Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02755592 2013-09-09
TITLE OF THE INVENTION
[0001] Down-the-Hole Drill Hammer Having a Sliding Exhaust Check Valve
[0002]
BACKGROUND OF THE INVENTION
[0003] The present invention relates to a down-the-hole drill ("DHD")
hammer. In particular,
the present invention relates to a DHD hammer having a sliding exhaust check
valve assembly and
more particularly, a sliding exhaust check valve assembly that combines supply
and exhaust check
valves into a single unit operation.
[0004] Typical DHD hammers utilize what is known as "reactive" seals for
sealing the DHD
hammer's interior from its exterior environment, such as water and debris. The
seals are known as
"reactive" seals because they require the movement of exhaust flow to displace
or open flow
passageways within the DHD hammer. However, such DHD hammers also require that
exhaust
pressures be minimized for proper functioning of the DHD hammer. As such, the
level of reactive
forces/pressures for the "reactive" seals were also minimized, thereby
potentially negatively
impacting the "reactive" seal's effectiveness.
[0005] A DHD hammer, such as the present invention, having a sliding
exhaust check valve
addresses the foregoing limitations of reactive seals.
BRIEF SUMMARY OF THE INVENTION
[0006] In a preferred embodiment, the present invention provides a down-
the-hole drill hammer
comprising a housing, a backhead and a tubular sliding check valve assembly.
The backhead is
positioned at a proximal end of the housing and includes a distal end, a
threaded male proximal end,
a supply inlet and an exhaust port. The supply inlet receives a supply of
working fluid to an interior
of the backhead. The exhaust port provides for communication between the
interior of the backhead
and an exterior of the backhead. The tubular sliding check valve assembly is
within the housing
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proximate to the backhead. The sliding check valve assembly includes a
distributor, a sliding valve,
and a biasing member. The distributor has a central opening, an aperture
extending through the
distributor and offset from the central opening for allowing the passage of
working fluid through the
distributor, and an exhaust gallery for communicating between the central
opening and the exhaust
port. The sliding valve is slidable along the central opening and movable
between a closed position
and an open position. The sliding valve has a closed proximal end, an open
distal end, and an
opening about a midsection of the sliding valve. In the closed position, a
proximal end of the sliding
valve sealingly engages the supply inlet and a distal end of the sliding valve
sealingly engages an
inlet opening of the exhaust gallery. In the open position, the sliding valve
is offset from the supply
inlet, the openings of the sliding valve are in communication with the exhaust
gallery, and the
supply inlet is in communication with the aperture extending through the
distributor. The biasing
member biases the sliding valve.
[0007] In accordance with another preferred embodiment, the present
invention provides a
down-the-hole drill hammer comprising a housing, a backhead, and a tubular
sliding check valve
assembly. The backhead is positioned at a proximal end of the housing and
includes a distal end, a
threaded male proximal end, a supply inlet for receiving a supply of working
fluid to an interior of
the backhead, an exhaust port for communicating between the interior of the
backhead and an
exterior of the backhead, a tubular distal end, and a tapered midsection
interior in communication
with the supply inlet. The tapered mid section interior includes a
frustroconical section adjacent the
supply inlet, and a tubular section adjacent the frustroconical section. The
tubular sliding check
valve assembly is housed within the housing proximate to the backhead. The
sliding check valve
assembly includes a distributor, a sliding valve, and a biasing member. The
distributor has a central
opening, an aperture extending through the distributor in an axial direction
and offset from the
central opening for allowing the passage of working fluid through the
distributor, and an exhaust
gallery for communicating between the central opening and the exhaust port.
The sliding valve is
slidable along the central opening and movable between a closed position and
an open position. The
sliding valve includes a closed proximal end, an open distal end, and an
opening about a midsection
of the sliding valve. The biasing member biasing the sliding valve to the
closed position. In the
closed position, a proximal end of the sliding valve sealingly engages the
supply inlet and a distal
end of the sliding valve sealingly engages an inlet opening of the exhaust
gallery. In the open
position, the sliding valve is offset from the supply inlet, the openings of
the sliding valve are in
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communication with the exhaust gallery, and the supply inlet is in
communication with the aperture
extending through the distributor.
[0008] In accordance with yet another preferred embodiment, the present
invention provides a
down-the-hole drill hammer that includes a housing, a backhead, a tubular
sliding check valve
assembly, a biasing member, a solid-core piston and a seal. The backhead is
located at a proximal
end of the housing and includes a supply inlet for receiving a supply of
working fluid to an interior
of the backhead. The tubular sliding check valve assembly is housed within the
housing and located
proximate the backhead. The sliding check valve assembly includes a
distributor and a sliding valve
slidable along the distributor. The sliding valve has a closed proximal end,
an open distal end, an
opening about a midsection of the sliding valve, and an inwardly extending
flange, wherein the
inwardly extending flange has a distally facing surface area. The biasing
member biases the sliding
valve to sealingly engage the closed proximal end to the supply inlet. The
seal is located proximate
a distal end of the housing between the solid-core piston and the housing.
[0009] In accordance with another preferred embodiment, the present
invention provides a
down-the-hole drill hammer that includes a housing, a backhead, a tubular
sliding check valve
assembly, a biasing member, a solid-core piston, a seal and a drive chamber.
The backhead is
located at a proximal end of the housing and includes a supply inlet for
receiving a flow of supply
pressure to an interior of the backhead. The tubular sliding check valve
assembly is housed within
the housing and located proximate the backhead. The sliding check valve
assembly includes a
distributor and a sliding valve slidable along the distributor. The sliding
valve has a closed proximal
end, an open distal end, and an opening about a midsection of the sliding
valve. The biasing
member biases the sliding valve to sealingly engage the closed proximal end to
the supply inlet.
The seal is located proximate a distal end of the housing between the solid-
core piston and the
housing. The driver chamber is positioned between the backhead and the solid-
core piston. The
closed proximal end of the sliding valve sealingly engages the supply inlet
while the solid-core
piston sealingly engages the seal proximate the distal end of the housing when
a flow of supply
pressure entering the down-the-hole drill hammer is discontinued to maintain
an elevated pressure
within the drive chamber.
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BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0010] The foregoing summary, as well as the following detailed
description of the invention,
will be better understood when read in conjunction with the appended drawings.
For the purpose of
illustrating the invention, there are shown in the drawings embodiments that
are presently preferred.
It should be understood, however, that the invention is not limited to the
precise arrangements and
instrumentalities shown.
[0011] In the drawings:
[0012] Fig. 1 is a perspective view of a DHD hammer in accordance
with a preferred
embodiment of the present invention;
[0013] Fig. 2 is a cross-sectional, elevational view of the DHD hammer of
Fig. 1;
[0014] Fig. 3 is a cross-sectional, elevational view of the DHD
hammer of Fig. 1 with a cross-
section taken through an exhaust port of a backhead;
[0015] Fig. 4 is a perspective view of a backhead of the DHD hammer
of Fig. 1;
[0016] Fig. 5 is a cross-sectional, elevational view of the backhead
of Fig. 4;
[0017] Fig. 6 is a perspective, cross-sectional view of the backhead of
Fig. 4;
[0018] Fig. 7 is a perspective view of a distributor of the DHD
hammer of Fig. 1;
[0019] Fig. 8 is a cross-sectional, elevational view of the
distributor of Fig. 7;
[0020] Fig. 9 is a cross-sectional, elevational view of the
distributor of Fig. 7 with a cross-
section taken through an exhaust gallery;
[0021] Fig. 10 is atop plan view of the distributor of Fig. 7;
[0022] Fig. 11 is a bottom perspective view of a sliding valve of the
DHD hammer of Fig. 1;
[0023] Fig. 11A is a bottom perspective view of an alternative
embodiment of a sliding valve of
a DHD hammer of Fig. 19A;
[0024] Fig. 12 is a top perspective view of the sliding valve of Fig.
11;
[0025] Fig. 13 is a cross-sectional, elevational view of the sliding valve
of Fig. 11 with a cross-
section taken through a through hole of the sliding valve;
[0026] Fig. 14 is a cross-sectional, elevational view of the sliding
valve of Fig. 11;
[0027] Fig. 15 is a perspective view of a dowel for assembly within
the sliding valve of Fig. 11;
[0028] Fig. 16 is a perspective view of a screen of the DHD hammer of
Fig. 1;
[0029] Fig. 17 is a perspective view of a belleville washer of the DHD
hammer of Fig. 1;
[0030] Fig. 18 is a cross-sectional, elevational view of the
belleville washer of Fig. 17;
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[0031] Fig. 19 is an enlarged, cross-sectional, elevational view of an
upper portion of the DHD
hammer of Fig. 1 showing the sliding valve in a closed position;
[0032] Fig. 19A is an enlarged, cross-sectional, elevational view of an
upper portion of a DHD
hammer showing the sliding valve of Fig. 11A in a closed position, in
accordance with another
embodiment of the present invention;
100331 Fig. 20 is an enlarged, cross-sectional, elevational view of an
upper portion of the MID
hammer of Fig. 1 showing the sliding valve in an open position;
[0034] Fig. 21 is an enlarged, cross-sectional, elevational view of an
upper portion of the DHD
hammer of Fig. 1 showing the sliding valve in a closed position with a cross-
section taken through
exhaust ports of the backhead;
[0035] Fig. 22 is an enlarged, cross-sectional, elevational view of an
upper portion of the DHD
hammer of Fig. 1 showing the sliding valve in an open position and with a
cross-section taken
through exhaust ports of the backhead;
[0036] Fig. 22A is an enlarged, cross-sectional, elevational view of an
upper portion of a DHD
hammer that includes the sliding valve of Fig. 11A;
[0037] Fig. 23 is an enlarged, perspective view of an inner housing of
the DHD hammer of Fig.
1;
[0038] Fig. 24 is an elevational view of the DHD hammer of Fig. 1
without a housing;
[0039] Fig. 25 is a cross-sectional, elevational view of the DHD hammer
of Fig. 22A in a drop-
down position; and
[0040] Fig. 26 is an enlarged, cross-sectional, elevational view of a
lower portion of the DHD
hammer of Fig. 1.
DETAILED DESCRIPTION OF THE INVENTION
[0041] Certain terminology is used in the following description for
convenience only and is not
limiting. The words "right," "left," "upper," and "lower" designate directions
in the drawings to
which reference is made. For purposes of convenience, "distal" is generally
referred to as toward
the drill bit end of the DHD hammer, and "proximal" is generally referred to
as toward the backhead
end of the DHD hammer, as illustrated in Fig. 1. Additionally, the term "a,"
as used in the
specification, means "at least one." The terminology includes the words above
specifically
mentioned, derivatives thereof, and words of similar import.
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[0042] In accordance with a preferred embodiment of the present
invention, there is shown a
DHD hammer that includes a housing 12, a backhead 14 and a tubular sliding
check valve assembly
46, as best shown in Figs. 1-4.
[0043] The housing 12 is generally cylindrical and configured to receive
a portion of the
backhead 14 and a portion of a drill bit 15, as best shown in Fig. 1. The
structure and operation of
the housing 12 is known in the art and therefore a detail description of the
housing 12 is not
necessary for complete understanding of the present invention. However, as
shown in Fig. 2, the
housing 12 includes internal threads 12a and 12b about its proximal end and
distal end, respectively.
The threads 12a and 12b provide for a threaded connection of the backhead 14
and the assembly of
the drill bit 15 to the housing 12.
[0044] The backhead 14 is generally configured, as shown in Figs. 1-6.
Referring to Fig. 4, the
backhead 14 includes a proximal end 22, a mid portion 35 and a distal end 20.
The proximal end 22
is generally configured as a tool-joint connection for assembly to a drill
string or other tool (not
shown) as known in the art. The proximal end 22 also includes male threads 24
for securing the
proximal end 22 to the drill string (not shown). The distal end 20 includes
threads 20 on the exterior
surface for connecting with the housing 12 via the housing threads 12a.
[0045] The tubular sliding check valve assembly 46, is shown in Figs. 2
and 3. The tubular
sliding check valve assembly 46 includes a distributor 48, a sliding valve 62
and a biasing member
108. The tubular sliding check valve assembly 46 is housed within the housing
12 proximate the
backhead 14. When fully assembled within the DHD hammer 10, the tubular
sliding check valve
assembly 46 is housed partially within the backhead 14 and partially within
the proximal end of the
housing 12.
[0046] Referring to Figs. 5 and 6, the backhead 14 also includes a
supply inlet 26 that extends
from the proximal end 22 to an interior region 28 of the backhead 14. Supply
pressures of about
150 to 450 pounds per square inch (p.s.i.) are typically supplied to the DHD
hammer 10 through the
supply inlet 26. The interior region 28 of the backhead 14 is configured, as
best shown in Fig. 5,
and includes a tapered midsection 33 and a tubular distal end 44. The interior
of the tapered
midsection 33 tapers inwardly in the proximal direction. The tapered
midsection 33 includes a first
frustroconical shaped wall section 34 that is adjacent the supply inlet 26.
Adjacent the first
frustroconical wall section 34 is a first tubular wall section 36. A second
frustroconical shaped wall
section 38 is adjacent the first tubular wall section 36. Adjacent the second
frustroconical wall
section 38 is a second tubular wall section 40. Adjacent the second tubular
wall section 40 is a third
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frustroconical shaped wall section 42. Preferably, the first frustroconical
wall section 34 is distal to
the supply inlet 26. Furthermore, the first tubular wall section 36 is distal
to the first frustroconical
wall section 34, the second frustroconical wall section 38 is distal to the
first tubular wall section 36,
the second tubular wall section 40 is distal to the second frustroconical wall
section 38, and the third
frustroconical wall section 42 is distal to the second tubular wall section
40.
[0047] The configuration of the tapered midsection 33 in combination
with the sliding valve 62
(shown in Fig. 11 and described below) advantageously provides for an
expandable inlet
passageway 41 (Fig. 20) between the backhead 14 and the sliding valve 62 for
communicating
between the supply inlet 26 and a plurality of apertures 52 (Fig. 8) extending
through the distributor
48, as further described below. That is, as the applied supply pressure of
working fluids supplied by
the drill string pressurizes the sliding valve 62, the sliding valve 62 moves
distally within the tapered
midsection 33. As the sliding valve 62 travels or slides distally, the inlet
passageway 41 expands
due to the distally expanding interior wall surface profile defined by the
progression of
frustroconical and tubular wall sections 34, 36, 38, 40 and 42.
[0048] The overall diameter of the sliding valve 62 is sized to provide a
relatively small
clearance of flow around the sliding valve 62 until an upper portion 62a
(i.e., a frustroconical
portion) of the sliding valve 62 (Fig. 11) moves distally past the second
frustroconical wall section
38. Preferably, the clearance between the outside surface of the upper portion
62a and the interior
wall surface of the interior 28 is about 0.02 to 0.05 inches, and more
preferably about 0.03 inches.
[0049] In general, the inlet passageway 41 is in communication between the
supply inlet 26 and
the apertures 52 of the distributor 48 when the sliding valve 62 is in the
open position. The inlet
passageway 41 is formed between the surfaces of the chamfered proximal end of
the sliding valve
62 and at least the frustroconical wall 34 and tubular wall 36 of the interior
28 of the backhead 14.
[0050] The expandable inlet passageway 41 advantageously ensures that
the supply of working
fluid volumes into the backhead 14 adequately compresses or forces the biasing
member 108 to
move the sliding valve 62 to the fully open position (Fig. 20). This is a key
feature of the tubular
sliding check valve assembly 46, because without the expandable inlet
passageway 41, the sliding
valve 62 can become stuck in mid-stroke or in only a partially opened position
due to the pressure
forces above and below the sliding valve 62 equalizing during the movement of
the sliding valve 62
to the fully open position.
[0051] The tubular distal end 44 of the backhead 14 is configured, as
best shown in Fig. 5 and is
distal to the tapered midsection 33. The tubular distal end 44 is configured
to receive the distributor
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48. About a proximal end of the tubular distal end 44 is an exhaust port 30
that extends radially
from the interior 28 through the wall of the tubular distal end 44. As such,
the exhaust port 30
provides for fluid communication between the interior 28 and an exterior of
the backhead 14 (Fig.
3). Preferably, the backhead 14 includes a plurality of exhaust ports 30, and
more preferably, six
exhaust ports 30. The plurality of exhaust ports 30 are circumferentially and
equally spaced apart.
The exhaust ports 30 also include a groove or galley 30a that extends from an
external surface of the
backhead 14 towards the proximal end, as best shown in Fig. 4. The galley 30a
is configured with a
substantially rectangular or oblong shape that is inset within the wall of the
backhead 14. As best
shown in Fig. 6, a proximal end of the galley 30a extends or tapers radially
and outwardly in the
proximal direction and terminates at an outlet end 30b that is proximate the
housing 12 (Fig. 3).
[0052] The backhead 14 also includes a flange 45 that extends radially
inwardly from an outside
surface of the mid portion 35 to the distal end 20 of the backhead 14. As best
shown in Fig. 4, the
flange 45 is positioned above the exhaust ports 30. The flange 45 provides a
distal surface that
engages a proximal end of the housing 12, as best shown in Fig. 2.
[0053] The distributor 48, is best shown in Figs. 7-10. The distributor 48
includes a main body
portion 48a and an exhaust stem 48b that is configured to extend into the
drive chamber 18 of the
DHD hammer 10. The distributor 48 also includes a central opening 50 that
extends axially through
the distributor 48, as shown in Fig. 8 and opens up to form an interior 51 of
the main body portion
48a. As such, the central opening 50 provides for fluid communication between
the proximal end
and the distal end of the distributor 48.
[0054] The distributor 48 further includes an aperture 52 that extends
through the distributor 48
in an axial direction. The aperture 52 is radially offset from the central
opening 50, as shown in Fig.
8. The aperture 52 provides for fluid communication through the distributor
48, as further discussed
below. Preferably, the distributor 48 includes a plurality of apertures 52,
and more preferably the
distributor 48 includes six apertures 52 that are circumferentially and
equally spaced apart, as shown
in Fig. 10.
[0055] The distributor 48 also includes an exhaust gallery 54, as shown
in Figs. 7 and 9. The
exhaust gallery 54 is configured with a first opening 54a, an enlarged opening
54b adjacent the
opening 54a and an inlet opening 54c adjacent the first opening 54a at an end
of the first opening
54a opposite the enlarged opening 54b. The first opening 54a is in
communication with the interior
51 of the distributor 48 and the enlarged opening 54b. The exhaust gallery 54
also provides for fluid
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communication between the central opening 50 and the exhaust port 30 of the
backhead, as shown in
Fig. 3.
[0056] The distributor 48 preferably includes glands 57a-d that each
receives a respective seal,
as further described below. Gland 57a receives a seal 94 (Fig. 19) and is
positioned about an
interior wall surface of the interior 51 and below or distal to the inlet
opening 54c while the gland
57b receives a seal 92 (Fig. 19) and is positioned about the interior wall
surface of the interior 51
and above or proximal to the inlet opening 54c. The glands 57a and 57b and
their respective seals
sealingly engage an outer surface of the sliding valve 62. The gland 57c is
positioned along an outer
wall surface of the distributor 48 and above the enlarged opening 54b while
the gland 57d is
positioned along the outer wall surface of the distributor 48 and positioned
below the enlarged
opening 54b. Furthermore, the distributor 48 includes a gland 56 about a
distal end of the interior
51 and a radially inwardly extending flange 59 about a proximal end of the
main body portion 48a
above the first openings 54a.
[0057] The sliding valve 62, is best shown in Figs. 2 and 11-14. The
sliding valve 62 is
assembled within the interior 51 of the distributor 48, as best shown in Fig.
2. When fully
assembled within the DHD hammer 10, the sliding valve 62 is slidable along the
interior 51 of the
distributor 48 and movable between a closed position and an open position, as
further discussed
below.
[0058] The sliding valve 62 includes a closed proximal end 64 (Fig.
12), an open distal end 66
(Fig. 11) and an opening 68 about a midsection of the sliding valve 62. The
opening 68 extends
radially through the wall of the sliding valve 62, as best shown in Figs. 11
and 14. The opening 68
is configured as an elongated opening about a mid portion of the sliding valve
62. Preferably, the
sliding valve 62 including a plurality of openings 68 that are
circumferentially spaced apart about
the mid portion of the main body portion 62b. The position of the opening 68
along the sliding
valve 62 is configured such that when the sliding valve 62 is moved to the
open position, the
opening 68 provides for fluid communication between the interior 51 of the
distributor 48 and the
exhaust gallery 54. However, when the sliding valve 62 moves to the closed
position, the opening
68 is spaced apart from the exhaust gallery 54 such that the bottom portion of
the sliding valve 62
sealingly engages the seals 92 and 94 to seal off the inlet opening 54c.
[0059] In general, the sliding valve 62 includes an upper portion 62a and a
main body portion
62b. The upper portion 62a is generally configured as a frustroconical portion
or as a chamfered
proximal end. The main body portion 62b is generally configured as a tubular
portion extending
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distally from the upper portion 62a. The sliding valve 62 is configured with a
hollow interior 62c
and a through hole 70 that extends through a proximal end of the main body
portion 62b. The
through hole 70 is configured to receive a dowel 76 (Fig. 15). The dowel 76
serves as a bypass plug
or a choke plug for the sliding valve 62, as known in the art. The sliding
valve 62 can optionally be
configured with a gland 74 recessed about an outer surface of the
frustroconical upper portion 62a.
The upper portion 62a also includes a distal surface 72 that extends radially
inwardly to the exterior
wall of the main body portion 62b.
[0060] The assembly of the sliding valve 62 within the DHD hammer 10,
owing to the openings
68 of the sliding valve 62 being in communication with the exhaust ports 30,
advantageously
ensures that the interior 62c is substantially at exhaust pressure or the
pressure external to DHD
hammer 10, which is significantly less (e.g., at about atmospheric pressure or
about 0-50 p.s.i.) than
the supply pressure (e.g., about 300-350 p.s.i. or about 150 to 450 p.s.i.)
being fed to the DHD
hammer 10 via the supply inlet 26. Thus, because the pressure within the
sliding valve 62 is
maintained at lower pressures, relative to the supply pressure of working
fluid volumes fed to the
DHD hammer 10, the tubular sliding check valve assembly 46 advantageously
ensures that the
supply pressure functions as a bias pressure to urge the tubular sliding check
valve assembly 46 to
the open position.
[0061] The biasing member 108 is assembled to the tubular sliding
check valve assembly 46 so
as to be positioned between the sliding valve 62 and the distributor 48, as
best shown in Fig. 2. The
biasing member 108 can be any biasing member know in the art and preferably a
coil spring biasing
member 108. A proximal end of the biasing member 108 engages the distal end 72
of the sliding
valve 62 while the distal end of the biasing member 108 engages the flange 59
extending radially
inwardly from the upper portion of the distributor's interior 51.
10062] Preferably, the biasing member 108 is configured to provide an
overall restoring force to
the sliding valve 62 sufficient to retain an elevated pressure of at least 35
p.s.i. within the DHD
hammer 10. This can be accomplished with a biasing member 108 the provides a
net restoring force
in lbs. that is about 90% to 125% of the numerical valve of the DHD hammer's
internal diameter
squared. The term "net restoring force" means the overall force applied to the
sliding valve 62 by
the biasing member 108 minus any counterforces acting on the sliding valve 62,
such as frictional
forces generated by seals on the sliding valve 62. Configuring the biasing
member 108 to have a net
restoring force of about 90% to 125% of the numerical valve of the DHD
hammer's internal
diameter squared advantageously allows the biasing member 108 to move the
sliding valve 62 to the
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closed position (Fig. 2) when a flow of supply pressure fed through the supply
inlet 26 is
discontinued, thereby sealing off the supply inlet 26, while the internal
pressure within the DHD
hammer 10 is maintained at elevated pressures e.g., at or above 35 p.s.i.
Elevated pressures are
maintained within the DHD hammer 10 in combination with a seal 17 and a solid-
core piston 16, as
further described below.
[0063] Thus, for example, Table 1 illustrates the preferred net
restoring force ranges for the
biasing member 108 over a range of DHD hammer 10 bore sizes.
Table 1.
Internal Diameter DHD Hammer (inches)
Net Restoring Force Range (lbs.) [provided by
biasing member to sliding valve]
4.6 19.3-
26.7
3 8.1-
11.25
4 14.4-
20.0
5 22.5-
31.25
6 32.4-
45.0
8 57.6-
80.0
[0064] During operation of the DHD hammer 10, the flow of working fluid
or supply pressure
pressurizes the internal areas of the DHD hammer 10 to elevated pressures
above 35 p.s.i., and
typically operates the DHD hammer 10 at pressures from about 150 p.s.i. to 450
p.s.i. Thus, with a
biasing member 108 having a sufficient net restoring force, the biasing member
108 allows the DHD
hammer 10 to partially retain the elevated pressures within the DHD hammer's
internal areas, such
as the drive chamber 18 at elevated pressures. Preferably, the internal areas
of the DHD hammer 10
are maintained at a pressure of at least 35 p.s.i. by the proper balancing of
the net restoring force of
the biasing member 108 on the sliding valve 62.
[0065] The internal areas of the DHD hammer 10, such as the drive
chamber 18, are sealed off,
and preferably hermetically sealed, owing to the combination of the solid-core
piston 16 and the seal
17, when the DHD hammer 10 is in a drop-down position. The DHD hammer 10 is
sealed off and
moved to the drop-down position upon the flow of supply pressure feed to the
DHD hammer 10
being discontinued i.e., stopped or reduced to a non-actuating level, such as
35 p.s.i. Fig. 25
illustrates the DHD hammer 10 in the drop-down position. Maintaining the
internal areas of the
DHD hammer 10 at elevated pressures advantageously prevents the ingress of
water and debris into
the DHD hammer's interior, which can negatively impact the overall operation
and startup of the
DHD hammer 10 after an intermittent stop. Typically, well bores can generate a
water column to
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heights of up to 80 feet of water, or about 35 p.s.i. Thus, maintaining the
internal areas of a DHD
hammer 10 at or above 35 p.s.i. upon an intermitted stop advantageously
prevents the ingress of
water and debris into the DHD hammer 10 when situated at a well bore bottom.
[0066] The seal 17 is best shown in Figs. 24-26. The seal 17 is housed
within a gland 17a of the
housing 12 located about a distal end of the housing 12 and above the threads
12b. The seal 17 is
preferably positioned so as to be engaged with a cylindrical bearing 19
located about the distal end
of the housing 12 and configured to receive a distal end of the piston 16. The
cylindrical bearing 19
is seated on a chuck assembly 21 that threadedly engages the housing 12 and
retains the drill bit 15.
Referring to Fig. 25, when the DHD hammer 10 is in the drop down position, the
solid-core piston
16 engages the seal 17, thereby preventing the ingress of external fluid and
debris into the internal
areas of the DHD hammer 10.
[0067] Figs. 11A, 19A and 22A illustrate an alternative sliding valve
62' embodiment that is
similar to the sliding valve 62, except for the inclusion of a reduced
diameter lower body portion
63b'. That is, the main body portion 62b' includes an upper body portion 63a'
and the lower body
portion 63b'. The lower body portion 63b' has an overall diameter that is
smaller then the upper
body portion 63a'. The main body portion 62b' also includes a stepped flange
having a distally
facing surface 63c' that forms the transition between the upper body portion
63a' and the lower body
portion 63b'. The stepped flange is positioned distal to the openings 68'. The
distally facing surface
63c' advantageously provides for a distally facing surface area i.e., a bias
area 63c', which is
exposed to exhaust pressure (which is less the supply pressure) to ensure that
the sliding valve 62'
moves distally to the open position upon exposure to supply pressure (see also
Fig. 22A).
[0068] The distally facing surface area 63c' is preferably about 2-4%
of the numerical valve of
the DHD hammer's internal diameter squared. Table 2, illustrates the preferred
distally facing
surface area 63c' over a range of DHD hammer bore sizes.
Table 2.
Internal Diameter DHD Hammer (inches) Distally Facing Surface
Area Range (in.2)
4.6 0.43-0.86
3 0.18-0.36
4 0.32-0.64
5 0.50-1.00
6 0.72-1.44
8 1.28-2.56
12
CA 02755592 2011-10-20
= '
-
. .
[0069] The combination of the distally facing surface area 63c' of the
sliding valve 62' and the
net restoring force of the biasing member 108 advantageously allows the DHD
hammer 10 to retain
elevated pressures within its internal areas at or above 35 p.s.i. upon an
intermittent stop of the DHD
hammer 10. This is accomplished by the proper balancing of the net restoring
force of the biasing
member 108 on the sliding valve 62' and the bias area 63c' of the sliding
valve 62' in combination
with the expandable inlet passageway 41 of the backhead 14.
[0070] Referring to Figs. 3, 9 and 16, the DHD hammer 10 can
optionally include a screen 78.
The screen 78 is configured, as best shown in Fig. 16, and is preferably
configured as a perforated
plate screen. The screen 78 is preferably configured as a split ring screen
for circumscribing the
distributor 48 about an outlet 54d of the exhaust gallery 54. As best shown in
Fig. 3, the screen 78
is sized and configured to circumscribe the exhaust gallery's enlarged opening
54b. The screen 78
advantageously provides a means to screen out and prevent debris from entering
the DHD hammer's
interior through the exhaust ports 30 of the backhead 14.
[0071] The DHD hammer 10 also includes a belleville washer 80 for
facilitating the mounting of
the tubular sliding check valve assembly 46 within the housing 12 and the
backhead 14. The
belleville washer 80 is configured, as best shown in Figs. 2, 17 and 18. The
belleville washer 80
includes a central through hole 82 and glands 86 and 88. The gland 88 is
configured about a surface
of the central through hole 82 for receiving a seal 102 (Fig. 19). The
belleville washer 80 also
includes a distally facing flange 84 about a mid portion along its axial
length, as shown in Fig. 18.
The gland 86 is positioned below the flange 84 and configured to receive a
seal 104 (Fig. 19). As
shown in Figs. 19 and 22, the belleville washer 80 is assembled within the
housing 12 such that the
flange 84 engages a proximal end of an inner housing 12c or sliding cylinder.
[0072] The inner housing 12c is preferably a separate component from
the rest of the housing
12. The structure, operation and assembly of the inner housing 12c is known in
the art and therefore
a detailed description of the inner housing 12c is not necessary for complete
understanding of the
present invention. However, as best shown in Fig. 23, the inner housing 12c is
generally configured
as a cylindrical housing having a plurality of spaced apart through holes 13
about the wall of the
inner housing 12c. The plurality of through holes 13 are arranged, as shown in
Fig. 23, with a first
row 13a of through holes 13 circumferentially and generally evenly spaced
apart about a proximal
end of the inner housing 12c and a second row 13b of through holes 13
circumferentially and
generally evenly spaced apart about a distal end of the inner housing 12c. The
position of the
through holes 13 of the first row 13a are circumferentially offset from the
position of the through
13
CA 02755592 2011-10-20
holes 13 of the second row 13b. The inner housing 12c also includes a third
row 13c of through
holes 13 circumferentially and generally evenly spaced apart and located
closer to the distal end of
the inner housing 12c than the holes of the second row 13b. The third row 13c
of through holes 13
are also circumferentially offset from the second row 13b of through holes 13.
[0073] A plurality of splines 15a are formed about the outer surface of the
inner housing 12c
that each connect a through hole 13 of the first row 13a to a through hole 13
of the second row 13b.
Each spline 15 provides fluid communication for the flow of fluid between the
through holes 13 of
the first and second rows 13a, 13b. A plurality of splines 15b are also formed
about the outer
surface of the inner housing 12c that are each in fluid communication with the
through holes 13 of
the third row 13c. Each spline 15b allows for fluid to flow around the
exterior of the inner housing
12c. As such, the splines 15b allow for the flow of working fluid volumes to
flow from the drive
chamber 18 though the through holes 13 of either the first, second or third
row 13a-c to a reservoir
chamber 18a (Fig. 2). Working fluid volumes then flow past the distal end of
the piston 16 into and
out of the return chamber 18b (Fig. 2). Owing to the circumferential offset of
the through holes 13
of the first and third rows 13a, 13c from the second row 13b, the plurality of
splines 15a, 15b are
formed as helical splines.
[0074] Such features of the through holes 13 and splines 15a,15b of the
inner housing 12c form
part of the DHD hammer's porting system. The porting features of a DHD hammer
function to
move working fluid volumes between the DHD hammer's drive chamber 18,
reservoir chamber 18a
and return chamber 18b to reciprocatively move the DHD hammer's piston 16. In
other words, the
flow of working fluid volumes from the supply inlet 26, check valve assembly
46, drive chamber 18,
reservoir chamber 18b and return chamber 18b, all function to drive the
operation of the DHD
hammer 10. Fig. 24 illustrates the assembly of the DHD hammer 10 without
housing 12, showing
the porting features of the instant invention.
[0075] Figs. 19-22 best show the tubular sliding check valve assembly 46
fully assembled to the
DHD hammer 10. Fig. 19 also illustrates the inclusion of seals 90, 92, 94, 96,
98, 100, 102 and 104
within their respective glands, as discussed above. The seals can be any seal
readily known in the
art, such as an elastomeric seal in the form of an 0-ring seal or the like.
[0076] The biasing member 108 biases the sliding valve 62 to the closed
position in the absence
of a supply of working fluid volumes being fed through the supply inlet 26.
The closed position is
illustrated in Figs. 19 and 21. In the closed position, the proximal end of
the sliding valve 62, i.e.,
the chamfered end of the upper portion 62a sealingly engages the supply inlet
26. Preferably, the
14
CA 02755592 2013-09-09
. .
upper portion 62a of the sliding valve 62 sealingly engages the first
frustroconical wall section 34 of
the backhead 14. Furthermore, a distal portion of the sliding valve 62, below
the openings 68,
sealingly engages an inlet opening 54c of the exhaust gallery 54. The sealing
engagement between
the distal end of the sliding valve 62 and the exhaust gallery 54 is
facilitated by seals 92 and 94. In
this position, the tubular sliding check valve assembly 46 seals off the
supply inlet 26 and any fluid
communication between an exterior of the DHD hammer 10 and an interior of the
DHD hammer 10
through the exhaust ports 30.
[0077] The open position of the tubular sliding check valve assembly
46, is best shown in Figs.
20 and 22. In the open position, the sliding valve 62 is offset from the
distal end of the supply inlet
26. Plus, the openings 68 are in communication with the exhaust gallery 54, as
best shown in Fig.
22. Furthermore, as shown in Fig. 20, the supply inlet 26 is in communication
with the apertures 52
extending through the distributor 48 to supply working fluid volumes to the
DHD hammer's drive
chamber 18.
[0078] Referring back to Fig. 2, the drill bit 15 is operatively
connected to a distal end of the
housing 12. The drill bit 15 can be operatively connected in a conventional
manner known in the art
and therefore a detailed description of such a connection is not necessary for
a complete
understanding of the present invention. However, an example of how the drill
bit 15 can be
operatively connected to the housing 12 is described in U.S. Patent
Application No. 12/621,155.
[0079] The DHD hammer 10, as discussed above has been described and
shown as including a
solid-core piston 16. That is, the solid-core piston 16 lacks any through hole
or central opening that
extends completely through the piston, such as in the axial direction.
However, the sliding check
valve assembly 46 of the DHD hammer 10 can alternatively be used with any
conventional piston
having a central through hole that extends axially through the piston to allow
exhaust through the
piston and drill bit.
[0080] The scope of the claims should not be limited by the preferred
embodiments set forth in
the examples, but should be given the broadest interpretation consistent with
the description as a
whole.
