U.S. patent application number 10/379886 was filed with the patent office on 2005-04-07 for integral bit retention system.
This patent application is currently assigned to Numa Tool Company. Invention is credited to Pascale, Jack H., Pelletier, Gary R., Vincent, Robert F..
Application Number | 20050072602 10/379886 |
Document ID | / |
Family ID | 34392853 |
Filed Date | 2005-04-07 |
United States Patent
Application |
20050072602 |
Kind Code |
A1 |
Pascale, Jack H. ; et
al. |
April 7, 2005 |
Integral bit retention system
Abstract
A percussion bit assembly includes a percussion bit having an
upper, elongated bit shank, a lower bit head, and a bit skirt
disposed intermediate the bit shank and the bit head. The
percussion bit has an axial bore extending longitudinally through
at least the bit shank and the bit skirt and at least one
receptacle extending radially outward from the lower portion of the
axial bore. A bit retainer includes at least one longitudinal
member and at least one lateral member. The longitudinal member
extends longitudinally within the axial bore of the percussion bit
from an upper end portion, mounted within the upper portion of the
axial bore, to a lower end portion disposed in the lower portion of
the axial bore. The lateral member extends laterally from a
radially inner end portion connected to the lower end portion of
the longitudinal member to a radially outer end portion mounted in
the receptacle.
Inventors: |
Pascale, Jack H.;
(Greentown, PA) ; Vincent, Robert F.; (Eastford,
CT) ; Pelletier, Gary R.; (N. Grosvenordale,
CT) |
Correspondence
Address: |
ALIX YALE & RISTAS LLP
750 MAIN STREET
SUITE 1400
HARTFORD
CT
06103
US
|
Assignee: |
Numa Tool Company
|
Family ID: |
34392853 |
Appl. No.: |
10/379886 |
Filed: |
March 5, 2003 |
Current U.S.
Class: |
175/414 ;
175/417 |
Current CPC
Class: |
E21B 10/36 20130101;
E21B 17/046 20130101 |
Class at
Publication: |
175/414 ;
175/417 |
International
Class: |
E21B 010/36 |
Claims
What is claimed is:
1. A percussion bit assembly for downhole boring operations
comprising: a percussion bit including an upper, elongated bit
shank, a lower bit head, and a bit skirt disposed intermediate the
bit shank and the bit head; the percussion bit defining an axial
bore extending longitudinally through at least the bit shank and
the bit skirt, the axial bore having upper and lower portions; the
percussion bit also defining at least one receptacle extending
radially outward from the lower portion of the axial bore; and a
bit retainer including at least one longitudinal member and at
least one lateral member; the longitudinal member extending
longitudinally within the axial bore of the percussion bit from an
upper end portion, mounted within the upper portion of the axial
bore, to a lower end portion disposed in the lower portion of the
axial bore; the lateral member extending laterally from a radially
inner end portion, connected to the lower end portion of the
longitudinal member, to a radially outer end portion mounted in the
receptacle.
2. The percussion bit assembly of claim 1 wherein the percussion
bit defines first and second circumferentially spaced receptacles,
the upper portion of the percussion bit axial bore defines a
circumferential shelf, and the bit retainer includes a pair of
retainer bars; each of the retainer bars including a longitudinal
portion and a lateral portion defining the longitudinal and lateral
members; a radially outer end portion of each lateral portion being
received in one of the receptacles; the upper end portion of each
longitudinal portion having a tab extending radially outward
therefrom, the tabs being supported on the shelf of the percussion
bit axial bore.
3. The percussion bit assembly of claim 2 wherein the bit retainer
also includes upper and lower spacers, the upper spacer being
positioned proximate to the upper end portions of the retainer bars
and the lower spacer being positioned proximate to the lower end
portions of the retainer bars, whereby the upper and lower spacers
prevent radial movement of the tabs and the lateral portion of the
retainer bars.
4. The percussion bit assembly of claim 3 wherein the lower end
portion of each retainer bar includes a protrusion extending
radially inward into the axial bore, the lower spacer being
supported on the protrusions of the retainer bars.
5. The percussion bit assembly of claim 4 wherein the lower spacer
is an H-shaped member defining a pair of oppositely disposed
indentations and an axial opening, the lower end portion of the
longitudinal portion of one of the retainer bars being received in
each of the indentations.
6. The percussion bit assembly of claim 3 wherein the upper spacer
is a substantially cylindrical member, having a wall defining an
axial opening and a pair of oppositely disposed indentations
extending radially inward into the opening.
7. The percussion bit assembly of claim 6 wherein the upper end
portion of the longitudinal portion of one of the retainer bars
being received in each of the indentations,
8. The percussion bit assembly of claim 7 wherein the upper spacer
is supported on the shelf of the percussion bit axial bore.
9. The percussion bit assembly of claim 1 wherein the at least one
receptacle extends radially outward into the bit skirt.
10. The percussion bit assembly of claim 1 wherein the at least one
receptacle extends radially outward into the bit head.
11. The percussion bit assembly of claim 1 wherein the at least one
receptacle extends radially outward at an obtuse angle from the
axial bore and lateral member extends at an obtuse angle from the
lower end portion of the longitudinal member.
12. The percussion bit assembly of claim 1 wherein the at least one
receptacle extends radially outward at an obtuse angle from the
axial bore and lateral member includes an upper segment that
extends substantially parallel to the longitudinal member and a
lower segment that extends at an obtuse angle from the upper
segment.
13. The percussion bit assembly of claim 12 wherein the at least
one receptacle extends through the bit skirt into the bit head.
14. The percussion bit assembly of claim 1 wherein the at least one
receptacle extends radially outward at an acute angle from the
axial bore and lateral member extends at an acute angle from the
lower end portion of the longitudinal member.
15. The percussion bit assembly of claim 1 wherein the bit skirt
has an outer surface; the receptacle is a transverse bore extending
from the outer surface on a first side of the bit skirt, through
the axial bore, and into an opposite, second side of the bit skirt;
the longitudinal member is a retainer tube having a lower end
portion defining oppositely disposed, first and second openings;
and the lateral member is a pin; the pin having a first end portion
positioned in a segment of the transverse bore in the first side of
the bit skirt, a middle portion extending through the openings of
the retainer tube lower end portion, and a second end portion
positioned in a segment of the transverse bore in the second side
of the bit skirt.
16. The percussion bit assembly of claim 15 wherein the upper
portion of the percussion bit bore defines a circumferential shelf
and a upper end portion of the retainer tube has a circumferential
collar extending radially outward therefrom, the collar being
supported on the shelf.
17. The percussion bit assembly of claim 16 wherein the transverse
bore and the openings of the retainer tube each have an inside
diameter; the first end portion of the pin includes outer and inner
segments, the outer segment extending from the outer surface of the
first side of the bit skirt to an intermediate position between the
outer surface of the first side of the bit skirt and the axial
bore, the inner segment extending from the intermediate position to
the axial bore; the second end portion of the pin, the middle
portion of the pin, and the inner segment of the first end portion
of the pin have a substantially uniform outside diameter which is
smaller than the inside diameters of the transverse bore and the
openings of the retainer tube, and the outer segment of the first
end portion of the pin has an outside diameter selected for
frictional engagement between the outer segment of the first end
portion of the pin and the transverse bore.
18. The percussion bit assembly of claim 16 wherein the bit
retainer also includes a plug; the segment of the transverse bore
in the first side of the bit skirt includes outer and inner
portions, the outer portion extending from the outer surface of the
first side of the bit skirt to an intermediate position between the
outer surface of the first side of the bit skirt and the axial
bore, the inner portion extending from the intermediate position to
the axial bore; the transverse bore and the openings of the
retainer tube each have an inside diameter and the pin has a
substantially uniform outside diameter which is smaller than the
inside diameters of the transverse bore and the openings of the
retainer tube; the first end portion of the pin being disposed in
the inner portion of the segment of the transverse bore in the
first side of the bit skirt and the plug being fixedly mounted in
the outer portion of the segment of the transverse bore in the
first side of the bit skirt.
19. The percussion bit assembly of claim 1 wherein the bit skirt
has an outer surface; the receptacle is a transverse bore having a
first segment extending from the outer surface on a first side of
the bit skirt to the axial bore and a second segment extending from
the axial bore to the outer surface on an opposite, second side of
the bit skirt; the longitudinal member is a retainer tube having a
lower end portion defining oppositely disposed, first and second
openings; and the lateral member is substantially identical first
and second pins; the transverse bore and the openings of the
retainer tube each have an inside diameter; each pin having outer
and inner segments; the inner segment of each pin having an outside
diameter which is smaller than the inside diameters of the
transverse bore and the openings of the retainer tube; the outer
segment of each pin having an outside diameter selected for
frictional engagement between the outer segment of the pin and the
transverse bore; the first and second pins being disposed in the
first and second segments of the transverse bore, the outer segment
of each pin extending from the outer surface of the bit skirt to an
intermediate position between the outer surface of the bit skirt
and the axial bore, the inner segment extending from the
intermediate position through a one of the openings of the retainer
tube.
20. The percussion bit assembly of claim 19 wherein the inner
segment of each pin extends a distance into the bit bore.
21. The percussion bit assembly of claim 20 wherein said distance
is substantially equal to 1/4 inch.
22. A percussion bit assembly for downhole boring operations
comprising: a percussion bit including an upper, elongated bit
shank, a lower bit head, and a bit skirt disposed intermediate the
bit shank and the bit head; the percussion bit defining an axial
bore extending longitudinally through at least the bit shank and
the bit skirt, the axial bore having upper and lower portions; the
upper portion of the axial bore defining a circumferential shelf;
the percussion bit also defining a plurality of circumferentially
spaced receptacles, each receptacle extending radially outward from
the lower portion of the axial bore; and a bit retainer including a
plurality of retainer bars and upper and lower spacers; each of the
retainer bars including a longitudinal segment and a lateral
segment; the longitudinal segment extending longitudinally within
the axial bore of the percussion bit from an upper end portion to a
lower end portion; the upper end portion of each longitudinal
portion having a tab extending radially outward therefrom, the tabs
being supported on the shelf of the percussion bit axial bore; the
lateral segment extending laterally from a radially inner end
portion, connected to the lower end portion of the longitudinal
segment, to a radially outer end portion; the outer end portion of
a one of the retainer bars being disposed within each of the
receptacles; the upper spacer being positioned proximate to the
upper end portions of the retainer bars and the lower spacer being
positioned proximate to the lower end portions of the retainer
bars, whereby the upper and lower spacers prevent radial movement
of the tabs and the lateral segments of the retainer bars.
23. A percussion bit assembly for downhole boring operations
comprising: a percussion bit including an upper, elongated bit
shank, a lower bit head, and a bit skirt disposed intermediate the
bit shank and the bit head; the bit skirt having an outer surface;
the percussion bit defining an axial bore extending longitudinally
through at least the bit shank and the bit skirt and a transverse
bore having a first segment extending from the outer surface on a
first side of the bit skirt to the axial bore and a second segment
extending from the axial bore to a position intermediate the axial
bore and the outer surface on an opposite, second side of the bit
skirt; the axial bore having upper and lower portions; the upper
portion of the axial bore defining a circumferential shelf; and a
bit retainer including a retainer tube and a pin; the retainer tube
extending longitudinally within the axial bore of the percussion
bit from an upper end portion to a lower end portion; the upper end
portion having a circumferential collar extending radially outward
therefrom, the collar being supported on the shelf; the lower end
portion defining oppositely disposed, first and second openings;
the pin having a first end portion positioned in the first segment
of the transverse bore, a middle portion extending through the
openings of the retainer tube lower end portion, and a second end
portion positioned in the second segment of the transverse bore;
the bit retainer also including a pin retaining element.
24. The percussion bit assembly of claim 23 wherein the transverse
bore and the openings of the retainer tube each have an inside
diameter; the first end portion of the pin includes outer and inner
segments, the outer segment extending from the outer surface of the
first side of the bit skirt to an intermediate position between the
outer surface of the first side of the bit skirt and the axial
bore, the inner segment extending from the intermediate position to
the axial bore; the second end portion of the pin, the middle
portion of the pin, and the inner segment of the first end portion
of the pin have a substantially uniform outside diameter which is
smaller than the inside diameters of the transverse bore and the
openings of the retainer tube, and the outer segment of the first
end portion of the pin has an outside diameter selected for
frictional engagement between the outer segment of the first end
portion of the pin and the transverse bore, whereby the outer
segment of the first end portion of the pin is the pin retaining
element.
25. The percussion bit assembly of claim 23 wherein the first
segment of the transverse bore includes outer and inner portions,
the outer portion extending from the outer surface of the first
side of the bit skirt to an intermediate position between the outer
surface of the first side of the bit skirt and the axial bore, the
inner portion extending from the intermediate position to the axial
bore; the transverse bore and the openings of the retainer tube
each have an inside diameter and the pin has a substantially
uniform outside diameter which is smaller than the inside diameters
of the transverse bore and the openings of the retainer tube; the
first end portion of the pin being disposed in the inner portion of
the first segment of the transverse bore; the pin retaining element
being a plug fixedly mounted in the outer portion of the first
segment of the transverse bore.
26. A percussion bit assembly for downhole boring operations
comprising: a percussion bit including an upper, elongated bit
shank, a lower bit head, and a bit skirt disposed intermediate the
bit shank and the bit head; the bit skirt having an outer surface;
the percussion bit defining an axial bore extending longitudinally
through at least the bit shank and the bit skirt and a transverse
bore having an inside diameter, a first segment extending from the
outer surface on a first side of the bit skirt to the axial bore,
and a second segment extending from the axial bore to the outer
surface on an opposite, second side of the bit skirt; the axial
bore having upper and lower portions; the upper portion of the
axial bore defining a circumferential shelf; and a bit retainer
including a retainer tube and substantially identical first and
second pins; the retainer tube extending longitudinally within the
axial bore of the percussion bit from an upper end portion to a
lower end portion; the upper end portion having a circumferential
collar extending radially outward therefrom, the collar being
supported on the shelf; the lower end portion defining oppositely
disposed, first and second openings, the first and second openings
each have an inside diameter; each pin having outer and inner
segments; the inner segment of each pin having an outside diameter
which is smaller than the inside diameters of the transverse bore
and the openings of the retainer tube; the outer segment of each
pin having an outside diameter selected for frictional engagement
between the outer segment of the pin and the transverse bore; the
first and second pins being disposed in the first and second
segments of the transverse bore, the outer segment of each pin
extending from the outer surface of the bit skirt to an
intermediate position between the outer surface of the bit skirt
and the axial bore, the inner segment extending from the
intermediate position through a one of the openings of the retainer
tube.
Description
BACKGROUND OF THE INVENTION
[0001] This invention relates generally to earth boring percussion
bits. More particularly, the invention relates to retention systems
for ensuring that even when broken during use, the percussion bit
remains connected to the drill string.
[0002] U.S. Pat. No. 5,065,827 discloses a conventional hammer and
percussion bit assembly having a percussion bit retention system.
The percussion bit retention system includes a retainer which is
mounted on the drive sub of the percussion bit assembly. The
retainer includes a lower section having an inner chamber and a
thread-shaped, inwardly extending projection. The bottom portion of
the percussion bit includes a head section, a threaded section and
a recess disposed intermediate the head section and the threaded
section. The percussion bit is installed by inserting the upper
portion of the percussion bit into the retainer until the threaded
section of the lower portion abuts the thread-shaped projection of
the retainer. The projection is brought into threaded engagement
with the threaded section of the retainer and the retainer is
rotated until the projection passes completely through the threaded
section of the retainer and enters the chamber. If the percussion
bit breaks in the shaft portion above the bottom portion of the
percussion bit, the projection will be captured within the chamber
by the threaded section of the retainer.
[0003] The threaded section of such retainers may become fouled
during drilling operations, making removal of the percussion bit
difficult. Bits may be difficult to install due to corrosion and
wear induced degradation of the threaded section of the
retainer.
[0004] U.S. Pat. No. 6,070,678, discloses a bit retention system
having a substantially tubular retainer member. The retainer member
has a bore of substantially uniform internal diameter which can
slip over the retention shoulder of the percussion bit, whether
that shoulder is solid or threaded. Pins are then driven through
holes in the retainer, under the retention shoulder. The pins
retain the head of the bit in the event of bit breakage. Although
this bit retention system eliminates many of the problems
associated with threaded bit retention systems of the type
described above, the system requires modification of the chuck.
Accordingly, the system cannot be used until a modified chuck is
installed on the drill string.
SUMMARY OF THE INVENTION
[0005] With the present invention, a novel percussion bit assembly,
and associated novel bit retainer, can be simply achieved without
the requirement for rotating the bit relative to the retainer, and
without the risk of thread fouling.
[0006] In accordance with the invention, a percussion bit assembly
comprises a percussion bit having an upper, elongated bit shank, a
lower bit head, and a bit skirt disposed intermediate the bit shank
and the bit head. The percussion bit has an axial bore extending
longitudinally through at least the bit shank and the bit skirt and
at least one receptacle extending radially outward from the lower
portion of the axial bore. A bit retainer includes at least one
longitudinal member and at least one lateral member. The
longitudinal member extends longitudinally within the axial bore of
the percussion bit from an upper end portion, mounted within the
upper portion of the axial bore, to a lower end portion disposed in
the lower portion of the axial bore. The lateral member extends
laterally from a radially inner end portion connected to the lower
end portion of the longitudinal member to a radially outer end
portion mounted in the receptacle.
[0007] The upper portion of the percussion bit axial bore forms a
circumferential shelf. In one embodiment, the bit retainer includes
a pair of retainer bars, with each of the retainer bars having a
longitudinal portion and a lateral portion defining the
longitudinal and lateral members. A radially outer end portion of
each lateral portion is received in one of a pair of
circumferentially spaced receptacles. The upper end portion of each
longitudinal portion has a tab extending radially outward therefrom
which are supported on the shelf of the percussion bit axial bore.
The bit retainer also includes upper and lower spacers. The upper
spacer is positioned proximate to the upper end portions of the
retainer bars and the lower spacer is positioned proximate to the
lower end portions of the retainer bars, such that the upper and
lower spacers prevent radial movement of the tabs and the lateral
portion of the retainer bars.
[0008] The lower end portion of each retainer bar includes a
protrusion extending radially inward into the axial bore, with the
lower spacer being supported on the protrusions of the retainer
bars. The lower spacer is an H-shaped member forming a pair of
oppositely disposed indentations and an axial opening. The lower
end portion of one of the retainer bars is received in each of the
indentations.
[0009] The upper spacer is a substantially cylindrical member,
having a wall forming an axial opening and a pair of oppositely
disposed indentations extending radially inward into the opening.
The upper end portion of the longitudinal portion of one of the
retainer bars is received in each of the indentations. The upper
spacer is supported on the shelf of the percussion bit axial
bore.
[0010] In another embodiment, the receptacle is a transverse bore
extending from the outer surface on a first side of the bit skirt,
through the axial bore, and into an opposite, second side of the
bit skirt. The longitudinal member is a retainer tube having a
lower end portion with oppositely disposed openings. The upper end
portion of the retainer tube has a radially extending
circumferential collar which is supported on a shelf formed in the
upper portion of the percussion bit bore. The lateral member is a
pin having a first end portion positioned in a segment of the
transverse bore in the first side of the bit skirt, a middle
portion extending through the openings of the retainer tube lower
end portion, and a second end portion positioned in a segment of
the transverse bore in the second side of the bit skirt.
[0011] In one variation of this embodiment, the first end portion
of the pin includes outer and inner segments. The outer segment
extends from the outer surface of the first side of the bit skirt
to an intermediate position between the outer surface of the first
side of the bit skirt and the axial bore, with the inner segment
extending from the intermediate position to the axial bore. The
second end and middle portions of the pin and the inner segment of
the first end portion of the pin have a substantially uniform
outside diameter which is smaller than the inside diameters of the
transverse bore and the openings of the retainer tube, to
facilitate insertion of the pin into the transverse bore. The outer
segment of the first end portion of the pin has an outside diameter
selected such that the outer segment frictionally engages the
transverse bore after the pin is inserted.
[0012] In a second variation of the embodiment, the segment of the
transverse bore in the first side of the bit skirt includes outer
and inner portions, with the outer portion extending from the outer
surface of the first side of the bit skirt to an intermediate
position between the outer surface of the first side of the bit
skirt and the axial bore. The pin has a substantially uniform
outside diameter which is smaller than the inside diameters of the
transverse bore and the openings of the retainer tube, to
facilitate insertion of the pin into the transverse bore. The first
end portion of the pin is disposed in the transverse bore segment
inner portion and a plug is fixedly mounted in the transverse bore
segment outer portion.
[0013] In still another embodiment, the receptacle is a transverse
bore which extends radially through the bit skirt, having a first
segment extending from the outer surface on a first side of the bit
skirt to the axial bore and a second segment extending from the
axial bore to the outer surface on an opposite, second side of the
bit skirt. The longitudinal member is a retainer tube having a
lower end portion with oppositely disposed openings. The lateral
member is substantially identical first and second pins, each
having outer and inner segments. The inner segment of each pin has
an outside diameter which is smaller than the inside diameters of
the transverse bore and the openings of the retainer tube while the
outer segment of each pin has an outside diameter selected such
that the outer segment frictionally engages the transverse bore
after the pin is inserted. The first and second pins are disposed
in the first and second segments of the transverse bore, with the
outer segment of each pin extending from the outer surface of the
bit skirt to an intermediate position between the outer surface of
the bit skirt and the axial bore and the inner segment extending
from the intermediate position through a one of the openings of the
retainer tube.
[0014] It is thus an object of the invention to provide a new and
improved retention system for a percussion bit assembly.
[0015] It is also an object of the invention to provide a retention
system for a percussion bit assembly that is self-contained within
the percussion bit.
[0016] Other objects and advantages of the invention will become
apparent from the drawings and specification.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] The present invention may be better understood and its
numerous objects and advantages will become apparent to those
skilled in the art by reference to the accompanying drawing in
which:
[0018] FIG. 1 is an elevation view, partly in section and partly in
phantom, of a conventional hammer-percussion bit assembly;
[0019] FIG. 2 is a simplified, enlarged view, partly in section and
partly in phantom, of the lower end portion of a hammer-percussion
bit assembly according to a first embodiment of the invention;
[0020] FIG. 3 is an enlarged top view of the upper spacer of FIG.
2;
[0021] FIG. 4 is an enlarged top view of the lower spacer of FIG.
2;
[0022] FIG. 5 is a side view of the retainer bar of FIG. 2;
[0023] FIG. 6 is a simplified, enlarged view, partly in section and
partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a second embodiment of
the invention;
[0024] FIG. 7 is a simplified, enlarged view, partly in section and
partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a third embodiment of
the invention;
[0025] FIG. 8 is a simplified, enlarged view, partly in section and
partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a fourth embodiment of
the invention;
[0026] FIG. 9 is a simplified, enlarged view, partly in section and
partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a fifth embodiment of
the invention;
[0027] FIG. 10 is a simplified, enlarged view, partly in section
and partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a sixth embodiment of
the invention;
[0028] FIG. 11 is an enlarged cross section view taken along line
XI-XI of FIG. 9;
[0029] FIG. 12 is an enlarged cross section view taken along line
XII-XII of FIG. 10; and
[0030] FIG. 13 is a simplified, enlarged view, partly in section
and partly in phantom, of the lower end portion of the
hammer-percussion bit assembly according to a seventh embodiment of
the invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0031] A hammer-percussion bit assembly 10 with a conventional bit
retention system 12, is shown in FIG. 1. The percussion bit
assembly comprises a hammer housing 14 threadably connected at its
upper end portion 16 to a drill string mounting member 18. An
opening in the lower end 20 of the housing 14 receives the upper
portion 22 of tubular chuck member 24 and is threadably connected
thereto.
[0032] A lock cylinder 26 and a split lock ring 28 are positioned
within the interior of the housing 14. The upper portion 30 of the
percussion bit shank 32 is disposed within the lock ring 28 and
lock cylinder 26 such that an upper radially extending shoulder 34
on the upper portion 30 is positioned within the lock cylinder 26
and above the lock ring 28. The inside diameters of the lock
cylinder 26 and the lock ring 28 and the outside diameter of the
upper shoulder 34 are selected such that the upper shoulder 34 is
free to move up and down within the lock cylinder 26 and is
captured by the lock ring 28.
[0033] The upper portion 30 of the percussion bit shank 32 also
includes an upper bearing surface 36. The percussion bit shank 32
has a lower bearing surface 38 adapted for bearing against the
lower surface 40 of the chuck member 24. The bottom surface 42 of
the hammer impact piston 44 impacts against the upper bearing
surface 36 to impart a percussive force to the bit 46.
Alternatively, the percussive force may be transmitted through the
lower surface 40 of the chuck member 24 to the lower bearing
surface 38 of the bit 46.
[0034] A percentage of all percussion bits shanks 32 fail due to
cyclic fatigue by fracturing below the lock ring 28 and above the
bit head 48. When this occurs during the drilling operation, the
lower section of the percussion bit is left at the bottom of the
hole, requiring a costly and cumbersome fishing operation.
[0035] Percussion bit retention system 12 employs a cylindrical
retainer member 50 disposed around the lower portion 52 of the
chuck member 24 and the shoulder 54 of the bit 46. A pair of pins
56 are insertable through a pair of holes in the lower portion of
the retainer member 50 below the shoulder 54 of the bit 46. A
longitudinal channel is defined between the upper end of retainer
member 50 and the pair of pins 56, having a length selected to
receive the lower portion 52 of the chuck member 24 and to allow
free vertical movement of the lower shoulder 54 of the percussion
bit 46. In the event of breakage of the bit shank 32 above the bit
shoulder 54, the shoulder 54 engages the pins 56 to retain the
broken bit.
[0036] A bit retention system 58, 106, 118, 126, 138, 140, 198 in
accordance with the invention is integral with the bit 60.
Accordingly, such a bit 60 may be used with any standard drill
without requiring modification of the drill. With reference to
FIGS. 2-5, a first embodiment of a bit retention system 58 in
accordance with the invention includes a pair of retainer bars 62
and upper and lower spacers 64, 66.
[0037] Each retainer bar 62 has an upper end portion 68 including a
radially extending tab 70, an intermediate portion 72 extending
downwardly from upper end portion 68, and a radial retainer portion
74 extending perpendicularly from the intermediate portion 72. The
bottom end of intermediate portion 72 includes a radially extending
protrusion 76. The retainer bars 62 are inserted longitudinally
into the upper end 78 of the bit axial bore 80, retainer portion 74
first, until the lower surface 82 of each tab 70 is positioned just
above the location of a shelf 84 formed in bore 80 and each
retainer portion 74 is positioned proximate to a receptacle 86, 86'
in extending radially outward from bore 80. Receptacle 86 is
positioned 180 degrees from receptacle 86'. The retainer bars 62
are urged radially outward such that the retainer portions 74 are
inserted into the receptacles 86, 86', whereby the retainer bars 62
are positioned on opposite sides of bore 80, and the tabs 70 are
positioned above shelf 84.
[0038] The lower spacer 66 is an H-shaped member (with the H laying
on its side) having a pair of oppositely disposed indentations 88
and an axial opening 90. The lower spacer 66 is inserted through
the upper end 78 of bore 80, with a retainer bar 62 sliding through
each of the indentations 88, until the lower surface 92 of the
lower spacer 66 rests on the retainer bar protrusions 76, thereby
locking each retainer portion 74 within the corresponding
receptacle 86, 86'. The H-shape of the lower spacer 66 and the
opening 90 provides sufficient mechanical strength to hold the
retainer portion 74 of each retainer bar 62 in position while
minimizing interference with flow through bore 80.
[0039] The upper spacer 64 is substantially cylindrical, having a
wall 94 forming an axial opening 96 and having a pair of oppositely
disposed indentations 98 extending radially inward into the opening
96. The upper spacer 64 is inserted into the upper end 78 of bore
80 such that the upper end portion 68 of each retainer bar 62 is
received in one of the indentations 98, thereby locking upper end
portion 68 in radial position, and the lower surface 100 of the
upper spacer 64 rests on shelf 84. An exhaust tube 102 is then
mounted within the upper end of bore 80 to prevent longitudinal
movement of the upper spacer 64. The wall 94 has a thickness
selected to provide sufficient mechanical strength to hold the
upper end portion 68 of each retainer bar 62 in position while
minimizing interference with flow through bore 80.
[0040] Shelf 84 is located on the bit shank 103 and receptacles 86,
86' are located in the skirt 104 of bit head 105. It should be
appreciated that substantially all of the bit shank failures
described above occur in the portion of the bit shank 103 located
between these two locations. It should also be appreciated that
while the upper and lower spacers 64, 66 lock the retainer bars 62
in position, the retainer bars 62 are not so rigidly mounted to the
bit 107 that they are subjected to the impact stress experienced by
the bit 107. Accordingly, the majority of broken bits will be
retained by the subject bit retention system 58.
[0041] In a second embodiment of the bit retention system 106 (FIG.
6), the upper end and intermediate portions 68, 72 of the retainer
bar 62' are substantially identical to the upper end and
intermediate portions 68, 72 of the retainer bar 62 of the first
embodiment 58. However in this embodiment, the retainer portion 108
includes an upper segment 110 that extends downward, parallel to
the intermediate portion 72, and a lower segment 112 that extends
at an obtuse angle from the upper segment 110. The retainer
portions 108 are received in oppositely disposed receptacles 114
which extend radially away from the bore axis 115 and
longitudinally toward the face 116 of the bit head 105.
[0042] In a third embodiment of the bit retention system 118 (FIG.
7), the upper end portion 68 of the retainer bar 62" is
substantially identical to the upper end portion 68 of the retainer
bar 62 of the first embodiment 58. However, the intermediate
portion 120 is longer, extending further into the bit skirt 104 in
the installed condition, and the retainer portion 122 extends at an
acute angle from the intermediate portion 120. The retainer
portions 122 are received in oppositely disposed pit-shaped
receptacles 124 which extend longitudinally away from the face 116
of the bit head 105.
[0043] In a fourth embodiment of the bit retention system 126 (FIG.
8), the upper end and intermediate portions 68, 72 of the retainer
bar 62'" are substantially identical to the upper end and
intermediate portions 68, 72 of the retainer bar 62 of the first
embodiment 58. The retainer portion 128 extends at an obtuse angle
from the intermediate portion 72. The retainer portions 128 are
received in oppositely disposed receptacles 130 which extend
radially away from the bore axis 115 and longitudinally toward the
face 116 of the bit head 105. However, the angle 132 formed between
retainer portion 128 and intermediate portion 72 is smaller than
the angle 134 formed between the upper and lower segments 110, 112
of retainer portion 108 (FIG. 6). Since retainer portion 128 does
not include the upper segment 110 of retainer portion 108,
receptacles 130 may be formed by drilling holes from the outer
surface 136 of the bit skirt 104.
[0044] In fifth, sixth and seventh embodiments of the bit retention
system 138, 140, 198 (FIGS. 9-13), a single retainer tube 142 is
used instead of the two retainer bars 62, 62', 62", 62'". The upper
end portion 144 of the tube 142 has a circumferential, radially
extending collar 146 which has a lower surface 148 that rests on
shelf 84. The tube 142 extends from upper end portion 144 to a
lower end portion 150 disposed in the bit skirt 104. For
embodiments 138 and 140, a single blind bore 152 extends from the
outer surface 136 of the bit skirt 104, through the first side 154
of the bit skirt 104, through the bit bore 80 and partially through
the second side 156 of the bit skirt 104. In embodiment 198,
oppositely disposed bores 200 extend from the outer surface 136 of
the bit skirt 104, through each of the first and second sides 154,
156 of the bit skirt 104, to the bit bore 80. When installed, a
pair of oppositely disposed openings 158 in the lower end portion
150 of the tube 142 align with the blind bore 152/bores 200. The
upper end portion 144 of the tube 142 is locked to the upper bit
shank 103 by the exhaust tube 102 and the lower end portion 150 of
the tube 142 is locked to the bit head 105 by a pin 160, 160'/pins
160". In the fifth and sixth embodiments 138, 140 pin 160, 160'
extends from the outer surface 136 of the bit skirt 104, through
the first side 154 of the bit skirt 104, through the bit bore 80.
The second end portion 162 of the pin 160, 160' is positioned in
blind bore segment 164, the middle portion 166 is positioned within
openings 158, and the first end portion 168, 168' is positioned in
the blind bore segment 170. In the seventh embodiment 198, each of
the pins 160" extends from the outer surface 136 of the bit skirt
104, through one of the sides 154, 156 of the bit skirt 104, with
the middle portion 166" extending through one of the openings 158
and partially into the bit bore 80.
[0045] In the embodiment 138 shown in FIGS. 9 and 11, the second
end portion 162, the middle portion 166 and an inner segment 172 of
the first end portion 168 have a uniform diameter 174 which is
sufficiently smaller than the inside diameter 176 of blind bore 152
and openings 158 to allow easy passage therethrough. An outer
segment 178 of the first end portion 168 has an outside diameter
180 which is greater than outside diameter 174. Diameter 180 is
selected such that the outer surface 182 of outer segment 178 will
frictionally engage the inner surface 184 of blind bore segment 170
to lock an installed pin 160 within blind bore 152. To install the
pin 160, the bit skirt 104 is heated sufficiently to increase
inside diameter 176, the pin 160 is inserted into blind bore 152,
and the bit skirt 104 is allowed to cool. As the bit skirt cools,
inside diameter 176 returns to its original size, thereby clamping
the outer segment 178 of the pin 160 within blind bore segment 170.
Any part of outer segment 178 which extends beyond the outer
surface 136 of bit skirt 104 may be machined flush with the surface
136.
[0046] In the embodiment 140 shown in FIGS. 10 and 12, the entire
pin 160' has a uniform diameter 186 which is sufficiently smaller
than the inside diameter 188 of blind bore 152 and openings 158 to
allow easy passage therethrough. The pin 160' has a length 190 that
is less than the length 192 of blind bore 152. Accordingly, an
outer portion 194 of bore segment 170 remains empty after the pin
160' is fully inserted into blind bore 152. A plug or a plug weld
196 is installed in this outer portion 194 to lock the pin 160' in
blind bore 152.
[0047] The embodiment 198 shown in FIG. 13 is a variation of
embodiment 138, with two pins 160" and two bores 200 in place of
the single pin 160 and blind bore 152 of embodiment 138. Preferably
the bores 200 are positioned substantially 180.degree. apart. Each
pin 160" has a first end portion 168 having an inner segment 172
and an outer segment 178, similar to pin 160. However, the middle
portion 166" of each pin 160" only extends through one of the
openings 158 and a short distance into retainer tube 142,
preferably about 1/4 inch. Neither pin 160" has the second end
portion 162 of pin 160. Similar to pin 160, the middle portion 166"
and the inner segment 172 of the first end portion 168 have a
uniform diameter 174 which is sufficiently smaller than the inside
diameter 202 of bore 200 and openings 158 to allow easy passage
therethrough. The outer segment 178 of the first end portion 168
has an outside diameter 180 which is greater than outside diameter
174 such that the outer surface of outer segment 178 will
frictionally engage the inner surface of bore 200 to lock an
installed pin 160" within bore 200. To install the pins 160", the
bit skirt 104 is heated sufficiently to increase inside diameter
202, one of the pins 160" is inserted into each bore 200, and the
bit skirt 104 is allowed to cool. As the bit skirt cools, inside
diameter 176 returns to its original size, thereby clamping the
outer segment 178 of the pins 160" within the bores 200. Any part
of outer segment 178 which extends beyond the outer surface 136 of
bit skirt 104 may be machined flush with the surface 136. The pins
160" of this embodiment 198 restrict the flow passage within the
retainer tube 142 less than the pin 160 of embodiment 138.
[0048] While preferred embodiments have been shown and described,
various modifications and substitutions may be made thereto without
departing from the spirit and scope of the invention. Accordingly,
it is to be understood that the present invention has been
described by way of illustration and not limitation.
* * * * *