Parison
The heart of blow molding is the perform. Generally in blow molding a hollow perform is formed by injection molding, compression molding or extrusion. This so-called prestructure is transferred to a blowing station where it is expanded by internal gas pressure. This perform may be transferred and blown in the softened state directly from the forming stage or it may be cooled, transferred to an intermediate storage place and later heated and, finally blown to form the final structure. (RDC 8/26/2011)
A sealed tube of molten material ( a "parison") is formed by extrusion or injection molding and placed between the mold halves. The mold is closed and fluid or gas under pressure is then introduced into the tube, forcing the molten tube against the cavity walls. The pressure is maintained until the molten material cools and solidifies. The pressure is then released, the mold halves are pulled apart, and the hardened article ejected. Scott and Naeve, US Patent 7,727,455 (6/1/2010)
Recent US Patents
9/13/2011
8,016,587
Stretch rod, apparatus and method for producing hollow bodies
Schuster and Knapp of Krones, Germany, developed a stretch rod used for forming a preform into a hollow body having in its surface bumps or dips for contacting the expanding cylinder. (RDC 9/14/2011)
2/15/2011
7,887,320
Auxiliary device and method for finishing preforms
Bock of Netstal-Maschinen, Switzerland, developed an auxiliary device for finishing and calibrating preforms that are removed from a multiple tool in an unstable shape. The calibration process involves compressed air immediately after removing and withdrawing the preforms from the multiple tool. Nipples that can be inserted into the preforms are provided with expandable press rings or sealing rings in order to seal the interior of the blow-molded part of the preforms. The compressed air is introduced via the nipples, the sealing process being performed by radially expanding the press rings or sealing rings in analogy to the closing process of thermoses, thus protecting the preforms from adverse forces. The sealing point can be randomly selected in the transition zone from the threaded part to the blow-molded part of the preforms. The interior of the blow-molded part is optimally sealed without affecting the form stability and dimensional stability of the preforms. (RDC 8/25/2011)
7,887,319
Apparatus for cooling preformed articles and method of cooling preformed articles
Takatomi et al of Toyo Seikan Kaisha, Japan, have developed an apparatus for cooling preformed articles while suppressing or preventing the damage to the preformed articles. A sprayof a cooling liquid and gas is blown onto the preformed articles passing through a cooling chamber. (RDC 8/25/2011)