WO2006043833A2

WO2006043833A2 - Apparatus and method for reprocessing plastics

Info

Publication number: WO2006043833A2
Application number: PCT/NZ2005/000272
Authority: WO
Inventors: Matthew Joseph Darby
Original assignee: Range Industries Limited
Priority date: 2004-10-20
Filing date: 2005-10-20
Publication date: 2006-04-27
Also published as: WO2006043833A3; NZ536058A

Abstract

A plastics extruder for re-processing solid plastics material has an auger with a blade (61) located inside a closely fitting housing (79). Rotation of the blade advances plastics material from an inlet portion (57) to an outlet end (59) of the auger. The auger blade includes a helical screw (63) with a compression portion at which the volume between adjacent turns of the helical screw successively reduces in a direction toward the outlet end of the auger. The solid plastics material being advanced through the compression portion is heated and converted to a viscous liquid which is extruded through an extrusion nozzle connected to the outlet end of the auger. The volume reduction along the compression portion may be achieved by decreasing the outer diameter of the helical screw and maintaining the close fit of the housing (79), and/or by increasing the diameter of the auger shaft (65), and/or by reducing the pitch of the helical screw. A laminator using a plurality of the extruders produces a multilayered extrusion.

Description

APPARATUS AND METHOD FOR REPROCESSING PLASTICS FIELD OF INVENTION

The present invention relates to methods and apparatus for the reprocessing of plastic materials and particularly the reprocessing of plastic films. One application of the invention is in recycling by reprocessing plastic shopping bags and industrial packaging films.

BACKGROUND

Today, many products are manufactured from plastics. In many cases, these products are used once, or only for a limited number of times, after which they are discarded as waste. Although the product may have limited utility after such use, the plastic material from which it has been manufactured is still generally viable, if not in a form that is readily useable. Attempts at reprocessing some forms of plastic and some plastic products have not always been successful.

The reprocessing or recycling of plastic films, in particular, has met with difficulties and has not been generally successful. This has meant that plastic films, and products made from plastic films, are usually discarded, which has created problems for disposal of this material as waste.

SUMMARY OF INVENTION

An object of the current invention is the provision of an improved apparatus and/or method by which plastic film can be recycled for reuse by being reprocessed, or to at least provide the public with a useful choice.

In a first aspect the invention may be broadly said to be an plastics extruder for re¬ processing solid plastics material, the extruder consisting, at least in part, of:

an auger having an auger blade located inside a closely fitting auger housing for advancing plastics material fed to an inlet portion of the auger to an outlet end of the auger by rotation of the auger blade, the auger blade including a helical screw with a compression portion at which the volume between adjacent turns of the helical screw successively reduces in a direction toward the outlet end of the auger; a heater for heating solid plastics material, when being advanced by the auger blade through the compression portion, to a temperature at which the solid plastics converts to a viscous liquid; and

an extrusion nozzle connected to the outlet end of the auger and through which the viscous liquid can be extruded.

The helical screw preferably extends substantially continuously along the auger from the inlet portion to the outlet end.

Preferably the compression portion of the helical screw includes a tapered portion at which the helical screw tapers from a relatively larger outer diameter to a relatively smaller outer diameter in a direction toward the outlet end of the auger and the auger housing tapers correspondingly to maintain the close fitting of the auger housing about the auger blade. The helical screw may extend between the tapered portion and the outlet end with a plurality of helical screw turns having a common outer diameter.

Preferably the auger has an axial auger shaft and at the compression portion the auger shaft tapers from a relatively smaller shaft diameter to a relatively larger shaft diameter toward the outlet end of the auger.

Preferably the pitch of the helical screw at the compression portion reduces in a direction toward the outlet end of the auger.

Preferably the heater consists, at least in part, of a jacket that surrounds the auger housing for circulation of a heated liquid around the auger housing.

In a second aspect the invention may be broadly said to be a laminator for producing a multilayered extrusion, the laminator consisting, at least in part, of a plurality of plastic extruders each according to the first aspect of the invention or any of its options or preferences, wherein the extruder nozzle of each plastics extruder is a common extruder nozzle through which viscous liquids from each of the plastics extruders can be extruded simultaneously. Preferably the laminator includes one or more pairs of rollers, the rollers of the or each pair having mutually parallel axes and being arranged one above the other to form a nip region therebetween, and the nip region being aligned to accept material extruded from the common nozzle. The rollers of the or each pair of rollers may be mechanically coupled to one another for rotation in opposite directions.

Preferably the common extruder nozzle of the laminator has a single nozzle outlet which is connected for viscous liquid flow via respective nozzle conduits to the outlet end of the auger of each of the plastics extruders. The plurality of plastic extruders is preferably three plastics extruders, and the single nozzle outlet is connected for viscous liquid flow via three respective nozzle conduits to the outlet end of the auger of each of the three plastics extruders. The three nozzle conduits may be arranged to converge at the single nozzle outlet with two of the three nozzle conduits on opposite sides of the third nozzle conduit, a first hopper is arranged for feeding solid plastics material to the inlet portion of the auger of each of the two plastics extruders connected to the third nozzle conduit, and a second hopper is arranged for feeding solid plastics material to the inlet portion of the auger of the plastics extruder connected to the other two nozzle conduits. Two cutter devices may be arranged respectively above the first and second hoppers for cutting solid plastics materials into pieces and for feeding the pieces into the respective first and second hoppers.

In a third aspect the invention may be broadly said to be a method of re-processing plastics material consisting, at least in part, of the following steps:

feeding solid plastics material into an inlet portion of an auger having an auger blade located inside a closely fitting auger housing, the blade including a helical screw with a compression portion at which the volume between adjacent turns of the helical screw successively reduces in a direction toward an outlet end of the auger;

advancing the plastics material through the compression portion of the helical screw and onward to the outlet end of the auger by rotating the auger blade; heating the solid plastics material being advanced by the auger blade through the compression portion to a temperature at which the solid plastics material converts to a viscous liquid; and

extruding the viscous liquid through an extruder nozzle connected to the outlet end of the auger.

The step of advancing the plastics material through the compression portion of the helical screw preferably includes advancing the plastics material through a tapered portion of the helical screw which tapers from a relatively larger outer diameter to a relatively smaller outer diameter in a direction toward the outlet end of the auger, the auger housing tapering correspondingly to maintain the close fitting of the auger housing about the auger blade. The step of advancing the plastics material onward to the outlet end of the auger may include advancing the plastics material along a portion of the helical screw which extends between the tapered portion and the outlet end with a plurality of helical screw turns having a common outer diameter.

Preferably, in the step of heating the solid plastics material, a heated liquid is circulated through a jacket that surrounds the auger housing.

In a fourth aspect the invention may be broadly said to be a method of producing a multilayered extrusion consisting, at least in part, of simultaneously performing the method of the third aspect of the invention, or any of its options or preferences, with a plurality of augers, wherein the extruder nozzle of each plastics extruder is a common extruder nozzle and viscous liquid is extruded simultaneously from each of the plastics extruders. Preferably the method of the fourth aspect of the invention includes the additional steps of:

arranging one or more pairs of rollers, the rollers of the or each pair having mutually parallel axes and being arranged one above the other to form a nip region therebetween, and the nip region being aligned to accept material extruded from the common nozzle; and

passing the material extruded from the common extruder nozzle through the nip region between the or each pair of rollers.

Preferably the method of the fourth aspect of the invention, or the immediately preceding preference, includes the additional step of:

mechanically coupling the two rollers of the or each pair to one another for rotation in opposite directions.

Preferably the common extruder nozzle has a single nozzle outlet which is connected for viscous liquid flow via respective nozzle conduits to the outlet end of the auger of each of the plastics extruders. The plurality of plastic extruders is preferably three plastics extruders, and the single nozzle outlet is connected for viscous liquid flow via three respective nozzle conduits to the outlet end of the auger of each of the three plastics extruders. The three nozzle conduits may be arranged to converge at the single nozzle outlet with two of the three nozzle conduits on opposite sides of the third nozzle conduit, the method of producing a multilayered extrusion also including the steps of:

feeding a first plastics material to a first hopper arranged to feed the first plastics material to the inlet portion of the auger of the plastics extruder connected to the third nozzle conduit, and

feeding a second plastics material to a second hopper arranged to feed the second plastics material to the inlet portion of the auger of each of the two plastics extruders connected to the other two nozzle conduits. Preferably the method of the fourth aspect of the invention, or any of its options or preferences, includes the further steps of:

cutting first and second solid plastics materials into pieces; and feeding the pieces of the first and second solid plastics materials into the first and second hoppers respectively.

The invention may further be said to consist in any alternative combination of parts, features or steps mentioned herein or shown in the accompanying drawings. Known equivalents of these parts, features or steps which are not expressly set out are nevertheless deemed to be included.

BRIEF DESCRIPTION OF DRAWINGS

Preferred embodiments of the invention will now be further described, by way of example only and without intending to be limiting, with reference to the accompanying drawings of which:

Figure 1 shows a perspective view of an apparatus for re-processing plastics materials into a three-layered extrusion,

Figure 2 shows a perspective exploded view of hoppers, cutters and chutes of the apparatus shown in Figure 1,

Figure 3 shows a perspective exploded view of a hopper and cutter shown in Figures 1 and 2, Figure 4 shows a perspective exploded view of some parts of the apparatus shown in Figure 1,

Figure 5 shows a perspective view of dis-assembled components of an extruder of the apparatus shown in Figures 1 and 4,

Figure 6 shows a side view of a compression auger blade, being part of an auger shown in Figure 5, and

Figure 7 shows a perspective exploded view of one pair of rollers of a set of rollers shown in Figures 1 and 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring to the drawings it will be appreciated that plastics reprocessing, extruding and laminating apparatus may be implemented in various forms. The following embodiments are described by way of example only. For convenience of explanation, the drawings show the device orientated as used in one exemplary application. However, it is to be understood that the invention is not limited to the orientation shown.

It is to be understood that the term "plastics" is used in this specification to refer to materials, including solid materials, which are typically made by polymerizing organic compounds and which, during manufacture or subsequent re-processing, have a plastic state in which they are capable of being formed or reformed into various shapes, for example by molding, extruding or casting. These "plastics" materials are commonly referred to as "plastic" materials or as "plastic", as in the above paragraphs under Field of Invention and Background, for example. It is also to be understood that the word "plastic", as used in this specification to refer to a material, does not by itself indicate that the material is in a plastic state, i.e. is capable of being shaped or formed, (unless the context is clearly not to the contrary).

Figure 1 shows an apparatus for re-processing solid plastics materials into a multi- laminated extrusion. Various components of this apparatus may also be seen, labelled with the same numerals, in the other figures. Plastics waste materials are fed into a pair of inlet hoppers IA, IB. Each inlet hopper feeds plastics material to a top cutter assembly 3 A, 3 B which is driven by a motor 5 A, 5B via toothed drive belt 7A, 7B.

The top cutter assemblies 3A, 3B may be best appreciated from Figure 3 which shows an exploded view of a representative cutter assembly 3, the other cutter assembly being generally the same. Each top cutter assembly 3 has a rotary shaft 9 which is driven by a toothed wheel 11 mounted at one end of the shaft.

Each top cutter assembly 3 includes an upstream shearing cutter 13 and a downstream shearing cutter 14, the latter being shown exploded in Figure 3. The two shearing fMittf»r<5 13 14 park VICWP nn rmςtream r.iitter ςtator 15 and a downstream cutter ςtatnr 17 which each have radial spokes converging at a central hub for supporting the shaft 9. The cutter stators 15, 17 are held apart by a spacer 19. The radial spokes of the downstream stator 17, ie the stator that is further from the inlet hopper 1, are cutting blades with bevelled cutting edges which co-operate with radial blades of a cutter rotor 21. The cutter rotor 21 is mounted on the shaft 9 between each pair of cutter stators 15, 17 to rotate inside the spacer 19. The two shearing cutters 13, 14 are spaced apart by a larger spacer 23.

A rotor 25, with flailing cutting blades 27, and a radially-bladed fan 29 are mounted on the shaft 9 to rotate inside the spacer 23. The shaft extends through a cylindrical outlet duct 31 which has a lower opening 33 at its underside.

Plastics material is fed into each hopper IA, IB to be drawn into the corresponding top cutter assembly 3A, 3B by suction provided by the flailing cutting blades 27, which have a slight twist, and the fan 29. As the plastics material is drawn into the cutting assembly, it is cut into pieces by the flailing cutting blades and the first, upstream, shearing cutter 13. The pieces of plastics materials are then blown on through the top cutter assembly by the fan 29 and flailing cutting blades 27, to be cut further by the second, downstream, shearing cutter 14 and then delivered to the cylindrical outlet duct 31, where the pieces drop through the lower opening 33 into a chute assembly 41 to be described further below.

As may be best appreciated from Figure 1 and the exploded view shown in Figure 2, the two top cutter assemblies 3 A, 3B, with their associated hoppers IA, IB attached, are mounted to the top side of the chute assembly 41, and the two top cutter drive motors 5 A, 5B are mounted to side walls of the chute assembly 41. The chute assembly 41, which is mounted on an upper support frame 43, is positioned over three vertical chutes 45, 46, 47.

The chute assembly 41 directs the flows of plastics pieces from the two top cutter assemblies 3A, 3B to the three vertical chutes. The chute assembly 41 directs the flow of plastics pieces delivered from one top cutter assembly 3 A to one vertical chute 45. The chute assembly 41 divides the flow of plastics pieces delivered from the other top cutter assembly 3B to the other two vertical chutes 46, 47. As will be discussed further below, this '2-into-3' arrangement allows one type of plastics material fed into one inlet hopper to be simultaneously delivered to two upper and lower extruders for forming the two outer layers of a three-layered, or sandwich, extrusion, while another type of plastics material fed into the other hopper is delivered to another intermediate extruder, located between the upper and lower extruders, for forming the inner layer of the three- layered extrusion.

As shown in Figure 1, the three vertical chutes 45, 46, 47 respectively guide the plastics pieces into three extruder assemblies 51, 52, 53. The arrangement of the vertical chutes and extruder assemblies may be best seen in Figure 4 which, for clarity, omits the upper support frame 43 and the components supported thereon including the inlet hoppers \, the top cutter assemblies 3, and the chute assembly 41. The three extruder assemblies 51, 52, 53 are each of similar construction and operate in substantially the same manner. The extruders share a common outlet extrusion nozzle 55 (shown exploded in Figure 4) but are otherwise mounted at different heights and splayed apart at their inlet ends which are coupled to the three vertical chutes.

Each extruder has an auger (some major parts of which are shown in Figures 5 and 6) which extends from an auger inlet portion 57 to an outlet end 59 at which the extruder connects to the common extruder nozzle 55. The length, orientation, and bottom shaping of the vertical chutes 45, 46, 47 are arranged so that each chute closely couples to a housing at the inlet portion 57 of the respective auger.

Each auger has an auger blade 61 with a helical screw 63 spiralling around an axial shaft 65. The auger blade is rotated inside a closely fitting housing 67 by a motor 69 via a speed reduction drive 71 and a belt 72 running around a pair of small and large diameter wheels 73.

For convenience of manufacture, the auger blade is made up of two length portions, an upstream portion 74 and a downstream portion 75. The two length portions are assembled and fixed together in axial alignment to form the assembled auger blade which is shown in Figure 5. The upstream length portion 74 has, at its downstream end, an axial end dowel 76. The dowel fits inside an axial bore (not shown) at the upstream end of the downstream length portion 74 for fastening the two auger portions together.

The helical screw has a compression portion at which the volume between adjacent turns of the helical screw successively reduces in a direction toward the outlet end of the auger. This compression portion extends approximately along the downstream half of the upstream portion 74 of the auger blade, downstream of the inlet portion 57.

The volume reduction of successive turns of the helical screw at the compression portion is provided, in part, by a tapering of the helical screw which tapers from a relatively larger outer diameter Dl at the inlet portion 57 to a relatively smaller outer diameter D2 toward the downstream or outlet end 59 of the auger. This may be best appreciated from the side view of the upstream portion 74 of the auger blade which is shown in Figure 6. The auger housing 67 is correspondingly tapered to maintain the close fitting of the auger housing about the auger blade. The auger housing has a tapered portion 77 (seen best in Figure 5) which tapers from a cylindrical housing 78 at the auger inlet 57, down to an elongate cylindrical housing tube 79.

The volume reduction of successive turns of the helical screw at the compression portion is also provided, in part, by a tapering of the axial auger shaft 65 from a relatively smaller shaft diameter dl at the inlet portion 57 of the auger to a relatively larger shaft diameter d2 in a direction toward the downstream or outlet end 59 of the auger.

The volume reduction of successive turns of the helical screw at the compression portion is also provided, in part, by reducing the pitch of successive turns of the helical screw from a relatively larger pitch length Pl at the inlet portion of the auger to a relatively smaller pitch length P2 in a direction toward the downstream or outlet end 59 of the auger.

The upstream end of the auger shaft 65 is supported in a bearing 81 carried in a bearing support plate 83, as shown in Figure 5. The helical screw 63 extends substantially continuously along the auger blade 61 from the inlet portion 57 at the upstream end, to the downstream outlet end 59. The smaller pitch P2 and smaller outer diameter D2 of the helical screw 63, and the larger diameter d2 of the shaft 65, pertaining at the downstream end of the upstream length portion 74 of the auger blade 61 also apply to, and remain substantially constant along, the downstream length portion 75 of the auger blade.

The auger housing tube 19 is surrounded by a cylindrical jacket 85. Oil is heated in a tank 89, located under the three extruder assemblies (as seen in Figure 1), and circulated by a pump 91 via a network of pipes 93 through each auger jacket 85 to heat the auger housing tubes 79 and the plastics material being advanced therethough.

The extruder assemblies 51, 52, 53, nozzle 55, auger motors 69 and their associated drive components, oil tank 89, circulation pump 91 and the piping network 93 are all supported on a lower main frame 95. The upper support frame 43 is also supported on the lower main frame 95.

In operation of the extruders, pieces of plastics material, falling down the vertical chutes 45, 46, 47 from the top cutter assemblies, are fed into the cylindrical auger inlet housing 78 at the auger inlet portion 57. The auger blade 61 is rotated by the drive motors 69 to move the plastics pieces into an elongate cylindrical auger housing tube 79. This housing tube is a heavy-walled tube to resist the compressive forces that are formed by the auger action. The auger inlet housing 78 has a semi-cylindrical extension with an upper opening at which the plastics pieces are fed from an associated vertical chute into the auger.

In some situations the plastics pieces jam or layer-up in the vertical chutes 45, 46, 47 and do not reliably move down into the inlet portions 57 of the respective augers. In this case, fingers (not shown) may be fitted to the inlet portion 57 of each auger blade 61. The fingers are attached to the auger blade to rotate with the blade and extend outwardly beyond the outer circumference of the auger blade. The outwardly extending fingers brush or 'tickle' the plastic pieces at the bottom of the vertical chute to help dislodge any jam and keep the pieces moving downward from the chute and into the auger. The fingers are inherently resilient or sprung biased so that, as the auger blade rotates through part of each rotation, the fingers move against the resilient biasing to be inside the outer circumference of the auger blade and inside the cylindrical housing 87 at the auger inlet 57.

The lower part of the semi-cylindrical extension may be provided with perforations opposite the upper opening, and a vacuum may be applied through the perforations to help draw the plastics pieces down from the vertical chutes 45, 46, 47 and into the inlet portion 57 of each respective auger.

The plastics pieces fed into the auger from the vertical chutes 45, 46, 47 from the top cutter assemblies, are engaged by the helical auger blade 63 and advanced by the rotating blade toward the common nozzle 55. As the plastics material passes through the auger housing tube 79, it is heated to a temperature at which the material softens to a paste. The decreasing pitch P and outer diameter D of the helical screw 63 and the increasing diameter d of the auger shaft 65 compress the material as it moves downstream and advances toward the common nozzle 55.

The common outlet nozzle 55 comprises four main parts as may be best appreciated from the exploded view of the nozzle shown in Figure 4. Two inner parts are the left and right nozzle inner halves 101, each of which has a similar or identical array of three channels 103 leading from an inlet side 105, where they are spaced apart vertically, to converge at an opposite outlet side 107. The two inner halves 101 are assembled and clamped together, as seen in Figure 1, the channels forming three conduits leading from the inlet side 105 to converge at an outlet orifice 109 of the common extruder nozzle 55.

The two inner halves 101 of the nozzle are flanked by two tanks 110 through which oil is circulated to control the nozzle temperature. The oil circulated through these tanks may be heated or cooled to soften or harden the viscous liquid as it passes through the nozzle just prior to being extruded from the nozzle.

In operation of the extruder system, plastics material is cut into pieces and converted to three viscous liquid flows which are pressurised and advanced by rotation of the augers to the commnn

*>*> wlipira the three flows are rvrrmσht +no-f>+li»r +r> V>» exv+rnA&A from the common nozzle outlet orifice 109 as a single three-layered extrusion. The inner layer is largely derived from the plastics material fed into the first hopper IA, and the upper and lower outer layers are largely derived from the plastics material fed into the second hopper IB. When the three viscous flows converge in the common nozzle 55, just before they issue from the outlet orifice 109, there is preferably some intermixing of the viscous flows. This intermixing helps the different layers to bond together and thereby improve the strength of the final product.

Aligned with the extruder nozzle outlet is a line of roller pairs 111 mounted on a beam 113 of the main support frame 95. Each roller pair has upper and lower rollers 115 which are carried on mutually parallel roller axle shafts 117 which are mechanically coupled together by toothed gear wheels 119 so that the rollers contra-rotate. The rollers and shafts are supported by a pair of parallel roller mounting plates 121 which are held together by three spacer rods 123. The roller mounting plates are attached to the beam 113 of the main support frame 95 with the nip region between the two rollers of each pair aligned with the outlet of the common extruder nozzle so that material extruded from the nozzle outlet passes successively between each pair of rollers to support and cool the extruded material. The rollers can be used to flatten and form the extruded material into a predetermined shape with a predetermined dimension. The roller diameter may be smaller than that of rims at each end of each roller. The rims of the upper roller ride on those of the lower roller to ensure a minimum spacing between the major roller surfaces at the nip region, and thus provide a predetermined thickness in the finished product after extruding and rolling.

At a distance out from the extruding nozzle, where the extruded material has cooled sufficiently, a flying cutter (not shown) may be used to cut the extruded material into predetermined lengths, e.g. up to 6 m long, which are then fed to a stacker (not shown).

The plastics re-processor described above converts plastics materials, for example plastic films, into a paste that is extruded as a continuous extrusion and then may be cut into lengths as required. In one embodiment, the rotary shaft 9 in the cutters 3 is rotated at about 380 rpm; the auger blade is rotated at about 22 rpm; the auger blade tapers with a ratio of 2:1 between the larger and smaller outer diameters, the auger blade has a single helical screw with an upstream portion having six screw turns of 200 mm outer diameter and 110 mm pitch on a shaft diameter of 62 mm, tapering down through an intermediate section having three screw turns of 85 mm outer diameter on a shaft diameter of 62 mm, to a screw portion having about seven screw turns of 55 mm pitch on a shaft diameter which increases from 62 mm up to about 90 mm; and the heated oil is circulated through the jacket to heat the plastics material to a temperature of between about 140 ⁰C to 160 ⁰C to remove any 'memory' of the form of the material and convert it to a paste.

The plastics is not melted to a readily flowing liquid but is just brought to a very viscous liquid with a paste-like consistency suitable for extrusion. The nozzle is heated to approximately the same temperature as the auger, i.e. about 140 ⁰C to 160 ⁰C. The plastics material is not heated, in the auger or nozzle, to a temperature causing out- gassing from the material. The residence time of plastics material within the auger, i.e. the time taken for the plastics material to traverse through the auger form inlet to extruder nozzle, is about 2 to 2.5 minutes. As will be appreciated, this is governed by the auger blade speed of about 22 rpm and the number of helical turns of the auger blade.

In one preferred use of the processing system, low density polyethylene (LDPE) Grade 4 plastic, for example industrial shrink wrap, is introduced into one hopper IA and fed to the middle extruder 51 to form the inner layer of the three-layered extrusion, while high density polyethylene (HDPE) Grade 2 plastic, for example supermarket shopping bags, is introduced into the hopper IB and fed to the upper and lower extruders 52, 53 to form the outer two layers of the three-layered extrusion.

The multi-layered or laminated product may be used for planks for assembly into pallets for freighting and storing of goods. The use of the reprocessed plastic material in this application avoids issues of transfer across borders of unwanted insects, fungi, diseases, and other wood-borne problems. The product is also suitable for use as poles, strainers, posts and droppers in fences, pergolas and other support structures for use in agriculture and horticulture, e.g. orchards, vineyards, etc, where it is desirable to avoid problems with leaching of chemical wood preservatives associated with similar products made from some woods. This may be particularly advantageous in situations where organic certification is required.

Another application of the extruded product is cladding for buildings, and particularly as a replacement for timber weatherboards.

The foregoing describes the invention including preferred forms thereof. Alterations and modifications as will be obvious to those skilled in the art are intended to be incorporated within the scope of the invention as defined in the accompanying claims. For example, other than three extruders may be used to forma multi-layered product having a corresponding number of layers. Or an additional extruder or extruders could be arranged to feed paste-like plastics material via a respective conduit or conduits to one or both sides of the nozzle orifice to form a extrusion with a three or four sided high density plastics outer layer around an inner low density plastics core.

LIST OF FEATURES LABELLED IN THE FIGURES

inlet hopper IA, IB speed reduction drive 71 top cutter assembly 3 A, 3B belt 72 motor 5A, 5B 35 wheels 73 drive belt 7A, 7B upstream auger blade portion 74 rotary shaft 9 downstream auger blade portion 75 wheel 11 dowel 76 upstream shearing cutter 13 tapered housing portion 77 downstream shearing cutter 14 40 auger inlet housing 78 upstream cutter stator 15 auger housing tube 79 downstream cutter stator 17 bearing 81 spacer 19 bearing support plate 83 cutter rotor 21 auger jacket 85 larger spacer 23 45 tank 89 rotor 25 pump 91 flailing cutting blades 27 network pipes 93 radially-bladed fan 29 main frame 95 cylindrical outlet duct 31 left and right nozzle inner halves 101 opening 33 50 three channels 103 chute assembly 41 inlet side 105 upper support frame 43 outlet side 107 vertical chutes 45, 46, 47 nozzle outlet orifice 109 extruder assemblies 51, 52, 53 nozzle tanks 110 common extrusion nozzle 55 55 roller pair 111 auger inlet portion 57 beam 113 auger outlet end 59 roller 115 auger blade 61 toller axle shaft 117 helical screw 63 toothed wheel 119 auger shaft 65 60 roller mounting plate 121 housing 67 spacer rod 123 large screw outer diameter Dl large shaft diameter d2 small screw outer diameter D2 5 large screw pitch length Pl small shaft diameter dl small screw pitch length P2

Claims

WHAT WE CLAIM IS:

1. A plasties extruder for re-processing solid plasties material, the extruder consisting, at least in part, of:

an auger having an auger blade located inside a closely fitting auger housing for advancing plastics material fed to an inlet portion of the auger to an outlet end of the auger by rotation of the auger blade, the auger blade including a helical screw with a compression portion at which the volume between adjacent turns of the helical screw successively reduces in a direction toward the outlet end of the auger;

a heater for heating solid plastics material, when being advanced by the auger blade through the compression portion, to a temperature at which the solid plastics converts to a viscous liquid; and

2. A plastics extruder as claimed in claim 1, wherein the helical screw extends substantially continuously along the auger from the inlet portion to the outlet end.

3. A plastics extruder as claimed in claim 1 or 2, wherein the compression portion of the helical screw includes a tapered portion at which the helical screw tapers from a relatively larger outer diameter to a relatively smaller outer diameter in a direction toward the outlet end of the auger and the auger housing tapers correspondingly to maintain the close fitting of the auger housing about the auger blade.

4. A plastics extruder as claimed in claim 3, wherein the helical screw extends between the tapered portion and the outlet end with a plurality of helical screw turns having a common outer diameter.

5. A plastics extruder as claimed in any one of the preceding claims, wherein the auger has an axial auger shaft and at the compression portion the auger shaft tapers from a relatively smaller shaft diameter to a relatively larger shaft diameter toward the outlet end of the auger.

6. A plastics extruder as claimed in any one of the preceding claims, wherein the pitch of the helical screw at the compression portion reduces in a direction toward the outlet end of the auger.

7. A plastics extruder as claimed in any one of the preceding claims, wherein the heater consists, at least in part, of a jacket that surrounds the auger housing for circulation of a heated liquid around the auger housing.

8. A laminator for producing a multilayered extrusion, the laminator consisting, at least in part, of a plurality of plastic extruders each as claimed in any one of claims 1 to

7, wherein the extruder nozzle of each plastics extruder is a common extruder nozzle through which viscous liquids from each of the plastics extruders can be extruded simultaneously.

9. A laminator as claimed in claim 8, including one or more pairs of rollers, the rollers of the or each pair having mutually parallel axes and being arranged one above the other to form a nip region therebetween, and the nip region being aligned to accept material extruded from the common nozzle.

10. A laminator as claimed in claim 9, wherein the rollers of the or each pair of rollers are mechanically coupled to one another for rotation in opposite directions.

11. A laminator as claimed in claim 8, 9 or 10, wherein the common extruder nozzle has a single nozzle outlet which is connected for viscous liquid flow via respective nozzle conduits to the outlet end of the auger of each of the plastics extruders.

12. A laminator as claimed in claim 11, wherein the plurality of plastic extruders is three plastics extruders, and the single nozzle outlet is connected for viscous liquid flow via three respective nozzle conduits to the outlet end of the auger of each of the three plastics extruders.

13. A laminator as claimed in claim 12, wherein the three nozzle conduits are arranged to converge at the single nozzle outlet with two of the three nozzle conduits on opposite sides of the third nozzle conduit, a first hopper is arranged for feeding solid plastics material to the inlet portion of the auger of each of the two plastics extruders connected to the third nozzle conduit, and a second hopper is arranged for feeding solid plastics material to the inlet portion of the auger of the plastics extruder connected to the other two nozzle conduits.

14. A laminator as claimed in claim 13, wherein two cutter devices are arranged respectively above the first and second hoppers for cutting solid plastics materials into pieces and for feeding the pieces into the respective first and second hoppers.

15. A method of re-processing plastics material consisting, at least in part, of the following steps:

advancing the plastics material through the compression portion of the helical screw and onward to the outlet end of the auger by rotating the auger blade;

heating the solid plastics material being advanced by the auger blade through the compression portion to a temperature at which the solid plastics material converts to a viscous liquid; and

16. A method of re-processing a plastics material as claimed in claim 15, wherein the step of advancing the plastics material through the compression portion of the helical screw includes advancing the plastics material through a tapered portion of the helical screw which tapers from a relatively larger outer diameter to a relatively smaller tapering correspondingly to maintain the close fitting of the auger housing about the auger blade.

17. A method of re-processing a plastics material as claimed in claim 16, wherein the step of advancing the plastics material onward to the outlet end of the auger includes advancing the plastics material along a portion of the helical screw which extends between the tapered portion and the outlet end with a plurality of helical screw turns having a common outer diameter.

18. A method of re-processing a plastics material as claimed in any one of claims 15, 16 or 17, wherein the auger has an axial auger shaft and at the compression portion the auger shaft tapers from a relatively smaller shaft diameter to a relatively larger shaft diameter toward the outlet end of the auger.

19. A method of re-processing a plastics material as claimed in any one of claims 15 to 18, wherein the pitch of the helical screw at the compression portion reduces in a direction toward the outlet end of the auger.

20. A method of re-processing a plastics material as claimed in any one of claims 15 to 19, wherein in the step of heating the solid plastics material, a heated liquid is circulated through a jacket that surrounds the auger housing.

21. A method of producing a multilayered extrusion consisting, at least in part, of simultaneously performing the method as claimed in any one of claims 15 to 20 with a plurality of augers, wherein the extruder nozzle of each plastics extruder is a common extruder nozzle and viscous liquid is extruded simultaneously from each of the plastics extruders.

22. A method of producing a multilayered extrusion as claimed in claim 21, including the additional steps of: arranging one or more pairs of rollers, the rollers of the or each pair having mutually parallel axes and being arranged one above the other to form a nip region therebetween, and the nip region being aligned to accept material extruded from the common nozzle; and passing the material extruded from the common extruder nozzle through the nip region between the or each pair of rollers.

23. A method of producing a multilayered extrusion as claimed in claim 22, including the additional step of:

24. A method of producing a multilayered extrusion as claimed in claim 21, 22 or 23, wherein the common extruder nozzle has a single nozzle outlet which is connected for viscous liquid flow via respective nozzle conduits to the outlet end of the auger of each of the plastics extruders.

25. A method of producing a multilayered extrusion as claimed in claim 24, wherein the plurality of plastic extruders is three plastics extruders, and the single nozzle outlet is connected for viscous liquid flow via three respective nozzle conduits to the outlet end of the auger of each of the three plastics extruders.

26. A method of producing a multilayered extrusion as claimed in claim 25, wherein the three nozzle conduits are arranged to converge at the single nozzle outlet with two of the three nozzle conduits on opposite sides of the third nozzle conduit, the method of producing a multilayered extrusion also including the steps of:

feeding a second plastics material to a second hopper arranged to feed the second plastics material to the inlet portion of the auger of each of the two plastics extruders connected to the other two nozzle conduits.

27. A method of producing a multilayered extrusion as claimed in claim 26, including the further steps of: cutting first and second solid plastics materials into pieces; and

feeding the pieces of the first and second solid plastics materials into the first and second hoppers respectively.