Patent Document

RELATED APPLICATION 
     This application claims the benefit of priority to U.S. Provisional Patent Application No. 61/035,883 filed Mar. 12, 2008, the entirety of which is incorporated by reference herein. 
    
    
     BACKGROUND OF THE INVENTION 
     This invention generally relates to refiners for lignocellulosic materials, and more specifically to a method and system for changing refiner plate segments in such a refiner. 
     Refiner plate segments are a critical component of the refining equipment. They are also a wear part that requires changing on a regular basis, in order to maintain the refining performance over time. A typical circle of refiner plates is composed of anywhere between 3 and 24 equally-sized segments, which together form a circle. At most, if not all, refiner plate changes, all segments are removed; the mounting surfaces (that is, the surfaces of the rotor and stator disk) are cleaned; and the new refiner segments are installed one-by-one, including shimming them to keep equal spacing and torquing the attachment bolts properly. 
     Refiners usually have 2 circles of plates running opposite each other, or in case of Twin refiners, they have 4 circles of plates (including a double-sided rotor). The refiner may be made with one rotor facing one stator (a rotating disk facing a stationary disk), or two opposing counter-rotating rotors. 
     Currently segmented refiner plates are either mounted individually to the rotor or stator surfaces in the refiner or fixed to separate plate holders that are of sufficient thickness to contain the full length of the required segment attachment bolts. These separate plate holders are then attached to the grinding machine as a complete assembly after the segments are fixed to the plate holder. 
     Converting machines not originally equipped with these thick plate holders may typically require a major rebuild of the machine as the plate holder thickness must be removed from the rotor and stator surfaces to allow the added thickness of the plate holders. This is a time consuming and costly process. 
     In certain aspects, the present invention may provide the labor saving and ergonomic benefits of the thick plate holder concept without the requirement for an extensive machine rebuild and the associated cost. Additional labor savings may be realized at the mill site when the face mounted carrying and installation fixture is supplied as a complete assembly with the segments precisely positioned for proper balancing required to minimize grinding machine rotational vibration. The assembly may then be ready for installation into the grinding machine as a single unit with significantly less mill site assembly labor and cost. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In a preferred embodiment, there is a face-mounted carrier for transporting a refiner plate segment to a refiner disk. The refiner plate segment may be bolted to the face-mounted carrier, then bolted to the refiner disk using the same set of threads. 
     In a preferred embodiment, there is a refiner plate segment for refining lignocellulosic material. The refiner plate includes a top surface comprising bars and grooves for refining lignocellulosic material; a bottom surface adapted to interface with a mounting surface of a refiner; a first hole in the top surface and a second hole in the bottom surface. The first hole includes a threaded portion adapted to receive a first threaded bolt, and the second hole includes a threaded portion adapted to receive a second threaded bolt. In certain embodiments, the first hole and second hole form a single hole through the plate segment. 
     The refiner plate may include a top surface comprising bars and grooves for refining lignocellulosic material; a bottom surface; a hole connecting the top surface to the bottom surface. The hole may comprise a threaded portion adapted to receive a first threaded bolt from both the top surface and a second threaded bolt the bottom surface. 
     In a preferred embodiment, there is an assembly for transporting a refiner plate segment to a refiner refining lignocellulosic material. The assembly may include a refiner plate segment including a top surface comprising bars and grooves for refining lignocellulosic material; a bottom surface; a hole connecting the top surface to the bottom surface, wherein the hole comprises a threaded portion adapted to receive a first threaded bolt from both the top surface and a second threaded bolt the bottom surface; and a face-mounted carrier adapted to be adjacent to the top portion of the refiner plate segment and adapted to receive a bolt that is threaded into the threaded portion of the refiner plate segment. 
     In a preferred embodiment, there is a method of attaching a refiner plate segment to a refiner for refining lignocellulosic material, wherein the refiner plate segment comprises (a) a top surface comprising bars and grooves for refining lignocellulosic material, (b) a bottom surface for interfacing a mounting surface of the refiner, (c) a hole connecting the top surface to the bottom surface, wherein the hole comprises a threaded portion adapted to receive a first threaded bolt from both the top surface and a second threaded bolt the bottom surface. The method may include the steps of: attaching a face-mounted carrier to the refiner plate segment by threading the first threaded bolt into the threaded portion of the hole such that the face-mounted carrier is cinched between a head of the first threaded bolt and the refiner plate segment; transporting the face-mounted carrier and the refiner plate segment to the refiner and placing the refiner plate segment on the mounting surface of the refiner; attaching the refiner plate segment to the refiner by threading the second threaded bolt into the threaded portion of the hole such that the refiner plate segment is cinched to the mounting surface of the refiner; and removing the face-mounted carrier from the refiner plate segment such that the refiner may refine lignocellulosic material using the bars and grooves of the refiner plate segment. The method may involve attaching the refiner plate segment substantially simultaneously with removing the face-mounted carrier. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  schematically illustrates an assembly comprising a face-mounted fixture and refiner plate segment in accordance with an embodiment of the present invention. 
         FIG. 2  schematically illustrates a refiner plate segment mounted to a refiner in accordance with an embodiment of the present invention. 
         FIG. 3  schematically illustrates a face-mounted fixture in accordance with an embodiment of the present invention. 
         FIG. 4  schematically illustrates a face-mounted fixture in accordance with an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     This invention generally relates to refiners for lignocellulosic materials, and more specifically to a method and system for changing refiner plate segments in such a refiner. In certain embodiments, the present invention may be applicable to a broad range of refiners, e.g., those operated from a consistency range of 1 to 90%. 
     In certain embodiments, the present invention comprises a segment transportation and installation fixture that is attached to the grinding face of the refiner segments. Depending upon the particular grinding machine type and design, these segments may comprise a full 360 degree circle or some smaller portion, e.g., a 180 degree half-circle. 
     The fixture with the attached segments may be positioned as a unit onto the refiner. The plate segments may then be fixed to the rotating and stationary machine surfaces utilizing a similar attachment method as when the segments were installed individually. Once the segments are fixed to the machine surfaces, the attachment method of the face-mounted installation fixture to the segments is released, and the fixture may be removed from the machine and stored until the segments become worn and are replaced. 
     The fixture may also be used in removing the worn segments. The carrying fixture may be attached to the face of the worn segments. The segments may then be unbolted from the machine mounting surface and removed as a full or partial (e.g., half) circle assembly from the machine. 
     The segments may be fixed directly to the machine mounting surfaces. Alternatively, a thin (e.g., 1 to 4 mm thick) plate carriers may be clamped between the segment and machine surfaces to protect the machine surface from fiber and resin deposits that must be removed prior to installing another new set of segments. Suitable thin plate carriers may be described in U.S. application Ser. No. 12/269,285 to Gingras. The thin backing plate need not be attached to the machine surface; it may be sandwiched between the segment and the machine surface. In certain embodiments, a thin plate holder may be temporarily fixed to the segments and/or to the face-mounted installation fixture. 
     In an embodiment, the face-mounted segment carrier and installation fixture has at least one hole through which a temporary installation bolt may slide. This hole facilitates attachment of the bolt to a threaded potion of the refiner plate segment (e.g., a threaded insert). The face-mounted segment carrier along with the segment(s) may then be moved to the rotor or stator disk of the refiner. The temporary installation bolt may be removed, and a second installation bolt may be used to connect the plate segment to the refiner disk using the same threads on the plate segment as used to secure the temporary installation bolt. In some embodiments, substantially the same installation bolt may be used. 
     The threaded portion of the refiner plate segment may be machined directly into the refiner plate itself if the hardness of the grinding segment material is low enough to allow direct machining. Alternatively for higher hardness materials where the segment cannot be directly machined, a lower hardness insert (e.g., when compared to the refiner plate&#39;s bars and grooves) can be placed in the casting mold and the segment metal poured around it. The softer insert material can then be drilled and tapped for the attachment bolts. Such inserts are currently drilled and tapped and used for attaching the segments individually from the back side into the grinding machine but the insert surface is only exposed on the back non-grinding side of the segments. 
     In preferred embodiments of the present invention, an insert face would be exposed on the face side of the segment for drilling and tapping to attach the installation fixture. That is, the threaded portion of the plate segment may be accessed from both the face-side of the segment and the disk-side of the segment. Most preferably, the refiner segment has a hole completely therethrough. In some embodiments, the refiner segment has one or more holes solely accessible from one side, either the top or the bottom. 
     In a preferred embodiment, the same insert location in the segment may be used for face attachment of the installation fixture and backside attachment of the segment to the grinding machine mounting surface. A common insert location would allow drilling through and tapping in one operation from either the back or face side reducing machining steps and set-up time. 
     In some embodiments, longer bolts for segment-to-machine attachment may be used. These bolts may extend through the full length of the tapped hole and remain just below the grinding face of the segment. Filling the face side of the tapped hole with the bolt might prevent material from the grinding process from filling and plugging the tapped hole. If the tapped hole(s) were plugged with solidified material during the refining process, the face fixture attachment bolts might be difficult to insert into the tapped holes when used segments are removed. 
     If the bolts for segment-to-machine attachment fill the full length of the tapped insert, the bolts for carrier-to-segment attachment cannot be simultaneously threaded into these same holes. In some embodiments, there may be two (or more) holes per plate segment. Only a portion of the holes would be used to attach the segment to the carrier. That is, the carrier may be fixed to the plate segment using at least one hole, while the plate segment is fixed to the refiner disk using another hole. Once the face-mounted carrier is unbolted and removed, the now-available set of holes may be used to further bolt the segment to the refiner disk. 
       FIG. 1  schematically illustrates an assembly comprising a face-mounted fixture and refiner plate segment in accordance with an embodiment of the present invention. Refiner plate segment  102  has a top surface  120  and a bottom surface  122 . Top surface  120  interfaces the lignocellulosic material during operation of the refiner, and the lignocellulosic material is pulverized using bars and grooves  104  near the top surface  120 . The precise pattern (if any) of the grooves is relatively unimportant. Face-mounted carrier  106  is connected to refiner plate segment  102  via a bolt  110  interlocking with threads  112  of insert  114 . As bolt  110  is rotated into place, head  108  cinches against face-mounted carrier  106  at interface  116 . 
     Once assembled, the face-mounted carrier and refiner plate segment may be positioned for attachment to the rotor or stator disk of a refiner. 
       FIG. 2  schematically illustrates a refiner plate segment mounted to a refiner in accordance with an embodiment of the present invention. As illustrated, the face-mounted carrier  206  may be unbolted and removed from the refiner plate segment  202 , such that grooved portion  204  may exposed to lignocellulosic material during operation of the refiner. Plate segment  202  is attached to refiner disk  216  via bolt  210 . Bolt  210  interfaces with threads  212  of insert  214 . As bolt  210  is rotated, head  208  cinches against disk  216  at interface  218 , pulling the refiner segment against the refiner disk. 
     The same threads used to bolt the face-mounted carrier to the refiner plate segment (e.g., threads  112  of  FIG. 1 ) may be used to bolt the refiner plate segment to the refiner disk (e.g., threads  212  of  FIG. 2 ). 
       FIG. 3  schematically illustrates a face-mounted fixture  350  in accordance with an embodiment of the present invention. As illustrated, face-mounted fixture  350  may carry eight refiner plate segments (with the segment positions illustrated by the broken lines), and may be carried and positioned using lifting hole  358 . 
     As illustrated, there are two attachment holes for each refiner plate segment: one dual-purpose hole  356  for attaching the segment to the face-mounted fixture  350  and for attaching the segment to the refiner disk, and one single-purpose hole for attaching the segment to the refiner disk. Other arrangements of dual- and single-purpose holes may also be used. In this manner, the plate segment may be partially secured to the refiner disk before being unbolted from the face-mounted fixture. 
       FIG. 4  schematically illustrates an assembly comprising a face-mounted carrier and refiner plate segment in accordance with an embodiment of the present invention. Refiner plate segment  402  has a top surface  420  and a bottom surface  422 . Top surface  420  interfaces the lignocellulosic material during operation of the refiner, and the lignocellulosic material is pulverized using bars  404  and grooves near the top surface  420 . The precise pattern (if any) of the grooves is relatively unimportant. As illustrated, top surface  420  is beveled and is thus not parallel to the bottom surface  424  of face-mounted carrier  406 . 
     Face-mounted carrier  406  is connected to refiner plate segment  402  via bolt  410  interlocking with threads  412  of insert  414 . As bolt  410  is rotated into place, head  408  cinches against face-mounted carrier  406  at interface  416 . As illustrated, face-mounted carrier  406  has a collar  440  that extends beyond the bottom surface  424 . Collar  440  rests against insert  414  at interface  442 . 
     Because face-mounted carrier  406  is beveled, face-mounted carrier only contacts refiner plate segment  402  at interface  442  (at the collar  440 ) and interface  434  (where top surface  420  contacts the bottom surface  424  of face-mounted carrier  406 ). Thus, gap  430  and gap  432  are formed between face-mounted carrier  406  and refiner plate segment  402 . In this respect, collar  440  (which may comprise a complete cylinder or only a portion of a cylinder) facilitates transport of various surface configurations (e.g., beveled or otherwise) of refiner plate  402 . In yet further embodiments, face-mounted carrier  406  may only contact the refiner plate segment at collar  440  and not contact the plate segment grinding face at any other location. 
     While the invention has been described in connection with what is presently considered to be the most practical and preferred embodiment, it is to be understood that the invention is not to be limited to the disclosed embodiment, but on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims.

Technology Category: b