Enclosure of a metal component in plastic involves use of component centering pins which are pushed back against springs by melt pressure during cavity filling

摘要

The component(1) is held away from the walls(5) by centering pins(3,4) which are pressed by spring loading(10) against the component. During the injection stage melt(6) fills the remaining space between component and cavity wall and pushes the pin ends away from the component leaving a chamber which is filled by the melt. The centering pins(3,4) and/or pin guiding sleeves(8) surrounding them are electrically heated until the chamber has been filled with melt following pin retraction. Pin guiding sleeves are initially flush with the tool cavity wall and when a pin is pushed back the sleeve moves forwards to force melt(6) into the vacant space. An independent claim is included for the process equipment including an injection molding tool(2) with component centering pins(3,4). A coil spring(10) is located between the rear end of each pin and a supporting surface(11) and presses each pin against the component. The leading end of each pin in contact with the component has profiled surfaces, in particular a conical tip, to aid flow and /or pressure difference, thus ensuring that a pin is lifted away from the component and compresses the spring.