Note: Descriptions are shown in the official language in which they were submitted.
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'A METHOD TO DETECT THE LEVEL OF GRANULAR MATERIAL
IN A BIN'
FIELD OF THE INVENTION
The present invention relates to an apparatus for detecting and announcing
when a
stortage bin becomes full. An agricultural operation stores the grains it
produces in
weather proof bins. When the bins are being filled the operator normally
monitors the
amount in the bin visually so that the bin does not overflow. The present
invention,
provides a remote indication to the operator when the bin is nearing full.
BACKGROUND
It is known that if a storage bin overflows while it is being filled, the
filling
machinery can become jammed and damaged. Also some of the overflowed granular
material can be spoilt or lost. A considerable amount of time is required to
fill a bin and
the operator must remain diligent for the duration.
The present invention allows the operator to rest or work at other tasks, as
the bin
fills. When a level is reached, that allows time for the operator to return to
the bin, a radio
signal is sent to a pager like device, causing an audible, tactile and visual
alarm to occur.
Also when a critical level is reached the invention sends another signal,
which causes a
second audible, tactile and visual alarm to occur. The operator then shuts the
filling
machinery off.
Capacitive sensors are used extensively for level measurement and proximity
detection. A proximity detector typically determines if materials are near the
sensor by
comparing the measured capacitance to the predetermined threshold. If the
capacitance
varies due to environmental changes, this method give false positive or
negative
detections.
It is known that circuits are available which sense the dramatic change in
capacitance when a human finger is placed on a touch pad as taught by Phillip;
Harald
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US patent 6,452,514. These circuits regularly zero themselves to the current
capacitance,
thus eliminating drift. These circuits are very low cost. It is also known
that Livingston in
US patent 6,539,797 teaches a method of using a separate reference capacitance
sensor to
correct for change in dielectric of the medium being sensed and that this
technique does
not work to negate the effects of dust build up, thus producing an erroneous
result..
DISCLOSURE OF THE INVENTION
It is known that dust will build up on any surface inside the bin and it has
been
discovered, by the inventors, that using the Phillip; Harald technique
eliminates the
problem of dust build up and can be used to detect when a metallic probe is
fully
immersed in granular material vers. covered in a build up of dust.
In the preferred embodiment of the invention, two metallic probes are
permanently mounted through the side of the storage bin. One is located near
the top of
the bin and the other at an appropriate distance below the first probe.
Circuits are
connected to the metallic probes such that the Phillip; Harald capacitive
proximity
technique is implemented. A cable connects the resulting two sensors to a
connector
mounted near the bottom of the bin.
Further circuits are provided in an easily removable housing that can be moved
from bin to bin as required. These circuits power the sensors and respond to
the detected
presence of granular material. This apparatus contains visual annunciation
devices and a
radio frequency transmitter capable of sending an encoded signal to a remote
portable
receiver.
Further circuits are provided in a portable, pager like, housing that can be
carried
by an operator. This apparatus contains a radio frequency receiver capable of
receiving
the signals sent from the above apparatus connected to the sensor via the
cable. It also
contains logic and circuits that decodes the signal and visual, audible and
tactile
annunciation devices to inform the operator of the event of the granular
material covering
either sensor.
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BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 is a fragmentary, vertical section of a storage bin with the level
sensors,
controller/transmitter and portable/receiver of this invention mounted
thereon;
Figure 2 is a block diagram of a prototypical system. It shows the major
blocks
that are required to realize the Invention;
Figure 3 is a mechanical drawing of fragmentary, sections of the preferred
embodiment of the sensor;
Figure 4 is a data flow diagram for a prototypical sensor apparatus. It shows
the
major blocks that are required to realize the Invention;
Figure 5 is a data flow diagram for a prototypical controller/transmitter
apparatus.
It shows the major blocks that are required to realize the Invention;
Figure 6 is a data flow diagram for a prototypical portable receiver
apparatus. It
shows the major blocks that are required to realize the Invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
The storage bin level sensing apparatus of the present invention includes one
or
more capacitive sensors, connected via a common cable to a
controller/transmitter which
sends a radio status signal to a portable/receiver to alert an operator of a
pending over fill
condition.
Figure 1 describes a fragmentary, vertical section of a storage bin 1 with the
level
sensors 3&4, controller/transmitter 5 and portable/receiver 6 of this
invention. In
operation a plurality of sensors 3&4 are inserted through the wall of a
storage bin 1.
When the granular material 2 rises to cover the lowest sensor 4, it is
detected and an
electrical signal is sent via the cable 8 to a removable
controller/transmitter 5. Said
controller/transmitter 5 is retained by a holder 9 located at the bottom of
the cable 8. The
controller/transmitter 5 turns on a visual annunciator and sends a radio
signal 7 to the
portable/ receiver 6. The portable/ receiver 6 receives the radio signal 7 and
turns on
visual, audible and tactile annunciators, thus alerting the operator. A
similar procedure is
preformed for each of the sensors 3 above the lowest one.
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Figure 2 describes a block diagram of the preferred embodiment of the grain
level
sensing system. The apparatus contains 8 major blocks; a plurality of sensors
3 & 4, a
controller/transmitter 5, visual alarms 29 for the controller/transmitter 5, a
portable
/receiver 6, a control button 27 for the portable/receiver 6, tactile, audible
& visual alarms
25,2 6 & 28. Either sensors 21 or 22, detects the presence of granular
material and sends
an electrical signal to the controller/transmitter 5. The
controller/transmitter 5 turns on the
appropriate visual alarm 29 and send an encoded radio signal 27 to the
portable/receiver
6. The portable/receiver 6 turns on the appropriate tactile, audible and
visual alarm 25,
26, and 28 thus warning the operator who acknowledges the alarm by pressing
the
control button 27.
Figure 3 describes fragmentary, sections of the preferred embodiment of the
capacitive proximity sensor 3 or 4. A cable 31 is molded into a solid potted
housing 33.
The housing 33 encapsulates circuits 32 which implements the logic described
in Figure
4 and a metallic probe 34. The capacitance of the probe 34 changes
dramatically when it
becomes immersed in granular material, thus triggering the logic to send an
electrical
signal to the controller/transmitter via the cable 31. The cable 31 also
delivers the
necessary electrical power and ground to the circuits. In the case of more
then one sensor,
the cable 31 continues 35 out the opposite side of the housing and connects to
the next
sensor.
Figure 4, describes the data flow within a prototypical sensor apparatus 3 or
4.
The apparatus contains 5 major blocks: calibration 41, measurement 42, test
for change
43, activate signal 44, and check if calibration required 45. On power up or
periodically
as determined by the logic in block 45, the sensor is calibrated 41 by
adjusting its zero
point to the current capacitance reading. The sensor then enters a loop which
measures 32
the capacitance of the metallic probe, 34. This measurement is checked to
determine if it
exceeds a fixed threshold 43. If it does exceed the threshold the sensor
activates 44 an
electrical output signal and returns to the head of the loop 42. If it does
not exceed the
threshold, the sensor checks to determine if the reading has changed in the
last 60
seconds 45. If it has changed the sensor is recalibrated 41. If not, the logic
returns to the
head of the loop 42. This loop is repeated continuously until the power is
removed.
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Figure 5, describes the data flow within a prototypical controller/transmitter
apparatus 55. The apparatus contains 8 major blocks: a delay timer 51, a test
for the lower
sensor signal 52, lower alarm control 54, a test for the upper sensor signal
3, upper alarm
control 55, test for low battery voltage 56, low battery alarm 57, and a radio
signal
control 58.
On power on, the apparatus directs power through a cable to the sensors 3 & 4
and enters a delay timer 51. A test, alarm, and signal loop 51 to 58 is then
executed
periodically when the timer elapses. This loop tests 52 for an electrical
signal from the
lower sensor which is on if it has detected the presence of granular material,
a visual
alarm indicator is latched on, a flag is set 54 and control passes to the test
for the upper
sensor 53. If not, a test 53 is made for an electrical signal from the upper
sensor which is
on if it has detected the presence of granular material, a visual alarm
indicator is latched
on, a flag is set 55 and control passes to the test for the low battery 56. If
not, the battery
voltage is measured 56 and if it is below a fixed threshold, a visual alarm
indicator is
latched 57 on and control passes to the test radio control logic 58. If not, A
radio signal
encoded with the status is sent 58 to the portable/receiver 6. If the upper
alarm flag is set
an upper alarm signal is sent via the radio 58 to the portable/receiver 6 or
if the lower
alarm flag is set a lower alarm signal is sent via the radio 58 to the
portable/receiver 6 or
if no alarm flags are set a no-alann signal is sent via the radio 58 to the
portable/receiver
6. Then the control passed back to the delay timer 51.
If more then 2 sensors are incorporated into the system, duplicates of logic
blocks 53 &
55 are inserted between blocks 53 & 55 and the battery test 56.
Figure 6, describes the data flow within a prototypical portable/receiver
apparatus
6. The apparatus contains 6 major blocks: a delay timer 61, a low battery test
62, a data
receiver 64, a test for no communications 65, a test for new alarm 68, a test
for control
button status 70.
On power on, the logic starts a delay timer 61. When the timer elapses, the
logic
tests for low battery voltage 62. If the battery voltage is below a fixed
threshold, a visual
alarm indicator is latched on 63 and control passes to the data receiver 64.
If not, control
passes to the data receiver 64. If data has been received, the data is
processed 67 ie:
decoded and checked if it is valid data. Then the processed data is checked 68
to
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determine if it represents a new status. If it is a change in status, change
69 the audible,
visual and/or tactile alarm indicator states, then the control button is
checked 60. If not,
check the control button 60. If no data is received, check if radio data has
been received
in the past 10 seconds 65. If no data has been received for 10 seconds ie:
loss of
communication, a visual, audible and tactile alarm indicators are latched on
66 and
control passes to the control button test 60. If it has been received, then
the control button
is checked 60.
If the control button is pressed continuously for more then 2 seconds 71, then
the
power is turned off 72. If the button pressed for less then 2 seconds 73, then
any audible
and/or tactile alarm indicators are turned off 74, the timer is reset 61 and
the loop starts
over. If the control button is not pressed the timer is reset 61 and the loop
starts over.
