HEUFT magnetic tracking
- the high-tech message in a bottle
It is a known fact that the quality of carbonated drinks deteriorates drastically when carbon dioxide has escaped. Even the slightest damage to the finish of a bottle which often cannot be seen at first glance leads to a gradual loss in carbon dioxide. The flavour is impaired and the consumer is left with a bad impression of the product.
The HEUFT sonic pressure detection has been in service for some years now in order to detect such containers. It is able to detect pressureless containers without touching them at a container output of up to 80,000 containers per hour in the production flow and to remove them from the production process by means of the proven HEUFT rejection systems.
Its operating principle has been inspired by music:
the sound of a drum changes when the tension of the drumhead is altered.
In our case the metal crown cork of the bottle is the drum and the tension of the drumhead is based on the internal pressure of the container. However the drum is not struck mechanically but electromagnetically. A short electromagnetic pulse leads to a mechanical deflection of the closure which then oscillates in its characteristic waveform.
This is recorded, amplified electronically, filtered and analysed by means of a microphone. The internal pressure can then be determined on the basis of the determined values.
However the waveform also depends on other parameters:
· the closure material (drumhead material)
· the force applied by the closer head (drumhead tension)
· the finish shape of the bottle (shape of the hollow space of the drum)
· the fill level of the bottle (size of the hollow space of the drum)
A relative measuring method is necessary in order to take all these parameters into account. The pitches of the bottles are compared and those which sound faulty are detected (= pressure not within the normal range). In other words we compare different drums and sort out those which do not sound good.
In music semitones only sound harmonious when they are surrounded by the right sounds and in the same way containers can have "off-key" crown corks which can only be evaluated as good when a knowledge of their surroundings is available.
This is exactly the point at which the development of information transfer via magnetic tracking starts. The HEUFT O2 inspection after the filler checks the wave pattern of the closure immediately after the filling process in order to detect bottles with an oxygen content which is too high. The pressure in the bottle is almost the same as the external pressure at this point along the line. The nominal pressure builds up later (especially in a pasteuriser).
The information received here then has to be transported container-related along the line. Conventional container tracking over multi-lane sections, for example through a pasteuriser, is not possible in this case. Therefore we use the magnetic properties of the closure again and use it as a diskette this time. We encode the result of the first measurement carried out at the HEUFT O2 detection on the closure and read it after the pasteuriser at the position of the HEUFT sonic detection. There are two measuring results for the same bottle at this point. The tone differs due to the varying pressure at the two measuring positions if the container has been correctly closed. However faulty bottles do not change the tone. Compared to single point measuring a considerable improvement concerning the accuracy of the measurement can be achieved because the individual character of each container is taken into account for the result.