Note: Descriptions are shown in the official language in which they were submitted.
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AGRICULTURAL SEED DRILLS
This invention relates to agricultural sowing of
seeds by a technique of slit sowing, in which seeds are
implanted in slits or narrow slots cut in the ground.
In particular the invention is concerned with apparatus
(hereinafter referred to as "àpparatus of the kind set
forth") for seeding ground in the use of which seeds
from container means mounted on a frame assembly con-
nected to a towing vehicle are delivered through tubes
to slits which are cut and opened in the ground by a
plurality of discs mounted on the frame assembly for
rotation about generally transverse axes, roller means
mounted on the frame assembly in a position rearwardly
of the discs for rotation about a transverse axis being
adapted to compact the ground and close the slits after
seeds have been implanted therein.
There is known an apparatus of the kind set forth
in which the frame assembly comprises first and second
relatively movable frames, ~f which the first frame
comprises a draw bar for connection to a towing vehicle,
and the second frame forms a mounting for a plurality of
transversely spaced, longitudinally extending, arm
assemblies carrying the discs, the arm assemblies being
located below the frames and being urged downwardly away
from the second frame by resilient means, and a resil-
ient connection being provided between the first and
second frames by adjustment of which the loading applied
to the discs can be varied to control penetration of the
discs into the ground and the depth of the slits thus
produced.
An apparatus as described in the last preceding
paragraph is hereinafter referred to as an "apparatus of
the particular kind set forthl'. One example of an
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apparatus of the particular kind set forth is described
in U.K. Patent Specification No. 1 218 785, in which the
second frame is pivotally mounted on the first frame.
Front and rear compression springs are located between
each of the arm assemblies and the second frame, and
each arm assembly trails from a transverse shaft,
carried by the second frame, to which it is pivotally
connected. The angular disposition of the second frame
on the first frame can be adjusted, to vary the loading
on the discs, by a screw arrangemen~ to which the second
frame is resiliently connected. The container means
comprises both a seed box and a fertilizer box for
fertilizer.
- In ~se of~a seed drill as described in Specifica-
tion number 1~21~ 785 it hàs been ~fo~nd ~th~t' as`sowing
. progre$se~s adjust~ents have to ~é~made in order to keep
adequate~,~eight'~on'~e discs, to provide the de~s'ired
penetration of t~e, ground,S whils:t` mai'ntaining sufficient
w~eight~on th~.~olier m~eans for compaction'of'the ground
after seeding.- - This difficulty arisës- bécause- the
weight of-materi~I (seed and, optionally, fertilizer) in
the container means decreases as sowing progresses, and
as a result the distribution of weight on to the discs
and rollers changes. The situation is complicated by
the fact that the varying weight distribution also
affects the loading on the towing point of a tractor
towing the drill, with the result that the attitude of
the tractor may vary, also to affect the loading on the
discs.
It is an object of the present invention to pro-
vide an apparatus of the particular kind set forth in
the use of which less difficulty arises with varying
weight distribution as sowing progresses.
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According to my invention in apparatus of the kind
set forth the frame assembly comprises a first frame for
connection to a towing vehicle, a second frame, and a
pivotal connection between the two frames, the arm
assemblies are independently pivotally mounted on the
second frame, and each arm assembly carries at least one
of the discs and at least one roller of the roller
means, and the resilient means comprise front and rear
springs acting between the arm assemblies and the second
frame, the front springs being mounted forward of the
transverse axis of the roller means and the rear springs
being mounted rearward of the transverse axis of the
roller means, the front and rear springs being so con-
structed and arranged that the loading on the discs is
substantially independent of the weight of the material
in the container means which is supported on the second
frame, depth control means act between said first and
second frames, and means manually-operable are provided
for operating said depth control means to determine the
loading on said discs and the consequent penetration of
said discs into the ground which remains constant
irrespective of the weight of material in such contaimer
means, constants for said front springs and said rear
springs being chosen such that once determined by said
depth control means said penetration of said discs into
the ground will remain a constant for a given terrain.
The weight of the mater`ial in the container means
is taken by the rollers and a draw-bar of a towing
vehicle in proportions dependent upon the distance of
the container means from the draw-bar and from the axis
of rotation of the rollers.
The loading on the discs is substantially dependent
upon a pre-load imparted to the front springs by moving
the first frame angularly with respect to the second
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frame about the pivotal connection between the frames
which is located at the rear ends of the frames remote
from the draw-bar.
Only a single pivotal connection is provided be-
tween each arm assembly and the second frame and such a
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connection is located at the forward end of the second
frame, the arm assemblies and the second frame being
otherwise unconnected apart from the provision of the
front and rear springs.
The relative spring strengths are preferably chosen
in accordance with the position of the container means
on the second frame. It is advantageous for the rear
springs to be as weak as possible so that the rollers
are able to follow closely the contours of the ground.
This, in turn, dictates the strength of the front
springs.
Preferably the container means is disposed on the
second frame at a location such that, in a normal atti-
tude of the apparatus during a sowing operation the
centre of gravity of material in the container means
remains substantially vertically above the transverse
axis of rotation of the roller means as sowing pro-
gresses.
By arranging the container means close to, or
substantially vertically above, the transverse axis of
rotation of the roller means ensures that a smaller
proportion of the weight is taken by the draw-bar, and a
larger proportion by the roller means.
There now follows a description, to be read with
reference to the accompanying drawings, of an agri-
cultural seed drill which illustrates the invention by
way of example.
In the accompanying drawings;
Figure 1 is a diagrammatic view in side elevation
of the drill in a first position of adjustment;
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Figure 2 is a view similar to Figure 1 but with the
drill in a second position of adjustment.
The drill is constructed very similarly to that
described with reference to Figures 1 to 7 of U.K.
Patent Specification number 1 218 785. The drill is an
apparatus of the particular kind set forth with a frame
assembly comprising a first frame 10, comprising a draw
bar 12 for connection to a towing vehicle, and a second
frame 14 which is pivotally mounted, at 16, on the first
frame. A plurality of arm assemblies 18 (one only
visible in the drawings) are located beneath the frames
and are independently pivotally mounted, at 20, on the
second frame, so as to trail from the pivotal mount-
ings 20. Each arm assembly carries rotatably mounted
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discs 22 and two rollers 24, one disc and one roller
being mounted on each side of the arm assembly. One
front spring 26 and one rear spring 28 act between each
arm assembly 18 and the second frame 14, the front
springs 26 being mounted in front of a common transverse
axis of rotation of the rollers 24 and the rear
springs 28 being mounted behind the transverse axis of
the rollers. The resilient connection between the first
and second frames, for adjustment of the loading ap-
plied to the discs 22 in use of the drill, comprises a
rotatable screw member 30 threadedly mounted in a trun-
nion block 32 on the -first frame 10. The second
frame 14 is secured to a second trunnion block 34
through which the screw member 30 extends. The second
trunnion block 34 is freely slidable along the screw
member 30 and is resiliently located between two abut-
ments on the screw member by compression springs 36
and 38. By rotation of the screw member 30, the angular
adjustment of the second frame 14 on the first frame 10
can be varied to vary the loading on the discs 22.
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The drill comprises container means in the form of
a seed box 40 mounted on the second frame 14 to contain
a supply of seeds to be dispensed in use of the drill.
Means for dispensing the seeds from the seed box, and
directing the seeds into slits cut in the ground by the
discs 22, is constructed and arranged substantially as
in the aforementioned drill described in Specification
number 1 218 785.
The drill shown in the drawinys differs from the
aforementioned drill described in Specification
~No. 1 218 785 in the arrangement of the front springs 26
~' and-thé rear springs 28, and in the mounting of the arm
assemblies 18 on the second frame 14.
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As shown in Figure 2 there are no pivotal mountings
between the rear ends of the arm assemblies 18 and the
second frame, and, apart from the front springs 26 and
the rear sp~ings 28, the arm assemblies are connected to
the second fra~e 14 only by the pivotal connection 20 at
their forward ends. Also the spring constants of the
front and rear springs 26 and 28 are selected so that
the weight of the material in the container means is
transferred through them to the rollers 24 and the
draw-bar with substantially none of that weight being
transferred to the discs. It follows therefore that the
loading on the discs 22, and in consequence the pene-
tration of the discs 22 in the ground during a drilling
operation, is independent of the loading on the second
frame 14 and is determined solely by operation of the
screw member 30 to urge the frames lO and 14 relatively
towards each other as shown in Figure 2, thereby pre-
loading the front springs 26.
Preferably the container means is arranged on the
frame assembly so that in the normal attitude of the
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drill during a sowing operation the centre of gravity of
material in the container means is vertically above the
transverse axis of rotation of the rollers 24 (as indi-
cated by the chain-dot line 42), and will so remain as
sowing progresses and the weight of material in the
container means falls. As a consequence the loading
from the draw bar 12 on the towing point of a towing
vehicle does not vary with weight of material in the
container means.
It will be appreciated that although the container
means of the drill shown in the drawings is in the form
of a single seed box 40, the container could take var-
ious alternative forms arranged so that the centre of
gravity of material therein remained vertically above
the axis of the rollers 24 during a sowing operation.
For example, the container means might comprise a seed
box and a separate fertilizer box, the two boxes being
located on opposite sides of the axis of the rollers 24
but being balanced about the axis so that the centre of
gravity of all the material in the two boxes remains
vertically over the axis during sowing. Alternatively
the container means could be in the form of a single box
which is compartmented to accommodate more than one
material.
As referred to above the springs 26 and 28 have
spring constants such that the loading on the discs 22
is substantially independent of the weight of material
in the container means. When a load is applied to the
second frame 14 by material in the container means, some
of this load is applied to the rear springs 2B. The
applied load causes a compression of the rear springs 28,
and accordingly the second frame is lowered at its rear
end. The loading from the draw bar 12 on the towing
point remaining constant, the height above the ground of
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the ~ront end of the draw bar can be considered to be
constant. The front springs 26 are mid-way between the
towing point and the rear springs 28, and accordingly a
lowering of the rear end of the second frame 14 by a
certain distance is accompanied by a lowering of the
second frame at the front springs 26 by one half of that
distance. In order that the discs 22 should not thus be
lowered, which lowering (which would alter with the load
in the container means) would affect the loading on the
discs 22 during a sowing operation, it is necessary that
the effect should be cancelled out by the tendency for
the arm assemblies 18 to pivot about the axis of the
rollers 24 due to the load from the springs 28. In the
drill shown in the drawings, the front springs 26 are
such that they will deflect 1 inch (2.54 cm.) for each
56 pounds (25.4 kg.) of loading, and the rear springs 28
are such that they will deflect 1 inch (2.54 cm.) for
each 63 pounds (28.6 kg.) of loading. The distance from
the axis of the rollers 24 to the front springs 26
is 36 inches (91.4 cm.) and to the rear springs 28
is 16 inches (40.6 cm.). A load of 260 pounds (118 kg)
in the container means acting through vertically above
the transverse axis of rotation of the rollers 24 is
bàlanced by the rollers 24 and this is taken up by the
rear springs 28 180 pounds (81.6 kg) and the front
springs 26 80 pounds (36.4 kg).
The rear sprin~s 28 will compress 180/63 = 2.86
inches (7.55 cm) because the rear springs 28 compress an
extra 2.86 inches (7.55 cm) the front springs 26 will
have to compress half of this amount i.e. an extra
1.43 inches (3.75 cm) so that the same loading of
70 pounds (31.8 kg) will be maintained on the front
springs 26 to keep the required depth of penetration of
the discs 22. The front springs 26 with a load of
80 pounds (36.4 kg) will compress 80/56 = 1.43 inches
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(3.75 cm). This is calculated compression required to
maintain the system in equilibrium. That is, to main-
tain a constant applied pressure to the front springs 26
(disc depth control) no matter what weight is applied to
the frame assembly:
This is irrespective of the quantity of seed and/or
fertili~er in the respective boxes. Suppose the weight
were reduced to 130 pounds (59 kg). Then a load of 90
pounds (40.8 kg) on the rear spring would compress (or
lower) it 90/63 = 1.43 inches (3.75 cm). To maintain
the proper depth control the front springs 26 ~ould have
to compress (or lower) half this amount i.e. .715 inches
(1.90 cm).
Since there is a load of 40 pounds (18.2 kg) on the
front springs 26 then they would each compress (or
lowex) 40/56 = .715 inches (1.90 cm).
By having the weight of the seeds and/or fertiliser
boxes balanced about the rollers 24 no extra weight is
added to or taken from the draw-bar hitch point no
matter whether the boxes are empty or full.
If the w~ight of the seed and/or fertiliser boxes
is moved forward on the main frame say to half ~ay
between the draw-bar hitch point and the rollers 24,
then half this weight would be taken up on the draw-bar
and half on the rollers 24. Depth control would still
be maintained by using the same spring arrangement as
above but would be influenced by the weight on the
draw-bar.
This extra weight on the draw-bar could vary from
nothing to 1000 pounds (454 kg) and could perhaps affect
the height of the hitch point and thus the depth control
of the drill.
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