Patent ID: 12214355

DETAILED DESCRIPTION

As shown inFIG.1A, a planetary roller mill (also referred to as “roller mill” herein) for processing (e.g., grinding, drying, and/or calcining) a feed material such as, but not limited to, synthetic gypsum, natural gypsum, mixtures of synthetic gypsum and natural gypsum, Kaolin clay, bentonite, limestone, pet coke and coal, is generally designated by element number10. Thus, the roller mill10has utility in removing moisture from the feed material in the grinding assembly. The roller mill10includes a vessel assembly20mounted to a stationary frame21. The vessel assembly20is shown in a vertical orientation about an axis A10. The vessel assembly20includes: 1) a grinding section20A located at a bottom portion of the vessel assembly; 2) a material feed section20B located axially above the grinding section20A; and 3) a classifier housing20C located axially above the feed section20B. A material feed apparatus22is in communication with and secured to the material feed section20B. The material feed apparatus22has an inlet22A for receiving material to be supplied thereto; and a feed outlet22B for supplying the feed material to the feed section20B through a side wall of the feed section20B. The feed outlet22B of the material feed apparatus22is positioned axially above the grinding section20A such that the feed material enters the grinding section20A axially above the rollers50and above an axial upper edge32X of a grinding ring32. As shown inFIG.12, the feed outlet22B has a bottom edge22X and top edge22Y and two side walls22C which extend between the top edge22Y and the bottom edge22X. A turbine classifier40is rotationally mounted to a top portion of the vessel assembly20via a shaft40A that is coupled to a drive assembly40B for rotation of the shaft40A and the turbine classifier40. The turbine classifier40is in communication with an outlet41of the vessel assembly20. The turbine classifier40allows properly ground material to be discharged through the outlet41while returning material that requires additional grinding, back to the grinding section20A. While the turbine classifier40is shown and described, the present invention is not limited in this regard as other classifiers may be employed including but not limited to the whizzer separator shown and described in U.S. Pat. No. 2,108,609 that issued on Feb. 15, 1938 to R. F. O'Mara and also described in PCT Application No. PCT/US2017/23560, with reference toFIGS.2and3contained therein.

As shown inFIGS.12and14, a ramp49extends from a bottom edge22X of the feed outlet22B and slopes downwardly and radially inward to the axial upper edge32X of the grinding ring32of a planetary type roller mill, such as those shown inFIGS.1A and1B. The upper ramp end49U is secured to the inside surface20D at the bottom edge22X of the feed outlet22B. While the ramp49is shown and described as being employed with the planetary type roller mill, the ramp49may also be employed in a pendulum type roller mill, such as those shown inFIGS.6and7. The ramp49may be employed in any type of grinding mill. In one embodiment, an upper ramp end49U of the ramp49is secured to the inside surface20D of the of the vessel assembly20by a weld22W, for example, the weld22W located at the bottom edge22X of the feed outlet22B. In one embodiment, a lower ramp end49B of the ramp49rests on (seeFIG.12) or is secured to (e.g., via a weld32W, seeFIG.15) the axial upper edge32X of the grinding ring32. In one embodiment, the ramp49, including the lower ramp end49B and upper ramp end49U, is positioned radially outward of an inner radial edge (e.g., proximate the grinding surface46) of the grinding ring32. While the weld22W is shown and described as securing the upper ramp end49U to the inside surface20D and the weld32W is shown securing the lower ramp end49B to the axial upper edge32X of the grinding ring32, the present invention is not limited in this regard as other configurations may be employed including but not limited to the use of mechanical fasteners, a ramp integrally formed with the inside surface20D or the grinding ring32; the ramp49can be spaced apart from the grinding ring32and/or the ramp49can be secured to the inside surface20D and/or the grinding ring32with one or more brackets, fixtures or covers. As shown inFIG.14, the lower ramp end49B of the ramp49terminates a distance G30from an edge of the grinding surface46. The distance G30is determined based upon a maximum allowable wear of the grinding ring32.

As shown inFIG.14, a cover59is positioned over the ramp49and the feed outlet22B. While the cover59is shown and described with reference toFIG.14as being positioned over the ramp49and the feed outlet22B, the present invention is not limited in this regard as the cover59may be positioned over the feed outlet22B and the ramp49may be eliminated, as shown inFIG.13. As shown inFIGS.13and14, the cover59includes a sloped surface59F (e.g., a front sloped wall) supported by opposing side walls59E (e.g., two opposing triangular shaped side walls secured to the inside surface20D and the sloped surface59F)). The sloped surface59F slopes downward and radially inward from a top cover end59U thereof. The sloped surface59F terminates at a bottom cover end59B of the cover59. In one embodiment, the bottom cover end59B terminates a distance G33above the axial upper edge32X of the grinding ring32. In one embodiment, the distance G33is zero and the bottom cover end59B terminates at a horizontal plane that is coplanar with the axial upper edge32X of the grinding ring32. The bottom cover end59B of the cover59extends radially inward from the grinding surface46by a distance G31to allow ample area for discharge of the material to be ground. While the bottom cover end59B of the cover59is shown and described as extending radially inward from the grinding surface46, the present invention is not limited in this regard as the bottom cover end59B of the cover59may terminate radially outward from the grinding surface46. As shown inFIG.14, the cover59has the top cover end59U that is secured to the inside surface20D at a position (e.g., by a distance G50) above the upper edge22Y of the feed outlet22B. However, the present invention is not limited in this regard as the top cover end59U can be secured to the inside surface20D proximate to the upper edge22Y of the feed outlet22B, as shown inFIG.13. The cover59extend over the entire extent of the feed outlet22B from the upper edge22Y to the bottom edge22X and continues down and radially inward from the bottom edge22X. The Applicant has discovered that where the grinding section20A is directly below the outlet of the material feed, that the cover59illustrated inFIGS.13and14is aerodynamic, minimizes disruption to the air flow, and has utility for grinding and drying fine feed materials such as synthetic gypsum, natural gypsum (i.e., Spanish fine), clay, or limestone, which contains more than 25% fine particle sizes of 1 mm or less. The Applicant has discovered that the ramp49and the cover59cooperate with each other and the inside surface20D to provide a direct and unobstructed flow path R22between the feed outlet22B and the grinding section20A for the material to be ground. The ramp49and the cover59allow the material to be ground to travel more quickly from the feed outlet22B to the grinding section20A, compared to a configuration as shown inFIG.11that has no ramp or cover. The Applicant has further discovered that use of the ramp49and the cover59cooperate to reduce the quantity of material carried away by the updraft51A, thereby increasing the percentage of material discharged through the feed outlet22B that enters the grinding section20A, compared to a configuration as shown inFIG.11that has no ramp and no cover. In some embodiments, the cover59cooperates with the inside surface20D to provide a direct and unobstructed flow path R22between the feed outlet22B and the grinding section20A for the material to be ground.

FIG.15illustrates another embodiment of a ramp49′ and cover59′ that results in a greater interior area compared to that created by the ramp49and cover59configuration ofFIGS.12and14. The ramp49′ has an upper ramp end49U′ that is secured to the inside surface20D at a position between the bottom edge22X of the feed outlet22B and the axial upper edge32X of the grinding ring32. Thus, the upper ramp end40U′ is secured to the inside surface20D at a position below the bottom edge22X by a distance G40, as shown inFIG.15. The lower ramp end49B′ is configured similar to the lower ramp end49B of the ramp49and is secured to the axial upper edge32X of the grinding ring32and/or the inside surface20D similar to the described for the lower ramp end49B shown inFIG.14. The cover59′ includes a sloped surface59F′ that extends downward and radially inward from a top cover end59U′ thereof. The sloped surface59F′ transitions into a vertical surface59G′. The vertical surface59G′ terminates at a bottom cover end59B′ of the cover59′. In one embodiment, the bottom cover end59B′ terminates a distance G33above the axial upper edge32X of the grinding ring32. In one embodiment, the distance G33is zero and the bottom cover end59B′ terminates at a horizontal plane that is coplanar with the axial upper edge32X of the grinding ring32. The bottom cover end59B′ extends radially inward from the grinding surface46by a distance G31to allow ample area for discharge of the material to be ground. The cover59′ has the top cover end59U′ that is secured to the inside surface20D at a position (e.g., by a distance G50) above the upper edge22Y of the feed outlet22B.

The Applicant has discovered that the cover59′, illustrated inFIG.15, is aerodynamic, minimizes disruption to the air flow, and has utility for fine grinding limestone with fine feed sizes. The Applicant has discovered that the ramp49′ and the cover59′ cooperate to provide a direct and unobstructed flow path R22between the feed outlet22B and the grinding section20A for the material to be ground. The ramp49′ and the cover59′ allow the material to be ground to travel more quickly from the feed outlet22B to the grinding section20A, compared to a configuration as shown inFIG.11that has no ramp or cover. The Applicant has further discovered that use of the ramp49′ and the cover59′ cooperate to reduce the quantity of material carried away by the updraft51A (see e.g.,FIG.13), thereby increasing the percentage of material discharged through the feed outlet22B that enters the grinding section20A, compared to a configuration as shown inFIG.11that has no ramp or cover.

In one embodiment, the ramp49or49′ is secured (e.g., welded) to the cover59or59′ to create an integral one piece ramp and cover assembly. In one embodiment, the side walls59E or59E′ flare outwardly from the cover59or59′. In one embodiment, the side walls59E or59E′ have flanges extending outwardly therefrom. In one embodiment, the cover59or59′; the ramp49or49′; and/or the integral one piece ramp and cover assembly are removably secured to the inside surface20D. For example, in one embodiment, clamps and lugs are secured to the inside surface20D and the flange slides into the clamps and the cover59or59′ seat on the lugs so that the cover59or59′ and/or the ramp49or49′ are removably secured to the inside surface20D and located at a predetermined position from the grinding ring32.

The Applicant has discovered that the ramps49and49′ and/or the covers59and59′ can be employed in the planetary roller mills10illustrated inFIGS.1A,1B,2A-2F,3A-3C,4A,4B, and5as well as the pendulum mills ofFIGS.6and7. They may also be used in any other configuration of grinding mill where fine feed raw material is to be gravity fed from an outlet port toward a grinding section20A.

As shown inFIG.1A, a grinding assembly30is positioned in the grinding section20A of the vessel assembly20below the feed outlet22B. The grinding assembly30includes the annular grinding ring32that is secured to the inside surface20D of the vessel assembly20via suitable fasteners32F. The grinding ring32has an outside surface32Q that is arranged in sealing engagement with the inside surface33Y of a support ring33of the vessel assembly20. Thus, there is no annular gap between the grinding ring32and the support ring33of the grinding section20A of the vessel assembly20for air to flow through and bypass the grinding assembly30. In one embodiment, the grinding ring32is a continuous annular ring with no circumferential openings or material feed inlets extending therethrough. A plurality of vanes34are positioned between the support ring33and a base plate36that is secured to the frame21. The vanes34are positioned below the grinding assembly30and extend an angled length from a position radially outward from the grinding ring32to a position radially inward from the grinding ring32. The vanes34are positioned in a circumferential configuration around the support ring33. Adjacent pairs of the vanes34define channels35(e.g., nozzles) therebetween for conveying heated air designated by the arrows35A into the grinding assembly30at velocities and flow rates sufficient to dry and/or calcining the material to be ground, as described herein.

As shown inFIG.1A, the vessel assembly20includes an air supply manifold45that has an inlet45A that extends into a circumferential duct45B that surrounds and opens into the grinding section20A as described herein. In one embodiment, the outlet of the air supply manifold45is connected to a bottom portion of the opening44of the grinding ring32, axially beneath the plurality of rollers50.

As best shown inFIGS.3A and4Athe grinding ring32has an opening44extending therethrough from the axial upper edge32X to an axial lower edge32Y thereof. The opening44is defined by a radially inward facing grinding surface46and having a first area A1. The first area A1is the area defined by the equation A1=π/4 (D7)2, where D7is the nominal inside diameter of the grinding ring32measured at the radially inward facing grinding surface46.

Referring toFIGS.1A,2A,2E and2F, the grinding assembly30includes a drive shaft39rotatably mounted to the frame21. A hub43is secured to an upper portion of the drive shaft39by a key connection (not shown). The hub43includes a flange43F on a lower end thereof. The grinding assembly30includes a sleeve43C that extends axially downward from another flange43G. A shim stack43J is positioned between the flange43F and the flange43G. A plurality of fasteners secure the flanges43F and43G to one another. A plurality of gussets47are secured to and extend radially from the sleeve43C. The shim stack43J includes a predetermined number of shims (e.g., annular discs, for example 0.0625 inches (1.5875 mm) thick). Variation of the number of shims in the shim stack43J adjusts the vertical position of the rollers50relative to the grinding ring32, as described herein. While the shim stack43J is shown and described as being employed to adjust the vertical position of the rollers50relative to the grinding ring32, the present invention is not limited in this regard as other means for adjusting the rollers50relative to the grinding ring32may be employed including but not limited to washers and jacking screws or indeed by appropriate sizing of parts determining the position of the rollers50relative to the grinding ring32.

As shown inFIGS.1A,2A,2E and/or2F, the grinding assembly30includes a first support plate52secured to the shaft39via the hub43, the sleeve43C and the gussets47. The first support plate52has a first axially facing surface52A defining a second area A2. The first support plate52is of a generally non-circular shape configured to establish an optimum magnitude of the area A2. In one embodiment, as shown inFIGS.3B and4B, the area A2′ of the first support plate52is increased over the area A2shown inFIGS.3A and4A, by extending the area A2′ outwardly to cover an entire axial end50Z of each of the rollers50, without reducing the flow area FA. Use of the increased area A2′ reduces the contact pressure between the axial end50Z and the first axially facing surface52A (i.e., underside) of each of the lobes52L. While the area A2′ of the first support plate52is shown and described as being increased, the present invention is not limited in this regard as the area of the second support plate54can be increased in a manner similar to that described for the first support plate52. The Applicant has discovered that circular shaped support plates are not suitable to provide the optimum magnitude of the area A2. In one embodiment, as shown inFIG.3A, the support plate52has a central area52C with three lobes52L extending radially outwardly therefrom. WhileFIG.3Aillustrates the support plate52having three lobes52L, the present invention is not limited in this regard as the support plate may have any number of lobes, for example, as shown inFIG.4A, the support plate52has the central area52C with six lobes52L extending radially outwardly therefrom.

As shown inFIGS.1A,2A,2E and2Fthe grinding assembly30includes a second support plate54secured to the shaft39via the hub43, the sleeve43C and the gussets47. The second support plate54has a second axially facing surface54A defining a third area A3. The second support plate54is of a generally non-circular shape configured to establish an optimum magnitude of the area A3. The Applicant has discovered that circular shaped support plates are not suitable to provide the optimum magnitude of the area A3. The second support plate54is spaced axially apart from the first support plate52by a gap G10. The second support plate54is configured in a shape similar to that shown (e.g.,FIGS.3A,3B,4A and4B) and described for the first support plate52.

As shown inFIGS.1A and2A, a plurality of rollers50are rotatably mounted to and positioned between the first support plate52and the second support plate54. Adding shims to the shim stack43J causes the sleeve43C, the first and second support plates52and54and the rollers50to move vertically downward to vertically align the rollers50in the grinding ring32. Reducing the number shims in the shim stack43J causes the sleeve43C, the first and second support plates52and54and the rollers50to move vertically upward to vertically align the rollers50in the grinding ring32.

As shown inFIG.2D, the first support plate52is shown in a cut away view to expose the axial end50Z of the roller50. Each of the plurality of rollers50is configured to move between the first and second support plates52and54, for example move between the first and second support plates52and54in the direction of the arrow R1, (as shown by the dashed lines50version of the roller50) as a result of rotation of the shaft39in the clockwise direction of the arrow R9. Each of the plurality of rollers50has a bore50B extending axially therethrough. The bore50B has an inside diameter D50. Each of the plurality of rollers50is mounted on a pin60secured to and extending between the first support plate52and the second support plate54in the area of the respective lobe52L (e.g.,FIGS.3and4). Referring back toFIG.2D, the pin60has an outside diameter D60that is less than the inside diameter D50of the bore50B. Each of the plurality of rollers has a radially outer surface50X. Due to rotation of the shaft39in the clockwise direction R9, the roller50moves circumferentially backward towards a trailing edge54T of the second support plate54and away from the pin60as shown by the arrow R1. As a result of the rotation of the shaft39the roller50moves between the first and second support plates52and54. For example, the roller50moves between the first support plate52and the second support plate54in the direction of the arrow R1(seeFIG.2D) to the roller position indicated by the dashed lines50so that the radially outer surface50X is in grinding communication with the grinding surface46of the grinding ring32, for example, the outer surface50X′ rollingly engages the grinding surface46of the grinding ring32or the outer surface50X′ is in sufficient proximity to the grinding surface46of the grinding ring32to effectuate grinding. In one embodiment, as a result of the rotation of the shaft39, the roller50is forced radially outward in the direction of the arrow R2by centrifugal force to increase the contact pressure between the outer surface50X of the roller and the grinding surface46. If the roller50encounters very large or abnormally hard chunks of material, the roller50may temporarily move radially inward in a direction opposite to the arrow R2.

As shown inFIG.2D, when the shaft39is not rotating, the roller may attain a neutral state wherein the bore50B is centered around the pin60. In the neutral state the radially outer surface50X of the roller50is equidistant from lateral edges of the lobes52L and54L, as indicated by the distances D10and D11. However, when the shaft39rotates in the direction of the arrow R9, the roller50moves in the general direction of the arrow R1. As a result, the radially outer surface50X of the roller50is asymmetrically spaced from the lateral edges (i.e., the leading edge54U and trailing edges54T) of the lobes54L, as indicated by the unequal distances D12and D13. Since D13is greater that D12, a lesser area of the second axially facing surface54A slidingly engages the axial end50Y (seeFIG.2E, for example) of the roller50, compared to the neutral position. This results in higher contact pressures and increased wear during operation when the shaft39is rotating, compared to a configuration in which a greater percentage of the area of the second axially facing surface54A slidingly engages the axial end50Y of the roller50. While the asymmetric spacing of the lateral edges (i.e., the leading edge54U and trailing edges54T) of the lobes54L relative to the radially outer surface50X of the roller50is shown to decrease the contact area between the second axially facing surface54A and the axial end50Y of the roller50as shown and described, a similar configuration exists between the axial end50X of the roller50and the first axially facing surface52A.

As shown inFIG.3C, the support plate152is similar to the first and second support plates52and54ofFIGS.3A and3B, thus similar elements of the first support plate52are designated with similar element numbers preceded by the numeral1. The rollers50shown inFIG.3Care contoured with convex exterior surfaces50X, similar to the rollers50shown inFIG.2E.

As shown inFIG.3C, the area A2″ of the first support plate152is increased over the area A2shown inFIG.3A, by extending the area A2″ asymmetrically outwardly to cover a portion of (i.e., less than the area A2′ shown inFIG.3Band greater than the area A2ofFIG.3A) the axial end50Z of each of the rollers50, without reducing the flow area FA. Use of the increased area A2″ reduces the contact pressure between the axial end50Z and the first axially facing surface152A of each of the lobes152L, as described herein.

As shown inFIG.3C, the direction of rotation of the shaft39, the first support plate152and the second support plate154(only a portion of the second support plate154is shown under the cut away portion of the first support plate152) is clockwise, relative to the stationary grinding ring32, is indicated by the arrow R9. The first support plate152has a central area152C that defines a center of rotation about the axis A10. Three lobes152L extend radially outward from the central area152C. As shown inFIGS.3E and3F, each of the lobes152L has an asymmetrical shape and an area152Q (e.g., a recess, an opening or surface) for receiving a roller mounting pin60. The area for receiving the roller mounting pin60has a center point60P. The asymmetric shape of the lobes152L is defined by a trailing edge152T and a leading edge152U, generally opposite the trailing edge152T. The trailing edge152T extends further away from the center point60P than does the leading edge152U. For example, as shown inFIG.3E, the trailing edge152T extends away from the center point60P a distance D21and the leading edge152U extends away from the center point60P by a distance D20. The distance D21is greater than the distance D20.

As shown inFIGS.3E and3F, the lobe152L has a straight section152V that transitions at transition point R12to the trailing edge152T. The trailing edge152T transitions into the leading edge152U which transitions into a straight section152W at transition point R13. The trailing edge152T and the leading edge152U have has a radius of curvature R15measured from a center point152P of the lobe152L. The transition point R12is located at about a 10 o'clock to 11 o'clock position; and the transition point R13is located at about a 7 o'clock position.

As shown inFIG.3F, the center point60P is positioned on the lobe152L such that during rotation of the support plate in a direction from the trailing edge152T to the leading edge152U (i.e., in the direction of the arrow R9), the lobe152L is configured to cover at least a portion of the axial end50Z of the roller50, adjacent to the leading edge152U and the trailing edge152T, thereby leaving the arcuate segment157A of the axial end50Z uncovered. As shown inFIG.3F, the uncovered segment157A extends around the lobe152L from the transition point R12to the transition point R13at a substantially uniform width W57between an edge of the axial end50Z of the roller50and a transition50ZZ to the exterior surface50Z of the roller50. Thus, as shown inFIG.3Fthe lobe152L covers a portion of the axial end50Z adjacent to the leading edge152U and the trailing edge152T.

As shown inFIG.3E, the center point60P is positioned on the lobe152L such that in a neutral state with the center point60P positioned coaxially with the axial center line50P of the roller50. The lobe152L is configured to cover at least a portion of the axial end50Z of the roller50, adjacent to the leading edge152U but none or less of the axial end50Z adjacent to the trailing edge152T, thereby leaving the arcuate segment157B of the axial end50Z, uncovered. As shown inFIG.3E, the uncovered arcuate segment157B extends around the leading edge152U of the lobe152L a non-uniform width W56between an edge of the axial end50Z of the roller50and a transition50ZZ to the exterior surface50Z of the roller50. Thus, as shown inFIG.3Ethe lobe152L covers a portion of the axial end50Z adjacent to the leading edge152U. As shown inFIG.3F, in the rotating state, the roller50moves in the direction of the arrow R1and an uncovered segment157A extends around the leading edge152U and trailing edge152T of the lobe152L a uniform width W57between an edge of the axial end50Z of the roller50and a transition50ZZ to the exterior surface50Z of the roller50.

The Applicant has discovered that use of the asymmetric shape of the lobe152L disclosed herein allows the bore50B to wear radially outward while maintaining the axial end50Z of the roller50partially covered. This is because as the wear occurs and the roller50migrates further away from the trailing edge152T, the greater distance D21that the trailing edge152T extends away from the center point60P compared to the distance D22, the lobe152L maintains greater coverage of the axial end50Z, compared to the lobes52L shown inFIG.3A.

While the asymmetric lobes152L are shown and described for the first support plate152, similar asymmetric lobes may be employed for the second support plate154.

As shown inFIG.3D, wear plates169A,169B is similar to the wear plates69A,69B illustrated inFIGS.2E and2F, except that the wear plates169A and169B have an asymmetric shape complementary to the asymmetric shape of the lobes152L described herein with reference toFIGS.3C,3E and3F. The wear plates169A,169B are installed in the grinding section20A similar to that shown and described herein with reference toFIGS.2E and2Ffor the wear plates69A and69B. Similar to the wear plates69A and69B, the wear plates169A,169B have holes171H extending there through for receiving fasteners69F that are threaded into the respective first and/or second support plates52,152,54,154for securing the wear plates169A,169B thereto. The Applicant has overcome difficulty in mounting (e.g., wear plates are too hard to form threads therein and may require periodic replacement) the wear members69A and69B to the respective one of the first support plate52and the second support plate54, by employing the fasteners69F proximate a radially inward edge thereof while employing spot welds on a radially outer edge thereof.

As shown inFIG.1A, the air supply manifold45has an outlet in the form of the circumferential duct45B that is in communication with the opening44in the grinding ring32for supplying heated air through the opening44at a velocity and flow rate sufficient for drying and calcining the moist material to be ground. As shown inFIGS.1A,1B,2A, and2B, the heated air flows upward through the grinding section20A and the feed section20B as indicated by the arrows51A. The feed material flows in a generally downward direction from the feed outlet22B in the general direction of the arrows51F and generally opposite to the direction indicated by the arrows51A.

As shown inFIGS.2E and2Fa first wear member69A (e.g., a plate) is removably secured to an first axially facing surface52A of each of the lobes52L of the first support plate52by suitable fasteners69F. The first wear member69A is manufactured from a heat treated alloy steel that has a hardness of about 500-600 BHN. An axial end50Z of the roller50slidingly engages the first wear member69A. Each of the first wear members69A has a shape that is complementary to the shape of a portion of the lobe52L.

As shown inFIGS.2E and2F, a second wear member69B (e.g., a plate) is removably secured to second axially facing surface54A (i.e., upper side) of each of the lobes54L of the second support plate54by suitable fasteners69F. The second wear member69B is manufactured from a heat treated alloy steel that has a hardness of about 500-600 BHN. An axial end50Y of the roller50slidingly engages and is seated on the second wear member69B. Each of the second wear members69B has a shape that is complementary to the shape of a portion of the lobe52L. In one embodiment, the wear members69A and/or69B are about ½ inch thick. In one embodiment, there is a small gap G9(e.g., about 0.10 to 0.15 inches) between the underside of the first wear member69A and the axial end50Z of the roller50.

As shown inFIG.2F, the grinding assembly430has conical rollers450that have the radially outer surface450X sloped at an angle δ relative to reference line A12that is parallel to an axial center line A11of the roller450. The grinding ring432has conical grinding surface446that is sloped radially inward and axially downward from the axial upper edge432X of a grinding ring432to the axial lower edge432Y of the grinding ring432at the angle δ measured relative to a vertical reference line A12. The roller450is installed in the grinding ring432with the axial end450Y (i.e., smaller diameter end compared to the axial end450Z) facing down and below the axial end450Z. The angle δ is between 5 and 15 degrees. The use of the conical rollers450and the conical grinding surface446has utility in providing a vertical lifting force which lifts the roller450to reduce the vertical force (e.g., about equal to 50-100% of the weight of the roller450) applied to the wear member69B. Reduction of the vertical force applied to the wear plate69B reduces friction, wear and power consumption. Use of the conical rollers450and the conical grinding surface446also has utility in compensating for misalignment of the rollers450relative to the grinding ring432during assembly, because after a period of operation the rollers450migrate to a position favorable to grinding performance. The conical rollers450and conical grinding surface446can also be employed in configurations without the wear plates69A and69B, for example, in the grinding assemblies30ofFIGS.2A,2B and2C. The conical rollers450have an overlay450K applied thereto, such as a cobalt based weld overlay (e.g., Stoody® 100 registered to Stoody Company or Stellite® registered to Kennametal Inc.). While the overlay450K is shown and described as being applied to the conical rollers450, the present invention is not limited in this regard as the overlay450K can be applied to any of the rollers50shown inFIGS.1A,1B,2A,2B,2C and2E. The overlay450K increases surface roughness and increases life of the rollers450,50and helps prevent skidding or sliding of the rollers450,50on the grinding surface446,46.

Employing the shim stack43J, as described herein and shown inFIG.2F, has utility in positioning the conical rollers450relative to the grinding ring432to maximize grinding surface area therebetween. Employing the shim stack43J also has utility in vertically positioning the contoured rollers50ofFIG.2Ein the grinding ring32to maximize the grinding surface area therebetween.

The first support plate and the second support plate are of a non-circular shape such that the optimum second area A2of the first support plate52and the optimum third area A3of the second support plate54are of magnitudes which configure a flow area FA (seeFIGS.3and4, for example showing the flow area FA as being the area A1minus the area A2) through the opening of at least 30 percent of the first area A1to provide a predetermined quantity of heated air in a ratio of 2-4 mass flow rate of air to mass flow rate of material being dried, to dry and/or calcining the feed material in the grinding assembly30and transport the ground material upwards through the grinding assembly30at a velocity (e.g., a velocity of about 20 feet per second to 40 feet per second) sufficient to entrain the ground material, in an air stream flowing upwardly through the grinding assembly30. In one embodiment, the flow area FA is from 40 to 70 percent of the first area A1so that the predetermined quantity of heated air is sufficient to dry and calcining synthetic gypsum, natural gypsum or mixtures of synthetic gypsum and natural gypsum. In one embodiment, the flow area FA is from 40 to 50 percent of the first area A1so that the predetermined quantity of heated air is sufficient to dry and calcining synthetic and natural gypsum. The flow area FA extends from a radially outer edge52E (seeFIGS.1A,1B,2A,2B,2C,3A,3B) of the first support plate52to the grinding surface46. The flow area FA extends from a radially outer edge54E (seeFIGS.1A,1B,2A,2B,2C,3A,3B) of the second support plate54to the grinding surface46. The flow area FA extends from a radially outer edge56E (seeFIG.2C) of the third support plate56to the grinding surface46. The flow area FA includes an outlet of the grinding section20A that transitions into the feed section20B.

Configuring the flow area FA from 40 to 70 percent or from 40 to 50 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry and calcining synthetic gypsum having about 10 wt % (i.e., weight percent) surface moisture and about 20 wt % chemical bond moisture (i.e., collectively referred to as high moisture). Configuring the flow area FA from 40 to 70 percent or from 40 to 50 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry and calcining natural gypsum having about 5 wt % (i.e., weight percent) surface moisture and about 20 wt % chemical bond moisture (i.e., collectively referred to as high moisture). Configuring the flow area FA from 40 to 70 percent or from 40 to 50 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry and calcining a mixture of synthetic gypsum and natural gypsum having about 5 wt % to about 10 wt % (i.e., weight percent) surface moisture and about 20 wt % chemical bond moisture (i.e., collectively referred to as high moisture). In addition, configuring the flow area FA from 40 to 70 percent or from 40 to 50 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air is sufficient to dry and calcining the feed material having about 10 wt % surface moisture and about 20 wt % chemical bond moisture. In one embodiment, the predetermined quantity of heated air is sufficient to dry and calcining the feed material having a particle size of less than 1 millimeter. In one embodiment, the predetermined quantity of heated air is sufficient to dry and calcining the feed material having a particle size of about 40 to about 80 microns.

In one embodiment, the flow area FA is from 30 to 60 percent of the first area A1so that the predetermined quantity of heated air is sufficient to dry the feed material that includes one or more of Kaolin clay, bentonite, limestone, pet coke and coal. Configuring the flow area FA from 30 to 60 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry the feed material having a moisture content of greater than 5 wt %. Configuring the flow area FA from 30 to 60 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry the feed material having a moisture content of greater than 5 wt % and having a particle size of about 0.05 mm to about 50 mm.

In one embodiment, the flow area FA is from 30 to 40 percent of the first area A1so that the predetermined quantity of heated air is sufficient to dry the feed material that includes one or more of Kaolin clay, bentonite, limestone, pet coke and coal. Configuring the flow area FA from 30 to 40 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry the feed material having a moisture content of greater than 5 wt %. Configuring the flow area FA from 30 to 40 percent of the first area A1yields the surprising result of providing the predetermined quantity of heated air sufficient to dry the feed material having a moisture content of greater than 5 wt % and having a particle size of about 0.05 mm to about 50 mm.

For grinding, drying and calcining synthetic or natural gypsum or mixtures thereof, the Applicant discovered that the 40-70% flow area are required to provide sufficient air flow with enough heating capacity, while providing sufficient dwell time in the grinding section to produce a ground calcined product of a predetermined particle size. The Applicant has discovered that for grinding and drying of other material such as Kaolin clay, bentonite, limestone, pet coke and coal, that the 30-60% flow area is required to provide sufficient air flow with enough heating capacity, while providing sufficient grinding section to produce a ground dried product of a predetermined particle size.

As shown inFIGS.1A and2A, the radially outer surface50X of each of the rollers is contoured (e.g., convex) and the grinding surface46of the grinding ring is contoured (e.g., concave). The present invention is not limited in this regard as in one embodiment, the radially outer surface50X′ of each of the rollers50′ is substantially straight and the grinding surface46′ of the grinding ring32′ is substantially straight, as shown inFIGS.1B and2B.FIGS.1B and2Bare similar toFIGS.1A and2Awith the exception of the aforementioned straight configuration and therefor include the same element numbers for identical components. Through computational analysis, the Applicant has found that the roller mills10(FIG.1A) with the rollers50having the convex radially outer surface50X and the concave grinding surface46consume less energy compared to the roller mills10′ (FIG.1B) having straight radially outer surface50X′ and straight grinding surface46′.

As best shown inFIG.5, the grinding assembly30includes a plow assembly70rotatable with the shaft39and configured to transport the feed material from below the grinding assembly30upwards to the plurality of rollers50′ and grinding ring32′. As shown inFIGS.2E and2F, the second support plate54is utilized as a mounting site for a plow support structure77to receive the plow assembly70. Adjusting the number of shims in the shim stack43J also adjusts the vertical position of the plow assembly70, similar to that described herein for adjusting the vertical position of the rollers50.

As shown inFIG.2C, in one embodiment, the roller mill30″ has a multiple roller layered configuration (e.g., 2 layers of contoured rollers are shown) includes a third support plate56secured to the shaft39via the sleeve43C (and the hub43shown inFIG.2A). A plurality of contoured rollers50is shown positioned between the first support plate and the second support plate54. The contoured rollers50have an arcuate curved circumferential surface50X. The third support plate56is spaced axially apart from the first support plate52and the second support plate54. An additional plurality of contoured rollers50″, similar to the contoured rollers50, is mounted to and positioned between the third support plate and the second support plate54. Each of the additional plurality of rollers50″ is configured to move between the first support plate, the second support plate and/or the additional support plate as a result of rotation of the shaft39. Each of the plurality of contoured rollers50has the radially outer surface50X that is in grinding communication with the contoured grinding surface46of the grinding ring32, for example, the outer surface50X rollingly engages the contoured grinding surface46of the grinding ring32″ or the outer surface50X is in sufficient proximity to the contoured grinding surface46of the grinding ring32to effectuate grinding. Each of the plurality of additional rollers50″ has the radially outer surface50X″ that is in grinding communication with the contoured grinding surface46″ of the grinding ring32″, for example, the outer surface50X″ rollingly engages the contoured grinding surface46″ of the grinding ring32″ or the outer surface50X″ is in sufficient proximity to the contoured grinding surface46″ of the grinding ring32″ to effectuate grinding. The Applicant has found that the use of the multiple roller layer configuration shown inFIG.2C, preferably a limit of two layers, is adequate because the two layers do not impede the upward flow of material to be ground as provided by the plow assembly70, compared to prior art mills200(FIG.8) that employ a top to bottom path for material being fed through the grinding assembly280.

WhileFIG.2Cillustrates a first support plate52and a second support plate54with a plurality of rollers50there between and the plurality of additional rollers50″ positioned between the second support plate54and the third support plate56, the present invention is not limited in this regard as any number of rows or layers of plurality of rollers between any number of support plates may be employed without departing from the broader aspects of the present invention.

The grinding assembly30has no lubrication system that provides a lubricant such as oil to the pin60and the bore50B of the rollers50,50′ or50″. As a result, the grinding assembly30is configured for grinding the feed material that requires an airstream supplied at a temperature that the pin60and the bore50B of the rollers50,50′ or50″ operate at greater than 177 degrees Celsius (350 degrees Fahrenheit) or higher (e.g., 232 degrees Celsius (450 degrees Fahrenheit)). Moreover, since the weight of the rollers50,50′ or50″ is significantly less (e.g., 40 percent of) than a comparably sized journal assembly188of the prior art pendulum mill100shown and described with reference toFIGS.6and7, with less grinding pressure and thus less vibration, but still able to achieve throughput required. As a result, the planetary roller mill10with the grinding assembly30is configured to grind, dry and calcining materials such as synthetic gypsum, natural gypsum or mixtures of synthetic gypsum and natural gypsum having a feed material particle size of 40 to 80 microns and a ground particle size of 25 to 35 microns.

The present invention includes a method of retrofitting a roller mill such as the pendulum mill100shown inFIG.6. The method includes providing a roller mill, such as the pendulum mill100, that has a vessel assembly105mounted to a stationary frame or base assembly110and a grinding assembly180positioned in the vessel assembly105. The grinding assembly180includes a first grinding ring133that has a first opening extending therethrough. The first opening is defined by a first radially inward facing grinding surface129and has a first area. The first grinding ring133is in sealing engagement with the inside surface of the vessel assembly105. A shaft182is rotatably mounted to the frame110, for example by suitable bearings. A hub186is mounted to one end of the shaft182, for example via a key and keyway configuration. A plurality of arms187(e.g., spider plates) extend from the hub186. The grinding assembly180includes a plurality of journal assemblies188as shown in detail inFIG.7. One of the plurality of journal assemblies188is pivotally secured to each of the plurality of arms187. The grinding assembly180includes a plurality of first rollers189. One of the plurality of first rollers189is rotatingly coupled to each journal assembly188. The method of retrofitting the roller mill includes removing the plurality of arms187, the plurality of journal assemblies188and the plurality of first rollers189from the roller mill. The shaft189and the hub186may be employed in the retrofitted roller mill, modified or replaced with the hub43and shaft39illustrated inFIGS.1A,2A,2E and2F, for example. The method includes providing a sleeve43C, a first support plate52, a second support plate54and a plurality of second rollers50such as, for example, those shown inFIGS.1A,2A,2E and2F. The sleeve43C is positioned over the shaft39and the sleeve43C is secured to the shaft39via the hub43. The method includes securing the first support plate52to the sleeve43C, for example by welding and use of the gussets47. The first support plate52has a first axially facing surface52A that defines a second area A2. The method includes securing the second support plate54to the sleeve43C, for example by welding. The second support plate54has a second axially facing surface54A that defines a third area A3. The second support plate54is spaced axially apart from the first support plate52. The method includes rotatably mounting the plurality of second rollers50to and between the first support plate52and the second support plate54so that each of the plurality of rollers50is configured to move between the first support plate52and the second support plate54as a result of rotation of the shaft, as shown and described herein with reference toFIG.2D. Each of the plurality of rollers50has a radially outer surface50X. The first support plate52and the second support plate54are of a non-circular shape such that the second area A2of the first support plate52and the third area A3of the second support plate54are of magnitudes which configure a flow area FA through the first opening44of at least 30 percent of the first area A1to provide a predetermined quantity of heated air to remove moisture from the feed material in the grinding assembly20A.

In one embodiment, the method includes providing a first plow assembly190secured to the hub186by the plow support191, as shown inFIG.6. The first plow assembly190is removed from the pendulum mill100. The method includes providing one or more second plow assemblies70and securing the second plow assembly70or assemblies to a bottom portion of the second support plate54.

In one embodiment, the method includes removing the first grinding ring133(FIG.6) from the mill100. A second grinding ring32is provided, such as that shown inFIGS.1A,2A,2E and2F. The second grinding ring32has the first opening defined by the first radially inward facing grinding surface46and has the first area A1. The first area A1of the first and second grinding rings133,32may be equal or different in magnitude. The method includes installing the second grinding ring32in sealing engagement with the inside surface of the vessel assembly.

In one embodiment, the method includes installing the second grinding ring32in sealing engagement with the inside surface20D of the vessel assembly20.

In one embodiment, the method includes adjusting the vertical position of the rollers50relative to the grinding ring32, for example, with the use of the shim stack43J.

Although this invention has been shown and described with respect to the detailed embodiments thereof, it will be understood by those of skill in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed in the above detailed description, but that the invention will include all embodiments falling within the scope of the appended claims.