Process and apparatus for purifying a fibrous suspension

Claim 2

Process for removing impurities, such as printing inks, binders, fibre fragments and pigments, from a fibrous suspension of waste paper containing water, comprising passing the fibrous suspension downwardly over an inclinded sieve from an upper end to a lower end and removing the impurities through the sieve with a proportion of the water from the fibrous suspension, wherein the improvement comprises interrupting the downward flow of the fibrous suspension over the inclined sieve at least once between the upper end and lower end and directing the interrupted downward flow into a groove-like trough in the downward flow path over the sieve and shaping the surfaces of the trough in the direction between the upper end and lower end for subjecting the fibrous suspension flowing into the trough to a swirling motion about an axis extending transversely of the direction between the upper and lower ends for homogenizing the flow entering the trough and returning the homogenized fibrous suspension from the trough onto the sieve for downward flow thereover below the trough.

Claim 3

Process, as set forth in claim 1, including the step of spreading the flow of the fiber suspension exiting from the trough to a uniform level across the sieve.

Claim 4

Process, as set forth in claim 1, including the step of arranging the inclination of the sieve in the range of 35° to 45° to the horizontal.

Claim 5

Apparatus for removing impurities, such as printing inks, binders, fibre fragments and pigments, from a fibrous suspension of waste paper containing water, in which the fibrous suspension is conveyed downwardly, comprising an inclined sieve over which the fibrous suspension flows downwardly with impurities being carried off through said sieve with a proportion of the water from the fibrous suspension, said sieve having an upper end and a lower end with the length of said sieve extending between the upper and lower ends, characterized in that said sieve is divided along its length into sections, a groove extending transversely of the length direction and located between the lower end of one said section and the upper end of the downwardly adjacent said section, said groove being arranged to receive the fibrous suspension from the lower end of said one section and being shaped for swirling the fibrous suspension about an axis extending transversely of the length direction of said and a flow-stemming device associated with each said groove and located at the upper end of the downwardly adjacent said section for homogenizing the flow exiting from said groove onto the upper end of the downwardly adjacent said section.

Claim 6

Apparatus for removing impurities, such as printing inks, binders, fibre fragments and pigments, from a fibrous suspension of waste paper containing water, in which the fibrous suspension is conveyed downwardly, comprising an inclined sieve over which the fibrous suspension flows downwardly with impurities being carried off through said sieve with a proportion of the water from the fibrous suspension, said sieve having an upper end and a lower end with the length of said sieve extending between the upper and lower ends, characterized in that said sieve is divided along its length into sections, a groove extending transversely of the length direction and located between the lower end of one said section and the upper end of the downwardly adjacent said section, said groove being arranged to receive the fibrous suspension from the lower end of said one section and being shaped for swirling the fibrous suspension about an axis extending transversely of the length direction of said and a flow-stemming device associated with each said groove and located at the upper end of the downwardly adjacent said section for homogenizing the flow exiting from said groove onto the upper end of the downwardly adjacent said section.

Claim 7

Apparatus according to claim 4, characterized in that the length of each of said individual sections is 600 to 1500 mm.

Claim 8

Apparatus according to one of the claims 4 or 3, characterized in that said groove has a triangular cross-section in the length direction of said sieve, said triangular cross-section comprising a short side and a long side with the apex formed by the intersection of said short and long sides being rounded.

Claim 9

Apparatus according to claim 6, characterized in that said short side of the triangular groove extending from the lower end of said one section and the long side of the triangular groove extending from the rounded apex to the upper end of the downwardly adjacent said section.

Claim 10

Apparatus according to claims 4 or 5, characterized in that said flow-stemming device comprises a weir rotatably mounted about an axis extending transversely of the length direction of said sieve and forming in combination with said groove an outlet opening which is adjustable in size.

Claim 11

Apparatus according to claim 8, characterized in that a weighted lever is connected to said weir for rotating said weir about the axis thereof for adjusting the size of said outlet opening.

Claim 12

Apparatus according to claims 4 or 5, characterized in that the inclination of said sieve is between 35° and 45° relative to the horizontal.

Claim 13

Apparatus according to claims 4 or 5, characterized in that said sieve having a surface formed of an alloyed stainless steel.

Claim 14

Apparatus according to claim 11, characterized in that said sieve surface comprises a wire cloth produced in the form of a three-end twill.

Claim 15

Apparatus according to claim 12, characterized in that the wire cloth is a twill with a register of 1:2.

Claim 16

Apparatus according to claims 4 or 5, characterized by means for applying a vacuum to said individual sections of said sieve.

Claim 17

Apparatus according to claim 14, characterized in that said means for applying the vacuum comprises a downpipe connected to the lower end of each of said individual sections.

Claim 18

Apparatus according to claim 4 or 5, characterized by a vibration being connected to said sieve.

Claim 19

Apparatus according to claim 16, characterized by rubber buffers mounting said sieve.

Claim 20

Apparatus according to claim 17, characterized in that said vibrator being connected to said individual section of said sieve extending downwardly from the upper end thereof.

Claim 21

Apparatus according to claim 18, characterized in that said vibrator has a frequency of between 1000 and 6000 Hz.