Multi-component injection process for molding products in different materials involves making pre-molding with integral or separate sealing lip, which after tool cavity enlargement, prevents flash formation by further injected material

摘要

A first material component(3) is injection molded in a tool(2a,2b) to form a pre-molding(4) and a seal(7) is either molded as part of the pre-molding or is injected separately onto it. The molding tool cavity(5) is then enlarged and the seal presses against the tool and/or contacts an area of the pre-molding. When a further material component(6) is injected into the enlarged tool cavity it is prevented by the seal from forming flash on the outside of the pre-molding. The seal(7) forms a sealing lip and is injected onto the edge of the pre-molding or forms an integral part of the latter. Several seals may be injected onto the pre-molding or form part of it. Seals project towards the tool half(2b) with the injection nozzle. During closure of the enlarged tool cavity(5) the sealing lip, which projects towards a tool edge or inner wall(12) of the second tool half, is deflected by the latter and presses against the cavity wall. A trough like recess(16) is formed in a transition area between the sealing lip and pre-molding surface(15) and the seal deflects towards the recess. When several seals are formed parallel to each other they act as a labyrinth seal. A separate recess may be created in the tool cavity wall or in the molding to accommodate the deflected sealing lip. An independent claim is included for a multi-component injection molded product which comprises a pre-molding(4) with a sealing lip which deflects during contact with a molding tool before molding a further material component onto the pre-molding.