Trenching Chain

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

FIELD OF THE INVENTION

The present invention relates to a chain, particularly a trenching chain.

BACKGROUND OF THE INVENTION

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.

The boom typically includes a bar and a trenching chain, that is, a cutting chain extending around at least a portion of the bar's periphery. In operation, the cutting chain rotates around the periphery of the bar.

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.

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

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.

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.

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.

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's lateral edges, and resist lateral displacement of the cutting chain relative to the boom.

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.

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.

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

FIG. 1 a is a perspective view of a link of the prior art.

FIG. 1 b is a side view of the prior art link of FIG. 1a.

FIG. 1 c is a front view of the prior art link of FIG. 1a.

FIG. 1 d is a bottom view of the prior art link of FIG. 1a.

FIG. 1 e is a perspective view of the prior art link of FIG. 1a with a top plate.

FIG. 1 f is a transverse cross-section of a boom with links of the prior art.

FIG. 2 is a perspective view of a link of the present invention.

FIG. 3 is a portion of a cutting chain comprising the links of FIG. 2.

FIG. 4 is a bottom view of the link of FIG. 2.

FIG. 5 is a side view of the link of FIG. 2.

FIG. 6 is a perspective view of a plug for a journal.

FIG. 7 is a perspective view of a link having location holes for bit blocks.

FIG. 8 is a perspective view of a cutting chain comprising the link of FIG. 2 around a drive sprocket.

FIG. 9 a is a side view of FIG. 8.

FIG. 9 b is a side view of the contact area of FIG. 8.

FIG. 9 c is a side view of an oversized drive sprocket condition.

FIG. 9 d is a side view of an undersized drive sprocket condition.

FIG. 10 a is a side view of a trenching boom.

FIG. 10 b is an alternative embodiment of a side view of the trenching boom.

FIG. 11 is a transverse cross-section of the trenching boom of FIG. 10a.

DETAILED DESCRIPTION OF THE INVENTION

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.

FIG. 1 a-1e show a section 1 of a prior art trenching or cutting chain. FIG. 1f 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.

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. 1c 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.

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.

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.

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.

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.

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.

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.

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.

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. 1a-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.

FIGS. 9 a-9d 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. 9a. 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. 9c. 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. 9d. In embodiments as shown in FIG. 9b, 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.

A plurality of links can form an endless cutting chain 130. FIGS. 10a and 10b 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.

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

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

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.

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.

Claims

1. A link for use in a cutting chain comprising a unitary body section comprising a top surface adapted to receive a cutting tooth and a bottom surface, and defining an entry journal at a forward end and an exit journal at a posterior end.

2. The link of claim 1, wherein the top surface includes a bit block for securing the cutting tooth.

3. The link of claim 2, wherein the bit block is secured to the top surface by a method selected from a group consisting of welding, adhesive, mechanical fastener, and combinations thereof.

4. The link of claim 1, wherein a plurality of cutting teeth are placed on the top surface in a pattern.

5. The link of claim 1, wherein the top surface defines a detail that permits foreign matter to pass through the link.

6. The link of claim 1, wherein the top surface defines a location hole for placement of the cutting tooth.

7. The link of claim 6, wherein a dowel connects the location hole and the cutting tooth.

8. The link of claim 1, wherein the bottom surface includes a continuous surface.

9. The link of claim 1, wherein the bottom surface includes a wear plate.

10. The link of claim 1, wherein at least one journal has a centerline and the bottom surface is offset from the centerline.

11. A cutting chain comprising an endless loop of a plurality of links, each link comprising a unitary body section defining an entry journal at a forward end and an exit journal at a posterior end, the unitary body section comprising a top surface adapted for receiving a cutting tooth and a bottom surface, the exit journal of a preceding link aligning with the entry journal of a following link to form an aligned journal, a journal pin extending at least partially through the aligned journal forming a connection between the following link and the preceding link, whereby a plurality of connections between a plurality of links forms the endless loop.

12. The cutting chain of claim 11, wherein a lock pin prevents removal of the journal pin.

13. The cutting chain of claim 11, wherein the journal pin includes a head that is larger than at least one journal.

14. The cutting chain of claim 11, wherein at least one journal defines a blind hole having an open end, and the journal pin extends into the blind hole and a lock pin secures the journal pin at the open end of the aligned journal.

15. The cutting chain of claim 11, wherein the journal pin is press fit into the entry journal and the exit journal.

16. The cutting chain of claim 11, wherein a plug seals the journal pin inside the entry journal and the exit journal.

17. A cutting device comprising: a. a boom assembly comprising a drive sprocket and having a periphery; andb. a cutting chain defining an endless loop around the periphery of the boom assembly, the cutting chain comprising a plurality of links, each link comprising a unitary body section defining an entry journal at a forward end and an exit journal at a posterior end, the unitary body section comprising a top surface adapted for receiving a cutting tooth, a bottom surface, and a lateral edge engaging the drive sprocket, the exit journal of a preceding link aligning with the entry journal of a following link to form an aligned journal, a journal pin extending at least partially through the aligned journal forming a connection between the following link and the preceding link, whereby a plurality of connections forms the endless loop.

18. The cutting device of claim 17, wherein the lateral edge includes an entering face and an exiting face, and the drive sprocket engages the entering face and the exiting face.

19. The cutting device of claim 17, wherein the cutting device includes a cutting region and a return region, and the cutting region includes a boom wear plate that contacts the bottom surface of the unitary body sections of the cutting chain.

20. The cutting device of claim 17, wherein the bottom surface of the unitary body section includes a lug that engages the boom assembly.