Plastic sealing of solenoid bobbins

摘要

A method and apparatus for overmolding a plastic shroud (16) onto a bobbin (110,210) including the step of providing a protrusion ring (128,228a,228b) on the surface (124,224) of the bobbin surrounding each standoff (22,222) between the bobbin and a mold wall and extending outwards from the surface of the bobbin. A plurality of standoffs (22,222) and protrusion rings (128,228a,228b) is presently preferred. The protrusion rings are small relative to the standoffs, have low thermal mass, and thus are readily melted by the injected molten plastic, causing interstitching between the bobbin material and the overmolding material. The interstitching creates a highly effective hermetic seal against moisture leakage along the surface of the bobbin away from the standoff site. Perfect melting of the standoffs is no longer required, and standoffs can be designed to assure proper positioning of the bobbin during the complete overmolding process.