Grinder with adjustable screens

1. A horizontal grinder, comprising:

a) a grinding drum;

b) at least two arcuate screens located adjacent to the grinding drum, the at least two arcuate screens having a leading edge and a trailing edge;

c) at least two screen supports, the at least two arcuate screens being positioned upon the at least two screen supports and being configured to slide into and out of place with respect to the at least two screen supports; and

d) a plurality of adjusting members that position each screen in a selected one of a plurality of positions relative to the grinding drum, the plurality of adjusting members being adapted to move the at least two screen supports to adjust the position of the at least two arcuate screens;

e) wherein the screens are positionable relative to the grinding drum independent of one another; and

f) wherein the adjusting members selectively vary the clearance between the leading edge of each screen and the grinding drum, and selectively vary the clearance between the trailing edge of each screen and the grinding drum, the leading edge clearance and the trailing edge clearance being adjustable independent of one another.

2. The grinder of claim 1 , wherein the adjusting members include cams that pivot to adjust the position of the screens in the selected one of the plurality of positions.

3. The grinder of claim 2 , wherein each cam defines a plurality of arc sections opposite a pivot point.

4. The grinder of claim 3 , wherein load and operational forces from the screen supports transfer from one of the arc sections of each cam to the center of the pivot point of each cam.

5. The grinder of claim 1 , wherein each of a first screen and a second screen of the plurality of arcuate screens is positioned relative to the grinding drum by two pairs of adjusting members.

6. The grinder of claim 5 , wherein the two pairs of adjusting members that position the first screen relative to the grinding drum are mounted to sides of a mill box, and wherein one of the pairs of adjusting members that positions the second screen relative to the grinding drum is carried by a mill box cover.

7. The grinder of claim 6 , wherein the one pair of adjusting members carried by the mill box cover varies the trailing edge clearance of the second screen.

8. The grinder of claim 7 , wherein another one pair of the adjusting members that positions the second screen relative to the grinding drum is mounted to the side of the mill box, the another one pair of the adjusting members varying the leading edge clearance of the second screen.

9. A screen arrangement for a horizontal grinder having a mill box, a mill box cover, and a grinding drum, the screen arrangement comprising:

a) at least two arcuate screens, the at least two arcuate screens having a leading edge and a trailing edge;

b) at least two screen supports, the at least two arcuate screens being positioned upon the at least two screen supports and being configured to slide into and out of place with respect to the at least two screen supports; and

c) a plurality of adjusting members that independently position each screen in a selected one of a plurality of positions, wherein the plurality of adjusting members are adapted to move the at least two screen supports to adjust the position of the at least two arcuate screens, at least one of the adjusting members defining a pivot point and a series of arc sections opposite the pivot point;

d) wherein the adjusting members selectively adjust the position of the leading edge of each screen, and selectively adjust the position of the trailing edge of each screen, the leading edge and the trailing edge being positionable independent of one another.

10. The arrangement of claim 9 , wherein the adjusting members are arranged in pairs, each of the screens being positioned in the selected one of the plurality of positions by two pairs of the adjusting members.

11. The arrangement of claim 10 , wherein the two pairs of adjusting members that position a first one of the screens are adjusting cam members that define the pivot point and the series of arc sections opposite the pivot point, and wherein one of the pairs of adjusting members that positions a second one of the screens is an adjusting set-screw member.

12. The arrangement of claim 11 , wherein the adjusting set-screw member adjusts that position of the trailing edge of the second one of the screens.

13. A method of maintaining a horizontal grinder, comprising the steps of:

a) providing a horizontal grinder having a mill box, a mill box cover, a grinding drum, and a screen arrangement, the screen arrangement including a first screen and a second screen respectively located in first and second screen positions about the circumference of the grinding drum; and

b) switching the positions of the first and second screens such that the heavier worn screen previously located in one of the first and second screen positions is positioned in the other of the first and second screen positions;

c) wherein the position of the leading edge and the position of the trailing edge of each screen is positionable in the respective screen position independent of one another.

14. The method of claim 13 , wherein the step of switching the positions of the first and second screens includes removing the second screen from the second screen position, removing the first screen from the first screen position, installing the second screen in the first screen position, and installing the first screen in the second screen position.

15. The grinder of claim 1 , wherein the at least two screen supports are positioned between the at least two arcuate screens and the plurality of adjusting members.

16. The arrangement of claim 9 , wherein the at least two screen supports are positioned between the at least two arcuate screens and the plurality of adjusting members.

17. The grinder of claim 1 , wherein at least one of the screen supports has a curvature that matches a curvature of at least one of the arcuate screens.