VEGETABLES

DETECTOR The present invention relates to a method and a detector for processing relatively hard and relatively round food products, for example, but not exclusively, eggs, fruits, and vegetables.

In particular, this technology finds application in determining whether eggs are broken or not, for instance upon their supply from laying hen coops to packaging machines, so that with great advantage the broken eggs, also called fractured eggs, can be timely removed from the supply stream.

For a very long time now, eggs have been tested for fracture prior to sale. Initially, eggs were tested for fracture manually by illuminating a broad stream of eggs on a roller conveyor from below, and thus exposing them for examination. Unlike large and immediately recognizable fractures and dents, in particular fracture lines of poorly visible fractures or eggshell cracks are thus visualized as dark, generally frayed, lines contrasting against a light background. This manner of testing is called candling and, though reliable with quite reasonable results, is highly strenuous for operators performing this task manually. Ever larger machines with correspondingly larger egg streams have made this manner of operation virtually unfeasible. Since the eighties, in the development and marketing of high-capacity sorting machines, testing for fracture has been automated, whereby acoustic detection instead of optical detection is performed in nearly all cases.

Examples of this are described in, inter alia, EP738888, EP 1238582, and WO2012060704, in which also reference is made to older publications. The general line in these publications is: (i) detecting and interpreting signals that upon tapping of the egg come from the tapper itself, and

(ii) detecting and interpreting signals that upon tapping come from the egg itself.

Furthermore, methodologies have been presented that make the eggshell quahty measurable, where in particular the strength and the stiffness of the eggshell are used as a criterion. Such methods are all non-destructive, for example as described in NL1018940.

In addition, for a very long time now, in the processing of batches of eggs, for each batch a fracture test is performed to determine eggshell strength, as described in, for example, P.W. Voisey, J.R. Hunt, Relationship between Applied Force, Deformation of Egg Shells and Fracture Force, J. agric.

Engng Res. (1967) 12 (1) 1-4. For a few eggs of each consecutive batch, compression force and extent of compression are measured until the eggs fracture and thus a fracture force value is obtained. It is a measure for the shell strength and hence for the quality of an egg, more particularly a measure for the quality of such a batch. Summarizing, the above testing methods are respectively intended:

either for fracture detection on high-capacity sorting machines, involving non- destructive handling,

or for measuring shell strengths only on samples, whereby an egg, upon such a determination of the fracture force value, fractures.

Unlike in the above-outlined situations, it appears that the advanced acoustic detection is less suitable for determining fracture in eggs that come directly from laying hen coops. Daily practice in this situation involves large numbers of eggs of greatly diverse quality because the coops accommodate a great diversity of poultry, viz. hens that are very young, or are nearly molting, or are very old, or of yet another qualification.

It has appeared that in such circumstances, fracture percentage can be relatively high and that the fractures, unlike those mentioned above, are comparatively large. In many cases, the eggshell is dented. Experience has shown that, unlike in the case of sorting eggs which have initially been carefully tested manually and then packaged, with fracture percentages of e.g. about 2%, in the case of egg supply from the coops fracture percentages as high as 20% may be involved.

The above described detectors for acoustic detection during the sorting process will not function properly in the case of such fractures and denting, either due to soiling that may occur or because the displacement of such a detector element is proportionally much greater in the case of such open fractures and dents than in the case of the relatively small fractures or eggshell cracks.

According to the present invention, however, it has been found that for the large fractures and dents mentioned, the above described technology applicable to samples can actually be utilized very well, the invention providing a method successively comprising,

- supporting the product on at least two surface locations,

- positioning the detector on an at least third surface location, whereby at least once the compression force (F) as a function of the compression distance (Δχ) is measured,

- determining the force constant k, and

- comparing the force constant k with a predetermined threshold value.

Positioning the detector here comprises in particular: compressing the product whereby an, egg-contacting, detector part (also called pressure force element or pressure body) travels an above-mentioned compression distance (Δχ) and exerts an associated (non- destructive) compression force (F) on the egg. The force constant k follows in particular from the Hooke's law: k=F/ Δχ wherein F is the compression force (N), Δχ is the associated path travelled (the compression distance) (m), and k is the force constant (N/m). The force constant k associated with a specific product can be determined from a single measurement, at a defined compression distance and associated compression force, or through a series of measurements (comprising at least two different compression distances and associated compression forces), which will be clear to the skilled person. In addition, for example, a parameter derived from the force constant can be determined, in particular when the force constant is determined at least twice per product (by two different measurements). According to an aspect of the invention, measuring the force constant k, at least, exerting the compression force (F) at a defined compression distance (Δχ), is carried out on each product in such a manner that a still intact product remains intact (i.e. without breaking or otherwise permanently damaging the intact product). In particular, the intact product, after the determination of the force constant, can be processed further, intact. To this end, for instance, each time, a relatively small compression force and associated relatively small compression distance can be applied, in contrast to the above-mentioned known method whereby a batch of intact products is broken.

The relatively round products to be processed can for instance be

substantially egg-shaped, ovoid or spherical.

Through support of the product on at least two surface locations, in particular on a limited number of (for example, two) surface locations, the relatively round product can be supported in a stable manner while the measurement of the force constant is carried out. Each supporting location mentioned can for instance be provided by a respective supporting element, for example, a respective roller or hourglass-shaped roller. In particular, the detector is part of a system that also comprises a product conveyor, which conveyor is configured to provide the at least two supporting locations (for example, a roller conveyor). In that case, a detector part that applies a compression force can for instance be disposed above a transport surface of the conveyor. Such a detector part (i.e. pressure force element, pressure body) can for example comprise a plate or a plate-shaped element, at least, an element having a flat pressure surface facing the conveyor, that is movable over a compression distance for compressing the product.

Furthermore, the present invention comprises a detector for determining the force constant of relatively hard and relatively round food products, for example, but not exclusively, eggs, fruits, and vegetables, whereby the detector slightly compresses such a product in fixed position for a short period of time (over a compression distance Δχ) whereby a compression force (F) is measured with a controllable pressure body, the product being supported by carriers on at least two surface locations, and whereby with the detector, of the product, compression force as a function of compression distance is measured, with which at least the force constant thereof is determined. In particular, the detector is configured for carrying out a method according to the present invention.

With great advantage, this simple method can be utilized on large numbers of eggs and such a detector can be built in on a roller conveyor. This detection, unlike the above described batch detection, is not destructive and can be carried out on a continuous stream of eggs.

It has been found that in a suitable manner, especially for eggs from one and the same batch, it can be established with only a single measurement whether an egg is intact or fractured. In a further exemplary embodiment, the method according to the invention is characterized in that, of the products, the compression force as a function of the compression distance is measured at least twice for determining a derived parameter of the force constant k.

It has been found that measuring compression force and compression distance a few times in this manner shows clear differences in terms of being broken or not for all types of examined eggs because, unlike with intact eggs, the strict correlation according to Hooke's law is less accurately met. These deviations in the linear relationship can be advantageously used as a further criterion for distinguishing intact and fractured eggs.

The choice of the materials with which the pressure force is exerted is of great importance. Clearly, it must be possible on the one hand to measure this force upon application and at the same time to measure the thus obtained compression of e.g. an egg. Consequently, the detection is preferably so configured that when the egg or product to be examined is being supported, the product itself does not function as transmitter of the compression force. This means that the stiffnesses of supporting elements and pressure force element are preferably a few orders of magnitude greater than that of the product to be examined.

Further features and implementations, summarized hereinafter in the subclaims, and, more particularly, various details of preferred embodiments of the present invention, will be elucidated on the basis of a drawing, in which:

FIGURES 1A, B schematically show a situation according to the prior art; FIGURE 2 schematically shows a first exemplary embodiment according to the present invention, and

FIGURE 3 schematically shows a further elaboration of the first exemplary embodiment according to the present invention.

In the different FIGURES, the same reference signs and symbols stand for the same parts or notions.

In FIGURES 1A, B the earlier-described situation from the prior art is schematically shown, with 1A and IB being cross sections through an egg E along two main axes of the egg E (in approximation to be regarded as an ellipsoid), i.e., respectively, along the longitudinal axis or major axis (see FIG. 1A), which runs between the two ends of the egg, i.e., between the sharp end and the convex end, and along a short axis (FIG. IB). Logically, they are elevational views, facing in the direction of the short axis and facing in the direction of the major axis, respectively.

The (intact) egg E shown is clamped between two metal plates 1 and 2 while the relative position of these plates 1, 2 is adjustable and the force exerted therewith can be measured. Upon further compression, the egg will fracture at a certain point, the force then applied being the fracture force. This force value, according to the known method, is regarded as a measure for the eggshell quality of such an egg, and, when used as a sample test, as a quality value of a corresponding batch from which this egg originates.

The materials to be used will be such that the egg is actually pushed in (and eventually broken) by these plates. Their hardness or stiffness must be clearly greater than that of the egg to be tested. At least one order of magnitude (factor 10) has been found to be necessary to measure a reliable force value. In the literature, values for fracture measured are generally between 30 N and 40 N. In FIGURES 1A, IB the local pushing forces Fl, F2 are schematically represented. It will be clear to those skilled in the art that ideally, i.e., in the case where the push body or bodies (here: top and bottom) is/are much harder than the object under detection, these pushing forces are

approximately equal.

An aspect of the present invention (see hereinbelow) comprises a

measurement then concerning this force, and logically the total push-in, i.e. a compression distance, of this object, but then without breaking the object. The quotient of the thus obtained measured values for the force and this compression distance give the (static) force constant or spring constant of this object. Force and distance are measured in a non-destructive manner, at values for the force not greater than 10 N. In this technology, this constant is often called 'static stiffness' and denoted as kstatic-

In FIGURE 2, schematically, a first exemplary embodiment of a method and apparatus according to the invention is shown. The figure shows a method for determining with a detector 1 the force constant of relatively hard and relatively round food products, for example, eggs E. The method comprises supporting the product E in at least two surface locations, positioning the detector 1 in an at least third surface location, whereby at least once

(preferably at least twice) compression force is measured as a function of compression distance. From compression force and associated compression distance, force constant k is determined (Hooke's law). The force constant k can then be compared with a predetermined threshold value (of the force constant). Such a determination can for instance be carried out (in an automated manner) by a data processor C or the like. After the one measurement mentioned or after the measurements mentioned, where an intact product E remains, in particular, intact, the detector 1 can be brought to an initial position, in which it does not contact the product E, for further processing of the measured product E. The method can be carried out fast and efficiently, for example in a continuous or semi-continuous process. As follows from the above, in particular a relatively small compression force is applied, for example, a compression force that is not greater than 10 N.

More particularly, FIG. 2 shows a side view of an egg E, facing in the direction of the long axis thereof, with the egg E resting on rollers 3, 4, for example, hourglass-shaped rollers which are commonly used in this technical field. FIG. 2 shows three forces that are exerted on the egg E, viz., a pressure force F 10 by the detector (in this case pressure plate) 1, a first supporting force F30 by the first supporting roller 3 and a second supporting force F40 by the second supporting roller 4. The rollers 3, 4 can be part of an endless roller conveyor RT (schematically represented, in part), configured for conveying eggs E in a transport direction T, see FIG. 3 where this is worked out. In this example, the compression force F10 is directed substantially downward (in a direction X), at least, normal relative to a transport surface presented by the conveyor RT. In particular, the direction of the pressure force F 10 is at right angles relative to the long axis of the egg E (as in FIG. 2), and in this case also at right angles relative to the short axis of the egg E. As follows from the drawing, the detector part 1 which exerts the pressure force is configured to contact the relatively round product E at a point of compression, to which end the detector part 1 comprises in particular a flat compressing side facing the conveyor RT.

Here, too, it holds that for the materials to be selected, a comparable hardness is desirable so that the intended interplay of forces is obtained. Forces and distances can then be measured in the usual manner again, for example with a force meter la and a distance meter lb which are connected with the detector plate 1 (see also FIG. 3) and/or integrated in the detector plate 1 or implemented in a different manner. For an example of a detector with which such measurements can be carried out, reference is made to US5952589 in which it is described in detail how an object can be

compressed over small distances in an accurately controlled manner and the associated measurements are realized. The detector 1 may be implemented in different manners. In the example, the detector 1 comprises, for example, a rigid pressure element having a flat pressure surface facing the conveyor, movable over a compression distance to compress the product E. The detector 1 may be provided with a drive 2 coupled to the detector plate, for moving the detector plate in a compression direction X, over a compression distance as mentioned (and for moving the plate away again from the product after measuring). A force meter la as mentioned may be implemented in various manners, and, for example, may comprise a pressure sensor or piezoelectric element, may be part of the drive or in a different manner. A distance meter lb as mentioned may also be configured in different manners, and, for example, comprise an optical or acoustic sensor and/or be integrated with the drive or another part of the apparatus. The sensors mentioned, at least, force meter la and distance meter lb, may, for example, transmit measuring data to a data processor C as mentioned (see FIG. 3) for the purpose of processing of the measuring data and central determination of force constant k. Transfer of data can be done, for instance, via wired and/or wireless communication links (not shown), as will be clear to those skilled in the art.

In the view according to FIGURE 2, only a static situation is presented and no particulars are represented concerning any possible movements of the various parts. A distinction is made for the movement of the object, in this case the egg E shown, and the movement of the detector, the plate 1.

For the rollers 3, 4 with egg E, it may be said that for a roller conveyor RT which is mostly used for that purpose, it can hold: that the conveyor RT is stopped under the detector in each case and the center of gravity of the substantially symmetrical egg body is in a fixed position,

that either the rollers 3, 4 are driven and thereby rotate the egg E about the long axis, or the rollers 3, 4 do not rotate and so the egg E does not rotate about the long axis. For instance, it is preferred that the product E does not rotate when the product is being compressed by the detector to determine a k-value as mentioned. According to this invention, there are several ways of contacting the detector with such an object.

For instance, a descending movement may be made (in compression direction X), with the detector, for instance, fixedly disposed, while only the plate element 1 is moved downwards substantially vertically, perpendicular to the advancing movement of the object, to make contact. In an alternative implementation, the detector plate may, for instance, be fixedly disposed, while the product supporting means (in this case, egg-carrying rollers 3, 4) are moved towards the detector plate for the purpose of the compression of the product by the plate. A combination of these movements is also one of the options.

In a further example, the detector, or a part of the detector, moves over a relatively small path (in the conveyor transport direction T), moving along with an advancing movement of the conveyor RT. More particularly, the detector pivots, moving along and at the same time downwards, towards the egg, is then briefly located on the egg during compression, and then pivots, moving along, away from the egg again. In the interval between this measurement and the next, the above-mentioned initial position is taken up again to start a corresponding, next pivoting movement. All combinations mentioned hereinabove for the object and for the detector can be carried out. In all cases, preferably, a plurality of measurements per cycle (per product E) are carried out, while the cycle will preferably take a length of time between 0.1 and 1.0 seconds. Multiple types of measurement can be carried out.

With a single compression of an intact egg, the force constant k can already be measured because for eggs it is generally known that for such

measurements always the same taut linear relation applies. In the case of a broken egg (at least, an egg having at the least a fracture line or weakened line in the eggshell), this constant will only be a fraction thereof, typically less than half of it. Therefore, when measuring on a batch of such eggs, the differentiation intact versus broken can be made instantly. It will be clear to those skilled in the art that for intact eggs, the force constant is in the range of between 100 kN/m and 200 kN/m. Making such a distinction can be automated, for instance, by setting a threshold value of 100 kN/m. It is noted that the present detector is especially configured to exert a relatively small compression force on the products E. The relatively small compression force is then such that an intact product (for example, a product without fracture line in a product rind/shell) remains intact (i.e., only undergoes elastic deformation) and sustains no fracture due to the temporary compression. The same compression force is also applied to products to be possibly rejected that already have a crack or weakened site, which can lead to plastic deformation of such a product. Experiments have shown that the stiffness of an eggshell (at least the force constant k) of either an intact egg or an egg with a fracture or crack in the shell can be accurately determined in the above described manner.

Depending on the type of batch, such a value is even suitable to remove weak-shelled eggs from a stream. For the different measuring situations as already mentioned hereinabove, it is also possible to obtain further results other than just the force constant k. In the following, these results are called derived parameters and, because of the similar character of the type of measurement, will give a statistical picture of the physical behavior of such an egg body (or other product).

More particularly, this is, in measuring on the same egg body at several positions and with different values of force and compression, preferably the standard deviation. In measuring different values of force and compression each time at the same position of an egg body (or other product), then, on the basis of the measuring results, a correlation coefficient can be obtained, for example, the well known Pearson correlation coefficient (see the website en.wildpedia.org/wiki/Pearson_product-moment_correlation_coe fficient). A data processor C as mentioned may for instance be configured to calculate or estimate this correlation coefficient for a product E, using the measured data supplied by the sensors la, lb (concerning a series of measurements) concerning that product E.

When the Pearson correlation coefficient is applied, it appears to end up for intact eggs at a value of > 0.99, or, to put it differently, the stiffness of eggs is linear and behaves according to Hooke's law, and the static stiffness k _s tatic of an egg has a constant value.

For fractured eggs as described hereinabove, for the Pearson correlation coefficient, values are chosen generally < 0.95, with which, via a derived parameter, a further criterion is given for making a distinction between intact and fractured eggs.

The data processor C may for instance be configured to deliver an approval signal if it appears that a measured product meets predetermined criteria, for example, the data processor C has determined that the force constant k is within a predetermined approval range (for example, the range of 100 kN/m to 200 kN/m), and/or if data processor C has determined that the force constant k runs linearly, and/or if the data processor C has determined that the Pearson correlation coefficient > 0.99. Similarly, the data processor C may for instance be configured to deliver a rejection signal if it appears that a measured product meets other

predetermined criteria, for example, the data processor C has determined that the force constant k is within a predetermined rejection range (for example, k < 100 kN/m), and/or if data processor C has determined that the force constant k does not run linearly, and/or if the data processor C has determined that the Pearson correlation coefficient < 0.95.

In case the standard deviation is applied, the value 5 kN/m can be used as guide number. This value or one close to it can therefore be set as a threshold in characterizing and sorting.

With great advantage this robust method has been applied to large quantities of eggs that were conveyed on a roller conveyor. Preferably, the detector was applied, whilst moving along in the transport direction of the roller conveyor, onto eggs lying still thereon, whereby reliable results were obtained with great efficiency.

It will be clear to those skilled in the art that various modifications in the above-described method and the apparatus are possible within the scope of protection of the present patent application as defined by the claims. To be considered, for example, is a frame with detectors for testing eggs placed in, for example, a tray.

Further, for example, an apparatus may be provided for packaging eggs which are supplied with at least a single conveyor RT from laying hen coops, with a detector 1 for carrying out a method according to the invention, intended for characterizing the eggs and for sorting on the basis of fracture.