AGRICULTURAL IMPLEMENT WITH DOWN-FORCE CONTROL

MACHINE AGRICOLE A REGLAGE DE FORCE DESCENDANTE

English Abstract

Down-force control is provided by a top-link, which presses down the rear end of a tool-bar carrying multiple rows of seeder tools. The height of the tool bar is set front and rear during operation. The top-link includes a hydraulic ram. The ram is supplied with pressure from a pressure-reducing-relieving valve, whereby the downward- force on the rear of the tool-bar remains constant during operation. The tool bar has side wings which are pressed down by a pressure that is regulated by the same valve. The system allows the seeder to maintain constant implantation depth, even over uneven ground.

French Abstract

Un réglage de force descendante est fourni par une bielle supérieure, qui exerce une pression descendante sur l'extrémité arrière d'une barre porte-outils portant de multiples rangées d'outils de semoir. La hauteur de la barre porte-outils est adaptée à l'avant et à l'arrière au cours du fonctionnement. La bielle supérieure comprend un bélier hydraulique. Le bélier est alimenté en pression par une soupape de détente de pression, moyennant quoi la force descendante exercée sur l'arrière de la barre porte-outils demeure constante au cours du fonctionnement. La barre porte-outils présente des ailes latérales qui subissent une force vers le bas sous l'effet d'une pression qui est régulée par la même soupape. Le système permet au semoir de maintenir une profondeur d'implantation constante, même sur un sol irrégulier.

Claims

Claim 1. Apparatus for mounting an agricultural implement with respect to a
towing tractor, wherein:
the implement includes a tool bar, on which are mounted one or more rows of
ground-penetrating tools;
the tool bar has a front end and a rear end;
the tool-bar includes a point TF located near the front of the tool-bar, the
point TF
being a height HF above the ground surface and the apparatus includes a
first-link means for setting the height HF above the ground surface;
the apparatus includes a means for maintaining the height HF constant, during
operation;
the apparatus includes a means for permitting pitch-mode pivoting movement of
the tool-bar relative to the tractor, about point TF;
the apparatus includes a hydraulically-operable second-link, which is
connected
between the tractor and a point CF on the tool-bar;
the point CF is a point on the tool-bar near the front end of the tool-bar,
the point
CF being spaced from the point TF;
the second-link is of such structure that its length, being the distance
between the
tractor and the point CF, can be changed by hydraulic operation;
the apparatus includes a means for supplying hydraulic pressure to the
aforesaid
second-link;
the second-link is effective, when operated by hydraulic pressure, to apply a
force
between the tractor and point CF, and thereby to exert on the tool-bar a
moment about point TF;
the means for supplying hydraulic pressure to the second link includes a means
for
maintaining the hydraulic pressure at a constant magnitude;
and the means for maintaining the hydraulic pressure at a constant magnitude
is
arranged to be effective to keep the magnitude of the hydraulic pressure
constant even through changes in the length of the second-link.
Claim 2. Apparatus of Claim 1, wherein the tool-bar includes two or more of
the
aforesaid rows of ground-penetrating tools, the rows being arranged one
behind the other, and including at least a front row and a rear row.
Claim 3. Apparatus of Claim 2, wherein:
the means for maintaining the height HF fixed, during operation, comprises a



means for keeping the point TF on the tool-bar fixed, during operation,
relative to the tractor;
the first-link means for setting the height HF of the point TF on the tool-
bar, relative
to the tractor, is included in a three-point-hitch, the point TF on the tool-
bar
being coupled to a point on the hitch;
the means for setting the height HF includes an operable hydraulic hitch-ram,
which is effective, when operated, to raise and lower the aforesaid point on
the hitch, and thereby to raise and lower the point TF on the tool-bar;
the means for maintaining the height HF constant comprises a settable travel-
limit-
stop, which is effective to limit movement of the point TF below a
predetermined height;
the travel-limit-stop includes a mechanically-operated hydraulic trip-valve;
the trip-valve is effective, when operated by mechanical movement of the first
link
to a point at which the height HF is the predetermined height, to lock the
hitch-ram hydraulically;
the tool-bar includes a point TR located near the rear of the tool-bar, the
point TR
being a height HR above the ground;
the apparatus includes a rear-height-setting-means, for maintaining the height
HR
constant, during operation;
the rear-height-setting-means, for maintaining the height HR constant, is
included in
the means for supplying hydraulic pressure to the second-link;
the means for maintaining the hydraulic pressure supplied to the second-link
at a
constant magnitude comprises a pressure-reducing-relieving valve;
the tool-bar includes hydraulically-operable side wings, and the means for
maintaining the hydraulic pressure supplied to the second-link at a constant
magnitude is effective to keep the down-force on the wings constant also;
the rear-height-setting-means includes a rear-wheel;
the means for maintaining the height HR fixed, during operation, comprises a
means for keeping a height HR, being the height of the point TR on the tool
bar, fixed relative to the rear wheel, during operation;
the rear-height-setting-means includes a hydraulic rear-wheel-ram;
the rear-wheel-ram is arranged in the apparatus for raising and lowering the
rear-
wheel relative to the tool-bar;
the means for keeping the height HR fixed includes a height-limit-stop, having
travel-limiting engagement with the rear-wheel ram;
the apparatus includes an operable means for raising the tool-bar, for non-
working


transport of the apparatus;
the apparatus includes a rear-wheel, mounted on the tool-bar, and a rear-wheel
ram for raising and lowering the rear-wheel relative to the tool-bar;
the means for raising the tool-bar comprises a means for operating the hitch-
ram in
the sense to raise the point TF, and a means for simultaneously operating
the rear-wheel-ram in the sense to raise the point TR;
the apparatus includes a connecting-means, for connecting the second-link to
the
point CF on the tool bar;
the connecting-means includes a pivotal arm;
the geometrical configuration of the second link and the connecting-means is
such
that:
(a) when the tool-bar is not raised, upon a force being applied to the
second-link in the sense to lower the rear of the tool-bar, the pivotal
arm can abut the tool-bar in such manner as to transmit said force
to the tool-bar;
(b) when the tool-bar is raised, upon a force being applied to the second-
link in the sense to move the second-link away from the tool-bar, the
second-link can so move;
the aforesaid configuration is such that, when the tool-bar is raised, the
movement
of the pivotal arm is enough to separate the second-link from the tool-bar to
such an extent that the raised tool-bar can undergo pitch-mode movements
relative to the tractor, being movements of such magnitude as arise from
transport of the apparatus, without interference from the second-link.
Claim 4. Apparatus of Claim 1, wherein the tools are seed-implantation-tools,
supplied with seeds from a seed hopper carried on the tractor.
Claim 5. Apparatus of Claim 1, wherein the means for maintaining the height HF
fixed, during operation, comprises a means for keeping the point TF on the
tool-bar fixed, during operation, relative to the tractor.
Claim 6. Apparatus of Claim 5, wherein:
the first-link means for setting the height HF of the point TF on the tool-
bar, relative
to the tractor, is included in a three-point-hitch, the point TF on the tool-
bar
being coupled to a point [H] on the hitch.


Claim 7. Apparatus of Claim 6, wherein:
the means for setting the height HF includes an operable hydraulic hitch-ram,
which is effective, when operated, to raise and lower the aforesaid point on
the hitch, and thereby to raise and lower the point TF on the tool-bar;
the means for maintaining the height HF constant comprises a settable travel-
limit-
stop, which is effective to limit movement of the point TF below a
predetermined height.
Claim 8. Apparatus of Claim 7, wherein:
the travel-limit-stop includes a mechanically-operated hydraulic trip-valve;
the trip-valve is effective, when operated by mechanical movement of the first
link
to a point at which the height HF is the predetermined height, to lock the
hitch-ram hydraulically.
Claim 9. Apparatus of Claim 1, wherein:
the tool-bar includes a point TR located near the rear of the tool-bar, the
point TR
being a height HR above the ground;
the apparatus includes a rear-height-setting-means, for maintaining the height
HR
constant, during operation.
Claim 10. Apparatus of Claim 9, wherein:
the rear-height-setting-means, for maintaining the height HR constant, is
included in
the means for supplying hydraulic pressure to the second-link.
Claim 11. Apparatus of Claim 10, wherein the means for maintaining the
hydraulic
pressure supplied to the second-link at a constant magnitude comprises a
pressure-reducing-relieving valve.
Claim 12. Apparatus of Claim 9, wherein:
the rear-height-setting-means includes a rear-wheel;
and the means for maintaining the height HR fixed, during operation, comprises
a
means for keeping a height HR, being the height of the point TR on the tool
bar, fixed relative to the rear wheel, during operation.
Claim 13. Apparatus of Claim 12, wherein:
the rear-height-setting-means includes a hydraulic rear-wheel-ram;


the rear-wheel-ram is arranged in the apparatus for raising and lowering the
rear-
wheel relative to the tool-bar;
the means for keeping the height HR fixed includes a height-limit-stop, having
travel-limiting engagement with the rear-wheel ram.
Claim 14. Apparatus of Claim 1, wherein the tool-bar includes hydraulically-
operable side wings, and the means for maintaining the hydraulic pressure
supplied to the second-link at a constant magnitude is effective to keep the
down-force on the wings constant also.
CLAIM 15. Apparatus of Claim 1, wherein the apparatus includes an operable
means for raising the tool-bar, for non-working transport of the apparatus.
Claim 16. Apparatus of Claim 15, wherein:
the apparatus includes a rear-wheel, mounted on the tool-bar, and a rear-wheel
ram for raising and lowering the rear-wheel relative to the tool-bar;
the tool-bar includes a point TR located near the rear of the tool-bar, the
point TR
being a height HR above the ground;
the first-link means for setting the height HF of the point TF on the tool-
bar, relative
to the tractor, is included in a three-point-hitch, the point TF on the tool-
bar
being coupled to a point on the hitch;
the apparatus includes an operable hydraulic hitch-ram, which is effective,
when
operated, to raise and lower the aforesaid point on the hitch, and thereby to
raise and lower the point TF on the tool-bar;
the means for raising the tool-bar comprises a means for operating the hitch-
ram in
the sense to raise the point TF, and a means for simultaneously operating
the rear-wheel-ram in the sense to raise the point TR.
Claim 17. Apparatus of Claim 15, wherein:
the apparatus includes a connecting-means, for connecting the second-link to
the
point CF on the tool bar;
the connecting-means includes a pivotal arm;
the geometrical configuration of the second link and the connecting-means is
such
that:
(a) when the tool-bar is not raised, upon a force being applied to the
second-link in the sense to lower the rear of the tool-bar, the pivotal


arm can abut the tool-bar in such manner as to transmit said force
to the tool-bar;
(b) when the tool-bar is raised, upon a force being applied to the second-
link in the sense to move the second-link away from the tool-bar, the
second-link can so move.
Claim 18. Apparatus of Claim 17, wherein the aforesaid configuration is such
that,
when the tool-bar is raised, the movement of the pivotal arm is enough to
separate the second-link from the tool-bar to such an extent that the raised
tool-bar can undergo pitch-mode movements relative to the tractor, being
movements of such magnitude as arise from transport of the apparatus,
without interference from the second-link.

Description

CA 02210238 1997-07-11
1 [Docket 801-~0 2nd DRAFT]
s Title: Agricultural Implement with Down-Force Control
This invention relates to agricultural implements in which one of the factors
6 that ensures the ground-penetrating tools of the implement are kept to the
correct working depth. during operation. is that the weight of the tool-bar is
s supplemented by' a press- down force. In some cases. the press-down force
9 can be reacted against the tractor, or another suitable heat' object. In the
io case of a seeder apparatus. the press-down force can be reacted against a
1 -1 separately-movable frame carrying the seed hopper. behind which the tool
m bar and seed implantation tools are towed. (In this specification. the term
m tractor includes any vehicle behind which a vehicle can be towed. and
m includes a vehicle which is itself towed behind another tractor.O
1 ~ BACKGROUND TO THE INVENTION
16 For many crops that are planted from seeds. the depth in the ground at
which
1 ~ the seeds are deposited can be a critical factor in the economical
production
1 s of the crop. The economies follow from the accuracy with which the depth
19 of penetration of the seed deposition tools into the soil can be
maintained.
~o The height of the tool-bar can be set; by the farmer. by setting the height
of
mthe tool- bar relative to a wheel or wheels. Adjustable travel-limit stops.
front and rear, can assist the farmer in getting the operational height of the
tool-bar just right. relative to the wheels. The correct depth having been
set.
it is necessan~~ for the tool bar to hea~-~- enough to maintain that depth of
?s penetration. even though the density of the soil might vary. If the tool-
bar
~s were too light. a local hard area of soil might cause the tool-bar to rise.
and
Specification anti claims P~;°~ 1


CA 02210238 1997-07-11
1 the depth of penetration to be lost. The supplementation of the weight of
the
tool bar b~~ the press-d~»i-n force ensures that the depth of penetration as
set
by the height of the tool bar relative to the wheels. is necessary to ensure
the
.~ tools do not ride up over areas of harder soil.
The ground-penetrating tools are mounted in rows, the rows being spaced
6 apart one behind the other. When the implement is being operated over
uneven ground, i.e over ground that can contain hills and valleys. a problem
s can arise over maintaining the press-down force at a constant magnitude.
9 The front row of tools are generally maintained accurately enough at the
Io correct depth. because the front row of tools lies close to the rear of the
1 i tractor. seeder, or other heave towing apparatus. and it is easy to
transmit a
i? substantial press-down force to the front row of tools. But it is
considerably
mmore difficult to transmit a good push dowTn force to the rear row of tools.
m and to keep that push-down force on the rear roi~-~ constant as the
implement
is passes over uneven ground.
ib Of course. SOIIlet1n1e5 the ground is level, 11 W''lllCh CdSe e~%eIl the
I210St
m simple design of press-down force arrangement will suffice. But i~-hen the
1 s ground is uneven. the task of ensuring a constant press-down force during
19 up/do~~-n movements of the tool- bar over the uneven ground requires a more
~o sophisticated design.
m Some seeds are susceptible to quite small variations in deposition depth_ as
little as one centimeter or so in some cases.
The tool-bar is mounted from the tractor or seeder by means of a three-point-
hitch. The front of the tool-bar can therefore be held at a tiled height
relati~-e to the tractor simple by adjusting the bottom link of the three-
point-
hitch to a particular height, and then locking the three-point-hitch at that
height. The strait that sets the height of the bottom link relative to the
tractor
Specification and claims Pa~~ -'


CA 02210238 1997-07-11
1 then serves to hold down the front of the tool-bar. Everi when the ground is
uneven. it is not so uneven that the front-row penetration iyould vary
sianiticantly. As mentioned. it is not the front but the back of the tool-bar
.~ that is difficult to press down.
As the rear of the tool bar can only be held down when a moment is
produced about the ends of the rigid ~-point hitch. the use of a spring has
been proposed. The spring being so mounted as to exert a moment or couple
s on the tool-bar. in the direction to urge the rear of the tool-bar
downwards.
However. if. during operation. the tool-bar should be inclined doivnw~ards
to .relative to the tractor. the spring would have to extend. and the load in
the
1 spring_ and hence the press-down force. would fall. Similarly. if the tool-
bar
mshould be inclined up~yards. the spring would be compressed. and the press
m down force would rise. Of course. this difficult- could be overcome if the
l~ loadllength rate of the spring were low. whereby the force of the spring
l, changed only a little vyith changes in length. Hovyever. it has been found
16 that the rates of the push-do~.yn springs that can be accommodated on
seeders
l~ and like implements have been too high and a spring with enoLyh effective
is motion would be too large. Given the kind of unevenness of terrain in ~i-
hich
19 it is desired to plant seeds. it has been found that the push-down force
?o achievable iyith a spring varies too much.
n It has also been proposed to include a rigid top-link to supplement the
three-
point- hitch. For operation, the bottom link of the three-point-hitch and the
top-link are adjusted in length so that the tool-bar lies parallel to the
(level)
ground. When .the tool-bar passes over uneven ground. the rigid top-link
ensures that the angle of the tool-bar remains constant relative to tractor.
Clearly. that condition does not favor the maintenance of a constant force on
the rear ropy of tools. When a rigid top-link is used bridging of the
Spzcification and claims pa"z ~ ~"~"~


CA 02210238 1997-07-11
1 implement occurs through valleys and the rear tools rise out of the ground
o~-er hills.
The rigid top-link systems that have been proposed have sometimes included
a hydraulic ram as, or as a component of. the top-link. The purpose of such
a ram was to enable the length of the top link to be adjusted; that is to say.
a
6 settable .travel-limit- stop ivas incorporated into the ram or link. and the
7 hydraulic action was used to move the link to that set limit. prior to
s operation. Once the limit was reached. during operation the hydraulic ram
9 served as a rigid stmt.
io The invention is aimed at providing a constant press-down force on the rear
n of the tool-bar. whereby the seed implantation depth can be kept accurate
m over ground that is more uneven than has been possible with prior
i3 implements.
i.~ GENERAL FEATURES OF THE II~TVENTION
is The preferred features of the invention may be summarised as follows.
16 The tool bar. «-hich carries the two or more rows of tools, has a front end
m and a rear end. A bottom-link means is included for setting the height HF
Is .above the ground surface of a point TF on the tool-bar. being a point near
19 the front end of the tool bar. and for maintaining the height HF constant.
~o during operation. The tool bar is pivoted for Pitch-mode pivoting relative
to
m the tractor. A polllt TR at the rear end of the tool bar is held tied at a
set
height HR.
~s The apparatus includes a hydraulic top-link-ram. which is connected
between the tractc.~r and a point CF on the tool-bar. The point CF is a point
~s on the tool-bar near the front end of the tool-bar. and is located above
the
~s point TF. The apparatus includes a means for supplying hydraulic pressure
Specification and claims page .+ ca~E-~


CA 02210238 2002-07-30
5/1
to the said hydraulic top-link-ram, and the said means includes a means for
maintaining
the hydraulic pressure supplied to the top-link-ram at a constant magnitude,
the means
being effective to keep the magnitude of the pressure constant even though the
degree
of extension of the top-link-ram may vary.
Preferably, the hydraulic pressure supplied to the top-link-ram during
operation is
regulated to a constant magnitude by means of a pressure-relieving-reducing
valve.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
By way of further explanation of the invention, exemplary embodiments of the
invention
will scow be described with reference to the accompanying drawings, in which:
Fig 1 is a side elevation of a seeder and tool-bar assembly that incorporates
the
invention, the assembly being shown in a non-operational condition;
Fig 2 is a plan view of the assembly of Fig 1;
Fig 3 is a rear elevation of the assembly of Fig 1;
Fig 4a is a diagram corresponding to Fig I showing some of the components when
the
assembly is in an operational condition;
Fig 4b is a diagram of a protion of the assembly of Fig 4a, shown in a non-
working,
raised-for-transport condition;
Fig 5 is a circuit diagram of some hydraulic components used with the assembly
of
Fig 1.
The apparatuses shown in the accompanying drawings and described below are
examples which embody the invention. It should be noted that the scope of the
invention is defined by the accompanying claims, and not necessarily by
specific
features of exemplary embodiments.
It is noted that not only seed depth, but seed spacing also is also a key
factor to
economic production. Seeding has to be done in a single pass; there is no


CA 02210238 1997-07-11
i question of coming back later. and filling in rows of seeds between rows
already planted. Because of mechanical limitations. often the seed
implantation tools have to be spaced further apart laterally on the tool-bar
~ than the desired spacing of the seeds. Therefore. the tools are provided in
rows. sometimes several rows, and the desired close lateral spacing of the
6 planted seeds is achieved by staggering the tools. But having several rows,
~ spaced one behind the other, gives rise to the problem as described. namely
s the problem of maintaining constancy of press-down force over uneven
9 ground.
m In Fig 1. a seeder 20, having a seed hopper 2~. is towed by a tractor (not
n shoizvn) connected at the hitch 23. The seeder is supported on wheels 2~.
i? Seed implantation tools 26 are adapted to receive seeds from the seeder,
and
m to deposit the seeds in the ground. The tools 26 are carried on a tool-bar
27.
m The tool bar 27 is supported with respect to the seeder 20 by means of a
m three-point-hitch assembly 28. and with respect to the ground by means of a
i6 rear castor wheel 29. The rear wheel can be raised and lowered reative to
i~ the tool bar by means of rear-wheel-ram 30.
1 s As shown in Fig 2. the tool-bar 27 is included as a middle section 27M of
a
i9 wide tool- bar assembly. which includes left and right side wings 27L,27R
?o of the tool-bar assembly.
m As shoi~vn in Fig 3. the wings 27L,27R are pivoted to the middle sectic.~n
at
hinges 3~L.3~R. The wings are raisable to a folded-up transport condition
by operation of hydraulic wino-rams 36L,36R. The hydraulic wing-rams
36L_36R are also used to control the down-pressure on the «-ings.
?s The three-point-hitch assembly 28 is shown in more detail in Fig ~. Fig 4
shows the tool-bar 27 in the operational or "down'' condition. In this
condition_ the rear of the tool-bar is down by virtue of the fact that the
castor
Specification and claims pa°~ E ~"~'~


CA 02210238 1997-07-11
1 wheel 29 has been raised. and the front of the tool-bar is down by virtue of
the fact that the bottom-link of the three- point-hitch 28 has been low -eyed.
s The bottom-lire ~ 7 of the three-point-hitch is acted upon by a hydraulic
:+ bottom-link- ram 32. The height HF of the point TF at the front of the tool
bar is determined by the extension of the bottom-link-ram 32. which in Fig ~
6 is shown fully e~-tended. The height HR of the point TR at the rear of the
7 tool-bar is determined by the e~-tension of the rear-wheel-ram 30. which in
s Fig ~ is shown fully contracted. The rams ~ 0. ~ 2 are provided with
9 adjustment means. such as that showrn at ~8. whereby the farmer can adjust
io .the heights HR. HF of points TR. TF for optimum seeding operation. The
n rams are controlled by hydraulic valve, :~~.
i? As will be elplained with reference to the circuit diagram. Fig ~. the base
m port of top- link-ram 32 and the rod port of rear-wheel-ram ~0. being both
l:+ connected to line A. are pressurized during operation. The pressure in
line A
1 ~ is high enough that the tivo rams are held immovably against their
respective
16 limit stops during operation. Ram ~ 0 is preferably provided with a
mmechanical stop while ram ~2 has a hydraulic valve stop. Thus. during
is operation. the height HF of the point TF on the tool-bar is constrained to
i9 remain constant relative to the seeder 20. and the height HR of the point
TR
~o on the tool-bar is constrained to remain constant relative to the rear
wheel
~l 29.
Point TF is a pivot point. and the tool-bar 27 is able to pivot about the
point
TF, if the ground is uneven. i.e. if the implement should encounter hills and
valle~~s. Such Pitch- mode motion of the tool-bar relative to the seeder 20 is
controlled by a hydraulic ram 3 9. The ram ~ 9 serves as a top-link between
the seeder and the tool-bar. being connected to the tool-bar at point CF.
When the base port of the top-link-ram ~ 9 is pressurized. the ram applies a
Specitication and claims pa~z ~


CA 02210238 1997-07-11
1 force to the point CF. and thereby exerts a downwards force to the rear end
of the tool bar. i.e a force which tends to press the rear of the tool-bar
s downwards. The reaction to the extra do«-n~i-ards force on the wheel 29 is
.~ of course experienced as a reduction of the weight on the wheel 2~ of the
seeder.
6 The magnitude of the downwards force on the rear end of the tool-bar
~ depends on:
s 1. the pressure applied to the top-link-rain 39. and
9 2. the distance apart of the points TF and CF, and
to ~. the direction of force through point CF.
11 DurlllQ Operat10I1. the base Ot the tOp-llllk-ralll ~ 9 1S cOIUleCted t0
lllle C. alld
1~ the pressure in line C is subject. during operation. to the action of a
pressure-
13 reducing-relieving valve ~0 (Fig ~). by means of which the pressure in the
la. line C is maintained substantially constant. The presslue-reducing-
relieving
is valve ~0 is of a conventional type. and is effective to keep the pressure
is constant. being effective to admit more pressure from the supply if the
l pressure should fall too low. and being effective to relieve pressure to
1 s exhaust if the pressure should rise too high. The valve arrangement is
such
19 that the famler can set the values of the pressures, and preferably he can
do
?o so remotely. from the tractor cab.
mAs a result of the action of the pressure-reducing-relieving valve. the force
exerted by the ram 3 9 on the tool-bar 27 remains constant. even if the
extension of the top-link-ram 39 should change. i.e. even if the tool-bar
should undergo Pitch-mode pivoting. due to the tool-bar passing over hills
and valleys. To ensure that the constant force is maintained. the designer
~n should see to it that the top-liW-ram 39 has enough stroke that the ram
does
Specification and claims pa~2 S c~-~


CA 02210238 1997-07-11
i not encounter its limits of tra~-el. neither in eltension nor in
contraction.
dLiring operation.
To raise the seed implantation tools 26 out of the ground. the tool-bar 27 is
:~ raised. That is to say. the rear-wheel-ram 30 is extended (which lowers the
rear wheel 29) and the bottom-link-ram 32 on the three-point-hitch is
6 contracted. which raises the point TF. The line B is pressurized (and line A
exhausted) to achieve this condition.
s As shown in Fig ~, the heights of the wings 27L. 27R of the tool-bar. which
9 .are set by the extension of the rams 36L. 36R. during operation are also
> o .under the control of the pressure-reducing-relieving valve ~0. whereby a
i 1 constant dow-force is maintained on the wings during operation. When the
mline B is pressurized. i.e. when the tool-bar is raised. for non-operation.
that
mpresslue is conveyed to pilot-operated valves ~2. which prevent the wings
m from being lowered. The pressure in line B also operates a top- link-pilot-
1 ~ valve :~3. which closes the rod end of the top-link-ram 3 9. ~.vhereby the
ram
> 6 3 9 cannot be operated while the tool-bar is raised. just as the wings
cannot
i7 be operated while the tool-bar is raised. The top-lire-ram 39 being then
i s locked. it will be understood that the top-link-ram 3 9 and the bottom-
link 3 7
>9 now function as a parallelogram-linkage. whereby the tool-bar remains at a
?o constant Pitch-angle relative to the seeder as the tool-bar is raised and
~i lowered. by the action of the bottom-link- ram 32.
As shown in Figure =la in a preferable embodiment top-link ram 39 is not
?3 parallel with bottom link 37 and is connected to a further link pivotally
attached to the tool-bar to pernlit pitch motion when in transport. For
~s transport the tool-bar is raised causing further link collapse out of the
abutment position to move away from abutment ~~-ith the tool-bar. On being
lo~i-ered the hmther liW abuts the tool-bar and beccmnes ti~ecl. In this
Specification and claims pate 9


CA 02210238 2004-10-13
loll
embodiment the 3 point hitch does not act as a parallel link to raise the tool-
bar because the
top link provides no tension, only compressive forces.
The travel limit stop 38 on the rear-wheel-ram 30 comprises a mechanical stop
on the rod of
the ram's piston. The travel limit stop for the bottom-link-ram 32 (actually
there are two
bottom-link-rams 32 in parallel) comprises a hydraulic bottom-link-trip-valve
45. The
extension of the bottom-link-ram 32 at which the valve 45 trips can be set by
the farmer.
With the use of the system as described, during operation the tools 26 can be
maintained at a
constant depth of penetration into the soil, even though the ground might be
uneven. If the
ground is uneven, i.e. if the ground contains hills and valleys over which the
implement
must pitch, the heights HF and HR remain substantially constant relative to
the ground
surface, even though the tool-bar 27 may be somewhat tilted (in the Pitch-
mode) relative to
the seeder 20. Also if the ground is uneven, the push-down force on the tool-
bar remains
substantially constant, as a result of the maintenance of constant pressure in
the top-link-ram
39. The push-down force in fact remains constant even if the Pitch-angle of
the tool-bar
should be considerable, due to the uneven ground.
For non-operation, the tools are withdrawn from the ground by raising the tool-
bar 27, front
and rear. The same hydraulic operation that raises the tool bar (i.e. the act
of pressurizing
line A) can be used not only to prevent the wings from then being lowered, but
can also be
used to disable the top-link ram. Therefore, the required operational
safeguards and
interlocks are provided automatically, and without the need for skilled
attention to a check-
list of procedures.
In an alternative embodiment, the position of the top link 39 and the bottom
link 37 may be
reversed.

Representative Drawing