Description:FIELD OF INVENTION
[0001] The present disclosure relates to the field of twin-screw processors. More particularly, the disclosure relates to an element for a twin-screw processor.
BACKGROUND OF THE INVENTION
[0002] Twin screw processors, such as a twin screw extruder, are typically used in production, compounding, and processing of materials such as plastics, food, paint and pharmaceuticals. A primary task carried out by the twin screw processor is mixing of the materials to produce a melt. Melting and homogenizing of the materials in a twin screw processor involves application of forces that cause shearing, smearing, elongation, bending, torsion, and compression. Generally, a progress of the materials through the twin screw processor is also controlled at every step of the melting and homogenizing process by the selective use of specific processor elements. The twin screw processors may include different processing elements mounted on screw shafts that allow the twin screw processors to be adapted to different processing requirements.
[0003] Elements may be self-wiping or non-self-wiping, where a self-wiping element wipes or cleans the corresponding element on the other shaft when the elements are rotated in the same direction. Each element has a flight formed thereon that extends along the length of the element and comprises of raised portions or lobes having larger radial diameter than the root diameter of the element. The number of lobes may be an integer or a non-integer forming integer lobe or non-integer lobe flights respectively.
[0004] US Patent No. 6,783,270 to Babu, discloses fractional lobe elements. US Patent No. 10,207,423B2 to Babu discloses an element comprising a continuous flight, having a lead L, that transforms from an integer lobe flight to a non-integer lobe flight and back to an integer lobe flight over a fraction of the lead L of the element. Further, US Patent No. 10,239,233B2 discloses an element comprising a continuous flight, having a lead L, that transforms from a first non-integer lobe flight to a second non-integer lobe flight and back to the first non-integer lobe flight over a fraction of the lead L of the element.
[0005] There remains a need for elements for a twin-screw processor that offer better control on the mixing capabilities of the processor. There is also a need for elements that permit lower temperature processing of material.
SUMMARY OF THE INVENTION
[0006] In an aspect of the disclosure, an element for a twin-screw processor is disclosed. The element has a lead ‘L’ and defines multiple sections each having a lead is a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the plurality of sections is the lead ‘L’. The element has at least one flight formed on the multiple sections. The flight transforms at least once from an infinite lobe flight defining a circular profile into a non-integer lobe flight in a first section of the multiple sections having a first fraction of the lead ‘L’. Further, the flight transforms at least once from the non-integer lobe flight to an infinite lobe flight defining a circular profile in a second section of the multiple sections having a second fraction of the lead ‘L’.
[0007] In another aspect of the present disclosure, a twin-screw processor is disclosed. The twin-screw processor comprises a housing having a first housing bore and a second housing bore. The first housing bore defines an axis disposed parallel to an axis of the second housing bore. The twin-screw processor also comprises a first screw shaft disposed in the first housing bore and a second screw shaft disposed in the second housing bore. Each of the first screw shaft and the second screw shaft is provided with at least one element. The element has a lead ‘L’ and defines multiple sections each having a lead is a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the plurality of sections is the lead ‘L’. The element has at least one flight formed on the multiple sections. The flight transforms at least once from an infinite lobe flight defining a circular profile into a non-integer lobe flight in a first section of the multiple sections having a first fraction of the lead ‘L’. The flight also transforms at least once from the non-integer lobe flight to an infinite lobe flight defining a circular profile in a second section of the multiple sections having a second fraction of the lead ‘L’.
BRIEF DESCRIPTION OF DRAWINGS
[0008] FIG. 1 is an exemplary illustration of a twin-screw processor, in accordance with an embodiment of the present disclosure;
[0009] FIG. 2 is an exemplary illustration of an isometric view of the processing elements used in the twin-screw processor of FIG. 1, in accordance with the embodiment of the present disclosure;
[0010] FIGS. 3A, 3B, and 3C are exemplary illustrations of right-side view, front view, and left-side view of each processing element of FIG. 1 comprising multiples sections, in accordance with the embodiment of the present disclosure;
[0011] FIG. 4 is an exemplary front-view illustration of the processing element of FIG. 1 comprising repeating sections of the sections illustrated in FIGS. 3A-3C, in accordance with another embodiment of the present disclosure; and
[0012] FIG. 5 is an exemplary front-view illustration of each processing element of FIG. 1 comprising repeating sections of the sections illustrated in FIGS. 3A-3C, in accordance with yet another embodiment of the present disclosure.
DETAILED DESCRIPTION
[0013] Referring to FIG. 1, an exemplary illustration of a twin-screw processor 100, herein referred to as “processor 100” is disclosed. The processor 100 may comprise a housing 102 having two cylindrical housing bores 104, 106. The two cylindrical housing bores 104, 106 may have an axis 108 and 110 respectively disposed parallelly with respect to each other. A first screw shaft 112 and a second screw shaft 114 are disposed in the first and second housing bores 104, 106 respectively. A pair of processing elements 116, 118 or ‘elements’ may be mounted on the screw shafts 112, 114 respectively. In an embodiment, a plurality of such element pairs mounted on respective screw shafts may define the various zones within the processor 100 including the intake zone, the mixing zone and the output zone. The elements 116, 118 may comprise grooved axial bores 120, 122 in which splines of the screw shafts 112, 114 respectively are engaged. It may be apparent that the elements 116, 118 may also be configured for mounting on the screw shafts 112, 114 via different engagement means. In an embodiment, the processor 100 may be a co-rotating twin-screw processor in which the elements 116, 118 are rotated in the same direction with respect to each other simultaneously.
[0014] Referring to FIG. 2, an exemplary illustration of exemplary illustration of an isometric view of the processing elements used in the twin-screw processor of FIG. 1 is disclosed. In an embodiment, the elements 116, 118 may be eccentrically mounted on the screw shafts 112, 114 respectively such that an axis 202 and 204 of the axial bores 120 and 122 respectively are eccentric to a central longitudinal axis 206 and 208 of the elements 116, 118 respectively. In another embodiment, the elements 116, 118 may be co-axially mounted with the screw shafts such that the axis 202 and 204 of the axial bores 120 and 122 respectively are co-axial with the central longitudinal axis 206 and 208 of the elements 116, 118 respectively. In an embodiment, the axis 202 and 204 of the axial bores 120 and 122 respectively may be co-axial with the axis 108 and 110 of the housing bores 104 and 106 respectively. In an embodiment, the elements 116, 118 may be fully self-wiping or self-cleaning such that, the element 116 effects a complete wiping of the element 118 and vice versa, when the elements 116, 118 are rotated simultaneously in the same direction. In an embodiment, the elements 116, 118 may together define a conjugate pair of elements such that for each cross-section of the element 116 on the first screw shaft 112 there exists a conjugate cross-section of the element 118 on the corresponding second screw shaft 114 that is fully self-wiping. For purposes of clarity and understanding, the element 116 will be described hereafter in detail and it may be understood that the same would also be applicable to the element 118.
[0015] Referring to FIGS. 3A-3C, exemplary right-side view, front-view, and left-side view illustrations of the element 116 of FIG. 1 respectively are disclosed, in accordance with an embodiment of the present disclosure. The element 116 has a lead ‘L’ and defines multiples sections S4, S1, S3, S2, and S8 along a longitudinal length ‘Y’ of the element 116. The sections S4, S1, S3, S2, and S8 have a lead L4, L1, L3, L2, and L8 respectively. Each lead of the leads L4, L1, L3, L2, and L8 corresponds to a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the sections is the lead ‘L’. The element 116 includes at least one flight 300 formed on the sections S4, S1, S3, S2, and S8. A number of flights formed in the element 116 corresponds to a number of lobes provided in the element 116. For example, in a tri-lobed element having three lobes may define three continuous self-wiping flights helically formed thereon. The flight 300 formed may be self-wiping. The flight 300 may transform one or more times along the length Y of the element 116. The flight transformation may involve a change in lobes along the longitudinal length Y. The change in the lobes may correspond to a change in a number of lobes and/or lobe profiles associated with the lobes formed on the element 116. In an embodiment, the flight 300 may have an infinite number of lobes defining a circular profile, referred to as “infinite lobes”. Such elements are referred to as “infinite lobe flight”, “infinite-lobe element”, or elements having an infinite lobe flight. The flight 300 may also have a non-integer number of lobes, referred to as “non-integer lobes”, such as a fractional lobe or irrational lobe, extending along the longitudinal length Y of the element 116. Such elements are referred to as “non-integer lobe flight”, “non-integer lobe elements”, or elements having a non-integer lobe flight. In addition, the flight 300 may also have different combinations of infinite and non-integer lobes extending along the longitudinal length Y of the element 116.
[0016] A non-integer lobe element may be a fractional lobed element. Examples of a fractional lobe element formed from an integer lobe element such as a single lobe element, a bi-lobe element, a tri-lobe element, and/or a four lobe element are described in U.S. Pat. No. 6,783,270, U.S. Pat. No. 10,207,423, and U.S. Pat. No. 10,239,233. It may be understood that the flight of an element having an integer number of lobes, referred to as “integer lobes”, extending along a longitudinal length of the element are referred to as “integer lobe flight”, “integer lobe elements”, or elements having a integer lobe flight. A non-integer lobe element may be an irrational number lobed element. Irrational number lobed elements are described in U.S. Pat. No. 8,753,003. A fractional lobed element is an element intermediate a first integer element (n) and a second integer element (N) by a predefined fraction, such that N/n is an integer and the fraction determines the degree of transition between the first integer and the second integer. A single flight lobe and a bi-lobe can form fractional lobes such as 1.2.xx, where xx can be any number from 1 to 99. The numbers 1 to 99 define whether the fractional lobe will look more like a single flight element or a bi-lobed element. The numbers 1 and 2 in the notation 1.2.xx represent the lobe element intermediate a single flight element (1) and a bi-lobe element respectively (2). Thus, a fractional lobe element represented as 1.4.50 represents an element mid-way between a single flight and a four lobe element.
[0017] In an embodiment, the flight 300 may transform from the infinite lobe flight to the non-integer-lobe flight or vice versa multiple times along the length Y of the element 116. For example, in an embodiment, the flight 300 may start and continue as an infinite lobe flight 302 defining a circular profile 301 in the section S4 having the lead L4. The flight 300 may then transform from the infinite lobe flight 302 to the non-integer lobe flight 304 in the section S1 having the lead L1. The flight 300 may continue as the non-integer lobe flight 304 in the section S3 having the lead L3. The flight 300 may then transform back from the non-integer lobe flight 304 to the infinite lobe flight 302 in the section S2 having the lead L2. In an embodiment, the flight 300 may extend or continue as the infinite lobe flight 302 in the section S8 having the lead L8 after transforming from the non-integer lobe flight to the infinite lobe flight defining the circular profile in the section S2 having the lead L2. In an embodiment, the flight 300 may be helical and continuous in the sections S1, S3, and S2 in which the flight 300 transforms from the infinite lobe flight to the non-integer lobe flight, continues as the non-integer lobe flight, and transforms back from the non-integer lobe flight to the infinite lobe flight respectively. In an embodiment, the flight 300 may begin and/or end as the infinite lobe flight or the non-integer lobe flight. For example, the flight 300 may begin as the infinite lobe flight 302 and end as the infinite lobe flight 302. In an embodiment, the flight 300 may also change hands along the sections S1, S2 having the non-integer lobe flights 304. For example, the flight 300 may be a right-handed flight RH in the section S1 having the lead L1 and may change into a left-handed flight LH in the section S2 having the lead L2 or vice versa.
[0018] The leads L4, L1, L3, and L2 in the sections S4, S1, S3, and S2 respectively may be equal to or different from each other. In an embodiment, the leads in at least two sections may be equal or different from one another. For example, the lead L1 of the section S1 may be equal to or different from the lead L2 of the section S2. Similarly, the leads L3 and L4 of the sections S3 and S4 respectively may be equal to or different from the leads L1 and/or L2 of the sections S1 and/or S2 respectively. In an embodiment, the leads of sections in which the flight 300 transforms from the infinite lobe flight to the non-integer lobe flight and/or vice versa may be equal. For example, the leads L1 and L2 of the sections S1 and S2 respectively in which the flight 300 transforms from the infinite lobe flight 302 to the non-integer lobe flight 304 and from the non-integer lobe flight 304 to the infinite lobe flight 302 respectively may be equal. Similarly, the leads of sections in which the flight 300 extends continuously without transformation may be equal. For example, the leads L4, L3, and L8 of sections S4, S3, and S8 in which the flight 300 extends continuously as the infinite lobe-flight 302, the non-integer flight 304, and another infinite lobe flight 302 respectively may be equal. In an embodiment, the leads in consecutive or alternative sections may be equal. For example, the leads L4 and L1 in the consecutive sections S4 and S1 respectively may be equal. Similarly, the leads L1 and L2 in the alternative sections S1 and S2 respectively may be equal. The sections S4, S1, S3, and S2 may have lengths Y4, Y1, Y3, and Y2 respectively and a sum of the lengths Y4, Y1, Y3, and Y2 is equal to the length ‘Y’ of the element 116. The lengths Y4, Y1, Y3, and Y2 of the sections S4, S1, S3, and S2 respectively may be equal or different. In an embodiment, the lengths in at least two sections may be equal or different from one another. In an embodiment, the lengths of sections in which the flight 300 transforms from the infinite lobe flight to the non-integer lobe flight and/or vice versa may be equal. For example, the lengths Y1 and Y2 of the sections S1 and S2 respectively in which the flight 300 transforms from the infinite lobe flight 302 to the non-integer lobe flight 304 and from the non-integer lobe flight 304 to the infinite lobe flight 302 respectively may be equal. Similarly, the lengths of sections in which the flight 300 extends continuously without transformation may be equal. For example, the lengths Y4, Y3, and Y8 of sections S4, S3, and S8 in which the flight 300 extends continuously as the infinite lobe-flight 302, the non-integer flight 304, and another infinite lobe flight 302 respectively may be equal. In an embodiment, the lengths in consecutive or alternative sections may be equal. For example, the lengths Y1 and Y2 in the alternative sections S1 and S2 respectively may be equal.
[0019] Referring to FIGS. 3A-3C and FIG. 4, in an embodiment, the transformation of the flight 300 from the infinite lobe flight 302 defining the circular profile 301 into the non-integer lobe flight 304 and the transformation of the flight 300 from the non-integer lobe flight 304 to the infinite lobe flight 302 defining the circular profile 301 takes place a multiple times along the lead ‘L’ of the element 116. For example, the transformations of the flight 300 in the sections S4, S1, S3, and S2 may repeat in sections S8, S5, S7, S6 having respective leads L8, L5, L7, and L6, sections S12, S9, S11, S10 having respective leads L12, L9, L11, and L10, and sections S16, S13, S15, S14 having respective leads L16, L13, L14, and L15. In an embodiment, the lengths Y4, Y1, Y3, and Y2 of the sections S4, S1, S3, and S2 may also repeat along the length ‘Y’ of the element 116. For example, the lengths Y4, Y1, Y3, and Y2 of the sections S4, S1, S3, and S2 may be equal to the lengths Y8, Y5, Y7, and Y6 of the sections S8, S5, S7, S6, the lengths Y12, Y9, Y11, and Y10 of the sections S12, S9, S11, S10, and the lengths Y16, Y13, Y15, and Y14 of the sections 16, 13, 15, 14 respectively. In an embodiment, the flight 300 may extend or continue as the infinite lobe flight 302 in section S17 having the lead L17 after transforming from the non-integer lobe flight to the infinite lobe flight defining the circular profile in the section S14 having the lead L14.
[0020] Referring to FIGS. 3A-3C and FIG. 5, in another embodiment, the leads and the lengths of the first and the last section of the element 116 may be equal. Similarly, the leads and the lengths of the intermediate sections between the first and the last sections of the element 116 may be also equal and different from the leads and the lengths of the first and the last sections respectively. For example, the leads L4 and L12 of the first section S4 and the last section S12 respectively may be equal. The leads L1, L3, L2, L8, L5, L7, L6 of the intermediate sections S1, S3, S2, S8, S5, S7, S6 respectively between the first section S4 and the last section S12 may also equal and different from the leads L4 and L12 of the first section S4 and the last section S12 respectively. Similarly, the lengths Y4 and Y12 of the first section S4 and the last section S12 respectively may be equal. The lengths Y1, Y3, Y2, Y8, Y5, Y7, Y6 of the intermediate sections S1, S3, S2, S8, S5, S7, S6 respectively between the first section S4 and the last section S12 may also equal and different from the lengths Y4 and Y12 of the first section S4 and the last section S12 respectively.
[0021] It may be appreciated that in other embodiments a different number of the sections, different arrangements of the sections, and different sequences of the repetitions of the sections having similar or different leads and/or lengths may be considered in the element 116 of the present disclosure.
Specific Embodiments are Described Below
[0022] An element for a twin-screw processor, the element having a lead ‘L’ and defining a plurality of sections each having a lead that is a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the plurality of sections is the lead ‘L’, the element including at least one flight formed thereon, wherein the at least one flight transforms at least once from an infinite lobe flight defining a circular profile into a non-integer lobe flight in a first section of the plurality of sections having a first fraction of the lead ‘L’, and wherein the at least one flight transforms at least once from the non-integer lobe flight to an infinite lobe flight defining a circular profile in a second section of the plurality of sections having a second fraction of the lead ‘L’.
[0023] Such element(s), wherein the at least one flight is a non-integer lobe flight in a third section of the plurality of sections having a third fraction of the lead ‘L’ before transforming from the non-integer lobe flight to the infinite lobe flight defining the circular profile in the second section of the plurality of sections.
[0024] Such element(s), wherein the at least one flight is an infinite lobe flight defining a circular profile in a fourth section of the plurality of sections having a fourth fraction of the lead ‘L’ before transforming from the infinite lobe flight defining the circular profile to the non-integer lobe flight in the first section of the plurality of sections.
[0025] Such element(s), wherein the first fraction of the lead ‘L’ is different from the second fraction of the lead ‘L’.
[0026] Such element(s), wherein the third fraction of the lead ‘L’ and the fourth fraction of the lead ‘L’ are different from the first fraction of the lead ‘L’ or the second fraction of the lead ‘L’.
[0027] Such element(s), wherein the at least one flight defines a right-hand flight in the first section of the plurality of sections and a left-hand flight in the second section of the plurality of sections.
[0028] Such element(s), wherein the transformation of the at least one flight from the infinite lobe flight defining the circular profile into the non-integer lobe flight and the transformation of the at least one flight from the non-integer lobe flight to the infinite lobe flight defining the circular profile takes place a plurality of times along the length of the element.
[0029] Such element(s), wherein the non-integer lobe flight is a fractional lobe flight.
[0030] Such element(s), including an axial bore configured to be engaged with a corresponding first screw shaft or a second screw shaft of the twin-screw processor, wherein an axis of the axial bore is eccentric to a central longitudinal axis of the element.
 
Industrial Applicability
[0031] The elements 116, 118 as taught by the present disclosure are self-wiping and suitable for use in twin-screw processors. Consequently, the elements 116, 118 as taught improve a mixing and/or melting capability of the processor 100 of FIG. 1 and also help in achieving a homogeneous melt mix. In addition, the elements 116, 118 as taught improve an elongational flow of the materials during the melting and homogenizing process. Furthermore, the elements 116, 118 as taught facilitate the melting and/or homogenizing of the materials at a process temperature lesser than generally involved in the melting and/or homogenizing process in the counter-rotating twin-screw processors. In particular, the elements 116, 118 are suitable for processing of temperature sensitive materials such as pharmaceutical ingredients including API. The elements 116, 118 may also be suitable for processing mixed materials with different melting or softening points such as waste material for recycling. , Claims:1. An element for a twin-screw processor, the element having a lead ‘L’ and defining a plurality of sections each having a lead that is a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the plurality of sections is the lead ‘L’, the element including at least one flight formed thereon,
wherein the at least one flight transforms at least once from an infinite lobe flight defining a circular profile into a non-integer lobe flight in a first section of the plurality of sections having a first fraction of the lead ‘L’, and
wherein the at least one flight transforms at least once from the non-integer lobe flight to the infinite lobe flight defining a circular profile in a second section of the plurality of sections having a second fraction of the lead ‘L’.
2. The element as claimed in claim 1, wherein the at least one flight is a non-integer lobe flight in a third section of the plurality of sections having a third fraction of the lead ‘L’ before transforming from the non-integer lobe flight to the infinite lobe flight defining the circular profile in the second section of the plurality of sections.
3. The element as claimed in claim 1 or 2, wherein the at least one flight is an infinite lobe flight defining a circular profile in a fourth section of the plurality of sections having a fourth fraction of the lead ‘L’ before transforming from the infinite lobe flight defining the circular profile to the non-integer lobe flight in the first section of the plurality of sections.
4. The element as claimed in claim 1, wherein the first fraction of the lead ‘L’ is different from the second fraction of the lead ‘L’.
5. The element as claimed in claim 3, wherein the third fraction of the lead ‘L’ and the fourth fraction of the lead ‘L’ are different from the first fraction of the lead ‘L’ or the second fraction of the lead ‘L’.
6. The element as claimed in claim 1, wherein the at least one flight defines a right-hand flight in the first section of the plurality of sections and a left-hand flight in the second section of the plurality of sections.
7. The element as claimed in claim 1, wherein the transformation of the at least one flight from the infinite lobe flight defining the circular profile into the non-integer lobe flight and the transformation of the at least one flight from the non-integer lobe flight to the infinite lobe flight defining the circular profile takes place a plurality of times along the lead ‘L’ of the element.
8. The element as claimed in claim 1, wherein the non-integer lobe flight is a fractional lobe flight.
9. The element as claimed in claim 1 includes an axial bore configured to be engaged with a corresponding first screw shaft or a second screw shaft of the twin-screw processor, wherein the axial bore is eccentric to a central longitudinal axis of the element.
10. A twin-screw processor, comprising:
a housing having a first housing bore and a second housing bore, the first housing bore having an axis disposed parallel to an axis of the second housing bore;
a first screw shaft disposed in the first housing bore and a second screw shaft disposed in the second housing bore, each of the first screw shaft and the second screw shaft is provided with at least one element having a lead ‘L’ and defining a plurality of sections each having a lead that is a fraction of the lead ‘L’ such that the sum of the fractions of the leads of the plurality of sections is the lead ‘L’, the element including at least one flight formed thereon,
wherein the at least one flight transforms at least once from an infinite lobe flight defining a circular profile into a non-integer lobe flight in a first section of the plurality of sections having a first fraction of the lead ‘L’, and
wherein the at least one flight transforms at least once from the non-integer lobe flight to an infinite lobe flight defining a circular profile in a second section of the plurality of sections having a second fraction of the lead ‘L’.
11. The twin-screw processor as claimed in claim 10, wherein the at least one flight is a non-integer lobe flight in a third section of the plurality of sections having a third fraction of the lead ‘L’ before transforming from the non-integer lobe flight to the infinite lobe flight defining the circular profile in the second section of the plurality of sections.
12. The twin-screw processor as claimed in claim 10 or 11, wherein the at least one flight is an infinite lobe flight defining a circular profile in a fourth section of the plurality of sections having a fourth fraction of the lead ‘L’ before transforming from the infinite lobe flight defining the circular profile to the non-integer lobe flight in the first section of the plurality of sections.
13. The twin-screw processor as claimed in claim 10, wherein the first fraction of the lead ‘L’ is different from the second fraction of the lead ‘L’.
14. The twin-screw processor as claimed in claim 12, wherein the third fraction of the lead ‘L’ and the fourth fraction of the lead ‘L’ are different from the first fraction of the lead ‘L’ or the second fraction of the lead ‘L’.
15. The twin-screw processor as claimed in claim 10, wherein the at least one flight defines a right-hand flight in the first section of the plurality of sections and a left-hand flight in the second section of the plurality of sections.
16. The twin-screw processor as claimed in claim 10, wherein the transformation of the at least one flight from the infinite lobe flight defining the circular profile into the non-integer lobe flight and the transformation of the at least one flight from the non-integer lobe flight to the infinite lobe flight defining the circular profile takes place a plurality of times along the lead ‘L’ of the element.
17. The twin-screw processor as claimed in claim 10, wherein the non-integer lobe flight is a fractional lobe flight.
18. The twin-screw processor as claimed in claim 10, wherein the at least one element includes an axial bore configured to be engaged with the corresponding first screw shaft or the second screw shaft of the twin-screw processor, wherein the axial bore is eccentric to a central longitudinal axis of the element.