CN1038616A - Three-stage type vented extruder screw - Google Patents

Abstract

The present invention relates to the three-stage type monoblock type vented extruder screw of dry blends such as a kind of suitable processing HPVC, ABS, it had both overcome that existing two stepwise vented extruder screws yield poorly and the unstable and shortcoming of overflow very easily, solved existing screw-rod structure complexity, low, the high deficiency of cost of intensity again, a kind of big L/D ratio, the whole vented extruder screw of three-stage type solid, that design has mixing ring of slot type and threaded screw head are provided.

Description

Three-stage type vented extruder screw

The present invention relates to a kind of vented extruder screw of processing dry blend, particularly a kind of draw ratio ratio of being made up of feeding section, compression section, exhaust section, metering section, the mixing ring of cellular type and screw head is 25 and the two stepwises boring vented extruder screw that formed by six part assembly, it is characterized in that it is that a kind of draw ratio ratio is between the 28-33, second metering section is a 7-9 pitch length, and it is solid or formed and the three-stage type dry blend vented extruder screw that bores the cooling hole arranged by two sections assembly to have the monoblock type of mixing ring of slot type and threaded screw head.

Fig. 1-4 is structural representation and partial sectional views of the dry blend vented extruder screw of processing HPVC packaging film that China in 1986 introduces from the luxuriant and rich with fragrance Up K.K. of Italy and that use in Xia Men Shandong Packaging Materials Plant.This screw rod 1 is made up of A, B two rank, wherein the A rank are made up of feeding section 4, first compression section 5, first metering section 6, the mixing ring 7 of cellular type, and the B rank are made up of decompression section 8, exhaust section 10, second compression section 11, second metering section 12, the mixing ring 7 of cellular type and screw head 13.Because the turning effort of screw rod 1 machine barrel 2 in, then be involved in after material is added by charge door 3 and be compressed gradually, mix, heat up and when half plastifying state, arrive exhaust section 10, gas and volatile matter are compressed again, heat up and extruded by the circular flow channel 15 of head 14 until the one-tenth molten condition after by exhaust outlet 9 discharges by the helicla flute of screw rod 1.In order to strengthen mixed effect, the mixing ring 7 of cellular type is housed at first metering section, 6 ends and second metering section, 12 ends.

First deficiency of this screw rod 1 is that draw ratio ratio has only 25, and is less than normal, and second metering section 12 has only 6 pitch length also short partially.Because draw ratio is little, the time of staying of material under same rotational speed is then short, and the material plasticizing quality is just relatively poor, in order to reach plasticizing quality, screw rod 1 is moved under low speed, and this has caused the decline of output again.The inclined to one side weak point of second metering section 12 on B rank has then caused all pressing weak effect, and its axial length can not guarantee to set up stable and enough head pressure, and the head pressure fluctuation is reached ± 5kg f/cm ²More than, caused extrusion capacity also to fluctuate.Simultaneously,, also caused the refluence amount to increase, the basic reason of exhaust outlet 9 a large amount of overflows of Here it is this board because 12 is short partially.Simultaneously little by this screw slenderness ratio, at 0.5-0.6, the segment length is more unreasonable than coupling than ratio for B/A stage length, so when screw speed raises, the pressure at head 14 places also increases thereupon, and refluence amount and overflow amount also increase thereupon, and when screw speed reduces, though overflow reduces, but head pressure descends again, and goods compactness and quality also descend, so this screw rod can only turn round under a lower rotating speed, so PR is lower, this also is a common weakness of degassing extruder.

Second deficiency of this screw rod is, when high-temperature material when the aperture 16 by second mixing ring 7 of cellular type enters into screw head 13 positions under the promotion of second metering section, 12 spiral shell ribs, because screw head 13 is extremely short and do not have a screw thread, so the remaining extruding force of the material that can only rely on the back to this melting charge after by aperture 16 continues to push ahead, because this thrust is very little (because screw rod 1 rotating speed is on the low side, extrusion capacity is less than normal), so melting charge is very easily at this slow stream, especially the laminar flow layer of screw head 13 conical surfaces produces strong shearing friction and temperature of charge is sharply risen even burns when screw rod rotates, and this burns material and just can stick to 13 surfaces and cumulative be brought into until peeling off in the goods and be forced to stop to produce.For solving the problem of burning that remains in a standstill and cause owing to material, so must on screw rod 1, be drilled with logical oil cooled axial deep hole 22, this has brought difficulty not only for the processing of screw rod 1, but also need to be equipped with a cover for the pipeline of regulating coolant temperature and flow, pump, instrument etc., make the huge and cost height of machine.

The thirdly deficiency of this screw rod is that the peripheral aperture 16 of the mixing ring 7 of cellular type is to be difficult to processing on the monoblock type screw rod, (because 7 external diameters are identical with screw rod 1 external diameter, processing can't be installed) therefore must be with 7 pre-processed as independent part, all be threaded 20 connection thread segment 18 with two again and couple together with adjacent with it part respectively.The described deep hole 22 bad processing in front in addition also must be with screw rod 1 segmentation.This just makes that screw rod 1 is by two mixing rings 7 of cellular type, screw head 13, thread segment 18, spiro rod section 19 and 21 6 parts serial connection form, simultaneously in order to prevent that heat-eliminating medium from bleeding in the screw rod 1 outside material, in each connection place seal 17 is arranged all, this has not only increased the number of part and the difficulty of processing, and brought very big inconvenience to dismounting maintenance, particularly caused the decline of screw rod 1 axial assembly precision and screw rod 1 strength and stiffness.

Task of the present invention just is to overcome the above-mentioned shortcoming and defect of existing in prior technology, and the three-stage type vented extruder screw that is suitable for processing dry blend that a kind of high-quality and efficient, easy to maintenance, cheap monoblock type is solid or have only two parts assembly to form is provided.

Fig. 1 is Italian import board screw-rod structure schematic diagram.

Fig. 2 is the E-E cutaway view of Fig. 1.(enlarged drawing)

Fig. 3 is the F-F cutaway view of Fig. 1.

Fig. 4 is the G-G cutaway view of Fig. 1.

Fig. 5 is the structural representation (embodiment 1) of screw rod of the present invention.

Fig. 6 is the structural representation of the embodiment of the invention 2.

Fig. 7 is Fig. 5,6,8,11 A-A cutaway view Amplified image.

Fig. 8 is the structural representation of the embodiment of the invention 3 screw rods.

Fig. 9, Figure 10 directly change the signal enlarged drawing at the bottom of the wave mode screw channel of Fig. 7, Fig. 8.

Figure 11 is the structural representation of the embodiment of the invention 4 screw rods.

Figure 12 is the B-B cutaway view of Figure 11.

Main feature of the present invention is increased to 28-33 with screw slenderness ratio ratio exactly, and the second metering section segment length on B rank brought up to 6 more than the pitch length, screw head is a screwed screw head, and the mixing ring on the screw rod is the mixing ring of slot type, and this ring and screw rod body are the monoblock type solid constructions.The difference that also can look processing materials is designed to two segments combined boring formula structure with screw rod, and it has These characteristics equally, is a kind of three-stage type vented extruder screw that is suitable for dry blend processing.

Present invention is described below in conjunction with accompanying drawing:

First characteristics of three-stage type vented extruder screw of the present invention (seeing Fig. 5 and Fig. 7) be exactly mixing ring on this screw rod 23 be the mixing ring 24 of slot type structure, dozens of slot 34 on 24 can directly mill out on screw rod 23 bodies with milling cutter, and will 24 as assembling with the screw rod body again after the independent part processing, therefore can make 23 one-tenths one solid monolithic construction that constitutes by a part of this screw rod.For screw rod being moved under high rotating speed and can processing the very strong material that is easy to thermal decomposition of thermal sensitivity, enlarge the scope of application and the serviceability of machine, this screw rod can also adopt boring cooled structure.In order to make deep hole 30(see Fig. 5,6 Fig. 8 and Figure 11) be easy to process, this screw rod can be divided into the A section with (B+C) two sections, the A section has internal thread, (B+C) section has external screw thread 29, mixing ring 24 of slot type this moment and screw rod body A section (B+C) section still are one, whole screw rod is assembled by two parts, and sealing surface reduces to a place by 4 original places.So not only reduced number of parts and processing cost, and increased the strength and stiffness of screw rod, also improved the axial assembly precision of screw rod and reduced sealing part.

The mixing ring 24 of slot type is within the axial location on the screw rod can last pitch at second metering section 28 on first metering section 6 on A rank and B rank or their end, the concrete condition of the visual processing materials of its layout and other parameter of screw rod is arranged on the one metering section, also can on two metering sections, be provided with simultaneously, the number of encircling on a certain metering section is decided by mixing requirement, be generally 1-2, also can be provided with 3.Peripheral slot 34 on 24 to be arranged in circumferencial direction uniform, run through at the slot thickness direction.The long-pending size of the quantity of slot 34 and opening section thereof should guarantee to allow its fluting sectional area summation equal or be slightly larger than each the metering section screw channel cross-sectional area that is adjacent, generally greater than the time amount be 5%, for good fluidity and the material of thermal sensitivity difference also can make the open and clear quantity of slot 34 and the long-pending summation of the opening section 5%-10% less than adjacent metering section screw channel cross-sectional area, to strengthen the effect that shunting mixes.

Second characteristics of the present invention are that the design of the draw ratio ratio of screw rod 23 is increased to 28-33, it is A that two common stepwises are designed to three-stage type, B, C three rank (see figure 5)s, and former B/A segment length is optimized for (B+C)/A segment length than ratio about 0.5 is 0.8-0.9 than ratio, so not only make the length of second metering section 28 be increased to 6 more than the pitch, be generally 7-9 pitch, but also increased special rank is the C rank, thereby big leap ahead the axial active length of screw rod 23, prolonged material in the time of staying in machine barrel 2 under the same screw speed, this has not only improved the product plasticizing quality, and guaranteed that screw rod 23 can move under higher rotation speed, seeing has higher output.Owing to increased the length of C rank and B rank second metering section 28, the voltage regulation result of screw rod 23 is improved in addition, the fluctuation that greatly reduces the head pressure fluctuation and extrude output reduces to ± 2kg f/cm the head pressure fluctuation ²Below.Simultaneously, head place feed back is backward reduced significantly, thereby makes exhaust outlet 9(see Fig. 1 because the C rank are the increase of threaded screw head 26) overflow reduce to few.Experimental results show that: even up to 350kg f/cm ²Head pressure under, overflow there is not any influence yet, this has proved absolutely that this screw rod has good voltage regulation result and the characteristics of steady operation in big head pressure scope, its output is on the twice of uniform machines, Datong District part of Here it is this screw rod and common two stepwise vented extruder screws.

The 3rd characteristics of this screw rod are that the C rank are designed to screwed screw head 26 dexterously, make that like this material of being pushed by the slot 34 of the mixing ring 24 of slot type is subjected to the push effect of rear portion material except continuing, also being subjected to the forced conveyance effect of threaded screw head 26 screw threads, so having overcome owing to seeing Fig. 1 effectively to head 14() the direction motive force causes inadequately that 27 delay and the decomposition of material on every side stick to the shortcoming of burning on 27 surfaces in screw head circular cone tip.In addition, the spiral groove depth on C rank is general than the dark 30%-40% of second metering section, 28 groove depths, thereby has reduced the shear rate to material, and the material temperature not only can not raise, and when low speed, also can slightly descend, can guarantee that fully material can the too high generation thermal decomposition of Yin Wendu.Therefore this screw rod has good low temperature extrusion performance and self-cleaning, can not need rapid long-play under any temperature control.

But for the serviceability and the scope of application that enlarges screw rod 23, in order to make the screw rod can be in that surpass under its limit speed also can operate as normal, we can be with screw rod 23 borings to carry out oily temperature control, for deep hole 30(in boring sees Fig. 6) convenient, the present invention is designed to two sections (being A section and B+C section) with screw rod, (B+C) the section back segment has an external screw thread head 29,29 to connect with A rank internal thread.Mixing ring 24 architecture advances of this design and slot type make three sections 6 serial connection assemblings of former screw rod 1 reduce to two sections 2 assemblings of this screw rod 23, not only number of parts significantly reduces, assembly precision improves, and sealing surface reduces to a place from original three, bring great convenience for the dismounting and the sealing of screw rod, therefore this screw rod can be the solid construction of drilling deep hole 30 not, also can be the hollow-core construction that is drilled with cooling hole 30.Boring formula screw rod can lead to oily temperature control at ordinary times can obstructed oily temperature control after surpassing critical speed, the 4th characteristics of Here it is this screw rod 23.

Second embodiment of the present invention (seeing Fig. 6, Fig. 9 and Figure 10) is exactly on the first embodiment basis, second compression section 25 and the one start screw on second metering section 28 of screw rod 23 are designed to single wavy helicitic texture, and this monophasic waveform thread segment 31 is formed the new wavy vented extruder screw 32 of three-stage type with the other parts of the embodiment of the invention 1.The screw thread groove depth of (the A rank are identical with Fig. 5 so do not draw) wavy thread segment 31 of this list changes at circumferencial direction (radially).First pitch that this thread segment joins with exhaust section 33 is starting point, in a period of change of zero degree to 540 degree, footpath outer surface 37(sees Fig. 9 and 10 at the bottom of the screw channel of wavy thread segment 31) with the inner surface 38 of machine barrel between the screw thread groove depth all be different to a point, at zero degree and 540 degree places for the most shallow, at the bottom of this moment screw rod 32 screw channels between the inner surface 38 of footpath outer surface 37 and machine barrel the gap be minimum, and volume also is minimum, and when 270 spend for the darkest, the gap is maximum between this moment 37 and 38, and volume also is maximum, since the groove depth variable effect variation of the volume between 37 and 38, make shear stress and shear rate that material is suffered also change, and this variation is per 540 degree circulation primary, in circumferential every variations one-period, at axial material then to heading 1.5 pitch that move forward.And this variation is the rotation gradual change and changing gradually along with screw rod 32, when material enters into the shallow screw channel zone, when 0 degree-180 is spent, because the volume small size is compressed, the shearing friction effect increases and the also just increase of suffered shear stress and shear rate each other, and the material caloric value is just big.But along with screw rod 32 rotates, material progresses into dark screw channel zone again, 180 degree-360 degree, material progresses into loose, the less state of pressure by the state of suppressing, thereby its mutual frictional force also descends thereupon, shearing force also just diminishes, and temperature of charge no longer rises even also descends to some extent certainly.In the time of after screw rod turns to 360 degree, because groove depth shoals again gradually, material is compressed again and strong the shearing again.So go round and begin again until material by single wavy spiro rod section 31 and by till the mixing ring 24 of slot type.This shows that the screw rod 32 in the present embodiment not only has embodiment 1 described advantage, also have a moment to shear by force, go here and there high the mixing and the effect of low temperature rise, be more suitable for processing the high material of thermal sensitivity.

The third embodiment of the present invention is exactly to replace second compression section 25 among the embodiment 1 and the former one start screw on second metering section 28 and form double wave shape vented extruder screw 36 with double wave shape thread segment 35.(seeing Fig. 8, Fig. 9 and Figure 10).As seen from the figure, double wave shape thread segment 35 is that the screw channel with single ripple becomes just in time two undulation sections of 180 degree dislocation of waveform, like this material except one loose as monophasic waveform thread segment 31, being squeezed, shear the immixture, can also be at two ripple countershafts to string is moving back and forth, therefore have than monophasic waveform screw thread better mixing effect, its action principle and monophasic waveform thread segment 31 are similar, no longer set forth herein.

The 4th embodiment of the present invention (seeing Figure 11 and Figure 12) is exactly on the first embodiment basis, the other parts that former one start screw section on second compression section 25 and second metering section 28 are designed to double end barrier type thread segment 39,39 and embodiment 1 have constituted new three-stage type barrier type vented extruder screw 40.Its main feature is that the spiral shell rib 44 of barrier type thread segment 39 is radially hanging down the 0.5-1 millimeter than original one start screw spiral shell rib 43, and promptly the barrier type screw channel is more shallow than original thread groove deeply.Because the screw thread starting point of initiate barrier screw thread is different with original thread with pitch, therefore just an original screw channel is divided into two screw channels, and the screw channel volume of the liquid phase screw channel 42 in these two screw channels is axially to become big gradually by little, and the screw channel volume of another solid phase screw channel 41 is by diminishing greatly gradually, when the material in the solid-liquid screw channel after melt film occurring with machine barrel inner surface 38 places, just be to go in the liquid phase screw channel 41 by rolling over to another screw channel on lower barrier spiral shell rib 44 tops, so constantly compress, cross, can strengthen the Combination of material greatly.Produce thermal decomposition in addition in order to prevent material from piling up at dead angle place, in order to improve the self-cleaning of screw rod 40, the screw thread start, end of this barrier screw thread are not sealed and are kept minimum clearance greater than 3 millimeters.

Therefore, three-stage type unitary solid of the present invention or two sections combination exhaust extruder screws of three-stage type boring formula, not only simple in structure, cheap, but also have the advantages that good quality and high output, low temperature are extruded, be a kind of desirable three-stage type vented extruder screw that is suitable for by direct extrusion moldings of dry blend such as HPVC, ABS.

Claims (3)

1, the present invention relates to a kind of vented extruder screw of processing dry blend, particularly a kind of draw ratio ratio of being made up of feeding section, compression section, exhaust section, metering section, the mixing ring of cellular type and screw head is 25 and the two stepwises boring vented extruder screw that formed by six part assembly, it is characterized in that it is that a kind of draw ratio ratio is between the 28-33, second metering section is a 7-9 pitch length, has mix ring and the monoblock type of threaded screw head is solid or the boring three-stage type dry blend vented extruder screw that formed by two sections assembly of slot type.

2, according to the described three-stage type dry blend of claim 1 vented extruder screw, it is characterized in that:

Mixing ring of a slot type and screw rod body are a unitary solid or whole hole structure, uniform dozens of slot on the mixing ring circumference of slot type, this ring on the screw rod axially be provided with the position can latter two pitch length at metering section within or its end, its quantity is generally 1-2 on some metering sections, mostly be most 3, this ring can be provided with separately or on two metering sections on the metering section simultaneously, it is long-pending that this ring slot quantity and slot sectional area size thereof should guarantee that slot fluting sectional area sum generally should equal adjacent with it metering section screw channel normal direction width section, itself and also can or be slightly less than the long-pending 5-10% in adjacent with it metering section screw channel normal section greater than the long-pending 1-5% in adjacent with it metering section screw channel normal section.

B, screw slenderness ratio ratio are between the 28-33, and the screw rod segment length is between 0.8 to 0.9 than (B+C)/A ratio, and the screw rod second metering section length is between 7 to 9 pitch length.

C, screw rod the 3rd rank C are screwed screw heads, and this screw head and screw rod body are an overall structure, and its screw thread groove depth is than the adjacent with it deep 30%-40% of the second metering thread groove.

The connection of d, the boring formula screw rod during by two sections assembly screws connection by screw thread, on the joining spiro rod section body external thread section is arranged, and on another spiro rod section body internal thread is arranged.

3, according to claim 1 or 2 described three-stage type dry blend vented extruder screws, it is characterized in that:

Former one start screw on a, second metering section and second compression section can be designed to single wavy screw thread or double wave shape screw thread, first pitch that this screw thread joins with exhaust section is starting point till the mixing ring of the slot type inboard, every zero degree to 540 degree is a period of change, screw channel at the bottom of its wavy thread groove between footpath outer surface and the machine letter inner surface all is different at the every bit of circumferential (radially) deeply, at zero degree and 540 degree places for the darkest, for the most shallow, circumferentially changing the one-period screw thread at 270 degree places in 1.5 pitch of axial advancement.Double wave shape screw thread is that single ripple screw channel is become just in time two undulation sections of 180 degree dislocation of waveform.

B, on the former one start screw basis on second compression section and second metering section, increased a barrier type screw thread again, this barrier type screw thread spiro edge height is than low 0.5 to 1 millimeter of former one start screw spiro edge height, this barrier type screw thread starting point does not all seal, it is divided into two screw channels with an original screw channel, cut apart back solid phase screw channel volume by diminishing greatly gradually, and liquid phase screw channel volume becomes big gradually by little.

Images