Barrel for an extruder, and an extruder including the same

Abstract

A barrel for an extruder. The barrel comprising a barrel wall defining a chamber for receiving a screw in use. The chamber includes at least a barrel feed section corresponding to a screw feed section in use, the barrel feed section configured to receive and process solid material pieces. At least one groove defined in the barrel wall. The groove extends along the barrel wall and is disposed only in the barrel feed section. A depth of the groove is less than a largest dimension of the solid material pieces. A width of the groove is at least as wide as the largest dimension of the solid material pieces.

Description

[0001] BARREL FOR AN EXTRUDER, AND AN EXTRUDER INCLUDING THE SAME

[0002] FIELD OF THE TECHNOLOGY

[0003] The present technology relates to barrels for extruders for converting solid polymers to polymer melts, and extruders including the same.

[0004] BACKGROUND

[0005] Extruders comprise one or more plasticizing screws having one or more flights rotatably housed in a barrel for converting solid material to a molten form, typically for an eventual molding step. There are many different designs of plasticizing screw which are tailored to perform specific functions such as conveying the material to be melted in the barrel, compressing the material, melting the material, pressurizing the material and mixing the material.

[0006] An extruder with optimal operation would have a consistent output in terms of a steady and uniform flow of molten material. However, extruders may operate non-optimally when material accumulates on the screw flights which may occur due to a breakup of the solid bed in the screw channel. This can in turn cause a partial blockage interrupting the smooth flow of material. In order to maintain an output rate, an rpm of the screw must be increased which also increases torque. The resultant increase in pressure and shear rate may dislodge the accumulation. However, it does not prevent the accumulation from building up again. Such cyclical accumulations create unnecessary demands on the extruder, ultimately limiting their lifespan, as well as affecting the quality of the melt during operation.

[0007] Therefore, there is a need for an extruder that avoids such accumulation for optimal operation.

[0008] SUMMARY

[0009] It is an object of the present invention to ameliorate at least some of the inconveniences present in the prior art. More specifically, it is an object of the present technology to provide an extruder that avoids accumulation and break up of the solid bed.

[0010] Broadly, in certain aspects of the present technology, there is provided a barrel for an extruder which is adapted so as to avoid accumulation and partial blockage. In other aspects of the present technology, there is provided an extruder including the adapted barrel and a screw.

[0011] Specifically, in one aspect, there is provided a barrel for an extruder, the barrel comprising: a barrel wall defining a chamber for receiving a screw in use, the barrel wall having an internal diameter, the chamber including at least a barrel feed section corresponding to a screw feed section in use, the barrel feed section configured to receive and process solid material pieces; at least one groove defined in the barrel wall, the at least one groove having a length, a width and a depth, the groove extending along the barrel wall and disposed only in the barrel feed section; the depth of the groove being less than a largest dimension of the solid material pieces; and the width of the groove being at least as wide as the largest dimension of the solid material pieces.

[0012] In certain embodiments, the groove has a non-tapered portion having a length and in which a depth of the groove is substantially constant along its length, and a tapered portion having a length and in which the depth decreases along its length.

[0013] In certain embodiments, in the non-tapered portion, a ratio of the length of the groove to the internal diameter of the barrel is less than about 3.

[0014] In certain embodiments, in the non-tapered portion, the ratio of the length of the groove to the internal diameter of the barrel is between about 0.9 to about 1.5.

[0015] In certain embodiments, in the non-tapered portion, the length of the groove is less than about 255 mm or less than about 200 mm.

[0016] In certain embodiments, in the tapered portion, the length is less than the internal diameter of the barrel.

[0017] In certain embodiments, in the tapered portion, the ratio of the internal diameter of the barrel to the length of the groove is between about 3.0 to about 5.0.

[0018] In certain embodiments, in the tapered portion, the length of the groove is less than about 50 mm.

[0019] In certain embodiments, the length of the groove in the tapered portion is less than the length of the groove in the non-tapered portion.

[0020] In certain embodiments, a ratio of (the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion) to an internal diameter of the barrel is less than about 3. In certain embodiments, the ratio of (the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion) to the internal diameter of the barrel is between about 1.2 to about 1.6.

[0021] In certain embodiments, the length of the tapered and non-tapered portions of groove is less than about 255 mm or less than about 245 mm.

[0022] In certain embodiments, one or more of (i) the length of the groove in the tapered portion, (ii) the length of the groove in the non-tapered portion, and (iii) the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion is proportional to the internal diameter of the barrel.

[0023] In certain embodiments, the width of the groove is agnostic (independent) of the internal diameter of the barrel.

[0024] In certain embodiments, the depth of the groove is agnostic (independent) of the internal diameter of the barrel.

[0025] In certain embodiments, the depth of the groove at the non-tapered portion is about 50% of the largest dimension of the solid material piece.

[0026] In certain embodiments, a width of the groove is configured such that it can house at least two pieces of the solid material pieces in side-by-side configuration.

[0027] In certain embodiments, the groove has ahead end and a tail end, the head end being longitudinally aligned with a feed throat of the barrel.

[0028] In certain embodiments, the at least one groove comprises a plurality of grooves that are circumferentially spaced from one another, the number of grooves being proportional to the internal diameter of the barrel.

[0029] In certain embodiments, the length of the groove extends along the entirety of the barrel feed section. From another aspect. There is provided an extruder comprising a barrel as defined herein, and a screw rotatably housed in the barrel.

[0030] By providing at least one groove in the barrel wall as defined above, accumulation of the solid material pieces can be avoided or reduced.

[0031] In the context of the present specification, the words “first”, “second”, “third”, etc. have been used as adjectives only for the purpose of allowing for distinction between the nouns that they modify from one another, and not for the purpose of describing any particular relationship between those nouns. Further, as is discussed herein in other contexts, reference to a “first” element and a “second” element does not preclude the two elements from being the same actual real-world element.

[0032] These and other aspects and features of non-limiting embodiments of the present technology will now become apparent to those skilled in the art upon review of the following description of specific non-limiting embodiments of the technology in conjunction with the accompanying drawings.

[0033] Embodiments of the present technology each have at least one of the above-mentioned object and / or aspects, but do not necessarily have all of them. It should be understood that some aspects of the present technology that have resulted from attempting to attain the above-mentioned object may not satisfy this object and / or may satisfy other objects not specifically recited herein.

[0034] Additional and / or alternative features, aspects and advantages of embodiments of the present technology will become apparent from the following description, the accompanying drawings and the appended claims.

[0035] BRIEF DESCRIPTION OF THE DRAWINGS

[0036] A better understanding of the embodiments of the present technology (including alternatives and / or variations thereof) may be obtained with reference to the detailed description of the nonlimiting embodiments along with the following drawings, in which:

[0037] Figure 1 is a schematic representation of an example molding system that includes a barrel assembly having a barrel according to embodiments of the present technology.

[0038] Figure 2 is the barrel assembly of Figure 1 according to embodiments of the present technology. Figure 3 is a top plan view of the barrel of Figure 1, according to embodiments of the present technology.

[0039] Figure 4 is a cross-section through the barrel of Figure 3 across the lines A-A and depicting a groove defined in a barrel wall, according to embodiments of the present technology.

[0040] Figure 5 is a cross-section through the barrel of Figure 3 across the lines B-B, according to embodiments of the present technology.

[0041] Figure 6 is a cross-section through the barrel of Figure 4 across the lines D-D, according to embodiments of the present technology.

[0042] Figure 7 is an enlarged view of detail C from Figure 5, according to embodiments of the present technology.

[0043] Figure 8 is an enlarged view of detail E from Figure 3, according to embodiments of the present technology.

[0044] Figure 9 is the enlarged view of detail C from Figure 5 and including molding material, according to embodiments of the present technology.

[0045] DETAILED DESCRIPTION

[0046] Reference will now be made in detail to various non-limiting embodiment(s) of a barrel 10 for an extruder 12 for converting solid material 14 to molten material 16. By molten material 16 is meant material that can flow whether or not it is fully in a melt state. The barrel 10 and the extruder 12 will be described with reference to an example molding system 18 in which the extruder 12 provides the molten material 16 to a mold 20 for manufacturing a molded article 22 from the molten material 16. For example, the solid material 14 may comprise solid material 14 pieces such as pellets. The solid material 14 may comprise a polymer such as polyethylene terephthalate (PET) and / or PET blends, or any other material suitable for molding. The mold 20 may be an injection molding system configured to make preforms for beverage containers, such as bottles and the like. However, it will be appreciated that the barrel 10 is not necessarily limited for use in the example extruder 12 as described nor limited for use with the example molding system 14 described and can be used alone or in conjunction with other systems and / or sub-systems.

[0047] It should be understood that other non-limiting embodiment(s), modifications and equivalents will be evident to one of ordinary skill in the art in view of the non-limiting embodiment(s) disclosed herein and that these variants should be considered to be within scope of the appended claims. Furthermore, it will be recognized by one of ordinary skill in the art that certain structural and operational details of the non-limiting embodiment(s) discussed hereafter may be modified or omitted (i.e. non-essential) altogether. In other instances, well known methods, procedures, and components have not been described in detail.

[0048] Referring to Figures 1 and 2, there is shown a depiction of the molding system 18 comprising the extruder 12 and the mold 20. As stated above, the molding system 18 is configured to manufacture the molded article 22 from the molten material 16 provided by the extruder 12 to the mold 20. The molding system 18 may also include a hot runner system 24 for conveying the molten material 16 from the extruder 12 to the mold 20. The mold 20 is not particularly limited and may comprise stationary and movable-mold assemblies 26, 28 and be associated, in use, with stationary and moveable platens 30, 32.

[0049] The extruder 12 comprises a barrel assembly 34 and a screw assembly 36. The barrel assembly 34 comprises the barrel 10. The barrel 10 has a barrel wall 38 that defines a chamber 40. The screw assembly 36 comprises a screw 42 which is rotatably housed in the chamber 40 of the barrel 10, and a controller 44 for controlling operation of the screw 42.

[0050] The barrel 10 has a feed end 46 and an outlet end 48. At the feed end 46, there is a hopper 50 connected to the barrel 10 by a feed throat 52. The solid material 14, such as plastic pellets, housed in the hopper 50 can be introduced into the chamber 40 of the barrel 10 through the feed throat 52. At the outlet end 48, the barrel 10 has a machine nozzle 54 through which a stream of the molten material 16 can be provided to the mold 20 by the hot-runner system 24. A heater assembly 56 is connected to an outside of the barrel wall 38 and disposed between the feed and outlet ends 46, 48 for providing heat through the barrel wall 38.

[0051] In operation, the screw assembly 36 converts the solid material 14 provided at the feed end 46 to the molten material 16 through heat supplied by the heater assembly 56 through the barrel wall 38 as well as through heat generated from shear with the screw 42 as the screw 42 rotates in the barrel chamber 40. The solid material 14 will convert to the molten material 16 as it is being conveyed within the chamber 40 towards the outlet end 48. It will be understood that, in use, there are portions of the chamber 40 between the feed and outlet ends 46, 48 which will contain both the solid material 14 and the molten material 16.

[0052] A configuration of the screw 42 is not particularly limited and generally comprises a screw root 58 having one or more flights 60 extending therefrom and spirally disposed around at least a portion of the screw root 58. The screw root 58 may have any desired diameter, which may be dependant at least on the specific application for the screw 10. The screw 42 can be rotatably driven at a desired rotational speed by the controller 44 at the feed end 46 of the screw 42. The screw 42 and an inner side 68 of the barrel wall 38 thus define one or more channels for housing the solid material 14 as it is transformed to the molten material 16. The inner side 68 of the barrel wall 38 is substantially cylindrical in shape.

[0053] A length of the screw root 58 can be generally subdivided functionally into a feed section 62, a melting section 64 downstream of the feed section 62, and a mixing section 66 downstream of the melting section 64. The feed section 62, the melting section 64 and the mixing section 66 may be defined by one or more parameters, such as: relative lengths of the sections along the screw root 58, a pitch of the flight of the screw, a shape of the flight of the screw and a depth of the flight of the screw.

[0054] In the feed section 62, the solid material 14 generally compacts. There is no external heat applied at the feed section 62 and melting of the solid material 14 is not expected. In the melting section 64, the solid material 14 is heated so as to melt the solid material 14. The heating may be supplied by the external heater assembly 56, through shear heating and / or through heat conduction from molten material 16 (or a combination thereof). In this respect, heaters of the heater assembly 56 are generally disposed adjacent or otherwise close to the melting section 64 of the screw 42. The mechanism of melting is not particularly limited and may comprise, for example, one or more of a layered melting effect and a dispersive melting effect. Further compression of the pellets of the solid material 14 may occur in the melting section 64 by squeezing the solid material 14 against the inner side 68 of the barrel wall 38 as the screw 10 is rotated. The mixing section 66 is configured to ensure mixing of the molten material 16 as well as any additives that may be added. In the mixing section 66, instead of flights 60, there may be provided helical ribs, a pineapple shaped component, a barrier flight, a blister ring, or any other structure that can capture non-melted material for the purposes of mixing and / or function as a pressure barrier for the upstream portions of the screw 42. It will be appreciated that the specific configurations of the feed section 62, the melting section 64 and the mixing section 66 such as their relative length can be determined according to manners known in the art such as to emphasize a desired function, such as high melt throughput or good mixing. The specific configurations of the feed section 62, the melting section 64 and the mixing section 66 of the screw 42 are not limited in embodiments of the present technology.

[0055] When the screw 42 is received in the barrel 10, the feed section 62 of the screw 42 is received in a barrel feed section 63 of the barrel 10, the melting section 64 of the screw 42 is received in a barrel melting section 65 of the barrel 10, and the mixing section 66 is received in a barrel mixing section 67 of the barrel 10. The barrel feed section 63 is not heated. It will be appreciated that as the screw reciprocates, the feed section 62 of the screw 42 may sometimes be received in the melting section 64 of the barrel 10, and the melting section 64 of the screw 42 may sometimes be received in the barrel melting section 65.

[0056] Turning now to Figures 3 to 5, there is shown a top plan view of an embodiment of the barrel 10 of the present technology together with longitudinal and transverse cross-sections of the barrel 10 through the feed throat 52.

[0057] According to embodiments of the present technology, the barrel wall 38 has at least one groove 70 defined therein. The at least one groove 70 is defined in the barrel feed section 63. Other than the grooves 70, the barrel 10 may or may not have other physical features that define one or more of the barrel feed section 63, the barrel melting section 65 and the barrel mixing section 67. In some embodiments of the present technology, the at least one groove 70 is defined only in the barrel feed section 63 (i.e. not in the other sections of the barrel 10). In some embodiments of the present technology, the at least one groove 70 length spans an entire length of the barrel feed section 63.

[0058] In the depicted embodiment, there are six grooves 70 spaced circumferentially about the inner side 68 of the barrel wall 38, three of which are visible in Figure 4. In certain embodiments, the number of grooves 70 provided are related to an internal diameter Db of the barrel 10: the larger the internal diameter Db, the more grooves 70 are provided. For example, seven grooves 70 are provided for an internal diameter Db of 155 mm, six grooves 70 are provided for an internal diameter Db of 140 mm, five grooves 70 are provided for an internal diameter Db of 120 mm, four grooves 70 are provided for an internal diameter Db of 100 mm, and three grooves 70 are provided for an internal diameter Db of 85 mm. Expressed a different way, the number of grooves 70 is also a function of a diameter Ds of the screw root 58: the larger the diameter Ds, the more grooves 70 are provided.

[0059] As best seen in Figure 4, each groove 70 has a groove longitudinal axis 72 that is parallel to a barrel longitudinal axis 74. The groove longitudinal axis 72 of each groove 70 is parallel to each other. The grooves 70 are equidistantly spaced from each other, but this does not need to be so in each and every embodiment of the present technology.

[0060] Each groove 70 has a head end 76 and a tail end 78. Each groove 70 is disposed such that the head end 76 is substantially longitudinally aligned with the feed throat 52. In some embodiments, the head end 70 is substantially longitudinally aligned with an edge 80 of the feed throat 52 that is closest to the feed end 46.

[0061] As best seen in Figure 5, the groove 70 includes a non-tapered portion 82 at the head end 76 and a tapered portion 84 at the tail end 78. The non-tapered portion 82 can also be referred to as a fulldepth portion 82.

[0062] Describing first the non-tapered portion 82, the groove 70 at the non-tapered portion 82 can be defined by a length 86, a depth 88, a width 90 and a surface area 92. The length 86 is proportional to the internal diameter Db of the barrel 10: the larger the internal diameter Db of the barrel 10, the longer the length 86. In certain embodiments, the length 86 is more than the internal diameter Db of the barrel 10. In certain embodiments, the length 86 is less than the internal diameter Db of the barrel 10. In certain embodiments, a ratio of the length 86 to the internal diameter Db of the barrel 10 is between about 0.9 to about 1.5, such as about 0.9, about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, or about 1.5. In certain embodiments the ratio of the length 86 of the non-tapered portion 82 of the groove 70 to the internal diameter Db of the barrel 10 is less than about 3. In certain embodiments, a ratio of the length 86 to the internal diameter Db of the barrel 10 is between about 1.0 to about 2.9, such as about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, or about 2.9. The length 88 may also be expressed as a function of the diameter Dsof the screw root 58. In certain embodiments, the length 86 of the non-tapered portion 82 of the groove 70 is between about 80 mm to about 200 mm, such as about 80 mm, about 90 mm, about 100 mm, about 110 mm, about 120 mm, about 130 mm, about 140 mm, about 150 mm, about 160 mm, about 170 mm, about 180 mm, about 190 mm, or about 200 mm. In certain embodiments the length of the groove 70 is less than about 255 mm.

[0063] The depth 88 of the non-tapered portion 82 of the groove 70, when viewed longitudinally, is constant. In certain embodiments, the depth 88 in the non-tapered portion 82 is about 1 mm. As the groove 70 is defined within the cylindrical inner side 68 of the barrel wall 10, the depth 88 of the groove 70 is not constant when viewed transversely because of a curvature of the inner side 68 (Figure 6). Therefore, by depth 88 is meant herein the depth 88 at a transverse midportion thereof (i.e. midway between side edges 94, 96 of the groove 70). The depth 88 of the non-tapered portion 82 of the groove 70 is agnostic of a size of the barrel 10, such as the internal diameter Db.

[0064] In certain embodiments, the depth 88 of the non-tapered portion 82 of the groove 70 may be defined relative to a largest dimension 98 of the solid material 14 pieces. To account for variability in size and shape of the different solid material 14 pieces, a largest dimension 98 of the different solid material 14 pieces may be taken into account. For example, for a spherical solid material 14 piece, the largest dimension 98 may comprise a diameter of each solid material 14 piece. For a cylindrical solid material 14 piece, the largest dimension 98 of the solid material 14 pieces may comprise a length of the cylindrical piece. As best seen in Figure 8, the depth 88 of the non-tapered portion 82 of the groove 70 is less than the largest dimension 98 of the solid material 14 pieces. In certain embodiments, the depth 88 of the non-tapered portion 82 of the groove 70 is about 50% of the largest dimension 98 of the solid material 14 pieces. When the solid material 14 pieces are housed in the groove 70 such that a given solid material 14 piece rests on a groove base 100, a portion of that given solid material 14 piece extends out of the groove 70 and extends radially beyond the inner side 68 barrel wall.

[0065] The width 90 of the non-tapered portion 82 of the groove 70 can be defined as a distance between the groove side edges 94, 96. The width 90 is greater than the depth 88, and is less than the length 86. In certain embodiments, the width 90 is 8x larger than the depth 88. In certain embodiments, the width 90 is about 4% to about 10% of the length 86. The width 90 is agnostic of a size of the barrel 10, such as the internal diameter Db. In certain embodiments, the width 90 is about 8 mm.

[0066] In certain embodiments, the width 90 of the non-tapered portion 82 of the groove 70 may be defined relative to the largest dimension 98 of the solid material 14 pieces. The width 90 is wider than the largest dimension 98 of the solid material 14 piece. In certain embodiments, the width 90 is configured such that the non-tapered portion 82 of the groove 70 can house more than one solid material 14 piece, such as at least two pieces, three pieces, or four pieces of the solid material 14. As best seen in Figure 8, in certain embodiments, the width 90 is configured to house three solid material 14 pieces when they rest on the groove base 100 in side-by-side configuration.

[0067] The surface area 92 of the non-tapered portion 82 of the groove 70 ranges from about 1900 mm2to about 11100 mm2, depending on a size of the barrel 10. In certain embodiments a ratio of the surface area of the non-tapered portion 82 of the groove 70 relative to a surface area of the barrel 10 at the region of the non-tapered portion 82 is between about 9% and about 12%, such as about 9%, about 10%, about 11% or about 12%.

[0068] Referring to Figure 6, the tapered portion 84 has a length 102, a depth 104, a width and a surface area. The length 102 of the tapered portion 84 of the groove 70 is less than the length 86 of the non-tapered portion 82. The length 102 of the tapered portion 84 of the groove 70 relative to the length 86 of the non-tapered portion 82 is about 15% to about 50%, such as for example, about 15%, about 20%, about 21%, about 22%, about 23%, about 24%, about 25%, about 30%, about 35%, about 40%, about 45% or about 50%.

[0069] A ratio of the internal diameter Db of the barrel 10 to the length 102 of the tapered portion 84 of the groove 70 is between about 3.0 to about 5.0, such as about 3.3, about 3.5, about 3.75, about 4.2, or about 4.5. Grooves 70 defined in larger internal diameter Db barrels may have a longer tapered portion 84 lengths 102 relative to grooves 70 defined in smaller internal diameter Db barrels. In certain embodiments, the ratio of the length 102 of the tapered portion 84 of the groove 70 relative to the internal diameter Db of the barrel 10 decreases as the internal diameter Db increases.

[0070] The length 102 of the tapered portion 84 plus the length 86 of the non-tapered portion 82 is larger than the internal diameter Db of the barrel 10. In certain embodiments, a ratio of (the length 102 of the tapered portion 84 plus the length 86 of the non-tapered portion 82) to the internal diameter Db of the barrel 10 is between about 1.2 to about 1.6, such as about 1.2, about 1.3, about 1.4, about 1.5, and about 1.6. In certain embodiments the ratio of (the length 102 of the tapered portion 84 and the length 86 of the non-tapered portion 82) to the internal diameter Db of the barrel 10 is less than about 3. In certain embodiments, a ratio of (the length 102 of the tapered portion 84 and the length 86 of the non-tapered portion 82) to the internal diameter Db of the barrel 10 is between about 1.0 to about 2.9, such as about 1.0, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2.0, about 2.1, about 2.2, about 2.3, about 2.4, about 2.5, about 2.6, about 2.7, about 2.8, about 2.9. The length 102 may also be expressed as a function of the diameter Dsof the screw root 58. In certain embodiments, the length 102 of the tapered portion 84 and the length 86 of the non-tapered portion 82 of the groove 70 is between about 80 mm to about 250 mm, such as about 80 mm, about 90 mm, about 100 mm, about 110 mm, about 120 mm, about 130 mm, about 140 mm, about 150 mm, about 160 mm, about 170 mm, about 180 mm, about 190 mm, about 200 mm, about 210 mm, about 220 mm, about 230 mm, about 240 mm or about 250 mm. In certain embodiments the length of the groove 70 is less than about 255 mm.

[0071] The width of the tapered portion 84 of the groove 70 is the same as the width 90 of the non-tapered portion 82 of the groove.

[0072] The depth 104 of the tapered portion 84 of the groove 70, where it meets the non-tapered portion 82 of the groove 70 is the same as the depth 88 of the non-tapered portion 82 of the groove 70. From there towards the tail end 78 of the groove 70, the depth 104 decreases linearly. Modifications and improvements to the above-described embodiments of the present technology may become apparent to those skilled in the art. The foregoing description is intended to be exemplary rather than limiting. The scope of the present technology is therefore intended to be limited solely by the scope of the appended claims. The description of the embodiments of the present technology provides only examples of the present technology, and these examples do not limit the scope of the present technology. It is to be expressly understood that the scope of the present technology is limited by the claims only. The concepts described above may be adapted for specific conditions and / or functions and may be further extended to a variety of other applications that are within the scope of the present technology. Having thus described the embodiments of the present technology, it will be apparent that modifications and enhancements are possible without departing from the concepts as described.

Claims

CLAIMS1. A barrel for an extruder, the barrel comprising: a barrel wall defining a chamber for receiving a screw in use, the barrel wall having an internal diameter, the chamber including at least a barrel feed section corresponding to a screw feed section in use, the barrel feed section configured to receive and process solid material pieces; at least one groove defined in the barrel wall, the at least one groove having a length, a width and a depth, the groove extending along the barrel wall and disposed only in the barrel feed section; the depth of the groove being less than a largest dimension of the solid material pieces; and the width of the groove being at least as wide as the largest dimension of the solid material pieces.

2. The barrel of claim 1, wherein the groove has a non-tapered portion having a length and in which a depth of the groove is substantially constant along its length, and a tapered portion having a length and in which the depth decreases along its length.

3. The barrel of claim 2, wherein, in the non-tapered portion, a ratio of the length of the groove to the internal diameter of the barrel is less than about 3.

4. The barrel of claim 3, wherein, in the non-tapered portion, the ratio of the length of the groove to the internal diameter of the barrel is between about 0.9 to about 1.5.

5. The barrel of any one of claims 2-4, wherein, in the non-tapered portion, the length of the groove is less than about 255 mm or less than about 200 mm.

6. The barrel of any one of claims 2-5, wherein, in the tapered portion, the length is less than the internal diameter of the barrel.

7. The barrel of claim 6, wherein, in the tapered portion, the ratio of the internal diameter of the barrel to the length of the groove is between about 3.0 to about 5.0.

8. The barrel of any one of claims 1-7, wherein, in the tapered portion, the length of the groove is less than about 50 mm.

9. The barrel of any one of claims 2-8, wherein the length of the groove in the tapered portion is less than the length of the groove in the non-tapered portion.

10. The barrel of any one of claims 2-9, wherein a ratio of (the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion) to an internal diameter of the barrel is less than about 3.

11. The barrel of claim 10, wherein the ratio of (the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion) to the internal diameter of the barrel is between about 1.2 to about 1.6.

12. The barrel of any one of claims 2-11, wherein the length of the tapered and non-tapered portions of groove is less than about 255 mm or less than about 245 mm.

13. The barrel of any one of claims 2-12, wherein one or more of (i) the length of the groove in the tapered portion, (ii) the length of the groove in the non-tapered portion, and (iii) the length of the groove in the tapered portion plus the length of the groove in the non-tapered portion is proportional to the internal diameter of the barrel.

14. The barrel of any one of claims 1-13, wherein the width of the groove is agnostic of the internal diameter of the barrel.

15. The barrel of any one of claims 1-14, wherein the depth of the groove is agnostic of the internal diameter of the barrel.

16. The barrel of any one of claims 2-15, wherein the depth of the groove at the non-tapered portion is about 50% of the largest dimension of the solid material piece.

17. The barrel of any one of claims 1-16, wherein a width of the groove is configured such that it can house at least two pieces of the solid material pieces in side-by-side configuration.

18. The barrel of any one of claims 1-17, wherein the groove has a head end and a tail end, the head end being longitudinally aligned with a feed throat of the barrel.

19. The barrel of any one of claims 1-18, wherein the at least one groove comprises a plurality of grooves that are circumferentially spaced from one another, the number of grooves being proportional to the internal diameter of the barrel.

20. The barrel of any one of claims 1-19, wherein the length of the groove extends along the entirety of the barrel feed section.

21. An extruder comprising a barrel as defined in any one of claims 1 to 20, and a screw rotatably housed in the barrel.

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