Boring or penetrating the earth – Below-ground impact members – With releasable means to detachably retain telescoping...
Reexamination Certificate
1999-06-07
2001-02-06
Bagnell, David (Department: 3671)
Boring or penetrating the earth
Below-ground impact members
With releasable means to detachably retain telescoping...
C175S320000, C175S414000
Reexamination Certificate
active
06182776
ABSTRACT:
TECHNICAL BACKGROUND
The present invention relates to a drilling equipment, a driver sub and a drill bit for overburden drilling operations.
PRIOR ART
Overburden drilling equipment is previously disclosed, for example, in llomäki U.S. Pat. No. 5,255,960 issued Oct. 26, 1993. It has been found favorable to construct overburden drilling equipment such that the casing and the rock drill bit are relatively rotatable while simultaneously axially connected, so that the drill bit pulls the casing along as the drill bit advances in the ground. The solution to such relative rotation is described in the abovenamed patent as a “lap-joint”, wherein the casing, or a casing shoe attached to the front of the casing, axially overlaps the drill bit. A split collar welded to the inside of the casing projects into a circumferential groove formed in the drill bit, enabling the drill bit to pull the casing along. Often, it is desirable for the casing to be left in the hole, but that is not possible with the known device.
It is furthermore known through for instance Jarvela U.S. Pat. No. 5,590,726 to leave the casing in the hole by unlatching a pilot drill bit from a ring bit of the casing and to retract the pilot bit and the hammer. However, in deep hole drilling the ring bit tends to wear out prematurely, i.e., the ring bit wears out before-the desired depth is reached. Thus the entire casing has to be retracted to change the ring bit for resuming the drilling operation.
OBJECTS OF THE INVENTION
One object of the present invention is to provide a down-the-hole hammer and a drill bit which include the advantages of prior art while obviating the above-mentioned drawbacks.
Specifically one object of the present invention is to provide efficient drilling equipment able to drill deeply into rock while casing the hole.
Another object of the present invention is to provide a drill bit for a down-the-hole hammer which provides for long drilling lengths.
Still another object of the present invention is to provide efficient drilling equipment, wherein the hammer is releaseably connected to a non-retractable one-piece road embankment drill bit.
SUMMARY OF THE INVENTION
One aspect of the present invention relates to an overburden drilling equipment for drilling a hole. The equipment comprises a cylindrical casing defining a longitudinal axis and having a diametrically reduced structure forming at least one longitudinally extending keyway. A drill bit is disposed in the casing and includes a cutting face located at a longitudinal front end thereof, and an anvil portion located at a longitudinal rear portion thereof. A generally cylindrical casing shoe is attached to the casing and mounted to the drill bit for longitudinal movement therewith. The drill bit is rotatable relative to the shoe. A down-the-hole hammer is disposed in the casing. The hammer includes a cylinder, and a piston reciprocable in the cylinder due to hydraulic fluid being directed alternately to upper and lower ends of the piston to effect its reciprocation in the cylinder. Each downward stroke inflicts an impact blow upon the anvil portion of the drill bit which extends upwardly within the lower portion of the cylinder. The cylinder is rotatable relative to the casing. A drill chuck is mounted at a lower end of the cylinder and receives an upper portion of the drill bit. The drill chuck includes at least one key defining a largest radius of the drill chuck and sized to pass longitudinally through the at least one keyway. The hammer and the drill chuck are separable from an assembly comprised of the casing, the casing shoe and the drill bit by rotating the cylinder to align the at least one key with the at least one keyway and raising the hammer.
Another aspect of the invention relates to a percussive drill bit adapted to be connected to a down-the-hole hammer. The drill bit is generally symmetrical about a rotational axis thereof and comprises a drill body having a shank and a head and a fluid passage formed therein for conducting flushing fluid to a front drilling face of the head. Button inserts are located in the front drilling face. The shank includes external projections for receiving rotational driving movement, and an anvil located at a free end of the shank for receiving axial impacts applied against the drill bit. Between the anvil and the projections, the shank forms an intermediate surface which is free from any recesses and retainers.
Yet another aspect of the invention relates to a driver sub which is adapted for transmitting rotary forces in a down-the-hole hammer. The driver sub comprises a cylindrical body having a central through-bore extending completely therethrough coaxially with respect to a longitudinal center axis of the body. A screw thread structure is formed along a portion of an outer peripheral surface of the body. The through-bore has a plurality of circumferentially spaced, axially extending projections. The body has a flange at a lower portion thereof. The flange carries at least one key which extends radially inwardly.
REFERENCES:
patent: 1033187 (1912-07-01), Metzger
patent: 2862738 (1958-12-01), Bayley
patent: 3612191 (1971-10-01), Martini
patent: 4632195 (1986-12-01), Emmerich
patent: 4919221 (1990-04-01), Pascale
patent: 5107944 (1992-04-01), Gustafsson
patent: 5131476 (1992-07-01), Harrington
patent: 5255960 (1993-10-01), Ilomäki
patent: 5261758 (1993-11-01), Vranish
patent: 5590726 (1997-01-01), Jarvela et al.
patent: 5803187 (1998-09-01), Javins
patent: 6035953 (2000-03-01), Rear
patent: 3731630 (1989-03-01), None
patent: 96703 (1989-03-01), None
Bagnell David
Burns Doane Swecker & Mathis L.L.P.
Mammen Nathan
Sandvik AB
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