METHOD AND APPARATUS FOR APPLYING POLYMER COATING ONTO METAL PIPE Russian patent published in 1997 - IPC

FIELD: coating application. SUBSTANCE: invention relates to fabricating metal pipes with polymer-coated inner and outer surfaces. When applying polymer coating onto metal pipe, formation of tubular adhesive shells is performed on both pipe surfaces in the zone where adhesive melt is applied. Then tubular polymer shells are formed on both pipe surfaces in the zone where polymer melt is applied. Zones of formation of adhesive and polymer tubular shells on inner surface are positioned against corresponding zones on outer surface. In the apparatus for applying polymer coating onto metal pipe, chambers for formation of tubular adhesive and polymer shells are separated from each other and disposed successively in direction of drawing metal pipe in adhesive and polymer melt application zones. Channels of core designed to force adhesive and polymer melts into formation chambers are isolated from each other. Core of inner extrusion head is mounted in axial passage of outer extrusion head. Chambers for formation of tubular adhesive and polymer shells of inner extrusion head are positioned against corresponding formation chambers of outer extrusion head. These chambers are made in the form of annular cuts on outer cylindrical surface of core of inner extrusion head and annular cuts on surface of outer extrusion head in the axial passage zone. Annular cuts are combined in pairs with core cuts. Formation chambers have shaping region with gradually decreasing depth in direction of drawing metal pipe and coupled with it calibrating region with constant depth. EFFECT: improved structure of apparatus. 8 cl, 4 dwg