch blow height can be surely detected and set. SOLUTION: When the neighborhood of the top of a prestretch-blown resin material 2 reaches the underside of a hole 8 and the hole 8 is closed with the resin material 2, pressure in a pipeline 9 is elevated. Then, change in the pressure is detected by means of a pressure sensor 10 and a valve 5 is closed through a control part 11 based on this detection and the prestretch blow is stopped. In addition, air may not be preferably fed to the pipeline 9. Furthermore, it may be preferable that timer action for a specified time is performed by the control part 11 in such a way that stopping of the prestretch blow is performed at a specified time a little later after the change in pressure is detected by means of the pressure sensor 10. Then, when the prestretch blow is stopped, a servo motor 12 is actuated by the control part 11 to control lowering of a mold 7. Elevating, lowering and stopping of the mold 7, opening and closing of the valve 5 and feeding/unfeeding of air into the pipeline 9 are controlled by a control signal from the control part 11.
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