Volume sensor for paddle elevator using laser light

A laser sensor for detecting the volume of particulate material being conveyed by a paddle conveyor. The sensor comprises two opposed units, a master unit and a slave unit. Each unit is provided with a single laser emitting diode and four photo detectors. The master unit is provided with a microprocessor for providing a square wave laser firing signal to the lasers. The slave unit is provided with an inverter for inverting the laser firing signal from the microprocessor. The lasers are fired sequentially when they receive a high pulse from the square wave emitted from the microprocessor. The photo detectors transmit their laser light detection signal when they receive a low pulse from the microprocessor which indicates the opposed laser has fired.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention is directed to a laser volume sensor used on a combine for 
either detecting the amount of tailings being transported by the tailings 
elevator, or the amount of clean grain being transported by the clean 
grain elevator. 
2. Description of the Prior Art 
Combines are large agricultural machines used to harvest a crop from a 
field. After the crop is harvested by a harvesting platform, the crop 
material is transported by a feederhouse into the interior of the combine. 
A threshing assembly threshes the harvested crop material breaking the 
grain apart from other grain and/or a husk. Next a separator assembly 
separates the clean grain the crop material other than grain. The crop 
material other than grain is returned to the field, while the grain and 
entrained small particles, chaff, are directed to a cleaning system. The 
cleaning system cleans the grain removing the chaff by blowing the chaff 
out the rear of the combine. The clean grain is transported by a clean 
grain elevator to a grain tank located on the combine. Photoelectric 
sensors for measuring the volume of clean grain passing through the clean 
grain elevator have been proposed, see German patent 2,445,046. 
Sometimes clean grain, unthreshed heads of grain and other crop material 
pass over the sieves of the cleaning system and become tailings. These 
tailings are caught before being expelled from the combine. The tailings 
are returned to the threshing assembly by a tailings elevator. Photodiode 
sensors for measuring the volume of tailings passing through the tailings 
elevator have also been proposed, see U.S. Pat. No. 4,441,513. 
SUMMARY 
It is an object of the present invention to provide a laser based sensor 
for detecting the volume of material being conveyed by a paddle conveyor. 
It is a feature of the presently invention that the sensor comprises an 
master unit and an opposed slave unit with each unit having a laser and 
each unit having at least two photo detectors. The opposed photo detectors 
are only triggered when the opposed laser is fired. 
In the preferred embodiment of the sensor, the master and slave units are 
substantially identical. In each unit the photo detectors and laser are 
arranged in a line with the laser being located at the highest position in 
the line. Each photo detector is provided with a photo detector circuit 
that transmits the laser light detection signal only when the opposed 
laser is fired. In this way, laser light detected from the laser located 
in the same unit is not transmitted to the microprocessor. 
The master unit is provided with a microprocessor which controls the 
operation of the sensor. More specifically, the microprocessor sends out a 
square wave of high-low pulses. The laser is fired on the high pulses and 
the photo detectors are triggered on the low pulses. Therefore when the 
master unit's laser is fired by a high pulse, the master unit's photo 
detectors are not triggered as they have also received a high pulse. 
The slave unit is electrically coupled to the master unit and is provided 
with an inverter that inverts the high-low pulses from the microprocessor. 
The inverter essentially changes the high pulse from the microprocessor to 
a low pulse and the low pulse to a high pulse. In this way when the 
microprocessor has issued a high pulse, the master unit's laser is fired 
and the opposed slave unit's photo detectors are triggered as the high 
pulse has been inverted into a low pulse. Similarly, when the 
microprocessor issues a low pulse, the master unit's photo detectors are 
triggered and the opposed slave unit's laser is fired as the low pulse has 
been inverted into a high pulse. It has been found that a microprocessor 
emitting a 400 hertz square wave works well in providing the high-low 
pulses. 
Both the master and slave units are provided with a protective lens of 
ultra high molecular weight polyethylene. This lens extends into the 
elevator and is cleaned by the particulate material passing by the lens.

DETAILED DESCRIPTION 
FIG. 1 shows an agricultural combine 10 comprising a supporting structure 
12 having ground engaging means 14 extending from the supporting 
structure. A harvesting platform 16 is used for harvesting a crop and 
directing it to a feederhouse 18. The harvested crop is directed by the 
feederhouse 18 to a beater 20. The beater directs the crop upwardly 
through an inlet transition section 22 to the axial crop processing unit 
24. The axial crop processing unit is located between the sidesheets of 
the combine. The sidesheets form part of the supporting structure. 
Although the invention is being described as being mounted on a rotary 
combine, it may also be used on other combines having a clean grain 
elevator and/or a tailings elevator, such as conventional straw walker 
machines. 
The axial crop processing unit 24 comprises an axial rotor housing 26 and 
an axial rotor 28 located in the housing. The harvested crop enters the 
housing through the inlet transition section 22. The rotor is provided 
with an infeed portion, a threshing portion and a separating portion. The 
rotor housing has a corresponding infeed section, a threshing section and 
a separating section. 
Both crop processing portions of the rotor 28, the threshing portion and 
the separating portion, are provided with crop engaging assemblies. The 
threshing section of the rotor housing is provided with a concave and the 
separating section is provided with a grate. Grain, including unthreshed 
heads of grain, chaff and other crop material are released from the crop 
mat and fall through the concave and the grate to the cleaning system. 
Larger crop material is expelled out the rear of the axial crop processing 
unit by beater 30. 
As illustrated in FIG. 1, grain and chaff falling through the concave and 
grate is directed to cleaning system 34 which removes the chaff from the 
grain. The cleaning system is provided with a blower that blows chaff out 
the rear of the combine. The heavier clean grain is collected by a 
transverse clean grain auger which directs the clean grain to a clean 
grain paddle elevator 36. The paddle elevator 36 directs the grain 
upwardly to a transition housing 38 where the grain is supplied to a 
loading auger 40 for loading the clean grain tank 42. The grain is removed 
from the clean grain tank 42 by unloading auger 44. Similarly, clean grain 
not falling through the sieves, unthreshed heads of grain and other crop 
material form tailings that are collected by a tailings cross auger which 
directs the tailings to a tailing paddle elevator 46. As best illustrated 
in FIG. 2, the tailing paddle elevator is provided with a series of chain 
driven paddles 47 on which the tailings are transported. The tailing 
paddle elevator 46 directs the tailings to a tailings cross auger located 
adjacent to the threshing portion of the axial separator for injecting the 
tailings back into the crop processing unit. The operation of the combine 
is controlled from operator's cab 48. A radio receiver 50 for receiving 
GPS signals is positioned over the operator's cab so that the sensor data 
from the sensor can be combined with the GPS signal data to provide a crop 
mapping option. 
The following description of the preferred embodiments directed to a volume 
sensor located in the tailings elevator of the combine. However it should 
be noted, that the sensor could also be located in the clean grain 
elevator. The sensor uses laser light to sense the crop material piled on 
the individual paddles as they pass the sensor's location. The sensor of 
the present invention could be used for measuring the volumetric flow rate 
(VFR) of any type of granular or particulate matter as it passes is 
conveyed by a paddle conveyor. 
It is advantageous to the farmer or combine operator to have an indication 
of the amount of tailings and/or clean grain that is being conveyed by the 
elevator systems of the combine so as to avoid jamming and to assist in 
maintaining proper combine adjustments. Further, it is beneficial to have 
a volumetric measurement (as opposed to another measurement, such as 
mass), since crop yield is measured in bushels, which is a volumetric 
measurement. 
The volume sensor 60 is mounted to the tailings elevator comprises two 
units, a master unit 62 and a slave unit 64. These units are mounted on 
either side of the enclosure of the tailings elevator 46 and are 
substantially parallel to and opposed to each other. Each unit is provided 
with a laser light emitting diode 66 (e.g., but not limited to, EG&G 
Optoelectronics C86137E or Siemens type SPL PL85) and four light emitting 
diodes forming photo detectors 68. The laser diode 66 and the photo 
detectors 68 are arranged in a line parallel to the elevator paddles. The 
laser diode 66 being the highest and the four photo detectors 68 extending 
downwardly therefrom. By having the laser diodes located at the highest 
point and opposed to one another the transverse slope of the tailings pile 
on the paddle can be sensed. By knowing the side profile of the material, 
the width of the elevator enclosure, and the time and distance between 
each paddle the volumetric flow rate of the tailings material can be 
predicted. 
The sensor 60 is housed in a box 70 having an open side. The open side of 
the box is the surface that abuts the outside enclosure of the tailings 
elevator. A portion of the open side is provided with a faceplate 72 with 
the remaining portion of the circuit board is potted sealing the box 70. 
The face plate 72 is formed from an ultra-high molecular weight 
polyethylene (UHMWP), which is designed for high wearability and abrasion 
resistance. The selected UHMWP also has the appropriate optical 
properties, i.e., it is diffusing and the index of refraction =1.54 
(unitless). The laser diode 66 and the photo detectors 68 are positioned 
as close to or in direct contact with the rear of the faceplate 72 facing 
outwardly therefrom. The faceplate forming a protective lens for the laser 
diode and the photo detectors. It has been found that the thickness of the 
faceplate 72 may effect the output of the laser diode 66 as detected by 
the opposed photo detectors 68. It has been found that a faceplate of 2.0 
millimeters thickness works satisfactory. 
The face plate is formed with a raised boss 74 forming the protective lens 
for the laser diode 66 and the photo detectors 68. The box 70 is mounted 
onto the exterior surface of the tailings elevator 46 by mounting bolts 
73, in such a manner that the raised boss 74 fits through a cutout in the 
tailings elevator. The tailings elevator 46 being large enough to 
accommodate the size and shape of the raised boss 74. The raised boss 74 
is designed such that it is thicker than the sheet metal comprising the 
tailings elevator enclosure (e.g., twice as thick as the sheet metal). 
This design allows increased exposure of the face of the raised boss to 
the tailings material, which acts as a self cleaning mechanism for the 
sensor face. The raised boss 74 is provided with tapered edges 76 in order 
to prevent a sharp edge inside the elevator 46. 
Each of the laser diodes 66 emits a pulsed infrared or near-infrared light 
(e.g., 905 nm). The laser diodes 66 are pulsed incrementally at a 
predefined frequency of 400 hertz. When the laser diodes 66 are pulsed, 
the emitted light is coherent, with a gaussian spatial distribution. The 
light illuminates the entire inner chamber of the unblocked tailings 
elevator between the firing laser and the opposed triggered photo 
detectors. 
FIG. 4 is a block diagram of the volume sensor electronics. The master unit 
is provided with a microprocessor 80 which is powered by a conventional 
power supply. The microprocessor is programmed to emit a 400 hertz 
high-low square wave pulse to the master unit's laser firing circuit 82 
through line 84. Line 86 taps into line 84 and couples the master unit's 
photo detector circuit 88 the 400 hertz output of the microprocessor. As 
discussed above when the laser firing circuit 82 receives a high pulse the 
laser is fired. When photo detector circuit 88 receives a high pulse the 
photo detector circuit 88 is not triggered and no output is received from 
the master unit's photo detector circuit. Similarly, if a low pulse is 
received by the laser firing circuit 82, the laser is not fired. The low 
pulse triggers the photo detector circuit 88 detecting light emitted from 
the slave unit's laser, if not blocked by tailings, and sending that 
information back to the microprocessor via lines 90, 92, 94 and 96. 
The slave unit is provided with an inverter 98 that inverts the 400 hertz 
high-low square wave received on line 100 making high pulses low pulses 
and low pulses high pulses. As with the master unit the laser firing 
circuit 82 of the slave unit is fired by high pulses and the photo 
detector circuit 88 is triggered by low pulses. As these pulses are 
inverted by the inverter 98, a high pulses from microprocessor 80, fires 
the master unit's laser firing circuit 82 and triggers the slave unit's 
photo detector circuit 88. The detected information by the slave unit's 
photo detectors 68 is transmitted back to the microprocessor 80 along 
lines 102,104,106, and 108. A low pulse from the microprocessor triggers 
the master unit photo detector circuit 88 and fires the slave unit's laser 
firing circuit 82. 
The laser firing circuits for the master unit and the slave unit are of a 
conventional configuration. The photo detector circuits for the master and 
slave units are substantially identical with the photo detector circuit 
for one of the photo detectors being illustrated in FIG. 5. Each photo 
detector is provided with an photo amplifier 110 amplifying the resulting 
signal from the photo detector, a second stage amplifier 112 further 
amplifying the signal, an analog to digital converter 114 for converting 
the analog signal to a digital signal, and a logic circuit 116 for 
directing the digitized output signal to the microprocessor when the logic 
circuit receives a low pulse. 
The photo diode LED1 produces a negative current pulse when it detects 
light. This signal is amplified by photo amplifier 110 with a gain of 100 
resulting in a positive voltage pulse. This positive voltage pulse is 
amplified by second stage amplifier 112 with a gain of 100 into a negative 
voltage pulse that is directed to analog to digital converter 114. The 
digitized signal is directed to the logic circuit 116 where it is inverted 
by inverter U4 and applied to flip flop U5. Flip flop U5 signals the 
microprocessor via an appropriate line (90, 92, 94, 96, 102, 104, 106 or 
108) as to the presence of laser light detected by the photo diode LED 1 
when the flip flop receives a low pulse via line 86 directly from the 
microprocessor 80 for the master unit or from the inverter 98 for the 
slave unit. 
The components of a single photo detector channel are listed in Table 1 and 
are disclosed as an example of a suitable circuit for the present 
application 
TABLE 1 
______________________________________ 
C1, C4 0.1 micro farad 50 Volt Package Style 08 capacitor 
C2 1000 pico farad 50 volt package style 08 capacitor 
C3 5 pico farad 50 volt package style 08 capacitor 
C5 15 pico farad 50 volt package style 08 capacitor 
R1 4.99K ohms 1/10 watt 1% resistor 
R2, R8 30.1K ohms 1/10 watt 1% resistor 
R3, R5, R9 
100K ohms 1/10 watt 1% resistor 
R4, R6 1.0K ohms 1/10 watt 1% resistor 
R7 243K ohms 1/10 watt 1% resistor 
R10 10K ohms 1/10 watt 1% resistor 
U1, U2 1/4 operational amplifier Motorola MC33074D 
U3 1/4 operational amplifier National LM2901 
U4 1/4 Hex inverter Motorola MX74HC14 
U5 1/2 Dual D Flip Flop with set/reset MC74HC74AD 
______________________________________ 
It should again be noted that FIG. 5 represents one photo detector channel 
for one photo detector. The operational amplifiers U1, U2, U3 and the 
inverter U4 are shared among the other photo detectors in the photo 
detectors respective master or slave unit. Similarly half the dual flip 
flop is shared by the adjoining photo detector and another flip flop is 
provided for the two remaining photo detectors in the respective master or 
slave unit. 
The present invention should not be limited to the above described 
embodiments but should be limited solely to the claims that follow.