Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
The present invention relates to drilling apparatus used in the
exploration of underground petroleum reserves and more specifically to a
rotary drill bit having a plurality of rotary cutters supported for rotation
on the drill bit body by a plurality of rolling elements, the rolling
elements being laterally guided at least at their axial ends facing the
drill bit body in a radially disposed outer bearing race groove incorporated
in the bore of the rotary cutter.
Rotary drill bits having conically shaped rotary cutters are
known wherein the rotary cutters are supported on a trulmion formed
integrally with the drill bit body and a radial roller bearing. The rollers
of this bearing are laterally guided in a bearing race groove in the bore
of the rotary cutter and supported in place at their axial ends facing
away from the drill bit body by means of a flange bolt secured in the trunnion
so that each rotary cutter is mounted in a manner preventing removal from
the trunnion. An arrangement of this type is shown in the British Patent
No. 4~5,570. This known assembly has several disadvantages and drawbacks.
For example, the construction requires that the flange bolt be shaped in
the form of a race element for the axial bearing of the rotary cutter and
be made of an expensive bearing material. In order to mount the flange bolt
in a precise manner in the trunnion, the bolt has to be machined with close
tolerances. Thus, the method of manufacturing is relatively costly.
Additionally, a center bore with a relatively large diameter must be
provided in the trunnion to receive the highly stressed flange bolt and
accordingly, the trunnion of the drill bit body is somewhat weakened and
consequently there is the risk of trunnion failure by breakage, especially
in heavy duty operations.
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In accordance with another known rotary drill bit assembly, the
rotary cutters are each supported on a trunnion connected in one piece with
the drill bit body in a radial roller bearing with conical roller elements.
This arrangement is shown in Vnited States Patent No. 2,076,000. This
arrangement has the advantage of providing a trunnion which is relatively
rigid and possesses good load bearing characteristics. However~ a so-called
edge ring is required which is located in the bore of the rotary cutter on
the side of the roller elements facing the drill bit body which axially
guides the roller elements to support the rotary cutter in place on the
trunnion. It has been found that the fabrication of the rotary cutter is
rather expensive because of the incorporation of the additional edge ring.
Furthermore, in heavy duty operations with high impact stresses, it has
been observed that seizing of the edge ring may result and accordingly~
presents the disadvan*age that the rotary cutter is not adequately secured
against being drawn off the trunnion.
SUMMARY OF THE INVENTIQN
The present invention provides in a rotary drill bit having a drill
bit body and at least one trunnion projecting from the drill bit body and
a rotary cutter supported on at least one radial roller bearing on the
trunnion, means for gu;ding the rolling elements of said bearing on at least
one axial end facing the drill bit body in an outer bearing race groove
incorporated in the bore of the rotary cutter, means defining an inner
bearing race groove on the trunnion for the rolling elements of said radial
roller bearing and means defining at least one filling opening extending
through the drill bit body and trunnion extending essentially axially having
one terminal end adjacenk the inner bearing race groove and at least one
filler piece for sealing the opening, including at least a pair of filler
pieces and wherein one of said filler pieces is made of an elastically
compressible m2terial~
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Since the one filler piece may be elastically compressed during
insertion in the filling opening the drill bit can be assembled without
having to maintain close finishing tolerances between the filler piece and
filling opening.
In accordance with one embodiment of the present invention, the
filler piece assembly comprises an inner filler piece which can be
extensively radially elastically compressed since the material of the inner
filler piece can give way radially inwardly in the direction of the bore
and after inserting the elastic filler piece, the filling opening can be
sealed with a rigid outer filler piece, the extended projections of which
engage into the bore of the elastic filler piece and expands the filler
piece so that is wedged into the opening. Consequently, firm seating of
the inner filler piece in the filling opening is always obtained (in spite of
economically attractive large finishing tolerances of the filling opening
and filler piece) while still providing a firm and accurate seal with the
appropriate bearing race groove in the trunnion.
In a rotary drill bit constructed in accordance with the present
invention, the rolling elements of the radial roller bearings guided between
the edges of the inside bearing race groove, are firmly supported on the
trunnion and are laterally held in place. In this manner there is no danger
of seizing of the bearing race groove edges. The trunnion has a filling '~
opening for inser~ion of the rolling elements of the radial roller bearings
which is of comparatively small diameter and does not detract appreciably
from the strength of the trunnion. The trunnion of each rotary cutter may
be constructed in one piece with the drill bit body, thus providing a further
simplification of the fabrication and assembly of the roller bit since the
assembly comprises relatively few parts. These parts are comparatively
easy to machine so that the fabrication and assembly of the rotary drill bit
is simple and economical.
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In the rotary drill bit of the present invention the outside
bearing race groove in the rotary cutter as well as the inside bearing race
groove on the trunnion of th0 radial roller ~earings have a relatively large
groove depth providing a good lateral guidance of the rolling elements and
strong impact resistant edges of the bearing race grooves. The filling
opening for the rolling ele~ents in the trunnion is of optimally small cross
section and does not harmfully effect the good strength characteristics of
the trunnion Further, the filling opening disposed in the machined bearing
race groove is preferably located in the unstressed zone of the radial roller
bearing so that the load-bearing ability of the radial roller bearing is not
affected by this filling opening. Additionally, the filling opening is
adjacent the inside heavy walled portion of the drill bit body so that a
relatively strong break-proof connection is guaranteed between the trunnion
and the drill bit body.
BRIEF DESCRIPTION OF THE DRAWINGS
The advantages of the present invention and various features and
details of the operation and construction thereof are hereinafter more fully
set forth with reference to the accompanying drawingsJ wherein:
Figure 1 is a fragmentary longitudinal sectional view of a rotary
drill bit in accordance with the present invention;
Figure 2 is a fragmentary cross-sectional view taken on lines B-B
of Figure l; and
Figure 3 is a perspective view of the inside ~iller piece of the
rotary drill bit of Fig~lres 1 and 2.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings and particularly to Fi~ure 1 thereof,
there is illustrated one of a plurality of conical rotary cutters of a
rotary drill bit constructed in accordance with the present invention. As
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illustrated, the rotary cutter which is generally designated by the
numeral 1 is rotatably supported on the trunnion 3, which, in the present
instance, is formed integrally with the drill bit body 2. The bearing
support illustrated includes an outer roller bearing 4 with cylindrical
rolling elements 7, an inner radial bearing 5 with cylindrical rolling
elements and intermediate axial bearing 6 with conical rolling elements.
The rollers 7 of ~he ou~er radial roller bearing 4 facing the drill bit body
run in the base of the outer bearing race groove 8 formed radially in the
rotary cutter l. The axial end of the rollers 7 which face the drill bit
body 2 are guided by a radially inwardly directed shoulder 9 of the bearing
race groove 8 which as illustrated is formed integrally with the rotary
cutter 1. The trunnion is formed with a bearing race groove 10 for the
rollers 7 of the radial bearing 4 so that rollers 7 are guided and held in
place on both sides in the bearing race groove 10. By this construction, the
rotary cutter 1 is secured against being drawn off the trunnion 3 by the
shoulder 9 and the rollers 7. The inner end of the rotary cutter is provided
with a pocket opposite the shoulder 9 to receive an annular seal 11 which as
illustrated engages and slides on the opposite confronting front surface of
the drill bit body 2 to seal the entire bearing space of the rotary cutter
against ingress of foreign matter from the outside of the assembly.
Means is provided for filling the outer radial bearing with the
rollers via the trunnion. To this end, an axially extending filling opening
12, in the present instance, of circular cross section is bored in the
trunnion 3 and extends from the outer end face of the ro~ary cutter 1 to the
bearing groove lO. The cylindrical filling opening 12 is sealed in this case,
with an inside filler piece 43 of an elastically compressible material such
as, for example, rubber or plastic which comes to rest under the roller bodies
7 of the radial roller bearing 4 and an outside filler piece 44, for
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example, of a weldable carbon steel.
As can be clearly seen in Figur~ 2 and 3, the inside filler piece
43 has a center bore 45 pointing in the direction of the longitudinal axis
of the cylindrical filling opening 12 in which an extended projection 46
of the adjacent outside filler piece engages with radial oversize.
After inserting the roller bodies 7 between rotary cutter 1 and
trunnion 3, ~he elastically compressible inside filler piece 43 is radially
compressed while narrowing down its bore 45 and is placed into the filling
opening 12. Next, the filler piece 43 is pushed to the inside end of the
filling opening 12. Here a radial projection 48 of the filler piece 43
snaps into the radial connecting opening 47 which opens into the bearing race
groove 10 of the radial roller bearing 7 so that this connecting opening
47 is at least partly sealed by the filler piece 43. Th~n, the outside
filler piece is pushed into the filling opening 12. The extended projection
46 of the filler piece 44 is pressed into the bore 45 in this way so that
the elastically compressible filler piece 43 slightly expands and comes,
therefore, in tight contact with the walls of the connecting opening 47. In
this way, firm seating of the inside filler piece 43 in the filling opening
12 with connecting opening 47 is obtained without having to maintain
expensive close finishing tolerances between iller p.iece 43 and filling
opening 12. After inse:rting the outside filler piece 44, this can be firmly
connected with the drill bit body 2 by means of welds 18.
The rotary drill bit according to the invention has the distinct
advantage that it is equipped with rotary cutters in a simple economic
fabrication, which are held in place securely and impact resistant against
being drawn off their trunnion via the roller bodies of at least one radial
roller bea~ing.
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Moreover, the rotary drill bit according to the invention is not
limited to the above described exemplified embodiments. It can rather be
modified within the scope of the basic concept of the invention. For example,
it is possible to insert through a common filling opening running essentially
parallel to the axis of rotation of the rotary cutter, the rolling elements
of more than two radial roller bearings between trunnion and rotary cutter
whereby the filling opening exits then in all bearing races of the appropriate
roller bearings. The filling opening can in addition also be used to insert
the roller bodies of one or more axial roller bearings. The rolling elements
of the individual roller bearings do not have to be constructed without cage,
in other words, rolls or spheres, they can rather be guided by conventional
cages, segments or spacers.
Instead of a common filling opening for the roller bodies of
several radial roller bearings, separate essentially axially extending
filling opening exiting into the appropriate bearing race groove of the
trunnion can be provided for each individual radial roller bearing in a
rotary cutter. The strength of the trunnion is then, of course, reduced in
comparison with the common filling opening for several radial roller bearings
through the single filling openings.
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