Plastics identification

Details Plastics identification Plastics identification

1996-09-30

1998-07-28

Pham, Hoa Q.

Optics: measuring and testing

Sample, specimen, or standard holder or support

356 36, G01N 2101

Patent

active

057868921

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
This invention relates to an apparatus for identifying different plastics materials. The apparatus is particularly (but not exclusively) suitable for use in the plastics industry, for separating plastics components into chemically similar groups as a first stage in, for instance, the recycling of the plastics materials.
2. Description of the Related Arts
One field of application is the recycling of motor car components. When a motor car is scrapped, its saleable components such as battery, tires or radio are removed, usually for use in other vehicles. The metal parts of the scrap car are generally re-cycled, and what remains is shredded and used as land-fill.
The remainder that is used for land-fill consists primarily of a mixture of plastics materials. For environmental and/or economic reasons, it is desirable to be able to recycle such waste plastics materials. However it is not possible effectively to recycle mixtures of waste plastics without first separating the plastics into chemically similar groups or families. Failure to achieve this separation would mean that unknown portions of different plastics were incorporated in the melt during the reclaim process. The presence of other plastics components in a blend may necessitate changes in processing conditions or lead to unacceptable changes in the physical properties of the finished recycled material.
Whilst a number of laboratory techniques are known for identifying different plastics materials, none of these are suitable for use in a continuously operating plastics recycling line, and none of them can cope easily with scrap motor car parts which are of irregular size and shape and are usually dirty.
European patent publication number 0 497 397 discloses apparatus for identifying plastics materials, the apparatus comprising a light source for producing short wave light impulses, spectral apparatus for producing an emission spectrum, a detector for converting the radiation intensities into electrical signals, and a computer for processing the electrical signals to produce sorting signals. The apparatus is used with particles of plastics materials which are carried by a conveyor belt from a delivery station. When a particle of plastics material passes a pre-set point by the apparatus it breaks a light beam, triggering the light source to take a reading. The reflection spectrum from a plastics material is used to identify that material and allow like materials to be sorted together. The surface of a particle of plastics material may be partially cleaned by means of a laser beam to remove surface dirt.
Our co-pending International Patent Application number PCT GB93/02244 describes a method and an instrument for identifying plastics materials using a spectroscopy technique.
While spectroscopy can lead to accurate results in terms of plastics identification, the instrumentation required is delicate and has to be carefully set up and maintained.
The present invention therefore seeks to provide an interface between spectroscopy apparatus and a piece of plastics to be identified, which will allow plastics components of a wide variety of shapes and conditions to be brought into a uniform position where they can be tested by the apparatus.


SUMMARY OF THE INVENTION

According to the present invention, there is provided apparatus for identifying plastics, the apparatus comprising a spectrometer, characterised in that the apparatus further comprises a protective casing surrounding the spectrometer with a sensing window formed in one face of the casing, and an interface device associated with the sensing window, the interface device comprising a front wall with a sample aperture against which the sample can be placed so that a surface of the sample is exposed through the aperture, means for cleaning a sample surface placed against the front wall, means for extracting debris resulting from the sample cleaning, and means for guiding the front wall towards the sensing window to enable the spectrometer to take a

REFERENCES:
patent: 4644163 (1987-02-01), Selander
patent: 5281798 (1994-01-01), Hemm et al.

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