Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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Background of the Invention
The present invention relates to the earth boring art
and more particularly to a rotary rock bit constructed from a
multiplicity of individual segments that are jcined together
using a beam of energy. A rotary rock bit in general consists of
a main bit body adapted to be connected to a rotary drill string.
Cutter means connected to the main bit body contact the formation
during the drilling operation to form the desired borehole. The
present invention provides a rotary rock bit that is constructed
from separate individual segments. The segments are joined together
using a beam of energy.
Th-e rotary rock bit must operate under extremely harsh
environmental conditions and must effectively disintegrate very
hard formations to produce the desired borehole. The gage size
f the bits must be precise Variation in the gage size of bits
has been a problem in the prior art. In some operations the bit
must pass through casing with a minimum clearance. In other
operations it is necessary for the bit to pass through bored and
still open holes which may be within a few thousandths of an inch
of the gage size of the bit. If the gage size of the bits varies
during the manufacturing process, the bits will encounter problems
during the drilling operation.
The prior art methods of manufacturing rotary rock bits
require the use of shims to size the bits to the proper gage size.
The present invention allows the bits to be manufactured with an
accurate and uniform gage size without the use of shims. During
the construction of a prior art rotary rock bit a substantial
amount of heat is generated when the separate segments of the
bit are welded together. It is necessary to cool the prior art
bits to prevent tempering of steel components and heat damage ~o
rubber components. The excessive heat creates a risk of a change
in temper of the metal of the rock bit, thereby creating the
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danger of a premature failure of the metal during the drilling op-
eration. Since the rock bit often includes rubber or synthetic
parts, any excessive heating in the vicinity of said parts may cause
a weakening or destruction of said parts. It has been necessary
to use dowels between the segments of prior art bits to insure
proper alignment.
The prior art method of manufacturing rotary rock bits
consists of forming a weld groove between adjacent segments of
the bit and filling the weld groove with a weld deposit by a
welding process. Surfaces on adjoining segments are in adjacent
relationship but the surfaces are not joined together and the
joining of the segments is through the weld deposit. The cross
sectional shape of the prior art weld is an irregular many sided
polygon. An excessive amount of weld deposit is produced during
the welding of prior art bits and the excessive amount of weld
`deposit often results in warpage of the bit body. The excessive
weld deposit also creates the danger of the lubrication system
and the bearing systems being contaminated during the manufac-
turing process by debris from the welding process. The weld deposit
is not as hard as the body segments, thereby creating fatigue
problems.
When the individual segments of the bit body are to be
joined together, they must be accurately positioned during the
welding process. If the individual segments are not properly
positioned, the gage size of the bit will not be accurate. When
a beam of energy is used to join the individual segments of the
bit, the individual segments must be accurately aligned with the
beam during the welding process.The joining of the individual
segments of the bit body in accordance with the present invention
insures that the gage size of the bit will be accurate.
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An illustration of the problems created with prior art
manufacturing processes will be presented with reference to a
rotary cone rock bit. A rotary cone rock bit includes at least
one rotatable cutter mounted on a bearing pin extending from
the main bit body. Bearings are provided between the cutter and
the bearing pin to promote rotation of the cutter and means are
provided on the outer surface of the cutter for disintegrating
the formations as the bit and cutter rotate and move through the
formation. A sufficient supply of lubricant must be provided
to the bearings throughout the lifetime of the bit. The lubricant
is maintained within the bearing area by a flexible rubber seal
between the cutter and the bearing pin. Any excessive heating
of the bit will damage the rubber seal and/or the lubricant. If
the bit body is not constructed to a precise gage size, the bits
will encounter difficulties when they are moved through casing
having a minimum clearance or through a borehole with minimum
clearance. Excessive weld deposits may result in warpage of the
bit and a resulting inaccurate gage size.
Description of Prior Art
In U. S. Patent No. 2,807,444 to W. H. Reifschneider,
patented September 24, 1957, a rotary earth boring drill is shown
and claimed in which the bit head is formed of a plurality of
arcuate segments each of said segments being asymmetric and
comprising a body portion having a downwardly extending leg and
a downwardly extending hollow boss in side-by-side relation
thereon, there being a passage communicating between the interior
of the bit head and bores of the bosses.
In U. S. Patent No. 2,831,661 to G. R. Brown, patented
April 22, 1958, a drill bit consisting of three segmental elements
which are adapted to fit together to constitute a bit is shown.
After forging, the segmental elements are machined to afford
accurately meeting surfaces when the elements are assembled
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together. The margins which represent the meeting of the segments
are given a chamfer for providing a weld groove. The three
segmental elements are assembled in a jig and welding is carried
out along the groove.
In U. S. Patent No. 2,778,926 to W. H. Schneider,
patented January 22, 1957, a method for welding and soldering by
bombarding by electrons the engaging surfaces of two parts to be
connected is shown. The method disclosed shows a system for
soldering, welding, or sintering suitable materials by heating
0 the parts to be connected with a beam of electrons.
Summary of the Invention
The present invention provides a unitized rotary rock
bit. The temper of the metal of the rock bit is not altered by
excessive heating and the less heat resistant elements of the rock
bit are prevented from being damaged by excessive heat. A multi-
plicity of individual segments of the rock bit are positioned
together and aligned in the proper position for the final assembled
bit. The adjoining segments have surface areas that are in
abutting relationship to each other. The alignment of the
individual segments of the rock bit provides seams between the
individual segments. The seams are in the form of square-butt
type joints. A beam of energy is directed into said seams to
~oin said individual segments together. The beam and the individual
segments of the rock bit are moved relative to one another causing
the beam to travel along said seams in the plane of the seams
joining said individual segments together throughout substantially
all of said abutting surface areas.
It is therefore an object of the present invention to
construct a rock bit that is not damaged or altered by excessive
3 heat during the construction process.
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The above object is met with the present invention
which provides a method of constructing a three cone rotary
rock bit from three individual rock bit segments, each of the
segments having a gage cutting surface for cutting the gage
diameter of a borehole having a gage diameter of a predeter-
mined size, comprising the steps of positioning the three
individual segments together aligned in the proper position
for the final assembled bit with the gage cutting surface of
each segment at the gage diameter thereby forming seams between
the individual segments of the rock bit; directing a high
intensity electron beam substantially all of the way through
the seams; and causing relative movement of the beam and the
segments in the plane of the seams to join the individual
segments together.
The product of the above mentioned method is defined
as a rotary rock bit comprising: a multiplicity of segments
each of th~ segments having faces with faces on each segment
! ~ contacting faces on next adjacent segments; the segments
positioned together to provide the rotary rock bit with an
accurate gage diameter, and means fusing the segments together,
the means extending throughout substantially all of the
contacting faces.
The above and other objects and advantages of the
present invention will become apparent from a consideration
of the following detailed description of the invention when
taken in conjunction with the drawings.
Brief Description of the Drawings
FIGURE 1 shows an individual segment of a rotary rock
bit.
FIGURE 2 shows three individual segments of a rotary
rock bit positioned together for welding.
FIGURE 3 shows the surface area that is joined by
the method of the present invention.
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FIGURE 4 shows the weld area of prior art rotary
rock bits.
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FIGURE 5 shows a horizontal section of a prior art weld.
FIGURE 6 shows a horizontal section of a weld of the
present invention.
Detailed Description of the Invention
Referring now to FIGURE 1, an individual segment of a
bit constituting one third of a rotary rock bit is shown in an
exploded view. The segment is generally designated by the reference
number 10. The individual segment 10 constitutes one arm of a
three cone rotary rock bit. A central passage 11 is located in
the rock bit to allow drilling mud to be transmitted through the
rock bit to the bottom of the well bore for removing cuttings and
cooling the bit. The drilling fluid is channeled through the
central passageway 11 and exits from the bit through nozzles, one
nozzle 12 being shown in FIGURE 1. The bit is adapted to be
connected to a rotary drill string by a threaded connection that
will be provided by the threading of the outside surface 13.
The segment 10 of the bit includes an arm 14 terminating
in a bearing pin 15. A rotatable cone cutter 16 is positioned
upon the bearing pin 15 and adapted to rotate thereon. Bearings
(not specifically shown) between the bearing pin 15 and cutter 16
facilitate rotation of cutter 16. The bearings include a series
of ball bearings that are positioned in the ball bearing race 17
on the bearing pin 15. After the cone cutter 16 is in place on
the bearing pin 15, the ball bearings are loaded into position
between a ball bearing race (not shown) on the inside of the cutter
16 and the ball bearing race 17 on the bearing pin 15 through a
hole 18 in the arm 14. Once the ball bearings are in place and
the cone cutter 16 is locked on the bearing pin 15, the hole 18 is
plugged to insure that the ball bearings will not be lost during
operation of the bit.
A multiplicity of inserts 19 are located on the
exterior surface of the cutter 16 for disintegrating the formations
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as the bit is rotated and moved through the formations. In order
to provide the bearings with a long life, a lubricant is main-
tained within the area between the cone 16 and the bearing pin 15.
A rubber seal 20 is positioned between the arm 14 and the cone 16
to insure that the lubricant remains within the bearing area.
Referring now to FIGURE 2, the segment 10 is shown
positioned together with two other individual segments 21 and 22.
The segments 10, 21, and 22 are aligned in the proper position
for the final bit. The segments are positioned within a fixture
23 that allows the seams 24 between the individual segments of the
rock bit to be properly positioned for the joining process. A
beam 29 of high velocity electrons is directed into the seams
24 between the individual segments of the rock bit to fuse the
segments together and produce a truly unitized rock bit.
The beam of electrons is produced by an electron beam
gun 30 and the beam 29 is caused to move in the plane of the seams
24 by relative movement between the segments 10, 21, 22 and the
electron beam gun 30. Because of the high intensity of the
electron beam (lOKW/mm2) and its high power capability (60KW)
the width of the area acted on between the segments is much
narrower than that found in prior art rock bits. In addition,
the electron beam gun produces a beam that penetrates substantially
throughout the area to be joined. The energy from the electron
beam is applied rapidly thereby preventing heat buildup and reducing
the danger of damaging the portions of the rock bit that have a
low tolerance to heat such as the rubber seal 20 and the lubricant.
The segments 10, 21, and 22 of the rock bit fit together to form
a square-butt type joint rather than the V-groove or the J-groove
joints that were required in prior art rotary rock bits. The
electron beam does not add material to produce a buildup of
deposit along the seams and there is very little if any warpage.
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Referring again to FIGURE 1, it will be noted that the
faces 25 and 26 are flat and adapted to be positioned in abutting
relationship to the other segments that make up the rock bit.
The edges 27 and 28 of the faces 25 and 26, respectively, are
substantially square and are notc~lamfered or beveled as in prior
art rock bits.
The method of the present invention provides a signifi-
cantly large area that is joined thereby providing greater
strength and rigidity in the bit. A comparison was made of~the
area joined on the individual segments used in the construction
of a rock bit by the method of the present invention and the weld
area of individual segments used in the construction of a rock
bit by a typical prior art method. The area measured corresponds
to the portion joined. The following table shows that a
substantially greater area is joined by the method of the present
invention:
Method of the Method of
Present Invention the Prior Art
Area Welded
20Segment JoinedSegment Area
80036 Special #1 11.29 in280036 Standard #4 5.o6 in2
80036 Special #2 11.31 in280036 Standard #5 4.27 in2
80036 Special #3 10.60 in80036 Standard #6 4.29 in
Referring now to FIGURE 3, the size of the areas of
adjacent segments that are joined by the method of the present
invention is illustrated. The face 25 shown in FIGURE 1 will be
placed in abutting relationship to an adjacent face on the next
adjacent segment 21. Substantially the entire surface areas
will be joined by the method of the present invention. The outline
32 shows the area that will be joined by the method of the present
invention. The only area that will not be joined is the area 33.
It will be appreciated that substantially the entire area of the
abutting surfaces will be joined by the method of the present
invention.
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Referring now to FIGURE 4, the weld area of a prior art
rotary rock bit is shown. The outline 34 shows the area of the
weld. A weld groove is formed between the adjacent segments and
the weld groove is filled with a weld deposit by a welding process.
The resulting weld is only in the area shown by the outline 34.
The area that will not be joined is the area 35. It will be
appreciated that a substantially larger area will be joined by the
present invention.
The method of the present invention prevents contamina-
tion of the bearing and lubrication systems of the bit during the
manufacturing process. The splatter from welding by the prior
art method creates a constant hazard of the bearing and the lubri-
cation systems being contaminated. Since a substantial weld
deposit is formed by the prior art method, particles of the weld
deposit may contaminate the bearing and lubrication systems.
Referring now to FIGURE 5, a horizontal sectional view
of a prior art weld is shown. The segment 36 is positioned
proximate the segment 37. A face 38 on segment 36 is opposite a
face 39 on segment 37. A dowel 40 extends into a hole 41 in segment
36 and into a hole 42 in segment 37. The dowel 40 is used to
align the segments of the bit in the proper position for welding.
The segment 36 includes a section 43 that will, when combined with
the matching section 44 on segment 37, form a weld groove. As
previously explained, the bit must have an accurate gage diameter.
25 In order to size the bits to the proper gage diameter, a shim 45
is positioned between the faces 38 and 39. Various numbers of
shims will be required in the bit depending upon the adjustment
needed to bring the bit to the proper gage size.
The weld groove formed by the sections 43 and 44 is
30 filled with a weld deposit 46. It will be noted that the faces 38
and 39 are not connected by a weld and that the segments 36 and 37
are joined solely by the weld deposit 46. The cross section of
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the weld deposit 46 is in the form of an irregular multi-sided
polygon. This shape of weld is subjected to complicated stress
forces and the fatigue life is shorter than fatigue life of the
weld of the present invention. The weld deposit is softer than
the metal of the segments 36 and 37. For example, the hardness of
the wèld deposit 46 will generally be within the range of 15-20
Rockwell C, whereas the hardness of the segments 36 and 37 will
generally be within the range of 25-35 Rockwell C. The softer
weld deposit 36 is therefore not as strong as the adjacent segments
36 and 37.
Referring now to FIGURE 6, a horizontal sectional view
of a weld of the present invention is shown. The segment 47 is
positioned next to the segment 48. A face 49 on segment 47 is in
abutting relationship to a face 50 on segment 48. The segments
47 and 48 are joined throughout substantially all of said faces
49 and 50 as previously explained. Ridges 52 and 53 are formed on
the segments 47 and 48 respectively by the flash left from the
forging of segments 47 and 48. Shims are not used to size the bit
to the proper gage size. Instead of using dowels to position the
segments 47 and 48, the segments 47 and 48 are moved relative to
one another to bring the bit to the proper gage size. For example,
the upper portions of segments 47 and 48 are moved slightly out-
ward. A portion 51 of face 50 will be exposed by the sliding move-
ment of faces 49 and 50 when the bit is being broug~ to the
proper gage size. It has been found desirable to maintain the
faces 49 and 50 precisely adjacent each other near the lower threaded
end of the bit whereas the small sliding movement of the faces 49
and 50 is accomplished near the upper portion of the body of the
bit.
A small heat affected zone will exist on each side of
faces 49 and 50, however, this heat affected zone will be even
harder than the segments 47 and 48. For example, this heat
affected zone or weld area will have a hardness generally within
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the range of 35-45 Rockwell C. This is compared to the segMents 47
and 48 that will generally have a hardness in the range of 25-35
Rockwell C. It will therefore be appreciated that the bit con-
struct in accordance with the present invention is substantially
stronger than the bits of the prior art. It will also be noted
that there is less hardness variation between the weld zone and
the segments of the bit of the present invention as compared to
the weld and the segments of the prior art bit. This can also be
described as the weld of the present invention having a substan-
tially less notch effect than the weld of the prior art.
The present invention provides greater reliability andreliable repeatability because a greater number of the manufacturing
operations can be done by machine as compared to the prior art.
The human factor, of course, results in substantial variation. The
present invention also provides precise control of the weld para-
meters throughout the length of the weld.
