Patent DE-3390482-C2 (DE)
Title: Blade flight for helical screw conveyor
Inventor: CALDWELL JOHN W
IPC: B04B1/16
Filed: 1983-05-16
Granted: 1996-01-11
Abstract: A screw conveyor centrifuge comprising an elongated bowl having an inner bowl surface, and including a cylindrical portion adapted to receive a solids/liquid mixture and a trunco-conical portion having a discharge port adapted to the discharge of solids separated from said mixture, said bowl being mounted for rotation about its longitudinal axis and conveying means including at least one blade having a leading surface facing in the direction of said port and a distal edge, said blade being helically and coaxially mounted within said bowl through the length of said bowl surface with the distal edge of said blade in a closely spaced, sweeping relationship to said bowl surface and means for rotating said bowl and said blade at a speed differential, wherein at least that part of the leading surface of the blade which lies within at least part of the trunco-conical portion of the centrifuge bowl is provided, adjacent the distal edge thereof, with an arcuate surface of defined curvature and shape adapted to contact said solids after separation, said arcuate surface being defined by a - concavity in said leading surface, said curvature of said arcuate surface having a profile defined in a plane through said axis whereby (i) a straight, first line tangent to the slope of said profile adjacent said distal edge and a second line disposed in said plane and perpendicular to said bowl surface subtend an angle alpha within said concavity of from 10 to 70 deg. and (ii) a straight, third line tangent to the slope of said profile most distant from said distal edge and a fourth line disposed in said plane and perpendicular to said axis, subtends an angle beta within said concavity of from 7 to 90 deg. DEAB- DE3390482 C The blade of a helical screw conveyor of a centrifuge is improved to reduce the amount of torque required in operation, to produce discharged solids drier than the solids discharged using a conventional blade. The distal end of the leading surface of the blade at or adjacent at least the trunco-conical end of the centrifuge bowl have a curved configuration concave in the direction of the solids discharge port. - The more distal blade portions peel the separated solids material from the bowl wall with minimum torque requirements, while the less distal curved portions tumble the solids to reduce the moisture content. The blade's curved leading surface is formed by add-on, wear-resistant members attached to a backing plate which in turn is mounted on the leading surface of the blade. (Dwg.1/9) GBAB- GB2149693 B A screw conveyor centrifuge comprising an elongated bowl having an inner bowl surface, and including a cylindrical portion adapted to receive a solids/liquid mixture and a trunco-conical portion having a discharge port adapted to the discharge of solids separated from said mixture, said bowl being mounted for rotation about its longitudinal axis and conveying means including at least one blade having a leading surface facing in the direction of said port and a distal edge, said blade being helically and coaxially mounted within said bowl through the length of said bowl surface with the distal edge of said blade in a closely spaced, sweeping relationship to said bowl surface and means for rotating said bowl and said blade at a speed differential, wherein at least that part of the leading surface of the blade which lies within at least part of the trunco-conical portion of the centrifuge bowl is provided, adjacent the distal edge thereof, with an arcuate surface of defined curvature and shape adapted to contact said solids after separation, said arcuate surface being defined by a  concavity in said leading surface, said curvature of said arcuate surface having a profile defined in a plane through said axis whereby (i) a straight, first line tangent to the slope of said profile adjacent said distal edge and a second line disposed in said plane and perpendicular to said bowl surface subtend an angle alpha within said concavity of from 10 to 70 deg. and (ii) a straight, third line tangent to the slope of said profile most distant from said distal edge and a fourth line disposed in said plane and perpendicular to said axis, subtends an angle beta within said concavity of from 7 to 90 deg. - GB2149693 B A screw conveyor centrifuge comprising an elongated bowl having an inner bowl surface, and including a cylindrical portion adapted to receive a solids/liquid mixture and a trunco-conical portion having a discharge port adapted to the discharge of solids separated from said mixture, said bowl being mounted for rotation about its longitudinal axis and conveying means including at least one blade having a leading surface facing in the direction of said port and a distal edge, said blade being helically and coaxially mounted within said bowl through the length of said bowl surface with the distal edge of said blade in a closely spaced, sweeping relationship to said bowl surface and means for rotating said bowl and said blade at a speed differential, wherein at least that part of the leading surface of the blade which lies within at least part of the trunco-conical portion of the centrifuge bowl is provided, adjacent the distal edge thereof, with an arcuate surface of defined curvature and shape adapted to contact said solids after separation, said arcuate surface being defined by a concavity in said leading surface, said curvature of said arcuate surface having a profile defined in a plane through said axis whereby (i) a straight, first line tangent to the slope of said profile adjacent said distal edge and a second line disposed in said plane and perpendicular to said bowl surface subtend an angle alpha within said concavity of from 10 to 70 deg. and (ii) a straight, third line tangent to the slope of said profile most distant from said distal edge and a fourth line disposed in said plane and perpendicular to said axis, subtends an angle beta within said concavity of from 7 to 90 deg. USAB- US4449967 A The blade of a helical screw conveyor of a centrifuge is improved to reduce the amount of torque required in operation, to produce discharged solids drier than the solids discharged using a conventional blade. The distal end of the leading surface of the blade at or adjacent at least the trunco-conical end of the centrifuge bowl have a curved configuration concave in the direction of the solids discharge port. - The more distal blade portions peel the separated solids material from the bowl wall with minimum torque requirements, while the less distal curved portions tumble the solids to reduce the moisture content. The blade's curved leading surface is formed by add-on, wear-resistant members attached to a backing plate which in turn is mounted on the leading surface of the blade. (3/9)