Blade segment for refiner
A blade segment ( 4, 8 ) for a refiner ( 1 ) for refining fibrous material has first ( 20 ) and second ( 21 ) end edges opposite one another in a direction of a longitudinal axis (LA) of the blade segment ( 4, 4 a, 4 b, 8, 8 a, 8 b ), and first ( 22 ) and second ( 23 ) side edges which extend between the first end edge and the second end edge. The blade segment has a refining surface ( 5, 9 ) with blade bars ( 26 ) and grooves ( 27 ) therebetween on a front surface ( 25 ) of the blade segment ( 4, 8 ). At least one side edge ( 22, 23 ) has at least two edge portions ( 31, 33, 35, 41, 43, 45 ) arranged to deviate from the direction of the longitudinal axis (LA) of the blade segment ( 4, 4 a, 4 b, 8; 8 a, 8 b ) and connected by an elbow ( 32, 34, 42, 44 ) between each two edge portions ( 31, 33, 35, 41, 43, 45 ).
1. A blade segment for a refiner for refining fibrous material, the blade segment comprising:
a first end edge and a second end edge opposite to the first end edge in a direction of a longitudinal axis of the blade segment;
a first side edge and a second side edge opposite to the first side edge, the first side edge and the second side edge extending between the first end edge and the second end edge;
a refining surface comprising blade bars and blade grooves therebetween on a front surface of the blade segment; and
wherein the first side edge and the second side edge each comprise at least two long edge portions which are inclined from the direction of the longitudinal axis of the blade segment and being connected by an elbow between each of said at least two long edge portions, the elbow having a first bend, a short edge portion which is shorter than the long edge portions, the short edge portion following the first bend and a second bend following the short edge portion;
wherein an edge axis extends in the longitudinal direction from a first shoulder at the first end edge at the first side edge to a second shoulder at the second end edge at the first side edge, and at least one of the elbows of the first side edge has portions which protrude beyond the edge axis.
2. The blade segment of claim 1 wherein the long edge portions of the first side edge are inclined in the same direction with respect to the direction of the longitudinal axis and each elbow of the first side edge is turned away from the long edge portions of the first side edge to be inclined in a different direction than the long edge portions of the first side edge.
3. The blade segment of claim 1 wherein the long edge portions of the first side edge are parallel to one another.
4. The blade segment of claim 1 , wherein the first side edge comprises, in a direction from the first end edge towards the second end edge, at least the straight first long edge portion of said at least two long edge portions inclined from the direction of the longitudinal axis of the blade segment, the first bend following the first long edge portion and turned away from the direction of the first long edge portion, the straight short edge portion following the first bend and inclined from the direction of the longitudinal axis of the blade segment to a different direction than the first long edge portion, the second bend following the first short edge portion and turned away from the direction of the first short edge portion and the straight second long edge portion of said at least two long edge portions following the second bend and inclined from the direction of the longitudinal axis of the blade segment to the same direction as the first long edge portion, wherein the first bend, the short edge portion and the second bend provide the elbow in the first side edge of the blade segment.
5. The blade segment of claim 1 , wherein the elbows at the opposite first side edge and second side edge lie on a same normal level with respect to the longitudinal axis.
6. The blade segment of claim 1 , wherein a number of elbows at each side edge is from two to seven.
7. The blade segment of claim 1 wherein of the short edge portion of each elbow is inclined with respect to the longitudinal axis by 10-90 degrees.
8. The blade segment of claim 1 wherein the blade bars and grooves extend in a first direction, and wherein the short edge portion of the elbow on each of the first side edge and the second side edge extends in a direction which is parallel to the first direction.
9. The blade segment of claim 1 wherein the first side edge and the second side edge are not mirror images of each other with respect to the longitudinal axis of the blade segment.
10. The blade segment of claim 1 , further comprising the first shoulder positioned radially outwardly from the second shoulder, said first shoulder and said second shoulder configured for contacting a neighboring blade segment when assembled to provide a part of a refining surface of a refining element of a refiner.
11. The blade segment of claim 1 wherein a ratio of a length of the short edge portions to a length of the long edge portions of the first side edge is 1:2-1:20.
12. The blade segment of claim 1 , wherein said blade segment is configured to be positioned on an apparatus defining with the blade segment a refiner for refining fibrous material.
13. The blade segment and refiner of claim 12 , wherein said blade segment is configured to be positioned alongside a second blade segment such that there is a continuous opening between the blade segment and the second blade segment.
14. The blade segment and refiner of claim 12 , wherein said blade segment is configured to be positioned alongside a second blade segment such that there is a discontinuous opening between the blade segment and the second blade segment.