BACKGROUND ART The harvesting of lettuce has been a manual operation. A worker walks through a field of lettuce selecting a ripe lettuce head for harvesting. The worker <BR> <BR> then bends over to sever the compact portion of the lettuce head (i. e. , with as few of the looser wrapper leaves as possible) from the ground, and then stands up and cores the lettuce with a stainless steel tube ("the corer"). The worker removes the waste wrapper leaves and places the finished head on a conveyor belt for subsequent washing and storing.

This method of harvesting of lettuce has is its drawbacks and disadvantages. For example, the number of workers to harvest a typical lettuce field is large. Moreover, this particular method of harvesting lettuce being a manual procedure, the farmer may incur human resource costs in attempting to hire and employ harvesters.

Machines have been used to harvest lettuce. For example, U. S. Pat. No.

3,731, 477 entitled"Harvester for Headed Vegetables" ("the'477 patent"). The '477 patent discloses a high speed lettuce harvesting machine comprising a vehicle adapted to move along vegetable rows to be harvested, a pair of vegetable head- engaging sensing arms mounted on the vehicle, a plurality of sensor belts

mounted on the arms, the sensor belts being adapted to be deflected by the circumference of the vegetable head to guide and actuate a cutting blade toward the stem of the vegetable head so as to sever only fully grown heads and to transport them to a conveyor.

In U. S. Pat. No. 4,094, 238, there is provided a lettuce harvester having a positive means for engaging the stems of lettuce to be trimmed whereby the trim cut is caused to take place at right angles to the stem, and the lettuce is left ready for packaging.

The Lenker patent U. S. Pat. No. 4,136, 509 discloses an apparatus for harvesting vegetable heads. A sensing means including a pair of parallel, laterally movable, head-engaging units, which are counter-rotated, is fixed to a frame. A cutting means is mounted on the frame and is responsive to the sensing means.

The cutting means includes a horizontal knife blade rotatable 180 degree for each head cut. The severed head is removed from the cutting area by a pair of counter- rotating lifter belts.

Although the above-mentioned patents describe an efficient method of harvesting vegetables, they do not perform all the tasks of the typical harvesters.

For example, these patents do not describe where the vegetable heads being cored in order to minimize handling. As a result, the farmer is still required to hire workers to complete the required tasks.

SUMMARY One embodiment pertains to a method of harvesting lettuce. The method includes providing a movable frame with a plurality of gripper arms and positioning a pair of gripper arms to engage a lettuce head. The method also

includes scanning the lettuce head to detect the position and size of a core of the lettuce head and separating the core from the lettuce head. The method further includes conveying the cored lettuce head for storage.

Another embodiment relates to a system for harvesting lettuce. The system includes a plurality of members, where a pair of members is configured to grip a lettuce head. The system also includes a frame configured to connect the plurality of members so to rotate the plurality members in a substantially circumferential manner around the frame and an imager configured to scan the lettuce head. The system further includes a cutter configured to remove the core of the lettuce head, where the pair of members is configured to grip the lettuce head and position the lettuce head for the imager to scan the lettuce head to determine the core of the lettuce head for removal by the cutter.

Yet another embodiment pertains to an apparatus for harvesting. The apparatus includes means for providing a plurality of gripper arms and means for positioning a pair of gripper arms to engage a lettuce head. The apparatus also includes means for scanning the lettuce head to detect the position and size of a core of the lettuce head and means for separating the core from the lettuce head.

The apparatus further includes means for conveying the cored lettuce head for storage.

BRIEF DESCRIPTION OF THE DRAWINGS Various features of the embodiments may be more fully appreciated as the same become better understood with reference to the following detailed description of the embodiments when considered in connection with the accompanying figures, in which:

Figure 1 illustrates a cross-section of a lettuce furrow supporting two heads of lettuce; Figure 2 is a flow chart illustrating a process for coring and harvesting lettuce heads according to an embodiment of the invention; Figure 3 is a schematic cross-section of the two lettuce heads after the severing operation from the cores, respectively; Figure 4 illustrates a lettuce harvester moving in a direction indicated by the arrow in a field of lettuce plants; Figure 5 is a schematic diagram of the harvester, with the labels shown describing the stages of operation in the harvesting process; Figure 5A shows additional detail of a lower portion of the harvester; Figure 5B is an end view of the harvester as it moves through the field harvesting lettuce; Figure 6 is an expanded view of one portion of the harvester during operation; Figures 6A-6D illustrate in storyboard fashion the progress of the harvester relative to lettuce heads A-G, and represents a sectional view taken on an interior plane of the harvester; Figure 7 illustrates the operation of one embodiment of gripper arms ; Figures 8A-8B illustrate an exemplary mechanism for rotating the grippers to grip lettuce heads; Figure 9 illustrates an embodiment wherein the imaging section includes a CT scanning apparatus under control of the control center;

Figure 10 illustrates an embodiment wherein the imaging section includes a reflectance scanning apparatus wherein the emitted signals are electromagnetic or acoustic signals; Figure I OA schematically illustrates both a head with a substantially symmetrically developed core (looking"into"the lettuce head, i. e. at an image of a lettuce head) and a head with an asymmetrically developed core; Figure 11 illustrates a generalized imaging mechanism configured to use reflected waves; Figure 12 illustrates how a dielectric scanner may be coupled to the grippers, which in this embodiment may be electrically conductive; Figure 12A shows an alternative to the embodiment of Figure 12; Figure 13 shows a water knife (or water jet); Figures 14A and 14B illustrate a mechanical cutting mechanism, in this embodiment using a narrow rod-shaped or flat-bladed cutter; Figures 15A and 15B illustrate a cutting mechanism using a curved blade which is brought into contact with a point on the lettuce head as determined by the imaging mechanism; Figures 16A-16C illustrate a multiblade cutting mechanism. The number of blades 1600 may be two, three, four or more; Figures 17A-17C illustrate another multiblade cutting mechanism, including blades with hinges; Figures 18A-18C illustrate how the cutting mechanism 1700 can be used to lift the lettuce head from the ground;

Figures 19A-19D are sectional views similar to Figures 6A-6D; and Figure 20 illustrates a mechanism for conveying lettuce heads from a first conveyor to a second conveyor.

DETAILED DESCRIPTION OF EMBODIMENTS For simplicity and illustrative purposes, the principles of the present invention are described by referring mainly to exemplary embodiments thereof.

However, one of ordinary skill in the art would readily recognize that the same principles are equally applicable to, and can be implemented in, all types of network systems, and that any such variations do not depart from the true spirit and scope of the present invention. Moreover, in the following detailed description, references are made to the accompanying figures, which illustrate specific embodiments. Electrical, mechanical, logical and structural changes may be made to the embodiments without departing from the spirit and scope of the present invention. The following detailed description is, therefore, not to be taken in a limiting sense and the scope of the present invention is defined by the appended claims and their equivalents.

The present invention relates to an integrated system for the harvesting, coring, cleaning, inspection and storing of lettuce, cabbage and other field crops.

For the purpose of discussing the features of the invention, the example of harvesting iceberg lettuce will be used, but it will be understood that the invention may be implemented with appropriate modifications for use with a wide variety of crops.

Figure 1 illustrates a cross-section of a lettuce furrow supporting two heads of lettuce. One lettuce plant 10 includes a core 20 extending into a head 30,

the core 20 having a root region 40 extending below the surface of the ground 50.

While the lettuce 10 is relatively symmetrical and its core 20 is illustrated as growing substantially vertically and central to the lettuce head 30, a common shape for a lettuce head is as shown for lettuce plant 60, which has a core 70 nonperpendicular to ground surface 50. This can lead to a position for head 80 being offset from the core 70 relative to the ground (and offset relative to the seed line), i. e. growing at a position other than directly above the core 70. In addition, or alternatively, the core 70 may not be symmetrical within the head 80, i. e. may extend more to one side or another. The lettuce plants 10 and 60 also include "wrapper"leaves 90, which are typically undesirable to harvest.

From a top view of the lettuce heads, Figure 10A schematically illustrates both a head 1010 with a substantially symmetrically developed core 1020 (looking"into"the lettuce head, i. e. at an image of a lettuce head) and a head 1030 with an asymmetrically developed core 1040.

The lettuce cores are typically removed at the time of harvest (referred to as"cored-in-field", or CIF, lettuce), for efficiency and to minimize handling of the lettuce. This is conventionally a manual operation wherein a worker bends over to sever the compact portion of the lettuce head (i. e. with as few of the looser wrapper leaves as possible) from the ground, and then stands up and cores the lettuce with a sharpened stainless steel tube (the"corer"). He then removes the waste wrapper leaves, and places the finished head on a conveyor belt for subsequent washing and storing.

The present invention uses an automated coring apparatus and operation, e. g. using a water knife such as the Digital Control"Scancut"water jet cutting system available from Digital Control, Montrabe, France (see http ://www. digital- control. fr/Anglais/Contacts. htm and http://www. digital- control. fr/Anglais/TheEquipments/SCANCUTUK. htm) or through DSL Food <BR> <BR> Machinery Ltd of Burton on Trent, Staffordshire, England (see http : //www. dsl- limited. com/waterjet cutting. htm). One feature of the present invention that represents a departure from prior practices is to remove the lettuce head from the core simultaneously with severing the head from the ground-that is, the removal of the head from the core constitutes the head severing procedure, effectively in one operation.

An implementation of one embodiment of the invention includes gripping a lettuce head and locating undesirable material (such as the core) within the head by a procedure such as CAT or CT (computer-aided tomography or computer tomography) scanning, dielectric pulsing, radar, transmission X-rays, reflectance X-rays, ultrasound, very low frequency sound, and/or sonar. The heads may be positioned for cutting using the aid of CT scan equipment or with other imaging techniques referred to herein or otherwise known. CT scans can image within microseconds, and therefore are suitably fast for an automated lettuce harvesting operation.

Using an automated coring procedure, the amount of lettuce wasted due to inaccurate cuts-which can remove good lettuce leaves along with the core- indicates that each lettuce head should be positioned optimally to allow the knife

to cut as close to the core as feasible without leaving any pieces of the core inside the head. Thus, a lettuce with an offset head or core may need greater manipulation and positioning than a symmetrical plant such as lettuce 10.

In order to detect the position of the core within the lettuce head, different technologies will have varying advantages. Electrical techniques may include measuring the dielectric properties of the lettuce head by effectively placing it in series in an electrical circuit including the ground. X-ray techniques may include a transmission process as mentioned above and/or a reflectance process executed by positioning multiple sensors around a lettuce head to receive X-rays that are transmitted through the lettuce head and reflected back to the sensors. CAT scans have an advantage that they readily provide three-dimensional images of the interior of the lettuce head.

An X-ray reflectance process may be more suitable for a top-down view of the lettuce heads, with the X-rays (or other suitable wavelengths of electromagnetic radiation) reflecting from the ground, while a CT scan technique may be more suitable for imaging from the sides of the lettuce heads, placing the CT scanning equipment around or partly enclosing each lettuce head for imaging.

A dielectric technique can involve applying a voltage to one portion of the lettuce head an measuring the dielectric (or alternatively, conductive) properties of the head. This can involve measuring, e. g. , dielectric properties from more than one point on the lettuce head, and by probing appropriately determining the position and shape of the core, which is a substantially continuous conductive

substance, and thus has different electrical properties from the relatively more loosely arranged leaf structure of the head.

Radar can be used for imaging the cores by determining the time and intensity of reflected radar signals transmitted into the lettuce heads. Other scanning and electromagnetic imaging technologies may be suitable.

Figure 2 is a flow chart illustrating a process for coring and harvesting lettuce heads according to the invention. As mentioned above, a head is first gripped for position stability and for imaging. The selected scanning operation is carried out to determine the position and size of the core. The head is then severed from the core, optionally leaving the core in the ground, and lifted from the core and the wrapper leaves.

The head is then washed, particularly the region where the core was removed, which being adjacent the ground is more likely to carry dirt and which typically expresses latex due the cutting operation. The head is then examined, either with automatic imaging equipment or by the human eye (with or without the use of video apparatus to a remote location). If the head is acceptable, it is conveyed to a primary use container or bulk bin for transport from the growing location, and if not then it is reworked until successful. If the reworking cannot or does not result in an acceptable lettuce head, the head is rejected.

Figure 3 is a schematic cross-section of the two lettuce heads 30 and 80 after the severing operation from the cores 20 and 70, respectively. Wrapper leaves 90 have for the most part been left on the ground.

Figure 4 illustrates a lettuce harvester 400 moving in a direction indicated by the arrow 410 in a field 420 of lettuce plants 430. Harvested lettuce heads 440 may be transported by conveyor belt 450 to a bin or mobile container such as transporter 460 for transport to a storage or other facility. Conveyor 470 may carry heads 445 that need reworking to a different portion of the transporter 460 or to a different container, e. g. for further removal of dirt.

Figure 5 is a schematic diagram of the harvester 400, with the labels shown describing the stages of operation in the harvesting process.

Figure 5A shows additional detail of a lower portion of the harvester 400, in an embodiment in which gripping arms, cables or the like 500 are arranged in a fashion as shown, and are slidably positioned so that they can move in a conveyor belt fashion to engage and grip lettuce heads as the harvester moves along. A drive mechanism (not separately shown) for the grippers 500 controls the speed of the rotational movement, so that at any given time the grippers may be effectively stationary relative to the ground, moving at the speed of the harvester relative to ground, or moving at a different speed, determined by the need at that time of the harvester in gripping, coring and retrieving lettuce heads.

The imaging of the cores is carried out at the imaging stage or section 510 indicated in Figure 5A, and this section may be provided with appropriate shielding 520 to protect workers from radiation from the imaging operation.

Once the heads are severed at the cutting section 530, they are <BR> <BR> automatically washed by nozzles 540 and inspected via, e. g. , a video camera 550.

The inspection may be carried out by automated computer-based imaging logic

("logic"including software, hardware, and/or firmware as appropriate) and/or with the help of a human. For instance, an automated inspection procedure can be carried out by detecting brown regions (or regions with other predetermined colors and/or textures) in the image, and if such regions constitute more than some predetermined percentage (e. g. greater than 1%, 5% or some other amount) of the image, it will be assumed that the head is too dirty, decayed, etc. for harvest, and it must be reworked (in this case, rewashed and/or the decay removed) before retrieval for storage. Other, more complex imaging logic and decision-making operations may be used.

In one embodiment, any amount of detected decay (bacterial soft rot, <BR> <BR> ground rot, etc. ) may be used as a basis for rejection of a lettuce head, while dirt exceeding some predetermined amount may be used as a basis for a reworking.

Absent either of these two faults or other bases for rejection or reworking, the lettuce head is accepted.

Control logic (not separately shown), which may be logic in the broad sense defined above and may in particular include a processor-based control system, can be provided to coordinate the inspection and rework/acceptance procedure. If a given head is accepted, an accept release 560 is activated at the correct time for that head (i. e. when it reaches conveyor 450) to convey the head to the bin for storage. If the head is determined to need reworking, the control logic activates the rework release mechanism 570 at the appropriate time to release it onto the conveyor 470 for reworking.

Figure 5B is an end view of the harvester 400 as it moves through the field harvesting lettuce.

Figure 6 is an expanded view of one portion of the harvester during operation. Figures 6A-6D illustrate in storyboard fashion the progress of the harvester relative to lettuce heads A-G, and represents a sectional view taken on an interior plane of the harvester (note that the grippers are not shown as occluding the view of the lettuce heads A-G). The entire apparatus may operate under the control of an automated control center with control logic (not separately <BR> <BR> shown), whose implementation (processors, programming, etc. ) is straightforward giving the teachings of the present disclosure. The control center may or may not include the control system for inspection, washing and acceptance/reworking as described above; that is, the harvesting control center and inspection/washing control system may constitute a single system, separate systems or modules under common control, or independently operating systems.

In Figure 6A, head B is just beginning to be gripped, while head C is being imaged by an imaging mechanism 600. Head D has already been imaged and is ready for cutting. Head E is undergoing the beginning of a cutting operation by a <BR> <BR> cutting mechanism (e. g. the water knife mentioned above, a metal knife, etc. ) 610, based upon information determined at the image stage.

In Figure 6B, head C continues to be imaged. Note that the imager 600 in this embodiment is caused by the control center (which tracks ground speed of the harvester and position/movement of the lettuce heads) to move rearward relative to the harvester 400 so as to track the lettuce head C, which at this point is

stationary relative to ground (since it has not yet been cut). Similarly, the control center causes cutting mechanism 610 to move rearward to track the position of head E, to perform an accurate cut before retrieving the head. This tracking of the imaging and cutting mechanisms continues in Figure 6C, and in Figure 6D the imaging and tracking mechanisms move forward relative to the harvester (faster relative to ground than the harvester) to be in correct position for the imaging of head B and the cutting of head D, respectively.

The imaging and cutting mechanisms need not track simultaneously, and in particular may operate independently and/or generally out of phase with one another, or may be designed to operate in phase as illustrated in the example of Figures 6A-6D. In general, having independently tracking imaging and cutting mechanisms will accommodate a broader variation in spacing of the lettuce heads along the ground.

The images of a given lettuce head are provided as digital information to the control center, which manipulates the grippers to position and rotate the head to allow the cutting mechanism to make an optimal cut to maximize core removal and minimize waste. In addition, the cutting mechanism can be manipulated to tailor its cut to the core size and position, e. g. to make a smaller cut for small cores, and to change the angles of the cutting blade or water stream even as the cutting operation proceeds to accommodate the shape of the core.

Figure 7 illustrates the operation of one embodiment of gripper arms 700- 730, which pivot about pivot points P under control of the control center to grip the lettuce heads as shown when they are encountered in the field.

Figures 8A-8B illustrate an exemplary mechanism for rotating the grippers to grip lettuce heads. In Figure 8A, stationary (relative to the body of the harvester) pads 800 are encountered by upper ends of the grippers, causing them (due to their shape and location of pivot points) to swing outwards as shown to surround an upcoming lettuce head. In Figure 8B, actuators 810 (which may, e. g., be solenoid-driven) can cause the grips to open to release a lettuce head as shown, or to prepare to grip a lettuce head. The grippers may be spring-biased (or otherwise biased) in the narrower, closed position shown in dotted fashion, so that they automatically return to this position when the actuators release, or they may be constantly under control of positioners (not shown) which are in turn under control of the control center.

Figure 9 illustrates an embodiment wherein the imaging section includes a CT scanning apparatus 900 (and 910) under control of the control center, which transmits a signal (indicated by the dotted lines) through each lettuce head as it is encountered. The CT signals are generated and/or received in multiple directions to generate two-and/or three-dimensional images as needed. Various wavelengths of electromagnetic radiation, including but not limited to X-rays, may be used, and acoustic signals may alternatively or additionally be used for imaging.

Figure 10 illustrates an embodiment wherein the imaging section includes a reflectance scanning apparatus wherein the emitted signals are electromagnetic or acoustic signals. In the case of electromagnetic signals, X-ray, radar or other appropriate signals may be used. The signals (indicated in dotted fashion) are

transmitted through the lettuce heads, reflect from a region at, near or underneath the ground, and are detected at transceivers 1000 for transmission to and processing by the control center.

Figure 10A illustrates two-dimensional images (or"slices"of three- dimensional images) generated by any suitable imaging mechanism of the invention, in conjunction with processing by the control center.

Figure 11 illustrates a generalized imaging mechanism 1100 configured to use reflected waves (electromagnetic and/or acoustic, as with each of the embodiments herein as applicable). Again, it may in this example be appropriate to use radar or X-rays, and two-or three-dimensional images may be generated.

Figure 12 illustrates how a dielectric scanner may be coupled to the grippers, which in this embodiment may be electrically conductive. The scanner is grounded, e. g. via a wheel or other device in contact with the ground. Electrical signals are transmitted via the scanner through the lettuce head, e. g. as pulses, alternating polarity signals or continuous signals. The scanner measures responses of the lettuce head and transmits the detected information to the control center for processing as two-or three-dimensional images.

Figure 12A shows an alternative to the embodiment of Figure 12, wherein a single dielectric scanner may be used to form images of multiple lettuce heads.

Figure 13 shows a water knife (or water jet) 1300, which pivots as indicated to spray its cutting water stream in a conical or other appropriate shape to cut the lettuce heads from their cores with minimal waste of otherwise usable lettuce material.

Figures 14A and 14B illustrate a mechanical cutting mechanism, in this embodiment using a narrow rod-shaped or flat-bladed cutter 1410, which is caused to penetrate the lettuce head and rotate to form a conical cut. The cutter 1410 may be flat, oval, round or some other shape in cross-section, with varying cutting shapes resulting from each, and may be formed from suitable metal (s), plastics, or other materials.

Figures 15A and 15B illustrate a cutting mechanism 1500 using a curved blade 1510 which is brought into contact with a point on the lettuce head as determined by the imaging mechanism, and the blade 1510 is then caused to penetrate the head, followed by a rotation as shown in Figure 15B. Due to the blade's arcuate shape, a region above the core where material might otherwise be removed is instead retained, thus increasing the usable amount of lettuce head retrieved.

Figures 16A-16C illustrate a multiblade cutting mechanism. The number of blades 1600 may be two, three, four or more. The blades are thrust into the lettuce head in similar fashion to the cutting mechanism of Figures 14A-14B, and may penetrate either simultaneously or at different times. The blades are rotated through a sufficient arc to form a complete cut, in the aggregate.

Figures 17A-17C illustrate another multiblade cutting mechanism 1700, including blades 1710 with hinges 1720, which are thrust through a conical guide 1730 into the lettuce head. In this embodiment, twelve blades are used, though more or fewer may be used. A plunge cut is made as illustrated in Figure 17B,

and then the blades 1710 are withdrawn, rotated, and again plunged into the lettuce head, sufficient times to sever the head from the core.

Figures 18A-18C illustrate how the cutting mechanism 1700 can be used to lift the lettuce head from the ground. The grippers are released as discussed above, and with the blades 1710 in an extended position the cutting mechanism is lifted, carrying the lettuce head with it. The blades 1710 are retracted at the appropriate time to release the lettuce head, which may be retained above the ground by the grippers (see Figure 18C) for transport to the washing stage, as in the description above.

Figures 19A-19D are sectional views similar to Figures 6A-6D, except that in this embodiment the lettuce heads are lifted at the an earlier point, as shown by head E in Figures 19C-19D, which may be useful in certain terrain or for certain types of crops.

Figure 20 illustrates a mechanism for conveying lettuce heads from a first conveyor to a second conveyor.

Using the above-described embodiments of the invention, lettuce heads are gripped, imaged, positioned as appropriate, and efficiently cut away from their cores, leaving the cores in the ground for mulching or retrieval as cattle feed or the like. The washing and inspection stages follow, and the heads are then accepted for harvest and storage or reworked. Human intervention may be used as desired for reworked heads. In this manner, most of the human labor usually needed for lettuce or other crop harvesting can be eliminated, with consistent and economical results.

While the invention has been described with reference to the exemplary embodiments thereof, those skilled in the art will be able to make various modifications to the described embodiments without departing from the true spirit and scope. The terms and descriptions used herein are set forth by way of illustration only and are not meant as limitations. In particular, although the method has been described by examples, the steps of the method may be performed in a different order than illustrated or simultaneously. Those skilled in the art will recognize that these and other variations are possible within the spirit and scope as defined in the following claims and their equivalents.