Introduction

To perceive the rationale for the inspection of the bottles’ colour, we recommended to take a look at the figure on right side.  That is what a Customer considered “a bottle format”.   

In this conditions the Bottler’s production face any or more of these negative effects:

  The differences of colour between bottles add false rejects and reduce the defects' detection ratio


  • bottles of the wrong colour, sometimes originating by a Competitor, reaching the Market labelled with the Bottler’s label and beverage.
  • huge false rejects originating by the EBI’s base and external sidewall inspections;
  • macroscopic and dangerous defects passing to the Market, a typical case encountered when the bottle has a colour much darker than that for which the bottle format has been commissioned in the EBI.




Technology

  The glass Colour inspection in an Empty Bottle Inspector controlling the colour of each one glass bottle.  In this special case, the design interposed its light projector-detector between the out feed external sidewall inspection of the EBI and final inspection system (picture GROLSCH®, a SABMiller company).


 The signals incoming by three separate channels, each one corresponding to a fundamental colour, are processed to deduce the bottle’s glass colour. The couple of yellow colour vertical lines are the inspection window, the range of distances measured in millimetres equivalent to Encoder pulses. In the vertical axe of the diagram they appear, digitized in a scale of 4096 bits, the signals’ amplitudes. In the example shown, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all bottles whose chromatic mix similar to this one shall be considered correctly coloured. Where “correctly” means their colour is coherent with the currect production

A solution pass thru the control of the colour of each one bottle directly in the Empty Bottle Inspector, where they present themselves yet washed and with a minimum amount of labels.   Colour control made illuminating with a source of known spectrum, typically a halogen lamp, the upper half of the bottle sidewall.  A portion of the light, after having been refracted by the glass, gets out on the opposite side of the bottle.  Finally enters the lens of a trichromatic detector part of the Colour inspection.   A device with three separate channels, referred to the familiar fundamental colours red, green and blue.   The signal in the outfeed of each one channel is separately amplified and later digitised and processed, comparing the digitised value with upper and lower limits set during the commissioning.   As an example, refer to the graphic below on right side:

  • a couple of yellow colour vertical lines represents the inspection window, the range of distances in the Inspector's Shifting-Register, where the three chromatic channels are evaluated;
  • red colour the red chroma signal, whose grey level is normalized (0 - 4096);
  • blue colour the blue chroma signal amplitude, whose grey level is normalized (0 - 4096);
  • green colour the green chroma signal, whose grey level is normalized (0 - 4096);
  • white colour their superimposed amplitude, whose grey level is normalized (0 - 4096).

Bottles whose tri-chromatic mix is out of each one of the three allowed ranges, shall be rejected. In the example shown, a cap has been measured thru all three channels with approximately the same amplitude ~1380 bits. The image setup in the meantime specifying a “good colour 1” implies that all bottles whose chromatic mix similar to this one shall be considered correctly coloured.  Where “correctly” means their colour is coherent with the currect production.  In the figure below, the black colour square box in the red circle hosts the tri-chromatic sensor assemble.   Not visible, on the opposite side with respect to the sensor, the 12 VDC halogen lamp used as a spectral reference.  The Sun in some special times of the day, may influence the thrichromatic sensor measurements, adding yellow colour centered values implying false rejects.  In these cases, it results necessary to shield the system.


 Bottles’ Colour Inspection adopts visible light like an instrument. Visible light 100 million times more energetic than Infrared and 100 times less energetic than, i.e. the X-rays used for the Fill Level, Case and Crate Inspections



The most complete Glass Returnable Empty Bottle Inspectors existing in the World double-check also the colour of each one bottle in the best metrologic conditions. Conditions only met only after the Bottle Washer Machine and not in the typical Sorting Units' position before the Bottle Washer Machine (picture GROLSCH®, 2013, a SABMiller company)


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This website has no affiliation with, endorsement, sponsorship, or support of Heuft Systemtechnik GmbH, MingJia Packaging Inspection Tech Co., Pressco Technology Inc., miho Inspektionsysteme GmbH, Krones AG, KHS GmbH, Bbull Technology, Industrial Dynamics Co., FT System srl, Cognex Co., ICS Inex Inspection Systems, Mettler-Toledo Inc., Logics & Controls srl, Symplex Vision Systems GmbH, Teledyne Dalsa Inc., Microscan Systems Inc., Andor Technology plc, Newton Research Labs Inc., Basler AG, Datalogic SpA, Sidel AG, Matrox Electronics Systems Ltd.

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