Note: Descriptions are shown in the official language in which they were submitted.
CA 02568676 2006-11-22
ELECTRIC WINCH MOTOR
FIELD OF THE INVENTION
The present invention relates to an electric winch for winding and unwinding
cable, and
in particular to a winch having an internal electric motor and to a method of
raising and lowering
down hole equipment using the winch.
BACKGROUND OF THE INVENTION
Winches used in commercial applications are generally constructed and operated
in a
similar manner. The basic elements comprise a large-diameter steel spool or
drum, brakes, a
power source and assorted auxiliary devices. The primary function of the winch
is to reel out and
reel in the cable, in a controlled fashion by rotating the drum. The reeling
out of the cable is
largely powered by gravity. The reeling in of the cable is powered by the
power source that is
usually an electric motor or diesel engine, which is coupled to an
intermediary gearing or drive
system.
An example of a winch used in a commercial application is a drawworks used in
oilfield
drilling. The drawworks is a winch found on an oil rig on or below the rig
deck. The primary
function of the drawworks is to wind in and unwind the drilling line, a large
diameter wire rope,
as required. The drilling line is reeled over a crown block and traveling
block to gain mechanical
advantage in a "block and tackle" or "pulley" fashion. This reeling out and in
of the drilling line
causes the traveling block, and whatever may be hanging underneath it, to be
lowered into or
raised out of the well bore.
Conventional commercial winches, such as a drawworks winch, have the power
source
configured in an indirect drive manner with the power source positioned
adjacent to the drum.
The power source is connected to one or more gearboxes in a variety of ways
including the use
of drive shafts, couplings, transmissions or clutches. The gearbox in turn is
connected to the
CA 02568676 2006-11-22
drum using chain drives or other conventional drive mechanisms. Such indirect
drive
conventional drawworks systems have a number of disadvantages. First, an
external power
source occupies more space. In the context of the drawworks winch, the extra
space required for
the power source makes it difficult to place the drawworks in an optimal
position on the already
crowded oil rig. External power sources are noisy and can present a hazard to
those working
around them. Further, conventional winch systems, in particular the gearbox of
conventional
systems, require frequent maintenance and must be lubricated regularly. Many
conventional
winches employ complex lubrication systems for the drum and gearbox that
require heating
systems for the winter and cooling systems for the summer. Also, during the
transmission of
power through the indirect drive system, there are significant energy losses
and a resulting
inefficiency associated therewith.
Prior art suggestions at improved winches have been largely focused on
providing
sophisticated gearing mechanisms to use with the remote power source, and on
improved braking
systems to try and increase the safety of the winch systems. However, such
suggestions do not
address the previously described disadvantages and limitations of conventional
winch systems.
SUMMARY OF THE INVENTION
The present invention is directed to an electric winch for winding and
unwinding cable,
and in particular to a winch having an intemal electric motor, and to a method
of positioning an
electric motor within the drum of a winch.
Accordingly, in one aspect of the invention, the invention comprises an
electric winch for
winding and unwinding cable comprising:
(a) a fixed, non-rotating shaft, whereby the shaft is supported at each end by
support
means;
(b) an electric motor comprising:
(i) a stator fixed to the shaft;
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(ii) a rotor rotating about the stator, the rotor forming a drum for winding
cable;
(c) bearing means between the motor stator and the motor rotor;
(d) means for connecting the electric motor to a source of electricity; and
(e) at least one brake for stopping the rotor.
In one embodiment, the motor may have a cooling system. In one embodiment, the
winch is a
drawworks for winding and unwinding drilling cable. In one embodiment, the
motor may be an
AC induction electric motor, a D/C traction electric motor, a DC switch
reluctant motor or a
permanent magnet electric motor. In a further embodiment, the shaft may be
hollow with power
cables and coolant hoses running through the hollow shaft to the stator.
In another aspect, the invention comprises a drawworks having an internal
electric motor for use
on an oil rig, the drawworks comprising;
(a) a fixed, non rotating shaft supported at each end by a pedestal;
(b) an electric motor comprising:
(i) a stator fixed to the shaft;
(ii) a rotor rotating about the stator, the rotor forming a drum for winding
drilling cable;
(c) bearing means between the motor stator and the motor rotor; and
(d) at least one brake for stopping the rotor.
In another aspect, the invention comprises a method of raising and lowering
down hole
equipment with a drilling or service rig using a drawworks comprising a winch
as described
herein.
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BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described by way of an exemplary embodiment with
reference
to the accompanying simplified, diagrammatic, not-to-scale drawings. In the
drawings:
Figure 1 is a diagrammatic front view of one embodiment of the present
invention.
Figure 2 is a diagrammatic front view of one embodiment of the present
invention.
Figure 3 is a diagrammatic front view of one embodiment of the present
invention.
Figure 4 is a diagrammatic end view of one embodiment of the present invention
Figure 5 is a diagranzmatic depiction of the stator and central shaft of one
embodiment of
the present invention.
Figure 6 is a diagrammatic front view of the rotor and drum of one embodiment
of the
present invention.
Figure 7 is a diagrammatic front view of the rotor and drum of one embodiment
of the
present invention.
Figure 8 is a diagrammatic depiction of the bearings of one embodiment of the
present
invention.
Figure 9 is a diagrammatic depiction of the pedestals of one embodiment of the
present
invention.
DETAILED DESCRIPTION OF THE INVENTION
Scope
The present invention provides for an electric winch for winding and unwinding
cable, and in
particular, to a winch having an internal electric motor. When describing the
present invention,
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all terms not defmed herein have their common art-recognized meanings. To the
extent that the
following description is of a specific embodiment or a particular use of the
invention, it is
intended to be illustrative only, and not limiting of the claimed invention.
The following
description is intended to cover all alternatives, modifications and
equivalents that are included
in the spirit and scope of the invention, as defined in the appended claims.
Definitions
In this patent the following words are intended to have the following meaning:
"AC" shall mean alternating current.
"DC" shall mean direct current.
"rotor" shall mean the rotating part of an electric motor.
"stator" shall mean the stationary part of an electric motor.
Description
The present invention is directed to a winch apparatus and to a method of
raising and lowering
down hole equipment using the winch.
As depicted in Figures 1, 2 and 3, the winch (10) has a fixed non-rotating
shaft (22). An electric
motor stator (16) is fixed to the shaft (22). The shaft (22) and the motor
stator (16) are supported
at each end by suitable support means (24). As shown in the Figures, pedestals
are suitable for
supporting the shaft (22) and stator (16).The pedestals are fixed to a stable
surface such as a
drilling deck (26) or lower level substructure by any suitable means as would
be selected by one
skilled in the art, including bolts (38) as shown in Figure 1, or by welded
joints. The use of
bolts, or other removable attachment means, allows the disassembly and removal
of the pedestals
(24) and winch (10) if required. It also facilitates the replacement of a
damaged pedestal (24) or
engine or drum component ' if required. The shaft (22) and support means (24)
may be
constructed from any suitable material but must be strong enough to support
the combined
weight of the motor stator (16), the rotor (16), the drum (12) and the cable
(14) and must be able
also be strong enough to withstand the torque placed on them by virtue of the
rotating motor and
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the braking loads exerted by the cable (14) during winding and unwinding
operations. Iron
alloys and steel alloys have been found to be suitable.
As shown in Figures 5 and 9, the support means (24) and the ends of the shaft
(22) and motor
stator (16) may be coupled and the stator and shaft held in place using a
splined system.
However, any other suitable coupling or restraint system that prevents
movement of the shaft
(22) and stator (16) may be employed including without limitation, ring
fetters, bolts and flanges,
or any combination of the same. End protectors (40) can be used to protect the
connection
between the stator (16), the shaft (22) and the support means (24). Neither
the shaft (22), nor the
stator (16), rotates and are held still by the support means (24) in a fixed
manner. The shaft may
be solid or hollow. As shown in Figure 1, a power cable (34) and coolant hoses
(36) or air ducts
(not shown) can be run through the end of the shaft to the motor stator (16).
In the case of a
hollow shaft, the cable, hoses or ducts, as the case may be, run through the
internal space of the
shaft to the stator. In the case of a solid shaft, preformed insulated
channels running through the
shaft may be used to convey hoses, cables or ducts, as the case may be, to the
stator.
The winch is optionally shrouded with guard plates (not shown in the Figures),
which may be
constructed from any suitable metallic material including twin plate steel.
The electric motor may preferably have a coolant system (not shown in the
Figures) for cooling
the electric motor. The coolant system can be a liquid-cooled system or an air-
cooled system
depending on the needs of the electric motor. In one embodiment employing a
liquid cooled
system, coolant is held in a reservoir and is then pumped through filters to a
coolant hose that
supplies that stator (16). As shown in Figure 1, the coolant hose (36) can run
through a hollow
shaft (22) connecting to the stator (16) at a central position. Alternatively,
the coolant hose could
run through channels in a solid shaft, or, in the further alternative, the
coolant hose does not have
to run through the shaft and can connect to the stator in proximity to the
support means (24).
The coolant is circulated through the stator (16) through tubes drawing heat
from the stator (16).
With a liquid cooled system, the coolant is circulated through the stator and
not through the rotor
(18) or any other components such as the stator windings. The heated coolant
is removed from
the stator (16) using a return hose or tube (36), or a plurality of hoses, and
is cooled using a
cooling radiator or shell and tube cooler system. After being cooled, the
coolant is returned to
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the reservoir. The system has a pump to circulate the coolant and has flow,
and temperature
controls and monitors. Dependant on the operation climate, the coolant may be
a water/glycol
mix, or the coolant may predominantly be comprised of an inhibitor to minimize
corrosion.
The stator (16) and rotor (18) can also be air cooled by force blowing large
volumes of air across
these components. An inlet can be created using a plate at one side of the
stator at a position
proximate to the bearings (20) and an outlet may be created at the other end
in a similar manner.
Air that has been filtered to remove debris and particles is passed across the
stator (16) and rotor
(18) using a fan from the inlet to the outlet, thereby cooling the motor.
The rotor (18) rotates about the longitudinal axis of the stator (16) and the
shaft(18). The outer
surface of the rotor (18) is formed to create a drum (12) for winding and
unwinding cable (14).
Alternatively, the rotor and the drum may be separate components with the drum
(12) being
mounted to the outside of the rotor (18). Therefore, it can be seen that the
present invention
comprises a direct drive winch system that does not rely on an external power
source, a drive
shaft or gearing system as found in conventional winches. The power source,
namely an electric
motor, is located inside the drum (12).
The drum (12) of the present invention may be the same size as a conventional
drum or it may be
larger than a conventional winch drum. As shown in the Figures, the drum (12)
has grooving to
assist with the alignment of the cable. The grooving may be cut into the drum
itself, or may be
casted onto the drum. Any suitable material may be used for the grooving,
however the
inventors have found 4130 HTDR, 4140 HTSR or 4330 vanadium modified steel
alloys to be
well suited. The electric winch (10) of the present invention is quieter than
conventional
winches with external power sources and furthermore, it is more compact
requiring less space.
The use of a larger drum generates greater torque and the larger drum rotates
more slowly than a
smaller conventional drum. The slower rotation speed and reduced cable turns
greatly reduces
the wear on the cable and extends its useful life. With a conventional
drawworks, the use of a
larger drum would require a larger motor or a greater gear ratio to rotate the
drum, however with
the present invention, the internal electric motor in its direct drive
configuration generates ample
torque to turn the larger drum.
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The motor (19) comprises a stator (16) and a rotor (18). Any suitable electric
motor may be
used, including without limitation, an AC induction motor, a DC traction
motor, a DC switch
reluctant motor or a permanent magnet motor. As shown in the Figures, there
may preferably be
an air gap between the rotor and the stator. In one embodiment, because there
is no gearing
system being utilized, the electric motor selected must be able to generate
sufficient torque for
the intended application. The electric motor is connected to a source of
electricity using
insulated cables, or any other suitable means commonly employed by those
skilled in the art.
A conventional drawworks has numerous heavy moving intermediary components
including, the
motor itself, the drive shaft, the gear box, the cable drum, the gear box
bearings, the drum
bearings, and the drawworks shaft. The cumulative inertial movement leads to
inefficiency and
wasted energy. The direct drive system of the present invention transfers
power directly to the
drum and is much more efficient. There are far less moving parts and the winch
is much lighter;
therefore there is less energy loss. The lighter drawworks of the present
invention, having less
inertial movement, makes it well suited for offshore drilling operations
subject to heave and
wave forces.
The rotor (18) rotates about the stator (16) on bearings (20) found at each
end of the stator. Any
appropriate bearing system as would be commonly used by one skilled in the art
may be used in
the electric winch of the present invention including without limitation,
roller bearings, angular
contact bearings, spherical bearings, ceramic bearings, plain bearings and
magnetic bearings.
The bearing assembly is sealed to prevent the entry of debris or foreign
matter into the space
between the stator (16) and the rotor (18). The electric winch has inspection
ports (32) for
checking that the bearings are appropriately greased. Unlike conventional
winch systems, the
electric winch of the present invention requires comparatively minimal
greasing and lubrication
and further, it requires less maintenance than a conventional winch system.
With a sealed
bearing system, the system only requires greasing approximately twice a year.
If a magnetic
bearing system is used, no such maintenance is required.
Unlike a conventional winch system, the electric motor (19) is used for all of
the braking of the
drum (14) however, in the event of a loss of power supply, such as a brown out
or black out,
separate emergency brakes would be applied. Any suitable types of brakes may
be used with the
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drawworks of the present invention for such emergencies including without
limitation, band
brakes, caliper brakes, Eaton brakes, water cooled brakes or disc brakes.
Figure 3 shows a winch
with band brakes (28). Figure 4 shows an end view of the drum (14) with
caliper brakes (30).
The brakes can also be used in a parking brake type manner if desired.
When the electric winch is used as a drawworks winch for winding and unwinding
drilling line
to raise and lower down hole equipment, there are a number of advantages. The
drawworks is
smaller and lighter taking less space on the drilling deck. This also allows
the drawworks to be
placed closer to the borehole or, alternatively, further away from the bore
hole. If placed further
away, this provides for a larger workspace for the rig hands to work and
allows the placement of
additional equipment such as an iron roughneck. The drill hands are not
exposed to the danger
of an external power source and the drawworks is much quieter, again creating
a safer work
environment. The drawworks using the electric winch of the present invention
does not require a
lubrication system and requires comparatively less maintenance. The drawworks
of the present
invention is light enough to leave in the substructure when a rig is moved
from well to well, and
it small enough that it can be placed in positions that conventional drawworks
cannot be placed
in, such as between the A-legs of a rig, further back in the rig substructure,
or on matting pinned
to the substructure.
The elements of the winch of the present invention may be constructed from any
suitable
materials including without limitation steel and iron and alloy mixtures of
the same. Any
materials used must be able to withstand the wear and torque that they will be
subjected to as
part of a winch system.
Although the electric winch of the present invention has been described in the
context of a
drawworks, it should be understood that it can be used in any suitable
commercial application
such as cranes, hoists and elevator motors.
As will be apparent to those skilled in the art, various modifications,
adaptations and
variations of the foregoing specific disclosure can be made without departing
from the scope of
the invention claimed herein.
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