Classifying – separating – and assorting solids – Sorting special items – and certain methods and apparatus for... – Sorting bottles – ampoules – jars – drinking vessels – or like...
Patent
1995-10-30
1998-08-18
Bollinger, David H.
Classifying, separating, and assorting solids
Sorting special items, and certain methods and apparatus for...
Sorting bottles, ampoules, jars, drinking vessels, or like...
209580, 209585, 209587, 209588, 209589, B07C 500
Patent
active
057947880
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a method for sorting materials, in particular plastic parts.
For the separation of plastics for recycling purposes, non-contact, optical methods based on NIR spectroscopy are known. The plastic parts are illuminated with a source of light in the near infra-red range, and the reflectance spectrum is obtained. This shows distinct differences, on the basis of which separation according to material types can take place. Known apparatuses of this kind detect a passing plastic part, such as a bottle, a cup or similar with one or several measuring spots and calculate the NIR spectrum from the light reflected by the illuminated measuring spot. However, a precondition is that the measuring spot is not disturbed by a label, metal stamp or similar stick-on labels which will falsify the reflectance spectrum. Sharp edges can also render the measuring result incorrect or uncertain. Similar non-contact sensors based on microwaves or X-radiation are known, but are subject to the same limitations.
On the other hand, an optical imaging system for sorting plastic parts by colour, based on the use of colour video cameras, is known. In this case, pictures of the plastic parts conveyed past are taken, either in incident or transmitted light, using a colour video camera, and the form and/or colour is classified by an image computer. An image computer suitable for this is already known, for example, from the PCT publication WO 90/10273, in which the classification of form and colour is described, using the automatic optical classification of plants as an example. However, with this known system it is not possible to distinguish and separate plastic parts according to material type.
The object of the invention is to provide a method, which enables materials to be sorted with reliable and undisturbed determination of the types of material and with a versatile selection of sorting criteria, as well as a device for implementing the method.
To achieve this object, a method for sorting materials, in particular plastic parts, wherein the items are carried at known conveying speed past a material recognition system, which uses non-contact scanning of each item within a measuring field to determine its material type and delivers a signal that identifies the material type and is used in sorting the items according to material type, is characterized according to the invention in that the items are conveyed past an imaging system which takes pictures of the items from which, using electronic image-processing techniques, features of colour and/or shape of the items are detected, that from the features of colour and/or shape position data are derived regarding spots on the item at which an undisturbed determination of material type is possible, and that the determination of the material type by the material recognition system is confined to such undisturbed spots as identified by the position data.
By linking the material type determination to the results of electronic image processing the method according to the invention enables the material type of the items to be determined only at those spots where undisturbed determination of the material type is possible. Moreover, it is also possible, in the case of items which contain components of different material types, to determine the material types of the individual components separately. Finally, the features of colour and/or shape obtained by electronic image processing are available as additional sorting criteria.
Advantageous configurations and further developments of the method according to the invention and a device f or implementing the method are characterized in the sub-claims.
Further features and advantages of the invention ensue from the following description of practical examples of embodiments shown in the drawings. In the drawings
FIG. 1 shows a diagrammatic representation of a sorting system designed to implement the method according to the invention,
FIG. 2 shows a detailed view to explain the material type determination in the sorting system of FIG. 1,
REFERENCES:
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patent: 5502559 (1996-03-01), Powell et al.
"Steuerungssysteme fur Verteil-and Sortieranlangen" (Control Systems for Distribution and Sorting Assemblies), Journal F+H Fordern und Heben 1990, No. 6, pp. 390-393.
Bollinger David H.
Brackett Jr. Tim L.
Ferguson Jr. Gerald J.
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