Patent Abstract:
A link belt for use in a sintering furnace, which is made of a plurality of first links, each of said links having working surfaces for supporting objects to be carried on the belt. A plurality of rollers are positioned intermediate certain of said first links, and a plurality of pins pass through apertures within said first links and within said rollers.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This is a continuation of U.S. National Stage application Ser. No. 13/128,416, filed Jun. 9, 2011, which is based upon and claims benefit of PCT Application No. PCT/U.S. Ser. No. 09/066,796, filed Dec. 4, 2009, which is based upon and claims benefit of U.S. Provisional Patent Application Ser. No. 61/119,908 filed Dec. 4, 2008, which is hereby incorporated herein by reference. 
     
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
       [0002]    Not Applicable. 
       PARTIES TO A JOINT RESEARCH AGREEMENT 
       [0003]    Not Applicable. 
       REFERENCE TO A SEQUENCE LISTING 
       [0004]    Not Applicable. 
       BACKGROUND OF THE INVENTION 
       [0005]    1. Field of the Invention 
         [0006]    The invention relates to a link belt for use in a continuous furnace and, more particularly, link belts having roller configurations. 
         [0007]    2. Background Art 
         [0008]    It is known to advantageously treat various articles by subjecting the articles to high temperatures for preselected periods of time. Such treatment may, for example, effect sintering of articles which are made by compacting powdered refractory metals or ceramics. In this regard, some of these processes include method steps where the articles are transported through a heat treating zone in a furnace, rather than being loaded and unloaded in batches. 
         [0009]    For example, it is known to transport articles through heating zones on link belts made of wire which are formed by conventional belt links. Somewhat similar to a wire belt is a transport belt disclosed in Miller, Jr. et al., U.S. Pat. No. 3,535,946 issued Nov. 15, 1995. The Miller, Jr. et al. patent discloses a belt made up of a succession of interwoven links, with each of the links formed of a length of tungsten wire which has been treated to a temperature of at least 400° C. The links are wound around an elliptical mandrel so as to provide, when cooled, a link which is in the form of a slightly flattened helix. Miller, Jr. et al. further disclose that they believe that by the avoidance of sharp bends in the link form and by the provision of a large number of interlocking contact points between links, strength and failure resistance are improved. 
         [0010]    Autenrieth, et al. U.S. Pat. No. 5,199,868 issued Apr. 6, 1993 discloses a continuous furnace which serves for the simultaneous two-sided sintering of sintered sheets upon substrates. The furnace of Autenrieth, et al. includes a muffle and a conveyor belt longitudinally traversing the muffle and carrying the substrates. The belt consists of a pair of individual belts which are guided in parallel next to each other in a synchronous manner. The belt surfaces are mutually inclined at a small angle to the horizontal in the muffle. The substrates are self supporting between two parallel lateral edges. The substrates lie with one lateral edge on the belt surface of one belt and with the second lateral edge on the belt surface of the other belt. In this manner, the bottom side of each substrate does not touch the individual belts. 
         [0011]    Fritsch, U.S. Pat. No. 2,994,917 issued Jul. 28, 1954 discloses an apparatus for converting metal powder into wrought metal shapes comprising at least one pair of oppositely disposed and laterally spaced vertical compactor elements. Each of the compactor elements includes an endless link belt mounted to travel about a pair of support wheels. The adjacent outer surfaces of the link belt form substantially continuous pressure surfaces inclined at an acute angle to the common axis of the pair of compactor elements. The adjacent pressure surfaces define a truncated V-shaped passageway. Means are provided for moving the link belt at the same rate of speed and in opposite directions so that the adjacent pressure surfaces travel uniformly toward the narrow end of the passageway defined by the compactor elements. In this manner, loose metal powder is compacted into a precompressed strip having sufficient mechanical strength to retain its form. This strip is introduced into a pair of pressure rolls. A power feed hopper is adapted to introduce loose metal powder into the wide end of the passageway. A pair of oppositely disposed pressure rolls having the axis of the rolls disposed in a horizontal plane define a roll gap with a width which is less than the width of the narrow end of the passageway. 
         [0012]    Daringer, U.S. Pat. No. 5,558,204 issued Sep. 24, 1996 describes a weld-free belt assembly in which elongated length modules are coupled in widthwise and side-by-side relationships by transversely-oriented coupling modules. An internal cavity is defined within each link along with a surface configuration on each side of the link. This configuration defines an entry access portion for a coupler and slot portions for enabling relative longitudinal movement of the coupler, while retaining the coupler within the internal cavity. The interfitting coactions of the links and couplers enable an assembled belt to move from linear planar travel into a curved path so as to establish an endless belt configuration. Relative movement of the couplers within a link cavity enables longitudinal collection of links along the inner circumference when the belt enters a curvilinear travel path in approximately the same plane, and enables re-extension for return to linear travel. An assembled belt can be driven longitudinally by sprockets. Also, the belt can be driven along a serpentine path by lateral-edge dynamic frictional drive. Alternatively, a similarly driven and layered helical-path “carousel” arrangement can be used. Special configuration lateral-edge links provide protrusion-free lateral edge surfaces enabling smooth dynamic frictional drive along inner circumference surfaces during curvilinear travel. 
       SUMMARY OF THE INVENTION 
       [0013]    In accordance with certain concepts of the invention, a continuous conveyor belt is provided, which primarily consists of five separate parts. These parts are center links, side links, rollers, pins and washers. Pins are utilized to hold the parts together, and the washers are utilized at the ends of the pins to keep the assembly from accidentally falling apart. 
         [0014]    A principal purpose of the invention is to convey “green” parts stacked on ceramic plates through a furnace. Most applications are between 2000° F. and 2250° F. The heat of the furnace allows the green parts to be sintered. 
         [0015]    Several challenges exist with respect to the applications for which the current invention has been designed. First, the market to which the continuous conveyor belt would be applied would greatly increase if the invention could be retrofitted into current furnace designs. Current furnaces utilize a drive mechanism called a pinch roll. This style of drive uses a roll to pinch the topside of the belt onto the larger drive roll, assuring that it has enough grip to convey the belt through the furnace. The second challenge was the amount of friction between the conveyor belt and hearth at application temperatures. In this case, friction could be as high as u=3. 
         [0016]    To overcome these challenges, a conveyor is provided which will have a grip on the pinch roller, with reduced friction. This configuration is provided by a conveyor belt produced from asymmetric links that utilize an offset roller, so that it can roll across the hearth but still track across the drive roll. Ceramic plates with parts, could still be set directly on top of the belt. 
         [0017]    One problem which was needed to be overcome in accordance with the invention relates to the concept that asymmetry produces what is simply called “bending stress.” To avoid this issue, finite element analysis was used to minimize parts bend moment. The result is a part which is an “interesting” I-beam configuration on its top surface. Because the green parts sit right on plates, a solid upper surface is not required. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0018]    The invention will now be described with respect to the drawings, in which: 
           [0019]      FIG. 1  is a partially schematic and partially diagrammatic view of a sintering furnace with which a link belt may be used in accordance with the invention; 
           [0020]      FIG. 2  is an underside, perspective view of a belt section in accordance with the invention; 
           [0021]      FIG. 3  is an upper, perspective view of the belt section shown in  FIG. 2 ; 
           [0022]      FIG. 4  is a perspective and exploded view of the belt section shown in  FIGS. 2 and 3 ; 
           [0023]      FIG. 5  is a side, elevation view of the belt section, showing the roller configuration; 
           [0024]      FIG. 6  is an underside, perspective view of a center link of the belt section shown in  FIG. 2 ; 
           [0025]      FIG. 7  is an upper, perspective view of a center link of the belt section shown in  FIG. 2 ; 
           [0026]      FIG. 8  is a plan view of the center link shown in  FIG. 6 ; 
           [0027]      FIG. 9  is a front, elevation view of the center link shown in  FIG. 6 ; 
           [0028]      FIG. 10  is a left-side elevation view of the center link shown in  FIG. 6 ; 
           [0029]      FIG. 11  is a right-side elevation view of the center link shown in  FIG. 6 ; 
           [0030]      FIG. 12  is an upper side view of the center link shown in  FIG. 6 ; 
           [0031]      FIG. 13  is an elevation view of the center link shown in  FIG. 6 ; 
           [0032]      FIG. 14  is a rear, elevation view of a side link of the belt section shown in  FIG. 2 ; 
           [0033]      FIG. 15  is a plan view of the side link shown in  FIG. 14 ; 
           [0034]      FIG. 16  is a front, elevation view of the side link shown in  FIG. 14 ; 
           [0035]      FIG. 17  is a left-side elevation view of the side link shown in  FIG. 14 ; 
           [0036]      FIG. 18  is a right-side elevation view of the side link shown in  FIG. 14 ; 
           [0037]      FIG. 19  is a bottom view of the side link shown in  FIG. 14 ; and 
           [0038]      FIG. 20  is a perspective view of the side link shown in  FIG. 14 . 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0039]    The principles of the invention will now be described, with respect to a sintering furnace  10  and a link belt  14  as illustrated in  FIGS. 1-20 . Advantageously and in accordance with various aspects of the invention, the link belt overcomes relatively high friction due to its roller configuration. In addition, as a result of the link belt in accordance with the invention having a relatively flat upper surface  142  (comprising lateral surface  144  and longitudinal surfaces  146 ) and offset rollers  128 , larger parts are allowed to be placed on the belt. Still further, the offset rollers allow for use in current furnaces which use friction drives. The belt uses rollers  128  which can be formed of ceramic material. The use of the ceramic precludes spot welding of the rollers  128  to the pins  132 . Still further, the use of ceramic material for the rollers avoids the potential for “stiction” if the belt is stopped while under relatively high temperatures. The belt links can be constructed of iron-nickel super alloys or other suitable metal. This type of construction will maintain relatively high strength, while also maintaining relatively better ductility than a fully ceramic belt. The belt has a relatively lower initial cost of ownership than belts which consist of wire mesh systems, or which otherwise consist of fully ceramic systems. 
         [0040]    Turning to  FIG. 1 , the drawing illustrates a sintering furnace system  10 . The furnace system  10  includes a sintering furnace  12 . It should be emphasized that link belts in accordance with the invention may be utilized with apparatus other than sintering furnaces. For background information, sintering consists of a method for making objects from powder, by heating the material (heating below its melting point for solid state sintering) until the particles adhere to each other. Sintering is traditionally used for manufacture of ceramic objects, and also has uses in fields such as metallurgy. 
         [0041]    For providing the sintering functions associated with the furnace  12 , a link belt  14  is utilized to transport the items to be sintered through the relatively high temperature furnace  12 . The link belt  14  can take on any of a number of different configurations, and will move through the furnace  12  in the direction shown by the arrows  16 . The link belt  14  itself moves along a path determined by a series of system rollers  18 . The drive mechanism for the link belt  14  is provided by a conventional motor drive  20  which exerts forces on the link belt  14  between the motor drive  20  itself and the drive system roller  22 . As further shown in  FIG. 1 , items (not shown) which are to be subjected to the sintering process through the furnace  12  can be placed on the link belt  14  at the charge end  24 . Once the sintering process is completed through the furnace  12 , the items which have been sintered can be removed at the discharge end  26  of the link belt  14 . 
         [0042]    The link belt  14  will now be described with respect to  FIGS. 2-20 . As shown in  FIG. 2 , the link belt  14  can include a series of belt sections  102 . The belt sections  102  can be linked together in a manner which will be apparent from the subsequent description herein. With reference to  FIGS. 2 ,  3 ,  4  and  6 - 13 , each of the belt sections  102  can include a series of alloy center links  104 , such as shown in the drawings. In the particular belt section  102  shown in  FIG. 2 , there are 8 center links  104  illustrated. With reference to  FIG. 6 , each of the center links  104  can include a horizontally disposed bottom section  106 . Integral with the horizontal section  106  are a pair of opposing end sections or noses  108 . As shown in  FIGS. 8-13 , the noses  108  include a first end section  110  and a second end section  112 . Each of the noses  108  can include a downwardly directed arcuate section  114 . In  FIG. 6 , the first end section  110  includes an arcuate section  114  which curves inwardly toward the horizontal section  106 . Correspondingly, the second end section  112  also includes a downwardly directed arcuate section  114  which curves inwardly toward the horizontal section  106 . In this manner, the end sections  108  oppose each other. 
         [0043]    As each of the arcuate sections depend downwardly, the sections form straight sections  140 . The straight sections  140  terminate in what can be characterized as working surfaces  142 . The working surfaces  142  act as the actual contact surfaces. These working surfaces  142  are particularly shown in  FIGS. 3 ,  4  and  7 . As particularly shown in  FIG. 7 , the working surfaces  142  include a pair of laterally extending surfaces  144 . Integral with the lateral working surfaces  144  is a longitudinally extending working surface  146 . 
         [0044]    In addition to the foregoing, and as particularly shown in  FIGS. 9 and 13 , the arcuate sections  114  and straight sections  140 , along with the bottom section  106 , form a pair of pin holes  148 . The pin holes  148  comprise apertures  116  which are utilized to receive pins as described in subsequent paragraphs herein. In addition to the pin holes  148 , each of the center links  144  also include a center post  150 . The center post  150  is utilized to provide rigidity and strength to the entirety of the center link  104 . With this particular configuration of the center link  104  in accordance with the invention, the link  104  is made relatively light weight by the structure of the link and portions of the structure which essentially comprise hollow interior. Advantageously, and in accordance with certain aspects of the invention, the links  104  may be constructed of iron-nickel super alloys. Such construction will maintain relatively high strength, while also maintaining and facilitating better ductility then may be obtained from a fully ceramic belt. Also, it should be noted that a crown may now exist on the top plates. This avoids any requirement of a corrugated plate, while still using a friction drive. 
         [0045]    In addition to the alloy center links  104 , the belt section  102  also includes a series of alloy side links  120 . In the particular illustration of the belt section  102  shown in  FIG. 2 , there are two alloy side links  120 . However, it should be emphasized that additional side links  120  would exist on the side of the belt section  102  opposing the side on which the side links  120  are shown. The side links  120  will now be described with respect to  FIGS. 14-20 . With reference thereto, each of the alloy side links  120  includes a vertically disposed central section  122 . At opposing ends of the central section  122  are a pair of end sections  124 . Each of the end sections  124  has a arcuate-shaped end surface. Formed horizontally through each of the end sections  124  is an aperture  126 . The alloy side links  120  are utilized to secure together the alloy center links  104 , and the apertures are utilized with alloy pins as described in subsequent paragraphs herein to secure the alloy center links and rollers together on a “widthwise” basis. Each of the alloy side links  120  can also be constructed of iron-nickel super alloys, for maintaining strength and ductility. 
         [0046]    Turning again to  FIGS. 2-4 , each belt section  102  also includes a series of rollers  128 . Advantageously, and in accordance with certain aspects of the invention, the belt section  102  essentially is formed of a flat upper surface (through the surfaces  142 ,  144 ,  146  of the alloy center links  104 ) and the rollers  128  are “offset” relative to the belt center links of the section. Such offset rollers  128  can be utilized with current furnaces having friction drives. As shown primarily in  FIG. 4 , each of the rollers  128  is of a cylindrical configuration and includes an aperture  130  ( FIG. 2 ) extending horizontally therethrough. 
         [0047]    Again, as earlier mentioned, development of the invention involved the conception of a conveyor that would have grip on the pinch roller and reduced friction. In accordance with the invention, a conveyor belt was produced from asymmetric links that utilize rollers  128  which are offset so that they can roll across the hearth, but still track across the drive roll. Ceramic plates, full of parts, can still be set directly on top of the belt. 
         [0048]    The rollers  128  may be formed of various materials. However, advantageously and in accordance with certain aspects of the invention, the rollers  128  maybe formed of ceramic materials. Ceramic material has a relatively high thermal conductivity. These materials are used in a number of different types of applications where it is necessary to withstand relatively extreme temperatures. For example, ceramic is often used in disc brakes. In this regard, the use of ceramic for the rollers  128  will tend to avoid spot welding of the rollers  128  to the alloy pins. Further, the rollers  128  will also avoid the potential for “stiction,” if the belt  14  for some reason has stopped while under temperature. 
         [0049]    In addition to the aforedescribed elements, the belt section  102  also includes a series of alloy pins  132 . The alloy pins  132  are particularly shown in  FIG. 4  and are of a cylindrical configuration. As shown primarily in  FIGS. 2 ,  3  and  4 , the pins  132  are utilized to secure together the rollers  128 , alloy side links  120  and alloy center links  104 . Where the pins extend through to the side links  120 , pin connectors  134  can be utilized to secure the pins in an appropriate manner. As also shown in  FIGS. 2 ,  3  and  4 , the alloy pins  132  will extend through the apertures  130 ,  126  and  116 . 
         [0050]    In accordance with the foregoing, the belt section  102  can be formed. It should be emphasized that the width of the belt section  102  can be adjusted as desired by adding or subtracting the individual elements of the belt sections  102 . 
         [0051]    In accordance with the foregoing, a continuous conveyor belt has been described, primarily consisting of five separate parts. These parts included center links, side links, rollers, pins and washers. As earlier stated, a primary purpose of the invention is to convey “green” parts stacked on ceramic plates through a furnace. With most applications operating between 2000° F. and 2250° F., the heat of the furnace allows the green parts to be sintered. 
         [0052]    Conveyor belts in accordance with certain concepts of the invention can be retrofitted into current furnace designs. Such current furnaces utilize a drive mechanism identified as a pinch roll. This style of drive utilizes a roll to pinch the top side of the belt onto the larger drive roll, assuring that it has enough grip to convey the belt through the furnaces. A second challenge is the amount of friction between the conveyor belt and hearth at application temperatures. Friction in these cases can be relatively high. 
         [0053]    As described in detail herein, these challenges are overcome by the concept of a conveyor that would have grip on the pinch roller and reduced friction. A conveyor belt was produced from asymmetric links which utilize an offset roller, so that they can roll across the hearth, but still track across the drive roll. 
         [0054]    Of primary importance, asymmetry produces another challenge, commonly referred to as bending stress. To avoid this issue, finite element analysis was used to minimize the parts bend moment. The result is a part which has a somewhat “interesting” I-beam shape on its top surface. Since the green parts ride on plates, a solid upper surface is not required. 
         [0055]    To insure adequate disclosure and clarification of the embodiments of the invention described herein, concepts associated with bending stress relate to the general concept of bending moments for structural elements. A bending moment is a reaction induced in a structural element when external force or moment is applied to the element, causing the element to bend. Correspondingly, finite element analysis relates to techniques originally developed for numerical solution of complex problems and structural mechanics. Utilizing the finite element method, a structural system can be modeled by a set of appropriate finite elements interconnected at points called nodes. Elements may have physical properties, such as thickness, coefficient of thermal expansion, density, Young&#39;s modules, shear modules, and Poisson&#39;s ratio. Elements are typically interconnected only at exterior nodes, although they are meant to cover an entire domain as accurately as possible. Nodes will have nodal displacements or degrees in freedom which may include translations, rotations and the like. Displacements of any points in the element will be interpolated from the nodal displacement, with this being the main reason for the approximate nature of a solution. 
         [0056]    It will be apparent to those skilled in the pertinent arts that other embodiments of link belts in accordance with the invention may be designed. That is, the principles of the invention are not limited to the specific embodiments described herein. Accordingly, it will be apparent to those skilled in the art that modifications and other variations of the above-described illustrative embodiments of the invention may be effected without departing from the spirit and scope of the novel concepts of the invention.

Technology Classification (CPC): 5