Boring or penetrating the earth – Bit or bit element – Bit with leading portion forming smaller diameter initial bore
Reexamination Certificate
1999-03-23
2001-03-20
Schoeppel, Roger (Department: 3672)
Boring or penetrating the earth
Bit or bit element
Bit with leading portion forming smaller diameter initial bore
C175S385000, C175S389000, C175S392000, C175S397000, C175S399000, C175S406000, C175S407000, C175S414000, C175S415000
Reexamination Certificate
active
06202768
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a rock drilling tool for percussive drilling, said rock drilling tool comprising a pilot bit having a first thread at one end, a rod for percussive drilling which at one end is provided with a second thread intended to cooperate with said first thread, and a reamer disposed around the pilot bit. The reamer is, at one axial end, provided with rock cutting means. The invention further relates to a reamer for percussive drilling.
PRIOR ART
To achieve reamed cut holes there are previously known rock drilling tools of the above-described type, such as that described in Kleine U.S. Pat. No. 4,275,796, wherein the drill bit has a pilot bit intended to guide the rock drilling tool in the preferably predrilled pilot hole. In some embodiments of a rock drilling tool of the known type, the pilot bit can be provided with a rock cutting means, for example in the form of a chisel. The pilot bit has a male thread, which is connected to a female thread of a rod for percussive drilling. A reamer is disposed around the pilot bit and connected with the same by means of a thread or a conical connection. Known rock drilling tools of this type have the drawback of frequently breaking in the threaded connection between the pilot bit and the rod, more exactly in the area of the shoulder abutment of the threaded joint. The reason therefor is that the relatively great radial dimension of the reamer mounted on the pilot bit causes large bending stresses in said threaded joint, which results in the above-mentioned breakage in the threaded connection.
OBJECTS AND SUMMARY OF THE INVENTION
A primary object of the present invention is to provide a rock drilling tool of the above-described type, which is more rigid and consequently has a better ability to handle the bending loads during tool performance, where said bending stresses are not transferred, in any great extent, to the threaded connection between the pilot bit and the rod for percussive drilling.
Another object of the present invention is to design the reamer in such a manner that the risk for entrance of drill cuttings into the threaded connection between the pilot bit and rod for percussive drilling is diminished.
The objects of the invention are realized by a drilling tool comprising a drill rod, a pilot bit, and a reamer. The drill rod includes a front portion having an outer cylindrical surface of uniform diameter. The pilot bit is threadedly mounted at a front end of the drill rod by a screw thread connection and projects longitudinally forwardly beyond the drill rod. The reamer surrounds the pilot bit and includes rock cutting structure at a forward end of the reamer. The reamer includes a rearwardly extending stiffening sleeve which extends along the uniform-diameter front portion of the outer surface of the drill rod for a portion of the drill thread connection.
The invention also pertains to a reamer adapted for use on a percussion rock drilling tool. The reamer comprises a body having a front end carrying a rock cutting structure. The body includes a central opening having a front portion for engaging a pilot bit, and a rear stiffening portion for engaging a drill rod. A smallest diameter of the central opening in the rear stiffening portion is larger than a smallest diameter of the front portion of the central opening.
REFERENCES:
patent: 1515819 (1924-11-01), Zublin
patent: 4275796 (1981-06-01), Kleine
patent: 4408669 (1983-10-01), Wiredal
patent: 4545443 (1985-10-01), Wiredal
Liljebrand Per-Olof
Lindgren Daniel
Lindström Håkan
Burns Doane Swecker & Mathis L.L.P.
Sandvik AB
Schoeppel Roger
LandOfFree
Rock drilling tool and reamer for percussive drilling does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Rock drilling tool and reamer for percussive drilling, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rock drilling tool and reamer for percussive drilling will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2506401