Centrifugal pulverizing mill
A pulverizer has arms connected to a vertically oriented rotating shaft at hubs. The arms are angled relative to radians extending from the shaft to be canted or offset. Pads can be oversized relative to the arms while being one of coplanar with the arms or recessed while possibly also having their radially inward face(s) angled to assist in resisting catching material thereon. A mechanical fuse connection can assist in connecting arms to the hub to prevent dangerous situations as well.
1. A pulverizer for size-reducing a material comprising:
a head having an input port;
a bottom having a discharge port;
a housing extending between the head and the bottom;
a rotatable shaft extending vertically within the housing;
a plurality of hubs connected to the rotatable shaft, wherein each of the plurality of hubs comprises a first plate and a second plate, wherein each of the first plate and the second plate encircles the rotatable shaft;
a plurality of arms respectively coupled to the plurality of hubs between the first plate and the second plate by first pins, wherein when the rotatable shaft is rotated, the plurality of arms rotate to generate vortices inside the housing;
a plurality of mechanical fuses each comprising a second pin, wherein the first pin pivotably couples and the second pin releasably couples one of the plurality of arms to one of the plurality of hubs between the first plate and the second plate of the one of the plurality of hubs to retain the one of the plurality of arms in a first position relative to the one of the plurality of hubs, the second pin being configured to release the one of the plurality of arms and allow the one of the plurality of arms to rotate between the first plate and the second plate about the first pin into a second position relative to the one of the plurality of hubs when the one of the plurality of arms is subjected to a force equal to or higher than a predetermined force; and
a first spacer plate and a second spacer plate each having a female end and a male end, wherein the female end and the male end on the first spacer plate are configured to interlock with the male end and the female end, respectively, on the second spacer plate, the first and second spacer plates being configured to interlock around the rotatable shaft adjacent to the first plate and the second plate.
2. The pulverizer as claimed in claim 1 , wherein when the one of the plurality of arms is positioned in the first position, the second pin prevents the one of the plurality of arms from rotating relative to the one of the plurality of hubs about the first pin.
3. The pulverizer as claimed in claim 1 , wherein the second pin comprises a shear pin which is breakable when the one of the plurality of arms is subjected to the force equal to or greater than the predetermined force to allow the one of the plurality of arms to rotate relative to the one of the plurality of hubs.
4. The pulverizer as claimed in claim 3 , wherein the shear pin has a diameter which is smaller than a diameter of the first pin.
5. The pulverizer as claimed in claim 3 , wherein the shear pin has one or more circumferential grooves defining a failure location along the shear pin.
6. The pulverizer as claimed in claim 5 , wherein the shear pin has two circumferential grooves.
7. The pulverizer as claimed in claim 3 , wherein the first one of the plurality of pins extends through the one of the plurality of arm along an axis of a first segment of the one of the plurality of arms extending outward from the one of the plurality of hubs, and the shear pin extends through the one of the plurality of arms offset from the axis of the first segment.
8. The pulverizer as claimed in claim 7 , wherein the one of the plurality of arms comprises a second segment that is angled at an angle of more than 90 degrees relative to the first segment.
9. The pulverizer as claimed in claim 1 , wherein the plurality of mechanical fuses break at the predetermined force, and the predetermined force is lower than a failure stress value of the one of the plurality of arms.
10. The pulverizer as claimed in claim 9 , wherein the predetermined force is less than ½ of the failure stress value of the one of the plurality of arms.
11. The pulverizer as claimed in claim 9 , wherein the predetermined force is equal to ½ of the failure stress value of the one of the plurality of arms.
12. The pulverizer as claimed in claim 9 , wherein the predetermined force is equal to ⅓ of the failure stress value of the one of the plurality of arms.
13. The pulverizer as claimed in claim 1 , wherein the one of the plurality of arms comprises a first segment extending outward away from the one of the plurality of hubs and a second segment oriented at a non-zero angle relative to the first segment, wherein the second segment is coupled to the one of the plurality of hubs.
14. The pulverizer as claimed in claim 13 , wherein in the first position, an axis of the first segment of the one of the plurality of arms extends from the one of the plurality of hubs at a canted angle being between 5 and 30 degrees in the direction of rotation relative to a radian of the rotor extending through the first segment of the one of the plurality of arms.
15. The pulverizer of claim 14 , wherein the one of the plurality of arms is configured to move from the first position into a third position having a second canted angle relative to the radian different than when in the first position, wherein the one of the plurality of hubs has a first bore and a second bore, wherein the shear pin extends through the first bore when the one of the plurality of arms is in the first position, and the shear pin extends through the second bore when the one of the plurality of arms is in the third position.
16. A hub assembly for a pulverizer configured to size reduce a material, the pulverizer including a housing and a rotatable shaft extending through the housing, the hub assembly comprising:
a hub connectable to the rotatable shaft, the hub comprising a first plate and a second plate, wherein each of the first plate and the second plate encircles the rotatable shaft;
each of a plurality of arms secured to the hub between the first plate and the second plate by a first pin; wherein when the rotatable shaft is rotated, the plurality of arms rotate to generate vortices inside the housing;
at least one mechanical fuse comprising a second pin releasably coupling at least one of the plurality of arms to the hub between the first plate and the second plate to retain the at least one of the plurality of arms in a first position relative to the hub, the second pin being configured to release the at least one of the plurality of arms and allow the at least one of the plurality of arms to pivot between the first plate and the second plate about the first pin into a second position relative to the hub when the at least one of the plurality of arms is subjected to a force equal to or higher than a predetermined force; and
a first spacer plate and a second spacer plate each having a female end and a male end, wherein the female end and the male end on the first spacer plate are configured to interlock with the male end and the female end, respectively, on the second spacer plate, the first and second spacer plates being configured to interlock around the rotatable shaft adjacent to the first plate and the second plate.
17. The hub assembly as claimed in claim 16 , wherein when the at least one of the plurality of arms is positioned in the first position, the second pin prevents the at least one of the plurality of arms from pivoting relative to the hub about the first pin.
18. The hub assembly as claimed in claim 16 , wherein the mechanical fuse includes a shear pin which is breakable when the at least one of the plurality of arms is subjected to the force equal to or greater than the predetermined force to allow the at least one of the plurality of arms to pivot relative to the hub.