Note: Descriptions are shown in the official language in which they were submitted.
ENG(PTD)5300 (2)
RLOUGH
The present invention relates to a pipe or cable burying plough.
more particularly to a plough suitable for use undarwater.
Ploughs which have been previously proposed for burying pipes or
cables usually consist of a share which forces soil upwards and
outwards to form a trench~ followed by two parallel faces which hold
the 80il apart while the cahle or pipe is lowered into the bottom of
the trench between them. Even though the sides of the share may
define a narrow steep sided trench, nevertheless the soil i9 disturbed
and weakened in triangular zones e~tendlng upwaLds on elther side of
the share. The soil displaced is not returned to the trench in any
controlled way wlth the res~lt that the trench i9 not completely
refilled and the burlal depth of the pipe or cable i9 le~s than the
depth cu~ by the plough share. The result i9 that the pipe or cable
lies in the bottom of a relatively shallow wide trench filled with
loosened and weakened soil, and inadequate protection is obtained.
The conveneional process moves a considerable volume of 80il in a
way which involves 2 great deal of internal shearing and con~equently
requires a high force to pull the plough.
I~ i8 an ob;ect of the present in~ention to provide a plough
which cuts an improved furrow shape, lifts the furrow slice a smaller
distance in order to permit the cable or pipe to be lnserted below it,
and allo~s the material to be replaced with m~nimllm disturbance~
Thus according to the present inventlon there ls provided a
plough for burying cable or pipe which plough comprises at least two
cuteers laterally spacad apart, one being offset at an angle relative
'7
to the other(s), for making two spaced apart cuts in a substrate to
form a wedge of materJal, means for lifting and movtng the wed~e
upwards and sldeways to form a trench and means for guiding the cable
or pipe into the trench under the lifted wedge.
After the cable or pipe ha~ been laid and the plough has passed
on, the wedge falls back into the trench without assistance and buries
th~ cable or pipe.
Conveniently the plough includes two longitudinally extending
sidefaces located rearwards of the cutters to assist in holding the
trench walls apart whilst the cable or pipe is guided lnto the trench.
Preferably these side faces converge towards their leading ends
to form the first of said cutters.
One of the sidefaces is preferably flat and the convergence i3
provided by angling or curving the otherO
The arrangement can be such that the cable or pipe is passed
between the longitudinally extending side faces into the trench under
tha liftad wedge.
The second cut~er is preferably located in fron~ of the first
cutter, laterally spaced apart from it and offset at an angle to it.
Preferably the angle between the planes of the first and second
cutters i9 in the range 15 to 45, most preferably about 30.
A third cutter may be lncluded located in front of the firsc
cutter and in line with it.
The second and third cutters may be fixed blades, freely rotating
2S discs, power driven discs~ water ~ets or other means.
The plough is normally intended for operation in a relatively
soft substrate such as sofl, sand, silt or clay. Elowever, by
modifying the second and th~rd cucters to act as saws, the plough can
operate in a harder substrate such as rock,
The first cutter preferably has a cutting edge pro~ecting from
its lower extremity adapted to engage the wedge cut by the cutters.
The means for lifting the wedge preferably comprises an inclined
plane rising from the cutting edge.
The wedge should be given sufficient lift initially to permit
sideways movement without jamming against the trench walls.
7~
Cab1es and pipes frequently contaln sections Oe larger cro~s
section at regular intervals along their lengths. These sections may,
for example, be caused by Joints or contain a~pliflers. Such sections
can give rise to problems in burial.
In order to accommodate these enlarged sections the inclined
plane can be modified ~o that it or a continuation thereof, which need
not be inclin0d, can be raised to such a height that the wedge of
material i8 forced up and out of the trench9 thereby making room for
the enlarged sectlons.
This can be done, for example, by hinging the inclined plane or
its continuation and automatically raising the rear of the hinged
section to the height of the trench on receipt of a signal from a
detector that the passage of an enlarged section is imminent. After
the latter is laid, the rear section drops to its normal level again~
According to ano~her aspect of the present invention there is
provided a method for burying a cable or pipe which method comprises
the steps of making two laterally spaced apart cuts ln a substrate to
form a wedge of material, lifting and moving the wedge upwards and
sideways to form a trenc~, guiding the cable or wedge into the trench
under the lifted wedge and allowing the wedge to fall back to cover
the cable or pipe.
Preferably the trench walls are held apart whilst the cable or
pipe is guided into the trench.
The invention i~ illustrated by reference to the accompanying
dra~ings in which:-
Figure 1 is a perspective diagrammatic view of a cable-laying
plough.
Figure 2, 3 and 4 show cross sections through the soil before
during and after passage of the plough.
The plough, indicated generally by numeral 1, includes two
longitudinally eYtending side faces 2 and 3, (being faces of a body
member 4) face 2 being flat and vertlcal (but not necessarily so) and
face 3 being cu~ved inwardly to meet face 2 and provide a cutting edge
5. EYtending through body 4 is a passage 6 through whlch ~he cable 7
is passed into the trench under the lifted soil wedge 8.
7~3~7
~,
The plough incorpora~es a second cu~ter in the form of a freely
rotating disc 9 whlch together with the cutting edge 5 make two
parallel spaced apart cuts in the 90il and thereby form a wedge or
slice 8. As can be seen from Fig. 2 the cut made by edge 5 i9
vertical wllilst the cut made by disc 9 is inclined to the vertical.
The plough also comprises means for lifting the 90il wedge 8 in the
form of a horlzontal cutting edge 10 and inclined face 11. The
inclined face 11 is at the leading end of a wedge shaped member 12
which also has a horizontal surface 13 (which can be slightly inclined
if desired).
The plough further includes a beam 14 which connects the body 4
to a supporting structure 15 which conveniently comprises a pair of
skids or wheels, one being located on each side. The supporting
structure 15 is ad~ustable by means not shown to control the depth of
the cuts. The plough is pulled by a tow rope 16 connected to a hitch
point 17 in the form of an eye.
In use the cutters 5 and 9 cut the ~ides of the soil wedge which
is to be lifted by the plough as shown in Fig. 2. The wedge or slice
ls trapezoidal in section, wider at the top than the bottom, and has
one vertical side and one at 30 to the vertical.
Fig~ 3 shows the way in which the plough body 4 moves the wedge
or slice upward by means of the upper surfaces 11 and 13 on the
projection 12 while the side face 3 moves it sideways, to leave room
for the plough body 4 to pass through the soil. The detailed geometry
of the curved side 3 and lifting surface 11 is arranged so that the
~oil slice is always lifted sufficiently first to permit sideways
~ovement without ~amming against the walls. The flatter is the
sloping wall the less the required lift but the greater the amount of
soil to be moved~ 30 is often a convenient angle but others may be
appropriate in particular cases.
Fig. 4 shows that when the plough body 4 moves on, the wedge or
slice will fall back on top oE the pipe or cable, to fill the trench
completely and provide improved protection.
The cutters 5 and 9 should be as narrow and sharp as possible to
cut the wedge or slice with the minimum 80il disturbance.
~7~
It may not be convenient to cut the side3 of ~he trench to the
full depth and the lower parts of the wedge walls may be left to crack
open. Alternatively water ~ets pro~ecting forward from the cuttlng
edges 5 and 10 may be used to complete the cutting of the wedge or
slice.
The disc cutter 9 making the sloping trench wall can be pivotted
about an axis 18 in front of the disc and parallel to the plane of the
disc as shown in Figs. 1 and 2 to provide some freedom of movemen~ if
an obstacle is encountered.
The advantage of the above illustrated plough is that it handles
the wedge in such a way as to reduce the strain~ in it, and therefore
reduce the pulling force. It leaves the cable or pipe beneath soil
which has suffered significantly reduced weakening as compared with
previously described ploughs.
When the plough i9 used for laying a cable lt will usually be
desirable to employ a pivotted curved plate (not shown and known to
those skilled in the art as a "dipper") attached to the plough beam 14
to urge the cable into the channel 6 so that the cable emerges from
the base of the channel.
