Note: Descriptions are shown in the official language in which they were submitted.
1;~7~ 8
_ACKGRO~ND OF THE INVENTION_ _
The present invention relates to a submersible platform
dredge.
Various types oE dredges have been developed over the
years to meet varied classes of materials and varied
excavation requirements. The various dredges generally fall
into two basic categories, namely, bucket dredges and
hydraulic dredges. Bucket dredges include grab, dipper and
ladder dredges while hydraulic dredges include plain-suction,
draghead and cutterhead dredges.
Bucket dredges all have one limitation--the discharge
must be alongside the place of excavation or put in barges or
scows which can carry it away. The grab dredge is essentially
a grab bucket operated from a derrick mounted on a flat topped
barge. Although a grab dredge works well in silts and stiff
muds, it is unsuitable for hard materials such as hard clays.
The dipper dredge is a power shovel operating from a barge.
It is effective in hard materials but has a limited dredging
depth of about a maximum of 65 feet.
Ladder dredges use a continuous chain of buckets which
are supported on an inclinable ladder and move up and down on
two pivots called tumblers. As the buckets go around the
lower tumbler, they scoop up the material, carry it up the
ladder and dump it into a chute or trough as they pass over
the upper tumbler. One disadvantage to the this dredge is
that it has to be moored with 5 or more lines and anchors.
These moorings are a constant hindrance to traffic and moving
and resetting them is time consuming. In addition to its poor
mobility, the ladder dredge also is unstable when towed due to
its high center of gravity. Maximum digging depth for the
ladder dredge is around 40 feet, but 75 feet is not uncommon.
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Hydraulic dredge.s employ a centrifugal pump ~ischarging
either into the hold of the dredge itself, into barges
alongside, or ashore. They also all have a suction line
through which the pump is supplied with material. The means
of loosening and picking up the material is where they differ.
A plain-suction dredge is similar to a ship in hull
construc-tion, but has its suction pipe in a well in the bow.
They often have water jets at the lower end of the suction to
break up the material. They are ineffective in hard
o materials.
Draghead dredges are formed by using a special suction
head called a draghead attached to the end of the suction
line. The draghead dredge requires the head to be in contact
with the bottom and the dredge in motion while dredging.
Material is pumped to hoppers on the dredge which when full
require the dredging to stop so that the material can be
transported to a disposal area. In addition to the
disadvantage of requiring the cessation of dredging while the
material is transported to a dumping area, such dredges are
extremely expensive.
Cutterhead dredges, also referred to as cutter suction
dredges, employ a rotating cutter mounted at the head of a
suction pipe, both of which are mounted on a ladder. The
ladder is pivotally mounted to the pivotal vertical dredge
hull pontoons and is raised and lowered and moved from side to
side by a series of winches and cables. This type of dredge
is mounted on a barge which is not self propelled and is held
in place and pivoted about a spud mounted at its aft end.
Cutter head dredges are effective for all type of materials,
but are limited to efficient dredging in only protected waters
of less than lO0 feet deep, although depths of 130 feet have
been attained. With depths greater than lO0 feet, dredging
accuracy is greatly reduced.
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AlL ot the above dredging systems are vulnerable to bad
weather, surface congestion, varying ocean bed soil
conditions, depth Limitations and c>ther ~actors depending on
the type of dredge.
The recent increase in interest in offshore drilling for
oil and gas has created a need tor a dredge which can
withstand a certain degree of bad weather, operate to depths
exceeding 300 feet, excavate at a hitherto greater rate than
previously known dredging systems presently in use at these
depths, function in ice packs of up to 2 feet or more in
thickness and be capable of underwater side cast discharge of
dredged material or surface discharge of such material to
hopper scows or throuyh a tloat line mono-buoy.
SUMMARY OE` THE INVENTION
According to the invention there is provided a
submersible hydraulic cutter suction dredging system, which
includes a self-propelled submersible dredger, a floating
vessel for controlling the dredger and a ladder universally
mounted to a ladder end of the dredger and extending outwardly
therefrom. An excavating head is affixed to a distal end of
the ladder for excavating material while hydraulic means are
provided for pivoting the ladder universally forwardly of the
platform. Pump means are coupled to the dredger for removing
material excavated by the excavating head. A buoyancy tank is
mounted on the ladder for providing lift thereto in order to
offset the weight of the ladder in response to being filled
with air. Means are provided for propelling said dredger over
a seabed.
Provision of a buoyancy tank on the ladder enables the use of
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heavier construction materials in the ladder assembly as well
as a laryer excavating head and excavating head drive system.
~bviously, the heavier construction material increases the
overall strenyth oL the ladder and the bouyancy tanks provide
stability and trim to the dredge platform. A larger
excavating head enables faster digging and, a greater
excavation rate and hence a lower cost per unit volume of
material excavated.
The platform interior is divided into one or more water
tight flotation compartments. Means for directing water into
and out of selected ones of the compartments and means for
supplying compressed air into the compartments to minimize the
pressure di~ferential across the walls of the compartments may
also be provided. Within each compartment are hard buoyancy
tanks used to provide trim and stability during ascent and
descent modes. Thus, by minimizing the pressure differential
across the walls of the compartments, the walls may be made of
siynificantly thinner gauge material which also results in a
lower expense, a lower overall weight of the dredger and a
much greater maneuverability of the latter.
The ladder may be mounted to a ladder gimbal including a
gimbal ring having opposed flat pivoting surfaces to which the
ladder is ~ournalled for horizontal pivoting movement, a pair
of flat gimbal mounting surfaces through which the gimbal is
~ournalled to brackets affixed to the platform for vertical
pivoting and a hollow interior to permit passage therethrough
of a suction hose coupled to the excavating head.
Hydraulically driven cables may be mounted on either side of
the ladder end of the platform and affixed to the ladder along
a line of action intersecting the ladder axis proximate a
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dital end thereo~. ~y utiLiziny cables which join the ladder
along a line of action intersectiny a longitudinal axis of the
Ladder proximate a distal end thereof, it is possible to apply
a much greater torque on the ladder for a given tension on the
cables. By so positioning the cab]es it is also possible to
obtain a greater swing of the ladder and a greater swing and
sloughing force thereby enabling the dredger to be operated in
harder materials with a taster rate of excavation.
Preferably an air line with nozzles is affixed to the
bottom o~ the platform for selectably blowing air downwardly
below the platform to assist in releasing the platform from
underwater mud. Because of the large underwater pressure
ordinarily encountered in the depths in which the dredger
operates, any air present between the mud and the platform
bottom is driven out and a vacuum forms therebetween. By
injecting air between the interface, the vacuum present is
broken, makiny it much easier to release the platform from the
sea bed.
Advantageously, a plurality of water jet emitting devices
or thrusters, one proximate each corner of the platform and
each independently operable enables selective orientation of
the platform while ascending or descending only. Thus, it is
possible to compensate for ocean currents which can often be
significant, when positioning the dredger at a desired
location while it is being submerged.
Means may be provided for propelling the platform
including a pair of augers mounted to the underside of the
platform on opposite sides thereof and motor means coupled to
the augers for independently rotatably driving the platform.
Ballast means may include a plurality of air tight
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compartments within the pLatform, and an air line and nozzles
runniny into each compartment ~or blowing air into, and
thereby controLliny the amount of water in, each compartment.
By providiny for selectably blowing air into each compartment
it is possible to provide ballast to the platform in order to
maintain it in a level orientation and to assist in releasing
the platform or any portion thereot from an ocean or seabed
A sonic receiver may be mounted on the platform and a
pair o~ sonic emitting transponders for positioning may be
mounted on either side of an area to be dredged. The
transponders and receiver provide position and orientation
information with respect to the submersible dredger. A like
system is utilized to position the surface vessel.
A plurality of forward and aft levelling and digging
spuds may be mounted on thé platform and are vertically
extendable and retractable. Each spud may have a levelling
pad for engaging the ocean floor and inhibiting further
penetration thereof by the spuds.
One or more hydraulic piston cylinder may have one end
horizontally and vertically pivotally mounted to the platform
below the ladder and the other end pivotally mounted to the
ladder for vertically raising and lowering the ladder relative
to the platform.
Means may be provided for loading the dredger into a
floating vessel for transport thereof. A pump mounted on the
platform and a suction line running along the ladder connected
to the pump at one end and proximate to the excavating head at
the other end exhausts material from the excavating head.
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BRIEE~ DESCRIPT:tUN OF THE DRAWINGS
In drawinys of a preferred embodimeqts of the invention:
F'IGUR~ 1 is an elevation view of the dredging system
showing the submersible dredger and its support barge;
F'IGURE ~ is a perspective view of the submersible
dredyer;
FIGURE 3 is a plan view of the submersible dredger;
E~IGURE 4 is an elevation view of a portion of the
submersible dredger plat~orm with a partial cut away of the
plat~orm showiny the driving augers;
FIGURE 5 is an elevation view of an alternative auger
drive;
FIGURE 6 is an elevation view of a top portion of the
mast of the submersible dredger;
FIGURE 7 is a side elevation view in section of the
ladder gimbal ring and bounce damper cylinder;
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FIGURE 8 is a front elevation view in section of the
ladder gimbal;
FIGURE 9 is a side elevation view of the loading area of
the barge showing the submersible barge in both the initial
loading and loaded positions; and
FIGURE 10 is a plan view of the barge with a helicopter
landing pad cut away to show the loaded submersible dredger
below.
DETAILED DESCRIPTION WITH REFERENCE TO THE DRAWINGS
10AS illustrated in figure 1, the dredging assembly
consists of a submersible dredger 10 operating on a floor 14
of a body of water 21 and a barge 16 anchored proximate the
dredger 10 by anchor lines 18 suspended from a plurality of
anchor cable spuds 20 affixed to the barge 16. Corresponding
15anchor winches 142 located on a deck of the barge 16 raise and
lower the anchor lines 18. A dredged material discharge line
extending between the barge 16 and dredger 10 is made up of a
plurality of sections of rubber hose 22 interconnected by
quick disconnect pipe ball and bell joints 23. A pair of
sonic transponders 24 and 26 are positioned on either side of
an area 12 to be excavated and transmit sound to an 360 sonic
receiver 31 positioned on the submersible dredger.
The submersible dredger 10 as shown in figures 2 and 3
has a platform 19 which is formed on the sides by a plurality
of dredging platform hull plates 15. The interior of the
platform is divided by water tight bulkheads 29 into a
plurality of flotation compartments. Passing through these
compartments are air pipes 28 having valve outlets in each of
the compartments. Also running through the bottom of the
compartments is an air piping 33 having nozzles which pass
through the bottom of the hull and communicate with the
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underside thereof. In the side external hull plates 15 of the
water tight compartments are respective water ports 57
controlled by a door (not shown) Eor letting water Elow in and
out thereof in response to externally supplied contol signals.
Exhaust air vent valves 97, normalLy closed, are located at
the highest point of each compartment to assist in compartment
flooding.
On either side of the platform 19 there is rotatably
mounted a travelling auger 76 shown in more detail in Figures
10 4 and 5 and located below auger tubes 85 and 98. The augers
are each coupled to hydraulic travel auger drive motors 88
through drive gears 86. On the forward and aft hull plates
are mounted respective pairs of spuds 74 and 72, respectively,
with spud levelling pads 71 affixed thereto. The spuds 72 and
74 are extendable and retractable in response to external
control signals.
On the deck 13 of the platform 19 there is mounted a pump
66 slightly recessed below the platform surface to lower the
center of gravity of the platform 19. The pump 66 is driven
by a variable speed electric motor 45 and has coupled thereto
a dredge pump suction pipe 62. A stone box cleanout 73
adjacent pump 66 on the suction pipe 62 provides access to
clean accumulated debris Erom the pump 66. To the discharge
of the pump 66 is connected a platform discharge pipe 17 which
in turn couples to the discharge rubber hose 22.
To the forward end of the platform, there is mounted a
ladder 40 which extends forwardly to the platform 19. To
either side of the ladder 40 there is affixed starboard and
port buoyancy pontoons 44 and 46, respectively. The buoyancy
pontoons admit therein and discharge therefrom water in
response to an external control signal. The end of the ladder
40 is inclined downwardly 15 degrees to enable excavation
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without 90i L b~tween the excavating head 42 and the platform
19 blockiny downward pivotiny of the l.ad~er 40. This angle
may be up to 3U degrees. To the torward end of the ladder is
mounted an excavating head 42 ~or breaking down into small
particles material to be dredged. The excavating head 42 is
driven by a variable speed drive motor 39. Suction pipe 62
extends along the la~der 40 to proximate the excavating head
42.
As seen in Figure 7 and 8 the ladder is coupled to an
octayonal yimbal ring 118 by means of ladder gimbal pins 120
which permit horizontal movement of the ladder 40. The gimbal
ring is ~ournalled to platform mounting brackets 119 by means
o~ trunnion ring pins 116 which provide for pivotal movement
of the ladder 40 in a vertical plane. Rubber suction hose 63
permits movement of ladder 40 through gimbal 118 without
breakiny pipe 62. A ladder mast 32 is coupled by means of
base pins 117 to bracket 119.
~ etween a ladder bracket 114 at the bottom of the ladder
40 and a cylinder mounting bearing 110 at the forward end of
the platform there is connected a hydraulic piston-cylinder
75. The cylinder 75 functions to absorb shock due to sudden
vertical movement of ladder 40. It also functions to provide
extra vertical force to force the excavating head 42 into hard
material and to hold the ladder in position in the event of a
failure of the ladder hoist cable 27. The mounting bearing
110 is pivotably connected to the platform 19 by a cylinder
bearing pin 112 to permit horizontal pivoting of cylinder
mounting bearing 110. Cylinder mounting bearing 110 includes
a thrust bearing surrounding pin 112. Bearing pin 111
coupling the piston cylinder 75 to mounting bearing 110
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permits verlical movement o~ the cylinder 75.
The top of the :Ladder mast 32 is pivotally coupled by
means ol a top mast trunnion pin 138, a swivel mast section 67
which is Journalled to a top mast swivel frame support 25 by
pin 137. The swivel frame support is affixed to mast 32 by a
ladder mast pin 55. The mast section 67 has journalled
thereto top mast swivel sheaves 51. A ladder hoist cable 27
is wound around swivel sheeves 51 and water block sheeves 53
Journalled to a water block 38. Cable 27 is wound around a
hydraulically operated ladder hoist winch 64 located behind
the mast 32. Upon tightening ladder hoist cable 27 the water
block 38 and attached ladder hog wires 47 and 49 (see F~igure
3) are pulled towards swivel sheeves 51 thereby raising the
excavatiny head 42 and ladder 40. At the top the swivel
frame support 25 is affixed the 360~ sonic receiver 31. To
the bottom end of swivel trame support 25 on either side
thereof are affixed starboard and port ladder mast strong
backs 36 and 34, respectively, which are coupled to the
platform 19.
Side to side movement of the ladder 40 and cutter or
excavating head 42 are controlled by swing cables 52 and 56
coupled to sheeve wheels 60 and 77 and dead ended at pad-eyes
54 and 58 on swing arms 65 and 69, respectively, on the
starboard and port sides of the ladder 40 proximate the distal
end thereof. The swing cables 52 and 56 are wound around
swing arm cable sheeves 59 and 61, respectively, journalled to
the distal end of swing arms 65 and 69, respectively. Where
lighter materials are involved, sheeve wheels 60 and 77 may be
eliminated and the lines dead ended on ladder 40 near sheeve
wheels 60 and 77. Swiny arms 65 and 69 are pivotally coupled
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by pins 3~7 to the starboard and port sides ot the pLatform 19
near the ~orwar~ end thereot. Swing arms 65 and 6Y are raised
and lowered by cyLinders 35 and are stabilized by swing arm
strong backs 41 and 43, respectively. Horizontal movement of
ladder ~0 and excavating head 42 are controLled by hydraulic
winches 48 a~ 50 which alternately apply tension to swing
cables 52 and 56, respectively. The winches 48 and 50 are
bidirectional variable speed units with tension pull off. The
angle measured in the horizontal plane between the ladder 40
and the platform 19 is indicated by a plurality of proximity
switches 153 spaced apart radially by angular increments of
approximately 5 degrees. A de-slugger valve 156 is located in
suction pipe 62 on the ladder 40 to prevent consolidation of
the solids passing through the dredge pump suction pipe 62 and
subsequent blockage thereo~. A pin connection (not shown) is
provided to lock movement of ladder 40 and retain it in a
fixed position before raising swing arms 65 and 69.
On each side of platform 19 are a plurality of dry
docking rollers 70 which roll on rails 130 as seen in Figure 9
on each side of a docking ramp on barge 16. The submersible
dredge is loaded onto barge 16 by a dry docking cable 132
attached to a bracket on the aft of the platform 19 and wound
on dry docking hauling winch 134.
Details of the auger drive system as shown in Figure 4
include the travelling auger 76 rotatably supported by thrust
carrier bearing 82, 83 and 84. Auger 76 extends below the
drive shaft 80 and hull 30 of platform 19. The forward and
aft ends of the travelling auger 76 is tapered to a narrower
diameter and the platform hull plates 30 on either side
upwardly incline to enable the submersible dredge to negotiate
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sudden increases in anyle ot torward or aft movement without
diyging into the ~sea bed.
An alternative travelling auyer drive mechanism as seen
in Fiyure 5 includes a central auyer blade 90 affixed to an
auyer shaft 81 rotatably supported by bearing 92, 94 and 96.
The central auger blade 90 and shaft 81 are coupled to an
upwardly inclined torward auger blade 102 and shaft 89 by a
universal auger shaft ~oint 104. The auger tube 85 is
upwardly inclined at the aft and forward ends of the platform
19 to accomodate the upwardly inclined auger blade 102 and
shaft 89. The latter shatt is rotatable supported by bearings
98 and 100.
The barge 16 as shown in F~igure 10 includes a helicopter
ladiny pad 140, below which is loaded the submersible dredger
10.
The barge 16 has an under deck discharge piping 143 to
which is attachable the discharge rubber hose 22. The piping
143 couples to a discharge float line deck pipe 144 through
discharge diversion gate valves 141. Piping 143 also couples
to a spider discharge rubber trunnion system 145 to a spider
discharge pipe 148 extendable by support davits 149 for
loading a barge docked alongside barge 16. Instrumentation,
control, power and air lines are wound around drum 147. At
the aft of barge 16 are located diesel electric generators 146
for generating electrical power for use by the submersible
dredge 10 and barge 16.
Housings for electric drive motors 45, 39 and others are
adjustably pressurized with air to a level equal to outside
water pressure and the electric motors cooled by an air water
heat exchanger.
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In operation, the barg~ 16 is anchored in position and
dredge 10 is lowered by unwinding dry dockiny hauliny winch
134. As the dredge 10 moves away from barge 16 dry dock bay,
winch 147 is unwound and discharge rubber hose 22 is connected
to pipe 17 and additional sections of hose 22 added as
required, swing arms 65 and 6~ are lowered and locked in
position and a ladder swiny lock disengaged. Pontoons 44 and
46 and compartments in the platform 19 are gradually loaded
with water permitting the dredge 10 to sink. Pressure
sensitive depth indicators 152 located on each corner of
platform deck 13 and pressure sensitive depth indicator 151
near cutter drive motor 39 on ladder 40 signal depth read-outs
to control level descent and ascent of dredger 10. Sonic
transponders 24 and 26 are dropped at convenient locations
within 1000 ~eet on either side of the area 12 to be
excavated. once on the sea bed the dredge 10 is propelled in
a desired direction by rotating augers 76.
On each corner of the deck 13 of platform 19 there is
mounted a jet or thruster pump 155 which directs a stream of
water outwardly of the platform 19 substantially along a
notion at extension of a diagonal line joining the corners
thereof. By selectively operating the jet pumps 155 the
platform can be rotated in any desired direction to maintain a
preselected heading during descent and ascent.
The position of the dredge 10 is determined by the
signals received by the sonic receiver 31 from transponders 24
and 26. Orientation of the dredge 10 is determined by signals
received from a magnetic compass 154 located on dredger 10.
Once in position the hydraulic dredge pump 66, the dredye
excavating head 42 are started and the dredge ladder 40 is
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lowered by unwindiny ladder cable winch 64 until cutter head
42 engages the sea bed. As excavating head 42 loosens and
cuts up the sea bed, material is then sucked up through
suction pipe 62, drawn into pump 66 and discharged therefrom
up discharye rubber hose 22. When dredging, it may be
necessary to lower spuds 72 and 74 in order to stabilize or to
level the plattorm 19 laterally. The ladder 40 is moved from
side to side by swing winches 48 and 50. In the event the in
situ material is hard, piston cylinder 75 is retracted to
assist in forciny excavatiny head 42 into the material.
~therwise cylinder 75 is used in a shock absorbing mode.
Sudden increases in slope encountered by the dredge l9 would
ordinariLy result in the forward end of the platform jamming
into the sea bed. Provision of tapered forward ends of the
travelling augers and hull 30 assists in engaging increased
slopes without digging into the slope and becoming stuck. A
taper on the auger aft ends is also provided for reverse
movement. The alternative auger drive system as shown in
~igure 5 provides another mechanism for engaging increased
slopes. The upwardly inclined front auger sections provide
lift up any increased slope and thereby prevent the platform
~rom becoming stuck.
In the event the submersible dredge becomes stuck in soft
material it may happen that a partial vacuum may develop
between the earth and the bottom of the platform 19. Thus
provision is made for blowing pressurized air in pipe 33 out
of nozzles passing through the bottom surface of the platform
19 to counteract any such vacuum.
The auger drive system allows the dredger 10 to work to
unlimited depths and to negotiate short radius turn dredging.
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Once dredyiny is complete and the pipe 22 is tlushed out,
the excavating head 42 and pump 66 are stopped and the ladder
levelled and centered to the platform 40. The dredye
compartments and pontoons are tilled with air thereby raising
the dredger 10 gradually to the water surface. Dry dockiny
cables 132 are attached to the aft end and the dredger 10
pulled toward the loading ramp by hauling winch 134 until dry
docking rollers 70 engage rails 130 thereby causing the
dredger 10 to roll into its loaded position as seen in Figure
9 and 10. Prior to docking however, the ladder swing locking
device is engayed and swiny arms 65 and 69 are raised to a
vertical position by extending piston cylinders 35 below the
swiny arms 65 and 69. As the dredger is docked, rubber hose
22 is removed in 40 foot sections and stored on the deck of
barge 16 so the control and air lines can be rolled onto drum
winch 147.
The inclined end of the ladder 40 may be hinged and
pivotally driven by hydraulic piston cylinders on each side of
the ladder 40.
Other modifications, variations and departures lying
within the spirit of the invention and scope as defined by the
appended claims will be obvious to those skilled in the art.
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