Method and apparatus for examining eggs

Abstract

This invention relates to a method and apparatus for examining eggs, in particular for determining eggshell characteristics of eggs, the method comprising, positioning the eggs to be examined, with a deformer, deforming a part of such an egg at least once, at least determining deformation contact time, and determining the shell stiffness and/or the eggshell strength of such an egg. Such a manner of detection can be suitably applied to sorting machines for eggs. With this methodology, in a short time, for a very large number of products, such as eggs in the present case, a quality parameter such as the strength and/or stiffness can be determined. With such determinations, in an advantageous manner, high requirements set in many fields of technology and industry can be met.

Claims

1. A method for examining eggs, in particular for determining eggshell characteristics of eggs, the method comprising, positioning the eggs to be examined, with a deformer, deforming a part of such an egg such that the deformer is in actual contact with the egg for a finite deformation contact time, determining deformation contact time, and determining shell stiffness and/or eggshell strength of such an egg, by utilizing as at least one factor the determined finite deformation contact time.

2. A method according to claim 1, including determining a deformer initial contact velocity.

3. A method according to claim 1, including measuring the deformation from an initial position.

4. A method according to claim 1, wherein the deformation step is carried out while bouncing, the deformer against the egg.

5. A method for sorting eggs wherein the method according to claim 1 is used for determining, during sorting, the eggshell stiffness and/or the eggshell strength.

6. An apparatus for examining eggs, in particular for determining eggshell characteristics of eggs, the apparatus comprising a deformer arranged to deform a part of such an egg such that the deformer is in actual contact with the egg for a finite deformation contact time, a detector arranged to determine the finite deformation contact time, and a central processing unit arranged to determine, using as at least one factor, the finite deformation contact time, shell stiffness and/or eggshell strength of such an egg.

7. An apparatus according to claim 6, wherein the deformer comprises a ball to be bounced on the egg, the apparatus optionally being configured for measuring an initial contact velocity of the ball as a derivative of a bouncing time, equal to the time duration between two successive impacts.

8. An apparatus according to claim 7, wherein the ball is arranged in the apparatus such that the bouncing of the ball is controlled substantially by gravity.

9. An apparatus according to claim 7, wherein the ball is arranged in the apparatus such that the bouncing of the ball is controlled substantially by an electromagnetic field.

10. An apparatus according to claim 7, wherein the ball is arranged in the apparatus such that the bouncing of the ball is controlled by a combination of an electromagnetic field and of gravity.

11. An apparatus according to claim 7, wherein the apparatus further comprises an optical detector which determines for such an egg the deformation from an initial position.

12. An apparatus according to claim 11, wherein the optical detector comprises a camera or a laser vibrometer.

13. An apparatus according to claim 6, wherein the apparatus is configured to determine an initial contact velocity of the deformer.

14. An apparatus according to claim 6, wherein the deformer is configured in use to have an initial contact velocity which together with the finite deformation contact time determines shell stiffness and/or the eggshell strength.

15. An apparatus for sorting eggs according to claim 6 which is arranged to determine during this sorting, the eggshell stiffness and/or the eggshell strength.

Description

(1) In the following, further details will be given and explained in further detail on the basis of a drawing, in which

(2) FIG. 1 schematically shows an example of an apparatus according to the invention, and

(3) FIG. 2 shows an example of a detection signal for determining the shell stiffness (and/or shell strength) of an egg.

(4) FIG. 1 gives a schematic view of a roller conveyor 1 as is generally known and used in sorting machines for eggs. An egg E rests on rollers 2, the rollers 2 forming at least one row, these rollers 2 being usually provided on axles (in this schematic drawing perpendicular to the plane of the drawing), and these rollers being usually mutually connected at the ends of the axles by endless chains that are guided over end wheels and are driven at one of the ends. It will be clear to the skilled person that use of such rollers 2 enables an accurate and repeatable positioning of products such as eggs. In this FIGURE, the conveying direction is indicated with T. Further, there is the possibility of arranging for rotation of the rollers with axles so that the eggs themselves rotate or spin. Such a rotating movement enables detection operations over the entire egg surface.

(5) Further, in FIG. 1, an excitation member or deformer 3 and an optical detector 4 are indicated. Such an excitation member or deformer is known in this field of technology and described in, for instance, EP738888 mentioned hereinabove, and in EP1198708 and in EP1238582. In contrast with what was customary hitherto, with this apparatus, contact times upon tapping or impacting can be determined. More particularly, a hammer as mentioned in EP1238582 can be provided with an accelerometer, for instance a piezo element, for measuring such a contact time. Such accelerometers can be of the type that energizes the inflation of air bags in automobiles upon collision. In the following, the use of the detector according to EP738888 will be described in further detail on the basis of FIG. 2.

(6) The optical detector 4 can be a camera for taking rapid shots, or also a laser vibrometer or measuring optics generally known. Such optical equipment allows determination of times, distances and velocities over very short time durations and is therefore highly suitable for carrying out such detection in the above mentioned sorting machines.

(7) In FIG. 2, a signal is represented that is produced by the detector as is extensively described in EP738888. This signal shape shows how a ball bounces on an egg several times. More particularly, there is shown the interval of time of the sound intensity I that is measured by a microphone in the column of which the bouncing ball forms the end. Four collisions between the ball and the egg can be seen and hence also four bouncing movements. The shape of the signal for one single bouncing movement is the result of the standing wave in the air column between the ball and the microphone, and is damped.

(8) More particularly, in FIG. 2 a time duration is indicated. This time duration is measured between two successive zero axis crossings of the first maximum intensity to be recognized for each bounce, and is substantially equal to the earlier mentioned contact time between the ball and an egg. Deviations thereof should be attributed to the construction of the detector, i.e. the distances to the microphone and the characteristics of the microphone. If required, this can be corrected for.

(9) Further indicated is the time duration of such a single reciprocating movement, also to be called bounce time t. This time duration makes it possible, with the control that is applied to the ball, i.e. in the field of gravity in combination with an electromagnetic field, to determine the velocity (V.sub.n0) of the ball at the time of impact, the initial contact velocity. For the ball bouncing on the egg, for instance, the following estimate can be derived for the initial contact velocity V.sub.n0:
v.sub.n0=K1.Math.tK2(1)
wherein t is the bouncing time(s) and K1 and K2 are empirically determinable constants.

(10) The initial contact velocity can also be determined in another manner (for instance by processing optical measuring data), which will be clear to the skilled person. As follows further from patent publication EP738888A1 incorporated herein by reference, the apparatus can be configured, for instance, for carrying out/controlling the bouncing such that a predetermined initial contact velocity (v.sub.c) is achieved.

(11) With the optical detectors mentioned, deflection or deformation from an initial position can be measured.

(12) The above-mentioned determinations make it possible to determine a shell stiffness parameter which parameter is derived with the Hertz model for such an egg-ball system. It is known to any skilled person how such a parameter relates to the above-mentioned shell stiffness or eggshell strength as determined according to the above-mentioned compression methodology, or also a specific stiffness determined in another way.

(13) It has appeared that for such an egg-ball system a highly effective shell stiffness parameter determination can already be carried out with the contact time alone. When a greater precision is required, the initial contact velocity (v.sub.n0) can be added in determining the shell stiffness parameter.

(14) Thus, it appears that the following relation can be used for determining the stiffness K.sub.H, also called Hertz stiffness:

(15) $\begin{array}{cc}{K}_H={\left(\frac{C}{}\right)}^{5/2}{V}_{n0}^{-1/2}m& \left(2\right)\end{array}$
wherein K.sub.H is the Hertz stiffness (N/m.sup.3/2), c is a constant (c=3.2145), v.sub.n0 is the initial contact velocity (m/s), is the deformation contact time(s) and m is the effective mass of the system, (kg), i.e.:

(16) $\begin{array}{cc}m=\frac{m_1+m_2}{m_1+m_2}& \left(3\right)\end{array}$
wherein m.sub.1 is the mass of the deformer (in this case the bouncing ball) and m.sub.2 is the mass of the respective egg.

(17) It will be clear to the skilled person that variants of the above-mentioned procedure are possible whereby, for instance, another combination of magnetic fields and electric fields is utilized. Further, the accelerometer will provide a different type of determination and calculation.

(18) Furthermore, apparatuses can be used where tapping is carried out not with a ball but with a pin or a needle. There too, in a manner similar to that indicated hereinabove, it is possible with the Hertz-model mentioned to derive the relation with which the shell stiffness can be determined. Further, unexpected deviations therefrom can provide an indication of, for instance, a defect or a contamination.

(19) Although the invention is directed to measuring the physical characteristic of eggs, a simple modification of such an apparatus can provide similar determinations on other products or articles. To be considered here are metal products such as bearings, and ceramic products, or also glass, or fruit products or food products suitable for such deformations, but the examples are not limited to these. It will therefore be clear that other variants are considered to fall within the scope of protection of the appended claims.