GB2187277A - Automatic surface colour grading of eggs - Google Patents

Abstract

Eggs are carried on a conveyor 14 past an illumination location in which electromagnetic radiation is directed at each egg. Reflected diffuse radiation is analysed and the amplitude compared with a selected value, The destination of each egg at the end of the conveyor is determined depending on whether the amplitude is greater or less than the selected value and the chosen destination for each egg on a row is stored in a memory until that row reaches the stage of the process at which the colour lanes diverge. In a preferred embodiment a plurality of sensors samples the reflected radiation received from different areas of each egg shell and the detected amplitudes are averaged before the average signal is compared with the selected value. <IMAGE>

Description

SPECIFICATION Automatic surface colour grading of eggs In the grading of eggs it is normal to grade by size or weight or even by some quantity dependent factor. However, consumer preferences now indicate a requirement for colour grading, not only to enable a uniform appearance in a tray of eggs but also to select particular groups for special markets. At present such grading, if carried out at all, is performed manually on trays of eggs after grading by size.

The present invention relates to an automatic surface colour sensing system which could be added to an existing size grading line or incorporated solely on its own line. The equipment consists of illumination means capable of emitting electromagnetic radiation usually, but not necessarily, in the visible light spectrum, conveying means for transporting the eggs through the illuminated area, one or more sensing means for detecting the amplitude of the reflected radiation from the surface of each egg at one or more specific wavelengths or wavelength bands and electronic signal processing means for averaging a plurality of samples and by comparing the resulting amplitude with predetermined quantities, determine into which category each egg should be subsequently directed.

The illuminating means is capable of providing even, uniform light over the inspected area of the egg and is arranged so that at the instance of sampling the sensors, only diffuse reflected radiation is detected and no spectural reflection from the egg shell surface can reach the sensors. The sampling of the sensors and the conveying means are synchronised so that such spectural reflections are avoided and the conveying means is partitioned so that only one egg in a known orientation may appear under a set of sensors at any one time. The conveying means may have a plurality of channels in which case the sensing means will also be duplicated to cover every channel across the conveyor.In order to enable sequential scanning of the sensors, the supporting framework for the sensors may be skewed slightly from the transverse position so that each egg will be in a similar position during sampling with respect to the sensors.

Each sensor in the sensing means may include an optical filter or filters such that the wavelength band selected gives the maximum discrimination for the variations in egg shell colour expected.

A specific embodiment of the invention is described by way of example with reference to the accompanying drawings in which: Figure 1 shows the overall schematic diagram Figure 2 illustrates the lighting and sensor arrangement above the conveyed produce Figure 3 is a block diagram of the electronic processing circuitry.

In this particular example the eggs are ail of a brown colour, which is now common in the United Kingdom, and a single colour filter has been identified, for placing in front of each sensor, which gives the maximum discrimination between pale and dark brown eggs. Referring to Fig. 1, a rolling table conveyor (14), similar to that used in present grading lines, is used to transport individual eggs in 12 channels past the sensor heads (12). A synchronising unit (13) fitted to the conveyor (14) sends signals to the electronic signal processing unit (11) when a row of eggs lies directly under each bank of sensors (12). The processor (11) then samples the amplitude of the reflected light in each sensor and after averaging and comparison with preset levels, records in electronic memory the destination of each egg observed.As the conveyor advances this information is advanced through the electronic memory so that when the eggs reach the deflecting mechanisms for selection lanes (15) the deflectors direct the eggs appropriately.

Because it is the amplitude of the light that is being measured the processor (11) also monitors and controls the lighting system (10).

Fig. 2 shows an end view of the lighting and sensor arrangement. Fiuorescent tubes (10) are mounted transversely above the conveyor and are energized at a high frequency to enable asynchronous sensor sampling. They are positioned such that when the egg, to be observed, lies under either sensor (16) in the sensor head (12) no specular refiection is seen by the sensor. The sensor head (12) comprises a minimum of 4 sensors per egg channel so that 4 areas of the egg shell are monitored. This is to enable an average reading to be taken and, if any serious differences are observed between the four readings, for dirty or excessively speckled eggs to be detected.

One pair of sensors lies on a transverse line, spaced about 1 cm apart and therefore the second sensor of this pair is not shown in Fig. 2 and the other pair are also mounted similarly but about 2.5 cm further along the conveyor. Because the egg rotates as it is transported, the second pair of sensors observe a different area of shell. They are sampled when the egg lies directly beneath them.

The light seen by the sensors is collimated by a slit or lens (23) to control the area observed and also an optical filter (17) controls the wavelength of the light observed.

The arrangement of the electronic signal processing circuit (11) is shown in Fig. 3.

Each set of 4 sensors per channel (16) are connected to individual amplifiers (18) in which adjustments are made to cater for device manufacturing tolerances. The four signals are then multiplexed (19) on to an analogue to digital converter (20). This process is controlled by the local microprocessor (21) which in turn is synchronised to the conveyor (14) by the Sync. unit (13). From the A/D convertor (20) the microprocessor unit (21) reads binary numbers relating to the sampled signal amplitude. When the processor has averaged the results and compared them against the levels preset on thumbwheel switches (24) and the conveyor has moved the eggs in question onto the point where they are directed into appropriate selection lanes then the output circuits (22) are energized appropriately.

If the colour grading system is included in a conventional grading line, using weight to determine size grades, then the output circuits may be connected to the control microcomputer for the grading line. The information transmitted may then be used to modify selection procedures so that certain lanes may have only eggs of a certain size and brownness.

Claims (20)

1. A method of colour grading eggs comprising the steps of conveying each egg through an illumination zone in which it is exposed to electromagnetic radiation, sensing diffuse radiation reflected by the egg shell, comparing the amplitude of reflected radiation with a preset value in an electronic signal processor and forwarding the egg to a chosen selection lane depending on the result of the amplitude comparison.

2. A method according to claim 1 wherein the step of sensing reflected radiation is carried out for a plurality of different shell areas for each egg, the signals received being averaged and the result compared with the preset value.

3. A method according to claim 2 wherein each egg changes position during its travel through the illumination zone and the method includes sensing reflected radiation from different shell areas at two distinct locations along the line of travel of the egg through the illumination zone.

4. A method according to claim 2 or 3 including sensing at a single location on the line of travel of the egg the radiation reflected from different areas of egg shell.

5. A method according to any preceding claim including the step of filtering the reflected radiation to permit sensing of a selected wavelength or wavelength band.

6. A method according to any preceding claim including conveying a row of eggs substantially simultaneously through the illumination zone and sensing the amplitude of reflected radiation from the eggs sequentially.

7. A method according to any preceding claim wherein the reflected radiation is collimated before it reaches the sensing means.

8. A method according to any preceding claim including using the electronic signal processor to control the electromagnet radiation emission.

9. A method according to any preceding claim wherein the electronic signal processor includes a memory and the method comprises the step of storing the required destination information for each egg in the memory and operating deflection means appropriately at the stage where the eggs are to be directed into appropriate selection lanes.

10. A method of colour grading eggs substantially as herein described with reference to the accompanying drawings.

11. An automatic surface colour sensing system comprising a conveyor for transporting eggs through an illumination zone, illuminator means for emitting electromagnetic radiation towards the illumination zone, sensing means for sensing the amplitude of radiation reflected by each egg, an electronic signal processor for comparing the sensed amplitude with a preset value and deflection means operable by the electronic signal processor for directing the eggs into appropriate selection lanes depending on the result of the comparison.

12. A system according to claim 11 including filter means adapted to confine the sensed reflected radiation to a predetermined wavelength or wavelength band.

13. A system according to claim 11 or 12 including collimating means disposed in the path of radiation reflected from the egg shell to the sensing means whereby the sensing means receives collimated radiation.

14. A system according to any of claims 11 to 13 wherein each sensing means comprises a plurality of sensors adapted to sense radiation reflected from different shell areas of an egg in the illumination zone, the electronic signal processor including means for averaging the results before a comparison is made with the preset value.

15. A system according to claim 14 wherein each sensing means comprises a plurality of sensors arranged transversely of the conveyor.

16. A system according to claim 13 or 14 including a plurality of sensors arranged longitudinally of the conveyor, the conveyor being adapted to roll the eggs to expose different areas of shell to each sensor.

17. A system according to any of claims 11 to 16 wherein the conveyor is adapted to transport a row of eggs, respective sensing means being provided for each egg in the row and the system including a multiplexer adapted to take readings sequentially from the sensing means and deliver them to the electronic signal processor.

18. A system according to claim 17 wherein the sensing means are arranged at an angle to the row of eggs so that the relative position of each egg to the respective sensor is optimum at the time of sensing radiation reflected from that egg.

19. A system according to any of claims 11 to 18 including a synchoniser unit adapted to detect the arrival of eggs at an optimum position in the illumination zone and to activate the sensing means at the appropriate time.

19. A system according to claim 17 or 18 wherein the illuminator means comprises two tubular sources of radiation arranged transversely of the conveyor, located one upstream and the other downstream of the sensing means substantially equidistant from the sensing means so that when an egg is under its respective sensing means the radiation from the tubular sources is incident obli quely on the egg shell.

20. An automatic surface colour sensing system substantially as herein described with reference to the accompanying drawings.