Multi-ply paper forming machine with upward and downward forming runs

Claim 1

A multi-ply board making machine comprising in combination: first and second looped forming wires; first and second wire guide means training the wires into a first vertically upwardly extending forming throat leading to a first vertically upwardly extending dewatering run with the wires applying a pressure against a web through said run; a first headbox positioned to direct a pressure jet of first stock into the first throat; first and second water receiving means within said first and second loops respectively receiving water expressed from the web in said first run; a third looped forming wire; a third wire guide means within the third wire positioned to guide the wire into a vertically downwardly extending second forming throat leading to a vertically downwardly extending second dewatering run with the second wire and the second and third wire applying pressure to the web through said second run; a second headbox directing a second stock into said second throat onto the web carried on the second wire from the first run thereby forming a second layer on the web; and a water receiving means within the third wire receiving water from said second layer with the first and second layers being bonded to each other by the flow of water during the second run; each of said forming runs including a series of successive spaced bars extending in a cross-machine direction sequentially engaging the second wire in the first forming run and the third wire in the second forming run, said bars lying in a broad arc of very large radius so that the first and second wires in the first forming run and the second and third wires in the second forming run travel through a plurality of chordal sectors and the web is gently dewatered in both directions in the first run and the second layer is gently dewatered in both directions in the second run so as to cause a bonding between the second layer and first layer.