An injection molding machine for simultaneously injection molding a plurality of articles each made of plural polymeric materials. The injection molding machine includes a source of a first polymeric material and a source of a second polymeric material. The injection molding machine also includes a plurality of co-injection nozzles, each of the nozzles has an associated injection cavity mold. Each of the nozzles also has a first flow channel for providing a stream of said first polymeric material to said mold and a second flow channel for providing a stream of said second polymeric material to said mold. The machine further includes a manifold for feeding the polymeric materials from their sources to each of the nozzles and each of the associated molds, such that each of the streams of the first polymeric materials flows from each nozzles into each associated mold simultaneously and each of the streams of the second polymeric materials flows from each nozzle into each associated mold simultaneously.
This application is a continuation of Ser. No. 08/657,622, filed May 29, 1996, now U.S. Pat. No. 5,853,772, which is a continuation of Ser. No. 08/341,700, filed Nov. 18, 1994, now U.S. Pat. No. 5,523,045, which is a continuation of Ser. No. 07/740,749 filed Aug. 5, 1991, now abandoned, which is a continuation of Ser. No. 07/563,169, filed Aug. 3, 1990, now U.S. Pat. No. 5,037,285, which is a continuation of Ser. No. 07/397,348, filed Aug. 22, 1989, now U.S. Pat. No. 4,946,365, which is a continuation of Ser. No. 07/283,000, filed Dec. 2, 1988, now abandoned, which is a continuation of Ser. No. 06/909,941, filed Sep. 19, 1986, now abandoned, which is division of Ser. No. 06/484,707, filed Apr. 13, 1983, now U.S. Pat. No. 4,712,990.
The process for manufacturing a preform from at least one thermoplastic resin in the form of granules (A) and in a substantially crystalline state, comprises following successive operations are carried out: drying the thermoplastic resin in the form of granules; melting the dried granules of resins; injecting the melted resin into a mould and removing the preform from the mould; The drying operation is carried out in at least two successive separate steps: in a first step (first hopper 5), the granules of resin substantially in a crystalline state are dried for a predetermined duration (t1) at a predetermined drying temperature (T1); in a second step (second hopper 5'), the drying of the granules from the first step is continued at a drying temperature (T2) that is markedly higher than the drying temperature (T1) of the first stage, and for a duration (t2) that is markedly shorter than the period (t1) of the first step.
An injection nozzle device including multi-polymer injection nozzles comprising an assembly of shells, and having fixed, tapered passageways communicating with annular orifices close to a nozzle gate and to each other, and polymer flow balancing and directing means in the passageways in the form of concentric and eccentric chokes.
