Boring or penetrating the earth – Processes
Patent
1997-08-12
1999-09-28
Tsay, Frank
Boring or penetrating the earth
Processes
175259, 175266, E21B 700, E21B 1064
Patent
active
059572248
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to a method for drilling a hole in the soil and to a bit assembly and a drill bit for use in drilling a hole or tunnel in the soil.
BACKGROUND OF THE INVENTION
Previously known are, for instance from patent specifications FI 933074 and GB 2 255 365, double bit assemblies where the inner bit that drills the center hole can be pulled out from the hole, while the ring bit that drills the outer hole circle is left in the bore. However, in these examples the inner bit can be pulled out from the hole after drilling and also reinstalled if drilling is continued.
On drilling a hole in the soil, the most general case is that the first portion of the hole is made in soft soil, whereby a protection tube is pulled into the drilled hole. Eventually, on hitting rock, the protection tube is not needed anymore. Drilling can then be continued without a protection tube if change of the drilling procedure is easy. A problem arises when the drilling procedure is changed. The inner bit must be pulled out from the hole and replaced by a bit that drills a hole with a smaller diameter. During this replacement, the complete drilling equipment is pulled out from the hole and reinstalled furnished with a new rock-drilling bit. This takes time and money, especially if the first bore in the soil is long.
SUMMARY OF THE INVENTION
By means of a method and bit assembly with a proper bit according to this invention, a surprising improvement is achieved.
The advantage of this invention is that a hole requiring a protection tube is drilled with the same bit assembly as a hole into rock. When the protection tube is not needed, drilling proceeds nonstop with the inner bit only. In case drilling is stopped in a dead end, the inner bit can be pulled out through the outer bit. Even the outer bit can be pulled out from the bore on condition that also the protection tube is also pulled out simultaneously.
The bit assembly and the method can be applied to drilling by hammering but also to bits rotating only. The groove in the bayonet joint that opens in both of the axial directions is favorably arranged as a flow channel for flushing medium, whereas the joint is a simple construction.
BRIEF DESCRIPTION OF THE DRAWINGS
In the following the invention is disclosed with reference to the enclosed drawing, where
FIG. 1 shows a section of the bit assembly along line A--A.
FIG. 2 shows the bit assembly viewed from the front.
FIG. 3 shows the inner bit surface viewed from one side.
FIG. 4 shows a section of bore, where drilling proceeds by the inner bit only.
FIG. 5 shows a cross-section of the ring bit.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
FIG. 1 illustrates a section of the bit assembly including a cylindric inner bit 1 fastened to the head of hammer 7, a ring-shaped outer bit 2 around the inner bit 1 and a protection tube 4 mounted in the hole while drilling and reaching the outer shell of outer bit 2. The inner bit 1 and outer bit 2 are interconnected by a bayonet joint, where rotation is transmitted to the outer bit 2 by the inner bit 1. The inner bit 1 also transmits the hammer impacts to outer bit 2. Outer bit 2 pulls protection tube 4 into the hole by means of the joint lap between them, which has restriction for the mutual axial motion.
FIG. 2 shows that in the circle between bits 1 and 2 three bayonet joints are placed. In the inner bit 1 three axial grooves 6 are formed to run through the bit. Correspondingly, there are in outer bit 2 three projecting parts 3 with the same spacing which move in grooves 6. Sidewards from grooves 6 in inner bit 1 surface, as per FIG. 3, there are notches for projecting parts 3, into which the projecting parts 3 are guided due to the mutual rotation of the bits 1 and 2. Thereby, bits 1 and 2 are in a locked state and bit 2 is rotated by bit 1, while the locking is retained. The locking is opened by reverse rotation. Projecting parts 3 are square in order to receive the impacts from a larger surface area of the inner bit 1 and to transmit them to
REFERENCES:
patent: 3190378 (1965-06-01), Davey, Sr. et al.
patent: 3375884 (1968-04-01), Bodine, Jr.
patent: 3835943 (1974-09-01), Bray
patent: 4759413 (1988-07-01), Bailey et al.
patent: 4842081 (1989-06-01), Parant
patent: 5417290 (1995-05-01), Barrow
patent: 5472057 (1995-12-01), Winfree
patent: 5791419 (1998-08-01), Valisalo
"New method of soil and overburden drilling", Mining Magazine, vol. 168, No. 10, Oct. 1993, pp. 218-219.
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