DRILLING TOOL
The invention relates to a drilling tool for drilling soft and fragmented rock. The drilling tool disclosed in the invention comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at its end, a converging part through which conduits pass for rinsing medium.
The invention relates to a drilling tool for drilling soft and fragmented rock.
Presently, when soft and fragmented rock is drilled, typically either a grooved guide tube or a separate protective tube is used, which is either left in the hole or withdrawn from the hole after the drilling. The intention is to prevent the material surrounding the hole from caving in to enable the withdrawal of the drill bit from the hole as the last action.
A prior art drawback is that when a grooved guide tube is used, the grooved portions of the tube may break the wall of the hole, which makes the hole cave in regardless of the intention to the contrary. Furthermore, if a separate protective tube is used, extra equipment is required for installing and disassembling the protective tubes.
BRIEF DESCRIPTION OF THE INVENTIONThe object of the present invention is to provide a drilling tool for preventing better than previously the caving in of the hole walls when fragmented or soft material is being drilled.
The drilling tool of the invention is characterized in that it comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at least at the end intended to be positioned towards the rock drill, a part converging towards the axis of the drill rod, and that it comprises, for rinsing medium, through-going conduits that terminate in said converging part.
It is an essential idea of the invention that the drilling tool is a part that has a smooth outer surface, is positioned symmetrically relative to the middle axis of the drill rod and comprises converging ends in such a manner that during the rotation of the drill rod it penetrates through the material that tends to cave in and simultaneously compresses and grinds the material tightly against the wall of the drill hole.
The tool of the invention is further characterized in that it comprises through-going longitudinal conduits, through which the rinsing medium is allowed to flow away from the drill hole.
An advantage of the invention is that during the drilling of soft or fragmented material, the drill hole can be kept open, as the tool compresses the detaching material tightly into the wall of the drill hole.
A further advantage of the invention is that since the flow of rinsing medium is arranged through the drilling tool, and not along the grooves on its outer surface, the flow of rinsing medium does not corrode or detach material from the wall of the drill hole very easily, and thus does not cause cave-ins very easily in a ready-made hole.
A still further advantage of the invention is that if for some reason the drill hole caves in, it can be opened quite easily by means of the drilling tool.
The invention will be described in more detail in the attached drawings, wherein
In the figures, some embodiments of the invention are shown in a simplified manner for the sake of clarity. In the figures, like parts are denoted with the same reference numerals.
DETAILED DESCRIPTION OF SOME EMBODIMENTS OF THE INVENTIONIn the above description and in the drawings, the invention is only described by way of example and in no way restricted thereto. In some cases, the characteristics disclosed in the present application may be utilized as such, irrespective of other characteristics. On the other hand, when desired, the characteristics disclosed in the present application may be combined for generating different combinations. The drilling tool may be fastened onto the drill rod in a plurality of manners known per se. For example, the drilling tool may be pushed onto the drill rod and then welded thereto at its ends, followed by finishing of the surface suitably smooth. Alternatively, the drilling tool, preferably comprising only a short drill rod, may be directly machined as a solid entity, for example. Other manners of manufacture and fastening are also usable.
The drawings and the related description are only intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.
Claims
1. A drilling tool for drilling soft and fragmented rock, which tool comprises a portion having a round cross section and a smooth surface and positioned substantially symmetrically relative to the middle axis of a drill rod and comprising, at least at the end intended to be positioned towards the rock drill, a part converging towards the axis of the drill rod, and that the tool comprises, for rinsing medium, through-going conduits that terminate in said converging part, wherein the largest outer diameter of the tool is dimensioned smaller than the outer diameter of the drill bit intended to be used therewith.
2. A drilling tool as claimed in claim 1, wherein the drilling tool is a part separate from the drill bit and both of its ends are provided with a part that converges towards the axis of the drill rod and that the conduits for the rinsing medium lead from the converging part to an opposite, converging part.
3. A drilling tool as claimed in claim 2, wherein the middle part of the drilling tool is substantially cylindrical and that one end of the drill rod is provided with an external thread, the other being provided similarly with an internal thread for connecting the drill bit and the drill rods, respectively, thereto.
4. A drilling tool as claimed in claim 2, wherein the drilling tool is installed at the end on the side of the external thread of the drill rod of a normal length.
5. A drilling tool as claimed in claim 1, wherein the drilling tool is a part integrated into the drill bit.
Type: Application
Filed: Jan 30, 2008
Publication Date: Jan 7, 2010
Inventors: Aulis Kataja (Tampere), Jorma Kalliomäki (Tampere), Ioannis Bournazos (Kadandriti)
Application Number: 12/525,189
International Classification: E21B 17/00 (20060101); E21B 21/12 (20060101); E21B 17/18 (20060101);