Note: Descriptions are shown in the official language in which they were submitted.
CA 02238922 1998-OS-28
IMPLEMENT FRAME LEVELLING SYSTEM FOR AGRICULTURAL
EQUIPMENT HAVING A LOWERED GROUND-WORKING MODE
AND A RAISED TRANSPORT MODE
BACKGROUND OF THE INVENTION
This invention relates to improvements in agricultural ground-working
implements having both a lowered ground-working mode and a raised transport
mode.
It is well known that an agricultural ground-working implement has
better ground following characteristics when the hitch of the implement is
pivotally attached to the implement frame. An implement with a pivoting hitch,
typically referred to as a floating hitch, follows the contour of the ground
independently of the elevation of the forward end of the hitch which is
attached
to the drawbar of the pulling vehicle, i.e. a tractor. The implement frame is
typically equipped with gauge wheels located near the front of the frame to
set
and control the penetration depth of the ground-working tools. The tractive
force produced by the tractor acts through the implement hitch to pull the
implement tools through the soil. The draft forces are substantial since
ground-
working tools have a substantial resistance to being pulled through the soil.
This draft force is offset from the reaction forces at the ground tools and
this
creates a moment force on the implement. An implement with a free floating
hitch is not restrained from rotation due to this draft moment force. Hence,
this
moment force causes the implement to rotate in a manner such that the rear of
the implement moves upwardly relative to the front of the implement with the
result being that the rearwardly disposed ground-engaging tools are raised
above the set and desired working depth.
The prior art has provided various forms of systems which act between
the implement hitch and the implement frame to counter the draft moment force
~ referred to above in an effort to maintain the implement generally parallel
to the
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ground. The earlier systems were in the form of spring loaded devices while
more recent systems have employed hydraulic systems which are designed to
act between the implement hitch and the implement frame in such a way as to
at least partially counter the draft moment force referred to above.
SUMMARY OF THE INVENTION
It is a general objective of the invention to provide improvements in
ground-working implements having both a lowered ground-working mode and
a raised transport mode and wherein means are provided to offset the effects
of
the moment forces noted above in the working mode.
A primary feature of the invention provides improvements in
implements of the type noted above by employing a fluid circuit means
connected to a fluid actuator for controlling forces exerted thereby between a
hitch member and an implement main frame and operable in a working mode to
exert a resilient biasing force on the hitch member thus enabling pivotal
floating motion of the hitch member while simultaneously countering force
moments applied to the main frame by the ground-working tools. This system
is also operable in a transport mode wherein the actuator exerts sufficient
force
between the hitch member and the forward end of the main frame as to assist in
lifting and maintaining the implement in a raised transport mode.
Accordingly the invention in one aspect provides an improved
agricultural ground-working implement having both a lowered ground-working
mode and a raised transport mode. This implement includes a main frame
having ground-working tools thereon with positioning wheels on said main
frame having means associated therewith for moving the positioning wheels
between ground working and transport positions. An elongated towing hitch
member has its rear end attached to a frontal end of said main frame for
pivotal
movement about a generally horizontal axis transverse to the forward travel
. direction of said main frame, and a forward end connectable to a tractor
drawbar. A fluid actuator is connected between the frontal end of said main
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frame and said hitch member at pivot points spaced from said horizontal axis
for exerting components of force on said hitch member which tend to effect
pivotal motion of said hitch member relative to said main frame. A fluid
circuit
means connectable to a source of fluid pressure is provided and is connected
to
said fluid actuator for controlling the forces exerted thereby between said
hitch
member and said main frame. This fluid circuit is selectively operable in:
(a) the working mode such that said actuator exerts a selected
resilient biasing force on said hitch member enabling a
pivotal floating motion of the hitch member relative to said
main frame while simultaneously countering force
moments applied to said main frame by said tools and
transferring downward force components to said hitch
member and thence to the tractor drawbar; and
(b) the transport mode wherein said actuator exerts sufficient
force between said hitch member and the forward end of
the main frame as to assist in lifting and maintaining said
implement in the raised transport mode.
In one form of the invention said fluid circuit means are also operatively
connected to said means for moving the positioning wheels such that on
selection of the transport mode, said transport wheels are moved to the
transport positions where they assist in maintaining said implement in the
raised transport mode.
In a preferred form of the invention said means for moving the
positioning wheels have a depth stop means associated therewith to help
establish the height of said implement above ground in the working mode.
In a typical embodiment of the invention said positioning wheels are
- located toward rear end portions of said frame, and gauge wheels are
positioned
adjacent forward end portions of said frame and co-operate with said
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positioning wheels to establish a selected implement height above ground in
the
working mode.
The above-noted fluid circuit means preferably includes an adjustable
pressure control valve to enable the biasing force exerted by said actuator on
said hitch member to be varied as required to offset the force moments
encountered in the working mode thereby to assist in keeping the implement in
a position generally parallel to the ground in the working mode.
In accordance with another preferred feature of the invention said fluid
circuit means includes means to disable said pressure control valve when in
the
raised transport mode such that said actuator is subject to the full pressure
available at said source (e.g. the tractor hydraulic system) whereby said
actuator tends to behave as a rigid link between said main frame and said
hitch
member in the raised transport mode.
It is to be noted that the term "transport mode" used herein includes
transport not only along a roadway but also the movement which takes place at
the headlands of a field, i.e. when the implement is raised and turned at the
end
of a field after completion of a lengthwise ground working pass.
Further aspects of the invention will become apparent from the
following description of preferred embodiments of same with reference being
had to the accompanying drawings.
BRIEF DESCRIPTION OF THE VIEWS OF DRAWINGS
Fig. 1 is a top plan view of an agricultural ground-working implement
in accordance with an embodiment of the present invention;
Fig. 2 is a side elevation view of the ground-working implement in the
lowered ground-working mode;
Fig. 3 is a side elevation view of the ground-working implement in the
raised transport mode;
Fig. 4 is a side elevation of a frontal portion of the main frame and a
rear portion of the towing hitch with the hydraulic actuator connected
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therebetween and also illustrating in schematic form a portion of the
hydraulic
circuit for supplying the hydraulic actuator;
Fig. 5 is a schematic illustration of one form of hydraulic circuit means
for controlling the several hydraulic actuators employed;
Fig. SA is a schematic diagram of a typical manually operated four-
position control valve together with hydraulic pump and reservoir;
Fig. 6 is a schematic diagram of an alternative form of hydraulic circuit
means for controlling the several hydraulic actuators;
Fig. 7 is a partial side elevation view somewhat similar to Fig. 4
showing the towing hitch in a free floating mode;
Fig. 8 is a side elevation view similar to Fig. 7 showing the hydraulic
actuator (hitch cylinder) extended as in the raised transport mode with the
cylinder being locked in the extended position;
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
Referring firstly to Figures 1, 2 and 3, there is shown an agricultural
ground-working implement 10 having both a lowered ground-working mode
and a raised transport mode. This implement includes a main frame 12 which,
as best seen in Figure 1, is of generally rectangular outline having a center
section 14 flanked by a pair of wing sections 16 pivotally connected to the
center section 14 by hinges in a manner well known in the art.
The frontal end portion of the main frame 12 carries a plurality of pairs
of gauge wheels 18, each pair of gauge wheels being secured to the main frame
by a gauge wheel support 20 which is manually adjustable in known manner
thereby to set the desired working depth. A plurality of positioning wheels 22
are mounted to the rear or trailing end of the main frame 12 in a manner well
known in the art by way of respective pivoting supports 24 which are movable
between the working position shown in Fig. 2 to the transport position
. illustrated in Fig. 3. These pivoting supports 24 are activated by means of
a
series of lift linkages 26, 28, 30, including bell crank arms 32, 34, all of
which
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linkages are ultimately connected to the rod end of a positioning cylinder 36
located at the mid point of the frame with the closed end of the positioning
cylinder 36 connected by a bracket 37 to the rear end of the frame center
section 14. A detailed description of the positioning wheels 22, their
pivoting
supports 24 and the lift linkages and the manner in which the linkages
interact
with each other and interconnect with the positioning cylinder 36 need not be
described in further detail as these features are well known in this art.
An elongated towing hitch 3 8 is attached to the front end of the center
section 14 of the main frame by way of pivot shafts 40 thereby permitting
pivotal movement of the towing hitch 3 8 about a generally horizontal axis
transverse to the forward travel direction of the main frame. The forward end
42 of the towing hitch is connectable to a tractor drawbar (not shown) in well
known fashion.
With reference to Figures 2 and 3, it will be seen that a plurality of
ground-working tools 44, e.g. disk harrows, are secured to the main frame 12,
again in a manner well known in the art. In the lowered ground-working mode
illustrated in Figure 2, these tools 44 penetrate into the earth a desired
distance
and, as is well known in the art, the reaction forces on these tools and the
draft
force exerted by the tractor through the towing hitch 38 exerts a couple or
moment force on the main frame 12 which tends to lift the rear of the
implement upwardly while forcing the frontal end downwardly during
operation.
Referring to Figs. 1 to 4, the towing hitch 38 is shown attached by pivot
shafts 40 to the frontal end of main frame 12 via brackets 46. A pair of
double
acting hydraulic actuators (hereafter referred to as hitch cylinders 50) have
their
closed ends secured at pivots 52 to brackets 54 fixed to the proximal ends of
towing hitch 38, and their rod ends connected at pivots 56 to "floating" links
58
. which in turn are pivotally connected to frame 12 at pivots 60. Each link 58
has a shoulder 62 which abuts frame 12 as shown in Fig. 4 whereby thrust
CA 02238922 1998-OS-28
forces generated by the hitch cylinders 50 are exerted between frame 12 and
towing hitch 38 thereby generating a force moment about towing hitch pivot
shafts 40. The primary function of links 58 will be described hereafter.
A restraint link 64 is attached by pivot 65 to frame 12 and by pin 66 on
hitch bracket 54, which pin 66 slides in elongated link slot 68 thereby to
limit
the maximum arc of swing of towing hitch 3 8 relative to frame 12.
Referring to Fig. l, the ram of positioning cylinder 36 has a limit arm
70 attached thereto which is arranged to come into contact with the actuator
of
a depth stop valve 72 (mounted to the machine frame 12) when the positioning
wheels have been moved to the desired working height. Suitable adjustment
means (not shown) are provided so that the working height may be varied to
suit conditions.
One form of hydraulic control circuit is shown in Fig. 5. This circuit
has a pair of main lines 74, 76 which in use are attached via suitable
couplings
74', 76' to the tractor hydraulic system (Fig. SA). The tractor system employs
a
pump 78 and a return reservoir 80 coupled to a 4-way, 4 position selective
control valve 82 operated by control lever 84. Control valve 82 is shown in
the
neutral position in Fig. SA. When control valve 82 is shifted to the transport
position T, high pressure fluid from pump 78 is supplied to line 74 (and line
76
is connected to reservoir 80) and when valve 82 is shifted to the working
position W, line 76 is pressurized from pump 78 and line 74 is connected to
reservoir 80.
With further reference to Fig. 5, main line 76 branches into two lines 86
and 88 having respective one-way check valves 90, 92 therein. Branch line 88
is connected via related lines 88a and 88b to the rod ends of the two hitch
cylinders 50 and to the closed or base end of the positioning cylinder 36.
Line
86 is connected to line 94 having check valve 96 therein, line 96 being
connected to one port 101 of a pressure reducing/relieving valve (PRRV) 100
having an adjustable spring 102 enabling the relief pressure to be adjusted as
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desired (e.g. a Vickers model PRV12-12). The second port 104 of PRRV 100
is connected to line 106 which leads into a special check valve 108 with a
line
110 leading from the other side of check valve 108 to a connection with line
88.
A pilot line 109 leads from main line 76 over to check valve 108, the latter
being arranged such that it is held open under the influence of fluid pressure
in
main line 76. The third port of PRRV 100 is connected to line 112 which, via
line 112a, is connected to the closed ends of the hitch cylinders 50.
A further line 114 extends between line 106 and the other main line 74
with main line 74 being connected to the rod end of positioning cylinder 36
via
the depth stop valve 72, which, as noted before, blocks flow through line 74
when the desired working height has been reached.
To raise the implement to the transport position, selector valve 82 is set
at the T position so that full pump pressure is applied to main line 74 which
applies fluid pressure to the rod end of positioning cylinder 36 through the
stop
valve 72 to extend the positioning wheels 22 to raise the implement upwardly.
At the same time, the full pump pressure is applied to the closed ends of
hitch
cylinders 50 via lines 114, 94, PRRV 100 and lines 112, 112a, PRRV 100 being
held open by the action of the pilot from line 106. Hence the hitch cylinders
50
extend fully to raise the forward end of the implement frame 12 upwardly into
the transport position illustrated in Fig. 8, in which position the hitch
cylinders
effectively act as rigid incompressible links. (For added safety, as shown in
Fig. 8, a transport lock 116 is installed on the ram of each hitch cylinder to
prevent accidental release in the event of hydraulic system failure).
To change to the working mode, selector valve 82 is set at the W
position such that line 76 receives full pump pressure while line 74 is
connected
to the reservoir 80. The rod end of positioning cylinder 36 drains to the
reservoir with the implement lowering downwardly under its own weight until
- the depth stop valve 72 is activated to block the flow from cylinder 36 at
the
desired depth setting. At the same time, pressure in line 76 is applied to the
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closed ends of the hitch cylinders 50 via PRRV 100. The special check valve
108 however is held open by the action of fluid pressure through the pilot
line
109. Fluid can flow freely into and out of the opposing ends of the hitch
cylinders 50. The relieving side of the PRRV 100 communicates with the
S reservoir via line 114 and the valve acts to limit the maximum pressure
applied
to the closed ends of these cylinders in the usual manner. The hitch cylinders
50 thus act as compressible links in the working mode with the degree of
biasing force created being selected by the adjusting of relief spring 102 on
the
PRRV 100. This mode of operation is illustrated in Fig. 4 wherein the relative
positions of the main frame 12 and towing hitch 38 during a ground-working
operation are illustrated. The biasing forces exerted by hitch cylinders 50
are
sufficient to counteract the moment forces applied to the main frame by the
combination of the draft forces and the ground tool reaction forces thus
keeping
the implement fairly parallel to the ground while allowing a measure of
"floating action" to take place, thus enhancing the ability of the equipment
to
follow the contour of the ground in the working mode while at the same time
effecting a measure of weight transfer to the tractor drawbar via the towing
hitch 38 to increase the tractive forces available. (It has been found that
pilot
line 109 can be removed and the special check valve 108 replaced with a simple
check valve. This valve releases fluid from the rod ends of the hitch
cylinders
50 (and from the base end of cylinder 36) when the motion is in one direction,
but in the other direction a vacuum is created in the rod ends of the hitch
cylinders but this does not appear to adversely affect their ability to move
and
function as compressible links.)
A modified form of hydraulic control system is shown in Figure 6.
However, two separate tractor control valves are used (not shown), one for the
positioning cylinder 36 and the other valve for the hitch cylinders 50.
To move into the transport mode, full tractor pump pressure is applied to
lines 120 and 122. Line 120 feeds the rod end of positioning cylinder 36 as
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before through depth stop valve 72 to retract cylinder 36 and lift the
implement
upwardly. Pressure via pilot line 124 is applied to pilot operated shut-off
valve
126 which blocks flow from the relief port of the pressure reducing/relieving
valve (PRRV) 100 through line 128. Valve 100 is held open in this condition
and full tractor hydraulic pressure is applied via lines 122, 130, 132 to the
closed ends of the hitch cylinders 50 with the result that they extend fully
and
act as rigid links as described before with reference to Figs. 5 and 8 thereby
to
establish the transport mode for the implement.
To move to the working mode, pressure at line 120 is released and the
rod end of cylinder 36 drains through depth stop valve 72 until the desired
implement working height is reached, at which point the valve 72 stops further
flow. At the same time, since pilot controlled valve 126 is open (there being
no
pressure in pilot line 124), the PRRV 100 can act to relieve the pressure of
fluid
being supplied to the closed ends of hitch cylinders 50 through its relief
port
and line 128 with the result being that they act as compressible links in the
working mode as described previously.
It had been noticed that when the depth stop valve 72 is actuated, a brief
pressure spike may cause valve 126 to close and remain closed. This causes the
hitch cylinders 50 to extend, which is not desired during the working mode.
The circuit is found to work well however provided that the operator sets the
tractor control connected to the positioning cylinder line 120 to the "float"
position after lowering from the transport position. This relieves pressure
that
builds in line 120 when the depth stop valve 72 is actuated and the tractor
control automatically shifts to neutral position in which case the lines are
blocked.
One last mode of operation will be described with reference to Fig. 7.
This is the "free floating" mode and in this case the hitch cylinders 50 are
fully
retracted and as the hitch "floats" freely, the pivotal action effects
pivoting of
the floating link 58 as indicated by the arrows. The restraining link 64
limits
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the amount of pivotal motion of towing hitch 3 8.
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.
