Note: Descriptions are shown in the official language in which they were submitted.
CA 02252293 1999-10-28
AGRICULTURAL GROUND WORKING IMPLEMENT
WITH HYDRAULIC DOWNPRESSURE CIRCUIT
Field of Invention
This invention relates to winged implements in which the wings are
biased by a hydraulic downpressure circuit to pivot toward the ground during
operation to provide force onto the ground working tools so that they better
penetrate hard ground to the set working depth.
Background
An earlier form of downpressure system shown in Flexi-coil's U.S.
Patent 5,687,798 uses PRRV (pressure reducing-relieving valve) as controls in
the downpressure circuit. A related system is shown in Flexi-coil's Patent
Application (U.S. Serial No. 08/891,204, corresponding to Canadian
2,210,238.
Recent tractor designs include hydraulic systems on the tractors that are
CCLS (closed center load sensing) systems. These systems attempt to
maintain a set flow volume through each of the tractor valves, when open. This
volume can be set by the operator. The tractor hydraulic pump is controlled
such that it will increase the system pressure until the flow volume at each
of
the open valves is satisfied. This system allows for efficiency to be gained
from previous systems in which the pump volume output was reduced only
after full pressure capability had been reached. Circuits connected to the
tractor
that have PRRV controls, will only accept flow when the PRRV senses a
requirement for flow in the circuit connected downstream of the valve. A
tractor having CCLS controls will attempt to deliver flow in any case, and the
tractor pump will raise the pressure to the system maximum. This not only
diminishes the efficiency of downpressure circuit which is causing the
problem,
but also diminishes the efficiency of any of the circuits being operated
because
CA 02252293 1999-10-28
-2-
the tractor control system introduces pressure drops at each valve to maintain
only the set flow.
Objects
It is an object of the invention to provide a downpressure circuit which
has reduced negative effects on CCLS tractor hydraulic systems, particularly
reducing efficiency losses that may be introduced by connecting other
downpressure circuits.
Summary of the Invention
This invention relates to an agricultural implement including a frame
having a pair of tool-carrying wings pivotally mounted thereon for pivotal
movement between raised transport positions and lowered ground-working
positions, each said wing having a hydraulic wing actuator connected thereto
which is extendable and retractible for effecting said pivotal motion, and a
hydraulic wing actuator circuit connected to each of said wing actuators,
which
circuit, when connected to a tractor hydraulic system, enables said wing
actuators to apply down pressure to said wings when the wings are in the
lowered working positions, and hydraulic pressure control valve means for
controlling the down pressure exerted by said wing actuators.
In one preferred feature of the invention said pressure control valve
means comprises at least one pressure relief valve.
In one form of the invention a hydraulic top link actuator is secured to
said implement frame and adapted to be interposed between said implement
frame and another vehicle to apply down pressure to the implement frame.
As a further feature of the invention said hydraulic top link actuator is
preferably connected to a portion of the wing actuator circuit.
In another form of the invention a pair of said relief valves are provided
to enable the down pressures exerted by said wing actuators and top link
actuator to be controlled separately.
CA 02252293 1999-10-28
-3-
The agricultural implement typically includes an implement lift
hydraulic circuit adapted to be connected to a lifting system for the
implement.
Advantageously, the system may include a valve to disable the down pressure
action of the top link actuator when the implement lift circuit is activated
to
raise the implement.
The agricultural implement may preferably include a valve responsive to
wing position to disable the pressure relief valve associated with the wing
actuators when the wings are raised upwardly beyond the working positions.
As a further preferred feature the agricultural implement includes a flow
divider in said wing actuator circuit to allow the connection of another
branch
circuit to the same tractor control to maintain constant flow to each branch
regardless of varying pressure in either branch or between branches.
Other features of the invention will become apparent from the following
description and the appended claims.
Brief Description of the Views of Drawings
Fig. 1 shows a perspective view of a winged implement in which the
actuator and downpressure system is incorporated;
Figs. 1A and 1B show in diagrammatic fashion the manner in which the
implement is attached to the three point hitch of an aircart;
Fig. 2 shows a simple wing lift circuit, i.e. without down pressure
capability with the actuator connected to the implement lift circuit;
(no rear lift assist wheels on this version)
Fig. 3 shows a wing lift circuit with down pressure control in
combination with the actuator system;
Fig. 4 shows a further hydraulic circuit with additional top link down
pressure and wherein the wing down pressure and top link down pressure are
controlled separately;
(alternately the top link pressure and wing down pressure could be
CA 02252293 1999-10-28
-4-
controlled by a single valve located as shown in Fig 3).
Detailed Description of Preferred Embodiments
Referring to Fig. 1, a first embodiment of the implement has
wing sections 10 and 12 pivotally attached via joints 14 and 16 to a frame
middle section 18 for carrying suitable ground working tools (not shown),
which joints each have an axis that is oriented generally horizontal in the
working position so that the wing sections are allowed pivotal movement over
uneven ground. In the headland position shown in Fig 1 the wing sections 10
and 12 are supported generally horizontally over the ground, suspended from
the middle section 18 by their joints and by hydraulic wing actuators 20. No
other means is supporting the wings in this position. When lowered to a
working position, gauge wheels 22 support each wing above the ground. The
gauge wheels 22 can be adjusted to set the working height above the ground for
each wing section. The wing can thereby float (pivot freely) to follow ground
contours, or it may be biased toward the ground, and the gauge wheel 22 will
limit the downward motion. Downward biasing may be required in soil
conditions in which ground engaging tools do not penetrate to the desired
depth
as set by the gauge wheel and the gauge wheel and wing section is suspended
off the ground by the ground tools.
Points 24 and 26 for' attachment to a 3 point hitch are provided on the
middle section 18 for towing and for controlling the height of the middle
section. (Alternately the invention would work on implements having ground
wheel means to support the middle section, with a floating or fixed hitch for
towing). The hitch of the implement shown is particularly suited for
connection to the 3 point hitch of a Flexi-Coil* aircart which provides double
acting lower link actuators. Most 3 point hitches on tractors or other
implements provide only lifting action by the lower links and allow free
* Reg.Trademark
CA 02252293 1999-10-28
-5-
upward movement of the links. The lower links of the Flexi-Coil aircart can be
maintained in a fixed position. The implement middle section 18 is pivotally
attached to the aircart lower links by connections at points 24 and 26
allowing
the implement movement about a horizontal transverse axis 28. A hydraulic
top link 30 is pivotally connected at one end to the aircart (offset from the
axis
of the lower links), and at the 2nd end is pivotally connected to the
implement
middle section 18 at a point offset from the horizontal axis 28. An
intermediate link 32, is connected between the 2nd end of the top link and the
implement middle section by pivotal connections on both ends. The implement
is allowed free downward pivotal movement about the horizontal axis 28
(limited by the length of the actuator and link 32, and by rear support
assembly
40) but upward pivotal movement is limited by an abutment 36 along the
intermediate link 32. The implement middle section 18 abuts the intermediate
link at abutment 36 and the top link 30 reacts to the upward pivotal movement.
Figures 1 A and 1 B help to illustrate the above and they show the
implement connected to an aircart by the preferred 3 point hitch with
hydraulic
top link 30 and intermediate link 32 in both working and raised positions.
This
shows how there is freedom of pivoting in the raised position, even though the
top link 30 may be locked out, and therefore rigid. The intermediate link 32
is
drawn away from the abutment 36, not by the top link but by the system
geometry and during the raising action from the lower links 3 8 and rear
support assembly 40. Rear support assembly 40 is well known per se and each
includes a castored ground 'wheel 42 connected by linkages 44 to frame middle
section 18. Actuator 46 effects movement of the linkages 44 during raising and
lowering in a well known fashion.
Alternately a rigid top link (not shown) may be connected directly
between the aircart and the implement, as in a conventional 3 point hitch.
This
is used on implements not having rear support assembly 40, so the rotation of
CA 02252293 1999-10-28
-6-
the frame middle section 18 about the horizontal axis 28 is controlled,
maintaining a generally constant relative orientation between the implement
and the aircart as the implement is raised or lowered.
When a rear lift support assembly 40 is provided on the implement, a
compressible top link is required so that the implement is allowed pivotal
movement about axis 28. This may be a spring connected directly to the
implement or via an abutting intermediate link 32. In the preferred
embodiment the required compressible link is a hydraulic top link operated by
a
biasing pressure and an intermediate link is also provided to create freedom
to
pivot in the transport position when hydraulic flow to the top link is
blocked.
The top link 30 is locked out of the circuit by valve 48 (Fig. 4) when the
implement is raised (by rear lift means and lower arms of hitch) and the link
32
pivots away from the frame middle section so it no longer abuts the frame. The
geometry between the lower links 38 and top link 30 causes this action. This
allows pivoting of the implement relative to the aircart about horizontal axis
28
when in transit over uneven ground.
Referring further to the embodiment of Fig. 1, the headland actuator
system includes a headlands cylinder 50, having its opposite ends pivotally
attached to elongated center links 52 and 54. The outer ends of links 52 and
54
are secured by pins 56, 58 to the inner ends of the wing actuators 20 and
these
pins are disposed for movement in slots 60 and 62 formed in the upper ends of
spaced towers 64, 66 fixed to the frame middle section 18. The headlands
cylinder 50 is stabilized by means of stabilizing links 68, 70 having upper
ends
connected at opposing ends of the cylinder 50 and their lower ends pivoted to
the middle section 18 of the implement frame. Thus, as cylinder 50 is extended
and retracted, the inner ends of the wing actuators 20 are caused to travel
along
the paths defined by slots 60, 62 between the inner and outer extremities of
these slots. (In an alternative arrangement an extra long headlands actuator
CA 02252293 1999-10-28
could be used with its opposing ends being directly connected to the inner
ends
of the wing actuators 20 and eliminating the need for links 52 to 70 described
above).
In operation without down pressure, (Fig. 2) the wing lift circuit CD
can be set to float mode in the tractor when the implement wings 10 and 12
have been lowered from their transport position. After the implement is
lowered to the ground, continued flow into line B builds pressure to further
operate the implement lift actuators until the depth stop (not shown) is
reached.
During this period pressure in line B causes pilot-to-open check valve 72 to
open to allow flow from the rod end of the cylinder 50, and the headlands
system is extended by pressure in line B. This forces the ends of the wing
actuators 20 to the outer ends of slots 60 and 62 for extra downward pivotal
range of the wings 10 and 12. The actuators 20 are held at the outer ends of
slots 60 and 62 during operation in the working position. When raising the
implement at headlands the cylinder 50 is retracted. This limits droop of the
wings when the middle section 18 is raised by applying pressure to line A. The
implement is typically raised just enough for working tools to clear the
ground
for turning at the field headlands. The pilot-to-open check 72 prevents fluid
from escaping from the cylinder 50 to the rear or front lift actuators which
may
be extended only to an intermediate position at headlands. The check valve 72
also limits the droop of the wings 10 and 12 until the implement is lowered to
the ground and line B is pressurized, repeating the cycle above.
To raise the wings to transport position, the implement is first raised.
Pressure is applied to line A, retracting the cylinder 50 and at the same time
operating the three point hitch actuators (and rear lift actuators if present)
which raise the middle section 18. After the middle section 18 is raised,
pressure is applied to line D and the wing actuators 20 rotate wings 10 and 12
to a generally vertical position for transport. The ends of the wing actuators
20
CA 02252293 1999-10-28
_$_
are held at the inner ends of slots 60 and 62 by the cylinder 50. In this held
position the headlands actuator motion is completely restricted so that motion
of one wing may not be transmitted to the opposite wing through the linkage
system when the wings are being raised. Otherwise the wings could freely
toggle side to side in the vertical position until they came to rest against
some
other abutment. Alternately the slots 60 and 62 could be replaced by links
pivotally connected to the middle section 18 and end of the wing actuator
providing the link's rotation is limited by stops corresponding to the inner
ends
of the slots of the present embodiment.
In operation with down pressure, ( see the hydraulic circuits of Figs 3
or 4) the operation of the headlands system is the same. The wing lift circuit
may be set to down pressure mode by setting the valve in the tractor to
pressurize line C. The down pressure circuit to the wings may be connected in
combination with the hydraulic top link 30, or may act alone as in the case of
a
rigid top link.
A hydraulic top link not connected to a down pressure circuit is known
in the prior art for adjusting the angle of an implement relative to a
tractor, and
remains fixed as a rigid link during operation.
Ball valve 74 (Figs. 3 or 4) is closed when wings 10 and 12 are raised to
the transport position. This allows full tractor pressure to be applied to
wing
actuators 20 to lower the wings which generally rest past an overcenter
position
in transport (generally vertical). The ball valve 74 is controlled by a cam or
link mechanism so that it is open when the wing position is lower than about
15
degrees up from horizontal as described in the above-noted U.S. patent.
Referring to Fig. 3 wing down pressure is controlled by relief valve 76,
which limits the pressure in line C2. This relief valve allows fluid to return
through line D when pressure in line C2 exceeds the setting. An optional top
link actuator may also be connected to line C2 via line C', and pressure to
both
CA 02252293 1999-10-28
-9-
the wing actuators and the top link actuator may be controlled by valve 76.
With reference to Fig. 4, valve 80 is provided when connecting a
hydraulic biasing top link to lockout the top link biasing function when the
implement is being raised. When the implement is lowered to the set working
height there is no pressure in line A or to pilot A', and valve 80 will open
with
any pressure at C4 or C 1 to allow the top link to extend or retract with the
biasing function.
A second relief valve 82 (Fig. 4) may be added to the circuit to control
the top link pressure separately. This valve may be set at pressures greater
than that of relief valve 76 to create a differential pressure between lines
C2
and C'.
The valve 82 allows pressure in C' to build higher, before continuing
into line C2, where relief valve 76 will control the pressure in that part of
the
circuit.
This type of down pressure circuit described above which uses relief
valves or pressure regulating valves rather than PRRV (pressure reducing -
relieving valve) controls is preferred when connecting to tractors having CCLS
(closed center-load sensing) controls. The tractor valve controlling this
circuit
is preferably set to deliver 3gpm which generally satisfies the rate at which
the
various actuators respond to uneven ground. This set flow will continuously
pass through circuit CD during operation of down pressure, and be used as
required by the actuators when they extend or retract as they provide bias to
force the middle section 18 and/ or wing sections 10 and 12 toward the ground.
A flow divider 84 can be used to separate equal portions of flow when a
second circuit is connected to the same control valve. In this case the
tractor
valve may be set to 6gpm. A 50/50 divider will split 3gpm to each circuit
regardless of the pressure at which either circuit is operation. In the
embodiment shown in Fig. 4, the second circuit operates hydraulic drives for
CA 02252293 1999-10-28
-10-
metering seed or other materials for planting. A check valve 86 in the second
circuit blocks reverse flow to the second circuit so that full pressure may be
applied to the wing actuators when raising the wings. Depending on the ratio
of flow required by the branch circuits, a flow divider with a different split
ratio could be used. Or a priority flow divider could be used which sets a
fixed
flow to one branch and delivers any excess flow to the other. Other multiple
number of branch circuits is conceivable by using primary and secondary flow
dividers and so on.
Preferred embodiments of the invention have been described and
illustrated by way of example. Those skilled in the art will realize that
various
modifications and changes may be made while still remaining within the spirit
and scope of the invention. Hence the invention is not to be limited to the
embodiments as described but, rather, the invention encompasses the full range
of equivalencies as defined by the appended claims.
20
