초록 ▼

The present invention concerns an apparatus and method for thermoforming a plastic article from a sheet of plastic material heated to a predetermined forming temperature. The apparatus includes a mold having forming surfaces defining a forming cavity generally conforming to the shape of the plastic

The present invention concerns an apparatus and method for thermoforming a plastic article from a sheet of plastic material heated to a predetermined forming temperature. The apparatus includes a mold having forming surfaces defining a forming cavity generally conforming to the shape of the plastic article to be formed. The heated plastic sheet is urged into contact with the forming surfaces of the mold to form the plastic article. The mold includes at least one undercut forming element moveable between an advanced position wherein the element projects into the forming cavity to form an undercut portion in the plastic article and a retracted position wherein the element is withdrawn from the forming cavity to enable the formed plastic article to be removed from the forming cavity. After the plastic article has been formed, the undercut forming element is moved to the retracted position and a stripper plate is utilized to remove the formed plastic article from the forming cavity. In the preferred embodiment of the invention, the undercut forming element is retracted simultaneously with the stripping movement of the stripper plate to minimize the cycle time associated with producing the plastic article.

대표청구항 ▼

A method of forming a plastic article from a sheet of plastic material heated to a predetermined forming temperature, comprising the steps of: (a) providing a first mold section having forming surfaces defining a forming cavity, the first mold section including at least one undercut forming element

A method of forming a plastic article from a sheet of plastic material heated to a predetermined forming temperature, comprising the steps of: (a) providing a first mold section having forming surfaces defining a forming cavity, the first mold section including at least one undercut forming element movable between an advanced position wherein the forming element projects into the forming cavity to form an undercut portion in the plastic article and a retracted position wherein the forming element is withdrawn from the forming cavity to enable the formed plastic article to be removed from the forming cavity; (b) moving a second mold section along a forming axis in one direction to urge at least a portion of the heated plastic sheet into the forming cavity of the first mold section to form the plastic article while the undercut forming element is in the advanced position; (c) moving a stripper plate a first predetermined distance along the forming axis in an opposite direction for partially removing the formed plastic article from the forming cavity by moving the formed plastic article a first predetermined distance in an opposite direction along the forming axis relative to the forming cavity; (d) simultaneously with step (c), operating a retracting mechanism to move the undercut forming element to the retracted position as the formed plastic article is moved the first predetrmined distance, the undercut forming element moving with the stripper plate in an opposite direction along the forming axis as the stripper plate travels a first predetermined distance such that the stripper plate, the undercut forming element, and the plastic article are all simultaneously moved in an opposite direction along the forming axis for the first predetermined distance; and (e) subsequent to steps (c) and (d), moving the second mold section with the plastic article a second predetermined distance away from the first mold section along the forming axis in an opposite direction relative to both the forming cavity and the undercut forming element to remove the formed plastic article from the forming cavity.