Stone detection method and apparatus for a harvester

A hard object or stone detection method and apparatus for detecting and removing discrete hard foreign objects from mobile agricultural equipment, particularly an agricultural harvester including apparatus for providing a flow of cut crop material to an elevator for delivery to a threshing system. The apparatus includes a foreign object detecting mechanism, including a foreign object detecting circuit for detecting foreign objects and an object exclusion or rejection mechanism operationally connected to be activated by the detecting circuit. The detecting circuit includes at least one vibration sensor operable for outputting a signal, and a combination of high pass filters and frequency bandpass filters and variable threshold comparators for processing the signal along first and second signal paths, and at least one microprocessor or microcontroller including a pulse rejection network. The microprocessor can be electronically connected to control the threshold comparators and programmable amplifiers, and activates the object exclusion or rejection mechanism when the pulse rejection network generates an internal signal indicating presence of a hard object.

FIELD OF THE INVENTION

The present invention pertains to a stone detection method and apparatus for detecting and removing discrete hard foreign objects from mobile agricultural equipment. Specifically, self-propelled combine harvesters and forage harvesters are adapted with an apparatus that performs the method of detection of rocks and other discrete hard objects to permit the reliable removal of the rocks and hard objects from harvested crop material during crop harvesting operations.

BACKGROUND OF THE INVENTION

In the art of mechanically harvesting crops, it is known that self-propelled agricultural vehicles, such as combine harvesters and forage harvesters, are used to mechanically harvest crops. Typically, these vehicles are equipped with a harvesting implement, or header, that can, for instance, include a reel or other apparatus for pulling crops into an array of blades for cutting the crops, wherein the cut crop material is pulled or otherwise conveyed farther into the header by an auger or other apparatus. Once past the auger, the cut crop material is carried by an elevator or feederhouse to a threshing and sorting mechanism or system that removes unwanted chaff material from the desired crop matter before the crop matter reaches a storage compartment or tank carried by the vehicle.

However, this simple crop harvesting process is complicated by the fact that stones and other discrete hard objects are often pulled into the header with the crops. In the context of this disclosure, the terms “stones,” “rocks,” “objects,” and “hard materials” are used interchangeably and define equivalent matter to include any discrete undesirable matter such as stones, rocks, pieces of metal, and pieces of wood, that is separable from the cut crop material (i.e., harvested crop plant material) and thus considered to be foreign to the crops. Unfortunately, stones and other hard debris can cause expensive damage to the elevator and threshing mechanisms; therefore, various methods and apparatuses have been developed to detect and remove stones and other potentially damaging foreign objects from the header before the cut crop material is carried by the elevator into the threshing and sorting mechanism.

Typically, the stone detection methods and apparatuses of the prior art include a stone detection circuit that operates a mechanism for removing any stones or hard objects. For example, U.S. Pat. No. 3,675,660 to Girodat, which is incorporated herein by reference in its entirety, discloses a rock detection circuit that includes a rock detector, a bandpass filter, a peak signal detector, an amplifier, and a solenoid operated trap door placed along the cut crop path before the crop elevator. The rock detector is a piezoelectric ceramic disc that picks up vibrations as the crop material passes and sends a sensing signal to the bandpass filter. Rocks of a certain size are known to generate higher frequency vibrations than the crop material, so the bandpass filter removes low frequency signals from the sensing signal before sending the filtered signal to the peak signal detector.

Extremely large stones entering the combine feeder housing sometimes are not detected by the system of the Girodat patent. Several mechanisms are responsible for this. First, the physical size of a very large stone and the feeder front roll configuration prevents the required direct impact of the stone on the existing flat sensor plate. Instead, the stone is pinched between the front roll and the sensor plate which results in the stone being scraped and dragged across the plate. Second, when a very large stone does impact the sensor plate, acoustical signatures below about 2 kHz are generated—well below the ASP (Advanced Stone Protection) electronic box bandpass filter center frequency of 5 kHz. Only a small amount of signal is generated within the pass band of the filter. Thus, a very large stone is often not sensed and is thrust into the combine resulting in damage.

Thus, the peak signal detector generates a signal only if the filtered signal has an amplitude greater than a predetermined amplitude (“threshold amplitude”), thereby filtering out background noise signals. When the filtered signal exceeds the predetermined amplitude, the peak signal detector generates a signal that is amplified by an amplifier, which sends an activating signal to a solenoid, which operates to open the trap door so that the hard foreign object will fall out of the header. Unfortunately, there is a lot of background noise due to vibrations generated by the vehicle's engine, jarring of the vehicle as it travels along the ground, and rock impacts on the exterior of the header during harvesting operations.

Consequently, unless sensitivity of the rock detection circuit is precisely set, either the trap door will open unnecessarily thereby spilling valuable crop on the ground or the trap door will not open when needed so that many large stones will reach the elevator and threshing mechanism resulting in damage to the vehicle. It is noted that Girodat's rock detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filter, or the threshold amplitude of the peak signal detector.

In an attempt to mitigate the effect of background vibrations, U.S. Pat. No. 4,275,546 to Bohman et al. discloses a stone discriminator circuit that uses a pair of piezoelectric crystals that are vibrationally isolated from the header and the harvester by two vibration isolators. The two piezoelectric crystals are set to detect different vibration frequencies, one crystal detects vibration generated by the crop material and the other crystal detects vibration generated by stones. Each crystal sends signals to its respective bandpass filter, then to a difference amplifier that receives input from both bandpass filters. The difference amplifier detects the difference between the signals from the two crystals and outputs an amplified signal to a threshold circuit.

The threshold circuit generates a signal to operate a trap door or an alarm only if the amplified signal from the difference signal exceeds a threshold amplitude. In other words, the two crystals provide comparative information with respect to the background vibrations and superimposed rock vibrations in an attempt to weed out the background events from stone impact events near the crystals. However, Bohman's circuit also has the drawback that the stone discriminator circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.

U.S. Pat. No. 4,720,962 to Klinner discloses a means for detecting stones and metal, which is a circuit including a vibration detector and a metal detector for detecting unwanted objects in a forage harvester. The vibration detecting portion of the circuit includes a vibration sensor, a high pass filter and a comparator, so that a vibration detecting signal is generated that is frequency filtered and that represents an event exceeding a minimum threshold amplitude. Input from a metal sensor and input from the vibration detecting portion feed into the remaining portion of the stone and metal detection circuit to activate a door system to get rid of the unwanted object. It is noted that the stone and metal detection circuit includes a timing circuit so that the door system stays open for only a predetermined period of time. However, Klinner's stone and metal detection circuit has no control components for adjusting the frequency sensitivity of the bandpass filters, or the threshold amplitude of the threshold circuit.

Some other known stone detection or protection systems include two sensor plates and related two electronic bandpass filters in the stone detection or protection module employed to process signals from each plate in order to produce stone trap door openings whenever a stone impacts one of the plates. Each of these two filters passes a range of frequencies centered about a certain frequency. For the upper plate the center frequency is 3.1 kHz and for the lower plate the center frequency is 5 kHz.

Controlled tests strongly suggest that the upper sensor plate is relatively ineffective in contributing to stone detection or protection. Lab testing has conclusively shown that very large stones generate impact signals in the lower frequency region below about 2 kHz. Only a small amount of signal from the very large stones is available in the 5 kHz filter pass band. Medium to small stones generate impact signals mainly in the region above 2 kHz.

It has also been discovered that high force impacts of the largest stones (or even hard ear corn) produces a very large low spectrum electrical signal that can sometimes overload the electronic circuitry of the 5 kHz filter in the ASP module. Whenever an overload occurs, the amount of signal available in the 5 kHz region is reduced. This will adversely affect detection performance.

Therefore, the present invention endeavors to provide an improved method for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester, and an apparatus for performing this method that reliably produces cut crop material that is essentially solely cut crop matter that is an improvement over the prior art devices and methods.

Accordingly, a primary object of the present invention is to overcome the disadvantages of the prior art methods and apparatuses for detecting and removing hard objects from cut crop material during crop harvesting with a mechanical harvester.

Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that achieves adequate detection rates for the hard foreign objects, so that the objects can be reliably removed.

Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for external adjustment of various detection parameters by an operator to achieve the improved detection rates for the hard foreign objects.

Another object of the present invention is to provide a method and apparatus for detecting and removing hard foreign objects from cut crop material that allows for the system to internally adjust to various internal and/or external influences that are transparent to the operator to achieve the improved detection rates for the hard foreign objects.

SUMMARY OF THE INVENTION

Accordingly, the present invention is proposed to overcome one or more of the problems, disadvantages, and shortcomings of the prior art, and achieve one or more of the objects, as set forth above.

According to a preferred aspect of the invention, as a modification of a known ASP system such as those discussed above including two sensor plates and bandpass filters, first, the known upper sensor system will be deleted or completely removed and the electronic filter in the stone protection module formerly used to process upper plate signals will be modified to process those signals from the lower plate caused primarily by very large stones. In order to accomplish this, the center frequency of the upper filter is changed from 3.1 kHz to 1 kHz—the region where large stones have been found to generate the most signal. This change means that signals generated by very large stones will generally be detected by the upper sensor bar filter and will more likely result in a stone trap door opening.

Second, to prevent 5 kHz filter overload, a high pass filter will be inserted in the signal path prior to the 5 KHz filter that will suppress signals below about 2 KHz. In addition to overload prevention, this modification will suppress unwanted low frequency ear corn impact signatures which can masquerade as large stones. Because of this modification, small to medium size stones will more likely be detected by the lower filter and be ignored by the upper filter. A sliding sensitivity scale is implemented in software so that in light grain crops both upper and lower filters can contribute to stone detection. When harvesting ear corn, the scale is adjusted downward by the operator so that much less of the upper filter is used in the detection process.

It is contemplated that the following advantages will result: (1) minimal impact on crop flow; (2) same user interface (0-100 percent gain in 10 percent increments); and (3) marked improved stone protection performance for very large stones, and incremental improvement performance for smaller stones.

In accordance with another preferred aspect of the present invention, there is provided a method for detecting and removing hard objects from a cut crop material that is not limited to any one particular apparatus, or combination of apparatuses, for performing the method. The method comprises the steps of providing a cut crop material that includes foreign hard objects in addition to cut crop matter; sensing the cut crop material and foreign hard objects using a sensor to generate a signal; amplifying the signal, wherein the magnitude of amplification is controlled by the microprocessor; processing the signal to filter a bandwidth to generate a bandwidth filtered signal, optionally wherein a microprocessor controls the frequency range of the filtered bandwidths; processing the bandwidth filtered signal to generate an amplitude threshold signal when the bandwidth filtered signal exceeds a minimum threshold amplitude, wherein the microprocessor controls a value of the minimum threshold amplitude; processing the amplitude threshold signal to generate an internal signal only when the amplitude threshold signal has a pulse width that exceeds a minimum pulse width value, thereby eliminating noise signals; and determining that a hard object is present based upon the internal signal, then removing the hard object based upon an output signal by using a hard object removal mechanism to produce a cut crop material that is essentially cut crop matter.

According to another preferred aspect of the present invention, an agricultural harvester is provided having a header. The header can be of conventional construction, for instance, a grain header with a reel and an auger or draper belt, wherein the reel and the auger or draper provide crop material to an elevator, or a corn head including an auger or draper to provide crop to an elevator, and including a foreign object detecting mechanism, wherein the foreign object detecting mechanism includes a foreign object detecting circuit to detect foreign objects and an object extrusion or removal mechanism operationally connected to be activated by the detecting circuit, wherein the detecting circuit is connected to a power supply and comprises a first vibration sensor that generates a first input signal in response to vibrations generated by a foreign object; a frequency high pass filter that removes low frequencies from the first input signal and produces a first high pass filtered input signal; a first programmable amplifier that receives the first high pass filtered input signal from the frequency high pass filter and generates an amplified first output signal; a frequency bandpass filter that receives and filters a bandwidth of the amplified first output signal to generate a first frequency filtered signal; a first variable threshold comparator that receives the first frequency filtered signal and generates a first pulse output signal when the first frequency filtered signal exceeds a minimum threshold amplitude; a first pulse rejection network that receives the first pulse output signal and generates an internal signal when a frequency calculated from the pulse train of the first pulse output signal corresponds to a specified frequency bandwidth; and a microprocessor that includes the pulse rejection network and that is electronically connected to the first threshold comparator and to the first programmable amplifier, wherein the microprocessor operates to control the value of the minimum threshold amplitude of the first threshold comparator and to control the magnitude of signal amplification performed by the first programmable amplifier, wherein the detecting circuit activates the object exclusion or removal mechanism whenever the detecting circuit generates a third output signal.

Furthermore, according to the preferred aspect, the present invention includes a second programmable amplifier, which receives the first input signal and produces a second amplified input signal; a low frequency band pass filter, which receives the second amplified input signal and produces a second frequency filtered signal; a second variable threshold comparator that receives the second frequency filtered signal and generates a second pulse output signal when the second frequency filtered signal exceeds a minimum threshold amplitude; a second pulse rejection network that receives the second pulse output signal and generates an internal signal when a frequency calculated from the pulse train of the second pulse output signal corresponds to a specified frequency bandwidth; and a microprocessor that includes the pulse rejection network and that is electronically connected to the second threshold comparator and to the second programmable amplifier, wherein the microprocessor operates to control the value of the minimum threshold amplitude of the second threshold comparator and to control the magnitude of signal amplification performed by the second programmable amplifier, wherein the detecting circuit activates the object exclusion or removal mechanism whenever the detecting circuit generates a third output signal.

Further objects, features and advantages of the invention will become apparent from the Detailed Description of Preferred Embodiments that follows, when considered together with the attached drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention generally includes a method and apparatus for detecting and removing hard objects from a flow of cut crop material, and a representative agricultural harvester with which the invention can be used. To facilitate an easy understanding of the present invention, the agricultural harvester will be described first, with reference to the Figures.

Referring toFIG. 1, an agricultural harvester1is typically a self-propelled vehicle having two wheel pairs8and9, engine7mechanically connected to rotate the wheels, cab2where the vehicle operator11sits, and a header12for harvesting crops. Header12includes reel assembly13for pulling crops into the header so that the crops are cut by blade assembly17in the conventional manner, and an auger15situated in an auger trough14for pushing cut crop material into the center of the header. As is conventionally known, the header12and the reel assembly13have position adjusting mechanisms (not shown) for moving and positioning the header and the reel assembly relative to the crops and the ground so that crops can be optimally harvested.

A cut crop elevator21, or “feederhouse,” is located at the center of the header12and is fed by the rotation of auger15. Cut crop material moves from auger15to elevator21where the cut crop material is carried along a flow path through the bottom of the feederhouse along a floor thereof by an elevator apron23from a front drum22to a rear drum24and into the forward portions of the harvester1. Essentially, elevator apron23includes at least two continuous chains which encircle drums22and24and include slats or bars which extend parallel to the drums and engage and convey or drag or push the crop material along the floor or bottom of the feederhouse as driven by rotation of the drums. Harvester1includes a threshing mechanism3which receives the flow of crop material fed into it by elevator21and which threshes the grain of the crop material from straw, cobs, pods, stems, and the like. The grain is then delivered to a grain/chaff separation system4which removes the chaff and other material other than grain from the grain. Once the grain or other crop has been threshed and the chaff removed, the product crop is conveyed to and stored in tank5. Tube6is used to unload the product crop and any chaff is discarded by the chaff spreader10.

To protect the elevator21, threshing mechanism3, and other systems of the harvester1from damage due to stones, rocks, metal pieces, and any other discrete foreign hard objects that are mixed in with the crop matter, the elevator21is fitted with a hard object detector35.

The hard object detector35serves to both detect and to remove any foreign hard objects from the flow of cut crop material passing through the elevator21, thereby producing a flow of cut crop matter that is essentially free of foreign hard objects. As schematically shown inFIG. 4, and as illustrated inFIG. 5, the hard object detector35of elevator21includes a detector element36which is preferably a plate such as a sounding plate positioned in spaced relation beneath the front drum22(deleted inFIG. 5for clarity but illustrated inFIG. 1), such that flows of cut crop material fed into elevator21will be forceably urged or driven over the upper surface of the sounding plate. The upper surface of the sounding plate is preferably at least generally parallel to the feederhouse floor and includes an array of “interruptions”38or “cleats” configured thereon, to ensure that a stone sliding thereover, or contained in a flow of crop material flowing thereover, impacts or contacts one or more of the interruptions38or otherwise “excites” or vibrates the plate to a sufficient magnitude so as to be detectable by an acoustic sensor, and such that the excitations or vibrations of the plate detected by the sensor will have at least one characteristic distinguishable from characteristics of excitations or vibrations of the plate caused by passage thereover of the crop material alone. It is contemplated that the interruptions could comprise many different embodiments.

For example, a preferred embodiment of the sounding plate shown inFIG. 5includes interruptions38as commonly used and embodied by “diamond plate” technology. Such “diamond plate” technology is frequently used as a “no-slip surface” or in the construction of heavy-duty toolboxes, storage systems, etc. However, it should be appreciated that the sounding plate of the present invention is not limited to use of diamond plate technology; the minimum requirement of the sounding plate of the present invention is that its surface include any array or pattern of interruptions38, such that the array or pattern of interruptions38would preclude a clear path of travel of an object from the front end to the rear of the sound plate in the direction of crop flow. Accordingly, the sound plate and surface interruptions38of detector element36of the present invention would dictate that an object (i.e. a stone) traveling from the front end to the rear of the sound plate would encounter at least one interruption38during its travel, thereby creating a sufficient “excitement” signature to qualify as a stone or other hard object event noise. It is thus contemplated that the sound plate interruptions38could include, but are not limited to, any array or pattern of obtrusions that would meet the aforementioned minimum requirement, such as a “dimple” configuration, array of random weld spatters, etc.

Referring also toFIGS. 6,7and8, the sound plate of detector element36is shown including various alternative embodiments of interruptions which are considered suitable for causing the desired excitations of element36as crop material flow containing one or more hard objects pass thereover, including raised, elongate weld beads38A in a diamond pattern (FIG. 6); an array of discrete raised obtrusions or bumps38B (FIG. 7); and an array of generally round beads or dimples38C (FIG. 8).

The excitations of detector element36signifying presence of a stone or other hard object in the crop flow thereover are sensed by at least one sensor40of an electrical detection circuit42operationally connected thereto and to a power supply70, and a hard object removal mechanism44operationally connected to and controlled by detection circuit42.

Preferably, each sensor40is an acoustic sensor, although the invention is not limited to acoustic sensors. Furthermore, the invention can be practiced using a sensor array, so that sensor40could actually be an array of two or several sensor devices, as illustrated by the two sensors inFIG. 4. Detection circuit42includes a high pass filter140, programmable amplifiers50and150, variable bandpass filters52and152, variable threshold comparators54and154, and microprocessor60that includes a pulse rejection network. Microprocessor60can be, for instance, the principal operating element of a microprocessor based microcontroller, as illustrated inFIG. 4. Power supply70is electrically connected to the detection circuit to provide power to run the system.

The details of detection circuit42are described below. Each sensor40is electrically connected to provide an object sensing input signal I1to the programmable amplifier50and high pass filter140of circuit42. Sensor40also provides an input signal I2to microprocessor60in response to a feedback signal F1from microprocessor60. This feedback loop between sensor40and microprocessor60gives the microprocessor the ability to monitor the operation (i.e., activation status or sensitivity) of the sensor40. In other words, signals I2and F1provide a self-diagnostic feedback loop between the sensor40and the microprocessor60, thereby providing the microprocessor60with the capability to monitor the signal levels of sensor40and to determine fault conditions for the input transducer of sensor40and other input sub-systems in conjunction with the current state of the harvester1(i.e., whether the reel assembly running/reel assembly is or is not running).

It is known by anyone reasonably knowledgeable in the art that very large stones produce vibration signals from a sensor40that are significantly lower in frequency than those produced by medium and smaller stones. In order to prevent interference by the signal of the very large stones with the signal of smaller stones, the signals of sensors40are processed through detection circuit42via two circuit or signal paths. Amplifier50, low frequency bandpass filter52, and voltage comparator54form one signal path to amplify, select, and qualify signals from sensors40that only correspond to the very largest of stones that can enter the feederhouse. Frequency bandpass filter52is set to reject signals produced from sensors40caused by medium and smaller size stones.

In like manner, amplifier150, high frequency bandpass filter152, and voltage comparator154form another path to amplify, select and qualify signals from sensors40that only correspond to medium and small stones. Vibrations in the plate of detector element36corresponding to very large stones and other low frequency crop and machine noises are rejected by high filter140so that only signals from sensors40corresponding to medium and small stones are passed on to bandpass filter152. A significant difference in this signal path is that high pass filter140is set to reject low frequency signals from the very large stones.

The signals from voltage comparators54and154are received by microprocessor60. The magnitude of amplification performed by amplifiers50and150on signal I1is controlled by microprocessor60, which sends a control signal C1and C2to control the degree to which amplifiers50and150amplifies, either positively or negatively, the magnitude of signal I1. In this manner, the microprocessor can adapt the amplifiers50and150to various internal and/or external influences on signal strength over a broader range of amplitudes.

Bandpass filters52and152are electrically connected to amplifiers50and150, respectively, and to comparators54and154, respectively, and to microprocessor60, and receive and filter signals I3and I7, respectively, to produce frequency filtered signals I4and I8, respectively, corresponding to a predetermined and preferred frequency bandwidth. In other words, high pass filter140and bandpass filter152generally filter out low frequency signals such as would be generated by soft organic crop material and very large stones passing through feederhouse21but transmit high frequency signals such as would be generated by medium and small hard objects or stones to be separated from the desired crop matter. Similarly, bandpass filter52accepts signals produced by the very largest stones and rejects signals produced by the smaller and medium size stones. In one preferred embodiment, bandwidth filters52and152are each a hardware-fixed bandwidth filter because such filters are relatively inexpensive.

In an alternative preferred embodiment, bandwidth filters52and152can be variable bandwidth filters that are electrically connected to receive input control signals directly from microprocessor60. In this case, the frequency bandwidths filtered by bandwidth filters52and152, respectively, are controlled by microprocessor60, which sends the input control signals to set the bandwidths filtered by filters52and152; therefore, filters52and152would be tunable by microprocessor60to adapt to varying internal and/or external influences on signal spectral content, theoretically improving the signal-to-noise ratio. In practice, however, it has been found that using an inexpensive fixed bandwidth filter provides a suitable degree of bandwidth filtering when used as bandwidth filters52and152and that utilizing the more expensive variable bandwidth filters do not significantly improve the operation of the hard object detector35.

Variable threshold comparators54and154are electrically connected to filters52and152, respectively, and to a pulse rejection network of microprocessor60.

Comparator54receives signal I4from filter52and generates signal I5only when the magnitude of signal I4exceeds a minimum threshold amplitude. Comparator54also receives a control signal C3from microprocessor60, which sets the voltage value of the minimum threshold amplitude. In this manner, microprocessor60provides comparator54with the ability to adapt to varying internal and/or external influences on signal strength.

In like manner, comparator154receives signal I8from filter152and generates signal I9only when the magnitude of signal I8exceeds a minimum threshold amplitude. Comparator154also receives a control signal C4from microprocessor60, which sets the voltage value of the minimum threshold amplitude. In this manner, microprocessor60provides comparator154with the ability to adapt to various internal and/or external influences on signal strength.

Microprocessor60is electrically connected to comparators54and154and receives signal I5and I9from comparators54and154respectively. More specifically, microprocessor60includes a pulse rejection network that receives signals I5and I9and generates an internal signal when the pulse trains of signals I5and I9fall within a specified bandwidth frequency. Generally, the pulse rejection network includes a calculation circuit for calculating the frequency of the pulse train of signals I5and I9, then this calculated frequency is inputted into a fixed bandpass filter that is also a part of the pulse rejection network of microprocessor60. In this manner, the pulse rejection network excludes “glitches,” that is, spurious signals failing to meet a specified pulse train frequency requirement, thereby minimizing false detections.

When the pulse rejection network generates the internal signal, microprocessor60subsequently utilizes the internal signal to generate activating signal A1that is transmitted from the microprocessor to activate a solenoid44sof hard object removal mechanism44that is electrically connected to microprocessor60. As will be appreciated by one skilled in the art, the internal signal ultimately generated by the pulse rejection network is the product of amplifying, frequency bandwidth filtering, threshold amplitude comparing, and pulse train frequency exclusion of initial signal I1. As will also be appreciated by one skilled in the art, microprocessor60can be preprogrammed to generate control signals C1, C2, C3and C4, and feedback signal F1, or the microprocessor can be operationally connected to receive signals from a control panel80preferably located in cab2for operator11to manipulate so that the operator has the ability to adjust the operation of sensor40and circuit42.

Preferably, hard object removal mechanism44is broadly conceived to include any electromechanical mechanism for removing the hard objects from the flow of crop material and is not limited to any one particular mechanism. One example of a suitable hard object removal system for removing the hard objects from the crop material flow is disclosed in U.S. Pat. No. 6,298,641 B1 to Digman et al., which is incorporated herein by reference in its entirety. In this specific embodiment of the present invention, the hard object removal mechanism44includes an aperture in the floor of the housing of elevator21.

The flow of cut crop material passes over this aperture and remains in the elevator21because a trap door covers the aperture, thereby substantially blocking the aperture and preventing the flow of cut crop material from passing out of the elevator through the aperture and onto the ground. A solenoid44soperated by the microprocessor60is activated whenever a foreign object is detected in the flow of cut crop material by the detection circuit42, which generates a solenoid activating output signal A1. The solenoid is operationally connected to activate a door opening mechanism that subsequently opens the trap door in response to the solenoid activating output signal.

Once the trap door is open, the aperture is no longer covered and gravity causes the crop material flow to exit the elevator21through the aperture. In addition, a sled can be used to help divert the crop flow towards the aperture. In this manner, those portions of the cut crop material flow containing the undesirable hard object or objects are selectively discharged (removed) to the ground. The trap door remains open only for a brief predetermined time period before the solenoid44sis deactivated by the microprocessor60and a door closing mechanism, such as a door closing cable and latch, automatically closes the trap door. It is stressed, however, that the present invention can be practiced using other electromechanical mechanisms for removing hard objects from the flow of crop material.

Having fully described the apparatus in accordance with the present invention, the method for detecting and removing hard objects, such as stones and the like, from a cut crop material in accordance with the present invention will be described.FIGS. 2 through 4outline important aspects the method of the present invention. First, a cut crop material that includes foreign hard objects in addition to cut crop matter is provided when the header12is activated to cut crops, as denoted by block82inFIG. 3. Second, sensors40sense the excitations generated by the passage of the cut crop material and the foreign hard objects over the plate of detector element36and generate signals representative thereof, as denoted at block84inFIG. 3. As mentioned above and as illustrated inFIG. 4, more than one sensor40can be used, and the signals outputted therefrom can be summed, as indicated at summing point43inFIG. 4. Third, the signal is outputted along the two signal paths, including a first signal path so as to be processed to reject frequencies below a first frequency using a high pass filter140(FIGS. 2 and 4), as denoted at block86inFIG. 3, then to be amplified by amplifier150(FIGS. 2 and 4), as denoted at block88inFIG. 3, and a second signal path so as to be amplified by amplifier50(FIGS. 2 and 4), as denoted at block90inFIG. 3, wherein the magnitudes of amplification are controlled by microprocessor60. A suitable value for the first frequency can be, for instance, about 2 kHz.

Next, the amplified signals are processed by bandwidth filters52and152(FIGS. 2 and 4), as denoted at blocks92and94inFIG. 3, to filter the bandwidths of the amplified signals to generate first and second bandwidth filtered signals, respectively, wherein optionally microprocessor60controls the frequency ranges of the filtered bandwidths. A suitable center frequency for the first bandwidth filtered signal can be, for instance, a frequency of about 5 kHz, and a suitable center frequency for the second bandwidth filtered signal can be about 1 kHz, as illustrated inFIG. 4. The bandwidth filtered signals are now processed by variable voltage threshold comparators54and154(FIG. 2), as denoted at blocks96and98inFIGS. 3 and 4, to generate amplitude thresholded signals when the respective bandwidth filtered signals exceed a minimum threshold amplitude, wherein microprocessor60controls the value of the minimum threshold voltage amplitude. Signals below the threshold minimum amplitudes are discarded, as denoted at block112inFIG. 4.

Now, the amplitude thresholded signals are each processed by a pulse rejection network of the microprocessor60to generate an internal signal only when the amplitude thresholded signal has a pulse train frequency that falls within a specified bandwidth frequency value, thereby eliminating noise signals, as denoted at blocks100and102inFIG. 3. The last step is determining that a hard object is present based upon the internal signal, which is generally performed by microprocessor60, then removing the hard object using a hard object removal mechanism44to produce a cut crop material that is essentially cut crop matter only and contains no hard foreign objects, as denoted at blocks104and106inFIG. 3. In this step, microprocessor60determines that a hard object is present based upon the internal signal from the pulse rejection network and transmits an activation signal to a solenoid44sof removal mechanism44(FIG. 2), thereby setting the removal mechanism44into action to remove the hard object. This is effected by opening the stone trap door, as denoted at block108inFIG. 4. Additionally, a stone detected message can be sent via the CAN (controller area network) or other suitable conductive path, to alert operator11, as denoted at block110inFIG. 4.

As will be appreciated by one skilled in the art, the sequence of steps in the method for detecting and removing hard objects from a cut crop in accordance with the present invention is not limited to the particular listed step sequence. Plainly, the first and last steps must remain as the first and last steps of the method; however, some steps such as the bandwidth filtering step and the amplitude thresholding step can be interchanged without departing from the scope and spirit of the method.

While the present invention has been described with reference to certain preferred embodiments, one of ordinary skill in the art will recognize that additions, deletions, substitutions, modifications and improvements can be made while remaining within the spirit and scope of the present invention as defined by the appended claims.