Two stage pressure pulp screen device with stationary cylindrical screen

Claim 2

A TWO STAGE PULP SCREENING DEVICE INCLUDING A UPPER PULP SCREENING CHAMBER AND A LOWER PULP SCREENING CHAMBER, THE UPPER PULP SCREENING CHAMBER HAVING A FIRST STATIONARY CYLINDRICAL SCREEN WITH AT LEAST ONE FOIL CLEANING BAR INTERNALLY MOUNTED FOR ROTATION ABOUT A VERTICAL AXIS, THE LOWE PULP SCREENING CHAMBER HAVING A SECOND STATIONARY CYLINDRICAL SCREEN BELOW AND IN LINE WITH THE FIRST SCREEN, A RATOR INTERNALLY MOUNTED FOR ROTATION ABOUT SAID VERTICAL AXIS, THE IMPROVEMENT COMPRISING A CYLINDRICAL INLET BAFFLE SURROUNDING THE FIRST SCREEN AND FORMING A FIRST ANNULAR SPACE BETWEEN THE INLET BAFFLE AND THE FIRST SCREEN, AT LEAST ONE HELICAL BAFFLE MOUNTED ON THE INLET BAFFLE IN THE FIRST ANNULAR SPACE AND EXTENDING ABOUT THE FIRST SCREEN TO FEED PULP SLURRY IN A HHELICAL PATH THROUGH THE FIRST ANNULAR SPACE DOWNWARDS TO A LOWER PORTION OF THE FIRST ANNULAR SPACE, A FURTHUR AANNULAR SPACE SURROUNDING THE INLET BAFFLE AND IN COMMUNICATION WITH A PULP SLURRY SUCH THAT PULP SLURRY IS FED INTO SAID FURTHUR ANNULAR SPACE, MEANS FOR BLOCKING OFF THE FIRST ANNULAR SPACE AND FURTHUR ANNULAR SPACE FROM COMMUNICATION WITH EACH OTHER AT THE LOWER ENDS THEREOF, SAID UPPER CHAMBER BEING OPENED OVER THE TOP OF SAID INLET BAFFLE, PLACING THE FIRST ANNULAR SPACE AND THE FURTHER ANNULAR SPACE INTO COMMUNICATION WITH EACH OTHER OVER THE

Claim 3

The two stage pulp screening device according to claim 1 including the addition of a means to provide a shower of dilution water to the lower portion of the first annular space.

Claim 4

The two stage pulp screening device according to any of claim 1 wherein the first screen is a coarse screen and the second screen is a fine screen.

Claim 5

The two stage pulp screening device according to any of claim 1 wherein the first screen comprises slotted plates, and the second screen comprises perforated plates.

Claim 6

The two stage pulp screening device according to claim 1 wherein the first screen and the second screen are both fine screens.

Claim 7

The two stage pulp screening device according to claim 1 wherein two helical baffles are mounted on the inlet baffle, starting approximately 180* apart and extending downwards terminating above the bottom of the first screen thus leaving the lower portion of the first annular space unobstructed.

Claim 8

The two stage pulp screening device according to any of claim 1 wherein the rotor has a streamlined shape in the form of a truncated cone with an upper portion having a peripheral wall disposed at a greater angle to the vertical axis than that of the peripheral wall of a lower portion of the truncated cone.

Claim 9

The two stage pulp screening device according to any of claim 1 wherein the first screen and the second screen are approximately the same diameter, and a means is provided to rotate the foil cleaning bar and the rotor as one unit.

Claim 10

The two stage pulp screening device according to claim 1, wherein the said inlet to the further annular chamber is a tangetial inlet adapted to feed pulp slurry into the further annular space so that the slurry rotates thereabout as it rises up therein.

Claim 11

A two stage pressure pulp screening device comprising: a cylindrical housing containing an upper pulp screening chamber and a lower pulp screening chamber: the lower pulp screening chamber having a first stationary cylindrical screen with a rotor mounted for rotation therein about a vertical axis, the rotor being in the form of a truncated cone with an upper portion and a lower portion, with the peripheral wall of the upper portion having an angle to the vertical axis greater than the angle of the peripheral wall of the lower portion, and impeller blades radiating from the rotor and extending to within a short distance of the inward facing surface of the first screen; the upper pulp screening chamber having a second stationary cylindrical screen approximately the same diameter as the first screen with at least one foil cleaning bar internally mounted for rotation about the vertical axis in conjunction with the rotor, a cylindrical inlet baffle surrounding the second screen forming a first annular space therebetween, at least one helical baffle mounted on the inlet baffle forming a spiral passageway within the first annular space to feed pulp slurry downwards through the first annular space along a spiral path, a further annular space surrounding the inlet baffle and in communication with a pulp slurry inlet such that pulp slurry is fed into said further annular space, means for blocking off the first annular space and the further annular space from communication with each other at the lower ends thereof, and said upper chamber being opened over the top of said inlet baffle placing the first annular space and the further annular spAce into communication with each other over the inlet baffle, whereby pulp slurry fed into the upper chamber is first received in the further annular space where it rises up the outer side of the inlet baffle and spills thereover into the first annular space, and a reject discharge means positioned in a lower portion of the first annular space.

Claim 12

A two stage pressure pulp screening device comprising: a cylindrical housing containing an upper pulp screening chamber and a lower pulp screening chamber: the lower pulp screening chamber having a first stationary cylindrical screen with a rotor mounted for rotation therein about a vertical axis, the rotor being in the form of a truncated cone with an upper portion and a lower portion, with the peripheral wall of the upper portion having an angle to the vertical axis greater than the angle of the peripheral wall of the lower portion, and impeller blades radiating from the rotor and extending to within a short distance of the inward facing surface of the first screen; the upper pulp screening chamber having a second stationary cylindrical screen approximately the same diameter as the first screen with at least one foil cleaning bar internally mounted for rotation about the vertical axis in conjunction with the rotor, a cylindrical inlet baffle surrounding the second screen forming a first annular space therebetween, at least one helical baffle mounted on the inlet baffle forming a spiral passageway within the first annular space to feed pulp slurry downwards through the first annular space along a spiral path, a further annular space surrounding the inlet baffle and in communication with a pulp slurry inlet such that pulp slurry is fed into said further annular space, means for blocking off the first annular space and the further annular space from communication with each other at the lower ends thereof, and said upper chamber being opened over the top of said inlet baffle placing the first annular space and the further annular spAce into communication with each other over the inlet baffle, whereby pulp slurry fed into the upper chamber is first received in the further annular space where it rises up the outer side of the inlet baffle and spills thereover into the first annular space, and a reject discharge means positioned in a lower portion of the first annular space.