Note: Descriptions are shown in the official language in which they were submitted.
9~
The present invention relates to devices for forming
elongate trenches such as are used for drainage purposes.
Previously known devices function in one of a number
of ways.
A first type of device, broadly described as a back
hoe, operates in the manner of a mechanical shovel and
progressively excavates a trench by repeated scooping
actions.
~ nile such devices are suitable for forming a trench
in confined areas and on uneven terrain, they include a
considerable number of components whic'n are exposed to a
h~rsh operating environment. The resulting wear requires
frequent repiacement of the components.
Additionally, since t'neir mode of operation requires
the repetitive performance of a number of manually
controlled, disjointed steps, the speed at which a back
hoe can be operated is determined primarily by the skill
of the operator.
A second type of device forms a trench by advancing a
continuously cycling plurality of cutting and scooping
elements through the ground. The elements may be mounted
on a chain or wheel.
While this type of device is suitable for use by a
relatively unskilled operator, it includes an inordinate
number of moving parts whicll, like those of the back hoe,
- 2 ~
7~
-- 3 --
are subject to considerable wear. Additionally, these devices
are generally inflexible with regard to the wid-th of trench which
they are capable of forming.
The complsxity of such devices also precludes the inclusion
of reasonably priced control gystems, which would enable them to
operate at an optimum speed having regard to the power of th0ir
driving motor and the power necessary to form the trench in any
particular type of ground.
It is an ob;ect of the present invention to provide a trench
forming device able to overcome or at least ameliorate the above
mentioned shortcomings of the prior art.
The presant invention consists in a trench digging device
comprising a frame to be drawn, a downwardly and forwardly
directed elongate chisel mounted for longitudinal movement with
1~ respect to said frame, chisel adjustment means connected witn
said frame and said chisel to adjustably position said chisel
relative to said frame, and spoil displacement means fixed to
said frame to move spoil displaced from a trench by said chisel
away from said trench, said spoil displacement means comprising a
~0 pair of forwardly and sidewardly directed blades meeting at an
apex, each blade having a lower edge adapted to contact the
ground into which a trench is being formed, said blades having an
aperture through said apex at the lower edge of said blades sized
and configured to receive said chisel, said chisel being
~5 configured such that operation of said chisel adjustment msans is
effective to vary the extent of downward and forward projection
of said chisel in relation to said blades from a retracted
position at which the lower extremity of the chisel is
substantially level with the lower edge of the blades of the
displacement means to selectively extended positions at which the
lower extremity of said chisel is positioned below and in front
of said lower edge, in which extended positions, in operation,
the chisel has means to cut both the bottom and sides of the
trench.
A preferred embodiment of the present invention will now be
described, by way of example only, with reference to the
accompanying drawings in which:
Figure 1 is a side elevation of a trench digging
device according to the invention;
Figure 2 is a plan view of the device of figure 1;
Figure 3 is a section taken on line 3-3 of figure 2
and
Figure 4 is a section taken on line 4-4 of figure 2.
DESCRIPTION OF THE PREFERRE~ EM~ODIMENT
Referring to the drawings, the trench digging device
indicated generally at 1 comprises a frame 2, a downwardly
and forwardly directed elongate chisel 3 adjustably
1~ mounted to the frame 2 for longitudinal sliding movement
relative thereto and spoil displacement means 4 also
mounted to the frame 2.
The frame 2 comprises two vertically extending
parallel spaced-apart triangular plates 5, and two
parallel spaced apart guide plates extending between the
triangular plates 5 in the form of an upper guide plate 6
and a lower guide plate 7.
The perpendicular distance between the guide plates 6
and 7 is su~ficient to enable the chisel 3 to slide
between them~
The frame 2 further includes a pair of parallel
spaced apart support bars 8, each of which is fixedly
attached to a respective one of the mutually facing sides
of the triangular plates 5 to guide and support the
chisel. The support bars 8, in conjunction with the guide
plates 6 and 7 define a channel through which the chisel 3
may slide. The frame 2 also includes attachment brackets
10 to enable the device 1 to be connected to the three
point linkages of a tractor.
The spoil displacement means 4 comprises a pair of
forwardly and outwardly directed blades 12 which meet at
an apex located in front of the frame 2. The blades 12
are mounted to the frame by a forward mounting plate 13
and a rear mounting bar 14. The plate 13 is bolted to a
bracket 15 on tihe frame and the bar 14 is bolted to the
lower guide plate 7. The spoil displacement means is thus
securely attached to the frame 2 with i-ts apex directed
forwardly.
In the preferred embodiment the c'nisel 3 comprises a
length of hollow steel tube having a wear plate 16
releasably attached along its upper side. The tube may be
circular or of any suitable section but is preferably
square.
The wear plate 16 may be replacèd when it becomes
excessively worn. It can also be interchanged with wear
plates of dif~ering widths as may be required. The wear
plate is attached to the tube by an array of bolts.
However, it may be attached by any suitable means such as
by being keyed to the tube or it may be formed integrally
with the tube.
An hydraulic ram 17 constitutes the chisel adjustment
means. One end of the hydraulic ram 17 is hingedly
mounted between the distal ends 18 of the support bars
by pin 19. The other end of the hydraulic ram 17 is
connected to the lower end o~ the chisel 3 by a further
pin 20 extending between opposed sides of the chisel. It
-- 5 --
will be appreciated that a substantial portion of the
hydraulic ram 17 is housed within the chisel itself.
The hydraulic ram 17 is supplied with operating fluid
by hoses (not shown) which extend from the distal ends of
tihe support bars 8 for connection to a suitable hydraulic
power source, for example, a tractor.
The blades 12 are provided with a passage at their
apex through which the chisel may project to a
preselected extent upon actuation of the hydraulic ram 17.
In operation, the trench digging device 1 is attached
to a tractor by attaching the tractor's three point
linkages to respective attachment brackets 10. The device
is thus able to be raised and lowered upon those linkages
in conventional manner.
Initially, the hydraulic ram 17 is retracted to its
maximum to thereby retract the chisel 3 so that its lower
end 21 is level with the lower edges 22 of the blades 12.
The three point linkage is then lowered until the lower
edges 22 of the blades 12 scrape the ground in-to which a
trench is to be formed. The hydraulic ram 17 is then
extended to project the lower end of the chisel 3
downwardly and forwardly into the ground through the
passage in the apex of the blades. The extent of this
projection is dependent upon a number o factors including
the power of the tractor, the available traction and the
hardness of the ground. The device is then hauled by the
tractor so that the chisel scores a trench in the ground.
The spoil displacement blades 12 direct progessively
excavated spoil down their length and away from the
trench, thereby preventing the spoil from spilling back
into the newly formed trench
If a deeper trench is required than that which can be
formed by a single pass, the tractor may be turned around
and the chisel re-positioned in the trench for a second
pass. The hydraulic ram is then further advanced so as to
extend the chisel further into the ground. The device is
then hauled back a~ong the partially formed trench to
increase its depth. It will be appreciated that if a
trench is required of considerable depth or in hard ground
a plurality of passes may be re~uired.
If the required width of the trench is greater than
that of the chisel 3, the wear plate 16 may be replaced by
a wear plate of greater width. The frame plates 5 are
sufficiently spaced to ccommodate a wear plate of greater
width than the tube. It will be appreciated that the
lower ends of the support bars 8 act to prevent lateral
movement of the chisel 3 irrespective of the width of the
ware plate 1~.
In the preferred em~odiment, the chisel is forwardly
and downwardly inclined at an angle of 4Sdegrees to the
horizontal. However, the chisel may be inclinded at any
suitable angle, preferably between 70 and 20.
It will be appreciated that the housing of the
hydraulic ram 17 within a square hollow chisel is
particularly advantageous since the hydraulic ram can be
relatively short in relation to tha extension length of
- 7
97~
the chisel. Additionally, it is protected during its
operation.
It will be appreciated that while the illustrated
device is adapted to be hauled by tractor or similar prime
mover, a self powered device or a device movecl by any
suitable means will fall within the scope of the present
invention.
It will further be appreciated that while the
illustrated device includes blades, any means for
preventing spoil from falling back into the formed trench
may be used, such as a conveyor belt, archimedean screw
arxangement or any other suitable means.
It will also be appreciated that any means may be
used for advancing the chisel through the passage in the
blades, such as a lead screw.
The device may also include a guide means for use on
a second or subsequent traversement so as to align the
device with a partially formed trench. The linkage
between the device and the tractor may also include an
articulated portion to accommodate some minor misalignment
of the tractor with a pre-formed trench.
