Note: Descriptions are shown in the official language in which they were submitted.
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VARIABLE RATE HYDRAULIC DRIVE CONTROL
Field of the Invention
This invention relates to a hydraulically operated variable rate rotational drive,
s particularly for use with agricultural implements such as feed and fertilizer meters.
Background of the Invention
A controlled rate rotational drive is needed in a variety of agricultural implements,
particularly for metering materials such as fertilizer and seed. An air cart, for example,
0 used to meter and deliver seed, fertilizer and other materials requires adjustable metering
control. For consistent application of these materials, delivery rates must be referenced
to the ground speed of the air cart. In the past this has been done by mechanically linking
axle rotation of a ground eng~ging wheel to the metering device. A change to themetering rate is made by manually altering the gear ratio when the device is stationary.
Typically an average fertilizer application is determined and the metering rate is set once
per field. However, this mechanical drive is not always an accurate indication of ground
speed. Cornering, for instance, forces the ground eng~ging wheels to travel at different
rates.
20 The practice of averaging fertilizer requirements for a complete field often results in
over-fertilizing of some areas and under-fertilizing others. For example, high spots,
where fertilizer often leaches out with the ground water, may be under-fertilized and the
low spots adjoining them, that receive the fertilizer from the high spots may be over-
fertilized. A more efficient method of applying fertilizer is needed to permit variation of
2s the amount applied over the field to make adjustments according to terrain, to adjust
application of herbicide to known problem areas, or to make other adjustments according
to the soil requirements or in response to past yields. With current equipment, the time
required to adjust the metering rate manually makes this practice prohibitively expensive.
30 Fertilizer rates are beginning to be evaluated from satellite or GPS field maps as
disclosed in C~n~ n Patent No. 2,095,462 issued in 1993 to Ag-Chem Equipment Co.
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Inc. This device requires a digital field map of soil types or other collected data and a
fertilizer map storing desired distribution rates, a position locator to determine implement
field position relative to the maps, a speed indicator and a processor for determining and
controlling the rate of dispensing of each fertilizer type. The patent, however, does not
disclose how the fertilizer rate is to be varied. The numerous changes implied are clearly
not practical manually.
A means for variable adjustment to the metering rate while in operation is needed. Some
designs have been proposed to provide this function. For example as disclosed in United
o States Patent No. 3,490,654 issued to Fischer in 1970, a manifold providing adjustment to
the flow and pressure of the air source is used to vary the distribution rate. This is a
costly arrangement, and the change in air flow is not always compatible with a controlled
distribution rate. Nor is the distribution accurately controlled without metering the
materials.
A Concord Inc. design for variable response to position and application data uses a flow
control valve such as a pressure compensated control valve responsive to a linear actuator
to regulate flow to a hydraulic motor which operates the meter. Speed control byautomatically adjusting the flow control is not precise, particularly for accurate metering
20 control. Hydraulic drive is subject to load changes depending on other systemrequirements affecting system pressure and flow rate. The flow control compensation is
not sufficient to accurately control the output. Variation in output resistance due to load
on the meter also causes fluctuation in the drive, and consequently metering rate.
25 Hydraulic motors, most conveniently available as an agricultural implement power
source, have proved difficult to control precisely enough for metering purposes. It is
desired to provide a hydraulic rotational drive adapted for variable adjustment in
operation suitable for operating a rotational metering device.
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Summary of the Invention
Hydraulic drive is commonly available *om the tractor for agricultural implements and
provides an available power source for a metering drive. It must, however, be responsive
to a controller providing electrical input to control the output rate of rotational drive.
Electrical input is advantageously made through a DC electric motor with a reduction
gear box. The controller provides a signal to the electric motor to vary the speed of the
electric motor in response to manually selected settings or automatically based on
preprogrammed and operational data. The electric motor provides rotational input into a
hydraulic torque generator which converts the hydraulic drive into a high torqueo rotational output which can be coupled to a meter. The rate of rotational input from the
electric motor determines an equal rate of output drive.
Accordingly, the present invention comprises an apparatus for use with a hydraulic power
source, for variable rate rotational drive comprising:
a hydraulic motor providing a rotational output drive, including a rotary valve for
operatively linking the hydraulic motor to the hydraulic power source;
rotational input means for operating the rotary valve;
controller means for selectively controlling the rate of the rotational input means,
wherein the rotational output rate is proportional to the rotational input rate.
In an alternative preferred embodiment the present invention comprises a controlled
variable rate drive for use with a hydraulic drive system for operating a rotational meter
comprising:
controller means for providing rotational rate signals;
electric motor for receiving rotational rate signals and providing rotational input
drive corresponding to the rate signal received;
torque generator having a rotary valve at an input for coupling to the rotational
input drive of the electric motor, and a hydraulic motor for producing a rotational drive
proportional to the rate of the rotational input for driving the meter.
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In a further preferred embodiment the present invention comprises a meter for granular
material having a variable rate drive comprising:
a rotational meter wheel for measuring a volume of material in regular intervals;
a hydraulic motor coupled to the meter wheel for providing rotational drive;
a rotary valve means for providing an operative connection from a hydraulic
power source to the hydraulic motor;
electric drive means for rotating the rotary valve means;
controller means for controlling the rate of drive from the electric drive means to
the rotary valve whereby the rate of the rotational drive from the hydraulic motor is
o proportional to the rate of drive from the electric drive means.
It is an advantage of the present invention to provide an accurately controllable hydraulic
rotational drive. Advantageously, the present invention provides a widely variable rate
control without discreet gearing limitations.
It is a further advantage of the present invention to provide variable adjustment during
operation.
Further advantages will be apparent to persons of skill in the art from the following
20 detailed description, by way of example only, with reference to the following drawings in
which:
Brief Description of Figures
Figure 1 is a block diagram illustrating the primary elements of the present invention;
25 Figure lA is a sectional view of a commercially available torque generator;
Figure 2 is a scrap drawing of the metering assembly of a seed and fertilizer delivery air
cart;
Figure 3 is a diagram of a hydraulic circuit incorporating the invention arranged in
parallel in the hydraulic drive line of an air cart.
Like numerals are used throughout to designate like elements.
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Detailed Description of Preferred Embodiments
The invention, shown generally at 10 in Figure 1 includes a controller 12 for processing
preprogrammed data with sensor input data such as ground speed or meter speed. The
controller 12 generates an input signal to an electric motor 14. The speed of rotation of
the motor 14 is controlled to input a low torque rotational drive rate into a torque
generator hydraulic motor 16. The torque generator 16 is coupled to an hydraulic drive
source 18, for instance from the tractor. The electric rotational input directly controls an
output rate 20 of high torque hydraulically powered rotation. The motor 14 may be
provided with a speed ch~nging tr~n~mi~ion which would change the proportion
0 between the motor and the torque generator 16. The input into the torque generator 16
and the output 20, however, remain equal.
Torque generators are primarily provided for use in power steering, and other
applications, where a limited number of rotations are permitted for input. In the present
application the rotations are not limited, and may be substantially continuous in either
direction. The torque generator is suited to this application because it provides an output
directly responsive to the input rate, offering a precise rate control mechanism to a
hydraulic motor.
20 The speed of the electric motor 14 is conveniently controlled by pulse width modulation.
Rotation of the motor 14 operates a rotary hydraulic valve in the torque generator 16.
The torque generator, such as the Eaton series #217 and #227, seen in Figure lA, consists
of a hydraulic motor 100 and a rotary hydraulic valve 102. The valve 102 includes two
cylindrical components, housing 106 fitting over the sleeve 104 co-axially with close
25 tolerance between mating surfaces. The cylinders 104, 106 each have an arrangement of
fluid ports. One valve cylinder 106 is attached to the rotational output 20 and sleeve 104
is attached to the rotational input 108 from the electric motor 14. As the input cylinder
104 is rotated, ports are aligned to direct hydraulic power to the motor 100 of the torque
generator 16. The motor 100 operates to rotate the output 20 in response to the flow, and
30 this causes the second valve cylinder 106 linked to it to move, ch~nging the alignment of
the ports to restrict flow. Movement between cylinders 104, 106 is limited by a link
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between them permitting a small relative movement for amplification. This ties the
output 20 to a direct 1:1 relationship to the input rate. Further movement of the input 108
affects following movement of the output 20 in a direct relationship. The valve 102 of
the torque generator allows operation in either direction or allows bypass of the fluid
s power when there is no rotation. The torque generator 16 thus acts as a torque amplifier
for providing a rotational power output 20 proportional to a low power, low torque
controlled rotational input. The electric motor 14 might rotate the motor 100 if the
hydraulic power fell below a required pressure, since there is a direct linkage. The small
1 2V motor could not stand such a load, consequently a pressure sensor for the hydraulic
10 pressure is provided to prevent this.
A number of agricultural implements may incorporate a controlled variable rate hydraulic
drive. Seed and fertilizer metering is one operation where a system for "on-the-go" or in
operation rate adjustment has been actively sought. In a seeding implement such as an air
5 cart, the controller 12 varies the speed of the electric motor 14 in response to data from a
ground speed sensor, such as a Hall effect sensor which detects rotation of a toothed
wheel, commonly used in the art, together with operator settings such as product delivery
rates (lbs./acre), width of the seeding implement and calibration data. The controller 12
may also vary the speed of the electric motor 14 in response to manual setting changes to
20 alter the application rate; or to a processor processing collected data in combination with
a satellite positioning system, such as GPS. The electric motor 14 is conveniently a 12
Volt DC motor with a reduction gear box. Only a small power source is needed to open
and close the valve of the torque generator 16 providing the impulse to control the drive
rate. The speed of the motor 14 is controllable by pulse width modulation.
2s
A seed cart metering device is shown in Figure 2. A portion of a product tank 50 is
shown, from which seed, fertilizer or other product drops by gravity onto a metering
wheel 52. The wheel 52 is fluted to measure a specific amount in regular increments.
Each measured quantity of product is introduced into a manifold 54 with a high velocity
30 air stream. A continuous rate of product is delivered in the air stream to the seeding or
fertilizing implement to be distributed through a plurality of distributor tubes across a
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width of soil. To apply a constant application rate of product, metering must beresponsive to the ground speed of the implement. Additional control may be desired to
vary the application rate according to demands of the terrain or other factors. Direct
drive from the output of the torque generator 16 provides controlled hydraulic drive to the
5 meter responsive to an electronic controller.
An air cart may have a number of separate tanks 50 for delivering different products
simultaneously, or the multiple tanks may be used sequentially to deliver one product.
Each tank 50 has a separately controllable meter which, depending on the products
o applied, may operate at different rates. The central controller 12 provides rate control
data to each meter. Each meter must be calibrated to the product delivered before
operation, since the size, granularity, moisture content and other factors will affect the
metering rate for the same metering wheel 52.
5 The drive from the hydraulic power source 18 for the meters may be arranged in series,
or preferably in parallel as illustrated in the hydraulic diagram shown in Figure 3. Most
torque generators available, originally designed for power steering applications, do not
accommodate back pressure and consequently include a fluid bypass 22. For use in an
agricultural hydraulic drive system, this bypass is not necessary. The additional
20 hydraulic circuitry reduces the available hydraulic power for other systems. A pressure
compensated flow control valve 24 is preferably incorporated in each meter drive line to
minimi7.e the total flow through the torque generator 16 to conserve fluid power for other
systems. A flow control valve such as the FXCA-XAN manufactured by SUN is
appropriate for the purpose. This valve 24 can limit flow to 1 gallon per minute to each
25 torque generator so that the amount of fluid bypassed during no rotation in minimi7ed. A
pressure reducing control valve may be used to control output pressure to prevent
possible damage to the metering mech~nism.
In operation in an air cart, as illustrated in the diagram of Figure 3, the tanks 50 are
30 loaded with one or more products. Calibration tests are run for each product and the
controller is programmed with delivery rates and width of application. A tractor draws
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.
the air cart and seeding implement on a seeding path in the field. A sensor provides the
controller with ground speed information which the controller processes to vary the
metering rate as necessary. With interface to an additional processor, field data may be
preprogrammed to be responsive to satellite positioning systems for signaling the
5 controller to change the application rates in operation. Alternatively, manual adjustments
for known field conditions can be made to the application rates on-the-go.
Hydraulic power 18 from the tractor provides drive to the hydraulic motor of each of the
three torque generators 16 in parallel. Rotational input from the electric motors 14 at a
o rate signaled from the controller opens a rotary valve in each of the torque generators 16.
This allows hydraulic fluid under pressure to rotate the hydraulic motor until the rotary
valve is closed again. In this manner the hydraulic rotational output 20 follows the
electrical rotational input directly. The rotational output 20 is coupled to the metering
wheel 52 providing a controlled drive rate.
The metering control is also advantageously adaptable to control metering devices for
row crop precision planting devices or "singulators" in addition to many other controlled
rotation implements.
20 Numerous alternative embodiments will be apparent to persons of skill in the art without
departing from the spirit and scope of the invention as defined in the claims attached.
