Note: Descriptions are shown in the official language in which they were submitted.
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IMPROVEMENTS IN OR RELATING TO
UNDERWATER EXCAVATION APPARATUS
This invention relates to an improved excavation
apparatus, and in particular to an improved underwater
excavation apparatus.
Underwater excavation apparatus are known, eg, from GB
2 240 568 (CONSORTIUM RESOURCE et al). In that disclosure
there is described an underwater excavation apparatus
comprising a hollow body with an inlet to receive water and
an outlet for discharge of water. A propeller is rotatably
mounted in-the hollow body to draw water through the inlet
and deliver a flow of water through the outlet. Water jets
on the propeller tips rotate the propeller when water is
supplied to the jets.
Such rotation causes water to be drawn into the body
through the inlet and expelled from the body as a flow
through the outlet. The flow can be used to displace
material on the seabed.
Known prior art underwater excavation apparatus suffer
from a number of problems/disadvantages, for example:
(a) Low energy efficiency due to e.g. hydrodynamic
limitations of fluid jets, thus requiring extremely
large and power hungry pumps to drive the system);
(b) tendency of apparatus to rotate in reaction to rotation
of the propeller;
(c) difficulty in steering and positioning of the
apparatus.
It is an object of at least some of the aspects of the
present invention to seek to obviate or mitigate one or more
of the aforementioned problems in the prior art.
According to a first aspect of the present invention
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there is provided an underwater excavation apparatus
comprising a hollow body having at least one inlet and at
least one outlet, at least one pair of impellers rotatably
mounted in the hollow body and means for driving the
impellers.
Advantageously, the driving means cause the impellers
to be driven in contrary rotating directions, in use.
The at least one inlet may be inclined at an angle to
an axis along which the at least one outlet is provided.
Preferably, there is provided at least one pair of
inlets.
Preferably, the at least one pair of inlets are
substantially symmetrically disposed around an axis
extending from the outlet.
In one embodiment the underwater excavation apparatus
comprises a pair of horizontally opposed inlets
communicating with a single outlet, the outlet being
disposed vertically downwards substantially midway between
the two inlets, in use. In this case, the excavation
apparatus is, therefore, substantially "T" shaped in
profile.
In an alternative embodiment the underwater excavation
apparatus comprises a pair of inlets communicating with a
single outlet, the inlets being substantially symmetrically
disposed around an axis extending from the outlet, the
outlet being disposed vertically downwards substantially
midway between the two inlets, in use. In this case, the
excavation apparatus is, therefore, substantially "Y" shaped
in profile.
Advantageously, the outlets are each spaced/inclined
substantially 45° from the axis extending from the outlet.
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At least one impeller may be provided within/adjacent
each inlet.
The means for driving the/each impellers) may include
at least one drilling motor.
The at least one drilling motor may comprise a stator
and a rotor rotatably mounted in the stator, the stator
being provided with a rod recess and an exhaust port, the
rotor being provided with a rotor channel and at least one
channel for conducting motive fluid from the rotor channel
to a chamber between the rotor and the stator, the rod
recess being provided with a rod which, in use, forms a seal
between the stator and the rotor.
Although not essential it is highly desirable that the
rotor be provided with a seal for engagement with the
stator.
Preferably, the seal is made from a material selected
from the group consisting of plastics materials,
polyethylethylketone, metal, copper alloys and stainless
steel.
Advantageously, the rod is made from a material
selected from the group consisting of plastics materials,
polyethylethylketone, metal, copper alloys and stainless
steel.
Preferably, the stator is provided with two rod
recesses which are disposed opposite one another, and two
- exhaust ports which are disposed opposite one another, each
of the rod recesses being provided with a respective rod,
the rotor having two seals which are disposed opposite one
another.
The drilling motor may advantageously comprise two
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drilling motors arranged with their respective rotors
connected together each motor comprising a stator and a
rotor rotatably mounted in the stator, the stator being
provided with a rod recess and an exhaust port, the rotor
being provided with a rotor channel and at least one channel
for conducting motive fluid from the rotor channel to a
chamber between the rotor and the stator, the rod recess
being provided with a rod which, in use, forms a seal
between the stator and the rotor.
Preferably, the drilling motors are connected in
parallel, although they could be connected in series if
desired.
Advantageously, the drilling motors are arranged so
that, in use, one drilling motor operates out of phase with
the other. Thus, in a preferred embodiment each drilling
motor has two chambers and the chambers in the first
drilling motor are 90° out of phase with the chambers in the
second drilling motor. Similarly, in an embodiment in which
each drilling motor has four chambers, the chambers in the
first drilling motor would preferably be 45° out of phase
with the chambers on the second drilling motor. This
arrangement helps ensure a smooth power output and inhibits
stalling.
Alternatively, the at least one drilling motor may be a
"Moineau", hydraulic or a suitably adapted electric motor.
The impellers may be driven by means of a gearbox or by
exploitation of the opposing reactive torque on a drive body
of the motor.
When the reactive torque upon the motor body is
utilised, at least one impeller may be connected to an
output shaft of said motor, while at least one other
impeller may be connected to the motor body.
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Alternatively the impellers may be driven by a pair
of motors operating in opposite directions. In such case
said motors and impellers are balanced and equal.
5 The underwater excavation apparatus may further
comprise an agitator device having mechanical disturbance
means and fluid flow disturbance means.
The underwater excavation apparatus may, in use, be
suspended from a surface vessel or mounted upon a sled of
the type currently known for use in subsea excavation
operations.
According to a second aspect of the present
invention there is provided an underwater apparatus
comprising a hollow body having a pair of inlets
communicating with an outlet, at least one pair of
impellers rotatably mounted in the hollow body and means
for driving the impellers, the inlets being substantially
symmetrically disposed around an axis extending from the
outlet, wherein the inlets are not horizontally opposed
to one another.
According to another aspect of the present invention.
there is providedan underwater excavation apparatus
comprising a hollow body having at least one pair of
inlets and at least one outlet, at least one pair of
impellers rotatably mounted in the hollow body and means
for driving the impellers, wherein the driving means
cause the impellers to be driven in contrary rotating
directions and wherein the at least one pair of inlets is
inclined at an angle to an axis along which the at least
one outlet is provided.
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5a
Embodiments of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings, in which:
Fig 1 shows a cross-sectional side view of
a first embodiment of an excavation
apparatus according to the present
invention;
Fig 2 shows a longitudinal cross-sectional
view of one embodiment of a drilling
apparatus for use in the excavation
apparatus in Fig 1 according to the
present invention;
Figs 3A-3D are cross-sectional views along line
A-A
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of Fig 2 showing a rotor of the motor in
four different positions; and
Figs 4A-4D are cross-sectional views along line B-B
of Fig 2 showing the rotor in four
different positions.
Fig 5 shows a cross-sectional side view of a
second embodiment of an excavation
apparatus according to the present
invention;
Fig 6 shows a cross-sectional side view of a
third embodiment of an excavation
apparatus according to the present
invention.
Ref erring to Fig l, there is shown a first embodiment
of an underwater excavation apparatus 300a according to the
present invention. The apparatus 300a comprises a hollow
body 370a formed from a pair of horizontally opposed inlet
ducts 371a and an outlet duct 373a, a drive motor 310a and a
pair of impellers 335a, 340a.
The apparatus 300a is further provided with deflection
baffles 302a within the hollow body 370a, suspension
brackets 306a to enable the apparatus 300a to be suspended
from a surface vessel, guide vanes 386a to regulate the flow
of fluid past the impellers 335a, 340a, and safety grids
385a to seek to prevent the ingress of solid matter which
may damage the impellers 335a, 340a.
In this first embodiment, the drive motor 310a is
provided along an axis common to the horizontally opposed
inlet ducts 371a and impellers 335a, 340a. An output shaft
330a of the motor 310a is connected to a first impeller 335a
while the second impeller 340a is attached to a shaft 342a
connected via a swivel 325a to an outer housing of the drive
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motor 310a.
In use, motive fluid is supplied to the motor 310a. via
fluid inlet 308a which in turn causes the output shaft 330a
and impeller 335a to rotate. Reactive torque from this
rotation causes the outer housing of the drive motor 310a to
rotate in a direction opposite to that of the output shaft
330a. This in turn results in the rotation of the second
impeller 340a. The impellers 335a, 340a are configured such
that, despite rotating in opposite directions, they ~=ach
provide an equal flowrate of water into the hollow body
370a, water drawn into the hollow body 370a thus is
directed via the deflection baffles 302a through the out=let
duct 373a and towards the seabed 400a.
The shaft 342a and swivel 325a may, in an alternative
embodiment, be replaced by a second motor which directly
drives the impeller 340a, as hereinbefore described with
reference to Fig 5.
The excavation device 300a may be suspended, f or
example, from the bow or stern of a .surface vessel, or
through a moonpool of a.dedicated subsea operations vessel.
In an alternative embodiment the device 300a may be
provided upon a sled (not shown) of the type currently u;aed
for subsea operations. The excavation apparatus 300a rnay
further be provided with an agitator device (not shown)
having mechanical disturbance means and fluid flow
disturbance means.
In an advantageous embodiment the motor 310 comprises'. a
drilling motor, such as that disclosed in W095/19488.
The drilling motor 310 may comprise a first motor 20
and a second motor 50.
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The first motor 20 comprises a stator 21 and a rotor
23. A top portion 22 of the rotor 23 extends through an
upper bearing assembly 24 which comprises a thrust bearing
26 and seals 25.
Motive fluid, e.g. water, drilling mud or gas under
pressure, flows down through a central sub channel 12 into a
central rotor channel 27, and then out through rotor flow
channels 28 into action chambers 31 and 32.
Following a motor power stroke, the motive fluid flows
through exhaust ports 33 in stator 21, and then downwardly
through an annular channel circumjacent the stator 21 and
flow channels 35 in a lower bearing assembly 34. A portion
36 of the rotor 23 extends through the lower bearing
assembly 34 which comprises a thrust bearing 37 and seals
38.
The ends of the stator 21 are castellated and the
castellations engage in recesses in the respective upper
bearing assembly 24 and lower bearing assembly 34
respectively to inhibit rotation of the stator 21. The
upper bearing assembly 24 and lower bearing assembly 34
are a tight fit in an outer tubular member 14 and are held
against rotation by compression between threaded sleeves 16
and 84.
A splined union 39 joins a splined end of the rotor 23
to a splined end of a rotor 53 of the second motor 50. The
second motor 50 has a stator 51.
A top portion 52 of the rotor 53 extends through an
upper bearing assembly 54. Seals 55 are disposed between the
upper bearing assembly 54 and the exterior of the top
portion 52 of the rotor 53. The rotor 53 moves on thrust
bearings 56 with respect to the upper bearing assembly 54.
Motive fluid flows into a central rotor channel 57 from
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the central rotor channel 27 and then out through rotor flow
channels 58 into action chambers 61 and 62. Following a
motor power stroke, the motive fluid flows through exhaust
ports 63 in stator 51, and then downwardly through an
annular channel circumjacent the stator 51 and flow channels
65 in a lower bearing assembly 64. A portion 66 of the
rotor 53 extends through a lower bearing assembly 64. The
rotor 53 moves on thrust bearings 67 with respect to the
lower bearing assembly 64 and seals 68 seal the rotor-
bearing assembly interface. Also motive fluid which flowed
through the flow channels 35 in the lower bearing assembly
34, flows downwardly through channels 79 in the upper
bearing assembly 54, past stator 51 and through flow
channels 65 in the Lower bearing assembly 64.
The upper bearing assembly 54 and lower bearing
assembly 64 are a tight fit in an outer tubular member 18
and are held against rotation by compression between
threaded sleeve 84 and a lower threaded sleeve (not shown).
Figs 2A-2D and 3A-3D depict a typical cycle for
the first and second motors 20 and 50 respectively, and show
the status of the two motors with respect to each other at
various times in the cycle. For example, Fig 2C shows an
exhaust period for the first motor 20 while Fig 3C, at that
same moment, shows a power period for the second motor 50.
As shown in Fig 2A, motive fluid flowing through the
rotor flow channels 28 enters the action chambers 31 and 32.
Due to the geometry of the chambers (as discussed below) and
the resultant forces, the motive fluid moves the rotor in a
clockwise direction as seen in Fig 2H. The action chamber
31 is sealed at one end by a rolling vane rod 71 which abuts
an exterior surface 72 of the rotor 23 and a portion 74 of a
rod recess 75.
At the other end of the action chamber 31, a seal 76 on
a lobe 77 of the rotor 23 sealingly abuts an interior
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surface of the stator 21.
As shown in Fig 2B, the rotor 23 has moved to a point
near the end of a power period.
5
As shown in Fig 2C, motive fluid starts exhausting at
this point in the motor cycle through the exhaust ports 33.
As shown in Fig 2D, the rolling vane rods 71 and seals
10 76 have sealed off the action chambers and motive fluids
flowing thereinto will rotate the rotor 23 until the seals
76 again move past the exhaust ports 33.
The second motor 50 operates as does the first motor
I5 20; but, as preferred, and as shown in Figs 3A-3D, the two
motors are out of phase by 90° so that as one motor is
exhausting motive fluid the other is providing power.
The seals 76 are, in one embodiment, made of
polyethylethylketone (PEEK). The rolling vane rods 71 are
also made from PEEK. The rotors (23, 25) and stators (21,
51) are preferably made from corrosion resistant materials
such as stainless steel.
When a seal 76 in the first motor 20 rotates past an
exhaust port 33, the motive fluid that caused the turning
exits and flows downward, then through the channels 79, past
the exhaust ports 63 and the flow channels 65.
It should be appreciated that although in the disclosed
embodiment the drilling motor 310 comprises two motors
20,50, with suitable adaptation, the drilling motor 310 may
comprise only one motor 20 or 50.
Referring now to Fig 5, there is shown a second
embodiment of an underwater excavation apparatus 300b
according to the present invention. Like parts of the
apparatus 300a are identified by numerals used to identify
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parts of the apparatus 300a of Fig 1, except subscripted
with "b" rather than "a".
The apparatus 300b differs from the apparatus 300a in
that the shaft 342a and swivel 325a are replaced by a second
motor 310'b and a T-coupling 326b. Thus in this embodiment
the impellers 335b, 340b are driven by respective motors
310b, 3I0'b. In use, motive fluid is supplied to motors
310b, 310'b via fluid inlet 308b and T-coupling 326b.
Referring now to Fig 6, there is shown a second
embodiment of an underwater excavation apparatus 300c
according to the present invention. Like parts of the
apparatus 300b are identified by numerals used to identify
parts of the apparatus 300b of Fig 5, except subscripted
with "c" rather than "b".
The apparatus 300c differs from the apparatus 300b in
that whereas in apparatus 300b the inlets 371b are
horizontally opposed, in apparatus 300c the inlets are
substantially symmetrically disposed around an axis
extending from outlet 373c, such that the apparatus 300c is
substantially "Y" shaped. In this embodiment there is,
therefore, provided a Y-coupling 326c.
The embodiments of the invention hereinbefore described
are given by way of example only, and are not meant to limit
the scope of the invention in any way. It should be
particularly appreciated that the drilling motor 310 is
suitable for use in any of the disclosed embodiments.
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