Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2000-01-12
2001-12-11
Lee, Kevin (Department: 3754)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S527000, C251S303000
Reexamination Certificate
active
06328062
ABSTRACT:
FIELD OF THE INVENTION
The field of this invention relates to connection systems for torsion spring closure, particularly useful for flappers and subsurface safety valves.
BACKGROUND OF THE INVENTION
Subsurface safety valves (SSVs) which incorporate a closure member which pivots 90°, also known as a flapper, have been in use for many years. Typically, the flapper is pushed downwardly by a tube to get it out of the way of the flowpath. The tubular that pushes the flapper out of the way is known as the flow tube. The flapper is typically spring loaded, such that when the flow tube is pushed or otherwise urged upwardly away from the flapper, the torsion spring or springs bias the flapper 90° to close the flowpath as the flapper engaged a mating seat.
Prior art designs for return springs on flappers are illustrated in
FIGS. 1 and 2
.
FIG. 1
illustrates a flapper
10
which has dual hinges
12
and
14
, which are secured by a pin
16
to the body
18
of the SSV. A torsion spring
20
has an annular shape and the pin
16
extends through it as well as through the hinges
12
and
14
. A tab
22
comprises the end of the torsion spring
20
and bear on the flapper
10
. At the opposite end of the spring
20
, another tab
24
is braced against the body
18
. When the flow tube (not shown) is pushed down, the torsion spring
20
winds up as the flapper
10
is pushed down through an arc of 90° to get it out of the way so that flow of fluids can occur through the flow tube. When the flow tube is allowed to move upwardly, the spring
20
, acting through tab
22
, initiates the reverse movement through an arc of 90° of the flapper
10
so that the flapper
10
closes against its mating seat (not shown). One of the problems with this design is limitation of space, which in turn forces the use of fairly high stresses in the springs, such as
20
, when used in SSVs. The design of
FIG. 1
also has limitations on the closure force available due to the space requirements for fitting the spring between two hinges
12
and
14
. Indeed, some designs do not accommodate the use of dual hinges
12
and
14
and, in those instances, the torsion springs have been disposed circumferentially around the periphery of the flapper, as is more clearly illustrated in FIG.
2
.
FIG. 2
is another prior art design that involves a flapper
26
which has a single hinge
28
. A pin
30
extends through hinge
28
to support the flapper
26
for 90° rotation. Pin
30
has passages or openings
32
and
34
on opposite ends thereof. A pair of torsion springs
36
and
38
are disposed circumferentially adjacent the periphery of the flapper
26
. On one end, the torsion springs
36
and
38
are respectively connected to the body
40
of the SSV at connections
42
and
44
. At the other end of torsion springs
36
and
38
, there are hooks
46
and
48
. Hooks
46
and
48
extend respectively through openings
32
and
34
. Accordingly, when the flapper
26
is pushed downwardly by the flow tube (not shown), the springs
36
and
38
, because of their connections through openings
32
and
34
to the pin
30
, resist such movement and coil up to store a closing force. Pin
30
rotates with flapper
26
, thus rotating the hooks
46
and
48
as the flapper
26
reaches the fully open position of the SSV. One of the potential problems with this design is the multi-axial movement of the hook ends
46
and
48
in openings
32
and
34
. This results in excessive friction and wear of the hook ends
46
and
48
, with the possibility of a fatigue failure adjacent the point where the hook ends
46
and
48
enter or exit the openings or passages
32
and
34
. This multi axial movement coupled with the multiple interfaces between the flapper and torsion springs can result in excessive play between the torsion spring hook ends, pin and flapper. During the rotation of the flapper and pin, the multi-axial movement of the hook ends can create excessive friction. This friction, combined with the excessive play in the system, can negate some of the force that is stored in the torsion springs.
Accordingly, the objective of the present invention is to facilitate the use of the wrap around style of torsion springs, such as
36
and
38
, while at the same time providing an improved torsional loading point which supports the flapper so that excessive play and friction is eliminated.
Accordingly, the objective of the present invention is to facilitate the use of a wraparound style of torsion springs, such as
36
and
38
, while at the same time providing an improved connection to the pin which supports the flapper so that concentrated zones of high stress are eliminated and the likelihood of fatigue failure is also severely reduced, if not completely eliminated.
Accordingly, alternative proposals are described to accomplish the objective as will be apparent to those skilled in the art from a review of the description of the preferred embodiments of the invention.
SUMMARY OF THE INVENTION
A torsion spring return system for a valve closure member, preferably for downhole use in an SSV, is described. The closure member or flapper uses torsion springs which can be wrapped circumferentially within the body of the downhole tool, generally following the periphery of the flapper. Downward rotation of the flapper stresses the torsion springs so that subsequently, when a flow tube or other device holding the flapper in one position is released, the torsion springs return the flapper to its seat. The connection between the torsion springs and the pin supporting the flapper is either a universal joint or involves an alignment rod running through the torsion spring, as well as other mechanisms which facilitate stress relief in the connection between the torsion spring and pivot pin.
REFERENCES:
patent: 4019532 (1977-04-01), Schittek
patent: 4407325 (1983-10-01), Cherniak
patent: 4531587 (1985-07-01), Fineberg
patent: 5156374 (1992-10-01), Fort et al.
patent: 5411056 (1995-05-01), Solaroli
patent: 6003605 (1999-12-01), Dickson et al.
patent: 1308954 (1973-03-01), None
patent: 1563487 (1978-02-01), None
patent: 2198170 (1988-06-01), None
patent: 2236549 (1991-04-01), None
patent: WO86/05853 (1986-10-01), None
Rawson Michael S.
Williams Ronald
Baker Hughes Incorporated
Lee Kevin
LandOfFree
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