Abstract:
A link for a cutting chain comprises a reduced number of parts including a body section and a journal pin. A plurality of links can be joined to form the cutting chain. The cutting chain can be used on a trenching machine having a boom encircled by an endless chain. The link includes a top surface for the placement of cutting teeth. The link increases the freedom of cutting teeth placement, can extend the useful life of the cutting chain and the drive sprocket, can reduce thermal cracking and failure, and can resist lateral forces that would force the cutting chain from the boom.

Description:
[0001]    The present invention is a non-provisional application of 61/104,148, which is hereby incorporated by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates to a chain, particularly a trenching chain. 
       BACKGROUND OF THE INVENTION 
       [0003]    Trenchers are used to dig trenches for laying underground pipe, cable, and other articles. Trenchers typically include a tractor unit that drives an elongated boom. The boom is often movable between a raised, generally horizontal position, and a lowered, operational position. 
         [0004]    The boom typically includes a bar and a trenching chain, that is, a cutting chain extending around at least a portion of the bar&#39;s periphery. In operation, the cutting chain rotates around the periphery of the bar. 
         [0005]    The cutting chain can include digging teeth for engaging and breaking up the soil. The cutting chain can also transport the excavated soil from the trench. The digging teeth are typically fixed to the cutting chain by a bit block and are replaced when worn. Replacing the digging teeth is frequently time consuming and expensive. 
         [0006]    The cutting chain includes a plurality of interlinked sections. Each section can include more than two dozen parts. For example, a prior art cutting chain comprises side plates, bushings, rollers, brackets, journal pins, retaining rings, top plate, bolts, nuts, and lock washers. The manufacture of each part and their assembly can be expensive and time consuming. 
       SUMMARY OF THE INVENTION 
       [0007]    The present invention describes a cutting chain comprising links consisting of a reduced number of parts. The links permit greater positioning freedom of cutting teeth along a top surface. A link comprises at least two parts and includes no nuts or bolts. The parts can include a body section and a journal pin. In loose fit journal pin designs, the link can also include a lock pin. 
         [0008]    The body section comprises a top surface and a bottom surface. The body section also defines an entry journal and an exit journal for insertion of journal pins. The entry journal of the body section aligns with an exit journal of a preceding body section, and a journal pin through the journals secures the sections together. The journal pin can be loose fit or press fit. In loose fit designs, a lock pin prevents removal of the journal pin. Similarly, the exit journal of the body section aligns with an entry journal of a following section, and a second journal pin through the journals secures the sections together. Loose-fit journal pins facilitate disassembly of the cutting chain or replacement of a section. Further, every section of the cutting chain can be a master link. 
         [0009]    The top surface of the cutting chain includes at least one cutting tooth and will usually include a plurality of cutting teeth. Typically, bit blocks that are secured to the top surface will receive the cutting teeth. Unlike prior art, the top surface of the cutting chain does not have elements that interfere with the placement of the bit blocks. This permits greater flexibility in the placement of the cutting teeth on the chain. Also, each link can include a top surface for receiving cutting teeth. 
         [0010]    The bottom surface contacts a wear plate on the boom. The bottom surface preferably includes a substantially continuous surface so that the wear plate can be completely consumed before needing replacement. Additionally, a continuous bottom surface can produce lower stresses, lower temperatures, and longer life than the typically discontinuous lower surfaces of prior art. In embodiments, the bottom surface includes at least one lug that engages the boom. In embodiments, the bottom surface includes a plurality of lugs that at least partially span the lateral sides of the bottom surface. The lugs engage the boom, such as for example, at the boom&#39;s lateral edges, and resist lateral displacement of the cutting chain relative to the boom. 
         [0011]    In embodiments, the bottom surface can be eccentric to the journal holes so that cracks on the bottom surface created by, for example, heat and stress, will not propagate to the journal hole. 
         [0012]    In further embodiments, the cutting chain can include openings through which foreign matter, such as dirt and debris, can escape. Foreign matter can interfere with the operation of the cutting chain and its contact with a drive sprocket. 
         [0013]    The cutting chain can include a body section comprising an entering face and an exiting face. A drive sprocket can act on either face or both faces to rotate the cutting chain around the boom thereby increasing the useful life of the cutting chain. In embodiments, the cutting chain when new can be made undersized relative to the drive sprocket so that only the exiting teeth of the drive sprocket are driving the chain. As the cutting chain wears, the sprocket can engage and drive both the entering face and the exiting face in a condition known as perfect pitch. As the cutting chain continues to wear, only the entering teeth of the drive sprockets are moving the chain. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1   a  is a perspective view of a link of the prior art. 
           [0015]      FIG. 1   b  is a side view of the prior art link of  FIG. 1   a.    
           [0016]      FIG. 1   c  is a front view of the prior art link of  FIG. 1   a.    
           [0017]      FIG. 1   d  is a bottom view of the prior art link of  FIG. 1   a.    
           [0018]      FIG. 1   e  is a perspective view of the prior art link of  FIG. 1   a  with a top plate. 
           [0019]      FIG. 1   f  is a transverse cross-section of a boom with links of the prior art. 
           [0020]      FIG. 2  is a perspective view of a link of the present invention. 
           [0021]      FIG. 3  is a portion of a cutting chain comprising the links of  FIG. 2 . 
           [0022]      FIG. 4  is a bottom view of the link of  FIG. 2 . 
           [0023]      FIG. 5  is a side view of the link of  FIG. 2 . 
           [0024]      FIG. 6  is a perspective view of a plug for a journal. 
           [0025]      FIG. 7  is a perspective view of a link having location holes for bit blocks. 
           [0026]      FIG. 8  is a perspective view of a cutting chain comprising the link of  FIG. 2  around a drive sprocket. 
           [0027]      FIG. 9   a  is a side view of  FIG. 8 . 
           [0028]      FIG. 9   b  is a side view of the contact area of  FIG. 8 . 
           [0029]      FIG. 9   c  is a side view of an oversized drive sprocket condition. 
           [0030]      FIG. 9   d  is a side view of an undersized drive sprocket condition. 
           [0031]      FIG. 10   a  is a side view of a trenching boom. 
           [0032]      FIG. 10   b  is an alternative embodiment of a side view of the trenching boom. 
           [0033]      FIG. 11  is a transverse cross-section of the trenching boom of  FIG. 10   a.    
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0034]    Cutting chains have been based on chains for conveying or crawling. A conveying chain moves materials in an industrial setting or factories so that exposure to foreign matter is generally not a problem. Conveyor chains use support elements that are not present or available on boom assemblies. Typically, conveyor chains move at less than 100 feet per minute, which is substantially less than the speed of a trenching chain which can move 200 to 800 feet per minute. Crawler chains are typically found on bulldozers and other earth moving equipment. Support elements for crawler chains consist essentially of wheels, which are generally not present on boom assemblies. 
         [0035]      FIG. 1   a - 1   e  show a section  1  of a prior art trenching or cutting chain.  FIG. 1   f  shows a prior art sections  1  on a boom  33  having a wear plates  32 . The section  1  includes a roller link  2  and a connecting link  3 . The trenching chain comprises a plurality of sections. The connecting link  3  includes top flanges  4  for receiving a top plate  15 . The top plate  15  bolts to the connecting link  3  through the orifices  5  defined by the top flanges  4 . The top plate  15  can receive bit blocks and cutting teeth (not shown). The bolts  16 , which extend through the top plate  15 , restrict the placement of the bit blocks and cutting teeth. 
         [0036]    The connecting link  3  defines an anterior journal opening  12  and a posterior journal opening  11 . The pitch  14  of the chain is defined by the distance between the anterior journal opening  12  and the posterior journal opening  11 . The roller link  2  defines a roller journal opening  13 . The roller journal  13  is adapted to align with the posterior journal opening  11  of a preceding link. A journal pin  44  extends through the journal openings  11 ,  12 ,  13 , and is typically press fit through the journal openings  11 ,  12 . Journal bushings  41 ,  42  often cover the journal pin  44 .  FIG. 1   c  shows a bottom surface  31  formed by the roller link  2  and connecting link  3 . The bottom surface  31  consists essentially of two rails consisting of edges of the roller links  2  and the connecting links  3 . In operation, the bottom surface  31  runs along a wear plate  32  of a boom  33  to which the trenching chain is secured. Movement of the bottom surfaces  31  of the links  3  over the wear plate  32  typically produce grooves in the wear plate  32  corresponding to the edges of the roller links  2  and the connecting links  3 . The middle of the wear plate  32  is substantially untouched. Accordingly, the wear plate  32  must be replaced before a substantial portion of the wear plate  32  is used. Of course, the bottom surfaces  31  also experiences wear and, because the bottom surface  31  is commonly only a fraction of the size of the wear plate  32  and the top plate  15 , wear of the bottom surface  31  can be substantial. 
         [0037]    As shown in  FIG. 2 , a link  50  of the present invention includes a unitary body section  51  and a journal pin  53 . Unitary means a single unit or part, preferably constructed from a single piece of material. A plurality of links  50  can produce a trenching or cutting chain. The links will typically be connected as an endless loop. In loose fit designs, the link  50  can also include at least one lock pin  54 . The unitary body section  51  includes a top surface  52 , and defines a least one entry journal  57  along a forward end, and at least one exit journal  58  at a posterior end. Two links can be united by aligning the entry journal  57  of a following link and an exit journal  58  of a preceding link so that the aligned journal can receive a journal pin  53 . The journal pin extends at least partially through the aligned journal forming a connection between the following link and the preceding link, whereby a plurality of connections forms chain or endless loop. Optionally, more than one journal pin can be used. 
         [0038]    A cutting chain includes a plurality of such combined links, and typically forms an endless loop. An entry journal  57  of the unitary body section of a following link aligns with an exit journal  58  of a unitary body section of a preceding link to form an aligned journal. A journal pin  53  extends through the aligned journals  57 ,  58  and secures the links together. A lock pin  54  can prevent removal of the journal pin  53 . This pattern of preceding and following links is repeated until the desired length of chain is achieved. The journal pin  53  can include a head that is larger than at least one of the journals  57 ,  58 . The lock pin  54  and the head prevent the journal pin  53  from being removed from the journals  57 ,  58 . Alternatively, at least one journal  57 ,  58  can include a blind hole for receiving the journal pin  53  and the lock pin  54  can the secure the journal pin  53  on the open end of the journals  57 ,  58 . In embodiments, the journal pin  53  is a bar and a plurality of lock pins  54  fix the journal pin  53  in the journals  57 ,  58 . The journals  57 ,  58  are loose fit and permit the adjacent body sections to move relative to each other. Loose-fit journal pins facilitate disassembly of the cutting chain or replacement of a section. Further, every section of the cutting chain can be a master link. In embodiments, the journal pin  53  is press fit into the journals  57 ,  58  and a lock pin  54  is unnecessary. 
         [0039]    The top surface  52  of the body section  51  is adapted to receive bit blocks  55  for securing cutting teeth  56  to the link. The bit blocks  55  can be secured by any known method such as, for example, welding, adhesives, mechanical fasteners, and combinations thereof. 
         [0040]      FIG. 3  shows a portion of a cutting chain  61  including a plurality of links  50 . The cutting chain  61  includes bit blocks  55  and cutting teeth  56  on the top surfaces  52  of at least a portion of the links  50 . The top surfaces  52  preferably contain no bolts or other obstructions that would limit the placement of the bit blocks  55  or cutting teeth  56 . This embodiment shows a lacing pattern designed to effectively and efficiently cut material. One skilled in the art would appreciate that other patterns could be used depending on conditions such as, for example, the material to be cut, the depth of the cut, and desired speed of the cut. The cutting chain  61  can also include details  62  that help convey foreign matter from the area being cut by allowing foreign matter to pass through the links  1 . Details  62  can include openings that permit dirt, stones or other debris to exit the interior defined by the endless cutting chain  61 . Conveniently, the material cut away to form the details can project to the exterior defined by the endless cutting chain  61  so that the cut away material functions as a paddle or scoop to remove debris from the trench. 
         [0041]    In contrast to prior art cutting chains, a body section  51  of the present invention as shown in  FIG. 4  includes a large bottom surface  71  that is capable of contacting the wear plate of the boom. In embodiments, the bottom surface  71  can be continuous. A continuous surface includes, for example, a surface that is not interrupted or that includes a discontinuity. In contrast, the bottom surface  31  of the prior art comprises two rails that are separated from each other. The large bottom surface  71  of the present invention can wear the wear plate more evenly. The larger surface area also reduces localized heating caused by friction between the bottom surface  71  and the wear plate. These properties permit the wear plate to last longer and reduce cracks in the bottom surface caused by heat or stress concentrations. As shown in  FIG. 5 , the bottom surface  71  can be thickened to create additional wear life for the cutting chain. In embodiments, the bottom surface  71  is offset from the entry journal centerline  82  and exit journal centerline  83 . The offset  81  reduces the likelihood that cracks from the bottom surface  71  will propagate to the journals  57 ,  58 . A crack in a journal can cause the cutting chain to fail. In embodiments, the offset can differ from the entry journal  57  and the exit journal  58 . 
         [0042]    The journal pin can be sealed in the journals to exclude foreign matter. Foreign matter is typically abrasive and can include, silica, silicates, and other compounds found in dirt and rock. For example,  FIG. 6  shows a body section  51  defining an exit journal  58 . A plug  91  can be inserted in the exit journal  58 . The plug may optionally include an O-ring  92  or alternative sealing device that seals the journal from foreign matter. A lock pin  54  extends through the body section  51  and can also extend at least into the plug  91 . The lock pin  54  secures the plug  91  in place. By reducing the chance of foreign matter entering into the journal, the plug  91  can extend the life of a journal pin. A plug  91  can also be used with the entry journal. 
         [0043]    The top surface  52  of the link  50  can define at least one location hole  100  as shown in  FIG. 7 . The location holes can identify the proper location of one or more bit blocks (not shown). Identifiers  101 , such as numbering, can assist the operator in placement of the bit blocks. The bit block would include a mating surface adjacent to the top surface  52 . The mating surface defines alignment holes. Dowels can connect the location holes  100  and the alignment holes so that the bit block is securely and accurately fixed to the top surface  52 . Preferably, the bit block is welded to the top surface  52  after fixing by the dowel. The bit block can also be secured to the top surface  52  with an adhesive or mechanical fastener. 
         [0044]    In embodiments, as shown in  FIG. 8 , a cutting chain comprising the links  50  of the present invention are driven by at least one drive sprocket  110  at the lateral edge  111  of the links  50 . Conveniently, a drive sprocket  110  will engage both lateral edges  111 . In operation, the drive sprocket  110  will be fixed to a shaft such as, for example, a shaft on a trencher at one end of a boom. Prior art includes a single drive sprocket at the lateral center of the cutting chain. For example,  FIG. 1   a - f  show a journal pin  44  substantially at the lateral center of the section  1 . Compared to a single sprocket design, two drive sprockets at the lateral edges  111  of the links  50  can reduce the stress on the sprockets and chain, and resist entrapment of foreign matter. 
         [0045]      FIGS. 9   a - 9   d  show embodiments of a body section  51  of a link  50  including both an entering face  121  and an exiting face  122 . A drive sprocket  110  can act on either face  121 ,  122  to move the links  50  around the boom (not shown). Having two useable faces can increase the useful life of the cutting chain. In embodiments, the cutting chain when new is undersized relative to the drive sprocket  110  so that the cutting chain is in an oversized drive sprocket condition as shown in  FIG. 9   a . Only the exiting teeth  123  of the drive sprocket  110  are driving the links  50 . As the links wear, all drive sprocket teeth contact and drive the links in a condition known as perfect pitch as shown in  FIG. 9   c . As the links continues to wear, only the entering teeth  124  of the drive sprocket  110  are moving the links, and the cutting chain is in an undersized drive sprocket condition as shown in  FIG. 9   d . In embodiments as shown in  FIG. 9   b , the entering face  121  and exiting face  122  are larger than the journal bushings  41 ,  42  of the prior art. The faces  121 ,  122  increase the contact surface area  125  between the link  50  and the drive sprocket teeth  123 ,  124  thereby reducing stress on the link  50 , the drive sprocket teeth  123 ,  124 , and the drive sprocket  110 . Lower stress can increase their useful lives. 
         [0046]    A plurality of links can form an endless cutting chain  130 .  FIGS. 10   a  and  10   b  show the endless chain  130  on a boom assembly  132 . The drive sprockets  110  rotate the endless cutting chain  130  around the boom assembly  132 . The endless cutting chain  130  includes a cutting region  134  and a return region  135 . The endless cutting chain  130  moves around idler  131 . The idler  131  could include an idler sprocket, idler roller, wheel, or combinations thereof. Like the drive sprockets  110 , the idlers  131  preferably are paired and fit on the lateral edge of the links. In embodiments, a second idler  133  reduces slack in the endless cutting chain  130 . 
         [0047]      FIG. 11  shows a transverse cross-section of a trenching boom  140  that includes a boom  132  and an endless cutting chain  130 . A cutting region  134  of the boom  132  includes a boom wear plate  141 . The boom wear plate  141  should be replaceable. The bottom surface  71  of the link  50  contacts the wear plate  141 . The bottom surface  71  of the link  50  can also include a wear plate. Optionally, the return region  135  can also include a wear plate  141 . In embodiments, a pair of lugs  142  on the lateral edge of the bottom surface  71  engages the boom  132 . The lugs  142  resists movement of the endless cutting chain  130  in the lateral direction  144 . The lugs  142  can engage, for example, the lateral edge of the boom  132 , grooves  145  in the boom  132 , or engage the boom  132  in any other manner known to one skilled in the art. 
       EXAMPLE 1 
       [0048]    A prior art trenching chain and a trenching chain of the present invention were placed into service. The prior art chain comprised a pair of adjacent crawler chains formed into endless loops. A top plate was bolted across the two chains. Bit blocks were welded to the top plate, and  180  cutting teeth were secured in the bit blocks. The bolts restricted the placement of the cutting teeth and prevented the teeth from being placed in an optimum pattern. The chain of the present invention was formed from a plurality of links forming an endless loop where the links were substantially conforming to  FIG. 2 . This chain was the same length as the prior art chain but included only  116  cutting teeth. The cutting teeth were secured to bit blocks that were welded on a top surface of a body section. The size of the top surface and the lack of bolts permitted the cutting teeth to be placed in a pattern designed to improve cutting efficiency. Each chain was used to cut through solid rock that was approximately the same hardness as marble. The prior art chain cut 120 yards per 8-hour day, or 15 yards/hour. The chain of the present invention cut about 200 yards per 8-hour day, or 25 yards/hour. The chain of the present invention cut nearly 70% faster and with over 40% fewer teeth. This represents a savings in time and material over the prior art. 
       EXAMPLE 2 
       [0049]    A prior art trenching chain and a trenching chain of the present invention were placed into service. The chains were similar to those described in Example 1. The pitch of each chain was 9 inches. The prior art chain engaged the drive sprocket through journal pins and bushings. For the prior art chain, a change in pitch of only ⅜ inch was sufficient to render the chain inoperable. This occurred at about 1000 hours of operation. Repair welds were necessary after only less than 500 hours of operation. Additionally, the 416 nuts and bolts that attached the top plates to the chains had to be checked and tightened as necessary. Tightening requires an air compressor. Unlike the prior art chain, the chain of the present invention engaged dual drive sprockets along lateral edges of the links. This modification permitted the chain to accommodate up to one inch of pitch change. Pitch wear was measured at only 1/64 th  inch per 200 hours of operation. A useful service life of nearly 13,000 hours was predicted, which was 12,000 hours longer than the prior art chain and a 1200% increase in service life. Further, the chain of the present invention has no nuts or bolts. 
         [0050]    Numerous modifications and variations of the present invention are possible. It is, therefore, to be understood that within the scope of the following claims, the invention may be practiced otherwise than as specifically described. While this invention has been described with respect to certain preferred embodiments, different variations, modifications, and additions to the invention will become evident to persons of ordinary skill in the art. All such modifications, variations, and additions are intended to be encompassed within the scope of this patent, which is limited only by the claims appended hereto.