U.S. patent number 3,632,172 [Application Number 04/842,454] was granted by the patent office on 1972-01-04 for method of and apparatus for weakening ice for assisting an icebreaker.
This patent grant is currently assigned to Dresser Industries, Inc.. Invention is credited to Frank Clynch, Charles L. Robinson.
United States Patent |
3,632,172 |
Robinson , et al. |
January 4, 1972 |
METHOD OF AND APPARATUS FOR WEAKENING ICE FOR ASSISTING AN
ICEBREAKER
Abstract
A self-powered vehicle is disclosed for moving across the ice
ahead of an icebreaker and carrying trench-cutting means for
cutting a trench along the path of travel of the icebreaker and
carrying means for placing an explosive cord in the trench which
can be exploded for weakening the ice. An air cushion vehicle
carries a rotary saw and means for removing ice cuttings from the
trench made by the saw with means for melting part of the ice
cuttings for backfilling along the trench after inserting an
explosive cord therein. Drill means are carried by the air cushion
vehicle for drilling spaced holes along the ice for additional
explosive charges. An elongate pipe has at least one opening in the
wall or bottom end thereof for insertion into spaced drilling holes
adjacent the trench with seal means normally covering the openings
and an air supply means carried by the vehicle and connected to the
pipe for building up pressure therein for rupturing the seal means
and creating an airblast adjacent the trench. A buoyant fish is
adapted to float under the ice and tow a length of buoyant
explosive cord connected thereto with control and/or motivation
means carried by the vehicle for controlling the direction of
movement of the fish thereby towing the explosive cord beneath the
ice in the desired direction. Additional floating explosive charges
are connected along the explosive cord.
Inventors: |
Robinson; Charles L. (Houston,
TX), Clynch; Frank (Houston, TX) |
Assignee: |
Dresser Industries, Inc.
(Dallas, TX)
|
Family
ID: |
25287333 |
Appl.
No.: |
04/842,454 |
Filed: |
July 17, 1969 |
Current U.S.
Class: |
299/13; 37/195;
114/42; 405/174; 102/301; 299/27 |
Current CPC
Class: |
B63B
35/08 (20130101) |
Current International
Class: |
B63B
35/00 (20060101); B63B 35/08 (20060101); B63b
035/08 () |
Field of
Search: |
;114/40,41,42 ;102/22,23
;61/72.5,72.6 ;299/13,24-28 ;172/1 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Primary Examiner: Purser; Ernest R.
Claims
What is claimed is:
1. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered vehicle for moving across the ice ahead of the
icebreaker,
trench-cutting means carried by the vehicle for cutting a trench
along the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
means carried by the vehicle for at least partially backfilling the
trench after placement of the explosive cord,
wherein said means for backfilling includes,
means carried by the vehicle for the melting of the ice for use as
backfill.
2. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered vehicle for moving across the ice ahead of the
icebreaker,
trench-cutting means carried by the vehicle for cutting a trench
along the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
drilling means carried by the vehicle for drilling spaced holes
near the trench for additional explosive charges.
3. The apparatus of claim 2 including,
an elongate pipe having at least one opening in the wall thereof
for insertion into said spaced drilling holes, and
air supply means carried by the vehicle connected to said pipe for
building up pressure therein for creating an airblast
therethrough.
4. The apparatus of claim 3 including,
sealing means normally closing said openings, but rupturing upon a
predetermined pressure.
5. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered vehicle for moving across the ice ahead of the
icebreaker,
trench-cutting means carried by the vehicle for cutting a trench
along the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
an extendable arm carried by the vehicle for extension in front of
the vehicle, and
a drill carried by the drill for drilling holes for clearing
barriers.
6. The apparatus of claim 5 wherein the drill is rotatable relative
to the extendable arm.
7. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered vehicle for moving across the ice ahead of the
icebreaker,
trench-cutting means carried by the vehicle for cutting a trench
along the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
a buoyant fish adapted to float under the ice,
a length of explosive cord connected to the fish, and
control means carried by the vehicle for controlling the direction
of movement of the fish thereby towing the cord beneath the ice in
the desired direction.
8. The apparatus of claim 7 wherein the cord is buoyant.
9. The apparatus of claim 7 including,
floating explosive dynamite charges connected along the cord.
10. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered hovercraft for moving across the ice ahead of the
icebreaker,
a rotary saw carried by the hovercraft for cutting a trench along
the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
means for at least partially melting ice, and inserting the melted
ice into the trench for backfill.
11. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered hovercraft for moving across the ice ahead of the
icebreaker,
a rotary saw carried by the hovercraft for cutting a trench along
the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and
drilling means carried by the hovercraft for drilling holes near
the trench for receiving additional explosive charges.
12. The apparatus of claim 11 wherein the drilling means
includes
an elongate pipe for insertion into the spaced drilling holes and
having openings in the wall thereof adapted to be aligned with the
trench, and
air supply means carried by the hovercraft and connected to said
pipe for building up pressure therein for creating an airblast
therethrough.
13. The apparatus of claim 12 including,
sealing means normally closing said openings, but rupturing upon a
predetermined pressure.
14. An apparatus for weakening ice for assisting an icebreaker
comprising,
a self-powered hovercraft for moving across the ice ahead of the
icebreaker,
a rotary saw carried by the hovercraft for cutting a trench along
the path of travel,
means carried by the vehicle for placing an explosive cord in the
trench which can be exploded for weakening the ice, and a buoyant
fish adapted to float under the ice,
a length of explosive cord connected to the fish,
control means carried by the vehicle for controlling the direction
of movement of the fish thereby towing the cord beneath the ice in
the desired direction.
15. The method of weakening ice for assisting an icebreaker
comprising,
cutting a trench in the ice in front of and along the proposed path
of travel of the icebreaker,
placing an explosive cord in the trench,
exploding the cord, and
backfilling the trench with partially melted ice after placing the
cord in the trench and waiting until the backfill freezes before
exploding the cord.
16. The method of weakening ice for assisting an icebreaker
comprising,
cutting a trench in the ice in front of and along the proposed path
of travel of the icebreaker,
placing an explosive cord in the trench,
exploding the cord, and
drilling spaced holes along the trench,
placing dynamite charges in the drilled holes,
exploding the dynamite charges.
17. The method of claim 16 wherein the charges are directional
exploding charges, and
positioning the charges in the drilled holes to direct the
explosion longitudinally along the trench.
18. The method of claim 16 including,
drilling spaced holes along the trench,
creating a directional airblast in the drilled holes along the
longitudinal axis of the trench.
19. The method of weakening ice for assisting an icebreaker
comprising,
cutting a trench in the ice in front of and along the proposed path
of travel of the icebreaker,
placing an explosive cord in the trench,
exploding the cord, and
placing a buoyant fish under the ice,
attaching a length of explosive cord to the fish,
moving the fish in the desired direction, and
exploding the cord to weaken the ice.
20. The method of weakening ice for assisting an icebreaker
comprising,
placing a buoyant fish under the ice,
attaching a length of explosive cord to the fish, and
exploding the cord.
21. The method of claim 20 including,
controlling the fish from an air cushion vehicle traveling over the
ice.
Description
BACKGROUND OF THE INVENTION
The discovery of oil on the northern slope of Alaska has increased
the commercial incentive for improving icebreaking methods since
the cost of moving oil by tanker as compared to the cost of moving
oil by pipeline over land would result in significant savings. At
the present time the general principle for breaking ice is to use
an icebreaker and propel the ship forward towards the ice to be
broken, drive the ship upon the top of the ice, and allow the
weight of the ship to push the ice downwardly and break the ice by
sheer weight. In addition, icebreakers sometimes use a special bow
similar to a plow which is driven under the ice, lifting the ice up
causing it to break. Breaking ice in this fashion is in a sense a
brute force approach using very high horsepower and very large and
heavily reinforced and strengthened icebreakers.
The present invention is directed to providing a method and means
to make the operation of the present icebreakers considerably more
efficient. The present invention is directed to creating zones of
weakness or fractures or ruptures in the ice ahead of the proposed
path of the icebreaker so that the icebreaker will be able to make
faster progress through the ice while breaking ice and/or will
require a lesser amount of horsepower to achieve a given rate of
progress through the ice than is required by present day
icebreaking methods.
SUMMARY
The present invention is directed to providing a method of and
apparatus for weakening ice for assisting an icebreaker by
providing a self-powered vehicle moving across the ice ahead of the
icebreaker and provided with a trench-cutting means for cutting a
trench along the path of travel of the icebreaker and carrying
means for placing an explosive cord along the trench which can be
exploded for weakening the ice.
Preferably, an air cushion vehicle is utilized since it can operate
when visibility is practically zero because of fog and other
weather conditions, is in no danger of breaking through thin places
in the ice, and provides a stable platform from which the necessary
operations can be performed, and yet can fly at high speeds to
return to the icebreaker ship for refueling, supplies, crew changes
or repairs.
Suitable trench-cutting means, such as a rotary saw may be carried
by the vehicle for cutting a trench in the ice. The vehicle also
carries means for implanting an explosive cord in the trench which
can be exploded to fracture and weaken the ice. Preferably, the
cuttings from the saw are removed from the trench for placing the
point of explosion as low as possible, and preferably the cuttings
would be at least partially melted and used to backfill the trench
in order to more fully utilize the explosive force by causing it to
be directed downwardly and laterally rather than having a part of
the explosion wasted by blowing out of the top of the trench.
A further feature of the present invention is the provision of an
ice drill carried by the vehicle for drilling spaced holes adjacent
the trench in which can be placed dynamite charges of airblasts
which would be preferably directed along the longitudinal axis of
the trench for additionally fracturing the ice. Airblasts can be
utilized in the drilled holes in place of dynamite by inserting an
elongate pipe having at least one opening in the wall and/or the
bottom end thereof for insertion in the drilling holes with or
without sealing means normally closing the opening but rupturing on
a predetermined pressure whereby an air supply means carried by the
vehicle and connected to the pipe can build up pressure in the pipe
and rupture the seal means for creating an airblast along the
trench thereby avoiding logistic and safety problems involved in
carrying dynamite.
A further feature of the present invention is the utilization of a
buoyant fish adapted to float under the ice and tow a length of
explosive cord, preferably buoyant, in which control means carried
by the vehicle controls the direction of movement of the fish
and/or provides the motivating force to propel the fish forward
under the ice to tow the cord in the desired direction for creating
an explosive force acting along the bottom of the ice.
Additionally, attached dynamite charges to the towed explosive cord
can be provided at desired intervals to rupture the ice and also to
create an opening to assist in recovering the fish so that it can
be used again.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view, partly schematic and partly in cross
section, illustrating the apparatus of the present invention,
FIG. 2 is a fragmentary perspective view of the apparatus of FIG. 1
but omitting the extending drill,
FIG. 3 is a fragmentary elevational view, partly in cross section,
illustrating part of the apparatus for creating an airblast,
and
FIG. 4 is a schematic elevational view illustrating the placement
of the drilled holes relative to the trench for weakening the
ice.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring now to the drawings, and particularly to FIG. 1, the
reference numeral 10 generally indicates an apparatus for weakening
ice for assisting an icebreaker and generally includes a
self-powered vehicle 12 for moving across the ice ahead of the
icebreaker. Obviously, it is easier to break a block of ice or to
break through ice with an icebreaker if there is a zone of
weakness. It is known that currents or tides sometime cause natural
cracks to develop in the ice, and icebreakers will often use and
follow these cracks or zones of weakness rather than try to break
their way through more difficult solid ice where cracks are not
present. The method and apparatus of the present invention are
directed to creating zones of weakness along a particular desired
path of travel of the icebreaker.
While various types of vehicles may be used such as helicopters or
tractors, an air-cushioned vehicle is preferably utilized as the
vehicle for providing the support base for carrying the equipment
for creating ruptures or cracks ahead of the icebreaker. For
instance, the vehicle used must be able to operate a high
percentage of days during which visibility is practically zero due
to fog and other weather conditions and must be able to operate
over and on the ice without the danger of breaking through in thin
places in the ice which would be particularly advantageous for the
path of travel of the icebreaker. A helicopter, for example, is
extremely limited in the number of days which it can operate during
certain periods of the year and does not provide a stable operating
platform. A track vehicle could also be used to crawl over the ice,
but it has the danger of breaking through the thin places in the
ice, which would be the ideal path of travel, and is also extremely
slow. The air cushion vehicle or hovercraft, such as a conventional
SRN-6 manufactured by British Hovercraft Corporation, is preferred
since it can fly in all types of weather, is equipped with radar so
that fog does not present a serious drawback and the radar can also
scan the path ahead for obstacles on the ice such as, for example,
ice ridges. The air cushion vehicle 12 flies at a fixed distance
off of the surface of the ice, such as 4 feet, and is therefore a
safe vehicle from the standpoint of engine failure and provides a
stable platform for operations. In addition, if the ice is thin,
the vehicle 12 can fly over water and in fact can land on water
since it has buoyancy tanks which will keep it afloat. Further, the
vehicle 12 can fly at dead slow speeds forward or sideways and can
fly at speeds as high as 50 or 60 knots which is useful for
returning to the icebreaker for refueling, supplies, and crew
changes as well as searching at high speeds along high ice ridges
for a low place which provides an easier crossing point for the
hovercraft 12 to cross the ice ridge.
Suitable means 14 are provided for cutting a trench 16 in the ice,
such as 2 or 3 feet deep or deeper. Such means 14 may preferably be
a rotary saw supported from supports 18 from the vehicle 12 which
can be raised or lowered by suitable piston and cylinder assemblies
20, preferably hydraulic, and driven by a chain 22 from auxiliary
power in the vehicle 12. The auxiliary power package 26 on the
hovercraft 12 may suitably include a diesel engine driving an air
compressor, electric generator, and of course the power driving the
chain 22 and saw 14 may be either mechanical, electrical, hydraulic
or compressed air.
The hovercraft 12 maintains a relatively constant distance above
the ice, for example in the SRN-6 model, the height which is
controlled by the skirt 24 height, is 4 feet. Upon reaching a
starting point, the ice saw 14 will be lowered to the surface of
the ice and started into rotation cutting a narrow trench 16 in the
ice and the hovercraft would then be started in motion forward
cutting a trench as it proceeded forward along the desired path of
travel in front of the icebreaker. Preferably, it is desirable to
clean the ice shavings from the trench 16 in order to place the
explosive cord as deep in the trench as possible. While the ice
shavings or cuttings may be blown out of the trench by the air from
the air compressor (part of the auxiliary power equipment 26), it
is advantageous to remove the ice cuttings from the trench 16 by a
suction line 28 and deposit them in a tank 30 where the ice
shavings would at least by partly melted by the surplus exhausted
heat from the main engine 32 of the hovercraft 12 or from the
diesel engine in the auxiliary power supply 26.
An explosive cord 34, such as Primacord, is preferably stored on a
reel 36, and is reeled off as the craft 12 moves forward and is
pushed down to the bottom of the trench 16 by guide means 38,
preferably a long arm which is spring loaded by spring 40 in order
to push the explosive cord 34 as deep as possible into the trench.
Positioned to the rear of the guide means 38 may be ice scrapers 42
and 44. Scraper 42 is preferably triangular in shape and sharp at
the edges to scrape ice shavings from the edge of the trench 16
onto the top of the laid cord 34. Scraper 44 is generally plow
shaped to scrape all of the shavings and cuttings and chips of ice
into the trench so as to fall in on top of the cord 34.
Rearwardly positioned from the scrapers is a hose 46 connected to
the water tank 30 for supplying additional backfill in the trench
16 above the cord 34. The water in the tank 30 is maintained at a
temperature only barely above freezing so that as it is applied to
the ice scrapings on top of the cord it will provide a tamping and
backfill action and will normally freeze soon after it is applied.
Thus, the frozen backfill on top of the cord 34 will have the
effect of causing the explosive force from the cord 34 to be
directed downwardly and laterally instead of wasting part of the
explosive force by simply blowing air out of the top of the trench
16.
After a suitable length, for example 1 mile of cord 34 is set in
the trench, the explosive cord is detonated by conventional means
to cause a rupture or crack in the ice to provide a zone of
weakness downwardly and below the level of the trench. The depth of
penetration of the crack or rupture will depend upon the strength
of the explosive cord. Of course, if a strength greater than that
normally commercially available is desired, several strands of the
explosive cord 34 may be twisted together to form a larger cable
prior to rolling on the reel 36.
Referring now to FIGS. 1 and 2, an ice drill 50 is provided carried
by the hovercraft 12, preferably, in the plane of and behind the
saw 14 which may be suitably powered by any of the auxiliary
equipment and is used to drill holes in or adjacent the trench 16,
as best seen in FIG. 4, such as at spaced positions 52 in the
trench 16. Dynamite charges may be placed in the holes 52 and
exploded either separately or in combination with the explosive
cord 34. Preferably, the dynamite placed in the holes is in the
form of conventional-shaped charges with the dynamite positioned in
the holes 52 so that the explosive force is generated
longitudinally along the trench whereby the combined effect of the
explosive cord 34 shock waves and the shock waves created by the
explosion of the dynamite in the holes 52 will increase the rupture
of fracturing force to a force level greater than the shock wave
created by firing the Primacord 34 and dynamite separately. The
dynamite in the holes 52 by being directed longitudinally along the
trench 16 will create shock waves 54 which travel along the trench
16 to increase the fracturing effect on the ice.
As an alternative to the use of a shaped dynamite charge in the
holes 52, an airblast may be used to create a shock blast in the
holes 52. Referring now to FIG. 3, the drill may consist of an
elongate pipe 56 having a suitable drill force 58 on the bottom
thereof and having one or more openings 60 in the sidewall and/or,
if desired, an opening 61 in the bottom. Seal means 62 such as a
disk or thin cylinder for instance, of aluminum, which is
replaceable, is, preferably, but not necessarily, inserted into the
pipe 56 covering the openings 60. After drilling the holes 52 an
air supply, such as from the air compressor of the auxiliary
equipment 26 is introduced into the pipe 56 to increase the
pressure therein. Upon a predetermined pressure, for example 300 to
1,000 p.s.i., the disk 62 will rupture causing a pressure wave to
travel through the ice which will crack or rupture the ice.
Preferably, the openings 60 are aligned with the longitudinal axis
of the trench 16 causing the shock wave to travel up and down the
trench helping to create a crack or zone of weakness along the
trench. If the seal means 62 are omitted, a sufficient airblast may
be transmitted to the pipe 56 to create shock waves through the
openings 60 and/or 61.
One limitation of the hovercraft 12 is that there may be an ice
ridge along the route of travel which would be too steep for the
craft 12. By the use of the ice saw 46 and/or drill 50, and/or a
separate drill mounted on extendable hydraulic arms to reach way
out in front of the saw and the hovercraft, a path of travel for
the craft 12 may be blasted through an ice ridge by using either
explosive cord, dynamite charges or airblast. Additionally, an
extendable drill 80 may be provided supported by extension arm 82
which in turn is pivotally connected to support 84. A cylinder and
piston assembly 86 is connected to arm 82 for extending and
retracting the arm 82 and drill 80. A cylinder and piston assembly
88 is connected between arm 82 and drill 80 for rotating the drill
80 for suitable drilling in an ice ridge. Preferably, the drill 80
is similar to that shown in FIG. 3, and is operated by an air motor
90 through an air line 92 which can also supply an airblast for
blasting an ice ridge.
Still another operation that may be performed with the present
apparatus 10 to create a zone of weakness in the ice is to blast a
hole through the ice such as by using the drill 50 and dynamite
charges through which a buoyant ferromagnetic fish 64 could be
inserted under the icecap. A length of explosive cord would be
attached to the end of the fish 64 and the fish could be motivated
and/or directed or maneuvered under the ice by the hovercraft 12
flying over the surface of the ice by means of an electromagnet 68
creating electromagnetic field 70 as it flew along the desired path
of flow causing the fish 64 to follow. The explosive cord could
then be towed under the ice either under the trench 16 or under ice
with no trench cut. The cord could also be embedded in or encased
in some conventional type of flotation material so that it would be
buoyant and float up against the underside of the bottom surface of
the ice. When exploded, the Primacord would then cause a rupture or
crack in the bottom of the ice. Additionally, dynamite charges 68
could be attached to the cord 66 that is being towed under the
water to increase the rupture force. If desired, a dynamite charge
could be attached a short distance, perhaps as little as 15 feet
behind the fish 64 to rupture the ice all the way to the surface
for access in recovering the fish 64 for reuse.
In use, one or more of the air cushion vehicles 12 could be used
aboard the icebreaker to search out thin zones in the ice or zones
where cracks have started to develop due to natural forces or
reasons in order to provide the most desired path that the
icebreaker would travel through the ice. In addition, the apparatus
10 could then create additional zones of weakness along the
particular desired path of travel to make the work of a standard
icebreaker considerably more efficient. After being furnished with
the proper supplies, the apparatus 10 would leave the icebreaker
and proceed to a point ahead of the icebreaker in the desired
direction of travel. Upon reaching the desired starting point, the
hovercraft 12 would come to a stop at the starting point, the ice
saw 14 would be lowered to the surface of the ice and started into
rotation cutting a narrow trench 16 in the ice, for example, 2 or 3
feet or more. The hovercraft 12 would then be started in forward
motion cutting a trench 16 in the ice as it proceeded along the
desired path of travel. The cuttings from the trench may be blown
out, but preferably are sucked up by an ice suction hose 28 and
deposited in a tank 30 where the ice shavings would be partially
melted by the exhaust heat from the engines in the craft 12. Thus
the trench 16 would be cleaned out leaving it in condition for
placing the explosive cord 34 as deep in the trench as possible.
The cord 34 would be reeled off of the reel 36 and pushed down into
the bottom of the trench by the guide means 38. The ice scrapers 42
and 44 would scrape ice shavings from the top of the trench and
onto the cord 34 to provide suitable backfill. Water from the water
tank 30 would flow into the trench and would quickly freeze the ice
scrapings on top of the cord 34 thereby providing a solid backfill.
Thus, when the cord 34 was exploded the explosive force would be
more effective in a downward and lateral direction. Obviously, one
or more hovercrafts 12 could work simultaneously with one scouting
the desired path of the icebreaker out ahead of the regular
operation, locating the ice ridges, and blasting a way therethrough
for another working craft 12.
Additionally, if desired, the ice drill 50 may be utilized to
create an explosive force by means of dynamite charges or by air
shock waves as described. Furthermore, and for the purpose of
creating an additional or a separate explosive action if necessary
on the ice, the buoyant fish 64 may be used to tow cord 66 on the
undersurface of the ice which can be exploded, with or without
additional dynamite charges 68, to create a force underneath the
surface of the ice to weaken the ice to make a path of the
icebreaker more easily accomplished.
The present invention, therefore, is well adapted to carry out the
objects and attain the ends and advantages mentioned as well as
others inherent therein.
* * * * *