U.S. patent number 3,918,538 [Application Number 05/484,838] was granted by the patent office on 1975-11-11 for rotary percussion earth boring bit.
This patent grant is currently assigned to Hughes Tool Company. Invention is credited to Mark Leslie Bender.
United States Patent |
3,918,538 |
Bender |
November 11, 1975 |
Rotary percussion earth boring bit
Abstract
Disclosed herein is a rotary-percussion earth boring bit that
has an improved geometric configuration to extend cutting insert
life and reduce cutting insert breakage. The bottom surface
contains a flat transverse face with a bevelled edge. Two rows of
circumferentially spaced cutting inserts protrude from the bevel.
One of the rows is spaced inwardly from an outer row to define an
inner row, which has inserts positioned between the
circumferentially spaced inserts of the outer row. The longitudinal
axes of these inserts are substantially perpendicular to the bevel
and inclined outward at an acute angle to the axis of rotation of
the bit. A generally longitudinally extending groove is formed
between each two adjacent inserts of the outer row. This
arrangement produces a symmetry that tends to minimize the number
of reflective surfaces. This equalizes the stresses generated by
the impact induced shock waves transmitted through the bit.
Inventors: |
Bender; Mark Leslie (Pearland,
TX) |
Assignee: |
Hughes Tool Company (Houston,
TX)
|
Family
ID: |
23925829 |
Appl.
No.: |
05/484,838 |
Filed: |
July 1, 1974 |
Current U.S.
Class: |
175/426;
175/417 |
Current CPC
Class: |
E21B
10/38 (20130101); E21B 10/56 (20130101); E21B
10/40 (20130101); E21B 10/26 (20130101) |
Current International
Class: |
E21B
10/56 (20060101); E21B 10/36 (20060101); E21B
10/38 (20060101); E21B 10/46 (20060101); E21C
013/01 () |
Field of
Search: |
;175/393,395,407,410,415,417,418,419,420,421,231,92,411,406 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Abbott; Frank L.
Assistant Examiner: Favreau; Richard E.
Attorney, Agent or Firm: Felsman; Robert A.
Claims
I claim:
1. An improved geometric configuration for a rotary-percussion
earth-boring bit that includes a body having torque transmission
means on an upper region, an anvil upper surface and an enlarged
lower region with a transverse face containing button type inserts,
the improvement comprising:
a bevel formed at the corner between the transverse face and the
enlarged lower region;
an outer row of circumferentially spaced inserts protruding from
said bevel;
an inner row of circumferentially spaced inserts located inwardly
wholly on said bevel and between the circumferentially spaced
inserts of the outer row;
the inserts of the inner and outer rows having longitudinal axes
that are substantially normal to the bevel.
2. An improved geometric configuration for a rotary-percussion
earth-boring bit that includes a body having torque transmission
means on an upper region, an anvil upper surface and an enlarged
lower region with a transverse face containing button type inserts,
the improvement comprising:
a bevel formed at the corner between the transverse face and the
enlarged lower region;
an outer row of circumferentially spaced inserts protruding from
said bevel;
an inner row of circumferentially spaced inserts located inwardly
on said bevel and between the circumferentially spaced inserts of
the outer row;
the inserts of the inner and outer rows having longitudinal axes
that are substantially normal to the bevel;
a longitudinally extending groove formed in the enlarged lower
region between each two adjacent circumferentially spaced inserts
of the outer row.
3. An improved geometric configuration for a rotary-percussion
earth-boring bit that includes a body having torque transmission
means on an upper region, an anvil upper surface and an enlarged
lower region with a transverse face containing button type inserts,
the improvement comprising:
a frusto-conical bevel formed at the corner between the transverse
face and the enlarged lower region;
an outer row of circumferentially and substantially spaced inserts
protruding from said bevel;
an inner row of circumferentially and substantially equally spaced
inserts located inwardly wholly on said bevel and between the
circumferentially spaced inserts of the outer row;
the inserts of the inner and outer rows having longitudinal axes
that are substantially perpendicular to the bevel.
4. An improved geometric configuration for a rotary-percussion
earth-boring bit that includes a body having torque transmission
means on an upper region, an anvil upper surface and an enlarged
lower region with a transverse face containing button type inserts,
the improvement comprising:
a frusto-conical bevel formed at the corner between the transverse
face and the enlarged lower region;
an outer row of circumferentially and substantially spaced inserts
protruding from said bevel;
an inner row of circumferentially and substantially equally spaced
inserts located inwardly on said bevel and between the
circumferentially spaced inserts of the outer row;
the inserts of the inner and outer rows having longitudinal axes
that are substantially perpendicular to the bevel;
a longitudinally extending groove formed in enlarged lower region
between each of the inserts of the outer row.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates in general to improved rotary-percussion
earth boring bits and in particular to improvements in the
geometric relationship of the lower region of the bit and cutting
inserts.
2. Description of the Prior Art
The first known commercially successful rotary-percussion earth
boring bit of the type having button inserts is described in U.S.
Pat. No. 3,185,228 which issued to the assignee of Joseph L. Kelly,
Jr. on May 25, 1965. While such bits have been successful, often
the outer or gage row of inserts wears out or break before inserts
on the inner portions of the bit serve their useful life.
There are several explanations that may explain the variation
between gage and inner row insert life. A greater amount of
material must be cut by the gage or outer row inserts, which have a
greater circumference to travel than the inner row inserts on each
revolution of the bit. Greater forces are exerted on the outer row
of inserts, for in addition to the vertical compressive forces,
large lateral forces occur, resulting from the cutting of the sides
of the borehole. The typically used tungsten carbide insert will
withstand great compressive forces, but not great lateral or
bending forces, thus breakage is more likely.
The outer row inserts are also more likely to be pulled from the
support metal of the body by large radial tearing forces. The outer
inserts protrude beyond the enlarged lower region of the bit to
avoid excessive wear on the lower region surface and wedging.
Because the outer inserts are close to the periphery of the bit,
support metal is thin in this area. This leads to rupture of the
support metal near the periphery.
A number of solutions to the problems of wear, breakage, and
tearing for the outer row and their supporting metal have been
proposed. However, improvements in the bit life are still
needed.
SUMMARY OF THE INVENTION
One of the objects of this invention is to provide an improved
geometric configuration for a rotary-percussion earth-boring bit
such that the outer row inserts are positioned to better withstand
vertical, lateral, and radial forces. Another object is to provide
the outer row inserts with additional supporting metal. Another
object is to provide a bevel at the corner between the transverse
base and lower region to increase stability and facilitate cuttings
removal. Another object is to provide larger equally spaced
generally longitudinal grooves to facilitate cuttings removal.
Another object is to minimize abrupt changes in adjacent transverse
cross sections through utilization of a configuration that
approaches symmetry as close as practicable near the outer
periphery of the bit.
In accordance with these objects, the body of the bit has torque
transmission means such as splines and an upper anvil surface to
receive successive impacts from a fluid operated hammer. An
enlarged lower region with a transverse face, containing button
type inserts, is formed on the bit, and the body is formed of a
single mass of metal. At the corner of the enlarged lower region
and the transverse face, a bevel is formed. The bevel contains two
circumferentially and alternately spaced rows of inserts protruding
outward with their longitudinal axes substantially perpendicular to
the bevel. Between each of the outer rows of these inserts,
generally longitudinal grooves for cuttings return are formed. The
inner row of inserts located on the bevel are spaced inwardly and
between the outer row.
Consequently the inner row leads the outer row in cutting the
bottom of the borehole to form a somewhat conical bottom hole
pattern. This increases the life of the inserts. Breakage is
reduced because the lateral forces are shared between more inserts.
The section of support metal for each insert is increased because
the longitudinal axes of inner and outer rows form substantially
the same angle with respect to the vertical axis of the bit.
Cuttings return flow is increased because of larger and uniform
cuttings return grooves. Other objects, features and advantages
will become apparent hereinafter.
BRIEF DESCRIPTION OF THE DRAWING
FIG. 1 is a perspective view as seen looking obliquely from a
corner on the lower region of the bit body to show the preferred
relationship of the transverse face of the bit with the button type
inserts and the bevel.
FIG. 2 is a longitudinal cross-section view of the bit shown in
FIG. 1, except some inserts have been moved to show their relative
paths on the borehole bottom during rotation of the bit.
FIG. 3 is a bottom view of the bit shown in FIG. 1.
FIG. 4 is a top view of the bit shown in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring initially to FIG. 1 of the drawing, a rotary percussion
type earth boring bit is shown in perspective and includes a torque
transmission means that includes splines 11, 13. These splines are
adapted to be assembled with mating splines in the housing (not
shown) of a motor having a fluid driven reciprocating piston that
periodically engages an anvil upper surface 17 of the bit. It is
conventional for a split-ring (not shown) to be assembled around a
cylindrical surface 15 to engage shoulders in the housing and
retain the bit for reciprocation in the housing and rotation with
the housing. Such arrangements are well known in the art and the
invention is not limited to use with any particular form of housing
or motor.
The bit also includes an enlarged lower region 18 that terminates
in a transverse face 19 containing a plurality of button type
inserts 21. The term "button type insert" refers to those wear
resistent inserts described in the previously mentioned U.S. Pat.
No. 3,185,228. Commonly, such inserts are constructed of sintered
tungsten carbide and are well known in the art.
The bottom surface of the bit includes a flat transverse face 19
and bevel 35. The bevel may be formed as a frusto-conical surface
at the corner of the transverse face 19 and enlarged lower region
18. However, it may also be formed as a somewhat curved surface. An
outer row of inserts 31 is spaced circumferentially about the bevel
35. Between each insert 31, a generally longitudinally extending
groove 37 forms a return course for cuttings. An inner row of
inserts 33 is circumferentially spaced on the bevel 35 inwardly and
between the circumferentially spaced inserts 31. Each of the
inserts 31, 33 protrudes from the bevel 35, being inserted in
machined holes with interference fit in the manner well known in
the art. The longitudinal axes of the inserts 31, 33 are
substantially perpendicular to the surface of the bevel 35. Since
the bevel 35 is substantially flat or only slightly curved, the
longitudinal axes of the inserts 31, 33 form substantially the same
acute angle with respect to the axis of revolution of the bit. The
remaining inserts 21 are distributed on the transverse face 19 to
cooperatively cover, during rotation, the borehole bottom as
indicated in FIG. 2.
The body of the bit is preferably constructed of a single mass of
metal through which a single air course 23 extends obliquely from
the anvil surface 17 until it intersects the transverse face 19.
The center of the resulting aperture on the transverse face 19 is
offset from the axis of revolution or centerline of the bit so that
an innermost insert can effectively remove earth from the center
region of the borehole bottom.
It should be apparent from the foregoing description that an
invention having significant advantages has been provided. The
invention solves the problem of how and where to place more inserts
to alleviate work and stress required of the outer row inserts 31,
without reducing the support metal section. Placing an inner row of
inserts 33 radially in-line with the outer row of inserts 31 was
not feasible since this led to loss of section of the supporting
metal. Staggering an inner row of inserts 33 between the outer row
31 and at a different angle resulted in reduction in the size of
cuttings return grooves 37. Also, having outer and inner row
inserts at different angles caused reduction in section of the
support metal between inserts.
Prior art solutions placed the inner row of inserts 33 in a
substantially vertical position or lesser angle of inclination than
the outer row 31, which inclined outwardly to cut the side of the
borehole. The reason for the differing angles of inclination was to
align the longitudinal axes of the inserts 31, 33 substantially in
the direction of the resultant of the lateral forces from the side
of the borehole. Thus it was thought that to align the inner row 33
outwardly at the same acute angle would subject it to too much
bending force from the vertical direction.
Placing the inner inserts 33 substantially vertical or at a lesser
angle of inclination than outer inserts 31 may have placed their
longitudinal axes more in line with the differing resultant forces,
however it deprived both rows 31, 33 of needed support section. It
is desirable to place inserts 33 as close to the cuttings return
groove 37 as possible to share the work load of outer inserts 31.
But because the longitudinal axes of the inner inserts 33 were near
vertical, the base 39 was also close to return groove 37 and
support section was reduced, leaving support only on the inward
periphery. Also, as the phantom lines designating bases 39, 41 in
FIG. 2 show, if adjacent inserts incline at different angles, the
phantom lines intersect. Less body section is available to resist
radial tearing forces than if the phantom lines do not intersect as
bases 39 and 43. Further outward, on base 43, the radial force is
greater than on base 41, requiring more section for support.
The use of a bevel 35 with inner and outer rows 31, 33 protruding
outward from it at substantially the same angles of inclination
with respect to the bit axis of revolution solves the problem. The
work load of the outer row 31 is reduced, body support section is
sufficient, yet cuttings return grooves 37 are increased in area.
The inner row 33 leads the outer row 31 in cutting portions of the
side of the borehole. This reduces the work required of the outer
row 31 and shares in lateral forces. The resultant forces acting on
each row 31, 33 are not precisely in the same direction, yet
because the rows 31, 33 are perpendicular to the surface of bevel
35, they are able to withstand bending forces. Because of the
outward inclination, the cutting tips of inserts 33 are on the
periphery of the bit where they are needed, yet their bases 39 are
inward where there is sufficient body section for support. Large
cutting return grooves 37 are possible because of the inward
placement of base 39.
Furthermore, the use of a large bevel 35 gives greater bit
stability because of the partial cone-shaped uncut bottom of the
borehole. Cutting chip removal is more effective because of the
gradual transition from the horizontal borehole bottom to the
vertical borehole sides. Flat chips cut from the bottom of the
borehole will not clog when they change directions from horizontal
to vertical on being carried outward and upward. Because the return
flow air is large and uniform, large cutting chips can be removed
quickly, thus avoiding inefficient cuttings regrinding.
While this invention has been shown in only one of its forms, it
should be apparent to those skilled in the art that it is not so
limited but is susceptible to various changes and modifications
without departing from the spirit thereof.
* * * * *