초록 ▼

A thermoforming apparatus includes a female die and a movable plug for thermoforming a softened thermoplastic resin sheet. The female die includes a rim forming recess in the shape of a bowl-shaped recess, communicating with a bottom opening and forming a bottom wall of the bowl, an outer wall, a bo

A thermoforming apparatus includes a female die and a movable plug for thermoforming a softened thermoplastic resin sheet. The female die includes a rim forming recess in the shape of a bowl-shaped recess, communicating with a bottom opening and forming a bottom wall of the bowl, an outer wall, a bottom wall and an inner wall of a rim of the bottom, and a bottom plate movable forward and backward relative to the rim forming recess. The softened thermoplastic resin sheet is thrust by the plug while the bottom plate is held at a first stop position. The thermoplastic resin sheet is brought into contact with an inner circumferential surface of the bowl-shaped recess and then the bottom plate is moved to a second stop position so that a rim is formed.

대표청구항 ▼

1. A method of thermoforming in which a thermoplastic resin sheet heated to be softened is brought into contact with an inner circumferential surface of thermoforming female die formed generally into a bowl-shaped recess, comprising the steps of:communicating a rim forming recess formed generally in

1. A method of thermoforming in which a thermoplastic resin sheet heated to be softened is brought into contact with an inner circumferential surface of thermoforming female die formed generally into a bowl-shaped recess, comprising the steps of:communicating a rim forming recess formed generally into a shape of a bowl-shaped recess with a bottom opening and forming a bottom wall of the bowl, an outer wall, a bottom wall and an inner wall of a rim of the bottom, wherein the rim forming recess includes a first portion spread outward so as to be continuous from the bowl bottom and a second portion continuous from the first portion and having a reduced inner diameter, the first and second portions forming the outer wall and the bottom wall; supporting a bottom plate inside the rim forming recess so that the bottom plate is moved forward and rear ward relative to the rim forming recess; bringing the thermoplastic resin sheet heated to be softened into contact with an inner circumferential surface of the bowl-shaped recess and immediately thereafter, moving the bottom plate to the second stop position so that a rim is formed; spreading the rim out from the bowl bottom opening and reducing its inner diameter to form a spread rim outer side wall surface and at the same time forming a bottom wall of the rim formed by a flat portion where the inner diameter is reduced; welding the rim inner wall surface turned up in the bowl bottom opening such that the rim forming recess has a generally triangular section and a cavity is formed inside the rim; and retreating the bottom plate to the first stop position.