A REAMER ASSEMBLY

ENSEMBLE DE TREPAN ALESEUR

English Abstract

The present invention relates to 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, 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). 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 said conical segments and
at least three of said segments (18) include drill buttons (16) that are
disposed equidistantly from the centre axis of the drill bit (15).

French Abstract

L'invention concerne un ensemble de trépan aléseur permettant d'élargir un avant-trou foré ou un trou ayant été élargi au cours d'une première étape dans une opération de forage au fond d'un puits, l'ensemble de trépan aléseur comprenant une tige (14) permettant de fixer le trépan aléseur sur l'extrémité d'un marteau perforateur de fond de puits et un trépan ou une couronne conique (15). Le trépan conique (15) du trépan aléseur est divisé en au moins trois segments (18) dont les extrémités présentent une surface terminale transversale (21) reliant directement les segments coniques et au moins trois des segments (18) comprennent des pastilles de forage (16) disposées à équidistance de l'axe central du trépan (15).

Claims

8
Claims
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 seg-
ments; and in that at least three of said segments (18) in-
clude drill buttons (16) that are disposed equidistantly from
the centre axis of the drill bit.
2. A reamer assembly according to Claim 1, charac-
terised in that each segment (18) includes a plural-
ity of drill buttons (16a - 16e).
3. A reamer assembly according to Claim 2, charac-
terised in that the drill buttons (16a - 16e) are
placed in mutually the same pattern in each of said segments
(18).
4. A reamer assembly according to Claim 2 or 3, charac-
terised in that a plurality of drill buttons (16) in
one and the same segment are disposed equidistantly from the
centre of the drill bit (15).
5. A reamer assembly according to any one of the preceding
Claims, characterised in that the drill buttons
(16a - 16e) of one segment are disposed so as to lie close to

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or to slightly overlap each other in a common plane projec-
tion. (Fig. 3).
6. A reamer assembly according to any one of the preceding
Claims, characterised in that drill buttons
(22) are provided in the transverse end surface (21) of the
drill bit (15).

Description

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A REAMER AS SEMBI~Y
The present invention relates to a reamer drill assembly,
i.e. a drill for widening a drilled pilot hole or for widen-
s ing 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 diame-
ter 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 opera-
2o tional 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
25 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
so 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

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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 pro-
s vide a novel reamer assembly which allows all of these prob-
lems 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
1o 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 Figure 1 is a schematic illustration of a known reamer
assembly used in rock drilling operations; Figure 2 is a
2o corresponding view of an inventive reamer assembly for use in
rock drilling operations; Figure 3 is a schematic illustra-
tion of a common plane projection of the drill buttons in one
segment of the reamer; Figure 4 illustrates schematically and
in perspective a reamer constructed in accordance with the
invention; and Figure 5 is an end view of the reamer shown in
Fig. 4, as seen from the side of the drill.
Fig. 1 thus shows a reamer assembly 1 used to drill in rock 2
in order to widen a predrilled pilot hole 3. The reamer 1
so includes a shank 4 and a conical drill bit 5 attached to the
shank 4. Attached to the conical surfaces of the drill bit
are a number of drill buttons 6 which are adapted to carry
out the actual rock drilling and rock removing operation.

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Arranged on the end of the bit or crown 5 distal from the
shank 4 is a generally cylindrical pilot body 7 which pro-
jects 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 ena-
bling 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.
Figure 2 illustrates a reamer assembly 11 constructed in
accordance with the present-winvention. The main difference
between this drill and the earlier known drill 1 shown in
Fig.1 is that the novel inventive reamer assembly 11 lacks a
guide pilot body. Instead, the drill buttons 16 are relied
upon to guide the reamer in the pilot hole. In the case of
reamers designed in accordance with the present invention,
the drill buttons 16 are given precise positions in the drill
bit 15 of the reamer 11 so that combined action of said but-
2o tons will ensure that the reamer 11 is guided in the pilot
hole 3 when drilling in rock 12. In other respects the reamer
11 has generally the same design as the reamer shown in Fig.
1, in other words includes a shank 14 and a generally conical
drill bit 15.
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
3o 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 16a in the segment 18 is the

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same distance from the centre axis of the reamer as the but
ton 16a° in the segment 18'; see Figs 4 and 5. Similarly, the
button 16c in the segment 18 is situated at the same distance
from the centre axis of the reamer as the button 16c' in the
s segment 18'.
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 fol
~o low 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
~s 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 Fig. 3, the buttons 16 will lie adjacent one another
or overlap each other to some extent. This will ensure that
at least one button 16 of each segment 18 will always be able
2o to support against the edge of a pilot hole and therewith
guide the reamer along the hole.
With the aid of different vertical chain lines 19a, 19b and
19c, Fig. 3 shows how different buttons 16a, 16b and 16c will
2s be those buttons that function as guides in a pilot hole
whose wall follows the lines 19a, 19b or 19c. Thus, as a
result of the close-by or overlapping relationship of respec-
tive buttons 16, there will always be one button in each
segment 18 that is able to guide the reamer in the pilot
so hole. Also shown are those buttons 16d and 16e that lie fur-
they out towards the edge 20 of the drill bit 15. These lat-
ter buttons do not normally have a guiding effect, but are
always those buttons that cut or remove rock irrespective of

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whether the edge of the pilot hole follows the line 19a, the
line 19b or the line 19c.
Those buttons that are furthest in towards the centre of the
s drill bit on its conical segments, i.e. the buttons 16a, 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
~o mm with one and the same reamer.
The buttons--16 are preferably-.p-laced in-mutually the same
pattern in each of the segments. Moreover, several buttons
may be placed equidistantly from the centre of the drill bit
~s in one and the same segment. See in particular Fig. 5.
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 ease of the illustrated embodiment,
2o 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 sur-
25 face 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 . cut-
tings that may have fallen down and fastened in the pilot
hole. When drilling a blind hole, these buttons 22 will also
ao support against the bottom of the hole so as to prevent mate-
rial damage to the drill bit 15.

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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 re-
suit 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.
2o 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 advan-
tage afforded by the invention is that a drill bit that does
2s 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
so same distance from the axial centre of the drill bit, as
defined in the accompanying claims, so as to obtain the nec-
essary stability in guiding the drill bit. The buttons in

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remaining segments may conveniently be positioned differ-
ently.

Representative Drawing