Note: Descriptions are shown in the official language in which they were submitted.
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HEADER FLOAT ARM LOAD COMPENSATION
Field of the Invention
This invention relates generally to harvesters. More particularly, it relates
to conveying systems for conveying cut crop material to the harvester vehicle.
Background of the invention
Harvesters have headers (typically called "Draper platforms") that carry
cut crop material on conveyor belts. These conveyor belts extend across the
width of the header to a central discharge region of the header. The conveyor
belts are supported on rollers that, in turn, are mounted on header float arms
that
are elongated and extend forwardly. These arms are pivotally mounted to a
frame of the header. The forward ends of the header float arms are coupled to
and support a cutter bar that extends across the width of the header.
The cutter bar and/or the forward ends of the arms skid across the surface
of the ground as the harvester goes through the field harvesting crop. As the
harvester is driven through the field, the ground rises and falls underneath
the
header and the arms pivot up and down responsibly, thereby permitting the
cutter
bar to follow the contours of the ground more closely.
If the cutter bar and/or the front ends of the arms apply too much pressure
to the ground they will dig into the ground and be damaged. Controlling the
downforce is therefore important in keeping the header and harvester operating
properly.
To reduce the downforce applied by the header to the ground, each arm is
partially supported by a hydraulic, pneumatic, or mechanical spring. The
springs
are coupled to the frame of the header and transmit some of the crop weight to
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the frame. They do this by exerting a lifting or "up" force on the arms that
counteracts the weight of the arms and the additional downforce exerted on the
arms by the cut crop material that falls backward onto the conveyor belts
after it
is cut by the cutter bar. The springs transfer some of the weight of the
header
float arms and cut crop material to the feeder house on which the header is
supported and transfer the weight off the cutter bar and ground.
The cut crop material is not evenly distributed across the width of the
header conveyors. The crop is cut by the cutter bar across the entire front of
the
header and then falls backwards onto the conveyor belts, a left conveyor belt
and
a right conveyor belt. The left conveyor belt carries the cut crop material
from the
left side of the header to the center section of the header, and the right
conveyor
belt carries the cut crop material from the right side of the header to the
center
section of the header. Once the cut crop material reaches the center section
of
the header, the left and right conveyors dump the cut crop material into a
center
conveyor that carries the cut crop material backwards, through the feeder
house,
and into the self-propelled vehicle portion of the harvester.
Depending upon its position across the front of the header, each header
float arm needs a different amount of upward counterbalancing force in order
that
each header float arm exerts the same downforce against the ground that all
the
other header float arms do. In the ideal situation, each header float arm
provides
the same, optimal downforce against the ground.
In order for each header float arm to provide the same downforce against
the ground, each spring must apply a different upforce to its associated
header
float arms. This is necessary since different portions of the conveyor (and
hence
each header float arm) support different quantities of cut crop material. As
the
conveyors move laterally across the width of the header toward the lateral
midpoint of the header, more and more cut crop material falls onto the
conveyor
belt. And the header float arms closer to the lateral midpoint of the header
carry
a greater and greater weight of cut crop material. This additional crop
material
resting on the header float arms closer to the lateral midpoint or center of
the
header means that the header float arms closer to the lateral midpoint require
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=
greater counterbalancing upforce ¨ the force exerted by the springs ¨ if each
header float arm is to apply a constant downforce against the ground.
What is needed, therefore, is a control system for applying to each header
float arm in the header a counterbalancing upforce that is appropriate to
support
the crop load and to maintain constant the downforce exerted by each header
float arm against the ground (either directly, or through the cutter bar). It
is an
object of this invention to provide such a system.
Summary of the Invention
in accordance with the first aspect of the invention of float arm load
compensation system for a header of an agricultural harvester is provided,
comprising a header frame; a plurality of header float arms pivotally coupled
to
the header frame; a cutter bar fixed to forward ends of the plurality of
header float
arms; at least one conveyor belt supported on the plurality of header float
arms
and configured to traverse the header perpendicular to the direction of travel
of
the header, wherein the conveyor belt is further configured to receive crop
material cut by the cutter bar; and a plurality of springs, wherein each
spring is
coupled to an associated header float arm of the plurality of header float
arms to
exert a force on the associated header float arm compensating for the weight
of
cut crop material supported by the associated header float arm.
The springs of the plurality of springs that support float arms closer to the
lateral midpoint of the header may be configured to exert a greater upforce on
their associated header float arms than other springs of the plurality of
springs
that support float arms farther from the lateral midpoint of the header. The
plurality of springs may be configured to maintain constant the downforce
exerted
by their associated header float arms against the ground across a width of the
header. The load compensation system may further include a control circuit
configured to monitor an operational parameter of the agricultural harvester
indicative of the load on the at least one conveyor belt. The control circuit
may
monitor an operational parameter indicative of a load on the rotor of the
harvester. The control circuit may be configured to automatically change the
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forces exerted by the plurality of springs on their associated header float
arms in
response to changes in the operational parameter. The load compensation
system may further include an accumulator containing gas charged hydraulic
fluid coupled to the plurality of springs. The load compensation system may
further include a valve configured to simultaneously change the force is
applied
by the plurality of springs by filling and emptying the accumulator. The load
compensation system may further include at feast first and second accumulators
containing hydraulic fluid under pressure, wherein the first accumulator is
coupled to a first group of springs of the plurality of springs, and wherein
the
second accumulator is coupled to a second group of springs of the plurality of
springs. The plurality of springs may be mechanical springs. The mechanical
springs may be coil springs.
Brief Description of the Drawines
FIGURE 1 is a plan view of a harvester having a header in the form of a
Draper platform in accordance with the present invention.
FIGURE 2 is a side view of the harvester of FIGURE 1.
FIGURE 3 is a fragmentary cross-sectional view of the header of
FIGURES 1-2 taken at section line 2-2 in FIGURE 1.
FIGURE 4 is a schematic diagram of the header of FIGURES 1-3 with
alternative springs and a control circuit for controlling the alternative
springs.
FIGURE 5 is a schematic diagram of the header of FIGURE 4 with an
alternative control circuit for controlling the alternative springs.
Description of the Preferred Embodiments
An "upforce", as that term is used herein, refers to a force applied to a
header float arm that tends to lift the forward end of the header float arm
upward
and away from the ground thereby reducing the force of the header float arm
against the ground. It does not imply or require that the force itself be
directed
upward at its point of application to the header float arm. Indeed, depending
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upon the geometry of the header float arm, the force may be applied to the
header float arm in any direction and at any point along the arm,
Referring now to FIGURES 1-2, a combine harvester 100 is illustrated,
comprising a vehicle 102 that is wheeled and self-propelled, and also
comprising
a header 104 which is a Draper platform that is mounted on the front of the
vehicle 102.
Vehicle 102 further comprises a feeder house 106 that is pivotally coupled
to the front of chassis 108 of vehicle 102. Header 104 is supported on the
front
of feeder house 106.
Header 104 comprises a frame 112, a plurality of arms 114 (identified
collectively as header float arms 114a-j), a plurality of springs 116
(identified as
springs 116a-j), conveyor belts 118, 120, a center conveyor 122, and a cutter
bar
assembly 124 that is fixed to the leading ends of the arms 114.
Referring now to FIGURE 3, arms 114 extend fore and aft and are
pivotally coupled at their rear ends to frame 112. This arrangement permits
them
to pivot about a substantially horizontal and laterally extending axis 126
with
respect to frame 112. This pivotal movement permits the front ends of arms 114
to move up and down with respect to frame 112 as the harvester traverses the
ground.
Each arm has an associated spring 116 (identified collectively as springs
116a-j) that is coupled to the arm and to the frame to provide an up will
force on
its associated arm 114, thereby reducing the force applied by the arm downward
on the ground.
Each arm supports a roller 128 that is supported at its front and rear ends
on arm 114. Roller 128 is disposed generally parallel to arm 114 and is
configured to roll about its longitudinal axis.
Arms 114 located on the left side of the header 104 centerline support a
left side conveyor belt 118. Left side conveyor belt 118 is driven such that
it
carries material falling on its top surface inwards towards the center region
of
header 104.
Arms 114 located on the right side of the header 104 centerline support a
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right side conveyor belt 120. Right side conveyor belt 120 is driven such that
it
carries material falling on its top surface inwards towards the center region
of
header 104.
Left side conveyor belt 118 and right side conveyor belt 120 are supported
on rollers 128.
Cutter bar assembly 124 extends laterally across the width of the header
104 and is fixed to the front ends of arms 114. A lower portion 130 of cutter
bar
assembly 124 functions as a skid plate, sliding along the ground as vehicle
102
transports header 104 across the field. A portion of the weight of the arms,
the
conveyor belts, and the crop material riding on the conveyor belts is
communicated to cutter bar assembly 124 and thence to the ground. The
remainder of the weight is communicated to feeder house 106.
Cutter bar assembly 124 is flexible in the lateral direction to permit
individual arms 114aj to rise and fall somewhat independently of each other as
the cutter bar assembly 124 follows the contours of the ground. This permits
the
header to more closely follow the contours of the ground. In turn, this close
ground-following ensures that the header 104 picks up all of the plant
material
bearing crop.
Each arm 114a-j is provided with a spring 116a-j that is coupled to the
arm and to the frame 112 of the header 104. Spring 116 may be mechanical,
hydraulic, or pneumatic. It applies an upward force to arm 114a-j, reducing
the
downforce exerted by arm 114a-j on the ground via cutter bar assembly 124.
Springs 116a-j transfer the weight of their associated arms (and the loads
they
carry) from the ground to frame 112.
The force that each spring 116a-j applies is not the same, however,
Springs 116 that are closer to the center of header 104 apply a greater
upforce to
their associated arms 114a-j than springs 116a-j located farther from the
center
of header 104. This differential additional upforce applied to arms 114a-j
closer
to the center of header 104 compensates for the increased weight of crop
material on the conveyor belt 118, 120 supported on those arms. The weight of
the plant material on the conveyor belts 118, 120 resting on arms 114a-j
changes
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as more and more crop accumulates on the Conveyor belts. The weight of the
plant material at the outer ends of the conveyor belts is relatively light. As
the
conveyor belt (supported on rollers 128) moves towards the lateral midpoint of
the header 104, more and more plant material is cut by the cutter bar assembly
124 and falls on the conveyor belts. This builds up a thick layer of cut plant
material on the conveyor belt that reaches a maximum thickness when the
conveyor belt reaches the lateral midpoint of the header 104 and center
conveyor
122. At this point, conveyor belts 113, 120 on the left and right sides,
respectively, of header 104 deposit their accumulated out plant material on
center conveyor 122, which moves the cut plant material backward, through
feeder house 106, and into vehicle 102 for further processing.
In order to maintain a relatively constant downforce across the entire width
of the cutter bar assembly 124, each of the arms 114a-j is counterbalanced by
its
associated spring 116a-j such that each arm 114a-j applies the same downforce
on the section of the cutter bar assembly 124 to which it is attached. This
provides an even ground load across the width of the header 104.
There are several ways that the springs 1163-) can be configured to
provide different upforces to arms 114a-j such as by adjusting their mounting
locations on the frame of the header or the arms, or by varying up reload to
the
springs.
Referring now to FIGURE 3, spring 116h has an upper end 132 that can
be coupled to frame 112 at several different mounting points 134 and a lower
end
136 that can be coupled to arm 114h at several different mounting points 138.
Spring 116h has a preload adjuster 139, here shown as an adjustable screw on
the barrel of the spring to vary the preload of the spring. By mounting the
lower
end of spring 116h closer to the pivot 141, the ground force at the end of arm
114h can be increased. By mounting the lower end of spring 116h farther from
the pivot, the ground force at the end of arm 114h can be decreased. By
mounting the upper end of spring 116h farther upward, the ground force at the
end of arm 114h can be decreased. By mounting the upper end of spring 116h
farther downward, a ground force at the end of arm 114h can be increased. By
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increasing the spring preload on spring 116h, the ground force at the end of
arm
114h can be decreased. By decreasing the spring preload one spring 116h, the
ground force at the end of arm 114h can be increased. The arrangement of
spring 116h and arm 114h in FIGURE 3 is typical of all the springs 116a-j ane
arms 114a-j in header 104. The springs 116aj are individually adjusted to
provide a greater upforce on the arms 114a-j that are closer to the lateral
midpoint or center of header 104 and to provide a smaller upforce on the arms
114a-j farther from the lateral midpoint or center of header 104.
Header 104 of FIGURES 1-3 is divided into several zones, comprising a
first zone including the two outer arms 114a, 114b on the far left side of the
header and the two outer arms 1141, 114j on the far right side of the header.
A
second zone includes the two arms on each side of the header just inside the
first zone, 114e, 114d, 114g, 114h, and the third zone including the two
center
arms 114e, 114f.
Springs 116a, 116b, 1161, 116j of the first zone are configured to provide
a first upforce to their associated arms. Springs 116c, 116d, 116g, 116h are
configured to provide a second upforce to their associated arms 114c, 114d,
1149, 114h that is greater than the first upforce applied to the arms in the
first
zone. This accommodates the additional weight of cut crop matter falling on
conveyor belts 118, 120 as the belts move from the first zone to the second
zone.
Springs 116e, 116f are configured to provide a third upforce to their
associated arms 114e, 114f that is greater than the second upforce applied to
the arms in the second zone. This accommodates the additional weight of cut
crop matter falling on conveyor belts 118, 120 as the belts move from the
second
zone to the third zone.
In an alternative embodiment, each of the springs 116a-j is configured to
apply an upforce that is greater than the upforce applied to the arm
immediately
adjacent to it and farther away from the centerline of the vehicle. In other
words,
the upforce applied by spring 116e to its arm is greater than that applied by
spring 116d to its arm, which is greater than that applied by spring 116e to
its
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arm, which is greater than that applied by spring 116b to its arm which is
greater
than that applied by spring 116a to its arm. An upforce applied by spring 116f
to
its arm is greater than the upforce applied by spring 116g to its arm, which
is
greater than the upforce applied by spring 116h to its arm, which is greater
than
the upforce applied by spring 1161 to its arm, which is greater than the
upforce
applied by spring 116j.
One drawback of this arrangement is the need to mechanically adjust
each spring 116a-116j for different crops and crop conditions. Any particular
adjustment of springs 116a-j in FIGURES 1-3 anticipates a particular crop load
on conveyor belts 118, 120. If the actual crop toad is different from this,
the
ground force exerted by each of arms 114 will not be ideal. Indeed, if a very
large crop load is expected on conveyor belts 118, 120, the compensating
upforce generated by springs 116a-j may be so great that the arms may actually
be lifted above the ground if the crop is not as heavy as anticipated and
therefore
the compensating upforce generated by springs 116a-j is too great.
To provide easier adjustment of the upforces generated by springs 116a-j,
other spring arrangements may be employed. In FIGURE 4, for example, each
of springs 116a-j is a hydraulic cylinder. Springs 116a-j in FIGURE 4 are all
coupled to an accumulator that is gas charged and contains hydraulic fluid
under
pressure. This pressure is applied equally to all of the springs 116a-j in
FIGURE
4. In one arrangement, springs 116a-j exert an equal upforce on their
associated
arms 114a-j to counterbalance the weight of the arm 114a-j and the weight of
the
crop material on conveyor belts 118, 120 that the arms support. In an
alternative
arrangement, springs 116a-j in FIGURE 4 are configured to exert different
upforces on their associated arms 114a-j to counterbalance the weight of the
arm
114a-j and the weight of the crop material on conveyor belts 118, 120 that the
arms support. In this alternative arrangement, the upforces exerted by springs
116a-j on arms 114a-j may be divided into multiple zones, such as the three
zones described above with regard to the header 104 of FIGURES 1-3.
Alternatively the upforces exerted by springs 116a-j on arms 114a-j may be
arranged such that the upforce generated by spring 116e is greater than the
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. .
force generated by spring 116d, which is greater than the force generated by
spring 116c, which is greater than the force generated by spring 116b, which
is
greater than the force generated by spring 116a. The upforce generated by
spring
116f is greater than the upforce generated by spring 116g, which is greater
than
the upforce generated by spring 116h, which is greater than the upforce
generated
by spring 116i to its arm, which is greater than the upforce generated by
spring
116j to its arm.
In order to generate different upforces when the hydraulic fluid pressure
applied to each of the springs 116a-j is the same, springs 116a-j may be made
with different piston diameters, or alternatively may be coupled to arms 114a-
j and
frame 112 of header 104 at different locations with different mechanical
advantages, such as at the different locations along the arms and the frame
shown
in FIGURE 3.
In the arrangement of FIGURE 4, the amount of upforce generated by all of
the springs 116a-j can be varied simultaneously by filling or emptying the
accumulator 133. A valve 135 is provided that is coupled to a hydraulic fluid
supply
137 and a hydraulic fluid reservoir 139. The valve 135, when opened, can
selectively empty hydraulic fluid from the accumulator 133 to the hydraulic
fluid
reservoir 139, or fill the accumulator 133 with hydraulic fluid from the
hydraulic fluid
supply 137. As the accumulator 133 is emptied, the pressure in the accumulator
133, and hence the pressure in each of springs 116a-j decreases. As the
accumulator 133 is filled, the pressure in the accumulator 133 and hence the
pressure in each of springs 116a-j increases. The change in pressure in
springs
116a-j causes a proportional change in the upforce applied by the springs to
arms
114a-j. Thus, by changing the fluid in the accumulator 133, all of the
compensating
upforces applied to arms 114a-j are simultaneously and proportionally changed
across the width of header 104.
Electronic control unit (ECU) 140 is coupled to the valve 135 to selectively
fill or empty the accumulator 133 under computer control. Electronic control
unit
140 is preferably a microprocessor based digital computer including the memory
circuit containing a program configured to perform all functions of the
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control unit described herein. A sensor 142 is coupled to the electronic
control unit
140 to transmit to the electronic control unit 140 a value indicative of a
desired
compensating upforce to be generated by springs 116a-j. In one embodiment, the
sensor 142 is a rotor load sensor, responsive to and indicative of the load on
a
threshing rotor in the vehicle 102 (not shown). In another embodiment, the
sensor
is a strain gauge coupled to a rotor drive element such as a rotor shaft or
gear
responsive to and indicative of the load on the rotor. In another embodiment,
the
sensor is a pressure sensor responsive to and in indicative of the hydraulic
pressure in the hydraulic circuit driving the rotor. In another embodiment,
the
sensor is a pressure sensor responsive to and indicative of the hydraulic
pressure
in the hydraulic circuit that drives conveyor belts 118, 120. In another
embodiment,
the sensor is a load sensor responsive to and indicative of the weight of
conveyor
belts 118, 120. In any of these embodiments, the sensed parameter is
indicative of
the load on the harvester and hence the volume of crop material being
harvested.
The volume of crop material being harvested is indicative of the weight of the
crop
material. The weight of the crop material is indicative of the downforce
exerted by
arms 114a-j and thus is indicative of the desired compensating upforce each
spring 116a-j needs to apply to its associated arm 114a-j to maintain the
downforce exerted by arms 114a-j on the cutter bar (and hence the force the
cutter
bar and arms exert on the ground). The electronic control unit 140 is
configured to
monitor the sensor and to open the valve an amount appropriate to maintain
constant the downforce exerted by arms 114a-j on the cutter bar (and hence the
force the cutter bar and arms exert on the ground).
In another embodiment, the sensor 142 is configured to sense the position
of an operator input device, for example a joystick, knob, dial, or lever,
that the
operator uses to directly command a desired compensating upforce. In this
arrangement, the operator monitors the crop load and selects the desired
upforce
to be generated by springs 116a-j. Once the operator has selected the desired
upforce, he adjusts the operator input device to indicate the desired upforce.
The
sensor 142 is responsive to this change in the operator input device and
signals
the electronic control unit. The electronic control unit 140, in turn, is
programmed
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to open or close the valve 135 as necessary to generate the desired upforce.
In
this manner, and even while the vehicle is underway, the operator can
simultaneously adjust the desired upforce of all the springs 116a-j.
FIGURE 5 illustrates another embodiment of the system in which a different
control circuit is provided to control the operation of springs 116a-j, the
control
circuit including three accumulators 144, 146, 148 to apply a different
hydraulic
pressure to three different groups of springs 116a-j. This embodiment is the
same
as the embodiment of FIGURE 4 in all respects, except the control circuit
includes
three valves and three accumulators to apply three different pressures to
three
different groups of valves 116a-j. In the embodiment of FIGURE 5, the control
circuit includes a first accumulator 144 containing gas charged hydraulic
fluid that
is coupled to springs 116a, 116b, 116i, and 116j. A second accumulator 146
containing gas charged hydraulic fluid is coupled to springs 116c, 116d, 116g,
and
116h. A third accumulator 148 containing gas charged hydraulic fluid is
coupled to
springs 116e and 116f. These three groups of springs 116a-j define three
different
zones of the header 104. These three accumulators are coupled to a first valve
150, a second valve 152, and a third valve 154, respectively that conduct
hydraulic
fluid to and from their respective accumulators 144, 146, 148. Each of the
three
valves 144, 146, 148 are also coupled to the hydraulic fluid supply 137 and
the
hydraulic fluid reservoir 139. As in the example of FIGURE 4, the electronic
control
unit 140 opens and closes the valves responsive to the signal provided by the
sensor 142 in order to maintain constant a desired downforce exerted by arms
114a-j and the cutter bar on the ground. In the embodiment of FIGURE 5,
however, the electronic control unit 140 is separately coupled to each of the
three
valves 150, 152, 154 such that it can change the hydraulic pressure in each of
the
three zones independently of the hydraulic pressure in the other zones.
Having described the preferred embodiment, it will become apparent that
various modifications can be made without departing from the scope of the
invention as defined in the accompanying claims.
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