Glass forming apparatuses and methods for making glass ribbons

A method for forming a laminated glass ribbon, the method comprising:

• directing streams of a molten core glass composition over a first outer forming surface and a second outer forming surface of a lower forming body such that the streams of the molten core glass composition converge and fuse at a root of the lower forming body thereby forming a core layer of the laminated glass ribbon;
• directing streams of a molten cladding glass composition over a first outer forming surface and a second outer forming surface of an upper forming body positioned over the lower forming body such that the streams of the molten cladding glass composition contact the streams of the molten core glass composition thereby forming a first glass cladding layer and a second glass cladding layer of the laminated glass ribbon;
• and
• extracting heat from the molten core glass composition flowing over the first outer forming surface and the second outer forming surface of the lower forming body with at least one first cooling tube extending substantially parallel to the first outer forming surface of the lower forming body and at least one second cooling tube extending substantially parallel to the second outer forming surface of the lower forming body, the lower forming body being disposed between the at least one first cooling tube and the at least one second cooling tube, wherein:
• a first refractory material is disposed between the at least one first cooling tube and the first outer forming surface of the lower forming body and in direct contact with the at least one first cooling tube thereby forming a first continuous heat conduction pathway extending away from the first outer forming surface of the lower forming body in a substantially horizontal direction;
• and
• a second refractory material is disposed between the at least one second cooling tube and the second outer forming surface and in direct contact with the at least one second cooling tube thereby forming a second continuous heat conduction pathway extending away from the second outer forming surface of the lower forming body in the substantially horizontal direction, the first continuous heat conduction pathway and the second continuous heat conduction pathway forming a vertical temperature gradient between the upper forming body and the lower forming body.