Forming undercut on thermoplastic moulding esp. window glazing - by elastic strips or tubes removably mounted on moulding die

摘要

Prodn. of thermoplastics mouldings possessing an undercut or back cut utilises normal shaping moulds for modifying thermoplastics plates. The thermoplastics is shaped, while in the softening range, by a shaping plunger or die on which one or more elastic strips are applied, extending around the die at the level of the desired undercut. These strips may opt. be hollow tubes inflated through a valve and subsequently deflated. Pref. after the undercut has been formed, the strips are removed from the plunger or die and it is separated from the mould and the moulded object. Used partic. for forming through-shaped depressions or grooves, for example in a conical semil finished product. Typical examples include double-walled plastics glazing in skylights, automobile windows, railway carriage windows. The elastic strips or tubes are of silicone rubbers.