Rotary expansible chamber devices – Multistage – Sliding vane
Reexamination Certificate
2001-08-17
2002-12-31
Vrablik, John J. (Department: 3748)
Rotary expansible chamber devices
Multistage
Sliding vane
C418S188000, C418S225000
Reexamination Certificate
active
06499976
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to downhole fluid driven motors used in the oil and gas drilling industry. In particular, the present invention relates to an improved roller vane motor.
There are various types of fluid driven motors which are designed to be incorporated into a drill string and are used to power (supply torque to) drill bits and other downhole tools. One type is the roller vane motor. The roller vane motor will normally be positioned in the drill string above the tool to be driven. A fluid (e.g. water, drilling mud, etc.) is pumped through the roller vane motor causing the motor to generate torque.
FIG. 1
shows a cross-sectional view of a typical prior art roller vane motor
60
. The motor
60
will generally comprise a stator
61
and a rotor
63
. Rotor
63
will further include a series of flutes
66
with pockets
67
formed between flutes
66
and rollers
65
positioned in pockets
67
. A fluid supply valve
68
will be formed through the center of rotor
63
. Fluid passages
69
will communicate between supply valve
68
and pockets
67
. Stator
61
will include interior stator walls which have varying radii. Portions of the stator wall will have a short radius (short radius portion
64
a
) approximate to the radius of flutes
66
, such that flutes
66
forms a seal as they pass the short radius. Other portions of the stator wall will have a long radius (long radius portion
64
b
) which allows roller
65
to travel partially out of pockets
67
. The stator will also have fluid exhaust ports
62
proximate said short radius stator wall portions. These fluid exhaust ports
62
are typically oriented radially outward from rotor
63
as suggested in FIG.
1
.
In operation, fluid will be pumped down the drill string and will enter fluid supply valve
68
. Rollers
65
which are facing a long radius portion
64
b
of the stator wall will tend to be pushed outward by the flow of fluid. Viewing in particular the roller designated
65
a
, it can be seen how rollers
65
will form a seal between rotor
63
and the long radius portion
64
b
of the stator wall and prevent the flow of fluid in the gap between rotor
63
and the stator wall. Another seal is formed between the flutes
66
of rotor
63
and the short radius portion
64
a
of the stator. Following the flow arrows in
FIG. 1
, it can be seen how fluid to the right of roller
65
a
may escape through exhaust port
62
and thus will be at the lower pressures existing outside the stator. On the other hand, higher pressure fluid flowing out of supply valve
68
into pockets
67
will be contained between the seal formed by flute
66
and short radius portion
64
a
and the seal formed by roller
65
a
engaging both the long radius portion
64
b
and the flute
66
. The net effect of this arrangement is the accumulation of high pressure on the left side of roller
65
a
and lower pressure on the right side. Therefore, roller
65
a
will tend to move right toward exhaust port
62
and impart torque to rotor
63
. Roller
65
a
will continue to impart torque to rotor
63
until roller
65
a
comes into contact with short radius portion
64
a
of the stator and roller
65
a
is forced into pocket
67
, allowing the high pressure fluid behind roller
65
a
to escape through exhaust port
62
.
One disadvantage with this prior art roller vane motor is that it is highly vulnerable to particulate matter in the power fluid. Very close tolerances are required where seals are intended to be formed, e.g. between flutes
66
and short radius portion
64
a
or between fluid passages
69
and the fins on supply valve
68
. Particulates in the driving fluid either tend to stall the motor and/or seriously abrade the sealing surfaces. Additionally, the fins on supply valve
68
provide a very inefficient mechanism for sealing fluid passages
69
. When these fins attempt to seal fluid passages
69
, they present a critical short leak path between high and low pressure regions. Another disadvantage is the abrupt or violent manner in which rollers
65
will be forced into pockets
67
as the rollers approach short radius portion
64
a
of the stator. This abrupt action causes severe wear on both the roller and stator wall, thereby significantly reducing the useful life of the motor. It is believed that the degree of force with which rollers
65
are shifted in and out of pockets
67
is increased by exhaust ports
62
being oriented at a high angle in relation to the tangent of the stator wall at the exhaust port. For example,
FIG. 1
illustrates a dashed line
71
tangent to the stator wall approaching exhaust port
62
. Dashed line
72
shows the orientation of the exhaust port
62
. The angle &agr; demonstrates the orientation of exhaust port
62
to tangent line
71
is approximately 90°. Additionally, when the roller vane motor is starting up from a stationary position, there is a tendency for the motor to “lock up” because the rollers are forced into exhaust ports
62
and tend to remain there. This tendency to lock-up is also believed to be caused or aggravated by exhaust ports being oriented at high angles relative to the tangent of the stator wall.
SUMMARY OF THE INVENTION
The present invention provides a roller vane motor for use in downhole drilling operations or various other applications. The roller vane motor has a housing and a stator positioned on an inside surface of the housing. The stator has an internal wall with an inlet port and an outlet port formed therein and the portion of this internal wall at the outlet port tapers open at an angle of less than 45 degrees relative to a tangent of the internal wall. A rotor assembly is positioned within the stator and includes: i) a rotor shaft, ii) a plurality of flutes extending from the rotor shaft; and iii) cylindrical rollers positioned between said flutes.
REFERENCES:
patent: 1944018 (1934-01-01), Thompson
patent: 2068570 (1937-01-01), Ross
patent: 2631544 (1953-03-01), Wilcox
patent: 3025802 (1962-03-01), Browne
patent: 3213801 (1965-10-01), Venygr
patent: 3247803 (1966-04-01), Halsey
patent: 3381622 (1968-05-01), Wilcox
patent: 3447476 (1969-06-01), Farris
patent: 3877442 (1975-04-01), Miller, Jr.
patent: 3966369 (1976-06-01), Garrison
patent: 4105377 (1978-08-01), Mayall
patent: 5030071 (1991-07-01), Simpson
patent: 5733113 (1998-03-01), Grupping
patent: 5785509 (1998-07-01), Harris et al.
patent: 610.744 (1926-09-01), None
patent: 47795 (1940-02-01), None
patent: WO92/14037 (1992-08-01), None
Fleming Douglas R.
McPhate Andrew J.
McPhate Matthew
Jones Walker Waechter Poitevent Carrere & Denegre, LLP
Vrablik John J.
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