[0001] The present invention relates to trenching apparatus, namely apparatus for excavating
a trench. Advantageously apparatus according to the present invention can be combined
with trench filling apparatus and with drain laying equipment whereby to act in a
single pass to excavate a trench, lay a drainage pipe in the bottom of the trench,
and fill the trench with a permeable material such as gravel or stones and then re-cover
the trench with the excavated material. The present invention also encompasses such
a combination.
[0002] Prior art attempts to produce drainage channels in one pass include the so-called
"mole" plough which comprises a rigid blade having a bulbous enlargement at the bottom
end and carried by an adjustable mounting on a tractor or track laying vehicle. The
blade is inserted into the ground substantially vertically with the bulbous portion
lowermost and by drawing this through the ground an inverted "keyhole" shape slot
is formed. The parallel sides cut by the blade quickly recombine leaving a subterranean
channel which assists drainage. Attempts have been made to combine a mole plough with
a drain laying machine, but these have not been entirely successful.
[0003] The object of the present invention is to provide a trench forming excavating tool
which acts to form a trench rapidly and easily, into which trench a drainage pipe
or _other permeable drainage-assisting material can be laid and which can then be
back-filled leaving the drainage pipe or drainage material in position.
[0004] According to one aspect of the present invention, therefore, apparatus for forming
a trench comprises a blade rigidly carried by a blade carrier for support by a tractor
vehicle ( the term "tractor" being used to define any vehicle for drawing the blade
through the ground) so as to be drawn in use through the ground in the manner of a
ploughshare, the blade being generally flat, lying in a plane generally normal to
the ground, and having a leading edge inclined at an angle to the plane of the ground,
a transverse plate being secured to at least part of the leading edge of the blade,
the width of the plate defining the width of the trench to be formed by the tool.
[0005] 'In use of the tool of the present invention the transverse plate is drawn through
the ground at an angle such that the soil contacted thereby experiences a "lift" from
the trench being formed whilst surplus soil can flow to either side of the trench
forming plate as the tool is drawn through the ground. The apparatus of the present
invention provides means for resisting any tendency of the trench forming plate to
sink into the ground, for which purpose the mounting assembly by which it is carried
preferably fixedly retains the tool to the tractor vehicle in a controlled or controllable
orientation.
[0006] In order to ensure adequate loosening of the soil for subsequent displacement by
the trench forming plate as this is drawn through the ground, the lower end of the
leading edge of the blade may be provided with a rigid tooth similar to the cutting
teeth with which buckets and other tools of a conventional excavating machine are
provided. Such tooth is preferably arranged with the major portion of its lower face
extending generally parallel to the ground and a cutting tip inclined slightly downwardly
whereby to exert a slight downward pressure on the tool as it is drawn through the
ground. Further in order to avoid clogging by vegetation when the tool is used on
grassland, there is preferably provided an additional downwardly directed blade, or
a wheel which serves to cut the surface of the ground as the tool is drawn through
it.
[0007] Preferably the blade and the plate are made from plate steel and reinforcing fillets
are provided at selected locations between the blade and the tooth. Such re- ,inforcing
fillets may be permanently secured to both the blade and the plate or may be so arranged
as to permit exchange of the plate for another of a different width. In a preferred
embodiment the blade carrier has a central slot within which the blade can be located,
and transverse pins are passed through spaced apertures in the blade carrier, traversing
the slot whereby to define locating points for the blade on the carrier. The blade
has cooperating apertures for receiving the pins, and different apertures may be provided
for locating the blade in various different positions with respect to the carrier
to vary the depth to which the blade extends thereby varying the depth of the trench
formed by the plate and blade as they are drawn through the ground.
[0008] If the tool is drawn by a track-laying vehicle having a three point linkage, however,
this depth can also be adjusted by varying the height at which the three point linkage
is set to carry the tool.
[0009] Preferably the blade carrier comprises two side members defining the said slot, these
side members being joined at the rear by a pivotal coupling member suitable for attaching
subsequent components of the apparatus in a train to be towed by the tool. Such pivotal
coupling also allows the components of a train to turn with respect to one another
making it easier to turn the equipment at each end of a field without requiring complex
uncoupling and recoupling operations.
[0010] In the preferred embodiment the slot for the blade is spanned at the forward end
by a transverse stiffening member. This transverse stiffening member may also carry
the lower pair of a three point linkage coupling for attachment to the three point
linkage of the tractor vehicle as mentioned above. Such side members may also carry
an upright member which supports the upper connection for the three point linkage.
Triangular braces on the transverse stiffening member and on the upright are provided
for ensuring complete rigidity of the tool in use. Such triangular braces, in the
form of triangular fillets or gusset plates, extend between the side members and the
transverse stiffening member, between the side members and the upright ( on either
side of the slot) and between the transverse stiffening member and the upright member.
[0011] In use of the tool soil is displaced by the transverse plate, lifted to the surface
and allowed to flow laterally outwardly onto the shoulders of the trench as the tool
is drawn through the ground. In order to prevent the soil from falling back into the
trench after the plate has passed, the side members are preferably provided with depending
lateral flaps which extend downwardly for a depth substantially equal to the depth
to which the transverse trench-forming plate extends whereby to prevent displaced
soil from re-entering the trench too soon. Such re-entry is not allowed in fact until
after the subsequent part of the apparatus has passed, whereupon back-filling is encouraged
by means which will be described in greater detail below.
[0012] According to another aspect of the present invention trench forming and filling apparatus
comprises, in combination, a trench forming tool and trench filling equipment including
a hopper for stones or other like 'trench filling material (hereinafter referred to
as "fill"), the hopper having two parallel depdning lower chute walls extending parallel
to the length of the equipment (that is parallel to the longitudinal axis thereof)
and two laterally inclined guide members spaced more widely at their forward end than
at their rearward end whereby to guide displaced soil inwardly towards the trench
as the apparatus is drawn along..
[0013] Such guide members may be attached to the hopper in any suitable manner, for example
by means of chains or guide'rods or the like.
[0014] Preferably the hopper is provided at its rear end with a lower gate which determines
the level of fill in the trench as the hopper is drawn past. The two parallel depending
lower chute walls extend in operation into the trench itself and constitute an effective
continuation of the depending flaps of the trench forming tool, being very slightly
closer together, for example by the thickness of the material of the flaps, and again
preventing displaced soil from re-entering the trench until the required filling material
has been placed in the bottom of the trench by the hopper. The rear gate determining
the "fill" level is preferably adjustable since the height of the hopper above the
ground is effectively fixed, so that the depth of fill can be varied simply without
requiring the apparatus to be removed from the ground.
[0015] The present invention also comprehends drain laying apparatus comprising a trench
forming tool as defined above, trench filling apparatus and a pipe guide operable
to direct a flexible pipe into a trench formed by the trench forming tool immediately
prior to filling the trench by the trench filling apparatus.
[0016] Such pipe guides are preferably carried on the hopper itself, and, in the preferred
embodiment, extend through the interior of the hopper to a point at the lowermost
region of the hopper where the pipe can be laid directly onto the floor of a trench
formed by the immediately preceding trench-forming tool.
[0017] The present invention also comprehends drain laying apparatus as hereinbefore described,
in combination with a stone separator acting to remove stones from the soil at least
in a broad strip adjacent the trench being formed, and operable to direct stones separated.
[0018] from the soil into the hopper whereby to de-stone the soil and lay the stones as
a permeable fill below the ground level and immediately above a drain pipe laid in
the bottom of the trench.
[0019] One embodiment of the present invention will now be more particularly described,
by way of example, with reference to the accompanying drawings, in which:
Figure 1 is a side view of the trench forming tool constituting a part of the embodiment
of the present invention;
Figure 2 is a plan view of the tool illustrated in Figure 1;
Figure 3 is a side view, partly in section, of the apparatus of the invention, including
a hopper having a pipe-laying guide;
Figure 4 is a perspective view from above and behind of the assembled apparatus;
Figure 5 is a perspective view from above and in front of the assembled apparatus;
and
Figure 6 is a sectional view taken on the line VI-VI of Figure 4.
[0020] Referring ow to the drawings, the tool illustrated is adapted to be mounted on a
three point linkage of a tractor vehicle. Because of the forces which will be involved
in drawing the tool through the ground it is anticipated that the tractor vehicle
will be a track-laying vehicle capable of exerting a considerable traction. As is
known, the conventional three point linkage as is used on, for example, agricultural
tractors and other such tractor vehicles, comprises two tongue-like elements lying
in a common horizontal plane, the third plane of the tongues being generally vertical,
and a third tongue which forms, with the other two, a triangle lying in a generally
perpendicular transverse plane with respect to.' the longitudinal axis of the vehicle.
These tongues are mounted at the ends of arms which can pivot about horizontal transverse
axes and suitable hydraulic actuators are provided for causing the arms to turn so
as to effectively raise and lower the implement attached to the linkage. The quadrilateral
linkage formed by the upper arm and the two lower arms ensures that the equipment
carried by the linkage is maintained in approximately the same orientation as it is
raised and lowered, although in practice the rear of the tool is raised more than
the front upon elevation. For mounting to such a linkage the tool of the present invention
is provided with three pairs of linkage connector plates generally indicated 11, 12
and 13. The two pairs of lower linkage connector plates, 11, 12 each have two coupling
holes 14, 15 for receiving a connector pin and the plates are mounted on a transverse
channel section member 16 such as by welding. The transverse channel member 16 is
secured to a main body assembly comprising two channel section elements 17, 18 secured
together to define a central slot 19 extending through-out the length of the tool
and only spanned by the transverse reinforcing member 16.
[0021] Secured to the channel section members 17, 18 the respective downwardly extending
plates 20, 21, these two plates being spaced, like the channel members mentioned above,
from one another by the slot 19.
[0022] The channels of the channel members 17, 18 are placed facing outwardly away from
the slot 19 with the upper channel members and the lower plate members being secured
by welding along the adjacent flange of the channel member to secure the two components
on each side of the slot 19-together. Two coupling rings 24, 25 of substantial dimensions
are welded to the rear end of the channel elements 17, 18 and the plates 20, 21 spanning
the slot 19 and securely retaining the left and right sides of the body element in
the predetermined configuration. The forward ends of the two sides are, of course,
retained in position by the upper transverse support 16 which spans the slot 19. The
lower plate members carry a cutter wheel 22 on an arm 23 which extends forwardly for
a short distance beyondhthe forward end of the channel members 17, 18.
[0023] Located in the slot 19 is the trench forming leg of , the tool, generally indicated
25. This leg comprises a generally flat substantially rectangular blade 26 having
two holes formed therein for receiving pins 27, 28 passing through pin housings 29,
30 respectively secured to the channel members 17, 18 and to the lower plate members
20, 21 respectively, to constitute a secure, but removable, fixing for securing the
blade 26 to the longitudinal body of the tool.
[0024] At the forward lower end of the blade 26 there is a foot 31 having a tapered tooth-like
shape with a chisel edge 32 for penetrating the soil. The leading edge of the blade
26 is covered by a transverse trench forming plate 33 the transverse width of which
determines the width of the trench being formed, and which may be tapered or have
parallel sides. Triangular reinforcing fillets 34 are welded in position between the
trench forming plate 33 and the plate 26 constituting the main support of the leg
25.
[0025] In operation the tool is drawn through the ground by a tractor vehicle in the manner
of a plough, but instead of cutting the soil and turning it like a plough share the
cutter wheel 22 parts the surface vegetation and the tooth 31 loosens the soil, whilst
the trench-forming plate 33 elevates it and allows it to fall loosely on either side
of the thus-formed trench. To prevent the loose soil from falling back into the trench
the tool is further provided with guard plates 35, one on either side of the longitudinal
body assembly and spaced slightly less than the width of the trench-forming plate
33 so that these project slightly into the upper part of the trench as the tool passes,
thereby preventing the loosened soil from falling back into the trench until such
time as this is required.
[0026] Because of the substantial forces which are applied to the tool in use, triangular
reinforcing webs are provided between the longitudinal body assembly and the transverse
arm 16, and the upper connector linkage 13 is supported on an upstanding column 37
which is reinforced by a pair of triangular webs 38 secured to the upper edge of the
upper channel members 17, 18 on either side of the slot 19.
[0027] A hopper 42 is attached to the trench-formingy tool at the rear by means of the two
rings 24, 25 which constitute upper and lower pivots for receiving at vertical pivot
pin 39 which passes through two lugs 40, 41 formed on the forward end of the hopper
42, and which are positioned so that the upper lug 40 passes over the upper ring 24
and the lower lug 41 passes under the lower ring 25. This allows the tool to support
the hopper 42, determining its vertical level with respect to the ground and at the
same time allowing it to pivot about the vertical axis defined by the pin 39 so that
the combination does not act rigidly when the equipment is being turned.
[0028] The hopper 42 comprises an upwardly open chamber defined by a forward wall 43, two
lateral inclined walls 44, 45 and a rear inclined wall 46. The front wall 43 is substantially
vertical and the two lateral inclined walls 44, 45 slope inwardly from a relatively
wide spacing at the top to define a narrow parallel sided slot 47 at the bottom. The
width of the slot 47 is very slightly less than the spacing of the guard plates 35
which in turn are spaced slightly less than the width of the trench-forming plate
33 which defines the width of the trench being formed by the tool in use.
[0029] Projecting downwardly from the lower parallel edges of the inclined sides 44, 45
are two guide plates 48, 49 the height of which is rather less than the depth to which
the digging tooth 31 of the tool projects so that the plates 48,49 constitute, in
use, reinforcing slide guides for holding up the sides of the trench and also for
preventing displaced soil from re-entering the trench. It is important to note that
the outwardly inclined walls 45,44 are spaced from the ground level generally indicated
by the line G in Figures 1 and 3 by the distance d in Figure 3 so that they do not
come into contact with the displaced soil which will be lying in a curving mound,
which contact would cause further displacement of the soil and thus waste of energy
in laterally displacing it further than is necessary.
[0030] At the rear the two guide plates 48,49 are spanned by an adjustable rear plate 50
the position of which can be varied in a vertical plane by means (not shown) and for
a purpose which will be described in greater detail below.
[0031] A grid of longitudinal bars 51 extend between the vertical front wall 43 and the
inclined rear wall 46 of the hopper 42 to act as a filter- for large stones which
are to be fed into the hopper by means of a chute 52 forming part of a stone feed
mechanism on a vehicle which is moved alongside the trench-forming tool of the present
invention in a manner which will be described in greater detail below. The grid 51
is carried by a rectangular frame 62 pivoted at pivots 63 to the side wall of the
hopper. An hydraulic ram 64 is provided for turning the grid from a closed position,
illustrated in Figure 4, to an open position past vertical to allow any. stones lodged
in the grid to be tipped over the side of the hopper 42.
[0032] The forward wall 43 is formed with a guide channel 53 having an upper forwardly facing
guide mouth 54 and a lower curved exit 55 defined by a curved front plate 56 and a
curved rear plate 57 extending into the slot 47 defined by the two. guide plates 48,
49. These components define a guide channel for a pipe 58 carried in a coil, for example
on the tractor vehicle and led through this guide into the bottom of the trench formed
by the tool.
[0033] Finally, the side walls 44, 45 of the hopper carry support legs 57, 58 in the form
of rigid lugs which carry trailing guides 59, 60 which act as soil displacement plates
widely spaced at the forward end and held more narrowly together at the rearward end
by the legs 57, 58. The guide plates 59, 60 act as the equipment is drawn across the
soil to laterally displace .the loose soil on either side of the hopper 42 inwardly
towards the trench line causing it to back fill into the trench as the equipment passes
it over it. Chains 61, 62 extend from the forward end of each leg 57, 58 to a cross
bar 63 carried by the hopper front wall 43.
[0034] In operation, then, the tool is drawn over the ground so that the trench forming
plate 33 cuts a trench the width of which is determined by the width of the plate
33 by lifting the soil and allowing it to fall freely on either side, where it is
retained by the cover plates 34 until the guide plates 48, 49 pass that particular
point. A pipe 58 is fed down the guide constituted by the entrance chute 54, the guide
channel 53 and the two curved plates 56, 57 and is laid in the bottom of the trench.
Stones entering the hopper 42 through the chute 52 and filtered by the grid of bars
51 are laid over the pipe 66 to form a permeable fill, and the level of this fill
is determined by the back plate 50 the vertical adjustment of which determines the
height above the pipe 58 to which the stones can reach before being cut off by the
plate 50 itself.
[0035] The stones may be introduced from a separate supply such as a quarry, in which case
they would most conveniently be in the form of gravel or chippings, fed by a suitable
mechanism from a lorry leading to the chute
52. Alternatively, a known stone separating machine may be used for separating stones
from the soil in a strip covered by the machine adjacent the trench-forming tool,
in which case the stones delivered by the chute 52 will have been separated from the
soil in the field being treated, and it is for this reason that the grid of bars 51
is required since the orange of sizes of stones thus separated may include rather
large stones which would block the trench or extend above the height defined by the
back plate 50. Finally, as the tool passes, the two guides 59, 60 cause the displaced
soil to be moved laterally to refill the trench leaving a drainage pipe covered with
a permeable fill at the bottom and a usable depth of tilth for agricultural purposes
in the upper layer, the depth of this upper layer being such that it can be worked
by ploughing or rotovating or any other cultivating process without disturbing the
stones in the lower part of the trench. Effective drainage is thus obtained without
causing any disruption to the working surface of the field as was previously the case
with surface laid drainage stone channels. The pipe 58 may be of any convenient flexible
type, although a corrugated pipe having a plurality of small apertures allowing the
entrance of drainage water along the whole of its length is preferred.
[0036] Additional chains 67 extend from the front cross beam 16 to the sides 44, 45 of the
hopper 42 to restrict pivoting movement during normal use; these can be released to
allow pivotting when required.
[0037] Within the hopper 42; along the inside of the wall 44 is a shutter plate 68 movable
between a retracted or open position as shown in Figure 6 and a closed or extended
position where it closes the bottom of the hopper 42. The shutter plate 68 is connected
to an hydraulic actuator 70 for effecting the movement.
[0038] A cover plate 69 extends over both the shutter plate 68 and the actuator 70 to protect
it from abrasion or damage by the material moving through the hopper in use of the
equipment. Thus when filling trenches with gravel, if the hopper is still partly full
at the end of a run the tool can be raised out of the ground by means of the three
point linkage and escape of gravel can be prevented by closing the bottom of the hopper
with the shutter plate 68.
[0039] In another embodiment, not shown, provision is made for ready interchange of the
trench-forming components to allow trenches of different widths to be produced. For
this purpose the soil plate 33 is held removably on the blade 26, and the side plates
35 and 48, 49 can be removed and replaced. In this embodiment the hopper is split
horizontally to allow the lower components to be replaced to effect such trench width
interchange. The line of the horizontal separation is approximately two thirds down
the inclined side walls 44, 45 of the hopper 42.
[0040] It has been found that the most satisfactory inclination of the soil lifting plate
33 is in the region of 45° although a shallower angle to the ground will result in
less tractive force being required. At steeper angles the soil tends to be compacted
by the forward motion rather than lifted.
1. Apparatus for forming a trench, characterised in that it comprises an elongate
blade (26) carried on a blade carrier (17, 18, 19) adapted to be supported by a tractor
vehicle so as to be drawn in use through the ground lying in a generally upright plane
with its leading edge inclined rearwardly and upwardly in relation to the direction
of forward movement of the apparatus, a soil lifting plate (33) being secured to the
said leading edge of the blade (26) so as to lie in a plane orthogonal to the plane
of the blade (26), the width of the said soil lifting plate determining the width
of the trench formed by the apparatus.
2. Apparatus according to Claim 1 characterised in that the said upright blade (26)
is removably housed in a slot (19) in the said blade carrier (17, 18, 19) and held
in such a way as to be movable between a working position in which its leading edge
is inclined upwardly and rearwardly, and a transport position in which the said leading
edge is inclined downwardly and rearwardly.
3. Apparatus according to Claim 1 or Claim 2, characterised in that the blade carrier
(17, 18, 19) has two generally parallel side walls (35) on either side of the said
blade (26), lying in planes generally parallel to the plane of the blade (26) and
spaced a distance not greater than the width of the soil lifting plate (33) on the
leading edge of the blade (26), the side walls extending downwardly from the blade
carrier so that in use they extend into at least the upper part of a trench formed
by the tool as it is drawn through the ground.
4. Trench forming and filling equipment, characterised in that it comprises trench
forming apparatus according to any preceding claim, in combination with trench filling
apparatus comprising a hopper (42) having inclined walls (44, 45, 46) defining a vessel
with a longitudinally extending opening (47) in the lower part thereof, and two generally
parallel depending side walls (48,49) extending downwardly from the said opening and
being in approximate alignment with the said side walls (35) of the trench forming
apparatus whereby to project at least partly into the trench formed by the trench
forming apparatus as it is drawn through the ground with the trench filling apparatus
attached thereto so as to follow in the same path.
5. Trench forming and filling equipment according to Claim 6, characterised in that
the said hopper (42) carries two laterally inclined soil deflection members (59,60)
in the form of elongate plates lying in generally upright planes and spaced more widely
at the forward ends than at the rear so as to deflect soil lifted out of the trench
by the soil lifting plate (33) and return it to the line of the trench, filling in
over any material introduced into the bottom of the trench through the said hopper.
6. Trench forming and filling equipment according to Claim 4 or Claim 5 characterised
in that the said hopper (42) includes guide means (53,54,56,57) by which elongate flexible pipes or cables can be introduced into the bottom of
the trench prior to the introduction of material through the opening (47) in the bottom
of the hopper (42) and the back-filling of soil by the said soil deflection plates
(59,60).
7. Trench forming and filling equipment according to any of claims 4,5 or -6, characterised
in that the hopper (42) has a rear wall (46) carrying an adjustable plate (50) which
extends transversely of and between the said two downwardly projecting lower side
walls (48,49) of the hopper (42), the said adjustable plate determining the level
in the trench of material introduced thereinto through the hopper (42).
8. Trench forming and filling equipment according to any of Claims 4 to 7, characterised
in that the said hopper (42) is provided with a shut-off plate (68) displaceable between
a first, retracted position, in which it leaves the hopper opening unobstructed and
a second, extended position, in which it projects into the said hopper opening (47)
whereby to prevent or at least substantially restrict the movement of material in
the hopper (42) through the said opening (47).
9. Trench forming and filling equipment according to any of claims 4 to 8, characterised
in that the top of the hopper is covered by a grid of bars (51) serving to prevent
the entry of large stones above a size range determined by the spacing of the bars
into the hopper: the bars being carried by a surrounding frame (62) which is mounted
by pivotal connection means (62) to the upper rim of the hopper to be tiltable to
an inclined position to allow any large stones caught by the bars (51) to be tipped
off.
10. Trench forming and filling equipment according to any of Claims 4 to 9, characterised
by the further addition of apparatus for removing a surface layer of soil adjacent
to or alongside the trench being formed, separating from the removed soil stone or
other particles above a given size or size range, returning the fine soil particles
to the ground and supplying the separated stones and other large particles to the
hopper (42) of the trench filling apparatus so as to be introduced thereby into the
bottom of the trench.