Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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This inVention is directed to a seeder monitor and
in particular to an apparatus which continuously monitors the
state of seed flow in seeding equipment to indicate a mal-
function to the operator.
Seeding equipment malfunctions can be caused by a
variety of reasons such as a low level of the seed hopper, a
loose or broken drive chain, a disengaged drive after headland
turning or in loose soil, or a breakdown at any other point in
the drive mechanism. Visual detection of these malfunctions
by the operator, remote in the tractor cab, is extremely
difficult under dusty poor visibility conditions or after dark,
especially when multiple unit arrangements are being used. The
result of these malfunctions going unnoticed is bare, unseeded
patches in the field which are not only expensive in the form
of lost productivity but are also embarassing to the farmer's
professional pride.
In order to detect malfunctions, the devices presently
in use either monitor the flow of seed by optical techniques or
they monitor the rotation of the shaft in the seed feed
mechanism. The optical techniques are particularly useful with
large seed crops such as corn or beans and are found not to be
suitable for small seed crops such as wheat, barley, rape and
other cereal or oil grain crops due to the differences in seeder
equipment construction, and seed size, seed flow rate and the
possibility of dust which can cover the sensors. The shaft
monitoring techniques provide useful information about the
functioning of the seed feed mechanism but do not directly
provide information as to the seed flow from the seeding equip-
ment into the 80il. Thus an empty seed hopper or the like
could go undetected.
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It is .herefore an object Gf this invention to provide
an appartus for monitoring the state of seed flow from the
seeding equipment seed hopper to the soil.
It is a further object of this in~ention to provide
a seeder ~onitor with sensors in direct contact with the seed
flow.
It is another object of this invention to provide a
seeder monitor having sensors which can be readily installed on
the various models of seeder equipment.
It is a ~urther object of this invention to provide a
seeder monitor which is reliable for all types of seed and/or
granular fertilizer.
These and other objects are achieved in a monitor for
a seeder having one or more seed hopper sections and metering
assemblies for feeding the seed from the hoppers to the soil,
wherein the monitoring apparatus includes at least one sensor
consisting of a piezoelectric transducer which provides an
output signal in response of being struck by seed, a vibration
i,solating mounting structure for positioning the sensor in the
seed flow path between the metering assembly and the soil, and
a circuit for receiving the sensor electronic response and
providing an indication of seed flow condition. The mounting
structure includes an elongated member such as a metal tubing,
to one end of which is fixed a cushion made of a material such
as closed cell foam and to the other end of which is fixed a
securing member to secure the mounting structure to the seeder.
The sensor is located on the cushion, a pair of leads connected
across the sensor pass through the tubing and are connected to '
twin conductors at the other end. The circuit for each sensor
includes a control circuit which processes the sensor signal
and which provides an output control signal representing a flow
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condition such as the no flow condition. The circuit further
includes visual and audio alarm circuits which indicate the flow
condition to the operator for each sensor.
In the drawings:
Figure 1 is a schematic of a typical seeder;
Figure 2 illustrates a typical seed metering mechanism
in a seeder;
Figure 3 illustrates one embodiment of a seed sensor
used with the present invention;
Figure 4 is a block diagram of the seeder monitor in
accordance with the present invention; and
Figure 5 illustrates one embodiment of the circuit
diagram of the seeder monitQr in accordance with the present
invention.
Referring to figure 1, a schematic of a conventional
seeder 1 is illustrated. A typical seeder includes one or
more seed hopper sections 2 in which seed is stored with a
number of feed mechanisms 4 positioned under each hopper. The
feed mechanisms 4 are normally driven by one of the seeder
wheels and control the rate of seed flow from the hopper 2
through seed tubes 5 into a furrow in the soil that is made
by a furrow opening device such as a disc or a hoe. Figure
2 shows one example of a typical feed mechanism 2. Seeding
equipment may consist of one or more seeders 1, and as each
seeder 1 is pulled by a tractor, a shaft 6 in the feed
mechanism 4 is rotated by a chain drive from one of the seeder
wheels, causing a metering wheel ? which is fixed to the shaft
6 to discharge seed 3 from the hopper 2 at a flow rate pro-
portional to the seeder 1 velocity. The seed 3 falls into a
seed cup 10 and down through the seed tube 5.
In addition, a seeder 1 may further have a second set
of hopper section~ with feed mechanisms to discharge fertilizer
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during the se~ding operation. The fertilizer may be dis-
charged directly to the soil or into cup 10 by a fertilizer
tube 9 as shown in figure 2.
In order to monitor the flow of seed 3, a sensor 8
is positioned in the path of the seed flow from the feed
mechanism 4. Sensor 8 may be mounted in the seed cup 10 by a
mounting structure 11 as shown in figure 2 o~ at some other
point in the seed tube 5 between the cup 10 and the soil. The
signal generated by the seed 3 falling on the sensor 8 is fed
via conductors 12 to control and indicating circuits.
A separate sensor 8 may be mounted in each of the seed
cups 10 of a seeder 1 to monitor the flow of seed to each
furrow during the seeding operation, however it has been found
that due to the shaking motion of the seeder 1 as it is pulled
across a field, the seed 3 tends to form a mound in the hopper
section 2 and thus the feeder mechanisms 4 at eaah end of the
hopper 2 run out of seed first. Therefore, it can be seen
that satisfactory monitoring results may be achieved by using
only one sensor 8 in oach hopper section 2 if it is placed
in one of the end cups 10.
Referring to figure 3, one embodiment of a sensor 8
and mounting structure 11 is illustrated. The sensor 8 consists
of an impact sensitive transducer 13 fixed to a cup shaped or
flat disc 14 which may have a diameter in the order of 2 cm. and
may be made of brass, aluminum or other metal. A pair of leads
20 are connected across the transducer 13 to pic~ up the signals
generated by the transducer 13 as individual seeds strike the
disc 14. Though transducer 13 need not resonate at a particular
frequency, a piezoelectric crystal which has a specific
resonant frequency may be used in sensor 8, the resonant
frequency of which will be governed by the size and shape of the
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crystal 13 and disc 14. If a resonant frequency crystal 13 is
used, it is preferred that the resonant frequency of sensor 8
be greater than 16 khz so as to be above the frequencies which
could be generated at low levels by vibrations in the seeder
equipment.
The mounting structure consists of a tube 15, again
made of aluminum, brass or other metal through which the leads
20 may pass, with a second disc 16 fixed to the one end of tube
lS. The sensor 8 is mounted on the mounting structure disc 16
by means of a cushion 17 such as closed cell foam rubber to
isolate the vibrations of the mounting structure 11 from the
sensor 8. A perforated tab 18 or the like is fixed to the
other end of tube 15 by which the mounting structure 11 may
be secured to the cup 10 or other location on the seeder
equipment. Finally the mounting structure 11 includes a
sealed connector 19 in which the leads 20 are connected to twin
conductors 12 b,y means of shrink tubing 21. The conductors
12 may be shielded to .prevent induced signals on the conductors
12, however need not be so as will be described with respect
to figures 4 and 5.
In the preferred embodiment of the ~.eeder monitor
in accordance with the present invention, as shown schematically
in figure 4 and in detail in figure 5, the seeder monitor .'~
includes a sensor 8 which produces a signal 22 for each seed
striking the sensor 8. This signal is fed via twin conductors
12 to a control circuit 23 which processes the signal 22. The `
output of control circuit 23 is fed to a display or alarm
circuit 24 which provides a visual and/or audio alarm signal
to the operator of the seeder e~uipment to indicate the seed
flow condition sensed by the sensor 8. The visual and audio
alarm circuit 24 is preferrably mounted on the tractor near the
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operator, however the control circuit 23 may be mounted on the
seeder equipment near the sensor 8 or with the alarm circuit
24 on the tractor.
In the embodiment o~ the monitor circuit in figure
5, the signal 22 from sensor 8 is fed to the two inputs of a
differential amplifier 25. As amplifier 25 is connected across
the sensor 8, any spurious signals induced 5.~ lines 12 will be
eliminated. Amplifier 25 may further have bendpass charac-
teristics so as to respond primarily to the frequency of the
signal 22. Thus if the resonant frequency of the sensor 8 is
in the order of 19 to 20 khz, the bandwidth of the bandpass
characteristics of amplifier 25 should be in the order of 16 to
23 khz. The output signal from the differential amplifier 25
is coupled to a high pass amplifier 26 to amplify the sensor
signal and further eliminate low frequency noise. The output
signal from amplifier 26 is coupled to a threshold circuit 27,
which provides pulse output signals 28 in response to input
signals having a predetermined set amplitude. Thus, the output
28 of threshold circuit 27 consists of a pulse for each seed
which strikes the sensor 8 with sufficient impact.
The output signal 28 from the threshold detector 27 ~ -
is coupled to a charging circuit 29. Charging circuit 29
consists of a capacitor 30 which is charged by a reference
source Vr through a resistor, and an amplifier 31 arranged to
provide an outpùt signal i.e. goes high when a pre-
determined voltage appears across the capacitor 30. In addition,
a transistor circuit 32 having its input coupled to the threshold
circuit 27 is connected across capacitor 30 such ~hat the
transistor 32 is fired by each of the pulse signals 28 to
discharge the capacitor 30. Thus, if seed flows onto the
sensor 8 at a predetermined raté,the output of the charging
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circuit 29 will remain zero or low. The time constant for
charging circuit 29 may be set such that if the seed ceases
to flow for approximately 1/2 second, capacitor 30 charges
sufficiently to fire amplifier 31.
In the present embodiment, the alarm circuit 24
consists of a transistor switch 33 which is controlled by the
output of amplifier 31 to fire when amplifier 31 is high,
connected in series with a lamp 34, such as a light emitting
diode and a square wave generator 35. Thus when transistor 33
is fired, sufficient current will periodically flow through lamp
34 to cause it to flash on and off, warning the operator that
seed flow has ceased. In addition, the alarm circuit may
include an audible alarm 36 such as a buzzer connected in series
between a square wave generator 37 and the transistor 33. The
square wave generator 37 would preferrably have a longer period
than the period of square wave generator 35, i.e. 2 seconds on
and 8 seconds off, such that the buzzer would sound every ten ~
seconds during continuous no seed flow condition. --
In a monitoring system having two or more sensors,
20 i.e. sensors 8, 8a, 8b, ........ , each sensor may have identical
control and alarm circuits to circuits 23 and 24 described
above. However as shown in figure 5, the alarm circuits may be -
intercoupled to eliminate the need to duplicate some of the
components such as the square wave generators 35 and 37 and
audio alarm 36. Each sensor 8, 8a,`8b, ....... , has a control
circuit 23, 23a, 23b, ...., respectively, and an alarm circuit
24, 24a, 24b, ..... , respectively. Each alarm circuit 24, 24a,
24b, ..... , includes a transistor switch 33, 33a, 33b,
with an isolating diode 38, 38a, 38b, ... connecting the audio
alarm 36 and the collectors of transistors 33, 33a, 33b,
re~pectively. The square wave generator 35 is connected to
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each of the lamps 34, 34a, 34b, ..., which are shown as light
emitting diodes and therefore do not need further isolating
diodes. In addition, each alarm circuit 24, 24a, 24b, ....
may include a second diode 39, 39a, 39b, ...., with the anode
coupled to the transistor 33, 33a, 33b, ..., collector and the
cathodes coupled together. These diodes 39, 39a, 39b, ....
provide a voltage on line 40 when at least one of the transistors
33, 33a, 33b, ..., is not conducting, this voltage may be used
to control square wave generator 37 such ~hat it is disabled
when all of the transistors 33, 33a, 33b, ..... , are conducting.
Thus when the operator stops the seeder equipment and seed flow
ceases at all of the sensors, the audio alarm is automatically
disabled, however the light-emitting diode for each sensor
continues to flash.
Though the monitor has been described with respect
to the monitoring of seed flow during seeding operations, if
a seeder is equipped to simultaneously fertilize the soil, one
or more of the sensors in the monitor may also be positioned
in the paths of fertilizer flow to monitor the flow of
fertilizer to the soil.
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