ROTARY RAPID EXCAVATION SYSTEM
BACKGROUND OF THE INVENTION
1. Field of the Invention 5 This invention relates generally to methods and apparatus for earth excavation with drills and augers, and more particularly to a method and apparatus for rapid earth excavation utilizing drills and augers having soft 1Q cutting edges and/or control of the torque and weight of the boring apparatus to prevent damage to buried pipe, cable, and other underground objects.
2. Brief Description of the Prior Art
A considerable portion of the operating budget of u gas, electric, and telecommunications industries is spent to maintain and repair the efficiency and safety of the buried distribution system connecting supplies to the end user. It is estimated that the U.S. gas distribution industry alone must maintain an estimated 866,000 miles 20 of distribution mains and 563,000 miles of services with the network expanding at a rate of 9,000 miles a year. The installation, repair, and maintenance of these mains and services is costly, requiring a significant amount of manpower and equipment. It is estimated that the gas 25 industry alone will dedicate over 450 million dollars in 1988 to repair leaks, replace aging lines, and to install corrosion protection.
Several methods are presently used to expose buried pipe, cables, and other utilities for repair and mainte- 30 nance. Most common among these methods are backhoes and hand digging Backhoes offer the advantage of high speed and minimal setup time but can cause serious damage to utilities contacted by the bucket while it is digging. The size of the excavation produced by the ^5 backhoe is often substantially larger than necessary, which increases the cost of restoration. Records filed with the Department of Transportation show that 60% of gas pipe incidents which occurred between 1974 and 1984 were caused by large excavation equipment.
Conversely, hand digging is effective in minimizing damage to buried utility lines, but is slow and highly labor intensive. Vacuum and soft excavators employing vacuum for spoil removal are limited in the range of 45 soils in which they are effective and the speed at which the lines are uncovered.
There are several patents which disclose various methods and apparatus for controlling the torque of the drilling or boring apparatus. 50
Bricken, U.S. Pat. No. 1,776,779 discloses a well drilling and pumping apparatus with torque control.
Hawk, U.S. Pat. No. 1,904,765 discloses a method of torque control and automatic drill control.
Vanderzee, U.S. Pat. No. 2,594,098 discloses a porta- 55 ble, truck-mounted drilling rig with torque control.
Pokorny, U.S. Pat. No. 2,734,722 discloses a post hole driller with hydraulic controls but no flexible cutting surface or auger.
Goodrich, U.S. Pat. No. 2,981,403 discloses an auger 60 with flexible flights but does not teach using soft flexible materials in the cutting surface.
Rumpp, U.S. Pat. No. 4,458,769 discloses a rock drill having a helical surface for removing cuttings but does not teach using soft flexible materials in the cutting 65 surface or on the flights of an auger.
Warren et al, U.S. Pat. No. 4,660,656 discloses a method and apparatus for controlling torque and a ro
tary earth drilling bit but does not teach using soft flexible materials in the cutting surface.
Muller, U.S. Pat. No. 4,699,226 discloses an interchangeable conveying spiral which can be removable mounted on a drill shaft for removing rock cuttings out does not teach using soft flexible materials in the cutting surface or on the flights of an auger.
Snyder, U.S. Pat. No. 2,714,500 discloses an impact drill with flexible blades which are used only for a wiping action on the side wall of the hole being drilled. There is no suggestion of using soft flexible materials in the cutting surfaces.
The present invention is distinguished over the prior art in general, and these patents in particular by a rapid earth excavation method and apparatus utilizing drills and augers having soft polymeric material on the cutting edges, control of the torque and weight of the boring apparatus, or an indicator mounted forward of and below the leading cutting surface of the auger to prevent damage to buried pipe, cable, and other underground objects.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide an inexpensive, reliable excavation system for boring holes in soils to access and repair utility systems which combines high boring speed with low damage potential.
It is another object of this invention to provide an excavation system for boring holes in soils which will not damage buried pipe, cable, or other utility lines when contacted during the boring operation.
Another object of this invention is to provide earth drilling apparatus having soft, yieldable polymeric materials on the cutting surfaces to prevent damage to buried pipe, cable, or other utility lines when contacted during drilling operations.
Another object of this invention is to provide earth drilling apparatus having smooth rounded edges appropriately treated to prevent abrasion of buried pipe, cable, or other utility lines when contacted during drilling operations.
Another object of this invention is to provide an earth drilling system wherein the drilling forces and weight of the drilling apparatus is accurately controlled to provide both a full power and torque mode and a weight-limited non-damaging mode of operation.
Another object of this invention is to provide an earth drilling system which provides a positive indication to the operator that a pipe or other buried article substantially different from the native soil has been hit.
Another object of this invention is to provide an earth drilling system which will automatically stop the drilling operation upon contact with a buried pipe or other buried article substantially different from the native soil.
A further object of this invention is to provide an earth drilling system utilizing concentric augers each capable of providing and maintaining a torque adequate to create a given hole diameter but sufficiently below that which would damage typical gas, electric, and telecommunications piping and cables.
A still further object of this invention is to provide an earth drilling system which will aid in preventing damage to buried utilities which is simple in construction, economical to manufacture, and rugged and durable in use.