Boring or penetrating the earth – Below-ground impact members – Fluid-operated
Reexamination Certificate
1999-06-11
2001-01-09
Pezzuto, Robert E. (Department: 3671)
Boring or penetrating the earth
Below-ground impact members
Fluid-operated
C091S317000
Reexamination Certificate
active
06170581
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to drill assemblies, and particularly to backheads and check valves used in drill assemblies having fluid-actuated pistons.
Drill assemblies, particularly percussive down-hole drills having fluid-actuated pistons, are well known, such as those disclosed in U.S. Pat. No. 5,085,284 of Fu, U.S. Pat. No. 5,301,761 of Fu et al., U.S. Pat. No. 5,562,170 of Wolfer et al., U.S. Pat. No. 5,711,205 (Wolfer et al.) and U.S. Pat. No. 5,566,771 of Wolfer et al. Referring to
FIGS. 1 and 2
, a typical down-hole drill assembly
1
includes a casing
2
containing the internal components of the drill assembly
1
, including a piston
3
and a backhead
4
that connects the drill assembly
1
to a drilling machine (not shown). The backhead
4
has a supply passage
5
for directing percussive fluid, generally high-pressure compressed air, into the drill assembly
1
. The upper end
4
a
of the backhead
4
is connected with a source of percussive fluid, for example, a fluid supply line connected with a compressor (not shown), such that percussive fluid is supplied to the drill assembly
1
to operate the piston
3
.
The piston
3
is slidably mounted within the casing
2
and is guided by an inner bearing surface
2
a
of the casing
2
so as to reciprocally impact with a drill bit
6
, which provides the work output of the drill assembly
1
. The piston
3
is actuated by the pressure of the percussive fluid, which is directed alternately to the upper and lower ends
3
a,
3
b,
respectively, of the piston
3
so as to thereby cause reciprocating sliding movement of the piston
3
. Typically, the drill assembly includes a fluid distributor
7
having at least one passage
8
, preferably a plurality of passages
8
, for directing percussive fluid to a drive chamber (not shown) defined within the casing
2
between the distributor
7
and the upper end
3
a
of the piston
3
. The flow of percussive fluid through the distributor passages
8
is preferably regulated by a distributor valve
10
disposed about and slidable along a cylindrical end portion
7
a
of the distributor
7
. However, such a distributor valve
10
, while enabling ideal operation of the drill assembly
1
, is not required for the drill assembly
1
to function in an appropriate manner.
In order to prevent contaminants, such a water or rock debris, from entering or “backflowing” into the casing
2
and potentially causing damage to and/or interfering with the proper functioning of the components of the drill assembly
1
, the pressure of the percussive fluid in the casing
2
should always remain above ambient pressure. However, when the supply of percussive fluid to the backhead
4
is turned off, percussive fluid within the casing
2
will flow out of the drill assembly
1
through the backhead supply passage
5
, if the passage
5
is not sealed, allowing the backflow of contaminants into the drill assembly
1
.
One known device to prevent backflow into the drill assembly
1
is to provide a check valve
11
disposed within the casing
2
between the fluid distributor
7
and the backhead
4
, as best shown in FIG.
2
. The check valve
11
includes a valve plug
12
that is movable toward and away from a valve seating surface
4
b,
which in
FIGS. 1 and 2
is provided by a tapered wall portion inside the backhead
4
surrounding an axial opening
4
c
that forms a section of the supply passage
5
. The plug
12
is biased toward the seating surface
4
a
by a valve spring
13
extending between the movable plug
12
and a stationary valve cap
14
. The valve cap
14
includes a first recess
14
a
at an upper side which retains the lower end of the spring
13
and a second recess
14
b
on the lower side, which is sized to receive the end of the distributor portion
7
a.
Further, to maintain the distributor
7
at a desired position within the casing
2
, a retainer member
16
is biased by a spring
17
to push against the valve cap
14
, such that the distributor
7
is “sandwiched” between the valve cap
14
and the upper end of a sleeve
18
(FIG.
1
).
Due to the fact that the above-described check valve
11
has several moving parts, at least some components of the valve
11
will eventually have to be replaced. The valve spring
13
will likely experience fatigue failure after a certain period of use. Further, the movable plug
12
may become worn due to repeated impact with the valve seating surface
4
a,
such that percussive fluid may flow or “seep” between the plug
12
and the seat
4
b
and cause the casing pressure to decrease to ambient pressure. Thus, the valve spring
13
and movable plug
12
may have to be replaced several times during the life of the drill assembly
1
. Further, due to the potential that one or more check valve components will wear or break, there is still a significant risk that the backflowing of contaminants may occur.
In view of the above-discussed limitations with the known check valve
11
, it would be desirable to have a check valve system that involved fewer moving parts. Further, it would be desirable to have a check valve that was simpler and thus less expensive to produce. Furthermore, it would also be desirable to have a device for maintaining the distributor
7
at a desired position that is simpler than the spring-biased retainer
16
and that preferably has no moving parts.
SUMMARY OF THE INVENTION
In one aspect, the present invention is a check valve system for a fluid-actuated percussive drill assembly. The drill assembly includes a casing and a backhead connected with and extending into the casing. The backhead has a longitudinal central axis, a supply passage extending along the central axis, and an outer surface section extending circumferentially about the central axis and disposed within the casing. The check valve system comprises a port extending between the outer circumferential surface section of the backhead and the supply passage. A check valve is disposed about the outer circumferential surface section of the backhead and is configured to alternately permit fluid flow through the backhead port and substantially seal the backhead port.
In another aspect, the present invention is a check valve for a fluid-actuated percussive drill assembly. The drill assembly includes a casing and a backhead connected with and extending into the casing. The backhead has a longitudinal central axis, a supply passage extending along the central axis, an outer surface extending circumferentially about the axis and disposed within the casing, and a port extending between the outer circumferential surface and the supply passage. The check valve comprises an annular member disposable about the outer circumferential surface of the backhead. The annular member is configured to alternately permit fluid flow through the backhead port and substantially seal the backhead port.
In yet another aspect, the present invention is a backhead for a fluid-actuated percussive drill assembly having a casing and a fluid distributor disposed within the casing. The backhead comprises a body connected with the casing and having an end disposed within the casing. The end of the body is configured to receive a portion of the distributor so as to generally retain the distributor at a desired position within the casing.
In an even further aspect, the present invention is also a backhead for a fluid-actuated percussive drill assembly. The backhead comprises a body having a first end, a second end, an inlet port at the first end, an outer circumferential surface section disposed between the first and second ends, a plurality of radial outlet ports spaced circumferentially about the outer surface section, and a supply passage extending between the inlet port and the outlet ports.
REFERENCES:
patent: 5085284 (1992-02-01), Fu
patent: 5301761 (1994-04-01), Fu et al.
patent: 5562170 (1996-10-01), Wolfer et al.
patent: 5566771 (1996-10-01), Wolfer et al.
patent: 5711205 (1998-01-01), Wolfer et al.
Ingersoll-Rand Company
Pezzuto Robert E.
Ussai Mark A.
LandOfFree
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