SADDLE CURVED-SURFACE TRANSITION-BASED STEPLESS BIDIRECTIONAL STRETCHING METHOD AND DEVICE FOR FILM

摘要

Disclosed are a saddle curved-surface transition-based stepless bidirectional stretching method and device for a film. A film is smoothly transited from a narrow plane to a saddle curved-surface and to a wide plane in a three-dimensional space by means of a transversely-stretching force and a longitudinally-stretching force that act on different tangent planes in a bidirectionally-stretching process of a curved surface of the film, and the thickness uniformity of the bidirectionally-stretched film is adjusted and controlled by controlling the shape of the saddle curved-surface. The device comprises a herringbone wheel unit and a parallel wheel unit. An adjustable included angle is formed between two transversely-stretching wheels in the herringbone wheel unit. Two longitudinally-stretching wheels in the parallel wheel unit are disposed in parallel. The film is transversely stretched under the driving of the rotation of the transversely-stretching wheels and is longitudinally stretched by means of a linear velocity differences between the transversely-stretching wheels and the longitudinally-stretching wheels. In the present invention, by using a bound wheel structure, a bowing phenomenon is effectively adjusted and controlled by means of the saddle curved-surface; in addition, the contact surface between the film and a stretching element is reduced, and the damage to surface performance caused by frictions is avoided, which helps to improve the thickness uniformity of a film product.