Film winding core, and wound film body using same

Abstract

A film winding core (10) of the present invention includes a core body (12) and a plurality of film supporting portions (14). The core body (12) has a tubular shape. The plurality of film supporting portions (14) are provided around the core body (12). The film supporting portions (14) protrude from the outer peripheral surface (12p) of the core body (12) respectively at a plurality of positions in a rotational direction of the core body (12) so that a film (18) is supported away from the outer peripheral surface (12p) of the core body (12). Each of the film supporting portions (14) is made of a material that can be deformed when the film (18) is wound on the film winding core (10).

Description

TECHNICAL FIELD[0001]The present invention relates to a film winding core and a wound film body using the core.BACKGROUND ART[0002]A long film is produced by a known method such as extrusion molding and wound on a cylindrical core for storage and shipment. The film thus wound on the cylindrical core is distorted (deformed) during storage, which may cause difficulties in unwinding the film. For example, Patent Literature 1 points out such a problem.[0003]Patent Literature 1 describes a core configured to prevent the distortion of a belt-like article resulting from the contraction of the wound article. Specifically, after the belt-like article is wound on the core in close contact with the outer periphery of the core, the core is contracted in the radial direction thereof. Then, after the core is expanded in the radial direction to increase the contact between the outer periphery of the core and the belt-like article, the belt-like article is unwound from the core.CITATION LISTPatent ...

AI Technical Summary

Benefits of technology

[0009]To the inventors' knowledge, a film is distorted based on the following mechanism. Depending on the production method of the film, a long film has not a little thickness unevenness (variations in the thickness) in a width direction. When such a film is wound on a conventional cylindrical core, a thick portion of the film expands outward more than a thin portion thereof. Then, tension is concentrated on the thick portion, and the thick portion is stretched in the longitudinal direction. On the other hand, sufficient tension is not applied to the thin portion, and so-called “gapping” occurs in some cases. “Gapping” refers to the formation of a gap between the inner layer and the outer layer of the wound film. In the case where the film is wound on the core and then the wound film is stored in a temperature environment in which the film contracts, a gapped portion of the film contracts in the longitudinal direction to eliminate the gap. As a result, distortion between the thick portion and the thin portion increases. This makes a difference in the longitudinal length between the thick portion and the thin portion.

[0010]This distortion is memorized in the film. Therefore, the film is unwound from the core while keeping the distortion. Then, sufficient tension is not applied to the thick portion, which causes a slack in the thick portion. This phenomenon is most obvious when the tension applied to the film is not high enough to unwind the film. The slack in the film causes errors in feeding the film, and reduces the yield of film-related products and the availability of the film.

[0011]According to the present invention, the plurality of film supporting portions are provided around the core body. Since the film supporting portions protrude from the outer peripheral surface of the core body, the film is supported by the film supporting portions. Therefore, it is possible to prevent the film from coming into close contact with the core body between two film supporting portions that are adjacent to each other in the rotational direction. Thus, it is possible to prevent as much as possible the distortion from being memorized in the film. In addition, the film supporting portions are made of a material that can be deformed when the film is wound. The deformation of the film supporting portions can alleviate or offset the influence of the uneven thickness of the film.

[0012]As described above, according to the core of the present invention, the distortion caused by the uneven thickness can be suppressed. Therefore, the bend or slack in the film can be prevented during unwinding of the film. As a result, stable feeding of the film can be achieved during unwinding thereof, and thus the incidence of manufacturing defects (feeding errors) can be reduced significantly. The yield of film-related products and the availability of the film are also improved.

Problems solved by technology

The film thus wound on the cylindrical core is distorted (deformed) during storage, which may cause difficulties in unwinding the film.

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