Segmented rotor cap assembly

Abstract

A rotor cap assembly has been conceived using multiple wedge-shaped rotor cap segments, in which the cap segments are disposed on a cap segment retainer and in which the cap segment retainer pilots the multiple rotor cap segments at a diameter intermediate the cap segments' outer diameter and the cap segments' middle diameter. By piloting multiple rotor cap segments with retaining means on the cap segment retainer and positioning means on the multiple cap segments, the rotor cap segments and cap segment retainer assembly may be fixed to a plate holder or directly to a rotor disc of a refiner without substantially altering either the plate holder or the rotor disc.

Claims

1. A rotor cap assembly comprising: multiple rotor cap segments configured to be disposed radially inward of refiner plate segments of a refiner, each rotor cap segment having a front side, a back side, a rotor cap segment inner diameter, a rotor cap segment outer diameter, and positioning means on the back side of each rotor cap segment; and a cap segment retainer configured to be engaged to a rotor through pre-existing fixing holes in the rotor, the cap segment retainer having a back side and retaining means on a front side of the cap segment retainer, wherein the multiple rotor cap segments are disposed on the front side of the cap segment retainer, and wherein the retaining means engage the positioning means on the back side of each rotor cap segment such that the retaining means and the positioning means pilot the multiple rotor cap segments at a rotor cap segment diameter.

2. The rotor cap assembly of claim 1, wherein the cap segment retainer further comprises holes aligning with pre-existing holes on the rotor and fasteners extending through the cap segment retainer and through pre-existing holes in the rotor to engage the cap segment retainer to the rotor.

3. The rotor cap assembly of claim 1, wherein the cap segment retainer further comprises holes aligning with holes in a plate holder disposed between the cap segment retainer and the rotor, wherein fasteners extend through the cap segment retainer and into the plate holder.

4. The rotor cap assembly of claim 1, wherein the retaining means and the positioning means pilot the multiple rotor cap segments at the outer diameter of the multiple rotor cap segments.

5. The rotor cap assembly of claim 1, wherein a rotor cap segment of the multiple rotor cap segments further comprises a middle diameter halfway between the rotor cap segment inner diameter and the rotor cap segment outer diameter and wherein the retaining means and the positioning means pilot the rotor cap segment at an intermediate diameter between the middle diameter and the outer diameter.

6. The rotor cap assembly of claim 1, wherein a rotor cap segment of the multiple rotor cap segments further comprises a middle diameter halfway between the rotor cap segment inner diameter and the rotor cap segment outer diameter and wherein the retaining means and the positioning means pilot the rotor cap segment at an intermediate diameter between the middle diameter and the inner diameter.

7. The rotor cap assembly of claim 1, wherein the cap segment retainer is an annular cap segment retainer.

8. A rotor cap assembly comprising: multiple rotor cap segments configured to be disposed radially inward of refiner plate segments of a refiner, each rotor cap segment having: a front side, a back side, a rotor cap segment inner diameter, a rotor cap segment outer diameter, a rotor cap segment middle diameter located between the rotor cap inner diameter and the rotor cap outer diameter, and a protrusion extending from the back side, wherein the protrusion has a protrusion sidewall at a side of the protrusion; and a cap segment retainer configured to be engaged to a rotor through pre-existing holes in the rotor, the cap segment retainer having: a back side, a front side, a body, and a retaining lip extending from the front side of the cap segment retainer, wherein the retaining lip has a retaining lip sidewall at a side of the retaining lip, wherein a top of the retaining lip sidewall and the body of the cap segment retainer define a concave space, and wherein the protrusion is disposed within the concave space such that the protrusion sidewall contacts the retaining lip sidewall.

9. The rotor cap assembly of claim 8, wherein the cap segment retainer further comprises holes aligning with the pre-existing holes on the rotor and fasteners extending through the cap segment retainer and through pre-existing holes in the rotor to engage the cap segment retainer to the rotor.

10. The rotor cap assembly of claim 8, wherein the cap segment retainer further comprises holes aligning with holes in a plate holder disposed between the cap segment retainer and the rotor, wherein fasteners extend through the cap segment retainer and into the plate holder.

11. The rotor cap assembly of claim 8, wherein the retaining lip sidewall contacts the protrusion sidewall to pilot a rotor cap segment of the multiple rotor cap segments at the rotor cap segment outer diameter.

12. The rotor cap assembly of claim 8, wherein the retaining lip sidewall contacts the protrusion sidewall to pilot a rotor cap segment of the multiple rotor cap segments at an intermediate diameter between the rotor cap segment outer diameter and the rotor cap segment middle diameter.

13. The rotor cap assembly of claim 8, wherein the retaining lip sidewall contacts the protrusion sidewall to pilot a rotor cap segment of the multiple rotor cap segments at an intermediate diameter between the rotor cap segment inner diameter and the rotor cap segment middle diameter.

14. The rotor cap assembly of claim 8 further comprising a central cap segment configured to be piloted on the cap segment retainer.

15. The rotor cap assembly of claim 8, wherein the cap segment retainer is an annular cap segment retainer.

16. The rotor cap assembly of claim 15, wherein the retaining lip sidewall contacts the protrusion sidewall to pilot a rotor cap segment of the multiple rotor cap segments at an intermediate diameter between the rotor cap segment outer diameter and the rotor cap segment middle diameter.

17. The rotor cap assembly of claim 16 further comprising a central cap segment having center of rotation, an outer diameter, and a central cap segment interlocking element is configured to engage a retainer interlocking element at a central cap diameter radially distal from the center of rotation.

18. The rotor cap assembly of claim 15, wherein the retaining lip sidewall contacts the protrusion sidewall to pilot a rotor cap segment of the multiple rotor cap segments at an intermediate diameter between the rotor cap segment inner diameter and the rotor cap segment middle diameter.

19. An annular rotor cap assembly comprising: multiple rotor cap segments configured to be disposed radially inward of refiner plate segments of a refiner, each rotor cap segment having a front side, a back side, a rotor cap segment inner diameter, a rotor cap segment outer diameter, and a cap segment interlocking element; and a cap segment retainer engaging a rotor through pre-existing holes in the rotor, the cap segment retainer having a back side, a front side, and a retainer interlocking element, wherein the cap segment interlocking element engages the retainer interlocking element at a rotor cap segment diameter radially distal from the rotor cap segment inner diameter.

20. The rotor cap assembly of claim 19, wherein the cap segment retainer further comprises holes aligning with the pre-existing holes on the rotor and fasteners extending through the cap segment retainer and through pre-existing holes in the rotor to engage the cap segment retainer to the rotor.

21. The rotor cap assembly of claim 19, wherein the cap segment retainer further comprises holes aligning with holes in a plate holder disposed between the cap segment retainer and the rotor, wherein fasteners extend through the cap segment retainer and into the plate holder.

22. The rotor cap assembly of claim 19, wherein the cap segment interlocking element and the retainer interlocking element define an interlocking mechanism and wherein the interlocking mechanism pilots a rotor cap segment of the multiple rotor cap segments at an intermediate diameter between the rotor cap inner diameter and the rotor cap outer diameter.

23. The rotor cap assembly of claim 19, wherein the cap segment retainer is an annular cap segment retainer.

24. The rotor cap assembly of claim 19 further comprising fasteners configured to engage the multiple rotor cap segments and the cap segment retainer to a rotor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The foregoing will be apparent from the following more particular description of exemplary embodiments of the disclosure, as illustrated in the accompanying drawings. The drawings are not necessarily to scale, with emphasis instead being placed upon illustrating the disclosed embodiments.

(2) FIG. 1A is a cross-section of a single disc refiner with a conventional single-piece rotor cap, a rotor plate holder, and a stator plate holder.

(3) FIG. 1B is an expanded view of the single disc refiner of FIG. 1A, which further depicts piloting the single-piece rotor cap around the center of rotation.

(4) FIG. 2A is a facing view of a conventional single-piece rotor cap.

(5) FIG. 2B is a cross-sectional side view of a conventional single-piece rotor cap.

(6) FIG. 3A is a facing view of an exemplary embodiment of the segmented rotor cap assembly.

(7) FIG. 3B is a cross-sectional side view of FIG. 3A, depicting the piloting arrangement for the rotor cap segments and center cap segment. FIG. 3C is a cross-sectional side view of another exemplary segmented rotor cap assembly depicting the piloting arrangement for the rotor cap segments.

(8) FIG. 4 is a perspective view of an exemplary segmented rotor cap disposed on a rotor disc with refiner plates.

(9) FIG. 5A if a facing view of rotor cap segment configured to be piloted with an annular cap segment retainer.

(10) FIG. 5B is a cross sectional side view of the rotor cap segment in FIG. 5A along the line 5B-5B further depicting the annular cap segment retainer.

(11) FIG. 5C is a facing view of an exemplary segmented annular rotor cap.

(12) FIG. 6A. is a cross-sectional side view of an exemplary rotor cap segment and annular cap segment retainer mounted around a rotor central part.

(13) FIG. 6B. is cross-sectional side view of another exemplary segmented rotor cap segment and annular cap segment retainer mounted around a rotor central part.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(14) The following detailed description of the preferred embodiments is presented only for illustrative and descriptive purposes and is not intended to be exhaustive or to limit the scope and spirit of the invention. The embodiments were selected and described to best explain the principles of the invention and its practical application. A person of ordinary skill in the art will recognize many variations can be made to the invention disclosed in this specification without departing from the scope and spirit of the invention. Except as otherwise stated, corresponding reference characters indicate corresponding parts throughout the several views. Although the drawings represent embodiments of various features and components according to the present disclosure, the drawings are not necessarily to scale and certain features may be exaggerated in order to better illustrate embodiments of the present disclosure, and such exemplifications are not to be construed as limiting the scope of the present disclosure in any manner.

(15) FIG. 1A is a cross-section of a conventional single-disc refiner 101 having a housing 104 defining a chamber 109. A rotor 105 resides within the chamber 109. The rotor 105 has a plate side 176.sub.a and a rotor shaft side 177. The rotor shaft side 177 engages a rotor shaft 190 that extends through a seal 178 disposed within the housing 104. Fasteners 183 may engage the seal 178 to the housing 104. The seal 178 isolates the temperature and pressure within the chamber 109 from the external environment. A motor (not depicted) engages the rotor shaft 190 and drives the rotor shaft 190 and rotor 105 around the center of rotation 106.

(16) A stator 107 is disposed opposite the rotor 105. The stator 107 has a plate side 176.sub.b opposite the plate side 176.sub.a of the rotor 105. Bolts 181 engage a plate holder 113 to the plate side 176.sub.b of the stator 107 through fixing holes 182 in the stator 107. These bolts 181 similarly engage the plate holder 113 to the plate side 176.sub.a of the rotor 105 through fixing holes 182 in the rotor 105. The bolts 181 may extend through the stator 107. The bolts 181 may extend through the rotor 105. Fasteners 183 can extend to the plate holder 113 to engage refiner plate segments 115.sub.b on the stator 107. Similarly, fasteners 183 can extend through the plate holder 113 to hold the refiner plate segments 115.sub.a on the rotor 105. The plate holders 113 may provide additional fastener holes that do not communicate with the rotor 105. This allows operators to assemble the refiner plate segments 115.sub.a, 115.sub.b on the single piece plate holder before installing the plate holder 113 to the rotor 105.

(17) Refiner plate segments 115 usually have an abrasive surface comprising a pattern of bars and grooves (see FIG. 4), a pattern of intermeshing teeth, or a combination thereof. The refiner plate segments 115.sub.a on the rotor 105 do not contact the refiner plate segments 115.sub.b on the stator 107; rather, a refining gap 119 exists between the opposing sets of refiner plate segments 115.sub.a and 115.sub.b.

(18) In the depicted single disc refiner, the stator 107 further defines a feed inlet 111 disposed opposite the single-piece rotor cap 103. As the rotor 105 spins, operators feed lignocellulosic feed material F through the feed inlet 111. Wide bars 130 may be disposed upon the single-piece rotor cap 103. As the lignocellulosic material F contacts the spinning single-piece rotor cap 103 or wide bars 130, the single-piece rotor cap 103 or wide bars 130 flings the lignocellulosic feed material F through the refining gap 119 in the refining area 168 (see path depicted by arrows in FIG. 1). As lignocellulosic fibers, steam, and debris flow through the refining gap 119, the abrasive surfaces on the refiner plate segments 115 generally separate, develop, and cut lignocellulosic fibers into desirable lengths and properties. After passing though the refining gap 119, operators may collect the refined lignocellulosic fibers for further processing, which may include additional refiner passes.

(19) FIG. 1B is a detailed view of the box B depicted in FIG. 1A. The rotor 105 may have a rotor shaft 190 having a weight evenly distributed around the center of rotation 106. The rotor shaft 190 has sides 192.sub.a, 192.sub.b extending outwardly from a core bottom 193 that define a concave space 195 at the plate side 176.sub.a of the rotor 105. The concave space 195 is disposed around the center of rotation 106. A first block 191 of the plate holder 113 extends into the concave space 195. In so doing, the first block 191 pilots the plate holder 113 at the rotor's center of rotation 106. That is, the sides 192.sub.a, 192.sub.b of the rotor shaft 190 pilot the plate holder 113 to the rotor 105 so that the plate holder 113 rotates around the plate holder's center of gravity.

(20) In FIG. 1B, the plate holder 113 further has a second block 196 extending into a concave space 197 defined by steps 187.sub.a, 187.sub.b extending from the back side 188 of the single-piece rotor cap 103. The steps 187.sub.a, 187.sub.b position the single-piece rotor cap 103 around the center of rotation 106 and the structural integrity of the single-piece rotor cap 103 provides the centripetal force that balances the inertia that the single-piece rotor cap 103 experiences as a result of the rotor's circular motion. The single-piece rotor cap 103 may be further positioned at a middle diameter (MD) by slanted walls 185.sub.a, 185.sub.b engaging a third block 184 of the plate holder 113.

(21) FIG. 2A is a front view of a conventional single-piece rotor cap 203. The single-piece rotor cap may weigh between 80 lbs. and 200 lbs. and is generally piloted around the center of rotation 206, which generally coincides with the single-piece rotor cap's center of gravity. The single-piece rotor cap's weight can encourage operators to use cranes, forklifts, or other heavy equipment when replacing worn rotor caps 203. The single-piece rotor cap 203 has wide bars 238 and wide channels 237 configured to direct lignocellulosic feed material F (FIG. 1A) into the refining gap 119 (FIG. 1A). In this version, the single-piece rotor cap 203 is fixed to the plate holder 113 (FIG. 1A) from the back through fasteners 183 extending through threaded holes 250. Single-piece rotor caps 203 have threaded holes 250 towards the periphery and lack such holes at smaller diameters.

(22) FIG. 2B is a cross-sectional side view of a traditional single-piece rotor cap 203. The single-piece rotor cap 203 has a front side 223 and a back side 288. The single-piece rotor cap 203 may have steps 287.sub.a, 287.sub.b extending from the back 288 side of the single-piece rotor cap 203 at the middle diameter MD. The steps 287.sub.a, 287.sub.b pilot the single-piece rotor cap 203 so that the single piece rotor cap 203 is centered on the rotor 205. As the single-piece rotor cap 203 rotates, the wide bars 238 and wide channels 237 direct lignocellulosic material F into the refining gap 119.

(23) FIG. 3A depicts a front view of an exemplary embodiment of a segmented rotor cap assembly 303. A central cap segment 365 is disposed around the center of rotation 306. In an exemplary embodiment, the central cap segment 365 may be piloted at an intermediate diameter IMD. The central cap segment's intermediate diameter IMD may be disposed between the center of rotation 306 and the central cap segment's outer diameter OD. The central cap segment's outer diameter OD may be disposed adjacent to a rotor cap segment's inner diameter ID. In other exemplary embodiments, the central cap segment 365 may be absent and the cap segment retainer 318 may be configured to have a center portion 365 exposed to the lignocellulosic feed material F while providing retaining means for rotor cap segments 317 (see FIG. 3C).

(24) In FIG. 3A, fasteners 383 extend through the central cap segment 365 and terminate in the cap segment retainer 318 to engage the central cap segment 365 to the cap segment retainer 318. Fasteners 383 extending through separate holes (354, see FIG. 3B) may engage the cap segment retainer 318 to pre-existing fixing holes in the rotor 105 or holes in the plate holder 113. The central cap segment 365 may have wide channels 337 defined by adjacent wide bars 338.sub.a on the front side 323 of the segmented rotor cap assembly 303. One or more of the wide bars 338.sub.a on the central cap segment 365 may align radially with one or more wide bars 338.sub.b on the rotor cap segments 317 such that the radially aligned wide bars 338.sub.a, 328.sub.b appear to extend from a point (see 306) on the central cap segment 365. In other exemplary embodiments, the wide bars 338.sub.a on the central cap segment 365 may not align radially with one or more wide bars 338.sub.b on the rotor cap segments 317.

(25) The rotor cap segments 317 are disposed radially outward from the center of rotation 306 around the central cap segment 365 or central cap portion 365. The rotor cap segments 317 are generally configured to be regular segments of a geometric annulus. In other exemplary embodiments, fasteners 383 may extend through the rotor cap segments 317, cap segment retainer 318, and through pre-existing holes in the rotor 105 to sandwich the cap segment retainer 318 between the rotor cap segments 317 and the rotor 105.

(26) FIG. 3B shows that each rotor cap segment 317 may have a protrusion 344 extending from the back side 371 of the rotor cap segment 317. The protrusion 344 may be bounded by sidewalls 359.sub.a, 359.sub.b. A retaining lip 311 extends from the body 347 of the cap segment retainer 318 toward the front side 323 of the segmented rotor cap assembly 303. The retaining lip 311 can be disposed annularly around the cap segment retainer 318. It will be understood that the retaining lip 311 may be a single continuous element that is disposed around a diameter of the cap segment retainer 318. In other exemplary embodiments, multiple retaining lips 311 may be disposed around a common diameter on the cap segment retainer 318. In still other exemplary embodiments, the cap segment retainer 318 may have more than one retaining lip 311 disposed at different diameters on the cap segment retainer 318. In still other exemplary embodiments, the cap segment retainer 318 may have more than one retaining lip 311 disposed around at least one first common diameter and more than one retaining lips disposed around subsequent common diameters. Combinations of the above embodiments are considered to be within the scope of this disclosure.

(27) For clarity, the use of the subscripts a or b after an element that may be configured to extend as a single piece around a diameter of a rotor 105, 605 rotor cap segment 317, 417, 517, 617, rotor cap segment retainer 318, central cap segment 365, or annular rotor cap segment retainer 527, 627 will be used to differentiate upper portions of the element from lower portions of the element.

(28) The retaining lip 311.sub.a, has a sidewall 326.sub.a configured to contact the sidewall 359.sub.a of the protrusion 344. The retaining lip sidewall 326.sub.a is disposed opposite a sidewall 326.sub.b that extends from the body 347 of the cap segment retainer 318 toward the front side 323 of the segmented rotor cap assembly 303. The retaining lip sidewall 326.sub.a, the body 347 of the cap segment retainer 318 disposed between sidewall 326.sub.a and 326.sub.b, and sidewall 326.sub.b define a concave space 362 configured to receive the rotor cap's protrusion 344. The rotor cap protrusion 344 can be disposed between the sidewalls 326.sub.a and 326.sub.b. In this manner, the sidewalls 326.sub.a, 326.sub.b can define a space configured to receive the positioning means (e.g. the rotor cap's protrusion 344) and thereby position the rotor cap segments 317 relative to the central cap segment 365 or central cap portion 365 while providing structures configured to balance the forces the refiner plate segments 317 experience as a result of the rotor's circular motion. Fasteners 383 can engage the rotor cap segments 317 to the cap segment to the rotor 105 or a plate holder 113 through the cap segment retainer 318. In the depicted exemplary embodiment, the fasteners 383 extend from holes 354 in the rotor cap segments 317 through holes 354 in the cap segment retainer 318 but the fasteners 383 do not extend into the rotor 105 or plate holder 113. The fasteners that extend through threaded holes 350 sandwich the cap segment retainer 318 between the central cap segment 365 and the plate holder 113 and thereby hold the central cap segment 365 and the cap segment retainer 318 to the plate holder 113. In the depicted embodiment, the fasteners 383 extending through holes 354 merely engage the rotor cap segments 317 to the cap segment retainer 318. In this manner, the cap segment retainer 318 with retaining means may have threaded holes 350 configured to align with pre-existing holes in the rotor 105 (see 450, FIG. 4) while further providing additional holes 354 that do not align with pre-existing holes in the rotor 105. The fasteners 383 generally provide axial force (e.g. force parallel with the line representing the center of rotation 306) sufficient to secure the rotor cap segments 317 to the cap segment retainer 318 when the rotor 105 is not spinning. The fasteners 383 are not configured to withstand the inertia I the rotor cap segments 317 experience when the rotor 105 is spinning. In other exemplary embodiments, each hole on the cap segment retainer 318 may align with a pre-existing hole in the rotor 105. In still other exemplary embodiments involving threaded holes 350, additional fasteners 383 may extend through central cap segment 365, and secure the central cap segment 365 to the threaded holes 350 in the cap segment retainer 318. Alternatively, threaded holes 350 can be found in the central cap segment 365, lining up with holes in the plate holder 113, and fasteners 383 can extend through the central cap segment 365 and the cap segment retainer 318 to secure the central cap segment 365 to the plate holder 113 such that the cap segment retainer is sandwiched between the central cap segment 365 and the plate holder 113.

(29) Without being bounded by theory, when the rotor 105 is spinning, the retaining lip 311.sub.a provides centripetal force C sufficient to cancel out the inertia I caused by the rotor's circular motion. In this example embodiment, retaining lip 311.sub.a is located near the outer diameter OD of the cap segment retainer 318 and is configured to pilot the rotor cap segment 317 at intermediate diameter IMD disposed between the rotor cap segment's outer diameter OD and the rotor cap segment's middle diameter MD. In FIGS. 3B and 3C, the outer diameter OD of the cap segment retainer 318 and rotor cap segment 317 are coextensive. In other exemplary embodiments, the outer diameter OD of the rotor cap segment 317 may not be coextensive with the outer diameter OD of the cap segment retainer 318. Retaining lip 311.sub.b preforms the same function at the bottom of the segmented rotor cap assembly 303. If the retaining lip 311.sub.a or similar means for nullifying the inertia I that the rotor cap segments 317 experience during rotational motion were absent, the rotor cap segments 317 may move radially outward beyond the outer diameter OD of the cap segment retainer 318. Such movement could unbalance the rotor 105, cause a rotor cap segment 317 to encroach into the refining gap 119, and generally accelerate the need for refiner maintenance or replacement.

(30) It will be understood that although a segmented rotor cap 317 having one protrusion 344 is depicted in these figures, rotor caps 317 having multiple protrusions, including multiple protrusions of different dimensions, as well as corresponding positioning means are considered to be within the scope of this disclosure.

(31) FIG. 3B further depicts a cross-sectional side view of an exemplary segmented rotor cap assembly 303 having a central cap segment 365 and rotor cap segments 317 disposed in a cap segment retainer 318. The central cap segment 365 and rotor cap segments 317 may be removable and replaceable after a desired time period, such as bi-annually to ensure suitable refiner performance and to preserve the integrity of fiber quality. Fasteners 383 generally engage the rotor cap segments 317 to the rotor 105 such that the cap segment retainer 318 is wedged between the rotor cap segments 317 and the rotor 105.

(32) The cap segment retainer 318 may have a central protrusion 345 extending from the body 347 of the cap segment retainer 318. The central cap segment 365 has steps 335.sub.a, 335.sub.b extending from the back side 361 of the central cap segment 365. The steps 335.sub.a, 335.sub.b, and the back side 361 of the central cap segment 365 define a concave space 367. In this exemplary embodiment, the steps 335.sub.a, 335.sub.b are located substantially halfway between the center of rotation 306 and the retaining lip 311.sub.b. The central protrusion 345 can be configured to extend into the concave space 365 such that the steps 335.sub.a and 335.sub.b contact the sidewalls 363.sub.a, 363.sub.b of the central protrusion 345 and thereby position the central cap segment around the center of rotation 306 at the central cap segment's middle diameter MD.

(33) Because the central cap segment 365 is a single piece, the continuous structure of the central cap segment 365 provides sufficient centripetal force C to nullify the inertia I caused by the rotor's circular motion around the center of rotation 306. The centripetal force C supplied by the central cap segment 365 and the positioning provided by the steps 335.sub.a and 335.sub.b and central protrusion 345 of the cap segment retainer 318 pilot the central cap segment 365 around the center of rotation 306 at the central cap segment's middle diameter MD. Other piloting means may be used to pilot the central cap segment 365. In other exemplary embodiments the central cap segment 365 may be piloted at the cap segment retainer's intermediate diameter (IMD), a cap segment retainer's outer diameter (OD), or a combination thereof. The cap segment retainer 318 may be forged and machined to precise specifications. In other exemplary embodiments, the cap segment retainer may be cast and machined. In the example embodiments of FIGS. 3B and 3C, the cap segment retainer 318 further comprises positioning steps 351.sub.a, 351.sub.b that extend from the back side 389 of the cap segment retainer 318. The positioning steps 351.sub.a, 351.sub.b, and the body 347 of the cap segment retainer 318 define a second concave space 373 configured to receive a center rotor protrusion (not depicted). Each positioning step 351.sub.a, 351.sub.b has an outer wall 353.sub.a, 353.sub.b respectively. Referring to positioning step 351.sub.b in particular, the outer wall 353.sub.b of the positioning step 351.sub.b engages the sidewall 396 of a pre-existing annular protrusion 398 on the rotor 105. The pre-existing annular protrusion 398 and the positioning step 351.sub.b position the cap segment retainer 318 on the rotor 105. The pre-existing annular protrusion 398 provides centripetal force C that is equal and opposite to the force of inertia I that the cap segment retainer 318 experiences as a result of the rotor's circular motion. In this manner the positioning step 351.sub.b and the pre-existing annular protrusion 398 pilot the cap segment retainer 318 on the rotor 103 using the outer wall 353.sub.b of the positioning step 351.sub.b. In this exemplary embodiment, positioning step 351.sub.a pilots the cap segment retainer 318 in substantially the same manner. It will be understood that on other exemplary embodiments, the cap segment retainer 318 may be piloted with the inner walls of positioning steps 351.sub.a, 351.sub.b. It will further be understood that in other exemplary embodiments, the rotor cap segments may be piloted by the outer walls or inner walls of interlocking elements.

(34) FIG. 3C depicts a cross-sectional side view of an exemplary segmented rotor cap assembly 303 in which the center portion 365, bounded by the inner diameter ID of the rotor cap segments 317, is an integral element in the cap segment retainer 318. In this exemplary embodiment, the cap segment retainer 318 is positioned on the rotor 105 around the center of rotation 306 in the same manner as the embodiment in FIG. 3B.

(35) Although retaining lip 311 and rotor cap protrusion 344 pilot the rotor cap segments 317 in FIGS. 3A-3C, it will be understood that any of the piloting means disclosed in this application may be used singularly or in combination with other piloting means to pilot the rotor cap segments 317 and cap segment retainer 318 consistent with the manner disclosed herein.

(36) FIG. 4 is a perspective view facing an exemplary segmented rotor cap assembly 403 surrounded by refiner plate segments 415. In this figure, fasteners 483 engage both the segmented rotor cap assembly 403 and the refiner plate segments 415 to a rotor (see 105). In this particular embodiment, the refiner plate segments 415 have a series of alternating bars 416 and grooves 414. Dams 412 may bridge two or more bars 416 thereby separating grooves in a generally radial direction (e.g. a direction originating at the center of rotation 406 and moving outward toward the outer diameter OD of the rotor 105). Dams 412 force lignocellulosic feed material F into the refining gap 119 and facilitate refining. It will be understood that although FIG. 4 depicts a refiner, the segmented rotor cap assembly 406 may be configured to be used with dispersers or other devices configured to separate, develop, and cut fibers in lignocellulosic material with plates having abrasive surfaces, which may include intermeshing teeth designs.

(37) In the exemplary embodiment depicted in FIG. 4, the segmented rotor cap assembly 403 comprises a set of rotor cap segments 417. The rotor cap segments 417 are removable and may be replaced after a desired time period. The embodiment in FIG. 4 has a rotor cap segment retainer 418 with an integrated central portion 465. Fasteners 483.sub.a can engage the cap segment retainer 418 to the rotor 105 using the original holes 450 in the rotor 105. The cap segment retainer 418 provides through holes 450 that align with the original holes of the rotor 105. The exemplary cap segment retainer 418 includes a first retaining lip 411.sub.a configured to apply centripetal force C to the rotor cap segments 417 at an intermediate diameter IMD (see FIG. 3B) near the rotor cap segment's outer diameter OD (See FIG. 3B).

(38) FIG. 5A depicts a single rotor cap segment 517 configured to be piloted around a central part 666 (FIG. 6A, 6B) of a rotor 605 (FIG. 6A, 6B) with an annular cap segment retainer 527 (FIG. 5B). The rotor cap segment 517 has wide bars 538 and wide channels 537 configured to fling lignocellulosic feed material F into the refining gap 619 (FIG. 6A, 6B). The rotor cap segment 517 may further have an area A around the fasteners 583 that has a thickness T (FIG. 5B) that is thicker than a thickness t (FIG. 5B) of the body 558 of the rotor cap segment 517. The area A around the fasteners 583 may protect the sides of the fasteners 583 from incoming lignocellulosic feed material F and thereby reduce fastener wear.

(39) FIG. 5B is a cross sectional side view of the embodiment in FIG. 5A taken along the line 5B-5B. The annular cap segment retainer 527 and rotor cap segment 517 define a hole 550 configured to receive a fastener 583. Although the fasteners 583 are not configured to pilot the rotor cap segments 517, the head 683.sub.a (FIG. 6A) of the fastener 583 provides weak centripetal force c to the lower portion of the area A.sub.b around the fasteners 583. This weak centripetal force c is insufficient to cancel out the inertia I of the rotor cap segment 517 and therefore, the fasteners 583 do not pilot the rotor cap segments 517. In certain exemplary embodiments, the thickness t of the rotor cap segment 517 at a rotor cap segment's inner diameter ID may exceed the thickness t of the rotor cap segment 517 at the rotor cap segment's outer diameter OD. The thickness t of the body 558 of the rotor cap segment 517 may decrease gradually and continuously along the body 558 from the inner diameter ID to the outer diameter OD.

(40) The annular cap segment retainer 527 is a single-piece rotor cap segment piloting plate. The annular cap segment retainer 527 may be configured to pilot the rotor cap segments 517 at a rotor cap segment's outer diameter OD. In other exemplary embodiments, the annular cap segment retainer 527 can be configured to pilot the rotor cap segments 517 at an intermediate diameter IMD disposed between the rotor cap segment's inner diameter ID and the rotor cap segment's outer diameter OD. In still other exemplary embodiments the annular cap segment retainer 527 can be configured to pilot the rotor cap segments 517 at a rotor cap segment's middle diameter MD.

(41) In the exemplary embodiment of FIG. 5B, the annular cap segment retainer 527 has a retaining lip 511.sub.a with a sidewall 526.sub.a configured to engage the sidewall 559.sub.a of rotor cap protrusion 544. In this exemplary embodiment, the protrusion 544 extends from the body 558 of the rotor cap segment 517 at the back side 571 of the rotor cap segment 517. The piloting lip 511.sub.a provides centripetal force C sufficient to nullify the inertia I the rotor cap segment 517 experiences as a result of the rotor's circular motion, and thereby pilots the rotor cap segment 517 near the outer diameter OD.

(42) FIG. 5C is a front view of three rotor cap segments 517 configured to be used with an annular cap segment retainer 527. The amount of rotor cap segments 517 in an exemplary segmented rotor cap assembly 503 is desirably three or more. In FIG. 5C, the segmented rotor cap assembly 503 has an area defining a center hole 555 in the center of the annular segmented rotor cap assembly 503.

(43) FIG. 6A is a cross sectional side view of a refiner 601 outfitted with an exemplary segmented rotor cap assembly 603 piloted at an intermediate diameter IMD between the rotor cap segment's outer diameter OD and the rotor cap segment's middle diameter MD. An annular cap segment retainer 627 has a retaining lip 511.sub.a that pilots the rotor cap segments 517 in the same manner described in FIG. 5B.

(44) The annular rotor cap assembly 503 may be disposed around a central part 666. The central part 666 may be conical to facilitate directing lignocellulosic feed material F from the feed inlet 611 toward the rotor cap segments 617 and ultimately the refining gap 619 defined by the opposing refiner plate segments 615.sub.a disposed on the rotor 605, 615.sub.b disposed on the stator 607.

(45) In this exemplary embodiment, the rotor 605 has a pre-existing annular protrusion 698. The annular cap segment retainer 627 is a single piece that has an inner diameter ID and an outer diameter OD. The body 699 of the annular cap segment retainer 627 has a height h that may equal the height h of the pre-existing annular protrusion 698. The pre-existing annular protrusion 698 can position the annular cap segment retainer 627 around the center of rotation 606. Because the annular cap segment retainer 627 is a single-annular piece, the structural integrity of the annular cap segment retainer 627 provides the centripetal force sufficient to cancel out the inertia I caused by the rotor's circular motion. In this manner, the pre-existing annular protrusion 698 and the annular cap segment retainer 627 pilot the annular cap segment retainer 627 at the cap segment retainer's inner diameter ID.

(46) FIG. 6B is a cross sectional view of another exemplary segmented rotor cap assembly 603 with an annular rotor cap retainer 627. The annular cap segment retainer 627 pilots the rotor cap segment 617 at an intermediate diameter IMD between the rotor cap segment's middle diameter MD and the rotor cap segment's inner diameter ID. The annular cap segment retainer 627 may have a length l that is generally shorter than a length l (FIG. 6A) of an annular cap segment retainer 627 configured to pilot a rotor cap segment at the rotor cap's outer diameter OD or at an intermediate diameter IMD between the rotor cap's outer diameter OD the rotor cap's middle diameter MD. Rotor caps segments may have a thickness t near the center of rotation 606 that is thicker than a rotor cap's thickness t at the outer diameter OD of the rotor cap segments. A rotor cap segment 617 may be thinner at the outer diameter OD to avoid blocking the refining gap 619. Piloting the rotor cap segments 617 at an intermediate diameter IMD between the rotor cap segments' middle diameter MD and the rotor cap segments' inner diameter ID may allow operators to use rotor cap segments where there is limited clearance between the rotor 605 and the refining gap 619.

(47) While this invention has been particularly shown and described with references to example embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims.