Title:
Earth saw
Kind Code:
A1


Abstract:
An apparatus used to excavate trenches. In a preferred embodiment the trenching machine has a cutting disc supported on a frame and adapted to operate with the center point of the cutting disc below ground. A spoils handler supported above the cutting disc and forward of the center point is used to move spoils away from the cutting disc. The ratio of cutting depth to weight of the trenching assembly and the cutting depth to wheel diameter is improved through the use of a cutting disc that is concave. The outer rim of the concave disc may support a plurality of replaceable cutting member. The cutting disc is rotated using a drive assembly that is contained within the cutting width of the cutting disc.



Inventors:
Greenlee, Joseph G. (Perry, OK, US)
Sewell, Cody L. (Perry, OK, US)
Buck, Michael D. (Perry, OK, US)
Talbot, Blaine S. (Ponca City, OK, US)
Application Number:
11/040402
Publication Date:
01/08/2009
Filing Date:
01/21/2005
Primary Class:
International Classes:
E02F5/08
View Patent Images:
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Primary Examiner:
MCGOWAN, JAMIE LOUISE
Attorney, Agent or Firm:
Tomlinson McKinstry, P.C. (Oklahoma City, OK, US)
Claims:
What is claimed is:

1. An apparatus for excavating trenches comprising: a work machine; a frame connected to the work machine; a trenching assembly connected to the frame, the trenching assembly comprising: a cutter disc comprising a central planar portion terminating peripherally in a rim extending generally perpendicular to the central planar portion, wherein the rim comprises an outer surface; a ring connected to the outer surface of the rim and circumscribing the cutter disc; and at least one cutting member supported on the ring; and a power supply supported by the frame and adapted to drive operation of the trenching assembly; a drive assembly disposed within the central planar portion and adapted to both support the cutter disc and transmit rotational energy from a power supply to the cutter disc to drive rotation of the cutter disc from only one side of the cutter disc.

2. The apparatus of claim 1 wherein the ring comprises one or more segments connected to the outer surface of the cutter disc.

3. The apparatus of claim 1 wherein the frame is further adapted to cover an above-ground portion of the trenching assembly, the apparatus further comprising a spoils handler supported within the frame and adapted to move spoils laterally away from the trenching assembly through an opening in the frame immediately above the cutter disc.

4. The apparatus of claim 1 further comprising a spoils handler connected to the frame and adapted to move spoils in a lateral direction away from the trenching assembly.

5. (canceled)

6. The apparatus of claim 5 wherein the power supply comprises a rotatable drive shaft and wherein the drive assembly comprises: a first gear operably connected to the drive shaft for rotation therewith; and a second gear connected to the cutter disc and adapted to rotate in response to rotation of the first gear and drive shaft.

7. (canceled)

8. (canceled)

9. A trenching assembly for excavating a trench comprising: a cutter disc comprising a central planar portion terminating peripherally in a rim extending generally perpendicular to the central planar portion, wherein the rim comprises an outer surface, and wherein the rim and central planar portion delimit an internal space; a ring connected to the outer surface and circumscribing the cutter disc; at least one cutting member connected to the ring; and a drive assembly disposed within the internal space and adapted to both support the cutter disc and transmit rotational energy from a power supply to the cutter disc to drive rotation of the cutter disc from only one side of the cutter disc.

10. The trenching assembly of claim 9 wherein the power supply comprises a hydrostatic motor.

11. The trenching assembly of claim 10 wherein the drive assembly comprises: a first gear connectable to the power supply; and a second gear supported within the internal space and adapted to rotate in response to rotation of the first gear.

12. The trenching assembly of claim 9 comprising a cutting depth and a cutting diameter, wherein the ratio of the cutting depth to the cutting diameter is between 0.5 and 0.8.

13. (canceled)

14. The trenching assembly of claim 9 wherein the cutter disc comprises a center point and wherein the cutter disc is adapted to operate with the center point of the cutter disc below ground.

15. An apparatus for excavating trenches comprising: a frame; a support assembly connected to the frame; a trenching assembly connected to the support assembly, wherein the trenching assembly comprises a cutter disc comprising a central planar portion terminating peripherally in a rim extending generally perpendicular to the central planar portion, and an internal space delimited by the rim and the central planar portion; a drive assembly for mounting the trenching assembly to the support assembly disposed within the internal space and adapted to support the cutter disc from only one side of the cutter disc and to transmit rotational energy from a power supply to the cutter disc to drive rotation of the cutter disc from only one side of the cutter disc.

16. The apparatus of claim 15 wherein the cutting depth of the trenching assembly is between twenty and forty inches.

17. The apparatus of claim 16 wherein the cutting width of the trenching assembly is between 4.75 and 7 inches.

18. The apparatus of claim 15 wherein the ratio of cutting depth of the trenching assembly to cutting diameter of the trenching assembly is 0.65.

19. (canceled)

20. The apparatus of claim 15 further comprising a spoils handler connected to the frame and disposed proximate to the trenching assembly.

21. The apparatus of claim 20 wherein the spoils handler is disposed immediately above the trenching assembly.

22. (canceled)

23. (canceled)

24. (canceled)

25. The apparatus of claim 15 wherein the cutting depth and the cutting diameter comprise a ratio of between 0.5 and 0.8.

26. (canceled)

27. The apparatus of claim 15 wherein the trenching assembly has a cutting width of between 4.75 and 7 inches and wherein the cutting depth of the trenching assembly is between twenty and forty inches.

28. The apparatus of claim 15 wherein the ratio of the cutting width to the cutting depth is approximately 0.16.

29. An apparatus for excavating a trench comprising: a frame comprising a hood; a trenching assembly supported by the frame, the trenching assembly comprising: a cutter disc, the cutter disc comprising a central planar portion terminating peripherally in a rim extending generally perpendicular to the central planar portion wherein the rim comprises an outer surface a ring connected to the outer surface and circumscribing the cutter disc, wherein the ring is adapted to support a plurality of cutting members; wherein the hood of the frame is adapted to cover an above-ground portion of the cutter disc; wherein the cutter disc is rotatable to excavate the trench; a spoils handler supported inside the hood immediately above the cutter disc and adapted to laterally displace spoils from immediately above the cutter disc and a drive assembly disposed within the central planar portion and adapted to both support the cutter disc and transmit rotational energy from a power supply to the cutter disc to drive rotation of the cutter disc from only one side of the cutter disc.

30. (canceled)

31. (canceled)

32. The apparatus of claim 29 further comprising a power supply having a drive shaft adapted to drive rotation of the cutter disc, and wherein the drive assembly comprises: a first gear operably connected to the drive shaft for movement therewith; and a second gear connected to a one side of the cutter disc and adapted to move in response to movement of the drive shaft and the first gear.

33. The apparatus of claim 29 wherein the trenching assembly comprises a cutting depth and a cutting diameter and wherein the ratio of the cutting depth to the cutting diameter is between 0.5 and 0.8.

34. An apparatus for excavating a trench comprising: a frame; a support assembly connected to the frame; a trenching assembly, the trenching assembly comprising a cutter disc comprising: a central planar portion terminating peripherally in a rim extending generally perpendicular to the central planar portion, the peripheral rim having an outer surface; and an internal space delimited by the peripheral rim and central planar portion; a drive assembly for mounting the trenching assembly to the support assembly disposed within the internal space and adapted to support the cutter disc from only one side of the cutter disc and to transmit rotational energy from a power supply to the cutter disc to drive rotation of the cutter disc from only one side of the cutter disc.

35. The apparatus of claim 34 wherein the trenching assembly further comprises a ring connected to the outer surface of the rim and circumscribing the rim, and wherein a plurality of cutting members are connected to the ring so that each connection between the ring and the plurality of cutting members is disposed beyond the rim of the cutter disc.

36. The apparatus of claim 35 wherein the cutter disc comprises a cutting width of at least 4.75 inches.

37. The apparatus of claim 35 wherein the cutter disc comprises a cutting depth of at least thirty inches.

38. The apparatus of claim 34 wherein the cutting width of the trenching assembly is between 4.75 and 7 inches and wherein the trenching assembly comprises a cutting depth of between twenty and forty inches.

39. The apparatus of claim 34 wherein the ratio of the cutting width to the cutting depth is approximately 0.16.

40. The apparatus of claim 34 wherein the ratio of cutting depth to cutting diameter is approximately 0.65.

41. (canceled)

42. (canceled)

Description:

FIELD OF THE INVENTION

This invention relates generally to the field of trenching machines and more specifically to earth saws capable of excavating trenches.

SUMMARY OF THE INVENTION

The present invention is directed to an apparatus for excavating trenches. The apparatus comprises a frame, a support assembly connected to the frame, a trenching assembly and a power supply supported on the frame. The trenching assembly is connected to the support assembly and comprises a concave cutting disc. The concave cutting disc has an outer rim and at least one cutting member supported by the outer rim. The power supply is adapted to drive operation of the trenching assembly.

The present invention is further directed to a trenching assembly for excavating a trench. The trenching assembly comprises a concave cutting disc, a cutting ring, at least one cutting member and a drive assembly. The cutting ring is connected to an outer rim of the concave cutting disc and circumscribes the outer rim. The cutting member is supported by the cutting ring. The drive assembly is disposed within the concave cutting disc and adapted to drive operation of the trenching assembly.

Further still, the present invention is directed to an apparatus for excavating trenches. The apparatus comprises a frame, a support assembly connected to the frame, and a trenching assembly connected to the support assembly. The trenching assembly comprises a cutting disc having a center point, a cutting ring connected to the cutting disc and circumscribing the cutting disc, and at least one cutting member supported on the cutting ring. The trenching assembly has a cutting depth and a cutting diameter. The trenching assembly is adapted to operate with the center point of the cutting disc below ground so that the ratio of cutting depth to cutting diameter is between 0.5 and 0.8.

The present invention further includes an apparatus for excavating a trench. The apparatus comprises a frame, a cutting disc and a spoils handler. The cutting disc is supported by the frame and has a center point and a cutting width. The cutting disc is rotatable about the center point to excavate the trench with the center point of the cutting disc disposed underground during excavation. The spoils handler is supported by the frame and adapted to laterally displace spoils from the cutting disc. The spoils handler is disposed above the cutting disc and forward of the center point and adapted to move spoils laterally and away from the cutting disc.

The present invention further includes an apparatus for excavating a trench. The apparatus comprises a frame, a support assembly connected to the frame, and a trenching assembly. The trenching assembly comprises a cantilevered drive assembly and a cutting width. The cantilevered drive assembly is contained within the cutting width.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevational view of a trenching machine constructed in accordance with the present invention. The trenching machine of FIG. 1 is equipped with a trenching assembly attached to the rear of the machine. The trenching assembly is shown with a cutting disc that is adapted to operate with the center point of the disc below ground surface.

FIG. 2 is an isometric view of the trenching assembly of FIG. 1. The trenching assembly is shown having a concave cutting disc, a cutting ring circumscribing the concave cutting disc, and a drive assembly.

FIG. 3 is a cross-sectional view of the trenching assembly of FIG. 2 showing the cutting ring circumscribing the outer rim of the concave cutting disc. FIG. 3 also illustrates the drive assembly supported within the cutting width of the concave cutting disc and driven by a motor.

DESCRIPTION OF THE INVENTION

Turning now to the figures and first to FIG. 1, there is shown therein an apparatus 10 for excavating trenches, constructed in accordance with the present invention. The trenching machine 10 comprises a tractor 12. The tractor 12 has a frame 16, having a front end 18, a rear end 20, and a power plant 22 adapted to provide power for various functions of the trenching machine 10. The tractor 12 further includes an operator station 24 supported by the frame 16. The operator station 24 is positioned on the frame 16 so that the operator has a relatively unobstructed view of the earth saw attachment 14. The earth saw attachment 14 comprises a support assembly 26 that connects the trenching assembly 27 to the frame 16. The power plant 22 may be positioned at the front end 18 of the frame 16 to counter-balance the earth saw attachment 14.

The frame 16 is adapted to support a drive system 28 for propelling the trenching machine 10 in a plurality of directions. The drive system 28 shown in FIG. 1 comprises pneumatic tires 30 with conventional front wheel steering. The drive system 28 may be controlled in a conventional manner using the combination of a steering wheel 32 and foot pedals 34 and hand controls 36. However, it will be appreciated that the drive system 28 may comprise an all-terrain endless track system and is capable of being steered in a skid, articulated or coordinated arrangement without departing from the spirit of the invention.

As previously discussed, the power plant 22 is supported near the front end 18 of the frame 16. The power plant 22 may comprise an internal combustion engine supported within an engine compartment 38. It will be appreciated, of course, that different types of engines or power sources may be used to power the trenching machine 10. The power plant 22 provides power to drive operation of the drive system 28 and the trenching assembly 27. The engine compartment 38 of the power plant 22 is sloped such that an operator positioned at the operator station 24 has a relatively unobstructed line-of-sight to the ground surface in front of the tractor 12.

Continuing with FIG. 1, a work member 40 may be supported at the front end 18 of the frame 16. The work member 40 may comprise a tool carrier 42 adapted to support a wide variety of work tools at the front end 18 of the frame 16. For illustrative purposes, the work tool shown attached to the tool carrier 42 in FIG. 1 is a backfill blade 44 that may be used to push excavated soil back into an open trench. The backfill blade 44 may be articulated (angled and tilted) to a number of varying angles of orientation using hydraulic cylinders (not shown). The tool carrier 42 and backfill blade 44 are supported by one or more lift arms 46 that are pivotally connected to the frame 16 at pivot point 48. The lift arms 46 are movable in a range of motion comprising a lower position and an upper position (shown in FIG. 1). The lift arms 46 may be raised and supported at any position within their range of motion using one or more hydraulic cylinders 50.

As previously discussed, the operator station 24 is supported by the frame 16 and may comprise the steering wheel 32, pedals 34, and various different work member 40 and earth saw attachment 14 controls 36. The operator station 24 may further comprise an operator seat 52 that has a vertical pivot axis 56 to allow the operator to turn and view the earth saw attachment 14 when in operation. The operator station 24 may further comprise a roll-over protective structure (“ROPS”) 58 supported by the frame 16. The ROPS 58 preferably has front 60 and rear 62 vertical posts and a canopy 64 supported by the vertical posts. It will be appreciated that alternative ROPS configurations may be used by one skilled in the art without departing from the spirit of the invention.

The earth saw attachment 14 comprises the support assembly 26, the trenching assembly 27 and a saw frame 89. The support assembly 26 attaches the trenching assembly 27 to the frame 16. The support assembly 26 supports the trenching assembly 27 so that it is movable about both a first axis 72 and a second 74 axis, both of which are orthogonal to a central longitudinal axis (not shown) of the frame 16. A first actuator 76 and a second actuator 78 are adapted to move the trenching assembly 27 about the first 72 and second axis 74, respectively.

The support assembly 26 may be cantilevered and comprises a removable attachment means 66, a tool carrier 80, a mounting bracket 82 connectable with the tool carrier and a swing post 84. The removable attachment means 66 forms part of the frame 16 and is adapted to support a wide variety of work attachments. The tool carrier 80 is connected to the removable attachment means 66 and may comprise a top rail 86 and a bottom rail 88 both of which extend across the width of the rear end 20 of the frame 16. The mounting bracket 82 is adapted to hang from and slide along the top 86 and bottom rails 88 of the tool carrier 80 so that the trenching assembly 27 may be traversed along the width of the tractor 12. Hydraulic cylinders (not shown) may be used to push and pull the mounting bracket 82 and the trenching assembly 27 along the tool carrier rails 86, 88. However, the saw can be mounted to the tractor in other configurations including 1) with the traversing frames 80 and 82 but without the swing post 84, 2) without the traversing frame but with the swing post and 3) without the traversing frame and without the swing post.

The swing post 84 and first actuator 76 form a cantilevered support assembly which allows the trenching assembly 27 to be pivoted about the first pivot axis 72. The first pivot axis 72 is orthogonal to the central longitudinal axis of the frame 16. The swing post 84 is pivotally connected to the mounting bracket 82 and defines the first axis 72. The first actuator 76 may comprise a hydraulic cylinder connected to the mounting bracket 82 at one end and the swing post 84 at the other end.

Continuing with FIG. 1, the swing post 84 supports a saw frame 89 at the rear 16 of the trenching machine 10. The saw frame 89 supports the trenching assembly 27 and covers the above ground portion of the assembly. The saw frame 89 may be connected to the swing post 84 using pins positioned through a mounting hole 92 in the swing post. The connection between the saw frame 89 and the swing post 84 defines a second pivot axis 74 about which the trenching assembly 27 may be raised and lowered. The second actuator 78 is connected to the swing post 84 and the saw frame 89. The second actuator 78 is adapted to raise and lower the trenching assembly 27. As shown in FIG. 1, when the second actuator 78 comprising a hydraulic cylinder is retracted the trenching assembly 27 is pivoted downward. The hydraulic cylinder 78 may be pressurized to extend the cylinder to any one of a plurality of lengths to vary the cutting depth 94 of the trenching assembly 27. Additionally, when the second actuator 78 is fully extended the trenching assembly 27 may be pivoted upward to a stowed position so that it does not contact the ground. When the saw is in the lowered position, floating shoe 91 rides on the ground surface closing the variable space between the saw frame 89 and the ground surface. Additionally, trench cleaner 93 is lowered into the cut trench with a hydraulic cylinder (not shown) to follow behind the cutting wheel for scraping cuttings forward into the wheel to provide a resultant trench with minimal residual cuttings.

The saw frame 89 is adapted to support trenching assembly 27. Power supply 96 is attached to drive assembly 102 to drive operation of the trenching assembly 27 and may comprise a hydraulic motor.

The trenching assembly 27 may comprise a concave cutting disc 98, cutting members 100 and a drive assembly 102. The concave cutting disc 98, cutting ring 124 and cutting members 100 comprise the cutting depth 94. The cutting depth 94 corresponds to the maximum depth at which the trenching assembly 27 is operable to excavate the desired trench. The cutting depth 94 of the embodiment shown in FIG. 1 is preferably between twenty (20) and forty (40) inches, and more preferably at least thirty (30) inches. Further, the trenching assembly 27 comprises a cutting diameter 103 that is related to the diameter of the concave cutting disc 98, cutting ring 124 and cutting members 100. The cutting diameter 103 of the trenching assembly 27 of FIG. 1 is preferably between thirty-six (36) inches and fifty-six (56) inches and more preferably forty-six (46) inches. Thus, the construction of the trenching assembly 27 as described herein and illustrated in FIG. 1 provides a ratio of cutting depth 94 to cutting diameter 103 that is preferably between 0.5 and 0.8, and more preferably 0.65.

A spoils handler 104 is supported by the saw frame 89 so that it is disposed proximate and tangentially in line to the concave cutting disc 98. The spoils handler 104 may comprise an impeller 105 positioned above the concave cutting disc 98 and forward of its center point 106. The blades of the impeller 105 are contoured in a concave manner to correspond to the arcuate path of the cutting members 100. It will be appreciated that the spoils handler 104 may be configured so that it is contained within the lateral width of the saw frame 89. Operation of the impeller 105 may be driven by a hydraulic motor (not shown) capable of selectively rotating the impeller either clockwise or counter-clockwise. Rotation of the impeller causes discharge of the spoils carried upward by the concave cutting disc 98 perpendicular to the concave cutting disc 98 through a discharge opening 112 in the saw frame 89. The largest radial diameter tips of the blades of the impeller 105 protrude through the side plates of saw frame 89 and into the discharge opening 112. It will be appreciated that a second discharge opening (not shown) may be provided on the opposing plate of the saw frame 89. Additionally, a cover (not shown) may be placed over the discharge opening 112 to facilitate discharge of spoils to the desired side of the trenching assembly 27 through the selected discharge opening.

Turning now to FIG. 2, there is shown therein an isometric view of the trenching assembly 27 of the present invention showing the relationship of the concave cutting disc 98 to the drive assembly 102. FIG. 2 illustrates that the drive assembly 102 is disposed within the concave cutting disc 98 and may be driven by the power supply 96. As shown in FIG. 2, the power supply 96 may be bolted to a drive assembly cover 116 and positioned to drive rotation of the concave cutting disc 98. The drive assembly cover 116 is constructed to support bolts 121 that are used to connect the trenching assembly 27 to the saw frame 89 in a cantilevered manner.

The concave cutting disc 98 may be constructed from a single hardened steel plate that has been pressed to form an outer rim 122. A cutting ring 124 is connected to the concave cutting disc 98 so that it circumscribes the outer rim 122. The cutting ring 124 is also preferably constructed from hardened steel and may be welded to the outer rim 122. Welding of the cutting ring 124 with cutting members 100 to the outer rim 122 allows the drive assembly 102 to be positioned in close proximity to the outer rim of the concave cutting disc 98 to maximize cutting depth 94 for a given disc diameter. The cutting ring 124 supports a plurality of cutting members 100 that are circumferentially spaced about the periphery of the cutting ring 124. The cutting members 100 may comprise sockets 126 that are welded to the cutting ring 124. The sockets 126 may comprise an aperture 127 adapted to receive a correspondingly shanked bit 128.

Sockets 126 with correspondingly insertable bits 128 allow for replacement of worn or broken cutting members. The bit 128 may comprise a shanked body (not shown) that corresponds to the aperture 127 of the socket 126 and a cutting member 100 having a cutting element 130. The body of the bit 128 is generally constructed from a hardened alloy such as steel while the cutting element 130 is made with a carbide insert or cap. The cutting member 100 comprising the socket 126 and bit 128 defines a plane 132 that may be centered or uncentered relative to the direction of rotation of the cutting disc 98 and defines the cutting width 108.

The construction of the earth saw attachment 14 permits the trenching assembly 27 to operate at greater depths than previously attained by earth saws and tractors 12 of same or similar size and weight. Containment of the drive assembly 102 within the cutting width 108 (FIG. 3) of the trenching assembly 27 permits the trenching assembly to operate with the center point 106 of the concave cutting disc 98 below ground surface. The cutting width 108 of the present embodiment is comprised of the cutting disc 98 and the cutting members 100 and is preferably between 4.75 inches and 7 inches for an earth saw attachment 14 adapted to reach cutting depths 94 of between twenty (20) to forty (40) inches, and more preferably a depth of thirty (30) inches. Thus, the trenching assembly 27 of the present invention may have a cutting width 108 to cutting depth 94 ratio between 0.24 and 0.12, with a preferred ratio of 0.16.

The single plate concave cutting disc 98, cutting ring 124 and drive assembly 102 significantly reduce the overall weight of the earth saw attachment 14 related to the cutting depth 94. For example, the earth saw attachment 14 comprised of the support assembly 26, the trenching assembly 27 and saw frame 89 may preferably have a gross attachment weight of between 1400 pounds and 3000 pounds, and more preferably a weight of 2200 pounds. The cutting depth 94 of the trenching assembly 27 in FIG. 1 is preferably between twenty (20) inches and forty (40) inches. Thus, the ratio of cutting depth 94 of the trenching assembly 27 shown in FIGS. 1 and 2 to attachment weight may preferably be between 0.01 and 0.02 inches per pound with a preferred ratio of 0.014 inches per pound. The reduced attachment weight of the earth saw attachment 14 reduces the amount of counterweights 134 (FIG. 1) and makes the tractor 12 lighter and more maneuverable. Additionally, it will be appreciated that the ability to operate with the center point 106 below the surface permits the use of a disc having a smaller diameter than traditionally required to reach the same cutting depth and further reduces the gross weight of the earth saw attachment 14.

Turning now to FIG. 3 there is shown therein a cross-sectional view of the trenching assembly 27. As previously discussed, the trenching assembly 27 comprises the drive assembly 102, concave cutting disc 98, cutting ring 124 and cutting members 100. The drive assembly 102 is operable in response to movement of a rotatable drive shaft 118 driven by the power supply 96. The drive assembly 102 comprises the first gear 120, the second gear 136 and a rotatable hub 138. The first gear 120 may be splined for mating connection with a splined drive shaft 118. The second gear 136 is operably connected to the hub 138. The first gear 120, second gear 136, hub 138 and concave cutting disc 98 are adapted to rotate in response to rotation of the drive shaft 118. A torque transfer device such as a chain (not shown) may be used to transfer the rotational energy generated by the power supply 96 to the second gear 136 and concave cutting disc 98. In a preferred embodiment, the first gear 120 may comprise eleven teeth and the second gear 136 may comprise thirty-two teeth. The relative size of the first gear 120 to the second gear 136 allows for the use of a hydraulic motor 96 that is adapted to rotate the drive shaft 118 at a higher speed and of less weight than motors typically used in similar applications.

The second gear 136 is supported on the drive assembly 102 by a rotatable hub 138. The rotatable hub 138 is bearingly mounted to the drive assembly cover 116. The second gear 136 is welded to the rotatable hub 138. However, it will be appreciated that the hub 138 and second gear 136 may be integrally formed or assembled such as with a splined or bolted connection. The concave cutting disc 98 is connected to the hub 138 using bolts 140 so that the concave cutting disc is rotated with the second gear 136 and hub. The concave cutting disc 98 and hub 138 may be supported in a cantilevered manner by the drive assembly cover 116. A cover plate 142 on the concave cutting disc 98 reduces the intrusion of spoils into the drive assembly 102 and substantially protects the bolts 140 from wear. Bolting the concave cutting disc 98 to the hub 138 permits removal of the concave cutting disc without disturbing the integrity of the drive assembly 102. Thus, alternative cutting discs having a different cut width can be installed on to the earth saw attachment 14.

Various modifications can be made in the design and operation of the present invention without departing from the spirit thereof. Thus, while the principal preferred construction and modes of operation of the invention have been explained in what is now considered to represent its best embodiments, which have been illustrated and described, it should be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically illustrated and described.