Measurement of Ice Cream Sticks
Measurements are made on wooden sticks for ice cream, tongue depressors and the like. Because of the further handling, i.e. packing and adding of ice cream it is important that the sticks are equal in thickness and shape. Furthermore, because of the users, the sticks must be free from splinters, knots, and discolorations.
Because of the large number of sticks to be measured (several hundred million pieces a year) and the very dusty environment, mechanical sensors cannot be used, since they would wear out very quickly. Inductive and capacitive sensors cannot be used on wood without a mechanical moving part added, thus the use of optical distance measurement is obvious.
The thickness of the sticks is measured in each end by means of two ODS sensors, coupled for thickness measurement. The wood is relatively thin and thus partly transparent to the infra red light used in ODS 30. Therefore, it is necessary to synchronize the sensors, so that they measure one at a time and thus do not disturb each other. The synchronizing is made automatically at the coupling for thickness measurement.
The sticks pass with a speed of app. 25 pcs. per second or app 0.5 m/s. On the basis of the measuring result, which is a 4 – 20 mA current loop and a 1 – 9 V voltage signal, it is decided if the sticks are passed or discarded according to preset tolerances.
The straightness of the sticks is also measured. This is done with a sensor placed in such a way as to measure the middle of the sticks. Crooked and oblique sticks are discarded.
