U.S. patent number 3,896,886 [Application Number 05/387,481] was granted by the patent office on 1975-07-29 for bore hole hammer drill.
This patent grant is currently assigned to Bakerdrill, Inc.. Invention is credited to Theodore J. Roscoe, Jr..
United States Patent |
3,896,886 |
Roscoe, Jr. |
July 29, 1975 |
**Please see images for:
( Certificate of Correction ) ** |
Bore hole hammer drill
Abstract
An air hammer embodying an outer housing structure connectable
to a rotatable drill pipe string through which compressed air is
conducted. A hammer piston reciprocates in the housing structure,
compressed air being directed alternately to the upper and lower
ends of the piston to effect its reciprocation in the structure,
each downward stroke inflicting an impact blow upon the anvil
portion of an anvil bit extending upwardly within the lower portion
of the housing structure. The flow of air to the upper and lower
ends of the hammer piston is controlled by valve passages formed in
the piston and a relatively stationary air supply tube which closes
the passage to the lower end of the piston when the outer housing
structure is lifted by the drill pipe string to allow the bit to
hang down from the housing during the circulation of air for
flushing cuttings from the bore hole.
Inventors: |
Roscoe, Jr.; Theodore J.
(Houston, TX) |
Assignee: |
Bakerdrill, Inc. (Spartanburg,
SC)
|
Family
ID: |
23530058 |
Appl.
No.: |
05/387,481 |
Filed: |
August 10, 1973 |
Current U.S.
Class: |
173/17; 173/66;
173/80; 173/131 |
Current CPC
Class: |
E21B
21/16 (20130101); E21B 4/14 (20130101) |
Current International
Class: |
E21B
21/00 (20060101); E21B 21/16 (20060101); E21B
4/00 (20060101); E21B 4/14 (20060101); E21b
005/00 (); E21c 007/00 () |
Field of
Search: |
;173/64-73,78,80,136,17 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Purser; Ernest R.
Assistant Examiner: Pate, III; William F.
Attorney, Agent or Firm: Kriegel; Bernard
Claims
I claim:
1. In percussion drilling apparatus: a housing structure
connectable to a drill string; an anvil in the lower portion of
said housing structure and operatively connectable to a drill bit;
said anvil having an exhaust passage; a hammer piston reciprocable
in said housing structure for intermittently impacting against said
anvil, said piston having an upper passage; inlet means for
directing a fluid medium under pressure into said upper passage;
first passage means for directing the fluid medium from said upper
passage into said housing structure above said piston upon upward
movement of said piston in said housing structure for driving said
hammer piston downwardly toward said anvil; second passage means
for directing the fluid medium from said upper passage into said
housing structure below said piston upon downward movement of said
piston in said housing structure; means for alternately exhausting
the fluid medium from the housing structure above and below said
piston; stop means for supporting said anvil in a lower position in
said housing upon elevation of said housing; means defining a fluid
circulating path from the interior of said inlet means to the
exterior of said housing structure when said anvil is supported by
said stop means; said circulating path including the region of said
housing structure around said inlet means above said piston and
also said anvil exhaust passage; and valve means for closing off
said second passage means when said anvil is supported by said stop
means to prevent flow of the fluid medium from said upper passage
into said second passage means and into said housing structure
below said piston.
2. In percussion drilling apparatus: a housing structure
connectable to a drill string; an anvil in the lower portion of
said housing structure and operatively connectable to a drill bit;
a hammer piston reciprocable in said housing structure for
intermittently impacting against said anvil, said piston having an
upper passage; inlet means for directing a fluid medium under
pressure into said passage; first passage means for directing the
fluid medium from said passage into said housing structure above
said piston upon upward movement of said piston in said housing
structure for driving said hammer piston downwardly toward said
anvil; second passage means for directing the fluid medium from
said passage into said housing structure below said piston upon
downward movement of said piston in said housing structure for
elevating said piston in said housing structure; means for
alternately exhausting the fluid medium from the housing structure
above and below said piston; stop means for supporting said anvil
in a lower position in said housing upon elevation of said housing;
means defining a fluid circulating path from the interior to he
exterior of said housing when said anvil is supported by said stop
means; and valve means for closing off said second passage means
when said anvil is supported by said stop means to prevent flow of
the fluid medium from said upper passage into said second passage
means and into said housing structure below said piston; the lower
portion of said passage being substantially closed, whereby the
fluid medium under pressure acts over substantially the full
cross-sectional area of said piston in driving said piston
downwardly toward said anvil.
3. In apparatus as defined in claim 1; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure.
4. In apparatus as defined in claim 1; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure; said inlet means
and said piston also having said valve means for closing off said
second passage means when said anvil is supported by said stop
means.
5. In apparatus as defined in claim 2; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure.
6. In apparatus as defined in claim 1; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure; said exhausting
means including exhaust passage means through which the exhaust
fluid medium passes alternately from said housing structure above
and below said hammer piston, said exhausting means further
including co-engaging valve means on said piston and housing
structure for controlling said alternate passage of the exhaust
fluid medium.
7. In apparatus as defined in claim 1; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure; said exhausting
means including exhaust passage means through which the exhaust
fluid medium passes alternately from said housing structure above
and below said hammer piston, said exhausting means further
including coengaging valve means on said piston and housing
structure for controlling said alternate passage of the exhaust
fluid medium; said inlet means and said piston also having said
valve means for closing off said second passage means when said
anvil is supported by said stop means.
8. In apparatus as defined in claim 2; said inlet means and piston
having coengaging valve means thereon opening said first passage
means and closing said second passage means upon upward movement of
said piston in said housing structure and closing said first
passage means and opening said second passage means upon downward
movement of said piston in said housing structure; said exhausting
means including exhaust passage means through which the exhaust
fluid medium passes alternately from said housing structure above
and below said hammer piston, said exhausting means further
including coengaging valve means on said piston and housing
structure for controlling said alternate passage of the exhaust
fluid medium; said inlet means and said piston also having said
valve means for closing off said second passage means when said
anvil is supported by said stop means.
9. In percussion drilling apparatus: a housing structure
connectable to a drill string; an anvil in the lower portion of
said housing structure and operatively connectable to a drill bit;
said anvil having an exhaust passage; a hammer piston reciprocable
in said housing structure for intermittently impacting against said
anvil, said piston having a central upper chamber therein; an inlet
tube piloted in said chamber and adapted to receive a fluid medium
under pressure from the drill string and direct such fluid medium
into said chamber; first passage means for directing the fluid
medium from said upper chamber into said housing structure above
said piston; second passage means for directing the fluid medium
from said upper chamber into said housing structure below said
piston; coengaging valve means on said tube and piston wall of said
chamber opening said first passage means and closing said second
passage means upon upward movement of said piston in said housing
structure and closing said first passage means and opening said
second passage means upon downward movement of said piston in said
housing structure; means for alternately exhausting the fluid
medium from the housing structure above and below said piston; stop
means for supporting said anvil in a lower position in said housing
upon elevation of said housing; means defining a fluid circulating
path from the interior of said inlet tube to the exterior of said
housing structure when said anvil is supported by said stop means;
said circulating path including the region of said housing
structure around said inlet tube above said piston and also said
exhaust passage; and valve means for closing off said second
passage means when said anvil is supported by said drop means to
prevent flow of the fluid medium from said upper chamber into said
second passage means and into said housing structure below said
piston.
10. In percussion drilling apparatus: a housing structure
connectable to a drill string; an anvil in the lower portion of
said housing structure and operatively connectable to a drill bit;
a hammer piston reciprocable in said housing structure for
intermittently impacting against said anvil, said piston having a
central upper chamber therein; an inlet tube piloted in said
chamber and adapted to receive a fluid medium under pressure from
the drill string and direct such fluid medium into said chamber;
first passage means for directing the fluid medium from said
chamber into said housing structure above said piston; second
passage means for directing the fluid medium from said chamber into
said housing structure below said piston; coengaging valve means on
said tube and piston wall of said chamber opening said first
passage means and closing said second passage means upon upward
movement of said piston in said housing structure and closing said
first passage means and opening said second passage means upon
downward movement of said piston in said housing structure; means
for alternately exhausting the fluid medium from the housing
structure above and below said piston; stop means for supporting
said anvil in a lower position in said housing upon elevation of
said housing; means defining a fluid circulating path from the
interior to the exterior of said housing when said anvil is
supported by said stop means; and valve means for closing off said
second passage means when said anvil is supported by said stop
means to prevent flow of the fluid medium from said upper chamber
into said second passage means and into said housing structure
below said piston; the lower portion of said chamber being
substantially closed, whereby the fluid medium under pressure acts
over substantially the full cross-sectional area of said piston in
driving said piston downwardly toward said anvil.
11. In apparatus as defined in claim 9; the last-mentioned valve
means including a valve section on said inlet tube for closing said
second passage means.
12. In apparatus as defined in claim 9; said exhausting means
including exhaust passage means through which the exhaust fluid
medium passes alternately from said housing structure above and
below said hammer piston, said exhausting means further including
coengaging valve means on said piston and housing structure for
controlling said alternate passage of the exhaust fluid medium;
said valve means for closing said second passage means when said
anvil is supported by said stop means including a valve section on
said inlet tube.
13. In apparatus as defined in claim 10; said exhausting means
including exhaust passage means through which the exhaust fluid
medium passes alternately from said housing structure above and
below said hammer piston, said exhausting means further including
coengaging valve means on said piston and housing structure for
controlling said alternate passage of the exhaust fluid medium;
said valve means for closing said second passage means when said
anvil is supported by said stop means including a valve section on
said inlet tube.
14. In apparatus as defined in claim 9; said exhausting means
including exhaust passage means through which the exhaust fluid
medium passes alternately from said housing structure above and
below said hammer piston, said exhausting means further including
coengaging valve means on said piston and housing structure for
controlling said alternate passage of the exhaust fluid medium;
said exhausting means further including said anvil passage which
communicates with an exhaust passage in the lower portion of said
piston and communicable with said exhaust passage means under the
control of said valve means on said piston and housing structure;
said valve means for closing said second passage means when said
anvil is supported by said stop means including a valve section on
said inlet tube.
15. In an air hammer: an elongated housing, a hammer piston
reciprocable in said housing, an anvil carried by said housing and
having an exhaust passage, said anvil and said housing having
abutment means coengageable to limit movement of said anvil
inwardly with respect to said housing and stop means for limiting
movement of said anvil outwardly with respect to said housing, air
inlet means including a valve tube connected to said housing, said
hammer piston having a bore receiving said valve tube, said hammer
piston having passage means alternately opened and closed by said
valve tube upon reciprocation of said hammer piston to supply and
exhaust air to said housing at opposite ends of said hammer piston,
said housing and said hammer piston defining therebetween an
exhaust passage communicating with said housing at one end of said
hammer piston, additional valve means on said tube and said hammer
piston when said anvil is limited by said stop means against
outward movement with respect to said housing, means defining a
fluid circulation path from the interior of said valve tube to the
exterior of said housing when said anvil is limited by said stop
means against outward movement with respect to said housing, said
circulation path including the region of said housing around said
valve tube above said hammer piston and also said anvil exhaust
passage.
16. In an air hammer as defined in claim 15; said valve tube having
longitudinally spaced cylindrical valve sections thereon, said
hammer piston having axially spaced cylindrical walls separating
said passage means and sealingly engageable with said cylindrical
valve section to open and close said passage means in said hammer
piston.
17. In an air hammer as defined in claim 15; spline type drive
means between said housing and said anvil for transmitting rotation
from said housing to said anvil while allowing relative axial
movement thereof.
18. In apparatus as defined in claim 1; said first passage means
being provided between said inlet means and upper piston passage
and opening centrally through the upper end of said upper passage
into said housing structure above said piston.
19. In apparatus as defined in claim 9; said first passage means
being provided between said inlet tube and upper chamber and
opening centrally through the upper end of said upper chamber into
said housing structure above said piston.
Description
BACKGROUND OF THE INVENTION
The present invention relates to drill pipe apparatus for drilling
a bore hole in a formation, and more particularly to pneumatically
operated apparatus that imparts a percussive action to a drill bit
while the latter is preferaby being rotated, in order that the bit
may cover substantially the full area of the bore hole bottom.
As disclosed in the pending application for letters Patent of the
United States, Ser. No. 246,837, filed Apr. 24, 1972, in the name
of Alfred R. Curington, an air hammer is disclosed wherein the
housing structure in which the hammer piston is reciprocable is of
a simple design and is economical to manufacture. The reciprocating
hammer piston coacts with the housing structure in such a manner as
to alternately direct compressed air into the housing structure at
the upper and lower ends of the piston, and alternately effects
exhaust of the air from the upper and lower portions of the housing
structure. The compressed air on the power stroke of the hammer
piston acts over its full cross-sectional area, which is the full
cross-sectional area of the inner wall of the housing structure
itself, such area having a maximum value. After traversing the
major portion of its power or downward stroke, the hammer piston
shifts to an exhaust condition. During the downward shifting of the
hammer piston on its power stroke, the air therebelow is compressed
to some extent, but despite the presence of such compressed air,
which remains after the hammer piston opens it exhaust passage
before the piston impacts upon the anvil, a continuing supply of
inlet air pressure acts over a portion of the hammer piston area to
assist in driving the hammer piston downwardly against the anvil
and against the resistance of the air compressed below the hammer
piston. Accordingly, a greater blow is struck against the anvil
than in prior devices.
In the use of the aforesaid air hammer drill, it sometimes is
necessary or desirable to circulate air down the drill pipe string,
from the lower end of the apparatus, and then upwardly in the bore
hole, while the drilling is interrupted. The prior air control
valve means for alternately directing air to the upper and lower
ends of the piston is such that when the hammer drill housing is
lifted by the drill pipe string and the bit hangs downwardly from
the housing, the air can flow downwardly between the piston and the
housing and between the anvil bit or drill and the housing into the
bore hole. However, the cooperative air supply tube or valve tube
and the piston passages are such that during circulation, as just
described above, air also has access to the bottom of the piston,
and reciprocation of the piston can result, causing undesired
impacts of the piston on the bit while the bit is off of the bottom
of the bore hole.
SUMMARY OF THE INVENTION
The present invention involves a hammer drill or air hammer of the
type referred to above which incorporates an improved air valve
cooperative with the hammer piston to close off the passage leading
to the bottom of the hammer piston during circulation of air when
the housing is lifted upwardly by the drill pipe string to allow
the anvil bit or drill to hand downwardly from the housing.
More particularly, the air supply tube has a lower cylindrical
sealing section which closes the fluid passage or opening, through
which air flows to the bottom of the piston during hammer strokes
of the piston, when the piston moves downwardly and rests upon the
anvil of the bit upon elevation of the housing prior to circulation
of the air down the drill pipe, from the lower end of the apparatus
and upwardly in the bore hole.
This invention possesses many other advantages, and has other
purposes which may be made more clearly apparent from a
consideration of a form in which it may be embodied. A form is
shown in the drawings accompanying and forming part of the present
specification. It will now be described in detail, for the purpose
of illustrating the general principles of the invention; but it is
to be understood that such detailed description is not to be taken
in a limiting sense.
Referring to the drawings:
FIGS. 1a and 1b together constitute a longitudinal section through
an apparatus embodying the invention, with parts in their relative
positions for drilling and in which the hammer piston has completed
delivering an impact blow against the companion anvil bit, FIG. 1b
being a lower continuation of FIG. 1a;
FIGS. 2a and 2b are views similar to FIGS. 1a and 1b, with the
hammer piston approaching its upper position, FIG. 2b being a lower
continuation of FIG. 2a;
FIGS. 3a and 3b are views similar to FIGS. 1a and 1b, illustrating
the relationship of parts when the drill bit has been elevated from
the bottom of the hole, allowing air to be circulated through the
apparatus, FIG. 3b being a lower continuation of FIG. 3a;
FIG. 4 is a cross-section taken along the line 4--4 on FIG. 1a;
FIG. 5 is a cross-section taken along the line 5--5 on FIG. 1a;
FIG. 6 is a cross-section taken along the line 6--6 on FIG. 1b;
and
FIG. 7 is a cross-section taken along the line 7--7 on FIG. 1b.
DESCRIPTION OF THE PREFERRED EMBODIMENT
As shown in the drawings an air hammer apparatus A is provided that
is secured to the lower end of a string of drill pipe B, by means
of which the apparatus is rotated to correspondingly rotate an
impact anvil bit C used for drilling a bore hole D, the apparatus
delivering repeated impact blows upon the anvil bit when compressed
air is forced down the drill pipe for actuating the apparatus and
for cleaning the cuttings from the bottom E of the hole. The
apparatus is relatively simple, consisting of an elongate housing
structure 10 that includes an upper sub 11 having an upper threaded
box 12 (or threaded pin, not shown) for threaded attachment to the
lower end 13 of the string of drill pipe, that extends to the
drilling rig (not shown) at the top of the bore hole D. This sub is
threadedly secured to the upper portion of an elongate housing
section 14, which can be of one piece, the lower end of which is
threadedly secured to a lower housing head or drive member 15, the
lower end 16 of the housing section bearing against an upwardly
facing shoulder 17 formed on the head.
An elongate anvil portion 18 of the anvil bit C is piloted upwardly
within the drive member 15 and lower portion 19 of the housing
section 14, a hammer piston 20 being reciprocable in the housing
section above the anvil 18 to deliver repeated impact blows
thereagainst. The anvil is preferably formed integrally with the
drill bit portion 21 of the anvil bit, and which has suitable
cutting elements 22 (such as sintered carbide buttons 22) mounted
in its drilling face 23 for impacting against the bottom E of the
bore hole, to produce cuttings therein, the cutting elements 22
also acting against the side of the bore hole adjacent to its
bottom to insure the production of a bore hole D of the desired
diameter.
During the reciprocation of the hammer piston 20 in the housing to
deliver impact blows upon the anvil bit, the drill pipe string B
and housing structure 10 are rotated at a desired speed, such as 20
r.p.m., to correspondingly rotate the anvil bit C and insure an
impacting action of the cutting members 22 over substantially the
entire cross-sectional area of the bottom E of the hole. During the
impacting action, suitable drilling weight is imposed on the anvil
bit through the drill pipe string B and the housing structure 10,
such drilling weight being transferred from the lower end 24 of the
housing head or drive member 15 to an upwardly facing shoulder 25
of the bit 21. The rotary drive itself is transferred from the
housing structure 10 to the anvil 18 through a slidable spline type
of connection 26, which can assume several different forms, the
particular drive connection illustrated constituting no portion of
the present invention. The specific drive connection is illustrated
in the application of Alfred R. Curington and Archer W. Kammerer,
Jr., for "Bore Hole Air Hammer Drive Mechanism", Ser. No. 239,047,
filed Mar. 29, 1972, now U.S. Pat. No. 3,804,181 to which attention
is directed.
In general, the upper portion of the anvil has circumferentially
spaced elongate chordal surfaces 27 (FIG. 7), which are preferably
concave in shape, against which correspondingly shaped segments 28
bear, these segments being carried in circumferentially spaced
windows 29 in the drive member 15. The chordal surfaces 27 are
substantially longer than the length of the segments 28, permitting
relative longitudinal movement of the anvil bit C with respect to
the housing structure 10. The rotary effort is transferred from the
housing section 19 to the drive member 15 by virtue of the threaded
connection 30d, and from the sides 29a of the opening or windows 29
of the segments 28, from where the turning effort is transmitted
through the abutting segment surfaces 27a on the segments 28 and
anvil surfaces 27 to the anvil 18 of the bit C.
The housing section 14 includes an elongate upper inner cylindrical
housing wall 30, the lower end 31 of which constitutes an upper
housing flow control corner at the upper end of an elongate
internal circumferential exhaust groove 32 of a substantially
larger internal diameter than the diameter of the inner cylindrical
housing wall 30. Below the lower end 33 of the exhaust groove 32,
the housing section 19 is provided with a lower inner cylindrical
housing wall 34, which may be of the same internal diameter as the
upper housing wall 30, the upper end of the lower wall being the
housing lower flow control corner 33. The lower end 35 of the lower
inner cylindrical housing wall 34 provides a by-pass corner at the
upper end of an enlarged internal diameter circumferential by-pass
groove 36.
The elongate hammer piston 20 includes an upper piston portion 37
having an external diameter 37a conforming to the diameter of the
upper inner cylindrical housing 30, this upper piston portion
terminating at the upper end 38 of an external circumferential
exhaust groove 39 of a lesser external diameter than the upper
piston portion 37. This external exhaust groove terminates at a
lower piston portion 40 having an external diameter conforming to
the internal diameter of the lower inner cylindrical housing wall
34. Below its lower piston portion 40, the hammer is of a reduced
external diameter 41, providing a downwardly facing shoulder 42
which may, upon removal of the anvil bit C from the housing 10,
engage a limit ring 43 mounted in the housing section 14, to
prevent the piston 20 from inadvertently dropping out of the
housing structure. The hammer piston extends upwardly to a
substantial distance above its upper piston portion 37, having a
plurality of circumferentially spaced relief spaces 44 (FIG. 5)
which may be formed by elongate chords 45 in the hammer portion
extending from the upper piston portion 37 to the upper end 46 of
the latter, there being circumferentially spaced elongate arcuate
sections 47 between the chords 45 having the same external diameter
as the upper piston portion 37 and assisting in guiding the hammer
piston 20 in its reciprocation within the housing section 14.
As described hereinbelow, when the hammer piston 20 is at the lower
end of its stroke, as shown in FIGS. 1a, 1b, a flow control piston
corner 50 at the upper end of the piston portion 37 is spaced below
the upper housing flow control corner 31, allowing air in the
housing above the piston 20 to flow down through the passages 44
and into the internal circumferential exhaust groove 32, around the
upper piston portion 37, then into radial exhaust ports 51, formed
through the hammer piston below its intermediate piston wall 52,
that communicate with an elongate central piston cavity 53 into
which an exhaust tube 54 extends upwardly from the anvil 18, the
tube forming a continuation of the exhaust passage 53 and
communicating with an exhaust passage 55 through the anvil and
through one or a plurality of exhaust passages 56 extending
downwardly through the bit 21 and opening outwardly thereof for the
purpose of enabling the drilling fluid to flow into the bore hole D
for removing the cuttings from the bottom E of the hole. The tube
54 makes a slidable seal with the wall 53a of the piston cavity 53,
being secured to the anvil 18 by a lower outwardly extending tube
flange 57 being received within an inner circumferential groove 58
in the anvil. The tube may be made of an elastic material, such as
Delrin, which permits it to be inserted within the anvil passage,
the flange 57 contracting sufficiently until it is opposite the
circumferential groove 58, whereupon the tube flange can snap
outwardly into the groove 58 and thereby lock the tube 54 to the
anvil 18.
When the piston 20 is shifted upwardly within the housing on its
return stroke, the return air corner 60 at the lower end of the
lower piston portion 40 will be disposed above the housing lower
flow control corner 33 (FIGS. 2a, 2b), whereupon the compressed air
below the piston can exhaust into the internal circumferential
housing groove 32 and flow through the exhaust ports 51 and exhaust
passages 53, 55, 56 to the bottom E of the bore hole. At this time,
the upper flow control piston corner 50 will be disposed above the
upper housing flow control corner 31, which will seal the upper
piston portion 37 against the upper inner cylindrical housing wall
30, whereupon compressed air can drive the piston 20 downwardly on
its hammer or power stroke. When the return air corner 60 moves
below the housing lower flow control corner 33, the air below the
piston and within the housing, which remains after the lower piston
portion 40 is closed within the lower end of the cylindrical
housing wall 34, is subject to compression, but such air will be at
a relatively low pressure.
As described hereinbelow, in the event the apparatus is elevated to
raise the bit 21 from the bottom E of the hole, the latter will
drop downwardly until its upper anvil head flange 110 engages the
upper ends of the segments or keys 28. This will allow the upper
piston by-pass corner 62 to shift below the housing by-pass corner
35 at the lower end of the lower inner cylindrical housing wall 34,
the upper flow control piston corner being well below the upper
housing flow control corner (FIGS. 3a, 3b). Accordingly, compressed
air above the piston can flow through the passages 44 and the
internal circumferential exhaust groove 32 into the air by-pass
groove 36 below the lower housing wall 34, the air passing
downwardly through the passages 63 in the upper portion of the
anvil rotary drive member 15 and into the by-pass passages 64
between the segments and the surrounding housing wall, flowing
through the lower slots 65 in the segments and into the concave
cavities 27 in the anvil 18, the air flowing past a head sealing
portion 66 within the drive member 15 and into elongate relief
groove 67 extending downwardly through the lower end of the drive
member 15. When the anvil 18 is in its upper position within the
housing and with the bit shoulder 25 engaging the lower end 24 of
the drive member 15, the head sealing portion 66 seals against the
periphery 68 of the anvil below its elongate grooves 27 in which
the segments or keys 28 are positioned. To facilitate such sealing,
the head portion 66 may have a plurality of longitudinally spaced
internal labyrinth seal grooves 69 formed therein.
Compressed air for reciprocating the hammer piston 20 passes
downwardly through the string of drill pipe B and into the upper
housing sub 11, flowing past a downwardly opening check valve 70
which may be in the form of a ball 71 received within a valve body
72 mounted in a counterbore 73 in the sub, the ball being movable
upwardly to engage a companion seat 74 surrounding a central
passage 75 through the body, the downward movement of the ball
being limited by its engagement with circumferentially spaced feet
76 extending inwardly from the body. With air being pumped
downwardly through the apparatus, the ball 71 engages the feet 76
and the air can flow around the ball and between the feet and into
a central passage 77 in the housing sub.
The inlet air under pressure is caused to flow alternately into the
housing below the piston 20 and the housing above the piston, to
effect reciprocation of the hammer piston. A housing inlet and
valve tube 78 is mounted in the sub passage 77, projecting
downwardly from the sub or head 11 and into an upper elongate
central piston cavity or chamber 79 above the intermediate piston
wall 52, which separates the upper chamber 79 from the lower
chamber 53. The tube 78 is secured in the sub by an upper external
flange 80 on the tube fitting within a companion internal
circumferential groove 81 in the sub. The inlet tube is made of a
flexible material, such as Delrin, which permits the upper portion
of the tube to be deflected inwardly of the sub passage 77 below
the circumferential groove 81, and when the flange 80 becomes
aligned with the groove, the latter inherently expands outwardly
into the groove to secure the tube to the sub 11. The elastic
nature of the tube is such that it also provides a slidable seal
with the inner walls of the piston 20, as explained
hereinbelow.
The piston has an elongate upper cylindrical surface 82 opening
through its upper end 46 and terminating at an inner, upper flow
control piston corner 83, which is the upper end portion of an
elongate internal circumferential impact passage groove 84 having a
substantially larger internal diameter than the inside diameter of
the upper piston portion 82. The circumferential impact passage
groove 84 terminates at an intermediate inner cylindrical piston
wall 85, which may have the same internal diameter as the upper
cylindrical piston wall 82, the intermediate wall terminating at an
internal circumferential return passage groove 86 formed in the
piston and terminating at a lower flow control piston corner 87,
which is the upper end of a lower internal piston seal wall portion
88 and forms a bore extending between the intermediate piston wall
52 and the corner 87. The inlet tube 78 has an upper external
cylindrical sealing surface 89 relatively slidably sealable with
the upper piston wall 82 and terminating in an external
circumferential inlet groove 90 communicating with radial inlet
ports 91 that open to the central inlet passage 92 through the
tube. Below this circumferential inlet groove 90, the tube is
formed with an intermediate cylindrical sealing surface section 93
slidably and sealingly engageable with the intermediate inner
cylindrical piston wall 85 and also with the lower piston wall 88.
In accordance with the invention and as distinguished from the
structure of the aforementioned application Ser. No. 246,837, the
tube and valve member 78 has a lower sealing section 88a which is
of elongated cylindrical form and slidably fits in the lower bore
wall 88 and in the cylindrical piston wall 85. This valve or tube
section 88a has a length between its lower end 88b and an upper
corner 88c greater than the axial dimension of the return groove
86. Between the corner 88c on the tube or valve section 88a and the
intermediate sealing section 93, the tube has an annular groove 88d
which is a return flow groove.
When the piston 20 is in its lowermost operative position, with the
drill bit 21 pressed against the bottom E of the bore hole D,
compressed air can flow downwardly through the inlet passage 92,
discharging through ports 91, groove 84 and groove 88d, into the
circumferential return passage 86 that communicates with the upper
portion of one or more longitudinal return passages 95 extending
downwardly through the hammer piston and opening outwardly through
its lower end 96. When the hammer piston 20 moves upwardly within
the housing 10 and along the inlet tube 78, the lower flow control
piston corner 87 shifts upwardly over the lower flow control
housing tube corner 93a to interrupt communication between the
inlet passage 92 and the return passages 95, continued upward
movement of the piston then placing the inner upper flow control
piston corner 83 above the upper flow control piston corner 83
above the upper flow control housing tube corner 98, which then
allows compressed air to flow from the inlet passage 92 through the
ports 91 into the circumferential inlet groove 90 into the internal
circumferential impact passage groove 84 and thence into the
housing above the upper end 46 of the piston (FIGS. 2a, 2b). At
this time, the upper piston portion 50 will have moved partially
above the upper housing flow control corner 31, so that the air
under pressure between the upper end 46 of the piston and the
housing sub or head 11 can act downwardly on the piston, urging it
in a downward direction. As also seen in FIGS. 2a and 2b, the
intermediate portion 93 of the tube 78 seals in the sealing wall 85
and the sealing section 88a is sealingly engaged in the bore wall
88 with the portion 88d of the tube 78 bridging the return passage
86 to prevent air from flowing through the return passages 95 to
the lower end of the piston.
The piston 20 will be shifted downwardly, from the position of
FIGS. 2a and 2b, until the upper flow control piston corner 83
moves below the flow control housing tube corner 98, which shuts
off air pressure into the housing above the piston, the piston
continuing to move downwardly, as the compressed air expands, until
the outer upper flow control piston corner 50 moves below the upper
housing flow control corner 31, which then permits air above the
piston to pass through the passages 44 into the internal
circumferential exhaust grooves 32, and through the exhaust ports
51 and exhaust passages 53, 55, 56 to the bottom of the hole below
the drill bit, the hammer piston being driven against the upper
face 100 of the anvil to deliver an impact blow to the impact bit
C. As the piston nears the end of its downward stroke, the lower
flow control piston corner 87 will move below the lower flow
control housing tube corner 93a, thereby allowing the compressed
air to flow from the inlet passage 92 into the upper piston cavity
79 and internal circumferential return passage groove 86, passing
downwardly through the longitudinal return passages 95 to the lower
end of the piston, such air then moving the piston in an upward
direction, until the lower flow control piston corner 87 passes
upwardly beyond the lower flow control housing tube corner 91a,
once again, to shut off the flow of air into the return passages
95. When this occurs, the outer upper flow control piston corner 50
moves above the upper housing flow control corner 31 to shut off
the exhaust of air from the housing region above the piston 20, the
compressed air below the piston expanding and driving the hammer
piston upwardly toward the head 11 of the housing. Before reaching
the head 11, the inner upper flow control piston corner 83 will
have shifted upwardly along the tube 78 to a position above the
upper flow control housing tube corner 98, allowing air under
pressure to pass from the inlet passage 92 through the impact
passage grooves 90, 84 to a position in the housing above the
piston 20.
The upward travel of the piston 20 is cushioned by the compression
of the air remaining in the housing above the piston. However, the
piston will still move upwardly sufficiently to place the lower
corner 60 of the lower piston portion 40 above the housing lower
flow control corner 33, which then permits the compressed air below
the piston to travel into the internal circumferential exhaust
groove 32 and through the exhaust ports 51 into the exhaust
passages 53, 55, 56 for discharge from the drill bit. The
compressed air in the housing structure above the piston then
expands to drive the piston downwardly, and the foregoing cycle of
operation is repeated, the piston reciprocating to deliver repeated
impact blows against the anvil portion 18 of the anvil bit C, while
the drill string B and the entire apparatus A is being rotated, to
insure that the drilling or cutting elements 22 will cover
substantially the entire cross-sectional area of the bore hole
bottom E.
When circulation of fluid to flush cuttings from the bore hole is
desired, while the drill bit 21 is off bottom, elevation of the
apparatus A, as seen in FIGS. 3a and 3b, will cause the impact bit
C to drop downwardly along the housing until the upper anvil head
110 engages the upper ends of the keys 28. The piston 20 will also
drop downwardly until its by-pass corner 62 is below the by-pass
corner 35 of the housing 10, the upper corner 62 of the piston
being disposed below the upper end of the internal circumferential
groove 36. Accordingly, compressed air flowing downwardly through
the drill string B and into the inlet passage 92 can pass through
the inlet ports 91 and upwardly between the tubing and the upper
seal portion 82 to a position above the piston, then flowing
downwardly through the passages 44 and into the internal
circumferential exhaust groove 32, flowing between the external
circumferential exhaust groove 39 in the piston and the opposed
lower inner cylindrical housing wall 34 into the enlarged diameter
groove 36 below the inner cylindrical housing wall, then passing
through the passages 63, 64, 65, 67 to the exterior of the bit 21.
Since the path just described is open, and since the sealing
section 88a of the tube valve 78 closes off the passage 86 which
leads to the return ports 95, compressed air cannot find access
below the piston 20, which might otherwise tend to cause the piston
to continue reciprocating and cyclng in the housing 10. It is also
evident that the compressed air being pumped through the apparatus
will also flow through the exhaust ports 51 and the exhaust
passages 53, 55, 56 and downwardly through the anvil bit C.
When the piston 20 is on its power stroke, air will be compressed
below the piston, as pointed out above, because of the sealing of
the lower piston portion 40 against the lower inner cylindrical
housing wall 34 and the sealing of the head portion 66 against the
periphery of the anvil 18. However, air under pressure is always
present within the upper central piston cavity or chamber 79,
acting over the cross-sectional area W of such chamber, and
continuing to exert its force to overcome the pressure acting
upwardly over the piston and tending to elevate it (FIGS. 1a, 1b).
Thus, the hammer piston 20 will strike its impact blow upon the
upper end 100 of the anvil with a greater force, in view of the
overcoming of a portion of the resisting force offered by the
compressed air acting upwardly over the cross-sectional area R
across the lower portion of the piston, such area existing between
the periphery of the exhaust tube 54 and the lower inner
cylindrical housing wall 34.
On its power stroke, the compressed air acts over the full
cross-sectional area S of the upper piston portion, which is the
same area as the area across the inner cylindrical housing wall 30.
It is acting downwardly over the cross-sectional area of the piston
between the periphery of the upper flow control tube and the upper
inner cylindrical housing wall 30, and also over the area W across
the central piston cavity or chamber 79. During the return stroke,
the compressed air is acting upwardly over the piston over the area
R, which is less than the full cross-sectional area S, but such
full area is not needed for the purpose of returning the piston
under comparatively little load toward the upper end of its
stroke.
As described above, the exhaust tube or sleeve 54 is made of an
elastic material, which is a suitable synthetic resin such as
Delrin. This sleeve must make a slidable seal with the wall 53a of
the piston cavity 53 to prevent or minimize leakage of air between
the tube and the wall 53a. Because of manufacturing tolerances, a
perfect alignment between the hammer piston 20 and the anvil 18 may
not exist. Accordingly, as the piston approaches the anvil and
impacts thereagainst, it imposes a lateral force on the exhaust
sleeve 54. If the exhaust tube made a close fit with the wall 58c
of the anvil downwardly from its upper face 100, even a small
amount of misalignment between the piston 20 and the anvil would
cause a high shearing stress to be imposed on the exhaust tube 54,
resulting in fatigue failure of the exhaust tube after a relatively
short period of use of the apparatus.
The above difficulty is overcome in the apparatus illustrated by
providing relief between the exterior of the exhaust tube or sleeve
54 and the wall 58c of the anvil 18, such relief extending
downwardly from the upper anvil face 100. As shown, a counterbore
58a is provided in the anvil that extends downwardly from it upper
face 100 to a substantial extent, which, by way of example, is of
the order of about 1 inch. In view of the counterbore, any
misalignments between the piston 20 and the anvil 18 will prevent
the high shearing stresses from occurring on the tube substantially
in the plane of the upper face 100 of the anvil. Instead, the
exhaust sleeve 54 can readily flex or bend about the base 58b of
the counterbore, which acts as a fulcrum point, particularly in
view of the elastic material from which the exhaust sleeve 54 is
made. The bending stresses to which the tube 54 is subjected as a
result of misalignment between the piston 20 and the anvil 18 are
maintained at a comparatively low value, which prevents the exhaust
sleeve 54 from fatigue failure.
* * * * *