BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to an undercut processing mechanism that is used in a state attached to a molding die assembly for forming a molded article having an undercut portion, a molding die assembly, and a molded article.

Description of Related Art

For a molding die assembly for forming a molded article having an undercut portion, various undercut processing mechanisms have been developed corresponding to forms of the undercut portions. For example, so called “loose core” is generally used as an undercut processing mechanism.

It has been difficult to mold some kind of molded articles by the use of an undercut processing mechanism utilizing a conventional loose core, for example, where a boss including a hollow portion projects in a direction intersecting a demolding direction of the entire body of the molded article. The applicant has proposed an undercut processing mechanism that allows a boss constituting an undercut portion to be easily demolded (see, for example, JP Laid-open Patent Publication No. 2010-155381).

The undercut processing mechanism described in JP Laid-open Patent Publication No. 2010-155381 includes: a holder provided in a fixed die (stationary die) or a movable die of a molding die assembly; and a mold core for forming an undercut portion, where the mold core includes a first core and a second core, and the first core and the second core have tilted side surfaces that are adjacent to each other. The undercut processing mechanism is configured to allow an undercut portion to be demolded by the first core and the second core sliding in the holder along the side surfaces.

According to the undercut processing mechanism described in JP Laid-open Patent Publication No. 2010-155381, it is made easier to form a molded article having a shape that is difficult to form by a conventional undercut processing mechanism using a loose core. In addition, a support rod, a guide rod, and the like become unnecessary, so that the undercut processing mechanism can be configured to be compact as compared to the conventional undercut processing mechanism using a loose core.

The present invention proposes: an undercut processing mechanism that has a structure different from that described in JP Laid-open Patent Publication No. 2010-155381, and that can make it easier to mold a molded article having an undercut portion, while downsizing the mechanism, and improving quality of the molded article; a molding die assembly; and a molded article.

An object of the present invention is to provide: an undercut processing mechanism that can be configured to be compact but can easily demold an undercut portion while improving quality of a molded article; a molding die assembly; and a molded article.

DISCLOSURE OF THE INVENTION

The present invention is directed to an undercut processing mechanism that is installed in a molding die assembly for forming a molded article having an undercut portion so as to allow demolding of the undercut portion, the undercut processing mechanism comprising: a pushing piece movable in a demolding direction of the molded article; a support element fixed to the pushing piece or formed so as to be integrated with the pushing piece and capable of supporting the undercut portion during movement of the pushing piece; a sliding piece configured to be slidable relative to the pushing piece and to move, in conjunction with movement of the pushing piece, in a direction intersecting the demolding direction of the molded article; and a retaining piece configured to retain the sliding piece such that the sliding piece is slidable, wherein the mechanism is configured such that when the pushing piece is moved in the demolding direction of the molded article, the sliding piece moves in conjunction with the pushing piece while the support element supports the undercut portion, so that the undercut portion is allowed to be demolded.

In the undercut processing mechanism, the pushing piece and the sliding piece may have molding surfaces for forming the undercut portion.

In the undercut processing mechanism, the pushing piece and/or the sliding piece is configured to be able to support the molded article when the pushing piece is moved in the demolding direction of the molded article.

In the undercut processing mechanism, the pushing piece and the retaining piece may each include restricting element for restricting a movement direction of the sliding piece to a direction in which the undercut portion is allowed to be demolded.

The undercut processing mechanism of the present invention may further includes: a molding member configured to form a hollow portion or a space portion of the undercut portion thereby enabling molding of the molded article having the hollow portion or the space portion in the undercut portion; and a molding member sliding piece fixed to the molding member or formed so as to be integrated with the molding member and configured to be slidable relative to the pushing piece and the retaining piece and to move such that the molding member is pulled out of the hollow portion or the space portion of the undercut portion when the pushing piece is moved in the demolding direction of the molded article.

The undercut processing mechanism may further include a holder fixed to the molding die assembly or formed so as to be integrated with the molding die assembly, and the holder may be configured such that, among components forming the undercut processing mechanism, other components excluding the holder are partially or fully housed in the holder in the time of die clamping.

The present invention is also directed to a molding die assembly including the undercut processing mechanism.

The present invention is also directed to a molded article formed by the undercut processing mechanism or the molding die assembly.

With the undercut processing mechanism and the molding die assembly of the present invention, the sliding piece moves in conjunction with movement of the pushing piece in the demolding direction of the molded article such that the undercut portion is allowed to be demolded. Thus, the undercut processing mechanism and the molding die assembly can be configured to be compact but allow the undercut portion to be easily demolded. In addition, since the undercut portion is supported by the support element during movement of the pushing piece and the sliding piece, damage to the undercut portion, etc., can be prevented, so that the molded article quality is improved.

