Device for screening fiber suspensions

Claim 1

A device for screening fiber suspensions comprising: a rotationally symmetric screen basket having an inside radius R 2 ; a rotor rotatable about an axis of rotation M O , said rotor being coaxial to and arranged radially inside said screen basket, said rotor having a circumference wherein at any cross section perpendicular to said axis of rotation said circumference is substantially formed of circular arcs having a uniform mutual angular offset and an equal radius R r that is smaller than said inside radius R s of said screen basket, according to the formula R r =R s -f max , where f max is the theoretical greatest spacing of the rotor circumference from the screen basket as the maximum spacing of the common tangent of adjacent circular arcs from said screen basket; f' max is the actual greatest spacing of said rotor circumference from said screen basket when said spacing of said rotor circumference from said screen basket does not follow said common tangent, which spacing is maximally equal to 1.15·f max ; f min is the least spacing of the rotor circumference from the screen basket wherein the spacing between f min and f' max increases generally steadily and wherein said radius R r has a maximum variation of 5% of the value as given by said formula in the form of a generally elliptic or similar rotor contour, and wherein said circular arcs have a contour transition therebetween, said contour transition being fashioned as a common tangent or secant of adjacent circular arcs; wherein e is the difference f max -f min , said difference e=f max -f min being maximally 60 mm, and f min ranges between 15 mm and 45 mm and E ranges between 5 mm and 100 mm, with a=360°/2n, E=e/(1-cos a) when angle a equals one-half the angular spacing of two rotor contour points that are adjacent in the circumferential direction of the rotor, with the least spacing f min from the screen basket, and E is the offset of the center M of the circular arcs of the rotor from said axis of rotation M O , e=f max -f min and n equals the number of circular arcs of each rotor cross section.

Claim 2

A device for screening fiber suspensions comprising: a rotationally symmetric screen basket having an inside radius R 2 ; a rotor rotatable about an axis of rotation M O , said rotor being coaxial to and arranged radially inside said screen basket, said rotor having a circumference wherein at any cross section perpendicular to said axis of rotation said circumference is substantially formed of circular arcs having a uniform mutual angular offset and an equal radius R r that is smaller than said inside radius R s of said screen basket, according to the formula R r =R s -f max , where f max is the theoretical greatest spacing of the rotor circumference from the screen basket as the maximum spacing of the common tangent of adjacent circular arcs from said screen basket; f' max is the actual greatest spacing of said rotor circumference from said screen basket when said spacing of said rotor circumference from said screen basket does not follow said common tangent, which spacing is maximally equal to 1.15·f max ; f min is the least spacing of the rotor circumference from the screen basket wherein the spacing between f min and f' max increases generally steadily and wherein said radius R r has a maximum variation of 5% of the value as given by said formula in the form of a generally elliptic or similar rotor contour, and wherein said circular arcs have a contour transition therebetween, said contour transition being fashioned as a common tangent or secant of adjacent circular arcs; wherein e is the difference f max -f min , said difference e=f max -f min being maximally 60 mm, and f min ranges between 15 mm and 45 mm and E ranges between 5 mm and 100 mm, with a=360°/2n, E=e/(1-cos a) when angle a equals one-half the angular spacing of two rotor contour points that are adjacent in the circumferential direction of the rotor, with the least spacing f min from the screen basket, and E is the offset of the center M of the circular arcs of the rotor from said axis of rotation M O , e=f max -f min and n equals the number of circular arcs of each rotor cross section.

Claim 6

A device for screening fiber suspensions comprising: a rotationally symmetric screen basket having an inside radius R s ; a rotor rotatable about an axis of rotation M O , said rotor being coaxial to and arranged radially inside said screen basket, said rotor having a circumference wherein at any cross section perpendicular to said axis of rotation said circumference is substantially formed of circular arcs having a uniform mutual angular offset and an equal radius R r that is smaller than said inside radius R s of said screen basket, according to the formula R r =R s -f max , where f max is the theoretical greatest spacing of the rotor circumference from the screen basket as the maximum spacing of the common tangent of adjacent circular arcs from said screen basket; further, f' max is the actual greatest spacing of said rotor circumference from said screen basket when said spacing of said rotor circumference from said screen basket does not follow said common tangent, which spacing is maximally equal to 1.15·f max ; f min is the least spacing of the rotor circumference from the screen basket wherein the spacing between f min and f'max increases generally steadily and wherein said radius R r has a maximum variation of 5% of the value as given by said formula in the form of a generally elliptic or similar rotor contour, and wherein said circular arcs have a contour transition therebetween, said contour transition being bowed and concave; further, e is the difference f max -f min , said difference e=f max -f min being maximally 60 mm, and f min ranges between 15 mm and 45 mm and E ranges between 5 mm and 100 mm, with a=360°/2n, E=e/(1-cos a) when angle a equals one-half the angular spacing of two rotor contour points that are adjacent in the circumferential direction of the rotor, with the least spacing f min from the screen basket, and when E is the offset of the center M of the circular arcs of the rotor from said axis of rotation M O , e=f max -f min and n equals the number of circular arcs of each rotor cross section.

Claim 7

A device for screening fiber suspensions comprising: a rotationally symmetric screen basket having an inside radius R s ; a rotor rotatable about an axis of rotation M O , said rotor being coaxial to and arranged radially inside said screen basket, said rotor having a circumference wherein at any cross section perpendicular to said axis of rotation said circumference is substantially formed of circular arcs having a uniform mutual angular offset and an equal radius R r that is smaller than said inside radius R s of said screen basket, according to the formula R r =R s -f max , where f max is the theoretical greatest spacing of the rotor circumference from the screen basket as the maximum spacing of the common tangent of adjacent circular arcs from said screen basket; further, f' max is the actual greatest spacing of said rotor circumference from said screen basket when said spacing of said rotor circumference from said screen basket does not follow said common tangent, which spacing is maximally equal to 1.15·f max ; f min is the least spacing of the rotor circumference from the screen basket wherein the spacing between f min and f'max increases generally steadily and wherein said radius R r has a maximum variation of 5% of the value as given by said formula in the form of a generally elliptic or similar rotor contour, and wherein said circular arcs have a contour transition therebetween, said contour transition being bowed and concave; further, e is the difference f max -f min , said difference e=f max -f min being maximally 60 mm, and f min ranges between 15 mm and 45 mm and E ranges between 5 mm and 100 mm, with a=360°/2n, E=e/(1-cos a) when angle a equals one-half the angular spacing of two rotor contour points that are adjacent in the circumferential direction of the rotor, with the least spacing f min from the screen basket, and when E is the offset of the center M of the circular arcs of the rotor from said axis of rotation M O , e=f max -f min and n equals the number of circular arcs of each rotor cross section.