US 20060096788 A1
A reamer assembly for widening a drilled pilot hole or for widening a hole that has been widened in a first step in a down-the-hole drilling operation, includes a shank (14) for attachment of the reamer to the end of a down-the-hole hammer drill and a conical drill bit or crown (15). The conical bit (15) of the reamer is divided into at least three segments (18) which are terminated with a transverse end surface (21) that directly connects the conical segments and at least three of the segments (18) include drill buttons (16) that are disposed equidistantly from the centre axis of the drill bit (15).
1. A reamer assembly (11) for widening a drilled pilot hole or for widening a hole that has been widened in a first step in a down-the-hole drilling operation, wherein the reamer assembly includes a shank (14) for attachment of the reamer to the end of a down-the-hole hammer drill and a conical drill bit or crown (15), characterised in that the conical bit (15) of the reamer is divided into at least three segments (18) which are terminated with a transverse end surface (21) which directly connects said conical segments; and in that at-least three of said-segments (18) include drill buttons (16) that are disposed equidistantly from the centre axis of the drill bit.
2. A reamer assembly according to
3. A reamer assembly according to
4. A reamer assembly according to
5. A reamer assembly according to
6. A reamer assembly according to
7. A reamer assembly according to
The present invention relates to a reamer drill assembly, i.e. a drill for widening a drilled pilot hole or for widening a hole that has been widened in a first step in a down-the-hole drilling operation.
Reamers, of this kind include a shank for attachment of the drill to the end of a down-the-hole hammer drill, a conical drill bit, and to a pilot body disposed on one end of the drill bit. The pilot body has a somewhat smaller outer diameter than that of the pre-drilled pilot hole, so as to enable the pilot body to slide down in the pre-drilled pilot hole and therewith guide the drill to follow the pilot hole.
One problem with such reamers is that if the drill bit, or crown, is slightly oblique and therewith causes the pilot body to contact the edge of the pilot hole, there is a risk that the shank will break or fracture, resulting in operational breakdowns and stoppages. Such breakages can also lead to other complications, for instance the need to fish up the drill bit lost down the drill hole.
Another problem is that larger drill cuttings may find it difficult to fall down in the pilot hole and therewith leave the drill location. Large cuttings that are able to fall down in the pilot hole despite their large size are liable to fasten in and block the hole, so as to present an obstacle to the pilot body, which lacks a cutter, and therewith halt drilling until the cuttings can be removed.
Another drawback with such reamers is that a reamer must be made available for each size of pilot hole, so that the pilot body will be able to pass down through the hole and therewith guide the reamer during the reaming process.
Accordingly, one object of the present invention is to provide a novel reamer assembly which allows all of these problems and drawbacks to be avoided.
This object is achieved in that the conical configuration of the drill bit of the reamer is divided into at least three segments which are terminated with a transverse end surface which directly connects said conical segments, and in that a drill button is provided in at least three of said segments with said buttons disposed equidistantly from the centre axis of the drill bit.
The invention will now be described in more detail by way of example only, with reference to the accompanying drawings, in which
Arranged on the end of the bit or crown 5 distal from the shank 4 is a generally cylindrical pilot body 7 which projects slightly outwards from the conical drill bit 5. The pilot body 7 has an outer diameter that is slightly smaller than the inner diameter of the pilot hole 3, therewith enabling the pilot body to guide the reamer 1 so that said drill will cut away or otherwise remove rock 2 symmetrically around the centre of the pilot hole and so that the widened hole will follow the earlier drilled pilot hole 3.
According to the present invention, the conical surface of the drill bit 15 of the reamer 11 is divided into a plurality of segments 18 each containing a plurality of drill buttons 16. These buttons 16 have mutually the same positions in respective segments 18, in other words each segment contains buttons that are situated at mutually the same distance from the centre axis of the drill bit/reamer as the buttons in other segments. Thus, the button 16 a in the segment 18 is the same distance from the centre axis of the reamer as the button 16 a′ in the segment 18′; see
By placing the buttons 16 in the drill bit 15 in this way, the buttons are themselves able to guide the reamer 11 when drilling in rock 12, so as to cause the drilled hole to follow the pilot hole 13.
The various buttons 16 of each segment 18 are positioned so as to lie at different radial distances from the axial centre of the drill bit, so that at least one button of each segment will be able to guide the reamer towards the edge of the pilot hole. As will be seen from the common plane projection shown in
With the aid of different vertical chain lines 19 a, 19 b and 19 c,
Those buttons that are furthest in towards the centre of the drill bit on its conical segments, i.e. the buttons 16 a, are those which determine the smallest size of the pilot hole with which the reamer can be used. For example, it has been possible with the aid of the present invention to widen a pilot hole with a diameter of from about 150 mm to about 205 mm with one and the same reamer.
The buttons 16 are preferably placed in mutually the same pattern in each of the segments. Moreover, several buttons may be placed equidistantly from the centre of the drill bit in one and the same segment. See in particular
The drill bit 15 must include at least three segments 18, in order to achieve correct guidance of the reamer 11. There are four segments in the case of the illustrated embodiment, although this number may be greater depending on the size of the drill 11.
The segments 18 are joined together at the end of the drill bit 15, by a planar or slightly concave transverse end surface 21. Drill buttons 22 are also provided in the transverse end surface 21 of the drill bit. The function of these latter buttons is not to cut away rock, but to grind down any cuttings that may have fallen down and fastened in the pilot hole. When drilling a blind hole, these buttons 22 will also support against the bottom of the hole so as to prevent material damage to the drill bit 15.
Thus, an inventive reamer assembly enables one and the same reamer to be used with pre-drilled pilot holes of mutually different sizes, although within certain limits of course, as distinct from the earlier case where it was necessary to use different reamers adapted to the size of respective pilot holes.
Because an inventive reamer lacks a pilot body, there is less risk of the drill being subjected to bending loads that result in breaking of the drill shank.
The design of the inventive reamer also lowers the risk of the drill being stopped by cuttings that remain in the pilot hole, by virtue of the fact that the buttons 22 situated on the end 21 of the drill bit 15 are able to grind away said cuttings. Drill cuttings can move past the drill bit and fall down through the pilot hole more easily than was previously the case, due to the absence of an obstructive pilot body.
The inventive reamer is also better than prior art reamers when reaming blind holes, since the risk of material damage to the drill bit is considerably less than in the case of prior art reamers that include a pilot body. Another advantage afforded by the invention is that a drill bit that does not include a pilot body is lighter than one that does.
As will be apparent from the above description, the inventive reamer may be divided into more than three segments, wherein buttons in at least three segments are placed at mutually the same distance from the axial centre of the drill bit, as defined in the accompanying claims, so as to obtain the necessary stability in guiding the drill bit. The buttons in remaining segments may conveniently be positioned differently.