Method and apparatus for runnerless injection-compression molding thermosetting materials

• Main Authors: BAINBRIDGE; ROBERT W, DANNELS; W. ANDREW
• Format: Patent
• Language: English
• Published: 05.01.1982
• Subjects: AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING; PERFORMING OPERATIONS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDEDFOR; SHAPING OR JOINING OF PLASTICS; TRANSPORTING; WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE, IN GENERAL

A method and apparatus are described. A thermosetting molding material, suitably a synthetic resin composition such as a phenolic molding composition, is initially heated and plasticized. The plasticized mass is passed as a stream through an injection nozzle which is maintained at a temperature sufficiently high to keep the mass in a plasticized condition but sufficiently low to avoid any substantial curing or setting-up of the mass. The plasticized mass is next passed through a temperature-controlled manifold maintained at a temperature sufficiently high to keep the mass in a plasticized condition but sufficiently low to avoid any substantial curing or setting-up of the mass. In the manifold the plasticized stream is divided into two or more smaller streams which are passed through a plurality of outlets into a plurality of partially open, heated molds. The mold cavities are maintained at temperatures sufficiently high to cure the thermosetting molding material. When the partially open molds are full, the feed stream is interrupted, and the molds are then completely closed to press and cure the plasticized material enclosed within them. The cured, finished article is removed from the mold and the process repeated. The apparatus of the present invention includes a stationary assembly and a movable assembly. The stationary assembly is comprised of a support plate which has a heat plate mounted thereon, a temperature-controlled manifold mounted on the heat plate and a plurality of mold faces positioned on the heat plate surrounding the periphery of the manifold. The movable assembly is comprised of a support plate which has a heat plate mounted thereon and a plurality of mold faces, corresponding to, and adapted to be aligned with the mold faces on the stationary assembly. Means are provided to move the movable assembly into close proximity with the stationary assembly to form partially open mold cavities. Means are provided to feed a supply of thermosetting molding material through the manifold into the partially open mold cavities. Means are also provided to completely close the mold cavities and for subsequent retracting the movable assembly to allow access to the mold face areas.