FORM 2
THE PATENTS ACT, 1970
(39 of 1970)
&
THE PATENT RULES, 2003
COMPLETE SPECIFICATION
(See Section 10 and Rule 13)
Title of the invention:
APPARATUS FOR SORTING OF POLYVINYL CHLORIDE CONTAMINANTS AS
PART OF POLYETHYLENE TERAPHTHALATE RECYCLING
Applicant:
RELIANCE INDUSTRIES LTD
Reliance Technology Group, Reliance Corporate Park,
Bldg 7B Gr Floor, Ghansoli, Thane-Belapur Road,
Navi Mumbai - 400701, Maharashtra, India.
The following specification describes the invention and more particularly the manner in which it is to be performed.

[001] FIELD OF THE INVENTION
[002] This invention relates generally to sorting systems and more particularly to an apparatus for sorting polyvinyl chloride contaminants from polyethylene teraphthalate articles being segregated for recycling.
[003] BACKGROUND OF THE INVENTION
[004] Bottles made of polyvinyl chloride (PVC) and polyethylene terephthalate (PET) are in widespread use as containers for beverages and other consumables. Post use, these containers are collected for recycling. Such collections generally include articles of both PET and PVC. Sometimes, the collected articles may appear translucent due to being soiled by use or remnants of the material originally contained. Color, if present in material of original articles, further compounds this problem. Clear colorless reclaimed PET is substantially more valuable for reprocessing when free of PVC. However, the similarity in visual appearance and similarity in density (1.34 g/cc for PET, 1,32 g/cc for PVC) precludes separation of the two materials on the basis of simple density / manual visualization methods most common in conventional recycling systems.
[005] Study of the art reveals attempts to resolve the said problem. US5675416 A and WO2004101178A1 disclose detection of PVC articles during the flight path between two conveyers and with perpendicularly incident radiation and detection based on transmitted radiation rather than reflection. Methods of both these patents require either a predetermined, minimum speed of the conveyers in case of projectile travel of the plastic between two conveyers or detection within the falling time in case of free fall from one upper conveyer to a lower conveyer, both being at same or different, predetermined speeds. These inventions have inherent shortcomings due to lack of flexibility as regards speed of detection and subsequent sorting as the available time for detection and sorting is limited by the minimum speeds of the conveyers and/or speed of flight or free fall of the plastic objects.
[006] US5141110A, US5448074A and US20010045518A1 disclose detection of PVC articles on the conveyer belt itself or on a joining section between two successive conveyers serving, in succession, as input of plastic feed and output to segregated plastic for further processing. However, the section or

joining section of conveyers on which detection is made in above cited references are as opaque as the rest of the belt sections and therefore, either a parallel incident beam (or such beams collimated) is required if the detection has to be based on transmitted radiation or the detection has to be from reflected radiation if the beams are incident perpendicularly on the plastic object. In former case, either the radiation received by detector is of low intensity if reflected by plastic objects or will be affected by surface characteristics (possible defects due to long use) of belt material if transmitted by plastic object followed by reflection by belt further followed by second transmission by plastic object, thereby limiting efficiency of detection and sorting. In the latter case, i.e. parallel incidence of radiation followed by detection after transmittance, available surface for receiving and transmitting radiation is relatively much less as in the art of sorting, plastic objects on conveyer are mostly flattened plastic bottles or chips.
[007] US5141110A discloses an optional way of detection in transmission mode against perpendicularly incident radiation, yet without a predetermined, minimum speed of the conveyer, wherein each plastic object at the detecting chamber end of the 1s', upper conveyer can individually held and placed on the radiation path (either manually or robotized) when detection occurs in transmission. However, this becomes an individual detection in one article-after-another mode, which can adversely affect overall turn around time and efficiency of the sorting process.
[008] Polarized light has been used in a variety of sorting and detection systems, for example, US 4659112 discloses an identification system for ID cards, similarly, US 3197647 discloses a system for sorting translucent objects such as colored rice grains, US 4262806 discloses a system using polarized infrared light to sort foreign objects from vegetables. None of these patents provide a system for sorting plastic articles such as PET and PVC containers which may have different degrees of crystallinity in a continuous mode of operation, for example, a conveyor belt system. The present invention addresses the various disadvantages of prior methods for sorting PVC articles as a preparatory phase of PET recycling.

[009] To address these and other problems of art, there still exists a need for sorting apparatuses which provide operational features to allow continuous, yet accurate and simple, sorting of PVC articles along multiple flow paths. It is a further need for design of such apparatus to allow muiti-point control for enabling adaptability over different speeds of mechanized or manual sorting,
[010] OBJECTS OF THE INVENTION
[011] It is an object of the present invention to provide an apparatus for inspection and sorting of articles being incident along moving conveyor means.
[012] Another object of the present invention is to adapt the means for conveyance of input plastic feed for detection of PVC articles via transmittance criteria of normally incident polarized light,
[013] Yet another objective of the present invention is to allow fine control over sorting rate and throughput of the apparatus by using combination of mechanized and gravity-based means for conveyance of the plastic articles.
[014] Yet another object of present invention is to limit exclusive use of mechanized means for transit of articles along the sorting section by harnessing gravitational force for such purposes.
[015] Still another object of the present invention is to reduce complexity of design and allow for maintenance-free, low cost architecture of the apparatus for sorting of PVC articles.
[016] Still another object of the present invention is to allow accurate identification of PVC articles irrespective of the mixed plastic feed being aligned as a monolayer, substantial overlaps or even heaps.
[017] These and other objects of the present invention shall present themselves to the reader upon the summary and detailed description of invention contained hereinafter.

[018] SUMMARY OF THE INVENTION
[019] The present invention comprises a static surface made of transparent glass or other non-birefringent materials for inspection and sorting of PVC articles.
[020] Juxtaposed in operational path of two conveyor belts serving, in sequence, for input of mixed plastic feed and output of sorted plastic for desired downstream processing, the said transparent surface provides for a non-moving platform for identification and sorting of PVC articles via visualization by human operators or suitable automated means. This provides a processing capability for simultaneous examination, detection and sorting amongst plastic articles which may be incident, in plurality, at any given point of time. The rate and throughput of sorting may be controlled via adjusting speed of said two conveyors and angle of disposition of the said static surface in conjunction with near ends of the said two conveyors.
[021] Identification of PVC articles is based on principle of birefringence of polarized light incident normally from suitable sources positioned underneath the glass surface. Detection of PVC articles is via detecting characteristics of transmitted light through the analyzer plate juxtaposed parallel to the flat inspection surface wherein PVC bottles appear opaque and PET articles remain transparent. Once detected, PVC articles may be sorted via manual / mechanized means.
[022] DETAILED DESCRIPTION OF THE INVENTION
[023] The present invention provides an apparatus and method for sorting PVC articles amongst a mixed group of plastic articles. Additionally, the present invention provides for improvement in active process control and throughput of conventional sorting mechanisms.
[024] According to principles of the present invention, the PVC articles are sorted on basis of their birefringence behavior in response to polarized light. Each plastic article in the input feed is subjected to one or more normally incident beams of polarized light and transmittance characters of such incident light are thereafter detected after passing first through the transparent section of the flat inspection surface and then through the analyzer plate. Principally the difference in refraction characters of PVC and PET articles renders the former

appearing opaque and latter remaining transparent. Once identified by human visualization or suitable photometric means, PVC articles are then sorted out and rest PET articles are conveyed for downstream recycling processes.
[025] According to one aspect of the present invention, the inspection and sorting of mixed plastic feed transmitted by input conveyor occurs over a static inspection surface. Construction of this surface is characterized by operability across a range of angles, the latter being responsible for achieving desired flow rate of articles moving under gravitational force.
[026] According to another aspect of the present invention, identification of PVC articles via principle of birefringence occurs over the said static inspection surface. The operative design of the said static surface comprises a transparent window attached above one or more sources of polarized light such that beams of polarized light emanating from said sources pass through the said window and are normally incident on the plastic articles moving along the upper surface of the said window. The source of polarizing light may comprise a CFL bulb followed by a polarizing plate. According to one embodiment of the present invention, the polarizing plate may itself be the transparent section of the flat inspection surface. Detection of PVC articles is via transmitted light as observed through an 'analyzer' plate oriented cross the inspection surface wherein PVC bottles appear opaque and PET articles remain transparent. Once detected, PVC articles may be sorted via manual / mechanized means.
[027] According to another aspect of the present invention, the active control over sorting rate and throughput of the apparatus is achieved by using combination of mechanized and gravity-based means for conveyance of the plastic articles. Such control may be exercised by the operator by selecting appropriate combination of speeds for input and output conveyors and angle of the said static inspection surface. As flow of articles along the static inspection surface is solely under gravitational force, the angle of slide / fall determines speed of movement of said plastic articles - steeper the angle, faster the flow. The angle of slide / fall, according to one embodiment of the present invention, may be adjusted between 30° to 90° to the floor, thus allowing rates of flow ranging from slow to free fall. Sorting means may be

thereupon chosen from manual / automated mechanisms that may pick up or deflect PVC articles thus resulting in their sorting from the initial mixed plastic feed. This control architecture provides fine control over the rate of sorting process and manual / automated override in instances of undesired idle / overflow conditions at the inspection surface.
[028] The present invention scores over citations of prior art by avoiding mandatory dependency on either belt material surface quality or requirement of a specific type of radiation (to reduce/ remove former dependency) of reflectance mode detection as is the case of detection performed upon the opaque conveyer belts, Also, limitation of detection speed being wholly dependent on conveyor belt speed is removed whereby an opportunity of relatively slow manual detection and sorting is opened, thus avoiding unnecessary procurement and maintenance costs of automated detection equipments. Additionally, the input plastic feed need not be sorted on an individual basis - the same may flow across the inspection window in configurations including monolayers, heaps or part overlapping of incident articles. Yet another advantage of the present invention lies in the usage of transmittance rather than reflection behavior of light as criteria for sorting of the PVC articles. This makes color, if any, of incident articles immaterial for accuracy and precision of the identification process.
[029] The present invention extends its applicability to detection of polypropylene (PP) and polyethylene (PE) articles - with the PP and PE articles exhibiting rainbow appearance when subjected to normally incident polarized light.
[030] Reference is now made to exemplary embodiments wherein is illustrated one way of performing the present invention
[031] Example 1
[032] Used, soiled, flattened/compressed PET bottles as received in bales for recycling were continuously discharged through a bale opener at the rate of about 500 bottles/min onto a conveyor belt of width 1 m and length 15 m moving at a speed of 10 m/min. During this conveying, workers manually pick out the bottles containing labels and closures, and return the bottles to belt after offline removal of labels and closures. End of this conveyor belt is

equipped with a permanent magnet mounted above, to automatically extract any ferrous metals contamination present.
[033] This conveyor has also the task to elevate bottles to the inlet of the trommel, which is a cylindrical (dia 1 m x length 3 m) rotating (30 rpm) screen employed to allow get small pieces such as remaining loose bottle closures to fall out through the screen perforations (dia 3 cm).
[034] At the exit of the trommel,the bottles fall onto the higher end of polarizer plate (width 0.5 m x length 1 m) placed at an angle of 45 degrees to the ground. The polarizer plate consists of a polarizing sheet (0.8 mm thick) placed between two glass sheets (6 mm thick), mounted on an angled iron frame, and illuminated from below with 4 tubelights of 40 W each. The frame also holds a similar analyzer plate (with polarization direction 'cross' to the polarizer in the polarizer plate) This is positioned parallel to the polarizer piate but 40 cm above the latter. As the bottles slide over the polarizer plate, the observer looks through the analyzer plate, detects the 'dark' appearing bottles and segregates the same The bright Appearing bottles continue to slide down to another conveyor belt that carries out the PET bottles, substantially free of the PVC bottles, to the subsequent processes of a recycle line, i.e. crushing into flakes, washing including density based separation, and drying followed by extrusion into desired shapes.
[035] It would be obvious to the reader that the present invention is capable of a wider application than represented by description and example contained hereinabove. Ability to discern between materials, plastics or otherwise, depends on knowledge of their differentia] responses to at least one distinguishing criterion and enabling incorporation of such criterion as a distinguishing test at site where the heterogeneous material input is to be-inspected. It is thus intended that source of illumination, polarizer elements, dimensions of mechanscal assembly may be chosen to suit input material and operation of distinguishing test without parting from applicability of the flat translationally stationary transparent inspection surface amenable, via selectablity in dimensions and angle of juxtaposition, to flow rate desired for materials inputted for sorting and further continuing in subsequence, the spirit and scope of the present invention

[036] Yet other advantages of the present invention will become apparent to those skilled in the art from the foregoing description and drawings wherein there is described and shown a preferred embodiment of the present invention. As will be realized, the present invention is capable of various other embodiments and that its several components and related details are capable of various alterations, all without departing from the basic concept of the present invention. Accordingly, the drawings and descriptions will be regarded as illustrative in nature and not as restrictive in any form whatsoever. Modifications and variations of the process and methods described herein will be obvious to those skilled in the art. Such modifications and variations are intended to come within the scope of the present invention.

Claims:
We claim,
1) An apparatus for sorting polyvinyl chloride articles from amongst plastic articles
being processed for polyethylene teraphthalate recycling, said apparatus
comprising:
• means for conveying plastic feed to the sorting site, said plastic feed being characterized by presence, in combination, of polyvinyl chloride and polyethylene teraphthalate articles;
• a flat translationally stationary transparent inspection surface substantially aligned at an operative angle to unloading end of said conveying means for providing an stationary inspection window for sorting of polyvinyl chloride articles from said plastic feed;
• means for Iillumination of said plastic feed by at least one beam of polarized light, said illumination means being suitably juxtaposed beneath the said transparent inspection surface to provide beam of polarized light perpendicular to plane of said inspection surface;
• a flat translationally stationary transparent analyzer component for identification of polyvinyl chloride articles from said plastic feed, said identification being based on opaque appearance of polyvinyl chloride articles due to birefringence of polarized light from said illumination means being incident upon the said plastic feed
• means for sorting of identified polyvinyl chloride articles from said plastic feed and resulting in sorted feed consisting solely of olyethylene teraphthalate articles, said sorting means being chosen among automated, semi-automated and manual alternatives common to the art; and

• means for conveying said sorted feed devoid of polyvinyl chloride 'articles downstream from said glass inspection window for recycling of polyethylene teraphthalate articles.
2) An apparatus for sorting polyvinyl chloride articles from amongst plastic articles being processed for polyethylene teraphthalate recycling according to claim 1, wherein said analyzer component is a polarization filter with polarization direction perpendicular to said source of illumination, said analyzer component being selected from among a flat panel juxtaposed parallel and above to plane of said flat inspection surface and at least one goggle lens to be worn by human sorters.
3) An apparatus for sorting polyvinyl chloride articles from amongst plastic articles being processed for polyethylene teraphthalate recycling according to claim 1, wherein means for conveying the plastic feed upstream and downstream of the said glass inspection window are synchronized motor-driven conveyor belts aligned parallel to the ground having option of independent manual override.
4) An apparatus for sorting polyvinyl chloride articles from amongst plastic articles being processed for polyethylene teraphthalate recycling according to claim 1, wherein movement of plastic feed over the said glass inspection surface is solely due to gravitational force.
5) An apparatus for sorting polyvinyl chloride articles from amongst plastic articles being processed for polyethylene teraphthalate recycling according to claim 1, wherein flow rate for plastic feed and process throughput are selectable by appropriate combination of motor speed for said conveying means and angle of

juxtaposition of said glass inspection surface to the trajectory path of said plastic feed at the edges of said conveying means.
6) An apparatus for sorting polyvinyl chloride articles from amongst polyethylene teraphthalate articles being recycled according to claim 1, wherein length and breadth of said glass inspection surface are in the range between 0.3m to 3m and 0.1m to 2m respectively.
7) An apparatus for sorting polyvinyl chloride articles from amongst polyethylene teraphthalate articles being recycled according to claim 1, wherein angle of juxtaposition of said glass inspection surface to the trajectory path of said plastic feed at the edges of said conveying means is in range of 30°to 90° to the ground.
8) An apparatus for sorting polyvinyl chloride articles from amongst polyethylene teraphthalate articles being recycled according to claim 1, wherein said means for illumination of incident plastic feed by polarized light comprise a polarizing filter affixed in operational confirmation with respect to a light emitter chosen among compact fluorescent lamps and fluorescent tubes.