Abstract:
Conveyor chains of the type utilized in commercial ovens and proofers are provided with improved bearing support for the rotating and pivoting components of the chains. The rotating components comprising anti-friction bearings constructed from superior components which support substantial improvements in the service life of the conveyor chains. The pivoting components are provided with plain bearings and/or anti-friction coating which also function to extend the service life of the conveyor chains.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of application Ser. No. 10/409,503 filed Apr. 8, 2003, currently pending, which is a continuation-in-part of application Ser. No. 10/309,530 filed Dec. 4, 2002, now U.S. Pat. No. 6,666,327, which is a continuation of application Ser. No. 10/000,240 filed Oct. 18, 2001, now U.S. Pat. No. 6,615,977, which is a continuation of application Ser. No. 09/837,917 filed Apr. 19, 2001, now U.S. Pat. No. 6,321,892, which is a continuation of application Ser. No. 09/405,294, filed Sep. 23, 1999, now U.S. Pat. No. 6,257,397. 
     
    
     TECHNICAL FIELD  
       [0002]     The present invention generally relates to proofing and baking apparatus of the type utilized in large commercial bakeries, and more particularly to an improved conveyor for use in continuous proofing and baking apparatus which is characterized by extended service life and greater adaptability to the requirements of diverse baking operations.  
       BACKGROUND OF THE INVENTION  
       [0003]     Modern large-scale commercial bakeries of the type utilized in the production of bread, sandwich buns, and similar dough products are frequently equipped with continuous proofing and baking apparatus. In the operation of a continuous proofer and/or oven, dough to be baked is received in bakery pans. The bakery pans are transported on grids which are supported on the links of a continuous chain. A drive mechanism actuates the chain to transport the bakery pans and the dough contained therein through a proofer wherein the dough is allowed to rise and/or through an oven wherein the dough is baked.  
         [0004]      FIGS. 1, 2 , and  3  illustrates a link  20  of the type comprising a prior art conveyor chain utilized in continuous proofing and baking apparatus. Each link  20  of the conveyor chain includes a first connection member  22 , a second connection member  24 , and a pair of spaced, parallel plates  26 . The first connection member  22  of a particular link  20  is connected to the second connection member  24  of the next preceding link in the chain by a pin  28  ( FIG. 3 ) which facilitates pivotal movement between adjacent links in the nominally vertical plane. The plates  26  are connected to the first connection member  22  and to the second connection member  24  by pins  30  which facilitate relative pivotal movement between adjacent links in the nominally horizontal plane.  
         [0005]     The first connection member  32  of each link  20  is provided with a pair of wheels  32 . The wheels  32  support the link  20  for movement along a conveyor track  36  ( FIG. 3 ). A wheel  34  is positioned between the plates  26 . The wheel  34  functions to center the link  20  in the conveyor track  36 .  
         [0006]     Conveyor chains of the type illustrated in  FIGS. 1-3  have gained widespread acceptance in the commercial baking industry and other industries. Notwithstanding this fact, such conveyor chains incorporate various deficiencies. For example, the wheels  32  which support each link  20  for moving along the conveyor track comprise anti-friction bearings which require periodic lubrication. Lubricating the chain is time consuming and expensive, and is frequently overlooked by bakery operators. Lack of lubrication leads to bearing failure which, at a minimum, requires the conveyor to be taken out of service to facilitate replacement of the failed bearings. As will be appreciated by those skilled in the art, substantially more serious consequences can and do result from bearing failure which can require the replacement of multiple links of the conveyor chain, entire sections of the conveyor track, etc.  
         [0007]     Various factors lead to improper conveyor chain maintenance and lubrication. One of the most important involves the demands made on commercial bakeries by their customers for continuous high level production leaving no time for maintenance and lubrication procedures. An equally important factor is the lack of technicians having the training and experience necessary to properly perform conveyor chain maintenance and lubrication procedures. When untrained and inexperienced personnel are employed to maintain and lubricate the conveyor chains used in continuous proofers and ovens, improper and inadequate maintenance and lubrication result.  
         [0008]     A related problem attendant to the use of conveyor chains comprising links of the type shown in  FIGS. 1-3  relates to the cleaning thereof. The lubricants which are used in the anti-friction bearings of the wheels  32  of the links  20  are incompatible with the use of water and detergents to clean the conveyor chain. It is therefore necessary to employ other, more costly, techniques in order to attain the level of cleanliness required in food manufacturing operations.  
         [0009]     Even when proper lubrication and cleaning procedures are in place, the problems inherent in the use of the prior art chain are not resolved. Lubricant from the chain combines with debris from the dough products being baked to form a sludge which cannot be disposed of except pursuant to strict EPA guidelines. When the chain is used in an oven the high temperature environment causes the lubricant to thicken to the point that the bearings seize causing increased load on the conveyor drive system and increased chain and track wear.  
       SUMMARY OF THE INVENTION  
       [0010]     The present invention comprises improvements in the design of conveyor chains adapted for use in conveyorized proofers, conveyorized ovens, and similar applications which overcome the foregoing and other difficulties long since associated with the prior art. In accordance with one feature of the invention, conveyor chains intended for use in baking operations are provided with bearings which do not require lubrication. For example, when used in proofers, the bearings of the conveyor chain may comprise sleeve bearings formed from plastic materials which are self-lubricating and adapted for utilization in high temperature environments of the type encountered in a bakery oven. Conveyor chains used in ovens may be equipped with self-lubricating graphite bearings of the type sold by Graphite Metallizing Corporation of Yonkers, N.Y., under the trademark GRAPHALLOY®. Alternatively, the conveyor chain may be provided with sealed self-lubricating anti-friction bearings suitable for high temperature applications.  
         [0011]     The use of bearings which do not require lubrication in conveyor chains intended for bakery applications is advantageous for at least two reasons. First, by eliminating the lubrication function which heretofore has proven to be problematical, substantial cost savings are effected. Of equal importance is the elimination of conveyor chain failures stemming from improper lubrication. The elimination of the lubrication requirement also facilitates the cleaning of the conveyor track by simply attaching a scraper to the conveyor chain. The scraper pushes bakery debris along the track to an opening in the bottom wall thereof where the debris is accumulated for disposal as ordinary refuse.  
         [0012]     The present invention comprises improvements in the bearing support for the rotating and pivoting components of conveyor chains of the type utilized in commercial proofers and ovens. The rotating components comprise anti-friction bearings constructed from superior components which afford substantial improvements in the service life of the conveyor chain. The pivoting components are provided with plain bearings and/or anti-friction coatings which also function to extend the service life of the conveyor chain.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     A more complete understanding of the invention may be had by reference of the following Detailed Description when taken in conjunction with the accompanying Drawings, wherein:  
         [0014]      FIG. 1  is an exploded perspective view of a link of a prior art conveyor chain;  
         [0015]      FIG. 2  is a perspective view of the link of  FIG. 1 ;  
         [0016]      FIG. 3  is a top view of a conveyor chain comprising links of the type shown in  FIGS. 1 and 2 ;  
         [0017]      FIG. 4  is a side view of a conveyor chain comprising a first embodiment of the present invention in which certain parts have been broken away more clearly to illustrate certain features of the invention;  
         [0018]      FIG. 5  is a view similar to  FIG. 4  showing the conveyor chain of  FIG. 4  operating in a vertically curved section of conveyor track;  
         [0019]      FIG. 6  is a top view of the conveyor chain of  FIG. 4  showing the conveyor chain operating in a horizontally curved section of conveyor track;  
         [0020]      FIG. 7  is a transverse sectional view of the conveyor chain of  FIG. 4 ;  
         [0021]      FIG. 8  is an enlargement of a portion of  FIG. 4 ;  
         [0022]      FIG. 9  is an enlargement of a portion of  FIG. 6 ;  
         [0023]      FIG. 10  is a view similar to  FIG. 4  showing a conveyor chain having a shorter pitch as compared with that of the conveyor chain of  FIG. 4 ;  
         [0024]      FIG. 11  is a side view similar to  FIG. 4  showing a conveyor chain having a longer pitch as compared with that of the conveyor chain of  FIG. 4 ;  
         [0025]      FIG. 12  is a side view similar to  FIG. 4  illustrating a conveyor chain comprising a second embodiment of the invention;  
         [0026]      FIG. 13  is a side view similar to  FIG. 4  illustrating a conveyor chain comprising a third embodiment of the invention;  
         [0027]      FIG. 14  is a side view of a conveyor chain comprising a fourth and preferred embodiment of the invention in which certain parts have been broken away more clearly to illustrate certain features of the invention;  
         [0028]      FIG. 15  is a side view of the conveyor chain of  FIG. 14  showing the conveyor chain operating in a vertically curved section conveyor track;  
         [0029]      FIG. 16  is a top view of the conveyor chain of  FIG. 14  showing the conveyor chain operating in a horizontally curved section of conveyor track;  
         [0030]      FIG. 17  is a transverse sectional view of the conveyor chain of  FIG. 14 ;  
         [0031]      FIG. 18  is an enlargement of a portion of  FIG. 14 ;  
         [0032]      FIG. 19  is a view similar to  FIG. 14  illustrating a conveyor chain having a longer pitch as compared with that of the conveyor chain of  FIG. 14 ;  
         [0033]      FIG. 20  is a diagrammatic illustration of a conveyor chain drive mechanism useful in the practice of the invention;  
         [0034]      FIG. 21  is a diagrammatic illustration of a conveyor chain drive mechanism comprising a variation of the conveyor chain drive mechanism of  FIG. 20 ;  
         [0035]      FIG. 22  is a diagrammatic illustration of the conveyor chain drive mechanism of  FIG. 21  showing the utilization thereof in conjunction with a conveyor chain having a longer pitch as compared with that of the conveyor chain of  FIG. 18 ;  
         [0036]      FIG. 23  is an illustration similar to  FIG. 18  showing a variation of the preferred embodiment of the invention;  
         [0037]      FIG. 24  is a diagrammatic illustration of a conveyor chain drive mechanism useful in conjunction with the apparatus of  FIG. 23 ;  
         [0038]      FIG. 25  is a perspective view of a portion of a conveyor chain incorporating the present invention;  
         [0039]      FIG. 26  is an exploded view of the conveyor chain of  FIG. 25 ;  
         [0040]      FIG. 27  is an enlarged view illustrating a component of the conveyor chain of  FIG. 25 ;  
         [0041]      FIG. 28  is a side view of a subcomponent of the device of  FIG. 25 ;  
         [0042]      FIG. 29  is a sectional view taken along the line  29 - 29  in  FIG. 28 ;  
         [0043]      FIG. 30  is a sectional view taken along the line  30 - 30  in  FIG. 28 ;  
         [0044]      FIG. 31  is a side view of a subcomponent of the device of  FIG. 25  which may be used therein in lieu of the device of  FIG. 28 ;  
         [0045]      FIG. 32  is a sectional view taken along the line  32 - 32  in  FIG. 31 ; and  
         [0046]      FIG. 33  is a sectional view of the wheel of the device of  FIG. 31 .  
     
    
     DETAILED DESCRIPTION  
       [0047]     Referring now to the Drawings, and particularly to  FIGS. 4, 5 ,  6 ,  7 ,  8 , and  9  thereof, there is shown a conveyor chain  50  comprising a first embodiment of the invention. The conveyor chain  50  comprises a plurality of identical compact carriages  52  which are connected end to end by a plurality of identical connection members  54 . The conveyor chain  50  operates in a conveyor track  56  comprising a solid bottom wall  58 ; opposed, solid side walls  60 ; and a top wall  62  having a center slot  64  formed therein.  
         [0048]     Each of the compact carriages  52  comprises a unitary structure which may be manufactured from a variety of materials utilizing conventional manufacturing techniques. For example, the compact carriages  52  may be manufactured from steel and/or other metals by means of die casting, investment casting, or other well known manufacturing processes. Alternatively, the compact carriages  52  may be formed from various plastic materials suitable for high temperature applications, and may be manufactured utilizing conventional processes such as injection molding. Preferably, the material and the process used in the manufacture of compact carriages  52  are selected such that few if any machining operations are required in order to complete the manufacture thereof.  
         [0049]     Each compact carriage  52  comprises a elongate body  74  having identical openings  76  formed in the opposite ends thereof. Each opening  76  receives a spherical bushing  78  which in turn receives the end portion of one of the connection members  54 . The spherical bushings  78  are retained in the openings  76  by pins  80 .  
         [0050]     Axles  82  extend through the body  74  at points situated inwardly from the opening  76 . The axles  82  support pairs of wheels  84  which in turn support the conveyor chain  54  for movement along the track  56 . Bosses  86  extend upwardly from the body  74  and in turn support a grid (not shown) which receives and transports bakery pans having dough received therein along the length of the track  56 . The bosses  86  may be provided with drilled and tapped apertures  88  which received threaded fasteners to secure the grid thereto. Examples of grids which may be used in the practice of the invention are shown and described in U.S. Pat. Nos. 4,729,470, 4,760,911, and 4,836,360, all of which are owned by the assignee hereof and incorporated herein by reference.  
         [0051]     Each of the bosses  86  may have a dimensionally reduced portion  90  at the upper end thereof. Top plates  92  are supported on the bosses  86  and receive the portions  90  therethrough. The top plates  92  function to prevent debris from entering the track  56  through the slot  64 .  
         [0052]     Each compact carriage  52  is further provided with a pair of wheels  100 . The wheels  100  function to locate the compact carriage  52  relative to the side walls  60  of the track  56 . The wheels  100  are rotatably supported on a pin  102  extending through the body  74  of the compact carriage  52 . As is best shown in  FIG. 7 , the wheels  100  cooperate with the wheels  84  to completely prevent bending and tipping of the conveyor chain  50 .  
         [0053]     Referring particularly to  FIG. 9 , the wheels  84  are secured to the axle  82  for rotation therewith. The axles  82  of conveyors intended for use in proofers may be supported by a self-lubricating plastic bearing  104  which may be of the type manufactured by Igus Spritzgussteile fur die Industrie GmbH (Igus) of Koln (Cologne), Germany and sold under the trademark IGLIDE®. In oven applications the self-lubricating bearings  104  may be of the type sold by Graphite Metallizing Corporation of Yonkers, N.Y., under the trademark GRAPHALLOY®. The bearings  104  do not require lubrication in order to rotatably support the axles  82  and the wheels  84  supported thereon. Therefore, by means of the present invention, the need for lubrication of the wheels which support the carriages  52  is eliminated as are the problems attended to the failure to provide required lubrication and difficulties associated with cleaning conveyor chains in which lubricating fluids are used. As is shown in  FIG. 4 , the wheels  84  may be rotatably supported by sealed self-lubricating anti-friction bearings  105  in lieu of the plastic bearings  104 .  
         [0054]     In accordance with one embodiment of the invention, the antifriction bearings  105  are constructed as follows: 
    ABEC-9 precision 4-point contact deep groove antifriction bearings, either ball bearings or cylindrical roller bearings, comprising: 
        Highly polished races (&lt;1.0 μin. rms);     Races constructed from silicon nitride ceramic or cobalt alloy (Stellite®)     Silicon nitride balls or rollers with sphericity &lt;2 μin., surface finish &lt;0.15 μin. Ra, and diameter variation &lt;3 μin.     Radial internal clearance between about 39.37 μin. and about 0.0018 in.;     Races and balls or rollers coated with a solid lubricant using an ion deposition technique;     The solid lubricant having a thickness of between about 2,000 angstroms and about 0.03 inch and comprising a material selected from the group consisting of:     tungsten disulfide, molybdenum disulfide, titanium nitride, silver, carbide diamond, and boron nitride;     Self-lubricating retainer formed from a material selected from the group consisting of: Vespel® (polyamide), molybdenum disulfide impregnated Teflon®, graphite, and fiberglass reinforced phenolic;     Internal volume of the bearing from between about 1% to about 100% filled with a high temperature solid lubricant selected from the group consisting of molybdenum disulfide, graphite, polytetrafluoroethylene polymer (PTFE) and a bearing grease selected from the group consisting of perflouropolyethers (PFPE), polyaphaolefin(PAO), polyphenylethers (PPE), synthetic esters, and silicon based greases. Bearing seal selected from the group consisting of: labyrinth fiberglass reinforced PTFE seals; viton rubber seals with stainless steel backings; and stainless steel shields with a 00.001″ gap between the inner race;     Heat stabilized to continuous exposure at 800° F.    
       
 
         [0066]     In accordance with another embodiment of the invention, the antifriction bearings  105  are constructed as follows: 
    Ball bearings or cylindrical roller bearings comprising: 
        Precision or semi-precision races (≦125.0 μin. rms);     Races constructed from a temperature resistant material selected from the group consisting of T1 high temperature tool steel, BG-42 high temperature corrosion resistant tool steel, M2 high temperature tool steel, M50 high temperature tool steel, High Molybdenum 440C stainless steel, 440C stainless steel (or similar alloy), Cronidur 30® nitrited corrosion resistant tool steel (or similar alloy), and 52100 bearing steel;     Balls or rollers selected from the group consisting of silicon nitride, alumina, zirconia, silicon carbide, 52100 bearing steel, 440C stainless steel, BG-42 high temperature corrosion resistant tool steel, M50 high temperature tool steel with sphericity &lt;48 μin., surface finish &lt;2.0 μin. Ra, and diameter variation &lt;48 μin.;     Radial internal clearance &lt;0.020 in.;     Races and balls or rollers coated with tungsten disulfide solid lubricant using an air impingement spray technique;     The solid lubricant having a thickness of between about 2,000 angstroms and about 0.003 in.;     Two-piece riveted stainless steel retainer with tight ball pockets and coated with tungsten disulfide solid film lubricant;     Internal volume of the bearing completely filled with a high temperature solid lubricant comprising graphite;     Bearing sealed with a fiberglass reinforced PTFE seals with stainless steel backings;     Heat stabilized to continuous exposure at 662° F.    
       
 
         [0078]     In accordance with yet another embodiment of the invention, the antifriction bearings  105  are constructed as follows: 
    ABEC-1 precision deep groove (Conrad or gothic arch type) ball bearings, self-aligning ball bearings, angular contact ball bearings, cylindrical roller bearings, spherical roller bearings, tapered roller bearings, thrust ball roller bearings, Sheedy® roller bearings, or needle roller bearings, comprising: 
        Polished races (≦12 μin. rms);     Races constructed BG-42 high temperature corrosion resistant tool steel or 440C stainless steel with an S2 heat treatment per ASTM-A756;     Silicon nitride balls or rollers with sphericity &lt;4 μin. surface finish, &lt;0.15 μin. Ra, and diameter variation &lt;5 μin.;     Radial internal clearance &lt;0.020 in.;     Races coated with tungsten disulfide solid lubricant applied by air impingement;     Two piece stainless steel (305 SS) riveted retainer with tight ball or roller pockets;     Internal volume of the bearing completely filled with a high temperature solid lubricant comprising graphite;     Bearing sealed with fiberglass reinforced PTFE seals with stainless steel (302 SS) shield backings;     Heat stabilized to continuous exposure at 662° F.    
       
 
         [0089]     Referring to  FIG. 8 , the wheels  100  are rotatably supported on the pin  102 . Self-lubricating antifriction bearings  106  also manufactured by Igus as described hereinabove in connection with the bearings  104  are provided at the opposite ends of the pin  102  and in turn rotatably support the wheels  100  thereon. Again, the use of self-lubricating bearings  106  to rotatably support the wheels  100  on the pin  104  eliminates the need for lubrication.  
         [0090]     As is best shown in  FIGS. 6 and 9 , each connector member  54  has an eye  108  at each end thereof. Each eye  108  receives the spherical bushing  78  of one of the compact carriages  52 . In this manner, the eyes  108  of the connection members  54  and the spherical bushings  78  of the compact carriages  52  facilitate the movement of the conveyor chain  50  along inclined and curved portions of the track  56 . For example,  FIG. 5  illustrates the movement of the conveyor chain  50  along a vertically curved portion  110  of the track  56 .  FIG. 6  illustrates the movement of the conveyor chain  50  along a horizontally curved portion  112  of the track  56 . As will be appreciated by reference to  FIGS. 5 and 6 , the movement of the conveyor chain  50  along vertically and horizontally curved portions of the track  56  is accomplished without interference between the conveyor chain  50  and the track  56 .  
         [0091]      FIG. 7  illustrates the relationship between the wheels  84  and  100  of the conveyor chain  50  and the track  56 . The wheels  84  travel along the bottom wall  58  of the track  56  and support the conveyor chain  50  of the movement through the track  56 . The wheels  100  serve to center the conveyor chain  50  in the track  56  and to prevent interference of the conveyor chain  50  with the track  56  as the conveyor chain  50  moves therethrough. Again, the wheels  84  and  100  cooperate to prevent bending and tipping of the conveyor chain  50 .  
         [0092]     Referring to  FIGS. 10 and 11 , one of the advantages in the use of the conveyor chain in the present invention comprises the adaptability thereof to changes in pitch. Thus, in  FIG. 10  the compact carriages  52  are connected end to end by connection members  54 ′ which are substantially shorter than the connection members  54  of the embodiment of the invention illustrated in  FIGS. 4, 5 , and  6 . The use of the connection members  54 ′ in lieu of the connection members  54  results in a conveyor chain  50  having a substantially shorter pitch. The use of a conveyor chain having a shorter pitch is advantageous in those instances in which the conveyor chain is used to transport either heavier bakery pans or bakery pans carrying heavier loads as compared with the loading of a conveyor chain having a longer pitch.  
         [0093]     Referring to  FIG. 11 , there is shown a conveyor chain  50  wherein the compact carriages  52  are connected end to end by connection members  54 ″ which are substantially longer than the connection members  54  of the conveyor chain  50  illustrated in  FIGS. 4, 5 , and  6 . The use of the longer connection members  54 ″ in the conveyor chain  50  of  FIG. 9  results in the conveyor chain having a substantially longer pitch as compared with the pitch of the conveyor chain  50  shown in  FIGS. 4, 5 , and  6 . The use of a conveyor chain having a longer pitch is advantageous in those instances in which the conveyor chain is called upon to carry either lighter bakery pans or bakery pans carrying lighter loads as compared with the loading of the conveyor chain  50  of  FIGS. 4, 5 , and  6 .  
         [0094]     Referring to  FIG. 12 , there is shown a conveyor chain  150  comprising a second embodiment of the invention. The conveyor chain  150  comprises a plurality of identical compact carriages  152  which are connected end to end by a plurality of identical connection members  154 . The conveyor chain  150  operates in a conveyor track  156  comprising a solid bottom wall  158 ; opposed, solid side walls  160 ; and a top wall  162  having a center slot formed therein.  
         [0095]     Each of the compact carriages  152  comprises a unitary structure which may be manufactured from a variety of materials utilizing conventional manufacturing techniques. For example, the compact carriages  152  may be manufactured from steel and/or other metals by means of die casting, investment casting, or other well known manufacturing processes. Alternatively, the compact carriages  152  may be formed from various plastic materials adapted for high temperature applications, and may be manufactured utilizing conventional processes such as injection molding. Preferably, the materials and the process used in the manufacture of compact carriages  152  are selected such that few if any machining operations are required in order to complete the manufacture thereof.  
         [0096]     Each compact carriage  152  comprises a elongate body  174  having identical openings  176  formed in the opposite ends thereof. Each opening  176  receives a spherical bushing  178  which in turn receives the end portion of one of the connection members  154 . The spherical bushings  178  are retained in the openings  176  by pins  180 .  
         [0097]     Axles  182  extend through the body  174  at points situated inwardly from the opening  176 . The axles  182  support pairs of wheels  184  which center the conveyor chain  154  in its movement along the track  156 . The axles are extended downwardly to prevent excess tipping of the compact carriages. A boss  186  extends upwardly from the body  174  and in turn support a grid (not shown) which receives and transports bakery pans having dough received therein along the length of the track  176 . The boss  186  may be provided with a drilled and tapped aperture  188  which receives a threaded fastener to secure the grid thereto. Examples of grids which may be used in the practice of the invention are shown and described in U.S. Pat. Nos. 4,729,470, 4,760,911, and 4,836,360, all of which are owned by the assignee hereof and incorporated herein by reference.  
         [0098]     Each boss  186  may have a dimensionally reduced portion  190  at the upper end thereof. A top plate  192  is supported on each boss  186  and receives the portion  190  therethrough. The top plates function to prevent debris from entering the track  156  through the slot in the top wall  162 .  
         [0099]     Each compact carriage  152  is further provided with a pair of wheels  200 . The wheels  200  function to support the compact carriage  152  for movement along the bottom wall  158  of the track  156 . The wheels  200  are rotatably supported on a pin  202  extending through the body  174  of the compact carriage  152 .  
         [0100]     The wheels  184  are secured to the axle  182  for rotation therewith. Each axle  182  is rotatably supported by a self-lubricating bearing  204 . The bearings  204  do not require lubrication in order to rotatably support the axles  182  and the wheels  184  supported thereon. Therefore, by means of the present invention, the need for lubrication of the wheels which support the carriages  152  is eliminated as are the problems attendant to the failure to provide required lubrication and difficulties associated with cleaning conveyor chains in which lubricating fluids are used.  
         [0101]     Like the rotational support for the wheels  184 , the wheels  200  are secured to the pin  202 . A self-lubricating bearing  206  rotatably supports the pin  202  and the wheels  200  mounted thereon. Again, the use of the self-lubricating bearings  206  to rotatably support the wheels  200  and the pin  202  eliminates the need for lubrication.  
         [0102]     Each connector member  154  has an eye  208  at each end thereof. Each eye  208  receives a spherical bushing  178  of one of the compact carriages  152 . In this manner, the eyes  208  of the connection members  154  and the spherical bushings  178  of the compact carriages  152  facilitate the movement of the conveyor chain  150  along vertically and horizontally curved portions of the track  156 .  
         [0103]     Referring to  FIG. 13 , there is shown a conveyor chain  250  comprising a third embodiment of the invention. The conveyor chain  250  comprises a plurality of identical compact carriages  252  which are connected at equally spaced intervals along a wire rope  254 . The conveyor chain  250  operates in a conveyor track  256  comprising a solid bottom wall  258 ; opposed, solid side walls  260 ; and a top wall  262  having a center slot formed therein.  
         [0104]     Each of the compact carriages  252  comprises a unitary structure which may be manufactured from a variety of materials utilizing conventional manufacturing techniques. For example, the compact carriages  252  may be manufactured from steel and/or other metals by means of die casting, investment casting, or other well known manufacturing processes. Alternatively, the compact carriages  252  may be formed from various plastic materials suitable for high temperature applications, and may be manufactured utilizing conventional processes such as injection molding. Preferably, the material and the process used in the manufacture of compact carriages  252  are selected such that few if any machining operations are required in order to complete the manufacture thereof.  
         [0105]     Each compact carriage  252  comprises a elongate body  274  having an opening  276  extending axially therethrough. The opening  276  receives the wire rope  254 . Compression sleeves  278  mounted on the wire rope  254  locate and secure each compact carriage  252  thereon.  
         [0106]     Axles  282  extend outwardly from the body  274  at points situated inwardly from ends thereof. The axles  282  support pairs of wheels  284  which center conveyor chain  254  for moving along the track  256 . A boss  286  extends upwardly from the body  274  and in turn supports a grid (not shown) which receives and transports bakery pans having dough received therein along the length of the track  276 . The boss  286  may be provided with a drilled and tapped aperture which receives a threaded fastener to secure the grid thereto. Examples of grids which may be used in the practice of the invention are shown and described in U.S. Pat. Nos. 4,729,470, 4,760,911, and 4,836,360, all of which are owned by the assignee hereof and incorporated herein by reference.  
         [0107]     The boss  286  may have a dimensionally reduced portion at the upper end thereof. A top plate may be supported on the boss  286  and receive the dimensionally reduced portion therethrough. If used, the top plates function to prevent debris from entering the track  256  through the slot in the top wall  262 .  
         [0108]     Each compact carriage  252  is further provided with a pair of wheels  300 . The wheels  300  function to support the compact carriage  52  for movement along the bottom wall of the track  256 . The wheels  300  are rotatably supported on pins  302  extending from the body  274  of the compact carriage  252 .  
         [0109]     The wheels  284  are each rotatably supported by a self-lubricating antifriction bearing constructed as disclosed herein above in connection with the bearing  105 . The self-lubricating bearings do not require lubrication in order to rotatably support the wheels  284 . Therefore, by means of the present invention, the need for lubrication of the wheels which support the carriages  252  is eliminated as are the problems attended to the failure to provide required lubrication and difficulties associated cleaning conveyor chains in which lubricating fluids are used. The wheels  300  are also rotatably supported by self-lubricating bearings.  
         [0110]     Referring to  FIGS. 14, 15 ,  16 ,  17 , and  18 , there is shown a conveyor chain  350  comprising a fourth and preferred embodiment of the invention. The conveyor chain  350  comprises a plurality of identical links  352  which are connected end to end to form the chain  350 . The conveyor chain  350  comprising the links  352  is adapted for movement along the length of a conveyor track  356  comprising a solid bottom wall  358 ; opposed, solid side walls  360 ; and a top wall  362  having a central slot formed therein.  
         [0111]     Each component of the links  352  comprises a unitary structure which may be manufactured from a variety of materials utilizing conventional manufacturing techniques. For example, the links  352  may be manufactured from steel and/or other metals by means of die casting, investment casting, or other well known manufacturing processes. Alternatively, the links may be formed from various plastic materials adapted for high temperature applications, and may be manufactured utilizing conventional processes such as injection molding. Preferably, the material and the process used in the manufacture of links are selected such that few if any machining operations are required in order to complete the manufacture thereof.  
         [0112]     Each link  352  comprises a first link portion  364  and a second link portion  366 . Each first link portion  364  is connected to its corresponding second link portion  366  by a pin  368  which facilitates relative pivotal movement between the link portions in the nominally vertical plane. Each pin  368  also has mounted thereon a pair of wheels  370  which support the link  352  for movement along the bottom wall  358  of the track  356 .  
         [0113]     The second link portion  366  of each link  352  is connected to the first link portion  364  of the immediately following link  352  by a pin  372 . Thus, the pins  372  facilitate relative pivotal movement the links  352  of the conveyor chain  350  in the nominally horizontal plane. Each pin  372  also supports two wheels  374  which serve to center the conveyor chain  350  and the track  356 . As is best shown in  FIG. 17 , the diameters of the wheels  370  and  374  are closely matched to the interior dimensions of the track  356  whereby the wheels  370  and  374  completely prevent bending or tipping of the chain  350 .  
         [0114]     The pins  368  and  372  of the links  352  facilitate the movement of the conveyor chain  350  along inclined and curved portions of the track  356 . For example,  FIG. 15  illustrates the movement of the conveyor chain  350  along a vertically curved portion of the track  356 .  FIG. 16  illustrates the movement of the conveyor chain  350  along a horizontally curved portion of the track  356 . As will be appreciated by reference to  FIGS. 15 and 16 , the movement of the conveyor chain  350  along inclined and curved portions of the track  356  is accomplished without interference between the conveyor chain  350  and the track  356 .  
         [0115]     Referring particularly to  FIGS. 14, 16 ,  17 , and  18 , the wheels  370  are rotatably supported on the pins  368  by self-lubricating bearings  376  which are preferably constructed as described hereinabove in connection with bearings  105 . Likewise, the wheels  374  are rotatably supported on the pins  372  by self-lubricating bearings  378 . The use of the self-lubricating bearings  376  and  378  to rotatably support the wheels  370  and  374 , respectively, eliminates the need for lubrication. As is shown in  FIG. 14 , the wheels  370  and  374  may be supported by sealed self-lubricating anti-friction bearings  379  adapted for high temperature applications in lieu of the bearings  376  and  378 .  
         [0116]     Each first portion  364  of each link  362  includes a boss  380  extending upwardly therefrom and through the slot in the top wall  362  of the track  356 . Each boss  380  supports a grid (not shown) which receives and transports bakery pans having dough received therein along the length of the track  356 . Each boss  380  may be provided with a drilled and tapped aperture  382  which receives a threaded fastener to secure the grid thereto. Examples of grids which may be used in the practice of the invention are shown and described in U.S. Pat. Nos. 4,729,470; 4,760,911; and 4,836,360, all of which are owned the assignee hereof and incorporated herein by reference.  
         [0117]     Each boss  380  may have a dimensionally reduced portion  384  at the upper end thereof. Top plates  386  are supported on the bosses  380  and receive the portions  384  therethrough. The top plates function to prevent debris from entering the track  356  through the slot in the top wall  362  thereof.  
         [0118]     Referring to  FIG. 19 , one of the advantages of the use of the conveyor chain in the present invention comprises the adaptability thereof to changes in pitch. Thus, in  FIG. 19  there is shown a conveyor chain  350  having links  352 ′ which are substantially longer than the links  352  of the conveyor chain  350  illustrated in  FIGS. 14, 15 , and  16 . The use of the longer links  352 ′ in the conveyor chain of  FIG. 19  results in the conveyor chain having a substantially longer pitch as compared with the pitch of the conveyor chain  350  shown in  FIGS. 14, 15 , and  16 . The use of a conveyor chain having a longer pitch is advantageous in those instances in which the conveyor chain is called upon to carry either lighter bakery pans or bakery pans carrying lighter loads as compared with the loading of the conveyor chain  350  of  FIGS. 14, 15 , and  16 .  
         [0119]     Referring now to  FIG. 20 , there is shown a drive mechanism  400  useful in conjunction with all of the conveyor chains illustrated in  FIGS. 4 through 19 , inclusive, and described hereinabove in conjunction therewith. The drive mechanism  400  includes a drive chain  402  which is trained around an idler sprocket  404 , an idler sprocket  406 , and a drive sprocket  407 . The drive sprocket  407  is actuated by a suitable drive mechanism to cause the drive chain  402  to move around the course defined by the sprockets  404  and  406 .  
         [0120]     A plurality of chain engaging members  408  are supported on the drive chain  402  for engagement therewith. Each chain engaging member  408  includes a forward roller  410  which is rotatably supported on a pin  412  secured in the drive chain  402  and a rearward roller  414  which follows the surface of a cam  416  extending adjacent to the path of the drive chain  402 .  
         [0121]     Referring particularly to the portion of the cam  416  extending adjacent to the idler roller  406 , if the rollers  410  and  412  were both secured to the drive chain  402 , the chain engaging members  408  would accelerate during movement around the idler roller  406 . However, the means of the engagement of the roller  414  with the cam  416 , each chain engaging member  408  remains parallel to its corresponding surface on the conveyor chain until the chain engaging member  408  has moved downwardly far enough to disengage from the conveyor chain. In this manner operating power is applied to the conveyor chain evenly and without periodic intervals of acceleration as would otherwise be the case.  
         [0122]      FIG. 21  illustrates an alternative drive mechanism  420  which may be utilized in the practice of the invention. The drive mechanism  420  includes a drive chain  422  which extends around a course defined by a drive sprocket  424  and two idler sprockets  426  and  428 .  
         [0123]     The drive mechanism further includes a plurality of conveyor chain engaging members  430  each dimensioned to fully fill the space between adjacent links of a conveyor chain. In this manner the drive mechanism  420  may be utilized to apply a breaking force to the conveyor chain. This is accomplished by slowly reducing the operating power that is supplied to the drive sprocket  424  or by completely reversing the direction of operation of the drive sprocket  424  depending upon the requirements of particular circumstances.  
         [0124]     Each conveyor chain engaging member  430  is secured to the drive chain  422  by a pin. Each conveyor chain engaging member  430  is provided with a forward roller  434  and a rearward roller  436 . The rearward roller  436  follows a cam which is substantially identical in shape and function to the cam  416  illustrated in  FIG. 20 . Thus, the rearward roller  436  causes the conveyor chain engaging member  430  to disengage from the conveyor chain without applying acceleration thereto.  
         [0125]     The forward roller  434  of each conveyor chain engaging member  430  follows a track  438 . The movement of the forward roller  434  in the track  438  causes each conveyor chain engaging member  430  to enter into the space between adjacent links of the conveyor chain without applying either acceleration forces or deceleration forces thereto. Thus, the conveyor chain engaging member moves smoothly into the gap between adjacent links of the conveyor chain and into engagement with both of the adjacent links without applying forces thereto which otherwise would tend to change the speed of travel of the conveyor chain.  
         [0126]      FIG. 22  illustrates the use of the drive mechanism  420  in those instances in which the pitch of the conveyor chain is too long for the conveyor engaging members  430  to fill the entire gap between adjacent links of the conveyor chain. In such instances a spacer  440  is mounted on each connection member of the conveyor chain at a suitable location between adjacent links thereof so as to receive the chain engaging member  430  between the spacer  440  and the link of the conveyor chain situated forwardly thereof. In this manner the drive mechanism  420  functions identically to the manner in which it functions as illustrated in  FIG. 21  but without the necessity of employing conveyor engaging members which are unduly long.  
         [0127]     Referring to  FIGS. 23 and 24 , there is shown a conveyor chain  450  comprising a variation of the conveyor chain  350  illustrated in  FIGS. 14 through 18 , inclusive, and described hereinabove in conjunction therewith. The conveyor chain  450  is identical to the conveyor chain  350  except that it comprises identical links  352 ′ each having upper and lower drive cams  452  and  454  secured thereto by fasteners  456 .  
         [0128]      FIG. 24  illustrates a drive mechanism  460  useful in conjunction with the drive chain  450 . The drive mechanism  460  includes a drive motor  462  which actuates a drive sprocket  464 . A drive chain  466  is trained around the drive sprocket  464  and two idler sprockets  468  and  470 .  
         [0129]     A drive chain cam  472  extends between the idler sprockets  468  and  470 . The drive chain  466  carries a plurality of drive forks  476 . Upon actuation by the drive motor  462 , the drive sprocket  464  actuates the drive chain  466  to move the drive forks  476  around a course extending from the drive sprocket  464  around the idler sprocket  468 , across the drive chain cam  472 , around the idler sprocket  470 , and back to the drive sprocket  464 .  
         [0130]     As each drive fork  476  moves into engagement with the drive chain cam  472  it is gradually lifted into engagement with one of the drive cams  452  on one of the links  352 ′ of the conveyor chain  450 , being understood that an identical drive fork engages the drive cam  454  on the opposite side of the particular link  352 ′. As will be appreciated by those skilled in the art, the drive chain  466  and the conveyor chain  450  move at the same speed. Therefore, the drive forks of the conveyor chain  466  engage the drive cams of the conveyor chain  450  without applying any acceleration force or any deceleration to the conveyor chain  450 . Subsequently, the drive chain cam  472  gradually lowers each drive fork  476  out of engagement with the drive cam  452  with which it has been engaged. Again, the disengagement between the drive forks and the drive cams is accomplished without applying any acceleration force or deceleration force to the conveyor chain  450 .  
         [0131]      FIGS. 25 through 30 , inclusive, illustrate a link  520  useful in the construction of conveyor chains of the type used in continuous proofing and baking apparatus. Each link  520  of the conveyor chain includes a first connection member  522 , a second connection member  524 , and a pair of spaced, parallel plates  526 . The first connection member  522  of a particular link  20  is connected to the second connection member  524  of the next preceding link in the chain by a horizontal pin  523  which facilitates pivotal movement between adjacent links in the nominally vertical plane. The plates  526  are connected to the first connection member  522  and to the second connection member  524  by vertical pins  530  which facilitate relative pivotal movement between adjacent links in the nominally horizontal plane. Each connection member  524  is provided with a boss  525  which is used to support and position a product pan supporting grid (not shown).  
         [0132]     The first connection member  522  of each link  520  is provided with a pair of wheels  532  which are rotatably supported on pins  531  by antifriction bearings constructed as described hereinabove in connection with bearings  105 . The pins  531  are provided with one or more removable fasteners  533  to facilitate replacement of the wheels  532 . The wheels  532  support the link  520  for movement along a conveyor track. A wheel  534  is positioned between the plates  526 . The wheels  534  are rotatably supported on pins  530  by antifriction bearings constructed as described hereinabove in connection with bearings  105  and function to center the link  520  in the conveyor track.  
         [0133]     The pins  523  and  530  are provided with a thin solid film lubricant selected from the group including molybdenum disulfide, tungsten disulfide, graphite, titanium nitrite, diamond carbide, and alloys of nickel. The solid film lubricant has a thickness &lt;0.003 in. Referring particularly to  FIG. 27 , the connection members  522  and  524  may be provided with self lubricating plain bearings  536  each formed from a material selected from the group comprising graphite, reinforced polytetrafluoroethylene, polyetheretherketon, vespel® viton® and bronze. Bearings  536  are press fit or heat shrunk into the bores comprising the connection members  522  and  524 . Alternatively, in lieu of the bearings  536  the entirety of the connection members  522  and  524  may be coated with a thin film solid lubricant selected from the group including molybdenum disulfide, tungsten disulfide, graphite, titanium nitrite, diamond carbide, and alloys of nickel.  
         [0134]     Referring to  FIGS. 31, 32 , and  33  there is shown a subassembly  550  which may be used in the construction of the link  520  of  FIGS. 25-30 , inclusive, in lieu of the first component  522 , the second component  524 , and the wheels  532 . As will be understood from the foregoing description thereof, the configuration of the link  520  shown in  FIGS. 25-30 , inclusive, is a two wheel configuration. That is, each link  520  employs two wheels  532 . As opposed thereto, when the subassembly  550  of  FIGS. 31, 32 , and  33  is used in the construction of the link  520 , there is provided a one wheel configuration.  
         [0135]     The subassembly  550  includes a first component  552 , and second component  554 , a pin  556 , and a single wheel  558 . The first component  552  is provided with a pin receiving aperture  562  which receives one of the pins  530  which join the plates  526  of the link  520 . Similarly, the second component  554  comprises a pin receiving aperture  564  which receives one of the pins  530  of the link  520 .  
         [0136]     The first component  552  and the second component  554  may be coated with a thin film solid lubricant selected from the group including molybdenum disulfide, tungsten disulfide, graphite, titanium nitrate, diamond carbide, and alloys of nickel. Alternatively, the pin receiving apertures  562  and  564  may be provided with press fit plain bearings which are identical in construction and function to the bearings  536  and  539  as illustrated in  FIGS. 27-30 , inclusive, and described hereinabove in conjunction therewith.  
         [0137]     The pin  556  may comprise a cold formed rivet which functions to retain the component parts of the subassembly  550  in the configuration illustrated in  FIGS. 31 and 32 . Alternatively, the pin  556  may comprise a bolt and nut similar to the bolt  531  and the nut  533  of  FIG. 30 . Another alternative configuration of the pin  556  comprises right-hand and left-hand threaded screws. Other configurations of the pin  556  will readily suggest themselves to those skilled in the art.  
         [0138]     The first component  552  and the second component  554  are each supported on the pin  556  for relative pivotal movement with respect thereto, and with respect to each other. This is accomplished by providing the first component  552  and the second component  554  with pin receiving apertures having inside diameters which are slightly larger than the outside diameter of the pin  556 . The portions of the exterior surface of the pin  556  which are aligned with the pin receiving apertures of the first component  552  and the second component  554 , the surfaces of the apertures of the first component  552  and the second component  554  that receive the pin  556 , and the engaging interior and exterior surfaces of the first component  552  and the second component  554  are all coated with a thin film solid lubricant selected from the group including molybdenum disulfide, tungsten disulfide, graphite, titanium nitrite, diamond carbide, and alloys of nickel.  
         [0139]     The single wheel  558  of the subassembly  550  comprises a cylindrical roller bearing. The specifications for the construction of the wheel  558  are the same as the specifications for the first, second, and third embodiments of the anti-friction bearing  105  as set forth hereinabove.  
         [0140]     Referring specifically to  FIG. 33 , the wheel  558  comprises an inner race  566 , a plurality of cylindrical rollers  568 , and an outer race  570 . Each end of the inner race  566  is provided with an axially extending boss  572 . Referring to  FIG. 32 , the bosses  572  of the inner race  566  of the wheel  558  are positioned in engagement with opposed interior surfaces of the second component  554 .  
         [0141]     The inner race  566  of the wheel  558  is secured against rotation relative to the second component  554 . This may be accomplished by providing an interference fit between the bosses  572  and the second component  554 . For example, the opposed legs of the second component  554  having the pin  556  extending therethrough may be spread slightly, the wheel  558  may then be positioned within the second component  554  and properly aligned therewith, after which the legs of the second component  554  are allowed to return to their original positions insofar as possible. Other techniques for restraining the inner race  566  of the wheel  558  against relative movement with respect to the second component  554  will suggest themselves to those skilled in the art.  
         [0142]     Although preferred embodiments of the invention as illustrated in the accompanying Drawings and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiments disclosed, but is capable of numerous rearrangements, modifications, and substitutions of parts and elements without departing from the spirit of the invention.