Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SOI~ MOVING D~VICE
This invention relates to a soil moving implement which
is suitable for towing, more particularly to a soil moving
implement for making a trench at an underwater site for burying
a submarine pipeline or cable hereafter referred to as a
trenching plough.
Trenching ploughs which have been previously proposed for
pipeline burial have usually been towed by a surface vessel and
obtained their steering from the surface vessel and for this it
is necessary to know accurately the position of both the pipeline
or cable and the plough and then to calculate the required course.
Even when this is done the line of action of the towing force may
sometime deviate significantly from the axis of the pipeline with
the risk of damage -thereto.
It is an object of the present invention to reduce this risk
by providing an implement in which the sideways component of the
towing force is resisted thereby reducing the side~ays force on the
pipeline.
According to the present invention a soil moving implement
which is suitable for towing underwater comprises:
(a) a body having attached thereto a soil cutting member, which
in use forms a soil surface in the direction of travel of the
implement,
(b) a landside which engages the soil surface,
(c) means for following a previously laid underwater pipeline or
cable whereby the implement can travel in a direction di~ferent
from the l~ne of the towing force, and
(d) a hitch point to which in use a towing means is connected,
the hitch point being located so that in use the line of the
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towing force passes through a point dîrectly above the landside
so that when the direction of travel of the implement is
different from the line of the towing force the sideways com-
ponent of the towing force is resisted by the landside. The
towing means can conveniently be a cable or rod or other link.
The soil cutting member and the landside can be formed in
one piece. For example, a soil cutting blade may be provided
whose edge constitutes the soil cutting member and whose sides
constiiute the landside. Alternatively, the landside can be
separate from the soil cutting member.
The point through which the towing force passes can be in
the region of the effective centre of the landside. The term
"effective centre" is well known to agricultural engineers and
is the point on the landside through which the resultant soil
force acts.
As stated above the line of the towin~ force passes through
a point in the region of the landside when the direction of
travel is different from the line of the towing force. This
can be achieved by the hitch point being located in the region
of the landside or the hitch point being located forward with
respect to the landside so that in use the projected line of the
towing force passes through the point in the region of the land-
side.
The effect of this is that the sideways component of the
towing force is resisted by the landside thereby enabling the
implement ~o be steered with a smaller steering force. In a
typical prior art trenching plough arrangement the hitch point
is located forward with respect to the landside, at or near the
front of the implement, with the effect that when the direction
of travel is different from the line of the towing force, there
is a significant sideways force on the implement. The implement
can only resist this sideways force by exerting a similar force
on the pipeline by means of guide arms or like means by which it
is constrained to the pipeline.
The landside is conveniently at, or near the rear of the
implement and consequently according to the invention the towing
force (projected if necessary) will pass through the rear portion
of the implement when the direction of travel is different from
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the line of the towing force.
The hitch point can be located over the landside (not
necessarily directly above in a vertical sense, see Figures 2
and 4) or the point through which the projected line of the
towing force passes can be over the landside (see Figure 6).
In most cases the point in the region of the landside will
be located at a posltion along the length of the implement where
the landside extends and rearward of the soil cutting member.
The hitch point can be movable on a laterally extending arm,
the arm being so disposed so that the point moves on the circum-
ference of a circle whose centre is at the point in the region
of the landside.
The point in the region of the landside through which the
line of the towing force passes can be located so that the
components of the towing force and the soil cutting force
perpendicular to the direction of travel create no significant
couple in the horizontal plane.
The soil moving implement can be used for making a trench
for a pipeline at an underwater site and can have in the reyion
of the front thereof a carriage adapted to run on the pipeline
so that at least a portion of the weight of the implement is
supported by the pipeline.
The implement can further have located forward with respect
to the carriage, a support member capable of contacting the
ground to reduce the risk of overloading an unsupported section
of pipeline.
The support member can be movable between a ground contac-
ting position and a raised position free of the ground and
means can be provided for moving the support member from one
position to the other.
References to "above", "forward", "sideways" and "rear"
refer to the implement in its disposition for normal use.
The term sea bed includes the bottom of any body of water
such as river, lake or ocean.
The term pipeline is intended to include flowlines.
Although the trenching device according to the invention is
intended primarily for use underwater it can nevertheless be
used on land.
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3a
Reference to the line of towing force means the line of
the towing force projected in the horizontal plane through the
hitch point.
According to another aspect of the present invention a
method of forming a trench in the sea bed comprises towing a
soil moving implement on the sea bed and following a previously
laid underwater cable or pipeline, the line of the towing force
being inclined to the direction of travel of the implement, and
wherein the line of the towing force passes through a point
directly above a landside which tends to resist the sideways
component of the towing force.
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The soil moving device according to the present invention may be
employed to make a trench parallel and close to a pipeline or cable
which can be moved sideways in-to the trench at a later time.
Alternatively,the trenching device can be employed to make the trench
and place the pipeline or cable therein in one opration.
The trenching device is particularly suitable or use where the
pipeline or cable has been previously installed on the sea bed although
it is possible to use the trenching device to bury a pipeline or cable
as it is laid from a surface vessel.
Although described with particular reference to making a trench
for a pipeline or cable, the soil moving implement according to the
invention may be used for other purposes, for example, for covering
a pipeline or cable previously installed in a trench (see Figures 1
to 4), for collecting material from or under the sea bed, for example,
obtaining samples of sea hed material or collecting manganese nodules
The invention is illustrated by reference to the accompanying
drawings in which:
Figure 1 is a side elevation of a soil moving implement in the
form of a trenching plough showing the location of the hitch point, and
Figure 2 is a plan view of the trenching plough shown in Figure 1.
Figure 3 is a side elevation of an alternative embodiment of the
trenching plough in which steering is effected by means of a sensor
which follows the pipeline and controls a servo mechanism and hydraulic
ram.
Figure 4 is a plan view of the embodiment shown in Figure 3.
Figure 5 is a side elevation of a further embodiment of the
trenching plough in which the hitch point is located on a laterally
extending arm, and
Figure 6 is a plan view of the trenching plough shown in Figure 5.
Referring to Figures 1 and 2 the trenching plough indicated
generally by numeral 1 comprises a body in the form of beam 4 attached
to the rear of which is a blade indicated generally by numeral 7, the
leading face 6 of which is the soil cutting member and the sides 5 of
which provide the landside. Located above the sides 5 is a hitch
point in the form of a towing eye 3 to which a towing cable 2 is
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connected. The forward part of the beam 4 is attached to a later-
ally extending cross member 13 one end of which is attached to and
supported by skid 10 on the sea bed 11. The trenching plough has
a steering means in the form of guide wheels 9 which straddle pipe-
line 8 and are attached to the other end of cross member 13 remotefrom skid 10. By means of the guide wheels 9 the trenching plough
follows the pipeline 8 thus requiring no additional steering. The
effect of the hitch point 3 located over the landside 5 is that the
sideways component of the towing force is resisted with the result
that the steering effect of the towing force is significantly
reduced. In the disposition shown in Figures 1 and 2 the plough
cuts a trench parallel to the pipeline 8 which has been previously
installed in its trench. At the rear of the plough is a scraper 12
to displace soil to cover the pipeline.
Referring to Figure 3 and 4 the trenching plough indicated by
reference numeral 21 is generally of similar construction to that
shown in Figures 1 and 2 with the exception of the steering means.
The plough comprises a body in the form of a beam 24 attached to
the rear of which is a blade indicated generally by numeral 27 the
leading face 26 of which is the soil cutting member and the sides
25 of which provide the landside. Located above the sides 25 is a
hitch point in the form of towing eye 23 to which a towing cable 22
is attached. The forward part of the beam 24 is attached to a
laterally extending cross member 28 the ends of which are attached
to, and supported by, skids 30 and 31 on the sea bed. The plough
has steering means in the form of sensor 32 which scans the pipe-
line 29 and controls a servo mechanism (not shown) which operates
a hydraulic ram 33 which moves the skids 30 and 31 which have soil
engaging blades ~only one of which 34 is shown). By means of this
arrangement the trenching plough is able to follow the pipeline 29
which may in places be buried as shown in Figure 3 and produce a
trench parallel to the axis of the pipeline. Attached to the rear
of the body 24 are a pair of scraper arms 35 to move the soil.
Referring to Figures 5 and 6 the trenching plough indicated
generally by numeral 41 comprises a body in the form of beam 44
attached to the rear of which is a blade indicated generally by
numeral 47, the leading face 46 of which is the soil cutting edge
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and the sides 45 of which provide the landside. In these respects
the trenching plough is similar to the two embodiments previously
described. The forward part of the beam 44 is attached to a
laterally extending arm 43 the end of which is supported by skid
55. On the arm ~3 is mounted a hitch point in the form of towing
eye 46 which is movable on the arm 43 by means of roller 48. The
arm 43 has a curved face 49 on which the roller 48 moves so that
the hitch point 46 moves on the circumference of a circle whose
centre is at poin~ 50 which is over the landside 45. The effect
of this is that the projected line o~ action of the towing force
passes through point 50 with the result that the sideways component
of the towing force is resisted by the landside 45.
The trenching plough has a steering means in the form of a
pair of guide wheels 52 straddling the pipeline 54 the latter resting
on a roller between the guide wheels 52. At the rear of the body
is a pair of scrapers 60 for displacing soil sideways.
In use the trenching plough is towed by means of a line 56
attached to hitch point 46. The trenching plough passes along and
under the pipeline 54. A trench is made into which the pipeline
settles.
In the three embodiments shown the point through which the
towing force passes, i.e. points 3, 23 and 50 are vertically above
the effective centre of the landside in each case.
The present invention provides improved control of the trenching
or other soil moving operation when the line of action of the towing
force is up to 45 from the line of travel of the implement and
particularly in the range up to 30. Further the line of the towing
force (when projected in the horizontal plane through the hitch point)
passes through, or close to, a point on the vertical axis passing
through the point of intersection of the lines of action of the soil
forces on the cutting member and landside. Thus, any sideways force
applied by the towing means is resisted by the landside to reduce
the resultant Gouple in the horizontal plane. ~t is thus possible
to steer the implement wi~h a smaller steering force, with reduced
risk of damage to the pipeline.
The embodiment of Figures 5 and ~ is particularly suitable for
towing by an underwater tractor or other similar vehicle which
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cannot conveniently straddle the pipeline with the result that the
towing force is always at an angle to the axis of the pipeline.
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