Screening apparatus for papermaking pulp

A rotor for a pulp fine-screening apparatus, comprising:

• a rotatable shaft upon which is constructed a supporting framework;
• a substantially disc-shaped first element mounted on a first end of said shaft;
• a substantially cylindrical hollow element fastened to said supporting framework and to said first element an extending therefrom toward a second end of said shaft;
• and
• means, on said cylindrical hollow element, for causing negative pressure excursions within a pulp slurry being screened, said means comprising at least one half-foil member disposed on the surface of the rotor, said at least one half-foil member having an axial extent substantially equal to that of said cylindrical hollow element and having a leading edge inclined at a spiral angle relative to the axis of said rotor, and an extension projecting axially toward said disc-shaped first element and tapering from a maximum radial thickness at said half-foil to a radially vanishing dimension near said disc-shaped first element.

A screening apparatus for paper-making pulp slurry comprising:

• a housing having a generally cylindrical shape, an axis, a pulp inlet chamber, a screening chamber downstream of said inlet chamber, a rejects chamber and discharge downstream of said screening chamber, an annular accepts chamber outboard of said screening chamber, and an accepts discharge in said accepts chamber;
• a rotor having an outer substantially cylindrical surface and an axis co-axial with said housing;
• a generally cylindrical apertured stationary screen member also co-axial with said housing and said rotor, said screen member having an inside diameter greater than an outside diameter of said rotor to define said screening chamber in a resulting annular space between said screen member and said rotor;
• means on the outer surface of said rotor for generating negative pressure excursions within said screening chamber, thereby causing flow reversals through the apertures of said screen;
• and
• means for deflocculating the pulp slurry and for accelerating said pulp slurry to a desired circumferential velocity for screening said means for deflocculating and accelerating comprising an extension means on one or more of a series of half-foil members arrayed upon the cylindrical surface of said rotor, said extension projecting axially into an annular pulp entrance chamber upstream from said screening chamber.

A screening apparatus for paper-making pulp comprising:

• a housing having a generally cylindrical shape, an axis, a pulp inlet chamber, a screening chamber downstream of said inlet chamber, a rejects chamber and discharge downstream of said screening chamber, an annular accepts chamber outboard of said screening chamber, and an accepts discharge in said accepts chamber;
• a rotor having an outer substantially cylindrical surface and an axis co-axial with said housing;
• a generally cylindrical apertured stationary screen member also co-axial with said housing and said rotor, said screen member having an inside diameter greater than an outside diameter of said rotor to define said screening chamber in a resulting annular space between said screen member and said rotor;
• and
• means on the outer surface of said rotor for substantially negative pressure excursions within said screening chamber, thereby causing flow reversals through the apertures of said screen, said means comprising one or more projections on the outer surface of said rotor, said projections collectively extending an axial distance at least substantially equal to the full length of said rotor, having a collective leading edge spiral inclination angle relative to the rotor axis, and
• a circumferential extent which increases continuously from a minimum at the top of said screening chamber to a maximum at the bottom of said screening chamber.

A rotor for a pulp fine-screening apparatus, comprising:

• a rotatable shaft upon which is constructed a supporting framework;
• a substantially disc-shaped first element mounted on a first end of said shaft;
• a substantially cylindrical hollow element fastened to said supporting framework and to said first element and extending therefrom towards a second end of said shaft;
• and
• means, on said cylindrical hollow element, for causing negative pressure excursions within a pulp slurry being screened, said means comprising a plurality of half-foil members disposed on the surface of the cylindrical hollow element, said half-foil members having a collective axial extent substantially equal to that of said cylindrical hollow element, ramp-like outboard surfaces tapering from a maximum radial dimension near leading edges to a minimum radial dimension near trailing edges;
• and fence-like means on one or more axial edges for limiting axial flow of said slurry into zones of negative pressure near said trailing edges.