FIELD OF THE INVENTION 
     This invention relates to refiners which treat paper pulp fibers in general and to high consistency disk refiners in particular. 
     BACKGROUND OF THE INVENTION 
     During the production of fibers for papermaking, wood or another source of fibers is processed into chips and mechanically or chemically treated such that the chips may be broken down further and refined into individual fibers. 
     High consistency disk refiners are used with stock containing eighteen to sixty percent fiber by weight. High consistency refiners produce mechanical and semichemical pulp or furnish from undigested wood chips and semidigested wood chips. The refiner breaks down wood chips and clumps of wood fibers into individual fibers from which paper may be formed. After processing in a high consistency refiner, the fibers may be further processed in, for example, a low consistency refiner to improve their freeness or bonding capability. 
     A refiner disk consists of a disk-shaped steel or steel-alloy casting which has a multiplicity of generally radially extending bars integrally cast to extend from the surface of the disk. A first refiner disk is mounted on a rotor for rotation and another disk is held opposed to the first refiner disk, either by rigid mounting or by mounting on an oppositely rotating rotor. The refiner disks, as they move past each other, separate and refine the wood pulp as it passes between the opposed disks. 
     When dealing with high consistency pulp and wood chips, the edges of the refiner bars act as cutting edges for separating fibers from wood chips or clumps of fibers. 
     Disc refiners are used in the papermaking industry to prepare the cellulose fibers prior to delivering the pulp to the papermaking machine. 
     It is the purpose of a stock refiner to modify and separate the fibers without significantly reducing the length or individual strength of these fibers. The action of the refiner requires that the fibers pass through the refiner disks slowly. The energy which is expended to drive the refiner results in the generation of steam between the refiner disks. Fibers are typically retained on the refiner disks by placing dams between the substantially radially extending bars on the disks. Dams between refiner bars prevent the fibers and stock from being rapidly pumped through the refining region created by the refiner disks. 
     The use of dams, however, blocks the flow of steam from the refiner disks. When steam is blocked, it can back up and prevent fibers from moving through the refiner disks. If the dams are removed, the steam can blow the stock out of the disks before sufficient refining action has taken place. Refiners are energy intensive pieces of equipment and building a better refiner means a higher throughput with the same or better refining action. 
     Refiner disks have been fabricated with curved steam exhaust channels which extend radially outwardly and cut across refining grooves and bars. These large-width channels provide a low-resistance path for the escape of steam generated in the refining process, but come only at the sacrifice of a significant portion of refiner bar length, and hence a reduction from the maximum potential refining capacity. 
     What is needed is a disc refiner which provides improved steam flow with better retention of fibers and increased refining action on the refiner disks. 
     SUMMARY OF THE INVENTION 
     The refiner plate of this invention has a pattern of projections in the shape of a series of interlocking serif roman capital letter I&#39;s which form channels. The bodies of the I&#39;s form the refiner bars which hold the fibers as they move between the refiner plates in a disk refiner. The pattern of I&#39;s retards the flow of fibers while at the same time providing a large open area for steam to pass through the refiner disks. The cross bars at the top and at the bottom of the I&#39;s support the body of the I producing a refiner bar which is reinforced for higher strength. The shape of the I has an increased edge length exposed to the flow of fibers. The result is a pattern of bars on a refiner disk which has a large open area for steam and at the same time improved retention and processing of wood fibers. 
     It is a feature of the present invention to provide a high consistency refiner disk with greater area for steam to escape. 
     It is a further feature of the present invention to provide a high consistency refiner disk with a bar element which provides greater refining capability. 
     It is a still further feature of the present invention to provide a high consistency refiner disk which employs refining bar elements of greater strength. 
     Further objects, features and advantages of the invention will be apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a cross-sectional view of a high consistency stock disk refiner which may be used with the refiner disks of this invention. 
     FIG. 2 is a top plan view of a sector of the refiner disk of this invention showing the pattern of refiner bars. 
     FIG. 3 is an enlarged fragmentary isometric view of the refiner disk of FIG. 2. 
     FIG. 4 is a schematic plan of the refiner disk of FIG. 2 showing the edges along which fibers are held as they move through the refiner disks. 
     FIG. 5 is a fragmentary top plan view of an alternative pattern of refiner bars which can be placed on the refiner disk of this invention. 
     FIG. 6 is a fragmentary top plan view of another alternate pattern of refiner bars which can be placed on the refiner disk of this invention. 
     FIG. 7 is a fragmentary top plan view of still further alternative pattern of refiner bars which can be placed on the refiner disk of this invention. 
     FIG. 8 is a fragmentary top plan view of an alternative arrangement of the refiner bars of FIG. 7 on the refiner disk of this invention. 
     FIG. 9 is a fragmentary top plan view of an further alternative pattern of refiner bars which can be placed on the refiner disk of this invention. 
     FIG. 10 is a fragmentary top plan view of a yet further alternative pattern of refiner bars which can be placed on the refiner disk of this invention. 
     FIG. 11 is a fragmentary plan view of yet another alternative pattern of refiner bars which can be placed on the refiner disk this invention. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring more particularly to FIGS. 1-8, wherein like numbers refer to similar parts, a typical high-consistency pulp refiner 20 is shown in FIG. 1. The refiner 20 has a housing 21 with a stock inlet 23 through which stock is introduced. The refiner 20 has an auger 22 which supplies a high consistency pulp or wood chip feed consisting of eighteen to sixty percent wood chips and wood fiber suspended in water. The auger 22 supplies fibers and/or wood chips to a breaker bar section 26 and hence to a refiner section comprised of a first refiner disk 28 and a second refiner disk 30. The refiner disks 28, 30 are generally annular members, typically composed of a number of cast sectors 31 as shown in FIG. 2. The refiner disks have inner edges 33 near the axis 36 and outer edges 35 spaced radially outwardly from the axis. The refiner disks define an annular refining region 37 between the inner edges 33 and the outer edges 35 through which wood chips and fibers flow under centrifugal force. The refiner disks 28, 30 have refiner bars or elements 50 in the shape of capital serif letter I&#39;s. The refiner elements 50 are integrally formed on the faces or refining surfaces of the opposed disks 28, 30 and thus face each other. 
     One refiner disk 28 is mounted to a rotor 32 parallel to a radially extending plane, the other refiner disk 30 is mounted to a counter-rotating rotor 34. The rotors 32, 34 and the attached refiner disks 28, 30 rotate about an axis 36. 
     Each refiner disk sector 31, as shown in FIG. 2, has a multiplicity of I-shaped refiner bars or elements 50. Each I-shaped refiner element 50 has a top segment 64 parallel to a bottom segment 68, the top and bottom segments being joined by a perpendicular body segment 66. Each segment is, for example, about one fourteenth of an inch wide and projects from the surface of the refiner plate about one quarter of an inch high. Adjacent &#34;I&#34; elements 50 are arranged as shown in FIGS. 2-4 to produce a regular pattern of interlocking elements 50 with channels or grooves 52 formed therebetween. Refiner disks are typically fourteen to forty-five inches in diameter, and may be between twelve and seventy inches in diameter. The refiner disks may have larger refiner bars 39, as shown in FIG. 2, which direct the stock into the refining elements 50. 
     The refiner disks 28, 30 rotate with respect to one another at rates of between nine hundred to eighteen hundred rpm. As the disks are spun about a common axis, the refiner bars of the opposed disks pass in close proximity to one another and perform the refining action. 
     In operation, the gap between the refiner disks 28, 30 mounted on the rotors 32, 34 is typically 0.003 to 0.008 inches. 
     The design of refiner disks requires recognition of criteria for improving the performance of the disks. The first of these design criteria is the km/rev. This criteria is a measure of the total length of cutting edges on bars on a given disk. The desirability of increasing the total length of the bars on the disk is understood in terms of the desirability of causing the abrasion of the pulp fibers with as low an intensity as possible. The power consumed by the disc refiner 20 is dissipated over the area of the refiner disks 28, 30. 
     By increasing the effective length of the bars or the number of the bars, the amount of power dissipated per unit length of edge bar is decreased. This goal is accomplished by using discrete elements 50 which are constructed of segments which intersect at approximately ninety degrees. The elements 50 are short, with an aspect ratio calculated as the ratio of the longer dimension of the element to the shorter dimension of the element, of less then about two and one-half. Because power dissipation is proportional to the abrasion action, the net result of increased bar edge length created by using low aspect ratio elements with greater edge length, is that the abrasion takes place over a longer period of time and is thus of lower intensity. Lower intensity results in fewer cut or damaged fibers caused by excessive abrasive action. 
     As shown in FIG. 4 the pulp flows along lines 54 which are angled with respect to the radial direction indicated by arrow 56, and slightly counter to the direction of rotation shown by arrow 58. As the pulp 60 flows along the direction indicated by arrows 56 it is retained along the sides 62 of the I&#39;s which defined the edge length. The increased linear length of the sides compared with conventional straight bars will increase the refining capability of the refiner 20. Refining within the refiner 20 is generally believed to take place principally if not exclusively as stock is forced to flow over the edges of the elements. 
     The I&#39;s of the elements 50 are thus composed of three short bar segments an upper segment 64 a body segment 66 and a lower segment 68 which is identical in shape to the upper segment 64. The upper and lower segments 64, 68 are joined at right angles to the body segment 66. Adjacent bar elements 50 are positioned so that individual segments 64, 66, 68 are arranged in spaced parallel relationship with adjacent segments of adjacent elements thus forming grooves 52 along which fiber stock and steam can flow. 
     The size of the individual &#34;I&#34; elements 50 can be varied considerably. The individual segments of the elements 50 have a pyramidal cross-section as shown in FIG. 3. The projection of the elements from the surface of the refiner disk can be from about one millimeter to about ten millimeters. The top and bottom bars have a corresponding size range of about 1.75 millimeters to about 10.5 millimeters with individual segments having a width of one to six millimeters. The body segment 66 has a typical height of the same or slightly greater then the length of the top and bottom segments 64, 68. The resulting aspect ratio of the elements 50 is approximately 1.8 to 1. 
     The shape of the elements 50 provides great strength because the top and bottom segments 64, 68 reinforce and support the body segment 66. Thus the elements 50 are resistant to breaking. The pattern of elements 50 provides grooves 52 which allow steam to readily pass through the elements while at the same time not providing a straight-through path which can allow stock to escape through the refiner disk 28, 30 before the stock has been subjected to the refining action of the bars. 
     The refiner disk 28, 30 can be constructed of multiple segments, for example twenty-four, or sixteen as shown in FIG. 2. The disk may also be formed as a unitary whole. 
     The arrangement of the elements 50 is shown in FIG. 2. The individual elements 50 are preferably arranged in rectangular arrays, such as those shown in FIGS. 3-8. Trapezoidal portions 72 of the rectangular arrays are cut to fit the pie-shaped refiner disk sectors. The narrowest side 73 of the trapezoidal portion 72 is oriented towards the axis 36 of the rotor when the disk is installed in the refiner 20. The number of trapezoidal portions 72 can be varied depending on the size of the sector 31. If the sector is large, more trapezoidal portions 72 may be required. In FIG. 2 the sector 31 has two trapezoidal array portions 72. The arrays of elements could also be arranged so that the elements 50 are angled zero to ten degrees from the radial direction as shown generally in FIG. 2. 
     An alternative embodiment refiner disk 80, shown in FIG. 5, has T-shaped elements 82. The T-shaped elements 82 have top segments 84 and body segments 86 which join at right angles. The top segments 84 and the body segments 86 are arranged in spaced parallel relation with the segments of adjacent elements 82 to form the pattern shown in FIG. 5. The pattern shown in FIG. 5 can be arranged similarly to the pattern shown in FIG. 2. The elements 82 have an aspect ratio of approximately two. 
     A further embodiment refiner disk 90, shown in FIG. 6, has S-shaped elements 91. Each S-shaped element 91 is composed of upper segments 92 middle segments 94 and bottom segments 96 joined by upper side segments 98 and lower side segments 100. The five segments join at right angles and form grooves 99 with adjacent elements 91. The aspect ratio of the elements 91 is approximately 1.4. 
     A still further embodiment refiner disk 102, shown in FIG. 7, has L-shaped elements 104. Each L-shaped element is composed of a short segment 106 and a long segment 108. The short segments 106 join the long segments 108 at right angles. The segments form grooves 109 with adjacent elements 104. The aspect ratio of the L-shaped segments is approximately two. 
     An alternative embodiment refiner disk 112, shown in FIG. 8, has an alternative arrangement of the L shaped elements 104. The long segments 108 are positioned adjacent to the long segments of adjacent elements. The short segments 106 are positioned adjacent to short segments of adjacent elements. 
     A yet further embodiment refiner disk 140, shown in FIG. 9, has F-shaped elements 141. Each F-shaped element 141 is composed of upper segments 142 middle segments 144 and long segments 146 which join the upper segments 142 with the middle segments 144. The segments form grooves 143 with adjacent elements 141. The aspect ratio of the elements 141 is approximately two. 
     A still further embodiment refiner disk 150, shown in FIG. 10, has E-shaped elements 151. Each E-shaped element 151 is composed of first segments 152, second segments 154, third segments 155 and long segments 156 which join the first, second, and third segments 152, 154, and 155. The segments form grooves 159 with adjacent elements 151. The aspect ratio of the elements 151 is approximately two. 
     A further embodiment refiner disk 160, shown in FIG. 11, has H-shaped elements 161. Each H-shaped element 161 is composed of a middle segments 164, joining a first and second long segments 166, 167. The segments form grooves 169 with adjacent elements 161. The aspect ratio of the elements 161 is approximately two. 
     As shown in FIGS. 2-8, the refiner disks of this invention provide increased openness, and eliminate the use of dams between refiner elements or bars while retaining necessary bar strength, by creating a tiled array of elements 50. The elements 50 protrude axially from the refiner disks 28, 30. 
     It is important that the bar patterns of the refiner disk result in most fibers being brought to the outwardly facing bar surfaces where the desirable fraying of fibers can take place. Fibers which reside within a groove between bars and pass the entire length of the disk without passing over the tops of the bars do not benefit from the refining processing. Fibers can be forced to the surface without flow dams between neighboring bars by the shape of the elements 50 which produce flow retaining bar portions or edges. The shape of the bars provides the retaining function without limiting the free flow of steam through the refiner disks. 
     Computer-aided design techniques make the manufacture of disk patterns with a complicated geometry an economical undertaking. The manufacture of the refiner bars 50 is aided by the use of casting techniques which allow features of smaller dimension to be formed, such as those techniques which employ fine-grained sands with an organic binder rather than conventional green sand castings. 
     It should be noted that the illustrated arrays of &#34;I&#34; elements may be arranged in various ways on the refiner disks. Furthermore, the refiner bars are preferably cast of white cast iron, stainless steel or other alloys combining the features of strength, wear resistance and cost-effectiveness. 
     It should also be understood that while the &#34;I&#34; and other shaped refiner bars or elements of this invention are illustrated as being of a uniform size and radial direction, the size of the I&#39;s or other refining element may be varied to adjust the open area of the disk. 
     The refiner elements have a maximum dimension which is vertical as the letters which correspond to the elements are normally written. This vertical dimension will typically be aligned within zero to five degrees from a radial direction. 
     It should be under stood that the individual elements are not connected by dams, and on the other hand down grooves formed between the elements have straight path lengths which are at most only a little longer than the maximum dimension of the elements. 
     It should also be understand that although the illustrated refiner 20 is of the Bauer style counter-rotating machine, other types of high consistency refiners, including but not limited to Sprout Twins, and Sunds RGP types may be employed with the refiner disks of this invention. 
     It should be understood that the invention is not limited to the particular construction and arrangement of parts herein illustrated and described, but embraces such modified forms thereof as come within the scope of the following claims.
The refiner plate of this invention has a pattern of interlocking or nested elements having a &#34;I&#34;s &#34;T&#34;s, &#34;S&#34;s, &#34;L&#34;s, &#34;F&#34;s, &#34;E&#34;s, or &#34;H&#34;s shape which form channels. The body of the elements forms the refiner bars which hold the fibers as they move between the refiner plates in a disk refiner. The pattern of elements retarded the flow of fibers while at the same time providing a large open area for steam to pass through the refiner disks. The segments making up the elements producing a refiner bar which is reinforced for higher strength. The shape of the elements has a increased edge length exposed to the flow of fibers.