Claims
- 1. A method for digging a trench in a hard earth formation, comprising the steps of:
positioning a multiple-chain trenching head assembly in the earth formation at a desired trench depth below a ground surface, the trenching head assembly comprising
a frame having a proximal end adapted for operably connecting to a prime mover positioned on the ground surface and thereby enabling positioning of the trenching head within the trench below the ground surface, a set of primary sprockets, the set comprising at least one proximal primary sprocket rotatably mounted on the frame and at least one distal primary sprocket rotatably mounted on the frame at a distal end thereof, at least one of the frame and the set of primary sprockets defining a primary chain path, a primary chain engaged with and circulating around the set of primary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation, a set of secondary sprockets, the set comprising at least one proximal secondary sprocket rotatably mounted on the frame and at least one distal secondary sprocket rotatably mounted on the frame at the distal end thereof, at least one of the frame and the set of secondary sprockets defining a secondary chain path, and a secondary chain engaged with and circulating around the set of secondary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation; driving the primary chain at a primary chain linear drive speed in a forward chain direction along the primary chain path, thereby disintegrating material at a leading edge of the trench and conveying disintegrated material upward and out of the trench; driving the secondary chain at a secondary chain linear drive speed along the secondary chain path, thereby disintegrating material from the leading edge of the trench; and moving the trenching head assembly in a forward trench-digging direction, at least one of the frame, the set of primary sprockets, and the set of secondary sprockets being adapted so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path, so that disintegration of material by the secondary chain produces a relief slot in the leading edge of the trench.
- 2. The method of claim 1, the secondary chain being no wider than about the width of the primary chain.
- 3. The method of claim 1, the secondary chain being narrower than the width of the primary chain.
- 4. The method of claim 1, an axis of the distal secondary sprocket being offset from an axis of the distal primary sprocket so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path.
- 5. The method of claim 1, an axis of the proximal secondary sprocket being offset from an axis of the proximal primary sprocket and an axis of the distal secondary sprocket being offset from an axis of the distal primary sprocket so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path.
- 6. The method of claim 1, the frame defining at least a portion of the secondary chain path extending farther toward the leading edge of the trench than the primary chain path.
- 7. The method of claim 1, the trenching head assembly further including multiple distal secondary sprockets rotatably mounted near the distal end of the frame for defining a portion of the secondary chain path.
- 8. The method of claim 1, the secondary chain being driven in a reverse chain direction around the secondary chain path, thereby conveying disintegrated material downward and depositing the disintegrated material within the trench.
- 9. The method of claim 8, further including the steps of:
positioning a crumbing shoe in the trench behind the trenching head assembly at a predetermined depth below the ground surface; moving the crumbing shoe in the forward trench-digging direction behind the trenching head assembly, the crumbing shoe being adapted for pushing disintegrated material that projects above a desired support bed surface forward toward the trenching head assembly, the crumbing shoe being adapted for leaving disintegrated material that lies below the desired support bed surface in the trench to form a support bed.
- 10. The method of claim 9, further including the steps of:
positioning a screen in the trench between the trenching head assembly and the crumbing shoe; moving the screen in the forward trench-digging direction behind the trenching head assembly and ahead of the crumbing shoe, the screen being adapted for pushing disintegrated material fragments above a desired mesh size forward toward the trenching head assembly, the screen being adapted for leaving disintegrated material fragments below the desired mesh size in the trench to form a support bed.
- 11. The method of claim 1, at least one of the frame, the distal primary sprocket, and the distal secondary sprocket being adapted so as to define distal portions of the primary and secondary chain paths substantially tangent to a common substantially horizontal plane, so that disintegration of material by the primary and secondary chains yields a substantially flat bottom surface of the trench.
- 12. The method of claim 1, further including the step of moving the secondary chain path relative to the primary chain path while driving the primary and secondary chains, thereby varying the depth of the relief slot in the leading edge of the trench, the trenching head assembly being adapted for actuating movement of the secondary chain path relative to the secondary chain path.
- 13. The method of claim 1, further including the steps of:
re-tensioning the primary chain while driving the primary chain; an re-tensioning the secondary chain while driving the secondary chain, re-tensioning of the primary and secondary chains being independent of one another.
- 14. A method for digging a trench in a hard earth formation, comprising the steps of:
digging a relief slot along a trench path using a slot-cutting trenching head assembly; and after digging the relief slot, digging the trench along the trench path using a trench-cutting trenching head assembly, the trench-cutting trenching head assembly being substantially wider than the slot-cutting trenching head assembly, the trench thereby encompassing the relief slot.
- 15. The method of claim 14, further including the step of digging multiple relief slots along the trench path using a slot-cutting trenching head assembly, the multiple relief slots being dug prior to digging the trench using the trench-cutting trenching head assembly.
- 16. A trenching head assembly for digging a trench in a hard earth formation, comprising:
a frame having a proximal end adapted for operably connecting to a prime mover positioned on the ground surface and thereby enabling positioning of the trenching head within the trench below the ground surface; a set of primary sprockets, the set comprising at least one proximal primary sprocket rotatably mounted on the frame and at least one distal primary sprocket rotatably mounted on the frame at a distal end thereof, at least one of the frame and the set of primary sprockets defining a primary chain path; a primary chain engaged with and circulating around the set of primary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation; a set of secondary sprockets, the set comprising at least one proximal secondary sprocket rotatably mounted on the frame and at least one distal secondary sprocket rotatably mounted on the frame at the distal end thereof, at least one of the frame and the pair of secondary sprockets defining a secondary chain path; and a secondary chain engaged with and circulating around the pair of secondary sprockets and comprising a plurality of pivotably connected links and a plurality of cutting tools substantially rigidly mounted thereon for disintegrating the earth formation, the primary chain being driven at a primary chain linear drive speed in a forward chain direction along the primary chain path, the primary chain being adapted for disintegrating material at a leading edge of the trench and conveying disintegrated material upward and out of the trench, the secondary chain being driven at a secondary chain linear drive speed along the secondary chain path, the secondary chain being adapted for disintegrating material at the leading edge of the trench, at least one of the frame, the set of primary sprockets, and the set of secondary sprockets being adapted so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path, so that disintegration of material by the secondary chain produces a relief cut in the leading edge of the trench.
- 17. The trenching head assembly of claim 16, the secondary chain being no wider than about the width of the primary chain.
- 18. The trenching head assembly of claim 16, the secondary chain being narrower than the width of the primary chain.
- 19. The trenching head assembly of claim 16, an axis of the distal secondary sprocket being offset from an axis of the distal primary sprocket so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path.
- 20. The trenching head assembly of claim 16, an axis of the proximal secondary sprocket being offset from an axis of the proximal primary sprocket and an axis of the distal secondary sprocket being offset from an axis of the distal primary sprocket so that at least a portion of the secondary chain path extends farther toward the leading edge of the trench than the primary chain path.
- 21. The trenching head assembly of claim 16, the frame defining at least a portion of the secondary chain path extending farther toward the leading edge of the trench than the primary chain path.
- 22. The trenching head assembly of claim 16, the trenching head assembly further including multiple distal secondary sprockets rotatably mounted near the distal end of the frame for defining a portion of the secondary chain path.
- 23. The trenching head assembly of claim 16, the secondary chain being driven in a reverse chain direction around the secondary chain path, thereby conveying disintegrated material downward and depositing the disintegrated material within the trench.
- 24. The trenching head assembly of claim 23, further including:
a crumbing shoe positioned behind the trenching head assembly at a pre-determined depth below the ground surface and adapted for moving in the forward trench-digging direction behind the trenching head assembly, the crumbing shoe being adapted for pushing disintegrated material that projects above a desired support bed surface forward toward the trenching head assembly, the crumbing shoe being adapted for leaving disintegrated material that lies below the desired support bed surface in the trench to form a support bed.
- 25. The trenching head assembly of claim 24, further including:
a screen positioned between the trenching head assembly and the crumbing shoe and adapted for moving in the forward trench-digging direction behind the trenching head assembly and ahead of the crumbing shoe, the screen being adapted for pushing disintegrated material fragments above a desired mesh size forward toward the trenching head assembly, the screen being adapted for leaving disintegrated material fragments below the desired mesh size in the trench to form a support bed.
- 26. The trenching head assembly of claim 16, at least one of the frame, the distal primary sprocket, and the distal secondary sprocket being adapted so as to define distal portions of the primary and secondary chain paths substantially tangent to a common substantially horizontal plane, so that disintegration of material by the primary and secondary chains yields a substantially flat bottom surface of the trench.
- 27. The trenching head assembly of claim 16, further including an actuator for moving the secondary chain path relative to the primary chain path while driving the primary and secondary chains, thereby varying the depth of the relief slot in the leading edge of the trench.
- 28. The trenching head assembly of claim 16, further including:
a primary re-tensioning mechanism adapted for re-tensioning the primary chain while the primary chain is being driven; and a secondary re-tensioning mechanism adapted for re-tensioning the secondary chain while the secondary chain is being driven, the primary and secondary re-tensioning mechanisms being independent of one another.
RELATED APPLICATIONS
[0001] This application is a continuation-in-part of prior-filed co-pending non-provisional App. No. 09/502,402, filed Feb. 10, 2000, which in turn claimed benefit of prior-filed provisional App. No. 60/119,699 filed Feb. 11, 1999. Non-provisional App. No. 09/502,402 and provisional App. No. 60/119,699 are each hereby incorporated by reference as if fully set forth herein.
Provisional Applications (1)
|
Number |
Date |
Country |
|
60119699 |
Feb 1999 |
US |
Continuation in Parts (1)
|
Number |
Date |
Country |
Parent |
09502402 |
Feb 2000 |
US |
Child |
10102065 |
Mar 2002 |
US |